scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Hot-filament-activated chemical-vapor deposition of carbon : film growth and filament reactions

15 Jul 1994-Journal of Applied Physics (American Institute of Physics)-Vol. 76, Iss: 2, pp 1220-1227
TL;DR: In this article, it was shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide.
Abstract: Pure glassy carbon films [no x‐ray photoelectron spectroscopy (XPS) detectable impurities above the 0.5% level] as thick as 25 000 A have been grown on nearby silicon substrates (T≳100 °C) as a result of reactions between a hot tungsten filament and cyclopentane. Above ∼2500 °C, cyclopentane‐tungsten reactions yield a liquid W/C eutectic which limits filament operation. Below ∼2500 °C, resistance changes of the filament and XPS spectra show such reactions form carbides and graphite. It is shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide. Moreover, it is also shown that C1, C2, and C3 (carbon monomers, dimers, and trimers) are evaporated from carbarized tungsten and also from graphite. These results suggest that carbon film growth is a consequence of evaporation of carbon from the carbarized tungsten filament, with steady‐state film deposition occurring as a result of a quasisteady state in the formation and ...
Citations
More filters
Journal ArticleDOI
TL;DR: It is demonstrated that inspiratory training induces a specific functional improvement of the inspiratory muscles and adaptive changes in the structure of external intercostal muscles.
Abstract: The present study was aimed at evaluating the effects of a specific inspiratory muscle training protocol on the structure of inspiratory muscles in patients with chronic obstructive pulmonary disease. Fourteen patients (males, FEV1, 24 +/- 7% predicted) were randomized to either inspiratory muscle or sham training groups. Supervised breathing using a threshold inspiratory device was performed 30 minutes per day, five times a week, for 5 consecutive weeks. The inspiratory training group was subjected to inspiratory loading equivalent to 40 to 50% of their maximal inspiratory pressure. Biopsies from external intercostal muscles and vastus lateralis (control muscle) were taken before and after the training period. Muscle samples were processed for morphometric analyses using monoclonal antibodies against myosin heavy chain isoforms I and II. Increases in both the strength and endurance of the inspiratory muscles were observed in the inspiratory training group. This improvement was associated with increases in the proportion of type I fibers (by approximately 38%, p < 0.05) and in the size of type II fibers (by approximately 21%, p < 0.05) in the external intercostal muscles. No changes were observed in the control muscle. The study demonstrates that inspiratory training induces a specific functional improvement of the inspiratory muscles and adaptive changes in the structure of external intercostal muscles.

350 citations

Journal ArticleDOI
TL;DR: The analysis suggests that many muscles operate over a narrow range of sarcomere lengths, covering 94+/-13 % of optimal Sarcomere length.
Abstract: The force generated by skeletal muscle varies with sarcomere length and velocity. An understanding of the sarcomere length changes that occur during movement provides insights into the physiological importance of this relationship and may provide insights into the design of certain muscle/joint combinations. The purpose of this review is to summarize and analyze the available literature regarding published sarcomere length operating ranges reported for various species. Our secondary purpose is to apply analytical techniques to determine whether generalizations can be made regarding the "normal" sarcomere length operating range of skeletal muscle. The analysis suggests that many muscles operate over a narrow range of sarcomere lengths, covering 94+/-13 % of optimal sarcomere length. Sarcomere length measurements are found to be systematically influenced by the rigor state and methods used to make these measurements.

281 citations

Journal ArticleDOI
TL;DR: It is concluded that sarcomere disruption is common in the human diaphragm, is more evident in patients with COPD, and is higher after inspiratory loading, especially in the diaphragem of those with COPd.
Abstract: Injury of the diaphragm may have clinical relevance having been reported in cases of sudden infant death syndrome or fatal asthma. However, examination of diaphragm injury after acute inspiratory loading has not been reported. The purpose of this study was to determine whether an acute inspiratory overload induces injury of the human diaphragm and to determine if diaphragm from chronic obstructive pulmonary disease (COPD) is more susceptible to injury. Eighteen patients with COPD and 11 control patients with normal pulmonary function (62 ± 10 yr) undergoing thoracotomy or laparotomy were studied. A threshold inspiratory loading test was performed prior to surgery in a subset of seven patients with COPD and five control patients. Samples of the costal diaphragm were obtained during surgery and processed for electron microscopy analysis. Signs of sarcomere disruption were found in all diaphragm samples. The range of values of sarcomere disruption was wide (density: 2–45 abnormal areas/100 μ m2; area fractio...

