Isotropic C6, C8 and C10 interaction coefficients for CH 4, C 2H 6, C 3H 8, n-C 4H 10 and cyclo- C3H 6

NASA Astrophysics Data System (ADS)

Thomas, Gerald F.; Mulder, Fred; Meath, William J.

1980-12-01

The non-empirical generalized Kirkwood, Unsöld, and the single-Δ Unsöld methods (with double-zeta quality SCF wave-functions) are used to calculate isotropic dispersion (and induction) energy coefficients C2n, with n ⩽ 5, for interactions involving ground state CH 4, C 2H 6, C 3H 8, n-C 4H 10 and cyclo-C 3H 6. Results are also given for the related multipole polarizabilities α l, multipole sums S1/(0) and S1(-1) which are evaluated using sum rules, and the permanent multipole moments. for l = 1 (dipole) to l = 3 (octupole). Estimates of the reliability of the non-empirical methods, for the type of molecules considered, are obtained by a comparison with accurate literature values of α 1S1(-1) and C6. This, and the asymptotic properties of the multipolar expansion of the dispersion energy, the use to discuss recommended representation for the isotropic long range interaction energies through R-10 where R is the intermolecular separation.

Antibody persistence and serological protection among seasonal 2007 influenza A(H1N1) infected subjects: Results from the FLUREC cohort study.

PubMed

Delabre, Rosemary Markovic; Salez, Nicolas; Lemaitre, Magali; Leruez-Ville, Marianne; de Lamballerie, Xavier; Carrat, Fabrice

2015-12-08

Haemagglutination-inhibition (HI) antibody titer is a correlate of protection against influenza; its persistence after infection or vaccination is important to determining susceptibility to subsequent infection. Few studies, however, have reported longitudinal data regarding the magnitude and duration of HI protection following natural seasonal influenza A infection. Using French influenza cohort study data collected from 2008 to 2010, we investigated persistence of serological protection among subjects according to influenza-like illness (ILI) and laboratory-confirmed seasonal 2007 influenza A(H1N1) infection status at inclusion in 2008 (ILI-A(H1N1) positive, ILI-A(H1N1) negative, or no-ILI). Antibody titers against seasonal 2007 A(H1N1) were determined using the HI technique for sera. Regression models for interval-censored data were used to estimate geometric mean titers (GMT) for HI assays. A logistic regression model adjusted for age group (subjects <30, 30-50 and >50 years old) was used to quantify the association between HI titer and protection against infection. Based on 310 total subjects, influenza A(H1N1) infection was confirmed in 39 of 115 ILI subjects at inclusion. GMT associated with 50% probability of protection among ILI subjects decreased with age group (subjects <30 yo: GMT of 40.8 was associated with 50% [95CI: 29.3%; 70.7%] probability of protection, subjects 30-50 yo: 26.8 [95CI: 34.4%; 65.6%] and subjects >50 yo: 8.9 [95CI: 15.3%; 84.7%]). GMT declined after the first annual study visit among ILI-A(H1N1) positive subjects but remained higher compared to inclusion at the 2010 study visit (41.5 [95CI: 34.8; 49.5], p=0.0157). GMT remained stable among ILI-A(H1N1) negative subjects (p=0.7502), but decreased among no-ILI subjects (p<0.0001). Our results confirm the positive relationship between HI titer and probability of protection among naturally infected subjects, and provides evidence that protection associated with HI titer varies with age

Electron scattering by the hydrocarbons C4H6,C5H8 , and C6H10

NASA Astrophysics Data System (ADS)

Kiataki, Matheus B.; Pastega, Diego F.; Bettega, Márcio H. F.

2017-10-01

We report calculated elastic integral and differential cross sections for electron collisions with the hydrocarbons 1,3-butadiene (C4H6 ), 2-methyl-1,3-butadiene (C5H8 ), and 2,3-dimethyl-1,3-butadiene (C6H10 ) for impact energies up to 15 eV. Our calculations were performed with the Schwinger Multichannel Method with pseudopotentials, in the static-exchange and static-exchange plus polarization approximations. These molecules differ for the presence of one methyl group, in the case of C5H8 , and two methyl groups, in the case of C6H10 in substitution of one and two hydrogen atoms in C4H6 , respectively (methylation effect). For the polar molecule 2-methyl-1,3-butadiene, we included the Born closure procedure in order to account for the long-range potential. We found two π* shape resonances in the integral cross section of each one of the molecules studied. The present results are also compared with the experimental values for the resonances positions and with total cross sections available in the literature. In particular, we show that the minimum in the total cross section of C5H8 located at around 1.6 eV and assigned by the authors as a Ramsauer-Townsend minimum is, actually, a valley between the two π* shape resonances. Also for the C5H8 molecule, the enhancement in the total cross section below 1.6 eV is the tail of the low-lying shape resonance and not an effect due to its permanent dipole moment, as suggested by the authors. We discuss the influence of the methylation effect in the shape and magnitude of the elastic cross sections and also in the location of the π* shape resonances of these hydrocarbons.

Absence of influenza A(H1N1) during seasonal and pandemic seasons in a sentinel nursing home surveillance network in the Netherlands.

PubMed

Enserink, Remko; Meijer, Adam; Dijkstra, Frederika; van Benthem, Birgit; van der Steen, Jenny T; Haenen, Anja; van Delden, Hans; Cools, Herman; van der Sande, Marianne; Veldman-Ariesen, Marie-Jose

2011-12-01

To describe the epidemiological, virological, and institutional characteristics of influenza-like illness (ILI) in nursing homes (NHs). Continuous clinical surveillance of ILI and virological surveillance of ILI and other acute respiratory infections (ARIs) during four influenza seasons. National sentinel NH surveillance network. National sentinel residents. Weekly registration of ILI cases (influenza seasons 2008/09-2009/10), influenza virus detection (influenza seasons 2006/07-2009/10), and collection of institutional characteristics of NHs at start of participation. During the 2008/09 influenza season, ILI incidence started to rise in Week 49 of 2008, peaked in Week 3 of 2009 (158 cases per 10,000 resident weeks), and flattened out by Week 16 of 2009 (mean ILI incidence during epidemic: 73 cases per 10,000 resident weeks). During the 2009/10 influenza pandemic, there was no epidemic peak. Influenza virus type and subtype varied throughout virological surveillance but was limited to influenza A(H3N2) and B viruses. Higher staff vaccination coverage (>15%) was associated with lower ILI-incidence in the 2008/09 influenza season in a univariate negative binomial regression analysis (incidence rate ratio = 0.3, 95% confidence interval = 0.1-0.8)). Neither seasonal nor pandemic influenza A(H1N1) viruses were detected in the network, despite widespread community transmission of seasonal and influenza A(H1N1) virus. ILI incidence trends corresponded to virological trends. Sentinel surveillance of ILI combining clinical and virological data in NHs increases understanding of transmission risks in this specific vulnerable population. © 2011, Copyright the Authors Journal compilation © 2011, The American Geriatrics Society.

Internet-based monitoring of influenza-like illness (ILI) in the general population of the Netherlands during the 2003-2004 influenza season.

PubMed

Marquet, Richard L; Bartelds, Aad I M; van Noort, Sander P; Koppeschaar, Carl E; Paget, John; Schellevis, François G; van der Zee, Jouke

2006-10-04

An internet-based survey of influenza-like illness (ILI)--the Great Influenza Survey or GIS--was launched in the Netherlands in the 2003-2004 influenza season. The aim of the present study was to validate the representativeness of the GIS population and to compare the GIS data with the official ILI data obtained by Dutch GPs participating in the Dutch Sentinel Practice Network. Direct mailings to schools and universities, and repeated interviews on television and radio, and in newspapers were used to kindle the enthusiasm of a broad section of the public for GIS. Strict symptomatic criteria for ILI were formulated with the assistance of expert institutes and only participants who responded at least five times to weekly e-mails asking them about possible ILI symptoms were included in the survey. Validation of GIS was done at different levels: 1) some key demographic (age distribution) and public health statistics (prevalence of asthma and diabetes, and influenza vaccination rates) for the Dutch population were compared with corresponding figures calculated from GIS; 2) the ILI rates in GIS were compared with the ILI consultation rates reported by GPs participating in the Dutch Sentinel Practice Network. 13,300 persons (53% of total responders), replied at least five times to weekly e-mails and were included in the survey. As expected, there was a marked under-representation of the age groups 0-10 years and 81->90 years in the GIS population, although the similarities were remarkable for most other age groups, albeit that the age groups between 21 and 70 years were slightly overrepresented. There were striking similarities between GIS and the Dutch population with regard to the prevalence of asthma (6.4% vs. 6.9%) and the influenza vaccination rates, and to a lesser degree for diabetes (2.4% vs. 3.5%). The vaccination rates in patients with asthma or diabetes, and persons older than 65 years were 68%, 85%, and 85% respectively in GIS, while the corresponding

CFD Growth of 3C-SiC on 4H/6H Mesas

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Trunek, Andrew J.; Spry, David J.; Powell, J. Anthony; Du, Hui; Skowronski, Marek; Huang, XianRong; Dudley, Michael

2006-01-01

This article describes growth and characterization of the highest quality reproducible 3C-SiC heteroepitaxial films ever reported. By properly nucleating 3C-SiC growth on top of perfectly on-axis (0001) 4H-SiC mesa surfaces completely free of atomic scale steps and extended defects, growth of 3C-SiC mesa heterofilms completely free of extended crystal defects can be achieved. In contrast, nucleation and growth of 3C-SiC mesa heterofilms on top of 4H-SiC mesas with atomic-scale steps always results in numerous observable dislocations threading through the 3C-SiC epilayer. High-resolution X-ray diffraction and transmission electron microscopy measurements indicate non-trivial in-plane lattice mismatch between the 3C and 4H layers. This mismatch is somewhat relieved in the step-free mesa case via misfit dislocations confined to the 3C/4H interfacial region without dislocations threading into the overlying 3C-SiC layer. These results indicate that the presence or absence of steps at the 3C/4H heteroepitaxial interface critically impacts the quality, defect structure, and relaxation mechanisms of single-crystal heteroepitaxial 3C-SiC films.

Continued dominance of pandemic A(H1N1) 2009 influenza in Victoria, Australia in 2010

PubMed Central

Grant, Kristina; Franklin, Lucinda; Kaczmarek, Marlena; Hurt, Aeron; Kostecki, Renata; Kelly, Heath

2011-01-01

The 2010 Victorian influenza season was characterized by normal seasonal influenza activity and the dominance of the pandemic A(H1N1) 2009 strain. General Practice Sentinel Surveillance rates peaked at 9.4 ILI cases per 1000 consultations in week 36 for metropolitan practices, and at 10.5 ILI cases per 1000 in the following week for rural practices. Of the 678 ILI cases, 23% were vaccinated, a significantly higher percentage than in previous years. A significantly higher percentage of ILI patients were swabbed in 2010 compared to 2003–2008, but similar to 2009, with a similar percentage being positive for influenza as in previous years. Vaccination rates increased with patient age. Melbourne Medical Deputising Service rates peaked in week 35 at 19.1 ILI cases per 1000 consultations. Of the 1914 cases of influenza notified to the Department of Health, Victoria, 1812 (95%) were influenza A infections – 1001 (55%) pandemic A(H1N1) 2009, 4 (< 1%) A(H3N2) and 807 (45%) not subtyped; 88 (5%) were influenza B; and 14 (< 1%) were influenza A and B co-infections. The World Health Organization Collaborating Centre for Reference and Research on Influenza tested 403 isolates of which 261 were positive for influenza, 250 of which were influenza A and 11 were influenza B. Ninety-two per cent of the influenza A viruses were pandemic A(H1N1) 2009, and following antigenic analysis all of these were found to be similar to the current vaccine strain. Three viruses (0.9%) were found to be oseltamivir resistant due to an H275Y mutation in the neuraminidase gene. PMID:23908889

Genetic polymorphisms, forensic efficiency and phylogenetic analysis of 15 autosomal STR loci in the Kazak population of Ili Kazak Autonomous Prefecture, northwestern China.

PubMed

Feng, Chunmei; Wang, Xin; Wang, Xiaolong; Yu, Hao; Zhang, Guohua

2018-03-01

We investigated the frequencies of 15 autosomal STR loci in the Kazak population of the Ili Kazak Autonomous Prefecture with the aim of expanding the available population information in human genetic databases and for forensic DNA analysis. Genetic polymorphisms of 15 autosomal short tandem repeat (STR) loci were analysed in 456 individuals of the Kazak population from Ili Kazakh Autonomous Prefecture, northwestern China. A total of 173 alleles at 15 autosomal STR loci were found; the allele frequencies ranged from 0.5022-0.0011. The combined power of discrimination and exclusion statistics for the 15 STR loci were 0.999 999 999 85 and 0.999 998 800 65, respectively. In addition, phylogenetic analysis involving the Ili Uygur population and other relevant populations was carried out. A neighbour-joining tree and multidimensional scaling plot were generated based on Nei's standard genetic distance. Results of the population comparison indicated that the Ili Uygur population was most closely related genetically to the Uygur populations from other regions in China. These findings are consistent with the historical and geographic backgrounds of these populations.

Epidemiology of influenza in West Africa after the 2009 influenza A(H1N1) pandemic, 2010-2012.

PubMed

Talla Nzussouo, Ndahwouh; Duque, Jazmin; Adedeji, Adebayo Abel; Coulibaly, Daouda; Sow, Samba; Tarnagda, Zekiba; Maman, Issaka; Lagare, Adamou; Makaya, Sonia; Elkory, Mohamed Brahim; Kadjo Adje, Herve; Shilo, Paul Alhassan; Tamboura, Boubou; Cisse, Assana; Badziklou, Kossi; Maïnassara, Halima Boubacar; Bara, Ahmed Ould; Keita, Adama Mamby; Williams, Thelma; Moen, Ann; Widdowson, Marc-Alain; McMorrow, Meredith

2017-12-04

Over the last decade, capacity for influenza surveillance and research in West Africa has strengthened. Data from these surveillance systems showed influenza A(H1N1)pdm09 circulated in West Africa later than in other regions of the continent. We contacted 11 West African countries to collect information about their influenza surveillance systems (number of sites, type of surveillance, sampling strategy, populations sampled, case definitions used, number of specimens collected and number of specimens positive for influenza viruses) for the time period January 2010 through December 2012. Of the 11 countries contacted, 8 responded: Burkina Faso, Cote d'Ivoire, Mali, Mauritania, Niger, Nigeria, Sierra Leone and Togo. Countries used standard World Health Organization (WHO) case definitions for influenza-like illness (ILI) and severe acute respiratory illness (SARI) or slight variations thereof. There were 70 surveillance sites: 26 SARI and 44 ILI. Seven countries conducted SARI surveillance and collected 3114 specimens of which 209 (7%) were positive for influenza viruses. Among influenza-positive SARI patients, 132 (63%) were influenza A [68 influenza A(H1N1)pdm09, 64 influenza A(H3N2)] and 77 (37%) were influenza B. All eight countries conducted ILI surveillance and collected 20,375 specimens, of which 2278 (11%) were positive for influenza viruses. Among influenza-positive ILI patients, 1431 (63%) were influenza A [820 influenza A(H1N1)pdm09, 611 influenza A(H3N2)] and 847 (37%) were influenza B. A majority of SARI and ILI case-patients who tested positive for influenza (72% SARI and 59% ILI) were children aged 0-4 years, as were a majority of those enrolled in surveillance. The seasonality of influenza and the predominant influenza type or subtype varied by country and year. Influenza A(H1N1)pdm09 continued to circulate in West Africa along with influenza A(H3N2) and influenza B during 2010-2012. Although ILI surveillance systems produced a robust number of samples

Case of seasonal reassortant A(H1N2) influenza virus infection, the Netherlands, March 2018.

PubMed

Meijer, Adam; Swaan, Corien M; Voerknecht, Martin; Jusic, Edin; van den Brink, Sharon; Wijsman, Lisa A; Voordouw, Bettie Cg; Donker, Gé A; Sleven, Jacqueline; Dorigo-Zetsma, Wendelien W; Svraka, Sanela; van Boven, Michiel; Haverkate, Manon R; Timen, Aura; van Dissel, Jaap T; Koopmans, Marion Pg; Bestebroer, Theo M; Fouchier, Ron Am

2018-04-01

A seasonal reassortant A(H1N2) influenza virus harbouring genome segments from seasonal influenza viruses A(H1N1)pdm09 (HA and NS) and A(H3N2) (PB2, PB1, PA, NP, NA and M) was identified in March 2018 in a 19-months-old patient with influenza-like illness (ILI) who presented to a general practitioner participating in the routine sentinel surveillance of ILI in the Netherlands. The patient recovered fully. Further epidemiological and virological investigation did not reveal additional cases.

Adult human metapneumonovirus (hMPV) pneumonia mimicking Legionnaire's disease.

PubMed

Cunha, Burke A; Irshad, Nadia; Connolly, James J

2016-01-01

In adults hospitalized with viral pneumonias the main differential diagnostic consideration is influenza pneumonia. The respiratory viruses causing viral influenza like illnesses (ILIs), e.g., RSV may closely resemble influenza. Rarely, extrapulmonary findings of some ILIs may resemble Legionnaire's disease (LD), e.g., adenovirus, human parainfluenza virus (HPIV-3). We present a most unusual case of human metapneumonovirus pneumonia (hMPV) with some characteristic extrapulmonary findings characteristic of LD, e.g., relative bradycardia, as well as mildly elevated serum transaminases and hyphosphatemia. We believe this is the first reported case of hMPV pneumonia in a hospitalized adult that had some features of LD. Copyright © 2016 Elsevier Inc. All rights reserved.

Analyzing Idioms and Their Frequency in Three Advanced ILI Textbooks: A Corpus-Based Study

ERIC Educational Resources Information Center

Alavi, Sepideh; Rajabpoor, Aboozar

2015-01-01

The present study aimed at identifying and quantifying the idioms used in three ILI "Advanced" level textbooks based on three different English corpora; MICASE, BNC and the Brown Corpus, and comparing the frequencies of the idioms across the three corpora. The first step of the study involved searching the books to find multi-word…

Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

DOEpatents

Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

2004-03-30

The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

Electrooxidative Rhodium-Catalyzed C-H/C-H Activation: Electricity as Oxidant for Cross-Dehydrogenative Alkenylation.

PubMed

Qiu, Youai; Kong, Wei-Jun; Struwe, Julia; Sauermann, Nicolas; Rogge, Torben; Scheremetjew, Alexej; Ackermann, Lutz

2018-05-14

Rhodium(III) catalysis has enabled a plethora of oxidative C-H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we herein describe the first electrochemical rhodium-catalyzed C-H activation that avoids hazardous chemical oxidants. Environmentally benign twofold C-H/C-H functionalizations were accomplished with weakly coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant and generating H 2 as the sole byproduct. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating obesity as a risk factor for influenza-like illness during the 2009 H1N1 influenza pandemic using the Health Survey for England.

PubMed

Murphy, Rachel; Fragaszy, Ellen B; Hayward, Andrew C; Warren-Gash, Charlotte

2017-01-01

Following the 2009 H1N1 influenza pandemic, obesity was shown to be associated with severe influenza outcomes. It remains unclear whether obesity was a risk factor for milder influenza-like illness (ILI). To determine whether obesity was associated with an increased risk of self-reported ILI during the 2009 H1N1 influenza pandemic using Health Survey for England (HSE) 2010 cross-sectional data. This study used HSE data collected from English households between January and December 2010. Weight and height measurements were taken by trained fieldworkers to determine obesity. ILI was defined as a positive response to the question "Have you had a flu-like illness where you felt feverish and had a cough or sore throat?" with illness occurring between May and December 2009. Multivariable logistic regression was used to evaluate the association between obesity and ILI. The study comprised 8407 participants (6984 adults, 1436 children), among whom 24.7% (95% CI: 23.6-25.9) were classified as obese. Of obese participants, 12.8% (95% CI: 11.1-14.8) reported ILI compared to 11.8% (95% CI: 10.8-12.8) of non-obese participants. The adjusted OR for ILI associated with obesity was 1.16 (95% CI: 0.98-1.38, P=.093). For adults and children, the adjusted ORs were 1.16 (95% CI: 0.97-1.38, P=.101) and 1.26 (95% CI: 0.72-2.21, P=.422), respectively. Household survey data showed no evidence that obesity was associated with an increase in self-reported ILI during the 2009 H1N1 influenza pandemic in England. Further studies using active prospective ILI surveillance combined with laboratory reporting would reduce bias and improve accuracy of outcome measurements. © 2016 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.

Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

DOEpatents

Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

2004-07-20

The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

Substrate-Mediated C-C and C-H Coupling after Dehalogenation.

PubMed

Kong, Huihui; Yang, Sha; Gao, Hongying; Timmer, Alexander; Hill, Jonathan P; Díaz Arado, Oscar; Mönig, Harry; Huang, Xinyan; Tang, Qin; Ji, Qingmin; Liu, Wei; Fuchs, Harald

2017-03-15

Intermolecular C-C coupling after cleavage of C-X (mostly, X = Br or I) bonds has been extensively studied for facilitating the synthesis of polymeric nanostructures. However, the accidental appearance of C-H coupling at the terminal carbon atoms would limit the successive extension of covalent polymers. To our knowledge, the selective C-H coupling after dehalogenation has not so far been reported, which may illuminate another interesting field of chemical synthesis on surfaces besides in situ fabrication of polymers, i.e., synthesis of novel organic molecules. By combining STM imaging, XPS analysis, and DFT calculations, we have achieved predominant C-C coupling on Au(111) and more interestingly selective C-H coupling on Ag(111), which in turn leads to selective synthesis of polymeric chains or new organic molecules.

Modeling and Forecasting Influenza-like Illness (ILI) in Houston, Texas Using Three Surveillance Data Capture Mechanisms.

PubMed

Paul, Susannah; Mgbere, Osaro; Arafat, Raouf; Yang, Biru; Santos, Eunice

2017-01-01

Objective The objective was to forecast and validate prediction estimates of influenza activity in Houston, TX using four years of historical influenza-like illness (ILI) from three surveillance data capture mechanisms. Background Using novel surveillance methods and historical data to estimate future trends of influenza-like illness can lead to early detection of influenza activity increases and decreases. Anticipating surges gives public health professionals more time to prepare and increase prevention efforts. Methods Data was obtained from three surveillance systems, Flu Near You, ILINet, and hospital emergency center (EC) visits, with diverse data capture mechanisms. Autoregressive integrated moving average (ARIMA) models were fitted to data from each source for week 27 of 2012 through week 26 of 2016 and used to forecast influenza-like activity for the subsequent 10 weeks. Estimates were then compared to actual ILI percentages for the same period. Results Forecasted estimates had wide confidence intervals that crossed zero. The forecasted trend direction differed by data source, resulting in lack of consensus about future influenza activity. ILINet forecasted estimates and actual percentages had the least differences. ILINet performed best when forecasting influenza activity in Houston, TX. Conclusion Though the three forecasted estimates did not agree on the trend directions, and thus, were considered imprecise predictors of long-term ILI activity based on existing data, pooling predictions and careful interpretations may be helpful for short term intervention efforts. Further work is needed to improve forecast accuracy considering the promise forecasting holds for seasonal influenza prevention and control, and pandemic preparedness.

Hyperfine excitation of C2H and C2D by para-H2

NASA Astrophysics Data System (ADS)

Dumouchel, Fabien; Lique, François; Spielfiedel, Annie; Feautrier, Nicole

2017-10-01

The [C2H]/[C2D] abundance ratio is a useful tool to explore the physical and chemical conditions of cold molecular clouds. Hence, an accurate determination of both the C2H and C2D abundances is of fundamental interest. Due to the low density of the interstellar medium, the population of the energy levels of the molecules is not at local thermodynamical equilibrium. Thus, the accurate modelling of the emission spectra requires the calculation of collisional rate coefficients with the most abundant interstellar species. Hence, we provide rate coefficients for the hyperfine excitation of C2H and C2D by para-H2(j=0), the most abundant collisional partner in cold molecular clouds. State-to-state rate coefficients between the lowest levels were computed for temperatures ranging from 5 to 80 K. For both isotopologues, the Δj = ΔF propensity rule is observed. The comparison between C2H and C2D rate coefficients shows that differences by up to a factor of two exist, mainly for Δj = ΔN = 1 transitions. The new rate coefficients will significantly help in the interpretation of recent observed spectra.

New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

NASA Astrophysics Data System (ADS)

Weng, Sheng-Feng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-04-01

Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La(1a), Ce(1b)) and [Ce2(C2O4)(C6H6O7)2] . 4H2O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1¯ (No. 2); compound 2 crystallized in monoclinic space group P21/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of CuII ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d1 excited state and two levels of the 4f1 ground state (2F5/2 and 2F7/2). Compounds 1b and 2 containing CeIII ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers.

Controlled growth of 3C-SiC and 6H-SiC films on low-tilt-angle vicinal (0001) 6H-SiC wafers

NASA Technical Reports Server (NTRS)

Powell, J. A.; Petit, J. B.; Edgar, J. H.; Jenkins, I. G.; Matus, L. G.

1991-01-01

It has been found that, with proper pregrowth surface treatment, 6H-SiC single-crystal films can be grown by chemical vapor deposition (CVD) at 1450 C on vicinal (0001) 6H-SiC with tilt angles as small as 0.1 deg. Previously, tilt angles of greater than 1.5 deg were required to achieve 6H on 6H at this growth temperature. In addition, 3C-SiC could be induced to grow within selected regions on the 6H substrate. the 3C regions contained few (or zero) double-positioning boundaries and a low density of stacking faults. A new growth model is proposed to explain the control of SiC polytype in this epitaxial film growth process.

Detections of Long Carbon Chains CH_{3}CCCCH, C_{6}H, LINEAR-C_{6}H_{2} and C_{7}H in the Low-Mass Star Forming Region L1527

NASA Astrophysics Data System (ADS)

Araki, Mitsunori; Takano, Shuro; Sakai, Nami; Yamamoto, Satoshi; Oyama, Takahiro; Kuze, Nobuhiko; Tsukiyama, Koichi

2017-06-01

Carbon chains in the warm carbon chain chemistry (WCCC) region has been searched in the 42-44 GHz region by using Green Bank 100 m telescope. Long carbon chains C_{7}H, C_{6}H, CH_{3}CCCCH, and linear-C_{6}H_{2} and cyclic species C_{3}H and C_{3}H_{2}O have been detected in the low-mass star forming region L1527, performing the WCCC. C_{7}H was detected for the first time in molecular clouds. The column density of C_{7}H is derived to be 6.2 × 10^{10} cm^{-2} by using the detected J = 24.5-23.5 and 25.5-24.5 rotational lines. The ^{2}Π_{1/2} electronic state of C_{6}H, locating 21.6 K above the ^{2}Π_{3/2} electronic ground state, and the K_a = 0 line of the para species of linear-C_{6}H_{2} were also detected firstly in molecular clouds. The column densities of the ^{2}Π_{1/2} and ^{2}Π_{3/2} states of C_{6}H in L1527 were derived to be 1.6 × 10^{11} and 1.1 × 10^{12} cm^{-2}, respectively. The total column density of linear-C_{6}H_{2} is obtained to be 1.86 × 10^{11} cm^{-2}. While the abundance ratios of carbon chains in between L1527 and the starless dark cloud Taurus Molecular Cloud-1 Cyanopolyyne Peak (TMC-1 CP) have a trend of decrease by extension of carbon-chain length, column densities of CH_{3}CCCCH and C_{6}H are on the trend. However, the column densities of linear-C_{6}H_{2}, and C_{7}H are as abundant as those of TMC-1 CP in spite of long carbon chain, i.e., they are not on the trend. The abundances of linear-C_{6}H_{2} and C_{7}H show that L1527 is rich for long carbon chains as well as TMC-1 CP.

Computational Study of Pincer Iridium Catalytic Systems: C-H, N-H, and C-C Bond Activation and C-C Coupling Reactions

NASA Astrophysics Data System (ADS)

Zhou, Tian

Computational chemistry has achieved vast progress in the last decades in the field, which was considered to be only experimental before. DFT (density functional theory) calculations have been proven to be able to be applied to large systems, while maintaining high accuracy. One of the most important achievements of DFT calculations is in exploring the mechanism of bond activation reactions catalyzed by organometallic complexes. In this dissertation, we discuss DFT studies of several catalytic systems explored in the lab of Professor Alan S. Goldman. Headlines in the work are: (1) (R4PCP)Ir alkane dehydrogenation catalysts are highly selective and different from ( R4POCOP)Ir catalysts, predicting different rate-/selectivity-determining steps; (2) The study of the mechanism for double C-H addition/cyclometalation of phenanthrene or biphenyl by (tBu4PCP)Ir(I) and ( iPr4PCP)Ir illustrates that neutral Ir(III) C-H addition products can undergo a very facile second C-H addition, particularly in the case of sterically less-crowded Ir(I) complexes; (3) (iPr4PCP)Ir pure solid phase catalyst is highly effective in producing high yields of alpha-olefin products, since the activation enthalpy for dehydrogenation is higher than that for isomerization via an allyl pathway; higher temperatures favor the dehydrogenation/isomerization ratio; (4) (PCP)Ir(H)2(N2H4) complex follows a hydrogen transfer mechanism to undergo both dehydrogenation to form N 2 and H2, as well as hydrogen transfer followed by N-N bond cleavage to form NH3, N2, and H2; (5) The key for the catalytic effect of solvent molecule in CO insertion reaction for RMn(CO)5 is hydrogen bond assisted interaction. The basicity of the solvent determines the strength of the hydrogen bond interaction during the catalytic path and determines the catalytic power of the solvent; and (6) Dehydrogenative coupling of unactivated C-H bonds (intermolecular vinyl-vinyl, intramolecular vinyl-benzyl) is catalyzed by precursors of the

Investigations of 3C-SiC inclusions in 4H-SiC epilayers on 4H-SiC single crystal substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, W.; Dudley, M.; Kong, H.S.

1997-03-01

Synchrotron white beam x-ray topography (SWBXT) and Nomarski optical microscopy (NOM) have been used to characterize 4H-SiC epilayers and to study the character of triangular inclusions therein. 4H-SiC substrates misoriented by a range of angles from (0001), as well as (1 1{bar 0}0) and (11 2{bar 0}) oriented substrates were used. No evidence was found for the nucleation of 3C-SiC inclusions at superscrew dislocations (along the [0001] axis) in the 4H-SiC substrates. Increasing the off-axis angle of the substrates from 3.5 to 6.5{degree} was found to greatly suppress the formation of the triangular inclusions. In the case of substrates misorientedmore » by 8.0{degree} from (0001) toward [112{bar 0}], the triangular inclusions were virtually eliminated. The crystalline quality of 4H-SiC epilayers grown on the substrates misoriented by 8.0{degree} from (0001) was very good. For the (11{bar 0}0) and (112{bar 0}) samples, there is no indication of 3C-SiC inclusions in the epilayers. Possible formation mechanisms and the morphology of 3C-SiC inclusions are discussed. 17 refs., 13 figs.« less

X-ray diffraction analysis of 4- and 4'-substituted C n H2 n + 1O-C6H3(OH)-CH=N-C6H4-C m H2 m + 1 ( n/ m = 2/1 and 3/4) salicylideneanilines

NASA Astrophysics Data System (ADS)

Kuz'mina, L. G.; Navasardyan, M. A.; Mikhailov, A. A.

2017-11-01

X-ray diffraction study of two crystalline modifications of C2H5O-C6H3(OH)-CH=N-C6H4-CH3 ( 1a, sp. gr. P21/ n, and 1b, sp. gr. C2/c) and C3H7O-C6H3(OH)-CH=N-C6H4-C4H9 ( 2, sp. gr. P212121) has been performed. The 1a crystal structure contains two independent molecules. The molecules are conformationally nonrigid with respect to the mutual rotation of benzene rings; the dihedral angles between their planes are 29.19° and 26.00° in the independent molecules of 1a, 18.72° in the molecule of 1b, and 50.35° in the molecule of 2. The crystal packing of the compounds is discussed.

Pandemic (H1N1) 2009: clinical and laboratory findings of the first fifty cases in Singapore.

PubMed

Chan, Monica; Chen, Mark I; Chow, Angela; Lee, Caroline P S; Tan, Adriana S H; Lye, David Chien; Leo, Yee Sin

2010-04-01

Since the fi rst imported case on 26 May 2009, pandemic (H1N1) 2009 has spread from travellers and has resulted in sustained community transmission. Singapore began with a strict containment policy where all suspected and confirmed cases of pandemic (H1N1) 2009 were admitted for testing. We describe here the clinical and laboratory characteristics of the fi rst 50 adult cases with confirmed pandemic (H1N1) 2009. A review was conducted of medical notes of adult patients with confirmed pandemic (H1N1) 2009 by polymerase chain reaction assay from combined nasal and throat swabs admitted to the Communicable Disease Centre, Tan Tock Seng Hospital. From 26 May to 18 June 2009, 50 patients with a median age of 27 years old were admitted at a median of 3 days from illness onset. Half were male and all were travellers arriving in Singapore. Non-Singaporean citizens (38%) and other ethnic groups (40%) were over-represented. History of fever was reported in 90% and respiratory symptoms in 92%. Gastrointestinal symptoms were uncommon, present in 4% only. Temperatures on presentation of >or=38.0 degrees C, >or=37.8 degrees C and >or=37.5 degrees C were present in 48%, 56% and 76%, respectively. Only 46% of patients met the United States Centers for Disease Control and Prevention (US CDC) case definition of influenza-like illness (ILI). Clinical and laboratory findings were unremarkable for the majority. All cases were treated with oseltamivir and had uncomplicated recovery. Pandemic (H1N1) 2009 had mild clinical and laboratory findings in immunocompetent patients. Use of the US CDC ILI criteria alone would have detected less than half of confirmed cases.

Control of an H1N1 outbreak in a correctional facility in central Taiwan.

PubMed

Chao, Wen-Cheng; Liu, Po-Yu; Wu, Chieh-Liang

2017-04-01

Controlling the outbreak of H1N1 in correctional facilities is difficult due to the inevitable close and prolonged contact between inmates. The current study reports an H1N1 outbreak in a correction facility and investigates the effectiveness of oseltamivir to control the spread of H1N1. All 2690 inmates at the prison received medical service from a single hospital. A list of patients with a diagnosis of influenza was compiled based on medical diagnoses with respiratory symptoms during the outbreak period. The outbreak was then investigated using both chart review and questionnaires. In the 4-week outbreak period, 24.6% (663/2690) of inmates experienced influenza-associated symptoms, 50.5% (335/663) fulfilled the criteria for influenza-like illness (ILI) with fever, and the overall attack rate of ILI was 12.8%. Twelve inmates were admitted for complicated influenza, and three of them experienced respiratory failure. Oseltamivir was provided at the end of the 2nd week, and the effectiveness of oseltamivir in the 1004 inmates from seven major sections in the prison was analyzed. The ILI incidence rate reduced from 12.6 ± 4.1% between the 1st and 2nd weeks to 4.8 ± 2.4% between the 3rd and 4th weeks (p = 0.018) after the oseltamivir intervention. In the 878 uninfected inmates 47.0% (413/878) of inmates received prophylactic oseltamivir at the end of the 2nd week, the incidence of ILI was lower than those without prophylaxis (6.2% versus 2.4%; p = 0.013). H1N1 influenza spread rapidly in the correctional facility. The use of oseltamivir may be a practical intervention to control an H1N1 outbreak an enclosed environment such as this. Copyright © 2015. Published by Elsevier B.V.

Energy and Spectroscopic Characterization of the Isomers of C4H3-, C6H3-, and C6H5-

NASA Technical Reports Server (NTRS)

Wright, Danielle; Bera, Partha P.; Lee, Timothy J.

2015-01-01

Organic and inorganic molecules, neutral and ions have been observed in the interstellar medium. A few anions of organic molecules have also been observed recently. The Cassini spacecraft in the upper atmosphere of Titan has observed anions of large organic molecules. In this project we have studied the physical and spectroscopic properties of C4H3-, C6H3-, and C6H5-. We have optimized the geometrical structures of all low-lying isomers of the anions, calculated rotational, and harmonic vibrational frequencies of the anions mentioned above using the B3LYP density functional along with the augmented correlation consistent polar valence triple zeta (aug-cc-pVTZ) basis set. We have found many low-lying isomers on the potential energy surface of these anions.

Regioselective functionalization of iminophosphoranes through Pd-mediated C-H bond activation: C-C and C-X bond formation.

PubMed

Aguilar, David; Navarro, Rafael; Soler, Tatiana; Urriolabeitia, Esteban P

2010-11-21

The orthopalladation of iminophosphoranes [R(3)P=N-C(10)H(7)-1] (R(3) = Ph(3) 1, p-Tol(3) 2, PhMe(2) 3, Ph(2)Me 4, N-C(10)H(7)-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C(6)H(4)-(PPh(2=N-1-C(10)H(7))-2)-κ-C,N](2) (5) or endo-[Pd(μ-Cl)(C(6)H(3)-(P(p-Tol)(2)=N-C(10)H(7)-1)-2-Me-5)-κ-C,N](2) (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7), [Pd(μ-Cl)(C(6)H(4)-(PPh(2)[=NPh)-2)](2) (17) and [Pd(μ-Cl)(C(6)H(3)-(C(O)N=PPh(3))-2-OMe-4)](2) (18) with I(2) or with CO results in the synthesis of the ortho-halogenated compounds [PhMe(2)P=N-C(10)H(6)-I-8] (19), [I-C(6)H(4)-(PPh(2)=NPh)-2] (21) and [Ph(3)P=NC(O)C(6)H(3)-I-2-OMe-5] (23) or the heterocycles [C(10)H(6)-(N=PPhMe(2))-1-(C(O))-8]Cl (20), [C(6)H(5)-(N=PPh(2)-C(6)H(4)-C(O)-2]ClO(4) (22) and [C(6)H(3)-(C(O)-1,2-N-PPh(3))-OMe-4]Cl (24).

Infrared spectra of the 1-pyridinium (C5H5NH+) cation and pyridinyl (C5H5NH and 4-C5H6N) radicals isolated in solid para-hydrogen.

PubMed

Golec, Barbara; Das, Prasanta; Bahou, Mohammed; Lee, Yuan-Pern

2013-12-19

Protonated pyridine and its neutral counterparts (C5H6N) are important intermediates in organic and biological reactions and in the atmosphere. We have recorded the IR absorption spectra of the 1-pyridinium (C5H5NH(+)) cation, 1-pyridinyl (C5H5NH), and 4-pyridinyl (4-C5H6N) produced on electron bombardment during matrix deposition of a mixture of pyridine (C5H5N) and p-H2 at 3.2 K; all spectra were previously unreported. The IR features of C5H5NH(+) diminished in intensity after the matrix was maintained in darkness for 15 h, whereas those of C5H5NH and 4-C5H6N radicals increased. Irradiation of this matrix with light at 365 nm diminished lines of C5H5NH(+) and C5H5NH but enhanced lines of 4-C5H6N slightly, whereas irradiation at 405 nm diminished lines of 4-C5H6N significantly. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/6-31++G(d,p) method. Assignments of C5H5NH and 4-C5H6N radicals were further supported by the observation of similar spectra when a Cl2/C5H5N/p-H2 matrix was irradiated first at 365 nm and then with IR light to generate H atoms to induce the H + C5H5N reaction.

C-H and H-H Activation in Transition Metal Complexes and on Surfaces.

DTIC Science & Technology

1983-01-01

IEEIIIIIEEEEI EEEIIEIIIIIII EEIIIEIIIEIII IIIEEEIIEIIII La.𔃻 m41. 12.2 1.4o 12.0 1.25 111.4 11. MICROCOP RE SOO TESTCHAR NATIONA BUREA OfSANAD 16m ~4 OFFICE...ML4 plane, bringing a C-H bond in proximity to the metal. The compounds will minimize M. . C-H re- -27 - pulsion by bringing the H atom into an axial...h) C-H activation has been shown also with organolanthanides and organo- actinide compounds : Watson, P.L. J.Chem.Soc. Chem.Commun. 1983, 176-177

Metal-Free Oxidative C-C Bond Formation through C-H Bond Functionalization.

PubMed

Narayan, Rishikesh; Matcha, Kiran; Antonchick, Andrey P

2015-10-12

The formation of C-C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C-C bond-forming reactions are well-known challenges. To achieve this goal through direct functionalization of C-H bonds in both of the coupling partners represents the state-of-the-art in organic synthesis. Oxidative C-C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C-C bond-forming reactions through direct C-H bond functionalization under completely metal-free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical Cobalt-Catalyzed C-H Activation.

PubMed

Sauermann, Nicolas; Meyer, Tjark H; Ackermann, Lutz

2018-06-19

Carbon-heteroatom bonds represent omnipresent structural motifs of the vast majority of functionalized materials and bioactive compounds. C-H activation has emerged as arguably the most efficient strategy to construct C-Het bonds. Despite of major advances, these C-H transformations were largely dominated by precious transition metal catalysts, in combination with stoichiometric, toxic metal oxidants. Herein, we discuss the recent evolution of cobalt-catalyzed C-H activations that enable C-Het formations with electricity as the sole sustainable oxidant until May 2018. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monohalogenated ferrocenes C5H5FeC5H4 X (X = Cl, Br and I) and a second polymorph of C5H5FeC5H4I

PubMed Central

Romanov, Alexander S.; Mulroy, Joseph M.; Khrustalev, Victor N.; Antipin, Mikhail Yu.; Timofeeva, Tatiana V.

2009-01-01

The structures of the three title monosubstituted ferrocenes, namely 1-chloro­ferrocene, [Fe(C5H5)(C5H4Cl)], (I), 1-bromo­ferrocene, [Fe(C5H5)(C5H4Br)], (II), and 1-iodo­ferrocene, [Fe(C5H5)(C5H4I)], (III), were determined at 100 K. The chloro- and bromo­ferrocenes are isomorphous crystals. The new triclinic polymorph [space group P , Z = 4, T = 100 K, V = 943.8 (4) Å3] of iodo­ferrocene, (III), and the previously reported monoclinic polymorph of (III) [Laus, Wurst & Schottenberger (2005 ▶). Z. Kristallogr. New Cryst. Struct. 220, 229–230; space group Pc, Z = 4, T = 100 K, V = 924.9 Å3] were obtained by crystallization from ethanolic solutions at 253 and 303 K, respectively. All four phases contain two independent mol­ecules in the unit cell. The relative orientations of the cyclo­penta­dienyl (Cp) rings are eclipsed and staggered in the independent mol­ecules of (I) and (II), while (III) demonstrates only an eclipsed conformation. The triclinic and monoclinic polymorphs of (III) contain nonbonded inter­molecular I⋯I contacts, causing different packing modes. In the triclinic form of (III), the mol­ecules are arranged in zigzag tetra­mers, while in the monoclinic form the mol­ecules are arranged in zigzag chains along the a axis. Crystallographic data for (III), along with the computed lattice energies of the two polymorphs, suggest that the monoclinic form is more stable. PMID:19893225

Growth of Defect-Free 3C-SiC on 4H- and 6H-SiC Mesas Using Step-Free Surface Heteroepitaxy

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Powell, J. Anthony; Trunek, Andrew J.; Huang, Xianrong R.; Dudley, Michael

2001-01-01

A new growth process, herein named step-free surface heteroepitaxy, has achieved 3CSiC films completely free of double positioning boundaries and stacking faults on 4H-SiC and 6H-SiC substrate mesas. The process is based upon the initial 2-dimensional nucleation and lateral expansion of a single island of 3C-SiC on a 4H- or 6H-SiC mesa surface that is completely free of bilayer surface steps. Our experimental results indicate that substrate-epilayer in-plane lattice mismatch (delta a/a = 0.0854% for 3C/4H) is at least partially relieved parallel to the interface in the initial bilayers of the heterofilm, producing an at least partially relaxed 3C-SiC film without dislocations that undesirably thread through the thickness of the epilayer. This result should enable realization of improved 3C-SiC devices.

