Effects of initial microstructure on the earring of aluminium alloys cartridge case

Defects obtained during impact extrusion of EN AW-5754 aluminium alloy during cartridge case production were investigated. In cartridge cases produced from the one metallurgical heat pronounced tendency to earing after impact extrusion observed/appeared. On the other hand the earing in cartridge cases from the other heat was not observed. Presence of earing is due to local difference in materials flow during extrusion. This behaviour is atriduted to dfference in second phase particle distribution in used preforms (slugs)

The Association of CHA2DS2-VASc Score and Blood Biomarkers with Ischemic Stroke Outcomes: The Belgrade Stroke Study

-VASc score with unfavourable functional outcome (defined as a 30-day modified Rankin Scale [mRS] ≥3) in patients presenting with acute ischemic stroke (AIS), and examined whether the addition of blood biomarkers (troponin I [TnI], fibrinogen, C-reactive protein [CRP]) affects the model discriminatory ability.We conducted an observational single-centre study of consecutive patients with AIS. All patients were admitted to hospital within 24 hours from the neurological symptoms onset.-VASc and TnI or TnI, fibrinogen and CRP (z statistic 0.369, p = 0.7119; integrated discrimination index 0.00801 and 0.00172, respectively, both p>0.05).-VASc score did not significantly increase the predictive ability of the model

Prevalence of the metabolic syndrome in patients with carotid disease according to NHLBI/AHA and IDF criteria: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Metabolic syndrome (MetS) has been related to type 2 diabetes and cardiovascular diseases. Different criteria for diagnosis of MetS have been recommended, but there is no agreement about which criteria are best to use. The aim of the present study was to investigate agreement between the National Heart, Lung, and Blood Institute, American Heart Association (NHLBI/AHA) and the International Diabetes Federation (IDF) definitions of MetS in patients with symptomatic carotid disease and to compare the frequency of cardiovascular risk factor in patients with MetS diagnosed by these two sets of criteria.</p> <p>Methods</p> <p>The study was a cross-sectional one involving 644 consecutive patients with verified carotid disease who referred to the Vascular Surgery Clinic Dedinje in Belgrade during the period April 2006 - November 2007. Anthropometric parameters blood pressure, fasting plasma glucose and lipoproteins were measured using standard procedures.</p> <p>Results</p> <p>MetS was present in 67.9% of participants, according to IDF criteria, and in 64.9% of participants, according to the NHLBI/AHA criteria. A total of 119 patients were categorized differently by the two definitions. Out of all participants 10.7% had MetS by IDF criteria only and 7.8% of patients had MetS by NHLBI/AHA criteria only. The overall agreement of IDF and NHLBI/AHA criteria was 81.5% (Kappa 0.59, <it>p </it>< 0.001). In comparison with patients who met only IDF criteria, patients who met only NHLBI/AHA criteria had significantly more frequently cardiovascular risk factors with the exception of obesity which was significantly more frequent in patients with MetS diagnosed by IDF criteria.</p> <p>Conclusion</p> <p>The MetS prevalence in patients with symptomatic carotid disease was high regardless of criteria used for its diagnosis. Since some patients with known cardiovascular risk factors were lost by the use of IDF criteria it seems that NHLBI/AHA definition is more suitable for diagnosis of MetS. Large follow-up studies are needed to test prognostic value of these definitions.</p

Some problems connected with boron determination by atomic absorption spectroscopy and the sensitivity improvement

Two atomizers were compared: an N2O-C2H2 flame and a stabilized U-shaped DC arc with aerosol supply. Both the high plasma temperature and the reducing atmosphere obtained by acetylene addition to the argon stream substantially increase the sensitivity of boron determination by atomic absorption spectroscopy (AAS) when the arc atomizer is used. The results were compared with those for silicon as a control element. The experimental characteristic concentrations for both elements were compared with the computed values. The experimentally obtained characteristic concentration for boron when using the arc atomizer was in better agreement with the calculated value. It was estimated that the influence of stable monoxide formation on the sensitivity for both elements was about the same, but reduction of analyte and formation of non-volatile carbide particles was more important for boron, which is the main reason for the low sensitivity of boron determination using a flame atomizer. The use of an arc atomizer suppresses this interference and significantly improves the sensitivity of the determination

