1,534 research outputs found
Parameterization of phytoplankton spectral absorption coefficients in the Baltic Sea: general, monthly and two-component variants of approximation formulas
This paper presents
approximate formulas (empirical equations) for parameterizing the coefficient
of light absorption by phytoplankton aph(λ) in Baltic Sea
surface waters. Over a thousand absorption spectra (in the 350–750 nm
range), recorded during 9 years of research carried out in different months
of the year and in various regions of the southern and central Baltic, were
used to derive these parameterizations. The empirical material was
characterized by a wide range of variability: the total chlorophyll a
concentration (Tchl a) varied between 0.31 and 142 mg m−3, the
ratio of the sum of all accessory pigment concentrations to chlorophyll a
( ∑ Ci∕Tchl a) ranged between 0.21 and 1.5, and the
absorption coefficients aph(λ) at individual light
wavelengths varied over almost 3 orders of magnitude. Different versions of
the parameterization formulas were derived on the basis of these data: a
one-component parameterization in the classic form of a power function
with Tchl a as the only variable and a two-component formula – the
product of the power and exponential functions – with Tchl a and ∑ Ci∕Tchl a as variables. We found distinct differences between
the general version of the one-component parameterization and its variants
derived for individual months of the year. In contrast to the general variant
of parameterization, the new two-component variant takes account of the
variability of pigment composition occurring throughout the year in Baltic
phytoplankton populations.</p
Generalised Decision Level Ensemble Method for Classifying Multi-media Data
In recent decades, multimedia data have been commonly generated and used in various domains, such as in healthcare and social media due to their ability of capturing rich information. But as they are unstructured and separated, how to fuse and integrate multimedia datasets and then learn from them eectively have been a main challenge to machine learning. We present a novel generalised decision level ensemble method (GDLEM) that combines the multimedia datasets at decision level. After extracting features from each of multimedia datasets separately, the method trains models independently on each media dataset and then employs a generalised selection function to choose the appropriate models to construct a heterogeneous ensemble. The selection function is dened as a weighted combination of two criteria: the accuracy of individual models and the diversity among the models. The framework is tested on multimedia data and compared with other heterogeneous ensembles. The results show that the GDLEM is more exible and eective
70. Ocena skuteczności przeciwbólowej radioterapii ostróg piętowych
Założenia i cel pracyOdokostnowy wzrost kości w miejscu przyczepu ścięgien do kości piętowej (ostrogi) często jest powodem uciążliwych bólów. Celem naszej pracy była ocena skuteczności radioterapii, jako metody leczenia tych zespołów bólowych.Materiał i metodykaRetrospektywny materiał obejmował 798 przypadków (181 M, 617 K) bolesnych ostróg kości piętowych napromienianych przy użyciu dawki frakcyjnej 1–3 Gy (średnia 1,5 Gy) do dawki całkowitej zawierającej się w przedziale od 1,5 do 22,5 Gy (średnia 8 Gy). Wiek chorych zawierał się w przedziale od 24 do 85 lat (średnia 56). Podobna liczba zmian była zlokalizowana po lewej i prawej stronie. Średnia wielkość ostrogi wynosiła 0,9 cm, a średnia wielkość napromienianego pola 57 cm2. Średni czas trwania objawów wynosił 32 miesiące. W 155 przypadkach było to powtórne napromienianie. W 768 przypadkach zastosowano promieniowanie X, w 18 wysokoenergetyczne fotony, w 9 elektrony, a w 3 promieniowanie gamma. Średni okres obserwacji wynosił 17,5 miesiąca. Oceniono stopień zmniejszenia bólu po zakończeniu leczenia oraz czas utrzymywania się efektu przeciwbólowego. Obliczono odsetek chorych nie zgłaszających bólu spoczynkowego oraz bólu w trakcie chodzenia podczas ostatniej kontroli.WynikiPo zakończeniu radioterapii całkowite ustąpienie bólu odnotowano w 44%. W pozostałej grupie zmniejszenie bólu o więcej niż 50% w stosunku do stanu z przed leczenia osiągnięto u 42%, o mniej niż 50% u 28%, a w 30% nie odnotowano efektu przeciwbólowego. Średni czas utrzymywania się efektu wyniósł 12 miesięcy. Podczas ostatniej kontroli 45% chorych nie zgłaszało bólów w spoczynku, a 29% podczas chodzenia.WniosekOtrzymane wyniki pozwa1ają na sformułowanie wniosku, że radioterapia jest skuteczną i bezpieczną metodą leczenia bolesnych ostróg kości piętowych oraz może być stosowane w przypadkach nie poddających się leczeniu konwencjonalnemu
Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
We use data from the Northern Sky Variability Survey (NSVS), obtained from
the first generation Robotic Optical Transient Search Experiment (ROTSE-I), to
identify and study RR Lyrae variable stars in the solar neighborhood. We
initially identified 1197 RRab (RR0) candidate stars brighter than the ROTSE
median magnitude V = 14. Periods, amplitudes, and mean V magnitudes are
determined for a subset of 1188 RRab stars with well defined light curves.
