Excited states of the quasi-one-dimensional hexagonal quantum antiferromagnets

We investigate the excited states of the quasi-one-dimensional quantum antiferromagnets on hexagonal lattices, including the longitudinal modes based on the magnon-density waves. A model Hamiltonian with a uniaxial single-ion anisotropy is first studied by a spin-wave theory based on the one-boson method; the ground state thus obtained is employed for the study of the longitudinal modes. The full energy spectra of both the transverse modes (i.e., magnons) and the longitudinal modes are obtained as functions of the nearest-neighbor coupling and the anisotropy constants. We have found two longitudinal modes due to the non-collinear nature of the triangular antiferromagnetic order, similar to that of the phenomenological field theory approach by Affleck. The excitation energy gaps due to the anisotropy and the energy gaps of the longitudinal modes without anisotropy are then investigated. We then compare our results for the longitudinal energy gaps at the magnetic wavevectors with the experimental results for several antiferromagnetic compounds with both integer and non-integer spin quantum numbers, and we find good agreement after the higher-order contributions are included in our calculations.Comment: 7 pages, 5 figure

Optical and electrical studies on crystalline tin sulphide

A Fourier transform far infrared spectrometer bas been constructed to perform reflectivity and transmission measurements on small semiconductor samples in the temperature range 10-300 grad. K. Far infrared and Raman spectra selection rules have been obtained by the Correlation method from the factor group analysis of the 5nS subset. Crystals of n- and p- type SnS bave been prepared, and the preparation methods are critically reviewed with reference to the T-p-x diagram. The electrical properties (Hall effect, carrier concentration, Hall mobility and barrier height) are measured for these specimens in the temperature range 40-3000 K. Methods of obtaining electrical contacts to SnS are exhaustively studied. Broadband photoconductivity and photovoltaic measurements are reported on n- and p-type specimens in the spectral range 0.5-2 .1 eV at temperatures from 300 grad. K to 10 grad. K. Band structure and impurity energies are suggested to account for the observed results. The band edge shift with temperature is also measured. Far infrared reflectivity and transmission measurements are made between 300 grad. K and 10 grad. K. in order to determine the lattice vibration frequencies. Kramers-Kroenig analysis and computer fitting routines are used to obtain this information from the reflectivity data. The interlayer forces are compared with those obtained in the isomorphic materials GeS and GeSe. Similar spectroscopic and analytic techniques have also been used to examine the room temperature optical properties of ZnS+Fe (Marmatite)

Optical and electrical studies on crystalline tin sulphide

A Fourier transform far infrared spectrometer bas been constructed to perform reflectivity and transmission measurements on small semiconductor samples in the temperature range 10-300 grad. K. Far infrared and Raman spectra selection rules have been obtained by the Correlation method from the factor group analysis of the 5nS subset. Crystals of n- and p- type SnS bave been prepared, and the preparation methods are critically reviewed with reference to the T-p-x diagram. The electrical properties (Hall effect, carrier concentration, Hall mobility and barrier height) are measured for these specimens in the temperature range 40-3000 K. Methods of obtaining electrical contacts to SnS are exhaustively studied. Broadband photoconductivity and photovoltaic measurements are reported on n- and p-type specimens in the spectral range 0.5-2 .1 eV at temperatures from 300 grad. K to 10 grad. K. Band structure and impurity energies are suggested to account for the observed results. The band edge shift with temperature is also measured. Far infrared reflectivity and transmission measurements are made between 300 grad. K and 10 grad. K. in order to determine the lattice vibration frequencies. Kramers-Kroenig analysis and computer fitting routines are used to obtain this information from the reflectivity data. The interlayer forces are compared with those obtained in the isomorphic materials GeS and GeSe. Similar spectroscopic and analytic techniques have also been used to examine the room temperature optical properties of ZnS+Fe (Marmatite)

Transferrin-modified chitosan nanoparticles for targeted nose-to-brain delivery of proteins

