Cooling supply with a new type of evacuated solar collectors: a techno-economic optimization and analysis.

Renewable cooling via absorption chillers being supplied by various green heat technologies such as solar collectors has been widely studied in the literature, but it is still challenging to get positive economic outcomes from such systems due to the large expenses of solar thermal systems. This study offers the use of a new generation of solar collectors, so-called eccentric reflective solar collectors, for driving single-effect absorption chillers and thereby reducing the levelized cost of cooling. This article develops the most optimal design of this system (based on several different scenarios) using multi-objective optimization techniques and employs them for a case study in Brazil to assess its proficiency compared to conventional solar-driven cooling methods. For making the benchmarking analyses fair, the conventional system is also rigorously optimized in terms of design and operation features. The results show that the eccentric solar collector would enhance the cost-effectiveness by 29%. In addition, using optimally sized storage units would be necessary to get acceptable economic performance from the system, no matter which collector type is used. For the case study, at the optimal sizing and operating conditions, the levelized cost of cooling will be 124 USD/MWh and an emission level of 18.97 kgCO2/MWh.

Calcium Intake and Iron Status in Human Studies: A Systematic Review and Dose-Response Meta-Analysis of Randomized Trials and Crossover Studies.

BACKGROUND: The interaction between dietary (and supplementary) divalent ions has been a long-standing issue in human nutrition research. Developing an optimal calcium and iron supplementation recommendation requires detailed knowledge of the potential trade-offs between: 1) the clinical effects of concurrent intake on iron absorption and hematological indices; and 2) the potentially negative effects of separated ingestion on adherence to iron and/or calcium supplements. Human clinical studies have examined the effects of calcium intake on iron status, but there are no meta-analyses or recent reviews summarizing the findings. OBJECTIVES: To synthesize peer-reviewed, human, randomized, and cross-over studies on effects of calcium consumption on iron indices without age, gender, or any other restrictions. METHODS: Weighted mean differences for total, heme, and nonheme iron absorption (%) and serum ferritin (µg/L) were obtained from pooled analysis of the highest daily calcium intake compared to the lowest daily calcium intake. RESULTS: The negative effect of calcium intake was statistically significant in short-term iron absorption studies, but the effect magnitude was low [weighted mean difference (WMD) = -5.57%; 95% CI: -7.09 to -4.04]. The effect of calcium on the iron status was mixed. The inverse dose-response association of calcium intake with the serum ferritin concentration was significant (P value = 0.0004). There was, however, no reduction in the hemoglobin concentration (WMD = 1.22g/L;  95% CI:  0.37-2.07). CONCLUSIONS: The existing body of studies is insufficient to make recommendations with high confidence due to heterogeneity in designs, limitations of ferritin as an iron biomarker, and a lack of intake studies in pregnant women. Prescribing separation of prenatal calcium and iron supplements in free-living individuals is unlikely to affect the anemia burden. There is a need for effectiveness trials comparing the effects of prescribing separated intake to concurrent intake, with functional endpoints as primary outcomes and adherence to each supplement as intermediate outcomes.

Hematological profile of normal pregnant women in Lagos, Nigeria.

BACKGROUND: Hematological profile is considered one of the factors affecting pregnancy and its outcome. Anemia is the most common hematological problem in pregnancy, followed by thrombocytopenia. Leukocytosis is almost always associated with pregnancy. The study reported here was designed to evaluate the overall mean values of seven major hematological parameters and their mean values at different trimesters of pregnancy. SUBJECTS AND METHODS: This examination was a cross-sectional study of 274 pregnant women who registered to attend the Lagos University Teaching Hospital or Lagos State University Teaching Hospital antenatal clinics between their first and third trimester. Blood (4.5 mL) was collected from each participant into a tube containing the anticoagulant ethylenediaminetetraacetic acid (EDTA). A full blood count was performed on each sample and the results were analyzed. RESULTS: Overall, the values obtained were (mean ± standard deviation [SD]): hematocrit level, 30.16% ± 5.55%; hemoglobin concentration, 10.94 ± 1.86 g/dL; white blood cells, 7.81 ± 2.34 × 10(9); platelets, 228.29 ± 65.6 × 10(9); cell volume 78.30 ± 5.70 fL, corpuscular hemoglobin, 28.57 ± 2.48 pg; and corpuscular hemoglobin concentration, 36.45 ± 1.10 g/dL. When grouped by trimester, the mean ± SD value of packed cell volume at first trimester was 32.07% ± 6.80%; of second trimester, 29.76% ± 5.21%; and of third, 33.04% ± 3.88%. The mean ± SD hemoglobin concentration values were 11.59 ± 2.35 g/dL, 10.81 ± 1.72 g/dL, and 10.38 ± 1.27 g/dL for women in their first, second, and third trimester, respectively. Mean ± SD white blood cell concentration for first, second, and third trimesters were 7.31 ± 2.38 × 10(9), 7.88 ± 2.33 × 10(9), and 8.37 ± 2.15 × 10(9), respectively, while the mean ± SD platelet values for first, second, and third trimesters were 231.50 ± 79.10 × 10(9), 227.57 ± 63 × 10(9), and 200.82 ± 94.42 × 10(9), respectively. A statistically significant relationship was found to exist between packed cell volume and white blood cell count with increase in gestational age (P = 0.010 and 0.001, respectively). However, there was no statistically significant association between platelet count and increase in gestational age (P = 0.296). CONCLUSION: These findings reinforce the need for supplementation and provide additional information on hematological reference values in pregnancy in Nigeria.

Comparison of 20-, 23-, and 25-gauge air infusion forces.

PURPOSE: To determine and compare 20-, 23-, and 25-gauge retinal infusion air jet impact pressure (force per unit area) in an experimental setting. METHODS: Experimental laboratory investigation. Infusion cannulas were connected to a compressed air system. A controlled valve mechanism was used to obtain increasing levels of infusion pressure. Each infusion tube was positioned in front of a manual transducer to measure force. Impact pressure was calculated using known formulas in fluid dynamics. RESULTS: The 20-gauge infusion jet showed similar impact pressure values compared with the 23-gauge infusion jet. Both showed higher levels than the 25-gauge infusion jet. This was because of the smaller jet force for the 25-gauge system. CONCLUSION: In this experimental study, both the 23- and the 20-gauge air infusion jet showed higher impact pressure values compared with the 25-gauge air infusion jet. This could be of concern regarding air infusion during 23-gauge vitrectomy since retinal damage has been shown in standard-gauge surgeries.