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Fruit production and processing result in a large amount of residues, which are usually discarded or underused. Passion fruit residues are source of fibers and other bioactive substances, which are antioxidant, protect cells against oxidative stress, and have pharmaceutical and food properties. This paper investigates the effects of freeze-drying on bioactive compounds of yellow passion fruit residues ( Passiflora edulis f. flavicarpa). It was analyzed the following compounds: Pectin, total phenolics, total flavonoids, citric acid, and ascorbic acid, and also the effect of freezing techniques (in freezer or liquid nitrogen) on moisture removal and product quality. The results indicated the best freeze-drying conditions for yellow passion fruit residues considering the preservation of the main compounds. Practical application Concerning processed fruits, the yellow passion fruit ( Passiflora edulis f. flavicarpa) has had great importance due to the quality of its juice and its great amount of minerals and vitamins. However, the processing of this fruit results in a substantial amount of residues, which may represent 65-70% of the fruit weight. These residues are usually discarded, causing environmental impact and loss of raw material and energy. Yellow passion fruit residues contain high levels of bioactive compounds, such as pectin, vitamins, minerals, polyphenolic antioxidants, and dietary fibers. This study investigated the freeze-drying of passion fruit residues. It was analyzed the effect of operating conditions on bioactive compounds content in the samples and determined the most suitable process conditions. [ABSTRACT FROM AUTHOR]

Abstract: EPR measurements have been performed on single crystals of [Cu(L‐tyrosine)2]∞ at 33.8GHz and at room temperature. The EPR spectra display partially resolved EPR lines for most orientations of the magnetic field in the ab plane, and only one resonance for orientations close to the crystal axes, while only a single line is observed along any direction in the ca and cb crystal planes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between the copper ions. The magnitudes of the exchange interactions between the copper ions were evaluated from the angular variation of the line width and the collapse of the EPR lines. The value |J AD/k B |=0.8K between neighboring copper atoms at 4.942Å is assigned to a syn−anti equatorial−apical carboxylate bridge with a total bond length of 6.822Å, while the small value |J AB/k B |=0.004K is assigned to a long bridge of 11 atoms with a total bond length of 19.186Å, that includes one resonance assisted hydrogen bond (RAHB). This finding is discussed in terms of values obtained for similar paths in other model compounds and in proteins. [Copyright &y& Elsevier]

A CuII⋯CuII pyrophosphate-bridged compound of formula {[Na3Cu(P2O7)(NO3)]·3H2O}n (1) has been characterized. X-ray diffraction measurements show that it crystallizes in the monoclinic space group P21/m, with unit cell dimensions a = 7.2492(5) Å, b = 8.2446(6) Å, c = 9.9050(7) Å, β = 107.123(1)°, and Z = 2. The structure consists of chains of CuII cations at inversion symmetry sites bound to four equatorial oxygen atoms provided by two pyrophosphate anions halved by a symmetry plane and two axial oxygen atoms of nitrate anions. The molar magnetic susceptibility ?0 of a powdered sample was measured in the temperature range 2 K < T < 273 K, and an isothermal magnetization curve, M(B0,T), was obtained at T = 30 K, with the magnetic field B0 between 0 and 5 T. Fitting a spin-chain model to the susceptibility data, we evaluate an antiferromagnetic exchange coupling 2J = -24.3(1) cm-1 (defined as Hex = -2JSiSj) between CuII neighbors. For any orientation of B0, single-crystal electron paramagnetic resonance (EPR) spectra obtained at 9.8 and 33.9 GHz at 300 K display a single signal having a g matrix with orthorhombic symmetry, arising from the merger produced by the exchange interaction of the resonances corresponding to the two rotated CuII sites. The g matrices of the individual molecules calculated assuming axial symmetry yielded principal values g = 2.367(1) and g = 2.074(1) at both frequencies, indicating a dx²-y² ground-state orbital for the CuII ions. The angular variation of the EPR line width suggests exchange narrowing in a system with one-dimensional spin dynamics, as expected from the structure and susceptibility data. The results, discussed in terms of the crystal and electronic structures and of the spin dynamics of the compound, are compared with those obtained in other materials. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline particles of La1−x Sr x CrO3 (0.000≤ x ≤0.020) compounds were synthesized in order to investigate the antiferromagnetic (AFM) to paramagnetic (PM) phase transition temperature, g-factor, line width and intensity by electron paramagnetic resonance (EPR). All samples were synthesized by combustion reaction method using strontium nitrate, lanthanum nitrate, chromium nitrate and urea as fuel without subsequent heat treatment. X-ray diffraction patterns of all systems showed broad peaks consistent with orthorhombic structure of LaCrO3. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures the phase purity. The average crystallite sizes determined from the prominent (112) peak of the diffraction using Scherrer''s equation was independent of the addition of Sr2+ ions; being ca. 31–29nm for x =0.000 and 0.020, respectively. The EPR line width and intensity were found to be dependent on Sr2+ addition and temperature. However, the AFM–PM transition temperature was found to be independent of strontium concentration, being ca. 296K. In the PM phase, g-factor was nearly temperature independent with increasing of x. The EPR results indicated that the addition of Sr2+ ions may induce creation of Cr3+–Cr4+ clusters. [Copyright &y& Elsevier]

