Letteratura scientifica selezionata sul tema "MAX phase synthesis"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "MAX phase synthesis".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "MAX phase synthesis"
1
Arlashkin, I. E., S. N. Perevislov e V. L. Stolyarova. "Synthesis and study of dense materials in the Zr–Al–C system". Журнал общей химии 93, n. 4 (15 aprile 2023): 622–27. http://dx.doi.org/10.31857/s0044460x23040145.
Testo completoAbstract (sommario):
The initial powders Zr, Al, C and Zr, Al, Sc were used for the synthesis of MAX phases of the composition Zr2AlC and Zr3AlC2. The highest content (50.4 vol%) of the MAX phase Zr3AlC2 was obtained using the initial powders Zr/Al/Zr in the ratio of components 1:1.5:2 with the addition of 5 vol% Al. The optimal temperature for the synthesis of a material based on the MAX phase Zr2AlC is 1525° C, a material based on Zr3AlC2 is 1575°C. The structure of the synthesized MAX materials obtained includes elongated grains of the composition Zr2AlC and Zr3AlC2, which determines their high strength. Zirconium carbide, as an intermediate phase, is always present in the final products. Due to the large evaporation of aluminum, the ZrO2 phase is also present in the synthesis products. Excess aluminum contributes to the greatest formation of Zr2AlC and Zr3AlC2 phases during synthesis.
2
Gurin, Mikhail S., Dmitry S. Shtarev, Alexander V. Syuy, Gleb I. Tselikov, Oleg O. Shichalin e Victor V. Krishtop. "FEATURES OF THE SYNTHESIS OF MAX-PHASES TixAlC1-x BY SPARK PLASMA SINTERING". Transactions of the Kоla Science Centre of RAS. Series: Engineering Sciences 3, n. 3/2023 (14 aprile 2023): 97–101. http://dx.doi.org/10.37614/2949-1215.2023.14.3.017.
Testo completoAbstract (sommario):
The results of the synthesis of MAX-phases TixAlC1-x by the method of spark plasma sintering are presented. It is shown that the purity of the synthesized composition depends on the regime of spark plasma sintering. The purity of the MAX phase was 84 %. The material was characterized by XRD. The optimal conditions for the synthesis of the MAX phase 211 were determined.
3
Kovalev, D. Yu, M. A. Luginina e A. E. Sytschev. "Reaction synthesis of Ti2AlN MAX-phase". Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Universitiesʹ Proceedings. Powder Metallurgy аnd Functional Coatings), n. 2 (1 gennaio 2016): 41–46. http://dx.doi.org/10.17073/1997-308x-2016-2-41-46.
Testo completo
4
Kovalev, I. D., P. A. Miloserdov, V. A. Gorshkov e D. Yu Kovalev. "Nb2AlC MAX phase synthesis by SHS metallurgy". Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Universitiesʹ Proceedings. Powder Metallurgy аnd Functional Coatings), n. 2 (19 giugno 2019): 42–48. http://dx.doi.org/10.17073/1997-308x-2019-2-42-48.
Testo completoAbstract (sommario):
A cast material based on the Nb2AlC MAX phase was obtained by SHS metallurgy. Synthesis was carried out from the Nb2O5– Al–C mixture with a high-energy CaO2–Al additive. Thermodynamic calculation results correlate well with experimental data. It was found that the CaO2–Al additive content has a substantial effect on the thermodynamic parameters and phase composition of the final product. It was shown that synthesis from the specified mixtures passed in a stationary mode with steady combustion wave. Increasing the additive content leads to increasing combustion rate (from 6 to 12 mm/s), and product yield to ingot increases (from 30 to 47 %) up to 15 wt.% of the additive and then decreases. Variation in the composition of initial mixtures can provide a significant impact on both synthesis parameters and final product phase composition. Optimal conditions of material synthesis to ensure maximum yield of the Nb2AlC MAX phase in the ingot composition were determined. The liquid phase lifetime during synthesis is a determining factor influencing the Nb2AlC content in the final product. It is shown that the maximum Nb2AlC phase amount (67 wt.%) is reached with 15 wt.% of the high-energy additive in the initial charge.
5
Kovalev, D. Yu, M. A. Luginina e A. E. Sytschev. "Reaction synthesis of the Ti2AlN MAX-phase". Russian Journal of Non-Ferrous Metals 58, n. 3 (maggio 2017): 303–7. http://dx.doi.org/10.3103/s1067821217030087.
Testo completo
6
El Saeed, M. A., F. A. Deorsola e R. M. Rashad. "Optimization of the Ti3SiC2 MAX phase synthesis". International Journal of Refractory Metals and Hard Materials 35 (novembre 2012): 127–31. http://dx.doi.org/10.1016/j.ijrmhm.2012.05.001.
Testo completo
7
Amosov, Aleksandr P., Evgeniy I. Latukhin, P. A. Petrov, E. A. Amosov, Vladislav A. Novikov e A. Yu Illarionov. "Self-Propagating High-Temperature Synthesis of Boron-Containing MAX-Phase". Key Engineering Materials 746 (luglio 2017): 207–13. http://dx.doi.org/10.4028/www.scientific.net/kem.746.207.
Testo completoAbstract (sommario):
An attempt was made to obtain boron-containing MAX-phase by the process of self-propagating high-temperature synthesis (SHS) of Ti3AlC2, replacing some carbon atoms by boron atoms. This was conducted by burning powder mixtures (charges) of the composition 3Ti+2Al+2((1-x)C+xB), where x is the fraction of boron atoms (0.10, 0.15, 0.25, 0.50, 0.75, 0.90), replacing the carbon atoms. X-ray diffraction analysis of the products of combustion have shown that the replacement of carbon with boron to half of the content of carbon atoms in the charge (x=0.10-0.50), does not change the phase composition of the products, including Ti3AlC2 and TiC, but leads to a shift of the peaks of these phases in the diffraction pattern in the direction of smaller angles. When replacing more than half of the carbon atoms with the boron (x=0.75 and 0.90), the peaks of titanium carbide and MAX-phase are not observed, and the XRD peaks appear of the titanium borides TiB and TiB2, and intermetallic compound Al3Ti. Photomicrographs obtained with an electron microscope show that the SHS products synthesized from the charge with replacing up to half of the carbon atoms with the boron represent plates with a thickness of about 1 μm typical for MAX-phases, but rounded particles of borides and intermetallic compound of titanium appear at a higher boron content. Based on these results, it is concluded that replacement of a part (up to 50%) of the carbon atoms with boron atoms in the SHS charge 3Ti+2Al+2C leads to the synthesis of boron-containing MAX-phase based on the crystal lattice of Ti3AlC2.
8
Kovalev, I. D., P. A. Miloserdov, V. A. Gorshkov e D. Yu Kovalev. "Synthesis of Nb2AlC MAX Phase by SHS Metallurgy". Russian Journal of Non-Ferrous Metals 61, n. 1 (gennaio 2020): 126–31. http://dx.doi.org/10.3103/s1067821220010083.
Testo completo
9
Fattahi, Mehdi, e Majid Zarezadeh Mehrizi. "Formation mechanism for synthesis of Ti3SnC2 MAX phase". Materials Today Communications 25 (dicembre 2020): 101623. http://dx.doi.org/10.1016/j.mtcomm.2020.101623.
Testo completo
10
Mane, Rahul B., Ampolu Haribabu e Bharat B. Panigrahi. "Synthesis and sintering of Ti3GeC2 MAX phase powders". Ceramics International 44, n. 1 (gennaio 2018): 890–93. http://dx.doi.org/10.1016/j.ceramint.2017.10.017.
Testo completoTesi sul tema "MAX phase synthesis"
1
Mockutė, Aurelija. "Synthesis and Characterization of New MAX Phase Alloys". Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104829.
Testo completoAbstract (sommario):
This Thesis explores synthesis and characterization of new MAX phase alloys (M = early transition metal, A = A-group element, and X = C or N), based on incorporation of M and X elements previously not considered. My primary focus is on M = Mn for attaining magnetic properties, and on X = O for potential tuning of the transport properties. A recent theoretical study predicted (Cr1-xMnx)2AlC MAX phase to be a stable magnetic nanolaminate. I aimed at realizing this material and through a combinatorial approach based on magnetron sputtering from elemental targets, the first experimental evidence of Mn incorporation (x = 0.16) in a MAX phase is presented. The corresponding MAX phase was also synthesized using cathodic arc film deposition (x = 0.20) and bulk synthesis methods (x = 0.06). The primary characterization techniques were X-ray diffraction and high-resolution (scanning) transmission electron microscopy in combination with energy dispersive X-ray spectroscopy and/or electron energy loss spectroscopy, to obtain a precise local quantification of the MAX phase composition and to perform lattice resolved imaging. For epitaxial film growth of (Cr1-xMnx)2AlC, evidence is presented for the formation of (Cr1-yMny)5Al8, exhibiting a bcc structure with an interplanar spacing matching exactly half a unit cell of the hexagonal MAX phase. Consequently, routinely performed X-ray diffraction symmetric θ-2θ measurements result in peak positions that are identical for the two phases. As (Cr1-yMny)5Al8 is shown to display a magnetic response, its presence needs to be taken into consideration when evaluating the magnetic properties of the MAX phase. Methods to distinguish between (Cr1-yMny)5Al8 and (Cr1-xMnx)2AlC are also suggested. As different A-element in the MAX phase is theoretically predicted to influence phase stability, attainable level of Mn incorporation, as well as magnetic properties, thin films of (Cr0.75Mn0.25)2GeC and bulk (Cr0.7Mn0.3)2GaC have also been synthesized. Vibrating sample magnetometry measurements display a magnetic response for all these materials, identifying (Cr,Mn)2AlC, (Cr,Mn)2GeC, and (Cr,Mn)2GaC as the first magnetic MAX phases. The results presented in this Thesis show that A = Al displays the highest magnetic transition temperature (well above room temperature) and A = Ga allows the highest Mn content. The attainable O incorporation in Ti2Al(C1-xOx)MAX phase was explored by arc deposition of Ti2AlC1-y thin films under high vacuum conditions, and solid-state reactions following deposition of understoichiometric TiCz on Al2O3. Ti2Al(C1-xOx)thin films with up to 13 at.% O (x = 0.52) were synthesized, and O was shown to occupy the C lattice site. The obtained O concentration is enough to allow future experimental investigations of the previously suggested (from theory) substantial change in anisotropic electronic properties with increasing O content. The experimental results obtained in this Thesis expand the MAX phase definition and the materials characteristics into new research areas, towards further fundamental understanding and functionalization.
