Bilingual Acquisition in Early Childhood

Bilingual Acquisition in Early Childhood Are bilingual children two monolingual children in one? Discuss. Research into bilingual acquisition in early childhood has investigated whether infants and toddlers brought up in bilingual settings can be said to have a single language system during the initial stages of language acquisition or whether these early bilinguals develop two separate language systems from the start. If the latter can be shown to be the case, it could be argued that bilingual children are indeed two monolingual children in one. However, there has been considerable debate over the merits of both claims for some period of time. This essay will consider the arguments and some of the evidence put forward in support of both points of view. Researchers differentiate between two languages acquired from birth (simultaneous bilingual acquisition) and the acquisition of a second language during early childhood. Research, intending to address the question of developing bilingual language systems in the infant, focuses on simultaneous bilingual acquisition. Although as Lanza points out it isn’t always easy to decide on â€Å"the cut-off point between first language acquisition and early second-language acquisition.† [1] The language environment, with both parents speaking both languages or the adoption of a one language one parent approach, is also a consideration. It is often pointed out that bilingual children acquire their languages in much the same way as monolingual children acquire theirs. Pearson and colleagues testing the acquisition of vocabulary found that â€Å"differences in average vocabulary size (between the bilingual and monolingual children in their study) across the age range tested were relat ively small.†[2] Studies of childhood bilingual development have shown that in almost all cases, children mix elements from the two languages they are acquiring. This has lead to claims that in the early stages of acquisition bilingual children have a single language system. Code mixing may involve any aspect of the child’s language system i.e., phonetic, lexical, phrasal, syntactic, semantic and pragmatic. Code mixing is not limited to children. Many researchers have investigated the phenomenon of code mixing or switching in adult bilinguals. However, there are important differences between the two. Adult code switching is rule governed. â€Å"What is thought to distinguish bilingual children’s mixing from adult mixing is the lack of systematicity or compliance to linguistic rules in the case of children.† [3] The fact that mixing declines with age has been cited as evidence that the child originally had one system that gradually separates into two. The period of mixing is followed by language differentiation sometime during the bilingual child’s third year. Volterra and Taeschner’s seminal paper interpreting code mixing in terms of a three-stage model of a single language system has had numerous supporters and critics. [4] A growing number of researchers have published papers in the past couple of decades supporting a two-language system. In 1985 Vihman looked at a bilingual Estonian/ English child. Having pointed out that there was insufficient data concerning the child’s comprehension skills in both languages to confirm whether or not he had a single system: â€Å"It seems likely that two receptive stores did exist in a rudimentary form even at this earliest stage, however, since comprehension appeared to develop rapidly in both English and Estonian contexts well before the development of a wide-ranging productive vocabulary.† [5] Considerable research has shown that monolingual children develop comprehension before production skills. The author agreed with Lindholm and Padilla[6] that â€Å"bilingual children are able, from an early age, to differentiate their two systems†. [7] Genesee also found evidence of â€Å"differentiated underlying language systems† in his study of early bilinguals. He argued that â€Å"bilingual children are able to differentiate their language systems from the beginning and that they are able to use their developing language systems differentially in contextually sensitive ways.† [8] Paradis and Genesee concluded the bilingual children in their study developed entirely distinct pronoun system for the two languages. [9]Their research therefore supports the separate language hypothesis. Likewise, Quay’s study of an English/ Spanish bilingual child â€Å"provides no evidence for the two-stage model of lexical development proposed by Volterra and Taeschner.† [10] Empirical and Interpretative Difficulties Methodology Most researchers criticise the methodology used by previous researchers in the field. Diary studies of a single child are common making any generalisation difficult. Other factors making comparison and therefore generalisation difficult include: the differing exposure to the languages experienced by each child, their different language backgrounds and history, the different methods of language sampling undertaken by the various researchers, and the fact that to date there is no standardised measurements to compare children at various stages of bilingual development. Furthermore, diary studies may be insufficient to accurately reflect the linguistic competence of the child studied, regardless of whether or not the findings can be shown to be valid for other bilinguals. â€Å"Diary data may not capture all translation equivalents.† [11] Quay also points out that studies making use of audio and video recordings tend not to make them frequently enough: â€Å"Infrequent recordings for a short duration each time do not allow for conclusive evidence with regard to bilingual children’s ability to produce translation equivalents.†[12] Radford reviewing Paradis and Genesee (1996) remarks on a methodological shortcoming noted in many other studies, the use of a small corpus of data: â€Å"This might lead us to the conclusion that PG simply didn’t have enough data from enough children to support the sweeping theoretical claims that they make.†[13] Pearson and colleagues also criticize the emphasis on case studies â€Å"a form in which systematic comparisons with other children are not generally attempted.† [14] Their own research compared the language development of 25 English/ Spanish bilinguals with 35 monolinguals: â€Å"Without detailed information from a wide range of children, it is difficult to gain a broad perspective on what is typical and what is exceptional in early bilingual development.†[15] Radford states, â€Å"much of the evidence VT (Volterra and Taeschner) bring to bear in support of their claim that children start out with a common syntax for their two languages is based to a large extent on code-mixing.†[16] He suggests the fact that bilingual children are known to code mix cannot be seen as evidence for a single language system because adult also code switch and they are â€Å"generally assumed to have separate grammars for each language.† However, as has been stated earlier, children do not code mix in the way adults do. More problematic for supporters of the single language system is the finding by Genesee and colleagues that code mixing in early bilinguals is not as common as Volterra and Taeschner claim.[17] These researchers discovered that code mixing takes place in only 1%-7% of bilingual children’s utterances. Like Radford, Genesee claims that there are serious methodological and interpretative shortcomings with much research into simultaneous bilingualism. In order for the single system hypothesis to be valid, bilingual children would need to â€Å"use items from both languages indiscriminately in all contexts of communication.†[18] However, as Genesee makes clear, most research in the field has failed to analyse the data by context. Volterra and Taeschner for example, present isolated examples of the child addressing one parent only.[19] Vihman did look at her bilingual child’s utterances in context but she focused on one language only.