380 research outputs found
Rank one lattice type vertex operator algebras and their automorphism groups, II: E-series
Let L be the A_1 root lattice and G a finite subgroup of Aut(V_L), where
is the associated lattice VOA (in this case, Aut(V) is isomorphic to
PSL(2,\Bbb C)). The fixed point subVOA, V^G was studied in q-alg/9710017, which
finds a set of generators and determines the automorphism group when G is
cyclic (from the "A-series") or dihedral (from the "D-series"). In the present
article, we obtain analogous results for the remaining possibilities for G,
that it belong to the "E-series": G\cong Alt_4, Alt_5 or Sym_4.Comment: Latex, 10 page
Embeddings of U 3 (8), Sz (8) and the Rudvalis group in algebraic groups of type E 7
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46579/1/222_2005_Article_BF01231561.pd
Influence of PbX2 (X = F, Cl, Br) content and thermal treatment on structure and optical properties of lead borate glasses doped with rare earth ions
Oxyhalide lead borate glasses doped with rare earth ions have been studied before and after thermal
treatment. The rare earths as optically active ions were limited to the Er3+ ions. Near-infrared
luminescence due to the main 4I13/2–4I15/2 laser transition of Er3+ was registered. The introduction
of PbX2 to the borate glass results in a reduction of spectral linewidth and an increase of luminescence lifetime of 4I13/2 state of Er3+ ions. The unusual large spectral linewidth for 4I13/2–4I15/2 transition of Er3+ in the oxide glass host was obtained, whereas the luminescence decay from 4I13/2 state is longer for a sample with PbF2 than PbCl2 and PbBr2. Heat treatment introduces transformation from a glass to transparent glass-ceramic (TGC). The coordination sphere around Er3+ ions is changed, giving important contribution to the luminescence characteristics. The spectroscopic consequence of this transformation is the increase of
luminescence lifetime and the narrowing of spectral lines of Er3+
Optical and EPR spectroscopy of Er3+ in lithium yttrium borate, Li6Y(BO3)3:Er single crystals
The energy levels of Er3+ ions have been determined in lithium yttrium borate (Li6Y(BO3)3) single crystals
in a wide spectral range between 6000 and 40000 cm-1 together with an analysis of the ground state,
using optical and EPR spectroscopy. The crystal field splittings of the 4I15/2 ground state and those of
nearly all excited states up to the 4D7/2 manifold have been obtained at low temperature from luminescence (T = 5 K) and absorption (T = 9 K) measurements, respectively. The numbers of experimentally observed Stark sublevels agree well with those expected theoretically for Er3+ ions occupying a single low symmetry (C1) site. A full set of g- and 167Er hyperfine tensor parameters are presented for the
ground state characterized by EPR; the measured Orbach-type spin-relaxation rates viz. the involved
activation energies correspond to the optically derived lowest excited sublevels
T2Rs Function as Bitter Taste Receptors
AbstractBitter taste perception provides animals with critical protection against ingestion of poisonous compounds. In the accompanying paper, we report the characterization of a large family of putative mammalian taste receptors (T2Rs). Here we use a heterologous expression system to show that specific T2Rs function as bitter taste receptors. A mouse T2R (mT2R-5) responds to the bitter tastant cycloheximide, and a human and a mouse receptor (hT2R-4 and mT2R-8) responded to denatonium and 6-n-propyl-2-thiouracil. Mice strains deficient in their ability to detect cycloheximide have amino acid substitutions in the mT2R-5 gene; these changes render the receptor significantly less responsive to cycloheximide. We also expressed mT2R-5 in insect cells and demonstrate specific tastant-dependent activation of gustducin, a G protein implicated in bitter signaling. Since a single taste receptor cell expresses a large repertoire of T2Rs, these findings provide a plausible explanation for the uniform bitter taste that is evoked by many structurally unrelated toxic compounds
Monocrystalline Heusler Co2FeSi alloy glass-coated microwires: Fabrication and magneto-structural characterization
About the results of the online conference “Sports psychology in the intercultural space”
