295,550 research outputs found
Seconde nozze e identità materna nella Firenze del tardo Medioevo,
No full textS. Seidel Menchi, A. Jacobson Schutte, Th. KuehnInternational audienc
Matching asteroid population characteristics with a model constructed from the YORP-induced rotational fission hypothesis
No full textFrom the results of a comprehensive asteroid population evolution model, we conclude that the YORP-induced rotational fission hypothesis is consistent with the observed population statistics of small asteroids in the main belt including binaries and contact binaries. These conclusions rest on the asteroid rotation model of Marzari et al. ([2011]Icarus, 214, 622-631), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis, described in detail within, and the binary evolution model of Jacobson et al. ([2011a] Icarus, 214, 161-178) and Jacobson et al. ([2011b] The Astrophysical Journal Letters, 736, L19). Our complete asteroid population evolution model is highly constrained by these and other previous works, and therefore it has only two significant free parameters: the ratio of low to high mass ratio binaries formed after rotational fission events and the mean strength of the binary YORP (BYORP) effect.We successfully reproduce characteristic statistics of the small asteroid population: the binary fraction, the fast binary fraction, steady-state mass ratio fraction and the contact binary fraction. We find that in order for the model to best match observations, rotational fission produces high mass ratio (> 0.2) binary components with four to eight times the frequency as low mass ratio (<0.2) components, where the mass ratio is the mass of the secondary component divided by the mass of the primary component. This is consistent with post-rotational fission binary system mass ratio being drawn from either a flat or a positive and shallow distribution, since the high mass ratio bin is four times the size of the low mass ratio bin; this is in contrast to the observed steady-state binary mass ratio, which has a negative and steep distribution. This can be understood in the context of the BYORP-tidal equilibrium hypothesis, which predicts that low mass ratio binaries survive for a significantly longer period of time than high mass ratio systems. We also find that the mean of the log-normal BYORP coefficient distribution μB10-2, which is consistent with estimates from shape modeling (McMahon and Scheeres, 2012a
Proper Ferroelectricity in the Dion?Jacobson Material CsBi2Ti2NbO10: Experiment and Theory
No full textA diverse range of materials and properties are exhibited by layered perovskites. We report on the synthesis, characterization, and computational investigation of a new ferroelectric?CsBi2Ti2NbO10, an n = 3 member of the Dion?Jacobson (DJ) family. Structural studies using variable temperature neutron powder diffraction indicate that a combination of octahedral rotations and polar displacements result in the polar structure. Density functional theory calculations reveal that the wider perovskite blocks in CsBi2Ti2NbO0 stabilize proper ferroelectricity, in contrast to the hybrid-improper ferroelectricity reported for all other DJ phases. Our results raise the possibility of a new class of proper ferroelectric materials analogous to the well-known Aurivillius phases
Ultra-low friction W-S-N solid lubricant coating
No full textW-S-N films were deposited by reactive magnetron sputtering from WS2 target in Ar/N2 atmosphere. Besides the standard evaluation of composition, structure, morphology, hardness and cohesion/adhesion, the core objective of this paper was to analyze coating tribological behavior. The chemical composition was 34 at.% N, 12 at.% O, 29 at.% W and 25 at.% S, and the as-deposited films were completely amorphous. The film thickness was 2.3 μm, including the approximately 300-nm thick adhesion improving titanium interlayer. The friction coefficient was lower than 0.003 when sliding in dry nitrogen. The coating showed remarkable wear resistance surviving more than 2 million laps on pin-on-dics. The excellent friction properties were attributed to the formation of a thin tungsten disulfide tribofilm on the top of the wear track of the coating and on the counterpart surface. Moreover, the coating showed ability to replenish damaged areas with solid lubricant. We demonstrated that a structural transformation of the coating from an amorphous-like to a gradient quasi-ordered structure and an ordered transfer layer formation improved mechanical properties and radically decreased friction and wear
Oral History Interview: Pam Jacobson (1109)
No full textAbstract: In her 2010 interview with Pat Calchina, Pam Jacobson details her life in Madison. She spoke of the time period between 1974 and 1996 and of the following topics: women?s studies classes at UW Madison, lesbianism, being part of the first class of women firefighters to be hired by the Madison fire department and her 17 years as a firefighter, various lesbian activities in Madison.
Key Words: Madison (WI), Fire Chief Durkin, Marcia Holtz, Bev Buhr, Rory Ward, Ronny Greer, Liz Estrada, GALVANIZE, shirts and skins basketball at Orton Park, Lesbian Variety Show
On the Jacobson radical of graded rings
No full textsummary:All commutative semigroups are described such that the Jacobson radical is homogeneous in each ring graded by
Pyrimidine nucleotides containing a (S)-methanocarba ring as P2Y6 receptor agonists
No full textBoth agonists and antagonists of the UDP-activated P2Y6 receptor (P2Y6R) have been proposed for therapeutic use, in conditions such as cancer, inflammation, neurodegeneration and diabetes. Uracil nucleotides containing a south-bicyclo[3.1.0]hexane ((S)-methanocarba) ring system in place of the ribose ring were synthesized and shown to be potent P2Y6R agonists in a calcium mobilization assay. The (S)-methanocarba modification was compatible with either a 5-iodo or 4-methoxyimino group on the pyrimidine, but not with a α,β-methylene 5′-diphosphate. (S)-Methanocarba dinucleotide potency was compatible with a N4-methoxy modification on the proximal nucleoside that is assumed to bind at the P2Y6R similarly to UDP; (N)-methanocarba was preferred on the distal nucleoside moiety. This suggests that the distal dinucleotide P2Y6R binding site prefers a ribose-like group that can attain a (N) conformation, rather than (S). Dinucleotide binding was modeled by homology modeling, docking and molecular dynamics simulations, which suggested the same ribose conformational preferences found empirically
Democratic imperialism and Risorgimento colonialism: European legionnaires on the Argentine Pampa in the 1850s
No full textIn the wake of the Revolutions of 1848 in Europe, democratic nationalism promoted the liberation of oppressed peoples from the shackles of absolutist empires and prophesied the emergence of a cosmopolitan brotherhood of nation states. From a global perspective, however, this political culture could be imperial. The governors of State of Buenos Aires modelled plans for the White colonization of the pampas on French Algeria. They sent a Military-Agricultural Legion to the enclave of Bahía Blanca, near the Patagonian frontier, to participate in the war against the Indians. Launched as the successor to Garibaldi’s Italian Legion of Montevideo, its leaders promised to bring civilization to savage lands in the spirit of Columbus and in the name of the Risorgimento. This case study offers a window into the cross-pollination of ideas concerning conquest and colonization between Latin America and Europe. Expansion and secession, empire and nation, mestizaje and racial hierarchies, cosmopolitanism and adventurism, all coexisted within an entangled republican universe.Partial research funding from Spain’s Ministry of Science and Innovation (Research Project Reference: PGC2018-096722-B-100)
A high-resolution TEM/EELS study of the effect of doping elements on the sliding mechanisms of sputtered WS2 coatings
No full textIt has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40–50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction materia
Jacobson, G A, 22102
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/394773Surname: JACOBSON. Given Name(s) or Initials: G A. Military Service Number or Last Known Location: 22102. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 53954.227900
Item: [2016.0049.27066] "Jacobson, G A, 22102
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