bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Biologically Derived Robotic Model of the Bluegill Sunfish Caudal Fin
Authors:   , Esposito Christopher J. , Tangorra James L
Published: July 2024

Fish inspired robots that have historically modeled the caudal fin as a rigid or semi-rigid plate with a single undulatory actuation from the peduncle caudal area. However, a two dimensional representation of a three dimensional motion ignores aspects that are crucial in producing variations in force vector direction and the magnitude. The primary objective of this research was to develop a biologically derived robotic model of a bluegill sunfish's caudal fin, and to use this model to investigate how changes in fin kinematics and stiffness affect hydrodynamic forces and flows. A six fin-rayed robotic caudal fin was developed using information obtained from biological studies of the bluegill sunfish caudal fin. The robot model tested five distinct motions that were deduced from caudal fin steady swimming motions of the bluegill sunfish (Lepomis macrochirus). These motions investigate both slight and large changes through phase, amplitude and frequency alterations. There were five fin stiffnesses tested, which retained similar curvature and tips deflection to those of the fish. The experimentation involved the use of high speed video, microtomography scans, force collection and particle image velocimetry. The results have shown that large changes in the motions caused large changes in the forces, while slight changes have led to small but constant changes in the forces. It was determined that the lift and thrust forces generated by the robotic caudal fin peaked at particular fin stiffnesses, indicating there are optimal stiffnesses for different scenarios (flapping frequencies, flow speeds). The results of this research have shown that alterations in the kinematics and mechanical properties of the fin rays can significantly affect the forces produced. This work has provided a better understanding of three dimensional caudal fin flapping and laid groundwork for future studies.
Effect of temperature and microstructure on tensile and tensile creep properties of Ti₃SiC₂ in air
Authors:   , Radovic Miladin , Barsoum Michel W.
Published: July 2024

The ternary carbide, Ti₃SiC₂, combines some of the best attributes of ceramics and metals. It is stable in inert atmospheres to temperatures above 2200 °C, stiff and yet is readily machinable, oxidation, fatigue and thermal shock resistant and damage tolerant. Thus, Ti₃SiC₂ is good candidate material for high temperature structural application. The aim of this work was to characterize its tensile and tensile creep properties. The mechanical behavior of Ti₃SiC₂ is characterized by a brittle-to-ductile (BTD) transition that is a function of strain rate. Its high strain rate sensitivity (~0.5-0.6) is in the range that is more typical for superplastic materials, although it does not exhibit other attributes of superplasticity. Polycrystalline samples do not exhibit linear elastic behavior in tension even at room temperature. Room temperature loading-unloading tests result in closed hysteresis loops when the stress exceeds ~120 MPa, suggesting that the mechanical response can be described as anelastic (viscoelastic). At high temperatures (1200 °C) intense stress relaxation takes place; cycling loading-unloading tests at high temperature and low strain rates, demonstrate that the samples continue to elongate even during unloading, suggesting that Ti₃SiC₂ deforms viscoplastically. Tensile creep curves exhibit primary, steady state and tertiary regimes. The minimum creep rate can be represented by power law equation with a stress exponent of 1.5 for fine-grained (3-5 [mu]m) samples, and 2 for coarse-grained (100-300 [mu]m) ones. For both microstructures the activation energy for creep is ~450 kJ/mol. The dependence on grain size is quite weak, implying that diffusion creep and/or creep mechanisms based on grain boundary sliding do not play a central role. Results of strain transient dip tests suggest that large internal stresses are developed during creep. Those internal stresses are believed to result in recoverable (anelastic) strains during unloading. The response on small stress decreases in strain-transient creep tests suggests that the steady state creep is recovery controlled. Finally, it is important to note that the mechanical response of Ti₃SiC₂ is quite similar to hexagonal ice. Both materials, if loaded rapidly are brittle, but if loaded slowly are quite plastic. This stems from the fact that both are plastically very anisotropic; deformation occurs overwhelmingly by basal slip. In both cases, stress concentrations, and the rate at which they can be relaxed, dictate the nature of the mechanical response.
Adolescents with psychopathic characteristics in a substance abusing cohort
Authors:   , O'Neill Melanie L. , Heilbrun Kirk
Published: July 2024

