ERROR PROPAGATION IN EXTENDED CHAOTIC SYSTEMS

A strong analogy is found between the evolution of localized disturbances in extended chaotic systems and the propagation of fronts separating different phases. A condition for the evolution to be controlled by nonlinear mechanisms is derived on the basis of this relationship. An approximate expression for the nonlinear velocity is also determined by extending the concept of Lyapunov exponent to growth rate of finite perturbations.Comment: Tex file without figures- Figures and text in post-script available via anonymous ftp at ftp://wpts0.physik.uni-wuppertal.de/pub/torcini/jpa_le

The role of microbiology and pharmacy departments in the stewardship of antibiotic prescribing in European hospitals

This observational, cross-sectional study describes the role played by clinical microbiology and pharmacy departments in the stewardship of antibiotic prescribing in European hospitals. A total of 170 acute care hospitals from 32 European countries returned a questionnaire on antibiotic policies and practices implemented in 2001. Data on antibiotic use, expressed as De.ned Daily Doses per 100 occupied bed-days (DDD/100 BD) were provided by 139 hospitals from 30 countries. A total of 124 hospitals provided both datasets. 121 (71%) of Clinical Microbiology departments and 66 (41%) of Pharmacy departments provided out of hours clinical advice. 70 (41%) of microbiology/infectious disease specialists and 28 (16%) of pharmacists visited wards on a daily basis. The majority of laboratories provided monitoring of blood cultures more than once per day and summary data of antibiotic susceptibility testing (AST) for empiric prescribing (86% and 73% respectively). Most of the key laboratory and pharmacy-led initiatives examined did not vary signi.cantly by geographical location. Hospitals from the North and West of Europe were more likely to examine blood cultures more than once daily compared with other regions (p < 0.01). Hospitals in the North were least likely routinely to report susceptibility results for restricted antibiotics compared to those in the South-East and Central/Eastern Europe (p < 0.01). Hospital wards in the North were more likely to hold antibiotic stocks (100%) compared with hospitals in the South-East which were least likely (39%) (p < 0.001). Conversely, hospital pharmacies in the North were least likely to dispense antibiotics on an individual patient basis (16%) compared with hospital pharmacies from Southern Europe (60%) (p = 0.01). Hospitals that routinely reported susceptibility results for restricted antibiotics had signi.cantly lower median total antibiotic use in 2001 (p < 0.01). Hospitals that provided prescribing advice outside normal working hours had signi.cantly higher antibiotic use compared with institutions that did not provide this service (p = 0.01). A wide range of antibiotic stewardship measures was practised in the participating hospitals in 2001, although there remains great scope for expansion of those overseen by pharmacy departments. Most hospitals had active antibiotic stewardship programmes led by specialists in infection, although there is no evidence that these were associated with reduced antibiotic consumption. There was also no evidence that pharmacy services reduced the amount of antibiotics prescribed.The ARPAC study was funded by the European Commission (project QLK2-CT-2001-00915). F.M. MacKenzie was supported by the European Study Group on Antibiotic Policies to write this manuscript

Конструкційна міцність багатошарових елементів машин з дефектами структури

У дисертаційній роботі вирішений ряд важливих науково-технічних завдань, які включають в себе обґрунтування моделей і методик розрахунку напружено-деформованого та термопружного стану багатошарових оболонок обертання з міжшаровими дефектами структури. Розроблені алгоритми, програми, методики досліджень та отримані на їх основі теоретикоекспериментальні результати показали наявність нових особливостей деформованого стану розглянутих конструкцій. Побудовано замкнену систему диференціальних рівнянь та відповідні крайові умови незв'язаної стаціонарної задачі термопружного деформування багатошарової композитної оболонки, що дозволяють врахувати деформації поперечного зсуву і трансверсального обтиснення, забезпечити умови механічного і теплового сполучення шарів і умови термомеханічного навантаження на лицьових поверхнях такої оболонки. На основі класичної теорії пружності анізотропного тіла розроблений чисельно-аналітичний підхід розв’язання термопружних незв’язаних крайових задач для циліндричних товстостінних оболонок за умови як ідеального, так і неідеального контакту суміжних шарів по сполученим поверхням. Встановлено вплив температурних навантажень на напружено-деформований стан ущільнення робочого колеса, виготовленого із композиційних матеріалів.В диссертационной работе решен ряд важных научно-технических задач, которые включают в себя обоснование моделей и методик расчета напряженно-деформированного и термоупругого состояния многослойных оболочек вращения с межслойными дефектами структуры. Разработанные алгоритмы, программы, методики исследований и полученные на их основе теоретико-экспериментальные результаты показали наличие новых особенностей деформированного состояния рассматриваемых конструкций. Построено замкнутую систему дифференциальных уравнений и соответствующие краевые условия несвязанной стационарной задачи термоупругого деформирования многослойной композитной оболочки, позволяющие учесть деформации поперечного сдвига и трансверсального обжатия, обеспечить условия механического и теплового сопряжения слоев и условия термомеханической нагрузки на лицевых поверхностях такой оболочки. На основе классической теории упругости анизотропного тела разработан численно-аналитический подход решения термоупругих несвязанных краевых задач для цилиндрических толстостенных оболочек при условии как идеального, так и неидеального контакта соседних слоев по сопряженным поверхностям. Установлено влияние температурных нагрузок на напряженно-деформированное состояние уплотнения рабочего колеса, изготовленного из композиционных материалов. Решена задача прочности и получена величина граничного внутреннего давления комбинированных газовых баллонов высокого давления. Исследовано напряженно-деформированное состояние стеклопластиковых труб в зоне фланцевых соединений в зависимости от жесткости фланцев.The thesis presents number of important scientific and technical problems, which include study models and methods of calculating the stress-strain and the thermoelastic state multilayer shells with interlayer structural defects. The algorithms, programs, research methodology, theoretical and experimental results showed the presence of new features deformed state considered structures. We construct a closed system of differential equations and appropriate boundary conditions unrelated stationary problem thermostatic deformation of the multilayer composite shell that allow for deformations of transverse shear and transversal compression, ensure conditions of mechanical and thermal connection layers and thermomechanical loading conditions on the front surface of this shell. Based on the classical theory of elasticity of an anisotropic body developed numerical-analytical approach solving of thermoelastic unrelated boundary problems for thick-walled cylindrical shells provided ideal and non-ideal contact of adjacent layers on surfaces mated. The influence of temperature loads on the stress-strain state seal rotor made from composite materials was found

