Spin-resolved electron waiting times in a quantum dot spin valve

We study the electronic waiting time distributions (WTDs) in a non-interacting quantum dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using scattering matrix approach. Since the quantum dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first passage time distributions to quantitatively characterize the spin flip process. The influence degree shows a similar behavior with spin transfer torque and can be a new pathway to characterize spin correlation in spintronics system.Comment: 9 pages, 7 figure

Imaging and Detection of Carboxylesterase in Living Cells and Zebrafish Pretreated with Pesticides by a New Near-Infrared Fluorescence Off–On Probe

A new near-infrared fluorescence off–on probe was developed and applied to fluorescence imaging of carboxylesterase in living HepG-2 cells and zebrafish pretreated with pesticides (carbamate, organophosphorus, and pyrethroid). The probe was readily prepared by connecting (4-acetoxybenzyl)­oxy as a quenching and recognizing moiety to a stable hemicyanine skeleton that can be formed via the decomposition of IR-780. The fluorescence off–on response of the probe to carboxylesterase is based on the enzyme-catalyzed spontaneous hydrolysis of the carboxylic ester bond, followed by a further fragmentation of the phenylmethyl unit and thereby the fluorophore release. Compared with the only existing near-infrared carboxylesterase probe, the proposed probe exhibits superior analytical performance, such as near-infrared fluorescence emission over 700 nm as well as high selectivity and sensitivity, with a detection limit of 4.5 × 10^–3 U/mL. More importantly, the probe is cell membrane permeable, and its applicability has been successfully demonstrated for monitoring carboxylesterase activity in living HepG-2 cells and zebrafish pretreated with pesticides, revealing that pesticides can effectively inhibit the activity of carboxylesterase. The superior properties of the probe make it of great potential use in indicating pesticide exposure

Carambola-like Ni@Ni_1.5Co_1.5S₂ for Use in High-Performance Supercapacitor Devices Design

Studies on supercapacitor devices constitute one of the most meaningful research topics in hastening the industrialization of electrode materials. Herein, uniform nanosheet-based carambola-like Ni@Ni_1.5Co_1.5S₂ was successfully synthesized and assembled into an asymmetric supercapacitor device with a high specific capacitance of 109 F g^–1 at a current density of 1 A g^–1. The large mass loading of this device, at ∼20 mg cm^–2, is compatible with the industry standard and considerably higher than those obtained in previous reports. The Ni@Ni_1.5Co_1.5S₂-based supercapacitor device exhibited excellent cycling stability with virtually no decrease in capacitance after 2000 cycles, and achieved a high energy density of 65.7 W h kg^–1 at a power density of 22.2 W kg^–1 and a high power density of 3 kW kg^–1 at energy density of 6.2 W h kg^–1. These outstanding characteristics of Ni@Ni_1.5Co_1.5S₂ as an electrode material for supercapacitor devices verify its promising applicability in the energy storage field

Achieving Fast and Reversible Sulfur Redox by Proper Interaction of Electrolyte in Potassium Batteries

Potassium–sulfur batteries have potential for low-cost and high-energy density energy storage. However, it is a challenge to find suitable electrolytes affording liquid environment for intermediate sulfur species to convert at high voltages. In this study, a series of ether/potassium salt systems were systematically studied to investigate the electrochemical stability and function of the electrolytes in sulfur electrochemistry by using in situ ultraviolet–visible and Fourier-transform infrared spectroscopies. Interactions of soluble polysulfides with the electrolyte were critical to the electrochemical performance. Under optimized conditions, the bis(trifluoromethanesulfonyl)imide anion demonstrated moderate interaction and reversible solvation/desolvation of polysulfides. Polar carboxyl groups in poly(acrylic acid) were effective for binding polysulfide in electrodes, enabling reversible sulfur conversions at high working voltages and improved initial Coulombic efficiency. This enhanced battery performance was achieved even using a conventional carbon host with a high sulfur loading of ∼69 wt %, i.e., ∼49 wt % in the cathode

Additional file 2 of Nutrition-related diseases and cardiovascular mortality in American society: national health and nutrition examination study, 1999–2006

Additional file 2:Supplementary Table 2. Sensitivity analyses for all-cause and cardiovascular mortality hazard ratios (HRs) for participants aged 20 years and older according to nutrition-related diseases: NHANES survey 1999–2006 with follow-up through 2015.

