Showing papers by "University of Pennsylvania published in 1972"
TL;DR: In this paper, an analysis of the individual taxpayer's decision on whether and to what extent to avoid taxes by deliberate underreporting is presented, based on a simple static model where this decision is the only one with which the individual is concerned, so that we ignore the interrelationships that probably exist with other types of economic choices.
4,106 citations
TL;DR: To help identify the depressed patient, the physician can use a simple 13 item questionnaire that the patient can complete in about five minutes that can indicate probable severity.
Abstract: Depression assumes many masks in general medical practice Thus, diagnosis is often difficult and may be missed To help identify the depressed patient, the physician can use a simple 13 item questionnaire that the patient can complete in about five minutes Although the physician may have to probe further for a more precise evaluation of the level of depression, the questionnaire can indicate probable severity
1,802 citations
TL;DR: The cytochrome c peroxidase assay is suitable for use with subcellular fractions from tissue homogenates as well as with pure enzyme systems to measure H(2)O( 2) generation and can be made on the basis of the rates with the isolated fractions under physiological conditions.
Abstract: 1. The enzyme–substrate complex of yeast cytochrome c peroxidase is used as a sensitive, specific and accurate spectrophotometric H 2 O 2 indicator. 2. The cytochrome c peroxidase assay is suitable for use with subcellular fractions from tissue homogenates as well as with pure enzyme systems to measure H 2 O 2 generation. 3. Mitochondrial substrates entering the respiratory chain on the substrate side of the antimycin A-sensitive site support the mitochondrial generation of H 2 O 2 . Succinate, the most effective substrate, yields H 2 O 2 at a rate of 0.5nmol/min per mg of protein in state 4. H 2 O 2 generation is decreased in the state 4→state 3 transition. 4. In the combined mitochondrial–peroxisomal fraction of rat liver the changes in the mitochondrial generation of H 2 O 2 modulated by substrate, ADP and antimycin A are followed by parallel changes in the saturation of the intraperoxisomal catalase intermediate. 5. Peroxisomes supplemented with uric acid generate extraperoxisomal H 2 O 2 at a rate (8.6–16.4nmol/min per mg of protein) that corresponds to 42–61% of the rate of uric acid oxidation. Addition of azide increases these H 2 O 2 rates by a factor of 1.4–1.7. 6. The concentration of cytosolic uric acid is shown to vary during the isolation of the cellular fractions. 7. Microsomal fractions produce H 2 O 2 (up to 1.7nmol/min per mg of protein) at a ratio of 0.71–0.86mol of H 2 O 2 /mol of NADP + during the oxidation of NADPH. H 2 O 2 is also generated (6–25%) during the microsomal oxidation of NADH (0.06–0.025mol of H 2 O 2 /mol of NAD + ). 8. Estimation of the rates of production of H 2 O 2 under physiological conditions can be made on the basis of the rates with the isolated fractions. The tentative value of 90nmol of H 2 O 2 /min per g of liver at 22°C serves as a crude approximation to evaluate the biochemical impact of H 2 O 2 on cellular metabolism.
1,499 citations
TL;DR: In this article, a direct method for determining both local and regional stability of systems described by nonlinear differential-difference equations is presented, with respect to a general class of initial curves.
Abstract: A direct method is presented for determining both local and regional stability of systems described by nonlinear differential-difference equations. Prediction of stability is with respect to a general class of initial curves. The practical as well as the conservative nature of the procedure is demonstrated by a numerical example.
1,087 citations
TL;DR: In this paper, a model of industrial and institutional buying behavior as an organizational decision-making process is proposed, and the major dimensions of the model are defined and some implications for mar...
Abstract: The authors suggest a model of industrial and institutional buying behavior as an organizational decision-making process. The major dimensions of the model are defined and some implications for mar...
853 citations
TL;DR: The expression Y = (1 + Zn)1/n where Y and Z are expressed in terms of the solutions for asymptotically large and small values of the independent variable is shown to be remarkably successful in correlating rates of transfer for processes which vary uniformly between these limiting cases as discussed by the authors.
Abstract: The expression Y = (1 + Zn)1/n where Y and Z are expressed in terms of the solutions for asymptotically large and small values of the independent variable is shown to be remarkably successful in correlating rates of transfer for processes which vary uniformly between these limiting cases. The arbitrary exponent n can be evaluated simply from plots of Y versus Z and Y/Z versus 1/Z. The expression is quite insensitive to the choice of n and the closest integral value can be chosen for simplicity. The process of correlation can be repeated for additional variables in series. Illustrative applications are presented only for flow, conduction, forced convection, and free convection, but the expression and procedure are applicable to any phenomenon which varies uniformly between known, limiting solutions.
