Noncommutative gravity at second order via Seiberg-Witten map

We develop a general strategy to express noncommutative actions in terms of commutative ones by using a recently developed geometric generalization of the Seiberg-Witten map (SW map) between noncommutative and commutative fields. We apply this general scheme to the noncommutative vierbein gravity action and provide a SW differential equation for the action itself as well as a recursive solution at all orders in the noncommutativity parameter \theta. We thus express the action at order \theta^n+2 in terms of noncommutative fields of order at most \theta^n+1 and, iterating the procedure, in terms of noncommutative fields of order at most \theta^n. This in particular provides the explicit expression of the action at order \theta^2 in terms of the usual commutative spin connection and vierbein fields. The result is an extended gravity action on commutative spacetime that is manifestly invariant under local Lorentz rotations and general coordinate transformations.Comment: 14 page

AdS-inspired noncommutative gravity on the Moyal plane

We consider noncommutative gravity on a space with canonical noncommutativity that is based on the commutative MacDowell-Mansouri action. Gravity is treated as gauge theory of the noncommutative $SO(1,3)_\star$ group and the Seiberg-Witten (SW) map is used to express noncommutative fields in terms of the corresponding commutative fields. In the commutative limit the noncommutative action reduces to the Einstein-Hilbert action plus the cosmological term and the topological Gauss-Bonnet term. After the SW expansion in the noncommutative parameter the first order correction to the action, as expected, vanishes. We calculate the second order correction and write it in a manifestly gauge covariant way.Comment: 22 pages, no figures, final versio

Influence of reducing agents and surfactants on size and shape of silver fine powder particles

Silver fine powder with different shapes and sizes were prepared by chemical reduction and characterized by scanning electron microscope. In this paper was presented the method for the preparation of the fine Ag powder with particles size smaller than 2.5 µm with suitability for the mass-production scale. Reduction was performed from nitrate solution directly by vigorous stirring at room temperature by three different reduction agents, with and without presence of two dispersants. Scanning electron microscopy revealed the preferred size of the particles obtained in all experiments with aim of the protecting agent. Larger particles and wider size distribution were obtained without surfactants although with average size of about 1 µm and small quantity of larger clusters of primary particles that is out of the fine powder classification. High purity, 99.999%, of silver was obtained in every experiment.  http://dx.doi.org/10.5937/metmateng1402073

The Standard Model on Non-Commutative Space-Time: Electroweak Currents and Higgs Sector

In this article we review the electroweak charged and neutral currents in the Non-Commutative Standard Model (NCSM) and compute the Higgs and Yukawa parts of the NCSM action. With the aim to make the NCSM accessible to phenomenological considerations, all relevant expressions are given in terms of physical fields and Feynman rules are provided.Comment: 33 pages, axodraw.sty; shortened, comments and references added, version to appear in EPJ

Cave bear (Ursus spelaeus Rosenmüller & Heinroth) males' den from Velika Pećina in Duboka Near Kučevo, Eastern Serbia

More a 100 years after the first research in the cave Velika pećina in Duboka near Kučevo cave bear remains were discovered in a small chamber cut off from the passable channels by a 7 m high slope. A whole skull, bones of a forearm in articulation, and other skeleton parts were laying on the cave floor encrusted in travertine cover and in some places overgrown by stalagmites. Bones belonged to adult males, which found there the shelter to hibernate, in a short epizode that ended by closing the channels that once linked this part of the cave to a surface

Electrochemical and surface characterization of ternary alloys of the system Ag-Cu-Zn in near neutral chloride solutions.

