Determinants of water quality in agricultural watersheds

U.S. Geological SurveyU.S. Department of the InteriorOpe

The development and application of aerodynamic uncertainties: And flight test verification for the space shuttle orbiter

The approach used in establishing the predicted aerodynamic uncertainties and the process used in applying these uncertainties during the design of the Orbiter flight control system and the entry trajectories are presented. The flight test program that was designed to verify the stability and control derivatives with a minimum of test flights is presented and a comparison of preflight predictions with preliminary flight test results is made. It is concluded that the approach used for the Orbiter is applicable to future programs where testing is limited due to time constraints or funding

Estimating the potential of U.S. urban infrastructure albedo enhancement as climate mitigation in the face of climate variability

The climate mitigation potential of U.S. urban infrastructure albedo enhancement is explored using multidecadal regional climate simulations. Increasing albedo from 0.2 to 0.4 results in summer daytime surface temperature decreases of 1.5°C, substantial reductions in health-related heat (50% decrease in days with danger heat advisory) and decreases in energy demand for air conditioning (15% decrease in cooling degree days) over the U.S. urban areas. No significant impact is found outside urban areas. Most regional modeling studies rely on short simulations; here, we use multidecadal simulations to extract the forced signal from the noise of climate variability. Achieving a ±0.5°C margin of error for the projected impacts of urban albedo enhancement at a 95% confidence level entails using at least 5 simulation years. Finally, single-year higher-resolution simulations, requiring the same computing power as the multidecadal coarser-resolution simulations, add little value other than confirming the overall magnitude of our estimates.This work was supported by the Concrete Sustainability Hub at MIT, with sponsorship provided by the Portland Cement Association and the RMC Research & Education Foundation, and by the US Department of Energy, Office of Biological and Environmental Research, under grant DE-FG02-94ER61937. The MIT Joint Program on the Science and Policy of Global Change is funded by a number of federal agencies and a consortium of 40 industrial and foundation sponsors. For a complete list of sponsors, see http://globalchange.mit.edu

Global prevalence and risk factors for mental health problems in police personnel: a systematic review and meta-analysis

Police face an increased risk of developing mental health problems, yet reliable estimates of their psychological difficulties remain unknown. This systematic review and meta-analysis estimate the pooled prevalence and risk factors for mental health problems among police personnel worldwide. Three independent reviewers searched 16 databases and screened 11 506 articles published between January 1980 and October 2019. Eligible studies involved at least 100 active police professionals and used validated instruments to ascertain specific mental health problems. Estimates were pooled using random-effects meta-analyses. In total, 60 cross-sectional and seven longitudinal studies, involving 272 463 police personnel from 24 countries met criteria for inclusion. The overall pooled point prevalence was 14.6% for depression (95% CI 10.9% to 18.6%), 14.2% for post-traumatic stress disorder (PTSD; 95% CI 10.3% to 18.7%), 9.6% for a generalised anxiety disorder (95% CI 6.7% to 12.9%), 8.5% for suicidal ideation (95% CI 6.1% to 11.2%), 5.0% for alcohol dependence (95% CI 3.5% to 6.7%) and 25.7% for hazardous drinking (95% CI 19.6% to 32.4%). The strongest risk factor for depression and suicidal ideation was higher occupational stress, and the strongest risk factors for PTSD were higher occupational stress and avoidant coping strategies. Higher levels of peer-support were associated with significantly lower PTSD symptoms. Our findings suggest that the prevalence of mental health problems among police exceeds twice that previously reported in mixed samples of first responders, and is associated with poor social support, occupational stress and maladaptive coping strategies. Without effective intervention, psychological difficulties will remain a substantial health concern among police

A Parameter Model of Gas Exchange for the Seasonal Sea Ice Zone

Carbon budgets for the polar oceans require better constraint on air–sea gas exchange in the sea ice zone (SIZ). Here, we utilize advances in the theory of turbulence, mixing and air–sea flux in the ice–ocean boundary layer (IOBL) to formulate a simple model for gas exchange when the surface ocean is partially covered by sea ice. The gas transfer velocity (k) is related to shear-driven and convection-driven turbulence in the aqueous mass boundary layer, and to the mean-squared wave slope at the air–sea interface. We use the model to estimate k along the drift track of ice-tethered profilers (ITPs) in the Arctic. Individual estimates of daily-averaged k from ITP drifts ranged between 1.1 and 22 m d−1, and the fraction of open water (f) ranged from 0 to 0.83. Converted to area-weighted effective transfer velocities (keff), the minimum value of keff was 10−55 m d−1 near f = 0 with values exceeding keff = 5 m d−1 at f = 0.4. The model indicates that effects from shear and convection in the sea ice zone contribute an additional 40% to the magnitude of keff, beyond what would be predicted from an estimate of keff based solely upon a wind speed parameterization. Although the ultimate scaling relationship for gas exchange in the sea ice zone will require validation in laboratory and field studies, the basic parameter model described here demonstrates that it is feasible to formulate estimates of k based upon properties of the IOBL using data sources that presently exist

