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We report the metal-organic chemical vapor deposition growth of high-quality AlN on sapphire enabled by an alternating V/III ratio AlN superlattice. We demonstrated that the insertion of an alternating V/III ratio AlN superlattice facilitates the relaxation of tensile stress during growth and assists the annihilation of threading dislocations. Dislocation inclination was proposed to play a major role in the stress relaxation and dislocation reduction, which not only provides an effective misfit-dislocation component but also increases the dislocation reaction probability. By this method, crack-free 3.25 μm-thick AlN films were grown on flat sapphire substrate (FSS) and nano-patterned sapphire substrate (NPSS) at 1180 °C, and the full width at half maximum of (002)/(102) rocking curves was 204/408 and 152/323 arcsec for such AlN/FSS and AlN/NPSS templates. [ABSTRACT FROM AUTHOR]

Molecules labelled with the unnatural isotope fluorine-18 are used for positron emission tomography. Currently, this molecular imaging technology is not exploited at its full potential because many 18F-labelled probes are inaccessible or notoriously difficult to produce. Typical challenges associated with 18F radiochemistry are the short half-life of 18F (<2 h), the use of sub-stoichiometric amounts of 18F, relative to the precursor and other reagents, as well as the limited availability of parent 18F sources of suitable reactivity ([18F]F- and [18F]F2). There is a high-priority demand for general methods allowing access to [18F]CF3-substituted molecules for application in pharmaceutical discovery programmes. We report the development of a process for the late-stage [18F]trifluoromethylation of (hetero)arenes from [18F]fluoride using commercially available reagents and (hetero)aryl iodides. This [18F]CuCF3-based protocol benefits from a large substrate scope and is characterized by its operational simplicity. [ABSTRACT FROM AUTHOR]

InGaN-based long-wavelength light-emitting diodes (LEDs) are indispensable components for the next-generation solid-state lighting industry. In this work, we introduce additional InGaN/GaN pre-wells in LED structure and investigate the influence on optoelectronic properties of yellow (~575 nm) LEDs. It is found that yellow LED with pre-wells exhibits a smaller blue shift, and a 2.2-fold increase in light output power and stronger photoluminescence (PL) intensity compared to yellow LED without pre-wells. The underlying mechanism is revealed by using Raman spectra, temperature-dependent PL, and X-ray diffraction. Benefiting from the pre-well structure, in-plane compressive stress is reduced, which effectively suppresses the quantum confined stark effect. Furthermore, the increased quantum efficiency is also related to deeper localized states with reduced non-radiative centers forming in multiple quantum wells grown on pre-wells. Our work demonstrates a comprehensive understanding of a pre-well structure for obtaining efficient LEDs towards long wavelengths. [ABSTRACT FROM AUTHOR]

A novel and highly convergent synthesis leading to 2‐phenyl‐quinolines has been developed. As demonstrated in the preparation of 6‐fluoro‐3‐(3‐oxo‐piperazin‐1‐ylmethyl)‐2‐phenyl‐quinoline‐4‐carboxylic acid [(S)‐1‐cyclohexyl‐ethyl]‐amide (8), the method provides fascile access to this class of analogues via the common intermediate 7. [ABSTRACT FROM AUTHOR]

Examines the photodeoxygenation of dibenzothiophene sulfoxide. Evidence for a unimolecular sulfur-oxygen cleavage mechanism; Measurements of quantum yields as a function of concentration, solvent, quenchers and excitation wavelength; Indications that the active oxidizing agent may be atomic oxygen or a closely related noncovalent complex.

