Magnetic field dependence of residual dipolar couplings measured in dilute liquid crystalline media

The effect of the magnetic field strength on the magnitude of residual dipolar couplings introduced by dilute liquid crystal media was investigated. One-bond heteronuclear residual dipolar couplings and residual deuterium quadrupolar splitting of the water were monitored at various static magnetic fields. It is suggested that the value of residual anisotropic NMR parameters resulting from exchange between ordered and non-ordered molecules decreases with increasing magnetic fields.     

Kinetics and mechanism of the hydrolytic disproportionation of iodine

Kinetics of the hydrolytic disproportionation of I₂ was studied by UV–VIS spectrophotometry at 298 K and at the ionic strength 0.2 M (NaClO₄) in buffered solutions in the pH range 8.91–10.50 at different initial iodide concentrations. The characterization of this reaction is fundamental for modeling oscillatory and front reactions in the presence of iodine as reactant or intermediate as well as for drinking water treatment. A matrix rank analysis confirmed three absorbing species in the beginning of the reaction, whereas later assumption of two species is enough to describe the experimental data in the visible part of the spectrum. A reaction mechanism was proposed for disproportionation by using fitting/simulation with a multipurpose program package ZiTa, by simultaneous evaluation of 17,906 points in 79 experimental curves. A parameter set was suggested, which was obtained by absolute, relative, and orthogonal fittings of the experimental data. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 596–602, 2004     

New 7‐phosphanorbornenes derived from 2‐methyl‐1‐phenyl‐ and 1‐cyclohexyl‐3‐ methyl‐2,5‐dihydro‐1H‐phosphole 1‐oxides

Novel 7‐phosphanorbornene derivatives, such as 4, 5, 10 , and 11 were synthesized utilizing 1‐phenyl‐2‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) and 1‐cyclohexyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 7 ) as the starting materials. Products 4 and 10 were prepared by trapping the corresponding phosphole oxide intermediates ( 3 and 9 , respectively) by N‐phenylmaleimide, while 5 and 11 were obtained by the dimerization of 3 and 9 , respectively. The trapping reaction was studied in details; on one hand, bromo‐2,3‐dihydro‐1H‐phosphole oxides ( 6‐1 and 6‐2 ) were pointed out as the intermediates, on the other hand, the trapping reaction was optimized. Bri‐ dged P‐heterocycles 4, 5, 10 , and 11 were tested in the fragmentation‐related phosphorylation of methanol. Hydrogenation of phosphanorbornenes 4 and 5 led to the corresponding phosphanorbornanes ( 12 and 14 , respectively) and to a reductive type of retro cycloaddition. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:320–326, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20097     

Development of antimicrobial packaging materials with immobilized glucose oxidase and lysozyme

Packaging based on immobilization of antimicrobial enzymes provides a promising form of active packaging systems applicable in food processing. Glucose oxidase and lysozyme were immobilized by the Ugi reaction with cyclohexyl isocyanide and glutaraldehyde on polyamide and ionomer films partially hydrolysed by hydrochloric acid. The immobilization of the enzymes on the surface of films was confirmed by FT-IR spectroscopy and the films were characterized by the specific activity of the immobilized enzymes. The enzyme migration into model solutions and the effect of pH, temperature and storage time on the activity of immobilized enzyme were also evaluated. Immobilization of lysozyme onto polyamide and ionomer films resulted in the loss of enzyme activity. The polyamide and ionomer films with immobilized glucose oxidase inhibited the growth of bacteria Escherichia coli CNCTC 6859, Pseudomonas fluorescens CNCTC 5793, Lactobacillus helveticus CH-1, Listeria ivanovii CCM 5884 and Listeria innocua CCM 4030 on agar media.      

Observation of two-neutrino double-beta decay in 136Xe with the EXO-200 detector

We report the observation of two-neutrino double-beta decay in (136)Xe with T(1/2) = 2.11 ± 0.04(stat) ± 0.21(syst) × 10(21) yr. This second-order process, predicted by the standard model, has been observed for several nuclei but not for (136)Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrinoless double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale.     

