Production and heat treatment of cast graphitic steels with additions of niobium

The optimal combination of the mechanical characteristics of austempered spheroidal graphitic cast steel together with modern casting techniques yielded an economically promising product. The maximum potential of the usage of these steels is related to fabrication and characterization techniques, among which, one of the most important is the cooling diagram (TTT curve). In this work, 3 heats of graphitic steels with the following nominal compositions were cast: 1.0 % C, 2.3 % Si, 0.4 % Mn, and with niobium contents of. 0.0 %, 0.5 % and 1.0 %. TTT curves were determined by dilatometric testing and test specimens of these steels were austempered. The samples were then characterized by hardness testing and optical and SEM microscopy. Tensile, impact (no notch) and wear testing were also performed. The addition of niobium produced significant alterations in the TTT diagrams. Increasing niobium content moves the pearlite transformation nose to the right and the bainitic transformation nose to the left. Tensile strength of these alloys was high, in the range of 1700 MPa and impact values were around of 45 Joules for alloy with 1 % Nb, 49 Joules for alloy with 0.5 % Nb and fracture did not occur for the alloy without the addition of Nb.

Production and heat treatment of cast graphitic steels with additions of niobium

The optimal combination of the mechanical characteristics of austempered spheroidal graphitic cast steel together with modern casting techniques yielded an economically promising product. The maximum potentiality of the usage of these steels is related to fabrication and characterization techniques, among which, one of the most important is the cooling diagram (TTT curve). In this work, 3 heats of graphitic steels with the following nominal compositions were cast: 1.0%C, 2.3%Si, 0.4% Mn, and with niobium contents of 0.0%, 0.5% and 1.0%. TTT curves were determined by dilatometric testing and test specimens of these steels were austempered. The samples were then characterized by hardness testing and optical and SEM microscopy. Tensile, impact (no notch) and wear testing were also performed. The addition of niobium produced significant alterations in the TTT diagrams. Increasing niobium content moves the pearlite transformation nose to the right and the bainitic transformation nose to the left. Tensile strength of these alloys was high, in the range of 1700 MPa and impact values were around of 45 Joules for alloy with 1% Nb, 49 Joules for alloy with 0.5% Nb and fracture did not occur for the alloy without the addition of Nb.

Effects of atrazine on female Wistar rats: Morphological alterations in ovarian follicles and immunocytochemical labeling of 90 kDa heat shock protein

Fertility in female mammals may be affected by a variety of endocrine disrupters present in the environment. Herbicide atrazine is an example of endocrine disrupter employed in agriculture, which disrupts estrous cyclicity in rats. Aiming to characterize morphologically the effect of low and sublethal doses of atrazine on the ovaries of Wistar rats, in an effort to determine the possible intrafollicular target site through which this herbicide acts adult females were submitted to both subacute and subchronic treatments. Additionally, immunocytochemical labeling of 90 kDa heat shock protein (HSP90) was performed in order to evaluate the role played by this protein in the ovary, under stressed conditions induced by herbicide exposure. The results indicated that atrazine induced impaired folliculogenesis, increased follicular atresia and HSP90 depletion in female rats submitted to subacute treatment, while the subchronic treatment with low dose of atrazine could compromise the reproductive capacity reflected by the presence of multioocytic follicle and stress-inducible HSP90. © 2007 Elsevier Ltd. All rights reserved.

Heat transfer in a packed sugar cane bagasse bed

Heat transfer in a packed bed of sugar cane bagasse, which is a potential biofuel used in cars and industries, percolated with air flow was studied. The fibers were washed, sieved, oven dried, and afterwards moisture content was adjusted to 4 and 47%. The relative humidity of the air, packing bed technique, and the initial moisture content of the porous media did not have a significant effect on the outlet temperature of the bed. Air flow rate influenced the averaged radial temperature profile, but not the temperature measured at the nearest position to the tube wall. At the end of the experiments, moisture segregation was observed, the lower bed depths being drier than the higher ones. This is an abstract of a paper presented at the 18th International Congress of Chemical Process Engineering (Praque, Czech Republic 8/24-28/2008).

