Showing papers by "Drexel University published in 1998"

Hydrodynamic and heat transfer study of dispersed fluids with submicron metallic oxide particles

Abstract: Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...

Visualizing a discipline: an author co-citation analysis of information science, 1972–1995

Abstract: This study presents an extensive domain analysis of a discipline—information science—in terms of its authors. Names of those most frequently cited in 12 key journals from 1972 through 1995 were retrieved from Social Scisearch via DIALOG. The top 120 were submitted to author co-citation analyses, yielding automatic classifications relevant to histories of the field. Tables and graphics reveal: (1) The disciplinary and institutional affiliations of contributors to information science; (2) the specialty structure of the discipline over 24 years; (3) authors' memberships in 1 or more specialties; (4) inertia and change in authors' positions on 2-dimensional subject maps over 3 8-year subperiods, 1972–1979, 1980–1987, 1988–1995; (5) the 2 major subdisciplines of information science and their evolving memberships; (6) “canonical” authors who are in the top 100 in all three subperiods; (7) changes in authors' eminence and influence over the subperiods, as shown by mean co-citation counts; (8) authors with marked changes in their mapped positions over the subperiods; (9) the axes on which authors are mapped, with interpretations; (10) evidence of a paradigm shift in information science in the 1980s; and (11) evidence on the general nature and state of integration of information science. Statistical routines include ALSCAL, INDSCAL, factor analysis, and cluster analysis with SPSS; maps and other graphics were made with DeltaGraph. Theory and methodology are sufficiently detailed to be usable by other researchers. © 1998 John Wiley & Sons, Inc.

An organization-level analysis of voluntary and involuntary turnover.

Abstract: Although there are many individual-level models of turnover, little research has examined the effects of human resource management practices on quit rates and discharge rates at the organizational level. This study used organization-level data from 227 organizations in the trucking industry to explore this issue. Results show that human resource management practices predict quit rates and discharge rates but that the determinants of each are quite different. Implications are derived and directions for future research suggested.

Olfaction in Neurodegenerative Disease: A Meta-analysis of Olfactory Functioning in Alzheimer's and Parkinson's Diseases

Abstract: Background Olfactory deficits in Alzheimer's disease (AD) and idiopathic Parkinson's disease (PD) have been well established. Objective To clarify and review the literature by evaluating the evidence for olfactory deficits in 3 olfactory domains, including odor identification, recognition, and detection threshold. Data Sources A literature search of English-language studies of olfaction in AD, PD, and healthy controls was conducted via online databases (PsycInfo and MEDLINE) and reference lists from review articles. Study Selection To meet selection criteria for meta-analysis, each study required a control group and complete and usable data. This review yielded 26 publications of olfactory identification, recognition, and/or detection threshold. Because of the inclusion of more than 1 relevant study of olfaction in several of these publications (eg, both identification and threshold assessed), 43 studies were ultimately appropriate for meta-analysis. Data Extraction Effect sizes were calculated for each study by expressing differences between patient and control group means in SD units (Cohen's d ). Data Synthesis Extremely large effect sizes were shown across all tasks in both AD and PD groups. Both between-group analyses using the Mann-Whitney U test and within-group analyses using Friedman 2-way analysis of variance did not reveal any significant differences (all P >.30). Conclusions As expected, severe deficits were found for both patients with AD and PD in each of the 3 olfactory domains relative to controls. However, no discriminating olfactory deficits were seen between patient groups or among the 3 measured olfactory domains, suggesting a similar disturbance in olfactory function between patients with AD and PD.

Using automatic clustering to produce high-level system organizations of source code

Abstract: We describe a collection of algorithms that we developed and implemented to facilitate the automatic recovery of the modular structure of a software system from its source code. We treat automatic modularization as an optimization problem. Our algorithms make use of traditional hill-climbing and genetic algorithms.

Relationship between donor age and the replicative lifespan of human cells in culture: a reevaluation.