Low Clinical Burden of 2009 Pandemic Influenza A (H1N1) Infection during Pregnancy on the Island of La Réunion

PubMed Central

Gérardin, Patrick; El Amrani, Rachid; Cyrille, Béatrice; Gabrièle, Marc; Guillermin, Philippe; Boukerrou, Malik; Boumahni, Brahim; Randrianaivo, Hanitra; Winer, Arnaud; Rouanet, Jean-Fabien; Bohrer, Michel; Jaffar-Bandjee, Marie-Christine; Robillard, Pierre-Yves; Barau, Georges; Michault, Alain

2010-01-01

Background Pregnant women have been identified as a group at risk, both for respiratory complications than for the admissions to the Intensive Care Unit (ICU) during the 2009 H1N1 influenza pandemic (pdm). The purpose of this prospective register-based cohort-study was to characterize the clinical virulence of the pdm (H1N1/09)v during pregnancy in La Réunion. Methods/Principal Findings Over a twelve-week pdm wave (13 July to 3 October 2009), 294 pregnant women presented with an influenza-like illness (ILI) to one of the three maternity departments of the South Reunion area, Indian Ocean. Out of these, 278 were checked by RT-PCR for influenza viruses (157 positive and 121 negative, of whom, 141 with pdm flu and 132 with ILIs of non pdm origin, 5 untyped). The median body temperature was higher in women experiencing pdm flu than in those with non pdm ILI (38.9°C versus 38.3°C, P<0.0001), without evidence linked to circulating viremia. Oseltamivir was given for 86% of pdm flu cases in a median time inferior than 48 hrs (range 0–7 days). The hospitalization rate for pdm flu was of 60% and not associated with underlying conditions. Six viral pneumonia and fourteen asthma attacks were observed among 84 hospitalized pdm flu cases, of whom, only one led to the ICU for an acute lung injury. No maternal death occurred during the pdm wave. None adverse pregnancy outcome was associated with pdm flu. No congenital birth defect, nor early-onset neonatal influenza infection was attributable to pdm flu exposure. Conclusions/Significance This report mitigates substantially the presumed severity of pandemic H1N1/09 influenza infection during pregnancy. The reasons for which the clinical burden of H1N1/09 influenza virus may differ worldwide raise questions about a differential local viral-strain effect and public health preparedness, notably in timely access to special care and antiviral treatments. PMID:20531946

Aluminum acceptor four particle bound exciton complex in 4H, 6H, and 3C SiC

NASA Technical Reports Server (NTRS)

Clemen, L. L.; Devaty, R. P.; Macmillan, M. F.; Yoganathan, M.; Choyke, W. J.; Larkin, D. J.; Powell, J. A.; Edmond, J. A.; Kong, H. S.

1993-01-01

Evidence is presented for a four particle acceptor complex in 3C, 6H, and 4H SiC, obtained in low-temperature photoluminescence and cathodoluminescence experiments. The new lines were observed in p-type films lightly doped with aluminum, of 6H, 4H, and 3C SiC grown on the silicon (0001) face of 6H SiC under special conditions. The lines increase in intensity as more aluminum is added during growth. The multiplicity of observed lines is consistent with symmetry-based models similar to those which have been proposed to describe 4A centers in p-type zincblende semiconductors.

Targeted vs. systematic early antiviral treatment against A(H1N1)v influenza with neuraminidase inhibitors in patients with influenza-like symptoms: Clinical and economic impact

PubMed Central

Deuffic-Burban, Sylvie; Lenne, Xavier; Dervaux, Benoit; Julien Poissy; Lemaire, Xavier; Sloan, Caroline; Carrat, Fabrice; Desenclos, Jean-Claude; Delfraissy, Jean-Francois; Yazdanpanah, Yazdan

2009-01-01

Capitalizing on available data, we used a decision model to estimate the clinical and economic outcomes associated with early initiation of treatment with neuraminidase inhibitors in all patients with influenza-like illnesses ( ILI ) (systematic strategy) vs. only those at high risk of complications (targeted strategy). Systematic treatment of ILI during an A(H1N1)v influenza epidemic wave is both effective and cost-effective. Patients who present to care with ILI during an A(H1N1)v influenza epidemic wave should initiate treatment with neuraminidase inhibitors, regardless of risk status. Administering neuraminidase inhibitors between epidemic waves, when the probability of influenza is low, is less effective and cost-effective. PMID:20029659

Volume properties and refraction of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids lysine, threonine, and oxyproline (C60(C6H13N2O2)2, C60(C4H8NO3)2, and C60(C5H9NO2)2) at 25°C

NASA Astrophysics Data System (ADS)

Semenov, K. N.; Ivanova, N. M.; Charykov, N. A.; Keskinov, V. A.; Kalacheva, S. S.; Duryagina, N. N.; Garamova, P. V.; Kulenova, N. A.; Nabieva, A.

2017-02-01

Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (H2O and corresponding bisadducts) are calculated for C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems at 25°C. Concentration dependences of the indices of refraction of C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

Carbon-Hydrogen (C-H) Bond Activation at PdIV: A Frontier in C-H Functionalization Catalysis.

PubMed

Topczewski, Joseph J; Sanford, Melanie S

2015-01-01

The direct functionalization of carbon-hydrogen (C-H) bonds has emerged as a versatile strategy for the synthesis and derivatization of organic molecules. Among the methods for C-H bond activation, catalytic processes that utilize a Pd II /Pd IV redox cycle are increasingly common. The C-H activation step in most of these catalytic cycles is thought to occur at a Pd II centre. However, a number of recent reports have suggested the feasibility of C-H cleavage occurring at Pd IV complexes. Importantly, these latter processes often result in complementary reactivity and selectivity relative to analogous transformations at Pd II . This Mini Review highlights proposed examples of C-H activation at Pd IV centres. Applications of this transformation in catalysis as well as mechanistic details obtained from stoichiometric model studies are discussed. Furthermore, challenges and future perspectives for the field are reviewed.

Step Free Surface Heteroepitaxy of 3C-SiC Layers on Patterned 4H/6H-SiC Mesas and Cantilevers

NASA Technical Reports Server (NTRS)

Neudeck, P. G.; Powell, J. A.; Trunek, A. J.; Spry, D. J.

2004-01-01

The off-axis approach to SiC epitaxial growth has not prevented many substrate crystal defects from propagating into SiC epilayers, and does not permit the realization of SiC heteropolytype devices. This paper reviews recent advancements in SiC epitaxial growth that begin to overcome the above shortcomings for arrays of device-sized mesas patterned into on-axis 4H/6HSiC wafers. These on-axis mesa growth techniques have produced 4H/6H-SiC homoepilayers and 3C-SiC heteroepilayers with substantially lower dislocation densities. The results should enable improved homojunction and heterojunction silicon carbide prototype devices.

Reactions of the linear tetranuclear complex Ru sub 4 (CO) sub 10 (CH sub 3 C double bond C(H)C(H) double bond N-i-Pr) sub 2 with oxidizing reagents. Syntheses of halide-bridged (Ru(CO) sub 2 X(CH sub 3 C double bond C(H)C(H) double bond N-i-Pr)) sub 2 and fac-Ru(CO) sub 3 X(CH sub 3 C double bond C(H)C(H) double bond N-i-Pr)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mul, W.P.; Elsevier, C.J.; van Leijen, M.

1991-01-01

The linear tetranuclear complex Ru{sub 4}(CO){sub 10}(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr){sub 2} (1), containing two {eta}{sup 5}-azaruthenacyclopentadienyl systems, reacts with oxidizing reagents (I{sub 2}, Br{sub 2}, NBS, CCl{sub 4}) at elevated temperatures (40-90C) in heptane or benzene to give the new dimeric halide-bridged organoruthenium(II) complexes (Ru(CO){sub 2}X(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr)){sub 2} (X = I (3a), X = Br (3b), Cl (3c); yield 30-80%) together with (Ru(CO){sub 3}X{sub 2}){sub 2}. The reactions of 1 with CX{sub 4} (X = I, Br, Cl) are accelerated by CO, probably because Ru{sub 4}(CO){sub 12}(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr){sub 2} (5), which contains two unbridged metal-metal bonds,more » is formed prior to oxidation. The halide-bridged dimers 3a-c are obtained as mixtures of four isomers, the configurations of which are discussed. Splitting of the halide bridges takes place when a solution of 3a-c is saturated with CO, whereby mononuclear fac-Ru(CO){sub 3}X(CH{sub 3}C{double bond}C(H)C(H){double bond}N-i-Pr) (4a-c) is obtained. This process is reversible; ie., passing a stream of nitrogen through a solution of 4a-c or removal of the solvent under vacuum causes the reverse reaction with reformation of 3a-c. Compounds 3a-c and 4a-c have been characterized by IR (3, 4), FD mass (3), {sup 1}H (3, 4), and {sup 13}C{l brace}H{r brace} NMR (4) spectroscopy and satisfactory elemental analyses have been obtained for 3a-c. Compounds 3 and 4 are suitable precursors for the preparation of new homo- and heteronuclear transition-metal complexes.« less

Full-dimensional quantum dynamics study of the H{sub 2} + C{sub 2}H → H + C{sub 2}H{sub 2} reaction on an ab initio potential energy surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liuyang; University of Chinese Academy of Sciences, Beijing 100049; Shao, Kejie

2016-05-21

This work performs a time-dependent wavepacket study of the H{sub 2} + C{sub 2}H → H + C{sub 2}H{sub 2} reaction on a new ab initio potential energy surface (PES). The PES is constructed using neural network method based on 68 478 geometries with energies calculated at UCCSD(T)-F12a/aug-cc-pVTZ level and covers H{sub 2} + C{sub 2}H↔H + C{sub 2}H{sub 2}, H + C{sub 2}H{sub 2} → HCCH{sub 2}, and HCCH{sub 2} radial isomerization reaction regions. The reaction dynamics of H{sub 2} + C{sub 2}H → H + C{sub 2}H{sub 2} are investigated using full-dimensional quantum dynamics method. The initial-state selected reactionmore » probabilities are calculated for reactants in eight vibrational states. The calculated results showed that the H{sub 2} vibrational excitation predominantly enhances the reactivity while the excitation of bending mode of C{sub 2}H slightly inhibits the reaction. The excitations of two stretching modes of C{sub 2}H molecule have negligible effect on the reactivity. The integral cross section is calculated with J-shift approximation and the mode selectivity in this reaction is discussed. The rate constants over 200-2000 K are calculated and agree well with the experimental measured values.« less

Highly Reactive Scandium Phosphinoalkylidene Complex: C-H and H-H Bonds Activation.

PubMed

Mao, Weiqing; Xiang, Li; Alvarez Lamsfus, Carlos; Maron, Laurent; Leng, Xuebing; Chen, Yaofeng

2017-01-25

The first scandium phosphinoalkylidene complex was synthesized and structurally characterized. The complex has the shortest Sc-C bond lengths reported to date (2.089(3) Å). DFT calculations reveal the presence of a three center π interaction in the complex. This scandium phosphinoalkylidene complex undergoes intermolecular C-H bond activation of pyridine, 4-dimethylamino pyridine and 1,3-dimethylpyrazole at room temperature. Furthermore, the complex rapidly activates H 2 under mild conditions. DFT calculations also demonstrate that the C-H activation of 1,3-dimethylpyrazole is selective for thermodynamic reasons and the relatively slow reaction is due to the need of fully breaking the chelating effect of the phosphino group to undergo the reaction whereas this is not the case for H 2 .

Influenza A(H1N1)pdm09 outbreak detected in inter-seasonal months during the surveillance of influenza-like illness in Pune, India, 2012-2015.

PubMed

Gurav, Y K; Chadha, M S; Tandale, B V; Potdar, V A; Pawar, S D; Shil, P; Deoshatwar, A R; Aarthy, R; Bhushan, A

2017-07-01

An outbreak of influenza A(H1N1)pdm09 was detected during the ongoing community-based surveillance of influenza-like illness (ILI). Among reported 119 influenza A(H1N1)pdm09 cases (59 cases in the year 2012 and 60 cases in 2015) in summer months, common clinical features were fever (100%), cough (90·7%), sore throat (85·7%), nasal discharge (48·7%), headache (55·5%), fatigue (18·5%), breathlessness (3·4%), and ear discharge (1·7%). Rise in ILI cases were negatively correlated with the seasonal factors such as relative humidity (Karl Pearson's correlation coefficient, i.e. r = -0·71 in the year 2012 and r = -0·44 in the year 2015), while rise in ILI cases were positively correlated with the temperature difference (r = 0·44 in the year 2012 and r = 0·77 in the year 2015). The effective reproduction number R, was estimated to be 1·30 in 2012 and 1·64 in 2015. The study highlights the rise in unusual influenza activity in summer month with high attack rate of ILI among children aged ⩽9 years. Children in this age group may need special attention for influenza vaccination. Influenza A(H1N1)pdm09 outbreak was confirmed in inter-seasonal months during the surveillance of ILI in Pune, India, 2012-2015.

Luminescence dating of the Zeketai loess section in the Ili Basin, northwestern China: Methodological considerations

NASA Astrophysics Data System (ADS)

Qin, Jintang; Zhou, Liping

2018-04-01

Loess deposits in Xinjiang, northwestern China are ideal archives for past environmental changes in the Westerlies-dominated central Asia. Among previous luminescence dating studies of loess in Xinjiang, few have attempted to systematically investigate the methodological aspects. In this study, we report results of a multiple-procedure luminescence dating of the Zeketai loess section in the Ili Basin, central Xinjiang. Optically stimulated luminescence (OSL) and post-infrared infrared stimulated luminescence (pIRIR) signals were used for quartz and polymineral grains of different sizes. The pIRIR ages obtained with two protocols agree well with each other and constrain the loess deposition between 50 ka and 88 ka. The OSL ages of fine-grained quartz are in stratigraphic order and range from 37 ka to 61 ka, but are ∼30% younger than the pIRIR295 ages of both fine and medium grained polyminerals. Although the causes of the discrepancy between the ages derived from different luminescence dating protocols are still to be understood, we stress that the quartz OSL ages of loess in this region are likely to be underestimated, especially for samples older than 40 ka. The polymineral or potassium feldspar pIRIR signal is recommended for dating loess in the Ili Basin, at least as an internal check.

H(C)P and H(P)C triple-resonance experiments at natural abundance employing long-range couplings.

PubMed

Malon, Michal; Koshino, Hiroyuki

2007-09-01

Modified two-dimensional (2D) triple-resonance H(C)P and H(P)C experiments based on INEPT/HMQC and double-INEPT schemes are applied to the study of organophosphorus compounds at natural abundances. The implementation of effective (1)H--(13)C gradient selection, additional purging pulsed field gradients, spinlock pulses, and improved phase cycling is demonstrated to allow weak correlation signals based on long-range couplings to be readily observed. Through the combination of two heteronuclear long-range coupling constants, (n)J(CH) and (n)J(PC) in H(C)P experiments or (n)J(PH) and (n)J(PC) in H(P)C experiments, protons can be correlated to a second heteronucleus through 4-7 chemical bonds. These experiments thus overcome the inherit limitations of classical (1)H-X HMBC experiments, which require a nonzero value of the heteronuclear coupling constant (n)J(XH). Ultra-broadband inversion composite pulses are successfully employed in the H(P)C INEPT/HMQC and H(P)C double-INEPT pulse sequences to increase the utility of the experiments and the quality of obtained spectra. This work extends and completes a set of 2D phase-sensitive triple-resonance experiments applicable at natural abundances, and also offers insight into the methodology of triple-resonance experiments and the application of pulsed field gradients. A one-dimensional triple-resonance experiment employing carbon detection is suggested for accurate determination of small (n)J(PC).

Infrared spectra of ovalene (C32H14) and hydrogenated ovalene (C32H15˙) in solid para-hydrogen.

PubMed

Tsuge, Masashi; Bahou, Mohammed; Wu, Yu-Jong; Allamandola, Louis; Lee, Yuan-Pern

2016-10-19

We report the infrared (IR) spectra of ovalene (C 32 H 14 ) and hydrogenated ovalene (C 32 H 15 ˙) in solid para-hydrogen (p-H 2 ). The hydrogenated ovalene and protonated ovalene were generated from electron bombardment of a mixture of ovalene and p-H 2 during deposition of a matrix at 3.2 K. The features that decreased with time have been previously assigned to 7-C 32 H 15 + , the most stable isomer of protonated ovalene (Astrophys. J., 2016, 825, 96). The spectral features that increased with time are assigned to the most stable isomer of hydrogenated ovalene (7-C 32 H 15 ˙) based on the expected chemistry and on a comparison with the vibrational wavenumbers and IR intensities predicted by the B3PW91/6-311++G(2d,2p) method. The mechanism of formation of 7-C 32 H 15 ˙ is discussed according to the observed changes in intensity and calculated energetics of possible reactions of H + C 32 H 14 and isomerization of C 32 H 15 ˙. The formation of 7-C 32 H 15 ˙ is dominated by the reaction H + C 32 H 14 → 7-C 32 H 15 ˙, implying that, regardless of the presence of a barrier, the hydrogenation of polycyclic aromatic hydrocarbons occurs even at 3.2 K.

Collisions of slow polyatomic ions with surfaces: dissociation and chemical reactions of C2H2+*, C2H3+, C2H4+*, C2H5+, and their deuterated variants C2D2+* and C2D4+* on room-temperature and heated carbon surfaces.

PubMed

Jasík, Juraj; Zabka, Jan; Feketeova, Linda; Ipolyi, Imre; Märk, Tilmann D; Herman, Zdenek

2005-11-17

Interaction of C2Hn+ (n = 2-5) hydrocarbon ions and some of their isotopic variants with room-temperature and heated (600 degrees C) highly oriented pyrolytic graphite (HOPG) surfaces was investigated over the range of incident energies 11-46 eV and an incident angle of 60 degrees with respect to the surface normal. The work is an extension of our earlier research on surface interactions of CHn+ (n = 3-5) ions. Mass spectra, translational energy distributions, and angular distributions of product ions were measured. Collisions with the HOPG surface heated to 600 degrees C showed only partial or substantial dissociation of the projectile ions; translational energy distributions of the product ions peaked at about 50% of the incident energy. Interactions with the HOPG surface at room temperature showed both surface-induced dissociation of the projectiles and, in the case of radical cation projectiles C2H2+* and C2H4+*, chemical reactions with the hydrocarbons on the surface. These reactions were (i) H-atom transfer to the projectile, formation of protonated projectiles, and their subsequent fragmentation and (ii) formation of a carbon chain build-up product in reactions of the projectile ion with a terminal CH3-group of the surface hydrocarbons and subsequent fragmentation of the product ion to C3H3+. The product ions were formed in inelastic collisions in which the translational energy of the surface-excited projectile peaked at about 32% of the incident energy. Angular distributions of reaction products showed peaking at subspecular angles close to 68 degrees (heated surfaces) and 72 degrees (room-temperature surfaces). The absolute survival probability at the incident angle of 60 degrees was about 0.1% for C2H2+*, close to 1% for C2H4+* and C2H5+, and about 3-6% for C2H3+.

Approximate thermochemical tables for some C-H and C-H-O species

NASA Technical Reports Server (NTRS)

Bahn, G. S.

1973-01-01

Approximate thermochemical tables are presented for some C-H and C-H-O species and for some ionized species, supplementing the JANAF Thermochemical Tables for application to finite-chemical-kinetics calculations. The approximate tables were prepared by interpolation and extrapolation of limited available data, especially by interpolations over chemical families of species. Original estimations have been smoothed by use of a modification for the CDC-6600 computer of the Lewis Research Center PACl Program which was originally prepared for the IBM-7094 computer Summary graphs for various families show reasonably consistent curvefit values, anchored by properties of existing species in the JANAF tables.

Properties of homoepitaxial 4H-SiC and characteristics of Ti/4H-SiC Schottky barrier diodes

NASA Astrophysics Data System (ADS)

Chen, G.; Li, Z. Y.; Bai, S.; Han, P.

2008-02-01

This paper describes the properties of the homoepitaxial 4H-SiC layer, the fabrication and electrical parameters of Ti/4H-SiC Schottky barrier diode (SBD). The 4H-SiC epitaxial layers, grown on the commercially available 8°off-oriented Si-face(0001) single-crystal 4H-SiC wafers, have been performed at 1550~1600°C by using the step controlled epitaxy with low pressure chemical vapor deposition. X-ray diffraction measurement result indicates the single crystal nature of the epilayer, and Raman spectrum shows the typical 4H-SiC feature peaks. When the off-oriented angle of substrate is 8°, the epitaxial growth perfectly replicates the substrate's polytype. High quality 4H-SiC epilayer has been generated on the 4H-SiC substrate. Ti/4H-SiC SBDs with blocking voltage 1kV have been made on an undoped epilayer with 12um in thick and 3×10 15cm -3 in carrier density. The ideality factor n=1.16 and the effective barrier height φ e=0.9V of the Ti/4H-SiC SBDs are measured with method of forward density-voltage (J-V). The diode rectification ratio of forward to reverse (defined at +/-1V) is over 10 7 at room temperature. By using B + implantation, an amorphous layer as the edge termination is formed. The SBDs have on-state current density of 200A/cm2 at a forward voltage drop of about 2V. The specific on-resistance for the rectifier is found to be as 6.6mΩ•cm2.

Directing-Group-mediated C-H-Alkynylations.

PubMed

Caspers, Lucien D; Nachtsheim, Boris J

2018-05-18

C-C triple bonds are amongst the most versatile functional groups in synthetic chemistry. Complementary to the Sonogashira coupling the direct metal-catalyzed alkynylation of C-H bonds has emerged as a highly promising approach in recent years. To guarantee a high regioselectivity suitable directing groups (DGs) are necessary to guide the transition metal (TM) into the right place. In this Focus Review we present the current developments in DG-mediated C(sp 2 )-H and C(sp 3 )-H modifications with terminal alkynes under oxidative conditions and with electrophilic alkynylation reagents. We will discuss further modifications of the alkyne, in particular subsequent cyclizations to carbo- and heterocycles and modifications of the DG in the presence of the alkyne. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen.

PubMed

Bahou, Mohammed; Wu, Yu-Jong; Lee, Yuan-Pern

2012-04-21

We use protonated benzene (C(6)H(7)(+)) and cyclohexadienyl radical (c-C(6)H(7)) to demonstrate a new method that has some advantages over other methods currently used. C(6)H(7)(+) and c-C(6)H(7) were produced on electron bombardment of a mixture of benzene (C(6)H(6)) and para-hydrogen during deposition onto a target at 3.2 K. Infrared (IR) absorption lines of C(6)H(7)(+) decreased in intensity when the matrix was irradiated at 365 nm or maintained in the dark for an extended period, whereas those of c-C(6)H(7) increased in intensity. Observed vibrational wavenumbers, relative IR intensities, and deuterium isotopic shifts agree with those predicted theoretically. This method, providing a wide spectral coverage with narrow lines and accurate relative IR intensities, can be applied to larger protonated polyaromatic hydrocarbons and their neutral species which are difficult to study with other methods.

High-level ab initio predictions for the ionization energy, electron affinity, and heats of formation of cyclopentadienyl radical, cation, and anion, C5H5/C5H5+/C5H5-.

PubMed

Lo, Po-Kam; Lau, Kai-Chung

2014-04-03

The ionization energy (IE), electron affinity (EA), and heats of formation (ΔH°f0/ΔH°f298) for cyclopentadienyl radical, cation, and anion, C5H5/C5H5(+)/C5H5(-), have been calculated by wave function-based ab initio CCSDT/CBS approach, which involves approximation to complete basis set (CBS) limit at coupled-cluster level with up to full triple excitations (CCSDT). The zero-point vibrational energy correction, core-valence electronic correction, scalar relativistic effect, and higher-order corrections beyond the CCSD(T) wave function are included in these calculations. The allylic [C5H5((2)A2)] and dienylic [C5H5((2)B1)] forms of cyclopentadienyl radical are considered: the ground state structure exists in the dienyl form and it is about 30 meV more stable than the allylic structure. Both structures are lying closely and are interconvertible along the normal mode of b2 in-plane vibration. The CCSDT/CBS predictions (in eV) for IE[C5H5(+)((3)A1')←C5H5((2)B1)] = 8.443, IE[C5H5(+)((1)A1)←C5H5((2)B1)] = 8.634 and EA[C5H5(-)((1)A1')←C5H5((2)B1)] = 1.785 are consistent with the respective experimental values of 8.4268 ± 0.0005, 8.6170 ± 0.0005, and 1.808 ± 0.006, obtained from photoelectron spectroscopic measurements. The ΔH°f0/ΔH°f298's (in kJ/mol) for C5H5/C5H5(+)/C5H5(-) have also been predicted by the CCSDT/CBS method: ΔH°f0/ΔH°f298[C5H5((2)B1)] = 283.6/272.0, ΔH°f0/ΔH°f298[C5H5(+)((3)A1')] = 1098.2/1086.9, ΔH°f0/ΔH°f298[C5H5(+)((1)A1)] = 1116.6/1106.0, and ΔH°f0/ΔH°f298[C5H5(-)((1)A1')] = 111.4/100.0. The comparisons between the CCSDT/CBS predictions and the experimental values suggest that the CCSDT/CBS procedure is capable of predicting reliable IE(C5H5)'s and EA(C5H5) with uncertainties of ± 17 and ± 23 meV, respectively.

Radical-molecule reaction C3H+H2O: a mechanistic study.

PubMed

Dong, Hao; Ding, Yi-Hong; Sun, Chia-Chung

2005-02-08

Despite the importance of the C(3)H radical in both combustion and interstellar space, the reactions of C(3)H toward stable molecules have never been studied. In this paper, we report our detailed mechanistic study on the radical-molecule reaction C(3)H+H(2)O at the Becke's three parameter Lee-Yang-Parr-B3LYP6-311G(d,p) and coupled cluster with single, double, and triple excitations-CCSD(T)6-311G(2d,p) (single-point) levels. It is shown that the C(3)H+H(2)O reaction initially favors formation of the carbene-insertion intermediates HCCCHOH (1a,1b) rather than the direct H- or OH-abstraction process. Subsequently, the isomers (1a,1b) can undergo a direct H- extrusion to form the well-known product propynal HCCCHO (P(5)). Highly competitively, (1a,1b) can take the successive 1,4- and 1,2-H-shift interconversion to isomer H(2)CCCHO(2a,2b) and then to isomer H(2)CCHCO(3a,3b), which can finally take a direct C-C bond cleavage to give product C(2)H(3) and CO (P(1)). The other products are kinetically much less feasible. With the overall entrance barrier 10.6 kcal/mol, the title reaction can be important in postburning processes. Particularly, our calculations suggest that the title reaction may play a role in the formation of the intriguing interstellar molecule, propynal HCCCHO. The calculated results will also be useful for the analogous C(3)H reactions such as with ammonia and alkanes.

Electrooxidative Ruthenium-Catalyzed C-H/O-H Annulation by Weak O-Coordination.

PubMed

Qiu, Youai; Tian, Cong; Massignan, Leonardo; Rogge, Torben; Ackermann, Lutz

2018-05-14

Electrocatalysis has been identified as a powerful strategy for organometallic catalysis, and yet electrocatalytic C-H activation is restricted to strongly N-coordinating directing groups. The first example of electrocatalytic C-H activation by weak O-coordination is presented, in which a versatile ruthenium(II) carboxylate catalyst enables electrooxidative C-H/O-H functionalization for alkyne annulations in the absence of metal oxidants; thereby exploiting sustainable electricity as the sole oxidant. Mechanistic insights provide strong support for a facile organometallic C-H ruthenation and an effective electrochemical reoxidation of the key ruthenium(0) intermediate. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amide-Directed Photoredox Catalyzed C-C Bond Formation at Unactivated sp3 C-H Bonds

PubMed Central

Chu, John C. K.; Rovis, Tomislav

2017-01-01

Carbon-carbon (C-C) bond formation is paramount in the synthesis of biologically relevant molecules, modern synthetic materials and commodity chemicals such as fuels and lubricants. Traditionally, the presence of a functional group is required at the site of C-C bond formation. Strategies that allow C-C bond formation at inert carbon-hydrogen (C-H) bonds allow scientists to access molecules which would otherwise be inaccessible and to develop more efficient syntheses of complex molecules.1,2 Herein we report a method for the formation of C-C bonds by directed cleavage of traditionally non-reactive C-H bonds and their subsequent coupling with readily available alkenes. Our methodology allows for the selective C-C bond formation at single C-H bonds in molecules that contain a multitude of seemingly indifferentiable such bonds. Selectivity arises through a relayed photoredox catalyzed oxidation of an N-H bond. We anticipate our findings to serve as a starting point for functionalization at inert C-H bonds through a hydrogen atom transfer strategy. PMID:27732580

Calculation and synthesis of ZrC by CVD from ZrCl4-C3H6-H2-Ar system with high H2 percentage

NASA Astrophysics Data System (ADS)

Zhu, Yan; Cheng, Laifei; Ma, Baisheng; Gao, Shuang; Feng, Wei; Liu, Yongsheng; Zhang, Litong

2015-03-01

A thermodynamic calculation about the synthesis of ZrC from the ZrCl4-C3H6-H2-Ar system with high percentage of H2 was performed using the FactSage thermochemical software. According to the calculation, ZrC coating was synthesized on graphite substrates and carbon fibers by a low pressure chemical vapor deposition (LPCVD) process, and growth rate of the ZrC coating as a function of temperature was investigated. The surface diagrams of condensed-phases in this system were expressed as the functions of the deposition temperature, total pressure and reactant ratios of ZrCl4/(ZrCl4 + C3H6), H2/(ZrCl4 + C3H6), and the yield of the products was determined by the diagrams. A smooth and dense ZrC coating could be synthesized under the instruction of the calculated parameters. The morphologies of the ZrC coatings were significantly affected by temperature and gases flux. The deposition temperature is much lower than that from the ZrCl4-CH4-H2-Ar system.

Sodium diffusion in 4H-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linnarsson, M. K., E-mail: marga@kth.se; Hallén, A.

Sodium diffusion has been studied in p-type 4H-SiC. Heat treatments have been performed from 1200 °C to 1800 °C for 1 min to 4 h. Secondary ion mass spectrometry has been used to measure the sodium distribution. We show that sodium has a considerable mobility at 1200 °C in p-type 4H-SiC. On the other hand for sodium atoms trapped at suitable sites the mobility is limited up to 1800 °C. Trap limited diffusion kinetics is suggested and an effective diffusivity has been extracted with an activation energy of 4 eV for sodium diffusion in p-type 4H-SiC.

Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza‐like illness and unexplained pneumonia

PubMed Central

Qian, Yan‐Hua; Su, Jing; Shi, Ping; He, En‐Qi; Shao, Jie; Sun, Na; Zu, Rong‐Qiang; Yu, Rong‐Bin

2011-01-01

Please cite this paper as: Qian et al. (2011) Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza‐like illness and unexplained pneumonia. Influenza and Other Respiratory Viruses 5(6), e479–e486. Background  To collect disease information and provide data for early detection of epidemics, two surveillance systems were established for influenza‐like illness (ILI) and unexplained pneumonia (UP) in Wuxi, People’s Republic of China. Objectives  The current study aims to describe the performance of these surveillance systems during 2004–2009 and to evaluate the value of surveillance data in detection of influenza epidemics. Methods  Two national ILI sentinel hospitals and three UP sentinel hospitals provided data to the surveillance systems. The surveillance data from hospital‐based outpatient clinics and emergency rooms were compared by year. The ILI data of 2009 were further modeled based on previous data using both a control chart method and a moving average regression method. Alarms of potential epidemics would be raised when the input surveillance data surpassed a threshold. Results  In 2009, the proportions of ILI and respiratory illness with fever (one surveillance syndrome of the UP system) to total patient visits (3·40% and 11·76%, respectively) were higher than the previous years. The surveillance data of both systems also showed developing trends similar to the influenza A (H1N1) pandemic in 2009. When the surveillance data of 2009 were fitted in the two detection models, alarms were produced on the occurrence of the first local case of influenza A (H1N1), outbreaks in schools and in general populations. Conclusions  The results indicated the potential for using ILI and UP surveillance data as syndromic indicators to detect and provide an early warning for influenza epidemics. PMID:21668678

Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colby, Denise; Bergman, Robert; Ellman, Jonathan

2010-05-13

Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the areamore » of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

Electrical properties of epitaxial 3C- and 6H-SiC p-n junction diodes produced side-by-side on 6H-SiC substrates

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Larkin, David J.; Starr, Jonathan E.; Powell, J. Anthony; Salupo, Carl S.; Matus, Lawrence G.

1994-01-01

3C-SiC (beta-SiC) and 6H-SiC p-n junction diodes have been fabricated in regions of both 3C-SiC and 6H-SiC epitaxial layers which were grown side-by-side on low-tilt-angle 6H-SiC substrates via a chemical vapor deposition (CVD) process. Several runs of diodes exhibiting state-of-the-art electrical characteristics were produced, and performance characteristics were measured and compared as a function of doping, temperature, and polytype. The first 3C-SiC diodes which rectify to reverse voltages in excess of 300 V were characterized, representing a six-fold blocking voltage improvement over experimental 3C-SiC diodes produced by previous techniques. When placed under sufficient forward bias, the 3C-SiC diodes emit significantly bright green-yellow light while the 6H-SiC diodes emit in the blue-violet. The 6H-SiC p-n junction diodes represent the first reported high-quality 6H-SiC devices to be grown by CVD on very low-tilt-angle (less than 0.5 deg off the (0001) silicon face) 6H substrates. The reverse leakage current of a 200 micron diameter circular device at 1100 V reverse bias was less than 20 nA at room temperature, and excellent rectification characteristics were demonstrated at the peak characterization temperature of 400 C.

Kinetics of the R + NO2 reactions (R = i-C3H7, n-C3H7, s-C4H9, and t-C4H9) in the temperature range 201-489 K.

PubMed

Rissanen, Matti P; Arppe, Suula L; Eskola, Arkke J; Tammi, Matti M; Timonen, Raimo S

2010-04-15

The bimolecular rate coefficients of four alkyl radical reactions with NO(2) have been measured in direct time-resolved experiments. Reactions were studied under pseudo-first-order conditions in a temperature-controlled tubular flow reactor coupled to a laser photolysis/photoionization mass spectrometer (LP-PIMS). The measured reaction rate coefficients are independent of helium bath gas pressure within the experimental ranges covered and exhibit negative temperature dependence. For i-C(3)H(7) + NO(2) and t-C(4)H(9) + NO(2) reactions, the dependence of ordinate (logarithm of reaction rate coefficients) on abscissa (1/T or log(T)) was nonlinear. The obtained results (in cm(3) s(-1)) can be expressed by the following equations: k(n-C(3)H(7) + NO(2)) = ((4.34 +/- 0.08) x 10(-11)) (T/300 K)(-0.14+/-0.08) (203-473 K, 1-7 Torr), k(i-C(3)H(7) + NO(2)) = ((3.66 +/- 2.54) x 10(-12)) exp(656 +/- 201 K/T)(T/300 K)(1.26+/-0.68) (220-489 K, 1-11 Torr), k(s-C(4)H(9) + NO(2)) = ((4.99 +/- 0.16) x 10(-11))(T/300 K)(-1.74+/-0.12) (241-485 K, 2 - 12 Torr) and k(t-C(4)H(9) + NO(2)) = ((8.64 +/- 4.61) x 10(-12)) exp(413 +/- 154 K/T)(T/300 K)(0.51+/-0.55) (201-480 K, 2-11 Torr), where the uncertainties shown refer only to the 1 standard deviations obtained from the fitting procedure. The estimated overall uncertainty in the determined bimolecular rate coefficients is about +/-20%.

A novel technique for measurement of thermal rate constants and temperature dependences of dissociative recombination: CO{sub 2}{sup +}, CF{sub 3}{sup +}, N{sub 2}O{sup +}, C{sub 7}H{sub 8}{sup +}, C{sub 7}H{sub 7}{sup +}, C{sub 6}H{sub 6}{sup +}, C{sub 6}H{sub 5}{sup +}, C{sub 5}H{sub 6}{sup +}, C{sub 4}H{sub 4}{sup +}, and C{sub 3}H{sub 3}{sup +}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fournier, Joseph A.; Shuman, Nicholas S.; Melko, Joshua J.

A novel technique using a flowing afterglow-Langmuir probe apparatus for measurement of temperature dependences of rate constants for dissociative recombination (DR) is presented. Low ({approx}10{sup 11} cm{sup -3}) concentrations of a neutral precursor are added to a noble gas/electron afterglow plasma thermalized at 300-500 K. Charge exchange yields one or many cation species, each of which may undergo DR. Relative ion concentrations are monitored at a fixed reaction time while the initial plasma density is varied between 10{sup 9} and 10{sup 10} cm{sup -3}. Modeling of the decrease in concentration of each cation relative to the non-recombining noble gas cationmore » yields the rate constant for DR. The technique is applied to several species (O{sub 2}{sup +}, CO{sub 2}{sup +}, CF{sub 3}{sup +}, N{sub 2}O{sup +}) with previously determined 300 K values, showing excellent agreement. The measurements of those species are extended to 500 K, with good agreement to literature values where they exist. Measurements are also made for a range of C{sub n}H{sub m}{sup +} (C{sub 7}H{sub 7}{sup +}, C{sub 7}H{sub 8}{sup +}, C{sub 5}H{sub 6}{sup +}, C{sub 4}H{sub 4}{sup +}, C{sub 6}H{sub 5}{sup +}, C{sub 3}H{sub 3}{sup +}, and C{sub 6}H{sub 6}{sup +}) derived from benzene and toluene neutral precursors. C{sub n}H{sub m}{sup +} DR rate constants vary from 8-12 Multiplication-Sign 10{sup -7} cm{sup 3} s{sup -1} at 300 K with temperature dependences of approximately T{sup -0.7}. Where prior measurements exist these results are in agreement, with the exception of C{sub 3}H{sub 3}{sup +} where the present results disagree with a previously reported flat temperature dependence.« less

Thermodynamic design of a high temperature chemical vapor deposition process to synthesize α-SiC in Si-C-H and Si-C-H-Cl systems

NASA Astrophysics Data System (ADS)

Kang, Yura; Yoo, Chang-Hyoung; Nam, Deok-Hui; Lee, Myung-Hyun; Seo, Won-Seon; Hong, Suklyun; Jeong, Seong-Min

2018-03-01

In this study, we thermodynamically reviewed the suitable growth process conditions of α-SiC in the Si-C-H system using tetramethylsilane (TMS) and in the Si-C-H-Cl system using methyltrichlorosilane (MTS). In the Si-C-H-Cl system, pure solid SiC was obtained at high temperatures under a larger range of hydrogen dilution ratios than that tolerated in the Si-C-H system. X-ray diffraction and micro-Raman analysis of the products obtained at 1900, 2000, and 2100 °C showed that the α-SiC becomes more dominant with increasing temperature in the Si-C-H-Cl system. While TMS was unsuitable for high temperature processing due to its high C/Si ratio, MTS was found to be appropriate for growing α-SiC crystals at high temperatures under a range of conditions. These results indicate that a novel method to grow α-SiC single crystals through HTCVD using MTS as a precursor could be established.

Recent Developments in C-H Activation for Materials Science in the Center for Selective C-H Activation.

PubMed

Zhang, Junxiang; Kang, Lauren J; Parker, Timothy C; Blakey, Simon B; Luscombe, Christine K; Marder, Seth R

2018-04-16

Abstract : Organic electronics is a rapidly growing field driven in large part by the synthesis of ∏-conjugated molecules and polymers. Traditional aryl cross-coupling reactions such as the Stille and Suzuki have been used extensively in the synthesis of ∏-conjugated molecules and polymers, but the synthesis of intermediates necessary for traditional cross-couplings can include multiple steps with toxic and hazardous reagents. Direct arylation through C-H bond activation has the potential to reduce the number of steps and hazards while being more atom-economical. Within the Center for Selective C-H Functionalization (CCHF), we have been developing C-H activation methodology for the synthesis of ∏-conjugated materials of interest, including direct arylation of difficult-to-functionalize electron acceptor intermediates and living polymerization of ∏-conjugated polymers through C-H activation.

Calculational and Experimental Investigations of the Pressure Effects on Radical - Radical Cross Combinations Reactions: C2H5 + C2H3

NASA Technical Reports Server (NTRS)

Fahr, Askar; Halpern, Joshua B.; Tardy, Dwight C.

2007-01-01

Pressure-dependent product yields have been experimentally determined for the cross-radical reaction C2H5 + C2H3. These results have been extended by calculations. It is shown that the chemically activated combination adduct, 1-C4H8*, is either stabilized by bimolecular collisions or subject to a variety of unimolecular reactions including cyclizations and decompositions. Therefore the "apparent" combination/disproportionation ratio exhibits a complex pressure dependence. The experimental studies were performed at 298 K and at selected pressures between about 4 Torr (0.5 kPa) and 760 Torr (101 kPa). Ethyl and vinyl radicals were simultaneously produced by 193 nm excimer laser photolysis of C2H5COC2H3 or photolysis of C2H3Br and C2H5COC2H5. Gas chromatograph/mass spectrometry/flame ionization detection (GC/MS/FID) were used to identify and quantify the final reaction products. The major combination reactions at pressures between 500 (66.5 kPa) and 760 Torr are (1c) C2H5 + C2H3 yields 1-butene, (2c) C2H5 + C2H5 yields n-butane, and (3c) C2H3 + C2H3 yields 1,3-butadiene. The major products of the disproportionation reactions are ethane, ethylene, and acetylene. At moderate and lower pressures, secondary products, including propene, propane, isobutene, 2-butene (cis and trans), 1-pentene, 1,4-pentadiene, and 1,5-hexadiene are also observed. Two isomers of C4H6, cyclobutene and/or 1,2-butadiene, were also among the likely products. The pressure-dependent yield of the cross-combination product, 1-butene, was compared to the yield of n-butane, the combination product of reaction (2c), which was found to be independent of pressure over the range of this study. The [ 1-C4H8]/[C4H10] ratio was reduced from approx.1.2 at 760 Torr (101 kPa) to approx.0.5 at 100 Torr (13.3 kPa) and approx.0.1 at pressures lower than about 5 Torr (approx.0.7 kPa). Electronic structure and RRKM calculations were used to simulate both unimolecular and bimolecular processes. The relative importance

Hydrogenation and Deuteration of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} on Cold Grains: A Clue to the Formation Mechanism of C{sub 2}H{sub 6} with Astronomical Interest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Hitomi; Kawakita, Hideyo; Hidaka, Hiroshi

We quantitatively investigated the hydrogen addition reactions of acetylene (C{sub 2}H{sub 2}) and ethylene (C{sub 2}H{sub 4}) on amorphous solid water (ASW) at 10 and 20 K relevant to the formation of ethane (C{sub 2}H{sub 6}) on interstellar icy grains. We found that the ASW surface enhances the reaction rates for C{sub 2}H{sub 2} and C{sub 2}H{sub 4} by approximately a factor of 2 compared to those on the pure-solid C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, probably due to an increase in the sticking coefficient and adsorption energy of the H atoms on ASW. In contrastmore » to the previous proposal that the hydrogenation rate of C{sub 2}H{sub 4} is orders of magnitude larger than that of C{sub 2}H{sub 2}, the present results show that the difference in hydrogenation rates of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} is only within a factor of 3 on both the surfaces of pure solids and ASW. In addition, we found the small kinetic isotope effect for hydrogenation/deuteration of C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 10 K, despite the requirement of quantum tunneling. At 20 K, the reaction rate of deuteration becomes even larger than that of hydrogenation. These unusual isotope effects might originate from a slightly larger number density of D atoms than H atoms on ASW at 20 K. The hydrogenation of C{sub 2}H{sub 2} is four times faster than CO hydrogenation and can produce C{sub 2}H{sub 6} efficiently through C{sub 2}H{sub 4} even in the environment of a dark molecular cloud.« less

Total reaction cross sections of electronic state-specified transition metal cations: V + +C2H6, C3H8, and C2H4 at 0.2 eV

NASA Astrophysics Data System (ADS)

Sanders, Lary; Hanton, Scott D.; Weisshaar, James C.

