Performance characteristics of a compact position-sensitive LSO detector module

We assembled a compact detector module comprised of an array of small, individual crystals of lutetium oxyorthosilicate:Ce (LSO) coupled directly to a miniature, metal-can, position-sensitive photomultiplier tube (PSPMT). We exposed this module to sources of 511-keV annihilation radiation and beams of 30- and 140-keV photons and measured spatial linearity; spatial variations in module gain, energy resolution, and event positioning; coincidence timing; the accuracy and sensitivity of identifying the crystal-of-first-interaction at 511 keV; and the effects of intercrystal scatter and LSO background radioactivity. The results suggest that this scintillator/phototube combination should be highly effective in the coincidence mode and can be used, with some limitations, to image relatively low-energy single photon emitters. Photons that are completely absorbed on their first interaction at 511 keV are positioned by the module at the center of a crystal. Intercrystal scatter events, even those that lead to total absorption of the incident photon, are placed by the module in a regular "connect-the-dot" pattern that joins crystal centers. As a result, the accuracy of event positioning can be made to exceed 90%, though at significantly reduced sensitivity, by retaining only events that occur within small regions-of-interest around each crystal center and rejecting events that occur outside these regions in the connect-the-dot pattern.     

Effects of diets containing oils from repeated frying on magnesium absorption

Olive oil, sunflower oil and palm olein were used in repeated potato fryings until the oils reached the limit of 25% of polar compounds allowed by law. Six groups of rats, over 28 days, were fed diets containing 8% of: olive oil; olive oil from 69 fryings; sunflower oil; sunflower oil from 48 frying; palm olein, and palm olein from 80 fryings. Body weight and food intake were monitored weekly, during days 21–28 faeces and urine were collected and finally blood and carcasses were also collected and stored. No significant differences were observed in food intake and body weight among the six groups of animals. The type of oil did not modify magnesium intake, the urinary and faecal excretion of this mineral nor its apparent absorption or retention. The consumption of oils from frying, however, induced an increase in apparent magnesium absorption due to a decrease in faecal magnesium excretion, but magnesium retention did not vary owing to the increase in urinary losses. Serum magnesium and magnesium contents and concentrations in carcasses were unaffected. Therefore, it was concluded that the consumption of used frying oils enhances magnesium absorption, independently from the type of oil, although magnesium retention is not affected due to a an elevation of urinary excretion. © 1999 Society of Chemical Industry     

Sunflower oil versus olive oil and iron metabolism in rats. Influence of a frying process

Olive oil and sunflower oil were used in repeated potato‐frying operations without turnover until the oils reached the limit of 25% polar compounds allowed by law. Over a 28 day period, five groups of rats were fed diets containing 8% unused olive oil, olive oil used in 48 and 69 potato frying operations, unused sunflower oil and sunflower oil used to fry potatoes 48 times. In the final week, faeces and urine were collected and, on day 28, animals were sacrificed. The type of oil, unused or used in frying, did not modify food intake, body weight, faecal iron and its apparent absorption or retention, but consumption of oils used in frying tended to increase urinary iron excretion. No differences were found in serum iron, total iron‐binding capacity and haemoglobin values. Iron contents and concentrations in liver, spleen and skin did not vary between groups. Iron concentrations in erythrocytes were significantly higher in rats fed sunflower oil, either unused or used in frying. It was concluded that the consumption of sunflower oil compared to olive oil could affect intra‐ and extracellular haematic distribution of iron, probably associated with changes in membrane permeability, and that some alteration products of the oils originated during frying tend to increase urinary iron losses without repercussions on iron metabolism. © 2000 Society of Chemical Industry     

Conservative management of mesencephalic tuberculoma. Case report

A case of clinically unsuspected mesencephalic tuberculoma that was diagnosed at operation is presented. After intraoperative diagnosis, the surgical procedure was interrupted and specific treatment with tuberculostatic agents was started. The symptoms remitted totally in a few months. This conservative management is preferable to surgical removal when diagnosis of brain-stem tuberculoma has been established.     

Potential use of the undersampling technique in the acquisition of nuclear magnetic resonance signals

This communication reviews the use of undersampling techniques to acquire NMR signals. Undersampling transforms bandpass free induction decay (FID) signals, centered at high frequencies, into lowpass signals or bandpass signals centered at much lower frequencies. Consequently, the analog electronic stages that perform the demodulation can be eliminated, gaining in stability and reducing the phase distortion while maintaining an equivalent or better signal to noise ratio when an adequate sampling rate is chosen. The technique has been tested on a BRUKER BIOSPEC BMT 47 40, and the results show that undersampling could be used to process NMR and MRI signals, extending the range of applications of the ‘digital radio’ techniques to NMR and MRI apparatus.     

Qualitative differences between implicit and explicit sequence learning.

Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In contrast, a manipulation that maintained the task surface, but decreased the sequence validity, affected the expression of learning specifically when it was explicit. These results are discussed in the context of a dynamic framework (Cleeremans & Jime'nez, 2002), which assumes that implicit knowledge is specially affected by contextual factors and that, as knowledge becomes explicit, it allows for the development of relevant metaknowledge that modulates the expression of explicit knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)