pinecone/core-2020-05-10-deduplication huggingface dataset:
Sensitivity and optimal forcing response in separated boundary layer flows

Publisher version : http://pof.aip.org/resource/1/phfle6/v21/i6/p064108_s1?isAuthorized=noThe optimal asymptotic response to time harmonic forcing of a convectively unstable two-dimensional separated boundary layer on a flat plate is numerically revisited from a global point of view. By expanding the flow disturbance variables and the forcing term as a summation of temporal modes, the linear convective instability mechanism associated with the response leading to the maximum gain in energy is theoretically investigated. Such a response is driven by a pseudoresonance of temporal modes due to the non-normality of the underlying linearized evolution operator. In particular, the considered expansion on a limited number of modes is found able to
accurately simulate the linear instability mechanism, as suggested by a comparison between the global linear stability analysis and a linearized direct numerical simulation. Furthermore, the dependence of such a mechanism on the Reynolds number and the adverse pressure gradient is investigated, outlining a physical description of the destabilization of the flow induced by the rolling up of the shear layer. Therefore, the convective character of the problem suggests that the considered flat plate separated flows may act as a selective noise amplifier. In order to verfy such a possibility, the responses of the flow to the optimal forcing and to a small level of noise are compared, and their connection to the onset of self-excited vortices observed in literature is investigated. For that purpose, a nonlinear direct numerical simulation is performed, which is initialized by a random noise superposed to the base flow at the inflow boundary points. The band of excited frequencies as well as the associated peak match with the ones computed by the asymptotic global analysis. Finally, the connection between the onset of unsteadiness and the optimal response is further supported by a comparison between the optimal circular frequency and a typical Strouhal number predicted by numerical simulations of previous authors in similar cases
Nonperturbative semiclassical stability of de Sitter spacetime for small metric deviations

We consider the linearized semiclassical Einstein equations for small deviations around de Sitter spacetime including the vacuum polarization effects of conformal fields. Employing the method of order reduction, we find the exact solutions for general metric perturbations (of scalar, vector and tensor type). Our exact (nonperturbative) solutions show clearly that in this case de Sitter is stable with respect to small metric deviations and a late-time attractor. Furthermore, they also reveal a breakdown of perturbative solutions for a sufficiently long evolution inside the horizon. Our results are valid for any conformal theory, even self-interacting ones with arbitrarily strong coupling
Generalised Spin Projection for Fermion Actions

The majority of compute time doing lattice QCD is spent inverting the fermion
matrix. The time that this takes increases with the condition number of the
matrix. The FLIC(Fat Link Irrelevant Clover) action displays, among other
properties, an improved condition number compared to standard actions and hence
is of interest due to potential compute time savings. However, due to its two
different link sets there is a factor of two cost in floating point
multiplications compared to the Wilson action. An additional factor of two has
been attributed due to the loss of the so-called spin projection trick. We show
that any split-link action may be written in terms of spin projectors, reducing
the additional cost to at most a factor of two. Also, we review an efficient
means of evaluating the clover term, which is additional expense not present in
the Wilson action.Comment: 4 page
The 2dF Galaxy Redshift survey : the dependence of galaxy clustering on luminosity and spectral type.

We investigate the dependence of galaxy clustering on luminosity and spectral type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned using the principal-component analysis of Madgwick et al. We divide the sample into two broad spectral classes: galaxies with strong emission lines ('late types') and more quiescent galaxies ('early types'). We measure the clustering in real space, free from any distortion of the clustering pattern owing to peculiar velocities, for a series of volume-limited samples. The projected correlation functions of both spectral types are well described by a power law for transverse separations in the range 2<(&#963;/h-1 Mpc)<15, with a marginally steeper slope for early types than late types. Both early and late types have approximately the same dependence of clustering strength on luminosity, with the clustering amplitude increasing by a factor of 2.5 between L* and 4L*. At all luminosities, however, the correlation function amplitude for the early types is 50 per cent higher than that of the late types. These results support the view that luminosity, and not type, is the dominant factor in determining how the clustering strength of the whole galaxy population varies with luminosity
A contact area function for Berkovich nanoindentation : Application to hardness determination of a TiHfCN thin ﬁlm

In nanoindentation, especially at very low indenter displacements, the indenter/material contact area must be deﬁned in the best possible way in order to accurately determine the mechanical properties of the material. One of the best methodologies for the computation of the contact area has been proposed by Oliver and Pharr [W.C.Oliver, G.M.Pharr, J.Mater. Res. 7 (1992) 1564], which involves a complex phenomenological area function. Unfortunately, this formulation is only valid when the continuous stiffness measurement mode is employed. For other conditions of indentation, different contact area functions, which take into account the effective truncation length or the radius of the rounded indentertip, as well as some ﬁtting parameters, have been proposed. However, most of these functions require a calibration procedure due to the presence of such parameters. To avoid such a calibration, in the present communication a contact area function only related to the truncation length representative of the indenter tip defect, which can be previously estimated with high resolution microscopy, has been proposed. This model allows the determination of consistent indentation data from indenter displacements of only few nanometers indepth. When this proposed contact area function is applied to the mechanical characterization of a TiHfCN ﬁlm of 2.6 μm in thickness deposited onto a tool steel substrate, the direct determination of the hardness and elastic modulus of the ﬁlm leads to values of 35.5±2 GPa and 490±50 GPa, respectively
Fatigue crack initiation and growth on a steel in the very high cycle regime with sea water corrosion