The article is presented an analysis of the results of the international online conference. The article is described the format of the conference and examined the topics of presentations by leading foreign and Russian sports psychologists.В статье представлен анализ результатов проведения международной онлайн-конференции. Дается характеристика формата проведения конференции и анализ тем выступлений ведущих зарубежных и российских спортивных психологов
Effect of symmetry reduction on the electronic transitions in polytypic GdAl3(BO3)4:Eu:Tb crystals
The existence of a recently described monoclinic phase (C2/c, Z=8) in addition to the well-known Huntite type rhombohedral (R32) polytypic modification of the GdAl3(BO3)4 (GAB) crystal at room temperature provides a unique possibility to investigate the incorporation of rare earth dopants into slightly modified crystal lattice by spectroscopic
methods. In these characteristic GAB structures the dopant ions, e.g Tb3+ or Eu3+ , possess slightly different neighbor geometries and local symmetries. The Tb3+:7F6 → 5D4 and Eu3+:7F0,1,2 → 5D0,1,2 electronic transitions were successfully identified in the absorption spectra
using polarization, concentration and temperature dependent measurements in both polytypic modifications. The positions of the investigated Tb lines are shifted by up to 10 cm−1 due to symmetry changes. In addition, some of the Eu lines show splittings of about 4–30 cm−1 as a consequence of the change of the local environment. From the room temperature absorption measurements some of the low energy crystal field levels of 7F and 5D states of the Eu3+ ions
were successfully determined for both modifications
The High Time Resolution Universe Survey II: Discovery of 5 Millisecond Pulsars
We present the discovery of 5 millisecond pulsars found in the mid-Galactic
latitude portion of the High Time Resolution Universe (HTRU) Survey. The
pulsars have rotational periods from ~2.3 to ~7.5 ms, and all are in binary
systems with orbital periods ranging from ~0.3 to ~150 d. In four of these
systems, the most likely companion is a white dwarf, with minimum masses of
~0.2 Solar Masses. The other pulsar, J1731-1847, has a very low mass companion
and exhibits eclipses, and is thus a member of the "black widow" class of
pulsar binaries. These eclipses have been observed in bands centred near
frequencies of 700, 1400 and 3000 MHz, from which measurements have been made
of the electron density in the eclipse region. These measurements have been
used to examine some possible eclipse mechanisms. The eclipse and other
properties of this source are used to perform a comparison with the other known
eclipsing and "black widow" pulsars.
These new discoveries occupy a short-period and high-dispersion measure (DM)
region of parameter space, which we demonstrate is a direct consequence of the
high time and frequency resolution of the HTRU survey. The large implied
distances to our new discoveries makes observation of their companions unlikely
with both current optical telescopes and the Fermi Gamma-ray Space Telescope.
The extremely circular orbits make any advance of periastron measurements
highly unlikely. No relativistic Shapiro delays are obvious in any of the
systems, although the low flux densities would make their detection difficult
unless the orbits were fortuitously edge-on.Comment: 11 pages, 5 figures, 4 tables, for publication in MNRA
The investigation of YAlO3-NdAlO3 system, synthesis and characterization
The binary phase diagram of the YAlO3 (YAP) - NdAlO3 (NAP) system was
determined by differential thermal analysis (DTA) and X-ray powder diffraction
(XRD) measurements. High purity nanocrystalline powders and small single
crystals of Y_{1-x}Nd_{x}AlO_3 (0 \leq x \leq 1) have been produced
successfully by modified sol-gel (Pechini) and micro-pulling-down methods,
respectively. Both end members show high mutual solubility >25% in the solid
phase, with a miscibility gap for intermediate compositions. A solid solution
with x \approx 0.2 melts azeotropic ca. 20 degrees below pure YAP. Such
crystals can be grown from the melt without segregation. The narrow
solid/liquid region near the azeotrope point could be measured with a "cycling"
DTA measurement technique.Comment: 12 pages, 8 figures, submitted to J. Alloys. Comp
- …