28,451 research outputs found
Massive stars dying alone: The extremely remote environment of SN 2009ip
We present late-time HST images of the site of supernova (SN) 2009ip taken
almost 3 yr after its bright 2012 luminosity peak. SN 2009ip is now slightly
fainter in broad filters than the progenitor candidate detected by HST in 1999.
The current source continues to be dominated by ongoing late-time CSM
interaction that produces strong H-alpha emission and a weak pseudo-continuum,
as found previously for 1-2 yr after explosion. The intent of these
observations was to search for evidence of recent star formation in the local
(1kpc; 10 arcsec) environment around SN 2009ip, in the remote outskirts of its
host spiral galaxy NGC 7259. We can rule out the presence of any massive
star-forming complexes like 30 Dor or the Carina Nebula at the SN site or
within a few kpc. If the progenitor of SN 2009ip was really a 50-80 Msun star
as archival HST images suggested, then it is strange that there is no sign of
this type of massive star formation anywhere in the vicinity. A possible
explanation is that the progenitor was the product of a merger or binary mass
transfer, rejuvenated after a lifetime that was much longer than 4-5 Myr,
allowing its natal H II region to have faded. A smaller region like the Orion
Nebula would be an unresolved but easily detected point source. This is ruled
out within 1.5 kpc around SN 2009ip, but a small H II region could be hiding in
the glare of SN 2009ip itself. Later images after a few more years have passed
are needed to confirm that the progenitor candidate is truly gone and to test
for the presence of a small H II region or cluster at the SN position.Comment: 8 pages, 5 figs. submitted to MNRA
Six-wave mixing: secular resonances in a higher-order mechanism for second-harmonic generation
Internal electrostatic discharge hazard risk assessment to the Galileo orbiter
A worst case assessment was performed on the Command Data System (CDS) multilayer printed circuit board and an output power transformer module in the power subsystem. An estimate of the Jovian environment during the 35 hour orbit insertion was supplied by JPL and used as an input to calculate the electron transport into the Galileo components. A radiation shielding analysis computer code, CHARGE, calculated the electron transport deposition trapped in the anticipated sensitive areas of the multilayer board and transformer module. Based on these trapped charge calculations electric fields were calculated between the identified isolated areas and the spacecraft ground. The results of the assessment of electrostatic discharge (DSD) in the CDS multilayer printed circuit board indicate that the probability of ESD in the FR4 is low. The probability of ESD in the components attached to the multilayer board, however, is uncertain based on a lack of prior experimental data
Optical binding in nanoparticle assembly: Potential energy landscapes
Optical binding is an optomechanical effect exhibited by systems of micro- and nanoparticles, suitably irradiated with off-resonance laser light. Physically distinct from standing-wave and other forms of holographic optical traps, the phenomenon arises as a result of an interparticle coupling with individual radiation modes, leading to optically induced modifications to Casmir-Polder interactions. To better understand how this mechanism leads to the observed assemblies and formation of patterns in nanoparticles, we develop a theory in terms of optically induced energy landscapes exhibiting the three-dimensional form of the potential energy field. It is shown in detail that the positioning and magnitude of local energy maxima and minima depend on the configuration of each particle pair, with regards to the polarization and wave vector of the laser light. The analysis reveals how the positioning of local minima determines the energetically most favorable locations for the addition of a third particle to each equilibrium pair. It is also demonstrated how the result of such an addition subtly modifies the energy landscape that will, in turn, determine the optimum location for further particle additions. As such, this development represents a rigorous and general formulation of the theory, paving the way toward full comprehension of nanoparticle assembly based on optical binding
Polynomial solutions of nonlinear integral equations
We analyze the polynomial solutions of a nonlinear integral equation,
generalizing the work of C. Bender and E. Ben-Naim. We show that, in some
cases, an orthogonal solution exists and we give its general form in terms of
kernel polynomials.Comment: 10 page
Identifying the development in phase and amplitude of dipole and multipole radiation
The spatial variation in phase and the propagating wave-front of plane wave electromagnetic radiation are widely familiar text-book territory. In contrast, the developing amplitude and phase of radiation emitted by a dipole or multipole source generally receive less attention, despite the prevalence of these systems. There is additional complexity in such cases where, in consequence of retardation, the character and features significantly and progressively change as radiation propagates onwards, from the near-field and out towards the wave-zone. Readily developed analytical representations of the electric field, cast as a function of distance from the source, provide illuminating insights into the most prominent and distinctive properties of radiant electromagnetic emission. Graphical implementations and animations of the results prove particularly instructive in revealing the spatial form and temporal evolution of the emergent electromagnetic fields
A Paraconsistent Higher Order Logic
Classical logic predicts that everything (thus nothing useful at all) follows
from inconsistency. A paraconsistent logic is a logic where an inconsistency
does not lead to such an explosion, and since in practice consistency is
difficult to achieve there are many potential applications of paraconsistent
logics in knowledge-based systems, logical semantics of natural language, etc.
Higher order logics have the advantages of being expressive and with several
automated theorem provers available. Also the type system can be helpful. We
present a concise description of a paraconsistent higher order logic with
countable infinite indeterminacy, where each basic formula can get its own
indeterminate truth value (or as we prefer: truth code). The meaning of the
logical operators is new and rather different from traditional many-valued
logics as well as from logics based on bilattices. The adequacy of the logic is
examined by a case study in the domain of medicine. Thus we try to build a
bridge between the HOL and MVL communities. A sequent calculus is proposed
based on recent work by Muskens.Comment: Originally in the proceedings of PCL 2002, editors Hendrik Decker,
Joergen Villadsen, Toshiharu Waragai (http://floc02.diku.dk/PCL/). Correcte
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