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排序方式: 共有85条查询结果,搜索用时 15 毫秒
71.
Abu Shahed Mohammad Moinuddin Mohammad Shah Alam Mamunur Rashid Talukder 《等离子体物理论文集》2020,60(7):e201900124
The effects of head-on collision on dust acoustic (DA) solitary and shock waves in dusty plasma are investigated considering positively charged inertial dust, Boltzmann distributed negatively charged heavy ions, positively charged light ions, and superthermal electrons in the plasma system. The nonlinear Korteweg-de-Vries (KdV) Burger equations are derived taking the extended Poincaré-Lighthill-Kuo method into account to study the characteristic properties of nonlinearity and production of solitary shock due to collisions. The study reveals that the amplitudes and widths of the DA shock waves are decreasing with increasing viscosity, electron to dust density ratio, and dust to ion temperature ratio, while they are increasing due to the presence of superthermal electrons. The nonlinearity of DA waves are enhanced with increasing density ratio of electron to dust and temperature ratio of dust to ion and electron, respectively, but it is reducing with superthermal electrons. The phase shifts of DA solitary waves are found to decrease with rising superthermality of electrons and increase with the density ratio of electron to dust. 相似文献
72.
Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Although a subject of intense research, the etiology of PD remains poorly understood. Recently, several lines of evidence have implicated an intimate link between aberrations in the ubiquitin proteasome system (UPS) and PD pathogenesis. Derangements of the UPS, which normally functions as a type of protein degradation machinery, lead to alterations in protein homeostasis that could conceivably promote the toxic accumulation of proteins detrimental to neuronal survival. Not surprisingly, various cellular and animal models of PD that are based on direct disruption of UPS function reproduce the most prominent features of PD. Although persuasive, new developments in the past few years have in fact raised serious questions about the link between the UPS and PD. Here I review current thoughts and controversies about their relationship and discuss whether strategies aimed at mitigating UPS dysfunction could represent rational ways to intervene in the disease. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com). 相似文献
73.
Pritha Talukder Shyamapada Shit Heinrich N?th Matthias Westerhausen Alexander Nikolai Kneifel Samiran Mitra 《Transition Metal Chemistry》2012,37(1):71-77
A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)3(NO)(μ-CN)]n·3H2O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized
by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis.
It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded
in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic
exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm−1) through long diamagnetic [Fe(CN)5(NO)]2− bridges. Spin state of the iron atom was established by 57Fe M?ssbauer spectroscopy. 相似文献
74.
Sen S Talukder P Dey SK Mitra S Rosair G Hughes DL Yap GP Pilet G Gramlich V Matsushita T 《Dalton transactions (Cambridge, England : 2003)》2006,(14):1758-1767
A series of Zn(II), Cd(II), Co(II), Co(III) and Mn(III) complexes with the Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin, has been synthesised and structures of all the products have been established by X-ray crystallography. In the cases of zinc and cadmium, dimeric complexes [Zn(LH)2(NCS)] [Zn2(L)(mu(1,1)-CH3COO)(NCS)3] (1), [Cd2(L)2(Cl)2] (2) and [Cd2(L)2(NCS)2] (3), and for cobalt and manganese, monomeric complexes [Co(LH)2(NCS)]2 [Co(NCS)4] (4), [Co(LH)2(NCS)]ClO4 (5), [Co(L)(N3)(o-vanillinate)] x 0.5 MeOH (6) and [Mn(LH)2(MeOH)2](ClO4)3 (7), are formed with various terminal ligands. All the complexes have been characterised by elemental analysis and IR spectra. UV-Vis and NMR spectroscopy, magnetic, and electrochemical studies, were also carried out where feasible. The Schiff base functions as a bi-, tri- or tetra-dentate chelating agent and coordinates via the protonated or deprotonated phenolic oxygen, amine and imine nitrogens, and only in case of 1 with the methoxy oxygen atoms, to the metal ion leading to the formation of mono- or bi-metallic complexes. 相似文献
75.
