Efficiency improvement of an all-vanadium redox flow battery by harvesting low-grade heat

Redox flow batteries (RFBs) are rugged systems, which can withstand several thousand cycles and last many years. However, they suffer from low energy density, low power density, and low efficiency. Integrating a Thermally Regenerative Electrochemical Cycle (TREC) into the RFB, it is possible to mitigate some of these drawbacks. The TREC takes advantage of the temperature dependence of the cell voltage to convert heat directly into electrical energy. Here, the performance increase of a TREC-RFB is investigated using two kinds of all-vanadium electrolyte chemistries: one containing a typical concentration of sulfuric acid and one containing a large excess of hydrochloric acid. The results show that the energy density of the system was increased by 1.3Wh L−1 and 0.8Wh L−1, respectively and the overall energy efficiency also increased by 9 and 5 percentage points, respectively. The integration of the heat exchangers necessary to change the battery temperature is readily facilitated by the design of the redox flow battery, which already utilizes fluid circulation loops

Charge Form Factor and Cluster Structure of 6^6Li Nucleus

The charge form factor of ${}^6$Li nucleus is considered on the basis of its cluster structure. The charge density of ${}^6$Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of ${}^4$He and the deuteron densities. Using the available experimental data for ${}^4$He and deuteron charge form factors, a good agreement of the calculations within the suggested scheme is obtained with the experimental data for the charge form factor of ${}^6$Li, including those in the region of large transferred momenta.Comment: 12 pages 5 figure

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Vanadium-oxygen cell for positive electrolyte discharge in dual-circuit vanadium redox flow battery

The “dual-circuit redox flow battery” takes advantage of a conventional all-vanadium redox flow battery (VRFB) combined with a separated catalytic hydrogen evolution reactor. Depending on demand, the VRFB can be conventionally discharged or supply H2 by using the catalytic reactor. However, during hydrogen generation, protons are consumed and a state-of-charge imbalance is created. Therefore, the corresponding discharge of the positive compartment is necessary to maintain proton and charge balance. Water oxidation is a suitable reaction providing regeneration of the positive electrolyte (reduction of VO2+ to VO2+) and also protons. VO2+/VO2+ does not possess a potential high enough to spontaneously drive the oxygen evolution reaction thus an additional energy input is required. We introduce the V–O2 cell, a secondary flow cell to integrate into the “dual-circuit redox flow battery” that provides a high rate of conversion while minimizing the energy required. This was tested in a complete dual-circuit system and required 140 mW cm−2 of additional energy at 110 mA cm−2. The total efficiency of the coupled system in term of electricity to hydrogen was between 42 and 62% depending on the current density and stable operation was demonstrated during extended tests

Reduced cortical bone density with normal trabecular bone density in girls with Turner syndrome

Summary: this study of 22 girls with Turner syndrome (TS) demonstrates a reduction in bone mineral apparent density (BMAD) at the femoral neck along with a reduction in cortical bone density at the radius (with sparing of trabecular bone). These findings may account for the increased fracture risk noted in this population.Introduction Increased fracture risk is a feature of TS; however, the reasons for this are unclear. Little is known regarding cortical and trabecular bone mineral density (BMD) in TS. We have addressed this by measurement of volumetric bone mineral density (vBMD) using peripheral quantitative computed tomography (pQCT).Methods: we studied 22 females with TS and 21 females without TS; mean ages 12.7 and 12.9 years, respectively. Bone mass measurements were made by dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femur and pQCT of the radius. BMAD was calculated from DXA values. We utilized published reference data to generate Z-scores for both populations.Results: the mean BMAD Z-score at the lumbar spine was not significantly different in individuals with TS compared to the controls. At the femoral neck, individuals with TS had a significantly lower BMAD Z-score compared to the controls (?1.32 vs. ?0.14, p?=?0.001). At the distal radius, total vBMD Z-score and trabecular vBMD Z-score were not significantly different between the TS group and controls. A significant reduction in cortical vBMD at the proximal radius was noted in the TS group however (?2.58 vs. ?1.38, p?=?0.02). There was also a trend towards reduced cortical thickness at this site in the TS group (Z-score ?2.89 vs. ?1.73, p?=?0.08).Discussion: TS is associated with reduced BMAD at the femoral neck; pQCT data suggests that cortical density is reduced with sparing of trabecular bone. This differential of cortical and trabecular BMD may predispose to fracture<br/

