Refinements on the pinhole camera measurements of the LDEF attitude

The results from the University of Alabama in Huntsville (UAH) pinhole camera were reanalyzed to include the effects of corotation of the atmosphere with the Earth as well as satellite oscillation. Previous results from the instrument showed that the satellite had stable attitude offsets in yaw of 8.0 deg and 1.0 deg in pitch; these offsets are unchanged by the present analysis. The primary impact zone of oxygen, i.e., the directly exposed spot on a silver detector, had a ratio of major to minor axes equal to 1.05, which was interpreted as being caused by a small oscillation of plus or minus 0.35 degrees (with precision plus or minus 0.15 degrees). The present analysis shows that the observed effect can largely be accounted for by atmospheric corotation, but that an additional oscillation in yaw of the order of a degree cannot be excluded. The sensitivity of the pinhole camera to satellite oscillations is shown to decrease nonlinearly with decreasing magnitude of the oscillation and to vary inversely with the gas temperature

Simulations of protostellar collapse using multigroup radiation hydrodynamics. I. The first collapse

Radiative transfer plays a major role in the process of star formation. Many simulations of gravitational collapse of a cold gas cloud followed by the formation of a protostellar core use a grey treatment of radiative transfer coupled to the hydrodynamics. However, dust opacities which dominate extinction show large variations as a function of frequency. In this paper, we used frequency-dependent radiative transfer to investigate the influence of the opacity variations on the properties of Larson's first core. We used a multigroup M1 moment model in a 1D radiation hydrodynamics code to simulate the spherically symmetric collapse of a 1 solar mass cloud core. Monochromatic dust opacities for five different temperature ranges were used to compute Planck and Rosseland means inside each frequency group. The results are very consistent with previous studies and only small differences were observed between the grey and multigroup simulations. For a same central density, the multigroup simulations tend to produce first cores with a slightly higher radius and central temperature. We also performed simulations of the collapse of a 10 and 0.1 solar mass cloud, which showed the properties of the first core to be independent of the initial cloud mass, with again no major differences between grey and multigroup models. For Larson's first collapse, where temperatures remain below 2000 K, the vast majority of the radiation energy lies in the IR regime and the system is optically thick. In this regime, the grey approximation does a good job reproducing the correct opacities, as long as there are no large opacity variations on scales much smaller than the width of the Planck function. The multigroup method is however expected to yield more important differences in the later stages of the collapse when high energy (UV and X-ray) radiation is present and matter and radiation are strongly decoupled.Comment: 9 pages, 5 figures, accepted for publication in A&

Interfacial separation between elastic solids with randomly rough surfaces: comparison between theory and numerical techniques

We study the distribution of interfacial separations P(u) at the contact region between two elastic solids with randomly rough surfaces. An analytical expression is derived for P(u) using Persson's theory of contact mechanics, and is compared to numerical solutions obtained using (a) a half-space method based on the Boussinesq equation, (b) a Green's function molecular dynamics technique and (c) smart-block classical molecular dynamics. Overall, we find good agreement between all the different approaches.Comment: 25 pages, 12 figure

Past land-use and land-cover change: the challenge of quantification at the subcontinental to global scales

No abstract available

The evolution of the holocene wetland landscape of the Humberhead Levels from a fossil insect perspective.

