The Multiple Roles of Na Ions in Highly Efficient CZTSSe Solar Cells.

Sodium (Na) doping is a well-established technique employed in chalcopyrite and kesterite solar cells. While various improvements can be achieved in crystalline quality, electrical properties, or defect passivation of the absorber materials by incorporating Na, a comprehensive demonstration of the desired Na distribution in CZTSSe is still lacking. Herein, a straightforward Na doping approach by dissolving NaCl into the CZTS precursor solution is proposed. It is demonstrated that a favorable Na ion distribution should comprise a precisely controlled Na+ concentration at the front surface and an enhanced distribution within the bottom region of the absorber layer. These findings demonstrated that Na ions play several positive roles within the device, leading to an overall power conversion efficiency of 12.51%.

Demyelination in the medial prefrontal cortex by withdrawal from chronic nicotine causes impaired cognitive memory.

Epidemiological studies revealed deficits in cognitive learning and memory in smokers who withdrawal from smoking, but the molecular mechanisms underlying it is unclear. Here, we employed the novel object recognition task (NORT) to evaluate cognitive memory and found impaired memory and motor skills after withdrawal from chronic nicotine. Myelin sheath hastens the conduction of signals along axons and thus plays a critical role in learning and memory. We found no effect of nicotine withdrawal on the myelination in both of the Ventral tegmental area (VTA) and Nucleus accumbens (NAc) regions, but unexpectedly, we observed a demyelination phenomenon in the medial prefrontal cortex (mPFC) after withdrawal from chronic nicotine. Moreover, we found a positive correlation between the impaired memory and demyelination, and pharmaceutical rescue of myelination by clemastine specifically improved the impaired recognition memory but not the decreased motor skills caused by withdrawal from chronic nicotine. We further found nicotine directly acts on oligodendrocytes with OPCs potential to decrease their myelination process. Taken together, these results demonstrate demyelination in the mPFC causes impaired recognition memory and reveal a potential of enhancing myelination as a therapeutic strategy to alleviate cognitive memory deficits caused by smoking withdrawal.

Temperature Dependence of the CdS Bandgap in the Extreme Confinement Regime.

A non-empirical equation describing the effect of size on the temperature dependence of the optical bandgap of CdS (dEg/dT) is obtained on the basis of the Brus equation. Intriguingly, we find that dEg/dT diverges strongly from bulk values only within the "extreme confinement" (EC) regime. We conducted both experimental and theoretical investigations of the absorption spectra of CdS clusters and quantum dots as a function of temperature above room temperature. Our results show that the value of dEg/dT obtained from absorption spectra in the EC regime is 2.5 times higher than in the strong confinement regime. Notable ligand sensitivities are also observed for dEg/dT in the case of CdS clusters. Ab initio molecular dynamics simulations and density functional theory calculations reveal that thermal fluctuations are the crucial factor influencing the bandgap temperature coefficient. Our results help resolve some long-standing debates regarding the dEg/dT behavior of semiconductor quantum dots.

Ligand and solvent effects on the absorption spectra of CdS magic-sized clusters.

The absorption spectra of congenetic wurtzite (WZ) and zincblende (ZB) CdS magic-sized clusters are investigated. We demonstrate that the exciton peak positions can be tuned by up to 500 meV by varying the strong coupling between X-type ligands and the semiconductor cores, while the addition of L-type ligands primarily affects cluster midgap states. When Z-type ligands are displaced by L-type ligands, red shifts in the absorption spectra are observed, despite the fact there is a small decrease in cluster size. Density functional theory calculations are used to explain these findings and they reveal the importance of Cd and S dangling bonds on the midgap states during the Z- to L-type ligand exchange process. Overall, ZB CdS clusters show higher chemical stability than WZ clusters but their optical properties exhibit greater sensitivity to the solvent. Conversely, WZ CdS clusters are not stable in a Lewis base-rich environment, resulting in various changes in their spectra. Our findings enable researchers to select capping ligands that modulate the optical properties of semiconductor clusters while maintaining precise control over their solvent interactions.

Enhancement of DNAzymatic activity using iterative in silico maturation.

