10,400 research outputs found
Deep anisotropic dry etching of silicon microstructures by high-density plasmas
No full textThis thesis deals with the dry etching of deep anisotropic microstructures in monocrystalline silicon by high-density plasmas. High aspect ratio trenches are necessary in the fabrication of sensitive inertial devices such as accellerometers and gyroscopes. The etching of silicon in fluorine-based plasmas is isotropic. To obtain anisotropy the addition of sidewall passivation is necessary. This is achieved with both oxygen passivation at low temperatures and fluorocarbon passivation at room temperature. A quantitative approach was pursued to explain the etching mechanism. The etch results were analysed using the measured plasma species fluxes and the surface composition. Moreover, the transport of the plasma species in narrow anisotropic structures is a fundamental factor determining the etch rate and the profile evolution. The experimental methods such as the etching equipment, plasma diagnostics, surface analysis and sample preparation are described in chapter 2. Three etching processes were investigated: the cryogenic etching process with oxygen passivation at low temperatures, the Bosch process with fluorocarbon passivation at room temperature and the novel triple pulse process that was developed in our laboratory. The polymer deposition mechanism and the characteristic role of the ions are also explained. The cryogenic etching process is discussed in chapter 3. Fluorine radicals, oxygen radicals and ion bombardment are responsible for the three main sub-processes, that is, etching, sidewall passivation and depassivation of the trench bottom, respectively. Etching experiments with an extremely low ion-to-radical flux ratio were used to reveal the etching mechanism. Crystal orientation dependent etching leading to Si(111) crystal facets is observed in a surface kinetics controlled regime. By varying the plasma conditions it is possible to adjust the etching mechanism from fluorine-limited to ion-limited. Controlled etching is obtained because the etching is tuned from aspect ratio dependent in the fluorine-limited domain to aspect ratio independent in the ion-limited domain. The transport of radicals in high aspect ratio trenches is an important limiting factor and was investigated with special structures. The etch results are described by an analytic model that is based on the surface site balance of fluorine and oxygen radicals. The results are further explained with a Monte Carlo simulation model. The Bosch process is clarified in chapter 4. The anisotropy of the etched structures is controlled by balancing the etching and passivation pulse. However, the maximal obtainable aspect ratio is limited by convergence of the trench sidewalls due to excessive passivation. The maximal obtainable aspect ratio increases if the ion-to-radical flux ratio increases. The transport of ions is an important limiting factor in the depassivation of the bottom of the trench. Divergence of the ion beam leads to a reduction of the ion flux, so that the fluorocarbon passivation is insufficiently removed near the base of the sidewalls. The average ion angle was measured and correlated to the maximal obtainable aspect ratio. The Bosch process was improved at the depassivation side with the triple pulse process and at the passivation side with preferential sidewall deposition. The triple pulse process that is described in chapter 5 has the aim to improve the depassivation in deep trenches. The three main sub-processes are decoupled using a separate depassivation pulse directly after the etching and passivation pulses. The fluorocarbon passivation is efficiently removed with low-pressure, high-density, oxygen-based plasmas. The investigated plasma chemistries include O2, CO2 and SO2. The triple pulse process leads to better profile control with a straight trench bottom. However, the maximal obtainable aspect ratio is comparable to the Bosch process because a larger etch depth and a small lateral etch cancel out. The polymer deposition mechanism is treated in chapter 6 with the aim to understand the fluorocarbon passivation in deep trenches. The deposition on plane surfaces and on special structures was investigated to