Effect of ultrasound processing on anthocyanins and color of red grape juice

Grape juice samples were sonicated with processing variables of amplitude level (24.4–61.0 μm) and treatment time (0–10 min) at a constant frequency of 20 kHz and pulse durations of 5 s on and 5 s off. A full factorial experimental design with regression modeling was employed to investigate the main effects of amplitude level and treatment time on anthocyanins and color parameters. Significant effects of sonication on major anthocyanins cyanidin-3-O-glucosides (CA), malvanidin-3-O-glucosides (MA) and delphinidin-3-O-glucosides (DA), color values (L*, a*, b*) and color index (CI) were observed. Prediction models were found to be significant (p < 0.05) with low standard errors and high coefficients of determination (R²). Model predictions for critical quality parameters of anthocyanins (CA; MA; DA), color values (L*, a*, b*), TCD and CI inactivation were closely correlated to the experimental results obtained. Significant retention of anthocyanin content in grape juice was observed for CA (97.5 %); MA (48.2 %) and DA (80.9%) during sonication. CI and other color combinations (L*a*b*, L*a*/b* and L*b*/a*) were found to be strongly correlated with anthocyanin content. This study shows that sonication could be employed for as a preservation technique for fruit juice processing where anthocyanin retention is desired.     

Tunable structural color of anodic tantalum oxide films

Tantalum(Ta) oxide films with tunable structural color were fabricated easily using anodic oxidation.The structure,components,and surface valence states of the oxide films were investigated by using gazing incidence X-ray diffractometry,X-ray photoelectron microscopy,and surface analytical techniques.Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum.Color was accurately defined using L*a*b* scale.The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage.The film color was tunable by adjusting the anodic voltage.The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide-metal.     

Comparative study of the photo-discoloration of moso bamboo (Phyllostachys pubescens Mazel) and two wood species

Bamboo or bamboo products undergo surface degradation during outdoor exposure resulting in lower quality in service. In this study, the effect of UV-vis light irradiation on changes in color and surface chemistry of moso bamboo (Phyllostachys pubescens Mazel) was investigated. For comparison purpose, two wood species (a soft and a hardwood) were also studied to present their differences in degradation performance. Color characterization was performed by measuring CIELab parameters (L*, a*, b* and ΔE*), and Fourier transform infrared (FTIR) spectroscopy was used to analyze the chemical changes induced by irradiation. The results showed that the surface color of bamboo changed rapidly during the irradiation process. Compared with the wood species, bamboo was less influenced by photo-irradiation. Chemical analysis indicated that irradiation altered the chemical structures of bamboo surfaces. Lignin was the most sensitive component to photo-degradation and the intensities of its characteristics bands decreased significantly during the irradiation process. This was accompanied by formation of new carbonyl groups at 1735 cm⁻¹. The rate of lignin degradation and carbonyl formation in bamboo was relatively lower compared with the wood species. The color changes (ΔE*) was well correlated with lignin degradation and carbonyl formation regardless bamboo or the wood species.     

Color changes in wood during heating: kinetic analysis by applying a time-temperature superposition method

This paper deals with the kinetics of the color properties of hinoki (Chamaecyparis obtusa Endl.) wood. Specimens cut from the wood were heated at 90–180°C as accelerated aging treatment. The specimens completely dried and heated in the presence of oxygen allowed us to evaluate the effects of thermal oxidation on wood color change. Color properties measured by a spectrophotometer showed similar behavior irrespective of the treatment temperature with each time scale. Kinetic analysis using the time-temperature superposition principle, which uses the whole data set, was successfully applied to the color changes. The calculated values of the apparent activation energy in terms of L ^*, a ^*, b ^*, and DE^*_ab\Delta E^{*}_{ab} were 117, 95, 114, and 113 kJ/mol, respectively, which are similar to the values of the literature obtained for other properties such as the physical and mechanical properties of wood.     

Effect of fluence on the discoloration of marble cleaned with UV lasers

The effect of fluence level on the discoloration of marble surfaces after the removal of the encrustation by 355 nm laser pulses is comparatively studied. Considering the thermochemical reaction possibly occurring in the encrustation during laser irradiation, the mechanism responsible for the discoloration of the cleaned marble surface is analyzed. The reduction of iron oxides by graphite plays a key role in determining the final color of the cleaned marble surface. A two-dimensional laser ablative cleaning model including the reaction heat is applied to calculate the temperature distribution during laser heating. The kinetics of the thermochemical reaction is estimated based on the simulated temperature field. The occurrence of the thermochemical reaction is also verified indirectly with experiments. The marble surfaces before and after laser irradiation are characterized in terms of the chemical components through surface enhanced Raman spectroscopy. The surface color is measured with a chromameter using a 1976 CIE L^*a^*b^* color system. The proposed mechanism is also applied to numerically analyze the severe discoloration of marble cleaned with laser pulses at 1064 nm.     