2
Palmquist, Jens-Petter. "Carbide and MAX-Phase Engineering by Thin Film Synthesis". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3972.
Testo completo
3
Petruhins, Andrejs. "Synthesis and characterization of Ga-containing MAX phase thin films". Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-110764.
Testo completoAbstract (sommario):
The study of magnetic Mn+1AXn (MAX) phases (n = 1 − 3, M – a transition metal, A – an A group element, X – C or N) is a recently established research area, fuelled by theoretical predictions and first confirmed experimentally through alloying of Mn into the well-known Cr2AlC and Cr2GeC. Theoretical phase stability investigations suggested a new magnetic MAX phase, Mn2GaC, containing Ga which is liquid close to room temperature. Hence, alternative routes for MAX phase synthesis were needed, motivating a further development of magnetron sputtering from liquid targets. In this thesis, (Cr1-xMnx)2GaC 0 ≤ x ≤ 1 MAX phase thin films have been synthesized from elemental and/or compound targets, using ultra high vacuum magnetron sputtering. Initial thin film synthesis of Cr2GaC was performed using elemental targets, including liquid Ga. Process optimization ensured optimal target size and crucible geometry for containing the Ga. Films were deposited at 650 °C on MgO(111) substrates. X-ray diffraction and transmission electron microscopy confirms the growth of epitaxial Cr2GaC MAX phase with minor inclusions of Cr3Ga. To explore the magnetic characteristics upon Mn alloying, synthesis of (Cr0.5Mn0.5)2GaC thin films was performed from elemental Ga and C and a composite Cr/Mn target of 1:1 composition. Films were deposited on MgO(111), Al2O3(0001) (with or without NbN seed layer), and 4° off-cut 4H-SiC(0001) substrates. The films are smooth and of high structural quality as confirmed by X-ray diffraction and transmission electron microscopy. The film composition measured by high resolution energy dispersive X-ray spectroscopy confirms a composition corresponding to (Cr0.5Mn0.5)2GaC. The magnetic response, as measured with vibrating sample magnetometry, displays a ferromagnetic component, however, the temperature dependence of the magnetic moments and saturation fields suggests competing magnetic interaction and possible non-collinear magnetic ordering. Finally, inspired by theoretical predictions, a new member of the MAX phase family, Mn2GaC, was synthesized. This is the first MAX phase containing Mn as a sole M element. X-ray diffraction and transmission electron microscopy confirms the characteristic MAX phase structure with a 2:1:1 composition. Theoretical work suggests that the magnetic ground state is almost degenerate between ferromagnetic and anti-ferromagnetic. Vibrating sample magnetometry shows ferromagnetic response with a transition temperature Tc of 230 K. However, also for this phase, complex magnetism is suggested. Altogether, the results indicate a new family of magnetic nanolaminates with a rich variation of magnetic ground states.
4
Mockutė, Aurelija. "Thin Film Synthesis and Characterization of New MAX Phase Alloys". Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-77775.
Testo completoAbstract (sommario):
The objective of this Thesis is synthesis and characterization of new MAX phase alloys (M = early transition metal, A = A-group element, and X = C or N) based on incorporation of M and X elements previously not used in any known MAX phases. This is motivated by a search for optimized and unique materials properties, such as different magnetic states. Two synthesis routes have been used to attain Ti2AlC1-xOx: deposition of Ti2AlCy under high vacuum conditions with residual gas acting as O source, and solid-state reactions following deposition of understoichiometric TiCy on Al2O3. Detailed local quantification by analytical transmission electron microscopy (TEM) including electron energy loss spectroscopy (EELS) shows up to 13 at.% O within high quality MAX phase structure. According to previous theoretical work, the range of experimentally obtained O content is enough to observe drastic changes in the materials anisotropic electronic properties. Calculations on effect of substitutional O on shear deformation have also been performed. In a recent theoretical study by Dahlqvist et al., (Cr,Mn)2AlC has been predicted as a new stable magnetic nanoscale laminate. Inspired by this work, thin films of (Cr,Mn)2AlC, as well as of a neighboring system (Cr,Mn)2GeC, have been synthesized by magnetron sputtering. Incorporation of 8 and 12.5 at.% of Mn, respectively, has been detected by analytical TEM including EELS and energy dispersive X-ray spectroscopy (EDX). The total saturation moment of 0.36μB per Mn atom at 50 K has been measured by vibrating sample magnetometry (VSM) for a (Cr,Mn)2GeC sample, providing the first experimental evidence of a magnetic MAX phase. The experimental results obtained in this Thesis provide a base for expanding the MAX phase definition and materials characteristics into new areas, towards further fundamental understanding and functionalization.
5
Zhang, Shiqi. "Etude de la Réactivité chimique des monocristaux de phase MAX". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI042/document.
Testo completoAbstract (sommario):
Les phases MAX forment une famille de carbures et de nitrures nano-lamellaires de formule chimique Mn+1AXn, où M est un métal de transition des premières colonnes, A appartient aux colonnes 13-16 et X est soit C, soit N, ou une combinaison des deux éléments. Ces phases combinent les mérites des céramiques et des métaux, comme une bonne stabilité chimique, l’usinabilité, la résistance aux chocs mécaniques, de bonnes conductivités thermique et électrique, etc. Malgré tout, l’étude de leurs propriétés intrinsèques et de leurs anisotropies a été jusqu’à présent limitée par l’indisponibilité de monocristaux. Cette thèse traite de la réactivité de tels monocristaux de phases MAX. Grâce à la large taille des cristaux produits au LMGP, il a été possible d’évaluer directement l’anisotropie de la réactivité chimique et d’obtenir des données originales. Nous avons montré le rôle prépondérant joué par l’élément A pour initier des transformations chimiques menant parfois à la synthèse de matériaux originaux, et nous nous sommes concentrés sur quatre aspects différents : Tout d’abord, nous avons tenté de synthétiser des MXènes de grande taille, en profitant de la grande taille des cristaux disponibles. Un effort particulier a été porté sur la description de la réactivité chimique de phases MAX plongées dans diverses solutions d’attaque, avec un accent particulier mis sur l’utilisation de HF. En second lieu, nous avons étudié la chloruration de phases MAX : l’objectif initial était de former des MXènes, mais nous avons finalement développé une méthode pour synthétiser des carbures de chrome poreux avec des propriétés intéressantes. Troisièmement, nous avons utilisé des cristaux de grande taille pour évaluer l’anisotropie des propriétés électrochimiques. Une anisotropie significative a été trouvée, soit en mesurant le courant durant la polarisation électrochimique, soit par mesure de spectroscopie d’impédance. Divers mécanismes ont été proposés afin d’expliquer cette anisotropie des propriétés de corrosion. Enfin, nous avons montré que les résultats électrochimiques pouvaient être utilisés pour révéler indirectement la présence de défauts structurels récemment identifiés dans la littérature. De tels défauts, appelés « ripplocations », sont spécifiques aux matériaux nano-lamellairesMAX phases are a family of layered ternary carbides and nitrides with chemical formula Mn+1AXn, where M is an early transition element, A is an element of groups 13 to16 and X is either C, N or both. These phases combine the merits of ceramics and metals, such as chemical stability, machinability, shock resistance, good electrical and thermal conductivity, etc. However, the investigation of their intrinsic properties and anisotropies has heretofore been limited by a lack of availability of single crystals. This thesis mainly deals with the chemical reactivity of MAX phase single crystals. Owing to the large size single crystals grown at LMGP, it was possible to directly assess the anisotropy of the chemical reactivity and to obtain original data. We showed that the prominent role played by the A element for initiating chemical transformations could lead to the synthesis of original materials, and we focused on four different aspects. First, we tried to synthesize MXenes from MAX phase single crystals: The purpose was to obtain large-scale MXenes by taking advantage of the large size of the single crystals. Effort was put on describing the chemical reactivity of MAX phases dipped in different etchants, focusing on HF. Secondly, we studied the MAX phase reactivity with chlorination: the initial purpose was to obtain MXenes, but we finally developed a method for synthesizing porous chromium carbides which exhibit several interesting properties. Thirdly, we used large size single crystals in order to assess the anisotropy of the electrochemical properties. A significant anisotropy was found, either by measuring the current during electrochemical polarization or by frequency-dependent impedance measurements. Several mechanisms were proposed in order to explain this anisotropy of the corrosion properties. Eventually, we showed that the electrochemical results could be used to indirectly evidence the presence of structural defects recently identified in the literature. Such defects, called ripplocations, are specific to nano-lamellar materials
6
Khan, Abbas. "Tailored oxides and carbides as active materials for high power energy storage devices". Electronic Thesis or Diss., Nantes Université, 2024. http://www.theses.fr/2024NANU4025.