[20] If the appearance, then decline, of code mixing in early bilingual development is not necessarily evidence of a single language system, what other factors may be responsible for the phenomenon? Vihman (1985) argues that the decline in mixing has more to do with the bilingual child gaining in sociolinguistic competence than evidence of the separation of language systems.[21] Lanza also suggests a more sociolinguistic explanation for code mixing: â€Å"Children do learn to differentiate their language: however, this differentiation process occurs in language socialisation through which they learn to differentiate ways of speaking according to the social demands of the situation.† [22] Other researchers point out that with the acquisition of more lexical items as the child’s language skills develop, there is less need to borrow between languages (the lexical gap hypothesis).[23] [24] Peterson claims bilingual children switch to their dominant language because they haven’t the lexicon or syntactic structure in the weaker one.[25] Bernardini agrees â€Å" in some young bilingual children†¦with uneven development, having one language that is clearly weaker than the other, sentence-internal code-mixing is a result of uneven lexical development in the two languages.† [26] Pearson and colleagues test the Volterra Taeschner (1978) claim â€Å"if children already have a lexical representation for a concept in either language, they will not be motivated to learn or use the word’s translation in the other.†[27] This follows Clark’s principle of contrast, which predicts an absence of synonymy in early lexical development in both monolingual and bilingual children.[28] Pearson and colleagues found no evidence to support Volterra Taeschner in their study of 27 early bilinguals. Quay also found â€Å"no foundation for the principle of contrast in (the) bilingual case (studied).† Quay points out â€Å"most studies do not take into account whether young bilinguals have the lexical resources to make a choice between their two languages.† [29] According to Grosjean one language may be dominant because the child is exposed to that language more frequently and needs it to communicate with more people.[30] Serratrice defined â€Å"language dominance in terms of the amount of input the child receives†. [31]It has been pointed out by a number of researchers that mixing may be linked to the child’s speech environment. [32] The bilingual child might code mix because he hears his parents or other adults doing so. It has been argued the â€Å"best way to avoid bilingual mixing in children is to have each parent speak only one language to the child.† [33] Quay suggests, â€Å"linguistic input from adult interlocutors must be taken into account in discussions of children’s language choices.†[34] Conclusions It is clear that many factors are involved in simultaneous bilingual acquisition. The debate over whether these young children develop one or two language systems initially has yet to be satisfactorily resolved. As many researchers point out parental input may well prove to be of particular importance. Whether the child has one system or two and thus resembles a single monolingual child or two monolingual children, it is clear that their â€Å"ability to understand two languages may be comparable in each language to monolingual children’s.†[35] Bernardini, P and Schlyter, S (2004) Growing syntactic structure and code-mixing in the weaker language: The Ivy hypothesis. Bilingualism: Language and Cognition 7, 49-70 Clark, E (1987) The principle of contrast: a constraint on language acquisition. In B. MacWhinney (ed.) Mechanisms of Language Acquisition. Hillsdale, NJ: Erlbaum. Genesee, F (1989) Early bilingual development: one language or two? Journal of Child Language 16, 161-179 Genesee, F. Nicoladis, E Paradis, J (1995) Language differentiation in early bilingual development. Journal of Child language 22, 611-630 Grosjean, F (1982) Life with two languages: an introduction to bilingualism. Cambridge MA: Harvard Uni press Lanza, E. (1992) Can bilingual two-year-olds code-switch? Journal of Child language 19, 633-657 Lindholm, K and Padilla, A (1978) Child bilingualism: report on language mixing, switching and translations. Linguistics 211, 23-44 Paradis, J. and Genesee, F. (1996). ‘Syntactic acquisition in bilingual children: autonomous orinterdependent?’ Studies in Second Language Acquisition 18: 1-25. Pearson, B, Fernandez, S and Oller, D 1993. Lexical development in bilingual infants and toddlers: comparison to Monolingual norms. Language Learning 43:1, 93-120 Pearson, B, Fernandez, S and Oller, D 1995. Cross-language synonyms in the lexicons of bilingual infants: One language or two? Journal of Child Language 22, 345-368 Pearson, B. Fernandez, S. Lewedeg, V Oller, K (1997). The relation of input factors to lexical learning by bilingual infants. Applied Psycholinguistics 18, 41-58 Peterson, J (1988) Word-internal code-switching constraints in a bilingual child’s grammar. Linguistics, 26, 479-493 Quay, S (1995) The bilingual lexicon: implications for studies of language choice. Journal of Child Language 22, 369-387 Radford, A (2005) Children’s English: Principles-and-Parameters Perspectives. University of Essex. Serratrice, L. Referential cohesion in the narratives of bilingual English-Italian children and monolingual peers. Journal of Pragmatics 39 (2007) 1058–1087 1083 Vihman, M. (1985) Language differentiation by the bilingual infant. Journal of Child Language 12, 297-324 Volterra, T and Taeschner, T (1978) The acquisition and development of language by bilingual children. Journal of Child Language 5, 311-326 1 Footnotes [1] Lanza (1992:634) [2] Pearson et al (1993:112) [3] Genesee (1989) [4] Volterra and Taeschner (1978) [5] Vihman (1985:316) [6] Lindholm and Padilla (1978) [7] Vihman (1985:317) [8] Genesee (1989:174) [9] Paradis and Genesee (1996). [10] Quay (1995:385) [11] Quay (1995:382) [12] Quay (1995:383) [13] Radford (2005) [14] Pearson et al (1993:95) [15] Pearson et al (1995:348) [16] Radford (2005) [17] Genesee et al (1995) [18] Genesee (1989:165) [19] Volterra and Taeschner (1978) [20] Vihman (1985) [21] Vihman (1985) [22] Lanza (1992:654) [23] Volterra and Taeschner (1978) [24] Lindholm and Padilla (1978) [25] Peterson (1988) [26] Bernardini and Schlyter (2004:49) [27] Pearson et al (1995:346) [28] Clark (1987) [29] Quay (1995:369) [30] Grosjean (1982) [31] Serratrice (2007) [32] Genesee (1989) [33] Genesee (1989:170) [34] Quay (1995:383) [35] Pearson et al (1993:113)

Evolution of Virulence in the Ebola Virus

Evolution of Virulence in the Ebola Virus The Ebola virus is a member of the Filoviridae family of virus and is the pathogen responsible for Ebola Hemorrhagic Fever, an emerging disease that appears in infrequent epidemic outbreaks mainly in sub-Saharan Africa. The Ebola Virus is composed of several distinct subspecies, ranging from the extremely virulent Ebola Sudan and Ebola Zaire Viruses to the asymptomatic (in humans) Ebola Reston. Many outbreaks of Ebola Hemorrhagic Fever display mortality rates approaching 90%. Application of evolutionary concepts of disease and virulence evolution can be used to help explain this high level of virulence. Another important factor is the possible presence of less virulent outbreaks of Ebola Hemorrhagic Fever that go unreported due to small scale and lack of characteristic virulence A further understanding of the selective mechanisms behind virulence may suggest strategies to impose selection for less virulent strains of the virus and to develop possible vaccines, thus helping to curb th e deadly effect of Ebola outbreaks. The Filovirus family contains the Ebola Virus genus and the closely related Marburg Virus. Both of these genera are known to cause extremely dangerous hemorrhagic fever type illnesses. These Viruses are contain a single strand of negative RNA and typically measure 1400 nm in length with a diameter of approximately 80 nm. The various species of Ebola virus sporadically infect both human and non-human