Suppressor of sable [Su(s)] and Wdr82 down-regulate RNA from heat-shock-inducible repetitive elements by a mechanism that involves transcription termination

Although RNA polymerase II (Pol II) productively transcribes very long genes in vivo, transcription through extragenic sequences often terminates in the promoter-proximal region and the nascent RNA is degraded. Mechanisms that induce early termination and RNA degradation are not well understood in multicellular organisms. Here, we present evidence that the suppressor of sable [su(s)] regulatory pathway of Drosophila melanogaster plays a role in this process. We previously showed that Su(s) promotes exosome-mediated degradation of transcripts from endogenous repeated elements at an Hsp70 locus (Hsp70-αβ elements). In this report, we identify Wdr82 as a component of this process and show that it works with Su(s) to inhibit Pol II elongation through Hsp70-αβ elements. Furthermore, we show that the unstable transcripts produced during this process are polyadenylated at heterogeneous sites that lack canonical polyadenylation signals. We define two distinct regions that mediate this regulation. These results indicate that the Su(s) pathway promotes RNA degradation and transcription termination through a novel mechanism

Contact process with long-range interactions: a study in the ensemble of constant particle number

We analyze the properties of the contact process with long-range interactions by the use of a kinetic ensemble in which the total number of particles is strictly conserved. In this ensemble, both annihilation and creation processes are replaced by an unique process in which a particle of the system chosen at random leaves its place and jumps to an active site. The present approach is particularly useful for determining the transition point and the nature of the transition, whether continuous or discontinuous, by evaluating the fractal dimension of the cluster at the emergence of the phase transition. We also present another criterion appropriate to identify the phase transition that consists of studying the system in the supercritical regime, where the presence of a "loop" characterizes the first-order transition. All results obtained by the present approach are in full agreement with those obtained by using the constant rate ensemble, supporting that, in the thermodynamic limit the results from distinct ensembles are equivalent

Rare Events Statistics in Reaction--Diffusion Systems

We develop an efficient method to calculate probabilities of large deviations from the typical behavior (rare events) in reaction--diffusion systems. The method is based on a semiclassical treatment of underlying "quantum" Hamiltonian, encoding the system's evolution. To this end we formulate corresponding canonical dynamical system and investigate its phase portrait. The method is presented for a number of pedagogical examples.Comment: 12 pages, 6 figure

Space-time estimation of a particle system model

13 pagesLet X be a discrete time contact process (CP) on the discrete bidimensional lattice as define by Durett - Levin (1994) . We study estimation of the model based on space-time evolution on a finite subset of sites. For this, we make use of a marginal pseudo-likelihood. The estimator obtained is consistent and asymptoticaly normal for non-vanishing supercritical CP. Numerical studies confirm these results

Non-equilibrium Phase Transitions with Long-Range Interactions

This review article gives an overview of recent progress in the field of non-equilibrium phase transitions into absorbing states with long-range interactions. It focuses on two possible types of long-range interactions. The first one is to replace nearest-neighbor couplings by unrestricted Levy flights with a power-law distribution P(r) ~ r^(-d-sigma) controlled by an exponent sigma. Similarly, the temporal evolution can be modified by introducing waiting times Dt between subsequent moves which are distributed algebraically as P(Dt)~ (Dt)^(-1-kappa). It turns out that such systems with Levy-distributed long-range interactions still exhibit a continuous phase transition with critical exponents varying continuously with sigma and/or kappa in certain ranges of the parameter space. In a field-theoretical framework such algebraically distributed long-range interactions can be accounted for by replacing the differential operators nabla^2 and d/dt with fractional derivatives nabla^sigma and (d/dt)^kappa. As another possibility, one may introduce algebraically decaying long-range interactions which cannot exceed the actual distance to the nearest particle. Such interactions are motivated by studies of non-equilibrium growth processes and may be interpreted as Levy flights cut off at the actual distance to the nearest particle. In the continuum limit such truncated Levy flights can be described to leading order by terms involving fractional powers of the density field while the differential operators remain short-ranged.Comment: LaTeX, 39 pages, 13 figures, minor revision