Testo completoAbstract (sommario):
La conception de matériaux sur mesure utilisant des approches innovantes permettant des processus de charge/décharge plus rapides pourrait être la clé pour l'avancement de la mobilité électrique. Cette thèse examine des matériaux novateurs pour les électrodes négatives de batteries Li-ion, en se concentrant sur les oxydes multicationiques à base de niobium et les carbures de métaux de transition à base de titane. Les travaux de recherche explorent la synthèse, la structure et les propriétés électrochimiques de ces matériaux, avec une attention particulière aux modifications structurales et aux mécanismes de stockage des charges. Les principaux résultats incluent l'étude de l'activation électrochimique in-situ des matériaux et du comportement unique de stockage du Li+ dans les matériaux pérovskite AgNbO 3 et Ag1-3xLa x□2xNbO 3 (avec 0 ≤ x ≤ 0,40 ; □ étant une lacune sur le site A).De plus, cette étude examine l'effet des lacunes du site A sur la structure et sur les propriétés d'insertion du Li+ dans les structures K1- 3xLa x□2xNbO 3 (avec 0 ≤ x ≤ 0,15 ; □ étant une lacune sur le site A). En outre, des informations sur la voie de synthèse polyacrylamide pour les phases MAX à base de Ti et Al sont fournies. Ce travail présente des approches pour ajuster les matériaux de manière à l’échelle atomique, sans sacrifier la phase initiale, suggérant l'utilisation potentielle de pérovskites de type ABO 3 peu étudiées comme électrodes négatives. De plus, il offre des perspectives mécanistiques sur la synthèse chimique en solution des phases MAX pour leur utilisation comme électrodes de batterie lithium-ionDesign of tailored materials using innovative approaches that allow faster charging/discharging processes could be the key for advancement of electric mobility. This thesis investigates novel materials for Li-ion battery negative electrodes, focusing on niobium-based multicationic oxides and titanium-based transition metal carbides. This research work explores the synthesis, structure, and electrochemical properties of these materials, with particular emphasis on atomic-scale structural modifications and Li+ storage mechanisms. Key findings include the investigation of in-situ electrochemical activation and unique Li+ storage behavior in AgNbO 3 model perovskite and Ag 1-3xLa x□2xNbO 3 (with 0 ≤ x ≤ 0.40; □ is an A -site vacancy) tailored materials. Additionally, the study examines the effect of A-site deficiency on the structure and Li+ insertion properties of K1-3xLa x□2xNbO 3 (with 0 ≤ x ≤ 0.15; □ is an A -site vacancy). Furthermore, insights into the polyacrylamide synthesis route for Ti and Al-based MAX phases are provided. These work present approaches to atomically tailor the materials without sacrificing the pristine phase, suggesting the potential use of less common ABO 3-type perovskites as negative electrodes. Additionally, it offers mechanistic insights into the wet chemical synthesis of MAX phases for their use as battery electrodes
7
Rampai, Tokoloho. "Synthesis of Ti₂AlC, Ti₃AlC₂ and Ti₃SiC₂ MAX phase ceramics; and their composites with c-BN". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/18463.
Testo completoAbstract (sommario):
MAX phase ceramics are ternary ceramics with both metallic and ceramic properties. The existing backing materials in grinding wheels can be made of ceramics or metals. In these applications, ceramics have the disadvantage of low toughness, and most metals have the disadvantages of relatively high density and intolerance to some very high temperatures. The MAX phases have a combination of the main advantages of both metals and ceramics: they are soft and machinable yet also heat-tolerant, strong and lightweight. Cubic boron nitride (c-BN) is a widely used abrasive in grinding wheels, which is exceeded in hardness only by diamond. Composites of c-BN and selected MAX phases may result in materials of some interesting and useful properties for application in industry. Firstly MAX phases, Ti₃SiC₂; Ti₃AlC₂ and Ti₂AlC were synthesised, then reaction couples of MAX-cBN are made in order to investigate the best conditions for composite synthesis, and to analyse the interfacial phases which occur. Finally, the MAX-cBN composites were synthesised from the reaction couple studies. The following results were obtained: 1. Samples synthesised to obtain Ti₃AlC₂ were largely composed of the Ti₂AlC, and thus synthesis of the Ti₃AlC₂ MAX phase was deemed unsuccessful. 2. Nearly pure samples of Ti₂AlC and Ti₃SiC₂ were successfully synthesised with high densities, 99.16% and 98.21%, respectively, of the theoretical density. 3. Reaction couple studies revealed that the Ti₃SiC₂ /c-BN couple was successfully made at 1400°C, 10MPa pressure for 30 minutes, and Ti₂AlC/c-BN couple was successfully made at 1500°C, 10MPa pressure for 30 minutes. The interfacial phases characterised by XRD and SEM found here were TiN, TiC, TiB₂ and AlN for the latter and TiN, TiS₂ and TiB₂ for the former. 4. These conditions were used to successfully synthesise MAX/c-BN composites where both could react and still remain intact. The interfacial phases characterised by XRD and SEM found here were TiAl, TiC, TiB₂ and AlN for Ti₂AlC/c-BN and TiN, TiC, TiS₂ and TiB₂ for Ti₃SiC₂ /c-BN. From these results the following conclusion was drawn: Ti₂AlC and Ti₃SiC₂ are fully compatible with c-BN in order to synthesise a composite with notable properties such as the fracture toughness, suggested by the observed fracture mechanism seen from the fracture surface of these composites.
8
Wilhelmsson, Ola. "Synthesis and Characterization of Ternary Carbide Thin Films". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8265.
Testo completo
9
Bei, Guo-Ping. "Synthesis, microstructural characterization and mechanical properties of nanolaminated Ti3AlxSn(1-x)C2 MAX phases". Poitiers, 2011. http://nuxeo.edel.univ-poitiers.fr/nuxeo/site/esupversions/9a20805b-0e53-47c0-8b16-c1a4ac3c2042.
Testo completoAbstract (sommario):
Les travaux exposés dans cet ouvrage portent sur l'élaboration, la caractérisation microstructurale et les propriétés mécaniques de solutions solides nanolamellaires de phases dites MAX. Les phases MAX représentent une classe exceptionnellement étendue de céramiques. Elles répondent à une formule générale du type Mn+1AXn (n=1, 2 ou 3) où M est un métal de transition, A est un métal des groupes IIIA ou IVA, et X est un métalloïde (C ou N). Nous avons dans un premier temps réalisé l'optimisation de la synthèse, par métallurgie des poudres, de Ti3AlC2 pur. Une nouvelle phase, Ti3SnC2, ayant été découverte au laboratoire en 2007, les travaux se sont alors focalisés sur la synthèse de solutions solides du type Ti3AlxSn(1-x)C2 par pressage isostatique à chaud. Nous nous sommes, par la suite, attachés à la caractérisation microstructurale de ces solutions solides en étudiant notamment les variations du paramètre de maille, du taux de distorsion des octaèdres [Ti6C] et des prismes trigonaux [Ti6AlxSn(1-x)]. Enfin, nous avons déterminé la dureté intrinsèque et le module d'élasticité des différentes solutions solides en fonction du taux de substitution en utilisant la nanoindentation. Par ailleurs, des essais de compression, uniaxiale et sous confinement de gaz, ont été réalisés à température ambiante, afin d'étudier et de comparer les mécanismes de déformation de Ti3AlC2 et de la solution solide Ti3Al0. 8Sn0. 2C2. Les relations entre modifications microstructurales et propriétés mécaniques sont discutées. Nous montrons notamment que Ti3AlC2 et Ti3Al0. 8Sn0. 2C2 peuvent être considérés comme des matériaux "Kinking Non-linear Elastic"The work described in this thesis concerns the elaboration, the microstructural characterization and the mechanical properties of nanolaminated MAX phases solid solutions. The MAX phases represent a large class of ceramics. They are a family of ternary nitrides and carbides, with the general formula Mn+1AXn (n=1, 2 or 3), where M is an early transition metal, A is a metal of the groups IIIA or IVA, and X is either carbon or nitrogen. We performed at first the optimization of the synthesis, by powder metallurgy, of highly pure Ti3AlC2. Since a new MAX phase, Ti3SnC2, has been discovered in the laboratory in 2007, the study has been further focused on the synthesis of Ti3AlxSn(1-x)C2 solid solutions by hot isostatic pressing. In a second step, the microstructural characterization of these solid solutions has been carried out, by studying, in particular, the variation of the cell parameters, the distortion rates of [Ti6C] octahedrons and [Ti6AlxSn(1-x)] trigonal prisms. Finally, we have determined the intrinsic hardness and the elastic modulus of the various solid solutions as a function of the Al content by using the nanoindentation. Besides, uniaxial and gas confining compression tests were realized at room temperature, to study and compare the deformation mechanisms of Ti3AlC2 and Ti3Al0. 8Sn0. 2C2. The relationship between microstructural modifications and mechanical properties are discussed. We show in particular that Ti3AlC2 and Ti3Al0. 8Sn0. 2C2 can be considered as "Kinking Non-linear Elastic" materials
10
Hamm, Christin Maria [Verfasser], Christina [Akademischer Betreuer] Birkel e Barbara [Akademischer Betreuer] Albert. "Synthese, Charakterisierung und magnetische Eigenschaften ausgewählter Laves- und MAX-Phasen / Christin Maria Hamm ; Christina Birkel, Barbara Albert". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1136078789/34.
