Distinguishing Initial State-Vectors from Each Other in Histories Formulations and the PBR Argument

Following the argument of Pusey et al. (in Nature Phys. 8:476, 2012), new interest has been raised on whether one can interpret state-vectors (pure states) in a statistical way (ψ-epistemic theories), or if each one of them corresponds to a different ontological entity. Each interpretation of quantum theory assumes different ontology and one could ask if the PBR argument carries over. Here we examine this question for histories formulations in general with particular attention to the co-event formulation. State-vectors appear as the initial state that enters into the quantum measure. While the PBR argument goes through up to a point, the failure to meet some of the assumptions they made does not allow one to reach their conclusion. However, the author believes that the “statistical interpretation” is still impossible for co-events even if this is not proven by the PBR argument.     

Chemometric Study of Fatty Acid Composition of Virgin Olive Oil from Four Widespread Greek Cultivars

Virgin olive oil (VOO) is one of the key components of the Mediterranean diet owing to the presence of monounsaturated fatty acids and various bioactive compounds. These beneficial traits, which are usually associated with the cultivar genotype, are highlighting the demand of identifying characteristics of olive oil that will ensure its authenticity. In this work, the fatty acid (FA) composition of 199 VOO samples from Koroneiki, Megaritiki, Amfissis, and Manaki cultivars was determined and studied by chemometrics. Olive cultivar greatly influenced the FA composition, namely, oleic acid (from 75.36% for Amfissis to 65.81% for Megaritiki) and linoleic acid (from 13.35% for Manaki to 6.70% for Koroneiki). Spearman’s rho correlation coefficients revealed differences and similarities among the olive oil cultivars. The use of the forward stepwise algorithm identified the FAs arachidonic acid, gadoleic acid, linoleic acid, α-linolenic acid, palmitoleic acid, and palmitic acid as the most significant for the differentiation of samples. The application of linear and quadratic cross-validation discriminant analysis resulted in the correct classification of 100.00% and 99.37% of samples, respectively. The findings demonstrated the special characteristics of the VOO samples derived from the four cultivars and their successful botanical differentiation based on FA composition.     

The general solution of Bianchi type <Emphasis Type="Italic">V I I</Emphasis><Subscript><Emphasis Type="Italic">h</Emphasis></Subscript> vacuum cosmology

The theory of symmetries of systems of coupled, ordinary differential equations (ODE) is used to develop a concise algorithm in order to obtain the entire space of solutions to vacuum Bianchi Einstein’s field equations (EFEs). The symmetries used are the well known automorphisms of the Lie algebra for the corresponding isometry group of each Bianchi Type, as well as the scaling and the time re-parametrization symmetry. The application of the method to Type V I I _h results in (a) obtaining the general solution of Type V I I ₀ with the aid of the third Painlevé transcendental P _{I I I} ; (b) obtaining the general solution of Type V I I _h with the aid of the sixth Painlevé transcendental P _{V I} ; (c) the recovery of all known solutions (six in total) without a prior assumption of any extra symmetry; (d) The discovery of a new solution (the line element given in closed form) with a G ₃ isometry group acting on T ₃, i.e., on time-like hyper-surfaces, along with the emergence of the line element describing the flat vacuum Type V I I ₀ Bianchi Cosmology.     

Control of susceptibility-related image contrast by spin-lock techniques

Macroscopic magnetic field inhomogeneities might lead to image distortions, while microscopic field inhomogeneities, due to susceptibility changes in tissues, cause spin dephasing and decreasing T₂ relaxation time. The latter effects are especially observed in the trabecular bone and in regions adjacent to air-containing cavities when gradient-echo sequences are applied. In conventional MRI, these susceptibility-related signal voids can be avoided by applying spin-echo (SE) techniques. In this study, an alternative method for the examination and control of susceptibility-related effects by spin-lock (SL) radiofrequency pulses is presented: SL pulses were applied in two different susceptibility-sensitive sequence types: (a) between the jump and return 90° pulses in a 90°_x−τ−90°_−x magnetization-prepared Fast Low Angle Shot (FLASH) sequence and (b) between the 90° pulse and the 180° pulse in an asymmetric SE sequence. The range of Larmor frequencies used for spin locking can be determined for different B₁ amplitudes of the SL pulses, allowing control of image contrast by the amplitude of the SL pulses.     

