5,103 research outputs found
Radical Generic Initial Ideals
In this paper, we survey the theory of Cartwright\u2013Sturmfels ideals. These are \u2124n-graded ideals, whose multigraded generic initial ideal is radical. Cartwright\u2013Sturmfels ideals have surprising properties, mostly stemming from the fact that their Hilbert scheme only contains one Borel-fixed point. This has consequences, e.g., on their universal Gr\uf6bner bases and on the family of their initial ideals. In this paper, we discuss several known classes of Cartwright\u2013Sturmfels ideals and we find a new one. Among determinantal ideals of same-size minors of a matrix of variables and Schubert determinantal ideals, we are able to characterize those that are Cartwright\u2013Sturmfels
Semi-regular sequences and other random systems of equations
The security of multivariate cryptosystems and digital signature schemes
relies on the hardness of solving a system of polynomial equations over a
finite field. Polynomial system solving is also currently a bottleneck of
index-calculus algorithms to solve the elliptic and hyperelliptic curve
discrete logarithm problem. The complexity of solving a system of polynomial
equations is closely related to the cost of computing Groebner bases, since
computing the solutions of a polynomial system can be reduced to finding a
lexicographic Groebner basis for the ideal generated by the equations. Several
algorithms for computing such bases exist: We consider those based on repeated
Gaussian elimination of Macaulay matrices. In this paper, we analyze the case
of random systems, where random systems means either semi-regular systems, or
quadratic systems in n variables which contain a regular sequence of n
polynomials. We provide explicit formulae for bounds on the solving degree of
semi-regular systems with m > n equations in n variables, for equations of
arbitrary degrees for m = n+1, and for any m for systems of quadratic or cubic
polynomials. In the appendix, we provide a table of bounds for the solving
degree of semi-regular systems of m = n + k quadratic equations in n variables
for 2 <= k; n <= 100 and online we provide the values of the bounds for 2 <= k;
n <= 500. For quadratic systems which contain a regular sequence of n
polynomials, we argue that the Eisenbud-Green-Harris Conjecture, if true,
provides a sharp bound for their solving degree, which we compute explicitly.Comment: 27 pages, 4 table
Sc substitution for Mg in MgB2: effects on Tc and Kohn anomaly
Here we report synthesis and characterization of Mg_{1-x}Sc_{x}B_{2}
(0.12T_{c}>6 K.
We find that the Sc doping moves the chemical potential through the 2D/3D
electronic topological transition (ETT) in the sigma band where the ``shape
resonance" of interband pairing occurs. In the 3D regime beyond the ETT we
observe a hardening of the E_{2g} Raman mode with a significant line-width
narrowing due to suppression of the Kohn anomaly over the range 0<q<2k_{F}.Comment: 8 pages, 4 EPS figures, to be published in Phys. Rev.
No measure for culture? Value in the new economy
This paper explores articulations of the value of investment in culture and the arts through a critical discourse analysis of policy documents, reports and academic commentary since 1997. It argues that in this period, discourses around the value of culture have moved from a focus on the direct economic contributions of the culture industries to their indirect economic benefits. These indirect benefits are discussed here under three main headings: creativity and innovation, employability, and social inclusion. These are in turn analysed in terms of three forms of capital: human, social and cultural. The paper concludes with an analysis of this discursive shift through the lens of autonomist Marxist concerns with the labour of social reproduction. It is our argument that, in contemporary policy discourses on culture and the arts, the government in the UK is increasingly concerned with the use of culture to form the social in the image of capital. As such, we must turn our attention beyond the walls of the factory in order to understand the contemporary capitalist production of value and resistance to it. </jats:p
La inserción de América Latina en las cadenas globales de valor
Se examina la integración de firmas latinoamericanas al modelo de Cadenas Globales de Valor (CGV), analizando la formación de cadenas lideradas por firmas de los países de América Latina y evaluando su impacto sobre el comercio, la inversión y el dualismo estructural. Aunque la adopción de cadenas globales de valor aún es incipiente en la región y es bastante heterogénea entre países, existen prácticas diversas de esta nueva forma de organizar la producción que son relevantes no sólo para la comprensión de su impacto en la economía de la región, sino también para la concepción de políticas e incentivos en este dominio. Se presentan reseñas sobre los países de América del Sur, América Central y México, así como análisis de casos específicos de las cadenas electrónica y automovilística brasileñas
