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We developed a new program, MSpin-RDC for the analysis of residual dipolar coupling data. This software, specially designed for small molecule analysis, can directly read many molecular-modeling and popular chemistry file formats and accept RDC values as a simple free-format table. Alignment tensor can then be computed by singular value decomposition, as well as predicted using inertia and gyration tensor-based methodologies. Trial structures are then ranked according to their Cornilescu's quality factor (Q) values. Analysis of multiconformational problems and fitting of RDC data to relative populations can be accomplished using the single-tensor approximation.

Short block copolymers in selective solvents (bad for A-block, good for B-block) are modeled by flexible bead-spring chains, where beads interact with short range Morse potentials of variable strength. It is shown that already very short chains (N A = N B = 2) exhibit a rather well-defined critical micelle concentration (cmc). The mass distribution of the micelles and their gyration tensor components as well as their internal structure are studied. It is shown that the relaxation time increases exponentially with the strength E AA of the attractive energy between the A-monomers, and thus frozen-in micelles of medium size are obtained when E AA is chosen too large. Our results are compared to studies of related but somewhat different models.

We theoretically investigate polymer deformation and shear thinning, i.e., a decrease of intrinsic viscosity, in a dilute polymer solution as a function of the applied shear rate γ. We use a bead-and-spring model with hydrodynamic interaction in the Rouse-Zimm framework, approximately accounting also for excluded-volume effects, and impose a constraint on the average mean-square spring length to prevent its stretching at large γ. When suitably normalized, both the intrinsic viscosity [η] and the components of the mean gyration tensor depend on the single variable ξ= γτ 1 (0) /N 1-v , where τ 1 (0) is the longest relaxation time for γ = 0, N is the number of chain springs and v is the Flory exponent. The full shear-rate dependence is obtained numerically, and compared with analytical results obtained under free-draining conditions both for low and for very large shear rates. The shortcomings of the theory are also discussed, in particular a substantial stretching under shear of the central springs, where the intramolecular tension is largest, with a corresponding strong contraction of the end springs due to the average character of the constraint.

The optical parameters of optically uniaxial γ 1 -(Ga x In 1-x ) 2 Se 3 single crystals are systematically measured and analyzed. The optical rotatory power along the optical c-axis is determined in visible spectral region at 77 K and at room temperature and complemented with theoretical estimates for other crystallographic directions. The g 33 component of the gyration tensor is calculated from the experimental data. The dichroism is studied in the vicinity of the absorption edges. The dispersion of ordinary and extraordinary refraction indices is determined at room temperature for the transparency window 0.57 to 10 μm. Up to 5 μm the dispersion can be interpreted in terms of noninteracting harmonic oscillators (single-term Sellmeier relation).

DNA motion during biased sinusoidal field gel electrophoresis around the antiresonance condition was investigated by direct observation using fluorescent microscopy and Brownian dynamics simulation. Time development of the center of mass velocity, vx, and the principal value of the gyration tensor, R1, was measured at this antiresonance condition. The typical stretch-contract motion, which is observed in steady field and at high frequency field, is severely suppressed, and there are two or more dominant kinks that compete with each other. Analysis of the kink motion from the simulation results supports this picture.

It has been known that oxo amide crystals made up of achiral molecules can be photochemically converted into optically active β-lactams by irradiation with a high pressure mercury lamp. Although the oxo amide crystal belongs to an enantiomorphic class D2, its optical activity could not be detected so far. We successfully measured the components of the gyration tensor of the oxo amide crystal by using the HAUP (high accuracy universal polarimeter) method: g11 = −3.5 × 10-4 (−79°/mm), g22 = −1.4 × 10-4 (−32°/mm), g33 = −3.0 × 10-4 (−68°/mm) at 305 K, where the optical rotatory powers are indicated in parentheses. It has been proved by direct experiments that the optical activity of the reactant and the product in this reaction system remains unchanged over the photocyclization process.

The natural optical activity (NOA) and the refractive index are measured in the temperature intervals of 4.2 to 400 K and of 293 to 400 K, respectively. The dispersion of the NOA is best approximated by a single-term Drude formula. The parameters of dispersion formulas are given for various temperatures. A temperature dependence of NOA in CdP2 is found. The temperature variation of the CdP2 rotational ability is shown to be mainly due to the temperature shift of the corresponding optically active band at E = 2.4 eV. In the 360 to 380 K temperature range a break is observed in the temperature dependence of the specific rotation and the refractive index, while the temperature dependence of the gyration tensor component displays a characteristic feature with well defined maxima, which indicates the presence of a phase transition in CdP2 crystals in this temperature range. Die naturliche optische Aktivitat (NOA) und der Brechungsindex werden in den Temperaturbereichen 4,2 bis 400 K bzw. 293 bis 400 K gemessen. Die Dispersion der NOA last sich am besten durch eine Drudeformel mit einem Term annahern. Fur verschiedene Temperaturen werden die Parameter der Dispersionsformel angegeben. Fur CdP2 wird eine Temperaturabhangigkeit der NOA gefunden. Es wird gezeigt, das die Temperaturanderung des Rotationsvermogens von CdP2 hauptsachlich von der Temperaturverschiebung der entsprechenden optisch aktiven Bande bei E = 2,4 eV hervorgerufen wird. Im Temperaturbereich von 360 bis 380 K wird ein Knick in der Temperaturabhangigkeit der spezifischen Rotation und des Brechungsindex beobachtet, wahrend die Temperaturabhangigkeit der Drehungstensorkomponenten ein charakteristisches Verhalten mit wohldefinierten Maxima aufweist, was auf die Anwesenheit eines Phasenubergangs in CdP2-Kristallen in diesem Temperaturbereich hinweist.

