Search

In this work temperature inhomogeneities and their influence on PEMWE performance of industrial-scale stacks are investigated. Three temperature differences are examined: (i) between the inlet and outlet, (ii) in-between the cells of a stack, (iii) between the cell’s solid materials and the fluids. A validated stack model for temperature and performance is presented which is used to quantify the above-mentioned temperature fields and their influences on current density distribution and cell voltages. For a chosen scenario, with current densities of 2.0 A cm−2, fluid inlet temperatures of 60 °C and flow-rates of 0.15 kg s−1m−2, peak temperature differences amount to 8.2 K along-the-channel. This relates to inhomogeneities of current density of up to 10% inside a cell and deviations of cell voltage of 9 mV in-between cells in the center of the stack and outer cells. For higher current densities these differences increase further. More homogeneous temperatures allow operation at elevated average temperatures without exceeding temperature limitations and reduce the spread of degradation mechanisms. Hence, homogenous profiles lead to a more hole-some utilization of electrolysis stacks. Therefore, the ability to homogenize via alternative operation such as higher flow-rate, higher pressure and altered routing of fluid-flow is analyzed.

In this study, the directional semivariogram is deployed to investigate the spatial variability of map-scale fracture network attributes in the Paradox Basin, Utah. The relative variability ratio (R) is introduced as the ratio of integrated anisotropic semivariogram models, and R is shown to be an effective metric for quantifying the magnitude of spatial variability for any two azimuthal directions. R is applied to a GIS-based data set comprising roughly 1200 fractures, in an area which is bounded by a map-scale anticline and a km-scale normal fault. This analysis reveals that proximity to the fault strongly influences the magnitude of spatial variability for both fracture intensity and intersection density within 1–2 km. Additionally, there is significant anisotropy in the spatial variability, which is correlated with trends of the anticline and fault. The direction of minimum spatial correlation is normal to the fault at proximal distances, and gradually rotates and becomes subparallel to the fold axis over the same 1–2 km distance away from the fault. We interpret these changes to reflect varying scales of influence of the fault and the fold on fracture network development: the fault locally influences the magnitude and variability of fracture network attributes, whereas the fold sets the background level and structure of directional variability.

Simulating the properties of lithium ion cells during charging becomes more and more important to understand the ongoing effects during fast charging. In this work special emphasis is given to the modelling of metallic lithium deposition on the surface of negative electrode particles, so-called lithium plating, and the linked mechanical behaviour. The basis of the parametrization of the electrochemical model was a previously published experimental study on the pressure behaviour under lithium plating conditions. The developed and parametrized simple pseudo two-dimensional model reproduces the experimental study on lithium plating with a satisfying accuracy of simulated voltage and pressure trend. The model enables prediction of lithium deposition onset by matching measured pressure behaviour to the model. In addition to reproducing the cell behaviour, the model was used to optimize a measurement based fast charging protocol by using the negative electrode potential. The optimization of the fast charging protocol resulted in a 6.3% decreased charging time from 0 to 85%SoC while using a maximum C-rate of 3C. A verification of the model-based optimization has been shown by short experimental study.

The use of focused ion beams, whilst permitting the targetted preparation of thin specimens for Transmission Electron Microscopy, also results in modification of the material to be investigated as a result of energy being transferred into the material. This undesirable effect is normally limited to the surface of the material, which is particularly unfavourably orientated towards the impinging ion beam. If the crystal structure and composition of areas close to the surface of such specimens need to be characterised, protective layers may be used. However, those layers, depending on the applied deposition technique, may interact with the sample surface as well thus affecting the results of the analysis. In the work presented here, the possible interactions which might occur between the various protective coatings of ion-beam deposited Platinum, electron beam deposited Platinum, Silicon Oxide or adhesively bonded Gold foil and the subsequent FIB-preparation of the oxide layers on Ni-Ti alloys are investigated, with respect to and how these might affect the TEM-images obtained of areas close to the surface of such specimens. It is shown that the use of adhesively bonded Gold foil as a protective coating, in particular, permits comprehensive characterisation of the surface, including the use of high-resolution TEM, to be carried out, up to the surface of the Oxide layer itself.

