A study of photoinduced processes in pyridine-based gels is presented. Poly(4-vinyl pyridine) dissolved in pyridine with water addition forms a photosensitive material. Under irradiation at the main absorption at 250 nm, a new intense absorption at 360 nm and an emission at 515 nm appeared. Upon continuation of radiation, together with an increase in the intensity of the new absorption, a prolonged tail through the whole visible range is observed. A new far red-shifted emission arises in correlation with the absorption spectrum changes. The presence of lower energy aggregates leads to polymer morphology changes. Short-range aggregates enhance polymer-polymer interactions. Long range aggregates have a tendency to crystallize. The photoinduced morphology changes was studied by transmission electron microscopy (TEM) of the polymer thin film and differential scanning calorimetry (DSC) of the gel. Phase separated species, micelles-like forms with domain size over 200 nm, and nanocrystals with average size 20-30 nm are demonstrated.
The structure of microemulsions prepd. by the anionic gemini surfactant didodecyl di-Ph ether disulfonate (C12-DADS) was investigated by a solvatochromic probe and NMR diffusion measurements. The NMR measurements indicate the presence of bicontinuous and oil-in-water microemulsions depending on microemulsion compn. The absorbance spectra of the solvatochromic probe, Nile red, indicate the solubilization of the probe in different sites, in agreement with the NMR findings. It was also found that the microemulsions were capable of dissolving the hydrophobic probe, Nile red, up to four times better than expected if it were simply dissolved in the toluene phase. [on SciFinder(R)]
Accelerating Turing machines are abstract devices that have the same computational structure as Turing machines, but can perform super-tasks. I argue that performing super-tasks alone does not buy more computational power, and that accelerating Turing machines do not solve the halting problem. To show this, I analyze the reasoning that leads to Thomson's paradox, point out that the paradox rests on a conflation of different perspectives of accelerating processes, and conclude that the same conflation underlies the claim that accelerating Turing machines can solve the halting problem.
The properties of didodecyldiphenylether disulfonate gemini-type surfactants were studied and compared to mono-alkylated and monosulfonated analogous surfactants. Dynamic and equil. surface tension measurements indicate that the gemini surfactants have a higher surface activity compared to that of the monoalkyl analogs. The gemini-type surfactants have much larger surface area per mol., opposite effect of C no. on CMC and considerable swelling of the micelles upon increasing surfactant concn. Detn. of aggregation nos. by fluorescence measurements reveals that the longer chain gemini surfactants form micelles having <10 mols. per micelle. [on SciFinder(R)]
The hypersonic impact of a molecular cluster at a hard surface generates a hot and compressed globule that in a very short while expands and shatters. Even at impact velocities below the onset of ionization this hot matter has a time varying transient dipole that can emit light. We discuss the spectral range and the power (in absolute units) of the emission spectrum. The computational results for the emission spectrum from our molecular dynamics simulation are compared to extrapolations of experimental results for collision-induced absorption at lower energies. The very short time interval during which the cluster survives intact means that the emitted power is low so options for increasing the yield of photons are discussed.
In addition to the familiar bending and stretching deformations, lipid monolayers and bilayers in their disordered state are often subjected to tilt deformations, occurring for instance in structural rearrangements accompanying membrane fusion, or upon insertion of ``oblique'' hydrophobic proteins into lipid bilayers. We study the elastic response of a flat lipid monolayer to a tilt deformation, using the spatial and conformational average of the chain end-to-end vector from the membrane normal to define a macroscopic membrane tilt. The physical origin and magnitude of the corresponding tilt modulus k(t) is analyzed using two complementary theoretical approaches. The first is a phenomenological model showing that the tilt and bending deformations are decoupled and the effects of inter-chain correlations on the tilt modulus is small. The second is based on a molecular-level mean-field theory of chain packing, enabling numerical evaluation of the tilt modulus for realistic, multi-conformation, chain models. Both approaches reveal that the tilt modulus involves two major contributions. The first is elastic in origin, arising from the stretching of the hydrocarbon chains upon a tilt deformation and reflecting the loss of chain conformational freedom associated with chain stretching. The second, purely entropic, contribution results from the constraints imposed by a tilt deformation on the fluctuations of chain director orientations. Using the chain-packing theory we compute the two contributions numerically as a function of the cross-sectional area per chain. The elastic and entropic terms are shown to dominate the value of k(t) for small and large areas per chain, respectively. For typical cross-sectional areas of lipid chains in biological membranes they areof comparable magnitude, yielding k(t) approximate to 0.2k(B)T/Angstrom(2).
