217 research outputs found
Viscoelastic and Dynamic Properties of Soft Liners and Tissue Conditioners
The creep compliance and dynamic modulus of two tissue conditioners and five soft liners were determined after storage in water at 37 C. Under static conditions the tissue conditioners functioned like viscous liquids, whereas the soft liners were more elastic. In general, linear viscoelasticity was not observed. Under dynamic conditions, the materials were stiffer.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67015/2/10.1177_00220345790580080601.pd
Probing Supersymmetry With Third-Generation Cascade Decays
The chiral structure of supersymmetric particle couplings involving third
generation Standard Model fermions depends on left-right squark and slepton
mixings as well as gaugino-higgsino mixings. The shapes and intercorrelations
of invariant mass distributions of a first or second generation lepton with
bottoms and taus arising from adjacent branches of SUSY cascade decays are
shown to be a sensitive probe of this chiral structure. All possible cascade
decays that can give rise to such correlations within the MSSM are considered.
For bottom-lepton correlations the distinctive structure of the invariant mass
distributions distinguishes between decays originating from stop or sbottom
squarks through either an intermediate chargino or neutralino. For decay
through a chargino the spins of the stop and chargino are established by the
form of the distribution. When the bottom charge is signed through soft muon
tagging, the structure of the same-sign and opposite-sign invariant mass
distributions depends on a set function of left-right and gaugino-higgsino
mixings, as well as establishes the spins of all the superpartners in the
sequential two-body cascade decay. Tau-lepton and tau-tau invariant mass
distributions arising from MSSM cascade decays are likewise systematically
considered with particular attention to their dependence on tau polarization.
All possible tau-lepton and tau-tau distributions are plotted using a
semi-analytic model for hadronic one-prong taus. Algorithms for fitting tau-tau
and tau-lepton distributions to data are suggested.Comment: 35 pages, 17 .eps figure
Vulnerability of Cape Fold Ecoregion freshwater fishes to climate change and other human impacts
1. Native freshwater fish populations throughout South Africa's Cape Fold Ecoregion (CFE) are in decline as a result of human impacts on aquatic habitats, including the introduction of nonnative
freshwater fishes. Climate change may be further accelerating declines of many species, although this has not yet been studied in the CFE. This situation presents a major conservation challenge that requires assigning management priorities through assessing species in terms of their vulnerability to climate change.
2. One factor hindering reliable vulnerability assessments and the concurrent development of effective conservation strategies is limited knowledge of the biology and population status of many species. This paper reports on a study employing a rapid assessment method used
in the USA, designed to capitalize on available expert knowledge to supplement existing empirical data, to determine the relative vulnerabilities of different species to climate change and other human impacts. Eight local freshwater fish experts conducted vulnerability assessments on 20 native and 17 nonânative freshwater fish species present in the CFE.
3. Results show (1) that native species were generally classified as being more vulnerable to extinction than were nonânative species, (2) that the climate change impacts are expected to increase the vulnerability of most native, and some nonânative, species, (3) that vulnerability
hotspots requiring urgent conservation attention occur in the OlifantsâDoring, upper Berg and upper Breede River catchments in the south west of the region, (4) that in addition to providing guidance for prioritizing management interventions, this study highlights the need for reliable data on the biology and distribution of many CFE freshwater fishes, and (5) that
identification of priority areas for protection should be based on multiple sources of data
D terms from D-branes, gauge invariance and moduli stabilization in flux compactifications
We elucidate the structure of D terms in N=1 orientifold compactifications
with fluxes. As a case study, we consider a simple orbifold of the type-IIA
theory with D6-branes at angles, O6-planes and general NSNS, RR and
Scherk-Schwarz geometrical fluxes. We examine in detail the emergence of D
terms, in their standard supergravity form, from an appropriate limit of the
D-brane action. We derive the consistency conditions on gauged symmetries and
general fluxes coming from brane-localized Bianchi identities, and their
relation with the Freed-Witten anomaly. We extend our results to other N=1
compactifications and to non-geometrical fluxes. Finally, we discuss the
possible role of U(1) D terms in the stabilization of the untwisted moduli from
the closed string sector.Comment: 1+31 pages, 1 figur
Phase diagrams of spin ladders with ferromagnetic legs
The low-temperature properties of the spin S=1/2 ladder with anisotropic
ferromagnetic legs are studied using the continuum limit bosonization approach.
The weak-coupling ground state phase diagram of the model is obtained for a
wide range of coupling constants and several unconventional gapless
''spin-liquid'' phases are shown to exist for ferromagnetic coupling. The
behavior of the ladder system in the vicinity of the ferromagnetic instability
point is discussed in detail.Comment: 11 pages, 4 figure
Warped Reheating in Multi-Throat Brane Inflation
We investigate in some quantitative details the viability of reheating in
multi-throat brane inflationary scenarios by estimating and comparing the time
scales for the various processes involved. We also calculate within
perturbative string theory the decay rate of excited closed strings into KK
modes and compare with that of their decay into gravitons; we find that in the
inflationary throat the former is preferred. We also find that over a small but
reasonable range of parameters of the background geometry, these KK modes will
preferably tunnel to another throat (possibly containing the Standard Model)
instead of decaying to gravitons due largely to their suppressed coupling to
the bulk gravitons. Once tunneled, the same suppressed coupling to the
gravitons again allows them to reheat the Standard Model efficiently. We also
consider the effects of adding more throats to the system and find that for
extra throats with small warping, reheating still seems viable.Comment: 29 pages, 4 figures, discussions on closed string decay expanded,
references adde
Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement - a finite element study
Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in-vitro testing, we used commercially-available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in-vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley
T-duality, Generalized Geometry and Non-Geometric Backgrounds
We discuss the action of O(d,d), and in particular T-duality, in the context
of generalized geometry, focusing on the description of so-called non-geometric
backgrounds. We derive local expressions for the pure spinors descibing the
generalized geometry dual to an SU(3) structure background, and show that the
equations for N=1 vacua are invariant under T-duality. We also propose a local
generalized geometrical definition of the charges f, H, Q and R appearing in
effective four-dimensional theories, using the Courant bracket. We then address
certain global aspects, in particular whether the local non-geometric charges
can be gauged away in, for instance, backgrounds admitting a torus action, as
well as the structure of generalized parallelizable backgrounds.Comment: 33 page
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