7,512 research outputs found
Four types of special functions of G_2 and their discretization
Properties of four infinite families of special functions of two real
variables, based on the compact simple Lie group G2, are compared and
described. Two of the four families (called here C- and S-functions) are well
known, whereas the other two (S^L- and S^S-functions) are not found elsewhere
in the literature. It is shown explicitly that all four families have similar
properties. In particular, they are orthogonal when integrated over a finite
region F of the Euclidean space, and they are discretely orthogonal when their
values, sampled at the lattice points F_M \subset F, are added up with a weight
function appropriate for each family. Products of ten types among the four
families of functions, namely CC, CS, SS, SS^L, CS^S, SS^L, SS^S, S^SS^S,
S^LS^S and S^LS^L, are completely decomposable into the finite sum of the
functions. Uncommon arithmetic properties of the functions are pointed out and
questions about numerous other properties are brought forward.Comment: 18 pages, 4 figures, 4 table
Non-universality of artificial frustrated spin systems
Magnetic frustration effects in artificial kagome arrays of nanomagnets with
out-of-plane magnetization are investigated using Magnetic Force Microscopy and
Monte Carlo simulations. Experimental and theoretical results are compared to
those found for the artificial kagome spin ice, in which the nanomagnets have
in-plane magnetization. In contrast with what has been recently reported, we
demonstrate that long range (i.e. beyond nearest-neighbors) dipolar
interactions between the nanomagnets cannot be neglected when describing the
magnetic configurations observed after demagnetizing the arrays using a field
protocol. As a consequence, there are clear limits to any universality in the
behavior of these two artificial frustrated spin systems. We provide arguments
to explain why these two systems show striking similarities at first sight in
the development of pairwise spin correlations.Comment: 7 pages, 6 figure
The spin-1/2 XXZ Heisenberg chain, the quantum algebra U_q[sl(2)], and duality transformations for minimal models
The finite-size scaling spectra of the spin-1/2 XXZ Heisenberg chain with
toroidal boundary conditions and an even number of sites provide a projection
mechanism yielding the spectra of models with a central charge c<1 including
the unitary and non-unitary minimal series. Taking into account the
half-integer angular momentum sectors - which correspond to chains with an odd
number of sites - in many cases leads to new spinor operators appearing in the
projected systems. These new sectors in the XXZ chain correspond to a new type
of frustration lines in the projected minimal models. The corresponding new
boundary conditions in the Hamiltonian limit are investigated for the Ising
model and the 3-state Potts model and are shown to be related to duality
transformations which are an additional symmetry at their self-dual critical
point. By different ways of projecting systems we find models with the same
central charge sharing the same operator content and modular invariant
partition function which however differ in the distribution of operators into
sectors and hence in the physical meaning of the operators involved. Related to
the projection mechanism in the continuum there are remarkable symmetry
properties of the finite XXZ chain. The observed degeneracies in the energy and
momentum spectra are shown to be the consequence of intertwining relations
involving U_q[sl(2)] quantum algebra transformations.Comment: This is a preprint version (37 pages, LaTeX) of an article published
back in 1993. It has been made available here because there has been recent
interest in conformal twisted boundary conditions. The "duality-twisted"
boundary conditions discussed in this paper are particular examples of such
boundary conditions for quantum spin chains, so there might be some renewed
interest in these result
A laser based accelerator for ultracold atoms
We present first results on our implementation of a laser based accelerator
for ultracold atoms. Atoms cooled to a temperature of 420 nK are confined and
accelerated by means of laser tweezer beams and the atomic scattering is
directly observed in laser absorption imaging. The optical collider has been
characterized using Rb87 atoms in the |F=2,mF=2> state, but the scheme is not
restricted to atoms in any particular magnetic substates and can readily be
extended to other atomic species as well.Comment: (c) 2012 The Optical Society, 3 pages, 4 figures, 1 movie lin
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
Atom gratings produced by large angle atom beam splitters
An asymptotic theory of atom scattering by large amplitude periodic
potentials is developed in the Raman-Nath approximation. The atom grating
profile arising after scattering is evaluated in the Fresnel zone for
triangular, sinusoidal, magneto-optical, and bichromatic field potentials. It
is shown that, owing to the scattering in these potentials, two
\QTR{em}{groups} of momentum states are produced rather than two distinct
momentum components. The corresponding spatial density profile is calculated
and found to differ significantly from a pure sinusoid.Comment: 16 pages, 7 figure