Abstract: Normal human diploid fibroblasts have a finite replicative lifespan in vitro, which has been postulated to be a cellular manifestation of aging in vivo. Several studies have shown an inverse relationship between donor age and fibroblast culture replicative lifespan; however, in all cases, the correlation was weak, and, with few exceptions, the health status of the donors was unknown. We have determined the replicative lifespans of 124 skin fibroblast cell lines established from donors of different ages as part of the Baltimore Longitudinal Study of Aging. All of the donors were medically examined and were declared “healthy,” according to Baltimore Longitudinal Study of Aging protocols, at the time the biopsies were taken. Both long- and short-lived cell lines were observed in all age groups, but no significant correlation between the proliferative potential of the cell lines and donor age was found. A comparison of multiple cell lines established from the same donors at different ages also failed to reveal any significant trends between proliferative potential and donor age. The rate of [3H]thymidine incorporation and the initial rates of growth during the first few subcultivations were examined in a subset of cell lines and were found to be significantly greater in fetal lines than in postnatal lines. Cell lines established from adults did not vary significantly either in initial growth rate or in [3H]thymidine incorporation. These results clearly indicate that, if health status and biopsy conditions are controlled, the replicative lifespan of fibroblasts in culture does not correlate with donor age.

NF-κB Mediates αvβ3 Integrin-induced Endothelial Cell Survival

Abstract: The αvβ3 integrin plays a fundamental role during the angiogenesis process by inhibiting endothelial cell apoptosis. However, the mechanism of inhibition is unknown. In this report, we show that integrin-mediated cell survival involves regulation of nuclear factor-kappa B (NF-κB) activity. Different extracellular matrix molecules were able to protect rat aorta- derived endothelial cells from apoptosis induced by serum withdrawal. Osteopontin and β3 integrin ligation rapidly increased NF-κB activity as measured by gel shift and reporter activity. The p65 and p50 subunits were present in the shifted complex. In contrast, collagen type I (a β1-integrin ligand) did not induce NF-κB activity. The αvβ3 integrin was most important for osteopontin-mediated NF-κB induction and survival, since adding a neutralizing anti-β3 integrin antibody blocked NF-κB activity and induced endothelial cell death when cells were plated on osteopontin. NF-κB was required for osteopontin- and vitronectin-induced survival since inhibition of NF-κB activity with nonphosphorylatable IκB completely blocked the protective effect of osteopontin and vitronectin. In contrast, NF-κB was not required for fibronectin, laminin, and collagen type I–induced survival. Activation of NF-κB by osteopontin depended on the small GTP-binding protein Ras and the tyrosine kinase Src, since NF-κB reporter activity was inhibited by Ras and Src dominant-negative mutants. In contrast, inhibition of MEK and PI3-kinase did not affect osteopontin-induced NF-κB activation. These studies identify NF-κB as an important signaling molecule in αvβ3 integrin-mediated endothelial cell survival.

Incorporation of deformation twinning in crystal plasticity models

Abstract: A new constitutive framework, together with an efficient time-integration scheme, is presented for incorporating the crystallography of deformation twinning in polycrystal plasticity models Previous approaches to this problem have required generation of new crystal orientations to reflect the orientations in the twinned regions or implementation of “volume fraction transfer” schemes, both of which require an update of the crystal orientations at the end of each time step in the simulation of the deformation process In the present formulation, all calculations are performed in a relaxed configuration in which the lattice orientation of the twinned and the untwinned regions are pre-defined based on the initial lattice orientation of the crystal The validity of the proposed constitutive framework and the time-integration procedures has been demonstrated through comparisons of predicted rolling textures in low stacking fault energy fcc metals and in hcp metals with the corresponding predictions from the earlier approaches as well as through qualitative comparisons with the measurements reported previously

