Reduction of the specific surface area of porous ZnO during sintering

In this paper reduction of the specifice surface area of porous ZnO during sintering was analyzed. ZnO was sintered at temperatures from 673K to 1173K. Reduction of the specific surface area was observed as a function of the temperature and time of sintering. Analysis of sintering kintetics was done by observing reduction of the specific surface area. We used three different models, defined the appropriate parameters, and also the activation energy of sintering using the Arrhenius equation. The LSE metod was applied for determining optimum parameter values

Investigation of sintering kinetics of ZnO by observing reduction of the specific surface area

Reduction of the specific surface area of porous ZnO during the sintering process was studied. ZnO powder was sintered at temperatures from 673 K to 1173 K. The decrease in the specific surface area was observed as a function of temperature and sintering time. Two different models were involved in order to define the appropriate parameters. The Arrhenius equation was used to give information on the activation energy of sintering. The LSE method was applied for determining optimum parameter values

Probabilistic approach to buckling analysis of thin panels subject to combined loads

This paper gives the procedure for the reliability calculation of mechanical components and structures. The stability (buckling) of a tin panel subjected to in-plane combined (normal and shearing) loads is considered in particular. The attention is focused on the buckling analysis of the typical thin-walled aircraft structure such as the skin of wings or fuselage. In this analysis the variables are treated as stochastic: loads, thickness and width of the panel. The numerical example illustrates the procedure. The probability of buckling is calculated for the wing skin of a light trainer aircraft. The effect of the panel thickness (t) and the load factor (j) on the buckling probability is shown. The dimensional tolerance levels affect the critical stress calculation as well as the buckling probability. The variation of the parameters (especially the thickness effect on the buckling) is facilitated by a software program for reliability calculation

Mathematical modelling of thermal behaviour of cylindrical roller bearing for towed railway vehicles

U radu je prikazan matematički model za predviđanje toplinskog ponašanja valjnog ležaja s valjčićima za uležištenje vučenih željezničkih vozila. Matematički model omogućava izračunavanje generirane topline uslijed podmazivanja, radijalnog i aksijalnog opterećenja za različite brzine gibanja vlaka. U radu je također prikazan način izračunavanja koeficijenata provođenja i prevođenja topline u ležaju. Uporabom programskog sustava opće namjene na bazi metode konačnih elemenata analizirano je toplinsko ponašanje valjnog ležaja s valjčićima za vučena željeznička vozila. Metodom konačnih elemenata određene su vrijednosti temperature ležaja u ovisnosti o brzini gibanja vlaka (v = 20 km/h, v = 40 km/h, v = 60 km/h, v = 80 km/h i v = 100 km/h), polumjera zakrivljenosti zavoja (R = 500 m), ambijentalne temperature od 20 °C i visine nadvišenja pruge u krivini (h = 110 mm, h = 140 mm, h = 180 mm).This paper presents a mathematical model for the prediction of the thermal behaviour of a cylindrical roller bearing for axle assembly of the wheel set of the towed railway vehicles. The mathematical model allows for the heat generated due to lubrication, radial and axial loads at different speeds of the train to be calculated. The method of calculating of the heat conducting and converting coefficients in the bearing is also shown. By using the general purpose software system based on the finite elements method, the thermal behaviour of the above mentioned cylindrical roller bearings was analysed. Temperature values of the bearings are determined by the finite elements method values depending on the speed of the train movement on a straight-line section and the curve (v = 20 km/h, v = 40 km/h, v = 60 km/h, v = 80 km/h and v = 100 km/h), the curve radius (R = 500 m), the ambient temperature of 20 °C and the cant height (h = 110 mm, h = 140 mm, h = 180 mm)

Association of acute Babesia canis infection and serum lipid, lipoprotein, and apoprotein concentrations in dogs

Background Babesia canis infection induces a marked acute phase response (APR) that might be associated with alteration in lipid and lipoprotein metabolism and disease prognosis. Hypothesis Dogs with B. canis-induced APR develop dyslipidemia with altered lipoprotein concentration and morphology. Animals Twenty-nine client-owned dogs with acute B. canis infection and 10 clinically healthy control dogs. Methods Observational cross-sectional study. Serum amyloid A (SAA) was measured using ELISA. Cholesterol, phospholipids, and triglycerides were determined biochemically. Lipoproteins were separated using agarose gel electrophoresis. Lipoprotein diameter was assessed by polyacrylamide gradient gel electrophoresis; correlation with ApoA-1 (radioimmunoassay) and SAA was determined. Results Dogs with B. canis infection had a marked APR (median SAA, 168.3 mu g/mL; range, 98.1-716.2 mu g/mL) compared with controls (3.2 mu g/mL, 2.0-4.2 mu g/mL) (P < .001). Dogs with B. canis infection had significantly lower median cholesterol (4.79 mmol/L, 1.89-7.64 mmol/L versus 6.15 mmol/L, 4.2-7.4 mmol/L) (P = .02), phospholipid (4.64 mmol/L, 2.6-6.6 mmol/L versus 5.72 mmol/L, 4.68-7.0 mmol/L) (P = .02), and alpha-lipoproteins (77.5%, 27.7%-93.5% versus 89.2%, 75.1%-93.5%) (P = .04), and higher ApoA-1 (1.36 U, 0.8-2.56 U versus 0.95 U, 0.73-1.54 U) concentrations (P = .02). Serum amyloid A correlated with high-density lipoproteins (HDLs) diameter (rho = .43; P = .03) and ApoA-1 (rho = .63, P < .001). Conclusions and Clinical Importance Major changes associated with B. canis-induced APR in dogs are related to concentration, composition, and morphology of HDL particles pointing to an altered reverse cholesterol transport. Parallel ApoA-1 and SAA concentration increase is a unique still unexplained pathophysiological finding

