778 research outputs found
Novel Approaches for SER Spectroscopic Analysis of Protein Cofactors
Biomimetic systems employed for biotechnological applications i.e. as biosensors or bio fuel cells, require initial formation of conducting support/protein complexes with controlled properties. The specific interaction of the protein with the support determines important qualities of the device such as electrical communication, long-term stability and catalytic efficiency. In this respect the system parameters have to be chosen in a way that high protein loading on the support is achieved while protein denaturation upon adsorption is prevented. The conditions on the surface have to be adjusted in such a way that the desired surface reaction of the protein i.e. electron transfer to either the electrode or a second redox partner, is still guaranteed. Hence the choice of support, its functionlisation as well as the right adjustment of solution parameters play a crucial role in the rational design of these support/protein constructs
Obesity Is A Modifier of Autonomic Cardiac Responses to Fine Metal Particulates
Background: Increasing evidence suggests that obesity may impart greater susceptibility to adverse effects of air pollution. Particulate matter, especially PM (particulate matter with aero-dynamic diameter â€2.5 ÎŒm), is associated with increased cardiac events and reduction of heart rate variability (HRV).Objectives Our goal was to investigate whether particle-mediated autonomic modulation is aggravated in obese individuals.Methods We examined PM-mediated acute effects on HRV and heart rate (HR) using 10 24-hr and 13 48-hr ambulatory electrocardiogram recordings collected from 18 boilermakers (39.5 ± 9.1 years of age) exposed to high levels of metal particulates. Average HR and 5-min HRV [SDNN: standard deviation of normal-to-normal intervals (NN); rMSSD: square-root of mean squared-differences of successive NN intervals; HF: high-frequency power 0.15â0.4 Hz] and personal PM exposures were continuously monitored. Subjects with body mass index â„ 30 kg/m were classified as obese. Mixed-effect models were used for statistical analyses. Results: Half (50%) of the study subjects were obese. After adjustment for confounders, each 1-mg/m increase in 4-hr moving average PM was associated with HR increase of 5.9 bpm [95% confidence interval (CI), 4.2 to 7.7] and with 5-min HRV reduction by 6.5% (95% CI, 1.9 to 11.3%) for SDNN, 1.7% (95% CI, â4.9 to 8.4%) for rMSSD, and 8.8% (95% CI, â3.8 to 21.3%) for HF. Obese individuals had greater PM-mediated HRV reductions (2- to 3-fold differences) than nonobese individuals, and had more PM-mediated HR increases (9-bpm vs. 4-bpm increase in HR for each 1-mg/m increase in PM; p < 0.001). Conclusions: Our study revealed greater autonomic cardiac responses to metal particulates in obese workers, supporting the hypothesis that obesity may impart greater susceptibility to acute cardiovascular effects of fine particles
Continuous extremal optimization for Lennard-Jones Clusters
In this paper, we explore a general-purpose heuristic algorithm for finding
high-quality solutions to continuous optimization problems. The method, called
continuous extremal optimization(CEO), can be considered as an extension of
extremal optimization(EO) and is consisted of two components, one is with
responsibility for global searching and the other is with responsibility for
local searching. With only one adjustable parameter, the CEO's performance
proves competitive with more elaborate stochastic optimization procedures. We
demonstrate it on a well known continuous optimization problem: the
Lennerd-Jones clusters optimization problem.Comment: 5 pages and 3 figure
Rotational Symmetry of Classical Orbits, Arbitrary Quantization of Angular Momentum and the Role of Gauge Field in Two-Dimensional Space
We study the quantum-classical correspondence in terms of coherent wave
functions of a charged particle in two-dimensional central-scalar-potentials as
well as the gauge field of a magnetic flux in the sense that the probability
clouds of wave functions are well localized on classical orbits. For both
closed and open classical orbits, the non-integer angular-momentum quantization
with the level-space of angular momentum being greater or less than is
determined uniquely by the same rotational symmetry of classical orbits and
probability clouds of coherent wave functions, which is not necessarily
-periodic. The gauge potential of a magnetic flux impenetrable to the
particle cannot change the quantization rule but is able to shift the spectrum
of canonical angular momentum by a flux-dependent value, which results in a
