813 research outputs found
Frobenius pairs in abelian categories: correspondences with cotorsion pairs, exact model categories, and Auslander-Buchweitz contexts
In this work, we revisit Auslander-Buchweitz Approximation Theory and find
some relations with cotorsion pairs and model category structures. From the
notions of relatives generators and cogenerators in Approximation Theory, we
introduce the concept of left Frobenius pairs in an
abelian category . We show how to construct from
a projective exact model structure on
, as a result of Hovey-Gillespie Correspondence applied to
two compatible and complete cotorsion pairs in . These
pairs can be regarded as examples of what we call cotorsion pairs relative to a
thick subcategory of . We establish some correspondences between
Frobenius pairs, relative cotorsion pairs, exact model structures and
Auslander-Buchweitz contexts. Finally, some applications of these results are
given in the context of Gorenstein homological algebra by generalizing some
existing model structures on the categories of modules over Gorenstein and
Ding-Chen rings, and by encoding the stable module category of a ring as a
certain homotopy category. We also present some connections with perfect
cotorsion pairs, covering classes, and cotilting modules.Comment: 54 pages, 10 figures. The statement and proof of 2.6.21 was
corrected. Typos corrected. Section 4 was improved, and new results in
Section 5 were adde
Balanced systems for
From the notion of (co)generator in relative homological algebra, we present
the concept of finite balanced system as a tool to induce balanced pairs for the functor with domain determined by the finiteness of
homological dimensions relative to and .
This approach to balance will cover several well known ambients where right
derived functors of are obtained relative to certain classes of
objects in an abelian category, such as Gorenstein projective and injective
modules and chain complexes, Gorenstein modules relative to Auslander and Bass
classes, among others
Cut cotorsion pairs
We present the concept of cotorsion pairs cut along subcategories of an
abelian category. This provides a generalization of complete cotorsion pairs,
and represents a general framework to find approximations restricted to certain
subcategories. We also exhibit some connections between cut cotorsion pairs and
Auslander-Buchweitz approximation theory, by considering relative analogs for
Frobenius pairs and Auslander-Buchweitz contexts. Several applications are
given in the settings of relative Gorenstein homological algebra, chain
complexes and quasi-coherent sheaves, but also to characterize some important
results on the Finitistic Dimension Conjecture, the existence of right adjoints
of quotient functors by Serre subcategories, and the description of cotorsion
pairs in triangulated categories as co--structures.Comment: 48 page
Expression of human eukaryotic initiation factor 3f oscillates with cell cycle in A549 cells and is essential for cell viability
<p>Abstract</p> <p>Background</p> <p>Transcriptional and postranslational regulation of the cell cycle has been widely studied. However, there is scarce knowledge concerning translational control of this process. Several mammalian eukaryotic initiation factors (eIFs) seem to be implicated in controlling cell proliferation. In this work, we investigated if the human eIF3f expression and function is cell cycle related.</p> <p>Results</p> <p>The human eIF3f expression has been found to be upregulated in growth-stimulated A549 cells and downregulated in G0. Western blot analysis and eIF3f promotor-luciferase fusions revealed that eIF3f expression peaks twice in the cell cycle: in the S and the M phases. Deregulation of eIF3f expression negatively affects cell viability and induces apoptosis.</p> <p>Conclusions</p> <p>The expression pattern of human eIF3f during the cell cycle confirms that this gene is cell division related. The fact that eIF3f expression peaks in two cell cycle phases raises the possibility that this gene may exert a differential function in the S and M phases. Our results strongly suggest that eIF3f is essential for cell proliferation.</p
Estrategia aplicada a simulador de negocios Capstone
El siguiente documento tiene como objetivo describir, analizar y reflexionar sobre la gestión estratégica de una compañía dentro de la industria de sensores durante un tiempo de ocho años en un ambiente virtual, el cual es facilitado por Capsima a través de su aplicación de simulador de negocios Capstone. De igual forma, se presentan conceptos, teorías y estudios de empresas líderes sobre estrategias de negocios que permiten entender con mayor profundidad el tema
Faint recombination lines in Galactic PNe with [WC] nucleus
We present spatially resolved high-resolution spectrophotometric data for the
planetary nebulae PB8, NGC2867, and PB6. We have analyzed two knots in NGC2867
and PB6 and one in PB8. The three nebulae are ionized by [WC] type nuclei:
early [WO] for PB6 and NGC2867 and [WC 5-6] in the case of PB8. Our aim is to
study the behavior of the abundance discrepancy problem (ADF) in this type of
PNe. We measured a large number of optical recombination (ORL) and
collisionally excited lines (CEL), from different ionization stages (many more
than in any previous work), thus, we were able to derive physical conditions
from many different diagnostic procedures. We determined ionic abundances from
the available collisionally excited lines and recombination lines. Based on
both sets of ionic abundances, we derived total chemical abundances in the
nebulae using suitable ionization correction factors. From CELs, we have found
abundances typical of Galactic disk planetary nebulae. Moderate ADF(O++) were
found for PB8 (2.57) and NGC2867 (1.63). For NGC2867, abundances from ORLs are
higher but still consistent with Galactic disk planetary nebulae. On the
contrary, PB8 presents a very high O/H ratio from ORLs. A high C/O was obtained
from ORLs for NGC2867; this ratio is similar to C/O obtained from CELs and with
the chemical composition of the wind of the central star, indicating that there
was no further C-enrichment in the star, relative to O, after the nebular
material ejection. On the contrary, we found C/O<1 in PB8. Interestingly, we
obtain (C/O)ORLs/(C/O)CELs < 1 in PB8 and NGC2867; this added to the similarity
between the heliocentric velocities measured in [OIII] and OII lines for our
three objects, argue against the presence of H-deficient metal-rich knots
coming from a late thermal pulse event.Comment: 25 pages, 13 Tables, 4 Figures Accepted for publication in A&A. First
page is blank for obscure latex reason
New measurement of the 242Pu(n,γ) cross section at n_TOF
WONDER-2015 – 4th International Workshop On Nuclear Data Evaluation for Reactor applicationsThe use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight capture cross section measurement. In order to contribute to a new evaluation, we have perfomed a neutron capture cross section measurement at the n_TOF-EAR1 facility at CERN using four C6D6 detectors, using a high purity target of 95 mg. The preliminary results assessing the quality and limitations (background, statistics and γ-flash effects) of this new experimental data are presented and discussed, taking into account that the aimed accuracy of the measurement ranges between 7% and 12% depending on the neutron energy regionMinisterio de Economía y Competitividad FPA2013-45083-PMinisterio de Economía y Competitividad FPA2014-53290-C2-2-
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