Controls on and trends in sediment and particulate organic matter storage by instream wood in north Saint Vrain Creek, Colorado

2017 Spring.Includes bibliographical references.Sediment and particulate organic matter (POM) retained by wood within the bankfull channel were evaluated for 58 stream reaches at the headwaters of North Saint Vrain Creek, Colorado. Wood-induced storage in headwater regions is hypothesized to be important in buffering downstream transport of material. However, the magnitude of storage has not been thoroughly investigated in relation to different potential control variables (e.g., wood volume, channel gradient, channel confinement, and riparian basal area) and spatial scales (jam, reach, and drainage basin) of control. Multiple and single variable linear regressions informed results. On the jam scale, no relationship was observed between storage and visually estimated jam porosity and permeability. In contrast, the reach-scale volume of stored coarse sediment (gravel, cobble) responds strongly to reach-scale wood volume. Reach-scale fine sediment (sand and finer) volume responds most strongly to wood piece characteristics (average piece length/average channel width and longitudinal spacing) and reach-scale coarse sediment storage. POM storage was most strongly related to riparian controls (channel confinement and riparian forest basal area). These results were translated into a drainage basin-scale analysis in ArcGIS. Despite comprising 14% of the stream network, third-order reaches were found to store 41% of total estimated coarse sediment, 34% of total wood, and 23% of total fine sediment. Large logjams likely exert a high cumulative storage effect in a relatively small portion of the watershed. In contrast, 60% of estimated total POM storage occurs in first-order streams (47% of network stream length). Low transport capacity in these small streams retains highly mobile POM and lateral roots from the nearby riparian forest may serve as retention structures. These results indicate that wood exerts different geomorphic effects depending on its location within the stream network. From a management perspective, road building and campsite development should avoid impacts to first-order streams, as they are important to overall drainage basin POM retention. Third-order streams are hotspots of wood, coarse sediment, and fine sediment; promoting or allowing wood recruitment processes in these areas can facilitate high sediment retention and buffering of downstream transport

Spin-Flipping Half Vortex in a Macroscopic Polariton Spinor Ring Condensate

We report the observation of vorticity in a macroscopic Bose-Einstein condensate of polaritons in a ring geometry. Because it is a spinor condensate, the elementary excitations are "half vortices" in which there is a phase rotation of $\pi$ in connection with a polarization vector rotation of $\pi$ around a closed path. This is clearly seen in the experimental observations of the polarization rotation around the ring. In the ring geometry, a new type of half vortex is allowed in which the handedness of the spin flips from one side of the ring to the other, in addition to the rotation of the linear polarization component; such a state is not allowed in a simply-connected geometry. Theoretical calculation of the energy of this state shows that when many-body interactions are taken into account, it is lower in energy than a simple half vortex. The direction of circulation of the flow around the ring fluctuates randomly between clockwise and counterclockwise from one shot to the next; this corresponds to spontaneous breaking of time-reversal symmetry in the system. These new, macroscopic polariton ring condensates allow for the possibility of direct control of the vorticity of the condensate.Comment: 21 pages, 10 figures, including supplemental information; Proceedings of the National Academy of Sciences (USA) (2015

A quantification of the changes in articular cartilage material properties during the onset of osteoarthritis using stress relaxation testing

This study aims to quantify the relationship between biomechanical properties of articular cartilage and varying levels of tissue damage. While other studies have investigated the relationship between osteoarthritis and mechanical properties, our study provides a method to achieve accurate and rapid results from a single test on a given sample while minimizing the impact of extraneous factors such as varied strain and pore compression which are common issues in creep tests. The results of our optimization show the expected change in aggregate modulus and permeability with tissue damage and provide the first step in determining a concrete, quantitative relationship between these properties.--Discussion"This study was funded by the Comparative Orthopaedic Laboratory.

Are cross-sectional safety climate survey results in operating room staff associated with the surgical site infection rates in Swiss hospitals?