Fabricating GaN-based light-emitting diodes (LEDs) on a silicon (Si) substrate, which is compatible with the widely employed complementary metal–oxide–semiconductor (CMOS) circuits, is extremely important for next-generation high-performance electroluminescence devices. We conducted a systematic investigation of the optical properties of vertical LEDs, to reveal the impacts of the manufacturing process on their optical characteristics. Here, we fabricated and characterized high-efficiency GaN-based LEDs with integrated surface textures including micro-scale periodic hemispherical dimples and nano-scale random hexagonal pyramids on a 4 inch p-type Si substrate. The highly reflective Ag/TiW metallization scheme was performed to decrease downward-absorbing light. We demonstrated the influence of transferring LED epilayers from a sapphire substrate onto the Si substrate on the emission characteristics of the vertical LEDs. The removal of the sapphire substrate reduced the adverse impacts of the quantum-confined Stark effect (QCSE). The influence of integrated surface textures on the light extraction efficiency (LEE) of the vertical LEDs was studied. With the injection current of 350 mA, vertical LEDs with integrated surface textures demonstrated an excellent light output power of 468.9 mW with an emission peak wavelength of 456 nm. This work contributes to the integration of GaN-based vertical LEDs into Si-based integrated circuits. [ABSTRACT FROM AUTHOR]

Reports the efficient oxenoid functionalization of hydrocarbons which takes place as a result of photolysis of certain aromatic sulfoxides, notably dibenzothiophene sulfoxide. Oxidation products; Competitive oxidation of several substrates.

Graphical abstract Abstract We describe the discovery and optimization of 5-substituted-N-pyridazinylbenzamide derivatives as potent and selective LRRK2 inhibitors. Extensive SAR studies led to the identification of compounds 18 and 23 , which demonstrated good in vitro pharmacokinetic profile and excellent selectivity over 140 other kinases. Both compounds demonstrated high unbound fractions in both blood and brain. Compound 18 proved to be brain penetrant, and the high unbound fraction of compound 18 in brain enabled its in vivo efficacy in CNS, wherein a significant inhibition of LRRK2 Ser935 phosphorylation was observed in rat brain following intravenous infusion at 5 mg/kg/h. [ABSTRACT FROM AUTHOR]

Laser direct writing (LDW) is a promising candidate for the fabrication of all-dielectric THz absorbers for its high flexibility and material compatibility. However, multi-step processing or multi-layer materials are required to compensate for the nonideal features of LDW to realize good absorption performance. To further explore the potential of LDW in flexible and cost-effective THz absorber fabrication, in this work, we demonstrate a design method of THz absorbers fully considering and utilizing the characteristics of laser processing. Specifically, we first numerically analyze that by properly combining basic structures processed by single-step LDW, good and adjustable absorption performance can be achieved on a single-layer substrate. Then we experimentally fabricate THz absorbers by processing periodic composite structures, which are combined by grooves and circular holes, on single-layer doped silicon using LDW. Experimental results show that our method can fabricate THz absorbers at a speed of 3.3 mm 2 /min with an absorptivity above 90% over a broadband of 1.8-3 THz. Our method provides a promising solution for the flexible and efficient fabrication of all-dielectric broadband THz absorbers.

High-efficiency GaN-based green LEDs are of paramount importance to the development of the monolithic integration of multicolor emitters and full-color high-resolution displays. Here, the InGaN quantum well with gradually varying indium (In) content was proposed for improving the performance of GaN-based green LEDs. The InGaN quantum well with gradually varying In content not only alleviates the quantum-confined Stark effect (QCSE), but also yields a low Auger recombination rate. Consequently, the gradual In content green LEDs exhibited increased light output power (LOP) and reduced efficiency droop as compared to constant In content green LEDs. At 60 A/cm 2 , the LOPs of the constant In content green LEDs and the gradual In content green LEDs were 33.9 mW and 55.2 mW, respectively. At 150 A/cm 2 , the efficiency droops for the constant In content green LEDs and the gradual In content green LEDs were 61% and 37.6%, respectively. This work demonstrates the potential for the gradual In content InGaN to replace constant In content InGaN as quantum wells in LED devices in a technologically and commercially effective manner.

