Pregnancy in porphyria and its complications: a case report

As with many rare diseases, little is known about the porphyrias and reproduction. Knowledge pertaining to complications in pregnancy in a patient with porphyria is even more scant. The information which we have is from attending on individual cases. The following case report demonstrates a rare case of porphyria cutanea tarda in a 30 year old female patient, diagnosed around pubertal age, who presented to the Emergency department as a case of severe anemia who had delivered a still born baby the same day. Still births along with spontaneous abortions, preeclampsia and low birth weights are few of the known complications of pregnancy in patients with porphyria

Computational simulation of matrix micro-slip bands in SiC/Ti-15 composite

Computational simulation procedures are used to identify the key deformation mechanisms for (0)(sub 8) and (90)(sub 8) SiC/Ti-15 metal matrix composites. The computational simulation procedures employed consist of a three-dimensional finite-element analysis and a micromechanics based computer code METCAN. The interphase properties used in the analysis have been calibrated using the METCAN computer code with the (90)(sub 8) experimental stress-strain curve. Results of simulation show that although shear stresses are sufficiently high to cause the formation of some slip bands in the matrix concentrated mostly near the fibers, the nonlinearity in the composite stress-strain curve in the case of (90)(sub 8) composite is dominated by interfacial damage, such as microcracks and debonding rather than microplasticity. The stress-strain curve for (0)(sub 8) composite is largely controlled by the fibers and shows only slight nonlinearity at higher strain levels that could be the result of matrix microplasticity

Bends in Non-Radiative Dielectric Guide

Curved bends in NRD waveguides have been developed. Measured insertion losses of 90º and 180º bends in an NRD guide are reported. Both the bends have insertion losses very near a reference straight guide in the frequency range from 33.5–36.5 GHZ

Scatter in Carbon/Silicon Carbide (C/SiC) Composites Quantified

Carbon-fiber-reinforced silicon carbide matrix (C/SiC) composites processed by chemical vapor infiltration are candidate materials for aerospace thermal structures. Carbon fibers can retain properties at very high temperatures, but they are known to have poor oxidation resistance in adverse, high-temperature environments. Nevertheless, the combination of CVI-SiC matrix with higher stiffness and oxidation resistance, the interfacial coating, and additional surface-seal coating provides the necessary protection to the carbon fibers, and makes the material viable for high-temperature space applications operating under harsh environments. Furthermore, C/SiC composites, like other ceramic matrix composites (CMCs), exhibit graceful non-catastrophic failure because of various inherent energy dissipating mechanisms. The material exhibits nonlinearity in deformation even at very low stress levels. This is the result of the severe matrix microcracking present in the as processed composite because of large differences between the coefficients of thermal expansion of the fiber and the matrix. Utilization of these advanced composites in next generation space vehicles will require innovative structural configurations, updated materials, and refined analyses. Structural safety issues for these vehicles are in direct competition with performance and cost. One would have to quantify the uncertainties associated with the design using formal probabilistic methods. Specifically four fundamental aspects on which analyses are based-- (1) loading conditions, (2) material behavior, (3) geometrical configurations, and (4) structural connections between the composite components and baseline structure--are stochastic in nature. A direct way to formally account for uncertainties is to develop probabilistic structural analysis methods where all participating variables are described by appropriate probability density functions. The present work, however, focuses on analyzing the stochastic material behavior of these advanced composites using formal probabilistic analysis methods. Often, some of the desirable property characteristics that allow composites to offer advantages over conventional structural materials (like tailoring of composite properties) and the complexity are in fact responsible for their greater statistical variability and the requirements for more characterization tests. Composite properties are anisotropic as well, having different properties in different directions. This means that characterization of a property such as stiffness--which will vary greatly depending on the orientation of the fiber relative to the direction of the testing--must be repeated for several different directions and loading conditions. The fabrication process for composites also introduces statistical variations in properties and geometry. A composite part is produced in a number of steps, each of which introduces statistical variability. The matrix is usually produced from a combination of raw materials; and the fiber, which has its own set of properties, is often coated or surface treated, introducing yet another source of variability

Probabilistic Modeling of High-Temperature Material Properties of a 5-Harness 0/90 Sylramic Fiber/ CVI-SiC/ MI-SiC Woven Composite

An integrated probabilistic approach has been developed to assess composites for high temperature applications. This approach was used to determine thermal and mechanical properties and their probabilistic distributions of a 5-harness 0/90 Sylramic fiber/CVI-SiC/Mi-SiC woven Ceramic Matrix Composite (CMC) at high temperatures. The purpose of developing this approach was to generate quantitative probabilistic information on this CMC to help complete the evaluation for its potential application for HSCT combustor liner. This approach quantified the influences of uncertainties inherent in constituent properties called primitive variables on selected key response variables of the CMC at 2200 F. The quantitative information is presented in the form of Cumulative Density Functions (CDFs). Probability Density Functions (PDFS) and primitive variable sensitivities on response. Results indicate that the scatters in response variables were reduced by 30-50% when the uncertainties in the primitive variables, which showed the most influence, were reduced by 50%

A hospital based retrospective study of thyroid disorders on obstetric and perinatal outcomes

Background: The study was undertaken in pregnant women to understand and analyze the obstetric and foetal outcomes of thyroid disorders.Methods: TSH estimation was used as universal screening in their first visit to our hospital. Those patients with abnormal TSH values, i.e. above 2.5 mIU/ml in first trimester and above 3 mIU/ml in second and third trimesters were evaluated for free T3, free T4 and TPO Abs. They were treated accordingly and dosage adjustments made and the tests repeated once in 4-6 weeks. They were followed throughout pregnancy and delivery.Results: Total no of pregnant women screened were 904 over a period of 1 year from 15 March 2019 to 14 March 2020, of which 115 had abnormal thyroid functions, thereby the prevalence of thyroid disorders being 12.72%. Of the 115 patients with thyroid disorders, 112 were hypothyroid and 3 were hyperthyroid. Among the 112 hypothyroid cases, 48 were known cases and 64 were new cases. The total cases of subclinical hypothyroidism were 88, prevalence being 9.73% and overt cases were 24, prevalence being 2.65%; 3 cases were overt hyperthyroid, prevalence being 0.33%. 66% of subclinical hypothyroidism were TPO positive and 34% of overt hypothyroidism were TPO positive (p<0.05). Out of 115 abnormal thyroid function patients, 92 patients delivered in our hospital. There were 15 abortions, 13 spontaneous and 2 terminations of pregnancies; 7 patients have delivered outside and 1 patient lost follow up.Conclusions: The prevalence of thyroid disorders during pregnancy was significantly more in our study, hypothyroidism being the commonest. Significant numbers of cases were newly diagnosed on universal screening. The commonest disorder was subclinical hypothyroidism. Adverse maternal and foetal outcomes were almost similar in both subclinical and overt hypothyroidism. The common adverse outcomes noted were abortions, pre-eclampsia, gestational diabetes mellitus, preterm births and increased rates of caesarean sections. The adverse outcomes were significantly more in autoimmune antibody positive patients

Telescoping Composite Mechanics for Composite Behavior Simulation

SUMMARY: Telescoping composite mechanics are described and implemented in terms of recursive laminate theory. The initial elemental scale is defined where simple equations are derived. Subsequently these mechanics are applied to homogeneous composites, composite structural components and hybrid composites. Results from those applications are presented in terms of tables/figures to illustrate the versatility and generality of telescoping composite mechanics. Comparisons with methods such as approximate, single cell, and 2-D and 3-D finite element demonstrate the predictive accuracy and computational effectiveness of composite telescoping mechanics