Photometric measurements are prone to systematic errors presenting a challenge to low-amplitude variability detection. In search for a general-purpose variability detection technique able to recover ...a broad range of variability types including currently unknown ones, we test 18 statistical characteristics quantifying scatter and/or correlation between brightness measurements. We compare their performance in identifying variable objects in seven time series data sets obtained with telescopes ranging in size from a telephoto lens to 1 m-class and probing variability on time-scales from minutes to decades. The test data sets together include light curves of 127 539 objects, among them 1251 variable stars of various types and represent a range of observing conditions often found in ground-based variability surveys. The real data are complemented by simulations. We propose a combination of two indices that together recover a broad range of variability types from photometric data characterized by a wide variety of sampling patterns, photometric accuracies and percentages of outlier measurements. The first index is the interquartile range (IQR) of magnitude measurements, sensitive to variability irrespective of a time-scale and resistant to outliers. It can be complemented by the ratio of the light-curve variance to the mean square successive difference, 1/..., which is efficient in detecting variability on time-scales longer than the typical time interval between observations. Variable objects have larger 1/... and/or IQR values than non-variable objects of similar brightness. Another approach to variability detection is to combine many variability indices using principal component analysis. We present 124 previously unknown variable stars found in the test data. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
A radiographic diagnostic has been developed to quantify the
plume of erosion products after the interaction between a target and
a relativistic electron beam. The diagnostic is based on a ...point
Z-pinch (PZ-pinch) with a metallic plasma jet. It creates an X-ray
source with a typical size of 10 μm, a photon energy of up to
3 keV and a flash duration of 3 ns. The X-ray visualization system
is based on a thin scintillator and a CCD camera. The spatial
resolution of the diagnostic was evaluated experimentally. The
spatial frequency limit was found to be about 1.5 line pairs per
millimeter.
The diagnostic was tested in an experiment performed using an LIA-5
linear induction accelerator. An electron beam with a current of
400 A, an energy of 3.5 MeV and a pulse duration of 80 ns was
focused on a plane tantalum target 1 mm in thickness. The FWHM of
the focal spot was ∼ 2 mm. Radiographs of the plume were taken
with different delays after different accelerator pulses. According
to our data, the plume most commonly propagates toward the
beam. After 70 μs its length was about 70 mm, i.e. the
plume expansion rate was about 1 km/s. The area density of the
semi-transparent regions of the plume was estimated as lying in the
range 3 · 10
-16
–2 · 10
17
cm
-2
.
Сomparative analysis of arthropod assemblages found in Cretaceous fossil resins is provided. Arthropod-bearing Cretaceous resin sites are reviewed, and a list of arthropod records (identified to the ...family level) published up to 2015 is provided. Also, new records of mites, and new arthropod records from the Siberian resins are given. An efficient method for extracting amber from loose sediments in situations of limited infrastructure but easy access to water is described as well.
The sequence of arthropod assemblages in Cretaceous resins according to their evolutionary aspect does not match their geological sequence. This can be only partly explained by taphonomic constraints and inadequacy of the material: there is a deeper difference between somewhat contemporary assemblages than was characteristic of Permian assemblages studied in a similar way in previous studies. Our results confirm the earlier hypothesis that the Palaeozoic–Mesozoic biotic crisis was not so much a mass extinction as a biotic reorganisation that opened the way to diversification. These results might indicate a peculiar feature of the immediate effects of such reorganisations, namely that Mesozoic–Cenozoic communities became differentiated in their compositions much deeper than Palaeozoic ones (i.e., that their constituent groups acquired the ability to evolve much deeper changes while adapting to the ecological specifics of their environments). A transformation of organisms and/or their communities took place, comparable in scope to the rise of skeletal fauna in the Cambrian. The difference between these two transformations is that the later one resulted not from a particular adaptation (the skeleton) but from the ability to specialize more deeply than was possible in the Palaeozoic.
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Even though the study of ion-atom collisions is a mature field of atomic physics, large discrepancies between experiment and theoretical calculations are still common. Here we present experimental ...results with high momentum resolution on the single ionization of helium induced by 1-MeV protons, and we compare these to theoretical calculations. The overall agreement is strikingly good, and even the first Born approximation yields good agreement between theory and experiment. This has been expected for several decades, but so far has not been accomplished. The influence of projectile coherence effects on the measured data is briefly discussed in terms of an ongoing dispute on the existence of nodal structures in the electron angular emission distributions.
