Formic acid in deuterium and hydrogen matrices

ABSTRACT

Formic acid (HCOOH, FA) was studied experimentally, by infrared spectroscopy, in H₂ and D₂ matrices, with focus on the preparation and characterisation in these matrix media of structures containing the higher-energy (cis) conformer. The cis-FA monomer and the cis-FA^?…?N₂ complex were successfully produced by selective vibrational excitation of corresponding trans-FA based species, and vibrationally characterised. The tunneling-induced conversion of the cis-FA^?…?N₂ complex in the studied matrices into the corresponding trans-FA complex was also investigated, and the found tunnelling properties discussed, in particular in comparison with those observed for the spontaneous conversion of cis-FA monomer into trans-FA. This article constitutes the first report on the infrared spectrum of FA conformers and stability of cis-FA monomer in a D₂ matrix, and on the structure, spectroscopy and stability of the cis-FA^?…?N₂ complex in both H₂ and D₂ matrices. Different attempts to prepare the cis-FA^?…?H₂O complex in the two investigated matrices are also described in detail, both from previously in situ generated cis-FA monomer followed by thermal mobilisation and by direct selective vibrational excitation of the trans-FA-H₂O complex.     

Study of isotopes of carbon,thorium, and uranium in travertine and thermal spring samples: implications for effects of changes in geochemical environment and processes

Data on modern radiocarbon activity in the old travertine formations of the Pymvashor hydrothermal system were used, in combination with ²³⁰Th/U dating of the travertine, to estimate the ¹⁴C contents of the total dissolved inorganic carbon in the ancient thermal water at the time of precipitation of the travertine (¹⁴C_calc). With the known values of ¹⁴C_calc and average age of the thermal water, and under the assumption that the residence time of the water in aquifer was constant over the last 13.9?±?1.5 ka, the initial ¹⁴C contents (¹⁴C₀) in the ancient thermal water were estimated. The findings in this study are that (1) both ¹⁴C₀ and δ¹³С have decreased in young waters compared to the ancient waters; (2) although atmospheric ¹⁴C activity (¹⁴C_atm) has also decreased in the same time, the decrease in ¹⁴C₀ is faster than the decrease in ¹⁴C_atm. Under certain assumptions, one could link changes in ¹⁴C₀ and δ¹³C to climate change. Decrease in δ¹³С of soil CO₂ and decrease in ¹⁴C₀ was caused predominantly by warmer and wetter climate, decomposition of fossil organic matter, and decrease in ¹⁴C_atm. There could be also increased dissolution of solid carbonate and increased carbon exchange between DIC and soil CO₂, caused by thawing permafrost.     

Experimental and theoretical indications for an intermediate σ-dressed dibaryon in the NN interaction

Numerous theoretical and experimental arguments in favor of the generation of intermediate σ-dressed dibaryon in NN interaction at middle and short distances are presented. We argue that this intermediate dibaryon should be responsible for the strong middle-range attraction and the short-range repulsion in the NN interaction, and also for the short-range correlations in nuclei. The suggested mechanism for the σ-dressing of the dibaryon is identical to that which explains the Roper-resonance structure, its dominant decay mode and its extraordinary low mass. It is arguing that the (partial) chiral symmetry restoration effects, common for the Roper resonance and dressed dibaryon, are responsible for strong renormalizing of their masses and widths and the observed σ-meson mass and decay width as well. The new experimental data on 2π-production in the scalar-isoscalar channel produced in pn- and pd-collisions and recent data on γγ correlations in pC and dC scattering in the GeV region seems to corroborate the existence of the σ-dressed dibaryon in two- and three-nucleon interactions. A similar transformation mechanism from the glue to the scalar field can be valid also in some J/Ψ decays and in enormous σ-meson production in central pp collisions at high energies.     

