Experimental and theoretical investigations of adsorption hysteresis and criticality in MCM-41: Studies with O-2, Ar, and CO2

MCM-41 materials of six different pore diameters were prepared and characterized using X-ray diffraction, transmission electron microscopy, helium pycnometry, small-angle neutron scattering, and gas adsorption (argon at 77.4 and 87.4 K, nitrogen and oxygen at 77.4 K, and carbon dioxide at 194.6 K). A recent molecular continuum model of the authors, previously used for adsorption of nitrogen at 77.4 K, was applied here for adsorption of argon, oxygen, and carbon dioxide. While model predictions of single-pore adsorption isotherms for argon and oxygen are in satisfactory agreement with experimental data, significant deviation was found for carbon dioxide, most likely due to its high quadrupole moment. Predictions of critical pore diameter, below which reversible condensation occurs: were possible by the model and found to be consistent with experimental estimates, for the adsorption of the various gases. On the other hand, existing models such as the Barrett-Joyner-Halenda (BJH), Saito-Foley, and Dubinin-Astakhov models were found to be inadequate, either predicting an incorrect pore diameter or not correlating the isotherms adequately. The wall structure of MCM-41 appears to be close to that of amorphous silica, as inferred from our skeletal density measurements.

Non-equilibrium energy and momentum accommodation coefficients of Ar atoms scattered from Ni(001) in the thermal regime: A molecular dynamics study

Molecular dynamics simulations are used to study energy and momentum transfer of low-energy Ar atoms scattered from the Ni(001) surface. The investigation concentrates on the dependence of these processes on incident energy, angles of incidence and surface temperature. Energy transfer exhibits a strong dependence on the surface temperature, at incident energies below 500 meV, and incident angles close to specular incidence. Above 500 meV, the surface temperature dependence vanishes, and a limiting value in the amount of energy transferred to the surface is attained. Momentum exchange is investigated in terms of tangential and normal components. Both components exhibit a weak surface temperature dependence, but they have opposite behaviours at all incidence angles. In each component, momentum can be lost or gained following the interaction with the surface. (C) 1997 Elsevier Science B.V.

Quaternary continental weathering geochronology by laser-heating Ar-40/Ar-39 analysis of supergene cryptomelane

Incremental laser-heating analyses of supergene cryptomelane clusters extracted from three distinct weathering profiles from the Mary Valley region, southeast Queensland, Australia, yield reproducible and well-defined plateau ages ranging from 346 +/- 15 to 291 +/- 14 ka (2 a). Precipitation of supergene cryptomelane in this period implies that relative humid climate prevailed in southeast Queensland from 340 to 290 ha, a result consistent with oxygen isotope analyses of marine sediments from Ocean Drilling Program Site 820 and with regional pollen and spore records. These results, the first report on the precise Ar-40/Ar-39 dating of Quaternary supergene cryptomelane, indicate that Ar-40/Ar-39 analysis of pedogenic minerals provides a reliable geochronometer for the study of Quaternary surficial processes useful in the study of soil formation rates, continental paleoclimates, and archaeological sites devoid of datable volcanic minerals.

Iminopropadienethiones, Ar-N=C=C=C=S

Aryliminopropadienethiones 9 have been generated by flash vacuum thermolysis of isoxazolones of the type 5 and characterized by mass spectrometry and matrix isolation IR spectroscopy in conjunction with DFT calculations and chemical trapping.

Cenozoic continental weathering and its implications for the palaeoclimate: evidence from Ar-40/Ar-39 geochronology of supergene K-Mn oxides in Mt Tabor, central Queensland, Australia

