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We studied the borohydride oxidation reaction (BOR) by voltammetry for BH4 − concentrations between 10−3 M and 0.1M NaBH4 in 0.1–1M NaOH for bulk polycrystalline Pt, Ag and alloyed Pt–Ag electrocatalysts. In order to compare the different electrocatalysts, we measured the kinetic parameters and the number of electrons exchanged (faradic efficiency). BOR on bulk Pt is more efficient when the concentration of NaBH4 increases ( ∼ 3 e − in 1mM and ∼ 6 e − in 10mM BH4 −/0.1M NaOH). BOR on Pt can occur both in a direct pathway and in an indirect pathway including hydrogen generation via heterogeneous hydrolysis of BH4 − and subsequent oxidation of its by-products (e.g. BH3OH− and H2). BOR on Ag strongly depends on the pH: improved faradic efficiency is monitored for high pH ( ∼ 2 e − at pH 12.6 and ∼ 6 e − at pH 13.9 at 25 ° C). The BOR kinetics is faster for Pt than for Ag ( i Pt = 0.02 Acm−2, i Ag = 1.4 10−7 Acm−2 at E = − 0.65 V vs. NHE in 1mM NaBH4/0.1M NaOH, 25 ° C) both as a result from Pt high activity regarding the BH4 − heterogeneous hydrolysis and subsequent HOR, above − 0.83 V vs. NHE and following direct oxidation of BH4 − or BH3OH− below − 0.83 V vs. NHE. Both Pt–Ag bulk alloys show unique behaviour: the number of electrons exchanged is rather high whatever the BH4 − concentration and pH, while the kinetic parameters are quite similar to that of platinum, showing possible synergistic alloying effect.
In this work, rutile TiO2 nanorod arrays (NRAs) are prepared on TiO2 seeding/FTO substrates by a hydrothermal process. The synthetic recipe is systematically studied to probe the morphology-synthesis interactions. Results indicate that increasing the seeding thickness greatly improves the uniformity of the top NRAs, and the initial growth for nanorods can be classified into three steps, i.e., nucleation, plant-shaped growth and array-appearance formation. The structural study suggests that each TiO2 nanorod is in fact closely-stacked by many tiny secondary nanorods parallel to each other, which could be opened by a chemical etching process. Upon etching, the performance of dye-sensitized solar cells (DSSCs) based on TiO2 NRAs is substantially improved. The device efficiency achieves a highest value of 4.46% using a 14μm NRAs etched for 3h. The charge dynamics of DSSCs was further investigated by intensity-modulated photocurrent/photovoltage spectroscopy, electrochemical impedance spectroscopy and open-circuit voltage decay. Results show that the electron collection efficiency in the TiO2 NRAs is greatly enhanced after etching, mainly due to the retarded charge recombination, which is probably induced by the morphology change of the etched NRAs. The present study reveals some important issues for growth of rutile TiO2 NRAs on seeded FTO substrates, introduces a novel etching way for improving charge collection in semiconductor NRAs, and would advance the applications of TiO2 NRAs in various areas, such as solar cells, sensors and batteries.
This article summarizes recent developments and applications of digital photogrammetry in industrial measurement. Industrial photogrammetry covers a wide field of different practical challenges in terms of specified accuracy, measurement speed, automation, process integration, cost-performance ratio, sensor integration and analysis. On-line and off-line systems are available, offering general purpose systems on the one hand and specific turnkey systems for individual measurement tasks on the other. Verification of accuracy and traceability to standard units with respect to national and international standards is inevitable in industrial practice. System solutions can be divided into the measurement of discrete points, deformations and motions, 6DOF parameters, 3D contours and 3D surfaces. Recent and future developments concentrate on higher dynamic applications, integration of systems into production chains, multi-sensor solutions and still higher accuracy and lower costs.