DNAzyme-based (catalytic nucleic acid) biosensing technology is recognised as a valuable biosensing tool in diagnostic medicine and seen as a cheaper, more stable alternative to antibodies or enzymes. However, like enzyme discovery, no method exists to predict DNAzyme sequences that result in high catalytic activity using computer software (in silico). In this work, iterative in silico maturation and in vitro evaluation were applied to a DNAzyme oligodeoxynucleotide (ODN) sequence to elucidate novel synthetic sequences with enhanced DNAzyme activity. An already well-known model DNAzyme, the G-quadruplex/hemin complex, was iterated over eight generations to elucidate synthetic sequences that were up to five times faster than the original parent sequence. By combining molecular dynamics simulations, we found that the POD-mimicking activities were largely affected by docking modes and the tightness of locking between complexes. Ultimately, the theoretical models showed significant sequence-dependencies.

The impact of the union of lesser trochanter fragments after intramedullary fixation of trochanteric femoral fractures: an X-ray based study.

BACKGROUND: Displacement of the lesser trochanter (LT) is not uncommon after managing intertrochanteric femoral fractures and the influence of nonunion of the LT-fragment on clinical outcomes remains controversial. This study aimed to investigate the relationship between the displacement distance and union of the LT-fragment and evaluate the influence of LT-fragment nonunion on hip function and complications. METHODS: This retrospective study included patients with intertrochanteric fractures and displaced LT treated with intramedullary fixation at Wenzhou Hospital of Integrated Traditional Chinese and Western Medicine from June 2015 to July 2017. The patients were grouped as union and nonunion of the LT-fragment at 1 year. The LT-fragment displacement distance of LT was measured by the anterior-posterior radiographs. RESULTS: Thirty-one and 22 patients showed union and nonunion at 1 year, respectively. The nonunion group had a higher postoperative complication rate than the union group (59% vs. 29%, P = 0.047), especially mechanical complications (45% vs. 6%, P = 0.001). There was no significant difference in hip function between the two groups (P > 0.05). The receiver operating characteristic (ROC) curve revealed an area under the curve of 0.933 of displacement ratio. Patients with a displacement ratio > 0.35 were more likely to have nonunion of the LT-fragment. CONCLUSIONS: The displacement ratio might be a reliable predictor of LT-fragment union. The incidence of postoperative complications might increase with LT-fragment nonunion.

Effects of mesoscale eddies on intraseasonal variability of intermediate water east of Taiwan.

The intraseasonal variability of the intermediate water (IW) and its characteristics east of Taiwan are studied utilizing 17 months of long-term, continuous and synchronous measurements of temperature, salinity and current from mooring sites deployed at 122° E/23° N from January 2016 to May 2017. Direct measurements revealed water masses east of Taiwan alternately show complete South China Sea Intermediate Water or North Pacific Intermediate Water (NPIW) characteristics, mostly in a mixed state, with NPIW dominating 70% of the time. For the first time, it is demonstrated that the variation of IW with periods of ~ 80 days is mainly related to mesoscale eddies. Anticyclonic (cyclonic) eddies corresponding to an increase (decrease) in temperature and salinity in the intermediate layer. Further mechanism analysis indicates the vertical motion of the water mass inside the eddies is one of the reasons for the thermohaline change in the intermedaiter layer. In addition, the anticyclonic eddies may increase the salinity concentration gradient across the Luzon Strait, and the enhanced advection is favorable to the outflow of water masses in the South China Sea. When the cyclonic eddies acts on the eastern part of Taiwan, the influence of the northward advection is weakened and the southward flow on its left side is more favorable to the transport of NPIW.

Observed three dimensional distributions of enhanced turbulence near the Luzon Strait.

Ocean turbulence can impact the transfer of heat, nutrients, momentum and sea level rise, which are crucially important to climate systems. The Luzon Strait, one of the mixing hotspots, is important for water exchange between the northeastern South China Sea and West Pacific. Here, for the first time, we carry out full-depth direct microstructure measurements surrounding the Luzon Strait to clarify the three-dimensional distributions of turbulence. We demonstrate that the turbulent kinetic energy dissipation rates in the upper and middle layers of the northeastern South China Sea are on the same order of magnitude as those in the West Pacific. The dissipation rates are only bottom enhanced near the rough topography of the South China Sea slope and Luzon Strait which is one order of magnitude larger than those at smooth area. The relevant bottom diapycnal diffusivity in the South China Sea is elevated in the West Pacific by a factor of three, instead of by two orders of magnitude as overestimated by indirect parameterization. These results may appear surprising in light of previous studies but are in fact consistent with predictions from internal wave-topography interaction theory.