784 citations
TL;DR: Observations of the vernacular provide the most systematic basis for linguistic theory, but have been the most difficult kinds of data for linguists to obtain; techniques for solving the problems encountered are outlined.
Abstract: Current difficulties in achieving intersubjective agreement in linguistics require attention to principles of methodology which consider sources of error and ways to eliminate them. The methodological assumptions and practices of various branches of linguistics are considered from the standpoint of the types of data gathered: texts, elicitations, intuitions and observations. Observations of the vernacular provide the most systematic basis for linguistic theory, but have been the most difficult kinds of data for linguists to obtain; techniques for solving the problems encountered are outlined. Intersubjective agreement is best reached by convergence of several kinds of data with complementary sources of error.
649 citations
TL;DR: The presence of both thick and thin myofilaments and of rough SR in smooth muscles supports the dual, contractile and morphogenetic, function of smooth muscle.
Abstract: The sarcoplasmic reticulum (SR) was studied in the smooth muscles of rabbit main pulmonary artery, mesenteric vein, aorta, mesenteric artery, taenia coli, guinea pig mesenteric artery, and human uterus, and correlated with contractions of the smooth muscles in Ca-free media. SR volumes were determined in main pulmonary artery (5.1%), aorta (5%), portal-anterior mesenteric vein (2.2%), taenia coli (2%), and mesenteric artery (1.8%): because of tangentially sectioned membranes these estimates are subject to a correction factor of up to +50% of the values measured. Smooth muscles that contained a relatively large volume of SR maintained significant contractile responses to drugs in the virtual absence of extracellular calcium at room temperatures, while smooth muscles that had less SR did not. The unequal maximal contractions of main pulmonary artery elicited by different drugs were also observed in Ca-free, high potassium-depolarizing solution, indicating that they were secondary to some mechanism independent of changes in membrane potential or calcium influx. Longitudinal tubules of SR run between and are fenestrated about groups of surface vesicles separated from each other by intervening dense bodies. Extracellular markers (ferritin and lanthanum) entered the surface vesicles, but not the SR. The peripheral SR formed couplings with the surface membrane: the two membranes were separated by gaps of approximately 10 nm traversed by electron-opaque connections suggestive of a periodicity of approximately 20–25 nm. These couplings are considered to be the probable sites of electromechanical coupling in twitch smooth muscles. Close contacts between the SR and the surface vesicles may have a similar function, or represent sites of calcium extrusion. The presence of both thick and thin myofilaments and of rough SR in smooth muscles supports the dual, contractile and morphogenetic, function of smooth muscle.
508 citations
TL;DR: Renal handling of calcium and phosphate during mineralocorticoid "escape" in man suggests decreased sodium transport in the proximal tubule may be associated with phosphaturia since phosphate is mostly unreabsorbed distally, while decreased sodium reabsorption in the distal tubules may occur with calciuria only.
401 citations
TL;DR: Synthetic thyrotropin releasing hormone (TRH) was administered intravenously to normal human subjects to define the normal range of serum TSH response to TRH and some of the variables that affect this response.
Abstract: Synthetic thyrotropin releasing hormone (TRH) was administered intravenously to normal human subjects to define the normal range of serum thyrotropin (TSH) response to TRH and some of the variables that affect this response. The maximum increase in serum TSH (maximum ΔTSH) following TRH was employed as the index of response. These were the results: 1) The maximum ΔTSH increased linearly when the TRH dose was increased from 6.25 to 400 μg. Since 800 μg produced no greater response than 400 μg, 400 μg is recommended as the standard test dose for evaluating TSH secretion. 2) Consistency of TSH response was evaluated by administration of the same dose (400 μg) of TRH to each of five subjects on four different occasions. The coefficients of variation of the maximum ΔTSH's in each subject ranged from 11–22% in four subjects and was 40% in the fifth. 3) TSH responsiveness to TRH was not significantly affected by sex. maximum ΔTSH in 20–39 year-old females was 16.8 ± 1.6 μU/ml (mean ± sem), and that in height- an...
385 citations
TL;DR: EPR parameters of nitric oxide complexes of ferrous hemoproteins are not significantly affected by substitutions of two vinyl groups at positions 2 and 4 of the porphyrin ring with two ethyl groups (mesoheme) or hydrogens (deuteroheme), indicating that the nucleophilicity of porphirin side chains has no appreciable effect on the metal-ligand bond strength.
