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61.
Carlos M. Nuez J. Kaye Whitfield Debra J. Mercurio John R. Ilzhoefer Richard J. Spontak Saad A. Khan 《Macromolecular Symposia》1996,106(1):275-286
Dibenzylidene sorbitol (DBS) is capable of gelling a variety of organic solvents and polymeric materials by forming a rigid, 3-D hydrogen-bonded network. In this work, two poly(siloxane)/poly(propylene oxide) segmented copolymers of equal composition and molecular weight, but different architectures (endblocked vs. pendant), as well as a pure poly(propylene oxide), have been gelled with DBS. We have investigated the dynamic rheological properties of these gels to ascertain the effect of copolymer architecture, PDMS comonomer and DBS concentration on network formation. 相似文献
62.
We reported the environmental benign synthesis of chalcones,2-pyrazolines and cyclohexanones under microwave irradiation.Chalcones were obtained by the condensation of each of 2-hydroxyacetophenone derivatives with a-naphthaldehyde under microwave irradiation.The condensation reactions of each of synthesized chalcones with phenyl hydrazine under microwave irradiation in the presence of dry acetic acid as a cyclizing agent gave 2-pyrazolines.Also,the new cyclohexenone derivatives,valuable intermediates to synthesize fused heterocycles,have been prepared by the cyclocondensation of each of hydroxychalcones with ethyl acetoacetate.The structures of the synthesized compounds were elucidated by infrared(IR) spectrometry,nuclear magnetic resonance(NMR),mass spectrometry(MS) and elmental analysis.The results indicate that unlike classical heating,microwave irradiation results in higher yields with shorter and cleaner reactions.The synthesized compounds were screened for antimicrobial activity against Staphylococcus aureus,Escherichia coli,Candida Albicans and Aspergillus niger.We clarified the effects of different substituents in the tested compounds on the obtaind antibacterial activities and antifungal activities. 相似文献
63.
64.
Kulsoom Zahara Yamin Bibi Saadia Masood Sobia Nisa Ahmad Sher Naushad Ali Sunjeet Kumar Abdul Qayyum Waseem Ahmed Rokayya Sami Amina A. M. Al-Mushhin Amani H. Aljahani 《Molecules (Basel, Switzerland)》2022,27(6)
The genus Bidens a member of family Compositae, is widely documented as an ethno-medicinally important genus of plants. In the present study, anticancer potential of three ethno-medicinally important species i.e., B. bipinnata, B. biternata and B. pilosa were tested. For in-vitro evaluation, an MTT (Thiazolyl blue tetrazolium bromide) assay was performed against cervical cancer cells (HeLa), hepatocellular carcinoma (HepG), and adenocarcinoma human alveolar basal epithelial cells (A549). For in vivo evaluation, Artemia salina, Danio rerio, and Caenorhabditis elegans were used. Among all the tested extracts, the ethanol extract of B. biternata appeared to have highest anticancer activity, and the compounds responsible for this activity were identified to be Tris (2,4-di-tert-butylphenyl), 4-hydroxy-2,4′-dimethoxychalcone, and 2,4-di-tert-butylphenol. This is the first report of the isolation of Tris (2,4-di-tert-butylphenyl) phosphate from the genus Bidens and the first report of 4-hydroxy-2,4′-dimethoxychalcone and 2,4-di-tert-butylphenol from B. biternata. Among the isolated compounds, 4-hydroxy-2,4′-dimethoxychalcone showed the highest anticancer activity with an LD50 value of 236.7 µg/mL. Therefore, this compound carries promising potential for being established as a pharmaceutical for chemoprevention and chemotherapy. 相似文献
65.
Amorphous gallium nitride (a-GaN) thin films were deposited on glass substrate by electron beam evaporation technique at room
temperature and high vacuum using N
2 as carrier gas. The structural properties of the films was studied by X-ray diffraction (XRD) and scanning electron microscope
(SEM). It was clear from XRD spectra and SEM study that the GaN thin films were amorphous. The absorbance, transmittance and
reflectance spectra of these films were measured in the wavelength range of 300–2200 nm. The absorption coefficient spectral
analysis in the sharp absorption region revealed a direct band gap of E
g = 3:1 eV. The data analysis allowed the determination of the dispersive optical parameters by calculating the refractive
index. The oscillator energy E
0 and the dispersion energy E
d, which is a measure of the average strength of inter-band optical transition or the oscillator strength, were determined.
Electrical conductivity of a-GaN was measured in a different range of temperatures. Then, activation energy of a-GaN thin
films was calculated which equalled E
a = 0:434 eV. 相似文献
66.
Saad S. M. Hassan M. L. Iskander N. E. Nashed 《Fresenius' Journal of Analytical Chemistry》1985,320(6):584-586
Summary A new liquid membrane electrode was developed which is highly selective and sensitive for vitamin B1. It is based on the thiamine-picrolonate ion-pair complex as an electroactive material in nitrobenzene solvent. The electrode has a remarkable selectivity for vitamin B1 in the presence of vitamins B2, B6, B12 and nicotinamide. The results obtained for the determination of vitamin B1 in various multivitamin preparations at levels as low as 1 g/ml show an average recovery of 98% (mean standard deviation 1.8%) and are favourably compared with those obtained by the official methods.
