Showing papers by "Drexel University published in 1996"
TL;DR: In this paper, a polycrystalline bulk sample of Ti sub 3, SiC sub 2 was fabricated by reactively hot-pressing Ti, graphite, and SiC powders at 40 MPa and 1,600 C for 4 h.
Abstract: Polycrystalline bulk samples of Ti{sub 3}SiC{sub 2} were fabricated by reactively hot-pressing Ti, graphite, and SiC powders at 40 MPa and 1,600 C for 4 h. This compound has remarkable properties. Its compressive strength, measured at room temperature, was 600 MPa, and dropped to 260 MPa at 1,300 C in air. Although the room-temperature failure was brittle, the high-temperature load-displacement curve shows significant plastic behavior. The oxidation is parabolic and at 1,000 and 1,400 C the parabolic rate constants were, respectively, 2 {times} 10{sup {minus}8} and 2 {times} 10{sup {minus}5} kg{sup 2}{center_dot}m{sup {minus}4}{center_dot}s{sup {minus}1}. The activation energy for oxidation is thus {approx}300 kJ/mol. The room-temperature electrical conductivity is 4.5 {times} 10{sup 6} {Omega}{sup {minus}1}{center_dot}m{sup {minus}1}, roughly twice that of pure Ti. The thermal expansion coefficient in the temperature range 25 to 1,000 C, the room-temperature thermal conductivity, and the heat capacity are respectively, 10 {times} 10{sup {minus}6} C{sup {minus}1}, 43 W/(m{center_dot}K), and 588 J/(kg{center_dot}K). With a hardness of 4 GPa and a Young`s modulus of 320 GPa, it is relatively soft, but reasonably stiff. Furthermore, Ti{sub 3}SiC{sub 2} does not appear to be susceptible to thermal shock; quenching from 1,400 C into water does not affect the postquench bend strength.more » As significantly, this compound is as readily machinable as graphite. Scanning electron microscopy of polished and fractured surfaces leaves little doubt as to its layered nature.« less
1,491 citations
TL;DR: In this article, the authors examined the influence of work and family variables on the career success and psychological well-being of 111 men and women entrepreneurs and found that work domain variables account for significant variation in time commitment to work, whereas family-domain variables explain substantial variation in times commitment to family.
767 citations
Book•
29 Oct 1996TL;DR: In this paper, the Gibbs-Duhem relation for binary oxides has been used to derive a Gibbs-Thompson equation for the relationship between Fick's First Law and Eq.
Abstract: INTRODUCTION Introduction Definition of Ceramics Elementary Crystallography Ceramic Microstructures Traditional Versus Advanced Ceramics General Characteristics of Ceramics Applications The Future BONDING IN CERAMICS Introduction Structure of Atoms Ionic versus Covalent Bonding Ionic Bonding Ionically Bonded Solids Covalent Bond Formation Covalently Bonded Solids Band Theory of Solids Summary Appendix 2A: Kinetic Energy of Free Electrons STRUCTURE OF CERAMICS Introduction Ceramic Structures Binary Ionic Compounds Composite Crystal Structures Structure of Covalent Ceramics Structure of Silicates Lattice Parameters and Density Summary Appendix 3A: Ionic Radii EFFECT OF CHEMICAL FORCES ON PHYSICAL PROPERTIES Introduction Melting Points Thermal Expansion Young's Modulus and the Strength of Perfect Solids Surface Energy Summary THERMODYNAMIC AND KINETIC CONSIDERATIONS Introduction Free Energy Chemical Equilibrium and the Mass Action Expression Chemical Stability Domains Electrochemical Potentials Charged Interfaces, Double Layers, and Debye Lengths Gibbs-Duhem Relation for Binary Oxides Kinetic Considerations Summary Appendix 5A: Derivation of Eq. (5.27) DEFECTS IN CERAMICS Introduction Point Defects Linear Defects Planar Defects Summary DIFFUSION AND ELECTRICAL CONDUCTIVITY Introduction Diffusion Electrical Conductivity Ambipolar Diffusion Relationships between Self-, Tracer, Chemical, Ambipolar, and Defect Diffusion Coefficients Summary Appendix 7A: Relationship between Fick's First Law and Eq. (7.30) Appendix 7B: Effective Mass and Density of States Appendix 7C: Derivation of Eq. (7.79) Appendix 