primates, causing Ebola Hemorrhagic Fever. Recent evidence suggests that the virus may have a natural reservoir in various bat populations. The virus sporadically jumps from this natural host species (in which it is avirulent) to host species such as chimpanzees, macaques, gorillas and humans where it typically exhibits high virulence. The mechanisms of this transition and the role of reservoir hosts is poorly understood at present (Leroy et al 2005) The Virus is transferred through direct contact with infected bodily fluids, most frequently by means of direct contact with an infected individual. Contaminated medical implements can also spread the infection in medical settings, especially during early stages when an epidemic has not yet been fully realized. In many of the early outbreaks this was a major means of transmission, due to the presence of the virus and nature of its transmission being poorly understood. Local funerary customs also contributed to the spread of the disease. Isolation of infectious patients, proper disposal of contaminated remains and excreta and use of efficient sanitation and barrier nursing techniques can effectively prevent transmission during an outbreak. It is important that these measures be implemented immediately upon suspicion of Ebola Hemorrhagic Fever in order to minimize spread of the virus within the community (Ebola virus disease in southern Sudan 1983). Initial during initial stages of infection the Ebola virus selectively targets dendritic cells, monocytes and macrophages, which spread through the circulatory and lymphatic systems to the liver spleen and lymph nodes. From here the virus can efficiently spread throughout the body. The infected monocytes and macrophages also release massive amounts of cytokines, helping to trigger virus-induced shock by causing damage to the endothelial structures. Infected dendritic cells are prevented from releasing costimulatory cytokines necessary for the production of T-cells, preventing sufficient immune response to the infection (Aleksandrowicz et al 2008). Symptoms of Ebola Hemorrhagic Fever usually manifest 2-21 days after infection. Initial symptoms include fever, weakness, aches in the muscles and joints, sore throat. These progress to rash, impaired liver and kidney function and in some cases both external and internal bleeding due to deterioration of the vascular lining (World Health Org anization). The massive release of cytokines and virus particles from monocytes and macrophages impairs the function of endothelial tissue, allowing it to become permeable to water and macromolecules (Aleksandrowicz et al 2008). Gastro-intestinal bleeding is a common symptom, and is frequently associated with lethal cases. (Ebola Haemorrhagic Fever in Zaire 1978) The First known outbreaks of the Ebola virus occurred nearly simultaneously in Zaire (modern Democratic Republic of the Congo) and Sudan in 1976. These outbreaks, although close both geographically and chronologically were caused by two distinct subspecies of the virus (Ebola Zaire and Ebola Sudan respectively). The Zaire outbreak was centered in the village of Yambuku and its environs. 318 cases were reported in this epidemic, of which 280 were fatal (mortality 88%). All cases in this epidemic were tied to either close contact with a confirmed case or receiving a parenteral injection at the local hospital (Ebola Haemorrhagic Fever in Zaire 1978). Early cases in the Sudan outbreak were textile workers from the town of Nzara. 151 of the 284 reported cases were fatal (mortality 53%) (Known Cases and Outbreaks of Ebola Hemorrhagic Fever). Three years later, in August of 1979 another, smaller scale outbreak occurred in Nzara and the nearby town of Yambio, resulting in 34 cases, with 22 f atalities (65% mortality) (Center for Disease Control, 2006). Communities affected by these outbreaks share several characteristics. One of the most significant of these is the nature of available medical care. All were served by small, undersupplied and understaffed hospitals. Unsanitary conditions within these hospitals and the prevalence of family members carrying out day to day care for afflicted individuals being allowed the virus to spread quickly through the local population. The Yambuku hospital utilized five needles and syringes for prenatal, inpatient and outpatient wards, with little sterilization between uses. This fact alone almost ensured transition of the virus between patients in the hospital. Lack of barrier nursing practices also allowed high transmission to the staff (11 of the 17 medical staff died as a result of Ebola Hemorrhagic Fever) and caregivers as well A high prevalence of infection was found amongst individuals present at funerals of deceased patients in all outbreaks. The reproductive success of a pathogen is dependent upon its ability to replicate itself and to infect new hosts by transfer of its propagules. Rapid replication can increase a pathogens chance of transference, but this requires a greater toll on the hosts system and is likely to lead to an increased chance of host mortality. Due to this, there is believed to be a natural correspondence between a pathogens growth rate and virulence. The relationship between these two factors is explained by the trade-off hypothesis of virulence evolution. This theory largely replaced the commonly accepted idea that a parasite or pathogen should evolve towards avirulence, but it not fully accepted. The avirulence theory assumed that a parasite low virulence would maximize a pathogens overall lifetime reproductive success by increasing the time of infection to nearly infinite limits. The reasoning behind this theory has been explained thusly: The parasite makes a profession out of living at its neighbours expenses and all its industry consists of exploiting it with economy, without putting its life in danger. It is like a poor person who needs help to survive, but who nevertheless does not kill its chicken in order to have the eggs (Van Beneden 1875). The frequent down trend in virulence from the time a pathogen is introduced to a novel population was offered as evidence for this theory. The trade-off theory developed when evolutionary ecologists began to question the avirulence theory. It proposes that there is a link between ease of transmission and virulence. According to this theory, virulence is an outgrowth of a rapid replication rate in the pathogen, which strains host resources and reduces host fitness (resulting in host mortality). The Trade-off theory links the variables of virulence, transmission and host recovery in a relationship summarized by the following mathematical model: (Alizon, Hurford, Mideo Van Baalen 2009) In the above equation R0 represents the pathogens baseline reproduction ratio, in this case a measure of relative fitness. The S value is the number of susceptible hosts within a population. ÃŽÂ ² represents rate of transmission, ÃŽÂ ± is the death rate in the host due to infection (virulence), ÃŽÂ ¼ stands for the natural death rate in the host population, and ÃŽÂ ³ is a factor representing the recovery rate from the infection. According to this model, any change in virulence, transmission rate or recovery rate will have an effect on the other two variables. A high transmission rate will typically go along with a high virulence and low recovery rate. The reproductive success of a pathogen comes from successfully balancing these variables to maximize R0 (Alizon et al). High Virulence will allow for high reproduction and transmission, but only up to a point. Natural selection should favor strains that are able to maximize this trade-off. Eventually, virulence can reach a l evel where the increased transmission is no longer balanced out by the risk of dying along with a host before being able to jump to a new one. This is especially true in isolated host populations or other conditions that limit horizontal transmission, which could possibly explain the low virulence and chronic nature of some infections. Virulence is typically defined