1,199 research outputs found
The retro-ene reaction of gaseous immonium ions revisited
The retro-ene reaction is a common reaction of metastable immonium ions, leading to the expulsion of an alkene molecule. The kinetic energy release that accompanies this reaction decreases with alkyl substitution on the γ-carbon of the immonium ion. A number of authors have taken this result to indicate that the retro-ene reaction proceeds in a non-concerted manner via a carbocation intermediate. Using ab initio calculations to test this hypothesis we find that the retro-ene reaction is a concerted process, in which the reactant immonium ion is connected to the products via a single six-membered cyclic transition state. The calculated energy barriers and the measured kinetic energy releases are highly sensitive to alkyl substitution at the γ-position, which indicates that a substantial fraction of the positive charge of the transition state resides at the γ-carbon, not that the retro-ene reaction is a stepwise process with a carbocation intermediate
Hypermultiplets and Topological Strings
The c-map relates classical hypermultiplet moduli spaces in compactifications
of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces
via a further compactification on a circle. We give an off-shell description of
the c-map in N=2 superspace. The superspace Lagrangian for the hypermultiplets
is a single function directly related to the prepotential of special geometry,
and can therefore be computed using topological string theory. Similarly, a
class of higher derivative terms for hypermultiplets can be computed from the
higher genus topological string amplitudes. Our results provide a framework for
studying quantum corrections to the hypermultiplet moduli space, as well as for
understanding the black hole wave-function as a function of the hypermultiplet
moduli.Comment: 21 pages, references adde
Interview with Mildred Jungels and C.D. Richardson, Class of 1941
Oral history interview with Illinois State Normal University alumnus Mildred Jungels and C.D. Richardson, Class of 1941. The interview was conducted on October 17, 1981, by Jewel Shockey of the Student Alumni Council. They discuss student entertainment, World War II, and changes to campus.https://ir.library.illinoisstate.edu/aoh/1009/thumbnail.jp
Transferência de Conhecimento para o Setor Produtivo em Escala Regional: o Caso da FURB
Desde que, no século XII, surgiram as primeiras Universidades , estas assumiram e refletiram peculiaridades do contexto social, econômico e polÃtico no qual estavam inseridas. No presente, a Universidade está desafiada a contribuir com a constituição de uma sociedade mais justa. É fato que ela vem buscando estreitar suas relações com a sociedade, inclusive com o Setor Produtivo [SP]. Um dos meios para concretizar o estreitamento de laços com o SP é pela via de Parques Tecnológicos e também de Incubadoras de Empresas. Aqui se parte da hipótese de que a FURB vem ampliando sua interação com a sociedade, inclusive com o SP da região em que ela se insere, assim contribuindo para o desenvolvimento socioeconômico do Médio Vale do ItajaÃ. A pesquisa de que resulta o presente artigo mostrou que, embora ainda de forma incipiente, a FURB tem produzido e transferido conhecimento a partir de demandas que lhe são encaminhadas pela sociedade regional – aà incluÃdo o SP. O propósito central deste artigo é examinar as modalidades de interação entre a FURB e o SP, bem como suas repercussões em termos de desenvolvimento regional a partir de casos selecionados – Instituto Gene, BLUSOFT e Parque Tecnológico Regional
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The occipital lateral plate mesoderm is a novel source for vertebrate neck musculature
In vertebrates, body musculature originates from somites, whereas head muscles originate from the cranial mesoderm. Neck muscles are located in the transition between these regions. We show that the chick occipital lateral plate mesoderm has myogenic capacity and gives rise to large muscles located in the neck and thorax. We present molecular and genetic evidence to show that these muscles not only have a unique origin, but additionally display a distinct temporal development, forming later than any other muscle group described to date. We further report that these muscles, found in the body of the animal, develop
like head musculature rather than deploying the programme used by the trunk muscles. Using mouse genetics we reveal that these muscles are formed in trunk muscle mutants but are absent in head muscle mutants. In concordance with this conclusion, their connective tissue is neural crest in origin. Finally, we provide evidence that the mechanism by which these neck muscles develop is conserved in vertebrates
Supergravity description of spacetime instantons
We present and discuss BPS instanton solutions that appear in type II string
theory compactifications on Calabi-Yau threefolds. From an effective action
point of view these arise as finite action solutions of the Euclidean equations
of motion in four-dimensional N=2 supergravity coupled to tensor multiplets. As
a solution generating technique we make use of the c-map, which produces
instanton solutions from either Euclidean black holes or from Taub-NUT like
geometries.Comment: 35 pages, some clarifications adde
Towards multireference equivalents of the G2 and G3 methods
The effect of replacing the standard single-determinant reference wave functions in variants of G2 and G3 theory by multireference (MR) wave functions based on a full-valence complete active space has been investigated. Twelve methods of this type have been introduced and comparisons, based on a slightly reduced G2-1 test set, are made both internally and with the equivalent single-reference methods. We use CASPT2 as the standard MR-MP2 method and MRCl+Q as the higher correlation procedure in these calculations. We find that MR-G2(MP2,SVP), MR-G2(MP2), and MR-G3(MP2) perform comparably with their single-reference analogs, G2(MP2,SVP), G2(MP2), and G3(MP2), with mean absolute deviations (MADs) from the experimental data of 1.41, 1.54, and 1.23 kcal mol−1, compared with 1.60, 1.59, and 1.19 kcal mol−1, respectively. The additivity assumptions in the MR-Gn methods have been tested by carrying out MR-G2/MRCI+Q and MR-G3/MRCI+Q calculations, which correspond to large-basis-set MRCI+Q+ZPVE+HLC calculations. These give MADs of 1.84 and 1.58 kcal mol−1, respectively, i.e., the agreement with experiment is somewhat worse than that obtained with the MR-G2(MP2) and MR-G3(MP2) methods. In a third series of calculations, we have examined pure MP2 and MR-MP2 analogs of the G2 and G3 procedures by carrying out large-basis-set MP2 and CASPT2(+ZPVE+HLC) calculations. The resultant methods, which we denote G2/MP2, G3/MP2, MR-G2/MP2, and MR-G3/MP2, give MADs of 4.19, 3.36, 2.01, and 1.66 kcal mol−1, respectively. Finally, we have examined the effect of using MCQDPT2 in place of CASPT2 in five of our MR-Gn procedures, and find that there is a small but consistent deterioration in performance. Our calculations suggest that the MR-G3(MP2) and MR-G3/MP2 procedures may be useful in situations where a multireference approach is desirable.The authors would also
like to thank the National Science Foundation International
Division for providing travel funds to ~M.S.G. and M.A.F.!
and the National Science Foundation Chemistry Division for
supporting the research
Superform formulation for vector-tensor multiplets in conformal supergravity
The recent papers arXiv:1110.0971 and arXiv:1201.5431 have provided a
superfield description for vector-tensor multiplets and their Chern-Simons
couplings in 4D N = 2 conformal supergravity. Here we develop a superform
formulation for these theories. Furthermore an alternative means of gauging the
central charge is given, making use of a deformed vector multiplet, which may
be thought of as a variant vector-tensor multiplet. Its Chern-Simons couplings
to additional vector multiplets are also constructed. This multiplet together
with its Chern-Simons couplings are new results not considered by de Wit et al.
in hep-th/9710212.Comment: 28 pages. V2: Typos corrected and references updated; V3: References
updated and typo correcte
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