Showing papers by "University of California, Irvine published in 1985"

Time-Optimal Control of Robotic Manipulators Along Specified Paths:

Abstract: The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. The optimal open-loop torques are found, and a method is given for implementing these torques with a conventional linear feedback control system. The algorithm allows bounds on the torques that may be arbitrary functions of the joint angles and angular velocities. This method is valid for any path and orientation of the end- effector that is specified. The algorithm can be used for any manipulator that has rigid links, known dynamic equations of motion, and joint angles that can be determined at a given position on the path.

Distribution of N-methyl-D-aspartate-sensitive L-[3H]glutamate-binding sites in rat brain

Abstract: N-methyl-D-aspartate (NMDA) is an acidic amino acid which depolarizes neurons by selectively interacting with a distinct class of excitatory amino acid receptor. Recent evidence has indicated that this receptor is a neurotransmitter receptor in the spinal cord, cerebral cortex, and hippocampus for which the endogenous ligand is likely to be L-glutamate or a structurally related compound. Using quantitative autoradiography, we have studied the anatomical distribution of the class of L- [3H]glutamate-binding sites displaced by NMDA, which appear to correspond to NMDA receptors. The CA1 region of the hippocampus contains the highest density of sites. In general, telencephalic regions have high levels of binding sites. The cerebral cortex shows significant density variations among the differing layers and regions, with the highest levels found in the frontal cortex layers I to III. Within the basal ganglia, the highest levels are found in the nucleus accumbens, intermediate levels are found in the caudate/putamen, and very low levels are found in the globus pallidus. Thalamic regions have moderate levels with variations among differing regions. Midbrain and brainstem have low levels of binding sites, but within these regions there are structures exhibiting higher levels, e.g., the nucleus of the solitary tract and the inferior olive. The distribution of NMDA sites is consistent with most, but not all, of the regions previously proposed to use glutamate as an excitatory transmitter. Thus, the distribution of NMDA-sensitive L-[3H]glutamate-binding sites suggests that the NMDA receptor represents a major, distinct subset of excitatory amino acid receptors and indicates regions in which neurotransmission may be mediated or modulated by this receptor.

The vasopressinergic innervation of the brain in normal and castrated rats.

Abstract: A detailed description is given of the distribution of vasopressin-immunoreactive structures in the brain of intact adult male rats. By application of a modified immunocytochemical procedure, vasopressin- immunoreactive fibers were detected in many new areas. In adult male rats which were castrated 15 weeks before death, vasopressin-immunoreactive cell bodies had disappeared from the bed nucleus of the stria terminalis and the medial amygdaloid nucleus. No obvious changes were found in vasopressin-immunoreactive cell bodies in other areas. Furthermore, a very strong reduction was seen in the density of vasopressin-immunoreactive fibers in the olfactory tubercle, nucleus of the diagonal band and its immediate surroundings, ventral pallidum, basal nucleus of Meynert, lateral septum, septofimbrial nucleus, ventral hippocampal formation, amygdaloid area, pre- and supramammillary nucleus, supramam-millary decussation, (inter)dorsomedial, parafascicular, and ventral aspect of paraventricular thalamic nuclei, zona incerta, lateral habenular nucleus, ventral tegmental area, substantia nigra, periventricular gray, dorsal and median raphe nucleus, and locus coeruleus. No changes were observed in other areas containing vasopressin-immunoreactive fibers. These changes following gonadectomy were not observed in castrated rats which had been treated with testosterone. The results suggest that vasopressin projections from the bed nucleus of the stria terminalis and possibly from the medial amygdaloid nucleus require the presence of gonadal hormones for their normal appearance. This is in contrast to pathways arising from the hypothalamic vasopressin-producing nuclei, which fail to show obvious changes following castration.

