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Metal-matrix composites (MMCs) offer a number of potential benefits to the aerospace industry, and these have led to important applications on systems such as the Space Shuttle Orbiter, the Hubble Space Telescope, and communications satellites. However, even after decades of development, MMCs have not seen widespread use. Several technical and non-technical challenges remain to their successful insertion into a variety of space applications. This article attempts to provide an overview of these challenges and potential pathways to resolving them.

It is shown that a periodic solution of the nonlinear infinite-dimensional Hamiltonian system describing a particle in a scalar wave field can have only certain discrete periods that are related to zeroes of the Fourier transform of the function that realizes the coupling.

Recent experimental studies of the hot isostatic consolidation of Ti-6Al-4V-coated SiC fibers contained in cylindrical canisters have revealed an unexpectedly high rate of creep densification. A creep consolidation model has been developed to analyze its origin. The initial stage of consolidation has been modeled using the results of contact analyses for perfectly plastic and power-law creeping cylinders that contain an elastic ceramic core. Final stage densification was modeled using a creep potential for a power-law material containing a dilute concentration of cusp-shaped voids with a shape factor similar to that observed in the experiments. Creep rates were microstructure sensitive and so the evolution of matrix grain size and the temperature dependence of the α/β-phase volume fractions were introduced into the model using micromechanics-based creep constitutive relationships for the matrix. To account for load shielding by the deformation resistant canister, the consolidation model was combined with an analysis of the creep collapse of a fully dense pressure vessel. The predicted densification rates were found to agree well with the experimental observations. The high densification rate observed in experiments was the result of the small initial grain size of the vapor-deposited matrix combined with retention of the cusp shape of the interfiber pores.

We consider a class of quasi-variational inequalities for certain second-order elliptic operators, where the set of admissible functions is required to satisfy an implicit gradient bound which depends on the solutions itself. We give sufficient conditions for the existence of a solution, and we apply our results to stationary problems arising in superconductivity, in thermoplasticity, and in electrostatics with implicit ionization threshold. Copyright © 2000 John Wiley & Sons, Ltd.

Here, we will demonstrate a new approach to merge high performance III/V-material properties with optical display technology. In a first step a low temperature grown and processed InP-FET structure not surpassing a temperature of 300°C is transferred to GaAs with the potential of future transfer to Si and other substrate materials. Future large area display panels require electronic overlay circuitry for optical arrays with high performance. FETs with high current densities grown on various substrate materials optimized to drive simultaneously a large number of light sources will be required. Furthermore each process step, including materials growth, has to be performed at extremely low temperatures to prevent degradation of the low-cost substrates, mainly glass and polymer.

We show the existence of periodic solutions to models in elastoplasticity, like the Chaboche model.

A trend to greater precision can be observed in production processes and technical testing procedures. Precision means that the process runs within narrow limits and that these limits are maintained with high probability. Even dyeing or printing processes in the laboratory or production plant are subject to greater or lesser fluctuations when the same processes are repeated. Quality Management according to the ISO 9000-9004 standard requires that, among other things, specifications, reproducibility levels and measurement uncertainties be defined or determined. Fundamental concepts of statistics are treated such as mean value, standard deviation, variation coefficient, confidence interval and measurement uncertainty and statistical process control (SPC). An attempt is made to reply to the question “How precisely can the colour strength of a dyestuff be determined?”. Narrower specifications can only be realistically fulfilled when the measurement uncertainty factor can be correspondingly reduced, which can often only be achieved by additional, cost-intensive measures. Value is attached to the simplest possible presentation. ©

We consider conservative non-smooth dynamical systems of the type ẍ+e+a sgn(x) = p(t) with an w-periodic forcing p, and we first prove the existence of periodic solutions in the non-resonant case for the corresponding differential inclusion. Moreover, in the resonant case w = 2π, we gave necessary and sufficient conditions on a and the first Fourier coefficient of p for periodic solutions to exist.

