Spectroscopy and Energy Transfer of Molecular Transients: Hydrogen Isocyanide and the Ketenyl Radical

Energy transfer from molecular species has been a long standing topic of profound interest to the chemical physics community. It is worth noting however, that to date, most studies have preferentially focused on chemically stable molecular species. While the literature does contain numerous examples of energy transfer of small radical or chemically unstable species, there have been extremely few studies which have actually probed highly vibrationally excited species. This apparent lack of attention should not be confused with a lack of interest. On the contrary, given the prevalence of vibrationally excited radicals in complex chemical systems such as planetary atmospheres and combustion, it is highly desirable to gain a complete understanding of the energetic deactivation processes of these delicate species. More often than not, the limiting factor which prevents examination of such species is a lack of spectroscopic information which is necessary for the identification as well as modeling of the corresponding species. In this thesis, we explore the use of time-resolved Fourier transform infrared emission spectroscopy, coupled with ab initio quantum chemical calculations, as a means of characterizing the vibrationally excited energy transfer dynamics from hydrogen isocyanide (HNC) as well as the ketenyl (HCCO) radical. It has been determined that each of these radical species can be generated in appreciable relative concentrations and with excess internal energy, following the 193 nm photolysis of specific stable molecular precursors. Through variation of the associated inert atomic collider species, and repeated spectral fitting analysis, it becomes feasible to obtain a measure the time-resolved average internal energy (as a function of the collider species), and hence a measure of the vibrational energy transfer efficiency of each radical species. It is observed that both HNC and HCCO exhibit enhanced vibrational energy transfer, for all average internal energies, relative to comparably sized stable molecular species. The roles and associated benefits of enhanced energy transfer of these radical species, to combustion chemistry (HCCO) as well as the interstellar medium (HNC), will be discussed

DNA sequence comparisons of Ophiostoma spp., including Ophiostoma aurorae sp. nov., associated with pine bark beetles in South Africa

Bark beetles (Coleoptera: Scolytinae) are well-recognized vectors of Ophiostoma species. Three non-native bark beetle species infest various Pinus species in South Africa, and they are known to carry at least 12 different species of ophiostomatoid fungi. Some of these fungi have not been identified to species level. The aim of this study was to determine or confirm the identities of Ophiostoma species associated with bark beetles in South Africa using comparisons of DNA sequence data. Identities of Ophiostoma ips, O. floccosum, O. pluriannulatum, O. quercus and O. stenoceras were confirmed. Ophiostoma abietinum, O. piliferum and Pesotum fragrans are recognised for the first time and the new species, O. aurorae sp. nov., is described from pine-infesting bark beetles in South Africa

Structure and dynamics of iron pentacarbonyl

The dynamics of CO ligand scrambling in Fe(CO)5 has been investigated by linear infrared spectroscopy in supercritical xenon solution. The activation barrier for the Berry pseudorotation in Fe(CO)5 was determined experimentally to be Ea = 2.5 ± 0.4 kcal mol–1 by quantitative analysis of the temperature-dependent spectral line shape. This compares well with the range of Ea/(kcal mol–1) = 2.0 to 2.3 calculated by various DFT methods and the value of 1.6 ± 0.3 previously obtained from 2D IR measurements by Harris et al. ( Science 2008, 319, 1820). The involvement of Fe(CO)5···Xe interactions in the ligand scrambling process was tested computationally at the BP86-D3/AE2 level and found to be negligible

The Century Survey Galactic Halo Project II: Global Properties and the Luminosity Function of Field Blue Horizontal Branch Stars

We discuss a 175 deg^2 spectroscopic survey for blue horizontal branch (BHB) stars in the Galactic halo. We use the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to select BHB candidates, and find that the 2MASS and SDSS color-selection is 38% and 50% efficient, respectively, for BHB stars. Our samples include one likely run-away B7 star 6 kpc below the Galactic plane. The global properties of the BHB samples are consistent with membership in the halo population: the median metallicity is [Fe/H]=-1.7, the velocity dispersion is 108 km/s, and the mean Galactic rotation of the BHB stars 3<|z|<15 kpc is -4 +- 30 km/s. We discuss the theoretical basis of the Preston, Shectman & Beers M_V-color relation for BHB stars, and conclude that intrinsic shape of the BHB M_V-color relation results from the physics of stars on the horizontal branch. We calculate the luminosity function for the field BHB star samples using the Efstathiou, Ellis, & Peterson maximum-likelihood method which is unbiased by density variations. The field BHB luminosity function exhibits a steep rise at bright luminosities, a peak between 0.8 < M_V < 1.0, and a tail at faint luminosities. We compare the field BHB luminosity functions with the luminosity functions derived from sixteen different globular cluster BHBs. Kolmogorov-Smirnov tests suggest that field BHB stars and BHB stars in globular clusters share a common distribution of luminosities, with the exception of globular clusters with extended BHBs.Comment: 14 pages, including 16 figures, accepted for publication in A