Predmet istraživanja disertacije bile su legure sistema Ag-Cu-Zn sličnog sastava faza u širokom opsegu sadržaja srebra. Metali za sve ispitivane legure dobijeni su reciklažom elektronskog otpada. Nakon dobijanja dvostrukim topljenjem i homogenizacionog žarenja u trajanju od 24h u atmosferi azota izvršena je površinska i elektrohemijska karakterizacija ovih legura. Kao legure za uporednu analizu korišene su legure sistema Ag-Zn i Cu-Zn, sastava sličnog fazama ispitivanih legura i legura Ag40Cu30Zn30 čiji se fazni sastav značajno razlikuje od preostale tri trokomponentne legure istog sistema. Termodinamička analiza Ag-Cu-Zn sistema izvršena je korišćenjem faznih dijagrama i Pandat softvera. Za površinsku karakterizaciju homogenizovanih legura korišćena je skenirajuća elektronska mikroskopija sa rentgenskom analizom (SEM/EDS) i rentgenskom difrakcijom (XRD). Elektrohemijsko ponašanje legura sistema Ag-Cu-Zn ispitivano je u deaerisanim i prirodno aerisanim neutralnim rastvorima NaCl koncentracije 3,5% (masenih), sintetičkoj morskoj vodi, prirodnim filtriranim morskim vodama i boratnom puferu (pH=8.1) sa (masenih) 3,5% NaCl, korišćenjem potenciodinamičkih merenja, linearne polarizacije, ciklične voltametrije i potenciostatskih merenja. Anodni film formiran na ispitivanim legurama hronoampermetrijski na 0,0 V i +0,25 V (vs. ZKE) je ispitivan: rentgenskom difrakcijom, FE SEM/EDS metodom, Raman spektroskopijom i MALDI masenom spektrometrijom. Utvrđen je isti mehanizam korozije prilikom anodne polarizacije za sve legure u svim hloridnim rastvorima, osim u puferisanom rastvoru NaCl. Naročito je slično ponašanje legura Ag43Cu37Zn20 i Ag25Cu52,5Zn22,5. Legura sa 25% (mas.) srebra ima sličnu otpornost na koroziju u 3,5% rastvoru NaCl kao legura sa 40% (mas.) srebra, što je nedvosmisleno uticaj faznog sastava. Pri sličnom faznom sastavu legura koroziona otpornost raste sa većim udelom srebra (faze bogate srebrom). Sve ispitivane legure sistema Ag-Cu-Zn nemaju pasivnu oblast u svim rastvorima osim puferskog, gde se javlja pseudo-pasivna oblast na polarizacionim krivama...Alloys of the Ag-Cu-Zn system with wide range of silver content, selected to have similar phase compositions, were the subject of the research. Metals for all examined alloys are obtained by recycling of electronic waste. After obtaining alloys by double melting and homogenization annealing for 24 h under nitrogen, surface and electrochemical characterization of these alloys were performed. For comparative analysis, binary alloys of Ag-Zn and Cu-Zn systems were used. They had similar composition as the phases of the examined alloys. For the same purposes the Ag40Cu30Zn30 alloy with different phase composition than three other alloys of the same system was used. Thermodynamic analysis of the Ag-Cu-Zn system was performed using phase diagrams and Pandat software. Surface characterization of the homogenizated alloys was performed by Scanning Electron Microscopy with X-ray microanalysis (SEM/EDS) and X-diffraction (XRD). Electrochemical behavior of the alloys of the Ag-Cu-Zn system in deaerated and naturally aerated neutral 3.5 wt.% NaCl solution, synthetic seawater, natural filtered seawaters and borate buffer (pH=8.1) with 3,5% NaCl has been investigated using the potentiodynamic measurements, linear polarization, cyclic voltammetry and potentiostatic measurements. The anodic layer formed on examined alloys by chronoamperometry at 0.0 and +0.25 V (vs. SCE) has been characterized by X-ray diffraction, FE SEM/EDS, Raman spectroscopy and MALDI mass spectrometry. The same mechanism of corrosion under anodic polarization was found for all alloys in all chloride solutions except buffered 3.5% NaCl solution. The behavior of alloys Ag43Cu37Zn20 and Ag25Cu52.5Zn22.5 is particularly similar. The alloy with 25 wt. % content of silver has similar corrosion resistance in 3.5% NaCl solution as the alloy with 40 wt. % silver, which is clearly the consequence of phase composition. For a similar phase composition of alloy, corrosion resistance increases with higher content of silver (Ag-rich phase). All investigated alloys of the Ag-Cu-Zn system have no passive area in all solutions, except in buffered solution, where a pseudo-passive area appears on polarization curves. Copper rich phase (Cu) is critical for corrosion resistance of alloys. Preferentially dissolution of this phase is determined by polarization curves analysis, chemical..

Synthesis, characterization and potential biological activity of the complexes of platinum(iv) and palladium(ii) ions with a derivative of ethylendiamine-n,n'-di-(s,s)-(2,2'-dibenzyl)acetate ligand

