Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon

Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700. nm. The substrates were disks made of UHMWPEs typically used for soft components in artificial joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100. kGy) UHMWPEs. Mechanical and tribological properties under bovine serum lubrication at body temperature were assessed on coated and uncoated polyethylenes by means of nano-hardness and ball-on-disk tests, respectively. Morphological features of the worn surfaces were obtained by confocal microscopy and scanning electron microscopy. This study confirms an increase in surface hardness and good wear resistance for coated materials after 24. h of sliding test compared to uncoated polyethylene. These results point out that to coat UHMWPE with DLCH films could be a potential method to reduce backside wear in total hip and knee arthroplasties.Ministerio de Ciencia y Educación MAT2006-12603- C02-01, CSD2008-0002

Identificação de deficiências minerais de bovinos na microrregião Alto Purus-Acre.

A Unidade de Execução de Pesquisa de Âmbito Estadual - UEPAE/Rio Branco, vem desenvolvendo estudos com os objetivos de identificar as deficiências minerais de bovinos na microrregião Alto Purus-Acre, determinando as interrelações entre os níveis de minerais no solo, nas forrageiras e nos tecidos animais durante as estações chuvosa e seca.bitstream/item/145816/1/1097.pd

Estudio de la tipología de preguntas sobre las temáticas átomo, tabla periódica y enlace químico en las pruebas de acceso a la universidad en Andalucía

Este trabajo analiza las pruebas de acceso a la universidad de química en Andalucía desde las temáticas átomo/tabla periódica (ATP) y enlace químico (EQ), estudiando su frecuencia de aparición y la tipología de preguntas con el sistema de categorías de Smith et al. (definición, algorítmicas y conceptuales). Los resultados muestran que son temáticas poco abordadas (5.4% ATP y 9.4% EQ), a pesar de su importancia en la química escolar. En ningún caso aparecen preguntas de tipo algorítmico y la mayoría son conceptuales en ambas temáticas. Son mayoritarias cuestiones de análisis e interpretación de datos (87%) en el tema ATP, y de explicación de ideas subyacentes y predicción de resultados (85%) y análisis de representación pictórica (76%) en EQ. Sólo el 45% y 13% son cuestiones de definición ATP y EQ, respectivamente

Effect of surface roughness and sterilization on bacterial adherence to ultra-high molecular weight polyethylene

AbstractSterilization with ethylene oxide (EO) and gas plasma (GP) are well-known methods applied to ultra-high molecular weight polyethylene (UHMWPE) surfaces in the belief that they prevent major material changes caused by gamma irradiation. However, the influence of these surface sterilization methods on bacterial adherence to UHMWPE is unknown. UHMWPE samples with various degrees of roughness (0.3, 0.8 and 2.0 µm) were sterilized with either GP or EO. The variations in hydrophobicity, surface free energy and surface functional groups were investigated before and after sterilization. Sterilized samples were incubated with either Staphylococcus aureus or Staphylococcus epidermidis in order to study bacterial adherence to these materials. Fewer bacteria adhered to UHMWPE after sterilization with EO than after sterilization with GP, especially to the smoothest surfaces. No changes in chemical composition of the UHMWPE surface due to sterilization were observed using X-ray photoemission spectroscopy analysis. The decreased bacterial adherence to UHMWPE found at the smoothest surfaces after sterilization with EO was not directly related to changes in chemical composition. Increased bacterial adherence to rougher surfaces was associated with increased polar surface energy of EO-sterilized surfaces

Changing Dose of Progesterone Results in Sudden Changes in Frequency of Luteinizing Hormone Pulses and Secretion of 17β-Estradiol in Bovine Females

