[5-Chloro-2-hy­droxy-N′-(2-oxidobenzyl­idene)benzohydrazidato]dimethyl­tin(IV)

In the title compound, [Sn(CH3)2(C14H9ClN2O3)], the SnIV ion is coordinated by one N and two O atoms from the tridentate 5-chloro-2-hy­droxy-N′-(2-oxidobenzyl­idene)benzohydrazidate (L) ligand and two methyl groups in a distorted trigonal–bipyramidal geometry. In the ligand, the hy­droxy group is involved in an intra­molecular O—H⋯N hydrogen bond and the two aromatic rings form a dihedral angle of 5.5 (1)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds and π–π inter­actions between the aromatic rings [centroid–centroid distance = 3.816 (3) Å] link the mol­ecules into centrosymmetric dimers

An observational study of precipitation types in the Alaskan Arctic

The effects of various precipitation types, such as snow, rain, sleet, hail and freezing rain, on regional hydrology, ecology, snow and ice surfaces differ significantly. Due to limited observations, however, few studies into precipitation types have been conducted in the Arctic. Based on the high-resolution precipitation records from an OTT Parsivel2 disdrometer in Utqiaġvik, Alaska, this study analysed variations in precipitation types in the Alaskan Arctic from 15 May to 16 October, 2019. Results show that rain and snow were the dominant precipitation types during the measurement period, accounting for 92% of the total precipitation. In addition, freezing rain, sleet, and hail were also observed (2, 4 and 11 times, respectively), accounting for the rest part of the total precipitation. The records from a neighbouring U.S. Climate Reference Network (USCRN) station equipped with T-200B rain gauges support the results of disdrometer. Further analysis revealed that Global Precipitation Measurement (GPM) satellite data could well characterise the observed precipitation changes in Utqiaġvik. Combined with satellite data and station observations, the spatiotemporal variations in precipitation were verified in various reanalysis datasets, and the results indicated that ECMWF Reanalysis v5 (ERA5) could better describe the observed precipitation time series in Utqiaġvik and the spatial distribution of data in the Alaskan Arctic. Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) overestimated the amount and frequency of precipitation. Japanese 55-year Reanalysis (JRA-55) could better simulate heavy precipitation events and the spatial distribution of the precipitation phase, but it overestimated summer snowfall

All-Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics

I), which were very recently reported as a high effi ciency luminescent materials. The CsPbX 3 IPQDs adopted here were fabricated following a recipe slightly modifi ed from the literature (see details in Experimental Section). Here, we present a new class of lasing materials with outstanding optical gain signatures of combined advantages of both QDs and halide perovskites: the colloidal all-inorganic cesium lead halide perovskite QDs (IPQDs) (CsPbX 3 , X = Cl, Br, Adv. Mater. 2015

Advances and prospects of lasers developed from colloidal semiconductor nanostructures

Since the first observation of stimulated emission from colloidal quantum dots (CQDs) in year 2000, tremendous progress has been made in developing solution-processed lasers from colloidal semiconductor nanostructures in terms of both understanding the fundamental physics and improving the device performance. In this review paper, we will start with a brief introduction about the fabrication of CQDs and the corresponding electronic structures. The emphasis will be put on the discussion about the optical gain and lasing from colloidal nanostructures including the gain mechanism, the main hurdles against optical gain and lasing as well as strategies to optimize the lasing performance. Afterwards, the recent advances in CQD lasers, exemplified by the achievement of continuous wave lasing, will be presented. Finally, the challenges and a perspective of the future development of lasers based on the colloidal semiconductor nanostructures will be presented.MOE (Min. of Education, S’pore)Accepted versio

