17,845 research outputs found
Public service employment : a review of programs in selected OECD countries and transition economies
This paper examines one type of program that is used by many OECD and CEEC countries (Central and Eastern European countries) to ease the pain of structural adjustment and create jobs, namely Public Service Employment (PSE). Such programs are characterized by the employment of unemployed persons, financed by the government, to provide services and/or support infrastructure development (public works). Many of those in the"non-interventionist"camp view these programs as a waste of public funds that could be used in more productive economic investments. Some of those in the"interventionist camp"also view the programs in a similar manner and feel that, while someintervention is needed, PSE programs are not an appropriate tool. However, a number of OECD and CEEC countries are implementing such programs. This report reviews and summarizes the experiences of several countries-Denmark, France, Germany, Spain, the United Kingdom, the United States, Poland, and Hungary. While not a representative sample, some of these countries heavily emphasized the use of such programs. The American program, discontinued over 15 years ago, remains relevant because this is where some of the best research has been conducted. Hungary and Poland are included because of their obvious relevance to the situation of countries in transition.Environmental Economics&Policies,ICT Policy and Strategies,Poverty Impact Evaluation,Banks&Banking Reform,Labor Standards
Using the distribution of cells by dimension in a cylindrical algebraic decomposition
We investigate the distribution of cells by dimension in cylindrical
algebraic decompositions (CADs). We find that they follow a standard
distribution which seems largely independent of the underlying problem or CAD
algorithm used. Rather, the distribution is inherent to the cylindrical
structure and determined mostly by the number of variables.
This insight is then combined with an algorithm that produces only
full-dimensional cells to give an accurate method of predicting the number of
cells in a complete CAD. Since constructing only full-dimensional cells is
relatively inexpensive (involving no costly algebraic number calculations) this
leads to heuristics for helping with various questions of problem formulation
for CAD, such as choosing an optimal variable ordering. Our experiments
demonstrate that this approach can be highly effective.Comment: 8 page
Program Verification in the presence of complex numbers, functions with branch cuts etc
In considering the reliability of numerical programs, it is normal to "limit
our study to the semantics dealing with numerical precision" (Martel, 2005). On
the other hand, there is a great deal of work on the reliability of programs
that essentially ignores the numerics. The thesis of this paper is that there
is a class of problems that fall between these two, which could be described as
"does the low-level arithmetic implement the high-level mathematics". Many of
these problems arise because mathematics, particularly the mathematics of the
complex numbers, is more difficult than expected: for example the complex
function log is not continuous, writing down a program to compute an inverse
function is more complicated than just solving an equation, and many algebraic
simplification rules are not universally valid.
The good news is that these problems are theoretically capable of being
solved, and are practically close to being solved, but not yet solved, in
several real-world examples. However, there is still a long way to go before
implementations match the theoretical possibilities
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Corytophanes cristatus
Number of Pages: 6Integrative BiologyGeological Science
Choosing a variable ordering for truth-table invariant cylindrical algebraic decomposition by incremental triangular decomposition
Cylindrical algebraic decomposition (CAD) is a key tool for solving problems
in real algebraic geometry and beyond. In recent years a new approach has been
developed, where regular chains technology is used to first build a
decomposition in complex space. We consider the latest variant of this which
builds the complex decomposition incrementally by polynomial and produces CADs
on whose cells a sequence of formulae are truth-invariant. Like all CAD
algorithms the user must provide a variable ordering which can have a profound
impact on the tractability of a problem. We evaluate existing heuristics to
help with the choice for this algorithm, suggest improvements and then derive a
new heuristic more closely aligned with the mechanics of the new algorithm
A "Piano Movers" Problem Reformulated
It has long been known that cylindrical algebraic decompositions (CADs) can
in theory be used for robot motion planning. However, in practice even the
simplest examples can be too complicated to tackle. We consider in detail a
"Piano Mover's Problem" which considers moving an infinitesimally thin piano
(or ladder) through a right-angled corridor.
