- Synaptic learning behavior of TiO<sub>2</sub> nanowire memristor. [Journal Article]
- NNanotechnology 2019 Jul 15
- TiO&lt;sub&gt;2&lt;/sub&gt; nanowire memristors were fabricated by dielectrophoresis. The responding current of the memristor continuously increases and decreases with the consecutive…
TiO&lt;sub&gt;2&lt;/sub&gt; nanowire memristors were fabricated by dielectrophoresis. The responding current of the memristor continuously increases and decreases with the consecutive positive and negative sweep voltage, which is similar to the nonlinear transmission characteristics of biological synapses. Spike-rate-dependent plasticity and learning behaviors of TiO&lt;sub&gt;2&lt;/sub&gt; memristor were studied by applying programmed pulses. The pulses with higher amplitude, bigger width and smaller interval cause a larger excitatory postsynaptic current. The number of relearning pulses is decreased with the learning experience, and a deepening memory will be consolidated by the repeated learning process. A mechanism based on the oxygen vacancy migration is proposed for the learning behavior. Excess oxygen vacancies are generated during the learning process and the conducting pathways are formed by the vacancy drift under the applied voltage. After removing the voltage at the forgetting process, back diffusion and electron trapping of the oxygen vacancies dominate the relaxation time, and the metastable atoms are formed with the involvement of the oxygen atoms. However, weak chemical bonding among the metastable atoms leads to the migration of the regenerated oxygen vacancies again, contributing to the enhanced current in the relearning process.
- A Divide-and-Conquer Approach to Compressed Sensing MRI. [Journal Article]
- MRMagn Reson Imaging 2019 Jul 12
- Compressed sensing (CS) theory assures us that we can accurately reconstruct magnetic resonance images using fewer k-space measurements than the Nyquist sampling rate requires. In traditional CS-MRI …
Compressed sensing (CS) theory assures us that we can accurately reconstruct magnetic resonance images using fewer k-space measurements than the Nyquist sampling rate requires. In traditional CS-MRI inversion methods, the fact that the energy within the Fourier measurement domain is distributed non-uniformly is often neglected during reconstruction. As a result, more densely sampled low-frequency information tends to dominate penalization schemes for reconstructing MRI at the expense of high-frequency details. In this paper, we propose a new framework for CS-MRI inversion in which we decompose the observed k-space data into "subspaces" via sets of filters in a lossless way, and reconstruct the images in these various spaces individually using off-the-shelf algorithms. We then fuse the results to obtain the final reconstruction. In this way we are able to focus reconstruction on frequency information within the entire k-space more equally, preserving both high and low frequency details. We demonstrate that the proposed framework is competitive with state-of-the-art methods in CS-MRI in terms of quantitative performance, and often improves an algorithm's results qualitatively compared with its direct application to k-space.
- Impacts of SO2, Relative Humidity, and Seed Acidity on Secondary Organic Aerosol Formation in the Ozonolysis of Butyl Vinyl Ether. [Journal Article]
- ESEnviron Sci Technol 2019 Jul 12
- Alkyl vinyl ethers are widely used as fuel additives. Despite this, their atmospheric chemistry and secondary organic aerosol (SOA) formation potentials are still not well known under complex polluti…
Alkyl vinyl ethers are widely used as fuel additives. Despite this, their atmospheric chemistry and secondary organic aerosol (SOA) formation potentials are still not well known under complex pollution conditions. In this work, we examined the impact of SO2, relative humidity (RH), and particle acidity on the formation and oxidation state (OSc) of SOA from butyl vinyl ether (BVE) ozonolysis. Increasing SO2 concentration produced a notable promotion of SOA formation and OSc due to the significant increase in H2SO4 particles and formation of more highly oxidized components. Increased RH in the presence of SO2 appeared to promote, suppress, and dominate the formation and OSc of SOA in the dry range (1%-10%), low RH range (10%-42%), and moderate RH range (42%-64%), respectively. This highlights the importance of competition between H2O and SO2 in reacting with the stabilized Criegee intermediate (sCI) in BVE ozonolysis at ambient RH. Increased particle acidity mainly contributed to the change in chemical composition of BVE-dominated SOA but not to SOA formation. Results presented here extend previous analysis of BVE-derived SOA and further aid our understanding of SOA formation potential of BVE ozonolysis under highly complex pollution conditions.
