Quantitative determination of oxocarboxylic and hydroxycarboxylic acids in normal individuals and ketoacidotic patients

Oxo- and hydroxycarboxylic acids as metabolites of valine, leucine, and isoleucine and of ketogenesis are simultaneously quantitated in the form of their methyl esters and methyl esters/O-methyloximes by gas chromatography using internal and external standards. Normal values for the urinary excretions of the amino acid metabolites are between 3 ± 2 μmol/24 h (mean value ± standard deviation) for 2-oxoisocaproic acid and 122 ± 58 μmol/24 h for 3-hydroxyisobutyric acid. In diabetic ketoacidosis the values are increased by a factor of 2-10.     

Investigation of single wall carbon nanotubes electrical properties and normal mode analysis: Dielectric effects

Besides thermodynamic information, vibration can identify modes of a molecule by comparison of the spectroscopy and parameterize force field. By the application of group theory with the state of projection operators, a systematic method for getting the vibrational model of molecules such as the (3, 0), (4, 0), (5, 0) nanotubes was proposed. The U matrix from the combination of primitive’s harmonic vibrations was calculated and the effect of dielectric constants on the mechanism of these vibrations in nanotubes was studied. We found that in the high dielectrics the frequency of vibration has alternative behavior, however by the decreasing of the dielectrics, this behavior change to stable situation of geometry. The calculated data shown in Tables and Figures are in correspondence with some behavior of nanotubes.     

The oxidation state of antimony and electrical properties in antimony-doped rutile

The reaction of TiO₂ with Sb₂O₄ for temperatures in the range of 650 to 1000°C indicates that Sb can dissolve in rutile up to the proportion of 7 mole% in an Sb₂O₄ equivalent. With increasing content of Sb, the unit cell volume increased gradually. From the results on the binding energies of 530.6 eV forSb(3d₃₂) and 540.1 eV forSb(3d₅₂), it is expected that Sb was substituted as Sb³⁺ ion for Ti⁴⁺ in the rutile structure. Theac resistivities of rutile with Sb are in the range of 10² to 10⁵ ohm · m at room temperature. The frequency and temperature dependencies of the dielectric constant can be elucidated by the ionic polarization model coupling Sb with oxygen vacancy. The activation energy, giving a loss maximum, was determined to be 0.15–0.17 eV over a frequency range of 10⁴ to 10⁷ Hz.     

Comparative study of natural autoantibodies in the serum and cerebrospinal fluid of normal individuals and patients with multiple sclerosis and other neurological diseases

Using a panel of antigens (actin, myosin, tubulin, albumin, transferrin, peroxidase, thyroglobulin, DNA, prolactin, TNP and myelin basic protein (MBP)), we have tested the antibody activity of serum and cerebrospinal fluid (CSF) from healthy individuals, patients with multiple sclerosis (MS) and individuals with other neurological diseases. No differences in the concentrations and specificities of the serum antibodies were observed among the 3 groups. In contrast, we found that MS patients often had elevated CSF antibody levels against many antigens of the panel. The MS patients with local immunoglobulin production in the central nervous system (CNS) had the highest antibody levels. Restricted antibody activity against a given antigen of the panel was not observed. Compared to the two other groups, the MS group had equivalent titres of anti-MBP antibodies in the CSF.These results suggest that, in MS, a general immune dysregulation exists which leads to a local expansion of B lymphocytes producing autoantibodies with reactivities similar to those of serum natural autoantibodies.     

The grain-boundary-related optical and electrical properties in polycrystalline p-type ZnO films

Cathodoluminescence spectra and electrical properties of the N doped and N–Al codoped p-type ZnO films and the dependence of these two properties on the post-annealing were investigated. Spectral analyses show that the intensity of the green emission strongly depends on the annealing ambient and closely relates with the width of the electron depletion region at the particle boundary. The conducting type and electrical properties of N doped and N–Al codoped ZnO films are greatly affected by the annealing process. The grain boundary effect was proposed to explain the green emission behavior and the p-type conduction in polycrystalline ZnO based films.     

