Frustration-induced eta inversion in the S=1/2 bond-alternating spin chain

We study the frustration-induced enhancement of the incommensurate correlation for a bond-alternating quantum spin chain in a magnetic field, which is associated with a quasi-one-dimensional organic compound F5PNN. We investigate the temperature dependence of the staggered susceptibilities by using the density matrix renormalization group, and then find that the incommensurate correlation becomes dominant in a certain range of the magnetic field. We also discuss the mechanism of this enhancement on the basis of the mapping to the effective S=1/2 XXZ chain and a possibility of the field-induced incommensurate long range order.Comment: 4 pages, 5 figures, replaced with revised version accepted to PR

Modelling Temperature Dependence of Hysteresis in Perovskite Solar Cells

In a recent publication [1], we have shown using a drift-diffusion model that mobile iodide vacancies within the bulk methylammonium lead tri-iodide (CH3NH3PbI3) active layer of perovskite solar cells are the most probably cause of the hysteresis observed in these devices. Reasonable agreement with experiment was obtained by setting the mobility of the vacancies to within an order of magnitude of that predicted by Eames et al. [2].Eames et al. assumed that the vacancy motion was thermally activated and that therefore the diffusion coefficient was subject to a Boltzmann-type temperature dependence. By incorporating this assumption into our drift-diffusion model, we have been able to reproduce temperature-dependent transient current decay measurements, suggesting that the vacancy motion is indeed thermally activated. The model can be used to explore the effects of different recombination mechanisms on the current-voltage characteristics; in particular, we have confirmed the hypothesis of Van Reenen et al. [3] that both vacancy motion and a trap-based recombination mechanism are required to observe significant hysteresis. Indeed, the current-voltage curves predicted for bimolecular recombination show a strong similarity to those published in reports of cells with “no hysteresis” [4].Despite qualitative agreement of the model with experiment there is still further work required before results can produce quantitative agreement with a variety of experimental data. In particular we are looking at extending the model to investigate why certain cell designs are able to limit hysteresis and what effects this has on cell performance. References[1] Giles Richardson et al., En. Environ. Sci., Feb. 2016 DOI: 10.1039/c5ee02740c [2] Chris Eames et al., Nat. Commun., vol. 6, pp. 7497, May 2015[3] Van Reenen et al., J. Phys. Chem. Lett., vol. 6, pp. 3808-3814, Sept. 2015[4] Nam Joong Jeon et al., Nat. Mater., vol. 13, pp. 897-903, July 2014[5] Aron Walsh et al., Angew. Chem., vol. 127, no. 6, pp. 1811-1814, Dec. 2014<br/

Efficacy and safety of luseogliflozin added to various oral antidiabetic drugs in Japanese patients with type 2 diabetes mellitus

Introduction: Two studies were carried out to investigate the efficacy and safety of luseogliflozin added to existing oral antidiabetic drugs (OADs) in Japanese type 2 diabetic patients inadequately controlled with OAD monotherapy. Materials and Methods: In the trial involving add‐on to sulfonylureas (study 03‐1), patients were randomly assigned to receive luseogliflozin 2.5 mg or a placebo for a 24‐week double‐blind period, followed by a 28‐week open‐label period. In the open‐label trial involving add‐on to other OADs; that is, biguanides, dipeptidyl peptidase‐4 inhibitors, thiazolidinediones, glinides and α‐glucosidase inhibitors (study 03‐2), patients received luseogliflozin for 52 weeks. Results: In study 03‐1, luseogliflozin significantly decreased glycated hemoglobin at the end of the 24‐week double‐blind period compared with the placebo (–0.88%, P < 0.001), and glycated hemoglobin reduction from baseline at week 52 was –0.63%. In study 03‐2, luseogliflozin added to other OADs significantly decreased glycated hemoglobin from baseline at week 52 (–0.52 to –0.68%, P < 0.001 for all OADs). Bodyweight reduction was observed in all add‐on therapies, even with agents associated with weight gain, such as sulfonylureas and thiazolidinediones. Most adverse events were mild in severity. When added to a sulfonylurea, incidences of hypoglycemia during the double‐blind period were 8.7% and 4.2% for luseogliflozin and placebo, respectively, but no major hypoglycemic episodes occurred. The frequency and incidences of adverse events of special interest for sodium glucose cotransporter 2 inhibitors and adverse events associated with combined OADs were acceptable. Conclusions: Add‐on therapies of luseogliflozin to existing OADs improved glycemic control, reduced bodyweight and were well tolerated in Japanese type 2 diabetic patients. These trials were registered with the Japan Pharmaceutical Information Center (add on to sulfonylurea: JapicCTI‐111507; add on to other OADs: JapicCTI‐111508)

Modelling Temperature Dependence of Hysteresis in Perovskite Solar Cells

In a recent publication [1], we have shown using a drift-diffusion model that mobile iodide vacancies within the bulk methylammonium lead tri-iodide (CH3NH3PbI3) active layer of perovskite solar cells are the most probably cause of the hysteresis observed in these devices. Reasonable agreement with experiment was obtained by setting the mobility of the vacancies to within an order of magnitude of that predicted by Eames et al. [2].Eames et al. assumed that the vacancy motion was thermally activated and that therefore the diffusion coefficient was subject to a Boltzmann-type temperature dependence. By incorporating this assumption into our drift-diffusion model, we have been able to reproduce temperature-dependent transient current decay measurements, suggesting that the vacancy motion is indeed thermally activated. The model can be used to explore the effects of different recombination mechanisms on the current-voltage characteristics; in particular, we have confirmed the hypothesis of Van Reenen et al. [3] that both vacancy motion and a trap-based recombination mechanism are required to observe significant hysteresis. Indeed, the current-voltage curves predicted for bimolecular recombination show a strong similarity to those published in reports of cells with “no hysteresis” [4].Despite qualitative agreement of the model with experiment there is still further work required before results can produce quantitative agreement with a variety of experimental data. In particular we are looking at extending the model to investigate why certain cell designs are able to limit hysteresis and what effects this has on cell performance. References[1] Giles Richardson et al., En. Environ. Sci., Feb. 2016 DOI: 10.1039/c5ee02740c [2] Chris Eames et al., Nat. Commun., vol. 6, pp. 7497, May 2015[3] Van Reenen et al., J. Phys. Chem. Lett., vol. 6, pp. 3808-3814, Sept. 2015[4] Nam Joong Jeon et al., Nat. Mater., vol. 13, pp. 897-903, July 2014[5] Aron Walsh et al., Angew. Chem., vol. 127, no. 6, pp. 1811-1814, Dec. 2014<br/