TL;DR: In this paper, the authors discuss the nature of the problem situations for which alternative decision criteria are more appropriate than optimality as an operational research criterion and develop a measure of the flexibility which an initial decision of a plan maintains for achieving near-optimal states in conditions of uncertainty.
Abstract: The use of "optimality" as an operational research criterion is insufficiently discriminating. Ample evidence exists that for many problems simple optimization (particularly profit maximization) does not represent the aims of management. In this paper we discuss the nature of the problem situations for which alternative decision criteria are more appropriate. In particular the structure of strategic planning problems is analysed. The provisional commitment involved in a plan (in contrast to the irrevocable commitment of a decision) leads to the development of a particular criterion, robustness—a measure of the flexibility which an initial decision of a plan maintains for achieving near-optimal states in conditions of uncertainty. The robustness concept is developed through the case study of a sequential factory location problem.
TL;DR: Mitochondria from mung bean hypocotyls and potato tubers have been separated from contaminating organelles and membrane fragments on discontinuous sucrose gradients and the influence of purification on oxidative capacities and carrier concentrations is detailed.
TL;DR: It is suggested that there were strong selective pressures in the evolutionary development of immunoglobulins, for the emergence of mutant heavy chains which could form suitable interchain disulfide linkages which could provide immunity at concentrations several orders of magnitude less.
TL;DR: The spatiotemporal characteristics of mechanisms that extract information from complex alphanumeric displays were investigated in a series of experiments using search and same-different detection tasks, finding that a model in which individual elements are examined by independent parallel channels was appropriate.
TL;DR: In this paper, the ages of apatites from the Swiss and Italian Alps were used to define the time when these rocks cooled down to temperatures to 125 ± 20°C.
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TL;DR: In this article, it was shown that every topos may be exactly embedded in a product of topoi each with 1 as a generator, and near-exactly embedded in the category of sets.
Abstract: After a review of the work of Lawvere and Tierney, it is shown that every topos may be exactly embedded in a product of topoi each with 1 as a generator, and near-exactly embedded in a power of the category of sets. Several metatheorems are then derived. Natural numbers objects are shown to be characterized by exactness properties, which yield the fact that some topoi can not be exactly embedded in powers of the category of sets, indeed that the “arithmetic” arising from a topos dominates the exactness theory. Finally, several, necessarily non-elementary, conditions are shown to imply exact embedding in powers of the category of sets.
TL;DR: For instance, this article found that when target and field categories were of the same category, reaction time increased with display size, while reaction times were independent of display size for the ambiguous target character 0.
Abstract: Evidence is presented for a processing mechanism in visual recognition that depends upon how the stimulus array is conceptually categorized rather than upon its physical characteristics. Ss had to detect a letter or digit target in a field of letters or digits. When target and field were of the same category, reaction time increased with display size. When target and field category differed, reaction times were independent of display size. This category effect held even for the ambiguous target character 0 that yielded reaction time functions appropriate to how it was specified prior to presentation: as “zero” or as “ō.”
TL;DR: Recordings of neuronal activity in the pudendal, genitofemoral, and pelvic nerves indicate that the sensory fields of these three nerves are the perineum, the caudal abdomen, and the vagino-cervical area and rectum, respectively.
Abstract: Recordings of neuronal activity in the pudendal, genitofemoral, and pelvic nerves indicate that the sensory fields of these three nerves are the perineum, the caudal abdomen, and the vagino-cervical area and rectum, respectively. The sensory field of the pudendal nerve was significantly larger in estrogen-treated ovariectomized female rats than in uninjected controls. This effect of estrogen was not mediated by pudendal efferents.
TL;DR: Activities of psychosine galactosidase (galactosylsphingosine gaelic hydrolase) were extremely deficient in the brain, liver and kidney of patients with globoid cell leukodystrophy, and the enzyme was similarly deficient in tissues of a fetus affected with this disease.
01 Mar 1972
TL;DR: In this article, a unified and rational treatment of the theory of fiber reinforced composite materials is presented, and detailed derivations of the effective elastic moduli for these materials are presented.
Abstract: A unified and rational treatment of the theory of fiber reinforced composite materials is presented. Fundamental geometric and elasticity considerations are throughly covered, and detailed derivations of the effective elastic moduli for these materials are presented. Biaxially reinforced materials which take the form of laminates are then discussed. Based on the fundamentals presented in the first portion of this volume, the theory of fiber-reinforced composite materials is extended to include viscoelastic and thermoelastic properties. Thermal and electrical conduction, electrostatics and magnetostatics behavior of these materials are discussed. Finally, a brief statement of the very difficult subject of physical strength is included.
