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151.
Journal of Statistical Physics - We prove Hohenberg–Kohn theorems for several models of quantum mechanics. First, we show that for possibly degenerate systems of several types of particles,... 相似文献
152.
Maleki T Chitnis G Park JH Cantor LB Ziaie B 《IEEE transactions on bio-medical engineering》2012,59(6):1507-1513
We report on the development of a batch fabricated biodegradable truncated-cone-shaped plug filter to overcome the postoperative hypotony in nonvalved glaucoma drainage devices. Plug filters are composed of biodegradable polymers that disappear once wound healing and bleb formation has progressed past the stage where hypotony from overfiltration may cause complications in the human eye. The biodegradable nature of device eliminates the risks associated with permanent valves that may become blocked or influence the aqueous fluid flow rate in the long term. The plug-filter geometry simplifies its integration with commercial shunts. Aqueous humor outflow regulation is achieved by controlling the diameter of a laser-drilled through-hole. The batch compatible fabrication involves a modified SU-8 molding to achieve truncated-cone-shaped pillars, polydimethylsiloxane micromolding, and hot embossing of biodegradable polymers. The developed plug filter is 500?μm long with base and apex plane diameters of 500 and 300?μm, respectively, and incorporates a laser-drilled through-hole with 44-μm effective diameter in the center. 相似文献
153.
Paul S.N. Lee Clement Y.K. So Francis Lee Louis Leung Michael Chan 《Telematics and Informatics》2018,35(7):1949-1957
Social media, as a subaltern public sphere (Fraser, 1990), have a democratic function in providing an alternative platform for minorities and marginalized to defy mainstream discourses in the public sphere. However, social media have been found to have an echo chamber effect, which may be detrimental to democracy. They may help to accelerate the ascendancy of a “post-truth” era in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief. A study on political polarization, however, showed that selective exposure and avoidance in social media are weak indicators of polarization (Johnson et al., 2017). This study examines the role of social media in democracy and partisan politics. The authors considered that despite the echo chamber effect, social media have a limited part to play in the formation of polarized stances compared with other factors, such as demographics, political orientation, and mass media use. The study tested two main hypotheses: H1: Social media use is associated with political stance that is marginalized in the mainstream media; H2: Political orientation has a stronger relationship than social media use with the stance toward political values and social issues.The results supported both hypotheses. Social media are associated with political stance that is marginalized in the mainstream media. However, when compared with other factors, the relationship between social media and stance becomes less obvious. Although the echo chamber effect may reinforce the original stance, social media do not exhibit a strong relationship with the stance toward political values and social issues. Partisan orientation and use of partisan mass media are found to have stronger links with variations in stance. Social media, however, provide a subaltern public sphere for those excluded from the dominant public sphere, thus extending the public sphere to accommodate multiple opinions and perspectives. 相似文献
154.
Paul J. Germann Roberta Aram A. Louis Odom Gerald Burke 《School science and mathematics》1996,96(4):192-201
The purpose of this study was to extend attempts to develop a research framework for encoding and analyzing students' responses to the tasks of asking questions, identifying variables, and formulating hypotheses, and to use the research framework to analyze and classify the responses of seventh grade students. A performance-based assessment instrument was used. The topic was heat and temperature. The responses of 364 seventh grade students were used to develop a framework for evaluating student written responses which allows researchers to classify student responses according to their general completeness and usefulness, and according to the manner in which responses were incomplete or not useful. Interrater reliability was 82%. Seventh grade students who reportedly have had instruction in the science processes did not perform well on this performance-based assessment. 相似文献
155.
156.
Bruno Albrecht Michael Allan Edwin Haselbach Louis Neuhaus Pierre-Alain Carrupt 《Helvetica chimica acta》1984,67(1):220-223
Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured. I = 8.20 eV and I = 8.65 eV were found, the dominant vibrational progression (? = 725 cm?1) indicating that in the course of 1(X)→1 +( X? ) flattening around the N-atom occurs. The Franck-Condon profile of this band, however, suggests that a skeletal mode of ? ≈ 1400 cm?1 (observed also in the iso-π-electronic systems vinyl-alcohol-cation and allyl radical) may also be excited. Comparison with the data for the isomer acetaldehyde-imine 2 and its cation s + shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from the neutrals to the cations. 相似文献
157.
158.
Arlette Clayer Louis Agneray Gérard Vandenbussche et Pierre Petel 《Fresenius' Journal of Analytical Chemistry》1968,236(1):240-249
Résumé Le procédé de séparation des isotopes de l'hydrogène par chromatographie en lit mobile présenté est un procédé continu.Le principe en est le suivant: dans une colonne verticale, un lit mobile de silicagel descend par gravité. Le mélange à séparer (protium/deutérium) est introduit au milieu de cette colonne. La séparation du mélange en ses deux constituants s'effectue par échange à contre-courant entre la phase gazeuse et la phase adsorbée. Le protium, moins adsorbé, est soutiré en tête de colonne, le deutérium est soutiré en pied. Le reflux en bas de colonne est obtenu de 2 façons différentes qui dépendent du type de désorption employé: désorption du silicagel par élévation de températuré et élution du deuté rium, par de l'hélium désorption du silicagel par élévation de température et déplacement du deutérium, par de l'azote.Dans le ler cas, les gaz produits sont dilués dans l'hélium, dans le 2ème cas ils sortent non dilués. Le silicagel est remonté en tête de colonne par un transport pneumatique. L'expérimentation présentée à été faite avec gaz de déplacement azote.
Summary The preparation-process of hydrogen isotopes by chromatography in a moving bed in a continuous process is described.The principle is as follows: In a vertical column silicagel flows downward, by gravity, in a moving bed. The gaseous mixture to be separated (protium/deuterium) is introduced into the central portion of this column. Separation of the mixture into its two constituents is achieved by a counter-current exchange between the gaseous phase and the adsorbed phase. Protium less adsorbed is withdrawn at the top, deuterium is withdrawn at the bottom. The reflux is produced, at the bottom of the column, by two differents means, depending on the type of desorption used: Silicagel-desorption by rise of temperature and deuterium-elution by helium or displacing of deuterium by nitrogen.The gases produced are mixed with helium (1st case), or not (2nd case). Silicagel is carried again onto the top of the column by pneumatic transport. The experiments presented were carried out by means of nitrogen as displacing gas.相似文献
159.
160.
The 13C? 13C spin coupling constants have been determined in substituted [1-13C]tetrahydronaphthylenes, [5-13C]hexahydrobenzanthracenes and [5-13C]benzanthracene. In addition, the 13C? 13C spin coupling constants for 7-hydroxy[7-13C]benzopyrene, trans-7,8-dihydro[7-13C]benzopyrene-7,8-diol and trans-7,8-dihydro[10-13C]benzopyrene-7,8-diol are reported, together with the one-bond carbon-carbon coupling constants between C-4 and C-5 in selected 4,5-disubstituted benzopyrenes. Values for the directly bonded coupling constants and long-range coupling constants are similar to those reported previously for other aromatic and aliphatic systems. Substituent effects on carbon-carbon coupling are compared for similarly substituted cyclic and acyclic systems. 相似文献