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31.
El Sayed H. El Ashry Atta-ur-Rahman M. Iqbal Choudhary Sherif H. Kandil Ahmed El Nemr Tahsin Gulzar Aida H. Shobier 《Chemistry of Natural Compounds》2011,47(3):335-338
Phytochemical investigations on a marine green alga Ulva lactuca led to the isolation of two new compounds (E)-6-heptacosen-5-one (1) and (E)-6-octadecen-5-ol (2), along with four known compounds, (Z)-10-hexacosene (3), docosanoic acid (4), palmitic acid (5), and isofucosterol (6). Compounds 3 and 4 were isolated for the first time from this species. The structures of the compounds were deduced with the help of modern
spectroscopic techniques. 相似文献
32.
Atkin R Borisenko N Drüschler M el-Abedin SZ Endres F Hayes R Huber B Roling B 《Physical chemistry chemical physics : PCCP》2011,13(15):6849-6857
The structure and dynamics of the interfacial layers between the extremely pure air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and Au(111) has been investigated using in situ scanning tunneling microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy measurements. The in situ scanning tunnelling microscopy measurements reveal that the Au(111) surface undergoes a reconstruction, and at -1.2 V versus Pt quasi-reference the famous (22 × √3) herringbone superstructure is probed. Atomic force microscopy measurements show that multiple ion pair layers are present at the ionic liquid/Au interface which are dependent on the electrode potential. Upon applying cathodic electrode potentials, stronger ionic liquid near surface structure is detected: both the number of near surface layers and the force required to rupture these layers increases. The electrochemical impedance spectroscopy results reveal that three distinct processes take place at the interface. The fastest process is capacitive in its low-frequency limit and is identified with electrochemical double layer formation. The differential electrochemical double layer capacitance exhibits a local maximum at -0.2 V versus Pt quasi-reference, which is most likely caused by changes in the orientation of cations in the innermost layer. In the potential range between -0.84 V and -1.04 V, a second capacitive process is observed which is slower than electrochemical double layer formation. This process seems to be related to the herringbone reconstruction. In the frequency range below 1 Hz, the onset of an ultraslow faradaic process is found. This process becomes faster when the electrode potential is shifted to more negative potentials. 相似文献
33.
The polarizations produced in the inelastic scattering of 185 MeV protons exciting the lowest octupole states in 12C and 208Pb are measured. The data together with earlier similar measurements for 40Ca and 90Zr are compared with existing theoretical models. The inclusion of a deformed spin-dependent interaction of the full Thomas form in the DWBA amplitude is found to considerably improve the theoretical fits to the data. For 12C, however, the DWBA fit is found to be inferior to that obtained using DWIA. The strong absorption model is found to give qualitatively good fits to the data for the heavier nuclei but again fails in the 12C case. 相似文献
34.
M. E. El-Hadary A. Kamar A. El-Kady S. H. Kandil M. A. El-Gamal S. E. Morsi 《Journal of Thermal Analysis and Calorimetry》1989,35(5):1351-1357
The isothermal dimensional changes of four types of dental amalgams during the setting and for the next 24 hours after condensation have been studied by means of a Heraeus TA 500 thermal analysis system. The four types of dental amalgams were the lathe-cut conventional lowcopper amalgam (Amalcap), the spherical conventional low-copper amalgam (Spheralloy), the ternary unicomposition high-copper amalgam (Sybralloy) and the admixed high-copper (Dispersalloy) amalgam.The dimensional changes of the four types of amalgams are explained on the basis of their particle sizes and shapes and their constitutions.
Zusammenfassung Mittels eines Heraeus TA 500 Thermoanalysensystemes wurden isotherme Größenveränderungen von Dentalamalgamen während des Setting und der 24 Stunden nach der Kondensation untersucht. Die Größenveränderungen der vier Amalgamgrundtypen (am Beispiel von Amalcap, Spheralloy, Sybralloy und Dispersalloy) wurden auf der Grundlage ihrer Teilchengröße und -form sowie auf der Grundlage ihrer Zusammensetzung erklärt.
500 24 . : (), (), () ( ). , .相似文献
35.
M. K. Sherif R. M. Awadallah A. H. Amrallah 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(1):53-60
Multielemental neutron activation analysis was used for the determination of Al, As, Au, Br, Ca, Cd, Co, Cr, Cu, Fe, La, Mn,
Mo, Sb, Se, W and Zn in African tea, and lady's fingers (Malvaceae Family), ginger (Zingiperaceae Family), canella bark (Laureceae
Family), black pepper (Piperaceae Family), cucumber seeds and vegetable marrow seeds (Cucurbitaceae Family), tomatos seed
(Solanaceae Family), safflower seeds (Compositae Family), jew's mallow seeds (Tiliaceae Family) and sesame (Pedaliaceae Family).
Trace elements determination was made to the analysis of destructive (using super pure nitric acid and adsorbing the metal-APDC
and metal-Dz complexes on activated charcoal) and nondestructive (dry seeds) samples. The method is simple, precise and sensitive
for the determination of microamounts of the elements (ppm to ppb). 相似文献
36.
37.
S. El-Sharkawy M. K. Hegab M. M. Sherif O. M. Osman M. A. Jilany 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(3):237-242
Central collisions of24Mg nuclei with the heavy (AgBr) group of emulsion nuclei are selected and analysed according to several selecting criteria. Theoretical calculations concerning cross sections for central events, average number of interacting protons from both projectile and target nuclei, multiplicity distributions of shower particles and dispersions, all based on the Glauber model, are performed to evaluate various criteria to select central events. The selection criterion based on the high multiplicity of total charged particles provides satisfactory agreement with the theoretical calculations. 相似文献
38.
39.
The matrix element for inelastic scattering of protons leading to the excitation of collective states in even-even nuclei is calculated in the framework of Dirac phenomenology using a DWBA approach. The deformed parts of the Lorentz scalar and four-vector optical potentials serve as the transition operators. The results are compared with the recently measured polarization transfer coefficients on 40Ca and 208Pb at 500 MeV. The agreement with experiment is good. 相似文献
40.
Zusammenfassung Bei laminarer Strömung eines Gases ist die Übertragung der Bewegungsgrösse quer zu Flächen senkrecht zur Strömungsrichtung berechnet und gleich der transversalen Bewegungsgrösse quer zu Flächen, die parallel zur Strömungsrichtung laufen, gefunden worden. Daraus kann der Schluss gezogen werden, dass ein Flüssigkeitswürfel mit Seiten, die parallel zu den angegebenen Richtungen sind, statisch im Dreh-Gleichgewicht ist. 相似文献