The construct of psychopathy has important consequences for those who experience it, and for the larger society in which these individuals with psychopathy live. While the assessment of psychopathy in adolescence remains somewhat controversial, mounting evidence suggests that the affective and behavioral traits of adult psychopathy begin to emerge in childhood (Lahey & Kazdin, 1990) and remain stable across the lifespan (Forth, Hart, & Hare, 1990). This study retrospectively examined the predictors, correlates, and treatment outcomes of 64 adolescents with psychopathic characteristics, as measured by scores on the Psychopathy Checklist:Youth Version (PCL:YV; Forth, Kosson, & Hare, in press), referred for treatment to a substance abuse program for adjudicated adolescents. First, this study examined the variables of Attention Deficit Hyperactivity Disorder, severity of childhood abuse/neglect, and severity of parental drug dependence in predicting psychopathic characteristics. Second, this study examined the association of psychopathic characteristics with substance use, drug trafficking, depression, and anxiety. Third, this study examined the relationship between psychopathic characteristics and treatment process and outcomes, including attrition rates, quality of participation, substance use throughout treatment, clinical improvement, and 12-month recidivism rates. Severity of childhood abuse and neglect significantly predicted psychopathic characteristics. Psychopathic characteristics were not associated with the correlates of substance use, depression, or anxiety. Psychopathic characteristics were negatively related to all treatment process and outcome variables. Implications for treatment and future research with adolescents displaying psychopathic characteristics are discussed.
Can cerebral blood flow be classically conditioned?
Authors:   , Zabel Theodore Andrew , Chute Douglas L.
Published: July 2024

Near infrared spectroscopy (nIRS) has recently emerged as a possible candidate for low-cost, portable monitoring of cerebral blood volume and oxygenation in humans. As nIRS utilizes low intensity light rather than radioactive tracers or magnetic fields, it can be safely used to monitor cognitive processes over longer periods of time than most forms of functional brain imaging. To determine the sensitivity of this technology, we conducted a replicated single-subject design, where nIRS was used to monitor hemodynamic activity of the inferior frontal and anterior temporal lobe cortex (right side) of 9 participants during a paired associates learning task. It was hypothesized that a pattern of increased blood volume and oxygenation (unconditioned response) normally elicited by aversive olfactory stimulation (unconditioned stimulus) could be trained to occur in conjunction with the presentation of computer generated color (conditioned stimulus). Two supra-threshold intensities of Hydrogen Sulfide (H₂S) were used as the unconditioned stimulus, and presented via an olfactometer (Kobel and Hummel, 1991). Visual comparative analysis of data from acquisition, extinction, and spontaneous recovery periods did not show a discrete response suggesting that there was insufficient specificity of nIRS for this type of task. While patterns of trained cortical evoked response have been observed during other learning tasks in MEG studies (Wik et al., 1996), the negative results of this study raise the question of whether such patterns can be observed in neurovascular activity. Visual analysis of nIRS data did provide moderate evidence of increased blood volume and/or oxygenation which was temporally associated with the delivery of H₂S during the behavioral acquisition phase. As such, nIRS holds potential as a means of monitoring neurovascular activity during extended learning tasks.
Confabulation and Self-Monitoring in Memory
Authors:   , Mott Tasha , Williams Joseph M
Published: July 2024

While confabulation is often attributed to a breakdown in self-monitoring, little empirical support for this assertion has been gathered to date. The present study examined the role of self-monitoring and frontal lobe functioning in memory distortion among normal controls and brain-damaged confabulating subjects. Specifically, control subjects were compared to frontal lobe damaged confabulators on their memory for narrative text and their capacity to self-monitor, as reflected in confidence ratings of remembered story elements. Recall and recognition memory scores for three narratives and corresponding confidence ratings in remembered story elements were assessed at three points in time: immediate, 30-minute delay, and, among controls only, after 1 week delay. It was expected that frontal lobe confabulators would fail to adjust their confidence ratings in free recall memory distortions relative to accurate memories. Control subjects, on the other hand, were expected to lower their confidence ratings in free recall memory distortions relative to accurate memories, even after 1 week when their memory was constrained similar to brain-damaged. These predictions were supported. On the recognition task, subjects were provided with corrective feedback following immediate assessment. It was predicted that frontal lobe confabulators would continue to show more recognition memory errors in conjunction with inflated confidence ratings. This prediction received only partial support. While frontal lobe confabulators continued to show more recognition memory errors than controls at delayed assessment, both groups' recognition memory improved, presumably due to the incorporation of corrective feedback. As a result, both groups were highly confident in their recognition memory at delayed assessment. Further, tests of frontal lobe functioning were significant predictors of both memory accuracy level and confidence ratings. These findings suggest that frontal lobe confabulation is associated with a breakdown in self-monitoring. However, this conclusion is qualified by the apparent incorporation of corrective feedback corresponding to an appropriate increase in confidence among brain-damaged subjects. The results are discussed in terms of the usefulness of self-monitoring as an explanatory concept in memory as well as its possible clinical implications.
Decision-level data fusion
Authors:   , Zhu Xiaoxun
Published: July 2024

