To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Winter half-year precipitation dominates variations in hydroclimatic conditions in North Xinjiang, but few researchers have focused on this very important aspect of the Holocene climate. Here we report multiproxy evidence of Holocene hydroclimate changes from the sediments of Wulungu Lake in North Xinjiang. The site is a closed terminal lake fed mainly by meltwater from snow and ice, and today the area is climatically dominated by the westerlies. Grain-size end-member analysis implies an important mode of variation that indicates a gradually increasing moisture trend, with superimposed centennial-scale variations, since 8000 cal yr BP. From 8000 to 5350 cal yr BP, a permanent lake developed, and the lake level gradually rose. Between 5350 and 500 cal yr BP, the moisture status increased rapidly, with the wettest climate occurring between 3200 and 500 cal yr BP. After 500 cal yr BP, the lake level fell. The trend of increasing Holocene wetness indicates a rising winter precipitation in North Xinjiang during the Holocene. This was due to an increase in upwind vapor concentrations caused by increased evaporation and strength of the westerlies, which were determined by the increasing boreal winter insolation and its latitudinal gradient.
We describe 14 yr of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements of pulse times of arrival from 26 millisecond pulsars using the 64-m Parkes radio telescope with a cadence of approximately 3 weeks in three observing bands. A comprehensive description of the pulsar observing systems employed at the telescope since 2004 is provided, including the calibration methodology and an analysis of the stability of system components. We attempt to provide full accounting of the reduction from the raw measured Stokes parameters to pulse times of arrival to aid third parties in reproducing our results. This conversion is encapsulated in a processing pipeline designed to track provenance. Our data products include pulse times of arrival for each of the pulsars along with an initial set of pulsar parameters and noise models. The calibrated pulse profiles and timing template profiles are also available. These data represent almost 21 000 h of recorded data spanning over 14 yr. After accounting for processes that induce time-correlated noise, 22 of the pulsars have weighted root-mean-square timing residuals of
in at least one radio band. The data should allow end users to quickly undertake their own gravitational wave analyses, for example, without having to understand the intricacies of pulsar polarisation calibration or attain a mastery of radio frequency interference mitigation as is required when analysing raw data files.
March 2020 was a pivotal month for the worldwide geographic and numeric expansion of the first wave of Coronavirus Disease 2019 (COVID-19). We examined the major storylines that depicted this explosive spread of COVID-19 around the globe.
A detailed review of World Health Organization (WHO) situation reports, surveillance summaries, and online resources allowed us to quantify the increases in cases and deaths by region and by country throughout the month of March 2020.
During March, COVID-19 was officially declared by the WHO to be a pandemic. COVID-19 emerged from a focalized outbreak in the Western Pacific Region and rapidly proliferated across all continents worldwide. Globally, cumulative numbers of confirmed cases increased by a factor of nine throughout the month. During the entire month, cases rose exponentially throughout Europe. Starting in mid-March, confirmed cases accelerated coast-to-coast throughout the United States and, on March 26, the United States surpassed all other nations to rank first in numbers of cases. COVID-19 mortality lagged several weeks behind but by month’s end, death tolls were also rising exponentially.
March 2020 was a consequential month when the COVID-19 pandemic wrapped completely around the planet, with outbreaks erupting in most nations worldwide.
This study investigated metabolic, endocrine, appetite and mood responses to a maximal eating occasion in fourteen men (mean: age 28 (sd 5) years, body mass 77·2 (sd 6·6) kg and BMI 24·2 (sd 2·2) kg/m2) who completed two trials in a randomised crossover design. On each occasion, participants ate a homogenous mixed-macronutrient meal (pizza). On one occasion, they ate until ‘comfortably full’ (ad libitum) and on the other, until they ‘could not eat another bite’ (maximal). Mean energy intake was double in the maximal (13 024 (95 % CI 10 964, 15 084) kJ; 3113 (95 % CI 2620, 3605) kcal) compared with the ad libitum trial (6627 (95 % CI 5708, 7547) kJ; 1584 (95 % CI 1364, 1804) kcal). Serum insulin incremental AUC (iAUC) increased approximately 1·5-fold in the maximal compared with ad libitum trial (mean: ad libitum 43·8 (95 % CI 28·3, 59·3) nmol/l × 240 min and maximal 67·7 (95 % CI 47·0, 88·5) nmol/l × 240 min, P < 0·01), but glucose iAUC did not differ between trials (ad libitum 94·3 (95 % CI 30·3, 158·2) mmol/l × 240 min and maximal 126·5 (95 % CI 76·9, 176·0) mmol/l × 240 min, P = 0·19). TAG iAUC was approximately 1·5-fold greater in the maximal v. ad libitum trial (ad libitum 98·6 (95 % CI 69·9, 127·2) mmol/l × 240 min and maximal 146·4 (95 % CI 88·6, 204·1) mmol/l × 240 min, P < 0·01). Total glucagon-like peptide-1, glucose-dependent insulinotropic peptide and peptide tyrosine–tyrosine iAUC were greater in the maximal compared with ad libitum trial (P < 0·05). Total ghrelin concentrations decreased to a similar extent, but AUC was slightly lower in the maximal v. ad libitum trial (P = 0·02). There were marked differences on appetite and mood between trials, most notably maximal eating caused a prolonged increase in lethargy. Healthy men have the capacity to eat twice the energy content required to achieve comfortable fullness at a single meal. Postprandial glycaemia is well regulated following initial overeating, with elevated postprandial insulinaemia probably contributing.
