Showing papers by "Clemson University published in 1972"

Tissue reaction to three ceramics of porous and non-porous structures.

Abstract: In this investigation, ceramics were studied to determine their role as rigid, abrasive implants in soft, living tissue. Discs and tubes of three ceramics, CaO·Al2O3, CaO·TiO2, and CaO·ZrO2, were introduced as porous and non-porous structures into muscle and connective tissue sites in rabbits. The animals were observed grossly to determine the duration of redness and swelling following surgery, and samples were retrieved at 1 week, 3 months, 6 months, and 9 months after implantation. A mild, acute inflammatory response immediately followed the implantation of all three materials in both the porous and non-porous forms. Histological sections of the ceramics and surrounding tissue, cut and stained for light microscopy, demonstrated the absence of inflammatory cells and revealed the normal morphology and organization of the cells present around all types of implants tested. Tissue around discs of porous ceramics healed faster and exhibited thinner fibrous encapsulations than with impervious discs of the same material. Healthy fibrous connective tissue with an ample blood supply occupied those implants with pores of 45–100 mμ, and even more rapidly filled the samples with a 100- to 150-μ pore size. The tissue ingrowth and tight adherence to the porous samples was believed responsible for the more moderate response to porous implants. No adverse responses of any kind were observed, except in a very few, atypical specimens.

Plasma Estrogen, Progesterone and Luteinizing Hormone Levels During the Estrous Cycle in Pigs

Abstract: Plasma estrogen progesterone and luteinizing hormone (LH) were det ermined during the estrous cycle in 6 pigs and during 24 hours on the 1st day of estrus (Day 0) in 4 pigs. Estrogen was low (less than 20 pg/ ml) during the cycle until Day 16 or 17 when it increased to a maximum of more than 50 pg/ml 1-2 days prior to estrus. Progesterone increased from 5.1 to 25.2 ng/ml between Days 2 and 6 and reached a maximum of 33.2 ng/ml by Day 12. Estrogen levels increased only after progesterone levels began to fall. LH decreased from 2.5 ng/ml on Day 0 to below 1 ng/ml until the next estrus when it increased to more than 5 ng/ml while estrogen was greater than 20 pg/ml and progesterone remained at 1 ng/ml.

Developmental Model for the Southern Appalachians

Abstract: A developmental model is proposed for the southern Appalachians This model integrates current ideas on structure, sedimentation, metamorphism, and igneous activity with the concept of plate tectonics Progressive metamorphism culminated about 1,000 my ago (middle Precambrian) and again about 400 my ago (Silurian-Devonian) Later, localized retrogressive metamorphism affected the rocks of the Blue Ridge and Piedmont Igneous activity occurred during the middle Precambrian (1,000 my ago), prior to, during, and after Paleozoic regional metamorphism, and during the Mesozoic The Valley and Ridge and Cumberland Plateau structures are treated as areas deformed by thin-skinned tectonics generated during the late Paleozoic, as is the Blue Ridge thrust sheet The Blue Ridge anticlinorium, Murphy syncline, Chauga belt, mobilized Inner Piedmont, Kings Mountain belt, Charlotte and Carolina slate belts developed during the deformational event accompanying early-mid-Paleozoic regional metamorphism The Blue Ridge anticlinorium, mobilized Inner Piedmont and Charlotte belts are interpreted as anticlinoria composed of middle Precambrian basement and later Precambrian metasedimentary and metavolcanic rocks mobilized to a greater or lesser degree The Murphy, Chauga, Kings Mountain, and Carolina slate belts are inferred to be synclinoria composed of younger (late Precambrian to early-mid-Paleozoic) metasedimentary and metavolcanic rocks The development of the sedimentary, deformational, metamorphic, and intrusive history of the southern Appalachians may be directly related to the Paleozoic history of movement of the North American and African continents as portions of major Paleozoic lithospheric plates This developmental scheme is divisible into several phases: (1) An early (late Precambrian to mid-Ordovician) phase of continental margin sedimentation, igneous activity, and initial compression occurred (2) This was followed by an intermediate (late Precambrian to late Devonian) phase of compression producing isoclinal folding, regional metamorphism, and intrusive activity with deposits from a rising tectonic source land These phenomena are the direct result of westward underflow of a proto-Atlantic plate beneath an eastward-moving proto-North American plate with concomitant development of a subduction zone along the continental margin (3) Next a later (mid-late Paleozoic) phase of compression and igneous activity accompanied by continued deposition from the rising mountain system occurred The Brevard Zone, Towaliga, Goat Rock, and Gold Hill faults developed early in phase 3 and experienced renewed movement during formation of the thrusts and folds in the Valley and Ridge, Cumberland Plateau, and the late structures in the Blue Ridge Compressional stresses that formed these structures were generated during the collision and suturing of Africa with southeastern North America (4) Finally, there was a tensional phase (Triassic-Jurassic) accompanied by normal faulting, igneous activity, and deposition related to the decoupling of Africa and North America and the formation of the present Atlantic Ocean and continental margin

