Search results for "vacuum"
showing 10 items of 352 documents
Vircator Technologies Comparison and Novel Anode Analysis
2021
High Power Microwave (HPM) sources are widely used as signal sources in radar, jammer, and Counter Improvised Explosive Devices (CIED). Such devices usually are heavy and bulky, characteristics that are in conflict with the small weight and power (SWaP) approach so that it is practically impossible to mount such HPMs on several platforms with reduced spaces (e.g., avionic, UAVs). During the last century, several devices have been proposed, all of them heavy due to the components that they need such as the magnetic material of the Magnetron, Klystron, or Gyrotron. Considering the HPM sources for pulsed applications, the VIRtual CAThode oscillatOR (Vircator) represents the best candidate due …
Mechanical behavior of carbon/flax hybrid composites for structural applications
2012
In this work, the influence of an unidirectional carbon fabric layer on the mechanical performances of bidirectional flax fabric/epoxy composites used for structural applications was studied. Two different bidirectional flax fabrics were used to produce flax fabric reinforced plastic (FFRP) laminates by a vacuum bagging process: one is normally used to make curtains; the other, heavier and more expensive than the previous one, is usually used as reinforcement in composite structures. In order to realize hybrid structures starting from FFRP, an unidirectional UHM carbon fabric was used to replace a bidirectional flax fabric. Tensile and three-point bending tests were performed to evaluate t…
Underestimation of atypical lobular hyperplasia and lobular carcinoma in situ at stereotaxic 11-gauge vacuum-assisted breast biopsy
2013
The aims of this study are to determine the frequency of diagnosis of atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS) at stereotaxic-guided 11-gauge vacuum-assisted breast biopsy (VABB) and to assess the rate of underestimation of these at subsequent surgical excision and follow-up. Moreover, we aimed to define clinical, radiological and histological features of nonpalpable lesions in core biopsies that predict the lesion upgrade. Retrospective review of 11-gauge VABB was performed to identify the underestimation rate of nonpalpable lesions diagnosed as ALH or LCIS at VABB. Thirteen cases of ALH and 36 cases of LCIS were sent to surgery, 29 cases of ALH and 14 cases…
Evaluation of innovative thermal insulation systems for a sustainable envelope
2017
La memoria presenta i risultati ottenuti su sistemi di isolamento termico per l’involucro edilizio. Si presentano i risultati ottenuti tramite simulazioni informatiche che hanno consentito di verificare e ottimizzare la trasmissione del calore attraverso un sistema sottovuoto in vetro per le facciate trasparenti. Inoltre la possibilità offerta dal riciclo del materiale di scarto della potatura dell’Opunthia Ficus Indica (fichi d’india) che,opportunamente trattato ha permesso di ottenere un materiale isolante (Brevetto n. 1402131), in forma di pannello o in grani sfusi, (valori di coibenza termica 0.0710.057 W/mK). The paper presents the results of the research on thermal insulation systems…
First Results of the Testing of the Liquid Gallium Jet Limiter Concept for ISTTOK
2006
The use of liquid metals as plasma facing components in tokamaks has recently experienced a renewed interest stimulated by their advantages to the development of a fusion reactor. Liquid metals have been proposed to solve problems related to the erosion and neutronic activation of solid walls submitted to high power loads allowing an efficient heat exhaustion from fusion devices. Presently the most promising materials are Lithium and Gallium. ISTTOK, a small size tokamak, will be used to test the behavior of a liquid Gallium jet in the vacuum chamber and its influence on the plasma. This paper presents a description of the conceived setup as well as experimental results. The liquid Gallium …
The carrier-loaded helium-jet transport method
1974
Abstract The suitability of commercial helium loaded with small amounts of different gases or vapors for the transport of radioactive reaction products over distances of several meters has been investigated experimentally. Negative results were obtained with gaseous carriers. Transport efficiencies of 50 to 100% were obtained with carrier vapors. The vapor appears to form droplets in the system. The recoils are adsorbed physically by the droplets and carried with them through a capillary. There appears to be an active mechanism that forces the heavy constituents to the centre of the capillary cross section. The heavy constituents emerge from the capillary as a very narrow beam. Collection o…
Kompakti automatisoitu laser-ionisointijärjestelmä
2011
In an experimental nuclear physics off-line systems are often used in situations where acceleration energies are relatively small. Main benefits are low price and meager radiated laboratory enviroments. In this master’s thesis I discuss mostly about automation which was used in our off-line system. The system was built at the Ion Guide Separator On-Line facility (IGISOL) in Jyväskylä University. The automation set up was made with the Phoenix Contacts inline terminals, which were programmed by using the Labview program. The system consists of thermistor, skimmer handling, mirror handling, gasline parts per billion (ppb) mixing and quadrupole mass spectrometer measurement. There were major p…
Optogenetically blocking sharp wave ripple events in sleep does not interfere with the formation of stable spatial representation in the CA1 area of …
2016
During hippocampal sharp wave/ripple (SWR) events, previously occurring, sensory inputdriven neuronal firing patterns are replayed. Such replay is thought to be important for plasticity-related processes and consolidation of memory traces. It has previously been shown that the electrical stimulation-induced disruption of SWR events interferes with learning in rodents in different experimental paradigms. On the other hand, the cognitive map theory posits that the plastic changes of the firing of hippocampal place cells constitute the electrophysiological counterpart of the spatial learning, observable at the behavioral level. Therefore, we tested whether intact SWR events occurring during th…
Why does vacuum drive to the loading of halloysite nanotubes? The key role of water confinement.
2019
The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the…
Comparison of speed-vacuum method and heat-drying method to measure brain water content of small brain samples
2016
Abstract Background A reliable measurement of brain water content (wet-to-dry ratio) is an important prerequisite for conducting research on mechanisms of brain edema formation. The conventionally used oven-drying method suffers from several limitations, especially in small samples. A technically demanding and time-consuming alternative is freeze-drying. New method Centrifugal vacuum concentrators (e.g. SpeedVac/speed-vacuum drying) are a combination of vacuum-drying and centrifugation, used to reduce the boiling temperature. These concentrators have the key advantages of improving the freeze-drying speed and maintaining the integrity of dried samples, thus, allowing e.g. DNA analyses. In t…