Introdução - A intoxicação por chumbo é um conhecido problema de saúde pública e o envenenamento por este metal pode causar danos a vários órgãos, especialmente ao Sistema Nervoso Central de crianças em desenvolvimento. Objetivo geral- estudar a associação entre exposição a chumbo e comportamento anti-social (CAS) em adolescentes brasileiros. Objetivos específicos: a) analisar a associação entre exposição a chumbo e CAS / cometimento de atos infracionais (CAI); b) estudar potenciais fontes de exposição domiciliar a chumbo que mais estão associadas a altas concentrações de chumbo no esmalte dentário (CCED) e; c) avaliar o impacto de alterações metodológicas na técnica de microbiópsia ácida de esmalte dentário superficial (MAEDS) sobre CCED e profundidade da bíópsia. Métodos- Um estudo transversal foi conduzido com 173 jovens (Bauru, SP). MAEDS foram realizadas nestes jovens por dois diferentes protocolos metodológicos. Além disso, questionários sobre comportamento dos adolescentes e exposição a possíveis fontes de contaminação por chumbo foram aplicados a pais e adolescentes. Análises de regressão logística, testes de Wilcoxon e testes t pareados foram aplicados aos dados. Resultados- Odd ratios ajustados para covariáveis indicaram que alta CCED está associada a risco aumentado de exceder o escore clínico para queixas somáticas, problemas sociais, comportamento de quebrar regras e problemas externalizantes (IC 95%). Alta CCED não foi associado com escores elevados de CAI. Os fatores de risco mais associados com alta CCED foram residir em área contaminada ou até 2 km da área contaminada e trabalhar na fabricação de tintas, pigmentos, cerâmicas ou baterias. A profundidade da biópsia, calculada pela fórmula da altura do cilindro, para um dos protocolos, levou a resultados errôneos de profundidade da biópsia, confirmados por testes de perfilometria. Conclusões- A exposição a altos níveis de chumbo parece disparar o estabelecimento de CAS, o que alerta para a necessidade de desenvolvimento e implantação de políticas públicas de saúde que previnam o envenenamento da população por chumbo. Adolescentes foram expostos ao chumbo por algumas fontes estudadas, no Brasil. O esmalte dentário é um marcador fidedigno e a MAEDS é bastante útil e confiável. No entanto, CCEDs não podem ser comparadas entre resultados de pesquisas diferentes quando houver qualquer variação metodológica entre os estudos, havendo a necessidade da padronização do procedimento. / Introduction - Lead poisoning is a long known public health problem. Thus, lead exposure may cause damage to diverse organs, especially in the Central Nervous System of children in developing process. Objectives- a) to analyze the association between lead exposure and antisocial / delinquent behavior; b) to study the potential sources of lead home exposure more associated to high dental enamel lead levels (DELL) and c) to evaluate two distinct enamel biopsy protocols in relation to biopsy depth and DELL. Methods- A cross-sectional study was conducted with 173 adolescents (Bauru, SP, Brazil). Surface dental enamel (SDE) etch-acid microbiopsies were performed in upper central incisors of these youths by two different methodological protocols. In addition, questionnaires about adolescents behavior and about possible sources of lead contamination were responded by youths and their parents. Logistic regression, Wilcoxon and paired t tests were applied to data. Results- Odd ratios adjusted for familial and social covariates indicated that high DELL is associated with increased risk of exceeding the clinical score for somatic complaints, social problems, rulebreaking behavior (T70) and externalizing problems (T63) (CI 95%). High DELL was not found to be associated with elevated SRD scores. The risk factors associated to high DELL were residing in contaminated area or close proximity and working in paints, pigments, ceramic or batteries manufacturing. The biopsy depth, calculated by the cylinder formula, for Protocol II induced misleading results, as confirmed by profilometry tests. Conclusions- It seems that exposure to high lead levels can indeed trigger antisocial behavior, which claims for public policies to prevent lead poisoning. Adolescents were exposed to lead, by some studied sources, in Brazil. SDE, measured by etch-acid microbiopsy, is a reliable biomarker, but DELL could not be compared when there is some methodological variation among the studies. A standardization of the procedure is necessary.

