A rigorous analysis of the cavity equations for the minimum spanning tree

We analyze a new general representation for the Minimum Weight Steiner Tree (MST) problem which translates the topological connectivity constraint into a set of local conditions which can be analyzed by the so called cavity equations techniques. For the limit case of the Spanning tree we prove that the fixed point of the algorithm arising from the cavity equations leads to the global optimum.Comment: 5 pages, 1 figur

Fractional diffusion emulates a human mobility network during a simulated disease outbreak

From footpaths to flight routes, human mobility networks facilitate the spread of communicable diseases. Control and elimination efforts depend on characterizing these networks in terms of connections and flux rates of individuals between contact nodes. In some cases, transport can be parameterized with gravity-type models or approximated by a diffusive random walk. As a alternative, we have isolated intranational commercial air traffic as a case study for the utility of non-diffusive, heavy-tailed transport models. We implemented new stochastic simulations of a prototypical influenza-like infection, focusing on the dense, highly-connected United States air travel network. We show that mobility on this network can be described mainly by a power law, in agreement with previous studies. Remarkably, we find that the global evolution of an outbreak on this network is accurately reproduced by a two-parameter space-fractional diffusion equation, such that those parameters are determined by the air travel network.Comment: 26 pages, 4 figure

Isolation and identification of antimicrobial compound from Mentha longifolia L. leaves grown wild in Iraq

<p>Abstract</p> <p>Background</p> <p><it>Mentha longifolia </it>L. (Lamiaceae) leaves have been traditionally implemented in the treatment of minor sore throat and minor mouth or throat irritation by the indigenous people of Iraq, although the compounds responsible for the medicinal properties have not been identified. In the present study, an antimicrobial compound was isolated and characterized, and its biological activity was assessed.</p> <p>Methods</p> <p>The compound was isolated and characterized from the extracted essential oil using different spectral techniques: TLC, FTIR spectra and HPLC. Antimicrobial activity of the compound was assessed using both disc diffusion and microdilution method in 96 multi-well microtiter plates.</p> <p>Results</p> <p>A known compound was isolated from the essential oil of the plant and was identified as (-) menthol. The isolated compound was investigated for its antimicrobial activity against seven selected pathogenic and non-pathogenic microorganisms: <it>Staphylococcus aureus, Streptococcus mutans, Streptococcus faecalis, Streptococcus pyogenis</it><it>, Lactobacillus acidophilus, Pseudomonas aeruginosa </it>and the yeast <it>Candida albicans</it>. Menthol at different concentrations (1:1, 1:5, 1:10, 1:20) was active against all tested bacteria except for <it>P. aeruginosa</it>, and the highest inhibitory effect was observed against <it>S. mutans </it>(zone of inhibition: 25.3 mm) using the disc diffusion method. Minimal inhibitory concentration MIC values ranged from 15.6–125.0 μg/ml, and the most promising results were observed against <it>S. aureus </it>and <it>S. mutans </it>(MIC 15.6 μg/ml) while, <it>S. faecalis, S. pyogenis </it>and <it>L. acidophilus </it>ranked next (MIC 31.2 μg/ml). Furthermore, menthol achieved considerable antifungal activity against the yeast <it>C. albicans </it>(zone of inhibition range: 7.1–18.5 mm; MIC: 125.0).</p> <p>Conclusion</p> <p>The isolation of an antimicrobial compound from <it>M. longifolia </it>leaves validates the use of this plant in the treatment of minor sore throat and minor mouth or throat irritation.</p

Belief-Propagation for Weighted b-Matchings on Arbitrary Graphs and its Relation to Linear Programs with Integer Solutions

We consider the general problem of finding the minimum weight \bm-matching on arbitrary graphs. We prove that, whenever the linear programming (LP) relaxation of the problem has no fractional solutions, then the belief propagation (BP) algorithm converges to the correct solution. We also show that when the LP relaxation has a fractional solution then the BP algorithm can be used to solve the LP relaxation. Our proof is based on the notion of graph covers and extends the analysis of (Bayati-Shah-Sharma 2005 and Huang-Jebara 2007}. These results are notable in the following regards: (1) It is one of a very small number of proofs showing correctness of BP without any constraint on the graph structure. (2) Variants of the proof work for both synchronous and asynchronous BP; it is the first proof of convergence and correctness of an asynchronous BP algorithm for a combinatorial optimization problem.Comment: 28 pages, 2 figures. Submitted to SIAM journal on Discrete Mathematics on March 19, 2009; accepted for publication (in revised form) August 30, 2010; published electronically July 1, 201

Full scale monitoring of the twin chimneys of the rovinari power plant

The presented paper deals with the structural identification and monitoring of two twin chimneys in very close arrangement. Due to twin arrangement, important interference effects are expected to modify the chimney response to wind action, causing vortex shedding and state-dependent excitation associated to the oscillatory motion of the leeward chimney, in and out of the windward chimney wake. The complexity of the physics of this problem is increased by the dependency of the aerodynamics of circular cylinders on Reynolds number; however, there is a weakness of literature about cylinders behaviour at critical and super-critical range of Reynolds number, due to experimental limitations. Also the International Committee on Industrial Chimneys (CICIND) does not provide, at present, any specific technical guideline about twin chimneys whose interaxis distance is less or equal two times the diameter, as in this case. For this reason a Tuned Mass Damper (TMD) has been installed in order to increase the damping of the chimney, as merely suggested. This work aims at assessing the effectiveness of the installed TMD and characterizing the tower dynamic behaviour itself due to the wind excitation, as well as providing full scale measurements for twin cylinders configuration at high Reynolds numbers

