7,167 research outputs found
Metal Distributions, Efficient n-Type Doping, and Evidence for in-Gap States in TiNiM<sub><i>y</i></sub>Sn (M = Co, Ni, Cu) half-Heusler Nanocomposites
XNi1+ySn nanocomposites consisting of a XNiSn half-Heusler (HH) matrix with segregated XNi2Sn Full Heusler (FH) inclusions promise improvements in thermoelectric efficiencies. We extend recent research by reporting on TiNiMySn (0 ≤ y ≤ 1) nanocomposites with M = Co (3d9), Ni (3d10) and Cu (3d104s1). Neutron powder diffraction reveals that the Ni and Cu series produce a matrix of TiNiSn with nanosegregated TiNi2Sn and TiNi1+dCu1–dSn, respectively. For the Co series, the Co inserts into both phases to obtain a TiNi1–yCoySn matrix with nanosegregated TiNi2–yCoySn. Systematic changes in Seebeck coefficient (S) and electrical resistivity (ρ) are observed in all three series. For M = Ni, changes in S and ρ are attributed to in-gap states arising from the nanosegregation. The M = Co composites show a complex interplay between the hole doped TiNi1–yCoySn matrix and similar in-gap states, where the p- to n-type transition temperature increases but the maximum S remains unchanged at +30 μV K–1. The 4s1 electron for M = Cu is delocalized in the HH matrix, leading to metal-like ρ(T) and up to 100% improved thermoelectric power factors compared to TiNiSn (S2/ρ = 2 mW m–1 K–2 at 600–700 K for y = 0.025). These results broaden the range of segregated FH phases that could be used to enhance HH thermoelectric performance
Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr
Density functional theory (DFT) calculations are carried out on ReOFeAs, Re =
Ce, Pr, the parent compounds of the high-T superconductors
ReOFFeAs, in order to determine the magnetic order of the ground
state. It is found that the magnetic moments on the Fe sites adopt a collinear
antiferromagnetic order, similar to the case of LaOFeAs. Within the generalized
gradient approximation along with Coulomb onsite repulsion (GGA+U), we show
that the Re magnetic moments also adopt an antiferromagnetic order for which,
within the ReO layer, same spin Re sites lie along a zigzag line perpendicular
to the Fe spin stripes. While within GGA the Re 4f band crosses the Fermi
level, upon inclusion of onsite Coulomb interaction the 4f band splits and
moves away from the Fermi level, making ReOFeAs a Mott insulator.Comment: 5 pages, 4 figure
Non-continuous Froude number scaling for the closure depth of a cylindrical cavity
A long, smooth cylinder is dragged through a water surface to create a cavity
with an initially cylindrical shape. This surface void then collapses due to
the hydrostatic pressure, leading to a rapid and axisymmetric pinch-off in a
single point. Surprisingly, the depth at which this pinch-off takes place does
not follow the expected Froude power-law. Instead, it displays two
distinct scaling regimes separated by discrete jumps, both in experiment and in
numerical simulations (employing a boundary integral code). We quantitatively
explain the above behavior as a capillary waves effect. These waves are created
when the top of the cylinder passes the water surface. Our work thus gives
further evidence for the non-universality of the void collapse
Synthesis and biodistribution of immunoconjugates of a human IgM and polymeric drug carriers
The synthesis and purification of radiolabelled immunoconjugates, composed of a human IgM monoclonal antibody directed against an intracellular tumour-associated antigen and either poly (alpha-L-glutamic acid) (PGA) or poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) is described. Coupling of polymers to the antibody was performed through disulfide bond formation involving a single thiol group at the C-terminus of the polymer chain and 2-pyridyldisulfide groups introduced onto the antibody. The antibody was iodinated with 131I before conjugation. The polymers contained tyrosinamide in a low degree of substitution and were radiolabelled with 125I. 125I-labelled PGA and PHEG were found to be stable for at least 3 days in murine and human plasma. The biodistribution in mice of the doubly labelled immunoconjugates was studied and was compared with the pharmacokinetics of the individual components.\ud
\ud
PHEG showed a relatively slow blood clearance, the half-life being approximately 10 h with low uptake in liver, kidneys and spleen. PGA was rapidly cleared from the circulation and was significantly taken up in liver, kidneys and spleen. The biodistribution of both immunoconjugates was indistinguishable from that of the IgM proper, with plasma half-lives of approximately 6 h, indicating that the pharmacokinetic properties of the immunoconjugates are largely determined by the antibody part
Local temperature perturbations in the boundary layer in regime of free viscous-inviscid interaction
We analyze the disturbed flow in the supersonic laminar boundary layer when
local heated elements are placed on the surface. It is exhibited that these
flows are described in terms of free interaction theory for specific sizes of
thermal sources. We construct the numerical solution for flat supersonic
problem in the viscous asymptotic layer in which the flow is described by
nonlinear equations for vorticity, temperature with the interaction condition
which provides influence of perturbations to the pressure in the main order.Comment: 9 pages, 5 figure
Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics
Nb vacancies maintain a semiconducting electron count and cause strong mass fluctuation phonon scattering enabling good thermoelectric performance.</p
- …