Dispersion Formula Research Articles

Variables Affecting the Preparation and Characterization of Axitinib as Oral Niosmoes

Axitinib is anticancer drug act on different solid tumors by inhibtion protein kinase enzyme which is responsible for support the tumors with blood demand. Due to its low solubility, it has low bioavailability when given orally also it is affected by liver metabolism. Axitinib formulated as non-ionic vesicles (niosomes) for the first time to study the effect of different variables on the in vitro behaviour of vesicles in a hope to improve drug oral bioavailability. Niosomal dispersion formulas were formulated by diverse techniques via multiple kinds of surface-active agent (tween also span), cholesterol and dicetyl phosphate then evaluated for visual appearance, efficiency of drug entrapment (EE%), size of the vesicles, poly dispersity index, zetapotential, viscosity, invitro drug release and study the vesicles morphology by FE-SEM. Many variables effect on EE% were studied such as effect of surfactant amount and type, effect of surfactant combination, impact of various ratios of cholesterol, impact of DCP in various amount , effect of preparation method and effect of sonication time. The results showed that the EE% between (50.97%-98.24%), the particle size was found within the range (64.5 nm - 530.79 nm), zeta potential which was between ( -16.6 to -31 mV), polydispersity index (PDI) <1 and viscosity between (584 – 889.6) centipoise. The niosomal dispersion F1 which contained 1:1 weight ratio (span60: cholesterol) was found with high EE% (96.5±0.16%), smallest particle size (64.5±0.5 nm), highest drug release (100%) of drug released at the end of 4 hours and FE-SEM photograph showed that niosomes were spherical with no aggregation and had a smooth surface. The results showed that thin film hydration method with sonication for four minutes was the best method for preparation of axitinib niosomes, the type and amount of surfactants used, cholesterol ratio, stabilizer and the time of sonication had a substantial effect on EE%, the size of the vesicles as well as drug release; which were investigated so as to optimize the niosomal dispersion of anti-tumour drug reaching to an optimum formula that may improve drug bioavailability. Key words: Axitinib, Anticancer, Vesicles, Surfactants, Invitro behaviour, Entrapment efficiency.

Optimization of solid dispersion technique and gliclazide to carrier (PVP K30) ratio for solubility enhancement

Background and objective: Poorly water-soluble dugs provide less dissolution rate and bioavailability; hence, it minimizes the pharmacological effect of orally administered medications. Gliclazide is a sulfonylurea antidiabetic medication of the second generation, used to treat type II diabetes mellitus. It belongs to the class II drugs of biopharmaceutic classification system, indicating that it has high permeability and poor aqueous solubility. The aim of this study is to determine an optimum solid dispersion method and drug to carrier ratio to improve the solubility of gliclazide. Methods: Solid dispersions of gliclazide were formulated with polyvinyl pyrrolidone K30 using various drug to carrier ratios (1:1, 1:3, and 1:5) by utilizing kneading and solvent evaporation methods. Solubility and dissolution rate of solid dispersion formulas were compared with pure drug and co-ground mixtures. The formulations were further evaluated in terms of percentage of yield, drug content, FTIR, SEM, DSC, and XRD studies. Results: The highest solubility improvement of gliclazide was obtained at the ratio 1:5 of gliclazide and PVP K30 utilizing solvent evaporation method, solubility increased about 2.54 folds (98.299 ± 5.77 µg/ml) as compared to pure gliclazide (38.739 µg/ml). Meanwhile, the greatest improvement in gliclazide dissolution rate was observed in the same solid dispersion formula that was about 105.76 % after 30 minutes. FTIR demonstrated no unwanted interaction between the drug and carrier. While, SEM, DSC, and XRD showed crystallinity of the drug was minimized and converted to amorphous form in solid dispersion formula. Conclusion: Based on the investigations of this study, it can be concluded that the drug to carrier weight ratios and preparation methods had the influence on the drug solubility and the release rate. The obtained data revealed that the solvent evaporation is the best method of solid dispersion for enhancing gliclazide solubility using PVP K30 with the ratio 1:5 of the drug and carrier.

Deriving the Kramers’ dispersion formula from the canonical transformations of Heisenberg’s equation of motion

We obtain the canonical transformations for the time-dependent Hamiltonian from Heisenberg’s equation of motion, based on which we derive the Kramers’ dispersion formula via the perturbation theory of matrix mechanics to the second order approximation.

