825 research outputs found
Unemployment Cycles
The labor market by itself can create cyclical outcomes, even in the absence of exogenous shocks. We propose a theory in which the search behavior of the employed has profound aggregate implications for the unemployed. There is a strategic complementarity between active on-the-job search and vacancy posting by firms, which leads to multiple equilibria: in the presence of sorting, active on-the-job search improves the quality of the pool of searchers. This encourages vacancy posting, which in turn makes costly on-the-job search more attractive — a self-fulfilling equilibrium. The model provides a rationale for the Jobless Recovery, the outward shift of the Beveridge curve during the boom and for pro-cyclical frictional wage dispersion. Central to the model's mechanism is the fact that the employed crowd out the unemployed when on-the-job search picks up during recovery. We also illustrate this mechanism in a stylized calibration exercise
Architectural support for probabilistic branches
A plethora of research efforts have focused on fine-tuning branch predictors to increasingly higher levels of accuracy. However, several important optimization, financial, and statistical data analysis algorithms rely on probabilistic computation. These applications draw random values from a distribution and steer control flow based on those values. Such probabilistic branches are challenging to predict because of their inherent probabilistic nature. As a result, probabilistic codes significantly suffer from branch mispredictions.
This paper proposes Probabilistic Branch Support (PBS), a hardware/software cooperative technique that leverages the observation that the outcome of probabilistic branches needs to be correct only in a statistical sense. PBS stores the outcome and the probabilistic values that lead to the outcome of the current execution to direct the next execution of the probabilistic branch, thereby completely removing the penalty for mispredicted probabilistic branches. PBS relies on marking probabilistic branches in software for hardware to exploit. Our evaluation shows that PBS improves MPKI by 45% on average (and up to 99%) and IPC by 6.7% (up to 17%) over the TAGE-SC-L predictor. PBS requires 193 bytes of hardware overhead and introduces statistically negligible algorithmic inaccuracy
Hard x-ray photon-in-photon-out spectroscopy with lifetime resolution – of XAS, XES, RIXSS and HERFD
Spectroscopic techniques that aim to resolve the electronic configuration and local coordination of a central
atom by detecting inner-shell radiative decays following photoexcitation using hard X-rays are presented. The
experimental setup requires an X-ray spectrometer based on perfect crystal Bragg optics. The possibilities arising from
non-resonant (X-Ray Emission Spectroscopy - XES) and resonant excitation (Resonant Inelastic X-Ray Scattering
Spectroscopy – RIXSS, High-Energy-Resolution Fluorescence Detected (HERFD) XAS) are discussed when the
instrumental energy broadenings of the primary (beamline) monochromator and the crystal spectrometer for x-ray
emission detection are on the order of the core hole lifetimes of the intermediate and final electronic states. The small
energy bandwidth in the emission detection yields line-sharpened absorption features. In transition metal compounds,
electron-electron interactions as well as orbital splittings and fractional population can be revealed. Combination with
EXAFS spectroscopy enables to extent the k-range beyond unwanted absorption edges in the sample that limit the
EXAFS range in conventional absorption spectroscopy
Neuropsychological constraints to human data production on a global scale
Which are the factors underlying human information production on a global
level? In order to gain an insight into this question we study a corpus of
252-633 Million publicly available data files on the Internet corresponding to
an overall storage volume of 284-675 Terabytes. Analyzing the file size
distribution for several distinct data types we find indications that the
neuropsychological capacity of the human brain to process and record
information may constitute the dominant limiting factor for the overall growth
of globally stored information, with real-world economic constraints having
only a negligible influence. This supposition draws support from the
observation that the files size distributions follow a power law for data
without a time component, like images, and a log-normal distribution for
multimedia files, for which time is a defining qualia.Comment: to be published in: European Physical Journal
Clinical features of myocardial infarction and myocarditis in young adults: a retrospective study.
OBJECTIVES: To evaluate the prevalence and clinical presentation of myocardial infarction (MI) and myocarditis in young adults presenting with chest pain (CP) and an elevated serum troponin I (TnI) to the emergency department (ED).