Testo completoLibri sul tema "MAX phase synthesis"
1
Rutherford, Gordon Bennett. Synthesis of perfluorinated ethers by solution phase direct fluorination: An adaptation of the La-Mar technique. 1990.
Cerca il testo completo
2
Golper, Thomas A., Andrew A. Udy e Jeffrey Lipman. Drug dosing in acute kidney injury. A cura di William G. Bennett. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0364.
Testo completoAbstract (sommario):
Drug dosing in acute kidney injury (AKI) is one of the broadest topics in human medicine. It requires an understanding of markedly altered and constantly changing physiology under many disease situations, the use of the drugs to treat those variety of diseases, and the concept of drug removal during blood cleansing therapies. Early in AKI kidney function may be supraphysiologic, while later in the course there may be no kidney function. As function deteriorates other metabolic pathways are altered in unpredictable ways. Furthermore, the underlying disorders that lead to AKI alter metabolic pathways. Heart failure is accompanied by vasoconstriction in the muscle, skin and splanchnic beds, while brain and cardiac blood flow proportionally increase. Third spacing occurs and lungs can become congested. As either kidney or liver function deteriorates, there may be increased or decreased drug sensitivity at the receptor level. Acidosis accompanies several failing organs. Protein synthesis is qualitatively and quantitatively altered. Sepsis affects tissue permeability. All these abnormalities influence drug pharmacokinetics and dynamics. AKI is accompanied by therapeutic interventions that alter intrinsic metabolism which is in turn complicated by kidney replacement therapy (KRT). So metabolism and removal are both altered and constantly changing. Drug management in AKI is exceedingly complex and is only beginning to be understood. Thus, we approach this discussion in a physiological manner. Critically ill patients pass through phases of illness, sometimes rapidly, other times slowly. The recognition of the phases and the need to adjust medication administration strategies is crucial to improving outcomes. An early phase involving supraphysiologic kidney function may be contributory to therapeutic failures that result in the complication of later AKI and kidney function failure.
3
Wilson, Deanna. Hepatitis. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199976805.003.0035.
Testo completoAbstract (sommario):
Hepatitis A (HAV) and E (HEV) viruses are spread via the fecal-oral route. Hepatitis B virus (HBV) exposure is via occupational or recreational activities. Hepatitis D virus (HDV; also spread parentally) can only coinfect or superinfect those with chronic HBV. Hepatitis C (HCV) transmission is predominantly parenteral; the highest risk group is injection drug users. Prodromal-period patients with acute hepatitis present with vague constitutional symptoms when serum transaminases peak, with elevated serum bilirubin and varying levels of hepatic protein synthesis impairment; during the icteric phase, patients develop abdominal pain, hepatomegaly, and jaundice. Acute hepatitis has limited therapy; treatment is predominantly supportive. However, most adults with acute phase HAV, HBV, HDV, and HEV spontaneously clear the virus. Most individuals with HCV develop chronic hepatitis. Patients with known HAV, HBV, or HEV exposures may be eligible for post-exposure prophylaxis to reduce their risk of infection.
4
Bever, Thomas G. The Unity of Consciousness and the Consciousness of Unity. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190464783.003.0005.
Testo completoAbstract (sommario):
Every language-learning child eventually automatically segments the organization of word sequences into natural units. Within the natural units, processing of normal conversation reveals a disconnect between listener’s representation of the sound and meaning of utterances. A compressed or absent word at a point early in a sequence is unintelligible until later acoustic information, yet listeners think they perceived the earlier sounds and their interpretation as they were heard. This discovery has several implications: Our conscious unified experience of language as we hear and simultaneously interpret it is partly reconstructed in time-suspended “psychological moments”; the “poverty of the stimulus language learning problem” is far graver than usually supposed; the serial domain where such integration occurs may be the “phase,” which unifies the serial percept with structural assignment and meanings; every level of language processing overlaps with others in a “computational fractal”; each level analysis-by-synthesis interaction of associative-serial and structure dependent processes.
5
Mattissen, Johanna. Nivkh. A cura di Michael Fortescue, Marianne Mithun e Nicholas Evans. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199683208.013.47.
Testo completoAbstract (sommario):
Nivkh (Paleosiberian group), spoken on the lower reaches of the Amur River and on Sakhalin island in Siberia by a few hundred speakers in four main varieties, but rapidly dying out, is a polysynthetic head-marking but configurational SOV language, with defective polypersonalism, noun incorporation, verb root serialization, and complex noun forms. Its dominant structural principle and characteristic design is dependent-head-synthesis, with dependents lexically head-marked and still referentially active. Nivkh displays compositional polysynthesis with a mixed internal structure, as the suffixal domain of a word-form may be described by a template, whereas the pre-root domain is scope-ordered due to dependent chaining. The evolutionary path of complex forms is best conceived of as coalescence of formerly adjacent words. Morphophonemic processes at the word-internal morpheme boundaries, especially consonant dissimilation and assimilation, and bound allomorphs prove the wordhood of the complexes. Non-root bound morphemes encode modalities, degree, scalar, and focus operators and phase of action.
6
Hickmann, Maya, e Dominique Bassano. Modality and Mood in First Language Acquisition. A cura di Jan Nuyts e Johan Van Der Auwera. Oxford University Press, 2015. http://dx.doi.org/10.1093/oxfordhb/9780199591435.013.20.
Testo completoAbstract (sommario):
This chapter aims to provide a large overview of research focusing on the development of modality and mood during first language acquisition. This overview synthesizes results concerning both early and later phases of development, within and across a large number of languages, and including some more peripheral categories, such as evidentials and tense–aspect markings. Results recurrently show the earlier acquisition of agent-oriented modality as compared to epistemic modality. However, cross-linguistic variation has raised some questions about this acquisition sequence, suggesting that language-specific properties may partially impact timing during acquisition. In addition, findings about later phases show a long developmental process whereby children gradually come to master complex semantic and pragmatic modal distinctions. The discussion highlights the contribution of these conclusions to current theoretical debates, such as the role of input factors and the relation between language and cognition during ontogenesis.
7
Stöltzner, Michael. The Logical Empiricists. A cura di Helen Beebee, Christopher Hitchcock e Peter Menzies. Oxford University Press, 2010. http://dx.doi.org/10.1093/oxfordhb/9780199279739.003.0007.
Testo completoAbstract (sommario):
Causation was a central theme for the movement of Logical Empiricism (LE); during its classical European phase — the 1920s and 1930s — and beyond. It would not become one of LE's alleged ‘dogmas’, unlike verificationism and the analytic–synthetic distinction. Rather, the topic of causation paradigmatically exhibits two important features of LE. First, the movement was intimately connected to the scientific developments of the day; its representatives tried to accommodate their analyses to those developments rather than insist on an unassailable philosophical outlook come what may. Second, their joint allegiance to scientific empiricism and modern logic, and the common agenda to replace traditional metaphysics by a scientific world conception, cannot conceal the fact that the members of LE stemmed from different intellectual backgrounds and pursued, the manifold cross-references notwithstanding, original trains of thought. Hence they reacted in different ways to the scientific revolutions that occurred during the heyday of LE, quantum theory foremost.
8
Budanov, Vladimir, Vladimir Arshinov, Yakov Svirskiy, Irina Beskova, Vadim Rozin, Vladimir Lepskiy, Elena Malahova et al. SCIENCE AND HUMAN PHENOMENA IN THE ERA OF CIVILIZATIONAL MACROSHIFT. Institute of Philosophy Russian Academy of Sciences, 2023. http://dx.doi.org/10.29039/978-5-88230-495-8.
Testo completoAbstract (sommario):
The monograph is part of a series of publications in the sector of interdisciplinary problems of scientific and technological development on the mega-theme of the Institute of Philosophy of the Russian Academy of Sciences “Science, man and the prospects of technogenic civilization.” This time the publication is focused on a philosophical and methodological understanding of the phenomenon of the global civilizational Macroshift of the 21st century, which is problematized in the materials of the Round Table that opens the monograph. The genesis, ontological, historical and metaphysical foundations of the global crisis, its singular nature are explored. The possibilities of an expanded environmental interpretation of the ecology of transformations of the techno-anthroposphere, which is considered from the position of the human-dimensional post-non-classical phase of the evolution of scientific and technological development, are analyzed. The contours of the science of the future are outlined, maintaining the connection of times, but also including the problems of digitalization, artificial intelligence, increasing complexity, cognitive and value changes, and also seeking to preserve a holistic view of man and his aspiration to achieve Truth and Good. The possibilities of holistic methodology, open synthetic thinking, taking into account the subtle nuances of the nature of human consciousness and worldview in the diversity of their manifestations, are convincingly shown on specific subjects. The monograph has both a theoretical and practical focus on the presented results for the actualization and use of humanitarian, socio-ethical examination of scientific projects and innovations, as well as strategic forecasting and decision-making.
Capitoli di libri sul tema "MAX phase synthesis"
1
Deysher, Grayson, Christopher Eugene Shuck, Kanit Hantanasirisakul, Nathan C. Frey, Alexandre C. Foucher, Kathleen Maleski, Asia Sarycheva et al. "Synthesis of Mo4VAlC4 MAX Phase and Two-Dimensional Mo4VC4 MXene with Five Atomic Layers of Transition Metals". In MXenes, 95–131. New York: Jenny Stanford Publishing, 2023. http://dx.doi.org/10.1201/9781003306511-8.
Testo completo
2
Chen, Jianyu, Shun Suzuki, Tao Morisaki, Yutaro Toide, Masahiro Fujiwara, Yasutoshi Makino e Hiroyuki Shinoda. "Sound Pressure Field Reconstruction for Ultrasound Phased Array by Linear Synthesis Scheme Optimization". In Haptics: Science, Technology, Applications, 147–54. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-06249-0_17.
