Solar-Driven Air-Conditioning Cycles: A Review

Most conventional cooling/refrigeration systems are driven by fossil fuel combustion, and therefore give rise to emission of environmentally damaging pollutants. In addition, many cooling systems employ refrigerants, which are also harmful to the environment in terms of their Global Warming Potential (GWP) and Ozone Depletion Potential (ODP). Development of a passive or hybrid solar-driven air-conditioning system is therefore of interest as exploitation of such systems would reduce the demand for grid electricity particularly at times of peak load. This paper presents a review of various cooling cycles and summarises work carried out on solar-driven air-conditioning systems

Small-scale absorption air-conditioning driven by solar louvre collector

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Solar-Driven Air-Conditioning Cycles: A Review

Most conventional cooling/refrigeration systems are driven by fossil fuel combustion, and therefore give rise to emission of environmentally damaging pollutants. In addition, many cooling systems employ refrigerants, which are also harmful to the environment in terms of their Global Warming Potential (GWP) and Ozone Depletion Potential (ODP). Development of a passive or hybrid solar-driven air-conditioning system is therefore of interest as exploitation of such systems would reduce the demand for grid electricity particularly at times of peak load. This paper presents a review of various cooling cycles and summarises work carried out on solar-driven air-conditioning systems

Formulation and Evaluation of Niosomal Alendronate Sodium Encapsulated in Polymeric Microneedles: In Vitro Studies, Stability Study and Cytotoxicity Study

The aim of this study is to design and evaluate a transdermal delivery system for alendronate sodium (ALS) loaded with nanocarrier to improve its permeability and prolong its release. This is due to its low bioavailability, potential gastrointestinal side effects, and the special administration needed for the oral dosage form of ALS. When using the ether injection method, various niosomal formulations were produced. Size of the particles, polydispersity index (PDI), surface charge (ZP), drug entrapment efficiency (EE), and in vitro release were used to characterize the resulting niosomes. The size of niosomes ranged between 99.6 ± 0.9 and 464.3 ± 67.6 nm, and ZP was from −27.6 to −42.27 mV. The niosomal formulation was then loaded to aqueous polymer solution of 30% polyvinyl pyrrolidone (PVP) (MN-1), 30% PVP with 15% poly(vinyl alcohol) (PVA) (2:1) (MN-2), and 30% PVP with 15% PVA (1:1) (MN-3). The cumulative amount of ALS (Q) was in the following order: MN-1 > MN-2 > MN-3. All formulations in this study were stable at room temperature over two months, in terms of moisture content and drug content. In conclusion, a transdermal delivery of ALS niosomes combined in microneedles (MNs) was successfully prepared to provide sustained release of ALS

Development and evaluation of an innovative approach using niosomes based polymeric microneedles to deliver dual antioxidant drugs

Ascorbic acid (AA) and caffeine (CAFF) work to protect cells from ultraviolet (UV) radiation and slow down the photoaging process of the skin. However, cosmetic application of AA and CAFF is limited due to poor penetration across the skin and rapid oxidation of AA. The aim of this study was to design and evaluate the dermal delivery of dual antioxidants utilizing microneedles (MNs) loaded with AA and CAFF niosomes. The niosomal nanovesicles were prepared using the thin film method and had particle sizes ranging from 130.6–411.2 nm and a negative Zeta potential of around −35 mV. The niosomal formulation was then combined with polyvinylpyrrolidone (PVP) and polyethylene glycol 400 (PEG 400) to create an aqueous polymer solution. The best skin deposition of AA and CAFF was achieved with the formulation containing 5% PEG 400 (M3) and PVP. Furthermore, the role of AA and CAFF as antioxidants in preventing cancer formation has been well-established. Here we validated the antioxidant properties of ascorbic acid (AA) and caffeine (CAFF) in a novel niosomal formulation referred to as M3 by testing its ability to prevent H2O2-indued cell damage and apoptosis in MCF-7 breast cancer cells. Results showed that M3 was able to shield MCF-7 cells from H2O2 induced damage at concentrations below 2.1 µg/mL for AA and 1.05 µg/mL for CAFF, and also exhibited anticancer effects at higher concentrations of 210 µg/mL for AA and 105 µg/mL. The formulations were stable for two months at room temperature in terms of moisture and drug content. The use of MNs and niosomal carriers could be a promising approach for dermal delivery of hydrophilic drugs like AA and CAFF