Effects of video games on children Essay Example for Free

Effects of video games on children Essay Although video games can increase aggressive behavior, they can improve memory and logistical thinking, as well as teach perseverance. Over the course of the last few decades video games have been integrated into the lives of our children. Video games are very appealing to children of all ages, and even to some adults. There is a variety of video games out there, and they range from educational to very violent. Because of this diverse selection of video games, there is a wide range of positive and negative side effects that these games can have on children. Because a large percentage of our children’s time is spent playing video games, there has been a lot of research in recent years on the positive and negative effects these games have on them. â€Å"Among elementary and middle-school populations, girls play for an average of about 5. 5 hours/week and boys average 13 hours/week,† (Gentile, D. A. 2004). Teenagers also spend a time playing video games. According to Media Analysis Laboratory (1998),†Eighty percent of teens said they played at least occasionally and the average amount of time spent gaming for the sample was 5 hours per week† (para. 19). Video game play has become not only a leisurely pastime for children, but for families also. When parents are not involved in some of their game play the outcome can become a little scary. Children who play video games with their families have a more pro-social attitude compared to their counterparts who play alone. Children who are less social or somewhat anti-social tend to develop aggressive tendancies when spending long hours gaming alone especially when violent video games are involved. Video games have been shown to increase aggressive behavior in some children. Neubert, S. P. (2004) said, â€Å"Individuals high in hostility are more likely to become aggressive when exposed to violent video games. † â€Å"Games in which the only positive outcome is the violent demise of enemies reinforces anti-social behavior. Violent video games desensitize people to aggression,† (Neubert, S. P. , 2004). According to a study done by Douglas A. Gentile. References Media Analysis Laboratory (1998). Video game culture: Leisure and play preferences of B. C. teens. Retrieved from http://www. media-awareness. ca In-Text Citation 1. [Insert the paraphrased material] (Simon Fraser University, Burnaby B. C. , 1998). 2. The Media Analysis Laboratory (1998) website [Insert the paraphrased material]. 3. , [Insert the quotation]† (para. 19).

Plasmodium Falciparum Life Cycle

Plasmodium Falciparum Life Cycle Malaria is one of the world leading causes of death, especially among people living in sub-Sahara Africa and other tropical regions. Of the five species of the genus Plasmodium, the malaria protozoan parasite, known to infect Man, Plasmodium falciparum is responsible for the most virulent, severe and dangerous form of human malaria. Over the years, chemotherapy has played central role in the strategies towards the eradication of this disease. However, ability of P. falciparum to develop resistance to effective and affordable drugs and to pyrathroids, the active principle of the insecticides treated nets (ITNs) has made constant search for new pharmacotherapy imperative. This review presents an overview of the life cycle of the causative organism (P. falciparum), the efforts at controlling the disease and the molecular and cellular basis of the infection, with special emphasis on molecular chaperones of the heat shock proteins family as critical components of the parasite intra-erythr ocytic development and survival. The motivation for the present work is also presented. 1.1 Introduction Malaria, whose pathogen is transmitted by female Anopheles mosquitoes, is both preventable and curable, but yet still impacting negatively on the health of millions of people and account for high rate of mortality, especially among children in sub-Sahara Africa (Breman, 2001; Greenwood et al., 2008; Hay et al., 2004; Rowe et al., 2006; Snow et al., 2005). Five species of the genus Plasmodium, the protozoan parasites, responsible for malaria infection are known to infect humans. They are P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi. It has been proposed that P. ovale consist of two species (Cox-Singh, 2010) and that zoonosis is the medium through which P. knowlesi infect humans (White, 2008). Of these, P. falciparum and P. vivax are numerically most important, with the former responsible for the most virulent, severe and dangerous form of human malaria (Greenwood et al., 2008). The World Health Organization (WHO) 2011 Malaria reports (WHO | World Malaria Report 2011, 2012) estimated a total of 216 million episodes of malaria in 2010 with at least 655 000 deaths, mostly in Africa and among children under the age of 5 years. Malaria was reported to be prevalent in 99 countries with an estimated 3.3 billion people at risk. Though, supports by international donors has led to rapid decrease in malaria mortality, especially among adults in Africa, Murray et al., (2012) contended that the malaria mortality burden may actually be larger than previously estimated and that for the necessary elimination and eradication to be achieved at larger scale, there is an urgent need for more supports. Factors, such as lack ofsanitation, malnutrition, lack or reduced access to medications, poverty and the location of many of the poor countries affected by malaria in the tropical zones, all combined together to create an enabling environment for the disease to thrive. Though pre ventive approaches such as good sanitation and distribution of insecticide treated nets (ITNs) (Curtis et al., 2006), have been employed as strategy towards the eradication of this disease, chemotherapy remains the most widely used approach. The ability of P. falciparum to develop resistance to effective and affordable drugs (Cheeseman et al., 2012; Jambou et al., 2005; Mller Hyde, 2010; Phyo et al., 2012) and to pyrethroids, the active principle of the insecticides treated nets (ITNs) (Fane et al., 2012; NGuessan et al., 2007) has made constant search for new pharmacotherapy imperative. Malaria parasite life cycle is a complex mechanism involving two hosts, human and female Anopheles mosquitoes. However, the clinical symptoms of the disease are associated with the invasion of the erythrocytes by the parasite, its growth, division inside the host cell and the cyclic cell lysis and reinvasion of new erythrocytes. The intra-erythrocytic survival and development of the parasite as well as the pathology of the infection are linked to structural and functional remodeling of the host cell through the export of parasite-encoded proteins (Botha et al., 2007; Miller et al., 2002; Pesce Blatch, 2009; Przyborski Lanzer, 2005). Meanwhile, attempts have been made to present an extensive description of the protein interaction network for P. falciparum (LaCount et al., 2005) and about 300 parasite-encoded proteins are predicted to be exported (Marti et al., 2004; Sargeant et al., 2006). Among the exported proteins are the molecular chaperones of the heat shock protein family (Nya lwidhe Lingelbach, 2006). Molecular chaperone are a family of proteins that function to stabilize proteins, facilitate their translocation across intracellular membranes, their degradation, and ensure that proteins in a cell are properly folded and functional (Hartl Hayer-Hartl, 2002; Hartl, 1996). PFA0660w belongs to an extended family of Hsp40 proteins predicted to be transported by the parasite into the host cell (Hiller et al., 2004; Marti et al., 2005; Sargeant et al., 2006). It is a Type II Hsp40 protein, said to be homologous to human DnaJB4, a cytosolic type II Hsp40, known to interact with human Hsp70 to facilitate protein folding, transport and assembly (Botha et al., 2007). Recent studies have localized PFA0660w into structures in the infected erythrocyte, called the J-dots (Kulzer et al., 2010); said to be exported in complex with P. falciparum Hsp70-x (PfHsp70-x) into the J dots (Kulzer et al., 2012) and failure to obtain a viable PFA0660w-knocked-out parasite (Maier et al., 2008), suggests that it may be essential for the survival of the parasite in the infected erythrocytes and therefore a potential target for drug action. 