Metallicities are determined for 589 stars by the Fourier parameter method and
by the relationship between period, amplitude, and [Fe/H]. We comment upon the
difficulties of clearly classifying RRc (RR1) variables in the NSVS dataset.
Distances to the RRab stars are calculated using an adopted
luminosity-metallicity relation with corrections for interstellar extinction.
The 589 RRab stars in our final sample are used to study the properties of the
RRab population within 5 kpc of the Sun. The Bailey diagram of period versus
amplitude shows that the largest component of this sample belongs to Oosterhoff
type I. Metal-rich ([Fe/H] > -1) RRab stars appear to be associated with the
Galactic disk. Our metal-rich RRab sample may include a thin disk as well as a
thick disk population, although the uncertainties are too large to establish
this. There is some evidence among the metal-rich RRab stars for a decline in
scale height with increasing [Fe/H], as was found by Layden (1995). The
distribution of RRab stars with -1 < [Fe/H] < -1.25 indicates that within this
metallicity range the RRab stars are a mixture of stars belonging to halo and
disk populations.Comment: 68 pages, 26 figures, 9 tables, accepted to A
The quest for companions to post-common envelope binaries. II. NSVS14256825 and HS0705+6700
We report new mid-eclipse times of the two close binaries NSVS14256825 and
HS0705+6700, harboring an sdB primary and a low-mass main-sequence secondary.
Both objects display clear variations in the measured orbital period, which can
be explained by the action of a third object orbiting the binary. If this
interpretation is correct, the third object in NSVS14256825 is a giant planet
with a mass of roughly 12 M_Jup. For HS0705+6700, we provide evidence that
strengthens the case for the suggested periodic nature of the eclipse time
variation and reduces the uncertainties in the parameters of the brown dwarf
implied by that model. The derived period is 8.4 yr and the mass is 31 M_Jup,
if the orbit is coplanar with the binary. This research is part of the
PlanetFinders project, an ongoing collaboration between professional
astronomers and student groups at high schools.Comment: Accepted by Astron. and Astrophy
The position of a duodenal diverticulum in the area of the major duodenal papilla and its potential clinical implications
Background: Although duodenal diverticula are associated with less frequent pathology than the colonic diverticula in the large intestine, their periampullary position may have significant clinical implications. The aim of the study was to identify any possible correlation between the type of localisation of the major duodenal papilla, duodenal diverticula, and some particular clinical issues.
Materials and methods: In total, 628 patients (408 females and 220 males; aged 21–91 years), who underwent endoscopic retrograde cholangiopancreatography were included in this study. The patients were divided into two groups: a study group comprising 66 (10.5%) patients with periampullary position of diverticula (group A), and a control group comprising 562 (89.5%) patients without diverticula (group B).
