190 research outputs found
Structure and stellar content of dwarf galaxies. III: B and R photometry of dwarf galaxies in the M101 group and the nearby field
We have carried out CCD photometry in the Cousins B and R bands of 21 dwarf
galaxies in and around the M101 group. Eleven are members and suspected members
of the group and ten are field galaxies in the projected vicinity of the group.
We have derived total magnitudes, effective radii, effective surface
brightnesses, as well as galaxy diameters at various isophotal levels in both
colours. Best-fitting exponential parameters and colour gradients are also
given for these galaxies. Some of the galaxies show a pronounced luminosity
excess above the best-fitting exponential at large radii, or surface
brightnesses fainter than approx 26 mag/sq_arcsec in R. This feature, while
non-significant for a single case and technically difficult to interpret, might
be an indication of the existence of an extended old stellar halo in dwarf
irregulars. The photometric parameters of the galaxies presented here will be
combined with previously published data for nearby dwarf galaxies and
statistically analysed in a forthcoming paper.Comment: 15 pages, 4 tables and 13 figures. For a full resolution version see
http://www.astro.unibas.ch/galaxies/papers.html To appear in A&A
Structure and stellar content of dwarf galaxies IV. B and R photometry of dwarf galaxies in the CVnI cloud
We have carried out CCD photometry in the Cousins B and R bands of 15
galaxies in the Canes Venatici I cloud. Total magnitudes, effective radii,
effective surface brightnesses, as well as galaxy radii at various isophotal
levels in both colors were determined. Best-fitting exponential parameters and
color gradients are also given for these galaxies. The photometric parameters
presented here will analyzed in a forthcoming paper, together with previously
published data for nearby dwarf galaxies.Comment: 10 pages, submitted to A&AS. For a full resolution version see
ftp://merkur.astro.unibas.ch/pub/bremnes/canesv.ps.g
B,V,I - photometry of 20 dwarf irregular galaxies within 10 Mpc
CCD - photometry is presented for 20 dIrr galaxies situated in the nearby
complexes CenA/M83, and CVnI as well as in the general field of the Local
Volume. We present integrated magnitudes of the galaxies in B,V,I - bands and
also surface brightness profiles to a median isophote mu_B ~ 28 mag /sq.arcsec.
The popular Sersic parameterization of surface brightness profiles generally
does a poor job of simultaneously fitting the inner cores and outer exponential
surface brightness fall-offs observed in many of our targets. The observed
sample is a part of a general project to image about 500 nearby (D < 10 Mpc)
dwarf galaxies in multiple bands.Comment: 3 figures, accepted to the MNRA
Using conditional kernel density estimation for wind power density forecasting
Of the various renewable energy resources, wind power is widely recognized as one of the most promising. The management of wind farms and electricity systems can benefit greatly from the availability of estimates of the probability distribution of wind power generation. However, most research has focused on point forecasting of wind power. In this paper, we develop an approach to producing density forecasts for the wind power generated at individual wind farms. Our interest is in intraday data and prediction from 1 to 72 hours ahead. We model wind power in terms of wind speed and wind direction. In this framework, there are two key uncertainties. First, there is the inherent uncertainty in wind speed and direction, and we model this using a bivariate VARMA-GARCH (vector autoregressive moving average-generalized autoregressive conditional heteroscedastic) model, with a Student t distribution, in the Cartesian space of wind speed and direction. Second, there is the stochastic nature of the relationship of wind power to wind speed (described by the power curve), and to wind direction. We model this using conditional kernel density (CKD) estimation, which enables a nonparametric modeling of the conditional density of wind power. Using Monte Carlo simulation of the VARMA-GARCH model and CKD estimation, density forecasts of wind speed and direction are converted to wind power density forecasts. Our work is novel in several respects: previous wind power studies have not modeled a stochastic power curve; to accommodate time evolution in the power curve, we incorporate a time decay factor within the CKD method; and the CKD method is conditional on a density, rather than a single value. The new approach is evaluated using datasets from four Greek wind farms