Research in data fusion is motivated by the potential for significant enhancement in multisensor and multi-algorithm decision making. Developed initially for radar applications, data fusion is now studied for general-purpose signal processing, diversity in communication, and high performance computing. In part I of this dissertation, we provide an overview of sensor fusion, focusing on a specific application-mobile robot navigation. We review the main techniques for sensor fusion in robot navigation, emphasizing algorithms for robot self location. The review provides an arsenal of tools for addressing this (rather ill-posed) problem in machine intelligence, including Kalman filtering, rule-based techniques, behavior-based algorithms, and approaches that borrow from information theory, Dempster-Shafer reasoning, fuzzy logic and neural networks. In part II, we investigate the parallel decision fusion architecture whose necessity was established in part I. This architecture comprises N local detectors (LDs) and a decision fusion center (DFC). The local detectors observe a common volume of surveillance. The i^[th] detector uses its observation vector, z_i [belongs to] R^M, in a local decision rule f_i : R^M [right arrow] {-1,1} : z_i [right arrow] u_i, to determine whether to accept the null hypothesis H₀ (u_i = -1), or the alternative hypothesis H₁ (u_i = 1). The local observations are assumed to be statistically independent, conditioned on the hypothesis. The local decision vector {u_i}^N_[i=1] is then transmitted to the DFC which uses a global decision rule f₀ : {-1,1}^N [right arrow] {-1,1} : {u_i}^N_[i=1] [right arrow] u₀ to generate the global decision, u₀. We extend the existing optimal design in two directions: (1) Adaptive decision fusion: when a priori probabilities and sensor characteristics are unknown, we devise an algorithm that learns the decision rule at the DFC on line. (2) M-ary hypothesis testing: when the local detectors are restricted to transmit only one bit (1 or -1), we provide the condition under which the probability of error at the DFC converges to zero asymptotically. We point to several future research needs, among them-adaptive algorithms, qualitative and quantitative issues, generalization of decision fusion systems, and hierarchical architectures.
Treatment outcome among methadone recipients
Authors:   , Smith Jennifer L.
Published: July 2024

Opiate dependence has become a public health concern as it effects more than 800,000 Americans (Committee of Methadone Program Administrators [COMPA], 2000). Methadone maintenance is a common and effective treatment for opiate dependence yet polysubstance abuse and relapse to opiate use remain problematic (Strain, Stitzer, Liebson, & Bigelow, 1994). The stress buffering effect of perceived social support is an established construct that has been shown to increase adherence to treatment protocols and lower recidivism rates in health psychology. The role of perceived social support in methadone maintenance treatment has not been fully clarified. This study investigated the role of orientation towards social support in moderating the effects of perceived social support on treatment outcome among methadone maintenance recipients. Eighty new admissions to outpatient methadone maintenance were recruited to participate in this research. The first interview, approximately 1 week post-admission, inquired about such items as drug use, perceived social support, and orientation towards social support. Standard methadone maintenance treatment was available to all participants. The second interview, approximately 12 weeks post-admission, inquired about drug use and therapeutic alliance. Multiple regression analyses were used to test for an interaction of perceived social support and orientation towards social support in predicting the treatment outcomes of opiate use, polydrug use, length of time in treatment, and therapeutic alliance while controlling for potential confounds. Sixty-one participants completed follow-up interviews. There were no significant differences between completers and dropouts on demographic variables, predictor variables, or drug use severity. Opiate use and polysubstance use were significantly reduced following 12 weeks of methadone maintenance. The outcome measures of opiate use and polydrug use were not significantly predicted by expected covariates, perceived social support and orientation towards social support, or the interaction. Length of time in treatment was significantly predicted by methadone dose, a variable included in analyses as a covariate. Perceived social support, orientation towards social support, and the interaction did not significantly add to the prediction of length of time in treatment. Therapeutic alliance was significantly predicted by the interaction of perceived social support and orientation towards social support when the confound, years of education, was statistically controlled. The lack of a statistically significant relationship between social support and drug use is consistent with findings of prior research in this area. Explanations and implications of findings are discussed.
Swellable bone anchors
Authors:   , Nien Yu-Hsun , Gobran Riad H. , Kalidindi Surya , Siegler Sorin
Published: July 2024

Our research group developed a new swellable polymeric material system that was targeted towards a range of applications requiring fixation in bone, such as suture anchors. The material system developed was a cross-linked Poly(methylmethacrylate-acrylic acid) random copolymer. Implants made from this copolymer exhibited an ability to absorb body fluids and swell in a controlled manner. In the applications mentioned above, the swelling of these anchors is constrained by the surrounding bone, and consequently an interfacial pressure developed at the bone-implant interface. This interfacial pressure, in turn, increased the frictional resistance and improved significantly the fixation strength of the implants. In our experience with these anchors, two major problems were found: (1) it took relatively long time for the swelling anchors to reach their equilibrium state and therefore immediate fixation of smooth swelling anchors was poor; (2) excessive swelling weakened the mechanical properties of the anchors and this lead to a decrease in holding strength. Therefore, it was necessary to: (1) design a built-in immediate fixation mechanism; (2) reduce the time required for the anchor to reach equilibrium, and (3) optimize the material composition for proper amount of swelling. In this thesis, swelling behavior of P(MMA-AA) was studied in order to understand its excessive swelling in vivo, while not in vitro. Then, the study of optimal swelling strain of anchors was performed in foam of various densities (Such foam is commonly used to simulate the mechanical properties of cancellous bone). In the end, fixation strengths of swellable anchors were evaluated on human cadaveric specimens in the shoulder and spine areas and compared to the fixation strengths of commercially available anchors.
Investigation of the unusual ATP synthase complexes in the alveolates Tetrahymena thermophila and Plasmodium falciparum
Authors:   , Nina Praveen Balabaskaran , Edlind Thomas D , Vaidya Akhil B.
Published: July 2024

