507 research outputs found
Random sequential adsorption on a dashed line
We study analytically and numerically a model of random sequential adsorption
(RSA) of segments on a line, subject to some constraints suggested by two kinds
of physical situations:
- deposition of dimers on a lattice where the sites have a spatial extension;
- deposition of extended particles which must overlap one (or several)
adsorbing sites on the substrate.
Both systems involve discrete and continuous degrees of freedom, and, in one
dimension, are equivalent to our model, which depends on one length parameter.
When this parameter is varied, the model interpolates between a variety of
known situations : monomers on a lattice, "car-parking" problem, dimers on a
lattice. An analysis of the long-time behaviour of the coverage as a function
of the parameter exhibits an anomalous 1/t^2 approach to the jamming limit at
the transition point between the fast exponential kinetics, characteristic of
the lattice model, and the 1/t law of the continuous one.Comment: 14 pages (Latex) + 4 Postscript figure
Prediction of Viral Loads for Diagnosis of Hepatitis C Infection in Human Plasma Samples Using Raman Spectroscopy Coupled with Partial Least Squares Regression Analysis
Raman spectroscopy has been used to identify the biochemical changes associated with the presence of the Hepatitis C virus (HCV) in infected human blood plasma samples as compared with healthy samples, as control. The aim of the study was to establish the Raman spectral markers of hepatitis infection, which could be used for diagnostic purposes. Moreover, multivariate data analysis techniques, including Principal Component Analysis (PCA), coupled with Linear Discriminant Analysis (LDA), and Partial Least Square Regression (PLSR) are employed to further demonstrate the diagnostic capability of the technique. The PLSR model is developed to predict the viral loads of the HCV infected plasma on the basis of the biochemical changes caused by the viral infection.
Specific Raman spectral features are observed in the mean spectra of HCV plasma samples which are not observed in the control mean spectra. PCA differentiated the ‘normal’ and ‘HCV’ groups of the Raman spectra and PCA-LDA was employed to increase the efficiency of prediction of the presence of HCV infection, resulting in a sensitivity and specificity 98.8% and 98.6%, with corresponding Positive Predictive Value of 99.2%, and Negative Predictive Value of 98%. PLSR modelling was found to be 99% accurate in predicting the actual viral loads of the HCV samples, as determined clinically using the Polymerase Chain Reaction (PCR) technique, on the basis of the Raman spectral changes caused by the virus during the process of the development of Hepatitis C. Copyright © 2017 John Wiley & Sons, Ltd
Irreversible Deposition of Line Segment Mixtures on a Square Lattice: Monte Carlo Study
We have studied kinetics of random sequential adsorption of mixtures on a
square lattice using Monte Carlo method. Mixtures of linear short segments and
long segments were deposited with the probability and , respectively.
For fixed lengths of each segment in the mixture, the jamming limits decrease
when increases. The jamming limits of mixtures always are greater than
those of the pure short- or long-segment deposition.
For fixed and fixed length of the short segments, the jamming limits have
a maximum when the length of the long segment increases. We conjectured a
kinetic equation for the jamming coverage based on the data fitting.Comment: 7 pages, latex, 5 postscript figure
Jamming coverage in competitive random sequential adsorption of binary mixture
We propose a generalized car parking problem where cars of two different
sizes are sequentially parked on a line with a given probability . The free
parameter interpolates between the classical car parking problem of only
one car size and the competitive random sequential adsorption (CRSA) of a
binary mixture. We give an exact solution to the CRSA rate equations and find
that the final coverage, the jamming limit, of the line is always larger for a
binary mixture than for the uni-sized case. The analytical results are in good
agreement with our direct numerical simulations of the problem.Comment: 4 pages 2-column RevTeX, Four figures, (there was an error in the
previous version. We replaced it (including figures) with corrected and
improved version that lead to new results and conclusions
Raman Spectral Signatures of Cervical Exfoliated Cells from Liquid-Based Cytology Samples
It is widely accepted that cervical screening has significantly reduced the incidence of cervical cancer worldwide. The primary screening test for cervical cancer is the Papanicolaou (Pap) test, which has extremely variable specificity and sensitivity. There is an unmet clinical need for methods to aid clinicians in the early detection of cervical precancer. Raman spectroscopy is a label-free objective method that can provide a biochemical fingerprint of a given sample. Compared with studies on infrared spectroscopy, relatively few Raman spectroscopy studies have been carried out to date on cervical cytology. The aim of this study was to define the Raman spectral signatures of cervical exfoliated cells present in liquid-based cytology Pap test specimens and to compare the signature of high-grade dysplastic cells to each of the normal cell types. Raman spectra were recorded from single exfoliated cells and subjected to multivariate statistical analysis. The study demonstrated that Raman spectroscopy can identify biochemical signatures associated with the most common cell types seen in liquid-based cytology samples; superficial, intermediate, and parabasal cells. In addition, biochemical changes associated with high-grade dysplasia could be identified suggesting that Raman spectroscopy could be used to aid current cervical screening tests
Adsorption of Line Segments on a Square Lattice
We study the deposition of line segments on a two-dimensional square lattice.