distinguish between the radical-induced and ion-enhanced components. A simple analytical model, which explains the main deposition characteristics, was developed. Preferential sidewall deposition is obtained for higher ion fluxes and higher bias voltages where sputtering plays an important role. In this case no fluorocarbon passivation has to be removed from the bottom of the trench. The trench profile was optimised in the Bosch process by tuning the bias voltage during etching and passivation independently. It resulted in perfectly anisotropic trenches but the maximal obtainable aspect ratio was still limited by a small lateral etch. The characteristic role of the ions in the etching mechanism is explained in chapter 7. Ion-induced etching of both SiC in a SF6-O2 plasma and Si in a Cl2 plasma were investigated. The impact of the ions on the profile evolution can be examined more explicitly because spontaneous chemical reactions are absent for these plasma-material systems. The etching mechanism varies from fluorine-limited to ion-limited depending on the radical-to-ion flux ratio. Microtrenches are observed for an ion-limited etching mechanism. Fluorine-limited SiC etching is aspect ratio dependent in contrast to ion-limited SiC etching, which is aspect ratio independent. The etching of high aspect ratio SiC structures is limited by the positive sidewall taper. This is presumably caused by insufficient removal of the thin fluorocarbon layer on the surface. Si etching in a Cl2 plasma is always aspect ratio independent in contrast to SiC etching because of the low reaction probability. The conclusions and recommendations of this thesis are given in chapter 8.Applied Science
The Private Cost of Long-Term Care in Canada: Where You Live Matters
No full textCanadians expect the same access to health care whether they are rich or poor, and wherever they live, often without direct charge at the point of service. However, we find that the private cost of long-term care differs greatly across the country, and within provinces, we find substantial variation, depending on income level, marital status, and, in Quebec alone, on assets owned. A non-married person with average income would pay more than twice as much in the Atlantic provinces as in Quebec, while a couple with one in care would pay almost four times as much in Newfoundland as in Alberta.long-term care, private cost
The use of MPM to estimate the behaviour of rigid structures during landslides
No full textIn geotechnical engineering, proper design of retaining structures is of great importance, since failure of these structures can lead to catastrophic consequences. Nowadays, the finite element method is seen as a reliable numerical technique to analyze soil behaviour and is widely used to assess the interaction be-tween soil and rigid structures. However, a disadvantage of this method is the difficulty of simulating contact between separate bodies. Because of this, the event of a slope failing and colliding with a rigid body cannot be analyzed, so that the additional forces acting against the rigid body caused by the motion of the ground are neglected. With the recent development of the material point method (MPM), this limitation has been over-come and problems involving large deformation and multiple bodies in contact can be analyzed. In this paper, the effect of a landslide colliding with a rigid wall has been studied, and multiple initial conditions have been considered in order to identify the critical case.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Geo-engineeringGeoscience and Engineerin
Interruptions and failure in higher education: evidence from ISEG-UTL
