Biomedical subjects

M Horvatić

Publications and source records attributed to M Horvatić.

17 recordsLinked to original sources

PubMed2006

Field-induced staggered magnetization and magnetic ordering in Cu2(C5H12N2)2Cl4.

We present a 2D NMR investigation of the gapped spin-1/2 compound Cu2(C5H10N2D2)2Cl4. Our measurements reveal the presence of a magnetic field-induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence, and symmetry can be explained by an intradimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.

Journal Article↗

PubMed2006

Observation of spin susceptibility enhancement in the possible Fulde-Ferrell-Larkin-Ovchinnikov state of CeCoIn(5).

We report (115)In nuclear magnetic resonance measurements of the heavy-fermion superconductor CeCoIn(5) in the vicinity of the superconducting critical field H(c2) for a magnetic field applied perpendicular to the ĉ axis. A possible inhomogeneous superconducting state, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, is stabilized in this part of the phase diagram. In an 11 T applied magnetic field, we observe clear signatures of the two phase transitions: the higher temperature one to the homogeneous superconducting state and the lower temperature phase transition to a FFLO state. We find that the spin susceptibility in the putative FFLO state is significantly enhanced as compared to the value in a homogeneous superconducting state. The implications of this finding for the nature of the low temperature phase are discussed.

Journal Article↗

PubMed2006

Impurity-induced local magnetism and density of states in the superconducting state of YBa2Cu3O7.

17O NMR is used to probe the local influence of nonmagnetic Zn and magnetic Ni impurities in the superconducting state of optimally doped high TC YBa2Cu3O7. Zn and Ni induce a staggered paramagnetic polarization, similar to that evidenced above TC, with a typical extension xi=3 cell units for Zn and xi>or=3 for Ni. In addition, Zn is observed to induce a local density of states near the Fermi energy in its neighborhood, which also decays over about 3 cell units. Its magnitude decreases sharply with increasing temperature. This allows direct comparison with the STM observations done in BiSCCO.

Journal Article↗

PubMed2005

Nonmagnetic insulator state in Na1CoO2 and phase separation of na vacancies.

Crystallographic, magnetic, and NMR properties of a Na1CoO2 single crystal with x approximately = 1 are presented. We identify the stoichiometric Na1CoO2 phase, which is shown to be a nonmagnetic insulator, as expected for homogeneous planes of Co3+ ions with S = 0. In addition, we present evidence that, because of slight average Na deficiency, chemical and electronic phase separation leads to a segregation of Na vacancies into the well-defined, magnetic, Na0.8CoO2 phase. The importance of phase separation is discussed in the context of magnetic order for x approximately = 0.8 and the occurrence of a metal-insulator transition for x --> 1.

Journal Article↗

PubMed2002

NMR investigation of how free composite fermions are at nu=1 / 2.

NMR measurements of the electron spin polarization (P) have been performed on a 2D electron system at and around half-filled lowest Landau level. Comparing the magnetic field and the temperature dependence of P to models of free and interacting composite fermions (CF), the imbalance of spin-up and spin-down CF Fermi seas is mapped as a function of Zeeman energy. Independent measurements of the CF effective mass, g factor, and Fermi energy are obtained from the thermal activation of P in tilted fields. The filling factor dependence of the P for 2 / 5<nu<2 / 3 reveals a broken particle-hole symmetry for the partially polarized CF Fermi sea.

Journal Article↗

PubMed2002

Magnetic superstructure in the two-dimensional quantum antiferromagnet SrCu2(BO3)2.

We report the observation of magnetic superstructure in a magnetization plateau state of SrCu2(BO3)2, a frustrated quasi-two-dimensional quantum spin system. The Cu and B nuclear magnetic resonance (NMR) spectra at 35 millikelvin indicate an apparently discontinuous phase transition from uniform magnetization to a modulated superstructure near 27 tesla, above which a magnetization plateau at 1/8 of the full saturation has been observed. Comparison of the Cu NMR spectrum and the theoretical analysis of a Heisenberg spin model demonstrates the crystallization of itinerant triplets in the plateau phase within a large rhomboid unit cell (16 spins per layer) showing oscillations of the spin polarization. Thus, we are now in possession of an interesting model system to study a localization transition of strongly interacting quantum particles.

