Investigation of the lead-free double perovskites Cs2AgSbX6 (X= Cl, Br, I) for optoelectronic and thermoelectric applications

Perovskite compounds have the potential to harvest solar energy as well as exploit the thermoelectric potential of a number of available materials. Here, we present the electronic, structural, thermoelectric, and optical properties of Cs2AgSbX6 (X = Cl, Br, I) perovskite with the help of the density functional theory (DFT). The WC-GGA approximation was used to calculate the structural parameters. All these compounds crystalize in a cubic unit cell with lattice constant increasing from 10.65 {\AA} (Cl) to 11.14 {\AA} (Br) to 11.86 {\AA} (I). The mBJ-functional shows a semiconducting nature for these compounds with an indirect band gap lying at the L-X symmetry points. The optical conductivity and absorption coefficient show their peaks in the ultraviolet region, moving towards a lower energy range by inserting large size anion. The band gap of these compounds (2.08, 1.37, 0.64 eV) indicates their potential in single and multijunction solar cells. The value of refractive index at zero energy was evaluated to be 3.1, 2.2, and 1.97 for Cs2AgSbCl6, Cs2AgSbBr6 and Cs2AgSbI6. Effective mass of electrons is smaller than those of holes resulting in higher carrier mobility for electrons. The Seebeck coefficient, power factor, and the figure of merit were computed using the BoltzTrap code. The negative temperature coefficient of resistivity also supports the semiconductor nature of these compounds. The high electrical, small thermal conductivity, positive Seebeck coefficient, and the optimum figure of merit make these compounds suitable for thermoelectric applications.Comment: 11 pages, seven figures. arXiv admin note: text overlap with arXiv:2008.0512

Microencapsulation of Diclofenac Sodium by Nonsolvent Addition Technique

Purpose: To prepare, using non-solvent addition technique, diclofenac sodium-ethylcellulose microparticles with modified drug release properties.Methods: Microparticles were prepared by non-solvent addition phase separation method and characterized by micromeritics, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), dissolution test and thermal analysis.Results: The microparticles were whitish, irregular, aggregated, and in the size range of 390 - 442 μm size. Drug embedment efficiency was 89 - 91 %. Characterisation studies indicate that there was no strong chemical interaction between the drug and the polymer in the microparticles. Polymer concentration and sustained release behavior were directly proportional.Conclusion: Non-solvent addition phase separation is a suitable method for preparing diclofenac sodium-ethylcellulose multi-unit controlled release drug delivery system.Keywords: Phase separation, Diclofenac sodium, Ethylcellulose, Non-solvent addition, Characterisation

Gold Nanoparticles: Synthesis and Applications in Drug Delivery

This review is focused essentially on the synthesis and applications of gold nanoparticles in the field of medicine and targeted drug delivery. Nanotechnology has become one of the most interesting and advanced areas of research in this field. Among nanoparticles, gold nanoparticles demonstrate special advantages in this field due to their unique properties, small size and high surface area-to-volume ratio. These particles have been widely used in various biomedical applications and drug delivery systems due to their inert nature, stability, high dispersity, non-cytotoxicity and biocompatibility.Keywords: Biosynthesis, Gold nanoparticles, Biomedical applications, Targeted drug delivery,Nanotechnology

Transcranial direct current stimulation and stroke recovery: opportunities and challenges