Plasma Estrogen and Progesterone Levels After Mating, and During Late Pregnancy and Postpartum in Cows12

Abstract: Peripheral blood plasma was analyzed for total estrogen and progesterone concentrations concurrently during several reproductive stages of the cow. In trial I, 18 beef heifers were mated and blood was collected every 3 days until they either returned to estrus or until day 39 of pregnancy. In trial II, 10 dairy cows were bled daily from 7–14 days prior to parturition, then on a twice a week basis for 60 days postpartum. Estrogen and progesterone concentrations were determined by radio assay. In mated cows that returned to estrus, the mean estrogen level was below 7 pg/ml on day 3, 6, 12 and 15. It increased to a minor peak on day 9 (13 pg/ml) and to a major peak just before estrus (25 pg/ ml). In pregnant cows, it was low (<5 pg/ml) from day 3 until 39. Plasma progesterone increased from 1.2 ng/ml on day 3 to levels of 8.2 ng/ml and 9.9 ng/ml on day 12, in the two groups, respectively. After day 12, the progesterone level declined in the nonpregnant cows and increased to 13.9 ng/ml in the pregnant cows. D...

Plasma estrogen, progesterone, and luteinizing hormone prior to estrus and during pregnancy in pigs.

Abstract: Total estrogen, luteinizing hormone (LH), and progesterone concentrations were measured in plasma samples collected on days −6, −5, −4, −3, −2, −1 before estrus, estrus (day 0) and days 3, 6, 12, 18 and 24 of pregnancy in six gilts. The mean progesterone concentration decreased from 16.1 ng/ml of plasma (per pig) on day −6 before estrus to 1 ng/ml or less on day −4. Progesterone levels remained low through estrus, increased to a peak value of 35.4 ng/ml on day 12 of pregnancy, and then declined to 17.2 ng/ml on day 24. Total estrogen began to increase on day −3, which coincided with the time of lowest progesterone levels in most animals, and reached maximum values of about 38 pg/ml on days −2 and −1 before estrus. Prior to the proestrous peak and during pregnancy, levels of estrogen fluctuated between 10 and 28 pg/ml. There was a significant negative linear correlation (r = −0.369, n = 65) between ng of progesterone and pg of estrogen (p < 0.01) during the experimental period. LH values were the following...

Thermally Enhanced Radiosensitivity of Cultured Chinese Hamster Cells

Abstract: X-IRRADIATION of mammalian cells in culture yields a survival curve of the threshold type (for review see ref. 1). It isjnter-esting to ask how one can enhance the radiation response by small changes of the physical environment of the cells, as can be done chemically, for example, by incorporation of 5-bromo-deoxyuridine into DNA1,2. Elevation of the temperature is a likely prospect for enhancement of radiosensitivity for the following reasons. It is known that proteins are heat labile and that temperature sensitive mutants of bacteria and phage can be obtained for many different enzymes3 which are operative at 37° C but not at 42° or 43°C. For example4, DNA polymerase is reversibly temperature sensitive; it is rendered inoperative above 42°C, but will be functional again when the temperature is lowered. It is not unreasonable to expect that temperature sensitive mutations for many enzymes occur frequently and that the use of temperatures somewhat higher than the normal range at which the cells grow might disclose sensitivities for specific enzymes in normal cells of higher organisms.

