AN INVESTIGATION ON CATIONIC POLYMERIZATION OF α-METHYLSTYRENE WITH Cl_2/TiCl_4 INITIATOR SYSTEM Ⅱ. EFFECTS OF PO1YMERIZATION TEMPERATURE, SOIVENT AND REACTION TIME
4-Tert-butylphenylboronic acid was synthesized with trimethyl borate and Grignard reagents which was prepared with 1-bromo-4-tert-butylbenzene and metal magnesium as raw materials under N2. An optimized process was obtained as follows: 1.5∶1molar ratio of 1-bromo-4-tert-butylbenzene to trimethyl borate,the temperature -20~-30℃,and the reaction time 140min. The final yield was 69.5%.
Methyl-furoate is synthesized from furfural by Cannizzaro reaction,acyl chloride reaction and esterification. It showed that the time of esterification is only 2.5 hours and the yield can reach 85.0%.
Study on Prediction of Long-term Mechanical Behaviors for Polymers──(Ⅶ) Depedence of Different Shear Stress Level on Dimensional Stability and Life Time of PVC
The proof is based on a variant of Moser's method using time-dependent vector fields.
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We present two-sided singular value estimates for a class of convolution-product operators related to time-frequency localization.
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The Balian-Low theorem (BLT) is a key result in time-frequency analysis, originally stated by Balian and, independently, by Low, as: If a Gabor system $\{e^{2\pi imbt} \, g(t-na)\}_{m,n \in \mbox{\bf Z}}$
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Gabor Time-Frequency Lattices and the Wexler-Raz Identity
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Gabor time-frequency lattices are sets of functions of the form $g_{m \alpha , n \beta} (t) =e^{-2 \pi i \alpha m t}g(t-n \beta)$ generated from a given function $g(t)$ by discrete translations in time and frequency.
A colorimetric method for the determination of antimony in the range 0.1 to 3.0μg per milliliter blood is described. The time needed for the destruction of organic matter is shortened to 8—12 minutes. The proposed method is as follows: Accurately transfer 1 ml of blood sample to a hard glass test tube (25×150 mm.), to which 1 ml of conc. HNO_3 is then added. Heat gently with a small flame till the solution changes to amber color. Add 0.5 ml conc. H_2SO_4 and heat again carefully until dense white fume...
Effects of vulcanizing temperature and time on the physico-mechanical properties of wet-gel and dry-film of vulcanized natural latex were studied. The physico-mechanical properties of wet-gel became worse when the temperature or the degree of vulcanization was increased. The properties of dry-film were improved by increasing the degree of vulcanization and became worse on increasing the vulcanizing temperature (while the combined sulphur is constant). The differences in these properties between the we...
A countercurrent distribution apparatus is described. It is more compact than the apparatus of Craig and Post. It can take a large number of tubes with greater capacity in the extraction train, and permits close mounting in compact racks. A 100-tube extraction train of 100 ml capacity (50 ml upper and 50 ml lower phases) per tube occupies a space of 28×55×40 cm. The tube shown in figure 1 (1), (2) is made from 2.8×55 cm glass tubing. "A"is a reservoir (more than 50 ml), "B"is an equilibration cell, approxim...