Rayleigh and Raman scattering cross-sections and phase matrices of the ground-state hydrogen atom, and their astrophysical implications

ABSTRACT We present explicit expressions for Rayleigh and Raman scattering cross-sections and phase matrices of the ground 1s state hydrogen atom based on the Kramers–Heisenberg–Waller dispersion formula. The Rayleigh scattering leaves the hydrogen atom in the ground-state while the Raman scattering leaves the hydrogen atom in either ns (n ≥ 2; s-branch) or nd (n ≥ 3; d-branch) excited state, and the Raman scattering converts incident ultraviolet (UV) photons around the Lyman resonance lines into optical-infrared (IR) photons. We show that this Raman wavelength conversion of incident flat UV continuum in dense hydrogen gas with a column density of NH > 1021 cm−2 can produce broad emission features centred at Balmer, Paschen, and higher level lines, which would mimic Doppler-broadened hydrogen lines with the velocity width of ≳1000 km s−1 that could be misinterpreted as signatures of active galactic nuclei, supernovae, or fast stellar winds. We show that the phase matrix of the Rayleigh and Raman s-branch scatterings is identical to that of the Thomson scattering while the Raman d-branch scattering is more isotropic, thus the Paschen and higher level Raman features are depolarized compared to the Balmer features due to the flux contribution from the Raman d-branch. We argue that observations of the line widths, line flux ratios, and linear polarization of multiple optical/IR hydrogen lines are crucial to discriminate between the Raman-scattered broad emission features and Doppler-broadened emission lines.

Effect of introducing KNO3 on the preparation of athermal fluorophosphate glass and investigation on its thermo-optical property

The effects of introducing some amount of KNO3 into the raw materials on preparation of fluorophosphate glass are investigated in terms of UV–vis transmittance, absorption coefficient and change of refractive index. As the content of KNO3 reaches 50%, the UV absorption coefficient of the optimized fluorophosphate glass reaches the minimum due to absence of microcrystals in the produced glass. The Schott's Sellmeier dispersion formula and Ghosh's two-polar wavelength-dependent Sellmeier equation were both used to calculate dispersion constants of the optimized fluorophosphate glass. The optimized fluorophosphate glass maintains special characteristics of negative temperature coefficient of refractive index and near-zero thermo-optical coefficient. The lower absorption both in UV and near-infrared (NIR) helps to improve its laser-induced damage resistance. The athermal fluorophosphate glass shows great potential for compensation of thermal-induced distortion in high-power solid-state lasers and high-resolution optical systems.

Dispersion formula of a free electron laser with two relativistic electron beams and water-bag distribution function

Theoretical work on a free electron laser (FEL) with two relativistic electron beams is presented. Using the kinetic approach, the dispersion formula (DF) of a helical magnetic wiggler pumped FEL is derived. Stability properties are studied by linearizing the governing equations and DF is obtained and solved numerically. For generality, the momentum spread of electron beams with a water-bag distribution function is considered. Bandwidths of two-beam FEL resonances have been shown and effects of momentum spread have been noticed. It is found that momentum spread causes the pick growth rates to decrease.

Refined Sellmeier equations for AgGaS2 down to 0.565 µm.

We revisit the 90° phase-matching conditions for second-harmonic, sum-frequency, and difference-frequency generation in A g G a S 2 thus far reported in the literature. We present refined Sellmeier equations coupled with an updated thermo-optic dispersion formula to correctly reproduce the experimental results for noncritical three-wave interactions obtained in the 0.565-10.5910µm spectral range.

Refined Sellmeier and thermo-optic dispersion formulas for BaGa4Se7

This paper reports on the refined Sellmeier and thermo-optic dispersion formulas for BaGa4Se7 that provide a good reproduction of the temperature-dependent phase-matching conditions for type-2 difference-frequency generation between the signal and idler outputs of a Nd:YAG laser-pumped KTiOPO4 optical parametric oscillator in the 8.457–9.092 µm and 12.075–14.201 µm spectral ranges at 20–150°C and recent experiments within these wavelength and temperature ranges performed by other authors.