Distribution of star-forming complexes in dwarf irregular galaxies
We study the distribution of bright star-forming complexes in a homogeneous
sample of 72 late-type (``irregular'') dwarf galaxies located within the 10 Mpc
volume. Star-forming complexes are identified as bright lumps in B-band galaxy
images and isolated by means of the unsharp-masking method. For the sample as a
whole the radial number distribution of bright lumps largely traces the
underlying exponential-disk light profiles, but peaks at a 10 percent smaller
scale length. Moreover, the presence of a tail of star forming regions out to
at least six optical scale lengths provides evidence against a systematic star
formation truncation within that galaxy extension. Considering these findings,
we apply a scale length-independent concentration index, taking into account
the implied non-uniform random spread of star formation regions throughout the
disk. The number profiles frequently manifest a second, minor peak at about two
scale lengths. Relying on a two-dimensional stochastic self-propagating star
formation model, we show these secondary peaks to be consistent with triggered
star formation; for a few of the brighter galaxies a peculiar peak distribution
is observed that is conceivably due to the onset of shear provided by
differential rotation. On scales between 100 and 1000 pc, and by taking into
account exponential-disk structure, bright lumps reveal cluster dimensions
between 1.3 and 2, with a weak trend to higher dimensions for brighter
galaxies. Interpreting cluster dimension in terms of porosity of a self-similar
intragalactic medium, we derive a relation between current star formation rate,
scale length, and porosity.Comment: 16 pages, accepted for publication in Astronomy & Astrophysic
PENGGUNAAN MODEL PEMBELAJARAN AKTIF TEAM QUIZ DALAM MENINGKATKAN KEMAMPUAN MEMBACA PEMAHAMAN BAHASA JEPANG
Penelitian ini mengambil judul “penggunaan model pembelajaran aktif team quiz dalam meningkatkan kemampuan membaca pemahaman bahasa Jepang” . membaca pemahaman adalah memahami suatu informasi dari sebuah tulisan. membaca pemahaman merupakan salah satu pembelajaran yang sulit. Disebabkan karena metode yang digunakan oleh pengajar monoton dan kurang memotivasi siswa dalam pembelajaran membaca pemahaman.
Penelitian ini bertujuan untuk mengetahui bagaimana penggunaan model pembelajaran aktif team quiz dalam meningkatkan kemampuan membaca pemahaman bahasa Jepang. Penelitian ini menggunakan metode quasi eksperiment dengan one group before-after (pretest dan posttest) design. Sampel dalam penelitian ini adalah siswa kelas XI Bahasa SMA Negeri 1 Parongpong tahun ajaran 2015/2016. Instrument penelitiannya adalah tes dan angket.
Berdasarkan analisis data dengan perhitungan statistic yang menggunakan t hitung diketahui bahwa t hitung > t tabel maka Ho ditolak dan Hk diterima yang dapat disimpulkan bahwa penggunaan model pembelajaran aktif team quiz dalam meningkatkan kemampuan membaca pemahaman bahasa jepang efektif. Sedangkan hasil analisis data angket diketahui bahwa penggunaan model pembelajaran aktif team quiz dalam meningkatkan kemampuan membaca pemahaman bahasa Jepang mendapat respon positif dari siswa. ;
Reading comprehension is the act of understanding information from a presented text. It is one of difficulties found in learning. It caused by monotonous method conducted by teacher and in turn, students have less motivation on learning reading comprehension.
This research aims for how the Team Quiz active learning method can improve reading comprehension in Japanese. The quasi-experiment method with “one group before-after (pretest and posttest)” design is conducted in this research, by taking XI language students from 2015/2016 academic year of SMA Negeri 1 Parongpong as sample. Test and questionnaire is instrument used in this research.