Introdução - A intoxicação por chumbo é um conhecido problema de saúde pública e o envenenamento por este metal pode causar danos a vários órgãos, especialmente ao Sistema Nervoso Central de crianças em desenvolvimento. Objetivo geral- estudar a associação entre exposição a chumbo e comportamento anti-social (CAS) em adolescentes brasileiros. Objetivos específicos: a) analisar a associação entre exposição a chumbo e CAS / cometimento de atos infracionais (CAI); b) estudar potenciais fontes de exposição domiciliar a chumbo que mais estão associadas a altas concentrações de chumbo no esmalte dentário (CCED) e; c) avaliar o impacto de alterações metodológicas na técnica de microbiópsia ácida de esmalte dentário superficial (MAEDS) sobre CCED e profundidade da bíópsia. Métodos- Um estudo transversal foi conduzido com 173 jovens (Bauru, SP). MAEDS foram realizadas nestes jovens por dois diferentes protocolos metodológicos. Além disso, questionários sobre comportamento dos adolescentes e exposição a possíveis fontes de contaminação por chumbo foram aplicados a pais e adolescentes. Análises de regressão logística, testes de Wilcoxon e testes t pareados foram aplicados aos dados. Resultados- Odd ratios ajustados para covariáveis indicaram que alta CCED está associada a risco aumentado de exceder o escore clínico para queixas somáticas, problemas sociais, comportamento de quebrar regras e problemas externalizantes (IC 95%). Alta CCED não foi associado com escores elevados de CAI. Os fatores de risco mais associados com alta CCED foram residir em área contaminada ou até 2 km da área contaminada e trabalhar na fabricação de tintas, pigmentos, cerâmicas ou baterias. A profundidade da biópsia, calculada pela fórmula da altura do cilindro, para um dos protocolos, levou a resultados errôneos de profundidade da biópsia, confirmados por testes de perfilometria. Conclusões- A exposição a altos níveis de chumbo parece disparar o estabelecimento de CAS, o que alerta para a necessidade de desenvolvimento e implantação de políticas públicas de saúde que previnam o envenenamento da população por chumbo. Adolescentes foram expostos ao chumbo por algumas fontes estudadas, no Brasil. O esmalte dentário é um marcador fidedigno e a MAEDS é bastante útil e confiável. No entanto, CCEDs não podem ser comparadas entre resultados de pesquisas diferentes quando houver qualquer variação metodológica entre os estudos, havendo a necessidade da padronização do procedimento. / Introduction - Lead poisoning is a long known public health problem. Thus, lead exposure may cause damage to diverse organs, especially in the Central Nervous System of children in developing process. Objectives- a) to analyze the association between lead exposure and antisocial / delinquent behavior; b) to study the potential sources of lead home exposure more associated to high dental enamel lead levels (DELL) and c) to evaluate two distinct enamel biopsy protocols in relation to biopsy depth and DELL. Methods- A cross-sectional study was conducted with 173 adolescents (Bauru, SP, Brazil). Surface dental enamel (SDE) etch-acid microbiopsies were performed in upper central incisors of these youths by two different methodological protocols. In addition, questionnaires about adolescents behavior and about possible sources of lead contamination were responded by youths and their parents. Logistic regression, Wilcoxon and paired t tests were applied to data. Results- Odd ratios adjusted for familial and social covariates indicated that high DELL is associated with increased risk of exceeding the clinical score for somatic complaints, social problems, rulebreaking behavior (T70) and externalizing problems (T63) (CI 95%). High DELL was not found to be associated with elevated SRD scores. The risk factors associated to high DELL were residing in contaminated area or close proximity and working in paints, pigments, ceramic or batteries manufacturing. The biopsy depth, calculated by the cylinder formula, for Protocol II induced misleading results, as confirmed by profilometry tests. Conclusions- It seems that exposure to high lead levels can indeed trigger antisocial behavior, which claims for public policies to prevent lead poisoning. Adolescents were exposed to lead, by some studied sources, in Brazil. SDE, measured by etch-acid microbiopsy, is a reliable biomarker, but DELL could not be compared when there is some methodological variation among the studies. A standardization of the procedure is necessary.

