Showing papers by "Cornell University published in 1983"
TL;DR: In this article, a simplified presentation of the basic ideas of the renormalization group and the ε expansion applied to critical phenomena is given, following roughly a summary exposition given in 1972.
Abstract: 1. Introduction This paper has three parts. The first part is a simplified presentation of the basic ideas of the renormalization group and the ε expansion applied to critical phenomena , following roughly a summary exposition given in 1972 1. The second part is an account of the history (as I remember it) of work leading up to the papers in I971-1972 on the renormalization group. Finally, some of the developments since 197 1 will be summarized, and an assessment for the future given.
1,587 citations
TL;DR: Fifty patients with acquired immune deficiency syndrome had complications affecting the central or peripheral nervous systems or both, and the patients were either male homosexuals, intravenous drug abusers, or recently arrived Haitian refugees.
Abstract: Fifty patients with acquired immune deficiency syndrome had complications affecting the central or peripheral nervous systems or both. The patients were either male homosexuals, intravenous drug abusers, or recently arrived Haitian refugees. They ranged in age from 25 to 56. Central nervous system complications were of four kinds: (1) Infections included Toxoplasma gondii abscesses in 5 patients, progressive multifocal leukoencephalopathy in 2, cryptococcal meningitis in 2, Candida albicans in 1, and possible Mycobacterium avium intracellulare in 3. Eighteen patients suffered a subacute encephalitis possibly attributable to cytomegalovirus infection. (2) Tumors consisted of primary lymphoma of the brain in 3 patients and meningeal invasion by systemic lymphoma in 4. (3) Vascular complications included nonbacterial thrombotic endocarditis in 2 patients and cerebral hemorrhages in the setting of thrombocytopenia in 3. (4) Undiagnosed central nervous system problems were evidenced as focal brain lesions in 3 patients and self-limiting aseptic meningitis in 4. Peripheral neuropathy occurred in 8 patients.
1,318 citations
TL;DR: Modifications of glutathione metabolism may be achieved by administration of selective enzyme inhibitors, and also by giving compounds that increase glutATHione synthesis, which are useful in chemotherapy and radiation therapy and in protecting cells against the toxic effects of drugs, other foreign compounds, and oxygen.
Abstract: Glutathione, a tripeptide thiol found in virtually all cells, functions in metabolism, transport, and cellular protection. It participates in the reduction of disulfides and other molecules, and conjugates with compounds of exogenous and endogenous origin. It protects cells against the destructive effects of reactive oxygen intermediates and free radicals. Modifications of glutathione metabolism may be achieved by administration of selective enzyme inhibitors, and also by giving compounds that increase glutathione synthesis. Such effects are useful in chemotherapy and radiation therapy and in protecting cells against the toxic effects of drugs, other foreign compounds, and oxygen.
1,245 citations
TL;DR: In this article, the authors focus on an idealized granular material comprised of identical, smooth, imperfectly elastic, spherical particles which is flowing at such a density and is being deformed at a rate that particles interact only through binary collisions with their neighbours.
Abstract: We focus attention on an idealized granular material comprised of identical, smooth, imperfectly elastic, spherical particles which is flowing at such a density and is being deformed at such a rate that particles interact only through binary collisions with their neighbours. Using general forms of the probability distribution functions for the velocity of a single particle and for the likelihood of binary collisions, we derive local expressions for the balance of mass, linear momentum and fluctuation kinetic energy, and integral expressions for the stress, energy flux and energy dissipation that appear in them. We next introduce simple, physically plausible, forms for the probability densities which contain as parameters the mean density, the mean velocity and the mean specific kinetic energy of the velocity fluctuations. This allows us to carry out the integrations for the stress, energy flux and energy dissipation and to express these in terms of the mean fields. Finally, we determine the behaviour of these fields as solutions to the balance laws. As an illustration of this we consider the shear flow maintained between two parallel horizontal plates in relative motion.