Reduced incidence of atrial fibrillation after cardiac surgery by continuous wireless monitoring of oxygen saturation on the normal ward and resultant oxygen therapy for hypoxia

Objective: Monitoring of cardiac surgical patients after transfer from the intensive care unit to the normal ward is incomplete. Undetected hypoxia, however, is known to be a risk factor for occurrence of atrial fibrillation. We have utilized Auricall® for continuous wireless monitoring of oxygen saturation and heart rate until discharge. The object of the study was to analyze if oxygen therapy as a result of Auricall® alerts of hypoxia can decrease the incidence of postoperative atrial fibrillation. Methods: Auricall® is a wireless portable pulse oximeter. An alert is generated depending on preset threshold values (heart rate, oxygen saturation). Over a period of 6 months, 119 patients were monitored with the Auricall® following coronary artery bypass graft and/or valve surgery. Oxygen therapy was started subsequent to an oxygen saturation below 90%. These patients were compared with a cohort of 238 patients from the time period before availability of Auricall®. The patient characteristics were comparable in both groups. In a retrospective study, the incidence of atrial fibrillation was measured in both groups. Results: The postoperative AF was observed in 22/119 patients (18%) in group I and in 66/238 patients (28%) in group II. This difference between the two groups approached significance (p=0.056). In the subgroup of patients with coronary artery bypass graft with our without simultaneous valve surgery (n=312), Auricall® monitoring resulted in a significantly reduced incidence of atrial fibrillation (14% vs 26%, p=0.016). Conclusions: Continuous monitoring of oxygen saturation on the normal ward and subsequent oxygen therapy for hypoxia can reduce the incidence of atrial fibrillation in a subgroup of patients after cardiac surgery. Prospective randomized trials are warranted to confirm these dat

Исследование влияния природы растворителя, используемого при получении электродной мембраны, на работу Ni-селективного электрода при определении ионов никеля (LL) в водных средах

Исследовано влияние природы растворителей (бензиловый спирт и хлорфенол), используемых для изготовления полимерной электродной мембраны твердофазного никельселективного электрода на основе никельгексационоферратов ({Ni2[Fe(CN)6]}), иммобилизованных в полиэтилентерефталатную (ПЭТФ) матрицу для определения ионов никеля в водных средах. Установлено, что мембраны, полученные на основе бензилового спирта имеют более высокие электродные показатели по сходимости и воспроизводимости потенциалов, стабильности работы, низком дрейфе и времени отклика электрода по сравнению с мембранами на основе хлорфенола и могут быть рекомендованы к использованию в никель селективных электродах.The influence of the nature of the solvents (benzyl alcohol and chlorophenol) used to fabricate a polymer electrode membrane of a solid-phase nickel selective electrode based on nickelhexacetanoferrates ({Ni2 [Fe (CN) 6]}) immobilized in a polyethylene terephthalate (PET) matrix for the determination of nickel ions in aqueous media . It has been established that membranes obtained on the basis of benzyl alcohol have higher electrode indices for the convergence and reproducibility of potentials, stability of operation, low drift and electrode response time compared to chlorophenol-based membranes, and can be recommended for use in nickel selective electrodes

An Experimental Investigation of 4-Layer Printed Circuit Board Decoupling

This paper examines the measured power bus impedance of fully populated 4-layer printed circuit boards with internal power and ground planes. Three boards provided by two leading computer companies were evaluated. Each of the state-of-the-art high-speed boards used in this study employed surface-mount decoupling capacitors to reduce noise on the power bus. The boards were measured with and without some or all of their decoupling capacitance. The effectiveness of the decoupling capacitors as a function of location and frequency and the relationship between board impedance and power bus noise was explored. The behavior of 4-layer boards is shown to be quite different than that of boards without planes or boards with closely spaced planes