40 research outputs found
Optical Sum Rule anomalies in the High-Tc Cuprates
We provide a brief summary of the observed sum rule anomalies in the
high-T cuprate materials. A recent issue has been the impact of a
non-infinite frequency cutoff in the experiment. In the normal state, the
observed anomalously high temperature dependence can be explained as a `cutoff
effect'. The anomalous rise in the optical spectral weight below the
superconducting transition, however, remains as a solid experimental
observation, even with the use of a cutoff frequency.Comment: 4 pages, 2 figures, very brief review of optical sum rule anomal
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Inhibition of ascitic ehrlich tumor cell growth by intraperitoneal injection of Pfaffia paniculata (Brazilian ginseng) butanolic residue
Comparison of amino acid uptake and incorporation inTetrahymean pyriformis and hela cells
Evolution of protein kinases: Identification of tyrosine kinases in sensory cilia of tetrahymena
The problem of transition from the chemical to the biological evolution: Some possible solutions
Effect of non-lytic concentrations of Brij series detergents on the metabolism-independent ion permeability properties of human erythrocytes
The Relationship of Arginine Deprivation, Argininosuccinate Synthetase and Cell Death in Melanoma
It has been shown that melanoma cells do not express argininosuccinate synthetase (ASS) and therefore are unable to synthesize arginine from citrulline. Depleting arginine using pegylated arginine deiminase (ADI-PEG20) results in cell death in melanoma but not normal cells. This concept was translated into clinical trial and responses were seen. However, induction of ASS expression does occur which results in resistance to ADI-PEG20. We have used 4 melanoma cell lines to study factors which may govern ASS expression. Although these 4 melanoma cell lines do not express ASS protein or mRNA as detected by both immunoblot and northernblot analysis, ASS protein can be induced after these cells are grown in the presence of ADI-PEG20, but again repressed after replenishing arginine in the media. The levels of induction are different and one cell line could not be induced. Interestingly, a melanoma cell line with the highest level of induction could also be made resistant to ADI-PEG20. This resistant line possesses high levels of ASS mRNA and protein expression which cannot be repressed with arginine. Our study indicates that ASS expression in melanoma cells is complex and governed by biochemical parameters which are different among melanoma cells