302 research outputs found
Data structures maxima
Projet EURECAThe purpose of this paper is to analyze the maxima properties (value and position) of some data structures. Our theorems concern the distribution of the random variables. Previously known results usually dealt with the mean and sometimes the variance of these random variables. Many of our results rely on diffusion techniques. That is a very powerful tool, which has already been used with some success in the analysis of algorithms
Generalized Integer Partitions, Tilings of Zonotopes and Lattices
In this paper, we study two kinds of combinatorial objects, generalized
integer partitions and tilings of two dimensional zonotopes, using dynamical
systems and order theory. We show that the sets of partitions ordered with a
simple dynamics, have the distributive lattice structure. Likewise, we show
that the set of tilings of zonotopes, ordered with a simple and classical
dynamics, is the disjoint union of distributive lattices which we describe. We
also discuss the special case of linear integer partitions, for which other
dynamical systems exist. These results give a better understanding of the
behaviour of tilings of zonotopes with flips and dynamical systems involving
partitions.Comment: See http://www.liafa.jussieu.fr/~latapy
d-Tubocurarine and Berbamine: Alkaloids That Are Permeant Blockers of the Hair Cell's Mechano-Electrical Transducer Channel and Protect from Aminoglycoside Toxicity
Aminoglycoside antibiotics are widely used for the treatment of life-threatening bacterial infections, but cause permanent hearing loss in a substantial proportion of treated patients. The sensory hair cells of the inner ear are damaged following entry of these antibiotics via the mechano-electrical transducer (MET) channels located at the tips of the hair cellâs stereocilia. d-Tubocurarine (dTC) is a MET channel blocker that reduces the loading of gentamicin-Texas Red (GTTR) into rat cochlear hair cells and protects them from gentamicin treatment. Berbamine is a structurally related alkaloid that reduces GTTR labeling of zebrafish lateral-line hair cells and protects them from aminoglycoside-induced cell death. Both compounds are thought to reduce aminoglycoside entry into hair cells through the MET channels. Here we show that dTC (â„6.25 ”M) or berbamine (â„1.55 ”M) protect zebrafish hair cells in vivo from neomycin (6.25 ”M, 1 h). Protection of zebrafish hair cells against gentamicin (10 ”M, 6 h) was provided by â„25 ”M dTC or â„12.5 ”M berbamine. Hair cells in mouse cochlear cultures are protected from longer-term exposure to gentamicin (5 ”M, 48 h) by 20 ”M berbamine or 25 ”M dTC. Berbamine is, however, highly toxic to mouse cochlear hair cells at higher concentrations (â„30 ”M) whilst dTC is not. The absence of toxicity in the zebrafish assays prompts caution in extrapolating results from zebrafish neuromasts to mammalian cochlear hair cells. MET current recordings from mouse outer hair cells (OHCs) show that both compounds are permeant open-channel blockers, rapidly and reversibly blocking the MET channel with half-blocking concentrations of 2.2 ”M (dTC) and 2.8 ”M (berbamine) in the presence of 1.3 mM Ca2+ at â104 mV. Berbamine, but not dTC, also blocks the hair cellâs basolateral K + current, IK,neo, and modeling studies indicate that berbamine permeates the MET channel more readily than dTC. These studies reveal key properties of MET-channel blockers required for the future design of successful otoprotectants
Design, synthesis and biological evaluation of a new series of carvedilol derivatives that protect sensory hair cells from aminoglycoside-induced damage by blocking the mechanoelectrical transducer channel
Aminoglycosides (AGs) are broad-spectrum antibiotics used for the treatment of serious bacterial infections but have use-limiting side effects including irreversible hearing loss. Here, we assessed the otoprotective profile of carvedilol in mouse cochlear cultures and in vivo zebrafish assays and investigated its mechanism of protection which, we found, may be mediated by a block of the hair cellâs mechanoelectrical transducer (MET) channel, the major entry route for the AGs. To understand the full otoprotective potential of carvedilol, a series of 18 analogues were prepared and evaluated for their effect against AG-induced damage as well as their affinity for the MET channel. One derivative was found to confer greater protection than carvedilol itself in cochlear cultures and also to bind more tightly to the MET channel. At higher concentrations, both carvedilol and this derivative were toxic in cochlear cultures but not in zebrafish, suggesting a good therapeutic window under in vivo conditions
Impacts, Trends and Sustainable Solutions
Infections with parasitic helminths (nematodes and trematodes) represent a
significant economic and welfare burden to the global ruminant livestock
industry. The increasing prevalence of anthelmintic resistance means that
current control programmes are costly and unsustainable in the long term.