ATP synthesis is carried out by the ATP synthase complex, which uses proton flow to drive the rotation of protein subunits to produce ATP. The enzyme has two sectors: F1 has the catalytic sites for ATP synthesis, and Fo forms channels for proton movement and functions as a bearing and stator. Because the parts of the complex have to interact with each other, critical protein subunits of the enzyme are conserved from bacteria to higher eukaryotes. We were surprised that a group of unicellular organisms called alveolates, which includes Plasmodium falciparum and Tetrahymena thermophila, lacked several critical proteins of the Fo sector, according to whole genome sequence analyses. The role of the putative mitochondria! ATP synthase in Plasmodium has been unclear, as blood stages of P. falcinarum appear to derive ATP largely through glycolysis, and the missing Fo subunits suggested a nonfunctional enzyme. However, Tetrahymena is fully capable of oxidative phosphorylation, suggesting the presence of undetected, divergent Fo subunits. We hypothesized that similar divergent Fo subunits might be shared by other alveolates, including Plasmodium. To test that, we isolated intact ATP synthase complexes from the ciliate Tetrahymena thermophila and examined their structure by electron microscopy and their protein composition by mass spectrometry. We found that the ATP synthase complex of this organism is highly divergent both in its overall structure and many of the associated protein subunits. At least 13 novel proteins are present within this complex that have no orthologues in any organism outside of the ciliates. Except for one possible protein (PF11_0262 - putative 1-) subunit), we could not identify any orthologues of the novel subunits in Plasmodium. Our investigation of Plasmodium ATP synthase has revealed the predominant form to be dimers, as seen in other eukaryotic organisms. Also, immunofluoresence microscopy of parasite lines expressing epitope-tagged versions of all the identified subunits of the ATP synthase was consistent with the localization of these subunits (with one exception) to the mitochondrion. Furthermore, our efforts to knock out key subunits (beta and gamma) of the enzyme were unsuccessful, suggesting an important role in the parasite life cycle.
Development and application of a finite element model for the study of left ventricular mechanics under normal and ischemic conditions
Authors:   , Zhang Youmin , Lewin Peter Andreas , Tan Tein-Min , Jaron Dov
Published: July 2024

Left ventricular (LV) mechanics, or LV stress and strain distribution, is an important determinant of the various characteristics of cardiac physiology and pathology. Numerous analytical and computational models have been developed in the past to study the LV mechanics and to correlate the stress distribution to the normal or pathological condition of the heart. In this research, a new computational model has been developed and applied successfully for studying the stress distribution and deformation of a heart under normal, regionally ischemic, or infarction condition. This finite element based model differs from all previous models in that it not only incorporates the complex LV geometry, anisotropic myocardial material properties, and realistic physiological boundary conditions, but also includes the effects of active fiber contraction force based on MRI strains and large deformation. The results of the study have shown that, under a normal condition the values of stresses in the LV gradually increase from the base to the apex, indicating that the apical region experiences higher stress than that of the basal region. As the heart condition changes from normal to regional ischemia and infarction, the stress values also decrease, particularly in the ischemic or infarcted region. Thus, with this new model, the relationship between the stress distribution and the condition of the heart can be quantitatively established. This significant contribution will definitely assist in the future studies of LV mechanics under both physiological and pathological conditions.
Regulation of bladder smooth muscle contraction and a new organ culture model to study bladder smooth muscle biology
Authors:   , Wang Tanchun , Moreland Robert S.
Published: July 2024