1,230 citations
TL;DR: In this paper, the authors show that tectonic segmentation of the Andes coincides with the subducted Nazca plate, which has nearly horizontal segments and 30° east-dipping segments.
Abstract: Seismological and geological data show that tectonic segmentation of the Andes coincides with segmentation of the subducted Nazca plate, which has nearly horizontal segments and 30° east-dipping segments. Andean tectonics above a flat-subducting segment between 28°S to 33°S are characterized by (from west to east): (1) a steady topographic rise from the coast to the crest of the Andes; (2) no significant Quaternary, and possibly Neogene, magmatism; (3) a narrow belt of eastward-migrating, apparently thin-skinned, Neogene to Quaternary shortening of the Andes; and (4) Plio-Pleistocene uplift of the crystalline basement on reverse faults in the Pampeanas Ranges. From about 15° to 24°S, over a 30°-dipping subducted plate, a west to east Andes cross section includes: (1) a longitudinal valley east of coastal mountains; (2) an active Neogene and Holocene andesitic volcanic axis; (3) the Altiplano-Puna high plateau; (4) a high Neogene but inactive thrust belt (Eastern Cordillera); and (5) an active eastward-migrating Subandean thin-skinned thrust belt. Tectonics above a steeply subducting segment south of 33°S are similar west of the volcanic axis, but quite different to the east. Early Cenozoic tectonics of western North America were quite similar to the Neogene Andes. However, duration of segmentation was longer and the width of deformation was greater in the western United States. Patterns of crustal seismicity are systematically related to Plio-Quaternary structural provinces, implying that current deformational processes have persisted since at least the Pliocene. Horizontal compression parallel to the plate convergence direction is indicated to a distance of 800 km from the trench. Above flat-subducting segments, crustal seismicity occurs over a broad region, whereas over steep segments, it is confined to the narrow thrust belt. Strain patterns in the forearc region are complex and perhaps extensional, and a broad region of the Altiplano-Puna and Eastern Cordillera appears to be aseismic.
964 citations
TL;DR: A new, extended Boolean information retrieval system is introduced which is intermediate between the Boolean system of query processing and the vector processing model, and Laboratory tests indicate that the extended system produces better retrieval output than either the Boolean or thevector processing systems.
Abstract: In conventional information retrieval Boolean combinations of index terms are used to formulate the users'' information requests. While any document is in principle retrievable by a Boolean query, the amount of output obtainable by Boolean processing is difficult to control, and the retrieved items are not ranked in any presumed order of importance to the user population. In the vector processing model of retrieval, the retrieved items are easily ranked in decreasing order of the query-record similarity, but the queries themselves are unstructured and expressed as simple sets of weighted index terms. A new, extended Boolean information retrieval system is introduced which is intermediate between the Boolean system of query processing and the vector processing model. The query structure inherent in the Boolean system is preserved, while at the same time weighted terms may be incorporated into both queries and stored documents; the retrieved output can also be ranked in strict similarity order with the user queries. A conventional retrieval system can be modified to make use of the extended system. Laboratory tests indicate that the extended system produces better retrieval output than either the Boolean or the vector processing systems.
909 citations
TL;DR: In this article, the authors established linear stability conditions for slip surfaces at fixed normal stress, where the shear resistance of slipping surfaces is given by r = r( v,state) /iJV>O.
Abstract: Assistant Professor, Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, N.Y. 14850 The shear resistance of slipping surfaces at fixed normal stress is given by r = r( v,state). Here V = slip velocity, dependence on «state" is equivalent to functional dependence with fading memory on prior V(t), and ar( v,state) /iJV>O. We establish linear stability conditions for steadY'slipstates (V(t), r(t) constant). For single degree-of-freedom elastic or viscoelastic dynamical systems, instability occurs, if at all, by a flutter mode when the spring stiffness (or appropriate viscoelastic generalization) .reduces to a critical value. Similar conclusions are reached for slipping continua with spatially periodic perturbations along their interface, and in this case the existence of propagating frictional creep waves is established at critical conditions. Increases in inertia of the slipping systems are found to be destabilizing, in that they increase the critical stiffness level requiredfor stability.