Corrosion of Ti-6Al-4V in simulated body fluids and bovine plasma

Abstract: The corrosion of Ti-6Al-4V at 37°C in several simulated body fluids and bovine plasma was studied using the passive current-time technique. A 0.9% NaCl (bw)-0.1 N NaH2PO4 solution gave results closest to those using bovine plasma as an electrolyte. All of the samples showed an activation period of 10–15 hr, after which an increase in the corrosion rate was observed. Several possible explanations for this effect are given. For comparison, a sample of Type 316 L stainless steel was tested using isotonic saline solution as the electrolyte. Both the initial and final current densities were considerably higher than those for Ti-6Al-4V indicating a corrosion rate considerably higher for the Type 316 L stainless steel.

Response of Soybeans to Foliage Losses in South Carolina

Abstract: Defoliations of 17, 33, 50, and 67% were made during periods of insect activity on soybeans at midbloom, pod-set, pod-fill, and on a continued basis from midbloom to pod-set. Foliage losses of 33% at bloom did not result in significant yield losses in any of 10 tests; 67% defoliation at pod-set, or on a continued basis from bloom to pod-set caused greatest losses; and 17% defoliation did not cause significant losses at any stage of growth or on a continued basis. Yield losses from defoliations at pod-fill were intermediate between those at bloom and pod-set. Yield reductions were generally accompanied by reductions in seed weight and protein content and increases in oil content. Seed germination was not affected. Although results were not affected significantly by date of planting and by use of irrigation or different varieties, there was a tendency toward generally lower yields at high production levels in the ‘Hampton’ variety after severe defoliations (50 and 67%) at bloom and pod-fill. It was concluded that foliage losses of 17 or 33% allowed additional light penetration to lower leaves, resulting in compensation by increased photosynthate production in these leaves.

Pyrolysis and combustion of cellulose. III. Mechanistic basis for the synergism involving organic phosphates and nitrogenous bases

Abstract: The flame retardation mechanisms for cellulose treated with systems based on aromatic phosphates and phosphoramides have been investigated through pyrolysis studies on cellulose and related model compounds. Pyrolysis of cellulose treated with phosphates or phosphoramides proceeds through formation of cellulose phosphate or phosphoramide esters, followed by subsequent ester pyrolysis to yield a dehydrated cellulose char. Formation of phosphoramides during pyrolysis of flame retardants containing phosphorus and nitrogen constitutes a possible basis for reported phosphorus-nitrogen synergistic effects observed in commercial flame retardants. Efficiency of ester formation is higher, and subsequent pyrolysis is lower for phosphoramides than for phosphate esters. The build-up of a thermally stable crosslinked matrix in the residue occurs on pyrolysis of cellulose treated with phosphoramides. Such crosslinking seems to be effective in enhancing flame retardation.

Second derivatives of the flutter velocity and the optimization of aircraft structures.

Abstract: Equations for the second partial derivatives of the eigenvalues of the flutter equation along with the equations for finding the second partial derivatives of the flutter velocity of an aircraft structure with respect to the structural parameters are derived. These partial derivatives are used to develop expressions for the step size in a projected gradient search along a constant mass hyperlane. A projected gradient search along with a gradient mass and a gradient velocity search is used to minimize the mass of a box beam which supports a lifting surface.

