Study of cosmic dust particles on board LDEF: The FRECOPA experiments AO138-1 and AO138-2

Two experiments, within the French Cooperative Payload (FRECOPA) and devoted to the detection of cosmic dust, were flown on the LDEF. A variety of sensors and collecting devices have made possible the study of impact processes on materials of technological interest. Preliminary examination of hypervelocity impact features gives valuable data on size distribution and nature of interplanetary dust particles in low earth orbit, within the 0.5 to 300 micrometer size range. Most of the events detected on the trailing face of LDEF are expected to be the result of impacts of meteoritic particles only. So far, chemical analysis of craters by EDS clearly shows evidence of elements (Na, Mg, Si, S, Ca, and Fe) consistent with cosmic origin. Systematic occurrence of C and O in crater residues is an important result, to be compared with the existence of CHON particles detected in P-Halley comet nucleus. Crater size distribution is in good agreement with results from other dust experiments flown on LDEF. However, no crater smaller than 1.5 micron was observed, thus suggesting a cutoff in the near earth particle distribution. Possible origin and orbital evolution of micrometeoroids is discussed

Laser Phase Front Measurements Using a Phase Conjugate Twyman-Green Interferometer

This study demonstrated the use of a phase conjugate TwymanGreen interferometer for measuring the phase fronts of beams emitted by infrared diode lasers operating at 830 nm. This interferometer successfully measured the phase front of a single element diode laser, providing better resolution than its conventional counterpart. The phase conjugate mirror compensated for aberrations introduced by imperfect optics in the phase conjugating arm of the interferometer. This interferometer was unable to measure the phase front of a diode array due to the array\u27s inability to create a phase conjugate return. The array\u27s short coherence length is believed to be the main cause preventing the phase conjugate return

A Measurement of the Interference Structure Function, R_LT, for the 12C(e,e'p) reaction in the Quasielastic Region

The coincidence cross-section and the interference structure function, R_LT, were measured for the 12C(e,e'p) 11B reaction at quasielastic kinematics and central momentum transfer of q=400 MeV/c. The measurement was at an opening angle of theta_pq=11 degrees, covering a range in missing energy of E_m = 0 to 65 MeV. The R_LT structure function is found to be consistent with zero for E_m > 50 MeV, confirming an earlier study which indicated that R_L vanishes in this region. The integrated strengths of the p- and s-shell are compared with a Distorted Wave Impulse Approximation calculation. The s-shell strength and shape are compared with a Hartree Fock-Random Phase Approximation calculation. The DWIA calculation overestimates the cross sections for p- and s-shell proton knockout as expected, but surprisingly agrees with the extracted R_LT value for both shells. The HF-RPA calculation describes the data more consistently, which may be due to the inclusion of 2-body currents in this calculation.Comment: 8 Pages LaTex, 5 postscript figures. Submitted to Phys. Rev.

Estimating brain volume loss after radiation therapy in children treated for posterior fossa tumors (Corpus callosum and whole brain volume changes following radiotherapy in children).

Background More than half of pediatric tumors of central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT).Objectives The objective of this study was to establish whether corpus callosum volumes (CCV) and whole brain volumes (WBV) are correlated and to determine the impact of whole-brain lowvs high-dose RT on brain parenchymal volume loss as assessed using each technique.Material and methods Of the 30 identified children (6-12 years) with newly diagnosed posterior fossa tumors treated with cranial RT, including focal and whole-brain RT, suitable imaging was obtained for 23. Radiotherapy regimens were the following: no whole-brain RT (Group 1, n = 7), low-dose whole-brain RT (30 Gy, Group 3, n = 7) in addition to focal boost. Magnetic resonance images (MRIs) were analyzed at baseline and follow-up (median 14 months). The CCVs were manually segmented on midline sagittal slice (n = 23), while WBVs were segmented semi-automatically using Freesurfer (n = 15). This was done twice (6-month interval) for all baseline CCV measurements and 5 randomly selected WBV measurements to establish measurement reproducibility. Correlations between CCV and WBV were investigated and percentage of children demonstrating reduction in CCV or WBV noted.Results Correlation between baseline CCV and WBV was not significant (p = 0.37). Measurement reproducibility was from 6% to -9% for CCV and from 4.8% to -1.2% for WBV. Among the children studied, 30.4% (7/23) had >9% reduction in CCV at follow-up, while 33.3% (5/15) had >1.2% reduction in WBV. Five of 7 patients with CCV loss were not picked up by WBV measurements. Similarly, 3 of 5 patients with WBV loss were not picked up by CCV measurements.Conclusions The CCV and the WBV are unrelated and may indicate different brain parenchymal losses following RT. Up to a third of posterior fossa tumors treated with RT have measurable CCV or WBV loss; incidence was equivalent in lowvs high-dose whole-brain RT

Interspecific competition impacts the occupancy and range limits of two ptarmigan species along the elevation gradient in Norway

