The deuteron-deuteron reaction and the stopping cross section of D_2O ice below 600 kev

The energy loss of protons and deuterons in D_2O ice has been measured over the energy range, E_p 18 - 541 kev. The double focusing magnetic spectrometer was used to measure the energy of the particles after they had traversed a known thickness of the ice target. One method of measurement is used to determine relative values of the stopping cross section as a function of energy; another method measures absolute values. The results are in very good agreement with the values calculated from Bethe’s semi-empirical formula. Possible sources of error are considered and the accuracy of the measurements is estimated to be ± 4%.

The D(dp)H^3 cross section has been measured by two methods. For E_D = 200 - 500 kev the spectrometer was used to obtain the momentum spectrum of the protons and tritons. From the yield and stopping cross section the reaction cross section at 90° has been obtained.

For E_D = 35 – 550 kev the proton yield from a thick target was differentiated to obtain the cross section. Both thin and thick target methods were used to measure the yield at each of ten angles. The angular distribution is expressed in terms of a Legendre polynomial expansion. The various sources of experimental error are considered in detail, and the probable error of the cross section measurements is estimated to be ± 5%.

I. Thermochemistry and reaction kinetics of disolvated protons by ion cyclotron resonance spectroscopy. II. Thermochemical studies of small fluorocarbons by photoionization mass spectrometry

The disolvated proton, H(OH₂)₂⁺ is employed as a chemical reagent in low pressure (˂ 10^-5 torr) investigations by ion cyclotron resonance spectroscopy. Since termolecular reactions are absent at low pressure, disolvated protons are not generally observed. However H(OH₂)₂⁺ is produced in a sequence of bimolecular reactions in mixtures containing H₂O and one of a small number of organohalide precursors. Then a series of hydrated Lewis bases is produced by H₃O⁺ transfer from H(OH₂)₂⁺. In Chapter II, the relative stability of hydrated bases containing heteroatoms of both first and second row elements is determined from the preferred direction of H₃O⁺ transfer between BH(OH₂)⁺ complexes. S and P containing bases are shown to bind H₃O⁺ more weakly than O and N bases with comparable proton affinities. A simple model of hydrogen bonding is proposed to account for these observations.

H⁺ transfer from H(OH₂)₂⁺ to several Lewis bases also occurs at low pressure. In Chapter III the relative importance of H₃O⁺ transfer and H⁺ transfer from H(OH₂)₂⁺ to a series of bases is observed to be a function of base strength. Beginning with CH₃COOH, the weakest base for which H⁺ transfer is observed, the importance of H⁺ transfer increases with increasing proton affinity of the acceptor base. The nature of neutral products formed from H(OH₂)₂⁺ by loss of H⁺ is also considered.

Chapters IV and V deal with thermochemistry of small fluorocarbons determined by photoionization mass spectrometry. The enthalpy of formation of CF₂ is considered in Chapter IV. Photoionization of perfluoropropylene, perfluorocyclopropane, and trifluoromethyl benzene yield onsets for ions formed by loss of a CF₂ neutral fragment. Earlier determinations of ΔH^°_f298 (CF₂) are reinterpreted using updated thermochemical values and compared with results of this study. The heat of formation of neutral perfluorocyclopropane is also derived. Finally, the energetics of interconversion of perfluoropropylene and perfluorocyclopropane are considered for both the neutrals and their molecular ions.

In Chapter V the heats of formation of CF₃⁺ and CF₃I⁺are derived from photoionization of CF₃I. These are considered with respect to ion-molecule reactions observed in CF₃I monitored by the techniques of ion cyclotron resonance spectroscopy. Results obtained in previous experiments are also compared.

Effects of turbulent reynolds number on the displacement speed statistics in the thin reaction zones regime of turbulent premixed combustion

The effects of turbulent Reynolds number on the statistical behaviour of the displacement speed have been studied using three-dimensional Direct Numerical Simulation of statistically planar turbulent premixed flames. The probability of finding negative values of the displacement speed is found to increase with increasing turbulent Reynolds number when the Damkhler number is held constant. It has been shown that the statistical behaviour of the Surface Density Function, and its strain rate and curvature dependence, plays a key role in determining the response of the different components of displacement speed. Increasing the turbulent Reynolds number is shown to reduce the strength of the correlations between tangential strain rate and dilatation rate with curvature, although the qualitative nature of the correlations remains unaffected. The dependence of displacement speed on strain rate and curvature is found to weaken with increasing turbulent Reynolds number when either Damkhler or Karlovitz number is held constant, but the qualitative nature of the correlation remains unaltered. The implications of turbulent Reynolds number effects in the context of Flame Surface Density (FSD) modelling have also been addressed, with emphasis on the influence of displacement speed on the curvature and propagation terms in the FSD balance equation. © 2011 Nilanjan Chakraborty et al.