Dependence of diatomic photofragment fluorescence polarization on triatomic predissociation lifetime

When a triatomic molecule, ABC, is dissociated by a beam of light to yield an electronically excited diatomic molecule, AB*, the degree of linear polarization of the AB* photofragment flourescence depends in general on the lifetime of the excited parent molecule, ABC*. Analytical expressions are developed for the polarization of diatomic flourescence as a function of predissociation lifetime. These calculations are carried out under the assumptions that: (a) the absorption and emission transition dipole moments can be replaced by classical hertzian dipole oscillators; (b) the AB* fragment rotates in the plane of the ABC* parent at the time of dissociation; and (c) the motion of the ABC* parent can be approximated by the classical motion of a prolate or oblate symmetric top.     

Optical characterization of pigments by reflectance spectroscopy in support of UV laser cleaning treatments

The study of optical properties of artwork materials is of fundamental importance for laser-based restoration techniques. In this work, reflectance spectroscopic measurements and colorimetric analyses of painted wooden models were performed to discriminate between pigments on the basis of their spectral features. In particular, the spectral reflection factors of different white pigments were recorded with a fibre optics reflectance spectroscopy module, both before and after excimer laser (248 nm) irradiation. Colour data were obtained and monitored with an integrating sphere spectrophotometer and expressed with the CIE L^*a^*b^* colour coordinates. Moreover, the laser-induced morphological changes of the samples were investigated by scanning electron microscopy. PACS  42.62-b; 61.80.Ba; 07.60.Dq     

Estimation of Color-Difference Formulae at Color Discrimination Threshold Using CRT-Generated Stimuli

The advanced color-difference formulae, CMC, CIE94, and the recently proposed CIEDE2000 formula, together with the basic CIELAB system, were estimated using the chromaticity discrimination threshold data at CIE Gray and Blue color centers. Gray is the most basic color and blue is, perceptually, in the most different region from other areas across the color space. The test stimuli, evenly distributed in the (a#x2217;, b#x2217;)-, (a#x2217;, L#x2217;)-, and (b#x2217;, L#x2217;)-plane of the CIELAB space, were generated on a CRT display, driven by a VSG system. Each direction from each color center was assessed 3 times by a panel of 9 normal color-vision observers with the psychophysical method of interleaved staircase. The experimental data were reliable and consistent with other studies according to the observer accuracy and fitted ellipse parameters. A comprehensive analysis shows the color discrimination tolerances could be well fitted by ellipses, and the CIEDE2000 and CIELAB formulae performed better than CIE94 while the CMC worst at the threshold level for the color centers studied.     

Evolution of the structure of Rb2ZnCl4 over the temperature range 4.2–310 K

X-ray diffraction is used to study the temperature dependence of the lattice parameters and the sequence of structural realignments in crystalline Rb₂ZnCl₄ over temperatures of 4.2–310 K. The appearance of and changes in the system of satellite reflexes indicative of structural ordering are studied. Below 74 K, on going into the monoclinic phase (space group A11a), anomalies are observed in the behavior of the lattice parameters, and superstructural reflexes develop with wave vectors q=a ^*/3+b ^*/2+c ^*/2 corresponding to an increase by a large factor in initial parameters a, b, and c of the Pnma-phase. Fiz. Tverd. Tela (St. Petersburg) 41, 1084–1090 (June 1999)     

Frustration between syn- and anticlinicity in mixtures of chiral and non-chiral tilted smectic-C-type liquid crystals

We study the effects of mixing ferroelectric and antiferroelectric liquid-crystal compounds (FLCs and AFLCs) when the former are strictly synclinic and the latter strictly anticlinic, i.e. one mixture component exhibits only SmC* and the other only SmC a* as tilted phase. Three different paths between syn- and anticlinicity were detected: transition directly between SmC* and SmC a*, transition via the SmC_β* and SmC_γ* subphases, or by “escaping” the clinicity frustration by reducing the tilt to zero, i.e. the SmA* phase is extended downwards in temperature, separating SmC* from SmC a* in the phase diagram. The most common path is the one via the subphases, demonstrating that these phases appear as a result of frustration between syn- and anticlinic and, consequently, between syn- and antipolar order. For assessing the role of chirality, we also replaced the FLC with non-chiral synclinics. With one of the AFLCs, the route via supbhases was detected even in this case, suggesting that chirality --although necessary-- does not have quite the importance that has previously been attributed to the appearance of the subphases. The path chosen in the mixture study seemed to be determined mainly by the synclinic component, the subphase induction occurring only when the SmA*-SmC* transition was second order.     