1990-03-01

We describe a crossed beam experiment which measures total cross sections for reaction of electronic state-specified V+ with small hydrocarbons at well-defined collision energy E=0.2 eV. The V+ state distribution created at each ionizing wavelength is directly measured by angle-integrated photoelectron spectroscopy (preceding paper). Reactant and product ions are collected and analyzed by pulsed time-of-flight mass spectrometry following a reaction time of 6 μs. Tests of the performance of the apparatus are described in detail. Our experiment defines the reactant V+ electronic state distribution and the collision energy much more precisely than previous work. For all three hydrocarbons C2H6, C3H8, and C2H4, H2 elimination products dominate at 0.2 eV. We observe a dramatic dependence of cross section on the V+ electronic term. The second excited term 3d34s(3F) is more reactive than either lower energy quintet term 3d4(5D) or 3d34s(5F) by a factor of ≥270, 80, and ≥6 for the C2H6, C3H8, and C2H4 reactions, respectively. The 3d34s(3F) reaction cross sections at 0.2 eV are 20±11 Å2, 37±19 Å2, and 2.7±1.6 Å2, respectively, compared with Langevin cross sections of ˜80 Å2. For the C2H6 and C3H8 reactions, cross sections are independent of initial spin-orbit level J within the 3F term to the limits of our accuracy. Comparison with earlier work by Armentrout and co-workers shows that electronic excitation to d3s(3F) is far more effective at promoting H2 elimination than addition of the same total kinetic energy to reactants. Electron spin is clearly a key determinant of V+ reactivity with small hydrocarbons. We suggest that triplet V+ reacts much more efficiently than quintet V+ because of its ability to conserve total electron spin along paths to insertion in a C-H bond of the hydrocarbon.

Growth and characterizaton of 3C-SiC and 6H-SiC films on 6H-SiC wafers

NASA Technical Reports Server (NTRS)

Powell, J. A.; Petit, J. B.; Matus, L. G.; Lempner, S. E.

1992-01-01

Single crystal SiC films were grown by CVD on vicinal (0001) SiC wafers cut from boules produced by the modified sublimation method. Wafers with tilt angles less than 0.5 deg yielded 3C-SiC; tilt angles of 3 to 4 deg resulted in 6H-SiC films. The surface morphology of these films, up to 24 microns thick, were investigated as a function of growth parameters such as the Si/C ratio in the input gases and the presence of dopant materials such as nitrogen and trimethylaluminum.

An effective quarantine measure reduced the total incidence of influenza A H1N1 in the workplace: another way to control the H1N1 flu pandemic.

PubMed

Miyaki, Koichi; Sakurazawa, Hirofumi; Mikurube, Hajime; Nishizaka, Mika; Ando, Hidehiko; Song, Yixuan; Shimbo, Takuro

2011-01-01

To evaluate the effectiveness of a non-vaccine quarantine measure against pandemic influenza A H1N1 in workplaces. Design was quasi-cluster randomized controlled trial in two sibling companies (Cohort 1 n=6,634, Cohort 2 n=8,500). The follow-up period was from July 1st, 2009 to February 19th, 2010 (233 days). Intervention was voluntary waiting at home on full pay if the family became Influenza like Illness (ILI). The incidences of influenza A H1N1 and those of the subgroups whose families got ILI in both cohorts were compared by a Cox regression model and log-rank test. There were 189 and 270 workers who got H1N1 infection during the follow-up period in each cohort. In this period 317 workers in Cohort 1 were asked to wait at home for several days (100% obeyed). The intervention group (Cohort 1) showed a statistically significant lower risk (p for log-rank test=0.033) compared with the control (Cohort 2), and the hazard ratio of the intervention was 0.799 [0.658-0.970] after adjusting for age, sex, BMI and smoking status. The workers who were asked to wait at home showed H1N1 infection more frequently (49 out of 317) compared with the workers whose family got ILI but were not asked to wait and work regularly (77 out of 990, RR=2.17 [1.48-3.18]). The waiting on full pay policy in the workplace reduced the overall risk of influenza A H1N1 by about 20% in one flu season in Japan. This kind of non-vaccine measure will be a promising option in workplaces to control the next flu pandemic.

Reactive carbon-chain molecules: synthesis of 1-diazo-2,4-pentadiyne and spectroscopic characterization of triplet pentadiynylidene (H-C[triple bond]C-:C-C[triple bond]C-H).

PubMed

Bowling, Nathan P; Halter, Robert J; Hodges, Jonathan A; Seburg, Randal A; Thomas, Phillip S; Simmons, Christopher S; Stanton, John F; McMahon, Robert J

2006-03-15

1-Diazo-2,4-pentadiyne (6a), along with both monodeuterio isotopomers 6b and 6c, has been synthesized via a route that proceeds through diacetylene, 2,4-pentadiynal, and 2,4-pentadiynal tosylhydrazone. Photolysis of diazo compounds 6a-c (lambda > 444 nm; Ar or N2, 10 K) generates triplet carbenes HC5H (1) and HC5D (1-d), which have been characterized by IR, EPR, and UV/vis spectroscopy. Although many resonance structures contribute to the resonance hybrid for this highly unsaturated carbon-chain molecule, experiment and theory reveal that the structure is best depicted in terms of the dominant resonance contributor of penta-1,4-diyn-3-ylidene (diethynylcarbene, H-C[triple bond]C-:C-C[triple bond]C-H). Theory predicts an axially symmetric (D(infinity h)) structure and a triplet electronic ground state for 1 (CCSD(T)/ANO). Experimental IR frequencies and isotope shifts are in good agreement with computed values. The triplet EPR spectrum of 1 (absolute value(D/hc) = 0.6157 cm(-1), absolute value(E/hc) = 0.0006 cm(-1)) is consistent with an axially symmetric structure, and the Curie law behavior confirms that the triplet state is the ground state. The electronic absorption spectrum of 1 exhibits a weak transition near 400 nm with extensive vibronic coupling. Chemical trapping of triplet HC5H (1) in an O2-doped matrix affords the carbonyl oxide 16 derived exclusively from attack at the central carbon.

Carboxylate-assisted ruthenium-catalyzed alkyne annulations by C-H/Het-H bond functionalizations.

PubMed

Ackermann, Lutz

2014-02-18

To improve the atom- and step-economy of organic syntheses, researchers would like to capitalize upon the chemistry of otherwise inert carbon-hydrogen (C-H) bonds. During the past decade, remarkable progress in organometallic chemistry has set the stage for the development of increasingly viable metal catalysts for C-H bond activation reactions. Among these methods, oxidative C-H bond functionalizations are particularly attractive because they avoid the use of prefunctionalized starting materials. For example, oxidative annulations that involve sequential C-H and heteroatom-H bond cleavages allow for the modular assembly of regioselectively decorated heterocycles. These structures serve as key scaffolds for natural products, functional materials, crop protecting agents, and drugs. While other researchers have devised rhodium or palladium complexes for oxidative alkyne annulations, my laboratory has focused on the application of significantly less expensive, yet highly selective ruthenium complexes. This Account summarizes the evolution of versatile ruthenium(II) complexes for annulations of alkynes via C-H/N-H, C-H/O-H, or C-H/N-O bond cleavages. To achieve selective C-H bond functionalizations, we needed to understand the detailed mechanism of the crucial C-H bond metalation with ruthenium(II) complexes and particularly the importance of carboxylate assistance in this process. As a consequence, our recent efforts have resulted in widely applicable methods for the versatile preparation of differently decorated arenes and heteroarenes, providing access to among others isoquinolones, 2-pyridones, isoquinolines, indoles, pyrroles, or α-pyrones. Most of these reactions used Cu(OAc)2·H2O, which not only acted as the oxidant but also served as the essential source of acetate for the carboxylate-assisted ruthenation manifold. Notably, the ruthenium(II)-catalyzed oxidative annulations also occurred under an ambient atmosphere of air with cocatalytic amounts of Cu(OAc)2·H

Association of age and comorbidity on 2009 influenza A pandemic H1N1-related intensive care unit stay in Massachusetts.

PubMed

Placzek, Hilary E D; Madoff, Lawrence C

2014-11-01

We compared comorbidity measures by age group and risk factors for influenza-like illness (ILI)-related intensive care unit (ICU) stay during the 2009 seasonal influenza and influenza A (pH1N1) pandemic. We identified all patients discharged from Massachusetts hospitals with ILI-related diagnoses between October 1, 2008, and April 25, 2009, and pH1N1-related diagnoses between April 26 and September 30, 2009. We calculated the Diagnostic Cost Group (DxCG) risk score as a measure of comorbidity. We used logistic regression predictive models to compare ICU stay predictors. Mean DxCG scores were similar for pH1N1 and seasonal influenza time periods (0.69 and 0.70). Compared with those aged 45 to 64 years, patients younger than 5, 5 to 12, and 13 to 18 years had an increased risk of pH1N1-related ICU stay. Within the pH1N1 cohort, an asthma diagnosis was highly predictive of ICU admission among those younger than 5, 5 to 12, and 13 to 18 years, and pregnancy among those aged 26 to 44 years. High-risk groups, including children with asthma or pregnant women, would benefit from improved surveillance and resource allocation during influenza outbreaks to prevent serious ILI-related complications.

3-Methyl-7-(2-thienyl)pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione: pi-stacked bilayers built from N-H...O, C-H...O and C-H...pi hydrogen bonds.

PubMed

Trilleras, Jorge; Quiroga, Jairo; Cobo, Justo; Glidewell, Christopher

2009-06-01

In the title compound, C(12)H(9)N(3)O(2)S, the thienyl substituent is disordered over two sets of sites with occupancies of 0.749 (3) and 0.251 (3). A combination of N-H...O, C-H...O and C-H...pi hydrogen bonds links the molecules into bilayers and these bilayers are themselves linked into a continuous structure by pi-pi stacking interactions.

An Outbreak of 2009 Pandemic Influenza A (H1N1) Virus Infection in an Elementary School in Pennsylvania

PubMed Central

Bhattarai, Achuyt; Fagan, Ryan P.; Ostroff, Stephen; Sodha, Samir V.; Moll, Mària E.; Lee, Bruce Y.; Chang, Chung-Chou H.; Ennis, Brent; Britz, Phyllis; Fiore, Anthony; Nguyen, Michael; Palekar, Rakhee; Archer, W. Roodly; Gift, Thomas L.; Leap, Rebecca; Nygren, Benjamin L.; Cauchemez, Simon; Angulo, Frederick J.; Swerdlow, David

2011-01-01

In May 2009, one of the earliest outbreaks of 2009 pandemic influenza A virus (pH1N1) infection resulted in the closure of a semi-rural Pennsylvania elementary school. Two sequential telephone surveys were administered to 1345 students (85% of the students enrolled in the school) and household members in 313 households to collect data on influenza-like illness (ILI). A total of 167 persons (12.4%) among those in the surveyed households, including 93 (24.0%) of the School A students, reported ILI. Students were 3.1 times more likely than were other household members to develop ILI (95% confidence interval [CI], 2.3–4.1). Fourth-grade students were more likely to be affected than were students in other grades (relative risk, 2.2; 95% CI, 1.2–3.9). pH1N1 was confirmed in 26 (72.2%) of the individuals tested by real-time reverse-transcriptase polymerase chain reaction. The outbreak did not resume upon the reopening of the school after the 7-day closure. This investigation found that pH1N1 outbreaks at schools can have substantial attack rates; however, grades and classrooms are affected variably. Additioanl study is warranted to determine the effectiveness of school closure during outbreaks. PMID:21342888

First Observation and Analysis of OCS-C_4H_2 Dimer and (OCS)_2-C_4H_2 Trimer

NASA Astrophysics Data System (ADS)

Sheybani-Deloui, S.; Yousefi, Mahdi; Norooz Oliaee, Jalal; McKellar, Bob; Moazzen-Ahmadi, Nasser

2014-06-01

Infrared spectrum of a slipped near parallel isomer of OCS-C_4H_2 was observed in the region of νb{1} fundamental band of OCS monomer (˜2062 wn) using a diode laser to probe the supersonic slit jet expansion. The ab initio calculations at MP2 level indicate that the observed structure is the lowest energy isomer. The OCS-C_4H_2 band is composed of hybrid a/b-type transitions and was simulated by a conventional asymmetric top Hamiltonian with rotational constants of A=2892.15(10) MHz, B=1244.178(84) MHz, and C=868.692(52) MHz. The spectrum shows a relatively large red-shift of ˜6 wn with respect to the OCS monomer band origin. Also, one band for (OCS)_2-C_4H_2 trimer is observed around 2065 wn. This band is blue-shifted by 3 wn relative to the νb{1} fundamental band of OCS monomer. Our analysis shows that this trimer has C2 symmetry with rotational constants of A= 855.854(61) MHz, B=733.15(11) MHz, and C=610.10(38) MHz and c-type transitions. This structure is comparable with that of (OCS)_2-C_2H_2 where the OCS dimer unit within the trimer is non-polar. In addition to the normal isotoplogues, OCS-C_4D_2 and (OCS)_2-C_4D_2 were observed. In this talk, we discuss our observations and analysis on OCS-C_4H_2 dimer and (OCS)_2-C_4H_2 trimer. Mojtaba Rezaei, A. R. W. McKellar, and N. Moazzen-Ahmadi, J. Phys. Chem. A, 115, 10416 (2011).

Growth and Characterization of 3C-SiC and 2H-AIN/GaN Films and Devices Produced on Step-Free 4H-SiC Mesa Substrates

NASA Technical Reports Server (NTRS)

Neudeck, P. G.; Du, H.; Skowronski, M.; Spry, D. J.; Trunek, A. J.

2007-01-01

While previously published experimental results have shown that the step-free (0 0 0 1) 4H-SiC mesa growth surface uniquely enables radical improvement of 3C-SiC and 2H-AlN/GaN heteroepitaxial film quality (greater than 100-fold reduction in extended defect densities), important aspects of the step-free mesa heterofilm growth processes and resulting electronic device benefits remain to be more fully elucidated. This paper reviews and updates recent ongoing studies of 3C-SiC and 2H-AlN/GaN heteroepilayers grown on top of 4H-SiC mesas. For both 3C-SiC and AlN/GaN films nucleated on 4H-SiC mesas rendered completely free of atomic-scale surface steps, TEM studies reveal that relaxation of heterofilm strain arising from in-plane film/substrate lattice constant mismatch occurs in a remarkably benign manner that avoids formation of threading dislocations in the heteroepilayer. In particular, relaxation appears to occur via nucleation and inward lateral glide of near-interfacial dislocation half-loops from the mesa sidewalls. Preliminary studies of homojunction diodes implemented in 3C-SiC and AlN/GaN heterolayers demonstrate improved electrical performance compared with much more defective heterofilms grown on neighbouring stepped 4H-SiC mesas. Recombination-enhanced dislocation motion known to degrade forward-biased 4H-SiC bipolar diodes has been completely absent from our initial studies of 3C-SiC diodes, including diodes implemented on defective 3C-SiC heterolayers grown on stepped 4H-SiC mesas.

MICROWAVE SPECTRA AND GEOMETRIES OF C2H_{2\\cdots AgI} and C2H_{4\\cdots AgI}

NASA Astrophysics Data System (ADS)

Stephens, Susanna L.; Tew, David Peter; Walker, Nick; Legon, Anthony

2015-06-01

A chirped-pulse Fourier transform microwave spectrometer has been used to measure the microwave spectra of both C2H_{2\\cdots AgI} and C2H_{4\\cdots AgI}. These complexes are generated via laser ablation at 532 nm of a silver surface in the presence of CF3I and either C2H_{2} or C2H_{4} and argon and are stabilized by a supersonic expansion. Rotational (A0, B0, C0) and centrifugal distortion constants (ΔJ and ΔJK) of each molecule have been determined as well the nuclear electric quadrupole coupling constants the iodine atom (χaa(I) and χbb-χcc(I)). The spectrum of each molecule is consistent with a C2v structure in which the metal atom interacts with the π-orbital of the ethene or ethyne molecule. Isotopic substitutions of atoms within the C2H_{2} or C2H_{4} subunits are in progress and in conjunction with high level ab initio calculations will allow for accurate determination of the geometry of each molecule. These to complexes are put in the context of the recently studied H2S\\cdots AgI, OC\\cdotsAgI, H3N\\cdots AgI and (CH3)_{3N\\cdots AgI}. S.Z. Riaz, S.L. Stephens, W. Mizukami, D.P. Tew, N.R. Walker, A.C. Legon, Chem. Phys. Let., 531, 1-12 (2012) S.L. Stephens, W. Mizukami, D.P. Tew, N.R. Walker, A.C. Legon, J. Chem. Phys., 136(6), 064306 (2012) D.M. Bittner, D.P. Zaleski, S.L. Stephens, N.R. Walker, A.C. Legon, Study in progress.

An observational investigation of the identity of B11244 (l-C{sub 3}H{sup +}/C{sub 3}H{sup -})

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuire, Brett A.; Carroll, P. Brandon; Gratier, Pierre

Pety et al. have reported the detection of eight transitions of a closed-shell, linear molecule (B11244) in observations toward the Horsehead photodissociation region (PDR), which they attribute to the l-C{sub 3}H{sup +} cation. Recent high-level ab initio calculations have called this assignment into question; the anionic C{sub 3}H{sup –} molecule has been suggested as a more likely candidate. Here, we examine observations of the Horsehead PDR, Sgr B2(N), TMC-1, and IRC+10216 in the context of both l-C{sub 3}H{sup +} and C{sub 3}H{sup –}. We find no observational evidence of K{sub a} = 1 lines, which should be present were themore » carrier indeed C{sub 3}H{sup –}. Additionally, we find a strong anticorrelation between the presence of known molecular anions and B11244 in these regions. Finally, we discuss the formation and destruction chemistry of C{sub 3}H{sup –} in the context of the physical conditions in the regions. Based on these results, we conclude there is little evidence to support the claim that the carrier is C{sub 3}H{sup –}.« less

Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zheng; Lü, Tie-Yu; Wang, Hui-Qiong

We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature,more » indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.« less

Hyperfine excitation of C2H in collisions with ortho- and para-H2

NASA Astrophysics Data System (ADS)

Dagdigian, Paul J.

2018-06-01

Accurate estimation of the abundance of the ethynyl (C2H) radical requires accurate radiative and collisional rate coefficients. Hyperfine-resolved rate coefficients for (de-)excitation of C2H in collisions with ortho- and para-H2 are presented in this work. These rate coefficients were computed in time-independent close-coupling quantum scattering calculations that employed a potential energy surface recently computed at the coupled-clusters level of theory that describes the interaction of C2H with H2. Rate coefficients for temperatures from 10 to 300 K were computed for all transitions among the first 40 hyperfine energy levels of C2H in collisions with ortho- and para-H2. These rate coefficients were employed in simple radiative transfer calculations to simulate the excitation of C2H in typical molecular clouds.

Characterization of 3C-SiC Films Grown on 4H- and 6H-SiC Substrate Mesas During Step-Free Surface Heteroepitaxy

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Powel J. Anthony; Spry, David J.; Trunek, Andrew J.; Huang, Xianrong; Vetter, William M.; Dudley, Michael; Skowronski, Marek; Liu, Jinqiang

2002-01-01

This paper reports detailed structural characterization of 3C-SiC heteroepitaxial films grown on 4H- and 6H-SiC mesa surfaces. 3C-SiC heterofilms grown by the "step-free surface heteroepitaxy" process, free of double-positioning boundary (DPB) and stacking-fault (SF) defects, were compared to less-optimized 3C-SiC heterofilms using High Resolution X-ray Diffraction (HRXRD), High Resolution Cross-sectional Transmission Electron Microscopy (HRXTEM), molten potassium hydroxide (KOH) etching, and dry thermal oxidation. The results suggest that step free surface heteroepitaxy enables remarkably benign partial lattice mismatch strain relief during heterofilm growth.

Van Der Waals heterogeneous layer-layer carbon nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on graphene and graphane sheets.

PubMed

Yuan, Kun; Zhao, Rui-Sheng; Zheng, Jia-Jia; Zheng, Hong; Nagase, Shigeru; Zhao, Sheng-Dun; Liu, Yan-Zhi; Zhao, Xiang

2017-04-15

Noncovalent interactions involving aromatic rings, such as π···π stacking, CH···π are very essential for supramolecular carbon nanostructures. Graphite is a typical homogenous carbon matter based on π···π stacking of graphene sheets. Even in systems not involving aromatic groups, the stability of diamondoid dimer and layer-layer graphane dimer originates from C - H···H - C noncovalent interaction. In this article, the structures and properties of novel heterogeneous layer-layer carbon-nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on [n]-graphane and [n]-graphene and their derivatives are theoretically investigated for n = 16-54 using dispersion corrected density functional theory B3LYP-D3 method. Energy decomposition analysis shows that dispersion interaction is the most important for the stabilization of both double- and multi-layer-layer [n]-graphane@graphene. Binding energy between graphane and graphene sheets shows that there is a distinct additive nature of CH···π interaction. For comparison and simplicity, the concept of H-H bond energy equivalent number of carbon atoms (noted as NHEQ), is used to describe the strength of these noncovalent interactions. The NHEQ of the graphene dimers, graphane dimers, and double-layered graphane@graphene are 103, 143, and 110, indicating that the strength of C-H···π interaction is close to that of π···π and much stronger than that of C-H···H-C in large size systems. Additionally, frontier molecular orbital, electron density difference and visualized noncovalent interaction regions are discussed for deeply understanding the nature of the C-H···π stacking interaction in construction of heterogeneous layer-layer graphane@graphene structures. We hope that the present study would be helpful for creations of new functional supramolecular materials based on graphane and graphene carbon nano-structures. © 2017 Wiley Periodicals, Inc. © 2017 Wiley

Catalyst- and Reagent-free Electrochemical Azole C-H Amination.

PubMed

Qiu, Youai; Struwe, Julia; Meyer, Tjark H; Oliveira, Joao Carlos Agostinho Carlos Agostinho; Ackermann, Lutz

2018-06-14

Catalyst-, and chemical oxidant-free electrochemical azole C-H aminations were accomplished via cross-dehydrogenative C-H/N-H functionalization. The catalyst-free electrochemical C-H amination proved feasible on azoles with high levels of efficacy and selectivity, avoiding the use of stoichiometric oxidants under ambient conditions. Likewise, the C(sp3)-H nitrogenation proved viable under otherwise identical conditions. The dehydrogenative C-H amination featured ample scope, including cyclic and acyclic aliphatic amines as well as anilines, and employed sustainable electricity as the sole oxidant. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

H2 formation via the UV photo-processing of a-C:H nano-particles

NASA Astrophysics Data System (ADS)

Jones, A. P.; Habart, E.

2015-09-01

Context. The photolysis of hydrogenated amorphous carbon, a-C(:H), dust by UV photon-irradiation in the laboratory leads to the release of H2 as well as other molecules and radicals. This same process is also likely to be important in the interstellar medium. Aims: We investigate molecule formation arising from the photo-dissociatively-driven, regenerative processing of a-C(:H) dust. Methods: We explore the mechanism of a-C(:H) grain photolysis leading to the formation of H2 and other molecules/radicals. Results: The rate constant for the photon-driven formation of H2 from a-C(:H) grains is estimated to be 2 × 10-17 cm3 s-1. In intense radiation fields photon-driven grain decomposition will lead to fragmentation into daughter species rather than H2 formation. Conclusions: The cyclic re-structuring of arophatic a-C(:H) nano-particles appears to be a viable route to formation of H2 for low to moderate radiation field intensities (1 ≲ G0 ≲ 102), even when the dust is warm (T ~ 50-100 K).

[Factors influencing antiretroviral therapy adherence among HIV-infected people on antiretroviral therapy in Ili Kazakh Autonomous Prefecture].

PubMed

Wang, W; Liu, W; Chen, T; Liu, N P; Zheng, Y J; Ye, S D; Zhang, Y; Wang, X M; Wang, G Z; Zhang, H B

2017-02-06

Objective: To analyze factors influencing antiretroviral therapy (ART) adherence among human immunodeficiency virus (HIV) patients receiving ART at the town level in Ili Kazakh Autonomous Prefecture (Ili) in May 2015 and to document enhanced ART for acquired immunodeficiency syndrome (AIDS) cases. Methods: A cross-sectional survey was conducted using one-on-one interviews and data collection from the system of AIDS follow-up management in three ART services centers at the town level of Ili. The subjects were HIV-infected individuals, aged 18 years or older, who were receiving ART during the survey. The surveys collected demographic characteristics, information related to ART and status of engaging ART, smoking and drinking behavior, depression, and quality of life. Results: A total of 412 participants completed the survey. The age was (41.1±8.0) years (range, 19-67 years). Approximately 60.9% (251) were male and 39.1% (161) were female. The survey showed that 75.0% (309) of participants were in good adherence and the P (50) ( P (25), P (75)) of quality of life was 56.31 (50.55, 59.42). Females demonstrated better adherence to ART (82.6% ( n= 133)) than males (70.1% ( n= 76)) (χ(2)=8.16, P= 0.005). The compliance rate of participants (78.0% ( n= 54)) with depression was higher than non-depressed participants (63.5% ( n= 255)) (χ(2)=7.52, P= 0.008). Multivariate logistic regression analyses showed that the probability of good adherence to ART increased with increasing quality of life ( OR= 1.06, 95% CI: 1.02-1.09). Moreover, participants who consumed alcohol or disclosed their HIV infection status to families were less likely to have good adherence to ART ( OR= 0.26, 95% CI: 0.13-0.53 and OR= 0.31, 95% CI: 0.13-0.72, respectively). Additionally, employed participants were also less likely to have good adherence to ART compared with unemployed participants ( OR= 0.45, 95% CI: 0.21-0.97). Conclusion: HIV/AIDS patients primarily showed good adherence to ART. Factors

Formation and infrared absorption of protonated naphthalenes (1-C10H9+ and 2-C10H9+) and their neutral counterparts in solid para-hydrogen.

PubMed

Bahou, Mohammed; Wu, Yu-Jong; Lee, Yuan-Pern

2013-02-14

Protonated naphthalene (C(10)H(9)(+)) and its neutral counterparts (hydronaphthyl radicals, C(10)H(9)) are important intermediates in the reactions of aromatic compounds and in understanding the unidentified infrared (IR) emissions from interstellar media. We report the IR spectra of 1-C(10)H(9)(+), 2-C(10)H(9)(+), 1-C(10)H(9), and 2-C(10)H(9) trapped in solid para-hydrogen (p-H(2)); the latter three are new. These species were produced upon electron bombardment of a mixture of naphthalene (C(10)H(8)) and p-H(2) during matrix deposition. The intensities of IR features of 1-C(10)H(9)(+) decreased after the matrix was maintained in darkness for 19 h, whereas those of 1-C(10)H(9) and 2-C(10)H(9) increased. Irradiation of this matrix sample with light at 365 nm diminished lines of 1-C(10)H(9)(+) and 2-C(10)H(9) and enhanced lines of 1-C(10)H(9) and 2-C(10)H(9)(+); the latter species was unstable and converted to 1-C(10)H(9)(+) in less than 30 min and 2-C(10)H(9) was converted to 1-C(10)H(9) at 365 nm. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++G(2d,2p) method. Compared with spectra recorded previously with IR photodissociation of Ar-tagged C(10)H(9)(+) or IR multiphoton dissociation of C(10)H(9)(+), our method has the advantages of producing high-resolution IR spectra with a wide spectral coverage, true IR intensity and excellent ratio of signal to noise; both protonated species and their neutral counterparts are produced with little interference from other fragments. With these advantages, the IR spectra of 1-C(10)H(9)(+), 2-C(10)H(9)(+), 1-C(10)H(9), and 2-C(10)H(9) are here clearly characterized.

Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

NASA Technical Reports Server (NTRS)

Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Romani, P. N.; Abbas, M.; LeClair, A.; Strobel, D.

2004-01-01

Hydrocarbons such as acetylene (C2H2) and ethane (C2H6) are important tracers in Jupiter's atmosphere, constraining our models of the chemical and dynamical processes. However, our knowledge of the vertical and meridional variations of their abundances has remained sparse. During the flyby of the Cassini spacecraft in December 2000, the Composite Infrared Spectrometer (CIRS) instrument was used to map the spatial variation of emissions from 10-1400 cm(sup -1) (1000-7 microns). In this paper we analyze a zonally-averaged set of CIRS spectra taken at the highest (0.5 cm(sup -1)) resolution, to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 band of CH4, and in the troposphere at 150-400 mbar, via the H2 absorption at 600-800 cm(sup -1). Simultaneously, we retrieve the abundances of C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIRS resolution, introducing a non-uniqueness into the retrievals, such that vertical gradient and column abundance cannot both be found without additional constraints. Assuming profile gradients from photochemical calculations, we show that the column abundance of C2H2 decreases sharply towards the poles by a factor approximately 4, while C2H6 is unchanged in the north and increasing in the south, by a factor approximately 1.8. An explanation for the meridional trends is proposed in terms of a combination of photochemistry and dynamics. Poleward, the decreasing UV flux is predicted to decrease the abundances of C2H2 and C2H6 by factors 2.7 and 3.5 respectively at a latitude 70 deg. However, the lifetime of C2H6 in the stratosphere (5 x 10(exp 9)) is much longer than the dynamical timescale for meridional motions inferred from SL-9 debris (5 x 10(exp 8 s)), and therefore the constant or rising abundance towards high latitudes likely indicates that meridional mixing dominates over photochemical effects. For C2H2, the opposite

Rate coefficients for the reactions of C2(a(3)Pi(u)) and C2(X(1)Sigma(g)(+)) with various hydrocarbons (CH4, C2H2, C2H4, C2H6, and C3H8): a gas-phase experimental study over the temperature range 24-300 K.

PubMed

Páramo, Alejandra; Canosa, André; Le Picard, Sébastien D; Sims, Ian R

2008-10-02

The kinetics of reactions of C2(a(3)Pi(u)) and C2(X(1)Sigma(g)(+)) with various hydrocarbons (CH4, C2H2, C2H4, C2H6, and C3H8) have been studied in a uniform supersonic flow expansion over the temperature range 24-300 K. Rate coefficients have been obtained by using the pulsed laser photolysis-laser induced fluorescence technique, where both radicals were produced at the same time but detected separately. The reactivity of the triplet state was found to be significantly lower than that of the singlet ground state for all reactants over the whole temperature range of the study. Whereas C2(X(1)Sigma(g)(+)) reacts with a rate coefficient close to the gas kinetic limit with all hydrocarbons studied apart from CH4, C2(a(3)Pi(u)) appears to be more sensitive to the molecular and electronic structure of the reactant partners. The latter reacts at least one order of magnitude faster with unsaturated hydrocarbons than with alkanes, and the rate coefficients increase very significantly with the size of the alkane. Results are briefly discussed in terms of their potential astrophysical impact.

C60H_2: Synthesis of the Simplest C60 Hydrocarbon Derivative

NASA Astrophysics Data System (ADS)

Henderson, Craig C.; Cahill, Paul A.

1993-03-01

The reaction of C60 with BH_3:tetrahydrofuran in toluene followed by hydrolysis yielded C60H_2. This product was separated by high-performance liquid chromatography and characterized as the addition product of H_2 to a 6,6-ring fusion (1a1b isomer). The ^1H nuclear magnetic resonance (NMR) spectrum of the product remained a sharp singlet between -80^circ and +100^circC, which suggests a static structure on the NMR time scale. Hydrolysis of the proposed borane addition product with acetic acid-d_1 or D_2O yielded C60HD, and its ^3JHD coupling constant is consistent with vicinal addition. The observation of a single C60H_2 isomer is in complete agreement with earlier calculations that indicated that at most 2 of the 23 possible isomers of C60 would be observable at equilibrium at room temperature. These results suggest that organoborane chemistry may be applied to further functionalization of fullerenes.

Synthesis of polycyclic molecules by double C(sp2)-H/C(sp3)-H arylations with a single palladium catalyst.

PubMed

Pierre, Cathleen; Baudoin, Olivier

2011-04-01

Polycyclic molecules were obtained in good yields by double C(sp(2))-H/C(sp(3))-H arylations mediated by a single palladium/phosphine catalyst. Both double intermolecular/intramolecular and intramolecular/intramolecular C-C couplings were performed successfully, which indicates that this concept has a broad applicability for the rapid construction of molecular complexity.

Observations of CH4, C2H6, and C2H2 in the stratosphere of Jupiter

NASA Technical Reports Server (NTRS)

Sada, P. V.; Bjoraker, G. L.; Jennings, D. E.; McCabe, G. H.; Romani, P. N.

1998-01-01

We have performed high-resolution spectral observations at mid-infrared wavelengths of CH4 (8.14 micrometers), C2H6 (12.16 micrometers), and C2H2 (13.45 micrometers) on Jupiter. These emission features probe the stratosphere of the planet and provide information on the carbon-based photochemical processes taking place in that region of the atmosphere. The observations were performed using our cryogenic echelle spectrometer CELESTE, in conjunction with the McMath-Pierce 1.5-m solar telescope between November 1994 and February 1995. We used the methane observations to derive the temperature profile of the jovian atmosphere in the 1-10 mbar region of the stratosphere. This profile was then used in conjunction with height-dependent mixing ratios of each hydrocarbon to determine global abundances for ethane and acetylene. The resulting mixing ratios are 3.9(+1.9)(-1.3) x 10(-6) for C2H6 (5 mbar pressure level), and 2.3 +/- 0.5 x 10(-8) for C2H2 (8 mbar pressure level), where the quoted uncertainties are derived from model variations in the temperature profile which match the methane observation uncertainties. c1998 Academic Press.

Conformation-induced remote meta-C-H activation of amines

NASA Astrophysics Data System (ADS)

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-01

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Conformation-induced remote meta-C-H activation of amines.

PubMed

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-13

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Expansion of antimonato polyoxovanadates with transition metal complexes: (Co(N3C5H15)2)2[{Co(N3C5H15)2}V15Sb6O42(H2O)]·5H2O and (Ni(N3C5H15)2)2[{Ni(N3C5H15)2}V15Sb6O42(H2O)]·8H2O.

PubMed

Antonova, Elena; Näther, Christian; Kögerler, Paul; Bensch, Wolfgang

2012-02-20

Two new polyoxovanadates (Co(N(3)C(5)H(15))(2))(2)[{Co(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·5H(2)O (1) and (Ni(N(3)C(5)H(15))(2))(2)[{Ni(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·8H(2)O (2) (N(3)C(5)H(15) = N-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V(15)Sb(6)O(42)(H(2)O)](6-) shell displays the main structural motif, which is strongly related to the {V(18)O(42)} archetype cluster. Both compounds crystallize in the triclinic space group P1 with a = 14.3438(4), b = 16.6471(6), c = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and V = 4401.4(2) Å(3) (1) and a = 14.5697(13), b = 15.8523(16), c = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and V = 4533.0(7) Å(3) (2). In the structure of 1 the [V(15)Sb(6)O(42)(H(2)O)](6-) cluster anion is bound to a [Co(N(3)C(5)H(15))(2)](2+) complex via a terminal oxygen atom. In the Co(2+)-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN(5)O octahedron. Similarly, in compound 2 an analogous NiN(5)O complex is joined to the [V(15)Sb(6)O(42)(H(2)O)](6-) anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in 1 and to Sb···N interactions in 2. In the solid-state lattices of 1 and 2, two additional [M(N(3)C(5)H(15))(2)](2+) complexes act as countercations and are located between the [{M(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)](4-) anions. Between the anions and cations strong N-H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the b axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni(2+) and Co(2+) cations do not

40 CFR 721.5540 - 1H,3H,5H-oxazolo [3,4-c] oxazole, dihydro-7a-methyl-.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1H,3H,5H-oxazolo [3,4-c] oxazole... Specific Chemical Substances § 721.5540 1H,3H,5H-oxazolo [3,4-c] oxazole, dihydro-7a-methyl-. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as 1H,3H,5H...

Room-temperature enantioselective C-H iodination via kinetic resolution.

PubMed

Chu, Ling; Xiao, Kai-Jiong; Yu, Jin-Quan

2014-10-24

Asymmetric carbon-hydrogen (C-H) activation reactions often rely on desymmetrization of prochiral C-H bonds on the same achiral molecule, using a chiral catalyst. Here, we report a kinetic resolution via palladium-catalyzed enantioselective C-H iodination in which one of the enantiomers of a racemic benzylic amine substrates undergoes faster aryl C-H insertion with the chiral catalysts than the other. The resulting enantioenriched C-H functionalization products would not be accessible through desymmetrization of prochiral C-H bonds. The exceedingly high relative rate ratio (k(fast)/k(slow) up to 244), coupled with the subsequent iodination of the remaining enantiomerically enriched starting material using a chiral ligand with the opposite configuration, enables conversion of both substrate enantiomers into enantiomerically pure iodinated products. Copyright © 2014, American Association for the Advancement of Science.

Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2-/3-Substituted Phenyl)-4-Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br, and X = CH3 or Cl

NASA Astrophysics Data System (ADS)

Gowda, B. Thimme; Shetty, Mahesha; Jayalakshmi, K. L.

2005-02-01

Twenty three N-(2-/3-substituted phenyl)-4-substituted benzenesulphonamides of the general formula, 4-X'C6H4SO2NH(2-/3-XC6H4), where X' = H, CH3, C2H5, F, Cl or Br and X = CH3 or Cl have been prepared and characterized, and their infrared spectra in the solid state, 1H and 13C NMR spectra in solution were studied. The N-H stretching vibrations, νN-H, absorb in the range 3285 - 3199 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1376 - 1309 cm-1 and 1177 - 1148 cm-1, respectively. The S-N and C-N stretching vibrations absorb in the ranges 945 - 893 cm-1 and 1304 - 1168 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbons of the two benzene rings. Incremental shifts of the ring protons and carbons due to -SO2NH(2-/3-XC6H4) groups in C6H5SO2NH(2-/3-XC6H4), and 4- X'C6H4SO2- and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H5) are computed and employed to calculate the chemical shifts of the ring protons and carbons in the substituted compounds, 4-X'C6H4SO2NH(2-/3-XC6H4). The computed values agree well with the observed chemical shifts.

Experimental ion mobility measurements in Xe-C2H6

NASA Astrophysics Data System (ADS)

Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2017-10-01

In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon (Xe) with ethane (C2H6) for pressures ranging from 6 to 10 Torr (8-10.6 mbar) and for low reduced electric fields in the 10 Td to 25 Td range (2.4-6.1 kVṡcm-1ṡ bar-1), at room temperature. The time of arrival spectra revealed two peaks throughout the entire range studied which were attributed to ion species with 3-carbons (C3H5+, C3H6+ C3H8+ and C3H9+) and with 4-carbons (C4H7+, C4H9+ and C4H10+). Besides these, and for Xe concentrations above 70%, a bump starts to appear at the right side of the main peak for reduced electric fields higher than 20 Td, which was attributed to the resonant charge transfer of C2H6+ to C2H6 that affects the mobility of its ion products (C3H8+ and C3H9+). The time of arrival spectra for Xe concentrations of 20%, 50%, 70% and 90% are presented, together with the reduced mobilities as a function of the Xe concentration calculated from the peaks observed for the low reduced electric fields and pressures studied.

Interconversion of η3-H2SiRR' σ-complexes and 16-electron silylene complexes via reversible H-H or C-H elimination.

PubMed

Lipke, Mark C; Neumeyer, Felix; Tilley, T Don

2014-04-23

Solid samples of η(3)-silane complexes [PhBP(Ph)3]RuH(η(3)-H2SiRR') (R,R' = Et2, 1a; PhMe, 1b; Ph2, 1c, MeMes, 1d) decompose when exposed to dynamic vacuum. Gas-phase H2/D2 exchange between isolated, solid samples of 1c-d3 and 1c indicate that a reversible elimination of H2 is the first step in the irreversible decomposition. An efficient solution-phase trap for hydrogen, the 16-electron ruthenium benzyl complex [PhBP(Ph)3]Ru[η(3)-CH2(3,5-Me2C6H3)] (3) reacts quantitatively with H2 in benzene via elimination of mesitylene to form the η(5)-cyclohexadienyl complex [PhBP(Ph)3]Ru(η(5)-C6H7) (4). This H2 trapping reaction was utilized to drive forward and quantify the elimination of H2 from 1b,d in solution, which resulted in the decomposition of 1b,d to form 4 and several organosilicon products that could not be identified. Reaction of {[PhBP(Ph)3]Ru(μ-Cl)}2 (2) with (THF)2Li(SiHMes2) forms a new η(3)-H2Si species [PhBP(Ph)3]Ru[CH2(2-(η(3)-H2SiMes)-3,5-Me2C6H2)] (5) which reacts with H2 to form the η(3)-H2SiMes2 complex [PhBP(Ph)3]RuH(η(3)-H2SiMes2) (1e). Complex 1e was identified by NMR spectroscopy prior to its decomposition by elimination of Mes2SiH2 to form 4. DFT calculations indicate that an isomer of 5, the 16-electron silylene complex [PhBP(Ph)3]Ru(μ-H)(═SiMes2), is only 2 kcal/mol higher in energy than 5. Treatment of 5 with XylNC (Xyl = 2,6-dimethylphenyl) resulted in trapping of [PhBP(Ph)3]Ru(μ-H)(═SiMes2) to form the 18-electron silylene complex [PhBP(Ph)3]Ru(CNXyl)(μ-H)(═SiMes2) (6). A closely related germylene complex [PhBP(Ph)3]Ru[CN(2,6-diphenyl-4-MeC6H2)](H)(═GeH(t)Bu) (8) was prepared from reaction of (t)BuGeH3 with the benzyl complex [PhBP(Ph)3]Ru[CN(2,6-diphenyl-4-MeC6H2)][η(1)-CH2(3,5-Me2C6H3)] (7). Single crystal XRD analysis indicated that unlike for 6, the hydride ligand in 8 is a terminal hydride that does not engage in 3c-2e Ru-H → Ge bonding. Complex 1b is an effective precatalyst for the catalytic Ge-H dehydrocoupling

Detection of interstellar ethylene oxide (c-C2H4O).