One hundred and twenty-five mineral grains from 45 visually pure K-bearing Mn oxide (hollandite group) samples collected from weathering profiles in the Mt Tabor region of central Queensland, Australia, were analysed by the Ar-40/Ar-39 laser probe technique. These K-Mn oxides precipitated mainly through a process of cavity filling (direct precipitation from weathering solution), with botryoidal texture formed by micrometric mineral bands. Well-defined and reproducible plateau ages have been obtained for most samples, ranging from 27.2 +/- 0.8 to 6.8 +/- 0.5 Ma (2 sigma). Statistical analysis of the geochronological results by mixture modelling suggests an episodic mineral precipitation history, with two major peaks at 20.2 +/- 0.22 Ma and 16.5 +/- 0.17 Ma. The geochronological results, when combined with information on paragenetic relationships and mineralogical textures obtained from petrographic, scanning electron microscopy, and electron microprobe investigations, indicate that warm and humid palaeoclimatic conditions favourable to intense chemical weathering prevailed in central Queensland from late Oligocene to middle Miocene, particularly in the early Miocene. These results, in conjunction with previous and ongoing investigations in NW and eastern Queensland, suggest that most of Queensland was dominated by humid climates during the Miocene. (C) 2002 Elsevier Science BN. All rights reserved.

Ar-40/-Ar-39 geochronology at the Instituto de Geociencias, USP: instrumentation, analytical procedures, and calibration

Laser heating Ar-40/Ar-39 geochronology provides high analytical precision and accuracy, mum-scale spatial resolution. and statistically significant data sets for the study of geological and planetary processes, A newly commissioned Ar-40/Ar-39 laboratory at CPGeo/USP, Sao Paulo, Brazil, equips the Brazilian scientific community with a new powerful tool applicable to the study of geological and cosmochemical processes. Detailed information about laboratory layout, environmental conditions, and instrumentation provides the necessary parameters for the evaluation of the CPGeo/USp Ar-40/Ar-39 suitability to a diverse range of applications. Details about analytical procedures, including mineral separation, irradiation at the IPEN/CNEN reactor at USP, and mass spectrometric analysis enable potential researchers to design the necessary sampling and sample preparation program suitable to the objectives of their study. Finally, the results of calibration tests using Ca and K salts and glasses, international mineral standards, and in-house mineral standards show that the accuracy and precision obtained at the Ar-40/Ar-39 laboratory at CPGeo/USP are comparable to results obtained in the most respected laboratories internationally. The extensive calibration and standardization procedures under-taken ensure that the results of analytical studies carried out in our laboratories will gain immediate international credibility, enabling Brazilian students and scientists to conduct forefront research in earth and planetary sciences.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

A jornada da aprendizagem: um guia para alcan??ar a excel??ncia; Um modelo canadense de administra????o p??blica?

Este Caderno traz dois relat??rios de pesquisa internacionais. O primeiro objetiva fazer um levantamento do que se sabe sobre organiza????es de aprendizagem, traduzir as informa????es resultantes em orienta????es pr??ticas e desenvolver abordagens que possam ajudar gerentes a transformar seus locais de trabalho. O segundo relat??rio objetiva verificar a exist??ncia de um modelo canadense de administra????o p??blica canadense, identificando suas principais caracter??sticas distintivas de outros modelos

Por terra, pelo ar, pelos rios, a Previd??ncia chega at?? voc?? !

Esta iniciativa partiu da necessidade de chegarmos mais perto de nosso cliente, o segurado. Dezoito milh??es de aposentados e pensionistas, quatro milh??es de contribuintes individuais, outros milh??es de contribuintes empregados, e todos ligados a maior seguradora do Brasil. Como atender a este p??blico, falar de seus direitos e deveres, enfim conceder-lhes os benef??cios? Na ??rea urbana ?? f??cil, s??o 1.600 ag??ncias com atendimento permanente, mesmo em cidades do interior. Mas e a zona rural? E a popula????o ribeirinha dos grandes rios? Como chegar at?? eles? Foi pensando em todas estas diversifica????es de p??blico que a Previd??ncia Social criou o Projeto "O INSS vai ?? Comunidade", uma a????o volunt??ria de equipes de servidores que se dedicam a atender, n??o importa a dist??ncia ou os meios de locomo????o, de carro, ??nibus, barco ou avi??o. N??s chegamos l??. Enfrentamos o frio do sul, o calor e a seca das regi??es do norte/nordeste para levar atendimento, esclarecimento ??s popula????es carentes com dificuldade de chegar aos grandes centros. Prosseguindo a pol??tica de aproxima????o com o segurado

