65,956 research outputs found
Chimpanzee hunting behavior
The pursuit, capture and consumption of small-and medium-sized vertebrates, appears to be typical of all chimpanzee (Pan troglodytes) populations, although large variation exists. Red colobus monkeys (Piliocolobus sp.) appear to be the preferred prey but intensity and frequency of hunting varies from month to month and between populations. Hunting is a predominately male activity and is typically opportunistic, although there is some evidence of searching for prey. The degree of cooperation during hunting, as well as prey selection, varies between East and West African populations and may be related to the way the kill is divided: in West Africa, hunters often collaborate, with kills tending to be shared according to participation, whereas in East Africa, the kill is typically divided tactically by the male in possession of the carcass, trading meat with females in return for sex or with other males to strengthen alliances, and cooperation in hunting is more limited. The adaptive function of chimpanzee hunting is not well understood, although it appears that it may be both a means to acquire a nutritionally valuable commodity that can then be traded and as a means for males to display their prowess and reliability to one another
Screening in Ionic Systems: Simulations for the Lebowitz Length
Simulations of the Lebowitz length, , are reported
for t he restricted primitive model hard-core (diameter ) 1:1 electrolyte
for densi ties and .
Finite-size eff ects are elucidated for the charge fluctuations in various
subdomains that serve to evaluate . On extrapolation to the
bulk limit for the low-density expansions (Bekiranov and
Fisher, 1998) are seen to fail badly when (with ). At highe r densities rises above the Debye
length, \xi_{\text{D}} \prop to \sqrt{T/\rho}, by 10-30% (upto ); the variation is portrayed fairly well by generalized
Debye-H\"{u}ckel theory (Lee and Fisher, 19 96). On approaching criticality at
fixed or fixed , remains finite with
but displays a
weak entropy-like singularity.Comment: 4 pages 5 figure
Ferromagnetic Transition in One-Dimensional Itinerant Electron Systems
We use bosonization to derive the effective field theory that properly
describes ferromagnetic transition in one-dimensional itinerant electron
systems. The resultant theory is shown to have dynamical exponent z=2 at tree
leve and upper critical dimension d_c=2. Thus one dimension is below the upper
critical dimension of the theory, and the critical behavior of the transition
is controlled by an interacting fixed point, which we study via epsilon
expansion. Comparisons will be made with the Hertz-Millis theory, which
describes the ferromagnetic transition in higher dimensions.Comment: 4 pages. Presentation improved. Final version as appeared in PR
Kinetic approach to the cluster liquid-gas transition
The liquid-gas transition in free atomic clusters is investigated
theoretically based on simple unimolecular rate theories and assuming
sequential evaporations. A kinetic Monte Carlo scheme is used to compute the
time-dependent properties of clusters undergoing multiple dissociations, and
two possible definitions of the boiling point are proposed, relying on the
cluster or gas temperature. This numerical approach is supported by molecular
dynamics simulations of clusters made of sodium atoms or C60 molecules, as well
as simplified rate equation
Criticality in multicomponent spherical models : results and cautions
To enable the study of criticality in multicomponent fluids, the standard
spherical model is generalized to describe an \ns-species hard core lattice
gas. On introducing \ns spherical constraints, the free energy may be
expressed generally in terms of an \ns\times\ns matrix describing the species
interactions. For binary systems, thermodynamic properties have simple
expressions, while all the pair correlation functions are combinations of just
two eigenmodes. When only hard-core and short-range overall attractive
interactions are present, a choice of variables relates the behavior to that of
one-component systems. Criticality occurs on a locus terminating a coexistence
surface; however, except at some special points, an unexpected
``demagnetization effect'' suppresses the normal divergence of susceptibilities
at criticality and distorts two-phase coexistence. This effect, unphysical for
fluids, arises from a general lack of symmetry and from the vectorial and
multicomponent character of the spherical model. Its origin can be understood
via a mean-field treatment of an XY spin system below criticality.Comment: 4 figure
Members are not the only fruit: Volunteer activity in British political parties at the 2010 general election
This is the accepted version of the following article: Fisher, J., Fieldhouse, E. and Cutts, D. (2014), Members Are Not the Only Fruit: Volunteer Activity in British Political Parties at the 2010 General Election. The British Journal of Politics & International Relations, 16: 75–95, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/1467-856X.12011/abstract.Existing research on volunteer activity in political parties has tended to focus on party membership, both in terms of numbers and activities undertaken. Recent developments in British political parties suggest however, an increasing role for party supporters—supporters of parties who are not formal members. Using data collected through surveys of election agents at the 2010 general election, this article examines the extent of supporter activity in constituency (district-level) campaigns, the extent to which active local parties stimulate supporter activity, the correlates of supporter and member activity, and whether supporter activity makes a positive and independent contribution to parties’ constituency campaigns. The article provides an important opportunity to question whether the evolution of party organisations suggests that formal members may be less important than has been previously assumed in the conduct of election campaigns and the extent to which supporter activity complements that of members.Economic and Social Research Counci
The Force Exerted by a Molecular Motor
The stochastic driving force exerted by a single molecular motor (e.g., a
kinesin, or myosin) moving on a periodic molecular track (microtubule, actin
filament, etc.) is discussed from a general viewpoint open to experimental
test. An elementary "barometric" relation for the driving force is introduced
that (i) applies to a range of kinetic and stochastic models, (ii) is
consistent with more elaborate expressions entailing explicit representations
of externally applied loads and, (iii) sufficiently close to thermal
equilibrium, satisfies an Einstein-type relation in terms of the velocity and
diffusion coefficient of the (load-free) motor. Even in the simplest two-state
models, the velocity-vs.-load plots exhibit a variety of contrasting shapes
(including nonmonotonic behavior). Previously suggested bounds on the driving
force are shown to be inapplicable in general by analyzing discrete jump models
with waiting time distributions.Comment: submitted to PNA
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