Vibrational spectroscopy and DFT calculations of N,N′‐dicyclohexylcarbodiimide

Infrared (IR) and Raman spectra were obtained for N,N′‐dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl₃ solution. Structures and vibrational spectra of isolated, gas‐phase DCC molecules with C₂ and C_i symmetries, computed at the B3‐LYP/cc‐pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C₂ structure in both the solid state and in CHCl₃ solution. Using a scaled quantum‐chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid‐state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid‐state effects were evident in the spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Interaction of longitudinal phonons with discrete breather in strained graphene

We numerically analyze the interaction of small-amplitude phonon waves with standing gap discrete breather (DB) in strained graphene. To make the system support gap DB, strain is applied to create a gap in the phonon spectrum. We only focus on the in-plane phonons and DB, so the issue is investigated under a quasi-one-dimensional setup. It is found that, for the longitudinal sound waves having frequencies below 6 THz, DB is transparent and thus no radiation of energy from DB takes place; whereas for those sound waves with higher frequencies within the acoustic (optical) phonon band, phonon is mainly transmitted (reflected) by DB, and concomitantly, DB radiates its energy when interacting with phonons. The latter case is supported by the fact that, the sum of the transmitted and reflected phonon energy densities is noticeably higher than that of the incident wave. Our results here may provide insight into energy transport in graphene when the spatially localized nonlinear vibration modes are presented.     

Novel Fluorometric Turn On Detection of Aluminum by Chalcone-Based Chemosensor in Aqueous Phase

A novel, 100% water-soluble chalcone based chemosensing receptor {1-[3-(2-Hydroxy-phenyl)-3-oxo-propenyl]-naphthalen-2-yloxy}-acetic acid, L was synthesized and characterized. The receptor L is designed based on the chelation enhanced fluorescence (CHEF) mechanism. The chemosensing properties of L were evaluated by UV–vis and fluorescence spectrometric methods. It exhibits highly selective recognition ability towards aluminum ions in water over other metal ions. The binding stoichiometry of L? Al³⁺ complex is 2:1 by means of Job’s plot and the detection limit is 5.66?×?10^??8 M.     

Study of the semileptonic charm decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu

We investigate the decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu, where l is e or mu, using approximately 7 fb(-1) of data collected with the CLEO III detector. We find R(0) identical with B(D(0)-->pi(-)e(+)nu)/B(D(0)-->K(-)e(+)nu)=0.082+/-0.006+/-0.005. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R(0) gives |f(pi)(+)(0)|(2)|V(cd)|(2)/|f(K)(+)(0)|(2)|V(cs)|(2)=0.038(+0.006+0.005)(-0.007-0.003).     

Evolutionarily stable strategies in quantum games

Evolutionarily stable strategy (ESS) in classical game theory is a refinement of Nash equilibrium concept. We investigate the consequences when a small group of mutants using quantum strategies try to invade a classical ESS in a population engaged in symmetric bimatrix game of prisoner's dilemma. Secondly we show that in an asymmetric quantum game between two players an ESS pair can be made to appear or disappear by resorting to entangled or unentangled initial states used to play the game even when the strategy pair remains a Nash equilibrium in both forms of the game.     

Mixed convection on a vertical circular cylinder

The problem of the mixed convection boundary-layer flow past an isothermal vertical circular cylinder is considered in both the cases when the buoyancy forces aid and oppose the development of the boundary layer. A series solution is obtained, valid near the leading edge, and this is extended by a numerical solution of the full equations, which in the aiding case, becomes inaccurate downstream. An approximate solution is also derived which gives a good estimate for the heat transfer near the leading edge and has the correct asymptotic form well downstream. In the opposing case, the boundary layer is seen to separate at a finite distance downstream, with, for moderate values of the buoyancy parameter, the numerical solution indicating a regular behaviour near separation.     

ΛΛ 6 hypernucleus in α + 2Λ cluster model

The binding energy of the double hypernucleus _ΛΛ ⁶ is calculated in α + 2Λ cluster model using the method of translation invariant basis TIMO. As regards the required interaction potentials we use a density dependent effective ΛN force and a gaussian form for ΛΛ potential. With these interactions a very reasonable value ofB _ΛΛ is obtained if the oscillator states up to the excitation quantum numberN=12 are taken into account in the expansion of wavefunction of the hypernucleus. This value ofN is much smaller than that obtained in an earlier study. This lowering inN value is attributed to a much better choice of ΛN potential used in the present study.     

Ion acoustic solitary waves with adiabatic ions in magnetized electron-positron-ion plasmas

Linear and nonlinear ion acoustic waves in the presence of adiabatically heated ions in magnetized electron-positron-ion plasmas are studied. The Sagdeev potential approach is employed to obtain the energy integral equation in such a mulitcomponent plasma using fluid theory. It is found that electron density humps are formed in the subsonic region in magnetized electron-positron-ion plasmas. The amplitude of electron density hump is decreased with the increase of hot ion temperature in electron-positron-ion plasmas. However, the increase in positron concentration and obliqueness of the wave increases the amplitude of nonlinear structure. The increase in positron concentration also reduces the width of the nonlinear structure in a magnetized multicomponent plasma. The numerical solutions in the form of solitary pulses are also presented for different plasma cases. The results may be applicable to astrophysical plasma situations, where magnetized electron-positron-ion plasma with hot ions can exist.     

Characterization of ion irradiated silicon surfaces ablated by laser-induced breakdown spectroscopy

Low energy metallic ions,generated by a Q-switched Nd:YAG laser(1064-nm wavelength,10-mJ energy,9-nm～12-ns-pulse width,10~(11)W/cm~2intensity)irradiated on a silicon substrate to modify various properties,such as electrical,morphological,and structural modifications.Thomson parabola technique is used to calculate the energy of these metallic ions whereas the electrical conductivity is calculated with the help of Four-point probe.Interestingly circular tracks forming chain like damage trails are produced via these energetic ions which are carefully examined by optical microscopy.It is observed that excitation,ionization,and cascade collisions are responsible for surface modifications of irradiated samples.Four-point probe analysis revealed that the electrical conductivity of substrate has reduced with increasing trend of atomic number of irradiated metallic ions(Al,Ti,Cu,and Au).The x-ray diffraction analysis elucidated the crystallographic changes leading to reduction of grain size of N-type silicon substrate,which is also associated with the metallic ions used.The decreasing trend of conductivity and grain size is due to thermal stresses,scattering effect,structural imperfections,and non-uniform conduction of energy absorbed by substrate atoms after the ion irradiation.