1.2 Malaria Infection 1.2.1 Background information Malaria, though curable and preventable, remains a life-threatening disease that was noted in more than 4,000 years ago and has being responsible for millions of death. World Health Organization (WHO) listed malaria among the most important infectious diseases of the tropics and form part of the sixth millennium development goal (MDG 6) (WHO | MDG 6: combat HIV/AIDS, malaria and other diseases, 2012). The target 6C of MDG 6 is to bring malaria and other major diseases to a halt by 2015 and begin to reverse their incidences. Strategies advocated by WHO to combat malaria includes prevention with the use of long-lasting insecticides treated bed-nets (ITNs) and indoor residual spraying, and rapid treatment with effective anti-malarial medicines with special focus on pregnant women and young children. WHO Roll Back Malaria further recommends that to control Plasmodium falciparum malaria during pregnancy, in addition to individual protection with ITNs and prompt management of anaemia and m alaria using effective anti-malaria drugs, intermittent preventive treatment (IPTp) or chemoprophylaxis should be encouraged (WHO | Malaria in pregnancy, 2012). Though, the World Health Organization (WHO) 2011 Malaria reports (WHO | World Malaria Report 2011, 2012) estimated at least 655 000 deaths as a result of malaria infection, mostly in Africa and among children under the age of 5 years, the mortality burden may actually be larger than previously estimated, thus, the need for improved supports by the funding organization to be able to achieve the much needed malaria elimination and eradication (Murray et al., 2012). Malaria is caused by the transmission of parasites to humans by female Anopheles mosquitoes during a blood meal. Plasmodium falciparum is known to be responsible for high rate of mortality, especially among children in sub-Saharan Africa, mostly under age 5 years (Breman, 2001; Greenwood et al., 2008; Hay et al., 2004; Rowe et al., 2006; Snow et al., 2005). Apart from the fact that many of the countries that are mostly affected are located in the tropical region of the world, increasing level of poverty, with its attendant economic consequences, coupled with lack of or improper sanitation and reduced access to prompt medication are factors that are creating enabling environment for the disease to thrive. Though preventive approaches such as the use of insecticide treated bed nets, IPTp and chemoprophylaxis with good sanitation (Curtis et al., 2006; WHO | Malaria in pregnancy, 2012), have been employed as strategy towards the eradication of this disease, the use of chemotherapeutic drugs remains the most widely used approach (Butler et al., 2010; DAlessandro, 2009). However, the success of this strategy has been hampered by the resilient of the parasite in continually creating resistance to the available drugs. The ability of P. falciparum to develop resistance to effective and affordable drugs (Cheeseman et al., 2012; Jambou et al., 2005; Mller Hyde, 2010; Phyo et al., 2012) and to pyrethroids, the active principle of the insecticides treated nets (ITNs) (Fane et al., 2012; NGuessan et al., 2007), has made constant search for new pharmacotherapy imperative. However, notwithstanding the centrality of chemoprophylaxis and chemotherapy in efforts at combating the menace of malaria infe ction (DAlessandro, 2009), and wide distribution of insecticide-impregnated bed nets, efforts aimed at enhancing long lasting protective immunity through vaccination, of which RTS,S is emerging as most promising vaccine formulation, have also been intensified (Ballou, 2009; Casares et al., 2010). 1.2.2 Life Cycle of Plasmodium falciparum Malaria parasite life cycle (Figure 1.1) is a complex mechanism involving two hosts, human and female Anopheles mosquitoes. The survival of the parasite during several stages of its development depends on its ability to invade and grow within multiple cell types and to evade host immune responses by using their specialized proteins (Florens et al., 2002; Greenwood et al., 2008). Sporozoites (infective stage), merozoites (erythrocytes invading stage), trophozoites (multiplying form in erythrocytes), and gametocytes (sexual stages) are stages involved in the development of the parasite. These stages are unique in shapes, structures and complementary proteins. The continuous changes in surface proteins and metabolic pathways during these stages help the parasites to survive the host immune response and create challenges for drugs and vaccines development (Florens et al., 2002). The sporogony or sexual phase occurs in mosquitoes, resulting in the development of numerous infective forms of the parasites which when ingested by human host induced disease. During a blood meal by female Anopheles mosquitoes from an individual infected with malaria, the male and female gametocytes of the parasite enter into the gut of the mosquito, adjust itself to the insect host environment and initiate the sporogonic cycle. The fusion of male and female gametes produced zygotes, which subsequently develop into actively moving ookinetes that pierced into the mosquito midgut wall to develop into oocysts. Each oocyst divides to produce numerous active haploid forms called sporozoites which are subsequently released into the mosquitos body cavity following the burst of the oocyst. The released sporozoites travel to and invade the mosquito salivary glands, from where they get injected into the human bloodstream during another blood meal, causing malaria infection (Barillas-Mury Kum ar, 2005; Ferguson Read, 2004; Hill, 2006). The parasite life cycle traverse two hosts (Man and Mosquito) with each stage involving complex cellular and molecular modifications. To prevent blood clots, Sporozoites infected saliva are deposited into Man during blood meal by female Anopheles mosquitoes, make their way to the liver, develop over time into hypnozoites (dormant stage, usually responsible for relapse of infection) or merozoites (that are released into blood stream to invade erythrocytes). The clinical symptoms of the disease are associated with the invasion of the erythrocytes by the parasite, its growth, division inside the host cell and the cyclic cell lysis and reinvasion of new erythrocytes. The schizogony or asexual phase of the life cycle occurs in human host. The cycle is initiated from the liver by the ingested sporozoites and later continues within the red blood cells, resulting in the clinical manifestations of the malaria disease. Following the introduction of invasive sporozoites into the skin after mosquito bite, they are either destroyed by macrophages, enter the lymphatics and drain into the lymph nodes from where they can develop into exoerythrocytic stages (Vaughan et al., 2008) and prime the T cells as a way of mounting protective immune response (Good Doolan, 2007) and/or blood vessel (Silvie et al., 2008b; Vaughan et al., 2008; Yamauchi et al., 2007), from where they made their way into the liver. While in the liver, sporozoites negotiate through the liver sinusoids, entered into hepatocytes, followed by multiplication and growth in parasitophorous vacuoles into schizonts, each of which contains thousands of merozoites, especially with P. falciparum (Ami no et al., 2006; Jones Good, 2006; Kebaier et al., 2009). Thrombospondin-related anonymous protein (TRAP) family and an actinmyosin motor has been show to help sporozoites in its continuous sequence of stick-and-slip motility (Baum et al., 2006; Mnter et al., 2009; Yamauchi et al., 2007) and that it growth and development within the liver cells is facilitated by the circumsporozoite protein of the parasite (Prudncio et al., 2006; Singh et al., 2007). This stick and slip motility prevent the parasite from been washed away by the circulating blood into kidney from where they can be destroyed and removed from the body. Motility is driven by an actin-myosin motor located underneath the plasma membrane. The sporozoite journey is propelled by a unique actin-myosin system, which allows extracellular migration, cell traversal and cell invasion (Kappe et al., 2004).This is a single cycle phase with no clinical symptoms, unlike the erythrocytic stage, which occurs repeatedly and characterize d with clinical manifestation. The hepatocytic merozoites are stored in vesicles called merosomes where they are protected from the phagocytotic action of Kupffer cells. The release of these merozoites into the blood stream via the lung capillaries initiates the blood stage of the infection (Silvie et al., 2008b). In some cases (as it can be found with P. vivax and P. ovale malaria) dormant sporozoites, called hypnozoites, are formed and remain in the liver for a long time. These hypnozoites are usually responsible for the development of relapse of clinical malaria infection and has been reported to be genotypically different from the infective sporozoites ingested after a mosquito bite (Cogswell, 1992; Collins, 2007). The development of the parasite within the red blood cells occur with precise cyclic accuracy with each repeated cycles producing hundreds of daughter cells that subsequently invades more red blood cells. The clinical symptoms of the disease are associated with the invasion of the erythrocytes by th e parasite, its growth, division inside the host cell and the cyclic cell lysis and reinvasion of new erythrocytes. The invasion of RBCs by the merozoites takes place within seconds and made possible by series of receptorligand interactions. The ability of the merozoites to quickly disappear from circulation into the RBCs protect its surface antigens from exposure to the host immune response (Cowman Crabb, 2006; Greenwood et al., 2008; Silvie et al., 2008b). Unlike P. Vivax, which invade the RBCs by binding to Duffy blood group, the more virulent P. falciparum possess varieties of Duffy binding-like (DBL) homologous proteins and the reticulocyte binding-like homologous proteins that allows it to recognize and bind effectively to different RBC receptors (Mayer et al., 2009; Weatherall et al., 2002). Micronemes, rhoptries, and dense granules are the specialized apical secretory organelles of the merozoite that help the merozoites to attach, invade, and establish itself in the red cel l. The successful formation of stable parasitehost cell junction is followed by entering into the cells through the erythrocyte bilayer. This entrance is made possible with the aid of the actinmyosin motor, proteins of the thrombospondin-related anonymous protein family (TRAP) and aldolase, leading to the creation of a parasitophorous vacuole, that isolate the intracellular ring parasite from the host-cell cytoplasm, thereby creating a conducive environment for its development (Bosch et al., 2007; Cowman Crabb, 2006; Haldar Mohandas, 2007). The intra-erythrocytic parasite is faced with the challenge of surviving in an environment devoid of standard biosynthetic pathways and intracellular organelles in the red cells. This challenge is overcome by the ability of the parasite to adjust its nutritional requirement to haemoglobin only, formation of a tubovesicular network, thereby expanding it surface area and by export of a range of remodeling and virulence factors into the red cell (Silvie et al., 2008b). Following the ingestion of the hemoglobin into the food vacuole, it is degraded to make available the amino acids for protein biosynthesis. Heme is a toxic free radical capable of destroying the parasite within the red blood cells. Heme polymerase is used by the parasite for the detoxification of heme and the resulting hemozoin is sequestrated as hemozoin. As the parasite grows and multiplies, new permeation pathways are created in the host cell membrane to help in the uptake of solutes from the extracellular medium, disp osal of metabolic wastes, and in initiating and sustaining electrochemical ion gradients, thereby preserving the osmotic stability of the infected red cells and thus, premature hemolysis (Kirk, 2001; Lew et al., 2003). 