Many mountain species are expected to respond to climate change through upslope shifts of their range limits, but competition may restrict or alter this response. Under traditional range-limit theory, it is expected that lower-elevation species are better competitors than closely related higher-elevation species. However, recent work finds that this prediction is often unmet. We investigated evidence for the impact of competition during breeding season on the elevational range limits of a pair of closely related bird species, willow ptarmigan Lagopus lagopus and rock ptarmigan L. muta, in mainland Norway. The species share overlapping ranges that loosely divide slightly upslope from the treeline ecotone, with willow ptarmigan generally occupying lower sites and rock ptarmigan occupying higher sites. We used multi-species occupancy models to test four competing hypotheses for how competition may affect the range limit between willow ptarmigan and rock ptarmigan: 1) asymmetric competition that restricts the lower range limit of rock ptarmigan; 2) asymmetric competition that restricts the upper range limit of willow ptarmigan; 3) condition-specific competition that restricts both species’ range limits; and 4) range limits unaffected by competition. We found evidence for a negative pairwise interaction between the two species. Changes in interaction strength along the elevation gradient suggested evidence for condition-specific competition. However, a strong positive correlation between rock ptarmigan and higher-elevation habitat resulted in a highly asymmetric outcome, where the upper range limit of willow ptarmigan was restricted but rock ptarmigan occupancy was fairly independent of willow ptarmigan. This outcome is opposite to the prediction of traditional range-limit theory and may suggest a greater climate threat to willow ptarmigan than has been previously projected. Thus, our results demonstrate the importance of considering biotic interactions at both the higher and lower ends of species’ range limits along elevation gradients. elevation gradient, interspecific competition, occupancy, ptarmigan, range limitspublishedVersio

Erosion and Accretion Trends of New Hampshire Beaches from December 2016 to March 2020: Results of the Volunteer Beach Profile Monitoring Program

New Hampshire Atlantic beaches were monitored from December 2016 to March 2020 to determine seasonal changes in morphology and elevation, assess the response of the beaches to storms with respect to erosion and subsequent recovery, and develop a baseline to determine long-term trends in beach size, elevation, and position. A unique aspect of this study was the involvement of community volunteers working together with the University of New Hampshire (UNH) Center for Coastal and Ocean Mapping, UNH Cooperative Extension, New Hampshire Sea Grant, and the New Hampshire Geological Survey. The monitoring network consisted of thirteen stations located at six of the major beaches, including each of the state beaches. Monitoring stations were located at Wallis Sands, Jenness Beach, North Hampton Beach, North Beach, Hampton Beach, and Seabrook Beach. At least two stations were located at each beach (Seabrook Beach had three stations). Beach elevation profiles were run routinely at each station at approximately three- to four-week intervals. Additional measurements were made following several major storms. In total, approximately 400 elevation profiles were run at the thirteen stations. The elevation profiles were run using the Emery (1961) method which utilizes two calibrated rods and the horizon for leveling. Sediment volume calculations were made for each profile that approximated the amount of material in the intertidal zone for that profile at that point in time for a one-meter wide swath of the beach. Seasonal changes and storm impacts on beach elevations, profile characteristics, and sediment volumes are discussed in detail for each beach and the major conditions and processes that control their stability discussed

The political views of doctors in the United Kingdom: A cross sectional study

Background: Little is known about the political views of doctors in the United Kingdom, despite their importance in the functioning of the National Health Service. Methods: Survey-based cross-sectional study in which we asked questions about voting behaviour in 2015 and 2017 UK general elections and 2016 referendum on leaving the European Union (Brexit) and questions relating to recent health policies. Results: 1,172 doctors (45.1% women) from 1,295 responded to an online survey. 60.5% described their political views as ‘left-wing’ and 62.2% described themselves as ‘liberal’. 79.4% of respondents voted to remain in the EU in the 2016 referendum compared to 48.1% of voters as a whole (χ2=819.8, p<0.001). 98.6% of respondents agreed that EU nationals working in the NHS should be able to remain in the UK after Brexit. The median score for the impact of Brexit on the NHS on a scale of 0 (worst impact) to 10 (best impact) was 2 (IQR=1-4). Most respondents agreed with the introduction of minimum alcohol pricing in the UK (73.9%), charging patients who are not eligible for NHS treatment for non-urgent care (70.6%) and protecting a portion of national spending for the NHS (87.1%). 65.8% thought there was too much use of NHS-funded private sector provision in their medical practice. Specialty, income and grade were associated with divergent opinions. Conclusions: UK doctors are left-leaning and liberal in general, which is reflected in their opinions on topical health policy issues. Doctors in the UK voted differently from the general electorate in recent polls

Exponential Distribution of Locomotion Activity in Cell Cultures

In vitro velocities of several cell types have been measured using computer controlled video microscopy, which allowed to record the cells' trajectories over several days. On the basis of our large data sets we show that the locomotion activity displays a universal exponential distribution. Thus, motion resulting from complex cellular processes can be well described by an unexpected, but very simple distribution function. A simple phenomenological model based on the interaction of various cellular processes and finite ATP production rate is proposed to explain these experimental results.Comment: 4 pages, 3 figure

Toxicosis from Range Lupine Ingestion in a Research Herd of Rafter 7 Merino Sheep

An outbreak of lupine alkaloid neurotoxicosis and death occurred in sheep grazed on rangeland areas of the Nevada Great Basin during the summer of 2023. Overall, 97 sheep died despite veterinary supportive care. Lupinus argenteus var. utahensis was implicated as the causative plant with high levels of lupanine (11.5 µg/mg) and spartiene (13.7 µg/mg) in collected and archived samples. Previous reports of sheep deaths due to lupine ingestion have not been recorded in this region. An increased abundance of the number plants producing seed pods having a high alkaloid content may have been associated with abnormally elevated levels of precipitation in the months leading to the event