896 research outputs found
Fluvio-Marine Sediment Partitioning as a Function of Basin Water Depth
Progradational fluvio-deltaic systems tend towards but cannot reach equilibrium, a state in which the longitudinal profile does not change shape and all sediment is bypassed beyond the shoreline. They cannot reach equilibrium because progradation of the shoreline requires aggradation along the longitudinal profile. Therefore progradation provides a negative feedback, unless relative sea level falls at a sufficient rate to cause non-aggradational extension of the longitudinal profile. How closely fluvio-deltaic systems approach equilibrium is dependent on their progradation rate, which is controlled by water depth and downstream allogenic controls, and governs sediment partitioning between the fluvial, deltaic, and marine domains. Here, six analogue models of coastal fluvio-deltaic systems and small prograding shelf margins are examined to better understand the effect of water depth, subsidence, and relative sea-level variations upon longitudinal patterns of sediment partitioning and grain-size distribution that eventually determine large-scale stratigraphic architecture. Fluvio-deltaic systems prograding in relatively deep-water environments are characterized by relatively low progradation rates compared to shallow-water systems. This allows these deeper water systems to approach equilibrium more closely, enabling them to construct less concave and steeper longitudinal profiles that provide low accommodation to fluvial systems. Glacio-eustatic sea-level variations and subsidence modulate the effects of water depth on the longitudinal profile. Systems are closest to equilibrium during falling relative sea level and early lowstand, resulting in efficient sediment transport towards the shoreline at those times. Additionally, the strength of the response to relative sea-level fall differs dependent on water depth. In systems prograding into deep water, relative sea-level fall causes higher sediment bypass rates and generates significantly stronger erosion than in shallow-water systems, which increases the probability of incised-valley formation. Water depth in the receiving basin thus forms a first-order control on the sediment partitioning along the longitudinal profile of fluvio-deltaic systems and the shelf clinoform style. It also forms a control on the availability of sand-grade sediment at the shoreline that can potentially be remobilized and redistributed into deeper marine environments. Key findings are subsequently applied to literature of selected shelf clinoform successions
Physiologically based modelling of tranexamic acid pharmacokinetics following intravenous, intramuscular, sub-cutaneous and oral administration in healthy volunteers
BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic drug that reduces surgical blood loss and death due to bleeding after trauma and post-partum haemorrhage. Treatment success is dependent on early intervention and rapid systemic exposure to TXA. The requirement for intravenous (IV) administration can in some situations limit accessibility to TXA therapy. Here we employ physiologically based pharmacokinetic modelling (PBPK) to evaluate if adequate TXA exposure maybe achieved when given via different routes of administration. METHODS: A commercially available PBPK software (GastroPlus®) was used to model published TXA pharmacokinetics. IV, oral and intramuscular (IM) models were developed using healthy volunteer PK data from twelve different single dose regimens (n=48 participants). The model was verified using separate IV and oral validation datasets (n=26 participants). Oral, IM and sub-cutaneous (SQ) dose finding simulations were performed. RESULTS: Across the different TXA regimens evaluated TXA plasma concentrations varied from 0.1 to 94.0 µg/mL. Estimates of the total plasma clearance of TXA ranged from 0.091 to 0.104 L/h/kg, oral bioavailability from 36 to 67 % and Tmax from 2.6 to 3.2 and 0.4 to 1.0 hours following oral and intramuscular administration respectively. Variability in the observed TXA PK could be captured through predictable demographic effects on clearance, combined with intestinal permeability and stomach transit time following oral administration and muscle blood flow and muscle/plasma partition coefficients following intra-muscular dosing. CONCLUSIONS: This study indicates that intramuscular administration is the non-intravenous route of administration with the most potential for achieving targeted TXA exposures. Plasma levels following an IM dose of 1000 mg TXA are predicted to exceed 15 mg/mL in < 15 minutes and be maintained above this level for approximately 3 hours, achieving systemic exposure (AUC0-6) of 99 to 105 µg*hr/mL after a single dose. Well-designed clinical trials to verify these predictions and confirm the utility of intramuscular TXA are recommended
