bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular analysis of the mechanisms regulating EPC-1 gene expression in WI-38 fibroblasts
Authors:   , Coljee Vincent W.
Published: July 2024

Abstract A cDNA, named EPC-1 for, early population doubling level (PDL) cDNA-1, was isolated by randomly selecting clones from an early PDL, subtracted, G0 library derived from WI-38 fibroblasts. EPC-1 is also known as pigment epithelium-derived factor (PEDF) and encodes for a protein belonging to the serine protease inhibitor (serpin) superfamily. This protein has been shown to induce differentiation of Y74 retinoblastoma cells into neuronal-like cells. In WI-38 fibroblasts, EPC-1 mRNA and secreted EPC-1 protein are detectable in early passage cells which are in G0, a growth-arrested state. The relative EPC-1 mRNA levels, determined by northern analysis, are more than 100-fold less in proliferating and senescent cells as compared to quiescent cells. This work focuses on elucidation of the mechanisms regulating the differential EPC-1 gene expression. Results from transcriptional assays suggest: post-transcriptional regulation of the EPC-1 gene. Measurements of EPC-1 mRNA stability using RNA synthesis inhibitors indicate that the half-life of EPC-1 mRNA is altered between quiescent and proliferating cells. The half-life of EPC-1 mRNA in proliferating cells is less than half that of quiescent cells. A combination of growth factors capable of inducing cellular proliferation, or transforming growth factor-[beta]1 (TGF-[beta]1) can decrease the EPC-1 mRNA levels. These studies also demonstrate that reduction of the EPC-1 mRNA levels caused by TGF-[beta]1 occurs in the absence of cellular proliferation. We propose that EPC-1 mRNA stability is decreased in proliferating cells due to a serum inducible protein. We also examined the relative EPC-1 pre-mRNA levels by reverse transcriptase-Polymerase chain reaction (RT-PCR) and observed that the pre-mRNA levels reflect steady-state mRNA levels. These results lead us to conclude that this quiescent specific differentiation factor is subject to two levels of regulation: both pre-mRNA and mRNA stability contribute to its differential expression.
Analytical and experimental studies of the degradation in hydrogenated amorphous silicon solar cells and materials
Authors:   , Yeung Ping Fai
Published: July 2024

An improved understanding of a-Si:H pin solar cells stability was obtained by studying light induced degradation in a-Si:H films and in devices. The current-voltage characteristics and the quantum efficiencies of a-Si:H pin solar cells were measured as a function of intrinsic layer thickness, bias light intensity and degradation condition. Photoconductivity measurements on device quality intrinsic a-Si:H thin film materials showed that the majority carrier (electron) [mu][tau] product degraded from 3x10⁻⁷ cm²/V to 2x10⁻⁷ cm²/V after 6 minutes of 50-Suns light illumination. Using a dual beam technique with steady white light and modulated monochromatic light, a degradation profile was detected in the degraded materials. These results suggest that inhomogeneous degradation may be important to understanding the stability of a-Si:H pin solar cells. An analytical model was developed for degradation in a-Si:H pin solar cells based on inhomogeneous degradation, which was used to explain the 'blue-dip' effect observed in the quantum efficiencies of degraded cells. A new method was developed to investigate the minority carrier (hole) diffusion length in device quality a-Si:H films as a function of degradation. This method uses the Schottky barrier structure to establish a depletion region, which can be controlled by the applied voltage and the bias light intensity. Modulated blue light is used to generate electron hole pairs near the ohmic contacts, and the holes diffuse across the neutral region to be collected. The modulated current is related to the diffusion length of the holes due to this current limiting hole transport. Comparing the results of this new technique to that of the Photocarrier Grating method, the electron drift mobility was found to degrade from 2.5cm²/Vs to 0.15cm²/Vs after 6 minutes of 50-Suns degradation.
Neuroprotective actions of the chemokine CXCL12
Authors:   , Nicolai Jaclyn , Fatatis Alessandro , Meucci Olimpia
Published: July 2024