208 citations

Journal ArticleDOI
TL;DR: The regional differences in mechanical and metabolic activity within the diaphragm and how such heterogeneities might influence diaphragem function in health and disease are reviewed.
Abstract: The diaphragm is the primary muscle of inspiration, and as such uncompromised function is essential to support the ventilatory and gas exchange demands associated with physical activity. The normal healthy diaphragm may fatigue during intense exercise, and diaphragm function is compromised with aging and obesity. However, more insidiously, respiratory diseases such as emphysema mechanically disadvantage the diaphragm, sometimes leading to muscle failure and death. Based on metabolic considerations, recent evidence suggests that specific regions of the diaphragm may be or may become more susceptible to failure than others. This paper reviews the regional differences in mechanical and metabolic activity within the diaphragm and how such heterogeneities might influence diaphragm function in health and disease. Our objective is to address five principal areas: 1) Regional diaphragm structure and mechanics (GAF). 2) Regional differences in blood flow within the diaphragm (WLS). 3) Structural and functional interrelationships within the diaphragm microcirculation (DCP). 4) Nitric oxide and its vasoactive and contractile influences within the diaphragm (MBR). 5) Metabolic and contractile protein plasticity in the diaphragm (SKP). These topics have been incorporated into three discrete sections: Functional Anatomy and Morphology, Physiology, and Plasticity in Health and Disease. Where pertinent, limitations in our understanding of diaphragm function are addressed along with potential avenues for future research.

86 citations

Journal ArticleDOI
TL;DR: In this article, diamond films were grown at various vol.% CH 4 in H 2 from 0.5% to 3.5%, at substrate temperature and pressure of 850 ÂC and 80 Âtorr, respectively.

86 citations

References
More filters
Book
01 Jan 1949
TL;DR: In this paper, the scientific foundations of the vacuum technique were discussed and the following papers were published: Scientific foundations of vacuum technique, Scientific foundations for vacuum technique and its application in computer vision.
Abstract: Scientific foundations of vacuum technique , Scientific foundations of vacuum technique , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

1,727 citations

Book
01 Jan 1981

923 citations

Journal ArticleDOI
TL;DR: In this paper, a C H O phase diagram is introduced providing a common scheme for all major diamond chemical vapour deposition (CVD) methods used to date, revealing that low pressure diamond synthesis is only feasible within a well-defined field of the phase diagram, a diamond domain that allows general predictions of gas phase compositions and starting materials suitable for diamond synthesis.

472 citations

Journal ArticleDOI
01 Dec 1973-Carbon
TL;DR: In this paper, the laser Raman spectra were studied of natural graphite (SP-1) and carbonaceous materials including pyrolytic graphite, carbon black, glassy carbon, coal, “white” carbon and sputtered carbon.

359 citations

Journal ArticleDOI
TL;DR: In this paper, infrared diode laser absorption spectroscopy was employed as an in situ method to examine gas phase species present during filament assisted deposition of diamond films, and the growth of polycrystalline diamond films was confirmed with x-ray and Raman scattering.
Abstract: Infrared diode laser absorption spectroscopy is employed as an in situ method to examine gas phase species present during filament‐assisted deposition of diamond films. From a reactant mixture of 0.5% methane in hydrogen, methyl radical (CH3 ), acetylene (C2H2), and ethylene (C2H4 ) are detected above the growing surface, while ethane (C2H6 ), various C3 hydrocarbons, and methylene (CH2) radicals are below our sensitivity levels. The growth of polycrystalline diamond films on Si wafers and polycrystalline Ni is confirmed with x‐ray and Raman scattering, scanning electron microscopy, and Auger electron spectroscopy.

229 citations