Characterisation of Micrococcaceae isolated from different varieties of chorizo

A total of 426 strains of Micrococcaceae bacteria isolated from chorizo (a traditional Spanish fermented sausage) were identified. The chorizos were sampled from three regions of Castilla and León in Spain: Burgos, Segovia and Salamanca. Two factories were chosen in each region and the samples were taken at three stages of ripening. Staphylococcus xylosus was the most predominant species isolated (95%). Twelve strain types of S. xylosus were established according to their fermentation patterns, and two of them, S. xylosus type 2 and S. xylosus type 5, made up the majority of the strains of S. xylosus isolated (27 and 52%). Production of acetoin, nitrate reductase, urease activity, proteolytic and lipolytic activity were determined for all isolates. The percentage of strains of S. xylosus producing acetoin depends on the manufacturing location. In general, the proteolytic and lipolytic activities of the S. xylosus isolated from chorizo from Castilla and León were low and moderate; 97% of the strains showed nitrate reductase and urease activity. According to our results and to previous investigations, it seems that S. xylosus type 5, showing nitrate reductase and urease activity, low-moderate proteolytic and lipolytic activities and not producing acetoin would be suitable as a starter culture. Of the strains isolated in this study, 38% comply with these requirements.     

Development of a valved linear compressor for a satellite borne J-T cryocooler

The provision of temperatures below 12 K is essential for sub-mm and FIR observations from satellite instruments. Historically this has been achieved with stored cryogens, however mechanical coolers could potentially provide higher reliability and flexibility. These cryocoolers typically incorporate a regenerative cold-finger, such as a pulse-tube, however this can be replaced by a recuperative Joule-Thompson stage to obtain the lowest temperatures required. The major change to the compressor is the requirement for steady flow. This paper describes the development of such a compressor using reed valves, based on space-qualified hardware. Long life potential was demonstrated by measuring the motion of the valves during operation. A model was also developed and validated to optimize performance.     

Very Low Voltage MOS Translinear Loops Based on Flipped Voltage Followers

A novel technique for operating MOS Translinear loops at very low supply voltages is described, based on the use of Flipped Voltage Followers for biasing the loops. The resulting topologies, suited to standard CMOS processes, can be successfully applied to a varied repertory of low-voltage analog circuits, such as squarers, multipliers, filters, oscillators, and RMS-DC converters. Measurement results for a geometric-mean and a squarer/divider circuit demonstrate on silicon the usefulness of this technique.     

Chemical pathways for the polymerization of enines

AM1 calculations are reported for enines with aromatic substituents. It was found that the position of the unsaturated bonds in each molecule may account for the reactivity of each isomer via different polymerization pathways. The resonant structure of the charged form of one of the molecules allowed speculation about the observed inhibition of the polymerization reaction.     

Dynamics of the modern Venezuelan research community profile

Summary The main characteristics, human resources, organizational development, R&D output and outcome of the Venezuelan scientific and technological community, are studied in depth for three specific dates - years 1954, 1983 and 1999 -, aiming to reveal its strengths and weaknesses and to establish its dynamics. During the first half of the twentieth century, Venezuela had no major organized or institutionalized scientific activity. From 1954 thru 1983, the State built a considerable number of institutions mostly for research and development activities. Initially, researchers came from classical professions but were later substituted by graduates in scientific and technological disciplines. Biomedical and basic sciences are the areas of knowledge favored by researchers while, in terms of intellectual creation, social sciences and humanities seem to be the less productive, despite being one of the fields of knowledge embraced by most professionals. Although from 1983 on there has been no major input to the national S&T system, the research community showed a few years of growth in absolute terms in the number of publications, however national productivity decreased during the last decade of the century. It is believed that this reflects an aging, asphyxiated and self-consuming community using its reserves at a maximum rate. The S&T system constructed exhibits a dominance of the public sector that privileged, financially, the hydrocarbon related technological/service industry at the expense of academic research in universities while maintaining agribusiness related service and developmental research at the same level of expenditure throughout the last twenty years of the twentieth century. While the generation - practically from zero - of a modern R&D community in Venezuela, together with higher education, could well be one of the most significant accomplishments of democracy in Venezuela, this remarkable social achievement has been put in peril by neglect and changes in public policies. Downturn of the national S&T system is bound to worsen due to a virtual collapse, on February 4, 2002, of the R&D centre of the nationalized oil industry.     

Maize processing waste water arabinoxylans: Gelling capability and cross-linking content

Water-soluble feruloylated arabinoxylans were extracted from maize processing waste water (nejayote) generated from tortilla-making industries. Nejayote arabinoxylans (NAX) presented a ferulic acid content of 0.23 μg/mg, an arabinose to xylose ratio (A/X) of 0.65, an intrinsic viscosity, [η], of 183 ml/g and a molecular weight (Mw) of 60 kDa. Laccase-induced gels were obtained from 4% (w/v) NAX solution while, at lower concentrations, no gelation was observed. Laccase covalent cross-linking of NAX led to the formation of diferulic (di-FA) and triferulic (tri-FA) acid structures. 4% (w/v) NAX gel presented di-FA and tri-FA contents of 0.02 and 0.01 μg/mg NAX, respectively, and a G′ value of 2 Pa. Recuperation of this gum from a low-value maize by-product could represent a commercial advantage over other gums commonly used in the food industry.     

Laser induced photoacoustic grating effects in molecular crystals

A transient grating of singlet electronic excited states is produced in a pentacene-doped p-terphenyl molecular crystal by optical absorption from two crossed time-coincident picosecond excitation pulses at 532 nm. The diffraction properties of this volume grating are probed by a weak, variably delayed, Bragg-matched picosecond probe pulse. At high excitation intensities, a strong oscillatory behavior in the time-dependent scattering efficiency is observed superimposed on the exponential decay pattern of the excited-state grating. We attribute the oscillatory behavior to a thermal grating which induces coherent microwave acoustic phonons. These in turn modulate, at the sound frequency, the optical absorption properties of the pentacene molecules in the excited state. An acoustically induced amplitude grating effect is thus obtained, in contrast to conventional acousto-optic phase grating effects.     

General intracavity method for laser transition characterization byrelaxation oscillations spectral analysis

Monitoring the transient buildup of laser emission is proposed as a simple method for spectro-temporal intracavity diagnostics of laser transitions and materials. Using this method, we determined the absolute magnitude of both laser emission and absorption cross sections for a line-narrowed tunable Er³⁺-fiber laser     

Echocaediographic determination of the etiology of severe mitral regurgitation

The effects of 3 lipidosis-inducing drugs on the incorporation and turnover of palmitic acid-1-14C in lung phospholipids was studied. In rats treated with 1 dose of chlorphentermine or RMI 10.393, the incorporation of palmitate-1-14C into most lung phospholipid fractions was moderately decreased, but markedly lowered after 1 dose of Ro 4-4318. Eight doses of chlorphentermine and RMI 10.393 strongly inhibited the incorporation of palmitate-1-14C into lung phospholipids, whereas with 8 doses of Ro 4-4318 the incorporation was highly increased. Thirty hours after the last of 3 injections of the labeled palmitic acid the turnover of most lung phospholipids was considerably lower in chlorphentermine- and RMI 10.393-treated rats than in controls. Ro 4-4318, however, induced a highly increased turnover of most phospholipids. After 54 h, this effect had practically disappeared. Our studies showed that phospholipid storage after treatment with chlorphentermine and RMI 10.393 is mainly due to decreased degradation of phospholipids, whereas increased synthesis accounts for the effect of Ro 4-4318.