A novel true random number generator based on a stochastic diffusive memristor

The intrinsic variability of switching behavior in memristors has been a major obstacle to their adoption as the next generation universal memory. On the other hand, this natural stochasticity can be valuable for hardware security applications. Here we propose and demonstrate a novel true random number generator (TRNG) utilizing the stochastic delay time of threshold switching in a Ag:SiO2 diffusive memristor, which exhibits evident advantages in scalability, circuit complexity and power consumption. The random bits generated by the diffusive memristor TRNG passed all 15 NIST randomness tests without any post-processing, a first for memristive-switching TRNGs. Based on nanoparticle dynamic simulation and analytical estimates, we attributed the stochasticity in delay time to the probabilistic process by which Ag particles detach from a Ag reservoir. This work paves the way for memristors in hardware security applications for the era of Internet of Things (IoT)

Anatomy of Ag/Hafnia‐Based Selectors with 1010 Nonlinearity

Sneak path current is a significant remaining obstacle to the utilization of large crossbar arrays for non-volatile memories and other applications of memristors. A two-terminal selector device with an extremely large current-voltage nonlinearity and low leakage current could solve this problem. We present here a Ag/oxide-based threshold switching (TS) device with attractive features such as high current-voltage nonlinearity (~1010 ), steep turn-on slope (less than 1 mV/dec), low OFF-state leakage current (~10-14 A), fast turn ON/OFF speeds (108 cycles). The feasibility of using this selector with a typical memristor has been demonstrated by physically integrating them into a multilayered 1S1R cell. Structural analysis of the nanoscale crosspoint device suggests that elongation of a Ag nanoparticle under voltage bias followed by spontaneous reformation of a more spherical shape after power off is responsible for the observed threshold switching of the device. Such mechanism has been quantitatively verified by the Ag nanoparticle dynamics simulation based on thermal diffusion assisted by bipolar electrode effect and interfacial energy minimization

Comparison of the () human (hs), () chimpanzee (pt), () rhesus monkey (mma), () baboon (pa), () dog (cf), () chicken (gg), and () zebrafish (dr) clusters

<p><b>Copyright information:</b></p><p>Taken from "Adaptive evolution of multiple-variable exons and structural diversity of drug-metabolizing enzymes"</p><p>http://www.biomedcentral.com/1471-2148/7/69</p><p>BMC Evolutionary Biology 2007;7():69-69.</p><p>Published online 2 May 2007</p><p>PMCID:PMC1885805.</p><p></p> Each cluster contains multiple variable first exons arrayed in tandem and a common set of 4 downstream constant exons. These exons are indicated by vertical colored bars: (green) phenol-group variable exons; (orange) bilirubin-group variable exons; (blue) zebrafish variable exons; (gray) pseudogene (ψ) or relic (r); and (red) constant exons. The approximate length of each cluster is shown below the corresponding panels

Phylogenetic tree of human (h), chimpanzee (c), rhesus monkey (m), baboon (b), dog (d), chicken (gg), and zebrafish (z) clusters

<p><b>Copyright information:</b></p><p>Taken from "Adaptive evolution of multiple-variable exons and structural diversity of drug-metabolizing enzymes"</p><p>http://www.biomedcentral.com/1471-2148/7/69</p><p>BMC Evolutionary Biology 2007;7():69-69.</p><p>Published online 2 May 2007</p><p>PMCID:PMC1885805.</p><p></p> The major tree branches are labeled with the percentage support (only when >50%) for that partition based on 1,000 bootstrap replicates. The scale bar equals a distance of 0.1

Comparison of the () human (hs), () chimpanzee (pt), () rhesus monkey (mma), () dog (cf), () mouse (mms), () rat (rn), () opossum (md), () chicken (gg), () frog (xt), and () zebrafish (dr) clusters

<p><b>Copyright information:</b></p><p>Taken from "Adaptive evolution of multiple-variable exons and structural diversity of drug-metabolizing enzymes"</p><p>http://www.biomedcentral.com/1471-2148/7/69</p><p>BMC Evolutionary Biology 2007;7():69-69.</p><p>Published online 2 May 2007</p><p>PMCID:PMC1885805.</p><p></p> Each cluster contains multiple-variable and highly-similar first exons (green boxes) arrayed in tandem and a common set of two downstream constant exons (red boxes). Exon length is indicated within each box. The approximate length of each cluster is shown below the corresponding panels

Asymmetric Catalytic 1,2-Hydroperoxidation of Isatin-Derived Ketimine with Hydrogen Peroxide in the Crowding Environment of PEGs

The first enantioselective catalytic 1,2-hydroperoxidation has been achieved in the presence of PEG-600 using an acid–base bifunctional chiral squaramide as the organocatalyst, affording a range of enantioenriched α-<i>N</i>-substituted hydroperoxides bearing an oxindole moiety with excellent stereoselectivities (up to 99% ee)

