1,144 research outputs found
Spectroscopic investigation of a 'Virgin of Sorrows' canvas painting : a multi-method approach
The accretion disk in the post period-minimum cataclysmic variable SDSS J080434.20+510349.2
This study of SDSS0804 is primarily concerned with the double-hump shape in
the light curve and its connection with the accretion disk in this bounce-back
system. Time-resolved photometric and spectroscopic observations were obtained
to analyze the behavior of the system between superoutbursts. A geometric model
of a binary system containing a disk with two outer annuli spiral density waves
was applied to explain the light curve and the Doppler tomography. Observations
were carried out during 2008-2009, after the object's magnitude decreased to
V~17.7(0.1) from the March 2006 eruption. The light curve clearly shows a
sinusoid-like variability with a 0.07 mag amplitude and a 42.48 min
periodicity, which is half of the orbital period of the system. In Sept. 2010,
the system underwent yet another superoutburst and returned to its quiescent
level by the beginning of 2012. This light curve once again showed a
double-humps, but with a significantly smaller ~0.01mag amplitude. Other types
of variability like a "mini-outburst" or SDSS1238-like features were not
detected. Doppler tomograms, obtained from spectroscopic data during the same
period of time, show a large accretion disk with uneven brightness, implying
the presence of spiral waves. We constructed a geometric model of a bounce-back
system containing two spiral density waves in the outer annuli of the disk to
reproduce the observed light curves. The Doppler tomograms and the
double-hump-shape light curves in quiescence can be explained by a model system
containing a massive >0.7Msun white dwarf with a surface temperature of
~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli
spirals. According to this model, the accretion disk should be large, extending
to the 2:1 resonance radius, and cool (~2500K). The inner parts of the disk
should be optically thin in the continuum or totally void.Comment: 12 pages, 15 figures, accepted for publication in A&
Quantifying Metal Interactions with the Antimicrobial Peptide Calcitermin
Antimicrobial Peptides (AMPs) are novel therapeutic agents that play important roles in the innate immune system with its ability to kill gram-positive and gram-negative bacteria. Antibiotics are losing their efficacy, thus requiring a larger dose of medicine for treatment resulting in the increase of antibiotic resistance. AMPs are an attractive approach for exploration due to their broad-spectrum activity and ease of synthesis. Furthermore, fewer bacteria have developed resistance to AMPs. Several AMPs have demonstrated increased antimicrobial activity with metal ions, like Zn(II) and Cu(II) binding to the peptide. In this study, we performed the purification of Calcitermin through high-performance liquid chromatography (HPLC) and will be analyzing the metal-binding thermodynamics through isothermal titration calorimetry (ITC)
Productivity of a \u3cem\u3eLeucaena Leucocephala-Cynodon Nlemfuensis\u3c/em\u3e Silvopastoral System with Sheep in Yucatan, Mexico
Animal production in the tropics of Mexico is based on grazed grasslands of low productivity; this type of production system has reduced the areas of natural vegetation and damaged the ecology (erosion of flora, fauna and soil). Silvopastoral technologies may improve the welfare and economic conditions of the rural population and, consequently, preserve their natural resources. The current work was designed to assess the introduction of Leucaena leucocephala in a silvopastoral system with Cynodon nlemfuensis (star grass) grazed by sheep
Scaling differences between large interplate and intraplate earthquakes
A study of large intraplate earthquakes with well-determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes, in which M_0 ∝ L^2 or u = αL, where L is rupture length and u is slip. In contrast to interplate earthquakes, for which α ≈ 1 × 10^(−5), for for the intraplate events α ≈ 6 × 10^(−5), which implies that these earthquakes have stress drops about 6 times higher than interplate events. This result is independent of focal mechanism type. This implies that intraplate faults have a higher frictional strength than do plate boundaries, and hence that faults are velocity or slip weakening in their behavior. This factor may be important in producing the concentrated deformation that creates and maintains plate boundaries
Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2
We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and
study the origin of a long-term variability found in its light curve.
Multi-longitude time-resolved photometric observations were carried out to
analyze the uncommon behavior also found recently in two newly discovered CVs.
This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the
nature of the observed double-humped light curve and its relation to a cyclic
brightening occurring during quiescence. The observations were obtained early
in 2007, when the object was at about V~17.1, 0.4 mag brighter than the
pre-outburst magnitude. The light curve shows a sinusoidal variability with an
amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of
the orbital period of the system. In addition, we have observed two
"mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days
each. The "mini-outburst" had a symmetric profile and repeated in about 32
days. Subsequent monitoring of the system shows a cyclical behaviour of such
"mini-outbursts" with a similar recurrence period. The origin of the
double-humped light curve and the periodic brightening is discussed in the
light of the evolutionary state of SDSS J080434.20+510349.2.Comment: 7 pages, 6 figures, Accepted by A&A, typos added, figure correcte
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