Processing of ultrafine-size particulate metal matrix composites by advanced shear technology

Copyright @ 2009 ASM International. This paper was published in Metallurgical & Materials Transactions A 40A(3) and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.Lack of efficient mixing technology to achieve a uniform distribution of fine-size reinforcement within the matrix and the high cost of producing components have hindered the widespread adaptation of particulate metal matrix composites (PMMCs) for engineering applications. A new rheo-processing method, the melt-conditioning high-pressure die-cast (MC-HPDC) process, has been developed for manufacturing near-net-shape components of high integrity. The MC-HPDC process adapts the well-established high shear dispersive mixing action of a twin-screw mechanism to the task of overcoming the cohesive force of the agglomerates under a high shear rate and high intensity of turbulence. This is followed by direct shaping of the slurry into near-net-shape components using an existing cold-chamber die-casting process. The results indicate that the MC-HPDC samples have a uniform distribution of ultrafine-sized SiC particles throughout the entire sample in the as-cast condition. Compared to those produced by conventional high-pressure die casting (HPDC), MC-HPDC samples have a much improved tensile strength and ductility.EP-SR

Ensaio terapêutico na infecção por Giardia muris em camundongo com metronidazole, tinidazole, secnidazole e furazolidone

Foi testado in vivo a sensibilidade de Giardia muris a quatro drogas comumente usadas no tratamento da giardíase humana. Foram utilizados 7 grupos de animais, com 12 camundongos cada, sendo que o grupo controle recebeu apenas solução salina 0,15M (0,5ml/animal). Os demais grupos receberam em dose única: metronidazole e furazolidone (500mg/kg), tinidazole e secnidazole (200mg/kg). A eficácia das drogas foi avaliada através da contagem de cistos nas fezes e pela ausência de trofozoítos no intestino. O metronidazole foi a droga mais eficaz. Os cortes histológicos mostraram diferenças entre o padrão da mucosa intestinal de animais normais e parasitados. No entanto, não se observou diferença entre o padrão de mucosa de animais infectados tratados e não tratados, o que sugere que estas alterações podem ser causadas pelo parasito e não pelas drogas.<br>A comparative study about the effectiveness of metronidazole, tinidazole, secnidazole and furazolidone was performed on Giardia muris from mice naturally infected. Groups of 12 animals each was constituted: the control treated with saline; one treated with metronidazole; one treated with furazolidone; one treated with tinidazole; one treated with secnidazole; histological normal control; histological infected. Samples of three stools were examined before and after treatment with quantification of cysts. Animals were cured when the trophozoites was not seen in the small bowel. The curative activity of drugs was 58.3% for metronidazole, 50% for furazolidone, 40% for secnidazole and 16% for tinidazole. It was also showed that there was a different pattern of the intestinal mucosa from the control and infected groups, treated or not, suggesting that the alterations encountered in the mucosa of infected animals were due to the parasitism either the action of the drugs

Biological control as an invasion process: disturbance and propagule pressure affect the invasion success of Lythrum salicaria biological control agents

Understanding the mechanisms behind the successful colonization and establishment of introduced species is important for both preventing the invasion of unwanted species and improving release programs for biological control agents. However, it is often not possible to determine important introduction details, such as date, number of organisms, and introduction location when examining factors affecting invasion success. Here we use biological control introduction data to assess the role of propagule pressure, disturbance, and residence time on invasion success of four herbivorous insect species introduced for the control of the invasive wetland plant, Lythrum salicaria, in the Columbia River Estuary. Two sets of field surveys determined persistence at prior release sites, colonization of new sites, and abundance within colonized sites. We quantified propagule pressure in four ways to examine the effect of different measurements. These included three measurements of introduction size (proximity to introduction site, introduction size at a local scale, and introduction size at a regional scale) and one measure of introduction number (number of introduction events in a region). Disturbance was examined along a tidal inundation gradient (distance from river mouth) and as habitat (island or mainland). Statistical models and model averaging were used to determine which factors were driving invasion success. In this study we found: (1) sparse evidence for the positive influence of propagule pressure on invasion success; (2) disturbance can negatively affect the invasion success of herbivorous insects; (3) the effects of disturbance and propagule pressure are species specific and vary among invasion stages, and (4) not all measures of propagule pressure show the same results, therefore single measures and proxies should be used cautiously