Method of making high strength articles from forged powder steel alloys

High strength steel parts or articles are made from a powder alloy by compacting the powder into a preform, sintering the preform in a sintering furnace or the like under a highly-reducing atmosphere and at a temperature of at least 1150° C., cooling the preform, preheating the sintered preform in a highly-reducing atmosphere, such as an inert gas-based atmosphere containing hydrogen or pure hydrogen, to a temperature of at least 1000° C. and transferring the preheated preform to an impact forging device and impacting the preform at a peak averaging forging pressure of at least about 1000 MPa to obtain a forged part or article. The time period between removal of the preheated preform from the preheater and the first forging impact is no more than about 8 seconds. The sintering and preheating steps can be combined with the sintered preform being cooled to the preheating temperature in the sintering furnace and transferred directly from the sintering furnace to the impact forging device.https://digitalcommons.mtu.edu/patents/1087/thumbnail.jp

Dip coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

To date, an experimental dip-coating facility was constructed. Using this facility, relatively thin (1 mm) mullite and alumina substrates were successfully dip-coated with 2.5 - 3.0 ohm-cm, p-type silicon with areas of approximately 20 sq cm. The thickness and grain size of these coatings are influenced by the temperature of the melt and the rate at which the substrate is pulled from the melt. One mullite substrate had dendrite-like crystallites of the order of 1 mm wide and 1 to 2 cm long. Their axes were aligned along the direction of pulling. A large variety of substrate materials were purchased or developed enabling the program to commence a substrate definition evaluation. Due to the insulating nature of the substrate, the bottom layer of the p-n junction may have to be made via the top surface. The feasibility of accomplishing this was demonstrated using single crystal wafers

Bases estructurales del mecanismo de reconocimiento y fosfotransferencia en los sistemas de señalización de dos componentes

Póster original presentado XXVII Congreso de la SEBBM, Sociedad Española de Bioquímica y Biología Molecular, celebrado en Lleida, 12-15 de septiembre, 2004.Los sistemas de dos componentes son el mecanismo principal de transducción de señal en microorganismos. Un sistema paradigmático se compone de dos proteínas: una histidina quinasa (HK) y un regulador de la respuesta (RR). El mecanismo de transducción de señal implica al menos tres reacciones (ver esquema): 1) Autofosforilación: la llegada de un estímulo al dominio extracelular sensor de la HK, induce la fosforilación en un residuo de His conservado en el dominio de dimerización (DHp) por parte del dominio de unión de ATP (CA). 2) Fosfotransferencia: este grupo fosforilo es transferido desde la His a un residuo de Asp del dominio regulador del correspondiente RR. 3) Defosforilación: el RR pierde el grupo fosforilo espontáneamente o mediado por la HK. El estado de fosforilación del dominio regulador en RR regula la actividad de su dominio efector, que es habitualmente un factor de transcripción.Financiado por la ayuda BIO2002-03709 del Ministerio de Ciencia y Tecnología. P. casino es becaria FPI del Ministerio de ciencia y TecnologíaPeer reviewe

Dip coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

The technical and economic feasibility of producing solar cell quality sheet silicon by dip-coating one surface of carbonized ceramic substrates with a thin layer of large grain polycrystalline silicon was investigated. The dip-coating methods studied were directed toward a minimum cost process with the ultimate objective of producing solar cells with a conversion efficiency of 10% or greater. The technique shows excellent promise for low cost, labor-saving, scale-up potentialities and would provide an end product of sheet silicon with a rigid and strong supportive backing. An experimental dip-coating facility was designed and constructed, several substrates were successfully dip-coated with areas as large as 25 sq cm and thicknesses of 12 micron to 250 micron. There appears to be no serious limitation on the area of a substrate that could be coated. Of the various substrate materials dip-coated, mullite appears to best satisfy the requirement of the program. An inexpensive process was developed for producing mullite in the desired geometry

Integrating Academic and Non-Academic Instruction for Students with Emotional/Behavioral Disorders