PubMed

Dickens, J E; Irvine, W M; Ohishi, M; Ikeda, M; Ishikawa, S; Nummelin, A; Hjalmarson, A

1997-11-10

We report the identification of 10 transitions that support the detection of the small cyclic molecule ethylene oxide (c-C2H4O) in Sgr B2N. Although one of these transitions is severely blended, so that an accurate intensity and line width could not be determined, and two other lines are only marginally detected, we have done Gaussian fits to the remaining seven lines and have performed a rotation diagram analysis. Our results indicate a rotation temperature T(rot) = 18 K and a molecular column density N(c-C2H4O) = 3.3 x 10(14) cm-2, corresponding to a fractional abundance relative to molecular hydrogen of order 6 x 10(-11). This is a factor of more than 200 higher than the abundance for this molecule suggested by the "new standard" chemistry model of Lee, Bettens, & Herbst. This result suggests that grain chemistry might play an effective role in the production of c-C2H4O. No transitions of this molecule were detected in either Sgr B2M or Sgr B2NW.

Studies of the kinetics and thermochemistry of the forward and reverse reaction Cl + C6H6 = HCl + C6H5.

PubMed

Alecu, I M; Gao, Yide; Hsieh, P-C; Sand, Jordan P; Ors, Ahmet; McLeod, A; Marshall, Paul

2007-05-17

The laser flash photolysis resonance fluorescence technique was used to monitor atomic Cl kinetics. Loss of Cl following photolysis of CCl4 and NaCl was used to determine k(Cl + C6H6) = 6.4 x 10(-12) exp(-18.1 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 578-922 K and k(Cl + C6D6) = 6.2 x 10(-12) exp(-22.8 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 635-922 K. Inclusion of literature data at room temperature leads to a recommendation of k(Cl + C6H6) = 6.1 x 10(-11) exp(-31.6 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) for 296-922 K. Monitoring growth of Cl during the reaction of phenyl with HCl led to k(C6H5 + HCl) = 1.14 x 10(-12) exp(+5.2 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 294-748 K, k(C6H5 + DCl) = 7.7 x 10(-13) exp(+4.9 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 292-546 K, an approximate k(C6H5 + C6H5I) = 2 x 10(-11) cm(3) molecule(-1) s(-1) over 300-750 K, and an upper limit k(Cl + C6H5I) < or = 5.3 x 10(-12) exp(+2.8 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 300-750 K. Confidence limits are discussed in the text. Third-law analysis of the equilibrium constant yields the bond dissociation enthalpy D(298)(C6H5-H) = 472.1 +/- 2.5 kJ mol(-1) and thus the enthalpy of formation Delta(f)H(298)(C6H5) = 337.0 +/- 2.5 kJ mol(-1).

Proton relays in anomalous carbocations dictate spectroscopy, stability, and mechanisms: case studies on C2H5+ and C3H3.

PubMed

Sager, LeeAnn M; Iyengar, Srinivasan S

2017-10-18

We present a detailed analysis of the anomalous carbocations: C 2 H 5 + and C 3 H 3 + . This work involves (a) probing electronic structural properties, (b) ab initio dynamics simulations over a range of internal energies, (c) analysis of reduced dimensional potential surfaces directed along selected conformational transition pathways, (d) dynamically averaged vibrational spectra computed from ab initio dynamics trajectories, and (e) two-dimensional time-frequency analysis to probe conformational dynamics. Key findings are as follows: (i) as noted in our previous study on C 2 H 3 + , it appears that these non-classical carbocations are stabilized by delocalized nuclear frameworks and "proton shuttles". We analyze this nuclear delocalization and find critical parallels between conformational changes in C 2 H 3 + , C 2 H 5 + , and C 3 H 3 + . (ii) The vibrational signatures of C 2 H 5 + are dominated by the "bridge-proton" conformation, but also show critical contributions from the "classical" configuration, which is a transition state at almost all levels of theory. This result is further substantiated through two-dimensional time-frequency analysis and is at odds with earlier explanations of the experimental spectra, where frequencies close to the classical region were thought to arise from an impurity. While this is still possible, our results here indicate an additional (perhaps more likely) explanation that involves the "classical" isomer. (iii) Finally, in the case of C 3 H 3 + our explanation of the experimental result includes the presence of multiple, namely, "cyclic", "straight", and propargyl, configurations. Proton shuttles and nuclear delocalization, reminiscent of those seen in the case of C 2 H 3 + , were seen all through and have a critical role in all our observations.

Photo-induced oxidant-free oxidative C-H/N-H cross-coupling between arenes and azoles

NASA Astrophysics Data System (ADS)

Niu, Linbin; Yi, Hong; Wang, Shengchun; Liu, Tianyi; Liu, Jiamei; Lei, Aiwen

2017-02-01

Direct cross-coupling between simple arenes and heterocyclic amines under mild conditions is undoubtedly important for C-N bonds construction. Selective C(sp2)-H amination is more valuable. Herein we show a selective C(sp2)-H amination of arenes (alkyl-substituted benzenes, biphenyl and anisole derivatives) accompanied by hydrogen evolution by using heterocyclic azoles as nitrogen sources. The reaction is selective for C(sp2)-H bonds, providing a mild route to N-arylazoles. The KIE (kinetic isotope effect) experiment reveals the cleavage of C-H bond is not involved in the rate-determining step. Kinetic studies indicate the first-order behaviour with respect to the arene component. It is interesting that this system works without the need for any sacrificial oxidant and is highly selective for C(sp2)-H activation, whereas C(sp3)-H bonds are unaffected. This study may have significant implications for the functionalization of methylarenes which are sensitive to oxidative conditions.

Effects of lithium-implantation on the hydrogen retention in both a-C:H and a-SiC:H materials submitted to deuterium bombardment

NASA Astrophysics Data System (ADS)

Barbier, G.; Ross, G. G.; El Khakani, M. A.; Chevarier, N.; Chevarier, A.

1997-02-01

The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from the a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both materials were implanted with different fluences of lithium ions. Before and after each irradiation, depth profiles of H, Li and deuterium were determined by nuclear microanalysis. After deuterium bombardment, it is shown that the retention of the initial hydrogen in both materials was enhanced by increasing the total dose of the implanted Li. For the a-C:H samples, the hydrogen desorption under deuterium bombardment was strongly reduced by lithium implantation. This effect was also evidenced in a-SiC:H samples, even though it is less spectacular than in a-C:H. Also, nuclear analyses showed that the retained dose of deuterium decreases when the lithium concentration increases. This could be a result of the formation of LiH bonds which occurs to the detriment of deuterium retention in both a-C:H and a-SiC:H materials. Preliminary results of both materials exposed to TdeV tokamak discharges confirms the role of Li in hydrogen retention, already observed in deuterium bombardment exposure.

C-H bond activation of hydrocarbons by an imidozirconocene complex.

PubMed

Hoyt, Helen M; Michael, Forrest E; Bergman, Robert G

2004-02-04

Monomeric imidozirconocene complexes of the type Cp2(L)Zr=NCMe3 (Cp = cyclopentadienyl, L = Lewis base) have been shown to activate the carbon-hydrogen bonds of benzene, but not the C-H bonds of saturated hydrocarbons. To our knowledge, this singularly important class of C-H activation reactions has heretofore not been observed in imidometallocene systems. The M=NR bond formed on heating the racemic ethylenebis(tetrahydro)indenyl methyl tert-butyl amide complex, however, cleanly and quantitatively activates a wide range of n-alkane, alkene, and arene C-H bonds. Mechanistic experiments support the proposal of intramolecular elimination of methane followed by a concerted addition of the hydrocarbon C-H bond. Products formed by activation of sp2 C-H bonds are generally more thermodynamically stable than those formed by activation of sp3 C-H bonds, and those resulting from reaction at primary C-H bonds are preferred over secondary sp3 C-H activation products. There is also evidence that thermodynamic selectivity among C-H bonds is sterically rather than electronically controlled.

Copper-promoted sulfenylation of sp2 C-H bonds.

PubMed

Tran, Ly Dieu; Popov, Ilya; Daugulis, Olafs

2012-11-07

An auxiliary-assisted, copper catalyzed or promoted sulfenylation of benzoic acid derivative β-C-H bonds and benzylamine derivative γ-C-H bonds has been developed. The method employs disulfide reagents, copper(II) acetate, and DMSO solvent at 90-130 °C. Application of this methodology to the direct trifluoromethylsulfenylation of C-H bonds was demonstrated.

Symmetry breaking and spectral considerations of the surprisingly floppy c-C3H radical and the related dipole-bound excited state of c-C3H-

NASA Astrophysics Data System (ADS)

Bassett, Matthew K.; Fortenberry, Ryan C.

2017-06-01

The C3H radical is believed to be prevalent throughout the interstellar medium and may be involved in the formation of polycyclic aromatic hydrocarbons. C3H exists as both a linear and a cyclic isomer. The C2 v cyclopropenylidenyl radical isomer was detected in the dark molecular cloud TMC-1, and the linear propenylidenyl radical isomer has been observed in various dark molecular clouds. Even though the c-C3H radical has been classified rotationally, the vibrational frequencies of this seemingly important interstellar molecule have never been directly observed. Established, highly accurate quartic force field methodologies are employed here to compute useful geometrical data, spectroscopic constants, and vibrational frequencies. The computed rotational constants are consistent with the experimental results. Consequently, the three a1 (ν1, ν2, and ν3) and one b1 (ν6) anharmonic vibrational frequencies at 3117.7 cm-1, 1564.3 cm-1, 1198.5 cm-1, and 826.7 cm-1, respectively, are reliable predictions for these, as of yet unseen, observables. Unfortunately, the two b2 fundamentals (ν4 and ν5) cannot be treated adequately in the current approach due to a flat and possible double-well potential described in detail herein. The dipole-bound excited state of the anion suffers from the same issues and may not even be bound. However, the trusted fundamental vibrational frequencies described for the neutral radical should not be affected by this deformity and are the first robustly produced for c-C3H. The insights gained here will also be applicable to other structures containing three-membered bare and exposed carbon rings that are surprisingly floppy in nature.

β-Selective C-H arylation of pyrroles leading to concise syntheses of lamellarins C and I.

PubMed

Ueda, Kirika; Amaike, Kazuma; Maceiczyk, Richard M; Itami, Kenichiro; Yamaguchi, Junichiro

2014-09-24

The first general β-selective C-H arylation of pyrroles has been developed by using a rhodium catalyst. This C-H arylation reaction, which is retrosynthetically straightforward but results in unusual regioselectivity, could result in de novo syntheses of pyrrole-derived natural products and pharmaceuticals. As such, we have successfully synthesized polycyclic marine pyrrole alkaloids, lamellarins C and I, by using this β-selective arylation of pyrroles with aryl iodides (C-H/C-I coupling) and a new double C-H/C-H coupling as key steps.

Hydrocarbon Chemistry in Planetary Nebulae: Observations of CCH and c-C3H2

NASA Astrophysics Data System (ADS)

Schmidt, Deborah Rose; Zack, Lindsay; Ziurys, Lucy M.

2018-06-01

In an effort to fully evaluate the molecular content of planetary nebulae (PNe), and the role of hydrocarbons, we have undertaken a search for CCH towards K4–47, K3–58, K3–17, M3–28, M4–14, Hb 5, K3-45, M1-7, M3-55, NGC 2440, NGC 6772, M1-12, and M1-20. These nebulae span a range of kinematic ages and morphologies. In addition, we observed CN, CCH, and c-C3H2 at eight positions sampling the Helix Nebula. Measurements at 3 mm of the N=1→0 transitions of CCH and CN and the J=21,2→10,1 of c-C3H2 were performed using the ALMA prototype 12-M antenna of the Arizona Radio Observatory (ARO), while the N=3→2 transition of CCH at 1 mm was observed using the ARO Sub-Millimeter Telescope. CCH was detected in 9 of the 13 survey PNe, while CCH, CN, and c-C3H2 were observed at all positions in the Helix, often with a complex velocity structure; c-C3H2 was also identified in K4-47. From radiative transfer modeling, column densities for CCH were found to range between Ntot(CCH) ~ 0.2-3.3 × 1015 cm-2 for the survey PNe, corresponding to fractional abundances with respect to H2 of f(CCH) ~ 0.2-47 × 10-7. The CN, CCH, and c-C3H2 column densities across the Helix were estimated to range between Ntot(CN) ~ 6.9-74 × 1011 cm-2, Ntot(CCH) ~ 3.2-28 × 1011 cm-2, and Ntot(c-C3H2) ~ 0.2-4.7 × 1011 cm-2, with fractional abundances of f(CN) ~ 0.9-9.8 × 10-7, f(CCH) ~ 0.4-3.7 × 10-7, and f(c-C3H2) ~ 0.3-6.5 × 10-8. Based on HCN measurements of the Helix by Schmidt & Ziurys (2017a), [CN]/[HCN] ratios are ~1-34, while [CCH]/[c-C3H2] ratios varied between ~3-46. The abundance of CCH in all observed PNe did not vary significantly across the nebular lifespan of ~10,000 years, in contrast to model predictions. These abundances are ~1-2 orders of magnitude greater than those measured in the diffuse ISM; moreover, the [CN]/[HCN] and [CCH]/[c-C3H2] ratios observed in the Helix are comparable to those in diffuse clouds, striking evidence that molecular material ejected from PNe

Synthesis of C60H2 by rhodium-catalyzed hydrogenation of C60

NASA Technical Reports Server (NTRS)

Becker, L.; Evans, T. P.; Bada, J. L.; Miller, S. L. (Principal Investigator)

1993-01-01

Reduction of C60 with rhodium(0) on alumina and hydrogen in deuterated benzene (C6D6) at ambient temperature and pressure yields a mixture of hydrogenated compounds; C60H2 has been characterized as the major product in 14% yield based on 1H NMR.

Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

NASA Technical Reports Server (NTRS)

Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Abbas, M.; LeClaire, A.; Romani, P. N.; Simon-Miller, A. A.

2004-01-01

The abundances of hydrocarbons such as acetylene (C2H2) and ethane (C2H6) in Jupiter's atmosphere are important physical quantities, constraining our models of the chemical and dynamical processes. However, our knowledge of these quantities and their vertical and latitudinal variations has remained sparse. The flyby of the Cassini spacecraft with Jupiter at the end of 2000 provided an excellent opportunity to observe the infrared spectrum with the Composite Infrared Spectrometer (CIRS) instrument, mapping the spatial variation of emissions from 10-1400 cm-1. CIRS spectra taken at the highest resolution (0.5 cm-1) in early December 2000 have been analysed to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 of CH4, and in the troposphere at 100-400 mbar, via the hydrogen collision-induced continuum absorption at 600-800 cm. Simultaneously, we have searched for meridional abundance variations in C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIM resolution, introducing a non-uniqueness into the retrievals, which means that vertical gradient and column abundance cannot be simultaneously found without additional constraints. If we assume the profile shapes from photochemical model calculations, we show that the column abundance of C2H2 must decrease sharply towards the poles, while C2H6 is constant or slightly increasing. The relevance of these results to current photochemical and dynamical knowledge of Jupiter's atmosphere is discussed.

Electroremovable Traceless Hydrazides for Cobalt-Catalyzed Electro-Oxidative C-H/N-H Activation with Internal Alkynes.

PubMed

Mei, Ruhuai; Sauermann, Nicolas; Oliveira, João C A; Ackermann, Lutz

2018-06-27

Electrochemical oxidative C-H/N-H activations have been accomplished with a versatile cobalt catalyst in terms of [4 + 2] annulations of internal alkynes. The electro-oxidative C-H activation manifold proved viable with an undivided cell setup under exceedingly mild reaction conditions at room temperature using earth-abundant cobalt catalysts. The electrochemical cobalt catalysis prevents the use of transition metal oxidants in C-H activation catalysis, generating H 2 as the sole byproduct. Detailed mechanistic studies provided strong support for a facile C-H cobaltation by an initially formed cobalt(III) catalyst. The subsequent alkyne migratory insertion was interrogated by mass spectrometry and DFT calculations, providing strong support for a facile C-H activation and the formation of a key seven-membered cobalta(III) cycle in a regioselective fashion. Key to success for the unprecedented use of internal alkynes in electrochemical C-H/N-H activations was represented by the use of N-2-pyridylhydrazides, for which we developed a traceless electrocleavage strategy by electroreductive samarium catalysis at room temperature.

A surge observed in H alpha and C IV

NASA Technical Reports Server (NTRS)

Schmieder, B.; Mein, P.; Vial, J. C.; Tandberg-Hanssen, E.

1982-01-01

Results are presented of simultaneous measurements of H-alpha (MSDP at Meudon) and C IV (UVSP onboard SMM) of Active Region 2701 made on October 2, 1980. Isodensity and velocity maps were obtained for both lines and these maps were superimposed. Results show a good correlation between the H-alpha and C IV velocities with a surge being observed for 10 minutes. The base of the surge was determined to be located in a bright point in C IV and H-alpha, while the escaping matter followed the same channel ('absorbing' in H-alpha, 'emitting' in C IV). It was found that the velocity along the surge was about 80 km/s in H-alpha and 100 km/s in C IV. In addition, a loop appeared in C IV during the surge. It is concluded that the vertical pressure gradient was capable of driving the surge.

Redox-neutral rhodium-catalyzed C-H functionalization of arylamine N-oxides with diazo compounds: primary C(sp(3))-H/C(sp(2))-H activation and oxygen-atom transfer.

PubMed

Zhou, Bing; Chen, Zhaoqiang; Yang, Yaxi; Ai, Wen; Tang, Huanyu; Wu, Yunxiang; Zhu, Weiliang; Li, Yuanchao

2015-10-05

An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The European I-MOVE Multicentre 2013-2014 Case-Control Study. Homogeneous moderate influenza vaccine effectiveness against A(H1N1)pdm09 and heterogenous results by country against A(H3N2).

PubMed

Valenciano, Marta; Kissling, Esther; Reuss, Annicka; Jiménez-Jorge, Silvia; Horváth, Judit K; Donnell, Joan M O; Pitigoi, Daniela; Machado, Ausenda; Pozo, Francisco

2015-06-04

In the first five I-MOVE (Influenza Monitoring Vaccine Effectiveness in Europe) influenza seasons vaccine effectiveness (VE) results were relatively homogenous among participating study sites. In 2013-2014, we undertook a multicentre case-control study based on sentinel practitioner surveillance networks in six European Union (EU) countries to measure 2013-2014 influenza VE against medically-attended influenza-like illness (ILI) laboratory-confirmed as influenza. Influenza A(H3N2) and A(H1N1)pdm09 viruses co-circulated during the season. Practitioners systematically selected ILI patients to swab within eight days of symptom onset. We compared cases (ILI positive to influenza A(H3N2) or A(H1N1)pdm09) to influenza negative patients. We calculated VE for the two influenza A subtypes and adjusted for potential confounders. We calculated heterogeneity between sites using the I(2) index and Cochrane's Q test. If the I(2) was <50%, we estimated pooled VE as (1 minus the OR)×100 using a one-stage model with study site as a fixed effect. If the I(2) was >49% we used a two-stage random effects model. We included in the A(H1N1)pdm09 analysis 531 cases and 1712 controls and in the A(H3N2) analysis 623 cases and 1920 controls. For A(H1N1)pdm09, the Q test (p=0.695) and the I(2) index (0%) suggested no heterogeneity of adjusted VE between study sites. Using a one-stage model, the overall pooled adjusted VE against influenza A(H1N1)pdm2009 was 47.5% (95% CI: 16.4-67.0). For A(H3N2), the I(2) was 51.5% (p=0.067). Using a two-stage model for the pooled analysis, the adjusted VE against A(H3N2) was 29.7 (95% CI: -34.4-63.2). The results suggest a moderate 2013-2014 influenza VE against A(H1N1)pdm09 and a low VE against A(H3N2). The A(H3N2) estimates were heterogeneous among study sites. Larger sample sizes by study site are needed to prevent statistical heterogeneity, decrease variability and allow for two-stage pooled VE for all subgroup analyses. Copyright © 2015 The Authors

The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6...(HF)1-4 complexes

NASA Astrophysics Data System (ADS)

Jouypazadeh, Hamidreza; Farrokhpour, Hossein; Solimannejad, Mohammad

2018-02-01

The effect of the hydrogen fluoride chain ((HF)n) on the aromaticity and π character of C-C bonds of C6H6 in the C6H6...(HF)n (n = 1-4) complexes were investigated using density functional theory employing RM05 functional. It was found that the binding energy between C6H6 and different (HF)n chains showed a maximum at n = 3 (C6H6...(HF)3). Also, the π-hydrogen interaction (πHI) and the bifurcated fluorine interaction (BFI) increased and decreased the π character of the C-C bond of C6H6, respectively. In addition, the change of aromaticity of the C6H6 due to the interaction with the HF chains was also studied using three different aspects such as aromatic fluctuation index (FLU), average two centre index (ATI) and proton nuclear magnetic resonance (HNMR) spectrum. The most change in the aromaticity happens when the C6H6 interacts with (HF)3 chain. The variation of aromaticity with the binding energy and the summation of two-body terms were investigated and very good linear correlations were observed.

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

NASA Technical Reports Server (NTRS)

Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

1991-01-01

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

Band gap narrowing in n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si

NASA Astrophysics Data System (ADS)

Persson, C.; Lindefelt, U.; Sernelius, B. E.

1999-10-01

Doping-induced energy shifts of the conduction band minimum and the valence band maximum have been calculated for n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si. The narrowing of the fundamental band gap and of the optical band gap are presented as functions of ionized impurity concentration. The calculations go beyond the common parabolic treatments of the ground state energy dispersion by using energy dispersion and overlap integrals from band structure calculations. The nonparabolic valence band curvatures influence strongly the energy shifts especially in p-type materials. The utilized method is based on a zero-temperature Green's function formalism within the random phase approximation with local field correction according to Hubbard. We have parametrized the shifts of the conduction and the valence bands and made comparisons with recently published results from a semi-empirical model.

Ligand-accelerated enantioselective methylene C(sp3)-H bond activation.

PubMed

Chen, Gang; Gong, Wei; Zhuang, Zhe; Andrä, Michal S; Chen, Yan-Qiao; Hong, Xin; Yang, Yun-Fang; Liu, Tao; Houk, K N; Yu, Jin-Quan

2016-09-02

Effective differentiation of prochiral carbon-hydrogen (C-H) bonds on a single methylene carbon via asymmetric metal insertion remains a challenge. Here, we report the discovery of chiral acetyl-protected aminoethyl quinoline ligands that enable asymmetric palladium insertion into prochiral C-H bonds on a single methylene carbon center. We apply these palladium complexes to catalytic enantioselective functionalization of β-methylene C-H bonds in aliphatic amides. Using bidentate ligands to accelerate C-H activation of otherwise unreactive monodentate substrates is crucial for outcompeting the background reaction driven by substrate-directed cyclopalladation, thereby avoiding erosion of enantioselectivity. The potential of ligand acceleration in C-H activation is also demonstrated by enantioselective β-C-H arylation of simple carboxylic acids without installing directing groups. Copyright © 2016, American Association for the Advancement of Science.

Chemistry through cocrystals: pressure-induced polymerization of C 2H 2·C 6H 6 to an extended crystalline hydrocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Matthew D.; Huang, Haw-Tyng; Zhu, Li

The 1:1 acetylene–benzene cocrystal, C 2H 2·C 6H 6, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

Chemistry through cocrystals: pressure-induced polymerization of C 2H 2·C 6H 6 to an extended crystalline hydrocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Matthew D.; Huang, Haw-Tyng; Zhu, Li

The 1 : 1 acetylene–benzene cocrystal, C 2H 2·C 6H 6, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

Cleavage of sp3 C-O bonds via oxidative addition of C-H bonds.

PubMed

Choi, Jongwook; Choliy, Yuriy; Zhang, Xiawei; Emge, Thomas J; Krogh-Jespersen, Karsten; Goldman, Alan S

2009-11-04

(PCP)Ir (PCP = kappa(3)-C(6)H(3)-2,6-[CH(2)P(t-Bu)(2)](2)) is found to undergo oxidative addition of the methyl-oxygen bond of electron-poor methyl aryl ethers, including methoxy-3,5-bis(trifluoromethyl)benzene and methoxypentafluorobenzene, to give the corresponding aryloxide complexes (PCP)Ir(CH(3))(OAr). Although the net reaction is insertion of the Ir center into the C-O bond, density functional theory (DFT) calculations and a significant kinetic isotope effect [k(CH(3))(OAr)/k(CD(3))(OAr) = 4.3(3)] strongly argue against a simple insertion mechanism and in favor of a pathway involving C-H addition and alpha-migration of the OAr group to give a methylene complex followed by hydride-to-methylene migration to give the observed product. Ethoxy aryl ethers, including ethoxybenzene, also undergo C-O bond cleavage by (PCP)Ir, but the net reaction in this case is 1,2-elimination of ArO-H to give (PCP)Ir(H)(OAr) and ethylene. DFT calculations point to a low-barrier pathway for this reaction that proceeds through C-H addition of the ethoxy methyl group followed by beta-aryl oxide elimination and loss of ethylene. Thus, both of these distinct C-O cleavage reactions proceed via initial addition of a C(sp(3))-H bond, despite the fact that such bonds are typically considered inert and are much stronger than C-O bonds.

Quantified pH imaging with hyperpolarized (13) C-bicarbonate.

PubMed

Scholz, David Johannes; Janich, Martin A; Köllisch, Ulrich; Schulte, Rolf F; Ardenkjaer-Larsen, Jan H; Frank, Annette; Haase, Axel; Schwaiger, Markus; Menzel, Marion I

2015-06-01

Because pH plays a crucial role in several diseases, it is desirable to measure pH in vivo noninvasively and in a spatially localized manner. Spatial maps of pH were quantified in vitro, with a focus on method-based errors, and applied in vivo. In vitro and in vivo (13) C mapping were performed for various flip angles for bicarbonate (BiC) and CO2 with spectral-spatial excitation and spiral readout in healthy Lewis rats in five slices. Acute subcutaneous sterile inflammation was induced with Concanavalin A in the right leg of Buffalo rats. pH and proton images were measured 2 h after induction. After optimizing the signal to noise ratio of the hyperpolarized (13) C-bicarbonate, error estimation of the spectral-spatial excited spectrum reveals that the method covers the biologically relevant pH range of 6 to 8 with low pH error (< 0.2). Quantification of pH maps shows negligible impact of the residual bicarbonate signal. pH maps reflect the induction of acute metabolic alkalosis. Inflamed, infected regions exhibit lower pH. Hyperpolarized (13) C-bicarbonate pH mapping was shown to be sensitive in the biologically relevant pH range. The mapping of pH was applied to healthy in vivo organs and interpreted within inflammation and acute metabolic alkalosis models. © 2014 Wiley Periodicals, Inc.

Sequence Variations in the Flagellar Antigen Genes fliC H25 and fliC H28 of Escherichia coli and Their Use in Identification and Characterization of Enterohemorrhagic E. coli (EHEC) O145:H25 and O145:H28

PubMed Central

Beutin, Lothar; Delannoy, Sabine; Fach, Patrick

2015-01-01

Enterohemorrhagic E. coli (EHEC) serogroup O145 is regarded as one of the major EHEC serogroups involved in severe infections in humans. EHEC O145 encompasses motile and non-motile strains of serotypes O145:H25 and O145:H28. Sequencing the fliC-genes associated with the flagellar antigens H25 and H28 revealed the genetic diversity of the fliC H25 and fliC H28 gene sequences in E. coli. Based on allele discrimination of these fliC-genes real-time PCR tests were designed for identification of EHEC O145:H25 and O145:H28. The fliC H25 genes present in O145:H25 were found to be very similar to those present in E. coli serogroups O2, O100, O165, O172 and O177 pointing to their common evolution but were different from fliC H25 genes of a multiple number of other E. coli serotypes. In a similar way, EHEC O145:H28 harbor a characteristic fliC H28 allele which, apart from EHEC O145:H28, was only found in enteropathogenic (EPEC) O28:H28 strains that shared some common traits with EHEC O145:H28. The real time PCR-assays targeting these fliC H25[O145] and fliC H28[O145] alleles allow better characterization of EHEC O145:H25 and EHEC O145:H28. Evaluation of these PCR assays in spiked ready-to eat salad samples resulted in specific detection of both types of EHEC O145 strains even when low spiking levels of 1–10 cfu/g were used. Furthermore these PCR assays allowed identification of non-motile E. coli strains which are serologically not typable for their H-antigens. The combined use of O-antigen genotyping (O145wzy) and detection of the respective fliC H25[O145] and fliC H28[O145] allele types contributes to improve identification and molecular serotyping of E. coli O145 isolates. PMID:26000885

Characterization of a n+3C/n−4H SiC heterojunction diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minamisawa, R. A.; Mihaila, A.; Farkas, I.

We report on the fabrication of n + 3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to ∼7 × 10{sup 17 }cm{sup −3} dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extractedmore » from CV measurement. We finally compare the electrical results of the n + 3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices.« less

Dynamics of C2H 2 3 +→H++H++C 2 + investigated by 50-keV/u Ne8 + impact

NASA Astrophysics Data System (ADS)

Xu, S.; Zhu, X. L.; Feng, W. T.; Guo, D. L.; Zhao, Q.; Yan, S.; Zhang, P.; Zhao, D. M.; Gao, Y.; Zhang, S. F.; Yang, J.; Ma, X.

2018-06-01

Breakup dynamics of C2H 2 3 + → H++H++C 2 + induced by 50-keV/u Ne8 + ion impact is investigated employing a reaction microscope. All three ionic fragments in the final state are detected in coincidence, and their momentum vectors as well as the kinetic energies are determined. The kinetic-energy correlation spectrum of the two protons displays very rich structures. Utilizing the Newton diagrams and the Dalitz plots, different dissociation mechanisms corresponding to these structures are identified. It was found that, besides the concerted and sequential breakup, fragmentation mechanisms associated with different vibration modes including molecular bending and asymmetric stretching also make significant contributions. We analyzed the correlation between different fragmentation mechanisms and the kinetic-energy release (KER) and found that the sequential process occurs with higher KER while, in contrast, the concerted process mainly contributes to the lower KER. This behavior is entirely opposite to the breakup of the CO2 molecule.

Ansa-Complexes of [Mn(η(5) -C5 H5 )(η(6) -C6 H6 )]: Preparation, Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3).

PubMed

Braunschweig, Holger; Damme, Alexander; Dück, Klaus; Fuß, Marco; Hörl, Christian; Kramer, Thomas; Krummenacher, Ivo; Kupfer, Thomas; Paprocki, Valerie; Schneider, Christoph

2015-10-12

We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa-bridging elements. Their preparation was achieved by salt-elimination reactions of the dilithiated precursor [Mn(η(5) -C5 H4 Li)(η(6) -C6 H5 Li)]⋅pmdta (pmdta=N,N,N',N',N''-pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single-atom-bridged derivatives, [Mn(η(5) -C5 H4 )(η(6) -C6 H5 )SntBu2 ] and [Mn(η(5) -C5 H4 )(η(6) -C6 H5 )SiPh2 ], could also be determined by X-ray structural analysis. We investigated for the first time the reactivity of these ansa-cyclopentadienyl-benzene manganese compounds. The reaction of the distannyl-bridged complex [Mn(η(5) -C5 H4 )(η(6) -C6 H5 )Sn2 tBu4 ] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn-Sn bond to give a triatomic ansa-bridge. The investigation of the ring-opening polymerization (ROP) capability of [Mn(η(5) -C5 H4 )(η(6) -C6 H5 )SntBu2 ] with [Pt(PEt3 )3 ] showed that an unexpected, unselective insertion into the Cipso -Sn bonds of [Mn(η(5) -C5 H4 )(η(6) -C6 H5 )SntBu2 ] had occurred. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laboratory detection of the C3N an C4H free radicals

NASA Technical Reports Server (NTRS)

Gottlieb, C. A.; Gottlieb, E. W.; Thaddeus, P.; Kawamura, H.

1983-01-01

The millimeter-wave spectra of the linear carbon chain free radicals C3N and C4H, first identified in IRC + 10216 and hitherto observed only in a few astronomical sources, have been detected with a Zeeman-modulated spectrometer in laboratory glow discharges through low pressure flowing mixtures of N2 + HC3N and He + HCCH, respectively. Four successive rotational transitions between 168 and 198 GHz have been measured for C3N, and five rotational transitions between 143 and 200 GHz for C4H; each is a well-resolved spin doublet owing to the unpaired electron present in both species. Precise values for the rotational, centrifugal distortion, and spin doubling constants have been obtained, which, with hyperfine constants derived from observations of the lower rotational transitions in the astronomical source TMC 1, allow all the rotational transitions of C3N and C4H at frequencies less than 300 GHz to be calculated to an absolute accuracy exceeding 1 ppm.

Basic surface-active properties in the homologous series of β-alkyl (C12H25/C18H37) polyethyleneoxy (n = 0-20) propionamides

PubMed Central

2013-01-01

Background Heterogeneous β-Alkyl (C12H25/C18H37) polyethyleneoxy (n = 0-20) propionamides [R(EO)nPD] represent new “hybrid” nonionic-ionic colloidal structures in the field of surface-active products (technical products). These “niche” compounds have three structural and compositional characteristics that also define their basic colloidal properties: mixture of R and PEO chain homologues; specific conformations due to the PEO chains; and the presence of side products from the addition of higher alcohols, polyethyleneglycols and traces of water to acrylamide. The proposed major objective of this paper is the basic informative colloidal characterization (functional classification, HLB balance, surface tension, critical micelle concentration) in direct correlation with the structural changes in the homologous series of LM(EO)nPD and CS(EO)nPD. The structures were obtained either indirectly by cyanoethylation followed by partial acid hydrolysis of the corresponding β-propionitriles, or directly by the nucleophilic addition under alkaline catalysis of linear higher alcohols C12H25/C14H29 (7/3) (LM) and C16H33/C18H37 (CS) as such and heterogeneous polyethoxylated (n = 3-20) to acrylamide monomer, through an adapted classic reaction scheme. Results In the series of basic colloidal characteristics investigated the structure-surface activity dependence is confirmed. Their indicative character for R(EO)nPD is based on the assumption that the structures studied are not unitary (heterogeneous) because: a) the hydrophobic chains C12H25/C18H37 have been grouped in two variants, C12H25/C14H29 (LM); C16H33/C18H37 (CS), each with an internal mass ratio of 7/3; b) the hydrophilic polyoxyethylene chains (n = 3-20) have polydisperse character; the meaning and value the oligomerization degree, n, is that of weighted average. In these conditions the surface tension increases proportionally with the oligomerization degree of the polyoxyethylene chain, while the

Theoretical study of radiative electron attachment to CN, C{sub 2}H, and C{sub 4}H radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Douguet, Nicolas; Fonseca dos Santos, S.; Orel, Ann E.

A first-principle theoretical approach to study the process of radiative electron attachment is developed and applied to the negative molecular ions CN{sup −}, C{sub 4}H{sup −}, and C{sub 2}H{sup −}. Among these anions, the first two have already been observed in the interstellar space. Cross sections and rate coefficients for formation of these ions by direct radiative electron attachment to the corresponding neutral radicals are calculated. For the CN molecule, we also considered the indirect pathway, in which the electron is initially captured through non-Born-Oppenheimer coupling into a vibrationally resonant excited state of the anion, which then stabilizes by radiativemore » decay. We have shown that the contribution of the indirect pathway to the formation of CN{sup −} is negligible in comparison to the direct mechanism. The obtained rate coefficients for the direct mechanism at 30 K are 7 × 10{sup −16} cm{sup 3}/s for CN{sup −}, 7 × 10{sup −17} cm{sup 3}/s for C{sub 2}H{sup −}, and 2 × 10{sup −16} cm{sup 3}/s for C{sub 4}H{sup −}. These rates weakly depend on temperature between 10 K and 100 K. The validity of our calculations is verified by comparing the present theoretical results with data from recent photodetachment experiments.« less

Multiple C-H Bond Activations and Ring-Opening C-S Bond Cleavage of Thiophene by Dirhenium Carbonyl Complexes.

PubMed

Adams, Richard D; Dhull, Poonam; Tedder, Jonathan D

2018-06-14

The reaction of Re 2 (CO) 8 (μ-C 6 H 5 )(μ-H) (1) with thiophene in CH 2 Cl 2 at 40 °C yielded the new compound Re 2 (CO) 8 (μ-η 2 -SC 4 H 3 )(μ-H) (2), which contains a bridging σ-π-coordinated thienyl ligand formed by the activation of the C-H bond at the 2 position of the thiophene. Compound 2 exhibits dynamical activity on the NMR time scale involving rearrangements of the bridging thienyl ligand. The reaction of compound 2 with a second 1 equiv of 1 at 45 °C yielded the doubly metalated product [Re 2 (CO) 8 (μ-H)] 2 (μ-η 2 -2,3-μ-η 2 -4,5-C 4 H 2 S) (3), formed by the activation of the C-H bond at the 5 position of the thienyl ligand in 2. Heating 3 in a hexane solvent to reflux transformed it into the ring-opened compound Re(CO) 4 [μ-η 5 -η 2 -SCC(H)C(H)C(H)][Re(CO) 3 ][Re 2 (CO) 8 (μ-H)] (4) by the loss of one CO ligand. Compound 4 contains a doubly metalated 1-thiapentadienyl ligand formed by the cleavage of one of the C-S bonds. When heated to reflux (125 °C) in an octane solvent in the presence of H 2 O, the new compound Re(CO) 4 [η 5 -μ-η 2 -SC(H)C(H)C(H)C(H)]Re(CO) 3 (5) was obtained by cleavage of the Re 2 (CO) 8 (μ-H) group from 4 with formation of the known coproduct [Re(CO) 3 (μ 3 -OH)] 4 . All new products were characterized by single-crystal X-ray diffraction analyses.

Investigation on the individual contributions of N-H...O=C and C-H...O=C interactions to the binding energies of beta-sheet models.

PubMed

Wang, Chang-Sheng; Sun, Chang-Liang

2010-04-15

In this article, the binding energies of 16 antiparallel and parallel beta-sheet models are estimated using the analytic potential energy function we proposed recently and the results are compared with those obtained from MP2, AMBER99, OPLSAA/L, and CHARMM27 calculations. The comparisons indicate that the analytic potential energy function can produce reasonable binding energies for beta-sheet models. Further comparisons suggest that the binding energy of the beta-sheet models might come mainly from dipole-dipole attractive and repulsive interactions and VDW interactions between the two strands. The dipole-dipole attractive and repulsive interactions are further obtained in this article. The total of N-H...H-N and C=O...O=C dipole-dipole repulsive interaction (the secondary electrostatic repulsive interaction) in the small ring of the antiparallel beta-sheet models is estimated to be about 6.0 kcal/mol. The individual N-H...O=C dipole-dipole attractive interaction is predicted to be -6.2 +/- 0.2 kcal/mol in the antiparallel beta-sheet models and -5.2 +/- 0.6 kcal/mol in the parallel beta-sheet models. The individual C(alpha)-H...O=C attractive interaction is -1.2 +/- 0.2 kcal/mol in the antiparallel beta-sheet models and -1.5 +/- 0.2 kcal/mol in the parallel beta-sheet models. These values are important in understanding the interactions at protein-protein interfaces and developing a more accurate force field for peptides and proteins. 2009 Wiley Periodicals, Inc.

Scalable and sustainable electrochemical allylic C-H oxidation

NASA Astrophysics Data System (ADS)

Horn, Evan J.; Rosen, Brandon R.; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

2016-05-01

New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact.

Reaction mechanisms at 4H-SiC/SiO2 interface during wet SiC oxidation

NASA Astrophysics Data System (ADS)

Akiyama, Toru; Hori, Shinsuke; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi; Shiraishi, Kenji

2018-04-01

The reaction processes at the interface between SiC with 4H structure (4H-SiC) and SiO2 during wet oxidation are investigated by electronic structure calculations within the density functional theory. Our calculations for 4H-SiC/SiO2 interfaces with various orientations demonstrate characteristic features of the reaction depending on the crystal orientation of SiC: On the Si-face, the H2O molecule is stable in SiO2 and hardly reacts with the SiC substrate, while the O atom of H2O can form Si-O bonds at the C-face interface. Two OH groups are found to be at least necessary for forming new Si-O bonds at the Si-face interface, indicating that the oxidation rate on the Si-face is very low compared with that on the C-face. On the other hand, both the H2O molecule and the OH group are incorporated into the C-face interface, and the energy barrier for OH is similar to that for H2O. By comparing the calculated energy barriers for these reactants with the activation energies of oxide growth rate, we suggest the orientation-dependent rate-limiting processes during wet SiC oxidation.

Ab initio study of C + H3+ reactions

NASA Technical Reports Server (NTRS)

Talbi, D.; DeFrees, D. J.

1991-01-01

The reaction C + H3+ --> CH(+) + H2 is frequently used in models of dense interstellar cloud chemistry with the assumption that it is fast, i.e. there are no potential energy barriers inhibiting it. Ab initio molecular orbital study of the triplet CH3+ potential energy surface (triplet because the reactant carbon atom is a ground state triplet) supports this hypothesis. The reaction product is 3 pi CH+; the reaction is to exothermic even though the product is not in its electronic ground state. No path has been found on the potential energy surface for C + H3+ --> CH2(+) + H reaction.

Transition-Metal-Catalyzed C-H Alkylation Using Alkenes.

PubMed

Dong, Zhe; Ren, Zhi; Thompson, Samuel J; Xu, Yan; Dong, Guangbin

2017-07-12

Alkylation reactions represent an important organic transformation to form C-C bonds. In addition to conventional approaches with alkyl halides or sulfonates as alkylating agents, the use of unactivated olefins for alkylations has become attractive from both cost and sustainability viewpoints. This Review summarizes transition-metal-catalyzed alkylations of various carbon-hydrogen bonds (addition of C-H bonds across olefins) using regular olefins or 1,3-dienes up to May 2016. According to the mode of activation, the Review is divided into two sections: alkylation via C-H activation and alkylation via olefin activation.

Isolated oxygen defects in 3C- and 4H-SiC: A theoretical study

NASA Astrophysics Data System (ADS)

Gali, A.; Heringer, D.; Deák, P.; Hajnal, Z.; Frauenheim, Th.; Devaty, R. P.; Choyke, W. J.

