291 research outputs found

    A High Pressure Distorted a-Uranium (Pnma) Structure in Plutonium

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    Under pressure many rare earths and actinide metals transform to a-U structure or its lower symmetry distorted forms. We have reinterpreted the diffraction data of Dabos et al for Pu (reference 4) and find that a Am IV type distorted a-U structure in Pnma space group can explain this for its high pressure phase. The structures of this phase and a-Pu are both shown to have a distorted hcp topology. The upturn in the atomic volume of Pu at 0.1 MPa can also be rationalized on the basis of this proposalComment: 10pages,3 figure

    The Glauber model and the heavy ion reaction cross section

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    We reexamine the Glauber model and calculate the total reaction cross section as a function of energy in the low and intermediate energy range, where many of the corrections in the model, are effective. The most significant effect in this energy range is by the modification of the trajectory due to the Coulomb field. The modification in the trajectory due to nuclear field is also taken into account in a self consistent way. The energy ranges in which particular corrections are effective, are quantified and it is found that when the center of mass energy of the system becomes 30 times the Coulomb barrier, none of the trajectory modification to the Glauber model is really required. The reaction cross sections for light and heavy systems, right from near coulomb barrier to intermediate energies have been calculated. The exact nuclear densities and free nucleon-nucleon (NN) cross sections have been used in the calculations. The center of mass correction which is important for light systems, has also been taken into account. There is an excellent agreement between the calculations with the modified Glauber model and the experimental data. This suggests that the heavy ion reactions in this energy range can be explained by the Glauber model in terms of free NN cross sections without incorporating any medium modification.Comment: RevTeX, 21 pages including 9 Postscript figures, submitted to Phys. Rev.

    On the inner Double-Resonance Raman scattering process in bilayer graphene

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    The dispersion of phonons and the electronic structure of graphene systems can be obtained experimentally from the double-resonance (DR) Raman features by varying the excitation laser energy. In a previous resonance Raman investigation of graphene, the electronic structure was analyzed in the framework of the Slonczewski-Weiss-McClure (SWM) model, considering the outer DR process. In this work we analyze the data considering the inner DR process, and obtain SWM parameters that are in better agreement with those obtained from other experimental techniques. This result possibly shows that there is still a fundamental open question concerning the double resonance process in graphene systems.Comment: 5 pages, 3 figure

    Effects of a nanoscopic filler on the structure and dynamics of a simulated polymer melt and the relationship to ultra-thin films

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    We perform molecular dynamics simulations of an idealized polymer melt surrounding a nanoscopic filler particle to probe the effects of a filler on the local melt structure and dynamics. We show that the glass transition temperature TgT_g of the melt can be shifted to either higher or lower temperatures by appropriately tuning the interactions between polymer and filler. A gradual change of the polymer dynamics approaching the filler surface causes the change in the glass transition. We also find that while the bulk structure of the polymers changes little, the polymers close to the surface tend to be elongated and flattened, independent of the type of interaction we study. Consequently, the dynamics appear strongly influenced by the interactions, while the melt structure is only altered by the geometric constraints imposed by the presence of the filler. Our findings show a strong similarity to those obtained for ultra-thin polymer films (thickness ≲100\lesssim 100 nm) suggesting that both ultra-thin films and filled-polymer systems might be understood in the same context

    Identification of individuals at high-risk for pancreatic cancer using a digital patient-input tool combining family cancer history screening and new-onset diabetes

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    Capturing family history might be a valuable tool for identification of individuals at increased risk of pancreatic cancer, which would allow enrollment into pancreatic surveillance programs. In addition, weight loss and concurrent new-onset diabetes may be utilized as an early marker for pancreatic cancer. This study evaluates the yield of combining family history and the Enriching New-Onset Diabetes for Pancreatic Cancer (ENDPAC) model to identify individuals who could benefit from pancreatic surveillance. A novel questionnaire and digital input tool was created that combined questions on family cancer history and criteria of the ENDPAC model. Individuals meeting ENDPAC criteria were enrolled directly in the high-risk pancreatic clinic. Individuals who met the criteria for a significant family history of cancer were offered referral to a genetic counselor. The questionnaire was completed by 453 patients. Of those, 25.8% (117/453) had significant familial risk factors. Eighteen individuals (15.4%) completed genetic testing previously, of whom five had a pathogenic variant. Thirty-four (29.9%) out of 117 individuals with a strong family history – flagged by the questionnaire – underwent genetic testing. Four (11.8%) of these patients harbored a pathogenic variant. Additionally, through cascade family testing, two siblings were found to carry pathogenic variants. Four (0.9%) of the 453 patients matched ENDPAC criteria. Two were diagnosed with pancreatic cancer and the others were enrolled in the surveillance program. In conclusion, identification of high-risk individuals for pancreatic cancer can be achieved by combining family history screening and the ENDPAC model to facilitate referral to genetic counseling and high-risk clinics.Gastroenterology and Hepatolog

