Restricted Orientation Research Articles

Phase transitions in molecular fluids

The structure of a confined fluid of hard circular cylinders confined to a slit is studied using a simple theory in the context of a restricted orientation model; previous work is extended to higher densities. It is shown that, as the density increases, the fluid within the central region of the slit undergoes phase transitions which depend on the ratio, l/d, of the length to the diameter of the cylinders, and these transitions are interpreted in terms of the bulk behaviour of the fluid. When l/d is 0·25, the bulk fluid first undergoes a first-order isotropic-nematic transition as the density increases and then makes a transition to a spatially ordered phase. On the other hand when l/d is 0·8, the fluid undergoes a transition to a spatially ordered phase and does not pass through a nematic phase at all. These results are qualitatively in agreement with results obtained by Frenkel and Mulder from the simulation of hard ellipsoids. The limitations of the model are discussed and suggestions made for modifications to improve upon the quantitative predictions of the model at high densities.

A density functional analysis of the restricted orientation model of liquid crystals and its implications for theories of orientational ordering

We compare the predictions of various density functional approximation schemes as applied to the restricted-orientation, hard, rectangular-parallelepiped model of liquid crystals. These calculations illustrate some features of density functional calculations which may aid in understanding other approximate, mean-field theories of orientational ordering phase transitions and their interfaces. The isotropic–nematic coexistence curve of this model is apparently well described by the so-called third-order y expansion, and the analytical expression for the nonideal free energy derived from the simple y expansion thus provides a benchmark against which to compare the density functional approximation schemes. Using standard relations applicable to inhomogeneous fluids, we show how expansions about the bulk isotropic phase compare more favorably with the ‘‘exact’’ y-expansion results when truncated at third order than do second-order truncations. Thus this model behaves somewhat differently than other hard-particle models of fluids, notably the hard-sphere one. We also examine the possibility of expanding the free energy about the ordered phase to obtain the properties of a disordered phase. An expansion about local values of the density leads to the widely used smoothed-density approximation and a hierarchy of systematic extensions. The latter appear more stable than conventional Taylor expansions about bulk disordered phases.

Sociosexuality and Romantic Partner Choice

ABSTRACT In three studies, we explored how individual differences in sociosexual orientation systematically relate to the types of attributes people prefer in romantic partners. In Investigation 1, individuals rated the importance of 15 partner attributes. Two factors emerged: personal/parenting qualities and attractiveness/social visibility. Individuals who possessed a restricted sociosexual orientation rated attributes that loaded highly on the former factor as being more important than those that loaded highly on the second one, whereas the reverse was true for unrestricted individuals. In Investigation 2, individuals evaluated two prospective romantic partners, one who was described as highly attractive and socially visible but less desirable in terms of personal/parenting qualities and one who had the opposite set of attributes. Unrestricted individuals tended to select the former partner, whereas restricted individuals chose the latter one. Investigation 3 examined the attributes actually possessed by their romantic partners. Unrestricted individuals were dating partners who were more socially visible and attractive, whereas restricted individuals were dating partners who were more responsible, faithful/loyal, and affectionate. Results are discussed in terms of an evolutionary model that links sociosexuality to mate selection.

The structure of inhomogeneous molecular fluids: a restricted orientation model

It is suggested that the structural properties of an inhomogeneous fluid of very anisotropic molecules can be studied through a theoretical model in which the orientations of the molecules are restricted to certain discrete values. The general basis of the model is explained and then for illustrative purposes, it is applied to a fluid of cylindrical molecule confined between parallel planar hard structureless walls. Density functional theory and the analogue of the PY equation are used to obtain equations for the density profiles of the fluid which depend on the direct correlation function of the bulk fluid. As this function is unknown, it is approximated by a linear combination of geometrical functions. The equations are solved and the results presented for various values of the packing fraction of the fluid, the separation of the walls and the length to diameter ratio (l/d) of the molecules. A comparison with a recent Monte Carlo simulation of the fluid indicates that the approximations provide as good ...

