Effect of Dexmedetomidine on Cerebral Vasospasm and Associated Biomarkers in a Rat Subarachnoid Hemorrhage Model.

BACKGROUND: The α2 adrenergic agonist dexmedetomidine (DEX) has huge potential for protecting against cerebral vasospasm, a leading cause of death and disability after subarachnoid hemorrhage (SAH). Biomarker assays for SAH have recently emerged as tools for predicting vasospasm and outcomes. We investigated the effects of DEX on vasospasm and assessed relevant biomarkers in a rat SAH model. METHODS: Male Wistar rats were randomly assigned to sham (n=10), vehicle (n=10), SAH (n=10), or SAH+ DEX (n=10) groups. The SAH and SAH+DEX groups received 0.3 mL injections of autologous blood into the cisterna magna, followed by intraperitoneal injections of normal saline or 10 µg/kg DEX. Forty-eight hours later, neurological deficits as well as the basilar artery (BA) wall thickness and cross-sectional area were measured. Cerebrospinal fluid (CSF) and blood samples were obtained to assess concentrations of interleukin (IL)-6, C-reactive protein (CRP), endothelin-1, and S100-ß using enzyme-linked immunosorbent assays. RESULTS: The SAH and SAH+DEX groups exhibited deteriorated neurological function as well as structural and morphological BA vasospasm. The SAH+DEX group showed an improved neurological function score (ie, a 52% decrease), a 10% reduction in wall thickness, and a BA cross-sectional area enlarged by 157%. Compared with the sham group, CSF levels of IL-6 and CRP in the SAH and SAH+DEX groups, as well as serum IL-6 and CRP levels in the SAH group, were significantly elevated. The SAH+DEX group showed significantly lower CSF IL-6 levels than the SAH group. Serum and CSF levels of endothelin-1 and S100-ß were similar across all groups. CONCLUSIONS: DEX administration reduced the severity of cerebral vasospasm and improved neurological function in SAH rats; this may be closely linked to reduced CSF IL-6 levels.

Impact of Al Pre-Deposition Layer on Crystalline Quality of GaN Grown on Si(111) Substrates.

The effects of Al metal pre-deposition under different conditions on GaN grown on Si(111) substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated. Al pre-deposition improves surface morphology and crystal quality of GaN grown on Si. The surface morphology of Al pre-deposition layer, AlN, and GaN vary depending on Al pre-deposition temperature. With the increase of Al pre-deposition temperature, Al cluster size is observed to increase in the Al predeposition layer due to increased lateral mobility of Al atoms. The Al pre-deposition carried out at about 750 °C enables to grow pit-free GaN layer on Si(111) substrate.

Urine Output During Cardiopulmonary Bypass Predicts Acute Kidney Injury After Cardiac Surgery: A Single-Center Retrospective Analysis.

Urine output is closely associated with renal function and has been used as a diagnostic criterion for acute kidney injury (AKI). However, urine output during cardiopulmonary bypass (CPB) has never been identified as a predictor of postoperative AKI. Considering altered renal homeostasis during CPB, we made a comprehensible approach to CPB urine output and evaluated its predictability for AKI.Patients undergoing cardiovascular surgery with the use of CPB, between January 2009 and December 2011, were retrospectively reviewed. AKI was defined as an increase in serum creatinine ≥0.3 mg/dL in the first postoperative 48 hours. We extrapolated a possible optimal amount of urine output from the plot of probability of AKI development according to CPB urine output. After separating patients by the predicted optimal value, we performed stepwise logistic regression analyses to find potential predictors of AKI in both subgroups.A total of 696 patients were analyzed. The amount of CPB urine output had a biphasic association with the incidence of AKI using 4 mL/kg/h as a boundary value. In a multivariate logistic regression to find predictors for AKI in entire patients, CPB urine output did not show statistical significance. After separating patients into subgroups with CPB urine output below and over 4 mL/kg/h, it was identified as an independent predictor for AKI with the odds ratio of 0.43 (confidence interval 0.30-0.61) and 1.11 (confidence interval 1.02-1.20), respectively.The amount of urine output during CPB with careful analysis may serve as a simple and feasible method to predict the development of AKI after cardiac surgery at an early time point.

Enhanced optical output performance in InGaN/GaN light-emitting diode embedded with SiO2nanoparticles.

We demonstrated the InGaN/GaN-based light-emitting diodes (LEDs) with SiO2 nanoparticles embedded in nanopillar GaN template. With the SiO2 nanoparticles placed between the GaN nanopillars, subsequent overgrowth of GaN layer started only on the exposed tips of the nanopillars and rapidly switched to the lateral growth mode. This resulted in a high quality GaN layer "sitting" on the nanopillars and the layer of pores formed over the SiO2 nanoparticles. For multi-quantum-well LEDs grown on top of such template, ~3 fold increase in optical output was observed compared to reference samples. The effect is attributed mainly to the improved light extraction efficiency due to additional scattering in the nanopillars-SiO2-pores portion of the structure, also to the increased internal quantum efficiency caused by a decreased dislocation density and relaxed strain due to the GaN nanopillars.

Facile fabrication of free-standing light emitting diode by combination of wet chemical etchings.