Testo completoAbstract (sommario):
AbstractUltrasound phased array is a device that is usually used to provide mid air tactile sensations like three-dimensional shape haptics images by generating various specific sound fields. Forming foci for the ultrasound phased array using the linear synthesis scheme (LSS) is a straightforward technique to induce tactile feeling. The matching phase set for each focal point is calculated separately in LSS, and then they are linearly superimposed to generate multiple focal points. Due to the fact that adding an arbitrary offset to the entire phase pattern has no effect on the generated focus patterns, adjusting the offset in linear summation may result in a superior sound field. In our study, we propose that optimize the offset before linear superposition. These offsets are determined based on the number of focal points, which means it will not cause an explosive increase in computing cost with the increase of transducers. To optimize the offset of each focus pressure generated by LSS, we used a greedy algorithm with a brute-force search optimization method. The computing cost of our proposed method is dictated by the number of foci after calculating the phase sets of LSS once. We demonstrate the proposed method’s optimum performance in varied numbers of foci and transducers in this study.
3
André, Étienne. "IMITATOR 3: Synthesis of Timing Parameters Beyond Decidability". In Computer Aided Verification, 552–65. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-81685-8_26.
Testo completoAbstract (sommario):
AbstractReal-time systems are notoriously hard to verify due to nondeterminism, concurrency and timing constraints. When timing constants are uncertain (in early the design phase, or due to slight variations of the timing bounds), timed model checking techniques may not be satisfactory. In contrast, parametric timed model checking synthesizes timing values ensuring correctness. takes as input an extension of parametric timed automata (PTAs), a powerful formalism to formally verify critical real-time systems. extends PTAs with multi-rate clocks, global rational-valued variables and a set of additional useful features. We describe here the new features and algorithms offered by 3, that moved along the years from a simple prototype dedicated to robustness analysis to a standalone parametric model checker for timed systems.
4
Salhotra, Ripenmeet, Adrian Wong e Manu L. N. G. Malbrain. "The Place for Starches and Other Colloids". In Rational Use of Intravenous Fluids in Critically Ill Patients, 243–57. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-42205-8_11.
Testo completoAbstract (sommario):
AbstractThis chapter provides a comprehensive review of synthetic colloids, specifically hydroxyethyl starch (HES) solutions, and their role in resuscitation of critically ill, perioperative, and trauma patients. This chapter addresses various questions, including the crystalloid versus colloid debate, the strengths and weaknesses of different fluid trials and meta-analyses, and the specific situations or patient groups where colloids may have an advantage. This chapter focuses on the results of five major trials that compare the use of crystalloids versus colloids in critically ill patients. The 6S study and the CHEST trial confirmed the suspicion of renal damage associated with HES solutions, and the European Medicines Agency’s (EMA) safety committee prohibited the use of HES solutions in critically ill, septic, and burn patients, or those with kidney injury in 2013. However, many questions and controversies remained thereafter and more recently the European Commission has suspended the marketing authorizations of HES solutions for infusion. The use of HES and other synthetic colloids should be restricted to resuscitation in the perioperative setting or in limited volumes with extreme caution in trauma settings outside of the EU. The take-home messages include the availability of natural and synthetic colloids, the lack of outcome benefit in clinical trials, the association of HES with renal failure and increased use of renal replacement therapy, and the unsafe use of synthetic colloids in perioperative patients. This chapter recommends limiting the dose of synthetic colloids to 30ml/kg when given in the peri- and postoperative phase.
5
Cristallo, Vincenzo, e Miriam Mariani. "The Role of Infographics in the Representation of Design Research". In Springer Series in Design and Innovation, 632–39. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-49811-4_60.
Testo completoAbstract (sommario):
AbstractThis paper examines what the “narrative task” of Communication Design, in its infographic declination, may be in the different stages of “doing research through design”. That is to say that - crossing simultaneously the fields of theory and praxis - design research is required to elaborate a visual language capable of coherently presenting the entirety of its development (from the meta-design to final products) made up of data processed in the ante, during and post phases. In other words, the actual, useful and inalienable results of doing research must fully include the communicative and visual design of its “process” that unfolds throughout its desk and field actions. The theme of the “representation of research” therefore becomes the core of the paper, which highlights how the descriptive development of the actions and manifestations of research proceeds through visual models known as process and result models. What is proposed, in fact, in this contribution, is a reflection on the visual models that describe research in its phases, through different tools such as scientific drawing, hypothetigraphy and infographic presentation, the latter to be understood as a conceptual and visual synthesis of complex processes.
6
Winter, Yoad. "On Partee’s “Noun Phrase Interpretation and Type-Shifting Principles”". In Studies in Linguistics and Philosophy, 367–85. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-85308-2_19.
Testo completoAbstract (sommario):
AbstractMontague’s classic article “The Proper Treatment of Quantification in Ordinary English” (PTQ, 1973) treated all NP occurrences as quantificational. Partee’s article “Noun Phrase Interpretation and Type-Shifting Principles” (1987) reconciles PTQ’s uniform quantificational strategy with the older distinction between three NP types: entities, predicates and quantifiers. On top of this distinction, Partee introduces operators that allow shifting the denotation of an NP to a different type than the one it is initially assigned. Using these type-shifters, one and the same NP may receive each of the three interpretations. In addition to this synthesis of previous approaches, Partee’s article contains a rather elaborate analysis of predicative NPs, as well as insightful hints about the treatment of definite NPs, nominalization phenomena, plural, mass and generic NPs, and the mathematical principles underlying type-shifting. At a more global level, Partee’s article marks a methodological transition in formal semantics, highlighting general principles that are relevant to different languages and to different linguistic frameworks, rather than technicalities of artificial language fragments. This general account and the new ways it opened for semantic theory, together with the paper’s lucid and friendly style, have made “Noun Phrase Interpretation and Type-Shifting Principles” one of the modern classics in formal semantics. After some necessary background on NPs in PTQ, this review covers the main innovations in Partee’s article, and comments on the work and its influence.
7
Hoffmann, Stefan R. K., Christine A. Deillon e Bernd Gutte. "Solid Phase Synthesis of Seleno-Methionine Peptides by tBoc/Bzl and Fmoc/tBu Protection Strategy Suitable for the Crystallographic Phase Determination by Multi-Wavelength Anomalous Diffraction (MAD)". In Peptides: The Wave of the Future, 166–67. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0464-0_74.
Testo completo
8
Qian, X. K. "Methods of MAX-phase synthesis and densification – I". In Advances in Science and Technology of Mn+1AXn Phases, 1–19. Elsevier, 2012. http://dx.doi.org/10.1533/9780857096012.1.
Testo completo
9
Zhou, A. "Methods of MAX-phase synthesis and densification – II". In Advances in Science and Technology of Mn+1AXn Phases, 21–46. Elsevier, 2012. http://dx.doi.org/10.1533/9780857096012.21.
Testo completo
10
Jiang, Wan, Jianfeng Zhang e Lianjun Wang. "Spark Plasma Sintering of MAX Phases and Their Related Composites". In MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments, 1–33. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4066-5.ch001.
Testo completoAbstract (sommario):
With the combined merits of both metals and ceramics, including good electrical and thermal conductivity, ready machinability, exceptional damage tolerance, light weight, high rigidity, etc., the ternary layered MAX compounds have attracted much attention in the world. For the synthesis and consolidation of MAX phases, the relatively novel spark plasma sintering (or SPS in short) represents a very competitive technique for its high efficiency and energy saving. Since 2000’s, SPS has been extensively used for this propose, especially in Ti3SiC2 and Ti3SiC2-based composites. The present general results indicate that Ti/Si/TiC is the most appropriate powder mixture and Al is a good aid for the synthesis of high purity Ti3SiC2 by SPS. Various Ti3SiC2-based composites have also been consolidated by SPS and the related properties were improved, such as hardness, strength, fracture toughness and conductivity. It is very important to notice that, Ti3SiC2 phase can also be in situ synthesized in its composites as the commercial Ti3SiC2 powder is hardly available. A few other MAX phases have also been synthesized and consolidated by SPS in one step using various powder mixtures. However, much work should be done to clarify the synthesis mechanism and various processing windows for MAX phases by SPS technique. Lowering the fabrication cost and finding appropriate applications of MAX phases are also eagerly expected.
Atti di convegni sul tema "MAX phase synthesis"
1
Miller, Joel, Elizabeth Wenzel e Martine Godfroy-Cooper. "ARSAD: An Augmented-Reality Spatial Auditory Display for Obstacle Avoidance during all Phases of Flight". In Vertical Flight Society 74th Annual Forum & Technology Display, 1–26. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12746.
Testo completoAbstract (sommario):
Spatial disorientation (SD) and the subsequent loss of situation awareness (SA) remain critical for low-level helicopter flight in degraded visual environments (DVE). In modern helicopter cockpits, synthetic vision systems (SVSs) employing conventional non-conformal two-dimensional (2D), egocentric three-dimensional (3D) conformal symbology (CS) and LADAR/RADAR imagery support guidance and control, especially during operations in DVE. Although 3D CS can decrease pilot's workload, it can also produce attentional tunneling and may not provide maximally effective depiction of the environment around the helicopter. In this context, it is crucial to develop integrated multimodal interfaces that allow extending the current operational envelope while enhancing flight safety. Several flight simulator studies have investigated the use of spatial, 3D auditory displays in combination with spatially and temporally congruent visual displays in tasks as diverse as collision avoidance, intruding aircraft detection, or warning for system malfunction. In this paper we propose a novel approach to spatial sonification design based on the premises that perception-based synthetic cueing, where the information can be accessed, selected, processed and reacted to intuitively can increase SA, improve overall performance, and allow mental workload to be kept at operationally effective levels. This paper describes the architecture and application suite of the Aviation Auditory Display Engine (AvADE) and the slab3d rendering engine and its use for the development of Augmented-Reality (AR) spatial sonifications for obstacle avoidance in the existing USAARL integrated cueing environment (ICE). Nine UH60M pilots evaluated the prototype in a 20-minute low-level free flight mission over a desert compound. The results are discussed in the context of pilot cueing synergies for DVE.
