53 research outputs found
Heterodyne-detected electrostrictive laser-induced gratings for gas-flow diagnostics
The signal of heterodyne-detected electrostrictive laser-induced gratings (LIGs) originates from the interference of a reference laser beam with the laser light diffracted at the counterpropagating sound-wave packets, which are generated in the overlap volume of crossed laser beams. The frequencies of the sound waves, which contain the information on the sound velocity and on the motion of the medium, can approximately be extracted from the frequencies at the maxima of the two peaks, which dominate the power spectrum of the heterodyne LIG signal intensity. In free-air jets behind a slot nozzle, flow velocities up to 60m s-1 were determined by quick fits from the power spectrum and by fitting the time-dependent signal intensity data to model functions. Results agree well, the standard deviations being about one-half in the latter case (1.6-2.6m s-1, for positions close to the nozzle). Problems arising from the sampling and from the finite observation time of the signal intensity are discussed. Furthermore, the results of the LIG measurements were compared with data provided by laser Doppler anemometry. As an application of the instantaneous and unseeded LIG measurement technique, temperatures in heated air jets were determined simultaneously with the flow velocity by quick fits from the power spectru
The value of 'positive' clinical signs for weakness, sensory and gait disorders in conversion disorder: a systematic and narrative review.
Experts in the field of conversion disorder have suggested for the upcoming DSM-V edition to put less weight on the associated psychological factors and to emphasise the role of clinical findings. Indeed, a critical step in reaching a diagnosis of conversion disorder is careful bedside neurological examination, aimed at excluding organic signs and identifying 'positive' signs suggestive of a functional disorder. These positive signs are well known to all trained neurologists but their validity is still not established. The aim of this study is to provide current evidence regarding their sensitivity and specificity. We conducted a systematic search on motor, sensory and gait functional signs in Embase, Medline, PsycINfo from 1965 to June 2012. Studies in English, German or French reporting objective data on more than 10 participants in a controlled design were included in a systematic review. Other relevant signs are discussed in a narrative review. Eleven controlled studies (out of 147 eligible articles) describing 14 signs (7 motor, 5 sensory, 2 gait) reported low sensitivity of 8-100% but high specificity of 92-100%. Studies were evidence class III, only two had a blinded design and none reported on inter-rater reliability of the signs. Clinical signs for functional neurological symptoms are numerous but only 14 have been validated; overall they have low sensitivity but high specificity and their use should thus be recommended, especially with the introduction of the new DSM-V criteria
Influence of human impact and bedrock differences on the vegetational history of the Insubrian Southern Alps
Vegetation history for the study region is reconstructed on the basis of pollen, charcoal and AMS14C investigations of lake sediments from Lago del Segrino (calcareous bedrock) and Lago di Muzzano (siliceous bedrock). Late-glacial forests were characterised byBetula andPinus sylvestris. At the beginning of the Holocene they were replaced by temperate continental forest and shrub communities. A special type of temperate lowland forest, withAbies alba as the most important tree, was present in the period 8300 to 4500 B.P. Subsequently,Fagus, Quercus andAlnus glutinosa were the main forest components andA. alba ceased to be of importance.Castanea sativa andJuglans regia were probably introduced after forest clearance by fire during the first century A.D. On soils derived from siliceous bedrock,C. sativa was already dominant at ca. A.D. 200 (A.D. dates are in calendar years). In limestone areas, however,C. sativa failed to achieve a dominant role. After the introduction ofC. sativa, the main trees were initially oak (Quercus spp.) and later the walnut (Juglans regia). Ostrya carpinifolia became the dominant tree around Lago del Segrino only in the last 100-200 years though it had spread into the area at ca. 5000 cal. B.C. This recent expansion ofOstrya is confirmed at other sites and appears to be controlled by human disturbances involving especially clearance. It is argued that these forests should not be regarded as climax communities. It is suggested that under undisturbed succession they would develop into mixed deciduous forests consisting ofFraxinus excelsior, Tilia, Ulmus, Quercus andAce
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Digital competence and SMEs: review of the relevant literature