as morbidity and mortality of the host organism as a result of parasite or pathogen activity. Measurements of a pathogens virulence are traditionally given in terms of parasite induced death rate (PIHD). This definition is suitable for a general discussion of a disease as it includes all deleterious effects on the host. A more specific and narrow definition is required in order to examine selective pressures on the evolution of virulence in a disease, however. The generalized definition, according to Ebert and Bull in their work on virulence evolution, fails to differentiate between virulences effects on host and pathogen fitness, and therefore fail to give an accurate assessment of selective pressure on the pathogens evolution. For this reason it is important to consider specific aspects of the host/pathogen system (such as means of transference, rate of pathogen growth, etc) before drawing conclusions about the selective pressures for increased or red uced virulence in the pathogen (Ebert Bull 2008). In the case of the Ebola virus and Ebola Hemorrhagic Fever virulence can be discussed in terms of host death. Unlike with some pathogens, death of the host does not immediately end transmission of the virus. Some studies indicate that the corpse can remain infectious for several days after death. Several epidemics have been traced to contact between the index case and the contaminated remains of a chimpanzee (Ivory Coast 1994, Gabon 1996, Gabon 1996-97) (Chart) and contaminated monkey meat may have played a role in the index case of the initial 1976 Zaire outbreak (Ebola Haemorrhagic Fever in Zaire 1978). Ebert and Bull define three general stages of evolution in a pathogen transferring to a novel host and the selective pressures involved in each. The first phase includes the initial interactions between a pathogen and the novel host. In some cases this infection is not capable of horizontal transfer between hosts in the novel population. Other situations involve short chains of secondary infection from the index infection. Infections in this phase are likely exposed to great selective pressures, as they are in an entirely new environment, one for which their genes may or may not be particularly suitable. Genes that may not have had a measureable fitness effect in the pathogens normal host environment can suddenly exert great selective pressure. Because of this there is frequently a great range of virulence expressed by different pathogens during this phase. The second phase occurs during the period when a pathogen has established a foothold within the novel population. It follows the epidemic infection model and increases rapidly within the population, because of this rapid growth it is possible for a pathogen to evolve rapidly in this phase. Selective pressure on the host can also be extreme in this phase. The second phase also applies when a mutation in a parasite that has already obtained equilibrium within a host population is significant enough that it gains a selective advantage over other strains and spreads rapidly. Ebert and Bulls third phase is reached when a pathogen has become firmly established within a host population. Pathogens in this phase are well adapted to the host, but will still experiences selective pressures due to host demographic and environmental changes. The Ebola virus, in human hosts, remains largely within the first phase, although it could be argued that it briefly enters the second phase on a local level during some outbreaks. It causes short lived epidemics when it does infect a human population, but fails to survive long term and become an endemic pathogen. During this initial stage the virus can be exposed to great selective pressure as it is in an unusual host. Evolutionary dynamics within an epidemic scenario, as proposed by Bolker et al, favor pathogens with a high growth and transference rates, and the high virulence that is associated with them, due to the large number of susceptible hosts in the novel population. This differs from a pathogen in later stages, which has reached dynamic equilibrium with the host. These situations tend to select for moderate virulence and longer duration of infection. (Bolker et al). A possible explanation for the extreme virulence in Ebola outbreaks may simply be reporting bias. Many of the early and milder symptoms of Ebola Hemorrhagic Fever are quite similar to those of other diseases endemic to the region, such as malaria, and measles. Some outbreaks are actually mistaken for cases of other diseases until post-infection laboratory tests detect particles of an Ebola strain. A 1994 outbreak in gold mining camps in Gabon (52 cases, 60% mortality) was believed to be a yellow fever epidemic until almost a year after the last case. It is possible that less virulent strains of the virus are simply mistaken for other common infections, treated as such, and never reported (CHART). Ebola virus antibodies were detected in sera from 18% of adults in the 1979 Nzara outbreak who were not infected. This is evidence that It is likely that sporadic infection is more common than can be appreciated from these dramatic outbreaks, which probably represent the extreme of the inter action between man and the virus. (Baron et al). This fits in with the inherent virulence variance in phase one pathogens suggested by Ebert and Bull above. Other factors that can affect the evolution of virulence in a pathogen are host population density and ease of transmission. These factors are frequently interrelated, as both directly influence the number of susceptible hosts a pathogen is able to infect during its lifespan. A high density of susceptible hosts (such as when a pathogen is emerging in a novel host population) is likely to greatly increase greatly increase a pathogens reproductive success, and select for pathogens that can replicate quickly and take advantage of the abundant hosts. Likewise, easy transition from one host to the next also selects for pathogens that are able to rapidly replicate and seize the day, as it were. Both of these conditions, which favor pathogens with high growth rates, also favor high virulence in accordance with the Trade-off hypothesis (Ebert Bull 2008). The abovementioned concepts and principles fit in with epidemiological data from outbreaks of Ebola Hemorrhagic Fever. Initial outbreaks of Ebola Hemorrhagic Fever took place within areas with a relatively high concentration of susceptible hosts. The 1976 outbreak centered on the Yambuku Mission Hospital is a good example. This hospital served as the primary medical facility for a local population of around 60,000 as well as travelers. This facility was relatively small, having 17 staff members and holding 120 beds in its crowded wards. It also processed some 6000-12000 outpatients on a monthly basis. Combine this with the five improperly sterilized syringes used to administer injections (the primary dosage method at this facility) and a severe lack of barrier nursing procedures. This would appear to be an optimal situation for the transmission of pathogens that spread through contaminated body fluids. According to the Trade-off Hypothesis and the selective conditions outlined above, pathogen strains that have high reproduction rates (and hence high virulence) would be at a distinct selective advantage. Cases cared for out of the hospital setting would also tend to favor quickly reproducing and more virulent pathogens. Horizontal transfer by physical contact is directly affected by the concentration of virus particles in a contaminated fluid; hence a virus with a higher reproduction rate would be able to successfully exploit a given number of transfer opportunities. This setting lacks the direct viral inoculation by contaminated needle present in the hospital setting, which would perhaps result in less effective transmission. This would also favor more strongly virulent pathogens, which reproduce quickly and successfully exploit transmission opportunities (Ebola Haemorrhagic Fever in Zaire 1978). The