Thermal,structural and electrical properties

The chloro compound of 3-hydroxy-2-quinoxalinecarboxylic acid with nickel(II) has been prepared in ethanolic solution from which a solid compound was isolated. Spectral and magnetic measurements show that the nickel ions are in an octahedral environment. Thermogravimetry, differential thermal analysis and electrical conductivity data are reported for 3-hydroxy-2-quinoxalinecarboxylic acid and its nickel complex. The conductivity measurements indicate that electron/hole traps are emptied during heating of the complex but repopulation occurs in about 24 h at room temperature.     

Synthesis and electrical properties of polyacetylene derivatives

Cyclopolymerization of 1,6‐heptadiyne derivatives containing the bulky substitutents was carried out by metathesis catalyst systems. The catalytic activity of molybdenum (V) chloride (MoCl₅) in homopolymerization is greater than that of the MoCl₅‐cocatalyst system, and copolymerization is vice versa in catalytic activity. Newly synthesized homo‐ and copolymers were soluble in common organic solvents and could afford thin film by solution‐casting onto the indium–tin oxide coated glass substrate. The NMR, Fourier transform infrared spectroscopic, and UV–visible spectra indicated that these polymers have a linear conjugated cyclic polyene structure having a bulky substitutent as a pendant group. The number‐average molecular weight of these polymers was in the range of 2.4–6.27 × 10³. The copolymers exhibited a relatively higher molecular weight than that of the homopolymers. The copolymers were stable up to 380 °C. The electrical conductivities of the I₂‐doped copolymer thin film by the four‐point probe method and surface plasmon resonance spectroscopy were about 500 and 600 S/cm, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 958–964, 2002     

Synthesis and electrical properties of triple molybdates

Triple molybdates of compositions M₅(Li_1/3Hf_5/3)(MoO₄)₆ (M is K, Rb, or Tl) and M₃LiHf₂ · (MoO₄)₆ (M is Na, K, Rb, or Tl) were synthesized by solid-phase reaction, and their conductivity in the temperature range 200–550°C was studied.     

Optical properties of in vitro epidermis and their possible relationship with optical properties of in vivo skin.

Using a spectrophotometer with an internal integrating sphere, the absorption (mu a) and reduced scattering (mu s') coefficients of in vitro epidermis were evaluated from reflectance and transmittance measurements. mu a and mu s' varied from 24 to 0.2 cm-1, and from 32 to 21 cm-1 respectively, on passing from 400 to 800 nm. Moreover, using an external integrating sphere, the reflectance spectrum of in vivo skin was compared with the reflectance spectrum calculated with a Monte Carlo model, in which the mean values of mu a and mu s' and different anisotropy parameters were used as input data. In vivo results show that the principle of similarity is entirely valid for wavelengths greater than 600 nm and may be considered a good approximation in the 400-600 nm band, and suggest that optical characteristics of in vivo skin may be inferred from reflectance measurements.     

The electrical properties of some 2-aminopyrimidine and 2-aminopyrazine schiff bases

The electrical properties of some Schiff bases of 2-aminopyrimidine and 2-aminopyrazine with benzaldehyde derivatives have been investigated. Such measurements have rarely been done on these compounds. The positive temperature coefficient of electrical conductivity (dσ/dT) found for all the samples investigated is evidence for the semiconducting character within the range of temperature studied. For the compounds studied, a correlation between the electrical properties and their chemical structure is established. The mechanism of the conduction process in these samples is also studied.     

Polymer blends filled with carbon black: structure and electrical properties

Morphology and electrical conductivity of polymer blends based on polypropylene, polyethylene, polyoxymethylene, polyamide 12, co‐polymer ABS filled with carbon black (CB) were studied. When filler is introduced in polymer blend, three cases of filler spatial distribution can be obtained. CB can be distributed randomly within polymer matrix, can be situated in one of the polymer components or can be localized on the boundary of the polymer components. The existence of different cases of filled blends structure is defined by following reasons: thermodynamic factors (relationship between interface surface tensions of polymer‐filler γ_pf and polymer‐polymer surface tension γ_pp); kinetic factors (relationship between viscosities of polymer components); processing factors (methods of the filler introduction in the complex polymer matrix, which can enhance or depress the influence of thermodynamic and kinetic factors).     

