ESR study of vanadyl ion in tripotassium citrate

ESR spectra of VO²⁺ doped tripotassium citrate are recorded at room temperature. The observed spectra are fitted to a spin Hamiltonian of orthorhombic symmetry with g_x = 2.001 ± 0.001, g_y = 1.997 ± 0.001, g_z = 1.945 ± 0.001, A_x = (49.0 ± 1) × 10⁻⁴ cm⁻¹, A_y = (66.8 ± 1) × 10⁻⁴ cm⁻¹ and A_z = (168.4 ± 1) × 10⁻⁴ cm⁻¹. The covalency and Fermi contact terms are evaluated and compared with those of other lattices.     

Interference of Electromagnetic and Weak Interactions at High Energies and Neutral-Current μe Universality

A review is given on three types of experiments which recently detected the interference of electromagnetic and weak interactions at high energies in the reactions eD₂ → eX (SLAC, 1979), e⁺e⁻ → μ⁺μ⁻ (PETRA/PEP, 1981–83) and μ±C→μ±X (BCDMS, 1982). Asymmetry formulae are explicitely derived using the quark-parton model and the SU(2) × U(1) standard theory. With particular emphasis on the deep inelastic muon scattering experiment, the corresponding experiments are described and their results summarized. Combined fits to the 1983 asymmetry and νe data verify completely the muon-electron universality of the weak neutral current interaction giving for the vector and axial-vector coupling constants v_e = 0.02 ± 0.06, a_e = −0.54 ± 0.03 (electrons) and v_μ = −0.05 ± 0.16, a_μ = −0.51 ± 0.05 (muons).     

Ionic conductivity of polymer electrolyte membranes based on polyphosphazene with oligo(propylene oxide) side chains

A polyphosphazene [NP(NHR)₂]_n with oligo[propylene oxide] side chains − R = –[CH(CH₃)–CH₂O]_m–CH₃ (m = 6 – 10) was synthesized by living cationic polymerisation and polymer-analogue substitution of chlorine from the intermediate precursor [NPCl₂]_n using the corresponding primary amine RNH₂. The polymer had an average molecular weight of 3.3 × 10⁵ D. Polymer electrolytes with different concentrations of dissolved lithium triflate (LiCF₃SO₃) were prepared. Mechanically stable polymer electrolyte membranes were formed using UV radiation induced crosslinking of the polymer salt mixture in the presence of benzophenone as photoinitiator. The glass transition temperature of the parent polymer was found to be − 75 °C before cross linking. It increases after crosslinking and with increasing amounts of salt to a maximum of − 55 °C for 20 wt.% LiCF₃SO₃. The ionic conductivity was determined by impedance spectroscopy in the temperature range 0–80 °C. The highest conductivity was found for a salt concentration of 20 wt.% LiCF₃SO₃: 6.5 × 10^− 6 S·cm^− 1 at 20 °C and 2.8 × 10^− 4 S cm^− 1 at 80 °C. The temperature dependence of the conductivities was well described by the MIGRATION concept.     

Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6‐mm‐thick sulfur specimen at 1500 m

The absolute Raman scattering cross sections (σ_RS) for the 471, 217, and 153 cm⁻¹ modes of sulfur were measured as 6.0 ± 1.2 × 10⁻²⁷, 7.7 ± 1.6 × 10⁻²⁷, and 1.2 ± 0.24 × 10⁻²⁶ cm² at 815, 799, and 794 nm, respectively, using a 785‐nm pump laser. The corresponding values of σ_RS at 1120, 1089, and 1081 nm were determined to be 1.5 ± 0.3 × 10⁻²⁷, 1.2 ± 0.24 × 10⁻²⁷, and 1.2 ± 0.24 × 10⁻²⁷ cm² using a 1064‐nm laser. A temperature‐controlled, small‐cavity (2.125 mm diameter) blackbody source was used to calibrate the signal output of the Raman spectrometers for these measurements. Standoff Raman detection of a 6‐mm‐thick sulfur specimen located at 1500 m from the pump laser and the Raman spectrometer was made using a 1.4‐W, CW, 785‐nm pump laser. Copyright © 2010 John Wiley & Sons, Ltd.     