Higgs boson enhancement effects on squark-pair production at the LHC
We study the Higgs boson effects on third-generation squark-pair production
in proton-proton collision at the CERN Large Hadron Collider (LHC), including
\Stop \Stop^*, \Stop\Sbot^*, and \Sbot \Sbot^*. We found that substantial
enhancement can be obtained through s-channel exchanges of Higgs bosons at
large , at which the enhancement mainly comes from , , and initial states. We compute the complete set of electroweak
(EW) contributions to all production channels. This completes previous
computations in the literature. We found that the EW contributions can be
significant and can reach up to 25% in more general scenarios and at the
resonance of the heavy Higgs boson. The size of Higgs enhancement is comparable
or even higher than the PDF uncertainties and so must be included in any
reliable analysis. A full analytical computation of all the EW contributions is
presented.Comment: 23 pages, 7 figures, 1 tabl
Casting Light on Dark Matter
The prospects for detecting a candidate supersymmetric dark matter particle
at the LHC are reviewed, and compared with the prospects for direct and
indirect searches for astrophysical dark matter. The discussion is based on a
frequentist analysis of the preferred regions of the Minimal supersymmetric
extension of the Standard Model with universal soft supersymmetry breaking (the
CMSSM). LHC searches may have good chances to observe supersymmetry in the near
future - and so may direct searches for astrophysical dark matter particles,
whereas indirect searches may require greater sensitivity, at least within the
CMSSM.Comment: 16 pages, 13 figures, contribution to the proceedings of the LEAP
2011 Conferenc
Physics Opportunities of e+e- Linear Colliders
We describe the anticipated experimental program of an e+e- linear collider
in the energy range 500 GeV -- 1.5 TeV. We begin with a description of current
collider designs and the expected experimental environment. We then discuss
precision studies of the W boson and top quark. Finally, we review the range of
models proposed to explain the physics of electroweak symmetry breaking and
show, for each case, the central role that the linear collider experiments will
play in elucidating this physics. (to appear in Annual Reviews of Nuclear and
Particle Science)Comment: 93 pages, latex + 23 figures; typos corrections + 1 reference adde
On the effect of resonances in composite Higgs phenomenology
We consider a generic composite Higgs model based on the coset SO(5)/SO(4)
and study its phenomenology beyond the leading low-energy effective lagrangian
approximation. Our basic goal is to introduce in a controllable and simple way
the lowest-lying, possibly narrow, resonances that may exist is such models. We
do so by proposing a criterion that we call partial UV completion. We
characterize the simplest cases, corresponding respectively to a scalar in
either singlet or tensor representation of SO(4) and to vectors in the adjoint
of SO(4). We study the impact of these resonances on the signals associated to
high-energy vector boson scattering, pointing out for each resonance the
characteristic patterns of depletion and enhancement with respect to the
leading-order chiral lagrangian. En route we derive the O(p^4) general chiral
lagrangian and discuss its peculiar accidental and approximate symmetries.Comment: v3: a few typos corrected. Conclusions unchange
Suitable thicknesses of base metal and interlayer, and evolution of phases for Ag/Sn/Ag transient liquid-phase joints used for power die attachment
Both real Si insulated gate bipolar transistors (IGBT) with conventional Ni\Ag metallization and a dummy Si die with thickened Ni\Ag metallization have been bonded on Ag foils electroplated with 2.7 m and 6.8 m thick Sn as an interlayer at 250ºC for 0 min, 40 min and 640 min. From microstructure characterization of the resulting joints, suitable thicknesses are suggested for the Ag base metal and the Sn interlayer for Ag/Sn/Ag transient liquid phase (TLP) joints used in power die attachment, and the diffusivities of Ag and Sn in the Ag phase are extracted. In combination with the kinetic constants of Ag3Sn growth and diffusivities of Ag and Sn in Ag reported in the literature, the extracted diffusivities of Ag and Sn in Ag phase are also used to simulate and predict the diffusion-controlled growth and evolution of phases in the Ag/Sn/Ag TLP joints during an extended bonding process and in service
Supersymmetry in the shadow of photini
Additional neutral gauge fermions -- "photini" -- arise in string
compactifications as superpartners of U(1) gauge fields. Unlike their vector
counterparts, the photini can acquire weak-scale masses from soft SUSY breaking
and lead to observable signatures at the LHC through mass mixing with the bino.
