1,784 research outputs found
Meeting with the Hebrew author Elias Hurwitz
No full textWhite paper; handpainted; on the reverse of Luftwaffe uniform pattern. Digitized posters are related to the activities of Jewish displaced persons drawn from the Records of Displaced Persons Camps and Centers in Germany (RG 294.2) Italy (RG 294.3) and Austria (RG 294.4) held by YIVO Archives. Please consult the historical note for those record groups for further information.Digital ImageDigital finding aid available
Obituary announcement about author and labor activist Sh. Mendelson
No full textBrown paper; handpainted. Digitized posters are related to the activities of Jewish displaced persons drawn from the Records of Displaced Persons Camps and Centers in Germany (RG 294.2) Italy (RG 294.3) and Austria (RG 294.4) held by YIVO Archives. Please consult the historical note for those record groups for further information.Digital ImageDigital finding aid available
Structural friction anisotropy on the nanometer scale
No full textThe ability to understand and control friction on an atomic scale is becoming increasingly important, not only considering the increasingly small scale of mechanical systems that are being developed, but also in respect of furthering the fundamental understanding of friction.
In this thesis, the friction anisotropy at the atomic level was investigated.
This investigation demanded special requirements from the experimental setup, and accordingly, in section 2, a detailed description of a newly developed scanning probe microscope incorporating new electronics and a significantly developed ultra-high vacuum system is given.
In particular, with this newly developed microscope, it is possible to use a specially designed sample holder which rotates the sample in situ, enabling the measurement of friction forces along arbitrary directions of the sample surface.
Measurements on NaCl(100), a well known surface in the field of nanotribology, were compared with Prandtl-Tomlinson simulations. Beside the anisotropy investigations, some newly discovered features along the [100] and [110] directions are presented. Three main conclusions can be drawn from these results: the tip path is influencing the average friction force, friction is reduced by 27\% on one ionic species (whether it is Na or Cl is depending on the tip), and the tip asymmetry is leading to a shift of forward and backward friction force maps along the slow scan direction.
In previous studies, the tip-sample interaction in the Prandtl-Tomlinson model was well described by a sinusoidal potential. This potential, however, fails to sufficiently describe the present results. New simulations were conducted and are presented, which are based on an ab initio calculated potential using density functional theory, and reproduce the main features of the experimental results well.
Investigations on the organic surface of a benzylammonium crystal have shown that the molecular orientation is influencing friction and producing a friction contrast on a molecular scale. While the experimental results clearly show that the corrugation potential is influenced by the molecular orientation, adequate simulations reproducing this phenomena require a potential which includes the relaxation of the surface and tip in contact.
In addition, anisotropy measurements show a strong increase of friction along the [100] orientation.
Friction measurements on patterned pristine and hydrogenated graphene initially revealed a contrast between these two surfaces which are initially covered by a contamination layer. In the course of continuous scanning, a mechanical cleaning occurs. The stability of the contamination layer under mechanical treatment is related to the extent of hydrogenation of the subjacent graphene, the hydrogenated regions require a more intense treatment for cleaning.
It is found that on the cleaned surface, friction reduces to approximately a quarter of its value, and, after this mechanical treatment, the friction contrast between graphene and hydrogenated graphene completely disappears.
It is concluded therefore that despite the strong effect of the hydrogenation to the electronic properties of graphene, it is not degrading its properties as a lubricant
Sweeping has no effect on renormalized turbulent viscosity
No full textWe perform renormalization group analysis (RG) of the Navier-Stokes equation in the presence of constant mean velocity field , and show that the renormalized viscosity is unaffected by , thus negating the ``sweeping effect", proposed by Kraichnan [Phys. Fluids {\bf 7}, 1723 (1964)] using random Galilean invariance. Using direct numerical simulation, we show that the correlation functions for and differ from each other, but the renormalized viscosity for the two cases are the same. Our numerical results are consistent with the RG calculations
BONDING AND DYNAMICS OF CNRg AND CRg COMPLEXES
No full textAuthor Institution: Department of Chemistry, Emory University, Atlanta, GA 30322The van der Waals complexes of CN and C with rare gas atoms (Rg) are of interest from the perspectives of their bonding characteristics and predissociation dynamics. Matrix isolation data indicate that that the bonding ranges from a weak van der Waals interaction for the Ne complexes to incipient chemical bonding for Xe. The low-lying vibronic states of CN and C are interleaved, which facilitates electronic energy transfer. Consequently, electronic predissociation of CNRg and CRg complexes provides a useful means to examine the detailed dynamics of electronic energy transfer. Predissociation processes for CNRg complexes have been characterized using double resonance techniques. The final state distributions exhibit symmetry preferences that yield insights concerning the topologies of the relevant potential energy surfaces. In addition, bond energies can be deduced from the predissociation dynamics. Data for the binary complexes CNRg (Rg=Ne, Ar, Kr, and Xe) and CRg will be presented, along with theoretical analyses based on potential energy surfaces