Partial Ion-Exchange of Nickel-Sulfide-Derived Electrodes for High Performance Supercapacitors

A novel method to adjust the composition of a material while maintaining its morphology was described in this study. Nickel sulfide, the material investigated in this work, was found to be useful as a high surface area electrode material for supercapacitor applications. First, a nest-like Ni₃S₂@NiS composite electrode with 1D nanorod as structural unit was synthesized by simultaneously using Ni foam as template and Ni as a source through a one-step <i>in situ</i> growth method. Co and Se ions, which respectively acted as beneficial cation and anion, were successfully introduced into the nest-like Ni₃S₂@NiS material, resulting in the formation of Ni₃S₂@Co₉S₈ and NiS@NiSe₂ composite electrodes with structures similar to those of the parent materials. The material structure was virtually retained and single-crystal-to-single-crystal transformation was achieved in the process. Introducing the cation and anion into the same type of material while maintaining topology could be important for the field of material synthesis and preparation of supercapacitor electrodes. Moreover, the electrochemical properties of these three materials were studied by cyclic voltammetry measurements and galvanostatic charge–discharge tests. The results indicated that the rate performance was improved significantly by ion exchange. In particular, the derived electrode with Se still showed superior oxidation and reduction ability at high scan rate of 10000 mV s^–1. In addition, the second charge–discharge specific capacity also increased from 516 F g^–1 to 925 F g^–1 and 1412 F g^–1 at the current density of 0.5 A g^–1 and by Co and Se exchange, respectively. This work contributes to the knowledge on electrode materials for supercapacitors and can provide good reference for the fabrication of desired materials

Double Metal Ions Synergistic Effect in Hierarchical Multiple Sulfide Microflowers for Enhanced Supercapacitor Performance

In this paper, the design, synthesis, and measurement of a new and hierarchically structured series of Ni_<i>x</i>Co_1–<i>x</i>S_1.097 electroactive materials are reported. The materials were synthesized through an ion-exchange process using hierarchically structured CoS_1.097 as precursors, and a strategy utilizing the synergistic effect of double metal ions was developed. Two complementary metal ions were used to enhance the performance of electrode materials. The specific capacitance of the electroactive materials was continuously improved by increasing the nickel ion content, and the electric conductivity was also enhanced when the cobalt ion was varied. Experimental results showed that the nickel ion content in Ni_<i>x</i>Co_1–<i>x</i>S_1.097 could be adjusted from <i>x</i> = 0 to 0.48. Specifically, when <i>x</i> = 0.48, the composite exhibited a remarkable maximum specific capacitance approximately 5 times higher than that of the CoS_1.097 precursors at a current density of 0.5 A g^–1. Furthermore, the specific capacitance of Ni_0.48Co_0.52S_1.097 electrodes that were modified with reduced graphene oxide could reach to 1152 and 971 F g^–1 at current densities of 0.5 and 20 A g^–1 and showed remarkably higher electrochemical performance than the unmodified electrodes because of their enhanced electrical conductivity. Thus, the strategy utilizing the synergistic effect of double metal ions is an alternative technique to fabricate high-performance electrode materials for supercapacitors and lithium ion batteries

Significant Increase in Ammonia Emissions in China: Considering Nonagricultural Sectors Based on Isotopic Source Apportionment

