The Many Hats of Sonic Hedgehog Signaling in Nervous System Development and Disease.

Sonic hedgehog (Shh) signaling occurs concurrently with the many processes that constitute nervous system development. Although Shh is mostly known for its proliferative and morphogenic action through its effects on neural stem cells and progenitors, it also contributes to neuronal differentiation, axonal pathfinding and synapse formation and function. To participate in these diverse events, Shh signaling manifests differently depending on the maturational state of the responsive cell, on the other signaling pathways regulating neural cell function and the environmental cues that surround target cells. Shh signaling is particularly dynamic in the nervous system, ranging from canonical transcription-dependent, to non-canonical and localized to axonal growth cones. Here, we review the variety of Shh functions in the developing nervous system and their consequences for neurodevelopmental diseases and neural regeneration, with particular emphasis on the signaling mechanisms underlying Shh action

Seroprevalence of Hepatitis E among Boston Area Travelers, 2009-2010

We determined the prevalence of IgG antibodies to hepatitis E virus (anti-HEV IgG) among travelers attending Boston-area travel health clinics from 2009 to 2010. Pre-travel samples were available for 1,356 travelers, with paired pre- and post-travel samples for 450 (33%). Eighty of 1,356 (6%) pre-travel samples were positive for anti-HEV IgG. Compared with participants who had never lived in nor traveled to a highly endemic country, the pre-travel prevalence odds ratio (POR) of anti-HEV IgG among participants born in or with a history of previous travel to a highly endemic country was increased (POR = 4.8, 95% CI = 2.3–10.3 and POR = 2.6, 95% CI = 1.4–5.0, respectively). Among participants with previous travel to a highly endemic country, anti-HEV IgG was associated with age > 40 years (POR = 3.7, 95% CI = 1.3–10.2) and travel history to ≥ 3 highly endemic countries (POR = 2.7, 95% CI = 1.2–5.9). Two participants may have contracted HEV infection during their 2009–2010 trip

Observation of Coulomb-Assisted Dipole-Forbidden Intraexciton Transitions in Semiconductors

We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum-well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the $1s$ exciton emission, which we attribute to the terahertz-induced $1s$-to-$2p$ excitation. Simultaneously, a pronounced enhancement of the $2s$-exciton emission is observed, despite the $1s$-to-$2s$ transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2$s$ and 2$p$ states, yielding an effective terahertz transition between the 1$s$ and 2$s$ populations.Comment: 5 pages, 3 figure

Many-Body Dynamics and Exciton Formation Studied by Time-Resolved Photoluminescence

The dynamics of exciton and electron-hole plasma populations is studied via time-resolved photoluminescence after nonresonant excitation. By comparing the peak emission at the exciton resonance with the emission of the continuum, it is possible to experimentally identify regimes where the emission originates predominantly from exciton and/or plasma populations. The results are supported by a microscopic theory which allows one to extract the fraction of bright excitons as a function of time.Comment: 11 pages, 5 figure

The choice to report cycling crashes in Denmark: The role of attitudes, norms and perceived difficulty

This study explores the behavioral factors underlying the reporting intentions of cycling accidents. The proposed analytical framework is an adapted version of the Theory of Planned Behavior (TPB), accounting for the linkage between attitudes and the perceived difficulties, in order to understand the barriers impeding cycling accident reporting intentions. The barriers consist of attitudes that accident reporting is useless, preference to allocate time to other activities, concerns about family distress and social image, distrust in the police, and medical consultation aversion. The framework was validated by means of a survey, which yielded 1,512 complete responses from cyclists. The estimated structural equation models revealed: (i) the perceived difficulties are related to reporting intentions, to attitudes that accident reporting is useless, and to the reference to allocate time to other activities; (ii) medical consultation aversion has a higher weight than distrust in the police in demotivating cycling accident reporting intentions; (iii) the latent factors are mainly related to the socio-economic characteristics and the characteristics of the last cycling accident; (iv) information provision regarding the societal benefits of accident reporting is important for increasing the reporting rate

Excitonic Photoluminescence in Semiconductor Quantum Wells: Plasma versus Excitons

Time-resolved photoluminescence spectra after nonresonant excitation show a distinct 1s resonance, independent of the existence of bound excitons. A microscopic analysis identifies excitonic and electron-hole plasma contributions. For low temperatures and low densities the excitonic emission is extremely sensitive to even minute optically active exciton populations making it possible to extract a phase diagram for incoherent excitonic populations.Comment: 9 pages, 4 figure

Public Health Violence Prevention: Supporting Law Enforcement

As frustrations over inequalities in policing and law enforcement continue despite attempted reforms (Beckett, 2016), many are asking for a more effective approach. A 2018 issue statement from the American Public Health Association (2018) highlights that violence is a public health issue that will not go away without the influence of a public health approach. The integrated biological-psychological-social model of health recognizes the complexity in the ways individuals are influenced by their situations, with violence as the unfortunate result of the wrong mix of circumstances. The public health approach to violence focuses on prevention as part of the solution. This fact sheet reviews public health approaches, examples of success, and what needs to happen next to bring public health and law enforcement together