1,362 research outputs found

    Explicit Description of HARA Forward Utilities and Their Optimal Portfolios

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    This paper deals with forward performances of HARA type. Precisely, for a market model in which stock price processes are modeled by a locally bounded dd-dimensional semimartingale, we elaborate a complete and explicit characterization for this type of forward utilities. Furthermore, the optimal portfolios for each of these forward utilities are explicitly described. Our approach is based on the minimal Hellinger martingale densities that are obtained from the important statistical concept of Hellinger process. These martingale densities were introduced recently, and appeared herein tailor-made for these forward utilities. After outlining our parametrization method for the HARA forward, we provide illustrations on discrete-time market models. Finally, we conclude our paper by pointing out a number of related open questions.Comment: 39 page

    Photoelectrochemical properties of texture-controlled nanostructured α-Fe2O3 thin films prepared by AACVD

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    This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Nanostructured α-Fe2O3 thin film electrodes were deposited by aerosol-assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α-Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current-voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 μA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C

    Electronic Tuning of Zinc Oxide by Direct Fabrication of Chromium (Cr) incorporated photoanodes for Visible-light driven Water Splitting Applications

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    This is the final version. Available on open access from Nature Research via the DOI in this recordHerein, we report the synthesis of Cr incorporated ZnO sheets arrays microstructures and construction of photoelectrode through a direct aerosol assisted chemical vapour deposition (AACVD) method. The as-prepared Cr incorporated ZnO microstructures were characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powdered X-ray spectroscopy, X-ray photoelectron spectroscopy and UV-Vis diffused reflectance spectroscopy. The Cr incorporation in ZnO red shifted the optical band gap of as-prepared photoanodes. The 15% Cr incorporation in ZnO has shown enhanced PEC performance. The AACVD method provides an efficient in situ incorporation approach for the manipulation of morphological aspects, phase purity, and band structure of photoelectrodes for an enhanced PEC performance.Higher Education Commission of PakistanUniversity of Mancheste

    Hydrophilic polymers as release modifiers for primaquine phosphate: Effect of polymeric dispersion

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    La primaquina (PQ), un compuesto sintético con actividad antimalaria fuerte, se caracteriza por tener una vida media de plasma baja, lo que requiere una administración frecuente y provoca varios efectos colaterales no deseados, con inconformidad del paciente. El objetivo del estudio actual fue diseñar una formulación de liberación prolongada que incorpora PQ en una matriz hidrofílica compuesta de HPMC, CMC de sodio y alginato de sodio. Se estudiaron también los efectos de las dispersiones poliméricas de etilcelulosa (EC) y polivinilpirrolidona (PVP). Los comprimidos se prepararon según el método de granulación húmeda. Los resultados de la respuesta de ángulo (<30) y el índice de compresibilidad (hasta el 15%) mostraron propiedades de flujo buenas. Los comprimidos se sometieron a pruebas de variación de peso, dureza, friabilidad y contenido de fármaco. La hinchazón y el perfil de liberación del fármaco se investigaron bajo condiciones de disolución. Los resultados mostraron que el índice de inflamación y la capacidad retardada de liberación son mayores con HPMC que con CMC de sodio, y que estos a su vez son mayores que con alginato de sodio, los cuales fueron más sostenidos por dispersiones poliméricas de EC y PVC. La cinética de los fármacos mostró una liberación prolongada de hasta 20 horas (F3) siguiendo una difusión no de Fick (0,45<n<0,89).Primaquine (PQ), a synthetic compound with potent antimalarial activity is characterized by low plasma half life, requiring frequent administration leading to several undesired side effects, patient incompliance. The objective of the present study was to design an extended release formulation incorporating PQ in hydrophillic matrix composed of HPMC,Sodium CMC, Sodium alginate. Effects of polymeric dispersions of ethyl cellulose (EC) and polyvinylpyrrolidone (PVP) was also studied. Tablets were prepared by wet granulation method. The results of angle of repose (<30) and compressiblity index (upto 15%) indicate good flow properties. Tablets were subjected to weight variation, hardness, friability and drug content tests. The swelling and drug release profile were investigated under dissolution condition. The result showed that the swelling index & release retarding capacity follows HPMC>Sodium CMC>Sodium alginate, which was further sustained by polymeric dispersions of EC and PVP. The kinetics of drugs showed extended release of up to 20 hrs (F3) following non fickian diffusion (0.45<n<0.89)

    Demonstration system of pumped heat energy storage (PHES) and its round-trip efficiency

