The effects of gamma irradiation on the microbiological, physical and sensory qualities of diced tomatoes

Diced Roma tomatoes were treated with gamma irradiation and evaluated for changes in microbial, physical, chemical and sensory properties. Dosages for Trial 1 were 0.0, 0.39, 0.56 and 1.82 kGy and in Trial 2, 0.0, 0.50, 1.24 and 3.70 kGy. Irradiation at 3.70 kGy resulted in no aerobic populations through day 12 and significantly fewer colonies through day 15 whereas yeast and mold populations experienced a 2 log reduction through day 12. Color, titratable acidity, and °Brix were not significantly affected by irradiation. Tissue firmness decreased with increasing dose but not with storage time. Treatment with 3.7 kGy decreased firmness by 50% and 20% with 0.5 kGy, however, the reduced firmness induced by 0.50 kGy was undetected by a 9 member trained sensory panel. A significant (p0.05) inverse correlation between changes in texture and water-soluble pectin (WSP) was determined while total pectin remained relatively constant and oxalate soluble pectin content decreased slightly with irradiation dose. The significant inverse correlation between the loss of firmness and WSP indicates that the changes in WSP play an important role in the tissue softening of tomatoes, This study indicates that irradiation at 0.5 kGy can reduce microbial counts substantially to improve microbial shelf life without adverse effects on sensory qualities.     

Optimization of experimental parameters in single-drop microextraction-gas chromatography-mass spectrometry for the determination of periodate by the Malaprade reaction, and its application to ethylene glycol

The aim of present work was to optimize the experimental parameters in single drop microextraction under solution immersion (SDME) and headspace (HS-SDME) extraction modes for the determination of periodate using guaifenesine [3-(2′-methoxyphenoxy)-1,2-propane diol] and norephedrine (phenylpropanolamine) as new and alternative reagents for the Malaprade reaction. The reactions were complete within 5 min resulting in the formation of 2-(2′-methoxyphenoxy)-acetaldehyde and benzaldehyde, respectively. SDME/HS-SDME of oxidation products with 2 μl of anisole or 1 μl of toluene, respectively, has permitted the determination of periodate at μg l⁻¹ concentration levels. The results indicated that HS-SDME (range 0.01-10 mg l⁻¹, r² = 0.9990; limit of detection 1.55 μg l⁻¹) was more sensitive than SDME (range 0.05-50 mg l⁻¹, r² = 0.9984; limit of detection 3.42 μg l⁻¹), and was inexpensive, rapid and convenient. Tolerance of excess of iodate has permitted the application of this method in the determination of ethylene glycol in motor oil; the average recovery on spiked sample was 98.6% with R.S.D. of 4.2%.     

High-performance thin layer chromatography method for quantitative determination of four major anthraquinone derivatives in Rheum emodi

A high-performance thin layer chromatographic (HPTLC) method for the rapid and simple quantification of the four major anthraquinone derivatives i.e. physcion, chrysophanol, emodin and chrysophanol glycoside in Rheum emodi is described. HPTLC of anthraquinone derivatives was performed on pre-coated RP-18 F254S HPTLC plates. For achieving good separation, the mobile phase of methanol-water-formic acid (80:19:1, v/v/v) was used. The densitometric determination of anthraquinone derivatives was carried out at 445 nm in reflection/absorption mode. The calibration curves were linear in the range of 20-100 ng for physcion, 80-400 ng for chrysophanol and emodin, and 200-1000 ng for chrysophanol glycoside. The method was found to be reproducible and convenient for quantitative analysis of anthraquinone derivatives in the methanolic extract of rhizomes of R. emodi collected from three different locations of Western Himalaya, India.     