TL;DR: Analysis of in vitro stimulation of clonal precursors of anti-2,4-dinitrophenyl (DNP) antibody-producing cells derived from both immune and nonimmune mice indicates that carrier-specific enhancement is obligatory for stimulation of primary precursor cells and increases both the size and number of detectable foci derived from secondary precursor.
Abstract: Cell transfers to carrier-immunized irradiated mice have permitted an analysis of the in vitro stimulation of clonal precursors of anti-2,4-dinitrophenyl (DNP) antibody-producing cells derived from both immune and nonimmune mice. The results indicate that: (a) carrier-specific enhancement is obligatory for stimulation of primary precursor cells and increases both the size and number of detectable foci derived from secondary precursors. (b) This carrier-specific enhancement is most apparent in the stimulation of precursors of high-affinity antibody producer cells. (c) The antibody produced by primary foci, like that of secondary foci, appears homogeneous. (d) The frequency of clonal precursors in normal spleens is 38% that in spleens from mice 4-8 months after immunization, and the number of such precursors in normal spleens can be reduced fivefold by specific suppression of donor mice with soluble antigen. (e) The average of association constants of primary monofocal antibodies, like that of primary serum antibody produced in carrier-primed mice, is less than 10-fold lower than that of secondary clonal or serum antibody. (f) The affinity of primary monofocal antibodies shows a slight dependence on stimulating antigen concentration; however, a minimum threshold affinity consonant with stimulation is apparent. (g) Free hapten inhibits antigenic stimulation of primary precursor cells at a much lower concentration than is required for the inhibition of secondary precursors. These results are interpreted as indicating that (a) primary stimulation, like secondary stimulation, results from the selective stimulation by antigen of a population of cells differing from one another in their potential antibody product but each having only a single such product; (b) the antigen receptors of primary cells interact with antigen as if they are monovalent while receptors of secondary cells evidence multivalence; (c) antigenic stimulation appears to require both a relatively high affinity of receptors for bound antigen and an interlinking of receptors through such antigen; stimulation is thus seen as resulting from a stabilization of receptors within antigen-receptor aggregates to the cell surface; (d) T-cells appear to serve both in cross-linking antigens and in amplifying the size of stimulated clones.
TL;DR: In this paper, a factorial design was used to investigate the effect of physical exercise on aggressive behavior, as measured by the intensity of shock ostensibly delivered to the earlier instigator, and found that subsequent aggressive behavior increased significantly with initial instigation, whereas its effect was negligible under minimal instigation.
TL;DR: Opinion leadership has been studied intensively but rather narrowly in most studies to date, but an attempt is made to broaden the scope of coverage in order to learn about many dimensions or aspects of this phenomenon as it applies to a single population at a particular point in time.
Abstract: Opinion leadership has been studied intensively but rather narrowly in most studies to date. An attempt is made here to broaden the scope of coverage in order to learn about many dimensions or aspe...
TL;DR: In this paper, an experimental study of the organic charge transfer salt NMP-TCNQ is presented, where magnetic-susceptibility, specific-heat, spin-resonance, and conductivity measurements indicate a metallic state above 200 K with a continuous transition to a small-band-gap magnetic Mott insulator below 200 K. The transition to the metallic state is attributed to electron-hole correlations which become important when the number of excitations is large.
Abstract: An experimental study of the organic charge-transfer salt $N$-methyl-phenazinium tetracyanoquinodimethan (NMP-TCNQ) is presented. Magnetic-susceptibility, specific-heat, spin-resonance, and conductivity measurements indicate a metallic state above 200 \ifmmode^\circ\else\textdegree\fi{}K with a continuous transition to a small-band-gap magnetic Mott insulator below 200 \ifmmode^\circ\else\textdegree\fi{}K. The ground-state and low-lying excitations indicate that this system can be quantitatively described in terms of the one-dimensional Hubbard model with a transfer integral of 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}2}$ eV and an effective Coulomb interaction of 0.17 eV. These values are discussed in terms of the fundamental molecular physics of the TCN${\mathrm{Q}}^{\ensuremath{-}}$ anion in the NMP-TCNQ crystal. It is concluded that in addition to the Heitler-London correlation which reduces the interaction between two excess electrons on a TCNQ molecule, the NMP cation polarizability plays a significant role in reducing the effective interaction. The transition to the metallic state is attributed to electron-hole correlations which become important when the number of excitations is large. These correlations persist into the metallic state where the electronic system behaves as a quasi-free-electron Fermi liquid as indicated by the unenhanced Pauli susceptibility and simple transport properties. The low-temperature one-dimensional antiferromagnetic state is studied using spin-resonance and specific-heat techniques. The linear temperature dependence of the specific heat predicted for the one-dimensional antiferromagnet has been observed. Electron-spin-resonance linewidth studies indicate motionally narrowed dipolar widths with the correlation time determined by the Fermi velocity in the metallic state and by exchange in the insulating state. The large fluctuations expected for a one-dimensional "phase transition" show up as a maximum in the correlation time, which however never exceeds ${10}^{\ensuremath{-}13}$ sec. The spin-lattice relaxation of the conduction electrons via phonons and molecular vibrations in the metallic state has been observed. The results are consistent with Elliot's theory in which ${T}_{1}^{\ensuremath{-}1}\ensuremath{\sim}{(\frac{\ensuremath{\Delta}g}{g})}^{2}{\ensuremath{\tau}}_{R}^{\ensuremath{-}1}$, where ${\ensuremath{\tau}}_{R}$ is the scattering time as determined from the resistivity.