U ovoj Doktorskoj disertaciji je opisana sinteza i karakterizacija (2S)-2- -(2-okso-1,3-oksazinan-3-il)propanske kiseline kao i estara tipa O-alkil-N-(3-hloropropil)-(2S)-alaninata monohlorhidrata (R = propil-, butil-) u nameri da se dobiju 1,3-propandiamin-N,N′-di-(S,S)-2-propanska kiselina, (H2-(S,S)-rddp) i O,O′-dialkil estara tetradentatnog liganda 1,3- -propandiamin-N,N′-di-(S,S)-2-propanske kiseline, R2-(S,S)-rddp). Estri O-alkil-N-(3-hloro-propil)-(2S)-alaninata monohlorhidrata dobijeni su direktnom reakcijom između (2S)-2-(2-okso-1,3-oksazinan-3-il) propanske kiseline i odgovarajućeg apsolutnog alkohola( 1-propanol, 1-butanol) u molskom odnosu 1:2, uz uvođenje gasovitog hlorovodonika. Potom je sintetisana etilendiamin-N,N′-di-S,S-(2,2'-dibenzil)etanska kiselina trihidrat, N2-(S,S)-eddba·3N2O. Na prethodno opisan način sintetisani su O,O'-dialkil estri etilendiamin-N,N′-di-(S,S)-(2,2'-dibenzil) etanske kiseline kao dihlorhidrati, R2-(S,S)-eddba·2NSl (R =etil-, propil-, butil- i pentil-). Strukture i sastav izolovanih liganada pretpostavljene su primenom elementalne mikroanalize, infracrvene, 1H i 13C NMR spektroskopije, a potvrđene na bazi rezultata rendgenske strukturne analize u slučaju: (2S)-2-(2- -okso-1,3-oksazinan-3-il)propanske kiseline, O-propil-N-(3-hloropropil)-(2S)- -alaninata i O-butil-N-(3-hloropropil)-(2S)-alaninata kao monohlorhidrati, i O,O'-dipropil-etilendiamin-N,N'-di-(S,S)-(2,2'-dibenzil)etanoat kao trihidrata, N2-(S,S)eddba·3N2O. Dobijeni O,O'-dialkil estri etilendiamin-N,N′-di-(S,S)-(2,2'-dibenzil) etanske kiseline su upotrebljeni za sintezu odgovarajućih kompleksa platine(IV) i paladijuma(II). Sastav dobijenih kompleksa platine(IV), [PtCl4(R2- -(S,S)-eddba)] i paladijuma(II), [PdCl2(R2-S,S-eddba)] potvrđeni su elementalnom mikroanalizom. Struktura izolovanih kompleksa potvrđena je na osnovu infracrvene, 1H i 13C NMR spektroskopije. In vitro antitumorska aktivnost kompleksa platine(IV) sa tetradentatnim ligandima (sa navedenim O,O′-dialkil estrima N2-(S,S)-eddba) određivana je na ćelijama CCL u periodu od 72 sata korišćenjem MTT tehnike. Zaključak je da kompleksi pokazuju jak citotoksični efekat. Citotoksični efekti svih kompleksa su dozno-zavisni i svi ispitivani kompleksi su pokazali znatno veći citotoksični efekat na CLL ćelije od cisplatine. In vitro antimikrobna aktivnost sintetisanih liganada i odgovarajućih kompleksa paladijuma(II) testirana je određivanjem minimalnih inhibitorskih (MIK) i minimalnih baktericidnih koncentracija (MBC). Ove supstance u poređenju sa pozitivnim kontrolama, pokazale su nisko antibakterijsko delovanje Antibakterijsko delovanje kompleksa je bilo izraženije na gram pozitivne bakterije, a znatno manje na gram negativne bakterije. Najsenzitivnija bila je bakterija vrste Enterococcus faecalis, Ligandi su pokazali slabo delovanje na gram negativne bakterije posebno na vrstu Proteus vulgaris.In this Work, the synthesis and characterization of the compounds (2S)-2-(2-oxo- -1,3-oxazinan-3-yl)propionic acid nd esters of type O-alkyl-N-(3-chloro-propyl)-(2S)-- alaninate monohlorhydrate (R = propyl-, butyl-) in order to obtain 1,3-propanediamine--N,N′-ди-(S,S)-2-propanoic acid, (H2-(S,S)-рddp) and O,O'-dialkyl esters with tetradentate ligand of 1,3-propanediamine-N,N'-di-(S,S)-2-propanoicb acid, (R2-(S,S)--pddp). Esters of O-alkyl-N-(3-chloropropyl)-(2S)-alaninate monohlorhydrate obtained by the direct reaction between (2S)-2-(2-oxo-1,3-oxazinan-3-yl)propionic acid and the corresponding absolute alcohol (1-propanol, 1-butanol) in the molar ratio 1:2, with the addition of gaseous hydrogenchloride. Then, the synthesized ethylenediamine-N,N'-di-(S,S)-(2,2'-dibenzyl) ethanoic acid trihydrate, Н2-(S,S)-eddbа·3Н2О. As described above were synthesized by the O,O'--dialkyl esters of ethylenediamine-N,N'-di-(S,S)-(2,2'-dibenzyl)ethanoic acid as the dihydrochloride, R2-(S,S)-eddbа·2НСl (R = ethyl-, propyl-, butyl- and pentyl-). Structure and composition of the isolated ligands were assumed using by elemental microanalysis, IR, 1H and 13C NMR spectroscopy, and confirmed by X-ray diffraction analysis in the case (2S)-2-(2-okso-1,3-oksazynan-3-yl)propanoic acid, О-аlkyl-N-(3-chloropropyl)-(2S)-alaninate monocholorohydrate, and O,O'-dipropyl- -ethylen dianine-N,N'-di-(S,S)-(2,2'-dibenzyl)etanoate threehydrate, Н2-(S,S)eddbа·3Н2О. The obtained ligands О,О'-dialkyl estars of ethylendianine-N,N'-di-(S,S)-(2,2'--dibenzyl)etanoic acide were used for synthesis of the corresponding platinum(IV) and palladium(II) complexes. The composition of obtained platinum(IV), [PtCl4(R2-(S,S)--eddbа)] and palladium(II) complexes, [PdCl2(R2-S,S-eddbа)] was confirmed by elemental microanalysis. The structure of isolated complexes is assumed on basis of infrared, 1H and 13C NMR spectroscopy. In vitro antitumor activity of platinum complex (IV) with tetradentate ligands (with the above O,O'-dialkyl esters of Н2-(S,S)-eddbа) was determined on cells of CCL for a period of 72 hours by using the MTT techniques. The conclusion is that the complexes show strong cytotoxic effect. Cytotoxic effects of the complex are dose-depe- -ndent, and all tested complexes showed much higher cytotoxic effect on CLL cells by cisplatin. The in vitro antimicrobial activity of the synthesized ligands and the corresponding complexes of palladium (II) was tested by determination of minimal inhibitory (MIC) and minimum bactericidal concentration (MBC). These substances when compared to the positive controls, showed high antibacterial activity. The antibacterial activity of the complex was more pronounced in the gram-positive bacteria and much less of the gramnegative bacteria. Was the most sensitive species of bacteria Enterococcus faecalis. Ligands showed weak activity against gram-negative bacteria in particular of the type of Proteus vulgaris

