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811.
Tuning a ring laser by using the Gouy phase is explored. We find a sensitive capability by moving a lens in the ring cavity. Application of the effect to ring laser gyro is discussed. 相似文献
812.
Analytical expressions are found for the wavenumbers and resonance frequencies in flexible, orthotropic shells using the asymptotic methods. These expressions are valid for arbitrary circumferential orders n. The Donnell-Mushtari shell theory is used to model the dynamics of the cylindrical shell. Initially, an in vacuo cylindrical isotropic shell is considered and expressions for all the wavenumbers (bending, near-field bending, longitudinal and torsional) are found. Subsequently, defining a suitable orthotropy parameter ?, the problem of wave propagation in an orthotropic shell is posed as a perturbation on the corresponding problem for an isotropic shell. Asymptotic expressions for the wavenumbers in the in vacuo orthotropic shell are then obtained by treating ? as an expansion parameter. In both cases (isotropy and orthotropy), a frequency-scaling parameter (η) and Poisson's ratio (ν) are used to find elegant expansions in the different frequency regimes. The asymptotic expansions are compared with numerical solutions in each of the cases and the match is found to be good. The main contribution of this work lies in the extension of the existing literature by developing closed-form expressions for wavenumbers with arbitrary circumferential orders n in the case of both, isotropic and orthotropic shells. Finally, we present natural frequency expressions in finite shells (isotropic and orthotropic) for the axisymmetric mode and compare them with numerical and ANSYS results. Here also, the comparison is found to be good. 相似文献
813.
I.N. PrakashB. Babu Ch. Venkata ReddyP. Narayana Murty Y.P. ReddyP. Sambasiva Rao R.V.S.S.N. Ravikumar 《Physica B: Condensed Matter》2011,406(17):3295-3298
EPR and optical absorption studies on Fe3+ and Mn2+ doped strontium tetraborate (SrB4O7) glasses are carried out at room temperature. The EPR spectrum of the Fe3+ doped glass consists of signals with g-values 9.04, 4.22 and 2.04, whereas the EPR spectrum of Mn2+ doped glass exhibits a characteristic hyperfine sextet around g=2.0. The spectroscopic analyses of the obtained results confirmed distorted octahedral site symmetry for the Fe3+ and Mn2+ impurity ions. Crystal field and Racah parameters evaluated from optical absorption spectra are: Dq=790, B=700 and C=3000 cm−1 for Fe3+doped glass and Dq=880, B=700 and C=2975 cm−1 for Mn2+ doped glass. 相似文献
814.
U. S. Udayachandran Thampy Ch. Rama Krishna Ch. Venkata Reddy B. Babu Y. P. Reddy P. S. Rao R. V. S. S. N. Ravikumar 《Applied magnetic resonance》2011,41(1):69-78
Cu2+-doped ZnO nanopowders, synthesized at room temperature by mild and simple solution method, are characterized by powder X-ray
diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier-transform
infrared (FT-IR) techniques. From XRD and SEM, the crystal structure is identified as hexagonal, and the average crystallite
size is around 53 nm. Lattice cell parameters are evaluated. The optical and EPR spectral investigations suggest that the
Cu2+ ion enters the host lattice in two tetragonally distorted octahedral sites. Crystal field, tetragonal field, spin Hamiltonian
and bonding parameters are estimated. 相似文献
815.
From the commercial extract of the leaves of Stevia rebaudiana, two additional new diterpenoid glycosides were isolated and their structures were characterized as 13-[(2-O-beta-glucopyranosyl-3-O-beta-D-xylopyranosyl-beta-D-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid beta-D-glucopyranosyl ester (1) and 13-[(2-O-beta-D-xylopyranosyl-beta-D-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid beta-D-glucopyranosyl ester (2) on the basis of extensive spectral data (NMR and MS) and chemical studies. 相似文献
816.
A concise assembly of the central tetrahydropyran unit of aflastatin A featuring a Pd-mediated alkynone cycloisomerization to provide a glycal and its subsequent stereoselective hydroboration to deliver the requisite stereochemistry at C(33) and C(34) centers is documented. 相似文献
817.
Kurhade SE Mengawade T Bhuniya D Palle VP Reddy DS 《Organic & biomolecular chemistry》2011,9(3):744-747
An efficient and convenient method for the synthesis of sugar-lactam conjugates is reported starting from readily available sugar azides using the Aubé reaction. Cyclic azido alcohols are used in the Aubé reaction for the first time in a carbohydrate setting. The resulting glycoconjugates could be further used to increase the chemical diversity on the sugar backbone, and may find potential applications as glycomimetics, peptidomimetics, in glycotargeting and in CNS drug delivery. 相似文献
818.
John Pal AP Kadigachalam P Mallick A Doddi VR Vankar YD 《Organic & biomolecular chemistry》2011,9(3):809-819
A series of sugar-derived spiroaminals has been synthesized by utilizing cross metathesis, ring closing metathesis and lactamization reactions as key steps from 1-C-alkylated glycosyl azides and important correlations in the spectral data between spiroaminals and their respective anomers are reported. 相似文献
819.
820.
Kondapalli Venkata Gowri Chandra Sekhar Thripuraribhatla Venkata Naga Varuna Tara Sasank Hunsur Nagendra Nagesh Narva Suresh Kalaga Mahalakshmi Naidu Amaroju Suresh 《中国化学快报》2013,24(12):1045-1048
A simple and efficient method has been developed for conversion of chalcone oximes to 3,5-diaryl isoxazoles in excellent yields under solvent-free conditions. The synthesized compounds were characterized by infrared spectroscopy, ^1H NMR, ^13C NMR and HRMS. 相似文献