1.2.3 Control of Malaria infection Preventive measures are a critical step towards the control and eradication of malaria. Preventive approach can broadly be divided into two Infection control and Vector control. Infection control focuses on preventing the development of the disease as a result of occasional mosquito bite or relapse of previous infection (Lell et al., 2000; Walsh et al., 1999b). This involves the use of chemoprophylaxis. Travellers to malaria endemic countries are expected to start prophylaxis at least two weeks before and to continue up to two weeks after. One important target group in the infection control using chemoprophylaxis are the pregnant women. Intermittent preventive treatment for pregnant women (IPTp) is the globally acknowledge approach for prevention of malaria in pregnancy (Vallely et al., 2007; WHO | Malaria in pregnancy, 2012). Sulphadoxin-pyrimethamine (SP) has been used for this purpose and there are compelling arguments for the use of artesunate-SP (Jansen, 2011). To ensure long lasting prevention, this approach should be combined with vector control. Vector control focuses on protecting against mosquitoes bite, thereby preventing the transmission of the parasite to Man. Strategies for vector control include the use of residual spraying of insecticides, insect repellent cream or spray, sleeping under bed nets, especially, the insecticide impregnated bed nets (ITNs) and proper sanitation (Curtis et al., 2006; Lavialle-Defaix et al., 2011; WHO | Insecticide-treated materials,). WHO provides guideline for the production, preparation, distribution and the use of the ITNs (WHO | Insecticide-treated materials,). With the reported resistance to pyrathroids, an active principle of the insecticides treated bed nets (Fane et al., 2012; NGuessan et al., 2007), all strategies involving the use of chemical agents, also faces the global challenge of developing resistance. Training in proper sanitation and its sustainability from generation to generation is most probably the best approach in controlling the malaria disease. Personal and general hygiene which involve in-door and out-door cleaning, good refuse disposal practices, eradication of stagnant water, proper sewage disposal and clean, dry and uninterrupted drainages are examples of good sanitation practices that will not only prevent malaria infection, but also other killer diseases of the tropics. Sanitation is not only cheap and affordable; it is within the reach of everybody. 1.2.3.2 Malaria Chemotherapy Despite the use of preventive approaches outlined above (Curtis et al., 2006; WHO | Malaria in pregnancy, 2012), as strategy towards the eradication of this malaria, the use of chemotherapeutic drugs remains the most widely used approach (Butler et al., 2010; DAlessandro, 2009). They are widely employed as prophylaxis, suppressive and curative. However, the success of this strategy has been hampered by the resilient of the parasite in continually creating resistance to the available drugs. The ability of P. falciparum to develop resistance to effective and affordable drugs (Cheeseman et al., 2012; Jambou et al., 2005; Mller Hyde, 2010; Phyo et al., 2012) and to pyrethroids, the active principle of the insecticides treated nets (ITNs) (Fane et al., 2012; NGuessan et al., 2007), has made constant search for new pharmacotherapy imperative. Various approaches have been employed to identify new antimalaria agents with a view to reducing cost, ensuring availability and reducing the incidences of resistance (Rosenthal, 2003). Chemical modification of the existing antimalarial is a simple approach and required no extensive knowledge of the mechanism of drug action and the biology of the infection. Many drugs in use today have been produced using this approach, including chloroquine, primaquine and mefloquine from quinine (Stocks et al., 2001), 8-aminoquinoline, tafenoquine, from primaquine (Walsh et al., 1999a) and lumefantrine from halofantrine (van Vugt et al., 2000). Another approach is the use of plant derived compound with little or no chemical modification has led to the discovery of potent antimalarial such as artemisinins (Meshnick, 2001). Also, the use of other agents not originally designed for malaria such as folate antagonists, tetracyclines and antibiotics that were reported to be active against malaria parasit es (Clough Wilson, 2001) is another viable approach to drug discovery. Resistance reversals such verapamil, desipramine and trifluoperazine (van Schalkwyk et al., 2001) have also been used in combination with antimalaria drugs to improve therapy. Optimization of therapy with existing antimalaria agents is widely used as a productive approach towards improving therapy. Optimization of therapy underscore the need for combination therapy with newer and older drugs and with agents that are not original designed as antimalaria but which can potentiate the antimalaria property and/or block resistance to antimalaria agents. Thus for the combination to be ideal, it should improve antimalarial efficacy, providing additive or synergistic antiparasitic activity and slow the progression of parasite resistance to the antimalaria agents. For example, combination of artesunate with sulfadoxine/pyrimethamine (von Seidlein et al., 2000) or with amodiaquine (Adjuik et al., 2002), if devoid of underlying resistance to the artesunate partners which can lead to high rates recrudescence (Dorsey et al., 2002), may prove to be optimal antimalarial agents. Other combinations that have been effectively used include artesunate and mefloquine (Price et al., 1997) and artemether and lumefantrine (Lefevre et al., 2001). The combination of analog of proguanil (chlorproguanil) with dihydropteroate synthase (DHPS) inhibitor (dapsone), originally produced to treat leprosy (Mutabingwa et al., 2001) has open up a new and effective approach in antimalaria drug therapy. The use of dapsone and other drug resistance reversers such as verapamil, desipramine, trifluoperazine (van Schalkwyk et al., 2001) and Chlorpheniramine (Sowunmi et al., 1997) has shown potential for reducing the rate of drug resistance. Table 1.1: Classes and Mechanism of Antimalarial drugs CLASSES OF DRUGS Gametocidal Tafenoquine Gamatocidal Gametocidal biguanides (proguanil, cycloguanil), Trimethoprim CLASSES OF DRUGS Clindamycin, Spiramycin m ubiquinol to cytochrome C (Vaidya, 2001). Meanwhile, one important and innovative approach towards drug discovery in malaria chemotherapy is the search for new antimalaria drug target. Such targets include parasite membrane (Vial Calas, 2001), food vacuole (Banerjee et al., 2002), mitochondrial and apicoplast (Ralph et al., 2001; Vaidya, 2001). The cytosol, which is the centre of metabolic activities (e.g. folate metabolism and glycolysis) and enzymes activities have proven to be valuable as potential target for drug action (Plowe, 2001; Razakantoanina et al., 2000). To survive and develop within the erythrocytes, Plasmodium falciparum export most of its virulent factors into the cytosol of the infected erythrocytes. Among these are the molecular chaperones of the heat shock proteins which are focus of many researches and are increasingly gaining ground as potential target of drug action (Behr et al., 1992; Kumar et al., 1990). 