Steady state and time resolved spectroscopic study of exciton splitting of the electronic state of 2,2-diphenylethylamine

The first excited singlet state of 2,2-diphenylethylamine (DPEA) shows a small exciton splitting of about 137 cm -1. The measured lifetimes of the upper and lower excitonic levels are τ 1 and τ 2, respectively, (τ 1 < τ 2) and only τ 2 is sensitive to polarity of solvents in which the spectrum of DPEA is measured. Flourescence emission mostly takes place from the lower level with longer lifetime which apparently indicates that the upper level is depopulated by rapid internal conversion. It is suggested that the geometry of DPEA, conformation of the NH 2 group, as also restricted orientation of the group, are not favourable for intramolecular CT interaction. Analysis of kinetic parameters of DPEA in different solvents in the presence of chloroalkanes at 77 K shows that it is lower excitonic level that is involved in CT complex formation with the heavy atom quenchers and that from this level the triplet excitation is enhanced.

Novel measurement method of electro-optic constant of polymers and doped polymers with nonlinear organic molecules

A very convenient method is proposed to determine the electro-optic (EO) constants and relevant nonlinear susceptibilities. It was applied to polycarbonate films doped with 4-diethylamino-4′-nitrostilbene (DEANS). The real and imaginary parts of the third-order nonlinear susceptibility X (3) (−ω;ω, 0,0) of the film with several concentrations of DEANS were obtained between 600 and 800 nm. The magnitude of relevant X (3) is proportional to the concentration of DEANS. The mechanism of the EO effect of these samples is discussed, in terms of the restricted orientation of doped molecules.

ChemInform Abstract: Ketene. Part 26. The Reactions of 3,4‐Dihydroisoquinoline N‐Oxide with Ketenes, and an Attempted Synthesis of 3,4‐Dihydro‐3,3‐dimethylquinoline N‐Oxide.

AbstractThe reactivity of 3,4‐dihydroisoquinoline N‐oxide (I) (with restricted relative orientation of the aromatic moiety and the nitrone function), which is known to be highly reactive in 1,3‐dipolar cycloadditions, is studied employing various ketenes.

Quenching of excited states of xylenols due to hydrogen bonding with triethylamine in different solvents

Hydrogen bonding between xylenols in the ground state and triethylamine (TEA) brings about red shift and increase of intensity of the absorption bands of the xylenol molecules. TEA quenches fluorescence of the xylenols at 300 K in varying degrees, possibly through a very short-lived CT species formed by strong hydrogen bonding interaction between excited xylenols and TEA, which leads to large charge transfer. At 77 K, restricted solvent relaxation or orientation impedes formation of such CT complex and consequently impedes the quenching process. Quenching is weak and absent in polar aprotic and alcoholic solvents, respectively. The monoexponential nature of phosphorescence decay of xylenols indicates establishment of very rapid equilibrium between hydrogen-bonded complexes in the triplet state and free molecules.

Effects of monocular exposure to oriented lines on monkey striate cortex

This study examines the extent to which the restriction of visual experience to lines of a single orientation influences the organization of the striate cortex in infant monkeys ( Macaca mulatta). Previous studies of kittens raised with monocular exposure to a single line orientation have consistently shown the response preference of cells driven by that eye to be biased towards the experienced orientation. Studies of binocular exposure to restricted orientations have been equivocal. In the infant monkey cortex responses to oriented lines have virtually all the specificity of responses seen in the adult animal. In an effort to clarify the phenomenon and the mechanism by which orientation bias might be obtained, we examined the effects of monocular exposure to a restricted orientation in infant macaques. Three monkeys were used. Each monkey was raised with one open eye exposed to lines of a single orientation and one eye occluded by lid suture. As in other cases of monocular deprivation in either cat or monkey, few binocularly driven cells were recorded and the majority of cells were dominated by the open eye. Cells driven by the open eye had normal representation of all orientation preferences and there was no overall increase in the number of cells preferring the orientation to which the eye had been exposed. The cells dominated by the occluded eye, however, showed a lack of cells responding to orientations to which the open eye had been exposed. These findings suggest that a competitive mechanism operates between the two eyes to provide an orientation-selective advantage to the open eye.

Personality and sexual relations.

