Showing papers by "University of Zagreb published in 1974"
TL;DR: In this article, the electrical resistivity for a series of Au Fe alloys with concentrations between 05- and 22-at% Fe, in the temperature range 0 - 300 K, was measured.
Abstract: Measurements are presented of the electrical resistivity for a series of Au Fe alloys with concentrations between 05- and 22-at% Fe, in the temperature range 05 - 300 K We have called the concentration range between about 05- and 8-at% Fe, the spin-glass regime Here we find that the impurity resistivity $\ensuremath{\Delta}\ensuremath{\rho}$ has a ${T}^{\frac{3}{2}}$ dependence down to the lowest temperatures of measurement, the coefficient of this dependence decreasing very slowly with concentration At higher temperatures, around the "freezing" temperature ${T}_{0}$ the impurity resistivity is increasing linearly with temperature, and this is followed, at much larger temperatures, by a very broad resistance maximum We have called the concentration range above \ensuremath{\cong}10-at% Fe, the mictomagnetic regime which is characterized by having large magnetic clusters and a sensitivity to thermal and magnetic history Upon further increasing the concentration to the percolation limit $c\ensuremath{\gtrsim}15$ at%, such that there is sufficient overlapping among these magnetic clusters, Au Fe gradually develops a long-range inhomogeneous ferromagnetic regime Again we observe a ${T}^{\frac{3}{2}}$ temperature dependence throughout both of these regimes at low temperatures, but at higher temperatures the deviation away from this dependence is much more complicated than in the spin-glass regime Further, the onset of magnetic ordering is clearly seen in $\ensuremath{\Delta}\ensuremath{\rho}$ We have also examined the temperature dependence of the derivative of the impurity resistivity $\frac{d(\ensuremath{\Delta}\ensuremath{\rho})}{\mathrm{dT}}$, and find that throughout our whole concentration range there is a well-defined maximum which correlates fairly well with ${T}_{0}$ The experimental and theoretical background of these measurements is fully discussed
85 citations
TL;DR: The induction of embryogenic callus in pumpkin seems to be strongly dependent on the genetic constitution of each individual plant.
Abstract: Embryogenic callus was induced by culturing explants of pumpkin hypocotyls on Murashige-Skoog-medium with the addition of 3% glucose and one of the following growth substances (or combinations of them): β-indolylbutyric acid, 2,4-dichlorophenoxyacetic acid, β-indolylacetic acid, α-naphthyl-acetic acid, adenine (natural), kinetin, autoclaved water-melon sap and yeast extract (Difco). A large number of embryoids and adventive buds were produced. These were able to develop to normal plants.
The 17 strains of embryogenic tissue obtained have maintained their embryogenic characteristics for more than 3 years. The induction of embryogenic callus in pumpkin seems to be strongly dependent on the genetic constitution of each individual plant.
70 citations
TL;DR: These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm is suggested.
Abstract: Single germ layers (or combinations of two of them) were isolated from the primitive streak and the head-fold stage rat embryos and grown for 15 days under the kidney capsule of syngeneic adult animals. The resulting teratomas were examined histologically for the presence of mature tissues, with special emphasis on derivatives of the primitive gut.
Ectoderm isolated together with the initial mesodermal wings at the primitive streak stage gave rise to tissue derivatives of all three definitive germ layers. Derivatives of the primitive gut were regularly present in these grafts. At the head-fold stage, isolated ectoderm (including the region of the primitive streak) differentiated into ectodermal and mesodermal derivatives only.
Endoderm isolated at the primitive streak stage did not develop when grafted and was always completely resorbed. At the head-fold stage, however, definitive endoderm differentiated into derivatives of the primitive gut if grafted together with adjacent mesoderm.
These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm.
43 citations
TL;DR: The Rh system may be associated with a gene or genes involved in immune response regulation, as well as different kinds of humoral and cell-mediated immune responses, which were determined in 133 volunteers.