Although death by neurologic criteria (brain death) is legally recognized throughout the United States, state laws and clinical practice vary concerning three key issues: (1) the medical standards used to determine death by neurologic criteria, (2) management of family objections before determination of death by neurologic criteria, and (3) management of religious objections to declaration of death by neurologic criteria. The American Academy of Neurology and other medical stakeholder organizations involved in the determination of death by neurologic criteria have undertaken concerted action to address variation in clinical practice in order to ensure the integrity of brain death determination. To complement this effort, state policymakers must revise legislation on the use of neurologic criteria to declare death. We review the legal history and current laws regarding neurologic criteria to declare death and offer proposed revisions to the Uniform Determination of Death Act (UDDA) and the rationale for these recommendations.
Objectives: To describe multivariate base rates (MBRs) of low scores and reliable change (decline) scores on Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) in college athletes at baseline, as well as to assess MBR differences among demographic and medical history subpopulations. Methods: Data were reported on 15,909 participants (46.5% female) from the NCAA/DoD CARE Consortium. MBRs of ImPACT composite scores were derived using published CARE normative data and reliability metrics. MBRs of sex-corrected low scores were reported at <25th percentile (Low Average), <10th percentile (Borderline), and ≤2nd percentile (Impaired). MBRs of reliable decline scores were reported at the 75%, 90%, 95%, and 99% confidence intervals. We analyzed subgroups by sex, race, attention-deficit/hyperactivity disorder and/or learning disability (ADHD/LD), anxiety/depression, and concussion history using chi-square analyses. Results: Base rates of low scores and reliable decline scores on individual composites approximated the normative distribution. Athletes obtained ≥1 low score with frequencies of 63.4% (Low Average), 32.0% (Borderline), and 9.1% (Impaired). Athletes obtained ≥1 reliable decline score with frequencies of 66.8%, 32.2%, 18%, and 3.8%, respectively. Comparatively few athletes had low scores or reliable decline on ≥2 composite scores. Black/African American athletes and athletes with ADHD/LD had higher rates of low scores, while greater concussion history was associated with lower MBRs (p < .01). MBRs of reliable decline were not associated with demographic or medical factors. Conclusions: Clinical interpretation of low scores and reliable decline on ImPACT depends on the strictness of the low score cutoff, the reliable change criterion, and the number of scores exceeding these cutoffs. Race and ADHD influence the frequency of low scores at all cutoffs cross-sectionally.
The patterns and drivers of late Quaternary vegetation dynamics in the southeastern United States are poorly understood due to low site density, problematic chronologies, and a paucity of independent paleoclimate proxy records. We present a well-dated (15 accelerator mass spectrometry 14C dates) 30,000-yr record from White Pond, South Carolina that consists of high-resolution analyses of fossil pollen, macroscopic charcoal, and Sporormiella spores, and an independent paleotemperature reconstruction based on branched glycerol dialkyl tetraethers. Between 30,000 and 20,000 cal yr BP, open Pinus-Picea forest grew under cold and dry conditions; elevated Quercus before 26,000 cal yr BP, however, suggest warmer conditions in the Southeast before the last glacial maximum, possibly corresponding to regionally warmer conditions associated with Heinrich event H2. Warming between 19,700 and 10,400 cal yr BP was accompanied by a transition from conifer-dominated to mesic hardwood forest. Sporormiella spores were not detected and charcoal was low during the late glacial period, suggesting megaherbivore grazers and fire were not locally important agents of vegetation change. Pinus returned to dominance during the Holocene, with step-like increases in Pinus at 10,400 and 6400 cal yr BP, while charcoal abundance increased tenfold, likely due to increased biomass burning associated with warmer conditions. Low-intensity surface fires increased after 1200 cal yr BP, possibly related to the establishment of the Mississippian culture in the Southeast.
