Electronic and optical properties of InAs/InP self-assembled quantum dots on patterned substrates

We present atomistic theory of electronic and optical properties of a single InAs quantum dot grown on a pyramidal InP nanotemplate. The shape and size of the dot is assumed to follow the nanotemplate shape and size. The electron and valence hole single particle states are calculated using atomistic effective–bond–orbital model with second nearest-neighbor interactions. The electronic calculations are coupled to separately calculated strain distribution via Bir–Pikus Hamiltonian. The optical properties of InAs dots embedded in InP pyramids are calculated by solving the many-exciton Hamiltonian for interacting electron and hole complexes using the configuration–interaction method. The effect of quantum-dot geometry on the optical spectra is investigated by a comparison between dots of different shapes.     

Means on solenoids

It is determined which solenoids admit 2-argument continuous means.

     

A tetranuclear nickel(II) heterocubane complex of a bidentate N,O-hydroxymethyl-oxazoline ligand. Synthesis,characterization, magnetic measurements and DFT investigations

Synthesis, structural, and magnetochemical characterization of the tetranuclear [Ni₄O₄] heterocubane cluster [NiCl(L1)(MeOH)]₄, 1, employing the bidentate N,O-ligand 2-hydroxymethyl-2-oxazoline, HL1, is reported. In the solid state, each nickel(II) is coordinated in a distorted octahedral environment, located on four corners of a [Ni₄(μ₃-O)₄] cubane core motif. Measurements of the magnetic susceptibility in solution (Evans method) as well as in the solid state (magnetic susceptibility balance) gave values of 5.74 and 6.08 unpaired electrons, respectively, indicating a spin ground state of S = 3. At maximum spin degeneracy (S = 4), eight unpaired electrons would be expected. Magnetic properties were further evaluated by SQUID measurements of 1, confirming the spin ground state of 1 to be S = 3. The observed deviation is caused by antiferromagnetic coupling between the four Ni atoms. In addition, broken-symmetry DFT calculations confirmed an overlap of magnetic orbitals resulting in exchange coupling between the four nickel(II) ions of 1.     

Soil stress and deformation determination under a landing airplane on an unsurfaced airfield

This paper presents a multidisciplinary approach to a problem of soil–wheel interaction during the landing of an airplane on a grass airfield, with terramechanical analysis of the forces acting between a wheel and the surface. The experiment on stress and deformation state in soil under a wheel on touchdown was performed in the field. The soil stress state (major stress S1, minor stresses S2 and S3, stress invariant in an octahedral system, MNS and OCTSS) was determined with the use of an SST (stress state transducer), which was installed at 15 cm depth. Soil deformation was determined with an inertial measuring system, integrated with the SST. These soil data were captured exactly at the moment touchdown. In the experiment, a four-passenger, STOL multirole airplane was used and pilots performed two landing patterns: normal landing and emergency landing (without propeller thrust).     

Structural,Vibrational and Electronic Properties of Defective Single‐Walled Carbon Nanotubes Functionalised with Carboxyl Groups: Theoretical Studies

Covalent sidewall functionalisation of defective zigzag single‐walled carbon nanotubes [SWCNTs(10,0)] with COOH groups is investigated by using DFT. Four types of point defects are considered: vacancy (V), divacancy [V₂(5‐8‐5), V₂(555‐777)], adatom (AA) and Stone–Wales (SW). The energetic, structural, electronic and vibrational properties of these systems are analysed. Decreasing reactivity is observed in the following order: AA>V>V₂(555‐777)>V₂(5‐8‐5)>SW. These studies also demonstrate that the position in which a carboxyl group is attached to a defective SWCNT is of primary importance. Saturation of two‐coordinate carbon atoms in systems with the vacancy V‐7 and with the adatom AA‐1(2) is 3.5–4 times more energetically favourable than saturation of three‐coordinate carbon atoms for all studied systems. Vibrational analysis for these two systems shows significant redshifts of the ν(C?O) stretching vibration of 96 and 123 cm^?1 compared to that for carboxylated pristine systems. Detailed electronic‐structure analysis of the most stable carboxylated systems is also presented.     

Non-rigid parabolic geometries of Monge type

In this paper we study a novel class of parabolic geometries which we call parabolic geometries of Monge type. These parabolic geometries are defined by gradings such that their −1 component contains a nonzero co-dimension 1 abelian subspace whose bracket with its complement is non-degenerate. We completely classify the simple Lie algebras with such gradings in terms of elementary properties of the defining set of simple roots. In addition we characterize those parabolic geometries of Monge type which are non-rigid in the sense that they have nonzero harmonic curvatures in positive weights. Standard models of all non-rigid parabolic geometries of Monge type are described by under-determined ODE systems. The full symmetry algebras for these under-determined ODE systems are explicitly calculated; surprisingly, these symmetries are all just prolonged point symmetries.     

Classical systems can be contextual too: Analogue of the Mermin–Peres square

Contextuality lays at the heart of quantum mechanics. In the prevailing opinion it is considered as a signature of “quantumness” that classical theories lack. However, this assertion is only partially justified. Although contextuality is certainly true of quantum mechanics, it cannot be taken by itself as discriminating against classical theories. Here we consider a representative example of contextual behaviour, the so-called Mermin–Peres square, and present a discrete toy model of a bipartite system which reproduces the pattern of quantum predictions that leads to contradiction with the assumption of non-contextuality. This illustrates that quantum-like contextual effects have their analogues within classical models with epistemic constraints such as limited information gain and measurement disturbance.     

Plastic plasma interaction with plasmas with growing atomic number

This paper describes the investigation of the influence of target material atomic number (Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5 - 73), i.e. plastic (CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging.     

Artificial Haldane gap material on a semiconductor chip

We show how nanostructuring of a metallic gate of a field-effect transistor (FET) converts the electron channel of an FET to an artificial Haldane chain with a gap in the energy spectrum. A specially designed gate structure creates a chain of triple quantum dot molecules. The electrons localized in the molecules realize a spin-half Heisenberg chain with spin–spin interactions alternating between ferromagnetic and antiferromagnetic. The quantum state of an FET is a semiconductor implementation of an integer spin-one antiferromagnetic Heisenberg chain with a unique correlated ground state and a finite energy gap, originally conjectured by Haldane.     

New contactless method to control the O/N ratio in SiON films

We propose new experimental method of contactless control of the O/N ratio in SiON films deposited on the Si1 1 1 surfaces. The proposed method consists of direct measurements of reflected light for the parallel R_p and perpendicular R_s light polarisations towards the Si1 1 1 plane. We have shown that the spectral dependence of the anisotropic ratio P=R_s/R_p is strictly connected with O/N ratio. Independently performed spectral measurements show good coincidence with experimental data. We show essentially the advantas by comparing with ellipsometry, XPS and other methods both concerning the precision and the technical realisation.