The high-resolution spectrum of the ν1 (A1) band of 12CD3F

The spectrum of the ν₁ (A₁) band of ¹²CD₃F has been recorded with a resolution of 0.010 cm⁻¹ and deconvolved to 0.005 cm⁻¹. Over 1050 transitions have been assigned with K ≤ 16 and J ≤ 42. The spectrum is highly perturbed, exhibiting avoided crossings in most of the observed sub-bands. The origin of most of the local and global resonances has been determined and the coupling constants estimated. Due to the complexity of the spectrum resulting from the 24 potential interacting states in the region, the assigned frequencies were fitted in a restricted manner (K ≤ 3, J ≤ 15), to obtain the following effective constants for the band: ν₀ = 2090.8118(20) cm⁻¹, α^A = 1.19743 × 10⁻² cm⁻¹, and α^B = −1.8489 × 10⁻³ cm⁻¹. From an unrestricted least-squares analysis, fixing the above parameters the β's (D_v^x = D₀^x − β_v^x) were calculated to be β^J = 1.7776 × 10⁻⁷ cm⁻¹, β^JK = 8.3406 × 10⁻⁷ cm⁻¹, and β^K = −6.3829 × 10⁻⁷ cm⁻¹. These constants serve as good starting parameters for the global analysis necessary to fully analyze the 5-μm region of the ¹²CD₃F spectrum.     

X-ray spectroscopy in the EC nucleus

The probabilities P_KK of double K-shell vacancy production per K electron capture decay and per K internal conversion of ¹⁰⁹Cd and ²⁰⁷Bi have been determined by means of the double- and triple-coincidence experiments using Kα X-ray and K internal conversion. For ¹⁰⁹Cd we find P_KK(EC) = (4.2 ± 0.5) × 10⁻⁵ and P_KK(IC) = (4.32 ± 0.46) × 10⁻⁵, and for ²⁰⁷Bi, P_KK(EC) = (2.54 ± 0.50) × 10⁻⁵. The observed X-ray energy shifts of the hypersatellite Ag (Kα₁^H) X-ray and the hypersatellite Pb (Kα₁^H) X-ray lines are 545±15 eV and 1238±45 eV, respectively.     

Electronic excitation of HgX (X = Cl,Br, I) due to electron and methyl mercury halide collisions

Electronic excitation of HgX (X = Cl, Br, I) radicals in the B-state has been observed as the result of collisions with low energy electrons and methyl mercury halide (CH₃HgX) molecules. The emission intensity has been observed to be much weaker than that observed for electron-HgX₂ collisions under similar experimental conditions. Using the strongest band head of the B-X band system, an attempt has been made to calculate the emission cross section due to electron CH₃HgX collisions at 10 eV electron kinetic energy. For HgCl, HgBr, and HgI radicals, these cross sections are 1 × 10^-18, 7 × 10^-17, and 2 × 10^-17 cm², respectively, with an estimated uncertainty of ±30%. Our measured threshold electron energy for excitation of CH₃HgX molecules and observation of the B-X emission band system and emission cross sections measured at 10 eV are greatly different from those measured by Allision and Zare [Chem. Phys. 35, 263 (1978)].     

Diffusion tensor imaging of oral carcinoma: Clinical evaluation and comparison with histopathological findings

PurposeThis study aims to assess the usefulness of diffusion tensor imaging (DTI) as a noninvasive method for the evaluation of histological grade and lymph node metastasis in patients with oral carcinoma (OC).Materials and methodsThirty-six consecutive patients with histologically confirmed OC underwent examination by 3-T MRI. DTI was performed using a single-shot echo-planar imaging sequence with b values of 0 and 1000 s/mm² and motion-probing gradients in 12 noncollinear directions. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) maps were compared with histopathological findings. The DTI parameters were correlated with the histological grade of the OCs based on the World Health Organization grading criteria and the presence or absence of lymph node metastasis.ResultsThe FA values (0.275 ± 0.058) of OC were significantly lower than those of normal tongue, muscle, and parotid glands (P < 0.001 for all), and the MD, AD, and RD values (1.220 ± 0.149, 1.434 ± 0.172, and 1.019 ± 0.165 × 10⁻³ mm²/s, respectively) were significantly higher than their respective normal values (P < 0.001 for all). Significant inverse correlations with histological grades were shown for FA, MD, AD, and RD values in OC patients (r = −0.862, r = −0.797, r = −0.747, and r = −0.844, respectively; P < 0.001 for all). In addition, there was a significant difference in the FA values of metastatic and nonmetastatic lymph nodes (0.186 vs. 0.276), MD (0.923 vs. 1.242 × 10⁻³ mm²/s), AD (1.246 vs. 1.621 × 10⁻³ mm²/s), and RD (0.792 vs. 1.100 × 10⁻³ mm²/s; P < 0.001 for all).ConclusionsDTI may be clinically useful for the noninvasive evaluation of histological grade and lymph node metastasis in OC patients.     