OBJECTIVES The aim of this study was to investigate the association between surgical site infections (SSIs), a major source of patient harm, and safety and teamwork climate. Prior research has been unclear regarding this relationship. DESIGN Based on the Swiss national SSI surveillance and a survey study assessing (a) safety climate and (b) teamwork climate, associations were analysed for three kinds of surgical procedures. SETTING AND PARTICIPANTS SSI surveillance data from 20 434 surgeries for hip and knee arthroplasty from 41 hospitals, 8321 for colorectal procedures from 28 hospitals and 4346 caesarean sections from 11 hospitals and survey responses from Swiss operating room personnel (N=2769) in 54 acute care hospitals. PRIMARY AND SECONDARY OUTCOMES The primary endpoint of the study was the 30-day (all types) or 1-year (knee/hip with implants) National Healthcare Safety Network-adjusted SSI rate. Its association with climate level and strength was investigated in regression analyses, accounting for respondents' professional background, managerial role and hospital size as confounding factors. RESULTS Plotting climate levels against infection rates revealed a general trend with SSI rate decreasing as the safety climate increased, but none of the associations were significant (5% level). Linear models for hip and knee arthroplasties showed a negative association between SSI rate and climate perception (p=0.02). For climate strength, there were no consistent patterns, indicating that alignment of perceptions was not associated with lower infection rates. Being in a managerial role and being a physician (vs a nurse) had a positive effect on climate levels regarding SSI in hip and knee arthroplasties, whereas larger hospital size had a negative effect. CONCLUSIONS This study suggests a possible negative correlation between climate level and SSI rate, while for climate strength, no associations were found. Future research should study safety climate more specifically related to infection prevention measures to establish clearer links

Observation of quantum depletion in a nonequilibrium exciton-polariton condensate

The property of superfluidity, first discovered in liquid 4He, is closely related to Bose-Einstein condensation (BEC) of interacting bosons. However, even at zero temperature, when one would expect the whole bosonic quantum liquid to become condensed, a fraction of it is excited into higher momentum states via interparticle interactions and quantum fluctuations -- the phenomenon of quantum depletion. Quantum depletion of weakly interacting atomic BECs in thermal equilibrium is well understood theoretically but is difficult to measure. This is even more challenging in driven-dissipative systems such as exciton-polariton condensates(photons coupled to electron-hole pairs in a semiconductor), since their nonequilibrium nature is predicted to suppress quantum depletion. Here, we observe quantum depletion of an optically trapped high-density exciton-polariton condensate by directly detecting the spectral branch of elementary excitations populated by this process. Analysis of the population of this branch in momentum space shows that quantum depletion of an exciton-polariton condensate can closely follow or strongly deviate from the equilibrium Bogoliubov theory, depending on the fraction of matter (exciton) in an exciton-polariton. Our results reveal the effects of exciton-polariton interactions beyond the mean-field description and call for a deeper understanding of the relationship between equilibrium and nonequilibrium BECs.Comment: 18 pages, 5 figures, with supplementary informatio

Performance of high-throughput DNA quantification methods

BACKGROUND: The accuracy and precision of estimates of DNA concentration are critical factors for efficient use of DNA samples in high-throughput genotype and sequence analyses. We evaluated the performance of spectrophotometric (OD) DNA quantification, and compared it to two fluorometric quantification methods, the PicoGreen(® )assay (PG), and a novel real-time quantitative genomic PCR assay (QG) specific to a region at the human BRCA1 locus. Twenty-Two lymphoblastoid cell line DNA samples with an initial concentration of ~350 ng/uL were diluted to 20 ng/uL. DNA concentration was estimated by OD and further diluted to 5 ng/uL. The concentrations of multiple aliquots of the final dilution were measured by the OD, QG and PG methods. The effects of manual and robotic laboratory sample handling procedures on the estimates of DNA concentration were assessed using variance components analyses. RESULTS: The OD method was the DNA quantification method most concordant with the reference sample among the three methods evaluated. A large fraction of the total variance for all three methods (36.0–95.7%) was explained by sample-to-sample variation, whereas the amount of variance attributable to sample handling was small (0.8–17.5%). Residual error (3.2–59.4%), corresponding to un-modelled factors, contributed a greater extent to the total variation than the sample handling procedures. CONCLUSION: The application of a specific DNA quantification method to a particular molecular genetic laboratory protocol must take into account the accuracy and precision of the specific method, as well as the requirements of the experimental workflow with respect to sample volumes and throughput. While OD was the most concordant and precise DNA quantification method in this study, the information provided by the quantitative PCR assay regarding the suitability of DNA samples for PCR may be an essential factor for some protocols, despite the decreased concordance and precision of this method