Chemokines are cellular mediators known for their role in immune/inflammatory responses - traditionally, yet simplistically, associated to neuronal damage. However, recent research has not only provided evidence about the beneficial nature of a controlled immune/inflammatory response in the central nervous system (CNS), but also suggested novel protective effects of a few chemokines (and their receptors) that are constitutively expressed in the CNS, namely CXCL12 and its receptor CXCR4. This chemokine/receptor pair is essential to brain development and involved in neuronal-glia communication. Thus, proper function of the CXCL12/CXCR4 axis is of utmost importance at all stages of life and its alterations are thought to contribute to different neuropathologies, including neuroAIDS. To date, the mechanisms implicated in the distinct physiologic and pathologic effects of CXCL12/CXCR4 are not entirely understood. This study focuses on the neuroprotective actions of CXCL12/CXCR4 in central neurons with a primary interest on molecular mechanisms that support survival and function of differentiated neurons. Our previous studies show that CXCL12 protects cultured neurons from NMDA-induced excitotoxicity by up-regulating the gene repressor protein Rb. Rb is involved in recruitment of chromatin modifiers, such as histone deacetylase (HDAC), to gene promoters. In neurons, the Rb/HDAC repression complex controls activity-dependent genes, such as NMDA receptor's subunit NR2B. Considering the reported role of NR2B in excitotoxicity and synaptic activity, we hypothesized that CXCL12 regulates NR2B expression in neurons. The results presented in this thesis show that CXCL12 selectively inhibits NR2B expression in vitro and in vivo altering NMDA-induced calcium responses associated with neuronal death while promoting pro-survival pathways associated with synaptic receptor activation. Importantly, CXCL12 regulates the NR2B subunit through an HDAC dependent mechanism. Further investigation into HDAC regulation indicates that CXCL12 modulates specific HDAC isoforms leading to multiple outcomes on neurons while CXCL12-induced inhibition of NR2B expression can result from HDAC1 recruitment via Rb, the chemokine controls dendritic spines density through a more direct regulation of HDAC4. These novel effects of CXCL12 may both contribute to neuroprotection and synaptic plasticity in the mature brain and suggest important clinical implications related to the therapeutic use and side effects of NMDA receptor antagonists and HDAC inhibitors.
Characterization of the Genotypes, Phenotypes and Neurotropism of the HIV-1 Envelope glycoproteins from two highly Neurotoxic CSF-derived Isolates
Authors:   , Sierra Luz-Jeannette , Martin-Garcia Julio
Published: July 2024

HIV-1 enters the central nervous system (CNS) early after systemic infection, leading to a variety of neurocognitive and motor impairments referred as HIV-1 associated neurocognitive disorders (HAND). Perivascular macrophages and microglia cells support productive viral infection in the brain allowing the virus to subsequently adapt to the CNS environment. Our goal is to elucidate the role of the HIV-1 envelope glycoprotein (Env) during HIV-1 infection in the CNS. We obtained viruses derived from the cerebrospinal fluid (CSF) of two HIV-1-infected individuals with HIV-1-associated dementia, the most severe form of HAND. These isolates are macrophage tropic and highly neurotoxic. We amplified Env genes using single genome amplification and performed extensive genotypic and phenotypic characterization. Interestingly, we found a mixture of Env genotypes and diverse phenotypes, such as macrophage and non-macrophage tropic Env, various degrees of fusogenicity, ability to use low levels of CD4, reduced sensitivity to entry and fusion inhibitors, and neutralization by antibody against the conserved CD4 binding site. Finally, we did not find specific correlations between genetic determinants and the above reported phenotypes. Importantly, in the context of isogenic recombinant viruses, some Env were able to mediate infection of macrophages and lead to the production of conditioned medium that induces neurotoxicity in primary pure neuronal cultures. In addition, we assessed whether the supernatants of the infected macrophages with viruses expressing Env that generates neurotoxicity affected other cells such as astrocytes, microglia and microvasculature endothelial cells. We found that recombinant viruses expressing the related envelopes did not infect such cells, but morphological changes were induced. The conditioned media also increased the permeability of microvasculature endothelial cells. The effects were likely caused by combinations of elevated levels of glutamate, soluble gp120 and diverse secretion profiles of cytokines, chemokines and pro-apoptotic proteins that differed within monocytes donors. We conclude that a subset of the Jago and Doge envelopes show neurotropic phenotypes representative of viruses that adapt better to the CNS microenvironment.
Magnesium Status and Bone Mineral Density in Obese and Overweight Adults
Authors:   , Diamond Samantha Rae , Sukumar Deeptha
Published: July 2024

Overweight and obese individuals have an altered bone metabolism. Increased serum parathyroid hormone (PTH) concentrations and low serum concentrations of 25- hydroxyvitamin D (25OHD), which are important contributors to poor bone quality in this population. Magnesium (Mg) is an important micronutrient whose deficiency can result in elevated serum PTH concentrations and decreased serum 25OHD concentrations. The main purpose of this study was to determine the relationship bet ween Mg status, including serum ionized Mg and dietary Mg intakes, and bone mineral density (BMD) and bone regulating hormones in overweight and obese individuals. Magnesium intakes were examined using a newly developed Mg food frequency questionnaire. Serum was assayed for concentrations of ionized Mg, PTH and 25OHD and other markers of bone turnover. Bone mineral density was evaluated using a dual energy absorptiometry (DXA) at the hip, lumbar spine, forearm and total body. Our results in 27 adults show that magnesium intake is a significant positive contributor to serum 25OHD concentrations (r=0.392 p=0.039). Ionized Mg concentrations and dietary Mg intakes did not predict BMD but Mg intake had a positive association with BMC at the l/3rd radius. Ionized magnesium concentrations was also positively correlated with serum PTH concentrations (r=0.436, p=0.042), however when included in a linear regression model along with BMI and age, PTH was no longer an independent predictor of ionized Mg. In summary, our findings suggest that dietary magnesium intake is a regulator of serum 25OHD concentrations in the overweight and obese population.
Couples coping with cancer
Authors:   , McClure Kelly Sprague
Published: July 2024

