2,071 research outputs found
Convex Hull of Arithmetic Automata
Arithmetic automata recognize infinite words of digits denoting
decompositions of real and integer vectors. These automata are known expressive
and efficient enough to represent the whole set of solutions of complex linear
constraints combining both integral and real variables. In this paper, the
closed convex hull of arithmetic automata is proved rational polyhedral.
Moreover an algorithm computing the linear constraints defining these convex
set is provided. Such an algorithm is useful for effectively extracting
geometrical properties of the whole set of solutions of complex constraints
symbolically represented by arithmetic automata
A high flux source of cold strontium atoms
We describe an experimental apparatus capable of achieving a high loading
rate of strontium atoms in a magneto-optical trap operating in a high vacuum
environment. A key innovation of this setup is a two dimensional
magneto-optical trap deflector located after a Zeeman slower. We find a loading
rate of 6x10^9/s whereas the lifetime of the magnetically trapped atoms in the
3P2 state is 54s.Comment: 12 pages, 16 figure
Magnetism: the Driving Force of Order in CoPt. A First-Principles Study
CoPt or FePt equiatomic alloys order according to the tetragonal L10
structure which favors their strong magnetic anisotropy. Conversely magnetism
can influence chemical ordering. We present here {\it ab initio} calculations
of the stability of the L10 and L12 structures of Co-Pt alloys in their
paramagnetic and ferromagnetic states. They show that magnetism strongly
reinforces the ordering tendencies in this system. A simple tight-binding
analysis allows us to account for this behavior in terms of some pertinent
parameters
Is Poverty Decentralising? Quantifying Uncertainty in the Decentralisation of Urban Poverty
In this paper we argue that the recent focus on the suburbanisation of poverty is
problematic because of the ambiguities and inconsistencies in defining suburbia. To
improve transparency, replicability and comparability, we suggest that research on the
geographical changes to the distribution of poverty should focus on three questions: (1)
How centralised is urban poverty? (2) To what extent is it decentralising? (3) Is it
becoming spatially dispersed? With respect to all three questions, the issue of
quantifying uncertainty has been under-researched. The main contribution of the paper
is to provide a practical and robust solution to the problem of inference based on a
Bayesian multivariate conditional autoregressive (CAR) model, made accessible via the
R-software package CARBayes. Our approach can be applied to spatio-temporally
autocorrelated data, and can estimate both levels of and change in global RCIs (relative
centralisation index), local RCIs and dissimilarity indices. We illustrate our method with
an application to Scotland's four largest cities. Our results show that poverty was
centralised in 2011 in Glasgow, Dundee and Aberdeen. Poverty in Edinburgh, however,
was decentralised: non-poor households tend to live closer to the centre than poor
ones, and increasingly so. We also find evidence of statistically significant reductions in
centralisation of poverty in all four cities. To test whether this change is associated with
poverty becoming more dispersed, we estimate changes to evenness and local
decentralisation of poverty, revealing complex patterns of change
Computational Complexity of Atomic Chemical Reaction Networks
Informally, a chemical reaction network is "atomic" if each reaction may be
interpreted as the rearrangement of indivisible units of matter. There are
several reasonable definitions formalizing this idea. We investigate the
computational complexity of deciding whether a given network is atomic
according to each of these definitions.
Our first definition, primitive atomic, which requires each reaction to
preserve the total number of atoms, is to shown to be equivalent to mass
conservation. Since it is known that it can be decided in polynomial time
whether a given chemical reaction network is mass-conserving, the equivalence
gives an efficient algorithm to decide primitive atomicity.
Another definition, subset atomic, further requires that all atoms are
species. We show that deciding whether a given network is subset atomic is in
, and the problem "is a network subset atomic with respect to a
given atom set" is strongly -.
A third definition, reachably atomic, studied by Adleman, Gopalkrishnan et
al., further requires that each species has a sequence of reactions splitting
it into its constituent atoms. We show that there is a to decide whether a given network is reachably atomic, improving
upon the result of Adleman et al. that the problem is . We
show that the reachability problem for reachably atomic networks is
-.
