Showing papers by "University at Buffalo published in 1986"

Fatigue of composites-fatigue modulus concept and life prediction

Abstract: Fatigue behavior of glass fiber reinforced epoxy composite materials has been studied analytically. A new concept called "fatigue modulus," which is defined as a slope of applied stress and resultant strain at a specific cycle is introduced. Fatigue modulus degradation is studied using an assumption that the fatigue modulus degrada tion rate follows a power function of fatigue cycle. Theoretical equation for predicting fatigue life is formulated using the fatigue modulus and its degradation rate. This rela tion is simplified by strain failure criterion for the practical application. It is proved that the final formula predicts the fatigue life of a glass fiber epoxy composite material better than S-N curve or Basquin's relation. An attempt is made to find the relation ship between fatigue modulus and elastic modulus by the geometric relation from stress-strain curve under the cyclic loading.

What are logical notions

Abstract: In this manuscript, published here for the first time, Tarski explores the concept of logical notion. He draws on Klein's Erlanger Programm to locate the logical notions of ordinary geometry as those invariant under all transformations of space. Generalizing, he explicates the concept of logical notion of an arbitrary discipline.

Cumulative Damage Models and Multi-Stress Fatigue Life Prediction:

Abstract: Cumulative damage during fatigue is studied analytically. Extensive reviews are per formed on the published damage models. Three different cumulative damage models are defined using several physical variables such as fatigue modulus and resultant strain. Proposed model I is defined using fatigue modulus, while models II and III are defined using resultant strains. Proposed models are derived as functions of nor malized applied stress level, r, and number of fatigue cycle, n. It is verified that the proposed cumulative damage model III has better agreement with the two stress level fatigue experimental data than other models.

Justification techniques for advanced manufacturing technologies

Abstract: A major problem in the adoption of advanced manufacturing systems for the automated factories of tomorrow is the prerequisite justification process. Many worthwhile projects have been turned down because the qualitative benefits could not be included in the justification procedure while the direct cost savings were insufficient to meet the financial hurdles set by the firm. This paper identifies and demonstrates the range of techniques that have been used by firms to justify automation investments and describes the conditions under which it is most appropriate to employ them.

SNePS considered as a fully intensional propositional semantic network

Abstract: We present a formal syntax and semantics for SNePS considered as the (modeled) mind of a cognitive agent. The semantics is based on a Meinongian theory of the intensional objects of thought that is appropriate for AI considered as "computational philosophy" or "computational psychology".

Role of glutathione in prevention of acetaminophen-induced hepatotoxicity by N-acetyl-L-cysteine in vivo: studies with N-acetyl-D-cysteine in mice.

Abstract: The revelation that many covalent binding estimates are falsely low due to flawed normalization discloses that protection by N-acetyl-L-cysteine against acetaminophen hepatotoxicity is accompanied routinely by a 50 to 80% decline in arylation. Elevated glutathione may be responsible for inhibiting covalent binding but above-normal concentrations have never been demonstrated in vivo after N-acetyl-L-cysteine treatment or separated adequately from other possible hepatoprotective actions including direct reduction of the toxic acetaminophen metabolite by the antidote. This led us to compare the conventional L-isomer of the antidote to its nonphysiologic stereoisomer, N-acetyl-D-cysteine, because the latter should be capable of reducing the toxic metabolite but not of stimulating glutathione biosynthesis. Oral coadministration of N-acetyl-D-cysteine (1200 mg/kg), however, failed in preventing the elevation of serum alanine aminotransferase activity, in decreasing hepatocellular necrosis, in interdicting covalent binding of the toxic metabolite to hepatocellular proteins and in preventing the depletion of liver glutathione caused by 500 mg/kg of acetaminophen. N-acetyl-L-cysteine succeeded in decreasing these measures of acetaminophen hepatotoxicity while driving liver glutathione concentrations 2-3 fold above control values. The L-isomer also increased urinary excretion of glutathione-derived acetaminophen metabolites whereas the D-isomer increased only acetaminophen sulfate excretion and reversed the customary predominance of acetaminophen cysteine over the mercapturic acid conjugate. Liver uptake of N-acetyl-D-cysteine was reflected in organ concentrations 7-fold higher than noted for the L-isomer.(ABSTRACT TRUNCATED AT 250 WORDS)

A biochemical approach to periodontal regeneration: tetracycline treatment of dentin promotes fibroblast adhesion and growth

Abstract: One objective of periodontal therapy after resolution of the infectious process is to facilitate a new connective tissue attachment to the root dentin surface. Here we report that a selective advantage for attachment and growth can be conferred on human gingival fibroblasts by biochemical manipulation of the dentin surface. Tetracycline HCL treatment of the dentin surface increases binding of fibronectin. The adsorbed fibronectin stimulates fibroblast attachment and growth, while suppressing epithelial cell attachment and growth. This biochemical manipulation may provide a useful approach for the treatment of periodontally involved teeth.

