LC Solutions Research Articles

COMPUTATIONAL SOLUTIONS OF FRACTIONAL ELECTRIC SYMMETRIC CIRCUITS BY SUMUDU TRANSFORMATION

In this research, we study the Caputo fractional and constant proportional derivative numerical approximation of electrical symmetric circuits. It has been assumed that the derivative is in the order [Formula: see text]. For the fractional electrical symmetric circuits, the RC, LC, and RLC solutions are obtained by using the Sumudu transformation. We also compare the numerical simulation of each equation to its classical equivalent. We use a highly efficient integral transform to examine the impact of the power-law kernel. In our upcoming works, we will apply this to electrical circuits that are more intricate.

Method Development of an Analytical Procedure for the Determination of Clofarabine in Pharmaceutical Formulations

A novel, simple and economic high performance liquid chromatography (HPLC) method has been developed for the estimation of Clofarabine in bulk and tablet dosage form with greater precision and accuracy.The method was validated as per ICH guidelines. Validation studies demonstrated that the proposed HPLC method is simple, specific, rapid, reliable and reproducible. Hence the proposed method can be applied for the routine quality control analysis of Clofarabine in bulk and tablet dosage forms. All the components of the system are controlled using SCL-10Avp System Controller. Data acquisition was done using LC Solutions software.

HPLC method for the development and validation of busulfan in pharmaceutical formulation

A validated HPLC method was developed for the determination of Busulfan (BUS) in pharmaceutical formulation.It is a new simple, accurate, precise and reproducible HPLC method has been developed for the estimation of Busulfan (1,4-butanediol dimethanesulfonate) in its inject able dosage.The method developed in High Performance Liquid Chromatographic method using suitable column (YMC Pack ODS-A (150 x 4.6) mm, 3µm). All the components of the system are controlled using SCL-10Avp System Controller. Data acquisition was done using LC Solutions software.The method was validated as per the ICH guidelines. Thus, the proposed HPLC method can be successfully applied for the routine quality control analysis of formulations. The method developed is simple and is better than the methods reported in the literature and the method is capable to give a good detector response, the recovery calculated was within the range of 98% to 102% of the specification limits.

Method development and validation of stability indicating rp-hplc for the estimation of felodipine pr tablets

The aim of the present work is to develop a new, simple, sensitive, accurate and analytical method of developing and validating the stability indicating estimation of felodipine in pharmaceutical tablet dosage form using RP-HPLC. The API was supplied by Aurobindo Pharma Ltd, Hyderabad. The chromatographic separation was done with Inertsil ODS _2 C_18 (100 × 4.6mm, 3μ) using HPLC Shimadzu (2010 CHT) instrument with LC solutions software. The suitable wavelength for the determination of felodipine is 238nm where it gave a good sensitivity for the assay using UV-Visible spectrophotometer. The mobile phase was optimized to Buffer: Acetonitrile: Methanol in proportion 2:2:1 v/v respectively. The method was performed with flow rates 1ml/min. Temperature was maintained at Ambient. Standard deviation and %RSD were calculated and obtained as 0.3% respectively. LOD and LOQ were found to be 0.56μg/ml, 1.71μg/ml respectively. The Accuracy i.e, %Recovery for 50, 100 and 150% levels are obtained as 98.13%, 99.56%, 98.52% respectively. The % degradation results were within the limits and the method was validated.

Dissipative operators, symplectic geometry, and limit-circle solutions

For a general symmetric ordinary differential expression M and a positive weight function w, the authors characterized the dissipative and strictly dissipative extensions of the minimal operator generated by M in terms of subspaces of a symplectic geometry space. Here we characterize these subspaces in terms of LC solutions, namely, we characterize the boundary conditions of the dissipative and strictly dissipative extensions by LC solutions in a Hilbert space.

Reducing pumping energy by using different flow rates of high and low concentration solutions in reverse electrodialysis cells

Energy use for pumping affects both net energy recovery and operational costs of reverse electrodialysis (RED) systems. In order to reduce the energy needed for pumping, electrical performance and hydrodynamic power losses in a RED stack were investigated by simultaneously (2–140mL/min) or independently varying the flow rates of the high concentration (HC, 35g/L NaCl) and low concentration (LC, 0.35g/L NaCl) solutions. Power was not consistently reduced at lower flow rates due to trade-offs between increases in diffusion boundary layer resistance and decreases in solution resistance of the LC channels. The maximum net power output (~0.04W) was obtained with both LC and HC flow rates at ~20mL/min. Separately varying the flow rates of the HC and LC solutions indicated that the optimum flow rate of the HC solution (10mL/min) was much lower than that of the LC solution (20mL/min) due to the more substantial impact of the LC channel on power production. The use of these two optimized flow rates minimized hydrodynamic power losses (pumping energy) while producing comparable power to that achieved with the two higher flow rates (50mL/min of both HC and LC solutions).