Vibrational spectroscopic studies,conformations and ab initio calculations of 1,2‐bis(trifluorosilyl)ethane (SiF3CH2CH2SiF3)

Infrared spectra of 1,2‐bis(trifluorosilyl)ethane (SiF₃CH₂CH₂SiF₃) were obtained in the vapour and liquid phases, in argon matrices and in the solid phase. Raman spectra of the compound as a liquid were recorded at various temperatures between 293 and 270 K and spectra of an apparently crystalline solid were observed. The spectra revealed the existence of two conformers (anti and gauche) in the vapour, liquid and in the matrix. When the vapour was chock‐frozen on a cold finger at 78 K and annealed to 150 K, certain weak Raman bands vanished in the crystal. The vibrational spectra of the crystal demonstrated mutual exclusion between IR and Raman bands in accordance with C_2h symmetry. Intensity variations between 293 and 270 K of pairs of various Raman bands gave ΔH(gauche—anti) = 5.6 ± 0.5 kJ mol⁻¹ in the liquid, suggesting 85% anti and 15% gauche in equilibrium at room temperature. Annealing experiments indicate that the anti conformer also has a lower energy in the argon matrices, is the low‐energy conformer in the liquid and is also present in the crystal. The spectra of both conformers have been interpreted, and 34 anti and 17 gauche bands were tentatively identified. Ab initio and density functional theory (DFT) calculations were performed giving optimized geometries, infrared and Raman intensities and anharmonic vibrational frequencies for both conformers. The conformational energy difference derived in CBS‐QB3 and in G3 calculations was 5 kJ mol⁻¹. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of Intracellular Carbonic Anhydrase Activity and Bicarbonate Permeability in Intact Colon Epithelia by Observation of the 18O-labelling of Co2

Abstract

We applied a mass spectrometric method, developed by Itada and Forster [1] for erythrocyte suspensions, which observes the exchange of ¹⁸O between HCO₃ ^?, CO₂ and H₂O, to determine intracellular carbonic anhydrase activity, A _i , and bicarbonate permeability, P, in intact guinea pig colon epithelium. To study the validity of the results with intact distal and proximal colon epithelia, we compared them with measurements of A_i and P in suspensions of isolated epithelial cells from the distal and proximal guinea pig colon. In both parts of the colon there is good agreement between the A_i values of colonocytes in suspension and in the intact colon epithelium. In addition we tested the temperature dependence of A_i and P, the oxygen supply to the colon during the measurements, and the intactness of the epithelial cells by trypan blue staining. We conclude that it is valid to use the method of Itada and Forster [1] with intact colon epithelial sheets.

This new application allows us to study separately the apical and serosal membrane of the epithelial cells. We used the method to determine whether there is a short chain fatty acid – bicarbonate exchanger in the apical or serosal membrane of proximal and distal colon epithelium. For this purpose we measured the membrane bicarbonate permeability in the presence and absence of 25 mM propionate in the reaction solution. Only in the apical membrane of the proximal colon we find a higher P in presence of propionate than in its absence, showing that there the transport of short chain fatty acids is coupled to that of bicarbonate.     

Anisotropy of photoconductivity and nonlinear effects in GaSe monocrystals at high optical excitation

In this work, the photoelectric properties of gallium selenide (GaSe) monocrystals in the edge absorption region, with various configurations of current contacts, at low and high optical excitation levels are investigated. The photoconductivity spectrum behavior is determined by localized electronic and excitonic states along c-axis. It is shown that the localization of electronic and excitonic states in one-dimensional fluctuation potential along c-axis results to an anisotropy in photoconductivity spectrum at various current contacts configurations. At E⊥c the photoconductivity is observed in the hν < E_g and hν > E_g regions. In the case of hv < E_g, the maximum photoconductivity, in the impurity and exciton absorption region are observed at 1.975 eV and 2.102 eV, respectively. With rising of excitation energy level, suppression of photoconductivity in the exciton absorption region and increases in impurity absorption region is observed. At E||c contact configuration, the considerable photoconductivity is observed only in the impurity absorption region, which also increases with rising of excitation level. It is supposed that, suppression of photoconductivity in the exciton absorption region at high excitation levels is connected with exciton-exciton interaction, which results to a nonlinear light absorption. The results are compared with the absorption and photoluminescence measurements.     