Urban heat islands and electrical energy consumption

This study proposes the development of thermal and energy consumption maps to generate useful planning information. A residential neighbourhood in a medium-sized city was selected as the study area. In this area, 40 points were taken as urban reference points where air temperatures at the pedestrian level were collected. At the same time, rural temperatures made available by the city meteorological station were registered. Data of electrical energy consumption of the building units (houses and apartments) were collected through a household survey that was also designed to identify the users' income levels. Then, maps were developed so that the configuration of urban heat islands and electrical energy consumption could be visualised, compared and analysed. The results showed that the income level was the most important variable influencing electrical energy consumption. However, a strong relationship of the consumption with the thermal environment was also observed.

Influence of pre-heat treatment and different light-curing units on Vickers hardness of a microhybrid composite resin

The aim of this study was to evaluate the hardness of a dental composite resin submitted to temperature changes before photo-activation with two light-curing unite (LCUs). Five samples (4 mm in diameter and 2 mm in thickness) for each group were made with pre-cure temperatures of 37, 54, and 60°C. The samples were photo-activated with a conventional quartz-tungsten-halogen (QTH) and blue LED LCUs during 40 s. The hardness Vickers test (VHN) was performed on the top and bottom surfaces of the samples. According to the interaction between light-curing unit and different pre-heating temperatures of composite resin, only the light-curing unit provided influences on the mean values of initial Vickers hardness. The light-curing unit based on blue LED showed hardness mean values more homogeneous between the top and bottom surfaces. The hardness mean values were not statistically significant difference for the pre-cure temperature used. According to these results, the pre-heating of the composite resin provide no influence on Vickers hardness mean values, however the blue LED showed a cure more homogeneous than QTH LCU. © 2009 Pleiades Publishing, Ltd.

Dietary restriction abrogates antibody production induced by a DNA vaccine encoding the mycobacterial 65 kDa heat shock protein

Background: Protein-calorie malnutrition (PCM) is the most common type of malnutrition. PCM leads to immunodeficiency and consequent increased susceptibility to infectious agents. In addition, responses to prophylactic vaccines depend on nutritional status. This study aims to evaluate the ability of undernourished mice to mount an immune response to a genetic vaccine (pVAXhsp65) against tuberculosis, containing the gene coding for the heat shock protein 65 from mycobacteria. Methods: Young adult female BALB/c mice were fed ad libitum or with 80% of the amount of food consumed by a normal diet group. We initially characterized a mice model of dietary restriction by determining body and spleen weights, hematological parameters and histopathological changes in lymphoid organs. The ability of splenic cells to produce IFN-gamma and IL-4 upon in vitro stimulation with LPS or S. aureus and the serum titer of specific IgG1 and IgG2a anti-hsp65 antibodies after intramuscular immunization with pVAXhsp65 was then tested. Results: Dietary restriction significantly decreased body and spleen weights and also the total lymphocyte count in blood. This restriction also determined a striking atrophy in lymphoid organs as spleen, thymus and lymphoid tissue associated with the small intestine. Specific antibodies were not detected in mice submitted to dietary restriction whereas the well nourished animals produced significant levels of both, IgG1 and IgG2a anti-hsp65. Conclusion: 20% restriction in food intake deeply compromised humoral immunity induced by a genetic vaccine, alerting, therefore, for the relevance of the nutritional condition in vaccination programs based on these kinds of constructs. © 2009 Ishikawa et al; licensee BioMed Central Ltd.

Development of a micro heat exchanger made with ceramic multi-layers (LTCC) and its setup to gas flow measurements

A green ceramic tape micro heat exchanger was developed using LTCC technology. The device was designed by using a CAD software and 2D and 3D simulations using a CFD package (COMSOL Multiphysics) to evaluate the fluid behavior in the microchannels. The micro heat exchanger is composed of five thermal exchange plates in cross flow arrangement and two connecting plates; heat exchanger dimensions are 26 × 26 × 6 mm3. Preliminary tests were carried out to characterize the device both in atmospheric pressure and in vacuum. The same techniques used in vacuum technology were applied to check the rotameters and to prevent device leakages. Thermal performance of the micro heat exchanger was experimentally tested. © 2009 Elsevier B.V. All rights reserved.

Infrared thermography applied to the evaluation of metabolic heat loss of chicks fed with different energy densities

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Entransy and its utilization in problems of thermodynamics and heat transfer

The concept of entransy was recently proposed in terms of the analogy to the electric energy stored in a capacitor. The entransy of a system describes its heat transfer ability, as the exergy of a system quantifies its work production potential. Hence, the concept of entransy can be useful in problems where the heat transfer is the main objective, as for example, in systems collecting solar energy. This concept is quite recent and there are only a few works related to this topic. It is expected, however, that this approach will soon be used more often in the analysis of problems in thermodynamics and heat transfer. The objective of this work is to present a review of the concept of entransy in a systematic way, beginning with its definition, balance equations and a few examples of simple applications. It is hoped that this concept of entransy becomes a useful tool in the analysis and design of more efficient thermal systems. © 2012 Praise Worthy Prize S.r.l.- All rights reserved.