No full textAbstract Failure in Higher Education (HE) is the outcome of multiple time-dependent determinants. Interruptions in student’s individual school trajectories are one of them and that’s why research on this topic has been attracting much attention these days. From an individual point of view, it is expected that interruptions in school trajectory, whatever the reason, influence success in undergraduate programs either this success is measured by time required to obtain a degree, the scores obtained in some more “critical” subjects in these programs or the number of enrolment registrations. Nevertheless, performing a paid job during interruption may in given circumstances positively affect academic success on account of the combination between learning and occupational experience The study of interruptions’ impact on failure in HE is also important to help Education institutions at all grades to think about changes in organisational procedures, class timetables, syllabuses contents or teachers recruitment and training in order to fight this problem. From a social and political point of view, interruptions are also a matter of concern since failure in HE affects individual’s lifelong learning opportunities, distort public funding allocation efficiency to HE institutions and create lag effects in the desired/planned outcomes of HE production functions. So, research on the impact of interruptions on failure in HE is important to support policy measures definition related to the articulation between Upper Secondary and HE programs. In previous research we have shed some light into the determinants of failure in 1st year of HE studies using longitudinal data on ISEG’s undergraduate students. A further insight into this database revealed the existence of a meaningful number of students with interruptions in their school trajectories either in the transition from Upper Secondary to HE or within HE programs. In this paper our major concern is to find some evidence on interruptions effects on HE failure among ISEG students using a life cycle approach with control group. We are interested in knowing whether the above mentioned effects are gender and/or specific graduation program neutral. We also want to search if work experience may counter balance the effect of interruption on academic success. We hope to be able to derive some useful recommendations to address policy making in the fields of pedagogic methodologies in HE, articulation between academic and occupational learning in the framework of Bologna Chart and public funding/fellowship policies in HE.Key words: Portuguese Higher Education; Interruption; Failure; Adult Students; Bologna Chart; Policy Implications
Frugivoria De Larvas De Neosilba Mcalpine (diptera, Lonchaeidae) Sobre Psittacanthus Plagiophyllus Eichler (santalales, Loranthaceae) No Sudoeste De Mato Grosso Do Sul, Brasil [larval Frugivory Of Neosilba Mcalpine (diptera, Lonchaeidae) On Psittacanthus Plagiophyllus Eichler (santalales, Loranthaceae) In Southwestern Mato Grosso Do Sul State, Brazil]
No full textLoranthaceae are hemiparasite plants with worldwide distribuition, represented in Brazil by six genera. The most important are Phthirusa, Psittacanthus and Struthanthus that parasitize a great diversity of host plants. This paper evaluated the occurrence and the seasonal fluctuation of flies infesting the fruits of Psittacanthus plagiophyllus in the municipalities of Anastácio, Aquidauana and Miranda, Mato Grosso do Sul, Brazil, where mistletoes are widespread. The samples were taken from June 1998 to July 2000 to obtain the hosts and its associated insects. All insects were reared until adult stage, and it were obtained 1,522 adults of Neosilba spp., of which 612 males were identified at species level: Neosilba bifida Strikis & Prado (6 specimens), N. certa (Walker) (26 specimens), N. pendula (Bezzi) (16 specimens), N. zadolicha McAlpine & Steyskal (4 specimens) and two different species, morphotype MSP1 (478 specimens) and morphotype 4 (82 specimens). The period of highest infestation by Neosilba spp. occurred during August 1998 and 1999, and morphotype MSP1 was significantly more abundant than all other species. The species morphotype 4 was the second most abundant, differing significantly from Neosilba zadolicha. Neosilba was the only genus of frugivorous fly infesting fruits of P. plagiophyllus and behaves as primary invader in this host. © 2009 Sociedade Brasileira De Entomologia.532272277Aguiar-Menezes, E.L., Souza, S.A.S., Santos, C.M.A., Resende, A.L.S., Strikis, P.C., Costa, J.R., Ricci, M.S.F., Susceptibilidade de seis cultivares de Café Arábica às moscas-das-frutas (Diptera: Tephritoidea) em sistema orgânico com e sem arborização em Valença (2007) RJ. Neotropical Entomology, 36, pp. 268-273Araújo, E.L., Zucchi, R.A., Hospedeiros e níveis de infestação de Neosilba pendula (Bezzi) (Diptera: Lonchaeidae) na região de Mossoró/Assu (2002) RN. Arquivos do Instituto Biológico, 69, pp. 91-94Ayres, M., Ayres M., Jr., Ayres, D.L., Santos, A.A.S., (2005) Bio Estat, , 4.0: aplicações estatísticas nas áreas das ciências Biológicas e Médicas. Belém-PABarros, M.G., Rico-Gray, V., Díaz-Castelazo, C., (2001) Sincronia de floração entre Lantana camara L. (Verbenaceae) e Psittacanthus calyculatus, 57, pp. 1-14. , (DC.) G. Don (Loranthaceae) ocorrentes em dunas de La Mancha, Veracruz, México. Acta Botanica MexicanaBittencourt, M.A.L., Silva, A.C.M., Bomfim, Z.V., Silva, V.E.S., Araújo, E.L., Strikis, P.C., Novos registros de espécies de Neosilba (Diptera: Lonchaeidae) na Bahia (2006) Brazil. Neotropical Entomology, 35, pp. 282-283Caires, C.S., Proença, C.E.B., (2005) Viscaceae, 4, pp. 41-76. , T. B. Cavalcanti & A. E. Ramos (eds.). Flora do Distrito Federal, Brasil. Embrapa Recursos Genéticos e Biotecnologia, BrasíliaCampos, D.F., Lista de los géneros de avispas parasitóides Braconidae (Hymenoptera: Ichneumonoidea) de la Región Neotropical (2001) Biota Colombiana, 2, pp. 193-232Eichler, A.G., (1868) Loranthaceae, 5 (2), pp. 1-135. , C. F. P. Martius (eds.). Flora BrasiliensisGemtchújnicov, I.D., (1976) Manual de taxonomia vegetal: plantas de interesse econômico, p. 368. , Ed. Agronômica Ceres, São PauloGuimarães, J.A., Zucchi, R.A., Diaz, N.B., Souza-Filho, M.F., Uchôa-Fernandes, M.A., Espécies de Eucoilinae (Hymenoptera: Cynipoidea: Figitidae) parasitóides de larvas frugívoras (Diptera: Tephritidae e Lonchaeidae) no Brasil (1999) Anais da Sociedade Entomológica do Brasil, 28, pp. 263-273Haigh, S.L., Saltcedar (Tamarix ramosissima), an uncommon host for desert mistletoe (Phoradendron californicum) (1996) Great Basin Naturalist, 56, pp. 186-187Joly, A.B., (1985) Botânica: Introdução à taxonomia vegetal, p. 777. , 7a ed. São Paulo. Ed. NacionalLourenção, A.L., Lorenzi, J.O., Ambrosano, G.M.B., Comportamento de clones de mandioca em relação a infestação por Neosilba perezi (Romero & Ruppell) (Diptera: Lonchaeidae) (1996) Scientia Agricola, 53, pp. 304-309Malavasi, A., Zucchi, R.A., (2000) Moscas-das-frutas de Importância Econômica no Brasil, p. 327. , conhecimento básico e aplicado. Ribeirão Preto: Holos.(eds)Martinez del Rio, C., Silva, A., Medel, R., Hourdequin, M., Seed dispersers as disease vectors: bird transmission of mistletoe seeds to plant hosts (1996) Ecology, 77, pp. 912-921McAlpine, J.F., Steyskal, G.C., A revision of Neosilba McAlpine with a key to the world genera of Lonchaeidae (Diptera) (1982) Canadian Entomologist, 114, pp. 105-137Pott, A.P.V.J., (1994) Plantas do Pantanal, p. 320. , Brasília, EMBRAPARaga, A., Machado, R.A., Souza-Filho, M.F., Sato, M.E., Siloto, R.C., Tephritoidea (Diptera) species from Myrtaceae fruits in the State of São Paulo (2005) Brazil. Entomotropica, 20, pp. 11-14Rizzini, C.T., (1978) Loranthaceae, 29, pp. 23-36. , The Botany of the Guayana Highland, Part X. B. Maguire (Ed.). Memories of New York Botanical GardenRizzini, C.T., Flora da Serra do Cipó (1995) Minas Gerais: Loranthaceae. Boletim do Instituto de Botânica, 14, pp. 207-221Santos, W.S., Carvalho, C.A.L., Marques, O.M., Registro de Neosilba zadolicha McAlpine & Steyskal (Diptera: Lonchaeidae) em Umbu-Cajá (Anacardiaceae) (2004) Neotropical Entomology, 33, pp. 653-654Silva, F.F., Meirelles, R.N., Redaelli, L.R., Soglio, F.K.D., Diversity of flies (Diptera: Tephritidae and Lonchaeidae) in organic citrus orchards in the Vale do Rio Caí, Rio Grande do Sul (2006) Southern Brazil. Neotropical Entomology, 35, pp. 666-670Strikis, P.C., Prado, A.P., (2005) A new species of the genus Neosilba (Diptera: Lonchaeidae), 828, pp. 1-4. , ZootaxaUchôa-Fernandes, M.A., Oliveira, I., Molina, R.M.S., Zucchi, R.A., Species diversity of frugivorous flies (Diptera: Tephritoidea) from hosts in the Cerrado of the State of Mato Grosso do Sul (2002) Brazil. Neotropical Entomology, 31, pp. 515-524Uchôa-Fernandes, M.A., Zucchi, R.A., Metodología de colecta de Tephritidae y Lonchaeidae frugívoros (Diptera: Tephritoidea) y sus parasitoides (Hymenoptera) (1999) Anais da Sociedade Entomológica do Brasil, 28, pp. 601-610Uchôa-Fernandes, M.A., Zucchi, R.A., Mato Grosso e Mato Grosso do Sul (2000) Moscas-das-frutas de importância econômica no Brasil: conhecimento