Numerous efforts have been made to design the cathode of Li–S batteries to enhance reversible capacity and long-term cycling stability. However, challenges remain in achieving high electronic/ionic conductivity and suppressing the shuttle effect, especially for cathodes with high sulfur loading. Here we report a 3D free-standing hierarchical structure of VO2(P) (paramontroseite VO2) nanoparticles grown on nitrogen-doped carbon nanotube (NCNT) arrays as a catalytic host for high-performance sulfur cathodes. In this architecture, the VO2(P) nanoparticles function as catalysts to oxidize the LiPS to produce thiosulfate due to the strong chemical interaction. Furthermore, thiosulfates act as a mediator to catenate long-chain LiPS together and convert short-chain Li2S2/Li2S and surface-bound polythionate complexes. Accordingly, the VO2(P)-NCNT/S cathode exhibits excellent performance with high discharge capacity output (≈1200 mA h g−1 at 0.2 C), stable long-term cycling (≈67% retention at 2 C for 500 cycles), and high sulfur loading cycling (initial areal capacity of 10.2 mA h cm−2 at 0.2 C for 200 cycles). This nanostructure catalytic cathode with high sulfur loadings, as well as stable cycling performances, is attractive for developing practically useable Li-S batteries.
Performance characteristics of a three electrolyte rechargeable acid–alkaline hybrid battery using a PbO2 positive plate and a nickel metal hydride (NiMH x ) negative electrode in separate electrolyte of H2SO4 and KOH were studied. This hybrid battery has three electrolytes in a single cell. A neutral K2SO4 salt solution was placed between the acid and alkaline compartments of the cell, in which a cation exchange membrane and an anion exchange membrane, were employed to separate these three electrolytes. The open circuit voltage of this hybrid cell was found to be 2.64V in an electrolyte configuration of 1M H2SO4|0.2MK2SO4|2M KOH electrolyte configuration, compared to 1.92V in the conventional lead-acid cell in 1M H2SO4 and 1.40V in a NiMH x cell in 2M KOH. This hybrid acid–alkaline PbO2/NiMH x battery was shown to operate with a voltage 20% higher than the conventional lead acid battery and 110% higher than nickel–metal hydride battery at 1/3C discharging rate. The concentrations of the three electrolytes, the dimension of the electrolyte chamber, and other cell/operation parameters with impacts on the hybrid cell performance were investigated.
We are conducting cycle-life testing of 10–100 Ah-class lithium-ion cells in a simulated satellite operation at the Japan Aerospace Exploration Agency (JAXA). This paper reviews the latest test results of these lithium-ion cells. Thus far, we have verified impressive life performance exceeding 30,000 cycles in a simulated low-earth-orbit (LEO) mode and 1800 cycles in a simulated geostationary-earth-orbit (GEO) mode for some of these cells. We optimized the thickness of the electrode layer to suppress cell-internal impedance and found that a lithium-ion cell with a thin electrode layer exhibited promising cycling performance in a simulated LEO operation. Since the electrode material is an important factor affecting the charge–discharge behavior of a lithium-ion cell, we also compared the cycling performance of lithium-ion cells with different cathode materials.
In this paper, the fluorescent mRNA differential display (DD) technique was applied to analyze transcriptional regulation in response to Cd treatment in a heavy-metal accumulator, Brassica juncea. 154 DD bands were identified, of which fragments corresponding to 15 and 13 cDNAs were successfully cloned from leaves and roots, respectively. Many of the genes were confirmed to have a 2–5 fold increase in expression in both roots and leaves after 48 h Cd exposure (∼22.4 ppm). However, several isolated genes, e.g., DD2, DD21, DD22, showed a reversed mRNA expression pattern. Sequencing revealed those Cd-induced up-regulated genes displayed mRNAs corresponding to 19 different genes, 18 of which had a clear identity to Arabidopsis thaliana sequences and a putative function was assigned to 15 of them, including the auxin-responsive GH3, ARF-like small GTPases/ARFs, ARD/ARD′, APS reductase, Nop, catalase, zinc finger (C3HC4-type RING finger), diacylglycerol kinase, and haloacid dehalogenase-like hydrolase families. Three cDNAs corresponded to predicted membrane proteins (KOG3491) or a ribosome-associated membrane protein RAMP4. One other clone, DD26, did not show significant identities to any translated sequence in the GenBank database, suggesting it may either encode unidentified proteins, or correspond to un-translated, non-conserved regions of mRNA molecules. These Cd-responsive up-regulated genes are mostly also regulated by abiotic or biotic stresses, e.g., dehydration, chilling, high salt, auxin, heat and infection, in other plants. The present study leads to an increased understanding of genes and/or the biochemical pathways involved in heavy-metal resistance and accumulation in plants.
