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)

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

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

Data Accuracy Dependence on Number of Bins in Stochastic Series Expansion for Spin-1/2 Antiferromagnetic Heisenberg Chains

Background: Antiferromagnetic systems exhibit complex quantum behaviours that require accurate numerical methods to analyse. The Stochastic Series Expansion (SSE) is a quantum Monte Carlo technique that simulates these systems. This study examines the effect of the number of bins on the accuracy of physical property measurements using SSE. Materials and Methods: The SSE simulations were performed using Fortran 90 on a Ryzen 7 processor. The system was initialised with varying lattice sizes (64, 128, 256, and 1024) and dimensionless temperatures (1/32, 1/16, 1/2, and 4) to analyse different configurations. Nbins and Monte Carlo steps were adjusted systematically to investigate their impact on the results. Results were visualised in Origin Lab. Results: Increasing the number of bins (Nbins) reduced fluctuations, leading to reliable results, especially at low temperatures. Lower temperatures lead to higher fluctuations in susceptibility and specific heat of the system. The Neel temperatures were observed around dimensionless temperature.  Indicating phase transitions. Conclusions:   The study shows that Nbins are crucial for accurate results in SSE simulations. Although the method is effective for most properties, specific heat calculations require higher computational costs and present limitations in precision. &nbsp

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)

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

UV absorblayıcı madde uygulamalarında ultrasonik enerjinin etkileri

Dünyayı çevreleyen ozon tabakasının gün geçtikçe incelmesi ve UV radyasyonunun insan sağlığını olumsuz etkilemesi nedeni ile insanların UV ışınlarından korunması gereklidir. UV radyasyonun belirli oranlardaki emilimi insan sağlığına yararlı iken, aşırı olanlar cilt kanseri, güneş yanığı ve katarakt gibi hastalıklara neden olmaktadır. Giysiler UV radyasyonuna karşı koruma sağlayabilirken, bu aşamada radyasyonun dozu da önem taşımaktadır. Bu nedenle tekstil materyallerine UV absorban maddeler, liflerin üretimi esnasında ya da bitim işlemlerinde uygulanmaktadır. UV absorban maddelerin kullanılmasıyla, tekstil ürünlerinde UV ışınlarının geçirgenliğinin yoğunluk derecesi azaltılır. UV absorbanları materyale gelen ışık tarafından meydana gelen olumsuz etkileri ergeller [1,3] Bu araştırmada UV absorbanların etkileri yöntemler açısından karşılaştırılmıştır. Bu yöntemler; klasik, ultrasonik prop ve ultrasonik banyo yöntemleridir. Araştırmada %100 pamuklu bezayağı, Dimi 2/1, Dimi 3/1, ve Rips 2/1 örgüsüne sahip dört farklı dokuma kumaşa ön terbiye işlemi uygulandıktan sonra, üç farklı yönteme göre, bu kumaşlara %0 ve % l UV absorban madde uygulanmıştır. Kumaşların 290-400 nm dalga boyu aralıklarında % transmitans değerleri ölçülmüştür. Bu değerler kullanılarak UFP değerleri hesaplanmış ve UV radyasyona karşı koruma kategorileri belirlenmiştir. Ayrıca kumaşların beyazlık derecesi ölçümleri yapılmış, ölçümler için UV absorban uygulanmamış ağartılmış materyal standart kabul edilmiştir. Klasik yöntem, ultrasonik prop ve ultrasonik banyo yöntemi bu yöntemle karşılaştırılmıştır

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