Abstract: Mineral particle size plays a significant role on the flotation process. The flotation performance (grade and recovery) of apatite particles in a complex carbonatite ore from Brazil was investigated in a flotation column as a function of particle size and reagent concentrations. Flotation feed samples were also mineralogically and chemically characterized. For the bench scale flotation experiments, the sample was fractioned into different size intervals. The experiments were conducted according to a factorial experimental design. The experimental data were analyzed using P2O5 grade/recovery curves, response surface methodology and canonical analysis. An optimum particle size was found under the experimental conditions studied. The P2O5 grade and recovery rates obtained with a particle size between 37μm and 105μm were simultaneously higher than those required industrially. [Copyright &y& Elsevier]

Abstract: A novel dinuclear copper(II) complex with the amino acid l-arginine (l-arg), with mono and bidentate HPO4 2− oxoanions and an OH− anion. [Cu2(l-arg)2(μ-HPO4-O)(μ-HPO4-O,O′)(μ-OH)]− ·(H3O)+ ·6H2O (1) was prepared and its structure was determined by X-ray diffraction methods. The two independent copper ions are in a distorted square pyramidal coordination, each bonded to one l-arginine molecule. These two Cu(l-arg) units are bridged by two monoatomic equatorial–apical oxygen ligands belonging to a monodentate hydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d =3.1948(8)Å are also connected by two equatorial oxygen belonging to a bidentate hydrogenphosphate. This dinuclear character and bridging scheme, not common for metal–amino acid compounds, is a consequence of the properties of the phosphate anions. The magnetic susceptibility at temperatures between 2 and 300K and the isothermal magnetization curves at T =2.29(1)K with applied fields up to 9T were measured. The magnetic data indicate an antiferromagnetic intradinuclear exchange coupling J/k B =−3.7(1)K and using a molecular field approximation we estimated a weaker ferromagnetic interaction J′/k B ∼0.3K between neighbour dinuclear units. [Copyright &y& Elsevier]

Structural, magnetic, and powder and single-crystal electron paramagnetic resonance (EPR) studies were performed on [{Cu(bipy)(en)}{Cu(bipy)(H2O)}{VO3}4]n (bipy = 2,2′-bipyridine, en = ethylenediamine), which is a new copper-vanadium hybrid organic-inorganic compound containing CuII and VV centers. The oxovanadium units provide an anionic scaffolding to the structure, where two types of CuII coordination modes, octahedral (Cu1) and square pyramidal (Cu2), contribute to the magnetic properties. The crystal structure contains layers including Cu1 and Cu2 ions, separated by stacked arrangements of 2,2′-bipyridine molecules. Each type of CuII ion in these layers forms parallel spin chains described by exchange coupling parameters J1 and J2 for Cu1 and Cu2, respectively (exchange couplings defined as ℋex(i,j)= -JijSiSj), which, for necessity, are assumed to be equal to J. These chains are coupled by much weaker Cu1-Cu2 exchange interactions J3 connecting neighbor Cu1 and Cu2 ions within a layer, through paths acting as rungs of a ladder chain structure. The average coupling J, which is antiferromagnetic (J < 0), according to the susceptibility data, is estimated with similar results with a mean field approximation (J = -1.4 cm-1), and with a uniform chain model (J = -1.7 cm-1). The EPR spectra of powdered samples and oriented single crystals are shown to be independent of J1 and J2, but are dependent on the weak coupling J3, and the data allow a lower limit to be established: ∣J3∣ > 0.04 cm-1. The spectra are also strongly sensitive to extremely weak coupling interactions with average magnitude J4 between copper atoms in neighboring layers, separated by 10 Å, using the stacked 2,2′-bipyridine molecules, which produce a 2D-to-3D quantum phase transition. This is observed in single-crystal samples when the energy levels are changed with the orientation of the magnetic field. From the characteristics of these transitions, we estimate a value of ∣J4∣ = 0.0034 ± 0.0004 cm-1 between CuII ions in neighboring layers. This work emphasizes the important possibilities of EPR to evaluate extremely small exchange couplings between metal ions in a solid material, even in the presence of other much larger couplings. [ABSTRACT FROM AUTHOR]

The Cu atom of the title compound, [Cu(C4H7N2O3)2], is in a tetragonally distorted octahedral environment. A carboxyl O atom and the α-amino N atom from each ligand coordinate to Cu in a trans square-planar configuration [Cu—O = 2.003 (3) and 2.020 (3) Å, and Cu—N = 2.029 (4) and 2.049 (4) Å]. The octa­hedron is completed by bridging amide O atoms from adjacent mol­ecules [Cu—O = 2.229 (4) Å and Cu—O = 2.885 (4) Å] separated by c translations. This arrangement creates infinite chains linked in the [001] direction, stabilized by intra- and intermolecular N—H⋯O bonds. The structure has already been published [Stephens, Vagg & Williams (1975). Acta Cryst. B 31, 841–845]; this redetermination reports the structure with higher precision. [ABSTRACT FROM AUTHOR]