1,289 research outputs found

    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

    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

    Influence of restraining devices on patterns of pediatric facial trauma in motor vehicle collisions.

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    In the Commonwealth of Pennsylvania, it is required that all children under the age of 4 years be restrained by an infant seat or car seat appropriate for their age and weight. Furthermore, all individuals riding in the front seat must be restrained by a seatbelt. This study examined the relationship between patterns of facial injuries and the use of restraining devices in the pediatric population. A retrospective analysis was performed on motor vehicle collision data submitted to the Pennsylvania Trauma Outcome Study database from 1990 through 1995. Criteria for submission included trauma patients who were admitted to the Intensive Care Unit, those who died during hospitalization, those who were hospitalized for more than 72 hours, or those who were transferred in or out of the receiving hospital. A subset of 412 pediatric patients, 15 years of age or younger, was analyzed for patterns of facial injury and the presence or absence of restraining devices. Restraining devices were categorized as a car seat or a seatbelt. Statistical analysis was performed using chi-square and Fisher\u27s exact tests. Of the 412 pediatric patients, only 17 children were restrained with a car seat and 121 were wearing a seatbelt. A total of 30 children sustained facial fractures, and 50 children suffered facial lacerations. There was a statistically significant increase in the incidence of facial fractures with increasing age of the child (p \u3c 0.001). Of children with facial fractures, 70 percent of those 5 to 12 years old and 90 percent of those 13 to 15 years old were unrestrained (p = 0.166). In conclusion, despite legislation mandating the use of restraints, a large proportion of children involved in motor vehicle collisions were unrestrained. Furthermore, there seems to be a direct relationship between the age of a child and the incidence of facial fractures sustained in motor vehicle collisions

    Designing for comfort in shared and automated vehicles (SAV): a conceptual framework

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    To date, automotive design and research is heavily biased towards the driver. However, with the rapid advance of vehicle automation, the driving task will increasingly being taken over by a machine. Automation by itself, however, will not be able to tackle the transport challenges we are facing and the need for shared mobility is now widely recognized. Future mobility solutions are therefore expected to consist of Shared and Automated Vehicles (SAV). This means that the passenger experience will take center stage in the design of future road vehicles. Whereas at first sight this may not appear to be different to the experience in other modes of transport, automation and shared mobility introduce different psychological, physical and physiological challenges. These are related to the fact that the occupant is no longer in control, has to put his or her life in the hands of a computer, while at the same time expects such future vehicles to render travel time more efficient or pleasurable and engage in so-called non-driving related tasks. Taking inspiration from work conducted in the field of aircraft passenger comfort experience, we discuss major comfort factors in the context of SAV and highlight both similarities and differences between transport modes. We present a human centered design framework to assist both the research agenda and the development of safe, usable, comfortable, and desirable future mobility solutions

    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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