This investigation examined the links between self-monitoring propensities and orientations toward sexual relations. A factor analysis of behavioral and attitudinal survey data revealed that high selfmonitoring individuals tend to establish an unrestricted orientation toward sexual relations (such that they may engage in sex with others to whom they are not necessarily psychologically close), whereas low self-monitoring individuals tend to establish a restricted orientation (such that they will engage in sex only with partners to whom they are psychologically close). At the behavioral level, high relative to low self-monitoring individuals indicated that they had a larger number of different sexual partners within the preceding year, could foresee themselves having sex with a larger number of different partners within the next 5 years, and were more likely to have engaged in sex with someone on only one occasion. At an attitudinal level, low relative to high self-monitoring individuals indicated that they would be more reluctant to have sex with someone to whom they were not committed, and that they would be more uncomfortable with, and less likely to enjoy engaging in, casual sex with different partners. Possible origins and implications of these contrasting orientations are discussed. Throughout the ages, it has been a matter for contemplation, debate, and personal statement: Given human nature, what is the role of love, closeness, and commitment in sexual relations between consenting partners? Are and commitment necessary prerequisites for sexual relations? Is the sexual experience empty and meaningless without psychological closeness between the partners? Or can sex be a comfortable, enjoyable, and even enriching experience for partners who, although attracted to each other, are not psychologically close? If one samples literary, academic, or personal statements made on this issue, one is likely to find pronounced disagreement. Compare and contrast, for instance, the views of Bertrand Russell, Civilized people cannot fully satisfy their sexual instinct without love (1929), and Adrienne Rich, I'd call it if love/ didn't take so many years/ but lust too is a jewel (1966). Indeed, at least within Western cultures, there may be reliable and substantive differences in orientations toward sexual relations. Some people believe that—at least for themselves—sexual relations need not be restricted to relationships in which they and their partners are psychologically close. They may claim, for instance, that if they were attracted to someone, they would feel comfortable and at ease engaging in sex with that person, even if they did not know him or her well. Such people may be said to

Solution structure of antifreeze glycopeptides: Determination of the major conformers of the glycosidic linkages

Using data obtained from 1H- 1H correlated spectroscopy and one- and two-dimensional NOE measurements, we have determined the preferential solution conformation of the disaccharide unit Galβ(1–3)Gal-NAc in the antifreeze glycopeptide (Galß(l-3)GalNAcαl-Thr-Ala-Ala) n derived from the blood of the antarctic fish Trematomas borchgrevinki. The disaccharide, which is a rigid unit, exists with a restricted orientation about the GalNAc-αl-Thr linkage. Preliminary evidence indicates that the backbone (Ala-Ala-Thr) n lies in an extended helical conformation. Antifreeze glycopeptide 1H NMR Glycosidic linkage Dissaccharide structure Nuclear Overhauser effect

Monte Carlo simulations and pair approximations on the phase transition of the restricted orientational lattice model for liquid crystals

The nematic-isotropic phase transition on the SC lattice model of uniaxial molecules is studied by Monte Carlo simulations and the pair approximation method. The interaction between nearest-neighbour sites is assumed to be proportional to (1-3 cos2theta )/2 where theta is the angle between the long axes of molecules. The models of restricted orientation with 3,4,6 and 10 directions are systematically investigated. The phase transitions are shown to be of first order. Analytical estimations by a pair approximation are in agreement with Monte Carlo results.

Structural changes in bacteriorhodopsin induced by electric impulses

Electric impulses of high field intensity (2 × 10 5 to 3 × 10 6 Vm −1, 1 to 20 μs duration) cause transient changes in the optical absorbance of suspended purple membranes of Halobacterium halobium. The electric dichroism at 1 m m NaCL, pH ≈ 6 and at 293K is dependent on field strength, pulse duration and wavelength of the monitoring, plane-polarized light in the range 400 to 650 nm. The optically detected processes are, however, independent of bacteriorhodopsin concentration, of ionic strenght and of the intensity of the monitoring light. These data together with the analysis of time course ands steady state of the reduced dichroism, suggest electric field-sensitive, intramemembraneous structural changes which lead to restricted orientation changes of the chromophore. A thoretical analysis of restricted orientation is developed and applied to the electro-optic data. As a result, it is found that the electric dichroism of purple membrane is associated with a large polarizability anisotropy of 2.4 × 10 −30 Fm 2 (2.2 × 10 −14 cm 3); the electric permanent dipole moment which is involved amounts to 4.7 × 10 −28 Cm(140 Debye). The kinetic data suggest a cyclic reaction scheme with at least five different conformations. The high polarizability is probably due to displaceable ionic groups within the cooperative lattice of bacteriorhodopsin molecules in purple membranes.