- Ammonolysis as an important loss process of acetaldehyde in the troposphere: energetics and kinetics of water and formic acid catalyzed reactions. [Journal Article]
- PCPhys Chem Chem Phys 2019 Jul 12
- The reaction of ammonia with acetaldehyde as a potential source of 1,1-aminoethanol in the troposphere has been investigated by electronic structure and chemical kinetics calculations. The reaction w…
The reaction of ammonia with acetaldehyde as a potential source of 1,1-aminoethanol in the troposphere has been investigated by electronic structure and chemical kinetics calculations. The reaction was found to involve very high activation energy and consequently the rate coefficient value was found to be too small to have any significant atmospheric implication. Therefore, the catalytic effects of water (monomer and dimer) and formic acid on the reaction have also been studied. The water catalyzed reaction involves significantly lower barrier height, more so for dimer than monomer, whereas formic acid makes the reaction effectively barrierless. In terms of rate coefficients too, formic acid was found to be the most efficient followed by water dimer and monomer. Further, comparative studies under various tropospheric conditions among the catalyzed reaction channels have been carried out using relative rate calculations with respect to the uncatalyzed channel. Relative rate calculations indicate that the formic acid catalyzed channel would dominate over the water catalyzed channels at 0 km altitude when the concentration of the former is high, but water catalyzed channels would dominate under hot and humid conditions if the concentration of formic acid remains low. At higher altitudes in the troposphere, 1,1-aminoethanol formation through ammonolysis of acetaldehyde would almost exclusively follow the formic acid catalyzed channel.
- Heterologous Expression of Argininosuccinate Synthase From Oenococcus oeni Enhances the Acid Resistance of Lactobacillus plantarum. [Journal Article]
- FMFront Microbiol 2019; 10:1393
- Oenococcus oeni can survive well in wine (an acid-stress environment) and dominate malolactic fermentation (MLF). To demonstrate a possible role of argininosuccinate synthase gene (argG) in the acid …
Oenococcus oeni can survive well in wine (an acid-stress environment) and dominate malolactic fermentation (MLF). To demonstrate a possible role of argininosuccinate synthase gene (argG) in the acid tolerance response of O. oeni, a related argG gene was inserted into a plasmid pMG36e and heterologously expressed in Lactobacillus plantarum SL09, a wine isolate belonging to a species of relevant importance in MLF. The expression levels of the argG gene in L. plantarum were analyzed by RT-qPCR, argininosuccinate synthase (ASS) activity and cell properties (amino acids, pH, H+-ATPase activity, and ATP levels) were determined at pH 3.7 in comparison with that at pH 6.3. Results showed that the recombinant strain L. plantarum SL09 (pMG36eargG) exhibited stronger growth performance compared with the control strain (without argG gene), and the expression levels of hsp1, cfa, atp, the citrate and malate metabolic genes were apparently increased under acid stress. In addition, the recombinant strain exhibited 11.0-, 2.0-, 1.9-fold higher ASS activity, H+-ATPase activity and intracellular ATP level, compared with the corresponding values for control strain during acid-stresses condition, which may take responsible for the acid tolerance enhancement of the recombinant strain. This is the first work report on heterologous expression of argG gene, and the results presented in this study will be beneficial for the research on acid stress response of O. oeni.
- A meta-analysis of bone morphogenetic protein-2 versus iliac crest bone graft for the posterolateral fusion of the lumbar spine. [Journal Article]
- JBJ Bone Miner Metab 2019 Jul 10
- The impact of autologous iliac crest bone graft versus BMP-2 to improve fusion rates for posterolateral fusion (PLF) of the lumbar spine remains unanswered. Single-institution-centered data dominate …
The impact of autologous iliac crest bone graft versus BMP-2 to improve fusion rates for posterolateral fusion (PLF) of the lumbar spine remains unanswered. Single-institution-centered data dominate the literature, providing results that may be contradictory or inconclusive. The aim of this paper is to analyze data pooled from multiple well-controlled studies that examined both ICBG and BMP-2 for use in PLF. This meta-analysis also provides details of success in different subsets of patients with variable risk factors for delayed and non-unions. Six high-quality randomized clinical trials were selected. Efficacy, morbidity, quality of life, and safety were compared between the BMP-2 group and the ICBG group. A total of 908 patients were included in the study. At 24 months, 94% of patients achieved fusion in the BMP-2 group and 83% in the ICBG group. At 6 and 12 months, the fusion was also greater in the BMP-2 group (86% vs. 60% and 88% vs. 80%, respectively). Surgical time, intraoperative blood loss, and hospitalization days also showed significant differences in favor of the experimental group (p < 0.01). There were no differences between two groups in the Oswestry Disability Index, 36-Item Short Form Health Survey and Back Pain Score, whereas a greater number of additional surgical procedures were performed in the ICBG group (p = 0.001). In conclusion, the use of BMP-2 in PLF reduced the surgical morbidity and had more beneficial effects on the fusion rate. The quality of life based on clinical scores was the same in both groups.