We have studied the preparation of LiCoO2 powder using the metallo-organic decomposition (MOD) route in air. Cobalt and lithium 2-ethylhexanoate were obtained from hydroxides and 2-ethylhexanoic acid. TG/DTA and XRD techniques were used to study the steps of formation of well-organized LiCoO2 (R-3m). The MOD route produced LiCoO2 (R-3m) at 700°C with specific surface area 1.7m2 g−1 and grain size distribution d 50=24μm. The electrochemical response of MOD LiCoO2 powder was tested by cyclic voltammetry and discharge/charge cycles in a composite electrode. The MOD method yields LiCoO2 agglomerated particles with size distribution and porosity that facilitate lithium diffusion in the composite electrode.
Large-scale atomistic simulations were performed to investigate the fracture behaviors of amorphous lithiated silicon. The simulation results revealed that as the lithium concentration increases, there exists a transition in fracture mechanism from intrinsic nanoscale cavitation to extensive shear banding ahead of the crack tip. It is shown that the observed fracture-mechanism transition can be understood from the changing ratio between critical stresses for cavitation and plastic yield under increasing lithium content. Furthermore, we investigated the mechanistic details of cavitation (i.e. growth of nanovoids) in amorphous lithiated silicon using fully three-dimensional atomistic simulations. It was revealed that in a low lithium concentration environment, an initial void grows heterogeneously by merging with neighboring nucleated voids. However, at high lithium concentrations, the initial void continues to grow in a homogeneous mode. These atomistic mechanisms provide a fundamental understanding of how silicon anodes in lithium-ion batteries fracture during lithiation.
Collecting sensory data using a mobile data sink has been shown to drastically reduce energy consumption at the cost of increasing delivery delay. Towards improved energy-latency trade-offs, we propose a biased, adaptive sink mobility scheme, that adjusts to local network conditions, such as the surrounding density, remaining energy and the number of past visits in each network region. The sink moves probabilistically, favoring less visited areas in order to cover the network area faster, while adaptively stopping more time in network regions that tend to produce more data. We implement and evaluate our mobility scheme via simulation in diverse network settings. Compared to known blind random, non-adaptive schemes, our method achieves significantly reduced latency, especially in networks with non-uniform sensor distribution, without compromising the energy efficiency and delivery success.
Background: The aim of the study is to elucidate the association between changes in sleep EEG and alteration of cognitive functions in patients with ischemic stroke. Methods: We studied 11 consecutive patients with first-ever hemispheric ischemic stroke admitted within 3 days after symptoms onset. Stroke volume was assessed by MR imaging. Sleep EEG and nocturnal breathing were examined with a validated portable system. Cognitive function was evaluated using a standardized battery of tests. A second examination of sleep EEG and cognitive function was performed in 9 patients at least 3 months after stroke. The patients were compared with 5 gender- and age-matched healthy controls. Results: Mean age was 43±12 years (range 18–60), 4 were males. In 5 patients stroke were right-sided, in 6 left-sided. Mean volume of the stroke lesion was 82±66 ml (range 5–200). In the acute stroke phase a significant correlation between (1) sleep efficiency and attention (p=0.039) and (2) amount of REM sleep and verbal fluency (p=0.016) was found. A significant improvement of sleep efficiency (p=0.005), verbal fluency (p=0.009) and non verbal fluency (p=0.02) was found in the control examination. In the chronic phase we observed a correlation between amount of REM sleep and visual learning ability (p=0.017). Conclusions: The results suggest the presence of a link between changes in sleep EEG pattern and alteration of cognitive functions during the acute and the recovery phase after hemispheric stroke.
N-doped hollow urchin-like anatase TiO2 spheres (HUTSs) with carbon coating (HUTS@C) are prepared through a facile and scalable hydrothermal reaction followed by coating of polypyrrole and carbonization. The HUTS is composed of radially grown anatase nanorods and possesses an enhanced percentage of exposed {001} facets compared with P25 TiO2 nanoparticles. After the carbon coating, the HUTS@C retains the hollow nanostructure although covered with an N-doped carbon layer. As an anode for Li-ion batteries, the HUTS@C delivers a higher capacity of 165.1 mAh g−1 at 1C after 200 cycles and better rate capability (111.7 mAh g−1 at 10C) than the HUTS. Further electrochemical studies reveal that the HUTS@C has a better electrochemical reversibility, lower charge-transfer resistance, and higher Li-ion diffusion coefficient due to its unique nanosctructure including the hollow core, anatase phase of TiO2 microspheres with high exposed {001} facets and the N-doped carbon layer, which facilitates mass transport and enhances electrical conductivity.
