Showing papers by "Sofia University published in 2001"

Capillary forces and structuring in layers of colloid particles

Abstract: ‘Capillary forces’ are interactions between particles mediated by fluid interfaces. Recent advances in this field have been achieved by experiments and theory on lateral capillary forces, which are due to the overlap of menisci formed around separate particles attached to an interface. In particular, we should mention the cases of ‘finite menisci’ and ‘capillary multipoles’. The capillary-bridge forces were investigated in relation to capillary condensation and cavitation, surface-force measurements and antifoaming by oily drops. The studies on colloidal self-assembly mediated by capillary forces developed in several promising directions. The obtained structures of particles have found numerous applications.

Aqueous humor and serum tumor necrosis factor-alpha in clinical uveitis.

Abstract: Objective: To study the local and systemic behavior of the tumor necrosis factor-α (TNF-α) in patients with active uveitis. Methods: TNF-α levels were measured in aqueous humor and peripheral blood samples using an enzyme-linked immunosorbent assay from 23 patients with uveitis and 16 control patients who had been operated on for uncomplicated cataracts. Results: Aqueous humor and sera of patients with uveitis showed higher levels of TNF-α than those of controls (p Conclusions: TNF-α is a cytokine that participates actively in the pathogenesis of clinical uveitis. Our data emphasize the greater systemic than local participation of TNF-α. Finally, an elevated serum TNF-α seems to be associated with a recurrent pattern of uveitis.

Vanishing theorems and string backgrounds

Abstract: We show various vanishing theorems for the cohomology groups of compact Hermitian manifolds for which the Bismut connection has a (restricted) holonomy contained in SU(n) and classify all such manifolds of dimension four. In this way we provide necessary conditions for the existence of such structures on compact Hermitian manifolds with vanishing first Chern class of non-Kahler type. Then we apply our results to solutions of the string equations and show that such solutions admit various cohomological restrictions such as, for example, that under certain natural assumptions the plurigenera vanish. We also find that under some assumptions the string equations are equivalent to the condition that a certain vector is parallel with respect to the Bismut connection.

Proofs from THE BOOK , by Martin Aigner and Günter M. Ziegler. Pp. 199. £19. 1999. ISBN 3 540 63698 6 (Springer-Verlag).

Abstract: Proofs from THE BOOK, by Martin Aigner and Giinter M. Ziegler. Pp.199. £19. 1999. ISBN 3 540 63698 6 (Springer-Verlag). I would like to begin with the authors' words from the Preface of this book: Paul Erd6s liked to talk about The Book, in which God maintains the perfect proofs for mathematical theorems, following the dictum of G. H. Hardy that there is no permanent place for ugly mathematics. ErdSs also said that 'you need not believe in God but, as a mathematician, you should believe in The Book'. This excellent book is dedicated to the memory of Paul ErdSs. Paul himself wrote several pages but he is not listed as a co-author because of his death in the summer of 1996. The idea of the book is to present beautiful proofs of some of the most exciting and historically important mathematical theorems. The book focuses on human endeavour to make the proofs more and more simple and striking.

Raman phonons and Raman Jahn-Teller bands in perovskite-like manganites

Abstract: The perovskite-like manganites RAMnO, where R is a trivalent rare earth or Y and A is a divalent alkaline earth element, are characterized by a strong interplay of magnetism, electric transport and crystallographic distortion At doping levels 015 < x < 045 the materials exhibit colossal magnetoresistance near the concomitant ferromagnetic and insulator-metal transitions At a fractional doping level, such as x = 05, the crystallographic and magnetic environment is strongly modified and charge ordering between Mn and Mn or phase separation takes place In this work, the polarized Raman spectra of the orthorhombic and rhombohedral phases of parent RMnO compound were analyzed in close comparison with results of lattice dynamic calculations We argue that the strong high-wavenumber bands between 400 and 700 cm, which dominate the Raman spectra of rhombohedral RMnO and magnetoresistive LaAMnO are not proper Raman modes for the R3c or Pnma structures Rather, the bands are of phonon density-of-states origin and correspond to oxygen phonon branches activated by the non-coherent Jahn-Teller distortions of the MnO octahedra The reduction of these bands upon doping of LaAMnO and their disappearance in the ferromagnetic metallic phase support the model The variation with temperature of the Raman spectra of LaCaMnO is also discussed The results give a strong indication for charge and orbital ordering and formation of superstructure at low temperatures

Melatonin versus vitamin E as protective treatment against oxidative stress after extra-hepatic bile duct ligation in rats.