7D: Derivation of Eq. (7.92) PHASE EQUILIBRIA Introduction Phase Rule One-Component Systems Binary Systems Ternary Systems Free-Energy Composition and Temperature Diagrams Summary FORMATION, STRUCTURE, AND PROPERTIES OF GLASSES Introduction Glass Formation Glass Structure Glass Properties Glass-Ceramics Summary Appendix 9A: Derivation of Eq. (9.7) SINTERING AND GRAIN GROWTH Introduction Solid-State Sintering Liquid-Phase Sintering Hot Pressing and Hot Isostatic Pressing Summary Appendix 10A: Derivation of the Gibbs-Thompson Equation Appendix 10B: Radii of Curvature Appendix 10C: Derivation of Eq. (10.20) Appendix 10D: Derivation of Eq. (10.22) MECHANICAL PROPERTIES: FAST FRACTURE Introduction Fracture Toughness Strength of Ceramics Toughening Mechanisms Designing with Ceramics Summary CREEP, SUBCRITICAL CRACK GROWTH, AND FATIGUE Introduction Creep Subcritical Crack Growth Fatigue of Ceramics Lifetime Predictions Summary Appendix 12A: Derivation of Eq. (12.24) THERMAL PROPERTIES Introduction Thermal Stresses Thermal Shock Spontaneous Microcracking of Ceramics Thermal Tempering of Glass Thermal Conductivity Summary DIELECTRIC PROPERTIES Introduction Basic Theory Equivalent Circuit Description of Linear Dielectrics Polarization Mechanisms Dielectric Loss Dielectric Breakdown Capacitors and Insulators Summary Appendix 14A: Local Electric Field MAGNETIC AND NONLINEAR DIELECTRIC PROPERTIES Introduction Basic Theory Microscopic Theory Para-, Ferro-, Antiferro-, and Ferrimagnetism Magnetic Domains and the Hysteresis Curve Magnetic Ceramics and their Applications Piezo- and Ferroelectric Ceramics Summary Appendix 15A: Orbital Magnetic Quantum Number OPTICAL PROPERTIES Introduction Basic Principles Absorption and Transmission Scattering and Opacity Fiber Optics and Optical Communication Summary Appendix 16A: Coherence Appendix 16B: Assumptions Made in Deriving Eq. (16.24) INDEX *Each chapter contains Problems and Additional Reading.
728 citations
TL;DR: It seems that cyclodextrin molecules are substantially more efficient than phospholipid acceptors, because cholesterol molecules desorbing from a membrane surface can diffuse directly into the hydrophobic core of a cyclodeXTrin molecule without having to desorb completely into the aqueous phase before being sequestered by the acceptor.
553 citations
TL;DR: Preliminary evidence is provided for the effectiveness of a specific cognitive-behavioral treatment model for sexually abused preschool children and their parents in CBT-SAP over NST.
Abstract: Objective Treatment outcome for sexually abused preschool-age children and their parents was assessed, comparing the effectiveness of a cognitive-behavioral intervention to nondirective supportive treatment. Method Sixty-seven sexually abused preschool children and their parents were randomly assigned to either (1) cognitive-behavioral therapy adapted for sexually abused preschool children (CBT-SAP) or (2) nondirective supportive therapy (NST). Treatment consisted of 12 individual sessions for both the child and parent, monitored for integrity with the therapeutic model through intensive training and supervision, use of treatment manuals, and rating of audio taped sessions. Parents completed the Child Behavior Checklist, the Child Sexual Behavior Inventory, and the Weekly Behavior Report to measure a variety of emotional and behavioral symptoms. Results Within-group comparison of pretreatment and posttreatment outcome measures demonstrated that while the NST group did not change significantly with regard to symptomatology, the CBT-SAP group had highly significant symptomatic improvement on most outcome measures. Repeated-measures analyses of variance demonstrated group × time interactions on some variables as well. Clinical findings also supported the effectiveness of the CBT-SAP intervention over NST. Conclusions Findings provide strong preliminary evidence for the effectiveness of a specific cognitive-behavioral treatment model for sexually abused preschool children and their parents.
