1,465 research outputs found
Calculated collision induced absorption spectrum for He-Ar
Calculation of collision induced absorption spectra for helium-argo
The StoreGate: a Data Model for the Atlas Software Architecture
The Atlas collaboration at CERN has adopted the Gaudi software architecture
which belongs to the blackboard family: data objects produced by knowledge
sources (e.g. reconstruction modules) are posted to a common in-memory data
base from where other modules can access them and produce new data objects. The
StoreGate has been designed, based on the Atlas requirements and the experience
of other HENP systems such as Babar, CDF, CLEO, D0 and LHCB, to identify in a
simple and efficient fashion (collections of) data objects based on their type
and/or the modules which posted them to the Transient Data Store (the
blackboard). The developer also has the freedom to use her preferred key class
to uniquely identify a data object according to any other criterion. Besides
this core functionality, the StoreGate provides the developers with a powerful
interface to handle in a coherent fashion persistable references, object
lifetimes, memory management and access control policy for the data objects in
the Store. It also provides a Handle/Proxy mechanism to define and hide the
cache fault mechanism: upon request, a missing Data Object can be transparently
created and added to the Transient Store presumably retrieving it from a
persistent data-base, or even reconstructing it on demand.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, LaTeX, MOJT00
Binding effects in multivalent Gibbs-Donnan equilibrium
The classical Gibbs-Donnan equilibrium describes excess osmotic pressure
associated with confined colloidal charges embedded in an electrolyte solution.
In this work, we extend this approach to describe the influence of multivalent
ion binding on the equilibrium force acting on a charged rod translocating
between two compartments, thereby mimicking ionic effects on force balance
during in vitro DNA ejection from bacteriophage. The subtle interplay between
Gibbs-Donnan equilibrium and adsorption equilibrium leads to a non-monotonic
variation of the ejection force as multivalent salt concentration is increased,
in qualitative agreement with experimental observations
Separation of suspended particles in microfluidic systems by directional-locking in periodic fields
We investigate the transport and separation of overdamped particles under the
action of a uniform external force in a two-dimensional periodic energy
landscape. Exact results are obtained for the deterministic transport in a
square lattice of parabolic, repulsive centers that correspond to a
piecewise-continuous linear-force model. The trajectories are periodic and
commensurate with the obstacle lattice and exhibit phase-locking behavior in
that the particle moves at the same average migration angle for a range of
orientation of the external force. The migration angle as a function of the
orientation of the external force has a Devil's staircase structure. The first
transition in the migration angle was analyzed in terms of a Poincare map,
showing that it corresponds to a tangent bifurcation. Numerical results show
that the limiting behavior for impenetrable obstacles is equivalent to the high
Peclet number limit in the case of transport of particles in a periodic pattern
of solid obstacles. Finally, we show how separation occurs in these systems
depending on the properties of the particles
First-principles kinetic Monte Carlo simulations for heterogeneous catalysis, applied to the CO oxidation at RuO2(110)
We describe a first-principles statistical mechanics approach enabling us to
simulate the steady-state situation of heterogeneous catalysis. In a first step
density-functional theory together with transition-state theory is employed to
obtain the energetics of all relevant elementary processes. Subsequently the
statistical mechanics problem is solved by the kinetic Monte Carlo method,
which fully accounts for the correlations, fluctuations, and spatial
distributions of the chemicals at the surface of the catalyst under
steady-state conditions. Applying this approach to the catalytic oxidation of
CO at RuO2(110), we determine the surface atomic structure and composition in
reactive environments ranging from ultra-high vacuum (UHV) to technologically
relevant conditions, i.e. up to pressures of several atmospheres and elevated
temperatures. We also compute the CO2 formation rates (turnover frequencies).
The results are in quantitative agreement with all existing experimental data.
