Showing papers by "Clemson University published in 1976"

An evaluation of bone growth into porous high density polyethylene

Abstract: The purpose of this investigation was to study bone growth into porous polyethylene rods as a function of time and pore structure. Previous studies have indicated the biocompatibility of solid polyethylene materials which are currently being used clinically. Porous polyethylene rods were implanted in the femurs of mongrel dogs which were sacrificed four, eight, and 16 weeks postoperatively. The implants were then sectioned and examined histologically and microradiographically. Quantitative techniques were employed to determine the amount of bone ingrowth as a function of time and pore size. The pore structures of the materials were evaluated using optical microscopy and mercury intrusion porosimetry. The results of this investigation have demonstrated that porous polyethylene is capable of accepting bone growth into pores as small as 40 μm. The optimum rate of bone ingrowth was observed in pore sizes of approximately 100 to 135 μm, with no increase in the rate of bone ingrowth observed in samples possessing larger pore sizes. No adverse tissue response was found at implant times up to 16 weeks in pore sizes of 100 μm or larger.

Bone growth into porous high-density polyethylene.

Abstract: The purpose of this study was to delineate the process by which bone comes to fill the pores of porous high-density polyethylene (PHDPE) implants. PHDPE (450μ pore size) pellets 4 mm in diameter and 1 cm long were implanted into the femurs of dogs. A bone biopsy procedure was utilized to obtain PHDPE pellets implanted for periods of 3 days through 8 weeks. A one-year biopsy specimen taken from the PHDPE coating on the stem of a canine total-hip prosthesis was also studied. The results demonstrated that significant amounts of bone formed within the PHDPE pellets as early as 14 days after implantation. Bone was identified throughout the specimens after 4 weeks. After 6 weeks, the tissue in the implants consisted of well-developed lamellar bone spicules and healthy hematopoietic marrow. Scanning electron microscopy was utilized in conjunction with light microscopy and microradiography to study the ultrastructural features of the bone ingrowth process.

Electrical conductivity of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ)

Abstract: New measurements of electrical conductivity along the $b$ axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) are combined with published results to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories The magnitudes of these measured conductivities do not necessitate the assumption of superconducting fluctuations or any other collective state in which the conductivity exceeds the limitations of single-particle scattering Since an adequate theory of the limitations of single-particle scattering for TTF-TCNQ does not exist at present, experiment alone does not rule out the possibility that collective effects may somewhat enhance or suppress the conductivity

Stress Analysis of Porous Rooted Dental Implants

Abstract: A model based on a continuously bonded interface predicts high punching stresses at the apex of the implant and low stresses in the cortical plates. A model based on a continuously bonded interface predicts high stiffness and a resultant low implant displacement-load ratio. A model based on a tissue ingrowth-bonded interface predicts uniform distribution of stresses around the implant through the cortical plates. A model based on a tissue ingrowth-bonded interface predicts an implant displacement-load ratio close to the ratio measured with actual implant specimens.

Thermal Potentiation of Mammalian Cell Killing: Clues for Understanding and Potential for Tumor Therapy

Abstract: Publisher Summary This chapter discusses the thermal potentiation of mammalian cell killing, which may provide clues for understanding and potential for tumor therapy. Thermal potentiation of lethality due to damage of DNA has been demonstrated for several types of cultured cells and for cells in vivo. It is a general effect that has been demonstrated for several agents or treatments, including x-rays, UV light, alkylating agents, radioactive suicide, and heating at ordinarily nonlethal temperatures following a heat shock at higher temperatures. Potentiation can occur by heating before, during, or after irradiation, although the details of the time dependence are far from complete. There is a minimum time of heating needed to express potentiation in the case of preheating. The synergism between mildly elevated temperature treatments and x-irradiation is dose-rate dependent and is illustrated best at low x-ray doses. It is discussed that there can be benefits in terms of application of the thermal-response properties of cells in designing better systems for treating tumors. The effects of heating or any other tumor treatment become terribly complex when interaction with the various physiological systems must be considered.

Probability Tables for Cluster Analysis Based on a Theory of Random Graphs

Abstract: Statistics based on a theory of random graphs have been proposed as an analytic aid to assess the randomness of a clustered structure. Probability tables for two such statistics are tabulated. Exact values of Pn,v , the cumulative probabilities of the minimum number of edges needed to connect a random graph, are tabulated for n = 10(1)30(5)80-(10)100. Exact and approximate values of En,v, the expected number of components in a random graph with n vertices and v edges, are tabulated for n = 10(1)30(5)100.

