2,408 research outputs found
Synthesis of Compounds Related to Fluoranthene
Part 1a. The known 4-methylfluoranthene and 4-phenylfluoranthene have been synthesised by condensation of methyl and phenyl vinyl ketones, or the corresponding Mannich bases, methyl 2-morpholinoethyl ketone and 2-diethylaminoethyl phenyl ketone respectively, with methyl fluorene-9-carboxylate, followed by hydrolysis and decarboxylation, reduction, cyclisation, and dehydrogenation. Unsuccessful attempts to evolve a new synthesis of methyl fluorene-9-carboxylate were made. Part lb. 1:2:5:6-Dibenzpyracylene was synthesised by a crossed Ullmann reaction between 4-iodofluoranthene and 2-bromonitrobenzene, followed by reduction, diazotisation, and ring-closure. An attempt at synthesis by the method described in Part la failed. The ultra-violet absorption spectrum is reported and discussed, especially in relation to Clar's Anellation Theory. Part 2. 2:3-Benzfluoranthene has been synthesised from o-diphenylenephthalide by Clar's zinc dust-zinc chloride fusion method. An attempt to synthesise 2:3-benzfluoranthene by cyclisation of 9-bromo-9-o-bromo-o-tolylfluorene gave a compound believed, in the light of spectrographic and analytical evidence, to be 1:9-diphenylanthracene. The spectrum of 2:3-benzfluoranthene is reported and discussed, especially in relation to the Anellation Theory. Part 3. 3:4-Dimethylfluoranthene was obtained by the Grignard reaction on 4-keto-3-methyl-1:2:3:4-tetra-hydrofluoranthene, followed by dehydration-dehydrogenation. 2-Methoxyfluoranthene was synthesised by a crossed Ullmann reaction between 1-iodo-2-methoxynaphthalene and o-bromonitrobenzene, followed by reduction, diazotisation, and ring-closure. Part 4. The ultra-violet absorption spectra of several mono-, di-, and trimethylfluoranthenes, methoxy-fluoranthenes, and 4-phenylfluoranthene, not previously recorded, have been measured. They are shown to be of value in characterisation of the pure compounds. Distortion due to overlapping of the substituent methyl- or methoxyl- group with a hydrogen atom in the 2- or 10- substituted derivatives appears to produce corresponding distortions in the ultraviolet absorption curve
Earthshine as an Illumination Source at the Moon
Earthshine is the dominant source of natural illumination on the surface of
the Moon during lunar night, and at locations within permanently shadowed
regions that never receive direct sunlight. As such, earthshine may enable the
exploration of areas of the Moon that are hidden from solar illumination. The
heat flux from earthshine may also influence the transport and cold trapping of
volatiles present in the very coldest areas. In this study, Earth's spectral
radiance at the Moon is examined using a suite of Earth spectral models created
using the Virtual Planetary Laboratory (VPL) three dimensional modeling
capability. At the Moon, the broadband, hemispherical irradiance from Earth
near 0 phase is approximately 0.15 watts per square meter, with comparable
contributions from solar reflectance and thermal emission. Over the simulation
timeframe, spanning two lunations, Earth's thermal irradiance changes less than
a few mW per square meter as a result of cloud variability and the
south-to-north motion of sub-observer position. In solar band, Earth's
diurnally averaged light curve at phase angles < 60 degrees is well fit using a
Henyey Greenstein integral phase function. At wavelengths > 0.7 microns, near
the well known vegetation "red edge", Earth's reflected solar radiance shows
significant diurnal modulation as a result of the longitudinal asymmetry in
projected landmass, as well as from the distribution of clouds. A simple
formulation with adjustable coefficients is presented for estimating Earth's
hemispherical irradiance at the Moon as a function of wavelength, phase angle
and sub-observer coordinates. It is demonstrated that earthshine is
sufficiently bright to serve as a natural illumination source for optical
measurements from the lunar surface.Comment: 27 pages, 15 figures, 1 tabl
Food for thought: a university-wide approach to stimulate curricular and extra-curricular ESD activity
Predictive Power of Strong Coupling in Theories with Large Distance Modified Gravity
We consider theories that modify gravity at cosmological distances, and show
that any such theory must exhibit a strong coupling phenomenon, or else it is
either inconsistent or is already ruled out by the solar system observations.
