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Search Results: 1 - 10 of 1359 matches for " Ari Cukierman "
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New Bounds on the Minimum Density of a Vertex Identifying Code for the Infinite Hexagonal Grid
Ari Cukierman,Gexin Yu
Mathematics , 2011,
Abstract: For a graph, $G$, and a vertex $v \in V(G)$, let $N[v]$ be the set of vertices adjacent to and including $v$. A set $D \subseteq V(G)$ is a vertex identifying code if for any two distinct vertices $v_1, v_2 \in V(G)$, the vertex sets $N[v_1] \cap D$ and $N[v_2] \cap D$ are distinct and non-empty. We consider the minimum density of a vertex identifying code for the infinite hexagonal grid. In 2000, Cohen et al. constructed two codes with a density of $3/7 \approx 0.428571$, and this remains the best known upper bound. Until now, the best known lower bound was $12/29 \approx 0.413793$ and was proved by Cranston and Yu in 2009. We present three new codes with a density of 3/7, and we improve the lower bound to $5/12 \approx 0.416667$.
Nezavisnost centralne banke i institucije monetarne politike - pro lost, sada njost i budu nost
Cukierman Alex
Panoeconomicus , 2007, DOI: 10.2298/pan0704367c
Abstract: nema
A criterion for positive polynomials
Fernando Cukierman
Mathematics , 2003,
Abstract: Let F be a homogeneous real polynomial of even degree in any number of variables. We consider the problem of giving explicit conditions on the coefficients so that F is positive definite or positive semi-definite. In this note we produce a necessary condition for positivity and a sufficient condition for non-negativity, in terms of positivity or semi-positivity of a one-variable characteristic polynomial of F. Also, we review another well-known sufficient condition.
Determinant of complexes and higher Hessians
Fernando Cukierman
Mathematics , 1996,
Abstract: Let $X \subset \Bbb P^r$ be a smooth algebraic curve in projective space, over an algebraically closed field of characteristic zero. For each $m \in \Bbb N$, the $m$-flexes of $X$ are defined as the points where the osculating hypersurface of degree $m$ has higher contact than expected, and a hypersurface $H \subset \Bbb P^r$ is called a $m$-Hessian if it cuts $X$ along its $m$-flexes. When $X$ is a complete intersection, we give an expression for a (rational) $m$-Hessian as the Div (in the sense of Grothendieck-Knudsen-Mumford) of a complex of graded free modules naturally associated to $X$. The construction of this complex involves relating sheaves of differential operators on a scheme and a subscheme, and higher Euler sequences on projective space.
Varieties of complexes and foliations
Fernando Cukierman
Mathematics , 2011,
Abstract: Let $\mathcal F(r, d)$ denote the moduli space of algebraic foliations of codimension one and degree $d$ in complex proyective space of dimension $r$. We show that $\mathcal F(r, d)$ may be represented as a certain linear section of a variety of complexes. From this fact we obtain information on the irreducible components of $\mathcal F(r, d)$.
Estegomiias em conserva e micróbios de vinha-d'alhos: o Brasil triunfa em Berlim
Cukierman, Henrique Luiz;
História, Ciências, Saúde-Manguinhos , 2001, DOI: 10.1590/S0104-59702001000600001
Abstract: this article investigates the circumstances leading to brazil being awarded the first prize at the xiv international conference on demography and hygiene, held in berlin in 1907. an examination of the unpublished correspondence between henrique da rocha lima and oswaldo cruz prior to the conference/exhibition reveals the peculiarities of a brazilian-style event, where the outcome seems to be determined by haphazard incidents rather than by meticulously planned strategies. their letters can also be read as a narrative celebrating individual qualities, as they attribute the victory in berlin much more to rocha lima's than oswaldo cruz's personal merits. in the light of raízes do brasil, a classic by sérgio buarque de holanda, this article also addresses the issue regarding the dispute between the iberian and anglo-saxon worlds over the brazilian victory.
