3,835 research outputs found
A first experimental test of de Broglie-Bohm theory against standard quantum mechanics
De Broglie - Bohm (dBB) theory is a deterministic theory, built for
reproducing almost all Quantum Mechanics (QM) predictions, where position plays
the role of a hidden variable. It was recently shown that different coincidence
patterns are predicted by QM and dBB when a double slit experiment is realised
under specific conditions and, therefore, an experiment can test the two
theories. In this letter we present the first realisation of such a double slit
experiment by using correlated photons produced in type I Parametric Down
Conversion. Our results confirm QM contradicting dBB predictions
Effect of pre-bloom anti-transpirant treatments and leaf removal on 'Sangiovese' (Vitis vinifera L.) winegrapes
Recent trials have shown that basal shoot leaf removal at pre-bloom is effective in reducing fruit-set and yield, leading to better grape quality composition. The present trial was designed to determine whether similar results can be achieved with 'Sangiovese' vines by testing a pre-bloom spray of film-forming anti-transpirant (P) against pre-bloom hand defoliation of basal shoots (HD) and no defoliation (C). The results of our threeyear experiment show that, compared to C, P reduced net assimilation of treated leaves for 20-40 days and photosynthetic compensation was not found after treatments in the upper untreated leaves of P and in the remaining upper HD leaves; berry-set, cluster weight and yield were significantly reduced in P and HD; bunch compactness decreased in HD, with P clusters registering an intermediate value; must soluble solids content (°Brix) and pH of P and HD were higher; no differences were found among treatments for titratable acidity. Berry and skin weight and anthocyanin content of P and C berries were similar, whereas HD berries, which were fully exposed to ambient light and temperature throughout each season, showed higher skin weight and skin weight-to-berry weight ratio, but a decreasing of total skin anthocyanins content compared to C and P.
Content, Construct, and Criterion Validity, Reliability, and Objectivity for Aquatic Readiness Assessment for Brazilian Children
The Aquatic Readiness Assessment (ARA) is an assessment instrument for measuring children\u27s aquatic readiness. The objective of the study was to translate the English version into Portuguese and to investigate the content, construct, and criterion validity as well as the reliability and rater objectivity of the ARA for Brazilian children. Twenty-three professionals and 464 children, newborn to 13 years-old participated in the study. We found strong content (94% to 100% of judges’ agreement) and criterion validity, internal consistency (α from .96 to .97), and inter-rater objectivity (ICC from .81 to .98), and test-retest reliability (ICC from .94 to .98). Appropriate fit indices were observed for the model (CFI = .99; TLI = .99; RMSEA .08, CI 90% = .67 to .10); the model was invariant for boys and girls (CFI = .99; RMSEA = .080; ΔCFI = .009; Δ RMSEA = .015) but not for age groups (CFI = .87, RMSEA = .160). The ARA presented adequate validity and reliability for evaluating the swimming performance of Brazilian children
Order in de Broglie - Bohm quantum mechanics
A usual assumption in the so-called {\it de Broglie - Bohm} approach to
quantum dynamics is that the quantum trajectories subject to typical `guiding'
wavefunctions turn to be quite irregular, i.e. {\it chaotic} (in the dynamical
systems' sense). In the present paper, we consider mainly cases in which the
quantum trajectories are {\it ordered}, i.e. they have zero Lyapunov
characteristic numbers. We use perturbative methods to establish the existence
of such trajectories from a theoretical point of view, while we analyze their
properties via numerical experiments. Using a 2D harmonic oscillator system, we
first establish conditions under which a trajectory can be shown to avoid close
encounters with a moving nodal point, thus avoiding the source of chaos in this
system. We then consider series expansions for trajectories both in the
interior and the exterior of the domain covered by nodal lines, probing the
domain of convergence as well as how successful the series are in comparison
with numerical computations or regular trajectories. We then examine a
H\'{e}non - Heiles system possessing regular trajectories, thus generalizing
previous results. Finally, we explore a key issue of physical interest in the
context of the de Broglie - Bohm formalism, namely the influence of order in
the so-called {\it quantum relaxation} effect. We show that the existence of
regular trajectories poses restrictions to the quantum relaxation process, and
