Papers by Nguyễn Lê Ngọc Châu
Journal of Polymer Science: Polymer Chemistry Edition
As model compounds for determining the potential adaptability of novel leaving group to polyamide... more As model compounds for determining the potential adaptability of novel leaving group to polyamide synthesis, 2‐aryl‐5‐benzoylthio‐1,3,4‐oxadiazoles having various electron accepting and donating groups in the oxadiazole unit were successfully prepared from the benzoylation of the corresponding 2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones under kinetically controlled conditions ( < −50°C). The aminolyses of all the benzoyl thioesters by aniline afforded quantitative yields of benzanilide at room temperature in a short reaction time. Polycondensations of new active dithioesters, 5,5′‐isophthaloyldithiobis‐2‐aryl‐1,3,4‐oxadiazoles, with both aliphatic and aromatic diamines occured quite rapidly even at room temperature to form polyamides with reduced viscosities up to 0.41 dL/g. The reactivities of the dithioesters having electron accepting groups such as p‐chloro and p‐nitro groups, particularly p‐nitro groups, toward diamines were much higher than that of the dithioester having no such gro...
Journal of Polymer Science: Polymer Chemistry Edition
A novel class of polyamide‐quinazolinediones was synthesized by the polymerization of 2,2′‐disubs... more A novel class of polyamide‐quinazolinediones was synthesized by the polymerization of 2,2′‐disubstituted bis(1,3,4‐oxadiazolin‐5‐ones) with aromatic bis‐o‐amino esters in m‐cresol. The polymerization probably proceeded in the formation of ring‐opening adducts, which in turn were cyclized by the elimination of alcohol to give polyamide–quinazolinediones. These polymers, which were soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, N‐methyl‐2‐pyrrolidone, and dimethyl sulfoxide, had, with one exception, reduced viscosities in the range of 0.12–0.32 dL/g. Thermogravimetric analyses indicated that they began to decompose at 310–360°C in air.
Die Makromolekulare Chemie
Poly(pyromellitdiimidoarylenecarbonyliminoaryleneiminocarbonylarylene)s [poly(amide‐imide)s] (7 a... more Poly(pyromellitdiimidoarylenecarbonyliminoaryleneiminocarbonylarylene)s [poly(amide‐imide)s] (7 and 12) were prepared from pyromellitic dianhydride (6) and dicarbamates (5) (diurethanes) containing amide linkages. The same polymers could also be prepared directly from aromatic isocyanatocarboxylic acid chlorides (10), diamines (11) and 6. In the latter method, the addition of an equimolar amount of water was required for the formation of the imide ring in the main chain of the polymer. Model reactions were carried out to determine the reaction conditions for the two methods. Reaction mechanisms are proposed.
Die Makromolekulare Chemie
Aromatic diphenyl esters containing the quinazolinedione unit (7a,b and 8a,b) were synthesized fr... more Aromatic diphenyl esters containing the quinazolinedione unit (7a,b and 8a,b) were synthesized from phenyl N‐(phenoxycarbonylphenyl)carbamates (3 and 5) and aromatic bis(o‐amino) esters (6a,b). The corresponding dicarboxylic acids (7c,d and 8c,d) were obtained by hydrolyzing the diphenyl esters. The condensation of either the diphenyl esters 7a,b and 8a,b or the dicarboxylic acids 7c,d and 8c,d with aromatic tetraamines (11a‐c) gave polymers 12 and 13 containing benzimidazole and quinazolinedione units. These polymers exhibited highly thermal stability.
Journal of Polymer Science: Polymer Chemistry Edition
Quang, Ngo Xuan, Chau, Nguyen Ngoc, Vanreusel, Ann (2014): Nematode morphometry and biomass patte... more Quang, Ngo Xuan, Chau, Nguyen Ngoc, Vanreusel, Ann (2014): Nematode morphometry and biomass patterns in relation to community characteristics and environmental variables in the Mekong Delta, Vietnam. Raffles Bulletin of Zoology 62: 501-512
Journal of Polymer Science: Polymer Chemistry Edition, 1982
New diamines containing amide and oxyethylene linkages were prepared by reduction of the correspo... more New diamines containing amide and oxyethylene linkages were prepared by reduction of the corresponding dinitro compounds which were obtained by the reaction of p‐nitrophenol with arylenebis(2‐oxazolines) in dimethylformamide at 130°C. Moderate‐ to high‐molecular‐weight polyamides and polyamide‐imides containing oxyethylene linkages were prepared by the polycondensation of the diamines with diacid chlorides and tetracarboxylic acid dianhydrides, respectively. The polyamides were soluble in dimethylacetamide containing 5% of lithium chloride and dichloroacetic acid, while the polyamide‐imides dissolved only moderately in the latter solvent. Thermogravimetric analysis showed that thermo‐oxidative decomposition started at 310–330°C and at around 325°C for the polyamides and polyamide‐imides, respectively.