2,5-Dihydroxyacetophenone oxime as an analytical reagent for the amperometric determination of copper,palladium, and nickel

Summary Copper, palladium and nickel can be titrated amperometrically with 2,5-dihydroxyacetophenone oxime at –0.15, –0.4 and, –1.2 V vs. S. C. E. respectively, the optimum p_H values being 4.6, 4.0, and 9.0. Alkali and alkaline earth metals, Al, Bi, Cd, Co, Cr. Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO, W, and Zr do not interfere with the estimation of copper and palladium. The interferences due to the presence of silver and iron(III) can be eliminated by adding excess of KCl and KF respectively. Most heavy metals interfere with the estimation of nickel and should be eliminated before titration.

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Zusammenfassung Kupfer, Palladium und Nickel können mit 2,5-Dihydroxyaeetophenonoxim bei –0,15, –0,4 bzw. –1,2 V gegen eine gesättigte Kalomelelektrode amperometrisch titriert werden, wobei man das p_H am besten auf 4,6, 4,0 bzw. 9,0 hält. Alkalimetalle, Erdalkalien, Al, Bi, Cd, Co, Cr, Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO₂, W und Zr stören die Bestimmung des Kupfers und des Palladiums. Silber und Eisen können mit Kaliumchlorid gefällt bzw. mit Kaliumfluorid maskiert werden. Die meisten Schwermetalle stören die Nickelbestimmung und müssen daher vor der Titration entfernt werden.

     

Valence fluctuation in some Yb intermetallics by X-ray photoemission and X-ray absorption

The valence state of Yb in some of its intermetallics, YbNi₂Ge₂, YbCu₂Si₂ and YbPd₂Si₂ has been investigated by L_III(Yb) absorption edges and X-ray pnotoelectron spectra in the 4f and 4d regions. These studies establish the presence of mixed valence in all three systems and illustrate the utility of 4f and 4d spectra in the study of mixed valence in Yb compounds.     

Phenomenological renormalization of free nucleon-nucleon interaction

Low-lying spectra of⁶Li,¹⁸F,¹⁸O,⁴²Sc,⁴²Ca,⁵⁸Ni and⁹²Zr are studied with Sussex matrix elements (SME) and their central, spin-orbit and tensor components. It is observed that major contribution to level energies comes from the central part, while the tensor part provides the finer details of spectra, particularly forT=0 levels. The spin-orbit part does not make any appreciable contribution to level energies. A phenomenological renormalization of the SME is carried out to improve the agreement with the experimental results. It turns out that some of the low-lyingT=0 levels can be satisfactorily described if the SME in the³S₁ relative state are made (1+α) times their bare interaction value, whereα is a constant to be determined from a comparison with experimental level energies. Similarly, forT=1 levels, better agreement with the experimental results is obtained if aδ-function-plus-quadrupole interaction is added to the SME.     

Algebraic immunity for cryptographically significant Boolean functions: analysis and construction

Recently, algebraic attacks have received a lot of attention in the cryptographic literature. It has been observed that a Boolean function f used as a cryptographic primitive, and interpreted as a multivariate polynomial over F/sub 2/, should not have low degree multiples obtained by multiplication with low degree nonzero functions. In this paper, we show that a Boolean function having low nonlinearity is (also) weak against algebraic attacks, and we extend this result to higher order nonlinearities. Next, we present enumeration results on linearly independent annihilators. We also study certain classes of highly nonlinear resilient Boolean functions for their algebraic immunity. We identify that functions having low-degree subfunctions are weak in terms of algebraic immunity, and we analyze some existing constructions from this viewpoint. Further, we present a construction method to generate Boolean functions on n variables with highest possible algebraic immunity /spl lceil/n/2/spl rceil/ (this construction, first presented at the 2005 Workshop on Fast Software Encryption (FSE 2005), has been the first one producing such functions). These functions are obtained through a doubly indexed recursive relation. We calculate their Hamming weights and deduce their nonlinearities; we show that they have very high algebraic degrees. We express them as the sums of two functions which can be obtained from simple symmetric functions by a transformation which can be implemented with an algorithm whose complexity is linear in the number of variables. We deduce a very fast way of computing the output to these functions, given their input.     

