Pressure-induced phase changes of cubic monoolein - Cytochrome C mesophases

Incorporation of the protein cytochrome c (cyt c) into the hydrated bicontinuous Ia3d cubic mesophase of monoolein (MO) was investigated within a wide range of pressures by small-angle X-ray scattering (SAXS). We found that incorporation of cyt c into the cubic phase of MO has a drastic effect on the structure and pressure stability of the system: At high pressures, the lipid systems with less than 0.2 wt.% embedded protein undergo a transition to a fluid lamellar phase with smaller partial molar lipid volume. Incorporation of cyt c at levels above 0.2 wt.% promotes the formation of a new cubic phase, probably a cubic micellar phase of space group P4₃32 (Q²¹²) whose pressure stability rises with increasing protein content.     

Dielectric-spectroscopic and a.c. conductivity studies on layered Na2-XKXTi3O7 (X=0.2, 0.3, 0.4) ceramics

The dependence of loss tangent (tanδ) and relative permittivity (ε_r) on temperature and frequency has been reported for Na_2-XK_XTi₃O₇ (with X=0.2, 0.3, 0.4) ceramics. The losses are characteristic of dipole mechanism and electrical conduction. The peaks of ε_r at high temperature indicate a possible ferroelectric phase transition for all three compositions. The results of a.c. conductivity studies on the same samples have also been reported. The corresponding ln(σT) versus 1000/T plots have been divided into five regions namely I, II, III, IV and V. The various conduction mechanisms in the different regions have been stressed. Furthermore, the log(σ) versus frequency plots for all the above samples reveal that the electronic hopping (polaron) conduction, which diminishes with the rise in temperature, is dominant in the lower temperature region. The interlayer ionic conduction seems to play a major role in conduction towards higher temperature.     

Tagged cine magnetic resonance imaging to quantify regional mechanical changes after acute myocardial infarction

PurposeThe conventional volumetric approaches of measuring cardiac function are load-dependent, and are not able to discriminate functional changes in the infarct, transition and remote myocardium. We examined phase-dependent regional mechanical changes in the infarct, transition and remote regions after acute myocardial infarction (MI) in a preclinical mouse model using cardiovascular magnetic resonance imaging (CMR).MethodsWe induced acute MI in six mice with left anterior descending coronary artery ligation. We then examined cardiac (infarct, transition and remote-zone) morphology and function utilizing 9.4 T high field CMR before and 2 weeks after the induction of acute MI. Myocardial scar tissue was evaluated by using CMR with late gadolinium enhancement (LGE). After determining global function through volumetric analysis, regional wall motion was evaluated by measuring wall thickening and radial velocities. Strain rate imaging was performed to assess circumferential contraction and relaxation at the myocardium, endocardium, and epicardium.ResultsThere was abnormal LGE in the anterior walls after acute MI suggesting a successful MI procedure. The transition zone consisted of a mixed signal intensity, while the remote zone contained viable myocardium. As expected, the infarct zone had demonstrated severely decreased myocardial velocities and strain rates, suggesting reduced contraction and relaxation function. Compared to pre-infarct baseline, systolic and diastolic velocities (v_S and v_D) were significantly reduced at the transition zone (v_S: −1.86 ± 0.16 cm/s vs −0.68 ± 0.13 cm/s, P < 0.001; v_D: 1.86 ± 0.17 cm/s vs 0.53 ± 0.06 cm/s, P < 0.001) and remote zone (v_S: −1.86 ± 0.16 cm/s vs −0.65 ± 0.12 cm/s, P < 0.001; v_D: 1.86 ± 0.16 cm/s vs 0.51 ± 0.04 cm/s, P < 0.001). Myocardial peak systolic and diastolic strain rates (SR_S and SR_D) were significantly lower in the transition zone (SR_S: −4.2 ± 0.3 s⁻¹ vs −1.3 ± 0.2 s⁻¹, P < 0.001; SR_D: 3.9 ± 0.3 s⁻¹ vs 1.3 ± 0.2 s⁻¹, P < 0.001) and remote zone (SR_S: −3.8 ± 0.3 s⁻¹ vs −1.4 ± 0.3 s⁻¹, P < 0.001; SR_D: 3.5 ± 0.2 s⁻¹ vs 1.5 ± 0.4 s⁻¹, P = 0.006). Endocardial and epicardial SR_S and SR_D were similarly reduced in the transition and remote zones compared to baseline.ConclusionsThis study, for the first time, utilized state-of-the art high-field CMR algorithms in a preclinical mouse model for a comprehensive and controlled evaluation of the regional mechanical changes in the transition and remote zones, after acute MI. Our data demonstrate that CMR can quantitatively monitor dynamic post-MI remodeling in the transition and remote zones, thereby serving as a gold standard tool for therapeutic surveillance.     