Solid electrochemical energy storage for aqueous redox flow batteries: The case of copper hexacyanoferrate

All redox flow batteries suffer from low energy storage density in comparison with conventional Li-ion batteries. However, this issue can be mitigated by utilization of solid energy storage materials to enhance the energy storage capacity. In this paper we demonstrate the utilization of copper hexacyanoferrate (CuHCF) Prussian blue analogue for this purpose, coupled with N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TEMPTMA) as a soluble redox mediator to target the redox transitions of the solid material. In this case, indirect charging and discharging of CuHCF suspended in the electrolyte by electrochemically oxidized/reduced TEMPTMA was observed by chronoamperometry. Secondly, electrochemistry of different CuHCF composites with carbon black and multi-walled carbon nanotubes were investigated, highlighting that the high conductivity of the solid energy storage materials is crucial to access the maximal charge storage capacity. Finally, a CuHCF-TEMPTMA/Zn aqueous redox flow battery achieved stable cycling performances with high coulombic efficiency of 95% and volumetric capacity of 350 C mL−1

Maternal vitamin D status during pregnancy and childhood bone mass at age 9 years: a longitudinal study

Bsckfround: Vitamin D insufficiency is common in women of childbearing age and increasing evidence suggests that the risk of osteoporotic fracture in adulthood could be determined partly by environmental factors during intrauterine and early postnatal life. We investigated the effect of maternal vitamin D status during pregnancy on childhood skeletal growth. Methods: In a longitudinal study, we studied 198 children born in 1991-92 in a hospital in Southampton, UK; the body build, nutrition, and vitamin D status of their mothers had been characterised during pregnancy. The children were followed up at age 9 years to relate these maternal characteristics to their body size and bone mass. Findings: 49 (31%) mothers had insufficient and 28 (18%) had deficient circulating concentrations of 25(OH)-vitamin D during late pregnancy. Reduced concentration of 25(OH)-vitamin D in mothers during late pregnancy was associated with reduced whole-body (r=0.21, p=0.0088) and lumbar-spine (r=0.17, p=0.03) bone-mineral content in children at age 9 years. Both the estimated exposure to ultraviolet B radiation during late pregnancy and the maternal use of vitamin D supplements predicted maternal 25(OH)-vitamin D concentration (p&lt;0.0001 and p=0.0110, respectively) and childhood bone mass (p=0.0267). Reduced concentration of umbilical-venous calcium also predicted reduced childhood bone mass (p=0.0286). Interpretation: Maternal vitamin D insufficiency is common during pregnancy and is associated with reduced bone-mineral accrual in the offspring during childhood; this association is mediated partly through the concentration of umbilical venous calcium. Vitamin D supplementation of pregnant women, especially during winter months, could lead to longlasting reductions in the risk of osteoporotic fracture in their offspring

Associations between perceived neighbourhood problems and quality of life in older adults with and without osteoarthritis: results from the Hertfordshire Cohort Study

This study examined whether the association of quality of life (QoL) with perceived neighbourhood problems is stronger in older adults with osteoarthritis (OA) than in those without OA. Of all 294 participants, 23.8% had OA. More perceived neighbourhood problems were associated with a stronger decrease in QoL over time in participants with OA (B=-0.018; p=0.02) than in those without OA (B=-0.004; p=0.39). Physical activity did not mediate this relationship. Older adults with OA may be less able to deal with more challenging environments