Evaluation of auditory efferent system function in children with autism

زمینه و هدف: مطالعات مختلف نشان داده اند که سیستم وابران شنیداری در توجه انتخابی نقش دارد و از این رو بررسی این سیستم در کودکان اوتیسمی بسیار ارزشمند است. هدف از این مطالعه بررسی مسیر وابران شنوایی در کودکان مبتلا به اوتیسم در مقایسه با کودکان با رشد هنجار بوده است. روش بررسی: در این مطالعه توصیفی-تحلیلی تعداد 34 کودک 11-5 ساله در قالب دو گروه هنجار (17 نفر) و مبتلا به اوتیسم (17 نفر) مورد بررسی قرار گرفتند. کلیه کودکان در آزمون های ادیومتری تون خالص (Pure-tone audionetry)، ادیومتری گفتاری (Speech audiometery)، تمپانومتری (Tympanometry) و گسیل های صوتی گوشی گذرا (otoacoustic emissions=TEOAE-evoked Transient)دارای نتایج طبیعی بودند. عملکرد سیستم وابران از طریق ثبت پاسخ های TEOAE در دو حالت ارائه نویز دگر طرفی و بدون ارائه نویز بررسی گردید. جهت آنالیز نتایج از از نرم افزار آماری SPSS و آزمون های تی مستقل و تی زوجی استفاده شد. یافته ها: نتایج این پژوهش نشان داد که تفاوت قابل ملاحظه ای بین میانگین میزان مهار در دو گروه وجود دارد (001/0=P). میانگین دامنه TEOAE در حالت بدون نویز دگر طرفی در گروه هنجار (09/4 ± 63/17) و در گروه اوتیسم (78/3 ± 40/17) به دست آمد که از لحاظ آماری نشان دهنده تفاوت معنی داری نبود (83/0=P). نتیجه گیری: یافته های کسب شده در مطالعه حاضر نشان دهنده کاهش فعالیت سیستم وابران شنوایی در کودکان مبتلا به اوتیسم نسبت به کودکان با رشد هنجار بود. با توجه به اینکه آزمون مورد استفاده در این مطالعه، مهار گسیل های صوتی گوشی گذرا (TEOAE suppression) است، می توان نتیجه گرفت این آزمون ابزار بالینی حساس، غیر تهاجمی، عینی و مناسب برای بررسی عملکرد سیستم وابران در کودکان مبتلا به اوتیسم است

A cutoff phenomenon in accelerated stochastic simulations of chemical kinetics via flow averaging (FLAVOR-SSA)

We present a simple algorithm for the simulation of stiff, discrete-space, continuous-time Markov processes. The algorithm is based on the concept of flow averaging for the integration of stiff ordinary and stochastic differential equations and ultimately leads to a straightforward variation of the the well-known stochastic simulation algorithm (SSA). The speedup that can be achieved by the present algorithm [flow averaging integrator SSA (FLAVOR-SSA)] over the classical SSA comes naturally at the expense of its accuracy. The error of the proposed method exhibits a cutoff phenomenon as a function of its speed-up, allowing for optimal tuning. Two numerical examples from chemical kinetics are provided to illustrate the efficiency of the method

Multidrug-Resistant Salmonella spp. Isolated from Local Food Markets: Molecular Factors

Antibiotic-resistant Salmonella spp. linked with food remains a primary concern globally as it is associated between animals and humans, causing foodborne illness and zoonotic diseases. One hundred Salmonella isolates out of 241 swab specimens taken from slaughtered chicken were identified and investigated for their antimicrobial susceptibility pattern. Ampicillin (62%), tetracycline (59%), amoxicillin-clavulanic acid (46%), trimethoprim-sulfamethoxazole (35%), and ceftriaxone (24%) were the drugs with the highest prevalence of impedance. At 12%, 11%, and 8%, respectively, resistance to ciprofloxacin, chloramphenicol, and azithromycin was very negligible. In order to assess the frequency of resistance genes, six different kinds of genes were examined in this research. The findings revealed that the proportion of these genes included in the survey were tetA (10%), blaCMY-2 (32%), dfrA7 (17%), tetC (20%), sul2 (25%) , and blaTEM-1 (47%)

Statistical Mechanics of Steiner trees

The Minimum Weight Steiner Tree (MST) is an important combinatorial optimization problem over networks that has applications in a wide range of fields. Here we discuss a general technique to translate the imposed global connectivity constrain into many local ones that can be analyzed with cavity equation techniques. This approach leads to a new optimization algorithm for MST and allows to analyze the statistical mechanics properties of MST on random graphs of various types

Finite Element Analysis in Porous Media for Incompressible Flow of Contamination from Nuclear Waste

A non-linear parabolic system is used to describe incompressible nuclear waste disposal contamination in porous media, in which both molecular diffusion and dispersion are considered. The Galerkin method is applied for the pressure equation. For the brine, radionuclide and heat, a kind of partial upwind finite element scheme is constructed. Examples are included to demonstrate certain aspects of the theory and illustrate the capabilities of the kind of partial upwind finite element approach