Coherent inelastic processes on nuclei at ultrarelativistic energies

The coherent inelastic processes of the type a → b, which may take place in the interaction of hadrons and γ quanta with nuclei at very high energies (the nucleus remains the same), are theoretically investigated. For taking into account the influence of the nucleus matter, the optical model, based on the conception of the refraction index, is used. Analytical formulas for the effective cross section σ _coh (a → b) are obtained, taking into account that, at ultrarelativistic energies, the main contribution into σ _coh (a → b) is provided by very small transferred momenta in the vicinity of the minimal longitudinal momentum transferred to the nucleus. It is shown that the cross section σ _coh (a → b) may be expressed through the “forward” amplitudes of inelastic scattering f _a+N+b+N (0) and elastic scattering f _a+N+a+N(0), f _b+N+b+N(0) on a separate nucleon, and it depends on the ratios L _a /R and L _b /R (L _a and L _b are the mean lengths of the free path in the nucleus matter for the particles a and b, respectively, and R is the nucleus radius). In particular, when L _a /R ≫ 1, but L _b /R ≪ 1 (or L _a /R ≪ 1, but L _b /R ≫ 1), σ _coh (a → b) is equal to the ratio of the “forward” cross sections of inelastic scattering a + N → b + N and elastic scattering of the particle b (or a) on a nucleon, multiplied by the cross section of scattering on the “black” nucleus πR ². When both conditions L _a /R ≫ 1 and L _b /R ≫ 1 are satisfied, σ _coh (a → b) is proportional to the factor R ⁴/k ², where k is the initial energy of particle a in the laboratory frame. The text was submitted by the authors in English.     

Spectral imaging system for non-contact colour measurement

This paper describes the development of a non-contact system for measuring colour of printed material at web speeds. The system proposed uses a non-contact spectrophotometer based on a holographic grating, in conjunction with a conventional monochrome area scan camera, from which colour spectral data is extracted, whilst a xenon flash is used to illuminate colour samples. Software and hardware details of the system are given, along with the underlying mathematics for colour space conversion and measurement. Conversion equations from X, Y, Z chromaticity co-ordinates to the RGB system are presented, and also equations to convert from the L^*a^*b^* colour space to X, Y, Z chromaticity co-ordinates. Experimental results are presented whereby the non-contact spectral system is shown to perform to a colour tolerance exceeding that of conventional colour video systems.     

Molecular and optical modifications in poly(vinyl chloride) due to N-phenylmaleimide additives and gamma irradiation

The effects of N-phenylmaleimide (NPMI) concentration and gamma dose on the molecular and optical properties of poly(vinyl chloride) (PVC) have been studied. The results reveal an improvement in the intrinsic viscosity of PVC in the presence of an organic material. The effective concentration that enhanced the intrinsic viscosity, from 1.02 to 1.28, was found to be 10 mmol NPMI per 100 g PVC. The effect of gamma irradiation on the PVC polymer stabilized with this concentration of NPMI has been studied. Samples from the 0.01 g NPMI/1 g PVC were irradiated with gamma doses in the range 5–180 kGy. It is found that irradiation in the dose range 120–180 kGy enhances the intrinsic viscosity of the samples. In addition, the transmission of these irradiated samples in the wavelength range 200–2500 nm, as well as any color changes was studied. The color intensity (Δ E) was greatly increased with the increasing gamma dose, and was accompanied by darkness with a significant increase in the yellow color component.     

Estimating the strength of single-ended dislocation sources in micron-sized single crystals

