1,706 research outputs found
Exploring close consumer-producer links to maintain and enhance on-farm biodiversity
This paper deals with the question of whether local selling of farm products improves on-farm biodiversity. In contrast to the main agricultural trend of farms specialising and increasing in size in response to the national and global markets, increasing numbers of Swedish farmers are instead diverting their efforts towards selling at local markets. Based on a study of six farms, the paper explores the nature of diversity on these farms and identifies factors supporting diversity. The study shows that farmers who interact with consumers are encouraged to diversify their production. The actual crops and varieties grown are determined by a combination of the natural conditions prevailing on the farm and the conditions created by the farmer in terms of marketing strategy for the products
What More Than Parental Income? An Exploration of What Swedish Siblings Get from Their Parents
Sibling correlations are used as overall measures of the impact of family background and community influences on individual outcomes. While most correlation studies show that siblings are quite similar in terms of future achievement, we lack specific knowledge of what it is about family background that really matters. Studies on intergenerational income mobility show that parental income matters to some extent, but they also show that more than half of the family background and community influences that siblings share are not even correlated with parental income. In this paper, we employ a data set that contains rich information about families in order to explore what factors in addition to parental income can explain why siblings tend to have such similar outcomes. Our results show that measures of family structure and social problems account for very little of sibling similarities in adult income above and beyond that already accounted for by parental income. However, when we add a set of indicators for parental involvement and attitudes, the explanatory power of all our variables increased from about a third (using only traditional indicators of socio-economic status) to just over half. Interestingly, indicators of parents' patience, i.e., propensity to plan ahead and willingness to postpone benefits to the future, are particularly important.family background, intergenerational mobility, parents, siblings, long-run income
Families with infants: a general approach to solve hard partition problems
We introduce a general approach for solving partition problems where the goal
is to represent a given set as a union (either disjoint or not) of subsets
satisfying certain properties. Many NP-hard problems can be naturally stated as
such partition problems. We show that if one can find a large enough system of
so-called families with infants for a given problem, then this problem can be
solved faster than by a straightforward algorithm. We use this approach to
improve known bounds for several NP-hard problems as well as to simplify the
proofs of several known results.
For the chromatic number problem we present an algorithm with
time and exponential space for graphs of average
degree . This improves the algorithm by Bj\"{o}rklund et al. [Theory Comput.
Syst. 2010] that works for graphs of bounded maximum (as opposed to average)
degree and closes an open problem stated by Cygan and Pilipczuk [ICALP 2013].
For the traveling salesman problem we give an algorithm working in
time and polynomial space for graphs of average
degree . The previously known results of this kind is a polyspace algorithm
by Bj\"{o}rklund et al. [ICALP 2008] for graphs of bounded maximum degree and
an exponential space algorithm for bounded average degree by Cygan and
Pilipczuk [ICALP 2013].
For counting perfect matching in graphs of average degree~ we present an
algorithm with running time and polynomial
space. Recent algorithms of this kind due to Cygan, Pilipczuk [ICALP 2013] and
Izumi, Wadayama [FOCS 2012] (for bipartite graphs only) use exponential space.Comment: 18 pages, a revised version of this paper is available at
http://arxiv.org/abs/1410.220
Corporate Financing in Great Britain
Background: The antifungal compound ketoconazole has, in addition to its ability to interfere with fungal ergosterol synthesis, effects upon other enzymes including human CYP3A4, CYP17, lipoxygenase and thromboxane synthetase. In the present study, we have investigated whether ketoconazole affects the cellular uptake and hydrolysis of the endogenous cannabinoid receptor ligand anandamide (AEA). Methodology/Principal Findings: The effects of ketoconazole upon endocannabinoid uptake were investigated using HepG2, CaCo2, PC-3 and C6 cell lines. Fatty acid amide hydrolase (FAAH) activity was measured in HepG2 cell lysates and in intact C6 cells. Ketoconazole inhibited the uptake of AEA by HepG2 cells and CaCo2 cells with IC50 values of 17 and 18 mu M, respectively. In contrast, it had modest effects upon AEA uptake in PC-3 cells, which have a low expression of FAAH. In cell-free HepG2 lysates, ketoconazole inhibited FAAH activity with an IC50 value (for the inhibitable component) of 34 mu M. Conclusions/Significance: The present study indicates that ketoconazole can inhibit the cellular uptake of AEA at pharmacologically relevant concentrations, primarily due to its effects upon FAAH. Ketoconazole may be useful as a template for the design of dual-action FAAH/CYP17 inhibitors as a novel strategy for the treatment of prostate cancer
Spotting Trees with Few Leaves
We show two results related to the Hamiltonicity and -Path algorithms in
undirected graphs by Bj\"orklund [FOCS'10], and Bj\"orklund et al., [arXiv'10].