Work-Family Conflict: The Effect of Job and Family Involvement

Abstract: : A review of past research revealed inconsistent findings concerning the relationship between job involvement and work-family conflict. This study tested whether family involvement moderates the relationship between job involvement and work-family conflict. Two types of family involvement (spouse and parent) and two types of work-family conflict (job-spouse and job-parent) were assessed. Data were gathered via questionnaire from a sample of nonteaching professionals employed by a large public university in northeastern United States. As hypothesized, job involvement and job-spouse conflict were positively related for individuals high in spouse involvement and unrelated for individuals low in spouse involvement. Contrary to prediction, parental involvement did not moderate the relationship between job involvement and job-parent conflict. Instead, job involvement was positively related to job-parent conflict regardless of the level of parental involvement. Results are discussed in terms of standards for role performance and strength of role demands. Implications for future research are also discussed.

A biochemical approach to periodontal regeneration: tetracycline treatment conditions dentin surfaces.

Abstract: Selective use of tetracycline HCl was studied to evaluate a potential treatment methodology. Tetracycline HCl adsorbed to dentin surfaces, binding 4.7 μg/mm2 after a 5 min exposure to a 50 mg/ml tetracycline HCl solution. Desorption in a discontinuous flow assay maintained biologically active concentrations of tetracycline HCl in the fluid phase for at least 48 h. The tetracycline HCl bound, and subsequently released from dentin retained antimicrobial activity with an ID50 of 3.7 μg/ml. Tetracycline HCl conditioning removed an amorphous surface layer, thereby exposing dentin with open tubules, as determined by scanning electron microscopy. These data suggest that tetracycline HCl-treated root surfaces may act as a depot for release of active antibiotic, as well as serve as an improved substrate for connective tissue components vital to healing at the interface between hard and soft tissues.

Reactive synovitis after silicone arthroplasty.

Abstract: A number of patients with silicone rubber implants performed by us and other surgeons initially had excellent results; however, they returned with swelling and discomfort. We studied 18 patients ranging in age from 16 years to 57 years who presented 8 to 78 months (average, 31.7 months) after silicone arthroplasty (four scaphoid, six lunate, one scapholunate, four finger, two wrist, one trapezium, and one ulnar head for metacarpal hemiarthroplasty). Erosive osteolysis was seen on x-ray films, with progressive destruction evident in patients followed serially. None of the patients' conditions responded to conservative care. The severity of the proliferative, inflammatory synovitis and the foreign material in the multinucleated giant cells correlated with the interval since arthroplasty. Implant surface analysis by scanning electron microscope and x-ray spectrometer showed that silicone microparticles were the result of implant degeneration and erosion. All joint cultures were negative. Silicone particulate synovitis and destruction were arrested by the removal of the implant, a synovectomy, and curettage of the lytic lesions at salvage (resection arthroplasty or arthrodesis.) Patients who have had silicone arthroplasties should be followed indefinitely, at regular intervals, by x-ray films and clinical examination.

Human image understanding: recent research and a theory

Abstract: The perceptual recognition of objects is conceptualized to be a process in which the image of the input is segmented at regions of deep concavity into simple volumetric components, such as blocks, cylinders, wedges, and cones. The fundamental assumption of the proposed theory, recognition-by-components (RBC), is that a modest set of components [N probably ≤ 36] can be derived from contrasts of five readily detectable properties of edges in a 2-dimensional image: curvature, collinearity, symmetry, parallelism, and cotermination. The detection of these properties is generally invariant over viewing position and image quality and consequently allows robust object perception when the image is projected from a novel viewpoint or degraded. RBC thus provides a principled account of the heretofore undecided relation between the classic principles of perceptual organization and pattern recognition: The constraints toward regularization (Pragnanz) characterize not the complete object but the object's components. Representational power derives from an allowance of free combinations of the components. A principle of componential recovery can account for the major phenomena of object recognition: If an arrangement of two or three primitive components can be recovered from the input, objects can be quickly recognized even when they are occluded, rotated in depth, novel, or extensively degraded. The results from experiments on the perception of briefly presented pictures by human observers provide empirical support for the theory. © 1985 Academic Press, Inc.

Free drug concentration monitoring in clinical practice. Rationale and current status.

