Tailored metal matrix composites for high-temperature performance

A multi-objective tailoring methodology is presented to maximize stiffness and load carrying capacity of a metal matrix cross-ply laminated at elevated temperatures. The fabrication process and fiber volume ratio are used as the design variables. A unique feature is the concurrent effects from fabrication, residual stresses, material nonlinearity, and thermo-mechanical loading on the laminate properties at the post-fabrication phase. For a (0/90)(sub s) graphite/copper laminate, strong coupling was observed between the fabrication process, laminate characteristics, and thermo-mechanical loading. The multi-objective tailoring was found to be more effective than single objective tailoring. Results indicate the potential to increase laminate stiffness and load carrying capacity by controlling the critical parameters of the fabrication process and the laminate

Metal Matrix Laminate Tailoring (MMLT) code: User's manual

The User's Manual for the Metal Matrix Laminate Tailoring (MMLT) program is presented. The code is capable of tailoring the fabrication process, constituent characteristics, and laminate parameters (individually or concurrently) for a wide variety of metal matrix composite (MMC) materials, to improve the performance and identify trends or behavior of MMC's under different thermo-mechanical loading conditions. This document is meant to serve as a guide in the use of the MMLT code. Detailed explanations of the composite mechanics and tailoring analysis are beyond the scope of this document, and may be found in the references. MMLT was developed by the Structural Mechanics Branch at NASA Lewis Research Center (LeRC)

Primary Xanthoma of the Mandible: Report of a Rare Case

Xanthoma is a lesion most commonly seen in soft tissues such as the skin, subcutis, or tendon sheaths. Xanthoma formation is often associated with primary or secondary hyperlipidemia. Primary bone xanthomas are extremely rare benign bone lesions not associated with hyperlipidemia, histopathologically characterized by histiocytes, abundant lipid containing macrophages (foam cells), and multinucleated giant cells. Cholesterol clefts can be found in the medullary bone. Less than ten cases of xanthoma in the mandible have been reported. We present a rare primary intrabony xanthoma in a normolipidemic patient

COMPARISON OF EXTRADURAL ADMINISTRATION OF SUFENTANIL, MORPHINE AND SUFENTANIL-MORPHINE COMBINATION AFTER CAESAREAN SECTION

We have studied postoperative analgesia and unwanted side effects of a single dose of a mixture of morphine and sufentanil administered extradurally with the effects produced by extradural injection of each opioid alone in 64 patients after Caesarean delivery. The patients were allocated randomly to receive morphine 4 mg (n = 21), sufentanil 50 μg (n = 22) or morphine 2 mg with sufentanil 25 μg (n = 21) via an extradural catheter in a double-blind design. Intensity of pain was measured using a linear visual analogue scale. Compared with the effect produced by morphine alone, the morphine-sufentanil combination produced more rapid onset of pain relief (19 (SD 5) min vs 79 (23) min for a 75% reduction of pain; P < 0.01), whereas the duration and quality of analgesia assessed during 12 h was similar for these two groups. In contrast, patients receiving sufentanil alone required significantly more supplementary analgesia 4 h after administration than with morphine alone or morphine combined with sufentanil. There were no significant changes in cardiorespiratory variables in any group. Side effects consisted mainly of pruritus and nausea and did not differ between groups, with the exception of early and transient dizziness which was observed only in patients given sufentanil either alone or in combination with morphine. We conclude that a single extradural injection of morphine and sufentanil combines the short onset time produced by sufentanil and the long duration of analgesia attributable to morphine, thus providing excellent and prolonged analgesia after Caesarean deliver

I.V. LABETALOL IN THE TREATMENT OF HYPERTENSION FOLLOWING CORONARY-ARTERY SURGERY

SUMMARY The cardiovascular effects of incremental fixed i.v. doses of labetalol were evaluated in 10 normovolaemic sedated patients presenting with hypertension and tachycardia in the early period after myocardial revas-cularizaoon. A first dose of 20 mg was sufficient to provoke a (P < 0.01) mean decrease in systolic (−9.3%), diastolic (−8.2%) and mean arterial (−7.9%) pressure (AP) and in the rate-pressure product (RPP) (−13.1%). The mean heart rate (HR) did not change significantly, but a linear correlation could be established between the change at 2 min and the value before injection (r = 0.73). A second dose of labetalol 40 mg given S min later did not decrease AP further, but a significant decrease in HR was noted. A marked difference in the individual response among patients was found as the range of effective total doses per kg body weight was 0.6-4.1 mg kg−1 (mean 2.2). Apart from one patient, no patient needed vagolytic or sympathomimetic drugs to oppose the alpha or beta actions of labetalol during the 24-h follow-up perio

Turbomachinery Forced Response Prediction System (FREPS): User's Manual

The turbomachinery forced response prediction system (FREPS), version 1.2, is capable of predicting the aeroelastic behavior of axial-flow turbomachinery blades. This document is meant to serve as a guide in the use of the FREPS code with specific emphasis on its use at NASA Lewis Research Center (LeRC). A detailed explanation of the aeroelastic analysis and its development is beyond the scope of this document, and may be found in the references. FREPS has been developed by the NASA LeRC Structural Dynamics Branch. The manual is divided into three major parts: an introduction, the preparation of input, and the procedure to execute FREPS. Part 1 includes a brief background on the necessity of FREPS, a description of the FREPS system, the steps needed to be taken before FREPS is executed, an example input file with instructions, presentation of the geometric conventions used, and the input/output files employed and produced by FREPS. Part 2 contains a detailed description of the command names needed to create the primary input file that is required to execute the FREPS code. Also, Part 2 has an example data file to aid the user in creating their own input files. Part 3 explains the procedures required to execute the FREPS code on the Cray Y-MP, a computer system available at the NASA LeRC

Current status of cardiac MRI in small animals

Cardiac magnetic resonance imaging (MRI) on small animals is possible but remains challenging and not well standardized. This publication aims to provide an overview of the current techniques, applications and challenges of cardiac MRI in small animals for researchers interested in moving into this field. Solutions have been developed to obtain a reliable cardiac trigger in both the rat and the mouse. Techniques to measure ventricular function and mass have been well validated and are used by several research groups. More advanced techniques like perfusion imaging, delayed enhancement or tag imaging are emerging. Regarding cardiac applications, not only coronary ischemic disease but several other pathologies or conditions including cardiopathies in transgenic animals have already benefited from these new developments. Therefore, cardiac MRI has a bright future for research in small animal

Lifetime Effects in Color Superconductivity at Weak Coupling

Present computations of the gap of color superconductivity in weak coupling assume that the quarks which participate in the condensation process are infinitely long-lived. However, the quasiparticles in a plasma are characterized by having a finite lifetime. In this article we take into account this fact to evaluate its effect in the computation of the color gap. By first considering the Schwinger-Dyson equations in weak coupling, when one-loop self-energy corrections are included, a general gap equation is written in terms of the spectral densities of the quasiparticles. To evaluate lifetime effects, we then model the spectral density by a Lorentzian function. We argue that the decay of the quasiparticles limits their efficiency to condense. The value of the gap at the Fermi surface is then reduced. To leading order, these lifetime effects can be taken into account by replacing the coupling constant of the gap equation by a reduced effective one.Comment: 16 pages, 2 figures; explanations on the role of the Meissner effect added; 2 references added; accepted for publication in PR