Results: A duodenal diverticulum was diagnosed in the periampullary position in 66/628 (10.5%) patients: 41 women (aged 52–91 years) and 25 men (aged 54–83 years).
Conclusions: Three types of localisation were observed for the major duodenal papilla with regard to the diverticula, with the most common type being next to each other (type III). In patients with diverticula, similar frequencies of gallstone occurrence are observed in men and women. Patients with papilla in the diverticulum who underwent cholecystectomy are more prone to develop lithiasis
An extensive photometric study of the Blazhko RR Lyrae star DM Cyg
DM Cyg, a fundamental mode RRab star was observed in the 2007 and 2008
seasons in the frame of the Konkoly Blazhko Survey. Very small amplitude light
curve modulation was detected with 10.57 d modulation period. The maximum
brightness and phase variations do not exceed 0.07 mag and 7 min, respectively.
In spite of the very small amplitude of the modulation, beside the frequency
triplets characterizing the Fourier spectrum of the light curve two quintuplet
components were also identified. The accuracy and the good phase coverage of
our observations made it possible to analyse the light curves at different
phases of the modulation separately. Utilizing the IP method (S\'odor, Jurcsik
and Szeidl, 2009) we could detect very small systematic changes in the global
mean physical parameters of DM Cyg during its Blazhko cycle. The detected
changes are similar to what we have already found for a large modulation
amplitude Blazhko variable MW Lyrae. The amplitudes of the detected changes in
the physical parameters of DM Cyg are only about 10% of that what have been
found in MW Lyr. This is in accordance with its small modulation amplitude
being about one tenth of the modulation amplitude of MW Lyr.Comment: 12 pages, 15 figures, 4 tables. Table 1 is available electronically
eg., from our website: http://www.konkoly.hu/24/publications/. Accepted for
publication in MNRA
OGLE small amplitude red giant variables in the Galactic Bar
Among over 200,000 Galactic Bulge variable stars in the public domain OGLE
catalogue, we found over 15,000 red giant variables following two well defined
period -- amplitude relations. The periods are in the range 10 < P < 100 days,
and amplitudes in the range 0.005 < A < 0.13 mag in I-band. The variables cover
a broad range of reddening corrected colours, 1 < (V-I)_0 < 5, and a fairly
narrow range of extinction corrected apparent magnitudes, 10.5 < I_0 < 13 . A
subset of variables (type A) has a rms scatter of only 0.44 mag. The average
magnitudes for these stars are well correlated with the Galactic longitude, and
vary from I_{k,0} = 11.82 for l = +8 deg to I_{k,0} = 12.07 for l = -5 deg,
clearly indicating that they are located in the Galactic Bar. Most variables
have several oscillation periods.Comment: 15 pages, 9 figures (7 in low resolution), submitted to MNRAS.
Article in full resolution can be obtained at
http://www.astro.princeton.edu/~leyer/wrayetal.p
Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE-II
We present a measurement of the microlensing optical depth toward the
Galactic Bulge based on 4 years of the OGLE-II survey using Red Clump Giant
(RCG). Using 32 events we find tau=2.55_{-0.46}^{+0.57}* 10^{-6} at
(l,b)=(1.16, -2.75). Taking into account the measured gradient along the
Galactic latitude b, tau = [ (4.48+/- 2.37) + (0.78+/- 0.84)* b]* 10^{-6}, this
value is consistent with previous measurements using RCG sources and recent
theoretical predictions. We determine the microlensing parameters and select
events using a model light curve with the flux blending. We find that ~38% of
the OGLE-II events which appear to have RCG sources are actually due to much
fainter stars blended with a bright companion. We show explicitly that model
fits without blending result in similar tau estimates through partial
cancellation of contributions from higher detection efficiency, underestimated
time-scales and larger number of selected events. This approach, however, leads
to biased time-scale distributions and event rates. Consequently, microlensing
studies should carefully consider source confusion effects even for bright
stars.Comment: 49 pages and 18 figures, ApJ in press, the value changed due to the
systematic correctio
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