Lightweight multiple output converter development

A high frequency, multiple output power conditioner was developed and breadboarded using an eight-stage capacitor diode voltage multiplier to provide +1200 Vdc, and a three-stage for -350 Vdc. In addition, two rectifier bridges were capacitively coupled to the eight-stage multiplier to obtain 0.5 and 0.65 a dc constant current outputs referenced to +1200 Vdc. Total power was 120 watts, with an overall efficiency of 85 percent at the 80 kHz operating frequency. All outputs were regulated to three percent or better, with complete short circuit protection. The power conditioner component weight and efficiency were compared to the equivalent four outputs of the 10 kHz conditioner for the 8 cm ion engine. Weight reduction for the four outputs was 557 grams; extrapolated in the same ratio to all nine outputs, it would be 1100 to 1400 grams

Searching the ideal inhaled vasodilator: From nitric oxide to prostacyclin

Today, the technique to directly administer vasodilators via the airway to treat pulmonary hypertension and to improve pulmonary gas exchange is widely accepted among clinicians. The flood of scientific work focussing on this new therapeutic concept had been initiated by a fundamental new observation by Pepke-Zaba {[}1] and Frostell in 1991 {[}2]: Both scientists reported, that inhalation of exogenous nitric oxide (NO) gas selectively dilates pulmonary vessels without a concomittant systemic vasodilation. No more than another decade ago NO was identified as an important endogenous vasodilator {[}3] while having merely been regarded an environmental pollutant before that time. Although inhaled NO proved to be efficacious, alternatives were sought-after due to NO's potential side-effects. In search for the ideal inhaled vasodilator another group of endogenous mediators - the prostanoids - came into the focus of interest. The evidence for safety and efficacy of inhaled prostanoids is - among a lot of other valuable work - based on a series of experimental and clinical investigations that have been performed or designed at the Institute for Surgical Research under the guidance and mentorship of Prof. Dr. med. Dr. h.c. mult. K. Messmer {[}4-19]. In the following, the current and newly emerging clinical applications of inhaled prostanoids and the experimental data which they are based on, will be reviewed. Copyright (C) 2002 S. Karger AG, Basel

Improved ventricular function during inhalation of PGI(2) aerosol partly relies on enhanced myocardial contractility

Inhaled prostacyclin (PGI(2)) aerosol induces selective pulmonary vasodilation. Further, it improves right ventricular ( RV) function, which may largely rely on pulmonary vasodilation, but also on enhanced myocardial contractility. We investigated the effects of the inhaled PGI(2) analogs epoprostenol (EPO) and iloprost (ILO) on RV function and myocardial contractility in 9 anesthetized pigs receiving aerosolized EPO (25 and 50 ng center dot kg(-1) center dot min(-1)) and, consecutively, ILO (60 ng center dot kg(-1) center dot min(-1)) for 20 min each. We measured pulmonary artery pressure ( PAP), RV ejection fraction (RVEF) and RV end-diastolic-volume (RV-EDV), and left ventricular end-systolic pressure-volume-relation (end-systolic elastance, E-es). EPO and ILO reduced PAP, increased RVEF and reduced RVEDV. E-es was enhanced during all doses tested, which reached statistical significance during EPO25ng and ILO, but not during EPO50ng. PGI(2) aerosol enhances myocardial contractility in healthy pigs, contributing to improve RV function. Copyright (C) 2005 S. Karger AG, Basel

Serum heparan sulfate levels are elevated in endotoxemia

<p>Abstract</p> <p>Background</p> <p>Increased vascular permeability is a characteristic feature of sepsis which, in the past, has been ascribed exclusively to a malfunction of endothelial cells. However, recently it has become evident that the endothelial glycocalyx is of considerable importance concerning various aspects of vascular physiology, e.g. the vascular barrier and inflammation. Heparan sulfate, one of its essential components is characteristically traceable in blood, in case the endothelial glycocalyx is damaged or destroyed.</p> <p>Methods</p> <p>In 15 pigs we investigated whether the administration of endotoxin from gram-negative bacteria (Escherichia coli) results in increased serum levels of heparan sulfate, signalizing a shedding of the glycocalyx. In addition, markers of inflammation (white blood cell count, platelet count, tumour necrosis factor-α and interleukin-6) were evaluated over an observation period of 6 hours.</p> <p>Results</p> <p>Serum heparan sulfate concentrations significantly increased over time in the endotoxin group and were significantly elevated in comparison to the control group 6 hours after administration of endotoxin (p < 0.001). In the endotoxin group all markers of inflammation significantly changed during the time course.</p> <p>Conclusions</p> <p>The administration of bacterial endotoxin induced a significant rise in degradation products of the endothelial glycocalyx.</p

Significance of K-Ar dating of very low-grade metamorphism in Triassic-Jurassic pelites from the Coastal Range of central Chile

