16,496 research outputs found

    Quenching of lamellar ordering in an n-alkane embedded in nanopores

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    We present an X-ray diffraction study of the normale alkane nonadecane C_{19}H_{40} embedded in nanoporous Vycor glass. The confined molecular crystal accomplishes a close-packed structure by alignment of the rod-like molecules parallel to the pore axis while sacrificing one basic principle known from the bulk state, i.e. the lamellar ordering of the molecules. Despite this disorder, the phase transitions observed in the confined solid mimic the phase behavior of the 3D unconfined crystal, though enriched by the appearance of a true rotator phase known only from longer alkane chains.Comment: 7 pages, 3 figure

    Oxygen isotope effect on the superconductivity and stripe phase in La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_4

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    The oxygen isotope effect on the superconductivity, stripe phase and structure transition is systematically investigated in La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_4 with static stripe phase. Substitution of 16^{16}O by 18^{18}O leads to a decrease in superconducting transition temperature TC_C, while enhances the temperature of the structural transition from low-temperature-orthorhombic (LTO) phase to low-temperature-tetragonal (LTT) phase. Compared to the Nd free sample, a larger isotope effect on TCT_C is observed in La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_4. These results indicate that the distortion of CuO2_2 plane suppresses the superconductivity, giving a direct evidence for the competing of stripe phase and superconductivity because the distortion of CuO2_2 plane enhances the stripe phase.Comment: 4 pages, 5 figure

    On Quantum-Mechanical Methods in Valence Theory

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    Crustal Deformation and Regional Metamorphism Across a Terrane Boundary, Coast Plutonic Complex, British Columbia

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    Audit of surgical delay in relationship to outcome after proximal femoral fracture.

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    To ascertain the influence of surgical delay on outcome after proximal femoral fracture in elderly females, a cohort study of patients presenting in 1987 was compared to 1989/90. Organisational changes in the intervening period were introduced to reduce delay to surgical intervention. Two hundred and eighty females aged 65 years and over presenting from the local catchment area of an acute inner-city teaching hospital were enrolled in the study. Seventy-nine patients received surgery in 1987 and 186 in 1989/90. The one year mortality was 34% and 26% respectively. The proportion receiving surgery within 24 hours rose from 34% in 1987 to 57% in 1989/90. The relative hazard of the group receiving surgery on day 2 in comparison to day 1 was 1.7 (95% CI 1.0 to 2.9) when adjusted for co-variance of age and mental score. Medically fit elderly patients presenting with proximal femoral fracture have improved survival with early surgery within 24 hours of admission. Improvements in the organisation of hospital care will result in important benefits for the increasing number of elderly females presenting with proximal femoral fracture

    Higher education, career opportunities, and intergenerational inequality

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    The UK government has expressed a desire to increase social mobility, with policies to help achieve this aim focused on reducing inequalities in educational attainment. This paper draws together established and new information about the contribution that higher education can make to social mobility using a life-course approach, considering differences by family background in terms of university attendance and achievement, as well as occupation and earnings following graduation. We find substantial socio-economic differences at each stage. Young people from poorer backgrounds are, on average, less likely to go to university than their richer peers. Even among the selected group who do go to university, they are less likely to attend the highest status institutions, less likely to graduate, and less likely to achieve the highest degree classes. These differences in degree outcomes contribute to the lower average earnings of graduates from poorer families, but earnings differentials go well beyond those driven purely by degree attainment or institution attended. The evidence strongly suggests that, even after taking these factors into account, graduates from affluent families are more likely to obtain a professional job and to see higher earnings growth in the labour market. We discuss the implications of these findings for the prospects of higher education as a route to greater social mobility

    Small scale statistics of viscoelastic turbulence

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    The small scale statistics of homogeneous isotropic turbulence of dilute polymer solutions is investigated by means of direct numerical simulations of a simplified viscoelastic fluid model. It is found that polymers only partially suppress the turbulent cascade below the Lumley scale, leaving a remnant energy flux even for large elasticity. As a consequence, fluid acceleration in viscoelastic flows is reduced with respect to Newtonian turbulence, whereas its rescaled probability density is left unchanged. At large scales the velocity field is found to be unaffected by the presence of polymers.Comment: 7 pages, 4 figure
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