Differential structure on kappa-Minkowski space, and kappa-Poincare algebra

We construct realizations of the generators of the $\kappa$-Minkowski space and $\kappa$-Poincar\'{e} algebra as formal power series in the $h$-adic extension of the Weyl algebra. The Hopf algebra structure of the $\kappa$-Poincar\'{e} algebra related to different realizations is given. We construct realizations of the exterior derivative and one-forms, and define a differential calculus on $\kappa$-Minkowski space which is compatible with the action of the Lorentz algebra. In contrast to the conventional bicovariant calculus, the space of one-forms has the same dimension as the $\kappa$-Minkowski space.Comment: 20 pages. Accepted for publication in International Journal of Modern Physics

Non-LTE calculations for neutral Na in late-type stars using improved atomic data

Neutral sodium is a minority species in the atmospheres of late-type stars, and line formation in local thermodynamic equilibrium (LTE) is often a poor assumption, in particular for strong lines. We present an extensive grid of non-LTE calculations for several NaI lines in cool stellar atmospheres, including metal-rich and metal-poor dwarfs and giants. For the first time, we constructed a Na model atom that incorporates accurate quantum mechanical calculations for collisional excitation and ionisation by electrons as well as collisional excitation and charge exchange reactions with neutral hydrogen. Similar to LiI, the new rates for hydrogen impact excitation do not affect the statistical equilibrium calculations, while charge exchange reactions have a small but non-negligible influence. The presented LTE and non-LTE curves-of-growth can be interpolated to obtain non-LTE abundances and abundance corrections for arbitrary stellar parameter combinations and line strengths. The typical corrections for weak lines are -0.1...-0.2dex, whereas saturated lines may overestimate the abundance in LTE by more than 0.5dex. The non-LTE Na abundances appear very robust with respect to uncertainties in the input collisional data.Comment: 9 pages, 8 figures, accepted for publication in A&

THE INFLUENCE OF RHODIUM CONTENT ON THE MECHANICAL PROPERTIES OF PLATINUM

The paper presents the results of investigation the influence of rhodium as an alloying element on the mechanical properties of platinum. A short-term and tensile strength were tested, at room and high temperatures, and also sliding rate and time to the destruction of the Pt-Rh system alloys at high temperatures. The results showed that alloying with rhodium strengthens the platinum while reducing its plasticity. Time to destruction is much longer in Pt-Rh alloys compared to pure platinum