El artículo original ha sido publicado por la Mineralogical Society disponible en: http://www.minersoc.org/pages/e_journals/clay.htmlK-Ar isotopic dating of very low-grade metamorphism affecting Triassic-Jurassic rocks in the Coastal Range of central Chile was carried out on whole rocks and their <2 mm size fractions. In the study area, a regional-burial low-grade metamorphism at anchizone conditions (T ≤ 190ºC) and low-pressure conditions (P ≥1.3 kbar) has been described. Observed temperatures are related to a contact metamorphism produced by nearby Jurassic intrusions, with a P-T estimate at the immediate contact zone of ~650-690ºC and 4 kbar. The whole-rock K-Ar age of 174?5 Ma is interpreted as belonging to the contact metamorphism due to the intrusion of Jurassic plutons (165±5 Ma to 175±5 Ma). A time-interval of ~20 Ma between the diagenesis (206 Ma) and the anchizonal very low-grade metamorphism (181-184 Ma) is obtained, and a rate of subsidence of ~120 m/Ma is proposed for these Triassic-Jurassic basins. A thermal influence on the burial, very low-grade, regional metamorphism is invoked.Departamento de Mineralogía y Petrologí

2023 roadmap on photocatalytic water splitting

As a consequence of the issues resulting from global climate change many nations are starting to transition to being low or net zero carbon economies. To achieve this objective practical alternative fuels are urgently required and hydrogen gas is deemed one of the most desirable substitute fuels to traditional hydrocarbons. A significant challenge, however, is obtaining hydrogen from sources with low or zero carbon footprint i.e. so called ‘green’ hydrogen. Consequently, there are a number of strands of research into processes that are practical techniques for the production of this ‘green’ hydrogen. Over the past five decades there has been a significant body of research into photocatalytic (PC)/photoelectrocatalytic processes for hydrogen production through water splitting or water reduction. There have, however been significant issues faced in terms of the practical capability of this promising technology to produce hydrogen at scale. This road map article explores a range of issues related to both PC and photoelectrocatalytic hydrogen generation ranging from basic processes, materials science through to reactor engineering and applications for biomass reforming

Ion-exchanged geopolymer for photocatalytic degradation of a volatile organic compound

In thepresentworkitisshownhowgeopolymerscanbeusedtocontrolindoorandoutdoorair pollution byphotolysisof2-ButanoneasaVolatileOrganicCompound(VOC).Anionexchange procedurewasfollowedtoincorporateTiO2 into ageopolymer(IEG),anddifferent2-Butanone concentrations wereusedinabatchreactorunderdryandhumidconditions.Variationon 2-Butanone concentrationwasfollowedbygaschromatography.ALangmuir Hinshelwood modelwas used todeterminethedisappearancerateofreactantattheinitialstageofthereaction.Gasca-Tirado, J.; Manzano-Ramirez, A.; Vazquez-Landaverde, PA.; Herrera-Diaz, EI.; Rodriguez-Ugarte, ME.; Rubio-Avalos, JC.; Amigó Borrás, V.... (2014). Ion-exchanged geopolymer for photocatalytic degradation of a volatile organic compound. Materials Letters. 134:222-224. doi:10.1016/j.matlet.2014.07.090S22222413

A transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence, North Wales, UK

High-resolution transmission electron microscopy (HRTEM) measurements of the thickness of white mica crystallites were made on three pelite samples that represented a prograde transition from diagenetic mudstone though anchizonal slate to epizonal slate. Crystallite thickness, measured normal to (001), increases as grade increases, whereas the XRD measured 10 Å peak-profile, the Kubler index, decreases. The mode of the TEM-measured size population can be correlated with the effective crystallite size N (001) determined by XRD. The results indicate that the Kubler index of white mica crystallinity measures changes in the crystallite size population that result from prograde increases in the size of coherent X-ray scattering domains. These changes conform to the Scherrer relationship between XRD peak broadening and small crystallite size. Lattice ‘strain’ broadening is relatively unimportant, and is confined to white mica populations in the diagenetic mudstone. Rapid increases in crystallite size occur in the anchizone, coincident with cleavage development. Changes in the distribution of crystallite thickness with advancing grade and cleavage development are characteristic of grain-growth by Ostwald ripening. The Kubler index rapidly loses sensitivity as an indicator of metapelitic grade within the epizone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47293/1/410_2004_Article_BF00306406.pd

Towards Visible Light Hydrogen Generation: Quantum Dot-Sensitization via Efficient Light Harvesting of Hybrid-TiO2

We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of similar to 16.2 mA/cm(2), which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of similar to 14.2 mA/cm(2), the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems.open3

Synthesis of iron-doped TiO2 nanoparticles by ball-milling process : the influence of process parameters on the structural, optical, magnetic, and photocatalytic properties

Titanium dioxide (TiO2) absorbs only a small fraction of incoming sunlight in the visible region thus limiting its photocatalytic efficiency and concomitant photocatalytic ability. The large-scale application of TiO2 nanoparticles has been limited due to the need of using an ultraviolet excitation source to achieve high photocatalytic activity. The inclusion of foreign chemical elements in the TiO2 lattice can tune its band gap resulting in an absorption edge red-shifted to lower energies enhancing the photocatalytic performance in the visible region of the electromagnetic spectrum. In this research work, TiO2 nanoparticles were doped with iron powder in a planetary ball-milling system using stainless steel balls. The correlation between milling rotation speeds with structural and morphologic characteristics, optical and magnetic properties, and photocatalytic abilities of bare and Fedoped TiO2 powders was studied and discussed.This work was partially financed by FCT-Fundacao para a Ciencia e Tecnologia-under the project PTDC/FIS/120412/2010: "Nanobased concepts for Innovative & Eco-sustainable constructive material's surfaces.