1,411 research outputs found
Higher rank numerical ranges of normal matrices
The higher rank numerical range is closely connected to the construction of
quantum error correction code for a noisy quantum channel. It is known that if
a normal matrix has eigenvalues , then its higher
rank numerical range is the intersection of convex polygons with
vertices , where . In this paper, it is shown that the higher rank numerical range of a
normal matrix with distinct eigenvalues can be written as the intersection
of no more than closed half planes. In addition, given a convex
polygon a construction is given for a normal matrix
with minimum such that . In particular, if
has vertices, with , there is a normal matrix with such that .Comment: 12 pages, 9 figures, to appear in SIAM Journal on Matrix Analysis and
Application
Radiative Tau Lepton Pair Production as a Probe of Anomalous Electromagnetic Couplings of the Tau
We calculate the squared matrix element for the process e+ e- --> tau+ tau-
gamma allowing for anomalous magnetic and electric dipole moments at the tau
tau gamma vertex. No interferences are neglected and no approximations of light
fermion masses are made. We show that anomalous moments affect not only the
cross section, but also the shape of the photon energy and angular
distributions. We also demonstrate that in the case of the anomalous magnetic
dipole moment, the contribution from interference involving Standard Model and
anomalous amplitudes is significant compared to the contribution from anomalous
amplitudes alone. A program to perform the calculation is available and it may
be employed as a Monte Carlo generator.Comment: 14 pages, 8 figures submitted to Nuclear Physics
A new chiral ligand: 2,6-bis 4(S)-isopropyl-1-phenyl-4,5-dihydro-1H-imidazol-2-yl pyridine
The title compound, C29H33N5, is a new chiral bis(imidazolyl) pyridine derivative with a skeleton similar to the bis(oxazolyl) pyridine derivatives, which have been extensively used as ligands in various asymmetric catalytic reactions. The most prominent feature of the present compound is the considerable sp(2) character of N atoms of the imidazoline rings. The substituents at the Nsp(2) atoms can provide a means for tuning the electronic and conformational properties of the compound
Limits on the Dipole Moments of the -Lepton via the Process $e^{+}e^{-}\to \tau^+ \tau^- \gamma in a Left-Right Symmetric Model
Limits on the anomalous magnetic moment and the electric dipole moment of the
lepton are calculated through the reaction at the -pole and in the framework of a left-right symmetric model.
The results are based on the recent data reported by the L3 Collaboration at
CERN LEP. Due to the stringent limit of the model mixing angle , the
effect of this angle on the dipole moments is quite small.Comment: 15 pages, 3 figure
Population Viability of Barren-ground Grizzly Bears in Nunavut and the Northwest Territories
We modelled probabilities of population decline as a function of annual kill for a population of barren-ground grizzly bears (Ursus arctos) inhabiting Nunavut and the Northwest Territories, Canada. Our results suggest that the population is at risk of decline, especially if annual removal rates increase from the 42-year mean of 13.4 bears per year. Adding six bears to the mean annual kill results in a greater than 40% chance of a decrease by one-quarter in population size over the next 50 years, compared to a 10% chance with the current level of human-caused mortality. Additional mortalities may result from increased problem behaviour by bears at mine sites or hunt and exploration camps, given recent increases in human activity in the region, and may already be present as unreported mortality. We believe any increase in current harvest quotas would considerably lessen conservation prospects for the population.On a simulĂ© les probabilitĂ©s de baisse de la population en fonction du prĂ©lĂšvement annuel dans le cadre de la chasse pour une population de grizzlis de la toundra (Ursus arctos) habitant le Nunavut et les Territoires du Nord-Ouest, au Canada. Nos rĂ©sultats suggĂšrent que la population risque de dĂ©cliner, surtout si les taux de prĂ©lĂšvement augmentent par rapport Ă la moyenne Ă©tablie sur 42 ans qui est de 13,4 ours par an. Le fait d'ajouter 6 ours au prĂ©lĂšvement de chasse annuel augmente Ă plus de 40 % le risque que la population dĂ©cline d'un quart au cours des prochains 50 ans, par rapport Ă 10 % dans le cas du niveau actuel de mortalitĂ© provoquĂ©e par les humains. Vu l'augmentation rĂ©cente de l'activitĂ© anthropique dans la rĂ©gion, d'autres individus pourraient ĂȘtre abattus Ă cause du nombre croissant de comportements problĂ©matiques des ours rĂ©sidant Ă des sites miniers et Ă des campements d'exploration, et il est possible que ce phĂ©nomĂšne existe dĂ©jĂ mais que les morts ne soient pas rapportĂ©es. Notre opinion est que toute augmentation des quotas actuels de prĂ©lĂšvement rĂ©duirait considĂ©rablement les perspectives de conservation pour la population