Neurodegeneration in Multiple Sclerosis: Symptoms of Silent Progression,Biomarkers and Neuroprotective Therapy—Kynurenines Are Important Players

Neurodegeneration is one of the driving forces behind the pathogenesis of multiple sclerosis (MS). Progression without activity, pathopsychological disturbances (cognitive impairment, depression, fatigue) and even optic neuropathy seems to be mainly routed in this mechanism. In this article, we aim to give a comprehensive review of the clinical aspects and symptomology, radiological and molecular markers and potential therapeutic targets of neurodegeneration in connection with MS. As the kynurenine pathway (KP) was evidenced to play an important role in the pathogenesis of other neurodegenerative conditions (even implied to have a causative role in some of these diseases) and more and more recent evidence suggest the same central role in the neurodegenerative processes of MS as well, we pay special attention to the KP. Metabolites of the pathway are researched as biomarkers of the disease and new, promising data arising from clinical evaluations show the possible therapeutic capability of KP metabolites as neuroprotective drugs in MS. Our conclusion is that the kynurenine pathway is a highly important route of research both for diagnostic and for therapeutic values and is expected to yield concrete results for everyday medicine in the future.     

Thermal degradation of crab shell biomass,a nitrogen-containing carbon precursor

Journal of Thermal Analysis and Calorimetry - The refrigerator unit based on electrically driven vapor compression technology consumes high energy, associated with high cost and loss of ecosystem....     

Some General Features in the Autocatalytic Reaction between Sulfite Ion and Different Oxidants

The autocatalytic oxidation of a weak acid is a common building block of the pH oscillators. These reactions can be described by a simple general scheme that includes a protonation equilibrium and the oxidation of the protonated form of the weak acid. Here we show that independently from the chemical nature of the oxidizing agent, these reactions bear some general features, namely (1) the change in pH (ΔpH) observed during the reaction is determined by the acidity constant (K_HA) and by the initial concentration of the unprotonated form of the weak acid (A^?): , (2) the inflection time of the autocatalytic reaction (t_i) depends reciprocally on K_HA and on the initial hydrogen ion concentration, and (3) in the presence of a competitive reversible proton‐binding component (D^?), that is not involved in the oxidation process, ΔpH follows a titration‐like curve as the concentration of D^? is increased, t_i is only slightly affected but the maximum rate of the autocatalytic process is significantly reduced. The slowing of the overall reaction is proportional to the acidity constant of the proton‐binding component.     

Comparison of pressurised fluid and ultrasonic extraction methods for analysis of plant antioxidants and their antioxidant capacity

The analytical method based on the high-performance liquid chromatography coupled with UV detection (HPLC/UV) for determination of selected antioxidants (i.e., esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Pressurised fluid extraction (PFE) and ultrasonic extraction (USE) methods for the isolation of these compounds from ten real plant samples were used. Both extraction methods were optimised and compared to each other. For the proposed HPLC/UV method the LOQ values (limit of quantification) in the range from 22.7 (xanthotoxin) to 97.2 ng mL⁻¹ (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also determined. Results ranged from 82.04 to 94.43% of DPPH radical inhibition for PFE method and from 76.01 to 89.94% in the case of USE method.     

Influence of the Phase Morphology on the Viscoelastic Behaviour of Polymer Blends (PP-EPR)

Summary. Melts of polyethylene-propylene-rubber (EPR, blends of linear polyethylene, linear polypropylene, and PE-PP copolymer) show phase separation. The influence of the phase morphology on the viscoelastic behaviour is studied with the aid of the dynamical moduli. The measured moduli of the fraction of the linear homopolymer of an EPR agree with the moduli calculated from the molar mass distribution of this fraction. In contrast, the copolymer fraction shows a strong rubber-like behaviour (represented by a characteristic relaxation time spectrum). Mixtures of 80 wt% linear PP and of EPRs with low copolymer content are not rubber-like liquids. In addition, the moduli from them can be calculated from the moduli of the components with the aid of Palierne’s emulsion model. This clearly reveals that the linear PP forms the matrix in this case. Mixtures of 80 wt% linear PP and of EPRs with high copolymer content show rubber-like behaviour and Palierne’s emulsion model is not applicable on them. Obviously, the copolymer fraction forms a physical network.