5,116 research outputs found
RURAL CREDIT RATIONING AND NATIONAL DEVELOPMENT BANKS IN DEVELOPING COUNTRIES
A common problem in agricultural credit markets in developing countries is the coexistence of a competitive market equilibrium interest rate and credit rationing. The literature typically explains the existence of credit rationing in competitive credit markets using adverse selection and moral hazard. Unfortunately these analyses are not consistent with the empirical reality that developing countries deal with in terms of subsidized credit, especially in the agricultural sector. This paper presents an alternative explanation for credit rationing in the agricultural sector in developing countries based on the fact that the requested loans are usually for small amounts, with many farmers making applications. As a result, the costs of operation increase with the number of loans given, so that inefficiencies in credit allocation occur when national development banks are present. It is shown that credit rationing can be reduced if shutting-down the national development bank is a feasible policy. Two other cases show that a national development bank is welfare-improving if an incentive compatible contract is used.Financial Economics,
Probabilistic models of individual and collective animal behavior
Recent developments in automated tracking allow uninterrupted,
high-resolution recording of animal trajectories, sometimes coupled with the
identification of stereotyped changes of body pose or other behaviors of
interest. Analysis and interpretation of such data represents a challenge: the
timing of animal behaviors may be stochastic and modulated by kinematic
variables, by the interaction with the environment or with the conspecifics
within the animal group, and dependent on internal cognitive or behavioral
state of the individual. Existing models for collective motion typically fail
to incorporate the discrete, stochastic, and internal-state-dependent aspects
of behavior, while models focusing on individual animal behavior typically
ignore the spatial aspects of the problem. Here we propose a probabilistic
modeling framework to address this gap. Each animal can switch stochastically
between different behavioral states, with each state resulting in a possibly
different law of motion through space. Switching rates for behavioral
transitions can depend in a very general way, which we seek to identify from
data, on the effects of the environment as well as the interaction between the
animals. We represent the switching dynamics as a Generalized Linear Model and
show that: (i) forward simulation of multiple interacting animals is possible
using a variant of the Gillespie's Stochastic Simulation Algorithm; (ii)
formulated properly, the maximum likelihood inference of switching rate
functions is tractably solvable by gradient descent; (iii) model selection can
be used to identify factors that modulate behavioral state switching and to
appropriately adjust model complexity to data. To illustrate our framework, we
apply it to two synthetic models of animal motion and to real zebrafish
tracking data.Comment: 26 pages, 11 figure
Rapes seldom reported
Statistics from the Rape Crisis Center in Bangor suggest that for every rape reported at UMO each year, 10 others have probably occurred, said UMO\u27s assistant director of police services William Prosser. The Rape Crisis Center bases unreported rape figures on calls [it] gets for assistance compared to the number of police reports generated due to rape, Prosser said
A generalization of Gabriel's Galois covering functors and derived equivalences
Let be a group acting on a category . We give a definition
for a functor to be a -covering and
three constructions of the orbit category , which generalizes
the notion of a Galois covering of locally finite-dimensional categories with
group whose action on is free and locally bonded defined by
Gabriel. Here is defined for any category and we
do not require that the action of is free or locally bounded. We show that
a -covering is a universal "-invariant" functor and is essentially given
by the canonical functor . By using this we
improve a covering technique for derived equivalence. Also we prove theorems
describing the relationships between smash product construction and the orbit
category construction by Cibils and Marcos (2006) without the assumption that
the -action is free. The orbit category construction by a cyclic group
generated by an auto-equivalence modulo natural isomorphisms (e.g., the
construction of cluster categories) is justified by a notion of the "colimit
orbit category". In addition, we give a presentation of the orbit category of a
