Critical behavior of electrical resistivity in polar + nonpolar binary liquid systems

The behavior of electrical resistivity in the critical region of three polar + nonpolar binary liquid systems CS2 +(CH3CO)2O, C6H12+(CH3CO)2O, and n‐C7H16+(CH3CO)2O is studied. For the mixtures with critical composition, the two phase region shows a conductivity behavior with σ1−σ2∼ (−ϵ)β with β?0.35. In the one phase region dR/dT has a singularity ϵ−b with b?0.35. A possible theory of the impurity conduction is given, which broadly explains these results. The possibility of dR/dT being positive or negative is also discussed.

Electromagnetic wave propagation at the interface between two polar semiconductors

The interface between two polar semiconductors can support three types of phonon-plasmon-polariton modes propagating in three well-defined frequency windows ??1?[min(?1,?3),?R1], ??2?[max(?2,?4),?R2], and ??3?[min(?2,?4),?R3]. The limiting frequencies ?1,2,3,4 are defined by ?1(?)=0, ?2(?)=0, and ?R1,2,3 by ?1(?)+?2(?)=0, where ?i(?) are dielectric functions of the two media with i=1,2. The dispersion, decay distances, and polarization of the three modes are discussed. The variation of the limiting frequencies with the interface plasma parameter ???p22/?p12 reveals an interesting feature in the dispersion characteristics of these modes. For the interfaces for which the bulk coupled phonon-plasmon frequencies of medium 1 are greater than the LO frequency or are less than the TO frequency of medium 2, there exist two values of ?=?1 and ?2(

Conformation of a 16-residue zervamicin IIA analog peptide containing three different structural features: 310-helix, alpha helix and ß-bend ribbon

Boc-Trp-Ile-Ala-Aib-Ile-Val-Aib-Leu-Aib- Pro-Ala-Aib-Pro-Aib-Pro-Phe-OM(we here Boc is t-butoxycarbonyla nd Aib is a-aminoisobutyriac cid), a synthetica polar analog of the membrane-activefu ngal peptide antibioticz ervamtycinII A, crystallizesi n spaceg roupP 1 withZ =1 and cell parameters a = 9.086 ?0.002 A, b = 10.410 ?+ 0.002 A, c = 28.188 ? 0.004 A, a = 86.13 ? 0.01?, 13 = 87.90 ? 0.01?, and y = 89.27 ? 0.01?;o veralla greementf actorR = 7.3% for 7180 data (Fo > 3cr) and 0.91-A resolution. The peptide backbone makes a continuous spiral that begins as a 310-helix at the N-terminus, changes to an a-helix for two turns, and ends in a spiral of three fl-bends in a ribbon. Each of the fl-bends contains a proline residue at one of the corners. The torsion angles 4i range from -51? to -91? (average value -64o), and the torsion angles ai range from -1? to -46? (average value -31?). There are 10 intramolecularN H...OCh ydrogenb onds in the helix and two directh ead-to-taihl ydrogenb ondsb etween successive molecules. Two H20 and two CH30H solvent molecules fill additional space with appropriate hydrogen bonding in the head-to-tail region, and two additional H20 molecules form hydrogen bonds with carbonyl oxygens near the curve in the helix at Pro-10. Since there is only one peptide molecule per cell in space group P1, the molecules repeat only by translation, and consequently the helices pack parallel to each other.

Relationship between microscopic and macroscopic orientational relaxation times in polar liquids

Microscopic relations between single-particle orientational relaxation time (T, ) , dielectric relaxation time ( T ~ )a,n d many-body orientational relaxation time ( T ~o)f a dipolar liquid are derived. We show that both T~ and T~ are influenced significantly by many-body effects. In the present theory, these many-body effects enter through the anisotropic part of the two-particle direct correlation function of the polar liquid. We use mean-spherical approximation (MSA) for dipolar hard spheres for explicit numerical evaluation of the relaxation times. We find that, although the dipolar correlation function is biexponential, the frequency-dependent dielectric constant is of simple Debye form, with T~ equal to the transverse polarization relaxation time. The microscopic T~ falls in between Debye and Onsager-Glarum expressions at large values of the static dielectric constant.

Nature of Cl center dot center dot center dot Cl Intermolecular Interactions via Experimental and Theoretical Charge Density Analysis:Correlation of Polar Flattening Effects with Geometry

The experimental charge density distribution in three compounds, 2-chloro-3-quinolinyl methanol, 2-chloro-3-hydroxypyridine, and 2-chloro-3-chloromethyl-8-methylquinoline, has been obtained using high-resolution X-ray diffraction data collected at 100 K based on the aspherical multipole modeling of electron density. These compounds represent type I (cis), type I (trans), and type II geometries, respectively, as defined for short Cl center dot center dot center dot Cl interactions. The experimental results are compared with the theoretical charge densities using theoretical structure factors obtained from a periodic quantum calculation at the B3LYP/6-31G** level. The topological features derived from the Bader's theory of atoms in molecules (AIM) approach unequivocally suggest that both cis and trans type I geometries show decreased repulsion, whereas type II geometry is attractive based on the nature of polar flattening of the electron density around the Cl atom.

Behaviour of the curve of critical exponents near and away from a double critical point

To investigate the nature of the curve of critical exponents (as a function of the distance from a double critical point), we have combined our measurements of the osmotic compressibility with all published data for quasibinary liquid mixtures. This curve has a parabolic shape. An explanation of this result is advanced in terms of the geometry of the coexistence dome, which is contained in a triangular prism.