Increased incidence of breast cancer in postmenopausal women with high body mass index at the modena screening program
Purpose: We conducted a study to evaluate the relationship between body mass index (BMI) and the risk of breast cancer (BC) and outcome in a population of 14,684 women aged 55 to 69 years eligible to participate in the Mammography Screening Program (MSP) in the Province of Modena, Italy. Methods: The study population was drawn from women who underwent mammography screening between 2004 and 2006 in the Province of Modena. Women were subdivided into obese, overweight, and normal-weight categories according to BMI and followed until July 31, 2010, to evaluate the BC incidence. The clinicopathological characteristics of BC were also evaluated in different groups of patients classified according to BMI. After BC diagnosis, patients were followed for a median period of 65 (range, 2\u2013104) months. Second events (recurrences and second tumors) were recorded, and the 5-year event-free survival (EFS) was calculated. Results: After a period of 73 months, 366 cases of BC were diagnosed. Compared with normal-weight women, obese women had a significantly higher incidence of BC (relative risk [RR], 1.32; p= 0.040) (RR=1), larger tumors (27% of tumors were larger than T2 size), and more nodal involvement (38.5% of tumors were node-positive). Furthermore, a significantly higher rate of total events was seen in obese women compared with overweight and normal-weight patients, respectively (17.9% vs. 11.4% vs. 10.8%, p=0.032). The 5-year EFS was 89.0%, 89.0%, and 80.0% for normal-weight, overweight, and obese patients, respectively. Conclusion: We observed a significantly higher risk of BC in obese women among those eligible to participate in the MSP in the Province of Modena. Finally, obese women had more second events and poorer EFS compared to nono bese women
Linear resolutions of powers and products
The goal of this paper is to present examples of families of homogeneous
ideals in the polynomial ring over a field that satisfy the following
condition: every product of ideals of the family has a linear free resolution.
As we will see, this condition is strongly correlated to good primary
decompositions of the products and good homological and arithmetical properties
of the associated multi-Rees algebras. The following families will be discussed
in detail: polymatroidal ideals, ideals generated by linear forms and Borel
fixed ideals of maximal minors. The main tools are Gr\"obner bases and Sagbi
deformation
Operating Parameters Optimization for the Production of Liposomes Loaded with Antibodies Using a Supercritical Fluid-Assisted Process
Encapsulation of antibodies represents a significant advance to protect and deliver these therapeutics in a controlled manner, increasing the stability requested to cover the temporal gap between particle production and their administration. Furthermore, using encapsulation, extracellular, cell surface, and intracellular targets can be reached. This work examines the feasibility of encapsulating mouse IgG isotype control antibodies within phosphatidylcholine-based liposomes using a supercritical fluid-based process called SuperLip (Supercritical-assisted Liposome formation). This process allows a continuous production of both nano- and micrometric liposomes with high encapsulation efficiency working under mild operative conditions. The effect of some operative parameters has been studied on liposome mean diameter, particle size distribution, and antibody entrapment efficiency, comparing these data with those collected working with liposomes obtained by the thin-layer hydration technique. In particular, the effect of water flow rate and of the antibody loading were studied. Antibody-loaded liposomes with mean diameters in the range between 205 and 501 nm have been obtained by using a supercritical fluid-assisted process. High entrapment efficiencies up to 94% have been calculated
Markov basis and Groebner basis of Segre-Veronese configuration for testing independence in group-wise selections
We consider testing independence in group-wise selections with some
restrictions on combinations of choices. We present models for frequency data
of selections for which it is easy to perform conditional tests by Markov chain
Monte Carlo (MCMC) methods. When the restrictions on the combinations can be
described in terms of a Segre-Veronese configuration, an explicit form of a
Gr\"obner basis consisting of moves of degree two is readily available for
performing a Markov chain. We illustrate our setting with the National Center
Test for university entrance examinations in Japan. We also apply our method to
testing independence hypotheses involving genotypes at more than one locus or
haplotypes of alleles on the same chromosome.Comment: 25 pages, 5 figure
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