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排序方式: 共有522条查询结果,搜索用时 359 毫秒
21.
Hareesh Iyer Paul Grandgeorge Andrew M. Jimenez Ian R. Campbell Mallory Parker Michael Holden Mathangi Venkatesh Marissa Nelsen Bichlien Nguyen Eleftheria Roumeli 《Advanced functional materials》2023,33(40):2302067
Since the 1950s, 8.3 billion tonnes (Bt) of virgin plastics have been produced, of which around 5 Bt have accumulated as waste in oceans and other natural environments, posing severe threats to entire ecosystems. The need for sustainable bio-based alternatives to traditional petroleum-derived plastics is evident. Bioplastics produced from unprocessed biological materials have thus far suffered from heterogeneous and non-cohesive morphologies, which lead to weak mechanical properties and lack of processability, hindering their industrial integration. Here, a fast, simple, and scalable process is presented to transform raw microalgae into a self-bonded, recyclable, and backyard-compostable bioplastic with attractive mechanical properties surpassing those of other biobased plastics such as thermoplastic starch. Upon hot-pressing, the abundant and photosynthetic algae spirulina forms cohesive bioplastics with flexural modulus and strength in the range 3–5 GPa and 25.5–57 MPa, respectively, depending on pre-processing conditions and the addition of nanofillers. The machinability of these bioplastics, along with self-extinguishing properties, make them promising candidates for consumer plastics. Mechanical recycling and fast biodegradation in soil are demonstrated as end-of-life options. Finally, the environmental impacts are discussed in terms of global warming potential, highlighting the benefits of using a carbon-negative feedstock such as spirulina to fabricate plastics. 相似文献
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Erythrinin A () has been synthesised by the oxidative rearrangement of dihydropyranochalcone with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal , followed by cyclisation to , demethylation to and dehydrogenation. Compound could also be obtained from chalcone on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone was oxidatively rearranged with TTN in TMOF, to which on treatment with HCl yielded . 相似文献
24.
R. I. Kureshy N. H. Khan S. H. R. Abdi P. Iyer A. K. Bhatt 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):101-108
A series of new dissymmetric chiral Schiff base complexes has been obtained by a systematic condensation of (1S,2S)(+)-diaminocyclohexane and 3-acetyl-4-hydroxy-6-methyl-2-pyrone with salicylaldehyde, 5-chloro-, 5-methoxy-and 5-nitrosalicylaldehyde and by subsequent metallation with manganese and ruthenium. The characterization of the complexes 1–8 was accomplished by physico chemical studies viz. microanalysis, IR-, UV/VIS-, and CD spectral studies, optical rotation, molar conductance measurements and cyclic voltammetry. Enantioselective epoxidation of non functionalised olefins, viz. cis-stilbene, trans-3-nonene and trans-4-octene with iodosyl benzene as oxidant was demonstrated in the presence of catalytic amounts of chiral Mn(III) and Ru(III) dissymmetric Schiff base complexes. Good optical yields of epoxides were obtained for the catalyst 4 with the substrates trans-3-nonene and cis-stilbene. 相似文献
25.
K. V. Dinesha Suman B. Iyer Saraswathi Vishveshwara 《International journal of quantum chemistry》1986,30(6):783-790
The matrix elements of the spin-free Hamiltonian between two atomic configuration state functions (CSF 'S ) in the L–S coupling scheme are expressed in terms of the atomic integrals Fk's and Gk's. Using these general expressions, the matrix elements have been obtained for all the atomic configurations with three valence electrons that have not been solved so far by earlier methods. The scope for applying this new approach to obtain the Auger line energies and the promotion energies of metals that involve more than two partially filled shells is indicated. The energy expressions for some of the relevant configurations are tabulated. 相似文献
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Observations of Faraday rotation of beacon signals from low orbiting satellite BE-B recorded at one station near the dip equator (Kodaikanal, dip 3·4° N) and at another station near the peak of the equatorial anomaly (Ahmedabad, dip 34° N) give a complete coverage of the equatorial anomaly belt in Indian zone. Contours of total elctron content (TEC) are obtained on a grid of latitudeversus local time for the different seasons of low (1964–66) and high (1967–69) solar activity epochs in the latitude belt 10° S to 26° N dip latitude. The development of the equatorial anomaly and its dependence on season and solar activity are discussed. Using similar contours of F2 layer critical frequency, f0F2 contours of equivalent slab-thickness, τ are also constructed. The dependence of τ on season and solar activity and its implications on temperature are discussed. 相似文献
28.
The determination of zirconium in the range 0.01-0.20% is required for some special alloy steels. A method has been developed, based on initial removal of iron as its chloro-complex by extraction with methyl isobutyl ketone, followed by further extraction after addition of potassium thiocyanate, and determination of the zirconium left in the aqueous phase, with Arsenazo III. The absorbance is measured at 665 nm. 相似文献
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Two noncentrosymmetric quaternary tin chalcoarsenates, Cs(2)SnAs(2)S(9) (1) and Cs(2)SnAs(2)Se(9) (2), were synthesized by the polychalcoarsenate flux method. Compound 1 crystallizes in the orthorhombic space group Pmc2(1) with a = 7.386(3) A, b = 14.614(5) A, c = 14.417(5) A, and Z = 4. Compound 2 crystallizes in the monoclinic space group P2(1) with a = 7.715(5) A, b = 17.56(1) A, c = 7.663(5) A, beta = 115.86(1) degrees, and Z = 2. Both structures contain the same tin-centered molecular cluster anions [Sn[AsQ(2)(Q(2))][AsQ(Q(2))(2)]](2)(-) (Q = S, Se) separated by Cs cations. The Sn(4+) ion is in a distorted octahedral environment coordinated by two different pyramidal-shaped tridentate ligands, [AsQ(2)(Q(2))](3)(-) and [AsQ(Q(2))(2)](3)(-). These compounds absorb visible light at energies above 1.98 and 1.45 eV for 1 and 2, respectively. Differential thermal analysis revealed that 1 melts at 350 degrees C and on cooling gives a glass. The glass recrystallizes at 268 degrees C upon subsequent heating. Compound 2 melts at 258 degrees C. 相似文献
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