Showing papers by "Drexel University published in 1973"
TL;DR: In this article, a detailed design of a laminate specimen which can exhibit catastrophic delamination induced by interlaminar tension is presented, along with a preliminary failure hypothesis to characterize this mode of rupture and the associated experimental demonstration of the phenomena.
290 citations
TL;DR: In this paper, Darstellung, Eigenschaften, Substituenteneffekte und Donoreigenschalkte werden zusammenfassend behandelt.
226 citations
TL;DR: In this paper, the authors discussed the difficulty in the experimental determination of the strength tensor of boron-epoxy composites by off-axis tests and proposed a method to determine the tensor tensor strength.
Abstract: Difficulty in the experimental determination of the interaction com ponent of strength tensor of boron-epoxy composites by off axis tests is discussed. Although off axis data agree well with the pr...
143 citations
TL;DR: In this article, a method for finding the coefficients of an nth-order linear recursive digital filter, which gives the best least squares approximation to a desired pulse response over a finite interval, is presented.
Abstract: A method for finding the coefficients of an nth-order linear recursive digital filter, which gives the best least squares approximation to a desired pulse response over a finite interval, is presented. A relationship is derived between the approximating error corresponding to an optimal set of numerator coefficients and the error produced by an overdetermined set of linear equations, which is a function of the denominator coefficients only. This relation provides a computational algorithm for calculating the optimal coefficients by iteratively solving weighted sets of linear equations in terms of the denominator coefficients only. Both theoretical and numerical results are presented. Also, bounds are found on the interval in which the norm of the optimum error must lie.
133 citations
01 Apr 1973
TL;DR: In this paper, a mathematical model of localized necking and fracture is presented that permits evaluation of the effects of material characteristics and process parameters, and a fracture criterion involving total strains at failure is also proposed.
Abstract: Deformation behavior and fracture of three iron alloys during cold working conditions were studied systematically under a range of stress and strain states by means of the upset test. As described in a previous publication by the authors, an anomalous strain behavior and sub-surface void formation are observed prior to fracture at the bulge surface. This anomaly, in the form of a perturbation in the strain path, has features that are similar to the strain instability in biaxial stretching of sheet material. Based on these experimental observations, a mathematical model of localized necking and fracture is presented that permits evaluation of the effects of material characteristics and process parameters. A fracture criterion involving total strains at failure is also proposed. The criterion accurately fits experimental data obtained in this study as well as that presented by other investigators. Essential features of the fracture criterion can be derived from the mathematical model of instability and fracture.
107 citations
TL;DR: Results suggest that undissociated short-chain fatty acids produced by the colon flora may be a mechanism of intestinal resistance to colonization by P. aeruginosa.
Abstract: Heat-stable antibacterial activity in the following suspensions was demonstrated against Pseudomonas aeruginosa at pH 6.5, 6.0, and 5.5: (i) pooled colon contents of normal mice; (ii) an anaerobic, 48-h culture of normal mouse feces; and (iii) anaerobic, 48-h cultures of different bacteria from human colon flora (Escherichia coli, Bacteroides fragilis, Klebsiella pneumoniae, and Proteus mirabilis). The lower the pH of the medium, the greater was the antibacterial activity of these suspensions. The antibacterial activity of five fatty acids (propionic, butyric, isobutyric, acetic, and formic acids) was greater against P. aeruginosa than against three Enterobacteriaceae (E. coli, K. pneumoniae, and P. mirabilis) at all fatty acid concentrations (0.16 M to 0.005 M) and at the 3 pH values studied (5.5, 6.0, and 6.5). As the pH value increased, the antibacterial activity decreased. Antibacterial activity was greater at higher fatty acid concentrations, and at each pH value it was greatest for the fatty acids having high pK(a) values. Lactic acid, with the lowest pK(a), exhibited little or no antibacterial activity. Acetic and butyric acids, two of the three predominant volatile fatty acids determined by gas chromatography in the mouse colon contents and in the anaerobic culture of mouse feces, occurred in vivo in concentrations which inhibited growth of P. aeruginosa in vitro at the pH of the mouse cecum. These results suggest that undissociated short-chain fatty acids produced by the colon flora may be a mechanism of intestinal resistance to colonization by P. aeruginosa.
102 citations
102 citations
TL;DR: Polyribocytidylic acid, endotoxin, polycarboxylate plastics or polysaccharides, and other polyanions induce interferon production and enhance antibody production, cell-mediated immunity, and reticuloendothelial activity.
Abstract: POLYRIBOINOSINIC acid: polyribocytidylic acid [poly (rI)·poly (rC)], endotoxin, polycarboxylate plastics or polysaccharides, and other polyanions induce interferon production (see reviews ref. 1 and 2). They also enhance antibody production3,4, cell-mediated immunity5, and reticuloendothelial activity4,6. It is not yet clear whether or not any of these latter effects are mediated through the action of interferon.
