9 research outputs found
B-orbits in abelian nilradicals of types B, C and D: towards a conjecture of Panyushev
Let be a Borel subgroup of a semisimple algebraic group and let
be an abelian nilradical in . Using
subsets of strongly orthogonal roots in the subset of positive roots
corresponding to , D. Panyushev \cite{Pan} gives in particular
classification of orbits in and and states
general conjectures on the closure and dimensions of the orbits in both
and in terms of involutions of the Weyl group.
Using Pyasetskii correspondence between orbits in and
he shows the equivalence of these two conjectures. In this
Note we prove his conjecture in types and for adjoint case.Comment: 12 page
Visualizing near-coexistence of massless Dirac electrons and ultra-massive saddle point electrons
Strong singularities in the electronic density of states amplify correlation
effects and play a key role in determining the ordering instabilities in
various materials. Recently high order van Hove singularities (VHSs) with
diverging power-law scaling have been classified in single-band electron
models. We show that the 110 surface of Bismuth exhibits high order VHS with an
usually high density of states divergence . Detailed mapping
of the surface band structure using scanning tunneling microscopy and
spectroscopy combined with first-principles calculations show that this
singularity occurs in close proximity to Dirac bands located at the center of
the surface Brillouin zone. The enhanced power-law divergence is shown to
originate from the anisotropic flattening of the Dirac band just above the
Dirac node. Such near-coexistence of massless Dirac electrons and ultra-massive
saddle points enables to study the interplay of high order VHS and Dirac
fermions
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Right atrial effects on right ventricular ejection fraction derived from thermodilution measurements
The thermodilution technique provides a convenient means to monitor cardiac output, right ventricular (RV) ejection fraction (EF), and volumes at the bedside. To calculate RVEF from the pulmonary artery temperature curve, the bolus thermodilution technique assumes that right atrial (RA) temperature returns to baseline value within 1 beat following the cold saline injection. The authors hypothesized that this assumption is the reason why the thermodilution technique consistently underestimates RVEF.
A theoretical analysis and animal study.
Laboratory, university, multi-institutional.
Animals.
Cold saline injections.
In 2 porcine experiments, after a rapid injection of cold saline into right atrium, RA temperature took several heartbeats to return to baseline. In a theoretical analysis, if after the cold saline injection RA temperature returned to baseline in 1 beat (RAEF = 1), then thermodilution-derived RVEF(T) = actual RVEF(A). In contrast, if RA temperature took several beats to return to baseline (RAEF = RVEF), then RVEF(T) consistently underestimated RVEF(A). A least square fit of RVEF(A) versus RVEF(T) resulted in RVEF(A) = 1.0 x RVEF(T) + 0.11. Applying this correction (adding 0.11 to RVEF(T)) to the data gave relatively small errors in estimating RVEF over a wide EF range.
After injecting cold saline into the right atrium, RA temperature takes several heart beats to return to baseline temperature, leading to underestimating RVEF and overestimating RV volumes. The pulsed thermal energy approach by injecting heat into the RV avoids these problems, but the impact of its small temperature signal on RVEF measurements needs to be determined