The high optical transparency of ion plated indium oxide combined with their mechanical hardness and good environmental stability have opened up numerous applications in the line of sophisticated optoelectronic devices. Indium is evaporated at a low oxygen pressure on to an ordinary glass substrate mounted under the cathode and biased by a r.f. generator at 13,6 M Hz. Infrared spectra are recorded in the range 5000–200 cm?1 by A.T.R. and reflexion-absorption spectroscopy, and show between 800 and 200 cm?1 bands due to stretching and bending modes predicted by a factor group analysis. A tentative assignment is made of the highest frequency. Last U.V. and visible spectra are discussed. 相似文献
76.
Anwar Hossain Talukder 《Annals of the Institute of Statistical Mathematics》1968,20(1):441-455
The theory on regression estimate based on one auxiliary variable has been extended to that for more than one auxiliary variable. It has been found that the multivariate regression estimate (MRE) is not unbiased in general. The form of the approximate standard error of MRE is the same as that of simple regression estimate based on one auxiliary variable with the exception that the multiple correlation coefficient replaces the total correlation coefficient in the expression. It has also been found that the precision of MRE is non-decreasing, rather usually increasing as the number of auxiliary variables correlated with the dependent variable increases, assuming sample size to be large compared to the number of auxiliary variables. 相似文献
77.
78.
A. I. Talukder P. Sultana A. F.M.Y. Haider M. Wahadoszamen K. M. Abedin S. F.U. Farhad 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):295-300
Silver nanoparticles have been produced by laser ablation of silver metal in
nanopure water without any chemical additives. It has been observed that
laser power has a control over the size of the nanoparticles. Increasing
laser power shows a clear blue shift in the absorption peak of fabricated
nanoparticles indicating that the average size of the particles decreases
with increasing laser power. Ablation for longer period reduces the average
size of nanoparticles which is attributed to the re-ablation of fabricated
nanoparticles. A good correlation has been observed between the peak of the
absorption spectrum measured by UV-VIS spectroscopy and the average particle
size measured by scanning electron microscope imaging method. The value of
the coefficient of correlation is determined to be 0.965. 相似文献
79.
We report a generalization of our earlier formalism [Pramana, 54, 663 (1998)] to obtain exact solutions of Einstein-Maxwell’s equations for static spheres filled with a charged fluid having
anisotropic pressure and of null conductivity. Defining new variables: w=(4π/3)(ρ+ε)r
2, u=4πξr
2, v
r=4πp
r
r
2, v
⊥=4πp
⊥
r
2[ρ, ξ(=−(1/2)F
14
F
14), p
r, p
⊥ being respectively the energy densities of matter and electrostatic fields, radial and transverse fluid pressures whereas
ε denotes the eigenvalue of the conformal Weyl tensor and interpreted as the energy density of the free gravitational field],
we have recast Einstein’s field equations into a form easy to integrate. Since the system is underdetermined we make the following
assumptions to solve the field equations (i) u=v
r=(a
2/2κ)r
n+2, v
⊥=k
1
v
r, w=k
2
v
r; a
2, n(>0), k
1, k
2 being constants with κ=((k
1+2)/3+k
2) and (ii) w+u=(b
2/2)r
n+2, u=v
r, v
⊥−v
r=k, with b and k as constants. In both cases the field equations are integrated completely. The first solution is regular in the metric as
well as physical variables for all values of n>0. Even though the second solution contains terms like k/r
2 since Q(0)=0 it is argued that the pressure anisotropy, caused by the electric flux near the centre, can be made to vanish reducing
it to the generalized Cooperstock-de la Cruz solution given in [14]. The interior solutions are shown to match with the exterior
Reissner-Nordstrom solution over a fixed boundary.
Dedicated to Prof. F A E Pirani. 相似文献
80.
A new coumarin based chemosensor has been developed for selective fluorescent recognition of Cu2+ in MeOH/H2O (4:1, v/v at pH = 7.2 aqueous solution) medium with 1:1 binding stoichiometry. The in-situ prepared Cu2+ complex displays high selectivity towards CN? via Cu2+ displacement approach with detection limit in the micro molar range. Moreover, in presence of Cu2+, the receptor exhibits reversible emission change with EDTA and thus offers an interesting property of molecular ‘IMPLICATION’ logic gate with Cu2+ and EDTA as chemical inputs. 相似文献