Gas‐phase reactions of Cl atoms with hydrochloroethers: relative rate constants and their correlation with substituents' electronegativities

Rate constants for the reactions of Cl atoms with CH₃OCHCl₂ and CH₃OCH₂CH₂Cl were determined at (296 ± 2) K and atmospheric pressure using synthetic air as bath gas. Decay rates of these organic compounds were measured relative to the following reference compounds: CH₂ClCH₂Cl and n‐C₅H₁₂. Using rate constants of 1.33 × 10^?12 and 2.52 × 10^?10 cm³ molecule^?1 sec^?1 for the reaction of Cl atoms with CH₂ClCH₂Cl and n‐C₅H₁₂, respectively, the following rate coefficients were derived: k(Cl + CH₃OCHCl₂) = (1.05 ± 0.11) × 10^?12 and k(Cl + CH₃OCH₂CH₂Cl) = (1.14 ± 0.10) × 10^?10, in units of cm³ molecule^?1 s^?1. The rate constants obtained were compared with previous literature data and a correlation was found between the rate coefficients of some CH₃OCHR¹R² + Cl reactions and ΔElectronegativity of ? CHR¹R². Copyright © 2008 John Wiley & Sons, Ltd.     

Observation of charmless B meson decays

Using the ARGUS detector at the e⁺e⁻ storage ring DORIS II, we have observed charmless decays of B mesons into the final states pp̄π^± and pp̄π⁺π⁻. The significance of the signal corresponds to more than five standard deviations. The branching ratios are (5.2±1.4±1.9)×10⁻⁴ for the three-body and (6.0±2.0±2.2)×10⁻⁴ for the four-body final state. These decays cannot proceed via the dominant b→c transitions, and we show that they are not the result of penguin-type processes. Thus, the observed decays must represent b→u quark transitions. Consequently, the Kobayashi-Maskawa matrix element V_ub is non-zero.     

Gas‐phase oxidation of CH2 = C(CH3)CH2Cl initiated by OH radicals and Cl atoms: kinetics and fate of the alcoxy radical formed

Relative kinetics of the reactions of OH radicals and Cl atoms with 3‐chloro‐2‐methyl‐1‐propene has been studied for the first time at 298 K and 1 atm by GC‐FID. Rate coefficients are found to be (in cm³ molecule^?1 s^?1): k₁ (OH + CH₂ = C(CH₃)CH₂Cl) = (3.23 ± 0.35) × 10^?11, k₂ (Cl + CH₂ = C(CH₃)CH₂Cl) = (2.10 ± 0.78) × 10^?10 with uncertainties representing ± 2σ. Product identification under atmospheric conditions was performed by solid phase microextraction/GC‐MS for OH reaction. Chloropropanone was identified as the main degradation product in accordance with the decomposition of the 1,2‐hydroxy alcoxy radical formed. Additionally, reactivity trends and atmospheric implications are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Observation of the orbitally excited Λ(1520) baryon in e+e− annihilation

We report the first observation of an orbitally excited baryon, the Λ(1520), in quark and gluon fragmentation. The production rate is found to be (1.15±0.21±0.16)×10⁻² and (0.80±0.17_−0.13^+0.10)×10⁻²Λ(1520) hyperons per event in direct ϒ decays and in the continuum, respectively. In contrast to the observed situation for ground state baryons, the production of the Λ(1520) in direct ϒ decays shows little or no enhancement with respect to continuum production.     

Diffusion of Fe,Co, Nd,and Dy in R2(Fe1−xCox)14B where R=Nd or Dy

Transition metal and rare earth diffusion coefficients at 1323 K in Dy_2−yNd_y(Fe_1−xCo_x)₁₄B were determined by field emission energy dispersive spectroscopy compositional analysis of diffusion couple specimens. Various arrangements of component materials and temperatures were examined in order to understand the mechanisms affecting diffusion of the components and to predict the stability of functionally graded microstructures consisting of a dysprosium-rich (Dy_2−yNd_y(Fe_1−xCo_x)₁₄B) outer layer and a neodymium-rich (Nd₂(Fe_1−xCo_x)₁₄B) interior. Estimates of the mutual interdiffusion coefficients of Dy, Nd, Fe, and Co in this system were obtained from the preparation of arc melted and annealed polycrystalline specimens, assuming that the diffusion coefficients were independent of concentration (Grube solution). Fifteen diffusion couples were prepared and heat treated at 1323 K for various times in order to provide data for calculation of the diffusion coefficients. The results indicate that the diffusion coefficients of Fe and Co (D_Fe=3.28×10⁻¹⁰ cm²/s and D_Co=7.63×10⁻¹⁰ cm²/s) were significantly higher at 1323 K in this system than those for Dy and Nd (D_Nd=2.3×10⁻¹² cm²/s and D_Dy=2.9×10⁻¹² cm²/s).     