René Géronimo Favaloro : pioneer of Cardiac Surgery
No full textDr. René G. Favaloro moved to the Cleveland Clinic in 1962 and proceeded to reshape the face of cardiac surgery as we knew it. Together with his colleagues at the Cleveland Clinic, Drs. Effler, Sones, Proudfit, Groves, Sheldon and countless others, he contributed to the double internal mammary arterymyocardial implantation by the Vineberg method, and by May 1967, he reconstructed the right coronary artery by the saphenous vein graft interposition. These landmark procedures paved the way for the aorto-coronary saphenous vein bypass graft in October 1967. Many similar breakthroughs ensued, with the application of the bypass technique to the left coronary artery, the combination of coronary artery bypass graft with left ventricular reconstruction and valve repair/replacement and finally, by December, a double bypass to the right coronary artery and anterior descending branch of the left coronary artery. In June, 1971, Dr. Favaloro decided to leave the Cleveland Clinic and return to Argentina where he created a medical centre, a teaching unit, a research department and finally an Institute of Cardiology and Cardiovascular Surgery. This was his greatest personal ambition. Over and above his brilliant mind and craft, Dr. Favaloro was a man of integrity, courage, honesty and humility, whose name will never cease to reverberate throughout the history of medicine.peer-reviewe
A non-classical synthetic strategy for organic mesocrystals
No full textMesocrystals are ordered nanoparticle superstructures, often with internal porosity, which receive much recent research interest in catalysis, energy storage, sensors, and biomedicine area. Understanding the mechanism of synthetic routes is essential for precise control of size and structure that affect the function of mesocrystals. The classical synthetic strategy of mesocrystal was formed via self-assembly of nanoparticles with a faceted inorganic core but a denser (or thicker) shell of organic molecules. However, the potential materials and synthetic handles still need to be explored to meet new applications. In this work, we develop a non-classical synthetic strategy for organic molecules, such as tetrakis (4-hydroxyphenyl) ethylene (TPE-4OH), tetrakis (4-bromophenyl) ethylene (TPE-4Br), and benzopinacole, to produce mesocrystals with composed of microrod arrays via co-solvent-induced crystal transformation. The aligned nanorods are grown epitaxially onto organic microplates, directed by small lattice mismatch between plates and rods. Thus, the present work offers general synthetic handle for establishing well-organized organic mesocrystals.Ministry of Education (MOE)Published versionThe author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This work was supported by the MOE of Singapore (RG 14/13 and RG 5/16), the National Natural Science Foundation of China (No. 21673117), recruitment Program of Global Experts, Jiangsu Provincial Foundation for Specially-Appointed Professor, start-up fund at Nanjing Tech University (39837102), SICAM Fellowship from Jiangsu National Synergetic Innovation Center for Advanced Materials, and Jiangsu Science and Technology Plan (Project No. BK20211258)
Modeling P-Rg conversions from isolated topographic features near the NORESS array
No full textUsing the T-matrix, or extended boundary condition, method, seismic-wave scattering is modelled from earth models with one-dimensional (1D) isolated topographic features. This study is motivated by observations suggesting that surface topography generates coda waves, which are relatively large-amplitude arrivals following major seismic phases. For sinusoidal periodic surfaces, large-amplitude anomalies in the surface displacement spectrum correspond to P-to-Rayleigh (P-Rg), S-to-Rayleigh (S-Rg), and other mode conversions. For isolated topographic features, these conversions still exist. Teleseismic P-Rg conversions from isolated hills were modelled in order to understand and confirm the origin of observed conversions near the NORESS array. -from Author
THEORETICAL INVESTIGATION OF THE M-RG (M = ALKALINE EARTH METAL; RG = RARE GAS) COMPLEXES
No full textAuthor Institution: School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, USAMetal cation rare gas complexes provide an expectedly simple system with which to investigate intermolecular interactions. Despite this, we have previously found the M-RG (M = alkaline earth metal) complexes to very complicated systems, with the complexes of the heavier rare gases displaying surprisingly large degrees of chemical character., \textbf{2000}, \textit{114}, 7631.}, \textbf{2010}, \textit{132}, 054302.}, \textbf{2009}, \textit{130}, 194305.} Here we extend these studies by examining the nature of these interactions with increasing degrees of solvation through investigating the M-RG complexes using high level \textit{ab initio} techniques. Intriguing trends in the geometries and dissociation energies of these complexes have been observed and are rationalized
- …