Proton NMR study of hemoproteins. Ionization and orientation of iron-bound imidazole in methemoglobin and metmyoglobin

Characteristics of imidazole derivatives bound to methemoglobin and metmyoglobin were investigated by proton NMR spectroscopy with concentration on the ionization of the imino proton and orientation of the imidazole ring in the heme crevice. 1. (1) The hyperfine-shifted heme methyl resonances of metmyoglobin complexes with imidazole, 4-methylimidazole and triazole were pH-dependent, while those of the N- methylimidazole complex were pH-independent. The pH-dependent shifts in the former complexes were attributed to the deprotonation of the imino proton of imidazole derivatives bound to the heme iron. In contrast, metmyoglobin complexes with 4-nitroimidazole and 4-fluoroimidazole, both of which have the ionizable NH proton, did not exhibit such pH-dependent shifts. This finding was interpreted in terms of the restricted orientation of the iron-bound 4-nitroimidazole and 4-fluoroimidazole in the heme crevice, where the imino proton is not exposed to the solvent sphere. In the methemoglobin-imidazole complex, however, the pH-dependence of the hyperfine shifts was observed, in contrast to the case of imidazole-metmyoglobin. This finding was also interpreted as arising from the specific orientation of the iron-bound exogenous imidazole in the methemoglobin heme pocket. 2. (2) Two sets of heme methyl proton resonances were detected for the 4-fluoroimidazole-metmyoglobin complex and these were attributed to the two tautomeric forms of the iron-bound 4-fluoroimidazole. The relative proportion of the two tautomers was dependent on both pH and temperature. The temperature dependence of the hyperfine shifts of the two species indicates that they are in a single spin state.

Three-dimensional display of human organs from computed tomograms

Methods of hidden surface removal and shading for computer-displayed surfaces are proposed. If the surface to be displayed is approximated by a large number of square faces of restricted orientation, the methods proposed in this paper work at least an order of magnitude faster than previously published methods. A situation in which such approximation is natural is the display of organs based on data obtained by the reconstruction of the internal structure of a body from multiple shadowgraphs such as X-ray photographs (computed tomography). The methods can also be used for rapidly achieving some but not all of the aims of surface modeling in more general situations. The hidden surface removal method is based on the Z-buffer algorithm (no sorting is required), with modifications which make use of the nature of the assumed surface approximation. The artifact caused by approximating the curved surface with squares is reduced by low-pass filtering of the picture to be displayed. The results are demonstrated by displays of actual human organs based on data provided by computed tomography.

High field 1H NMR studies. Influence of the cis/trans isomerism on the N-acetyl 4-hydroxy proline ring conformation

Complete analysis of the high resolution NMR spectra of N-acetyl 4-hydroxy Proline (AcOH-PRO) has been made and it is shown that conformational cyclic changes may be explained in terms of cis/trans isomerism of the N-Acetyl group. In extension it is suggested that the greater stabilities of the trans forms of poly(PRO) and poly(OH-PRO) as well as many proline-containing peptides and polymers may be explained in terms of restricted orientation of the C-4 carbon atoms.

Thermodynamics of the Rate of Binding of Ouabain to the Sodium, Potassium-Adenosine Triphosphatase

