Likelihood-based estimation of continuous-time epidemic models from time-series data: application to measles transmission in London

We present a new statistical approach to analyse epidemic time-series data. A major difficulty for inference is that (i) the latent transmission process is partially observed and (ii) observed quantities are further aggregated temporally. We develop a data augmentation strategy to tackle these problems and introduce a diffusion process that mimics the susceptible-infectious-removed (SIR) epidemic process, but that is more tractable analytically. While methods based on discrete-time models require epidemic and data collection processes to have similar time scales, our approach, based on a continuous-time model, is free of such constraint. Using simulated data, we found that all parameters of the SIR model, including the generation time, were estimated accurately if the observation interval was less than 2.5 times the generation time of the disease. Previous discrete-time TSIR models have been unable to estimate generation times, given that they assume the generation time is equal to the observation interval. However, we were unable to estimate the generation time of measles accurately from historical data. This indicates that simple models assuming homogenous mixing (even with age structure) of the type which are standard in mathematical epidemiology miss key features of epidemics in large populations.     

Older adults prefer less choice than young adults.

Previous research has demonstrated that older adults prefer less autonomy and seek less information when making decisions on their own relative to young adults (for a review, see M. Mather, 2006). Would older adults also prefer fewer options from which to choose? The authors tested this hypothesis in the context of different decision domains. Participants completed a choice preferences survey in which they indicated their desired number of choices across 6 domains of health care and everyday decisions. The hypothesis was confirmed across all decision domains. The authors discuss implications from these results as they relate to theories of aging and health care policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The responsive bystander: How social group membership and group size can encourage as well as inhibit bystander intervention.

Four experiments explored the interaction of group size, social categorization, and bystander behavior. In Study 1, increasing group size inhibited intervention in a street violence scenario when bystanders were strangers but encouraged intervention when bystanders were friends. Study 2 replicated and extended these findings to social category members. When gender identity was salient, group size encouraged intervention when bystanders and victim shared social category membership. In addition, group size interacted with context-specific norms that both inhibit and encourage helping. Study 3 used physical co-presence and gender identities to examine these social category effects. Increasing group size of women produced greater helping of a female victim, but increasing group size of men did not. Additionally, increasing numbers of out-group bystanders resulted in less intervention from women but more intervention from men. Study 4 replicated these findings with a measure of real-life helping behavior. Taken together, the findings indicate that the bystander effect is not a generic consequence of increasing group size. When bystanders share group-level psychological relationships, group size can encourage as well as inhibit helping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficacy of an organization skills intervention to improve the academic functioning of students with attention-deficit/hyperactivity disorder.

Children with attention-deficit/hyperactivity disorder (ADHD) exhibit significant academic impairments, as evidenced by poor academic achievement, grade retention, and school dropout. Deficits in organization skills may contribute to these academic impairments, as children with ADHD frequently lose assignments, misplace their completed work, and have difficulty planning for tests. The present study examined the pilot efficacy of an 8-week organization skills intervention for children with ADHD. Thirty-seven children were randomly assigned to receive the intervention immediately or to a wait-list control. Participants made significant improvements in organization and homework management skills during the intervention and these gains were maintained at 8-week follow-up. Parents of children in the intervention group reported decreased homework problems. Children in the intervention group also demonstrated pre-post gains on teacher ratings of academic impairment and GPA. This study suggests that targeted academic skills interventions have the potential to improve overall academic performance among children with ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Improving the clinical potential of ultra-high field fMRI using a model-free analysis method based on response consistency

Objective

To develop an analysis method that is sensitive to non-model-conform responses often encountered in ultra-high field presurgical planning fMRI. Using the consistency of time courses over a number of experiment repetitions, it should exclude low quality runs and generate activation maps that reflect the reliability of responses.

Materials and methods

7 T fMRI data were acquired from six healthy volunteers: three performing purely motor tasks and three a visuomotor task. These were analysed with the proposed approach (UNBIASED) and the GLM.

Results

UNBIASED results were generally less affected by false positive results than the GLM. Runs that were identified as being of low quality were confirmed to contain little or no activation. In two cases, regions were identified as activated in UNBIASED but not GLM results. Signal changes in these areas were time-locked to the task, but were delayed or transient.

Conclusion

UNBIASED is shown to be a reliable means of identifying consistent task-related signal changes regardless of response timing. In presurgical planning, UNBIASED could be used to rapidly generate reliable maps of the consistency with which eloquent brain regions are activated without recourse to task timing and despite modified hemodynamics.

     

The traveling heads: multicenter brain imaging at 7 Tesla

Objective

This study evaluates the inter-site and intra-site reproducibility of 7 Tesla brain imaging and compares it to literature values for other field strengths.

