An Auger event triggered by electron-capture (EC) decay of 57 Co incorporated in a chelate molecule results in the loss of an average of 5 electrons. During subsequent charge neutralization, the molecule acquires >50 eV of excitation energy. Only molecules having a large -electron system were found to escape fragmentation. The fate of the molecule was followed by the 14.4 keV Mössbauer emission which occurs 10-7 second after the EC event. For a conjugated molecule to survive fragmentation, it should be able to disperse its energy in a time interval shorter than the period of atomic vibrations. We had proposed earlier that p-electrons undergo collective excitation and that the plasmon decays in <10-14 second accompanied by ejection of an electron leaving the molecule unscathed. Intermolecular energy transfer is not important and even an isolated molecule of 57 Co(II) phthalocyanine encapsulated in a zeolite supercage escapes fragmentation following an Auger event. Our model for rapid disposal of large excitation energy receives additional support from recent reports of single or mulitphoton plasmon excitation (20 eV) in an isolated C60 and C70 fullerene molecule followed by ejection of a single energetic electron leaving the molecule intact.
Activation energies for electrolyte diffusion of Zn(NO3)2, ZnBr2 and ZnI2 in 1% agar gel at different concentrations are determined by the least-squares fitting of the diffusion coefficient data obtained at various temperatures through the Arrhenius plots. Energy of activation is found to decrease with an increase in electrolyte concentration. This trend is explained by considering the changes in the physical properties of the solution with concentration at microscopic level, as envisaged in Wang's model.
Authors:C. Nath Nath, L. Zeng, A. Eslick, J. Trotman, and J. Earl Earl
A simple isocratic HPLC-UV assay for measurement of total and free melphalan concentrations in human plasma is described. Samples were prepared by methanol precipitation (total melphalan assay) and ultrafiltration (free melphalan assay). On a 25 cm × 4.6 mm C18 column with 0.016 m mixed soldium phosphate citrate buffer (pH 3.75)-acetonitrile 87:13 as mobile phase, at a flow rate of 1 mL min−1, the retention time of melphalan was 11.5 min. Detection was at 254 nm. For total melphalan assay response was a linear function of concentration up to 40 μg mL−1, with excellent interday precision (<6% for 0.5–40 μg mL−1 melphalan), accuracy (<2% deviation from the true concentration), and recovery (91–110%). For free melphalan assay response was a linear function of concentration up to 2.5 μg mL−1, with good precision (<11% for 0.7–2.5 μg mL−1 melphalan) and recovery (89–93%). Detection limits were 0.1 μg mL−1 and 0.05 μg mL−1 for total and free melphalan assays, respectively. The assays were clinically applied in a study of myeloma patients.
Authors:E. Kuzmann, Z. Klencsár, Z. Homonnay, L. Pöppl, A. Vértes, M. Bódogh, I. Kotsis, and A. Nath
57Fe Mössbauer spectroscopy measurements were performed on the perovskite compounds Eu0.7Pr0.3Ba2(Cu0.9957Fe0.01)3O7-, EuBa1.5Pr0.5(Cu0.9957Fe0.01)3O7- and EuBa1.3Pr0.7(Cu0.9957Fe0.01)3O7-. The observed 57Fe Mössbauer spectra provided an evidence for the correct site assignment of subspectra originating from 57Fe in different microenvironments. Apart from a minor component which was assigned to the 57Fe in the Cu(2) site of the copper oxide plane, all the subspectra could be attributed to the 57Fe in the Cu(1) copper oxide chain site with a fourfold (doublet D1), fivefold (doublet D2) or sixfold (doublet D3) oxygen coordination. In contrast, in the compound EuBa2(Cu0.9957Fe0.01)3O7- the 6-coordinated (D3) species has not been observed. The substitution of Pr for Eu or for Ba resulted in an increased occupancy of the O(5) antichain oxygen sites, which was explained by the charge neutrality criterion. Especially, the replacement of Ba2+ with Pr3+ led to an unusually high degree of occupancy of O(5) sites. In the 57Fe Mössbauer spectra the relative area of the 6-coordinated species (D3) increased, and that of the 4-coordinated one (D1) vanished completely in the case when Pr was substituted for Ba. Furthermore, the proportion of the 6-coordinated (D3) species increased at the expense of the 5-coordinated (D2) one with an increasing concentration of Pr at the Ba site. These experimental results are consistent with the variety of Mössbauer results reported so far.
