113 research outputs found
Possibility of local pair existence in optimally doped SmFeAsO(1-x) in pseudogap regime
We report the analysis of pseudogap Delta* derived from resistivity
experiments in FeAs-based superconductor SmFeAsO(0.85), having a critical
temperature T_c = 55 K. Rather specific dependence Delta*(T) with two
representative temperatures followed by a minimum at about 120 K was observed.
Below T_s = 147 K, corresponding to the structural transition in SmFeAsO,
Delta*(T) decreases linearly down to the temperature T_AFM = 133 K. This last
peculiarity can likely be attributed to the antiferromagnetic (AFM) ordering of
Fe spins. It is believed that the found behavior can be explained in terms of
Machida, Nokura, and Matsubara (MNM) theory developed for the AFM
superconductors.Comment: 5 pages, 2 figure
Pseudogap from ARPES experiment: three gaps in cuprates and topological superconductivity
A term first coined by Mott back in 1968 a `pseudogap' is the depletion of
the electronic density of states at the Fermi level, and pseudogaps have been
observed in many systems. However, since the discovery of the high temperature
superconductors (HTSC) in 1986, the central role attributed to the pseudogap in
these systems has meant that by many researchers now associate the term
pseudogap exclusively with the HTSC phenomenon. Recently, the problem has got a
lot of new attention with the rediscovery of two distinct energy scales
(`two-gap scenario') and charge density waves patterns in the cuprates. Despite
many excellent reviews on the pseudogap phenomenon in HTSC, published from its
very discovery up to now, the mechanism of the pseudogap and its relation to
superconductivity are still open questions. The present review represents a
contribution dealing with the pseudogap, focusing on results from angle
resolved photoemission spectroscopy (ARPES) and ends up with the conclusion
that the pseudogap in cuprates is a complex phenomenon which includes at least
three different `intertwined' orders: spin and charge density waves and
preformed pairs, which appears in different parts of the phase diagram. The
density waves in cuprates are competing to superconductivity for the electronic
states but, on the other hand, should drive the electronic structure to
vicinity of Lifshitz transition, that could be a key similarity between the
superconducting cuprates and iron based superconductors. One may also note that
since the pseudogap in cuprates has multiple origins there is no need to recoin
the term suggested by Mott.Comment: invited review, more info at http://www.imp.kiev.ua/~kor
Paraconductivity of K-doped SrFe2As2 superconductor
Paraconductivity of the optimally K-doped SrFe2As2 superconductor is
investigated within existing fluctuation mechanisms. The in-plane excess
conductivity has been measured in high quality single crystals, with a sharp
superconducting transition at Tc=35.5K and a transition width less than 0.3K.
The data have been also acquired in external magnetic field up to 14T. We show
that the fluctuation conductivity data in zero field and for temperatures close
to Tc, can be explained within a three-dimensional Lawrence-Doniach theory,
with a negligible Maki-Thompson contribution. In the presence of the magnetic
field, it is shown that paraconductivity obeys the three-dimensional
Ullah-Dorsey scaling law, above 2T and for H||c. The estimated upper critical
field and the coherence length nicely agree with the available experimental
data.Comment: 12 pages, 5 figure
Subthreshold antiproton production in proton-carbon reactions
Data from KEK on subthreshold antiproton as well as on pi(+-) and K(+-)
production in proton-nucleus reactions are described at projectile energies
between 3.5 and 12.0 GeV. We use a model which considers a hadron-nucleus
reaction as an incoherent sum over collisions of the projectile with a varying
number of target nucleons. It samples complete events and allows thus for the
simultaneous consideration of all particle species measured. The overall
reproduction of the data is quite satisfactory. It is shown that the
contributions from the interaction of the projectile with groups of several
target nucleons are decisive for the description of subthreshold production.
