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Length Dependence (length + dependence)

Distribution by Scientific Domains
Physics and Astronomy40%

Selected Abstracts

Length dependence of polarization in spontaneous edge emissions from InGaN/AlGaN MQWs laser diodes

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2007
Chuanyu Jia
Abstract The polarization of spontaneous edge-emitting electroluminescence from near-UV LDs with different cavity lengths (from 400 ,m to 1000 ,m) was studied. It was found that TE mode dominates in InGaN/AlGaN MQWs LDs, which is consistent with the theoretical calculation results of similar MQWs. An obvious polarization decrease from P = 0.57 to 0.42 as the LD cavity length changed from 400 ,m to 1000 ,m was also observed, corresponding to a ratio r changing from 3.67 to 2.43, which indicated that, the TE mode attenuated more grievously than the TM mode with increasing cavity length. This is due to the inherent property of polarization selective emission from the alloys. The optical loss coefficient of TE mode was determined to be 35 cm,1, while, 10 cm,1 for TM mode, which is in good agreement with the results obtained from other methods. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Force,frequency and force,length properties in skeletal muscle following unilateral focal ischaemic insult in a rat model

ACTA PHYSIOLOGICA, Issue 3 2009
G. N. Dormer
Abstract Aim:, Our purpose was to quantify skeletal muscle properties following unilateral focal ischaemic insult (stroke) in a rat model. Methods:, Male rats were divided into two groups: stroke and 2 weeks recovery (n = 8) and control group (n = 7). Stroke was induced in the area of the motor neocortex containing hind limb corticospinal neurones. Contractile properties of the medial gastrocnemius muscle were measured in situ in both limbs. Force,length and force,frequency properties were measured before and 35 min after 5 min fatiguing stimulation. Results:, Stroke resulted in bilateral tetanic fade during 200 Hz stimulation. When normalized to 100 Hz contractions, force at 200 Hz was 95.4 ± 0.9% for the paretic muscles, 96.7 ± 1.7% for non-paretic muscles and 102.2 ± 1.0% for muscles of control rats (P = 0.006). Prior to fatiguing contractions, there was no difference in the length dependence of force. During repetitive contractions, active force fell significantly to 19 ± 4 and 25 ± 5% of initial force in paretic and non-paretic muscles of animals with a stroke respectively. In control animals active force fell to 37 ± 5%. During repetitive contractions, fusion index increased in muscles of stroke animals to 1.0 ± 0 but in control animals it was 0.95 ± 0.02. There was selective force depression at short lengths for fatigued paretic muscle (significant difference at muscle lengths less than reference length ,2 mm). Conclusion:, The tetanic fade at high stimulation frequencies indicates that there may be activation failure following focal ischaemic insult. The greater magnitude of fatigue and selective depression at short lengths following repetitive contractions should be investigated further. [source]

Extreme multielectron ionization of elemental clusters in ultraintense laser fields

ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2007
Andreas Heidenreich
In this paper we present computational and theoretical studies of extreme multielectron ionization in Xen clusters (n = 55-2171, initial cluster radii R0 = 8.7-31.0 Å) driven by ultraintense Gaussian infrared laser fields (peak intensity IM = 1015 -1020 W cm,2, temporal pulse length , = 10-100 fs, and frequency v = 0.35fs,1). The microscopic approach, which rests on three sequential-parallel processes of inner ionization, nanoplasma formation, and outer ionization, properly describes the high ionization levels (with the formation of {Xeq+}n with q = 5-36), the inner/outer cluster ionization mechanisms, and the nanoplasma response. The cluster size and laser intensity dependence of the inner ionization levels are determined by a complex superposition of laser-induced barrier suppression ionization (BSI), with the contributions of the inner field BSI manifesting ignition enhancement and screening retardation effects, together with electron impact ionization. The positively charged nanoplasma produced by inner ionization reveals intensity-dependent spatial inhomogeneity and spatial anisotropy, and can be either persistent (at lower intensities) or transient (at higher intensities). The nanoplasma is depleted by outer ionization that was semiquantitatively described by the cluster barrier suppression electrostatic model, which accounts for the cluster size, laser intensity, and pulse length dependence of the outer ionization yield. [source]

Living free-radical polymerization (reversible addition,fragmentation chain transfer) of 6-[4-(4,-methoxyphenyl)phenoxy]hexyl methacrylate: A route to architectural control of side-chain liquid-crystalline polymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2003
Xiaojuan Hao
Abstract Side-chain liquid-crystalline polymers of 6-[4-(4,-methoxyphenyl)phenoxy]hexyl methacrylate with controlled molecular weights and narrow polydispersities were prepared via reversible addition,fragmentation chain transfer (RAFT) polymerization with 2-(2-cyanopropyl) dithiobenzoate as the RAFT agent. Differential scanning calorimetry studies showed that the polymers produced via the RAFT process had a narrower thermal stability range of the liquid-crystalline mesophase than the polymers formed via conventional free-radical polymerization. In addition, a chain length dependence of this stability range was found. The generated RAFT polymers displayed optical textures similar to those of polymers produced via conventional free-radical polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2949,2963, 2003 [source]

Strong spin relaxation length dependence on electric field gradients

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006
D. Csontos
Abstract We discuss the influence of electrical effects on spin transport, and in particular the propagation and relaxation of spin polarized electrons in the presence of inhomogeneous electric fields. We show that the spin relaxation length strongly depends on electric field gradients, and that significant suppression of electron spin polarization can occur as a result thereof. A discussion in terms of a drift-diffusion picture, and selfconsistent numerical calculations based on a Boltzmann-Poisson approach shows that the spin relaxation length in fact can be of the order of the charge screening length. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]