Magnetic order and transport in the heavy-fermion system CeCuAu

We report on extensive elastic neutron scattering to determine the wave vector of the magnetic order in CeCu_6-xAu_x single crystals for x > 0.1. For all values of x investigated (0.2, 0.3, 0.5, 1.0) we find long-range incommensurate antiferromagnetic order with an ordering vector (0.625 0.275) for x =0.2, nearly unchanged for x =0.3, and (0.59) for x =0.5, staying roughly the same for x =1.0. In addition, short-range correlations are observed for x =0.2, reminiscent of those found previously for x =0.1. The ordered magnetic moment is found to increase rapidly for small x, and more slowly for the larger x values. The increase of the specific-heat anomaly at the ordering temperature with x is in qualitative accord with this behavior. Finally, data of the electrical resistivity for current flow along the three crystallographic directions are presented, showing a clear signature of the magnetic order. A theoretical interpretation of the interplay of magnetic order and transport in terms of (i) the partial suppression of the Kondo effect by the staggered magnetization and (ii) the anisotropic band structure induced by the staggered field is shown to account well for the data, provided the ordering vector is close to 2 k F, where k F is a typical Fermi momentum. Received: 20 February 1998 / Accepted: 17 April 1998     

The role of enhanced aromatic -electron donating aptitude of the tyrosyl sidechain with respect to that of phenylalanyl in intramolecular interactions

An exhaustive ab initio and DFT search for energetically stable conformers from the topologically possible set was undertaken on the N-acetyl-phenylalanyl-N-methylamide and N-acetyl-tyrosyl-N-methylamide systems. The geometries of all 81 phenylalanyl and 162 tyrosyl possible rotamers, described under the rules outlined by Multi-Dimensional Conformational Analysis (MDCA), were attempted at each of the RHF/3-21G, RHF/6-31G(d) and B3LYP/6-31G(d) levels of theory. A total of 32 and 66 stable conformational minima were found for the phenylalanyl and tyrosyl amino acid diamides, respectively, at the B3LYP/6-31G(d) level. From the tyrosyl set, 33 unique conformers emerge when the orientation of the A _i ³ dihedral angle (p-OH orientation) is disregarded. A total of 31 conformers were common to both sets and showed nearly identical geometries. The comparison of the optimized DFT geometries of the two systems showed near by perfect linear fits with R² values of 0.9997, 0.9994, 0.9997, and 0.9996 for the φ _i , ψ _i , A _i ¹ , and A _i ² dihedral angles, respectively. Relative energies of the matching 31 conformers also fitted to a linear plot with an R² value of 0.9985. The geometric centroid of the aromatic ring in the sidechain of both systems was found to be within 4.1 ?of the H and O atoms of the peptide groups, in 21 and 2 of the conformers, respectively. None of the non-matching conformers showed any such interaction distance ≤4.1 ?. Received 1st February 2002 / Received in final form 28 May 2002 Published online 13 September 2002     

Ferromagnetism in lacunar perovskite manganites Pr 0.7 Sr 0.3 - x x MnO 3 and Pr 0.7 - x x Sr 0.3 MnO 3

Deficiency effects in the A site upon the structural, magnetic and electrical properties in the lacunar perovskite manganite oxides Pr_0.7Sr_{0.3-x x}MnO₃ ( 0 ? x ? 0.3) and Pr_{0.7-x x}Sr_0.3MnO₃ ( 0 ? x ? 0.23) have been investigated. This study focuses on the different parameters which govern the magnetic and electrical properties in such samples. The powder X-ray diffraction patterns for all samples could be indexed either with a rhombohedral perovskite structure and R c space group for x ? 0.2 in strontium deficient samples and for x ? 0.1 for praseodymium deficient ones. For other values of x the samples could be indexed in the orthorhombic structure with Pbnm space group. Magnetic and electrical investigations show that praseodymium and strontium vacancies do not have similar effects on the lacunar compounds. Magnetization measurements versus temperature show that all our samples exhibit a magnetic transition when the temperature decreases. All the praseodymium deficient samples exhibit a paramagnetic-ferromagnetic transition when the temperature decreases while the strontium deficient ones exhibit this transition only for low x values. The magnetic transition temperature shifts to lower values as the strontium deficiency increases (from 265 K for x = 0 to 90 K for x = 0.3) and to higher values with the praseodymium deficiency increase (from 265 K for x = 0 to 315 for x = 0.23). Resistivity measurements as a function of temperature show a semiconducting-metallic transition for all x values in the praseodymium lacunar samples and only for low x values ( 0 ? x ? 0.1) in the strontium lacunar ones when the temperature decreases. Received 12 April 2000 and Received in final form 8 January 2001     