Caf?? com debate: desenvolvendo aprendizagem para alcan??ar uma cultura de excel??ncia

Richard Rochefort, especialista na tem??tica de melhoria do atendimento ao p??blico por meio da capacita????o, e Rodrigo Ortiz Assump????o, secret??rio-adjunto de Log??stica e Tecnologia da Informa????o do Minist??rio do Planejamento, Or??amento e Gest??o, relataram experi??ncias do Canad?? e do Brasil e destacaram a import??ncia de uma ???revolu????o cultural??? na administra????o p??blica. Para Rochefort, a sabedoria dos servidores mais experientes, aliada ?? energia dos jovens, ?? capaz de impulsionar e melhorar a qualidade do atendimento ao cidad??o. "A m??dia de idade dos servidores, no Canad??, ?? de 50 anos. Estamos ensinando como devem se adaptar a diferentes situa????es. Agora sabem o que est??o fazendo e por que est??o fazendo determinado servi??o e isso ?? motivo de orgulho, para eles. Sentem-se mais preparados e valorizados. J?? os jovens, que est??o ingressando na administra????o p??blica, devem se manifestar, demonstrar sua criatividade. ?? preciso fazer a diferen??a", disse. O canadense ressaltou, ainda, que o conhecimento ?? o ??nico ativo que aumenta de valor ?? medida que ?? compartilhado

O uso da ren??ncia fiscal na ??rea de museus

O objetivo desse artigo ?? investigar como a ren??ncia fiscal ?? utilizada na ??rea de museus. A fundamenta????o te??rica faz breve apresenta????o da literatura sobre implementa????o e descreve o uso da ren??ncia fiscal na ??rea de museus mediante an??lise de seis vari??veis: incentivos, autonomia, informa????o, apoio institucional, apoio social e etapas e tempo. A metodologia utilizada foi a an??lise documental e entrevistas. A an??lise foi feita com ajuda do programa NVIVO9. As principais conclus??es s??o que embora haja incentivos e autonomia em graus suficientes para permitir boa implementa????o via ren??ncia fiscal, h?? quest??es informacionais e referentes ??s etapas e tempo que dificultam sua implementa????o. Al??m disso, a ren??ncia fiscal ?? concentradora, desigual e apresenta baixa participa????o de empresas do setor privado. Esses problemas parecem diminuir a capacidade de a implementa????o de museus mediante o uso da ren??ncia fiscal alcan??ar os efeitos almejados.

Uma an??lise dos principais efeitos da Lei n?? 11.890, de 24 de dezembro de 2008, sobre a carreira de Especialista em Pol??ticas P??blicas e Gest??o Governamental

As altera????es introduzidas pela Lei n?? 11.890, de 24 de dezembro de 2008, as mais significativas e relevantes e avaliam-se seus efeitos sobre a carreira de Especialista em Pol??ticas Publicas e Gest??o Governamental. Levantam-se quest??es de interpreta????o sistem??tica desses novos dispositivos legais aplic??veis ?? carreira e suas poss??veis implica????es sobre as regulamenta????es por elaborar conforme a previs??o legal. Apresenta-se, ainda, um instrumento para realizar proje????es e simula????es sobre como os limites quantitativos por classe estabelecidos na nova Lei tender??o a afetar as promo????es dos integrantes da carreira nos pr??ximos anos. Sua aplica????o, com o horizonte no ano 2021, indicou a tend??ncia de falha na tentativa do legislador de moldar a carreira em formato piramidal, mas, outrossim, significativo e inquestion??vel avan??o em tal dire????o na compara????o com o cen??rio sem as altera????es legais, em que poderia haver uma concentra????o superior a 80% do contingente na Classe Especial. O instrumento de proje????es poder?? ser facilmente aplicado ??s demais carreiras abrangidas na Lei em foco, bastando aplicar seus dados e premissas espec??ficos.