1,278 research outputs found
On rationality of the intersection points of a line with a plane quartic
We study the rationality of the intersection points of certain lines and
smooth plane quartics C defined over F_q. For q \geq 127, we prove the
existence of a line such that the intersection points with C are all rational.
Using another approach, we further prove the existence of a tangent line with
the same property as soon as the characteristic of F_q is different from 2 and
q \geq 66^2+1. Finally, we study the probability of the existence of a rational
flex on C and exhibit a curious behavior when the characteristic of F_q is
equal to 3.Comment: 17 pages. Theorem 2 now includes the characteristic 2 case;
Conjecture 1 from the previous version is proved wron
Duality with expanding maps and shrinking maps, and its applications to Gauss maps
We study expanding maps and shrinking maps of subvarieties of Grassmann
varieties in arbitrary characteristic. The shrinking map was studied
independently by Landsberg and Piontkowski in order to characterize Gauss
images. To develop their method, we introduce the expanding map, which is a
dual notion of the shrinking map and is a generalization of the Gauss map. Then
we give a characterization of separable Gauss maps and their images, which
yields results for the following topics: (1) Linearity of general fibers of
separable Gauss maps; (2) Generalization of the characterization of Gauss
images; (3) Duality on one-dimensional parameter spaces of linear subvarieties
lying in developable varieties.Comment: 28 pages, v3: added some examples, v2: the title has been changed
from v1 "Linearity of general fibers of separable Gauss maps
Metal Preferences of Zinc-Binding Motif on Metalloproteases
Almost all naturally occurring metalloproteases are monozinc enzymes. The zinc in any number of zinc metalloproteases has been substituted by some other divalent cation. Almost all Co(II)- or Mn(II)-substituted enzymes maintain the catalytic activity of their zinc counterparts. However, in the case of Cu(II) substitution of zinc proteases, a great number of enzymes are not active, for example, thermolysin, carboxypeptidase A, endopeptidase from Lactococcus lactis, or aminopeptidase B, while some do have catalytic activity, for example, astacin (37%) and DPP III (100%). Based on structural studies of various metal-substituted enzymes, for example, thermolysin, astacin, aminopeptidase B, dipeptidyl peptidase (DPP) III, and del-DPP III, the metal coordination geometries of both active and inactive Cu(II)-substituted enzymes are shown to be the same as those of the wild-type Zn(II) enzymes. Therefore, the enzyme activity of a copper-ion-substituted zinc metalloprotease may depend on the flexibility of catalytic domain
La coordinación disyuntiva en español: aspecto sincrónico
Análisis de aspectos como la disyunción no exclusiva, disyunción y distribución, o la concordancia verbal, con especial atención a las teorías de G. Fält sobre los factores que intervienen en la concordancia del verbo con sujetos unidos por coordinación disyuntiva, a la luz de las estadísticas. An analysis of aspects such as the non exclusive disjunction, disjunction and distribution, or the verb’s concordance, with special attention to G. Fält’s theories about the intervening factors in concordance of the verb with subjects united by a disjunctive coordination, lightened by statistics
Towards Retinoid Therapy for Alzheimer’s Disease
Alzheimer’s disease(AD) is associated with a variety of pathophysiological features, including amyloid plaques, inflammation, immunological changes, cell death and regeneration processes, altered neurotransmission, and age-related changes. Retinoic acid receptors (RARs) and retinoids are relevant to all of these. Here we review the pathology, pharmacology, and biochemistry of AD in relation to RARs and retinoids, and we suggest that retinoids are candidate drugs for treatment of AD
Effects of Herbage Species on the Spatial Heterogeneity of Biomass in Grazed Pasture: Kentucky Bluegrass vs. White Clover
The Hard Life: A Pedagogical Experience in Industrial Design
Thispaperseekstoanalyzeanddiscussaredesignprojectdeveloped by students of master’s degree in industrial design. Based on the book The Hard Life, from English designer Jasper Morrison, the briefing proposed the devel- opment of concepts for new products inspired by the selection of objects in the book, and respective written interpretations. It seeks to explore the dialogue between the original objects – their use, Morrison’s interpretation - and the reinterpretation made by the students considering the current material culture.
