Fast detection of the magnetic easy axis on steel sheet using the continuous rotational Barkhausen method

The magnetic behaviour of most commercial ferromagnetic steels is usually anisotropic presenting a magnetic easy axis. Changes in the direction of this axis can be related to mechanical changes and anomalies that occur in the fabrication process. The present work describes a method that uses a device with permanent magnets to create a precise rotational magnetic field. The device measures continuous Magnetic Barkhausen Noise signals related to the angle of magnetization, in order to determine the direction of the macroscopic magnetic easy axis. It also offers the possibility of obtaining real time parameters that quantify the magnetic anisotropy of the sample. (C) 2011 Elsevier Ltd. All rights reserved.

High Cholesterol Feeding May Induce Tubular Dysfunction Resulting in Hypomagnesemia

Background/Aims: Hypomagnesemia may induce hypercholesterolemia, but the contrary has not been described yet. Thus, magnesium homeostasis was evaluated in rats fed a cholesterol-enriched diet for 8 days. This study has a relevant clinical application if hypomagnesemia, due to hypercholesterolemia, is confirmed in patients with long-term hypercholesterolemia. Methods: Both hypercholesterolemic (HC) and normocholesterolemic rats (NC) were divided into sets of experiments to measure hemodynamic parameters, physiological data, maximum capacity to dilute urine (C-H2O), variations (Delta) in [Ca2+](i) and the expression of transporter proteins. Results: HC developed hypomagnesemia and showed high magnesuria in the absence of hemodynamic abnormalities. However, the urinary sodium excretion and C-H2O in HC was similar to NC. On the other hand, the responses to angiotensin II by measuring Delta [Ca2+](i) were higher in the thick ascending limb of Henle's loop (TAL) of HC than NC. Moreover, high expression of the cotransporter NKCC2 was found in renal outer medulla fractions of HC. Taken together, the hypothesis of impairment in TAL was excluded. Actually, the expression of the epithelial Mg2+ channel in renal cortical membrane fractions was reduced in HC. Conclusion: Impairment in distal convoluted tubule induced by hypercholesterolemia explains high magnesuria and hypomagnesemia observed in HC. Copyright (C) 2011 S. Karger AG, Basel

Predicting Delta Ferrite Content in Stainless Steel Castings

The distribution of delta ferrite fraction was measured with the magnetic method in specimens of different stainless steel compositions cast by the investment casting (lost wax) process. Ferrite fraction measurements published in the literature for stainless steel cast samples were added to the present work data, enabling an extensive analysis about practical methods to calculate delta ferrite fractions in stainless steel castings. Nineteen different versions of practical methods were formed using Schaeffler, DeLong, and Siewert diagrams and the nickel and chromium equivalent indexes suggested by several authors. These methods were evaluated by a detailed statistical analysis, showing that the Siewert diagram, including its equivalent indexes and iso-ferrite lines, gives the lowest relative errors between calculated and measured delta ferrite fractions. Although originally created for stainless steel welds, this diagram gives relative errors lower than those for the current ASTM standard method (800/A 800M-01), developed to predict ferrite fractions in stainless steel castings. Practical methods originated from a combination of different chromium/nickel equivalent indexes and the iso-ferrite lines from Schaeffler diagram give the lowest relative errors when compared with combinations using other iso-ferrite line diagrams. For the samples cast in the present work, an increase in cooling rate from 0.78 to 2.7 K/s caused a decrease in the delta ferrite fraction, but a statistical hypothesis test revealed that this effect is significant in only 50% of the samples that have ferrite in their microstructures.