101 citations
100 citations
TL;DR: The urinary concentration and percentage of the dose excreted in the urine within the first 4 or 6 hr after administration of cefazolin decreased significantly in patients with compromised renal function, but the urinary concentration was adequate, even in Patients with Ccr of 12-17 ml/min, to treat urinary-tract infection caused by cefzolin-sensitive pathogens.
Abstract: Levels of cefazolin in serum and urine were determined after a 500-mg parenteral dose in patients with normal and various degrees of compromised renal function. The mean peak concentration in serum, corrected for body weight, did not differ significantly among patients with different endogenous creatinine clearances (Ce). The urinary concentration and percentage of the dose excreted in the urine within the first 4 or 6 hr after administration of cefazolin decreased significantly in patients with compromised renal function, but the urinary concentration of cefazolin was adequate, even in patients with Ccr of 12-17 ml/min, to treat urinary-tract infection caused by cefazolin-sensitive pathogens. The half-life (TY) of cefazolin in serum increased significantly in patients with Cer < 26 ml/min.
TL;DR: In this article, an approach to control system design based on optimal linear regulator theory and which recognizes the limitation of an imperfect model has been developed, which produces "integral-type" action which guarantees zero steady-state errors.
Abstract: The demand for improved dynamic response of fossil-fired power plants has motivated a comprehensive program of control system design and analysis. Previous papers have reported the development of a nonlinear mathematical model of a drum-type, twin furnace, reheat boiler-turbine-generator (RBTG) system which is suitable for control system analysis and has been extensively verified by field test. On the basis of this model, local stability, observability, and controllability have been examined over the load range, using linearization and modal analysis. An approach to control system design has been developed based on optimal linear regulator theory and which recognizes the limitation of an imperfect model. This approach produces "integral-type" action which guarantees zero steady-state errors. The controller does not require complete state feedback. Improved performance has been demonstrated by comparison with the existing control structure through simulation using the nonlinear process model.
TL;DR: A new parenterally administered semisynthetic cephalosporin with a broad spectrum of antibacterial activity, cefazolin, has been shown to be effective in adults and children against infections caused by a variety of gram-positive and gramnegative bacteria.
Abstract: A new parenterally administered semisynthetic cephalosporin with a broad spectrum of antibacterial activity, cefazolin, has been shown to be effective in adults and children against infections caused by a variety of gram-positive and gramnegative bacteria. Levels of cefazolin in serum are two to three times higher than those following equal doses of cephaloridine or cephalothin. Cefazolin is generally well.tolerated when administered by the im or iv route and, thus far, has proved to be relatively free from significant side effects.
TL;DR: Analysis of urea-disrupted coxsackievirus B3 substructures provides the basis for a T = 3 structural model of the picornaviruses, with 12 pentamers (VP2 and VP4) and 20 hexamers(VP1 and VP3) per virion.
TL;DR: The value of combining the Hp-D fiuorascence procedure and colposcopic-colpophotographic examination may be valudble for outlining the extent of minimal lesions of the cervix and vagina.
TL;DR: Lowe and Phillips* reported that chelating agents influence the reaction rate by both their nature and their concentration relative to the metal ion, believed to have a common mode of operation which may prove similar to that of enzyme catalysts.
Abstract: A number of kinetic studies of metalloporphyrin formation have been published and the early work has been reviewed by Phillips1s2, Wi l l iam~,~ andFalkandPerr i~~.~ A more recent comprehensive review of the general chemistry of metalloporphyrins has been given by Hambright.5 Since the solvent systems, metal salts, porphyrins, and other conditions have varied greatly in these published kinetic studies, a quantitative comparison is difficult. It is known that the order of thermodynamic stability for several metalloporphyrins in aqueous solution does not correspond to their rates of formation.' The rate of incorporation is fastest for Cu(II), followed by Zn(II), Co(II), Fe(II), and Ni(II), while the order of thermodynamic stability is Ni(II), Co(II), Cu(II), Fe(II), and Zn(I1). Several factors influence the nature of the reaction. The rate of metal incorporation is decreased by an increase in electron withdrawing character of 8-substituted groups, favoring a displacement over a dissociation type of reaction (described below).' The nature of the solvent influences the reaction rate, probably by changing the nature of the metal species and the state of aggregation of the porphyrin. A solvent which works well for synthesis may not give interpretable kinetic results.' Detergents, which have been used to solubilize porphyrins, affect the rate. Anionic detergents increase the rate more than cationic or nonionic detergents. Lowe and Phillips' have postulated the occurrence in aqueous detergent solutions of a doughnut-like structure around the porphyrin. The pyrrole rings are held in the hydrocarbon portion, while the outer, polar part of the detergent molecule keeps the porphyrin nitrogen atoms in contact with the aqueous phase. Ions would be attracted to or repelled by the nitrogen atoms depending on the charges of the detergent and the metal ion. Lowe and Phillips* reported that chelating agents influence the reaction rate by both their nature and their concentration relative to the metal ion. The most active chelating agents belong to a class of antifungal and antibacterial agents believed to have a common mode of operation which may prove similar to that of enzyme catalysts. Nearly every study of metal ion incorporation has led to a different detailed mechanism. Broadly speaking, however, they can be classified as one of two types, dissociation or displacement. In the dissociation mechanism protons are removed
TL;DR: Neurogenic atrophy is described in biopsy specimens of laryngeal muscles in seven large breed dogs, a consistent finding upon histological examination of the resected tissues.
