Thermal degradation of keratin waste

Thermal degradation of sheep wool, human hair and chicken feathers was studied by TG-MSD/FTIR and by pyrolysis followed by GC-MSD analysis in order to identify the degradation compounds and the temperature range in which they are formed. Only small differences were found between the studied keratin samples. They consist mainly in shift of characteristic temperatures of degradation and in relative amounts of compounds in degradation products, especially in aqueous phase. Degradation started with formation of ammonia and CO₂ (from 167 and 197 °C respectively and with maximum evolution at 273 and 287 °C respectively), continues with formation of sulphur-containing inorganic compounds (SCS, SCO, H₂S and SO₂ at 240, 248, 255 and 253-260 °C respectively) and of water (255 °C). Thiols are formed in two stages (257 and 320 °C) while the evolution of nitriles is maximum around 340 °C and continues up to about 480 °C. Phenol and 4-methylphenol are the most important degradation compounds, formed at 370 and 400 °C respectively. Nitrogen was present mainly in aliphatic/aromatic nitriles, pyrroles, pyridines and amides while sulphur was found mainly as sulphides, thiols, thiazoles and thiophenes.     

A thermogravimetric study of structural changes of lime wood (Tilia cordata Mill.) induced by exposure to simulated accelerated UV/Vis-light

A series of experiments were carried out to investigate photodegradation of lime wood (Tilia cordata Mill.) during artificial UV/Vis light irradiation for 600 h. Photodegradation of the wood samples was evaluated by thermogravimetry throughout the irradiation period at an interval of 100 h.The alteration of wood was observed by means of the peak temperatures of DTG variation and by the mass losses observed during heating, evaluated on the basis of the measured thermal data. The results obtained indicate a shifting of the DTG maxima to lower temperatures which may be related to the decreasing in the stability components during photodegradation. The values of the overall activation energies corresponding of the decomposition process progressively decreases.The decreased temperatures decomposition processes, weight losses and integral area of the peaks assigned to lignin, the increased integral area of the peaks assigned to hemicelluloses could be explained by new formed structures, mainly due to formation of reactive species.     

Preparation and characterization of PbTiO3–epoxy resin compositionally graded thick films

The preparation and properties of compositionally graded PbTiO₃ (PT)–epoxy resin (EPR) composite thick films are reported in this study. Various graded specimens were prepared using gravity casting method by embedding PT powders into the EPR matrix. The existence of a graded structure with two distinct phases, a good intermixing, some air pores, and different morphologies, was confirmed by scanning electron microscopy micrographs. The dielectric constants of these composites have values in the range 5–12 at the frequency of ～10⁴?Hz and about 3–13 at ～5?×?10^8?Hz. The composites with permittivity gradient act as a natural impedance match system in the frequency range 2–4?GHz, resulting in very low reflections. Therefore, the compositionally graded PT–EPR composite thick films are suitable as adapting impedance materials for microwave applications.     

Catalyzed Vinylogous Mukaiyama Aldol Reactions with Controlled Enantio‐ and Diastereoselectivities

In control : A new catalytic vinylogous Mukaiyama aldol reaction provides products with high diastereo‐ and enantioselectivities (up to 99 % de and ee; see scheme). The relative and absolute stereochemistry of a representative product was rigorously assigned by NMR and CD spectroscopies (measured and calculated), X‐ray diffraction, and quantum‐chemical calculations.

     

Electrical control of spin relaxation in a quantum dot

We demonstrate electrical control of the spin relaxation time T1 between Zeeman-split spin states of a single electron in a lateral quantum dot. We find that relaxation is mediated by the spin-orbit interaction, and by manipulating the orbital states of the dot using gate voltages we vary the relaxation rate W identical withT1(-1) by over an order of magnitude. The dependence of W on orbital confinement agrees with theoretical predictions, and from these data we extract the spin-orbit length. We also measure the dependence of W on the magnetic field and demonstrate that spin-orbit mediated coupling to phonons is the dominant relaxation mechanism down to 1 T, where T1 exceeds 1 s.     

