Gain spectroscopy of a type-II VECSEL chip

Using optical pump-white light probe spectroscopy the gain dynamics is investigated for a VECSEL chip which is based on a type-II heterostructure. The active region the chip consists of a GaAs/(GaIn)As/Ga(AsSb)/(GaIn)As/GaAs multiple quantum well. For this structure, a fully microscopic theory predicts a modal room temperature gain at a wavelength of 1170 nm, which is confirmed by experimental spectra. The results show a gain buildup on the type-II chip which is delayed relative to that of a type-I chip. This slower gain dynamics is attributed to a diminished cooling rate arising from reduced electron-hole scattering.Comment: 4 pages, 4 figure

Snowmass 2001: Jet Energy Flow Project

Conventional cone jet algorithms arose from heuristic considerations of LO hard scattering coupled to independent showering. These algorithms implicitly assume that the final states of individual events can be mapped onto a unique set of jets that are in turn associated with a unique set of underlying hard scattering partons. Thus each final state hadron is assigned to a unique underlying parton. The Jet Energy Flow (JEF) analysis described here does not make such assumptions. The final states of individual events are instead described in terms of flow distributions of hadronic energy. Quantities of physical interest are constructed from the energy flow distribution summed over all events. The resulting analysis is less sensitive to higher order perturbative corrections and the impact of showering and hadronization than the standard cone algorithms.Comment: REVTeX4, 13 pages, 6 figures; Contribution to the P5 Working Group on QCD and Strong Interactions at Snowmass 200

Types of Stickiness in BHV Phylogenetic Tree Spaces and Their Degree

It has been observed that the sample mean of certain probability distributions in Billera-Holmes-Vogtmann (BHV) phylogenetic spaces is confined to a lower-dimensional subspace for large enough sample size. This non-standard behavior has been called stickiness and poses difficulties in statistical applications when comparing samples of sticky distributions. We extend previous results on stickiness to show the equivalence of this sampling behavior to topological conditions in the special case of BHV spaces. Furthermore, we propose to alleviate statistical comparision of sticky distributions by including the directional derivatives of the Fr\'echet function: the degree of stickiness.Comment: 8 Pages, 1 Figure, conference submission to GSI 202

The impact of a history of child abuse on cognitive performance:a cross-sectional study in older patients with a depressive, anxiety, or somatic symptom disorder

Background: Child abuse is a major global burden with an enduring negative impact on mental and physical health. A history of child abuse is consistently associated with worse cognitive performance among adults; data in older age groups are inconclusive. Since affective symptoms and cognitive functioning are interrelated among older persons, a synergistic effect can be assumed in patients with affective symptoms who also have suffered from child abuse. This study examines the association between a history of child abuse and cognitive performance in such patients. Methods: Cross-sectional data were collected from the ‘Routine Outcome Monitoring for Geriatric Psychiatry & Science’ project, including 179 older adults (age 60–88 years) with either a unipolar depressive, any anxiety, or somatic symptom disorder referred to specialized geriatric mental health care. A history of physical, sexual, and psychological abuse, and emotional neglect was assessed with a structured interview. Cognitive functioning was measured with three paper and pencils tests (10-words verbal memory test, Stroop Colour-Word test, Digit Span) and four tests from the computerized Cogstate Test Battery (Detection Test, Identification Test, One Card Learning Test, One Back Test). The association between a history of child abuse and cognitive performance was examined by multiple linear regression analyses adjusted for covariates. Results: Principal component analyses of nine cognitive parameters revealed four cognitive domains, i.e., visual-verbal memory, psychomotor speed, working memory and interference control. A history of child abuse was not associated with any of these cognitive domains. However, when looking at the specific types of child abuse separately, a history of physical abuse and emotional neglect were associated with poorer interference control. A history of physical abuse was additionally associated with better visual-verbal memory. Conclusions: The association between a history of child abuse and cognitive performance differs between the different types of abuse. A history of physical abuse might particularly be a key determinant of cognitive performance in older adults with a depressive, anxiety, or somatic symptom disorder. Future studies on the impact of these disorders on the onset of dementia should take child abuse into account. Trial registration: ROM-GPS is registered at the Dutch Trial Register (NL6704 at www.trialregister.nl)

Impact of childhood trauma on multidimensional frailty in older patients with a unipolar depressive-, anxiety- or somatic symptom