507 citations
TL;DR: Reduction in cost estimates for social events, but not in probability estimates, mediated improvement in social phobia, discussed in light of emotional processing theory.
Abstract: Judgmental biases for threat-relevant stimuli are thought to be important mechanisms underlying the etiology and maintenance of anxiety disorders. The authors hypothesized (a) that people with generalized social phobia (GSP) would rate negative social events but not nonsocial events as more probable and costly than would nonanxious controls (NACs) and (b) that cognitive behavioral treatment would decrease probability and cost estimates for social but not nonsocial events. Participants with GSP and NACs were assessed twice, 14 weeks apart, during which the former received cognitive behavioral therapy. Those with GSP evidenced socially relevant judgmental biases prior to treatment, and these were attenuated following treatment. Reduction in cost estimates for social events, but not in probability estimates, mediated improvement in social phobia. Results are discussed in light of emotional processing theory.
399 citations
TL;DR: The purpose of this article was to define those groups of individuals who would be at the greatest risk of serious illness and mortality from water and foodborne enteric microorganisms, which were found to include the very young, the elderly, pregnant women, and the immunocompromised.
382 citations
TL;DR: Whether chronic, medicated schizophrenia patients show deficits in emotion recognition compared to nonpatients, and whether deficits in emotions recognition are related to poorer social competence are evaluated, are evaluated.
Abstract: This study evaluated (a) whether chronic, medicated schizophrenia patients show deficits in emotion recognition compared to nonpatients, and (b) whether deficits in emotion recognition are related to poorer social competence. Two emotion recognition tests developed by S. L. Kerr and J. M. Neale ( 1993 ) and Benton's Test of Facial Recognition ( A. Benton, M. VanAllen, K. Hamsher, & H. Levin, 1978) were given to patients with chronic schizophrenia and nonpatient controls. Patients' social skills, social adjustment, and symptomatology were assessed. Like Kerr and Neale's unmedicated patients, these patients performed worse than controls on both emotion recognition tests and the control test. For patients, facial perception was related to the chronicity of illness and social competence. Chronicity of illness may contribute to face perception deficits in schizophrenia, which may affect social competence. Recent research has evaluated whether schizophrenia patients have impairments in emotion recognition. The findings have been inconsistent: some studies reported differences (Kerr & Neale, 1993), but others did not (Novic, Luchins, & Perline, 1984). Discrepant findings may be partly due to the variety of methods used to study emotion recognition, which has made it impossible to compare the results across different studies. Also, many measures have been developed for a single study, with little attention given to their psychometric properties and cross-validation. An exception to this problem is a set of instruments recently developed by Kerr and Neale (1993) for the assessment of emotion recognition in schizophrenia patients: The Face Emotion Identification Test, the Face Emotion Discrimination Test, the Voice Emotion Identification Test, and the Voice Emotion Discrimina
345 citations
TL;DR: Re-examination of single channel EEG data obtained from normal human subjects suggests that the previous indication of low-dimensional structure was an artifact of autocorrelation in the oversampled signal, and discriminatory analysis indicates that the correlation dimension is a poor discriminator for distinguishing between EEGs recorded at rest and during periods of cognitive activity.
302 citations
TL;DR: The dendritic localization of trkB receptors supports the hypothesis that dendrites, as well as axons, are important sites for neurotrophin actions in the central nervous system.