2
Rud, Alexander, Inna Kirian, Andrey Lakhnik, Yuliya Lepeeva, Oleksandr Marunyak, Iryna Vynnychenko, Mykola Skoryk, Vitaliy Bevz, Yuriy Zagorodniy e Vladimir Trachevski. "Synthesis of the Ti3SiC2 MAX-phase by pressureless technique". In IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-ar1353.
Testo completoAbstract (sommario):
Recently, the practical interest of researchers has attracted the MAX phase of Ti3SiC2. This phase is characterized by high electrical and thermal conductivities, low density, high Young’s modulus and fracture toughness. The main disadvantage of existing methods for the synthesis of this MAX phase is the presence of impurity phases such as TiC, SiC, Ti5Si3 or TiSi2. The current investigation represents the results of Ti3SiC2 MAX phase synthesis by pressureless sintering. The Ti, Si, and spectrally pure graphite were used to prepare the powder blend. The homogenization of the mixture was carried out at room temperature for duration of 1 hour using a high-energy laboratory planetary mill (Fritsch Pulverisette P-6). Homogenized powder blends were compacted as cylindrical pellets which was sintered at different temperatures in an argon atmosphere for 3 h. The processes of phase formation during synthesis and the structural parameters of individual phases have been studied by SEM, XRD and NMR spectroscopy. The sample sintered at 1300 ºC from Ti3:Si1.1:C2 mixture contained several phase: Ti3SiC2, TiC, SiC and graphite. The percentage of the Ti3SiC2 estimated by full-profile analysis is only about ~ 33 wt.%. An increase in temperature leads to a growth in the content of the phase Ti3SiC2 in the sample. The highest maximum yield of the phase Ti3SiC2 ~ 81 wt.% was achieved for the Ti3:Si1.1:C2 mixture at a temperature of 1385 ºC. In addition, about 19 wt% TiC was also observed in this sample. During the heating of the powder mixture to the synthesis temperature of the MAX phase, partial evaporation of silicon occurs. It results in a significant stoichiometric ratio violation of the elements, which leads to a decrease in the content of the Ti3SiC2 phase in the sample. Increasing the silicon content in the initial mixture to ~ 2 wt.% contributed to the production of the MAX phase with a purity of ~ 95 wt.%.
3
Kumar, Rakesh, Bikas C. Maji e Madangopal Krishnan. "Synthesis of 2D material MXene from Ti3AlC2 MAX-phase for electromagnetic shielding applications". In DAE SOLID STATE PHYSICS SYMPOSIUM 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0025338.
Testo completo
4
Burlachenko, Oleksii, e Tetiana Tsymbalista. "Powders produced by the method of mechanochemical synthesis for thermal spraying of coatings containing MAX phases". In IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-ob1530.
Testo completoAbstract (sommario):
To produce protective coatings containing MAX phases, methods of thin films deposition such as physical vapour deposition and magnetron sputtering are mainly used [1]. Such coatings are only a few microns thick and do not meet the requirements for operation in extreme conditions. Thermal spraying (TS) makes it possible to form coatings several millimetres thick. This work is dedicated to developing compositions and technology of producing powders using commercially available starting materials for thermal spraying of coatings containing MAX phases. The technology of mechanochemical synthesis (MChS) by processing mixtures of powders of the compositions 60.9TiC+39.1TiAl, 75TiAl-25SiC, 68.5(Ti,Cr)C-31.5Al, 82Cr3C2-18Al (wt.%) in a high-energy planetary ball mill was used to produce powders for TS. The compositions were calculated to form the most promising MAX phases: Ti3SiC2, Ti2AlC, Ti3AlC2 and Cr2AlC. The MChS process was performed in air during 1.5 hours. The produced powders products of MChS have a conglomerate structure with particles size <50 μm. In the powder product of MChS of the TiAl-TiC system, the synthesis of MAX phases Ti3AlC2 and Ti2AlC occurs; in the powder of the TiAl-SiC system, Ti2AlC, Ti3AlC2, and Ti3SiC2 are synthesized; in the powder of the (Ti,Cr)C-Al system, Ti2AlC and Cr2AlC are synthesized; in the powder of the Cr3C2-Al system, Cr2AlC is synthesized. In addition to the MAX phases and the phases of the initial components of powder mixtures, the MChS products also contain phases of Ti3AlC, Ti5Si3 and Cr5Al8. It is preferable to use high velocity thermal spraying methods such as HVOF and cold spraying to preserve MAX phases in coatings. The interaction time with oxygen and the high-temperature jet is reduced, and coatings phase composition corresponds to the phase composition of the sprayed powder. In the case of using plasma spraying methods, the synthesis of MAX phases can occur directly during spraying and the formation of the coating layer.
5
Sonoda, T., S. Nakao e M. Ikeyama. "Synthesis of MAX-Phase Containing Ti-Si-C Films by Sputter-Deposition Using Elemental Targets". In 2013 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2013. http://dx.doi.org/10.7567/ssdm.2013.ps-8-19.
Testo completo
6
"In situ (S)TEM Study of Thermal Reduction Synthesis Pathway for Sulfur Containing Titanium MAX Phase to MXene Phase". In Microscience Microscopy Congress 2023 incorporating EMAG 2023. Royal Microscopical Society, 2023. http://dx.doi.org/10.22443/rms.mmc2023.260.
Testo completo
7
"Effect of Added Molybdenum on Material Properties of Zr2SC MAX Phase Produced by Self-Propagating High Temperature Synthesis". In Explosion Shock Waves and High Strain Rate Phenomena. Materials Research Forum LLC, 2019. http://dx.doi.org/10.21741/9781644900338-14.
Testo completo
8
"The effect of fluoride based salt etching in the synthesis of Mxene". In Sustainable Processes and Clean Energy Transition. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902516-8.
Testo completoAbstract (sommario):
Abstract. Here we reported the effect of fluoride-based salt etching in the synthesis of Ti3C2 MXene by etching Ti3AlC2 MAX phase precursor. Lithium fluoride (LiF) and ammonium fluoride were the fluoride-based salts were chosen as an etching agent in this study. The optimum etchant concentration and etching temperature of the MAX phase were evaluated. The presence of aluminium etched was determined by using the Inducted Couple Plasma Optical Emission Spectrometry (ICP-OES). The initial concentration of aluminium in Ti3AlC2 precursor was estimated based on the data from Energy Dispersive X-Ray Analysis (EDX). The study shows that the optimum etchant concentration of LiF is 5M and NH4F is 3M. Room temperature is the optimum etching temperature due to the exothermic reaction of the process. Compared to LiF, NH4F is the preferred salt for in-situ HF fluoride-based salt etchant due to the capability of the salt to etch the maximum amount of Al at a low concentration of 3M within 24 hours at room temperature.
9
Ochs, Karlheinz, Bakr Al Beattie e Sebastian Jenderny. "An Ising Machine Solving Max-Cut Problems based on the Circuit Synthesis of the Phase Dynamics of a Modified Kuramoto Model". In 2021 IEEE International Midwest Symposium on Circuits and Systems (MWSCAS). IEEE, 2021. http://dx.doi.org/10.1109/mwscas47672.2021.9531734.
Testo completo
10
Terwilliger, T. C. "The map-likelihood function and improvement of phases in X-ray crystallography and general phase recovery". In Signal Recovery and Synthesis. Washington, D.C.: OSA, 2001. http://dx.doi.org/10.1364/srs.2001.stuc1.
Testo completoRapporti di organizzazioni sul tema "MAX phase synthesis"
1
Mahajan, D. Low temperature liquid phase catalytic synthesis of methanol from synthesis gas. Final report, May 20, 1994--May 20, 1995. Office of Scientific and Technical Information (OSTI), settembre 1995. http://dx.doi.org/10.2172/10130283.
Testo completo
2
Foh, Stephen, N. Poonawala e J. Pritchett. PR-4-172-R01 Modeling of Mixing in Porous Media. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), novembre 1985. http://dx.doi.org/10.55274/r0011433.
Testo completoAbstract (sommario):
The objective of this work was to define potential problems for storage field operators who stored non-traditional (supplemental) gas supplies (imported LNG, synthetic natural gas, peakshaving gases, etc.) in reservoirs originally using natural gas from traditional sources. Findings indicated that changes in storage field performance could be expected, including changed field inventory, deliverability and base gas requirements. The degree to which supplemental and traditional gases mix in storage reservoirs was identified as the key issue with respect to accounting for and dealing with these changes. The development of a reservoir simulator capable of handling gas-phase mixing in porous media was recommended. Such a model should account for mixing due to gravity segregation and hydrodynamic dispersion.
3
Meidan, Rina, e Joy Pate. Roles of Endothelin 1 and Tumor Necrosis Factor-A in Determining Responsiveness of the Bovine Corpus Luteum to Prostaglandin F2a. United States Department of Agriculture, gennaio 2004. http://dx.doi.org/10.32747/2004.7695854.bard.