Nanosized precipitates in H13 tool steel low temperature plasma nitriding

A comprehensive study of pulsed nitriding in AISI H13 tool steel at low temperature (400 degrees C) is reported for several durations. X-ray diffraction results reveal that a nitrogen enriched compound (epsilon-Fe2-3N, iron nitride) builds up on the surface within the first process hour despite the low process temperature. Beneath the surface, X-ray Wavelength Dispersive Spectroscopy (WDS) in a Scanning Electron Microscope (SEM) indicates relatively higher nitrogen concentrations (up to 12 at.%) within the diffusion layer while microscopic nitrides are not formed and existing carbides are not dissolved. Moreover, in the diffusion layer, nitrogen is found to be dispersed in the matrix and forming nanosized precipitates. The small coherent precipitates are observed by High-Resolution Transmission Electron Microscopy (HR-TEM) while the presence of nitrogen is confirmed by electron energy loss spectroscopy (EELS). Hardness tests show that the material hardness increases linearly with the nitrogen concentration, reaching up to 14.5 GPa in the surface while the Young Modulus remains essentially unaffected. Indeed, the original steel microstructure is well preserved even in the nitrogen diffusion layer. Nitrogen profiles show a case depth of about similar to 43 mu m after nine hours of nitriding process. These results indicate that pulsed plasma nitriding is highly efficient even at such low temperatures and that at this process temperature it is possible to form thick and hard nitrided layers with satisfactory mechanical properties. This process can be particularly interesting to enhance the surface hardness of tool steels without exposing the workpiece to high temperatures and altering its bulk microstructure. (c) 2012 Elsevier B.V. All rights reserved.

Kinetic and growth parameters of Arthrospira (Spirulina) platensis cultivated in tubular photobioreactor under different cell circulation systems

Arthrospira platensis was cultivated in tubular photobioreactor in order to evaluate growth and biomass production at variable photosynthetic photon flux density (PPFD?=?60, 120, and 240?mu mol photons m-2?s-1) and employing three different systems for cell circulation, specifically an airlift, a motor-driven pumping and a pressurized system. The influence of these two independents variables on the maximum cell concentration (Xm), cell productivity (Px), nitrogen-to-cell conversion factor (YX/N), photosynthetic efficiency (PE), and biomass composition (total lipids and proteins), taken as responses, was evaluated by analysis of variance. The statistical analysis revealed that the best combination of responses' mean values (Xm?=?4,055?mg?L-1, Px?=?406?mg?L-1?day-1, YX/N?=?5.07?mg?mg-1, total lipids?=?8.94%, total proteins?=?30.3%, PE?=?2.04%) was obtained at PPFD?=?120?mu mol photons m-2?s-1; therefore, this light intensity should be considered as the most well-suited for A. platensis cultivation in this photobioreactor configuration. The airlift system did not exert any significant positive statistical influence on the responses, which suggests that this traditional cell circulation system could successfully be substituted by the others tested in this work. Biotechnol. Bioeng. 2012; 109:444450. (c) 2011 Wiley Periodicals, Inc.

Modeling of continuous thermal processing of a non-Newtonian liquid food under diffusive laminar flow in a tubular system

The classic conservative approach for thermal process design can lead to over-processing, especially for laminar flow, when a significant distribution of temperature and of residence time occurs. In order to optimize quality retention, a more comprehensive model is required. A model comprising differential equations for mass and heat transfer is proposed for the simulation of the continuous thermal processing of a non-Newtonian food in a tubular system. The model takes into account the contribution from heating and cooling sections, the heat exchange with the ambient air and effective diffusion associated with non-ideal laminar flow. The study case of soursop juice processing was used to test the model. Various simulations were performed to evaluate the effect of the model assumptions. An expressive difference in the predicted lethality was observed between the classic approach and the proposed model. The main advantage of the model is its flexibility to represent different aspects with a small computational time, making it suitable for process evaluation and design. (C) 2012 Elsevier Ltd. All rights reserved.

Wear and corrosion resistance of pack chromised carbon steel

Pack chromising treatment is an environmentally friendly alternative to hard chromium to form wear and corrosion resistant surface layers. In this work, samples of AISI 1060 steel were pack chromised for 6 and 9 h at 1000 and 1050 degrees C using different activator concentrations. Wear tests were performed in dry conditions and corrosion tests in natural sea water for the pack chromised samples and hard chromium. Pack chromising yielded the formation of layers with high chromium concentrations, high hardness and wear resistance. Increasing activator concentration causes no significant change on the morphology and thickness of the layers. The layers produced at 1050 degrees C yielded only a (Cr,Fe)(2)N1-x phase, and those obtained at 1000 degrees C are composed of a carbide mixture with (Cr,Fe)(2)N1-x. The sample treated at 1050 degrees C for 9 h resulted in an optimum condition by means of better wear resistance and corrosion properties, which were close to that exhibited by the hard chrome, indicating that pack chromising is a promising alternative.

