Universal torsion-induced interaction from large extra dimensions

We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to Z-pole observables, we find the 3sigma bound on the scale of quantum gravity to be 28 TeV for n = 2. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to sqrt[n] M(S)>/=210 TeV.     

New Route to Polymeric Nanoparticles by Click Chemistry Using Bifunctional Cross-Linkers

A new route to functional polymeric nanoparticles (PNPs) of different chemical nature in the 3 to 20 nm size range is reported by combining both radical addition fragmentation chain transfer (RAFT) polymerization and “click” chemistry (CC) techniques. RAFT polymerization was employed for the synthesis of well-defined statistical copolymers with pending –Cl groups along the macromolecular chain. After transformation of the –Cl groups to –N₃ groups by treatment with sodium azide, an appropriate bifunctional cross-linker is employed to obtain PNPs under CC conditions promoting intramolecular cycloaddition (cross-linking). Following this new route, polystyrene, poly(alkyl (meth)acrylate), polymethacrylic acid, poly(sodium styrenesulfonate) and poly(N-isopropyl) NPs have been synthesized and in-deep characterized.     

Tuning Surface Wettability of Poly(3‐sulfopropyl methacrylate) Brushes by Cationic Surfactant‐Driven Interactions

In this communication, polyanionic poly(potassium 3‐sulfopropyl methacrylate) (PSPM) brushes were switched from hydrophilic to hydrophobic by exchange of the counter cations. First, poly(potassium 3‐sulfopropyl methacrylate) brushes were grown by means of atom transfer radical polymerization (ATRP) from thiol monolayers of initiating ω‐mercaptoundecyl bromoisobutyrate and mixed monolayers of thiol initiator and 1‐undecanothiol (blank thiol) attached to gold surfaces. The kinetics of the polymerization reaction were followed by means of the quartz microbalance technique with dissipation (QCM‐D). The collapse of PSPM brushes in the presence of cationic surfactants like quaternary ammonium salts (tetraethylammonium bromide, hexadecyltrimethylammonium bromide) and imidazolium salts (1‐dodecyl‐3‐methylimidazolium bromide, 1H,1H,2H,2H‐perfluoro‐1‐decyl‐3‐methylimidazolium bromide) was shown by QCM‐D. Water contact angle measurements proved that the wettability of the surface could be tuned reversibly from hydrophilic values (<30 °) to hydrophobic ones (>85 °).

     

Coinage Metal–Glutathione Thiolates as a New Class of Supramolecular Hydrogelators

Summary: Coinage metal salts (e.g. Au^III, Ag^I and Cu^II salts) readily react with thiols to give the corresponding metal(I) thiolates. These thiolate species are known to either self-assemble into insoluble polymeric species or to form soluble oligomers, depending on the nature of the thiol ligand. Here we demonstrate that this self-assembling ability can be applied to create supramolecular hydrogels. Glutathione (GSH), a naturally occurring tripeptide, has been used in combination with Au^III, Ag^I and Cu^II salts to obtain pH responsive hydrogels that are able to gelate 100 times their weight in water.     

Phase and Element Contents of the cBN Based Composites as Estimated by XPS

X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB₂ phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti₃SiC₂/TiC but in different amount. The Ti₃SiC₂ additive was found more chemically active then TiC.     

Oxalato complexes of Pd(II) with Co(II) and Ni(II) as single-source precursors for bimetallic nanoalloys

Journal of Thermal Analysis and Calorimetry - The explanation of abnormal enhancement of transported energy in colloidal nanoparticles in a liquid has sparked much interest in recent years. The...     

Bimetallic single-source precursors [M(NH3)4][Co(C2O4)2(H2O)2]·2H2O (M = Pd, Pt) for the one run synthesis of CoPd and CoPt magnetic nanoalloys

All the steps of the proposed technique, from the synthesis of single-source precursors to the preparation of CoPd and CoPt nanoalloys, are described. The double complex salts (DCS) [M(NH₃)₄][Co(C₂O₄)₂(H₂O)₂]·2H₂O (M = Pd, Pt), which were synthesized by mixing solutions containing [M(NH₃)₄]²⁺ cations and [Co(C₂O₄)₂(H₂O)₂]²⁻ anions, have been used as precursors. The salts obtained were characterized by IR spectroscopy, thermal analysis, XRD and single crystal X-ray diffraction. The prepared compounds crystallize in the monoclinic (space group I2/m, M = Pd) and orthorhombic (space group I222, M = Pt) crystal systems. Thermal decomposition of the salts in helium or hydrogen atmosphere at 200-600 °C results in the formation of nanoalloys powders (random solid solution Co_0.50Pd_0.50 and chemically ordered CoPt). The size of the bimetallic particles varied from 5 to 20 nm. Order-disorder structural transformations in Co_0.50Pt_0.50 nanoalloys were studied. The magnetic properties of both chemically disordered Co_0.50Pd_0.50 and ordered CoPt clusters have also been measured.     

Study on the Chemistry and Structure of (Na(1−x)Bix)(Nb(1−y)Mny)O3 Ceramics by XPS, AES and EPMA

The (Na_1–xBi_x)(Mn_yNb_1–y)O₃ ceramics are new compounds, obtained for the first time, on the base of sodium niobate with substitution of bismuth manganite. It was shown that the solubility limit for Mn ions in sodium niobate lattice does not exceed 1% at. Therefore, the co-doping with Bi ions was proposed to increase this limit. Bismuth ions are expected to replace Na ions and to ensure charge compensation in the formed compound, thus enhancing possibility of accumulation of the Mn ions in solution without losing the appropriate electrical and optical properties. To study the morphology of produced ceramic four methods of sample characterization were used: X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron microprobe analysis (EPMA) and Scanning Electron Microscopy (SEM).     

Poly[3-(3,4-dihydroxyphenyl)glyceric acid], a new biologically active polymer from Symphytum asperum Lepech. and S. caucasicum Bieb. (Boraginaceae)

Two high-molecular water-soluble preparations with high anticomplementary, antioxidant, antilipoperoxidant and antiinflammatory activities were isolated from the roots of Symphytum asperum and S. caucasicum. Their main chemical constituent was found to be poly[oxy-1-carboxy-2-(3,4-dihydroxyphenyl)ethylene], according to IR and NMR spectroscopy. The Symphytum high-molecular preparations can modulate in vitro B- chronic lymphocytic leukaemia (B-CLL) cells apoptosis and cell cycle progression.