92 research outputs found
A Coboundary Morphism For The Grothendieck Spectral Sequence
Given an abelian category with enough injectives we show that a
short exact sequence of chain complexes of objects in gives rise
to a short exact sequence of Cartan-Eilenberg resolutions. Using this we
construct coboundary morphisms between Grothendieck spectral sequences
associated to objects in a short exact sequence. We show that the coboundary
preserves the filtrations associated with the spectral sequences and give an
application of these result to filtrations in sheaf cohomology.Comment: 18 page
Categorification of a linear algebra identity and factorization of Serre functors
We provide a categorical interpretation of a well-known identity from linear
algebra as an isomorphism of certain functors between triangulated categories
arising from finite dimensional algebras.
As a consequence, we deduce that the Serre functor of a finite dimensional
triangular algebra A has always a lift, up to shift, to a product of suitably
defined reflection functors in the category of perfect complexes over the
trivial extension algebra of A.Comment: 18 pages; Minor changes, references added, new Section 2.
The Intrinsic Fundamental Group of a Linear Category
We provide an intrinsic definition of the fundamental group of a linear
category over a ring as the automorphism group of the fibre functor on Galois
coverings. If the universal covering exists, we prove that this group is
isomorphic to the Galois group of the universal covering. The grading deduced
from a Galois covering enables us to describe the canonical monomorphism from
its automorphism group to the first Hochschild-Mitchell cohomology vector
space.Comment: Final version, to appear in Algebras and Representation Theor
Hole-Doping Effects on a Two-dimensional Kondo Insulator
We study the effects of hole doping on the two-dimensional Heisenberg-Kondo
model around the quantum critical point, where the spin liquid phase (Kondo
insulator) and the magnetically ordered phase are separated via a second-order
phase transition. By means of the self-consistent Born approximation within the
bond operator formalism as well as the standard spin wave theory, we discuss
dynamical properties of a doped hole. It is clarified that a quasi-particle
state stabilized in the spin liquid phase is gradually obscured as the system
approaches the quantum critical point. This is also the case for the
magnetically ordered phase. We argue the similarity and the difference between
these two cases.Comment: 8 pages, 14 figure
Scalar extensions of triangulated categories
Given a triangulated category over a field and a field extension ,
we investigate how one can construct a triangulated category over . Our
approach produces the derived category of the base change scheme if the
category one starts with is the bounded derived category of a smooth projective
variety over and the field extension is finite and Galois. We also
investigate how the dimension of a triangulated category behaves under scalar
extensions.Comment: 15 pages, comments welcom
Tag-Aware Recommender Systems: A State-of-the-art Survey
In the past decade, Social Tagging Systems have attracted increasing
attention from both physical and computer science communities. Besides the
underlying structure and dynamics of tagging systems, many efforts have been
addressed to unify tagging information to reveal user behaviors and
preferences, extract the latent semantic relations among items, make
recommendations, and so on. Specifically, this article summarizes recent
progress about tag-aware recommender systems, emphasizing on the contributions
from three mainstream perspectives and approaches: network-based methods,
tensor-based methods, and the topic-based methods. Finally, we outline some
other tag-related works and future challenges of tag-aware recommendation
algorithms.Comment: 19 pages, 3 figure
Spatial Distribution of Human Schistosoma japonicum Infections in the Dongting Lake Region, China
BACKGROUND: The aim of this study was to spatially model the effect of demographic, reservoir hosts and environmental factors on human Schistosoma japonicum infection prevalence in the Dongting Lake area of Hunan Province, China and to determine the potential of each indicator in targeting schistosomiasis control. METHODOLOGY/PRINCIPAL FINDINGS: Cross-sectional serological, coprological and demographic data were obtained from the 2004 nationwide periodic epidemiologic survey for Hunan Province. Environmental data were downloaded from the USGS EROS data centre. Bayesian geostatistical models were employed for spatial analysis of the infection prevalence among study participants. A total of 47,139 participants from 47 administrative villages were selected. Age, sex and occupation of residents and the presence of infected buffaloes and environmental factors, i.e. NDVI, distance to the lake and endemic type of setting, were significantly associated with S. japonicum infection prevalence. After taking into account spatial correlation, however, only demographic factors (age, sex and occupation) and the presence of infected buffaloes remained significant indicators. CONCLUSIONS/SIGNIFICANCE: Long established demographic factors, as well presence of host reservoirs rather than environmental factors are driving human transmission. Findings of this work can be used for epidemiologic surveillance and for the future planning of interventions in the Dongting Lake area of Hunan Province
Developing Global Maps of the Dominant Anopheles Vectors of Human Malaria
Simon Hay and colleagues describe how the Malaria Atlas Project has collated anopheline occurrence data to map the geographic distributions of the dominant mosquito vectors of human malaria
Spatial Proximity and Similarity of the Epigenetic State of Genome Domains
Recent studies demonstrate that the organization of the chromatin within the nuclear space might play a crucial role in the regulation of gene expression. The ongoing progress in determination of the 3D structure of the nuclear chromatin allows one to study correlations between spatial proximity of genome domains and their epigenetic state. We combined the data on three-dimensional architecture of the whole human genome with results of high-throughput studies of the chromatin functional state and observed that fragments of different chromosomes that are spatially close tend to have similar patterns of histone modifications, methylation state, DNAse sensitivity, expression level, and chromatin states in general. Moreover, clustering of genome regions by spatial proximity produced compact clusters characterized by the high level of histone modifications and DNAse sensitivity and low methylation level, and loose clusters with the opposite characteristics. We also associated the spatial proximity data with previously detected chimeric transcripts and the results of RNA-seq experiments and observed that the frequency of formation of chimeric transcripts from fragments of two different chromosomes is higher among spatially proximal genome domains. A fair fraction of these chimeric transcripts seems to arise post-transcriptionally via trans-splicing
A look back to move ahead: New directions for research on proactive performance and other discretionary work behaviours
Over the last two decades, the multi-dimensional notion of job performance has been fully brought to life. The differentiation between core task performance and various aspects of discretionary work behaviour is now commonly applied. A multitude of empirical studies, enhancing our knowledge of the antecedents and consequences of the different performance aspects, have recently been summarised through various meta-analyses. We use this as an occasion for taking stock in order to identify new areas of theorising and empirical research. Focusing in particular on proactive performance aspects, the present paper identifies three themes that could inspire new research and model development. We suggest taking a new approach to the treatment of time in order to account for the dynamic nature of performance on the one hand, and to consider life-span changes on the other, developing comprehensive models on proactivity-enhancing interventions, and more strongly incorporating a cross- cultural perspective
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