5,242 research outputs found
Determination of dissolved oxygen in water with leukoberbelin-blue I. A quick Winkler method. [Translation from: Z.analyt.Chem. 262 97-99, 1972.]
The reaction of Mn(II) with water-dissolved oxygen, to a higher manganese hydroxide in an alkaline medium, as with the longstanding classic Winkler method, is the first step in the method described here. The assumption for faultless results by the conventional and modified Winkler method is clean water, which contains no organic substances by Mn(III) or Mn(IV). In many cases, however, eg. in river and lake-water tests, it can be seen with the naked eye that after some time the originally brown-coloured precipitate of manganese hydroxide becomes more and more colourless. Oxygen content was analysed in the water samples and evaluated by raising the amount of the leuko-base and giving the corresponding dilution of the colouring matter solution formed still higher oxygen contents can be measured
Toric rings, inseparability and rigidity
This article provides the basic algebraic background on infinitesimal
deformations and presents the proof of the well-known fact that the non-trivial
infinitesimal deformations of a -algebra are parameterized by the
elements of cotangent module of . In this article we focus on
deformations of toric rings, and give an explicit description of in
the case that is a toric ring.
In particular, we are interested in unobstructed deformations which preserve
the toric structure. Such deformations we call separations. Toric rings which
do not admit any separation are called inseparable. We apply the theory to the
edge ring of a finite graph. The coordinate ring of a convex polyomino may be
viewed as the edge ring of a special class of bipartite graphs. It is shown
that the coordinate ring of any convex polyomino is inseparable. We introduce
the concept of semi-rigidity, and give a combinatorial description of the
graphs whose edge ring is semi-rigid. The results are applied to show that for
, is not rigid while for , is
rigid. Here is the complete bipartite graph with one
edge removed.Comment: 33 pages, chapter 2 of the Book << Multigraded Algebra and
Applications>> 2018, Springer International Publishing AG, part of Springer
Natur
Insect folivore damage in Nothofagus Blume trees of central Chile and its association with bottom-up plant community attributes
El estudio del daño por folivorÃa de insectos en Nothofagus spp. es importante para monitorear la salud de estos árboles aunque la información empÃrica es escasa. Evidencias previas sobre árboles de Nothofagus macrocarpa (A. DC.) F.M. Vásquez y R.A. Rodr, y Nothofagus glauca (Phil.) Krasser de Chile central sugirieron que el daño por este tipo de folivorÃa puede ser intenso en estas especies. En este trabajo exploré los niveles de daño sobre estas dos especies y su relación con atributos de la comunidad vegetal (bottom-up) tales como la arquitectura de la planta, disponibilidad de luz y edad del huésped. Se recolectaron muestras de follaje en cinco sitios de campo al fi nal de la época productiva 2007-2008 en árboles de N. macrocarpa y N. glauca y el daño fue estimado a partir de la remoción de lámina (ausencia completa de la lámina) y necrosis de lámina y posteriormente analizado estadisticamente en términos de remoción de lámina y daño de folivorÃa (remoción y necrosis de lámina). Los datos para N. macrocarpa fueron divididos en dos grupos basados sobre la elevación de los sitios de campo (alta y baja), mientras los datos para N. glauca correspondieron estrictamente a sitios de baja elevación. Nothofagus macrocarpa de sitios de baja elevación tuvieron una remoción de lámina y daño de folivorÃa mayor que N. glauca y un mayor daño de folivorÃa que en los individuos de N. macrocarpa (alta). Los individuos de N.macrocarpa (baja) asociados con una menor cobertura aérea vegetativa (y presumiblemente más expuestos a la luz solar) tuvieron una mayor remoción de lámina que los individuos asociados con una mayor cobertura aérea vegetativa (y supuestamente menos expuestos a luz solar). El follaje de N. glauca con mayor exposición al sol mostró una mayor remoción de lámina que el correspondiente a una menor exposición al sol, y este patrón fue marginalmente similar para N. macrocarpa (baja). La remoción de lámina de N. macrocarpa (baja) se correlacionó de forma positiva con la relación largo:ancho de la hoja a nivel de rama. Finalmente, los árboles juveniles de N. macrocarpa (baja) tuvieron una mayor remoción de lámina que árboles más maduros.The study of insect folivore damage in South American Nothofagus spp. is important for monitoring the health of these trees and for basic research, although empirical information is scarce. Previous