Journal Article↗

PubMed2002

Observation of magnetic level repulsion in Fe6:Li molecular antiferromagnetic rings.

Heat capacity (C), magnetic torque, and proton NMR relaxation rate (1/T(1)) measurements were performed on Fe6:Li single crystals in order to study the crossings between S = 0 and S = 1 and between S = 1 and S = 2 magnetic states of the molecular rings, at magnetic fields B(c1) = 11.7 T and B(c2) = 22.4 T, respectively. C vs B data at 0.78 K show that the energy gap between two states remains finite at B(c)'s (Delta(1)/k(B) = 0.86 K and Delta(2)/k(B) = 2.36 K) thus proving that levels repel each other. The large Delta(1) value may also explain the anomalously large width of the peak in 1/T(1) vs B, around B(c1). This anticrossing, unexpected in a centrosymmetric system, requires a revision of the Hamiltonian.

Journal Article↗

PubMed2002

Wheat flour confectionery products as a source of inorganic nutrients: iron and manganese contents in hard biscuits.

To evaluate some wheat flour based hard biscuits produced in Croatia with regard to their Fe and Mn contents and thereby their functionality, Fe and Mn are determined by cold-vapor atomic absorption spectrometry (CVAAS) in seven biscuits: classic white wheat flour biscuits and in dietetic biscuits enriched with whole wheat grain flour or whole wheat grain grits, soya flour and milk. Presented data show that Fe contents in seven analyzed biscuits range from 9.32 up to 24.80 mg/kg while Mn contents range from 3.76-16.37 mg/kg depending on type and share of cereal milling products and mineral content of other raw materials used. Thus, enriched biscuits produced from wheat flour type 850 and whole wheat grain flour, having the highest concentrations of Fe and Mn, were about 150% and 250%, respectively, richer in those elements in comparison with classic white flour biscuits of Petit Beurre type. Data show that wheat flour based hard biscuits, particularly enriched biscuits, can be considered as a good additional source of Fe and Mn in diets.

Bread↗

PubMed2001

New phase transition between partially and fully polarized quantum Hall states with charge and spin gaps at nu = 2/3.

The average electron spin polarization Rho of a two-dimensional electron gas confined in GaAs/GaAlAs multiple quantum wells was measured by NMR near the fractional quantum Hall state with filling factor nu = 2/3. Above this filling factor (2/3< or = nu < 0.85), a strong depolarization is observed corresponding to two spin flips per additional flux quantum. The most remarkable behavior of the polarization is observed at nu = 2/3, where a quantum phase transition from a partially polarized (Rho approximately 3/4) to a fully polarized (Rho = 1) state can be driven by increasing the ratio between the Zeeman and the Coulomb energy above a critical value eta(c) = Delta(Z)/Delta(C) = 0.0185.

Journal Article↗

PubMed2000

Magnetic-field-induced low-energy spin excitations in YBa(2)Cu(4)O(8) measured by high field Gd(3+) electron spin resonance.

We have measured the spin susceptibility, chi(s), of the CuO(2) planes in the underdoped high T(c) superconductor, YBa(2)Cu(4)O(8) by Gd(3+) electron spin resonance (ESR) in single crystals and aligned powders in fields up to 15.4 T. At low temperatures and high fields, chi(s) is enhanced slightly in the B parallel c orientation with respect to the B perpendicular c orientation. The enhancement at 15.4 T (approximately equal to 0.15H(c2)) at 16 K (0.2 T(c)) is small: approximately 10% of chi(s)(T(c)), suggesting that the second critical field of superconductivity, H(c2) approximately equal to 100 T, would not suppress the pseudogap. This work demonstrates the potential of high field ESR in single crystals for studying high T(c) superconductors.

Journal Article↗

PubMed1994

Spectrofluorometric method for determination of the total mercury content in natural waters.

A simple and highly selective spectrofluorometric method for the determination of the total mercury (Hg) in natural waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, has been made the basis of this sensitive method. Organic and inorganic Hg compounds in water samples were decomposed with sulphuric acid and potassium permanganate. Precipitated manganese dioxide and excess oxidants (permanganate) were destroyed with hydroxylammonium chloride. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. This method is suitable for the determination of total Hg in drinking and surface waters. The method gives reliable results down to a concentration of 0.5 micrograms Hg per litre of water. The water samples analysed by this method gave a mean recovery and standard error of 97.3 +/- 2.39 for added Hg.

