60,088 research outputs found
Specific Heat of Disordered He
Porous aerogel is a source of elastic scattering in superfluid 3He and
modifies the properties of the superfluid, suppressing the transition
temperature and order parameter. The specific heat jumps for the B-phase of
superfluid 3He in aerogel have been measured as a function of pressure and
interpreted using the homogeneous and inhomogeneous isotropic scattering
models. The specific heat jumps for other p-wave states are estimated for
comparison.Comment: Manuscript prepared for LT 2
Uniaxial-stress induced phase transitions in [001]c-poled 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3
First-order, rhombohedral to orthorhombic, stress-induced phase transitions
have been evidenced by bulk charge-stress measurements and X-ray diffraction
derived lattice strain measurements in [001]c-poled PZN-4.5PT. The transitions
are induced by uniaxial, compressive loads applied either along or
perpendicular to the poling direction. In each case, they occur via rotation of
the polar vector in the Cm monoclinic plane and the induced lattice strain is
hysteretic yet reversible. Although no depoling is observed in the transverse
mode, net depolarization is observed under longitudinal stress which is
important for the use of [001]c-poled PZN-PT and PMN-PT single crystals in
Tonpilz-type underwater projectors.Comment: To be published in Applied Physics Letters, 16 pages, 3 figure
Absolute instabilities of travelling wave solutions in a Keller-Segel model
We investigate the spectral stability of travelling wave solutions in a
Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity
function and a constant, sublinear, and linear consumption rate. Linearising
around the travelling wave solutions, we locate the essential and absolute
spectrum of the associated linear operators and find that all travelling wave
solutions have essential spectrum in the right half plane. However, we show
that in the case of constant or sublinear consumption there exists a range of
parameters such that the absolute spectrum is contained in the open left half
plane and the essential spectrum can thus be weighted into the open left half
plane. For the constant and sublinear consumption rate models we also determine
critical parameter values for which the absolute spectrum crosses into the
right half plane, indicating the onset of an absolute instability of the
travelling wave solution. We observe that this crossing always occurs off of
the real axis
Semi-Empirical Bound on the Chlorinr-37 Solar Neutrino Experiment
The Kamiokande measurement of energetic Boron-8 neutrinos from the sun is
used to set a lower bound on the contribution of the same neutrinos to the
signal in the \Chlorine\ experiment. Implications for Beryllium-7 neutrinos are
discussed.Comment: Latex, 6 pages + 1 postscript figure (included). UTAPHY-HEP-
Water Vapour Effects in Mass Measurement
Water vapour inside the mass comparator enclosure is a critical parameter. In
fact, fluctuations of this parameter during mass weighing can lead to errors in
the determination of an unknown mass. To control that, a proposal method is
given and tested. Preliminary results of our observation of water vapour
sorption and desorption processes from walls and mass standard are reported
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Helping out: a national survey of volunteering and charitable giving
This report details the main findings of a national survey of volunteering and charitable giving – termed Helping Out – carried out by the National Centre for Social Research (NatCen) in partnership with the Institute for Volunteering Research (IVR) in 2006/07. The study was carried out for the Office of the Third Sector in the Cabinet Office.
The main aims of the study were to examine:
- how and why people give unpaid help to organisations, and what they think of their experiences;
- what stops people from giving help;
- the links between giving time and giving money;
- how, why and how much people give money to charity;
- what stops people from giving money to charity.
There was also interest in estimates of the prevalence of volunteering and charitable giving. However, for a number of reasons (detailed in Chapters 2 and 10), prevalence estimates derived from this study should not be used to look at changes in these measures over time. Other study series are better suited to this purpose.
In terms of volunteering, the study focused on formal help given through groups and organisations rather than informal help (given as an individual, e.g. to family and friends)
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