Nose-to-brain delivery presents a promising alternative route compared to classical blood-brain barrier passage, especially for the delivery of high molecular weight drugs. In general, macromolecules are rapidly degraded in physiological environment. Therefore, nanoparticulate systems can be used to protect biomolecules from premature degradation. Furthermore, targeting ligands on the surface of nanoparticles are able to improve bioavailability by enhancing cellular uptake due to specific binding and longer residence time. In this work, transferrin-decorated chitosan nanoparticles are used to evaluate the passage of a model protein through the nasal epithelial barrier in vitro. It was demonstrated that strain-promoted azide-alkyne cycloaddition reaction can be utilized to attach a functional group to both transferrin and chitosan enabling a rapid covalent surface-conjugation under mild reaction conditions after chitosan nanoparticle preparation. The intactness of transferrin and its binding efficiency were confirmed via SDS-PAGE and SPR measurements. Resulting transferrin-decorated nanoparticles exhibited a size of about 110-150 nm with a positive surface potential. Nanoparticles with the highest amount of surface bound targeting ligand also displayed the highest cellular uptake into a human nasal epithelial cell line (RPMI 2650). In an air-liquid interface co-culture model with glioblastoma cells (U87), transferrin-decorated nanoparticles showed a faster passage through the epithelial cell layer as well as increased cellular uptake into glioblastoma cells. These findings demonstrate the beneficial characteristics of a specific targeting ligand. With this chemical and technological formulation concept, a variety of targeting ligands can be attached to the surface after nanoparticle formation while maintaining cargo integrity

Renormalization Group Approach to Generalized Cosmological models

We revisit here the problem of generalized cosmology using renormalization group approach. A complete analysis of these cosmologies, where specific models appear as asymptotic fixed-points, is given here along with their linearized stability analysis.Comment: 10 pages, to appear in the International Journal of Theoretical Physic

Challenges scoring radiation pneumonitis in patients irradiated for lung cancer

To quantify uncertainties in scoring radiation pneumonitis

Surface preparation of powder metallurgical tool steels by means of wire electrical discharge machining

The surface of two types of powder metallurgical (PM) tool steels (i.e., with and without nitrogen) was prepared using wire electrical discharge machining (WEDM). From each grade of tool steel, seven surfaces corresponding to one to seven passes of WEDM were prepared. The WEDM process was carried out using a brass wire as electrode and deionized water as dielectric. After eachWEDM pass the surface of the tool steels was thoroughly examined. Surface residual stresses were measured by the X-ray diffraction (XRD) technique. The measured stresses were found to be of tensile nature. The surface roughness of the WEDM specimens was measured using interference microscopy. The surface roughness as well as the residual stress measurements indicated an insignificant improvement of these parameters after four passes of WEDM. In addition, the formed recast layer was characterized by means of scanning electron microscopy (SEM), XRD, and X-ray photoelectron spectroscopy (XPS). The characterization investigation clearly shows diffusion of copper and zinc from the wire electrode into the work material, even after the final WEDM step. Finally, the importance of eliminating excessive WEDM steps is thoroughly discussed

Fractional modeling dynamics of HIV and CD4+ T-cells during primary infection

In this paper, we introduce fractional-order into a model of HIV-1 infection of CD4+ T cells. We study the effect of the changing the average number of viral particles N with different sets of initial conditions on the dynamics of the presented model. Generalized Euler method (GEM) will be used to find a numerical solution of the HIV-1 infection fractional order model

Finite-size scaling above the upper critical dimension in Ising models with long-range interactions

The correlation length plays a pivotal role in finite-size scaling and hyperscaling at continuous phase transitions. Below the upper critical dimension, where the correlation length is proportional to the system length, both finite-size scaling and hyperscaling take conventional forms. Above the upper critical dimension these forms break down and a new scaling scenario appears. Here we investigate this scaling behaviour in one-dimensional Ising ferromagnets with long-range interactions. We show that the correlation length scales as a non-trivial power of the linear system size and investigate the scaling forms. For interactions of sufficiently long range, the disparity between the correlation length and the system length can be made arbitrarily large, while maintaining the new scaling scenarios. We also investigate the behavior of the correlation function above the upper critical dimension and the modifications imposed by the new scaling scenario onto the associated Fisher relation.Comment: 16 pages, 5 figure