Fluorescent Dyes↗

PubMed1993

[The effect of gamma radiation on the methionine and tryptophan content of soy protein products].

Effect of gamma irradiation on the content of methionine and tryptophan in soya protein products were investigated. Irradiation with doses of 1, 3 and 5 kGy caused significant (p = 0.05) decrease of methionine contents. Parallel with the decrease in methionine also the relative quality of proteins is lowered. Tryptophan content were significantly reduced (p = 0.05) at irradiation doses of 3 and 5 kGy. The relative decrease of methionine and tryptophan contents are significantly correlated (p = 0.05) with relative increase in amount of products by the irradiation induced oxidation of lipids; correlation coefficients were 0.576 and 0.715.

Gamma Rays↗

PubMed1991

[Content of available lysine in gamma-irradiated soybean products].

The content in available lysine of soya protein products irradiated in a 60Co-gamma cell were investigated. The results indicate that available lysine content and crude protein content at irradiation doses of 1, 3 and 5 kGy were unaffected at the 95% significance level. During 3-month storage the irradiated samples showed no significant (p = 0,05) changes of available lysine content. In samples with high content of lecithin, which were irradiated at 1 kGy as well as non-irradiated the content of available lysine was significantly (p = 0,05) reduced after 8-month storage; the other products as well as the at 3 and 5 kGy irradiated samples showed no significant decrease. Immediately after irradiation the microflora was significantly (p = 0,05) reduced. Under the effect of radiation treatment at 3 and 5 kGy the microflora was reduced to nearly 100% after 3-month storage.

Bacteria↗

PubMed1989

[Changes in the tryptophan content during the technological manufacturing processes of several wheat flour products].

The change of tryptophan contents in proteins of bread and cookies under technological processing conditions were investigated. Tryptophan contents in all cookie samples were noted to be significantly (p = 0.05) reduced in relation to corresponding dough. The relative decreases are significantly correlated with fat content and the degree of unsaturation of fats in the dough of cookies (r = 0.802 and r = 0.777, p = 0.01), independently of various physical parameters during different cookie samples' processing. Tryptophan decrease in proteins of bread during baking was not significant.

Bread↗

PubMed1989

Relationship between protein nutritive quality and technological property parameters of wheat flour.

The biological value of proteins as well as their importance for the technological quality of wheat flours have been extensively researched. Apart from the other factors, gluten content, structure and functional characteristics are responsible for the flour's technological properties. Functional properties of gluten complex and thus also rheological properties of flour are influenced by the specificity and intensity of interactions among individual protein fractions and likewise of protein interactions with other flour components. Rheological properties of flour and quality parameters of bread are changed to a greater or lesser extent, among other, by addition of free amino acids. The purpose of this work was to explore the relationship between certain essential amino acids of wheat flour and the parameters of flour rheology and bread baking quality.

Absorption↗

PubMed1981

[Changes in the biological protein value of wheat grain caused by manufacture into flour and gluten].

The authors determined the amino-acid composition of the proteins of whole wheat grain, flour and gluten, and calculated the biological protein values of these products from the data obtained. The decrease in the contents of the single amino acids was as follows: flour, 8--13% (as compared to whole grain); and gluten, 2--5% (as compared to flour). The decrease in the biological protein value according to Mitchell was: wheat flour, 5% (as compared to whole grain); and gluten, 8% (as compared to flour). The decrease in the biological protein value according to Oser was: flour, 9% (as compared to whole grain); and gluten, 26% (as compared to flour).

Amino Acids↗

PubMed1978

[Biological value of wheat proteins as dependent on maturity of the wheat grain].

The authors studied the dependence of the change in biological protein value of the wheat grains upon the degree of maturity. The biological protein value (as calculated according to MITCHELL) decreases during the period of ripening and, at the time of full ripeness, it is significantly lower than in the initial stage. This decrease varies from 10.7 to 19.0%, according to wheat variety. In contrast to this, the essential amino-acid index changes but insignificantly with ripening. Virtually identical biological protein values were obtained with both methods from full-ripe wheat grains.

Amino Acids, Essential↗