Electrical stimulation of bone growth into porous Al2O3

Abstract: Porous, cylindrical, high alumina, ceramic structures were fabricated for implantation in the superior third of canine femoral medullary canals. Implant durations of one, two, four, and eight weeks using three animals per time period were studied. A constant current (10 muA) power supply was used to attempt to stimulate bone growth into the porous ceramic structures. Osseous tissue in-growth was evaluated using a mechanical push-out test, microadiography, and histological thin sectioning. The interfacial shear strength and tissue micro-structure was studied as a function of implant residence site and implant residence site and implant residence time. The results indicate that initially the proximal implants have a higher interfacial shear strength, however, after eight weeks of implantation the distal implants have a shear strength about twice that of the proximal implants. This trend is observed for both the electrically stimulated and nonstimulated specimens. The 10 muA current level used in this investigation was found to have a small but significant effect on shear strength increasing it at implantation times of less than eight weeks.

Ambushing Random Walks I: Finite Models

Abstract: We consider a two-person competitive problem in which one player blue wishes to move across a rectangular lattice in such a way as to avoid being ambushed by his opponent red, who has placed obstacles in blue's path. Under some conditions, optimal strategies for blue and red are obtained and the value of the game is computed.

Brucellosis in feral swine.

Abstract: Some 255 feral hogs were serologically tested for Brucella titers at a location in the lower coastal plain of South Carolina. Eighteen percent were reactors. The organism was cultured from lymph node tissues in one 3+ years old boar and identified as Brucella suis biotype 1. Prevalence of sero-positive animals increased with age. There were no important differences between sexes.

Absorption heating-cooling system

Abstract: An improved heating or cooling system based on absorption principles is disclosed and claimed herein. A closed system is provided with a refrigerant-absorbent solution where separation of the refrigerant-absorbent is accomplished by a semi-permeable membrane. The refrigerant-absorbent solution at its normal concentration is pumped under pressure to a membrane separation unit where the refrigerant is selectively passed through a membrane separator in some proportion while a remaining absorbent enriched refrigerant-absorbent solution is rejected. The membrane separated refrigerant is then circulated through a heat exchange leg of the system for heating and/or cooling of affected areas depending upon the particular treatment of the refrigerant. At the end of the heat exchange leg, the refrigerant is fed to an absorber where it is recombined with the absorbent enriched solution to reconstitute the original refrigerant-absorbent solution which is then recirculated by the pump and the cycle is repeated. The apparatus and process of heat transfer systems utilizing the present membrane separation are claimed.

A hierarchical, restructurable multi-microprocessor architecture

Abstract: This paper introduces a system architecture which allows a high degree of restructuring so that system resources may be tailored to processing requirements. The proposed system organization consists of a large number of byte-slice processors interconnected through a system of busses. Each processor is capable of communicating with every other processor in the system and any number of adjacent processors may be strung together to create a wider arithmetic capability than is possible with a single processor. Processors may be organized into a number of independent teams while processor teams may, in turn, be organized in a hierarchical fashion to allow for concurrent processing. Processor teams may function either in cooperation with or completely independent of other processor teams. All communication throughout the system consists of information packets containing the data to be transferred and a series of tags which indicate the destination address for the data and the action to be taken by the processor upon receipt of the information packet. Two types of busses are employed; Conventional busses and the circulating loop (or Pierce loop). The circulating loop moves an information packet in a fixed direction a uniform distance in each unit of time and therefore allows independent data transfer operations to be carried out simultaneously. Several examples illustrate the utility of the proposed architecture.

Development of the Parasitoids Spalangia endius and Muscidifurax raptor in Relation to Constant and Variable Temperature: Simulation and Validation

Abstract: When parasitized house fly pupae were placed at 8 different constant temperatures in the laboratory, the parasitoid Spalangia endius Walker, failed to develop completely at 12.8 and 15.6°C. The length of successful development ranged from 66 days at 18° to 17 days at 35°C. Another fly parasitoid, Muscidifurax raptor Girault and Sanders, failed to complete its development at 12.8 and 35°C, but generally developed faster than S. endius . Under field conditions, parasitoid developmental rates varied on a seasonal basis and ranged between 21 and 183 days for S. endius and from 19–126 days for M. raptor . Developmental rates of both species were similar during summer, but M. raptor developed at a significantly faster rate during cooler months. An algorithm was used to predict development of parasitoids by providing simulation of responses to constant and variable temperatures. High correlation coefficients between predicted and observed developmental rates were obtained with both parasitoid species.