ANNEALING BEHAVIOR OF RAFM ODS-EUROFER STEEL

Oxide-dispersion-strengthened (ODS) ferritic-martensitic steels are candidates for applications in fusion power plants where micro structural long-term stability at temperatures of 650 degrees C to 700 degrees C are required. The microstructural stability of 80% cold-rolled reduced-activation ferritic-martensitic 9% Cr ODS-Eurofer steel was investigated within a wide range of temperatures (300 degrees C to 1350 degrees C). Fine oxide dispersion is very effective to prevent recrystallization in the ferritic phase field. The low recrystallized volume fraction (<0.1) found in samples annealed at 800 degrees C is associated with the nuclei found at prior grain boundaries and around coarse M23C6 particles. The combination of retarding effects such as Zener drag and concurrent recovery decrease the local stored energy and impede further growth of the recrystallization nuclei. Above 90 degrees C, martensitic transformation takes place with consequent coarsening. Significant changes in crystallographic texture are also reported.

Photosynthetic efficiency and rate of CO2 assimilation by Arthrospira (Spirulina) platensis continuously cultivated in a tubular photobioreactor

Similar to other photosynthetic microorganisms, the cyanobacterium Arthrospira platensis can be used to produce pigments, single cell proteins, fatty acids (which can be used for bioenergy), food and feed supplements, and biofixation of CO2. Cultivation in a specifically designed tubular photobioreactor is suitable for photosynthetic biomass production, because the cultivation area can be reduced by distributing the microbial cells vertically, thus avoiding loss of ammonia and CO2. The aim of this study was to investigate the influence of light intensity and dilution rate on the photosynthetic efficiency and CO2 assimilation efficiency of A. platensis cultured in a tubular photobioreactor in a continuous process. Urea was used as a nitrogen source and CO2 as carbon source and for pH control. Steady-state conditions were achieved in most of the runs, indicating that continuous cultivation of this cyanobacterium in a tubular photobioreactor could be an interesting alternative for the large-scale fixation of CO2 to mitigate the greenhouse effect while producing high protein content biomass.

Effect of Plastic Deformation on the Excess Loss of Electrical Steel

The interpretation of the effect of plastic deformation on the calculated excess loss component (anomalous-loss) supports the concept of loss separation. Magnetic losses and Barkhausen noise of nonoriented electrical steel sheets were measured on Epstein strips taken from a single coil of 0.8% Si nonoriented electrical steel. Sheets were extracted in the annealed condition, without any skin pass and with a grain size of 18 mu m. This material was cold rolled in order to obtain sets of samples with true strain from 2% up to 29%. X-ray diffraction was used to estimate the dislocation density. The analysis of magnetic properties was performed by Barkhausen noise measurements and also by analyzing the hysteresis loops obtained from Epstein frame measurements for different inductions and different frequencies (including the quasi-static regime for hysteresis loss measurements). These data allowed us to observe that most of the well known total loss increase with plastic deformation is due to an increase in the hysteresis loss component, while excess loss decreases to become negligible. This behavior can be explained if it is assumed that the plastic deformation lead to an increase in the number of domain walls per unit volume, thereby decreasing the excess loss. Barkhausen peak area increases with plastic deformation, reproducing results taken from samples of different silicon content.

Experimental study on vortex-induced motions of a semi-submersible platform with four square columns, Part I: Effects of current incidence angle and hull appendages

An experimental study on Vortex-Induced Motion (VIM) of the semi-submersible platform concept with four square columns is presented. Model tests were carried out to check the influence of different headings and hull appendages (riser supports located at the pontoons; fairleads and the mooring stretches located vertically at the external column faces; and hard pipes located vertically at the internal column faces). The results comprise in-line, transverse and yaw motions, as well as combined motions in the XY plane, drag and lift forces and spectral analysis. The main results showed that VIM in the transverse direction occurred in a range of reduced velocity 4.0 up to 14.0 with amplitude peaks around reduced velocities around 7.0 and 8.0. The largest transverse amplitudes obtained were around 40% of the column width for 30 degrees and 45 degrees incidences. Another important result observed was a considerable yaw motion oscillation, in which a synchronization region could be identified as a resonance phenomenon. The largest yaw motions were verified for the 0 degrees incidence and the maxima amplitudes around 4.5 degrees. The hull appendages located at columns had the greatest influence on the VIM response of the semi-submersible. (C) 2012 Elsevier Ltd. All rights reserved.

