Polymorphic structure and physical properties of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate)

X-ray diffraction studies of fibers of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate) (PEET) produced by high-speed melt spinning show the existence of two polymorphic forms, designated α and β, in the solid state. The α form is obtained by annealing filaments melt spun at takeup speeds below 3000 m/min and is also found in samples crystallized from the melt and from dilute solutions. The α form has a monoclinic unit cell with dimensions a = 7.83, b = 10.33, c = 18.68 Å, and β = 83.1°. The equilibrium melting temperature and heat of fusion of the α form are 288.3°C and 19.1 cal/g, respectively. The β form predominates in highly oriented filaments obtained at takeup velocities above 6000 m/min. The unit cell is orthorhombic with dimensions a = 7.28, b = 5.65, and c = 18.64 Å. The β form does not transform to the α form on annealing.     

Eine Bermekung zu den Mikrofibrillen im Poly?thylen

Ohne Zusammenfassung     

A new method for synthesis of 7-deoxytaxane analogues by hydrogenation of delta(6,7)-taxane derivatives

A new method for the synthesis of 7-deoxytaxane analogues has been established through hydrogenation of Delta(6,7)-taxane derivatives. Among several catalysts examined, Pd-C was found to be a most effective catalyst for the preparation of target compound.     

On the robust estimation in poisson processes with periodic intensities

Under some regularity conditions, it is well known that the maximum likelihood estimator (MLE) is asymptotically normal and efficient. However, if the observation is contaminated, the MLE is not always an appropriate estimator. In this paper, we treat M-estimators and study their asymptotic behavior. By choosing estimation equations, robust M-estimators are presented for phase parameters.     

Regioselective transformation of O-propargylic arylaldoximes to four-membered cyclic nitrones by copper-catalyzed skeletal rearrangement

(E)-O-Propargylic arylaldoximes were regioselectively converted, in the presence of copper catalysts, into their corresponding four-membered cyclic nitrones in good to excellent yields. The reactions proceeded via a tandem [2,3]-rearrangement and 4π-electrocyclization of the N-allenylnitrone intermediate and involved cleavage of the carbon-oxygen bond.     

Improvement in the quality of hematopoietic prostaglandin D synthase crystals in a microgravity environment

Human hematopoietic prostaglandin synthase, one of the better therapeutic target enzymes for allergy and inflammation, was crystallized with 22 inhibitors and in three inhibitor-free conditions in microgravity. Most of the space-grown crystals showed better X-ray diffraction patterns than the terrestrially grown ones, indicating the advantage of a microgravity environment on protein crystallization, especially in the case of this protein.