conditions present during the 1976 Sudan outbreak were largely similar. Transmission occurred mainly to family members providing nursing care (without barrier nurs ing techniques) and through contaminated medical equipment and direct contact in a hospital setting. These conditions would also seem to favor more virulent pathogens. Other examples of particularly high virulence outbreaks (in terms of host mortality) also occur under conditions with large amounts of close contact between potential hosts, likely resulting in high transmission. Examples of these situations are found in the 1994 and 1996-97 Gabon outbreaks, which took place at a mining camp and (initially) a remote forest camp respectively. Both of these outbreaks featured transmission of numerous secondary infections through close contact with infected individuals. According to the Trade-off hypothesis, high transmission rates are linked to high levels of virulence. By reducing rate of transmission it may be possible to artificially select for less virulent strains. In the hospital and home care setting, hosts suffering from highly virulent strains with high symptom manifestation (high virulence) are likely to transmit the virus to other hosts, favoring virulent strains. Application of sanitation and barrier nursing practices can reduce transmission of the virulent strains present under these conditions. This could potential favor any less virulent strains, i.e. ones that do not manifest severe symptoms that require hospitalization and are unlikely to be fatal, present in the environment. This could gradually reduce overall virulence over the course of the outbreak. Even if less virulent strains are not present, prevention of transmission is likely to slow and eventually stop the outbreak as the number of remaining susceptible hosts is reduced through various means (Ewald 2004). The Ebola Virus and Ebola Hemorrhagic Fever present an interesting case for evolution of virulence in a pathogen. The periodic outbreaks of the disease offer examples of how selective pressures imposed on a pathogen follow the predictions of the Trade-off hypothesis linking virulence (and attendant host mortality) with rate of transmission. This hypothesis and the conclusions it suggests fit with data observed in outbreaks of virulent Ebola Hemorrhagic Fever. Conditions of dense susceptible host population and rapid and effective transmission seem to demonstrate high incidences of virulence indicating that there may be selective pressure for virulent strains under these conditions. Evidence of strains showing low virulence is suggested by the Ebola virus presence in a natural reservoir species and by the formation of antibodies by healthy individuals not linked to current epidemics. Due to this (presumed) variation amongst strains and the relationship between transmission and virulen ce proposed by the Trade-off hypothesis, reduction of transmission of the virus in hospital and homecare settings may lead to a reduction in strain virulence in prolonged outbreaks.

A Bintel Brief :: essays research papers

The Eastern European Jews had many troubles before immigrating to America. Jews are well known for overcoming hardships that are thrown at them. In A Bintel Brief, they weren’t exactly overcoming genocide, but they were having many hardships that would be tough for anyone including love, missing family members, poverty, and different religious problems. Many Jews had nothing but the clothes on their backs when they arrived in America. Few had money to bring along with them, all though some did have money. The majority of the people or families that came to America had to start with nothing, and work from the ground up. Some of the people were working for a measly two dollars a week. The Eastern European Jews at that time weren’t working for themselves most of the time. Most of the time they had whole families to feed, or they had prior obligations they had to fulfill. Many of the Jewish people’s wages were put towards a ship fare, to get their family out of Easte rn Europe and into the free America. The majority of the Jews were working in shops all over. Many of the Jews were persecuted. They weren’t allowed to have certain jobs. One instance in the book a mother wrote in for her son, who desperately wanted to be a chemist. The mother was outraged, because many people were saying that they wouldn’t hire a Jewish chemist. A lot of the immigrated Jews were finding partners that weren’t of the same religion. The book mentions Gentile and Jewish relationships a countless number of times. Many of the submitters found their relationship with a gentile was not working, that they started out in love, but the other is teaching the wrong things to their children. On the other hand, many Jews were becoming freethinkers.   Ã‚  Ã‚  Ã‚  Ã‚  The â€Å"Bintel Brief† itself gave an amazing amount of aid in the adjustment for Jews. All people need is hope, and when there’s hope you can do anything. These people poured their hearts out into their letters, and confided in the â€Å"Bintel Brief† for answers. The â€Å"Bintel Brief† in return would give sound advice, and would give hope that everything would turn out alright. Because there were few Jewish newspapers, they had nothing else to look forward too, or read. Many of them, just coming from Europe, still did not know English. These people could only read the Yiddish articles.

brady bill :: essays research papers

Brady Law Falsehoods The Brady law has received much credit for the country's rapidly dropping crime rate. Yet with the Supreme Court striking down the laws background check requirements, it faces its ultimate test. If gun control advocates are correct, the court's decision will unleash a new crime wave. The Justice Department continually releases "new" studies crediting the law with reducing crime. Actually, the downward crime trend started in 1991, well before the Brady law became effective in March 1994. My research shows that this decline is in great measure because of higher arrest rates and more states allowing law-abiding citizens to carry concealed handguns. Others estimate that the Brady bill had a much smaller effect on gun sales than the 100,000 rejections its proponents claim. Last year the General Accounting Office reported that initial rejections numbered about 60,000, and more than half were for purely technical reasons, mostly paperwork errors that eventually were corrected. A much smaller number of rejections, 3,000, were due to violent crime convictions--and presumably many of these people just proceeded to buy a gun on the street. Brady law backers have focused almost exclusively on the value of background checks, the one part of the law that the Supreme Court specifically struck down. Yet there never was much controversy over this issue: When Congress debated the law, no one, not even the National Rifle Assn., opposed background checks. The dispute was over a five-day waiting period versus an "instant check." Ultimately, the success of background checks and waiting periods must be judged by their impact on crime. To seriously evaluate their impacts, however, one must recognize that other legal changes also occurred. For example, during 1995 and 1996, 10 more states adopted nondiscretionary concealed handgun laws. In the belief that concealed handguns deter crime, 31 states now grant permits automatically to citizens who have no significant criminal records or histories of major mental illness. In all 31 states, more people now carry legally concealed handguns. Considerable evidence supports the notion that permitted handguns deter criminals. Polls show that there are at least 760,000 and possibly as many as 3.6 million defensive uses of guns per year. In 98% of the cases, people simply brandish weapons to stop attacks. This is further reflected in the different rates of "hot burglaries," where a resident is at home when a criminal strikes. In Canada and Britain, both with tough gun control laws, almost half of all burglaries are "hot.

