Compressional States Research Articles

Individual dipole toroidal states: Main features and search in the ( e,e′ ) reaction

Individual low-energy E1 toroidal and compressional states (TS and CS) produced by the convective nuclear current ${\bf j}_{\rm c}$ were recently predicted for $^{24}$Mg in the framework of quasiparticle random-phase-approximation (QRPA) with Skyrme forces. In the present QRPA study with Skyrme parametrization SLy6, we explore in more detail properties of these states (toroidal and compressional responses, current distributions, and transitions probabilities $B(E1K, 0^+0 \to 1^-K),\; B(E3K, 0^+0 \to 3^-K)$, $B(M2K, 0^+0 \to 2^-K)$ with $K=$0 and 1) and analyze the possibility to discriminate and identify TS in inelastic electron scattering to back angles. The interplay of the convective ${\bf j}_{\rm c}$ and magnetization ${\bf j}_{\rm m}$ nuclear currents is thoroughly scrutinized. A two-step scheme for identification of TS in $(e,e')$ reaction is proposed. The key element of the scheme is the strong interference of the orbital and spin contributions, resulting in specific features of E1 and M2 transversal form factors.

Interactions of a non-ionic surfactant with mixed phospholipid—oleic acid monolayers. Surface potential and surface pressure studies at constant area

Surface pressure and surface potential isotherms of mixed phospholipid—oleic acid monolayers were shown to be substantially modified in the presence of poloxamer non-ionic surfactant in the aqueous phase. The results reveal the ability of poloxamer molecules to penetrate these monolayers even at high compressional states. On addition of oleic acid molecules to the phospholipid, the compressibilities of the monolayers increased, giving rise to the enhanced poloxamer penetration. Although at the precollapse state poloxamer molecules seem to be unable to penetrate into these monolayers, as indicated by the negative ΔΠ values, the surface potential data indicate that poloxamer adsorption takes place beneath these films. The effect of oleic acid in the monolayers upon the orientation of adsorbing poloxamer molecules and monolayer surface potential is discussed.

Implications of principal stress axes and eigenvalue ratios on critical orientation of fractures. Application to two tectonic regions in Alaska

The principal stress axes and eigenvalue ratios of the stress tensors from two active seismic regions in Alaska (eastern Aleutian Arc and eastern Gulf of Alaska) are computed. These results are obtained using focal mechanisms of earthquakes with magnitudes ranging from 5.5 to 8.2 and show for both regions slightly different compressional states with an orientation of the pressure axis of N26°W for the eastern Gulf of Alaska and N27°W for the east Aleutian Arc. The eigenvalue ratios for the eastern Gulf of Alaska and east Aleutian Arc are 0.84 and 0.99, respectively. The algorithm used in computations allows us to detect some focal mechanisms which are incoherent with respect to the obtained stress tensors. These incoherences are explained in terms of some tectonic features of the region. The orientations of possible pre-existing fractures which would need an unrealistically high maximum shear stress to start a slip on their fault planes are also investigated. These critical orientations depend on a constitutive frictional law as well as on eigenvalue ratios and eigenvectors of the stress tensors. The orientation, which is given in our case by the angle between the normal vector to a fracture and the regional tensional axis, is approximately 59° for the eastern Aleutian Arc. This angle ranges from 49° to 59° for the eastern Gulf of Alaska. It must be pointed out that fractures which need unrealistically high shear stress to start slip on their fault planes are defined by a very narrow band of possible angles between tensional direction and the normal vector to fault plane.

Penetration of 1-alkanols into monolayers of α-helical polypeptides with hydrophobic side chains

Penetration of 1-alkanols into monolayers of α-helical polypeptides with hydrophobic side chains at two different compressional states is studied by surface potential and surface pressure measurements. It was found that at an initial surface pressure of 3.0 mN m −1 there existed a time difference in achieving the final equilibrium between the surface potential and the surface pressure for poly (γ-dodecyl-L-glutamate) (PDOLG) and poly (γ-methyl-L-glutamate) (PMLG) monolayers after adsorption of 1-alkanol. This disagreement was accounted for by the time-dependent reorientation of polypeptide side chains at the interface after adsorption. The free energies of adsorption per CH 2 group of 1-alkanol to the monolayers spread at the initial surface pressures of 3.0 and 13.5 mN m −1 were −2.90 and −2.46 kJ mol −1 for PDOLG, and −2.70 and −2.57 kJ mol −1 for PMLG, respectively. The affinity of 1-alkanol to the PDOLG monolayer was stronger than that of the PMLG monolayer.

Atypical langmuir adsorption of inhalation anesthetics on phospholipid monolayer at various compressional states: difference between alkane-type and ether-type anesthetics

Adsorption of chloroform, halothane, enflurane and diethyl ether on the air/water interface was compared with adsorption on the dipalmitoylphosphatidylcholine monolayer, spread on the air/water interface, at four compressional states; 88.5, 77.0, 66.5 and 50.5 Å 2 surface area per phosphatidylcholine molecule. Anesthetics were administered from the gas phase. The affinities of these agents to the phosphatidylcholine monolayer varied according to the state of the monolayer. Chloroform and halothane showed a stronger affinity to the highly compressed phosphatidylcholine monolayer (50.5Å 2) than to the expanded monolayer (88.5Å 2) or to the air/water interface without the monolayer. Diethyl ether behaved in reverse; a stronger affinity to the expanded monolayer was exhibited than to the compressed monolayer. Enflurane showed the highest affinity to the intermediately compressed monolayer (77.0 Å 2). The adsorption isotherm of anesthetics to the monolayer was characterized by atypical Langmuir-type, in which available number of binding sites changed when anesthetics were adsorbed. The mode of adsorption onto the monolayer was dissimilar to adsorption onto air/water interface, where adsorption followed the Gibbs surface excess. A theory is presented to explain the above differences. The adsorbed anestheic molecules do not stick to phosphatidylcholine molecules but penetrate into the monolayer lattice and occupy the phosphatidylcholine sites at the interface. Quantitative agreement between the theory and the experimental data was excellent. For the monolayer at 50.5 Å 2 compression, the changes in the transfer free energy accompanying the anesthetic adsorption from the gas phase to the monolayer were in the order of chloroform > halothane > enflurane > diethyl ether , in agreement with the clinical potencies.

Some constraints on levels of shear stress in the crust from observations and theory

In situ stress determinations in North America, southern Africa, and Australia indicate that on the average the maximum shear stress increases linearly with depth to at least 5.1 km measured in soft rock, such as shale and sandstone, and to 3.7 km in hard rock, including granite and quartzite. Regression lines fitted to the data yield gradients of 3.8 MPa/km and 6.6 MPa/km for soft and hard rock, respectively. Generally, the maximum shear stress in compressional states of stress for which the least principal stress is oriented near vertically is substantially greater than in extensional stress regimes, with the greatest principal stress in a vertical direction. The equations of equilibrium and compatibility can be used to provide functional constraints on the state of stress. If the stress is assumed to vary only with depth z in a given region, then all nonzero components must have the form A+Bz, where A and B are constants which generally differ for the various components. This implies that the deviatoric stress changes linearly with depth, and the general solution also allows the directions of the horizontal principal stresses to change monotonically with depth. Solutions to the equations, a churning stress to vary with both z and x, were fit to the observations of Zoback and Roller, who measured stress along a horizontal profile near Palmdale, California. The results indicate that the average shear stress in the upper 8 km of the fault zone is about 3.5 MPa less than the shear stress in the far field, but this far field term, which is part of the solution and has the form A+Bz, cannot be evaluated using the existing constant depth data.