Magnetic susceptibility studies of polycrystalline chromium and chromium-0.3 at.% tungsten alloy in the neighborhood of the Néel temperature

Magnetic susceptibility (χ) measurements of the relative precision of 1 part in 10⁴ have been made on pure Cr and Cr-0.3 at.% W alloy about 10 K below and above the respective Néel temperatures, T_N. For Cr, T_N = (311.8 ± 0.2)N, and for Cr-0.3 at.% W, T_N = (305.0 ± 0.2)K. Temperature dependence of d(χT)/dT above T_N is very sensitive to heat treatments while below T_N the values of d(χT)/dT remain the same for Cr-0.3 at.% W sample and approximately the same for pure Cr specimen. Below T_N the critical behavior of Cr and Cr-0.3 at.% W is essentially logarithmic.     

Electron-electron bound states in Maxwell-Chern-Simons-Proca QED <Emphasis Type="Bold">3</Emphasis>

We start from a parity-breaking MCS QED₃ model with spontaneous breaking of the gauge symmetry as a framework for evaluation of the electron-electron interaction potential and for attainment of numerical values for the e ^- e ^- - bound state. Three expressions ( V _eff , V _eff , V _eff ) are obtained according to the polarization state of the scattered electrons. In an energy scale compatible with condensed matter electronic excitations, these three potentials become degenerated. The resulting potential is implemented in the Schr?dinger equation and the variational method is applied to carry out the electronic binding energy. The resulting binding energies in the scale of 10-100 meV and a correlation length in the scale of 10-30 ? are possible indications that the MCS-QED₃ model adopted may be suitable to address an eventual case of e ^- e ^- pairing in the presence of parity-symmetry breakdown. The data analyzed here suggest an energy scale of 10-100 meV to fix the breaking of the U (1)-symmetry. Received 24 September 2002 / Received in final form 15 January 2003 Published online 1st April 2003 RID="a" ID="a"e-mail: belich@cbpf.br RID="b" ID="b"e-mail: delcima@cbpf.br RID="c" ID="c"e-mail: manojr@cbpf.br RID="d" ID="d"e-mail: helayel@cbpf.br     

Messungen an 19,8 GeV-Protonen und ihren Wechselwirkungen in Emulsionen

In Ilford K 5-emulsions 190 nuclear interactions produced by 19.8 GeV protons have been analysed systematically. The mean interactionlength was found to be 34.7±2.5 cm, the mean number of shower particles isn _s=4.5±0.2, the mean number of heavy particlesN _h=9.0±0.6. The integral momentum spectrum between the emission angles of 31° and 55° in the centre of mass system shows a steep descent beyond 0.3 GeV/c with an exponent of ?1.5±0.3, the mean momentum isP ^*=0.60±0.05 GeV/c and the mean inelasticity was found to beK=0.37±0.06. Scattering measurements could be done successfully up to an energy of 20 GeV. The scattering constant was found to beK(t)=20.4t ^0.055 (t in μ). Moreover there was found in treating errors that only the nonoverlapping cells are statistically independent, i.e. the standard deviation must be calculated only with half of the number of second differences.     

autoionizing levels in Ca: laser optogalvanic spectroscopy and theoretical analysis

We report the even parity J =4,5 autoionizing spectra of calcium below the 3d threshold, investigated by two-step laser excitation from the 3d4s metastables through the 3d4p , intermediate states and subsequent optogalvanic detection. The 3d4s states are populated by electronic collisions in a d.c. glow discharge sustained in a Ca heat-pipe. More than a hundred resonant transitions have been measured with an accuracy of for the narrow ones using standard laser calibration techniques. The high lying levels are assigned to all expected autoionizing series. Moreover, some levels are observed. The theoretical interpretation is achieved by a combination of the nearly ab initio eigenchannel R-matrix and multichannel quantum-defect (MQDT) methods as well as by an empirical determination of the MQDT parameters in the phase-shifted formulation. Theoretical energy level positions and excitation profiles are compared with the experimental data confirming the identification of the observed structures. Strong mixing between series is found, while the ones do not couple with the series. Further insight into the strong channel mixing in the studied energy range is provided by a comprehensive review of the excitation profiles in the vicinity of the 4p5p perturber as obtained from a number of intermediate levels used in the present and in earlier experiments. Systematic electron correlation trends for series of , and are discussed. Received: 20 November 1997 / Accepted: 15 January 1998     