Measurement and modelling of dark current decay transients in perovskite solar cells

The current decay in response to a sudden change of applied bias up to 1 V has been measured on a methylammonium lead triiodide perovskite solar cell with titania and spiro-OMeTAD transport layers, for temperatures between 258 and 308 K. These measurements are highly reproducible, in contrast to most other techniques used to investigate perovskite cells. A drift-diffusion model that accounts for slow moving ions as well as electrons and holes acting as charge carriers was used to predict the current transients. The close fit of the model predictions to the measurements shows that mobile ions in the perovskite layer influence transient behaviour on timescales of up to 50 s. An activation energy of 0.55 eV is inferred from fitting simulations to measurements made at room temperature

Restoration of E-cadherin expression by selective Cox-2 inhibition and the clinical relevance of the epithelial-to-mesenchymal transition in head and neck squamous cell carcinoma

BACKGROUND: The epithelial-to-mesenchymal transition (EMT) accompanied by the downregulation of E-cadherin has been thought to promote metastasis. Cyclooxygenase-2 (Cox-2) is presumed to contribute to cancer progression through its multifaceted function, and recently its inverse relationship with E-cadherin was suggested. The aim of the present study was to investigate whether selective Cox-2 inhibitors restore the expression of E-cadherin in head and neck squamous cell carcinoma (HNSCC) cells, and to examine the possible correlations of the expression levels of EMT-related molecules with clinicopathological factors in HNSCC. METHODS: We used quantitative real-time PCR to examine the effects of three selective Cox-2 inhibitors, i.e., celecoxib, NS-398, and SC-791 on the gene expressions of E-cadherin (CDH-1) and its transcriptional repressors (SIP1, Snail, Twist) in the human HNSCC cell lines HSC-2 and HSC-4. To evaluate the changes in E-cadherin expression on the cell surface, we used a flowcytometer and immunofluorescent staining in addition to Western blotting. We evaluated and statistically analyzed the clinicopathological factors and mRNA expressions of Cox-2, CDH-1 and its repressors in surgical specimens of 40 patients with tongue squamous cell carcinoma (TSCC). RESULTS: The selective Cox-2 inhibitors upregulated the E-cadherin expression on the cell surface of the HNSCC cells through the downregulation of its transcriptional repressors. The extent of this effect depended on the baseline expression levels of both E-cadherin and Cox-2 in each cell line. A univariate analysis showed that higher Cox-2 mRNA expression (p = 0.037), lower CDH-1 mRNA expression (p = 0.020), and advanced T-classification (p = 0.036) were significantly correlated with lymph node metastasis in TSCC. A multivariate logistic regression revealed that lower CDH-1 mRNA expression was the independent risk factor affecting lymph node metastasis (p = 0.041). CONCLUSIONS: These findings suggest that the appropriately selective administration of certain Cox-2 inhibitors may have an anti-metastatic effect through suppression of the EMT by restoring E-cadherin expression. In addition, the downregulation of CDH-1 resulting from the EMT may be closely involved in lymph node metastasis in TSCC

Elucidating the long-range charge carrier mobility in metal halide perovskite thin films

Many optoelectronic properties have been reported for lead halide perovskite polycrystalline films. However, ambiguities in the evaluation of these properties remain, especially for long-range lateral charge transport, where ionic conduction can complicate interpretation of data. Here we demonstrate a new technique to measure the long-range charge carrier mobility in such materials. We combine quasi-steady-state photo-conductivity measurements (electrical probe) with photo-induced transmission and reflection measurements (optical probe) to simultaneously evaluate the conductivity and charge carrier density. With this knowledge we determine the lateral mobility to be ~ 2 cm2/Vs for CH3NH3PbI3 (MAPbI3) polycrystalline perovskite films prepared from the acetonitrile/methylamine solvent system. Furthermore, we present significant differences in long-range charge carrier mobilities, from 2.2 to 0.2 cm2/Vs, between films of contemporary perovskite compositions prepared via different fabrication processes, including solution and vapour phase deposition techniques. Arguably, our work provides the first accurate evaluation of the long-range lateral charge carrier mobility in lead halide perovskite films, with charge carrier density in the range typically achieved under photovoltaic operation

Measurement and modelling of dark current decay transients in perovskite solar cells

The current decay in response to a sudden change of applied bias up to 1 V has been measured on a methylammonium lead triiodide perovskite solar cell with titania and spiro-OMeTAD transport layers, for temperatures between 258 and 308 K. These measurements are highly reproducible, in contrast to most other techniques used to investigate perovskite cells. A drift-diffusion model that accounts for slow moving ions as well as electrons and holes acting as charge carriers was used to predict the current transients. The close fit of the model predictions to the measurements shows that mobile ions in the perovskite layer influence transient behaviour on timescales of up to 50 s. An activation energy of 0.55 eV is inferred from fitting simulations to measurements made at room temperature