Sex differences in brain aging : A quantitative magnetic resonance imaging study

Abstract: Background Little is known about the effect of sex on age-related changes in brain structure. Methods Quantitative magnetic resonance imaging of the brain was performed in 330 elderly (age range, 66-96 years) volunteers living independently in the community, all of whom were participants in the Cardiovascular Health Study. Blinded measurements of global and regional brain size were made from T 1 -weighted axial images by means of computer-assisted edge detection and trace methods. High measurement reliabilities were obtained. Results Age-specific changes in brain size were significantly greater in men than women for the peripheral (sulcal) cerebrospinal fluid volume, the lateral (sylvian) fissure cerebrospinal fluid volume, and the parieto-occipital region area. Main effects of age were observed for all the remaining brain regions examined (cerebral hemisphere volume, frontal region area, temporo-parietal region area, lateral ventricular volume, and third ventricle volume), but these effects were similar in men and women. Asymmetries in brain structures were not affected by aging in either sex. Conclusions Our results are generally consistent with the few published studies on sex differences in brain aging and suggest that, for at least some structures, aging effects may be more apparent in men than women. The neurobiological bases and functional correlates of these sex differences require further investigation.

The Murine CAR Homolog Is a Receptor for Coxsackie B Viruses and Adenoviruses

Abstract: Complementary DNA clones encoding the murine homolog (mCAR) of the human coxsackievirus and adenovirus receptor (CAR) were isolated. Nonpermissive CHO cells transfected with mCAR cDNA became susceptible to infection by coxsackieviruses B3 and B4 and showed increased susceptibility to adenovirus-mediated gene transfer. These results indicate that the same receptor is responsible for virus interactions with both murine and human cells. Analysis of receptor expression in human and murine tissues should be useful in defining factors governing virus tropism in vivo.

Prevalence of Intimate Partner Abuse in Women Treated at Community Hospital Emergency Departments

Abstract: Context.—The majority of prior studies examining intimate partner abuse in the emergency department (ED) setting have been conducted in large, urban tertiary care settings and may not reflect the experiences of women seen at community hospital EDs, which treat the majority of ED patients in the United States.Objective.—To determine the prevalence of intimate partner abuse among female patients presenting for treatment in community hospital EDs and describe their characteristics.Design.—An anonymous survey conducted from 1995 through 1997 inquiring about physical, sexual, and emotional abuse.Setting.—Eleven community EDs in Pennsylvania and California.Participants.—All women aged 18 years or older who came to the ED during selected shifts.Main Outcome Measures.—Reported acute trauma from abuse, past-year physical or sexual abuse, and lifetime physical or emotional abuse.Results.—Surveys were completed by 3455 (74%) of 4641 women seen. The prevalence of reported abuse by an intimate partner was 2.2% (95% confidence interval [CI], 1.7%-2.7%) for acute trauma from abuse, 14.4% (95% CI, 13.2%-15.6%) for past-year physical or sexual abuse, and 36.9% (95% CI, 35.3%-38.6%) for lifetime emotional or physical abuse. California had significantly higher reported rates of past-year physical or sexual abuse (17% vs 12%, P<.001) and lifetime abuse (44% vs 31%, P<.001) than Pennsylvania. Logistic regression modeling identified 4 risk factors for reported physical, sexual, or acute trauma from abuse within the past year: age, 18 to 39 years (odds ratio [OR], 2.2; 95% CI, 1.7-3.0); monthly income less than $1000 (OR, 1.7; 95% CI, 1.3-2.1); children younger than 18 years living in the home (OR, 2.0; 95% CI, 1.5-2.6); and ending a relationship within the past year (OR, 7.0; 95% CI, 5.5-8.9).Conclusion.—If the prevalence of abuse in community hospitals throughout the United States is similar to the range of prevalence estimates found in this study, then heightened awareness of intimate partner abuse is warranted for patients presenting to the ED.

