Availability of Isoflavones (Genistin,Genistein and Daidzein) in Soybean ( Glycine Max ) Curd Treated under High Pressure

The article describes the concentration of isoflavones (genistin, genistein and daidzein) in a Spanish commercial tofu treated under high-pressure. The tofu was subjected to pressure of 400 MPa, in cycles of 10 min each with a total of 4 cycles with the progression of 10, 20, 30 and 40 min, and a temperature of about 10-12 °C. The isoflavones were extracted from tofu with aqueous methanol solution (80:20). The content of isoflavones went up directly proportional to the pressure applied for the first 30 minutes. Afterwards, at 40 min, the values dropped close to the control. Significant differences were found in genistein, genistin and daidzein treated for 20 and 30 min in comparison to control values. Finally, we came to the conclusion that, the isoflavones (genistin, genistein and daidzein) of treated tofu were not destroyed at 400 Mpa for 30 min and a major extraction was observed when compared with the untreated tofu.     

Diastereoselectivity and kinetics of hetero diels-alder reactions under high pressure

Abstract

The Hetero Diels-Alder reaction of enamino ketones and ethyl vinyl ether to give dihydropyrans is studied in different solutions under pressure up to 7 kbar. The kinetics is measured via on-line FT IR spectroscopy. The cycloaddition shows a remarkable pressure dependent increase in diastereo-selectivity. For the difference in activation volumes referring to the reaction to the two diastereomers, values up to 5.9 ± 0.5 cm³/mol are observed. The ratio of cis and trans diastereomers can be improved by almost one order of magnitude by changing pressure and temperature from 1 bar and 90 °C to 6 kbar and 0.5 °C.     

Stability of MgAl 2 O 4 Under High-Pressure Conditions

A theoretical investigation of the MgAl 2 O 4 crystal response to high-pressure conditions has been carried out to determine its stability against decomposition towards MgO and f -Al 2 O 3 , and towards recently observed orthorhombic phases. We have evaluated total energy versus volume curves using the density functional formalism under the non-local B3LYP approximation, as implemented in the CRYSTAL package. Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation of state parameters for all the structures and compounds involved in the phase diagram. The macroscopic compressibility of the spinel phase is interpreted considering the compressibility of its elementary MgO 4 and AlO 6 coordination polyhedra, and implications to understand the phase stability are suggested.     

Valence Changes at High Pressure in Systems Containing Lanthanoids

Pressure-induced valence change in samarium sulfide SmS is reminiscent of alchemy, for when the electronic transition has taken place, the originally dull looking substance glitters like gold. Although it is not the realization of the alchemist's dream in the true sense, the material in the new state exhibits extraordinarily interesting behavior. As a novel feature, the valence state of the samarium fluctuates between two electronic configurations at a very fast rate. The physical properties of systems containing lanthanoids can be profoundly altered by manipulating the valence state by pressure or by chemical substitution. These phenomena will be described and discussed in the present article.     

X-ray absorption study of Cu,Zn SOD under high pressure

Abstract

We have investigated Cu, Zn Superoxide Dismutase (Cu, Zn SOD) metal sites at high pressure using X-ray absorption. XAS (X-ray Absorption Spectroscopy) gives information on local structure and it is particularly suited to metal site investigation. To the best of our knowledge, this is the first time that protein conformational states have been investigated using the high pressure XAS technique. Cu, Zn SOD catalyses the dismutation of toxic oxygen radicals produced in cells; this reaction occurs at the copper metal site. Structural changes around the copper, induced by pressure, can be directly related to protein substates. Their characterisation is thus important in the understanding of protein activity.

The high-pressure device was a Paris-Edinburgh large volume cell.

Experiments were performed on lyophilised Cu, Zn SOD between 0 and 48 kbar at the copper and zinc K-edges. The two metal local atomic environments have a different behaviour as pressure increases: copper exhibits a more flexible environment; on the contrary, zinc shows small structural modifications. We have identified a state, formed between 3 and 8 kbar, which is stable up to 48 kbar.     

The use of the high pressure hydrothermal method for tailored synthesis of zeolites without structure directing agents. Instance: Synthesis of natural zeolites with 5-1 building units

Abstract

The synthetic counterparts of natural alumosilicate zeolites containing 5-1 structural building units have been synthesized by simulating the natural hydrothermal formation conditions. Synthetic glasses of the respective zeolite composition were used as starting materials, while distilled water under hydrothermal conditions was used as pressure and reaction medium. No structure directing agents, additional solutions or sol-gel material has been employed.