Interaction of neutrons with zinc and its isotopes

Coherent neutron scattering lengths and total cross sections have been measured for elemental Zn,Zn-compounds and on isotopicly enriched samples for neutron energies from 0.5 meV up to 143 keV using different techniques. From the experimental data the following quantities were obtained:

the coherent scattering lengths (b in fm) of Zn (5.689±0.014);⁶⁴Zn (5.23±0.04);⁶⁶Zn (5.98±0.05);⁶⁷Zn (7.58±0.08;b ₊=9.4±0.5/5.8±0.5;b _?=5.0±0.7/10.1±0.7);⁶⁸Zn (6.04 ±0.03);

the potential scattering radii (R′ in fm) of Zn (6.2±0.2),⁶⁴Zn (6.0±0.3) and⁶⁶Zn (6.2 ±0.3);

the absorption cross sections (σ _γ at 0.025 eV in barn) of Zn (1.11±0.02);⁶⁴Zn (1.1 ±0.1) and⁶⁶Zn (0.62±0.06).

Derived quantities are the “zero energy” scattering cross sections (σ ₀ in barn) for Zn (4.128±0.010) and⁶⁷Zn (7.8±0.3) and the incoherent bound cross sections of Zn (0.061 ±0.023) and⁶⁷Zn (0.6±0.4). In the epithermal region the Zn-cross section can be described by introduction of two strong bound levels of⁶⁷Zn+n for which estimated parameters are given.     

Isotope shifts and hyperfine structure in the transitions in calcium II

The isotope shift and hyperfine structure in the three - transitions in Ca II have been studied by fast ion beam collinear laser spectroscopy for all stable Ca isotopes. The metastable 3d states were populated within the surface ionization source of a mass separator with a probability of about 0.1%. After resonant excitation to the 4p levels with diode laser light around 850 nm the uv photons from the transitions to the ground state were used for detection. Hyperfine structure parameters A and B for the odd isotope ⁴³Ca, as evaluated from the splittings observed, agree well with theoretical predictions from relativistic many-body perturbation theory. Field shift constants and specific mass shift constants were extracted from the measured isotope shifts and are discussed in comparison with expectation values from theory. Received: 19 September 1997 / Revised: 5 December 1997 / Accepted: 27 January 1998     

Correlation of light scattering and molecular dynamics in superionic Ba1−xLaxF2+x

Abstract

The squares of the Brillouin frequencies (Δω_B)² of the LA mode in the [100] direction related to the C₁₁ elastic constant show a linear decrease with temperature followed by significant deviations that occur above the corresponding transition temperatures (T_c), being at 850, 800, 970, 950 and 920 K for samples with x = 0.05, 0.1, 0.2, 0.3 and 0.5, respectively. The Raman linewidths show linear increases with temperature followed by rapid increases around the same temperatures at which the elastic constants start to show marked decreases. The complementary studies using Molecular Dynamics show that the diffusion coefficients start to increase markedly around the same temperatures observed experimentally.     

Search for double beta decay of Mo with liquid argon ionization chamber (first results)

First two runs with 138.7 g of ¹⁰⁰Mo were done 9202 h and 238 h). Limits on half-lives for 0ν- and 0νχ⁰-decays of ¹⁰⁰Mo were obtained, > 2.3 · 10²¹ y and 0.8 · 10²⁰ y, respectively at 90% CL. Also the limit on the content of radioactive ⁴²Ar in the natural Ar was obtained, < 5 · 10⁻²¹ g/g. Perspectives for the future are discussed.     

