Showing papers by "Drexel University published in 1986"
TL;DR: In this paper, the authors present an analysis of static stability in electric power systems based on a model consisting of the classical swing equation characterization for generators and constant admittance, PV bus and/or PQ bus load representations which leads to a semi-explicit (or constrained) system of differential equations.
Abstract: This paper presents an analysis of static stability in electric power systems. The study is based on a model consisting of the classical swing equation characterization for generators and constant admittance, PV bus and/or PQ bus load representations which, in general, leads to a semi-explicit (or constrained) system of differential equations. A precise definition of static stability is given and basic concepts of static bifurcation theory are used to show that this definition does include conventional notions of steady-state stability and voltage collapse, but it provides a basis for rigorous analysis. Static bifurcations of the load flow equations are analyzed using the Liapunov-Schmidt reduction and Taylor series expansion of the resulting reduced bifurcation equation. These procedures have been implemented using symbolic computation (in MASYMA). It is shown that static bifurcations of the load flow equations are associated with either divergence-type instability or loss of causality. Causality issues are found to be an important factor in understanding voltage collapse and play a central role in organizing global power system dynamics when loads other than constant admittance are present.
246 citations
TL;DR: Bacteriuria is common in the elderly and appears related to functional status, however, the turnover of infected and noninfected subjects was high, and surprisingly, persistence was not found in most.
185 citations
TL;DR: The method of Fourier descriptors (FD's) is presented for ECG data compression, resistant to noisy signals and is simple, requiring implementation of forward and inverse FFT.
Abstract: The method of Fourier descriptors (FD's) is presented for ECG data compression. The two-lead ECG data are segmented into QRS complexes and S-Q intervals, expressed as a complex sequence, and are Fourier transformed to obtain the FD's. A few lower order descriptors symmetrically situated with respect to the dc coefficient represent the data in the Fourier (compressed) domain. While compression ratios of 10:1 are feasible for the S-Q interval, the clinical information requirements limit this ratio to 3:1 for the QRS complex. With an overall compression ratio greater than 7, the quality of the reconstructed signal is well suited for morphological studies. The method is resistant to noisy signals and is simple, requiring implementation of forward and inverse FFT. The results of compression of ECG data obtained from more than 50 subjects with rhythm and morphological abnormalities are presented.
183 citations
TL;DR: In this article, authors in macroeconomics and Drosophila genetics were compared with independent judgments of inter-author similarity collected from 14 macroeconomists and 15 geneticists via a card-sorting technique.
Abstract: It is generally assumed that cocitation studies of specialties and fields yield valid representations of intellectual structure. To test the validity of this assumption, 5–6 years aggregate cocitation data for 41 authors in macroeconomics and 49 authors in Drosophila genetics (the genetics of fruit flies) were compared with independent judgments of inter-author similarity collected from 14 macroeconomists and 15 geneticists via a card-sorting technique. Non-metric multidimensional scaling (ALSCAL), and Johnson's “smallest diameter” clustering were used to create two-dimensional cluster-enhanced maps. Congruence between maps of cocitations and similarity judgments was assessed using canonical correlation of the spatial coordinates of points (authors) in each of a given pair of maps. Two significant canonical correlations were found in each test. The majority of clusters appeared in both cocitation and judgment maps. In macroeconomics, differences between maps and clusters represent the influence, on judgments, of individual authors' perceived policy orientation. In Drosophila genetics, major differences arise from a time lag in the incorporation of authors' recent work in the formal literature. Cocited author mapping is a valid representation of the intellectual structure in both macroeconomics and Drosophila genetics. © 1986 John Wiley & Sons, Inc.
176 citations
TL;DR: Bacteriuria without dysuria in the elderly appears to be asymptomatic, and no differences in symptoms were found when bacteriuric subjects were compared with themselves when they were nonbacteriURic.
166 citations
TL;DR: Findings indicate that more effective screening for psychosocial problems and referral to supportive services is needed.
Abstract: Six hundred twenty-nine persons with cancer (PWC) selected from the Pennsylvania Cancer Registry plus 397 nonprofessional (support) persons involved in their care (SP) were interviewed to determine their views of the unmet psychological, social and economic needs of PWC. The most frequently mentioned unmet need was for help in dealing with emotional problems (estimated at 25% of PWC state-wide). Other unmet need estimates ranged from 14% for financial to 4% for transportation, with 59% of PWC reporting at least one unmet need. Characteristics of PWC reporting unmet needs included being younger, a history of emotional problems, a chronic illness in addition to cancer, more advanced stage at diagnosis, and a diagnosis of lung cancer. The percent of PWC and CP reporting unmet needs were very similar. These findings indicate that more effective screening for psychosocial problems and referral to supportive services is needed.
