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  • Author or Editor: F. Martins x
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Abstract  

Breast muscles from three different birds were subjected to hydrostatic high-pressure (400 MPa)/temperature (10–75°C) combinations, and the denaturation-induced effects on the pressurized proteins monitored by DSC. Comparisons with parallel results from heating-alone processes were established. Actin was the most labile moiety to pressurization and myosin together with sarcoplasmic proteins were next in observing pressure-induced denaturation at low temperatures. Some myosin derivatives (fragments or aggregates) and collagen remained native-like under pressure at any temperature. As previously reported, pressure and temperature showed interdependent and antagonistic-like effects. Hydrostatic high-pressure caused severe proteins denaturation at non thermal denaturing temperatures. At thermally active conditions, pressure preserved proteins from subsequent thermal denaturation. This last effect was lower than in similar but destructured myosystems (batters) because of the absence of functional salts but presumably also by steric hindrance.

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Abstract  

The thermal stability of selected straight-chain (C6-C14) esters of fatty acids has been studied by TG-DTG and DTA analysis. In DTG, a peak is detected between 84° and 125° C followed by a main effect in the range 105°–215°C, whereas in DTA only an exothermic peak appears in the range of 126.5° to 187°C (onset temperatures). The temperatures of these effects have been related with ignition points, molecular weights and boiling points. The characteristics of melting and recrystallization of the above fatty acid methyl esters and those with carbon numbers between C14 and C24 have been established by DSC along the melting range between −83° and 50°C. Polymorphism appears in caproic, heptanoic, palmitic and stearic acid methyl esters.

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Abstract  

The use of a232U spike as a yield monitor of chemical and physical processes to prepare and measure natural uranium in environmental samples by alpha-spectrometry is discussed versus the use of other artificially made isotopes of uranium.

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Abstract  

Some remarks are given comparing two recently published methods of electrodeposition of uranium on stainless steel planchets to prepare sources for -spectrometry. Parameters used in the two procedures are discussed, and a general method of determining the best electrodeposition yield is proposed.

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Abstract  

A device consisting of poly allyl diglycol carbonate (PADC) foils with a polyethylene and polyvinyl chloride (PVC) radiator was calibrated in order to perform the dosimetry of an 241Am-Be source covering a dose range from 0 to 3.1 mSv. Working conditions were established for a good visualization and counting of tracks: chemical attack was made in two steps with different solutions and etching times. A good fit was obtained for the dose as a function of the number of tracks per unit surface area. The calculated decision threshold was 0.12 mSv.

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