It is well accepted that phosphorylation of the 20 kDa regulatory myosin light chain (MLC) catalyzed by the MLC kinase and dephosphorylation catalyzed by the MLC phosphatase plays a primary role in the regulation of smooth muscle contraction and relaxation. Inhibition of MLC phosphatase causes a net increase in MLC phosphorylation levels. The goal of this dissertation was to clarify the signaling pathways in intact bladder smooth muscle, especially the roles of protein kinase C (PKC) and Rho kinase (ROCK) and their downstream effectors in regulating MLC phosphatase activity and force during the phasic and sustained phases of bladder smooth muscle agonist stimulated contraction and stretch-induced basal tone. To achieve these goals, the studies were performed in the presence and absence of the PKC inhibitor bisindolylmaleimide-1 (Bis) or the ROCK inhibitor H-1152. Phosphorylation levels of PKCpotentiated PP1 inhibitory protein of 17 kDa (Thr38-CPI-17) and myosin phosphatase targeting subunit (Thr696/Thr85O-MYPT1) were measured at different time points during carbachol and phorbol dibutyrate stimulation and at different degrees of stretch using site specific antibodies. By removing Ca²⁺ during stretch, the significance of Ca²⁺ signaling in the stretch-induced regulation was also studied in this dissertation. Our results suggest that during agonist stimulation, PKC regulates MLC phosphatase activity through phosphorylation of CPI-17. In addition ROCK phosphorylates both Thr850MYPT1 and CPI-17, partly through cross-talk with the PKC pathway. Secondly, our results demonstrate that there is a constitutively activate pool of ROCK that phosphorylates MYPT1 in the basal state. Lastly, our results show that stretch-induced force generation in bladder smooth muscle is regulated by an increase in MLC phosphorylation through a stretch-induced influx of extracellular Ca²⁺ and an inhibition of MLC phosphatase activity. This dissertation also describes the development and characterization of a novel bladder smooth muscle organ culture model. The viability of this model was tested by its contractility and smooth muscle specific protein expression following 9 days of culture. Our results suggest that this novel organ culture model maintains the contractile phenotype of smooth muscle for up to 9 days. Therefore this organ culture model provides a new and useful method to study bladder smooth muscle biology with preserved contractility and smooth muscle phenotype.
Collagen Fibrillogenesis is Modulated by Biomimetic Proteoglycans
Authors:   , Yang Tao , Marcolongo Michele S
Published: July 2024

Collagen is one of the leading components in extracellular matrix (ECM), proving durability, structural integrity, and functionality for many tissues. Deregulation of collagen fibrillogenesis and excessive collagen degradation of many interstitial connective tissues have been associated with a number of dysfunctions and diseases. Recently, we developed a novel, biocompatible, semisynthetic biomimetic proteoglycan (BPG), which consists of an enzymatically resistant synthetic polymer core and natural chondroitin sulfate bristles arranged in a three-dimensional bottle-brush configuration similar to natural aggrecan. We demonstrated that BPGl 0 (~180 BCDa) is an effective factor to regulate type I collagen fibrillogenesis, reflected by its efficient regulatory role in controlling the end-to-end fusion and lateral growth during collagen fibril formation. In addition, the network structure of formed fibrils could be modulated by the presence of BPGl 0 significantly. Similarly, BPG250 ( -2000 KDa) did affect the collagen self-assembly but it was less effective than BPGIO. Structural property of collagen scaffolds could be modulated by two proteoglycan mimic, suggesting endogenous ECM could be structural altered by incorporation of a synthetic proteoglycan without a core protein.
Experimental and analytical study of the fiberoptic based recirculating memory systems
Authors:   , Saedi Reza A. , Daryoush Afshin S.
Published: July 2024

Fiberoptic links are useful in many microwave signal processing applications, one of which is the recirculating RF memory loop. As an integral part of memory loop systems, the fiber optic link offers several clear advantages: small size, light weight, immunity to EMI, and low loss over long delays. The development of several alternative techniques for predicting and realizing the total time delay achievable through the fiberoptic (FO) based memory loop was the objective of this study. On the basis of current literature, the FO link was established as the only practical option for the long delay element. The analytical expressions, predicting the total time delay achievable were developed in terms of gain, flatness, noise figure, intermodulation distortion, and dynamic range characteristics of FO delay element. Among them, nose figure and gain flatness greatly influence the performance of the recirculating memory loop. Two sets of low-loss, low noise figure, optical modules operating at 850 and 1300 nm for long and short delays were designed. These achieved optimum performance over the bandwidth of 2-4 GHz. The basic building blocks of the FO links, reactively matched optical transmitter and actively matched optical receiver modules, were fabricated and characterized, and then used in several experiments. The first set of experiments led to a sub-millisecond recirculation of the RF signal; however, gain flatness curtailed the total recirculation times over the full bandwidth. To overcome this limitation, the concept of the adaptive gain equalization technique was demonstrated via a tunable filter. The phase coherency of each individual pulse was then investigated through a circuit designed to sampled pulses after a tunable delay. Finally, the degradation of the offset carrier noise power spectral density and the effect of recirculation on the FM modulated signals were studied. An alternative approach to overcoming the gain flatness problem-to facilitate full recirculation in the optical domain-was considered, and analytical models for predicting the performance of the optical amplifier-based memory loop were developed. Finally, a system architecture, capable of providing time delays over milliseconds for the full instantaneous bandwidth of 2-4 GHz, was analyzed. To extend this approach over full 2-18 GHz, a special optical coding method with a higher dynamic range was recommended.
A large area, high speed phototube employing a metal-semiconductor-metal anode
Authors:   , Yost Tamera A. , Herczfeld Peter R
Published: July 2024

