1,474 research outputs found
Spectropolarimetric Study on Circumstellar Structure of Microquasar LS I +61deg 303
We present optical linear spectropolarimetry of the microquasar LS I
+61 303. The continuum emission is mildly polarized (up to 1.3 %) and
shows almost no temporal change. We find a distinct change of polarization
across the H emission line, indicating the existence of polarization
component intrinsic to the microquasar. We estimate the interstellar
polarization (ISP) component from polarization of the H line and derive
the intrinsic polarization component. The wavelength dependence of the
intrinsic component is well explained by Thomson scattering in equatorial disk
of the Be-type mass donor. The position angle (PA) of the intrinsic
polarization represents the rotational axis of the Be disk.
This PA is nearly perpendicular to the PA of the radio jet found during
quiescent phases. Assuming an orthogonal disk-jet geometry around the compact
star, the rotational axis of the accretion disk is almost perpendicular to that
of the Be disk. Moreover, according to the orbital parameters of the
microquasar, the compact star is likely to get across the Be disk around their
periastron passage. We discuss the peculiar circumstellar structure of this
microquasar inferred from our observation and possible connection with its
high-energy activities.Comment: 17pages, 7figures; accepted for Publications of the Astronomical
Society of Japa
Oxidative stress and breast cancer biomarkers : the case of the cytochrome P450 2E1
Aim: The aim of the study is to investigate the impact of the cytochrome P450 2E1, which is the most efficient CYP450 family
member in generating reactive oxygen species (ROS), on cellular energy metabolism of breast cancer cells and therefore the
effects of CYP2E1 on breast carcinogenesis. Methods: The estrogen receptor positive MCF-7 and the triple negative MDAMB-
231 breast cancer cells were used as experimental system to estimate ROS generation in these cells overexpressing CYP2E1
and treated with the glycolytic inhibitors 3-bromopyruvate or 2-deoxyglucose in the presence or absence of the CYP2E1 inhibitor
chlormethiazole. Adenosine triphosphate (ATP) assay was used to measure ATP production and lactate assay to quantify the efflux
of lactic acid in breast cancer cells treated with the CYP2E1 inhibitor chlormethiazole, the mitochondrial membrane potential
and cell viability assays were employed to assess the pathway of cellular energy production and cellular death respectively after
treatment of MCF-7 and MDA-MB-231 with the CYP2E1 activator acetaminophen or the CYP2E1 inhibitor chlormethiazole.
Results: T he r esults i ndicated i ncreased ROS generation i n b reast c ancer c ells overexpressing C YP2E1. ROS generation was
differentially regulated in breast cancer cells upon treatment with the CYP2E1 inhibitor chlormethiazole. Chlormethiazole
treated MCF-7 cells exhibited reduced lactate efflux implying that CYP2E1 directly or indirectly regulates the glycolytic rate
in these cells. Furthermore the mitochondrial membrane potential of both MCF-7 and MDA-MB-231 cells was differentially
affected by the CYP2E1 activator acetaminophen versus the CYP2E1 inhibitor chlormethiazole providing additional support for
the involvement of CYP2E1 in energy metabolic pathways in breast cancer. Conclusion: Results presented in this study provide
evidence to suggest that CYP2E1 regulates cellular energy metabolism of breast cancer cells in a manner dependent on cell type
and potentially on the clinical staging of the disease therefore CYP2E1 is a possible breast cancer biomarker
Correlation between Interstellar Polarization and Dust Temperature: Alignment of Grains by Radiative Torques is Ubiquitous?
We investigate the efficiency of interstellar polarization
where is the fractional linear polarization
and is extinction, in 16 lines of sight as a function of wavelength
. We have used the data obtained with the low-dispersion
spectropolarimeter HBS as well as those in literature. It is found that the
polarization efficiency is proportional to
in wavelength \lambda \approx 0.4-0.8 \micron, where
is a parameter which varies from 0.5 to 1.2 \micron. We find that
is negatively correlated with the dust temperature deduced from
infrared data by Schlegel et al., suggesting that the polarization efficiency
is higher in short wavelength for higher temperature. According to the
alignment theory by radiative torques (RATs), if the radiation is stronger and
bluer, RATs will make small grains align better, and the polarization
efficiency will increase in short wavelength. Our finding of the correlation
between and the temperature is consistent with what is expected with
the alignment mechanism by RATs.Comment: 5 pages, 3 figures. Accepted for publication in PASJ Letters, Vol.63,
October 2011 issu
Tumour enhancement with newly developed Mn-metalloporphyrin (HOP-9P) in magnetic resonance imaging of mice
The purpose of the study is to evaluate the tumour enhancing characteristics and biodistribution of a newly developed metalloporphyrin derivative, HOP-9P (13, 17-bis (1-carboxypropionyl) carbamoylethyl-3, 8-bis (1-phenylpropyloxyethyl)-2,7,12,18-tetra- methyl-porphynato manganese (III)). Seven mice bearing SCC VII tumours were imaged using T1-weighted conventional spin echo magnetic resonance images before and 5 min, 2 h and 24 h after intravenous injection of 0.1 mmol/kg of HOP-9P. For the acquired images, signal intensities of the tumour, muscle and oil-phantom were measured. Then, tumor/oil and tumor/muscle signal intensity ratios were calculated. Nineteen mice were sacrificed before or after the administration of HOP-9P (at 5 min, 2 h and 24 h), and the biodistribution of manganese in the tumour, muscle, liver, blood and kidneys was measured using optical emission spectrometers and was expressed as micrograms of manganese per gram of tissue. The tumour/muscle signal intensity ratio at 24 h (3.18 ± 0.34) was significantly higher than precontrast ratio (1.77 ± 0.20) (P < 0.05). The biodistribution assessment of manganese demonstrated that HOP-9P gradually and consistently accumulated in the tumour to reach the highest concentration at 24 h (3.49 ± 1.22 μ gMn/g). It is concluded that HOP-9P is a potential tumour-specific MR contrast agent. © 2001 Cancer Research Campaign http://www.bjcancer.co