The consolidation of metalized ceramic fibers by hot isostatic pressing (HIP) offers an attractive route for the manufacture of continuous fiber reinforced titanium matrix composites (TMCs). The performance of this class of composites is controlled by the fiber/matrix properties and by the composite's relative density, the grain size of the matrix alloy and the interfacial reaction layer thickness at the fiber–matrix interface after processing. Recently developed process models that predict the evolution of these microstructural attributes during consolidation processing are summarized and combined with consolidation equipment dynamics to simulate the microstructural evolution of PVD Ti–6Al–4V coated Sigma 1240 (SiC) monofilaments during HIP. For this system, diffusion accommodated grain sliding is the dominant densification mechanism for process cycles that preserve the refined grain size of the PVD metal coating.

The vacuum hot pressing (VHP) of silicon carbide monofilaments coated with nanocrystalline Ti–6Al–4V has been studied. During consolidation, very high densification rates were observed, even at temperatures and pressures well below those normally used for processing conventional Ti–6Al–4V. From the cross-sections of partially consolidated specimens, the evolution of coated fiber–fiber contacts and pore shapes were determined. The pores were found to be cusp-shaped throughout the consolidation process. Columns of coated fibers were observed to form along the loading direction and resulted in regions of locally high fiber volume fraction. Simulations of the VHP experiments were performed using a model which incorporated time and temperature dependent microstructure relationships. In the model, the initial densification was based upon a recent micromechanical contact analysis for a metal coated fiber. Final stage densification was analyzed by modifying the Qian et al. strain rate potential for a power law creeping body containing isolated cusp-shaped pores. Overall, the simulations compared well with the experimental density data, although the load supported by the regions of locally high fiber volume fraction resulted in the model slightly overestimating the observed densification time response.

The π 0 momentum dependence of the decay η → π + π − π 0 has been measured with the Crystal Barrel detector. The analysis is based on 3230 events. The results of this independent measurement are compared to new chiral perturbation theory calculations and previous measurements.

The annihilation channel p p →K + K − π 0 in liquid hydrogen at rest has been studied with the Crystal Barrel detector at LEAR. The measured branching ratio is: BR ( p p → K + K − π 0 )=(2.37±0.15)×10 −3 . A partial wave analysis shows that this reaction is dominated by the π (K K ) S , K K ∗ (892) and π φ (1020) intermediate states. Weak signals are observed for π a 2 (1320), π f 2 (1270), π f 2 ′(1525) and K(Kπ) S . A satisfactory description of the Dalitz plot requires the introduction of π (K K ) P intermediate states with at least one pole.

Genital chlamydial infections persist for years in both women and men. Because of low numbers of organisms found in the urogenital tract direct detection of Chlamydia trachomatis may be difficult. In these cases serology serves as a useful diagnostic supplement in clinically suspected infection or tubal factor sterility. A total of 178 sterility patients (63 with pelviscopically proven occluded, 115 with open fallopian tubes), 103 women with positive cervical swabs, 100 obstetric patients (6% with positive cervical swabs), and 100 blood donors were serologically tested. The following tests were used: 1. microimmunofluorescence test (MIF, Graystone), 2. a commercial test using lipopolysaccharide (LPS) extracted elementary bodies as antigen, 3. a commercial whole inclusion test, 4. a commercial recombinant chlamydial LPS test. The positive predictive values of these tests were 71%, 65%, 66%, 52% for tubal occlusion and 40%, 40%, 21%,13% for a positive cervical swab (obstetric patients), respectively. Principally, only the Chlamydia trachomatis species-specific tests (MIF test and LPS extracted elementary body test) were suited for gynaecological chlamydial diagnostics. Due to its cross-reactivity with Chlamydia pneumoniae the whole inclusion test should be restricted to high prevalence groups such as sterility patients. The genus-specific LPS test proved to be of no help for the gynaecologist. No serological test allowed any differentiation between past and present infection with Chlamydia trachomatis.

