13,165 research outputs found
On the production mechanism of radio-pulses from large extensive air showers
None of the theories put forward so far to explain the radio emission from cosmic ray showers, has been successful in giving a satisfactory explanation for all the experimental data obtained from various laboratories over the globe. It is apprehended that emission mechanism at low and high frequencies may be quite different. This calls for new theoretical look into the phenomenon. Theoretical as well as the experimental results indicate that the frequency spectrum is rather flat in the frequency range (40 to 60 MHz. Above 80 MHz, the radio emission can be explained with the help of geomagnetic mechanism. But at very low frequency ( 10 MHz), mechanisms other than geomagnetic are involved
LMI based Stability and Stabilization of Second-order Linear Repetitive Processes
This paper develops new results on the stability and control of a class of linear repetitive processes described by a second-order matrix discrete or differential equation. These are developed by transformation of the secondorder dynamics to those of an equivalent first-order descriptor state-space model, thus avoiding the need to invert a possibly ill-conditioned leading coefficient matrix in the original model
Peeling Back the Onion Competitive Advantage Through People: Test of a Causal Model
Proponents of the resource-based view (RBV) of the firm have identified human resource management (HRM) and human capital as organizational resources that can contribute to sustainable competitive success. A number of empirical studies have documented the relationship between systems of human resource policies and practices and firm performance. The mechanisms by which HRM leads to firm performance, however, remain largely unexplored. In this study, we explore the pathways leading from HRM to firm performance. Specifically, we use structural equation modeling to test a model positing a set of causal relationships between high performance work systems (HPWS), employee retention, workforce productivity and firm market value. Within a set of manufacturing firms, results indicate the primary impact of HPWS on productivity and market value is through its influence on employee retention
HRM and Firm Productivity: Does Industry Matter?
Recent years have witnessed burgeoning interest in the degree to which human resource systems contribute to organizational effectiveness. We argue that extant research has not fully considered important contextual conditions which moderate the efficacy of these practices. Specifically, we invoke a contingency perspective in proposing that industry characteristics affect the relative importance and value of high performance work practices (HPWPs). We test this proposition on a sample of non-diversified manufacturing firms. After controlling for the influence of a number of other factors, study findings support the argument that industry characteristics moderate the influence of HPWPs on firm productivity. Specifically, the impact of a system of HPWPs on firm productivity is significantly influenced by the industry conditions of capital intensity, growth and differentiation
Views and experiences of men who have sex with men on the ban on blood donation: a cross sectional survey with qualitative interviews.
OBJECTIVE: To explore compliance with the UK blood services' criterion that excludes men who have had penetrative sex with a man from donating blood, and to assess the possible effects of revising this policy. DESIGN: A random location, cross sectional survey followed by qualitative interviews. SETTING: Britain. PARTICIPANTS: 1028 of 32,373 men in the general population reporting any male sexual contact completed the survey. Additional questions were asked of a general population sample (n=3914). Thirty men who had had penetrative sex with a man participated in the qualitative interviews (19 who had complied with the blood services' exclusion criterion and 11 who had not complied). Main outcome measure Compliance with the blood services' lifetime exclusion criterion for men who have had penetrative sex with a man. RESULTS: 10.6% of men with experience of penetrative sex with a man reported having donated blood in Britain while ineligible under the exclusion criterion, and 2.5% had donated in the previous 12 months. Ineligible donation was less common among men who had had penetrative sex with a man recently (in previous 12 months) than among men for whom this last occurred longer ago. Reasons for non-compliance with the exclusion included self categorisation as low risk, discounting the sexual experience that barred donation, belief in the infallibility of blood screening, concerns about confidentiality, and misunderstanding or perceived inequity of the rule. Although blood donation was rarely viewed as a "right," potential donors were seen as entitled to a considered assessment of risk. A one year deferral since last male penetrative sex was considered by study participants to be generally feasible, equitable, and acceptable. CONCLUSIONS: A minority of men who have sex with men who are ineligible to donate blood under the current donor exclusion in Britain have nevertheless done so in the past 12 months. Many of the reasons identified for non-compliance seem amenable to intervention. A clearly rationalised and communicated one year donor deferral is likely to be welcomed by most men who have sex with men
On the Observability of "Invisible" / "Nearly Invisible" Charginos
It is shown that if the charginos decay into very soft leptons or hadrons +
due to degeneracy/ near- degeneracy with the LSP or the sneutrino,
the observability of the recently proposed signal via the single photon (+ soft
particles) + channel crucially depends on the magnitude of the \SNU
mass due to destructive interferences in the matrix element squared. If the
\SNU's and, consequently, left-sleptons are relatively light, the size of the
signal, previously computed in the limit \MSNU \to \infty only, is
drastically reduced. We present the formula for the signal cross section in a
model independent way and discuss the observability of the signal at LEP 192
and NLC energies.Comment: 27 pages, Late
Brans-Dicke theory: Jordan vs Einstein Frame
It is well known that, in contrast to general relativity, there are two
conformally related frames, the Jordan frame and the Einstein frame, in which
the Brans-Dicke theory, a prototype of generic scalar-tensor theory, can be
formulated. There is a long standing debate on the physical equivalence of the
formulations in these two different frames. It is shown here that gravitational
deflection of light to second order accuracy may observationally distinguish
the two versions of the Brans-Dicke theory.Comment: 10 pages, Accepted by Mod. Phys. Letts.
Electron transport through multilevel quantum dot
Quantum transport properties through some multilevel quantum dots sandwiched
between two metallic contacts are investigated by the use of Green's function
technique. Here we do parametric calculations, based on the tight-binding
model, to study the transport properties through such bridge systems. The
electron transport properties are significantly influenced by (a) number of
quantized energy levels in the dots, (b) dot-to-electrode coupling strength,
(c) location of the equilibrium Fermi energy and (d) surface disorder. In
the limit of weak-coupling, the conductance () shows sharp resonant peaks
associated with the quantized energy levels in the dots, while, they get
substantial broadening in the strong-coupling limit. The behavior of the
electron transfer through these systems becomes much more clearly visible from
our study of current-voltage (-) characteristics. In this context we also
describe the noise power of current fluctuations () and determine the Fano
factor () which provides an important information about the electron
correlation among the charge carriers. Finally, we explore a novel transport
phenomenon by studying the surface disorder effect in which the current
amplitude increases with the increase of the surface disorder strength in the
strong disorder regime, while, the amplitude decreases in the limit of weak
disorder. Such an anomalous behavior is completely opposite to that of bulk
disordered system where the current amplitude always decreases with the
disorder strength. It is also observed that the current amplitude strongly
depends on the system size which reveals the finite quantum size effect.Comment: 12 pages, 7 figure
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