Abstract: The aims of the present study were first to compare the effects of melatonin and vitamin E on the cholestasis syndrome and their protective effect on liver injury, and second, to evaluate the activity of antioxidant enzymes after treatment with these antioxidant drugs. Cholestasis was achieved in adult male Wistar rats by double ligature and section of the extra-hepatic biliary duct. Hepatic and plasma oxidative stress markers were evaluated by changes in the amount of lipid peroxides, measured as malondialdehyde (MDA) and reduced glutathione (GSH) in plasma and homogenates of hepatic tissue. Serum bilirubin, alkaline phosphatase (AP), and gamma-glutamyl-transpeptidase (GGT) were used to evaluate the severity of cholestasis, and serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were used to evaluate the hepatic injury. Both vitamin E and melatonin were administrated 1 day before and 7 days after bile duct ligation. Acute ligation of the bile duct was accompanied by a significant increased in MDA and a decrease in GSH levels in both plasma and liver, as well as a significant reduction in antioxidant enzymes activities. The overall analysis of both treatments showed that melatonin (500 microg/kg daily) offered significantly better protection against cholestasis and a superior protective effect on hepatic injury than did vitamin E (15 mg/kg daily). Although vitamin E treatment resulted in a reduction of parameters of oxidative stress, the results were significantly better after a much lower daily dose of melatonin. Moreover, melatonin treatment was associated with a significant recovery of antioxidative enzymes. In conclusion, the present paper demonstrates a correlation between the intensity of biliary tract obstruction and increased free radical generation, as well as a direct correlation between the level of oxidative stress and the biochemical markers of liver injury. Melatonin (at a much lower dose than vitamin E) was much more efficient than vitamin E in reducing the negative parameters of cholestasis, the degree of oxidative stress and provided a significantly greater hepatoprotective effect against the liver injury secondary to the acute ligation of the biliary duct.

Drosophila melanogaster transferrin. Cloning, deduced protein sequence, expression during the life cycle, gene localization and up-regulation on bacterial infection.

Abstract: Drosophila melanogaster transferrin cDNA was cloned from an ovarian cDNA library by using a PCR fragment amplified by two primers designed from other dipteran transferrin sequences. The clone (2035 bp) encodes a protein of 641 amino acids containing a signal peptide of 29 amino acids. Like other insect transferrins, Drosophila transferrin appears to have a functional iron-binding site only in the N-terminal lobe. The C-terminal lobe lacks iron-binding residues found in other transferrins, and has large deletions which make it much smaller than functional C-terminal lobes in other transferrins. In-situ hybridization using a digoxigenin labeled transferrin cDNA probe revealed that the gene is located at position 17B1-2 on the X chromosome. Northern blot analysis showed that transferrin mRNA was present in the larval, pupal and adult stages, but was not detectable in the embryo. Iron supplementation of the diet resulted in lower levels of transferrin mRNA. When adult flies were inoculated with bacteria (Escherichia coli), transferrin mRNA synthesis was markedly increased relative to controls.

Particles with an Undulated Contact Line at a Fluid Interface: Interaction between Capillary Quadrupoles and Rheology of Particulate Monolayers

Abstract: We consider solid particles attached to a liquid−fluid interface. If the solid−liquid−fluid contact line (at the particle surface) is undulated, the convex and concave local deviations of the meniscus shape from planarity can be treated as positive and negative capillary charges, which form capillary multipoles. Correspondingly, the meniscus shape can be expressed as a multipole expansion. The leading terms of the capillary multipole expansion turn out to be the charges and quadrupoles. In the present article, we derive theoretical expressions, which enable one to calculate the energy and force of interaction between two capillary quadrupoles for arbitrary interparticle distance. Depending on the amplitudes of the contact-line undulations, and on the particle mutual orientations, the interaction is either monotonic attraction or attraction at long distances but repulsion at short distances. As a rule, the interaction energy is much larger than the thermal energy kT, even for undulations of nanometer ampli...