There were two aims to this study. The first was to examine how the interactional model of depression applies to couples coping with cancer. The second was to examine whether social problem-solving is an individual variable that is related to how partners respond to the depressive symptoms that people with cancer experience. Sixty couples participated in this cross-sectional study. The hypotheses were tested with a series of hierarchical multiple regression analyses. The results showed that the interactional model was applicable. Cancer patients' negative affect was related to the negative responses (i.e., negative affect, hostility, negative behaviors) of their partners. However, the severity of the cancer patients' depressive symptoms was not related to the negative responses of their partners. Furthermore, the results showed that the partners' positive problem orientation, one component of the problem-solving process, moderated the relationship between patient negative affect and partner negative affect. However, other components of the problem-solving process did not moderate these relationships. Research and clinical implications are discussed.
Development of the fetish interest scale
Authors:   , Wasserman Adam Lawrence
Published: July 2024

Using Forced-Choice and Visual Reaction Time Methodologies ABSTRACT Sexual offending behavior is recognized as a major societal concern in need of further investigation. Studies of sex offender recidivism have identified paraphilic interest as a significant dynamic risk factor for future sexual offending behaviors. Although psychometrically reliable and valid assessment tools exist for a number of paraphilic disorders (e.g., pedophilia), the scientific literature describes few such measures for assessing for interest in fetish themes. This study describes the development and initial psychometric properties of a new measure of sexual interest, the Fetish Interest Scale [FIS], that uses both subjective (forced choice) and objective (visual reaction time) methods to determine the degree of sexual interest in paraphilic visual stimuli. The Fetish Interest Scale measures interest in the following seven categories: (1) adult women, (2) female feet, (3) female hair, (4) female hands, (5) panties and bras, (6) shoes, and (7) stockings. The scale was developed in three stages. During the first stage, operational definitions for each of the seven measured categories were elicited and used to identify a population of visual images that were categorized and classified during the second phase of this study. The goal of the second stage was to arrive at an empirically selected sample of images to be included in the final stage of development. Two hundred and eighty images were categorized into discrete groups and rated to help identify 126 items to be included in the third phase of development. The final phase of this study examined the psychometric properties of the Fetish Interest Scale. Participants viewed a series of single images that represent the primary content areas for the purpose of measuring reaction time (measured in milliseconds). Participants also viewed a series of images presented side by side (e.g., feet vs. hair) to determine which item they found to be most sexually interesting. Results from bivariate correlations identified a significant relationship between the visual reaction time and forced-choice preference data. Significant methodological concerns, however, temper this finding. A critical examination of the research design and suggestion for future research is discussed.
Trapping skinning
Authors:   , Vinjamur Madhu , Cairncross Richard Allan
Published: July 2024

Drying gas flow rate, temperature and solvent composition are three important operating conditions in any industrial dryer. The operating conditions are manipulated to produce defect-free coatings that meet residual solvent specifications. As the drying conditions become more intense, the initial drying rate becomes faster and one might expect the residual solvent to be lower in dried coating. The residual solvent, however, can be higher in coatings dried under more intense conditions. This behavior is called trapping skinning and is not well understood and remains undocumented in the literature. This thesis reports experimental measurements of trapping skinning and a mathematical model that predicts it. Industrial dryers have evolved from festoon dryers with low airflow to state-of-the-art hybrid dryers with high airflow with a corresponding increase in the rate at which heat can be transferred to the coating (or solvent removed). Laboratory experiments, however, have not evolved to similar heat transfer coefficients because of fluctuations in weight measurements in conventional gravimetric experiments at high airflows. This thesis demonstrates a High Airflow Drying Experimental Set up (HADES) that simulates drying in spiral and single-side impingement dryers. Experiments from HADES show that poly (methyl methacrylate)/acetone coatings exhibit trapping skinning at higher gas flows and the anomalous behavior is due to a glass transition occurring during drying and stress-driven diffusion. A diffusion Deborah number, De, characterizes stress development in a coating and the magnitude of stress-driven diffusion to mass transfer. Glassy polymer coatings are likely to show trapping skinning if the De approaches O(1) from below during drying. The stress develops due to coating shrinkage during drying and decays with a relaxation time that depends on solvent concentration and temperature. Fick's law of diffusion with concentration dependent diffusion coefficient cannot explain trapping skinning. So, a non-Fickian non-isothermal model is developed to capture this behavior. The non-Fickian model includes the solvent mass transport due to stress gradients. This thesis shows how stress relaxation inside the coating causes trapping skinning. This thesis also illustrates the implications of the non-Fickian model on dryer design.
Cloning and characterization of the haemocin locus of Haemophilus influenzae and assessment of its role in virulence
Authors:   , Murley Yvette Marie
Published: July 2024

