1,506 research outputs found
Syntheses of small cluster oligosaccharide mimetics
We designed multiple Small Cluster Oligosaccharide Mimetics (SCOMs) - potential glycosidase inhibitors - to be metabolically stable and small enough to enter cells or bacteria. Therefore, minimal scaffolds (urea, amide, ammonia) or simply non-glycosidic linkages of carbohydrate structures were central to our synthetic strategy, including: (a) coupling of several natural carbohydrate precursors; (b) total syntheses of aminomethyl tetrahydropyrans and their chiral amides with quinic acid; (c) glycopyranosyl cyanide reduction to prepare crowded clusters on a urea scaffold; (d) total syntheses via cycloadditions leading to amide-linked C-glycosides; (e) reduction of nitromethyl C-glycosides; and (f) a synthesis of hydroxylated 1,2- cyclohexanedicarboxylic acids
Synthesis and NMR-Characterization of Three Quinamide-Based Disaccharide Mimetics with Unusual Cyclohexane twist-Conformation
The synthesis of amide-linked disaccharide mimetics has been explored starting with carbohydrate-based amines and a protected quinic acid lactone. Benzyl-2-amino-4,6-Obenzylidene-2-deoxy-α/ÎČ-D-glucopyranose (12) and D-glucamine (14) were successfully coupled to give the corresponding quinamides (13 and 15), while the quinoylation of Oacetylated L-fucopyranosyl methylamine (7) failed. The latter was prepared from per-O-acetylL-fucopyranose via the improved multigram scale synthesis of the corresponding per-O-acetylL-fucopyranosyl cyanide (3). Compound 3 was subsequently hydrogenated to yield a mixture of compound 7 and the per-O-acetylated bis-(fucopyranosylmethyl) amine (5). The vicinal coupling constants in the NMR spectra of all quinamide products revealed considerable flexibility of the cyclohexane ring in solution and substantial contributions by twist-chair conformations
Tunable coupling engineering between superconducting resonators: from sidebands to effective gauge fields
In this work we show that a tunable coupling between microwave resonators can
be engineered by means of simple Josephson junctions circuits, such as dc- and
rf-SQUIDs. We show that by controlling the time dependence of the coupling it
is possible to switch on and off and modulate the cross-talk, boost the
interaction towards the ultrastrong regime, as well as to engineer red and blue
sideband couplings, nonlinear photon hopping and classical gauge fields. We
discuss how these dynamically tunable superconducting circuits enable key
applications in the fields of all optical quantum computing, continuous
variable quantum information and quantum simulation - all within the reach of
state of the art in circuit-QED experiments.Comment: 11 pages, 4 figure
Covariant description of inelastic electron--deuteron scattering:predictions of the relativistic impulse approximation
Using the covariant spectator theory and the transversity formalism, the
unpolarized, coincidence cross section for deuteron electrodisintegration,
, is studied. The relativistic kinematics are reviewed, and simple
theoretical formulae for the relativistic impulse approximation (RIA) are
derived and discussed. Numerical predictions for the scattering in the high
region obtained from the RIA and five other approximations are presented
and compared. We conclude that measurements of the unpolarized coincidence
cross section and the asymmetry , to an accuracy that will distinguish
between different theoretical models, is feasible over most of the wide
kinematic range accessible at Jefferson Lab.Comment: 54 pages and 24 figure
BPS kinks in the Gross-Neveu model
We find the exact spectrum and degeneracies for the Gross-Neveu model in two
dimensions. This model describes N interacting Majorana fermions; it is
asymptotically free, and has dynamical mass generation and spontaneous chiral
symmetry breaking. We show here that the spectrum contains 2^{N/2} kinks for
any . The unusual \sqrt{2} in the number of kinks for odd comes from
restrictions on the allowed multi-kink states. These kinks are the BPS states
for a generalized supersymmetry where the conserved current is of dimension
N/2; the N=3 case is the {\cal N}=1 supersymmetric sine-Gordon model, for which
the spectrum consists of 2\sqrt{2} kinks. We find the exact S matrix for these
kinks, and the exact free energy for the model.Comment: 22 pages, 5 figure
The impact of marketisation on postgraduate career preparedness in a high skills economy
This study focuses on the consequences for high skills development of the erosion of the once clear demarcation between higher education and business. It contributes to the broader debate about the relevance of higher education for thewell-being of the society of the future. The research explores the effects of marketisation on the postgraduate curriculum and studentsâ preparedness for careers in public relations and marketing communications. Interviews with lecturers and students in two universities in the UK and Australia indicate that a tension exists between academic rigour and corporate relevancy. The consequences are a diminution of academic attachment to critique and wider social/cultural engagement, with a resulting impoverishment of studentsâ creative abilities and critical consciences. Subsequently, graduates of public relations and marketing communications, and to some extent those from other profession-related disciplines, are insufficiently prepared for careers as knowledge workers in a future high-skills economy
Relativistic three-body bound states and the reduction from four to three dimensions
Beginning with an effective field theory based upon meson exchange, the
Bethe-Salpeter equation for the three-particle propagator (six-point function)
is obtained. Using the one-boson-exchange form of the kernel, this equation is
then analyzed using time-ordered perturbation theory, and a three-dimensional
equation for the propagator is developed. The propagator consists of a
pre-factor in which the relative energies are fixed by the initial state of the
particles, an intermediate part in which only global propagation of the
particles occurs, and a post-factor in which relative energies are fixed by the
final state of the particles. The pre- and post-factors are necessary in order
to account for the transition from states where particles are off their mass
shell to states described by the global propagator with all of the particle
energies on shell. The pole structure of the intermediate part of the
propagator is used to determine the equation for the three-body bound state: a
Schr{\"o}dinger-like relativistic equation with a single, global Green's
function. The role of the pre- and post-factors in the relativistic dynamics is
to incorporate the poles of the breakup channels in the initial and final
states. The derivation of this equation by integrating over the relative times
rather than via a constraint on relative momenta allows the inclusion of
retardation and dynamical boost corrections without introducing unphysical
singularities.Comment: REVTeX, 21 pages, 4 figures, epsf.st
Transfer of K-types on local theta lifts of characters and unitary lowest weight modules
In this paper we study representations of the indefinite orthogonal group
O(n,m) which are local theta lifts of one dimensional characters or unitary
lowest weight modules of the double covers of the symplectic groups. We apply
the transfer of K-types on these representations of O(n,m), and we study their
effects on the dual pair correspondences. These results provide examples that
the theta lifting is compatible with the transfer of K-types. Finally we will
use these results to study subquotients of some cohomologically induced
modules
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