Dye laser traveling wave amplifier

A flashlamp pumped dye laser suitable for use as a single stage amplifier is described. Particular emphasis is placed on the efforts to increase output pulse energy and improve the temporal profile of the injected pulse. By using high power thin film polarizers, output energies reach from 4 to 45 mJ. Various dispersive elements are used to develop an amplified pulse with an extremely clean temporal profile

Dye laser traveling wave amplifier

Injection locking was applied to a cavity-dumped coaxial flashlamp pumped dye laser in an effort to obtain nanosecond duration pulses which have both high energy and narrow-linewidth. In the absence of an injected laser pulse, the cavity-dumped dye laser was capable of generating high energy (approx. 60mJ) nanosecond duration output pulses. These pulses, however, had a fixed center wavelength and were extremely broadband (approx. 6nm FWHM). Experimental investigations were performed to determine if the spectral properties of these outputs could be improved through the use of injection-locking techniques. A parametric study to determine the specific conditions under which the laser could be injection-locked was also carried out. Significant linewidth reduction to 0.0015nm) of the outputs was obtained through injection-locking but only at wavelengths near the peak lasing wavelength of the dye. It was found, however; that by inserting weakly dispersive tuning elements in the laser cavity, these narrow-linewidth outputs could be obtained over a wide (24nm) tuning range. Since the tuning elements had low insertion losses, the tunability of the output was obtained without sacrificing output pulse energy

S-Adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated by cAMP and reactivated by NAD+

AbstractPurified S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated when incubated at 25°C with cAMP. Half maximal velocity of the inactivation process occurs at 10 μM cAMP. Catalytic activity is fully restored by further incubation with NAD+, but not with NADP+ or NADH. The enzyme must be preincubated with cAMP or NAD+ to induce inactivation or reactivation, respectively, since neither of these ligands has an effect on the active or inactive enzyme when added directly to the assay. These results suggest a role for cAMP and NAD+ in the regulation of cellular methylation reactions by altering the level of S-adenosyl-L-homocysteine via S-adenosyl-L-homocysteine hydrolase

Changes in Land Cover and Breeding Bird Populations with Restoration of Riparian Habitats in East-central Iowa

Conversion of Midwestern riparian areas for agricultural production has greatly altered their function and suitability for birds and other wildlife. Recently, however, restoration of riparian functions has been a major focus of land management agencies in the Midwest. We used historic land-use data to describe land-cover changes since European settlement and the subsequent effects of habitat restoration efforts on the landscape along a section of the Iowa River in east-central Iowa. We then used bird-density data collected in a subset of the study area in 2001 and 2002 to estimate changes in breeding bird populations of the entire study area resulting from these habitat restoration efforts. Before settlement, the (\u3e24,000 ha) Iowa River Corridor was dominated by herbaceous vegetation (72%), with wooded areas accounting for less than one-third of the area. Between the mid-1800s and 1992, agricultural conversion decreased the amount of herbaceous cover by \u3e75%, and the cover of woody vegetation increased by \u3e25%. After the 1993 flood, establishment of USDA conservation easements increased the amount of herbaceous cover in the corridor by \u3e135% (\u3e5,000 ha). Populations of most grassland and wetland bird species in the corridor (13 of 17) increased with habitat restoration, although some species associated with open habitats, such as those that often breed in rowcrop fields, decreased. We estimated that these restored habitats provide habitat for \u3e12,000 additional birds of grassland- or wetland-dependent species in the Iowa River Corridor, 5,000 of which are members of eight species that are of moderate or high conservation priority. An understanding of presettlement land cover, the extent of land-cover alteration, and the effects of habitat restoration on the landscape and breeding bird populations provides a useful guide for both evaluating the efficacy of past restoration and for guiding future conservation and restoration efforts

ElectroLens: Understanding Atomistic Simulations Through Spatially-resolved Visualization of High-dimensional Features

In recent years, machine learning (ML) has gained significant popularity in the field of chemical informatics and electronic structure theory. These techniques often require researchers to engineer abstract "features" that encode chemical concepts into a mathematical form compatible with the input to machine-learning models. However, there is no existing tool to connect these abstract features back to the actual chemical system, making it difficult to diagnose failures and to build intuition about the meaning of the features. We present ElectroLens, a new visualization tool for high-dimensional spatially-resolved features to tackle this problem. The tool visualizes high-dimensional data sets for atomistic and electron environment features by a series of linked 3D views and 2D plots. The tool is able to connect different derived features and their corresponding regions in 3D via interactive selection. It is built to be scalable, and integrate with existing infrastructure.Comment: accepted to IEEE visualization 2019 conferenc