Regional sea level response to global climatic change: Black Sea examples

Abstract: The sensitivity of Black Sea level to variations in the global forcing is studied here using tide gauge and satellite altimeter data, as well as hydro-meteorological data for the fresh water flux components. The consistency between satellite and sea borne data is analyzed and the characteristics of variability with monthly to interannual time scales are revealed. The analysis of 6-year-long data series of TOPEX/Poseidon altimeter shows that the first EOF accounts for 85% of the total variance and is associated with the water cycle, the latter forced by the air–sea exchange, continental hydrological budgets and straits outflow. This result is a demonstration that the Black Sea level integrates the variations of global forcing over vast catchment area, thus making them quite distinguishable. The second EOF describes the seasonal variability of circulation. The third and higher EOFs describe synoptic and basin-oscillations, and the corresponding principal components are characterized by strong interannual variability. By analyzing the correlation of sea level and water balance in the last 70 years, we quantify the response to the external forcing. The mean sea level trend during 1993–1997, derived from the TOPEX/Poseidon data, of ∼12 cm is much lower than the largest trends of this type observed in the last 120 years, which are associated with interannual-to-decadal variability and reach ∼20–30 cm. The correlation between the sea level and NAO index, starting from 1870s, is well pronounced, suggesting that future variations of sea level could be predicted using global climate indices. It is shown that the long-term changes of water balance are strong enough to substantially affect the exchange between Black Sea and Mediterranean Sea. This in turn might result in changing the conditions of water mass formation in the Aegean Sea and motivates further studies on the prediction of extreme events of deep water mass formation in the Eastern Mediterranean Sea as function of the global and regional water cycles.

Vanishing theorems on Hermitian manifolds

Abstract: We prove the vanishing of the Dolbeault cohomology groups on Hermitian manifolds with dd c -harmonic Kahler form and positive (1,1) -part of the Ricci form of the Bismut connection. This implies the vanishing of the Dolbeault cohomology groups on complex surfaces which admit a conformal class of Hermitian metrics, such that the Ricci tensor of the canonical Weyl structure is positive. As a corollary we obtain that any such surface must be rational with c 1 2 >0 . As an application, the p th Dolbeault cohomology groups of a left-invariant complex structure compatible with bi-invariant metric on a compact even dimensional Lie group are computed.

High rate of tuberculosis reinfection during a nosocomial outbreak of multidrug-resistant tuberculosis caused by Mycobacterium bovis strain B.

Abstract: We present a study of a nosocomial outbreak of multidrug-resistant tuberculosis caused by Mycobacterium bovis in 31 patients, 30 of whom were infected with human immunodeficiency virus; all 31 died of progressive tuberculosis. All M. bovis strains had identical spoligotyping patterns and showed resistance to 12 antituberculosis drugs. Reinfection was suggested in 11 cases and confirmed in 4 by molecular typing methods. The causative strain was named "B strain."

Lymphoepithelioma-like carcinoma of the urinary bladder: a clinicopathologic study of 13 cases

Abstract: Lymphoepithelioma-like carcinoma (LELCA) of the urinary bladder is a rare variant of bladder cancer characterized by a malignant epithelial component densely infiltrated by lymphoid cells. It is characterized by indistinct cytoplasmic borders and a syncytial growth pattern. These neoplasms deserve recognition and attention, chiefly because they may be responsive to chemotherapy. We report on the clinicopathologic features of 13 cases of LELCA recorded since 1981. The chief complaint in all 13 patients was hematuria. Their ages ranged from 58 years to 82 years. All tumors were muscle invasive. A significant lymphocytic reaction was present in all of these tumors. There were three pure LELCA and six predominant LELCA with a concurrent transitional cell carcinoma (TCC). The remainder four cases had a focal LELCA component admixed with TCC. Immunohistochemistry showed LELCA to be reactive against epithelial membrane antigen and several cytokeratins (CKs; AE1/AE3, AE1, AE3, CK7, and CK8). CK20 and CD44v6 stained focally. The lymphocytic component was composed of a mixture of T and B cells intermingled with some dendritic cells and histiocytes. Latent membrane protein 1 (LMP1) immunostaining and in situ hybridization for Epstein-Barr virus were negative in all 13 cases. DNA ploidy of these tumors gave DNA histograms with diploid peaks (n=7) or non-diploid peaks (aneuploid or tetraploid; n=6). All patients with pure and 66% with predominant LELCA were alive, while all patients having focal LELCA died of disease. Our data suggest that pure and predominant LELCA of the bladder appear to be morphologically and clinically different from other bladder (undifferentiated and poorly differentiated conventional TCC) carcinomas and should be recognized as separate clinicopathological variants of TCC with heavy lymphocytic reaction relevant in patient management.