DESIGN: Retrospective, observational, single-centre study.
PARTICIPANTS: All consecutive patients 18-40 years old admitted to the ED for CP with an elevated TnI concentration.
PRIMARY OUTCOME MEASURES: Prevalence of MI, myocarditis and the characterisation of clinical presentation.
RESULTS: 1588 patients between 18 and 40 years old were admitted to the ED with CP during 30 consecutive months. 49 (3.1%) patients with an elevated TnI (>0.09 μg/l) were included. 32.7% (16/49) were diagnosed with MI (11 ST-elevation myocardial infarction (STEMI) and 5 non-ST-elevation myocardial infarction (NSTEMI)) and 59.2% (29/49) with myocarditis. Compared with patients with myocarditis, MI patients were older (34.1±3.8 vs 26.9±6.4, p=0.0002) with more cardiovascular risk factors (mean 2.06 vs 0.69). Diabetes (18.8% vs 0%, p=0.0039), dyslipidaemia (56.2% vs 3.4%, p<0.0001) and family history of coronary artery disease (CAD) (37.5% vs 10.3% p=0.050) were associated with MI. Fever or recent viral illness were present in 75.9% (22/29) of patients with myocarditis, and in 0% of MI patients (p<0.0001). During follow-up, two patients with myocarditis were re-admitted for CP.
CONCLUSIONS: In this study, 32.7% of patients <40-year-old admitted to an ED with CP and elevated TnI had a diagnosis of MI. Key distinctive clinical factors include diabetes, dyslipidaemia, family history of CAD and fever or recent viral illness
Depolarizing metrics for plant samples imaging
Optical methods, as fluorescence microscopy or hyperspectral imaging, are commonly used for plants visualization and characterization. Another powerful collection of optical techniques is the so-called polarimetry, widely used to enhance image contrast in multiple applications. In the botanical applications framework, in spite of some works have already highlighted the depolarizing print that plant structures left on input polarized beams, the potential of polarimetric methods has not been properly exploited. In fact, among the few works dealing with polarization and plants, most of them study light scattered by plants using the Degree of Polarization (DoP) indicator. Other more powerful depolarization metrics are nowadays neglected. In this context, we highlight the potential of different depolarization metrics obtained using the Mueller matrix (MM) measurement: the Depolarization Index and the Indices of Polarimetric Purity. We perform a qualitative and quantitative comparison between DoP- and MM-based images by studying a particular plant, the Hedera maroccana. We show how Mueller-based metrics are generally more suitable in terms of contrast than DoP-based measurements. The potential of polarimetric measurements in the study of plants is highlighted in this work, suggesting they can be applied to the characterization of plants, plant taxonomy, water stress in plants, and other botanical studies
X-ray Linear Dichroism in cubic compounds: the case of Cr3+ in MgAl2O4
The angular dependence (x-ray linear dichroism) of the Cr K pre-edge in
MgAl2O4:Cr3+ spinel is measured by means of x-ray absorption near edge
structure spectroscopy (XANES) and compared to calculations based on density
functional theory (DFT) and ligand field multiplet theory (LFM). We also
present an efficient method, based on symmetry considerations, to compute the
dichroism of the cubic crystal starting from the dichroism of a single
substitutional site. DFT shows that the electric dipole transitions do not
contribute to the features visible in the pre-edge and provides a clear vision
of the assignment of the 1s-->3d transitions. However, DFT is unable to
reproduce quantitatively the angular dependence of the pre-edge, which is, on
the other side, well reproduced by LFM calculations. The most relevant factors
determining the dichroism of Cr K pre-edge are identified as the site
distortion and 3d-3d electronic repulsion. From this combined DFT, LFM approach
is concluded that when the pre-edge features are more intense than 4 % of the
edge jump, pure quadrupole transitions cannot explain alone the origin of the
pre-edge. Finally, the shape of the dichroic signal is more sensitive than the
isotropic spectrum to the trigonal distortion of the substitutional site. This
suggests the possibility to obtain quantitative information on site distortion
from the x-ray linear dichroism by performing angular dependent measurements on
single crystals
- …