Genetic variation modifies risk for neurodegeneration based on biomarker status

Background: While a great deal of work has gone into understanding the relationship between CSF biomarkers, brain atrophy, and disease progression, less work has attempted to investigate how genetic variation modifies these relationships. The goal of this study was two-fold. First, we sought to identify high-risk v. low-risk individuals based on their CSF tau and Aβ load and characterize these individuals with regard to brain atrophy in an AD-relevant region of interest. Next, we sought to identify genetic variants that modified the relationship between biomarker classification and neurodegeneration.Methods: Participants were categorized based on established cut-points for biomarker positivity. Mixed model regression was used to quantify longitudinal change in the left inferior lateral ventricle. Interaction analyses between single nucleotide polymorphisms (SNPs) and biomarker group status were performed using a genome wide association study (GWAS) approach. Correction for multiple comparisons was performed using the Bonferroni procedure. Results: One intergenic SNP (rs4866650) and one SNP within the SPTLC1 gene (rs7849530) modified the association between amyloid positivity and neurodegeneration. A transcript variant of WDR11-AS1 gene (rs12261764) modified the association between tau positivity and neurodegeneration. These effects were consistent across the two sub-datasets and explained approximately 3% of variance in ventricular dilation. One additional SNP (rs6887649) modified the association between amyloid positivity and baseline ventricular volume, but was not observed consistently across the sub-datasets.Conclusions: Genetic variation modifies the association between AD biomarkers and neurodegeneration. Genes that regulate the molecular response in the brain to oxidative stress may be particularly relevant to neural vulnerability to the damaging effects of amyloid-β

Randomized clinical trial of the effects of screening and brief intervention for illicit drug use: the Life Shift/Shift Gears study.

BackgroundAlthough screening, brief intervention, and referral to treatment (SBIRT) has shown promise for alcohol use, relatively little is known about its effectiveness for adult illicit drug use. This randomized controlled trial assessed the effectiveness of the SBIRT approach for outcomes related to drug use among patients visiting trauma and emergency departments (EDs) at two large, urban hospitals.MethodsA total of 700 ED patients who admitted using illegal drugs in the past 30 days were recruited, consented, provided baseline measures of substance use and related problems measured with the Addiction Severity Index-Lite (ASI-Lite), and then randomized to the Life Shift SBIRT intervention or to an attention-placebo control group focusing on driving and traffic safety (Shift Gears). Both groups received a level of motivational intervention matched to their condition and risk level by trained paraprofessional health educators. Separate measurement technicians conducted face-to-face follow-ups at 6 months post-intervention and collected hair samples to confirm reports of abstinence from drug use. The primary outcome measure of the study was past 30-day drug abstinence at 6 months post-intervention, as self-reported on the ASI-Lite.ResultsOf 700 participants, 292 (42%) completed follow-up. There were no significant differences in self-reported abstinence (12.5% vs. 12.0% , p = 0.88) for Life Shift and Shift Gears groups, respectively. When results of hair analyses were applied, the abstinence rate was 7 percent for Life Shift and 2 percent for Shift Gears (p = .074). In an analysis in which results were imputed (n = 694), there was no significant difference in the ASI-Lite drug use composite scores (Life Shift +0.005 vs. Shift Gears +0.017, p = 0.12).ConclusionsIn this randomized controlled trial, there was no evidence of effectiveness of SBIRT on the primary drug use outcome.Trial registrationClinicalTrials.gov NCT01683227

Translational approaches to understanding resilience to Alzheimer\u27s disease.

Individuals who maintain cognitive function despite high levels of Alzheimer\u27s disease (AD)-associated pathology are said to be \u27resilient\u27 to AD. Identifying mechanisms underlying resilience represents an exciting therapeutic opportunity. Human studies have identified a number of molecular and genetic factors associated with resilience, but the complexity of these cohorts prohibits a complete understanding of which factors are causal or simply correlated with resilience. Genetically and phenotypically diverse mouse models of AD provide new and translationally relevant opportunities to identify and prioritize new resilience mechanisms for further cross-species investigation. This review will discuss insights into resilience gained from both human and animal studies and highlight future approaches that may help translate these insights into therapeutics designed to prevent or delay AD-related dementia