Abstract: Recent advances in techniques to determine free drug concentrations have lead to a substantial increase in the monitoring of this parameter in clinical practice. The majority of drug binding to macromolecules in serum can be accounted for by association with albumin and alpha 1-acid glycoprotein. Albumin is the primary binding protein for acidic drugs, while binding to alpha 1-acid glycoprotein is more commonly observed with basic lipophilic agents. Alterations in the concentrations of either of these macromolecules can result in significant changes in free fraction. Diseases such as cirrhosis, nephrotic syndrome and malnourishment can result in hypoalbuminaemia. Burn injury, cancer, chronic pain syndrome, myocardial infarction, inflammatory diseases and trauma are all associated with elevations in the concentration of alpha 1-acid glycoprotein. Treatment with a number of drugs has also been shown to increase alpha 1-acid glycoprotein serum concentrations. A wide variety of biological fluids have been examined for their ability to provide an estimation of free drug concentration at receptor sites. The most useful fluid for estimating free drug concentrations appears to be plasma or serum, with subsequent treatment of the sample to separate free and bound drug by an appropriate technique. The two most widely used methods are equilibrium dialysis and ultrafiltration. Of these two, ultrafiltration has the greatest utility clinically because it is rapid and relatively simple. The major difficulty associated with this method involves the binding of drug to the ultrafilters, but significant progress has been made in solving this problem. Several authors have endorsed the routine use of free drug concentration monitoring. Data examining the clinical usefulness of free drug concentration monitoring for phenytoin, carbamazepine, valproic acid, disopyramide and lignocaine (lidocaine) are reviewed. While available evidence suggests that free concentrations may correlate with clinical effects better than total drug concentrations, there are insufficient data to justify the recommendation of the routine use of free drug concentration monitoring for any of these agents at present.

A new visible light-cured resin system applied to removable prosthodontics

Abstract: Preliminary studies of VLC resins have produced promising results; however, additional research is necessary to completely define qualities of this material. Biologic testing of VLC (Triad) resins indicated that they are nontoxic and biocompatible. They have a wide range of uses in all subdisciplines of prosthodontics. Advantages such as accuracy of fit, superior strength, complete polymerization without residual compounds, ease of fabrication and manipulation, patient acceptance, ability to bond with other denture base resins, and low bacterial adherence make this material an important addition to the choices available to dentists. As with many new materials, there are initial problems or hurdles that must be overcome before there is widespread use. Initial formulations of material had insufficient flexural strength and tended to fracture when flexed over uncut sites on a stone cast. This problem has been reduced by Dentsply International, Inc. with the introduction of the new improved formulation. The original VLC bonding agent did not provide sufficient bond strength with acrylic resin denture base materials, but this also has been improved with development of a new VLC bonding agent. The problem of microporosity and small voids produced when adapting VLC resin sheets against a stone cast may be overcome with pressure or vacuum adaptation techniques. A promising application of VLC resin material is in direct intraoral procedures such as relining of dentures. Physical and chemical properties are superior to autopolymerizing methacrylates. Preliminary studies have shown successful patient acceptance to this clinical procedure. It is of particular advantage to the patient not to be without dentures for the period of at least 1 day necessary for a laboratory-processed relining. Immediate light-curing is time-saving and convenient compared to indirect (heat-cured) relining. Until recently, most direct intraoral applications of autopolymerizing acrylic resin reliner material were considered temporary or expedient to a permanent procedure. The patient and dentist may now have another treatment choice. The release of residual methyl methacrylate, among other shortcomings of AP materials, is not a concern when using the VLC reliner material. Some patients may notice a nonobjectionable taste to the uncured material; however, they can be reassured that the taste will be only temporary until the material is completely polymerized in the curing unit. The flow of the material can be regulated by selection of appropriate viscosity, warming and cooling measures, and partial intraoral polymerization with hand-held curing lights.(ABSTRACT TRUNCATED AT 400 WORDS)

Field measurement of the velocity of overland flow using dye tracing

Abstract: A new method of computing the mean velocity of overland flow using dye tracing is proposed in which a specified cross-section is divided into zones of relatively uniform flow characteristics, termed partial sections. The mean surface velocity for each partial section is determined by timing the passage of injected dye, and this figure is multiplied by 0.67, 0.70, or 0.80, depending on whether the flow is laminar, transitional, or turbulent, to give mean velocity. The mean velocity for the entire cross-section is calculated by multiplying the mean velocity of each partial section by its cross-sectional area, summing the products for all the partial sections, and dividing by the total area of the cross-section. A field test shows that mean velocity derived in this manner differs from mean velocity derived by the discharge method (i.e. by dividing discharge measured volumetrically by cross-sectional area) by an average of only 7.07 per cent. Thus the partial-section technique appears to provide a reliable method of estimating mean velocity of overland flow.

1985 Kreshover lecture. Molecular Factors Influencing Neutrophil Defects in Periodontal Disease

Abstract: Major advances in our understanding of the role of the neutrophil in host defense against periodontal organisms have been made through studies of localized juvenile periodontitis (LJP). Several.lines of evidence suggest that LJP is an infectious process closely associated with Actinobacillus (Haemophilus) actinomycetemcomitans as a causative agent, although other organisms may also participate. The immunologic profile of LJP patients suggests that a cell-associated neutrophil locomotory dysfunction is a key underlying immunodeficiency resulting in increased susceptibility to periodontal infection. In addition, LJP patients often exhibit cervical lymphadenopathy and IgG-hypergammaglobulinemia, and a markedly elevated antibody response to the infecting organism, A. actinomycetemcomitans, is found in the serum and crevicular fluid of most patients.Evaluation of the locomotory properties of LJP neutrophils shows that random migration and chemokinesis are normal; however, about 70% of the LJP patients suffer f...