Analytical solutions of peridynamic equations. Part II: Elastic wave propagation

We use the separation of variables technique to construct analytical solutions for peridynamic models of dynamic elasticity. We show that, similar to the case of peridynamic models for transient diffusion, infinite series nonlocal solutions for peridynamic elasticity can be obtained directly from the solutions of the corresponding classical model by inserting “peridynamic/nonlocal factors” in the time-exponential part of the solution. The analytical solutions show that wave dispersion, caused by nonlocality, is contained in the horizon-dependent nonlocal factor. We obtain formulas for wave dispersion and group velocities for 1D and 2D peridynamic elastic wave propagation with three commonly-used peridynamic kernels. We observe interesting complexity in nonlocal solutions, generated by nonlocal wave dispersion, and “proportional” to the size of the nonlocal interaction region. Different from the diffusion case, as time goes to infinity, the nonlocal solution for elasticity does not converge to the classical one for a fixed horizon size, meaning that nonlocal effects persist in time. We solve several examples of wave propagation with Dirichlet boundary conditions and smooth or discontinuous initial conditions and compare these analytical solutions with those corresponding to the classical model, which is seen as a particular case of the PD model for horizon equal to zero. Interestingly, we find that in PD solutions, initial discontinuities in space persist at the same location, in time. While most of the analytical solutions we present here are formal, for some of the cases, we are able to prove uniform convergence of the series solutions. This work is the first presentation of a systematic analytical treatment of peridynamic problems in 2D finite domains.

A method of underwater sound source range estimation without prior knowledge based on single sensor in shallow water

Introduction: The lack of prior knowledge of the marine environment increases the difficulty of passive ranging of underwater sound sources by using a single hydrophone. The dispersion curve of the normal mode contains extensive marine environmental information, which can be extracted without prior knowledge, but the characteristics of dispersion curves of different modes vary, and the mode order cannot be determined from the received data.Methods: Herein, a method based on a single hydrophone that can jointly identify the mode order and estimate the propagation range in unknown marine environment is proposed. The method uses Bayesian theory as the main methodology and is applicable to broadband pulse sound sources in shallow seas with long-range propagation. The dispersion curves extracted from the data and those calculated by the dispersion formula are the input signal and the replica of the methods, respectively. Accurate identification of the normal mode order and estimation of the propagation range can be achieved by establishing the joint cost function.Results: In the case of unknown a priori knowledge of the marine environment, the method enables rapid inversion, is tolerant to environmental parameter mismatch, and is low cost and practical.Discussion: The simulation and measured data analysis results demonstrate the accuracy and validity of the method. The measured data contains linear frequency modulation impulse source signal and explosion sound source signals, and the mean relative error of range estimation is less than 5%.

Least‐squares reverse time migration based on an efficient pure qP‐wave equation

AbstractSeismic waves propagating in anisotropic earth media suffer from waveform distortion, which leads to degraded resolution in seismic data imaging if this adverse effect is not corrected. Additionally, the wavefields simulated by the traditional coupled pseudo‐acoustic wave equations contain undesired shear wave artefacts and are unstable when Thomsen's anisotropy parameter ε is less than δ. To address these issues, many pure qP‐wave equations are proposed to describe wave propagation in anisotropic media. However, these equations are either low precision or high accuracy but computationally expensive. Considering the trade‐off between the computation efficiency and simulation accuracy, we derive a pure qP‐wave equation from the exact dispersion formula in tilted transverse isotropic media. The newly derived equation has only two higher order partial derivatives, which can better balance the accuracy and efficiency than the previous pure qP‐wave equations. The least‐squares reverse time migration method can balance amplitudes, suppress migration artefacts and improve imaging resolution. Then, based on the newly derived pure qP‐wave equation, we derive the Born modelling operator and adjoint migration operator and develop an anisotropic least‐squares reverse time migration method. To achieve the accelerated convergence, we introduce a generalized minimum residual algorithm to implement the anisotropic least‐squares reverse time migration method. Numerical simulation results show that the proposed pure qP‐wave equation outperforms the previous equations in balancing the trade‐off between accuracy and efficiency. In addition, synthetic examples demonstrate the effectiveness and robustness of our proposed anisotropic least‐squares reverse time migration method in correcting the deviations due to anisotropic effects.