The rupture of a gravid uterus is a serious threat to the mother's life and her fetus, associated with high maternal and perinatal mortality and morbidity and the loss of future fertility as hysterectomy is inevitable in many cases. A case of a patient with a uterine rupture caused by a cone biopsy is described. Intrapartally no typical signs of a uterine rupture were observed with the exception of a vaginal bleeding and painful contractions. Because there was a fetal bradycardia, a cesarean section was conducted. A complete rupture of the cervical, vaginal and uterine wall on the left side and an incomplete rupture of the cervical and uterine wall on the right side with large hematomas in the left and right parametrium were seen at surgery. A subtotal hysterectomy was inevitable after cesarean section. On the 18th postoperative day the patient and her healthy baby were discharged from hospital. To prevent this obstetric hazard we conclude that it is necessary to conduct a correct supervision of the pregnant women and to conduct a correct supervision of delivery in all patients with a history of cone biopsy. Midwives' and physicians' training and hospital deliveries are other important factors in prevention. Furthermore a well estimated use of cone biopsy to clarify critical cervical findings in younger women is necessary.

An experimental study of the consolidation and associated grain growth kinetics of silicon carbide monofilaments sputter coated with nanocrystalline Ti6Al4V has been conducted. Bundles of coated fibers were consolidated using a hot isostatic press (HIP) equipped with an eddy current sensor for in situ measurement of the specimens' relative density. The experiments were conducted at temperatures of 760°, 840°, and 900°C using a variety of pressure cycles that resulted in both fully and partially consolidated composites. The sensor data was used to determine the densification-time response of the specimens and to construct experimental HIP maps. Cross-sections of the partially consolidated specimens were used to investigate the evolution of coated fiber-fiber contacts and interfiber void shapes. The analysis indicated that the initial packing density was approximately random with an average of only about two contacts per coated fiber at a relative density of 70%. The number of contacts was a linear function of relative density reaching a maximum of almost six contacts per coated fiber at the theoretical density. The pores were found to be cusp-shaped throughout the consolidation process, indicative of a densification rate that greatly exceeded the (pore rounding) rate of sintering.

Thirteen isolates from African AIDS patients and from the environment in Zaire were identified as members of the Mycobacterium avium complex by phenotypic tests. RFLP analysis showed that the isolates belong to a genetically homogeneous cluster. The 16S rRNA sequence analysis suggests a close relationship with the P-49 strain (ATCC 35847), a reference strain for the serotype 7 of M. avium complex. This work shows the close relationship between certain M. avium complex strains responsible for disseminated infection in AIDS patients and M. avium complex strains isolated from the environment in Zaire. Further, our findings confirm that atypical mycobacteria may disseminate in AIDS patients in Africa and suggest that infection in these patients probably originates in their environment.

Near net shape titanium and nickel matrix composites can be produced by the hot isostatic/vacuum hot pressing of alloy coated ceramic fibers. During the initial stage of consolidation, densification occurs by the inelastic deformation of metal-metal contacts. When the temperature is low and the consolidation pressure is high, the dominant mechanism of contact deformation is matrix plasticity. This densification process is investigated by analysing the elastic-plastic contact deformation of aligned fibers. Applying a methodology developed for modelling the consolidation of alloy powders and spray deposited composite monotapes, a contact yield criterion has been proposed and used to predict the dependence of the relative density upon process conditions and matrix mechanical properties. The resulting densification model contains unknown plastic flow (F) and contact area evolution (c) coefficients. A deformation theory elastic-plastic finite element analysis of a representative coated fiber unit cell loaded in compression is used to find these coefficients. The analysis shows the ceramic fiber significantly constrains plasticity in the alloy coating resulting in fiber volume fraction dependent coefficients and a fiber volume fraction dependent density-pressure relationship for coated fiber consolidation.

We describe how to systematically develop an algorithm to simulate the nonsmooth dynamics of multibody systems with impacts and friction. Our approach works by using the theory of linear complementary problems.