908 citations
TL;DR: In this paper, the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle, and the theoretical basis of these computations and results of experiments performed in the AEP power system simulation laboratory are also outlined.
Abstract: With the advent of Substation Computer Systems dedicated to protection, control and data logging functions in a Substation, it becomes possible to develop new applications which can utilize the processing power available within the substation. The microcomputer based Symmetrical Component Distance Relay (SCDR) described in the references cited at the end of this paper possesses certain characteristics which facilitate real-time monitoring of positive sequence voltage phasor at the local power system bus. With a regression analysis the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle. This paper describes the theoretical basis of these computations and describes results of experiments performed in the AEP power system simulation laboratory. Plans for future field tests on the AEP system are also outlined.
906 citations
TL;DR: The results indicate that the basis for patterning of branchial arch skeletal and connective tissues resides within the neural crest population prior to its emigration from the neural epithelium, and not within the pharynx or pharyngeal pouches as had previously been suggested.
837 citations
TL;DR: In this article, a single-degree of freedom non-linear oscillator is considered and the nonlinearity is in the restoring force and is piecewise linear with a single change in slope.
802 citations
Book•
01 Jan 1983TL;DR: Tandem mass spectrometry can achieve specificities and sensitivities equivalent of those of methods such as radioimmunoassay and gas chromatography/mass spectromaetry, while performing analyses in much shorter times.
Abstract: Coupling mass spectrometers in series provides a new technique that has many advantages for the analysis of specific organic compounds in complex mixtures. Sensitivity to picograms of targeted compounds can be achieved with high specificity and nearly instantaneous response. The targeted compound is selectively ionized, and its characteristic ions are separated from most others of the mixture in the first mass spectrometer. The selected primary ions are then decomposed by collision, and from the resulting products the final mass analyzer selects secondary ions characteristic of the targeted compound. Tandem mass spectrometry can achieve specificities and sensitivities equivalent of those of methods such as radioimmunoassay and gas chromatography/mass spectrometry, while performing analyses in much shorter times.
TL;DR: It is concluded that hypertensive LVH is poorly related to clinical or home measurements of blood pressure but that a substantially closer relationship exists betweenLVH and blood pressure during recurring stress at work and between LVH and home blood pressure on a workday.
Abstract: Left ventricular hypertrophy (LVH), a target organ response in essential hypertension, is only weakly related to clinical measurements of blood pressure. To determine whether blood pressure measured under basal or stress conditions more closely determines LVH, we compared echocardiographic left ventricular mass index and relative wall thickness with clinical blood pressure and with 24 hr recordings (home, work, and sleep) in 19 normal subjects and 81 patients with mild hypertension. Only a weak correlation was observed in the entire group between left ventricular mass index and clinical measurements of systolic and diastolic blood pressure (r = .24, p < .02; r = .20, p < .05, respectively), which was only slightly improved by use of systolic and diastolic blood pressure readings taken in the home (r = .31, p < .005; r = .21, p < .05, respectively). Sleep and total 24 hr blood pressure also related poorly to left ventricular mass index. In contrast, substantially higher correlations existed between left ventricular mass index and systolic and diastolic blood pressure measured by portable recorder in 60 subjects at work (r = .50, p < .001; r = .39, p < .01, respectively). Similarly, work diastolic blood pressure bore the closest relationship to relative wall thickness (r = .59, p < .001). Home blood pressure readings taken on a work day also showed a moderate relationship with indices of LVH, whereas weaker correlations were found in employed subjects whose blood pressure was recorded on a non-workday, and no relationship between blood pressure and LVH existed in subjects who were not employed. We conclude that hypertensive LVH is poorly related to clinical or home measurements of blood pressure but that a substantially closer relationship exists between LVH and blood pressure during recurring stress at work and between LVH and home blood pressure on a workday. Thus hypertensive cardiac hypertrophy appears to be more closely related to blood pressure during stressful Circulation 68, No. 3, 470-476, 1983. NUMEROUS STUDIES