Infrared and Raman spectra of Ga2O3–P2O5 glasses

Abstract: The structure of x Ga 2 O 3 (1−x) P 2 O 5 (0.15 ⩽ x ⩽ 0.4) glasses is studied by infrared (IR) and Raman spectroscopy. The results of quantitative electron microprobe analysis reveal that two sets of glasses are formed with compositions corresponding to the gallium meta and pyrophosphates. Crystalline Ga(PO 3 ) 3 metaphosphate is also obtained and its IR and Raman spectra recorded in order to examine the spectral differences glass → crystal. The IR spectra of metaphosphate glasses show bands at 1250, 930, 775 and 485 cm −1 which, are assigned to the ν as PO 2 , ν as POP, ν s POP and δPO 2 modes of the metaphosphate chain. In the Raman spectra are found patterns due to symmetric modes of PO 2 terminal and POP bridging bonds as well as features due to vibrations of GaO 4 tetrahedra and Ga–O–P bridges. Comparisons of the spectra of glasses with those of the crystal indicate that the interaction of Ga with the polyphosphate anions is more covalent in the glasses. The bands observed in the spectra of pyrophosphate glasses provide evidence for the involvement of ortho-, pyro- and polyphosphate groupings in the glass structure. The Raman spectra of both sets of glasses display intense low frequency bands, which we assigned to a symmetric bending of Ga–O–P bridging bonds involving four-coordinated gallium atoms. It is concluded that structure of Ga 2 O 3 –P 2 O 5 glasses is a highly polymerized network consisting of a variety of phosphate anions cross-linked by GaO 4 tetrahedra. This account on glass structure is consistent with the great glass forming ability of the compositions studied.

Nanosize gold catalysts promoted by vanadium oxide supported on titania and zirconia for complete benzene oxidation

Abstract: The complete benzene oxidation reaction was used to test the reactivity of the Au-V 2 O 5 /TiO 2 and Au-V 2 O 5 /ZrO 2 catalytic systems. A strong synergistic effect between gold and vanadia was established when molecular oxygen was used as an oxidizing agent. This effect was more pronounced for titania than for the zirconia support. In the presence of gold, predominantly polyvanadate structures are formed on the surface which are more active in the reaction of complete benzene oxidation in comparison with monovanadate species and bulk V 2 O 5 . The deposition of gold leads to a relative lengthening of the VO bond and to a higher electron delocalization. The B and C parameters calculated from ESR spectra showed no differences for the fresh and spent gold-containing samples, i.e. the catalytic systems seemed to be “stabilized” under the working conditions. The effect of gold on the vanadium oxide reducibility, which could be related to the strength of the VO-support bond, results in a considerable lowering of the temperature of the V 5+ → V 3+ transition. With ozone as the oxidizing agent, an additional lowering of the reaction temperature was achieved and very close values of the catalytic activity on all investigated samples were registered. Upon oxidation by molecular oxygen the oxidant activation takes place on the nanosize gold particles while the vanadium oxide surface species are responsible for the activation of benzene. This is in agreement with synergistic effect between the finely dispersed gold and the surface vanadium structures.

The buccal fat pad flap in oral reconstruction

Abstract: Background The aim of this study is to describe the surgical technique, indications, advantages, and possible complications of the buccal fat pad flap and to report our clinical experience with this flap for intraoral reconstruction after tumor removal. Methods The flap has been used to reconstruct oral defects after tumor resection in 32 patients, who have been retrospectively analyzed. Results Adequate closure of the defect was achieved during surgery in all cases. In one case, there was partial loss of the flap; this was treated conservatively. In five cases there was some retraction in the reconstructed area. Conclusions Buccal fat pad as a flap offers an adequate reconstructive option to be born in mind when reconstructing small to medium defects in the oral cavity. It is a simple and quick surgical technique with a low incidence of complications. © 2001 John Wiley & Sons, Inc. Head Neck 23: 383–388, 2001.