Time-dependent density functional theory study on electronic excited states of the hydrogen-bonded solute-solvent phenol-(H2O)n (n=3-5) clusters

The solute-solvent interactions of hydrogen-bonded phenol-(H₂O)_n (n=3-5) clusters in electronic excited states were investigated by means of the time-dependent density functional theory (TDDFT) method. The geometric structures and IR spectra in ground state, S₁ state, and T₁ state of the clusters, were calculated using the density functional theory (DFT) and TDDFT methods. Only the ring form isomer, the most stable one of the cluster, was considered in this study. Four, five and six intermolecular hydrogen bonds were formed in phenol-(H₂O)₃, phenol-(H₂O)₄, and phenol-(H₂O)₅ clusters, respectively. Based on the analysis of IR spectra, it is revealed that the “window region” between unshifted and shifted absorption bands in both S₁ and T₁ state becomes broader compared with that in ground state for the corresponding clusters. Furthermore, two interesting phenomenon were observed: (1) with the anticlockwise order of the ring formed by the intermolecular hydrogen bonds in the H-bonded phenol-(H₂O)_n (n=3-5) clusters, the strengths of the intermolecular hydrogen bonds decrease in all the S₀, S₁ and T₁ states; (2) upon electronic excitation, the smaller the distance between phenol and water is, the larger the change of intermolecular hydrogen bonds strength is. Moreover, the intermolecular hydrogen bond (phenolic OH is the H donor) is strengthened in excited state compared with that in ground state. But the intermolecular hydrogen bond (phenolic OH is the H acceptor) is weakened in excited state.     

Assessment of the beneficial combination of electrochemical and ultrasonic activation of compounds originating from biomass

The electro-oxidation of organic molecules at the anode with simultaneous generation of hydrogen at the cathode in electrosynthesis reactors is considered as a promising and efficient process for the co-production of hydrogen and bio-sourced value-added chemicals. In this study and for the first time, we investigated the electro-oxidation of glucose and methylglucoside in 0.1 mol L⁻¹ NaOH on polycrystalline Pt (real surface area = 14.5 ± 0.5 cm², roughness ≈ 5) in the potential range [0; +1.20 V vs. rhe] under silent and ultrasonic (bath, 45 kHz, P_acous = 11.20 W) conditions. A series of linear sweep voltammograms, chronoamperograms and high-performance liquid chronoamperograms were generated. It was found that higher current densities were obtained under ultrasonic conditions over the potential range of +0.25 V to +1.10 V vs. rhe, indicating that higher oxidation rates were provided under ultrasonication. It was observed that the desorption of species from the Pt surface in the medium potential region was favoured, allowing free catalytic Pt sites for further adsorption and oxidation of reactants; and in the high potential region, high peak current densities in the presence of ultrasound was due to enhanced mass transport of the electroactive species from the bulk electrolyte to the Pt-polycrystalline electrode surface. HPLC studies confirmed that higher electrochemical activity was obtained in the presence of ultrasound than in the absence. In our conditions, it was also found that low frequency ultrasound did not change the selectivity of the glucose and methylglucoside electro-oxidation reactions but instead, a significant increase in the rate of conversion was observed.     

Manipulating nonclassical quantum statistical properties of light field by an f-deformed Bose–Einstein condensate

We consider the interaction between an f-deformed Bose–Einstein condensate and a single-mode quantized light field. By using the Gardiner’s phonon operators, we find that there exists a natural deformation in the model which modifies the Bogoliubov approximation under the condition of large but finite number of particles in condensate. This approach introduces an intrinsically deformed Bose–Einstein condensate, where the deformation parameter, well-defined by the particle number N in condensate, controls the strength of the associated nonlinearity. By introducing the deformed Gardiner’s phonon operators we modify the very dilute-gas approximation through including atomic collisions in condensate. The rate of atomic collisions κ, as a new deformation parameter in the deformed Bose–Einstein condensate, controls the nonlinearity related to the atomic collisions. We show that by controlling the nonlinearities in the f-deformed atomic condensate through the two atomic parameters N and κ, it is possible to generate and manipulate the nonclassical quantum statistical properties of radiation field, such as, the sub-Poissonian photon statistics and quadrature squeezing. Also, it is possible to control the collapses and revivals phenomena in the average number of photons by atomic parameters N and κ.     