Analysis of The Goal by Eliyahu Goldratt :: The Goal Business Management Essays

Analysis of The Goal by Eliyahu Goldratt The Goal is a book that focuses on the theory of constraints in order to improve production. Eliyahu Goldratt brings us a pleasant story that shows the important strategies that any manager or CEO should follow to be successfully productive, and capable of reaching their goals. The book easily explains and demonstrates many attainable ways for any human being to learn how to manage their industrial relations, business processes, and also, their personal lives. Many people believe that in order to succeed in a business that is having difficulties, it is important to focus on a particular area in order to be better productive in each of them, and be able to reach the goal. Instead, Goldratt and Jonah demonstrates that is important to focus on the company as a whole, but at the same time, it shows that it is incorrectly to only focus in an specific manufacturing department, or one plant, or a department within the plant, because people should not be concerned in local optimums. The Goal is a book that has an immense support on improvement, which will undoubtedly encourage the Total Quality Management terminology when trying to built up and improve their productivity. However, the Theory of Constraints also plays a very important role in this book, because it guide us to not only focus on the improvements of the business as a whole, but also to focus intensively on the constrains, â€Å" Herbies†, or bottlenecks. In order for a company to push its improvement and create a balanced plant, it is necessary to increase the throughput, while reducing inventory an operating expense. But, what is most important is to identify the bottlenecks to be able to focus on them. After focusing and solving the constraints, everything else is going to be less powerful but important at the same time. Any company is unable to manufacture a 100%. Therefore, people should really focus on the constraints, in a way that it will prevent a failure that will damage the entire system. Bottlenecks are the key in every plant, because it will determine the activity that will create a profit and maximize the business output.

Dinosaurs and Man May Have Co-Existed

Dinosaurs and Man may have Co-existed It has been a constant debate between creationists and evolutionists on how old the world is. Evolutionists believe that earth was created over 4. 5 billion years ago while, creationists believe in a young earth created only about 6,000 years old. With that debate is the argument on when the dinosaurs walked the earth. Evolutionism teaches that humans and dinosaurs lived millions of years apart from each other.What many people are not aware of is that there exists a considerable body of evidence that supports the Biblical account of humans and dinosaurs living at the same time and even interacting with each other. Some of this evidence suggests that this may still be happening today in certain parts of the world like the African Congo. (1) Dinosaurs are often portrayed as having lived in a time before man. However, the available evidence shows that man and dinosaur coexisted. Legends of dragons are found among most people groups.For example, ther e are the stories of Bel and the dragon, the Kulta of Australian aborigines, St. George and the dragon, and of course many Chinese legends. Often, the anatomical descriptions given are consistent, even though they come from separate continents and various times. (2) These depictions match what we know from the fossil evidence of certain dinosaurs. Thus, dinosaurs are known directly from their fossils, and indirectly from cave drawings, tapestries, textiles, figurines, carvings, bas reliefs, and many oral and written eyewitness accounts, most of which are quite old. 2) Pick up just about any book on dinosaurs, and it will say that dinosaurs lived from 230 million to 65 million years ago. That’s always stated as a fact, but how do they know? The ages of dinosaur fossils are determined by the layer of rock in which they are found. How do they know how old the rock layer is? It is usually the case that when layers of rock are piled up upon each other, the bottom one is the oldest , and the top one is the youngest, because the bottom one had to be there before the other ones formed on top of it.So, one can make a cross-sectional cut through a rock formation, examine the layers, and be reasonably confident that the lower layers formed before the upper layers (3). The questions are, â€Å"How long did it take for each layer to form? † and, â€Å"How much time elapsed between layers? † Traditionally, geologists have used the â€Å"geologic column† to answer these questions. Although the rapid formation of rock layers is an obvious fact, it makes evolutionists uncomfortable because it isn’t compatible with a neat uniformitarian explanation.If rock layers form rapidly in short periods of time, separated by longer time intervals of undetermined length, which makes it impossible to tell how long ago the rock layers were formed. Geologists are coming to the consensus that fossil-bearing rock layers were produced rapidly, and that there wer e unknown periods of time between the rock layers (3). Therefore, most of â€Å"geologic time† is represented by the rocks that aren’t there. Geologists have given traditional dates to sedimentary rock layers.They do that based upon the kind of fossils found in the rocks, and the evolutionary assumptions of the stages through which life evolved, and how long it took to evolve through each stage. The fossils in a sedimentary rock layer tell you what kinds of critters were living in that area at the time they were buried by a flood, landslide, or sandstorm (3). The dating and correlation of the geologic column is based on the assumption that all the wildlife living all over the world is the same at any given time.Therefore, floods, landslides, and sandstorms that occur in North America, South America, Africa, Europe, and Asia, will all bury the same kind of critter in any given year. (3) Believe it or not, dinosaur footprints, and the footprints of man, are found in the same strata, in the very same formation, in some cases only 18 inches apart, at a geological dig in Glen Rose, Texas, called the Paluxy River Bed. The ancient footprints of â€Å"man† at the site are found to be evenly spaced, and go under overhanging shale formations, continuing under the formations, and have been excavated. 