Physical Principles of Developing Pressure Sensors Using Refractive Index Changes in Optical Fiber Microbending

Russian Physics Journal - The paper deals with the physical principles of development of pressure sensors using changes in the refractive index in the optical fiber microbending. The development of...     

A combined phenomenological model for the representation of anisotropic hardening behavior in high strength steel line pipes

Line pipes have anisotropic mechanical properties, such as tensile strength, ductility and toughness. These properties depend on both prestrain during the cold forming process and on the anisotropy of the mother plates. In this study, a phenomenological model combining isotropic and kinematic hardening is developed to represent anisotropic hardening behavior of high strength steel line pipes. The model is adjusted on experiments carried out on smooth and notched axisymmetric bars and plane strain specimens. The model is used to simulate bending tests carried out on large pipes containing a geometric imperfection. Numerical results suggest that prestraining in pipe forming process significantly affects the bending capacity of pipes.     

Biomimetic approach towards the preparation of hydroxyapatite and hydroxyapatite/chitosan/β-cyclodextrin nanoparticles: application to controlled drug release

Hydroxyapatite (HAp) and hydroxyapatite/chitosan/β-cyclodextrin (HAp/CS/β-CD) nanoparticles were successfully prepared in the modified simulated body fluid (SBF) solution at the physiological conditions (pH 7.4, temperature?=?37 °C). CS/β-CD nanoparticles acted as templates for the synthesis of HAp/CS/β-CD nanoparticles to improve the nanoarchitecture of HAp and its crystallinity.The nanoparticles were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Kneading and coprecipitation methods were applied to prepare the inclusion complex involving β-CD and p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin), a photosensitizer for anti-cancer drugs. The 1:1 stoichiometric ratio of the formed inclusion complex was characterized by a formation constant of 7.216?×?10² mol^?1 dm³ and analyzed by ¹H NMR, FTIR, and UV–Vis. The p-THPP delivery release in vitro was in this order: HAp/CS/β-CD?<?CS/β-CD?<?<?HAp/β-CD?<?β-CD, hinting at a better controlled release by HAp/CS/β-CD nanoparticles.     

Mass redistribution causes the structural richness of ion-irradiated surfaces

We show that the "sputter patterning" topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion--the consensus predominant cause--is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.     

Numerical simulation of one- and two-dimensional ESEEM experiments

Numerical simulation has become an indispensable tool for the interpretation of pulse EPR experiments. In this work it is shown how automatic orientation selection, grouping of operator factors, and direct selection and elimination of coherences can be used to improve the efficiency of time-domain simulations of one- and two-dimensional electron spin echo envelope modulation (ESEEM) spectra. The program allows for the computation of magnetic interactions of any symmetry and can be used to simulate spin systems with an arbitrary number of nuclei with any spin quantum number. Experimental restrictions due to finite microwave pulse lengths are addressed and the enhancement of forbidden coherences by microwave pulse matching is illustrated. A comparison of simulated and experimental HYSCORE (hyperfine sublevel correlation) spectra of ordered and disordered systems with varying complexity shows good qualitative agreement.     

Computational study on the encapsulation of ethylparaben into β-cyclodextrin

Two models namely A and B were considered to investigate the inclusion process of ethylparaben into β-CD cavity by means PM3, HF/6-31G (d) and B3LYP/6-31G (d). The obtained results with PM3 method clearly indicate that the formed complexes are energetically favored with or without solvent; the B complex is found more favored than A complex. The calculated deformations energies show that the geometry of β-CD is deformed in the complexation process on the other hand the ethylparaben do not undergo deformation. Finally, From NBO analysis, the donor and acceptor interactions between ethylparaben and β-CD were analyzed and discussed.     