Abstract The binding of [3H]ouabain to sodium and potassium ion-activated adenosine triphosphatase in the presence of [magnesium, ATP, sodium, and potassium] adheres to first order kinetics over a wide range of monovalent cation concentrations and over a temperature range of 0–37°. The kinetic data fit an equation of the type [see PDF for equation] The thermodynamic quantities calculated for Ki, the dissociation constant for potassium for the site which modulates the rate of ouabain interaction, were ΔH0 = -13.6 Cal per mole and ΔS0 = -27.1 cal per mole deg. The thermodynamic quantities calculated for Ka, the dissociation constant for sodium for this same site, were ΔH0 = 4.1 Cal per mole and ΔS0 = 21.7 cal per mole deg. These values indicate that a restricted orientation of the receptor is required for binding of potassium and that the binding leads to a stable complex. In contrast, sodium binding has a large positive entropy. These differences suggest that the site has a size restriction for the binding of the cations. The activation energy for the rate of ouabain binding in the presence of [magnesium, ATP plus sodium] was 21.2 ± 1.0 Cal per mole and is quite close to the values of the activation energy of [3H]ouabain binding that occurs in the presence of [magnesium plus ATP] (Ea = 23.4 ± 0.8 Cal per mole) and in the presence of [magnesium plus inorganic phosphate] (Ea = 22.8 ± 1.5 Cal per mole). This is consistent with the concept that a single conformation of the glycoside receptor is required for drug interaction. Lack of curvature in the Arrhenius plots suggests that, in contrast to the hydrolysis of ATP, ouabain binding is not influenced by the fluidity of the lipid matrix.

Properties of Reduced Charge Montmorillonites: Hydrated Cu(II) Ions as a Spectroscopic Probe

AbstractA series of Cu(II) reduced charge montmorillonites (RCM) of varying charge reduction has been prepared by exchange of the parent Li(I)-Na(I) mineral with CuCl2 in 95 per cent ethanol solution. The Cu(II) exchange capacity, as determined by Na(I) exchange in 1:1 (v/v) ethanol-water, is a linear function of the fraction of Li(I) initially present on the exchange sites, F. Selective Cu(II)-saturation on internal and external sites was achieved at maximum charge reduction (F = 1.0). Water sorption isotherms and (001) basal spacings are interpreted in terms of an increasing tendency toward interlayer collapse with increasing charge reduction. Because of the higher hydration energy of the Cu(II) ion, however, the fraction of non-expansible interlayers at a given F value is lower than those present in the corresponding Li(I)-Na(I) RCM. Electron spin resonance spectra of oriented samples show that under air-dried conditions (ca. 40 per cent r.h.) the predominant Cu(II) species present, whether on internal or external sites, is the planar Cu(H2O)2+4 ion. The symmetry axis of the ion is oriented perpendicular to the a-b plane of the silicate sheets. In the presence of a full partial pressure of water, the Cu(II) ions on the external sites and those which are in expansible interlayers become totally hydrated Cu(H2O)2+6 and tumble rapidly. The Cu(H2O)2+4 ions in non-expansible layers retain their restricted orientation on the silicate surface. Some general conclusions have been drawn regarding the nature of charge distribution in the mineral.

CLASSIFICATION OF INFLAMMATIONS OF THE THROAT

THE CLASSIFICATION of the different involvements and diseases of the throat is a problem which has defied and tried the skill and the didactic ability of laryngologists. The difficulty is due to several factors: first, to the existing confusion of terminology, which, in turn, is due to the fact that the throat does not represent anatomically or physiologically one single organ but a space made up of somewhat independent elements in which the upper digestive and respiratory systems are related; second, to the restricted orientation of those who have undertaken the task of dividing the conditions encountered in this region into classes. The two factors just given are, from my point of view, the greatest obstacles which one has to overcome in trying to distribute methodically and didactically the various pathologic conditions of the throat. CRITERIA The criterion to be followed when separating the pathologic processes located in the throat

Deformation lamellae in quartz from the Ajibik formation, Michigan

Petrofabric study of a specimen of quartzite from a shear zone in the Ajibik formation of the Marquette district, Michigan, contributes the following to the quartz lamellae problem: Excellent orientation relations of the deformation lamellae and crystal axes indicate the control of the quartz orientation by the lamellae rather than by the axes. A translation hypothesis is considered to explain the relations best. A fixed glide line [ m : r ] and variable glide planes containing [ m : r ] satisfy best the irrational lamellae planes and the restricted orientation of the axes associated with them. The character of the lamellae orientation leads to the tentative conclusion that the strain was nonrotational. The possibility is mentioned that some of the quartz maxima in recrystallized tectonites may be remnants of axis concentrations related to lamellae which have since been obliterated by the recrystallization.