We numerically study the bifurcation structure (in dependence of the amplitude and frequency of the forcing) of a non-smooth friction-oscillator system with dry friction.

In MR images, the median nerve of carpal tunnel syndrome (CTS) patients frequently appears flatter than in healthy subjects. The purpose of this work was to develop a metric to quantify localized median nerve deformation rather than global nerve flattening, the hypothesis being that localized median nerve deformation would be elevated in CTS patients. Twelve patients with CTS and 12 matched normals underwent MRI scanning in eight isometrically loaded hand conditions. 2D cross sections of the proximal and distal tunnel were analyzed for nerve cross sectional area, flattening ratio, and a position shift to the dorsal side of the tunnel. Additionally, new metrics based on the angulation of the nerve perimeter in 0.5-mm lengths around the boundary were calculated. The localized deformation metrics were able to detect differences between CTS patients and healthy subjects that could not be appreciated from the flattening ratio. During most hand activities, normal subjects had a higher average percentage of locally deformed nerve boundary than did CTS patients, despite having a rounder overall shape. Less local nerve deformation in the CTS patient group resulting from its interaction with flexor tendons suggests that the nerve may be less compliant in CTS patients.

An improved ion source based on laser ablation was developed which allows to implant a great variety of impurity ions into liquid helium ( 4 He). This ion source can be operated in the gas phase as well as inside the liquid helium opening up the opportunity to use pressurized liquid helium for the mobility studies also. Low field mobilities have been remeasured for He + , Ca + , Sr + and Ba + ions and measured for the so far unknown case of Mg + . The data for the ions investigated previously agree well with former measurements at similar temperatures. The mobility data for the Mg + ion fit well into the trend extrapolated from the other ions.

Compared to static beam Intensity-Modulated Radiation Therapy (IMRT), the main advantage of Volumetric Modulated Arc Therapy (VMAT) is a shortened delivery time, which leads to improved patient comfort and possibly smaller intra-fraction movements. This study aims at a treatment planner-independent comparison of radiotherapy treatment planning of IMRT and VMAT for head-and-neck cancer performed by several institutes and based on the same CT- and contouring data., info:eu-repo/semantics/published

HISTORY AND AIM: A 36-year-old woman (primigravida, nullipara) at 25 + 3 weeks of gestation and a 27-year-old (primigravida, nullipara) at 22 + 7 weeks of gestation presented with oligo-/anhydramnios at our department of obstetrics. Both patients suffered from diabetes type 1 and 2, respectively, complicated by diabetic nephropathy, renal hypertension and retinopathy. The first woman had received an AT1 receptor antagonist and a beta blocker, the other one an ACE inhibitor and a beta blocker. At initial clinical examination both patients were in a good general state of health. Respiration, pulse and blood pressure were within normal limits.Sonography showed oligy-/anhydramnion with enlarged echogenic kidneys of both fetuses. Having ruled out premature rupture of the membranes the reduced amount of amniotic fluid was interpreted as a consequence of the antihypertensive medication.The medication was changed to methyldopa which resulted in an adequate and moderate increase of amniotic fluid in both patients. At post partum examination renal failure was confirmed in both infants. The first infant, now a boy at the age of two years, still suffers from chronic renal failure, needing antihypertensive medication with an ACE blocker. Follow-up of the second baby has so far shown normal growth of the kidneys and normotensive blood pressure.When planning a pregnancy, a preexisting hypertension should be treated with either methyldopa (1st choice) or a beta blocker as a second choice (e. g. Metoprolol). In patients who are treated with ACE blockers or AT1 antagonists, medication should be changed as soon as the pregnancy is ascertained.