Band Structure Engineering: Insights from Defects, Band Gap, and Electron Mobility, from Study of Magnesium Tantalate

Anion doping of semiconductors with nitrogen is a strategy often adopted to narrow the band gap of semiconductors and increase the range of light absorption. However, the influence of nitrogen doping on the electron mobility in the semiconductor is not fully understood and characterized. In this work, we used magnesium tantalate MgTa2O6 as a model system and hybrid density-functional theory calculations to characterize the mobility of electrons using the small polaron model in the presence of nitrogen-doping defects as well as oxygen-vacancy defects. We found that electron mobility is not significantly affected when MgTa2O6 is doped with a molar ratio N/O of ∼2%. However, in the presence of oxygen vacancies combined with nitrogen doping with the same molar ratio N/O of ∼2%, the barrier to electron hopping in the vicinity of the defects is much lower than that in pristine MgTa2O6 and in MgTa2O6 with oxygen-vacancy defects only. These results suggest that nitrogen doping combined with anion vacancy not only narrows band gap but also enhances electron mobility, a finding that may lead to new strategies toward synthesizing more efficient photocatalysts

Guidelines for Therapeutic Drug Monitoring of Vancomycin: A Systematic Review

<div><p>Background and Objective</p><p>Despite the availability of clinical practice guidelines (CPGs) for therapeutic drug monitoring (TDM) of vancomycin, vancomycin serum concentrations still do not reach therapeutic concentrations in many patients. Thus, we sought to systematically review the quality and consistency of recommendations for an international cohort of CPGs regarding vancomycin TDM.</p><p>Methods</p><p>PubMed, Embase, guidelines' websites and Google were searched for CPGs for vancomycin TDM. Two independent assessors rated the quality of each CPG using the Appraisal of Guidelines for Research & Evaluation II (AGREEII) instrument and data were independently extracted.</p><p>Results</p><p>Twelve guidelines were evaluated and the overall quality of guidelines for vancomycin TDM was moderate. The highest score was recorded in the domain of clarity of presentation, and the lowest score was recorded in the domain of rigor of development and stakeholder involvement. The specific recommendations for vancomycin TDM were moderately consistent and guidelines varied in trough concentration monitoring, frequency of TDM, and serum concentration targets.</p><p>Conclusion</p><p>The overall guideline quality for vancomycin TDM was not optimal and effort is needed to improve guideline quality, especially in the domain of rigor of development and stakeholder involvement.</p></div

Theoretical Study of Structure, Stability, and the Hydrolysis Reactions of Small Iridium Oxide Nanoclusters

The geometric structures and relative stabilities of small iridium oxide nanoclusters, Ir_<i>m</i>O_<i>n</i> (<i>m</i> = 1–5 and <i>n</i> = 1–2<i>m</i>), have been systematically investigated using density functional theory (DFT) calculations at the B3LYP level. Our results show that the lowest-energy structures of these clusters can be obtained by the sequential oxidation of small “core” iridium clusters. The iridium-monoxide-like clusters have relatively higher stability because of their relatively high binding energy and second difference in energies. On the basis of the optimized lowest-energy structures of neutral and cationic (IrO₂)_<i>n</i> (<i>n</i> = 1–5), DFT has been used to study the hydrolysis reaction of these clusters with water molecules. The calculated results show that the addition of water molecules to the cationic species is much easier than the neutral ones. The overall hydrolysis reaction energies are more exothermic for the cationic clusters than for the neutral clusters. Our calculations indicate that H₂O can be more easily split on the cationic iridium oxide clusters than on the neutral clusters

Methanol Steam Reforming for Hydrogen Production over CuZnZrOx: Promotion Effect of Cu

Mixed metal oxides catalyze steam reforming of methanol (SRM) usually at reaction temperatures of >400 °C, leading to high energy consumption. Herein, we report that a small amount of Cu doping can greatly promote the activity of ZnZrOx in the SRM at low temperatures. The 2%CuZnZrOx can efficiently catalyze the SRM at temperatures as low as 300 °C to give 95.3% methanol conversion, but ZnZrOx only shows low methanol conversion (23.6%) under similar reaction conditions. Structural characterizations show that CuZnZrOx catalysts are ternary solid solutions rich in Ov, which is favorable for water activation. CuZnZrOx with low-valence Cuδ+ shows faster kinetics for the generation and decomposition of HCOOH intermediate than ZnZrOx. The co-presence of Cuδ+ and Ov contributes to the excellent performance of CuZnZrOx. These findings provide an efficient strategy for promoting the catalytic performance of metal oxides toward SRM