Abstract: HL-A, ABO, and Rh antigens, as well as different kinds of humoral and cell-mediated immune responses, were determined in 133 volunteers. These were selected from 463 subjects immunized with U ( D ) , or staphylococcus, or pertussis antigens according to their low and high immune responsiveness. HL-A and blood group antigens were correlated by a computer program to categorized immune parameters (low, medium, high values). The latter were correlated with each other. The only notable association of the immune parameters with HL-A antigens was found between HL-A 3 and 7 and spontaneous lymphocytotoxic activity in mouse fibroblast monolayer. A striking correlation was, however, found between R h antigens and a number of antibacterial antibody levels and parameters of cell-mediated immune responses. These correlations indicate that Rho(D)-positive subjects had rather high ‘natural‘ antibody levels and PHA-reactive lymphocytes. The latter were stimulated, however, only with high doses of PHA (PHA hyposensitivity) and they lacked spontaneous lymphocytotoxic activity. A reverse correlation was found in Rho(D)-negative subjects, the ability to produce anti-Rh,(D) antibodies being negatively associated with the level of some antibacterial antibodies. Natural antibody, immunoglobulin level and lymphocyte activity were significantly lower in males. Correlation was seldom found between categorized values of the individual immune parameters such as antibacterial antibodies, immunoglobulins, complement, and cellmediated immunity factors. Negative correlations were obtained between PHA hyposensitivity and a low antibacterial antibody level, and a positive one between IgA, complement level and lymphocyte stimulation. These results the Rh system may be associated with a gene or genes involved in immune response regulation.
39 citations
TL;DR: In this article, a case-control study of cervical cancer among Moslems and non-Moslems in Yugoslavia was conducted and the authors investigated the role of genital herpes virus in the pathogenesis of the cervical cancer.
Abstract: To investigate the possible role of a genital herpes virus in the pathogenesis of cervical cancer epidemiological factors were sought in a case-control study of cervical cancer among Moslems and non-Moslems in Yugoslavia. Women who developed cervical cancer were more likely to manifest behavorial characteristics such as smoking drinking of alcohol and diminished religiosity. The cases were significantly shorter lighter and less endomorphic than controls similar in age marital status religion and urban/rural residence. They also had somewhat higher systolic and diastolic blood pressures at 2 different readings. Parents of cases tended to be older especially 40 years than parents of controls at the time of the patients births. Multiple marriages and early initiation of coitus were more common among the cases. However coital frequency was consistently lower among Moslem and non-Moslem cases than controls both at the onset of coital practice and later cases tended to have more normal menstrual histories than controls with relatively fewer long heavy painful or irregular cycles. Absences from home and extramarital sexual experiences were significantly more common among the first husbands of the cases. An unexpected finding was the twofold or threefold greater mortality especially at young ages of first husbands of cases as compared with those of controls. The cases tended to experience more frequent and longer widowhoods beginning at earlier ages than controls. For most of the variables studied case-con trol differences among the Moslem women closely resembled those among the non-Moslems. The results of this investigation are consistent with the venereal hypothesis of cervical carcinogenesis but suggest the need for further investigations of the role of steroid hormones in this disease.(AUTHORS MODIFIED)
31 citations
TL;DR: The concentration of 5-hydroxyincdoleacetic acid in the lumbar fluid of animals and man reflects the biochemical changes of 5.hydroxytryptamine in the spinal cord.
Abstract: In cats, 19 days after the lower thoracic cord was injllred, the concentrations of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid in the lumbosacral cord and that of 5-hydroxyindoleacetic acid in the lumbar fluid decreased. At the same time the concentrations of these substances in the cord above the lesion and that of 5-hydroxyindoleacetic acid in the cisternal fluid was not significantly altered. Since high concentrations of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid are present in the human lumbosacral cord, it appears that the concentration of 5-hydroxyincdoleacetic acid in the lumbar fluid of animals and man reflects the biochemical changes of 5-hydroxytryptamine in the spinal cord.
29 citations
TL;DR: In this article, it was shown that only the graphs 1-7 have integral spectra, and only these molecular graphs have integral spectral properties, and the proof of this theorem elucidates also several interesting spectral properties of graphs which represent unsaturated conjugated compounds.
25 citations
TL;DR: In this article, the stereoselectivity in the aerobic, microbial oxidation of thioethers and sulphoxides is shown to be dependent on species and strain, and a strain of Aspergillus niger was used to obtain an optically active dialkyl sulphoxide.
24 citations
20 citations
TL;DR: In this article, a novel way of tetrazolium salt preparation by anodic oxidation of formazan is described, and the mechanism of oxidation was deduced from voltammetric data and by coulometry at controlled potential.
17 citations
TL;DR: In this paper, a Monte Carlo method was used for the determination of the areas under chromatographic curves (peaks) based on the application of the Monte Carlo procedure, and its advantage lies in its successful application to irregular curves.
Abstract: A rapid method is described for the determination of the areas under chromatographic curves (peaks) The method is based on the application of the Monte Carlo procedure, and its advantage lies in its successful application to irregular curves
TL;DR: In this article, the solid solubility of Pt in Al was extended from 0 to 2 at. % by two-piston quenching technique, and the stability of the Al-Pt solid solution during annealing was discussed.
