Advanced microwave radiometer antenna system study

The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison

Down By The Nile

https://digitalcommons.library.umaine.edu/mmb-vp/5149/thumbnail.jp

Absolute conservation law for black holes

In all 2d theories of gravity a conservation law connects the (space-time dependent) mass aspect function at all times and all radii with an integral of the matter fields. It depends on an arbitrary constant which may be interpreted as determining the initial value together with the initial values for the matter field. We discuss this for spherically reduced Einstein-gravity in a diagonal metric and in a Bondi-Sachs metric using the first order formulation of spherically reduced gravity, which allows easy and direct fixations of any type of gauge. The relation of our conserved quantity to the ADM and Bondi mass is investigated. Further possible applications (ideal fluid, black holes in higher dimensions or AdS spacetimes etc.) are straightforward generalizations.Comment: LaTex, 17 pages, final version, to appear in Phys. Rev.

A Vector Supersymmetry in Noncommutative U(1) Gauge Theory with the Slavnov Term

We consider noncommutative U(1) gauge theory with the additional term, involving a scalar field lambda, introduced by Slavnov in order to cure the infrared problem. we show that this theory, with an appropriate space-like axial gauge-fixing, wxhibits a linear vector supersymmetry similar to the one present in the 2-dimensional BF model. This vector supersymmetry implies that all loop corrections are independent of the $\lambda AA$-vertex and thereby explains why Slavnov found a finite model for the same gauge-fixing.Comment: 18 pages, 3 figures; v2 Acknowledgments adde

Stellar triples with chemically homogeneously evolving inner binaries

Observations suggest that massive stellar triples are common. However, their evolution is not yet fully understood. We investigate the evolution of hierarchical triples in which the stars of the inner binary experience chemically homogeneous evolution (CHE), particularly to understand the role of the tertiary star in the formation of gravitational-wave (GW) sources. We use the triple-star rapid population synthesis code tres to determine the evolution of these systems at two representative metallicities: Z = 0.005 and Z = 0.0005. About half of all triples harbouring a CHE inner binary (CHE triples) experience tertiary mass transfer (TMT) episodes, an event which is rare for classically evolving stars. In the majority of TMT episodes, the inner binary consists of two main-sequence stars (58--60 per cent) or two black holes (BHs, 24-31 per cent). Additionally, we explore the role of von Zeipel-Lidov-Kozai (ZLK) oscillations for CHE triples. ZLK oscillations can result in eccentric stellar mergers or lead to the formation of eccentric compact binaries in systems with initial outer pericentre smaller than ∼ 1200 R⊙. Approximately 24-30 per cent of CHE triples form GW sources, and in 31 per cent of these, the tertiary star plays a significant role and leads to configurations that are not predicted for isolated binaries. We conclude that the evolution of CHE binaries can be affected by a close tertiary companion, resulting in astronomical transients such as BH--BH binaries that merge via GW emission orders of magnitude faster than their isolated binary counterparts and tertiary-driven massive stellar mergers

Area spectrum in Lorentz covariant loop gravity

We use the manifestly Lorentz covariant canonical formalism to evaluate eigenvalues of the area operator acting on Wilson lines. To this end we modify the standard definition of the loop states to make it applicable to the present case of non-commutative connections. The area operator is diagonalized by using the usual shift ambiguity in definition of the connection. The eigenvalues are then expressed through quadratic Casimir operators. No dependence on the Immirzi parameter appears.Comment: 12 pages, RevTEX; improved layout, typos corrected, references added; changes in the discussion in sec. IIIB and

Universal conservation law and modified Noether symmetry in 2d models of gravity with matter

It is well-known that all 2d models of gravity---including theories with nonvanishing torsion and dilaton theories---can be solved exactly, if matter interactions are absent. An absolutely (in space and time) conserved quantity determines the global classification of all (classical) solutions. For the special case of spherically reduced Einstein gravity it coincides with the mass in the Schwarzschild solution. The corresponding Noether symmetry has been derived previously by P. Widerin and one of the authors (W.K.) for a specific 2d model with nonvanishing torsion. In the present paper this is generalized to all covariant 2d theories, including interactions with matter. The related Noether-like symmetry differs from the usual one. The parameters for the symmetry transformation of the geometric part and those of the matterfields are distinct. The total conservation law (a zero-form current) results from a two stage argument which also involves a consistency condition expressed by the conservation of a one-form matter ``current''. The black hole is treated as a special case.Comment: 3

Enhanced Recovery Pathway for Right and Left Colectomy: Comparison of Functional Recovery.

Enhanced recovery (ERAS) guidelines do not differentiate between left- and right-sided colectomies, but differences in recovery have been reported for the two procedure types. We aimed to compare compliance with the ERAS protocol and outcomes after right versus left colectomy. Between June 2011 and September 2014, all patients undergoing elective colonic resection were treated according to a standardized ERAS protocol and entered a prospective database. This retrospective analysis compared right and left colectomy regarding application of the ERAS pathway, bowel recovery, complications, and hospital stay. Eighty-five patients with right colectomy matched well with 138 left-sided resections for baseline demographics. Overall compliance with the ERAS protocol was 76 % for right versus 77 % for left colectomy patients (p = 0.492). First flatus occurred at postoperative day 2 in both groups (p = 0.057); first stool was observed after a median of 3 (right) and 2 days (left), respectively (p = 0.189). Twenty patients (24 %) needed postoperative nasogastric tube after right colectomy compared to 11 patients (8 %) after left colectomy (p = 0.002). Overall complication rates were 49 and 37 % for right and left colectomy, respectively (p = 0.071). Median postoperative length of stay was 6 days (IQR 4-9) after right and 5 days (IQR 4-7.5) after left colectomy (p = 0.020). Overall compliance with the protocol was equally high in both groups showing that ERAS protocol was applicable for right and left colectomy. Functional recovery however, tended to be slower after right colectomy, and postoperative ileus rate was significantly higher. More cautious early feeding after right colectomy should be considered

Two-dimensional effective action for matter fields coupled to the dilaton

We revise the calculation of the one-loop effective action for scalar and spinor fields coupled to the dilaton in two dimensions. Applying the method of covariant perturbation theory for the heat kernel we derive the effective action in an explicitly covariant form that produces both the conformally invariant and the conformally anomalous terms.For scalar fields the conformally invariant part of the action is nonlocal. The obtained effective action is proved to be infrared finite. We also compute the one-loop effective action for scalar fields at finite temperature.Comment: LaTeX, 25 page

Quantum Averaging I: Poincar\'e--von Zeipel is Rayleigh--Schr\"odinger

An exact analogue of the method of averaging in classical mechanics is constructed for self--adjoint operators. It is shown to be completely equivalent to the usual Rayleigh--Schr\"odinger perturbation theory but gives the sums over intermediate states in closed form expressions. The anharmonic oscillator and the Henon--Heiles system are treated as examples to illustrate the quantum averaging method.Comment: 12 pages, LaTeX, to appear in Journ. Phys.