An efficient procedure for preparation of 2-monoalkyl or 2-monoaryl-3-ethoxycyclobutanones

Optimized reaction conditions for the preparation of various 2-monosubstituted 3-ethoxycyclobutanones are described. 2-Monoalkyl 3-ethoxycyclobutanones were efficiently prepared by the reaction of the corresponding carboxylic acid chlorides and an excess amount of ethyl vinyl ether in the presence of diisopropylethylamine at 90 °C in a sealed tube. 2-Monoaryl 3-ethoxycyclobutanones were prepared by using 2,6-lutidine as a base in the above-mentioned procedure.     

Hardness measures for gridworld benchmarks and performance analysis of real-time heuristic search algorithms

Gridworlds are one of the most popular settings used in benchmark problems for real-time heuristic search algorithms. However, no comprehensive studies have been published so far on how the difference in the density of randomly positioned obstacles affects the hardness of the problems. This paper presents two measures for characterizing the hardness of gridworld problems parameterized by obstacle ratio, and relates them to the performance of the algorithms. We empirically show that the peak locations of those measures and actual performance degradation of the basic algorithms (RTA* and LRTA*) almost coincide with each other for a wide variety of problem settings. Thus the measures uncover some interesting aspects of the gridworlds.     

Melt rheology of hyperbranched‐polystyrene synthesized with multisite macromonomer

Melt rheological behaviors of hyperbranched‐polystyrene (PS) copolymerized by dendric macromonomer technique are presented. The time–temperature superposition principle was applicable to the hyperbranched‐PS. The branched‐PS showed slightly lower zero‐shear viscosity in comparison with linear PS regardless of a presence of a number of branches expected from the dendric macromonomer technique. Although the influence of use of multimethacryloyl macromonomer in the polymerization process was marginal for linear viscoelastic regime, nonlinear shear and uniaxial elongational flows showed distinct differences between linear and branched‐PS. The strain dependence of the damping function became weak as increase of macromonomer content. The branched‐PS exhibited the growing elongational viscosity function comparing with linear PS. This prominent effect on the elongational flow behavior can be explained by the molecular architecture of the branched‐PS. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2226–2237, 2009     

Photoluminescence of CdGeP2 and (Cd,Mn)GeP2

Photoluminescence of CdGeP₂ (112) single crystal and CdGeP₂ epitaxial film grown on GaAs (001) substrate have been studied and their spectral similarity found. Spectral bands associated with donor/acceptor transitions peak at close energies for both substances and all are lower than the energy gap of the chalcopyrite crystal.On the other hand, the growth of (Cd,Mn)GeP₂ ferromagnetic layer on CdGeP₂ (112) single crystal was performed to make it possible observation of PL from both the ferromagnetic layer and substrate. The green laser excitation (514, 532 nm) produces a proper photoluminescence similar to that in the undoped CdGeP₂ crystal and film. An extra emission from the ferromagnetic-nonmagnetic heterojunction occurs to extend up to photon energies exceeding E_g of the host semiconductor. The short wavelength photoluminescence is to be due to (Cd,Mn)GeP₂ dilute magnetic semiconductor (DMS). This fact states that Mn-doped II-IV-V₂ chalcopyrites are closer to II-VI DMS than to another group III-V DMS, where the heavy Mn-doping suppresses photoluminescence at all. Features of the observed short wavelength emission are discussing based on the temperature and spectral analyses.     

Sensitive detection of oxo-steroids and oxo-bile acids by liquid chromatography with peroxyoxalate chemiluminescence detection

Oxo-steroids and oxo-bile acid ethyl esters were derivatized with 5-N,N-dimethylamino-naphthalene-1-sulphonohydrazide (DNS-hydrazine) to DNS-hydrazone in the presence of hydrochloric acid in ethanol or trifluoroacetic acid in benzene, purified by high-performance gel-permeation chromatography, separated on an ODS column with an eluent containing tetrahydrofuran and detected via a peroxyoxalate chemiluminescence reaction using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate (TDPO). Sensitive detection (femtomole level) of each oxo-steroid which appeared as a single peak was achieved. The procedure for the isolation of oxo-bile acids developed for GC-MS allowed the detection by this system of an unusual oxo-bile acid, 7α-hydroxy-3-oxo-5β-cholanic acid, at the nanomole l^?1 level in urine from a patient with cholestatic liver disease.     

Feasibility of using [18O2]11-dehydrothromboxane B2 as an internal standard of immunoaffinity purification followed by gas chromatography/selected ion monitoring

[1,1-18O2]11-Dehydrothromboxane B2 (11-dehydro-TXB2) was prepared by repetitive base-catalyzed hydrolysis of the lactone ring of its [1,1,11-18O3]-analogue, and evaluated for its suitability as an internal standard in gas chromatography/selected ion monitoring (GC/SIM) of 11-dehydro-TXB2. Use of the present [18O2]-analogue as an internal standard may make it a suitable candidate for specific immunoaffinity purification followed by GC/SIM.     

Potentiometric and spectrophotometric flow-injection determinations of metal ions with use of metal ion buffers

Potentiometric and spectrophotometric flow-injection determinations of metal ions, based on metal ion buffers, are described. A copper(II) ion-selective electrode and copper(II) ion buffers containing nitrilotriacetic acid (NTA) or ethylenebis(oxyethylenedinitrilo)tetraacetic acid (EGTA) are used for determination of ca. 10^?3 M transition metal ions or of calcium in the presence of magnesium. Spectrophotometric determination of transition metal ions is achieved by using a zinc ion buffer solution containing NTA and xylenol orange as indicator. Zinc concentrations up to 2 M can be determined by using large dispersion in the manifold. The factors influencing the sensitivity of the proposed methods are discussed.     

Rheological properties of poly(vinyl chloride)/plasticizer systems—relation between sol–gel transition and elongational viscosity

Poly(vinyl chloride) (PVC)/di-isononyl phthalate systems with PVC content of 45.5 (PVC8) and 70.4 wt% (PVC6) were prepared by a hot roller at 150 °C and press molded at 180 °C. The dynamic viscoelasticity and elongational viscosity of PVC8 and PVC6 were measured in the temperature range from 150 to 220 °C. We have found that the storage and loss shear moduli, G′ and G″, of PVC8 and PVC6 exhibited the power-law dependence on the angular frequency ω at 190 and 210 °C, respectively. Correspondingly, the tan δ values did not depend on ω. These temperatures indicate the critical gel temperature T _gel of each system. The critical relaxation exponent n obtained from these data was 0.75 irrespective of PVC content, which was in agreement with the n values reported previously for the low PVC concentration samples. These results suggest that the PVC gels of different plasticizer content have a similar fractal structure. Below T _gel, the gradual melting of the PVC crystallites takes place with elevating temperature, and above T _gel, a densely connected network throughout the whole system disappears. Correspondingly, the elongational viscosity behavior of PVC8 and PVC6 exhibited strong strain hardening below T _gel, although it did not show any strain hardening above T _gel. These changes in rheological behavior are attributed to the gradual melting of the PVC crystallites worked as the cross-linking domains in this physical gel, thereby inapplicability of the of time–temperature superposition for PVC/plasticizer systems.