Adenovirus-mediated wild-type P53 Transfer radiosensitizes H1299 cells to subclinical-dose carbon-ion irradiation through the restoration of p53 function

To determine whether adenovirus-mediated wild-type p53 transfer after radiotherapy could radiosensitize non-small-cell lung cancer (NSCLC) cells to subclinical-dose carbon-ion beam (C-beam), H1299 cells were exposed to a C-beam or -ray and then infected with 5 MOI of AdCMV-p53 or GFP (C-beam or -ray with p53 or GFP).Cell cycle was detected by flow cytometric analysis. The apoptosis was examined by a fluorescent microscope with DAPI staining. DNA fragmentation was monitored by the TUNEL assay. P53 mRNA was detected by reverse-transcriptase polymerase chain reaction. The expression of p53, MDM2, and p21 was monitored by Western blot. Survival fractions were determined by colony-forming assay. The percentages of G1-phase cells in C-beam with p53 increased by 8.2%–16.0%, 5.2%–7.0%, and 5.8%–18.9%, respectively, compared with C-beam only, -ray with p53, or p53 only. The accumulation of G2-phase cells in C-beam with p53 increased by 5.7%–8.9% and 8.8%–14.8%, compared with those in -ray with p53 or p53 only, respectively. The percentage of apoptosis for C-beam with p53 increased by 7.4%–19.1%, 5.8%–11.7%, and 5.2%–19.2%, respectively, compared with C-beam only, -ray with p53, or p53 only. The level of p53 mRNA in C-beam with p53 was significantly higher than that in p53 only. The expression level of p53 and p21 in C-beam with p53 was significantly higher than that in both C-beam with GFP and p53 only. The survival fractions for C-beam with p53 were significantly less than those for the other groups (p 0.05). The data suggested that AdCMV-p53 transfer could more efficiently radiosensitize H1299 cells to subclinical-dose C-beam irradiation through the restoration of p53 function.

Angular dispersion and deflection function for heavy ion elastic scattering

The differential cross sections for elastic scattering products of F-17 on Pb-208 have been measured. The angular dispersion plots of ln(d sigma/d theta) versus theta(2) are obtained from the angular distribution of the elastic scattering differential cross sections. Systematical analysis on the angular dispersion for the available experimental data indicates that there is an angular dispersion turning angle at forward angular range within the grazing angle. This turning angle can be clarified as nuclear rainbow in classical deflection function. The exotic behaviour of the nuclear rainbow angle offers a new probe to investigate the halo and skin phenomena.

Rotation and deformation of the dinuclear system formed in dissipative reaction of F-19+Al-27

Excitation functions of the reaction products B, C, N, O, F and Ne emitted from the dissipative reaction of (19) F+(27) Al have been measured at incident energies from 110.25MeV to 118.75MeV in steps of 250keV. The moments of inertia of the intermediate dinuclear system formed in the reaction are extracted from the energy autocorrelation functions of the products. Comparing the moment of inertia extracted from the experimental data with the calculated one by using the sticking limit, it indicates that the formed dinuclear system has a large deformation in the reaction process.

Measurement of the total reaction cross section for the mirror nuclei N-12 and B-12

The mirror nuclei N-12 and B-12 are separated by the Radioactive Ion Beam Line in Lanzhou (RIBLL) at HIRFL from the breakup of 78.6 MeV/u N-14 on a Be target. The total reaction cross-sections of N-12 at 34.9 MeV/u and B-12 at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming N-12 consists of a C-11 core plus one halo proton, the excitation function of N-12 and B-12 on a Si target and a C target were calculated with the Glauber model. It can fit the experimental data very well. The characteristic halo structure for N-12 was found with a large diffusion of the protons density distribution.

Accurate quantum mechanical calculation for the N+OH reaction

Accurate three-dimensional time-dependent quantum wave packet calculations for the N+OH reaction on the (3)A' potential energy surface [Guadagnini, Schatz, and Walch, J. Chem. Phys. 102, 774 (1995)] have been carried out. The calculations show for the first time that the initial state-selected reaction probabilities are dominated by resonance structures, and the lifetime of the resonance is generally in the subpicosecond time scale. The calculated reaction cross sections indicate that they are a decreasing function of the translational energy, which is in agreement qualitatively with the quasiclassical trajectory calculations. The rate constants obtained from the quantum mechanical calculations are consistent with the quasiclassical trajectory results and the experimental measurements. (C) 2003 American Institute of Physics.