The bacteriocin haemocin (HMC) is produced by most type b strains of Haemophilus influenzae, including strains determined to be genetically diverse, and is toxic to virtually all non-type b strains of H. influenzae, both encapsulated and nonencapsulated. We prepared a protein preparation enriched for HMC that was useful in subsequent cloning efforts. Complementation of a HMC-deficient H. influenzae mutant resulted in the identification of a recombinant plasmid containing several ORFs involved in HMC expression. Subsequent deletional and site-directed mutagenesis of this plasmid identified the HMC immunity gene, hmcI. This gene encodes a protein similar in size to a number of other characterized bacteriocin immunity proteins, although it has little homology to other nucleotide sequences in available databases. Cloning of DNA flanking hmcI in the H. influenzae chromosome led to the identification of several other genes involved in HMC production and transport. Examination of the deduced amino acid sequences of these genes revealed several features common to class II bacteriocins of certain gram-positive bacteria. Specifically, the HMC structural gene encodes the characteristic class II double-glycine leader peptide. Interestingly, the HMC proteolytic processor and transporter are encoded by different genes rather than a single gene, as with all other class II transporter systems described to date. While subcloning of the locus into a HMC- Escherichia coli resulted in HMC immune transformants, they did not produce HMC, suggesting that additional genes are required for HMC production. The effects of a mutation in the HMC structural gene, hmcA, were examined in vitro and in vivo by using cell culture and the H. influenzae infant rat model of infection. Loss of HMC production did not have an apparent effect on cytotoxicity, but significantly delayed the onset of bacteremia in infant rats.
Psychological mindedness and psychotherapy orientation preference as predictors of treatment outcome for social phobia
Authors:   , Kadish Daniel A. , Herbert James D
Published: July 2024

Although social phobia is a common and often debilitating anxiety disorder, little is known about the psychological factors that mediate socially phobic adults, responsiveness to psychotherapy. This study explored whether socially phobic adults' psychological mindedness (as measured by the Psychological Mindedness Scale) and treatment preference (cognitive-behavioral vs. psychodynamic) predicted treatment outcome in a seven week cognitive-behavioral treatment program. In addition, socially phobic adults, treatment preference and psychological mindedness scores were compared to scores from a general psychiatric outpatient population. Results for 22 treatment completers, 5 treatment drop-outs, and 22 psychiatric controls are reported. Most notably, adults with social phobia improved significantly in treatment and improvement was predicted by one factor of the Psychological Mindedness Scale (interest in meaning and motivation of own and others' behavior). Improvement was not predicted by overall scores on the Psychological Mindedness Scale, or by treatment preference. In addition, socially phobic adults, self-ratings of psychological mindedness were not correlated with therapist ratings, and socially phobic adults preferred cognitive behavioral treatment more then psychiatric controls. Additional results and implications are discussed.
Identification of multiple substrates of the PHO85 cyclin dependent protein kinase as dey regulators of acid phosphatase expression and glycogen metabolism in the yeast Saccaromyces cerevisiae
Authors:   , Waters Norman C. , Bergman Lawrence W
Published: July 2024

In Saccharomyces cerevisiae, multiple signalling pathways allow the cell to respond to environmental variation and therefore are essential for the survival of the yeast. During nutrient stress, expression of acid phosphatase, encoded by PH05, is upregulated and functions to scavenge for inorganic phosphate required for cell growth. In addition, a hyperaccumulation of glycogen results to provide the cell an intracellular energy source in the event of long term starvation. The Pho85 cyclin dependent protein kinase regulates several metabolic pathways in the cell. Cyclin dependent protein kinases were initially identified as regulators of the cell cycle; however, in yeast Pho85 regulates not only the cell cycle, but also expression of acid phosphatase and glycogen metabolism. In the work described here, we further characterize Pho85 as a cyclin dependent protein kinase and identify key substrates of Pho85 involved in the mechanics of regulating PHO5 expression and glycogen biosynthesis. In the regulation of acid phosphatase expression, Pho85 associates with the Pho80 cyclin to form a Pho85-Pho80 kinase complex. During high phosphate conditions, this complex phosphorylates and inhibits the transcriptional activator Pho4. In addition, the Pho80 cyclin subunit is phosphorylated at Ser-234 and Ser-267 by Pho85. Phosphorylation of Ser-234 is required for a functional Pho85-Pho80 kinase complex, which represses PHO5 expression. We demonstrate that Pho81 is also phosphorylated by Pho85, and we localize the phosphorylation sites to the ankyrin repeat motifs within Pho81 that are essential for inhibiting the kinase activity of the Pho85-Pho80 complex. Disruption of Pho85 kinase activity results in a hyperaccumulation of glycogen. Glycogen synthase, Gsy2, is responsible for production of 90% of the glycogen in the cell. Gsy2 is regulated by reversible phosphorylation and allosteric activation. We identify Pho85 as a glycogen synthase kinase and show that phosphorylation by Pho85 inhibits glycogen synthase activity. By site directed mutagenesis, we identify Ser-654 as the Pho85 phosphorylation site. These results identify Pho85 as a key kinase in regulating several metabolic pathways, and they provide a mechanism for crosstalk between environmental stimuli and cell growth and development.
Effects of privileged communications law on perceived willingness to disclose in psychotherapy
Authors:   , Marsh Jennifer Evans , Bersoff Donald N
Published: July 2024