Idiopathic facial (Bell's) palsy occurring during pregnancy or post partum is a rare disease. Reports regarding incidence, prognosis and associated risk factors are still inconsistent.We performed a retrospective analysis of patients presenting with idiopathic facial palsy who had been treated in cooperation between obstetric and otorhinolaryngological departments (tertiary referral centers). The time of onset of paralysis, grading according to House and Brackman, treatment modalities and results were analyzed for the years 1999-2010.The incidence of Bell's palsy in pregnancy was 56 in 100,000 live births. Preeclampsia was reported in one case only. Therapy included prednisolone, methylprednisolone and/or pentoxifylline (up to 2005). All results were favorable (House-Brackman 1-2).The incidence of Bell's palsy in pregnancy within our cohort is not increased with regard to the international reports. Early treatment with corticosteroids in consultation with the treating obstetrician is indicated in both pregnant and post-partum patients to achieve optimal results.

A methodology for virtual EMC tests - comprising pre-processing, EM simulation, and post-processing - is presented. An aircraft application serves as an example for solving large multi-scale problems in CST STUDIO SUITTE™. The EM problem of the aircraft was solved for up to 12 billion Degrees of Freedom (DOF) on CST's computing cluster.

This paper provides an example of a reverberant environment application. A metallic box in different configurations has been simulated with CST STUDIO SUITE™ and the calculated results have been compared to measurements.

Fragestellung: Der vorzeitige Blasensprung (VBS) ist eine haufige Komplikation in der Schwangerschaft. Methode: Wir fuhrten eine retrospektive Studie an Frauen mit VBS >24 SSW mit vitaler Einlingsgraviditat durch. Alle Patientinnen wurden in standardisierten Weise von 10/2005 bis 01/2010 behandelt. Primares maternales Outcome war der Geburtsmodus; primares neonatales Outcome waren Mortalitat und Aufnahme auf die Neugeborenen- Intensivstation. Die Datenauswertung erfolgte mittels SAS 9.2. Ergebnisse: 1026 Frauen erfullten die Einschlusskriterien. Davon hatten 137 (13,4%) Kontraindikationen fur Wehen oder Spontangeburt. Von 355 eingeleiteten Frauen wurden 82% und von 534 Frauen mit spontanem Wehenbeginn 87% spontan entbunden (p=0,003). Wir konnten signifikante Risikofaktoren fur eine Sectio caesarea definieren (BMI, Latenzzeit zwischen VBS und Geburt, Erstgebarende, Chorioamnionitis, vorzeitige Plazentalosung), jedoch keiner dieser Faktoren war hoch pradiktiv. Die Sectiorate in der Einleitungsgruppe war hoher als bei den Frauen mit spontanem Wehenbeginn (18% vs. 13%; p=0,03). Keine Subgruppe hatte eine Sectiorate uber 27% und in den meisten Subgruppen war sie deutlich niedriger, sogar unter Einbeziehung mehrer Risikofaktoren wie Schwangerschaftsalter

The Crystal Barrel Detector has been in operation since October 1989. Results on the analysis of the annihilation of protonium at rest into three pseudoscalars is presented. The π 0 π 0 π 0 final state confirms the existence of ƒ 2 (1520)→π 0 π 0 . In the ηη system of the π 0 ηη final state an isoscalar J PC = 0 ++ resonance with a mass of 1560 MeV/c 2 and a width of 245 MeV/c 2 is observed. The identification with ƒ 0 (1590) is doubtful since the ηη' decay is not observed with the corresponding strength. Our analysis yields an upper limit for the relative branching ratio BR(ƒ 0 (1560)→ηη') BR(ƒ 0 (1560)→ηη) .

We discuss φ production in p p annihilation at rest from the Asterix and Crystal Barrel experiments and compare the branching ratios to similar final states without strangeness. The ωπ 0 φπ 0 production ratio is unexpectedly low. In the search for new states, the φπ0 mass spectrum shows no evidence for a resonance in the 1450 MeV/c2 mass range but the K☆K0π0 Dalitz plot shows interesting structure.