Journal of Polymer Science: Polymer Chemistry Edition, 1983
New active bisamides, 4,4′ ‐diacylbis‐2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones having variou... more New active bisamides, 4,4′ ‐diacylbis‐2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones having various electron accepting groups in the oxadiazoline units were synthesized, and their reactivities toward diamines were investigated. The polycondensation reactions of the bisamides derived from 2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones with both aliphatic and aromatic diamines occurred rapidly even at room temperature to form high‐molecular‐weight polyamides in quantitative yields. The reactivities of the bisamides having electron accepting groups such as p‐chloro and p‐nitro groups, particularly p‐nitro groups, toward diamines were much higher than that of the corresponding bisamide having no such group. It was also found that reaction conditions such as solvent, monomer concentration, and temperature had a strong influence on the molecular weight of the resulting polyamides. Aminolysis of several benzoyl derivatives of 2‐aryl‐1,3,4‐oxadiazoline‐5‐thiones and ‐ones was also carried out as a mode...
Journal of Polymer Science: Polymer Chemistry Edition, 1981
Die makromolekulare Chemie, Jun 1, 1979
Diamines containing ester and amide linkages were obtained by the addition reaction of p-aminoben... more Diamines containing ester and amide linkages were obtained by the addition reaction of p-aminobenzoic acid with arylenebis(2-oxazolines) in N,N-dimethylformamide. These diamines were subjected to polycondensation with various diacid dichlorides to obtain polyamides containing regular ester and amide sequences in the polymer chain.
Die makromolekulare Chemie, Jul 1, 1974
Aromatic isocyanatocarboxylic acid chlorides (1 a-i) reacted with stoichiometrical quantities of ... more Aromatic isocyanatocarboxylic acid chlorides (1 a-i) reacted with stoichiometrical quantities of dimethyl sulfoxide in ether to yield poly(N-carb0xyanhydride)s (5) which were converted into polyamides (6) by heating them at elevated temperatures. Isocyanatocarboxylic acid chlorides also reacted with water to produce polyamides 6. The reaction paths were followed by quantitative analysis of carbon dioxide evolved, by measurement of IR spectra, and by thermal analysis of the polymers. ZUSAMMENFASSUNG: Aromatische Isocyanatocarbonsaurechloride (1 a-i) reagieren mit stochiometrischen Mengen von Dimethylsulfoxid in Ather und ergeben Poly(N-carboxyanhydride) (5), diedurch Erhitzen auf hohere Temperaturen in Polyamide (6) iiberfuhrt werden. Isocyanatocarbonsaurechloride reagieren ebenso mit Wasser unter Bildung von Pol yamiden 6. Der Reaktionsweg wurde durch quantitative Analyse des gebildeten Kohlendioxids verfolgt sowie mit Hilfe der IR-Spektren und durch thermische Analyse der Polymeren.
II International Symposium on Papaya, 2010
A papaya breeding program was initiated at the Southern Fruit Research Institute, Vietnam in 2006... more A papaya breeding program was initiated at the Southern Fruit Research Institute, Vietnam in 2006 using gamma rays to induce mutation. Germinated seeds of popular local papaya variety Dai Loan Tim were irradiated with gamma rays ranging from 10 to 60 Gy. Radio sensitivity test of germinated seeds showed that LD 50 was 30 Gy, two doses below LD 50 value viz. Ten and 20 were selected for field planting. A total 1000 M 1 plants were planted and screened in the field. Among these, four mutant plants, which were particularly outstanding in vigor with medium dwarf stature, bearing the first flower at a height of 50-60 cm from the ground and improved fruit quality when compared to control were selected. The average fruit weight of four mutant lines ranged from 1.3-1.9 kg/fruit, average total soluble solids from 10.8-11.6 Brix %. Usefulness of these economic mutants for improving precocity and reducing plant height in papaya breeding program is discussed.
Journal of Polymer Science: Polymer Chemistry Edition, 1973
Anticancer research
Clinical and experimental observations indicate that resistance to anticancer drugs may be sponta... more Clinical and experimental observations indicate that resistance to anticancer drugs may be spontaneously reversible over time. This work is a mathematical and statistical analysis of the relationship, during a 9-month experiment, between the resistance of repeatedly re-seeded hepatoma cells to methotrexate (MTX) or to cisplatin (cisP) and untreated cell proliferation, telomere length and telomerase activity. All variables showed complex oscillations, as previously published. In this work, cell proliferation was modelized by the logistic model, and the proliferation rates (a-values) together with their variations (va-values) were calculated. Significant correlations were discovered between cell resistance to treatments and a-values, va-values, telomere length and telomerase activities. These results open new insights into the handling of chemotherapy in the treatment of cancers.