have demonstrated that the risk of disease and death increases as blood pressure rises.'4 However, despite the consistency of this finding and its high statistical significance in large populations, the actual correlations between blood pressure measurements and the incidence of morbid events have generally been relatively low.'4 One possible explanaFrom the Division of Cardiology, The Hypertension Center, and the Department of Neurology, The New York Hospital-Cornell Medical Center, New York, and the Department of Statistics and Data Analysis Research, Bell Laboratories, Murray Hill, NJ. Supported in part by grant HL-18323 from the NHLBI. Address for correspondence: Richard B. Devereux, M.D., Division of Cardiology, Box 222, The New York Hospital, 525 East 68th St., New York, NY 10021. Received Dec. 13, 1982; revision accepted April 28, 1983. Dr. Devereux is the recipient of a Teacher-Scientist Award from the Andrew W. Mellon Foundation. Dr. Borer is an Established Investigator of the American Heart Association. 470 situations than to basal blood pressure. tion for the lack of a closer relationship is that blood pressure itself is highly variable7-' and that clinical measurements may be unrepresentative of the longterm overload placed on the circulation.9-10 The observation by some investigators that target organ manifestations in subjects with essential hypertension are more closely related to basal,9 home, \"I or ambulatory blood pressure readings'2 has supported this hypothesis, although this finding has not been consistent.'3 Another factor that may have contributed to the poor correlations is the weak relationship between cardiac changes and their manifestations in the electrocardiogram (ECG)'4 or chest x-ray.'5 The development of methods for recording blood pressure accurately during unrestricted in-hospital or normal out-of-hospital activity\"\"lS has provided furCIRCULATION by gest on N ovem er 8, 2017 http://ciajournals.org/ D ow nladed from PATHOPHYSIOLOGY AND NATURAL HISTORY-HYPERTENSION ther information about blood pressure variability in normal subjects and in patients with essential hypertension. These studies have confirmed earlier reports that hypertensive patients have greater increases in blood pressure from basal levels in response to stresses such as clinic visits,'9-21 the work environment,22 isometric exercise,23 and dynamic exercise2' than do normals. However, the significance of different patterns of blood pressure reactivity and of blood pressure levels during recurring activities of daily living has not been assessed with regard to target organ manifestations of hypertension or occurrence of morbid events. The recent development of an accurate echocardiographic method for measurement of left ventricular mass24 has provided an improved \"bioassay\" for one of the most important target organ effects of hypertension. Previous studies have indicated that detectable left ventricular hypertrophy (LVH) is important not only as an indicator of the current severity of hypertension but also as a source of prognostic information independent of the level of blood pressure. 1-2, 5, 25 The present study has been designed to evaluate the relationship between blood pressure during different phases of normal activity and echocardiographic measurements of left ventricular mass. We compared clinical blood pressure readings (measured by physicians) with measurements taken by automatic portable recorder in the clinic, at work, at home, and during sleep. Methods Subjects. We studied a total of 100 subjects, 19 of whom were normal and 81 of whom had borderline26 or sustained essential hypertension. All subjects underwent quantitative echocardiographic examination and ambulatory blood pressure recording as described below. No subjects were receiving antihypertensive or other cardioactive medication at the time of study; antihypertensive drugs had been eliminated at least 3 weeks before study. No subject had evidence of coronary artery disease or other etiologic forms of heart disease by cardiovascular history, physical examination, ECG, or echocardiogram. However, three patients with mitral valve prolapse and trivial mitral regurgitation were included, since we have previously shown that this is not associated with LVH.2? Further exclusion of coronary artery disease was accomplished by performance of maximal upright treadmill exercise testing in 67 subjects and maximum supine bicycle exercise, with rest and exercise radionuclide cineangiographic studies28 in an additional nine patients; angina was not provoked in any subject, and there was no objective evidence of coronary disease. Subjects were classified by clinical blood pressure readings into normal and hypertensive groups, as described below. Normals. Nineteen normal subjects were studied in whom multiple clinical blood pressure determinations never exceeded 140 mm Hg systolic or 90 mm Hg diastolic. There were 11 men and eight women (ages 28 to 64 years, mean 40). Mean