710 research outputs found
Is there a 'Neutral theory of Anthropology'?
Lansing and Cox open a welcome discussion of the potential for neutral models in anthropologyâit has been almost 50 years since the original neutral models were applied to DNA sequences (e.g., Kimura 1968) and then later to biological phenotypes (e.g., Lande 1976) and cultural data (Cavalli-Sforza and Feldman 1981; Neiman 1995). This long history of research is a gold mine for studies of culture evolution
Fast Diffusion Process in Quenched hcp Dilute Solid He-He Mixture
The study of phase structure of dilute He - He solid mixture of
different quality is performed by spin echo NMR technique. The diffusion
coefficient is determined for each coexistent phase. Two diffusion processes
are observed in rapidly quenched (non-equilibrium) hcp samples: the first
process has a diffusion coefficient corresponding to hcp phase, the second one
has huge diffusion coefficient corresponding to liquid phase. That is evidence
of liquid-like inclusions formation during fast crystal growing. It is
established that these inclusions disappear in equilibrium crystals after
careful annealing.Comment: 7 pages, 3 figures, QFS200
Actinorhodopsin genes discovered diverse in freshwater habitats and among cultivated Actinobacteria
Microbial rhodopsins are membrane proteins that utilize a retinal chromophore to harvest sunlight for energetic and photosensory functions. Recently, a group of novel rhodopsin sequences named âactinorhodopsinsâ (ActRs) was hypothesized to exist among uncultured planktonic Actinobacteria. ActRs were discovered by mining metagenomic data obtained during the Venter Instituteâs Global Ocean Sampling expedition, from a hypersaline lagoon, two estuaries and a freshwater lake. On the basis of these findings, and many studies that show Actinobacteria are common inhabitants of lakes, we predicted that ActR genes would likely be present in other freshwater habitats and among the genomes of cultivated Actinobacteria. Using degenerate polymerase chain reaction primers, we discovered an ActR gene present in an actinobacterial isolate of the family Microbacteriaceae. Isolate MWH-Uga1 was cultivated prior to this study from a freshwater pond in Uganda and belongs to a group of Actinobacteria previously identified in freshwater ecosystems. ActR genes were also discovered present in numerous mixed cultures containing freshwater Actinobacteria and among environmental DNA samples obtained from three freshwater sources; a small woodland pond and the Laurentian Great Lakes Superior and Erie. An analysis of small subunit ribosomal RNA genes from metagenomic DNA samples harboring ActR genes suggests that organisms belonging to the acI lineage, an uncultured group of Actinobacteria commonly present in fresh waters, may utilize rhodopsins. The co-occurrence of an acI organism with a specific ActR variant in a mixed culture supports our hypothesis
MW and sin^2\theta_eff in Split SUSY: present and future expectations
We analyse the precision electroweak observables MW and sin^2\theta_eff and
their correlations in the recently proposed Split SUSY model. We compare the
results with the Standard Model and Minimal Supersymmetric Standard Model
predictions, and with present and future experimental accuracies. Present
experimental accuracies in (MW, sin^2\theta_eff) do not allow constraints to be
placed on the Split SUSY parameter space. We find that the shifts in (MW,
sin^2\theta_eff) induced by Split SUSY can be larger than the anticipated
accuracy of the GigaZ option of the International Linear Collider, and that the
most sensitive observable is sin^2\theta_eff. These large shifts are possible
also for large chargino masses in scenarios with small tan(\beta) =~ 1.Comment: LaTeX, 13 pages, 4 figures. Comments adde
A probabilistic model for gene content evolution with duplication, loss, and horizontal transfer
We introduce a Markov model for the evolution of a gene family along a
phylogeny. The model includes parameters for the rates of horizontal gene
transfer, gene duplication, and gene loss, in addition to branch lengths in the
phylogeny. The likelihood for the changes in the size of a gene family across
different organisms can be calculated in O(N+hM^2) time and O(N+M^2) space,
where N is the number of organisms, is the height of the phylogeny, and M
is the sum of family sizes. We apply the model to the evolution of gene content
in Preoteobacteria using the gene families in the COG (Clusters of Orthologous
Groups) database
Measurement of Cosmic-ray Muon-induced Spallation Neutrons in the Aberdeen Tunnel Underground Laboratory
AbstractMuon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented
The Kuiper Belt and Other Debris Disks
We discuss the current knowledge of the Solar system, focusing on bodies in
the outer regions, on the information they provide concerning Solar system
formation, and on the possible relationships that may exist between our system
and the debris disks of other stars. Beyond the domains of the Terrestrial and
giant planets, the comets in the Kuiper belt and the Oort cloud preserve some
of our most pristine materials. The Kuiper belt, in particular, is a
collisional dust source and a scientific bridge to the dusty "debris disks"
observed around many nearby main-sequence stars. Study of the Solar system
provides a level of detail that we cannot discern in the distant disks while
observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book
"Astrophysics in the Next Decade
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
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