Noise regulation by quorum sensing in low mRNA copy number systems

<p>Abstract</p> <p>Background</p> <p>Cells must face the ubiquitous presence of noise at the level of signaling molecules. The latter constitutes a major challenge for the regulation of cellular functions including communication processes. In the context of prokaryotic communication, the so-called quorum sensing (QS) mechanism relies on small diffusive molecules that are produced and detected by cells. This poses the intriguing question of how bacteria cope with the fluctuations for setting up a reliable information exchange.</p> <p>Results</p> <p>We present a stochastic model of gene expression that accounts for the main biochemical processes that describe the QS mechanism close to its activation threshold. Within that framework we study, both numerically and analytically, the role that diffusion plays in the regulation of the dynamics and the fluctuations of signaling molecules. In addition, we unveil the contribution of different sources of noise, intrinsic and transcriptional, in the QS mechanism.</p> <p>Conclusions</p> <p>The interplay between noisy sources and the communication process produces a repertoire of dynamics that depends on the diffusion rate. Importantly, the total noise shows a non-monotonic behavior as a function of the diffusion rate. QS systems seems to avoid values of the diffusion that maximize the total noise. These results point towards the direction that bacteria have adapted their communication mechanisms in order to improve the signal-to-noise ratio.</p

The interaction of bacterial pathogens with platelets.

In recent years, the frequency of serious cardiovascular infections such as endocarditis has increased, particularly in association with nosocomially acquired antibiotic-resistant pathogens. Growing evidence suggests a crucial role for the interaction of bacteria with human platelets in the pathogenesis of cardiovascular infections. Here, we review the nature of the interactions between platelets and bacteria, and the role of these interactions in the pathogenesis of endocarditis and other cardiovascular diseases

An Investigation of Production Workers’ Performance Variations and the Potential Impact of Attitudes

In most manufacturing systems the contribution of human labour remains a vital element that affects overall performance and output. Workers’ individual performance is known to be a product of personal attitudes towards work. However, in current system design processes, worker performance variability is assumed to be largely insignificant and the potential impact of worker attitudes is ignored. This paper describes a field study that investigated the extent to which workers’ production task cycle times vary and the degree to which such variations are associated with attitude differences. Results show that worker performance varies significantly, much more than is assumed by contemporary manufacturing system designers and that this appears to be due to production task characteristics. The findings of this research and their implications are discussed

Photometric analysis applied in determining facial type

INTRODUCTION: In orthodontics, determining the facial type is a key element in the prescription of a correct diagnosis. In the early days of our specialty, observation and measurement of craniofacial structures were done directly on the face, in photographs or plaster casts. With the development of radiographic methods, cephalometric analysis replaced the direct facial analysis. Seeking to validate the analysis of facial soft tissues, this work compares two different methods used to determining the facial types, the anthropometric and the cephalometric methods. METHODS: The sample consisted of sixty-four Brazilian individuals, adults, Caucasian, of both genders, who agreed to participate in this research. All individuals had lateral cephalograms and facial frontal photographs. The facial types were determined by the Vert Index (cephalometric) and the Facial Index (photographs). RESULTS: The agreement analysis (Kappa), made for both types of analysis, found an agreement of 76.5%. CONCLUSIONS: We concluded that the Facial Index can be used as an adjunct to orthodontic diagnosis, or as an alternative method for pre-selection of a sample, avoiding that research subjects have to undergo unnecessary tests.<br>INTRODUÇÃO: em Ortodontia, a determinação do tipo facial é um elemento-chave na prescrição de um diagnóstico correto. Nos primórdios de nossa especialidade, a observação e a medição das estruturas craniofaciais eram feitas diretamente na face, em fotografias ou em modelos de gesso. Com o desenvolvimento dos métodos radiográficos, a análise cefalométrica foi substituindo a análise facial direta. Visando legitimar o estudo dos tecidos moles faciais, esse trabalho comparou a determinação do tipo facial pelos métodos antropométrico e cefalométrico. MÉTODOS: a amostra constou de sessenta e quatro indivíduos brasileiros, adultos, leucodermas, de ambos os sexos, que aceitaram participar da pesquisa. De todos os indivíduos da amostra foram feitas telerradiografias laterais e fotografias faciais frontais, e os tipos faciais determinados pelo Índice Vert (cefalometricamente) e pelo Índice Facial (fotografias). RESULTADOS: pela análise de concordância (Kappa), feita para os dois tipos de análise, encontramos uma concordância de 76,5%. CONCLUSÕES: foi possível considerar que o Índice Facial pode ser utilizado como um coadjuvante do diagnóstico ortodôntico, ou como método alternativo para pré-seleção de uma amostra, evitando que os sujeitos de pesquisas sejam submetidos a exames desnecessários

Drugs, crime and methadone.

This paper seeks to examine the evidence of causal links between drug -misuse, particularly heroin, and criminal behaviour. While it is generally accepted that such a link*exists, the question is asked whether the treatment of drug misuse has an effect on levels of drug misuse and on criminal activity. The value of methadone treatment as one of several treatment modalities, is examined in this context. The author does not wish to advocate one form of treatment over another but merely to investigate what can be gained from a study of the literature

The Motivational Assessment Tool (Mat) Development And Validation Study

The purpose of the present research is to validate a measure of motivation collimated from an individual’s motivational, affective, and personality traits. The Motivational Assessment Tool (MAT) is being developed to assess multiple variables for an Intelligent Tutoring System (ITS) to deploy individualized adaptations through various levels of learner profiling. This first study factor analyzed a pool of 303 questions aimed at reducing, refining, and developing scales. Overall, the results of the first factor analysis shows that the MAT is composed of 28 factors. The produced scales are supported by correlations with other factors identified in psychology. The MAT is envisioned to provide inputs into an intelligent tutor’s pedagogical strategy to adapt its learning methods to support the learner’s motivational type