2002-09-01

Ab initio calculations in the local-density approximation have been carried out in SiC to determine the possible configurations of the isolated oxygen impurity. Equilibrium geometry and occupation levels were calculated. Substitutional oxygen in 3C-SiC is a relatively shallow effective mass like double donor on the carbon site (OC) and a hyperdeep double donor on the Si site (OSi). In 4H-SiC OC is still a double donor but with a more localized electron state. In 3C-SiC OC is substantially more stable under any condition than OSi or interstitial oxygen (Oi). In 4H-SiC OC is also the most stable one except for heavy n-type doping. We propose that OC is at the core of the electrically active oxygen-related defect family found by deep level transient spectroscopy in 4H-SiC. The consequences of the site preference of oxygen on the SiC/SiO2 interface are discussed.

Differential Immune Profiles in Two Pandemic Influenza A(H1N1)pdm09 Virus Waves at Pandemic Epicenter.

PubMed

Arriaga-Pizano, Lourdes; Ferat-Osorio, Eduardo; Rodríguez-Abrego, Gabriela; Mancilla-Herrera, Ismael; Domínguez-Cerezo, Esteban; Valero-Pacheco, Nuriban; Pérez-Toledo, Marisol; Lozano-Patiño, Fernando; Laredo-Sánchez, Fernando; Malagón-Rangel, José; Nellen-Hummel, Haiko; González-Bonilla, César; Arteaga-Troncoso, Gabriel; Cérbulo-Vázquez, Arturo; Pastelin-Palacios, Rodolfo; Klenerman, Paul; Isibasi, Armando; López-Macías, Constantino

2015-11-01

Severe influenza A(H1N1)pdm2009 virus infection cases are characterized by sustained immune activation during influenza pandemics. Seasonal flu data suggest that immune mediators could be modified by wave-related changes. Our aim was to determine the behavior of soluble and cell-related mediators in two waves at the epicenter of the 2009 influenza pandemic. Leukocyte surface activation markers were studied in serum from peripheral blood samples, collected from the 1(st) (April-May, 2009) and 2(nd) (October 2009-February 2010) pandemic waves. Patients with confirmed influenza A(H1N1)pdm2009 virus infection (H1N1), influenza-like illness (ILI) or healthy donors (H) were analyzed. Serum IL-6, IL-4 and IL-10 levels were elevated in H1N1 patients from the 2(nd) pandemic wave. Additionally, the frequency of helper and cytotoxic T cells was reduced during the 1(st) wave, whereas CD69 expression in helper T cells was increased in the 2(nd) wave for both H1N1 and ILI patients. In contrast, CD62L expression in granulocytes from the ILI group was increased in both waves but in monocytes only in the 2(nd) wave. Triggering Receptor Expressed on Myeloid cells (TREM)-1 expression was elevated only in H1N1 patients at the 1(st) wave. Our results show that during the 2009 influenza pandemic a T cell activation phenotype is observed in a wave-dependent fashion, with an expanded activation in the 2(nd) wave, compared to the 1(st) wave. Conversely, granulocyte and monocyte activation is infection-dependent. This evidence collected at the pandemic epicenter in 2009 could help us understand the differences in the underlying cellular mechanisms that drive the wave-related immune profile behaviors that occur against influenza viruses during pandemics. Copyright © 2015 IMSS. Published by Elsevier Inc. All rights reserved.

The reaction H + C4H2 - Absolute rate constant measurement and implication for atmospheric modeling of Titan

NASA Technical Reports Server (NTRS)

Nava, D. F.; Mitchell, M. B.; Stief, L. J.

1986-01-01

The absolute rate constant for the reaction H + C4H2 has been measured over the temperature (T) interval 210-423 K, using the technique of flash photolysis-resonance fluorescence. At each of the five temperatures employed, the results were independent of variations in C4H2 concentration, total pressure of Ar or N2, and flash intensity (i.e., the initial H concentration). The rate constant, k, was found to be equal to 1.39 x 10 to the -10th exp (-1184/T) cu cm/s, with an error of one standard deviation. The Arrhenius parameters at the high pressure limit determined here for the H + C4H2 reaction are consistent with those for the corresponding reactions of H with C2H2 and C3H4. Implications of the kinetic carbon chemistry results, particularly those at low temperature, are considered for models of the atmospheric carbon chemistry of Titan. The rate of this reaction, relative to that of the analogous, but slower, reaction of H + C2H2, appears to make H + C4H2 a very feasible reaction pathway for effective conversion of H atoms to molecular hydrogen in the stratosphere of Titan.

Palladium-catalysed electrophilic aromatic C-H fluorination

NASA Astrophysics Data System (ADS)

Yamamoto, Kumiko; Li, Jiakun; Garber, Jeffrey A. O.; Rolfes, Julian D.; Boursalian, Gregory B.; Borghs, Jannik C.; Genicot, Christophe; Jacq, Jérôme; van Gastel, Maurice; Neese, Frank; Ritter, Tobias

2018-02-01

Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.

Directed C-H Bond Oxidation of (+)-Pleuromutilin.

PubMed

Ma, Xiaoshen; Kucera, Roman; Goethe, Olivia F; Murphy, Stephen K; Herzon, Seth B

2018-05-01

Antibiotics derived from the diterpene fungal metabolite (+)-pleuromutilin (1) are useful agents for the treatment Gram-positive infections in humans and farm animals. Pleuromutilins elicit slow rates of resistance development and minimal cross-resistance with existing antibiotics. Despite efforts aimed at producing new derivatives by semisynthesis, modification of the tricyclic core is underexplored, in part due to a limited number of functional group handles. Herein, we report methods to selectively functionalize the methyl groups of (+)-pleuromutilin (1) by hydroxyl-directed iridium-catalyzed C-H silylation, followed by Tamao-Fleming oxidation. These reactions provided access to C16, C17, and C18 monooxidized products, as well as C15/C16 and C17/C18 dioxidized products. Four new functionalized derivatives were prepared from the protected C17 oxidation product. C6 carboxylic acid, aldehyde, and normethyl derivatives were prepared from the C16 oxidation product. Many of these sequences were executed on gram scales. The efficiency and practicality of these routes provides an easy method to rapidly interrogate structure-activity relationships that were previously beyond reach. This study will inform the design of fully synthetic approaches to novel pleuromutilins and underscores the power of the hydroxyl-directed iridium-catalyzed C-H silylation reaction.

The impact of alternative diagnoses on the utility of influenza-like illness case definition to detect the 2009 H1N1 pandemic.

PubMed

Rumoro, Dino P; Bayram, Jamil D; Silva, Julio C; Shah, Shital C; Hallock, Marilyn M; Gibbs, Gillian S; Waddell, Michael J

2012-01-01

To investigate the impact of excluding cases with alternative diagnoses on the sensitivity and specificity of the Centers for Disease Control and Prevention's (CDC) influenza-like illness (ILI) case definition in detecting the 2009 H1N1 influenza, using Geographic Utilization of Artificial Intelligence in Real-Time for Disease Identification and Alert Notification, a disease surveillance system. Retrospective cross-sectional study design. Emergency department of an urban tertiary care academic medical center. 1,233 ED cases, which were tested for respiratory viruses from September 5, 2009 to May 5, 2010. The main outcome measures were positive predictive value, negative predictive value, sensitivity, specificity, and accuracy of the ILI case definition (both including and excluding alternative diagnoses) to detect H1N1. There was a significant decrease in sensitivity (chi2 = 9.09, p < 0.001) and significant improvement in specificity (chi2 = 179, p < 0.001), after excluding cases with alternative diagnoses. When early detection of an influenza epidemic is of prime importance, pursuing alternative diagnoses as part of CDC's ILI case definition may not be warranted for public health reporting due to the significant decrease in sensitivity, in addition to the resources required for detecting these alternative diagnoses.

Theoretical microwave spectral constants for C2N, C2N/+/, and C3H

NASA Technical Reports Server (NTRS)

Green, S.

1980-01-01

Theoretical microwave spectral constants have been computed for C2N, C3H, and C2N(+). For C2N these are compared with values obtained from optical data. Calculated hyperfine constants are also presented for HNC, DNC, and HCNH(+). The possibility of observing these species in dense interstellar clouds is discussed.

Downregulation of p-coumaroyl quinate/shikimate 3'-hydroxylase (C3'H) or cinnamate-4-hydrolylase (C4H) in Eucalyptus urophylla x Eucalyptus grandis leads to increased extractability

DOE PAGES

Ziebell, Angela; Gjersing, Erica; Hinchee, Maud; ...

2016-01-20

Lignin reduction through breeding and genetic modification has the potential to reduce costs in biomass processing in pulp and paper, forage, and lignocellulosic ethanol industries. Here, we present detailed characterization of the extractability and lignin structure of Eucalyptus urophylla x Eucalyptus grandis RNAi downregulated in p-coumaroyl quinate/shikimate 3'-hydroxylase (C3'H) or cinnamate-4-hydroxylase (C4H). Both the C3'H and C4H downregulated lines were found to have significantly higher extractability when exposed to NaOH base extraction, indicating altered cell wall construction. The molecular weight of isolated lignin was measured and lignin structure was determined by HSQC NMR-based lignin subunit analysis for control and themore » C3'H and C4H downregulated lines. The slight reductions in average molecular weights of the lignin isolated from the transgenic lines (C3'H = 7000, C4H = 6500, control = 7300) does not appear to explain the difference in extractability. The HSQC NMR-based lignin subunit analysis showed increases in H lignin content for the C3'H but only slight differences in the lignin subunit structure of the C3'H and C4H downregulated lines when compared to the control. The greatest difference between the C3'H and C4H downregulated lines is the total lignin content; therefore, it appears that overall lowered lignin content contributes greatly to reduced recalcitrance and increased extractability of cell wall biopolymers. Furthermore, studies will be conducted to determine how the reduction in lignin content creates a less rigid cell wall that is more prone to extraction and sugar release.« less

Calculations of thermal radiation transfer of C2H2 and C2H4 together with H2O, CO2, and CO in a one-dimensional enclosure using LBL and SNB models

NASA Astrophysics Data System (ADS)

Qi, Chaobo; Zheng, Shu; Zhou, Huaichun

2017-08-01

Generally, the involvement of hydrocarbons such as C2H4 and its derivative C2H2 in thermal radiation has not been accounted in the numerical simulation of their flames, which may cause serious error for estimation of temperature in the early stage of combustion. At the first, the Statistical Narrow-Band (SNB) model parameters for C2H2 and C2H4 are generated from line by line (LBL) calculations. The distributions of the concentrations of radiating gases such as H2O, CO2, CO, C2H2 and C2H4, and the temperature along the centerline of a laminar ethylene/air diffusion flame were chosen to form a one-dimensional, planar enclosure to be tested in this study. Thermal radiation transfer in such an enclosure was calculated using the LBL approach and the SNB model, most of the relative errors are less than 8% and the results of these two models shows an excellent agreement. Below the height of 20 mm, which is the early stage of the flame, the average fraction contributed by C2H2 and C2H4 in the radiative heat source is 33.8%, while that by CO is only 5.8%. This result indicates that the involvement of C2H2 and C2H4 in radiation heat transfer needs to be taken into account in the numerical modeling of the ethylene/air diffusion flame, especially in the early stage of combustion.

Synergistic Heterobimetallic Manifold for Expedient Manganese(I)-Catalyzed C-H Cyanation.

PubMed

Liu, Weiping; Richter, Sven C; Mei, Ruhuai; Feldt, Milica; Ackermann, Lutz

2016-12-12

The manganese-catalyzed cyanation of inert C-H bonds was achieved within a heterobimetallic catalysis regime. The manganese(I) catalysis proved widely applicable and enabled C-H cyanations on indoles, pyrroles and thiophenes by facile C-H manganesation. The robustness of the manganese catalyst set the stage for the racemization-free C-H cyanation of amino acids with excellent levels of positional and chemo selectivity by the new cyanating agent NCFS. Experimental and computational mechanistic studies provided strong support for a synergistic heterobimetallic activation mode, facilitating the key C-C formation. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidative C-H/C-H Cross-Coupling Reactions between N-Acylanilines and Benzamides Enabled by a Cp*-Free RhCl3/TFA Catalytic System.

PubMed

You, Jingsong; Shi, Yang; Zhang, Luoqiang; Lan, Jingbo; Zhang, Min; Zhou, Fulin; Wei, Wenlong

2018-06-03

Using the dual chelation-assisted strategy, a completely regiocontrolled oxidative C-H/C-H cross-coupling reaction between an N-acylaniline and a benzamide has been accomplished for the first time, which enables a step-economical and highly efficient pathway to 2-amino-2'-carboxybiaryl scaffolds from readily available substrates. A Cp*-free RhCl3/TFA catalytic system has been developed to replace the generally used [Cp*RhCl2]2/AgSbF6 (Cp* = pentamethyl cyclopentadienyl) in oxidative C-H/C-H cross-coupling reactions between two (hetero)arenes. The RhCl3/TFA system avoids the use of expensive Cp* ligand and AgSbF6. As an illustrative example, the protocol developed herein greatly streamlines access to naturally occurring benzo[c]phenanthridine alkaloid oxynitidine in an excellent overall yield. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revised Atomistic Models of the Crystal Structure of C-S-H with high C/S Ratio

NASA Astrophysics Data System (ADS)

Kovačević, Goran; Nicoleau, Luc; Nonat, André; Veryazov, Valera

2016-09-01

The atomic structure of calcium-silicate-hydrate (C1.67-S-Hx) has been studied. Atomistic C-S-H models suggested in our previous study have been revised in order to perform a direct comparison of energetic stability of the different structures. An extensive set of periodic structures of C-S-H with variation of water content was created, and then optimized using molecular dynamics with reactive force field ReaxFF and quantum chemical semiempirical method PM6. All models show organization of water molecules inside the structure of C-S-H. The new geometries of C-S-H, reported in this paper, show lower relative energy with respect to the geometries from the original definition of C-S-H models. Model that corresponds to calcium enriched tobermorite structure has the lowest relative energy and the density closest to the experimental values.

The effect of school dismissal on rates of influenza-like illness in New York City schools during the spring 2009 novel H1N1 outbreak.

PubMed

Egger, Joseph R; Konty, Kevin J; Wilson, Elisha; Karpati, Adam; Matte, Thomas; Weiss, Don; Barbot, Oxiris

2012-03-01

The effects of individual school dismissal on influenza transmission have not been well studied. During the spring 2009 novel H1N1 outbreak, New York City implemented an individual school dismissal policy intended to limit influenza transmission at schools with high rates of influenza-like illness (ILI). Active disease surveillance data collected by the New York City Health Department on rates of ILI in schools were used to evaluate the impact. Sixty-four schools that met the Health Department's criteria for considering dismissal were included in the analysis. Twenty-four schools that met criteria subsequently dismissed all classes for approximately 1 school week. A regression model was fit to these data, estimating the effect of school dismissal on rates of in-school ILI following reconvening, adjusting for potential confounders. The model estimated that, on average, school dismissal reduced the rate of ILI by 7.1% over the entire average outbreak period. However, a large proportion of in-school ILI occurred before dismissal criteria were met. A separate model estimated that school absenteeism rates were not significantly affected by dismissal. Results suggest that individual school dismissal could be considered in situations where schools have a disproportionate number of high-risk students or may be unable to implement recommended preventive or infection control measures. Future work should focus on developing more sensitive indicators of early outbreak detection in schools and evaluating the impact of school dismissal on community transmission. © 2012, American School Health Association.

Breakdown of the Coulomb friction law in TiC/a-C:H nanocomposite coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pei, Y. T.; Huizenga, P.; Galvan, D.

2006-12-01

Advanced TiC/a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system (Hauzer HTC-1000 or HTC 1200). In this paper, we report on the tribological behavior of TiC/a-C:H nanocomposite coatings in which ultralow friction is tailored with superior wear resistance, two properties often difficult to achieve simultaneously. Tribotests have been performed at room temperature with a ball-on-disk configuration. In situ monitoring of the wear depth of the coated disk together with the wear height of the ball counterpart at nanometer scale reveals that the self-lubricating effects are induced by the formation of transfer films onmore » the surface of the ball counterpart. A remarkable finding is a breakdown of the Coulomb friction law in the TiC/a-C:H nanocomposite coatings. In addition, the coefficient of friction of TiC/a-C:H nanocomposite coatings decreases with decreasing relative humidity. A superior wear resistance of the coated disk at a level of 10{sup -17} m{sup 3}/N m (per lap) has been achieved under the condition of superlow friction and high toughness, both of which require fine TiC nanoparticles (e.g., 2 nm) and a wide matrix separation that must be comparable to the dimensions of the nanoparticles.« less

Palladium-catalysed transannular C-H functionalization of alicyclic amines

NASA Astrophysics Data System (ADS)

Topczewski, Joseph J.; Cabrera, Pablo J.; Saper, Noam I.; Sanford, Melanie S.

2016-03-01

Discovering pharmaceutical candidates is a resource-intensive enterprise that frequently requires the parallel synthesis of hundreds or even thousands of molecules. C-H bonds are present in almost all pharmaceutical agents. Consequently, the development of selective, rapid and efficient methods for converting these bonds into new chemical entities has the potential to streamline pharmaceutical development. Saturated nitrogen-containing heterocycles (alicyclic amines) feature prominently in pharmaceuticals, such as treatments for depression (paroxetine, amitifadine), diabetes (gliclazide), leukaemia (alvocidib), schizophrenia (risperidone, belaperidone), malaria (mefloquine) and nicotine addiction (cytisine, varenicline). However, existing methods for the C-H functionalization of saturated nitrogen heterocycles, particularly at sites remote to nitrogen, remain extremely limited. Here we report a transannular approach to selectively manipulate the C-H bonds of alicyclic amines at sites remote to nitrogen. Our reaction uses the boat conformation of the substrates to achieve palladium-catalysed amine-directed conversion of C-H bonds to C-C bonds on various alicyclic amine scaffolds. We demonstrate this approach by synthesizing new derivatives of several bioactive molecules, including varenicline.

Dehydrogenation reactions of cyclic C(2)B(2)N(2)H(12) and C(4)BNH(12) isomers.

PubMed

Matus, Myrna H; Liu, Shih-Yuan; Dixon, David A

2010-02-25

The energetics for different dehydrogenation pathways of C(2)B(2)N(2)H(12) and C(4)BNH(12) cycles were calculated at the B3LYP/DGDZVP2 and G3(MP2) levels with additional calculations at the CCSD(T)/complete basis set level. The heats of formation of the different isomers were calculated from the G3(MP2) relative energies and the heats of formation of the most stable isomers of c-C(2)B(2)N(2)H(6), c-C(2)B(2)N(2)H(12), and c-C(4)BNH(12) at the CCSD(T)/CBS including additional corrections together with the previously reported value for c-C(4)BNH(6). Different isomers were analyzed for c-C(2)B(2)N(2)H(x) and c-C(4)BNH(x) (x = 6 and 12), and the most stable cyclic structures were those with C-C-B-N-B-N and C-C-C-C-B-N sequences, respectively. The energetics for the stepwise loss of three H(2) were predicted, and the most feasible thermodynamic pathways were found. Dehydrogenation of the lowest energy c-C(2)B(2)N(2)H(12) isomer (6-H(12)) is almost thermoneutral with DeltaH(3dehydro) = 3.4 kcal/mol at the CCSD(T)/CBS level and -0.6 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation of the lowest energy c-C(4)BNH(12) isomer (7-H(12)) is endothermic with DeltaH(3dehydro) = 27.9 kcal/mol at the CCSD(T)/CBS level and 23.5 kcal/mol at the G3(MP2) level at 298 K. Dehydrogenation across the B-N bond is more favorable as opposed to dehydrogenation across the B-C, N-C, and C-C bonds. Resonance stabilization energies in relation to that of benzene are reported as are NICS NMR chemical shifts for correlating with the potential aromatic character of the rings.

Oxidative esterification via photocatalytic C-H activation

EPA Science Inventory

Direct oxidative esterification of alcohol via photocatalytic C-H activation has been developed using VO@g-C3N4 catalyst; an expeditious esterification of alcohols occurs under neutral conditions using visible light as the source of energy.

Suggestion for search of cyclopropenone (c-C3H2O) in a cosmic object

NASA Astrophysics Data System (ADS)

Sharma, M. K.; Sharma, M.; Chandra, S.

2017-03-01

Following Minimum Energy Principle, out of the three isomers of chemical formula C3H2O, the cyclopropenone (c-C3H2O) is the most stable and therefore may be the most abundant and easily detectable in a cosmic object. The cyclopropenone is detected in Sgr B2(N). Owing to half-spin of each of two hydrogen atoms, the c-C3H2O has two distinct ortho and para species. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of c-C3H2O and the Einstein A-coefficients for radiative transitions between the levels. The values of Einstein A-coefficients along with the scaled values for collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer. Brightness temperatures of seven rotational transitions of each of the ortho and para species of c-C3H2O are investigated. Out of fourteen transitions, seven are found to show anomalous absorption and rest seven are found to show emission feature. We find that the transitions 110 -111 (1.544 GHz) may play important role in identification of cyclopropenone in a cosmic object.

Ab Initio Reaction Kinetics of CH 3 O$$\\dot{C}$$(=O) and $$\\dot{C}$$H 2 OC(=O)H Radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Ting; Yang, Xueliang; Ju, Yiguang

The dissociation and isomerization kinetics of the methyl ester combustion intermediates methoxycarbonyl radical (CH3Omore » $$\\dot{C}$$(=O)) and (formyloxy)methyl radical ($$\\dot{C}$$H2OC(=O)H) are investigated theoretically using high-level ab initio methods and Rice–Ramsperger–Kassel–Marcus (RRKM)/master equation (ME) theory. Geometries obtained at the hybrid density functional theory (DFT) and coupled cluster singles and doubles with perturbative triples correction (CCSD(T)) levels of theory are found to be similar. We employ high-level ab initio wave function methods to refine the potential energy surface: CCSD(T), multireference singles and doubles configuration interaction (MRSDCI) with the Davidson–Silver (DS) correction, and multireference averaged coupled-pair functional (MRACPF2) theory. MRSDCI+DS and MRACPF2 capture the multiconfigurational character of transition states (TSs) and predict lower barrier heights than CCSD(T). The temperature- and pressure-dependent rate coefficients are computed using RRKM/ME theory in the temperature range 300–2500 K and a pressure range of 0.01 atm to the high-pressure limit, which are then fitted to modified Arrhenius expressions. Dissociation of CH3O$$\\dot{C}$$(=O) to $$\\dot{C}$$H3 and CO2 is predicted to be much faster than dissociating to CH3$$\\dot{O}$$ and CO, consistent with its greater exothermicity. Isomerization between CH3O$$\\dot{C}$$(=O) and $$\\dot{C}$$H2OC(=O)H is predicted to be the slowest among the studied reactions and rarely happens even at high temperature and high pressure, suggesting the decomposition pathways of the two radicals are not strongly coupled. The predicted rate coefficients and branching fractions at finite pressures differ significantly from the corresponding high-pressure-limit results, especially at relatively high temperatures. Finally, because it is one of the most important CH3$$\\dot{O}$$ removal mechanisms under atmospheric conditions, the reaction kinetics of

Rhodium-catalyzed C-H functionalization with N-acylsaccharins.

PubMed

Wu, Hongxiang; Liu, Tingting; Cui, Ming; Li, Yue; Jian, Junsheng; Wang, Hui; Zeng, Zhuo

2017-01-18

A rhodium-catalyzed C-H functionalization with activated amides by decarbonylation has been developed. Notably, this is the first C-H arylation employing N-acylsaccharins as coupling partners to give biaryls in good to excellent yields. The highlight of the work is the high tolerance of functional groups such as formyl, ester, and vinyl and the use of a removable directing group.

40 CFR 721.10024 - 10H-Phenothiazine, ar-(C9-rich C8-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 10H-Phenothiazine, ar-(C9-rich C8-10... New Uses for Specific Chemical Substances § 721.10024 10H-Phenothiazine, ar-(C9-rich C8-10-branched... substance identified as 10H-phenothiazine, ar-(C9-rich C8-10-branched alkyl) derivs (PMN P-01-771; CAS No...

Tribological properties of TiC/a-C:H nanocomposite coatings prepared via HiPIMS

NASA Astrophysics Data System (ADS)

Sánchez-López, J. C.; Dominguez-Meister, S.; Rojas, T. C.; Colasuonno, M.; Bazzan, M.; Patelli, A.

2018-05-01

High power impulse magnetron sputtering (HiPIMS) technology has been employed to prepare TiC/a-C:H nanocomposite coatings from a titanium target in acetylene (C2H2) reactive atmospheres. Gas fluxes were varied from 1.3 to 4.4 sccm to obtain C/Ti ratios from 2 to 15 as measured by electron probe microanalysis (EPMA). X-ray diffraction and transmission electron microscopy demonstrate the presence of TiC nanocrystals embedded in an amorphous carbon-based matrix. The hardness properties decrease from 17 to 10 GPa as the carbon content increases. The tribological properties were measured using a pin-on-disk tribometer in ambient air (RH = 30-40%) at 10 cm/s with 5 N of applied load against 6-mm 100Cr6 balls. The friction coefficient and the film wear rates are gradually improved from 0.3 and 7 × 10-6 mm3/N m to 0.15 and 2 × 10-7 mm3/N m, respectively, by increasing the C2H2 flux. To understand the tribological processes appearing at the interface and to elucidate the wear mechanism, microstructural and chemical investigations of the coatings were performed before and after the friction test. EPMA, X-ray photoelectron and electron energy-loss spectroscopies were employed to obtain an estimation of the fraction of the a-C:H phase, which can be correlated with the tribological behavior. Examination of the friction counterfaces (ball and track) by Raman microanalysis reveals an increased ordering of the amorphous carbon phase concomitant with friction reduction. The tribological results were compared with similar TiC/a-C(:H) composites prepared by the conventional direct current process.

Infrared spectra of C2H4 dimer and trimer

NASA Astrophysics Data System (ADS)

Barclay, A. J.; Esteki, K.; McKellar, A. R. W.; Moazzen-Ahmadi, N.

2018-05-01

Spectra of ethylene dimers and trimers are studied in the ν11 and (for the dimer) ν9 fundamental band regions of C2H4 (≈2990 and 3100 cm-1) using a tunable optical parametric oscillator source to probe a pulsed supersonic slit jet expansion. The deuterated trimer has been observed previously, but this represents the first rotationally resolved spectrum of (C2H4)3. The results support the previously determined cross-shaped (D2d) dimer and barrel-shaped (C3h or C3) trimer structures. However, the dimer spectrum in the ν9 fundamental region of C2H4 is apparently very perturbed and a previous rotational analysis is not well verified.

Towards mild metal-catalyzed C-H bond activation.

PubMed

Wencel-Delord, Joanna; Dröge, Thomas; Liu, Fan; Glorius, Frank

2011-09-01

Functionalizing traditionally inert carbon-hydrogen bonds represents a powerful transformation in organic synthesis, providing new entries to valuable structural motifs and improving the overall synthetic efficiency. C-H bond activation, however, often necessitates harsh reaction conditions that result in functional group incompatibilities and limited substrate scope. An understanding of the reaction mechanism and rational design of experimental conditions have led to significant improvement in both selectivity and applicability. This critical review summarizes and discusses endeavours towards the development of mild C-H activation methods and wishes to trigger more research towards this goal. In addition, we examine select examples in complex natural product synthesis to demonstrate the synthetic utility of mild C-H functionalization (84 references). This journal is © The Royal Society of Chemistry 2011

Experimental Durability Testing of 4H SiC JFET Integrated Circuit Technology at 727 C

NASA Technical Reports Server (NTRS)

Spry, David; Neudeck, Phil; Chen, Liangyu; Chang, Carl; Lukco, Dorothy; Beheim, Glenn M

2016-01-01

We have reported SiC integrated circuits (IC's) with two levels of metal interconnect that have demonstrated prolonged operation for thousands of hours at their intended peak ambient operational temperature of 500 C [1, 2]. However, it is recognized that testing of semiconductor microelectronics at temperatures above their designed operating envelope is vital to qualification. Towards this end, we previously reported operation of a 4H-SiC JFET IC ring oscillator on an initial fast thermal ramp test through 727 C [3]. However, this thermal ramp was not ended until a peak temperature of 880 C (well beyond failure) was attained. Further experiments are necessary to better understand failure mechanisms and upper temperature limit of this extreme-temperature capable 4H-SiC IC technology. Here we report on additional experimental testing of custom-packaged 4H-SiC JFET IC devices at temperatures above 500 C. In one test, the temperature was ramped and then held at 727 C, and the devices were periodically measured until electrical failure was observed. A 4H-SiC JFET on this chip electrically functioned with little change for around 25 hours at 727 C before rapid increases in device resistance caused failure. In a second test, devices from our next generation 4H-SiC JFET ICs were ramped up and then held at 700 C (which is below the maximum deposition temperature of the dielectrics). Three ring oscillators functioned for 8 hours at this temperature before degradation. In a third experiment, an alternative die attach of gold paste and package lid was used, and logic circuit operation was demonstrated for 143.5 hours at 700 C.

Gas-phase reactivity of lanthanide cations with fluorocarbons: C-F versus C-H and C-C bond activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cornehl, H.H.; Hornung, G.; Schwarz, H.

1996-10-16

The gas-phase reactivity of the fluorinated hydrocarbons CF{sub 4}, CHF{sub 3}, CH{sub 3}F, C{sub 2}F{sub 6}, 1,1-C{sub 2}H{sub 4}F{sub 2}, and C{sub 6}F{sub 6} with the lanthanide cations Ce{sup +}, Pr{sup +}, Sm{sup +}, Ho{sup +}, Tm{sup +}, and Yb{sup +} and the reactivity of C{sub 6}H{sub 5}F with all lanthanide cations Ln{sup +} (Ln = La-Lu, with the exception of Pm{sup +}) have been examined by Fourier-transform ion cyclotron resonance mass spectrometry. The perfluorinated compounds tetrafluoromethane and hexafluoroethane as well as trifluoromethane do not react with any lanthanide cation. Selective activation of the strong C-F bonds in fluoromethane, 1,1-difluoroethane,more » hexafluorobenzene, and fluorobenzene appears as a general reaction scheme along the 4f row. Experimental evidence is given for a `harpoon`-like mechanism for the F atom abstraction process which operates via an initial electron transfer from the lanthanide cation to the fluorinated substrate in the encounter complex Ln{sup +}RF. The most reactive lanthanides La{sup +}, Ce{sup +}, Gd{sup +}, and Tb{sup +} and also the formal closed-shell species Lu{sup +} exhibit additional C-H and C-C bond activation pathways in the reaction with fluorobenzene, namely dehydrohalogenation as well as loss of a neutral acetylene molecule. In the case of Tm{sup +} and Yb{sup +} the formation of neutral LnF{sub 3} is observed in a multistep process via C-C coupling and charge transfer. 17 refs., 2 figs., 2 tabs.« less

C+/H2 gas in star-forming clouds and galaxies

NASA Astrophysics Data System (ADS)

Nordon, Raanan; Sternberg, Amiel

2016-11-01

We present analytic theory for the total column density of singly ionized carbon (C+) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C+ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. When assuming the typical relation between UV and density in the cold neutral medium, the C+ column becomes a function of the metallicity alone. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C+ column is mixed with hydrogen that is primarily molecular (H2), and this `C+/H2' gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C+/H2 column density is limited by dust shielding and is inversely proportional to the metallicity down to ˜0.1 solar. At lower metallicities, H2 line blocking dominates and the C+/H2 column saturates. Applying our theory to CO surveys in low-redshift spirals, we estimate the fraction of C+/H2 gas out of the total molecular gas to be typically ˜0.4. At redshifts 1 < z < 3 in massive disc galaxies the C+/H2 gas represents a very small fraction of the total molecular gas (≲ 0.16). This small fraction at high redshifts is due to the high gas surface densities when compared to local galaxies.

Measured Attenuation of Coplanar Waveguide on 6H, p-type SiC and High Purity Semi-Insulating 4H SiC through 800 K

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Schwartz, Zachary D.; Alterovitz, Samuel A.; Downey, Alan N.

2004-01-01

Wireless sensors for high temperature applications such as oil drilling and mining, automobiles, and jet engine performance monitoring require circuits built on wide bandgap semiconductors. In this paper, the characteristics of microwave transmission lines on 4H-High Purity Semi-Insulating SiC and 6H, p-type SiC is presented as a function of temperature and frequency. It is shown that the attenuation of 6H, p-type substrates is too high for microwave circuits, large leakage current will flow through the substrate, and that unusual attenuation characteristics are due to trapping in the SiC. The 4H-HPSI SiC is shown to have low attenuation and leakage currents over the entire temperature range.

Iridium complexes containing mesoionic C donors: selective C(sp3)-H versus C(sp2)-H bond activation, reactivity towards acids and bases, and catalytic oxidation of silanes and water.

PubMed

Petronilho, Ana; Woods, James A; Mueller-Bunz, Helge; Bernhard, Stefan; Albrecht, Martin

2014-11-24

Metalation of a C2-methylated pyridylimidazolium salt with [IrCp*Cl2]2 affords either an ylidic complex, resulting from C(sp(3))-H bond activation of the C2-bound CH3 group if the metalation is performed in the presence of a base, such as AgO2 or Na2CO3, or a mesoionic complex via cyclometalation and thermally induced heterocyclic C(sp(2))-H bond activation, if the reaction is performed in the absence of a base. Similar cyclometalation and complex formation via C(sp(2))-H bond activation is observed when the heterocyclic ligand precursor consists of the analogous pyridyltriazolium salt, that is, when the metal bonding at the C2 position is blocked by a nitrogen rather than a methyl substituent. Despite the strongly mesoionic character of both the imidazolylidene and the triazolylidene, the former reacts rapidly with D(+) and undergoes isotope exchange at the heterocyclic C5 position, whereas the triazolylidene ligand is stable and only undergoes H/D exchange under basic conditions, where the imidazolylidene is essentially unreactive. The high stability of the Ir-C bond in aqueous solution over a broad pH range was exploited in catalytic water oxidation and silane oxidation. The catalytic hydrosilylation of ketones proceeds with turnover frequencies as high as 6,000 h(-1) with both the imidazolylidene and the triazolylidene system, whereas water oxidation is enhanced by the stronger donor properties of the imidazol-4-ylidene ligands and is more than three times faster than with the triazolylidene analogue. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ILI-related school dismissal monitoring system: an overview and assessment.

PubMed

Kann, Laura; Kinchen, Steve; Modzelski, Bill; Sullivan, Madeline; Carr, Dana; Zaza, Stephanie; Graffunder, Corinne; Cetron, Marty

2012-06-01

This report provides an overview and assessment of the School Dismissal Monitoring System (SDMS) that was developed by the Centers for Disease Control and Prevention (CDC) and the US Department of Education (ED) to monitor influenza-like illness (ILI)-related school dismissals during the 2009-2010 school year in the United States. SDMS was developed with considerable consultation with CDC's and ED's partners. Further, each state appointed a single school dismissal monitoring contact, even if that state also had its own school-dismissal monitoring system in place. The SDMS received data from three sources: (1) direct reports submitted through CDC's Web site, (2) state monitoring systems, and (3) media scans and online searches. All cases identified through any of the three data sources were verified. Between August 3, 2009, and December 18, 2009, a total of 812 dismissal events (ie, a single school dismissal or dismissal of all schools in a district) were reported in the United States. These dismissal events had an impact on 1947 schools, approximately 623 616 students, and 40 521 teachers. The SDMS yielded real-time, national summary data that were used widely throughout the US government for situational awareness to assess the impact of CDC guidance and community mitigation efforts and to inform the development of guidance, resources, and tools for schools.

Histone HIST1H1C/H1.2 regulates autophagy in the development of diabetic retinopathy.

PubMed

Wang, Wenjun; Wang, Qing; Wan, Danyang; Sun, Yue; Wang, Lin; Chen, Hong; Liu, Chengyu; Petersen, Robert B; Li, Jianshuang; Xue, Weili; Zheng, Ling; Huang, Kun

2017-05-04

Autophagy plays critical and complex roles in many human diseases, including diabetes and its complications. However, the role of autophagy in the development of diabetic retinopathy remains uncertain. Core histone modifications have been reported involved in the development of diabetic retinopathy, but little is known about the histone variants. Here, we observed increased autophagy and histone HIST1H1C/H1.2, an important variant of the linker histone H1, in the retinas of type 1 diabetic rodents. Overexpression of histone HIST1H1C upregulates SIRT1 and HDAC1 to maintain the deacetylation status of H4K16, leads to upregulation of ATG proteins, then promotes autophagy in cultured retinal cell line. Histone HIST1H1C overexpression also promotes inflammation and cell toxicity in vitro. Knockdown of histone HIST1H1C reduces both the basal and stresses (including high glucose)-induced autophagy, and inhibits high glucose induced inflammation and cell toxicity. Importantly, AAV-mediated histone HIST1H1C overexpression in the retinas leads to increased autophagy, inflammation, glial activation and neuron loss, similar to the pathological changes identified in the early stage of diabetic retinopathy. Furthermore, knockdown of histone Hist1h1c by siRNA in the retinas of diabetic mice significantly attenuated the diabetes-induced autophagy, inflammation, glial activation and neuron loss. These results indicate that histone HIST1H1C may offer a novel therapeutic target for preventing diabetic retinopathy.

Dynamics of the Ili delta with consideration of fluctuations of the level of Lake Balkhash

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdrasilov, S.A.; Tulebaeva, K.A.

1995-02-01

This article examines the dynamics of the Ili delta region of Russia, with consideration of the fluctuations of the level of Lake Balkhash. Level fluctuations over a period of approximately 700 years are reviewed, and numerical data is presented. It is shown that the dynamics of the delta region affect both the amplitude and duration of the cycle of fluctuations of the lake level. In particular, the phase of the delta cycle that started cuts off the peak of the maximum ordinate of the level at the end of the tranasgressive period reduces still more the minimum elevations of themore » lake level at the end of the regressive period. It also accelerates the time of occurence of individual phases of the intrasecular cycle.« less

Inelastic rate coefficients for collisions of C6H- with H2 and He

NASA Astrophysics Data System (ADS)

Walker, Kyle M.; Lique, François; Dumouchel, Fabien; Dawes, Richard

2017-04-01

The recent detection of anions in the interstellar medium has shown that they exist in a variety of astrophysical environments - circumstellar envelopes, cold dense molecular clouds and star-forming regions. Both radiative and collisional processes contribute to molecular excitation and de-excitation in these regions so that the 'local thermodynamic equilibrium' approximation, where collisions cause the gas to behave thermally, is not generally valid. Therefore, along with radiative coefficients, collisional excitation rate coefficients are needed to accurately model the anionic emission from these environments. We focus on the calculation of state-to-state rate coefficients of the C6H- molecule in its ground vibrational state in collisions with para-H2, ortho-H2 and He using new potential energy surfaces. Dynamical calculations for the pure rotational excitation of C6H- were performed for the first 11 rotational levels (up to j1 = 10) using the close-coupling method, while the coupled-states approximation was used to extend the H2 rate coefficients to j1 = 30, where j1 is the angular momentum quantum number of C6H-. State-to-state rate coefficients were obtained for temperatures ranging from 2 to 100 K. The rate coefficients for H2 collisions for Δj1 = -1 transitions are of the order of 10-10 cm3 s-1, a factor of 2 to 3 greater than those of He. Propensity rules are discussed. The collisional excitation rate coefficients produced here impact astrophysical modelling since they are required for obtaining accurate C6H- level populations and line emission for regions that contain anions.

How Does Lithiation Affect Electro-Optical Features of Corannulene (C20H10) and Quadrannulene (C16H8) Buckybowls?

NASA Astrophysics Data System (ADS)

Shakerzadeh, Ehsan; Kazemimoghadam, Fatemeh; Anota, Ernesto Chigo

2018-04-01

The influence of lithiation process on the HOMO-LUMO gap and the first hyperpolarizability values of corannulene (C20H10) and quadrannulene (C16H8) buckybowls are investigated using density functional theory (DFT) calculations. Lithiation is performed at the bridging position of the C-C bond of benzene rings of quadrannulene and corannulene. The HOMO-LUMO gap of lithiated buckybowls is reduced with respect to pristine ones. The results indicate that the lithiation process causes the remarkable enhancement of the first hyperpolarizability. The time-dependent density functional theory (TD-DFT) calculations are also performed to understand how lithiation affects the first hyperpolarizability values. The present results might be valuable for further theoretical and experimental studies on the electronic and nonlinear optical properties of buckybowl compounds.

Rhodium(III)-Catalyzed Amidation of Unactivated C(sp(3) )-H Bonds.

PubMed

Wang, He; Tang, Guodong; Li, Xingwei

2015-10-26

Nitrogenation by direct functionalization of C-H bonds represents an important strategy for constructing C-N bonds. Rhodium(III)-catalyzed direct amidation of unactivated C(sp(3) )-H bonds is rare, especially under mild reaction conditions. Herein, a broad scope of C(sp(3) )-H bonds are amidated under rhodium catalysis in high efficiency using 3-substituted 1,4,2-dioxazol-5-ones as the amide source. The protocol broadens the scope of rhodium(III)-catalyzed C(sp(3) )-H activation chemistry, and is applicable to the late-stage functionalization of natural products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Layered Solution Crystal Growth Technique and the Crystal Structure of (C 6H 5C 2H 4NH 3) 2PbCl 4

NASA Astrophysics Data System (ADS)

Mitzi, D. B.

1999-07-01

Single crystals of the organic-inorganic perovskite (C6H5C2H4NH3)2PbCl4 have been grown at room temperature using a layered solution approach. The bottom solution layer, contained within a long straight tube, consists of PbCl2 dissolved in concentrated aqueous HCl. A less dense layer of methanol is carefully placed on top of the HCl/PbCl2 solution using a syringe. Finally, a stoichiometric quantity of C6H5C2H4NH2 (relative to the PbCl2) is added to the top of the column. As the layers slowly diffuse together, well-formed crystals of (C6H5C2H4NH3)2PbCl4 appear near the interface between the HCl/PbCl2 and C6H5C2H4NH2 solutions. The thick, plate-like crystals are well suited for X-ray crystallography studies. Room temperature intensity data were refined using a triclinic (Poverline1) cell (a=11.1463(3) Å, b=11.2181(3) Å, c=17.6966(5) Å, α= 99.173(1)°, β=104.634(1)°, γ=89.999(1)°, V=2111.8(1) Å3, Z=4, Rf/Rw=0.031/0.044). The organic-inorganic layered perovskite structure features well-ordered sheets of corner-sharing distorted PbCl6 octahedra separated by bilayers of phenethylammonium cations. Tilting and rotation of the PbCl6 octahedra within the perovskite sheets, coupled with organic cation ordering, leads to the unusual in-sheet 2ap×2ap superstructure, where ap is the lattice constant for the ideal cubic perovskite.

