1,196 research outputs found
Face processing limitation to own species in primates: a comparative study in brown capuchins, Tonkean macaques and humans
Full text linkMost primates live in social groups which survival and stability depend on
individuals' abilities to create strong social relationships with other group
members. The existence of those groups requires to identify individuals and to
assign to each of them a social status. Individual recognition can be achieved
through vocalizations but also through faces. In humans, an efficient system
for the processing of own species faces exists. This specialization is achieved
through experience with faces of conspecifics during development and leads to
the loss of ability to process faces from other primate species. We hypothesize
that a similar mechanism exists in social primates. We investigated face
processing in one Old World species (genus Macaca) and in one New World species
(genus Cebus). Our results show the same advantage for own species face
recognition for all tested subjects. This work suggests in all species tested
the existence of a common trait inherited from the primate ancestor: an
efficient system to identify individual faces of own species only
Dynamics of DNA Ejection From Bacteriophage
Get PDFThe ejection of DNA from a bacterial virus (``phage'') into its host cell is
a biologically important example of the translocation of a macromolecular chain
along its length through a membrane. The simplest mechanism for this motion is
diffusion, but in the case of phage ejection a significant driving force
derives from the high degree of stress to which the DNA is subjected in the
viral capsid. The translocation is further sped up by the ratcheting and
entropic forces associated with proteins that bind to the viral DNA in the host
cell cytoplasm. We formulate a generalized diffusion equation that includes
these various pushing and pulling effects and make estimates of the
corresponding speed-ups in the overall translocation process. Stress in the
capsid is the dominant factor throughout early ejection, with the pull due to
binding particles taking over at later stages. Confinement effects are also
investigated, in the case where the phage injects its DNA into a volume
comparable to the capsid size. Our results suggest a series of in vitro
experiments involving the ejection of DNA into vesicles filled with varying
amounts of binding proteins from phage whose state of stress is controlled by
ambient salt conditions or by tuning genome length.Comment: 17 pages, 5 figure
Status of the LUX Dark Matter Search
Full text linkThe Large Underground Xenon (LUX) dark matter search experiment is currently
being deployed at the Homestake Laboratory in South Dakota. We will highlight
the main elements of design which make the experiment a very strong competitor
in the field of direct detection, as well as an easily scalable concept. We
will also present its potential reach for supersymmetric dark matter detection,
within various timeframes ranging from 1 year to 5 years or more.Comment: 4 pages, in proceedings of the SUSY09 conferenc
What is Learned from Longitudinal Studies of Advertising and Youth Drinking and Smoking? A Critical Assessment
Get PDFThis paper assesses the methodology employed in longitudinal studies of advertising and youth drinking and smoking behaviors. These studies often are given a causal interpretation in the psychology and public health literatures. Four issues are examined from the perspective of econometrics. First, specification and validation of empirical models. Second, empirical issues associated with measures of advertising receptivity and exposure. Third, potential endogeneity of receptivity and exposure variables. Fourth, sample selection bias in baseline and follow-up surveys. Longitudinal studies reviewed include 20 studies of youth drinking and 26 studies of youth smoking. Substantial shortcomings are found in the studies, which preclude a causal interpretation
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