678 research outputs found
Matching subsidies and voluntary contributions: A review
This paper provides a synthesis of the experimental literature on matching subsidies in the context of charitable giving. We classify results according to four different outcome variables frequently considered in the literature and address (i) short-term effects of linear matching, (ii) the role of the matching rate, (iii) context-dependence of behavioural responses, (iv) the relevance of the price of giving, (v) long-term effects and (vi) nonlinear matching schemes. Based on this comprehensive review, we highlight several avenues for future research, such as putting stronger emphasis on competition in fundraising, long-term effects or heterogeneity in responses
The large-scale modulation of the density distribution in standard axionic CDM and its cosmological and physical impact
It is shown, that the energy density of coherent axion field oscillations in
the cosmology of standard invisible axion should be distributed in the Universe
in the form of archioles, being nonlinear inhomogeneous structure, reflecting
the large scale distribution of Brownian structure of axion strings in the very
early Universe. Spectrum of inhomogeneities, generated by archioles, is
obtained and their effects in the spectrum and quadrupole anisotropy of relic
radiation are considered. The axionic-string-decay-model-independent
restriction on the scale of axion interaction is obtained.Comment: 8 pages, Talk presented at Workshop on Fundamental Physics at the
Birth of the Universe II, Roma, May 19-24, 199
Analysis of Strong-Coupling Parameters for Superfluid 3He
Superfluid He experiments show strong deviation from the weak-coupling
limit of the Ginzburg-Landau theory, and this discrepancy grows with increasing
pressure. Strong-coupling contributions to the quasiparticle interactions are
known to account for this effect and they are manifest in the five
-coefficients of the fourth order Ginzburg-Landau free energy terms. The
Ginzburg-Landau free energy also has a coefficient to include magnetic
field coupling to the order parameter. From NMR susceptibility experiments, we
find the deviation of from its weak-coupling value to be negligible at
all pressures. New results for the pressure dependence of four different
combinations of -coefficients, _{345}, _{12},
_{245}, and _{5} are calculated and comparison is made with
theory.Comment: 6 pages, 2 figures, 1 table. Manuscript prepared for QFS200
Axion-photon Couplings in Invisible Axion Models
We reexamine the axion-photon couplings in various invisible axion models
motivated by the recent proposal of using optical interferometry at the ASST
facility in the SSCL to search for axion. We illustrate that the assignment of
charges for the fermion fields plays an important role in
determining the couplings. Several simple non-minimal invisible axion models
with suppressed and enhanced axion-photon couplings are constructed,
respectively. We also discuss the implications of possible new experiments to
detect solar axions by conversion to -rays in a static magnetic apparatus
tracking the sun.Comment: 14 pages, LaTeX fil
Examining how health navigation affects mental health among gay, bisexual, and other men who have sex with men living with human immunodeficiency virus in Guatemala
Gay, bisexual, and other men who have sex with men (GBMSM) are disproportionately affected by mental health problems and human immunodeficiency virus (HIV). Health navigation has the potential to improve both HIV and mental health outcomes; however, few studies have measured the impact of navigation on mental health among people living with HIV. We analyzed longitudinal data from a sociobehavioral survey and navigation monitoring system with GBMSM living with HIV in Guatemala (n = 346) that participated in a 12-month differentiated care intervention. We examined relationships between navigation characteristics (frequency, duration, mode of interactions, and level of emotional, instrumental, and informational navigation support) and anxiety and depression using fixed-effects regression. We also examined if these relationships were moderated by baseline social support. We found that as navigation interactions increased, anxiety significantly improved [B = -0.03, standard error (SE) = 0.01 p = 0.05]. Participants who received high levels of informational navigator support also experienced a significant improvement in anxiety compared with those receiving low levels of informational support (B = -0.81, SE = 0.40, p = 0.04). Unexpectedly, we found that as the proportion of in-person navigation interactions increased, anxiety worsened (B = 1.12, SE = 0.54, p = 0.04). No aspects of navigation were significantly associated with depression and baseline social support did not moderate the relationship between navigation and anxiety and depression. To improve the mental health of key populations affected by HIV, health navigation programs should prioritize frequent interaction and informational navigation support for clients with anxiety while considering other strategies that specifically target reducing depressive symptoms, including other cost-effective modalities, such as mobile apps
Magnetized cosmological perturbations
A large-scale cosmic magnetic field affects not only the growth of density
perturbations, but also rotational instabilities and anisotropic deformation in
the density distribution. We give a fully relativistic treatment of all these
effects, incorporating the magneto-curvature coupling that arises in a
relativistic approach. We show that this coupling produces a small enhancement
of the growing mode on superhorizon scales. The magnetic field generates new
nonadiabatic constant and decaying modes, as well as nonadiabatic corrections
to the standard growing and decaying modes. Magnetized isocurvature
perturbations are purely decaying on superhorizon scales. On subhorizon scales
before recombination, magnetized density perturbations propagate as
magneto-sonic waves, leading to a small decrease in the spacing of acoustic
peaks. Fluctuations in the field direction induce scale-dependent vorticity,
and generate precession in the rotational vector. On small scales, magnetized
density vortices propagate as Alfv\'{e}n waves during the radiation era. After
recombination, they decay slower than non-magnetized vortices. Magnetic
fluctuations are also an active source of anisotropic distortion in the density
distribution. We derive the evolution equations for this distortion, and find a
particular growing solution.Comment: Revised version, typos corrected, to appear in Phys. Rev.
Mutations of the BRAF gene in human cancer
Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS RAF MEK ERK MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma
Indirect search for dark matter: prospects for GLAST
Possible indirect detection of neutralino, through its gamma-ray annihilation
product, by the forthcoming GLAST satellite from our galactic halo, M31, M87
and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are
evaluated for the two representative energy thresholds, 0.1 GeV and 1.0 GeV, at
which the spatial resolution of GLAST varies considerably. Apart from dwarfs
which are described either by a modified Plummer profile or by a
tidally-truncated King profiles, fluxes are compared for halos with central
cusps and cores. It is demonstrated that substructures, irrespective of their
profiles, enhance the gamma-ray emission only marginally. The expected
gamma-ray intensity above 1 GeV at high galactic latitudes is consistent with
the residual emission derived from EGRET data if the density profile has a
central core and the neutralino mass is less than 50 GeV, whereas for a central
cusp only a substantial enhancement would explain the observations. From M31,
the flux can be detected above 0.1 GeV and 1.0 GeV by GLAST only if the
neutralino mass is below 300 GeV and if the density profile has a central cusp,
case in which a significant boost in the gamma-ray emission is produced by the
central black hole. For Sagittarius, the flux above 0.1 GeV is detectable by
GLAST provided the neutralino mass is below 50 GeV. From M87 and Draco the
fluxes are always below the sensitivity limit of GLAST.Comment: 14 Pages, 7 Figures, 3 Tables, version to appear on Physical Review
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