The involvement/exclusion paradox of spontaneous volunteering:new lessons from winter flood episodes in England

This article focuses on the involvement and management of spontaneous volunteers (SVs). It develops a new theory—which we call the “involvement/exclusion” paradox—about a situation which is frequently manifested when SVs converge in times of disaster. After reviewing research and policy guidance relating to spontaneous volunteering, we present findings from a study of responses to winter flood episodes in England. Taking together the empirical findings and the literature, the article analyzes elements inherent in the involvement/exclusion paradox and develops a conceptual model to illustrate and explain the paradox. Implications for managers and future research are discussed

Generation of phase-matched circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy

Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, this capability was available only at large-scale X-ray facilities such as synchrotrons. Here we demonstrate the first bright, phase-matched, extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to the linearly polarized high harmonic sources that have been used very successfully for ultrafast element-selective magneto-optic experiments. This work thus represents a critical advance that makes possible element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution, using tabletop-scale setups.Comment: 12 text pages, 4 figures, supplamentary information 6 page

Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution. Circularly-polarized radiation in the extreme ultraviolet (EUV)and soft X-ray spectral regions has proven to be extremelyuseful for investigating chirality-sensitive light–matter inter-actions. It enables studies of chiral molecules using photoelectron circular dichroism1, ultrafast molecular decay dynamics2, the direct measurement of quantum phases (for example, Berry’s phase and pseudo-spin) in graphene and topological insulators3,4 and reconstruction of band structure and modal phases in solids5

Sampling Bias Overestimates Climate Change Impacts on Forest Growth in the Southwestern United States

Climate−tree growth relationships recorded in annual growth rings have recently been the basis for projecting climate change impacts on forests. However, most trees and sample sites represented in the International Tree-Ring Data Bank (ITRDB) were chosen to maximize climate signal and are characterized by marginal growing conditions not representative of the larger forest ecosystem. We evaluate the magnitude of this potential bias using a spatially unbiased tree-ring network collected by the USFS Forest Inventory and Analysis (FIA) program. We show that U.S. Southwest ITRDB samples overestimate regional forest climate sensitivity by 41–59%, because ITRDB trees were sampled at warmer and drier locations, both at the macro- and micro-site scale, and are systematically older compared to the FIA collection. Although there are uncertainties associated with our statistical approach, projection based on representative FIA samples suggests 29% less of a climate change-induced growth decrease compared to projection based on climate-sensitive ITRDB samples

Spectral decomposition of EEG microstates in post-traumatic stress disorder

Microstates offer a promising framework to study fast-scale brain dynamics in the resting-state electroencephalogram (EEG). However, microstate dynamics have yet to be investigated in post-traumatic stress disorder (PTSD), despite research demonstrating resting-state alterations in PTSD. We performed microstate-based segmentation of resting-state EEG in a clinical population of participants with PTSD (N = 61) and a non-traumatized, healthy control group (N = 61). Microstate-based measures (i.e., occurrence, mean duration, time coverage) were compared group-wise using broadband (1–30 Hz) and frequency-specific (i.e., delta, theta, alpha, beta bands) decompositions. In the broadband comparisons, the centro-posterior maximum microstate (map E) occurred significantly less frequently (d = -0.64, pFWE = 0.03) and had a significantly shorter mean duration in participants with PTSD as compared to controls (d = -0.71, pFWE \u3c 0.01). These differences were reflected in the narrow frequency bands as well, with lower frequency bands like delta (d = -0.78, pFWE \u3c 0.01), theta (d = -0.74, pFWE = 0.01), and alpha (d = -0.65, pFWE = 0.02) repeating these group-level trends, only with larger effect sizes. Interestingly, a support vector machine classification analysis comparing broadband and frequency-specific measures revealed that models containing only alpha band features significantly out-perform broadband models. When classifying PTSD, the classification accuracy was 76 % and 65 % for the alpha band and the broadband model, respectively (p = 0.03). Taken together, we provide original evidence supporting the clinical utility of microstates as diagnostic markers of PTSD and demonstrate that filtering EEG into distinct frequency bands significantly improves microstate-based classification of a psychiatric disorder

Measuring NIR Atmospheric Extinction Using a Global Positioning System Receiver

Modeling molecular absorption by Earth's atmosphere is important for a wide range of astronomical observations, including broadband NIR photometry and high-resolution NIR spectroscopy. Using a line-by-line radiative transfer approach, we calculate theoretical transmission spectra in the deep red optical (700 to 1050 nm) for Apache Point Observatory. In this region the spectrum is dominated by H2O, which is known to be highly variable in concentration on short timescales. We fit our telluric models to high-resolution observations of A stars and estimate the relative optical depth of H2O absorption under a wide range of observing conditions. We compare these optical depth estimates to simultaneous measurements of Precipitable Water Vapor (PWV) based on data from a Global Positioning System (GPS) receiver located at Apache Point. We find that measured PWV correlates strongly with the scaling of H2O absorption lines in our spectra, indicating that GPS-based PWV measurements combined with atmospheric models may be a powerful tool for the real-time estimation of total molecular absorption in broad NIR bands. Using photometric measurements from the Sloan Digital Sky Survey (SDSS) DR8 database we demonstrate that PWV biases the calibrated r-z colors and z-band fluxes of mid-M stars but not mid-G stars. While this effect is small compared to other sources of noise in the SDSS z-band observations, future surveys like the Large Synoptic Survey Telescope aim for higher precision and will need to take time-variable molecular transmission into account for the global calibration of NIR measurements of objects having strong spectral features at these wavelengths. Empirical calibrations based on PWV may be immediately applicable to ongoing efforts to make mmag differential measurements of M stars to detect transiting exoplanets.Comment: 19 pages, 9 figures. Accepted for publication in PAS

Isolation of the Bacteriophage DinoHI from Dichelobacter nodosus and its Interactions with other Integrated Genetic Elements

The Gram-negative anaerobic pathogen Dichelobacter nodosus carries several genetic elements that integrate into the chromosome. These include the intA, intB, intC and intD elements, which integrate adjacent to csrA and pnpA, two putative global regulators of virulence and the virulence-related locus, vrl, which integrates into ssrA. Treatment of D. nodosus strains with ultraviolet light resulted in the isolation of DinoHI, a member of the Siphoviridae and the first bacteriophage to be identified in D. nodosus. Part of the DinoHI genome containing the packaging site is found in all D. nodosus strains tested and is located at the end of the vrl, suggesting a role for DinoHI in the transfer of the vrl by transduction. Like the intB element, the DinoHI genome contains a copy of regA which has similarity to the repressors of lambdoid bacteriophages, suggesting that the maintenance of DinoHI and the intB element may be co-ordinately controlled