Linear solvation energy relations

Abstract: Solvents have been parameterized by scales of dipolarity/polarizability π*, hydrogen-bond donor (HBD) strength α, and hydrogen-bond acceptor strength β. Linear dependence (LSER's) on these solvent parameters are used to correlate and predict a wide variety of solvent effects, as well as to provide an analysis in terms of knowledge and theoretical concepts of molecular structural effects. Some recent applications utilizing this approach are presented. Included are analyses of solvent effects on (a) the free energies of transfer of tetraalkylammonium halide ion pairs and dissociated ions, (b) rates of nucleophilic substitution reactions, (c) the contrast in solvent effects of water (HBD) and dimethyl sulfoxide (non-HBD) on the acidities of m- and p-substituted phenols, (d) partition coefficients of non-HBD solutes between solvent bilayers, and (e) family relationships between proton transfer (and non-protonic Lewis acid) basicities and corresponding β values for monomer HBA. A comprehensive summary of LSER with references is given.

Plasticity of hippocampal circuitry in Alzheimer's disease

Abstract: Two markers of neuronal plasticity were used to compare the response of the human central nervous system to neuronal loss resulting from Alzheimer's disease with the response of rats to a similar neuronal loss induced by lesions. In rats that had received lesions of the entorhinal cortex, axon sprouting of commissural and associational fibers into the denervated molecular layer of the dentate gyrus was paralleled by a spread in the distribution of tritiated kainic acid-binding sites. A similar expansion of kainic acid receptor distribution was observed in hippocampal samples obtained postmortem from patients with Alzheimer's disease. An enhancement of acetylcholinesterase activity in the dentate gyrus molecular layer, indicative of septal afferent sprouting, was also observed in those patients with a minimal loss of cholinergic neurons. These results are evidence that the central nervous system is capable of a plastic response in Alzheimer's disease. Adaptive growth responses occur along with the degenerative events.

The somatotopic organization of primary afferent terminals in the superficial laminae of the dorsal horn of the rat spinal cord.

Abstract: Transganglionic transport of wheatgerm agglutinin conjugated horse-radish peroxidase (WGA-HRP) was used to reveal the central distribution of terminals of primary afferent fibers from peripheral nerves innervating the hind leg of the rat. In separate experiments the sizes and locations of cutaneous peripheral receptive fields were determined by electrophysiological recording techniques for each of the nerves that had been labeled with WGA-HRP. By using digital image analysis, the sizes and positions of the peripheral receptive fields were correlated with the areas of superficial dorsal horn occupied by terminals of primary afferents from each of these receptive fields. Data were obtained from the posterior cutaneous nerve of the thigh, lateral sural, sural, saphenous, superficial peroneal, and tibial nerves. The subdivisions of the sciatic nerve, the sural, lateral sural, superficial peroneal, and tibial nerves each projected to a separate and distinct region of the superficial dorsal horn and collectively formed a "U"-shaped zone of terminal labeling extending from lumbar spinal segments L2 to the caudal portions of L5. The gap in the "U" extended from L2 to the L3-4 boundary and was occupied by terminals from the saphenous nerve. Collectively, all primary afferents supplying the hindlimb occupied the medial 3/4 of the superficial dorsal horn with terminals from the tibial nerve lying most medially and occupying the largest of all the terminal fields. Afferents from the superficial peroneal lay in a zone between the medially situated tibial zone and the more laterally placed sural zone. Afferents from the posterior cutaneous nerve were located most caudally and laterally. Terminal fields from the posterior cutaneous and saphenous nerves differed from the others in having split representations caused presumably by their proximity to the mid-axial line of the limb. Comparisons between the peripheral and the central representations of each nerve revealed that 1 mm2 of surface area of the superficial dorsal horn serves approximately 600-900 mm2 of hairy skin and roughly 300 mm2 of glabrous skin. The vast majority of terminal labeling observed in the dorsal horn was found in the marginal layer and substantia gelatinosa, suggesting that small diameter afferents have an orderly somatotopic arrangement in which each portion of the skin surface is innervated by afferent fibers that terminate in preferred localities within the dorsal horn.

A scatter plot for identifying stimulus control of problem behavior.

Abstract: Line graphs that average response frequency over long periods obscure the major rate changes that indicate sources of behavioral control. A scatter plot can make patterns of responding identifiable and, in turn, suggest environmental features that occasion undesirable behavior. Use of scatter diagrams is illustrated in three cases.