With the considerable development in sulfur cathode, Li-S batteries have recently witnessed a significant improvement, especially in the gravimetric capacity and cycling performance. However, maintaining high energy density of Li-S batteries and their commercialization relies on the high areal loading and high utilization of active material on the electrode, which are always ignored in the most fundamental research reports. For the Li-S batteries with much higher sulfur loading, except for the well-known issues about polysulfide dissolution, some new issues such as electron and ion transport in thick cathode, depletion of electrolyte and lithium dendrite growth need to be addressed. Here, a Li-S battery with a high areal capacity is proposed by a systematic strategy incorporating two approaches as follows: 1) a hierarchically porous carbon host containing graphene (G), mesoporous carbon (MPC) and super P (SP) diminishes polysulfide migration and guarantees fast electron and ion transport in thick cathode; 2) a glass-fiber (GF) membrane severs as the electrolyte reservoir to prevent the short circuit resulted from the deficiency of liquid electrolyte. With these methods, the Li-S batteries with an ultrahigh sulfur loading of 13mgcm−2 provide a high areal capacity of 14.3mAhcm−2 (1099mAhg−1) at the first cycle and stable cycling performance with a reversible capacity of 628mAhg−1 (8.16mAhcm−2) after 75 cycles at 0.1C.
The generalized equivalent circuit for Hebb–Wagner polarization in the frequency domain proposed by Jamnik and Maier (J Electrochem Soc 146:4183, 1999) includes the space-charge polarization that was previously neglected. In the present work, using a self-coded Fortran program, the completely generalized equivalent circuit is successfully applied to a mixed conducting silver sulfide with an AgI electrode that suppresses the electronic flow. A whole set of fit parameters, such as geometric capacitance, partial conductivities, chemical capacitance or diffusivity, and the blocking and shunting characteristics of electrodes are independently but self-consistently obtained over a range of silver activities, as controlled by a galvanic cell. The interfacial capacitance was found to be much larger than the diffuse space-charge double-layer capacitance and was thus ascribed to the adsorption capacitance at the core of the interface, which should be connected in parallel with the space-charge double-layer polarization. Two simplified equivalent circuits were shown to be good approximations for the spectra at the extreme low and high silver activity, respectively.
Electrochemical behavior of spinel-type Li[Li x Mn2−x ]O4 samples is examined in sodium containing non-aqueous electrolyte solution. Li ions in stoichiometric LiMn2O4 sample are electrochemically extracted in sodium containing electrolyte solution, forming Li x Mn2O4 (x =0.1) by first oxidation process. Sodium ions are inserted into the lithium extracted spinel phase, which results in the phase transition. From structural analysis by X-ray diffraction and phase transition behavior in the sodium cells, it is found that an original spinel phase in part converts into a layered phase, Na y MnO2. Thus prepared Na y MnO2 can deliver approximately 190–200mAhg−1 of reversible capacity with relatively good capacity retention as positive electrode materials for rechargeable sodium batteries. Nonstoichiometric Li-rich manganese spinel, Li[Li0.2Mn1.8]O4, also accommodates the sodium ions, similarly to the stoichiometric phase. However, phase transition to the layered phase is not observed. Instead, the sodium insertion into Li[Li0.2Mn1.8]O4 induces strain in the crystal lattice.
A Pt–Zr catalyst coated FeCrAlYmesh is introduced into the combustion outlet conduit of a newly designed microchannel reactor (MCR) as an igniter of hydrogen combustion to decrease the start-up time. The catalyst is coated using a wash-coating method. After installing the Pt–Zr/FeCrAlYmesh, the reactor is heated to its running temperature within 1min with hydrogen combustion. Two plate-type heat-exchangers are introduced at the combustion outlet and reforming outlet conduits of the microchannel reactor in order to recover the heat of the combustion gas and reformed gas, respectively. Using these heat-exchangers, methane steam reforming is carried out with hydrogen combustion and the reforming capacity and energy efficiency are enhanced by up to 3.4 and 1.7 times, respectively. A compact fuel processor and fuel-cell system using this reactor concept is expected to show considerable advancement.