clinical blood pressure was 118 ± 15/76 ± 7 mm Hg. Twelve of the normal subjects also underwent blood pressure determinations during each stage of maximum upright treadmill exercise tests by the Bruce protocol. Patients with hypertension. Eighty-one subjects with mild essential hypertension were studied. There were 70 men and 11 women (ages 18 to 66 years, mean 43). Mean clinical blood pressure was 152 ± 15/96 + 7 mm Hg; the duration of hypertension was 5.5 ± 5.5 years. Treadmill exercise tests were performed in 55 hypertensive patients, and radionuclide cineangiograms were obtained in nine subjects. Employment status. In view of the potential importance of the blood pressure response to occupational stress in causing target organ manifestations of hypertension and of the emphasis placed by Sokolow et al. 12 on obtaining daytime blood pressure recordings on a workday, we also stratified our subjects according to employment status. A total of 60 subjects worked on the day of recording, 28 were employed but had recordings performed on a non-workday, and 12 were not employed. As seen in table 1, these groups differed only slightly with regard to age and sex, except for a higher number of women in the unemployed group, and had similar 24 hr blood pressure measurements. Echocardiographic methods. Echocardiograms were performed with standard techniques previously reported from this laboratory.29, 30 Echocardiographic tracings were coded and read blindly and in random order. End-diastolic measurements of interventricular septal thickness (IVS), left ventricular internal dimension (LVID), and posterior wall thickness (PWT) were made according to the Penn Convention protocol to measure left ventricular mass.24 This was calculated by a simple anatomically validated formula: LVM = 1.04((IVS + LVID + PWT)3 LVID)3 13.6 To minimize the impact of variation in body size on left ventricular mass, it was indexed for body surface area. End-diastolic and end-systolic measurements were also made according to the recommendations of the American Society of Echocardiography.3' End-diastolic relative wall thickness32 was calculated from these values. Blood pressure by portable recorder. The 24 hr blood pressure recordings were obtained with the Del Mar Avionics Ambulatory Blood Pressurometer II. Subjects were fitted with the recorder on the morning of the day of the recording, and a minimum of five readings were taken with the subject in the sitting position. These had to be within 5 mm Hg of simultaneous readings obtained with a stethoscope and mercury column for the recording to be considered acceptable. The recorder was then set to take readings at 15 min intervals, and subjects were TABLE 1 Employment status of subjects
TL;DR: A structural aspect of personal memories was examined in four studies as discussed by the authors, and the existence of observer and field memories was confirmed in Study 1, using a recall questionnaire, and the similarity structure of a specified set of eight to-be-recalled situations was established: the significant dimensions were emotionality and self-awareness.
TL;DR: The method of embryonic tissue transplantation was used to confirm the dual origin of avian cranial sensory ganglia, to map precise locations of the anlagen of these sensory neurons, and to identify placodal and neural crest-derived neurons within ganglia.
Abstract: The method of embryonic tissue transplantation was used to confirm the dual origin of avian cranial sensory ganglia, to map precise locations of the anlagen of these sensory neurons, and to identify placodal and neural crest-derived neurons within ganglia. Segments of neural crest or strips of presumptive placodal ectoderm were excised from chick embryos and replaced with homologous tissues from quail embryos, whose cells contain a heterochromatin marker. Placode-derived neurons associated with cranial nerves V, VII, IX, and X are located distal to crest-derived neurons. The generally larger, embryonic placodal neurons are found in the distal portions of both lobes of the trigeminal ganglion, and in the geniculate, petrosal and nodose ganglia. Crest-derived neurons are found in the proximal trigeminal ganglion and in the combined proximal ganglion of cranial nerves IX and X. Neurons in the vestibular and acoustic ganglia of cranial nerve VIII derive from placodal ectoderm with the exception of a few neural crest-derived neurons localized to regions within the vestibular ganglion. Schwann sheath cells and satellite cells associated with all these ganglia originate from neural crest. The ganglionic anlagen are arranged in cranial to caudal sequence from the level of the mesencephalon through the third somite. Presumptive placodal ectoderm for the VIIIth, the Vth, and the VIIth, IXth, and Xth ganglia are located in a medial to lateral fashion during early stages of development reflecting, respectively, the dorsolateral, intermediate, and epibranchial positions of these neurogenic placodes.
