1,350 research outputs found
Eyes in the dark ... Shedding light on the antlion phylogeny and the enigmatic genus Pseudimares Kimmins (Neuropterida: Neuroptera: Myrmeleontidae)
The systematic position of the antlion Pseudimares Kimmins has been disputed since description of the genus. Pseudimares is one of the most enigmatic and unusual members of Myrmeleontidae and probably of all Neuroptera. The taxon has been usually tied to the antlion subfamily Palparinae, although its phylogenetic affinities have never been thoroughly investigated and the monophyly of the subfamily as a whole has never been corroborated. We reconstruct for the first time the phylogenetic affinities of Pseudimares based on both morphological and molecular genetic data. The widely accepted subfamily level subdivision of antlions (Stilbopteryginae, Palparinae, Myrmeleontinae) is refuted in all our analyses, since Stilbopteryginae in the traditional sense are recovered as deeply nested within Myrmeleontidae forming a monophylum with Palparinae, while Myrmeleontinae are poorly supported by the parsimony analysis. In our morphology-based parsimony analysis, Pseudimares is the sister taxon of Stilbopteryx and Aeropteryx, which makes the traditional Palparinae paraphyletic. This result is further supported by our phylogenetic reconstruction based on molecular data, which found a clade including Pseudimares and Stilbopteryx, which is nested within the traditional Palparinae. The high genetic distances measured among the analysed taxa suggest that these groups quickly diverged in ancient times, although they remained morphologically homogeneous. In conformity with the results of the phylogenetic analyses, we propose a new classification scheme for antlions, one that merges Stilbopteryx and Aeropteryx into an expanded concept of the subfamily Palparinae
Structures of electromagnetic type on vector bundles
10 pages.Structures of electromagnetic type on a vector bundle are introduced and studied. The metric case is also defined and studied. The sets of compatible connections are determined and a canonical connection is defined.MICINN-CSIC.Peer reviewe
VLT Diffraction Limited Imaging and Spectroscopy in the NIR: Weighing the black hole in Centaurus A with NACO
We present high spatial resolution near-infrared spectra and images of the
nucleus of Centaurus A (NGC 5128) obtained with NAOS-CONICA at the VLT. The
adaptive optics corrected data have a spatial resolution of 0.06" (FWHM) in K-
and 0.11" in H-band, four times higher than previous studies. The observed gas
motions suggest a kinematically hot disk which is orbiting a central object and
is oriented nearly perpendicular to the nuclear jet. We model the central
rotation and velocity dispersion curves of the [FeII] gas orbiting in the
combined potential of the stellar mass and the (dominant) black hole. Our
physically most plausible model, a dynamically hot and geometrically thin gas
disk, yields a black hole mass of M_bh = (6.1 +0.6/-0.8) 10^7 M_sun. As the
physical state of the gas is not well understood, we also consider two limiting
cases: first a cold disk model, which completely neglects the velocity
dispersion; it yields an M_bh estimate that is almost two times lower. The
other extreme case is to model a spherical gas distribution in hydrostatic
equilibrium through Jeans equation. Compared to the hot disk model the best-fit
black hole mass increases by a factor of 1.5. This wide mass range spanned by
the limiting cases shows how important the gas physics is even for high
resolution data. Our overall best-fitting black hole mass is a factor of 2-4
lower than previous measurements. With our revised M_bh estimate, Cen A's
offset from the M_bh-sigma relation is significantly reduced; it falls above
this relation by a factor of ~2, which is close to the intrinsic scatter of
this relation. (Abridged)Comment: 12 pages, 14 figures, including minor changes following the referee
report; accepted for publication in The Astrophysical Journa
Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals
A time-resolved analysis of the amplitude and phase of THz pulses propagating through three-dimensional photonic crystals is presented. Single-cycle pulses of THz radiation allow measurements over a wide frequency range, spanning more than an octave below, at and above the bandgap of strongly dispersive photonic crystals. Transmission data provide evidence for slow group velocities at the photonic band edges and for superluminal transmission at frequencies in the gap. Our experimental results are in good agreement with finite-difference-time-domain simulations
Features of water chemical composition of oligotrophic and eutrophic bogs in the South of the Tomsk region
On the basis of the actual material the analysis of chemical composition of bog waters in the territory of the South of the Tomsk region is carried out. The data on average concentration of macro and trace components, organic matter, pH of bog waters are obtained. Significant distinctions in a chemical composition of surface water for different types of bogs are revealed. The composition and macrostructure of humic acids by the example of eutrophic bogs is studied
Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals
A time-resolved analysis of the amplitude and phase of THz pulses propagating
through three-dimensional photonic crystals is presented. Single-cycle pulses
of THz radiation allow measurements over a wide frequency range, spanning more
than an octave below, at and above the bandgap of strongly dispersive photonic
crystals. Transmission data provide evidence for slow group velocities at the
photonic band edges and for superluminal transmission at frequencies in the
gap. Our experimental results are in good agreement with
finite-difference-time-domain simulations.Comment: 7 pages, 11 figure
Rethinking scientists’ ongoing participation in “feeding the world”
Agricultural science necessarily involves a commitment to some form of humanitarian and environmental ethics. For the past century, agricultural science has been based on a productivist ethic of maximizing agricultural production in pursuit or support of food security. Recognition of the ethical and political disposition of contemporary agricultural science can help scientists reorient their work to better address the urgent problems of the upcoming century: environmental degradation, climate change, and social inequality. A commitment to solving these problems is well within the scope of modern agricultural science. Supporting and furthering multidimensional food systems should replace productivism as an explicit goal of agricultural development and scientific innovation
Расчет ГИН по схеме Аркадьева-Маркса
Объектом исследования является генератор импульсного напряжения по схеме Аркадьева-Маркса. Цель работы: спроектировать и рассчитать генератор импульсных напряжений. В процессе работы рассчитаны количественные значения элементов ГИНа: значения коэффициентов использования разрядной схемы и волны; емкость и индуктивность конденсатора; количество ступеней; фронтовое и разрядное сопротивления. Был выполнен расчет ресурсов, ставки налогов, отчислений. Так же было описаны рабочее место и законодательные и нормативные документы.The object of study is the generator of pulse voltage according to the scheme Arkadiev-Marx. Objective: to design and calculate the voltage impulse generator. In the process, the calculated quantitative values of the elements of a Hin: the coefficients of use of the discharge circuit and wave; the capacitance and inductance of the capacitor; number of steps; the front and discharge resistors. Calculated resources, tax rates, deductions. As described workplace and legislative and regulatory documents
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