The adsorption of gold on activated carbon from thiosulfate-ammoniacal solutions

The adsorption of gold on activated carbon in ammoniacal thiosulfate solution was studied. The variables affecting the adsorption of gold on the carbon included, among others, temperature, concentrations of ammonium hydroxide and thiosulfate, and those of accompanying cations and anions. The apparent activation energy for the adsorption process was estimated to be 19.4 kJ/mol, and this value indicates that the gold adsorption is film diffusion-controlled. It was also found that the rate of initial adsorption rate was fast, when compared to that of the overall adsorption process.     

Galactose inhibition of the constitutive transport of hexoses in Saccharomyces cerevisiae

The relationship between the pathways of glucose and galactose utilization in Saccharomyces cerevisiae has been studied. Galactose (which is transported and phosphorylated by inducible systems) is a strong inhibitor of the utilization of glucose, fructose and mannose (which have the same constitutive transport and phosphorylation systems). Conversely, all these three hexoses inhibit the utilization of galactose, though with poor efficiency. These cross-inhibitions only occur in yeast adapted to galactose or in galactose-constitutive mutants. The efficiency of galactose as inhibitor is even greater than the efficiencies of each of the other three hexoses to inhibit the utilization of each other. Phosphorylation is not involved in the inhibition and the transport of sugars is the affected step. The cross-inhibitions between galactose and either glucose, fructose or mannose do not implicate utilization of one hexose at the expense of the other, as it occurs in the mutual interactions between the latter three sugars. It seems that, by growing the yeast in galactose, a protein component is synthesized, or alternatively modified, that once bound to either galactose or any one of the other three hexoses (glucose, fructose or mannose), cross-interacts respectively with the constitutive or the inducible transport systems, impairing their function.     

Astigmatism in reflector antennas: measurement and correction

Investigates astigmatism is Cassegrain antennas from cross scans through in-and-out-of-focus diffraction images of extended radio sources. The use of extended sources is of interest for large (mm-wavelength) telescopes where the bright planets subtend a substantial fraction of the beam. The experimental and theoretical results presented refer to the IRAM 30-m telescope and measurements at 7.3 mm-1.3 mm wavelength; however, extrapolation to other telescopes is evident. The authors report on an experiment to correct the astigmatism (phase) at a position close to the focal plane of the telescope, i.e. the flat surface of the corotating Nasmyth mirror     

Fractionation of fungal pectic enzymes by immobilised metal ion affinity chromatography

A juice-clarifying fraction that will not produce methanol was obtained from a commercial pectic enzyme by separating the pectin lyase (EC4.2.2.10) from pectinesterase (EC3.1.1.11). This was achieved by immobilised metal ion affinity chromatography (IMAC) on Sepharose—iminodiacetic acid—Cu(II). Pectin lyase did not bind to the chromatographic matrix at pH 8.0, while pectinesterase was retained and only eluted when the pH of the buffer was brought down to 3.0. Polygalacturonase activity (EC3.2.1.15) was found in both fractions thus suggesting that IMAC can discriminate between two forms of that enzyme Both fractions have the ability to clarify apple juice, the first without producing methanol. The behaviour of each of the above enzymes in IMAC suggests that pectin lyase lacks accessible histidine residues, while pectinesterase could have one or more of them.     

Alternatives for Efficient and Sustainable Production of Surimi: A Review

ABSTRACT: The links between fish processing and negative environmental impact need to be minimized. The overexploitation of white fish stocks has compromised supply, the use of energy contributes to a high‐carbon footprint, and the water resources required are also high. An option is to resort to the use of alternative species and fisheries by‐catch, together with the maximum utilization of fish. In addition, edible proteins from a range of sources could be converted into added‐value products using surimi‐like processes. The surimi industry requires large amounts of freshwater and discharges wastewater with a high organic load. By exploring available options on processing technologies and management of the environmental impact, this review discusses the potential role of surimi and opportunities for sustainable fish processing.     

The effect of low temperatures on the intermediate and high velocity impact response of CFRPs

The influence of low temperature on the damage produced on CFRPs by intermediate and high velocity impacts is analyzed. Spherical projectiles were launched against different carbon fiber/epoxy laminates (tape and woven). Experimental tests were done at temperatures ranging from 25 to −150 °C. The extension of the damage was measured by C-Scan. Results show a clear dependence of damage on temperature, impact velocity and the type of the laminate.     

An RF electronically controlled impedance tuning network design and its application to an antenna input impedance automatic matching system

A novel design is proposed for an electronically tunable impedance unit. The prototypes include lumped elements, but no electromechanical control methods. The devices can tune many different complex impedances at minimum manufacture costs. Two antenna input impedance automatic matching systems are also presented, based on the tuning network. One includes a simplified version of the generic tuner, which can achieve good matching levels between the antenna and the power module with low losses. In a more complete version, an application specific integrated circuit control unit is developed including a complex search algorithm. In order to obtain a good matching level, both systems require a control module to select the proper tuner impedance configuration. The measurements and results of both constructed prototypes are presented. The designs were carried on terrestrial trunked radio mobile stations in the 380-400-MHz frequency band and supported high power levels (greater than 40 dBm).     

Cricoid calcification in the study of esophageal foreign bodies

Lateral radiography of the neck is performed for the study of radio-opaque esophageal foreign bodies that are not visualized by indirect laryngoscopy. This projection may reveal a calcified linear image behind the cricoid cartilage due to calcification of the posterior lamina. In such cases, esophagoscopy and/or computed tomography must be performed to determine whether the image is due to an anatomic variant or a true foreign body.     

NMDA receptor antagonists block stress-induced prolactin release in female rats at estrus

In order to evaluate the role of glutamate in prolactin secretion, we examined the effects of N-methyl-D,L-aspartic acid (NMDA) receptor antagonists on serum prolactin levels at both resting and restraint-stress conditions in female rats at estrus. NMDA increased basal serum prolactin levels. Administration of the selective NMDA receptor antagonist, cis-4-phosphonomethyl-2-piperidine carboxylic acid (CGS 19755) (5 and 10 mg/kg i.p.), to rats under resting conditions enhanced basal prolactin levels. A low dose of CGS 19755 (3 mg/kg) was unable to modify the hormone serum level. Under stress conditions the pretreatment with CGS 19755 (3 and 5 mg/kg) prevented the increase in serum prolactin levels. This effect was reversed by NMDA (60 mg/kg s.c.). The NMDA receptor antagonist (5 mg/kg) decreased the median eminence concentration of the dopamine metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), without modifying dopamine content. To examine the probable link between serotonin (5-HT) and glutamate in prolactin release, the 5-HT2A/5-HT2C receptor antagonist, ritanserin, was used. Under resting conditions, a dose of 5 mg/kg s.c. blocked the NMDA-induced prolactin release. In rats submitted to restraint, ritanserin decreased the prolactin response and NMDA was unable to correct the stress serum prolactin levels. The 5-HT1A receptor agonist, 8-hidroxypropyl-amino tetralin (8-OH-DPAT) (3 mg/kg s.c.), increased basal serum prolactin levels and restored serum prolactin in stressed animals pretreated with CGS 19755 (5 mg/kg). The present data strongly suggest that the glutamatergic system participates in the regulation of prolactin secretion. A stimulation tone seems to be exerted via the tuberoinfundibular dopaminergic system, and the prolactin release evoked by restraint apparently involves glutamate/NMDA receptors linked to a serotoninergic pathway.