A new type of STATCOM based on cascading voltage source inverters with phase-shifted unipolar SPWM

Abstract: In this paper, a new type of static compensator (STATCOM) is proposed. This new STATCOM is constructed by cascading several identical full-bridge (H bridge) voltage-source inverters (VSIs). A so-called phase-shifted sinusoidal pulsewidth modulation (SPWM) unipolar voltage switching scheme is applied to control the switching devices of each VSI. The harmonics in STATCOM current caused by the DC voltage ripple is rejected by a new method developed in this paper. As a result, the size of inductor and DC capacitors can be further reduced. A very effective startup procedure is proposed to start up the STATCOM. The proposed STATCOM has the advantage of a fewer number of VSIs, the VSIs being identical and extremely fast in response to reactive power change.

Correlates of daytime sleepiness in 4578 elderly persons: The cardiovascular health study

Abstract: Objectives: To describe the prevalence of self-reported daytime sleepiness in older men and women and to describe their relationships with demographic factors, nocturnal complaints, health status, and cardiovascular diseases (CVD). Design: Cross-sectional survey and clinical exam. Setting: Participants in the Cardiovascular Health Study, 4578 adults aged 65 and older, recruited from a random sample of non-institutionalized Medicare enrollees in four U.S. communities. Measures: Daytime sleepiness measured by the Epworth Sleepiness Scale (ESS), magnetic resonance imaging of the brain (MRI), cognitive function tests, and standardized questionnaires for cardiopulmonary symptoms and diseases, depressive symptoms, social support, activities of daily living, physical activity, and current medications. Results: Approximately 20% of the participants reported that they were usually sleepy in the daytime. Although elderly black men were less likely to report frequent awakenings than those in the other three race and gender groups, they had significantly higher mean ESS scores. The following were independently associated with higher ESS scores in gender-specific models: non-white race, depression, loud snoring, awakening with dyspnea or snorting, frequent nocturnal awakenings, medications used to treat congestive heart failure, non-use of sleeping pills, a sedentary lifestyle, and limitation of activities of daily living in both men and women; additional correlates included hip circumference and current smoking in men, and hayfever in women. The following were not independently associated with ESS in the models: age, education, use of wine or beer to aid sleep, use of tricyclic antidepressants, long- or short-acting benzodiazepines, asthma, angina, myocardial infarction, congestive heart failure itself, forced vital capacity, social support, cognitive function, or MRI evidence of global brain atrophy or white matter abnormality. Conclusions: Daytime sleepiness is common in the elderly, probably due to nocturnal disturbances such as frequent awakenings and snoring. The occasional use of sleeping pills for insomnia is associated with reduced daytime sleepiness in the elderly, while the use of medications for congestive heart failure is associated with daytime sleepiness. Surprisingly, anatomic abnormalities such as evidence of previous strokes and brain atrophy (as seen on brain MRI scans) were not associated with daytime sleepiness in these non-institutionalized elderly persons.

The impact of developer responsiveness on perceptions of usefulness and ease of use: an extension of the technology acceptance model

Abstract: The Technology Acceptance Model (TAM) suggests that the perceived usefulness (PU) and the perceived ease of use (PEOU) of an information system (IS) are major determinants of its use. Previous research has demonstrated the validity of this model across a wide variety of IS types. However, prior research has not identified antecedents of PU and there has been only limited research on the antecedents of PEOU. Consequently, research has provided little guidance to IS managers on methods to increase use by augmenting PU and PEOU.Viewing IS development as an instance of Social Exchange Theory (SET), this study proposes that IS managers can influence both the PU and the PEOU of an IS through a constructive social exchange with the user. One means of building and maintaining a constructive social exchange is through developer responsiveness. The results of this study, examining the adoption of an expert system, indeed support this notion. Specifically, developer responsiveness strongly influenced both PU and PEOU, but only indirectly affected actual behavior --- IS use --- in accordance with the predictions of SET. An extension of TAM based on SET is presented and the implications of this extended model are discussed from both a managerial and theoretical perspective.

