A Validated Chiral LC Method for the Determination of Enantiomeric Purity of Pemetrexed Disodium on an Amylose-Based Chiral Stationary Phase

A simple and new isocratic normal phase chiral HPLC method has been developed for the determination of enantiomeric purity of pemetrexed disodium (l-enantiomer) in bulk drugs with a short run time of about 20 min. Chromatographic separation of l and d-enantiomers of pemetrexed disodium was achieved on an amylose based chiral stationary phase using a mobile phase consists of hexane, ethanol and trifluoro acetic acid. The resolution between the enantiomers was found to be more than 2.0. The system precision and method precision were found to be within 5% RSD for the distomer (d-enantiomer) at its specification level (i.e. not more than 1.0% w/w). The limit of detection and limit of quantification of distomer were 1.6 and 5 μg mL⁻¹, respectively for 10 μL injection volume. The percentage recovery of distomer was ranged from 90.6 to 105.7 in bulk drug samples. The test solution was found to be stable in the diluent for 48 h. The method was found to be specific for the enantiomers of pemetrexed disodium and can be conveniently used for the quantification of undesired d-enantiomer present in the bulk drug samples of pemetrexed disodium.     

Further studies on dynamic crack branching

The newly derived dynamic-crack-branching criterion with its modifications is verified by the dynamicphotoelastic results of dynamic crack branchings in thinpolycarbonate, single-edged crack-tension specimens. Successful crack branching was observed in four specimens and unsuccessful branching in another. Crack branching consistently occurred when the necessary conditions ofK _I =K _{I b} =3.3 MPa \(\sqrt m\) and the sufficiency condition ofr _o =r _c =0.75 mm were satisfied simultaneously. In the unsuccessful branching test, the necessary condition was not satisfied sinceK _I was always less thanK _{I b} .     

Small surface and corner crack propagation in aluminum and steel alloys

The purpose of the investigation reported here was to examine experimentally the transition behavior of a short crack in detail using surface-crack measurements with a traveling microscope and micromeasurements obtained by scanning-electron microscopy (SEM). The cyclic growth and transition of initial part-through cracks into through the thickness flaws are documented through experiments by using compact-type specimens fabricated from 7075-T6 aluminum, 2024-T3 aluminum, and mild-steel material, with a keyhole notch. Paper was presented at the 1986 SEM Fall Conference on Experimental Mechanics held in Keystone, CO on November 2–5.     

Analysis of the waterjet contact/impact on target material

Numerical modeling via finite element analyses (FEA) and experimental measurements via moiré interferometry were applied to the investigation of abrasive waterjet (AWJ) drilling. Polycarbonate and alumina blocks with dimensions of 25.4 mm×19.5 mm×6.25 mm were subjected to concentrated static loads experimentally and numerically. The assumptions of the FEA model are verified by comparing the experimental results with the numerical solution. A closed-form solution confirmed the correlation between the two. It was concluded that the assumption of the FEA model (e.g. mesh, boundary conditions, pressure loading, etc.) represented the static conditions. This conclusion allowed the application of a hybrid numerical/experimental technique to understand the complex interaction of the target material and the AWJ slurry column during drilling.     

Edge Finishing Effects on the Impact Behavior of Chopped GFRP Composites

The low velocity and low energy impact response of two common sheet mold compound (SMC) material systems—SMC-R27, and SMC-R37—were investigated. In addition to characterizing the low velocity impact response and failure progression of the material systems, the edge effects of diamond saw cutting, waterjet cutting and abrasive waterjet cutting were investigated using optical microscopy and contact surface profilometry. Impact force–time and displacement–time responses were measured and used to characterize energy absorption capabilities and potential correlation to post processing operation and fiber volume fraction. Pre and post-impact edge surface micrographs were examined to relate the failure behavior on the machined surfaces. Experiments and measurements all show that the failure zone size and growth behavior are clearly dependent on the edge finishing process.     

Investigation of displacement fields in an abrasive waterjet drilling process: Part 1. Experimental measurements

The transient state of displacement fields in the machining zone of a target material during abrasive waterjet impinging and drilling was investigated. A moiré interferometry experimental setup for recording displacement fields and a dynamometer for measuring the reaction force were developed. Whole fields of surface displacement fields and the reaction force of the ceramic and polycarbonate target materials were successfully recorded when the specimen was being pierced by high-pressure abrasive waterjet (AWJ). This paper demonstrates that bothu andv displacement fields of a workpiece during AWJ drilling can be recorded in real time and simultaneously by the moiré interferometry experimentation. The measured surface displacement distributions and the machining forces will be used to drive a finite element model in the second part of this investigation, in which the authors study the stress and strain state for the target material associated with the jet-materials interaction during the jet penetration process.     

Synthesis of new unsymmetrical polyarylester dendrimers

Preparation of polyarylester dendrimers containing 2-(hydroxymethyl)-1,4-butanediol and 2,2-bis(hydroxymethyl)-1,4-butanediol cores is described. These polyarylester dendrimers are unsymmetrical with respect to chain lengths and function as model systems for studying in vitro controlled drug release systems. Reaction conditions for deprotection of trichloroethyl group of the dendritic wedges have been improved.     

Strain energy density criteria for dynamic fracture and dynamic crack branching

Dynamic extension of Sih's fracture criterion based on strain energy density factor, r_c (dW/dV), is used to analyze dynamic crack propagation and branching. Influence of the nonsingular components, which are known as the higher order terms (HOT) in the crack tip stress field, on the strain energy density distribution at a critical distance surrounding the crack tip moving at constant crack velocity is examined. This r_c (dW/dV) fracture criterion is then used to analyze available dynamic photoelastic results of crack branching and of engineering materials.     

Highly Enantioselective Formation of α‐Allyl‐α‐Arylcyclopentanones via Pd‐Catalysed Decarboxylative Asymmetric Allylic Alkylation

A highly enantioselective Pd‐catalysed decarboxylative asymmetric allylic alkylation of cyclopentanone derived α‐aryl‐β‐keto esters employing the (R,R)‐ANDEN‐phenyl Trost ligand has been developed. The product (S)‐α‐allyl‐α‐arylcyclopentanones were obtained in excellent yields and enantioselectivities (up to >99.9 % ee). This represents one of the most highly enantioselective formations of an all‐carbon quaternary stereogenic center reported to date. This reaction was demonstrated on a 4.0 mmol scale without any deterioration of enantioselectivity and was exploited as the key enantioselective transformation in an asymmetric formal synthesis of the natural product (+)‐tanikolide.     

Net shape manufacturing and the performance of polymer composites under dynamic loads

An experimental investigation was conducted to determine the influence of postmold trimming and resultant edge quality on the performance of fiber-reinforced plastics (FRP) under dynamic loads. Graphite/epoxy and graphite/bismaleimide laminates were machined using three state-of-the-art industrial techniques and subjected to three-point bend impact to failure. The load load-line displacement records were used to obtain the load, bend deflection and energy absorbed to fracture. High-speed photography was also employed to identify the initiation and progression of failure and record the time dependent fracture process. From a comparison of edge quality and subsequent material performance for both polymeric composites, it was found that the impact response of FRPs is highly process dependent. In general, the load and energy absorbed to fracture decreases with increasing surface roughness. Reductions in the load and energy to the onset of fracture with degrading surface quality were as high as 20 percent. The dynamic response was also found to be dependent on the constituents, stacking sequence and impact velocity.