Finally, we demonstrate equivalence relationships between our definitions and
some special cases of another existing definition of atomicity due to Gnacadja
LO-phonon assisted polariton lasing in a ZnO based microcavity
Polariton relaxation mechanisms are analysed experimentally and theoretically
in a ZnO-based polariton laser. A minimum lasing threshold is obtained when the
energy difference between the exciton reservoir and the bottom of the lower
polariton branch is resonant with the LO phonon energy. Tuning off this
resonance increases the threshold, and exciton-exciton scattering processes
become involved in the polariton relaxation. These observations are
qualitatively reproduced by simulations based on the numerical solution of the
semi-classical Boltzmann equations
Characterization of potential biomarkers of reactogenicity of licensed antiviral vaccines: randomized controlled clinical trials conducted by the BIOVACSAFE consortium
Funding text The authors are grateful for the vital contributions of the participating study volunteers, clinicians, nurses, and laboratory technicians at the Surrey study site. The work by Roberto Leone, laboratory technician at Humanitas Clinical and Research Center, is gratefully acknowledged. Finally, they thank Ellen Oe (GSK) for scientific writing assistance. The research leading to these results has received support from the Innovative Medicines Initiative Joint Undertaking under grant agreement n°115308, resources of which are composed of financial contribution from the European Union’s Seventh Framework Programme (FP7/2007–2013) and EFPIA companies’ in-kind contribution. The contribution of the European Commission to the Advanced Immunization Technologies (ADITEC) project (grant agreement n° 280873) is also gratefully acknowledged. Publisher Copyright: © 2019, The Author(s).Biomarkers predictive of inflammatory events post-vaccination could accelerate vaccine development. Within the BIOVACSAFE framework, we conducted three identically designed, placebo-controlled inpatient/outpatient clinical studies (NCT01765413/NCT01771354/NCT01771367). Six antiviral vaccination strategies were evaluated to generate training data-sets of pre-/post-vaccination vital signs, blood changes and whole-blood gene transcripts, and to identify putative biomarkers of early inflammation/reactogenicity that could guide the design of subsequent focused confirmatory studies. Healthy adults (N = 123; 20–21/group) received one immunization at Day (D)0. Alum-adjuvanted hepatitis B vaccine elicited vital signs and inflammatory (CRP/innate cells) responses that were similar between primed/naive vaccinees, and low-level gene responses. MF59-adjuvanted trivalent influenza vaccine (ATIV) induced distinct physiological (temperature/heart rate/reactogenicity) response-patterns not seen with non-adjuvanted TIV or with the other vaccines. ATIV also elicited robust early (D1) activation of IFN-related genes (associated with serum IP-10 levels) and innate-cell-related genes, and changes in monocyte/neutrophil/lymphocyte counts, while TIV elicited similar but lower responses. Due to viral replication kinetics, innate gene activation by live yellow-fever or varicella-zoster virus (YFV/VZV) vaccines was more suspended, with early IFN-associated responses in naïve YFV-vaccine recipients but not in primed VZV-vaccine recipients. Inflammatory responses (physiological/serum markers, innate-signaling transcripts) are therefore a function of the vaccine type/composition and presence/absence of immune memory. The data reported here have guided the design of confirmatory Phase IV trials using ATIV to provide tools to identify inflammatory or reactogenicity biomarkers.Peer reviewe
Probing impulsive strain propagation with x-ray pulses
Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden
reflections in InSb is used to follow the propagation of a coherent acoustic
pulse generated by ultrafast laser-excitation. The surface and bulk components
of the strain could be simultaneously measured due to the large x-ray
penetration depth. Comparison of the experimental data with dynamical
diffraction simulations suggests that the conventional model for impulsively
generated strain underestimates the partitioning of energy into coherent modes.Comment: 4 pages, 2 figures, LaTeX, eps. Accepted for publication in Phys.
Rev. Lett. http://prl.aps.or
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