Targeted drug delivery.

Abstract: Cancer chemotherapy drugs are neither specific, i.e., they do not act exclusively on the metabolic pathways of cancer cells, nor are they targeted solely toward cancer cells. However, recent research has begun to address, in part, the latter issue. Improved delivery of chemotherapeutic agents to tumor tissue in man appears to be an achievable goal in the next decade. Improved drug delivery includes developing predictive models that allow for laboratory assessment of the best treatment for a patient's cancer without exposing the patient to an empirical trial or to the possible morbidity from exposure to a less useful drug, or to the loss of time in the fight against cancer because of ineffectual therapy. Monoclonal antibodies directed against tumor-associated antigens have the potential to achieve major advances in targeted drug delivery. Monoclonal antibodies may have direct antitumor effects, or they can be used as "homing devices" when attached to a payload and can guide diagnostic or therapeutic agents to the targeted tissues. Carrier systems of all types have become available; these include liposomes and polymeric compounds which can carry drugs, radionuclides, toxins, or other materials in a protected environment. These carriers can also be bound to monoclonal antibodies for possible targeted delivery. Pharmacological sanctuaries have been recognized as a problem in cancer treatment. The best known of these is the central nervous system (CNS). Techniques to temporarily disrupt the blood-brain barrier are now appearing. Mechanisms to administer therapy directly into the CNS are also being reassessed. Implantable pumps and reservoirs have been used to treat selected organs or for regional perfusions. Other treatments that are regional in scope include administration directly into a cavity or into a tumor. Computerized implantable devices should play a major role in cancer therapy in the future, in pain control as well as antibiotic and hormone administration. In recent years, mathematical models have been developed that can more accurately predict drug distribution and metabolism in various tissues of the body. Such models point the way to more logical designs of chemotherapeutic administration. The expanded use of autologous bone marrow transplantation, along with improving techniques of "purging" the marrow of tumor cells before reinfusion can be anticipated. Pro-drugs are substances that must be biotransformed in vivo to exert their pharmacologic effect.(ABSTRACT TRUNCATED AT 400 WORDS)

The quadriplegia index of function (QIF): sensitivity and reliability demonstrated in a study of thirty quadriplegic patients

Abstract: The Quadriplegia Index of Function (QIF) was originally developed by the authors in 1980 because the popular Barthel Index was deemed too insensitive to document the small but significant functional gains made by quadriplegics (tetraplegics) during medical rehabilitation. The QIF has now been tested on a group of 30 complete quadriplegic patients at admission to and discharge from inpatient medical rehabilitation. Resultant scores were compared to those simultaneously obtained by the Barthel Index and the Kenny Self-Care Evaluation. The QIF was found to be more sensitive (46 per cent improvement as opposed to 30 per cent by the Kenny Self Care Evaluation and 20 per cent by the Barthel Index). The QIF was also tested for reliability. Ratings by three different nurses, working independently, were found to be significantly positively correlated for all sub-scores (p less than .001). We conclude that the QIF provides a useful option in choosing a functional assessment instrument for use with quadriplegic patients.

Biophysics of mechanoreception.

Abstract: Several types of cells' skeletal, muscle, nerve, epithelia, and heart have been shown to contain ion channels which are sensitive to membrane tension. In chick skeletal muscle, the transduction persists in excised patches and involves no chemical messengers. Quantitative analysis of single channel records reveals that the sensitivity to stretch can be described by a linear four state model with three closed (C) and one open (O) state: (Formula: see text). Only the rate constant k12 is sensitive to tension (and membrane potential) following the law: k12 = kO12 exp/(theta T2 + alpha V) where theta is a constant describing the sensitivity to tension, T, and alpha is a constant describing the sensitivity to voltage, V, and kO12 is a constant. The form of the tension sensitivity can be accounted for by a model in which strain energy is used to gate the channel. Analysis of strain sensitivity, theta, indicates that the channel must concentrate energy from a large (ca. 500-nm diameter) area of membrane which suggests that the channel is in series with a component of the cytoskeleton. Treatment with cytochalasins suggests that actin is mechanically in parallel with the channel. When a channel with the above properties is incorporated into a simple model of mechanical transduction in hair cells, the resulting model is capable of explaining the kinetic features and the sensitivity found in the cochlear-vestibular system. The proposed gating mechanism of mechanical transduction appears to be general and can account for existing data on a variety of systems.