According to data analysis with statistical calculation using t count, noting that t count > t table, therefore Ho is rejected and Hk is accepted. To conclude, Team Quiz active learning method is effective in improving reading comprehension in Japanese. Moreover, according to data analysis conducted in questionnaire, the Team Quiz active learning method gains positive responses from students
The Gas Content in Galactic Disks: Correlation with Kinematics
We consider the relationship between the total HI mass in late-type galaxies
and the kinematic properties of their disks. The mass for galaxies with
a wide variety of properties, from dwarf dIrr galaxies with active star
formation to giant low-brightness galaxies, is shown to correlate with the
product ( is the rotational velocity, and is the radial
photometric disks scale length), which characterizes the specific angular
momentum of the disk. This relationship, along with the anticorrelation between
the relative mass of HI in a galaxy and , can be explained in terms of the
previously made assumption that the gas density in the disks of most galaxies
is maintained at a level close to the threshold (marginal) stability of a
gaseous layer to local gravitational perturbations. In this case, the
regulation mechanism of the star formation rate associated with the growth of
local gravitational instability in the gaseous layer must play a crucial role
in the evolution of the gas content in the galactic disk.Comment: revised version to appear in Astronomy Letters, 8 pages, 5 EPS
figure
Color, Structure, and Star Formation History of Dwarf Galaxies over the last ~3 Gyr with GEMS and SDSS
We present a study of the colors, structural properties, and star formation
histories for a sample of ~1600 dwarfs over look-back times of ~3 Gyr
(z=0.002-0.25). The sample consists of 401 distant dwarfs drawn from the Galaxy
Evolution from Morphologies and SEDs (GEMS) survey, which provides high
resolution Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)
images and accurate redshifts, and of 1291 dwarfs at 10-90 Mpc compiled from
the Sloan Digitized Sky Survey (SDSS). The sample is complete down to an
effective surface brightness of 22 mag arcsec^-2 in z and includes dwarfs with
M_g=-18.5 to -14 mag. Rest-frame luminosities in Johnson UBV and SDSS ugr
filters are provided by the COMBO-17 survey and structural parameters have been
determined by S\'ersic fits. We find that the GEMS dwarfs are bluer than the
SDSS dwarfs by ~0.13 mag in g-r, which is consistent with the color evolution
over ~2 Gyr of star formation histories involving moderate starbursts and long
periods of continuous star formation. The full color range of the samples
cannot be reproduced by single starbursts of different masses or long periods
of continuous star formation alone. Furthermore, an estimate of the mechanical
luminosities needed for the gas in the GEMS dwarfs to be completely removed
from the galaxies shows that a significant number of low luminosity dwarfs are
susceptible to such a complete gas loss, if they would experience a starburst.
On the other hand, a large fraction of more luminous dwarfs is likely to retain
their gas. We also estimate the star formation rates per unit area for the GEMS
dwarfs and find good agreement with the values for local dwarfs.Comment: 31 pages, 13 figures, accepted for publication in the Ap
Background risk of breast cancer and the association between physical activity and mammographic density
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Palliative chemotherapy beyond three courses conveys no survival or consistent quality-of-life benefits in advanced non-small-cell lung cancer
This randomised multicentre trial was conducted to establish the optimal duration of palliative chemotherapy in advanced non-small-cell lung cancer (NSCLC). We compared a policy of three vs six courses of new-generation platinum-based combination chemotherapy with regard to effects on quality of life (QoL) and survival. Patients with stage IIIB or IV NSCLC and WHO performance status (PS) 0–2 were randomised to receive three (C3) or six (C6) courses of carboplatin (area under the curve (AUC) 4, Chatelut's formula, equivalent to Calvert's AUC 5) on day 1 and vinorelbine 25 mg m−2 on days 1 and 8 of a 3-week cycle. Key end points were QoL at 18 weeks, measured with EORTC Quality of Life Questionnaire (QLQ)-C30 and QLQ-LC13, and overall survival. Secondary end points were progression-free survival and need of palliative radiotherapy. Two hundred and ninety-seven patients were randomised (C3 150, C6 147). Their median age was 65 years, 30% had PS 2 and 76% stage IV disease. Seventy-eight and 54% of C3 and C6 patients, respectively, completed all scheduled chemotherapy courses. Compliance with QoL questionnaires was 88%. There were no significant group differences in global QoL, pain or fatigue up to 26 weeks. The dyspnoea palliation rate was lower in the C3 arm at 18 and 26 weeks (P<0.05), but this finding was inconsistent across different methods of analysis. Median survival in the C3 group was 28 vs 32 weeks in the C6 group (P=0.75, HR 1.04, 95% CI 0.82–1.31). One- and 2-year survival rates were 25 and 9% vs 25 and 5% in the C3 and C6 arm, respectively. Median progression-free survival was 16 and 21 weeks in the C3 and C6 groups, respectively (P=0.21, HR 0.86, 95% CI 0.68–1.08). In conclusion, palliative chemotherapy with carboplatin and vinorelbine beyond three courses conveys no survival or consistent QoL benefits in advanced NSCLC
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