The complexity of pathogen defense in plants

Abstract: Summary. Plants defend themselves against pathogen attack by activating a multicomponent defense response. In host defense, pathogen invasion is recognized by proteins encoded by plant disease resistance (R) genes that bind specific pathogen-derived avirulence (Avr) proteins. In nonhost resistance, specific pathogen or plant cell wall derived exogenous or endogenous elicitors are recognized. A complex signalling network, involving cytosolic Ca 2+ and H + ions, reactive oxygen intermediates, jasmonate, salicylic acid, ethylene, triggers the induction of the defense mechanisms. Defense genes encode pathogenesis-related proteins, such as glucanases, chitinases; enzymes involved in the biosynthesis of phytoalexins; the enzymes of oxidative stress protection, tissue repair, lignification, and others.

Enhancing Mechanisms of Neutrino Transitions in a Medium of Nonperiodic Constant - Density Layers and in the Earth

Abstract: The enhancement of the transitions ${\ensuremath{ u}}_{\ensuremath{\mu}}({\ensuremath{ u}}_{e})\ensuremath{\rightarrow}{\ensuremath{ u}}_{e}({\ensuremath{ u}}_{\ensuremath{\mu};\ensuremath{\tau}}),$ ${\ensuremath{ u}}_{2}\ensuremath{\rightarrow}{\ensuremath{ u}}_{e},$ ${\overline{\ensuremath{ u}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{ u}}}_{s},$ ${\ensuremath{ u}}_{e}\ensuremath{\rightarrow}{\ensuremath{ u}}_{s},$ etc. of neutrinos passing through a medium of nonperiodic density distribution, consisting of (i) two layers of different constant densities (e.g., Earth core and mantle), or (ii) three layers of constant density with the first and the third layers having identical densities and widths which differ from those of the second layer (e.g., mantle-core-mantle in the Earth), is studied. We find that, in addition to the known local maxima associated with the MSW effect and the neutrino oscillation length resonance (NOLR), the relevant two-neutrino transition probabilities have new resonance-like absolute maxima. The latter correspond to a new effect of total neutrino conversion and are absolute maxima in any independent variable: the neutrino energy, the layers widths, etc. We find the complete set of such maxima. We prove that the NOLR and the new absolute maxima are caused by a maximal constructive interference between the amplitudes of the neutrino transitions in the different density layers. We show that the strong resonance-like enhancement of the transitions in the Earth of the Earth-core-crossing solar and atmospheric neutrinos is due to the effect of total neutrino conversion.

Stability and interpersonal agreement of the interview-based diagnosis of autism.

Abstract: Interpersonal agreement and stability of the Autism Diagnostic Interview-Revised (ADI-R) was examined in this study. Four raters judging 55 subjects agreed moderately to excellently on the items of the diagnostic algorithm, operationalizing the main autistic symptoms according to the classification guidelines of ICD-10 and DSM-IV. When retesting 33 individuals, some items revealed only weak stability. On the level of domains of autistic behavior and diagnosis, the interrater reliability and retest reliability were consistently convincing.

Rheological Model for the Study of Dilational Properties of Monolayers. Comportment of Dipalmitoylphosphatidylcholine (DPPC) at the Dichloromethane (DCM)/Water Interface under Ramp Type or Sinusoidal Perturbations

Abstract: The dilational properties of monolayers are analyzed using the classical linear approximation. In most cases, the observed interfacial behavior can be approached by a model corresponding to a two-dimensional viscoelastic solid. The monolayer is characterized by two dilational elasticity terms (Ee, equilibrium elasticity, and Ene, nonequilibrium elasticity) and by one relaxation time (τ). These three physical constants are obtained from the responses of a ramp type perturbation, or from the responses (as a function of the frequencies) after sinusoidal area variations. Using axisymmetric drop shape analysis experiments, a dipalmitoyl phosphatidylcholine (DPPC) layer at the dichloromethane/water interface is characterized. Measurements of the surface pressure variations as the response to linear or sinusoidal variations of surface area are performed. Identical rheological physical constants (equilibrium elasticity, nonequilibrium elasticity, and relaxation time) are obtained using both methods. Dilational be...

Coexistence of Superconductivity and Ferromagnetism in Ferromagnetic Metals

Abstract: We address the question of coexistence of superconductivity and ferromagnetism. Using a field theoretical approach we study a one-fermion effective model of a ferromagnetic superconductor in which the quasiparticles responsible for the ferromagnetism form the Cooper pairs as well. For the first time we solve self-consistently the mean-field equations for the superconducting gap and the spontaneous magnetization. We discuss the physical features which are different in this model and the standard BCS model and consider their experimental consequences.