Outage probability calculation for two-ray ground reflection scenarios with frequency diversity

We consider a two-ray ground reflection scenario with only statistical knowledge about the distance between transmitter and receiver. Additionally, two frequencies are used in parallel to mitigate possible destructive interference. In the context of ultrareliability, it is important to be able to quantify the reliability of such communication systems. In this work, we analyze the outage probability of the described system and present a semi-closed form expression to calculate it. Based on this, results on optimizing the spacing between the two frequencies will be derived

An efficient frequency diversity scheme for ultra-reliable communications in two-path fading channels

We consider a two-ray ground reflection scenario with unknown distance between transmitter and receiver. By utilizing two frequencies in parallel, we can mitigate possible destructive interference and ensure ultra-reliability with only very limited knowledge at the transmitter. In order to achieve this ultra-reliability, we optimize the frequency spacing such that the worst-case receive power is maximized. Additionally, we provide an algorithm to calculate the optimal frequency spacing. Besides the receive power, we also analyze the achievable rate and outage probability. It is shown that the frequency diversity scheme achieves a significant improvement in terms of reliability over using a single frequency. In particular, we demonstrate the effectiveness of the proposed approach by a numerical simulation of an unmanned aerial vehicle (UAV) flying above flat terrain

Shiga toxin-producing Escherichia coli (STEC) other than the top-7: multiplex PCR assays development and validation for detection and identification of the predominant serogroups in cattle feces.

Master of Science in Biomedical SciencesDepartment of Diagnostic Medicine/PathobiologyTiruvoor G. NagarajaShiga toxin-producing E. coli (STEC) are major food borne pathogens that cause mild to severe hemorrhagic colitis in humans. Seven serogroups, which include O26, O45, O103, O111, O121, O145 and O157, considered the ‘top-7 STEC’, cause a majority of food borne STEC infections. Cattle are a major reservoir for the STEC. These organisms reside in the hindgut and are shed in the feces. Additionally, cattle harbor a number of other serogroups (n=113) of STEC. A few of the serogroups have been implicated to cause sporadic human infections. Traditionally, serogrouping of E. coli is done by agglutination reaction with serogroup-specific antisera. Multiplex PCR (mPCR) assays targeting STEC serogroups, other than the top-7, were designed, optimized, and validated. The assays targeted one or more serogroup-specific genes, wzx, wzy, gnd, wbdA of the O-antigen gene cluster. A total of 11 sets of mPCR assays targeting 113 serogroups of STEC were designed and validated with known strains of STEC. The assays were utilized to identify serogroups of E. coli strains (n=358), positive for stx1, stx2 (Shiga toxins 1 and 2), and or eae (intimin) genes, and negative for the top 7 serogroups, isolated from fecal samples collected from commercial; feedlots. Of the 358 strains from multiple feedlots located in two states, 298 (83.2%) strains belonged to 21 serogroups and 60 strains (16.8%) were unidentifiable. The twenty one sergogroups included O168 (29.9%), O109 (17.9%), O131 (8.1%), O2 (7.0%), O104 (4.7%), O171 (4.2%), O74 (3.6%), O8 (2.8%), O136 (0.84%), O178 (0.56%), O102 (0.56%), O175 (0.56%), O98 (0.28%), O118 (0.28%), O113 (0.28%), O96 (0.28%), O76 (0.28%),O35 (0.28%), O20 (0.28%), O160 (0.28%), and O169 (0.28%). The detection of the STEC strains indicated that serogroups, O2, O74, O109, O131, O168, and O171, were the most predominant. A six-plex PCR was designed and validated to detect the prevalence of the top six major non top-7 STEC in cattle feces from feedlot cattle. Among the six serogroups of the major non-top 7 STEC, serogroups of O2 (48.7%), O109 (88.1%), O168 (67.9%), and O171 (80.4%) were the dominant serogroups in cattle feces collected from commercial feedlots. Fecal samples that contained the six serogroups were also positive for the three major virulence genes, stx1, stx2, and eae. In conclusion, cattle harbor and shed in the feces a number of serogroups of STEC other than the top 7, with O2, O109, O168, and O171 being the predominant STEC. The potential risk of these STEC to cause human infections is not known

Modelling the potential of integrated vegetation bands (IVB) to retain stormwater runoff on steep hillslopes of Southeast Queensland, Australia

Rainfall intensity is predicted to increase under a changing climate, leading to increased risks of hillslope erosion, downstream sedimentation and flooding. For many catchments used for grazing and agricultural land uses, it will become increasingly important to maintain ecohydrological functioning despite climatic extremes. One means to achieve this is through strategic reforestation using locally endemic species, in spatial configurations that effectively intercept, retain or and redistribute overland flows. This paper adopts a modelling approach for investigating the potential of one such design termed “integrated vegetation bands” (IVB), to increase the retention of runoff across steep hillslopes, particularly in the sub-tropics where rainstorms are becoming increasingly intense. A spatially distributed simulation model (MIKE-SHE) was applied to a steep, grazed catchment (Maronghi Creek catchment, Southeast Queensland, Australia) to compare stormwater runoff characteristics between: (1) the existing pasture land cover; and (2) a series of hypothetical IVB added across this pasture land. The IVB were approximately 20 m wide, and configured at 5% gradient towards ridgelines. Results for estimates of overland flow depth and infiltration (spatial), and accumulative water balance (temporal), confirm that the area of hillslope retaining > 10 mm/day more runoff increased by 22% under IVB compared to the pasture land use. Excluding the IVB themselves, the area of hillslope where runoff retention increased was 11%. During the most intense rainfall, IVB held up to 25% greater water depth and had 10% greater infiltration at the hillslope scale. At the sub-catchment scale, discharge decreased by 7% and infiltration increased by 23%. The findings for sub-tropical landscapes presented here are consistent with studies conducted in temperate regions. Based on the results of this preliminary modelling work, the IVB concept has been established as a paired-catchment field trial in a high rainfall catchment in Southeast Queensland, Australia