TL;DR: A review of the anatomy and ultrastructure of the meniscus, and its relationship to normal function in terms of load transmission, shock absorption, joint stability, lubrication, and nutrition will enable a better understanding of the rationale for meniscal preservation techniques, including meniscal repair and meniscal transplant.
Abstract: True appreciation of the structure and function of the knee joint meniscus is a relatively recent occurrence. Even decades after studies were published documenting the detrimental effects of meniscectomoy such as osteoarthritis, many physicians continued to advocate total meniscectomy for even minor meniscal pathology. Fortunately, the clinical approach to these problems has undergone dramatic change over the past 20 years. A review of the anatomy and ultrastructure of the meniscus, and its relationship to normal function in terms of load transmission, shock absorption, joint stability, lubrication, and nutrition will enable a better understanding of the rationale for meniscus preservation techniques, including meniscal repair and meniscal transplant.
TL;DR: The effects of changes in ICP and SAP on CBF in the same animal, with intact and defective autoregulation, are discussed as a means of further evaluating several proposed mechanisms of autOREgulation; the sensitivity of autoreGulation to raised ICP; and the response of CBF to a concomitant increase in SAP and ICP at a constant CPP.
Abstract: Publisher Summary Continuous monitoring of intracranial pressure (ICP) has become an increasingly common practice in neurosurgical units. Intracranial hypertension is produced by a variety of pathological states, and the increased pressure rather than the underlying disorder may be primarily responsible for death in patients. There is general agreement that the intracranial hypertension disturbs brain function by reducing cerebral blood flow (CBF) and causing brain herniation with brainstem compression or displacement. This chapter measures ICP continuously in patients with severe head injury, brain tumor, subarachnoid hemorrhage, hydrocephalus, cerebral hypoxia, pseudotumor cerebri, or encephalitis, and regional CBF has been measured in some of these patients using the 133 Xe clearance technique. Several models have been developed in an attempt to simulate clinical conditions in the laboratory animal. This report describes observations in one of these animal models. In recent reports on the effects of increased ICP on CBF increasing emphasis has been placed on the concept that changes in ICP affect CBF through alterations in cerebral perfusion pressure (CPP), and that in this respect, they may be compared with changes in systemic arterial pressure (SAP) by considering CPP to be the difference between SAP and ICP. This chapter discusses the effects of changes in ICP and SAP on CBF in the same animal, with intact and defective autoregulation, as a means of further evaluating several proposed mechanisms of autoregulation; the sensitivity of autoregulation to raised ICP;)and the response of CBF to a concomitant increase in SAP and ICP at a constant CPP, with intact and defective autoregulation.
TL;DR: A general model for cell speciation based on the central roles of DNA synthesis and cell cycle is presented, and it is likely that they will prove to be separable mechanistically as well.
Abstract: Publisher Summary This chapter presents a general model for cell speciation based on the central roles of DNA synthesis and cell cycle. Two phases of differentiation can be recognized. The first involves the rapid commitment of cells to their respective lineages during the early cleavage stages, and in this regard there is no basic difference between the regulative and mosaic systems. The end product of the early cleavage stages is the “definitive stem cell.” The definitive stem cell retains the capacity to yield the daughter cells that are either replicate stem cells or terminally differentiated cells. The second phase of differentiation involves the biological conditions either in vivo or in vitro that manipulate these stable stem cells for growth, for morphogenesism, and for maintaining populations that turn over. During the early cleavage stage, these two phases are usually separable temporally. It is likely that they will prove to be separable mechanistically as well.