136 research outputs found
Charge Carrier Transport in Silicon-Germanium Heterojunction Bipolar Transistors
No full textElectrical Engineering, Mathematics and Computer Scienc
Nozzlestroming in het gritstraalproces
No full textHet gritstraalproces is een verfverwijderingstechniek die gebruik maakt van kleine deeltjes die met perslucht versneld worden. Een onderdeel van dit proces is de versnelling van lucht en grit in de spuitmond of nozzle. Dit afstudeeronderzoek heeft zich op dat onderdeel gericht. Het doel van het onderzoek is tweeledig: enerzijds verificatie van het bestaande model SIMNOZ voor nozzlestroming en anderzijds optimalisatie van de nozzleparameters. Voor de verificatie zijn metingen uitgevoerd aan de snelheden van uittredende deeltjes m.b.v. Laser-Doppler Anemometrie. De wandtemperatuur van de nozzle is bepaald met thermokoppels, terwijl de druk bepaald is met een differentiële druksensor. Voor de optimalisatie zijn criteria en parameters geleverd. De Laser-Dopplermetingen zijn uitgevoerd aan een Tetrabor 6 mm nozzle en met WS-170 staalshot bij een nozzledruk van 5 tot ruim 7 bar en een beladingsgraad van 1 tot ruim 5 kg grit / kg lucht. De gemeten snelheden blijken goed overeen te komen met de uitkomsten van SIMNOZ. Wel zijn er tweedimensionale profielen waargenomen. De wandtemperatuur komt echter niet overeen met de temperatuur van de stroming. De reden hiervoor is warmteproductie door wandwrijving. Het gemeten drukprofiel komt goed overeen met de voorspellingen. Enige discrepantie wordt veroorzaakt door frictie en schok-grenslaaginteractie. Optimalisatie van het gritstraalproces kan gekoppeld worden aan de snelheden aan de nozzle-uitlaat en het gritdebiet. Hierbij blijkt een nozzle beter te werken naarmate hij langer is. Daarbij is het gebruik van licht grit voordelig. Optimalisatie is pas echt mogelijk indien een winstfunctie gedefinieerd kan worden. Daarbij moeten tevens de invloed van de jet en inslag van deeltjes bekend zijn.Kramers Laboratorium voor Fysische TechnologieApplied Science
The minimisation of copper losses during iron and aluminium precipitation from zinc leach liquors
No full textThe basis for this research project was that copper is lost in the Leaching Plant of the Nyrstar Budel zinc smelter. In the section of the Leaching Plant copper is lost, iron and aluminium are precipitated. Sampling of this process showed that the removal of copper from the solution is a function of pH and is mainly linked to the removal of aluminium. Tests with process fluids at stable pH levels showed that ferric ion and aluminium are mainly removed as jarosites at pH = 2 and pH =2,5. Copper is also removed at those pH values and is thus precipitated in jarosite form. This is the actual loss of copper. At pH = 3 and 3,5 more aluminium was removed, but now also in the form of aluminium hydroxides. It was found that copper is adsorbed onto these hydroxides and hence more copper is removed from the solution. At these pH values also jarosites are formed which permanently remove copper, but it is assumed that the adsorption onto aluminium hydroxides prevails. The result of the adsorption of copper onto these hydroxides is that it eventually returns to the FeP in which it has another chance to get lost to jarosites. Hence the only way to prevent copper from being lost is to prevent copper from reaching the FeP. One way to prevent copper from reaching the FeP is not using calcine to neutralise the acid from the SiHALO, but with alternative neutralising agents which do not contain copper. Another way is to prevent copper from leaving the SiHAL. Copper cementation is a method which can totally remove the copper dissolved in the SiHALO. Copper cementation with iron was found to yield the highest recovery and is thus also the most cost effective. Key words: Copper incorporation, jarosite, alunite, copper cementationResource EngineeringCivil Engineering and Geoscience
The green-leaved variant of Eucalyptus largiflorens: a story involving hybridization and observant local people
No full textEucalyptus largiflorens (Black Box) is the most common tree in the Chowilla anabranch system on the Murray River floodplain. It typically has dull, glaucous, grey-green leaves. Occasional trees with smaller, glossy green leaves (Green Box) occur scattered amongst the Black Box. In areas with increasing salinity, they usually appear much healthier than adjacent, normal Black Box trees. Green Box plants are intermediate between normal Eucalyptus largiflorens plants and Eucalyptus gracilis plants in many morphological and allozyme characters, strongly suggesting that they are hybrids between those species. Green Box plants tolerate salinity better and use water more conservatively than normal Black Box plants, traits that they have probably inherited from Eucalyptus gracilis. In 1994, the Botanic Gardens of Adelaide used tissue culture and micropropagation to produce nearly 9,000 cloned Green Box plants which were planted out on Riverland floodplains. Since the 1990s, the high cost of producing clonal plants has meant that no further such plantings have occurred. Because Green Box plants can be a considerable distance from the nearest plants of one putative parent (Eucalyptus gracilis), more detailed studies could contribute to the existing work on such phantom hybrids
Cancer Immunotherapy Getting Brainy: Visualizing the Distinctive CNS Metastatic Niche to Illuminate Therapeutic Resistance
No full textThe advent of cancer immunotherapy (CIT) and its success in treating primary and metastatic cancer may offer substantially improved outcomes for patients. Despite recent advancements, many malignancies remain resistant to CIT, among which are brain metastases, a particularly virulent disease with no apparent cure. The immunologically unique niche of the brain has prompted compelling new questions in immuno-oncology such as the effects of tissue-specific differences in immune response, heterogeneity between primary tumors and distant metastases, and the role of spatiotemporal dynamics in shaping an effective anti-tumor immune response. Current methods to examine the immunobiology of metastases in the brain are constrained by tissue processing methods that limit spatial data collection, omit dynamic information, and cannot recapitulate the heterogeneity of the tumor microenvironment. In the current review, we describe how high-resolution, live imaging tools, particularly intravital microscopy (IVM), are instrumental in answering these questions. IVM of pre-clinical cancer models enables short- and long-term observations of critical immunobiology and metastatic growth phenomena to potentially generate revolutionary insights into the spatiotemporal dynamics of brain metastasis, interactions of CIT with immune elements therein, and influence of chemo- and radiotherapy. We describe the utility of IVM to study brain metastasis in mice by tracking the migration and growth of fluorescently-labeled cells, including cancer cells and immune subsets, while monitoring the physical environment within optical windows using imaging dyes and other signal generation mechanisms to illuminate angiogenesis, hypoxia, and/or CIT drug expression within the metastatic niche. Our review summarizes the current knowledge regarding brain metastases and the immune milieu, presents the current status of CIT and its prospects in targeting brain metastases to circumvent therapeutic resistance, and proposes avenues to utilize IVM to study CIT drug delivery and therapeutic efficacy in preclinical models that will ultimately facilitate novel drug discovery and innovative combination therapies
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