Testo completoAbstract (sommario):
The corpus luteum (CL) is a transient endocrine gland that has a vital role in the regulation of the estrous cycle, fertility and the maintenance of pregnancy. In the absence of appropriate support, such as occurs during maternal recognition of pregnancy, the CL will regress. Prostaglandin F2a (PGF) was first suggested as the physiological luteolysin in ruminants several decades ago. Yet, the cellular mechanisms by which PGF causes luteal regression remain poorly defined. In recent years it became evident that the process of luteal regression requires a close cooperation between steroidogenic, endothelial and immune cells, all resident cells of this gland. Changes in the population of these cells within the CL closely consort with the functional changes occurring during various stages of CL life span. The proposal aimed to gain a better understanding of the intra-ovarian regulation of luteolysis and focuses especially on the possible reasons causing the early CL (before day 5) to be refractory to the luteolytic actions of PGF. The specific aims of this proposal were to: determine if the refractoriness of the early CL to PGF is due to its inability to synthesize or respond to endothelin–1 (ET-1), determine the cellular localization of ET, PGF and tumor necrosis factor a (TNF a) receptors in early and mid luteal phases, determine the functional relationships among ET-1 and cytokines, and characterize the effects of PGF and ET-1 on prostaglandin production by luteal cell types. We found that in contrast to the mature CL, administration of PGF2a before day 5 of the bovine cycle failed to elevate ET-1, ETA receptors or to induce luteolysis. In fact, PGF₂ₐ prevented the upregulation of the ET-1 gene by ET-1 or TNFa in cultured luteal cells from day 4 CL. In addition, we reported that ECE-1 expression was elevated during the transitionof the CL from early to mid luteal phase and was accompanied by a significant rise in ET-1 peptide. This coincides with the time point at which the CL gains its responsiveness to PGF2a, suggesting that ability to synthesize ET-1 may be a prerequisite for luteolysis. We have shown that while ET-1 mRNA was exclusively localized to endothelial cells both in young and mature CL, ECE-1 was present in the endothelial cells and steroidogenic cells alike. We also found that the gene for TNF receptor I is only moderately affected by the cytokines tested, but that the gene for TNF receptor II is upregulated by ET-1 and PGF₂ₐ. However, these cytokines both increase expression of MCP-1, although TNFa is even more effective in this regard. In addition, we found that proteins involved in the transport and metabolism of PGF (PGT, PGDH, COX-2) change as the estrous cycle progresses, and could contribute to the refractoriness of young CL. The data obtained in this work illustrate ET-1 synthesis throughout the bovine cycle and provide a better understanding of the mechanisms regulating luteal regression and unravel reasons causing the CL to be refractory to PGF2a.
4
Goff, Fraser, Shari A. Kelley, Cathy J. Goff, David J. McCraw, G. Robert Osburn, John R. Lawrence, Paul G. Drakos e Steven J. Skotnicki. Geologic Map of Mount Taylor Volcano Area, New Mexico. New Mexico Bureau of Geology and Mineral Resources, 2019. http://dx.doi.org/10.58799/gm-80.
Testo completoAbstract (sommario):
The Geologic Map of the Mount Taylor Volcano Area, New Mexico is a 1:36,000 compilation of six recent NMBGMR 1:24,000 geologic quadrangles that encompass this extinct composite stratovolcano. Mount Taylor is New Mexico's second-largest volcano after the Valles Caldera in the Jemez Mountains. This timely map and accompanying report, resulting from over a decade of thorough work, synthesizes the current geologic understanding of such an important landscape feature of the state.For such a complex volcanic landform, the report provides an exhaustive description of the volcano area in an easy-to-read format. In addition to providing a detailed description of each of the map's 339 units and dikes, it documents the volcano's history and history of research, its geochemical and petrographic composition, the phases of its construction ranging from the initial to the terminal eruptions, 3.72-1.26 million years ago, and its subsequent erosion, resulting in the summit Amphitheater and its extensive apron of debris. It describes the surrounding volcanic centers, the structure of the area, and the extensive dikes and maars. After touching on the water resources, hydrothermal alteration and mineralization, and geothermal potential, the report concludes with a conceptual model of volcano evolution.
5
Delmer, Deborah P., Douglas Johnson e Alex Levine. The Role of Small Signal Transducing Gtpases in the Regulation of Cell Wall Deposition Patterns in Plants. United States Department of Agriculture, agosto 1995. http://dx.doi.org/10.32747/1995.7570571.bard.
Testo completoAbstract (sommario):
The combined research of the groups of Delmer, Levine and Johnson has led to a number of interesting findings with respect to the function of the small GTPase Rac in plants and also opened up new leads for future research. The results have shown: 1) The Rac13 protein undergoes geranylgeranlyation and is also translocated to the plasma membrane as found for Rac in mammals; 2) When cotton Rac13 is highly- expressed in yeast, it leads to an aberrant phenotype reminiscent of mutants impaired in actin function, supporting a role for Rac13 in cytoskeletal organization; 3) From our searches, there is no strong evidence that plants contain homologs of the related CDC42 genes found in yeast and mammals; 4) We have identified a rather unique Rac gene in Arabidopsis that has unusual extensions at both the N- and C-terminal portions of the protein; 5) New evidence was obtained that an oxidative burst characterized by substantial and sustained production of H202 occurs coincident with the onset of secondary wall synthesis in cotton fibers. Further work indicates that the H202 produced may be a signal for the onset of this phase of development and also strongly suggests that Rac plays an important role in signaling for event. Since the secondary walls of plants that contain high levels of lignin and cellulose are the major source of biomass on earth, understanding what signals control this process may well in the future have important implications for manipulating the timing and extent of secondary wall deposition. 6) When the cotton Rac13 promoter is fused to the reporter gene GUS, expression patterns in Arabidopsis indicate very strong and specific expression in developing trichomes and in developing xyelm. Since both of these cell types are engaged in secondary wall synthesis, this further supports a role for Rac in signaling for onset of this process. Since cotton fibers are anatomically defined as trichomes, these data may also be quite useful for future studies in which the trichomes of Arabidopsis may serve as a model for cotton fiber development; the Rac promoter can therefore be useful to drive expression of other genes proposed to affect fiber development and study the effects on the process; 7) The Rac promoter has also been shown to be the best so far tested for use in development of a system for transient transformation of developing cotton fibers, a technique that should have many applications in the field of cotton biotechnology; 8) One candidate protein that may interact with Rac13 to be characterized further in the future is a protein kinase that may be analogous to the PAK kinase that is known to interact with Rac in mammals.
6
Casey, Therese, Sameer J. Mabjeesh, Avi Shamay e Karen Plaut. Photoperiod effects on milk production in goats: Are they mediated by the molecular clock in the mammary gland? United States Department of Agriculture, gennaio 2014. http://dx.doi.org/10.32747/2014.7598164.bard.
Testo completoAbstract (sommario):
US scientists, Dr. Theresa Casey and Dr. Karen Plaut, collaborated with Israeli scientists, Dr. SameerMabjeesh and Dr. AviShamay to conduct studies proposed in the BARD Project No. US-4715-14 Photoperiod effects on milk production in goats: Are they mediated by the molecular clock in the mammary gland over the last 3 years. CLOCK and BMAL1 are core components of the circadian clock and as heterodimers function as a transcription factor to drive circadian-rhythms of gene expression. Studies of CLOCK-mutant mice found impaired mammary development in late pregnancy was related to poor lactation performance post-partum. To gain a better understanding of role of clock in regulation of mammary development studies were conducted with the mammary epithelial cell line HC11. Decreasing CLOCK protein levels using shRNA resulted in increased mammary epithelial cell growth rate and impaired differentiation, with lower expression of differentiation markers including ad herens junction protein and fatty acid synthesis genes. When BMAL1 was knocked out using CRISPR-CAS mammary epithelial cells had greater growth rate, but reached stationary phase at a lower density, with FACS indicating cells were growing and dying at a faster rate. Beta-casein milk protein levels were significantly decreased in BMAL1 knockout cells. ChIP-seq analysis was conducted to identify BMAL1 target genes in mammary epithelial cells. Studies conducted in goats found that photoperiod duration and physiological state affected the dynamics of the mammary clock. Effects were likely independent of the photoperiod effects on prolactin levels. Interestingly, circadian rhythms of core body temperature, which functions as a key synchronizing cue sent out by the central clock in the hypothalamus, were profoundly affected by photoperiod and physiological state. Data support that the clock in the mammary gland regulates genes important to development of the gland and milk synthesis. We also found the clock in the mammary is responsive to changes in physiological state and photoperiod, and thus may serve as a mechanism to establish milk production levels in response to environmental cues.
7
Paynter, Robin A., Celia Fiordalisi, Elizabeth Stoeger, Eileen Erinoff, Robin Featherstone, Christiane Voisin e Gaelen P. Adam. A Prospective Comparison of Evidence Synthesis Search Strategies Developed With and Without Text-Mining Tools. Agency for Healthcare Research and Quality (AHRQ), marzo 2021. http://dx.doi.org/10.23970/ahrqepcmethodsprospectivecomparison.