Strategic Management in Public and Private Organizations: Implications of Distinctive Contexts and Constraints

Abstract: Public and private sector strategic managers operate in different contexts that generate distinctive constraints on their behaviors and choices. Key constraints on public sector managers are identified in five propositions. Implications for the evaluation of public sector management and for the behavior of public managers are drawn. It is argued that application of private sector models to the public sector is problematic; that general models of strategic management are needed.

Mechanical Power output from Striated Muscle during Cyclic Contraction

Abstract: 1.The mechanical power output of a synchronous insect muscle was determined by measuring tension as the muscle was subjected to sinusoidal length change and stimuli which occurred at selected phases of the length cycle. The area of the loop formed by plotting muscle tension against length over a full cycle is the work done on that cycle; the work done times the cycle frequency is the mechanical power output. The muscle was a flight muscle of the tettigoniid Neoconocephalus triops . The measurements were made at the normal wing-stroke frequency for flight (25 Hz) and operating temperature (30°C). 2.The power output with a single stimulus per cycle, optimal excursion amplitude, and optimal stimulus phase was 1.52 J kg −1 cycle −1 or 37W kg −1 . The maximum power output occurs at a phase such that the onset of the twitch coincides with the onset of the shortening half of the length cycle. The optimum excursion amplitude was 5.5% rest length; with greater excursion, work output declined because of decreasing muscle force associated with the more rapid shortening velocity. 3.Multiple stimulation per cycle increases the power output above that available with twitch contractions. In this muscle, the maximum mechanical power output at 25 Hz was 76 W kg −1 which was achieved with three stimuli per cycle separated by 4-ms intervals and an excursion amplitude of 6.0% rest length. 4.The maximum work output during the shortening of an isotonic twitch contraction was about the same as the work done over a full sinusoidal shortening-lengthening cycle with a single stimulus per cycle and optimum excursion amplitude and phase.

Stress-induced recovery of fears and phobias.

Abstract: Accounts of human fears and phobias based on current conditioning models using data from adults are examined and found wanting. Instead, the characteristics of human phobias resemble the kind of learning found during the amnesic period of infancy. As certain neural systems mature, conditioning begins to exhibit adult characteristics: context dependency, sharp generalization, and rapid extinction. Although direct behavioral control by the early learning systems wanes, the adult learning system seems to be structured at least/partially through the lasting influence of infantile experience. Under (hormonal) stress, residues of early experience are reinstated and incorporated into adult memory where they directly control behavior. This control exhibits infantile characteristics. The evidence suggests that once acquired, such conditional fears might never be eliminated using traditional extinction or countercondit ioning procedures. The view leads to a renewed emphasis upon the role of experience in human development, accepting the disproportionate importance of infant experience as the foundation upon which subsequent learning and cognitive function rest. It is plain from clinical experience that certain patients experience critical incidents in which the fear has an onset. What is particularly interesting is the fact that quite frequently these same people have been exposed to the same stimulus repeatedly in the past without acquiring the fear. It seems that for acute onset fears, there are certain psychological states in which the person is vulnerable to the acquisition of fears. To take a clinical example, in those agoraphobic patients who report an acute onset of fear, one needs to know why the fear arose on the day that it did, at the time that it did. And why do they acquire a fear

The development, ultrastructure and synaptic connections of the mossy cells of the dentate gyrus.

