129 research outputs found
Classical Spinning Branes in Curved Backgrounds
The dynamics of a classical branelike object in a curved background is
derived from the covariant stress-energy conservation of the brane matter. The
world sheet equations and boundary conditions are obtained in the pole-dipole
approximation, where nontrivial brane thickness gives rise to its intrinsic
angular momentum. It is shown that intrinsic angular momentum couples to both,
the background curvature and the brane orbital degrees of freedom. The whole
procedure is manifestly covariant with respect to spacetime diffeomorphisms and
world sheet reparametrizations. In addition, two extra gauge symmetries are
discovered and utilized. The examples of the point particle and the string in 4
spacetime dimensions are analyzed in more detail. A particular attention is
paid to the Nambu-Goto string with massive spinning particles attached to its
ends
MEDICAL NUTRITION THERAPY IN MANAGEMENT OF EATING DISORDERS
The treatment of eating disorders demands a comprehensive medical approach, where a dietitian has an important role, primarily due to numerous instances of malnutrition. The objective of this paper was to recapitulate the research findings and clinical evidence which show the importance of medical nutrition therapy in the treatment of eating disorders; furthermore, they present significant guidelines for clinical practice. The research methods have entailed a thorough exploration of literature available at research data bases. The results of the research studies published so far have unambiguously pointed out that, when eating disorders are concerned, there is an urgent need for a diet therapy in order for the patient to restore the appropriate body weight as well as normal eating habits. On the one hand, certain authors suggest returning to normal nutritional habits immediately, whereas, on the other hand, certain others advocate a diet therapy program, that is, a gradual process of recovery. Patients incapable of oral food intake receive enteral nutrition. Parenteral nutrition is applied for recovering the lost electrolytes and fluids, but it should be applied rarely, primarily in states of urgency. For patients suffering from eating disorders the increase in weight indicates good chances of recovery; therefore, the patient’s nutritional status should be carefully and continuously noted. Finally, it is important that our country, too, should adopt a carefully prescribed and conducted diet therapy as an obligatory step in the treatment of patients with eating disorders
Spinning branes in Riemann-Cartan spacetime
We use the conservation law of the stress-energy and spin tensors to study
the motion of massive brane-like objects in Riemann-Cartan geometry. The
world-sheet equations and boundary conditions are obtained in a manifestly
covariant form. In the particle case, the resultant world-line equations turn
out to exhibit a novel spin-curvature coupling. In particular, the spin of a
zero-size particle does not couple to the background curvature. In the string
case, the world-sheet dynamics is studied for some special choices of spin and
torsion. As a result, the known coupling to the Kalb-Ramond antisymmetric
external field is obtained. Geometrically, the Kalb-Ramond field has been
recognized as a part of the torsion itself, rather than the torsion potential
Effective action and semiclassical limit of spin foam models
We define an effective action for spin foam models of quantum gravity by
adapting the background field method from quantum field theory. We show that
the Regge action is the leading term in the semi-classical expansion of the
spin foam effective action if the vertex amplitude has the large-spin
asymptotics which is proportional to an exponential function of the vertex
Regge action. In the case of the known three-dimensional and four-dimensional
spin foam models this amounts to modifying the vertex amplitude such that the
exponential asymptotics is obtained. In particular, we show that the ELPR/FK
model vertex amplitude can be modified such that the new model is finite and
has the Einstein-Hilbert action as its classical limit. We also calculate the
first-order and some of the second-order quantum corrections in the
semi-classical expansion of the effective action.Comment: Improved presentation, 2 references added. 15 pages, no figure
Bis{N,N,N-trimethyl-2-oxo-2-[2-(2,3,4- trihydroxybenzylidene)hydrazinyl]ethanaminium} tetrachloridozincate(II) methanol solvate1
The asymmetric unit of the title compound, (C12H18N3O4)2[ZnCl4]·CH3OH, consists of two Girard reagent-based cations, a tetrachloridozincate anion and a molecule of methanol as solvate. These components are interconnected in the crystal structure by an extensive network of O—H⋯O, N—H⋯O, C—H⋯O, O—H⋯N, O—H⋯Cl, N—H⋯Cl and C—H⋯Cl hydrogen bonds. The shortest intermolecular interaction is realized between the cation and anion [H⋯Cl = 2.29 (5) Å; O—H⋯Cl = 167 (3)°]. C—H⋯O interactions also play a important role in the interconnection of the cations
FLOTATION KINETICS OF MAGNESIUM HYDROXIDE SEDIMENTED FROM SEA WATER