Palaeoentomological investigations have been carried out on a series of profiles and contexts in the Humberhead Levels (eastern England), principally from the raised mires of Thome and Hatfield Moors, and from floodplains of the rivers Tome and Idle at Rossington, near Doncaster, and Misterton Carr, Nottinghamshire. Research has attempted to elucidate the effect of peatland development on the composition of the insect fauna, with particular emphasis on Hatfield Moors, as well as investigate the transition from Quercus-Pinus forest to mire and the faunal characteristics of those forests. The study of the fossil insects, together with other palaeoecological evidence, has enabled the genesis and development of these mires to be reconstructed in some detail. However, the palaeoenvironmental record from Thome and Hatfield Moors indicate significant differences in initiation, development and rate of growth between the two sites. The research highlights the valuable palaeoecological record of the peat deposits on Hatfield Moors, which have long been ignored in favour of Thome Moors. In particular, research highlights the importance of Pirns woodland and wet heath, components reflected in the invertebrates today. The study of the floodplain deposits have enabled the research from the Moors to be placed within a regional context. Faunal successions highlight the transition from Urwald (undisturbed woodland), c. 4000 cal BC, to a largely cleared landscape by the late Roman period (c. 400 cal AD). The research has highlighted the nature and diversity of Holocene Urwald and illustrates the important habitat provided by abundant dead wood within these systems. The fossil record emphasises the contraction in range of many elements of the British Coleopterous fauna, both at a regional and national level. A total of eleven extirpated Coleóptera have been recovered, including two species of beetle previously unknown in the British Isles. The significance of these and other Urwaldrelikt species is discussed in relation to the human fragmentation of forest habitats and the decline of Pirns sylvestris L. The importance of fire as a natural agent within the landscape, within coniferous woodland and Pinus-mire and heath systems is highlighted. The dependence of some pinicolous taxa on fire habitats suggests that the decline of this habitat has had a detrimental impact on the biogeography of some species. The role of climate as a limiting factor in distribution of thermophilous species is also discussed

Neuraminidase Activity in \u3cem\u3eDiplococcus pneumoniae\u3c/em\u3e

Kelly, R. T. (Marquette University School of Medicine, Milwaukee, Wis.), D. Greiff, and S. Farmer. Neuraminidase activity in Diplococcus pneumoniae. J. Bacteriol. 91:601–603. 1966.—A method for the quantitation of neuraminidase in the presence of N-acetylneuraminic acid aldolase is described. The neuraminidase content of Diplococcus pneumoniae was found to be dependent on the media employed for growth; the highest enzyme activity per milligram of bacterial protein was obtained with Todd-Hewitt broth. Neuraminidase production was stimulated in D. pneumoniae by the addition of N-acetylneuraminlactose, N-acetylneuraminic acid, or N-acetylmannosamine to the growth medium. Three rough strains of D. pneumoniae, which were nonpathogenic for mice, lacked neuraminidase activity. Seven of 12 smooth strains contained neuraminidase; enzyme activity was not detected in the remaining 5 smooth strains. There was no correlation between the presence of neuraminidase activity and the capsular type or between neuraminidase production and animal virulence

Outbreak of gastroenteritis caused by Yersinia pestis in Afghanistan.

Plague, which is most often caused by the bite of Yersinia pestis-infected fleas, is a rapidly progressing, serious disease that can be fatal without prompt antibiotic treatment. In late December 2007, an outbreak of acute gastroenteritis occurred in Nimroz Province of southern Afghanistan. Of the 83 probable cases of illness, 17 died (case fatality 20·5%). Being a case was associated with consumption or handling of camel meat (adjusted odds ratio 4·4, 95% confidence interval 2·2-8·8, P<0·001). Molecular testing of patient clinical samples and of tissue from the camel using PCR/electrospray ionization-mass spectrometry revealed DNA signatures consistent with Yersinia pestis. Confirmatory testing using real-time PCR and immunological seroconversion of one of the patients confirmed that the outbreak was caused by plague, with a rare gastrointestinal presentation. The study highlights the challenges of identifying infectious agents in low-resource settings; it is the first reported occurrence of plague in Afghanistan

Effectiveness and safety of cemented and uncemented hemiarthroplasty for the treatment of intracapsular hip fractures:a systematic review and meta-analysis of randomised controlled trials