Lithium (Li) metal battery is one of the ideal candidates for the next-generation high-energy-density batteries, but its practical application is still plagued by its large volume change, low coulombic efficiency (CE), and safety issues related to dendrite growth. This work describes a potential solution to these issues using a cross-linked Li9Al4-Li3N-AlN (LLA) structure as a stable host for Li metal anode. The in situ-formed uniform Li9Al4 and Li3N sites on AlN nano-clusters can suppress dendrite growth during the Li plating/stripping process. The intrinsic lithiophilicity of Li9Al4 sites with adjacent Li3N attracts Li+ ions for fast migration and uniform plating/stripping. These unique features lead to dimensional stability of Li@LLA composite anodes (1540 mAh g−1 and 1600 mAh cm−3). High-rate, high-capacity cycling of Li metal anodes has been maintained with a CE of ~98% in carbonate-based electrolytes. High capacity retention of 90.1% is achieved for a Li@LLA||LiNi0.8Co0.1Mn0.1O2 full cell at the 200th cycle. Therefore, the LLA structure with a simple fabrication process could be a promising candidate to enhance the safety of next-generation Li metal batteries.
The effect of fast and three-step charge mode on the capacity and cycle life of lead–acid battery negative plates was investigated using a model mini electrode (ME). It has been found that the charge algorithm exerts a strong effect on the charge acceptance of the negative electrode. In the two-step charging mode I 1, ϕ 2 with increase of the current at the first step of charge, the capacity of the negative electrode decreases and the cycle life shortens. This phenomenon is reversible as it is probably due to the incomplete reduction of PbSO4 to Pb. The phenomenon is explained based on the mechanism of the process of reduction of PbSO4. At high initial charge currents, the concentration of H2SO4 in the pores of NAM increases, which decreases the solubility of PbSO4 crystals and limits the charge acceptance of the negative plate. The higher initial charge current influences markedly the formation of smaller Pb crystals that build up the energetic structure of the negative active material. It is essential that a third step with a small constant current, I 3 is added to the charge algorithm. The third step of charge in the I 1, ϕ 2, I 3 charge mode decreases the Ohmic resistance and ensures complete charge of the lead electrode.
Biotelemetry offers an increasing set of tools to monitor animals. Acceleration sensors in particular can provide remote observations of animal behavior at high temporal resolution. While recent studies have demonstrated the capability of this technique for a wide range of species and behaviors, a coherent methodology is still missing (1) for behavior monitoring of large herbivores that are usually tagged with neck collars and frequently switch between diverse behaviors and (2) for monitoring of vigilance behavior. Here, we present an approach that aims at remotely monitoring different types of large herbivore behavior including vigilance with acceleration data.
Hybrid Mg2+/Li+ batteries featuring dendrite-free Mg anode and Li-storage cathode are promising safe energy storage systems. However, improving the energy density remains a grand challenge due to the quite limited capacities of traditional Li-intercalation cathodes. To circumvent this limitation, a new type of conversion cathode for hybrid Mg2+/Li+ batteries, microflower-like Cu9S5, is reported herein. The Cu9S5 cathode is compatible with the dual-salt Mg2+/Li+ electrolyte, and delivers a high reversible capacity of 300 mAh g−1 at 50 mA g−1 via electrochemical conversion reaction, with 94% capacity retention over 100 cycles in hybrid Mg2+/Li+ batteries. The electrode also shows an outstanding rate capability providing 155 mAh g−1 at 1000 mA g−1 and a superior long-term cycleability over 1000 cycles. This excellent performance is attributed to the hierarchical architecture of Cu9S5 which facilitates the reversible conversion reactions and stabilizes the electrode structure during discharge/charge process. This work provides new insight for the nanostructure design of stable conversion electrodes, and opens a new avenue for building safe and high-performance hybrid Mg2+/Li+ batteries for practical applications.
Pelvic exenteration remains one of the most mutilating procedures, with important postoperative morbidity, an altered body image, and long-term physical and psychosocial concerns. This study aimed to assess quality of life (QOL) during the first year after pelvic exenteration for gynecologic malignancy performed with curative intent.
Harry Nussbaumer, Professor Emeritus at the Swiss Federal Institute of Technology, and Lydia Bieri, an assistant professor in the mathematics department at Harvard, have written an engaging history of our unfolding understanding of one of the most important discoveries of 20th-century astronomy—the expanding universe. Beginning with an overview of some seeds of modern cosmology planted in late medieval texts, they use primary documents to focus on the work of major contributors to the idea.