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Streamer-to-filament transition is a general feature of high pressure high voltage (HV) nanosecond surface dielectric barrier discharges. The transition was studied experimentally using time- and ...space-resolved optical emission in UV and visible parts of spectra. The discharge was initiated by HV pulses 20 ns in duration and 2 ns rise time, positive or negative polarity, 20-60 kV in amplitude on the HV electrode. The experiments were carried out in a single-shot regime at initial pressures P > 3 bar and ambient initial temperature in air, N2, H2:N2 and O2:Ar mixtures. It was shown that the transition to filamentary mode is accompanied by the appearance of intense continuous radiation and broad atomic lines. Electron density calculated from line broadening is characterized by high absolute values and long decay in the afterglow. The possible reasons for the continuous spectra were analyzed.
The Russian Federation is one of many countries that have signed the Montreal Protocol and Pan-European Forest Process. These initiatives are aimed at harmonizing national forest inventory systems ...with criteria and indicators for sustainable forest management. In Russia, the classification of forest type is at the heart of national forest inventory systems. For various historical reasons, Russian scientific advancements in the field of forest typology remain little known in the rest of the world. This paper is aimed at addressing this deficiency. Here, we provide an overview of the main trends in the field of forest typology studies in the previous political states of the Russian Empire, the Soviet Union, and the Russian Federation from the end of the nineteenth century to the beginning of the twenty-first century. We detail the principles that formed the basis of the most significant forest type classifications. We also perform similarity and differences analyses comparing approaches used by members of different scientific schools in the field of forest typology. The historical relationship between ecological, phytocoenotic, genetic, and dynamic forest type classifications are discussed as well as the reasons for the prevalence of certain forest type classifications in different regions of Russia.
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The development of a nanosecond surface dielectric barrier discharge in air at pressures 1-6 bar is studied. At atmospheric pressure, the discharge develops as a set of streamers starting ...synchronously from the high-voltage electrode and propagating along the dielectric layer. Streamers cover the dielectric surface creating a 'quasi-uniform' plasma layer. At high pressures and high voltage amplitudes on the cathode, filamentation of the discharge is observed a few nanoseconds after the discharge starts. Parameters of the observed 'streamers-to-filaments' transition are measured; physics of transition is discussed on the basis of theoretical estimates and numerical modeling. Ionization-heating instability on the boundary of the cathode layer is suggested as a mechanism of filamentation.
•Applicability of resin based on hydrophobic substrate in mixed-mode chromatography.•Compatibility of prepared column with suppressed IC, HILIC, and RP HPLC modes.•Separation of polar analytes in ...HILIC on stationary phase based on PS-DVB substrate.•Dominating effect of analyte nature on the retention mechanism using various eluents.
Evaluation of the chromatographic properties of covalently bonded hyperbranched stationary phase based on poly(styrene-divinylbenzene) (PS-DVB) and containing zwitterionic fragments in the structure of functional layer was conducted in suppressed ion chromatography (IC), reversed phase high performance liquid chromatography (RP HPLC), and hydrophilic interaction liquid chromatography (HILIC) modes. Besides the possibility of resolving 20 inorganic anions and organic acids using KOH eluent in suppressed IC, prepared resin provided the separation of alkylbenzenes in RP HPLC, water-soluble vitamins, amino acids, and sugars in HILIC mode. Trends in the retention of hydrophobic and polar analytes on the prepared stationary phase indicated the dominating effect of analyte nature on the retention mechanism and proved satisfactory hydrophilization of PS-DVB surface with hyperbranched functional layer for retaining polar compounds. The obtained results revealed good prospects of using hydrophobic PS-DVB substrate for preparing stationary phases for mixed-mode chromatography.
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Recent advances in DNA sequencing open prospects to make whole-genome analysis rapid and reliable, which is promising for various applications including personalized medicine. However, existing ...techniques for de novo genome assembly, which is used for the analysis of genomic rearrangements, chromosome phasing, and reconstructing genomes without a reference, require solving tasks of high computational complexity. Here we demonstrate a method for solving genome assembly tasks with the use of quantum and quantum-inspired optimization techniques. Within this method, we present experimental results on genome assembly using quantum annealers both for simulated data and the Formula: see textX 174 bacteriophage. Our results pave a way for a significant increase in the efficiency of solving bioinformatics problems with the use of quantum computing technologies and, in particular, quantum annealing might be an effective method. We expect that the new generation of quantum annealing devices would outperform existing techniques for de novo genome assembly. To the best of our knowledge, this is the first experimental study of de novo genome assembly problems both for real and synthetic data on quantum annealing devices and quantum-inspired techniques.
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