125,593 research outputs found
A tension approach to controlling the shape of cubic spline surfaces on FVS triangulations
No full textWe propose a parametric tensioned version of the FVS macro-element to control the shape of the composite surface and remove artificial oscillations, bumps and other undesired behaviour. In particular, this approach is applied to C1 cubic spline surfaces over a four-directional mesh produced by two-stage scattered data fitting methods
Polynomial cubic splines with tension properties
No full textIn this paper we present a new class of spline functions with tension properties. These splines are composed by polynomial cubic pieces and therefore are conformal to the standard, NURBS based CAD/CAM systems
Hoch-Adeliche und gottseelige Versammlung vom Sternkreuz genannt : so von Ihro kaiserl. Majestät Eleonora verwittibten römischen Kaiserinn aufgerichtet
No full text[G. B. Manni
Refining Cubic parametric B-Splines
No full textWe present re nement properties of cubic parametric B-splines: a
family of functions introduced some years ago in the context of shape-
preserving approximation of curves. The re nement equations deter-
mine a related subdivision scheme which turns out to be irregular,
nonstationary and nonuniform
On the Coble quartic and Fourier-Jacobi expansion of theta relations
No full textIn [Q. Ren, S. Sam, G. Schrader and B. Sturmfels, The universal Kummer threefold, Experiment Math.22(3) (2013) 327–362], the authors conjectured equations for the universal Kummer variety in genus 3 case. Although, most of these equations are obtained from the Fourier–Jacobi expansion of relations among theta constants in genus 4, the more prominent one, Coble's quartic, cf. [A. Coble, Algebraic Geometry and Theta Functions, American Mathematical Society Colloquium Publications, Vol. 10 (American Mathematical Society, 1929)] was obtained differently, cf. [S. Grushevsky and R. Salvati Manni, On Coble's quartic, preprint (2012), arXiv:1212.1895] too. The aim of this paper is to show that Coble's quartic can be obtained as Fourier–Jacobi expansion of a relation among theta-constants in genus 4. We get also one more relation that could be in the ideal described in [Experiment Math.22(3) (2013) 327–362]
Quatuor Regulæ Fundamentales Sapientiæ Christianæ : è quatuor considerationibus Æeternitatis deductæ
No full textà P. Joanne Baptista Manni S.J. Italicè conscriptæ, à P. Daniele Papebrochio S.J. Belgicè versæ, Ab Alio S.J. Sacerdote Monasterii latinitate donatæ, Ac Sodalitati B. Mariæ Virg. majori ibidem in strenam oblatæ Anno 1693Vorlageform des Erscheinungsvermerks: Typis Viduæ Raesfeldi
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Typhlops manni Loveridge 1941
No full text<i>Typhlops manni</i> Loveridge, 1941 <p>Fig. 3</p> <p> <i>Typhlops Angeli</i> Guibé, 1952: 79</p> <p> <i>Typhlops angeli ¢</i> Angel <i>et al.</i> 1954b: 383-384.</p> <p> <i>Typhlops manni ¢</i> Roux-Estève 1974: 41-43.</p> <p> MATÉRIEL EXAMINÉ. — [1 exemplaire]: Guinée: Nzo (alt. 500 m), MNHN 1951.1 [holotype de <i>Typhlops Angeli</i>] (Angel <i>et al.</i> 1954b: 383).</p> <p> <b>FIG. 3.</b> <i>Typhlops manni</i> Loveridge,1941. Face supérieure,face inférieure et profil de la tête de <i>Typhlops angeli</i> Guibé, 1952 d’après Angel <i>et al.</i> (1954b: 384). <i>FIG. 3.</i> Typhlops manni <i>Loveridge, 1941</i>. <i>Upper view, lower view and lateral view of the head of</i> Typhlops angeli <i>Guibé, 1952</i> <i>after Angel et al. (1954b: 384).</i></p>Published as part of <i>Ineich, Ivan, 2003, Contribution à la connaissance de la biodiversité des régions afro-montagnardes: les Reptiles du mont Nimba, pp. 597-638 in Mémoires du Muséum national d'Histoire naturelle 190</i> on pages 606-60
Structural and functional characterization of the intracellular kinase domain of vascular endothelial growth factor receptor-2
No full textVascular Endothelial Growth Factors (VEGFs) are key players in blood and lymphatic
vessel development and homeostasis. The family consists of five members, VEGF-A,
-B, -C, -D and placenta growth factor (PLGF). They bind to three type V receptor
tyrosine kinases (RTKs): VEGF-receptor-1 (VEGFR)-1 (Flt1), VEGFR-2 (KDR/Flk1),
and VEGFR-3 (Flt4). VEGFR-2 is the major receptor responsible for angiogenic and
vasculogenic signaling by VEGFs involving cell survival, migration and mitogenesis.
