Estudo da utilização de ferramentas a base de nitreto de silício (Si3N4) e alumina (Al2O3) na usinagem do ferro fundido vermicular

Machining is one of the most commonly manufacturing processes used in the modern world, consuming millions of dollars annually. Because of this, it is crucial for the automotive industry to reduce costs on their heat-resistant alloy machining processes, such as compacted graphite iron (CGI), which has shown an increasing trend of its application in diesel engine blocks, brakes disks, among other applications, due to its superior mechanical properties to gray cast iron. Despite this advantage, its use is still limited due to its difficulty of machining, moreover, cutting tools are displayed as the main factor in increasing the machining cost. Seeking an alternative to a better machinability of CGI, this paper aims to study two types of ceramic tools developed in Brazil, and benchmark their performance by dry turning. For this, were used CGI class 450 and two tools: ceramic of silicon nitride (Si3N4) and alumina-based (Al2O3), with a cutting speed (Vc) of 300, 400 and 500 m / min; feed (f) of 0.2 mm / rev and depth of cut (ap) of 0.5 mm, using three replicates and starting with new cutting edges. The results showed that the Al2O3 tool had the best performance in Vc of 500 m / min, while the Si3N4 tool had the best results in Vc of 300 m / min. This can be explained by the tool of Si3N4 based include soft intergranular phase, called amorphous, while alumina has higher abrasion resistance due to its high refractoriness. The results make it clear that the tools have significant potential for machining of compacted graphite iron, being necessary a strict control of the cutting parameters used

The presence of genes encoding for different virulence factors in clonally related Escherichia coli that produce CTX-Ms

Successful international clones have recently emerged among Escherichia coli that produce CTX-M beta-lactamases as important causes of community-onset urinary tract and bloodstream infections. One hundred and seven isolates that belong to sequence types (STs) ST38, ST131, ST405, ST648, and 38 nonrelated CTX-M producing E. coli from Canada and the Netherlands were assigned to phylogenetic groups and tested for the presence of genes encoding for virulence factors (VFs) using established multiplex polymerase chain reaction. The STs E. coli were significantly more resistant to antibiotics-ST38, ST405, and ST648 belonged to phylogenetic group D while ST131 belonged to B2. Secreted autotransporter toxin (sat), aerobactin receptor, and pathogenicity island marker were significantly more common among the STs; the heat-resistant agglutinin (hra) was present in ST38, sat, and uropathogenic-specific protein, and putative adhesin-siderophore receptor was more common in ST131, while outer membrane protease T was present in ST648. ST131 had a significantly higher VF score. In conclusion, the precise role of these VFs remains to be elucidated; however, we have identified certain putative VFs that possibly contribute to the fitness and success of certain sequence types. (C) 2012 Elsevier Inc. All rights reserved.

Ethanolamine modulates the rate of rat hepatocyte proliferation in vitro and in vivo

A low molecular weight, heat-resistant hepatotrophic factor in an extract from the bovine intestinal mucosa was purified and identified as ethanolamine by structural analyses. The mode of action of ethanolamine in vitro and in vivo coincided with that of the crude extract of the tissue, indicating that ethanolamine is the active component. Ethanolamine synergistically elevated the stimulation of DNA synthesis in hepatocytes in primary culture when added together with a growth factor, such as epidermal growth factor, with the ED50 being 20 μM, although it showed little stimulatory effect by itself. Contrary to these in vitro results, the intraperitoneal administration of ethanolamine hydrochloride (24 mg of ethanolamine per kg of body weight) enhanced hepatocyte proliferation in regenerating rat livers after two-thirds hepatectomy without the administration of any growth factors. In the regenerating liver, hepatocyte proliferation may be initiated by an endogenous growth factor, but the supply of ethanolamine in circulation may not be sufficient for optimal hepatocyte proliferation; thus, the exogenous administration of ethanolamine may further enhance hepatocyte proliferation. Ethanolamine in circulation may be a humoral hepatotrophic factor.

Refractory metals and their alloys : a literature search /

"January 1959."

Development of high temperature sensors : July 1, 1959-April 30, 1961 /

"Contract AT(11-1)-229."

Refractory metal constitution diagrams

Mode of access: Internet.

The vaporization and physical properties of certain refractories.

pt. 1. Techniques and preliminary studies, by A. A. Hasapis, M. B. Panish and C. Rosen.--pt. 2. Experimental studies, by A. A. Hasapis and others.

Investigation of the Ti-Al-Cb system as a source of alloys for use at 1200⁰-1800⁰F

"Materials Central, Contract No. AF 33(616)-6125, Project No. 7351."