In June 1996, the United States Supreme Court recognized the federal psychotherapist-patient privilege (Jaffee v. Redmond, 1996), holding that a law enforcement officer's statements to her therapist during sessions were protected from compelled disclosure under Federal Rule of Evidence 501. The Court also extended the privilege to psychologists, psychiatrists, and social workers. Resolving disagreement among the federal circuit courts of appeal, the decision set new precedent and therefore, is of significance to legal and mental health professionals. Prior to Jaffee, few studies had examined the effects of personal characteristics on willingness to disclose sensitive information in psychotherapy. This study explored the relationships between the dependent variables (individuals' predictions about willingness to disclose in therapy in five scenarios), two independent variables (privilege condition and therapy experience), and eight proposed covariates (age, education, gender, race and four dimensions of general disclosiveness-amount, honesty, intent and depth). Scenarios involved the following: (1) a suicidal patient, (2) a gravely disabled patient, (3) a physically abusive patient, (4) a sexually abusive patient, and (5) a police officer-patient who shot a suspect. One-hundred twenty-nine subjects completed survey packets consisting of a consent form, the General Disclosiveness Scales (GDS), The Willingness to Self-Disclose Questionnaire (WSDQ), and a demographic data form. Subjects were systematically assigned to receive the N form (scenario protagonists' communications not privileged) or the P form (communications privileged). Data screening indicated that none of the proposed covariates were substantially correlated with the dependent variables, thus they were deleted from the analysis. A 2 x 2 (Privilege Condition x Therapy Experience) factorial fixed-effects ANOVA was performed on willingness-to-disclose scores for each of the five scenarios. Data supported the first hypothesis that subjects in the privilege condition would have significantly higher willingness-to-disclose scores than subjects in the no-privilege condition. In contrast, the data did not support the second hypothesis. There were no significant differences between willingness-to-disclose scores of subjects with therapy experience and subjects without therapy experience. Finally, there was no significant interaction between privilege condition and therapy experience. Personal characteristics and therapy experience were not as predictive of willingness to disclose as was privilege condition.
Using the yeast two-hybrid system to identify human epithelial cell proteins that bind gonococcal Opa proteins
Authors:   , Williams John Michael , Rest Richard F
Published: July 2024

Neisseria gonorrhoeae Opacity-associated (Opa) proteins are a family of outer membrane proteins involved in gonococcal adherence to and invasion of human cells. Although gonococci possess alternative surface-exposed molecules involved in adhesion and invasion, the expression of Opa proteins appears to be necessary for gonococcal disease. Since little is known about the interaction of gonococci with host cell "constituents" that mediate post-adhesion and post-invasion processes, including intracellular replication and survival, we wanted to identify novel roles for Opa in the infectious process. Specifically, we wanted to use the yeast two-hybrid system as a relatively rapid screen to identify human epithelial cell proteins that specifically interact with gonococcal Opa proteins. Prior to the initiation of these studies, the yeast two-hybrid system had not been employed to screen a human cell cDNA library for the binding partners of a prokaryotic outer membrane protein. Therefore, a major aim of this thesis was to explore the versatility of the yeast two-hybrid system in identifying bacteria-host interactions. Using OpaP from N. gonorrhoeae strain F62SF as bait, we screened a HeLa cell cDNA library for Opa-interacting proteins (OIPs). We identified 5 different OIPs, designated OIP1-OIP5, three of which are homologous to characterized human proteins-thyroid hormone receptor interacting protein (TRIP6), pyruvate kinase isoenzyme M2 (PK), and preferentially expressed antigen of melanoma (PRAME). In the studies presented here, we investigated the interaction between Opa proteins and PK in more depth. Opa-PK interactions were confirmed by in vitro binding assays and in vivo co-localization studies, independent of the yeast two-hybrid system. Using a mutant of N. gonorrhoeae unable to grow on pyruvate or lactate, we also demonstrated that intracellular pyruvate is essential for gonococcal growth and survival. These results illustrate a novel mechanism in bacterial pathogenesis, i.e., the requirement for direct molecular interaction with a host metabolic enzyme (PK) for the acquisition of an essential intracellular carbon source and growth substrate (pyruvate). These results further demonstrate that the yeast two-hybrid system is a valuable tool for rapidly identifying biologically relevant interactions between bacteria and host proteins, providing valuable leads for further investigations into novel mechanisms of bacterial pathogenesis.
Simplification of nonlinear controllers
Authors:   , Min Hong , Yousuff Ajmal
Published: July 2024