Effect of a low-frequency magnetic field on the structure of globular blood proteins

We used IR Fourier absorption spectra of blood to study changes in the structure of globular blood proteins with extracorporeal autohemomagnetotherapy, used to treat ischemic heart disease. We compare the spectra of blood before and after magnetotherapy in the regions: amide I (1655 cm⁻¹), amide II (1545 cm⁻¹), amide III (1230–1350 cm⁻¹), amide IV and amide V (400–700 cm⁻¹). We have shown that pronounced changes in the spectra in the indicated regions on direct exposure of blood in vivo to a low-frequency pulsed magnetic field are connected with conformational changes in the secondary structure of globular blood proteins, which are apparent in the increase in the contribution of the α-helix conformation. We discuss the magnetotherapy-initiated appearance of new IR absorption bands at 1018 and 1038 cm⁻¹ and an increase in the intensity of a number of other bands located in the 1000–1200 cm⁻¹ region, which suggests a change in the concentration of some blood components. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 665–669, September–October, 2007.     

Tb0.3Dy0.7Fe2合金的本构参数辨识方法研究

建立了一种简便的、适用于磁畴模型应用的Tb_0.3Dy_0.7Fe₂ 合金本构参数辨识方法. 针对Tb_0.3Dy_0.7Fe₂合金磁畴模型中本构参数不明确且直接实验测试困难的问题, 提出了一种数值计算与实验测试相结合的参数辨识方法. 采用坐标变换与绘制自由能等势曲线相结合的方法, 简化了载荷作用下Tb_0.3Dy_0.7Fe₂ 合金内磁畴角度偏转的数值计算, 研究了合金磁畴角度偏转模型的参数依赖性. 在此基础上, 结合简单的实验测试, 建立了Tb_0.3Dy_0.7Fe₂合金各向异性常数K₁ 和K₂、能量分布因子ω、晶轴取向分布的辨识及修正方法. 该方法能够简单、快速地完成Tb_0.3Dy_0.7Fe₂ 合金磁畴模型中本构参数的辨识, 对完善磁致伸缩材料磁畴偏转的数值计算模型非常有意义. 理论分析可为类磁致伸缩材料磁机耦合模型的建立、完善, 以及材料本构参数的辨识、获取提供参考.     

Measurement of T1 of human arterial and venous blood at 7 T

Techniques for measuring cerebral perfusion require accurate longitudinal relaxation (T1) of blood, an MRI parameter that is field dependent. T1 of arterial and venous human blood was measured at 7 T using three different sources — pathology laboratory, blood bank and in vivo. The T1 of venous blood was measured from sealed samples from a pathology lab and in vivo. Samples from a blood bank were oxygenated and mixed to obtain different physiological concentrations of hematocrit and oxygenation. T1 relaxation times were estimated using a three-point fit to a simple inversion recovery equation. At 37 °C, the T1 of blood at arterial pO₂ was 2.29 ± 0.1 s and 2.07 ± 0.12 at venous pO₂. The in vivo T1 of venous blood, in three subjects, was slightly longer at 2.45 ± 0.11 s. T1 of arterial and venous blood at 7 T was measured and found to be significantly different. The T1 values were longer in vivo than in vitro. While the exact cause for the discrepancy is unknown, the additives in the blood samples, degradation during experiment, oxygenation differences, and the non-stagnant nature of blood in vivo could be potential contributors to the lower values of T1 in the venous samples.     

