2,081 research outputs found
Ages and abundances in large-scale stellar disks of nearby S0 galaxies
By undertaking deep long-slit spectroscopy with the focal reducer SCORPIO of
the Russian 6m telescope, we studied stellar population properties and their
variation with radius in 15 nearby S0 galaxies sampling a wide range of
luminosities and environments. For the large-scale stellar disks of S0s, we
have measured SSP-equivalent metallicities ranging from the solar one down to
[Z/H]=-0.4 - -0.7, rather high magnesium-to-iron ratios, [Mg/Fe] > +0.2, and
mostly old SSP-equivalent ages. Nine of 15 (60%) galaxies have large-scale
stellar disks older than 10 Gyr, and among those we find all the galaxies which
reside in denser environments. The isolated galaxies may have intermediate-age
stellar disks which are 7-9 Gyr old. Only two galaxies of our sample, NGC 4111
and NGC 7332, reveal SSP-equivalent ages of their disks of 2-3 Gyrs. Just these
two young disks appear to be thin, while the other, older disks have scale
heights typical for thick stellar disks. The stellar populations in the bulges
at radii of 0.5r_eff are on the contrary more metal-rich than the solar
metallicity, with the ages homogeneously distributed between 2 and 15 Gyr,
being almost always younger than the disks. We conclude that S0 galaxies could
not form in groups at z=0.4 as is thought now; a new scenario of the general
evolution of disk galaxies is proposed instead.Comment: Accepted to the MNRA
Pathogen-derived methods for improving resistance of transgenic plums (Prunus domestica L.) for Plum pox virus infection
Plum pox virus (PPV), the causal agent of Sharka disease, is considered to be one of the most serious pathogens of stone fruits including apricots, plums and peaches. This disease is of particular concern in central and southern Europe, the Mediterranean areas and North America. The transformation of plum with viral genes, such as coat protein, can provide virus resistant varieties or gene resources for breeding new resistant varieties. In the current study we report the evaluation of two technologies for producing plants resistance to PPV, one based on co-suppression and another on RNA-silencing. Two gene constructs were evaluated; the binary vector pCamPPVcp that contained the selective hpt gene and ppv-cp gene in sense-orientation (driven by double 35S promoter) and vector pCamPPVRNAi that contained self-complementary fragments of gene ppvcp (698bp) driven by double 35S promoter and the hpt and gus genes.The fragments of the ppv-cp gene in pCamPPVRNAi were separated by a pdk-intron to produce a “hairpin” RNA structure in antisense-sense orientation. Seven independent transgenic lines with the sense-oriented ppv-cp gene and five transgenic lines with inverted repeats of the ppv-cp gene fragment were produced. The accumulation of coat protein in five pCamPPVcp lines was confirmed by Western blotting. Transgenic shoots were rooted and acclimatized to the greenhouse. After grafting with PPV infected buds PPV-CP was detected by Western blotting in all control and pCamPPVcp transformed plants whereas no PPV coat protein were observed in samples from plants transformed with the pCamPPVRNAi “hairpin” construct. These preliminary results confirmed the efficiency of the RNAi strategy for producing virus resistant plants in general and PPV resistant stone fruits in particular.Keywords: RNA interference, PPV, transformation, coat protein, Prunus domestic
"Digital petrophysics" in studies of porosity properties of low- permeable reservoirs
The article focuses on study in the properties of low-permeable reservoirs. The object of the research is the Bazhenov formation rocks taken from a well drilled in an oilfield of the West Siberian basin. A series of experiments were carried out to determine porosity of rocks by different methods: the helium saturation, nuclear magnetic resonance (NMR), microcomputed tomography (mCT). A comparative analysis was conducted to assess the efficiency of different methods. The obtained results have shown that common methods of petrophysical surveys are insufficient for carbonate-argillaceous Low-permeable rocks, containing a great amount of hand extractable organic matter. The additional data received by the mCT method gave an opportunity to increase sufficiently the reliability of the research results. We have concluded that the most efficient method for the study of low-permeable rocks is a combined use of the NMR and the mCT
Transcranial magnetic stimulation set-up for small animals
Transcranial magnetic stimulation (TMS) is widely applied on humans for research and clinical purposes. TMS studies on small animals, e.g., rodents, can provide valuable knowledge of the underlying neurophysiological mechanisms. Administering TMS on small animals is, however, prone to technical difficulties, mainly due to their small head size. In this study, we aimed to develop an energy-efficient coil and a compatible experimental set-up for administering TMS on rodents. We applied a convex optimization process to develop a minimum-energy coil for TMS on rats. As the coil windings of the optimized coil extend to a wide region, we designed and manufactured a holder on which the rat lies upside down, with its head supported by the coil. We used the set-up to record TMS-electromyography, with electromyography recorded from limb muscles with intramuscular electrodes. The upside-down placement of the rat allowed the operator to easily navigate the TMS without the coil blocking their field of view. With this paradigm, we obtained consistent motor evoked potentials from all tested animals.Peer reviewe