<p>Ricin je prirodni protein, toksin koji spada među najpristupačnije i najsmrtonosnije otrove. Nalazi se u biljci Ricinus (Ricinus communis), sa najvećim sadržajem u semenu (1-5 %). Ricin se smatra potencijalnim bioterorističkim oružjem i prema riziku za ljudsko zdravlje svrstan je u B kategoriju biolo&scaron;kog oružja. U novije vreme kori&scaron;ćen je za konstruisanje imunotoksina protiv tumorskih ćelija u terapiji maligniteta. Dokumentovana su mnoga trovanja ricinom, kako zadesna, tako i samoubilačka i ubilačka. U tu svrhu koristilo se intaktno seme ricinusa ili ekstrahovani ricin. Osim ricina, u semenu ricinusa je prisutan toksični alkaloid ricinin u količini 0.3-0.8 %. Ricinus je jedini poznati prirodni izvor ricinina, koji se ko-ekstrahuje sa ricinom iz semena biljke. Ricinin se jednostavno detektuje u kliničkim uzoracima metodom tečne hromatografije i masene spektrometrije i, s obzirom na komplikovanu identifikaciju ricina u biolo&scaron;kim uzorcima, smatra se biomarkerom za intoksikaciju ricinusom, odnosno ricinom. Osnovni ciljevi ovog istraživanja su da se uz pomoć HS-GC metode i patohistolo&scaron;kom&nbsp; analizom dokaže prisustvo ricinina u krvi laboratorijskih pacova u odnosu na vremenski interval koji je protekao od oralne aplikacije suspenzije do vremena žtvovanja, da se odredi distribucija i koncentracija ricinina u organima laboratorijskih pacova u različitim vremenima žrtvovanja, kao i da se utvrdi da li postoji značajna razlika u razvoju patomorfolo&scaron;kih promena na organima laboratorijskih pacova u različitim vremenima žrtvovanja. Istraživanje je bilo otvoreno, randomizirano i prospektivnog tipa. Laboratorijski pacovi su u istom vremenu oralno tretirani suspenzijom koja je sadržaja subletalnu koncentraciju ricina. Nakon žrtvovanja u precizno definisanim vremenskim intervalima uzeti su uzorci krvi i unutra&scaron;njih organa radi daljih analiza. Odgovarajući uzorci su analizirani metodom HC-GS u cilju određivanja koncentracije i distribucije ricinina, kao pouzdanog markera trovanja ricinom, u krvi i unutra&scaron;njim organima. Takođe je izvr&scaron;ena patohistolo&scaron;ka analiza uzoraka tkiva unutra&scaron;njih organa u cilju utvrđivanja promena izazvanim delovanjem ricina u odnosu na vreme proteklo od aplikacije suspenzije. Dobijeni rezultati su obrađeni odgovarajućim statističkim metodama. Rezultati istraživanja omogućavaju standardizaciju postupaka odabira reprezentativnih uzoraka prilikom sumnje na trovanje ricinusom i metode dokazivanja akutnog trovanja. Na taj način može se pouzdano i efikasno dokazati trovanje ricinusom.</p> / <p>Ricin is a naturally occurring protein, a toxin which belongs to the category of the most accessible and the most lethal poisons. It is obtained from the castor oil plant ( Ricinus communis), whose seeds contain its highest content (1-5%). Ricin is also thought to be a potential weapon of bioterrorism and taking into account the risk for human health, it is classified as a biological weapon category B. Lately it has been used for the construction of the immunotoxins against tumor cells in the therapy of malignant diseases. Numerous poisonings using ricin have been documented, not only accidental poisoning, but also in case of suicides and homicides. In those cases, intact ricin seeds or extracted ricin were used. Apart from ricin, castor oil plants also contain a toxic alkaloid ricinine (0.3-0.8%). Castor oil plants are the only known natural source of ricinine, which is co-extracted with ricin from the seeds of this plant. Ricinine is simply detected in clinical samples by using the method of liquid chromatography and mass spectrometry. Taking into account a complicated identification of ricin in biological samples, it is considered to be a biomarker for the intoxication by castor oil plant, or ricin itself. The main aim of this research is to use the HS-GC method and pathohistological analysis in proving the existence of ricinine in the blood of experimental rats in relation to the time interval between the oral application of solution of castor seeds in water and the time of sacrificing, to determine the distribution and concentration of ricinine in the organs of experimental rats, as well as to establish whether there was a significant difference in the development of pathomorphological changes on the organs of experimental rats at various points of sacrificing. The research was open, randomised and prospective. Experimental rats were simultaneously orally tested by the solution which contained sublethal concentration of ricin. After sacrificing, blood samples were taken from inner organs in specifically defined intervals of time and used for further analysis. The appropriate samples were analysed by HC-GS method