Rheology–Structure Interrelationships of Hydroxypropylcellulose Liquid Crystal Solutions and Their Nanocomposites under Flow

A new approach to study the flow-induced orientation in LC polymer-based nanocomposites has been developed. This approach is a combination of optical, mechanical, and X-ray methods that allowed us to “visualize” physical processes taking place in these systems under flow. The HPC/water solution (matrices) concentrations were selected based on the accurate phase equilibrium lines determined with the optical interferometry method. Flow curves and the concentration dependence of the viscosity provide additional information on the phase state and structure of the samples. Rheo-X-ray data were obtained using a specially developed micro-Couette geometry consisting of a coaxial arrangement of two standard X-ray capillaries (the inner one rotates at different speeds). The orientation development of HPC in two-phase and full anisotropic solutions, as well as of the clay and HPC in the nanocomposites were measured (separately) as a function of shear rate. In addition, the decay of the orientation parameter with time after cessation of flow was analyzed to reveal several stages related to the disorientation and reformation of the cholesteric helix in HPC solutions. Crystalline nanoclay in flowing LC solutions also formed a mesophase structure. Specifically, the columnar mesophase of clay formed under certain conditions could be completely or partially converted to a discotic phase. Comparison of these results with optical images of the regular (circle-like) morphology observed under strong flow suggested that the elasticity is the general driving force for development of the regular instability in length scales of optical and X-ray scattering measurements.

Structural evolution of liquid-crystalline solutions of hydroxypropyl cellulose and hydroxypropyl cellulose-based nanocomposites during flow

The phase state and orientation and dissipative characteristics of biphasic LC HPC-water solutions and filled systems formed on their basis during shear flow are studied by various methods. The concentration of solutions is selected on the basis of the corrected phase diagram constructed with the use of optical interferometry. Flow curves and concentration dependences of viscosity provide additional information about the phase state and structure of the samples and the role of fillers in the rheological properties of solutions. X-ray diffraction data are obtained with the use of a Couette cell consisting of two coaxial capillaries. In the case of a clay suspension in water, practically no orientation is attained. However, in the isotropic 30% solution, clay particles easily orient, a result that indicates an important role of the viscoelasticity of a medium in the orientation process. The development of orientation of HPC macromolecules and clay particles in relation to the shear rate is analyzed separately for systems with the biphasic matrix (LC + isotropic phase). In addition, the time decay of the orientation parameter during relaxation is investigated. It is shown that higher shear rates cause a more rapid relaxation of orientation, for which recovery of the cholesteric helix typical for LC solutions of cellulose derivatives in the equilibrium state plays an important role. Order parameters (separately for the two components) are calculated, and their evolution with the shear rate and total deformation is investigated for systems containing clay nanoparticles (also the structure-active component) in LC solutions. On the basis of these data, it is hypothesized that clay particles form the columnar mesophase, which, under certain conditions, may transform into the discotic mesophase. This transition is responsible for a certain decrease in the order parameter of HPC apparently due to the instability effect of the director. It is found that shearing substantially affects the structure of the system composed of two mesophase species; specifically, it either facilitates the reinforcement of one of them or provokes structural transitions.

Discover Dionex IC LC Solutions for Better Chemistry

RETURN TO ISSUEPREVAdvertisementNEXTDiscover Dionex IC LC Solutions for Better ChemistryCite this: Chem. Eng. News 2005, 83, 25, 83Publication Date (Print):June 20, 2005Publication History Published online14 November 2010Published inissue 20 June 2005https://doi.org/10.1021/cen-v083n025.p083Copyright © 2005 AMERICAN CHEMICAL SOCIETYArticle Views17Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (672 KB) SUBJECTS:Chromatography Get e-Alerts

Discover Dionex IC·LC Solutions for Better Chemistry

RETURN TO ISSUEPREVAdvertisementNEXTDiscover Dionex IC·LC Solutions for Better ChemistryCite this: Chem. Eng. News 2005, 83, 5, 57Publication Date (Print):January 31, 2005Publication History Published online14 November 2010Published inissue 31 January 2005https://doi.org/10.1021/cen-v083n005.p057Copyright © 2005 American Chemical SocietyArticle Views63Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (587 KB) Get e-Alerts

The Influence of Polymer Molecular Weight on the First Normal-Stress Difference and Shear-Viscosity of LC Solutions of Hydroxypropylcellulose

The first normal-stress difference N1() and the shear viscosity η() have been measured for liquid crystalline solutions of HPC in acetic acid (AA) as functions of the shear rate and the molecular mass of HPC. The measurements were done over four decades in , for two samples of HPC with Mw = 60,000 and 100,000 (Klucel E and L, respectively) and solution concentration c = 37% (c > c*). N1 () is observed to change from positive to negative and again to positive, as the shear rate increases. The values at which N1 changes sign depend on Mw. The viscosity η() shows a small Newtonian plateau at low shear rates and a strong shear-thinning at higher values of , including an “hesitation” similar to one previously observed in LC solutions of PBLG [2]. All these observations are rationalized within the framework of the constitutive equations for liquid crystalline polymers recently proposed by one of us [1]. Expressions for η() and N1() derived from this I theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system are thereby obtained for the first time.