Effects of heat stress on development, quality and survival of Bos indicus and Bos taurus embryos produced in vitro

Heat stress is an important cause of poor development and low survival rates in bovine embryos. Experiments were conducted to test the hypothesis that Bos indicus embryos are more resistant to heat stress than are Bos taurus embryos. In experiment 1, Nelore and Jersey embryos from oocyte pick-up-derived oocytes were submitted to heat stress (96 hours post-insemination, 41 °C, 6 hours), developmental ratios were assessed at Day 7 (Day 0 = day of fertilization), and blastocysts were frozen for RNA extraction. Experiment 2 evaluated expression of COX2, CDX2, HSF1, and PLAC8 in previously frozen blastocysts. In experiment 3, Nellore and Angus embryos from oocyte pick-up-derived oocytes were submitted to heat stress (96 hours post-insemination, 41 °C, 12 hours) and transferred to recipients on Day 7. In experiment 4, embryos developed as in experiment 3 were fixed for Terminal deoxynucleotidyl transferase dUTP nick end labeling labeling and total cell counting. In experiment 1, heat stress decreased the percentage of Jersey oocytes that became blastocysts, but had no effect on Nellore embryos (34.6%, 25.0%, 39.5%, and 33.0% for Jersey control, Jersey heat-stressed, Nellore control, and Nellore heat-stressed oocytes, respectively; P < 0.05). In experiment 2, heat stress decreased (P < 0.05) expression of CDX2 and PLAC8, with higher expression of these genes in Nellore embryos than in Jersey embryos. Heat stress also decreased (P < 0.05) expression of COX2 in Jersey embryos, but had no effect on Nellore embryos. Expression of HSF1 was decreased (P < 0.05) by heat stress in both breeds, with a greater effect in Nellore embryos. In experiment 3, heat stress tended (P = 0.1) to decrease the percentage of pregnancies among cows (Day 30 to 35) that received Angus embryos. In experiment 4, heat stress increased (P < 0.05) the percentage of apoptotic blastomeres, but had no breed-specific effects. In addition, Nellore embryos had fewer (P < 0.05) Terminal deoxynucleotidyl transferase dUTP nick end labeling- positive blastomeres than did Angus embryos. We concluded that the detrimental effects of heat stress were dependent upon embryo breed and were more evident in Bos taurus embryos than in Bos indicus embryos. © 2013 Elsevier Inc.

Carcass and meat quality traits of rabbits under heat stress

Rabbits are very sensitive to heat stress because they have difficulty eliminating excess body heat. The objective of the current study was to evaluate the effects of heat stress on slaughter weight, dressing percentage and carcass and meat quality traits of rabbits from two genetic groups. Ninety-six weaned rabbits were used: half were from the Botucatu genetic group and half were crossbreds between New Zealand White sires and Botucatu does. They were assigned to a completely randomized design in a 2 × 3 factorial arrangement (two genetic groups and three ambient temperatures: 18°C, 25°C and 30°C) and kept under controlled conditions in three environmental chambers from 5 to 10 weeks of age. Slaughter took place at 10 weeks, on 2 consecutive days. Meat quality measurements were made in the longissimus muscle. Actual average ambient temperature and relative humidity in the three chambers were 18.4°C and 63.9%, 24.4°C and 80.2% and 29.6°C and 75.9%, respectively. Purebred rabbits were heavier at slaughter and had heavier commercial and reference carcasses than crossbreds at 30°C; however, no differences between genetic groups for these traits were found at lower temperatures. No genetic group × ambient temperature interaction was detected for any other carcass or meat quality traits. The percentages of distal parts of legs, skin and carcass forepart were higher in crossbred rabbits, indicating a lower degree of maturity at slaughter in this group. The percentage of thoracic viscera was higher in the purebreds. Lightness of the longissimus muscle was higher in the purebreds, whereas redness was higher in the crossbreds. Slaughter, commercial and reference carcass weights and the percentages of thoracic viscera, liver and kidneys were negatively related with ambient temperature. Commercial and reference carcass yields, and the percentage of distal parts of legs, on the other hand, had a positive linear relationship with ambient temperature. Meat redness and yellowness diminished as ambient temperature increased, whereas cooking loss was linearly elevated with ambient temperature. Meat color traits revealed paler meat in the purebreds, but no differences in instrumental texture properties and water-holding capacity between genetic groups. Purebred rabbits were less susceptible to heat stress than the crossbreds. Heat stress resulted in lower slaughter and carcass weights and proportional reductions of organ weights, which contributed to a higher carcass yield. Moreover, it exerted a small, but negative, effect on meat quality traits. © 2012 The Animal Consortium.

