A review of solar driven absorption cooling with photovoltaic thermal systems

The aim of this investigation is to evaluate the recent advances in the field of solar absorption cooling systems from the viewpoint of solar collector types. A review in the area of photovoltaic thermal (PVT) absorption cooling systems is conducted. This review includes experimental and computational work focusing on collector types and their efficiencies and performance indicators. Compared to vapour compression air conditioning systems, 50% of primary energy was saved by using solar absorption cooling systems and 10–35% maximum electrical efficiency of PVT was achieved. This review shows that Coefficient of Performance (COP) for solar cooling systems is in the range of 0.1–0.91 while the thermal collector efficiencies are in the range of 0.06–0.64. The average area to produce cooling for single effect absorption chillers for experimental and computational projects is 4.95 m2/kWc and 5.61 m2/kWc respectively. The specific area for flat plat collector (FPC) is in the range of 2.18–9.4 m2/kWc, while for evacuated tube collector (ETC) is in the range of 1.27–12.5 m2/kWc. For concentrated photovoltaic thermal collector (CPVT) and PVT, the average area to produce cooling for solar absorption chillers are 2.72 m2/kWc and 3.1 m2/kWc respectively

Improving thermal and electrical efficiency in photovoltaic thermal systems for sustainable cooling system integration

Research into photovoltaic thermal systems is important in solar technologies as photovoltaic thermal systems are designed to produce both electrical and thermal energy, this can lead to improved performance of the overall system. The performance of photovoltaic thermal systems is based on several factors that include photovoltaic thermal materials, design, ambient temperature, inlet and outlet fluid temperature and photovoltaic cell temperature. The aim of this study is to investigate the effect of photovoltaic thermal outlet water temperatures and solar cell temperature on both electrical and thermal efficiency for different range of inlet water temperature. To achieve this, a mathematical model of a photovoltaic thermal system was developed to calculate the anticipated system performance. The factors that affect the efficiency of photovoltaic thermal collectors were discussed and the outlet fluid temperature from the photovoltaic thermal is investigated in order to reach the highest overall efficiency for the solar cooling system. An average thermal and electrical efficiency of 65% and 13.7%, respectively, was achieved and the photovoltaic thermal mathematical model was validated with experimental data from literature

Effect of obesity on the population pharmacokinetics of meropenem in critically ill patients

Severe pathophysiological changes in critical illness can lead to dramatically altered antimicrobial pharmacokinetics (PK). The additional effect of obesity on PK potentially increases the challenge for effective dosing. The aim of this prospective study was to describe the population PK of meropenem for a cohort of critically ill patients, including obese and morbidly obese patients. Critically ill patients prescribed meropenem were recruited into the following three body mass index (BMI) groups: nonobese (18.5 to 29.9 kg/m(2)), obese (30.0 to 39.9 kg/m(2)), and morbidly obese (>= 40 kg/m(2)). Serial plasma samples were taken, and meropenem concentrations were determined using a validated chromatographic method. Population PK analysis and Monte Carlo dosing simulations were undertaken with Pmetrics. Nineteen critically ill patients with different BMI categories were enrolled. The patients' mean +/- standard deviation (SD) age, weight, and BMI were 49 +/- 15.9 years, 95 +/- 22.0 kg, and 33 +/- 7.0 kg/m(2), respectively. A two-compartment model described the data adequately. The mean +/- SD parameter estimates for the final covariate model were as follows: clearance (CL), 15.5 +/- 6.0 liters/h; volume of distribution in the central compartment (V-1), 11.7 +/- 5.8 liters; intercompartmental clearance from the central compartment to the peripheral compartment, 25.6 +/- 35.1 liters h(-1); and intercompartmental clearance from the peripheral compartment to the central compartment, 8.32 +/- 12.24 liters h(-1). Higher creatinine clearance (CLCR) was associated with a lower probability of target attainment, with BMI having little effect. Although obesity was found to be associated with an increased V-1, dose adjustment based on CLCR appears to be more important than patient BMI

Modeling and Optimization of a Photoelectrochemical Solar Hydrogen Cell with TiO2 as a Photo-anode