Infrared and optical properties of pure and cobalt-doped LuNi_2B_2C
We present optical conductivity data for Lu(NiCo)BC over
a wide range of frequencies and temperatures for x=0 and x=0.09. Both materials
show evidence of being good Drude metals with the infrared data in reasonable
agreement with dc resistivity measurements at low frequencies. An absorption
threshold is seen at approximately 700 cm-1. In the cobalt-doped material we
see a superconducting gap in the conductivity spectrum with an absorption onset
at 24 +/- 2 cm-1 = 3.9$ +/- 0.4 k_BT_c suggestive of weak to moderately strong
coupling. The pure material is in the clean limit and no gap can be seen. We
discuss the data in terms of the electron-phonon interaction and find that it
can be fit below 600 cm-1 with a plasma frequency of 3.3 eV and an
electron-phonon coupling constant lambda_{tr}=0.33 using an alpha^{2}F(omega)
spectrum fit to the resistivity.Comment: 10 pages with 10 embedded figures, submitted to PR
Modulating effect of liposomal miR-101 on the processes of amyloidogenesis, smell, sleep and neuroinflammation in experimental Alzheimer's disease
The current therapy for Alzheimer's disease does not give patients a chance of recovery. Therefore, it is relevant to study the novel factors of influence, in particular microRNA, on the pathogenic mechanisms of amyloidosis. The aim of this work was to determine the effect of miR-101 on early predictors of amyloidosis in experimental Alzheimer's disease in animals. The study was carried out on 25 male rats of 14 months of age. A model of Alzheimer's disease was created by intrahippocampal administration of Aβ40 aggregates to animals. Ten days later, a 10-day course of nasal administration of miR-101 in liposomes was launched. The level of endogenous Aβ42 and cytokines (TNFα, IL-6 and IL-10) was determined in the supernatants of the nerve tissues of the target brain structures (hippocampus, olfactory bulbs, and olfactory tubercles). A neuroethological method of presenting smells of isovaleric acid and peanut butter was used to assess the olfactory system functional state in the experimental rats. In the course of polygraphic registration of the sleep-wakefulness cycle, the representation of wakefulness and individual sleep phases, as well as proportion of incomplete and complete sleep cycles were determined. It was shown that injection of Aβ40 aggregates into the hippocampus simulates an amyloidogenic state in the rat’s hippocampus and olfactory tubercles, but not in the olfactory bulbs. Moreover, a pro-inflammatory state was registered in the hippocampus of the animal brain (an increase in the concentration of pro-inflammatory cytokines TNFα and IL-6), while the cytokine level in the olfactory bulbs and tubercles did not change. When studying the functional state of olfactory analyzers in the rats with Alzheimer's disease, we revealed negative changes in behavioral response to the smell of isovaleric acid and peanut butter. In terms of somnograms, the Aβ40 toxicity caused reduction in the deep slow-wave sleep stage combined with deficiency of the paradoxical sleep phase, and predominance of incomplete sleep cycles. Nasal therapy with miR-101 in liposomes normalized the level of Aβ42 in the hippocampus and olfactory tubercles and decreased the level of proinflammatory cytokines in the hippocampus. MiR-101 prevented olfactory disfunctions in assessing smells of isovaleric acid and peanut butter, increased the ratio of deep slow-wave sleep and paradoxical sleep in the cycle structure and restored proportion of complete sleep cycles in animals. Thus, liposomal miR-101 has an anti-amyloidogenic and anti-inflammatory effect in rats with a model of Alzheimer's disease. It helps to restore the functional state of olfactory analyzer and optimize structural organization of the sleep-wakefulness cycle in sick animals
Optical absorption in the strong coupling limit of Eliashberg theory
We calculate the optical conductivity of superconductors in the
strong-coupling limit. In this anomalous limit the typical energy scale is set
by the coupling energy, and other energy scales such as the energy of the
bosons mediating the attraction are negligibly small. We find a universal
frequency dependence of the optical absorption which is dominated by bound
states and differs significantly from the weak coupling results. A comparison
with absorption spectra of superconductors with enhanced electron-phonon
coupling shows that typical features of the strong-coupling limit are already
present at intermediate coupling.Comment: 10 pages, revtex, 4 uuencoded figure
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
Specific heat of MgB in a one- and a two-band model from first-principles calculations
The heat capacity anomaly at the transition to superconductivity of the
layered superconductor MgB is compared to first-principles calculations
with the Coulomb repulsion, , as the only parameter which is fixed to
give the measured . We solve the Eliashberg equations for both an
isotropic one-band and a two-band model with different superconducting gaps on
the and Fermi surfaces. The agreement with experiments is
considerably better for the two-band model than for the one-band model.Comment: final published versio
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