VEGFRs consist of an extracellular domain (ECD) with seven immunoglobulinhomology
domains (Ig-homology domains). The ECD is responsible for ligand binding and
contributes to the dimerization process of the receptors by forming homotypic
receptor contacts. A single transmembrane helix connects the ECD to the
intracellular kinase domain. Ligand binding to VEGFR ectodomains induces
dimerization of receptor monomers followed by autophosphorylation of specific
tyrosine residues in the intracellular kinase domains. The phosphotyrosine containing
activated kinase subsequently recruits signaling proteins thereby activating distinct
cellular pathways. Here we show that the introduction of glutamic acid residues into
the transmembrane domain (TMD) of VEGFR-2 leads to dimerization and induces
conformational changes in the TMD. A subsequent rearrangement of the intracellular
kinase domains gives rise to either active or inactive receptor dimers. We also show
that the ECD of VEGFR-2 plays an essential autoinhibitory role in the absence of
ligand. Furthermore, high-resolution structural analysis of isolated wild type (wt) and
mutant TMD by NMR spectroscopy reveal TMD conformations presumably essential
for receptor activation.
In a second project, we analysed the function of the kinase insert domain (KID) and
the C-terminal domain (CD) in VEGFR-2 activation. We show that these domains
regulate VEGFR-2 activity. The KID, and particularly a canonical tyrosine residue
located at position 951 are highly relevant for kinase activation. Deletion of the CD
renders VEGFR-2 constitutively active and we thus think that the CD of VEGFR-2
maintains the receptor in the inactive state in the absence of ligand. Low resolution
structural data derived from small angle X-ray scattering (SAXS) and MALS (Multi
Angle Light Scattering) give evidence that the kinase domain of VEGFR-2 undergoes
significant conformational changes when switching from the inactive to the active
state. The activated kinase domain adopts an elongated, open conformation whereas
the inactivated kinase domain remains in a globular compact conformation with the
CD presumably blocking the catalytic site of the kinase similar to the autoinhibited
conformation previously demonstrated for the Tie-2 kinase domain. Additional
sedimentation equilibrium analytical ultracentrifugation (AUC) experiments of kinase
domain mutants demonstrated that the KID and the CD are necessary to sustain an
intrinsic dimerization propensity that potentially supports the dimerization process
induced by ligand binding to the ECD. Deletion mutants showed lower affinity forming
dimers only at higher concentration. In experiments aiming to investigate
phosphorylation kinetics of the VEGFR-2 kinase domain we finally showed that
VEGFR-2 follows a well-ordered sequence of residue-by-residue phosphorylation.
In a third project we were interested in characterizing the in vitro interaction between
TSAd and activated VEGFR-2. Y951 mediated complex formation of TSAd with
VEGFR-2 was found to be critical for VEGF-induced actin reorganization and
migration but did not affect mitogenicity in endothelial and tumour cells. We were
interested to gain insights on the binding mode by means of high and low-resolution
structural biology methods. Initial size exclusion chromatography (SEC) and MALS
analysis verified TSAd-VEGFR-2 interaction in vitro. SAXS analysis of the isolated
binding partners and the complex revealed that pY951 mediated binding of TSAd
resulted in an elongated multiprotein complex in which the binding partners orient in
a presumably parallel orientation. ---------- Zusammenfassung: Die Familie der vaskulären endothelialen Wachstumsfaktoren (VEGFs) spielt eine
entscheidende Rolle bei der Entwicklung und Aufrechterhaltung des Blut- und
Lymphgefässsystems. Die Familie besteht aus VEGF-A, -B, -C, -D und PLGF. Die
Wachstumshormone binden an drei Typ V Rezeptor-Tyrosin-Kinasen: VEGFR-1
(Flt1), VEGFR-2 (Flk1) und VEGFR-3 (Flt4). VEGFR-2 ist mehrheitlich für die VEGF
induzierte Aktivierung von angiogenen und vaskulogenen Signalwegen und den
daraus resultierenden biologischen Effekten verantwortlich. Die VEGF-Rezeptoren
besitzen eine extrazelluläre Domäne bestehend aus sieben immunoglobulinähnlichen
Proteindomänen, die nebst der Rekrutierung von Liganden auch der
Dimerisierung des Rezeptors durch Ausbildung von homotypischen Kontakten dient.