Dynamics of the C/H and C/F exchanges in the reaction of 3P carbon atoms with vinyl fluoride

NASA Astrophysics Data System (ADS)

Lee, Shih-Huang; Chen, Wei-Kan; Chin, Chih-Hao; Huang, Wen-Jian

2013-08-01

Two product channels C3H2F + H and C3H3 + F were identified in the reaction of C(3P) atoms with vinyl fluoride (C2H3F) at collision energy 3.7 kcal mol-1 in a crossed molecular-beam apparatus using selective photoionization. Time-of-flight (TOF) spectra of products C3H2F and C3H3 were measured at 12-16 laboratory angles as well as a TOF spectrum of atomic F, a counter part of C3H3, was recorded at single laboratory angle. From the best simulation of product TOF spectra, translational-energy distributions at seven scattering angles and a nearly isotropic (forward and backward peaked) angular distribution were derivable for exit channel C3H2F + H (C3H3 + F) that has average kinetic-energy release of 14.5 (4.9) kcal mol-1. Products C3H2F + H and C3H3 + F were estimated to have a branching ratio of ˜53:47. Furthermore, TOF spectra and photoionization spectra of products C3H2F and C3H3 were measured at laboratory angle 62° with photoionization energy ranging from 7 eV to 11.6 eV. The appearance of TOF spectra is insensitive to photon energy, implying that only single species overwhelmingly contributes to products C3H2F and C3H3. HCCCHF (H2CCCH) was identified as the dominant species based on the measured ionization threshold of 8.3 ± 0.2 (8.6 ± 0.2) eV and the maximal translational-energy release. The C/H and C/F exchange mechanisms are stated.

U.S. EPA, Pesticide Product Label, O-C CLENCIDE DETERGENT SANITIZER, 01/27/1981

EPA Pesticide Factsheets

2011-04-21

... 11 ... III .... 01111 lOll fOl' ~ to ;j lIIiuUh!S. H"llIm·,'. lll' .... f' \\lolita Iu)I.!1Il.· ',\\tll', .tI,,j dl\\. ro: ll.Jt :"dIlLln·:-, . f'an [0 1t'1II0V(! .~IW"'''' 111111 ;twi Il";I\\'\\' soli. ...

Ligand-accelerated non-directed C-H functionalization of arenes.

PubMed

Wang, Peng; Verma, Pritha; Xia, Guoqin; Shi, Jun; Qiao, Jennifer X; Tao, Shiwei; Cheng, Peter T W; Poss, Michael A; Farmer, Marcus E; Yeung, Kap-Sun; Yu, Jin-Quan

2017-11-22

The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.

Ligand-accelerated non-directed C-H functionalization of arenes

NASA Astrophysics Data System (ADS)

Wang, Peng; Verma, Pritha; Xia, Guoqin; Shi, Jun; Qiao, Jennifer X.; Tao, Shiwei; Cheng, Peter T. W.; Poss, Michael A.; Farmer, Marcus E.; Yeung, Kap-Sun; Yu, Jin-Quan

2017-11-01

The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.

Tuning the conductance of H2O@C60 by position of the encapsulated H2O

PubMed Central

Zhu, Chengbo; Wang, Xiaolin

2015-01-01

The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

Spin-forbidden and spin-allowed cyclopropenone (c-H{sub 2}C{sub 3}O) formation in interstellar medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmadvand, Seyedsaeid; Zaari, Ryan R.; Varganov, Sergey A., E-mail: svarganov@unr.edu

2014-11-10

Three proposed mechanisms of cyclopropenone (c-H{sub 2}C{sub 3}O) formation from neutral species are studied using high-level electronic structure methods in combination with nonadiabatic transition state and collision theories to deduce the likelihood of each reaction mechanism under interstellar conditions. The spin-forbidden reaction involving the singlet electronic state of cyclopenylidene (c-C{sub 3}H{sub 2}) and the triplet state of atomic oxygen is studied using nonadiabatic transition state theory to predict the rate constant for c-H{sub 2}C{sub 3}O formation. The spin-allowed reactions of c-C{sub 3}H{sub 2} with molecular oxygen and acetylene with carbon monoxide were also investigated. The reaction involving the ground electronicmore » states of acetylene and carbon monoxide has a very large reaction barrier and is unlikely to contribute to c-H{sub 2}C{sub 3}O formation in interstellar medium. The spin-forbidden reaction of c-C{sub 3}H{sub 2} with atomic oxygen, despite the high probability of nonadiabatic transition between the triplet and singlet states, was found to have a very small rate constant due to the presence of a small (3.8 kcal mol{sup –1}) reaction barrier. In contrast, the spin-allowed reaction between c-C{sub 3}H{sub 2} and molecular oxygen is found to be barrierless, and therefore can be an important path to the formation of c-H{sub 2}C{sub 3}O molecule in interstellar environment.« less

Do Genetic Modifiers of HDL-C and Triglyceride Levels also Modify Their Response to a Lifestyle Intervention in the Setting of Obesity and Type-2 Diabetes Mellitus? The Look AHEAD Study

PubMed Central

Huggins, Gordon S.; Papandonatos, George D.; Erar, Bahar; Belalcazar, L. Maria; Brautbar, Ariel; Ballantyne, Christie; Kitabchi, Abbas E.; Wagenknecht, Lynne E.; Knowler, William C.; Pownall, Henry J.; Wing, Rena R.; Peter, Inga; McCaffery, Jeanne M.

2014-01-01

Background High-density lipoprotein cholesterol (HDL-C) and triglycerides are cardiovascular risk factors susceptible to lifestyle behavior modification and genetics. We hypothesized that genetic variants identified by genome-wide association studies (GWASs) as associated with HDL-C or triglyceride levels will modify 1-year treatment response to an intensive lifestyle intervention (ILI), relative to a usual care of diabetes support and education (DSE). Methods and Results We evaluated 82 SNPs, representing 31 loci demonstrated by GWAS to be associated with HDL-C and/or triglycerides, in 3,561 participants who consented for genetic studies and met eligibility criteria. Variants associated with higher baseline HDL-C levels, cholesterol ester transfer protein (CETP) rs3764261 and hepatic lipase (LIPC) rs8034802, were found to be associated with HDL-C increases with ILI (p=0.0038 and 0.013, respectively) and had nominally significant treatment interactions (p=0.047 and 0.046, respectively). The fatty acid desaturase-2 (FADS-2) rs1535 variant, associated with low baseline HDL-C (p=0.017), was associated with HDL-C increases with ILI (0.0037) and had a nominal treatment interaction (p= 0.035). ApoB (rs693) and LIPC (rs8034802) SNPs showed nominally significant associations with HDL-C and triglyceride changes with ILI and a treatment interaction (p<0.05). A PGS1 SNP (rs4082919) showed the most significant triglyceride treatment interaction in the full cohort (p=0.0009). Conclusions This is the first study to identify genetic variants modifying lipid responses to a randomized lifestyle behavior intervention in overweight/obese diabetic individuals. The effect of genetic factors on lipid changes may differ from the effects on baseline lipids and are modifiable by behavioral intervention. PMID:23861364

Mechanistic Comparison Between Pd-Catalyzed Ligand Directed C-H Chlorination and C-H Acetoxylation

PubMed Central

Stowers, Kara J.; Sanford, Melanie S.

2009-01-01

This communication describes detailed investigations of the mechanism of the Pd-catalyzed C-H chlorination and acetoxylation of 2-ortho-tolylpyridine. Under the conditions examined, both reactions proceed via rate limiting cyclopalladation. However, substrate and catalyst order as well as Hammett data indicate that the intimate mechanism of cyclopalladation differs significantly between PdCl2-catalyzed chlorination and Pd(OAc)2-catalyzed acetoxylation. PMID:19754074

Analysis of 2009 pandemic influenza A/H1N1 outcomes in 19 European countries: association with completeness of national strategic plans

PubMed Central

Meeyai, Aronrag; Cooper, Ben S; Coker, Richard

2013-01-01

Objective To describe changes in reported influenza activity associated with the 2009 H1N1 pandemic in European countries and determine whether there is a correlation between these changes and completeness of national strategic pandemic preparedness. Design A retrospective correlational study. Setting Countries were included if their national strategic plans had previously been analysed and if weekly influenza-like illness (ILI) data from sentinel networks between week 21, 2006 and week 20, 2010 were more than 50% complete. Outcome measures For each country we calculated three outcomes: the percentage change in ILI peak height during the pandemic relative to the prepandemic mean; the timing of the ILI peak and the percentage change in total cases relative to the prepandemic mean. Correlations between these outcomes and completeness of a country's national strategic pandemic preparedness plan were assessed using the Pearson product–moment correlation coefficient. Results Nineteen countries were included. The ILI peak occurred earlier than the mean seasonal peak in 17 countries. In 14 countries the pandemic peak was higher than the seasonal peak, though the difference was large only in Norway, the UK and Greece. Nine countries experienced more total ILI cases during the pandemic compared with the mean for prepandemic years. Five countries experienced two distinct pandemic peaks. There was no clear pattern of correlation between overall completeness of national strategic plans and pandemic influenza outcome measures and no evidence of association between these outcomes and components of pandemic plans that might plausibly affect influenza outcomes (public health interventions, vaccination, antiviral use, public communication). Amongst the 17 countries with a clear pandemic peak, only the correlation between planning for essential services and change in total ILI cases significantly differed from zero: correlation coefficient (95% CI) 0.50 (0.02, 0.79). Conclusions

Synthetic, Infrared, 1Hand 13CNMR Spectral Studies on N-(p-Substituted Phenyl)-p-Substituted Benzenesulphonamides, p-X'C6H4SO2NH- (p-XC6H4), where X' or X = H, CH3, C2H5, F, Cl or Br

NASA Astrophysics Data System (ADS)

Gowda, B. Thimme; Jayalakshmi, K. L.; Shetty, Mahesha

2004-05-01

Thirty N-(p-substituted phenyl)-p-substituted benzenesulphonamides of the general formula, p-X'C6H4SO2NH(p-XC6H4), where X' or X = H, CH3, C2H5, F, Cl or Br, are synthesised and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution are measured. The N-H stretching vibrational frequencies, νN-H vary in the range 3334 - 3219 cm-1, while the asymmetric and symmetric SO2 vibrations appear in the ranges 1377 - 1311 cm-1 and 1182 - 1151 cm-1, respectively. The compounds exhibit S-N and C-N stretching vibrational absorptions in the ranges 937 - 898 cm-1 and 1310 - 1180 cm-1, respectively. There are no particular trends in the variation of these frequencies on substitution with either electron withdrawing or electron donating groups. The 1H and 13C chemical shifts of N-(p-substituted phenyl)-p-substituted benzenesulphonamides, are assigned to various protons and carbons of the two benzene rings. Further, incremental shifts of the ring protons and carbons due to -SO2NH(p-XC6H4) groups in the compounds of the formula, C6H5SO2NH(p-XC6H4), and p-X'C6H4SO2- and p-X'C6H4SO2NH- groups in the compounds of the formula, p-X'C6H4SO2NH(C6H5) are computed and used to calculate the 1H and 13C chemical shifts of the parallely substituted compounds of the general formula p-X'C6H4SO2NH(p-XC6H4). The computed values agree well with the observed chemical shifts. The above incremental shifts are found to correlate with the Hammett substituent parameters.

Selective sp3 C-H alkylation via polarity-match-based cross-coupling.

PubMed

Le, Chip; Liang, Yufan; Evans, Ryan W; Li, Ximing; MacMillan, David W C

2017-07-06

The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp 3 )-C(sp 2 ) coupling, there is a growing demand for C-H alkylation reactions, wherein sp 3 C-H bonds are replaced with sp 3 C-alkyl groups. Here we describe a polarity-match-based selective sp 3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp 3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

Selective sp3 C-H alkylation via polarity-match-based cross-coupling

NASA Astrophysics Data System (ADS)

Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

2017-07-01

The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp3)-C(sp2) coupling, there is a growing demand for C-H alkylation reactions, wherein sp3 C-H bonds are replaced with sp3 C-alkyl groups. Here we describe a polarity-match-based selective sp3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

Epitaxial growth of 6H silicon carbide in the temperature range 1320 C to 1390 C

NASA Technical Reports Server (NTRS)

Will, H. A.; Powell, J. A.

1974-01-01

High-quality epitaxial layers of 6H SiC have been grown on 6H SiC substrates with the grown direction perpendicular to the crystal c-axis. The growth was by chemical vapor deposition from methyltrichlorosilane (CH3SiCl3) in hydrogen at temperatures in the range of 1320 to 1390 C. Epitaxial layers up to 80 microns thick were grown at rates of 0.4 microns/min. Attempts at growth on the (0001) plane of 6H SiC substrates under similar conditions resulted in polycrystalline cubic SiC layers. Optical and X-ray diffraction techniques were used to characterize the grown layers.

31 CFR Appendix H to Subpart C of... - United States Mint

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false United States Mint H Appendix H to Subpart C of Part 1 Money and Finance: Treasury Office of the Secretary of the Treasury DISCLOSURE OF RECORDS Privacy Act Pt. 1, Subpt. C, App. H Appendix H to Subpart C of Part 1—United States Mint 1. In...

Catalyst-Dependent Chemoselective Formal Insertion of Diazo Compounds into C-C or C-H Bonds of 1,3-Dicarbonyl Compounds.

PubMed

Liu, Zhaohong; Sivaguru, Paramasivam; Zanoni, Giuseppe; Anderson, Edward A; Bi, Xihe

2018-05-08

A catalyst-dependent chemoselective one-carbon insertion of diazo compounds into the C-C or C-H bonds of 1,3-dicarbonyl species is reported. In the presence of silver(I) triflate, diazo insertion into the C(=O)-C bond of the 1,3-dicarbonyl substrate leads to a 1,4-dicarbonyl product containing an all-carbon α-quaternary center. This reaction constitutes the first example of an insertion of diazo-derived carbenoids into acyclic C-C bonds. When instead scandium(III) triflate was applied as the catalyst, the reaction pathway switched to formal C-H insertion, affording 2-alkylated 1,3-dicarbonyl products. Different reaction pathways are proposed to account for this powerful catalyst-dependent chemoselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preliminary Analysis of LORAN-C System Reliability for Civil Aviation.

DTIC Science & Technology

1981-09-01

overviev of the analysis technique. Section 3 describes the computerized LORAN-C coverage model which is used extensively in the reliability analysis...Xth Plenary Assembly, Geneva, 1963, published by International Telecomunications Union. S. Braff, R., Computer program to calculate a Karkov Chain Reliability Model, unpublished york, MITRE Corporation. A-1 I.° , 44J Ili *Y 0E 00 ...F i8 1110 Prelim inary Analysis of Program Engineering & LORAN’C System ReliabilityMaintenance Service i ~Washington. D.C.

Ultra high voltage MOS controlled 4H-SiC power switching devices

NASA Astrophysics Data System (ADS)

Ryu, S.; Capell, C.; Van Brunt, E.; Jonas, C.; O'Loughlin, M.; Clayton, J.; Lam, K.; Pala, V.; Hull, B.; Lemma, Y.; Lichtenwalner, D.; Zhang, Q. J.; Richmond, J.; Butler, P.; Grider, D.; Casady, J.; Allen, S.; Palmour, J.; Hinojosa, M.; Tipton, C. W.; Scozzie, C.

2015-08-01

Ultra high voltage (UHV, >15 kV) 4H-silicon carbide (SiC) power devices have the potential to significantly improve the system performance, reliability, and cost of energy conversion systems by providing reduced part count, simplified circuit topology, and reduced switching losses. In this paper, we compare the two MOS based UHV 4H-SiC power switching devices; 15 kV 4H-SiC MOSFETs and 15 kV 4H-SiC n-IGBTs. The 15 kV 4H-SiC MOSFET shows a specific on-resistance of 204 mΩ cm2 at 25 °C, which increased to 570 mΩ cm2 at 150 °C. The 15 kV 4H-SiC MOSFET provides low, temperature-independent, switching losses which makes the device more attractive for applications that require higher switching frequencies. The 15 kV 4H-SiC n-IGBT shows a significantly lower forward voltage drop (VF), along with reasonable switching performance, which make it a very attractive device for high voltage applications with lower switching frequency requirements. An electrothermal analysis showed that the 15 kV 4H-SiC n-IGBT outperforms the 15 kV 4H-SiC MOSFET for applications with switching frequencies of less than 5 kHz. It was also shown that the use of a carrier storage layer (CSL) can significantly improve the conduction performance of the 15 kV 4H-SiC n-IGBTs.

The Rate Constant for the Reaction H + C2H5 at T = 295 - 150K

NASA Technical Reports Server (NTRS)

Pimentel, Andre S.; Payne, Walter A.; Nesbitt, Fred L.; Cody, Regina J.; Stief, Louis J.

2004-01-01

The reaction between the hydrogen atom and the ethyl (C2H3) radical is predicted by photochemical modeling to be the most important loss process for C2H5 radicals in the atmospheres of Jupiter and Saturn. This reaction is also one of the major sources for the methyl radicals in these atmospheres. These two simplest hydrocarbon radicals are the initial species for the synthesis of larger hydrocarbons. Previous measurements of the rate constant for the H + C2H5 reaction varied by a factor of five at room temperature, and some studies showed a dependence upon temperature while others showed no such dependence. In addition, the previous studies were at higher temperatures and generally higher pressures than that needed for use in planetary atmospheric models. The rate constant for the reaction H + C2H5 has been measured directly at T = 150, 202 and 295 K and at P = 1.0 Torr He for all temperatures and additionally at P = 0.5 and 2.0 Torr He at T = 202 K. The measurements were performed in a discharge - fast flow system. The decay of the C2H5 radical in the presence of excess hydrogen was monitored by low-energy electron impact mass spectrometry under pseudo-first order conditions. H atoms and C2H5 radicals were generated rapidly and simultaneously by the reaction of fluorine atoms with H2 and C2H6, respectively. The total rate constant was found to be temperature and pressure independent. The measured total rate constant at each temperature are: k(sub 1)(295K) = (1.02+/-0.24)x10(exp -10), k(sub 1)(202K) = (1.02+/-0.22)x10(exp -10) and k(sub 1)(150K) = (0.93+/-0.21)x10(exp -10), all in units of cu cm/molecule/s. The total rate constant derived from all the combined measurements is k(sub 1) = (l.03+/-0.17)x10(exp -10) cu cm/molecule/s. At room temperature our results are about a factor of two higher than the recommended rate constant and a factor of three lower than the most recently published study.

Sc2C2@D3h(14246)-C74: A Missing Piece of the Clusterfullerene Puzzle.

PubMed

Wang, Yaofeng; Tang, Qiangqiang; Feng, Lai; Chen, Ning

2017-02-20

Clusterfullerenes with variable carbon cages have been extensively studied in recent years. However, despite all these efforts, C 74 cage-based clusterfullerene remains a missing piece of the puzzle. Herein, we show that single-crystal X-ray crystallographic analysis unambiguously assigns the previously reported dimetallofullerene Sc 2 @C 76 to a novel carbide clusterfullerene, Sc 2 C 2 @D 3h (14246)-C 74 , the first experimentally proven clusterfullerene with a C 74 cage. In addition, Sc 2 C 2 @D 3h (14246)-C 74 was charaterized by mass spectrometry, ultraviolet-visible-near-infrared absorption spectroscopy, 45 Sc nuclear magnetic resonance, and cyclic voltammetry. Comparative studies of the motion of the carbide cluster in Sc 2 C 2 @D 3h (14246)-C 74 and Sc 2 C 2 @C 2n (n = 40-44) revealed that a combination of factors, involving both the shape and size of the cage, is crucial in dictating the cluster motion. Moreover, structural studies of D 3h (14246)-C 74 revealed that it can be easily converted to C s (10528)-C 72 and T d (19151)-C 76 cages via C 2 desertion/insertion and Stone-Wales transformation. This suggests that D 3h (14246)-C 74 might play an important role in the growth pathway of clusterfullerenes.

[Comparison of sentinel surveillance of influenza like infections in Martinique and in Guadeloupe during influenza A(H1N) 2009 pandemic: use of a phone survey and hospital surveillance].

PubMed

Ledrans, M; Cassadou, S; Chappert, J-L; Quénel, P

2011-12-01

Sentinel general practitioner networks monitor influenza-like infections (ILI) in Martinique and in Guadeloupe (French West Indies). During the A(H1N1)2009 pandemic, they gave an ILI incidence estimation higher in Martinique than in Guadeloupe. In October 2009, a telephonic survey was launched in both islands to assess the number of ILI diagnoses performed by general practitioners since the beginning of the pandemic. This paper compares the results of sentinel surveillance, of telephonic survey and of hospital surveillance in Guadeloupe and in Martinique. On each island, the sentinel network gathers a representative sample of voluntary general practitioners. Each week, they report the number of ILI they diagnosed the past week. Times series of these weekly numbers were modelized using the Serfling method with the upper limit of the confidence interval of the expected value representing the epidemic threshold. The telephone survey was conducted from October 2, 2009 to October 12, 2009 in Martinique and from October 13, 2009 to October 21, 2009 in Guadeloupe. The quota method was used for sampling individuals older than 14 years, leading to 507 interviews in Guadeloupe and 508 in Martinique. The epidemic lasted 12 weeks in both islands, from August 3 to October 25 in Martinique and from August 17 to November 8 in Guadeloupe. During August and September, estimated attack rate in Martinique was 5.52% (CI95: 5.23-5.83) from the sentinel network versus 8.3% (CI95: 6.0-11.0) from the telephone survey. In Guadeloupe, it was 2.13% (CI95: 1.97-2.24) from the sentinel network versus 6.9% (CI95: 4.8-9.5) from the telephone survey. An equivalent number of confirmed hospitalized cases was observed in the two islands. These results suggest that the sentinel network underestimates ILI incidence in Guadeloupe. According to Emergency Room activity for ILI, it seems possible that ILI incidence was actually higher in Martinique. A lower proportion of swab sampling among ILI

Reinvestigation of the elementary chemical kinetics of the reaction C2H5(•) + HBr (HI) → C2H6 + Br(•) (I(•)) in the range 293-623 K and its implication on the thermochemical parameters of C2H5(•) free radical.

PubMed

Leplat, N; Wokaun, A; Rossi, M J

2013-11-14

A reinvestigation of the absolute rate constants of the metathesis reactions C2H5• + HBr → C2H6 + Br• (R1) and C2H5• + HI → C2H6 + I• (R2) has been performed and led to the following Arrhenius expressions: k1 = 3.69(±0.95) × 10–11 exp(−10.62(±0.66)/RT), k2 = 1.20(±0.38) × 10–11 exp(−7.12(±1.059)/RT) in the temperature range 293–623 K (A/cm3 molecule–1 s–1, Ea/kJ mol–1). The study has been performed using a Knudsen reactor coupled to single-photon (VUV) photoionization mass spectrometer (SPIMS). Hydrocarbon free radicals have been generated externally before admission into the Knudsen reactor according to two different chemical schemes, enabling the generation of thermalized C2H5• free radicals. A minor correction to k1 and k2 for the wall loss of C2H5• (kw) has been applied throughout the temperature range. The obtained results are consistent regarding both the disappearance of C2H5• and the formation of closed shell products (n-C4H10, C2H4, C2H6), indicating that the chemical mechanism is largely understood and complete. Thermochemical parameters for C2H5• free radical resulting from the present kinetic measurements are discussed and point toward a slightly lower value for the standard heat of formation ΔfH298°(C2H5•) compared to some presently recommended values. On the basis of the present results and suitable data on the reverse reaction taken from the literature, we recommend ΔfH298°(C2H5•) = 117.3 ± 3.1 kJ/mol resulting from an average of “third law” evaluations using S298°(C2H5•) = 242.9 ± 4.6 J/K mol. The present work yields a standard heat of formation in satisfactory agreement with the results obtained by W. Tsang (ΔfH298°(C2H5•) = 119 ± 2 kJ/mol) despite using two very different experimental techniques.

Photodissociation of pyrene cations: structure and energetics from C16H10(+) to C14(+) and almost everything in between.

PubMed

West, Brandi; Useli-Bacchitta, Francesca; Sabbah, Hassan; Blanchet, Valérie; Bodi, Andras; Mayer, Paul M; Joblin, Christine

2014-09-11

The unimolecular dissociation of the pyrene radical cation, C16H10(+•), has been explored using a combination of computational techniques and experimental approaches, such as multiple photon absorption in the cold ion trap Piège à Ions pour la Recherche et l'Etude de Nouvelles Espèces Astrochimiques (PIRENEA) and imaging photoelectron photoion coincidence spectrometry (iPEPICO). In total, 22 reactions, involving the fragmentation cascade (H, C2H2, and C4H2 loss) from the pyrene radical cation down to the C14(+•) fragment ion, have been studied using PIRENEA. Branching ratios have been measured for reactions from C16H10(+•), C16H8(+•), and C16H5(+). Density functional theory calculations of the fragmentation pathways observed experimentally and postulated theoretically lead to 17 unique structures. One important prediction is the opening of the pyrene ring system starting from the C16H4(+•) radical. In the iPEPICO experiments, only two reactions could be studied, namely, R1 C16H10(+•) → C16H9(+) + H (m/z = 201) and R2 C16H9(+) → C16H8(+•) + H (m/z = 200). The activation energies for these reactions were determined to be 5.4 ± 1.2 and 3.3 ± 1.1 eV, respectively.

Loss Process for the C2H5 Radical in the Atmospheres of Jupiter and Saturn: First Direct, Absolute Measurement of the Rate Constant for the Reaction H + C2H5 at Low Pressure and Temperature

NASA Astrophysics Data System (ADS)

Stief, L. J.; Pimentel, A. S.; Payne, W. A.; Nesbitt, F. L.; Cody, R. J.

2003-05-01

Photochemical models of the atmospheres of Jupiter and Saturn predict the reaction H + C2H5 to be the most important loss process for C2H5 in these atmospheres. In addition, the reaction channel H + C2H5 -> 2 CH3 is a significant source of the methyl radical. There are only two relatively modern studies of the H + C2H5 reaction, both of which depend on extensive modeling involving eight elementary reactions. The motivation for the present study is the lack of direct, absolute measurements of the rate constant for the H + C2H5 reaction at low pressures and temperatures appropriate for outer planet models. In the present experiments the reactants H and C2H5 are rapidly and simultaneously generated by reaction of F with appropriate mixtures of H2 and C2H6. Using the technique of discharge-flow with collision-free sampling to a mass spectrometer, we monitor the decay of C2H5 in excess H. In contrast to previous studies of this reaction, the primary H + C2H5 reaction is isolated and the radical decays only by reaction with H and by loss at the wall. Secondary reactions such as the self-reaction of C2H5 are negligible. At P = 1 Torr He we measure k (298K) = 1.13 x 10-10 cm3 molecule-1 s-1 and k (202K) = 1.18 x 10-10 cm3 molecule-1 s-1. Experiments at T = 155 K are in progress. The reaction is temperature independent as expected based on studies of other atom-radical reactions. Our result at T = 298 K lies between those of the two relatively modern but complex studies of this reaction. The present total rate constant data and planned product yield studies at low pressures and temperatures will then be available for use in future photochemical models of the atmospheres of the outer planets. The Planetary Atmospheres Program of NASA Headquarters is supporting this research.

Manganese-catalysed benzylic C(sp3)-H amination for late-stage functionalization

NASA Astrophysics Data System (ADS)

Clark, Joseph R.; Feng, Kaibo; Sookezian, Anasheh; White, M. Christina

2018-06-01

Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst [MnIII(ClPc)] for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the [MnIII(ClPc)]-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.

Manganese-catalysed benzylic C(sp3)-H amination for late-stage functionalization.

PubMed

Clark, Joseph R; Feng, Kaibo; Sookezian, Anasheh; White, M Christina

2018-06-01

Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst [MnIII(ClPc)] for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the [MnIII(ClPc)]-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.

Low Temperature Ohmic Contact Formation of Ni2Si on N-type 4H-SiC and 6H-SiC

NASA Technical Reports Server (NTRS)

Elsamadicy, A. M.; Ila, D.; Zimmerman, R.; Muntele, C.; Evelyn, L.; Muntele, I.; Poker, D. B.; Hensley, D.; Hirvonen, J. K.; Demaree, J. D.;

Late metal carbene complexes generated by multiple C-H activations: examining the continuum of M=C bond reactivity.

PubMed

Whited, Matthew T; Grubbs, Robert H

2009-10-20

Unactivated C(sp(3))-H bonds are ubiquitous in organic chemicals and hydrocarbon feedstocks. However, these resources remain largely untapped, and the development of efficient homogeneous methods for hydrocarbon functionalization by C-H activation is an attractive and unresolved challenge for synthetic chemists. Transition-metal catalysis offers an attractive possible means for achieving selective, catalytic C-H functionalization given the thermodynamically favorable nature of many desirable partial oxidation schemes and the propensity of transition-metal complexes to cleave C-H bonds. Selective C-H activation, typically by a single cleavage event to produce M-C(sp(3)) products, is possible through myriad reported transition-metal species. In contrast, several recent reports have shown that late transition metals may react with certain substrates to perform multiple C-H activations, generating M=C(sp(2)) complexes for further elaboration. In light of the rich reactivity of metal-bound carbenes, such a route could open a new manifold of reactivity for catalytic C-H functionalization, and we have targeted this strategy in our studies. In this Account, we highlight several early examples of late transition-metal complexes that have been shown to generate metal-bound carbenes by multiple C-H activations and briefly examine factors leading to the selective generation of metal carbenes through this route. Using these reports as a backdrop, we focus on the double C-H activation of ethers and amines at iridium complexes supported by Ozerov's amidophosphine PNP ligand (PNP = [N(2-P(i)Pr(2)-4-Me-C(6)H(3))(2)](-)), allowing isolation of unusual square-planar iridium(I) carbenes. These species exhibit reactivity that is distinct from the archetypal Fischer and Schrock designations. We present experimental and theoretical studies showing that, like the classical square-planar iridium(I) organometallics, these complexes are best described as nucleophilic at iridium. We discuss

40 CFR 721.10025 - 10H-Phenothiazine, ar, ar′-(C9-rich C8-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 10H-Phenothiazine, ar, arâ²-(C9-rich... Significant New Uses for Specific Chemical Substances § 721.10025 10H-Phenothiazine, ar, ar′-(C9-rich C8-10... chemical substances identified as 10H-phenothiazine, ar, ar′-(C9-rich C8-10-branched alkyl) derivs (PMN P...

Epidemiology and viral etiology of the influenza-like illness in corsica during the 2012-2013 Winter: an analysis of several sentinel surveillance systems.

PubMed

Minodier, Laëtitia; Arena, Christophe; Heuze, Guillaume; Ruello, Marc; Amoros, Jean Pierre; Souty, Cécile; Varesi, Laurent; Falchi, Alessandra

2014-01-01

Influenza-like illness (ILI) surveillance is important to identify circulating and emerging/reemerging strains and unusual epidemiological trends. The present study aimed to give an accurate picture of the 2012-2013 ILI outbreak in Corsica by combining data from several surveillance systems: general practice, emergency general practice, hospital emergency units, intensive care units, and nursing homes. Twenty-eight respiratory viruses were retrospectively investigated from patients in general practice with ILI. Sequence analysis of the genetic changes in the hemagglutinin gene of influenza viruses (A(H1N1)pdm2009, A(H3N2) and B) was performed. The trends in ILI/influenza consultation rates and the relative illness ratios (RIRs) of having an ILI consultation were estimated by age group for the different surveillance systems analyzed. Of the 182 ILI patients enrolled by general practitioners, 57.7% tested positive for influenza viruses. Phylogenetic analyses suggested a genetic drift for influenza B and A(H3N2) viruses. The ILI/influenza surveillance systems showed similar trends and were well correlated. In accordance with virological data, the RIRs of having an ILI consultation were highest among the young (<15 years old) and decreased with age. No clusters of acute respiratory illness were declared by the sentinel nursing homes. This study is noteworthy in that it is the first extensive description of the 2012-2013 ILI outbreak in Corsica as monitored through several surveillance systems. To improve ILI surveillance in Corsica, a consortium that links together the complementary regional surveillance ILI systems described here is being implemented.

Metal-organic cooperative catalysis in C-H and C-C bond activation and its concurrent recovery.

PubMed

Park, Young Jun; Park, Jung-Woo; Jun, Chul-Ho

2008-02-01

The development of an efficient catalytic activation (cleavage) system for C-H and C-C bonds is an important challenge in organic synthesis, because these bonds comprise a variety of organic molecules such as natural products, petroleum oils, and polymers on the earth. Among many elegant approaches utilizing transition metals to activate C-H and C-C bonds facilely, chelation-assisted protocols based on the coordinating ability of an organic moiety have attracted great attention, though they have often suffered from the need for an intact coordinating group in a substrate. In this Account, we describe our entire efforts to activate C-H or C-C bonds adjacent to carbonyl groups by employing a new concept of metal-organic cooperative catalysis (MOCC), which enables the temporal installation of a 2-aminopyridyl group into common aldehydes or ketones in a catalytic way. Consequently, a series of new catalytic reactions such as alcohol hydroacylation, oxo-ester synthesis, C-C triple bond cleavage, hydrative dimerization of alkynes, and skeletal rearrangements of cyclic ketones was realized through MOCC. In particular, in the quest for an optimized MOCC system composed of a Wilkinson's catalyst (Ph 3P) 3RhCl and an organic catalyst (2-amino-3-picoline), surprising efficiency enhancements could be achieved when benzoic acid and aniline were introduced as promoters for the aldimine formation process. Furthermore, a notable accomplishment of C-C bond activation has been made using 2-amino-3-picoline as a temporary chelating auxiliary in the reactions of unstrained ketones with various terminal olefins and Wilkinson's catalyst. In the case of seven-membered cyclic ketones, an interesting ring contraction to five- or six-membered ones takes place through skeletal rearrangements initiated by the C-C bond activation of MOCC. On the other hand, the fundamental advances of these catalytic systems into recyclable processes could be achieved by immobilizing both metal and organic

Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

2003-01-01

This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

Carbon Dioxide-Mediated C(sp3)-H Arylation of Amine Substrates.

PubMed

Kapoor, Mohit; Liu, Daniel; Young, Michael C

2018-05-25

Elaborating amines via C-H functionalization has been an important area of research over the past decade but has generally relied on an added directing group or sterically hindered amine approach. Since free-amine-directed C(sp 3 )-H activation is still primarily limited to cyclization reactions and to improve the sustainability and reaction scope of amine-based C-H activation, we present a strategy using CO 2 in the form of dry ice that facilitates intermolecular C-H arylation. This methodology has been used to enable an operationally simple procedure whereby 1° and 2° aliphatic amines can be arylated selectively at their γ-C-H positions. In addition to potentially serving as a directing group, CO 2 has also been demonstrated to curtail the oxidation of sensitive amine substrates.

Epitaxy of boron phosphide on AlN, 4H-SiC, 3C-SiC and ZrB2 substrates

NASA Astrophysics Data System (ADS)

Padavala, Balabalaji

The semiconductor boron phosphide (BP) has many outstanding features making it attractive for developing various electronic devices, including neutron detectors. In order to improve the efficiency of these devices, BP must have high crystal quality along with the best possible electrical properties. This research is focused on growing high quality crystalline BP films on a variety of superior substrates like AlN, 4H-SiC, 3C-SiC and ZrB2 by chemical vapor deposition. In particular, the influence of various parameters such as temperature, reactant flow rates, and substrate type and its crystalline orientation on the properties of BP films were studied in detail. Twin-free BP films were produced by depositing on off-axis 4H-SiC(0001) substrate tilted 4° toward [11¯00] and crystal symmetry matched zincblende 3C-SiC. BP crystalline quality improved at higher deposition temperature (1200°C) when deposited on AlN, 4H-SiC, whereas increased strain in 3C-SiC and increased boron segregation in ZrB2 at higher temperatures limited the best deposition temperature to below 1200°C. In addition, higher flow ratios of PH 3 to B2H6 resulted in smoother films and improved quality of BP on all substrates. The FWHM of the Raman peak (6.1 cm -1), XRD BP(111) peak FWHM (0.18°) and peak ratios of BP(111)/(200) = 5157 and BP(111)/(220) = 7226 measured on AlN/sapphire were the best values reported in the literature for BP epitaxial films. The undoped films on AlN/sapphire were n-type with a highest electron mobility of 37.8 cm2/V˙s and a lowest carrier concentration of 3.15x1018 cm -3. Raman imaging had lower values of FWHM (4.8 cm-1 ) and a standard deviation (0.56 cm-1) for BP films on AlN/sapphire compared to 4H-SiC, 3C-SiC substrates. X-ray diffraction and Raman spectroscopy revealed residual tensile strain in BP on 4H-SiC, 3C-SiC, ZrB2/4H-SiC, bulk AlN substrates while compressive strain was evident on AlN/sapphire and bulk ZrB2 substrates. Among the substrates studied, Al

The molecular core in G34.3 + 0.2 - Millimeter interferometric observations of HCO(+), H(C-13)N, H(C-15)N, and SO

NASA Technical Reports Server (NTRS)

Carral, Patricia; Welch, William J.

1992-01-01

This study presents high-resolution observations of the molecular core in the star-forming region G34.3 + 0.2. Maps at 6-arcsec resolution of emission and absorption of the J = 1 - 0 transitions of HCO(+), H (C-13)N, H(C-15)N, and of the 2(2) - 1(1) transition of SO were obtained in addition to a map of the 3.4-mm continuum emission from the compact H II component. The HCL(+) emission toward G34.3 + 0.2 traces a warm molecular core about 0.9 pc in size. Emission from H (C-13)N is detected over about 0.3 pc. The cometary H II region lies near the edge of the molecular core. The blueshift of the radio recombination lines with respect to the molecular emission suggests that gas from the H II region is accelerated in a champagne flow caused by a steep gradient in the ambient gas density.

Severe acute respiratory infections caused by 2009 pandemic influenza A (H1N1) among American Indians--southwestern United States, May 1-July 21, 2009.

PubMed

Suryaprasad, Anil; Redd, John T; Hancock, Kathy; Branch, Alicia; Steward-Clark, Evelene; Katz, Jacqueline M; Fry, Alicia M; Cheek, James E

2013-11-01

During April-July 2009, U.S. hospitalization rates for 2009 pandemic influenza A (H1N1) virus (H1N1pdm09) infection were estimated at 4·5/100 000 persons. We describe rates and risk factors for H1N1pdm09 infection among American Indians (AIs) in four isolated southwestern U.S. communities served by the Indian Health Service (IHS). We reviewed clinical and demographic information from medical records of AIs hospitalized during May 1-July 21, 2009 with severe acute respiratory infection (SARI). Hospitalization rates were determined using denominator data provided by IHS. H1N1pdm09 infection was confirmed with polymerase chain reaction, rapid tests, or convalescent serology. Risk factors for more severe (SARI) versus milder [influenza-like illness (ILI)] illness were determined by comparing confirmed SARI patients with outpatients with ILI. Among 168 SARI-hospitalized patients, 52% had confirmed H1N1pdm09 infection and 93% had >1 high-risk condition for influenza complications. The H1N1pdm09 SARI hospitalization rate was 131/100 000 persons [95% confidence interval (CI), 102-160] and was highest among ages 0-4 years (353/100 000; 95% CI, 215-492). Among children, asthma (adjusted odds ratio [aOR] 3·2; 95% CI, 1·2-8·4) and age<2 years (aOR 3·8; 95% CI, 1·4-10·0) were associated with H1N1pdm09 SARI-associated hospitalization, compared with outpatient ILI. Among adults, diabetes (aOR 3·1; 95% CI, 1·5-6·4) was associated with hospitalization after controlling for obesity. H1N1pdm09 hospitalization rates among this isolated AI population were higher than reported for other U.S. populations. Almost all case patients had high-risk health conditions. Prevention strategies for future pandemics should prioritize AIs, particularly in isolated rural areas. Published 2013. This article is U.S. Government work and in the public domain in the USA.

Synthesis of [.sup.13C] and [.sup.2H] substituted methacrylic acid, [.sup.13C] and [.sup.2H] substituted methyl methacrylate and/or related compounds

DOEpatents

Alvarez, Marc A [Santa Fe, NM; Martinez, Rodolfo A [Santa Fe, NM; Unkefer, Clifford J [Los Alamos, NM

2008-01-22

The present invention is directed to labeled compounds of the formulae ##STR00001## wherein Q is selected from the group consisting of --S--, --S(.dbd.O)--, and --S(.dbd.O).sub.2--, Z is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group selected from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each independently selected from the group consisting of a C.sub.1-C.sub.4 lower alkyl, an aryl, and an alkoxy group, and X is selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl group, and a fully-deuterated C.sub.1-C.sub.4 lower alkyl group. The present invention is also directed to a process of preparing labeled compounds, e.g., process of preparing [.sup.13C]methacrylic acid by reacting a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13CH.sub.2)-- aryl sulfone precursor with .sup.13CHI to form a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate, and, reacting the (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate with sodium hydroxide, followed by acid to form [.sup.13C]methacrylic acid. The present invention is further directed to a process of preparing [.sup.2H.sub.8]methyl methacrylate by reacting a (HOOC--C(C.sup.2H.sub.3).sub.2-- aryl sulfinyl intermediate with CD.sub.3I to form a (.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate, and heating the(.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate at temperatures and for time sufficient to form [.sup.2H.sub.8]methyl methacrylate.

Implementation of a sentinel surveillance system for influenza-like illness (ILI) and severe acute respiratory infection (SARI) in the country of Georgia, 2015-2016.

PubMed

Chakhunashvili, Giorgi; Wagner, Abram L; Machablishvili, Ann; Karseladze, Irakli; Tarkhan-Mouravi, Olgha; Zakhashvili, Khatuna; Imnadze, Paata; Boulton, Matthew L

2017-12-01

Due to reports of substandard influenza preparedness, the country of Georgia developed two influenza surveillance systems. This paper describes these surveillance systems in their capacity to detect influenza. Two surveillance systems for influenza operate in Georgia: an influenza-like illness (ILI) sentinel surveillance system for out-patient cases, based in the capital, Tbilisi, and a severe acute respiratory infection (SARI) sentinel surveillance system for in-patient cases with five sentinel sites - one in Tbilisi, and four in Kutaisi. Patients in these surveillance systems provide samples for laboratory testing, including influenza confirmation. From 2015-2016, 825 cases were surveilled in the ILI surveillance system and 1367 cases were surveilled in the SARI surveillance system, with 222 (26.9%) and 451 (33.0%) positive for influenza, respectively. Influenza positivity varied by age with adults 30-64 years having highest proportion of influenza-positive cases at 42.2%. The sensitivity of the surveillance systems to influenza was relatively high compared to neighboring countries. These findings show the importance of influenza surveillance in the country of Georgia. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Abnormal flexor carpi radialis H-reflex as a specific indicator of C7 as compared with C6 radiculopathy.

