10,836 research outputs found
Vertical structure of Arctic haze observed by lidar
In the study of the Arctic Haze phenomenon, understanding the vertical structure of the haze aerosol is crucial in defining mechanisms of haze transport. Questions have also arisen concerning the representativeness of surface observations of Arctic Haze. Due to the strongly stratified nature of the Arctic troposphere, the mechanisms which transport aerosol to the surface from the transport altitudes of the lower troposphere are not obvious. In order to examine these questions, a Mie scattering lidar was installed at Alert, NWT, Canada. Lidar observes atmospheric aerosols and hydrymeteors as they appear in nature, unmodified by sampling effects. As such the results obtained are more realistic of the light scattering characteristics of the in situ aerosol than are those obtained by integrating nephelometers, for example, which heat the aerosol and dry it before measurement. With this lidar, a pulse was transmitted vetically through an evacuated tube in the roof of a building at Alert. The receiver consisted of a 20cm diameter Fresnel telescope, neutral density and polarizing filters, and RCA C31000A PMT, Analog Modules LA-90-P logarithmic amplifier and a Lecroy TR8827 32 MHz digitizer. The lidar equation was solved for the backscattering coefficient of the aerosol assuming no two way transmission losses in the signal. The lidar results have shown that intercomparison between lidar obtained visibilities and observer visibilities are in much better agreement than for other optical or aerosol monitors. Three new effects were identified in the lidar profiles which contribute to the vertical transport of haze. These effects are briefly discussed
Bevacizumab plus Irinotecan-Based Regimens in the Treatment of Metastatic Colorectal Cancer
Objectives: Bevacizumab is a monoclonal antibody that directly inhibits vascular endothelial growth factor, a key regulator of angiogenesis. Bevacizumab significantly improves progression-free and/or overall survival in metastatic colorectal cancer in combination with standard chemotherapy. This review describes the evolution of irinotecan-based regimens for metastatic colorectal cancer and evaluates the addition of bevacizumab to these regimens. Methods: Literature searches from large publication databases (PubMed, ASCO, ASCO GI, ESMO) were performed to capture key data relevant to bevacizumab, irinotecan, and the treatment of colorectal cancer. Results: Data from numerous large, multinational studies support the addition of bevacizumab to irinotecan-containing chemotherapy regimens for further improvement in patient outcomes. In a randomized, placebo-controlled trial, addition of bevacizumab to irinotecan significantly improved progression-free survival, overall survival and response rate in patients with metastatic colorectal cancer, and these results are supported by a number of other clinical trials and observational studies. Furthermore, the addition of bevacizumab to irinotecan improves outcomes regardless of K-ras mutational status. Bevacizumab has a well-established safety profile and the toxicities associated with its use are usually mild in severity and easily manageable. Conclusions: Addition of bevacizumab to irinotecan-containing regimens is an effective therapy option for the treatment of metastatic colorectal cancer. Copyright (C) 2010 S. Karger AG, Base
Inexpensive high-temperature furnace for thermocouple calibration
New furnace calibrates unknown thermocouple by comparing its electrical output to a reference thermocouple /previously calibrated by optical pyrometry/, as both are heated simultaneously. Thermocouples may be radioactive, thus heat source must be accessible by remote manipulation and inspection measurements. Advantages of furnace operation are cited
High-temperature rapid-response thermocouple for reducing atmospheres
Thermocouple measures continuously in flowing gaseous hydrogen at temperatures up to 4000 deg F, in environments made hazardous by radiation, and where rapid response and calibration reproducibility are critically important. Thermocouple wires extend continuously, without splice or foreign material, from cold junction to probe's tip
The (restricted) Inomata-McKinley spinor representation and the underlying topology
The so called Inomata-McKinley spinors are a particular solution of the
non-linear Heisenberg equation. In fact, free linear massive (or mass-less)
Dirac fields are well known to be represented as a combination of
Inomata-McKinley spinors. More recently, a subclass of Inomata-McKinley spinors
were used to describe neutrino physics. In this paper we show that Dirac
spinors undergoing this restricted Inomata-McKinley decomposition are
necessarily of the first type, according to the Lounesto classification.
Moreover, we also show that this type one subclass spinors has not an exotic
counterpart. Finally, implications of these results are discussed, regarding
the understanding of the spacetime background topology.Comment: 7 pages, to appear in EP
Braneworld Remarks in Riemann-Cartan Manifolds
We analyze the projected effective Einstein equation in a 4-dimensional
arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The
Israel-Darmois matching conditions are investigated, in the context where the
torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of
torsion terms in the connection does not modify such conditions whatsoever,
despite of the modification in the extrinsic curvature and in the connection.
Then, by imposing the Z_2-symmetry, the Einstein equation obtained via
Gauss-Codazzi formalism is extended, in order to now encompass the torsion
terms. We also show that the factors involving contorsion change drastically
the effective Einstein equation on the brane, as well as the effective
cosmological constant.Comment: 7 pages. A corrected misprint in def.(18), and the respective terms
in Eqs.(20-23). All physical consequences remain unchange
Gravitational constraints of dS branes in AdS Einstein-Brans-Dicke bulk
We derive the full projected Einstein-Brans-Dicke gravitational equations
associated with a n-dimensional brane embedded in a (n+1)-dimensional bulk. By
making use of general conditions, as the positivity of the Brans-Dicke
parameter and the effective Newton gravitational constant as well, we are able
to constrain the brane cosmological constant in terms of the brane tension, the
Brans-Dicke scalar field, and the trace of the stress tensor on the brane, in
order to achieve a brane. Applying these constraints to a specific
five-dimensional model, a lower bound for the scalar field on the brane is
elicited without solving the full equations. It is shown under which conditions
the brane effective cosmological constant can be ignored in the brane projected
gravitational field equations, suggesting a different fine tuning between the
brane tension and the bulk cosmological.Comment: 9 pages, revTe
Unfolding Physics from the Algebraic Classification of Spinor Fields
After reviewing the Lounesto spinor field classification, according to the
bilinear covariants associated to a spinor field, we call attention and unravel
some prominent features involving unexpected properties about spinor fields
under such classification. In particular, we pithily focus on the new aspects
--- as well as current concrete possibilities. They mainly arise when we deal
with some non-standard spinor fields concerning, in particular, their
applications in physics.Comment: 6 pages, accepted for publication in PL
- …