5,971 research outputs found
On unitary convex decompositions of vectors in a -algebra
No full textsummary:By exploiting his recent results, the author further investigates the extent to which variation in the coefficients of a unitary convex decomposition of a vector in a unital -algebra permits the vector decomposable as convex combination of fewer unitaries; certain -algebra results due to M. Rørdam have been extended to the general setting of -algebras
Effects of reduced pH on shell integrity of a common whelk from a natural undersea CO2 vent community off Vulcano Island, Italy.
No full textHexaplex trunculus is a widespread Mediterranean gastropod mollusc that plays a crucial role in benthic ecosystem dynamics. Individuals occur in shallow, sublittoral habitats near Vulcano Island, Italy, where an undersea CO2 vent provides a gradient of seawater acidification mimicing future predicted levels of ocean acidification. Individuals were collected from three sites with declining pH [ambient ( pH 8.18), medium (pH 8.05) and low (pH 7.49)]. Dissolution of shells was clearly evident at the medium (smoothing of outer shell ) and low (pitting and holes) pH sites. Scanning electron microcroscopy will provide a qualitative comparative assessment of micro-scale impacts of shell dissolution of individuals from the three sites. X-ray diffraction will provide a quantitative comparative assessment of carbonate composition in shells of individuals from the three pH sites. This study indicates that end of century anticipated levels of ocean acidification are capable of causing severe shell damage that may render individuals more susceptible to infection and predation
Erratum: Half-supersymmetric solutions in five-dimensional supergravity (Journal of High Energy Physics (2007) 12 (025))
No full text[No abstract available]Gutowski JB, 2007, J HIGH ENERGY PHYS11
Surjective isometries between unitary sets of unital JB∗-algebras
No full textWe would like to thank Prof. Lajos Molnár for encouraging us to explore this problem.
We are also indebted to the anonymous reviewer for several useful comments.
First and fifth authors partially supported by the Spanish Ministry of Science, Innovation and Universities (MICINN) and European Regional Development Fund project
no. PGC2018-093332-B-I00, Programa Operativo FEDER 2014-2020 and Consejería de
Economía y Conocimiento de la Junta de Andalucía grant numbers A-FQM-242-UGR18
and FQM375. First author partially supported by EPSRC (UK) project “Jordan Algebras, Finsler Geometry and Dynamics” ref. no. EP/R044228/1. Second author partially
supported by JSPS KAKENHI Grant Number JP 21J21512. Fourth author partially
supported by JSPS KAKENHI (Japan) Grant Number JP 20K03650.
* Funding for open access charge: Universidad de Granada / CBUAThis paper is, in a first stage, devoted to establishing a topological–algebraic characterization of the principal component, U0(M), of the set of unitary elements, U(M), in a unital JB⁎-algebra M. We arrive to the conclusion that, as in the case of unital C⁎-algebras, U0(M)=M1−1∩U(M)={Ue⋯Ue(1):n∈N,hj∈Msa∀1≤j≤n}={u∈U(M): there exists w∈U0(M) with ‖u−w‖<2} is analytically arcwise connected. Actually, U0(M) is the smallest quadratic subset of U(M) containing the set eiM. Our second goal is to provide a complete description of the surjective isometries between the principal components of two unital JB⁎-algebras M and N. Contrary to the case of unital C⁎-algebras, we shall deduce the existence of connected components in U(M) which are not isometric as metric spaces. We shall also establish necessary and sufficient conditions to guarantee that a surjective isometry Δ:U(M)→U(N) admits an extension to a surjective linear isometry between M and N, a conclusion which is not always true. Among the consequences it is proved that M and N are Jordan ⁎-isomorphic if, and only if, their principal components are isometric as metric spaces if, and only if, there exists a surjective isometry Δ:U(M)→U(N) mapping the unit of M to an element in U0(N). These results provide an extension to the setting of unital JB⁎-algebras of the results obtained by O. Hatori for unital C⁎-algebras.CBUAConsejería de Economía y Conocimiento de la Junta de Andalucía
A-FQM-242-UGR18, FQM375Ministerio de Ciencia, Innovación y UniversidadesEngineering and Physical Sciences Research Council
EP/R044228/1Universidad de GranadaMinisterio de Ciencia e InnovaciónJapan Society for the Promotion of Science JP 20K03650, JP 21J21512European Regional Development Fund
PGC2018-093332-B-I0
Linear maps on real C* - algebras and related structures
No full textPhDIn this thesis we obtain new results on the structures of real C*-algebras and nonsurjective
isometries between them. Some of the results have been published in
[1].
We prove a spectral inequality for real Banach*-algebras and give characterisations
of real C*-algebras among Banach*-algebras.
We study the ideal and facial structures in real C*-algebras and show that
there is a bijection from the class of norm-closed left ideals I of a real C*-algebra
A to the class of weak*-closed faces F of the state space S(A). The bijection
is given by I 7! F = f 2 S(A) : (a a) = 0 for all a 2 Ig, with inverse
F 7! I = fa 2 A : (a a) = 0 for all 2 Fg.
As an application, we use the structures of faces to show an algebraic property
of linear maps on real C*-algebras. We prove that if T : A ! B is a linear
contraction between real C*-algebras A and B, then there is a projection p in the
second dual B00 of B such that
T(aa a)p = T(a)T(a) T(a)p (a 2 A).
If T is an isometry, not necessarily surjective, we obtain a stronger result which
also extends a celebrated result of Kadison on surjective isometries between complex
C*-algebras. We prove the following theorem.