básico e aplicado, 327, pp. 241-245. , A. Malavasi, R. A. Zucchi (eds.), Ribeirão Preto: HolosVenturelli, M., Estudos sobre Struthanthus vulgaris Mart.: anatomia do fruto e semente e aspectos de germinação, crescimento e desenvolvimento (1981) Revista Brasileira de Botânica, 4, pp. 131-147Vilela, E.F., Zucchi, R.A., Cantor, F., (2001) Histórico e impacto das pragas introduzidas no Brasil, p. 173. , (eds.), Ribeirão Preto: HolosZucchi, R.A., Taxonomia (2000) Moscas-das-frutas de importância econômica no Brasil: conhecimento básico e aplicado, 327, pp. 13-24. , A. Malavasi, R. A. Zucchi (eds.), Ribeirão Preto: HolosZucchi, R.A., Malavasi, A., Nascimento, A.S., Walder, J.M.M., (2004) Prejuízos das moscas-das-frutas na exportação de citros, 2, pp. 73-77. , Visão Agrícol
Assessment of Models for Near Wall Behavior and Swirling Flows in Nuclear Reactor Sub-system Simulations
No full textAccurate simulation of turbulence remains one of the most challenging problems in nuclear reactor analysis and design. Due to limitations in computing resources, Reynolds averaged Navier Stokes models (RANS) continue to play an important role in reactor simulations. The Consortium for advanced simulations of light water reactors (CASL) is a Department of Energy technology hub that is investing in research and developmentof a state-of-the-art computational fluid dynamics capabilityto meet the challenges of turbulent simulation of nuclear reactors. In this presentation, we assess several RANS eddy viscosity models appropriate for single-phase incompressible turbulent flows. Specifically, we compare the single equation Splalart-Allmaras to several variations of the model. The assessment takes into consideration elements of full system reactor cores such as complex geometries, heterogeneous meshes, swirling flow, near wall flow behavior, heat transfer and robustness issues. The goal of this strategically oriented assessment is to provide an accurate and robust turbulent simulation capability for the CASL community. Metrics of performance will be constructed by comparing different models on a strategically chosen set of problems that represent reactor core sub-systems
O zarubežnoj dejatel'nosti professora M.A. Kumaxova
No full textOn professor M.A. Kumakhov's work and research abroad (in Russian)
Professor Mukhadin A. Kumakhov and the author collaborated in the area of Northwest Caucasian languages under a period from 1991 to 2008. The fruitful collaboration at Lund and Malmö universities resulted in three joint monographs and a number of articles, which is outlined in the article. Mukhadin A. Kumakhov became Honorary Doctor of the Philosophical Faculty of Lund University in 1998
Bringing clouds into our lab!: The influence of turbulence on early stage rain droplets
No full textWe are investigating a droplet-laden flow in an air-filled turbulence chamber, forced by speaker-driven air jets. The speakers are running in a random manner; yet they allow us to control and define the statistics of the turbulence. We study the motion of droplets with tunable size in a turbulent flow, mimicking the early stages of raindrop formation. 3D Particle Tracking Velocimetry (PTV) is chosen as the experimental method to track the droplets and collect data for statistical analysis. Thereby it is possible to study the spatial distribution of the droplets in turbulence using the so-called Radial Distribution Function (RDF), a statistical measure to quantify the clustering of particles. Additionally, this technique allows us to measure velocity statistics of the droplets and the influence of the turbulence on droplet trajectories, both individually and collectively. In this contribution, we will present velocity statistics of the droplets and quantify their clustering using the RDF for different turbulence conditions
Process simulation: NdFeB permanent magnet production
No full textThis file contains an HSC model for NdFeB permanent magnet production, from ore processing to magnet production and two possible recycling routes. Data to build the model is found in key literature studies and from internal project data obtained by the various partners in four work packages (rare earth oxide separation, reduction and purification, alloy design, and powder magnet production).
