Phase competition induced nonlinear elastoresistance effect in thin films of Pr0.7Sr0.3MnO3

Thin films of Pr 0.7Sr 0.3MnO 3 grown on 0.7PbMg 1/3Nb 2/3O 3-0.3PbTiO 3 substrates were reversibly strained via the converse piezoelectric effect. The transport properties of Pr 0.7Sr 0.3MnO 3 were effectively modulated by the electric fields across the substrate. The roles of strain were explored by measuring resistance as a function of electric field and temperature. For all samples, deviations from a linear resistance-voltage relation were found. Two quantities, area difference and standard deviation, were used to characterize the nonlinearity. Both the nonlinearity and magnitude of resistance modulation peak at temperatures close to those of metal-insulator transition, indicating that the competing phases significantly changes the behaviors of strain responses. © 2012 American Institute of Physics.published_or_final_versio

Persistent photoconductivity induced by electric currents in epitaxial thin films of Pr0.7Sr0.3MnO3

The effects of electric currents on the photoconductivity of epitaxial Pr0.7Sr0.3MnO3 films were studied. The as-prepared films showed a transient photoconductivity in a wide temperature range. After the films were processed by a current of density ∼10 5 A/cm2 for certain duration at room temperature, a highly resistive and metastable state was excited at low temperature. This induced state exhibited significant electroresistance and persistent photoconductivity. The phenomena found in films grown on LaAlO3 were similar to those on SrTiO3. The observed effects might be related to the coexistence and instability of the multiphases in manganites. © 2011 American Institute of Physics.published_or_final_versio

Insights from Modeling the 3D Structure of New Delhi Metallo-β-Lactamse and Its Binding Interactions with Antibiotic Drugs

New Delhi metallo-beta-lactamase (NDM-1) is an enzyme that makes bacteria resistant to a broad range of beta-lactam antibiotic drugs. This is because it can inactivate most beta-lactam antibiotic drugs by hydrolyzing them. For in-depth understanding of the hydrolysis mechanism, the three-dimensional structure of NDM-1 was developed. With such a structural frame, two enzyme-ligand complexes were derived by respectively docking Imipenem and Meropenem (two typical beta-lactam antibiotic drugs) to the NDM-1 receptor. It was revealed from the NDM-1/Imipenem complex that the antibiotic drug was hydrolyzed while sitting in a binding pocket of NDM-1 formed by nine residues. And for the case of NDM-1/Meropenem complex, the antibiotic drug was hydrolyzed in a binding pocket formed by twelve residues. All these constituent residues of the two binding pockets were explicitly defined and graphically labeled. It is anticipated that the findings reported here may provide useful insights for developing new antibiotic drugs to overcome the resistance problem

Nanoimaging of Organic Charge Retention Effects: Implications for Nonvolatile Memory, Neuromorphic Computing, and High Dielectric Breakdown Devices

While a large variety of organic and molecular materials have been found to exhibit charge memory effects, the underlying mechanism is not well-understood, which hinders rational device design. Here, we study the charge retention mechanism of a nanoscale memory system, an organic monolayer on a silicon substrate, with Au nanoparticles on top serving as the electrical contact. Combining scanning probe imaging/manipulation and density functional simulations, we observe stable charge retention effects in the system and attributed it to polaron effects at the amine functional groups. Our findings can pave the way for applications in nonvolatile memory, neuromorphic computing, and high dielectric breakdown devices

Influences of leakage currents on the transport properties and photoelectric effects in heterojunctions composed of colossal magnetoresistance manganites and Nb-doped titanates

The effects of leakage currents were investigated for Pr 0.7Sr 0.3MnO 3/Nb-SrTiO 3 heterojunctions. It was found that small amounts of leakage currents could cause pronounced detriment to the rectifying properties but had very limited impacts on the barrier heights determined from the forward currents. Significant open circuit voltages V OC were observed when the highly rectified junctions were illuminated by a visible light with a wavelength of 532 nm. For the less rectified junctions, the leakage currents reduced V OC severely and resulted in an anomalous temperature dependence of V OC. Theories for semiconductor contacts were employed in order to discuss these results. © 2012 American Institute of Physics.published_or_final_versio

Flow patterns and cleaning behaviour of horizontal liquid jets impinging on angled walls