A photoelectrochemical (PEC) cell model for solar hydrogen production with titanium dioxide (TiO2) as a photo anode and platinum (Pt) as a cathode is developed. Despite the wide bandgap of TiO2 resulting in limited photon absorption from the sun, it is still a good candidate due to its stability in liquid electrolytes and reasonable cost. In this model, Beer-Lambert law is used in conjunction with the empirical diode equation to calculate the electron/hole pair generation rate in the photo-anode, and the external current reaching the cathode to estimate and optimize the hydrogen generation rate evolving at the cathode with TiO2 and ITO thicknesses as optimization variables. The model revealed an optimal solution of TiO2 thickness of 3230 nm at 400 nm ITO thickness, with optimal external current value of 26.9 A/m2, hydrogen generation rate of 1.394x10-4 mol/(m2s), and an overall cell efficiency of 3.4 %

Enhancing Type 1 Diabetes Self-Management: Investigating the Role of Physical Activity and Sedentary Behaviours in Glucose Control

Physical activity (PA), sedentary behaviour (SB), and interruptions to prolonged sitting may influence glucose control in adults with type 1 diabetes (T1D). This thesis investigates their impact using experimental studies. One study explored attitudes and barriers to exercise in adults with T1D, stratified by insulin resistance (IR), using estimated glucose disposal rate (eGDR) as a marker. The study found that hypoglycaemia was the main concern for those with IR, whereas non-glycaemic factors were the main barriers for those without IR. A systematic review and meta-analysis showed that adults with T1D are more inactive and sedentary than guidelines recommended (Part A). It also found that acute exercise led to short-term reductions in plasma glucose concentrations, but chronic exercise had no significant impact on glycated haemoglobin (HbA1c) levels or fasting plasma glucose concentrations (Part B). A 14-day observational study using continuous glucose monitoring (CGM) indicated that moderate-intensity PA was associated with higher blood glucose concentrations, while vigorous-intensity PA improved time in range (TIR). Finally, a randomised controlled trial (RCT), demonstrated that interrupting prolonged sitting with short bouts of low-intensity walking improved glucose control, increasing TIR, and reducing hyperglycaemia without raising hypoglycaemia risk in T1D. These findings highlight the importance of reducing sedentary time and incorporating activity breaks to enhance glucose control in T1D, supporting the development of future long-term interventions

Developing immune-regulatory materials using immobilized monosaccharides with immune-instructive properties

New strategies for immune modulation have shown real promise in regenerative medicine as well as the fight against autoimmune diseases, allergies and cancer. Dendritic cells (DCs) are gatekeepers of the immune system and their ability in shaping the adaptive immune responses makes DCs ideal targets for immune modulation. Carbohydrates are abundant in different biological systems and are known to modulate DC phenotype and function. However, how simple monosaccharides instruct DC function is less well understood. In this study we used a combinatorial array of immobilized monosaccharides to investigate how they modulate DC phenotype and function, and crucially the impact of such changes on downstream adaptive immune responses. Our data show a selection of monosaccharides significantly suppress lipopolysaccharide (LPS) induced DC activation as evidenced by reduction in CD40 expression, IL-12 production and 2,3 indoleamine dioxygenase activity, while inducing a significant increase in IL-10 production. These changes are indicative of induction of an anti-inflammatory or regulatory phenotype in DCs which was further confirmed in DC-T cell co-cultures where DCs cultured on the ‘regulatory’ monosaccharaide coated surfaces were shown to induce naïve T cell polarization towards regulatory phenotype. Our data also highlighted a selection of monosaccharides that are able to promote mixed Treg and Th17 cell differentiation, a T cell phenotype expected to be highly immune suppressive. These data show the potential immunomodulatory effects of immobilized monosaccharides in priming DCs and skewing T cell differentiation towards an immune-regulatory phenotype. The ability to fine tune immune responses using these simple carbohydrate combinations (e.g. as coatings for existing materials) can be utilized as novel tools for immune modulation with potential applications in regenerative medicine, implantable medical devices and wound healing where reduction of inflammatory responses and maintaining immune homeostasis are desirable

Determining the effect of inlet flow conditions on the thermal efficiency of a flat plate solar collector

The main objective of this study was to investigate the effect of inlet temperature (Tin) and flowrate ( m˙ ) on thermal efficiency (ηth) of flat plate collectors (FPC). Computational Fluid Dynamics (CFD) was employed to simulate a FPC and the results were validated with experimental data from literature. The FPC was examined for high and low level flowrates and for inlet temperatures which varied from 298 to 373 K. Thermal efficiency of 93% and 65% was achieved at 298 K and 370 K inlet temperature’s respectively. A maximum temperature increase of 62 K in the inlet temperature was achieved at a flowrate of 5 × 10−4 kg/s inside the riser pipe. Tin and m˙ were optimised in order to achieve the minimum required feed temperature for a 10 kW absorption chiller