Free-standing GaN light-emitting diode (LED) structure with high crystalline quality was fabricated by combining electrochemical and photoelectrochemical etching followed by regrowth of LED structure and subsequent mechanical detachment from a substrate. The structural quality and composition of the regrown LED film thus produced was similar to standard LED, but the photoluminescence and electroluminescence intensity of the LED structures on the etched template were several times higher than for standard LED. The performance enhancement was attributable to additional light scattering and improved crystalline quality as a result of the combined etching scheme.

Improved photoluminescence efficiency in UV nanopillar light emitting diode structures by recovery of dry etching damage.

In this study, we have fabricated 375-nm-wavelength InGaN/AlInGaN nanopillar light emitting diodes (LED) structures on c-plane sapphire. A uniform and highly vertical nanopillar structure was fabricated using self-organized Ni/SiO2 nano-size mask by dry etching method. To minimize the dry etching damage, the samples were subjected to high temperature annealing with subsequent chemical passivation in KOH solution. Prior to annealing and passivation the UV nanopillar LEDs showed the photoluminescence (PL) efficiency about 2.5 times higher than conventional UV LED structures which is attributed to better light extraction efficiency and possibly some improvement of internal quantum efficiency due to partially relieved strain. Annealing alone further increased the PL efficiency by about 4.5 times compared to the conventional UV LEDs, while KOH passivation led to the overall PL efficiency improvement by more than 7 times. Combined results of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) suggest that annealing decreases the number of lattice defects and relieves the strain in the surface region of the nanopillars whereas KOH treatment removes the surface oxide from nanopillar surface.

Enhanced light output of InGaN/GaN blue light emitting diodes with Ag nano-particles embedded in nano-needle layer.

2.7 times increase in room temperature photoluminescence (PL) intensity and 3.2 times increase in electroluminescence (EL) intensity were observed in blue multi-quantum-well (MQW) GaN/InGaN light emitting diodes (LEDs) as a result of introduction of nano-needle structure embedded with Ag nanoparticles (NPs) into n-GaN film underlying the active MQW region and thick p-GaN contact layer of LEDs. The nano-needle structure was produced by photoelectrochemical etching. Simultaneously a measurable decrease in room temperature decay time from 2.2 ns in control samples to 1.6 ns in PL was observed. The results are explained by strong coupling of recombination in GaN/InGaN MQWs with Ag NPs related localized surface plasmons.

Localized surface plasmon enhanced quantum efficiency of InGaN/GaN quantum wells by Ag/SiO2 nanoparticles.

Optical properties of InGaN/GaN multi-quantum-well (MQW) structures with a nanolayer of Ag/SiO2 nanoparticle (NP) on top were studied. Modeling and optical absorption (OA) measurements prove that the NPs form localized surface plasmons (LSP) structure with a broad OA band peaked near 440-460 nm and the fringe electric field extending down to about 10 nm into the GaN layer. The presence of this NP LSP electrical field increases the photoluminescence (PL) intensity of the MQW structure by about 70% and markedly decreases the time-resolved PL (TRPL) relaxation time due to the strong coupling of MQW emission to the LSP mode.

Multi-wavelength emitting InGan/GaN quantum well grown on V-shaped gan(1101) microfacet.

InGaN/GaN multiple quantum wells (MQWs) were successfully grown on the inclined GaN(1101) microfacets. Conventional photolithography and subsequent growth of GaN were employed to generate the V-shaped microfacets along (1120) direction. The well-developed microfacets observed by scanning electron microscopy and the clear transmission electron microscope interfacial images indicated that the MQW was successfully grown on the GaN microfacets. Interestingly, cathodoluminescence (CL) spectra measured on the microfacets showed a continuous change in the luminescence peak positions. The CL peaks were shifted to a longer wavelength from 420 nm to 440 nm as the probing points were changed along upward direction. This could be attributed to the nonuniform distribution of the In composition and/or the wavefunction overlapping between adjacent wells. Present works thus propose a novel route to fabricate a monolithic white light emitting diode without phosphors by growing the InGaN/GaN MQWs on (1101) facet.

Formation of conjugated linoleic acids in soybean oil during hydrogenation with a nickel catalyst as affected by sulfur addition.

The effects of sulfur addition on the formation of conjugated linoleic acid (CLA) isomers were studied during the hydrogenation of soybean oil with a nonselective type nickel catalyst. Sulfur addition greatly promoted CLA formation in soybean oil during hydrogenation. As the amount of sulfur increased to a certain level, the maximal quantity of CLA in soybean oil during hydrogenation increased greatly. However, further increase in sulfur addition above the certain level decreased CLA formation. The optimal sulfur level for the promotion of CLA formation differed greatly with the amount of nickel used. It was of great interest to find that the optimal ratio of sulfur to nickel for the promotion of CLA formation was always 0.06:1, regardless of the nickel amount used. At the same ratio of sulfur to nickel, higher nickel content induced significantly higher production of CLA (p < 0.05). At the optimal sulfur to nickel ratio, an increase in the nickel amount from 0.05 to 0.15% produced approximately 1.5 times higher levels of CLA during hydrogenation under the tested conditions. The CLA isomer compositions were greatly affected by both sulfur addition and amounts of nickel used for treatment. This is the first report of the possibility that the total quantity of CLA and their isomer composition could be manipulated during hydrogenation by controlling the amounts of sulfur and nickel.