Neue Flüssig-Membranelektrode zur Bestimmung von Vitamin B1 in Multivitaminpräparaten
Zusammenfassung Eine neue, für Vitamin B1 hochselektive Flüssig-Membranelektrode wurde entwickelt. Sie beruht auf dem Thiamin-Picrolonat-Ionenpaarkomplex als elektroaktives Material im Lösungsmittel Nitrobenzol. Die Elektrode besitzt eine beachtliche Selektivität für Vitamin B1 in Gegenwart der Vitamine B2, B6, B12 und Nicotinamid. Bei Bestimmungen in verschiedenen Multivitaminpräparaten mit Konzentrationen bis herab zu 1 g/ml erhielt man eine durchschnittliche Wiederfindung von 98% (mittlere Standardabweichung 1,8%). Die erhaltenen Resultate zeigen gute Übereinstimmung mit den nach amtlichen Methoden erhaltenen Werten.相似文献
67.
Summary A simple and accurate method is described for the microdeter-mination of phosphorus and arsenic in some pharmaceutical organic compounds. It is based on the conversion of phosphorus and arsenic into phosphate and arsenate ions respectively, followed by precipitation with quinoline and sodium molybdate reagents. The excess quinoline in the supernatant is spectrophotometrically measured at 312.5 nm in an ammonium acetate background of pH 5.5. The results obtained with 24 structurally different phosphorus and arsenic compounds show an average recovery of 99% and a mean standard deviation of ±1%. Excipients and diluents normally used in drug formulations do not interfere.
Spektrophotometrische Bestimmung von Phosphor und Arsen in organischen Arzneimitteln
Zusammenfassung Eine einfache und genaue Methode zur Mikrobestimmung von Phosphor und Arsen in einigen organischen Arzneimitteln wurde angegeben. Sie beruht auf der Umsetzung des Phosphors zu Phosphat und des Arsens zu Arsenat sowie deren Fällung mit Chinolin und Natriummolybdat. Der Chinolinüberschuß wird spektrophotometrisch bei 312,5 nm in Ammonium-acetat bei pH 5,5 gemessen. Die mit 24 strukturell verschiedenen Phosphorbzw. Arsenverbindungen erhaltenen Resultate ergaben eine durchschnittliche Wiederfindungsrate von 99% und eine rel. Standardabweichung von ±1%. Arzneimittelträger und Verdünnungsmittel stören nicht.相似文献
68.
Summary Divalent sulphur in structurally different aliphatic compounds including thiols, sulphides, disulphides and thiocarbonyls is selectively determined by reaction with solid potassium hydroxide at 250–280° for 5–10 min, followed by addition of alkali plumbite whereby lead sulphide is stoichiometrically formed. The excess lead ions are measured by: (a) atomic absorption spectrometry at 217 nm; or (b) potentiometric titration with EDTA at pH 4.6 using the lead ion selective electrode; or (c) visual titration with EDTA using urotropine buffer and Xylenol Orange indicator. An average recovery of 99%, and a mean standard deviation of 0.9% are obtainable with samples down to 2 mg. Divalent sulphur in many aromatic compounds, and tetra- and hexa-valent sulphur in both aliphatic and aromatic compounds do not interfere.
Based on a paper presented at the Euroanalysis III Conference, Dublin, August 20–25, 1978. 相似文献
Mikrobestimmung von zweiwertigem Schwefel in aliphatischen Verbindungen durch visuelle Maanalyse, Potentiometrie und Atomabsorptionsspektrometrie
Zusammenfassung Zweiwertiger Schwefel in verschieden strukturierten aliphatischen Verbindungen wie Thiolen, Sulfiden, Disulfiden und Thiocarbonylverbindungen, lät sich durch Umsetzung mit festem Kaliumhydroxid bei 250–280° C durch 10 min und Zugabe von Alkaliplumbit bestimmen, wobei Bleisulfid in stöchiometrischer Menge gebildet wird. Der Überschuß an Bleiionen wird gemessen: a) durch Atomabsorptionsspektrometrie bei 217 nm; b) durch potentiometrische Titration mit ÄDTA bei pH 4,6 mit einer bleiionenspezifischen Elektrode; oder c) durch visuelle Titration mit ÄDTA, Urotropin als Puffer und Xylenolorange als Indikator. Ein durchschnittliches Ergebnis von 99% und eine mittlere Standardabweichung von 0,9% sind bei Einwaagen von wenigstens 2 mg erreichbar. Zweiwertiger Schwefel in vielen aromatischen Verbindungen, vier- und sechswertiger Schwefel sowohl in aliphatischen als auch in aromatischen Verbindungen stört nicht.
Based on a paper presented at the Euroanalysis III Conference, Dublin, August 20–25, 1978. 相似文献
69.
The time-differential perturbed angular correlation (TDPAC) experiments involving the 133–482 keV γ-γ cascade in181Ta have been performed in the presence of an external magnetic field along the quantization axis to measure the hyperfine magnetic field experienced by181Ta nuclei at the Hf site in the pseudobinary compounds HfFe2?xSix with x=0.1 and x=0.3. The hyperfine magnetic fields measured at 298 K are Hhf=133.1±12.0 kG in the cubic (C15) Laves phase compound HfFe1.9Si0.1 and Hhf=76.8±7.0 kG in the hexagonal (C14) Laves phase compound HfFe1.7Si0.3. The measured hyperfine fields are discussed within the framework of the Campbell-Blandin model. 相似文献
70.
M. I. El-Zaiki W. Z. Megalaa H. R. Saad A. A. Youssef 《Zeitschrift für Physik A Hadrons and Nuclei》1970,234(5):398-404
Angular distributions of gamma rays following the inelastic scattering of protons from Mn55 have been measured at proton energies below 2.50 MeV. The mixture multipole orders for the transition 983→126 keV and 1,530→0 in Mn55 have been obtained. 相似文献