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101.
Four new diterpenes, cespihypotins W–Z ( 1 – 4 ), having the verticillane skeleton and characterized by an α,β‐unsaturated γ‐hydroxycyclopentanone moiety, and a new eudesmanolide‐type sesquiterpene, cespilactam A ( 5 ), containing an α,β‐unsaturated γ‐lactam residue, were isolated from the AcOEt‐soluble fraction of the Taiwanese soft coral Cespitularia hypotentaculata. The structure and relative configuration of these metabolites was elucidated through extensive interpretation of MS, COSY, HSQC, HMBC, and NOESY experiments and by comparison of their NMR data with those of related compounds. 相似文献
102.
Kaustubh Joshi Warren Batchelor Khairunnisaa Abd Rasid 《Cellulose (London, England)》2011,18(6):1407-1421
No reliable method exists for measuring the cellulose fiber–fiber shear bond strength in paper. This paper reports a simple
method for measuring the fiber–fiber shear bond strength by weakening the fibers independently of the bonds in a sheet of
paper, using acid vapor, until all the fibers break across the fracture line. The bond strength is then calculated from the
fiber strength, as measured by the zero span test, at the point where the fibers first are weakened such that they all break.
The method was used to calculate the average bond strength of handsheets made out of two different pulps. The first pulp was
a never dried, 60% yield, unbleached radiata pine. The bond strength was 25.0 ± 3.3 MPa. Drying the fibers before reslushing
and making sheets reduced the bond strength by up to 33%, with the reduction depending on the severity of the drying treatment.
The second pulp was a bleached dried softwood kraft and was used to investigate the effect of low consistency refining on
bond strength. The bond strength increased from 13.7 ± 1.0 MPa for the sheets made from the unrefined pulp to 37.0 ± 1.0 MPa,
for the sheets made from the most heavily refined pulp. The bond strength measurements are considerably higher than previous
literature estimates for the shear bond strength. The causes for the discrepancy include stress concentrations in tests of
single fiber–fiber bonds. 相似文献
103.
Summary. Indole-2-carboxylic acid hydrazide was prepared and allowed to react with aromatic aldehydes in acidic medium to give the
corresponding hydrazone derivatives in good yields. The hydrazones were cyclized to indolo[2,3-d]pyridazine derivatives by refluxing with acetyl chloride. The indole carbohydrazide was converted to 2-triazolylindoles which
acted as starting materials for several indole derivatives. A number of new indole derivatives were also prepared and structurally
confirmed.
Received October 17, 2000. Accepted (revised) December 12, 2000 相似文献
104.
H.A.AbdEl-Ghanny 《低温物理学报》2002,24(2):149-160
采用熔化淬火工艺制备Bi6Se9Ge4CuOx。块材和粉末压实样品均在300℃进行了热处理,该温度远低于玻璃转变温度419℃(由DTA热重分析得知)。无论是末经处理还是热处理后的样品,都具有多相结构。热电势测量结果表明,可能有电子和空穴的导电。载流子的导电类型主要取决于热处理条件。热电势以扩散分量为主,声子曳引可以忽略。跳跃导电是常见的,而半金属行为只在特殊的热处理条件下出现。 相似文献
105.
M. Nabil Yasin M. M. Sherif S. M. Abd El-Halim M. A. Jilany 《Journal of Experimental and Theoretical Physics》1997,84(4):635-640
Projectile multifragment breakup of 16O, 2C and 7Li at energies 3.0–4.5 A-GeV is studied by means of the Weizsäcker-Williams method. The fragmentation channels of the 16O projectile at 4.5 A-GeV are investigated and compared with that of 16O at 200 A-GeV. The events characterized by N h=0 and the events due to both Coulomb and diffraction dissociation have been selected and analyzed as a function of impact parameter. Also, the dependence of the electromagnetic dissociation cross-section on incident energy and the charge of projectile and target is found. 相似文献
106.
