Translational diffusion and fluid domain connectivity in a two-component, two-phase phospholipid bilayer.

The two-dimensional connectivity is examined for mixed bilayers of dimyristoyl phosphatidylcholine (DMPC) and distearoyl phosphatidylcholine (DSPC) as a function of composition and temperature at constant pressure using the fluorescence recovery after photobleaching (FRAP) method. These phospholipid mixtures exhibit peritectic behavior with a large region in which both gel and liquid crystalline phases coexist. Dilauroyl phosphatidylethanolamine covalently linked through the amino function in its head group to the fluorescent nitrobenzodiazolyl group (NBD-DLPE) was used as the fluorescent probe in this study, because it was found to partition almost exclusively in the liquid crystalline phase. The results of these studies show the line of connectivity to be close to the liquidus line on the phase diagram over a rather broad range of concentrations. In this range, a gel phase comprising approximately 20% of the system disconnects a liquid crystalline phase comprising 80% of the system. The implications of this result are discussed for domain shape and the organization of biological membrane components

Історико-методологічна конкуренція етноцентризму та антропоцентризму в євроінтеграції України

Статтю присвячено актуальній проблемі гуманістичної трансформації методологічних підстав критичного мислення у дослідженні та викладанні історії. Наголошується на ключовій ролі ідеї свободи у теоретико-методологічному дискурсі. На прикладі конфлікту інтерпретацій, акцентується потреба розвитку навичок самостійного аналізу історичних фактів і процесів як найважливішої передумови продуктивного соціального діалогу й гарантії особистої свободи громадянина.Статья посвящена актуальной проблеме гуманистической трансформации методологических оснований критического мышления в изучении и преподавании истории. Подчеркивается ключевая роль идеи свободы в теоретико-методологическом дискурсе. На примере объективной оценки существующего конфликта интерпретаций, акцентируется потребность развития навыков самостоятельного анализа исторических фактов и процессов как важнейшей предпосылки продуктивного социального диалога и гарантии личной свободы гражданина.The article deals with the problem of humanistic transformation of critical thinking methodology in history (teaching and learning aspects).The key-role of the idea of freedom in theoretic and methodological discourse is being underlined.The example to evaluate objectively the existing conflict of interpretations helps to accentuate the necessity of developing the skills to analyse historical facts and processes as an important precondition for effective social dialogue and private civil freedom guarantees

Gamma-Ray Bursts and Quantum Cosmic Censorship

Gamma-ray bursts are believed to result from the coalescence of binary neutron stars. However, the standard proposals for conversion of the gravitational energy to thermal energy have difficulties. We show that if the merger of the two neutron stars results in a naked singularity, instead of a black hole, the ensuing quantum particle creation can provide the requisite thermal energy in a straightforward way. The back-reaction of the created particles can avoid the formation of the naked singularity predicted by the classical theory. Hence cosmic censorship holds in the quantum theory, even if it were to be violated in classical general relativity.Comment: Latex File, 6 pages. This essay received the third award from the Gravity Research Foundation for the year 199

Hidden Consequence of Active Local Lorentz Invariance

In this paper we investigate a hidden consequence of the hypothesis that Lagrangians and field equations must be invariant under active local Lorentz transformations. We show that this hypothesis implies in an equivalence between spacetime structures with several curvature and torsion possibilities.Comment: Some misprints appearing in the published version have been correcte