High accuracy curve fits for chirality, length and diameter dependent initial modulus of single walled carbon nanotubes

Many previous studies regarding the estimation of mechanical properties of single walled carbon nanotubes (SWCNTs) report that, the modulus of SWCNTs is chirality, length and diameter dependent. Here, this dependence is quantitatively described in terms of high accuracy curve fit equations. These equations allow us to estimate the modulus of long SWCNTs (lengths of about 100-120 nm) if the value at the prescribed low lengths (lengths of about 5-10 nm) is known. This is supposed to save huge computational time and expense. Also, based on the observed length dependent behavior of SWCNT initial modulus, we predict that, SWCNT mechanical properties such as Young's modulus, secant modulus, maximum tensile strength, failure strength, maximum tensile strain and failure strain might also exhibit the length dependent behavior along with chirality and length dependence. (C) 2010 Elsevier B.V. All rights reserved.

Symmetry Properties of the Large-Deviation Function of the Velocity of a Self-Propelled Polar Particle

A geometrically polar granular rod confined in 2D geometry, subjected to a sinusoidal vertical oscillation, undergoes noisy self-propulsion in a direction determined by its polarity. When surrounded by a medium of crystalline spherical beads, it displays substantial negative fluctuations in its velocity. We find that the large-deviation function (LDF) for the normalized velocity is strongly non-Gaussian with a kink at zero velocity, and that the antisymmetric part of the LDF is linear, resembling the fluctuation relation known for entropy production, even when the velocity distribution is clearly non-Gaussian. We extract an analogue of the phase-space contraction rate and find that it compares well with an independent estimate based on the persistence of forward and reverse velocities.

Propagating intensity disturbances in polar corona as seen from AIA/SDO

Context. Polar corona is often explored to find the energy source for the acceleration of the fast solar wind. Earlier observations show omni-presence of quasi-periodic disturbances, traveling outward, which is believed to be caused by the ubiquitous presence of outward propagating waves. These waves, mostly of compressional type, might provide the additional momentum and heat required for the fast solar wind acceleration. It has been conjectured that these disturbances are not due to waves but high speed plasma outflows, which are difficult to distinguish using the current available techniques. Aims. With the unprecedented high spatial and temporal resolution of AIA/SDO, we search for these quasi-periodic disturbances in both plume and interplume regions of the polar corona. We investigate their nature of propagation and search for a plausible interpretation. We also aim to study their multi-thermal nature by using three different coronal passbands of AIA. Methods. We chose several clean plume and interplume structures and studied the time evolution of specific channels by making artificial slits along them. Taking the average across the slits, space-time maps are constructed and then filtration techniques are applied to amplify the low-amplitude oscillations. To suppress the effect of fainter jets, we chose wider slits than usual. Results. In almost all the locations chosen, in both plume and interplume regions we find the presence of propagating quasi-periodic disturbances, of periodicities ranging from 10-30 min. These are clearly seen in two channels and in a few cases out to very large distances (approximate to 250 `') off-limb, almost to the edge of the AIA field of view. The propagation speeds are in the range of 100-170 km s(-1). The average speeds are different for different passbands and higher in interplume regions. Conclusions. Propagating disturbances are observed, even after removing the effects of jets and are insensitive to changes in slit width. This indicates that a coherent mechanism is involved. In addition, the observed propagation speed varies between the different passpands, implying that these quasi-periodic intensity disturbances are possibly due to magneto-acoustic waves. The propagation speeds in interplume region are higher than in the plume region.

Molecular interpretation of the linear relationship between the entropy and the enthalpy of activation of charge transfer reactions in polar liquids

The well-known linear relationship (T?S# =??H# +?, where 1 >? > 0,? > 0) between the entropy (?S#) and the enthalpy (?H#) of activation for reactions in polar liquids is investigated by using a molecular theory. An explicit derivation of this linear relation from first principles is presented for an outersphere charge transfer reaction. The derivation offers microscopic interpretation for the quantities? and?. It has also been possible to make connection with and justify the arguments of Bell put forward many years ago.

The approximate parametrization of the curve of intersection of implicit surfaces

A clear definition of an approximate parametrization of the curve of intersection of (n-1) implicit surfaces in Rn is given. It is justified that marching methods yield such an approximation.

Vesicle formation from dimeric surfactants through ion-pairing. Adjustment of polar headgroup separation leads to control over vesicular thermotropic properties

Eight new vesicle-forming dimeric surfactants are synthesized: the polar headgroup separation in such dimeric amphiphiles strongly influences their vesicular thermotropic phase-transition behaviour.

Polar and nonpolar solvation dynamics, ion diffusion, and vibrational relaxation: Role of biphasic solvent response in chemical dynamics

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Solvation dynamics in nonassociated polar solvents

Ultrafast solvation dynamics in three nonassociated polar solvents, namely, acetonitrile, dimethyl sulfoxide, and acetone, have been studied by using the molecular hydrodynamic theory. For solvation in acetonitrile, the solvent memory function required for this study has been obtained from recent dielectric relaxation measurements of Venabales and Schuttenmaer; earlier theoretical studies used only the Kerr relaxation data. As the latter provides only an indirect information regarding the polar dynamical response of the dipolar liquid, it fails to provide a fully quantitative description of the solvation time correlation function, S(t). The present study with full dielectric data, on the other hand, gives excellent agreement with the experimental results. The theory shows that the ultrafast part of the solvation dynamics originates almost entirely from the high-frequency component of dielectric relaxation (with time constant 0.177 ps), although the latter represents only a small part of the latter. For DMSO and acetone, however, the present theory predicts a decay slower than the experimental observation. It is proposed that for these two solvents specific chromophore-solvent interactions might be responsible for the-large discrepancy. On the basis of the theory, two experimental studies have also been proposed.