1.2.3.3 Malaria Vaccines Notwithstanding the centrality of chemoprophylaxis and chemotherapy in efforts at combating the menace of malaria infection (DAlessandro, 2009), and wide distribution of insecticide-impregnated bed nets, efforts aimed at enhancing long lasting protective immunity through vaccination, of which RTS,S is emerging as most promising vaccine formulation, has been intensified (Ballou, 2009; Casares et al., 2010). These attempts at producing an effective vaccine against malaria infection has, however, for many years proved unsuccessful (Andr, 2003; Artavanis-Tsakonas et al., 2003). Having a vaccine that can completely block transmission from human to mosquito host can be a major limp towards global eradication of malaria. But, the absences of such immunity may explain the possible partnership between the parasite and the host, developed over a long time of co-habitation (Evans Wellems, 2002). On the other hand, a vaccine developed in line with the model of naturally acquired immunity that o ffers protections against morbidity and mortality, offers more encouragement. Such a vaccine will be a major step in the right direction and may not require regular booster vaccination like it would with vaccine that target infection transmission blockage (Struik Riley, 2004). Meanwhile, the development of natural immunity, after a long term exposure to the infection, especially with people living in the endemic areas has been reported (Baird, 1995; Hoffman et al., 1987; Rogier et al., 1996). The rate of acquired immunity in infants is faster than older children, but they also stand the chance of higher risk of developing severe malaria infection and anaemia (Aponte et al., 2007). Though, adults who, having obtained naturally acquired immunity, migrated to malaria-free zones, stands the risk of contacting the diseases upon return to their endemic region, documentary evidences however revealed that their responses to such re-infection are very rapid and tend to respond to treatment and recover faster than those who have not been previously xposed. (Di Perri G et al., 1994; Jelinek et al., 2002; Lepers et al., 1988). While this naturally acquired immunity is beneficial, it leaves the most vulnerable population (children and pregnant women though the mother may be immune, the foetus is not) at risk, as they are yet to gain enough exposure for such immunity to take place. Aponte et al., (2007) also showed that a reduced exposure toP. falciparumantigens through chemoprophylaxis early in life have the potential to delay immunity acquisition. Furthermore, it does not appear that naturally acquired immunity have any effect on transmission of malaria. This further explained the possibility of an evolving host-parasite relationship (Evans Wellems, 2002), which might have been developed over a long time host-parasite co-evolution. Therefore, understanding the compromises that may have developed over time between the parasite and the host may be an important approach towards developing a much needed vaccine. 1.3 Molecular and Cellular Basis of Malaria Infection Following blood meal by an Anopheles female mosquito accompany with the release of saliva to prevent blood coagulation (Beier, 1998), malaria parasites are deposited or ejection of into the skin (Frischknecht et al., 2004; Vanderberg Frevert, 2004). By continuous gliding in the skin, the sporozoite reach a blood vessel, breach the endothelial barrier and enter the blood circulation (Amino et al., 2007; Vanderberg Frevert, 2004) and/or breach a lymphatic vessel to enter the draining lymph node, where exoerythrocytic stages of sporozoites development may take place (Amino et al., 2006). A micronemal protein, called thrombospondin-related anonymous protein (TRAP), has been shown to be responsible for the gliding motility and invasion mosquito vector salivary gland and in mammalian host (Kappe et al., 1999). The sporozoite transversal to the liver and the merozoites invasion and remodeling of the host cells are complex but necessary processes for the survival and development of the par asite. 1.3.1 Cell Transversal Sporozoite possesses the ability to transverse cells i.e move in and out of the host cells by membrane disruption (Mota et al., 2002, 2001; Vanderberg Stewart, 1990). Among the proteins secreted by the micronemes that have been implicated in host cell traversal are SPECT1 (sporozoite microneme proteinessential forcelltraversal 1) and SPECT2 (Ishino et al., 2005, 2004). The absence of SPECT1orSPECT2in mutant sporozoite does not prevent gliding motility but prevent migration through host cells (Ishino et al., 2004).Other proteins of importance to sporozoite cell traversal prior to hepatocyte infection, includes TRAP-Like Protein (Moreira et al., 2008), a sporozoite secreted phospholipase (Bhanot et al., 2005), and celltraversal protein forookinete andsporozoite (Kariu et al., 2006). Similarly, the circumsporozoite protein (CSP) probably plays a role in targeting sporozoites to hepatocytes by interacting with heparin sulfate proteoglycans (Sinnis Sim, 1997). 1.3.2 Liver stage development Upon entering the bloodstream, infectious sporozoite makes it way to the liver. Circumsporozoite protein (CSP) is highly expressed at this stage of the parasite life cycle. Using the sporozoites that expresses fluorescent proteins under the control of CSP and intravital imaging, Frevert and colleagues were able to show the movement of sporozoites in the liver (Frevert et al., 2005). The study showed that sporozoite migrates through several hepatocytes before finally settling in one, form PV and begin the liver stage development. CSP, mediated by low-density lipoprotein receptor-related protein LRP-1, and other highly expressed proteins by Kupffer cells, play an important role in inhibiting the generation of reactive oxygen species via the generation of cyclic AMP (cAMP) which stimulates adenyl cyclase activity (Usynin et al., 2007). Ishino and co-workers reported that two parasite molecules P36 and P52/P36p are involved in sporozoite invasion of hepatocytes with the formation of a PV membrane (PVM) (Ishino et al., 2005). Apart from CSP, other gene product that has been implicated in liver stage development of the parasite includes sporozoite low complexity asparagine-rich protein (SAP1) (Aly et al., 2008) and sporozoite and liver stage asparagine-rich protein (SLARP) (Silvie et al., 2008a) 1.3.3 Erythrocyte Invasion Erythrocyte invasion involves four steps, namely, initial merozoites binding, reorientation and erythrocyte deformation, specific interaction and junction formation and parasite entry (Figure 1.2). Merozoite surface protein-1 (MSP-1) is a well characterized merozoite surface proteins implicated in initial merozoite binding. It has been reported to be uniformly distributed over the merozo

Geotechnical Structure For Basement Car Park

Geotechnical Structure For Basement Car Park Abstract The aim of this design/investigate project is to design a geotechnical structure for a basement car park. The objective of the project is to maximize the parking area available by designing a permanent retaining structure for a basement car park during construction excavation. The various types of retaining structure will be compared and considered first by logical and engineering point of view which includes several aspect includes durability, cost, sustainability and environmental impact. For design purposes, BS EN 1997 -1 :2004 Eurocode 7 is used to design the main retaining structure and temporary works necessary. The design considered Ultimate Limit State of a structure which takes structure stability into accounts. Chapter 1 Introduction Brief Introduction A hotel chain wishes to use land previously serving as a car park for a new accommodation block. Car parking space to service this is to be constructed beneath the new structure. Therefore, a geotechnical retaining structure needed to be design to support the soil during construction and after construction. A plan view and elevation view of the site is given and also list of requirement for this project are given too. Project Design Design of the main retaining walls Design of any temporary work necessary Detail of the Project Site This is an urban Brown Field site. The previous use was known to be low rise domestic structures followed by conversion to a car parking space. The site is flanked on three sides by public highway and a desk study reveals services as indicated in (Figure 1.1) Site Plan. Extensive site investigation has been undertaken in the past. The interpreted geological profile is indicated in Figure 1 too. The interpreted geotechnical design parameters are summarized in Table 1.1. General Arrangement The proposed scheme is shown in plan and sectional elevation in Figure 1. The new extension is to be developed on the existing car parking area and includes an extended basement as indicated. Construction Restraint One of the key constraints concerns the noise and vibration limits imposed. The project requirement is to keep the existing hotel buildings around the proposed structure in full operation throughout the construction period. The limits proposed by the local authority are given in Table 1.2 below. It is also clear that the basement excavation will affect the rafted foundation to the original hotel wing. To ensure that the serviceability of this structure is assured it has been deemed necessary to limit the lateral deflections of the new basement walls at 20 mm into the excavation. The construction site is very close to a public sewer which runs in the highway footpath near one site boundary. Therefore, this aspect had been considered in the final decision for choosing types of retaining structure. Construction Time Rates And Costs As in many construction projects the speed of construction influences overall cost. In this case it is essential that the new hotel is operational in the minimum possible of time. Notional construction costs and time rates are indicated in Table 3. These figures have been given for the purposes of the project. The overhead rate for possession of the site, fixed costs for establishment and use of site area are shown in the Table 3 too. The construction sequences is to be assumed that activities above and below ground can be run in parallel but above and below ground activities are sequential. Chapter 2 Site/Soil Profile 2.1 Soil Description and Classification To understand the soil profile and the behavior of every single type of soil is an important step for a geotechnical engineer before starting any design works. In general, soil is kind of mineral particles formed by the weathering of rocks which weakly cemented or uncemented [1]. The void space between the particles contain water and/or air [1]. Weak cementation are due to carbonates or oxides precipitated between the particles or due to organic matter [1]. There is several type of soil. Every type of soil is classified in different categories by their particle size. The three main type of soil are Sands/Gravel, Silts, and Clays. Particle sizes in soils can vary from over 100mm to less than 0.001mm. The particle size distribution of a coarse-grained soil is to be determined by the method of sieving [1]. The typical size of soil ranges is shown in Figure 2.1 below.figure 2.1.jpg Basically, the terms clay , silt , sand or gravel are used to differ the sizes of soil and type of soils. Two or more size usually consists in a graded mixture of particles [1]. For example, it is not necessarily all clay size particles are clay mineral particles because clay normally consist of particles in both the clay size and silt size ranges where clay is type of soil possessing cohesion and plasticity [1]. In general, a cohesive soil is said that if the particles adhere after wetting and subsequent drying and if significant force is then required to crumble the soil [1]. 