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    Among the known energy storage technologies aiming to increase the efficiency and stability of power grids, Pumped Heat Energy Storage (PHES) is considered by many as a promising candidate because of its flexibility, potential for scale-up and low cost per energy storage unit. Whilst there are numerous demonstration systems under development, as it stands the only PHES demonstration system to be realised at scale is located in Hampshire, UK. This paper aims to present the results and analysis obtained from its commissioning and testing as part of an on-going study. The system was designed to offer a nominal power size of 150 kWe and energy storage capacity of 600 kWhe for an 8-hour storage cycle. This work presents evidence of the system Round-trip efficiency (RTE), which is considered as a fundamental performance metric for large-scale energy storage technologies. Recorded Pressure-Volume (P-V) measurements from recent heat pump/engine testing at part-load offers useful insight in terms of overall performance. Models are also developed to simulate the system to finally predict the performance at full-load conditions. The system and principle of operation are described first, followed by mathematical modelling outlining heat transfer mechanism and associated key losses involved in thermodynamic processes within components, and finally results are presented and compared at different operating conditions using different working gases. The results show good agreement with earlier studies, which indicate that expected electricity-to-electricity RTE is quite comparable to other mature technologies such as Pumped Hydropower Storage and Compressed Air Energy Storage. The cyclic operation of the system is also discussed. One-off storage cycle results in lower RTEs compared to a load-levelling cyclic operation where the efficiency is significantly improved due to stable packed-bed behaviour and better utilisation after an initial transient state

    Experimental study and analysis of a novel layered packed-bed for thermal energy storage applications: A proof of concept

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    This paper presents a study carried out as part of commissioning and testing of world’s first grid-scale 150 kWe Pumped Heat Energy Storage (PHES) demonstration system. The system employs two novel layered packed-bed thermal stores. The present study experimentally investigates one of the stores designated as “hot thermal store”, which has an energy storage density of 1072 MJ/m3 and stores heat at 500 °C and 12 bar. The layered store is an enhancement of a normal packed-bed store and offers a higher degree of thermal stratification. Experiments show that layering results in about 64 % reduction in pressure loss along with yielding considerably narrower thermocline. Round-trip efficiency, storage capacity and utilisation were calculated based on 1st Law analysis considering both simple and layered mode operation at nominal design conditions. Two cycle control scenarios were considered: time-based and temperature-based. In the time-based scenario, the store shows nearly similar performance in both modes. However, in temperature-based scenario, layered mode outperforms. During cyclic operation, layered mode outperforms as it reaches steady-state in merely 3rd cycle, without any loss in efficiency, capacity and utilisation; simple mode yields competitive efficiency but capacity and utilisation deteriorate after each successive cycle and steady-state is achieved in 20th cycle. 2nd Law analysis was additionally performed to gain insight into various losses and their impact on the performance

    Physician Associate and General Practitioner Consultations: A Comparative Observational Video Study.

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    BACKGROUND: Physician associates, known internationally as physician assistants, are a mid-level practitioner, well established in the United States of America but new to the United Kingdom. A small number work in primary care under the supervision of general practitioners, where they most commonly see patients requesting same day appointments for new problems. As an adjunct to larger study, we investigated the quality of the patient consultation of physician associates in comparison to that of general practitioners. METHOD: We conducted a comparative observational study using video recordings of consultations by volunteer physician associates and general practitioners with consenting patients in single surgery sessions. Recordings were assessed by experienced general practitioners, blinded to the type of the consulting practitioner, using the Leicester Assessment Package. Assessors were asked to comment on the safety of the recorded consultations and to attempt to identify the type of practitioner. Ratings were compared across practitioner type, alongside the number of presenting complaints discussed in each consultation and the number of these which were acute, minor, or regarding a chronic condition. RESULTS: We assessed 62 consultations (41 general practitioner and 21 physician associates) from five general practitioners and four physician associates. All consultations were assessed as safe; but general practitioners were rated higher than PAs in all elements of consultation. The general practitioners were more likely than physician associates to see people with multiple presenting complaints (p<0.0001) and with chronic disease related complaints (p = 0.008). Assessors correctly identified general practitioner consultations but not physician associates. The Leicester Assessment Package had limited inter-rater and intra-rater reliability. CONCLUSIONS: The physician associate consultations were with a less complex patient group. They were judged as competent and safe, although general practitioner consultations, unsurprisingly, were rated as more competent. Physician associates offer a complementary addition to the medical workforce in general practice