Transcranial direct current stimulation (tDCS) is one type of neuromodulation, which is an emerging technology that holds promise for the future studies on therapeutic and diagnosis applications in treatment of neurological and psychiatric diseases. However, there is a serious question among developing countries with limited financial and human resources, about the potential returns of an investment in this field and regarding the best time to transfer this technology from controlled experimental settings to health systems in the public and private sectors. This article reviews the tDCS as tools of neuromodulation for stroke and discusses the opportunities and challenges available for clinicians and researchers interested in advancing neuromodulation therapy. The aim of this review is to highlight the usefulness of tDCS and to generate an interest that will lead to appropriate studies that assess the true clinical value of tDCS for brain diseases in developing countries. Methods: Literature review was done on PubMed from 2016 on neuromodulation in under-developed countries (UDCs) by non-invasive brain stimulation methods, using the key words “stroke”, “rehabilitation”, and “tDCS”. Results: We first identified articles and websites, of which were further selected for extensive analysis mainly based on clinical relevance, study quality and reliability, and date of publication. Conclusion: Despite the promising results obtained with tDCS in basic and clinical neuroscience, further progress has been impeded by a lack of clarity to use in mostly UDCs

Pharmacokinetic Study of Nifedipine in Healthy Adult Male Human Volunteers

Purpose: To evaluate the pharmacokinetics of nifedipine in healthy adult Pakistani subjects. Methods: Each of six fasting volunteers received 20 mg nifedipine (2 x Adalat® 10 mg capsules) orally once and then another one week later. Their blood samples were obtained at regular time intervals and analysed by HPLC. Using the non-compartmental approach, plasma levels of nifedipine were employed to compute their individual disposition kinetics, including Cmax (maximum plasma concentration), Tmax(time to reach maximum plasma concentration), MRT (mean residence time), AUC0-∞ (area under curve), AUMC0-∞ (area under first moment curve) and Ka (absorption rate constant). Results: The suggested therapeutic level of nifedipine for the treatment of hypertension (15-35 ng.mL-1) was achieved in all six volunteers within 0.25 h after dose administration, and maintained for more than 6 h. Tmax was 1.58 h and Cmax varied from 140 – 300 ng.mL-1. Mean absorption rate constant was 2.22 h-1 while mean absorption half-life was 0.43 h. The mean elimination rate constant was 0.16 h-1 while 5.7 h was recorded for terminal half-life. AUC0-¥, AUMC0-¥ and MRT were 1879.86 ng.h.mL-1, 8244.04ng.h2.mL-1 and 4.2 h, respectively. Conclusion: This study confirms the rapid absorption of nifedipine in humans. AUC was similar to thatpreviously reported for Nigerians but slightly lower than that stated in the literature for other south Asian races. Further studies on large segments of the local population using the non-compartmental model forkinetic analysis is recommended

Comparative Analgesic and Anti-inflammatory Activities of Two Polyherbal Tablet Formulations (Aujaie and Surangeen) in Rats

Purpose: To investigate the analgesic and anti-inflammatory activities of two herbal polymedicines - Aujaie and Surangeen to ascertain their therapeutic claims.Methods: A total of 96 rats were divided into two equal groups; one for determination of antiinflammatory activity and the other for analgesic activity. Anti-inflammatory and analgesic activities were evaluated by carrageenan-induced paw edema and formalin-induced paw licking test, respectively. For both studies, group I (untreated control) received 1 ml/kg, (po) of gum suspension 1 h before carrageenan injection. Aspirin (100 mg/kg, po) was given to group II (treated control) before injection. Groups III, IV and V were administered orally aujaie (3, 4 and 5 mg/kg, po, respectively), while surangeen tablets (10, 20 and 40 mg/kg, po) were given to groups VI, VII and VIII, respectively. Pain was experimentally induced by injecting 0.1 ml of 2.5 % formalin (40 % formaldehyde in distilled water) via the subplantar region of the left hind paw.Results: Significant (p < 0.05) anti-inflammatory activity for aspirin (group II as well as for groups III - VIII with paw edema inhibition (PDI) ranging from 24.6 - 90.2 %, There was significant ((p < 0.05) analgesic activity in group II, VI and VII while in groups III - V and VIII the activity was insignificant (p < 0.05).Conclusion: Aujaie and surangeen tablets exhibited pronounced analgesic and anti-inflammatory activities in rats depending on the dose employed.Keywords: Aujaie, Surangeen, Anti-inflammatory, Analgesic