2.2 Borehole Data A set of borehole data (Figure 2.4) is given for design purposes.Figure 2.4.jpg From the borehole data given shows that water table on the site is 1m below the ground level. From top level to 3m below is a kind of coarse gravel. It is then followed by soft to firm grey brown slightly sandy clay (alluvium) and mixture of soft brown very silty clay down to 6m below ground level. From 6m below ground level to 7.5m, the soil is covered by loose brown clayey silt. It is then followed by loose to medium dense red brown silty clayey sand with a 4.5m depth. From 12m to 16m below ground level the soil is covered by large amount of gravel. A simplify table of soil in the site is shown in table 2.1 below for better and clearler understanding. Borehole Data Depth 0 0.2 Tarmacadam surfacing ( MADE GROUND) 0.2 3.0 Dark grey angular to sub-rounded coarse gravel with ash, concrete and rubble fragments (FILL) 3.0 6.0 Soft to firm grey brown slightly sandy CLAY with some organic matter (alluvium) Very soft to soft brown very silty CLAY 6.0 7.50 Loose brown clayey SILT (alluvium) 7.50 12.0 Loose to medium dense red-brown silty clayey SAND with occasional sub-angular fine to medium gravel of sandstone (alluvium) 12.0 16.0 Loose to medium dense, becoming dense red grey silty very sandy, sub rounded GRAVEL (alluvium) 16.0 22.95 Weathered MARL Reddy brown and grey green weathered (iii iv) weak MUDSTONE Chapter 3 Types of Retaining Structure There are several factors that influence the difficulty of basement design and construction. These factors normally are existing problems on the site and cannot be easily changed. Engineers somehow need to go for different option when designing structure to overcome the constraints. For example, the location of the proposed structure, proposed use of the structure, groundwater, the site surrounding existing structure and services. The type of basement wall will be then selected to support soils and groundwater of the basement and also to design as economically as possible. The walling or sheeting selected for this project is to provide temporary soil support for permanent substructure construction, or it may also serve as soil retention. The walling or sheeting will be selected after comparison in terms of cost and time, constructability and etc. Several methods include the following. Plate and anchor wall King post wall Contigous bored piling Secant piling Steel sheet piling Diaphragm walls Reinforced concrete cast in situ Reinforced concrete precast Post-tensioned Soldier piling 3.1 Brief Introduction for each Options i) Plate and Anchor Wall by underpining The total excavation depth of basement work is typically fall in the range 8 to 12m and also the ground conditions are dry and able to support 1.5 2m face deep[2]. The anchored plate method is an economical temporary wall support. Pre-grouting is to be used in granular soils where the soils were unable to stand unsupported to this modest depth [2]. Figure 4.2.jpg ii ) King Post Wall King Post method is usually popular for two following factor which is cheapness of materials by using timber and economy method of boring by using power augers. This method require boring holes on wall line at 2 3m centre depending on soil strength, depth of excavation and surcharges loads. The hole is then placed with vertical beam and to be concreted with lean mix concrete at the base of each joist below final formation level [2]. King post wall usually used as a temporary soil support and to be used in dry or dewatered soils. Vertical settlements of wall is one of the disadvantages where failure of vertical force transferring to the base of pile. iii ) Contigous Bored Pile Wall Bored pile wall is usually used as an economic and efficient method for retaining structure. This techniques is very suitable for deep basements excavation and underground structure where working space is limited. This method prevent large amount of soil excavation and also help to control ground movements. Piles are usually drills into ground by using continuous flight auger (CFA) with a certain gap distance between piles. A maximum length of piles is usually around 20m depending on ground condition. Contiguous bored pile wall is not suitable for site with high water level due to the gaps between piles. Advantages of contiguous pile walls are : Comparative low cost and speed of construction Low level of sound pollution ( low level of vibration) Pile can be drill in limited spaces Has the ability to minimize the distance between bored pile wall and existing wall for small excavation depthcontiguous bored pile wall.jpg iv ) Secant Piles Disadvantages of contiguous bored pile are overcome by using secant piles where interlocking method is introduced. Secant pile walls are constructed by concreting primary (female) piles first then secondary (piles) are bored through female piles before concrete reach full strength [2]. By this the piles forms overlapping between each other. Advantages : a)Can be installed in hard ground (cobbles /boulders) b)Low noise pollution c) Better wall stiffness compare to sheet piles secant-pilingBig.jpg v ) Sheet Pile Wall Sheet Pile wall are made up from a group of piles that interlock each other and is driven into the soil. Most sheet pile wall nowadays is using steel sheet which fabricated in factory. The use of sheet pile for temporary soil support for basement at urban area is not that popular where noise is the main constraint. Sheet pile may be installed using hydraulic can reduce the noise pollution. Sheet pile wall can be design as cantilever wall or anchored wall depends on the basement depth and soil condition that vary. Advantages : a) High resistance to driving stresses. b) Sheet can be reuse c) Easy to install Disadvantages : a) Sheet pile can hardly be use as permanent structure. b) Installation of piles are hard where soil contain boulders and cobblers c) Noise pollution (High vibration) vi ) Diaphragm walls Diaphragm walls are reinforced concrete wall constructed in slurry supported by machine digging a trench in panels of certain length. This slurry can be bentonite slurry where has thixotropic properties [8]. The wall is first constructed in short panels length, by installing reinforced cages and concreting, then later intermediate panels are excavated to complete the whole wall. There is 3 type of diaphragm walls in use in industry, which is cast in-situ diaphragm wall, precast reinforced diaphragm wall and post-tensioned diaphragm wall. Advantages : a) Allow effective transfer of vertical load from the building to subsoil b) Minimum noise and vibration disturbance c) Allow construction on limited site area. 3.2 Comparison of each option A table (table 3.2) of matrix below is to compare the advantages and disadvantages of several retaining structure. This comparison results will shows the most suitable retaining wall to design and construct for this project. Durability Durability is not usually a problem for a temporary wall depending on the soil condition. But when wall is to be design as a permanent structure, the wall should satisfy the durability requirement where wall should reach design life. For example, durability requirement for concrete wall depends on the design life, cement content, water cement ratio, cover of reinforcement and also quality of workmanship. Rigidity Rigidity means a structure property that does not bend under an applied force in vertical or horizontal load [10]. Different type of retaining walls could sustain different loading. Some walls are good in resisting vertical loading and does not bend but some walls can only sustain horizontal force. For example, reinforced diaphragm wall is much more rigid than a sheet pile wall. Reinforced concrete diaphragm wall can be design as a permanent structure that carry load from superstructure above and does not bend in any way. Comparing 6 types of retaining structure above, Diaphragm walls, contiguous pile wall and secant pile walls are three best on rigidity. Constructability on Site Constructability of a structure means a structure to be constructed on site easily from start to finish by fulfilling clients requirement. Constructability also means ease of construction. A constructability review must be done before starting any construction process to prevent error, construction delay or cost overrun [11]. The space to construct the proposed structure is limited. Figure 1.1 shows that a existing sewer pipe line is 1m beside the proposed structure on the right and also a existing structure 2m