160 citations
TL;DR: Peritoneal fluid was studied for the presence of endometrial tissue in a consecutive series of 67 women undergoing diagnostic laparoscopy, tubal lavage, and hysteroscopy and it is proposed that these processes may represent two distinct pathophysiologic disease processes.
139 citations
TL;DR: A classification scheme for D SS techniques is presented that provides a common theoretical framework for DSS research and structures and simplifies the process of designing application systems.
Abstract: The Decision Support Systems (DSS) field has grown rapidly, drawing technology from many disciplines and pursuing applications in a variety of domains but developing little underlying theoretical structure and poor linkage between research and practice. This article presents a classification scheme for DSS techniques that provides a common theoretical framework for DSS research and also structures and simplifies the process of designing application systems. The classification system is functional, grouping DSS techniques according to their ability to provide similar kinds of support (i.e., functions) to a human decision maker. It is also cognitively based, defining the kinds of support that decision makers need in terms of architectural features and procedural aspects of human cognition. The classification is expressed as a taxonomy, encompassing six primary classes of decision support techniques representing the six general kinds of cognitive support that human decision makers need. The six classes are process models, which assist in projecting the future course of complex processes; choice models, which support integration of decision criteria across aspects and/or alternatives; information control techniques, which help in storage, retrieval, organization, and integration of data and knowledge; analysis and reasoning techniques, which support application of problem-specific expert reasoning procedures; representation aids, which assist in expression and manipulation of a specific representation of a decision problem; and judgment amplification/refinement techniques, which help in quantification and debiasing of heuristic judgments. Additional distinctions are provided to distinguish the individual techniques in each of these primary categories. The taxonomy also has practical use as a design aid for decision support systems. The kinds of decision support needs represented by the taxonomy are general and can be used to guide the analysis and decomposition of a given decision prior to decision aid design. Specific needs for assistance can then be tied to specific computational techniques in the taxonomy. Methodological suggestions for using the taxonomy as a design aid are given.
131 citations
TL;DR: The non-basement membrane proteins studied often codistributed with type I collagen, between and apparently attached to fibers, suggesting that they may act as binding proteins, linking type I fibers and bundles, to themselves and to other structures.
Abstract: The human term placenta is used extensively as a source of extracellular matrix components. To elucidate the tissue distribution and interrelationships of seven of these components, monospecific antibodies directed against collagen types I, III, IV, V, VI, fibronectin, and laminin were reacted with human term placenta and studied by light and electron immunohistochemistry. Type I collagen was the basic structural unit of human term placenta, present as 30\2-35 nm, cross-banded fibers, often in the form of large fiber bundles. Type III collagen was present as thin 10\2-15 nm, beaded fibers often forming a meshwork which encased type I collagen fibers. Types V and VI collagen were present as 6\2-10 nm filaments, often closely associated with types I and III collagen. Type VI collagen also coated collagen fibers of all diameters, enhancing their periodicity, providing a staining pattern often similar to that observed with anti-fibronectin antibodies. Fibronectin was present in both maternal and fetal plasma and throughout the stroma of the chorionic villus, as both free filaments and coating collagen fibers. Basement membranes contained laminin and type IV collagen, but no fibronectin. In summary, the non-basement membrane proteins studied often codistributed with type I collagen, between and apparently attached to fibers, suggesting that they may act as binding proteins, linking type I fibers and bundles, to themselves and to other structures.
129 citations
TL;DR: In this paper, the effects of the gamma-aminobutyric acid (GABA) antagonist bicuculline (BCC) on hindlimb motor performance was examined in mature spinal cats with spinal cord transections made either on the day of birth or at approximately two weeks postpartum and in chronic adults with spinal transection made in adulthood.
Abstract: The effects of the gamma-aminobutyric acid (GABA) antagonist bicuculline (BCC) on hindlimb motor performance was examined in mature spinal cats with spinal cord transections made either on the day of birth or at approximately two weeks postpartum and in chronic adult cats with spinal transections made in adulthood. In those adult operates, whose pre-drug performance was poor compared to neonatal operates, treadmill locomotion and weight support were improved dramatically by BCC administration. In neonatal operates (examined as adults), BCC administration increased the force of extension to abnormal levels and this increase appeared to disrupt locomotion. Immunocytochemical localization of GABA's synthetic enzyme, glutamic acid decarboxylase (GAD) within the spinal cords of these animals revealed an abnormal distribution of GAD reaction product only in newborn operates. The behavioral results indicate that the full extent of recovery in adult operates is prevented by inhibitory influences and this may contribute to the comparatively superior performance of neonatal operates i.e., the infant lesion effect. The anatomical results suggest that one requirement for the normal development of some intrinsic spinal circuitry is transneuronal regulation mediated by the maturation of descending systems.
