Prussian Blue Analogue (PBA)-Zn aqueous batteries are attractive because of the high potential of PBA against Zn (~1.7 V), relative safety of the system, and high rate capability. But, despite the long cycle life of PBA half-cells, full PBA-Zn battery systems studied thus far have typically reported only up to 100 cycles and suffer significant capacity fade beyond that. In this work we demonstrate that the loss in capacity retention and cycle life is a combined effect of Zn 2+ ion poisoning at the PBA cathode, as well as dendrite formation in the zinc anode. We address both these issues via the use of a dual ion (Na + as the primary charge carrier) electrolyte and hyper-dendritic Zinc (HD Zn) as the anode. The copper hexacyanoferrate (CuHcf) vs. HD Zn system with Na + ion electrolyte demonstrated herein exhibits 90% (83%) capacity retention after 300 (500) cycles at a 5C rate and a 3% reduction in usable capacity from 1C to 5C. Detailed characterization is done using in situ synchrotron energy-dispersive XRD (EDXRD), conventional XRD, XPS, SEM, TEM, and electrochemical techniques.
The low cost, significant reduction potential and relative safety of the zinc electrode is a common hope for a reductant in secondary batteries, but it is limited mainly to primary implementation due to shape change. In this work, we exploit such shape change for the benefit of static electrodes through the electrodeposition of hyper-dendritic nanoporous zinc foam. Electrodeposition of zinc foam resulted in nanoparticles formed on secondary dendrites in a three-dimensional network with a particle size distribution of 54.1-96.0 nm. The nanoporous zinc foam contributed to highly oriented crystals, high surface area and more rapid kinetics in contrast to conventional zinc in alkaline mediums. The anode material presented had a utilization of 88% at full depth-of-discharge (DOD) at various rates indicating a superb rate capability. The rechargeability of Zn 0 /Zn 2+ showed significant capacity retention over 100 cycles at a 40% DOD to ensure that the dendritic core structure was imperforated. The dendritic architecture was densified upon charge-discharge cycling and presented superior performance compared with bulk zinc electrodes.
PurposeWe examined racial/ethnic differences in the usage and results of germ-line multiple-gene sequencing (MGS) panels to evaluate hereditary cancer risk.MethodsWe collected genetic testing results and clinical information from 1,483 patients who underwent MGS at Stanford University between 1 January 2013 and 31 December 2015.ResultsAsians and Hispanics presented for MGS at younger ages than whites (48 and 47 vs. 55; P = 5E-16 and 5E-14). Across all panels, the rate of pathogenic variants (15%) did not differ significantly between racial groups. Rates by gene did differ: in particular, a higher percentage of whites than nonwhites carried pathogenic CHEK2 variants (3.8% vs. 1.0%; P = 0.002). The rate of a variant of uncertain significance (VUS) result was higher in nonwhites than whites (36% vs. 27%; P = 2E-4). The probability of a VUS increased with increasing number of genes tested; this effect was more pronounced for nonwhites than for whites (1.1% absolute difference in VUS rates testing BRCA1/2 vs. 8% testing 13 genes vs. 14% testing 28 genes), worsening the disparity.ConclusionIn this diverse cohort undergoing MGS testing, pathogenic variant rates were similar between racial/ethnic groups. By contrast, VUS results were more frequent among nonwhites, with potential significance for the impact of MGS testing by race/ethnicity.
The Science Writing Heuristic (SWH)
laboratory instruction approach
has been used successfully over a decade to engage students in laboratory
activities. SWH-based instruction emphasizes knowledge construction
through individual writing and reflection, and collaborative learning
as a group. In the SWH approach, writing is a core component of learning.
Previous studies on the SWH approach have reported effective implementation
of the SWH approach leads to an improvement in overall student academic
performance and content knowledge. Using a rubric developed by Maria
Oliver-Hoyo, we compared the critical thinking (CT) skills of students
across three groups, based on their written laboratory reports for
various traits of CT, and the cognitive skills embedded in the rubric.
Participants in this study were first-year general chemistry students
who received traditional laboratory instruction, first-year general
chemistry students who were instructed using the SWH approach, and
fourth-year chemistry students who received traditional laboratory
instruction. First-year students and fourth-year chemistry students
who received traditional laboratory instruction scored statistically
significantly lower on various CT traits, suggesting the SWH-based
laboratory instruction is valuable in promoting CT thinking skills
The use of liquid cell electron microscopy as a quantitative probe of nanomaterial structures and reactions requires an accurate understanding of how the sample is altered by the imaging electron beam. In particular, changes in the chemical environment due to beam-induced radiolysis can strongly affect processes such as solution-phase nanocrystal synthesis or electrochemical deposition. It is generally assumed that beam effects are uniform throughout the irradiated liquid. Here we show that for a liquid cell filled with water, the inevitable presence of interfaces between water and the surrounding surfaces causes a spatial variation in the energy absorbed by the water near the walls. The mechanism for this effect is that the walls act as a source of secondary and backscattered electrons which diffuse and deposit energy in the water nearby. This increased dose rate then changes the local concentrations of radiolysis species. We quantify and compare the effects for different materials used in practical liquid cells. We show that the dose rate can increase by several times within tens of nanometers of a water/Au interface, locally increasing the concentrations of species such as the hydrated electron. We discuss the implications for materials processes that are typically triggered at the solid-liquid interface.
Moringa oleifera Lam., the miracle tree, is widely used as a traditional medicine. The analyses of phytochemicals and antioxidant potential of hydroethanolic extract of various plant parts of M. oleifera revealed that leaves possessed the highest content of total phenolics (9.58 mg/g), b-carotene (14.10 mg/g) and lycopene (2.60 mg/g). Flowers and bark showed the highest content of total flavonoids (3.5 mg/g) and anthocyanin (52.80 mg/g), respectively. Leaves also showed maximum antioxidant potential using nitric oxide scavenging assay (IC 50 -120 lg/ml) and deoxyribose degradation assay (IC 50 -178 lg/ml). Highest DPPH radical scavenging activity was observed in flowers (IC 50 -405 lg/ml). The GC-MS study revealed the presence of 29, 36 and 24 compounds in bark, leaf and flower, respectively. The major constituent identified were epiglobulol (41.68% in bark), phytol (23.54% in leaf) and b-sitosterol (15.35% in flower).The phytochemicals identified possess several therapeutic activity, including antioxidant potential, which was confirmed through earlier reports. Moreover, the presence of 1,1,3-triethoxubutane in all the plant parts analyzed, projects it as an important source of waste water treatment as hydrophobic modifiers.
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