Ultrastructure of the spermatheca of the granary weevil, Sitophilus granarius (L.) (Coleoptera : Curculionidae)

Abstract: In Sitophilus granarius (L.) the spermatheca is sickle-shaped and is attached to the bursa copulatrix by two nerves and a single spermathecal duct. No muscles are present either on the surface of the spermatheca or the surface of the duct but are found connecting the 2 arms of the spermatheca. The duct is composed of a single layer of epithelial cells, which produce the cuticular lining of the lumen and which appear to perform some osmoregulatory function on the duct contents. Two cell types comprise the spermathecal tissue. The first and most common are epithelial cells, which are derivatives of the integumentary ectoderm, and which are always in association with cuticle. The second type are secretory cells found only in the spermathecal gland. This presumably nutritive gland is attached to the proximal end of the spermatheca adjacent to the attachment of the spermathecal duct. Each glandular cell contains the typical cellular organelles of an active, protein-synthesizing, exocrine cell. The synthesized material is discharged into the central lumen of each cell which connects to epithelial ductules leading out of the gland and into the spermatheca.

Pyrolysis and combustion of cellulose. II. Thermal analysis of mixtures of methyl α‐D‐glucopyranoside and levoglucosan with model phosphate flame retardants

Abstract: The thermal degradation of methyl α-D-glucopyranoside, a cellulose model of intermediate complexity, was investigated in an attempt to gain insight into the pyrolytic reactions of analogous cellulose systems The pure glucoside pyrolysis proceeds through formation of an intermediate of higher thermal stability Nitrogenous bases bring about decomposition of the glucoside at lower temperatures and without formation of a detectable intermediate Phenyl phosphates and phosphoramides induce thermal degradation of methyl α-D-glucopyranoside at lower temperatures than observed for the pure glucoside The postulated degradation mechanism involves esterification of the glucoside followed by dehydration and skeletal rearrangements Nitrogenous bases assist the dehydration process but reduce the yield of residue and bound phosphorus Levoglucosan, the cellulose degradation product responsible for flaming combustion, was pyrolyzed in the presence of model flame retardants Nitrogenous bases were found to inhibit thermal polymerization of levoglucosan and to induce its decomposition at lower temperatures Zinc chloride exerted its effects in two stages: acid-catalyzed polymerization at lower temperatures and dehydration at higher temperatures Phenyl phosphates and phosphoramides alter levoglucosan pyrolysis by action as Lewis acids in a manner similar to zinc chloride

Effect of selected herbicides on bacterial growth rates.

Abstract: Specific growth rate constants were used to evaluate the effects of selected herbicides on Erwinia carotovora, Pseudomonas fluorescens, and Bacillus sp. Comparison of growth rate constants permitted the identification of either stimulatory or inhibitory effects of these substances. E. carotovora was inhibited by 6,7-dihydrodipyrido(1,2-a:2'-c)pyrazinediium (diquat) and 4-hydroxy-3,5-diiodobenzonitrile (ioxynil) at 25 mug/ml; 1,1'-dimethyl-4,4'-bipyridinium (paraquat) at 50 mug/ml; and pentachlorophenol (PCP) at 10 mug/ml. P. fluorescens was inhibited by paraquat and PCP at 25 mug/ml and by 4-amino-3,5,6-trichloropicolinic acid (picloram) at 50 mug/ml. Stimulation of P. fluorescens was observed with 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) at 25 mug/ml. The Bacillus species was inhibited by diquat (25 mug/ml), ioxynil (10 mug/ml), and paraquat and PCP (5 mug/ml). No significant effect of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), or 1,1-dimethyl-3-(alpha,alpha,alpha-trifluoro-m-tolyl)urea (fluometuron) on growth rates of the bacteria was observed at 25 and 50 mug/ml.

Hormonal Interrelations in Beef Cows with Induced Multiple Ovulations

Abstract: ALTHOUGH there is wide interest in hormonal induction of multiple births in cattle1, it is not possible to induce two or three ovulations reliably. Further advances will require a better understanding of the patterns of hormone concentrations during follicle growth. This report describes peripheral plasma concentrations of oestrogens, progesterone and luteinizing homone (LH) during the 96 h before induced oestrus and multiple ovulations.

The numerical solution of Fredholm integral equations using product type quadrature formulas

Abstract: Product type quadrature formulas are applied to obtain approximate solutions of Fredholm integral equations. A convergence theorem, and several numerical examples which demonstrate the efficacy of the technique, are presented.