This thesis concerns the controller reduction for nonlinear systems with dynamic output feedback controllers. Using the concept of nonlinear balancing, algorithms to reduce controller order are proposed. The balancing involves a series of state coordinates transformations in which the contribution to controllability by each state is measured by a singular value function and this singular value function also indicates the contribution to observability by the same state. By truncating states associate with smaller singular value functions, the order of the controller is reduced. In the case when controller is stable, controller reduction is extended from model reduction. The discussion for unstable controller reduction focuses on H[infinity] suboptimal output feedback controller and other controllers that employ observer-based structures. An unstable controller is reconstructed based on its stable left (right) coprime factorization, so that the above controller reduction technique can be applied. Four such algorithms are proposed. It is essential that a reduced controller still stabilizes the closed system and does not significantly degrade performance. Three of the five reduction approaches are evaluated with respect to stability and H[infinity] performance. Using small-gain theorem, it is found, in each of the three cases, that when the error between the full order and the reduced controllers has an L2-gain less than certain value as determined by singular value functions in balancing, the closed-loop stability is guaranteed. The above finding is used to choose the order r of the reduced controller to ensure stability. As a measure of the degradation in performance, a formula has been derived to compute the increase in the disturbance attenuation level. The increase is smaller if less states are truncated. Computational issues for balancing reduction are discussed. The impact of approximate controllability and observability functions on balancing and reduction is investigated. Another issue discussed is the construction of the diffeomorphism in balancing controllability and observability functions.
Point contact tunneling study of the high transition temperature superconductor Bi₂Sr₂CaCu₂O₈
Authors:   , Jiang Mian Heng , Rothwarf Allen , Scoles Kevin James
Published: July 2024

The point-contact (Pt-Ir probe) tunneling measurements on high-T_c superconducting Bi₂Sr₂CaCu₂O₈ single crystals (T_c = 82 K) have been performed at low temperatures of 4.2 K to 77 K. A high conductance region around the origin, which is attributed to the junction of the pure-metallic-bridge type of point-contact tunneling, has been observed. There are also several current steps beyond the high conductance region in the I-V curves, corresponding to conductance troughs, which are either zero or negative, in the dI/dV characteristics in the tunneling spectra. These are pronounced structures indicative of bound states in tunneling spectroscopy. A superconducting energy gap of [Delta] = 28 ± 2 meV has been identified from tunneling spectra taken at T = 4.2 K and as a function of temperature. Current jumps and drops with some regularity in voltage intervals between jumps occur at high applied voltage (>100 mV). This resonance tunneling is the result of the effects of quantization due to the layered-structure of the crystal. A model based on the superlattice-like nature of the crystal has been developed to interpret the tunneling observation of the bound states and the energy gap. Based upon such a model and experimental data, the energy levels of the bound states have been estimated to be "n[epsilon]₀" with n an integer and energy spacing [epsilon]₀ = 8.3 ± 0.3 meV. The Fermi velocity of quasiparticles in the Bi₂Sr₂CaCu₂O₈ single crystal can be calculated from the energy spacing [epsilon]₀ and lattice constant of the crystal, and the value of v_F [approx equals] 1.2x10⁶ cm·sec⁻¹ has been obtained. Hence the coherence length [xi] has been evaluated to be around 0.9 Å using this value of the Fermi velocity. The values of the superconducting energy gap, [Delta], the Fermi velocity, v_F, and the coherence length, [xi], obtained in the present work, are in good agreement with the results reported in the literature. The modeling and the results reported here are original.
In vivo measurement of cervical spine flexibility
Authors:   , McClure Philip W.
Published: July 2024

