765 research outputs found
Loess caves of Austria - a preview
[Abstract] Loess caves account for a negligible amount of Austriaâs caves only - despite the fact that the areas covered by loess and loess-loam comprise several thousand square kilometres. Loess can be found in the northern and eastern foreland of the Alpine Mountain Range as well as in the Styrian Basin south of the Alps. Only a handful of caves have been mapped so far, concentrated at a few spots. This eye-catching fact documents a certain lack of exploration rather than a general lack of loess caves. According to Striebel (2005) and others most loess caves are formed by piping and gully erosion, initiated by inhomogeneities like disintegrating roots and animal burrows where the infiltrating water causes fast-growing pipe structures, subsequently enlarging to caves that can be entered by cavers. The rate of cave evolution is tremendous. In several cases - so far investigated - the earliest onset of cave formation lies within the early 20th Century. This can be dated as the required gradient was man-made at that time. On the other hand distinctive alterations of the caves took place within 30 years. This can be documented strikingly by comparing old and new cave maps. The crucial points â from a quantitative point of view - for the formation of loess caves are still under fundamental discussion as there are severe differences in local climatic parameters â some of the areas belong to the driest in Austria â lithologies, gradients and human interventions. Furthermore, the role of dissolution of calcitic components enhancing the subsequent erosion remains ambiguous
Emergence of chaos in a viscous solution of rods
It is shown that the addition of small amounts of microscopic rods in a
viscous fluid at low Reynolds number causes a significant increase of the flow
resistance. Numerical simulations of the dynamics of the solution reveal that
this phenomenon is associated to a transition from laminar to chaotic flow.
Polymer stresses give rise to flow instabilities which, in turn, perturb the
alignment of the rods. This coupled dynamics results in the activation of a
wide range of scales, which enhances the mixing efficiency of viscous flows.Comment: 4 pages, 5 figures, 1 tabl
Overcoming the risk of inaction from emissions uncertainty in smallholder agriculture
The potential for improving productivity and increasing the resilience of smallholder agriculture, while also contributing to climate change mitigation, has recently received considerable political attention (Beddington et al 2012). Financial support for improving smallholder agriculture could come from performance-based funding including sale of carbon credits or certified commodities, payments for ecosystem services, and nationally appropriate mitigation action (NAMA) budgets, as well as more traditional sources of development and environment finance. Monitoring the greenhouse gas fluxes associated with changes to agricultural practice is needed for performance-based mitigation funding, and efforts are underway to develop tools to quantify mitigation achieved and assess trade-offs and synergies between mitigation and other livelihood and environmental priorities (Olander 2012)
Estimation in high dimensions: a geometric perspective
This tutorial provides an exposition of a flexible geometric framework for
high dimensional estimation problems with constraints. The tutorial develops
geometric intuition about high dimensional sets, justifies it with some results
of asymptotic convex geometry, and demonstrates connections between geometric
results and estimation problems. The theory is illustrated with applications to
sparse recovery, matrix completion, quantization, linear and logistic
regression and generalized linear models.Comment: 56 pages, 9 figures. Multiple minor change
Metamorphic titaniteâzircon pseudomorphs after igneous zirconolite
The formation of metamorphic zircon after baddeleyite is
a well-known reaction that can be used to date the metamorphism of igneous
silica-undersaturated rocks. By contrast, metamorphic minerals formed after
igneous zirconolite have rarely been reported. In this paper, we document
metamorphic titaniteâ+âzircon pseudomorphs formed from the metamorphic
breakdown of igneous zirconolite in syenodiorite and syenite, in the
southeastern Sveconorwegian Province, Sweden. Water-rich fluid influx during
tectonometamorphism in epidoteâamphibolite-facies metamorphic conditions
caused the release of silica during a metamorphic reaction involving igneous
feldspar and pyroxene and the simultaneous breakdown of igneous Zr-bearing
phases. Typical titaniteâ+âzircon intergrowths are elongated or platy
titanite crystals speckled with tiny inclusions of zircon. Most intergrowths
are smaller than 15â”m; some are subrounded in shape. Locally,
bead-like grains of titanite and zircon are intergrown with silicate
minerals. The precursor igneous zirconolite was found preserved only in a
sample of near-pristine igneous syenodiorite, as remnant grains of mainly
<â2â”m in size. Two somewhat larger crystals, 8 and 12â”m, allowed semiquantitative confirmation using microprobe analysis.
Analogous with zircon pseudomorphs after baddeleyite, titaniteâ+âzircon
pseudomorphs after zirconolite potentially offer dating of the metamorphic
reaction, although the small size of the crystals makes dating with today's
techniques challenging. The scarcity of reports of zirconolite and
pseudomorphs reflects that they are either rare or possibly overlooked.</p
Pourquoi les politiques publiques sont-elles si peu suivies dâeffets ?:Quelques interrogations
Lâinsertion des femmes sur le marchĂ© du travail a connu Ă la fois des avancĂ©es et des reculs. Si davantage de femmes accĂšdent Ă lâĂ©ducation supĂ©rieure et aux emplois qualifiĂ©s, dâautres sont touchĂ©es par la prĂ©caritĂ© et connaissent une dĂ©gradation de leurs conditions de travail et de vie.
Face Ă ce constat ambivalent, on peut questionner la mise en Ćuvre et lâefficacitĂ© des politiques qui visent Ă promouvoir lâĂ©galitĂ© entre les femmes et les hommes. Cet article a pour objectif de soulever quelques dĂ©bats.