First, we demonstrate that the technique used can be generalized to finding
some -vertex tree with leaves in an -vertex undirected graph in
time. It can be applied as a subroutine to solve the
-Internal Spanning Tree (-IST) problem in
time using polynomial space, improving upon previous algorithms for this
problem. In particular, for the first time we break the natural barrier of
. Second, we show that the iterated random bipartition employed by
the algorithm can be improved whenever the host graph admits a vertex coloring
with few colors; it can be an ordinary proper vertex coloring, a fractional
vertex coloring, or a vector coloring. In effect, we show improved bounds for
-Path and Hamiltonicity in any graph of maximum degree
or with vector chromatic number at most 8
Violator Spaces: Structure and Algorithms
Sharir and Welzl introduced an abstract framework for optimization problems,
called LP-type problems or also generalized linear programming problems, which
proved useful in algorithm design. We define a new, and as we believe, simpler
and more natural framework: violator spaces, which constitute a proper
generalization of LP-type problems. We show that Clarkson's randomized
algorithms for low-dimensional linear programming work in the context of
violator spaces. For example, in this way we obtain the fastest known algorithm
for the P-matrix generalized linear complementarity problem with a constant
number of blocks. We also give two new characterizations of LP-type problems:
they are equivalent to acyclic violator spaces, as well as to concrete LP-type
problems (informally, the constraints in a concrete LP-type problem are subsets
of a linearly ordered ground set, and the value of a set of constraints is the
minimum of its intersection).Comment: 28 pages, 5 figures, extended abstract was presented at ESA 2006;
author spelling fixe
New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars II. A grid of O-type stars in the Galaxy and the Magellanic Clouds
Reliable predictions of mass-loss rates are important for massive-star
evolution computations. We aim to provide predictions for mass-loss rates and
wind-momentum rates of O-type stars, carefully studying the behaviour of these
winds as functions of stellar parameters like luminosity and metallicity. We
use newly developed steady-state models of radiation-driven winds to compute
the global properties of a grid of O-stars. The self-consistent models are
calculated by means of an iterative solution to the equation of motion using
full NLTE radiative transfer in the co-moving frame to compute the radiative
acceleration. In order to study winds in different galactic environments, the
grid covers main-sequence stars, giants and supergiants in the Galaxy and both
Magellanic Clouds. We find a strong dependence of mass-loss on both luminosity
and metallicity. Mean values across the grid are
and , however we also find a somewhat stronger
dependence on metallicity for lower luminosities. Similarly, the mass
loss-luminosity relation is somewhat steeper for the SMC than for the Galaxy.
In addition, the computed rates are systematically lower (by a factor 2 and
more) than those commonly used in stellar-evolution calculations. Overall, our
results agree well with observations in the Galaxy that account properly for
wind-clumping, with empirical vs. scaling relations, and
with observations of O-dwarfs in the SMC. Our results provide simple fit
relations for mass-loss rates and wind momenta of massive O-stars stars as
functions of luminosity and metallicity, valid in the range \,K. Due to the systematically lower , our new models
suggest that new rates might be needed in evolution simulations of massive
stars.Comment: Accepted for publication in A&A. 16 pages, 13 figure
New Deterministic Algorithms for Solving Parity Games
We study parity games in which one of the two players controls only a small
number of nodes and the other player controls the other nodes of the
game. Our main result is a fixed-parameter algorithm that solves bipartite
parity games in time , and general parity games in
time , where is the number of distinct
priorities and is the number of edges. For all games with this
improves the previously fastest algorithm by Jurdzi{\'n}ski, Paterson, and
Zwick (SICOMP 2008). We also obtain novel kernelization results and an improved
deterministic algorithm for graphs with small average degree
Eliminating Recursion from Monadic Datalog Programs on Trees
We study the problem of eliminating recursion from monadic datalog programs
on trees with an infinite set of labels. We show that the boundedness problem,
i.e., determining whether a datalog program is equivalent to some nonrecursive
one is undecidable but the decidability is regained if the descendant relation
is disallowed. Under similar restrictions we obtain decidability of the problem
of equivalence to a given nonrecursive program. We investigate the connection
between these two problems in more detail
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