Synthetic sea water has been taken as a referential sample, in which Mg(OH)2 had been sedimented, in order to reduce biological effects and confirm reproducibility of results of the familiar composition sample. The synthetic sea water was prepared according to the scientifically developed procedure. Flotation experiments were performed in the apparatus for flotation under pressure and recoveries of floated Mg(OH)2 were determined depending on the time of flotation. The results obtained on the referential sample of the synthetic water were also tested on the sample of natural sea water and presented comparatively during work. Flotation kinetics is in most cases described by an equation of the first or second degree. However, it was established that flotation kinetics of Mg(OH)2 as chemical sediment with both types of prepared magnesium hydroxide suspension, sedimented in both the synthetic and natural sea water corresponded to the velocity of reaction n = 1.5 degree, which fully corresponds to Horst Morris’s theoretical postulates in the theory of flotation kinetics
FLOTATION KINETICS OF MAGNESIUM HYDROXIDE SEDIMENTED FROM SEA WATER
Synthetic sea water has been taken as a referential sample, in which Mg(OH)2 had been sedimented, in order to reduce biological effects and confirm reproducibility of results of the familiar composition sample. The synthetic sea water was prepared according to the scientifically developed procedure. Flotation experiments were performed in the apparatus for flotation under pressure and recoveries of floated Mg(OH)2 were determined depending on the time of flotation. The results obtained on the referential sample of the synthetic water were also tested on the sample of natural sea water and presented comparatively during work. Flotation kinetics is in most cases described by an equation of the first or second degree. However, it was established that flotation kinetics of Mg(OH)2 as chemical sediment with both types of prepared magnesium hydroxide suspension, sedimented in both the synthetic and natural sea water corresponded to the velocity of reaction n = 1.5 degree, which fully corresponds to Horst Morris’s theoretical postulates in the theory of flotation kinetics
Synthesis, physico-chemical characterization and biological activity of 2-aminobenzimidazole complexes with different metal ions
Complexes of 2-aminobenzimidazole (L) with nitrates of cobalt(II) nickel(II), copper (II), zinc(II) and silver(I) were synthesized. The molar ratio metal:ligand in the reaction of the complex formation was 1:2. It should be noticed, that the reaction of all the metal salts yielded bis(ligand) complexes of the general formula M(L)2(NO3)2 × nH2O (M=Co, Ni Cu, Zn or Ag; n=0, 1, 2 or 6). The complexes were characterized by elemental analysis of the metal, molar conductivity, magnetic susceptibility measurements and IR spectra. Co(II), Ni(II) and Cu(II) complexes behave as non-electrolytes, whilst Zn(II) and Ag(I) are 1:1 electrolytes. Cu(II) complex has a square-planar stereochemistry, Ag(I) complex is linear, whilst the Co(II), Ni(II) and Zn(II) complexes have a tetrahedral configuration. In all the complexes ligand is coordinated by participation of the pyridine nitrogen of the benzimidazole ring. The antimicrobial activity of the ligand and its complexes against Pseudomonas aeruginosa, Bacillus sp. Staphylococcus aureus and Saccharomyces cerevisiae was investigated. The effect of metal on the ligand antimicrobial activity is discussed
Transition metal complexes with Girard reagents and their hydrazones
This is the first review dealing with the coordination chemistry of metal complexes with Girard's reagents and their hydrazones. The short introduction points out to chemical properties and significance of these organic compounds. The next section briefly describes synthetic methods for preparing complexes with Girard's reagents, as well as modes of coordination of these ligands. The last two extensive sections review the preparation, stereochemistry and structural characteristics of metal complexes with Girard's hydrazones, including some newer non-hydrazonic derivatives of Girard's reagents, also.[Acknowledgments. Projekat Ministarstva nauke Republike Srbije, br. 172014
Classical String in Curved Backgrounds
The Mathisson-Papapetrou method is originally used for derivation of the
particle world line equation from the covariant conservation of its
stress-energy tensor. We generalize this method to extended objects, such as a
string. Without specifying the type of matter the string is made of, we obtain
both the equations of motion and boundary conditions of the string. The world
sheet equations turn out to be more general than the familiar minimal surface
equations. In particular, they depend on the internal structure of the string.
The relevant cases are classified by examining canonical forms of the effective
2-dimensional stress-energy tensor. The case of homogeneously distributed
matter with the tension that equals its mass density is shown to define the
familiar Nambu-Goto dynamics. The other three cases include physically relevant
massive and massless strings, and unphysical tahyonic strings.Comment: 12 pages, REVTeX 4. Added a note and one referenc
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