Tackling the hurdles of electrically pumped colloidal quantum dot lasers

Lasers are devices that produce light by the process of stimulated emission (SE) which amplifies light coherently. They are distinguished from other light sources by their beams with good coherence, directionality, high brightness and spectral purity. As such, lasers have found widespread applications in various fields, including scientific research, industry, medicine and military defense, and actually become ubiquitous in our daily life. Despite of the diversity in laser classification, compact lasers are dominantly made from semiconductors. Especially, electrically driven semiconductor lasers are indispensable components for optical communication. At present, electrically driven semiconductor lasers, or laser diodes, are fabricated by the high-vacuum and high-temperature epitaxy methods, which are not only costly but also difficult to integrate with other optoelectronic devices [1]. As a complement to the epitaxial semiconductor lasers, the cost-effective solution-processed laser diodes have been pursued for the past decades yet demonstrated to be extremely challenging.Accepted versio

Three-Dimensional Induced Polarization Parallel Inversion Using Nonlinear Conjugate Gradients Method

Four kinds of array of induced polarization (IP) methods (surface, borehole-surface, surface-borehole, and borehole-borehole) are widely used in resource exploration. However, due to the presence of large amounts of the sources, it will take much time to complete the inversion. In the paper, a new parallel algorithm is described which uses message passing interface (MPI) and graphics processing unit (GPU) to accelerate 3D inversion of these four methods. The forward finite differential equation is solved by ILU0 preconditioner and the conjugate gradient (CG) solver. The inverse problem is solved by nonlinear conjugate gradients (NLCG) iteration which is used to calculate one forward and two “pseudo-forward” modelings and update the direction, space, and model in turn. Because each source is independent in forward and “pseudo-forward” modelings, multiprocess modes are opened by calling MPI library. The iterative matrix solver within CULA is called in each process. Some tables and synthetic data examples illustrate that this parallel inversion algorithm is effective. Furthermore, we demonstrate that the joint inversion of surface and borehole data produces resistivity and chargeability results are superior to those obtained from inversions of individual surface data

Microlasers enabled by soft‐matter technology

Soft‐matter microlasers are an interesting part of soft‐matter photonics, which are based on liquids, liquid crystals, polymers, biological materials, and fabricated mainly by solution‐processing approaches. Soft‐matter microlasers comprehend a multitude of attractive features, including low‐cost, mechanical flexibility, wide range wavelength tunability and, in some cases, biocompatibility, and biodegradability. As such, they are recognized as versatile candidates for efficient light sources with enhanced performances and applications as ultrasensitive physical, chemical, and biological sensors. Here, the recent developments of soft‐matter microlasers are reviewed in time and the prospect in this field is provided. First, the characteristics of the representative soft‐matter microlasers are discussed with focus on their laser structures, lasing mechanisms, fabrication approaches, and gain material origins, followed by an introduction about the current cutting‐edge soft‐technologies that are applied in soft‐matter microlasers. Afterward, their potential applications as wavelength tunable sources, sensors, and displays are highlighted. Finally, the work is summarized and the prospect of soft‐matter microlasers for expanding this emerging research field is presented.MOE (Min. of Education, S’pore)Accepted versio

Bis(acetohydroxamato-κ2O,O′)diphenyltin(IV)

The complex molecule of the title compound, [Sn(C6H5)2(C2H4NO2)2], has crystallographically imposed twofold symmetry. The Sn atom is coordinated by four O atoms from two acetohydroxamate ligands and by two C atoms from phenyl groups in a distorted octahedral geometry. In the crystal, molecules are connected by N—H...O hydrogen-bonding interactions, forming a chain structure along the c axi

Quaternary alloy quantum dots : toward low-threshold stimulated emission and all-solution-processed lasers in the green region

Ultra-low threshold stimulated emission is demonstrated upon both one- and two-photon pumping from quaternary alloyed Cd(1−x)ZnxSe(1−y)Sy/ZnS quantum dots (QDs) in the green region for the first time. Moreover, an all-solution-processed whispering gallery mode laser is produced by coating Cd(1−x)ZnxSe(1−y)Sy/ZnS QDs on a self-assembled hemisphere. These results represent a significant progress in green lasers and hold great potential in addressing the “green gap” challenge