Serological diagnosis of echinococcosis: the diagnostic potential of native antigens
Purpose: Human alveolar (AE) and cystic echinococcosis (CE) caused by the metacestode stages of Echinococcus multilocularis and E. granulosus, respectively, lack pathognomonic clinical signs. Diagnosis therefore relies on the results of imaging and serological studies. The primary goal of this study was to evaluate the efficacy of several easy-to-produce crude or partially purified E. granulosus and E. multilocularis metacestode-derived antigens as tools for the serological diagnosis and differential diagnosis of patients suspicious for AE or CE. Methods: The sera of 51 treatment-naïve AE and 32 CE patients, 98 Swiss blood donors and 38 patients who were initially suspicious for echinococcosis but suffering from various other liver diseases (e.g., liver neoplasia, etc.) were analysed. Results: According to the results of enzyme-linked immunosorbent assays (ELISA), metacestode-derived antigens of E. granulosus had sensitivities varying from 81 to 97% and >99.9% for the diagnosis of CE and AE, respectively. Antigens derived from E. multilocularis metacestodes had sensitivities ranging from 84 to 91% and >99.9% for the diagnosis of CE and AE, respectively. Specificities ranged from 92 to >99.9%. Post-test probabilities for the differential diagnosis of AE from liver neoplasias, CE from cystic liver lesions, and screening for AE in Switzerland were around 95, 86 and 2.2%, respectively. Cross-reactions with antibodies in sera of patients with other parasitic affections (fasciolosis, schistosomosis, amebosis, cysticercosis, and filarioses) did occur at variable frequencies, but could be eliminated through the use of confirmatory testing. Conclusions: Different metacestode-derived antigens of E. granulosus and E. multilocularis are valuable, widely accessible, and cost-efficient tools for the serological diagnosis of echinococcosis. However, confirmatory testing is necessary, due to the lack of species specificity and the occurrence of cross-reactions to other helminthic disease
On the next-to-leading-order correction to the effective action in N=2 gauge theories
I attempt to analyse the next-to-leading-order non-holomorphic contribution
to the Wilsonian low-energy effective action in the four-dimensional N=2 gauge
theories with matter, from the manifestly N=2 supersymmeric point of view, by
using the harmonic superspace. The perturbative one-loop correction is found to
be in agreement with the N=1 superfield calculations of de Wit, Grisaru and
Rocek. The previously unknown coefficient in front of this non-holomorphic
correction is calculated. A special attention is devoted to the N=2
superconformal gauge theories, whose one-loop non-holomorphic contribution is
likely to be exact, even non-perturbatively. This leading (one-loop)
non-holomorphic contribution to the LEEA of the N=2 superconformally invariant
gauge field theories is calculated, and it does not vanish, similarly to the
case of the N=4 super-Yang-Mills theory.Comment: 15 pages, LaTeX; changes in the abstract and in sect.
Unified Approach to Imidodiphosphate-Type Brønsted Acids with Tunable Confinement and Acidity
We have designed and realized an efficient and operationally simple single-flask synthesis of imidodiphosphate-based Brønsted acids. The methodology proceeds via consecutive chloride substitutions of hexachlorobisphosphazonium salts, providing rapid access to imidodiphosphates (IDP), iminoimidodiphosphates (iIDP), and imidodiphosphorimidates (IDPi). These privileged acid catalysts feature a broad acidity range (pKa from ∼11 to 95:5 er) sulfoxidation of methyl n-propyl sulfide. Furthermore, the methodology delivers a novel, rationally designed super acidic catalyst motif, imidodiphosphorbis(iminosulfonylimino)imidate (IDPii), the extreme reactivity of which exceeds commonly employed super-Brønsted acids, such as trifluoromethanesulfonic acid. The unique reactivity of one such IDPii catalyst has been demonstrated in the first α-methylation of a silyl ketene acetal with methanol as the electrophilic alkylating reagent
c-Abl and Src-family kinases cross-talk in regulation of myeloid cell migration
AbstractCytoskeleton dynamics are regulated by Src-family tyrosine kinases (SFKs) and c-Abl. We found that the SFK members Hck and c-Fgr regulate tyrosine phosphorylation of c-Abl and c-Abl associates with β1 integrin-bound Hck or c-Fgr in murine macrophages. Studies with selective inhibitors and cells from SFK-deficient mice showed that c-Abl and SFK regulate migration and activation of the small GTPases Cdc42 and Rac in macrophages. Additionally, human neutrophil chemotactic activity was reduced by c-Abl inhibitors, and neutrophils from chronic myeloid leukaemia patients displayed an increased chemotactic ability. Hence, Src-family kinase and c-Abl cross-talk in the regulation of myeloid cell migration.Structured summaryMINT-7296608: Integrin beta-1 (uniprotkb:P09055) physically interacts (MI:0914) with Hck (uniprotkb:P08103), Abl (uniprotkb:P00520) and Fgr (uniprotkb:P14234) by anti bait coimmunoprecipitation (MI:0006) MINT-7296596: Integrin beta-1 (uniprotkb:P09055) physically interacts (MI:0914) with Fgr (uniprotkb:P14234) and Abl (uniprotkb:P00520) by anti bait coimmunoprecipitation (MI:0006
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