Search results for " ring"
showing 10 items of 478 documents
Rashkova, T. The Robson cubics for matrix algebras with involution (Acta Univ. Apulensis Math. Inform.).
2008
Let R be the free associative algebra over a field K on $n^2$ generators $a_{ij}$ and let $R\langle x\rangle$ be the free associative $K$-algebra in one further indeterminate $x.$ Consider the set of polynomials in $R\langle x\rangle$ which are satisfied by the $n\times n$ matrix $\alpha=(a_{ij}).$ Such polynomials are called laws over $R$ of the matrix $\alpha.$ Robson in [Robson, J. C. Polynomials satisfied by matrices. J. Algebra 55 (1978), no. 2, 509--520; MR523471 (80j:15012)] proved that such laws are a ``consequence" of a finite set of laws and for $n=2$ he exhibited $4$ generators called Robson cubics. Here the author considers the special case when $\alpha$ is a symmetric or skew-s…
Classification of Fragility Fractures of the Pelvis
2017
The characteristics of fragility fractures of the pelvis are different from pelvic fractures in adolescents and adults. There are specific fracture morphologies such as U- or H-shaped fractures of the sacrum and bilateral fractures. The classification systems of AO/ASIF and Young-Burgess reflect the trauma mechanism and the type of instability in high-energy pelvic injuries. Not all types of fragility fractures of the pelvic ring fit into these classification systems. A new, comprehensive classification (FFP classification) includes all morphologies of fragility fractures of the pelvis, whether acute or chronic. It provides a framework for how to look at these lesions. The first criterion o…
The J-invariant, Tits algebras and Triality
2012
In the present paper we set up a connection between the indices of the Tits algebras of a simple linear algebraic group $G$ and the degree one parameters of its motivic $J$-invariant. Our main technical tool are the second Chern class map and Grothendieck's $\gamma$-filtration. As an application we recover some known results on the $J$-invariant of quadratic forms of small dimension; we describe all possible values of the $J$-invariant of an algebra with orthogonal involution up to degree 8 and give explicit examples; we establish several relations between the $J$-invariant of an algebra $A$ with orthogonal involution and the $J$-invariant of the corresponding quadratic form over the functi…
Steiner systems and configurations of points
2020
AbstractThe aim of this paper is to make a connection between design theory and algebraic geometry/commutative algebra. In particular, given any Steiner SystemS(t, n, v) we associate two ideals, in a suitable polynomial ring, defining a Steiner configuration of points and its Complement. We focus on the latter, studying its homological invariants, such as Hilbert Function and Betti numbers. We also study symbolic and regular powers associated to the ideal defining a Complement of a Steiner configuration of points, finding its Waldschmidt constant, regularity, bounds on its resurgence and asymptotic resurgence. We also compute the parameters of linear codes associated to any Steiner configur…
Synthesis of Lamellarin U and Lamellarin G Trimethyl Ether by Alkylation of a Deprotonated α-Aminonitrile
2008
1,2,3,4-Tetrahydroisoquinoline-1-carbonitriles can serve as starting materials for the one-pot synthesis of 5,6-dihydropyrrolo[2,1 a]isoquinolines and 1-benzyl-3,4-dihydroisoquinolines. The latter compounds were transformed to lamellarin G trimethyl ether and lamellarin U in short reaction sequences. This method allows the introduction of acid-sensitive protecting groups for the phenolic hydroxy functions which would be cleaved under the harsh conditions of the classical Bischler-Napieralski reaction.
New Tetromycin Derivatives with Anti-Trypanosomal and Protease Inhibitory Activities
2011
Four new tetromycin derivatives, tetromycins 1-4 and a previously known one, tetromycin B (5) were isolated from Streptomyces axinellae Pol001(T) cultivated from the Mediterranean sponge Axinella polypoides. Structures were assigned using extensive 1D and 2D NMR spectroscopy as well as HRESIMS analysis. The compounds were tested for antiparasitic activities against Leishmania major and Trypanosoma brucei, and for protease inhibition against several cysteine proteases such as falcipain, rhodesain, cathepsin L, cathepsin B, and viral proteases SARS-CoV M(pro), and PL(pro). The compounds showed antiparasitic activities against T. brucei and time-dependent inhibition of cathepsin L-like proteas…
Methodological Approach to Use Fresh and Cryopreserved Vessels as Tools to Analyze Pharmacological Modulation of the Angiogenic Growth
2016
The sprouting of new vessels is greatly influenced by the procedure chosen. We sought to optimize the experimental conditions of the angiogenic growth of fresh and cryopreserved vessels cultured in Matrigel with the aim to use this system to analyze the pharmacological modulation of the process. Segments of second-order branches of rat mesenteric resistance arteries, thoracic aorta of rat or mouse, and cryopreserved rat aorta and human femoral arteries were cultured in Matrigel for 7-21 days in different mediums, as well as in the absence of endothelial or adventitia layer. Quantification of the angiogenic growth was performed by either direct measurement of the mean length of the neovessel…
A retrospective analysis of myelodysplastic syndromes with thrombocytosis: reclassification of the cases by WHO proposals.
2004
Myelodysplastic syndromes (MDS) show occasionally thrombocytosis, common feature of myeloproliferative diseases (MPD), with the overlapping of both disorders. Classically, thrombocytosis has been associated with some MDS subtypes: refractory anaemia with ringed sideroblasts (RARS), 5q- syndrome and those MDS with 3q chromosome rearrangements. The recent WHO classification recognises an unclassifiable MDS/MPD category including some of these disorders. Our aim is to determine the frequency of presentation, subtype classification and chromosome abnormalities of MDS with thrombocytosis diagnosed in our institution. Between 1990 and 2003 we studied 317 SMD patients according to FAB and WHO revi…
Treatment of Malignant Ascites with a Second Cycle of Catumaxomab in Gastric Signet Cell Carcinoma - a Report of 2 Cases
2014
<b><i>Summary</i></b><b><i>Background: </i></b>Malignant ascites is a frequent complication in gastrointestinal malignancy and is unresponsive to systemic therapies. Therapeutic options are limited, and repeated paracentesis is associated with increased loss of fluids and proteins, and impaired quality of life. The bi-specific trifunctional antibody catumaxomab has been approved for the treatment of refractory ascites. It has been proposed that repeated application leads to formation of human anti-mouse antibodies with a decrease in effectiveness and potentially hypersensitivity reactions. <b><i>Case Report: </i></b>Her…
Visual quality with corneo-scleral contact lenses after intracorneal ring segment (ICRS) implantation for keratoconus management
2019
Purpose: To evaluate the visual quality results when fitting a corneo-scleral contact lens (CScL) after intracorneal ring segment (ICRS) implantation for keratoconus management. Methods: Twenty-seven eyes of 27 patients with keratoconus underwent ICRS implantation and had CScL fitted as their visual quality was unsatisfactory with their spectacles or contact lenses. Patients received a complete eye examination, refraction and visual acuity assessment, anterior eye biomicroscopy, ocular fundus examination, corneal topographic analysis, endothelial-cell count, and visual quality assessment using contrast sensitivity and aberrometry tests. A diagnostic trial set was used in the fitting process…