in order to determine the concentration and distribution of ricinine as a reliable marker of ricin poisoning in blood and inner organs. Also, pathohistological analysis of the samples of inner organ tissues was made with the purpose of establishing the changes caused by the effects of ricinine in relation to time which passed from the application of the solution. The obtained results were processed by appropriate statistical methods. The results of this research allow for the standardisation of the actions in selecting the representative samples in case there is a possibility of ricin poisoning and the method of proving the acute poisoning. Following these steps, ricin poisoning can be proved in a reliable and an efficient way.</p>

Brodifacoum is a highly effective anticoagulant rodenticide that presents a secondary hazard to some non-target wildlife. The high acute toxicity of brodifacoum to mammals and birds, and its prolonged persistence in liver predicates secondary risk to predators and scavengers of poisoned rodents. Hence there is a need to improve ability to monitor and predict hazards of brodifacoum to non-targets, and optimise use patterns accordingly. Use of a less persistent anticoagulant rodenticide, diphacinone, is an alternative approach currently under investigation in New Zealand. This thesis describes a series of laboratory and pen studies that address information gaps relevant to the assessment of non-target hazards in continued use of brodifacoum, and of using diphacinone as an alternative. Non-lethal techniques for determining sublethal brodifacoum exposure in birds was investigated in chickens. Elevation of prothrombin time was a less reliable index than residual concentrations in tissues. Samples requiring less invasive procedures, such as dried blood spots or faeces, have potential to detect recent sublethal brodifacoum exposure and refinement of these indices could be useful in proactive monitoring of avian wildlife. Residual brodifacoum in eggs of sublethally-exposed hens raised further questions regarding wider non-target hazard and adverse effects on development of fertile eggs or chicks. A laboratory trial with rats found a positive correlation between residual brodifacoum concentrations in liver and the amount of brodifacoum ingested as bait. An estimated 14-22% of ingested brodifacoum was excreted in rat faeces in the period between ingestion of a lethal dose and death, indicating another potentially significant environmental pathway for brodifacoum transfer. In considering diphacinone as a less persistent alternative rodenticide to brodifacoum, evaluation of residual concentrations and persistence in pig tissues was required to estimate secondary hazard to human consumers and adequate with-holding periods for hunting feral pigs in areas where diphacinone was applied. A pen trial showed that domestic pigs were more susceptible to diphacinone toxicity, and thus primary poisoning risk, than previously estimated. Hepatic half-life of diphacinone in pigs was approximately 14 days, indicating reduced persistence in comparison to brodifacoum and enabling estimates of with-holding periods for hunting feral pigs from areas where diphacinone baits were applied. To investigate potential hazards of diphacinone use to invertebrates a trial using tree weta, a native New Zealand invertebrate, was undertaken. Weta readily ate diphacinone wax block baits with no mortality or weight loss evident, indicating low susceptibility. Residual whole-body diphacinone concentrations did not increase with the amount of diphacinone bait eaten. A simple, deterministic risk assessment suggested that, as a single secondary exposure, the maximum diphacinone concentration measured in weta would present a low risk to non-target birds. Given international recognition of the high secondary hazard and corresponding restrictions on use of brodifacoum, continued availability of brodifacoum to non-licensed users and sustained field applications for possum and rodent control in New Zealand is an exceptional use pattern. New data in this thesis suggest that baiting strategies that minimise the amount of brodifacoum available in the environment are important and regulatory review of some New Zealand brodifacoum applications should address this. In parallel, development of diphacinone as an alternative to brodifacoum should continue, as new data here confirms lower persistence in mammalian liver than brodifacoum, and also indicates low toxicity to invertebrates. However further investigation of multiple-exposure hazard and potential sublethal effects of diphacinone on non-target mammals and birds is warranted before extensive and sustained field applications of diphacinone are undertaken.