For free-space communication, inter-satellite communication and microwave modulated lidar-radar applications, a large area photodetector with low noise, high gain, and a bandwidth of a few gigahertz is needed. Commercially available avalanche photodiodes and photomultiplier tubes satisfy all the necessary requirements except bandwidth, limiting the free-space communication system data rate and underwater target detection sensitivity of microwave modulated lidar-radar applications. The work presented in this thesis is directed toward meeting the needs of these systems and involves the bandwidth extension of an existing vacuum phototube to 5 GHz to provide a large area, high speed and high gain photodetector for such applications. The approach taken in achieving this goal is to replace the currently used electron bombarded Schottky diode anode of the phototube with an interdigital metal-semiconductor-metal (MSM) device. The MSM device has been used primarily as a photodetector. This application is the first known use of an MSM device as an electron bombarded semiconductor device. The scope of this work includes the MSM device modeling, design, fabrication, optical characterization for functionality, and integration of the MSM anode in the phototube. A variety of devices were fabricated and characterized optically to prove functionality. Novel static and dynamic models are proposed for the electron bombarded MSM. Characterization of the experimental phototube showed the metal-semiconductor-metal device anode suffered damage during the fabrication process, causing a degradation in the overall performance of the anode and the phototube. The metal-semiconductor-metal device anode gain was limited to <2 and the bandwidth to 2.1 GHz, rather than a model predicted gain of 844 and bandwidth of 3 GHz. The overall responsivity of the phototube is 0.2 A/W, rather than a typical 100 A/W. Although the experimental phototube did not meet the design specifications, the results were not due to a design error, but rather to a manufacturing flaw. With a fine-tuned manufacturing process, the design and theory proposed in this work clearly indicates that the use of a metal-semiconductor-metal device as the anode of a phototube to be a viable and promising approach to increasing the phototube bandwidth while maintaining a large area and high gain.
Self-reported potential community response to sexual offender release notification
Authors:   , Blain Natacha
Published: July 2024

Through the use of vignettes and a self-report outcome questionnaire 300 discharged jurors from the New York Supreme Court, Bronx County, were asked to rate their potential willingness to participate in certain activities when notified that a released child sex offender plans to move into their neighborhood. Results indicate that the order in. which responses were presented to participants significantly affected their willingness to engage in potential activities. Specifically, participants reported an unwillingness to engage in proactive behaviors when notified of a non-sex offender and a willingness to engage in reactive behaviors when notified of a sex offender on the order 2 version of the 30 item questionnaire. These findings suggest that the order of responses had a priming effect on the way participants scored the questionnaire. Results are discussed in terms of their implications for future research and for policy.
Comparison of the first order frontal model with aircraft data and numerical simulations
Authors:   , Trout Joseph Jude , Kreitzberg Carl William
Published: July 2024

A comparison of aircraft data to the first order frontal model is made. Data collected by WP-3D research aircraft during the ERICA Field Project (Experiment on Rapidly Intensifying Cyclones Over the Atlantic) is scanned to find data recorded during constant altitude transects of atmospheric fronts. Statistics are compiled on magnitude of the change of equivalent potential temperature, potential temperature, virtual temperature, and the front normal and front parallel components of wind and on the width of the fronts. Single value decomposition of the data is performed to smooth the data and analyze the signal without the smallest scale features or noise. At least 90 percent of the signal is retained. The fronts defined by the individual components are normalized to compare with the first order frontal model. The first order frontal model is one of three zones, two constant, but different, valued zones of either equivalent potential temperature, potential temperature, virtual temperature, and the front normal and front parallel components of wind separated by a zone of strong, linear gradient of the observable. Several numerical experiments are performed using the numerical weather prediction computer model, LAMPS90 (Limited Area Mesoscale Prediction System), to simulate the development of the storm which occurred during IOP2 of ERICA (13 December 1988 to 15 December 1998). LAMPS90 has a long history of simulations using grid spacing of 140km and 70km. For this study, simulations at higher resolution (smaller grid spacing) are desirable, therefore simulations were performed at 140km, 70km and 35km grid spacing to check the stability and reproducibility of the results of the model at higher resolutions. Various simulations of different grid domain size and initial times times performed and the implications are discussed. The mesoscale features of the model simulations are then analyzed. The general appearance and characteristics of the fronts produced by the simulations are examined. Transects of the model fronts at constant altitude of equivalent potential temperature, potential temperature, and the front normal and front parallel components of wind are compared to the first order frontal model. Finally, transects of the model simulation are compared to transects of the observed data collected by the WP-3D aircraft. It is concluded that the first order frontal model adequately describes the thermal characteristics of the transects through the front. The average width of the cold fronts at low levels is 54 km and the average width of the warm fronts at low levels is 88 km. The change in equivalent potential temperature across the cold front is 9 K and across the warm front is 11 K. The average change the front normal component of wind is 14 m/s across the cold fronts and is 20 m/s across the warm fronts. The average change in the front parallel component of wind is 20 m/s across the cold fronts and is 23 m/s across the warm fronts. (Abstract shortened by UMI.).
Antimicrobial action of Histone H1
Authors:   , Hand Christopher Michael , Emrich Jacqueline
Published: July 2024