Many pathologies and treatment interventions affect the mechanical behavior of the cervical spine. However, current methods of assessment are limited to range of motion testing without regard to the applied loads. The goal of this study was to develop a reliable method of evaluating the load-displacement behavior of the cervical spine in vivo and to apply this method to evaluate the effects of a forward head posture, aging and osteoarthritis on the mechanical properties of the neck. Testing was conducted on young asymptomatic subjects (age < 35, n=20), older asymptomatic subjects (age > 50, n = 16) and subjects with documented degenerative changes and a history of neck-related symptoms (n = 17) using a unique six degree of freedom instrumented linkage. This linkage allowed measurement of the six degrees of freedom translatory and rotatory flexibility of the neck in an anatomical reference frame following Grood and Suntay parameters Range of motion and flexibility (deg/Nm) were calculated from the experimental load-displacement curves. For analysis, curves were divided into an early flexible portion (neutral zone), and a less flexible end portion (elastic zone). Parameters used in the analysis were neutral zone flexibility and range of motion, elastic zone flexibility, total flexibility and range of motion and the amount of torque tolerated. The results indicated acceptable test-retest reliability for range of motion and flexibility measurements performed several days apart (most ICC's above.7). Older and osteoarthritis subjects demonstrated decreased range of motion and tolerated less torque compared to young subjects. There were no differences between groups in flexibility. Forward head posture caused a significant decrease in axial rotation range of motion but did not affect lateral bending. In younger subjects, males were less flexible than females and males could tolerate greater amounts of passively applied torques. In vivo measurements of neck flexibility have several important differences from in vitro measurements and further work is necessary to clarify the role of these measurements.
Novel organic-inorganic hybrid and nano-structured materials
Authors:   , Jin Danliang , Hutchins Robert O. , Wei Yen
Published: July 2024

Organic polymers, i.e. polymethacrylates and polystyrene, and inorganic silica were successfully integrated covalently into one body, i.e. hybrid materials, at molecular level in a continuum ranging from pure polymer to pure silica via the sol-gel process. The synthetic conditions have been systematically studied and optimized. A fast and convenient method for the synthesis of polymethacrylate-silica hybrids with significantly low volume-shrinkages has been developed to address the intrinsic problems of the sol-gel process, i.e. large volume shrinkage and long drying times. The relationship of properties of the hybrids with the structures and organic-inorganic compositions have been established. The density, hardness and thermal stability increase with the silica content. Atomic force microscopy study of the morphology shows that the transparent hybrid materials, in which the polymer chains have a strong and intimate interaction with the silica matrix, have significantly different surface features from a translucent control sample. The compressive behavior of the hybrid materials is completely different from that of traditional composites. Toughness of the hybrid materials can be maximized and the strength can be dramatically increased by varying the silica content. Possible mechanisms for the formation of hybrid materials are proposed. Potential applications of the hybrid materials as dental fillers and cation exchangers were investigated. Amorphous silica was functionalized by doping with optically active compounds such as scD-glucose, diphenyl tartaric acid and maltose. The resultant nano-structured materials show excellent optical transparency to visible light. Optical rotation of the materials in the solid state was demonstrated quantitatively to be the same as that in solution. The specific rotation can be calculated directly according to Biot's equation. A non-surfactant templating approach has been developed for the preparation of mesoporous silica by removing the organic compounds (i.e. template) through solvent extraction. The mesoporous nature of the materials is evidenced by the large BET surface area and pore volumes, the controllable pore sizes of ~2 to 6 nm and their narrow distributions, the powder X-ray diffraction patterns, and transmission electron microscopy images. The pore size can be tuned simply by adjusting the template concentration. This non-surfactant structure-directing pathway possesses many advantages over the known surfactant approaches.
The GABA-A receptor in aging and Alzheimer's disease
Authors:   , Rissman Robert Andrew , Armstrong David M.
Published: July 2024

The GABAA ([gamma]-aminobutyric acid) receptor is an integral component of mediating inhibitory neurotransmission in the adult brain via an intrinsic Cl- channel. Presently, it is unknown how alterations in the subunit composition GABAA receptors may contribute to altered drug responses or progression of neurodegenerative disease, such as Alzheimer's disease (AD). The investigations of this thesis strive to analyze several highly prevalent GABAA receptor subunits in the aged and AD brain. First, as an initial investigation into the GABAA receptor in the aged brain, protein levels of GABAA receptor subunits al and [beta]2/3 were examined in the hippocampus of young and aged non-human primates using immunohistochemical techniques. The results of this study demonstrated that the [beta]2/3 subunit was relatively unchanged between young and aged animals, while the [alpha]1 subunit was found to be reduced between these two groups. Next, two subsequent experiments were performed to assess the presence of both protein levels and mRNA expression of GABAA receptor subunits [alpha]1, [alpha]5, [beta]1, and [beta]2 in the AD hippocampus. The first study included subjects with a broad range of AD neuropathology (mild, moderate, and severe), as assessed by Braak stage classification. In this experiment, the [alpha]1, [beta]1 and [beta]2 subunits were found to be relatively unchanged with increasing AD pathologic severity. In contrast, the [alpha]5 subunit was found to be modestly, but significantly reduced (-13.5%) between pathologically mild patients and those with severe neuropathology within the CA1/CA2 and CA3 subregions. Finally, mRNA expression for those GABAA receptor subunits demonstrating alterations in protein levels (i.e. [alpha]5) were analyzed in patients with a broad range of increasing clinical severity of AD cognitive deficits. mRNA levels of both [alpha]1 and [alpha]5 were found to be modestly reduced between patients with no cognitive impairment (NCI) and patients with mild cognitive impairment (MCI). While [alpha]5 subunit mRNA expression was found to be further reduced that of the [alpha]1 subunit between NCI and MCI, and NCI and Probable AD patients, such reductions were not observed between MCI and Probable AD patient groups. (Abstract shortened by UMI.).
A comparison of document clusters derived from co-cited references and co-assigned index terms
Authors:   , Rapp Barbara Ann
Published: July 2024