ABSTRACT Although Cotton Mather, as the official chronicler of the 1692 Salem witch trials, is infamously associated with those events, and excerpts from his apologia on Salem, Wonders of the Invisible World, are widely anthologized today, no annotated critical edition of the entire work has appeared in print since the nineteenth century. This present edition of Wonders seeks to remedy this lacuna in modern scholarship. In Wonders, Mather applies both his views on witchcraft and on millennialism to events at Salem. This edition to Mather's Wonders presents this seventeenth-century text beside an integrated theory of the initial causes of the Salem witch panic. The juxtaposition of the probable natural causes of Salem's bewitchment with Mather's implausible explanations exposes the disingenuousness of his writing about Salem. My theory of what happened at Salem includes the probability that a group of conspirators led by the Rev. Samuel Parris deliberately orchestrated the "witchcraft" and that a plant, the thorn apple, used in Algonquian initiation rites, caused the initial symptoms of bewitchment (39-189). Furthermore, key spectral evidence used at the Salem witch trials and recorded by Mather in Wonders appears to have been generated by intense nightmares, commonly thought at the time to be witch visitations, resulting from what is today termed sleep paralysis (215-310). This dissertation provides a detailed look at some of the testimony given in the Salem court records and in Wonders of the Invisible World as it relates to the interpretation in folklore of the phenomenology of nightmares associated with sleep paralysis. The third chapter of this dissertation focuses extensively on Mather's text as a disingenuous response to the Salem witch trials (320-456). The final section of chapter three posits a "Scythian" or Eurasian connection between Swedish and Salem witchcraft. Similarities in shamanic practices among respective indigenous populations of Lapland, Eurasia, Asia, and New England, caused the devil's involvement in both the visible and invisible worlds to appear more than theoretical to writers like Jose Acosta, Johannes Scheffer, Nicholas Fuller, Joseph Mede, Anthony Horneck, and Cotton Mather, inducing Mather to include a lengthy abstract of the Swedish account in Wonders (404-449).

No description available.

Background and motivation Informal food vending has many benefits that range from food security for the urban poor, to contribution to local economies. Yet, the street food sector is not recognized and is treated as a major public health risk. This is based partly on perceptions of local authorities that street food vendors are undesirable, or are a temporary phenomenon that will disappear in due course as a result of development. Moreover, a number of studies have documented contamination of street foods with pathogenic microorganisms like Staphylococci aureus and enteric organisms. The former can grow and express virulence in foods such as meat and meat products post cooking. To date no participatory risk analysis methods have been applied to informal markets in Tshwane, to study the food value chain of ready-to-eat (RTE) chicken and quantify the risk of exposure to selected foodborne diseases, or to determine predictors for contamination of RTE chicken sold by informal vendors. Methodology A cross-sectional analytical study design was adopted to achieve the objectives of the present study. The study area was city of Tshwane, Gauteng Province, South Africa. The study population was informal vendors selling RTE chicken to commuters at taxi and bus stations and the sampling design involved cluster sampling. Markets were the sampling units and the informal vendors the units of concern. All clusters (n=13) that were identified were included in the study and all informal vendors located within the markets were invited to be part of the study. A total of 237 vendors agreed to be interviewed, have checklists filled in for their vending stalls, and provided a sample of RTE chicken (n= 237) for laboratory analysis. Participatory Risk Analysis, a novel approach to understanding food safety in data scarce environments, was used to collect data for analysis. Participatory research methods employed in this study included: check-lists and structured interviews with informal vendors, proportional piling and focus group discussions. Enumeration of bacterial colonies from RTE chicken samples was performed using 3MTM PetrifilmTM plates (3M, St. Paul. Mn, USA). Data for the demographic profile of vendors (n=237) was analysed using descriptive statistics to establish means and proportions. Thematic analysis combined with descriptive statistical analysis was used to establish and quantify the food value chain of informally traded RTE chicken. Stochastic risk analysis using @Risk 4.5 (Palisade Corp., Ithaca, N.Y.), was used to estimate the risk of staphylococcal food poisoning from consumption of street-vended RTE chicken. Univariable and multivariable regression