Plasmon assisted photonic crystal quantum dot sensors

We report Quantum Dot Infrared Detectors (QDIP) where light coupling to the self assembled quantum dots is achieved through plasmons occurring at the metal-semiconductor interface. The detector structure consists of an asymmetric InAs/InGaAs/GaAs dots-in-a-well (DWELL) structure and a thick layer of GaAs sandwiched between two highly doped n-GaAs contact layers, grown on a semi-insulating GaAs substrate. The aperture of the detector is covered with a thin metallic layer which along with the dielectric layer confines light in the vertical direction. Sub-wavelength two-dimensional periodic patterns etched in the metallic layer covering the aperture of the detector and the active region creates a micro-cavity that concentrate light in the active region leading to intersubband transitions between states in the dot and the ones in the well. The sidewalls of the detector were also covered with metal to ensure that there is no leakage of light into the active region other than through the metal covered aperture. An enhanced spectral response when compared to the normal DWELL detector is obtained despite the absence of any aperture in the detector. The spectral response measurements show that the Long Wave InfraRed (LWIR) region is enhanced when compared to the Mid Wave InfraRed (MWIR) region. This may be due to coupling of light into the active region by plasmons that are excited at the metal-semiconductor interface. The patterned metal-dielectric layers act as an optical resonator thereby enhancing the coupling efficiency of light into the active region at the specified frequency. The concept of plasmon-assisted coupling is in principle technology agnostic and can be easily integrated into present day infrared sensors

Plasmon assisted photonic crystal quantum dot sensors

We report Quantum Dot Infrared Detectors (QDIP) where light coupling to the self assembled quantum dots is achieved through plasmons occurring at the metal-semiconductor interface. The detector structure consists of an asymmetric InAs/InGaAs/GaAs dots-in-a-well (DWELL) structure and a thick layer of GaAs sandwiched between two highly doped n-GaAs contact layers, grown on a semi-insulating GaAs substrate. The aperture of the detector is covered with a thin metallic layer which along with the dielectric layer confines light in the vertical direction. Sub-wavelength two-dimensional periodic patterns etched in the metallic layer covering the aperture of the detector and the active region creates a micro-cavity that concentrate light in the active region leading to intersubband transitions between states in the dot and the ones in the well. The sidewalls of the detector were also covered with metal to ensure that there is no leakage of light into the active region other than through the metal covered aperture. An enhanced spectral response when compared to the normal DWELL detector is obtained despite the absence of any aperture in the detector. The spectral response measurements show that the Long Wave InfraRed (LWIR) region is enhanced when compared to the Mid Wave InfraRed (MWIR) region. This may be due to coupling of light into the active region by plasmons that are excited at the metal-semiconductor interface. The patterned metal-dielectric layers act as an optical resonator thereby enhancing the coupling efficiency of light into the active region at the specified frequency. The concept of plasmon-assisted coupling is in principle technology agnostic and can be easily integrated into present day infrared sensors

Aristolochic acid exposure in Romania and implications for renal cell carcinoma

Background: Aristolochic acid (AA) is a nephrotoxicant associated with AA nephropathy (AAN) and upper urothelial tract cancer (UUTC). Whole-genome sequences of 14 Romanian cases of renal cell carcinoma (RCC) recently exhibited mutational signatures consistent with AA exposure, although RCC had not been previously linked with AAN and AA exposure was previously reported only in localised rural areas. Methods: We performed mass spectrometric measurements of the aristolactam (AL) DNA adduct 7-(deoxyadenosin-N6-yl) aristolactam I (dA-AL-I) in nontumour renal tissues of the 14 Romanian RCC cases and 15 cases from 3 other countries. Results: We detected dA-AL-I in the 14 Romanian cases at levels ranging from 0.7 to 27 adducts per 108 DNA bases, in line with levels reported in Asian and Balkan populations exposed through herbal remedies or food contamination. The 15 cases from other countries were negative. Interpretation: Although the source of exposure is uncertain and likely different in AAN regions than elsewhere, our results demonstrate that AA exposure in Romania exists outside localised AAN regions and provide further evidence implicating AA in RCC

Modular total synthesis of lamellarin G trimethyl ether

A modular synthesis of the lamellarin G trimethyl ether has been developed based on the application of several reaction -sequences which include Friedel-Crafts acylation, esterification, haloarylation, and oxidative cyclization. The formation of pyrrolo [2,1-a]isoquinoline core, the key step for the successful completion of lamellarin G trimethyl ether synthesis, is comfortably accomplished through the haloarylation of 3-bromo-4-(3,4-dimethoxy-benzoyl)-6,7-dimethoxy-chroman-2-one which has resulted in exclusive endo product

[Bmim]PF<SUB>6</SUB>/RuCl<SUB>3</SUB>·xH<SUB>2</SUB>O: a novel and recyclable catalytic system for the oxidative coupling of β-naphthols

2-Naphthols readily undergo oxidative coupling in the presence of RuCl<SUB>3</SUB>·xH<SUB>2</SUB>O in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF<SUB>6</SUB>) ionic liquid under aerobic conditions to afford binaphthols in excellent yields with high selectivity. The β-naphthols show enhanced reactivity in ionic liquids, thereby reducing reaction times and improving the yields significantly. The recovered ionic liquid containing ruthenium catalyst can be reused in three to four successive runs with a gradual decrease in activity

Bismuth (III) triflate catalyzed condensation of isatin with indoles and pyrroles: a facile synthesis of 3,3-diindolyl-and 3,3-dipyrrolyl oxindoles

Indoles and pyrroles undergo a rapid condensation with isatin in the presence of 2 mol&#x0025; of Bi(OTf)<SUB>3</SUB>, under mild reaction conditions, to afford the corresponding 3,3-di(3-indolyl)- and 3,3-di(2-pyrroryl)oxindoles in excellent yields and high regioselectivity. This method is ideal for the direct introduction of indoles and pyrroles onto an isatin moiety at the 3-position

A Tet-Inducible CRISPR Platform for High-Fidelity Editing of Human Pluripotent Stem Cells

Pluripotent stem cells (PSCs) offer an exciting resource for probing human biology; however, gene-editing efficiency remains relatively low in many cell types, including stem cells. Gene-editing using the CRISPR-Cas9 system offers an attractive solution that improves upon previous gene-editing approaches; however, like other technologies, off-target mutagenesis remains a concern. High-fidelity Cas9 variants greatly reduce off-target mutagenesis and offer a solution to this problem. To evaluate their utility as part of a cell-based gene-editing platform, human PSC lines were generated with a high-fidelity (HF) tetracycline-inducible engineered Streptococcus pyogenes SpCas9 (HF-iCas9) integrated into the AAVS1 safe harbor locus. By engineering cells with controllable expression of Cas9, we eliminated the need to include a large Cas9-expressing plasmid during cell transfection. Delivery of genetic cargo was further optimized by packaging DNA targeting guide RNAs (gRNAs) and donor fragments into a single plasmid backbone. The potential of homology-directed repair (HDR) based gene knock-in at the CLYBL safe harbor site and endogenous SOX2 and SIX6 genes were demonstrated. Moreover, we used non-homologous end-joining (NHEJ) for gene knockout of disease-relevant alleles. These high-fidelity CRISPR tools and the resulting HF-iCas9 cell lines will facilitate the production of cell-type reporters and mutants across different genetic backgrounds