Insights into tribofilm formation on Ti-6V-4Al in a bioactive environment: Correlation between surface modification and micro-mechanical properties.

Ti-6Al-4V has been used as a surgical implant material for a long time because of its combination of strength, corrosion resistance and biocompatibility. However, there remains much that is not understood about how the surface reacts with the environment under tribocorrosion conditions. In particular, the conditions under which tribofilms form and their role on friction and wear are not clear. To evaluate the complicated nature of the dynamic surface microstructural changes on the wear track, high resolution transmission electron microscopy (TEM), scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) have been used to characterise the structure and chemical composition of the tribofilm. Detailed analysis of the formation and structure of the tribofilm and the metal surface deformation behaviour were studied as a function of applied potential and the role of proteins in the lubricant. For the first time, graphitic and onion-like carbon structures from wear debris were found in the testing solution. The presence of carbon nanostructures in the tribocorrosion process and the formation of the tribofilm leads to an improved tribocorrosion behaviour of the system, in particular a reduction in wear and friction. A detailed, quantitative, analysis of surface deformation was undertaken, in particular, the geometrically necessary dislocation (GND) density was quantified using precession electron diffraction (PET). A clear correlation between applied potential, tribofilm formation and the surface strain was established. STATEMENT OF SIGNIFICANCE: The formation of tribofilm and microstructure modification of the Ti-6Al-4V surface during tribocorrosion in a physiological environment is not fully understood. In particular, the correlation between microstructural changes and electrochemical conditions is not clear. This study presents a detailed investigation of the structure and chemical composition of tribofilms at the nanoscale during tribocorrosion tests in simulated body fluid and gives a detailed and quantitative description of the evolved surface structure. A clear correlation between applied potential, tribofilm formation and the surface strain was established. Moreover, particular attention is paid to the wear debris particles captured from the lubricating solution, including nanocarbon onion structures. The implications for tribocorrosion of the alloy in its performance as an implant are discussed.

Tomographic Study of Mesopore Formation in Ceria Nanorods.

Porosity in functional oxide nanorods is a recently discovered new type of microstructure, which is not yet fully understood and still under evaluation for its impact on applications in catalysis and gas/ion storage. Here we explore the shape and distribution of pores in ceria in three dimensions using a modified algorithm of geometric tomography as a reliable tool for reconstructing defective and strained nanoobjects. The pores are confirmed as "negative-particle" or "inverse-particle" cuboctahedral shapes located exclusively beneath the flat surface of the rods separated via a sub-5 nm thin ceria wall from the outside. New findings also comprise elongated "negative-rod" defects, seen as embryonic nanotubes, and pores in cube-shaped ceria. Furthermore, we report near-sintering secondary heat treatment of nanorods and cubes, confirming persistence of pores beyond external surface rounding. We support our experiments with molecular modeling and predict that the growth history of voids is via diffusion and aggregation of atomic point defects. In addition, we use density functional theory to show that the relative stability of pore (shape) increases in the order "cuboidal" < "hexagonal-prismatic" < "octahedral". The results indicate that by engineering voids into nanorods, via a high-temperature postsynthetic heat treatment, a potential future alternative route of tuning catalytic activities might become possible.

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels.

Hydrogen embrittlement is shown to proceed through a previously unidentified mechanism. Upon ingress to the microstructure, hydrogen promotes the formation of low-energy dislocation nanostructures. These are characterized by cell patterns whose misorientation increases with strain, which concomitantly attracts further hydrogen up to a critical amount inducing failure. The appearance of the failure zone resembles the "fish eye" associated to inclusions as stress concentrators, a commonly accepted cause for failure. It is shown that the actual crack initiation is the dislocation nanostructure and its associated strain partitioning.

Relationship of selected body composition and training variables to 17 B-estradiol in eumenorrheic runners.