Let T be a linear isometry between two real C*-algebras A and B, which can
be non-surjective. Then for each a 2 A there exists a partial isometry u 2 B00 and
a projection p 2 B00 such that
(i) fu; T(ff; g; hg); ug = fu; fT(f); T(g); T(h)g; ug;
(ii) T(ff; g; hg)p = fT(f); T(g); T(h)gp,
for all f; g; h in the real JB*-triple A(a) generated by a 2 A, where ff; g; hg is
the triple product defined by 2ff; g; hg = fg h + hg f. Moreover, fu; T( ):ug :
A(a) ! B00 and T( )p : A(a) ! B00 are isometries.
This theorem cannot be proved by simple complexification. We give an example
of a real linear isometry which cannot be complexified to a complex isometry.
We conclude by proving a theorem which states that a Jordan*-homomorphism
T : A ! B between real C*-algebras A and B is a sum of a C*-homomorphism
and a C*-antihomomorphism, extending a well-known result for complex C*-
algebras
Flexible time–space network formulation and hybrid metaheuristic for conflict-free and energy-efficient path planning of automated guided vehicles
No full textOperations of Automated Guided Vehicles (AGVs) are desired to be more energy-efficient while maintaining high transport productivity, motivated by the green production requirements. This paper investigates a new energy-efficient planning problem for determining conflict-free paths of the AGVs in its transport roadmap. In this problem, the vehicle path and transport time in the roadmap are jointly optimized, based on a flexible time–space network (FTSN). We provide the mathematical problem formulation of the energy-efficient path planning problem. The resulting optimization problem is proved to be a non-convex mixed-integer nonlinear programming which is computationally intractable. We further propose a hybrid metaheuristic that integrates the genetic algorithm and estimation of the distribution algorithm to improve its computational efficiency. Numerical results show the effectiveness of the developed algorithm based on the FTSN framework, compared to the existing metaheuristics, the conventional path planning method, and a commercial solver. The proposed method has a wide application in improving energy use of material handling, providing a guiding significance on promoting cleaner production of flexible manufacturing systems.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
Temperature-driven biogeography of the deep-sea family Lithodidae (Crustacea: Decapoda: Anomura) in the Southern Ocean
No full textSpecies’ distributions are dynamic and are linked to the changing physical environment. Temperature is considered to be a major factor influencing biogeography, especially in ectotherms such as the family Lithodidae. Lithodids are rare amongst decapods in their ability to inhabit the higher latitudes of the Southern Ocean; however, they are usually found in locations where water temperature is above 0.5°C. This study, for the first time, provides a baseline indication of the limits of the lithodid distribution around Antarctica, which will be instrumental in any future work on range extensions in this group. The distribution of lithodids is likely to change as temperatures along the West Antarctic Peninsula continue to rise, and range extensions by durophagous predators, such as the lithodids, are regarded as a potential threat to the unique structure of Antarctic continental-shelf ecosystems
Decoupling of genome size and sequence divergence in a symbiotic bacterium
No full textAuthor Posting. © American Society for Microbiology, 2000. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Journal of Bacteriology 182 (2000): 3867-3869, doi:10.1128/JB.182.13.3867-3869.2000.In contrast to genome size variation in most bacterial taxa, the small genome size of Buchnera sp. was shown to be highly conserved across genetically diverse isolates (630 to 643 kb). This exceptional size conservation may reflect the inability of this obligate mutualist to acquire foreign DNA and reduced selection for genetic novelty within a static intracellular environment.Financial support was provided by a National Institute of Health
postdoctoral training grant to J.J.W. (Center for Insect Science, University
of Arizona) and a National Science Foundation grant (DEB-
9815413) to N.A.M
Vertical transmission of biosynthetic plasmids in aphid endosymbionts (Buchnera)
No full textAuthor Posting. © American Society for Microbiology, 2001. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Journal of Bacteriology 183 (2001): 785-790, doi:10.1128/JB.183.2.785-790.2001.This study tested for horizontal transfer of plasmids among Buchnera aphidicola strains associated with
ecologically and phylogenetically related aphid hosts (Uroleucon species). Phylogenetic congruence of Buchnera
plasmid (trpEG and leuABC) and chromosomal (dnaN and trpB) genes supports strictly vertical long-term transmission
of plasmids, which persist due to their contributions to host nutrition rather than capacity for infectious
transfer. Synonymous divergences indicate elevated mutation on plasmids relative to chromosomal genes.This work was supported by a National Institutes of Health postdoctoral
training grant in Molecular Insect Science (Center for Insect
Science, University of Arizona) to J.J.W. and a National Science Foundation
grant (DEB-9815413) to N.A.M
Tn5 synaptic complex formation : role of transposase residue W450
No full textAuthor Posting. © American Society for Microbiology, 2008. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Journal of Bacteriology 190 (2008): 1484-1487, doi:10.1128/JB.01488-07.A series of Tn5 transposases (Tnp's) with mutations at the conserved amino acid position W450, which was structurally predicted to be important for synapsis, have been generated and characterized. This study demonstrates that W450 is involved in hydrophobic (and possibly aromatic) contacts within the Tnp monomer that negatively regulate synaptic complex formation.This work was supported by the NIH (grant no. GM50693) and the University of Wisconsin—Madison (grant no. WIS04792) and through the Evelyn Mercer Professorship in Biochemistry and Molecular Biology
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