evidence on N. macrocarpa (A.DC.) F.M. Vásquez and R.A. Rodr, and N. glauca (Phil.) Krasser trees of central Chile suggested that insect folivore damage in these species can be intense and here I explored damage levels of the two species and their relationship with bottom-up community attributes such as plant architecture, light availability and host age. Foliage samples were collected at fi ve fi eld sites at the end of the 2007-2008 productive season in trees of N. macrocarpa and N. glauca and damage was measured based on lamina removal (complete absence of lamina) and lamina necrosis, and then analzyed statistically in terms of lamina removal and folivore damage (lamina removal and necrosis). Data for N. macrocarpa were divided into two groups based on fi eld site elevation (high and low) whereas data for N. glauca corresponded strictly to low elevation sites. N. macrocarpa of lower elevation sites (low) had greater lamina removal and folivore damage than N. glauca and greater folivore damage than in individuals of N. macrocarpa (high). N. macrocarpa (low) associated with a lower aerial vegetative cover (and presumably more exposed to sun light) had greater lamina removal than individuals associated with a greater aerial vegetative cover (and presumably less exposed to sun light). Nothofagus glauca foliage with greater sun exposure showed greater lamina removal than that corresponding to lower sun exposure, and this pattern was marginally similar for N. macrocarpa (low). Lamina removal of N. macrocarpa (low) was positively correlated with leaf thinness (leaf length-width ratio) at the branch level. Finally, N. macrocarpa (low) juvenile trees had greater lamina removal than more mature trees
Torus invariant divisors
Using the language of polyhedral divisors and divisorial fans we describe
invariant divisors on normal varieties X which admit an effective codimension
one torus action. In this picture X is given by a divisorial fan on a smooth
projective curve Y. Cartier divisors on X can be described by piecewise affine
functions h on the divisorial fan S whereas Weil divisors correspond to certain
zero and one dimensional faces of it. Furthermore we provide descriptions of
the divisor class group and the canonical divisor. Global sections of line
bundles O(D_h) will be determined by a subset of a weight polytope associated
to h, and global sections of specific line bundles on the underlying curve Y.Comment: 16 pages; 5 pictures; small changes in the layout, further typos
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XenDB: Full length cDNA prediction and cross species mapping in Xenopus laevis
BACKGROUND: Research using the model system Xenopus laevis has provided critical insights into the mechanisms of early vertebrate development and cell biology. Large scale sequencing efforts have provided an increasingly important resource for researchers. To provide full advantage of the available sequence, we have analyzed 350,468 Xenopus laevis Expressed Sequence Tags (ESTs) both to identify full length protein encoding sequences and to develop a unique database system to support comparative approaches between X. laevis and other model systems. DESCRIPTION: Using a suffix array based clustering approach, we have identified 25,971 clusters and 40,877 singleton sequences. Generation of a consensus sequence for each cluster resulted in 31,353 tentative contig and 4,801 singleton sequences. Using both BLASTX and FASTY comparison to five model organisms and the NR protein database, more than 15,000 sequences are predicted to encode full length proteins and these have been matched to publicly available IMAGE clones when available. Each sequence has been compared to the KOG database and ~67% of the sequences have been assigned a putative functional category. Based on sequence homology to mouse and human, putative GO annotations have been determined. CONCLUSION: The results of the analysis have been stored in a publicly available database XenDB . A unique capability of the database is the ability to batch upload cross species queries to identify potential Xenopus homologues and their associated full length clones. Examples are provided including mapping of microarray results and application of 'in silico' analysis. The ability to quickly translate the results of various species into 'Xenopus-centric' information should greatly enhance comparative embryological approaches. Supplementary material can be found at
Proper motions of Local Group dwarf spheroidal galaxies I: First ground-based results for Fornax
In this paper we present in detail the methodology and the first results of a
ground-based program to determine the absolute proper motion of the Fornax
dwarf spheroidal galaxy.