Recently, the emergence of multi-drug resistant bacterial strains has become an increased health-care problem of pandemic proportions. There is a clear need for new and more effective therapeutics that can also be used in antibiotic-resistant bacteria. This project focuses on the antimicrobial effects of H1 in several bacterial strains and attempts to suggest a mechanism through which H1 might exert its antimicrobial properties. Activity of H1, isolated from calf thymus with a purity of >99%, was tested against early to mid-log phase bacterial cultures utilizing the standard colony formation assay. The interaction of H1 with the LPS component of the outer membrane was investigated by studying the changes in H1 toxicity using the ionic interactions of magnesium and calcium (the 2 predominant divalent cations found on the LPS) with LPS. The ability of H1 to displace polymyxin (known to interact strongly with the LPS) off purified LPS was studied. Changes in sensitivity to H1 of Salmonella typhimurium lipid A mutants was also examined. The potential changes in membrane permeabilization were studied utilizing the synergistic effects of H1 with lysozyme and through the use of a flow cytometer and spectrofluorometer to measure the uptake of different fluorescent probes. H1 proved to be highly effective in killing numerous bacterial strains. The effect of H1 were dose- and time-dependent. Maximal toxicity was achieved within a 10-minute, incubation time. H1 demonstrated a strong affinity to the LPS component, specifically the lipid A, of the outer membrane of the gram-negative organisms. Flow cytometric, and fluorometric analysis further showed that H1 causes a rapid loss of membrane integrity, which was proportional to cell killing. In summary, H1 proved a potent antibiotic for numerous bacteria including gram-negative strains, having cytotoxic rather than cytostatic effect. The mechanism by which H1 exerts its bacteria-killing properties involves several steps. First is the high-affinity binding of H1 to the lipid A component of the bacterial cell membrane. Second by the incorporation of H1 into the membrane, through the interaction with phosphotidylglyocerol and cardiolipin, that leads to irreversible disruption of the membrane integrity and subsequent death.
Strain hardening of titanium
Authors:   , Salem Ayman A. , Doherty Roger D , Kalidindi Surya
Published: July 2024

The quasi-static mechanical response of high purity, polycrystalline [alpha]-titanium is investigated in terms of the underlying deformation mechanisms that govern its macroscopic behavior at room temperature. Constant strain rate tests were conducted on this material in simple compression, plane-strain compression and simple shear, and the true stress ([sigma])-true strain ([epsilon]) responses were documented. From the measured data, the strain hardening rates were numerically computed, normalized with shear modulus (G), and plotted against both normalized stress. These normalized strain hardening plots exhibited three distinct stages of strain hardening, Stage A with falling strain hardening rate, followed by stage B with increasing strain hardening rate, and finally stage C characterized by a falling strain hardening rate. The microstructure evolution has been characterized using both optical microscopy and orientation imaging microscopy at different strain levels. It was found that the onset of deformation twinning correlated with an increase in strain hardening rate in compression tests. In shear tests, a much lower rate of strain hardening was found, at all strains, and this correlated with a lower density of deformation twinning. The increase in the strain-hardening rate was found to match quantitatively with Hall-Petch hardening mechanism. The new twin boundaries appear to act as barriers to dislocations and reduce the effective slip length in the matrix. Moreover, Microhardness measurements indicated that twinned regions are harder than the untwinned areas, enhancing the increase in the strain hardening rate, stage B. On the other hand, the observed increase of twin volume fraction at low and moderate strain levels was observed to saturate at high strain levels explaining the falling strain hardening rate in stage C. The saturated twin volume fraction is believed to be a result of reorienting twinned regions into new orientations, favorable for slip, by twin transformation. Conveying the insights from the experiments, new functions for slip hardening and twin hardening were introduced to a Taylor type crystal plasticity model. The model was able to predict the anisotropic strain hardening behavior and texture evolution. The predictions were in agreement with the experimental measurements.
Techniques for blind system identification and application to the equalization of PAM/QAM modulated signals
Authors:   , Pozidis Haralampos , Petropulu Athina P.
Published: July 2024