Students with emotional/behavioral disorders exhibit a wide range of academic and behavioral problems. Not surprisingly, there is growing support for integrating instruction to address overlapping students\u27 needs in both areas. In this article, we discuss instructional variables that contribute to a positive classroom climate and that serve as setting events for more focused group-individual instructional programs. We draw on the accumulated research to identify common non-academic challenges that should be incorporated into those programs. We examine issues that relate to the efficacy of instruction and also the cultural and chronological age differences among students and how they relate to planning for instruction. Finally, we offer several forms that illustrate ways to combine academics and non-academics into a manageable instructional plan

Tunneling Splittings in Mn12-Acetate Single Crystals

A Landau-Zener multi-crossing method has been used to investigate the tunnel splittings in high quality Mn$_{12}$-acetate single crystals in the pure quantum relaxation regime and for fields applied parallel to the magnetic easy axis. With this method several individual tunneling resonances have been studied over a broad range of time scales. The relaxation is found to be non-exponential and a distribution of tunnel splittings is inferred from the data. The distributions suggest that the inhomogeneity in the tunneling rates is due to disorder that produces a non-zero mean value of the average transverse anisotropy, such as in a solvent disorder model. Further, the effect of intermolecular dipolar interaction on the magnetic relaxation has been studied.Comment: Europhysics Letters (in press). 7 pages, including 3 figure

Chinese and African migrant entrepreneur's articulation shaped by African agency

Much has been written on the relationship of China and Africa in the past decade. However, the subject of Chinese migrant entrepreneurs in Africa and their articulation with African counterparts was little explored up to the early 2010s. Apparently, this research gap has been closed, as shown by four publications in recent years: three edited volumes and one monography, focusing on this subject. In view of early prejudices on the passive or even disapproving reception of Chinese migrants by Africans, the state of the art underlines the importance and scope of African agency vis à vis Chinese migrant entrepreneurs in Africa. This has been underlined unison in the four books under review. Book review of:(1) Giese, Karsten, Marfaing, Laurence (eds) (2016): Entrepreneurs Africains et Chinois. Les impacts sociaux d’une rencontre particulière. Paris: Karthala. (2) Gadzala, Aleksandra W. (ed) (2015): Africa and China: how Africans and their governments are shaping relations with China. Lanham/Md.: Rowman & Littlefield. (3) Mohan, Giles, Lampert, Ben et al (eds) (2014): Chinese Migrants and Africa's Development: new imperialists or agents of change? London: Zed books. (4) French, Howard W. (2015): China's Second Continent: how a million migrants are building a new empire in Africa. London: Penguin Random House / New York: Knopf.On a beaucoup écrit sur la relation entre la Chine et l'Afrique dans la dernière décennie. Cependant, le sujet des entrepreneurs migrants chinois en Afrique et leur articulation avec leurs homologues africains a été peu exploré jusqu'au début des années 2010. Apparemment, cet écart de recherche a été fermé, comme indiqué par quatre publications au cours des dernières années: trois volumes édités et une monographie, en se concentrant sur ce sujet. Compte tenu des premiers préjugés sur la réception passive ou même désapprobateur des migrants chinois par les Africains, l'état de l'art souligne l'importance et la portée de l'agence africaine vis-à-vis des entrepreneurs migrants chinois en Afrique

Low temperature magnetic hysteresis in Mn12_{12} acetate single crystals

Precise magnetic hysteresis measurements of small single crystals of Mn$_{12}$ acetate of spin 10 have been conducted down to 0.4 K using a high sensitivity Hall magnetometer. At higher temperature (>1.6K) step-like changes in magnetization are observed at regularly spaced magnetic field intervals, as previously reported. However, on lowering the temperature the steps in magnetization shift to higher magnetic fields, initially gradually. These results are consistent with the presence of a second order uniaxial magnetic anisotropy, first observed by EPR spectroscopy, and thermally assisted tunnelling with tunnelling relaxation occurring from levels of progressively lower energy as the temperature is reduced. At lower temperature an abrupt shift in step positions is found. We suggest that this shift may be the first evidence of an abrupt, or first-order, transition between thermally assisted and pure quantum tunnelling, suggested by recent theory.Comment: 8 pages, 4 figures, submitted to Europhys. Let