2,647 research outputs found
Exercise training and detraining process affects plasma adiponectin level in healthy and spontaneously hypertensive rats
BACKGROUND: Adiponectin levels with long-term swimming exercise have been never investigated in spontaneously hypertensive rats (SHR). OBJECTIVE: This study was aimed to investigate the effects of exercise and detraining process on the adiponectin plasma levels of spontaneously hypertensive rats (SHR) and healthy Wistar-Kyoto rats (WKY). MATERIAL AND METHODS: The rats in the exercise groups were swimming for 10 weeks, 5 days/week, one hour in a day. The detraining rats were left to be sedentary in their cages for 5 weeks after 10 weeks of exercise period. RESULTS: The plasma adiponectin levels decreased in E and SHRE groups compared to the SC and the SHR groups, respectively. In addition, blood pressure was decreased in the exercise groups vs their controls. The adiponectin level was not found to be significantly different in ED and SHRED groups compared to their controls. The blood pressure did not differ between SDC and ED groups, although in the SHRED group it was found to be lower than in SHRSD group rats. CONCLUSION: The results of this study showed that exercise reduced plasma levels of adiponectin in healthy and spontaneously hypertensive rats. However, this difference disappeared at the end of the training processes. Our results suggest, that changes in plasma adiponectin levels are not responsible for changes in blood pressure
SDSS J163030.58+423305.8: A 40 minute Orbital Period Detached White Dwarf Binary
We report the discovery of a new detached, double white dwarf system with an
orbital period of 39.8 min. We targeted SDSS J163030.58+423305.8 (hereafter
J1630) as part of our radial velocity program to search for companions around
low-mass white dwarfs using the 6.5m MMT. We detect peak-to-peak radial
velocity variations of 576 km/s. The mass function and optical photometry rule
out main-sequence companions. In addition, no milli-second pulsar companions
are detected in radio observations. Thus the invisible companion is most likely
another white dwarf. Unlike the other 39 min binary SDSS J010657.39-100003.3,
follow-up high speed photometric observations of J1630 obtained at the McDonald
2.1m telescope do not show significant ellipsoidal variations, indicating a
higher primary mass and smaller radius. The absence of eclipses constrain the
inclination angle to <82deg. J1630 contains a pair of white dwarfs, 0.3 Msun
primary + >0.3 Msun invisible secondary, at a separation of >0.32 Rsun. The two
white dwarfs will merge in less than 31 Myr. Depending on the core composition
of the companion, the merger will form either a single core-He burning subdwarf
star or a rapidly rotating massive white dwarf. The gravitational wave strain
from J1630 is detectable by instruments like the Laser Interferometer Space
Antenna (LISA) within the first year of operation.Comment: MNRAS Letters, in pres
A Detailed Model Atmosphere Analysis of Cool White Dwarfs in the Sloan Digital Sky Survey
We present optical spectroscopy and near-infrared photometry of 126 cool
white dwarfs in the Sloan Digital Sky Survey (SDSS). Our sample includes high
proper motion targets selected using the SDSS and USNO-B astrometry and a dozen
previously known ultracool white dwarf candidates. Our optical spectroscopic
observations demonstrate that a clean selection of large samples of cool white
dwarfs in the SDSS (and the SkyMapper, Pan-STARRS, and the Large Synoptic
Survey Telescope datasets) is possible using a reduced proper motion diagram
and a tangential velocity cut-off (depending on the proper motion accuracy) of
30 km/s. Our near-infrared observations reveal eight new stars with significant
absorption. We use the optical and near-infrared photometry to perform a
detailed model atmosphere analysis. More than 80% of the stars in our sample
are consistent with either pure hydrogen or pure helium atmospheres. However,
the eight stars with significant infrared absorption and the majority of the
previously known ultracool white dwarf candidates are best explained with mixed
hydrogen and helium atmosphere models. The age distribution of our sample is
consistent with a Galactic disk age of 8 Gyr. A few ultracool white dwarfs may
be as old as 12-13 Gyr, but our models have problems matching the spectral
energy distributions of these objects. There are only two halo white dwarf
candidates in our sample. However, trigonometric parallax observations are
required for accurate mass and age determinations and to confirm their
membership in the halo.Comment: ApJ Supplements, in pres
Two New Tidally Distorted White Dwarfs
We identify two new tidally distorted white dwarfs (WDs), SDSS
J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both
stars are extremely low mass (ELM, < 0.2 Msun) WDs in short-period, detached
binary systems. High-speed photometric observations obtained at the McDonald
Observatory reveal ellipsoidal variations and Doppler beaming in both systems;
J1741, with a minimum companion mass of 1.1 Msun, has one of the strongest
Doppler beaming signals ever observed in a binary system (0.59 \pm 0.06%
amplitude). We use the observed ellipsoidal variations to constrain the radius
of each WD. For J1741, the star's radius must exceed 0.074 Rsun. For J2119, the
radius exceeds 0.10 Rsun. These indirect radius measurements are comparable to
the radius measurements for the bloated WD companions to A-stars found by the
Kepler spacecraft, and they constitute some of the largest radii inferred for
any WD. Surprisingly, J1741 also appears to show a 0.23 \pm 0.06% reflection
effect, and we discuss possible sources for this excess heating. Both J1741 and
J2119 are strong gravitational wave sources, and the time-of-minimum of the
ellipsoidal variations can be used to detect the orbital period decay. This may
be possible on a timescale of a decade or less.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical
Journa
Design of master and slave modules on battery management system for electric vehicles
Nowadays, electric vehicle usage and the use of LiFePO4 batteries in electric vehicles gradually increase. However, there are important features to be considered to use these batteries safely and efficiently. Incorrect use of these batteries can lead to burning, explosion or shortening of the life of batteries.
