Iskanje po repozitoriju

A+ | A- | | SLO | ENG

Povzetek: Stainless steel forms a native film of mixed metal oxides, and organic impurities are likely to adsorb on the surface upon exposure to ambient conditions. For many applications, oxides and impurities should be removed, and several techniques have been used for decades. An innovative method is presented in this paper. The organic impurities were oxidized using a water solution of 1 M peroxynitric acid (PNA). Stainless steel samples were immersed in the solution, and the oxidation of organic impurities was evaluated by the ultra-thin depth profiling using secondary ion mass spectrometry (SIMS). A minute of treatment with PNA caused oxidation of organic impurities and a decrease in the SIMS CN– signal over an order of magnitude. Prolonged treatment caused the selective removal of the native iron oxide film, leaving a protective film of chromium oxide. Removal of the iron oxide film was also observed when stainless steel was treated with 1 M HNO3. The PNA method is useful for routine cleaning of stainless steel to remove the organic contaminants from the surface and keep the passive chromium oxide film intact. It is ecologically friendly and enables rapid decomposition of the traces of organic impurities likely to be adsorbed on the metallic surfaces.
Ključne besede: peroxynitric acid, surface modifications, secondary ion mass spectrometry
Objavljeno v DiRROS: 11.11.2025; Ogledov: 175; Prenosov: 88
Celotno besedilo (1,14 MB)
Gradivo ima več datotek! Več...

Objavljeno v DiRROS: 11.11.2025; Ogledov: 136; Prenosov: 101
Celotno besedilo (973,28 KB)
Gradivo ima več datotek! Več...

Povzetek: Spatial encoding in MRI is usually performed using gradient coils that produce a linearly increasing magnetic field Bz in a desired spatial direction such that its gradient is constant. However, it has been shown that spatial encoding in MRI can also be performed with coils that produce nonlinear magnetic fields. In this study, the performance of different types of nonlinear encoding coils, which have a simple design based on the use of a straight wire segment as a building block and a source of a highly nonlinear magnetic field, was experimentally tested in 2D and by simulation in 3D on coils with a nonsymmetric and a symmetric arrangement of these wire segments. All images were reconstructed using our newly presented method, in which the signals are first transformed from the time- to the frequency-domain, yielding a distorted image (spectrum), which is then geometrically and intensity corrected. The quality of the reconstructed images was quantified by comparing them with corresponding reference images obtained with conventional gradient coils. The reconstruction method was accurate for all tested encoding coils and showed that the symmetric coil type produced results that required significantly less corrections compared to the nonsymmetric coil type. Quantitative image quality measurements showed that all encoding coils, despite large differences in the magnetic field of the encoding coils, produce images of similar quality. The results of the study may help advance the design of “gradient” coils towards freer geometries, higher magnetic field gradients or lower inductance and thus faster switching times.
Ključne besede: spatial signal encoding, gradient coils, k-space, nonlinear coils, image reconstruction
Objavljeno v DiRROS: 11.11.2025; Ogledov: 199; Prenosov: 88
Celotno besedilo (4,92 MB)
Gradivo ima več datotek! Več...

Ključne besede: dietary survey, dietary intake, energy, macronutrients, 24-h recall, FPQ, adults, elderly, Slovenia
Objavljeno v DiRROS: 11.11.2025; Ogledov: 204; Prenosov: 86
Celotno besedilo (346,94 KB)
Gradivo ima več datotek! Več...

Povzetek: Vitamin B12 deficiency poses a health concern, especially in vulnerable populations. Dietary vitamin B12 intake was obtained by two 24 h dietary recalls and food propensity questionnaires in a representative Slovenian cross-sectional food consumption survey, SI.Menu (n = 1248 subjects; 10–74 years). For a subgroup of 280 participants, data on serum vitamin B12 were available through the Nutrihealth study. The estimated usual population-weighted mean daily vitamin B12 intakes were 6.2 µg (adults), 5.4 µg (adolescents), and 5.0 µg (elderly). Lower intakes were observed in females. Inadequate daily vitamin B12 intake (<4 µg) was detected in 37.3% of adolescents, 31.7% of adults, and 58.3% elderlies. The significant predictors for inadequate daily vitamin B12 intake were physical activity score in all age groups, sex in adolescents and adults, financial status and smoking in elderly, and employment in adults. Meat (products), followed by milk (products), made the highest vitamin B12 contribution in all age groups. In adolescents, another important vitamin B12 contributor was cereals. The mean population-weighted serum vitamin B12 levels were 322.1 pmol/L (adults) and 287.3 pmol/L (elderly). Low serum vitamin B12 concentration (<148 nmol/L) and high serum homocysteine (>15 µmol/L) were used as criteria for vitamin B12 deficiency. The highest deficiency prevalence was found in elderlies (7.0%), particularly in males (7.9%). Factors associated with high serum homocysteine were also investigated. In conclusion, although vitamin B12 status was generally not critical, additional attention should be focused particularly to the elderly.
Ključne besede: vitamin B12, deficiency, homocysteine, folate, EU menu
Objavljeno v DiRROS: 11.11.2025; Ogledov: 132; Prenosov: 87
Celotno besedilo (1,86 MB)
Gradivo ima več datotek! Več...