999 research outputs found
Spiral Magnets as Gapless Mott Insulators
In the large limit, the ground state of the half-filled, nearest-neighbor
Hubbard model on the triangular lattice is the three-sublattice
antiferromagnet. In sharp contrast with the square-lattice case, where
transverse spin-waves and charge excitations remain decoupled to all orders in
, it is shown that beyond leading order in the three Goldstone modes
on the triangular lattice are a linear combination of spin and charge. This
leads to non-vanishing conductivity at any finite frequency, even though the
magnet remains insulating at zero frequency. More generally, non-collinear spin
order should lead to such gapless insulating behavior.Comment: 10 pages, REVTEX 3.0, 3 uuencoded postscript figures, CRPS-94-0
Variational formulas of higher order mean curvatures
In this paper, we establish the first variational formula and its
Euler-Lagrange equation for the total -th mean curvature functional
of a submanifold in a general Riemannian manifold
for . As an example, we prove that closed
complex submanifolds in complex projective spaces are critical points of the
functional , called relatively -minimal submanifolds,
for all . At last, we discuss the relations between relatively -minimal
submanifolds and austere submanifolds in real space forms, as well as a special
variational problem.Comment: 13 pages, to appear in SCIENCE CHINA Mathematics 201
Nine genes abundantly expressed in the epididymis are not essential for male fecundity in mice
Noda, T., Sakurai, N., Nozawa, K., Kobayashi, S., Devlin, D. J., Matzuk, M. M., & Ikawa, M. (2019). Nine genes abundantly expressed in the epididymis are not essential for male fecundity in mice. Andrology, 7(5), 644-653. doi:10.1111/andr.1262
Total energy calculation of high pressure selenium: The origin of incommensurate modulations in Se-IV and the instability of proposed Se-II
We present calculation of the high pressure crystal structures in selenium,
including rational approximants to the recently reported incommensurate phases.
We show how the incommensurate phases can be intuitively explained in terms of
imaginary phonon frequencies arising from Kohn anomalies in the putative
undistorted phase. We also find inconsistencies between the calculated and
experimental Se-II phase - the calculations show it to be a metastable metal
while the experiment finds a stable semiconductor. We propose that the
experimentally reported structure is probably in error.Comment: 4 pages 4 figure
Resolvent estimates for normally hyperbolic trapped sets
We give pole free strips and estimates for resolvents of semiclassical
operators which, on the level of the classical flow, have normally hyperbolic
smooth trapped sets of codimension two in phase space. Such trapped sets are
structurally stable and our motivation comes partly from considering the wave
equation for Kerr black holes and their perturbations, whose trapped sets have
precisely this structure. We give applications including local smoothing
effects with epsilon derivative loss for the Schr\"odinger propagator as well
as local energy decay results for the wave equation.Comment: Further changes to erratum correcting small problems with Section 3.5
and Lemma 4.1; this now also corrects hypotheses, explicitly requiring
trapped set to be symplectic. Erratum follows references in this versio
Correlations for pairs of periodic trajectories for open billiards
In this paper we prove two asymptotic estimates for pairs of closed
trajectories for open billiards similar to those established by Pollicott and
Sharp for closed geodesics on negatively curved compact surfaces. The first of
these estimates holds for general open billiards in any dimension. The more
intricate second estimate is established for open billiards satisfying the so
called Dolgopyat type estimates. This class of billiards includes all open
billiards in the plane and open billiards in satisfying some
additional conditions
Design of a five-axis ultra-precision micro-milling machine—UltraMill. Part 1: Holistic design approach, design considerations and specifications
High-accuracy three-dimensional miniature components and microstructures are increasingly in demand in the sector of electro-optics, automotive, biotechnology, aerospace and information-technology industries. A rational approach to mechanical micro machining is to develop ultra-precision machines with small footprints. In part 1 of this two-part paper, the-state-of-the-art of ultra-precision machines with micro-machining capability is critically reviewed. The design considerations and specifications of a five-axis ultra-precision micro-milling machine—UltraMill—are discussed. Three prioritised design issues: motion accuracy, dynamic stiffness and thermal stability, formulate the holistic design approach for UltraMill. This approach has been applied to the development of key machine components and their integration so as to achieve high accuracy and nanometer surface finish
Referrals to a facial pain service
AIM: To assess the quality of referral letters to a facial pain service and highlight the key requirements of such letters.
METHOD: The source of all referral letters to the service for five years was established. For one year the information provided in 94 referrals was assessed. Using a predetermined checklist of essential information the referral letters were compared to these set criteria.
RESULTS: The service received 7,001 referrals and, on average, general dental practitioners (GDPs) referred 303 more patients per year than general medical practitioners (GMPs). Seventy-one percent of all referrals were from primary care practitioners, the rest were from specialists. Over 70% of GMP and 52% of GDP letters included a past medical history, with GMPs more likely to suggest a possible diagnosis and include previous secondary care referrals. The mean score for GMP referrals compared to the standard proforma (maximum of 12) was 5.6 and for GDP referrals 5.0. A relevant drug history was included by 75.6% GMP compared to 38.7% of GDPs. GMPs were more likely to include any relevant mental health history.
CONCLUSIONS: The overall quality of referral letters is low which makes it difficult for the specialists to provide robust treatment plans
Notch signaling during human T cell development
Notch signaling is critical during multiple stages of T cell development in both mouse and human. Evidence has emerged in recent years that this pathway might regulate T-lineage differentiation differently between both species. Here, we review our current understanding of how Notch signaling is activated and used during human T cell development. First, we set the stage by describing the developmental steps that make up human T cell development before describing the expression profiles of Notch receptors, ligands, and target genes during this process. To delineate stage-specific roles for Notch signaling during human T cell development, we subsequently try to interpret the functional Notch studies that have been performed in light of these expression profiles and compare this to its suggested role in the mouse
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