Two-Dimensional Correlation Analysis of Temperature-Dependent FT-IR Spectra of Oleic Acid

ABSTRACT

In the present study, variable temperature FT-IR spectroscopic investigations were used to characterize the spectral changes in oleic acid during heating oleic acid in the temperature range from ?30°C to 22°C. In order to extract more information about the spectral variations taking place during the phase transition process, 2D correlation spectroscopy (2DCOS) was employed for the stretching (C?O) and rocking (CH₂) band of oleic acid. However, the interpretation of these spectral variations in the FT-IR spectra is not straightforward, because the absorption bands are heavily overlapped and change due to two processes: recrystallization of the γ-phase and melting of the oleic acid. Furthermore, the solid phase transition from the γ- to the α-phase was also observed between ?4°C and ?2°C. Thus, for a more detailed 2DCOS analysis, we have split up the spectral data set in the subsets recorded between ?30°C to ?16°C, ?16°C to 10°C, and 10°C to 22°C. In the corresponding synchronous and asynchronous 2D correlation plots, absorption bands that are characteristic of the crystalline and amorphous regions of oleic acid were separated.     

Transverse momentum distribution and elliptic flow of charged hadrons in $$$$ collisions at $$\sqrt{s_{NN}}=193$$sNN=193 GeV using HYDJET++

Recent experimental observations of the charged hadron properties in \(U+U\) collisions at 193 GeV contradict many of the theoretical models of particle production including two-component Monte Carlo Glauber model. The experimental results show a small correlation between the charged hadron properties and the initial geometrical configurations (e.g. body–body, tip–tip etc.) of \(U+U\) collisions. In this article, we have modified the Monte Carlo HYDJET++ model to study the charged hadron production in \(U+U\) collisions at 193 GeV center-of-mass energy in tip–tip and body–body initial configurations. We have modified the hard as well as soft production processes to make this model suitable for \(U+U\) collisions. We have calculated the pseudorapidity distribution, transverse momentum distribution and elliptic flow distribution of charged hadrons with different control parameters in various geometrical configurations possible for \(U+U\) collision. We find that HYDJET++ model supports a small correlation between the various properties of charged hadrons and the initial geometrical configurations of \(U+U\) collision. Further, the results obtained in modified HYDJET++ model regarding \(dn_{ch}/d\eta \) and elliptic flow (\(v_{2}\)) suitably matches with the experimental data of \(U+U\) collisions in minimum bias configuration.     

Enhanced transmission by a grating composed of left-handed materials

We present a detailed theoretical analysis about the influence of surface polaritons on the transmission properties of electromagnetic waves at the periodically corrugated interface between the vacuum and left-handed material by using nonlinear boundary condition approach. The principle behind this approach is to match the wave fields across the grating interface by using a set of linear wave equation with nonlinear boundary conditions. The resonant transmission of the incident electromagnetic radiation in this structure is feasible within a certain frequency band, where there is a range of frequency over which both the electric permittivity and the magnetic permeability are simultaneously negative. The enhanced transmission is attributed to the coupling of the incident electromagnetic wave with the excited surface polaritons on grating interface. Finally, we present the numerical results illustrating the effect of the structural parameters and angle of incidence on the transmission spectra of a TM polarized electromagnetic wave.     

A general method for deriving boundary conditions associated with reduced distribution functions

A systematic procedure based on projection operator methods for deriving boundary conditions on the reduced distribution functions arising from those imposed on the full distribution function is given. The method is illustrated by applying it to Brownian motion.     

Equivalence of stochastic quantization to field theories from supersymmetry

Using the Ward-Takahashi identities from the hidden supersymmetry in Langevin equation we present a very simple proof of the equivalence of stochastic quantization to field theories.     

Laminar boundary layer over a flexible surface in oscillatory flow

A two-dimensional oscillatory flow over a flat flexible surface is analysed. Low and high frequency solutions are developed separately. Results depicting the effect of surface flexibility on the flow in comparison to that over a rigid surface are presented.     

Limit cycles and detailed balance in Fokker-Planck equations

A class of non-linear Fokker Planck equations with exactly known steady state solution is investigated and its relation with the models considered earlier in the literature is discussed. A characterisation of the absence of detailed balance and possible existence of limit cycles is given. The implications of detailed balance on the existence and the character of limit cycle behaviour are studied. It is shown that detailed balance does not determine the existence or non-existence of limit cycles but rather their character.     

Dynamical current correlations in simple liquids

Expressions for the longitudinal and transverse current correlation functions of simple liquids are obtained using Mori's formalism. These involve unknown damping functions. The use of damping functions for a free gas gives results which are in complete disagreement with experiments. The results obtained on the basis of a renormalized free particle memory function in which the collisional damping of collective excitations is incorporated show remarkable improvement over earlier results and are in reasonable agreement with the molecular dynamics data of Rahman. Therefore, the choice of the memory function is as important as the satisfaction of lower order moments.