Eine einzelne Transmembranhelix verbindet die extrazelluläre Domäne mit der
intrazellulär geteilten Kinasedomäne. Die Ligandenbindung an den Rezeptor führt zu
Dimerisierung und der darauf folgenden Aktivierung durch Autophosphorylierung an
spezifischen Tyrosinen in der Kinasedomäne. Die Phosphotyrosine rekrutieren
daraufhin Signalmoleküle, die in der Lage sind spezifische Signalwege zu aktivieren.
Wir konnten zeigen, dass Glutaminsäure-Mutationen in der Transmembrandomäne
von VEGFR-2 zu Konformationsänderungen in der Helix führen. Die daraus folgende
Neuausrichtung der Kinasedomänen resultierte in aktiven und inaktiven
Rezeptorkonformationen. Es gelang uns auch aufzuzeigen, dass die extrazelluläre
Domäne von VEGFR-2 eine wichtige Rolle bei der Blockierung des Rezeptors im
inaktiven Zustand in Abwesenheit des Liganden spielt. Hochaufgelöste
Strukturanalysen von isolierten Wildtyp und mutierten Transmembrandomänen
ergaben Strukturen, die höchstwahrscheinlich bei der Aktivierung des Rezeptors eine
essentielle Rolle spielen.
Ein zweites Projekt hatte zum Ziel, die Rolle der Kinase-Insertions-Domäne (KID)
und der C-terminalen Domäne (CD) bei der VEGFR-2 Aktivierung zu entschlüsseln.
Wir konnten zeigen, dass die KID und die CD die VEGFR-2 Aktivierung regulieren.
Die KID und ein spezifisches Tyrosin in Position 951 innerhalb der KID waren
essentiell für die Kinaseaktivierung. Deletion der CD führte zu konstitutiver
Aktivierung von VEGFR-2. Wir denken, dass die CD den Rezeptor in Abwesenheit
des Liganden im inaktiven Zustand behält. Mittels Small Angle X-ray Scattering
(SAXS) und Multi Angle Light Scattering (MALS) erhaltene Strukturdaten beweisen,
dass die Aktivierung der Kinasedomäne von VEGFR-2 mit einer signifikanten
Änderungen in der Konformation einhergeht. Die aktive Kinasedomäne nimmt eine
längliche, offene Konformation ein, wohingegen die Inaktive in einer globulären,
geschlossenen Konformation verbleibt. Sehr wahrscheinlich blockiert die CD dabei
das katalytische Zentrum des Enzyms, vergleichbar mit dem Mechanismus der von
der Tie-2 Kinasedomäne verwendet wird. Sedimentation Equillibrium Analytical
Ultracentrifugation (AUC) Experimente haben gezeigt, dass die KID und die CD
wichtig sind, um die intrinsische Dimerisierungskapazität der Kinasedomäne zu
erhalten. Diese intrinsische Tendenz unterstützt vermutlich die ligandeninduzierte
Dimerisierung bei der Rezeptoraktivierung. Deletionsmutanten zeigen eine niedrigere
Tendenz zur Dimerisierung mit steigender Proteinkonzentration. Experimente, die
zum Ziel hatten die Phosphorylierungskinetik der Kinasedomäne zu untersuchen,
ergaben eine zeitlich geordnete sequentielle Aktivierungssequenz.
In einem dritten Projekt untersuchten wir die in vitro Interaktion von T-Zell
spezifischem Adapterprotein (TSAd) mit der aktiven Kinasedomäne von VEGFR-2.
Es wurde gezeigt, dass die Y951 vermittelte Komplexbildung von TSAd mit VEGFR-2
zu VEGF induzierter Aktinreorganisation in den Zellen führt. Die Endothel- und
Tumorzellen wurden dadurch zur Migration gebracht, wobei die Mitogenität
unverändert blieb. Unser Ziel war es, mittels hoch- und niedrigauflösenden
strukturbiologischen Methoden spezifische Informationen zur Interaktion von TSAd
und VEGFR-2 abzuleiten. Erste chromatographische Analysen und Experimente
mittels Multi Angle Light Scattering (MALS) bewiesen die Interaktion der beiden
Proteine in vitro. SAXS Analysen der isolierten Bindungspartner und des Komplexes
ergaben einen länglichen Signalkomplex, in dem sich die Bindungspartner parallel
ausrichten
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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