158 research outputs found
Determination of failure limits for sterilizable solid rocket motor
A structural evaluation to establish probable failure limits and a series of environmental tests involving temperature cycling, sustained acceleration, and vibration were conducted on an 18-inch diameter solid rocket motor. Despite the fact that thermal, acceleration and vibration loads representing a severe overtest of conventional environmental requirements were imposed on the sterilizable motor, no structural failure of the grain or flexible support system was detected. The following significant conclusions are considered justified. It is concluded that: (1) the flexible grain retention system, which permitted heat sterilization at 275 F on the test motor, can readily be adopted to meet the environmental requirements of an operational motor design, and (2) if further substantiation of structural integrity is desired, the motor used is considered acceptable for static firing
Demonstration of a sterilizable solid rocket motor system
A solid propellant rocket motor containing 60.9 Kg (134-lb) of propellant was successfully static fired after being subjected to eight heat sterilization cycles (three 54-hour cycles plus five 40-hour cycles) at 125 C (257 F). The test motor, a modified SVM-3 chamber, incorporated a flexible grain retention system of EPR rubber to relieve thermal shrinkage stresses. The propellant used in the motor was ANB-3438, and 84 wt% solids system (18 wt% aluminum) containing 66 wt% stabilized ammonium perchlorate oxidizer and a saturated hydroxylterminated polybutadiene binder. Bonding of the propellant to the EPR insulation (GenGard V-4030) was provided by the use of SD-886, an epoxy urethane restriction
Intersection Numbers in Quantum Mechanics and Field Theory
By elaborating on the recent progress made in the area of Feynman integrals,
we apply the intersection theory for twisted de Rham cohomologies to simple
integrals involving orthogonal polynomials, matrix elements of operators in
Quantum Mechanics and Green's functions in Field Theory, showing that the
algebraic identities they obey are related to the decomposition of twisted
cocycles within cohomology groups, and which, therefore, can be derived by
means of intersection numbers. Our investigation suggests an algebraic approach
generically applicable to the study of higher-order moments of probability
distributions, where the dimension of the cohomology groups corresponds to the
number of independent moments; the intersection numbers for twisted cocycles
can be used to derive linear and quadratic relations among them. Our study
offers additional evidence of the intertwinement between physics, geometry, and
statistics
Twistor-Inspired Construction of Electroweak Vector Boson Currents
We present an extension of the twistor-motivated MHV vertices and
accompanying rules presented by Cachazo, Svrvcek and Witten to the construction
of vector-boson currents coupling to an arbitrary source. In particular, we
give rules for constructing off-shell vector-boson currents with one fermion
pair and n gluons of arbitrary helicity. These currents may be employed
directly in the computation of electroweak amplitudes. The rules yield
expressions in agreement with previously-obtained results for Z,W,\gamma^* -->
qbar q + n gluons (analytically up to n=3, beyond via the Berends--Giele
recursion relations). We also confirm that the contribution to a seven-point
amplitude containing the non-abelian triple vector-boson coupling obtained
using the next-to-MHV currents matches the previous result in the literature.Comment: 22 pages, 4 figures, v2 minor corrections and added commentary on
multiple vector boson
Characteristics and outcome of influenza-Associated encephalopathy/encephalitis among children in a tertiary pediatric hospital in Italy, 2017-2019
Some triviality results for quasi-Einstein manifolds and Einstein warped products
In this paper we prove a number of triviality results for Einstein warped
products and quasi-Einstein manifolds using different techniques and under
assumptions of various nature. In particular we obtain and exploit gradient
estimates for solutions of weighted Poisson-type equations and adaptations to
the weighted setting of some Liouville-type theorems.Comment: 15 pages, fixed minor mistakes in Section
LMWH in the prevention of preeclampsia and fetal growth restriction in women without thrombophilia. A systematic review and meta-analysis.
SummaryPlacental mediated pregnancy complications such as preeclampsia and fetal growth restriction (FGR) are common, serious, and associated with increased morbidity and mortality. We conducted a systematic review and meta-analysis to determine the effect of treatment with low-molecular-weight heparins (LMWHs) for secondary prevention of these complications in non thrombophilic women. We searched the electronic databases PubMed, Scopus, and Cochrane Library for randomised controlled trials addressing this question. Five studies including 403 patients met the inclusion criteria, 68 developed preeclampsia and 118 FGR. The studies were very heterogeneous in terms of inclusion criteria, LMWH preparation, and dosage. Meta-analyses were performed using random-effect models. The overall use of LMWHs was associated with a risk reduction for preeclampsia (Relative risk (RR) 0.366; 95 % confidence interval (CI), 0.219–0.614) and FGR (RR 0.409; 95 % CI, 0.195–0.932) vs. no treatment. From the data available for analysis it appears that the use of Dalteparin is associated with a risk reduction for preeclampsia (p=0.002) and FGR (p<0.001); while Enoxaparin is associated with risk reduction for preeclampsia (p=0.013) but not for FGR (p=0.3). In spite of the small number of studies addressing the research question, and the high variability among them, our meta-analysis found a modest beneficial effect of LMWH for secondary prevention of preeclampsia and FGR. Further studies are needed to address these questions before a definite conclusion can be reached.Supplementary Material to this article is available online at www.thrombosis-online.com.</jats:p
Fast recovery of cardiac function in PIMS-TS patients early using intravenous anti-IL-1 treatment
To , or not to : Recent developments and comparisons of regularization schemes
We give an introduction to several regularization schemes that deal with
ultraviolet and infrared singularities appearing in higher-order computations
in quantum field theories. Comparing the computation of simple quantities in
the various schemes, we point out similarities and differences between them.Comment: 61 pages, 12 figures; version sent to EPJC, references update
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