The electrical properties of schungite-containing compositions based on polypropylene and high-density polyethylene

Variations in the dc and ac conductivities of schungite-containing compositions based on polypropylene-high-density polyethylene (PP-PE) blends were studied depending on the composition of the polymeric blend, the volume concentration of the filler, and the order of the introduction of the composition components during the preparation of compositions. It was shown that the conductivities of the compositions could depend on the order of the introduction of the components. The structure of initial and schungite-containing PP-PE blends of different compositions was studied by atomic-force microscopy. It was shown that the structure of the compositions depended on the composition of the initial PP-PE blends and the order of the introduction of the components into schungite-filled PP-PE compositions.     

Some electrical properties of wood pulp treated with sodium hydroxide

The effect of the degree of crystallinity and degree of polymerization on the electrical properties of soda-treated wood pulp has been investigated. The dielectric constant (E′) and the dielectric loss (E″) were measured for the treated samples over a frequency band 0.2–10 MHz at 20°C. Also, the electrical conductivity (σ) was calculated from the measured data of the dielectric constant. From the results obtained we found that the degree of crystallinity and the degree of polymerization decrease with time of oxidation while the number of carboxylic groups increased. E″,E′, and σ were found to increase with the decrease in the degree of crystallinity.     

Fabrication and characteristics of polyHEMA artificial skin with improved tensile properties

PolyHEMA-based hydrogel synthesized by the UV-radiation induced polymerization technique is used to prepare the strength-proved artificial skin in order to improve the handling procedure for curing the burned wound. The tensile strength of the artificial skin membrane is measured following the ASTM standard. The strength decreases with increasing amount of the initial water added to the mixture of HEMA (2-hydroxyethyl methacrylate) monomer, ethylene glycol dimethacrylate (EGDMA) cross linker and benzoin isobutyl ether (BIE) initiator. The maximum strength of the artificial skin membrane reaches 9 kg/cm², as the hydrogel contains equilibrium water around 30 wt%. The artificial skin so fabricated presents several additional characteristics including good wettability, complete transparency and dimensional change during water absorption and evaporation.     

Structural and electrical properties of doped polypyrrole and its composite with montmorillonite clay

Polypyrrole is synthesized and doped with Dodecylbenzenesulphonic acid. The doped Polypyrrole with Dodecylbenzenesulphonic acid is intercalated into the layers of Montmorillonite clay successfully by in situ polymerization. The structural properties of synthesized doped Polypyrrole and intercalated doped Polypyrrole were studied by XRD analysis. The crystallinity of intercalated doped Polypyrrole into the layers of Montmorillonite clay is confirmed by means of X-rays diffraction studies, which is more than the doped Polypyrrole. Enhanced d-spacing of Montmorillonite confirmed that doped Polypyrrole is interclated into the layers of Montmorillonite clay at nanoscale. The scanning electron micrographs also confirm the formation of dual phase of platelet as well as of flaky structure of intercalated doped Polypyrrole. Temperature dependant conductivity showed three dimensional variable ranges hopping model. Activation energy, density of states and hopping length are calculated and found to be influenced by intercalating Doped Polypyrole into the layers of Montmorillonite clay.     

Single-crystal growth and electrical properties of CaSi2

Single crystals of CaSi₂ were grown by a floating zone method. Like mica, the single crystals exhibited a smooth cleavage surface over extended regions. The cleavage occurred on the {111} plane. CaSi₂ behaved as a metal. The electrical resistivity showed a positive temperature dependence with high residual resistivity and some crystallographic orientation dependence. The Hall measurements showed that electrons were the predominant carriers in CaSi₂.