Mechanistic Study of Oxygen Reduction at Liquid/Liquid Interfaces by Hybrid Ultramicroelectrodes and Mass Spectrometry.

Proton-coupled electron transfer (PCET) reactions at various interfaces (liquid/membrane, solid/electrolyte, liquid/liquid) lie at the heart of many processes in biology and chemistry. Mechanistic study can provide profound understanding of PCET and rational design of new systems. However, most mechanisms of PCET reactions at a liquid/liquid interface have been proposed based on electrochemical and spectroscopic data, which lack direct evidence for possible intermediates. Moreover, a liquid/liquid interface as one type of soft interface is dynamic, making the investigation of interfacial reactions very challenging. Herein a novel electrochemistry method coupled to mass spectrometry (EC-MS) was introduced for in situ study of the oxygen reduction reaction (ORR) by ferrocene (Fc) under catalysis from cobalt tetraphenylporphine (CoTPP) at liquid/liquid interfaces. The key units are two types of gel hybrid ultramicroelectrodes (agar-gel/organic hybrid ultramicroelectrodes and water/PVC-gel hybrid ultramicroelectrodes), which were made based on dual micro- or nanopipettes. A solidified liquid/liquid interface can be formed at the tip of these pipettes, and it serves as both an electrochemical cell and a nanospray emitter for mass spectrometry. We demonstrated that the solidified L/L interfaces were very similar to typical L/L interfaces. Key CoTPP intermediates of the ORR at the liquid/liquid interfaces were identified for the first time, and the four-electron oxygen reduction pathway predominated, which provides valuable insights into the mechanism of the ORR. Theoretical simulation has further supported the possibility of formation of intermediates. This type of platform is promising for in situ tracking and identifying intermediates to study complicated reactions at liquid/liquid interfaces or other soft interfaces.

Stationary state distribution and efficiency analysis of the Langevin equation via real or virtual dynamics.

Langevin dynamics has become a popular tool to simulate the Boltzmann equilibrium distribution. When the repartition of the Langevin equation involves the exact realization of the Ornstein-Uhlenbeck noise, in addition to the conventional density evolution, there exists another type of discrete evolution that may not correspond to a continuous, real dynamical counterpart. This virtual dynamics case is also able to produce the desired stationary distribution. Different types of repartition lead to different numerical schemes, of which the accuracy and efficiency are investigated through studying the harmonic oscillator potential, an analytical solvable model. By analyzing the asymptotic distribution and characteristic correlation time that are derived by either directly solving the discrete equations of motion or using the related phase space propagators, it is shown that the optimal friction coefficient resulting in the minimum characteristic correlation time depends on the time interval chosen in the numerical implementation. When the recommended "middle" scheme is employed, both analytical and numerical results demonstrate that, for good numerical performance in efficiency as well as accuracy, one may choose a friction coefficient in a wide range from around the optimal value to the high friction limit.

A unified thermostat scheme for efficient configurational sampling for classical/quantum canonical ensembles via molecular dynamics.

We show a unified second-order scheme for constructing simple, robust, and accurate algorithms for typical thermostats for configurational sampling for the canonical ensemble. When Langevin dynamics is used, the scheme leads to the BAOAB algorithm that has been recently investigated. We show that the scheme is also useful for other types of thermostats, such as the Andersen thermostat and Nosé-Hoover chain, regardless of whether the thermostat is deterministic or stochastic. In addition to analytical analysis, two 1-dimensional models and three typical real molecular systems that range from the gas phase, clusters, to the condensed phase are used in numerical examples for demonstration. Accuracy may be increased by an order of magnitude for estimating coordinate-dependent properties in molecular dynamics (when the same time interval is used), irrespective of which type of thermostat is applied. The scheme is especially useful for path integral molecular dynamics because it consistently improves the efficiency for evaluating all thermodynamic properties for any type of thermostat.