775 research outputs found

    z+: Neutron cross section separation from wide-angle uniaxial polarization analysis from wide-angle uniaxial polarization analysis

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    We introduce a simple method to extract the nuclear coherent and isotope incoherent, spin incoherent, and magnetic neutron scattering cross section components from powder scattering data measured using a single neutron beam polarization direction and a position-sensitive detector with large out-of-plane coverage. The method draws inspiration from polarized small-angle neutron scattering and contrasts with conventional so-called “ xyz” polarization analysis on wide-angle instruments, which requires measurements with three orthogonal polarization directions. The viability of the method is demonstrated on both simulated and experimental data for the classical “spin ice” system Ho2Ti2O7, the latter from the linear energy transfer direct geometry spectrometer at the International Science Information Service facility. The cross section components can be reproduced with good fidelity by either fitting the out-of-plane angle dependence around a Debye–Scherrer cone or grouping the data by angle and performing a matrix inversion. The limitations of the method and its practical uses are discussed

    The Real Combination Problem : Panpsychism, Micro-Subjects, and Emergence

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    Panpsychism harbors an unresolved tension, the seriousness of which has yet to be fully appreciated. I capture this tension as a dilemma, and offer panpsychists advice on how to resolve it. The dilemma, briefly, is as follows. Panpsychists are committed to the perspicuous explanation of macro-mentality in terms of micro-mentality. But panpsychists take the micro-material realm to feature not just mental properties, but also micro-subjects to whom these properties belong. Yet it is impossible to explain the constitution of a macro-subject (like one of us) in terms of the assembly of micro-subjects, for, I show, subjects cannot combine. Therefore the panpsychist explanatory project is derailed by the insistence that the world’s ultimate material constituents (ultimates) are subjects of experience. The panpsychist faces a choice of abandoning her explanatory project, or recanting the claim that the ultimates are subjects. This is the dilemma. I argue that the latter option is to be preferred. This needn’t constitute a wholesale abandonment of panpsychism, however, since panpsychists can maintain that the ultimates possess phenomenal qualities, despite not being subjects of those qualities. This proposal requires us to make sense of phenomenal qualities existing independently of experiencing subjects, a challenge I tackle in the penultimate section. The position eventually reached is a form of neutral monism, so another way to express the overall argument is to say that, keeping true to their philosophical motivations, panpsychists should really be neutral monists.Peer reviewedFinal Accepted Versio

    Role of defects in determining the magnetic ground state of ytterbium titanate.

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    Pyrochlore systems are ideally suited to the exploration of geometrical frustration in three dimensions, and their rich phenomenology encompasses topological order and fractional excitations. Classical spin ices provide the first context in which it is possible to control emergent magnetic monopoles, and anisotropic exchange leads to even richer behaviour associated with large quantum fluctuations. Whether the magnetic ground state of Yb2Ti2O7 is a quantum spin liquid or a ferromagnetic phase induced by a Higgs transition appears to be sample dependent. Here we have determined the role of structural defects on the magnetic ground state via the diffuse scattering of neutrons. We find that oxygen vacancies stabilise the spin liquid phase and the stuffing of Ti sites by Yb suppresses it. Samples in which the oxygen vacancies have been eliminated by annealing in oxygen exhibit a transition to a ferromagnetic phase, and this is the true magnetic ground state

    Stalking influenza by vaccination with pre-fusion headless HA mini-stem.

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    Inaccuracies in prediction of circulating viral strain genotypes and the possibility of novel reassortants causing a pandemic outbreak necessitate the development of an anti-influenza vaccine with increased breadth of protection and potential for rapid production and deployment. The hemagglutinin (HA) stem is a promising target for universal influenza vaccine as stem-specific antibodies have the potential to be broadly cross-reactive towards different HA subtypes. Here, we report the design of a bacterially expressed polypeptide that mimics a H5 HA stem by protein minimization to focus the antibody response towards the HA stem. The HA mini-stem folds as a trimer mimicking the HA prefusion conformation. It is resistant to thermal/chemical stress, and it binds to conformation-specific, HA stem-directed broadly neutralizing antibodies with high affinity. Mice vaccinated with the group 1 HA mini-stems are protected from morbidity and mortality against lethal challenge by both group 1 (H5 and H1) and group 2 (H3) influenza viruses, the first report of cross-group protection. Passive transfer of immune serum demonstrates the protection is mediated by stem-specific antibodies. Furthermore, antibodies indudced by these HA stems have broad HA reactivity, yet they do not have antibody-dependent enhancement activity

    Cell lineage transport: a mechanism for molecular gradient formation

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    Gradient formation is a fundamental patterning mechanism during embryo development, commonly related to secreted proteins that move along an existing field of cells. Here, we mathematically address the feasibility of gradients of mRNAs and non-secreted proteins. We show that these gradients can arise in growing tissues whereby cells dilute and transport their molecular content as they divide and grow, a mechanism we termed ‘cell lineage transport.' We provide an experimental test by unveiling a distal-to-proximal gradient of Hoxd13 in the vertebrate developing limb bud driven by cell lineage transport, corroborating our model. Our study indicates that gradients of non-secreted molecules exhibit a power-law profile and can arise for a wide range of biologically relevant parameter values. Dilution and nonlinear growth confer robustness to the spatial gradient under changes in the cell cycle period, but at the expense of sensitivity in the timing of gradient formation. We expect that gradient formation driven by cell lineage transport will provide future insights into understanding the coordination between growth and patterning during embryonic development