Streptococcus pneumoniae is a main cause of child mortality worldwide, but strains also asymptomatically colonize the upper airways of most children and form biofilms. Recent studies have demonstrated that ∼50% of colonized children carry at least two different serotypes (i.e., strains) in the nasopharynx; however, studies of how strains coexist are limited. In this work, we investigated the physiological, genetic, and ecological requirements for the relative distribution of densities, and spatial localization, of pneumococcal strains within biofilm consortia. Biofilm consortia were prepared with vaccine type strains (i.e., serotype 6B [S6B], S19F, or S23F) and strain TIGR4 (S4). Experiments first revealed that the relative densities of S6B and S23F were similar in biofilm consortia. The density of S19F strains, however, was reduced to ∼10% in biofilm consortia, including either S6B, S23F, or TIGR4, in comparison to S19F monostrain biofilms. Reduction of S19F density within biofilm consortia was also observed in a simulated nasopharyngeal environment. Reduction of relative density was not related to growth rates, since the Malthusian parameter demonstrated similar rates of change of density for most strains. To investigate whether quorum sensing (QS) regulates relative densities in biofilm consortia, two different mutants were prepared: a TIGR4Δ luxS mutant and a TIGR4Δ comC mutant. The density of S19F strains, however, was similarly reduced when consortia included TIGR4, TIGR4Δ luxS , or TIGR4Δ comC . Moreover, production of a different competence-stimulating peptide (CSP), CSP1 or CSP2, was not a factor that affected dominance. Finally, a mathematical model, confocal experiments, and experiments using Transwell devices demonstrated physical contact-mediated control of pneumococcal density within biofilm consortia. IMPORTANCE Streptococcus pneumoniae kills nearly half a million children every year, but it also produces nasopharyngeal biofilm consortia in a proportion of asymptomatic children, and these biofilms often contain two strains (i.e., serotypes). In our study, we investigated how strains coexist within pneumococcal consortia produced by vaccine serotypes S4, S6B, S19F, and S23F. Whereas S6B and S23F shared the biofilm consortium, our studies demonstrated reduction of the relative density of S19F strains, to ∼10% of what it would otherwise be if alone, in consortial biofilms formed with S4, S6B, or S23F. This dominance was not related to increased fitness when competing for nutrients, nor was it regulated by quorum-sensing LuxS/AI-2 or Com systems. It was demonstrated, however, to be enhanced by physical contact rather than by a product(s) secreted into the supernatant, as would naturally occur in the semidry nasopharyngeal environment. Competitive interactions within pneumococcal biofilm consortia regulate nasopharyngeal density, a risk factor for pneumococcal disease.

BACKGROUND:We assessed nasopharyngeal (NP) carriage of five pathogens in febrile children with and without acute respiratory infection (ARI) of the upper (URTI) or lower tract, attending health facilities in Tanzania. METHODS:NP swabs collected from children (N = 960) aged 2 months to 10 years, and with a temperature ≥38°C, were utilized to quantify bacterial density of S. pneumoniae (Sp), H. influenzae (Hi), M. catarrhalis (Mc), S. aureus (Sa), and N. meningitidis (Nm). We determined associations between presence of individual species, densities, or concurrent carriage of all species combination with respiratory diseases including clinical pneumonia, pneumonia with normal chest radiography (CXR) and endpoint pneumonia. RESULTS:Individual carriage, and NP density, of Sp, Hi, or Mc, but not Sa, or Nm, was significantly associated with febrile ARI and clinical pneumonia when compared to febrile non-ARI episodes. Density was also significantly increased in severe pneumonia when compared to mild URTI (Sp, p

Background: Pneumococcal conjugate vaccines (PCV) have decreased nasopharyngeal carriage of vaccine types but little data exist from rural areas. We investigated bacterial density, serotype distribution and antibiotic resistance of pneumococcal strains within the nasopharynx of young children in the Peruvian Andes, 2 years after PCV7 was introduced. Methods: Pneumococcal strains were isolated from a subset of 125 children from our Peruvian cohort, who entered the study in 2009 and had pneumococcus detected in the nasopharynx in both 2009 and during follow-up in 2011. Strains were Quellung serotyped and tested for susceptibility to antibiotics. Bacterial density was determined by quantitative polymerase chain reaction. Results: The prevalence of PCV7 strains decreased from 48% in 2009 to 28.8% in 2011, whereas non-PCV7 types increased from 52% to 71.2% (P = 0.002). There was a 3.5-fold increase in carriage of serotype 6C in 2011 (P = 0.026). Vaccination with PCV7 did not affect pneumococcal density in children colonized by a PCV7 type but did increase density in those colonized with a non-PCV7 type. Antibiotic resistance did not change after vaccine introduction; strains were nonsusceptible to tetracycline (97.2%), trimethoprim-sulfamethoxazole (56.4%), penicillin (34%), erythromycin (22.4%), chloramphenicol (18.8%) and clindamycin (12.4%). Conclusions: Serotype replacement was observed post-PCV7 vaccination with a concomitant, not previously recognized, increased nasopharyngeal density.

