292 research outputs found
Bubbling and bistability in two parameter discrete systems
We present a graphical analysis of the mechanisms underlying the occurrences
of bubbling sequences and bistability regions in the bifurcation scenario of a
special class of one dimensional two parameter maps. The main result of the
analysis is that whether it is bubbling or bistability is decided by the sign
of the third derivative at the inflection point of the map function.Comment: LaTeX v2.09, 14 pages with 4 PNG figure
Measurement of Dust Optical Properties in Coalsack
We have used FUSE and Voyager observations of dust scattered starlight in the
neighborhood of the Coalsack Nebula to derive the optical constants of the dust
grains. The albedo is consistent with a value of and the phase
function asymmetry factor with a value of throughout the
spectral range from 900 -- 1200 \AA, in agreement with previous determinations
as well as theoretical predictions. We have now observed two regions (Ophiuchus
and Coalsack) with intense diffuse background radiation and in both cases have
found that the emission is due to light from nearby hot stars scattered by a
relatively thin foreground cloud, with negligible contribution from the
background molecular cloud.Comment: Total 19 pages, Figures 9, Accepted for publication in Astrophysical
Journa
GALEX Observations of Diffuse UV Radiation at High Spatial Resolution from the Sandage Nebulosity
Using the GALEX ultraviolet imagers we have observed a region of nebulosity
first identified as starlight scattered by interstellar dust by Sandage (1976).
Apart from airglow and zodiacal emission, we have found a diffuse UV background
of between 500 and 800 \phunit in both the \galex FUV (1350 -- 1750 \AA) and
NUV (1750 -- 2850 \AA). Of this emission, up to 250 \phunit is due to \htwo
fluorescent emission in the FUV band; the remainder is consistent with
scattering from interstellar dust. We have estimated the optical constants to
be in the FUV and in the NUV, implying
highly forward scattering grains, plus an extragalactic contribution of as much
as 150 \phunit. These are the highest spatial resolution observations of the
diffuse UV background to date and show an intrinsic scatter beyond that
expected from instrumental noise alone. Further modeling is required to
understand the nature of this scatter and its implications for the ISM.Comment: Total 20 pages, Figures 9, Accepted for publication in Astrophysical
Journa
Observations of Diffuse Ultraviolet Emission from Draco
We have studied small scale (2 arcmin) spatial variation of the diffuse UV
radiation using a set of 11 GALEX deep observations in the constellation of
Draco. We find a good correlation between the observed UV background and the IR
100 micron flux, indicating that the dominant contributor of the diffuse
background in the field is the scattered starlight from the interstellar dust
grains. We also find strong evidence of additional emission in the FUV band
which is absent in the NUV band. This is most likely due to Lyman band emission
from molecular hydrogen in a ridge of dust running through the field and to
line emissions from species such as C IV (1550 A) and Si II (1533 A) in the
rest of the field. A strong correlation exists between the FUV/NUV ratio and
the FUV intensity in the excess emission regions in the FUV band irrespective
of the optical depth of the region. The optical depth increases more rapidly in
the UV than the IR and we find that the UV/IR ratio drops off exponentially
with increasing IR due to saturation effects in the UV. Using the positional
details of Spitzer extragalactic objects, we find that the contribution of
extragalactic light in the diffuse NUV background is 49 +/- 13 photon units and
is 30 +/- 10 photon units in the FUV band.Comment: 30 pages, 13 figures, Accepted for publication in The Astrophysical
Journal (ApJ), November 2010, v723 issu
Fuzzy Knowledge Based System for Suitability of Soils in Airfield Applications
Proper design of roads and airfield pavements requires an in-depth soil properties evaluation to determine suitability of soil. Soft computing is used to model soil classification system's dynamic behaviour and its properties. Soft computing is based on methods of machine learning, fuzzy logic and artificial neural networks, expert systems, genetic algorithms. Fuzzy system is a strong method for mimicking human thought and solves question of confusion. This paper proposes a new decision-making approach for soil suitability in airfield applications without a need to perform any manual works like use of tables or chart. A fuzzy knowledge - based approach is built to rate soil suitability in qualitative terms for airfield application. The proposed model describes a new technique by defining fuzzy descriptors using triangular functions considering the index properties of soils as input parameters and fuzzy rules are generated using fuzzy operators to classify soil and rate its suitability for airfield applications. The data obtained from the results of the laboratory test are validated with the results of the fuzzy knowledge-based system indicating the applicability of the Fuzzy model created. The approach developed in this work is more skilled to other prevailing optimization models. Due to its system’s flexibility, it can be suitably customized and applied to laboratory test data available, thus delivering a wide range for any geotechnical engineer. Doi: 10.28991/cej-2021-03091643 Full Text: PD
Dust Properties in the FUV in Ophiuchus
We have derived the albedo () and phase function asymmetry factor () of
interstellar dust grains at 1100 \AA ~ using archival {\it Voyager}
observations of diffuse radiation in Ophiuchus. We have found that the grains
are highly forward scattering with 0.55 0.25 and 0.40
0.10. Even though most of the gas in this direction is in the Ophiuchus
molecular cloud, the diffuse FUV radiation is almost entirely due to scattering
in a relatively thin foreground cloud. This suggests that one cannot assume
that the UV background is directly correlated with the total amount of gas in
any direction.Comment: 11 pages, 7 figures, 2 tables, ApJ, accepte
Identification & differentiation of Mycobacterium avium & M. intracellulare by PCR- RFLP assay using the groES gene
Background & objectives: We report a new polymerase chain reaction (PCR) – restriction fragment
length polymorphism (RFLP) assay using mycobacterial groES as a target to identify Mycobacterium
avium and M. intracellulare in clinical samples.
Methods: The assay was standardized using M. avium and M. intracellulare standard strains obtained
from ATCC and was tested with 45 M. avium-M. intracellulare complex (MAC) clinical isolates (Of
which 31 were from HIV+ individuals). The standard and clinical strains were typed with HPLC based
mycolic acid fingerprinting.
Results: Three polymorphisms (BamHI, BstNI and HgaI) were identified for inter-species differentiation
among standard strains; of which, only HgaI was found to be useful in clinical isolates. Of the 45 isolates,
25 were M. avium and 20 were M. intracelluare. MAC isolates, which could not be differentiated by
HPLC analysis, were also typed by this method.
Interpretation & conclusions: The use of mycobacterial groES as a PCR-RFLP target for M. avium and
M. intracellulare is a simple and rapid method that can complement HPLC in their differentiation
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