The authors acknowledge Arts et Métiers ParisTech and Foundation Arts et Métiers for the financial support of P.C. Paris’
stay at LAMEFIP. They acknowledge Vicinay Cadenas S.A. for its financial support, and both the PCP France-Mexique and the
CONACYT for their financial support too.This paper is devoted to the effect of corrosion on the gigacycle fatigue strength of a martensitic–bainitic hot rolled steel used for manufacturing offshore mooring chains for petroleum platforms. Smooth specimens were tested under fully reversed tension between 1E6 and 1E10 cycles in three testing conditions and environments: (i) in air, (ii) in air after precorrosion and (iii) in air under real time artificial sea water flow. The fatigue strength at greater than 108 cycles is reduced by a factor more than five compared with non-corroded specimens. Fatigue cracks initiate at corrosion pits due to pre-corrosion, if any, or pits resulting from corrosion in real time during the cyclic loading. It is shown that under sea water flow, the fatigue life in the gigacycle regime is mainly governed by the corrosion process. Furthermore, the calculation of the mode I stress intensity factor at hemispherical surface defects (pits) combined with the Paris–Hertzberg–Mc Clintock crack growth rate model shows that fatigue crack initiation regime represents most of the fatigue life.PCP France Mexique, Conacyt, Arts et Métiers ParisTech (professeur invité Paul C Paris
A new class of superregular matrices and MDP convolutional codes

This paper deals with the problem of constructing superregular
matrices that lead to MDP convolutional codes. These matrices are
a type of lower block triangular Toeplitz matrices with the property
that all the square submatrices that can possibly be nonsingular
due to the lower block triangular structure are nonsingular. We
present a new class of matrices that are superregular over a
sufficiently large finite field
F
. Such construction works for any
given choice of characteristic of the field
F
and code parameters
(
n
,
k
,δ)
such that
(
n
−
k
)
|
δ
. We also discuss the size of
F
needed
so that the proposed matrices are superregular
Global food security under climate change

This article reviews the potential impacts of climate change on food security. It is found that of the four main elements of food security, i.e., availability, stability, utilization, and access, only the first is routinely addressed in simulation studies. To this end, published results indicate that the impacts of climate change are significant, however, with a wide projected range (between 5 million and 170 million additional people at risk of hunger by 2080) strongly depending on assumed socio-economic development. The likely impacts of climate change on the other important dimensions of food security are discussed qualitatively, indicating the potential for further negative impacts beyond those currently assessed with models. Finally, strengths and weaknesses of current assessment studies are discussed, suggesting improvements and proposing avenues for new analyses
Application of photon detectors in the VIP2 experiment to test the Pauli
  Exclusion Principle

The Pauli Exclusion Principle (PEP) was introduced by the austrian physicist
Wolfgang Pauli in 1925. Since then, several experiments have checked its
validity. From 2006 until 2010, the VIP (VIolation of the Pauli Principle)
experiment took data at the LNGS underground laboratory to test the PEP. This
experiment looked for electronic 2p to 1s transitions in copper, where 2
electrons are in the 1s state before the transition happens. These transitions
violate the PEP. The lack of detection of X-ray photons coming from these
transitions resulted in a preliminary upper limit for the violation of the PEP
of $4.7 \times 10^{-29}$. Currently, the successor experiment VIP2 is under
preparation. The main improvements are, on one side, the use of Silicon Drift
Detectors (SDDs) as X-ray photon detectors. On the other side an active
shielding is implemented, which consists of plastic scintillator bars read by
Silicon Photomultipliers (SiPMs). The employment of these detectors will
improve the upper limit for the violation of the PEP by around 2 orders of
magnitude
More Sensors or Better Algorithm?