Thermal dependence of conduction properties in the Bi2O3Pb2OF2 system

Conduction properties of bismuth-lead oxyfluorides (Bi,Pb)₂(O,F)₃ have been investigated by complex impedance analysis. A special attention has been drawn to a hexagonal solid solution Bi_(1−x)Pb_xO_(1.5−x)F_x (0.45⩽x⩽0.741 at 770 K), which is isostructural with ALa₂O₃. Conductivity values range from 3 × 10⁻⁵ to 3 × 10⁻² (ω cm)⁻¹ at 585 K. A minimum associated with a maximum in activation energy is observed for the composition x = 0.5 i.e. BiPbO₂F.     

Single-pulse shock-tube study on the pyrolysis of small esters (ethyl and propyl propanoate,isopropyl acetate) and methyl isopropyl carbonate

Single-pulse shock-tube experiments were used to study the thermal decomposition of selected oxygenated hydrocarbons: Ethyl propanoate (C₂H₅OC(O)C₂H₅; EP), propyl propanoate (C₃H₇OC(O)C₂H₅; PP), isopropyl acetate ((CH₃)₂HCOC(O)CH₃; IPA), and methyl isopropyl carbonate ((CH₃)₂HCOC(O)OCH₃; MIC) The consumption of reactants and the formation of stable products such as C₂H₄ and C₃H₆ were measured with gas chromatography/mass spectrometry (GC/MS). Depending on the considered reactant, the temperatures range from 716–1102 K at pressures between 1.5 and 2.0 bar. Rate-coefficient data were obtained from first-order analysis. All reactants primarily decompose by six-center eliminations: EP → C₂H₄ + C₂H₅COOH (propionic acid); PP → C₃H₆ + C₂H₅COOH; IPA → C₃H₆ + CH₃COOH (acetic acid); MIC → C₃H₆ + CH₃OC(O)OH (methoxy formic acid). Experimental rate-coefficient data can be well represented by the following Arrhenius expressions: k(EP → products) = 10^13.49±0.16 exp(−214.95±3.25 kJ/mol/RT) s⁻¹; k(PP → products) = 10^12.21±0.16 exp(–191.21±2.79 kJ/mol/RT) s⁻¹; k(IPA → products) = 10^13.10±0.31 exp(–186.38±5.10 kJ/mol/RT) s⁻¹; k(MIC → products) = 10^12.43±0.29 exp(–165.25±4.46 kJ/mol/RT) s⁻¹. The determination of rate coefficients was based on the amount of C₂H₄ or C₃H₆ formed. The potential energy surface (PES) of the thermal decomposition of these four reactants was determined with the G4 composite method. A master-equation analysis was conducted based on energies and molecular properties from the G4 computations. The results indicate that the length of a linear alkyl substituent does not significantly influence the rate of six-center eliminations, whereas the change from a linear to a branched alkyl substituent results in a significant reactivity increase. The comparison between rate-coefficient data also shows that alkyl carbonates have higher reactivity towards decomposition by six-center elimination than esters. The results are discussed in in the context of reactivity patterns of carbonyl compounds.     

Measurement of the absolute Raman scattering cross section of the 1584‐cm−1 band of benzenethiol and the surface‐enhanced Raman scattering cross section enhancement factor for femtosecond laser‐nanostructured substrates

The absolute Raman scattering cross section (σ_RS) for the 1584‐cm⁻¹ band of benzenethiol at 897 nm (1.383 eV) has been measured to be 8.9 ± 1.8 × 10⁻³⁰ cm² using a 785‐nm pump laser. A temperature‐controlled, small‐cavity blackbody source was used to calibrate the signal output of the Raman spectrometer. We also measured the absolute surface‐enhanced Raman scattering cross section (σ_SERS) of benzenethiol adsorbed onto a silver‐coated, femtosecond laser‐nanostructured substrate. Using the measured values of 8.9 ± 1.8 × 10⁻³⁰ and 6.6 ± 1.3 × 10⁻²⁴ cm² for σ_RS and σ_SERS respectively, we calculate an average cross‐section enhancement factor (EF) of 0.8 ± 0.3 × 10⁶. Copyright © 2009 John Wiley & Sons, Ltd.     