Since the collective features of subthreshold production become especially
significant far below the threshold, the results are extrapolated down to COSY
energies. It is concluded that an antiproton measurement at ANKE-COSY should be
feasible, if the high background of other particles can be efficiently
suppressed.Comment: 15 pages, 5 figures, gzipped tar file, submitted to J. Phys. G v2:
Modification of text due to demands of referee
ΠΠ΅Π½ΠΎΠΌΠ½ΡΠ΅ ΡΠ΅Ρ Π½ΠΎΠ»ΠΎΠ³ΠΈΠΈ Π² ΠΏΡΠ»ΡΠΌΠΎΠ½ΠΎΠ»ΠΎΠ³ΠΈΠΈ: ΡΠΎΠ»Ρ ΠΌΠΈΠΊΡΠΎΠ ΠΠ Π² ΡΠ°Π·Π²ΠΈΡΠΈΠΈ Π±ΡΠΎΠ½Ρ ΠΈΠ°Π»ΡΠ½ΠΎΠΉ Π°ΡΡΠΌΡ ΠΈ Ρ ΡΠΎΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΎΠ±ΡΡΡΡΠΊΡΠΈΠ²Π½ΠΎΠΉ Π±ΠΎΠ»Π΅Π·Π½ΠΈ Π»Π΅Π³ΠΊΠΈΡ
MicroRNAs (miRNAs) are small noncoding RNA molecules that affect gene expression and thus take part in the epigenetic regulation of almost all physiological and pathological processes. About 1,800 human miRNAs have been discovered to date; however, biological functions and protein targets for the majority remain to be unknown. Within the respiratory system, miRNAs contribute to the lung growth and lifelong maintenance of pulmonary homeostasis. Recently, the leading role of miRNAs in pathogenesis of various pulmonary diseases has been found, including asthma, chronic obstructive pulmonary disease (COPD) and lung cancer. Due to a significant progress in studying interactions between genes and their products and environmental factors, a great role of epigenetic variability, which is gene expression change not related to DNA damage, but could be inherited consistently, became apparent. There are three levels of epigenetic regulation corresponding to three main mechanisms: genomic (DNA methylation), proteomic (histone modification) and transcriptomic (regulation through RNA, primarily miRNA). Extending our knowledge on a role of miRNAs for the respiratory system could open new therapeutic targets and diagnostic markers for respiratory diseases, particularly asthma and COPD.ΠΠΈΠΊΡΠΎΠ ΠΠ β ΡΡΠΎ ΠΌΠ°Π»ΡΠ΅ Π½Π΅ΠΊΠΎΠ΄ΠΈΡΡΡΡΠΈΠ΅ ΠΌΠΎΠ»Π΅ΠΊΡΠ»Ρ Π ΠΠ, ΠΊΠΎΡΠΎΡΡΠ΅ Π²Π»ΠΈΡΡΡ Π½Π° ΡΠΊΡΠΏΡΠ΅ΡΡΠΈΡ Π³Π΅Π½ΠΎΠ² ΠΈ ΡΠ°ΠΊΠΈΠΌ ΠΎΠ±ΡΠ°Π·ΠΎΠΌ ΡΡΠ°ΡΡΠ²ΡΡΡ Π² ΡΠΏΠΈΠ³Π΅Π½Π΅ΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΈΠΈ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΈ Π²ΡΠ΅Ρ
ΡΠΈΠ·ΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈ ΠΏΠ°ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ². ΠΡΠΈΠΌΠ΅ΡΠ½ΠΎ 1Β 800 ΠΌΠΈΠΊΡΠΎΠ ΠΠ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ° Π½Π° ΡΠ΅Π³ΠΎΠ΄Π½ΡΡΠ½ΠΈΠΉ Π΄Π΅Π½Ρ ΠΎΡΠΊΡΡΡΡ, ΠΎΠ΄Π½Π°ΠΊΠΎ Π±ΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠ°Ρ ΡΡΠ½ΠΊΡΠΈΡ ΠΈ Π±Π΅Π»ΠΊΠΈ-ΠΌΠΈΡΠ΅Π½ΠΈ Π΄Π»Ρ Π±ΠΎΠ»ΡΡΠΈΠ½ΡΡΠ²Π° ΠΈΠ· Π½ΠΈΡ
