Steady-state gain and saturation flux measurements in a high efficiency, electron-beam-pumped, Ar-Xe laser

Flat-top, Ar-Xe laser pulses at 1.73 ,um have been achieved by pumping the laser medium with a constant-current electron beam for pulse durations of up to 2.5 ms. The 220 keV electron beam pumped an active volume of 50X 8X6 cm3 at power loadings of 6-100 W/cm3. Small signal gain, saturation flux, and nonsaturable absorption were determined as a function of Xe concentration, total gas pressure, and pump power density by a Rigrod analysis. In the experimental regime investigated, the small signal gain increased as the total laser pressure decreased and as the partial pressure of Xe decreased. The Xe concentration was varied from 0.5% to 2.0% and the total pressure was varied from 250 to 860 Torr. The results are consistent with Xe quenching of the upper laser level being the dominant deexcitation process and with the collisional broadening dominating the linewidth. The peak intrinsic efficiency observed was 2.2%

Oxidative Stress in Oocytes during Midprophase Induces Premature Loss of Cohesion and Chromosome Segregation Errors

In humans, errors in meiotic chromosome segregation that produce aneuploid gametes increase dramatically as women age, a phenomenon termed the maternal age effect. During meiosis, cohesion between sister chromatids keeps recombinant homologs physically attached and premature loss of cohesion can lead to missegregation of homologs during meiosis I. A growing body of evidence suggests that meiotic cohesion deteriorates as oocytes age and contributes to the maternal age effect. One hallmark of aging cells is an increase in oxidative damage caused by reactive oxygen species (ROS). Therefore, increased oxidative damage in older oocytes may be one of the factors that leads to premature loss of cohesion and segregation errors. To test this hypothesis, we used an RNAi strategy to induce oxidative stress in Drosophila oocytes and measured the fidelity of chromosome segregation during meiosis. Knockdown of either the cytoplasmic or mitochondrial ROS scavenger superoxide dismutase (SOD) caused a significant increase in segregation errors, and heterozygosity for an smc1 deletion enhanced this phenotype. FISH analysis indicated that SOD knockdown moderately increased the percentage of oocytes with arm cohesion defects. Consistent with premature loss of arm cohesion and destabilization of chiasmata, the frequency at which recombinant homologs missegregate during meiosis I is significantly greater in SOD knockdown oocytes than in controls. Together these results provide an in vivo demonstration that oxidative stress during meiotic prophase induces chromosome segregation errors and support the model that accelerated loss of cohesion in aging human oocytes is caused, at least in part, by oxidative damage

Anne E. Perkins, MD Correspondence

Entries include brief biographical information, a typed biographical letter, and handwritten biographical letters on personal stationery from her relatives

Is the incidence of depressive disorders increased following cerebral concussion?

Q: Is the incidence of depressive disorders increased following cerebral concussion? Evidence-based answer: yes, in some populations. Youth and adolescents with self-reported history of concussion had increased risk of depressive disorders (strength of recommendation [SOR]: B, based on a prospective cohort study and a retrospective cohort study). Evidence was inconsistent for college athletes. Athletes with ≥ 3 concussions exhibited more depressive disorders, but no association was observed for those with 1 or 2 concussions compared to nonconcussion injuries (SOR: B, based on a cross-sectional study, a small prospective cohort study, and a case-control study). In semiprofessional and professional athletes, evidence was variable and may be sport related. Retired rugby players with a history of concussion showed no increase in depression compared to controls with no concussion history (SOR: B, based on a case-control study). Retired football players with previous concussions displayed increased incidence of depression, especially after ≥ 3 concussions (SOR: B, based on a prospective cohort study and a small case-control study). There is a significant risk of bias in these studies because of their reliance on self-reported concussions, differing definitions of depression, and possible unmeasured confounders in the study designs, making a causative relationship between concussion and depression unclear.Jason W. Deck, MD; Thomas Kern, MD; LaMont Cavanagh, MD; Matthew Bartow, DO; Franklin T. Perkins III, MD (Department of Family and Community Medicine, OU-TU School of Community Medicine, University of Oklahoma Health Sciences Center, Tulsa); Toni Hoberecht, MA, MLIS, AHIP; Alyssa Migdalski, MLIS (Schusterman Library, University of Oklahoma-Tulsa

Estimating the impact of city-wide Aedes aegypti population control: An observational study in Iquitos, Peru.

During the last 50 years, the geographic range of the mosquito Aedes aegypti has increased dramatically, in parallel with a sharp increase in the disease burden from the viruses it transmits, including Zika, chikungunya, and dengue. There is a growing consensus that vector control is essential to prevent Aedes-borne diseases, even as effective vaccines become available. What remains unclear is how effective vector control is across broad operational scales because the data and the analytical tools necessary to isolate the effect of vector-oriented interventions have not been available. We developed a statistical framework to model Ae. aegypti abundance over space and time and applied it to explore the impact of citywide vector control conducted by the Ministry of Health (MoH) in Iquitos, Peru, over a 12-year period. Citywide interventions involved multiple rounds of intradomicile insecticide space spray over large portions of urban Iquitos (up to 40% of all residences) in response to dengue outbreaks. Our model captured significant levels of spatial, temporal, and spatio-temporal variation in Ae. aegypti abundance within and between years and across the city. We estimated the shape of the relationship between the coverage of neighborhood-level vector control and reductions in female Ae. aegypti abundance; i.e., the dose-response curve. The dose-response curve, with its associated uncertainties, can be used to gauge the necessary spraying effort required to achieve a desired effect and is a critical tool currently absent from vector control programs. We found that with complete neighborhood coverage MoH intra-domicile space spray would decrease Ae. aegypti abundance on average by 67% in the treated neighborhood. Our framework can be directly translated to other interventions in other locations with geolocated mosquito abundance data. Results from our analysis can be used to inform future vector-control applications in Ae. aegypti endemic areas globally