The aim of the present study was to elucidate the time course according to which changes in circulating concentrations of progesterone influence pulsatile secretion of LH and secretion of 17β-estradiol. Our working hypothesis was that changing the dose of progesterone would result in changes in frequency of LH pulses and secretion of 17β-estradiol within 72 h. Five days after behavioral estrus, thirty-three cows were randomly assigned to one of five groups: 1) control, no treatment (CONT, n = 5); 2) treatment with two progesterone-releasing intravaginal devices (PRIDs) for 11 days (2PRID, 5-6 ng/ml plasma progesterone, n = 7); 3) treatment with a 0.5 PRID for 11 days (0.5PRID, 1-2 ng/ml plasma progesterone, n = 7); 4) treatment with 2 PRIDs for 8 days followed by treatment with a 0.5 PRID for 3 days (2-0.5PRID, n = 7); and 5) treatment with a 0.5 PRID for 8 days followed by treatment with 2 PRIDs for 3 days (0.5-2PRID, n = 7). Cows subject to PRID treatments received injections of prostaglandin F2 on Days 1 and 2 (Day 0 = day of initiation of PRID treatments, fifth day of the estrous cycle in CONT cows) to lyse the existing corpus luteum. Cows were bled for 12 h at 15-min intervals on Day 7.5 of the treatment period (twelfth day of the estrous cycle in CONT cows). The dose of progesterone was changed on Day 8 in cows that were assigned to the 2-0.5PRID and 0.5-2PRID groups, and blood collections continued an additional 72 h to characterize profiles of circulating concentrations of LH and 17β-estradiol. Cows treated with a 0.5 PRID had a greater (p \u3c 0.05) number of LH pulses and higher (p \u3c 0.05) concentrations of 17β-estradiol throughout the entire blood collection period than cows in the 2PRID and CONT groups. An increase in the number of LH pulses was detected within 6 h after the change from the high to the low dose of progesterone (2-0.5PRID), and frequency of LH pulses was similar to that of cows in the 0.5PRID group for the remainder of the period of blood collection. LH pulse frequency declined within 6 h after the shift from the low to the high dose of progesterone (0.5-2PRID) and was similar to that of cows in the 2PRID group by 12 h after the dose was changed. Within 6 h after the dose of progesterone was changed, circulating concentrations of 17p-estradiol increased (p \u3c 0.05) in cows shifted from the high to low dose (2-0.5PRID) and declined (p \u3c 0.05) after the dose of progesterone was changed from low to high (0.5-2PRID). We conclude that changing the circulating concentrations of progesterone concurrently affects frequency of pulsatile LH release and secretion of 17β-estradiol within 6-24 h

Changing Dose of Progesterone Results in Sudden Changes in Frequency of Luteinizing Hormone Pulses and Secretion of 17β-Estradiol in Bovine Females

The aim of the present study was to elucidate the time course according to which changes in circulating concentrations of progesterone influence pulsatile secretion of LH and secretion of 17β-estradiol. Our working hypothesis was that changing the dose of progesterone would result in changes in frequency of LH pulses and secretion of 17β-estradiol within 72 h. Five days after behavioral estrus, thirty-three cows were randomly assigned to one of five groups: 1) control, no treatment (CONT, n = 5); 2) treatment with two progesterone-releasing intravaginal devices (PRIDs) for 11 days (2PRID, 5-6 ng/ml plasma progesterone, n = 7); 3) treatment with a 0.5 PRID for 11 days (0.5PRID, 1-2 ng/ml plasma progesterone, n = 7); 4) treatment with 2 PRIDs for 8 days followed by treatment with a 0.5 PRID for 3 days (2-0.5PRID, n = 7); and 5) treatment with a 0.5 PRID for 8 days followed by treatment with 2 PRIDs for 3 days (0.5-2PRID, n = 7). Cows subject to PRID treatments received injections of prostaglandin F2 on Days 1 and 2 (Day 0 = day of initiation of PRID treatments, fifth day of the estrous cycle in CONT cows) to lyse the existing corpus luteum. Cows were bled for 12 h at 15-min intervals on Day 7.5 of the treatment period (twelfth day of the estrous cycle in CONT cows). The dose of progesterone was changed on Day 8 in cows that were assigned to the 2-0.5PRID and 0.5-2PRID groups, and blood collections continued an additional 72 h to characterize profiles of circulating concentrations of LH and 17β-estradiol. Cows treated with a 0.5 PRID had a greater (p \u3c 0.05) number of LH pulses and higher (p \u3c 0.05) concentrations of 17β-estradiol throughout the entire blood collection period than cows in the 2PRID and CONT groups. An increase in the number of LH pulses was detected within 6 h after the change from the high to the low dose of progesterone (2-0.5PRID), and frequency of LH pulses was similar to that of cows in the 0.5PRID group for the remainder of the period of blood collection. LH pulse frequency declined within 6 h after the shift from the low to the high dose of progesterone (0.5-2PRID) and was similar to that of cows in the 2PRID group by 12 h after the dose was changed. Within 6 h after the dose of progesterone was changed, circulating concentrations of 17p-estradiol increased (p \u3c 0.05) in cows shifted from the high to low dose (2-0.5PRID) and declined (p \u3c 0.05) after the dose of progesterone was changed from low to high (0.5-2PRID). We conclude that changing the circulating concentrations of progesterone concurrently affects frequency of pulsatile LH release and secretion of 17β-estradiol within 6-24 h