We consider the problem of blind system identification, that is, estimating an unknown system excited by an unknown input, based solely on the system output. This problem appears in applications such as speech recognition, image restoration and data transmission. In this study we focus on digital data transmission. In modern digital communication systems which transmit millions of symbols per second from dense constellations, smearing of adjacent symbols is inevitable due to the dispersive nature of the propagation medium. This distortion effect is termed Intersymbol Interference (ISI). ISI (channel) identification and equalization are necessary to compensate for distortion. Two classes of techniques for blind channel estimation exist: Higher Order Statistics (HOS) methods applied to the received signal, and Second Order Statistics (SOS) methods applied to oversampled versions of the received signal (temporal diversity), or to multichannel versions of it obtained by several antennas (spatial diversity). Each class has different characteristics and limitations: HOS-based methods require long data and usually exhibit high complexity, while SOS-based ones are sensitive to noise and require knowledge of channel length. In this dissertation we propose novel methods in both classes, aimed at addressing the limitations of each class. We first propose a SOS-based channel estimation method that utilizes the information embedded in the Fourier-phase of the cross-spectrum of functions of two observations. Approximate analytical expressions of the statistics of the estimation error are provided. Both analysis and simulation results indicate that the proposed approach possesses the desirable features of data efficiency, robustness to noise, and insensitivity to channel length mismatch. We next propose a HOS-based method, which achieves channel identification based on HOS of the received signal. The key feature is the requirement of a pair of HOS slices as opposed to the entire HOS. This allows for significant computational savings. We establish channel identifiability conditions, and show that appropriate selection of slices leads to reduction of estimation variance. We also propose a criterion for selection of "good' slices. Both our SOS and HOS methods are tested on channels extracted from actual microwave measurements, and demonstrate robustness in highly dispersive and noisy environments.
The Impact of HIV-1 and mu-opioids on the Bone Marrow and Blood-Brain Barrier
Authors:   , Strazza Marianne , Nonnemacher Michael R. , Wigdahl Brian
Published: July 2024

One third of AIDS cases in the United States are attributable to injection drug use, a significant predisposing risk factor to contracting HIV-1. In addition to the increased risk of exposure, there is accumulating evidence that levels of drug in circulation can impact HIV-1 disease progression and neuropathogenesis. Opioid exposure in vivo and in vitro result in increased HIV replication in monocytes and CD4+ T cells. In the simian immunodeficiency virus (SIV) in vivo model, increased replication rate, viral load, and frequency of mutation in the periphery along with increased viral load detected in the cerebrospinal fluid (CSF) were observed in animals treated with opioids. Epidemiological studies have indicated an increased incidence of HIV-associated neurocognitive disorders (HAND) in patients abusing drugs. Additionally, opioids have been shown to potentiate HIV protein mediated neurotoxicity. Two classifications of HAND existed in the early stages of the HIV epidemic: HIV-associated dementia (HAD) and minor cognitive motor disorder. Approximately 15% of individuals infected with HIV-1 developed HAD, and approximately 30% to 60% of individuals developed less severe forms of HAND. Although highly active antiretroviral therapy (HAART) has increased survival, reduced viral loads, increased CD4 cell counts, and reduced opportunistic infections, one outcome has not changed: HAND is still a serious concern. Although the incidence of the most severe form of HAND, HAD, has decreased, the overall prevalence of HAND has not declined, potentially because patients with the more mild forms of HAND, are living longer with persistent impairment. While the mechanism underlying increased onset and severity of HAND in an opioid abusing population is not fully understood, it likely involves accelerating the overcoming of the major obstacle to viral neuropathogenesis, the blood-brain barrier (BBB). This can likely be attributed to dysregulation within the bone marrow, the origin of circulating cells within the periphery, and at the site of entry of this population into the CNS, the BBB. Damage to the BBB allows increased transendothelial migration from peripheral circulation, increasing the access of virally infected cells, viral proteins, and free virus to the central nervous system (CNS). These studies show that mu-opioids alter hematopoietic progenitor cell susceptibility to HIV-1 infection within the bone marrow through decreased surface expression of CXCR4. In addition, prolonged exposure of the endothelial cells that comprise the BBB to morphine increases firm adhesion and transmigration of a subpopulation of PBMCs across the BBB through a mechanism involving increased surface expression of cellular adhesion molecules. These studies suggest that morphine influences HIV-1 neuropathogensis on multiple fronts.
An interactive facility for power system studies
Authors:   , Erkmen Ismet
Published: July 2024

The work of the author in developing an interactive facility for power systems research and instruction is described. Design specifications emphasize the need for a user-friendly environment in which a highly flexible, yet efficient interface provides simple access to several application programs. Computer graphics play a key role, helping the user visualise the nature of the problem in hand and, in so doing, making it possible to gain significant insight into the complex behavior of practical power system networks. The application programs, also designed and implemented by the author, permit very fast analysis in terms of load-flow, contingency and short-circuit studies. In developing the interactive facility, the author has made a number of important contributions. Apart from the significant impact of the facility itself, as used for research and instructional purposes within Drexel's power computational techniques. Thus, for load-flow analysis, new sparse matrix algorithms are introduced with the emphasis on efficient implementation to reduce execution times and storage requirements. Furthermore, a novel sequencing algorithm is introduced in connection with the Z-bus impedance construction process. This algorithm is the basis for the author's approach to short-circuit analysis. The result is much shorter execution times. A variation of the fast decoupled load-flow model is also presented where an attempt is made to de-sensitize the decoupling effect and thereby yield more efficient and reliable convergence properties.