far from the proposed building on the left. One of the project requirement is to minimize the sound of construction in urban area. Choice of excavation is limited to prevent any damage to the existing properties. Trench excavation is ideal for this project. Therefore, constructing diaphragm wall is the best solution where diaphragm wall can be constructed in limited space by using trench excavation, low noise produce and machinery is not big. Soil Condition The soil profile is needed to take into consideration when designing retaining structure. Some structures construction is hardly to process when the soil contains cobbles or boulders. Most of the structure is suitable to be constructs on this project site because of the clayey soil from ground level to a minimum depth of 12m. Only when initial design for retaining structure with required depth over 12m into gravel layer, retaining structure like diaphragm wall is not that suitable due to the stability of wall. Water Table Ground water on site are mainly from rainfall or groundwater flow through soil from rivers and seas [2]. By reducing the groundwater within the excavation depth and structure depth by dewatering process will increase the strength of soil as the pore water pressure is reduced. Groundwater control is crucial to prevent any leakage of water into the basement car park or cause instability of structure, for example, ground heave. Retaining wall usually acts as a groundwater cut off. Several alternative ways of groundwater cut-off are: To lower the groundwater by temporary dewatering process where ground movement is to be considered. Temporary sump pumping is to be done is ground is sufficiently impermeable Excavation is to be done under water and so permanent wall is to be construct under water by tremie concreting techniques. Diaphragm wall serves as a good water barrier compare to sheet pile or secant piles where sheet pile might corrode and water will flow through the gap between secant pile. Depth of wall Designer needs to consider the depth of a retaining structure can be construct. Some structure is cheaper to be built in deeper depth compare to shallow depth. Table 3.1 shows the different type of retaining structure that can be construct up to the maximum height of wall in order for the structure to stay stable and safe. Storage of Materials Proper storage of raw materials is very important for a construction. Raw materials like reinforcement cages, cement, sand, and etc. needed to be on site on time to prevent any delay of construction. For example, steel sheet and reinforcement cages both are made in large size and needed large space to store up. Therefore, it is worth to consider this problem when choosing a retaining structure. Environmental Impact Environmental impact is one designer to be consider when structure is construct in urban area. The choice of wall can affect the environmental during construction, during in use and demolition [12]. Three main causes to environmental impacts:- During Installation Noise and vibration when boring pile. (sheet piling) Number of vehicle used. Use of sustainable materials (Guidewall construction for diaphragm wall) When used Effects on groundwater around the wall. End of life Ease of removal Ability of material to be reused 3.3 Final Decision Diaphragm wall is to be used for my design project. FUCK WHAT TO WRITE o0o Chapter 4 Diaphragm Wall 4.1 Preplanning and Design For designing purposes and construction of diaphragm walls, a number of item require to be considered in preplanning and design of diaphragm wall. Excavation Sequence The sequence of excavation from ground level to the basement walls is to be well planned to minimize rig movement and to avoid changing places and moving of pipework from panel to panel of panel excavation. Soil dump truck, slurry removal vehicle, cranes and concrete mixing trucks, and to allow curing of concrete in completed panels are all parts of construction and excavation sequence that needed to be well planned. Guide Trench Construction The successful of trench excavation for diaphragm wall depends on the temporary guide wall. The guide walls must be design and construct to be robust to avoid any movement due to extreme loads from excavation rig service cranes or placement of reinforcement cages and reaction from stop end jacking systems. In some construction, reuseable precast concrete guide wall had been used and be interlocked each other by bolted to ensure the same standard of rigidity as in-situ cast concrete wall [2]. Panel Size Diaphragm wall is to be constructed by a panel trench excavation first. The panel length typically will vary from a minimum of one grab bite (trench excavation machine grab width) to a multiple of grab bites which will extend to 7m. A grab bites vary between 2.3 and 2.8m depending on machine used. The panel length include two stop ends for the primary panels (Stop ends will be discussed on following pages). Secondary panels are those panels dug between two concreted panels. The panel length is limited to a certain length, and therefore panel volume, this is to ensure that sufficient concrete can be fill up the whole panel within concreting period in a day. This takes maximum daily working hours and concrete supply into account. Panel size more depends on designer and contractor decision. Wall-Slab Construction Joints Joints between basement floors slabs and wall is to be design carefully because the joints can transmit vertical shear and bending moment which could cause instability of structure and basement. Bend out bars and Threaded-end couplers are both used in the joints. Reinforcement cage The depth of diaphragm wall has led to the size of reinforcement cages. These cages are usually fix off-site and delivered to site when is needed. The maximum length of cages is restricted because of transportation of long and large cages. Slot for Tremie Tubes A tremie tube is used to ensure concrete is placed in correct position and that no separation of aggregate occurs during concreting pouring concrete from top to bottom of walls. Therefore, reinforcement cage is to be designed to allow sufficient access for tremie tubes. For some construction of diaphragm with large panels, two tremie is to be used to maintain the concreting rate of 60 to 80m3 per hour. 4.2 Construction Sequence End Of Construction Site Clearing Top Down Basement Construction Diaphragm Wall Construction Site Preparation 4.3 Work to be Done 4.3.1 Site Preparation Basement and retaining wall construction methods involve a high degree of mechanization. A clear working space give maximum mobility for machinery, materials and workers, hence optimize the working speeds increasing construction period. Therefore, several steps are needed to be done before any construction work progress. For example, temporary road should be provided to achieve a rapid tempo of construction in wet or dry weather. Traffic Management Local authorities are highly concern on the traffic management especially in urban area. Construction in central of urban area could cause serious traffic congestion due to slow moving construction vehicles and parts of road are occupied by machinery. A slightly highway direction will be changed on A marked in figure 4.2 below to provide access for construction vehicle into the site. On road marked A in figure 4.2, the road is to be assumed that is a typical single lane carriageway. Therefore, the road length will be slightly reduced nearby the construction site. An alternative road for vehicle towards junction is to be proposed to local authorities to prevent any traffic congestion. Clear barricades and road sign will be provided along the road closure. Location of Underground Services Site preparation in urban area includes tracing and clear marking of existing services includes underground telephone, power cables, water and sewer pipe, gas pipe, etc. Underground services is to be assumed to present in any circumstances. Trench excavation is more likely to encounter underground service in the face of excavation parallel to the line of excavation [13]. Many serious accidents have been caused by men or machines when underground services are struck, penetrated or during excavation. Electric shock may result from striking electricity cables during excavation. On this project, it is clearly shown on figure 1.1 that a 1200mm diameter concrete sewer pipeline is just 1m away from the side of proposed structure. A sewer pipeline bursting could cause contamination of the ground and odour smell to nearby citizens. Many sewer pipes are under high pressure too. As a solution, first, a confirmation of sewer pipe location is to be done on site. Once the records are obtained, it will be kept on site and be accessible to workers. Furthermore, construction of diaphragm wall uses trench excavation techniques, which highly reduce the chance of striking the sewer pipe. Any other services includes telecommunication cables, gas pipe and electric pipe which are not shown in figure 1.1 given will be examine on site before excavation. Existing Building Building located around the site are needed to be protected from damage and dirt-staining. Cleaning and maintaining existing building in the end of construction can be costly. In figure 1.1 shows that there is existing 3 storey with raft foundation building 2m away from basement wall. Before any excavation start, careful inspection is to be done to the existing building to determine whether there are any existing cracks due to settlement or any damage on external wall of building. Cracks and damage is to be recorded down and photographed as a proof to prevent any claims from property owner. Overhead Obstruction The most common overhead obstruction is high tension electricity cables nearby the site. Most construction vehicle are high. There is a danger when tall vehicle pass by those overhead cables and cause unwanted accident. Therefore, a clearance is to be done between the overhead cables and ground. For example, a typical goal post protection will be erect along the entry to the site. Figure 4.3 below shows typical goal post protection. figure 4.3.jpg Public Safety It is important to taking care about public safety. Any pedestrian is not allowed to enter construction site. A warning sign is to be displayed around the boundary site and barriers is to be set up along perimeter of construction. 