Abstract: The neurotrophins brain-derived neurotrophic factor (BDNF) and NT-4/5 exert their trophic effects on the nervous system via signaling through trkB receptors. These receptors occur as splice variants of the trkB gene that encodes a full-length receptor containing the signal transducing tyrosine kinase domain as well as truncated forms lacking this domain. Because the importance of the trkB isoforms for development and maturation of the nervous system is unknown, we have examined the expression of trkB receptor isoforms during development of the rat forebrain using 1) a sensitive ribonuclease protection assay to distinguish full-length and truncated trkB transcripts, 2) western blot analysis to characterize developmental changes in trkB proteins, and 3) immunohistochemistry to determine the cellular localization of trkB receptors. In the rat forebrain, adult mRNA levels for full-length trkB are reached by birth, whereas truncated trkB message does not peak until postnatal days 10-15. Western blot analysis indicates that full-length trkB protein is the major form during early development, whereas truncated trkB protein predominates in all forebrain regions of late postnatal and adult rats. These data also suggest that the glycosylation state of these receptors changes during postnatal maturation. TrkB immunoreactivity is present predominately within neurons, where it is localized to axons, cell soma, and dendrites. Strong dendritic immunostaining is particularly evident in certain neuronal populations, such as pyramidal neurons in the hippocampus and in layer V of the neocortex. The dendritic localization of trkB receptors supports the hypothesis that dendrites, as well as axons, are important sites for neurotrophin actions in the central nervous system.
285 citations
TL;DR: Treatment with AHAs produced significant reversal of epidermal and dermalmarkers of photoaging and papillary dermal changes included increased thickness, increased acid mucopolysaccharides, improved quality of elastic fibers, and increased density of collagen.
Abstract: Background : α-Hydroxy acids (AHAs) have been reported to improve aging skin. The mechanisms of action of AHAs on epidermal and dermal compartments need clarification. Objective : Our purpose was to determine the effects of AHAs on photoaged human skin by clinical and microanalytic means. Methods : Patients applied a lotion containing 25% glycolic, lactic, or citric acid to one forearmand a placebo lotion to the opposite forearm for an average of 6 months. Thickness of forearm skin was measured throughout the study. Biopsy specimens from both forearms were processed for analysis at the end of the study. Results : Treatment with AHAs caused an approximate 25% increase in skin thickness. The epidermis was thicker and papillary dermal changes included increased thickness, increased acid mucopolysaccharides, improved quality of elastic fibers, and increased density of collagen. No inflammation was evident. Conclusion : Treatment with AHAs produced significant reversal of epidermal and dermalmarkers of photoaging.
TL;DR: It is proposed that tau in growing axons has functions other than promoting microtubule assembly and stability and that key sites for these functions are the distal axon and growth cone.
Abstract: It is widely held that tau determines the stability of microtubules in growing axons, although direct evidence supporting this hypothesis is lacking. Previous studies have shown that the microtubule polymer in the distal axon and growth cone is the most dynamic of growing axons; it turns over more rapidly and is more sensitive to microtubule depolymerizing drugs than the polymer situated proximally. We reasoned that if the stability of axonal microtubules is directly related to their content of tau, then the polymer in the distal axon should have less tau than the polymer in the proximal axon. We tested this proposition by measuring the relative tau content of microtubules along growing axons of cultured sympathetic neurons immunostained for tau and tubulin. Our results show that the tau content of microtubules varies along the axon, but in the opposite way predicted. Specifically, the relative tau content of microtubules increases progressively along the axon to reach a peak near the growth cone that is severalfold greater than that observed proximally. Thus, tau is most enriched on the most dynamic polymer of the axon. We also show that the gradient in tau content of microtubules does not generate corresponding gradients in the extent of tubulin assembly or in the sensitivity of axonal microtubules to nocodazole. On the basis of these findings, we propose that tau in growing axons has functions other than promoting microtubule assembly and stability and that key sites for these functions are the distal axon and growth cone.
TL;DR: It was found that loud snoring, observed apneas, and daytime sleepiness are not associated cross-sectionally with hypertension or prevalent CVD in elderly persons.