TL;DR: The potential global atmospheric and climatic consequences of nuclear war are investigated using models previously developed to study the effects of volcanic eruptions, finding long-term exposure to cold, dark, and radioactivity could pose a serious threat to human survivors and to other species.
Abstract: The results of a computerized simulation of the potential global environmental effects of dust and smoke clouds that would be generated by a nuclear war are presented. Short term effects of blast, fire, and radiation are neglected in the series of physical models that include a nuclear war scenario, a particle microphysics model, and a radiative convective model. Account is taken of the altitude-dependent dust, smoke, radioactivity, and NO(x) injections, the temporal evolution of dust and smoke clouds, land and ocean environments, and temperature contrasts. A nuclear exchange would produce thousands of individual smoke and dust clouds rising up to 30 km altitude in the midlatitudes. The smoke, dust, and radioactive debris would cover the entire midlatitudes within 1-2 weeks. The smoke would arise from conflagrations of forests, suburbs, and urban areas. Obscuration of sunlight would induce subfreezing temperatures for several months, disruption of the global circulation patterns, and the arrival of a nuclear winter, followed and accompanied by radioactive fallout, pyrogenic air pollution, and UV-B flux enhancements. It is estimated that a total of only 100 Mtons would be sufficient to plunge the Northern Hemisphere summer to subfreezing temperatures lasting months. Since the probable exchange in a nuclear war would exceed 5000 Mtons, it is expected that many species, including humans, may not survive the war.
TL;DR: In this paper, it was shown that the classical theory of he Laplacian remains valid for the Laplace-Beltrami operator on a complete Riemannian manifold.
TL;DR: Gender schema theory has been introduced into the psychological literature by as mentioned in this paper to explain how the developing child comes to match the template defined as sex appropriate by his or her culture, which is referred to within psychology as the process of sex typing.
Abstract: As every parent, teacher, and developmental psychologist knows, male and female children become "masculine" and "feminine," respectively, at a very early age. By the time they are four or five, for example, girls and boys have typically come to prefer activities defined by the culture as appropriate for their sex and also to prefer same-sex peers. The acquisition of sex-appropriate preferences, skills, personality attributes, behaviors, and self-concepts is typically referred to within psychology as the process of sex typing. The universality and importance of this process is reflected in the prominence it has received in psychological theories of development, which seek to elucidate how the developing child comes to match the template defined as sex appropriate by his or her culture. Three theories of sex typing have been especially influential: psychoanalytic theory, social learning theory, and cognitive-developmental theory. More recently, a fourth theory of sex typing has been introduced into the psychological literature-gender schema theory. This article is designed to introduce gender schema theory to feminist scholars outside the discipline of psychology. In order to provide a background for the conceptual issues that have given rise to gender schema theory, I will begin with a discussion of the three theories of sex typing that have been dominant within psychology to date.
TL;DR: This paper identifies the major concepts and describes some of the more important language notations for writing concurrent programs and three general classes of concurrent programming languages are identified and compared.
Abstract: Much has been learned in the last decade about concurrent programming. This paper identifies the major concepts and describes some of the more important language notations for writing concurrent programs. The roles of processes, communication and syhchronization are discussed from both an operational and an axiomatic viewpoint. Language notations for expressing concurrent execution and for specifying process interaction are surveyed. Synchronization primitives based on shared variables and on message passing are described. Finally, three general classes of concurrent programming languages are identified and compared.