Parametrically forced pattern formation

Pattern formation in a nonlinear damped Mathieu-type partial differential equation defined on one space variable is analyzed. A bifurcation analysis of an averaged equation is performed and compared to full numerical simulations. Parametric resonance leads to periodically varying patterns whose spatial structure is determined by amplitude and detuning of the periodic forcing. At onset, patterns appear subcritically and attractor crowding is observed for large detuning. The evolution of patterns under the increase of the forcing amplitude is studied. It is found that spatially homogeneous and temporally periodic solutions occur for all detuning at a certain amplitude of the forcing. Although the system is dissipative, spatial solitons are found representing domain walls creating a phase jump of the solutions. Qualitative comparisons with experiments in vertically vibrating granular media are made. (c) 2001 American Institute of Physics.     

Energy-dependent tunneling in a quantum dot

We present measurements of the rates for an electron to tunnel on and off a quantum dot, obtained using a quantum point contact charge sensor. The tunnel rates show exponential dependence on drain-source bias and plunger gate voltages. The tunneling process is shown to be elastic, and a model describing tunneling in terms of the dot energy relative to the height of the tunnel barrier quantitatively describes the measurements.     

Validated ion pair liquid chromatography/fluorescence detection method for assessing the variability of the loratadine metabolism occurring in bioequivalence studies

Inter- and intra-individual variability of the loratadine (LOR) metabolism in Caucasian subjects was assessed during a bioequivalence study for two pharmaceutical formulations (solid oral dosage forms) containing 10 mg of the active substance. The analytical data were obtained by applying a reliable, low-cost and sensitive ion pair liquid chromatography/fluorescence (IPLC/FLD) method for determination of both loratadine and descarboethoxyloratadine (DCL) in human plasma samples. The sample preparation procedure is based on liquid-liquid extraction of the target analytes from alkalinized plasma using diethyl-ether. The separation of the analytes and 8-chloroazatadine as internal standard (IS) was achieved through an isocratic ion pair (IP) elution on a Purospher((R)) STAR RP-18 column. The mobile phase containing sodium dodecyl sulfate (SDS) as ion pairing agent was pumped at a flow rate of 1 mL/min. Fluorescence detection (FLD) was achieved at 280 nm (excitation) and 440 nm (emission) wavelengths. The increased sensitivity of the method is also based on a large sample injected volume (250 microL). Linear response was found over the 0.5-20 ng/mL concentration interval for both target compounds. Low limits of quantification (LLOQ) around 0.3 ng/mL were found for LOR and DCL. Method validation is presented.     

Tsallis Entropy for Loss Models and Survival Models Involving Truncated and Censored Random Variables

The aim of this paper consists in developing an entropy-based approach to risk assessment for actuarial models involving truncated and censored random variables by using the Tsallis entropy measure. The effect of some partial insurance models, such as inflation, truncation and censoring from above and truncation and censoring from below upon the entropy of losses is investigated in this framework. Analytic expressions for the per-payment and per-loss entropies are obtained, and the relationship between these entropies are studied. The Tsallis entropy of losses of the right-truncated loss random variable corresponding to the per-loss risk model with a deductible d and a policy limit u is computed for the exponential, Weibull, χ2 or Gamma distribution. In this context, the properties of the resulting entropies, such as the residual loss entropy and the past loss entropy, are studied as a result of using a deductible and a policy limit, respectively. Relationships between these entropy measures are derived, and the combined effect of a deductible and a policy limit is also analyzed. By investigating residual and past entropies for survival models, the entropies of losses corresponding to the proportional hazard and proportional reversed hazard models are derived. The Tsallis entropy approach for actuarial models involving truncated and censored random variables is new and more realistic, since it allows a greater degree of flexibility and improves the modeling accuracy.