Справа Івана Дзюби
У статті автор, використовуючи документи Галузевого державного архіву СБ України, досліджує постать видатного літературознавця, громадського діяча Івана Дзюби у контексті боротьби співробітників органів держбезпеки УРСР з «українським буржуазним націоналізмом».В статье автор, используя документы Отраслевого государственного архива СБ Украины, исследует личность выдающегося литературоведа, общественного деятеля Ивана Дзюбы в контексте борьбы сотрудников органов госбезопасности УССР с «украинским буржуазным национализмом».Using the documents of State branch archive of State Security of Ukraine, the author investigates the personality of Ivan Dzyuba during the struggle of KGB of the UkSSR against the «Ukrainian bourgeois nationalism»
Low- and Medium-Dispersion Spectropolarimetry of Nova V475 Sct (Nova Scuti 2003): Discovery of an Asymmetric High-Velocity Wind in a Moderately Fast Nova
We present low-resolution () and medium-resolution ()
spectropolarimetry of Nova V475 Sct with the HBS instrument, mounted on the
0.91-m telescope at the Okayama Astrophysical Observatory, and with FOCAS,
mounted on the 8.2-m Subaru telescope. We estimated the interstellar
polarization toward the nova from the steady continuum polarization components
and H line emission components. After subtracting the interstellar
polarization component from the observations, we found that the H
emission seen on 2003 October 7 was clearly polarized. In the polarized flux
spectrum, the H emission had a distinct red wing extending to km s and a shoulder around km s, showing a
constant position angle of linear polarization \theta_{\rm *}\simeq
155\arcdeg\pm 15\arcdeg. This suggests that the nova had an asymmetric outflow
with a velocity of km s or more, which is six
times higher than the expansion velocity of the ionized shell at the same
epoch. Such a high-velocity component has not previously been reported for a
nova in the `moderately fast' speed class. Our observations suggest the
occurrence of violent mass-loss activity in the nova binary system even during
the common-envelope phase. The position angle of the polarization in the
H wing is in good agreement with that of the continuum polarization
found on 2003 September 26 (--0.6 %), which disappeared
within the following 2 d. The uniformity of the PA between the continuum
polarization and the wing polarization on October 7 suggests that the axis of
the circumstellar asymmetry remained nearly constant during the period of our
observations.Comment: 27 pages, 7 figures, accepted for publication in A
Dwarf Novae in the Shortest Orbital Period Regime: I. A New Short Period Dwarf Nova, OT J055717+683226
We report the observation of a new dwarf nova, OT J055717+683226, during its
first-ever recorded superoutburst in December 2006. Our observation shows that
this object is an SU UMa-type dwarf nova having a very short superhump period
of 76.67+/- 0.03 min (0.05324+/-0.00002 d). The next superoutburst was observed
in March 2008. The recurrence time of superoutbursts (supercycle) is, hence,
estimated to be ~480 d. The supercycle is much shorter than those of WZ
Sge-type dwarf novae having supercycles of >~ 10 yr, which are a major
population of dwarf novae in the shortest orbital period regime (<~85 min).
Using a hierarchical cluster analysis, we identified seven groups of dwarf
novae in the shortest orbital period regime. We identified a small group of
objects that have short supercycles, small outburst amplitudes, and large
superhump period excesses, compared with those of WZ Sge stars. OT
J055717+683226 probably belongs to this group.Comment: 14 pages, 11 figures, accepted for publication in PAS
Optical and Near-Infrared Photometry of Nova V2362 Cyg : Rebrightening Event and Dust Formation
We present optical and near-infrared (NIR) photometry of a classical nova,
V2362 Cyg (= Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening
with a long duration from 100 to 240 d after the maximum of the nova. Our
multicolor observation indicates an emergence of a pseudophotosphere with an
effective temperature of 9000 K at the rebrightening maximum. After the
rebrightening maximum, the object showed a slow fading homogeneously in all of
the used bands for one week. This implies that the fading just after the
rebrightening maximum ( less or equal 1 week ) was caused by a slowly shrinking
pseudophotosphere. Then, the NIR flux drastically increased, while the optical
flux steeply declined. The optical and NIR flux was consistent with blackbody
radiation with a temperature of 1500 K during this NIR rising phase. These
facts are likely to be explained by dust formation in the nova ejecta. Assuming
an optically thin case, we estimate the dust mass of 10^(-8) -- 10^(-10)
M_solar, which is less than those in typical dust-forming novae. These results
support the senario that a second, long-lasting outflow, which caused the
rebrightening, interacted with a fraction of the initial outflow and formed
dust grains.Comment: 6 pages, 4 figures, 2010, PASJ, 62, 1103--1108, in pres
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