Abstract: One of the most distinctive and common cell types in Golgi preparations of the hilus of the rat dentate gyrus is the mossy cell. We have used a variety of techniques including the Golgi method, the combined Golgi and electron microscopic (EM) method and the retrograde transport of horseradish peroxidase (HRP) to study the development, ultrastructure and synaptic connections of this cell type. The mossy cells identified in our light microscopic preparations are characterized by: triangular or multipolar shaped somata; three to four primary dendrites that arise from the soma and bifurcate once or more to produce an extensive dendritic arborization restricted, for the most part, to the hilus; numerous thorny excrescences on their somata and proximal dendrites with typical spines on distal dendrites; and axons that bifurcate and are directed toward the fimbria and the molecular layer of the dentate gyrus. The mossy cells have an immature appearance at birth and on subsequent days their maturation appears to lag somewhat behind that of the hippocampal pyramidal cells. On postnatal day 1, many of the dendrites bear growth cones primarily at their termini and have long, thin filipodia emanating from various points along their lengths. Many of the dendrites enter the molecular layer of the dentate gyrus, though this is rarely seen in the mature brain. Typical pedunculate spines are first commonly seen on the distal dendrites around postnatal day 7 while thorny excrescences are first commonly seen between postnatal days 11 and 14. By postnatal day 21, the dendrites have attained a mature appearance although the density of both typical spines and thorny excrescences is less than that found in adults. Two different retrograde transport methods were used to confirm that mossy cells give rise to the commissural projection to the contralateral dentate gyrus. The first method combined HRP histochemistry with a silver intensification procedure and the second method combined HRP histochemistry with Golgi staining. While the majority of commissurally projecting hilar neurons had the appearance of mossy cells, there were others that were smaller and either ovoid or fusiform. In EM preparations, the somata of mature mossy cells display round nuclei that lack infoldings and intranuclear rods. The perikaryal cytoplasm contains the organelles typically found in pyramidal cells of the hippocampus. Somal spines with complex shapes and branching patterns are commonly observed. The thorny excrescences on the proximal dendrites correspond to spines with long thin stalks and complex end bulbs that may appear mushroom shaped.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence for adrenocortical adaptation to severe illness.

Abstract: During serious illness, there are characteristic increases in serum cortisol concentrations and urinary cortisol excretion. In the present studies, we investigated these changes i n glucocorticoid metabolism in relation to adrenal androgen metabolism, as measured by RIA of dehydroepiandrosterone (DHA) and DHA sulfate (DHAS). A group of 23 seriously ill men with various disorders, ill for a week or longer, was age-matched to a control group of 25 men, and the following changes were found: 1) basal serum cortisol concentrations were elevated n i the ill group (P < 0.001), 2) basal serum DHA and DHAS concentrations tended to be lower in the ill group (P < 0.1); 3) basal serum DHA to cortisol and DHAS to cortisol ratios were decreased in the ill group by 80.3‰ and 77.2‰, respectively (P < 0.001); 4) ACTH-stimulated serum cortisol concentrations increased by the same absolute amount in both groups, whereas the increase in stimulated DHA concentrations in the ill group was 57.2‰ less (P < 0.05), indicating a de...

Experimental tests of the gravitational inverse-square law for mass separations from 2 to 105 cm.

Abstract: We report two experiments which test the inverse-square distance dependence of the Newtonian gravitational force law. One experiment uses a torsion balance consisting of a 60-cm-long copper bar suspended at its midpoint by a tungsten wire, to compare the torque produced by copper masses 105 cm from the balance axis with the torque produced by a copper mass 5 cm from the side of the balance bar, near its end. Defining ${R}_{\mathrm{expt}}$ to be the measured ratio of the torques due to the masses at 105 cm and 5 cm, and ${R}_{\mathrm{Newton}}$ to be the corresponding ratio computed assuming an inverse-square force law, we find \ensuremath{\delta}\ensuremath{\equiv}(${R}_{\mathrm{expt}}$/${R}_{\mathrm{Newton}}$-1)=(1.2 \ifmmode\pm\else\textpm\fi{}7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. Assuming a force deviating from an inverse-square distance dependence by a factor [1+\ensuremath{\epsilon} lnr(cm)], this result implies \ensuremath{\epsilon}=(0.5 \ifmmode\pm\else\textpm\fi{}2.7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. An earlier experiment, which has been reported previously, is described here in detail. This experiment tested the inverse-square law over a distance range of approximately 2 to 5 cm, by probing the gravitational field inside a steel mass tube using a copper test mass suspended from the end of a torsion balance bar. This experiment yielded a value for the parameter \ensuremath{\epsilon} defined above: \ensuremath{\epsilon}=(1\ifmmode\pm\else\textpm\fi{}7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$. The results of both of these experiments are in good agreement with the Newton- ian prediction. Limits on the strength and range of a Yukawa potential term superimposed on the Newtonian gravitational potential are discussed.

