571 research outputs found
A Guide to Delineate the Logic of Neurovascular Signaling in the Brain
The neurovascular system may be viewed as a distributed nervous system within the brain. It transforms local neuronal activity into a change in the tone of smooth muscle that lines the walls of arterioles and microvessels. We review the current state of neurovascular coupling, with an emphasis on signaling molecules that convey information from neurons to neighboring vessels. At the level of neocortex, this coupling is mediated by: (i) a likely direct interaction with inhibitory neurons, (ii) indirect interaction, via astrocytes, with excitatory neurons, and (iii) fiber tracts from subcortical layers. Substantial evidence shows that control involves competition between signals that promote vasoconstriction versus vasodilation. Consistent with this picture is evidence that, under certain circumstances, increased neuronal activity can lead to vasoconstriction rather than vasodilation. This confounds naïve interpretations of functional brain images. We discuss experimental approaches to detect signaling molecules in vivo with the goal of formulating an empirical basis for the observed logic of neurovascular control
Communication Strategy, Central Banking and Credibility Bonus - A Study Dealing with 'Impossible Trinity' in Indian Context
Monetary Policy and Polish Labour Market in the years 1999 - 2008
This article sets out to analyse how the monetary policy pursued by the National Bank of Poland (NBP) determined the labour market situation in the country in the decade 1999-2008. The article consists of introduction as well as five sections. Section one discusses NBP's strategy of monetary policy in the defined period against monetary strategies implemented in other countries. Section two uses the growth rates of money supply and of real GDP to verify whether the primary purpose of monetary policy, i.e. the inflationary target, was achieved. Section three generally characterises the country's labour market using the levels and dynamics of employment and of unemployment. Section four discusses major instruments of NBP's monetary policy, mainly analysing changes in the central bank's interest rates and their effect on the economic situation and on the labour market. The article concludes with a summation providing synthetic conclusions.Celem artykułu jest analiza wpływu polityki monetarnej Narodowego Banku Polskiego (NBP) na sytuację na rynku pracy w Polsce w ciągu dekady obejmującej lata 1999-2008. Opracowanie składa się z wprowadzenia oraz pięciu części. W pierwszej z nich omówiona została strategia polityki monetarnej NBP w badanym okresie wraz z porównaniem ze strategią przyjmowaną w innych krajach. W części drugiej sprawdzono, czy realizowany był podstawowy cel polityki monetarnej, czyli cel inflacyjny, w kontekście kształtowania się stóp wzrostu podaży pieniądza oraz realnego PKB. W punkcie kolejnym ukazana została ogólna charakterystyka rynku pracy na podstawie kształtowania się poziomu i dynamiki zatrudnienia oraz bezrobocia. W części czwartej omówiono podstawowe instrumenty polityki pieniężnej NBP. Uwaga skoncentrowana została głównie na analizie zmian stóp procentowych banku centralnego oraz ich wpływu na sytuację gospodarczą i rynek pracy. Całość zamknięta została podsumowaniem, w którym zawarto syntetyczne wnioski końcowe
Quantifying loopy network architectures
Biology presents many examples of planar distribution and structural networks
having dense sets of closed loops. An archetype of this form of network
organization is the vasculature of dicotyledonous leaves, which showcases a
hierarchically-nested architecture containing closed loops at many different
levels. Although a number of methods have been proposed to measure aspects of
the structure of such networks, a robust metric to quantify their hierarchical
organization is still lacking. We present an algorithmic framework, the
hierarchical loop decomposition, that allows mapping loopy networks to binary
trees, preserving in the connectivity of the trees the architecture of the
original graph. We apply this framework to investigate computer generated
graphs, such as artificial models and optimal distribution networks, as well as
natural graphs extracted from digitized images of dicotyledonous leaves and
vasculature of rat cerebral neocortex. We calculate various metrics based on
the Asymmetry, the cumulative size distribution and the Strahler bifurcation
ratios of the corresponding trees and discuss the relationship of these
quantities to the architectural organization of the original graphs. This
algorithmic framework decouples the geometric information (exact location of
edges and nodes) from the metric topology (connectivity and edge weight) and it
ultimately allows us to perform a quantitative statistical comparison between
predictions of theoretical models and naturally occurring loopy graphs.Comment: 17 pages, 8 figures. During preparation of this manuscript the
authors became aware of the work of Mileyko at al., concurrently submitted
for publicatio
The blind monks and the elephant : contrasting narratives of financial crisis
Three persuasive narratives of the US subprime crisis are explored with reference both to theory and to emergency acts of public policy undertaken. First the role of pecuniary externalities that amplify any shocks to the quality of risk-assets held by Investment Banks and others. Second is adverse selection in marketing these assets; and third the role of financial panic in making investment-banking disaster-prone. How relevant these differing perspectives proved is attested by the nature of state support and by subsequent findings in courts of law.
As Chair of the US Federal Reserve, Janet Yellen argued that vulnerabilities within the US financial system in the mid-2000s were “numerous and familiar from past financial panics”. That the varied threats to stability featuring in these narratives should be complements and not substitutes is of more than technical interest: it helps to explain why the US financial system was so exposed to radical failure
Why are Prices Sticky? Evidence from Business Survey Data
This paper offers new insights on the price setting behaviour of German retail firms using a novel dataset that
consists of a large panel of monthly business surveys from 1991-2006. The firm-level data allows matching changes
in firms' prices to several other firm-characteristics. Moreover, information on price expectations allow analyzing
the determinants of price updating. Using univariate and bivariate ordered probit specifications, empirical menu
cost models are estimated relating the probability of price adjustment and price updating, respectively, to both
time- and state- dependent variables. First, results suggest an important role for state-dependence; changes in
the macroeconomic and institutional environment as well as firm-specific factors are significantly related to the
timing of price adjustment. These findings imply that price setting models should endogenize the timing of price
adjustment in order to generate realistic predictions concerning the transmission of monetary policy. Second, an
analysis of price expectations yields similar results providing evidence in favour of state-dependent sticky plan
models. Third, intermediate input cost changes are among the most important determinants of price adjustment
suggesting that pricing models should explicitly incorporate price setting at different production stages. However, the results show that adjustment to input cost changes takes time indicating "additional stickiness" at the last stage of processing
Green functions for generalized point interactions in 1D: A scattering approach
Recently, general point interactions in one dimension has been used to model
a large number of different phenomena in quantum mechanics. Such potentials,
however, requires some sort of regularization to lead to meaningful results.
The usual ways to do so rely on technicalities which may hide important
physical aspects of the problem. In this work we present a new method to
calculate the exact Green functions for general point interactions in 1D. Our
approach differs from previous ones because it is based only on physical
quantities, namely, the scattering coefficients, and , to construct .
Renormalization or particular mathematical prescriptions are not invoked. The
simple formulation of the method makes it easy to extend to more general
contexts, such as for lattices of general point interactions; on a line; on
a half-line; under periodic boundary conditions; and confined in a box.Comment: Revtex, 9 pages, 3 EPS figures. To be published in PR
Understanding Dermatan Sulfate−Heparin Cofactor II Interaction through Virtual Library Screening
- …