Aims We conducted a systematic review and meta-analysis to compare the mortality, morbidity, and functional outcomes of cemented versus uncemented hemiarthroplasty in the treatment of intracapsular hip fractures, analyzing contemporary and non-contemporary implants separately. Methods PubMed, Medline, EMBASE, CINAHL, and Cochrane Library were searched to 2 February 2020 for randomized controlled trials (RCTs) comparing the primary outcome, mortality, and secondary outcomes of function, quality of life, reoperation, postoperative complications, perioperative outcomes, pain, and length of hospital stay. Relative risks (RRs) and mean differences (with 95% confidence intervals (CIs)) were used as summary association measures. Results A total of 18 studies corresponding to 16 non-overlapping RCTs with a total of 2,819 intracapsular hip fractures were included. Comparing contemporary cemented versus uncemented hemiarthroplasty, RRs (95% CIs) for mortality were 1.32 (0.44 to 3.99) perioperatively, 1.01 (0.48 to 2.10) at 30 days, and 0.90 (0.71 to 1.15) at one year. The use of contemporary cemented hemiarthroplasty reduced the risk of intra- and postoperative periprosthetic fracture. There were no significant differences in the risk of other complications, function, pain, and quality of life. There were no significant differences in perioperative outcomes except for increases in operating time and overall anaesthesia for contemporary cemented hemiarthroplasty with mean differences (95% CIs) of 6.67 (2.65 to 10.68) and 4.90 (2.02 to 7.78) minutes, respectively. The morbidity and mortality outcomes were not significantly different between non-contemporary cemented and uncemented hemiarthroplasty. Conclusion There are no differences in the risk of mortality when comparing the use of contemporary cemented with uncemented hemiarthroplasty in the management of intracapsular hip fractures. Contemporary cemented hemiarthroplasty is associated with a substantially lower risk of intraoperative and periprosthetic fractures

Incidence and predictive factors of problems after fixation of trochanteric hip fractures with sliding hip screw or intramedullary devices

Introduction: Hip fractures are common and disabling injuries, usually managed surgically. The most common type outside the joint capsule are trochanteric fractures, usually fixed with either sliding hip screw or intramedullary nail. Data are available in the National Hip Fracture Database (NHFD) on early failure and other major complications, but late or subtler complications may escape recording. This study sought to quantify such problems after fixation performed at 3different sites and identify their predictors. Methods: Patients with a trochanteric fracture treated at 1 of 3 sites were identified from the NHFD over a 3-year period. Any with further, related episodes of care were identified, and reasons recorded, then age- and sex-matched with those with no such episodes. Data was collected on Arbeitsgemeinschaft für Osteosynthesefragen classification, tip-apex distance, American Society of Anesthesiologists (ASA) grade, Abbreviated Mental Test Score and pre-injury mobility. The cohorts were compared, and a binomial logistic regression model used to identify predictors of problems. Results: A total of 4010 patients were entered in the NHFD across 3 sites between January 2013 and December 2015. Of these, 1260 sustained trochanteric fractures and 57 (4.5%) subsequently experienced problems leading to re-presentation. The most common was failure of fixation, occurring in 22 patients (1.7%). The binomial logistic regression model explained 47.6% of the variance in incidence of postoperative problems with ASA grade and tip-apex distance being predictive. Discussion: The incidence of re-presentation with problems was around of 5%. A failure rate of less than 2% was seen, in keeping with existing data. This study has quantified the incidence of subtler postoperative problems and identified their predictors. The type of implant used was not amongst them and patients with both implants experienced problems. Fixation continues to yield imperfect results, but patient health and robust surgical technique remain important factors in a good outcome.</p

Carbon-enhanced stars with short orbital and spin periods

Many characteristics of dwarf carbon stars are broadly consistent with a binary origin, including mass transfer from an evolved companion. While the population overall appears to have old-disc or halo kinematics, roughly 2 per cent of these stars exhibit Hα emission, which in low-mass main-sequence stars is generally associated with rotation and relative youth. Its presence in an older population therefore suggests either irradiation or spin-up. This study presents time-series analyses of photometric and radial-velocity data for seven dwarf carbon stars with Hα emission. All are shown to have photometric periods in the range 0.2–5.2 d, and orbital periods of similar length, consistent with tidal synchronisation. It is hypothesised that dwarf carbon stars with emission lines are the result of close-binary evolution, indicating that low-mass, metal-weak or metal-poor stars can accrete substantial material prior to entering a common-envelope phase