    Short-term quality of life after myomectomy for uterine fibroids from the compare-uf fibroid registry

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    Background Uterine fibroids may decrease quality of life in a significant proportion of affected women. Myomectomy offers a uterine-sparing treatment option for patients with uterine fibroids that can be performed abdominally, laparoscopically (with or without robotic assistance), and hysteroscopically. Quality of life information using validated measures for different myomectomy routes, especially hysteroscopic myomectomy, is limited. Objective To compare women’s perception of their short-term health-related quality of life measures and reported time to return to usual activities and return to work for different routes of myomectomy. Materials and Methods Comparing Options for Management: Patient-centered Results for Uterine Fibroids (COMPARE-UF) is a prospective nationwide fibroid registry that enrolled premenopausal women seeking treatment for uterine fibroids at 8 clinical sites. For this analysis, we included women undergoing hysteroscopic, abdominal, or laparoscopic myomectomy who completed the postprocedure questionnaire scheduled between 6 and 12 weeks after surgery. Health-related quality of life outcomes, such as pain, anxiety, and return to usual activitie, were assessed for each route. The hysteroscopic myomectomy group had large differences in demographics, fibroid number, and uterine size compared to the other groups; thus, a direct comparison of quality of life measures was performed only for abdominal and laparoscopic approaches after propensity weighting. Propensity weighting was done using 24 variables that included demographics, quality of life baseline measures, and fibroid and uterine measurements. Results A total of 1206 women from 8 COMPARE-UF sites underwent myomectomy (338 hysteroscopic, 519 laparoscopic, and 349 abdominal). All women had substantial improvement in short-term health-related quality of life and symptom severity scores, which was not different among groups. Average symptom severity scores decreased about 30 points in each group. Return to usual activities averaged 0 days (interquartile range, 0–14 days) for hysteroscopic myomectomy, 21 days (interquartile range, 14–28 days) for laparoscopic myomectomy, and 28 days (interquartile range, 14–35 days) for abdominal myomectomy. After propensity adjustment, quality of life outcomes in the laparoscopic and abdominal myomectomy groups were similar except for more anxiety in the laparoscopic myomectomy group and slightly more pain in the abdominal myomectomy group. After propensity weighting, return to usual activities favored laparoscopic compared to abdominal procedures; median time was the same at 21 days, but the highest quartile of women in the abdominal group needed an additional week of recovery (interquartile range,14.0–28.0 for laparoscopic versus 14.0–35.0 for abdominal, P < .01). Time to return to work was also longer in the abdominal arm (median, 22 days; interquartile range, 14–40 days, versus median, 42; interquartile range, 27–56). Conclusion Women who underwent myomectomy had substantial improvement in health-related quality of life, regardless of route of myomectomy. After propensity weighting, abdominal myomectomy was associated with a nearly 2-week longer time to return to work than laparoscopic myomectomy

    Defining the 'Social' in 'Social Entrepreneurship': Altruism and Entrepreneurship

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    Abstract. What is social entrepreneurship? In, particular, what’s so social about it? Understanding what social entrepreneurship is enables researchers to study the phenomenon and policy-makers to design measures to encourage it. However, such an understanding is lacking partly because there is no universally accepted definition of entrepreneurship as yet. In this paper, we suggest a definition of social entrepreneurship that intuitively accords with what is generally accepted as entrepreneurship and that captures the way in which entrepreneurship may be altruistic. Based on this we provide a taxonomy of social entrepreneurship and identify a number of real cases from Asia illustrating the different forms it could take. Keywords: social entrepreneurship, definition, taxonomy, altruism Social entrepreneurship is a concept that has captured the imagination of many researchers and policy-makers in recent years. Social entrepreneurship suggests that entrepreneurship may be aimed at benefiting society rather than merely maximising individual profits. It appears to promise an altruistic form of capitalism that does not evaluate all human activities in business terms. It enables a bridge to be built between enterprise and benevolence (Roberts and Woods, 2005). The history of the term ‘social entrepreneurship ’ can be traced to the publication of a Demos thinktank report entitled The Rise of the Social Entrepreneur (Leadbeater, 1997) in the United Kingdom and probably a little earlier in the United States to the publication of New Social Entrepreneurs by the Roberts Foundation (Emerson and Twerksy, 1996). Prior to this, some of the activities under the rubric of social entrepreneurship were either termed ‘community development ’ or those in ‘social purpose organizations’. There is considerable use of the term in popular literature although academic literature on it is thin (Taylor, Hobbs, Nilsson, O’Halloran and Preisser, 2000). Recent interest saw a call for papers for a special issue on social entrepreneurship (Honig an
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