16,004 research outputs found
Cranial sutures work collectively to distribute strain throughout the reptile skull
The skull is composed of many bones that come together at sutures. These sutures are important sites of growth, and as growth ceases some become fused while others remain patent. Their mechanical behaviour and how they interact with changing form and loadings to ensure balanced craniofacial development is still poorly understood. Early suture fusion often leads to disfiguring syndromes, thus is it imperative that we understand the function of sutures more clearly. By applying advanced engineering modelling techniques, we reveal for the first time that patent sutures generate a more widely distributed, high level of strain throughout the reptile skull. Without patent sutures, large regions of the skull are only subjected to infrequent low-level strains that could weaken the bone and result in abnormal development. Sutures are therefore not only sites of bone growth, but could also be essential for the modulation of strains necessary for normal growth and development in reptiles
Microfabricated high-finesse optical cavity with open access and small volume
We present a microfabricated optical cavity, which combines a very small mode volume with high finesse. In contrast to other micro-resonators, such as microspheres, the structure we have built gives atoms and molecules direct access to the high-intensity part of the field mode, enabling them to interact strongly with photons in the cavity for the purposes of detection and quantum-coherent manipulation. Light couples directly in and out of the resonator through an optical fiber, avoiding the need for sensitive coupling optics. This renders the cavity particularly attractive as a component of a lab-on-a-chip, and as a node in a quantum network
Evidence for fast thermalization in the plane-wave matrix model
We perform a numerical simulation of the classical evolution of the
plane-wave matrix model with semiclassical initial conditions. Some of these
initial conditions thermalize and are dual to a black hole forming from the
collision of D-branes in the plane wave geometry. In particular, we consider a
large fuzzy sphere (a D2-brane) plus a single eigenvalue (a D0-particle) going
exactly through the center of the fuzzy sphere and aimed to intersect it.
Including quantum fluctuations of the off-diagonal modes in the initial
conditions, with sufficient kinetic energy the configuration collapses to a
small size. We also find evidence for fast thermalization: rapidly decaying
autocorrelation functions at late times with respect to the natural time scale
of the system.Comment: 5 pages, 5 figures, revtex4 format; v2: minor typos fixed; v3: 8
pages, 9 figures, minor changes, includes a supplement as appeared on PR
From hidden symmetry to extra dimensions: a five dimensional formulation of the Degenerate BESS model
We consider the continuum limit of a moose model corresponding to a
generalization to N sites of the Degenerate BESS model. The five dimensional
formulation emerging in this limit is a realization of a RS1 type model with
SU(2)_L x SU(2)_R in the bulk, broken by boundary conditions and a vacuum
expectation value on the infrared brane. A low energy effective Lagrangian is
derived by means of the holographic technique and corresponding bounds on the
model parameters are obtained.Comment: Latex file, 40 pages and 5 figure
Zeeman Slowers for Strontium based on Permanent Magnets
We present the design, construction, and characterisation of longitudinal-
and transverse-field Zeeman slowers, based on arrays of permanent magnets, for
slowing thermal beams of atomic Sr. The slowers are optimised for operation
with deceleration related to the local laser intensity (by the parameter
), which uses more effectively the available laser power, in contrast
to the usual constant deceleration mode. Slowing efficiencies of up to
are realised and compared to those predicted by modelling.
We highlight the transverse-field slower, which is compact, highly tunable,
light-weight, and requires no electrical power, as a simple solution to slowing
Sr, well-suited to spaceborne application. For Sr we achieve a slow-atom
flux of around atomss at ms, loading
approximately atoms in to a magneto-optical-trap (MOT), and
capture all isotopes in approximate relative natural abundances
A multi-method approach to delineate and validate migratory corridors
Context:
Managers are faced with numerous methods for delineating wildlife movement corridors, and often must make decisions with limited data. Delineated corridors should be robust to different data and models.
Objectives:
We present a multi-method approach for delineating and validating wildlife corridors using multiple data sources, which can be used conserve landscape connectivity. We used this approach to delineate and validate migration corridors for wildebeest (Connochaetes taurinus) in the Tarangire Ecosystem of northern Tanzania.
Methods:
We used two types of locational data (distance sampling detections and GPS collar locations), and three modeling methods (negative binomial regression, logistic regression, and Maxent), to generate resource selection functions (RSFs) and define resistance surfaces. We compared two corridor detection algorithms (cost-distance and circuit theory), to delineate corridors. We validated corridors by comparing random and wildebeest locations that fell within corridors, and cross-validated by data type.
Results:
Both data types produced similar RSFs. Wildebeest consistently selected migration habitat in flatter terrain farther from human settlements. Validation indicated three of the combinations of data type, modeling, and corridor detection algorithms (detection data with Maxent modeling, GPS collar data with logistic regression modeling, and GPS collar data with Maxent modeling, all using cost-distance) far outperformed the other seven. We merged the predictive corridors from these three data-method combinations to reveal habitat with highest probability of use.
Conclusions:
The use of multiple methods ensures that planning is able to prioritize conservation of migration corridors based on all available information
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