We show that all the ghost-free theories that modify dynamics of spin-2
graviton on asymptotically flat backgrounds, automatically have this property.
Due to the strong coupling effect, modification of the gravitational force is
source-dependent, and for lighter sources sets in at shorter distances. This
universal feature makes modified gravity theories predictive and potentially
testable not only by cosmological observations, but also by precision
gravitational measurements at scales much shorter than the current cosmological
horizon. We give a simple parametrization of consistent large distance modified
gravity theories and their predicted deviations from the Einsteinian metric
near the gravitating sources.Comment: 12 pages, Latex, to be published in New Journal of Physic
Discovery and Characterization of a Caustic Crossing Microlensing Event in the SMC
We present photometric observations and analysis of the second microlensing
event detected towards the Small Magellanic Cloud (SMC), MACHO Alert 98-SMC-1.
This event was detected early enough to allow intensive observation of the
lightcurve. These observations revealed 98-SMC-1 to be the first caustic
crossing, binary microlensing event towards the Magellanic Clouds to be
discovered in progress.
Frequent coverage of the evolving lightcurve allowed an accurate prediction
for the date of the source crossing out of the lens caustic structure. The
caustic crossing temporal width, along with the angular size of the source
star, measures the proper motion of the lens with respect to the source, and
thus allows an estimate of the location of the lens. Lenses located in the
Galactic halo would have a velocity projected to the SMC of v^hat ~1500 km/s,
while an SMC lens would typically have v^hat ~60 km/s.
We have performed a joint fit to the MACHO/GMAN data presented here,
including recent EROS data of this event. These joint data are sufficient to
constrain the time for the lens to move an angle equal to the source angular
radius; 0.116 +/- 0.010 days. We estimate a radius for the lensed source of 1.4
+/- 0.1 R_sun. This yields a projected velocity of v^hat = 84 +/- 9 km/s. Only
0.15% of halo lenses would be expected to have a v^hat value at least as small
as this, while 31% of SMC lenses would be expected to have v^hat as large as
this. This implies that the lensing system is more likely to reside in the SMC
than in the Galactic halo.Comment: 16 pages, including 3 tables and 3 figures; submitted to The
Astrophysical Journa
Hole doping dependences of the magnetic penetration depth and vortex core size in YBa2Cu3Oy: Evidence for stripe correlations near 1/8 hole doping
We report on muon spin rotation measurements of the internal magnetic field
distribution n(B) in the vortex solid phase of YBa2Cu3Oy (YBCO) single
crystals, from which we have simultaneously determined the hole doping
dependences of the in-plane Ginzburg-Landau (GL) length scales in the
underdoped regime. We find that Tc has a sublinear dependence on
1/lambda_{ab}^2, where lambda_{ab} is the in-plane magnetic penetration depth
in the extrapolated limits T -> 0 and H -> 0. The power coefficient of the
sublinear dependence is close to that determined in severely underdoped YBCO
thin films, indicating that the same relationship between Tc and the superfluid
density is maintained throughout the underdoped regime. The in-plane GL
coherence length (vortex core size) is found to increase with decreasing hole
doping concentration, and exhibit a field dependence that is explained by
proximity-induced superconductivity on the CuO chains. Both the magnetic
penetration depth and the vortex core size are enhanced near 1/8 hole doping,
supporting the belief by some that stripe correlations are a universal property
of high-Tc cuprates.Comment: 12 pages, 13 figure
APOLLO: the Apache Point Observatory Lunar Laser-ranging Operation: Instrument Description and First Detections
A next-generation lunar laser ranging apparatus using the 3.5 m telescope at
the Apache Point Observatory in southern New Mexico has begun science
operation. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation)
has achieved one-millimeter range precision to the moon which should lead to
approximately one-order-of-magnitude improvements in the precision of several
tests of fundamental properties of gravity. We briefly motivate the scientific
goals, and then give a detailed discussion of the APOLLO instrumentation.Comment: 37 pages; 10 figures; 1 table: accepted for publication in PAS
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