Dirac-Hestenes spinor fields in Riemann-Cartan spacetime

In this paper we study Dirac-Hestenes spinor fields (DHSF) on a four-dimensional Riemann-Cartan spacetime (RCST). We prove that these fields must be defined as certain equivalence classes of even sections of the Clifford bundle (over the RCST), thereby being certain particular sections of a new bundle named Spin-Clifford bundle (SCB). The conditions for the existence of the SCB are studied and are shown to be equivalent to the famous Geroch's theorem concerning to the existence of spinor structures in a Lorentzian spacetime. We introduce also the covariant and algebraic Dirac spinor fields and compare these with DHSF, showing that all the three kinds of spinor fields contain the same mathematical and physical information. We clarify also the notion of (Crumeyrolle's) amorphous spinors (Dirac-K\"ahler spinor fields are of this type), showing that they cannot be used to describe fermionic fields. We develop a rigorous theory for the covariant derivatives of Clifford fields (sections of the Clifford bundle (CB)) and of Dirac-Hestenes spinor fields. We show how to generalize the original Dirac-Hestenes equation in Minkowski spacetime for the case of a RCST. Our results are obtained from a variational principle formulated through the multiform derivative approach to Lagrangian field theory in the Clifford bundle.Comment: 45 pages, special macros kapproc.sty and makro822.te

Simultaneous Water Vapor and Dry Air Optical Path Length Measurements and Compensation with the Large Binocular Telescope Interferometer

The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 $\mu$m). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feedforward approach to stabilize the path length fluctuations seen by the LBTI nuller.Comment: SPIE conference proceeding

The Mass Spectrum of Neutrinos

In a previous paper we showed that Weyl equation possess superluminal solutions and moreover we showed that those solutions that are eigenstates of the parity operator seem to describe a coupled pair of a monopole anti-monopole system. This result suggests to look for a solution of Maxwell equation \partialF^{\infty}=-gJ with a current J as source and such that the Lorentz force on the current is null. We first identify a solution where J={\gamma}^{5}J_{m}is a spacelike field (even if F is not a superluminal solution of the homogeneous Maxwell equation). More surprisingly we find that there exists a solution F of the free Maxwell \partialF=0 that is equivalent to the non homogeneous equation for F^{\infty}. Once this result is proved it suggests by itself to look for more general subluminal and superluminal solutions F of the free Maxwell equation equivalent to a non homogeneous Maxwell equation for a field F_{0} with a current term as source which may be subluminal or superluminal. We exhibit one such subluminal solution, for which the Dirac-Hestenes spinor field {\psi} associated the electromagnetic field F_{0} satisfies a Dirac equation for a bradyonic neutrino under the ansatz that the current is ce^{{\lambda}{\gamma}^{5}}g{\psi}{\gamma}^{0}{\psi}, with g the quantum of magnetic charge and {\lambda} a constant to be determined in such a way that the auto-force be null. Together with Dirac's quantization condition this gives a quantized mass spectrum (Eq.49) for the neutrinos, with the masses of the different flavor neutrinos being of the same order of magnitude (Eq.50) which is in accord with recent experimental findings. As a last surprise we show that the mass spectrum found in the previous case continues to hold if the current is taken spacelike, i.e., ce^{{\lambda}{\gamma}^{5}}g{\psi}_{>}{\gamma}^{3}{\psi}_{>} with {\psi}_{>}, in this case, satisfying a tachyonic Dirac-Hestenes equation.Comment: This version corrects some misprints, has a new remark and a new referenc

Bose Condensation and the BTZ Black Hole

Although all popular approaches to quantum gravity are able to recover the Bekenstein-Hawking entropy-area law in the thermodynamic limit, there are significant differences in their descriptions of the microstates and in the application of statistics. Therefore they can have significantly different phenomenological implications. For example, requiring indistinguishability of the elementary degrees of freedom should lead to changes in the black hole's radiative porperties away from the thermodynamic limit and at low temperatures. We demonstrate this for the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. The energy eigenstates and statistical entropy in the thermodynamic limit of the BTZ black hole were obtained earlier by us via symmetry reduced canonical quantum gravity. In that model the BTZ black hole behaves as a system of Bosonic mass shells moving in a one dimensional harmonic trap. Bose condensation does not occur in the thermodynamic limit but this system possesses a finite critical temperature, $T_c$, and exhibits a large condensate fraction below $T_c$ when the number of shells is finite.Comment: 5 pages, 5 figures. Published versio