Most present applications of time-dependent density functional theory use adiabatic functionals, i.e. the effective potential at time t is determined solely by the density at the same time. This paper discusses a method that aims to go beyond this approximation, by incorporating "memory" effects: the potential will depend not only on present behavior but also on the past. In order to ensure the derived potentials are causal, we formulate the action on the Keldysh contour for electrons in electromagnetic fields, from which we derive suitable Kohn-Sham equations. The exchange correlation action is now a functional of the electron density and velocity field. A specific action functional is constructed which is Galilean invariant and yields a causal vector potential term to the Kohn-Sham equations that incorporates causal memory effects. We show explicitly that the exchange-correlation Lorentz force is zero. The potential is consistent with known dynamical properties of the homogeneous electron gas (in the linear response limit).
Beginning with Durkheim's analysis of secular rituals, this essay explores the spillover from love-talk to religious-talk in Plato's 'Phaedrus', Shakespeare's 'Romeo and Juliet' and Sacher-Masoch's 'Venus in Furs'. Religious categories are deployed in these texts in three distinct ways: in Plato, the temptation to worship the beloved is present but is also avoided because of shame; in Shakespeare, the category of worship enables positing the loved one's supposed holiness in order for it to be transgressed; whilst in Sacher-Masoch, worship and ritual in relation to the love object are literally acted out. I claim that such moments exemplify three ways of relating to erotic merging and three modalities of creating erotic force. The essay's grander thesis is that the contemporary aggrandizing of love, the present-day "religion of love" in secular culture, can be understood through erotic love's (rather limited) ability to channel and feed needs that were previously organized into religious experience.
The UV absorption spectra of neat water clusters (H2O)(n) of sizes in the range of n = 8-50 are computed. The simple model used for the excited states includes the dependence of the excitonic interactions on both the intermolecular and intramolecular coordinates. For a cluster (H2O)(n), n excitonic potential energy surfaces are computed for geometries in the Franck-Condon region. The Coker-Watts potential is used to describe the interactions in the electronic ground state, and molecular dynamics simulations are performed to sample geometries for the classical Franck-Condon calculations. There are numerous crossings of different excitonic potential surfaces for (H2O)(n) in the range of the geometries sampled. The main findings are (i) the main absorption peak of (H2O)(n) shifts to the blue and increases in width as the cluster size n is increased; (ii) the widths of the absorption bands increase with temperature, e.g., for (H2O)(20), the width is 1.2 eV at 80 K and 1.6 eV at 220 K; (iii) several well-resolved peaks within the absorption band are found for some of the systems at certain temperatures, and in such cases, each of the peaks generally results from absorption into different excitonic states; (iv) although the absorption peaks are strongly shifted to the blue, with respect to the (H2O) monomer, for some cluster sizes, a weak absorption tail to the red side is also observed as the temperature increases.
Betty Rojtman. 2004. “Un texte sans autorité: La Bible.” In Text and Voice, The Rhetoric of Authority in the Middle Ages, edited by Marianne Borch. Odense: University Press of Southern Denmark.
Global precipitation is monitored from a variety of platforms including spaceborne, ground-, and ocean-based platforms. Intercomparisons of these observations are crucial to validating the measurements and providing confidence for each measurement technique. Probability distribution functions of rain rates are used to compare satellite and ground-based radar observations. A preferred adjustment technique for improving rain rate distribution estimates is identified using measurements from ground-based radar and rain gauges within the coverage area of the radar. The underwater measurement of rainfall shows similarities to radar measurements, but with intermediate spatial resolution and high temporal resolution. Reconciling these different measurement techniques provides understanding and confidence for all of the methods.
Global precipitation is monitored from a variety of platforms including spaceborne, ground-, and ocean-based platforms. Intercomparisons of these observations are crucial to validating the measurements and providing confidence for each measurement technique. Probability distribution functions of rain rates are used to compare satellite and ground-based radar observations. A preferred adjustment technique for improving rain rate distribution estimates is identified using measurements from ground-based radar and rain gauges within the coverage area of the radar. The underwater measurement of rainfall shows similarities to radar measurements, but with intermediate spatial resolution and high temporal resolution. Reconciling these different measurement techniques provides understanding and confidence for all of the methods.