In the past decade, hard x-ray transmission microscopy experienced tremendous developments. With the avail-ability of efficient Fresnel zone plates, even set-ups utilizing laboratory sources were developed [1]. In order to improve the performance of these x-ray microscopes, novel approaches to fabricate optical elements [2] and brighter x-ray tubes [3] are promising candidates. We are currently building a laboratory transmission x-ray microscope for 9.25 keV, using an electron impact liquid-metal-jet anode source. Up to now, the further elements of our setup are: a polycapillary condenser, a tungsten zone plate, and a scintillator which is optically coupled to a CMOS camera. However, further variations in terms of optical elements are intended. Here we present the current status of our work, as well as first experimental results.

A human phenylalanine hydroxylase cDNA clone was isolated from a human liver cDNA library. The size of the cDNA insert is approximately 2.4 kb and appears to be a near full length copy of a phenylalanine hydroxylase mRN A. This cDN A was used to probe for Hindlll restriction enzyme polymorphisms in heterozygote typing of families with phenylketonuria. The use of three alleles of this polymorphism, as opposed to the two alleles as previously described, increases the informativity for typing - and therefore also for prenatal diagnosis -in certain families from 75% to 100%.

The current chapter surveys high-pressure water electrolysis. In the first part, general thermodynamic considerations for high-pressure electrolyzers are discussed. Instructive relations are derived for electric energy demand and the amount of heat released under both reversible and irreversible conditions. Classical simplifications are reviewed. Furthermore, different configurations for high-pressure electrolyzers are compared from an energetic viewpoint. In the second part, technology-specific aspects are discussed for high-pressure alkaline electrolyzers and high-pressure solid polymer electrolyzers. Typical technical realizations and operating conditions are reviewed. Governing processes and their pressure dependence are discussed and technology developments are sketched.

There is an increasing need for adequate modelling and simulation tools for the design and analysis of fuel cell systems. In the present contribution, a modular modelling strategy is proposed, which is based on network theory for chemical engineering processes. According to this network theory, a fuel cell system is decomposed into elementary units on several hierarchical levels (process unit level, phase level, storage level). After decomposition, the model formulation starts on the storage level: electrochemical source terms were combined with the diffusive and convective transport phenomena and state equations, forming an elementary unit of the phase level. On the phase level several thermodynamic phases (e.g. fluid compartments, electrode backings, catalyst layers, and the membrane electrolyte) are aggregated to a single fuel cell unit. Finally on the top level, the process unit level, single cells or fuel cell stacks are combined with other process units to form a complete process model. This modelling procedure is demonstrated with a simple proton exchange membrane fuel cell system operated with hydrogen and oxygen.

Im Kranbau werden aufgrund der Leichtbauweise und der dynamischen Beanspruchung hohe Anforderungen an die Stahlkonstruktion gestellt. Hochfeste Werkstoffe wie insbesondere die Feinkornbaustahle und deren schweistechnische Verarbeitung spielen eine zentrale Rolle in der Produktion. Entsprechend vielseitig und verantwortungsvoll sind die Aufgaben der Schweisaufsicht: Sie reichen von Werkstoffen und Schweisverfahren uber die Schweiserqualifikation und Verfahrensprufungen bis zu Reparaturanweisungen und Produktivitatssteigerung.

Success in the development of hemocompatible biomaterials depends on adequate equipment and procedures for standardized analysis of blood-materials interactions in vitro. In view of the limited standard of knowledge on that important aspect, two novel incubation systems were designed, built, and evaluated for the in vitro assessment of the hemocompatibility of planar solid surfaces: A screening setup was introduced for the comparison of up to 12 different samples. A perfusion setup was developed to model the directed blood flow in the vascular system during incubation by a recirculation circuit, allowing the variation of the wall shear rate at the sample surface. The incubation procedures utilized freshly drawn, heparinized whole human blood. Hemocompatibility in terms of selected aspects of coagulation, thrombogenicity, and immune responses was quantified through plasma levels of characteristic molecules (immunoassays), cell counting, and analysis of adherent cells and fibrin formation (scanning electron microscopy), respectively. Prevention of blood-air contact and mechanical stress, constant temperature and blood pH during incubation, and the suitable choice of reference materials were found to be crucial for reliable testing. Considering those requirements, screening and perfusion system both provided sensitive discrimination between a given set of planar solid surfaces. In conclusion, the suggested methods for an in vitro hemocompatibility assessment permit versatile, sensitive, and efficient analysis of important blood-material interactions despite the unavoidable variability of blood characteristics in different experiments.