A.M. Zahran M. Azab. Abd-Allah Abd El-Nasser G. Abd El-Rahman 《Chaos, solitons, and fractals》2009,39(3):1158-1168
In this paper, we introduce and characterize fuzzy weakly preopen and fuzzy weakly preclosed functions between L-fuzzy topological spaces in Kubiak–?ostak sense and also study these functions in relation to some other types of already known functions. 相似文献
107.
S.F. Abdullah S. Radiman M.A. Abd. Hamid N.B. Ibrahim 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):88-94
The effect of calcination temperature on the surface morphology and crystallinity of tungsten (VI) oxide, WO3 nanorods prepared using colloidal gas aphrons (CGAs) as template was studied. The synthesized WO3 nanorods were calcined in a furnace for 4 h at four different temperatures, i.e., 400, 500, 600 and 700 °C. The morphology of the calcined WO3 nanorods have been characterized by both transmission electron microscope (TEM) and variable pressure scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX). The results showed that the calcination temperature influenced the shape and size of the WO3 nanorods produced. It is also found that the calcination at various temperature do not effect the composition and the purity of the WO3 nanorods. In order to characterize the crystalinity of WO3, X-ray diffraction (XRD) has been used. It shows that all the calcined WO3 produced are in crystalline form compared to the as-prepared WO3 nanorods, which is in amorphous form. 相似文献
108.
An analytical study of slow modulation has been made of cylindrical interface between two inviscid streaming fluids, in the presence of a relaxation of electrical charges at the interface, and stressed by an axial electric field. A new technique based on the perturbation theory, to derive the non-linear evolution equations has been introduced. These equations are combined to yield a non-linear Ginzburg–Landau equation and a non-linear modified Schrödinger equation describing the evolution of wave packets. The linear analysis showed that the streaming has a destabilizing effect and the electric field has stabilizing influence associated with parameters condition involving the electric conductivity and permittivity of the fluids. While the non-linear approach indicated that the streaming may become unstable for sufficiently high velocities, with a new condition on the material properties, involving weak electric relaxation times in both fluids. 相似文献
109.
Utility of 4‐Benzylidene‐2‐phenyl‐5(4H)‐oxazolone in Synthesis of Triazine,Oxadiazole and Imidazole Derivatives of Anticipated Biological Activity
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Ahmed S. A. Youssef Fatma A. El‐Mariah Fatma T. Abd‐Elmottaleb Heba E. Hashem 《Journal of heterocyclic chemistry》2015,52(5):1467-1473
Treatment of oxazolone 1 with hydrazine hydrate at room temperature gave the (Z)‐configurated isomer hydrazide (Z)‐ 3 (high yield). However, refluxing 1 with hydrazine hydrate yielded the (E)‐configurated isomer hydrazide (E)‐ 2 (low yield).The hydrazide derivative (Z)‐ 3 has been utilized as synthon for the synthesis of 1,2,4‐triazinone, imidazolone, and oxadiazole derivatives through appropriate routes. The thiosemicarbazide and semicarbazide derivatives are synthesized by different routes. The structures of the new compounds were established on the basis of IR, 1H‐NMR, mass spectral data, and elemental analysis. 相似文献
110.
Synthesis of 5‐Cyano‐2‐Carbethoxythieno[2,3‐b]thiophenyl‐3,4‐Diisothiocyanates and Its Utility IN Heterocyclic Synthesis under Phase Transfer Catalytic Technique
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O. A. Abd Allah 《中国化学会会志》2015,62(11):991-999
Regarding to the importance of thieno[2,3‐b]thiophens and isothiocyanaetes reactiveties in the physical, chemical and pharmaceutical fields, this study has been undertaken to prepare the target compound 5‐cyano‐2‐carbethoxythieno[2,3‐b]thiophenyl‐3,4‐diisothiocyanates via a safe method. The formed isothiocyanates derivative was reacted with aromatic amines, acid hydrazied and some active methylene groups, followed by cyclization reaction for the formed intermediates to give new series of heterocyclic compounds 相似文献