8,396 research outputs found
CN and HNC Line Emission in IR Luminous Galaxies
We have observed HNC 1-0, CN 1-0 and 2-1 line emission in a sample of 13 IR
luminous (LIRGs, L_IR > 10E11 Lo) starburst and Seyfert galaxies. HNC 1-0 is
detected in 9, CN 1-0 is detected in 10 and CN 2-1 in 7 of the galaxies. We
also report the first detection of HC3N (10-9) emission in Arp220. The
excitation of HNC and CN emission requires densities n > 10E4 cm-3. We compare
their intensities to that of the usual high density tracer HCN. The
I(HCN)/I(HNC}) and I(HCN)/I(CN) 1-0 line intensity ratios vary significantly,
from 0.5 to >6, among the galaxies. This implies that the actual properties of
the dense gas is varying among galaxies who otherwise have similar I(CO)/I(HCN)
line intensity ratios. We suggest that the HNC emission is not a reliable
tracer of cold (10 K) gas at the center of LIRGs, as it often is in the disk of
the Milky Way. Instead, the HNC abundance may remain substantial, despite high
gas temperatures, because the emission is emerging from regions where the HCN
and HNC formation and destruction processes are dominated by ion-neutral
reactions which are not strongly dependent on kinetic temperature. We find five
galaxies (four AGNs and one starburst) where the I(HCN)/I(HNC) intensity ratio
is close to unity. In other AGNs, however, I(HCN)/I(HNC}) is >4. The CN
emission is on average a factor of two fainter than HCN, but the variation is
large and there seems to be a trend of reduced relative CN luminosity with
increasing IR luminosity. One galaxy, NGC3690, has a CN luminosity twice that
of HCN and its ISM is thus strongly affected by UV radiation. We discuss the
I(HCN)/I(HNC) and I(HCN)/I(CN) line ratios as indicators of starburst
evolution.Comment: 12 pages, 4 figures. Accepted for publication in Astronomy and
Astrophysic
The effects of ground hydrology on climate sensitivity to solar constant variations
The effects of two different evaporation parameterizations on the climate sensitivity to solar constant variations are investigated by using a zonally averaged climate model. The model is based on a two-level quasi-geostrophic zonally averaged annual mean model. One of the evaporation parameterizations tested is a nonlinear formulation with the Bowen ratio determined by the predicted vertical temperature and humidity gradients near the earth's surface. The other is the linear formulation with the Bowen ratio essentially determined by the prescribed linear coefficient
The New York Pharmaceutical Cost Transparency Act: How a Narrow View of the Prescription Drug Pricing Puzzle Renders a Well-intentioned Bill Irrational
Pricing prescription pharmaceuticals is a complex process that entails the consideration of a multitude of factors, not the least of which is the research and development expenditure exhausted by drug makers to gain FDA approval. While public sentiment has increasingly turned against the pharmaceutical industry due to its perceived greed as manifested in the high cost of its drugs, the intricacies of pricing such unique products is rarely discussed. A recently proposed New York state bill, the Pharmaceutical Cost Transparency Act (the NYPCTA), continues this unfortunate trend, by requiring companies to disclose the R&D costs of newly approved drugs in an effort to educate the public—and to shame drug makers into lowering their prices. The NYPCTA, however, paints an overly simplistic picture of the prescription drug pricing formula, leaving out important variables including the cost of drugs that failed in testing and price controls on drugs in many foreign markets. Given these shortcomings, the bill finds itself at risk of failing the minimal scrutiny constitutional standard applied to government regulation of businesses. This risk would be eliminated with minor amendments and additions to the NYPCTA, which would bolster the legislation to where it would genuinely educate the public on the factors that converge in setting a drug\u27s price
The Military Trial at Rennes: Text and Subtext of the Dreyfus Affair
Discusses the Dreyfus affair and how the outside world viewed France\u27s conduct. This article provides insight into how the trial was conducted and the evidence that was offered
The New York Pharmaceutical Cost Transparency Act: How a Narrow View of the Prescription Drug Pricing Puzzle Renders a Well-intentioned Bill Irrational
Pricing prescription pharmaceuticals is a complex process that entails the consideration of a multitude of factors, not the least of which is the research and development expenditure exhausted by drug makers to gain FDA approval. While public sentiment has increasingly turned against the pharmaceutical industry due to its perceived greed as manifested in the high cost of its drugs, the intricacies of pricing such unique products is rarely discussed. A recently proposed New York state bill, the Pharmaceutical Cost Transparency Act (the NYPCTA), continues this unfortunate trend, by requiring companies to disclose the R&D costs of newly approved drugs in an effort to educate the public—and to shame drug makers into lowering their prices. The NYPCTA, however, paints an overly simplistic picture of the prescription drug pricing formula, leaving out important variables including the cost of drugs that failed in testing and price controls on drugs in many foreign markets. Given these shortcomings, the bill finds itself at risk of failing the minimal scrutiny constitutional standard applied to government regulation of businesses. This risk would be eliminated with minor amendments and additions to the NYPCTA, which would bolster the legislation to where it would genuinely educate the public on the factors that converge in setting a drug\u27s price
A condition-specific codon optimization approach for improved heterologous gene expression in Saccharomyces cerevisiae
All authors are with the Department of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St. Stop C0400, Austin, TX 78712, USA -- Hal S. Alper is with the Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Avenue, Austin, TX 78712, USA
-- Amanda M. Lanza Current Address: Bristol-Myers Squibb, Biologics Development, 35 South Street, Hopkinton, MA 01748, USABackground: Heterologous gene expression is an important tool for synthetic biology that enables metabolic engineering and the production of non-natural biologics in a variety of host organisms. The translational efficiency of heterologous genes can often be improved by optimizing synonymous codon usage to better match the host organism. However, traditional approaches for optimization neglect to take into account many factors known to influence synonymous codon distributions. Results: Here we define an alternative approach for codon optimization that utilizes systems level information and codon context for the condition under which heterologous genes are being expressed. Furthermore, we utilize a probabilistic algorithm to generate multiple variants of a given gene. We demonstrate improved translational efficiency using this condition-specific codon optimization approach with two heterologous genes, the fluorescent protein-encoding eGFP and the catechol 1,2-dioxygenase gene CatA, expressed in S. cerevisiae. For the latter case, optimization for stationary phase production resulted in nearly 2.9-fold improvements over commercial gene optimization algorithms. Conclusions: Codon optimization is now often a standard tool for protein expression, and while a variety of tools and approaches have been developed, they do not guarantee improved performance for all hosts of applications. Here, we suggest an alternative method for condition-specific codon optimization and demonstrate its utility in Saccharomyces cerevisiae as a proof of concept. However, this technique should be applicable to any organism for which gene expression data can be generated and is thus of potential interest for a variety of applications in metabolic and cellular engineering.Chemical EngineeringInstitute for Cellular and Molecular [email protected]
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