HPLC Determination of Lansoprazole and Method Application for the Formulation Development of Enteric‐coated Lansoprazole Pellets

The aim of this study was to develop a validated HPLC method for the determination of lansoprazole in dissolution medium and pellets. For the formulation development, we investigated the role of 2‐hydroxypropyl‐β‐cyclodextrin (HPβCD) on the dissolution of enteric‐coated pellets of lansoprazole prepared by the solution layering technique using a fluid bed coater. Dissolution results demonstrated the coating using Acryl‐Eze protected the formulations from releasing lansoprazole in acid medium for the first 2 h, and the addition of HPβCD improved the dissolution performance by 189%, compared with the group without HPβCD. The DSC analysis displaced an absence of the endothermic peak for the lyophilized products lansoprazole and HPβCD, and FTIR analysis demonstrated the band broadening, shifting or disappearance compared to the spectra of the physical mixture, which indicated the formation of the inclusion complex between lansoprazole and HPβCD. This study has developed a validated HPLC method to measure lansoprazole in test media and pellets, which was applied successfully to the formula tion development of enteric‐coated pellets.     

Molecular dynamical study of the energy relaxation processes after heating the vibrational degree of freedom in a diatomic molecular crystal

Energy relaxation processes initiated by sudden heating of the vibrational degree of freedom were studied with molecular dynamical method. A unit cell of bee structure containing 128 diatomic molecules with periodic boundary conditions was considered. Compound Morse potential was assumed as the atom-atom interactions. It was found that the logarithra of the equilibration time depends linearly upon a factorf ₂₁ which is proportional to the frequency ratio of the intra- and inter-molecular vibrations. The project is supported by the National Natural Science Foundation of China.     

The effect of friction reduction in the presence of in-plane vibrations

A reduction of friction by vibrations has been observed in various experiments. This effect can be applied to actively control frictional forces by modulating vibrations. Moreover, common methods of controlling friction rely on lubricants and suitable material combinations. The superimposition of vibrations can further reduce the friction force. This study presents a theoretical approach based on the Dahl friction model that describes the friction reduction observed in the presence of the tangential vibrations at an arbitrary angle. Analysis results indicated that the tangential compliance should be considered in modeling the effect of vibrations in reducing friction. At any vibration angle, the tangential compliance of the contacts reduces the friction reduction effect. The vibrations parallel to the macroscopic velocity are most effective for friction reduction.     

Computer-aided photoelastic analysis of orthogonal 3D textile composites: Part 2. Combining least squares and finite-element methods for stress analysis

An approach combining least squares methods and finite element methods (FEM) is presented for subsequent photoelastic stress analysis of orthogonal 3D textile composites withR and α obtained in Part 1. Through this approach, these photoelastic stresses are obtained over a region of interest as if the composites were homogeneous materials. The least squares method is used for requiring the solution strain fields to best correlate with the distribution of the two photoelastic strain data of ɛ _x − ɛ _y and γ _xy calculated directly from the measuredR and α. The FEM uses the homogenized composite properties to construct the nodal force equilibrium equations as constraints in the least squares formulation. As a result of combining this least squares method and FEM with lagrange multipliers, a linear system of equations is formulated with the unknown nodal displacements. Once these nodal displacements are solved, the strains and stresses can be calculated through FEM formulations. This approach is tested with the two experimental results completed in Part 1 for the aluminum and composite plates. The stresses obtained for the aluminum plate show close agreement with those obtained with the plain FEM computation. In the case of the orthogonal 3D composite plate, the local variations as observed inR and α are already necessarily eliminated from these solved photoelastic stresses. Furthermore, these stresses also match well with those computed with the plain FEM from the homogenized composite properties.     

An inverse heat conduction problem of estimating boundary fluxes in an irregular domain with conjugate gradient method

A Boundary Element Method (BEM)-based inverse algorithm utilizing the iterative regularization method, i.e. the Conjugate Gradient Method (CGM), is used to solve the Inverse Heat Conduction Problem (IHCP) of estimating the unknown transient boundary heat flux in a multi-dimensional domain with arbitrary geometry. Results show that the advantages of applying the CGM in the inverse calculations lie in that the major difficulties in (i) choosing a suitable quadratic norm, (ii) determining a proper regularization order and (iii) determining the optimal smoothing (or regularization) coefficient in the conventional Regularization Method (RM) are avoided. Received on 27 October 1997     

Neighbor Distinguishing Edge Colorings Via the Combinatorial Nullstellensatz Revisited

Consider a simple graph and its proper edge coloring c with the elements of the set . We say that c is neighbor set distinguishing (or adjacent strong) if for every edge , the set of colors incident with u is distinct from the set of colors incident with v. Let us then consider a stronger requirement and suppose we wish to distinguishing adjacent vertices by sums of their incident colors. In both problems the challenging conjectures presume that such colorings exist for any graph G containing no isolated edges if only . We prove that in both problems is sufficient. The proof is based on the Combinatorial Nullstellensatz, applied in the “sum environment.” In fact the identical bound also holds if we use any set of k real numbers instead of as edge colors, and the same is true in list versions of the both concepts. In particular, we therefore obtain that lists of length ( in fact) are sufficient for planar graphs.     

Oligoepicatechins from the Leaves of Machilus konishii

Epicatechin ( 3 ) and five oligomers ( 2 , 4 , 5 , 10 , 11 ) together with five other type compounds were isolated and characterized from n‐BuOH and EtOAc soluble fractions of the ethanol extract of the leaves of Machilus konishii Hayata. Their structures were elucidated by means of MS and NMR spectroscopic analyses. Dehydrodiepicatechin A ( 11 ) is the first occurrence as a natural product although it has been prepared from epicatechin. The stereochemistry of 11 is elucidated for the first time on the basis of 1D NOESY and chemical model analyses. Tiliroside ( 7 ) and kaempferol 3‐O‐α‐L‐(2″,4″‐di‐E‐p‐coumaroyl)‐rhamnopyranoside ( 8 ) showed moderate inhibitory activity against α‐glucosidase.     

Quantitation of branched-chain amino acids in ascites by capillary electrophoresis with light-emitting diode-induced fluorescence detection

Branched-chain amino acids (BCAAs) are one of the important biomarkers for monitoring liver disease such as hepatitis or hepatoma. In this communication, we present the determination of the concentrations of BCAA in ascites by CE light-emitted diode-induced fluorescence (LEDIF) using 1.5% m/v poly(ethylene oxide) (average M(v) : ~8?000?000?g/mol) that was prepared in 10?mM sodium tetraborate solution (pH 9.3). Naphthalene-2,3-dicarboxaldehyde was used to derivatize 15 amino acids (AAs) to form naphthalene-2,3-dicarboxaldehyde (NDA)-AA derivatives prior to CE analysis. The separation of 15 NDA-AA derivatives was accomplished within 15?min, with RSD values of <5.8% (within-day) and 7.4% (between-days) with respect to their migration times. The limits of detection for the tested BCAAs ranged from 10.6 to 10.9?nM. We determined the concentrations of three BCAAs--leucine, isoleucine and valine--in ascites by applying a standard addition method, with recovery percentages ranging from 93.9 to 111%. The results obtained from this CE-LEDIF method is in good agreement with those by a gold standard method using an AA analyzer. We have found that the concentrations of the three BCAAs in ascites obtained from patients suffering from liver diseases were lower than those from healthy individuals. Our approach is highly efficient, sensitive, and cost-effective, which holds great potential for the diagnosis of liver diseases.