common topological phase for all wave functions in the given model. The quantum
mechanical model of anyon proposed by Wilczek (Phys. Rev. Lette. 48, 1144)
becomes a special case of the arbitrary-quantization.Comment: 6 pages, 5 figure
Quadratic Volume Preserving Maps
We study quadratic, volume preserving diffeomorphisms whose inverse is also
quadratic. Such maps generalize the Henon area preserving map and the family of
symplectic quadratic maps studied by Moser. In particular, we investigate a
family of quadratic volume preserving maps in three space for which we find a
normal form and study invariant sets. We also give an alternative proof of a
theorem by Moser classifying quadratic symplectic maps.Comment: Ams LaTeX file with 4 figures (figure 2 is gif, the others are ps
Cathodoluminescence studies of chevron features in semi-polar (1122) InGaN/GaN multiple quantum well structures
Epitaxial overgrowth of semi-polar III-nitride layers and devices often leads to arrowhead-shaped surface features, referred to as chevrons. We report on a study into the optical, structural, and electrical properties of these features occurring in two very different semi-polar structures, a blue-emitting multiple quantum well structure, and an amber-emitting light-emitting diode. Cathodoluminescence (CL) hyperspectral imaging has highlighted shifts in their emission energy, occurring in the region of the chevron. These variations are due to different semi-polar planes introduced in the chevron arms resulting in a lack of uniformity in the InN incorporation across samples, and the disruption of the structure which could cause a narrowing of the quantum wells (QWs) in this region. Atomic force microscopy has revealed that chevrons can penetrate over 150ânm into the sample and quench light emission from the active layers. The dominance of non-radiative recombination in the chevron region was exposed by simultaneous measurement of CL and the electron beam-induced current. Overall, these results provide an overview of the nature and impact of chevrons on the luminescence of semi-polar devices
Larmor precession and tunneling time of a relativistic neutral spinning particle through an arbitrary potential barrier
The Larmor precession of a relativistic neutral spin-1/2 particle in a
uniform constant magnetic field confined to the region of a one-dimensional
arbitrary potential barrier is investigated. The spin precession serves as a
clock to measure the time spent by a quantum particle traversing a potential
barrier. With the help of general spin coherent state it is explicitly shown
that the precession time is equal to the dwell time.Comment: 10 pages, 1 figure. To be published in Phys. Rev. A (01 February
2002
Obesity Is A Modifier of Autonomic Cardiac Responses to Fine Metal Particulates
Background: Increasing evidence suggests that obesity may impart greater susceptibility to adverse effects of air pollution. Particulate matter, especially PM (particulate matter with aero-dynamic diameter â€2.5 ÎŒm), is associated with increased cardiac events and reduction of heart rate variability (HRV).Objectives Our goal was to investigate whether particle-mediated autonomic modulation is aggravated in obese individuals.Methods We examined PM-mediated acute effects on HRV and heart rate (HR) using 10 24-hr and 13 48-hr ambulatory electrocardiogram recordings collected from 18 boilermakers (39.5 ± 9.1 years of age) exposed to high levels of metal particulates. Average HR and 5-min HRV [SDNN: standard deviation of normal-to-normal intervals (NN); rMSSD: square-root of mean squared-differences of successive NN intervals; HF: high-frequency power 0.15â0.4 Hz] and personal PM exposures were continuously monitored. Subjects with body mass index â„ 30 kg/m were classified as obese. Mixed-effect models were used for statistical analyses. Results: Half (50%) of the study subjects were obese. After adjustment for confounders, each 1-mg/m increase in 4-hr moving average PM was associated with HR increase of 5.9 bpm [95% confidence interval (CI), 4.2 to 7.7] and with 5-min HRV reduction by 6.5% (95% CI, 1.9 to 11.3%) for SDNN, 1.7% (95% CI, â4.9 to 8.4%) for rMSSD, and 8.8% (95% CI, â3.8 to 21.3%) for HF. Obese individuals had greater PM-mediated HRV reductions (2- to 3-fold differences) than nonobese individuals, and had more PM-mediated HR increases (9-bpm vs. 4-bpm increase in HR for each 1-mg/m increase in PM; p < 0.001). Conclusions: Our study revealed greater autonomic cardiac responses to metal particulates in obese workers, supporting the hypothesis that obesity may impart greater susceptibility to acute cardiovascular effects of fine particles
- âŠ