Traffic engineering using a class ofM/G/1models

The dominant-term approximation of theM/G/1queuing system is thoroughly investigated and its application in a number of traffic engineering problems is considered. The effective rate of traffic streams associated with theirM/G/1modelling is defined, the summability property of which is formally proven. Special attention is paid to theM/D/1model, the usage of which in ATM traffic control is demonstrated. An effective-rate shaping mechanism (based on this kind of modelling) is finally devised. The performance of the proposed shaper has been fully validated, both theoretically and experimentally.     

Influence of turbulence on transient premixed flame propagation inside closed vessels

The explosion behaviour of CH₄/air mixtures inside a closed 0.065 m³ spherical and a 1 m³ cylindrical vessel was investigated to determine the effect of turbulence on the structure and propagation rate of transient turbulent flames for different initial turbulence levels generated by 4 ventilators installed inside the equipment. Laser-Doppler and hot wire anemometry were used to measure the turbulent motion. It was found that fairly uniform turbulence could be achieved in the central zones of the vessels and that the RMS-values of flow velocity were proportional to the ventilator speed. The evaluation of burning velocity from the pressure/time records showed that, starting from an initial burning velocity which depends on the initial turbulence level, the flame accelerates as a result of pressure, temperature and turbulence effects. Maximum burning velocity coincides with the inflexion point of the pressure/time curve, and is followed by a rapid deceleration of the flame front. A linear relationship between burning velocity and measured RMS-velocity is recognized in the observed range of RMS-values.     

Classification criteria and probability risk maps: limitations and perspectives

Delineation of polluted zones with respect to regulatory standards, accounting at the same time for the uncertainty of the estimated concentrations, relies on classification criteria that can lead to significantly different pollution risk maps, which, in turn, can depend on the regulatory standard itself. This paper reviews four popular classification criteria related to the violation of a probability threshold or a physical threshold, using annual (1996-2000) nitrogen dioxide concentrations from 40 air monitoring stations in Milan. The relative advantages and practical limitations of each criterion are discussed, and it is shown that some of the criteria are more appropriate for the problem at hand and that the choice of the criterion can be supported by the statistical distribution of the data and/or the regulatory standard. Finally, the polluted area is estimated over the different years and concentration thresholds using the appropriate risk maps as an additional source of uncertainty.     

Process modeling of stress and chemical effects in SiGe alloys using kinetic Monte Carlo

In state-of-the-art silicon based process technologies, strained and relaxed SiGe, strained-silicon layers, and process-induced stress are widely present. Based on a literature review, we developed and calibrated continuum and kinetic Monte Carlo process models for chemical and stress effects in SiGe (Zographos et al. in AIP Conf. Proc. 1496:212–216, 2012). In this paper, we explain in full detail the corresponding kinetic Monte Carlo models and calibration. The models take into account the effects on band gap, amorphization, recrystallization, point defect generation and diffusion, extended defect evolution, dopant diffusion and clustering, and dopant segregation. The influence of Ge concentration and strain profile on Si self-interstitials and vacancies properties are deducted from experimental data as well as from ab-initio studies. The {311} interstitial clusters are less stable in the presence of Ge or compressive hydrostatic pressure, and the transformation of {311} defects into dislocation loops is faster. The corresponding parameter adjustments have been calibrated based on experimental data generated within the ATOMICS research project. The effects of Ge and stress on dopant diffusion have been calibrated for boron, arsenic and phosphorus taking into account that in experiments using epitaxial layers of strained SiGe embedded in Si, or strained silicon embedded in relaxed SiGe, boron and phosphorus have been found to segregate at Si/SiGe interfaces.     

Calcium Signalling in Heart and Vessels: Role of Calmodulin and Downstream Calmodulin-Dependent Protein Kinases

Cardiovascular disease is the major cause of death worldwide. The success of medication and other preventive measures introduced in the last century have not yet halted the epidemic of cardiovascular disease. Although the molecular mechanisms of the pathophysiology of the heart and vessels have been extensively studied, the burden of ischemic cardiovascular conditions has risen to become a top cause of morbidity and mortality. Calcium has important functions in the cardiovascular system. Calcium is involved in the mechanism of excitation–contraction coupling that regulates numerous events, ranging from the production of action potentials to the contraction of cardiomyocytes and vascular smooth muscle cells. Both in the heart and vessels, the rise of intracellular calcium is sensed by calmodulin, a protein that regulates and activates downstream kinases involved in regulating calcium signalling. Among them is the calcium calmodulin kinase family, which is involved in the regulation of cardiac functions. In this review, we present the current literature regarding the role of calcium/calmodulin pathways in the heart and vessels with the aim to summarize our mechanistic understanding of this process and to open novel avenues for research.     

Indole-3-Glycerol Phosphate Synthase From Mycobacterium tuberculosis: A Potential New Drug Target

Tuberculosis (TB), caused by the pathogen Mycobacterium tuberculosis, affects millions of people worldwide. Several TB drugs have lost efficacy due to emerging drug resistance and new anti-TB targets are needed. Recent research suggests that indole-3-glycerol phosphate synthase (IGPS) in M. tuberculosis (MtIGPS) could be such a target. IGPS is a (β/α)₈-barrel enzyme that catalyzes the conversion of 1-(o-carboxyphenylamino)-1-deoxyribulose 5’-phosphate (CdRP) into indole-glycerol-phosphate (IGP) in the bacterial tryptophan biosynthetic pathway. M. tuberculosis over expresses the tryptophan pathway genes during an immune response and inhibition of MtIGPS allows CD4 T-cells to more effectively fight against M. tuberculosis. Here we review the published data on MtIGPS expression, kinetics, mechanism, and inhibition. We also discuss MtIGPS crystal structures and compare them to other IGPS structures to reveal potential structure-function relationships of interest for the purposes of drug design and biocatalyst engineering.