Le plus souvent, les politiques publiques au sens large (y compris la protection sociale) sont dĂ©finies en termes de compensation et de correction des inĂ©galitĂ©s et des discriminations. Mais elles ne concernent pas les causes effectives de lâextension du sous-emploi des femmes, qui relĂšvent du fonctionnement mĂȘme du marchĂ© du travail. Câest donc la dĂ©finition des politiques publiques quâil faut interroger, en dĂ©passant une vision binaire qui oppose dâune part un champ Ă©conomique extĂ©rieur, dâautre part un champ social, juridique et culturel qui, seul, pourrait ĂȘtre lâobjet dâinflexions. En rĂ©alitĂ©, le champ Ă©conomique est aussi le produit des politiques publiques : la libre-concurrence et la prĂ©Ă©minence du marchĂ© sont le rĂ©sultat dâune action volontaire des Ătats. Il faut donc rĂ©intĂ©grer les politiques Ă©conomiques dans le champ de la rĂ©flexion sur les moyens de combattre les discriminations Ă lâencontre des femmes.The integration of women into the labour market has gone through both upswings and downturns. In view of this ambivalent result, we can question the efficiency of public policies set up to overcome gender inequality and fight gender discrimination. Does a real will exist, and if so why is it so inefficient or so poorly implemented? What forms do individual and collective resistance take? Most of the time, public policies are defined in terms of compensation and correction. But they donât deal with the actual causes of womenâs underemployment resulting from labour market adjustments. It is therefore the definition of the public policies that we need to examine, going beyond a binary view that opposes economic issues, on the one hand, to social, juridical and cultural concerns on the other
M31 Pixel Lensing PLAN Campaign: MACHO Lensing and Self Lensing Signals
We present the final analysis of the observational campaign carried out by
the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal
in form of MACHOs through the microlensing effect. The campaign consists of
about 1 month/year observations carried out during 4 years (2007-2010) at the
1.5m Cassini telescope in Loiano ("Astronomical Observatory of BOLOGNA", OAB)
plus 10 days of data taken in 2010 at the 2m Himalayan Chandra Telescope (HCT)
monitoring the central part of M31 (two fields of about 13'x12.6'). We
establish a fully automated pipeline for the search and the characterization of
microlensing flux variations: as a result we detect 3 microlensing candidates.
We evaluate the expected signal through a full Monte Carlo simulation of the
experiment completed by an analysis of the detection efficiency of our
pipeline. We consider both "self lensing" and "MACHO lensing" lens populations,
given by M31 stars and dark matter halo MACHOs, in the M31 and the Milky Way
(MW), respectively. The total number of events is compatible with the expected
self-lensing rate. Specifically, we evaluate an expected signal of about 2
self-lensing events. As for MACHO lensing, for full 0.5 (0.01) solar mass MACHO
halos, our prediction is for about 4 (7) events. The comparatively small number
of expected MACHO versus self lensing events, together with the small number
statistics at disposal, do not enable us to put strong constraints on that
population. Rather, the hypothesis, suggested by a previous analysis, on the
MACHO nature of OAB-07-N2, one of the microlensing candidates, translates into
a sizeable lower limit for the halo mass fraction in form of the would be MACHO
population, f, of about 15% for 0.5 solar mass MACHOs.Comment: ApJ accepted, 13 pages, 5 figures, 2 table
Quantization and Compressive Sensing
Quantization is an essential step in digitizing signals, and, therefore, an
indispensable component of any modern acquisition system. This book chapter
explores the interaction of quantization and compressive sensing and examines
practical quantization strategies for compressive acquisition systems.
Specifically, we first provide a brief overview of quantization and examine
fundamental performance bounds applicable to any quantization approach. Next,
we consider several forms of scalar quantizers, namely uniform, non-uniform,
and 1-bit. We provide performance bounds and fundamental analysis, as well as
practical quantizer designs and reconstruction algorithms that account for
quantization. Furthermore, we provide an overview of Sigma-Delta
() quantization in the compressed sensing context, and also
discuss implementation issues, recovery algorithms and performance bounds. As
we demonstrate, proper accounting for quantization and careful quantizer design
has significant impact in the performance of a compressive acquisition system.Comment: 35 pages, 20 figures, to appear in Springer book "Compressed Sensing
and Its Applications", 201
Efficient and feasible state tomography of quantum many-body systems
We present a novel method to perform quantum state tomography for
many-particle systems which are particularly suitable for estimating states in
lattice systems such as of ultra-cold atoms in optical lattices. We show that
the need for measuring a tomographically complete set of observables can be
overcome by letting the state evolve under some suitably chosen random circuits
followed by the measurement of a single observable. We generalize known results
about the approximation of unitary 2-designs, i.e., certain classes of random
unitary matrices, by random quantum circuits and connect our findings to the
theory of quantum compressed sensing. We show that for ultra-cold atoms in
optical lattices established techniques like optical super-lattices, laser
speckles, and time-of-flight measurements are sufficient to perform fully
certified, assumption-free tomography. Combining our approach with tensor
network methods - in particular the theory of matrix-product states - we
identify situations where the effort of reconstruction is even constant in the
number of lattice sites, allowing in principle to perform tomography on
large-scale systems readily available in present experiments.Comment: 10 pages, 3 figures, minor corrections, discussion added, emphasizing
that no single-site addressing is needed at any stage of the scheme when
implemented in optical lattice system
Social support for and through exercise and sport in a sample of men with serious mental illness.
Social support is important for people experiencing serious mental illness and is also important during the initiation and maintenance of exercise. In this article we draw on interpretive research into the experiences of 11 men with serious mental illness to explore four dimensions of social support both for and through exercise. Our findings suggest that informational, tangible, esteem, and emotional support were both provided for and given by participants through exercise. We conclude that experiences of both receiving and giving diverse forms of support in this way are significant for some people living with and recovering from serious mental illness
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