4.3.2 Diaphragm Wall Construction Construction of diaphragm wall uses trench excavation supported by slurry. The slurry is typically bentonite and water. Diaphragm walls are constructed in the following steps : 1) Pretrenching to remove obstruction 2) Guidewall construction 3) Trench excavation (panel excavation) 4) Endstop placement 5) Panel desanding 6) Reinforcement cages placement 7) Concreting work (Tremie technique) 8) End Stop removal 9) Excavation of Intermediate Panel 10) Reinforcement cages placement 11) Concreting work for remaining panels (Tremie technique) 12) End of Diaphragm wall construction 4.3.2.1Detail steps Pretrenching to remove obstruction Pretrenching is a process to remove soil by open excavation to a certain depth, typically 1-2 m depth for guidewall construction. It is also a purpose for removing shallow obstruction and provide stable support for the guidewall. GuideWall Construction Guide wall is to be constructed after pre-trenching process. There are several purpose of constructing guidewall, these include: To prevent the collapsing of soil near trench excavation surface. As a template for wall excavation and panel layout To provide a temporary supports for reinforcement cage. (by holding down the cage during concreting work) To provide support for end-stop joint. (restrain end-stop) To support Tremie Pipe To provide a reference elevation for inserting props, slabs, etc. For this project, the guidewall is to be constructed with reinforce concrete and be made from grade M20 grade reinforced concrete. The distance between both guidewall will be thickness of diaphragm wall plus a tolerance of 50mm. The dimension of guidewall (one side) will be 300mm(w) x 1000mm(d). Trench Excavation (Panel excavation) Construction of diaphragm wall uses trench excavation method which produce a vertical strip in soil that can collapse easily. Special excavation machinery are used to excavate the soil. Several type of machinery is used in construction field nowadays. These machinery can be cable hug or Kelly mounted and the digging mechanics can be cable or hydraulic operated. figure 4.7 2.pdf The excavation is to be excavated in panels. The panel length varies typically from a minimum of one grab bite (trench excavation machine grab width) to a multiple of grab bites which will extend to 7m. A grab bites vary between 2.3 and 3m depending on machine used. figure 4.8.jpg The trench excavated is to be supported by bentonite slurry. Bentonite is basically clay of montmorillonite group, and when added with water it forms an impervious slurry with large viscosity. The slurry will produce large lateral pressure to retain the vertical soil. In case of granular soils, the bentonite slurry will penetrates into the sides under positive pressure and forms jelly. When bentonite slurry is fills in impervious clay, it will not penetrate into the soil but form a layer of thin film to gives strength supporting vertical soils. The bentonite slurry is to be placed continuously into the trench throughout excavation. For this project, Kelly Grab is to be used for excavation. The depth and width of excavation will be discussed in following chapters. The panel length and bentonite slurry density is to be designed and results will be shown in following chapter too. End stop Placement Endstops are placed in both panel fronts to provide the concrete at each vertical edge of panels with a predetermined shape. The shape of stop ends can be a pipe or special keyway end stops. End stop can be place in to be permanent or temporary. For this project, a temporary cylinder end stop is to be used. The end stops will be removed by vertical extraction shortly after the concrete has been poured. Somehow, a delay of few hours is allowed in order to enable the concrete to gain some early strength and able to stay vertical. The timing and removal of end stops will be judge by the site contractor and to be carefully observed. If end stops is extract out before the concrete is stable (gained sufficient strength to stay vertical), there is a risk that the concrete will slump.

Anna Karenina Booknotes :: essays research papers

Count Lev Nikolayevich Tolstoy ranks as one of the world's great writers. He was also an important moral thinker and reformer. Tolstoy was born at Yasnaya Polyana, Russia, the fourth of five children. After being educated at Kazan in 1844, he joined the army in 1852. He fought proudly in the Crimean War, and after he left the army, he traveled abroad. He inspected German schools to insure their quality before going to his brother's side outside of Marseille, France. Nicolai died at a spa with his brother at his side. This death affected Tolstoy so deeply that his writing was the only thing that kept him afloat. Upon his return, Tolstoy settled on his Volga estate, where he wrote his epic masterpiece War and Peace - the story of five families during Napoleon's invasion of Russia. His next novel, Anna Karenina, written in the romantic period, is one of the great love stories of the world. He married Sofya Andreyevna Bers, a.k.a. Sonya, and had nine children. Tolstoy then experienced a spiritual crisis which led to such works as A Confession and What I Believe. Some of his similar, earlier struggles were recorded in Anna Karenina, which he had previously published. Tolstoy converted to his religion, Tolstoyism. This faith said that "only through emotional and religious commitment can one discover this natural truth". His family disapproved of this and made life around the Tolstoy house unbearable for almost everyone. In his last days, he transferred his fortune to his wife and lived poorly as a peasant under her roof. Leaving home secretly, Lev Nikolayevich Tolstoy died of pneumonia some days later at nearby railway station. Anna is portrayed as a beautiful, mysterious woman who encompasses the quest for personal discovery. She is content in her life, but sees something that she wants more. This love, the love for Vronsky, drives her to unimaginable heights to keep her life and mental state at a safe level. As a woman, Anna suffers great injustices for her actions. These unfair laws of society drive her to her grave. Levin is representative of Tolstoy's life. He is a respected, educated, and well off landowner in the aristocracy. His quest for self-discovery leads him out into the fields with his workers, thrashing grass with the rest of them. He also lusts after Kitty, and finally attains her love when she realizes what a good and true man he is.

Battle of the Sexes :: essays papers

Battle of the Sexes Had the daughters and wives of the countryside played a part in the committees in Tunnel Six and elsewhere? Was it common for a woman to bring a dispute before the assembly? What did the fact of the conflict’s setting a pair of women against each other say about solidarity and division by gender in the countryside? Could a woman ever be a rondero? In 1977, a woman’s committee was organized in Cuyumalca by Omelia Lopez. Omelia was soon to be the first president of the women’s committee. The question is why did it take this long for women to be heard? At the time women’s complaints of domestic violence and village thefts were almost completely dismissed and ignored by Peru’s national authorities. Also many women chose not to get involved. They strongly were believers that men were the ones in charge and the woman belonged in the home. Women were to believe that they were tied by nature to the pettiness of jealousy and scandal, less able than men to see what was best for the family and village. From what they were taught, it was just not possible, until Omelia. Omelia did have some help from Daniel Idrogo, an organizer from the Communist Party of Peru-Red Homeland. Daniel is a strong believer in Maoism. The Chinese leader had often repeated that â€Å"without the participation of women there can be no victory against imperialism†. Daniel said. â€Å"The rondas would be stronger if everybody participated†. So what were their goals? The main task was to accompany and support their men. The women’s committee was only an appendage of the ronda committee, which was run by men. So even if the women weren’t as high as the men’s status, they were still doing something about and being heard for once. The chief duty was to enforce the male obligation to take a turn on the nightwatch. Women were necessary in the making the rondas an instrument of peasant power and revolution. With each organization came problems. For instance, Lack of female solidarity. Rumors flowed, like women committees were â€Å"an excuse for lazy senoras to get together to gossip†. The larger problem was a backlash against the new activism. Which is stated that a husband controlled a wife, who was not to take a step without the boss’s permission. A final factor was outside opposition given by other newspapers.

