The 3.1 Μm Infrared Spectra Of Vibrationally Excited C3 In A Supersonic Plasma Jet

The linear triatomic carbon (C$_3$), one of the most important molecules that have been identified in both dense and diffuse interstellar environments, has attracted great interest to astronomers and astrochemists. It is also of fundamental interest as it serves as a benchmark system for quantum chemistry. In this presentation, we report the high-resolution infrared spectra of C$_3$ in the 3.1 $\mu$m region. The $C_3$ molecules are produced in a supersonic pulsed planar plasma by discharging a propyne/helium/argon gas mixture. Continuous-wave cavity ringdown spectroscopy is used to record the infrared absorption spectra of C$_3$. In total, eighteen vibrational bands are observed in the 3110 - 3290 \wn range, and sixteen of them are reported for the first time. It is found that, the vibrational temperatures for the two CC stretch modes of C$_3$ are up to 8000 K in our plasma source, allowing to experimentally determine the ro-vibrational levels of C$_3$ to the 10 000 \wn region. Accurate spectroscopic parameters are obtained from the detailed analysis of our spectra. The molecular data reported here are used to test the very recent theoretical work beyond the 'gold standard' \footnote{P. Botschiwina, private communication.} for a comprehensive understanding of the ground-state potential energy surface of C$_3$

High-resolution Infrared Spectra Of The Ν1 Fundamental Bands Of 13c Mono-substituted Propyne In A Supersonic Slit Jet

In the past few decades, many high-resolution spectroscopic studies have been dedicated to the C-H stretch vibrations in propyne (CH$_3$-C$\equiv$CH), aiming to understand the intramolecular vibrational redistribution in isolated small hydrocarbons. In this talk, we present the sensitive detection of the $\nu_1$ (acetylenic C-H stretch) fundamental bands of the three $^{13}$C mono-substituted isotopologues of propyne. The infrared absorption spectra are recorded using continuous-wave cavity ring-down spectroscopy (CRDS) in combination with a supersonic jet expansion of propyne/argon gas mixtures. A 0.05x30 mm slit nozzle is used in the present experiment to realize an effective rotational cooling to $\approx$14 K and a reduced Doppler width of $\approx$90 MHz. The high sensitivity of CRDS allows us to detect the three $^{13}$C isotopologues in their 1.1\% natural abundance. Different infrared band intensities of $\nu_1$ are found for the three isotopologues. Detailed rotational analyses of the experimental spectra are performed to derive effective spectroscopic constants for the upper $\nu_1$ vibrational state. The $^{13}$C-substitution effect of the near/non-resonant perturbations to $\nu_1$ of propyne is discussed. In addition, more accurate infrared data of $^{12}$C-propyne, including the $\nu_1$ fundamental band, are also obtained from our experimental spectra

The B2Π−^2\Pi-X2Π^2\Pi electronic origin band of 13^{13}C6_6H

The rotationally resolved spectrum of the B$^2\Pi-$X$^2\Pi$ electronic origin band transition of $^{13}$C$_6$H is presented. The spectrum is recorded using cavity ring-down spectroscopy in combination with supersonic plasma jets by discharging a $^{13}$C$_2$H$_2$/He/Ar gas mixture. A detailed analysis of more than a hundred fully-resolved transitions allows for an accurate determination of the spectroscopic parameters for both the ground and electronically excited state of $^{13}$C$_6$H.Comment: 4 pages, 1 figure, 2 table

Reaction kinetics of CN + toluene and its implication on the productions of aromatic nitriles in the Taurus molecular cloud and Titan's atmosphere

Reactions between cyano radical and aromatic hydrocarbons are believed to be important pathways for the formation of aromatic nitriles in the interstellar medium (ISM) including those identified in the Taurus molecular cloud (TMC-1). Aromatic nitriles might participate in the formation of polycyclic aromatic nitrogen containing hydrocarbons (PANHs) in Titan's atmosphere. Here, ab initio kinetics simulations reveal a high efficiency of $\rm \sim10^{-10}~cm^{3}~s^{-1}$ and the competition of the different products of 30-1800 K and $10^{-7}$-100 atm of the CN + toluene reaction. In the star-forming region of TMC-1 environment, the product yields of benzonitrile and tolunitriles for CN reacting with toluene may be approximately 17$\%$ and 83$\%$, respectively. The detection of main products, tolunitriles, can serve as proxies for the undetected toluene in the ISM due to their much larger dipole moments. The competition between bimolecular and unimolecular products is extremely intense under the warmer and denser PANH forming region of Titan's stratosphere. The computational results show that the fractions of tolunitriles, adducts, and benzonitrile are 19$\%$-68$\%$, 15$\%$-64$\%$ and 17$\%$, respectively, at 150-200 K and 0.0001-0.001 atm (Titan's stratosphere). Then, benzonitrile and tolunitriles may contribute to the formation of PANHs by consecutive $\rm C_{2}H$ additions. Kinetic information of aromatic nitriles for the CN + toluene reaction calculated here helps to explain the formation mechanism of polycyclic aromatic hydrocarbons (PAHs) or PANHs under different interstellar environments and constrains corresponding astrochemical models