category with a monoid action by a quiver with relations, which enables us to
calculate many examples.Comment: Title changed. Definitions of and
in section 6 were corrected. Proof of Theorem 8.1
is slightly changed to make it more readable. Other minor change
Global Dimension of Polynomial Rings in Partially Commuting Variables
For any free partially commutative monoid , we compute the global
dimension of the category of -objects in an Abelian category with exact
coproducts. As a corollary, we generalize Hilbert's Syzygy Theorem to
polynomial rings in partially commuting variables.Comment: 11 pages, 2 figure
Contribution du régulon sigma B à la pathogenèse de variants de STAPHYLOCOCCUS AUREUS formant de petites colonies lors d'infections pulmonaires chroniques chez les patients atteints de fibrose kystique
Bien que la fibrose kystique soit fondamentalement causée par une défectuosité génétique, les infections microbiennes sont la plus grande cause de mortalité des gens qui en sont atteints. La bactérie Staphylococcus aureus est un des pathogènes les plus communs associés à cette maladie et est la cause d'infections persistantes et difficiles à traiter. Des souches variantes de S. aureus formant de petites colonies (les s[barbelow]mall-c[barbelow]olony v[barbelow]ariants ou SCVs) sont fréquemment isolées des voies respiratoires des patients atteints de fibrose kystique lors d'infections bactériennes chroniques. Mon projet de doctorat a consisté à déterminer les bases moléculaires de la persistance des infections pulmonaires à S. aureus chez les patients atteints de fibrose kystique et, plus particulièrement, le rôle des SCVs dans l'établissement d'infections chroniques. Mes principaux efforts de recherche ont été dirigés vers la compréhension du rôle de gènes et de phénotypes influencés par le facteur de transcription sigma alternatif sigma B dont l'activité est accrue chez les SCVs. Les mécanismes moléculaires par lesquels ce facteur de transcription influence la formation de biofilm, la persistance à l'intérieur des cellules de l'hôte et l'infection proprement dite ont été étudiés. Je me suis aussi intéressé à la compréhension des différents facteurs environnementaux et mécanismes moléculaires favorisant la présence et la persistance de S. aureus dans les poumons des patients fibrokystiques. Mes efforts de recherche ont également été dirigés vers l'élaboration d'antibiothérapies alternatives permettant de combattre les infections chroniques à S. aureu
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Cas9+ conditionally-immortalized macrophages as a tool for bacterial pathogenesis and beyond.
Macrophages play critical roles in immunity, development, tissue repair, and cancer, but studies of their function have been hampered by poorly-differentiated tumor cell lines and genetically-intractable primary cells. Here we report a facile system for genome editing in non-transformed macrophages by differentiating ER-Hoxb8 myeloid progenitors from Cas9-expressing transgenic mice. These conditionally immortalized macrophages (CIMs) retain characteristics of primary macrophages derived from the bone marrow yet allow for easy genetic manipulation and a virtually unlimited supply of cells. We demonstrate the utility of this system for dissection of host genetics during intracellular bacterial infection using two important human pathogens: Listeria monocytogenes and Mycobacterium tuberculosis
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Evasion of autophagy mediated by Rickettsia surface protein OmpB is critical for virulence.
Rickettsia are obligate intracellular bacteria that evade antimicrobial autophagy in the host cell cytosol by unknown mechanisms. Other cytosolic pathogens block different steps of autophagy targeting, including the initial step of polyubiquitin-coat formation. One mechanism of evasion is to mobilize actin to the bacterial surface. Here, we show that actin mobilization is insufficient to block autophagy recognition of the pathogen Rickettsia parkeri. Instead, R. parkeri employs outer membrane protein B (OmpB) to block ubiquitylation of the bacterial surface proteins, including OmpA, and subsequent recognition by autophagy receptors. OmpB is also required for the formation of a capsule-like layer. Although OmpB is dispensable for bacterial growth in endothelial cells, it is essential for R. parkeri to block autophagy in macrophages and to colonize mice because of its ability to promote autophagy evasion in immune cells. Our results indicate that OmpB acts as a protective shield to obstruct autophagy recognition, thereby revealing a distinctive bacterial mechanism to evade antimicrobial autophagy
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