A density function theory study on the properties and decomposition of CF3OF

The density function theory was used to calculate the potential energy surface for the decomposition of CF3OF. The geometries, vibrational frequencies and energies of all stationary points were obtained. The calculated harmonic frequencies agreed well with the experimental ones. Three decomposition channels of CF3OF were studied. The calculated reaction enthalpy (29.85 kcal/mol) of the elimination reaction CF3OF --> CF2O + F-2 was in good agreement with the experimental value (27.7 kcal/mol). The O-F bond of CF3OF is broken easily by comparing the energies, while the decomposition channel to yield the CF30 and F radicals is the main reaction path. (C) 2002 Published by Elsevier Science B.V.

Spectroscopic investigation of the function of aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution as a dentin desensitizer

Fourier-transform (FT)-Raman and -infrared (IR) spectroscopy were employed to investigate the function of the aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution (Gluma) as a desensitizer. 2-Hydroxyethylmethacrylate (HEMA), glutaraldehyde (GA), and the mixture of HEMA/GA (i.e. Gluma) were used to interact with dentin, collagen, hydroxyapatite (HAP), and bovine serum albumin (BSA) individually. All the interactions were monitored by an FT-Raman spectrometer. FT-IR spectroscopy was also used in this study. The results show that HEMA could be absorbed by dentin and collagen; GA could cross-link collagen and BSA; and when BSA was added to Gluma, polymerization of HEMA occurred. The results suggest that Gluma acts as a desensitizer whereby, first, GA reacts with part of the serum albumin in dentinal fluid, which induces a precipitation of serum albumin, then, second, a reaction of GA with serum albumin induces polymerization of HEMA. The function of Gluma as a desensitizer to block dentinal tubules occurs via these two reactions.

Diluting thiol-derivatized oligonucleotide monolayers on Au(111) by mercaptohexanol replacement reaction

Surface replacement reaction of thiol-derivatized, single-stranded oligonucleotide (HS-ssDNA) by mercaptohexanol (MCH) is investigated in order to reduce surface density of the HS-ssDNA adsorbed to Au(111) surface. Cyclic voltammograms (CVs) and scanning tunneling microscopy (STM) are employed to assess the composition and state of these mixed monolayers. It is found that each CV of mixed self-assembled monolayers (SAMs) only shows a single reductive desorption peak, which suggests that the resulted, mixed SAMs do not form discernable phase-separated domains. The peak potential gradually shifts to negative direction and the peak area increases step by step over the whole replacement process. By analyzing these peak areas, it is concluded that two MCH molecules will replace one HS-ssDNA molecule and relative coverage can also be estimated as a function of exposing time. The possible mechanism of the replacement reaction is also proposed. The DNA surface density exponentially reduces with the exposing time increasing, in other words, the replacement reaction is very fast in the first several hours and then gradually slows down. Moreover, the morphological change in the process is also followed by STM.

Structure, function, and phylogeny of the mating locus in the Rhizopus oryzae complex.

The Rhizopus oryzae species complex is a group of zygomycete fungi that are common, cosmopolitan saprotrophs. Some strains are used beneficially for production of Asian fermented foods but they can also act as opportunistic human pathogens. Although R. oryzae reportedly has a heterothallic (+/-) mating system, most strains have not been observed to undergo sexual reproduction and the genetic structure of its mating locus has not been characterized. Here we report on the mating behavior and genetic structure of the mating locus for 54 isolates of the R. oryzae complex. All 54 strains have a mating locus similar in overall organization to Phycomyces blakesleeanus and Mucor circinelloides (Mucoromycotina, Zygomycota). In all of these fungi, the minus (-) allele features the SexM high mobility group (HMG) gene flanked by an RNA helicase gene and a TP transporter gene (TPT). Within the R. oryzae complex, the plus (+) mating allele includes an inserted region that codes for a BTB/POZ domain gene and the SexP HMG gene. Phylogenetic analyses of multiple genes, including the mating loci (HMG, TPT, RNA helicase), ITS1-5.8S-ITS2 rDNA, RPB2, and LDH genes, identified two distinct groups of strains. These correspond to previously described sibling species R. oryzae sensu stricto and R. delemar. Within each species, discordant gene phylogenies among multiple loci suggest an outcrossing population structure. The hypothesis of random-mating is also supported by a 50:50 ratio of plus and minus mating types in both cryptic species. When crossed with tester strains of the opposite mating type, most isolates of R. delemar failed to produce zygospores, while isolates of R. oryzae produced sterile zygospores. In spite of the reluctance of most strains to mate in vitro, the conserved sex locus structure and evidence for outcrossing suggest that a normal sexual cycle occurs in both species.