6,994 research outputs found
Universality in Fluid Domain Coarsening: The case of vapor-liquid transition
Domain growth during the kinetics of phase separation is studied following
vapor-liquid transition in a single component Lennard-Jones fluid. Results are
analyzed after appropriately mapping the continuum snapshots obtained from
extensive molecular dynamics simulations to a simple cubic lattice. For near
critical quench interconnected domain morphology is observed. A brief period of
slow diffusive growth is followed by a linear viscous hydrodynamic growth that
lasts for an extended period of time. This result is in contradiction with
earlier inclusive reports of late time growth exponent 1/2 that questions the
uniqueness of the non-equilibrium universality for liquid-liquid and
vapor-liquid transitions.Comment: 6 pages, 5 figure
Relativistic calculations of the lifetimes and hyperfine structure constants in Zn
This work presents accurate {\it ab initio} determination of the magnetic
dipole (M1) and electric quadrupole (E2) hyperfine structure constants for the
ground and a few low-lying excited states in Zn, which is one of
the interesting systems in fundamental physics. The coupled-cluster (CC) theory
within the relativistic framework has been used here in this calculations. Long
standing demands for a relativistic and highly correlated calculations like CC
can be able to resolve the disagreements among the lifetime estimations
reported previously for a few low-lying states of Zn. The role of
different electron correlation effects in the determination of these quantities
are discussed and their contributions are presented.Comment: 9 pages, 1 figure. submitted to J. Phys. B Fast Trac
Long-range and short-range magnetic correlations, and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14
Spin-spin correlations and microscopic origin of net magnetization in the
spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder
neutron diffraction. The present study reveals a 3D long-range magnetic
ordering below 16 K where the magnetic structure consists of ferromagnetic
trimers that are coupled ferromagnetically along the spin-chain. The moment
components along the a and c axes arrange antiferromagnetically. Our study
establishes that the uncompensated moment components along the b axis result in
a net magnetization per unit cell. The magnetic structure, determined in the
present study, is in agreement with the results of recent first principles
calculation; however, it is in contrast to a fascinating experimental
prediction of ferrimagnetic ordering based on the periodicity of the exchange
interactions in CaNi3P4O14. Our study also confirms the presence of broad
diffuse magnetic scattering, due to 1D short-range spin-spin correlations, over
a wide temperature range below ~50 K down to a temperature well below the Tc.
Total neutron scattering analysis by the RMC method reveals that the dominating
spin-spin correlation above Tc is ferromagnetic and along the b axis. The
nearest neighbour spin-spin correlations along the a and c axes are found to be
weakly antiferromagnetic. The nature of the trimer spin structure of the
short-range state is similar to that of the 3D long-range ordered state. The
present investigation of microscopic nature of the magnetic ground state also
explains the condition required for the 1/3 magnetization plateau to be
observed in the trimer spin-chains. In spite of the S=1 trimer chain system,
the present compound CaNi3P4O14 is found to be a good realization of 3D magnet
below the Tc=16 K with full ordered moment values of ~2 mu_B/Ni2+ (1.98 and
1.96 mu_B/Ni2+ for two Ni sites, respectively) at 1.5 K.Comment: 10 pages, 8 figure
Local electromagnetic properties of magnetic pnictides: A comparative study probed by NMR measurement
75As and 31P NMR studies are performed in PrCoAsO and NdCoPO respectively.
The Knight shift data in PrCoAsO indicate the presence of an antiferromagnetic
interaction between the 4f moments along the c axis in the ferromagnetic state
of Co 3d moments. We propose a possible spin structure in this system. The 75As
quadrupolar coupling constant, increases continuously with the decrease
of temperature and is found to vary linearly with the intrinsic spin
susceptibility, Kiso. This indicates a possibility of the presence of a
coupling between charge density and spin density fluctuations. Further, 31P NMR
Knight shift and spin lattice relaxation rate (1/T1) in the paramagnetic state
of NdCoPO indicate that the differences between LaCoPO and NdCoPO with SmCoPO
are due to the decrement of inter layer separation and not due to the moments
of 4f electrons. Nuclear spin lattice relaxation time (T1) in NdCoPO shows weak
anisotropy at 300 K. Using self consistent renormalization (SCR)theory of
itinerant ferromagnet, it is shown that in the ab plane, the spin fluctuations
are three dimensional ferromagnetic in nature. From SCR theory the important
spin fluctuation parameters (, , ) are evaluated. The
similarities and dissimilarities of the NMR results in As and P based systems,
with different rare earths have also been discussed.Comment: 18 pages,13 figures, accepted for publication in J. Phys. Condens.
Matte
Support vector machine for optical diagnosis of cancer
We report the application of a support vector machine (SVM) for the development of diagnostic algorithms for optical diagnosis of cancer. Both linear and nonlinear SVMs have been investigated for this purpose. We develop a methodology that makes use of SVM for both feature extraction and classification jointly by integrating the newly developed recursive feature elimination (RFE) in the framework of SVM. This leads to significantly improved classification results compared to those obtained when an independent feature extractor such as principal component analysis (PCA) is used. The integrated SVM-RFE approach is also found to outperform the classification results yielded by traditional Fisher's linear discriminant (FLD)-based algorithms. All the algorithms are developed using spectral data acquired in a clinical in vivo laser-induced fluorescence (LIF) spectroscopic study conducted on patients being screened for cancer of the oral cavity and normal volunteers. The best sensitivity and specificity values provided by the nonlinear SVM-RFE algorithm over the data sets investigated are 95 and 96% toward cancer for the training set data based on leave-one-out cross validation and 93 and 97% toward cancer for the independent validation set data. When tested on the spectral data of the uninvolved oral cavity sites from the patients it yielded a specificity of 85%
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