11,381 research outputs found
Changes in pathogen prevalence and resistance related to the introduction of macrolide maintenance therapy in cystic fibrosis patients
Selective low concentration ammonia sensing in a microfluidic lab-on-a-chip
In the medical community, there is a considerable interest in a diagnostic breath analyzer for ammonia that is selectively enough to measure in exhaled air and small enough for the small volumes available in such an application. An indirect measurement system for low gaseous ammonia concentrations has been miniaturized and integrated on a chip in order to reach this goal. The detection limit of the system was calculated to be 1.1 parts per billion (ppb). The response time was determined to be 1.6 min with a gas How of 50 ml/min. The required gas volume for one measurement is therefore sufficiently small, although sampling assistance is required for breath analysis. The selectivity of the system is sufficient to measure ammonia concentrations in the low-ppb range. The system is even sufficiently selective to be used in environments that contain elevated carbon dioxide levels, like exhaled air. The lower ammonia concentration expected in diagnostic breath analysis applications, 50 ppb, was demonstrated to be detectable
High orders of Weyl series for the heat content
This article concerns the Weyl series of spectral functions associated with
the Dirichlet Laplacian in a -dimensional domain with a smooth boundary. In
the case of the heat kernel, Berry and Howls predicted the asymptotic form of
the Weyl series characterized by a set of parameters. Here, we concentrate on
another spectral function, the (normalized) heat content. We show on several
exactly solvable examples that, for even , the same asymptotic formula is
valid with different values of the parameters. The considered domains are
-dimensional balls and two limiting cases of the elliptic domain with
eccentricity : A slightly deformed disk () and an
extremely prolonged ellipse (). These cases include 2D domains
with circular symmetry and those with only one shortest periodic orbit for the
classical billiard. We analyse also the heat content for the balls in odd
dimensions for which the asymptotic form of the Weyl series changes
significantly.Comment: 20 pages, 1 figur
Out of Equilibrium Solutions in the -Hamiltonian Mean Field model
Out of equilibrium magnetised solutions of the -Hamiltonian Mean Field
(-HMF) model are build using an ensemble of integrable uncoupled pendula.
Using these solutions we display an out-of equilibrium phase transition using a
specific reduced set of the magnetised solutions
Trajectory Deflection of Spinning Magnetic Microparticles, the Magnus Effect at the Microscale
The deflection due to the Magnus force of magnetic particles with a diameter
of 80 micrometer dropping through fluids and rotating in a magnetic field was
measured. With Reynolds number for this experiment around 1, we found
trajectory deflections of the order of 1 degree, in agreement within
measurement error with theory. This method holds promise for the sorting and
analysis of the distribution in magnetic moment and particle diameter of
suspensions of microparticles, such as applied in catalysis, or objects loaded
with magnetic particles.Comment: 12 pages, 3 figures. Appendix with 6 figure
Laboratory-evolved Vanillyl-alcohol Oxidase Produces Natural Vanillin
The flavoenzyme vanillyl-alcohol oxidase was subjected to random mutagenesis to generate mutants with enhanced reactivity to creosol (2-methoxy-4-methylphenol). The vanillyl-alcohol oxidase-mediated conversion of creosol proceeds via a two-step process in which the initially formed vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol) is oxidized to the widely used flavor compound vanillin (4-hydroxy-3-methoxybenzaldehyde). The first step of this reaction is extremely slow due to the formation of a covalent FAD N-5-creosol adduct. After a single round of error-prone PCR, seven mutants were generated with increased reactivity to creosol. The single-point mutants I238T, F454Y, E502G, and T505S showed an up to 40-fold increase in catalytic efficiency (k(cat)/K-m) with creosol compared with the wild-type enzyme. This enhanced reactivity was due to a lower stability of the covalent flavin-substrate adduct, thereby promoting vanillin formation. The catalytic efficiencies of the mutants were also enhanced for other ortho-substituted 4-methylphenols, but not for p-cresol (4-methylphenol). The replaced amino acid residues are not located within a distance of direct interaction with the substrate, and the determined three-dimensional structures of the mutant enzymes are highly similar to that of the wild-type enzyme. These results clearly show the importance of remote residues, not readily predicted by rational design, for the substrate specificity of enzymes
On the brink: identifying psychological indicators of societal destabilization in Donetsk, Luhansk and Crimea
On the brink: identifying psychological indicators of societal destabilization in Donetsk, Luhansk and Crimea
Rigorous investigation of the reduced density matrix for the ideal Bose gas in harmonic traps by a loop-gas-like approach
In this paper, we rigorously investigate the reduced density matrix (RDM)
associated to the ideal Bose gas in harmonic traps. We present a method based
on a sum-decomposition of the RDM allowing to treat not only the isotropic
trap, but also general anisotropic traps. When focusing on the isotropic trap,
the method is analogous to the loop-gas approach developed by W.J. Mullin in
[38]. Turning to the case of anisotropic traps, we examine the RDM for some
anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes.
For such models, we bring out an additional contribution in the local density
of particles which arises from the mesoscopic loops. The close connection with
the occurrence of generalized-BEC is discussed. Our loop-gas-like approach
provides relevant information which can help guide numerical investigations on
highly anisotropic systems based on the Path Integral Monte Carlo (PIMC)
method.Comment: v3: Minor modifications of v2. v2: Major modifications: the former
version (v1) has been completely rewritten. New results concerning the
anisotropic traps and generalized Bose-Einstein condensation have been added.
The connection with the loop-gas approach is further discussed. 40 page
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