Abstract: The solid solubility of Pt in Al was extended from 0 to 2 at. % by “two-piston” quenching technique. The stability of the Al-Pt solid solution during annealing is discussed. During the decomposition an intermediate metastable phase was detected, the unit cell constants of which were determined.
TL;DR: In this article, the phonon renormalization and the occurrence of phonon instabilities in quasi-one-dimensional systems are considered. But the results for the phonons density of states are analogous to those obtained in the usual, adiabatic approximation.
Abstract: In this paper we review some of our previous calculations and present several new results. We consider the phonon renormalization and the occurrence of the phonon instabilities in quasi-one-dimensional systems. Using the self-consistent tight-binding electron-phonon coupling, the renormalization of various phonon modes is compared. The characteristics of the most unstable mode are considered in some detail. By considering the ω-dependence of the phonon self-energy at temperatures above the critical temperatureTϰ, we establish the criteria for the appearance of dynamic effects in the phonon spectrum. For systems with very low critical temperature (Tϰ much smaller than the unrenormalized phonon frequency ωϰ0 an additional phonon branch appears and becomes soft whenT→Tϰ. For other systems the results for the phonon density of states are analogous to those obtained in the usual, adiabatic approximation. In this latter limit we obtain the following new results: i) the long-wavelength (ϰz=0) instability continuously changes to the Peierls-type one (ϰz=2kF) when the characteristic electron-phonon parameter is varied; ii) in this transition regime the temperature-independent longitudinal coherence length ξ0 for the crystal instability can vanish; iii) the band contribution to the chain deformation energy is, in the harmonic approximation, independent of the phase of the chain distortion with respect to the lattice, except in the extreme commensurate case of the half-filled band.
TL;DR: In this article, the existence of wave operators is proved for the case where the unperturbed operator is the operator of multiplication by a smooth function in momentum space and the perturbation is an arbitrary operator satisfying a fall off condition near infinity or a weighted L p -estimate in configuration space.
TL;DR: It was concluded that some host related factors, possibly of an immunologic nature, govern and regulate the outgrowth of tumors from mouse egg cylinders and determine whether the grafted embryo will give rise to benign teratomas or teratocarcinomas.
Abstract: 7 day old mouse egg cylinders transplanted under the renal capsule give rise to both teratomas and teratocarcinomas in mice of C3H/H, CBA and A strains. The proportion of benign to malignant tumors is approximately the same in the three strains. In C57BL mice, only an occasional graft examined histologically 2 months after transplantation of the embryo contains undifferentiated embryonal cells and could thus be considered a teratocarcinoma. None of these “teratocarcinomas” in C57BL mice could be retransplanted and thus unequivocally proven to be malignant. C57BL egg cylinders grafted to C57BL × C3H/H F1 hybrids gave rise to numerous teratocarcinomas. It was possible to obtain teratocarcinomas from C57BL egg cylinders grafted to lethally irradiated isogenic hosts salvaged with the bone marrow cells of C57BL × C3H/HF1 hybrids. These tumors were retransplantable in hybrids but not in inbred C57BL recipients. It was concluded that some host related factors, possibly of an immunologic nature, govern and regulate the outgrowth of tumors from mouse egg cylinders and determine whether the grafted embryo will give rise to benign teratomas or teratocarcinomas.
TL;DR: This unique combination of properties distinguishes the aspartate trans-carbamylases of flatworms from those of bacteria, fungi, plants and mammalian tissues.
Abstract: 1. 1. The properties of aspartate transcarbamylases of Fasciola hepatica, Moniezia benedeni and Paramphistomumcervi are very similar:they are most active at pH 9·2, and are precipitated at 30% ammonium sulphate concentration. ATP stimulates and malate inhibits their activity, while CTP has no effect upon them. They all are temperature-stable and are localized in the cytosol fraction. 2. 2. This unique combination of properties distinguishes the aspartate trans-carbamylases of flatworms from those of bacteria, fungi, plants and mammalian tissues. 3. 3. Even in the absence of carbamyl phosphate synthetases certain formation of carbamyl aspartate occurs in vitro in crude homogenates of all platyhelminths examined. The possible sources of carbamyl phosphate are discussed.
TL;DR: The longitudinal proton magnetic relaxation times T1 were measured and it was concluded that the correlation time τC for the dipole–dipole interaction of electron and nuclear spins is in fact the electron (ferric) spin relaxation time τS being close to 1.5 × 10−10 sec for both metHb and metMb at 5°C.