The experience of former investigations on the tailored synthesis of alumosilicate zeolites showed, that 220°C is the expected temperature of maximum gain. Synthesis time was always 60 d. Synthesis pressure for mazzite (MAZ), mordenite (MOR), fer-rierite (FER), epistilbite (EPI) and dachiardite PAC) was 1 kbar while bikitaite (BIK) could only be synthesized at 2 kbar pressure.

The results of the investigations on hand show, that this process can be applied for the tailored synthesis of zeolites with completely new properties (e.g., semiconducting frameworks).     

Effects of pressure and temperature on the solubility of monosodium L-glutamate monohydrate in water

Abstract

The solubility of monosodium L-glutamate monohydrate (MSG.H₂O) in water was measured at pressures in the range of 0.10-300MPa and 298.15K. The density of MSG solution at high concentrations and heat of solution at saturated concentration were also measured at atmospheric pressure. The solubility, m_s, increased with increasing pressure and the pressure coefficient, Θ_p, [?(? In m_s,? p)_T] at 0.10 MPa was (2.0 ± 0.1) × 10-¹⁰Pa-1. It agrees well with (2.1 ±0.2)× 10-¹⁰ Pa-¹ thermodynamically estimated using the partial molar volume, the activity coefficient of the solute in solution, and the molar volume of the crystal. The excellent agreement at 0.10MPa gives us confidence in the solubility data at higher pressures. The heat of solution data and other pertinent values were used to calculate the temperature coefficient of solubility, Θ_T [? (? In m_s/?(1/T))_p], by a thermodynamic equality. The resulting Θ_T compares well with the data directly measured by Ogawa.     

Phase Relations and EOS of ZrO 2 and HfO 2 Under High-temperature and High-pressure

The phase relations and equations of state of ZrO 2 and HfO 2 high-pressure polymorphs have been investigated by means of in situ observation using multi-anvil type high-pressure devices and synchrotron radiation. Baddeleyite (monoclinic ZrO 2 ) transforms to two distorted fluorite (CaF 2 )-type phases at 3-4 GPa depending on temperature: an orthorhombic phase, orthoI, below 600 °C and a tetragonal phase, which is one of the high-temperature forms of ZrO 2 , above 600 °C. Both orthoI and tetragonal phases then transform into another orthorhombic phase, orthoII, with a cotunnite (PbCl 2 )-type structure above 12.5 GPa and the phase boundary is almost independent of temperature. OrthoII is stable up to 1800 °C and 24 GPa. In case of HfO 2 , orthoI is stable from 4 to 14.5 GPa below 1250-1400 °C and transforms to the tetragonal phase above these temperatures. OrthoII of HfO 2 appears above 14.5 GPa and is stable up to 1800 °C at 21 GPa. The unit cell parameters and the volumes of these high-pressure phases have been determined as functions of pressure and temperature. The orthoI/tetragonal-to-orthoII transition of both ZrO 2 and HfO 2 is accompanied by about 9% volume decrease. The bulk moduli of orthoII calculated using Birch-Murnaghan's equations of state are 296 GPa and 312 GPa for ZrO 2 and HfO 2 , respectively. Since orthoII of both ZrO 2 and HfO 2 are quenchable to ambient conditions, these are candidates for super-hard materials.     

Continuous-wave far-infrared ESR spectrometer for high-pressure measurements

We present a newly-developed microwave probe for performing sensitive high-field/multi-frequency electron spin resonance (ESR) measurements under high hydrostatic pressures. The system consists of a BeCu-made pressure-resistant vessel, which accommodates the investigated sample and a diamond microwave coupling window. The probe’s interior is completely filled with a pressure-transmitting fluid. The setup operates in reflection mode and can easily be assembled with a standard oversized microwave circuitry. The probe-head withstands hydrostatic pressures up to 1.6 GPa and interfaces with our home-built quasi-optical high-field ESR facility, operating in a millimeter/submillimeter frequency range of 105–420 GHz and in magnetic fields up to 16 T. The overall performance of the probe was tested, while studying the pressure-induced changes in the spin-relaxation mechanisms of a quasi-1D conducting polymer, KC₆₀. The preliminary measurements revealed that the probe yields similar signal-to-noise ratio to that of commercially available low-frequency ESR spectrometers. Moreover, by observing the conduction electron spin resonance (CESR) linewidth broadening for KC₆₀ in an unprecedented microwave frequency range of 210–420 GHz and in the pressure range of up to 1.6 GPa, we demonstrate that a combination of high-pressure ESR probe and high-field/multi-frequency spectrometer allows us to measure the spin relaxation rates in conducting spin systems, like the quasi-1D conductor, KC₆₀.