2,311 research outputs found
Austrian Economics Re-examined
Austrian Economics Re-examined: The Economics of Time and Ignorance is an expanded version of the 1996 edition of The Economics of Time and Ignorance. This work is a classic statement of the role of subjectivism, radical uncertainty and change through real time in Austrian economics specifically, and in modern economics more generally. The new book contains the full text and Introductions of the earlier edition as well as the comprehensive previously-unpublished essay "What is Austrian Economics?" and a new Introduction. The essay is a comprehensive overview of the central themes of the book from a somewhat different perspective than in the book itself. It supplements the analysis in the book. The new Introduction explains that the 2007-8 financial crisis and recent developments in behavioural economics have made the book more relevant than ever before. Austrian Economic Re-examined develops and systematizes the fundamental principles of the Austrian tradition to the analysis of rational expectations, business cycles, monetary theory competition and monopoly, and capital theory
Austrian Economics Re-examined
Austrian Economics Re-examined: The Economics of Time and Ignorance is an expanded version of the 1996 edition of The Economics of Time and Ignorance. This work is a classic statement of the role of subjectivism, radical uncertainty and change through real time in Austrian economics specifically, and in modern economics more generally. The new book contains the full text and Introductions of the earlier edition as well as the comprehensive previously-unpublished essay "What is Austrian Economics?" and a new Introduction. The essay is a comprehensive overview of the central themes of the book from a somewhat different perspective than in the book itself. It supplements the analysis in the book. The new Introduction explains that the 2007-8 financial crisis and recent developments in behavioural economics have made the book more relevant than ever before. Austrian Economic Re-examined develops and systematizes the fundamental principles of the Austrian tradition to the analysis of rational expectations, business cycles, monetary theory competition and monopoly, and capital theory
Sensitive CO and 13CO survey of water fountain stars Detections towards IRAS 18460-0151 and IRAS 18596+0315
 This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this recordContext. Water fountain stars represent a stage between the asymptotic giant branch (AGB) and planetary nebulae phases, when the mass loss changes from spherical to bipolar. These types of evolved objects are characterized by high-velocity jets in the 22 GHz water maser emission. Aims. The objective of this work is to detect and study in detail the circumstellar gas in which the bipolar outflows are emerging. The detection and study of thermal lines may help in understanding the nature and physics of the envelopes in which the jets are developing. Methods. We surveyed the CO and 13CO line emission towards a sample of ten water fountain stars through observing the J = 1 → 0 and 2 → 1 lines of CO and 13CO, using the 30 m IRAM radio-telescope at Pico Veleta. All the water fountains visible from the observatory were surveyed. Results. Most of the line emission arises from foreground or background Galactic clouds, and we had to thoroughly analyse the spectra to unveil the velocity components related to the stars. In two sources, IRAS 18460-0151 and IRAS 18596+0315, we identified wide velocity components with a width of 35 - 40 km s-1 that are centred at the stellar velocities. These wide components can be associated with the former AGB envelope of the progenitor star. A third case, IRAS 18286-0959, is reported as tentative; in this case a pair of narrow velocity components, symmetrically located with respect to the stellar velocity, have been discovered. We also modelled the line emission using an LVG code and derived some global physical parameters, which allowed us to discuss the possible origin of this gas in relation to the known bipolar outflows. For IRAS 18460-0151 and IRAS 18596+0315, we derived molecular masses close to 0.2 M⊙, mean densities of 104 cm-3, and mass-loss rates of 10 -4 M⊙ yr-1. The kinetic temperatures are rather low, between 10 and 50 K in both cases, which suggests that the CO emission is arising from the outer and cooler regions of the envelopes. No fitting was possible for IRAS 18286-0959, because line contamination can not be discarded in this case. Conclusions. The molecular masses, mean densities, and mass-loss rates estimated for the circumstellar material associated with IRAS 18460-0151 and IRAS 18596+0315 confirm that these sources are at the end of the AGB or the beginning of the post-AGB evolutionary stages. The computed mass-loss rates are among the highest ones possible according to current evolutionary models, which leads us to propose that the progenitors of these water fountains had masses in the range from 4 to 8 M ⊙. We speculate that CO emission is detected in water fountains as a result of a CO abundance enhancement caused by current episodes of low-collimation mass-loss. © ESO, 2013.MICINNJunta de AndalucĂ