Melengestrol Acetate at Greater Doses Than Typically Used for Estrous Synchrony in Bovine Females Does Not Mimic Endogenous Progesterone in Regulation of Secretion of Luteinizing Hormone and 17β-Estradiol

Our working hypothesis was that doses of melengestrol acetate (MGA) greater than those typically administered in estrous synchrony regimens would regulate secretion of LH and 17β-estradiol (E2) as endogenous progesterone (P4) does during the midluteal phase of the estrous cycle. We also hypothesized that endogenous P4 from the CL would interact with MGA to further decrease the frequency of LH pulses and E2. Cows on Day 5 of their estrous cycle (Day 0 = estrus) were randomly assigned to an untreated control group (CONT, n = 5) or to one of six MGA treatment groups (n = 5 per group): 1) MGA administered orally each day via a gelatin capsule at a dose of 0.5 mg MGA/cow with the CL present (0.5CL); 2) 0.5 mg MGA/cow daily in the absence of CL (0.5NO); 3) 1.0 mg MGA with CL present (1.OCL); 4) 1.0 mg MGA without CL (1.ONO); 5) 1.5 mg MGA with CL present (1.5CL); 6) 1.5 mg without CL (1.5NO). MGA was administered for 10 days (Day 5 = initiation of treatment). To regress CL, cows assigned to groups without CL received injections of prostaglandin F2α (PGF, 0; 25 mg) on Days 6 and 7 of their estrous cycle. All cows were administered PGF2α. at the end of the 10-day treatment period. During the treatment period, daily blood samples were collected to determine concentrations of E2. Serial blood samples were collected at 15-min intervals for 24 h on Days 8, 11, and 14 to determine pattern of LH secretion. Frequency of LH pulses on Days 8, 11, and 14 was greater (p \u3c 0.05) in cows without CL (0.5NO, 1.ONO, and 1.5NO) than in cows with CL (0.5CL, 1.OCL, 1.5CL, and CONT). Mean concentrations of LH were greater (p \u3c 0.05) in cows from the 0.5NO group on Days 8 and 11 and were greater (p \u3c 0.05) in cows from the 0.5NO, 1.ONO, and 1.5NO groups on Day 14 as compared to cows with CL. Overall mean concentrations of LH across Days 8, 11, and 14 were greatest (p \u3c 0.05) in cows from the 0.5NO group and were also greater (p \u3c 0.05) in cows from the 0.5NO, 1.ONO, and 1.5NO groups as compared to cows in the 0.5CL, 1.OCL, 1.5CL, and CONT groups. Mean concentrations of E2 during the treatment period were greater (p \u3c 0.05) in cows from the 0.5NO group than in cows from either the 1.ONO or the 1.5NO group; these values were also greater (p \u3c 0.05) in cows of the 0.5NO, 1.ONO, and 1.5NO groups as compared to cows of the 1.OCL and CONT groups. Therefore, we reject our working hypothesis because doses of MGA greater than those typically used in estrous synchrony protocols did not suppress LH and E2 to the same extent that endogenous P4 does. In addition, MGA treatment when CL were present did not result in a further suppression of LH pulse frequency or of E2 as compared to the values in control cows with functional CL

Comparison of Circulating Concentrations of Reproductive Hormones in Boars of Lines Selected for Size of Testes or Number of Ovulations and Embryonal Survival to Concentrations in Respective Control Lines

The objectives of this study were to determine whether circulating concentrations of gonadotropins and gonadal hormones of boars were altered as a result of selection of pigs for size of testes or for embryonal survival and(or) number of ovulations. Included in Exp. 1 and 2 were boars with the greatest estimated paired weight of testes (TS) and boars from a control (C) line. Concentrations of FSH were similar ( P \u3e .10) in boars from the TS and C lines. In Exp. 3, 4, and 5, circulating concentrations of FSH and 17β-estradiol (E2) were evaluated in neonates, during pubertal development, and in mature boars of lines selected for an index of number of ovulations and embryonal survival ( I ) , and data were compared to those for boars from a respective C line. Concentrations of E2 were not different in boars from the I line and those from the C line during the early neonatal period but were greater ( P \u3c .05) in boars of the C line than in those from the I line during pubertal development. Concentrations of FSH were greater ( P \u3c .05) in mature boars from the I line than in those from the C line. In summary, selection for size of testes did not influence circulating concentrations of FSH in mature boars. The secretory pattern of E2 in boars before puberty changed as a result of selection for embryonal survival and number of ovulations in females of the I line, and the different patterns of circulating E2 early in life may result in enhanced circulating concentrations of FSH in adult boars of the I line compared with boars of the C line