Materials and methods

The same two subjects were imaged at eight different 7 T sites. MP2RAGE, TSE, TOF, SWI, EPI as well as B1 and B0 field maps were analyzed quantitatively to assess inter-site reproducibility. Intra-site reproducibility was measured with rescans at three sites.

Results

Quantitative measures of MP2RAGE scans showed high agreement. Inter-site and intra-site reproducibility errors were comparable to 1.5 and 3 T. Other sequences also showed high reproducibility between the sites, but differences were also revealed. The different RF coils used were the main source for systematic differences between the sites.

Conclusion

Our results show for the first time that multi-center brain imaging studies of the supratentorial brain can be performed at 7 T with high reproducibility and similar reliability as at 3T. This study develops the basis for future large-scale 7 T multi-site studies.

     

Paralytic shellfish poisoning detection by surface plasmon resonance-based biosensors in shellfish matrixes

The detection of paralytic shellfish poisoning (PSP) toxins in contaminated shellfish is essential for human health preservation. Ethical and technical reasons have prompted the search for new detection procedures as an alternative to the mouse bioassay. On the basis of the detection of molecular interactions by surface plasmon resonance (SPR) biosensors, an inhibition assay was developed using an anti-GTX2/3 antibody (GT13-A) and a saxitoxin-CM5 chip. This assay allowed for quantification of saxitoxin (STX), decarbamoyl saxitoxin (dcSTX), gonyautoxin 2,3 (GTX2/3), decarbamoyl gonyautoxin 2,3 (dcGTX2/3), gonyautoxin 5 (GTX5), and C 1,2 (C1/2) at concentrations from 2 to 50 ng/mL. The interference of five shellfish matrixes with the inhibition assay was analyzed. Mussels, clams, cockles, scallops, and oysters were extracted with five published methods. Ethanol extracts and acetic acid/heat extracts (AOAC Lawrence method) performed adequately in terms of surface regeneration and baseline interference, did not inhibit antibody binding to the chip surface significantly, and presented STX calibration curves similar to buffer controls in all matrixes tested. Hydrochloric acid/heat extracts (AOAC mouse bioassay method) presented surface regeneration problems, and although ethanol-acetic acid/dichloromethane extracts performed well, they were considered too laborious for routine sample testing. Overall the best results were obtained with the ethanol extraction method with calibration curves prepared in blank matrix extracts. STX recovery rate with the ethanol extraction method was 60.52+/-3.72%, with variations among species. The performance of this biosensor assay in natural samples, compared to two AOAC methods for PSP toxin quantification (mouse bioassay and HPLC), suggests that this technology can be useful as a PSP screening assay. In summary, the GT13-A-STX chip inhibition assay is capable of PSP toxin detection in ethanol shellfish extracts, with sufficient sensitivity to quantify the toxin in the range of the European regulatory limit of 80 microg/100 g of shellfish meat.     

Three-dimensional time-resolved optical mammography of the uncompressed breast

Optical tomography is being developed as a means of detecting and specifying disease in the adult female breast. We present a series of clinical three-dimensional optical images obtained with a 32-channel time-resolved system and a liquid-coupled interface. Patients place their breasts in a hemispherical cup to which sources and detectors are coupled, and the remaining space is filled with a highly scattering fluid. A cohort of 38 patients has been scanned, with a variety of benign and malignant lesions. Images show that hypervascularization associated with tumors provides very high contrast due to increased absorption by hemoglobin. Only half of the fibroadenomas scanned could be observed, but of those that could be detected, all but one revealed an apparent increase in blood volume and a decrease in scatter and oxygen saturation.     

Development of a miniature calorimeter for identification and detection of explosives and other energetic compounds

The development of versatile systems capable of providing rapid, portable, and inexpensive detection of explosives and energetic compounds are critically needed to offer enhanced levels of protection against current and future threats to homeland security, as well as satisfying a wide range of applications in the fields of forensic analysis, emergency response, and industrial hazards analysis. Calorimetric techniques have been largely overlooked in efforts to develop advanced chemical analysis technology, largely because of limitations associated with the physical size of the instruments and the relatively long timescales (>30 min) required to obtain a result. This miniaturized calorimeter circumvents these limitations, thereby creating a first-of-its-kind system allowing thermal analysis to be performed in a portable format that can be configured for use in a variety of field operations with a significantly reduced response time (approximately 2 min). Unlike current explosives detectors, this system is based on calorimetric techniques that are inherently capable of providing direct measurements of energy release potential and therefore do not depend on prior knowledge of familiar compounds.