Objectives: The objective of this study was to evaluate the feasibility and implementation of a standardized medically supervised concussion protocol established between a city-wide AAA hockey league and a multi-disciplinary concussion program. Methods: We conducted a retrospective review of injury surveillance, clinical and healthcare utilization data from all athletes evaluated and managed through the Winnipeg AAA Hockey concussion protocol during the 2016-2017 season. We also conducted post-season email surveys of head coaches and parents responsible for athletes who competed in the same season. Results: During the 2016-2017 season, 28 athletes were evaluated through the medically supervised concussion protocol, with two athletes undergoing evaluation for repeat injuries (a total of 30 suspected injuries and consultations). In all, 96.7% of the athletes managed through the concussion protocol were captured by the league-designated Concussion Protocol Coordinator and 100% of eligible athletes underwent complete medical follow-up and clearance to return to full hockey activities. Although 90% of responding head coaches and 91% of parents were aware of the concussion protocol, survey results suggest that some athletes who sustained suspected concussions were not managed through the protocol. Head coaches and parents also indicated that athlete education and communication between medical and sport stakeholders were other elements of the concussion protocol that could be improved. Conclusion: Successful implementation of a medically supervised concussion protocol for youth hockey requires clear communication between sport stakeholders and timely access to multi-disciplinary experts in traumatic brain and spine injuries. Standardized concussion protocols for youth sports may benefit from periodic evaluations by sport stakeholders and incorporation of national guideline best practices and resources.
The ~492 Ma Shetland Ophiolite Complex contains an extensive mantle section, within which numerous podiform chromitite bodies formed during melt percolation in a supra-subduction zone setting. One of the Shetland ophiolite chromitite localities has an unusual style of platinum-group element (PGE) mineralization. Specifically, the Cliff chromitite suite has relatively high (>250 ppm) Pt plus Pd, compared to other chromitites in the Shetland Ophiolite Complex. In this study, we apply petrographic observation, mineral chemistry and novel X-ray microtomography data to elucidate the petrogenesis of PGE-bearing phases at Cliff. The combined datasets reveal that the PGE at Cliff have probably been fractionated by an As-rich fluid, concentrating Pt and Ir into visible (0.1–1 µm) platinum-group minerals (PGM) such as sperrylite and irarsite, respectively. The high (>1 ppm) bulk-rock concentrations of the other PGE (e.g. Os) in the Cliff chromitites suggests the presence of abundant fine-grained unidentified PGM in the serpentinized groundmass. The spatial association of arsenide phases and PGM with alteration rims on Cr-spinel grains suggests that the high Pt and Pd abundances at Cliff result from a late-stage low-temperature (e.g. 200–300°C) hydrothermal event. This conclusion highlights the potential effects that secondary alteration processes can have on modifying and upgrading the tenor of PGE deposits.
The grain-size distribution (GSD) of sediments provides information on sediment provenance, transport processes, and the sedimentary environment. Although a wide range of statistical parameters have been applied to summarize GSDs, most are directed at only parts of the distribution, which limits the amount of environmental information that can be retrieved. Endmember modeling provides a flexible method for unmixing GSDs; however, the calculation of the exact number of endmembers and geologically meaningful endmember spectra remain unresolved using existing modeling methods. Here we present the methodology hierarchical clustering endmember modeling analysis (CEMMA) for unmixing the GSDs of sediments. Within the CEMMA framework, the number of endmembers can be inferred from agglomeration coefficients, and the grain-size spectra of endmembers are defined on the basis of the average distance between the samples in the clusters. After objectively defining grain-size endmembers, we use a least squares algorithm to calculate the fractions of each GSD endmember that contributes to individual samples. To test the CEMMA method, we use a grain-size data set from a sediment core from Wulungu Lake in the Junggar Basin in China, and find that application of the CEMMA methodology yields geologically and mathematically meaningful results. We conclude that CEMMA is a rapid and flexible approach for analyzing the GSDs of sediments.
We use numerical simulations from the Community Coordinated Modeling Center to provide, for the first time, a coherent temporal description of the magnetic reconnection process of two dayside Electron Diffusion Regions (EDRs) identified in Magnetospheric Multiscale Mission data. The model places the MMS spacecraft near the separator line in these most intense and long-lived events. A listing of 31 dayside EDRs identified by the authors is provided to encourage collaboration in analysis of these unique encounters.
Although meta-analytic neuroimaging studies demonstrate a relative lack of specificity in the brain, this evidence may be the result of limits inherent to these types of studies. From this perspective, we review recent findings that suggest that brain function is most appropriately categorized according to the computational capacity of each brain system, rather than the specific task states that elicit its activity.