Authors:A. Nath, S. Mondal, A. Csighy, M.A. Molnár, K. Pásztorné-Huszár, Z. Kovács, A. Koris, and Gy. Vatai
In the dairy industry different types of prebiotics, such galacto-oligosaccharide, lactulose, lactosucrose, tagatose, lactitol, lactobiono- and glucono-δ-lactone are synthesized through different chemical and biochemical reactions (hydrolysis, transgalactosylation, isomerization, fructosyl-transfer, reduction, and oxidation) as well as microbial fermentation processes using raw whey or isolated lactose as feedstock. Lactose-derived prebiotics have several functional and nutritional values. The biochemical activities of lactose-based prebiotics are expressed in the presence of probiotics (lactic acid bacteria, yeasts, Bacillus spp.). Galacto-oligosaccharide and lactosucrose reduce the risk of bowel disorder (diarrhea), inflammatory bowel disease (ulcerative colitis and crohn’s disease), and colon cancer. Galacto-oligosaccharide helps colonic absorption of minerals (iron, magnesium and calcium) and prevents osteoporosis. Lactulose, galacto-oligosaccharide, and lactitol promote laxative activity. Furthermore, lactulose may decrease the risk of hepatic encephalopathy. Prebiotics have low calorific value and glycemic index. Galacto-oligosaccharide and tagatose reduce the risks of hyperglycemia (Type 2 diabetes) and low density lipid (lipoprotein) accumulation in blood stream. Moreover, prebiotics improve immunomodulation, which reduces the risk of respiratory infection and allergies. This review describes unique biochemical mechanisms of several types of lactose-derived prebiotics.
Authors:N. Kopelev, V. Chechersky, A. Nath, B. O, M. Larkin, J. Markert, J. Peng, and R. Greene
The as-prepared electron-doped system Nd2–xCexCuO4 (where x0.16) is not superconducting. It becomes superconducting only after removal of a minuscule amount of extraneous oxygen (0.02 of O per unit formula). Mössbauer effect studies were carried out for oxygenated and deoxygenated Nd2–xCexCu(57Co)O4 with x=0.14, 0.16, and 0.18. The spectra show evidence of oxygen anions attaching to the probe57Co in apical positions, to form 5- and 6-coordinated species. A conventional procedure for deoxygenation brings about little change in the Mössbauer spectra both above and below the optimal superconducting concentration; however, for x=0.16, a dramatic change is observed—a major fraction of the magnetically split five-coordinated species manifests itself as a paramagnetically relaxed doublet upon deoxygenation, which costitutes a microscopic measure of the superconducting volume fraction. This apparently anomalous behavior at x0.16, where the extraneous oxygen is more readily desorbed, may be related to an electronic and/or local structural change in the CuO2 plane.
Authors:E. Kuzmann, Z. Klencsár, Z. Homonnay, A Vértes, G. Braga, A. De Oliveira, V. Garg, M. Bódogh, I. Kotsis, and A. Nath
57Fe and 151Eu Mössbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu1–xPrxBa2Cu3O7– and EuBa2–xPrxCu3O7–, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of 57Fe Mössbauer spectroscopy. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution.
Authors:Abraham Hafiz Rodriguez, Sarah Nath Zallek, Michael Xu, Jean Aldag, Lori Russell-Chapin, Tobias A. Mattei, and N. Scott Litofsky
Music has been associated with therapeutic properties for thousands of years across a vast number of diverse regions and cultures. This study expands upon our current understanding of music’s influence on human neurophysiology by investigating the effects of various music genres on cerebral cortex activity using electroencephalography (EEG).
A randomized, controlled study design was used. EEG data were recorded from 23 healthy adults, ages 19–28, while listening to a music sequence consisting of five randomized songs and two controls. The five studied music genres include: Classical, Tribal Downtempo, Psychedelic Trance (Psytrance), Goa Trance, and Subject Choice.
Controls were associated with lower percentages of beta frequencies and higher percentages of alpha frequencies than the music genres. Psytrance was associated with higher percentages of theta and delta frequencies than the other music genres and controls. The lowest percentages of beta frequencies and highest percentages of alpha frequencies occurred in the occipital and parietal regions. The highest percentages of theta and delta frequencies occurred in the frontal and temporal regions. Subjects with prior music training exhibited increased percentages of delta frequencies in the frontal region. Subject gender and music preference did not have a significant influence on frequency band percentages.
Findings from this study support those of previous music therapy studies and provide novel insights regarding music’s influence on human neurophysiology. These findings also support the hypothesis that music may promote changes in cerebral cortex activity that have similarities to non-rapid eye movement (NREM) sleep, while the listener remains awake.