Iridium-Catalyzed Silylation of C-H Bonds in Unactivated Arenes: A Sterically Encumbered Phenanthroline Ligand Accelerates Catalysis.

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]2 and 2,9-Me2-phenanthroline (2,9-Me2-phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H2 byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me2-phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me2-phen ligand are due to a more thermodynamically favorable oxidative addition of aryl C-H bonds

Physical Structure and Nature of Supernova Remnants in M101

Supernova remnant (SNR) candidates in the giant spiral galaxy M101 have been previously identified from ground-based H-alpha and [SII] images. We have used archival Hubble Space Telescope (HST) H-alpha and broad-band images as well as stellar photometry of 55 SNR candidates to examine their physical structure, interstellar environment, and underlying stellar population. We have also obtained high-dispersion echelle spectra to search for shocked high-velocity gas in 18 SNR candidates, and identified X-ray counterparts to SNR candidates using data from archival observations made by the Chandra X-ray Observatory. Twenty-one of these 55 SNR candidates studied have X-ray counterparts, although one of them is a known ultra-luminous X-ray source. The multi-wavelength information has been used to assess the nature of each SNR candidate. We find that within this limited sample, ~16% are likely remnants of Type Ia SNe and ~45% are remnants of core-collapse SNe. In addition, about ~36% are large candidates which we suggest are either superbubbles or OB/HII complexes. Existing radio observations are not sensitive enough to detect the non-thermal emission from these SNR candidates. Several radio sources are coincident with X-ray sources, but they are associated with either giant HII regions in M101 or background galaxies. The archival HST H-alpha images do not cover the entire galaxy and thus prevents a complete study of M101. Furthermore, the lack of HST [SII] images precludes searches for small SNR candidates which could not be identified by ground-based observations. Such high-resolution images are needed in order to obtain a complete census of SNRs in M101 for a comprehensive investigation of the distribution, population, and rates of SNe in this galaxy.Comment: 37 pages, 4 Tables, 7 Figures, accepted for publication in the Astronomical Journa

Effects of Soy Peptide on Dendritic Cells

poster abstractInnate immunity is mediated by effector cells, including NK cells, dendritic cells (DCs), macrophages, and polymorphonuclear phagocytes, which can respond immediately after activation through receptors encoded by germ-line genes. Innate immune responses represent the first line of defense in immunosurveillance. Interventions that enhance the functions of innate immunity will be an important armamentarium to human health. We recently exploited a natural dietary soy peptide called lunasin to improve the immune functions. The hypothesis was that lunasin peptide has stimulatory effects on immune cells. To test this hypothesis, human peripheral blood mononuclear cells (PBMCs) of healthy donors were stimulated with or without lunasin. We found that lunasin is capable of stimulating DCs to up-regulate chemokines (CCL2, CCL3, and CCL4), cytokines (TNFα and IFNα), and co-stimulatory molecules (CD80, CD86). In addition, lunasin-treated DCs can provide NK with required signals for activation. Taken together, our results support the immunomodulatory activity of soy peptide on DCs, which leads to enhancement of innate immunity

Post-prohibition changes in cannabis genetics

This research examines changes in Cannabis genetics with a focus on Cannabis genetic bottlenecking. Significant knowledge gaps exist in the study of how and why Cannabis genetics have changed over time. To fill these gaps, a series of semi-structured qualitative interviews were conducted with self-identified Cannabis breeders around the world. Previous qualitative Cannabis research has centered around users, growers, and dealers with few studies looking exclusively at Cannabis breeders. Results include insights into becoming a Cannabis breeder, Cannabis ideotypes, as well as Cannabis genetic bottlenecking due to unanticipated genetic linkages combined with the emphasis on breeding for agronomic factors such as shorter flowering times and solventless hashish extraction yields caused by Post-Prohibition economic pressures. These results may be meaningful in highlighting the role of government action on declining genetic diversity in the worldwide Cannabis market - and its impacts on the medicinal potential and therapeutic index of available Cannabis products

Nonnegative Tensor Completion via Integer Optimization

Unlike matrix completion, tensor completion does not have an algorithm that is known to achieve the information-theoretic sample complexity rate. This paper develops a new algorithm for the special case of completion for nonnegative tensors. We prove that our algorithm converges in a linear (in numerical tolerance) number of oracle steps, while achieving the information-theoretic rate. Our approach is to define a new norm for nonnegative tensors using the gauge of a particular 0-1 polytope; integer linear programming can, in turn, be used to solve linear separation problems over this polytope. We combine this insight with a variant of the Frank-Wolfe algorithm to construct our numerical algorithm, and we demonstrate its effectiveness and scalability through computational experiments using a laptop on tensors with up to one-hundred million entries

Direct-detection Free-space Laser Transceiver Test-bed

NASA Goddard Space Flight Center is developing a direct-detection free-space laser communications transceiver test bed. The laser transmitter is a master-oscillator power amplifier (MOPA) configuration using a 1060 nm wavelength laser-diode with a two-stage multi-watt Ytterbium fiber amplifier. Dual Mach-Zehnder electro-optic modulators provide an extinction ratio greater than 40 dB. The MOPA design delivered 10-W average power with low-duty-cycle PPM waveforms and achieved 1.7 kW peak power. We use pulse-position modulation format with a pseudo-noise code header to assist clock recovery and frame boundary identification. We are examining the use of low-density-parity-check (LDPC) codes for forward error correction. Our receiver uses an InGaAsP 1 mm diameter photocathode hybrid photomultiplier tube (HPMT) cooled with a thermo-electric cooler. The HPMT has 25% single-photon detection efficiency at 1064 nm wavelength with a dark count rate of 60,000/s at -22 degrees Celsius and a single-photon impulse response of 0.9 ns. We report on progress toward demonstrating a combined laser communications and ranging field experiment

A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms

We describe a genetic variation map for the chicken genome containing 2.8 million single-nucleotide polymorphisms ( SNPs). This map is based on a comparison of the sequences of three domestic chicken breeds ( a broiler, a layer and a Chinese silkie) with that of their wild ancestor, red jungle fowl. Subsequent experiments indicate that at least 90% of the variant sites are true SNPs, and at least 70% are common SNPs that segregate in many domestic breeds. Mean nucleotide diversity is about five SNPs per kilobase for almost every possible comparison between red jungle fowl and domestic lines, between two different domestic lines, and within domestic lines - in contrast to the notion that domestic animals are highly inbred relative to their wild ancestors. In fact, most of the SNPs originated before domestication, and there is little evidence of selective sweeps for adaptive alleles on length scales greater than 100 kilobases