Structure and Transcription of Eukaryotic tRNA Genes

Abstract: (1985). Structure and Transcription of Eukaryotic tRNA Gene. Critical Reviews in Biochemistry: Vol. 19, No. 2, pp. 107-144.

A model of complex travel behavior: part i. theoretical development

Abstract: This paper presents a policy sensitive approach to modeling travel behavior based on activity pattern analysis. A theoretical model of complex travel behavior is formulated on a recognition of a wide range of interdependencies associated with an individual's travel decisions in a constrained environment. Travel is viewed as input to a more basic process involving activity decisions. A fundamental tenet of this approach is that travel decisions are driven by the collection of activities that form an agenda for participation; the utility of any specific travel decision can be determined only within the context of the entire agenda. Based on the theoretical model of complex travel behavior, an operational system of models, STARCHILD (Simulation of Travel/Activity Responses to Complex Household Interactive Logistic Decisions), has been developed to examine the formation of household travel/activity patterns, and is presented in a companion paper (Recker et al, 1985).

Hormones and growth factors induce the synthesis of glial fibrillary acidic protein in rat brain astrocytes.

Abstract: Glial fibrillary acidic protein (GFAP) is the major constituent of glial filaments and is restricted within the CNS to astrocytes. As with other classes of intermediate filament proteins, the regulation of GFAP expression is poorly understood. Utilizing highly purified cultures of astrocytes and a chemically defined (CD) medium, we have demonstrated that the expression of GFAP is subject to regulation by hormones and growth factors. The concentration of GFAP/mg protein was induced 2-4-fold in the presence of hydrocortisone, putrescine, prostaglandin F-2 alpha (PGF2 alpha), and pituitary fibroblast growth factor (FGF). Augmentation of the levels of GFAP continued for up to 3 weeks after conversion to CD medium and paralleled the morphological maturation of astrocytes. The accumulation of GFAP resulted from an increase in its specific rate of synthesis. Conversion of astrocytes from serum-supplemented (SS) to CD medium did not alter its rate of degradation. GFAP appeared quite stable under both sets of conditions, exhibiting a half-life of approximately 7.5 days. The data demonstrate that GFAP expression in astrocytes is subject to hormonal regulation, which may have implications for gliosis.

Localization effects in the scattering of light from a randomly rough grating

Abstract: We calculate the resonant scattering of p-polarized light incident on a randomly rough grating ruled on a medium characterized by a dielectric constant \ensuremath{\epsilon}(\ensuremath{\omega})=${\ensuremath{\epsilon}}_{1}$(\ensuremath{\omega})+i${\ensuremath{\epsilon}}_{2}$(\ensuremath{\omega}), where ${\ensuremath{\epsilon}}_{1}$(\ensuremath{\omega})-1 and \ensuremath{\Vert}${\ensuremath{\epsilon}}_{2}$(\ensuremath{\omega})\ensuremath{\Vert}\ensuremath{\ll}\ensuremath{\Vert}${\ensuremath{\epsilon}}_{1}$(\ensuremath{\omega})\ensuremath{\Vert}. Particular emphasis is placed on determining the contribution to the scattering that arises from the localization of surface polaritons due to the surface roughness. This localization is found to contribute a maximum to the angular dependence of the intensity of the nonspecularly reflected light in the antispecular direction.

Adding range restriction capability to dynamic data structures

Abstract: A database is said to allow range restrictions if one may request that only records with some specified field in a specified range be considered when answering a given query. A transformation is presented that enables range restrictions to be added to an arbitrary dynamic data structure on n elements, provided that the problem satisfies a certain decomposability condition and that one is willing to allow increases by a factor of O(log n) in the worst-case time for an operation and in the space used. This is a generalization of a known transformation that works for static structures. This transformation is then used to produce a data structure for range queries in k dimensions with worst-case times of O(logk n) for each insertion, deletion, or query operation.

Effects of age on the p300 component of the event-related potential from auditory-stimuli - peak definition, variation, and measurement

Abstract: An auditory "oddball" paradigm was used to elicit the P300 component of the event-related brain potential (ERP) from a large sample of young (5 to 15 years) and older (20 to 86 years) persons. Distinct P3a and P3b subcomponents of the P300 were observed within individuals and across trial blocks. Age affected P300 latency in a similar fashion for both subcomponents with latency increasing about 65 msec between 20 and 70 years. P300 latency variability also was found to increase somewhat with advanced age. These results confirmed previous age-related ERP changes and extended them to the P3a and P3b subcomponents.