Little is known about the impact of the blood-nerve barrier (BNB) on drug distribution into peripheral nerves. In this study, we examined the peripheral nerve penetration in rats of 11 small-molecule drugs possessing diverse physicochemical and transport properties and ProTx-II, a tarantula venom peptide with molecular mass of 3826 Daltons. Each drug was administered as constant rate intravenous infusion for 6 hours (small molecules) or 24 hours (ProTx-II). Blood and tissues including brain, spinal cord, sciatic nerve, and dorsal root ganglion (DRG) were collected for drug concentration measurements. Unbound fractions of a set of compounds were determined by equilibrium dialysis method in rat blood, brains, spinal cords, sciatic nerves, and DRG. We also investigated the influence of N -[4-[2-(6,7-dimethoxy-3,4-dihydro-1 H -isoquinolin-2-yl)ethyl]phenyl]-5-methoxy-9-oxo-10 H -acridine-4-carboxamide (GF120918), a P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) inhibitor, on the peripheral nerve and central nervous system (CNS) tissue penetration of imatinib. We found that: 1) the unbound fraction in brain tissue homogenate highly correlates with that in the spinal cord, sciatic nerve, and DRG for a set of compounds and thus provides a good surrogate for spinal cord and peripheral nerve tissues, 2) small-molecule drugs investigated can penetrate the DRG and sciatic nerve, 3) P-gp and BCRP have a limited impact on the distribution of small-molecule drugs into peripheral nerves, and 4) DRG is permeable to ProTx-II, but its distribution into sciatic nerve and CNS tissues is restricted. These results demonstrate that small-molecule drugs investigated can penetrate peripheral nerve tissues, and P-gp/BCRP may not be a limiting factor at the BNB. Biologics as large as ProTx-II can access the DRG but not sciatic nerve and CNS tissues., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

Lp-PLA 2 has been explored as a target for a number of inflammation associated diseases, including cardiovascular disease and dementia. This article describes the discovery of a new fragment derived chemotype that interacts with the active site of Lp-PLA 2 . The starting fragment hit was discovered through an X-ray fragment screen and showed no activity in the bioassay (IC 50 > 1 mM). The fragment hit was optimized using a variety of structure-based drug design techniques, including virtual screening, fragment merging, and improvement of shape complementarity. A novel series of Lp-PLA 2 inhibitors was generated with low lipophilicity and a promising pharmacokinetic profile.

A new reagent trimethylsilyl chlorodifluoroacetate (TCDA) is reported for the introduction of a -CF3 group to arenes and heteroarenes. Compared with current known reagents, TCDA shows very broad scope with respect to electron-deficient, -neutral, and -rich aryl/heteroaryl iodides as well as excellent functional group tolerance, including ester, amide, aldehyde, hydroxyl, and carboxylic acid.

Molecules labelled with the unnatural isotope fluorine-18 are used for positron emission tomography. Currently, this molecular imaging technology is not exploited at its full potential because many (18)F-labelled probes are inaccessible or notoriously difficult to produce. Typical challenges associated with (18)F radiochemistry are the short half-life of (18)F (<2 h), the use of sub-stoichiometric amounts of (18)F, relative to the precursor and other reagents, as well as the limited availability of parent (18)F sources of suitable reactivity ([(18)F]F(-) and [(18)F]F2). There is a high-priority demand for general methods allowing access to [(18)F]CF3-substituted molecules for application in pharmaceutical discovery programmes. We report the development of a process for the late-stage [(18)F]trifluoromethylation of (hetero)arenes from [(18)F]fluoride using commercially available reagents and (hetero)aryl iodides. This [(18)F]CuCF3-based protocol benefits from a large substrate scope and is characterized by its operational simplicity.

Novel tropane derivatives were characterized as muscarinic acetylcholine receptor antagonists (mAChRs). Through optimization of the structure-activity relationship around the tropane scaffold, the quaternary ammonium salt 34 was identified as a very potent M(3) mAChR antagonist. The compound was functionally active and displayed greater than 24 h duration of action in a mouse model of bronchoconstriction.

A series of novel biphenyl piperazines was discovered as highly potent muscarinic acetylcholine receptor antagonists via high throughput screening and subsequent optimization. Compound 5c with respective 500- and 20-fold subtype selectivity for M3 over M2 and M1 exhibited excellent inhibitory activity and long duration of action in a bronchoconstriction in vivo model in mice via intranasal administration. The novel inhaled mAChR antagonists are potentially useful therapeutic agents for the treatment of chronic obstructive pulmonary disease.