Availability to repairable systems when repair and failure rates are not constant

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Influence of ZnO specific surface area on its sintering kinetics

The aim of this work is an investigation of isothermal sintering kinetics by observing the reduction of the specific surface area of ZnO. Zinc oxide powder is sintered isothermally in air for 5 to 120 min at temperatures from 400 to 900°C. The decrease in the specific surface area is observed as a function of temperature and sintering time. Models of Ristic-Jovanovic and German are applied in order to define the appropriate parameters. Information on the activation energy of sintering is obtained by the Arrhenius equation. The least square estimation (LSE) method was applied for determining optimum parameter values. © 2009 Springer Science+Business Media, Inc

The usefulness of advanced lipid and oxidative stress testing for diagnosis and management of low HDL-cholesterol phenotype: A case report

Objective: Plasma high-density lipoprotein cholesterol (HDL-C) level is a strong inverse predictor of cardiovascular disease (CVD) development. Tangier disease, a consequence of mutations in the ATP binding cassette transporter 1 (ABCA1) gene, is associated with very low HDL-C levels. Still, the relationship between Tangier disease and CVD is not always evident. The study investigates usefulness of lipoprotein subfractions, oxidative stress and paraoxonase 1 (PON1) status assessment for evaluation and management of patient with low HDL-C phenotype. Patient and methods: A 12-year-old boy was hospitalised due to hypertension. Laboratory evaluation revealed low HDL-C level, and subsequent molecular diagnostic confirmed Tangier disease. Lipoprotein subfractions were assessed by gradient-gel electrophoresis. Oxidative stress status was estimated by measuring total antioxidative status, total oxidative status, prooxidative-antioxidative balance, malondialdehyde and advanced oxidation protein products levels. Activity of paraoxonase 1 in serum and its distribution within HDL subclasses was also determined (ten healthy boys aged 13.1 +/- 3.4 years served as the reference group). Results: Analysis of oxidative stress status biomarkers revealed a state of prolonged prooxidants activity. In turn, serum PON1 activity was substantially reduced. The majority of PON1 activity was present on HDL 2 particles. Conclusion: Impaired antioxidative potential of HDL may point toward hidden cardiovascular risk in isolated low HDL-phenotype

In vitro antioxidant, antihyperglycemic, anti-inflammatory, and antimicrobial activity of Satureja kitaibelii Wierzb. ex Heuff. subcritical water extract

As the main goal of this study was the verification of Satureja kitaibelii Wierzb. ex Heuff. in form of the crude extract obtained by subcritical water extraction (SWE) technique in terms of polyphenolic composition, in vitro antioxidant capacity, antihyperglycemic, and anti-inflammatory activities as well as an antimicrobial effect against 10 microorganisms. HPLC analysis showed the presence of ten compounds in a total concentration of 89.33 mg/g of the SWE extract, and demonstrated that subcritical water polarity was the most selective for extracting syringic and caffeic acid, as well as epicatechin (37.88 18.06, and 10.04 mg/g, respectively), while flavonoids like rutin, luteolin, and apigenin were present in low concentration (<2 mg/g). Results of antioxidant activity assays revealed that superoxide anion and ABTS•+ radical models expressed the highest scavenging abilities (437.35 and 412.09 μmol TE/g, respectively), followed by lipid radicals (69.61 μmol TE/g), and DPPH• (32.28 μmol TE/g), while in the case of ferric ion reducing ability was noted a high value (118.19 μmol TE/g). S. kitaibelii SWE was less efficient in the antihyperglycemic assay (AhgA = 30.72 %), but the high antiinflammatory activity of S. kitaibelii SWE was observed (30.35 %). The antimicrobial activity was demonstrated against Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Listeria monocytogenes as well as Saccharomyces cerevisiae, Candida albicans, and Aspergillus brasiliensis through antimicrobial screening, minimal inhibitory concentration, and pharmacodynamics study