Structured light using pseudorandom codes

Abstract: We solve the correspondence problem in active stereo vision using a novel pseudorandom coded structured light (SL). This coding scheme performs well in the presence of occlusion. In settings where color coding is feasible, 3D information can be obtained using a single image.

Sphingoid base 1-phosphate phosphatase: A key regulator of sphingolipid metabolism and stress response

Abstract: The sphingolipid metabolites ceramide and sphingosine-1-phosphate are second messengers with opposing roles in mammalian cell growth arrest and survival; their relative cellular level has been proposed to be a rheostat that determines the fate of cells. This report demonstrates that this rheostat is an evolutionarily conserved stress-regulatory mechanism that influences growth and survival of yeast. Although the role of sphingosine-1-phosphate in yeast was not previously examined, accumulation of ceramide has been shown to induce G1 arrest and cell death. We now have identified a gene in Saccharomyces cerevisiae, LBP1, that regulates the levels of phosphorylated sphingoid bases and ceramide. LBP1 was cloned from a yeast mutant that accumulated phosphorylated long-chain sphingoid bases and diverted sphingoid base intermediates from sphingolipid pathways to glycerophospholipid biosynthesis. LBP1 and its homolog, LBP2, encode very hydrophobic proteins that contain a novel-conserved sequence motif for lipid phosphatases, and both have long-chain sphingoid base phosphate phosphatase activity. In vitro characterization of Lbp1p shows that this phosphatase is Mg2+-independent with high specificity for phosphorylated long-chain bases, phytosphingosine and sphingosine. The deletion of LBP1 results in the accumulation of phosphorylated long-chain sphingoid bases and reduced ceramide levels. Moreover, deletion of LBP1 and LBP2 results in dramatically enhanced survival upon severe heat shock. Thus, these phosphatases play a previously unappreciated role in regulating ceramide and phosphorylated sphingoid base levels in yeast, and they modulate stress responses through sphingolipid metabolites in a manner that is reminiscent of their effects on mammalian cells.

Dietary and Nutritional Factors and Pancreatic Cancer: a Case-Control Study Based on Direct Interviews

Abstract: Background: The relationship between diet and pancreatic cancer remains unclear. In this study, we assessed the role of diet and nutrition as risk factors for pancreatic cancer, using data obtained from direct interviews only, rather than data from less reliable interviews with next of kin. We evaluated whether dietary factors could explain the higher incidence of pancreatic cancer experienced by black Americans compared with white Americans. Methods: We conducted a population-based case-control study of pancreatic cancer diagnosed in Atlanta (GA), Detroit (MI), and 10 New Jersey counties from August 1986 through April 1989. Reliable dietary histories were obtained for 436 patients and 2003 general-population control subjects aged 30-79 years. Results: Obesity was associated with a statistically significant 50%-60% increased risk of pancreatic cancer that was consistent by sex and race. Although the magnitude of risk associated with obesity was identical in blacks and whites, a higher percentage of blacks were obese than were whites (women: 38% versus 16%; men: 27% versus 22%). A statistically significant positive trend in risk was observed with increasing caloric intake, with subjects in the highest quartile of caloric intake experiencing a 70% higher risk than those in the lowest quartile. A statistically significant interaction between body mass index (weight in kg/height in m 2 for men and weight in kg/height in m 1,5 for women) and total caloric intake was observed that was consistent by sex and race. Subjects in the highest quartile of both body mass index and caloric intake had a statistically significant 180% higher risk than those in the lowest quartile. Conclusions: Obesity is a risk factor for pancreatic cancer and appears to contribute to the higher risk of this disease among blacks than among whites in the United States, particularly among women. Furthermore, the interaction between body mass index and caloric intake suggests the importance of energy balance in pancreatic carcinogenesis.