Part 4: Enterprise ArchitectureInternational audienceFor the development of a successful indoor navigation system it is essential to know the nature of signals broadcasted by different access points and other signal broadcasting/transmitting equipments, since we can’t rely on the help of navigation satellites inside buildings. However we need to use the original signal in each case for accurate positioning, so we have to be able to filter out the interfering signals with the help of different algorithms
Design Theory Projectability

Part 6: IS DesignInternational audienceTechnological knowledge has been characterized as having a scope that is specific to a particular problem. However, the information systems community is exploring forms of design science research that provide a promising avenue to technological knowledge with broader scope: design theories. Because design science research is materially prescriptive, it requires a different perspective in developing the breadth of applications of design theories. In this paper we propose different concepts that embody forms of general technological knowledge The concept of projectability, developed originally as a means of distinguishing realized generalizations from unrealized generalizations, helps explain how design theories, being prescriptive, possess a different form of applicability. The concept of entrenchment describes the use of a theory in many projections. Together these concepts provide a means for comparative discussions of the importance of design theories. Projectable design theories guide designers in the design of artifacts similar in principle, but different in context. These can also help design researchers understand interrelationships between design theories
Dissolved gases in groundwater and groundwater dating methods: How useful for hydrogeological modeling? – Foreword to the special issue

International audienceOne of the major challenges in hydrogeology is the basic spatial lack of continuous data as this is restricted to available boreholes. Basic information is provided by the measurements of physical parameters (e.g. porosity and permeability) at the well-scale. Information related to a larger part of the aquifer are provided for example, by continuous measurement of piezometric levels or spring flow. Temporal information is extremely powerful in order to characterize aquifer functioning globally. Groundwater dating has thus been developed in order to provide time-constraints in aquifer studies
Studying Dynamics by Magic-Angle Spinning Solid-State NMR Spectroscopy: Principles and Applications to Biomolecules

International audienceMagic-angle spinning solid-state NMR spectroscopy is an important technique to study mo- lecular structure, dynamics and interactions, and is rapidly gaining importance in biomolecu- lar sciences. Here we provide an overview of experimental approaches to study molecular dy- namics by MAS solid-state NMR, with an emphasis on the underlying theoretical concepts and differences of MAS solid-state NMR compared to solution-state NMR. The theoretical foundations of nuclear spin relaxation are revisited, focusing on the particularities of spin re- laxation in solid samples under magic-angle spinning. We discuss the range of validity of Redfield theory, as well as the inherent multi-exponential behavior of relaxation in solids. Ex- perimental challenges for measuring relaxation parameters in MAS solid-state NMR and a few recently proposed relaxation approaches are discussed, which provide information about time scales and amplitudes of motions ranging from picoseconds to milliseconds. We also discuss the theoretical basis and experimental measurements of anisotropic interactions (chemical-shift anisotropies, dipolar and quadrupolar couplings), which give direct infor- mation about the amplitude of motions. The potential of combining relaxation data with such measurements of dynamically-averaged anisotropic interactions is discussed. Although the focus of this review is on the theoretical foundations of dynamics studies rather than their ap- plication, we close by discussing a small number of recent dynamics studies, where the dy- namic properties of proteins in crystals are compared to those in solution
A regularized nonnegative canonical polyadic decomposition algorithm with preprocessing for 3D fluorescence spectroscopy

International audienceWe consider blind source separation in chemical analysis focussing on the 3D fluorescence spectroscopy framework. We present an alternative method to process the Fluorescence Excitation-Emission Matrices (FEEM): first, a preprocessing is applied to eliminate the Raman and Rayleigh scattering peaks that clutter the FEEM. To improve its robustness versus possible improper settings, we suggest to associate the classical Zepp's method with a morphological image filtering technique. Then, in a second stage, the Canonical Polyadic (CP or Cande-comp/Parafac) decomposition of a nonnegative 3-way array has to be computed. In the fluorescence spectroscopy context, the constituent vectors of the loading matrices should be nonnegative (since standing for spectra and concentrations). Thus, we suggest a new NonNegative third order CP decomposition algorithm (NNCP) based on a non linear conjugate gradient optimisation algorithm with regularization terms and periodic restarts. Computer simulations performed on real experimental data are provided to enlighten the effectiveness and robustness of the whole processing chain and to validate the approach
1D action and partition function for the 2D Ising model with boundary magnetic field

In this article we obtain some exact results for the 2D Ising model with a general boundary magnetic field and for a finite size system, by an alternative method to that developed by B. McCoy and T.T. Wu. This method is a generalization of ideas from V.N. Plechko presented for the 2D Ising model in zero field, based on the representation of the Ising model using a Grassmann algebra. In this way, a Gaussian 1D action is obtained for a general configuration of the boundary magnetic field. In the special case where the magnetic field is homogeneous, we check that our results are in agreement with McCoy and Wu's previous work, and we also compute the two point correlation functions on the boundary. We use this correlation function to obtain the exact partition function and the free energy in the special case of an inhomogeneous boundary magnetic field
Textural characterization using P. Gy heterogeneity functions.

