New data on direct ion storage dosemeters

The DIS-1 dosemeter from the Finnish company RADOS is an innovative kind of passive electronic dosemeter for photon and beta radiation. This study examines the 'long-term' linear response behaviour, the calibration and readout accuracy with large samples of 'used' DIS-1 dosemeters especially in the low-dose region, which is of special interest for radiation protection issues. Our measurements prove the adequacy of the DIS-1 dosemeter for long-term-personal dosimetry. The fast and precise readout seems to make the DIS-1 dosemeter an ideal choice for personal dosimetry in low-dose environments.     

Criteria to optimise a dynamic flat detector system used for interventional radiology

An analysis of the relationship between image quality and incident air kerma has been carried out for a dynamic flat detector X-ray system used for interventional radiology. A phantom of polymethyl methacrylate (PMMA) to simulate patients and two different image test objects, Leeds TOR 18FG and NEMA XR 21, were used to evaluate the quality of the obtained images. Measurements were made simulating clinical configuration with different PMMA thicknesses (16, 20, 24 and 28 cm), available fields of view of 22, 31, 42 and 48 cm (diagonal dimension), in the three default fluoroscopy modes and in one of the most used digital subtraction angiography image acquisition modes. The obtained results are being used to help in the optimisation of clinical procedures.     

Precursor system of liquid crystalline phase containing propolis microparticles for the treatment of periodontal disease: development and characterization

Precursor systems of liquid crystalline phase were prepared using the surfactant PPG-5-Ceteth-20, isopropyl myristate, and water; gelatin microparticles containing propolis were then added into these systems. Homogeneity of dispersion, the in-system microparticle morphology, and sedimentation behavior of each formulation were evaluated. The rheological and mechanical properties (hardness, compressibility, and adhesiveness), the work of syringing, and the propolis release profile were also evaluated. All the formulations exhibited pseudoplastic flow and thixotropy, and they displayed storage modulus, loss modulus, dynamic viscosity, and loss tangent that depended on temperature, frequency, and composition. Mechanical properties varied significantly among the formulations being affected by changes in the composition and temperature. Raising the concentration of surfactant and adding propolis microparticles significantly decreased the work of syringing. The drug release was non-Fickian (anomalous) and there was no significant difference between the tested systems in the times required for 10%, 30%, and 50% release of the initial drug loading.     

Group refractive index reconstruction with broadband interferometric confocal microscopy

We propose a novel method of measuring the group refractive index of biological tissues at the micrometer scale. The technique utilizes a broadband confocal microscope embedded into a Mach-Zehnder interferometer, with which spectral interferograms are measured as the sample is translated through the focus of the beam. The method does not require phase unwrapping and is insensitive to vibrations in the sample and reference arms. High measurement stability is achieved because a single spectral interferogram contains all the information necessary to compute the optical path delay of the beam transmitted through the sample. Included are a physical framework defining the forward problem, linear solutions to the inverse problem, and simulated images of biologically relevant phantoms.     

Validation of image segmentation by estimating rater bias and variance

The accuracy and precision of segmentations of medical images has been difficult to quantify in the absence of a 'ground truth' or reference standard segmentation for clinical data. Although physical or digital phantoms can help by providing a reference standard, they do not allow the reproduction of the full range of imaging and anatomical characteristics observed in clinical data.An alternative assessment approach is to compare with segmentations generated by domain experts. Segmentations may be generated by raters who are trained experts or by automated image analysis algorithms. Typically, these segmentations differ due to intra-rater and inter-rater variability. The most appropriate way to compare such segmentations has been unclear.We present here a new algorithm to enable the estimation of performance characteristics, and a true labelling, from observations of segmentations of imaging data where segmentation labels may be ordered or continuous measures. This approach may be used with, among others, surface, distance transform or level-set representations of segmentations, and can be used to assess whether or not a rater consistently overestimates or underestimates the position of a boundary.     

Pressure-dependent structures of amorphous red phosphorus and the origin of the first sharp diffraction peaks

Characterizing the nature of medium-range order (MRO) in liquids and disordered solids is important for understanding their structure and transport properties. However, accurately portraying MRO, as manifested by the first sharp diffraction peak (FSDP) in neutron and X-ray scattering measurements, has remained elusive for more than 80 years. Here, using X-ray diffraction of amorphous red phosphorus compressed to 6.30 GPa, supplemented with micro-Raman scattering studies, we build three-dimensional structural models consistent with the diffraction data. We discover that the pressure dependence of the FSDP intensity and line position can be quantitatively accounted for by a characteristic void distribution function, defined in terms of average void size, void spacing and void density. This work provides a template to unambiguously interpret atomic and void-space MRO across a broad range of technologically promising network-forming materials.     

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)