The enhancement of luminescence in Co-doped cubic Eu2O3 using Li and Al ions

The co-doping of Li⁺ and Al³⁺ ions drastically enhances the luminescence of cubic Eu₂O₃. The integrated emission intensity of ⁵D₀→⁷F_J bands (J=1-4) at 580-710 nm increases by a factor of about 6.7 in the co-doped Eu₂O₃ compared to the un-doped Eu₂O₃. In order to confirm that the co-doped ions were actually incorporated into the host lattice, the structural characteristics were studied using Raman spectroscopy, XPS, XRD, photoluminescence lifetime, and an SEM. These analyses consistently indicate a certain structural evolution in their results with an increase in the co-doping concentration. Variations in the crystal structure, the crystal morphology, and the intensity variation of the Raman modes at 465 and 483 cm⁻¹ are presented as the evidences showing the incorporation of the co-doped ions into the host. The luminescence enhancement is discussed in terms of concentration quenching, reduction of defect sites, and the modification of the local symmetry of the Eu³⁺ ions, especially in the inversion symmetry sites.     

Studies on the valence state of Ce and Eu in some new boron and silicon containing rare earth intermetallic compounds

Compounds of the formula RPd₃B _x (R=rare earth with 0?x?1) and RPd₃Si _x (R=La, Ce, Eu with 0?x?0.3) can be prepared by alloying boron or silicon with parent RPd₃ compounds. Addition of boron (silicon) does not change the structure but results in lattice expansion. The valence state of Ce in CePd₃ and that of Eu in EuPd₃ is strongly influenced by boron and silicon. Ce is known to be in a valence fluctuating state in CePd₃ while Eu is trivalent (J=0) in EuPd₃. The increase in the lattice parameter as a function of boron concentration is observed to be larger in CePd₃B _x and EuPd₃B _x compared to that in other RPd₃B _x alloys giving the first indication of the change in the valence state of Ce and Eu. This is confirmed from susceptibility measurements. With the addition of boron, susceptibility increases and the effective paramagnetic moments approach the values corresponding to Ce³⁺ (J=5/2, μ_eff=2.54 μ _B ) and Eu²⁺ (J=7/2, μ_eff=7.94 μ _B ) in the two alloy systems CePd₃B _x and EuPd₃B _x respectively. In the case of europium alloys,¹⁵¹Eu Mössbauer studies point out the importance of near-neighbour environment effects. Further, in EuPd₃B, where all the europium ions are crystallographically equivalent, a single Mössbauer line, with an isomer shift characteristic of europium ions in valence-fluctuating state, is observed at 300 K. However, at 88 K the Mössbauer absorption splits into two lines corresponding to europium ions in two valence states,e.g. divalent- and trivalent-like. Such a behaviour indicates thermally-induced charge ordering of europium ions. Addition of silicon to CePd₃, like boron, results in unusual lattice expansion and changes the valency of cerium towards 3⁺. the valence change is further corroborated by susceptibility measurements. In EuPd₃Si _x alloys, susceptibility and Mössbauer studies indicate that in the limiting single phase alloy EuPd₃Si_0.25 the europium ions are on the verge of valence instability. Susceptibility results on CeRh₃B _x alloys are also presented.     

Theoretical investigations on ZnCdO2 and ZnMgO2 alloys: A first principle study

We report on the calculations related to the electronic structure of ZnO, CdO, MgO, ZnMgO₂ and ZnCdO₂ in the wurtzite, rocksalt and chalcopyrite structures. From this study we found that ZnO and MgO are of direct band semiconductor, CdO is of semi metallic in nature. ZnMgO₂ and ZnCdO₂ are direct band semiconductors. From the energy considerations, we found that ZnMgO₂ and ZnCdO₂ are more stable in chalcopyrite structure rather than in rocksalt structure. Using the calculated band gap values, the bowing parameter for ZnMgO₂ and ZnCdO₂ is deduced and found to be in agreement with the reported value.     