TL;DR: In this article, the authors discuss Polyakov's quantization of the string in the presence of a boundary allowing for an arbitrary topology for the world sheet, and show that the model is renormalizable if one performs a mass renormalization and an additive field renormalisation.
TL;DR: In this article, a special tight-binding model is solved exactly by a renormalization group whose fixed points determine the scaling properties of both the energy spectrum and certain features of the eigenstates.
Abstract: Recent theories of scaling in quasiperiodic dynamical systems are applied to the behavior of a particle in an almost periodic potential. A special tight-binding model is solved exactly by a renormalization group whose fixed points determine the scaling properties of both the energy spectrum and certain features of the eigenstates. Similar results are found empirically for Harper's equation. In addition to ordinary extended and localized states, "critical" states are found which are neither extended nor localized according to conventional criteria.
TL;DR: The combined findings of both studies support the decreased use of serotonin in suicide victims and may also throw light on the mechanism of action of antidepressant drugs.
TL;DR: Empirical data and several theoretical arguments are presented which suggest that differences in pest abundance between diverse and simple systems can frequently be accounted for by the response of herbivore host-finding behavior to the patterns of resource availability, rather than the activities of natural enemies.
Abstract: Recent criticism of the theory that increased diversity leads to increased stability has led to widespread skepticism about the value of using ecological theory to suggest strategies of agricultural diversification to better control insect pests. A total of 150 published studies which examine the effect of diversifying an agroecosystem on insect pest abundance are summarized; 198 total herbivore species were examined in these studies: 53% of these species were found to be less abundant in the more diversified system, 18% were more abundant in the diversified system, 9% showed no difference, and 20% showed a variable response. Two major problems with the studies were: (1) proper experiments were not conducted to show that differences in pest abundance between more and less diverse systems resulted in yield differences; (2) the ecological mechanisms accounting for the differences in pest abundance were carefully examined in only a few of the studies. A fundamental understanding of these ecological mechanisms is critical to the development of a predictive theory of how agricultural diversification affects insect pests. Empirical data and several theoretical arguments are presented which suggest that differences in pest abundance between diverse and simple systems can frequently be accounted for by the response of herbivore host-finding behavior to the patterns of resource availability, rather than the activities of natural enemies. The development of ecologically sound agroecosystems may well utilize within-field plant diversity, both in developing and in developed regions.
TL;DR: These results indicate that muscles associated with branchial arch skeletal structures are derived from paraxial mesoderm, as are all other voluntary muscles in the vertebrate embryo, and theories of vertebrate ontogeny and phylogeny based in part on proposed unique features of branchiomeric muscles must be critically reappraised.
Abstract: The objective of these experiments was to determine the embryonic origins of craniofacial and cervical voluntary muscles and associated connective tissues in the chick. To accomplish this, suspected primordia, including somitomeres 3-7, somites 1-7, and cephalic neural crest primordia have been transplanted from quail into chick embryos. Quail cells can be detected by the presence of a species-specific nuclear marker. The results are summarized as follows: (table; see text) These results indicate that muscles associated with branchial arch skeletal structures are derived from paraxial mesoderm, as are all other voluntary muscles in the vertebrate embryo. Thus, theories of vertebrate ontogeny and phylogeny based in part on proposed unique features of branchiomeric muscles must be critically reappraised. In addition, many of these cephalic muscles are composites of two separate primordia: the myogenic stem cells of mesodermal origin and the supporting and connective tissues derived from the neural crest or lateral plate mesoderm. Defining these embryonic origins is a necessary prerequisite to understanding how the mesenchymal primordia of cephalic muscles and connective tissues interact to form patterned, species-unique musculoskeletal systems.
TL;DR: A computer memory with defects is modeled as a discrete memoryless channel with states that are statistically determined, and Arimoto-Blahut type algorithms are used to compute the storage capacity.