Temporal responses of spectral line intensities emitted by d.c. arc plasma with aerosol supply studied by power interruption technique

The responses to the fast interruption of the arc current have been studied for the spectral line intensities of several elements emitted by U-shaped direct current (d.c.) arc plasma with aerosol supply. The arc was burned at atmospheric pressure. Solutions containing the investigated elements were introduced with a concentric glass nebulizer into the argon stream of 2.7 1 min(-1). The arc current of 6 A was interrupted in periods that lasted up to 200 mus. At the moment of power interruption, the spectral line intensities are either suddenly increased indicating Saha balance or suddenly decreased indicating Boltzmann balance. Plots of intensity vs. time are used to evaluate the mechanisms that maintain the populations of excited states in the stationary state and processes occurring in the plasma during the power-off period. Excited levels of the elements with high ionization energies, like Ar, H and O, are predominantly populated by three-body recombination process i.e. they are controlled by the Saha balance. Excited levels of elements with medium ionization energies are predominantly populated by collisions with electrons i.e. controlled by the Boltzmann balance. Some of the spectral lines of C, P and Hg with high-excited levels missed the sudden intensity change, a cooling jump, which could be interpreted by the presence of two opposite mechanisms, Saha and Boltzmann balances, that cancel out the effect. Spectral line responses of easily ionized elements were found to depend on the plasma region. In a 2-mm axis region, the intensities do not show a cooling jump, but increase slowly during the power-off period. At medium distances from the arc axis, the spectral lines show typical Boltzmann type response. Farther to the arc periphery, where the electron concentration is very low but emission is still high, the power interruption does not influence the intensities and this indicates that the excitation is not prevailed by electron collisions. (C) 2002 Elsevier Science B.V All rights reserved

Thermochromic complex compounds in phase change materials: Possible application in an agricultural greenhouse

The possibility to combine two physico-chemical phenomena is studied in this work in order to attain simultaneous control of temperature and light intensity in a greenhouse: (a) isothermal heat storage in phase change materials and (b) thermochromic behavior of complex compounds dissolved in the phase change materials. Two binary mixtures melting near the ambient temperature were studied: (a) 0.925 Ca(NO3)(2) . 4.06 H2O + 0.075 CaCl2 . 6.11 H2O melting at 35.6 degrees C and (b) 0.9 CH3CONH2 + 0.1 Ca(NO3)(2) . 4 H2O, melting at 27.7 degrees C. The melting temperature, the enthalpy of fusion and the heat capacity of both mixtures were determined from DSC measurements. Both mixtures showed to be suitable solvents for the formation of consecutive cobalt(II) chloride complexes. The compositions of the complex compounds were adjusted in each mixture so that the absorption spectra in visible spectral range exhibited low absorbance at the melting temperature and a pronounced increase of the absorbance and/or change of color with the increase of temperature in the range relevant for passive solar energy receivers. The combined latent heat storage and the outstanding reversible change of the optical properties of the dissolved complex compounds with temperature is proposed to be applied in solar heated agricultural greenhouses in areas with fluctuating climate conditions. The increase of absorbance with temperature acts as an auto-regulated shading protection from overheating. (C) 1998 Elsevier Science B.V. All rights reserved

Multichannel optical emission spectrometers developed and manufactured by the Vinca Institute

An experimental series of four multichannel optical emission spectrometers developed and manufactured by the Vinca Institute has been described. The spectrometers, designed to satisfy users requirements, are intended for monitoring composition of aluminum alloys, carbon- and high-alloyed steels, raw materials and final products in glass industry. All spectrometers offer simultaneous determination for large numbers of elements and very rapid analysis time. The spectrometers components are mainly made by domestic manufacturers: imported components (diffraction gratings, photomultipliers, electronic components) amounted to less then 20% of total price.Conference on Applied Physics in Serbia, May 27-29, 2002, Belgrade, Yugoslavi