Abstract: The objectives of this study were to describe the prevalence of snoring, observed apneas, and daytime sleepiness in older men and women, and to describe the relationships of these sleep disturbances to health status and cardiovascular diseases (CVD). A cross-sectional design was employed to study sleep problems, CVD, general health, psychosocial factors, and medication use. The subjects were participants in the Cardiovascular Health Study, which included 5,201 adults, aged 65 and older, who were recruited from a random sample of Medicare enrollees in four U.S. communities. Study measures employed were sleep questions, echocardiography, carotid ultrasound, resting electrocardiogram, cognitive function, cardiopulmonary symptoms and diseases, depression, independent activities of daily living (IADLs), and benzodiazepine use. Thirty-three percent of the men and 19% of the women reported loud snoring, which was less frequent in those over age 75. Snoring was positively associated with younger age, marital status, and alcohol use in men, and obesity, diabetes, and arthritis in women. Snoring was not associated, however, with cardiovascular risk factors or clinical CVD in men or women. Observed apneas were reported much less frequently (13% of men and 4% of women) than snoring, and they were associated with alcohol use, chronic bronchitis, and marital status in men. Observed apneas were associated with depression and diabetes in women. In both men and women, daytime sleepiness was associated with poor health, advanced age, and IADL limitations. The conclusions of the study were that loud snoring, observed apneas, and daytime sleepiness are not associated cross-sectionally with hypertension or prevalent CVD in elderly persons.
TL;DR: Three‐dimensional magnetization transfer imaging was used to estimate the global burden of disease in large volumes of brain tissue and suggests that in MS, volumetric MTI provides quantitative information reflecting the globalurden of disease.
Abstract: Magnetization transfer imaging (MTI) has been shown to be sensitive to both macroscopic and microscopic disease in multiple sclerosis (MS). In this study three-dimensional MTI was used to estimate the global burden of disease in large volumes of brain tissue. MTI was performed in 15 MS patients and 11 normal controls. In seven MS patients MTI was performed on two different occasions. MTI data were displayed as magnetization transfer ratio (MTR) histograms and analyzed. The peak height of the histograms, presumably reflecting the residual amount of normal brain tissue, was lower in MS patients as compared with normal controls (P < 0.001), and was found to correlate with the duration of disease (P < 0.05). A decrease of the MTR histogram peak height was observed in the course of the disease (P < 0.01). These findings suggest that in MS, volumetric MTI provides quantitative information reflecting the global burden of disease.
TL;DR: Although the LC is not typically considered in the context of emotion, the analysis suggests that the LC system could play an important role in the process of emotional activation.
Abstract: Publisher Summary This chapter discusses recent studies of the noradrenergic locus coeruleus (LC) system to consider its possible roles in emotion. It describes the recent studies of the effects of manipulating LC neurons on electroencephalographic (EEG) activity and attentional behavior. Emotional responses are typically measured by EEG or autonomic arousal. Emotionally arousing stimuli produce activation of the cortical EEG, and parallel activation of autonomic measures such as blood pressure, heart rate, or galvanic skin response (as commonly used in lie detector tests). Recent results link the LC both to the EEG and autonomic responses that accompany emotionally arousing events LC neuronal projections, effects of NE on LC target cells, and discharge characteristics of LC neurons in unanesthetized, unconditioned animals are reviewed. More recent studies on the effects of stress on LC neurons, and on activity of LC neurons in behaving monkeys during a conditioned attentional task are also examined. The chapter reviews new findings on afferents to the LC that indicate the status of this key noradrenergic system in brain circuitry. Although the LC is not typically considered in the context of emotion, the analysis suggests that the LC system could play an important role in the process of emotional activation.
TL;DR: A strong correlation between parental emotional distress related to the abuse and treatment outcome in sexually abused preschool children, independent of the type of treatment provided is indicated.