Das dynamische Rontgen in Kombination mit der digitalen Bildverarbeitung last eine weitgehend objektive Erfassung des Verformungszustandes von belasteten Bauteilen zu, wobei die Entwicklung der Deformationen bei veranderlichen Belastungszustanden verfolgt werden kann. Am Beispiel von Ausziehkorpern aus Porenbeton wurden Untersuchungen durchgefuhrt, um festzustellen, welche Genauigkeit mit dieser Mesmethode erreicht werden kann. Dabei ist besonders zu beachten, das im Hinblick auf die Bildqualitat ein unmittelbarer Zusammenhang zwischen den Durchstrahlungszeiten und der Belastungsgeschwindigkeit besteht. Gemas den Versuchen kann festgestellt werden, das die zur Durchstrahlung der Proben eingestellte Zeit von ca. 0,27 s eine dynamische Verformungsmessung mit einer Genauigkeit von bis zu ca. 5 hundertstel Millimetern zulast, wenn die Belastungsgeschwindigkeit in dem fur quasistatische Einwirkungen ublichen Bereich liegt. Verformungen konnen somit auch bei sukzessiver Lastveranderung erfast werden. Die Genauigkeit des vorgestellten Mesverfahrens ist herkommlichen Mesmethoden aquivalent, bietet jedoch wegen des beruhrungslosen Mesprinzips wesentliche Vorteile. Verformungen, insbesondere solche im Bauteilinneren, konnen ohne Beeinflussung des mechanischen Zustandes bildhaft erfast und durch eine anschliesende Auswertung quantifiziert werden. Der hohe Genauigkeitsgrad des Mesverfahrens in Verbindung mit den Vorteilen der beruhrungslosen Messung eroffnet die Moglichkeit einer vollig neuen Qualitat der Verformungsmessung und somit der Interpretation mechanischer Zustande an belasteten Bauteilen.

Proliferating smartphones and mobile software offer linguists a scalable, networked recording device. This paper describes Aikuma, a mobile app that is designed to put the key language documentation tasks of recording, respeaking, and translating in the hands of a speech community. After motivating the approach we describe the system and briefly report on its use in field tests.

Die neue Neckarbruecke Kirchheim-Gemmrigheim ist - nach einer Bogenbruecke und einem SKR-Fachwerk - der dritte Brueckenschlag an dieser Stelle. Sie fuehrt die zweispurige Kreisstrasse K 1625 ueber den Neckar und eine zweigleisige Bahnlinie. Die 11,50 m breite und insgesamt 217 m lange Bruecke besteht im wesentlichen aus dem Verbundfachwerk-Ueberbau ueber dem Fluss, dem Verbundtraegerrost ueber der Bahnlinie, zwei Fluss- und einem Landpfeiler sowie drei Widerlagern. Die erforderliche Aufrechterhaltung des Bahn-, Strassen- und Schiffsverkehrs machte die Herstellung des Neckar-Ueberbaus in provisorischer Lage, den Querverschub auf die ertuechtigten Unterbauten und den Einsatz von drei Behelfsbruecken erforderlich. (A*)

Non-isotopic single-strand conformation polymorphism (SSCP) and direct sequencing was used for carrier diagnosis in four families of DMD/BMD patients with previously characterized point mutations, leading to the identification of eight carriers and four non-carriers. When the mutation caused a distinctly altered migration pattern of the single strands, in principle, the SSCP-technique allowed determination of carrier status in the extended family of the probands without direct sequencing. However, because SSCP measures a function of not only the mutation, but of the entire sequence of the PCR product, it can lead to false negative and/or false positive diagnoses due to intronic and exonic sequence heterogeneity in the family. As we discovered this pitfall in one of the reported families, we concluded that for carrier testing the SSCP approach must be performed in essential conjunction with an independent assessment of the mutation site by direct sequencing.

By using a combination of multiplex polymerase chain reaction and allele-specific labelled probes, the oligo-ligation assay is designed to detect known cystic fibrosis transmembrane regulator mutations. This study shows that this assay may also be useful to detect new mutations. The second child of a family of Bosnic origin showed all the symptoms of intestinal and pulmonary manifestations of cystic fibrosis. No signal could be obtained for the allele-specific probe 1898+1G>A. This could be explained by a nearby localized sequence change that prevented polymerase chain reaction primers or oligonucleotide probes from binding to the target sequence. Indeed, sequence analysis revealed a new 1894G>T exchange (Glu587Stop). Both parents and the healthy brother carried this mutation. Thus, the index patient was homozygous for 1894G>T, which was inherited from both parents.

