702 research outputs found
Naive Noncommutative Blowing Up
Let B(X,L,s) be the twisted homogeneous coordinate ring of an irreducible
variety X over an algebraically closed field k with dim X > 1. Assume that c in
X and s in Aut(X) are in sufficiently general position. We show that if one
follows the commutative prescription for blowing up X at c, but in this
noncommutative setting, one obtains a noncommutative ring R=R(X,c,L,s) with
surprising properties. In particular:
(1) R is always noetherian but never strongly noetherian.
(2) If R is generated in degree one then the images of the R-point modules in
qgr(R) are naturally in (1-1) correspondence with the closed points of X.
However, both in qgr(R) and in gr(R), the R-point modules are not parametrized
by a projective scheme.
(3) qgr R has finite cohomological dimension yet H^1(R) is infinite
dimensional.
This gives a more geometric approach to results of the second author who
proved similar results for X=P^n by algebraic methods.Comment: Latex, 42 page
Noncommutative Blowups of Elliptic Algebras
We develop a ring-theoretic approach for blowing up many noncommutative
projective surfaces. Let T be an elliptic algebra (meaning that, for some
central element g of degree 1, T/gT is a twisted homogeneous coordinate ring of
an elliptic curve E at an infinite order automorphism). Given an effective
divisor d on E whose degree is not too big, we construct a blowup T(d) of T at
d and show that it is also an elliptic algebra. Consequently it has many good
properties: for example, it is strongly noetherian, Auslander-Gorenstein, and
has a balanced dualizing complex. We also show that the ideal structure of T(d)
is quite rigid. Our results generalise those of the first author. In the
companion paper "Classifying Orders in the Sklyanin Algebra", we apply our
results to classify orders in (a Veronese subalgebra of) a generic cubic or
quadratic Sklyanin algebra.Comment: 39 pages. Minor changes from previous version. The final publication
is available from Springer via http://dx.doi.org/10.1007/s10468-014-9506-
Algebras in which every subalgebra is noetherian
We show that the twisted homogeneous coordinate rings of elliptic curves by
infinite order automorphisms have the curious property that every subalgebra is
both finitely generated and noetherian. As a consequence, we show that a
localisation of a generic Skylanin algebra has the same property.Comment: 5 pages; comments welcome; v2 only minor changes, most suggested by
refere
PA6 nanofibre production: A comparison between rotary jet spinning and electrospinning
© 2018 by the authors. Polymer nanofibres are created from many different techniques, with varying rates of production. Rotary jet spinning is a relatively new technique for making nanofibres from both polymer solutions and melt. With electrospinning being by far the most widespread processing method for polymer nanofibres, we performed a direct comparison of polyamide 6 (PA6) nanofibre production between these two methods. It was found that electrospinning produced slightly smaller-diameter fibres, which scaled with a decrease in solution viscosity. In comparison, rotary jet spun fibres could be produced from a reduced range of polymer concentrations and exhibited therefore slightly larger diameters with greater variation. Crystallinity of the fibres was also compared between the two techniques and the bulk polymer, which showed a decrease in crystallinity compared to bulk PA6
Some Noncommutative Minimal Surfaces
In the ongoing programme to classify noncommutative projective surfaces
(connected graded noetherian domains of Gelfand-Kirillov dimension three) a
natural question is to determine the minimal models within any birational
class. In this paper we show that the generic noncommutative projective plane
(corresponding to the three dimensional Sklyanin algebra R) as well as
noncommutative analogues of P^1 x P^1 and of the Hirzebruch surface F_2
(arising from Van den Bergh's quadrics R) satisfy very strong minimality
conditions. Translated into an algebraic question, where one is interested in a
maximality condition, we prove the following theorem. Let R be a Sklyanin
algebra or a Van den Bergh quadric that is infinite dimensional over its centre
and let A be any connected graded noetherian maximal order containing R, with
the same graded quotient ring as R. Then, up to taking Veronese rings, A is
isomorphic to R. Secondly, let T be an elliptic algebra (that is, the
coordinate ring of a noncommutative surface containing an elliptic curve).
Then, under an appropriate homological condition, we prove that every connected
graded noetherian overring of T is obtained by blowing down finitely many lines
(line modules).Comment: 42 pages; Third and final version to appear in Advances in
Mathematics: minor revisions from second versio
Formation and action of lignin-modifying enzymes in cultures of Phlebia radiata supplemented with veratric acid
Transformation of veratric (3,4-dimethoxybenzoic) acid by the white rot fungus Phlebia radiata was studied to elucidate the role of ligninolytic, reductive, and demeth(ox)ylating enzymes. Under both air and a 100% O2 atmosphere, with nitrogen limitation and glucose as a carbon source, reducing activity resulted in the accumulation of veratryl alcohol in the medium. When the fungus was cultivated under air, veratric acid caused a rapid increase in laccase (benzenediol:oxygen oxidoreductase; EC 1.10.3.2) production, which indicated that veratric acid was first demethylated, thus providing phenolic compounds for laccase. After a rapid decline in laccase activity, elevated lignin peroxidase (ligninase) activity and manganese-dependent peroxidase production were detected simultaneously with extracellular release of methanol. This indicated apparent demethoxylation. When the fungus was cultivated under a continuous 100% O2 flow and in the presence of veratric acid, laccase production was markedly repressed, whereas production of lignin peroxidase and degradation of veratryl compounds were clearly enhanced. In all cultures, the increases in lignin peroxidase titers were directly related to veratryl alcohol accumulation. Evolution of 14CO2 from 3-O14CH3-and 4-O14CH3-labeled veratric acids showed that the position of the methoxyl substituent in the aromatic ring only slightly affected demeth(ox)ylation activity. In both cases, more than 60% of the total 14C was converted to 14CO2 under air in 4 weeks, and oxygen flux increased the degradation rate of the 14C-labeled veratric acids just as it did with unlabeled cultures
Ring-theoretic blowing down: I
One of the major open problems in noncommutative algebraic geometry is the
classification of noncommutative projective surfaces (or, slightly more
generally, of noetherian connected graded domains of Gelfand-Kirillov dimension
3). Earlier work of the authors classified the connected graded noetherian
subalgebras of Sklyanin algebras using a noncommutative analogue of blowing up.
In order to understand other algebras birational to a Sklyanin algebra, one
also needs a notion of blowing down.
This is achieved in this paper, where we give a noncommutative analogue of
Castelnuovo's classic theorem that (-1)-lines on a smooth surface can be
contracted. The resulting noncommutative blown-down algebra has pleasant
properties; in particular it is always noetherian and is smooth if the original
noncommutative surface is smooth.
In a companion paper we will use this technique to construct explicit
birational transformations between various noncommutative surfaces which
contain an elliptic curve.Comment: 40 page
Production of laccase, lignin peroxidase and manganese-dependent peroxidase by various strains of Trametes versicolor depending on culture conditions
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