Three-dimensional (3D) discrete dislocation dynamics simulations were used to calculate the effects of anisotropy of dislocation line tension (increasing Poisson's ratio, ν) on the strength of single-ended dislocation sources in micron-sized volumes with free surfaces and to compare them with the strength of double-ended sources of equal length. Their plastic response was directly modelled within a 1?µm³ volume composed of a single crystal fcc metal. In general, double-ended sources are stronger than single-ended sources of an equal length and exhibit no significant effects from truncating the long-range elastic fields at this scale. The double-ended source strength increases with ν, exhibiting an increase of about 50% at ν?=?0.38 (value for Ni) as compared to the value at ν?=?0. Independent of dislocation line direction, for ν greater than 0.20, the strengths of single-ended sources depend upon the sense of the stress applied. The value for α in the expression for strength, τ?=?α(L)µb/L is shown to vary from 0.4 to 0.84 depending on the character of the dislocation and the direction of operation of the source at ν?=?0.38 and L?=?933b. By varying the lengths of the sources from 933 to 233b, it was shown that the scaling of the strength of single-ended and double-ended sources with their length both follow a ln(L/b)/(L/b) dependence. Surface image stresses are shown to have little effect on the critical stress of single-ended sources at a length of ～250b or greater. This suggests that for 3D discrete dislocation dynamics simulations of the plastic deformation of micron-sized crystals in the size range 0.5–20?µm, image stresses making the surface traction-free can be neglected. The relationship between these findings and a recent statistical model for the hardening of small volumes is discussed.     

Self-diffusion at grain boundaries with a disordered atomic structure

A change in the free energy of a grain boundary is analyzed in the case when lattice vacancies come to the boundary and are then delocalized in its disordered atomic structure. It is shown that the free energy of the boundary is minimized at some excess atomic volume Δv _b =Δv _b ^* , whose value depends on the energy of vacancy formation in the crystal lattice and the boundary energy. The formation of a metastable localized grain-boundary vacancy as a result of thermal fluctuations of the density in a group of n ₀=\gM_v/Δv _b atoms (\gM_v is the vacancy volume), followed by the jump of an adjacent atom into this vacancy, is taken as an elementary event of grain-boundary diffusion. Expressions for the activation energy of diffusion and the diffusion coefficient are derived for equilibrium (Δv _b =Δv _b ^* ) and nonequilibrium (Δv _b >Δv _b ^* ) boundaries.     

Similarity rules of magnetic minor hysteresis loops in Fe and Ni metals

We have studied similarity rules of quasistatic minor hysteresis loops for Fe and Ni single crystals in the wide temperature range from 10 to 600 K. Two similarity rules of M_R*/M_a*∼3/4 and W_R*/W_F*∼1/6, were found in a medium field range where irreversible movement of Bloch walls plays a crucial role for magnetization; M_a*, M_R*, W_F*, and W_R* are magnetization, remanence, hysteresis loss, and remanence work of a minor hysteresis loop. The similarity rules hold true, being almost independent of kinds of ferromagnets, applied stress, and temperature. The origin was discussed from the viewpoint of pinning effects due to dislocations as well as eddy current effects which become predominant at low temperatures for samples with low dislocation density.     

Macrokinetics of decomposition of loose packed RDX in shock and detonation waves

The boundary retardation method was used to study the decomposition of loose packed density RDX behind the front of shock waves with amplitudes ranges from values critical for reaction initiation to those typical of detonation. The threshold pressure P* and temperature T* at which the transition from a relatively slow decomposition in hotspots to fast bulk conversion occurs. It was demonstrated that this transition is associated with a change in the macrokinetics of the conversion of HE material behind the shock front. At pressures below P*, an analogy with the kinetic regularities of the thermal decomposition of RDX at normal pressure is observed. At P > P*, the conversion occurs in the regime of an adiabatic thermal explosion at a very high rate and has no analogues in chemical kinetics. The normal detonation regime is realized at P > P*. It was shown that the macrokinetic characteristics of normal detonation cannot be described within the framework of traditional approaches, with the help of the Arrhenius law or the concept of deflagration propagating from hotspots.     

Symmetry coupling coefficients for the double groups C n*, D n* and T*

By coupling linear combinations of the |JM ket vectors which transform as irreducible representations of C_n *, D_n * and T*, symmetry coupling coefficients for these groups are calculated. Also, ? coefficients as defined by Golding [1] are evaluated.     

Low temperature photoconductivity in electron - irradiated p-type Si

The photoconductivity spectra of p-type silicon irradiated at ～15 °K with 1.2 MeV electrons were studied in the wavelength range from 1.2 to 5.5 μ at temperatures from 23 to 80 °K. The 3.9 μ photoconductivity band appears immediately after irradiation in all crystals already at low temperatures, giving further evidence that it is due to the divacancy formed directly during irradiation by electrons. Three main annealing stages of the photoconductivity have been observed; (a) below 160 °K, (b) 160–250 °K, and (c) 280–360 °K. A radiation-induced deep level at E_v , +(0.12±0.02 eV disappears upon annealing at stage b. The annealing behavior of the spectra depends strongly on the measuring temperature. The dependence of the spectra on chopper speed was also investigated.