FeSiB Amorphous Alloy Prepared by Mechano-Synthesis

In this work we show that mechano-synthesis is a good method to prepare the FeSiB amorphous alloy starting from Fe, Si, B pure elements with relative atomic composition of 75, 15 and 10%, respectively. We have used a high-energy ball-milling system keeping the material under an Ar atmosphere. The evolution of the microstructure inside the grains is followed by X-ray diffraction and Mössbauer spectroscopy at room temperature. The dependence of crystalline size, lattice parameter and hyperfine parameters on milling time is discussed. Our results show that the milled samples obtained after 10 h of milling contained a bcc structure in the amorphous matrix. After 19 h of milling the sample became fully amorphous.     

Polyvalent display of heme on hepatitis B virus capsid protein through coordination to hexahistidine tags

The addition of a hexahistidine tag to the N terminus of the hepatitis B capsid protein gives rise to a self-assembled particle with 80 sites of high local density of histidine side chains. Iron protoporphyrin IX has been found to bind tightly at each of these sites, making a polyvalent system of well-defined spacing between metalloporphyrin complexes. The spectroscopic and redox properties of the resulting particle are consistent with the presence of 80 site-isolated bis(histidine)-bound heme centers, comprising a polyvalent b-type cytochrome mimic.     

Operator algebras and a theorem of Dieudonne

LetA be aC*-algebra with second dualA″. Let (φ _n)(n=1,...) be a sequence in the dual ofA such that limφ _n(a) exists for eacha εA. In general, this does not imply that limφ _n(x) exists for eachx εA″. But if limφ _n(p) exists whenever p is the range projection of a positive self-adjoint element of the unit ball ofA, then it is shown that limφ _n(x) does exist for eachx inA″. This is a non-commutative generalisation of a celebrated theorem of Dieudonné. A new proof of Dieudonné’s theorem, for positive measures, is given here. The proof of the main result makes use of Dieudonné’s original theorem.     

Faradaic efficiency of porous electrodeposits: an application to β-Ni(OH)<Subscript>2</Subscript> films

Electrodeposition is a common technique for coating metallic or semiconducting substrates. The growth of the layers occurs through faradaic processes in which charges are transferred across the substrate-electrolyte interface. Since more than one reaction can occur simultaneously, it is important to study the faradaic efficiency (ε) associated to the growth of the desired layers and relate it to other parameters in order to optimize the process. In this work, an indirect method to determine the faradaic efficiency of electrodeposits with porosity (p) is proposed. The method was satisfactorily applied to porous β-Ni(OH)₂ films obtained by light-assisted anodic electrodeposition. These films were grown using different electrolyte concentrations (C) and temperatures (T). In this case, a direct dependence of p and ε with C and T was found.

Open image in new window

Graphical abstract ?

     

Riemann surfaces defined over the reals

The known (explicit) examples of Riemann surfaces not definable over their field of moduli are those with that field being a subfield of the reals but which cannot be defined over the reals. In this paper we provide explicit families of Riemann surfaces which are definable over the reals but cannot be defined over the field of moduli.     

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.     

Fields of moduli and fields of definition of odd signature curves

Let X be a smooth projective curve of genus ${g \geq 2}$ defined over a field K. We show that X can be defined over its field of moduli K _X if the signature of the covering ${X \rightarrow X/ Aut(X)}$ is of type ${(0;c_1,\dots,c_k)}$ , where some c _i appears an odd number of times. This result is applied to cyclic q-gonal curves and to plane quartics.