1,193 research outputs found

    Spin reorientation in Na-doped BaFe2_2As2_2 studied by neutron diffraction

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    We have studied the magnetic ordering in Na doped BaFe2_2As2_2 by unpolarized and polarized neutron diffraction using single crystals. Unlike previously studied FeAs-based compounds that magnetically order, Ba1x_{1-x}Nax_xFe2_2As2_2 exhibits two successive magnetic transitions: For x=0.35 upon cooling magnetic order occurs at \sim70\ K with in-plane magnetic moments being arranged as in pure or Ni, Co and K-doped BaFe2_2As2_2 samples. At a temperature of \sim46\ K a second phase transition occurs, which the single-crystal neutron diffraction experiments can unambiguously identify as a spin reorientation. At low temperatures, the ordered magnetic moments in Ba0.65_{0.65}Na0.35_{0.35}Fe2_2As2_2 point along the cc direction. Magnetic correlations in these materials cannot be considered as Ising like, and spin-orbit coupling must be included in a quantitative theory.Comment: 5 pages, 4 figure

    The two-loop five-particle amplitude in N=8\mathcal{N}=8 supergravity

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    We compute for the first time the two-loop five-particle amplitude in N=8\mathcal{N}=8 supergravity. Starting from the known integrand, we perform an integration-by-parts reduction and express the answer in terms of uniform weight master integrals. The latter are known to evaluate to non-planar pentagon functions, described by a 31-letter symbol alphabet. We express the final result for the amplitude in terms of uniform weight four symbols, multiplied by a small set of rational factors. The amplitude satisfies the expected factorization properties when one external graviton becomes soft, and when two external gravitons become collinear. We verify that the soft divergences of the amplitude exponentiate, and extract the finite remainder function. The latter depends on fewer rational factors, and is independent of one of the symbol letters. By analyzing identities involving rational factors and symbols we find a remarkably compact representation in terms of a single seed function, summed over all permutations of external particles. Finally, we work out the multi-Regge limit, and present explicitly the leading logarithmic terms in the limit. The full symbol of the IR-subtracted hard function is provided as an ancillary file.Comment: 22 pages, 1 figure, 8 ancillary file

    Species and gender differentiation between and among domestic and wild animals using mitochondrial and sex-linked DNA markers

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    In many African countries accurate and reliable identification of poached wildlife products like carcasses or meat presents a big problem when morphological characters such as skin hair or bones are missing. We describe a molecular based approach that has a potential of serving as a forensic tool in game meat identification in Africa. A mitochondial DNA marker (mt700) and one restriction enzyme, Rsa1 were used in the PCR-RFLP species identification of game meat obtained from two National Parks in Tanzania. Species-specific reference DNA fragment patterns were obtained using fresh meat from ten wildlife and four domesticated species. All species except the zebra, produced unique monomorphic RFLP patterns. Collectively, these patterns demonstrate the potential ability of genetic techniques for discriminating between and among wildlife and domestic species. The reference PCR-RFLP fragments enabled species identification of about 79% of unknown meat samples. In addition, sex was alsoassigned to all of the samples following successful amplification of gender-specific, SRY and ZFY/X, chromosomal domains. Although the present study has been conducted on a limited range both in numbers and genetic diversity of wildlife species present in Africa, the results demonstrate thepotential usefulness of the DNA approach in wildlife forensics in the continent

    The potential of mitochondrial DNA markers and polymerase chain reaction-restriction fragment length polymorphism for domestic and wild species identification

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    Poaching is increasingly presenting challenge to conservational authorities in Africa. Accurate and reliable methods for the identification of poached wildlife meat when morphological features aremissing, has been lacking in Africa. We describe a molecular based approach that has a potential of serving as a tool for game and domestic meat identification in Africa. A mitochondrial (mt246) markerand Rsa1 restriction enzyme were used in the PCR-RFLP species identification of game and domestic meat. Species-specific reference DNA fragment patterns were obtained using fresh meat from ten majorwild herbivores, representing the highly targeted wild meat species in Tanzania and four domesticated animal species. With the exception of the zebra, all species produced unique monomorphic RFLPpatterns that were species specific. These reference fragment patterns enabled identification of about 75% of unknown meat samples, demonstrating the ability of the technique in discriminating betweenand among wild and domestic species. The results provide preliminary promising fingerprints which need further validation for future use for the control of the up-surging bush meat trade in the continent

    All master integrals for three-jet production at NNLO

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    We evaluate analytically all previously unknown nonplanar master integrals for massless five-particle scattering at two loops, using the differential equations method. A canonical form of the differential equations is obtained by identifying integrals with constant leading singularities, in DD space-time dimensions. These integrals evaluate to Q\mathbb{Q}-linear combinations of multiple polylogarithms of uniform weight at each order in the expansion in the dimensional regularization parameter, and are in agreement with previous conjectures for nonplanar pentagon functions. Our results provide the complete set of two-loop Feynman integrals for any massless 232\to 3 scattering process, thereby opening up a new level of precision collider phenomenology.Comment: 6 pages, 1 figure, 5 ancillary files; v2: references added; full boundary values in s12 physical region included; v3: values of the master integrals in the ancillary files update

    Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources

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    Radiation from the highly-charged ions contained in the plasma of Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of X-rays. Because the ions have a relatively low kinetic energy (1\approx 1 eV) transitions can be very narrow, containing only small Doppler broadening. We describe preliminary accurate measurements of two and three-electron ions with Z=16--18. We show how these measurement can test sensitively many-body relativistic calculations or can be used as X-ray standards for precise measurements of X-ray transitions in exotic atoms

    Applying real-world data from expanded-access (“compassionate use”) patients to drug development

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    Our drug development process has produced many life-saving medications, but patients experiencing rare diseases and similar conditions often are left with limited options for treatment. For an approved treatment to be developed, research on a new candidate or existing drug must validate safety and efficacy based on contemporary research expectations. Randomized clinical trials are conducted for this purpose, but they are also costly, laborious, and time-consuming. For this reason, The 21st Century Cures Act mandates that the US Food and Drug Administration look for alternative methods for approving drugs, in particular exploring the uses of real-world data and evidence. Expanded access (“compassionate use”) is a pathway for the clinical treatment of patients using drugs that are not yet approved for prescribing in the United States. Using real-world evidence generated from expanded-access patients presents an opportunity to provide critical data on patient outcomes that can serve regulatory approval in conjunction with other observational datasets or clinical trials, and in limited circumstances may be the best data available for regulatory review. In doing so, we may also support and encourage patient-centered care and a personalized medicine approach to drug development

    Human Social Behavior and Demography Drive Patterns of Fine-Scale Dengue Transmission in Endemic Areas of Colombia

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    Dengue is known to transmit between humans and A. aegypti mosquitoes living in neighboring houses. Although transmission is thought to be highly heterogeneous in both space and time, little is known about the patterns and drivers of transmission in groups of houses in endemic settings. We carried out surveys of PCR positivity in children residing in 2-block patches of highly endemic cities of Colombia. We found high levels of heterogeneity in PCR positivity, varying from less than 30% in 8 of the 10 patches to 56 and 96%, with the latter patch containing 22 children simultaneously PCR positive (PCR22) for DEN2. We then used an agent-based model to assess the likely eco-epidemiological context of this observation. Our model, simulating daily dengue dynamics over a 20 year period in a single two block patch, suggests that the observed heterogeneity most likely derived from variation in the density of susceptible people. Two aspects of human adaptive behavior were critical to determining this density: external social relationships favoring viral introduction (by susceptible residents or infectious visitors) and immigration of households from non-endemic areas. External social relationships generating frequent viral introduction constituted a particularly strong constraint on susceptible densities, thereby limiting the potential for explosive outbreaks and dampening the impact of heightened vectorial capacity. Dengue transmission can be highly explosive locally, even in neighborhoods with significant immunity in the human population. Variation among neighborhoods in the density of local social networks and rural-to-urban migration is likely to produce significant fine-scale heterogeneity in dengue dynamics, constraining or amplifying the impacts of changes in mosquito populations and cross immunity between serotypes

    On the characterisation of a Bragg spectrometer with X-rays from an ECR source

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    Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source have been used to determine the response function of a Bragg crystal spectrometer equipped with large area spherically bent silicon (111) or quartz (101ˉ\bar{1}) crystals. The measured spectra are compared with simulated ones created by a ray-tracing code based on the expected theoretical crystal's rocking curve and the geometry of the experimental set-up.Comment: Version acceptee (NIM

    Systematic approach towards reliable estimation of abdominal aortic aneurysm size by ultrasound imaging and CT

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    Background: The management of abdominal aortic aneurysm (AAA) is fully dictated by AAA size, but there are no uniform measurement guidelines, and systematic differences exist between ultrasound- and CT-based size estimation. The aim of this study was to devise a uniform ultrasound acquisition and measurement protocol, and to test whether harmonization of ultrasound and CT readings is feasible. Methods: A literature review was undertaken to evaluate evidence for ultrasound-based measurement of AAA. A protocol for measuring AAA was then developed, and intraobserver and interobserver reproducibility was tested. Finally, agreement between ultrasound readings and CT-based AAA diameters was evaluated. This was an observational study of patients with a small AAA who participated in two pharmaceutical intervention trials. Results: Based on a literature review, an ultrasound acquisition and reading protocol was devised. Evaluation of the protocol showed an intraobserver repeatability of 1.6 mm (2s.d.) and an interobserver intraclass correlation coefficient (ICC) of 0.97. Comparison of protocolled ultrasound readings and local CT readings indicated a good correlation (r = 0.81), but a systematic +4.1-mm difference for CT. Harmonized size readings for ultrasound imaging and CT increased the correlation (r = 0.91) and reduced the systematic difference to +1.8 mm by CT. Interobserver reproducibility of protocolized CT measurements showed an ICC of 0.94 for the inner-to-inner method and 0.96 for the outer-to-outer method. Conclusion: The absence of harmonized size acquisition and reading guidelines results in overtreatment and undertreatment of patients with AAA. This can be avoided by the implementation of standardized ultrasound acquisition and a harmonized reading protocol for ultrasound- and CT-based readings
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