4) Dinosaurs were said to have lived 250 million to 65 million years ago because their bones are found in rocks that are said to be Triassic, Jurassic, or Cretaceous. Rocks are classified as Triassic, Jurassic, or Cretaceous because they contain fossils that evolutionists presume were alive all over the Earth only during those periods of time. If you found a rock with a dinosaur bone in it, you would not be able to convince an evolutionary geologist that it was anything other than a Triassic, Jurassic, or Cretaceous rock.If radioisotope dating indicated the rock was less than 65 million years old, or more than 250 million year old, the evolutionist would flatly reject the radioisotope date. It is a fundamental article of faith that dinosaurs lived 250 to 65 million years ago. (3) New evidence from the Paluxy river bed in Glen Rose, Texas, as well as from South America, Mexico, and California, demonstrates beyond any doubt that dinosaurs and mankind co-existed, and walked the planet earth at the very same time — during the age of man.Believe it or not, dinosaur footprints, and the footprints of man, are found in the same strata, in the very same formation, in some cases only 18 inches apart, at a geological dig in Glen Rose, Texas, called the Paluxy River Bed. The ancient footprints of â€Å"man† at the site are found to be evenly spaced, and go under overhanging shale formations, continuing under the formations, and have been excavated (4). How is it possible that human footprints found in Mexico, Arizona, Texas, Illinois, New Mexico, Kentucky, and other states, are in rocks supposedly 250,000,000 years old† (4) Winkie Pratney in  Creation or Evolution?Part III, the Fossil Record: discusses the mysterious dinosaur tracks and human footprints found close together at the Paluxy River Bed: â€Å"Though the dino tracks (in the Paluxy River Bed in Glen Rose, Texas, for instance) are real, perhaps the human prints were later ‘clever carvings' by Indians. Recent research, however, has shown that they continue under shale bulldozed away, and paleontologists like Dr. Camp of the University of California and Dr. G. Wescott of Ypsilanti, Michigan, have pronounced them genuine.Scores of other similar finds have come in: human skulls in the Pliocene strata; pollen and anthropods in Pre-Cambrian layers; even pictographs of a dinosaur among other animals on ancient canyon walls, which would knock some 70 million years out of the geologic column† (Acts, p. 15, June 1996). (4) Since dinosaurs supposedly died out 65 million years ago, it is not possible that anyone in historic times has ever seen a living dinosaur. But what if people have seen living dinosaurs? Wouldn’t that completely refute the assumptions upon which the dating of the geologic column rests?For that reason, it is worth evaluating the evidence that man and dinosaurs might have lived together. If dinosaurs and man lived together, don’t you think they would be mentioned in ancient books? Certainly they would. They would not be called â€Å"dinosaurs† because that word wasn’t coined until 1841. If they were mentioned, you would expect them to be called something else, but would expect their descriptions to match dinosaurs (3). You would expect to read things like this, written by Philostratus (200 – 230 AD) wrote in the  Life of Apollonius of Tyana, Northern â€Å"India is girt with dragons of enormous size; not only are the arshes full of them but the mountains as well and not a single ridge is without one. †¦ The dragons of the foothills have crests, of moderate height when young but they grow with them and extend to a great height when they reach full size. † The bodies of the plains dragons are sometimes found with elephants, a great reward for hunters. Their tusks resemble those of swine, but more twisted and sharp. â€Å"They say that in the skulls of the mountain dragons are stored stones of flowery colors that flash out all kinds of hues. † They tell us that â€Å"a great many dragons' skulls are enshrined† in the center of the great city of Paraka (Peshawar? close by the mountain. (3)For over 2 hundred years there have been reports of a living dinosaur in Africa. This creature, which the natives call â€Å"Mokele-Mbembe† is believed to be a sauropod type of dinosaur (5). Sauropod means â€Å"Lizard-Footed† dinosaur. Sauropods are four-legged, herbivorous dinosaurs. These incidents were reported long before the word â€Å"dinosaur† was coined, and long before anyone (in this century) knew they existed. If Mokele-Mbembe is a living dinosaur, then it makes the claim of total dinosaur extinction unfounded.The Congolese people are very familiar with the aquatic dinosaur living in the Likoula swamp region. They call this Apatosaurus-like creature â€Å"Mokele-Mbembe† which means:  Ã¢â‚¬Å"one who stops the flow of rivers† (5). From the size of this awesome beast this name is sure fitting! They believe this animal  (which they greatly fear)  is sacred. This belief is due to the illness and death of many in the pygmy tribe after one was killed with a spear and eaten by the people. Of course, the deaths and illness were probably more likely due to spoilage of its meat.An animal this large could have been eaten for several weeks. (5) â€Å"Persistent reports of strange creatures in remote, swampy jungles of western Africa have led two scientists to believe that dinosaurs still may walk the Earth. Both historical reports from Westerners and firsthand accounts fr om natives indicate dinosaur-like creatures may exist today in a virtually unexplored jungle in the People’s Republic of the Congo, the researchers said yesterday. Dr. Roy Mackal, a research associate at the University of Chicago, said he believes the animals may be elephant-sized dinosaurs (5). In an article in Science magazine, published by the American Association for the Advancement of Science, the researchers say natives call the creature ‘Mokele-Mbembe. ‘ â€Å"The researchers say they believe it actually may be a dinosaur that looks like a smaller version of the brontosaurus, a giant plant-eater that died out 70 million years ago. Natives shown pictures of many kinds of animals picked illustrations of the brontosaurus as most closely resembling the creatures they say they saw, Mackal said. †Ã‚   Source: Warren E. Leary â€Å"Dinosaurs May Inhabit Remote Jungle. † San Diego Union Tribune, Oct 18, 1980 (Washington date Line). as quoted in  "That their words may be used against them† by Henry Morris, pg. 258) Roy Mackal, an American Biochemist (and evolutionist) has headed several expeditions since 1980 to the Likouala swamp. Mackal has collected numerous eyewitness accounts from the Congo natives. Many live in different locations, yet their descriptions of the creature are the same despite lack of communication with each other. Descriptions of the dinosaurs physical appearance and behavioral traits are consistent with each other. (5)| â€Å"I am not at all convinced it has been proven that the dinosaurs became extinct prior to the advent of man.I believe there is much evidence, ancient and modern, to indicate that dinosaurs and human kind existed on earth contemporaneously, and that human beings, while they probably lived in different regions than dinosaurs for the most part, did on many occasions encounter the sometimes huge and fearsome creatures. The memories of these encounters were so vivid and deep that t hey were passed down in a multitude of cultures as legends, painted on cave walls, represented in pottery, and written of in literature† (Quote from Francis Schaeffer (a well known Christian Historian) .Though most are now gone, I believe that some small species of dinosaurs may still alive today in remote parts of the world. | Works cited page 1. Swift, Dennis. â€Å"More Evidence That Dinosaurs and Man Co-existed ! †Ã‚  Angelfire: Welcome to Angelfire. 2011. Web. 13 Apr. 2011. . 2. â€Å"Men and Dinosaurs Coexisted. †Ã‚  Www. icr. org. Web. 13 Apr. 2011. . 3. Jones, Do-While. â€Å"The Age of Dinosaurs. †Ã‚  Ridgecrest, California – Your Community Portal. June 2004. Web. 13 Apr. 2011. lt;http://www. ridgecrest. ca. us/~do_while/sage/v8i9f. htm>. 4. Keyser, John D. â€Å"Dinosaurs and Man? †Ã‚  Hope of Israel Ministries. Web. 13 Apr. 2011. . 5. â€Å"Mokele-Mbembe Search Living Dinosaurs Dinosaur Embryos Uncovered. †Ã‚  Angelfire: Wel come to Angelfire. Web. 13 Apr. 2011. . 6. Warren E. Leary â€Å"Dinosaurs May Inhabit Remote Jungle. † San Diego Union Tribune, Oct 18, 1980 (Washington date Line) Griffin Bearicks Spring semester 2011 April 13, 2011 Geology 1304 Roger Sigler