Moribund fry from several families of Atlantic salmon Salmo salar had a conspicuous cranial defect that corresponded with 18.3% (SD, 4.5%) mortality of fry. The lesion was characterized by a domed, epithelium-covered swelling centered over the optic tectum. The swelling was an edematous reaction to the extension of a fulminating necrotizing mycotic stomatitis and bronchitis into the cranial tissues including the ventral meninges. An oomycete is believed to be the pathogen. The percentage mortality of fry in each separately reared family ranged from 1.0 to 63.3%. An analysis of variance revealed that the differences in mortality among families were significant (P < 0.0001), and that the difference between replicates of each family, reared apart, were not significant. A possible genetic basis for resistance to fungal infection is discussed.

The Physikalisch-Technische Bundesansalt (PTB) calibrates inductance standards in the frequency range from 100 Hz to 100 kHz and beyond. The relative uncertainties achieved range from less than 5*10/sup -5/ to 5*10/sup -4/ (2 sigma ) depending on the frequency and the value of the standards. Because of the strong frequency dependence of the inductance standards it is of interest to use a suitable equivalent circuit to calculate the most accurate approximation for the frequency variation. A model is presented which allows the values of a GR1482 inductance standard to be calculated over the whole frequency range from 100 Hz to 100 kHz within the measurement uncertainties. >

A precise realization of the unit of capacitance is important for the determination of both the Josephson and the von Klitzing constants. The main design criteria of the PTB's cross capacitor, the maintenance of the unit of capacitance over the last 10 years, and a special capacitance-measuring bridge for tracing back the electrode capacitance in the absolute volt experiment to SI units are described in this paper. >

Inductance calibrations at PTB are carried out with a Maxwell-Wien bridge. This bridge has the advantage that the first order bridge equation is independent of frequency which means that the bridge has the potential to be operated in a large frequency range. However, the actual frequency range, from power frequencies up to 1 MHz, requires an investigation of higher order effects.

Success in the development of hemocompatible biomaterials depends on adequate equipment and procedures for standardized analysis of blood-materials interactions in vitro. In view of the limited standard of knowledge on that important aspect, two novel incubation systems were designed, built, and evaluated for the in vitro assessment of the hemocompatibility of planar solid surfaces: A screening setup was introduced for the comparison of up to 12 different samples. A perfusion setup was developed to model the directed blood flow in the vascular system during incubation by a recirculation circuit, allowing the variation of the wall shear rate at the sample surface. The incubation procedures utilized freshly drawn, heparinized whole human blood. Hemocompatibility in terms of selected aspects of coagulation, thrombogenicity, and immune responses was quantified through plasma levels of characteristic molecules (immunoassays), cell counting, and analysis of adherent cells and fibrin formation (scanning electron microscopy), respectively. Prevention of blood-air contact and mechanical stress, constant temperature and blood pH during incubation, and the suitable choice of reference materials were found to be crucial for reliable testing. Considering those requirements, screening and perfusion system both provided sensitive discrimination between a given set of planar solid surfaces. In conclusion, the suggested methods for an in vitro hemocompatibility assessment permit versatile, sensitive, and efficient analysis of important blood-material interactions despite the unavoidable variability of blood characteristics in different experiments.

Development of the first US national fiber-optic transmission network, during a period marked by the rapid and technology-intensive introduction of single-mode cable and high-capacity optical transmission equipment is discussed. The authors examine some of the important design issues addressed during the development phase including baseband treatment, surveillance system homogeneity, capacity upgrade capability, network survivability, and flexibility for future growth. >

Two computer-controlled capacitance bridges for different fields of application have been developed at the PTB. The first one, the universal bridge, works in the capacitance range of less than 1 pF up to 1 /spl mu/F and in a frequency range up to 1 kHz, The total calculated relative uncertainties (2/spl sigma/) are in the order of 5/spl middot/10/sup -6/ and 20/spl middot/10/sup -6/. The second one, the fixed ratio bridge, calibrates primary standards with capacitance values from 1 pF to 1 nF in 1:1, 1:2, 1:5 or 1:10 steps at frequencies from 100 Hz to 10 kHz. The relative uncertainty of one 1:10 step at a frequency of 1592 Hz is estimated to be 3/spl middot/10/sup -8/ (1/spl sigma/). >

An intercomparison of standard capacitor of value 10 pF has been carried out between NPL (India) and Physikalisch-Technische Bundesanstalt (Germany) under the PTB-NPL Cooperation programme. The measurements of a 10 pF silica capacitor at the frequency 1592 Hz for two different temperatures agreed within 0.15 ppm.