Abstract: Objective The role of demographic, developmental, and familial mediating factors on treatment outcome of sexually abused preschool children was evaluated. Method Sixty-seven sexually abused preschool children and their parents were evaluated shortly after disclosure of sexual abuse and then were provided with one of two treatment interventions. At the completion of treatment, the parents and their children were reevaluated. Parents completed the Child Behavior Checklist, the Child Sexual Behavior Inventory, and the Weekly Behavior Report to measure a variety of emotional and behavioral symptoms in children. Parents also completed the Beck Depression Inventory, the Family Adaptability and Cohesion Evaluation Scale-III, the Parent Emotional Reaction Questionnaire, the Parental Support Questionnaire, and the Maternal Social Support Index. Children completed the Preschool Symptom Self-Report to assess self-reported affective symptoms and the Battelle Developmental Inventory and the Peabody Picture Vocabulary Test to assess developmental level. Results Correlational analyses were conducted to analyze the relationships between the hypothesized mediating variables and the outcome measures at posttreatment across the two treatment groups. Multiple regression analyses were also performed. Both parental depression and parental emotional distress correlated significantly with several of the child outcome measures. Battelle scores were significantly negatively correlated with several outcome measures. Multiple regression analyses demonstrated that the Parent Emotional Reaction Questionnaire remained a highly significant predictor of treatment outcome. Conclusions The findings indicate a strong correlation between parental emotional distress related to the abuse and treatment outcome in sexually abused preschool children, independent of the type of treatment provided. The findings indicate the importance of addressing parental distress related to the abuse in providing effective treatment to sexually abused preschool children.
TL;DR: It is suggested that one of the most important aspects of a primary care physician's care of female patients is to screen for and treat common mental disorders, and the HRQL scores were poorer in women than men, although most of this difference was accounted for by the difference in prevalence of mental disorders.
TL;DR: The basal activation of the Jak/STAT pathway involved in IL-2R signal transduction in ALCL and SzS cells reported here suggests that this pathway may play a role in the pathogenesis of cutaneous T-cell lymphomas, although the mechanism (induced versus constitutive) may vary between different lymphoma types.
Abstract: Signaling through the interleukin 2 receptor (IL-2R) involves phosphorylation of several proteins including Jak3, STAT5, and, in preactivated cells, STAT3. In the present study, we examined the functional status of the IL-2R-associated Jak/STAT pathway in malignant T lymphocytes from advanced skin-based lymphomas: anaplastic large T-cell lymphoma (ALCL) and Sezary syndrome (SzS). Proliferation of three ALCL cell lines (PB-1, 2A, and 2B) was partially inhibited by rapamycin, a blocker of some of the signals mediated by IL-2R, but not by cyclosporin A, FK-506, and prednisone, which suppress signals mediated by the T-cell receptor. All the cell lines expressed on their surface the high-affinity IL-2R (alpha, beta, and gamma c chains). They showed basal, constitutive phosphorylation, and coassociation of Jak3, STAT5, and STAT3. Weak basal phosphorylation of IL-2R gamma c was also detected. In regard to SzS, peripheral blood mononuclear cells from 10 of 14 patients showed basal phosphorylation of Jak3, accompanied by phosphorylation of STAT5 in 9 patients, and STAT3 in 4 patients. However, in vitro overnight culture of SzS cells without exogenous cytokines resulted in markedly decreased Jak3 and STAT5 phosphorylation, which could be reversed by stimulation with IL-2. This indicates that the basal phosphorylation of Jak3 and STAT5 in freshly isolated SzS cells is induced rather than constitutive. The basal activation of the Jak/STAT pathway involved in IL-2R signal transduction in ALCL and SzS cells reported here suggests that this pathway may play a role in the pathogenesis of cutaneous T-cell lymphomas, although the mechanism (induced versus constitutive) may vary between different lymphoma types.
TL;DR: This first report from a longitudinal study of 84 lesbian families, 70 of which include a co-mother as well as a birthmother whose child was conceived by donor insemination, presents interview data on parental relationships, social supports, pregnancy motives and preferences, stigmatization concerns, and coping strategies.
Abstract: This first report from a longitudinal study of 84 lesbian families, 70 of which include a co-mother as well as a birthmother whose child was conceived by donor insemination, presents interview data on parental relationships, social supports, pregnancy motives and preferences, stigmatization concerns, and coping strategies. Methodological limitations of studying this special population are noted, and plans for follow-up interviews over the course of 25 years are outlined.
TL;DR: In this article, the problem of a piezoelectric body with an elliptic cavity is revisited within the frame-work of two-dimensional electro-elasticity.