PubMed

Zheng, Chaojun; Zhu, Yu; Lv, Feizhou; Ma, Xiaosheng; Xia, Xinlei; Wang, Lixun; Jin, Xiang; Weber, Robert; Jiang, Jianyuan; Anuvat, Kevin

2014-12-01

The H-reflex of the flexor carpi radialis (FCR H-reflex) has not been commonly used for the diagnosis of cervical radiculopathy when compared with the routinely tested soleus H-reflex. Although both S1 and S2 roots innervate the soleus, the H-reflex is selectively related to S1 nerve root function clinically. Flexor carpi radialis is also innervated by two nerve roots which are C6 and C7. Although they are among the most common roots involved in cervical radiculopathy, few studies reported if the attenuation of the FCR H-reflex is caused by lesions affecting C7 or C6 nerve roots, or both. We aimed to identify whether an abnormal FCR H-reflex was attributed to the C7 or C6 nerve root lesion, or both. The sensitivities of needle electromyography, FCR H-reflex, and provocative tests in unilateral C7 or C6 radiculopathy were also compared in this study. A concentric needle electrode recorded bilateral FCR H-reflexes in 41 normal subjects (control group), 51 patients with C7 radiculopathy, and 54 patients with C6 radiculopathy. Clinical, radiological, and surgical approaches identified the precise single cervical nerve root involved in all patient groups. The H-reflex and M-wave latencies were measured and compared bilaterally. Abnormal FCR H-reflex was defined as the absence of the H-reflex or a side-to-side difference over 1.5 milliseconds which was based on the normal side-to-side difference of the H-reflex latency of 16.9 milliseconds (SD = 1.7 milliseconds) from the control group. We also determined standard median and ulnar conduction and needle electromyography. The provocative tests included bilateral determination of the Shoulder Abduction and Spurling's tests in all radiculopathy group patients. Abnormal FCR H-reflexes were recorded in 45 (88.2%) of C7 radiculopathy group patients, and 2 (3.7%) of C6 radiculopathy group patients (P < 0.05). Needle electromyography was abnormal in 41 (80.4%) of C7 radiculopathy patients and 43 (79.6%) of C6 radiculopathy

Carbon stars with alpha-C:H emission

NASA Technical Reports Server (NTRS)

Gerbault, Florence; Goebel, John H.

1989-01-01

Many carbon stars in the IRS low resolution spectra (LRS) catalog were found which display emission spectra that compare favorable with the absorption spectrum of alpha-C:H. These stars have largely been classified as 4X in the LRS which has led to their interpretation by others in terms of displaying a mixture of the UIRF's 8.6 micron band and SiC at 11.5 microns. It was also found that many of these stars have a spectral upturn at 20+ microns which resembles the MgS band seen in carbon stars and planetary nebulae. It was concluded that this group of carbon stars will evolve into planetary nebulae like NGC 7027 and IC 418. In the presence of hard ultraviolet radiation the UIRF's will light up and be displayed as narrow emission bands on top of the broad alpha-C:H emission bands.

Concurrent 2009 pandemic influenza A (H1N1) virus infection in ferrets and in a community in Pennsylvania.

PubMed

Campagnolo, E R; Moll, M E; Tuhacek, K; Simeone, A J; Miller, W S; Waller, K O; Simwale, O; Rankin, J T; Ostroff, S M

2013-03-01

We report a fall 2010 cluster of pandemic influenza A/H1N1 (pH1N1) infections in pet ferrets in Lehigh Valley region of Pennsylvania. The ferrets were associated with one pet shop. The influenza cluster occurred during a period when the existing human surveillance systems had identified little to no pH1N1 in humans in the Lehigh Valley, and there were no routine influenza surveillance systems for exotic pets. The index case was a 2.5-month-old neutered male ferret that was presented to a veterinary clinic with severe influenza-like illness (ILI). In response to laboratory notification of a positive influenza test result, and upon request from the Pennsylvania Department of Health (PADOH), the Pennsylvania Department of Agriculture (PDA) conducted an investigation to identify other ill ferrets and to identify the source and extent of infection. PDA notified the PADOH of the pH1N1 infection in the ferrets, leading to enhanced human surveillance and the detection of pH1N1 human infections in the surrounding community. Five additional ferrets with ILI linked to the pet shop were identified. This simultaneous outbreak of ferret and human pH1N1 demonstrates the important link between animal health and public health and highlights the potential use of veterinary clinics for sentinel surveillance of diseases shared between animals and humans. © 2012 Blackwell Verlag GmbH.

Tetrahedral silsesquioxane-C2H2Ti complex for hydrogen storage

NASA Astrophysics Data System (ADS)

Konda, Ravinder; Tavhare, Priyanka; Ingale, Nilesh; Chaudhari, Ajay

2018-04-01

The interaction of molecular hydrogen with tetrahedral silsesquioxane (T4)-C2H2Ti complex has been studied using Density Functional Theory with M06-2X functional and MP2 method with 6-311++G** basis set. T4-C2H2Ti complex can absorb maximum five hydrogen molecules with the gravimetric hydrogen storage capacity of 3.4 wt %. Adsorption energy calculations show that H2 adsorption on T4-C2H2Ti complex is favorable at room temperature by both the methods. We have studied the effect of temperature and pressure on Gibbs free energy corrected adsorption energies. Molecular dynamics simulations for H2 adsorbed T4-C2H2Ti complex have also been performed at 300K and show that loosely bonded H2 molecule flies away within 1fs. Various interaction energies within the complex are studied. Stability of a complex is predicted by means of a gap between Highest Occupied Molecular Orbital (HUMO) and Lowest Unoccupied Molecular Orbital (LUMO). The H2 desorption temperature for T4-C2H2Ti complex is calculated with Van't Hoff equation and it is found to be 229K.

Prolonged 500 C Operation of 6H-SiC JFET Integrated Circuitry

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith, Roger D.; Ferrier, Terry L.; Krasowski, Michael J.;

Thermochemistry of C7H16 to C10H22 alkane isomers: primary, secondary, and tertiary C-H bond dissociation energies and effects of branching.

PubMed

Hudzik, Jason M; Bozzelli, Joseph W; Simmie, John M

2014-10-09

Standard enthalpies of formation (ΔH°f 298) of methyl, ethyl, primary and secondary propyl, and n-butyl radicals are evaluated and used in work reactions to determine internal consistency. They are then used to calculate the enthalpy of formation for the tert-butyl radical. Other thermochemical properties including standard entropies (S°(T)), heat capacities (Cp(T)), and carbon-hydrogen bond dissociation energies (C-H BDEs) are reported for n-pentane, n-heptane, 2-methylhexane, 2,3-dimethylpentane, and several branched higher carbon number alkanes and their radicals. ΔH°f 298 and C-H BDEs are calculated using isodesmic work reactions at the B3LYP (6-31G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, CBS-APNO, and G3MP2B3 levels of theory. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level for contributions to entropy and heat capacities. Enthalpy calculations for these hydrocarbon radical species are shown to have consistency with the CBS-QB3 and CBS-APNO methods using all work reactions. Our recommended ideal gas phase ΔH°f 298 values are from the average of all CBS-QB3, CBS-APNO, and for G3MP2B3, only where the reference and target radical are identical types, and are compared with literature values. Calculated values show agreement between the composite calculation methods and the different work reactions. Secondary and tertiary C-H bonds in the more highly branched alkanes are shown to have bond energies that are several kcal mol(-1) lower than the BDEs in corresponding smaller molecules often used as reference species. Entropies and heat capacities are calculated and compared to literature values (when available) when all internal rotors are considered.

C Chondrite Clasts in H Chondrite Regolith Breccias: Something Different

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Fries, M.; Utas, J.; Chan, Q. H.-S.; Kebukawa, Y.; Steele, A.; Bodnar, R. J.; Ito, M.; Nakashima, D.; Greenwood, R.;

Chemoselective Aliphatic C-H Bond Oxidation Enabled by Polarity Reversal.

PubMed

Dantignana, Valeria; Milan, Michela; Cussó, Olaf; Company, Anna; Bietti, Massimo; Costas, Miquel

2017-12-27

Methods for selective oxidation of aliphatic C-H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C-H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C-H bonds within a molecule would enable rapid diversification of the resulting oxidation products. Herein we show that by engaging in hydrogen bonding, fluorinated alcohols exert a polarity reversal on electron rich functional groups, directing iron and manganese catalyzed oxidation toward a priori stronger and unactivated C-H bonds. As a result, selective hydroxylation of methylenic sites in hydrocarbons and remote aliphatic C-H oxidation of otherwise sensitive alcohol, ether, amide, and amine substrates is achieved employing aqueous hydrogen peroxide as oxidant. Oxidations occur in a predictable manner, with outstanding levels of product chemoselectivity, preserving the first-formed hydroxylation product, thus representing an extremely valuable tool for synthetic planning and development.

Allosterism in human complement component 5a ((h)C5a): a damper of C5a receptor (C5aR) signaling.

PubMed

Rana, Soumendra; Sahoo, Amita Rani; Majhi, Bharat Kumar

2016-06-01

The phenomena of allosterism continues to advance the field of drug discovery, by illuminating gainful insights for many key processes, related to the structure-function relationships in proteins and enzymes, including the transmembrane G-protein coupled receptors (GPCRs), both in normal as well as in the disease states. However, allosterism is completely unexplored in the native protein ligands, especially when a small covalent change significantly modulates the pharmacology of the protein ligands toward the signaling axes of the GPCRs. One such example is the human C5a ((h)C5a), the potent cationic anaphylatoxin that engages C5aR and C5L2 to elicit numerous immunological and non-immunological responses in humans. From the recently available structure-function data, it is clear that unlike the mouse C5a ((m)C5a), the (h)C5a displays conformational heterogeneity. However, the molecular basis of such conformational heterogeneity, otherwise allosterism in (h)C5a and its precise contribution toward the overall C5aR signaling is not known. This study attempts to decipher the functional role of allosterism in (h)C5a, by exploring the inherent conformational dynamics in (m)C5a, (h)C5a and in its point mutants, including the proteolytic mutant des-Arg(74)-(h)C5a. Prima facie, the comparative molecular dynamics study, over total 500 ns, identifies Arg(74)-Tyr(23) and Arg(37)-Phe(51) "cation-π" pairs as the molecular "allosteric switches" on (h)C5a that potentially functions as a damper of C5aR signaling.

Synthesis, molecular structure, and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units.

PubMed

Braun, Thomas; Münch, Gerhard; Windmüller, Bettina; Gevert, Olaf; Laubender, Matthias; Werner, Helmut

2003-06-06

The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato

31 CFR Appendix H to Subpart C of... - United States Mint

Code of Federal Regulations, 2012 CFR

2012-07-01

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31 CFR Appendix H to Subpart C of... - United States Mint

Code of Federal Regulations, 2014 CFR

2014-07-01

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31 CFR Appendix H to Subpart C of... - United States Mint

Code of Federal Regulations, 2011 CFR

2011-07-01

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31 CFR Appendix H to Subpart C of... - United States Mint

Code of Federal Regulations, 2013 CFR

2013-07-01

... 31 Money and Finance: Treasury 1 2013-07-01 2013-07-01 false United States Mint H Appendix H to... RECORDS Privacy Act Pt. 1, Subpt. C, App. H Appendix H to Subpart C of Part 1—United States Mint 1. In general. This appendix applies to the United States Mint. It sets forth specific notification and access...

Cs-137 immobilization in C-S-H gel nanopores.

PubMed

Duque-Redondo, Eduardo; Kazuo, Yamada; López-Arbeloa, Iñigo; Manzano, Hegoi

2018-04-04

Cementation is a widespread technique to immobilize nuclear waste due to the low leachability of cementitious materials. The capacity of calcium silicate hydrate (C-S-H), the main component of cement, to retain radionuclide Cs has been empirically studied at the macroscale, yet the specific molecular scale mechanisms that govern the retention have not been determined. In this work, we employed molecular dynamics simulations to investigate the adsorption and diffusivity of Cs into a C-S-H gel nanopore. From the simulations, it was possible to distinguish three types of Cs adsorption configurations on the C-S-H: an inner-sphere surface site where Cs is strongly bound, an outer-sphere surface site where Cs is loosely bound, and Cs free in the nanopore. For each configuration, we determined the sorption energy, and the diffusion coefficients, up to two orders of magnitude lower than in bulk water due to the effect of nanoconfinement in the worst case scenario. It has also proved that Cs cannot displace the intrinsic Ca from the C-S-H surface, and we calculated the binding strength and the residence time of the cations in the surface adsorption sites. Finally, we quantified the average number of adsorption sites per nm2 of the C-S-H surface. All these results are the first insights into Cs retention in cement at the molecular scale and will be useful to build macroscopic diffusion models and devise cement formulations to improve radionuclide Cs retention from spent nuclear fuel.

Enantioselective C(sp3)‒H bond activation by chiral transition metal catalysts.

PubMed

Saint-Denis, Tyler G; Zhu, Ru-Yi; Chen, Gang; Wu, Qing-Feng; Yu, Jin-Quan

2018-02-16

Organic molecules are rich in carbon-hydrogen bonds; consequently, the transformation of C-H bonds to new functionalities (such as C-C, C-N, and C-O bonds) has garnered much attention by the synthetic chemistry community. The utility of C-H activation in organic synthesis, however, cannot be fully realized until chemists achieve stereocontrol in the modification of C-H bonds. This Review highlights recent efforts to enantioselectively functionalize C(sp 3 )-H bonds via transition metal catalysis, with an emphasis on key principles for both the development of chiral ligand scaffolds that can accelerate metalation of C(sp 3 )-H bonds and stereomodels for asymmetric metalation of prochiral C-H bonds by these catalysts. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Particle Generation And Evolution In Silane (SiH4)/Acetylene (C2H2) Flames In Microgravity

NASA Technical Reports Server (NTRS)

Keil, D. G.

2003-01-01

The objective of this experimental program is to advance the understanding of the coupling of particle formation with gas phase combustion processes. The work utilizes the unique SiH4/C2H2 combustion system which generates particulate products ranging from high purity, white SiC to carbonaceous soot depending on equivalence ratio (Ref. 1). A goal of this work is to identify gas phase or particle formation processes that provide the enthalpy release needed to drive the combustion wave, and to locate the steps of the particle formation process that determine SiC stoichiometry and crystallinity. In a real sense, these SiH4/C2H2 flames act like highly sooty hydrocarbon flames, but with simpler chemistry. This simplification is expected to allow them to be used as surrogates to advance understanding of soot formation in such rich hydrocarbon flames. It is also expected that this improved understanding of SiC particle generation and evolution in these self-sustaining flames will advance the commercial potential of the flame process for the generation of high purity SiC powders.

Remote site-selective C-H activation directed by a catalytic bifunctional template

NASA Astrophysics Data System (ADS)

Zhang, Zhipeng; Tanaka, Keita; Yu, Jin-Quan

2017-03-01

In chemical syntheses, the activation of carbon-hydrogen (C-H) bonds converts them directly into carbon-carbon or carbon-heteroatom bonds without requiring any prior functionalization. C-H activation can thus substantially reduce the number of steps involved in a synthesis. A single specific C-H bond in a substrate can be activated by using a ‘directing’ (usually a functional) group to obtain the desired product selectively. The applicability of such a C-H activation reaction can be severely curtailed by the distance of the C-H bond in question from the directing group, and by the shape of the substrate, but several approaches have been developed to overcome these limitations. In one such approach, an understanding of the distal and geometric relationships between the functional groups and C-H bonds of a substrate has been exploited to achieve meta-selective C-H activation by using a covalently attached, U-shaped template. However, stoichiometric installation of this template has not been feasible in the absence of an appropriate functional group on which to attach it. Here we report the design of a catalytic, bifunctional nitrile template that binds a heterocyclic substrate via a reversible coordination instead of a covalent linkage. The two metal centres coordinated to this template have different roles: one reversibly anchors substrates near the catalyst, and the other cleaves remote C-H bonds. Using this strategy, we demonstrate remote, site-selective C-H olefination of heterocyclic substrates that do not have the necessary functional groups for covalently attaching templates.

Remote site-selective C-H activation directed by a catalytic bifunctional template.

PubMed

Zhang, Zhipeng; Tanaka, Keita; Yu, Jin-Quan

2017-03-23

In chemical syntheses, the activation of carbon-hydrogen (C-H) bonds converts them directly into carbon-carbon or carbon-heteroatom bonds without requiring any prior functionalization. C-H activation can thus substantially reduce the number of steps involved in a synthesis. A single specific C-H bond in a substrate can be activated by using a 'directing' (usually a functional) group to obtain the desired product selectively. The applicability of such a C-H activation reaction can be severely curtailed by the distance of the C-H bond in question from the directing group, and by the shape of the substrate, but several approaches have been developed to overcome these limitations. In one such approach, an understanding of the distal and geometric relationships between the functional groups and C-H bonds of a substrate has been exploited to achieve meta-selective C-H activation by using a covalently attached, U-shaped template. However, stoichiometric installation of this template has not been feasible in the absence of an appropriate functional group on which to attach it. Here we report the design of a catalytic, bifunctional nitrile template that binds a heterocyclic substrate via a reversible coordination instead of a covalent linkage. The two metal centres coordinated to this template have different roles: one reversibly anchors substrates near the catalyst, and the other cleaves remote C-H bonds. Using this strategy, we demonstrate remote, site-selective C-H olefination of heterocyclic substrates that do not have the necessary functional groups for covalently attaching templates.

C-O and O-H Bond Activation of Methanole by Lanthanum

NASA Astrophysics Data System (ADS)

Silva, Ruchira; Hewage, Dilrukshi; Yang, Dong-Sheng

2012-06-01

The interaction between methanol (CH_3OH) molecules and laser-vaporized La atoms resulted in the cleavage of C-O and O-H bonds and the formation of three major products, LaH_2O_2, LaCH_4O_2 and LaC_2H_6O_2, in a supersonic molecular beam. These products were identified by time-of-flight mass spectrometry, and their electronic spectra were obtained using mass-analyzed threshold ionization (MATI) spectroscopy. From the MATI spectra, adiabatic ionization energies of the three complexes were measured to be 40136 (5), 39366 (5) and 38685 (5) cm-1 for LaH_2O_2, LaCH_4O_2 and LaC_2H_6O_2, respectively. The ionization energies of these complexes decrease as the size of the coordinated organic fragments increases. The most active vibrational transitions of all three complexes were observed to be the M-O stretches in the ionic state. A metal-ligand bending mode with a frequency of 127 cm-1 was also observed for [LaH_2O_2]^+. However, the spectra of the other two complexes were less resolved, due to the existence of a large number of low frequency modes, which could be thermally excited even in the supersonic molecular beams, and of multiple rotational isomers formed by the free rotation of the methyl group in these systems. The electronic transitions responsible for the observed spectra were identified as ^1A_1 (C2v) ← ^2A_1 (C2v) for LaH_2O_2 and ^1A (C_1) ← ^2A (C_1) for LaCH_4O_2 and LaC_2H_6O_2.

Quantum Dynamics Scattering Study of AB+CDE Reactions: A Seven Dimensional Treatment for the H2+C2H Reaction

NASA Technical Reports Server (NTRS)

Wang, Dunyou

2003-01-01

A time-dependent wave-packet approach is presented for the quantum dynamics study of the AB+CDE reaction system for zero total angular momentum. A seven-degree-of-freedom calculation is employed to study the chemical reaction of H2+C2H yields H + C2H2 by treating C2H as a linear molecule. Initial state selected reaction probabilities are presented for various initial ro-vibrational states. This study shows that vibrational excitation of H2 enhances the reaction probability, whereas the excitation of C2H has only a small effect on the reactivity. An integral cross section is also reported for the initial ground states of H2 and C2H. The theoretical and experimental results agree with each other very well when the calculated seven dimensional results are adjusted to account for the lower transition state barrier heights found in recent ab initio calculations.

Modelling the role of electron attachment rates on column density ratios for C n H-/C n H (n=4,6,8) in dense molecular clouds

NASA Astrophysics Data System (ADS)

Gianturco, F. A.; Grassi, T.; Wester, R.

2016-10-01

The fairly recent detection of a variety of anions in the interstellar molecular clouds have underlined the importance of realistically modelling the processes governing their abundance. To pursue this task, our earlier calculations for the radiative electron attachment (REA) rates for C4H-, C6H-, and C8H- are employed in the present work, within a broad network of other concurrent reactions, to generate the corresponding column density ratios of anion/neutral (A/N) relative abundances. The latter are then compared with those obtained in recent years from observational measurements. The calculations involved the time-dependent solutions of a large network of chemical processes over an extended time interval and included a series of runs in which the values of REA rates were repeatedly scaled over several orders of magnitude. Macroscopic parameters for the Clouds’ modelling were also varied to cover a broad range of physical environments. It was found that, within the range and quality of the processes included in the present network,and selected from state-of-the-art astrophysical databases, the REA values required to match the observed A/N ratios needed to be reduced by orders of magnitude for C4H- case, while the same rates for C6H- and C8H- only needed to be scaled by much smaller factors. The results suggest that the generally proposed formation of interstellar anions by REA mechanism is overestimated by current models for the C4H- case, for which is likely to be an inefficient path to formation. This path is thus providing a rather marginal contribution to the observed abundances of C4H-, the latter being more likely to originate from other chemical processes in the network, as we discuss in some detail in the present work. Possible physical reasons for the much smaller differences against observations found instead for the values of the (A/N) ratios in two other, longer members of the series are put forward and analysed within the evolutionary modelling

Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

2017-04-01

UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C II] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C II] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C II λ2325 absorption data. We detect [C II] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| < 1°, we also present position-velocity maps of [C II] emission observed by Herschel Heterodyne Instrument in the Far Infrared (HIFI) in on-the-fly spectral-line mapping. We use the velocity-resolved [C II] spectra observed by the HIFI instrument toward the target LOSs observed by FUSE to identify [C II] velocity components associated with the H2 clouds. We analyze the observed velocity integrated [C II] spectral-line intensities in terms of the densities and thermal pressures in the H2 gas using the H2 column densities and temperatures measured by the UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C II] intensities derive a mean thermal pressure in the range of ˜6100-7700 K cm-3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C I and CO. Our results demonstrate the richness of the far-IR [C II] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C II] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity structures.

Tricosane (C23H48) and Octacosane (C28H58) mixture phase transition insight via Light scattering techniques

NASA Astrophysics Data System (ADS)

Kuryakov, V. N.; De Sanctis Lucentini, P. G.; Ivanova, D. D.

2018-04-01

In this study we analyse several emulsion samples of pure Tricosane (C23H48) and Octacosane (C28H58) paraffins as well as their mixtures with different component concentrations, prepared by means of ultrasonic dispersion without the addition of surfactants. We show that from the measurements of Static Light Scattering temperature dependences it is possible to determine the phase transition temperatures of the paraffins emulsion during the heating and cooling cycles (melting, crystallization and rotator phases). The results for the pure paraffin are in good agreement with the literature data. We produce the outcomes of the Dynamic Light Scattering technique to determine the cluster size of the obtained emulsions (radius 70-120 nm). Those emulsions proved to remain stable during several months.

Theoretical Prediction on [5]Radialene Sandwich Complexes (CpM)2(C10H10) (Cp = η5-C5H5; M = Fe, Co, Ni): Geometry, Spin States, and Bonding.

PubMed

Liu, Nan-Nan; Xue, Ying-Ying; Ding, Yi-Hong

2017-02-09

[5]Radialene, the missing link for synthesis of radialene family, has been finally obtained via the preparation and decomplexation of the [5]radialene-bis-Fe(CO) 3 complex. The stability of [5]radialene complex benefits from the coordination with Fe(CO) 3 by losing free 1,3-butadiene structures to avoid polymerization. In light of the similar coordination ability of half-sandwiches CpM(Cp = η 5 -C 5 H 5 ; M = Fe, Co, Ni), there is a great possibility that the sandwiched complexes of [5]radialene with CpM are available. Herein, we present the first theoretical prediction on the geometry, spin states and bonding of (CpM)(C 10 H 10 ) and (CpM) 2 (C 10 H 10 ). For M = Fe, Co, Ni, the ground states of (CpM)(C 10 H 10 ) and (CpM) 2 (C 10 H 10 ) are doublet and triplet, singlet and singlet, and doublet and triplet states, where each Fe, Co, and Ni adopts 17, 18, and 19 electron-configuration, respectively. In particular, (CpFe) 2 (C 10 H 10 ) and (CpNi) 2 (C 10 H 10 ) have considerable open-shell singlet features. Generally the trans isomers of (CpM) 2 (C 10 H 10 ) with two CpM fragments on the opposite sides of the [5]radialene plane are apparently more stable than the cis ones with CpM fragments on the same side. However, for the singlet and triplet isomers of (CpNi) 2 (C 10 H 10 ) (both cis and trans isomers), the energy differences are relatively small, indicating that these isomers all have the opportunity to exist. Besides, the easy Diels-Alder (DA) dimerization between the [3]dendralene-like fragments of (CpM)(C 10 H 10 ) suggests the great difficulty in isolating the (CpM)(C 10 H 10 ) monomer.

The first potential energy surfaces for the C{sub 6}H{sup −}–H{sub 2} and C{sub 6}H{sup −}–He collisional systems and their corresponding inelastic cross sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Kyle M., E-mail: kyle.walker@univ-lehavre.fr; Dumouchel, Fabien, E-mail: fabien.dumouchel@univ-lehavre.fr; Lique, François, E-mail: francois.lique@univ-lehavre.fr

2016-07-14

Molecular anions have recently been detected in the interstellar and circumstellar media. Accurate modeling of their abundance requires calculations of collisional data with the most abundant species that are usually He atoms and H{sub 2} molecules. In this paper, we focus on the collisional excitation of the first observed molecular anion, C{sub 6}H{sup −}, by He and H{sub 2}. Theoretical calculations of collisional cross sections rely generally on ab initio interaction potential energy surfaces (PESs). Hence, we present here the first PESs for the C{sub 6}H{sup −}–H{sub 2} and C{sub 6}H{sup −}–He van der Waals systems. The ab initio energymore » data for the surfaces were computed at the explicitly correlated coupled cluster with single, double, and scaled perturbative triple excitations level of theory. The method of interpolating moving least squares was used to construct 4D and 2D analytical PESs from these data. Both surfaces are characterized by deep wells and large anisotropies. Analytical models of the PESs were used in scattering calculations to obtain cross sections for low-lying rotational transitions. As could have been anticipated, important differences exist between the He and H{sub 2} cross sections. Conversely, no significant differences exist between the collisions of C{sub 6}H{sup −} with the two species of H{sub 2} (para- and ortho-H{sub 2}). We expect that these new data will help in accurately determining the abundance of the C{sub 6}H{sup −} anions in space.« less

Ab initio/GIAO-CCSD(T) (13)C NMR study of the rearrangement and dynamic aspects of rapidly equilibrating tertiary carbocations, C6H13(+) and C7H15(+).

PubMed

Olah, George A; Prakash, G K Surya; Rasul, Golam

2016-01-05

The rearrangement pathways of the equilibrating tertiary carbocations, 2,3-dimethyl-2-butyl cation (C6H13(+), 1), 2,3,3-trimethyl-2-butyl cation (C7H15(+), 5) and 2,3-dimethyl-2-pentyl cation (C7H15(+), 8 and 9) were investigated using the ab initio/GIAO-CCSD(T) (13)C NMR method. Comparing the calculated and experimental (13)C NMR chemical shifts of a series of carbocations indicates that excellent prediction of δ(13)C could be achieved through scaling. In the case of symmetrical equilibrating cations (1 and 5) the Wagner-Meerwein 1,2-hydride and 1,2-methide shifts, respectively, produce the same structure. This indicates that the overall (13)C NMR chemical shifts are conserved and independent of temperature. However, in the case of unsymmetrical equilibrating cations (8 and 9) the Wagner-Meerwein shift produces different tertiary structures, which have slightly different thermodynamic stabilities and, thus, different spectra. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level structure 8 is only 90 calories/mol more stable than structure 9. Based on computed (13)C NMR chemical shift calculations, mole fractions of these isomers were determined by assuming the observed chemical shifts are due to the weighted average of the chemical shifts of the static ions. © 2015 Wiley Periodicals, Inc.

Carbon dioxide utilization via carbonate-promoted C-H carboxylation.

PubMed

Banerjee, Aanindeeta; Dick, Graham R; Yoshino, Tatsuhiko; Kanan, Matthew W

2016-03-10

Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon-carbon (C-C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon-heteroatom bonds or relatively acidic carbon-hydrogen (C-H) bonds. These requirements negate the environmental benefit of using CO2 as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO3(2-)) to deprotonate very weakly acidic C-H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C-H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)--a highly desirable bio-based feedstock with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET). Since 2-furoic acid can readily be made from lignocellulose, CO3(2-)-promoted C-H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

Carbon dioxide utilization via carbonate-promoted C-H carboxylation

NASA Astrophysics Data System (ADS)

Banerjee, Aanindeeta; Dick, Graham R.; Yoshino, Tatsuhiko; Kanan, Matthew W.

2016-03-01

Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon-carbon (C-C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon-heteroatom bonds or relatively acidic carbon-hydrogen (C-H) bonds. These requirements negate the environmental benefit of using CO2 as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO32-) to deprotonate very weakly acidic C-H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C-H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)—a highly desirable bio-based feedstock with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET). Since 2-furoic acid can readily be made from lignocellulose, CO32--promoted C-H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

π-stacking and C-X...D (X = H, NO2; D = O, π) interactions in the crystal network of both C-H...N and π-stacked dimers of 1,2-bis(4-bromophenyl)-1H-benzimidazole and 2-(4-bromophenyl)-1-(4-nitrophenyl)-1H-benzimidazole.

PubMed

González-Padilla, Jazmin E; Rosales-Hernández, Martha C; Padilla-Martínez, Itzia I; García-Báez, Efren V; Rojas-Lima, Susana; Salazar-Pereda, Veronica

2014-01-01

Molecules of 1,2-bis(4-bromophenyl)-1H-benzimidazole, C19H12Br2N2, (I), and 2-(4-bromophenyl)-1-(4-nitrophenyl)-1H-benzimidazole, C19H12BrN3O2, (II), are arranged in dimeric units through C-H...N and parallel-displaced π-stacking interactions favoured by the appropriate disposition of N- and C-bonded phenyl rings with respect to the mean benzimidazole plane. The molecular packing of the dimers of (I) and (II) arises by the concurrence of a diverse set of weak intermolecular C-X...D (X = H, NO2; D = O, π) interactions.

Hole injection and dielectric breakdown in 6H-SiC and 4H-SiC metal-oxide-semiconductor structures during substrate electron injection via Fowler-Nordheim tunneling

NASA Astrophysics Data System (ADS)

Samanta, Piyas; Mandal, Krishna C.

2015-12-01

Hole injection into silicon dioxide (SiO2) films (8-40 nm thick) is investigated for the first time during substrate electron injection via Fowler-Nordheim (FN) tunneling in n-type 4H- and 6H-SiC (silicon carbide) based metal-oxide-semiconductor (MOS) structures at a wide range of temperatures (T) between 298 and 598 K and oxide electric fields Eox from 6 to 10 MV/cm. Holes are generated in heavily doped n-type polycrystalline silicon (n+ -polySi) gate serving as the anode as well as in the bulk silicon dioxide (SiO2) film via hot-electron initiated band-to-band ionization (BTBI). In absence of oxide trapped charges, it is shown that at a given temperature, the hole injection rates from either of the above two mechanisms are higher in n-4H-SiC MOS devices than those in n-6H-SiC MOS structures when compared at a given Eox and SiO2 thickness (tox). On the other hand, relative to n-4H-SiC devices, n-6H-SiC structures exhibit higher hole injection rates for a given tox during substrate electron injection at a given FN current density je,FN throughout the temperature range studied here. These two observations clearly reveal that the substrate material (n-6H-SiC and n-4H-SiC) dependencies on time-to-breakdown (tBD) or injected charge (electron) to breakdown (QBD) of the SiO2 film depend on the mode of FN injections (constant field/voltage and current) from the substrate which is further verified from the rigorous device simulation as well.

Remote C-H Activation of Quinolines through Copper-Catalyzed Radical Cross-Coupling.

PubMed

Xu, Jun; Shen, Chao; Zhu, Xiaolei; Zhang, Pengfei; Ajitha, Manjaly J; Huang, Kuo-Wei; An, Zhongfu; Liu, Xiaogang

2016-03-18

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a formidable challenge in organic chemistry. Herein, we report a novel approach to activating remote C-H bonds at the C5 position of 8-aminoquinoline through copper-catalyzed sulfonylation under mild conditions. Our strategy shows high conversion efficiency, a broad substrate scope, and good toleration with different functional groups. Furthermore, our mechanistic investigations suggest that a single-electron-transfer process plays a vital role in generating sulfonyl radicals and subsequently initiating C-S cross-coupling. Importantly, our copper-catalyzed remote functionalization protocol can be expanded for the construction of a variety of chemical bonds, including C-O, C-Br, C-N, C-C, and C-I. These findings provide a fundamental insight into the activation of remote C-H bonds, while offering new possibilities for rational design of drug molecules and optoelectronic materials requiring specific modification of functional groups. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detailed Studies of Hydrocarbon Radicals: C 2H Dissociation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittig, Curt

2014-10-06

The goal of this research at its outset was a chemical physics investigation of C 2H properties: spectroscopy, dynamics (including non-adiabatic), thermodynamics, etc. using mainly the Rydberg-tagging technique that had been a mainstay of my laboratory for two decades. We encountered a number of technical obstacles that bogged us down for about a year and a half before switching to a very different approach. It was believed that the new approach would yield the UV absorption spectrum of cold, gas-phase C 2H. It involved using a cold CO 2 matrix (which does not react with C 2H) to simultaneously preparemore » the radical and propel it into vacuum. Many things happened. There was no shortage of data, and interesting phenomena were uncovered. About the only thing that did not happen was a clean UV spectrum of C 2H. I would say, to put it bluntly, that from the perspective of our original goal the whole effort was a colossal failure. I rarely come up empty handed, but I did this time. Excuses are a dime a dozen, so let's just say that things like this happen every so often.« less

Fe-C and Fe-H systems at pressures of the Earth's inner core

NASA Astrophysics Data System (ADS)

Bazhanova, Zulfiya G.; Oganov, Artem R.; Gianola, Omar

2012-05-01

The solid inner core of Earth is predominantly composed of iron alloyed with several percent Ni and some lighter elements, Si, S, O, H, and C being the prime candidates. To establish the chemical composition of the inner core, it is necessary to find the range of compositions that can explain its observed characteristics. Recently, there have been a growing number of papers investigating C and H as possible light elements in the core, but the results were contradictory. Here, using ab initio simulations, we study the Fe-C and Fe-H systems at inner core pressures (330-364 GPa). Based on the evolutionary structure prediction algorithm USPEX, we have determined the lowest-enthalpy structures of all possible carbides (FeC, Fe2C, Fe3C, Fe4C, FeC2, FeC3, FeC4, Fe7C3) and hydrides (Fe4H, Fe3H, Fe2H, FeH, FeH2, FeH3, FeH4) and have found that Fe2C (space group Pnma) is the most stable iron carbide at pressures of the inner core, while FeH, FeH3, and FeH4 are the most stable iron hydrides at these conditions. For Fe3C, the cementite structure (space group Pnma) and the Cmcm structure recently found by random sampling are less stable than the I-4 and C2/m structures predicted here. We have found that FeH3 and FeH4 adopt chemically interesting thermodynamically stable crystal structures, containing trivalent iron in both compounds. We find that the density of the inner core can be matched with a reasonable concentration of carbon, 11-15 mol.% (2.6-3.7 wt.%) at relevant pressures and temperatures, yielding the upper bound to the C content in the inner core. This concentration matches that in CI carbonaceous chondrites and corresponds to the average atomic mass in the range 49.3-51.0, in close agreement with inferences from Birch's law for the inner core. Similarly made estimates for the maximum hydrogen content are unrealistically high: 17-22 mol.% (0.4-0.5 wt.%), which corresponds to the average atomic mass of the core in the range 43.8-46.5. We conclude that carbon is a

Outbreak of influenza in an overseas student travel group--Taiwan 2008.

PubMed

Tsou, Tsung-Pei; Lin, Chien-Hui; Lo, Yi-Chun; Li, Yi-Syue; Chiu, Chan-Hsien

2010-05-01

Influenza is a frequent cause of acute respiratory illness (ARI). In July 2008, we conducted a retrospective cohort study to investigate an influenza outbreak occurring in an overland travel group of overseas students. ARI was defined as the presence of any respiratory symptom such as cough, rhinorrhoea, sore throat or stuffy nose. Influenza-like illness (ILI) was defined as ARI plus fever > or =38 degrees C. Throat swabs were taken from symptomatic participants and a real-time polymerase chain reaction (RT-PCR) was performed. One hundred and seventy participants were interviewed. Forty-four (26%) had an ARI and 22 (13%) had an ILI. Of the 33 specimens collected, 18 (54%) were positive for influenza A/H3N2. Taiwanese group leaders had increased risk of acquiring both ARI and ILI (ARI relative risk (RR) 2.2, 95% confidence interval (CI) 1.3-3.7 and ILI RR 2.8, 95% CI 1.2-6.3). Fifteen participants were vaccinated. The vaccine effectiveness was 52% for ILI (p = 0.70). The outbreak stopped after cohorting and the use of surgical masks. Vaccination appeared to be effective in preventing infection.

Long-Term Characterization of 6H-SiC Transistor Integrated Circuit Technology Operating at 500 C

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith Roger D.; Ferrier, Terry L.; Krasowski, Michael J.;

Cobalt-Catalyzed C(sp(2))-H Borylation: Mechanistic Insights Inspire Catalyst Design.

PubMed

Obligacion, Jennifer V; Semproni, Scott P; Pappas, Iraklis; Chirik, Paul J

2016-08-24

A comprehensive study into the mechanism of bis(phosphino)pyridine (PNP) cobalt-catalyzed C-H borylation of 2,6-lutidine using B2Pin2 (Pin = pinacolate) has been conducted. The experimentally observed rate law, deuterium kinetic isotope effects, and identification of the catalyst resting state support turnover limiting C-H activation from a fully characterized cobalt(I) boryl intermediate. Monitoring the catalytic reaction as a function of time revealed that borylation of the 4-position of the pincer in the cobalt catalyst was faster than arene borylation. Cyclic voltammetry established the electron withdrawing influence of 4-BPin, which slows the rate of C-H oxidative addition and hence overall catalytic turnover. This mechanistic insight inspired the next generation of 4-substituted PNP cobalt catalysts with electron donating and sterically blocking methyl and pyrrolidinyl substituents that exhibited increased activity for the C-H borylation of unactivated arenes. The rationally designed catalysts promote effective turnover with stoichiometric quantities of arene substrate and B2Pin2. Kinetic studies on the improved catalyst, 4-(H)2BPin, established a change in turnover limiting step from C-H oxidative addition to C-B reductive elimination. The iridium congener of the optimized cobalt catalyst, 6-(H)2BPin, was prepared and crystallographically characterized and proved inactive for C-H borylation, a result of the high kinetic barrier for reductive elimination from octahedral Ir(III) complexes.

Site-selective and stereoselective functionalization of non-activated tertiary C-H bonds

NASA Astrophysics Data System (ADS)

Liao, Kuangbiao; Pickel, Thomas C.; Boyarskikh, Vyacheslav; Bacsa, John; Musaev, Djamaladdin G.; Davies, Huw M. L.

2017-11-01

The synthesis of complex organic compounds usually relies on controlling the reactions of the functional groups. In recent years, it has become possible to carry out reactions directly on the C-H bonds, previously considered to be unreactive. One of the major challenges is to control the site-selectivity because most organic compounds have many similar C-H bonds. The most well developed procedures so far rely on the use of substrate control, in which the substrate has one inherently more reactive C-H bond or contains a directing group or the reaction is conducted intramolecularly so that a specific C-H bond is favoured. A more versatile but more challenging approach is to use catalysts to control which site in the substrate is functionalized. p450 enzymes exhibit C-H oxidation site-selectivity, in which the enzyme scaffold causes a specific C-H bond to be functionalized by placing it close to the iron-oxo haem complex. Several studies have aimed to emulate this enzymatic site-selectivity with designed transition-metal catalysts but it is difficult to achieve exceptionally high levels of site-selectivity. Recently, we reported a dirhodium catalyst for the site-selective functionalization of the most accessible non-activated (that is, not next to a functional group) secondary C-H bonds by means of rhodium-carbene-induced C-H insertion. Here we describe another dirhodium catalyst that has a very different reactivity profile. Instead of the secondary C-H bond, the new catalyst is capable of precise site-selectivity at the most accessible tertiary C-H bonds. Using this catalyst, we modify several natural products, including steroids and a vitamin E derivative, indicating the applicability of this method of synthesis to the late-stage functionalization of complex molecules. These studies show it is possible to achieve site-selectivity at different positions within a substrate simply by selecting the appropriate catalyst. We hope that this work will inspire the design of

Gas-phase hydrogen atom abstraction reactions of S- with H2, CH4, and C2H6

NASA Astrophysics Data System (ADS)

Angel, Laurence A.; Dogbevia, Moses K.; Rempala, Katarzyna M.; Ervin, Kent M.

2003-11-01

Reaction cross sections, product axial velocity distributions, and potential energy surfaces are presented for the hydrogen atom abstraction reactions S-+RH→R+HS- (R=H, CH3, C2H5) as a function of collision energy. The observed threshold energy, E0, for S-+H2→H+HS- agrees with the reaction endothermicity, ΔrH0. At low collision energies, the H+HS- products exhibit symmetric, low-recoil-velocity scattering, consistent with statistical reaction behavior. The S-+CH4→CH3+HS- and S-+C2H6→C2H5+HS reactions, in contrast, show large excess threshold energies when compared to ΔrH0. The excess energies are partly explained by a potential energy barrier separating products from reactants. However, additional dynamical constraints must account for more than half of the excess threshold energy. The observed behavior seems to be general for collisional activation of anion-molecule reactions that proceed through a tight, late transition state. For RH=CH4 and C2H6, the HS- velocity distributions show anisotropic backward scattering at low collision energies indicating small impact parameters and a direct rebound reaction mechanism. At higher collision energies, there is a transition to HS- forward scattering and high velocities consistent with grazing collisions and a stripping mechanism.

Trapping-mediated dissociative chemisorption of C3H8 and C3D8 on Ir(110)

NASA Astrophysics Data System (ADS)

Kelly, D.; Weinberg, W. H.

1996-07-01

We have employed molecular beam techniques to investigate the molecular trapping and trapping-mediated dissociative chemisorption of C3H8 and C3D8 on Ir(110) at low beam translational energies, Ei≤5 kcal/mol, and surface temperatures, Ts, from 85 to 1200 K. For Ts=85 K, C3H8 is molecularly adsorbed on Ir(110) with a trapping probability, ξ, equal to 0.94 at Ei=1.6 kcal/mol and ξ=0.86 at Ei=5 kcal/mol. At Ei=1.9 kcal/mol and Ts=85 K, ξ of C3D8 is equal to 0.93. From 150 K to approximately 700 K, the initial probabilities of dissociative chemisorption of propane decrease with increasing Ts. For Ts from 700 to 1200 K, however, the initial probability of dissociative chemisorption maintains the essentially constant value of 0.16. These observations are explained within the context of a kinetic model which includes both C-H (C-D) and C-C bond cleavage. Below 450 K propane chemisorption on Ir(110) arises essentially solely from C-H (C-D) bond cleavage, an unactivated mechanism (with respect to a gas-phase energy zero) for this system, which accounts for the decrease in initial probabilities of chemisorption with increasing Ts. With increasing Ts, however, C-C bond cleavage, the activation energy of which is greater than the desorption energy of physically adsorbed propane, increasingly contributes to the measured probability of dissociative chemisorption. The activation energies, referenced to the bottom of the physically adsorbed molecular well, for C-H and C-C bond cleavage for C3H8 on Ir(110) are found to be Er,CH=5.3±0.3 kcal/mol and Er,CC=9.9±0.6 kcal/mol, respectively. The activation energies for C-D and C-C bond cleavage for C3D8 on Ir(110) are 6.3±0.3 kcal/mol and 10.5±0.6 kcal/mol, respectively. The desorption activation energy of propane from Ir(110) is approximately 9.5 kcal/mol. These activation energies are compared to activation energies determined recently for ethane and propane adsorption on Ir(111), Ru(001), and Pt(110)-(1×2), and ethane

An Infection Control Program for a 2009 Influenza A H1N1 Outbreak in a University-Based Summer Camp

ERIC Educational Resources Information Center

Tsalik, Ephraim L.; Cunningham, Coleen K.; Cunningham, Hannah M.; Lopez-Marti, Maria G.; Sangvai, Devdutta G.; Purdy, William K.; Anderson, Deverick J.; Thompson, Jessica R.; Brown, Monte; Woods, Christopher W.; Jaggers, L. Brett; Hendershot, Edward F.