models were developed using Stata 9.0 (StataCorp, College Station, Texas, USA) to determine predictors for contamination of RTE chicken with E. coli and coliform bacteria respectively. Results The majority of vendors in the markets studied were females (92%), and were between 25-50 years of age. Very few young people (< 25 years) were involved. More than half of the vendors (69.47%) ran the informal food outlet as a personal business. The minority were long term employees (15.04%) or were hired to help out for a short period of time (0.88%). A high level of literacy was observed among informal vendors. Assessment of hygiene practices showed a low level of compliance with regard to possession of a certificate of acceptance, washing of hands and utensils in the same container and controlling flies at the vending site. The environment in which informal vendors operated was not conducive to production of safe food. This means that Key 1 of the WHO five keys to safer food that requires that food production takes place in a clean environment was violated. Contamination of RTE chicken was associated with the use of water collected and supplied in containers of questionable microbiological status. This was because vendors also violated Key 5 of the WHO five keys to safer food, which requires that raw materials, including water used to prepare food should be of a high microbiological quality. However, high compliance was observed with regard to the following aspects: not wearing jewellery while preparing food, using cutlery to pick up RTE chicken, washable floors (concrete slabs and cemented floors), use of potable municipal water, preparing food in a closed structure (temporary or permanent) and locating vending stalls within 30m from the toilets. Four food value chains for RTE chicken, sold by informal vendors, were identified showing extensive cross-over from the formal to informal sector. This extensive cross-over, was corroborated by the fact that over 79.3% of the RTE chicken sold on informal markets in Tshwane metropolis, was sourced from formal markets such as supermarkets or wholesalers. The food value chain for RTE chicken was short, meaning that it involved very few stages from farm to fork. Furthermore the tendency was for the RTE chicken to be purchased, cooked and consumed the same day. Although the prevalence of contamination of RTE chicken with S. aureus was high (44%), the risk of staphylococcal food poisoning was estimated to be only 1.3% (90% CI: 0% - 2.7%) for each meal of RTE chicken consumed. The mean S. aureus counts in the RTE chicken was 103.6 (90% CI: 103.3 – 103.9). This level was lower than the 105 CFU/g needed to induce staphylococcal food poisoning. While contamination of RTE chicken with E. coli (6.32 %) was low, contamination with coliforms (23.21 %) was moderate. This suggests a moderate level of food hygiene. The fly population at the stalls where the RTE was on display, intermittent washing of hands, the location of the stall >30 m from the toilets and holding RTE chicken at <70 C were identified as important predictors of contamination with E. coli. Whereas, the use of potable toilets without hand washing facilities and poor hand washing practices were a positive predictor for contamination with coliforms. Conclusions The informal trade in food in Tshwane is dominated by women and for the majority of these vendors the informal trade in food, is the main source of employment. A risk communication strategy needs to take this into consideration. There is need for intervention to improve the hygiene in the informal markets and ensure that informal vendors observe the WHO five keys to safe food. The high level of literacy observed among informal vendors is good news, as it presents a situation of educated vendors; a fertile ground for initiatives aimed at improving their lives and the service they offer to their customers. There is neither a food policy aimed at ensuring food security for the urban poor nor evidence it is being implemented. This is supported by the high number of vendors operating in temporary structures. There is a need for the municipal authorities to intervene, to provide appropriate structures. Planning of new taxi ranks should include a proper food market, with facilities that meet the legal requirements for production of safe food. Informal vendors have demonstrated an awareness of the need to practice good food hygiene as proved by the compliance with certain hygienic food handling practices. The link between the formal and informal markets suggests that the informal market of RTE chicken is well-established with a reliable source of raw chicken. Furthermore, the strong inter-linkage between the formal and informal value chain for RTE chicken, further confirms the informal sector as a potential market for locally produced product. It also emphasizes its potential to impact on the economy of the city. In addition, this strong inter-linkage, suggests that the risks associated with the formal sector might be mirrored