Abstract: A computer memory with defects is modeled as a discrete memoryless channel with states that are statistically determined. The storage capacity is found when complete defect information is given to the encoder or to the decoder, and when the defect information is given completely to the decoder but only partially to the encoder. Achievable storage rates are established when partial defect information is provided at varying rates to both the encoder and the decoder. Arimoto-Blahut type algorithms are used to compute the storage capacity.
TL;DR: In this paper, the spectral nearedge structure (NES) of metal and oxides is analyzed and compared to symmetry-based molecular-orbital (MO) theory for both the metal and oxide data.
Abstract: The metal $K$-edge absorption spectra of $3d$ transition metals and oxides are measured by x-ray-absorption spectroscopy. Experiments are performed on metal foils or fine powders dusted onto Scotch tape, at the Cornell High Energy Synchrotron Source. Comparisons to theory are made for both the metal and oxide data. We concentrate on the spectral nearedge structure (NES) and attempt to interpret its origins. For the metals, we find excellent agreement between the data and one-electron calculations. This agreement is much closer than previously found for the ${L}_{23}$ edges in the same materials. The picture for the oxide near-edge structure is not so auspicious. Although symmetry-based molecular-orbital (MO) theory has been widely invoked, it is probably inadequate. Recent calculations indicate that while some of the near-edge peaks are indeed attributable to one-electron MO-type transitions whose energies are modified by the presence of the core hole, other features have no such simple origin. Finally we compare the oxide NES of the metal ${L}_{23}$,$K$ edges and the oxygen $K$ edge altogether. These are found to agree with each other and to MO theory only for Ti${\mathrm{O}}_{2}$. The mismatch of the three NES's in the other oxides indicates the failure of one-electron theory for insulators. Instead, the near-edge structure must be dominated by core excitons, as previously shown for NiO. The presence of excitons explains the lack of agreement between the NES for core excitations of different atoms in the same solid.
TL;DR: In 48 patients, excitatory effects ranging from mild nervousness to tremors, twitches, multifocal myoclonus, and seizures were directly correlated with accumulation of normeperidine in plasma, suggesting that renal dysfunction may contribute to but is not the sole factor in the accumulation ofnormeperidine or its relation to adverse neurological signs.
Abstract: The analgesic meperidine has been reported to produce signs of central nervous system excitation in human beings. To determine the relationship between signs and symptoms of central nervous system excitation and plasma levels of meperidine and normeperidine, we studied 67 patients receiving meperidine for the relief of postoperative or chronic pain. In 48 patients, excitatory effects ranging from mild nervousness to tremors, twitches, multifocal myoclonus, and seizures were directly correlated with accumulation of normeperidine in plasma. Evidence of compromised renal function occurred in only 14 of the 48 symptomatic patients, suggesting that renal dysfunction may contribute to but is not the sole factor in the accumulation of normeperidine or its relation to adverse neurological signs. In a second study we surveyed mood alterations in 47 patients receiving meperidine and 29 receiving other narcotic analgesics for postoperative pain. The repeated administration of meperidine was associated with adverse alterations in various elements of mood (e.g., apprehension, sadness, restlessness).
01 Jan 1983
TL;DR: The speech of 6 mothers to their healthy infants was examined longitudinally during the neonatal period and at 4, 12, and 24 months in a semi-naturalistic setting, finding that the extent of pitch contouring and repetitiveness was greater than at earlier or later ages.
Abstract: The speech of 6 mothers to their healthy infants was examined longitudinally during the neonatal period and at 4, 12, and 24 months in a semi-naturalistic setting. Features of speech analysed were: contour of fundamental frequency, repetitiveness, timing (durations of vocalizations and pauses), tempo and MLU. The neonatal period was characterized by elongated pauses. During the 4-month period the extent of pitch contouring and repetitiveness was greater than at earlier or later ages. By 24 months, the duration of vocalizations and length of MLU became markedly greater. The period of intense face-to-face interaction around the fourth month proved to involve more changes in certain prosodic features. Some of the possible functions of these changes during this phase are discussed.