Topological analysis of chaotic dynamical systems

Abstract: Topological methods have recently been developed for the analysis of dissipative dynamical systems that operate in the chaotic regime. They were originally developed for three-dimensional dissipative dynamical systems, but they are applicable to all ‘‘low-dimensional’’ dynamical systems. These are systems for which the flow rapidly relaxes to a three-dimensional subspace of phase space. Equivalently, the associated attractor has Lyapunov dimension d L,3. Topological methods supplement methods previously developed to determine the values of metric and dynamical invariants. However, topological methods possess three additional features: they describe how to model the dynamics; they allow validation of the models so developed; and the topological invariants are robust under changes in control-parameter values. The topological-analysis procedure depends on identifying the stretching and squeezing mechanisms that act to create a strange attractor and organize all the unstable periodic orbits in this attractor in a unique way. The stretching and squeezing mechanisms are represented by a caricature, a branched manifold, which is also called a template or a knot holder. This turns out to be a version of the dynamical system in the limit of infinite dissipation. This topological structure is identified by a set of integer invariants. One of the truly remarkable results of the topological-analysis procedure is that these integer invariants can be extracted from a chaotic time series. Furthermore, self-consistency checks can be used to confirm the integer values. These integers can be used to determine whether or not two dynamical systems are equivalent; in particular, they can determine whether a model developed from time-series data is an accurate representation of a physical system. Conversely, these integers can be used to provide a model for the dynamical mechanisms that generate chaotic data. In fact, the author has constructed a doubly discrete classification of strange attractors. The underlying branched manifold provides one discrete classification. Each branched manifold has an ‘‘unfolding’’ or perturbation in which some subset of orbits is removed. The remaining orbits are determined by a basis set of orbits that forces the presence of all remaining orbits. Branched manifolds and basis sets of orbits provide this doubly discrete classification of strange attractors. In this review the author describes the steps that have been developed to implement the topological-analysis procedure. In addition, the author illustrates how to apply this procedure by carrying out the analysis of several experimental data sets. The results obtained for several other experimental time series that exhibit chaotic behavior are also described. [S0034-6861(98)00304-3]

Bond Rating Agencies and Stock Analysts: Who Knows What When?

Abstract: Both bond rating agencies and stock analysts evaluate publicly traded companies and com? municate their opinions to investors. Comparing the timeliness of each, we find that Granger causality flows both ways. While most bond downgrades are preceded by declines in actual and forecast earnings, both actual earnings and forecasts of future earnings tend to fall following downgrades. Although part of this post-downgrade forecast revision can be attributed to negative news regarding actual earnings, most appears to be reaction to the downgrade itself. We find little change in actual earnings following upgrades. Analysts, however, tend to increase their forecasts of future earnings.

Immunoablative High-Dose Cyclophosphamide without Stem-Cell Rescue for Refractory, Severe Autoimmune Disease

Abstract: Background: Immunoablative high-dose cyclophosphamide without stem-cell rescue induces durable, complete remission in most patients with aplastic anemia. Objective: To determine the efficacy of hig...

Predicting Response to Exposure Treatment in PTSD: The Role of Mental Defeat and Alienation

Abstract: Not all patients with posttraumatic stress disorder benefit from exposure treatment. The present paper describes two cognitive dimensions that are related to inferior response to exposure in rape victims. First, individuals whose memories during reliving of the trauma reflected mental defeat or the absence of mental planning showed little improvement. Second, inferior outcome was correlated with an overall feeling of alienation or permanent change following the trauma. These results are based on blind ratings of transcripts of exposure treatment sessions from 10 women with good outcome and 10 women with inferior outcome. Patients in the two groups were matched for initial symptom severity and were comparable in many aspects of the assault. Patients who experienced mental defeat, alienation, or permanent change may require cognitive restructuring in addition to exposure.