Optical study on mesa structures with adjustable absorption based on Mn1.56Co0.96Ni0.48O4 thin films

In order to improve the infrared detection performance, mesa structures of Mn1.56Co0.96Ni0.48O4/Aluminum/Silicon dioxide/Silicon (MCN/Al/SiO2/Si) were prepared by chemical solution deposition method. Raman spectroscopy results indicate that increasing the thickness causes a change in the Mn3+–O band stretching vibration and the Mn4+–O band bending vibration. Spectroscopic elllipsometry was used to obtain the dielectric function of the films by fitting the experiment data using the classical middle-infrared dispersion formula. The evaluated real part of the dielectric constants ε1 and refractive index n decreased as the wavelength increase, the imaginary part ε2 and extinction coefficient k monotonically increased as the wavelength increase in the entire measuring range of 2–10 μm. The calculated absorption spectra of the MCN/Al/SiO2/Si structure showed that the absorption peak position could be adjusted by varying the thickness of the MCN films. Our results are important in the design and application of MCN film infrared detectors.

IMPROVING SOLUBILITY OF METHOTREXATE BY SOLID DISPERSION

Objective: Methotrexate (MTX) is a folate antimetabolite used for the management of neoplastic diseases like leukemia and breast cancer, Methotrexate is also used in the treatment of psoriasis as well as rheumatoid arthritis. The goal of this research was to improving the solubility and dissolution profile of methotrexate solid dispersion by using different polymers. Methods: A total six formulas were prepared as solid dispersion of methotrexate by solvent evaporation method by using polyethylene glycol (PEG-4000) and poly Vinyl pyrolidone (PVP-K30) as polymeric solubilizer in ratio (1:1,1:2,1:4), Then the solid dispersion of methotrexate were evaluated by solubility test, permeability test and FTIR study. Results: All six solid dispersion formulas showed a significant improvement in the solubility of methotrexate, and the formulations demonstrated improved in the rate of drug release of approximately 99.8±0.9 within 60 min. FTIR study for F3 and F6 show no drug-excipients interaction. Conclusion: Methotrexate was successfully enhanced its water solubility by using solid dispersion.

High efficiency non-critical phase-matching 9.3–10.6 μm optical parametric oscillator in BaGa4Se7 crystal

In this letter, a non-critical phase-matching (NCPM) BaGa4Se7 (BGSe) optical parametric oscillator (OPO) was demonstrated with a home-made acousto-optic (AO) Q-switched Ho:YLF laser as the pump source. The idler wavelength tunability was recorded to be 9393.3 to 10627.4 nm with BGSe crystal temperature varying from 45 to 5 Celsius (˚C), corresponding to an average wavelength adjustment of 30.85 nm/˚C. Up to 200 mW of idler average output power at 10219 nm was obtained with pulse repetition frequency (PRF) at 200 Hz, the slope efficiency and pump-to-idler efficiency are 8.04 % and 5 %, respectively. In addition, in the angle tuning experiment, a refined Sellmeier Equation (S-E) was derived based on the discrepancy between the experimental data and the theoretical calculations based on the existing S-Es. However, it was found that the deviations between experimental measurement data and theoretical calculations in NCPM experiment were still too large to be ignored after using the refined S-E. Probably, the phenomenon was caused by the thermo-optic dispersion formula dn/dT provided by references were not precise enough for describing NCPM BGSe crystal in waveband ∼ 10 μm.

Temperature-dependent phase-matching properties of BaGa2GeS6 in the 0.767-10.5910 µm spectral range.

We report experimental results on the temperature-dependent phase-matching properties of BaGa2GeS6 for second-harmonic generation and sum-frequency generation in the 0.7674-10.5910µm range. We also derive refined Sellmeier and thermo-optic dispersion formulas that provide a good reproduction of the present experimental results.