Spinning of poly-p-phenylenebenzobisthiazole fibres

The effect of the intrinsic viscosity and concentration of polymer in LC solution on the mechanical properties of PPBT yarn was demonstrated. In examining the spinning stability of PPBT yarns, use of spinnerets with an opening diameter of 0.25 mm and conditions ensuring cooling of the jets of heated LC solutions in an air gap are preferred. The isometric conditions of drawing of jets of a LC solution of PPBT with a ratio greater than 7–8 initiate one-dimensional flow with stable pulsation of the diameter. The phenomenon is known as draw resonance.

Some parameters of spinning poly-p-phenylene terephthalamide fibres through an air gap

The spinneret draw ratio for jets of LC solutions of PPTA (range of 1 to 10) is a basic parameter in spinning of high-strength fibres through an air gap. The strength of the fibres is a function of the conditions of intense spinneret drawing of the jets of LC solutions of PPTA and the spinning speed. Most of the sulfuric acid (solvent) passes into the spinning bath as a result of brief contact of the jet of LC PPTA solution and fibres with it during spinning.

Rheological properties of liquid-crystalline solutions of poly(p-phenylene terephthalamide) and behavior of the jet in spinning through an air space

LC solutions of PPTA behave like liquids with a power law of flow and n =0.65–0.78 for flow through the channels of standard spinnerets with small diameters and q =0.88–0.95 for longitudinal flow in jets. Spinneret expansion of a freely falling jet in channels with small diameters is equal to 1.70–1.75 and is not a function of the shear rate on the wall. Spinneret expansion is preserved in conditions of repeated drawing of the jets in the air space until very small air spaces at 1.5–2.5 mm are used. In spinning PPTA fibres through an air space with a high jet draw ratio, only a small fraction of this drawing in the spinning bath is possible.

Aging Effects on the Rheology of LC Solutions of Hydroxypropylcellulose

Abstract We apply the recently developed continuum theory of liquid crystalline polymers1 to interpret the behavior of the shear viscosity η(γ.) and the first normal-stress difference N1(γ.) measured for liquid crystalline solutions (c = 37%, c > c*) of HPC (Aldrich, Mw = 100,000) in acetic acid (AA) with different ages: 1 day, 1 month and 2 years. η(γ.) and N1(γ.) were measured over four decades in γ. N1(γ.) is observed to change from positive to negative and again to positive, as the shear rate γ. increases. η(γ.) shows a small newtonian plateau at low shear rates and a strong shear-thinning at higher values of γ. The rate of decrease of η(γ.) in this region is not monotonous, as usual, but shows an “hesitation” similar to one previously observed in a different system2. The aging effect promotes a “depolymerization”3 of HPC. This, in turn, should have a strong influence on the behavior of Nl(γ.) and η(γ.) which is indeed observed4. All these observations can be rationalized within the framework of the t...

High-strength fibres based on liquid-crystalline polymers

-- The high degree of polymer order in LC solutions and melts predetermines the preparation of high-strength fibres and yarns based on them. -- High-strength yarns from LC solutions of PPTA are produced on an industrial scale (Kevlar and Tveron) and on a pilot-plant scale (Terlon). -- The preparation of high-strength yarns based on LC thermotropic copolyesters is a promising trend from the point of view of an economical and ecologically clean method of spinning from the melt. -- Experimental and pilot-plant units are being developed for the preparation of such fibres at present. -- Ultrahigh-modulus yarns of the PVZ type for low-tonnage purposes present much interest for the development of new composite materials for contemporary aerospace technology. -- Studies in the direction of increasing compressional strength of high-strength fibres based on rigid-chain LC polymers are promising.

Non-linear visco-elasticity of liquid crystalline solutions and pastes of aromatic polyamides of para-structure

The results of measurement of the visco-elastic properties of LC solutions and pastes of aromatic PAs with para-structure in the dynamic ans static regimes of shear deformation are compared. The amplitude of strain significantly influences the convergence of the data obtained by different methods. The role of the orientational processes for LC solutions and three-dimensional structuring in the pastes in determining the features of the rheological behaviour and the correlation of their dynamic and static visco-elastic characteristics is discussed.

Liquid crystalline structure of solutions of poly- γ-benzyl- L-glutamate

Over a wide interval of change in concentrations, temperature and MM from the texture of the “fingerprints” the authors have determined the pitch of the cholesteric helix P for LC solutions of poly- γ-benzyl- L-glutamate in DMFA. The experimentally obtained dependences of the pitch of the cholesteric helix on temperature, concentration and MM are discussed in relation to various theories. In particular, in relation to the kinetic approach an explanation is for the first time offered for the experimentally discovered maximum in the dependence of the pitch on MM according to which non-monotonic change in pitch is a consequence of change in the form of the molecule with increase in its contour length to a value equal to and beyond the persistent length.