Recalibration of U-doped standard glasses through uranium thin film for neutron-fluence measurements

This work presents a recalibration of U-doped standard glasses using natural uranium thin films to be used as most dedicated neutron monitor for fission-track dating. The recalibrated U-doped glasses were used to determine fission-track ages in apatite samples from Brazilian alkaline formations (Alto Paranaíba) and standard Durango apatite. Samples were irradiated in two nuclear reactors with different characteristics and the results were compared. For well-thermalized neutron facility, metal activation monitor was also used. The ages of Alto Paranaíba arch and Durango apatite agree with those determined by other radiometric dating methods and metal activation monitors. These results suggest that the presented recalibration is suitable to be used routinely for fission-track dating studies even in a non-well thermalized neutron facility.     

Purity assessment of recombinant human granulocyte colony‐stimulating factor in finished drug product by capillary zone electrophoresis

Current methods for determination of impurities with different charge‐to‐volume ratio are limited especially in terms of sensitivity and precision. The main goal of this research was to establish a quantitative method for determination of impurities with charges differing from that of recombinant human granulocyte colony‐stimulating factor (rhG‐CSF, filgrastim) with superior precision and sensitivity compared to existing methods. A CZE method has been developed, optimized, and validated for a purity assessment of filgrastim in liquid pharmaceutical formulations. Optimal separation of filgrastim from the related impurities with different charges was achieved on a 50 μm id fused‐silica capillary of a total length of 80.5 cm. A BGE that contains 100 mM phosphoric acid adjusted to pH 7.0 with triethanolamine was used. The applied voltage was 20 kV while the temperature was maintained at 25°C. UV detection was set to 200 nm. Method was validated in terms of selectivity/specificity, linearity, precision, LOD, LOQ, stability, and robustness. Linearity was observed in the concentration range of 6–600 μg/mL and the LOQ was determined to be 0.3% relative to the concentration of filgrastim of 0.6 mg/mL. Other validation parameters were also found to be acceptable; thus the method was successfully applied for a quantitative purity assessment of filgrastim in a finished drug product.     

The effect of Pb2+ dopant in the crystal of CsI and its application as scintillation detector: a study of alpha particles

Scintillation crystals have been used in various fields, such as high energy physics, nuclear instrumentation, radiation measurements, medical imaging, nuclear tomography, astrophysics and other fields of science and engineering. For these applications, the development of scintillation crystals with good performance is required. Scintillation crystals based on cesium iodide (CsI) matrix are matters with relatively low hygroscopicity, easy to handle and of low cost, characteristics that favor their use as radiation detectors. In this study, pure CsI crystal and lead doped CsI crystals were grown using the Bridgman vertical technique. The concentration of the lead doping element (Pb) was studied in the range of 10^?2 to 5×10^?4 M. The distribution of the doping element in the crystalline volume was determined by atomic absorption technique. The CsI:Pb crystal with nominal concentration of 10^?3 M was cut into 14 slices of 6 mm. The results show a higher concentration at the top of the crystal with a decrease in the initial phase of growth. The dopant concentration of Pb showed good uniformity from the slice 2 to the slice 12: the region is, therefore, suitable for use as a radiation detector. The luminescence emission of these crystals was measured. A predominant luminescence band near 450 nm and a single broad band around 320 nm were found with the addition of the Pb²⁺ ions in the CsI matrix. Alpha particles spectrometry measurements were carried out to evaluate the developed scintillators.The resolution of 5.6% was obtained for the CsI:Pb 5×10^?4 M crystal, when excited with alpha particles from a ²⁴¹Am source, with energy of 5.54 MeV.     

Changes in the electrical properties of pure and doped polymers under the influence of small doses of X-rays

Abstract

A study has been made of the temperature dependence of the d.c. conductivity of pure and borated low density polyethylene LDPE (4% and 8% borax). The above calculations were carried out before and after X-ray irradiation. The irradiation dose was varied from 0 to 1000 rad.

The d.c. electrical conductivity of Polyvinyl chloride (PVC) and perspex was measured as a function of temperature ranging from 20°C to 100°C. These samples were irradiated with X-rays of dose 200 rad. The variation of the d.c. conductivity of the treated samples versus temperature was investigated.

The results reveal that the d.c. conductivity of LDPE is highly affected by radiation and/or dopant. In addition, the sensitivity of the explored polymers to X-ray irradiation is strongly dependent on its chemical nature.