- Stability and flexibility in cognitive control: Interindividual dynamics and task context processing. [Journal Article]
- PlosPLoS One 2019; 14(7):e0219397
- Adaptive behaviour requires cognitive control for shielding current goals from distractors (stability) but at the same time for switching between alternative goals (flexibility). In this behavioural …
Adaptive behaviour requires cognitive control for shielding current goals from distractors (stability) but at the same time for switching between alternative goals (flexibility). In this behavioural study, we examine the stability-flexibility balance in left- and right-handers during two types of decision-making, instructed (sensory cued) and voluntary (own choice), by means of distractor inhibition and hand/task switching. The data revealed that both groups showed opposite tendencies for instructed decision-making. Moreover, right-handers resisted distracting information more efficiently whereas left-handers showed superior switching abilities. When participants were involved in voluntary decision-making, no effects of handedness were noted, which suggests that free-choice processing alters the balance between stability and flexibility. These data illustrate that handedness is an index of individual variation during instructed decision-making, biasing the proficiency of cognitive control towards stability and flexibility of information processing. These biases can however be overruled by top-down strategies that dominate during voluntary decision-making. Overall, the research underlines the antagonistic functions of stability and flexibility in decision-making, and offers an approach for examining cognitive control and the role of internal and external factors in balancing the stability-flexibility trade-off.
- Engineering unique ball-in-ball structured (Ni0.33Co0.67)9S8@C nanospheres for advanced sodium storage. [Journal Article]
- AAACS Appl Mater Interfaces 2019 Jul 10
- Constructing hollow architectures based on metal sulfides is of great interest for high-performance electrode materials for sodium ion batteries due to their intriguring properties and various applic…
Constructing hollow architectures based on metal sulfides is of great interest for high-performance electrode materials for sodium ion batteries due to their intriguring properties and various applications. However, the relatively low volumetric density and high fragile structure are the obstacles blocking the development of hollow-structured electrode materials. In this work, ball-in-ball structured (Ni0.33Co0.67)9S8@C nanospheres have been synthesized by using NiCo-glycerate as the precursor via solvothermal reaction, which was followed by a carbon coating treatment. In this structural design, hollow cavities are generated between the inner and outer balls to effectively accommodate the volume changes of the metal sulfides in the processes of charging/discharging, while the uniform carbon coating can increase the electrical conductivity and maintain the structural stability during repeated cycling. The Rietveld refinement, in situ X-ray diffraction, and ex situ X-ray photoelectron spectroscopy analyses provide evidence for an enlarged lattice parameter, weaker Co-S and Ni-S bonding, and a synergistic effect in the (Ni0.33Co0.67)9S8@C towards boosting the conversion reaction and reversible formation of sulfur in the fully charged state, with the sulfur trapped within the composite to additionally account for the superior cycling stability of this material. Capacitive behavior has been verified to dominate the electrochemical reaction, enabling fast charge transport kinetics. Impressively, the double structural protection combined with the free hollow space and complete carbon layer endows the (Ni0.33Co0.67)9S8@C nanospheres with good electrochemical performance, featuring high cyclability and good rate capability.
- Nanodiamond for Sample Preparation in Proteomics. [Journal Article]
- ACAnal Chem 2019 Jul 10
- Protein analysis of potential disease markers in blood is complicated by the fact that proteins in plasma show very different abundances. As a result, highly abundant proteins dominate the analysis, …
Protein analysis of potential disease markers in blood is complicated by the fact that proteins in plasma show very different abundances. As a result, highly abundant proteins dominate the analysis, which often render analysis of low abundance proteins impossible. Depleting highly abundant proteins is one strategy to solve this problem. Here we present for the first time a very simple approach based on selective binding of serum proteins to the surface of nanodiamonds. In our first proof of principle experiments we were able to detect on average 8 proteins that are below a ng/ml (instead of 0,5 in the control without sample prepa-ration). Remarkably, we detect proteins down to a concentration of 400 pg/ml after only one simple depletion step. Among the proteins we could analyze are also numerous disease biomarkers including markers for multiple cancer forms, cardiovascular dis-eases or Alzheimer's disease. Remarkably, many of the biomarkers we find could also not be detected with a state-of-the-art UHPLC column (which depletes the 64 most abundant serum proteins).
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- Abortion among adolescents in Africa: A review of practices, consequences, and control strategies. [Review]
- IJInt J Health Plann Manage 2019 Jul 09
- CONCLUSIONS: Adolescents are more likely to use clandestine methods of abortion whose consequences are devastating, lifelong, or even fatal. Awareness and utilization of youth-friendly services would minimize the problem.