Testo completoAbstract (sommario):
Background: In an era of explosive growth in biomedical evidence, improving systematic review (SR) search processes is increasingly critical. Text-mining tools (TMTs) are a potentially powerful resource to improve and streamline search strategy development. Two types of TMTs are especially of interest to searchers: word frequency (useful for identifying most used keyword terms, e.g., PubReminer) and clustering (visualizing common themes, e.g., Carrot2). Objectives: The objectives of this study were to compare the benefits and trade-offs of searches with and without the use of TMTs for evidence synthesis products in real world settings. Specific questions included: (1) Do TMTs decrease the time spent developing search strategies? (2) How do TMTs affect the sensitivity and yield of searches? (3) Do TMTs identify groups of records that can be safely excluded in the search evaluation step? (4) Does the complexity of a systematic review topic affect TMT performance? In addition to quantitative data, we collected librarians' comments on their experiences using TMTs to explore when and how these new tools may be useful in systematic review search¬¬ creation. Methods: In this prospective comparative study, we included seven SR projects, and classified them into simple or complex topics. The project librarian used conventional “usual practice” (UP) methods to create the MEDLINE search strategy, while a paired TMT librarian simultaneously and independently created a search strategy using a variety of TMTs. TMT librarians could choose one or more freely available TMTs per category from a pre-selected list in each of three categories: (1) keyword/phrase tools: AntConc, PubReMiner; (2) subject term tools: MeSH on Demand, PubReMiner, Yale MeSH Analyzer; and (3) strategy evaluation tools: Carrot2, VOSviewer. We collected results from both MEDLINE searches (with and without TMTs), coded every citation’s origin (UP or TMT respectively), deduplicated them, and then sent the citation library to the review team for screening. When the draft report was submitted, we used the final list of included citations to calculate the sensitivity, precision, and number-needed-to-read for each search (with and without TMTs). Separately, we tracked the time spent on various aspects of search creation by each librarian. Simple and complex topics were analyzed separately to provide insight into whether TMTs could be more useful for one type of topic or another. Results: Across all reviews, UP searches seemed to perform better than TMT, but because of the small sample size, none of these differences was statistically significant. UP searches were slightly more sensitive (92% [95% confidence intervals (CI) 85–99%]) than TMT searches (84.9% [95% CI 74.4–95.4%]). The mean number-needed-to-read was 83 (SD 34) for UP and 90 (SD 68) for TMT. Keyword and subject term development using TMTs generally took less time than those developed using UP alone. The average total time was 12 hours (SD 8) to create a complete search strategy by UP librarians, and 5 hours (SD 2) for the TMT librarians. TMTs neither affected search evaluation time nor improved identification of exclusion concepts (irrelevant records) that can be safely removed from the search set. Conclusion: Across all reviews but one, TMT searches were less sensitive than UP searches. For simple SR topics (i.e., single indication–single drug), TMT searches were slightly less sensitive, but reduced time spent in search design. For complex SR topics (e.g., multicomponent interventions), TMT searches were less sensitive than UP searches; nevertheless, in complex reviews, they identified unique eligible citations not found by the UP searches. TMT searches also reduced time spent in search strategy development. For all evidence synthesis types, TMT searches may be more efficient in reviews where comprehensiveness is not paramount, or as an adjunct to UP for evidence syntheses, because they can identify unique includable citations. If TMTs were easier to learn and use, their utility would be increased.
8
Lapidot, Moshe, e Vitaly Citovsky. molecular mechanism for the Tomato yellow leaf curl virus resistance at the ty-5 locus. United States Department of Agriculture, gennaio 2016. http://dx.doi.org/10.32747/2016.7604274.bard.
Testo completoAbstract (sommario):
Tomato yellow leaf curl virus (TYLCV) is a major pathogen of tomato that causes extensive crop loss worldwide, including the US and Israel. Genetic resistance in the host plant is considered highly effective in the defense against viral infection in the field. Thus, the best way to reduce yield losses due to TYLCV is by breeding tomatoes resistant or tolerant to the virus. To date, only six major TYLCV-resistance loci, termed Ty-1 to Ty-6, have been characterized and mapped to the tomato genome. Among tomato TYLCV-resistant lines containing these loci, we have identified a major recessive quantitative trait locus (QTL) that was mapped to chromosome 4 and designated ty-5. Recently, we identified the gene responsible for the TYLCV resistance at the ty-5 locus as the tomato homolog of the gene encoding messenger RNA surveillance factor Pelota (Pelo). A single amino acid change in the protein is responsible for the resistant phenotype. Pelo is known to participate in the ribosome-recycling phase of protein biosynthesis. Our hypothesis was that the resistant allele of Pelo is a “loss-of-function” mutant, and inhibits or slows-down ribosome recycling. This will negatively affect viral (as well as host-plant) protein synthesis, which may result in slower infection progression. Hence we have proposed the following research objectives: Aim 1: The effect of Pelota on translation of TYLCV proteins: The goal of this objective is to test the effect Pelota may or may not have upon translation of TYLCV proteins following infection of a resistant host. Aim 2: Identify and characterize Pelota cellular localization and interaction with TYLCV proteins: The goal of this objective is to characterize the cellular localization of both Pelota alleles, the TYLCV-resistant and the susceptible allele, to see whether this localization changes following TYLCV infection, and to find out which TYLCV protein interacts with Pelota. Our results demonstrate that upon TYLCV-infection the resistant allele of pelota has a negative effect on viral replication and RNA transcription. It is also shown that pelota interacts with the viral C1 protein, which is the only viral protein essential for TYLCV replication. Following subcellular localization of C1 and Pelota it was found that both protein localize to the same subcellular compartments. This research is innovative and potentially transformative because the role of Peloin plant virus resistance is novel, and understanding its mechanism will lay the foundation for designing new antiviral protection strategies that target translation of viral proteins. BARD Report - Project 4953 Page 2
9
Meidan, Rina, e Robert Milvae. Regulation of Bovine Corpus Luteum Function. United States Department of Agriculture, marzo 1995. http://dx.doi.org/10.32747/1995.7604935.bard.
Testo completoAbstract (sommario):
The main goal of this research plan was to elucidate regulatory mechanisms controlling the development, function of the bovine corpus luteum (CL). The CL contains two different sterodigenic cell types and therefore it was necessary to obtain pure cell population. A system was developed in which granulosa and theca interna cells, isolated from a preovulatory follicle, acquired characteristics typical of large (LL) and small (SL) luteal cells, respectively, as judged by several biochemical and morphological criteria. Experiments were conducted to determine the effects of granulosa cells removal on subsequent CL function, the results obtained support the concept that granulosa cells make a substaintial contribution to the output of progesterone by the cyclic CL but may have a limited role in determining the functional lifespan of the CL. This experimental model was also used to better understand the contribution of follicular granulosa cells to subsequent luteal SCC mRNA expression. The mitochondrial cytochrome side-chain cleavage enzyme (SCC), which converts cholesterol to pregnenolone, is the first and rate-limiting enzyme of the steroidogenic pathway. Experiments were conducted to characterize the gene expression of P450scc in bovine CL. Levels of P450scc mRNA were higher during mid-luteal phase than in either the early or late luteal phases. PGF 2a injection decreased luteal P450scc mRNA in a time-dependent manner; levels were significantly reduced by 2h after treatment. CLs obtained from heifers on day 8 of the estrous cycle which had granulosa cells removed had a 45% reduction in the levels of mRNA for SCC enzymes as well as a 78% reduction in the numbers of LL cells. To characterize SCC expression in each steroidogenic cell type we utilized pure cell populations. Upon luteinization, LL expressed 2-3 fold higher amounts of both SCC enzymes mRNAs than SL. Moreover, eight days after stimulant removal, LL retained their P4 production capacity, expressed P450scc mRNA and contained this protein. In our attempts to establish the in vitro luteinization model, we had to select the prevulatory and pre-gonadotropin surge follicles. The ratio of estradiol:P4 which is often used was unreliable since P4 levels are high in atretic follicles and also in preovulatory post-gonadotropin follicles. We have therefore examined whether oxytocin (OT) levels in follicular fluids could enhance our ability to correctly and easily define follicular status. Based on E2 and OT concentrations in follicular fluids we could more accurately identify follicles that are preovulatory and post gonadotropin surge. Next we studied OT biosynthesis in granulosa cells, cells which were incubated with forskolin contained stores of the precursor indicating that forskolin (which mimics gonadotropin action) is an effective stimulator of OT biosynthesis and release. While studying in vitro luteinization, we noticed that IGF-I induced effects were not identical to those induced by insulin despite the fact that megadoses of insulin were used. This was the first indication that the cells may secrete IGF binding protein(s) which regonize IGFs and not insulin. In a detailed study involving several techniques, we characterized the species of IGF binding proteins secreted by luteal cells. The effects of exogenous polyunsaturated fatty acids and arachidonic acid on the production of P4 and prostanoids by dispersed bovine luteal cells was examined. The addition of eicosapentaenoic acid and arachidonic acid resulted in a dose-dependent reduction in basal and LH-stimulated biosynthesis of P4 and PGI2 and an increase in production of PGF 2a and 5-HETE production. Indomethacin, an inhibitor of arachidonic acid metabolism via the production of 5-HETE was unaffected. Results of these experiments suggest that the inhibitory effect of arachidonic acid on the biosynthesis of luteal P4 is due to either a direct action of arachidonic acid, or its conversion to 5-HETE via the lipoxgenase pathway of metabolism. The detailed and important information gained by the two labs elucidated the mode of action of factors crucially important to the function of the bovine CL. The data indicate that follicular granulosa cells make a major contribution to numbers of large luteal cells, OT and basal P4 production, as well as the content of cytochrome P450 scc. Granulosa-derived large luteal cells have distinct features: when luteinized, the cell no longer possesses LH receptors, its cAMP response is diminished yet P4 synthesis is sustained. This may imply that maintenance of P4 (even in the absence of a Luteotropic signal) during critical periods such as pregnancy recognition, is dependent on the proper luteinization and function of the large luteal cell.