In this paper, a Battery Management System (BMS) for lithium based batteries is designed that operates more efficiently and communicates with UART between master and slave modules and can communicate via CAN protocol with external devices. Micro controller based control and protection equipment is designed that help to measure and monitor the voltage, temperature and current values of the batteries. They protect the battery cells from the conditions such as over charge, over discharge, high current, high temperature. BMS balances battery cell voltages during charging process with passive cell voltage balancing. In addition to the main controller module in the BMS, slave controller modules have been added to provide high resolution voltage and temperature tracking. A modular BMS has been devised which can be used in groups of batteries of different voltage values thanks to electrically isolated slave control modules
First Results from Pan-STARRS1: Faint, High Proper Motion White Dwarfs in the Medium-Deep Fields
The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands
(Pan-STARRS1 gps, rps, ips, zps, and yps) on twelve "Medium Deep Fields", each
of which spans a 3.3 degree circle. For the period between Apr 2009 and Apr
2011 these fields were observed 50-200 times. Using a reduced proper motion
diagram, we have extracted a list of 47 white dwarf (WD) candidates whose
Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6-sigma level,
with a typical 1-sigma proper motion uncertainty of 10 mas/yr. We also used
astrometry from SDSS (when available) and USNO-B to assess our proper motion
fits. None of the WD candidates exhibits evidence of statistically significant
parallaxes, with a typical 1-sigma uncertainty of 8 mas. Twelve of these
candidates are known WDs, including the high proper motion (1.7"/yr) WD LHS
291. We confirm three more objects as WDs through optical spectroscopy. Based
on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170
K Teff 5000 K and cooling ages <9 Gyr. We classify these objects as likely
thick disk WDs based on their kinematics. Our current sample represents only a
small fraction of the Pan-STARRS1 data. With continued coverage from the Medium
Deep Field Survey and the 3pi survey, Pan-STARRS1 should find many more high
proper motion WDs that are part of the old thick disk and halo.Comment: 33 pages, 8 figures, submitted to Ap
A Dusty Disk Around WD1150-153: Explaining the Metals in White Dwarfs by Accretion from the Interstellar Medium versus Debris Disks
We report the discovery of excess K-band radiation from a metal-rich DAV
white dwarf star, WD1150-153. Our near infrared spectroscopic observations show
that the excess radiation cannot be explained by a (sub)stellar companion, and
is likely to be caused by a debris disk similar to the other DAZ white dwarfs
with circumstellar debris disks. We find that the fraction of DAZ white dwarfs
with detectable debris disks is at least 14%. We also revisit the problem of
explaining the metals in white dwarf photospheres by accretion from the
interstellar medium (ISM). We use the observed interstellar column densities
toward stars in close angular proximity and similar distance as DAZ white
dwarfs to constrain the contribution of accretion from the ISM. We find no
correlation between the accretion density required to supply metals observed in
DAZs with the densities observed in their interstellar environment, indicating
that ISM accretion alone cannot explain the presence of metals in nearby DAZ
white dwarfs. Although ISM accretion will certainly contribute, our analysis
indicates that it is not the dominant source of metals for most DAZ white
dwarfs. Instead, the growing number of circumstellar debris disks around DAZs
suggests that circumstellar material may play a more dominant role in polluting
the white dwarf atmospheres.Comment: ApJ, in pres
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