Electronic phase separation in the rare earth manganates, (La1-xLnx)0.7Ca0.3MnO3 (Ln = Nd, Gd and Y)

All the three series of manganates showsaturation magnetization characteristic of ferromagnetism, with the ferromagnetic Tc decreasing with increasing in x up to a critical value of x, xc (xc = 0.6, 0.3, 0.2 respectively for Nd, Gd, Y). For x > xc, the magnetic moments are considerably smaller showing a small increase around TM, the value of TM decreasing slightly with increase in x or decrease in . The ferromagnetic compositions (x xc) show insulator-metal (IM) transitions, while the compositions with x > xc are insulating. The magnetic and electrical resistivity behavior of these manganates is consistent with the occurrence of phase separation in the compositions around xc, corresponding to a critical average radius of the A-site cation, , of 1.18 A. Both Tc and TIM increase linearly when < rA > > or x xc as expected of a homogenous ferromagnetic phase. Both Tc and TM decrease linearly with the A-site cation size disorder at the A-site as measured by the variance s2. Thus, an increase in s2 favors the insulating AFM state. Percolative conduction is observed in the compositions with > < rAc >. Electron transport properties in the insulating regime for x > xc conforms to the variable range hopping mechanism. More interestingly, when x > xc, the real part of dielectric constant (e') reaches a high value (104-106) at ordinary temperatures dropping to a very small (~500) value below a certain temperature, the value of which decreases with decreasing frequency.Comment: 27 pages; 11 figures, Submitted to J.Phys:Condens Matte

Extraction of Cr(VI) from Orthophosphoric Acid Solutions by Trilauryl Amine

635-63

Dispersive Wave Analysis – Method and Applications

A technique for estimating the dispersion characteristics of propagating waves as measured by an array is detailed. The technique consists of bandpass filtering the data through a filterbank and then processing the filtered waveforms non-dispersively. The results can show the dispersion of the entire time series or be parsed in time to analyze the dispersion characteristics of any section of the time series. Processing LWD field data shows that this method can extract dispersion characteristics over a broadband of frequencies and with low amplitude signals. Both the field data and laboratory scale data show that multiple modes present over the same frequency band can be identified.Halliburton CompanyMassachusetts Institute of Technology. Earth Resources LaboratoryMassachusetts Institute of Technology. Borehole Acoustics and Logging Consortiu

XX Cam-the inactive R CrB star

Infrared observations obtained six years apart of the R CrB type star XX Cam do not show any infrared excess, unlike all the other members of the class. The observed colours match a 7000 K black body energy distribution quite well. From the year 1898 till todate, apparently XX Cam has undergone only one visual light minimum in 1940. The lack of infrared excess, the abundance peculiarities and further lack of small amplitude light variations with periods of few tens of days, which are characteristic of R CrB type stars, are discussed in terms of theoretical pulsation models of helium stars

The eigenspectra of Indian musical drums

In a family of drums used in the Indian subcontinent, the circular drum head is made of material of non-uniform density. Remarkably, and in contrast to a circular membrane of uniform density, the low eigenmodes of the non-uniform membrane are harmonic. In this work we model the drum head by a non-uniform membrane whose density varies smoothly between two prescribed values. Using a Fourier-Chebyshev spectral collocation method we obtain the eigenmodes and eigenvalues of the drum head. For a suitable choice of parameters, which we find by optimising a cost function, the eigenspectra obtained from our model are in excellent agreement with experimental values. Our model and the numerical method should find application in numerical sound synthesis

Isomorphism testing of read-once functions and polynomials

In this paper, we study the isomorphism testing problem of formulas in the Boolean and arithmetic settings. We show that isomorphism testing of Boolean formulas in which a variable is read at most once (known as read-once formulas) is complete for log-space. In contrast, we observe that the problem becomes polynomial time equivalent to the graph isomorphism problem, when the input formulas can be represented as OR of two or more monotone read-once formulas. This classifies the complexity of the problem in terms of the number of reads, as read-3 formula isomorphism problem is hard for coNP. We address the polynomial isomorphism problem, a special case of polynomial equivalence problem which in turn is important from a cryptographic perspective[Patarin EUROCRYPT\u2796, and Kayal SODA\u2711]. As our main result, we propose a deterministic polynomial time canonization scheme for polynomials computed by constant-free read-once arithmetic formulas. In contrast, we show that when the arithmetic formula is allowed to read a variable twice, this problem is as hard as the graph isomorphism problem

Catalytic activity of nickel ferrite nanoparticles in synthesis of 4-aryl benzelidene-2- ((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one and its evalute the biological activity

ABSTRACT. Seven 4-arylbenzelidene-2-((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one derivatives were synthesized by the condensation of 2-(2-(5-fluoro-1H-indol-1-yl) acetoamide) acetic acid, substituted aromatic aldehydes with acetic anhydride and sodium acetate in the presence of MgO/Al2O3 under reflux using nickel ferrite nanoparticles. Seven of the compounds are new derivatives. 2-(2-(5-fluoro-1H-indol-1-yl)acetoamide) acetic acid was obtained from 2-(5-fluoro-1H-indol-1-yl)acetyl chloride with lysine in the presence of NaOH and HCl in the ice cold solution. 2-(5-fluoro-1H-indol-1-yl)acetyl chloride can be prepared from 5-fluoro indole with chloroacetyl chloride in triethylamine and dichloromethane. The structures of the compounds were evaluated based on 1H-NMR, 13C-NMR and LC-MS and by elemental analysis. These compounds were screened by anti-oxidant as well as anti-microbial activity.               KEY WORDS: 2-(5-Fluoro-1H-indol-1-yl)acetyl chloride, 2-(2-(5-Fluoro-1H-indol-1-yl)acetoamide) acetic acid, 4-Aryl Benzelidene-2-((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one, Anti-oxidant, Anti-microbial activity, Nickel ferrite Bull. Chem. Soc. Ethiop. 2019, 33(3), 517-526.  DOI: https://dx.doi.org/10.4314/bcse.v33i3.1

Solitary Dust--Acoustic Waves in a Plasma with Two-Temperature Ions and Distributed Grain Size

The propagation of weakly nonlinear dust--acoustic waves in a dusty plasma containing two ion species with different temperatures is explored. The nonlinear equations describing both the quadratic and cubic plasma nonlinearities are derived. It is shown that the properties of dust--acoustic waves depend substantially on the grain size distribution. In particular, for solitary dust--acoustic waves with a positive potential to exist in a plasma with distributed grain size, it is necessary that the difference between the temperatures of two ion species be large that that in the case of unusized grains.Comment: 16 pages, 6 figure