On the radial expansion of tubular structures in a quark-gluon plasma

We study the radial expansion of cylindrical tubes in a hot QGP. These tubes are treated as perturbations in the energy density of the system which is formed in heavy ion collisions at RHIC and LHC. We start from the equations of relativistic hydrodynamics in two spatial dimensions and cylindrical symmetry and perform an expansion of these equations in a small parameter, conserving the nonlinearity of the hydrodynamical formalism. We consider both ideal and viscous fluids and the latter are studied with a relativistic Navier-Stokes equation. We use the equation of state of the MIT bag model. In the case of ideal fluids we obtain a breaking wave equation for the energy density fluctuation, which is then solved numerically. We also show that, under certain assumptions, perturbations in a relativistic viscous fluid are governed by the Burgers equation. We estimate the typical expansion time of the tubes. (C) 2012 Elsevier B.V. All rights reserved.

Niobium Effects on the Recrystallization Behavior on a Full Austenitic 15Cr-15Ni Stainless Steel Investigated Using Adaptive Neural Networks (ANN)

A new series of austenitic stainless steels-Nb stabilized, without Mo additions, non-susceptible to delta ferrite formation and devoid of intemetallic phases (sigma and chi), without deformation induced martensite is being developed, aiming at high temperature applications as well as for corrosive environments. The base steel composition is a 15Cr-15Ni with normal additions of Nb of 0.5, 1.0 and 2 wt%. Mechanical properties, oxidation and corrosion resistance already have been invetigated in previous papers. In this paper, the effects of Nb on the SFE, strain hardening and recrystallization resistance are evaluated with the help of Adaptive Neural Networks (ANN).

CHEMICAL PROFILE COMPARISON OF SUGARCANE SPIRITS FROM THE SAME WINE DISTILLED IN ALEMBICS AND COLUMNS

CHEMICAL PROFILE COMPARISON OF SUGARCANE SPIRITS FROM THE SAME WINE DISTILLED IN ALEMBICS AND COLUMNS. Six wines were distilled in two different distillation apparatus (alembic and column) producing 24 distillates (6 for each alembic fraction - head, heart and tail; 6 column distillates). The chemical composition of distillates from the same wine was determined using chromatographic techniques. Analytical data were subjected to Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) allowing discrimination of four clusters according to chemical profiles. Both distillation processes influenced the sugarcane spirits chemical quality since two types of distillates with different quantitative chemical profiles were produced after the elimination of fermentation step influence.

Carvedilol protects against apoptotic cell death induced by cisplatin in renal tubular epithelial cells

Cisplatin is a highly effective chemotherapeutic drug; however, its use is limited by nephrotoxicity. Studies showed that the renal injury produced by cisplatin involves oxidative stress and cell death mediated by apoptosis and necrosis in proximal tubular cells. The use of antioxidants to decrease cisplatin-induced renal cell death was suggested as a potential therapeutic measure. In this study the possible protective effects of carvedilol, a beta blocker with antioxidant activity, was examined against cisplatin-induced apoptosis in HK-2 human kidney proximal tubular cells. The mitochondrial events involved in this protection were also investigated. Four groups were used: controls (C), cisplatin alone at 25 mu M (CIS), cisplatin 25 mu M plus carvedilol 50 mu M (CV + CIS), and carvedilol alone 50 mu M (CV). Cell viability, apoptosis, caspase-9, and caspase-3 were determined. Data demonstrated that carvedilol effectively increased cell viability and minimized caspase activation and apoptosis in HK-2 cells, indicating this may be a promising drug to reduce nephrotoxicity induced by cisplatin.