Abstract: The longitudinal proton magnetic relaxation times T1 were measured for ferri (met)-and carbonmonoxy-bovine haemoglobin and equine myoglobin in 0.1 M KH2PO4 aqueous solutions near pH 6 at 5°C and 35°C from 1.5- to 60-MHz Larmor frequencies. It is concluded that the correlation time τC for the dipole–dipole interaction of electron and nuclear spins is in fact the electron (ferric) spin relaxation time τS being close to 1.5 × 10−10 sec for both metHb and metMb at 5°C. At 35°C the paramagnetic relaxation rates are not determined solely by the relaxation of protons exchanging from the haem pocket with bulk solvent. Hence, τC at 35°C cannot be calculated from the dispersion data obtained at this temperature. The relevance of this for the determination of interspin distances r is discussed.
TL;DR: It seems that the stability of perceived intensity during current flow is principally due to some irritation of the sensitive tissue of the tongue, whereas cross-adaptation effects may be attributed to the potential changes across the excitable membranes caused by electrical properties of adapting electrolytic solutions.
Abstract: In spite of a clear increment in absolute thresholds as an effect of self-adaptation, the electrically provoked taste sensation does not show a reduction in subjective intensity during the protracted stimulation time. Chemical cross-adaptation effects on the threshold and suprathreshold levels of electrical taste are observed only when the adapting solutions are electrolytes regardless of their taste qualities. It seems that the stability of perceived intensity during current flow is principally due to some irritation of the sensitive tissue of the tongue, whereas cross-adaptation effects may be attributed to the potential changes across the excitable membranes caused by electrical properties of adapting electrolytic solutions.
Journal Article•
TL;DR: There is no tightening of the haem-pockets upon addition of IHP to solutions of any of the three haemoglobin samples, and it is suggested that the structural aspect of ligand affinity is not as decisive in altering the affinity by IHP as is possibly the change in theHaem-iron spin-state induced by !
Abstract: Inositol hexaphosphate is the strongest allosteric effector even for the metform of haemoglobin. Its effects upon the quaternary structure of the tetramer have been studied in relation to the overall conformational state(s) of the haem-pockets in aqueous solutions of human haemoglobins. The method useci, proton magnetic relaxation, yields information about the accessibility of solvent pl.'otons towards the haem-iron. No differences in the relaxation rates were detected by this method between the unstripped carbonmonoxyhaemoglobin and the phosphate-stripped sample in the presence and absence of IHP. There are considerable changes in those relaxation rate·s due to the paramagnetic haem-iron of aquomethaemoglobin when IHP is added to the stripped adult haemoglobin, but none is observed for the foetal haemoglobin, although a similar shift in the spin-state equilibrium ts expected for both haemoglobins on addition of ,!HP. Neither was there any change with IHP in solutions of adult fluoromethaemoglobin. It is concluded thart there is no tightening of the haem-pockets upon addition of IHP to solutions of any of the three haemoglobin samples. An increase in the accessibility of the haem-pockets is probable only for the aquometfom1 of the adult haemoglobin. It is suggested that the structural aspect of ligand affinity, i.e. the haem-pocket conformation, is not as decisive in altering the affinity by IHP as is possibly the change in the haem-iron spin-state induced by !HP-binding.
TL;DR: In this paper, the authors used IR correlation function analysis for benzene ring rotaions of liquid crystal HOAB and found that these rotations occur in random angular jumps of 30[ddot] in the smectic phase and of 60 [ddot]- in the nematic and isotropic phases.
Abstract: By using IR correlation function analysis for benzene ring rotaions of liquid crystal HOAB it has been found that these rotations occur in random angular jumps of 30[ddot] in the smectic phase and of 60[ddot] in the nematic and isotropic phases. The corresponding rotaional correlation times are of the order of 10−12 s which aapears to be comparable with those for benzene ring rotations in ordinary organic liqids.
TL;DR: In this paper, it was shown that small amounts of lead can be detected on chromatograms (0.2-0.3 μg on cellulose thin layers and about 0.4 μg on paper) as the fluorescent [PbCl 4 ] 2− complex (excitation maximum 254 nm; emission maximum 480 nm).
TL;DR: In this paper, the crystal structure was determined by three-dimensional X-ray analysis and the structure was solved from Patterson and electron-density maps and refined by least-squares methods to a conventional R index of 0.105 for 724 independent, non-zero reflexions collected by the use of equi-inclination Weissenberg photographs.