126 citations
TL;DR: The present study conclusively demonstrates that T cell response is decreased in the elderly, and suggests that there may be a selection process in which subjects who live to the age of 90 are those in whom the least decrease in immune response is demonstrated.
TL;DR: A mathematical model of a simple inverted double-pendulum locomotion system was developed and the stability of the nonlinear model was analysed.
Abstract: A mathematical model of a simple inverted double-pendulum locomotion system was developed. The stability of the nonlinear model was analysed. Periodic impact of the system with the ground plays a major role in the achievement of stable locomotion. Phase-plane portraits of the generalized coordinates and velocities were utilized to study the behaviour of the system.
TL;DR: The history of satellite missions and their measurements of the earth radiation budget from the beginning of the space age until the present time are reviewed in this article, emphasizing the early struggle to develop instrument systems to monitor reflected shortwave and emitted long-wave exitances from the earth, and the problems associated with the interpretation of these observations from space.
Abstract: The history of satellite missions and their measurements of the earth radiation budget from the beginning of the space age until the present time are reviewed. The survey emphasizes the early struggle to develop instrument systems to monitor reflected shortwave and emitted long-wave exitances from the earth, and the problems associated with the interpretation of these observations from space. In some instances, valuable data sets were developed from satellite measurements whose instruments were not specifically designed for earth radiation budget observations.
TL;DR: Children ranging in age from 3 years and 6 months to 12 years and 5 months and young adults sorted 23 pictures of a variety of edible and inedible items according to 13 different attributes to determine the degree to which the children understood adult motivations for acceptance and rejection of food.
TL;DR: It is demonstrated that antibodies raised against bacterial phospholipase C may be useful in purifying phospholIPase C from a human source.
TL;DR: It is postulate that reticular cells, normal and activated, have the following functions: to fabricate the locules of the filtration beds; to control the migration of free cells through these beds'; to trap free cells, including parasitized erythrocytes, by cell-surface adherence; to create a dynamic blood-spleen barrier; and to secrete antiplasmodial substances.
Abstract: By complex stromal responses, the spleen controls the course of nonlethal Plasmodium yoelii murine malaria. The course of disease may be divided into four phases. In the immediate postinfective phase, lasting several days, the filtration beds of the spleen are open. Parasitized and nonparasitized erythrocytes, many plasma cells, lymphocytes, and macrophages are sequestered from the blood; and most or all of the parasitized erythrocytes are phagocytized. In the following precrisis phase, approximately 1 week long, there is increasing parasitemia and anemia. The filtration beds of the spleen support large-scale erythropoiesis, lymphopoiesis, plasmacytopoiesis, and monocyte-to-macrophage differentiation. Reticular cells, the stromal cells which form the splenic filtration beds, become activated, showing signs of intense protein secretion and increased branching and mitosis. The locules of the filtration beds appear sealed off from the blood by branches of activated reticular cells. A blood-spleen barrier is thereby formed, protecting splenic hematopoiesis from the parasite. Factors are produced, moreover, which damage intraerythrocytic parasites, producing crisis forms. Crisis follows. It may occur over several days, presaged by the appearance of circulating crisis forms. The filtration beds are opened to the blood. Circulating crisis forms are trapped within the locules of the filtration beds and phagocytized while the stores of reticulocytes produced there in the precrisis period are released to the blood. The malaria, as a result, is no longer patent and the anemia is relieved. In the fourth or postcrisis phase, lasting many months, the normal structure of the spleen is approached. We postulate that reticular cells, normal and activated, have the following functions: to fabricate the locules of the filtration beds; to control the migration of free cells through these beds; to trap free cells, including parasitized erythrocytes, by cell-surface adherence; to open or close the filtration locules, creating a dynamic blood-spleen barrier; to control the circulation of the spleen--by contraction and alignment in normal spleens and by activation and closing of locules in enlarged spleens; to synthesize collagen III; to synthesize factors which influence marrow release of monocytes; and to secrete antiplasmodial substances.
TL;DR: The distribution of myosin heads on the surface of frog skeletal muscle thick filaments has been determined by computer processing of electron micrographs of isolated filaments stained with tannic acid and uranyl acetate, and a three-dimensional reconstruction cannot be produced from a single view.
TL;DR: It may be feasible to begin low-dose estrogen therapy to promote growth at an earlier age than would be conventionally used to induce pubertal development in girls with Turner syndrome, according to the data.
TL;DR: The observation of period-doubling transitions into chaos that are in good agreement with the predictions of the theory of one-dimensional maps are described and evidence for the appearance of generalized multistability is provided.