in the informal. Therefore, as the supermarket proliferation takes root in the rest of Africa, this food value chain and its associated risks might become the norm on the continent. The present study shows that participatory risk analysis is a good way to obtain data on informal markets. Such data can then be subjected to quantitative microbial risk analysis using sophisticated biostatistical techniques, to determine and quantify the microbial risks. The low risk of staphylococcal food poisoning proved that despite the poor working conditions under which the informal food vendors prepare food, they are able to produce food that is unlikely to result in food poisoning. However, due to the high prevalence of contamination of RTE chicken with S. aureus, there is a need for the informal vendors in these markets to be trained to improve hygienic food handling practices. On the positive side, the present study demonstrated that high prevalence of contamination does not always translate into high risk. The relatively low to moderate level of contamination with E. coli and coliforms respectively, suggests a low risk of enteric foodborne diseases from ingestion of RTE chicken. Given that some and not all hygiene practices were significantly associated with contamination of RTE chicken, monitoring authorities should emphasise identified predicators to reduce the risk of contamination and the subsequent risk of contracting foodborne diseases. The difference in hygiene scoring highlights that the one-size-fits all approach to monitoring of informal markets may not be effective. These need to be tailored to suit the individual informal markets. / Thesis (PhD)--University of Pretoria, 2015. / tm2015 / Paraclinical Sciences / PhD / Unrestricted

Background: Methanol poisoning is a life-threatening condition which induces acute toxic optic neuropathy with possible long-term visual sequelae in survivors. Aim: To study the prevalence, character, dynamics, and key determinants of chronic morphological and functional visual pathway changes during 4 years after methanol-induced optic neuropathy. Methods: A total of 55 patients with confirmed methanol poisoning with mean age 46.7 ± 3.6 years (46 males and 9 females), and 41 controls were included in this prospective longitudinal cohort study. The patients were examined 4.9 ± 0.6, 25.0 ± 0.6, and 49.9 ± 0.5 months after discharge. The following tests were performed: visual evoked potential (VEP), optical coherence tomography with retinal nerve fiber layer (RNFL) measurement, brain magnetic resonance imaging (MRI), complete ocular examination, biochemical tests, and apolipoprotein E (ApoE) genotyping. Results: Of 42/55 patients with all three consecutive examinations, abnormal RNFL thickness was registered in 13 (31%) and chronic axonal loss during the observation period was found in 10 (24%) patients. The risk estimate of chronic global RNFL loss for arterial blood pH<7.3 at admission was: 11.65 (1.91-71.12; 95% CI) after adjusting for age and sex. The patients with chronic axonal degeneration demonstrated...

<p dir="ltr">Federated Learning (FL), a novel subclass of Artificial Intelligence, decentralizes the learning process by enabling participants to benefit from a comprehensive model trained on a broader dataset without direct sharing of private data. This approach integrates multiple local models into a global model, mitigating the need for large individual datasets. However, the decentralized nature of FL increases its vulnerability to adversarial attacks. These include backdoor attacks, which subtly alter classification in some categories, and byzantine attacks, aimed at degrading the overall model accuracy. Detecting and defending against such attacks is challenging, as adversaries can participate in the system, masquerading as benign contributors. This thesis provides an extensive analysis of the various security attacks, highlighting the distinct elements of each and the inherent vulnerabilities of FL that facilitate these attacks. The focus is primarily on backdoor attacks, which are stealthier and more difficult to detect compared to byzantine attacks. We explore defense strategies effective in identifying malicious participants or mitigating attack impacts on the global model. The primary aim of this research is to evaluate the effectiveness and limitations of existing server-level defenses and to develop innovative defense mechanisms under diverse threat models. This includes scenarios where the server collaborates with clients to thwart attacks, cases where the server remains passive but benign, and situations where no server is present, requiring clients to independently minimize and isolate attacks while enhancing main task performance. Throughout, we ensure that the interventions do not compromise the performance of both global and local models. The research predominantly utilizes 2D and 3D datasets to underscore the practical implications and effectiveness of proposed methodologies.</p>

No description available.