Anesthesia Technique, Mortality, and Length of Stay After Hip Fracture Surgery

Importance: More than 300 000 hip fractures occur each year in the United States. Recent practice guidelines have advocated greater use of regional anesthesia for hip fracture surgery. Objective: To test the association of regional (ie, spinal or epidural) anesthesia vs general anesthesia with 30-day mortality and hospital length of stay after hip fracture

The Thermodynamics of Quantum Systems and Generalizations of Zamolodchikov's C-theorem

In this paper we examine the behavior in temperature of the free energy on quantum systems in an arbitrary number of dimensions. We define from the free energy a function $C$ of the coupling constants and the temperature, which in the regimes where quantum fluctuations dominate, is a monotonically increasing function of the temperature. We show that at very low temperatures the system is controlled by the zero-temperature infrared stable fixed point while at intermediate temperatures the behavior is that of the unstable fixed point. The $C$ function displays this crossover explicitly. This behavior is reminiscent of Zamolodchikov's $C$-theorem of field theories in 1+1 dimensions. Our results are obtained through a thermodynamic renormalization group approach. We find restrictions on the behavior of the entropy of the system for a $C$-theorem-type behavior to hold. We illustrate our ideas in the context of a free massive scalar field theory, the one-dimensional quantum Ising Model and the quantum Non-linear Sigma Model in two space dimensions. In regimes in which the classical fluctuations are important the monotonic behavior is absent.Comment: 25 pages, LateX, P-92-10-12

Toward understanding I/O behavior in HPC workflows

Scientific discovery increasingly depends on complex workflows consisting of multiple phases and sometimes millions of parallelizable tasks or pipelines. These workflows access storage resources for a variety of purposes, including preprocessing, simulation output, and postprocessing steps. Unfortunately, most workflow models focus on the scheduling and allocation of com- putational resources for tasks while the impact on storage systems remains a secondary objective and an open research question. I/O performance is not usually accounted for in workflow telemetry reported to users. In this paper, we present an approach to augment the I/O efficiency of the individual tasks of workflows by combining workflow description frameworks with system I/O telemetry data. A conceptual architecture and a prototype implementation for HPC data center deployments are introduced. We also identify and discuss challenges that will need to be addressed by workflow management and monitoring systems for HPC in the future. We demonstrate how real-world applications and workflows could benefit from the approach, and we show how the approach helps communicate performance-tuning guidance to users

Dirac Fermions and Domain Wall Defects in 2+1 Dimensions

We investigate some properties of a system of Dirac fermions in 2+1 dimensions, with a space dependent mass having domain wall like defects.These defects are defined by the loci of the points where the mass changes sign. In general, they will be curves lying on the spatial plane. We show how to treat the dynamics of the fermions in such a way that the existence of localized fermionic zero modes on the defects is transparent. Moreover, effects due to the higher, non zero modes, can be quantitatively studied. We also consider the relevance of the profile of the mass near the region where it changes sign. Finally, we apply our general results to the calculation of the induced fermionic current, in the linear response approximation, in the presence of an external electric field and defects.Comment: 23 pages, 1 Postscript figur

The 4-loop beta-function in the 2D Non-Abelian Thirring model, and comparison with its conjectured "exact" form

Recently, B. Gerganov, A. LeClair and M. Moriconi [Phys. Rev. Lett. 86 (2001) 4753] have proposed an "exact" (all orders) beta-function for 2-dimensional conformal field theories with Kac-Moody current-algebra symmetry at any level k, based on a Lie group G, which are perturbed by a current-current interaction. This theory is also known as the Non-Abelian Thirring model. We check this conjecture with an explicit calculation of the beta-function to 4-loop order, for the classical groups G= SU(N), SO(N) and SP(N). We find a contribution at 4-loop order, proportional to a higher-order group-theoretical invariant, which is incompatible with the proposed beta-function in all possible regularization schemes.Comment: 26 pages, 24 figures, latex2

Two-dimensional conformal field theory for disordered systems at criticality

Using a Kac-Moody current algebra with $U(1/1)\times U(1/1)$ graded symmetry, we describe a class of (possibly disordered) critical points in two spatial dimensions. The critical points are labelled by the triplets $(l,m,k^{\ }_j)$, where $l$ is an odd integer, $m$ is an integer, and $k^{\ }_j$ is real. For most such critical points, we show that there are infinite hierarchies of relevant operators with negative scaling dimensions. To interpret this result, we show that the line of critical points $(1,1,k^{\ }_j>0)$ is realized by a field theory of massless Dirac fermions in the presence of $U(N)$ vector gauge-like static impurities. Along the disordered critical line $(1,1,k^{\ }_j>0)$, we find an infinite hierarchy of relevant operators with negative scaling dimensions$\{\Delta^{\ }_q|q\in {\rm I}\hskip -0.08 true cm{\bf N}\}$, which are related to the disorder average over the$q$-th moment of the single-particle Green function. Those relevant operators can be induced by non-Gaussian moments of the probability distribution of a mass-like static disorder.Comment: 47 pages, REVTEX-3.0, no figure