Item does not contain fulltextObjectives: Frailty marks an increased risk for adverse health outcomes. Since childhood trauma is associated with the onset of physical and mental health diseases during the lifespan, we examined the link between childhood trauma and multidimensional frailty. Method: A cross-sectional study embedded in a clinical cohort study (ROM-GPS) of older (>=60 years) patients (n=182) with a unipolar depressive-, anxiety- and/or somatic symptom disorder according to DSM-criteria referred to specialized geriatric mental health care. Frailty was assessed with the Tilburg Frailty Indicator (TFI), comprising a physical, psychological, and social dimension. Physical, sexual and psychological abuse and emotional neglect before the age of 16 years was measured with a structured interview. Results: Of 182 patients, 103 (56.6%) had experienced any childhood trauma and 154 (84.6%) were frail (TFI sum score >=5). Linear regression analyses, adjusted for lifestyle, psychological and physical-health factors, showed that the presence of any type of childhood trauma was not associated with the TFI sum score, however when considered separately, physical abuse was (ß=0.16, p=.037). Regarding the specific frailty dimensions, any childhood trauma was associated with social frailty (ß=0.18, p=.019), with emotional neglect as main contributor. Conclusion: These findings demonstrate a complex link between different types of childhood trauma and multidimensional frailty among older psychiatric patients. Regarding the three dimensions of frailty, social frailty seems most affected by childhood trauma. This may have been underestimated until now and should receive more attention in clinical care and future research.7 p

Atomic structure and segregation in alkali-metal heteroclusters

The ground-state atomic and electronic distributions in NamCsn clusters with composition m=n and m=2n have been calculated by minimizing the total cluster energy using the density-functional formalism. The approximation is made by replacing the total external potential of the ions by its spherical average around the cluster center during the iterative process of solving the Kohn-Sham equations for each geometry tested. In the size range studied here (up to 90 atoms per cluster), the cluster is composed of well-separated homoatomic Na and Cs shells, the external one always being a Cs shell. We have also found that the cohesive energy goes rapidly to the bulk limit. An analysis of the geometries shows strong cluster reconstruction with increasing size. By comparing the geometry of pure Nan with that of the Nan core in NanCsn for clusters formed by only an inner Na layer and an outer Cs layer, we have observed that the Nan core adopts a geometry different in most cases from that of the free Nan cluster, and such that the number of faces of the polyhedron formed by the Nan core is as close as possible to the number of external Cs atoms, in order to accomodate these Cs atoms on top of the faces of the polyhedron

A Checklist of the Vascular Flora of Lee County, Iowa

The vascular flora of Lee County, Iowa, based upon field and herbarium study, is composed of 876 taxa (species plus hybrids), including 25 endangered and 5 threatened Iowa species. Naturalized species totaled 154. The study added 318 species to the county flora, a 57% increase to the flora of what had been called one of lowa\u27s best collected counties. Two species are reported as additions to the state flora: Habenaria lacera (Michx.) Lodd. and Vitis baileyana Munson. The flora is most notable for the presence of many species which do not occur much farther northward in Iowa, being plants with floristic affinity to the Ozark Plateau in Missouri

Quantization and Compressive Sensing

Quantization is an essential step in digitizing signals, and, therefore, an indispensable component of any modern acquisition system. This book chapter explores the interaction of quantization and compressive sensing and examines practical quantization strategies for compressive acquisition systems. Specifically, we first provide a brief overview of quantization and examine fundamental performance bounds applicable to any quantization approach. Next, we consider several forms of scalar quantizers, namely uniform, non-uniform, and 1-bit. We provide performance bounds and fundamental analysis, as well as practical quantizer designs and reconstruction algorithms that account for quantization. Furthermore, we provide an overview of Sigma-Delta ($\Sigma\Delta$) quantization in the compressed sensing context, and also discuss implementation issues, recovery algorithms and performance bounds. As we demonstrate, proper accounting for quantization and careful quantizer design has significant impact in the performance of a compressive acquisition system.Comment: 35 pages, 20 figures, to appear in Springer book "Compressed Sensing and Its Applications", 201

Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane

During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113 ± 5% and 395 ± 82% (Baltic Sea, February and July 1992) and 126 ± 8% (south central North Sea, September 1992). On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a concept of regional gas transfer coefficients. Our estimates computed with two different air-sea exchange models lie in the range of 11-18 Tg CH4 yr-1. Despite the fact that shelf areas and estuaries only represent a small part of the world's ocean they contribute about 75% to the global oceanic emissions. We applied a simple, coupled, three-layer model to numerically simulate the time dependent variation of the oceanic flux to the atmosphere. The model calculations indicate that even with increasing tropospheric methane concentration, the ocean will remain a source of atmospheric methane