Evaluation of self-sealing structures for space vehicle application

Self-sealing structures to protect pressurized space vehicle compartments in micrometeorite environmen

Determination of sixteen polycyclic aromatic hydrocarbons in aqueous and solid samples from an Italian wastewater treatment plant

This study addresses the issue of whether it is possible to accurately predict the removalefficiencies of metals of environmental concern (i.e., Al, Ag, As, B, Ba, Cd, Cr, Fe, Mn, Hg, Ni,Pb, Cu, V, and Zn) in a wastewater treatment plant. The plant in question (at Fusina, Venice,Italy) is fed by mixed wastes from municipal and industrial sources (300 000 equivalentinhabitants) and discharges the treated effluent into the Venice lagoon. The year-long samplingcampaign (2001-2002) yielded a substantial amount of analytical data and relatively wide rangesof concentrations of metals in the influent samples, which made it possible to study the removalefficiencies by plotting the terms (inlet concentration - outlet concentration) vs (inlet concentration)for each metal investigated. The data in the plots were fitted using the linear regressionmodel Y ) BX. The slope rates (terms B), which were estimated by the least-squares method,have been adopted as the removal efficiencies, and they can be considered as constants in theconcentration ranges recorded in this work. The relative abundance of metals in the rawwastewaters feeding Fusina WWTP followed the order Al > Fe > B > Zn > Ba > Mn > Cu >Pb > Hg ) Ni > Cr ) As > V > Ag > Cd, while in the effluent the order was Fe > Al > Zn >Mn > Ba > Ni > Cu > Pb > Cr > Ag > As > Hg ) V > Cd. The removal percentages (%) of themetals were Al ) 92 ( 1; Ag ) 94 ( 1; As ) 76 ( 3; B ) n.d.; Ba ) 85 ( 2; Cd ) 85 ( 2; Cr )87 ( 1; Fe ) 90 ( 1; Mn ) 61 ( 2; Hg ) 93 ( 1; Ni ) 50 ( 3; Pb ) 92 ( 1; Cu ) 93 ( 1; V )74 ( 2; and Zn ) 75 ( 3

Effect of quantum confinement on exciton-phonon interactions

We investigate the homogeneous linewidth of localized type-I excitons in type-II GaAs/AlAs superlattices. These localizing centers represent the intermediate case between quasi-two-dimensional (Q2D) and quasi-zero-dimensional localizations. The temperature dependence of the homogeneous linewidth is obtained with high precision from micro-photoluminescence spectra. We confirm the reduced interaction of the excitons with their environment with decreasing dimensionality except for the coupling to LO-phonons. The low-temperature limit for the linewidth of these localized excitons is five times smaller than that of Q2D excitons. The coefficient of exciton-acoustic-phonon interaction is 5 ~ 6 times smaller than that of Q2D excitons. An enhancement of the average exciton-LO-phonon interaction by localization is found in our sample. But this interaction is very sensitive to the detailed structure of the localizing centers.Comment: 6 pages, 4 figure

Multiband theory of multi-exciton complexes in self-assembled quantum dots

We report on a multiband microscopic theory of many-exciton complexes in self-assembled quantum dots. The single particle states are obtained by three methods: single-band effective-mass approximation, the multiband $k\cdot p$ method, and the tight-binding method. The electronic structure calculations are coupled with strain calculations via Bir-Pikus Hamiltonian. The many-body wave functions of $N$ electrons and $N$ valence holes are expanded in the basis of Slater determinants. The Coulomb matrix elements are evaluated using statically screened interaction for the three different sets of single particle states and the correlated $N$-exciton states are obtained by the configuration interaction method. The theory is applied to the excitonic recombination spectrum in InAs/GaAs self-assembled quantum dots. The results of the single-band effective-mass approximation are successfully compared with those obtained by using the of $k\cdot p$ and tight-binding methods.Comment: 10 pages, 8 figure

Thromboelastometry (ROTEM®) in children: age-related reference ranges and correlations with standard coagulation tests

Background The small sample volume needed and the prompt availability of results make viscoelastic methods like rotational thromboelastometry (ROTEM®) attractive for monitoring coagulation in small children. However, data on reference ranges for ROTEM® parameters in children are scarce. Methods Four hundred and seven children (ASA I and II) undergoing elective surgery were recruited for this prospective, two-centre, observational study. Subjects were grouped as follows: 0-3, 4-12, 13-24 months, 2-5, 6-10, and 11-16 yr. Study objectives were to establish age-dependent reference ranges for ROTEM® assays, analyse age dependence of parameters, and compare ROTEM® data with standard coagulation tests. Results Data from 359 subjects remained for final analysis. Except for extrinsically activated clot strength and lysis, parameters for ROTEM® assays were significantly different among all age groups. The most striking finding was that subjects aged 0-3 months exhibited accelerated initiation (ExTEM coagulation time: median 48 s, Q1-Q3 38-65 s; P=0.001) and propagation of coagulation (α angle: median 78o, Q1-Q3 69-84o; P<0.001) and maximum clot firmness (median 62 mm, Q1-Q3 54-74 mm), although standard plasma coagulation test results were prolonged (prothrombin time: median 13.2 s, Q1-Q3 12.6-13.6 s; activated partial thromboplastin time: median 42 s, Q1-Q3 40-46 s). Lysis indices of <85% were observed in nearly one-third of all children without increased bleeding tendency. Platelet count and fibrinogen levels correlated significantly with clot strength, and fibrinogen levels correlated with fibrin polymerization. Conclusions Reference ranges for ROTEM® assays were determined for all paediatric age groups. These values will be helpful when monitoring paediatric patients and in studies of perioperative coagulation in childre