Templeting of Thin Films Induced by Dewetting on Patterned Surfaces
The instability, dynamics and morphological transitions of patterns in thin
liquid films on periodic striped surfaces (consisting of alternating less and
more wettable stripes) are investigated based on 3-D nonlinear simulations that
account for the inter-site hydrodynamic and surface-energetic interactions. The
film breakup is suppressed on some potentially destabilizing nonwettable sites
when their spacing is below a characteristic lengthscale of the instability,
the upper bound for which is close to the spinodal lengthscale. The thin film
pattern replicates the substrate surface energy pattern closely only when, (a)
the periodicity of substrate pattern matches closely with the characteristic
lengthscale, and (b) the stripe-width is within a range bounded by a lower
critical length, below which no heterogeneous rupture occurs, and an upper
transition length above which complex morphological features bearing little
resemblance to the substrate pattern are formed.Comment: 5 pages TeX (REVTeX 4), other comments: submitted to Phys. Rev.Let
Dewetting of thin films on heterogeneous substrates: Pinning vs. coarsening
We study a model for a thin liquid film dewetting from a periodic
heterogeneous substrate (template). The amplitude and periodicity of a striped
template heterogeneity necessary to obtain a stable periodic stripe pattern,
i.e. pinning, are computed. This requires a stabilization of the longitudinal
and transversal modes driving the typical coarsening dynamics during dewetting
of a thin film on a homogeneous substrate. If the heterogeneity has a larger
spatial period than the critical dewetting mode, weak heterogeneities are
sufficient for pinning. A large region of coexistence between coarsening
dynamics and pinning is found.Comment: 4 pages, 4 figure
Toward a Sustainable Marketplace: Expanding Options and Benefits for Consumers
While popular interest in sustainable consumption continues to grow, there is a persistent gap between consumersâ typically positive explicit attitudes towards sustainability and their actual consumption behaviours. This gap can be explained, in part, by the belief that choosing to consume sustainably is both constraining and reduces individual-level benefits. While the belief that sustainable consumption depends on making trade-offs is true in some contexts, increasingly consumers are finding that more sustainable forms of consumption can provide both an expanded set of options and additional, individual-level benefits. In this essay, we discuss and illustrate an expanded set of options and benefits across the consumption cycle: from acquisition to usage and disposition. An underlying theme is the separation of material ownership from the extraction of consumer benefits across the consumption cycle. We believe that this ongoing evolution of products - and even business models - has the potential to simultaneously increase value to consumers as well as speed progress towards a more sustainable marketplace
Sibling relationships and family functioning in siblings of early adolescents, adolescents and young adults with autism spectrum disorder
The purpose of the study was to investigate how family functioning (defined as the ability that family members hold to manage stressful events, and intimate and social relationships), the degree to which family members feel happy and fulfilled with each other (called family satisfaction), and the demographical characteristics of siblings (age and gender) impacted on sibling relationships. The Circumplex Model of Marital and Family Systems and Behavioral Systems constituted the theoretical frameworks that guided our study. Eighty-six typically developing adolescents and young adults having a sister or a brother with autism spectrum disorder were enrolled. Results indicated that the youngest age group (early adolescents) reported to engage more frequently in negative behaviors with their siblings with ASD than the two older age groups (middle adolescents and young adults). No significant differences were found among the three age groups regarding behaviors derived from attachment, caregiving and affiliative systems. Family satisfaction and age significantly predicted behaviors during sibling interactions. Suggestions on prevention and intervention programs were discussed in order to prevent parentification among typically developing
siblings and decrease episodes of quarrels and overt conflicts between brothers and sisters with and without AS
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