Biomedical subjects

A Trucco

Publications and source records attributed to A Trucco.

4 recordsLinked to original sources

PubMed2004

A stochastic approach for the apodization of very short arrays.

The problem addressed in this paper is the synthesis of the weight coefficients to be assigned to the elements of a linear array that has a spatial aperture shorter than one wavelength. The aim is to obtain a data-independent beam pattern that fulfills some a priori fixed constraints. The analytical approach, expressed in terms of a linear least-squares problem, has been attempted, resulting in very large noise sensitivity and beam pattern instability. To overcome this problem a mixed methodology, based on a combination of a stochastic technique and a local descent method that provides very robust weight coefficients with reduced noise sensitivity, is proposed. Here, robust means that, even if unavoidable fluctuations occur in the transducer gains, the beam pattern obtained maintains the desired features.

Journal Article↗

PubMed2001

Small cargo proteins and large aggregates can traverse the Golgi by a common mechanism without leaving the lumen of cisternae.

Procollagen (PC)-I aggregates transit through the Golgi complex without leaving the lumen of Golgi cisternae. Based on this evidence, we have proposed that PC-I is transported across the Golgi stacks by the cisternal maturation process. However, most secretory cargoes are small, freely diffusing proteins, thus raising the issue whether they move by a transport mechanism different than that used by PC-I. To address this question we have developed procedures to compare the transport of a small protein, the G protein of the vesicular stomatitis virus (VSVG), with that of the much larger PC-I aggregates in the same cell. Transport was followed using a combination of video and EM, providing high resolution in time and space. Our results reveal that PC-I aggregates and VSVG move synchronously through the Golgi at indistinguishable rapid rates. Additionally, not only PC-I aggregates (as confirmed by ultrarapid cryofixation), but also VSVG, can traverse the stack without leaving the cisternal lumen and without entering Golgi vesicles in functionally relevant amounts. Our findings indicate that a common mechanism independent of anterograde dissociative carriers is responsible for the traffic of small and large secretory cargo across the Golgi stack.

Animals↗

PubMed2001

Determination of virus abundance in marine sediments.

In this study, we optimized procedures to enumerate viruses from marine sediments by epifluorescence microscopy using SYBR Green I as a stain. The highest virus yields from the bulk of the sediments were obtained by utilizing pyrophosphate and 3 min of sonication. The efficiency of extraction benthic viruses by pyrophosphate-ultrasound treatment was about 60% of the extractable virus particles. Samples treated with nucleases had increased virus counts, suggesting a masking effect of extracellular DNA. No significant differences were observed between virus counts obtained by epifluorescence microscopy and transmission electron microscopy. Both formaldehyde and glutaraldehyde gave significant reductions of virus counts after only 24 h of sediment storage, but no further loss occurred after 7 days.

Benzothiazoles↗

PubMed2000

Aperture and element minimization in linear sparse arrays with desired beam patterns

In this paper, an optimization method aimed at designing aperiodic linear sparse arrays is proposed that is based on the stochastic optimization methodology called simulated annealing. Such a method optimizes the positions and the weight coefficients of each element of a linear array in order to obtain a beam pattern that meets given requirements. Moreover, while positions and weights are optimized, minimization of both the number of elements and the spatial aperture is carried out. In this way, a beam pattern without grating lobes and close to the desired one is produced using a small number of elements and a short aperture. The results obtained are impressive in terms of improvement of array characteristics and performance over those reported in the literature, while a great flexibility in defining the desired beam pattern is allowed. Finally, it is proved that the array configurations need a number of elements very close to the absolute minimum to achieve the desired beam pattern.

Journal Article↗