A simple and rapid HPLC technique for vanillin determination in alcohol extract

This paper describes a simple and rapid HPLC technique for vanillin determination in alcohol vanilla extract. Vanillin was separated on a Nucleosil C18 column by using water and methanol (40:60) as the mobile phase and retention time was only 2.2 min. The measurements were made by using a photodiode array detector of the most adequate maximum wavelength absorbance at 231 nm. This method has been successfully applied for the determination of vanillin in some commercial extracts.     

Unusual Quadrupedal Locomotion in Rat during Recovery from Lumbar Spinal Blockade of 5-HT7 Receptors

Coordination of four-limb movements during quadrupedal locomotion is controlled by supraspinal monoaminergic descending pathways, among which serotoninergic ones play a crucial role. Here we investigated the locomotor pattern during recovery from blockade of 5-HT₇ or 5-HT_2A receptors after intrathecal application of SB269970 or cyproheptadine in adult rats with chronic intrathecal cannula implanted in the lumbar spinal cord. The interlimb coordination was investigated based on electromyographic activity recorded from selected fore- and hindlimb muscles during rat locomotion on a treadmill. In the time of recovery after hindlimb transient paralysis, we noticed a presence of an unusual pattern of quadrupedal locomotion characterized by a doubling of forelimb stepping in relation to unaffected hindlimb stepping (2FL-1HL) after blockade of 5-HT₇ receptors but not after blockade of 5-HT_2A receptors. The 2FL-1HL pattern, although transient, was observed as a stable form of fore-hindlimb coupling during quadrupedal locomotion. We suggest that modulation of the 5-HT₇ receptors on interneurons located in lamina VII with ascending projections to the forelimb spinal network can be responsible for the 2FL-1HL locomotor pattern. In support, our immunohistochemical analysis of the lumbar spinal cord demonstrated the presence of the 5-HT₇ immunoreactive cells in the lamina VII, which were rarely 5-HT_2A immunoreactive.     

Hydrothermal Crystallization of Zirconia and Zirconia Solid Solutions

Zirconia as well as yttria-zirconia and calcia-zirconia solid-solution powders were crystallized under hydrothermal conditions from (co)precipitated hydroxides. The morphology of the powder particles is strongly dependent on the crystallization conditions. The powders crystallized in a water solution of Na, K, and Li hydroxides show elongated particles of much larger sizes than those which result from the process carried out in pure water or a water solution of Na, K, or Li chlorides. The shapes of the latter particles are isometric. The growth mechanism of the elongated particles is suggested.     

Crystallization of Zirconia under Hydrothermal Conditions

Amorphous zirconia gel was hydrothermally treated at 250°C for 1–326 h in water and in NaOH water solution. Changes of the crystallite sizes and shapes were observed using TEM. The nature of these changes seems to be independent of the crystallization environment, but the rate of the process is much faster in the NaOH solution. The mechanism of the crystal growth is suggested.     

On a class of limit reliability functions for series-parallel and parallel-series systems

In the reliability investigation of large-scale systems, the problem of the complexity of their reliability functions arises. This problem may be approximately solved by the assuming that the number of system components tends to infinity and finding the limit reliability function. This paper presents the solution of this problem and some applications. The classes of asymptotic reliability functions for series-parallel and parallel-series systems with identical and unlike components are presented. They are ten-element and more extensive than the known three-element classes of asymptotic distributions of maximum and minimum statistics of independent random variables with a common distribution function. The results may be useful in the reliability evaluation of large scale systems.     

Reasoning about Prolog programs: From modes through types to assertions

We provide here a systematic comparative study of the relative strength and expressive power of a number of methods for program analysis of Prolog. Among others we show that these methods can be arranged in the following hierarchy: mode analysis ? type analysis ? monotonic properties ? nonmonotonic run-time properties. We also discuss a method allowing us to prove global run-time properties.     

Study of Passive Deck-Flaps Flutter Control System on Full Bridge Model. II: Results

Using the analytical format set forth in the first of these two companion papers, numerical simulations of a passive aerodynamic control method for suppression of the wind-induced instabilities of a very long span bridge are presented in this paper. At first, the aerodynamic stability of the uncontrolled system is discussed using a sectional model and full bridge model, respectively. Next, the efficiency of the proposed asymmetric and symmetric cable connection control systems is studied. Both systems offer similar maximum improvements in critical wind speed. The asymmetric cable connection system turns out to be very sensitive to horizontal motions, which strongly degrade its effectiveness. On the contrary, the symmetric cable connection system is not sensitive to horizontal motions, but its efficiency is limited by divergence.     

Intrinsic Kinetics of Carbon Dioxide Degradation of YBa2Cu3O7-x

The intrinsic kinetics, unaffected by diffusional and masstransfer effects, of the CO₂ degradation of superconducting particles have been determined using a nonisothermal technique. Below 900°C, the carbonization of YBa₂Cu₃O_{7- x} leads to formation of BaCO₃, Y₂Cu₂O₅, CuO, and Cu₂O. A further increase in temperature results in formation of BaCuO₂ from BaCO₃ and CuO. The carbonization rate shows the 1.5th-order dependence on the amount of unreacted YBa₂Cu₃O_{7- x} for the temperature range of 550° to 815°C. The activation energy of carbonization was determined to be 95.1 kJ · mol⁻¹.