Applied Entomology and Zoology, 2009
Meteorus pulchricornis is a solitary endoparasitoid of various lepidopteran larvae that attacks f... more Meteorus pulchricornis is a solitary endoparasitoid of various lepidopteran larvae that attacks free-living hosts exposed on plant foliage. We tested the necessity of host movement for oviposition behavior in M. pulchricornis using dummy hosts as well as natural host larvae (Spodoptera litura). We quantified the occurrence of three steps in oviposition behavior, i.e., host orientation, oviposition stance, and oviposition attack, to natural hosts under light and dark conditions. We also examined the incidence of these behaviors on natural hosts, moving dummy hosts, and motionless dummy hosts under light conditions. Few successful attacks occurred on natural hosts under dark conditions and no oviposition attempts were made against motionless dummy hosts. These results indicate that visual cues from moving host larvae are necessary for successful oviposition. Furthermore, host movement seems important for female wasps to orient the ovipositor toward the host body, since the location of the oviposition attack on natural hosts changed markedly with the mode of host movement.
Polymer Journal, 1974
Some aromatic bisurethanes containing amide linkage were synthesized from p-phenoxycarbonylaminob... more Some aromatic bisurethanes containing amide linkage were synthesized from p-phenoxycarbonylaminobenzoyl chloride and aromatic diamines. Polyamides containing quinazolinedione rings in the main chain were obtained by either heating a mixture of bisurethane and aromatic bis-a-amino ester in pyridine or directly in solid state at elevated temperatures. The model reaction for the formation of quinazolinedione was carried out in pyridine. The formation of quinazolinedione ring in the polymer was investigated by infrared spectroscopy and thermal analysis. The poly(amide-quinazolinediones) were reasonably thermal stable.
Mathematical Biosciences, 1985
Resolution of kinetic equations and parameter identification are discussed for ,I-compartment lin... more Resolution of kinetic equations and parameter identification are discussed for ,I-compartment linear catenary models with elimination allowed from any compartment. For a given input. general formulas are derived to describe the tracer amount in any compartment as a function of the model parameters. Conversely, explicit procedures are given to identify the model parameters when the concentration-time curve is known in one arbitrary compartment, the tracer being injected into the same compartment, In this inverse problem, the solution is not unique: the model transfer rate constants can only be localized in a finite set of intervals.
Journal of Experimental Nanoscience, 2010
Radiation-induced synthesis of colloidal silver nanoparticles (Ag-NPs) using chitosan (CTS) as a ... more Radiation-induced synthesis of colloidal silver nanoparticles (Ag-NPs) using chitosan (CTS) as a stabiliser and free radical scavenger is feasible and satisfiable to green method. The conversion dose (Ag þ into Ag 0) was determined by UV-Vis spectroscopy and Ag-NPs size was characterised by transmission electron microscopy. The average diameter of Ag-NPs was smaller than 10 nm with narrow size distribution and the colloidal Ag-NPs have good stability for a long time of storage. The effect of several parameters, such as pH, Ag þ and CTS concentration and molecular weight of CTS on Ag-NPs size was also investigated. Ag-NPs of $7 nm exhibited highly antimicrobial effect. The inhibitory efficiency of Ag-NPs for Staphylococcus aureus was more than 99.9% at 5 ppm and the effective dose (ED 50) of inhibition for Corticium salmonicolor was of 27.2 ppm.
Journal of Environmental Radioactivity, 2012
The paper presents the activity concentrations of radium isotopes (226 Ra, 228 Ra) and chemical c... more The paper presents the activity concentrations of radium isotopes (226 Ra, 228 Ra) and chemical compositions of above 70 mineral water samples collected from several dozens of springs and boreholes localized in the Polish Outer Carpathians. The activity concentrations of both radium isotopes clearly increase with the increase of water TDS, but decrease when the SO 2À 4 content increases. These concentrations vary in the broad interval from a few to near 1000 mBq/L. The coefficient of the linear correlation between concentrations of these isotopes amounts to 0.85, and the activity ratio 226 Ra/ 228 Ra is >1 for chloride-sodium waters, being z1 for hydrogen-carbonate and <1 for the sulfate ones.
Journal of Clinical Microbiology, 2010
The microscopic observation drug susceptibility assay (MODS) is a novel and promising test for th... more The microscopic observation drug susceptibility assay (MODS) is a novel and promising test for the early diagnosis of tuberculosis (TB). We evaluated the MODS assay for the early diagnosis of TB in HIV-positive patients presenting to Pham Ngoc Thach Hospital for Tuberculosis and Lung Diseases in southern Vietnam. A total of 738 consecutive sputum samples collected from 307 HIV-positive individuals suspected of TB were tested by smear, MODS, and the mycobacteria growth indicator tube method (MGIT). The diagnostic sensitivity and specificity of MODS compared to the microbiological gold standard (either smear or MGIT) were 87 and 93%, respectively. The sensitivities of smear, MODS, and MGIT were 57, 71, and 75%, respectively, against clinical gold standard (MODS versus smear, P < 0.001; MODS versus MGIT, P = 0.03). The clinical gold standard was defined as patients who had a clinical examination and treatment consistent with TB, with or without microbiological confirmation. For the ...
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Papers by Nguyễn Lê Ngọc Châu