In this work we investigate the collider consequences of adding photini to the
neutralino sector of the MSSM. Relatively large mixing of one or more photini
with the bino can lead to prompt decays of the lightest ordinary supersymmetric
particle; these extra cascades transfer most of the energy of SUSY decay chains
into Standard Model particles, diminishing the power of missing energy as an
experimental handle for signal discrimination. We demonstrate that the missing
energy in SUSY events with photini is reduced dramatically for supersymmetric
spectra with MSSM neutralinos near the weak scale, and study the effects on
limits set by the leading hadronic SUSY searches at ATLAS and CMS. We find that
in the presence of even one light photino the limits on squark masses from
hadronic searches can be reduced by 400 GeV, with comparable (though more
modest) reduction of gluino mass limits. We also consider potential discovery
channels such as dilepton and multilepton searches, which remain sensitive to
SUSY spectra with photini and can provide an unexpected route to the discovery
of supersymmetry. Although presented in the context of photini, our results
apply in general to theories in which additional light neutral fermions mix
with MSSM gauginos.Comment: 23 pages, 8 figures, references adde
Cosmic Ray Anomalies from the MSSM?
The recent positron excess in cosmic rays (CR) observed by the PAMELA
satellite may be a signal for dark matter (DM) annihilation. When these
measurements are combined with those from FERMI on the total () flux
and from PAMELA itself on the ratio, these and other results are
difficult to reconcile with traditional models of DM, including the
conventional mSUGRA version of Supersymmetry even if boosts as large as
are allowed. In this paper, we combine the results of a previously
obtained scan over a more general 19-parameter subspace of the MSSM with a
corresponding scan over astrophysical parameters that describe the propagation
of CR. We then ascertain whether or not a good fit to this CR data can be
obtained with relatively small boost factors while simultaneously satisfying
the additional constraints arising from gamma ray data. We find that a specific
subclass of MSSM models where the LSP is mostly pure bino and annihilates
almost exclusively into pairs comes very close to satisfying these
requirements. The lightest in this set of models is found to be
relatively close in mass to the LSP and is in some cases the nLSP. These models
lead to a significant improvement in the overall fit to the data by an amount
dof in comparison to the best fit without Supersymmetry
while employing boosts . The implications of these models for future
experiments are discussed.Comment: 57 pages, 31 figures, references adde
General Analysis of Antideuteron Searches for Dark Matter
Low energy cosmic ray antideuterons provide a unique low background channel
for indirect detection of dark matter. We compute the cosmic ray flux of
antideuterons from hadronic annihilations of dark matter for various Standard
Model final states and determine the mass reach of two future experiments
(AMS-02 and GAPS) designed to greatly increase the sensitivity of antideuteron
detection over current bounds. We consider generic models of scalar, fermion,
and massive vector bosons as thermal dark matter, describe their basic features
relevant to direct and indirect detection, and discuss the implications of
direct detection bounds on models of dark matter as a thermal relic. We also
consider specific dark matter candidates and assess their potential for
detection via antideuterons from their hadronic annihilation channels. Since
the dark matter mass reach of the GAPS experiment can be well above 100 GeV, we
find that antideuterons can be a good indirect detection channel for a variety
of thermal relic electroweak scale dark matter candidates, even when the rate
for direct detection is highly suppressed.Comment: 44 pages, 15 Figure
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