Side-hole to anti-hole conversion in time-resolved spectral hole burning of ruby: Long-lived spectral holes due to ground state level population storage

We report time-resolved transient spectral hole burning of Verneuil-grown 20 ppm and ca. 0.6 ppm ruby (Al₂O₃:Cr³⁺) in zero field and low magnetic fields B∥c at 4 K. The hole-burning spectroscopy of the 20 ppm sample implies relatively rapid cross relaxation in the ⁴A₂ ground state on the ∼1 ms timescale both in zero field and in low magnetic fields, B∥c, up to 0.2 T. In the 0.6 ppm sample, side-hole to anti-hole conversion is observed both in zero field and in low magnetic fields. This conversion is caused by population storage in ⁴A₂ ground state levels. Spin-lattice relaxation, on the 200 ms timescale, is directly observed from the time dependence of the resonant hole and anti holes in B∥c, consistent with a very low cross-relaxation rate. However, in zero field cross relaxation in the ⁴A₂ ground state is still a significant relaxation mechanism for the 0.6 ppm sample resulting in hole decay in ∼50 ms.     

Stabilization of the pesticide Fenitrothion toward O and N nucleophiles in the presence of cyclodextrins

The reaction of Fenitrothion with O and N nucleophiles (H₂O₂, NH₂OH, n‐butylamine and piperidine) was studied at 25 °C in water containing 2% 1,4‐dioxane in the presence of native cyclodextrins (α‐, β‐, and γ‐CD). For all the nucleophiles, the presence of CD produces reaction inhibition with saturation kinetics. The greatest effect in all cases is observed with β‐CD, and the greatest inhibition was observed for the reaction of Fenitrothion with H₂O₂ (81%), which is the most efficient nucleophile in promoting Fenitrothion degradation in homogeneous media. In the absence of CD, competition between the S_N2(P) and the S_N2(C) pathways was observed with piperidine as was reported before for the reaction with NH₂OH and n‐butylamine. The presence of β‐CD does not modify product distribution in the case of the reaction with NH₂OH and n‐butylamine, whereas there is an increase in S_N2(C) pathway when the nucleophile is piperidine. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemical characteristics of amorphous silicon thin film electrode with fluoroethylene carbonate additive

The electrochemical and compositional changes of a solid electrolyte interphase (SEI) layer formed on the surface of silicon thin film are investigated in order to determine the effect of the content of fluoroethylene carbonate (FEC) additive in the electrolyte. Comparisons are made with FEC-free electrolyte, in which the major components are (CH₂OCO₂Li)₂ and Li₂CO₃. The (CH₂OCO₂Li)₂ and Li₂CO₃ of the SEI layer in the FEC-containing electrolyte decreases, and polycarbonate and LiF increase relatively with the repression of –OCO₂Li groups. The additive affects the composition of the SEI layer, which leads to lower resistance. The electrochemical performance regarding cycle retention, coulombic efficiency, rate capability, and discharge capacity in the FEC-containing cell are significantly enhanced compared to that of the FEC-free electrolyte. The observed optimum FEC concentration in the electrolyte is 1.5%, due to the reduced charge transfer and SEI resistance in our experimental range.     

Tuning of carbon bonds by substituent effects: an ab initio study

ABSTRACT

An ab initio study, at the MP2/aug-cc-pVTZ level of theory, is performed to study σ-hole bond in binary XH₃C···CNY complexes, where X = CN, F, NO₂, CCH and Y = H, OH, NH₂, CH₃, C₂H₅, Li. This type of interaction is labelled as ‘carbon bond’, since a covalently bonded carbon atom acts as the Lewis acid in these systems. The geometrical and energetic parameters of the resulting complexes are analysed in details. The interaction energies of these complexes are between ?4.97 kJ/mol in (HCC)H₃C···CNH and ?23.07 kJ/mol in (O₂N)H₃C···CNLi. It is found that the electrostatic interaction plays a key role in the overall stabilisation of these carbon-bonded complexes. To deepen the understanding of the nature of the carbon-bonding, the molecular electrostatic potential, natural bond orbital, quantum theory of atoms in molecules and non-covalent interaction index analyses are also used. Our results indicate that the carbon bond is favoured over the C-H···C hydrogen bond in the all complexes considered and may suggest the possible important roles of the C···C interactions in the crystal growth and design.