Recent changes in the epidemiology, seasonality and geographic distribution of
helminth infections have been attributed to climate change. However, other
changes in environment (e.g., land use) and in livestock farming, such as
intensification and altered management practices, will also have an impact on
helminth infections. Sustainable control of helminth infections in a changing
world requires detailed knowledge of these interactions. In particular, there
is a need to devise new, sustainable strategies for the effective control of
ruminant helminthoses in the face of global change. In this paper, we consider
the impact of helminth infections in grazing ruminants, taking a European
perspective, and identify scientific and applied priorities to mitigate these
impacts. These include the development and deployment of efficient, high-
throughput diagnostic tests to support targeted intervention, modelling of
geographic and seasonal trends in infection, more thorough economic data and
analysis of the impact of helminth infections and greater translation and
involvement of end-users in devising and disseminating best practices. Complex
changes in helminth epidemiology will require innovative solutions. By
developing and using new technologies and models, the use of anthelmintics can
be optimised to limit the development and spread of drug resistance and to
reduce the overall economic impact of helminth infections. This will be
essential to the continued productivity and profitability of livestock farming
in Europe and its contribution to regional and global food security. View
Full-Tex
AMI-LA radio continuum observations of Spitzer c2d small clouds and cores: Perseus region
We present deep radio continuum observations of the cores identified as
deeply embedded young stellar objects in the Perseus molecular cloud by the
Spitzer c2d programme at a wavelength of 1.8 cm with the Arcminute Microkelvin
Imager Large Array (AMI-LA). We detect 72% of Class 0 objects from this sample
and 31% of Class I objects. No starless cores are detected. We use the flux
densities measured from these data to improve constraints on the correlations
between radio luminosity and bolometric luminosity, infrared luminosity and,
where measured, outflow force. We discuss the differing behaviour of these
objects as a function of protostellar class and investigate the differences in
radio emission as a function of core mass. Two of four possible very low
luminosity objects (VeLLOs) are detected at 1.8 cm.Comment: 18 pages, 9 figures, accepted MNRA
AMI Large Array radio continuum observations of Spitzer c2d small clouds and cores
We perform deep 1.8 cm radio continuum imaging towards thirteen protostellar
regions selected from the Spitzer c2d small clouds and cores programme at high
resolution (25") in order to detect and quantify the cm-wave emission from
deeply embedded young protostars. Within these regions we detect fifteen
compact radio sources which we identify as radio protostars including two
probable new detections. The sample is in general of low bolometric luminosity
and contains several of the newly detected VeLLO sources. We determine the 1.8
cm radio luminosity to bolometric luminosity correlation, L_rad -L_bol, for the
sample and discuss the nature of the radio emission in terms of the available
sources of ionized gas. We also investigate the L_rad-L_IR correlation and
suggest that radio flux density may be used as a proxy for the internal
luminosity of low luminosity protostars.Comment: submitted MNRA
Spanning Trees on Graphs and Lattices in d Dimensions
The problem of enumerating spanning trees on graphs and lattices is
considered. We obtain bounds on the number of spanning trees and
establish inequalities relating the numbers of spanning trees of different
graphs or lattices. A general formulation is presented for the enumeration of
spanning trees on lattices in dimensions, and is applied to the
hypercubic, body-centered cubic, face-centered cubic, and specific planar
lattices including the kagom\'e, diced, 4-8-8 (bathroom-tile), Union Jack, and
3-12-12 lattices. This leads to closed-form expressions for for these
lattices of finite sizes. We prove a theorem concerning the classes of graphs
and lattices with the property that
as the number of vertices , where is a finite
nonzero constant. This includes the bulk limit of lattices in any spatial
dimension, and also sections of lattices whose lengths in some dimensions go to
infinity while others are finite. We evaluate exactly for the
lattices we considered, and discuss the dependence of on d and the
lattice coordination number. We also establish a relation connecting to the free energy of the critical Ising model for planar lattices .Comment: 28 pages, latex, 1 postscript figure, J. Phys. A, in pres
- âŠ