Viagem(ns) a Santos
Cukierman, Henrique Luiz;
História, Ciências, Saúde-Manguinhos , 1998, DOI: 10.1590/S0104-59701998000100002
Abstract: the article intends to shed some light on the creation of the manguinhos laboratory by recounting an episode which predates it: the journey to santos taken in 1899 by oswaldo cruz, a young physician about to become a national hero and the brazilian symbol of science. destined to confirm the arrival of the infamous bubonic plague in brazil for the first time, this journey was a milestone in justifying construction of a factory to produce anti-plague serum in rio de janeiro - the future instituto soroterápico federal, inaugurated in 1900 and later embryo of the manguinhos laboratory. four different narratives of this journey reveal different processes of ?creating the world?, each arriving at its own interpretation of the same journey.
Estegomiias em conserva e micróbios de vinha-d'alhos: o Brasil triunfa em Berlim
Cukierman Henrique Luiz
História, Ciências, Saúde-Manguinhos , 2001,
Abstract: O artigo investiga as circunstancias que levaram o Brasil a alcan ar o primeiro prêmio na XIV Exposi o de Higiene e Demografia, em Berlim, em 1907. A partir da inédita correspondência trocada entre Henrique da Rocha Lima e Oswaldo Cruz às vésperas da exposi o, é possível observar as agruras do empreendimento à brasileira, onde aquilo que se parecia a uma cuidadosa estratégia revela-se como um turbilh o de acontecimentos, no qual a sorte da participa o brasileira dependeu de situa es pouco ou nada delineadas por planejamento meticuloso e previdente. A correspondência revela ainda que, se assumidas as narrativas glorificadoras de méritos pessoais, a vitória em Berlim foi muito mais de Rocha Lima que de Oswaldo Cruz. à luz de Raízes do Brasil, de Sérgio Buarque de Holanda, outra quest o abordada diz respeito ao embate entre os mundos ibérico e anglo-sax nico na constru o e no reconhecimento da vitória brasileira.
Development and Environmental Applications of Activated Carbon Cloths
Ana Lea Cukierman
ISRN Chemical Engineering , 2013, DOI: 10.1155/2013/261523
Abstract:
Development and Environmental Applications of Activated Carbon Cloths
Ana Lea Cukierman
ISRN Chemical Engineering , 2013, DOI: 10.1155/2013/261523
Abstract: Activated carbon cloths have received growing attention because they offer comparative advantages over the traditional powdered or granular forms of this well-known adsorbent, providing further potential uses for technological innovations in several fields. The present article provides an overview of research studies and advances concerned with the development of activated carbon cloths and their use as adsorbent in environmental applications, mostly reported in the last years. The influence of some fabrics and textile wastes used as precursors, and of main activation process variables on the development and physicochemical, mechanical and/or electrical properties of the resulting activated carbon cloths are first reviewed. Then, investigations dealing with the removal of water and air pollutants by adsorption onto activated carbon cloths, including advances toward optimizing their regeneration after organic vapors saturation, are presented. 1. Introduction Activated carbon in powdered and granular forms is a well-known, versatile adsorbent of widespread use in a broad spectrum of applications, including purification, remediation of polluted aquatic environments, treatment of liquid and gaseous effluents generated in industry, gas storage and delivery, metal recovery, catalysis, and biomedical applications, among various others [1–12]. Growing concern and stricter regulations pertaining to environmental pollution have led to the increase of the activated carbon demand, which is forecasted to continue raising in the near future [13, 14]. In the last years, activated carbon cloths (ACCs) have gained increasing interest because they offer comparative advantages over the traditional forms and potentialities for technological innovation in different fields, including their potential use in cell therapy, as a support for stem cell growth [15]. Main advantages arise from the small diameter of the fibers constituting ACC [16]. They include faster adsorption kinetics, higher efficiency, and larger capacity for adsorption due to the higher surface area and pore volume of the ACC. In particular, micropores (<2?nm) of ACC are directly connected to the external surface area, thus diminishing heat and mass transfer resistances and lowering pressure drops in flow units [3, 17–20]. Besides, activated carbon cloths are light materials that can be arranged in different stable configurations and provide a contiguous carbon form suited for electrical and electrochemical applications [21–24]. Moreover, Joule effect heating of ACC offers additional benefits in terms of
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