Mechanical properties of selected alloys at elevated temperatures

"PB 161761."

Investigation of diffusion barriers for refractory metals

Mode of access: Internet.

High-temperature technology.

Mode of access: Internet.

Development of the ASTM E681 Standard

ASHRAE 34, based on ASTM E681, was improved by identifying and rectifying deficiencies in ASTM E681. An ASTM E681 apparatus and procedure was developed with gaseous refrigerant testing in mind. The plumbing was improved by ensuring that the pressure readings could be constantly monitored while decreasing leakage potential. An original electrical system was designed and constructed for the ignition system. Additionally, a control panel was constructed to isolate hazardous electrical elements, and facilitate the testing, while simultaneously organizing the critical plumbing and ignition components. 3D printing efficiently produced heat-resistant, nonreactive, and structurally stable lower electrode spacers, propellers, and propeller bars. The heating system was designed to ensure even temperature throughout the apparatus. The humidity system was designed to accurately condition the air. Recommendations to improve ASTM E681 are provided. The research can be built on to improve the accuracy and reproducibility of ASTM E681.

ENHANCEMENT OF THERMAL INACTIVATION OF CRONOBACTER SAKAZAKII WITH INCLUSION OF PARABENS

Parabens are a family of p-hydroxybenzoic acid esters, which have antimicrobial activity over a broad pH range (4-8). This study was designed to evaluate the enhanced thermal inactivation of Cronobacter sakazakii by the inclusion of “parabens” and to ultimately develop mathematical models to describe this effect. A heat-resistant strain, Cronobacter sakazakii 607, was heated at three mild heating temperatures in combination with treatments with five parabens in various concentrations. Results showed the presence of parabens significantly enhanced thermal inactivation in a concentration-dependent manner, and the effect increased with increasing alkyl chain length. The concentration of parabens, alkyl side chain length, and heating temperature acted synergistically, causing bacterial inactivation even at low temperatures that were not effective in killing C. sakazakii. The survival data were used to develop primary and secondary mathematical models that accurately describe how this synergistic activity can be applied in the food industry.

Mass loss of four commercially available heat-polymerized acrylic resins after toothbrushing with three different dentifrices

The association between a toothbrush and a dentifrice is the most used denture cleaning method. The purpose of this study was to evaluate the abrasiveness of specific and non-specific denture cleaning dentifrices on different heat-polymerized acrylic resins. Sixteen specimens (90x30x3mm) of each acrylic resin (QC-20, Lucitone 550, Clássico, Vipi-Cril) were prepared and randomly assigned to 4 groups: 1: control (distilled water), 2: Colgate, 3: Bonyplus and 4: Dentu-Creme. The specimens were subjected to simulated toothbrushing in an automatic brushing machine using 35,600 brush strokes for each specimen. Brushing abrasion run at a 200-g load with the specimens immersed in 2:1 dentifrice/water slurry. Specimens were reconditioned to constant mass and the mass loss (mg) was evaluated. Data were analyzed by 2-way ANOVA and Tukey's test (a=0.05). Analysis of dentifrices' abrasive particles was made by scanning electron microscopy. Colgate produced the greatest mass reduction (42.44 mg, p<0.05), followed by Dentu-Creme (33.60 mg). Bonyplus was the less abrasive (19.91 mg), similar to the control group (19.69 mg) (p>0.05). The mass loss values indicated that QC-20 (33.13 mg) and Lucitone 550 (33.05 mg) resins were less (p<0.05) resistant to abrasion than Clássico (26.04 mg) and Vipi-Cril (23.43 mg). In conclusion, Colgate produced the greatest abrasion. Specific dentifrices for dentures tend to cause less damage to acrylic resins.

Design and Characterization of Novel Wear Resistant Multilayer CVD Coatings with Improved Adhesion Between Al(2)O(3) and Ti(C,N)

Multilayer CVD coatings for high speed cutting applications were designed to achieve high wear and heat resistance during machining of steel alloys. In this work the microstructure and cutting performance of these novel multilayer CVD coatings are investigated and compared with standard CVD multilayer coatings. 3D-FIB tomography is used to characterize the microstructure of the layers, especially the transition between the Ti(C,N) and the Al(2)O(3) layer. The 3D reconstruction of the surface of the Ti(C,N) layer shows the formation of protruded Ti(C,N) grains with a very particular architecture, which penetrate into the Al(2)O(3) top-layer, providing a mechanical anchoring between both layers. Cemented carbides coated with the novel CVD multilayer present reduced crater and flank wear as well as improved adherence between the Al(2)O(3) top-layer and the Ti(C,N) layer leading to a dramatic improvement of cutting performance.