Liquid jets are widely used in cleaning operations in the food sector. Morison and Thorpe (2002) reported an experimental investigation of the flow patterns and cleaning behaviour of horizontal jets impinging on vertical walls. The Wilson et al. (2012) model, which described Morison and Thorpe's flow pattern data well, is extended to describe the flow pattern generated by a liquid jet, approaching a surface at a given angle to the horizontal, impinging on a plate inclined at a known angle to the vertical. The results are compared with experimental data collected for horizontal water jets impinging on inclined Perspex and glass plates. Tests employed nozzle diameters of 1, 2 and 3mm at room temperature, using flow rates of 0.78–2.23gs−1, 3.7–9.9gs−1 and 7.1–17.3gs−1 (0.025–0.062m3h−1) respectively. These are lower than industrial cleaning flow rates. The angle at which the horizontal jet impinged on the plate was varied from 30° to 120°. Two important dimensions are evaluated: (i) the width of the fast moving radial flow zone on the plate (the region bounded by the film jump, the feature similar to a hydraulic jump) at the plane of impingement; (ii) the distance on the plate to which the radial flow zone extends above the point of impingement. Both are described reasonably well by the model. Empirical relationships are reported for the width of the wetted region at the level of impingement, and the maximum width of the draining film. A short study of cleaning of layers of washable paint on glass, similar to the tests reported by Morison and Thorpe, show that the cleaning model recently developed by Wilson et al. (2014) gives a good description of the initial cleaning of such layers using an impinging stationary coherent water jet.A PhD scholarship for TW from Chengda Engineering Co. is gratefully acknowledged.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.fbp.2014.09.00

Electric currents induced step-like resistive jumps and negative differential resistance in thin films of Nd0.7Sr0.3MnO3

Electric-currents-induced emergent phenomena were found in microbridges of Nd 0.7Sr 0.3MnO 3. After the samples were processed by currents of high densities, a second metal-insulator transition appeared at low temperatures. This resistance peak was very sensitive to weak currents. More salient features were the step-like resistance jumps. At temperatures near these resistance steps, negative differential resistance was observed. Interfacial effects related to electrodes could be ruled out. These effects might be due to current-enhanced inhomogeneity. © 2012 American Institute of Physics.published_or_final_versio

Rectifying Unfairness in Recommendation Feedback Loop

The issue of fairness in recommendation systems has recently become a matter of growing concern for both the academic and industrial sectors due to the potential for bias in machine learning models. One such bias is that of feedback loops, where the collection of data from an unfair online system hinders the accurate evaluation of the relevance scores between users and items. Given that recommendation systems often recommend popular content and vendors, the underlying relevance scores between users and items may not be accurately represented in the training data. Hence, this creates a feedback loop in which the user is not longer recommended based on their true relevance score but instead based on biased training data. To address this problem of feedback loops, we propose a two-stage representation learning framework, B-FAIR, aimed at rectifying the unfairness caused by biased historical data in recommendation systems. The framework disentangles the context data into sensitive and non-sensitive components using a variational autoencoder and then applies a novel Balanced Fairness Objective (BFO) to remove bias in the observational data when training a recommendation model. The efficacy of B-FAIR is demonstrated through experiments on both synthetic and real-world benchmarks, showing improved performance over state-of-the-art algorithms

Evolution of superconductivity in K2-xFe4+ySe5: Spectroscopic studies of X-ray absorption and emission.

This study investigates the evolution of superconductivity in K2-xFe4+ySe5 using temperature-dependent X-ray absorption and resonant inelastic X-ray scattering techniques. Magnetization measurements show that polycrystalline superconducting (SC) K1.9Fe4.2Se5 has a critical temperature (T c) of ∼31 K with a varying superconducting volume fraction, which strongly depends on its synthesis temperature. An increase in Fe-structural/vacancy disorder in SC samples with more Fe atoms occupying vacant 4d sites is found to be closely related to the decrease in the spin magnetic moment of Fe. Moreover, the nearest-neighbor Fe-Se bond length in SC samples exceeds that in the non-SC (NS) sample, K2Fe4Se5, which indicates a weaker hybridization between the Fe 3d and Se 4p states in SC samples. These results clearly demonstrate the correlations among the local electronic and atomic structures and the magnetic properties of K2-xFe4+ySe5 superconductors, providing deeper insight into the electron pairing mechanisms of superconductivity

Proteomic characterization of the cytotoxic mechanism of gold (III) porphyrin 1a, a potential anticancer drug

There has been increasing interest in the potential applications of gold (III) complexes as anticancer drugs with higher cytotoxicity and fewer side effects than existing metal anticancer drugs. Our previous findings demonstrated that gold (III) porphyrin la preferentially induced apoptosis in a cancer cell line (SUNE1). In this study, we identified differentially expressed proteins related to the drug's cytotoxic action by comparing the protein alterations induced by gold (III) porphyrin la and cisplatin treatments. Several clusters of altered proteins were identified, including cellular structure and stress-related chaperone proteins, proteins involved in reactive oxygen species and enzyme proteins, translation factors, proteins that mediate cell proliferation or differentiation, and proteins participating in the internal degradation systems. Our results indicated that multiple factors leading to apoptosis were involved in drug cytotoxicity in SUNE1 cells. The balance between pro-apoptotic and anti-apoptotic signals determined the final fate of cancer cells. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.postprin