Computer-aided detection of temporal clusters of organisms reported to the Communicable Disease Surveillance Centre

This article describes a computer system developed to assist in the identification of temporal clusters among the several hundred different organisms reported each week to the PHLS Communicable Disease Surveillance Centre. A threshold value is calculated for each organism on the basis of past reports. Organisms in excess of their threshold are identified for further investigation. The calculation of the thresholds allows for past outbreaks, long-term trends, and scatter in the data.     

Investigating causation in cancer clusters

A case of 19 year old male with hydrocephalus is reported whose aggressive self-injurious behaviors were resistant to conventional pharmacotherapy but successfully treated by trazodone. In addition to the self-injurious behaviors, this patient displayed withdrawal and eating refusal, which initially resulted in his admission to a psychiatric ward. Various conventional treatments with pharmacotherapy (e.g., tricyclic antidepressants, antipsychotics, anxiolytics and anticonvulsants) in combination with psychotherapy and family therapy proved not to be effective for 15 months. Neither was electroconvulsive therapy successful. Administration of trazodone for 5 months after tapering of the above agents improved his aggressive behaviors. A survey of previous cases with organic brain syndromes who had aggressive behaviors and responded well to trazodone revealed that most of the cases were aged individuals and that cases in adolescence are rare.     

Genetic variation in heterogeneous environments

A model of population structure in heterogeneous environments is described and conditions sufficient for maintaining a polymorphism are derived. The absolute fitness of any genotype is regarded as a function of location in the niche space and the population density at that location. Two modes of habitat selection are examined: (1) organisms are distributed uniformly over the environment; and (2) each organism selects to occupy that habitat in which it is most fit ("optimal habitant selection"). Sufficient conditions for maintenance of genetic polymorphisms are derived for both models. In populations which do not practice habitat selection heterozygote superiority averaged over the environment is sufficient to guarantee the existence of polymorphisms. Comparable conditions for populations which practice optimal habitat selction are much less restrictive. If the heterozygotes are superior to one homozygote in any one part of the niche and to the other homozygote in any other part of the niche then a polymorphism will be defined. A positive correlation between genetic and environmental variation follows from the model with habitat selection, but not from the other. The adaptive significance of polymorphisms thus depends on how animals behave.     

Biofilms in food processing environments

Biofilms are a constant concern in food processing environments. Our overall research focus has been to understand the interaction of factors affecting bacterial attachment and biofilm formation with the ultimate goal of devising strategies to control this problem. This paper briefly describes three areas of biofilm research in which we have been involved. Listeria monocytogenes, a foodborne pathogen, survived for prolonged periods on stainless steel and buna-n rubber, materials commonly used in food-processing equipment. Survival was affected by temperature, relative humidity, attachment surface, and soil. Some components in the rubber inhibited growth of the organism on buna-n, which also affected the efficacy of sanitizers on biofilm inactivation. In cheese manufacture, biofilms of Lactobacillus curvatus could lead to a defect caused by the formation of calcium lactate crystals in Cheddar cheese. This hardy organism persisted in low numbers on equipment surfaces and was difficult to eradicate. We investigated the relative contributions and interactions of mechanical, thermal, and chemical processes in an air-injected clean-in-place method for milking systems. Overall, it is important to study the interactions between bacteria and the surfaces in a specific food processing environment to provide more effective measures for prevention of biofilm formation and for its removal.     

Mobility of interstitial clusters in alpha-zirconium

Clusters of self-interstitial atoms (SIAs) formed in displacement cascades in metals irradiated with energetic particles play an important role in microstructure evolution under irradiation. They have been studied in the fcc and bcc metals by atomic-scale computer simulation, and in this article, we present the results of a similar study in a hexagonal close-packed (hcp) crystal. Static and dynamic properties of clusters of up to 30 SIAs were studied using a many-body Finnis-Sinclair type interatomic potential for Zr. The results show a qualitative similarity of some properties of clusters to those for cubic metals. In particular, all clusters larger than four SIAs exhibit fast thermally activated one-dimensional (1-D) glide, which is in a <1120> direction in the hcp lattice. Due to the structure of the hcp lattice, this mechanism leads to two-dimensional mass transport in basal planes. Some clusters exhibit behavior peculiar to the hcp structure, for they can migrate two-dimensionally (2-D) in the basal plane. The jump frequency, activation energy, and correlation factors of clusters have been estimated, and comparisons drawn between the behavior of SIA clusters in different structures. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.     

Groupness and adherence in structured exercise settings.

This study examined the relationship between groupness and self-reported exercise adherence. Exercise participants (N = 86) recalled a structured setting where they had been active with others during the last six months. To capture groupness, five group variables (i.e., common fate, mutual benefit, social structure, group processes, and self-categorization) were assessed. Indicators of self-reported adherence were participant's recall of frequency (times/month) and percent attendance in a specified structured exercise setting. Results from structural equation modeling revealed an acceptable fit: χ2 = 18.89, p > .05, Root Mean Square Error of Approximation (RMSEA) = 0.075, Comparative Fit Index (CFI) = 0.95 for the hypothesized model. Groupness was positively related to self-reported adherence explaining 20% of the variance in adherence. These findings provide preliminary support for the idea that perceiving a collection of exercise participants as being more like a group may be associated with adherence in a structured exercise setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence and reward in structured two-person interactions.

8 pairs of Ss were run in each of 4 different dyadic reward systems using a continuous response task. The 2 Ss within each pair were made interdependent in their rewards by imposing a functional relationship between the responses made by one S and the outcomes delivered to the other S, and vice versa. Each pair was given 100 consecutive trials. 3 influence responses were appended to the task for 4 of the 8 pairs in each reward system. These appended responses permitted an S to communicate a request to the other S concerning the latter's continuous response on the next trial. Results from systems with no communication confirm the predictions of reward stability based on a stochastic model. Without communication, 1 of the 4 systems stabilize; with communication, 2 systems stabilize. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mobility of interstitial clusters in alpha-zirconium

Clusters of self-interstitial atoms (SIAs) formed in displacement cascades in metals irradiated with energetic particles play an important role in microstructure evolution under irradiation. They have been studied in the fcc and bcc metals by atomic-scale computer simulation, and in this article, we present the results of a similar study in a hexagonal close-packed (hcp) crystal. Static and dynamic properties of clusters of up to 30 SIAs were studied using a many-body Finnis-Sinclair type interatomic potential for Zr. The results show a qualitative similarity of some properties of clusters to those for cubic metals. In particular, all clusters larger than four SIAs exhibit fast thermally activated one-dimensional (1-D) glide, which is in a 〈11 0〉 direction in the hcp lattice. Due to the structure of the hcp lattice, this mechanism leads to two-dimensional mass transport in basal planes. Some clusters exhibit behavior peculiar to the hcp structure, for they can migrate two-dimensionally (2-D) in the basal plane. The jump frequency, activation energy, and correlation factors of clusters have been estimated, and comparisons drawn between the behavior of SIA clusters in different structures. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.