Kinetics of dissolution of powdered Pentelic marble in under-saturated solutions: the role of particle characteristics

In the present study, the effect of mesopore and particle size distributions on the kinetics of dissolution of powdered Pentelic marble was investigated. Powders obtained by grinding marble slabs in an agate mortar with a pestle (1-3.5 min) were found to be non-porous by nitrogen absorption measurements. These powders, upon dissolution under conditions of constant under-saturation, 25 degrees C, pH 8.25, showed that the kinetics in the absence of mesopores depended on the number of active sites on the exposed surface. Thus, powders consisting of smaller particles, having higher specific surface areas, yielded higher rates of dissolution. Powders, however, which were prepared by grinding marble slabs in a cylinder mill for time periods between 2.0 and 30.0 min, and which exhibited considerable mesoporosity, showed the opposite trend. The rates of dissolution measured for these powders in under-saturated solutions increased with increasing mean particle size and decreased with increasing specific surface area. This finding suggested that the presence of mesopores resulted in lower dissolution rates even though the exposed total surface area was larger. Furthermore, the larger the number of mesopores in a powder sample the slower the corresponding dissolution rates in under-saturated solutions.     

The effect of high tempered firing cycle on the bioactive behavior of sol–gel derived dental porcelain modified by bioactive glass

The purpose of the present study was to investigate the influence of end-temperature over the structural properties, chemical composition and bioactivity of dental porcelain modified by bioactive glass. In particular, sol–gel derived specimens of bioactive glass dental porcelain underwent firing at two increased end-temperatures. All specimens were characterized using Scanning Electron Microscopy, Fourier Transform Infrared and Raman Spectroscopy, X-ray diffraction and N₂-porosimetry. In vitro bioactivity test was performed too. SEM analysis of both specimens revealed smooth morphology of particles, which were sintered together. Spherical and closed porei were evident. N₂- adsorption isotherms of specimens represented non nano-/meso-porous materials. FTIR and Raman spectroscopy revealed the predominance of b-wollastonite as well as the appearance of a-cristobalite. XRD confirmed the results. In vitro tests evidenced the bioactivity of the specimens regardless of temperature. However, the increased temperature caused delayed apatite precipitation. In conclusion, increased temperature favored the sintering process initiation, along with the surface crystallization, which in turn delayed bioactivity.     

A quantum Monte Carlo study of the localizable entanglement in anisotropic ferromagnetic Heisenberg chains

We study the localizable entanglement in large one-dimensional anisotropic XYZ ferromagnetic Heisenberg chains interacting with a uniform magnetic field. With the use of quantum Monte Carlo simulations we calculate the bounds of localizable entanglement by means of the correlation functions. The present quantum Monte Carlo method has the advantage over existing methods that it can be readily applied to fully anisotropic magnetic chains.     

Democracy in action: Quantization, saturation, and compressive sensing

Recent theoretical developments in the area of compressive sensing (CS) have the potential to significantly extend the capabilities of digital data acquisition systems such as analog-to-digital converters and digital imagers in certain applications. To date, most of the CS literature has been devoted to studying the recovery of sparse signals from a small number of linear measurements. In this paper, we study more practical CS systems where the measurements are quantized to a finite number of bits; in such systems some of the measurements typically saturate, causing significant nonlinearity and potentially unbounded errors. We develop two general approaches to sparse signal recovery in the face of saturation error. The first approach merely rejects saturated measurements; the second approach factors them into a conventional CS recovery algorithm via convex consistency constraints. To prove that both approaches are capable of stable signal recovery, we exploit the heretofore relatively unexplored property that many CS measurement systems are democratic, in that each measurement carries roughly the same amount of information about the signal being acquired. A series of computational experiments indicate that the signal acquisition error is minimized when a significant fraction of the CS measurements is allowed to saturate (10–30% in our experiments). This challenges the conventional wisdom of both conventional sampling and CS.