Theoretical study on structures and stability of SiC3S isomers

Various levels of calculations are carried out to explore the potential energy surfaces (PES) of singlet and triplet SiC₃S, a molecule of potential interest in interstellar chemistry. At the DFT/B3LYP/6-311G(d) level, a total of 57 minimum isomers and 92 interconversion transition states are located. The structures of the most relevant isomers and transition states are further optimized at the QCISD/6-311G(d) level followed by CCSD(T)/6-311?+?G(2df) single-point energy calculations. At the QCISD level, the lowest-lying isomer is the chain-like SiCCCS ³ 1 (0.0?kcal/mol) with a great kinetic stability of 54.1?kcal/mol. In addition, ring isomers CC-cCSSi ¹ 9 (19.8?kcal/mol), S-cCCCSi ¹ 12 (30.4?kcal/mol), S-cCCSiC ¹ 18 (9.4?kcal/mol), S-cSiCCC ¹ 21 (34.4?kcal/mol) and cage-like isomer cage-SiSCCC ¹ 23 (51.8?kcal/mol) also possess considerable kinetic stability (more than 10.0?kcal/mol). As a result, these six isomers are predicted to be possible candidates for future experimental and astrophysical detection. The bond natures and possible formation pathways in interstellar space of the SiCCCS are discussed. The predicted structure and spectroscopic properties for it are expected to be informative for the identification of SiC₃S and even larger SiC _n S species either in laboratory or in space.     

Structural features of the La-Sr-Fe-Co-O system

A structural study has been performed on the La_0.8Sr_0.2Fe_xCo_1-xO₃ (x = 0.025 to 0.3) system displaying large magnetoresistance (MR) at room temperature. A detailed analysis of the crystal structure and microstructure was done by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM). The atomic resolution TEM images and the appearing superreflections in the corresponding SAED patterns revealed that a superstructure is formed due to the presence of iron. The correlation between the ordered microstructure and the observed large MR ratio is discussed. ⁵⁷Fe M?ssbauer spectroscopy was utilized to gain information on the valence state of iron in the sample with x = 0.3. The lattice parameters of Fe- doped La_0.8Sr_0.2Fe_xCo_1-xO₃ compounds were found to increase monotonously with increasing Fe content. The valence state of iron was found to be Fe³⁺. Received 22 January 2001     

<Emphasis Type="Italic">Comment on</Emphasis>¶Low temperature specific heat of blue bronze K <Emphasis Type="Bold">0.30</Emphasis>MoO <Emphasis Type="Bold">3</Emphasis>, by J. Odin,J.C. Lasjaunias,K. Biljaković, K. Hasselbach,and P. Monceau

Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K_0.3MoO₃ and (TaSe₄)₂I. We have shown that the anomaly in the C _P / T ³ data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds. Received 21 February 2002 Published online 19 July 2002     

Simultaneous Determination of Seven Sulfonylurea-Type Oral Anti-Diabetic Agents in Adulterated Dietary Supplements and Traditional Chinese Medicines by Ultraperformance Liquid Chromatography–Tandem Mass Spectrometry

An ultraperformance liquid chromatography–tandem mass spectrometry method was developed for simultaneous determination of seven sulfonylurea-type oral anti-diabetic agents (glipizide, tolbutamide, tolazamide, gliclazide, glibenclamide, glimepiride, and glurenor) in dietary supplements and traditional Chinese medicines. The samples were extracted twice with methanol by ultrasound. The separation was achieved on a C18 column with the mobile phase consisting of acetonitrile and water (0.2% formic acid (v/v) and 5 mM ammonium acetate), at a flow rate of 0.3 mL/min with gradient elution. The analysis time was 8 min per sample. The proposed method was validated for linearity (r > 0.99), precision (relative standard deviation better than 6.0%), recoveries (83–110%), and the limit of detection in the range 0.3–2 µg kg^?1. The proposed method is rapid, reliable, sensitive, accurate, and good applicability, and it was successfully applied to analyze 20 real samples of 15 dietary supplements and five traditional Chinese medicines.     

Spectroscopic Study on the Interaction of Pyronine Y with Nucleic Acids and Its Analytical Application

ABSTRACT

The interaction of pyronine Y (PY) with nucleic acids was studied by resonance Rayleigh scattering (RRS) for nucleic acid detection. The enhanced RRS intensity of nucleic acids reacted with PY was proportional to the concentration of nucleic acids in the ranges of 27.0–625 ng ml^?1 for fish sperm DNA, 39.0–500 ng ml^?1 for calf thymus DNA, and 59.0–375 ng ml^?1 for yeast RNA. The limits of determination were 0.2 ng ml^?1 for fish sperm DNA, 0.6 ng ml^?1 for calf thymus DNA, and 0.7 ng ml^?1 for yeast RNA. The method had been successfully applied to the quick determination of nucleic acids in synthetic and natural samples.