Insights into the physics of spray coating of SWNT films

Spray coating is a scalable and high-throughput process for fabrication of transparent and conducting coatings (TCCs) composed of single-walled carbon nanotubes (SWNTs). Presently the fundamentals of this process are not well understood. We show that suppression of coalescence of spray droplets by sufficiently rapid heat- and mass-transfer yields homogeneous SWNT films by preventing the formation of ‘coffee stains’ of larger length scale. Such heat and mass transfer is driven by differential evaporation between the top and edges of the drops, whereas thermal and compositional effects on surface tension and buoyancy are weak. Ultrasonic spraying ensures that the droplets are deposited without significant splashing, and delayed splashing at higher Weber number is evidenced. We find that the performance of spray-coated TCCs made from HiPCO SWNTs is limited by bundle diameter rather than length of the constituent SWNTs and bundes. Vapor acid doping with concentrated sulfuric acid roughly doubles the conductivity of the TCCs.     

S-nitrosylation and S-glutathiolation of protein sulfhydryls by S-nitroso glutathione

The modification of reactive protein sulfhydryls by S-nitrosoglutathione and other NO donors has been studied by gel isoelectric focusing. S-nitrosylated, unmodified, and S-glutathiolated protein forms are differentiated by this method. With specific antibodies for the protein of interest, both S-nitrosylation and S-glutathiolation of the protein were analyzed in mixtures obtained as soluble tissue or cell extracts. The effect of S-nitrosoglutathione (GSNO) on purified phosphorylase b, on carbonic anhydrase III in an extract from rat liver, and on H-ras expressed in Escherichia coli was examined. When fresh GSNO reacted with pure phosphorylase b, only S-nitrosylated forms of the protein were observed. Likewise the NO donors, amyl nitrite, spermine NONOate, and diethylamine NONOate, all generated S-nitrosylated phosphorylase b. When crude mixtures of proteins from rat liver (containing carbonic anhydrase III) or from E. coli (containing an overexpressed form of H-ras) were exposed to fresh GSNO, both the S-nitrosylated and the S-glutathiolated forms of the proteins were observed. It is suggested that reactive intermediates from the breakdown of GSNO are responsible for the observed S-glutathiolation. These experiments show that both S-nitrosylated and S-glutathiolated forms of proteins may be generated by the addition of GSNO to mixtures containing proteins with reactive sulfhydryls. These protein modifications may exhibit metabolic consequences independent of the release of nitric oxide.     

Critical Issues in Sol-Gel Derived Ferroelectric Thin Films: A Review

In this article we have reviewed our recent research efforts on the synthesis and characterization of a wide spectrum of ferroelectric thin films for a variety of electronic and electro-optic devices including computer memories, tunable microwave devices, infra-red detectors, and electro-optic modulators. The review is separated into three sections; first we have described the process induced modifications of the properties of perovskite films prepared by sol-gel technique. The next section reviews the effect of certain impurity elements (e.g. La, Nd, Ce etc) in modifying the electrical characteristics of perovskite thin films followed by our experimental observations on the synthesis of epitaxially grown perovskite thin films by sol-gel technique. The epitaxial quality of BST thin films has been evaluated by fabricating eight element coupled microstrip phase shifters at NASA Glenn Research Center. Finally, future directions of sol-gel thin film research have been highlighted in view of these experimental observations.     

The effect of exercise and rehabilitation on anterior-posterior knee displacements after anterior cruciate ligament autograft reconstruction

We studied the effect of rehabilitation strength training and return to activities on anterior-posterior knee displacements after patellar tendon autogenous anterior cruciate ligament reconstruction. A total of 938 measurements were sequentially collected for 142 patients with the KT-2000 arthrometer. Rehabilitation included immediate knee motion and early weightbearing, light sports at 6 months, and competitive sports at 8 months or later. At a minimum of 2 years after surgery, 121 patients (85%) had normal displacements (less than 3 mm of increase at 134 N), 14 (10%) had 3 to 5.5 mm of increase (partial function), and 7 (5%) had more than 5.5 mm of increase (failed). There was no association found between the initial onset of the abnormal displacements in the 21 knees and either the amount of time after surgery or the rehabilitation program. Six of the seven grafts that failed did so in the 1st postoperative year. Serial displacement measurements allow early detection of graft stretching and subsequent modification of rehabilitation or delay in return to strenuous activities. These measurements showed that the rehabilitation program used in this study was not itself injurious and resulted in an acceptable failure rate of 5%.     

Comparison of the Electrical Characteristics of PZT and SBT Thin Films

The electrical properties of lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) thin films are compared for nonvolatile random access memory applications. PZT thin films have high switchable polarization with poor fatigue resistance and higher leakage current densities as compared to SBT thin films deposited on platinized silicon substrates. Characterization of these films in terms of their domain dynamics under application of sub-switchable and switchable electric fields give valuable insight about the observed differences in the electrical behavior. In the present work the dielectric behaviors of SBT and PZT thin films at sub-switchable electric field were analyzed in terms of Rayleigh law. The reversible and irreversible polarization component of switchable polarization was separated by the measurement of capacitance-voltage (C-V) and polarization hysteresis loops. The conduction mechanisms in these films were evaluated by measuring field dependence of leakage current densities at various temperatures. The observed differences in electrical properties are explained in terms of the intrinsic defects and defect-domain interaction of these two materials.     

Absence of modulating effects of cytokines on antioxidant enzymes in peritoneal mesothelial cells

Erectile dysfunction is a common (affecting 10-20 million men in the USA) and multifactorial disease due to organic and/or psychological factors that strongly impairs the quality of life in man. During the past decade many advances in the understanding of the pathophysiology of erectile dysfunction have been made and new therapeutic strategies have become available. It has been established that an insufficient production of nitric oxide by penile nerve terminals and/or vascular endothelium may result in an impaired erection or complete impotence. Nowadays, intracavernous injection of vasoactive drugs represents a standardized approach for the diagnosis, and the treatment of choice, for erectile dysfunction, but is not widely accepted by the patients. The possibility of treating erectile dysfunction with intraurethral administration of prostaglandin-E1 has recently become available in the USA, and is a therapy more acceptable to the patients. Other noninvasive medical therapies are undergoing evaluation.     

Is it possible to predict limb viability in complex Gustilo IIIB and IIIC tibial fractures? A comparison of two predictive indices

The patient with severe lower limb trauma presents a management dilemma; whether to amputate primarily or to attempt limb salvage. In recent years, many predictive indices have been published which purport to identify limbs which are non-viable. We retrospectively applied two recently described indices, the Mangled Extremity Severity Score (MESS) and the Limb Salvage Index (LSI), to 54 limbs in 50 patients with either Gustilo IIIB or IIIC complex tibial fractures. There were 22 amputations (40.7 per cent) in the series. The mean MESS score in the limb salvage group was 3.8 (range 2-10), and the mean MESS score in the amputation group was 7.7 (range 4-13) (P < 0.0001). The mean LSI score in the limb salvage group was 3.6 (range 3-8), and the mean LSI score in the amputation group was 6.9 (P < 0.01). However, in the group with MESS scores > 7 (which recommends amputation), there were three limbs which were salvaged with acceptable functional outcome. Similarly, in those with LSI scores > 6 (which recommends amputation), there were seven limbs successfully salvaged. A MESS > 7 offered a greater relative risk of amputation (9.2) than a LSI score > 6 (5.3). We found both indices of use in predicting limb salvage and functional outcome. However, neither is sufficiently accurate to be considered absolutely reliable in clinical practice.