Studies on adsorption equilibrium of xylenes in AEL framework using biased GCMC and energy minimization

The adsorption of xylene isomers in AlPO₄-11 (AEL network) was investigated using biased grand canonical Monte Carlo (GCMC) simulations. Preferential o-xylene adsorption was predicted by the simulations, in agreement with previously reported experimental data. In AlPO₄-11 the selective adsorption behavior comes from the smaller length of the o-xylene molecule along the crystallographic c-axis compared to p-xylene. This is in contrast to AlPO₄-5 and AlPO₄-8, where the ortho-selectivity is caused by the characteristic face-to-face positioning of o-xylene. Energy minimization studies were also performed in a flexible AlPO₄-11 lattice to study the structural changes upon xylene adsorption. The energy minimization study showed that the AlPO₄-11 crystal distorts upon p- and o-xylene adsorption. The distortion mechanism is related to the strong interaction between xylene methyl groups and the sieve oxygen atoms in the O3 position in the wide region of the pore.     

Gyrotron coaxial cylindrical resonators with corrugated innerconductor: Theory and experiment

Gyrotron coaxial resonators with a longitudinally slotted inner cylinder are examined analytically using a surface impedance model, from which expressions for the electromagnetic field, ohmic quality (Q) factor, and characteristic equation of the transverse eigenvalues χ _m,p are obtained. The major attributes of such resonators are expressed by the dependence of χ_m,p on the parameter C-defined as the ratio of the outer to inner radii of the coaxial structure. In that connection, the effect of the corrugation parameters on χ_m,p is particularly investigated on the basis of an expression derived for the slope function dχ_m,p,p/dC. It is shown that the χ_m,p(C) curve may either exhibit oscillatory behavior or present a flat portion over a wide range of C depending on the corrugation parameters chosen. The theory is checked against experiment in which resonant frequencies and total Q factors were measured for TE modes operating in the range of 8-16 GHz in a coaxial cavity with 40 slots. Good agreement is found in that the magnitude of the relative error in frequency is less than 0.5%. Corrugated coaxial resonators prove to be relevant to megawatt gyrotrons where highly selective cavities are required to ensure high conversion efficiency     

Cold tests of open coaxial resonators in the range 9–17 GHz

A study of selective properties of coaxial open cylindrical resonators have been conducted experimentally and compared with theory. The resonator consists of an inner circular cylinder symmetrically located inside an outer weakly irregular open waveguide. Several fundamental TE modes were identified over the range 9 to 17 GHz through measurements of the resonant frequencies and the associated loaded quality factors. It has been verified that the structure and the number of resonant modes are both strongly dependent on the diameter of the coaxial insert. Such an electrodynamical system proves to be useful in guided wave applications requiring, for example, filters, frequency-tunable resonators and devices for analyzing the modal composition of a signal.     

Silver electrodeposition from air and water-stable ionic liquid: An environmentally friendly alternative to cyanide baths

The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1-butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200 °C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath.     

Electrical Conductivity Measurement Through the Loaded Q Factor of a Resonant Cavity

We present a method for measuring the electrical conductivity of metallic materials that relies on the ratio of two loaded Q factors, Q_R/Q_X, with Q_R corresponding to a TE₀₁₁-mode reference cavity made of aluminum, and Q_X the Q that results upon replacing the aluminum plate with the one fabricated from the material to be examined. Electrical conductivity is mathematically inferred from the ratio Q_R/Q_X where the loaded Q factors are measured by using the transmission-type method. Within a 3.0 percent accuracy, conductivities determined at 8.7 GHz for electrolytic copper (5.6 times 10⁷ S/m) and brass (1.6 times 10⁷ S/m) show to be in good agreement with those reported in the literature.     

Estimation of thermal diffusivity of foods using transfer functions

The effective thermal diffusivity of foodstuffs was estimated from time-temperature histories in the geometric center of samples exposed to heating and cooling processes.Transfer functions methodology was used as an alternative method to estimate the thermal diffusivity assuming that conduction was the main heat transfer mechanism. The samples were characterized as delayed first-order systems with unit gain, dead time (L) and time constant (τ).The results were compared with those obtained from the f_h value and with results reported in the literature.     

There's more to touch than meets the eye: The salience of object attributes for haptics with and without vision.

The availability and salience of object attributes under haptic exploration, with and without vision, were assessed by 2 tasks in which Ss sorted objects that varied factorially in size, shape, texture, and hardness. In the directed-discrimination task, Ss were instructed to sort along a particular dimension. Although levels on all dimensions were easily discriminated, shape was relatively less so for haptic explorers without vision, as was hardness for those using vision and haptics. Size was least discriminable for both groups. In the free-sorting task, Ss were to sort objects by similarity. Three groups used haptic exploration only; these were differentiated by the experimenters' definition of object similarity: unbiased haptics, haptically biased haptics, haptics plus visual imagery. A 4th group used vision as well as haptics, with instructions like those of the unbiased haptics group. Results support the contention that the haptic and visual systems have distinct encoding pathways, with haptics oriented toward the encoding of substance rather the shape. This may reflect a direct influence of haptic exploratory procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study of behavioural groupings of polyphenolic species in "fino" sherry wine. Evolution during vinification and mechanical treatment of the grape

The different groups and/or classes among phenolic acids and aldehydes identified during the elaboration process of "fino" sherry wine have been studied. The study was carried out using different processes during the elaboration of the wine and we have attempted to establish whether the different treatments of the grape affect these groupings. The study was undertaken by means of cluster and multifactorial analysis on the data obtained by the quantitative determination of phenolic acids and aldehydes during vinification and in experiments carried out on the grape under different mechanical treatments. The analysis of phenolic acids and aldehydes was done with HPLC, using a C-18 mu-Bondapak and a stepwise composite gradient. The samples were previously extracted with ethylic ether.     

Synthesis and Evaluation of Voltage-Gated Sodium Channel Blocking Pyrroline Derivatives Endowed with Both Antiarrhythmic and Antioxidant Activities

Under the hypothesis that cardioprotective agents might benefit from synergism between antiarrhythmic activity and antioxidant properties, a small series of mexiletine analogues were coupled with the 2,2,5,5-tetramethylpyrroline moiety, known for its antioxidant effect, in order to obtain dual-acting drugs potentially useful in the protection of the heart against post-ischemic reperfusion injury. The pyrroline derivatives reported herein were found to be more potent as antiarrhythmic agents than mexiletine and displayed antioxidant activity. The most interesting tetramethylpyrroline congener, a tert-butyl-substituted analogue, was at least 100 times more active as an antiarrhythmic than mexiletine.