Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy

We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics

Global distribution of two fungal pathogens threatening endangered sea turtles

This work was supported by grants of Ministerio de Ciencia e Innovación, Spain (CGL2009-10032, CGL2012-32934). J.M.S.R was supported by PhD fellowship of the CSIC (JAEPre 0901804). The Natural Environment Research Council and the Biotechnology and Biological Sciences Research Council supported P.V.W. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Thanks Machalilla National Park in Ecuador, Pacuare Nature Reserve in Costa Rica, Foundations Natura 2000 in Cape Verde and Equilibrio Azul in Ecuador, Dr. Jesus Muñoz, Dr. Ian Bell, Dr. Juan Patiño for help and technical support during samplingPeer reviewedPublisher PD

The nitridation of ZnO nanowires

ZnO nanowires (NWs) with diameters of 50 to 250 nm and lengths of several micrometres have been grown by reactive vapour transport via the reaction of Zn with oxygen on 1 nm Au/Si(001) at 550°C under an inert flow of Ar. These exhibited clear peaks in the X-ray diffraction corresponding to the hexagonal wurtzite crystal structure of ZnO and a photoluminescence spectrum with a peak at 3.3 eV corresponding to band edge emission close to 3.2 eV determined from the abrupt onset in the absorption-transmission through ZnO NWs grown on 0.5 nm Au/quartz. We find that the post growth nitridation of ZnO NWs under a steady flow of NH3 at temperatures ≤600°C promotes the formation of a ZnO/Zn3N2 core-shell structure as suggested by the suppression of the peaks related to ZnO and the emergence of new ones corresponding to the cubic crystal structure of Zn3N2 while maintaining their integrity. Higher temperatures lead to the complete elimination of the ZnO NWs. We discuss the effect of nitridation time, flow of NH3, ramp rate and hydrogen on the conversion and propose a mechanism for the nitridation

Human physiologically based pharmacokinetic model for propofol

BACKGROUND: Propofol is widely used for both short-term anesthesia and long-term sedation. It has unusual pharmacokinetics because of its high lipid solubility. The standard approach to describing the pharmacokinetics is by a multi-compartmental model. This paper presents the first detailed human physiologically based pharmacokinetic (PBPK) model for propofol. METHODS: PKQuest, a freely distributed software routine , was used for all the calculations. The "standard human" PBPK parameters developed in previous applications is used. It is assumed that the blood and tissue binding is determined by simple partition into the tissue lipid, which is characterized by two previously determined set of parameters: 1) the value of the propofol oil/water partition coefficient; 2) the lipid fraction in the blood and tissues. The model was fit to the individual experimental data of Schnider et. al., Anesthesiology, 1998; 88:1170 in which an initial bolus dose was followed 60 minutes later by a one hour constant infusion. RESULTS: The PBPK model provides a good description of the experimental data over a large range of input dosage, subject age and fat fraction. Only one adjustable parameter (the liver clearance) is required to describe the constant infusion phase for each individual subject. In order to fit the bolus injection phase, for 10 or the 24 subjects it was necessary to assume that a fraction of the bolus dose was sequestered and then slowly released from the lungs (characterized by two additional parameters). The average weighted residual error (WRE) of the PBPK model fit to the both the bolus and infusion phases was 15%; similar to the WRE for just the constant infusion phase obtained by Schnider et. al. using a 6-parameter NONMEM compartmental model. CONCLUSION: A PBPK model using standard human parameters and a simple description of tissue binding provides a good description of human propofol kinetics. The major advantage of a PBPK model is that it can be used to predict the changes in kinetics produced by variations in physiological parameters. As one example, the model simulation of the changes in pharmacokinetics for morbidly obese subjects is discussed

Physiologically based pharmacokinetic modeling of arterial – antecubital vein concentration difference

BACKGROUND: Modeling of pharmacokinetic parameters and pharmacodynamic actions requires knowledge of the arterial blood concentration. In most cases, experimental measurements are only available for a peripheral vein (usually antecubital) whose concentration may differ significantly from both arterial and central vein concentration. METHODS: A physiologically based pharmacokinetic (PBPK) model for the tissues drained by the antecubital vein (referred to as "arm") is developed. It is assumed that the "arm" is composed of tissues with identical properties (partition coefficient, blood flow/gm) as the whole body tissues plus a new "tissue" representing skin arteriovenous shunts. The antecubital vein concentration depends on the following parameters: the fraction of "arm" blood flow contributed by muscle, skin, adipose, connective tissue and arteriovenous shunts, and the flow per gram of the arteriovenous shunt. The value of these parameters was investigated using simultaneous experimental measurements of arterial and antecubital concentrations for eight solutes: ethanol, thiopental, (99)Tc(m)-diethylene triamine pentaacetate (DTPA), ketamine, D(2)O, acetone, methylene chloride and toluene. A new procedure is described that can be used to determine the arterial concentration for an arbitrary solute by deconvolution of the antecubital concentration. These procedures are implemented in PKQuest, a general PBPK program that is freely distributed . RESULTS: One set of "standard arm" parameters provides an adequate description of the arterial/antecubital vein concentration for ethanol, DTPA, thiopental and ketamine. A significantly different set of "arm" parameters was required to describe the data for D(2)O, acetone, methylene chloride and toluene – probably because the "arm" is in a different physiological state. CONCLUSIONS: Using the set of "standard arm" parameters, the antecubital vein concentration can be used to determine the whole body PBPK model parameters for an arbitrary solute without any additional adjustable parameters. Also, the antecubital vein concentration can be used to estimate the arterial concentration for an arbitrary input for solutes for which no arterial concentration data is available

Wing pathology of white-nose syndrome in bats suggests life-threatening disruption of physiology

White-nose syndrome (WNS) is causing unprecedented declines in several species of North American bats. The characteristic lesions of WNS are caused by the fungus Geomyces destructans, which erodes and replaces the living skin of bats while they hibernate. It is unknown how this infection kills the bats. We review here the unique physiological importance of wings to hibernating bats in relation to the damage caused by G. destructans and propose that mortality is caused by catastrophic disruption of wing-dependent physiological functions. Mechanisms of disease associated with G. destructans seem specific to hibernating bats and are most analogous to disease caused by chytrid fungus in amphibians