Adhesion and friction properties of hydrogenated amorphous carbon films measured by atomic force microscopy

Atomic force microscopy has been used to measure adhesion and friction forces at the interface between an oxidized metal probe tip and amorphous carbon films of varying hydrogen contents (12.3–39.0 atomic percent hydrogen). The interface of an oxide surface and a hard carbon coating models the unlubricated head-disk interface of current hard disk products. Adhesion forces normalized by the radius of curvature of the contacting tip range from 1.09 to 8.53 N/m. Coefficients of friction values, measured as the slope of the friction versus load plot, range from 0.33 to 0.87. A trend of increasing adhesion forces and coefficients of friction is observed for increasing hydrogen content in the films. We attribute the increase in adhesion and friction to increases in the surface free energy of the carbon films with the incorporation of hydrogen.     

Atomic Force Microscopy and X-ray Photoelectron Spectroscopy Investigation of the Onset of Reactions on Alkali Silicate Glass Surfaces

Atomic force microscopy was used to measure forces acting on a sharp tungsten tip as it was brought into contact with silica and 30 mol% binary alkali silicate glasses. Experiments were performed in controlled atmospheres and under vacuum. Attractive forces and liquid-layer thicknesses were found to vary markedly between the glasses, and heterogeneity was observed on the binary alkali silicates analyzed in vacuo . Air or wet carbon dioxide exposure resulted in the penetration of the tip into a soft surface layer on the alkali silicates. In addition, liquid layer formation on the alkali silicates was found to be promoted by exposure to water vapor in the order lithium < sodium < potassium. X-ray photoelectron spectroscopy indicated that reaction between the potassium silicate surface and water vapor occurred on exposure to only 10⁻⁴ torr (1 torr = 1.33 × 10² Pa) water. Surface segregation and leaching of potassium occurred under the same conditions.     

Bonding and tribological properties of perfluorinated lubricantsand hydrogenated amorphous carbon films

Molecular properties of perfluorinated lubricants and amorphous carbon films relevant to the tribological performance of hard disk drives have been measured. The bonding of water and model perfluorinated lubricants to amorphous carbon surfaces has been studied by thermal desorption spectroscopy. Binding energies consistent with a physisorbed state are found for each of these small molecules. Binding energies are found to increase with increasing molecular weight and polarity of the adsorbate as well as increasing surface free energy of the carbon film. Adhesion forces and coefficients of friction have been measured with atomic force microscopy at hydrogenated amorphous carbon surfaces as a function of hydrogen content. An increase in both adhesion and friction forces is observed with increasing hydrogen contents and is attributed to changes in the surface free energy of the carbon films     

Capacitation and the acrosome reaction in marsupial spermatozoa

Although yet to be established definitively, it appears that marsupial spermatozoa require a process of capacitation and that the mechanisms involved may be quite different between the Australian and American species. For Australian species, failure to induce this functional event in culture has meant that in vitro fertilization (IVF) is yet to be achieved. However, in the American species with paired spermatozoa, IVF and subsequent embryo development have been obtained under quite simple culture conditions. Our understanding of the interactions of marsupial spermatozoa with the female tract, and in particular the oviduct, the most likely site of capacitation, is discussed. Although the acrosome reaction (AR) is an equally critical event in marsupial fertilization it appears to be regulated quite differently. The uniquely stable character of the marsupial acrosome is examined as well as our current understanding of the regulation of the marsupial sperm AR in vivo and in vitro.     

Preface

Preface

Preface     

Granulomatous epididymal lesion of possible ischemic origin

In a histologic review of adult epididymides obtained at autopsy (both epididymides of 408 men) or during surgery (261 men with testicular or epididymal nontumoral pathology), a peculiar granulomatous lesion was observed in two autopsy specimens (unilateral) and three surgical specimens. The lesion was located in the caput epididymidis and consisted of a zone of necrosis that involved efferent ducts and interstitial connective tissue and was not associated with an acute inflammatory response. Immunohistochemical study with anticytokeratin antibodies showed the presence of some epithelial cells in the damaged efferent ducts. At the periphery of the lesion, where damage was less severe, the efferent ducts only showed partial necrosis of their wall through which the necrotic material was released to the ductal lumen. Inflammatory infiltrates were scanty and consisted of lymphocytes and CD68-positive macrophages. Lymphocytes were mainly located around the necrotic zone or surrounding the adjacent, well-preserved efferent ducts, whereas macrophages formed large clusters in the ductal lumen. In these clusters, cholesterol crystals and giant cells of foreign body type were frequent. Intratubular epithelial regeneration as well as proliferation of small ducts showing epithelial regeneration and numerous spermatozoa in their lumen were observed. Ceroid granulomata, spermatic granulomata, and epidermoid metaplasia of the efferent ducts were observed in some cases. On the basis of the histologic study, the following developmental stages of the lesion are suggested: ischemic necrosis, granulomatous reaction, cicatrization, and sequelae. The term "granulomatous ischemic lesion" is proposed to designate this reactive lesion.