Anti-phospholipid-antibodies in patients with relapsing polychondritis

Relapsing polychondritis (RP) is an extremly rare multisystemic disease thought to be of autoimmune origin. In order to assess if RP is associated with anti-phospholipid antibodies (aPL), clinical data and sera of 21 patients with RP were collected in a multicentre study. Concentration of anti-cardiolipin antibodies (aCL) (IgG-, IgM-and IgA-isotypes), anti-phosphatidylserine-antibodies (aPS) (IgG-and IgM-isotypes) and anti-β-2-glycoprotein I-antibodies (aβ2 GPI) were measured by ELISA. In eight patients aCL were found to be elevated. One patient had elevated aPS. No patient had elevated aβ2 GPI. No patient had clinical signs and symptoms of a aPL syndrome. Interestingly, the two RP patients with the highest aPL had concomitant systemic lupus erythematosus (SLE). Therefore the presence of elevated aPL in RP is probably more closely related to an associated SLE than to RP itself. There is no convincing evidence that aPL are associated with RP

Tracer Applications of Noble Gas Radionuclides in the Geosciences

The noble gas radionuclides, including 81Kr (half-life = 229,000 yr), 85Kr (11 yr), and 39Ar (269 yr), possess nearly ideal chemical and physical properties for studies of earth and environmental processes. Recent advances in Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, have enabled routine measurements of the radiokrypton isotopes, as well as the demonstration of the ability to measure 39Ar in environmental samples. Here we provide an overview of the ATTA technique, and a survey of recent progress made in several laboratories worldwide. We review the application of noble gas radionuclides in the geosciences and discuss how ATTA can help advance these fields, specifically determination of groundwater residence times using 81Kr, 85Kr, and 39Ar; dating old glacial ice using 81Kr; and an 39Ar survey of the main water masses of the oceans, to study circulation pathways and estimate mean residence times. Other scientific questions involving deeper circulation of fluids in the Earth's crust and mantle also are within the scope of future applications. We conclude that the geoscience community would greatly benefit from an ATTA facility dedicated to this field, with instrumentation for routine measurements, as well as for research on further development of ATTA methods

Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms

We demonstrate a novel experimental arrangement which rotates a 2D optical lattice at frequencies up to several kilohertz. Ultracold atoms in such a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, allowing investigation of phenomena such as the fractional quantum Hall effect. Our arrangement also allows the periodicity of a 2D optical lattice to be varied dynamically, producing a 2D accordion lattice.Comment: 7 pages, 5 figures, final versio

Vibration-tolerant narrow-linewidth semiconductor disk laser using novel frequency-stabilisation schemes

This paper will present developments in narrow-linewidth semiconductor-disk-laser systems using novel frequency-stabilisation schemes for reduced sensitivity to mechanical vibrations, a critical requirement for mobile applications. Narrow-linewidth single-frequency lasers are required for a range of applications including metrology and high-resolution spectroscopy. Stabilisation of the laser was achieved using a monolithic fibre-optic ring resonator with free spectral range of 181 MHz and finesse of 52 to act as passive reference cavity for the laser. Such a cavity can operate over a broad wavelength range and is immune to a wide band of vibrational frequency noise due to its monolithic implementation. The frequency noise of the locked system has been measured and compared to typical Fabry-Perot-locked lasers using vibration equipment to simulate harsh environments, and analysed here. Locked linewidths of < 40 kHz have been achieved. These developments offer a portable, narrow-linewidth laser system for harsh environments that can be flexibly designed for a range of applications

An examination of the precipitation delivery mechanisms for Dolleman Island, eastern Antarctic Peninsula

Copyright @ 2004 Wiley-BlackwellThe variability of size and source of significant precipitation events were studied at an Antarctic ice core drilling site: Dolleman Island (DI), located on the eastern coast of the Antarctic Peninsula. Significant precipitation events that occur at DI were temporally located in the European Centre for Medium-Range Weather Forecasting (ECMWF) reanalysis data set, ERA-40. The annual and summer precipitation totals from ERA-40 at DI both show significant increases over the reanalysis period. Three-dimensional backwards air parcel trajectories were then run for 5 d using the ECMWF ERA-15 wind fields. Cluster analyses were performed on two sets of these backwards trajectories: all days in the range 1979–1992 (the climatological time-scale) and a subset of days when a significant precipitation event occurred. The principal air mass sources and delivery mechanisms were found to be the Weddell Sea via lee cyclogenesis, the South Atlantic when there was a weak circumpolar trough (CPT) and the South Pacific when the CPT was deep. The occurrence of precipitation bearing air masses arriving via a strong CPT was found to have a significant correlation with the southern annular mode (SAM); however, the arrival of air masses from the same region over the climatological time-scale showed no such correlation. Despite the dominance in both groups of back trajectories of the westerly circulation around Antarctica, some other key patterns were identified. Most notably there was a higher frequency of lee cyclogenesis events in the significant precipitation trajectories compared to the climatological time-scale. There was also a tendency for precipitation trajectories to come from more northerly latitudes, mostly from 50–70°S. The El Niño Southern Oscillation (ENSO) was found to have a strong influence on the mechanism by which the precipitation was delivered; the frequency of occurrence of precipitation from the east (west) of DI increased during El Niño (La Niña) events