Multiple scattering of ultrasound in weakly inhomogeneous media: application to human soft tissues

Waves scattered by a weakly inhomogeneous random medium contain a predominant single scattering contribution as well as a multiple scattering contribution which is usually neglected, especially for imaging purposes. A method based on random matrix theory is proposed to separate the single and multiple scattering contributions. The experimental set up uses an array of sources/receivers placed in front of the medium. The impulse responses between every couple of transducers are measured and form a matrix. Single-scattering contributions are shown to exhibit a deterministic coherence along the antidiagonals of the array response matrix, whatever the distribution of inhomogeneities. This property is taken advantage of to discriminate single from multiple-scattered waves. This allows one to evaluate the absorption losses and the scattering losses separately, by comparing the multiple scattering intensity with a radiative transfer model. Moreover, the relative contribution of multiple scattering in the backscattered wave can be estimated, which serves as a validity test for the Born approximation. Experimental results are presented with ultrasonic waves in the MHz range, on a synthetic sample (agar-gelatine gel) as well as on breast tissues. Interestingly, the multiple scattering contribution is found to be far from negligible in the breast around 4.3 MHz.Comment: 35 pages, 11 figures, final version, contains the appendix of the original articl

Organizational stressors associated with job stress and burnout in correctional officers: a systematic review.

BackgroundIn adult correctional facilities, correctional officers (COs) are responsible for the safety and security of the facility in addition to aiding in offender rehabilitation and preventing recidivism. COs experience higher rates of job stress and burnout that stem from organizational stressors, leading to negative outcomes for not only the CO but the organization as well. Effective interventions could aim at targeting organizational stressors in order to reduce these negative outcomes as well as COs' job stress and burnout. This paper fills a gap in the organizational stress literature among COs by systematically reviewing the relationship between organizational stressors and CO stress and burnout in adult correctional facilities. In doing so, the present review identifies areas that organizational interventions can target in order to reduce CO job stress and burnout.MethodsA systematic search of the literature was conducted using Medline, PsycINFO, Criminal Justice Abstracts, and Sociological Abstracts. All retrieved articles were independently screened based on criteria developed a priori. All included articles underwent quality assessment. Organizational stressors were categorized according to Cooper and Marshall's (1976) model of job stress.ResultsThe systematic review yielded 8 studies that met all inclusion and quality assessment criteria. The five categories of organizational stressors among correctional officers are: stressors intrinsic to the job, role in the organization, rewards at work, supervisory relationships at work and the organizational structure and climate. The organizational structure and climate was demonstrated to have the most consistent relationship with CO job stress and burnout.ConclusionsThe results of this review indicate that the organizational structure and climate of correctional institutions has the most consistent relationship with COs' job stress and burnout. Limitations of the studies reviewed include the cross-sectional design and the use of varying measures for organizational stressors. The results of this review indicate that interventions should aim to improve the organizational structure and climate of the correctional facility by improving communication between management and COs

ABC transporters and azole susceptibility in laboratory strains of the wheat pathogen Mycosphearella graminicola

Laboratory strains of Mycosphaerella graminicola with decreased susceptibilities to the azole antifungal agent cyproconazole showed a multidrug resistance phenotype by exhibiting cross-resistance to an unrelated chemical, cycloheximide or rhodamine 6G, or both. Decreased azole susceptibility was found to be associated with either decreased or increased levels of accumulation of cyproconazole. No specific relationship could be observed between azole susceptibility and the expression of ATP-binding cassette (ABC) transporter genes MgAtr1 to MgAtr5 and the sterol P450 14-demethylase gene, CYP51. ABC transporter MgAtr1 was identified as a determinant in azole susceptibility since heterologous expression of the protein reduced the azole susceptibility of Saccharomyces cerevisiae and disruption of MgAtr1 in one specific M. graminicola laboratory strain with constitutive MgAtr1 overexpression restored the level of susceptibility to cyproconazole to wild-type levels. However, the level of accumulation in the mutant with an MgAtr1 disruption did not revert to the wild-type level. We propose that variations in azole susceptibility in laboratory strains of M. graminicola are mediated by multiple mechanisms

Formation of thin films of organic-inorganic perovskites for high-efficiency solar cells

Organic-inorganic perovskites are currently one of the hottest topics in photovoltaic (PV) research, with power conversion efficiencies (PCEs) of cells on a laboratory scale already competing with those of established thin-film PV technologies. Most enhancements have been achieved by improving the quality of the perovskite films, suggesting that the optimization of film formation and crystallization is of paramount importance for further advances. Here, we review the various techniques for film formation and the role of the solvents and precursors in the processes. We address the role chloride ions play in film formation of mixed-halide perovskites, which is an outstanding question in the field. We highlight the material properties that are essential for high-efficiency operation of solar cells, and identify how further improved morphologies might be achieved

Mobile Robot Navigation Under Pose Uncertainty in Unknown Environments

The navigation of a mobile robot under uncertainty in its pose information in an unknown environment is the subject of this paper. The mobile robot is equipped with a limited-field of view limited-range finder and a magnetometer to infer its orientation. The target location is known, while the robot’s localization suffers from measurement errors. The uncertainty is taken into consideration by calculation of the Guaranteed Visibility and Guaranteed Sensed Area, where safe navigation can be assumed regardless of the measurement error. A switching objective function initially guarantees the exploration towards the target area and afterwards safely guides the robot towards it. Simulation results that prove the efficiency of the proposed scheme are presented.<br/

How did a Housing First intervention improve health and social outcomes among homeless adults with mental illness in Toronto? Two-year outcomes from a randomised trial.

OBJECTIVES: We studied the impact of a Housing First (HF) intervention on housing, contact with the justice system, healthcare usage and health outcomes among At Home/Chez Soi randomised trial participants in Toronto, a city with an extensive service network for social and health services for individuals who are experiencing homelessness and mental illness. METHODS: Participants identified as high needs were randomised to receive either the intervention which provided them with housing and supports by an assertive community treatment team (HF+ACT) or treatment as usual (TAU). Participants (N=197) had in-person interviews every 3 months for 2 years. RESULTS: The HF+ACT group spent more time stably housed compared to the TAU group with the mean difference between the groups of 45.8% (95% CI 37.1% to 54.4%, p<0.0001). Accounting for baseline differences, HF+ACT group showed significant improvements over TAU group for community functioning, selected quality-of-life subscales and arrests at some time points during follow-up. No differences between HF+ACT and TAU groups over the follow-up were observed for health service usage, community integration and substance use. CONCLUSIONS: HF for individuals with high levels of need increased housing stability and selected health and justice outcomes over 2 years in a city with many social and health services. TRIAL REGISTRATION NUMBER: ISRCTN42520374