International audienceA solid can be regarded as a set of contiguous elementary units. The distribution within the solid of any properties, measurable within each elementary unit, can be characterized using two parameters. These parameters are built using the constitution and distribution heterogeneities of P. Gy (1982, 1988). The former account for the granularity of the elementary units, whereas the latter assess the spatial distribution of the property. A texture which definition involves several properties can be described using a diagram where both parameters work as variables. Potential applications encompass: (i) the textural classification of soils, ore, breccia and concrete and (ii) the monitoring of textural transformation during process like dolomitization, metamorphism, weathering, deformation or annealing
Stable-isotope dilution measurement of isovalerylglycine by tandem mass spectrometry in newborn screening for isovaleric acidemia

Background: Recent neonatal screening for isovaleric acidemia by tandem mass spectrometry based on dried blood spot levels of C5-acylcarnitines, including isovalerylcarnitine and its isomer, pivaloylcarnitine, which is derived from pivalate-generating antibiotics, has caused many false-positive results. We have developed a method to overcome this interference.
	Methods: The amounts of isovalerylglycine were determined by a stable-isotope dilution electrospray tandem mass spectrometric analysis, using multiple reaction monitoring with product ions of m/z 132, which were generated predominantly from quasi-molecular ions of isovalerylglycine butylester but apparently not from those of pivaloylglycine butylester. 
	Results: Isovalerylglycine concentrations in dried blood spots of control newborns were 0.17 ± 0.03 nmol/ml, and those of patients with isovaleric acidemia ranged from 1.3 to 80.0 nmol/ml. Those of the newborns treated with antibiotics, which caused high C5-acylcarnitine levels (1.9 ± 1.7 nmol/ml) in dried blood spots, were 0.22 ± 0.05 nmol/ml. 
	Conclusions: Our data showed that the present method is useful in eliminating the false-positive results due to antibiotics use in newborn screening for isovaleric acidemia
Structure determination in 55-atom Li–Na and Na–K nanoalloys

Producción CientíficaThe structure of 55-atom Li–Na and Na–K nanoalloys is determined through combined empirical potential (EP) and density functional theory (DFT) calculations. The potential energy surface generated by the EP model is extensively sampled by using the basin hopping technique, and a wide diversity of structural motifs is reoptimized at the DFT level. A composition comparison technique is applied at the DFT level in order to make a final refinement of the global minimum structures. For dilute concentrations of one of the alkali atoms, the structure of the pure metal cluster, namely, a perfect Mackay icosahedron, remains stable, with the minority component atoms entering the host cluster as substitutional impurities. At intermediate concentrations, the nanoalloys adopt instead a core-shell polyicosahedral (p-Ih) packing, where the element with smaller atomic size and larger cohesive energy segregates to the cluster core. The p-Ih structures show a marked prolate deformation, in agreement with the predictions of jelliumlike models. The electronic preference for a prolate cluster shape, which is frustrated in the 55-atom pure clusters due to the icosahedral geometrical shell closing, is therefore realized only in the 55-atom nanoalloys. An analysis of the electronic densities of states suggests that photoelectron spectroscopy would be a sufficiently sensitive technique to assess the structures of nanoalloys with fixed size and varying compositions
Model reproduces individual, group and collective dynamics of human contact networks

Empirical data on the dynamics of human face-to-face interactions across a variety of social venues have recently revealed a number of context-independent structural and temporal properties of human contact networks. This universality suggests that some basic mechanisms may be responsible for the unfolding of human interactions in the physical space. Here we discuss a simple model that reproduces the empirical distributions for the individual, group and collective dynamics of face-to-face contact networks. The model describes agents that move randomly in a two-dimensional space and tend to stop when meeting "attractive" peers, and reproduces accurately the empirical distributions
Human Eccrine Sweat Gland Cells Can Reconstitute a Stratified Epidermis

Eccrine sweat glands are generally considered to be a possible epidermal stem cell source. Here we compared the multilayered epithelia formed by epidermal keratinocytes and those formed by eccrine sweat gland cells. We demonstrated both in vitro and in vivo the capability of human eccrine sweat gland cells to form a stratified interfollicular epidermis substitute on collagen hydrogels. This is substantiated by the following findings: (1) a stratified epidermis consisting of 10–12 cell layers is formed by sweat gland cells; (2) a distinct stratum corneum develops and is maintained after transplantation onto immuno-incompetent rats; (3) proteins such as filaggrin, loricrin, involucrin, envoplakin, periplakin, and transglutaminases I and III match with the pattern of the normal human skin; (4) junctional complexes and hemidesmosomes are readily and regularly established; (5) cell proliferation in the basal layer reaches homeostatic levels; (6) the sweat gland-derived epidermis is anchored by hemidesmosomes within a well-developed basal lamina; and (7) palmo-plantar or mucosal markers are not expressed in the sweat gland-derived epidermis. These data suggest that human eccrine sweat glands are an additional source of keratinocytes that can generate a stratified epidermis. Our findings raise the question of the extent to which the human skin is repaired and/or permanently renewed by eccrine sweat gland cells