Abstract: The crystal structure has been determined by three-dimensional X-ray analysis. The monoclinic unit cell of dimensions a = 14.886 ± 0.005, b = 9.337 ± 0.005, c = 8.230 ± 0.005 A, β = 124.4 ± 0.2° contains four formula units of Hg2(CF3CO2)2. The space group is C2/c. The structure was solved from Patterson and electron-density maps and refined by least-squares methods to a conventional R index of 0.105 for 724 independent, non-zero reflexions collected by the use of equi-inclination Weissenberg photographs. The crystal structure is built up of discrete molecules with the molecular symmetry C2. The molecules are connected by intermolecular Hg … O bonds 2.64 A long to form puckered ribbons extending along the c direction. The Hg-Hg distance is 2.505 ± 0.003 A. The carboxy group is bonded to the mercury atom by one oxygen atom at a distance of 2.14 ± 0.03 A with the bond angle HgHgO of 166.6°, the other oxygen atom being located 2.81 ± 0.05 A from the same mercury atom.
TL;DR: An immunological reaction of the host against embryonic antigens in the egg-cylinder might determine whether the transplant develops as teratoma or teratocarcinoma, and Splenectomy reduced the growth of the transplanted embryos.
Abstract: MOUSE egg-cylinders transplanted to extrauterine sites develop either as teratomas (benign tumours composed of adult tissues) or as teratocarcinomas (retransplantable malignant tumours containing, in addition, undifferentiated embryonic carcinoma cells)1–4. Rat egg-cylinders similarly transplanted, however, always develop as teratoma5. When transplanted to a syngeneic host, C57BL mouse egg-cylinders develop as teratomas but when transplanted to (C3H × C57BL)F1 hybrids they develop into teratocarcinoma3,4. This suggests that the host reaction is important in determining the fate of a transplanted embryo. Specific embryonic and foetal antigens which are re-expressed during malignant transformation are now well established6–8, and we thought that an immunological reaction of the host against embryonic antigens in the egg-cylinder might determine whether the transplant develops as teratoma or teratocarcinoma. Splenomegaly is considered to be a sign that a host has reacted to the antigenic stimulation of a graft or tumour9,10, and we have found that although it is always present in mice with transplanted egg-cylinders, it is much more pronounced in those with teratocarcinoma. Splenectomy, however, reduced the growth of the transplanted embryos, suggesting that the immunological reaction of the host stimulates the growth of the graft.
TL;DR: Some new syntheses of 1-[2′-(ethylsulfonyl)ethyl]-2-methyl-5-nitroimidazole (IV), a new antitrichomonal agent are described in this paper.
TL;DR: Four cerebrins (ceramides) and two cerebrosides were isolated from the mushroom Clitocybe tabescens by combining column chromatography and preparative thin-layer chromatography, and glucose was detected as the sole sugar constituent in cereBrosides.
TL;DR: The males who subsequently participated in the screening examination were more likely than non-participants to have been previously involved with the local medical system and utilizers of various health services, and availability and general willingness to participate in voluntary activities other than the screenings examination also characterized the screening participants more than was true of the non- participation.
TL;DR: The phase composition of material formed at 150-600° C and 5-300 bar, for bulk molar Ca/Si ratios between 3.0 and 1.5 has been determined by Speakman et al. as discussed by the authors.
Abstract: HYDROTHERMALLY treated γ-dicalcium silicates–quartz mixtures have been investigated by several authors as a potential calcium silicate building product which, because of its low water content, could be used as refractory or heat insulating material. The phase composition of material formed at 150–600° C and 5–300 bar, for bulk molar Ca/Si ratios between 3.0 and 1.5 has been determined by Speakman et al.1. Jernejcic et al.2,3 investigated lower Ca/Si molar ratios, that is, between 1.5 and 0.5 at 180–250° C, under saturated and superheated steam conditions. Superheated steam conditions during the initial period of hydrothermal reaction gave an unknown phase with a strongly pronounced diffraction maximum of 3.15 A in the multiphase reaction products for bulk Ca/Si ratios lower than 1.25. Using previously recorded crystallographic data for calcium silicates and calcium silicate hydrates, the maximum of about 3.15 A could be assigned to the gyrolite group of hydrates. These phases, however, exhibit strong basal reflections at 22 and 19 A. These basal reflection were not observed and identification was therefore necessary, particularly because there were no signs of pseudo-wollastonite in samples heated to 1000° C, as should have been the case if gyrolite or truscotite or a mixture of both were originally present.