Explaining the Symptomatology of Separated and Divorced Women and Men: The Role of Material Conditions and Social Networks

Abstract: Past research consistently finds that marital dissolution is associated with psychological distress. In this paper, we propose that the explanation for this association varies by gender. Specifically, we hypothesize that it is material conditions (income and parental obligations) that are most important in accounting for the greater symptomatology of separated and divorced women while it is dimensions of social networks (both structural and experiential) that are more important in accounting for the symptomatology of separated and divorced men. Our analyses largely support the hypotheses. Our findings suggest that marriage protects men and zwmen in very different ways. Researchers consistently find that marital dissolution is associated with psychological distress (Bachrach; Bloom et al.; Riessman and Gerstel). Compared with the married, the separated and divorced-both male and female-have higher rates of mental health symptoms as well as admission to psychiatric hospitals and outpatient clinics (Briscoe et al.; Radloff; Redick and Johnson; Somers; Warheit et al.). In this sense, marriage is protective of mental health. Various explanations have been offered for the relationship between separation and divorce and psychiatric symptoms. In general, two

The Concept of “Coalition” in Organization Theory and Research

Abstract: This paper provides an historical review of coalitions in organizations and presents key issues that must be confronted if research on coalitions is to contribute to an understanding of intraorganizational dynamics. Included are: an explicit definition of a coalition within an organization, consideration of how the organizational context differs from the contexts of previous coalition research, a specification of the process that leads to coalitions, and a discussion of the impact of coalitions.

Postnatal enlargement of human tracheobronchial airways and implications for particle deposition

Abstract: In support of predictions for inhaled particle deposition, morphometric measurements were taken on 20 replica airway casts of people aged 11 days to 21 years. Measurements of right upper lobe airway lengths, diameters, and branching angles were made such that a growth model suitable as input to predictive equations for particle deposition efficiency was obtained. The tracheobronchial airways growth was describable by linear regressions on body length. The length-to-diameter ratio of growing airways did not change in any simple way as a function of airway generation. Airflow rates for a given state of physical activity for various ages were found from previously published data to be describable by linear regressions on body mass. Three states of physical exertion-low activity, light exertion, and heavy exertion-were used for modeling purposes. The computed particle deposition efficiencies indicate that under most circumstances smaller (younger) people will have greater tracheobronchial deposition efficiencies than larger (older) people. For example, tracheobronchial dose on a per kilogram body mass basis for 5-micron-diameter particles may be more than 6 times higher in the resting newborn than in the resting adult assuming equivalent deposition efficiencies above the larynx.

Role of Alternaria and Penicillium spores in the pathogenesis of asthma.

Abstract: The ability to harvest spore-rich isolates of molds permitted quantitative studies of their role in the pathogenesis of asthma. Alternaria and Penicillium were selected as examples of ubiquitous molds that readily induce IgE antibodies and are of contrasting sizes. Extracts from those spores were prepared for skin tests and aerosol bronchial challenges. Intact spores were used in the same subjects in bronchial challenges delivered by a Spinhaler. Seven patients with a history of mild asthma received a total of 16 bronchial challenges with the mold to which they had been sensitized. Provocative doses in spore equivalents for a 35% drop in SG aw , 20% drop in FEV 1 , or 25% drop in PEER were sought for each challenge. Density dependence-flow rates were also determined. Environmental spore survey data were obtained and compared with the challenge doses for these spores. It was found that (1) immediate-type asthma was readily provoked by both whole spores and by their extracts, (2) in some subjects fewer intact than extracted spores were required, (3) delayed-type asthma occurred only after whole spore challenges, (4) SG aw was the most sensitive and equally specific of the pulmonary function tests, and (5) provocative doses of spore equivalents were within natural exposure ranges. The study confirmed that Alternaria and Penicillium spores in relatively natural states and numbers were potent immunopathogens for asthma.