Although the relationships among body composition, training, and physical characteristics and 17 B-estradiol (estradiol) have been described in active amenorrheic women, little is known about these relationships in eumenorrheic women. This study examined the relationship between selected body composition and training variables, physical characteristics, maximal oxygen consumption (VO2max), luteinizing hormone (LH) and estradiol in eumenorrheic runners. Fifteen women (25.8 +/- 0.8 years) running 19.8 +/- 1.8 miles per week were studied during the midluteal phase of the menstrual cycle. Estradiol and LH were determined by radioimmunoassay. Body composition was measured by hydrostatic weighing. Age, Ponderal Index, and menstrual cycle length (days) were inversely related to estradiol (r = -0.56, r = -0.55, r = -0.52, respectively, p less than 0.05). A significant relationship (R2 = 0.91; p less than 0.05) was found among age, menstrual cycle length, LH (mIU/ml), VO2max (ml/kg/min), weight training (hr/wk), miles run per week, height (cm), additional aerobic training (hr/wk), relative body fat (%), and Ponderal Index and estradiol (pg/ml). These data suggest the midluteal concentration of estradiol in moderately trained eumenorrheic runners is the result of a complex interaction of many factors.

Seasonal changes in female athletes' diets.

Dietary intakes of 24 female athletes in various sports were compared inseason and postseason to those reported by 24 nonathletes during the same time period. Diets were analyzed for energy, carbohydrate, fat, protein, vitamins A and C, thiamin, riboflavin, niacin, folacin, calcium, and iron. During the study, the athletes' and nonathletes' diets were similar. Their energy intakes were lower than recommended while their iron and calcium intakes were marginal (less than 70% of the recommended dietary allowance). Although few dietary changes were observed, the nonathletes' diets changed more than those of the athletes during the study. Both groups reduced their energy intakes but only the nonathletes' reduction was significant. Initially many subjects were dieting. More subjects reported dieting during the second recording period. These results suggest that the desire to be thin may influence dietary intakes of female athletes more than changes in exercise training.

Agglutinin response of rabbits to combined Pasteurella tularensis-Brucella abortus vaccination.

A schedule was developed for the simultaneous production of a Pasteurella tularensis-Brucella abortus antiserum in rabbits. Three doses of 10(8) viable P. tularensis LVS organisms were given intravenously at weekly intervals. One day prior to the final dose of P. tularensis, the rabbits received 10(9) viable cells of B. abortus strain 19 intravenously. The use of live vaccines, administered in this sequence, resulted in high agglutinin titers within 3 weeks. The maximal agglutinin titer to either organism was observed 1 week after the final injection.

Effect of vaccine, route, and schedule on antibody response of rabbits to Pasteurella tularensis.

The response of the rabbit to viable or killed whole-cell Pasteurella tularensis vaccines was studied. The most practical preparation for the production of anti-P. tularensis antibodies was viable organisms of the live vaccine strain (LVS). The intravenous route of administration proved superior to either the subcutaneous or intradermal routes, and incorporation of LVS into Freund's adjuvants did not result in increased levels of antibody. Short-term hyperimmunization, three injections at weekly intervals, constituted the most efficient method for increasing levels of the antibodies.

Antigens of Pasteurella tularensis: preparative procedures.

Ether-water (EW) extraction of Pasteurella tularensis produced better antigens than five other chemical procedures. EW extracts produced from stationary-phase, liquid-grown, saline suspensions of strain SCHU S4 cells regularly induced agglutinin and precipitin formation in rabbits. Mice, guinea pigs, and monkeys also responded to EW extracts but with lower antibody levels. The use of strains of lower virulence, acetone-dried cells, organisms grown on a solid medium, and abbreviated extraction conditions all resulted in extracts with a diminished antigenicity, but logarithmic-phase and stationary-phase cells yielded equivalent EW extracts. The use of adjuvant, hyperimmunization, and large doses of antigen increased the precipitin responses of rabbits without appreciably altering the agglutinin response. By the appropriate combination of centrifugal fractionation of EW extracts, use of adjuvant, and vaccination schedule, rabbit antisera with either predominantly agglutinating or precipitating activities were obtained.