    Mitochondrial and nuclear genes suggest that stony corals are monophyletic but most families of stony corals are not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria)

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    Modern hard corals (Class Hexacorallia; Order Scleractinia) are widely studied because of their fundamental role in reef building and their superb fossil record extending back to the Triassic. Nevertheless, interpretations of their evolutionary relationships have been in flux for over a decade. Recent analyses undermine the legitimacy of traditional suborders, families and genera, and suggest that a non-skeletal sister clade (Order Corallimorpharia) might be imbedded within the stony corals. However, these studies either sampled a relatively limited array of taxa or assembled trees from heterogeneous data sets. Here we provide a more comprehensive analysis of Scleractinia (127 species, 75 genera, 17 families) and various outgroups, based on two mitochondrial genes (cytochrome oxidase I, cytochrome b), with analyses of nuclear genes (ßtubulin, ribosomal DNA) of a subset of taxa to test unexpected relationships. Eleven of 16 families were found to be polyphyletic. Strikingly, over one third of all families as conventionally defined contain representatives from the highly divergent "robust" and "complex" clades. However, the recent suggestion that corallimorpharians are true corals that have lost their skeletons was not upheld. Relationships were supported not only by mitochondrial and nuclear genes, but also often by morphological characters which had been ignored or never noted previously. The concordance of molecular characters and more carefully examined morphological characters suggests a future of greater taxonomic stability, as well as the potential to trace the evolutionary history of this ecologically important group using fossils

    Skills training in minimally invasive surgery in Dutch obstetrics and gynecology residency curriculum

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    The complexity of acquiring minimally invasive surgical (MIS) skills, combined with smaller case volumes for residents have pushed the development of skills training facilities on simulators outside the operating room (OR). Medico-legal and financial constraints have stimulated this development even more. However, the implementation of simulator training into a residency curriculum is shown to be troublesome. MIS skills training is organized in a uniform and easily applicable way in the Dutch obstetrics and gynecology residency curriculum. Every resident is obliged to attend the same basic surgical skills course, named Cobra-alpha course, intentionally during postgraduate year (PGY) 1 or 2. Furthermore, surgical skills are trained, evaluated and expanded on simulators in teaching hospitals. Additional to the Cobra-alpha course, residents may attend advanced training courses and congresses focusing on laparoscopy and hysteroscopy. This organization guarantees a uniform introduction to MIS skills training for every resident. However, preconditions for continuous training and evaluation after this introduction have to be optimized

    Initial Medical Attention on Patients with Early-Stage Non-Small Cell Lung Cancer

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    Detection of early stage non-small cell lung cancer (NSCLC) is commonly believed to be incidental. Understanding the reasons that caused initial detection of these patients is important for early diagnosis. However, these reasons are not well studied.We retrospectively reviewed medical records of patients diagnosed with stage I or II NSCLC between 2000 and 2009 at UT MD Anderson Cancer Center. Information on suggestive LC-symptoms or other reasons that caused detection were extracted from patients' medical records. We applied univariate and multivariate analyses to evaluate the association of suggestive LC-symptoms with tumor size and patient survival.Of the 1396 early stage LC patients, 733 (52.5%) presented with suggestive LC-symptoms as chief complaint. 347 (24.9%) and 287 (20.6%) were diagnosed because of regular check-ups and evaluations for other diseases, respectively. The proportion of suggestive LC-symptom-caused detection had a linear relationship with the tumor size (correlation 0.96; with p<.0001). After age, gender, race, smoking status, therapy, and stage adjustment, the symptom-caused detection showed no significant difference in overall and LC-specific survival when compared with the other (non-symptom-caused) detection.Symptoms suggestive of LC are the number one reason that led to detection in early NSCLC. They were also associated with tumor size at diagnosis, suggesting early stage LC patients are developing symptoms. Presence of symptoms in early stages did not compromise survival. A symptom-based alerting system or guidelines may be worth of further study to benefit NSCLC high risk individuals

    Academic Performance and Behavioral Patterns

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    Identifying the factors that influence academic performance is an essential part of educational research. Previous studies have documented the importance of personality traits, class attendance, and social network structure. Because most of these analyses were based on a single behavioral aspect and/or small sample sizes, there is currently no quantification of the interplay of these factors. Here, we study the academic performance among a cohort of 538 undergraduate students forming a single, densely connected social network. Our work is based on data collected using smartphones, which the students used as their primary phones for two years. The availability of multi-channel data from a single population allows us to directly compare the explanatory power of individual and social characteristics. We find that the most informative indicators of performance are based on social ties and that network indicators result in better model performance than individual characteristics (including both personality and class attendance). We confirm earlier findings that class attendance is the most important predictor among individual characteristics. Finally, our results suggest the presence of strong homophily and/or peer effects among university students
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