The power of social media in political communication

Research Question To determine the impact of social media on the way that political institutions and organizations communicate to the public including the unintended impact of social media on political communication. Research Objective The track the evolution of social media use in political communication both as intended by those disseminating the information and the unintended impact of having such assessable communication methods for the general public. Significance and Context of Research Increasingly in political communication, social media has been used as a primary method of disseminating information, gathering information and testing public opinion. Indeed certain countries continue to use these methods as a primary means of lobbying support. However, not only does it present enormous benefit to political organizations, it also presents a unique opportunity to the public combating abuse of power and an increased awareness and accountability. Some research even goes as far as to suggest that the impact of social media has enhanced the citizen participation in democracy increasing the commitment thereto. In the age of social media as a primary means of communication, the role and impact of this on political communication is boundless and significant. Methodology The primary method of research will be the analysis of different systems of social media usage. There is some literature written on the topic, examining different facets of the social media usage in political communication and this will serve as a useful indicator of the ways that social media is used in political communication. Thereafter, individual case studies on various methods that have been employed to great effect need to be examined. In other words, by examining how different political organizations have used social media to their advantage. The sources of these case studies will be evident in the literature written on the topic. How the organizations use social media and the effect that it has will be the primary focus of the research. The effect of social media usage will include the benefits on participation as well as the disadvantages relating to sensationalism and accuracy. References Clay Shirky (2011) ‘The Political Power of Social Media’ Foreign Affairs, 90(1), p28-41 Erik Qualman (2009) ‘How Social Media Transforms the Way We Live and Do Business’ [online] Available on http://www.ebscohost.com.ezproxy.uct.ac.za/uploads/corpLearn/pdf/bbs_socialnomics.pdf [Accessed on 7 July 2012] Erik C. Nisbet, Elizabeth Stoycheff, & Katy E. Pearce (2012) ‘Internet Use and Democratic Demands: A Multinational, Multilevel Model of Internet Use and Citizen Attitudes About Democracy’ Journal of Communication, 62, 249–265 Henry Farrell (2011) ‘The Internet’s Consequences for Politics’ [online] Available on http://crookedtimber.org/wp-content/uploads/2011/09/ARPS.pdf [Accessed on 7 July 2012] John C. Bertot, Paul T. Jaeger, Justin M. Grimes (2010) ‘Using ICTs to create a culture of transparency: E-government and social media as openness and anti-corruption tools for societies’ Government Inform ation Quarterly, 27, 264–271 Michael J. Magro, (2012) ‘A Review of Social Media Use in E-Government’ Sci., 2, 148-161 Wenfang Tang and Shanto Iyengar (2011) ‘ The Emerging Media System in China: Implications for Regime Change’ Political Communication, Special Issue [online] Available at http://myweb.uiowa.edu/wenftang/p/scanned%20publications/Tang%20and%20Iyengar%202011.pdf [Accessed on 7 July 2012]

Renaissance Patronage

Renaissance Patronage This paper explores different motivations for art patronage throughout the Renaissance. Art in the renaissance was often commissioned by a patron who wanted to use it as a way to communicate something to the intended viewer. Art was usually commissioned for religious and political reasons or used as proof of wealth or power. The corruption of the church allowed for wealthy patrons to make a donation in order to buy his or her way into heaven. This is called a sale of indulgence, and it is the motivation behind countless works of renaissance art.The entire Arena Chapel painted by the artist Giotto was commissioned by Enrico Scrovegni to atone for his sin of usury. The Chapel was completed 1305 and is located in Padua, Italy. As was a common practice at the time, Enrico himself is depicted in on the wall of the chapel. â€Å"On the wall of The Last Judgment, Enrico kneels to offer a model of his church to three figures. It is commonly accepted that Enrico saw his church and its paintings as a votive gift made as a partial atonement for his father’s mortal sin of usury and to strengthen his own hope of salvation. By having his image painted into the scene, Enrico assures that his intended audience knows it was his money that paid for the art. This is both politically and religiously motivated. Masaccio’s Pisa Altarpiece commissioned in 1426 Pisa is another example of religiously motivated art patronage. This altarpiece was commissioned by â€Å"Ser Giuliano di Colino di Pietro degli Scarsi and the Carmelite church of S. Maria del Carmine† The intention behind this altarpiece was simply to give churchgoers a piece of relevant art to view during church and to attract more members.An example of politically motivated art can be found in Sienna’s Palazzo Pubblico. Allegory of Good and Bad Government by Ambrogio Lorenzetti was commissioned by the Sienese government. The frescos of Allegory span the walls of the building depicting life in the city under good government versus bad government. The intended audience for this commission was the citizens of Siena. The paintings were propaganda meant to show the viewers how successful and prosperous the city was under the current leadership of the Council of the Nine. Another politically motivated piece is the well known portrait by Jan Van Eyck, Giovanni Arnolfini and his Wife.This portrait was commissioned in 1434 by Giovanni Arnolfini and is meant to be a physical documentation or witness to him giving his wife leave to conduct household affairs in his absence. This portrait would have been displayed in the Arnolfini household to be seen by visitors and servants and served as proof that Giovanna was in charge of Giovanni’s affairs while he was traveling. Tres Riches Heures by the Limbourg Brothers was commissioned by the Duke of Berry in 1412 France. This book is an example of royal patronage. It is meant to depict and glorify daily life in the court while simultaneously belittling those of the lower class.Tres Riches Heures is personalized for the Duke and includes his likeness and some scholars believe that because the faces in the book are so diverse, that they must be portraits of individual members of the court. This fact and the use of the rare pigment lapis lazuli, the intricacy of the book, and the heavy use of hidden symbolism are all meant to illustrate the wealth of the duke. The court was the intended audience of this commission. Patronage was a defining element of renaissance art. There were many motivations to purchase art such as religion, proof of power or wealth, or political reasons.Commissions varied depending on the motivation and the intended audience. Works Cited Carroll, Margaret D. â€Å"†In the Name of God and Profit†: Jan Van Eyck's Arnolfini Portrait. † Representations 44. 1 (1993): 96-132. http://www. jstor. org/stable/2928641 Web. 26 Feb. 2013 James, Sara Nair. â€Å"Masacc io: St. Andrew And â€Å"The Pisa Altarpiece.. † Sixteenth Century Journal 35. 4 (2004): 1178. Academic Search Complete. Web. 27 Feb. 2013. Perkinson, Stephen. â€Å"Likeness, Loyalty, And The Life Of The Court Artist: Portraiture In The Calendar Scenes Of The Tres Riches Heures. † Quaerendo 38. /3 (2008): 142-174. Academic Search Complete. Web. 27 Feb. 2013. Polzer, Joseph. Ambrogio Lorenzetti's â€Å"War and Peace† Murals Revisited: Contributions to the Meaning of the â€Å"Good Government Allegory† Artibus et Historiae. Vol. 23, No. 45 (2002), pp. 63-105 http://www. jstor. org. ezproxy2. drake. brockport. edu/stable/1483682 Web. 24 Feb. 2013 Rough, Robert H. â€Å"Enrico Scrovegni, The Cavalieri Gaudenti, And The Arena Chapel In Padua. † Art Bulletin 62. 1 (1980): 24. Academic Search Complete. Web. 24 Feb. 2013. ——————————————– [ 2 ].Robert H Rough, Enrico Scrovegni, the Cavalieri Gaudenti, and the Arena Chapel in Padua, pg. 26. [ 3 ]. Sara Nair James, Masaccio: St. Andrew and â€Å"The Pisa Altarpiece. † Pg. 1178 [ 4 ]. Joseph Polzer, Ambrogio Lorenzetti's â€Å"War and Peace† Murals Revisited: Contributions to the Meaning of the â€Å"Good Government Allegory† Pg. 64 [ 5 ]. Margaret D. Carroll, â€Å"In the Name of God and Profit†: Jan van Eyck's Arnolfini Portrait. Pg. 99 [ 6 ]. Steven, Perkinson, Likeness, Loyalty, and the Life of the Court Artist: Portraiture in the Calendar Scenes of the Tres Riches Heures Pg. 144