10,113 research outputs found
Developmental and tissue-specific expression of the Q5k gene
Expression of the Q5k gene was examined by
northern blot analysis and polymerase chain reaction
(PCR) in the AKR mouse and various cell lines, each of
the H-2k haplotype. Our results show that Q5k mRNA is
present during the whole postimplantational development
of the AKR embryo/fetus (gestation day 6 to 15). In the
juvenile mouse (week 2 to 4) transcription of the Q5k
gene persisted in all organs examined. In contrast, in the
adult animal expression of the Q5k gene was limited to
the thymus and uterus of the pregnant mouse. Upon malignant
transformation, the amount of Q5k-specific mRNA
increased dramatically in thymus and could also be
observed in the spleen of thymoma bearing animals. Expression
of the Q5k gene was also detectable in several
transformed mouse cell lines. Mitogen stimulation or
treatment with cytokines induced Q5k expression in
primary spleen cell cultures. A possible explanation for
the tissue-restricted expression in the adult AKR mouse
is discussed
Recommended from our members
Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks
Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability. Insertion of well-defined, evenly spaced nanoscale pores into the two-dimensional (2D) layers of graphene invokes exciting properties due to the modulation of its electronic band gaps and surface functionalities. A bottom-up synthesis approach to such porous graphitic frameworks (PGFs) is appealing but also remains a great challenge. The current methods of building covalent organic frameworks rely on a small collection of thermodynamically reversible reactions. Such reactions are, however, inadequate in generating a fully annulated aromatic skeleton in PGFs. With the discovery of dynamic pyrazine formation, we succeeded in applying this linking chemistry to obtain a crystalline PGF material, which has displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries. We envision that the demonstrated success will open the door to a wide array of fully annulated 2D porous frameworks, which hold immense potential for clean energy applications. We report the unusual dynamic characteristics of the C=N bonds in the pyrazine ring promoted under basic aqueous conditions, which enables the successful synthesis of two-dimensional porous graphitic frameworks (PGFs) featuring fully annulated aromatic skeletons and periodic pores. The PGF displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries, far outperforming the amorphous counterparts in terms of capacity and cycle stability
Symmetric Versus Nonsymmetric Structure of the Phosphorus Vacancy on InP(110)
The atomic and electronic structure of positively charged P vacancies on
InP(110) surfaces is determined by combining scanning tunneling microscopy,
photoelectron spectroscopy, and density-functional theory calculations. The
vacancy exhibits a nonsymmetric rebonded atomic configuration with a charge
transfer level 0.75+-0.1 eV above the valence band maximum. The scanning
tunneling microscopy (STM) images show only a time average of two degenerate
geometries, due to a thermal flip motion between the mirror configurations.
This leads to an apparently symmetric STM image, although the ground state
atomic structure is nonsymmetric.Comment: 5 pages including 3 figures. related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Nanoscale structuring of tungsten tip yields most coherent electron point-source
This report demonstrates the most spatially-coherent electron source ever
reported. A coherence angle of 14.3 +/- 0.5 degrees was measured, indicating a
virtual source size of 1.7 +/-0.6 Angstrom using an extraction voltage of 89.5
V. The nanotips under study were crafted using a spatially-confined,
field-assisted nitrogen etch which removes material from the periphery of the
tip apex resulting in a sharp, tungsten-nitride stabilized, high-aspect ratio
source. The coherence properties are deduced from holographic measurements in a
low-energy electron point source microscope with a carbon nanotube bundle as
sample. Using the virtual source size and emission current the brightness
normalized to 100 kV is found to be 7.9x10^8 A/sr cm^2
Global behavior of cosmological dynamics with interacting Veneziano ghost
In this paper, we shall study the dynamical behavior of the universe
accelerated by the so called Veneziano ghost dark energy component locally and
globally by using the linearization and nullcline method developed in this
paper. The energy density is generalized to be proportional to the Hawking
temperature defined on the trapping horizon instead of Hubble horizon of the
Friedmann-Robertson-Walker (FRW) universe. We also give a prediction of the
fate of the universe and present the bifurcation phenomenon of the dynamical
system of the universe. It seems that the universe could be dominated by dark
energy at present in some region of the parameter space.Comment: 8 pages, 7 figures, accepted for publication in JHE
Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity
Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops
A Computational Investigation of Sooting Limits of Spherical Diffusion Flames
Limiting conditions for soot particle inception in spherical diffusion flames were investigated numerically. The flames were modeled using a one-dimensional, time accurate diffusion flame code with detailed chemistry and transport and an optically thick radiation model. Seventeen normal and inverse flames were considered, covering a wide range of stoichiometric mixture fraction, adiabatic flame temperature, and residence time. These flames were previously observed to reach their sooting limits after 2 s of microgravity. Sooting-limit diffusion flames with residence times longer than 200 ms were found to have temperatures near 1190 K where C/O = 0.6, whereas flames with shorter residence times required increased temperatures. Acetylene was found to be a reasonable surrogate for soot precursor species in these flames, having peak mole fractions of about 0.01
Hartree-Fock-Bogoliubov theory versus local-density approximation for superfluid trapped fermionic atoms
We investigate a gas of superfluid fermionic atoms trapped in two hyperfine
states by a spherical harmonic potential. We propose a new regularization
method to remove the ultraviolet divergence in the Hartree-Fock-Bogoliubov
equations caused by the use of a zero-range atom-atom interaction. Compared
with a method used in the literature, our method is simpler and has improved
convergence properties. Then we compare Hartree-Fock-Bogoliubov calculations
with the semiclassical local-density approximation. We observe that for systems
containing a small number of atoms shell effects, which cannot be reproduced by
the semiclassical calculation, are very important. For systems with a large
number of atoms at zero temperature the two calculations are in quite good
agreement, which, however, is deteriorated at non-zero temperature, especially
near the critical temperature. In this case the different behavior can be
explained within the Ginzburg-Landau theory.Comment: 12 pages, 8 figures, revtex; v2: references and clarifying remarks
adde
Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei
The properties of the states of the alternating parity bands in actinides,
Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based
on the assumption that cluster type shapes are produced by the collective
motion of the nuclear system in the mass asymmetry coordinate. The calculated
spin dependences of the parity splitting and of the electric multipole
transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure
- …