Producing a CAD for the original formulation of this problem is still
infeasible after 25 years of improvements in both CAD theory and computer
hardware. We review some alternative formulations in the literature which use
differing levels of geometric analysis before input to a CAD algorithm. Simpler
formulations allow CAD to easily address the question of the existence of a
path. We provide a new formulation for which both a CAD can be constructed and
from which an actual path could be determined if one exists, and analyse the
CADs produced using this approach for variations of the problem.
This emphasises the importance of the precise formulation of such problems
for CAD. We analyse the formulations and their CADs considering a variety of
heuristics and general criteria, leading to conclusions about tackling other
problems of this form.Comment: 8 pages. Copyright IEEE 201
Bitter taste stimuli induce differential neural codes in mouse brain.
A growing literature suggests taste stimuli commonly classified as "bitter" induce heterogeneous neural and perceptual responses. Here, the central processing of bitter stimuli was studied in mice with genetically controlled bitter taste profiles. Using these mice removed genetic heterogeneity as a factor influencing gustatory neural codes for bitter stimuli. Electrophysiological activity (spikes) was recorded from single neurons in the nucleus tractus solitarius during oral delivery of taste solutions (26 total), including concentration series of the bitter tastants quinine, denatonium benzoate, cycloheximide, and sucrose octaacetate (SOA), presented to the whole mouth for 5 s. Seventy-nine neurons were sampled; in many cases multiple cells (2 to 5) were recorded from a mouse. Results showed bitter stimuli induced variable gustatory activity. For example, although some neurons responded robustly to quinine and cycloheximide, others displayed concentration-dependent activity (p<0.05) to quinine but not cycloheximide. Differential activity to bitter stimuli was observed across multiple neurons recorded from one animal in several mice. Across all cells, quinine and denatonium induced correlated spatial responses that differed (p<0.05) from those to cycloheximide and SOA. Modeling spatiotemporal neural ensemble activity revealed responses to quinine/denatonium and cycloheximide/SOA diverged during only an early, at least 1 s wide period of the taste response. Our findings highlight how temporal features of sensory processing contribute differences among bitter taste codes and build on data suggesting heterogeneity among "bitter" stimuli, data that challenge a strict monoguesia model for the bitter quality
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Corytophanes hernandesii
Number of Pages: 6Integrative BiologyGeological Science
Doping driven structural distortion in the bilayer iridate (SrLa)IrO
Neutron single crystal diffraction and rotational anisotropy optical second
harmonic generation data are presented resolving the nature of the structural
distortion realized in electron-doped (SrLa)IrO with
and . Once electrons are introduced into the bilayer
spin-orbit assisted Mott insulator SrIrO, previous studies have
identified the appearance of a low temperature structural distortion and have
suggested the presence of a competing electronic instability in the phase
diagram of this material. Our measurements resolve a lowering of the structural
symmetry from monoclinic to monoclinic and the creation of two
unique Ir sites within the chemical unit cell as the lattice distorts below a
critical temperature . Details regarding the modifications to oxygen
octahedral rotations and tilting through the transition are discussed as well
as the evolution of the low temperature distorted lattice as a function of
carrier substitution.Comment: 8 pages, 4 figure
Do the surface Fermi arcs in Weyl semimetals survive disorder?
We theoretically study the topological robustness of the surface physics
induced by Weyl Fermi-arc surface states in the presence of short-ranged
quenched disorder and surface-bulk hybridization. This is investigated with
numerically exact calculations on a lattice model exhibiting Weyl Fermi-arcs.
We find that the Fermi-arc surface states, in addition to having a finite
lifetime from disorder broadening, hybridize with nonperturbative bulk rare
states making them no longer bound to the surface (i.e. they lose their purely
surface spectral character). Thus, we provide strong numerical evidence that
the Weyl Fermi-arcs are not topologically protected from disorder. Nonetheless,
the surface chiral velocity is robust and survives in the presence of strong
disorder, persisting all the way to the Anderson-localized phase by forming
localized current loops that live within the localization length of the
surface. Thus, the Weyl semimetal is not topologically robust to the presence
of disorder, but the surface chiral velocity is.Comment: Single column; 24 pages, 12 figure
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