The estimates for the coverage at jamming obtained by Monte-Carlo simulations
and by -order time-series expansion are successfully compared. The
non-trivial limit of adsorption of infinitely long segments is studied, and the
lattice coverage is consistently obtained using these two approaches.Comment: 19 pages in Latex+5 postscript files sent upon request ; PTB93_
Fractal dimension and degree of order in sequential deposition of mixture
We present a number models describing the sequential deposition of a mixture
of particles whose size distribution is determined by the power-law , . We explicitly obtain the scaling function in
the case of random sequential adsorption (RSA) and show that the pattern
created in the long time limit becomes scale invariant. This pattern can be
described by an unique exponent, the fractal dimension. In addition, we
introduce an external tuning parameter beta to describe the correlated
sequential deposition of a mixture of particles where the degree of correlation
is determined by beta, while beta=0 corresponds to random sequential deposition
of mixture. We show that the fractal dimension of the resulting pattern
increases as beta increases and reaches a constant non-zero value in the limit
when the pattern becomes perfectly ordered or non-random
fractals.Comment: 16 pages Latex, Submitted to Phys. Rev.
Fractal formation and ordering in random sequential adsorption
We reveal the fractal nature of patterns arising in random sequential
adsorption of particles with continuum power-law size distribution, , . We find that the patterns become more and
more ordered as increases, and that the Apollonian packing is obtained
at limit. We introduce the entropy production rate as a
quantitative criteria of regularity and observe a transition from an irregular
regime of the pattern formation to a regular one. We develop a scaling theory
that relates kinetic and structural properties of the system.Comment: 4 pages, RevTex, 4 postscript figures. To appear in Phys.Rev.Let
Polydisperse Adsorption: Pattern Formation Kinetics, Fractal Properties, and Transition to Order
We investigate the process of random sequential adsorption of polydisperse
particles whose size distribution exhibits a power-law dependence in the small
size limit, . We reveal a relation between pattern
formation kinetics and structural properties of arising patterns. We propose a
mean-field theory which provides a fair description for sufficiently small
. When , highly ordered structures locally identical
to the Apollonian packing are formed. We introduce a quantitative criterion of
the regularity of the pattern formation process. When , a sharp
transition from irregular to regular pattern formation regime is found to occur
near the jamming coverage of standard random sequential adsorption with
monodisperse size distribution.Comment: 8 pages, LaTeX, 5 figures, to appear in Phys.Rev.
A strong-coupling analysis of two-dimensional O(N) sigma models with on square, triangular and honeycomb lattices
Recently-generated long strong-coupling series for the two-point Green's
functions of asymptotically free lattice models are
analyzed, focusing on the evaluation of dimensionless renormalization-group
invariant ratios of physical quantities and applying resummation techniques to
series in the inverse temperature and in the energy . Square,
triangular, and honeycomb lattices are considered, as a test of universality
and in order to estimate systematic errors. Large- solutions are carefully
studied in order to establish benchmarks for series coefficients and
resummations. Scaling and universality are verified. All invariant ratios
related to the large-distance properties of the two-point functions vary
monotonically with , departing from their large- values only by a few per
mille even down to .Comment: 53 pages (incl. 5 figures), tar/gzip/uuencode, REVTEX + psfi
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