Abstract: Neurogenic atrophy is described in biopsy specimens of laryngeal muscles in seven large breed dogs. Signs shown by the dogs were similar but varied in degree of severity; most had a rough bark and stridorous respiration of several months' duration which progressed to obstructive dyspnoea and, in some cases, to glottic obstruction with collaspe on exertion. At laryngoscopy, there were signs of both chronic and acute laryngitis; vocal cords were oedematous and almost midline; they did not abduct with vigorous inspiratory efforts.
A tracheotomy was performed in six dogs. Laryngeal cup forceps were used for unilateral excision of the vocal cord and ventricular band, the obstructing portion of the arytenoid cartilage and the aryepiglottic fold. Neurogenic atrophy of laryngeal muscles was a consistent finding upon histological examination of the resected tissues.
Resume. On decrit, chez sept chiens de grosse race, une atrophie neurogene dans des specimens de biopsie de muscles laryngiens. Les signes que montraient les chiens etaient semblables, mais leur degre de severite variait. La plupart avaient un aboiement rauque et une respiration striduleuse d'une duree de plusieurs mois progressant jusqu'a une dyspnee obstructive et dans certains cas jusqu'a une obstruction glottique avec collapsus sous l'effort. a la laryngoscopie, il y avait des signes et de laryngite chronique et de laryngite aigue; les cordes vocales etaient oedemateuses et presque a ligne mediane; elles ne s'ecartaient pas sous de vigoureux efforts inspiratoires.
Six chiens ont subi une tracheotomie. On a utilise des forceps laryngiens a pinces pour excision unilaterale de la corde vocale et de la bande ventriculaire, de la partie obstruante du cartilage arytenoid et du repli arytenoepiglottique. Sur examen histologique des tissus reseques, on a trouve, de facon consistante, une atrophie neurogenique des muscles laryngiens.
Zusammenfassung. Nervurspriingliche Atrophie wurde in Biopsie Proben von Kehlkopfmuskeln in sieben grossen Zuchthunden beschrieben. Symptome die die Hunde zeigten waren ahnlich aber verschieden in der Schwere des Leidens; die meisten hatten ein rauhes Bellen und kreischende Respiration iiber mehrere Monate hin, welche sich zur obstruensen Dyspnoe entwickelte und in einigen Fallen zu Stimmritzen Verschluss mit Kollaps bei Anstrengung. Bei Laryngoscopie fand man Anzeichen von beiden chronischer wie akuter Laryngitis; Stimmbander waren odematos und fast Mittellinie, sie abduzierten nicht bei heftigen inspiratorischen Anstrengungen.
Eine Tracheotomie wurde in sechs Hunden ausgefuhrt. Kehlkopfschalenzangen gebrauchte man zur einseitigen Exzision des Stimmbandes und des ventrikularen Bandes, der obstruensen Menge des Giessbeckenknorpels und der Giessbecken-Kehldeckelfalte. Nervursprunglich Atrophie war ein ubereinstimmender Befund bei histologischer Untersuchung des resezierten Gewebes.
TL;DR: In this article, a 1:6 complex with pyrazine (pyzNO) with 3d metal perchlorates was synthesized by allowing ligand and hydrated metal salt to interact in ethanoltriethyl orthoformate.
TL;DR: In this paper, the authors examined the impact of size, technology, dependence, market condition, and organizational concern toward task environmental factors on decentralization, and found that the degree of environmental concern depends on the size of the decentralization system.
Abstract: This study examines the impact of size, technology, dependence, market condition, and organizational concern toward task environmental factors on decentralization. The results show that the degree ...
TL;DR: Comparisons of antiviral and these non-antiviral activity titres of interferon preparations have usually shown a strict correlation of antiv viral and non-anti-viral activities regardless of the degree of purification, suggesting that activities are attributable tointerferon itself.
Abstract: EVIDENCE has accumulated that interferons exert effects on cells other than causing them to become resistant to viruses. In addition to inducing antiviral and antimicrobial1, activities, interferon preparations of various degrees of purity have been shown to inhibit cell growth2–11, facilitate interferon induction by ‘priming’12–15, suppress interferon production by ‘blocking’14, 16, 17, enhance phagocytic activity18, 19, enhance lysis of target cells by lymphocytes20 and enhance the susceptibility of cells to the toxicity of doukie-stranded RNAs (dsRNA)21–23. Comparisons of antiviral and these non-antiviral activity titres of interferon preparations have usually shown a strict correlation of antiviral and non-anti-viral activities regardless of the degree of purification8, 13, 14, 17, 21, suggesting that activities are attributable to interferon itself.