Prediction of the SYM-H Index Using a Bayesian Deep Learning Method with Uncertainty Quantification

We propose a novel deep learning framework, named SYMHnet, which employs a graph neural network and a bidirectional long short-term memory network to cooperatively learn patterns from solar wind and interplanetary magnetic field parameters for short-term forecasts of the SYM-H index based on 1-minute and 5-minute resolution data. SYMHnet takes, as input, the time series of the parameters' values provided by NASA's Space Science Data Coordinated Archive and predicts, as output, the SYM-H index value at time point t + w hours for a given time point t where w is 1 or 2. By incorporating Bayesian inference into the learning framework, SYMHnet can quantify both aleatoric (data) uncertainty and epistemic (model) uncertainty when predicting future SYM-H indices. Experimental results show that SYMHnet works well at quiet time and storm time, for both 1-minute and 5-minute resolution data. The results also show that SYMHnet generally performs better than related machine learning methods. For example, SYMHnet achieves a forecast skill score (FSS) of 0.343 compared to the FSS of 0.074 of a recent gradient boosting machine (GBM) method when predicting SYM-H indices (1 hour in advance) in a large storm (SYM-H = -393 nT) using 5-minute resolution data. When predicting the SYM-H indices (2 hours in advance) in the large storm, SYMHnet achieves an FSS of 0.553 compared to the FSS of 0.087 of the GBM method. In addition, SYMHnet can provide results for both data and model uncertainty quantification, whereas the related methods cannot.Comment: 28 pages, 8 figure

Role of the posterodorsal medial amygdala in predator odour stress induced puberty delay in female rats

Puberty onset is influenced by various factors including psychosocial stress. The present study investigated cat‐odour stress on puberty onset and oestrous cyclicity in rats. Female weanling rats were exposed to either soiled cat litter or fresh unused litter for 10 consecutive days. Following vaginal opening (VO), rats were smeared for 14 days to determine oestrous cyclicity. Anxiety‐like behaviour was assessed using standard anxiety tests. Brains were collected to determine CRF, CRF‐R1 and CRF‐R2 mRNA in the PVN and amygdala (CeA and MeA). Cat odour delayed VO and first oestrus, disrupted oestrous cycles and caused anxiogenic responses. Cat odour elicited increased CRF mRNA expression in the PVN, but not in the CeA. CRF‐R1 and CRF‐R2 mRNA levels in the PVN and CeA were unaffected by cat odour, however, CRF‐R1 mRNA levels were decreased in the MeA. The role of CRF signalling in the MeA, particularly its posterodorsal subnucleus (MePD), on pubertal timing was directly examined by using unilateral intra‐MePD administration of CRF (0.2nmol/day for 14 days) via osmotic mini‐pump from postnatal day 24 and was shown to delay VO and first oestrus. These data suggest that CRF signalling in the MePD may be associated with predator‐odour induced puberty delay

Empowerment and social inclusion through Para sports: a qualitative study on women with physical impairments in Saudi Arabia

BackgroundParticipation in sports represents a potent means of empowerment and social inclusion. Nevertheless, women with physical impairments encounter specific challenges in accessing Para sports. The main aim of this study is to present the experiential participation and achievements in sports of women with physical impairments in Saudi Arabia.MethodsTwenty women athletes with physical impairments who engaged in competitive Para sports in Saudi Arabia were interviewed. Interpretive phenomenological analysis was employed to extract themes elucidating the experiences of women athletes with physical impairments in Para sports.ResultsFour dimensions were identified: (i) Exploring participation in sports; (ii) The positive impact of participation in sports; (iii) obstacles in participation in sport; and (iv) hopes and aspirations to improve participation in Para sports.ConclusionIn Saudi Arabia, participation in Para sports functions as a powerful tool for empowering and socially integrating women with physical impairments. However, these women encounter challenges in accessing sports. Achieving empowerment in Para sports necessitates the establishment of an inclusive ecosystem that celebrates diversity and equality. Collaborative efforts from governments, sports organizations, communities, and individuals are indispensable in creating an environment where women with impairments can flourish in sports