TL;DR: It is suggested that the observed disorder is due to phosphorylation-induced increased mobility and/or changed conformation of myosin heads, which places an increased population of them close to thin filaments, thereby potentiating actin-myosin interaction at low calcium levels.
TL;DR: In this article, resource-based physiology of the eight important planktonic diatom species in the large lakes of the Yellowstone region can be used to explain their relative abundances and seasonal changes.
Abstract: Resource-based physiology of the eight important planktonic diatom species in the large lakes of the Yellowstone region can be used to explain their relative abundances and seasonal changes. The diatoms are ranked along resource ratio gradients according to their relative abilities to grow under limitation by Si, N, P, and light. Hypotheses based on resource physiology can be integrated with observations on seasonal changes in diatom assemblages to explain the present distributions of diatoms and to test the causal factors proposed to explain diatom distributions over the Holocene. Knowledge of the limnology of these lakes and process-oriented physiology provide the basis for a more detailed interpretation of the paleorecord and a firmer basis for landscape-level transfer functions for fine-scale climate reconstruction.
01 Jan 1996
TL;DR: The diagnosis of posttraumatic stress disorder (PTSD) is made when posttrauma symptoms occur in three domains: emotional, cognitive, and visual re-experiencing of the trauma; avoidance of trauma-relevant stimuli; and general arousal as mentioned in this paper.
Abstract: Pathological reactions to trauma and extreme stress have been noted in the psychological literature for over a century. These reactions were codified in the psychiatric literature as posttraumatic stress disorder (PTSD) (American Psychiatric Association, 1980). The diagnosis of PTSD is made when posttrauma symptoms occur in three domains: emotional, cognitive, and visual reexperiencing of the trauma; avoidance of trauma-relevant stimuli; and general arousal. Since the inception of PTSD as a diagnostic entity, experts have focused on the fear and anxiety components of the disorder (Foa, Steketee, & Rothbaum, 1989; Keane, Zimering, & Caddell, 1985). More recently, trauma researchers have become interested in the phenomenon of affective and cognitive avoidance that is commonly observed following a trauma and has been referred to as dissociation (e.g., Spiegel, Hunt, & Dondershine, 1988), denial (Horowitz, 1986; van der Kolk, 1987), or numbing (e.g., Foa, Riggs, & Gershuny, 1995; Horowitz, Wilner, Kaltreider, & Alvarez, 1980; Litz, 1993; van der Kolk & Ducey, 1989). Common to these constructs is a diminished awareness of one’s emotions or thoughts, which is hypothesized to be motivated by self-preservation.
TL;DR: Analysis indicates that significant risks of disease could result for drinking and recreational waters in which rotavirus has been detected, and the major limitation in assessing the risks of waterborne rotaviral infections at present is the lack of data on its occurrence in water and the potential for human exposure.
TL;DR: Previous proteolysis experiments coupled with the present DSC results suggest that the lipid-associating domains of apo A-I are distributed throughout the length of the 243 amino acid residues, and it is proposed that the terminal amphipathic helical domains are involved in the initial binding of api A- I to the lipid surface to form HDL particles.
Abstract: Human apolipoprotein A-I (apo A-I) possesses multiple tandem repeating 22-mer amphipathic α-helixes. Computer analysis and studies of model synthetic peptides and recombinant protein-lipid complexes of phospholipids have suggested that apo A-I interacts with HDL surface lipids through cooperation among its individual amphipathic helical domains. To delineate the overall lipid-associating properties of apo A-I, the first step is to understand the lipid-associating properties of individual amphipathic helical domains. To this end, we synthesized and studied each of the eight tandem repeating 22-mer domains of apo A-I: residues 44-65, 66-87, 99-120, 121-142, 143-164, 165-186, 187-208, and 220-241. Among the 22-mers, only the N- and C-terminal peptides (44-65 and 220-241) were effective in clarifying multilamellar vesicles (MLVs) of dimyristoylphosphatidylcholine (DMPC). These two peptides also exhibited the highest partition coefficient into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine lipo...
TL;DR: Phylogenetic analysis of rRNA sequences from these amitochondrial organisms suggests that G. lamblia, T. vaginalis, and microsporidia are near the base of the eukaryotic tree, while E. histolytica clusters with mitochondria-containing species.