Conformation gating as a mechanism for enzyme specificity

Abstract: Acetylcholinesterase, with an active site located at the bottom of a narrow and deep gorge, provides a striking example of enzymes with buried active sites. Recent molecular dynamics simulations showed that reorientation of five aromatic rings leads to rapid opening and closing of the gate to the active site. In the present study the molecular dynamics trajectory is used to quantitatively analyze the effect of the gate on the substrate binding rate constant. For a 2.4-A probe modeling acetylcholine, the gate is open only 2.4% of the time, but the quantitative analysis reveals that the substrate binding rate is slowed by merely a factor of 2. We rationalize this result by noting that the substrate, by virtue of Brownian motion, will make repeated attempts to enter the gate each time it is near the gate. If the gate is rapidly switching between the open and closed states, one of these attempts will coincide with an open state, and then the substrate succeeds in entering the gate. However, there is a limit on the extent to which rapid gating dynamics can compensate for the small equilibrium probability of the open state. Thus the gate is effective in reducing the binding rate for a ligand 0.4 A bulkier by three orders of magnitude. This relationship suggests a mechanism for achieving enzyme specificity without sacrificing efficiency.

C-C Chemokines, Pivotal in Protection Against HIV Type 1 Infection

Abstract: Exposure to HIV type 1 (HIV-1) does not usually lead to infection. Although this could be because of insufficient virus titer, there is now abundant evidence that some individuals resist infection even when directly exposed to a high titer of HIV. This protection recently has been correlated with homozygous mutations of an HIV-1 coreceptor, namely CCR5, the receptor for the β-chemokines. Moreover, earlier results already had shown that the same chemokines markedly suppress the nonsyncitial inducing variants of HIV-1, the chief virus type transmitted from person to person. CCR5 mutation, as a unique mechanism of protection, is, however, suspect because HIV-1 variants can use other chemokine receptors as their coreceptor. Moreover, recent results have established that infection can indeed sometimes occur with such mutations. Here, we report on transient natural resistance over time of most of 128 hemophiliacs who were inoculated repeatedly with HIV-1-contaminated Factor VIII concentrate from plasma during 1980–1985 before the development of the HIV blood test. Furthermore, and remarkably, 14 subjects remain uninfected to this date, and in these subjects we found homozygous CCR5 mutations in none but in most of them overproduction of β chemokines. In vitro experiments confirmed the potent anti-HIV suppressive effect of these chemokines.

Advantages of Subharmonic Over Second Harmonic Backscatter for Contrast-To-Tissue Echo Enhancement

Abstract: It is shown experimentally that backscatter from two ultrasonic contrast agents suspended in water or saline contains subharmonics of the incident frequency that are stronger than those backscattered at the same incident pressure from chicken breast. It is also shown that the ratio of subharmonic backscattered from contrast to that backscattered from tissue, is stronger than the ratio of backscattered second harmonic. In consequence, blood that contains contrast should be more easily detectable with respect to tissue if the subharmonic, rather than the second harmonic, is used for imaging.

Arthroscopic microdiscectomy and selective fragmentectomy.

Abstract: A prospective outcome study to determine the efficacy and complications associated with posterolateral arthroscopic discectomy was initiated in April 1988. One hundred seventy-five patients with symptoms consistent with a lumbar disc herniation and correlative imaging studies were treated operatively, and 169 were available for followup evaluation. Fifty-nine patients with a central herniation or a nonmigrated sequestered fragment were treated using bilateral biportal posterolateral access, whereas 116 patients with radiographic evidence of a paramedial, foraminal, or extra-foraminal herniation were treated using the unilateral uniportal approach. The minimum duration of nonoperative management ranged from 3.5 to 28 months (average, 16 months), and all patients had a minimum of 24 months of postoperative followup. Outcome analysis indicated that 149 procedures were successful, whereas 20 (11.8%) procedures were failures because of persistent radicular symptoms that, in some cases, required open laminotomy. Complications associated with the procedures included one disc space infection, one transient peroneal neuropraxia, and four index extremity skin hypersensitivity. All of these complications resolved without sequelae, and there were no neurovascular complications directly related to the surgical approach.