In 1969, Robert E. Gregg collected five species of ants (Hymenoptera: Formicidae) in three Subarctic localities near the town of Churchill, Manitoba, Canada, which he documented in a 1972 publication in The Canadian Entomologist. To determine whether there have been any additions to the local fauna – as might be predicted to occur in response to a warming climate and increased traffic to the Port of Churchill in the intervening 40 years – we re-collected ants from the same localities in 2012. We identified the ants we collected from Gregg’s sampling sites using both traditional morphological preparations and DNA barcoding. In addition, we examined specimens from Gregg’s initial collection that are accessioned at the Field Museum of Natural History (Chicago, Illinois, United States of America). Using this integrative approach we report seven species present at the same sites Gregg sampled 40 years earlier. We conclude that the apparent increase is likely not due to any arrivals from more southerly distributed ants, but to the increased resolution provided by DNA barcodes to resident species complexes with a complicated history. We provide a brief synopsis of these results and their taxonomic context.
The number of pediatric antimicrobial stewardship programs (ASPs) is increasing and program evaluation is a key component to improve efficiency and enhance stewardship strategies.
To determine the antimicrobials and diagnoses most strongly associated with a recommendation provided by a well-established pediatric ASP.
DESIGN AND SETTING
Retrospective cohort study from March 3, 2008, to March 2, 2013, of all ASP reviews performed at a free-standing pediatric hospital.
ASP recommendations were classified as follows: stop therapy, modify therapy, optimize therapy, or consult infectious diseases. A multinomial distribution model to determine the probability of each ASP recommendation category was performed on the basis of the specific antimicrobial agent or disease category. A logistic model was used to determine the odds of recommendation disagreement by the prescribing clinician.
The ASP made 2,317 recommendations: stop therapy (45%), modify therapy (26%), optimize therapy (19%), or consult infectious diseases (10%). Third-generation cephalosporins (0.20) were the antimicrobials with the highest predictive probability of an ASP recommendation whereas linezolid (0.05) had the lowest probability. Community-acquired pneumonia (0.26) was the diagnosis with the highest predictive probability of an ASP recommendation whereas fever/neutropenia (0.04) had the lowest probability. Disagreement with ASP recommendations by the prescribing clinician occurred 22% of the time, most commonly involving community-acquired pneumonia and ear/nose/throat infections.
Evaluation of our pediatric ASP identified specific clinical diagnoses and antimicrobials associated with an increased likelihood of an ASP recommendation. Focused interventions targeting these high-yield areas may result in increased program efficiency and efficacy.
The addition of a CdMgTe (CMT) layer at the back of a CdTe solar cell should improve its performance by reflecting both photoelectrons and forward-current electrons away from the rear surface. Higher collection of photoelectrons will increase the cell’s current, and reduction of forward current will increase its voltage. To achieve electron reflection, conformal CMT layers were deposited at the back of CdTe cells, and a variety of measurements including performance curves, transmission electron microscopy, x-ray photoelectron spectroscopy, and energy-dispersive x-ray spectroscopy were performed. Oxidation of magnesium in the CMT layer was addressed by adding a CdTe capping layer. MgCl2 passivation was substituted for CdCl2 in some cases, but little difference was seen.
The traditional CdCl2 passivation of CdTe is expanded by adding other chlorides such as MgCl2, NaCl, and MnCl2 into the process through a two-step passivation procedure that combines closed space sublimation step with a vapor process. This allows the possibility of forming a highly doped field at the back of the device that could act as an electron reflector that could boost device performance by directing electrons back into the absorber layer and increasing the voltage while limiting recombination at the back of the device. The effects the two-step passivation process on device performance are characterized by current-voltage measurements, and by electroluminescence and laser-beam induced current images to show the degree of device uniformity. Additionally, capacitance voltage measurements are used to study doping density, depletion width, and possible formation of a field at the back of the device.
Relationships between the X-ray and radio behavior of black hole X-ray binaries during outbursts have established a fundamental coupling between the accretion disks and radio jets in these systems. I begin by reviewing the prevailing paradigm for this disk-jet coupling, also highlighting what we know about similarities and differences with neutron star and white dwarf binaries. Until recently, this paradigm had not been directly tested with dedicated high-angular resolution radio imaging over entire outbursts. Moreover, such high-resolution monitoring campaigns had not previously targetted outbursts in which the compact object was either a neutron star or a white dwarf. To address this issue, we have embarked on the Jet Acceleration and Collimation Probe Of Transient X-Ray Binaries (JACPOT XRB) project, which aims to use high angular resolution observations to compare disk-jet coupling across the stellar mass scale, with the goal of probing the importance of the depth of the gravitational potential well, the stellar surface and the stellar magnetic field, on jet formation. Our team has recently concluded its first monitoring series, including (E)VLA, VLBA, X-ray, optical, and near-infrared observations of entire outbursts of the black hole candidate H 1743-322, the neutron star system Aquila X-1, and the white dwarf system SS Cyg. Here I present preliminary results from this work, largely confirming the current paradigm, but highlighting some intriguing new behavior, and suggesting a possible difference in the jet formation process between neutron star and black hole systems.