We find that the high catalytic activity of this system is intimately connected
with a disordered, dynamic surface ``phase'' with significant compositional
fluctuations. In this active state the catalytic function results from a
self-regulating interplay of several elementary processes.Comment: 18 pages including 9 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
The South African child death review pilot: A multiagency approach to strengthen healthcare and protection for children
Background. Child mortality trends in South Africa (SA) show a decrease, but remain high and appear to have plateaued. To attain the new sustainable development goals, we need a better understanding of causes of death and the associated factors.Objectives. To describe the SA child death review (CDR) pilot, the pattern of child deaths reviewed and the factors associated with these deaths.Methods. CDR teams were established at two pilot sites, Salt River mortuary (Western Cape Province) and Phoenix mortuary (KwaZulu-Natal Province). All child deaths were reviewed by a multidisciplinary team at the pilot sites for the period 1 January 2014 - 31 December 2014.Results. The CDR pilot reviewed 711 cases. Over half (53.3%) were natural deaths, as opposed to 42.6% non-natural deaths. Most infant deaths (83.9%) were due to natural causes, while 91.7% of deaths in the 15 - 17-year-old age group were due to injuries. The leading cause of deaths reviewed (30.8%) was respiratory tract infection (RTI), mainly among infants (51.6%). Homicide was the second most common cause of death and affected children of all ages, with the highest burden (52.8%) in the 15 - 17-year age group. Child abuse and neglect accounted for 11.3% of deaths. RTI was shown to be more likely after the neonatal period (odds ratio (OR) 2.92; p<0.000) and in preterm infants (OR 1.98; p=0.005).Conclusions. CDR teams have been effective in improving identification of the causes of out-of-hospital deaths, as well as by identifying remediable factors critical to reducing child deaths further
Kinetic Characterisation of a Single Chain Antibody against the Hormone Abscisic Acid: Comparison with Its Parental Monoclonal
A single-chain Fv fragment antibody (scFv) specific for the plant hormone abscisic acid (ABA) has been expressed in the bacterium Escherichia coli as a fusion protein. The kinetics of ABA binding have been measured using surface plasmon resonance spectrometry (BIAcore 2000) using surface and solution assays. Care was taken to calculate the concentration of active protein in each sample using initial rate measurements under conditions of partial mass transport limitation. The fusion product, parental monoclonal antibody and the free scFv all have low nanomolar affinity constants, but there is a lower dissociation rate constant for the parental monoclonal resulting in a three-fold greater affinity. Analogue specificity was tested and structure-activity binding preferences measured. The biologically-active (+)-ABA enantiomer is recognised with an affinity three orders of magnitude higher than the inactive (-)-ABA. Metabolites of ABA including phaseic acid, dihydrophaseic acid and deoxy-ABA have affinities over 100-fold lower than that for (+)-ABA. These properties of the scFv make it suitable as a sensor domain in bioreporters specific for the naturally occurring form of ABA
Alloy surface segregation in reactive environments: A first-principles atomistic thermodynamics study of Ag3Pd(111) in oxygen atmospheres
We present a first-principles atomistic thermodynamics framework to describe
the structure, composition and segregation profile of an alloy surface in
contact with a (reactive) environment. The method is illustrated with the
application to a Ag3Pd(111) surface in an oxygen atmosphere, and we analyze
trends in segregation, adsorption and surface free energies. We observe a wide
range of oxygen adsorption energies on the various alloy surface
configurations, including binding that is stronger than on a Pd(111) surface
and weaker than that on a Ag(111) surface. This and the consideration of even
small amounts of non-stoichiometries in the ordered bulk alloy are found to be
crucial to accurately model the Pd surface segregation occurring in
increasingly O-rich gas phases.Comment: 13 pages including 6 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
First Report of the Simulation Optimization Group
This is the first report of the ATLAS Simulation Optimization Group, established in June of 2007. This article justifies the selected Geant4 version, physics list, and range cuts to be used by the default ATLAS simulation for initial data taking and beyond. The current status of several projects, including detector description, simulation validation, studies of additional Geant4 parameters, and cavern background, are reported
- …