Intravoxel incoherent motion MR imaging analysis for diagnosis of placenta accrete spectrum disorders: A pilot feasibility study

BackgroundPlacenta accreta spectrum (PAS) disorders occur when the placenta adheres abnormally to the uterine myometrium and can have devastating effects on maternal health due to risks of massive postpartum hemorrhage and possible need for emergency hysterectomy. PAS can be difficult to diagnose using routine clinical imaging with ultrasound and structural MRI.ObjectiveTo determine feasibility of using intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) analysis in the diagnosis of the placenta accreta spectrum disorders in pregnant women.MethodsA total of 49 pregnant women were recruited including 14 with pathologically confirmed cases of PAS and 35 health controls without prior cesarean delivery and no suspected PAS by ultrasound. All women underwent diffusion-weighted imaging with an 8 b-value scanning sequence. A semi-automated method for image processing was used, creating a 3D object map, which was then fit to a biexponential signal decay curve for IVIM modeling to determine slow diffusion (D_s), fast diffusion (D_f), and perfusion fraction (P_f).ResultsOur results demonstrated a high degree of model fitting (R² ≥ 0.98), with P_f significantly higher in those with PAS compared to healthy controls (0.451 ± 0.019 versus 0.341 ± 0.022, p = 0.002). By contrast, no statistical difference in the D_f (1.70 × 10⁻² ± 0.38 × 10⁻² versus 1.48 × 10⁻² ± 0.08 × 10⁻² mm²/s, p = 0.211) or D_s (1.34 × 10⁻³ ± 0.10 × 10⁻³ versus 1.45 × 10⁻³ ± 0.007 × 10⁻³ mm²/s, p = 0.215) was found between subjects with PAS and healthy controls.ConclusionsThe use of MRI, and IVIM modeling in particular, may have potential in aiding in the diagnosis of PAS when other imaging modalities are equivocal. However, the widespread use of these techniques will require generation of large normative data sets, consistent sequencing protocols, and streamlined analysis techniques.     

Far-infrared spectrum of sodium hydride

Rotational spectra in the v = 0, 1, 2, and 3 levels of the ground (¹Σ) state of sodium hydride have been observed using tunable far-infrared radiation generated from the difference frequency between two CO₂ lasers. The Dunham coefficients, which have been determined without the use of optical data or isotopic scaling relations, are Y₀₁ = 146 999.138(38) MHz, Y₀₂ = −10.29481(54) MHz, Y₀₃ = 6.243(49) × 10⁻⁴ MHz, Y₁₁ = −4109.912(68) MHz, Y₁₂ = 0.14695(68) MHz, Y₂₁ = 33.341(34) MHz, Y₂₂ = −2.69(20) × 10⁻³ MHz, and Y₃₁ = −1.0517(55) MHz. The constants are typically an order of magnitude more accurate than the best values previously available, and where comparison is possible, agreement is found to be excellent.     

Ionic conductivity and crystal structure for the Li3−2xCr2−xTax(PO4)3 system

The monoclinic phase (P2₁/n) was formed for 0≤x≤0.6 and the NASICON-type rhombohedral phase (R3̄c) was obtained for the region 0.8≤x≤1.2 in the Li_3−2xCr_2−xTa_x(PO₄)₃ system. The activation energy for Li⁺ migration was ca. 0.45 eV for the monoclinic structure and ca. 0.36 eV for the rhombohedral structure. The maximum conductivity of 8.4×10⁻⁶ S cm⁻¹ at 298 K was obtained for x=0.8 of the Li_3−2xCr_2−xTa_x(PO₄)₃ system. The conductivity of LiCrTa(PO₄)₃ was enhanced about three to five times by the addition of the lithium salt due to the improvement of the sinterablity. The maximum conductivity was 2.4×10⁻⁵ S cm⁻¹ at 298 K for LiCrTa(PO₄)₃–0.2Li₃BO₃.     

Pressure-Broadened Linewidth Measurements in the ν2Band of the CH3Radical

Pressure broadening coefficients for an infrared transition of the methyl radical have been measured for the first time. CH₃radicals, generated by pyrolyzing di-tert-butyl peroxide in a flow of either N₂or Ar, were probed using a tunable diode laser and a multipass absorption cell. The Lorentz half-width of theQ(6,6) line of the ν₂band of CH₃at 607.024 cm⁻¹was measured as a function of pressure at 295 K. The broadening coefficients (HWHM) areb(Ar) = 0.0310 ± 0.0012 cm⁻¹atm⁻¹andb(N₂) = 0.0390 ± 0.0020 cm⁻¹atm⁻¹. These coefficients are lower than those for CH₄–Ar, N₂broadening. This may be due to a lower polarizability or smaller effective hard collision diameter for CH₃relative to CH₄.