GraphStep: A System Architecture for Sparse-Graph Algorithms
Many important applications are organized around
long-lived, irregular sparse graphs (e.g., data and knowledge
bases, CAD optimization, numerical problems, simulations). The
graph structures are large, and the applications need regular
access to a large, data-dependent portion of the graph for each
operation (e.g., the algorithm may need to walk the graph, visiting
all nodes, or propagate changes through many nodes in the
graph). On conventional microprocessors, the graph structures
exceed on-chip cache capacities, making main-memory bandwidth
and latency the key performance limiters. To avoid this
“memory wall,” we introduce a concurrent system architecture
for sparse graph algorithms that places graph nodes in small
distributed memories paired with specialized graph processing
nodes interconnected by a lightweight network. This gives us a
scalable way to map these applications so that they can exploit
the high-bandwidth and low-latency capabilities of embedded
memories (e.g., FPGA Block RAMs). On typical spreading activation
queries on the ConceptNet Knowledge Base, a sample
application, this translates into an order of magnitude speedup
per FPGA compared to a state-of-the-art Pentium processor
A real-time proximity querying algorithm for haptic-based molecular docking
Intermolecular binding underlies every metabolic and regulatory processes of the cell, and the therapeutic and pharmacological properties of drugs. Molecular docking systems model and simulate these interactions in silico and allow us to study the binding process. Haptic-based docking provides an immersive virtual docking environment where the user can interact with and guide the molecules to their binding pose. Moreover, it allows human perception, intuition and knowledge to assist and accelerate the docking process, and reduces incorrect binding poses. Crucial for interactive docking is the real-time calculation of interaction forces. For smooth and accurate haptic exploration and manipulation, force-feedback cues have to be updated at a rate of 1 kHz. Hence, force calculations must be performed within 1ms. To achieve this, modern haptic-based docking approaches often utilize pre-computed force grids and linear interpolation. However, such grids are time-consuming to pre-compute (especially for large molecules), memory hungry, can induce rough force transitions at cell boundaries and cannot be applied to flexible docking. Here we propose an efficient proximity querying method for computing intermolecular forces in real time. Our motivation is the eventual development of a haptic-based docking solution that can model molecular flexibility. Uniquely in a haptics application we use octrees to decompose the 3D search space in order to identify the set of interacting atoms within a cut-off distance. Force calculations are then performed on this set in real time. The implementation constructs the trees dynamically, and computes the interaction forces of large molecular structures (i.e. consisting of thousands of atoms) within haptic refresh rates. We have implemented this method in an immersive, haptic-based, rigid-body, molecular docking application called Haptimol_RD. The user can use the haptic device to orientate the molecules in space, sense the interaction forces on the device, and guide the molecules to their binding pose. Haptimol_RD is designed to run on consumer level hardware, i.e. there is no need for specialized/proprietary hardware
Higgs friends and counterfeits at hadron colliders
We consider the possibility of "Higgs counterfeits" - scalars that can be
produced with cross sections comparable to the SM Higgs, and which decay with
identical relative observable branching ratios, but which are nonetheless not
responsible for electroweak symmetry breaking. We also consider a related
scenario involving "Higgs friends," fields similarly produced through gg fusion
processes, which would be discovered through diboson channels WW, ZZ, gamma
gamma, or even gamma Z, potentially with larger cross sections times branching
ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs
counterfeit, rather than directly pointing towards the origin of the weak
scale, would indicate the presence of new colored fields necessary for the
sizable production cross section (and possibly new colorless but electroweakly
charged states as well, in the case of the diboson decays of a Higgs friend).