Isotopic source apportionment results revealed that nonagricultural sectors are significant sources of ammonia (NH3) emissions, particularly in urban areas. Unfortunately, nonagricultural sources have been substantially underrepresented in the current anthropogenic NH3 emission inventories (EIs). Here, we propose a novel approach to develop a gridded EI of nonagricultural NH3 in China for 2016 using a combination of isotopic source apportionment results and the emission ratios of carbon monoxide (CO) and NH3. We estimated that isotope-corrected nonagricultural NH3 emissions were 4370 Gg in China in 2016, accounting for an increase in the total NH3 emissions from 7 to 31%. As a result, compared to the original NH3 EI, the annual emissions of total NH3 increased by 35%. Thus, in comparison to the simulation driven by the original NH3 EI, the WRF-Chem model driven by the isotope-corrected NH3 EI has reduced the model biases in the surface concentrations and dry deposition flux of reduced nitrogen (NHx = gaseous NH3 + particulate NH4+) by 23 and 31%, respectively. This study may have wide-ranging implications for formulating targeted strategies for nonagricultural NH3 emissions controls, making it facilitate the achievement of simultaneously alleviating nitrogen deposition and atmospheric pollution in the future

Electrospun Flexible Cellulose Acetate-Based Separators for Sodium-Ion Batteries with Ultralong Cycle Stability and Excellent Wettability: The Role of Interface Chemical Groups

Na-ion batteries are one of the best technologies for large-scale applications depending on almost infinite and widespread sodium resources. However, the state-of-the-art separators cannot meet the engineering needs of large-scale sodium-ion batteries to match the intensively investigated electrode materials. Here, a kind of flexible modified cellulose acetate separator (MCA) for sodium-ion batteries was synthesized via the electrospinning process and subsequently optimizing the interface chemical groups by changing acetyl to hydroxyl partly. Upon the rational design, the flexible MCA separator exhibits high chemical stability and excellent wettability (contact angles nearly 0°) in electrolytes (EC/PC, EC/DMC, diglyme, and triglyme). Moreover, the flexible MCA separator shows high onset temperature of degradation (over 250 °C) and excellent thermal stability (no shrinkage at 220 °C). Electrochemical measurements, importantly, show that the Na-ion batteries with flexible MCA separator exhibit ultralong cycle life (93.78%, 10 000 cycles) and high rate capacity (100.1 mAh g^–1 at 10 C) in the Na/Na₃V₂(PO₄)₃ (NVP) half cell (2.5–4.0 V) and good cycle performance (98.59%, 100 cycles) in the Na/SnS₂ half cell (0.01–3 V), respectively. Moreover, the full cell (SnS₂/NVP) with flexible MCA separator displays the capacity of 98 mAh g^–1 and almost no reduction after 40 cycles at 0.118 A g^–1. Thus, this work provides a kind of flexible modified cellulose acetate separator for Na-ion batteries with great potential for practical large-scale applications

Electrospun Flexible Cellulose Acetate-Based Separators for Sodium-Ion Batteries with Ultralong Cycle Stability and Excellent Wettability: The Role of Interface Chemical Groups

Na-ion batteries are one of the best technologies for large-scale applications depending on almost infinite and widespread sodium resources. However, the state-of-the-art separators cannot meet the engineering needs of large-scale sodium-ion batteries to match the intensively investigated electrode materials. Here, a kind of flexible modified cellulose acetate separator (MCA) for sodium-ion batteries was synthesized via the electrospinning process and subsequently optimizing the interface chemical groups by changing acetyl to hydroxyl partly. Upon the rational design, the flexible MCA separator exhibits high chemical stability and excellent wettability (contact angles nearly 0°) in electrolytes (EC/PC, EC/DMC, diglyme, and triglyme). Moreover, the flexible MCA separator shows high onset temperature of degradation (over 250 °C) and excellent thermal stability (no shrinkage at 220 °C). Electrochemical measurements, importantly, show that the Na-ion batteries with flexible MCA separator exhibit ultralong cycle life (93.78%, 10 000 cycles) and high rate capacity (100.1 mAh g^–1 at 10 C) in the Na/Na₃V₂(PO₄)₃ (NVP) half cell (2.5–4.0 V) and good cycle performance (98.59%, 100 cycles) in the Na/SnS₂ half cell (0.01–3 V), respectively. Moreover, the full cell (SnS₂/NVP) with flexible MCA separator displays the capacity of 98 mAh g^–1 and almost no reduction after 40 cycles at 0.118 A g^–1. Thus, this work provides a kind of flexible modified cellulose acetate separator for Na-ion batteries with great potential for practical large-scale applications