The model was used to perform a resource efficiency, including exergy, and environmental impact (LCA) evaluation of the life cycle of a NdFeB permanent magnet produced from primary and secondary resources. This work has been submitted to JOM, in its special edition “Thermodynamic modeling of sustainable non-ferrous metals production” and has been accepted for publication with a digital object identifier (DOI): https://doi.org/10.1007/s11837-020-04185-6. Detailed information about the literature sources used for developing the model can be found in the original research paper. The model was built using HSC Chemistry version 9.9 (https://www.outotec.com/products-and-services/technologies/digital-solutions/hsc-chemistry/).Funding agency: German Federal Ministry of Education and Research (BMBF).
Grant number / name: REGINA - Rare Earth Global Industry and New Applications - project (funding number 033R185B), promoted within the Framework Program FONA - Forschung für nachhaltige Entwicklung, under the funding priority CLIENT II - International Partnerships for Sustainable Innovation.
Related publication: Fernandes, I.B., Abadías Llamas, A. & Reuter, M.A. Simulation-Based Exergetic Analysis of NdFeB Permanent Magnet Production to Understand Large Systems. JOM 72, 2754–2769 (2020). https://doi.org/10.1007/s11837-020-04185-
The Story about the constructed SARS COV-2 Virus - A Review of three Research Groups
No full textAbstract
A literature research on synthetic recombinant SARS Coronavirus was made to answer two questions. Is the SARS CoV-2 virus designed in a laboratory? And why has the SARS CoV-2 such a high mutation rate? A total of 12 research articles, 2 reviews and 10 experimental studies were attributed to three Research Groups, the Wadsworth Center New York, the Vanderbilt Medical Center, and the Chapel Hill North Carolina. The research papers were published between 1991 and 2014. All 12 research papers reported the successful construction of recombinant SARS Coronaviruses based on RNA reverse genetic and molecular techniques. The Research group from the Medical Center at Vanderbilt University proved how an engineered SARS Coronavirus with an impaired Exonuclease resulted in a progeny virus with high mutation rate. Furthermore, the review showed that a zoonotic-human transmission was just possible with specific genetic manipulations at the SARS CoV virus genome through selection of virus species for recombination, and targeted manipulation at non-structural virus domains. But importantly, the studies showed that a SARS Coronavirus cross-species infection such as between zoonotic and humans or between different animal species without the exchange of the virus spike protein domain with the host-specific receptor-binding domain (RBD) and additional point mutations was not possible. Therefore, the SARS CoV-2 was deliberately constructed to overcome the receptor limiting factor for animal-human infection. Interestingly, the review revealed that the study purpose of constructed recombinant SARS CoV changed from the scientific research point of view to vaccine production and development. Competing interests for all reviewed studies by grants from private investors such as the Gates Foundation and vaccine production companies were part of the discussion. Keywords: SARS CoV-2, Covid19, Spike protein, gene sequencing, Vanderbilt University, University North Carolina, Wadsworth Research Center, New York Health Department, Coronavirus, Bill & Melinda Gates Foundation, WHO, Pfizer, Merck, Novartis, AlphaVaxThe author declares no competing interests.
[email protected]
- …