we give examples in which the relaxation is suppressed even when we consider
initial ensembles of only chaotic trajectories, provided, however, that the
system as a whole is characterized by a certain degree of order.Comment: 25 pages, 12 figure
Hydrogen Re-Embrittlement of Aerospace grade High Strength Steels
Hydrogen Re-Embrittlement on anodically coated high strength steels is a relevant risk for aerospace structures due to the possibility of hydrogen uptake during the operative life of the components. AISI 4340 and Maraging 250 unnotched tensile specimens were subjected to SSRT in order to evaluate the influence of test environment on time to failure. Fracture surfaces were examined by SEM analysis to evaluate the degree of embrittlement and to correlate it with hydrogen diffusivity of the tested steels
Hydrogen Re-embrittlement of Aerospace Grade High Strength Steels
Hydrogen Re-Embrittlement on anodically coated high strength steels is a relevant risk for aerospace structures due to the possibility of hydrogen uptake during the operative life of the components. AISI 4340 and Maraging 250 unnotched tensile specimens were subjected to SSRT in order to evaluate the influence of test environment on time to failure. Fracture surfaces were examined by SEM analysis to evaluate the degree of embrittlement and to correlate it with hydrogen diffusivity of the tested steels
Application of kaolin and italian natural chabasite-rich zeolitite to mitigate the effect of global warming in vitis vinifera l. Cv. sangiovese
High temperatures and the anomalous distribution of rainfall during the growing season may have a negative impact on grapevine yield and berry composition. In recent years, many studies have focused on the application of agronomical techniques to reduce the negative impact of heat waves on secondary metabolites such as phenols. In particular, treatments with kaolin have shown positive effects on reducing canopy temperatures, enhancing the accumulation of anthocyanins. In regard to the above, three treatments were evaluated: untreated control (C), kaolin (CAO), and chabasite-rich zeolitites (ZEO) applications on cv. Sangiovese in order to verify the cooling effects on leaves and bunches, and the impact on gas exchange, yield parameters, berry composition, and on both chemical and sensory notes of wine. Minerals were sprayed twice around the veraison on the entire canopy at a 3% concentration. The results showed that the application of the minerals was able to reduce the berry temperatures in both years of the trial as compared to the untreated control (C), without affecting vine gas exchange, yield, and soluble solid accumulation. Furthermore, the cooling effect determined an increase in anthocyanin on both the grapes and the wine. At testing, CAO and ZEO wines stood out regarding greater color intensity and were preferred by the judges
Inflationary Cosmology as a Probe of Primordial Quantum Mechanics
We show that inflationary cosmology may be used to test the statistical
predictions of quantum theory at very short distances and at very early times.
Hidden-variables theories, such as the pilot-wave theory of de Broglie and
Bohm, allow the existence of vacuum states with non-standard field fluctuations
('quantum nonequilibrium'). We show that inflationary expansion can transfer
microscopic nonequilibrium to macroscopic scales, resulting in anomalous power
spectra for the cosmic microwave background. The conclusions depend only weakly
on the details of the de Broglie-Bohm dynamics. We discuss, in particular, the
nonequilibrium breaking of scale invariance for the primordial (scalar) power
spectrum. We also show how nonequilibrium can generate primordial perturbations
with non-random phases and inter-mode correlations (primordial
non-Gaussianity). We address the possibility of a low-power anomaly at large
angular scales, and show how it might arise from a nonequilibrium suppression
of quantum noise. Recent observations are used to set an approximate bound on
violations of quantum theory in the early universe.Comment: 44 pages. Minor changes in v
Existential Contextuality and the Models of Meyer, Kent and Clifton
It is shown that the models recently proposed by Meyer, Kent and Clifton
(MKC) exhibit a novel kind of contextuality, which we term existential
contextuality. In this phenomenon it is not simply the pre-existing value but
the actual existence of an observable which is context dependent. This result
confirms the point made elsewhere, that the MKC models do not, as the authors
claim, ``nullify'' the Kochen-Specker theorem. It may also be of some
independent interest.Comment: Revtex, 7 pages, 1 figure. Replaced with published versio
- …