Histomorphometry of the optic nerves of normal dogs and dogs with hereditary glaucoma

The beagle dog with hereditary primary open-angle glaucoma, unlike other animal models of human glaucoma, possesses a slowly progressive, sustained elevation of intraocular pressure. The effects of this insidious elevation in intraocular pressure on the axons of the optic nerves of three beagles at early stages of glaucoma and two beagles with advanced signs of glaucoma were compared to the optic nerves of four age-matched normal dogs. Plastic embedded optic nerve cross-sections (1 micron) 1 mm posterior to the lamina cribrosa were osmicated and stained with Toluidine Blue. Axons from 0.2 to > 2.0 microns in diameter were counted and measured in 16 cross-sectional regions of equal size within the whole optic nerve using a computerized image analysis system. The mean optic nerve axon diameters in the normal, early glaucomatous, and advanced glaucomatous dogs were 1.53, 1.25 and 1.13 microns respectively. The average total optic nerve axon count in the normal dogs was 148,303. Approximately 16% of the total axonal fibers were counted in each nerve. The counts of optic nerve axons 2.0 microns or greater in diameter were reduced by up to 60% in the central regions of the optic nerves of affected beagles. The large diameter axons of the peripheral optic nerve of the beagle dogs with glaucoma were more resistant to the elevated intraocular pressure. The counts of axons > 0.6 to 0.8 micron in diameter were significantly increased in glaucomatous beagles.     

Band-filling in InP dots: Single dot spectroscopy and carrier dynamics

We have measured band-filling in InP dots inbetween GaInP barriers. We find that band-filling occurs at very low optical power densities. About 200 times less optical power density is required for the InP dots, compared with quantum wells, for the same amount of band-filling. We have measured photon emission from single dots and also here we find band-filling. The time-evolution of the emission has been followed and also been modelled using a simple model. Good agreement between theory and experiment is found. The capture time into the dots is around 3 ns and the decay time constant is about 1 ns.     

Conformational analysis of the conducting copolymer poly(3,4-ethylenedioxythiophene-co-pyrrole)

Electronic structure methods have been used to investigate conducting copolymers of 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py). The calculations show the planar anti conformation and the syn conformers have extended conjugation. In the anti conformation the EDOT–Py dimer is calculated to have a lower reorganization energy (0.390 eV) than either homodimer (0.423 eV EDOT; 0.455 eV Py) and consequently is expected to have higher charge carrier mobility. The HOMO–LUMO gap of the copolymers is intermediate between the two homopolymers and for regular sequences varies monotonically as a function of the monomer content.     

Xanthine oxidase mediates myocardial injury after hepatoenteric ischemia-reperfusion

OBJECTIVES: To determine if myocardial injury results from hepatoenteric ischemia-reperfusion. We also proposed to determine if this remote heart injury is mediated by a xanthine oxidase-dependent mechanism. DESIGN: Randomized, controlled animal study. SETTING: University-based animal research facility. SUBJECTS: Thirty-six New Zealand white male rabbits, weighing 1.8 to 3 kg. INTERVENTIONS: Anesthetized rabbits were randomly assigned to one of four groups (n = 9 per group): a) a sham-operated group; b) a sham-operated group pretreated with sodium tungstate (xanthine oxidase inactivator); c) an aorta occlusion group; and d) an aorta occlusion group pretreated with sodium tungstate. Descending thoracic aorta occlusion was maintained for 40 mins with a 4-Fr Fogarty embolectomy catheter, followed by 2 hrs of reperfusion. MEASUREMENTS AND MAIN RESULTS: Myocardial injury, manifested by increased circulating creatine kinase-MB fraction activity, was significantly associated with aortic occlusion and reperfusion (p < .05). Sodium tungstate pretreatment significantly (p < .05) reduced circulating and myocardial xanthine oxidase activity. Xanthine oxidase inactivation by sodium tungstate significantly decreased circulating creatine kinase-MB fraction activity after hepatoenteric ischemia-reperfusion (p < .05). Finally, circulating creatine kinase-MB fraction activity was significantly associated with circulating xanthine oxidase activity (r2 = .85; p < .001). CONCLUSIONS: We conclude that remote myocardial injury is caused by hepatoenteric ischemia-reperfusion. The pathoetiology of this myocardial injury involves a xanthine oxidase-dependent mechanism.     

Automatic ergonomic work analysis

To reduce occupational-related diseases, injuries and impairments to the musculo-skeletal systems, an ergonomics analysis of the work process is necessary. The authors describe a project to develop an automatic ergonomic work analysis method using existing and developed models of work stress factors. It was designed to record the work accurately without disrupting activities, and describe the situation so that production engineers and designers can be supplied with basic information for ameliorative measures. The system determines such parameters as the position and movement of 14 parts of the body, and such measurements as force exerted, range of movement and static stress. A pilot study with a prototype of the system has been completed and tested with simple work sequences.     

Improved subthreshold slope in an InAs nanowire heterostructure field-effect transistor

An n-type InAs/InAsP heterostructure nanowire field-effect transistor has been fabricated and compared with a homogeneous InAs field-effect transistor. For the same device geometry, by introduction of the heterostructure, the threshold voltage is shifted 4 V, the maximum current on-off ratio is enhanced by a factor of 10,000, and the subthreshold swing is lowered by a factor 4 compared to the homogeneous transistor. At the same time, the drive current remains constant for a fixed gate overdrive. A single nanowire heterostructure transistor has a transconductance of 5 muA/V at a low source-drain voltage of 0.3 V. For the homogeneous InAs transistor, we deduced a high electron mobility of 1500 cm2/Vs.     

InAs1-xPx nanowires for device engineering

We present the growth of homogeneous InAs(1-x)P(x) nanowires as well as InAs(1-x)P(x) heterostructure segments in InAs nanowires with P concentrations varying from 22% to 100%. The incorporation of P has been studied as a function of TBP/TBAs ratio, temperature, and diameter of the wires. The crystal structure of the InAs as well as the InAs(1-x)P(x) segments were found to be wurtzite as determined from high-resolution transmission electron microscopy. Furthermore, temperature-dependent electrical transport measurements were performed on individual heterostructured wires to extract the conduction band offset of InAs(1-x)P(x) relative to InAs as a function of composition. From these measurements we extract a value of the linear coefficient of the conduction band versus x of 0.6 eV and a nonlinear coefficient, or bowing parameter, of 0.2 eV. Finally, homogeneous InAs(0.8)P(0.2) nanowires were shown to have a nondegenerate n-type doping and function as field-effect transistors at room temperature.     

Colorful InAs nanowire arrays: from strong to weak absorption with geometrical tuning

One-dimensional nanostructure arrays can show fascinatingly different, tunable optical response compared to bulk systems. Here we study theoretically and demonstrate experimentally how to engineer the reflection and absorption of light in epitaxially grown vertical arrays of InAs nanowires (NWs). A striking observation is optically visible colors of the array, which we show can be tuned depending on the geometrical parameters of the array. Specifically, larger diameter NW arrays absorb light more effectively out to a longer wavelength compared to smaller diameter arrays. Thus, controlling the diameter provides a way to tune the optically observable color of an array. We also find that arrays with a larger amount of InAs material reflect less light (or absorb more light) than arrays with less material. On the basis of these two trends, InAs NW arrays can be designed to absorb light either much more or much less efficiently than a thin film of an effective medium containing the same amount of InAs as the NW array. The tunable absorption and low area filling factor of the NW arrays compared to thin film bode well for III-V photovoltaics and photodetection.