In the new digital world, globalisation as well as automation have reduced the number of routine, low-skills jobs. Instead, we see a rising demand in jobs with tertiary education and a shift in an enhanced skills set that could enable organisations to seek new opportunities and product innovations. Therefore, the European Union (EU), and various national governments, emphasised on the need of digitally capable graduates to satisfy organisational needs (Bilal et al., 2017; European Union, 2015; Stifterverband für die Deutsche Wissenschaft, 2018; Staatssekretariat für Bildung, Forschung und Innovation SBFI, 2017). As SMEs make out a large proportion of most national economies, it is worthwhile exploring how SMEs value digital competences on behalf of potential recruits (graduates)
Exploring digital competencies and likelihood to recruit graduates amongst SMEs in UK and Switzerland
QCD Sum Rules for Hyperons in Nuclear Matter
Within finite-density QCD sum-rule approach we investigate the self-energies
of hyperons propagating in nuclear matter from a correlator of
interpolating fields evaluated in the nuclear matter ground state. We
find that the Lorentz vector self-energy of the is similar to the
nucleon vector self-energy. The magnitude of Lorentz scalar self-energy of the
is also close to the corresponding value for nucleon; however, this
prediction is sensitive to the strangeness content of the nucleon and to the
assumed density dependence of certain four-quark condensate. The scalar and
vector self-energies tend to cancel, but not completely. The implications for
the couplings of to the scalar and vector mesons in nuclear matter and
for the spin-orbit force in a finite nucleus are discussed.Comment: 20 pages in revtex, 6 figures available under request as ps files,
UMD preprint #94--11
Decay constants, light quark masses and quark mass bounds from light quark pseudoscalar sum rules
The flavor and pseudoscalar correlators are investigated using
families of finite energy sum rules (FESR's) known to be very accurately
satisfied in the isovector vector channel. It is shown that the combination of
constraints provided by the full set of these sum rules is sufficiently strong
to allow determination of both the light quark mass combinations ,
and the decay constants of the first excited pseudoscalar mesons in
these channels. The resulting masses and decay constants are also shown to
produce well-satisfied Borel transformed sum rules, thus providing non-trivial
constraints on the treatment of direct instanton effects in the FESR analysis.
The values of and obtained are in good agreement with the
values implied by recent hadronic decay analyses and the ratios obtained
from ChPT. New light quark mass bounds based on FESR's involving weight
functions which strongly suppress spectral contributions from the excited
resonance region are also presented.Comment: 28 pages, 10 figure
Pade-Improvement of QCD Running Coupling Constants, Running Masses, Higgs Decay Rates, and Scalar Channel Sum Rules
We discuss Pad\'e-improvement of known four-loop order results based upon an
asymptotic three-parameter error formula for Pad\'e-approximants. We derive an
explicit formula estimating the next-order coefficient from the previous
coefficients in a series . We show that such an
estimate is within 0.18% of the known five-loop order term in the O(1)
-function, and within 10% of the known five-loop term in the O(1)
anomalous mass-dimension function . We apply the same formula to
generate a [22] Pad\'e-summation of the QCD -function and anomalous
mass dimension in order to demonstrate both the relative insensitivity of the
evolution of and the running quark masses to higher order
corrections, as well as a somewhat increased compatibility of the present
empirical range for with the range anticipated via evolution
from the present empirical range for . For
we demonstrate that positive zeros of any [22] Pad\'e-summation estimate of
the all-orders -function which incorporates known two-, three-, and
four-loop contributions necessarily correspond to ultraviolet fixed points,
regardless of the unknown five-loop term. Pad\'e-improvement of higher-order
perturbative expressions is presented for the decay rates of the Higgs into two
gluons and into a pair, and is used to show the relative
insensitivity of these rates to higher order effects. However,
Pad\'e-improvement of the purely-perturbative component of scalar/pseudoscalar
current correlation functions is indicative of large theoretical uncertainties
in QCD sum rules for these channels, particularly if the continuum-threshold
parameter is near 1 GeV.Comment: latex, 22 pages, 8 figures, references correcte
QCD sum rules at finite temperature
We derive thermal QCD sum rules for the correlation function of two vector
currents in the rho-meson channel. It takes into account the leading
non-perturbative corrections from the additional operators, which appear due to
the breakdown of Lorentz invariance at finite temperature. The mixing of the
new operators has a drastic effect on their coefficients. The thermal average
of all the operators can be related to that of the quark condensate and the
energy density. The sum rules then yield the temperature dependence of the
parameters of the -meson, namely its mass and coupling to the vector
current. Our result is that these parameters are practically independent of
temperature at least up to a temperature of 125 MeV.Comment: 11 pages, revtex, 2 figure
Reanalysis of the Y ( 3940 ) , Y ( 4140 ) , Z c ( 4020 ) , Z c ( 4025 ) , and Z b ( 10650 ) as molecular states with QCD sum rules
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