Modeling of transient electroluminescence overshoot in bilayer organic light-emitting diodes using rate equations

When a voltage pulse is applied under forward biased condition to a spin-coated bilayer organic light-emitting diode (OLED), then initially the electroluminescence (EL) intensity appearing after a delay time, increases with time and later on it attains a saturation value. At the end of the voltage pulse, the EL intensity decreases with time, attains a minimum intensity and then it again increases with time, attains a peak value and later on it decreases with time. For the OLEDs, in which the lifetime of trapped carriers is less than the decay time of the EL occurring prior to the onset of overshoot, the EL overshoot begins just after the end of voltage pulse. The overshoot in spin-coated bilayer OLEDs is caused by the presence of an interfacial layer of finite thickness between hole and electron transporting layers in which both transport molecules coexist, whereby the interfacial energy barrier impedes both hole and electron passage. When a voltage pulse is applied to a bilayer OLED, positive and negative space charges are established at the opposite faces of the interfacial layer. Subsequently, the charge recombination occurs with the incoming flux of injected carriers of opposite polarity. When the voltage is turned off, the interfacial charges recombine under the action of their mutual electric field. Thus, after switching off the external voltage the electrons stored in the interface next to the anode cell compartment experience an electric field directed from cathode to anode, and therefore, the electrons move towards the cathode, that is, towards the positive space charge, whereby electron–hole recombination gives rise to luminescence. The EL prior to onset of overshoot is caused by the movement of electrons in the electron transporting states, however, the EL in the overshoot region is caused by the movement of detrapped electrons. On the basis of the rate equations for the detrapping and recombination of charge carriers accumulated at the interface expressions are derived for the transient EL intensity I, time t_m and intensity I_m corresponding to the peak of EL overshoot, total EL intensity I_t and decay of the intensity of EL overshoot. In fact, the decay prior to the onset of EL overshoot is the decay of number of electrons moving in the electron transporting states. The ratio I_m/I_s decreases with increasing value of the applied pulse voltage because I_m increases linearly with the amplitude of applied voltage pulse and I_s increases nonlinearly and rapidly with the increasing amplitude of applied voltage pulse. The lifetime τ_t of electrons at the interface decreases with increasing temperature whereby the dependence of τ_t on temperature follows Arrhenius plot. This fact indicates that the detrapping involves thermally-assisted tunneling of electrons. Using the EL overshoot in bilayer OLEDs, the lifetime of the charge carriers at the interface, recombination time of charge carriers, decay time of the EL prior to onset of overshoot, and the time delay between the voltage pulse and onset time of the EL overshoot can be determined. The intense EL overshoot of nanosecond or shorter time duration may be useful in digital communication, and moreover, the EL overshoot gives important information about the processes involving injection, transport and recombination of charge carriers. The criteria for appearance of EL overshoot in bilayer OLEDs are explored. A good agreement is found between the theoretical and experimental results.     

On Some Properties of (Θ+) Excited States

The mass splitting and the decay width of pentaquark (Θ⁺) at the higher angular momentum states have been investigated in the framework of flux tube model considering the diquark-diquark-antiquark configuration for Θ⁺ along with statistical model. A quasi particle model for diquark has been considered. The Regge trajectory of Θ⁺ has also been investigated with interesting some observations.     

Cycloaddition profile of pentafulvenes with 3-oxidopyrylium betaine: experimental and theoretical investigations

A detailed investigation on the effect of solvent polarity, temperature, and microwave irradiation on periselectivity in cycloaddition reactions of pentafulvenes with 3-oxidopyrylium betaine is described. The base catalyzed generation of 3-oxidopyrylium betaine in CHCl₃ resulted in the exclusive formation of [6+3] adducts. With increase in solvent polarity and temperature, mixtures of [6+3] and [3+2] adducts were formed, where as under microwave irradiation, [3+2] adducts were formed exclusively. The experimental results have been rationalized on the basis of theoretical calculations.