These particles could easily be confused for an ordinary Higgs, perhaps with an
additional generation to explain the different cross section, and we emphasize
the importance of vector boson fusion as a channel to distinguish a Higgs
counterfeit from a true Higgs. Such fields would naturally be expected in
scenarios with "effective Z's," where heavy states charged under the SM produce
effective charges for SM fields under a new gauge force. We discuss the
prospects for discovery of Higgs counterfeits, Higgs friends, and associated
charged fields at the LHC.Comment: 27 pages, 5 figures. References added and typos fixe
Neutralino dark matter in mSUGRA/CMSSM with a 125 GeV light Higgs scalar
The minimal supergravity (mSUGRA or CMSSM) model is an oft-used framework for
exhibiting the properties of neutralino (WIMP) cold dark matter (CDM). However,
the recent evidence from Atlas and CMS on a light Higgs scalar with mass
m_h\simeq 125 GeV highly constrains the superparticle mass spectrum, which in
turn constrains the neutralino annihilation mechanisms in the early universe.
We find that stau and stop co-annihilation mechanisms -- already highly
stressed by the latest Atlas/CMS results on SUSY searches -- are nearly
eliminated if indeed the light Higgs scalar has mass m_h\simeq 125 GeV.
Furthermore, neutralino annihilation via the A-resonance is essentially ruled
out in mSUGRA so that it is exceedingly difficult to generate
thermally-produced neutralino-only dark matter at the measured abundance. The
remaining possibility lies in the focus-point region which now moves out to
m_0\sim 10-20 TeV range due to the required large trilinear soft SUSY breaking
term A_0. The remaining HB/FP region is more fine-tuned than before owing to
the typically large top squark masses. We present updated direct and indirect
detection rates for neutralino dark matter, and show that ton scale noble
liquid detectors will either discover mixed higgsino CDM or essentially rule
out thermally-produced neutralino-only CDM in the mSUGRA model.Comment: 17 pages including 9 .eps figure
Revealing the electroweak properties of a new scalar resonance
One or more new heavy resonances may be discovered in experiments at the CERN
Large Hadron Collider. In order to determine if such a resonance is the
long-awaited Higgs boson, it is essential to pin down its spin, CP, and
electroweak quantum numbers. Here we describe how to determine what role a
newly-discovered neutral CP-even scalar plays in electroweak symmetry breaking,
by measuring its relative decay rates into pairs of electroweak vector bosons:
WW, ZZ, \gamma\gamma, and Z\gamma. With the data-driven assumption that
electroweak symmetry breaking respects a remnant custodial symmetry, we perform
a general analysis with operators up to dimension five. Remarkably, only three
pure cases and one nontrivial mixed case need to be disambiguated, which can
always be done if all four decay modes to electroweak vector bosons can be
observed or constrained. We exhibit interesting special cases of Higgs
look-alikes with nonstandard decay patterns, including a very suppressed
branching to WW or very enhanced branchings to \gamma\gamma and Z\gamma. Even
if two vector boson branching fractions conform to Standard Model expectations
for a Higgs doublet, measurements of the other two decay modes could unmask a
Higgs imposter.Comment: 23 pages, two figures; v2: minor revision and version to appear in
JHE
A kinematic analysis of a haptic handheld stylus in a virtual environment: a study in healthy subjects
<p>Abstract</p> <p>Background</p> <p>Virtual Reality provides new options for conducting motor assessment and training within computer-generated 3 dimensional environments. To date very little has been reported about normal performance in virtual environments. The objective of this study was to evaluate the test-retest reliability of a clinical procedure measuring trajectories with a haptic handheld stylus in a virtual environment and to establish normative data in healthy subjects using this haptic device.</p> <p>Methods</p> <p>Fifty-eight normal subjects; aged from 20 to 69, performed 3 dimensional hand movements in a virtual environment using a haptic device on three occasions within one week. Test-retest stability and standardized normative data were obtained for all subjects.</p> <p>Results</p> <p>No difference was found between test and retest. The limits of agreement revealed that changes in an individual's performance could not be detected. There was a training effect between the first test occasion and the third test occasion. Normative data are presented.</p> <p>Conclusion</p> <p>A new test was developed for recording the kinematics of the handheld haptic stylus in a virtual environment. The normative data will be used for purposes of comparison in future assessments, such as before and after training of persons with neurological deficits.</p
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