ΠΎΡΡΠ°ΡΡΡΡ Π½Π΅ΠΈΠ·Π²Π΅ΡΡΠ½ΡΠΌΠΈ. Π ΡΠ°ΠΌΠΊΠ°Ρ
Π΄ΡΡ
Π°ΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ ΠΌΠΈΠΊΡΠΎΠ ΠΠ Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΡ Π΄Π»Ρ ΡΠ°Π·Π²ΠΈΡΠΈΡ Π»Π΅Π³ΠΊΠΈΡ
ΠΈ ΠΏΠΎΠ΄Π΄Π΅ΡΠΆΠ°Π½ΠΈΡ Π»Π΅Π³ΠΎΡΠ½ΠΎΠ³ΠΎ Π³ΠΎΠΌΠ΅ΠΎΡΡΠ°Π·Π° Π½Π° ΠΏΡΠΎΡΡΠΆΠ΅Π½ΠΈΠΈ Π²ΡΠ΅ΠΉ ΠΆΠΈΠ·Π½ΠΈ. Π ΠΏΠΎΡΠ»Π΅Π΄Π½ΠΈΠ΅ Π³ΠΎΠ΄Ρ Π±ΡΠ»Π° ΠΎΡΠΊΡΡΡΠ° Π³Π»Π°Π²Π½Π΅ΠΉΡΠ°Ρ ΡΠΎΠ»Ρ ΠΌΠΈΠΊΡΠΎΠ ΠΠ Π² ΠΏΠ°ΡΠΎΠ³Π΅Π½Π΅Π·Π΅ ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π½ΠΈΠΉ, Π² Ρ. Ρ. Π±ΡΠΎΠ½Ρ
ΠΈΠ°Π»ΡΠ½ΠΎΠΉ Π°ΡΡΠΌΡ (ΠΠ), Ρ
ΡΠΎΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΎΠ±ΡΡΡΡΠΊΡΠΈΠ²Π½ΠΎΠΉ Π±ΠΎΠ»Π΅Π·Π½ΠΈ Π»Π΅Π³ΠΊΠΈΡ
(Π₯ΠΠΠ) ΠΈ ΡΠ°ΠΊΠ° Π»Π΅Π³ΠΊΠΎΠ³ΠΎ. ΠΠ»Π°Π³ΠΎΠ΄Π°ΡΡ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΌΡ ΠΏΡΠΎΠ³ΡΠ΅ΡΡΡ Π² ΠΈΠ·ΡΡΠ΅Π½ΠΈΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠΉ ΠΌΠ΅ΠΆΠ΄Ρ Π³Π΅Π½Π°ΠΌΠΈ ΠΈ ΠΈΡ
ΠΏΡΠΎΠ΄ΡΠΊΡΠ°ΠΌΠΈ Ρ ΡΠ°ΠΊΡΠΎΡΠ°ΠΌΠΈ ΠΎΠΊΡΡΠΆΠ°ΡΡΠ΅ΠΉ ΡΡΠ΅Π΄Ρ ΡΡΠ°Π»Π° ΠΎΡΠ΅Π²ΠΈΠ΄Π½ΠΎΠΉ ΠΎΠ³ΡΠΎΠΌΠ½Π°Ρ ΡΠΎΠ»Ρ ΡΠΏΠΈΠ³Π΅Π½Π΅ΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΈΠ·ΠΌΠ΅Π½ΡΠΈΠ²ΠΎΡΡΠΈ β ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠΉ ΡΠΊΡΠΏΡΠ΅ΡΡΠΈΠΈ Π³Π΅Π½ΠΎΠ², Π½Π΅ ΡΠ²ΡΠ·Π°Π½Π½ΡΡ
Ρ Π½Π°ΡΡΡΠ΅Π½ΠΈΠ΅ΠΌ ΡΡΡΡΠΊΡΡΡΡ ΠΠΠ, ΠΎΠ΄Π½Π°ΠΊΠΎ ΡΠΏΠΎΡΠΎΠ±Π½ΡΡ
ΡΡΡΠΎΠΉΡΠΈΠ²ΠΎ ΠΏΠ΅ΡΠ΅Π΄Π°Π²Π°ΡΡΡΡ Π² ΡΡΠ΄Ρ ΠΏΠΎΠΊΠΎΠ»Π΅Π½ΠΈΠΉ. Π‘ΡΡΠ΅ΡΡΠ²ΡΡΡ 3 ΡΡΠΎΠ²Π½Ρ ΡΠΏΠΈΠ³Π΅Π½Π΅ΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΈΠΈ ΠΈ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎ β 3 Π΅Π΅ ΠΎΡΠ½ΠΎΠ²Π½ΡΡ
ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΠ°: Π³Π΅Π½ΠΎΠΌΠ½ΡΠΉ (ΠΌΠ΅ΡΠΈΠ»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΠΠ), ΠΏΡΠΎΡΠ΅ΠΎΠΌΠ½ΡΠΉ (ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΡ Π³ΠΈΡΡΠΎΠ½ΠΎΠ²) ΠΈ ΡΡΠ°Π½ΡΠΊΡΠΈΠΏΡΠΎΠΌΠ½ΡΠΉ (ΡΠ΅Π³ΡΠ»ΡΡΠΈΡ ΠΏΠΎΡΡΠ΅Π΄ΡΡΠ²ΠΎΠΌ Π ΠΠ, Π² ΠΏΠ΅ΡΠ²ΡΡ ΠΎΡΠ΅ΡΠ΅Π΄Ρ ΠΌΠΈΠΊΡΠΎΠ ΠΠ). Π£ΡΠΏΠ΅Ρ
ΠΈ Π² ΠΏΠΎΠ½ΠΈΠΌΠ°Π½ΠΈΠΈ ΡΠΎΠ»ΠΈ ΠΌΠΈΠΊΡΠΎΠ ΠΠ Π² Π΄ΡΡ
Π°ΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΠ΅ ΠΏΠΎΠΌΠΎΠ³ΡΡ ΠΏΡΠΎΠ»ΠΈΡΡ ΡΠ²Π΅Ρ Π½Π° Π½ΠΎΠ²ΡΠ΅ ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Ρ Π² ΠΏΠΎΠΈΡΠΊΠ΅ ΡΠ΅ΡΠ°ΠΏΠ΅Π²ΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠΈΡΠ΅Π½Π΅ΠΉ ΠΈ Π΄ΠΈΠ°Π³Π½ΠΎΡΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ°ΡΠΊΠ΅ΡΠΎΠ² Π΄Π»Ρ Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π½ΠΈΠΉ ΡΠ΅ΡΠΏΠΈΡΠ°ΡΠΎΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ, Π² ΡΠ°ΡΡΠ½ΠΎΡΡΠΈ ΠΠ ΠΈ Π₯ΠΠΠ
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