Markov image models and non-linear estimation algorithms on the quad-tree

Non-causal Markov Random Field (MRF) models are now widely used for representing images, but are known to yield iterative , often computational intensive, estimation algorithms . In this paper we consider a special class of Markov models which allow t o circumvent the latter drawback : MRF attached to the nodes of a quad-tree . The specific structure of these models results in a n appealing causality property through scale, which allows the design of exact, non-iterative inference algorithms which are simila r to those used in the context of Markov chain models . We first introduce an original extension of the Viterbi algorithm for the exac t computation of Maximum A Posteriori (MAP) estimates, along with two other algorithms respectively related to a modified MA P estimator, and to the Marginal Posterior Mode (MPM) estimator. The estimation of the parameters of the model is then addresse d with two original Expectation-Maximization (EM)-type algorithms, allowing an unsupervised use of these models . The practica l relevance of the different algorithms is investigated in the context of a standard image classification problem, both on syntheti c and natural images .Les modèles markoviens spatiaux non causaux utilisés dans le domaine de l'analyse d'images conduisent à des algorithmes d'estimation itératifs, réputés pour leur complexité calculatoire. Dans cet article, nous considérons une classe de processus markoviens hiérarchiques et non linéaires, définis sur le quadarbre. Ces modèles markoviens présentent des propriétés de causalité en échelle qui permettent de construire des algorithmes non itératifs exacts, similaires à ceux existant pour les chaînes de Markov, dans le cas des signaux mono-dimensionnels. Nous présentons ainsi une version originale de l'algorithme de Viterbi sur le quadarbre, associé à une estimation exacte au sens du Maximum A Posteriori (MAP), ainsi que deux autres algorithmes d'estimation, respectivement associés à un critère du MAP modifié et au critère du MPM (mode de la marginale a posteriori). Deux nouveaux algorithmes EM, permettant une estimation non supervisée sur le quadarbre, sont également introduits pour cette classe de représentations. Les propriétés de ces modèles et algorithmes sont illustrées et comparées, pour un problème simple de classification d'images, sur des images synthétiques et réelles

General insights on obstacles to dog vaccination in Chad on community and institutional level

Domestic dogs are responsible for 95% of all human rabies cases worldwide and continue to be the main reservoir for this fatal virus in African and Asian countries. Interrupting the spread of the disease in the domestic dog population is therefore necessary for long-term, sustainable rabies control. Chad has been recognized as a rabies-endemic country since 1961, but no national control strategy is in place to date and dog vaccination coverage is very low. This qualitative, descriptive study aims to describe the main barriers to dog vaccination on both the community and the institutional level from a socio-anthropological point of view in Chad. The study was embedded in an overall project conducted from 2016 to 2018, to determine rabies burden and vaccine demand in West and Central Africa, funded by GAVI, the vaccine alliance. Data collection was conducted on the occasion of the project's closing workshops with stakeholders organized between August to September 2018 in the four (4) project areas: Logone Occidental, Ouaddai, Hadjer Lamis and Chari Baguirmi. We conducted interviews and focus group discussions (FGD) among veterinary officers and dog owners. Participants were selected purposively based on their place of residence (dog owners) or work place (veterinary officers) and their previous contact with the project through reporting (dog owner) or management (veterinary officers) of a suspect dog rabies case. In each region, one FGD was organized with dog owners, and one FGD with heads of veterinary posts. At the end of the FGDs, a few participants were randomly selected for interviews. In addition, in each region an interview was conducted with the head of the livestock sector, the chief district medical officers and the head of a civil society association. The identified barriers to dog vaccination access are grouped into three main aspects: the economic, the socio-cultural and the institutional level. Economic constraints encountered relate to the cost of the vaccine itself and the expenses for transporting the dogs to the vaccination site. The cultural belief that the vaccine will have an impact on the therapeutic properties of dog meat for consumers (observed in Southern Chad), and the fact that dogs are considered impure animals in Muslim faith, which prohibits handling of dogs, are obstacles identified on the sociocultural level. At the institutional level, the unavailability of vaccines in veterinary services, the lack of communication about the law on dog vaccination, the absence of rabies in the training curricula of veterinary agents, and the lack of intersectoral collaboration limit vaccination coverage. In order to improve vaccination coverage and rabies surveillance with a view to eradicate rabies by 2030, communication strategies that are adapted to the context and that take cultural obstacles into account must be put in place in a synergy of interdisciplinary action. In addition, factors such as affordability, geographical access and availability of dog rabies vaccines needs to be addressed throughout the country. Although our study design did not allow a detailed analysis of obstacles related to socio-economic level, gender and age the broad insights gained can provide general guidance for future interventions in Chad and similar countries

Ultrafast Demagnetization of Iron Induced by Optical versus Terahertz Pulses

We study ultrafast magnetization quenching of ferromagnetic iron following excitation by an optical versus a terahertz pump pulse. While the optical pump (photon energy of 3.1 eV) induces a strongly nonthermal electron distribution, terahertz excitation (4.1 meV) results in a quasithermal perturbation of the electron population. The pump-induced spin and electron dynamics are interrogated by the magneto-optic Kerr effect (MOKE). A deconvolution procedure allows us to push the time resolution down to 130 fs, even though the driving terahertz pulse is about 500 fs long. Remarkably, the MOKE signals exhibit an almost identical time evolution for both optical and terahertz pump pulses, despite the 3 orders of magnitude different number of excited electrons. We are able to quantitatively explain our results using a nonthermal model based on quasielastic spin-flip scattering. It shows that, in the small-perturbation limit, the rate of demagnetization of a metallic ferromagnet is proportional to the excess energy of the electrons, independent of the precise shape of their distribution. Our results reveal that, for simple metallic ferromagnets, the dynamics of ultrafast demagnetization and of the closely related terahertz spin transport do not depend on the pump photon energy