Rubidium as a marker for mexican bean beetles, epilachna varivestis (coleoptera: coccinellidae)

Abstract: Mexican bean beetles, Epilachna varivestis Mulsant, were marked with rubidium by allowing larvae and adults to feed on foliage of bean plants treated with a rubidium chloride solution. Detection of rubidium was effected by atomic absorption spectroscopy. Adults which had fed for 4 days on rubidium-chloride-treated plants then transferred to untreated plants contained elevated levels of rubidium up to 34 days. The presence of rubidium was not detectable in the progeny of treated beetles at levels significantly different from controls. Consumption of rubidium-chloride-treated foliage produced no observable detrimental effects on the beetles. The technique allowed them to acquire a relatively permanent label through their normal feeding activity.

Factoring Absolutely Convergent Series

Abstract: It is a well known fact that if p > l and 1 / p + l / q = l , every sequence (x.) in 11 (absolutely convergent series) can be factored in the form (x,,)=(u,,v,,) where (u.) is ha 1 p (p-absolutely convergent series) and (v.) is in t q. A related fact is the familiar exercise in advanced calculus that every sequence (x.) in 11 can be factored in the form (x.)= (u.v.) where (u.) is in Co (sequences convergent to 0) and (v.) is again in 11. Our purpose in this paper is to prove a natural generalization of this fact in the setting of K6the sequence spaces [6]. Our main result states essentially that 11 factors through every balanced Banach sequence space and its K6the dual. The proof is not easy and constitutes a nice exercise in non-linear functional analysis. Some consequences of this result concerning the structure of Banach spaces will appear in [9]. To prove the main result (the theorem in Section 2) we first establish a corresponding statement in the finite dimensional case and proceed to the infinite dimensional case via a compactness argument. Throughout this paper we assume our vector spaces to be over the field of real numbers. The complex case of the main theorem, however, follows immediately from the real case.

Distribution of insects in soybean fields.

Abstract: A 3-year study of spatial distribution patterns of insect pests in soybean fields revealed that the Poisson series described the distribution of most species. These species were: green cloverworms, Plathypena scabra (Fabricius); velvetbean caterpillars, Anticarsia gemmatalis Hubner; loopers Trichoplusia ni (Hubner), Pseudoplusia includens (Walker), and Heliothis spp. The Poisson with zeros distribution was second in characterizing the spatial patterns of many of the species. Field counts of Mexican bean beetles, Epilachna varivestis Mulsant, fitted the Neyman’s type A and negative binomial distributions most often.

Influence of Temperature on Oviposition by the Parasites Spalangia endius and Muscidifurax raptor

Abstract: Mated females of the parasites, Spalangia endius Walker and Muscidifurax raptor Girault and Sanders, were exposed to house fly, Musca domestica L., pupae at 8 different constant temperatures for 12, 24 and 36-h time periods. While oviposition rates of both species increased with an increase in temperature and time of exposure, these species displayed different tolerances to temperature. Lower temperature levels generally favored oviposition by M. raptor, while S. endius oviposited most successfully at higher temperatures.

Age and Growth of Red Drum from a Saltwater Marsh Impoundment in South Carolina

Abstract: Adult and juvenile red drum, Sciaenops ocellata (Linnaeus), confined to a saltwater marsh impoundment at South Island, Georgetown County, South Carolina, were studied to determine their length-weight relationship, age according to otoliths, and the time of annulus formation in the otoliths. The equation log W = −1.29596 + 2.74031 log L was determined for the relationship of length to weight. Sectioned otoliths revealed no annulus formed in fish up to 1,070 g and 38.5 cm in standard length, suggesting that no annulus was formed the first spring after hatching in September through November. Annuli were formed in spring (April-May). The largest fish belonged to the 1966 and 1967 year classes, which were in the marsh when the impoundment was formed in May 1968. Reading otoliths before they were cut produced erroneous results.