TL;DR: The major steps involved in the catabolism of chylomicrons are now known, the determinants for apolipoprotein exchange, processing of remnants in the space of Disse, as well as the mechanism of uptake of these particles by extra-hepatic tissue needs further exploration.
TL;DR: Light microscopic analysis indicated that CRF processes are dense and highly varicose in the rostral LC region in the vicinity of noradrenergic dendrites, and immunoperoxidase labeling for CRF was mainly restricted to axons and axon terminals and was rarely seen in somata or dendrite.
Abstract: Physiological and immunohistochemical studies have suggested that corticotropin-releasing factor (CRF), the hypophysiotropic peptide that initiates endocrine responses to stress, may serve as a neurotransmitter to activate noradrenergic neurons in the nucleus locus coeruleus (LC). We combined immunoperoxidase labeling for CRF and immunogold-silver localization of the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in single sections through the rat LC to determine potential substrates for interactions between these two transmitters. Light microscopic analysis indicated that CRF processes are dense and highly varicose in the rostral LC region in the vicinity of noradrenergic dendrites. Electron microscopy of this rostral region revealed that immunoperoxidase labeling for CRF was mainly restricted to axons and axon terminals and was rarely seen in somata or dendrites. Axon terminals containing CRF immunoreactivity varied in size, content of synaptic vesicles, and formation of synaptic specializations. The postsynaptic targets of the CRF-labeled axon terminals consisted of both TH-labeled dendrites and dendrites lacking detectable TH-immunoreactivity. Of 113 CRF-immunoreactive axon terminals, approximately 70% were in direct contact with TH-labeled and unlabeled dendrites. Of the CRF-labeled axon terminals forming synapses with TH-labeled and unlabeled dendrites, they were either of the asymmetric (excitatory type; 19%) or symmetric (inhibitory type; 11%) variety or did not form identifiable contacts in the plane of section analyzed. Unlabeled axon terminals and glial processes were also commonly located adjacent to the plasma membranes of CRF-labeled axon terminals.
These results provide the first direct ultrastructural evidence that axon terminals containing CRF-immunoreactivity 1) directly contact catecholamine-containing dendrites within the rostral pole of the LC, 2) may presynaptically modulate other afferents, and 3) are often enveloped by astrocytic processes. © 1996 Wiley-Liss, Inc.
TL;DR: A degradable 3-dimensional osteoblast cell-polymer matrix designed as a construct for skeletal tissue regeneration and found to be suitable for use as a bioerodible scaffold for regeneration of skeletal tissue.
Abstract: Current methods for the replacement of skeletal tissue in general involve the use of autografts or allografts. There are considerable drawbacks in the use of either of these tissues. In an effort to provide an alternative to traditional graft materials, a degradable 3-dimensional (3-D) osteoblast cell–polymer matrix was designed as a construct for skeletal tissue regeneration. A degradable amino acid containing polymer, poly[(methylphenoxy)(ethyl glycinato) phosphazene], was synthesized and a 3-D matrix system was prepared using a salt leaching technique. This 3-D polyphosphazene polymer matrix system, 3-D-PHOS, was then seeded with osteoblast cells for the creation of a cell–polymer matrix material. The 3-D-PHOS matrix possessed an average pore diameter of 165 μm. Environmental scanning electron microscopy revealed a reconnecting porous network throughout the polymer with an even distribution of pores over the surface of the matrix. Osteoblast cells were found attached and grew on the 3-D-PHOS at a steady rate throughout the 21-day period studied in vitro, in contrast to osteoblast growth kinetics on similar, but 2-D polyphosphazene matrices, that showed a decline in cell growth after 7 days. Characterization of 3-D-PHOS osteoblast-polymer matrices by light microscopy revealed cells growing within the pores as well as on surface of the polymer as early as day 1. This novel porous 3-D-PHOS matrix may be suitable for use as a bioerodible scaffold for regeneration of skeletal tissue. © 1996 John Wiley & Sons, Inc.