Heat transfer and magnetovortical antiresonance of a ferrofluid with a rotating magnetic field

We investigate theoretically a ferrofluid in the presence of a rotating magnetic field using a phenomenological approach based on a equation of motion for the magnetization. We verify that the heating rates of the system display a heat transfer between the host liquid and the magnetic nanoparticles (MNPs), with symmetric profiles dependent on the vorticity value. As a result, the total heating rate reveals a magnetovortical antiresonance and characterizes the suppression of the dissipation. © 2012 Springer Science+Business Media, LLC.

Effect of dietary betaine supplementation on the performance, carcass yield, and intestinal morphometrics of broilers submitted to heat stress

The objective of this study was to evaluate the effect of betaine in methionine- and choline-reduced diets fed to broilers submitted to heat stress. In total, 1,408 male broilers were randomly distributed into eight treatments, according to 2 × 4 (environment x diet) factorial arrangement, with eight replicates of 2 birds each. Birds were reared environmental chambers under controlled temperature (25-26 °C) or cyclic heat-stressing temperature (25-31 °C). The following diets were tested: positive control (PC), formulated to meet broiler nutritional requirements; negative control (NC), with reduced DL-methionine and choline chloride levels; and with two supplementation levels of natural betaine to the negative control diet (NC+NB1 and NC+NB2). Live performance, carcass traits, and intestinal morphometrics were evaluated when broilers were 45 days of age. The results showed that all evaluated parameters were influenced by the interaction between environment and diet, except for breast meat drip loss. The breakdown of the interactions showed that birds fed the PC diet and reared in the controlled environment had greater breast drip loss than those submitted to the cyclic heat-stress environment. Birds submitted to cyclic heat stress and fed the PC diet presented the lowest feed intake. Feed conversion ratio was influenced only by diet. The FCR of broilers fed the NC+NB2 diet was intermediate relative to those fed the PC and NC diets. The addition of betaine in the diet, with 11.18% digestible methionine and 24.73% total choline reductions, did not affect broiler live performance, carcass yield, or intestinal morphometrics.

High levels of heat shock protein 70 are associated with pro-inflammatory cytokines and may differentiate early- from late-onset preeclampsia

Preeclampsia (PE), a specific syndrome of pregnancy, can be classified into early and late onset, depending on whether clinical manifestations occur before or after 34 weeks' gestation. We determined whether plasma concentrations of Hsp60 and Hsp70 were related to circulating cytokine levels, as well as kidney and liver functions, in early- and late-onset PE. Two hundred and thirty-seven preeclamptic women (95 with early- and 142 with late-onset PE) were evaluated. Plasma levels of Hsp60, Hsp70, and their specific antibodies, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1, IL-10, IL-12, and soluble TNF-α-receptor I (sTNFRI) concentrations, were determined by enzyme-linked immunosorbent assay (ELISA). Concentrations of Hsp70, TNF-α, IL-1β, IL-12, and sTNFRI were significantly elevated in patients with early-onset PE compared with women with late-onset PE; IL-10 levels were significantly lower in the early-onset PE group. Concentrations of urea, uric acid, proteinuria, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and lactate dehydrogenase (LDH) were also significantly higher in early-onset PE. The percentage of infants with intrauterine growth restriction was also significantly higher in women with early-onset PE. There were positive correlations between Hsp70 levels and TNF-α, TNFRI, IL-1β, IL-12, GOT, GPT, LDH, and uric acid concentrations in early-onset PE group. Thus, early-onset PE was associated with greater maternal and fetal impairment. There are differences in pathophysiology between early- and late-onset PE, highlighting by the difference in Hsp70 levels. © 2013 Elsevier B.V. All rights reserved.