The occurrence of 4 bone fractures associated with birth by Caesarean section (CS) prompted us to examine the incidence and predisposing factors of bone injuries sustained during birth.The 4 cases with fractures were evaluated retrospectively and discussed in combination with a short review of the literature.With the increasing number of Caesarean sections the incidence of birth trauma has decreased. Nevertheless, when performing a CS there is still a risk of serious trauma to the neonate, including bone fractures. A Caesarean section for breech presentation constitutes a predisposition for femoral fractures. When diagnosed early and treated properly, the prognosis for these fractures is good without sequelae and one can expect a satisfactory clinical outcome for the child. We suggest that the possibility of this complication be mentioned when counselling the mother and getting informed consent.

Few papers have been published concerning the efficacy of community-based memory and dementia screening programs. This article examines the descriptive, clinical, and outcome characteristics of participants attending the Memory Screening Outreach Program (MSOP). The program provided free screenings of participants' short-term memory processes, neurocognitive complaints, and depressive and psychiatric symptomatology. Screening results were subsequently forwarded to participants and their designated healthcare providers (HCPs), and approximately 8 weeks later, participants who received follow-up recommendations were mailed a survey assessing screening-related outcomes. One thousand community-based persons aged 44 to 91 participated in the program at 16 screening sites. Results indicated that 44.3% of the MSOP participants received follow-up recommendations secondary to age-inappropriate memory impairments, depressive or psychiatric symptomatology, significant neurocognitive complaints, need for respite, or a combination thereof. Memory impairments and depressive or psychiatric symptomatology contributed, at least in part, to the recommendations of 24.0% and 30.9% of the sample, respectively. The prevalence of impaired Wechsler Memory Scale-III subtest performances ranged from 20.5% to 5.4%, and 28.7% of the participants exhibited elevated depression inventory scores. Of the participants who returned follow-up surveys, 49.5% visited their primary HCPs regarding their screening results; of the participants who had not followed up, 36.8% indicated plans to do so. Of the participants who followed up, contributing conditions and diagnoses were identified in 50.9%, medication or supplement recommendations or regimen changes were provided to 47.1%, and 17.0% were referred to healthcare specialists. Overall, the MSOP proved efficacious in identifying age-inappropriate memory impairments, notable depressive and psychiatric symptomatology, and significant neurocognitive complaints in an appreciable portion of a large, community-based, sample of middle-aged and older adults, which, in turn, contributed to the identification and treatment of a diversity of conditions at follow-up.

Next generation microwave devices require to be multifunctional for efficient, cost effective operation in light weight, low volume structures. A miniature tunable negative index metamaterial phase shifter and an ultra wideband phased array antenna have been designed using ferrite materials. Negative permeability ferrite material in combination with negative permittivity of plasmonic wires produces a tunable negative refractive index metamaterial (TNIM). The TNIM shows a phase shift with a figure of merit of nearly 180° / kOe o of applied magnetic field. Investigation of loss in X- and Q-band TNIM reveals that high frequency loss is more due to ferrite quality rather that the design of the TNIM. The miniature, 10:1 bandwidth current sheet phased array antenna is designed using magnetic ferrite as absorber.

This letter treats the finite-difference (FD) analysis of transmission lines including metallic loss. Computational costs are reduced drastically by incorporating correction factors into the FD equations in frequency domain. These factors are obtained from the quasistatic field behavior in the vicinity and within the metallic conductors. Thus, FD analysis can be performed using a coarse grid without loss of accuracy. The new method is verified for a typical monolithic microwave integrated circuit (MMIC) coplanar waveguide.

In a recent work, a frequency method based on linear programming was proposed to design fixed-order linearly parameterized controllers for stable linear multi-model SISO systems. The method is based on the shaping of the open-loop transfer functions in the Nyquist diagram under a set of linear constraints guaranteeing a lower bound on the crossover frequency and a linear stability margin. In this paper, this method is extended to guarantee quadratic stability. For this purpose, new linear constraints based on the phase difference of the characteristic polynomials of the closed-loop systems are added in the Nyquist diagram. A simulation example illustrates the effectiveness of the proposed approach.