Abstract: This is a detailed experimental study of the dynamical behavior of a ${\mathrm{CO}}_{2}$ laser with modulated losses. We describe the observation of period-doubling transitions into chaos that are in good agreement with the predictions of the theory of one-dimensional maps and give examples of temporal evolutions, phase-space portraits, power spectra, and Poincar\'e sections. With the help of bifurcation diagrams we provide evidence for the appearance of generalized multistability. We also discuss the results of dimensionality tests that we have carried out on both our experimental data and corresponding numerical simulations based on the Maxwell-Bloch equations after the adiabatic elimination of the polarization. We conclude with an evaluation of the Kolmogorov entropy.
TL;DR: Data show that cell-CAM 120/80 is found on cells arranged into epithelial layers in the early embryo and extraembryonic tissues, but is not expressed in the dissociated cells differentiating from these epithelia, and appears to be developmentally regulated.
01 Jan 1986
TL;DR: In this article, a deterministic dynamical law is used to detect disordered behavior in biological control systems, where the system can undergo reversible transitions to and from chaotic dynamics in response to small changes in parameter values.
Abstract: Deterministic systems can display a form of highly irregular, quasirandom behavior called chaos. Even though the observed behavior is very complex, the systems which generate it can be very simple. Thus, in at least some instances, irregular biological systems may obey a simple, potentially discoverable, deterministic dynamical law. These systems can undergo reversible transitions to and from chaotic dynamics in response to small changes in parameter values. As a long term goal, this form of analysis may suggest more effective responses to disordered behavior in physiological control systems.
TL;DR: It is concluded that behavior therapy has the potential to make a number of vital contributions and that there is a social and professional mandate for behavior therapists to increase their involvement with this needy population of schizophrenia.
TL;DR: The present findings suggest that similar mechanisms may operate in certain T cell neoplasms, although the activating gene is not necessarily the same.
TL;DR: It is strongly suggested that failure to measure concurrent sleep parameters and screen for occult sleep disorders could result in the incorrect diagnosis of abnormal nocturnal penile tumescence.
TL;DR: The preparation and characterization of synthetic ferritin-like particles produced by precipitation of magnetite from a mixture of ferrous and ferric ions in the presence of dextran are described and a 400-fold enrichment for Legionella was obtained.
TL;DR: T theoretical and experimental evidence is presented for a new type of multimode instability in a homogeneously broadened ring-laser system and some of the predictions are verified with the help of a CO/sub 2/ laser whose observed bistable behavior is in good qualitative agreement with the theoretical predictions.
Abstract: We present theoretical and experimental evidence for a new type of multimode instability in a homogeneously broadened ring-laser system. The unstable behavior discussed in this paper is the result of multimode competition and can manifest itself either through self-pulsing or hysteretic behavior of the bistable type in the laser output intensity and operating frequency. We have verified some of our predictions with the help of a ${\mathrm{CO}}_{2}$ laser whose observed bistable behavior is in good qualitative agreement with the theoretical predictions.
TL;DR: The spread of carcinoma cells into plasma clot is markedly enhanced by endothelial channels, developed in the absence of blood flow, which may represent an important element in the preferential growth of the tumor along the vascular route.
Abstract: Bovine capillary endothelial cells (BCEC), cultured in suspension on a rotary shaker, formed aggregates ranging from 50 to 300 µm in diameter. In plasma clot these aggregates sprouted in multiple directions and gave rise to vascular channels. Aggregates of the squamous cell carcinoma line of rat bladder NBT-II-81, cultured in plasma clot, formed solid spheroids that grew slowly by expansion. When cultured together with BCEC, however, NBT-I I-81 infiltrated the plasma clot extensively. The tumor cells, after establishing contacts with the vascular channels, spread into the fibrin meshwork using the subendothelial space as their path of propagation. Endothelial cells that were separated from the surrounding matrix by invading tumor cells degenerated, leaving behind channels lined only by neoplastic epithelium. The adhesive properties of the subendothelial matrix were studied by seeding NBT-I I-81 cells on dishes coated with the extracellular matrix produced by BCEC. Tumor cells attached readily and in large numbers to dishes coated with the subendothelial matrix. In contrast they attached poorly to dishes coated with fibrin. We conclude that the spread of carcinoma cells into plasma clot is markedly enhanced by endothelial channels, developed in the absence of blood flow. The production of a highly adhesive extracellular matrix by the capillary endothelium during angiogenesis may represent an important element in the preferential growth of the tumor along the vascular route.
TL;DR: In this paper, the authors evaluated the toxicity response of chloroform in an anaerobic digestion setting with methylacetate enrichment cultures and found that the duration of exposure was directly related to the degree of residual inhibition.
TL;DR: The primary effect of the apolipoproteins in promoting cellular cholesterol efflux seems to be the solubilization of PC so that the PC is present in the extracellular medium as many small particles.