608 research outputs found
Esterase activity and isoenzymes in relation to morphogenesis in Mammillaria gracillis Pfeiff. tissue culture
Cactus Mammillaria gracillis Pfeiff. (Cactaceae), cultivated in vitro, spontaneously switches from an organised to unorganised way of growth, producing a habituated organogenic callus which regenerates normal and hyperhydric shoots without the addition of any growth regulators. Tumour tissues, induced by A. tumefaciens wild strain B6S3 (tumour TW) and rooty mutant GV3101 (tumour TR), do not express any organogenic potential. The esterase (arylesterase EC 3.1.1.2 and carboxylesterase EC 3.1.1.1) activity and isoenzyme pattern of morphologically different cactus tissues: shoot, callus, hyperhydric regenerant, tumours TW and TR, were compared. Tissue samples were frozen at â80 °C and lyophilized before protein extraction. Two esterase substrates, 1- and 2-naphthylacetate, were used. Esterase activity of all tissues varied during the period of one subculture. In shoots and tumours, the highest esterase activity for both substrates was measured on the 21st day, while in the callus and hyperhydric regenerants the highest activity was on the 7th day. Esterases were separated electrophoretically in polyacrylamide gradient gels under non-denaturating conditions. In total, 13 isoesterases, reacting with both substrates, were resolved. No differences in isoenzyme profile were noticed in correlation with the age of tissues, but the esterase activity varied among tissues. The significance of these results is discussed
Esterase activity and isoenzymes in relation to morphogenesis in Mammillaria gracillis Pfeiff. tissue culture
Cactus Mammillaria gracillis Pfeiff. (Cactaceae), cultivated in vitro, spontaneously switches from an organised to unorganised way of growth, producing a habituated organogenic callus which regenerates normal and hyperhydric shoots without the addition of any growth regulators. Tumour tissues, induced by A. tumefaciens wild strain B6S3 (tumour TW) and rooty mutant GV3101 (tumour TR), do not express any organogenic potential. The esterase (arylesterase EC 3.1.1.2 and carboxylesterase EC 3.1.1.1) activity and isoenzyme pattern of morphologically different cactus tissues: shoot, callus, hyperhydric regenerant, tumours TW and TR, were compared. Tissue samples were frozen at â80 °C and lyophilized before protein extraction. Two esterase substrates, 1- and 2-naphthylacetate, were used. Esterase activity of all tissues varied during the period of one subculture. In shoots and tumours, the highest esterase activity for both substrates was measured on the 21st day, while in the callus and hyperhydric regenerants the highest activity was on the 7th day. Esterases were separated electrophoretically in polyacrylamide gradient gels under non-denaturating conditions. In total, 13 isoesterases, reacting with both substrates, were resolved. No differences in isoenzyme profile were noticed in correlation with the age of tissues, but the esterase activity varied among tissues. The significance of these results is discussed
DERIVATION AND OPTIMIZATION OF A STOCHASTIC LIVESTOCK WEIGHT GAIN RESPONSE TO STOCKING DENSITY MODEL
Dual-purpose winter wheat production is an important economic enterprise in the southern Great Plains of the United States. Because of the complex interactions involved in producing wheat grain and beef gain from a single crop, stocking density is an important decision. The objective of the research is to determine the stocking density that maximizes expected net returns from dual-purpose winter wheat production. Statistical tests rejected a conventional linear-response plateau function in favor of a linear-response stochastic plateau function. The optimal stocking density of 1.48 steers per hectare (0.60 steers per acre) is 19% greater with a stochastic plateau than with a nonstochastic one.Livestock Production/Industries,
Agricultural intensification and efficiency in the West African savannahs: Evidence from northern Nigeria
BPS Domain Wall Junctions in Infinitely Large Extra Dimensions
We consider models of scalar fields coupled to gravity which are
higher-dimensional generalizations of four dimensional supergravity. We use
these models to describe domain wall junctions in an anti-de Sitter background.
We derive Bogomolnyi equations for the scalar fields from which the walls are
constructed and for the metric. From these equations a BPS-like formula for the
junction energy can be derived. We demonstrate that such junctions localize
gravity in the presence of more than one uncompactified extra dimension.Comment: 17 pages, uses RevTeX, new references adde
Bounds for State Degeneracies in 2D Conformal Field Theory
In this note we explore the application of modular invariance in
2-dimensional CFT to derive universal bounds for quantities describing certain
state degeneracies, such as the thermodynamic entropy, or the number of
marginal operators. We show that the entropy at inverse temperature 2 pi
satisfies a universal lower bound, and we enumerate the principal obstacles to
deriving upper bounds on entropies or quantum mechanical degeneracies for fully
general CFTs. We then restrict our attention to infrared stable CFT with
moderately low central charge, in addition to the usual assumptions of modular
invariance, unitarity and discrete operator spectrum. For CFT in the range
c_left + c_right < 48 with no relevant operators, we are able to prove an upper
bound on the thermodynamic entropy at inverse temperature 2 pi. Under the same
conditions we also prove that a CFT can have a number of marginal deformations
no greater than ((c_left + c_right) / (48 - c_left - c_right)) e^(4 Pi) - 2.Comment: 23 pages, LaTeX, minor change
Non-birational twisted derived equivalences in abelian GLSMs
In this paper we discuss some examples of abelian gauged linear sigma models
realizing twisted derived equivalences between non-birational spaces, and
realizing geometries in novel fashions. Examples of gauged linear sigma models
with non-birational Kahler phases are a relatively new phenomenon. Most of our
examples involve gauged linear sigma models for complete intersections of
quadric hypersurfaces, though we also discuss some more general cases and their
interpretation. We also propose a more general understanding of the
relationship between Kahler phases of gauged linear sigma models, namely that
they are related by (and realize) Kuznetsov's `homological projective duality.'
Along the way, we shall see how `noncommutative spaces' (in Kontsevich's sense)
are realized physically in gauged linear sigma models, providing examples of
new types of conformal field theories. Throughout, the physical realization of
stacks plays a key role in interpreting physical structures appearing in GLSMs,
and we find that stacks are implicitly much more common in GLSMs than
previously realized.Comment: 54 pages, LaTeX; v2: typo fixe
The Omega Deformation From String and M-Theory
We present a string theory construction of Omega-deformed four-dimensional
gauge theories with generic values of \epsilon_1 and \epsilon_2. Our solution
gives an explicit description of the geometry in the core of Nekrasov and
Witten's realization of the instanton partition function, far from the
asymptotic region of their background. This construction lifts naturally to
M-theory and corresponds to an M5-brane wrapped on a Riemann surface with a
selfdual flux. Via a 9-11 flip, we finally reinterpret the Omega deformation in
terms of non-commutative geometry. Our solution generates all modified
couplings of the \Omega-deformed gauge theory, and also yields a geometric
origin for the quantum spectral curve of the associated quantum integrable
system.Comment: LaTeX, 35 pages, 1 figure. Appendix on couplings of hypermultiplets
in N=4 SYM adde
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