Accompanied and coordinated with Bisarro, contemporary studio dedicated to the artisan production of small series in Bisalhães black clay, UNESCO Immaterial Cultural Heritage, the project seeks to explore the boundaries and common ground between memory and contemporary times.
More than the results, it is intended to discuss proposals and approaches, from functional interpretations, formal inspiration, to the appropriation of affordance and gesture.info:eu-repo/semantics/publishedVersio
Nucleotide sequence of the putative regulatory region of mouse lactate dehydrogenase-A gene
In rat dipeptidyl peptidase III, His⁵⁶⁸ is essential for catalysis, and Glu⁵⁰⁷ or Glu⁵¹² stabilizes the coordination bond between His⁴⁵⁵ or His⁴⁵⁰ and zinc ion.
Dipeptidyl peptidase (DPP) III is a zinc-dependent exopeptidase that has a unique motif, "HELLGH," as the zinc-binding site. In the present study, a three-dimensional (3D) model of rat DPP III was generated with the X-ray crystal structure of human DPP III (PDB: 3FVY [Dobrovetsky E. et al. (2009) SGC]) as a template. The replacement of the seven charged amino acid residues with a hydrophobic amino acid around the zinc ion did not cause any significant changes in K(m) values or in the substrate specificity. However, the k(cat) values of H568R and H568Y were remarkably reduced, by factors of 50 and 400, respectively. The His⁵⁶⁸ residue of rat DPP III is essential for enzyme catalysis. The k(cat) values of the mutants E507A and E512A were 2.38 and 3.88 s⁻¹ toward Arg-Arg-NA, and 0.097 and 0.59 s⁻¹ toward Phe-Arg-NA, respectively. These values were markedly lower than those of the wild-type DPP III. Furthermore, the zinc contents of E507A and E512A were 0.29 and 0.08 atom per mol of protein, respectively, and those mutations caused remarkable increases in the dissociation constants of the zinc ions from DPP III by factors of 5 x 10³ to 2 x 10⁴. The 3D model of the catalytic domain of rat DPP III showed that the carboxyl oxygen atoms of Glu⁵⁰⁷ and Glu⁵¹² form the hydrogen bonds to the nitrogen atoms of His⁴⁵⁵ and His⁴⁵⁰. All of these results showed that Glu⁵⁰⁷ or Glu⁵¹² stabilizes the coordination bond between the zinc ion and His⁴⁵⁵ or His⁴⁵⁰.Dipeptidyl peptidase (DPP) III is a zinc-dependent exopeptidase that has a unique motif, "HELLGH," as the zinc-binding site. In the present study, a three-dimensional (3D) model of rat DPP III was generated with the X-ray crystal structure of human DPP III (PDB: 3FVY [Dobrovetsky E. et al. (2009) SGC]) as a template. The replacement of the seven charged amino acid residues with a hydrophobic amino acid around the zinc ion did not cause any significant changes in K(m) values or in the substrate specificity. However, the k(cat) values of H568R and H568Y were remarkably reduced, by factors of 50 and 400, respectively. The His⁵⁶⁸ residue of rat DPP III is essential for enzyme catalysis. The k(cat) values of the mutants E507A and E512A were 2.38 and 3.88 s⁻¹ toward Arg-Arg-NA, and 0.097 and 0.59 s⁻¹ toward Phe-Arg-NA, respectively. These values were markedly lower than those of the wild-type DPP III. Furthermore, the zinc contents of E507A and E512A were 0.29 and 0.08 atom per mol of protein, respectively, and those mutations caused remarkable increases in the dissociation constants of the zinc ions from DPP III by factors of 5 x 10³ to 2 x 10⁴. The 3D model of the catalytic domain of rat DPP III showed that the carboxyl oxygen atoms of Glu⁵⁰⁷ and Glu⁵¹² form the hydrogen bonds to the nitrogen atoms of His⁴⁵⁵ and His⁴⁵⁰. All of these results showed that Glu⁵⁰⁷ or Glu⁵¹² stabilizes the coordination bond between the zinc ion and His⁴⁵⁵ or His⁴⁵⁰
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