Tunable defect modes through the (YBCO-Yttria) based on Octonacci photonic quasicrystals

The transmission spectra by a one-dimensional (1D) inhomogeneous stratified medias organized following the Octonacci sequence are investigated. The transfer-matrix method and the Frequency-dependent dispersion formula according to the two-fluid Gorter–Casimir theory are deployed. The proposed hetero-structures are made up of Yttrium oxide, known as yttria,Y2O3 (A) and superconductor (B): yttrium–barium–copper oxide (YBa2Cu3O7), resulting in the (BTO/Y2O3)N/YBCO/(Y2O3/BTO)N multilayered nanostructure array. We report the localization of modes through the multilayered stacks built accordingto the inflation rule of quasi-periodic Octonacci sequence. Localized defect modes were obtained for specific generation of Octonacci structure and for both TE and TM modes. The optical properties exhibiting different regions with zero transmission called photonic bandgaps (PBGs) that can be tuned by Octonacci order and temperature of Bulk superconductor. The performance of defect modes that allows the propagation of optical signals and the inter-channels are evaluated by tailoring the superconductor temperature, the Octonacci order, the direction of the incident wave, and the deformation degree (parameter that control the thickness of superconductor lattices). The proposed system exhibits similar localized resonators operating at cryogenic temperature environments. We verify that bandgaps modifications are influenced by the deformation strain applied along whole thicknesses slab.

The Comparison of QTc Dispersion Between Renal Transplant Recipients and Healthy Individuals.

Introduction Cardiovascular diseases are the most common cause of death in patients with end-stage renal failure. The increase in QTc interval time and QT dispersion increases the risk of cardiac arrhythmia and mortality. In our study, QT and QTc dispersions (QTcd) of patients who underwent renal transplantation were compared with normal healthy individuals. Methods Electrocardiograms (ECGs) of 80 renal transplant recipients and 70 healthy individuals were taken. QTc dispersion was calculated by using the longest and the shortest QT interval and QT dispersion and Bazett's formula. Results When the groups were compared, similar QT dispersion and QTc dispersion were observed(control group and renal transplant recipient patients: 35 ± 17 ms and 36 ± 16 ms and 52 ± 18 ms and 54 ± 22 ms, respectively). Conclusion No statistical difference was observed between QT and QTc dispersions of renal transplantpatients compared to healthy individuals. This result shows that the increase in QT dispersion and pathophysiological mechanisms observed frequently in uremic patients can be reversed by renal transplantation.

Hybrid Dispersion Model Characterization of PAZO Azopolymer Thin Films over the Entire Transmittance Spectrum Measured in the UV/VIS/NIR Spectral Region.

Notwithstanding the significant optical applicability of PAZO polymer films, there are no accurate data about their optical characteristics. To remedy this shortcoming, in this study three PAZO polymer thin films are characterized, with dissimilar thicknesses, on glass substrates using only one UV/VIS/NIR transmittance spectrum T(λ) per sample and an original hybrid dispersion model (HDM). HDM is based on the Tauc-Lorentz model, the new amorphous dispersion formula, the Tauc-Lorentz-Urbach model of Foldyna and the Tauc-Lorentz-Urbach model of Rodriguez. HDM with two oscillators is employed in characterizations of the PAZO polymer films in the range [300, 2500] nm, whereby the root-mean-square deviation (RMSD) of the fitted transmittance spectrum with respect to T(λ) does not exceed 1.6 × 10-3. Decreasing RMSD by 2.3% to 94.4% is demonstrated by employing HDM compared with the above mentioned four popular dispersion models, for each one of the studied films. HDM is applicable to amorphous films independent of their thickness as well as to cases of non-transparent substrate.

Phase-matching properties of Ba2Ga8GeS16

We report experimental results on the phase-matching properties of the quaternary B a 2 G a 8 G e S 16 crystal for second-harmonic generation (SHG) and sum-frequency generation (SFG) of Nd:YAG laser-pumped K T i O P O 4 (KTP) and H g G a 2 S 4 (HGS) optical parametric oscillators (OPOs) and a waveguide C O 2 laser in the 0.8054–10.5910 µm range. Based on these experimental data, we derive refined Sellmeier equations and thermo-optic dispersion formulas that are expected to enable practical applications of this new uniaxial nonoxide nonlinear crystal in the mid-IR part of the spectrum.

The perturbation theory of matrix mechanics based on its canonical transformations

We elucidate that the canonical transformations of matrix mechanics are just the transformations of different representations of the standard quantum mechanics, reproduce the non-degenerate, degenerate and time-dependent perturbation theory in three men’s paper, we solve the mystery of time-dependent perturbation theory of matrix mechanics. The Kramers’ dispersion formula from time-dependent perturbation theory of matrix mechanics is also derived from that of wave mechanics.