2,893 research outputs found
Congenital abnormalities reported in Pelger-Huet homozygosity as compared to Greenberg/HEM dysplasia: highly variable expression of allelic phenotypes
Landscape equivalent of the shoving model
It is shown that the shoving model expression for the average relaxation time
of viscous liquids follows largely from a classical "landscape" estimation of
barrier heights from curvature at energy minima. The activation energy involves
both instantaneous bulk and shear moduli, but the bulk modulus contributes less
than 8% to the temperature dependence of the activation energy. This reflects
the fact that the physics of the two models are closely related.Comment: 4 page
Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?
Among vertebrates, the sense of smell is mediated by olfactory receptors (ORs) expressed in sensory neurons within the olfactory epithelium. Comparative genomic studies suggest that the olfactory acuity of mammalian species correlates positively with both the total number and the proportion of functional OR genes encoded in their genomes. In contrast to mammals, avian olfaction is poorly understood, with birds widely regarded as relying primarily on visual and auditory inputs. Here, we show that in nine bird species from seven orders (blue tit, Cyanistes caeruleus; black coucal, Centropus grillii; brown kiwi, Apteryx australis; canary, Serinus canaria; galah, Eolophus roseicapillus; red jungle fowl, Gallus gallus; kakapo, Strigops habroptilus; mallard, Anas platyrhynchos; snow petrel, Pagodroma nivea), the majority of amplified OR sequences are predicted to be from potentially functional genes. This finding is somewhat surprising as one previous report suggested that the majority of OR genes in an avian (red jungle fowl) genomic sequence are non-functional pseudogenes. We also show that it is not the estimated proportion of potentially functional OR genes, but rather the estimated total number of OR genes that correlates positively with relative olfactory bulb size, an anatomical correlate of olfactory capability. We further demonstrate that all the nine bird genomes examined encode OR genes belonging to a large gene clade, termed γ-c, the expansion of which appears to be a shared characteristic of class Aves. In summary, our findings suggest that olfaction in birds may be a more important sense than generally believed
Analyzing Powers for Deuteron-Induced Reactions Leading to Continuum Final States
This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit
Unifying flipped SU(5) in five dimensions
It is shown that embedding a four-dimensional flipped SU(5) model in a
five-dimensional SO(10) model, preserves the best features of both flipped
SU(5) and SO(10). The missing partner mechanism, which naturally achieves both
doublet-triplet splitting and suppression of d=5 proton decay operators, is
realized as in flipped SU(5), while the gauge couplings are unified as in
SO(10). The masses of down quarks and charged leptons, which are independent in
flipped SU(5), are related by the SO(10). Distinctive patterns of quark and
lepton masses can result. The gaugino mass M_1 is independent of M_3 and M_2,
which are predicted to be equal.Comment: revised version-to appear in PRD, 23 pages, 3 figures, ReVTeX
Decoherence in Bose-Einstein Condensates: towards Bigger and Better Schroedinger Cats
We consider a quantum superposition of Bose-Einstein condensates in two
immiscible internal states. A decoherence rate for the resulting Schroedinger
cat is calculated and shown to be a significant threat to this macroscopic
quantum superposition of BEC's. An experimental scenario is outlined where the
decoherence rate due to the thermal cloud is dramatically reduced thanks to
trap engineering and "symmetrization" of the environment which allow for the
Schroedinger cat to be an approximate pointer states.Comment: 12 pages in RevTex; improved presentation; a new comment on
decoherence-free pointer subspaces in BEC; accepted in Phys.Rev.
Lepton masses in a supersymmetric 3-3-1 model
We consider the mass generation for both charginos and neutralinos in a 3-3-1
supersymmetric model. We show that R-parity breaking interactions leave the
electron and one of the neutrinos massless at the tree level. However the same
interactions induce masses for these particles at the 1-loop level. Unlike the
similar situation in the MSSM the masses of the neutralinos are related to the
masses of the charginos.Comment: RevTex, 11 pages incluing 2 .eps figures. Extended published versio
Tachyon warm inflationary universe model in the weak dissipative regime
Warm inflationary universe model in a tachyon field theory is studied in the
weak dissipative regime. We develop our model for an exponential potential and
the dissipation parameter =constant. We describe scalar and
tensor perturbations for this scenario.Comment: 9 pages, accepted by European Physical Journal
Social and cultural origins of motivations to volunteer a comparison of university students in six countries
Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces
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