The spectra of the gyration tensor component g11, are measured at 300 K for CdSiP2, CdSnP2, ZnSiP2, ZnGeP2, and CuInS2, using the polarization modulation technique. The dispersion of g11 is analyzed according to the model of the effective oscillators and the band theory of optical activity. A correlation between the magnitude of the optical activity and the distortion of the characteristic building units of the chalcopyrite structure is found. [Russian Text Ignored].

The stress–strain relation is analyzed in terms of the gyration tensor where the sum is over all N atomic groups comprising the elastomeric material. All groups are taken for convenience to have the same mass. This tensor is linear in the strain, and furthermore it may be evaluated from a configuration integral. The definition of the strain by use of Sαβ gives new insight into the connection between statistical and continuum mechanics, and further clarifies the significance of “affine deformation.” Stress components are obtained as derivatives of the (Helmholtz) free energy A with respect to the invariants of Sαβ. The first invariant is just the radius of gyration S2 of the network, and the dependence of A on S2 alone provides a basis for analysis of stress–strain isotherms.

The formation of a gel or elastomer entails the linking together of molecules to form a contiguous random network that has macroscopic dimensions. Forces are propagated in networks along polymer chains and through junctions to other chains. It is important to understand the structure of the force constant matrix that describes a system as complicated as this, even in the case where the potential energy is approximated by a simple harmonic function. This force constant matrix was first formulated by James, but because it is a large random matrix, very little progress can be made in the analysis of its properties. We have opted to approach this problem with the use of large scale computations that are based upon simulations of the formation of networks. Subsequent evaluation of the eigenvalue spectrum of the matrix lends considerable insight into the equilibrium and dynamic properties of elastomers. For present purposes this analysis is couched in terms of the calculation of the probability distribution of the gyration tensor for a phantom network in which non-bonded interactions are not considered.

Spectral dependences of the gyration tensor components g11, g33, refraction indices and birefringence of tetragonal CdP2 are investigated at 300 K. The optical activity of the crystal is found to be determined by both the crystal and the molecular contributions, the latter being due to the distortion of the tetrahedral symmetry of the structural elements. The dispersion of the refractive indices is discussed on the basis of a single-effective-oscillator model. The ionicity of CdP2 is equal to 0.56 and is close to the values of AIIBVI compounds and the ionicity of CdP bond in AIIBIVC semiconductors. The dispersion of the spectroscopic properties of CdP2 is concluded to be mainly determined by the CdP bound. [Russian Text Ignored].

Optical rotatory power of Ca2Sr(C2H5CO2)6 was accurately measured over a wide temperature range containing both paraelectric and ferroelectric states. The gyration tensor g33 has been determined from the experimental data; for instance, g33 = 2.131 × 10−5, paraelectric at 20 °C, and 2.129 × 10−5, ferroelectric at −20 °C (λ = 546 nm). A theory of optical activity based upon Born's theory has been developed in order to apply it to the ferroelectricity. In the light of the theory the ferroelectric property of Ca2Sr(C2H5CO2)6 is discussed, and it has been revealed that some change occurs around −64 °C in either antisymmetrical parts of interelectronic coupling tensor or shifts of the atoms responsible for its ferroelectricity. Nous avons mesure avec precision le pouvoir rotatoire de Ca2Sr(C2H5CO2)6 dans un large domaine de temperature comprenant a la fois les etats para et ferroelectriques, et nous avons ainsi pu determiner le tenseur de gyration g33; par exemple, g33 = 2,131 × 10−5 dans la phase paraelectrique a 20 °C, et 2,129 × 10−5 dans la phase ferroelectrique a −20 °C, pour la longuer d'onde λ = 546 nm. Nous avons developpe la theorie de Born de maniere a l'appliquer au cas de la ferroelectricite, et nous pouvons ainsi interpreter les resultats experimentaux. Nous sommes alors amenes a supposer q'un changement doit intervenir aux environs de −64 °C, soit dans la partie antisymmetrique du tenseur d'interactions entre electrons, soit dans le deplacement des atomes responsables de la ferroelectricite.