1,451 research outputs found
Active Mass Under Pressure
After a historical introduction to Poisson's equation for Newtonian gravity,
its analog for static gravitational fields in Einstein's theory is reviewed. It
appears that the pressure contribution to the active mass density in Einstein's
theory might also be noticeable at the Newtonian level. A form of its
surprising appearance, first noticed by Richard Chase Tolman, was discussed
half a century ago in the Hamburg Relativity Seminar and is resolved here.Comment: 28 pages, 4 figure
Procedimentos para viagens a serviço.
Este documento busca orientar, de forma simplificada, os empregados da Embrapa Uva e Vinho sobre os procedimentos obrigatórios em caso de viagem a serviço.bitstream/item/123759/1/FD00117.pd
Gradient catastrophe and flutter in vortex filament dynamics
Gradient catastrophe and flutter instability in the motion of vortex filament
within the localized induction approximation are analyzed. It is shown that the
origin if this phenomenon is in the gradient catastrophe for the dispersionless
Da Rios system which describes motion of filament with slow varying curvature
and torsion. Geometrically this catastrophe manifests as a rapid oscillation of
a filament curve in a point that resembles the flutter of airfoils.
Analytically it is the elliptic umbilic singularity in the terminology of the
catastrophe theory. It is demonstrated that its double scaling regularization
is governed by the Painlev\'e-I equation.Comment: 11 pages, 3 figures, typos corrected, references adde
Clinical, Laboratory and Lung Ultrasound Assessment of Congestion in Patients with Acute Heart Failure
Congestion is the main cause of hospitalization in patients with acute heart failure (AHF), however its precise assessment by simple clinical evaluation remains elusive. The recent introduction of the lung ultrasound scan (LUS) allowed to physicians to more precisely quantify pulmonary congestion. The aim of this study was to compare clinical congestion (CC) with LUS and B-type natriuretic peptide (BNP) in order to achieve a more complete evaluation and to evaluate the prognostic power of each measurement. Methods: All patients were submitted to clinical evaluation for blood sample analysis and LUS at admission and before discharge. LUS protocol evaluated the number of B-lines for each chest zone by standardized eight site protocol. CC was measured following ESC criteria. The mean difference between admission and discharge congestion logBNP and B-lines values were calculated. Combined end points of death and rehospitalization was calculated over 180 days. Results: 213 patients were included in the protocol; 133 experienced heart failure with reduced ejection fraction (HFrEF), and 83 presented with heart failure with preserved ejection fraction (HFpEF). Patients with HFrEF had a more increased level of BNP (1150 (812-1790) vs. 851 (694-1196); p = 0.002) and B lines total number (32 (27-38) vs. 30 (25-36); p = 0.05). A positive correlation was found between log BNP and Blines number in both HFrEF (r = 0.57; p < 0.001) and HFpEF (r = 0.36; p = 0.001). Similarly, dividing B-lines among tertiles the upper group (B-lines >= 36) had an increased clinical congestion score. Among three variables at admission only B-lines were predictive for outcome (AUC 0.68 p < 0.001) but not LogBNP and CC score. During 180 days of follow-up, univariate analysis showed that persistent Delta B-lines <-32.3% (HR 6.54 (4.19-10.20); p < 0.001), persistent Delta BNP < -43.8% (HR 2.48 (1.69-3.63); p < 0.001) and persistent Delta CC < 50% (HR 4.25 (2.90-6.21); p < 0.001) were all significantly related to adverse outcome. Multivariable analysis confirmed that persistent Delta B-lines (HR 4.38 (2.64-7.29); p < 0.001), Delta BNP (HR 1.74 (1.11-2.74); p = 0.016) and Delta CC (HR 3.38 (2.10-5.44); p < 0.001 were associated with the combined end point. Conclusions: a complete clinical laboratory and LUS assessment better recognized different congestion occurrence in AHF. The difference between admission and discharge B-lines provides useful prognostic information compared to traditional clinical evaluation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
Harmonic fields on the extended projective disc and a problem in optics
The Hodge equations for 1-forms are studied on Beltrami's projective disc
model for hyperbolic space. Ideal points lying beyond projective infinity arise
naturally in both the geometric and analytic arguments. An existence theorem
for weakly harmonic 1-fields, changing type on the unit circle, is derived
under Dirichlet conditions imposed on the non-characteristic portion of the
boundary. A similar system arises in the analysis of wave motion near a
caustic. A class of elliptic-hyperbolic boundary-value problems is formulated
for those equations as well. For both classes of boundary-value problems, an
arbitrarily small lower-order perturbation of the equations is shown to yield
solutions which are strong in the sense of Friedrichs.Comment: 30 pages; Section 3.3 has been revise
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