    Hepatic transaminase and alkaline phosphatase enzyme levels in HIV/HBV co‑infected and HIV mono‑infected patients in Maiduguri, Nigeria

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    Background: Studies have shown that HIV‑HBV co‑infected patients have an increased risk of liver‑related morbidity and mortality compared to their HIV‑mono‑infected counterparts. Furthermore, it has been reported that HIV‑HBV co‑infected patients have a significantly high incidence of drug‑induced hepatotoxicity following commencement of HAART than HIV‑mono‑infected patients.Objectives: To compare the levels of aspartate amino transferase (AST), alanine amino transferase (ALT) and alkaline phosphatase (ALKPO4) enzyme levels between HAART naïve HIV‑HBV co‑infected patients and their HIV‑mono‑infected counterparts.Materials and Methods: A cross‑sectional descriptive study in which 142 newly diagnosed HIV/HBV co‑infected and HIV mono‑infected adults were investigated for alkaline aminotransferase, aspartate aminotransferase and alkaline phosphatase enzyme levels.Results: The study subjects comprised of 80 (56.3%) females and 62 (46.7%) males. The age range of the study population was 15‑65 years. The mean ages of male and female subjects were 45.5 ± 10.5 years and 39.1 ± 7.5 years respectively (P &lt; 0.05). Sixty‑three (44.4%) study subjects were HIV/HBV co‑infected while 79 (55.6%) were HIV mono‑infected. The mean ALT enzyme level of HIV/HBV co‑infected subjects was significantly higher than that of HIV mono‑infected ones i.e., 42.12 IU/l vs. 27.86 IU/l, (P = 0.038). However, there was no statistically significant difference in the mean AST (30.14 IU/l vs. 29.09 IU/l, P = 0.893) and ALKPO4 (55.86 IU/l vs. 60.97 IU/l, P = 0.205) enzyme levels between HIV‑HBV co‑infected and HIV mono‑infected subjects albeit the two enzymes were moderately elevated in both categories of subjects.Conclusion: The significantly elevated ALT enzyme levels amongst HIV‑HBV co‑infected subjects suggest that HIV‑HBV co‑infected patients may have an increased risk of liver‑related morbidity and mortality than their HIV mono‑infected counterparts. Screening for serological markers of chronic HBV infection, as well as hepatic transaminase enzyme levels in all newly diagnosed HIV‑positive patients is therefore recommended before commencement of HAART.Keywords: Alkaline phosphatase enzyme, hepatitis B virus surface antigen, hepatic transaminase enzymes, human immunodeficiency virusNigerian Journal of Clinical Practice • Oct-Dec 2013 • Vol 16 • Issue

    Effect of Permeation Enhancers on the Release Behavior and Permeation Kinetics of Novel Tramadol Lotions

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    Purpose: The aim of this research work was to formulate, characterize and evaluate the in vitro permeation behavior of tramadol lotion containing propylene glycol (PG) and polyethylene glycol (PEG) as permeation enhancers.Methods: The permeation experiments were conducted in vitro using full thickness rabbit skin in Franz diffusion cells. The donor compartment was filled with PBS (phosphate buffered saline) at pH 7.4 ± 0.1. The receptor phase was continuously stirred PBS (pH 7.4) at 37 °C ± 0.5. The amount of tramadol permeated into the receptor phase was determined spectrophotometrically at 271 nm. Various permeation parameters such as permeation coefficient (Kp), diffusion coefficient (D), flux (J), input rate,and enhancement ratio were obtained using Fick’s diffusion laws.Results: Permeation increased with increase in the concentrations of both enhancers tested. Maximum cumulative amount permeated for control lotion (Lc) was 357 ìg/cm2/min with input rate 0.574 ìg/min and lag time (tlag) of 34.93 min, while for the optimum test lotion (L4, containing 8 % PG/PEG in ratio of 1:1 v/v), it was 926 ìg/cm2/min, 1.482 ìg/min and 58.36 min, respectively. The significantly (p &lt; 0.05) higher permeability shown by the test lotion L4 can be attributed, in part, to the interaction of PG withintercellular lipids leading to the disruption of their organization and increasing their fluidity, and also partly as a result of solubilization of lipid bilayers by PEG.Conclusion: A binary system of PG and PEG in lotion can be successfully utilized for the permeation enhancement of tramadol.Keyword: Tramadol, Transdermal delivery, Permeation, Propylene glycol, Polyethylene glycol, Rabbit skin
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