The proper motion was determined using bona-fide Fornax star members measured
with respect to a fiducial at-rest background spectroscopically confirmed
Quasar, \qso. Our homogeneous measurements, based on this one Quasar gives a
value of (\mua,\mud) \masy. There are only
two other (astrometric) determinations for the transverse motion of Fornax: one
based on a combination of plates and HST data, and another (of higher internal
precision) based on HST data. We show that our proper motion errors are similar
to those derived from HST measurements on individual QSOs. We provide evidence
that, as far as we can determine it, our motion is not affected by magnitude,
color, or other potential systematic effects. Last epoch measurements and
reductions are underway for other four Quasar fields of this galaxy, which,
when combined, should yield proper motions with a weighted mean error of
as y, allowing us to place important constraints on the
orbit of Fornax.Comment: Accepted for publication in Publications of the Astronomical Society
of the Pacific, PASP. To appear in July issue. 64 pages, 18 figure
Electroweak Supersymmetry with an Approximate U(1)_PQ
A predictive framework for supersymmetry at the TeV scale is presented, which
incorporates the Ciafaloni-Pomarol mechanism for the dynamical determination of
the \mu parameter of the MSSM. It is replaced by (\lambda S), where S is a
singlet field, and the axion becomes a heavy pseudoscalar, G, by adding a mass,
m_G, by hand. The explicit breaking of Peccei-Quinn (PQ) symmetry is assumed to
be sufficiently weak at the TeV scale that the only observable consequence is
the mass m_G. Three models for the explicit PQ breaking are given; but the
utility of this framework is that the predictions for all physics at the
electroweak scale are independent of the particular model for PQ breaking. Our
framework leads to a theory similar to the MSSM, except that \mu is predicted
by the Ciafaloni-Pomarol relation, and there are light, weakly-coupled states
in the spectrum. The production and cascade decay of superpartners at colliders
occurs as in the MSSM, except that there is one extra stage of the cascade
chain, with the next-to-LSP decaying to its "superpartner" and \tilde{s},
dramatically altering the collider signatures for supersymmetry. The framework
is compatible with terrestrial experiments and astrophysical observations for a
wide range of m_G and . If G is as light as possible, 300 keV < m_G < 3 MeV,
it can have interesting effects on the radiation energy density during the
cosmological eras of nucleosynthesis and acoustic oscillation, leading to
predictions for N_{\nu BBN} and N_{\nu CMB} different from 3.Comment: 45 pages, 2 colour figures, a reference added, minor correction
Effects of attractiveness on face memory separated from distinctiveness: Evidence from event-related brain potentials
The present study examined effects of attractiveness on behavioral and event-related potential (ERP) correlates of face memory. Extending previous reports, we controlled for potential moderating effects of distinctiveness, a variable known to affect memory. Attractive and unattractive faces were selected on the basis of a rating study, and were matched for distinctiveness. In a subsequent recognition memory experiment, we found more accurate memory for unattractive relative to attractive faces. Additionally, an attractiveness effect in the early posterior negativity (EPN) during learning, with larger amplitudes for attractive than unattractive faces, correlated significantly with the magnitude of the memory advantage for unattractive faces at test. These findings establish a contribution of attractiveness to face memory over and above the well-known effect of distinctiveness. Additionally, as the EPN is typically enhanced for affective stimuli, our ERP results imply that the processing of emotionally relevant attractive faces during learning may hamper their encoding into memory
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