Polymorphisms of TGFB1 and VEGF genes and survival of patients with gastric cancer

<p>Abstract</p> <p>Background</p> <p>Some <it>TGFB1 </it>and <it>VEGF </it>polymorphisms are believed to be functional. Given that these genes are involved in tumor growth and progression including angiogenesis, dissemination, and invasiveness, we hypothesized that these polymorphisms would be associated with survival in patients with gastric cancer.</p> <p>Methods</p> <p>We genotyped <it>TGFB1 </it>-509 C>T, +1869 T>C, and +915 G>C and <it>VEGF </it>-1498T>C, -634G>C, and +936C>T in 167 patients with gastric cancer. Using the Kaplan and Meier method, log-rank tests, and Cox proportional hazard models, we evaluated associations among <it>TGFB1 </it>and <it>VEGF </it>variants with overall, 1-year, and 2-year survival rates.</p> <p>Results</p> <p>Although there were no significant differences in overall survival rates among all polymorphisms tested, patients with <it>TGFB1</it>+915CG and CC genotypes had a poorer 2-year survival (adjusted hazard ratio (HR), 3.06; 95% confidence interval (CI), 1.09–8.62; <it>P </it>= 0.034) than patients with the GG genotype had. In addition, patients heterozygous for <it>VEGF </it>-634CG also had a poorer 1-year survival (adjusted HR, 2.08; 95% CI, 1.03–4.22; <it>P </it>= 0.042) than patients with the -634GG genotype.</p> <p>Conclusion</p> <p>Our study suggested that <it>TGFB1</it>+915CG/CC and <it>VEGF </it>-634CG genotypes may be associated with short-term survival in gastric cancer patients. However, larger studies are needed to verify these findings.</p

A Spectroscopic Survey of Electronic Transitions of C6_6H, 13^{13}C6_6H, and C6_6D

Electronic spectra of C$_6$H are measured in the $18\,950-21\,100$ cm$^{-1}$ domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon plasma. In total, 19 (sub)bands of C$_6$H are presented, all probing the vibrational manifold of the B$^2\Pi$ electronically excited state. The assignments are guided by electronic spectra available from matrix isolation work, isotopic substitution experiments (yielding also spectra for $^{13}$C$_6$H and C$_6$D), predictions from ab initio calculations as well as rotational fitting and vibrational contour simulations using the available ground state parameters as obtained from microwave experiments. Besides the $0_0^0$ origin band, three non-degenerate stretching vibrations along the linear backbone of the C$_6$H molecule are assigned: the $\nu_6$ mode associated with the C-C bond vibration and the $\nu_4$ and $\nu_3$ modes associated with C$\equiv$C triple bonds. For the two lowest $\nu_{11}$ and $\nu_{10}$ bending modes, a Renner-Teller analysis is performed identifying the $\mu^2\Sigma$($\nu_{11}$) and both $\mu^2\Sigma$($\nu_{10}$) and $\kappa^2\Sigma$($\nu_{10}$) components. In addition, two higher lying bending modes are observed, which are tentatively assigned as $\mu^2\Sigma$($\nu_9$) and $\mu^2\Sigma$($\nu_8$) levels. In the excitation region below the first non-degenerate vibration ($\nu_6$), some $^2\Pi-^{2}\Pi$ transitions are observed that are assigned as even combination modes of low-lying bending vibrations. The same holds for a $^2\Pi-^{2}\Pi$ transition found above the $\nu_6$ level. From these spectroscopic data and the vibronic analysis a comprehensive energy level diagram for the B$^2\Pi$ state of C$_6$H is derived and presented.Comment: Accepted for publication in The Journal of Physical Chemistry A (26 July 2016