Down these mean streets by Thomas Piri Essay

Years after its original publication, Piri Thomas’s Down These Mean Streets remains as powerful, immediate, and shocking as it was when it first stunned readers. In this classic confessional autobiography, firmly in the tradition of Eldridge Cleaver’s Soul on Ice and The Autobiography of Malcolm X, Piri Thomas describes the experience of growing up in the barrio of Spanish Harlem, a labyrinth of lawlessness, drugs, gangs, and crime. The teenaged Piri seeks a place for himself in barrio society by becoming a gang leader, and as he grows up his life spirals into a self-destructive cycle of drug addiction and violence, the same cycle that he sees all around him and hardly knows how to break. Piri is also troubled by a very personal problem: much darker than his brothers and sisters, he decides that he, unlike his siblings, is black, and that he must come to terms with life as a black American. Eventually arrested for shooting two men in an armed robbery, Piri spends six years in Sing and Comstock prisons. With insight and poetry he describes his time in prison, the dreams and emotions that prompted him finally to start life again as a writer, street poet, and performer, and how he became an activist with a passionate commitment to reaching and helping today’s youth. One of the most striking features of Down These Mean Streets is its language. â€Å"It is a linguistic event,† said The New York Times Book Review. â€Å"Gutter language, Spanish imagery and personal poetics†¦mingle into a kind of individual statement that has very much its own sound. † Piri Thomas’s brilliant way with words, his ability to make language come alive on the page, should prove attractive to young people and inspire them to look at writing and literature in fresh new ways. Thirty years ago Piri Thomas made literary history with this lacerating, lyrical memoir of his coming of age on the streets of Spanish Harlem. Here was the testament of a born outsider: a Puerto Rican in English-speaking America; a dark-skinned morenito in a family that refused to acknowledge its African blood. Here was an unsparing document of Thomas’s plunge into the deadly consolations of drugs, street fighting, and armed robbery–a descent that ended when the twenty-two-year-old Piri was sent to prison for shooting a cop. As he recounts the journey that took him from adolescence in El Barrio to a lock-up in Sing to the freedom that comes of self-acceptance, faith, and inner confidence, Piri Thomas gives us a book that is as exultant as it is harrowing and whose every page bears the irrepressible rhythm of its author’s voice. Thirty years after its first appearance, this classic of manhood, marginalisation, survival, and transcendence is available in an anniversary edition with a new Introduction by the author. The questions, assignments, and discussion topics that follow are designed to guide your students as they approach the many issues raised in Down These Mean Streets. The questions of race and culture, of drugs, and of crime and punishment are all treated in the book, and should provide jumping-off points for many fruitful discussions. Another important element of the book is its vivid description of the youth culture of the barrio. Ask your students not only to pay special attention to that culture, but also to compare it with their own, and to look for similarities even when similarities might not be immediately evident. Piri Thomas gained the distance and objectivity to observe his world without prejudice or self-deception; your students should try to do the same. Finally, the students should be encouraged to look at the book not only as a cultural document, but also as a work of literature. Ask them to examine the language Thomas uses, his choice of words, the â€Å"flow† of the story. How does he create his informal tone, his sense of immediacy? This work might help change your students’ ideas about the â€Å"right† way to write, and inspire them to try to find their own individual voices. To what extent is Harlem’s communal code of pride, masculinity, and â€Å"rep† re-created in prison life? How does life inside prison resemble life outside? â€Å"The reasoning that my punishment was deserved was absent. As prison blocks off your body, so it suffocates your mind.† [pp. 255–56] Does this indicate to you an essential fault in the prison system? Do you think that the advice Piri gives Tico about how to deal with Rube is good? Is prison a purely negative experience for Piri, or are there good things about it? Which of the people he meets while in prison enrich and improve his life? Does Piri decide not to join the rioters, or is the decision essentially made for him by the hacks? Why does Chaplin/Muhammed believe that Christianity is the white man’s religion, Islam the black man’s? Do outside or societal factors play a role in Chaplin/ Muhammad’s choice of religions? As he leaves prison, Piri says, â€Å"I am not ever going to be the same. I’m changed all right. † [p. 306] In what ways has Piri changed, and what has changed him? Which of his ideas have been altered by his time in prison? Piri presents himself as a product of his race, culture, and community, but many of his traits are purely his own. How would you describe Piri’s personality? Poppa: What kind of a person is Poppa? What makes him proud, what makes him ashamed? Is he a good or bad father, a good or bad husband? Do you find him sympathetic? Trina: Piri sees Trina as nearly perfect. How would you describe her? Do you think that she behaves passively toward Piri, or does she demonstrate spirit of her own? What do you think of her response to Dulcien’s baby? Brew: How would you describe Brew’s character? What has given him his outlook on life, and how does it differ from Alayce’s? How does he perceive Piri? Why does he agree to go south with Piri? Chaplin/Muhammed: What has made Muhammed hate Christianity? What does Islam mean to him? Piri Thomas uses a number of pungent expressions, both in Spanish and English. How does the language he uses express his character and his world? Write a two-page essay describing one day in your life. Use your own style of talking, and try to be as colloquial as possible. What might your essay tell the reader about you, your friends, and your world? The youth culture in Spanish Harlem to which Piri and his friends belong has certain firm, if unwritten, rules. Would you say the same is true of your own school or neighborhood? What are the rules that govern the behavior of young people you know? What do you feel you have to do to be â€Å"cool,† to be accepted, to belong? Write a short essay describing the social rules your own friend’s follow. Piri is describing a specific period in time: the 1940s. Do you find that the life a family like the Thomas’s lived has changed much since that time? Make a list of the things that have changed for teenagers like Piri, and of the things that have stayed the same. Reference †¢ Down these mean streets by Thomas Piri