2011-01-01

Objectives: Describe two 2009-H1N1 influenza outbreaks in university-based summer camps and the implementation of an infection control program. Participants: 7,906 campers across 73 residential camps from May 21-August 2, 2009. Methods: Influenza-like-illness (ILI) was defined as fever with cough and/or sore throat. Influenza A was identified…

Fine and hyperfine collisional excitation of C6H by He

NASA Astrophysics Data System (ADS)

Walker, Kyle M.; Lique, François; Dawes, Richard

2018-01-01

Hydrogenated carbon chains have been detected in interstellar and circumstellar media and accurate modelling of their abundances requires collisional excitation rate coefficients with the most abundant species. Among them, the C6H molecule is one of the most abundant towards many lines of sight. Hence, we determined fine and hyperfine-resolved rate coefficients for the excitation of C6H(X2Π) due to collisions with He. We present the first interaction potential energy surface for the C6H-He system, obtained from highly correlated ab initio calculations and characterized by a large anisotropy due to the length of the molecule. We performed dynamical calculations for transitions among the first fine structure levels (up to J = 30.5) of both spin-orbit manifolds of C6H using the close-coupling method, and rate coefficients are determined for temperatures ranging from 5 to 100 K. The largest rate coefficients for even ΔJ transitions conserve parity, while parity-breaking rate coefficients are favoured for odd ΔJ. Spin-orbit changing rate coefficients are several orders of magnitude lower than transitions within a single manifold. State-to-state hyperfine-resolved cross-sections for the first levels (up to J = 13.5) in the Ω = 3/2 spin-orbit manifold are deduced using recoupling techniques. Rate coefficients are obtained and the propensity rule ΔJ = ΔF is seen. These new data will help determine the abundance of C6H in astrophysical environments such as cold dense molecular clouds, star-forming regions and circumstellar envelopes, and will help in the interpretation of the puzzling C6H-/C6H abundance ratios deduced from observations.

Publications - Plafker, George and Berg, H.C., 1994 | Alaska Division of

Science.gov Websites

, M.S., Smith, T.E., Berg, H.C., Andersen, G.L., Chipp, E.R., Gaard, D.R., Burton, P.J., Dunbler, John ., Newberry, R.J., Rogers, R.K., Rubin, C.M., Swainbank, R.C., Smith, P.R., and Stephens, Jackie, 1994 , H.C., Brew, D.A., Grybeck, Donald, Robinson, M.S., Smith, T.E., and Yeend, Warren, 1994, Metallogenic

Zinc-induced Self-association of Complement C3b and Factor H

PubMed Central

Nan, Ruodan; Tetchner, Stuart; Rodriguez, Elizabeth; Pao, Po-Jung; Gor, Jayesh; Lengyel, Imre; Perkins, Stephen J.

2013-01-01

The sub-retinal pigment epithelial deposits that are a hallmark of age-related macular degeneration contain both C3b and millimolar levels of zinc. C3 is the central protein of complement, whereas C3u is formed by the spontaneous hydrolysis of the thioester bridge in C3. During activation, C3 is cleaved to form active C3b, then C3b is inactivated by Factor I and Factor H to form the C3c and C3d fragments. The interaction of zinc with C3 was quantified using analytical ultracentrifugation and x-ray scattering. C3, C3u, and C3b associated strongly in >100 μm zinc, whereas C3c and C3d showed weak association. With zinc, C3 forms soluble oligomers, whereas C3u and C3b precipitate. We conclude that the C3, C3u, and C3b association with zinc depended on the relative positions of C3d and C3c in each protein. Computational predictions showed that putative weak zinc binding sites with different capacities exist in all five proteins, in agreement with experiments. Factor H forms large oligomers in >10 μm zinc. In contrast to C3b or Factor H alone, the solubility of the central C3b-Factor H complex was much reduced at 60 μm zinc and even more so at >100 μm zinc. The removal of the C3b-Factor H complex by zinc explains the reduced C3u/C3b inactivation rates by zinc. Zinc-induced precipitation may contribute to the initial development of sub-retinal pigment epithelial deposits in the retina as well as reducing the progression to advanced age-related macular degeneration in higher risk patients. PMID:23661701

Synthetic and Spectroscopic Studies on N-(i,j-Disubstituted Phenyl)-4- Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i, j = 2, 3; 2, 4; 2, 5; 2, 6 or 3, 4; and X = CH3 or Cl

NASA Astrophysics Data System (ADS)

Shetty, Mahesha; Gowda, B. Thimme

2005-02-01

Fifty four N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides of the general formula 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i,j = 2,3; 2,4; 2,5; 2,6 or 3, 4; and X = CH3 or Cl, are prepared and characterized and their infrared, 1H and 13C NMR spectra in solution are studied. The N-H stretching vibrations νN-H absorb in the range 3305 - 3205 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1377 - 1307 cm-1 and 1184 - 1128 cm-1, respectively. The N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides show C-S, S-N and C-N stretching vibrations in the ranges 844 - 800 cm-1, 945 - 891 cm-1 and 1309 - 1170 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbon atoms of the two benzene rings. Incremental shifts of the ring protons and carbon atoms due to -SO2NH(i,j-X2C6H3) groups in C6H5SO2NH(i,j-X2C6H3) and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H*) are computed and employed to calculate the chemical shifts of the ring protons and carbon atoms in the substituted compounds 4-X'C6H4SO2NH(i,j-X2C6H3). The different methods of calculation lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating the validity of the principle of additivity of the substituent effects with chemical shifts in these compounds.

Isotopic Ratios of H, C, N, O, and S in Comets C2012 F6 (lemmon) and C2014 Q2 (lovejoy) * ** ***

NASA Technical Reports Server (NTRS)

Biver, N.; Moreno, R.; Sandqvist, Aa.; Bockelee-Morvan, D.; Colom, P.; Crovisier, J.; Lis, D. C.; Bossier, J.; Debout, V.; Paubert, G.;

Syntheses, structures, and 1H, 13C{ 1H} and 119Sn{ 1H} NMR chemical shifts of a family of trimethyltin alkoxide, amide, halide and cyclopentadienyl compounds

DOE PAGES

Lichtscheidl, Alejandro G.; Janicke, Michael T.; Scott, Brian L.; ...

2015-08-21

The synthesis and full characterization, including Nuclear Magnetic Resonance (NMR) data ( 1H, 13C{ 1H} and 119Sn{ 1H}), for a series of Me 3SnX (X = O-2,6-tBu 2C 6H 3 (1), (Me 3Sn)N(2,6- iPr 2C 6H 3) (3), NH-2,4,6- tBu 3C 6H 2 (4), N(SiMe 3) 2 (5), NEt 2, C 5Me 5 (6), Cl, Br, I, and SnMe 3) compounds in benzene-d 6, toluene-d 8, dichloromethane-d 2, chloroform-d 1, acetonitrile-d 3, and tetrahydrofuran-d 8 are reported. The X-ray crystal structures of Me 3Sn(O-2,6- tBu 2C 6H 3) (1), Me 3Sn(O-2,6- iPr 2C 6H 3) (2), and (Me 3Sn)(NH-2,4,6- tBumore » 3C 6H 2) (4) are also presented. As a result, these compiled data complement existing literature data and ease the characterization of these compounds by routine NMR experiments.« less

2,4-Dinitrophenylhydrazine, redetermined at 120 K: a three-dimensional framework built from N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

PubMed

Wardell, James L; Low, John N; Glidewell, Christopher

2006-06-01

In the title compound, C6H6N4O4, the bond distances indicate significant bond fixation, consistent with charge-separated polar forms. The molecules are almost planar and there is an intramolecular N-H...O hydrogen bond. The molecules are linked into a complex three-dimensional framework structure by a combination of N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

Rh(I) -Catalyzed Intramolecular Carbonylative C-H/C-I Coupling of 2-Iodobiphenyls Using Furfural as a Carbonyl Source.

PubMed

Furusawa, Takuma; Morimoto, Tsumoru; Nishiyama, Yasuhiro; Tanimoto, Hiroki; Kakiuchi, Kiyomi

2016-08-19

Synthesis of fluoren-9-ones by a Rh-catalyzed intramolecular C-H/C-I carbonylative coupling of 2-iodobiphenyls using furfural as a carbonyl source is presented. The findings indicate that the rate-determining step is not a C-H bond cleavage but, rather, the oxidative addition of the C-I bond to a Rh(I) center. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photochemical Carboxylation of Activated C(sp3 )-H Bonds with CO2.

PubMed

Gui, Yong-Yuan; Zhou, Wen-Jun; Ye, Jian-Heng; Yu, Da-Gang

2017-04-10

From ugly duckling to beautiful C1: Although CO 2 may represent an ideal C1 source, it is challenging to use it as a raw material and direct carboxylation with CO 2 has mainly been confined to highly reactive species. However, recent significant breakthroughs have been made in photochemical carboxylation of challenging, un-acidic, C(sp 3 )-H bonds, including benzylic, allylic and amine C-H bonds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synergistic Manganese(I) C-H Activation Catalysis in Continuous Flow: Chemoselective Hydroarylation.

PubMed

Wang, Hui; Pesciaioli, Fabio; Oliveira, João C A; Warratz, Svenja; Ackermann, Lutz

2017-11-20

Chemoselective hydroarylations were accomplished by a novel synergistic Brønsted acid/manganese(I)-catalyzed C-H activation manifold. Thus, alkynes bearing O-leaving groups could, for the first time, be employed for C-H alkenylations without concurrent β-O elimination, thereby setting the stage for versatile late-stage diversifications. Also described is the first manganese-catalyzed C-H activation in continuous flow, thus enabling efficient hydroarylations within only 20 minutes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The selective activation of a C-F bond with an auxiliary strong Lewis acid: a method to change the activation preference of C-F and C-H bonds.

PubMed

Wang, Lin; Sun, Hongjian; Li, Xiaoyan; Fuhr, Olaf; Fenske, Dieter

2016-11-15

The selective activation of the C-F bonds in substituted (2,6-difluorophenyl)phenylimines (2,6-F 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-n'-R-C 6 H 4 (n' = 2, R = H (1); n' = 2, R = Me (2); n' = 4, R = tBu (3))) by Fe(PMe 3 ) 4 with an auxiliary strong Lewis acid (LiBr, LiI, or ZnCl 2 ) was explored. As a result, iron(ii) halides ((H 5 C 6 -(C[double bond, length as m-dash]NH)-2-FH 3 C 6 )FeX(PMe 3 ) 3 (X = Br (8); Cl (9)) and (n-RH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-FH 3 C 6 )FeX(PMe 3 ) 3 (n = 2, R = Me, X = Br (11); n = 4, R = tBu, X = I (12))) were obtained. Under similar reaction conditions, using LiBF 4 instead of LiBr or ZnCl 2 , the reaction of (2,6-difluorophenyl)phenylimine with Fe(PMe 3 ) 4 afforded an ionic complex [(2,6-F 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-H 4 C 6 )Fe(PMe 3 ) 4 ](BF 4 ) (10) via the activation of a C-H bond. The method of C-F bond activation with an auxiliary strong Lewis acid is appropriate for monofluoroarylmethanimines. Without the Lewis acid, iron(ii) hydrides ((2-RH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-FH 3 C 6 )FeH(PMe 3 ) 3 (R = H (13); Me (14))) were generated from the reactions of Fe(PMe 3 ) 4 with the monofluoroarylmethanimines (2-FH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-RC 6 H 4 (R = H (4); Me (5))); however, in the presence of ZnCl 2 or LiBr, iron(ii) halides ((2-RH 4 C 6 -(C[double bond, length as m-dash]NH)-H 4 C 6 )FeX(PMe 3 ) 3 (R = H, X = Cl (15); R = Me, X = Br (16))) could be obtained through the activation of a C-F bond. Furthermore, a C-F bond activation with good regioselectivity in (pentafluorophenyl)arylmethanimines (F 5 C 6 -(C[double bond, length as m-dash]NH)-2,6-Y 2 C 6 H 3 (Y = F (6); H (7))) could be realized in the presence of ZnCl 2 to produce iron(ii) chlorides ((2,6-Y 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-F 4 C 6 )FeCl(PMe 3 ) 3 (Y = F (17); H (18))). This series of iron(ii) halides could be used to catalyze the hydrosilylation reaction of

Influenza Risk Management: Lessons Learned from an A(H1N1) pdm09 Outbreak Investigation in an Operational Military Setting

DTIC Science & Technology

2013-07-10

of the virus in Spain was detected during an outbreak investigation of influenza -like illness (ILI) in soldiers from an engineering military academy...SwInfA primer and probe set) and specific A(H1N1) pdm09 influenza A viruses using SwH1 primer and probe set developed by CDC, Atlanta (WHO...CY062374, CY062375 and CY062376. Viral culture Influenza viruses were isolated from clinical samples by infecting Madin Darby Canine Kidney (MDCK

Anti-inflammatory activity of Arnica montana 6cH: preclinical study in animals.

PubMed

Macêdo, S B; Ferreira, L R; Perazzo, F F; Carvalho, J C

2004-04-01

The anti-inflammatory effect of Arnica montana 6cH was evaluated using acute and chronic inflammation models. In the acute, model, carrageenin-induced rat paw oedema, the group treated with Arnica montana 6cH showed 30% inhibition compared to control (P < 0.05). Treatment with Arnica 6cH, 30 min prior to carrageenin, did not produce any inhibition of the inflammatory process. In the chronic model, Nystatin-induced oedema, the group treated 3 days previously with Arnica montana 6cH had reduced inflammation 6 h after the inflammatory agent was applied (P < 0.05). When treatment was given 6 h after Nystatin treatment, there was no significant inhibitory effect. In a model based on histamine-induced increase of vascular permeability, pretreatment with Arnica montana 6cH blocked the action of histamine in increasing vascular permeability.

Isotope effect in acetylene C2H2 and C2D2 rotations on Cu(001)

NASA Astrophysics Data System (ADS)

Shchadilova, Yulia E.; Tikhodeev, Sergei G.; Paulsson, Magnus; Ueba, Hiromu

2014-04-01

A comprehensive analysis of the elementary processes behind the scanning tunneling microscope controlled rotation of C2H2 and C2D2, isotopologues of a single acetylene molecule adsorbed on the Cu(001) surface, is given, with a focus on the isotope effects. With the help of density-functional theory we calculate the vibrational modes of C2H2 and C2D2 on Cu(001) and estimate the anharmonic couplings between them, using a simple strings-on-rods model. The probability of the elementary processes, nonlinear and combination band, is estimated using the Keldysh diagram technique. This allows us to clarify the main peculiarities and the isotope effects of the C2H2 and C2D2 on Cu(001) rotation, discovered in the pioneering work [B. C. Stipe et al., Phys. Rev. Lett. 81, 1263 (1998), 10.1103/PhysRevLett.81.1263], which have not been previously understood.

HFE gene C282Y, H63D and S65C mutations frequency in the Transylvania region, Romania.

PubMed

Trifa, Adrian P; Popp, Radu A; Militaru, Mariela S; Farcaş, Marius F; Crişan, Tania O; Gana, Ionuţ; Cucuianu, Andrei; Pop, Ioan V

2012-06-01

HFE-associated haemochromatosis is one of the most frequent autosomal recessive disorders in the Caucasian population. Although most of the cases are homozygous individuals for the C282Y mutation, another two mutations, H63D and S65C, have been reported to be associated with milder forms of the disease. This study was a first attempt to evaluate the distribution of these HFE gene mutations in the Transylvania region. Two-hundred and twenty-five healthy, unrelated volunteers originating from the Transylvania region, Romania, were screened for the HFE gene C282Y, H63D and S65C mutations, using molecular genetics assays (Polymerase Chain Reaction-Restriction Fragments Length Polymorphism). For the C282Y mutation, 7 heterozygotes (3.1%) were found, but no homozygous individual. In the case of the H63D mutation, 40 heterozygotes (17.8%) and 4 homozygotes (1.75%) for the mutant allele were evidenced. We found a compound heterozygous genotype (C282Y/H63D) in one individual (0.45%). Thus, the allele frequencies of the C282Y and H63D were 1.75% and 10.9%, respectively. Three individuals (1.3%) were found to harbour the S65C mutation in a heterozygous state, but none in a homozygous state: the allele frequency of the mutant allele was 0.75%. The distribution of the HFE gene C282Y, H63D and S65C mutations found in our group matches the tendencies observed in other European countries: a decreasing gradient from Northern to Southern Europe for the C282Y mutation; high frequency for the H63D mutation, and low frequency for the S65C mutation in most of the countries.

Protective effect of Dendrobium officinale polysaccharides on H2O2-induced injury in H9c2 cardiomyocytes.

PubMed

Zhao, Xiaoyan; Dou, Mengmeng; Zhang, Zhihao; Zhang, Duoduo; Huang, Chengzhi

2017-10-01

The preliminary studies have shown that Dendrobium officinale possessed therapeutic effects on hypertension and atherosclerosis. Studies also reported that Dendrobium officinale polysaccharides showed antioxidant capabilities. However, little is known about its effects on myocardial cells under oxidative stress. The present study was designed to study the protective effect of Dendrobium officinale polysaccharides against H 2 O 2 -induced oxidative stress in H9c2 cells. MTT assay was carried out to determine the cell viability of H9c2 cells when pretreated with Dendrobium officinale polysaccharides. Fluorescent microscopy measurements were performed for evaluating the apoptosis in H9c2 cells. Furthermore, effects of Dendrobium officinale polysaccharides on the activities of antioxidative indicators (malondialdehyde, superoxide dismutase), reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) levels were analyzed. Dendrobium officinale polysaccharides attenuated H 2 O 2 -induced cell death, as determined by the MTT assay. Dendrobium officinale polysaccharides decreased malondialdehyde levels, increased superoxide dismutase activities, and inhibited the generation of intracellular ROS. Moreover, pretreatment with Dendrobium officinale polysaccharides also inhibited apoptosis and increased the MMP levels in H9c2 cells. These results suggested the protective effects of Dendrobium officinale polysaccharides against H 2 O 2 -induced injury in H9c2 cells. The results also indicated the anti-oxidative capability of Dendrobium officinale polysaccharides. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Recent Results from Epitaxial Growth on Step Free 4H-SiC Mesas

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Trunek, Andrew J.; Spry, David J.; Powell, J. Anthony; Du, Hui; Skowronski, Marek; Bassim, Nabil D.; Mastro, Michael A.; Twigg, Mark E.; Holm, Ronald T.;

C-H activations at iridium(I) square-planar complexes promoted by a fifth ligand.

PubMed

Martín, Marta; Torres, Olga; Oñate, Enrique; Sola, Eduardo; Oro, Luis A

2005-12-28

In the presence of ligands such as acetonitrile, ethylene, or propylene, the Ir(I) complex [Ir(1,2,5,6-eta-C8H12)(NCMe)(PMe3)]BF4 (1) transforms into the Ir(III) derivatives [Ir(1-kappa-4,5,6-eta-C8H12)(NCMe)(L)(PMe3)]BF4 (L = NCMe, 2; eta2-C2H4, 3; eta2-C3H6, 4), respectively, through a sequence of C-H oxidative addition and insertion elementary steps. The rate of this transformation depends on the nature of L and, in the case of NCMe, the pseudo-first-order rate constants display a dependence upon ligand concentration suggesting the formation of five-coordinate reaction intermediates. A similar reaction between 1 and vinyl acetate affords the Ir(III) complex [Ir(1-kappa-4,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (7) via the isolable five-coordinate Ir(I) compound [Ir(1,2,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (6). DFT (B3LYP) calculations in model complexes show that reactions initiated by acetonitrile or ethylene five-coordinate adducts involve C-H oxidative addition transition states of lower energy than that found in the absence of these ligands. Key species in these ligand-assisted transformations are the distorted (nonsquare-planar) intermediates preceding the intramolecular C-H oxidative addition step, which are generated after release of one cyclooctadiene double bond from the five-coordinate species. The feasibility of this mechanism is also investigated for complexes [IrCl(L)(PiPr3)2] (L = eta2-C2H4, 27; eta2-C3H6, 28). In the presence of NCMe, these complexes afford the C-H activation products [IrClH(CH=CHR)(NCMe)(PiPr3)2] (R = H, 29; Me, 30) via the common cyclometalated intermediate [IrClH{kappa-P,C-P(iPr)2CH(CH3)CH2}(NCMe)(PiPr3)] (31). The most effective C-H oxidative addition mechanism seems to involve three-coordinate intermediates generated by photochemical release of the alkene ligand. However, in the absence of light, the reaction rates display dependences upon NCMe concentration again indicating the intermediacy of five

Interface Trap Profiles in 4H- and 6H-SiC MOS Capacitors with Nitrogen- and Phosphorus-Doped Gate Oxides

NASA Astrophysics Data System (ADS)

Jiao, C.; Ahyi, A. C.; Dhar, S.; Morisette, D.; Myers-Ward, R.

2017-04-01

We report results on the interface trap density ( D it) of 4H- and 6H-SiC metal-oxide-semiconductor (MOS) capacitors with different interface chemistries. In addition to pure dry oxidation, we studied interfaces formed by annealing thermal oxides in NO or POCl3. The D it profiles, determined by the C- ψ s method, show that, although the as-oxidized 4H-SiC/SiO2 interface has a much higher D it profile than 6H-SiC/SiO2, after postoxidation annealing (POA), both polytypes maintain comparable D it near the conduction band edge for the gate oxides incorporated with nitrogen or phosphorus. Unlike most conventional C- V- or G- ω-based methods, the C- ψ s method is not limited by the maximum probe frequency, therefore taking into account the "fast traps" detected in previous work on 4H-SiC. The results indicate that such fast traps exist near the band edge of 6H-SiC also. For both polytypes, we show that the total interface trap density ( N it) integrated from the C- ψ s method is several times that obtained from the high-low method. The results suggest that the detected fast traps have a detrimental effect on electron transport in metal-oxide-semiconductor field-effect transistor (MOSFET) channels.

Chlorogenic acid analogues from Gynura nepalensis protect H9c2 cardiomyoblasts against H2O2-induced apoptosis

PubMed Central

Yu, Bang-wei; Li, Jin-long; Guo, Bin-bin; Fan, Hui-min; Zhao, Wei-min; Wang, He-yao

2016-01-01

Aim: Chlorogenic acid has shown protective effect on cardiomyocytes against oxidative stress-induced damage. Herein, we evaluated nine caffeoylquinic acid analogues (1–9) isolated from the leaves of Gynura nepalensis for their protective effect against H2O2-induced H9c2 cardiomyoblast damage and explored the underlying mechanisms. Methods: H9c2 cardiomyoblasts were exposed to H2O2 (0.3 mmol/L) for 3 h, and cell viability was detected with MTT assay. Hoechst 33342 staining was performed to evaluate cell apoptosis. MMPs (mitochondrial membrane potentials) were measured using a JC-1 assay kit, and ROS (reactive oxygen species) generation was measured using CM-H2 DCFDA. The expression levels of relevant proteins were detected using Western blot analysis. Results: Exposure to H2O2 markedly decreased the viability of H9c2 cells and catalase activity, and increased LDH release and intracellular ROS production; accompanied by a loss of MMP and increased apoptotic rate. Among the 9 chlorogenic acid analogues as well as the positive control drug epigallocatechin gallate (EGCG) tested, compound 6 (3,5-dicaffeoylquinic acid ethyl ester) was the most effective in protecting H9c2 cells from H2O2-induced cell death. Pretreatment with compound 6 (1.56–100 μmol/L) dose-dependently alleviated all the H2O2-induced detrimental effects. Moreover, exposure to H2O2 significantly increased the levels of Bax, p53, cleaved caspase-8, and cleaved caspase-9, and decreased the level of Bcl-2, resulting in cell apoptosis. Exposure to H2O2 also significantly increased the phosphorylation of p38, JNK and ERK in the H9c2 cells. Pretreatment with compound 6 (12.5 and 25 μmol/L) dose-dependently inhibited the H2O2-induced increase in the level of cleaved caspase-9 but not of cleaved caspase-8. It also dose-dependently suppressed the H2O2-induced phosphorylation of JNK and ERK but not that of p38. Conclusion: Compound 6 isolated from the leaves of Gynura nepalensis potently protects H9c2

Special hydrogen bonds observed in two monovalent metal carboxylate-phosphinates: {NaH(Phsbnd PO2sbnd C2H4sbnd COOH)2}∞ and {[KH(Phsbnd PO2sbnd C2H4sbnd COOH)2]·H2O}∞

NASA Astrophysics Data System (ADS)

Zhao, Cui-Cui; Zhang, Jian-Wei; Zhou, Zhong-Gao; Du, Zi-Yi

2013-02-01

The addition of strong base such as sodium hydroxide or potassium hydroxide to the aqueous solution of (2-carboxyethyl)(phenyl)phosphinic acid afforded two novel monovalent metal carboxylate-phosphinates, namely, {NaH(Phsbnd PO2sbnd C2H4sbnd COOH)2}∞ (1) and {[KH(Phsbnd PO2sbnd C2H4sbnd COOH)2]·H2O}∞ (2). They represent the first examples of phosphinate containing short, symmetric or almost symmetric O⋯H⋯O hydrogen bonds.

Forward and Inverse Modeling of Near-Field Seismic Waveforms from Underground Nuclear Explosions for Effective Source Functions and Structure Parameters.

DTIC Science & Technology

1987-04-05

IP o , I-S " M4.7 :" * AMIWILTON & U, .-- EALY(I969) : o H CARROLL(1966) HADLEY (19811 C . Figure 2. P and S-wave velocity structure for Pahute Mesa...8217; 0 .02 s wh ilIe S -. cI by C ) >, s) thIe kta i Is o f t he wav e for:7s are quite well modeled bot h ir tr~~e inversion nd in tefrad mod e Iin~ indi...ESTIMATION 7-Te source parameters determined through waveform inversion for the fo: s o r c ri i c e h v h s~ ahute Mesa events studied are sum.:rarited in

Stability of methane in reduced C-O-H fluid at 6.3 GPa and 1300-1400°C

NASA Astrophysics Data System (ADS)

Sokol, A. G.; Tomilenko, A. A.; Bul'bak, T. A.; Palyanova, G. A.; Palyanov, Yu. N.; Sobolev, N. V.

2017-06-01

The composition of a reduced C-O-H fluid was studied by the method of chromatography-mass spectrometry under the conditions of 6.3 GPa, 1300-1400°C, and fO2 typical of the base of the subcratonic lithosphere. Fluids containing water (4.4-96.3 rel. %), methane (37.6-0.06 rel. %), and variable concentrations of ethane, propane, and butane were obtained in experiments. With increasing fO2, the proportion of the CH4/C2H6 peak areas on chromatograms first increases and then decreases, whereas the CH4/C3H8 and CH4/C4H10 ratios continually decrease. The new data show that ethane and heavier HCs may be more stable to oxidation, than previously thought. Therefore, when reduced fluids pass the "redox-front," carbon is not completely released from the fluid and may be involved in diamond formation.

The impact of altitude on hospitalization and hospital mortality from pandemic 2009 influenza A (H1N1) virus pneumonia in Mexico.

PubMed

Pérez-Padilla, Rogelio; García-Sancho, Cecilia; Fernández, Rosario; Franco-Marina, Francisco; López-Gatell, Hugo; Bojórquez, Ietza

2013-01-01

To determine the effect of altitude of residence on influenza A (H1N1). We analyzed 207 135 officially notified of influenza-like illness (ILI) cases, 23 048 hospitalizations and 573 deaths during the first months of the novel pandemic influenza A H1N1 virus, to examine if residents of high altitude had more frequently these adverse outcomes. Adjusted rates for hospitalization and hospital mortality rates increased with altitude, probably due to hypoxemia.

The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH3, PH3, C2H2, C2H6, CH3D, CH4, and the Saturnian D/H isotopic ratio

NASA Technical Reports Server (NTRS)

Courtin, R.; Gautier, D.; Marten, A.; Bezard, B.; Hanel, R.

1984-01-01

The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3/H2 ratio of 1.4 + or - 0.8 x 10 to the -6th is higher than the value derived from the solar P/H ratio. The stratospheric C2H2/H2 and C2H6/H2 ratios are, respectively, 2.1 + or - 1.4 x 10 to the -7th and 3.0 + or - 1.1 x 10 to the -6th; the latter decreases sharply below the 20-50 mbar level. The results for CH3D/H2 and CH4/H2 imply an enrichment of Saturn's upper atmosphere in carbon by a factor of at least three over the solar abundance. The interpretation of two NH3 lines in the five-micron window suggests a NH3/H2 ratio at the two bar level below the solar value.

Optically detected cyclotron resonance investigations on 4H and 6H SiC: Band-structure and transport properties

NASA Astrophysics Data System (ADS)

Meyer, B. K.; Hofmann, D. M.; Volm, D.; Chen, W. M.; Son, N. T.; Janzén, E.

2000-02-01

We present experimental data on the band-structure and high-mobility transport properties of 6H and 4H-SiC epitaxial films based on optically detected cyclotron resonance investigations. From the orientational dependence of the electron effective mass in 6H-SiC we obtain direct evidence for the camels back nature of the conduction band between the M and L points. The broadening of the resonance signal in 4H-SiC as a function of temperature is used to extract information on electron mobilities and to conclude on the role of the different scattering mechanisms. Under high microwave powers an enhancement of the electron effective mass is found which is explained by a coupling of the electrons with longitudinal optical phonons.

Diodes of nanocrystalline SiC on n-/n+-type epitaxial crystalline 6H-SiC

NASA Astrophysics Data System (ADS)

Zheng, Junding; Wei, Wensheng; Zhang, Chunxi; He, Mingchang; Li, Chang

2018-03-01

The diodes of nanocrystalline SiC on epitaxial crystalline (n-/n+)6H-SiC wafers were investigated, where the (n+)6H-SiC layer was treated as cathode. For the first unit, a heavily boron doped SiC film as anode was directly deposited by plasma enhanced chemical vapor deposition method on the wafer. As to the second one, an intrinsic SiC film was fabricated to insert between the wafer and the SiC anode. The third one included the SiC anode, an intrinsic SiC layer and a lightly phosphorus doped SiC film besides the wafer. Nanocrystallization in the yielded films was illustrated by means of X-ray diffraction, transmission electronic microscope and Raman spectrum respectively. Current vs. voltage traces of the obtained devices were checked to show as rectifying behaviors of semiconductor diodes, the conduction mechanisms were studied. Reverse recovery current waveforms were detected to analyze the recovery performance. The nanocrystalline SiC films in base region of the fabricated diodes are demonstrated as local regions for lifetime control of minority carriers to improve the reverse recovery properties.

Effect of influenza-like illness and other wintertime respiratory illnesses on worker productivity: The child and household influenza-illness and employee function (CHIEF) study.

PubMed

Palmer, Liisa A; Rousculp, Matthew D; Johnston, Stephen S; Mahadevia, Parthiv J; Nichol, Kristin L

2010-07-12

Acute respiratory illnesses (ARI), comprising influenza-like illness (ILI) and other wintertime respiratory illnesses (ORI), impose substantial health and economic burdens on the United States. Little is known about the impact of ILI among household members (HHM), particularly children, on employees' productivity. To quantify the impact of employee and HHM-ILI and ARI on employee productivity, a prospective, observational cohort study was conducted among employees from three large US companies. Employees who had at least one child living at home (N=2013) completed a monthly survey during the 2007-2008 influenza season, reporting the number of days missed from work and hours of presenteeism due to: (1) personal ILI, (2) HHM-ILI, and (3) personal and HHM-ARI. Employee ILI ranged from 4.8% (April) to 13.5% (February). Employees reporting ILI reported more absences than employees not reporting ILI (72% vs 30%, respectively; P<0.001). Overall, 61.2% of employees surveyed had at least one child with an ILI; these employees missed more days of work due to HHM illness than employees without an ARI-ill child (0.9 days vs 0.3 days, respectively; P<0.001). Employees with ILI were less productive, on average, for 4.8h each day that they worked while sick, 2.5h of which was attributable to ILI. HHM illnesses accounted for 17.7% (1389/7868 days) of employee absenteeism, over half of which was due to HHM-ARI. ILI causes a significant amount of employee absence. Household members, particularly children, comprise a sizable proportion of general illness and injury-related employee absences. Copyright 2010 Elsevier Ltd. All rights reserved.

The Relationship of HCN, C2H6, & H2O in Comets: A Key Clue to Origins?

NASA Astrophysics Data System (ADS)

Mumma, Michael J.; Charnley, Steven B.; Cordiner, Martin; Paganini, Lucas; Villanueva, Geronimo Luis

2017-10-01

Background: HCN, C2H6, and H2O are three of the best characterized volatiles in comets. It is often assumed that all three are primary volatiles, native to the nucleus. Here, we compare their properties in 26 comets (9 JFC and 17 Oort-cloud), making 6 points:1. Both HCN and C2H6 are poor proxies for water production. The production rate ratio (Q-ratio) of each trace gas relative to water varies by a factor of six among these comets.2. All 26 comets have Q-ratios HCN/C2H6 > 0.1. In 18 comets the Q-ratios HCN/H2O and C2H6/H2O are correlated, with a mean ratio of 0.33. In 6 comets undergoing complete disruption, this Q-ratio exceeds 0.5.3. Q-ratios HCN/C2H6 are not correlated with Q(H2O), nor are they correlated with dynamical class (Oort cloud vs. JFC).4. The nucleus-centered rotational temperatures measured for H2O and other primary species (C2H6, CH3OH) usually agree within error, but those for HCN are often slightly cooler. Could this mean that HCN is not fully developed in the warm near-nucleus region, and instead is at least in part a product species?5. With its strong dipole moment and H-bonding character, HCN should be linked more strongly in the nuclear ice to other molecules with similar properties (H2O, CH3OH), but instead its spatial release in some comets seems strongly coupled to volatiles that lack a dipole moment and thus do not form H-bonds (methane, ethane). Is HCN produced in part from an apolar precursor?6. ALMA maps of HCN and the dust continuum show a slight displacement in their centroids. Is this the signature of extended production of HCN?HCN as a product species: Points 4-6 suggest that HCN may have a significant distributed source. The astrochemical species ammonium cyanide is a strong candidate for this HCN precursor; at moderately low temperatures (< 200K) NH4CN is a stable solid, but it dissociates into HCN and NH3 when warmed. Disruption could eject macroscopic solid NH4CN into the coma where subsequent warming and release could augment

Temporal Clustering in the Multi-Target Tracking Environment

DTIC Science & Technology

1988-08-01

UNLASS IliED % ,, SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)_ REPORT DOCUMENTATION PAGE BF READ INSTRUCTIONS6. PEFORE COMPLETING FORM...1. REPORT NUMBER (. )OVT ACCESSION No. 3. RE-Ur-’SAFIT/CI/NR 88- 1 ? ,7 1 11 - _t tA Jr TITLE (and Subtitle) S. TYPE OF REPORT A PERIOD COVEREDTLMfP6...AL C405TEW .GI )K T 4 MULT)- F11M9THESI I, TiNtLqET TOLFNCK lUG 6.mVjllop,3MrJT TEI ~6. PERFORMING O-4O. REPORT hUMBER AU THOR(s) 8. CONTRACT OR

Charge-transfer-directed radical substitution enables para-selective C-H functionalization

NASA Astrophysics Data System (ADS)

Boursalian, Gregory B.; Ham, Won Seok; Mazzotti, Anthony R.; Ritter, Tobias

2016-08-01

Efficient C-H functionalization requires selectivity for specific C-H bonds. Progress has been made for directed aromatic substitution reactions to achieve ortho and meta selectivity, but a general strategy for para-selective C-H functionalization has remained elusive. Herein we introduce a previously unappreciated concept that enables nearly complete para selectivity. We propose that radicals with high electron affinity elicit arene-to-radical charge transfer in the transition state of radical addition, which is the factor primarily responsible for high positional selectivity. We demonstrate with a simple theoretical tool that the selectivity is predictable and show the utility of the concept through a direct synthesis of aryl piperazines. Our results contradict the notion, widely held by organic chemists, that radical aromatic substitution reactions are inherently unselective. The concept of radical substitution directed by charge transfer could serve as the basis for the development of new, highly selective C-H functionalization reactions.

Characterizing the Epidemiology of the 2009 Influenza A/H1N1 Pandemic in Mexico

PubMed Central

Chowell, Gerardo; Echevarría-Zuno, Santiago; Viboud, Cécile; Simonsen, Lone; Tamerius, James; Miller, Mark A.; Borja-Aburto, Víctor H.

2011-01-01

Background Mexico's local and national authorities initiated an intense public health response during the early stages of the 2009 A/H1N1 pandemic. In this study we analyzed the epidemiological patterns of the pandemic during April–December 2009 in Mexico and evaluated the impact of nonmedical interventions, school cycles, and demographic factors on influenza transmission. Methods and Findings We used influenza surveillance data compiled by the Mexican Institute for Social Security, representing 40% of the population, to study patterns in influenza-like illness (ILIs) hospitalizations, deaths, and case-fatality rate by pandemic wave and geographical region. We also estimated the reproduction number (R) on the basis of the growth rate of daily cases, and used a transmission model to evaluate the effectiveness of mitigation strategies initiated during the spring pandemic wave. A total of 117,626 ILI cases were identified during April–December 2009, of which 30.6% were tested for influenza, and 23.3% were positive for the influenza A/H1N1 pandemic virus. A three-wave pandemic profile was identified, with an initial wave in April–May (Mexico City area), a second wave in June–July (southeastern states), and a geographically widespread third wave in August–December. The median age of laboratory confirmed ILI cases was ∼18 years overall and increased to ∼31 years during autumn (p<0.0001). The case-fatality ratio among ILI cases was 1.2% overall, and highest (5.5%) among people over 60 years. The regional R estimates were 1.8–2.1, 1.6–1.9, and 1.2–1.3 for the spring, summer, and fall waves, respectively. We estimate that the 18-day period of mandatory school closures and other social distancing measures implemented in the greater Mexico City area was associated with a 29%–37% reduction in influenza transmission in spring 2009. In addition, an increase in R was observed in late May and early June in the southeast states, after mandatory school

Time resolved infrared studies of C-H bond activation by organometallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asplund, M.C.

This work describes how step-scan Fourier Transform Infrared spectroscopy and visible and near infrared ultrafast lasers have been applied to the study of the photochemical activation of C-H bonds in organometallic systems, which allow for the selective breaking of C-H bonds in alkanes. The author has established the photochemical mechanism of C-H activation by Tp{sup *}Rh(CO){sub 2}(Tp{sup *} = HB-Pz{sup *}{sub 3}, Pz = 3,5-dimethylpyrazolyl) in alkane solution. The initially formed monocarbonyl forms a weak solvent complex, which undergoes a change in Tp{sup *} ligand connectivity. The final C-H bond breaking step occurs at different time scales depending on themore » structure of the alkane. In linear solvents, the time scale is <50 ns and cyclic alkanes is {approximately}200 ps. The reactivity of the Tp{sup *}Rh(CO){sub 2} system has also been studied in aromatic solvents. Here the reaction proceeds through two different pathways, with very different time scales. The first proceeds in a manner analogous to alkanes and takes <50 ns. The second proceeds through a Rh-C-C complex, and takes place on a time scale of 1.8 {micro}s.« less

Mercury-Bridged Cobaltacarborane Complexes Containing B-Hg-B Three-Center Bonds. Synthesis and Structure of mu, mu’-((n5-C5R5)Co(CH3)2C2B3H4)Hg, mu-(n(5)-C5R5)Co(CH3)2C2B3H4)HgCl, (R=H, CH3) and Related Compounds.

DTIC Science & Technology

1980-11-01

MERCURY-BRIDGED COBALTACARBORANE COMPLEXES CONTAINING B-HG-B TH--ETC(U) NOV 80 D C FINSTER . R N GRIMES N0 0 0 1 4-75-0305 UNCLASSXFIED TR󈧨 NL ILn...C5R5) Co 3)2C2B3 4 2 5 .- -C5R5 )Co(CH3)2C2B3H4 ]HgCl, (R=H, CH3 ) and Related Compounds, David C./ Finster -- Russell N./Grimes ( Department of Chemistry...Compounds 1 \\David C. Finster And Russell N. Grimes* Abstract. Reactions of the nid~p-cobaltacarborane anions 01CR )(C 3 )C BH and [n (H 1oC ihH~5n 5

C-H Hot Bands in the Near-IR Emission Spectra of Leonids

NASA Technical Reports Server (NTRS)

Freund, F. T.; Scoville, J.; Holm, R.; Seelemann, R.; Freund, M. M.

2002-01-01

The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4 micron C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the nu(sub )CH emission band in the Leonid emission spectra arises from matrix-embedded C(sub n)-H-O entities that are protected from instant pyrolysis. Our model is based on IR absorption nu(sub )CH bands, which we observed in laboratory-grown MgO and natural olivine single crystals, where they arise from C(sub n)-H-O units imbedded in the mineral matrix, indicative of aliphatic -CH2- and -CH3 organics. Instead of being pyrolyzed, the C(sub n)-H-O entities in the Leonid trails become vibrationally excited to higher levels n = 1, 2, 3 etc. During de-excitation they emit at 3.4 microns, due to the (0 => 1) transition, and at longer wavelengths, due to hot bands. As a first step toward verifying this hypothesis we measured the C-H vibrational manifold of hexane (C6H14). The calculated positions of the (2 => l ) , (3 => 2), and possibly (4 => 3) hot bands agree with the Leonid emission bands at 3.5, 3.8 and 4.l microns.

The Dissociation Energies of CH4 and C2H2 Revisited

NASA Technical Reports Server (NTRS)

Partridge, Harry; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

The bond dissociation energies of CH4 and C2H2 and their fragments are investigated using basis set extrapolations and high levels of correlation. The computed bond dissociation energies (D(sub e)) are accurate to within 0.2 kcal/mol. The agreement with the experimental (D(sub 0)) values is excellent if we assume that the zero-point energy of C2H is 9.18 kcal/mol. The effect of core (1s) correlation on the bond dissociation energies of C-H bonds is shown to vary from 0.2 to 0.7 kcal/mol and that for C-C bonds varies from 0.4 to 2.2 kcal/mol.