The major objective of this dissertation was to determine how similarly co-cited references and co-assigned MeSH terms structure a set of documents. It was a large-scale, exploratory study of the database partitioning effects of two fundamentally different indexing systems, both of which have the common information retrieval purpose of identifying documents related in subject, yet each of which, judging from our results, performs quite independently. We draw a matched dataset of over 8500 documents, published during the years 1975 to 1977 in 20 cardiology journals, from the MEDLINE database and from the Institute for Scientific Information's citation database. Single-link clustering was used to partition the data set in three different ways. Co-citation clustering was used to partition on the basis of reference relationships. To partition on the basis of MeSH index terms, we used both term clustering and document clustering. Results of the three cluster analyses were compared pairwise to measure similarity of document placement. Overlap between cluster systems was measured in two ways. First, an asymmetric measure of percent overlap was computed between all cluster pairs in two systems being compared. Second, beginning with selected clusters in one of the systems based on MeSH term relationships, we traced their member papers in each of the other two cluster systems. When seed papers mapped to several clusters, inter-cluster relationships of the clusters so identified were examined. In both overlap analyses, we found extremely low overlap between the clusters derived from co-citation analysis and those derived from term clustering or document clustering based on MeSH term relationships. Consistent findings of low overlap suggest that, as alternative document representations, cited references and MeSH index terms organize a database in very different ways. Differences in organization are most likely accounted for by differences in intellectual structure of the systems for assigning references and index terms. Subject analysis of selected clusters showed that, in spite of low overlap between cluster systems, clusters within each system were cohesive in subject content. Our results illustrate the complementary nature of references and index terms in how they partition a database. Results are consistent with low overlap observed in comparative retrieval studies, and reinforce the notion that these two methods of representing document content are complementary in retrieval performance.
Industrial application and assessment of waste energy recovery technologies
Authors:   , Koluch Michael J.
Published: July 2024

The increased costs and availability of fuels make it necessary to reduce industrial energy consumption. Waste energy recovery technologies provide such a means for saving energy. Nine generic waste energy recovery technologies, divided into eighteen classifications, were examined for potential applications in industry. These were heat exchangers, Rankine power cycles, Brayton power cycles, Stirling power cycles, heat pumps, absorption cooling systems, expanders, burners and cogeneration systems. The major industries examined included Food and Kindred Products, Textile Mill Products, Lumber and Wood Products, Paper and Allied Products, Chemicals, Rubber and Miscellaneous Plastic Products, Stone, Clay and Glass Products, Fabricated Metal Products and Transportation Equipment. A methodology was developed to assess waste energy recovery technologies. It comprises an industry waste flow/technology compatibility prescreeen computer model, prescreen evaluation, specific technology application computer model and technology application assessment. Both the prescreen and technology application models incorporate the Drexel University/Department of Energy Industrial Data Base. Technology limitations were incorporated into a computer model to prescreen potential applications in 87 industrial processes. This represented 9000 waste stream, technology, enduse application assessments. Results of that prescreen indicated that heat exchangers, heat pumps, Rankine cycles and cogeneration systems ranked highest in the utilization of waste streams. Numerous specific waste stream, technology, end use applications were examined in detail. Performance technology models developed by United Technologies Research Center were used to simulate applications. Comparison of the results generated from these models indicated that heat exchangers offer a payback of invested capital in less than one year. The heat pump applications indicate a payback in the four year to nine year range for large plants. Cogeneration systems applications in large plants offer payback times of five to eleven years. Rankine power cycles, when used to generate electricity, indicated payback of capital investment in the eight to fourteen year range for large plant sizes.
Structural relationships within medical informatics
Authors:   , Morris Theodore Allan , McCain Katherine Wootton
Published: July 2024

Medical informatics is the application of information science and information technology to the theoretical and practical problems of biomedical research, clinical practice, and medical education. Although it is broadly interdisciplinary, its internal structure and the nature of its interactions with other disciplines have not been studied in depth. Co-occurrence analyses using classification codes and indexing terms assigned to medical informatics literature reveal interpretable internal subject structures, which differ between information science/information technology and biomedical perspectives. Highly visible topics within medical informatics include diagnostic imaging; decision-support systems; computing in general, expressed as biomedical computing, computing systems per se, data analysis and management, and human-computer interaction; artificial intelligence modeling; biophysics; biotechnology; and biomechanics. Underlying themes in the structure of medical informatics include knowledge discovery/knowledge management, information systems engineering/information system management, and biological investigations and applications. Further study of the role of bioinformatics within medical informatics is needed.