Ammonia exchange on clinoptilolite from mineral deposits located in Mexico

This work investigated the ion exchange of ammonia on clinoptilolite obtained from mineral deposits located in San Luis Potosi and Sonora, Mexico. Experimental ion exchange isotherm data were obtained in a batch adsorber. The effects of temperature and solution pH on the ion exchange capacity were studied and it was found that the exchange capacity was slightly increased by augmenting the temperature and by decreasing the pH from 6 to 3. The ion exchange capacity was independent of the diameter of the zeolite particles. The reversibility of ion exchange was analyzed by desorbing the ammonia exchanged on the zeolite. The ion exchange was reversible when 1% NaCl solution was used as the desorbing solution, but more ammonia was desorbed using 1% KCl solution in the desorption step. It was concluded that a considerable amount of ammonia was exchanged on the clinoptilolite and that the exchange capacity was slightly dependent on the temperature and pH. Copyright © 2004 Society of Chemical Industry     

Ab initio determination of the crystal structure of cytochrome c6 and comparison with plastocyanin

BACKGROUND: Electron transfer between cytochrome f and photosystem I (PSI) can be accomplished by the heme-containing protein cytochrome c6 or by the copper-containing protein plastocyanin. Higher plants use plastocyanin as the only electron donor to PSI, whereas most green algae and cyanobacteria can use either, with similar kinetics, depending on the copper concentration in the culture medium. RESULTS: We report here the determination of the structure of cytochrome c6 from the green alga Monoraphidium braunii. Synchrotron X-ray data with an effective resolution of 1.2 A and the presence of one iron and three sulfur atoms enabled, possibly for the first time, the determination of an unknown protein structure by ab initio methods. Anisotropic refinement was accompanied by a decrease in the 'free' R value of over 7% the anisotropic motion is concentrated at the termini and between residues 38 and 53. The heme geometry is in very good agreement with a new set of heme distances derived from the structures of small molecules. This is probably the most precise structure of a heme protein to date. CONCLUSIONS: On the basis of this cytochrome c6 structure, we have calculated potential electron transfer pathways and made comparisons with similar analyses for plastocyanin. Electron transfer between the copper redox center of plastocyanin to PSI and from cytochrome f is believed to involve two sites on the protein. In contrast, cytochrome c6 may well use just one electron transfer site, close to the heme unit, in its corresponding reactions with the same two redox partners.     

Perceptions of nuclear and other risks in Japan and the United States

As part of a study of nuclear power development in Japan and the United States, surveys of perceptions of risk toward 30 activities, substances, and technologies have been carried out in the Pacific Northwest and Tokyo, Japan. The results show that people in both countries have the highest level of dread toward nuclear waste disposal, nuclear accidents, and nuclear war, greater even than their dread of crime and AIDS. In addition to comparisons of dread, the paper also discusses similarities and differences between Japanese and American responses for other dimensions of risk perception.     

Gray-scale image enhancement as an automatic process driven by evolution.

Image enhancement is the task of applying certain transformations to an input image such as to obtain a visually more pleasant, more detailed, or less noisy output image. The transformation usually requires interpretation and feedback from a human evaluator of the output result image. Therefore, image enhancement is considered a difficult task when attempting to automate the analysis process and eliminate the human intervention. This paper introduces a new automatic image enhancement technique driven by an evolutionary optimization process. We propose a novel objective criterion for enhancement, and attempt finding the best image according to the respective criterion. Due to the high complexity of the enhancement criterion proposed, we employ an evolutionary algorithm (EA) as a global search strategy for the best enhancement. We compared our method with other automatic enhancement techniques, like contrast stretching and histogram equalization. Results obtained, both in terms of subjective and objective evaluation, show the superiority of our method.     

Enhanced release from proactive interference in nonamnesic alcoholic individuals: Implications for impaired associative binding.

Proactive interference (PI) occurs when previously learned information reduces the ability to acquire new, related information. Given that PI is modulated by the cholinergic system in rats (E. De Rosa & M. E. Hasselmo, 2000) and that chronic alcohol dependence disrupts cholinergic function in rats and humans, associative properties of PI in patients with alcoholism were examined. It was hypothesized that normal PI contingencies would be disrupted in alcoholic participants. When tested with a paired-associate simultaneous discrimination paradigm, analogous to that used in the rat model, alcoholic participants showed significantly less PI than controls yet performed comparably on a control response reversal task. The absence of PI in alcoholic participants may reflect impaired configural binding of paired-associate stimuli while sparing the elemental ability to process each stimulus component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Solution properties of polyelectrolytes. II. Comparison of the effects of both polyion and eluent salt concentrations on the calibrations in aqueous exclusion chromatography

The elution behaviour of charged water-soluble polymers (sodium polystyrene sulphonate) in both salt-free and NaCl-containing aqueous mobile phases has been investigated by size-exclusion chromatography. A comparative analysis has been established between the results as a function of polyion and salt concentrations, which demonstrates that the chromatographic behaviour is similar in both cases. The variation of the slopes of the different concentration-dependent calibration curves is discussed in terms of polyelectrolyte conformational changes. Finally, a semi-empirical model has been developed to predict the dependence of the elution volume in either polyion or salt concentration, and its validity has been checked in a range from very dilute to moderate concentrations.     

EBOFERA: A companion for FERA ADCs

A data transfer problem using FERA modules was found in a heavy ion nuclear physics experiment. The source of the problem was spotted in the handling of some signals on the FERA control bus. A modification of this handling is proposed and performed by means of a new CAMAC-FERA control module, the EBOFERA. Furthermore, this module has a number of useful features like the master gate and clear signals handling, event tagging, pattern unit and event counter.     

Heterogeneity among neuroepithelial cells in the chick retina revealed by immunostaining with monoclonal antibody PM1

Endothelin (ET) 1 is a powerful vasoconstrictor of coronary arteries and may play a role in coronary spasm, atherosclerosis, and myocardial infarction. Previous studies have demonstrated that intracoronary ET caused marked vasoconstriction of the coronary circulation; however, it remains unclear which ET receptor types are present and which of these receptors mediate this vasoconstriction. To characterize the ET receptors present in dog coronary arteries, competition binding assays with radiolabeled ET-1 using ET-1, ET-3, ETA receptor antagonist BQ-123, and sarafotoxin S6c were performed. Three binding sites were apparent in the left circumflex coronary artery: an ETA receptor, a high-affinity ETB receptor, and a lower-affinity ETB receptor. To investigate the in vivo effects of ETB receptor stimulation, intracoronary sarafotoxin S6c, a highly selective ETB agonist, was administered in anesthetized open-chest dogs in a constant-pressure coronary artery perfusion model. Sarafotoxin S6c doses of 0.1 and 0.3 microgram caused a transient pronounced decrease in coronary resistance. Doses of 1.0 and 3.0 micrograms caused marked decreases in coronary diameter and blood flow, as well as myocardial segmental shortening. These effects of sarafotoxin S6c were not inhibited by constant infusion of BQ-123. The present study demonstrates the presence of ETB receptors in the canine coronary circulation that can mediate both vasodilation and vasoconstriction. These findings have important implications for an understanding of the pathophysiological function of ET in the coronary vasculature and for the development of therapeutically effective ET antagonists.