In vitro interactions between rabbit alveolar macrophages and Pasteurella tularensis.

Nutter, J. E. (Fort Detrick, Frederick, Md.), and Q. N. Myrvik. In vitro interactions between rabbit alveolar macrophages and Pasteurella tularensis. J. Bacteriol. 92:645-651. 1966.-Rabbit alveolar macrophages were successfully employed in a study of host cell-Pasteurella tularensis interactions in vitro. Under cell culture conditions in which inhibitory antibiotics were not employed and small infection ratios were used, the relative in vivo virulence of two strains of P. tularensis was duplicated. As a consequence of intracellular multiplication, normal macrophages were killed in relation to the virulence of the strain employed. Alveolar macrophages were also collected from immune rabbits, and macrophage mortality and bacterial growth were significantly suppressed below levels observed with normal macrophage preparations. The effect of immune serum could only be ascribed a minor role in the observed reactions. A marked intravenous toxicity of P. tularensis for the rabbit was observed with both virulent and attenuated strains. The toxicity was possessed only by viable preparations and could be elicited in animals immune to virulent challenge.

Inherited deficiency of delta-aminolevulinic acid dehydratase.

Delta-aminolevulinic acid dehydratase (ALA-D) is the second enzyme in the porphyrin-heme pathway and converts delta-aminolevulinc acid (ALA) to porphobilinogen (PBG). A family is reported with an inherited deficiency of red cell ALA-D activity occurring over three generations in an autosomal dominant pattern. Intial experiments support the hypothesis that the mutation in this family may affect a regulatory gene, but enzyme purification and further study are required. Although no clinical manifestations of deficient ALA-D activity have been found in affected persons, families such as this may be at increased risk for the serious consequences of lead poisoning, which produces marked inhibition of ALA-D activity.

Aggressive epithelioid hemangioendothelioma of the lower extremity: a case report and review of the literature.

A case of epithelioid hemangioendothelioma (EHE) of the left lower extremity in a 50-year-old male is discussed. The neoplasm presented as a tan-purple, painful mass involving the fourth digit of the left foot. Following an excisional biopsy and partial amputation of the fourth digit, the lesion recurred with a multifocal distribution. A physical exam following the recurrence demonstrated multiple palpable lymph nodes in the left inguinal region. A complete amputation of the fourth digit was performed in conjunction with local excisions of the remaining lesions. Additionally, an inguinal lymphadenectomy was performed for staging purposes. Histologically, the tumor was predominantly composed of epithelioid endothelial cells forming nests, cords, and sheets and occasionally forming irregular, primitive vascular structures. Less commonly, nests of tumor cells assumed a spindled morphology. Patches of necrosis and hemorrhage were apparent throughout the neoplasm. There was minimal atypia and mitoses were not identified. Immunohistochemical stains for CD34, CD31, and Ulex europaeus antigens were positive in tumor cells. This case illustrates the potential aggressive behavior of this rare neoplasm and argues against the designation "tumor of low-grade malignancy" with which it is commonly attributed.

A simple analytical test and a formula to predict the potential for dermal carcinogenicity from petroleum oils.

A correlation for predicting dermal carcinogenicity of petroleum oils in laboratory animals has been developed using two simple analytical tests. The tests are the Food and Drug Administration test (FDA) commonly used to measure white oil purity, and a viscosity test. In the correlation, FDA is a measure of aromaticity, and viscosity is used to account for molecular weight. The FDA test alone appears to be comparable to other predictors now in use, but incorporating viscosity significantly increases the accuracy of predicting dermal carcinogenicity. A formula is proposed, using both the FDA test results and viscosity, that predicts the percentage of mice which will develop neoplastic skin tumors.