Increasing permeability of phospholipid bilayer membranes to alanine with synthetic α-aminophosphonate carriers

A series of aminophosphonates was synthesized, and their ability to carry alanine, a model hydrophilic molecule, across phospholipid bilayer membranes was evaluated. Aminophosphonates facilitate the membrane transport at moderate rates, which make them a suitable platform for the design of carriers for continuous drug release devices. © 2008 Elsevier Ltd. All rights reserved

Speakable and unspeakable in cosmology: dark matter vs. gravitational self energies. Hubble's constant, the cosmological term and all that

The inadequacy of the present cosmological picture is underlined. The central issue of energy and particles-photons number conservation is addressed. It is shown that consideration of gravitational self energy is paramount both for matter and for radiation to bring present data estimates of matter and radiation density and the radius of the universe towards agreement with the Planck scale quantities from which it should have consistently evolved. Particle creation is proven to play a fundamental role in the evolution of the Universe. It is argued that we might be living inside an expanding black hole

Panoramic Views of the Cygnus Loop

We present a complete atlas of the Cygnus Loop supernova remnant in the light of [O III] (5007), H alpha, and [S II] (6717, 6731). Despite its shell-like appearance, the Cygnus Loop is not a current example of a Sedov-Taylor blast wave. Rather, the optical emission traces interactions of the supernova blast wave with clumps of gas. The surrounding interstellar medium forms the walls of a cavity through which the blast wave now propagates, including a nearly complete shell in which non-radiative filaments are detected. The Cygnus Loop blast wave is not breaking out of a dense cloud, but is instead running into confining walls. The interstellar medium dominates not only the appearance of the Cygnus Loop but also the continued evolution of the blast wave. If this is a typical example of a supernova remnant, then global models of the interstellar medium must account for such significant blast wave deceleration.Comment: 28 pages AAS Latex, 28 black+white figures, 6 color figures. To be published in The Astrophysical Journal Supplement Serie

A Century of Cosmology

In the century since Einstein's anno mirabilis of 1905, our concept of the Universe has expanded from Kapteyn's flattened disk of stars only 10 kpc across to an observed horizon about 30 Gpc across that is only a tiny fraction of an immensely large inflated bubble. The expansion of our knowledge about the Universe, both in the types of data and the sheer quantity of data, has been just as dramatic. This talk will summarize this century of progress and our current understanding of the cosmos.Comment: Talk presented at the "Relativistic Astrophysics and Cosmology - Einstein's Legacy" meeting in Munich, Nov 2005. Proceedings will be published in the Springer-Verlag "ESO Astrophysics Symposia" series. 10 pages Latex with 2 figure

Beyond a pale blue dot : how to search for possible bio-signatures on earth-like planets

The Earth viewed from outside the Solar system would be identified merely like a pale blue dot, as coined by Carl Sagan. In order to detect possible signatures of the presence of life on a second earth among several terrestrial planets discovered in a habit-able zone, one has to develop and establish a methodology to characterize the planet as something beyond a mere pale blue dot. We pay particular attention to the periodic change of the color of the dot according to the rotation of the planet. Because of the large-scale inhomogeneous distribution of the planetary surface, the reflected light of the dot comprises different color components corresponding to land, ocean, ice, and cloud that cover the surface of the planet. If we decompose the color of the dot into several principle components, in turn, one can identify the presence of the different surface components. Furthermore, the vegetation on the earth is known to share a remarkable reflection signature; the reflection becomes significantly enhanced at wave-lengths longer than 760nm, which is known as a red-edge of the vegetation. If one can identify the corresponding color signature in a pale blue dot, it can be used as a unique probe of the presence of life. I will describe the feasibility of the methodology for future space missions, and consider the direction towards astrobiology from an astrophysicist's point of view.Comment: 11 pages, 5 figures, published in Yamagishi A., Kakegawa T., Usui T. (eds) Astrobiology. Springer, Singapore (2019

Lemaitre-Tolman-Bondi model and accelerating expansion

I discuss the spherically symmetric but inhomogeneous Lemaitre-Tolman- Bondi (LTB) metric, which provides an exact toy model for an inhomogeneous universe. Since we observe light rays from the past light cone, not the expansion of the universe, spatial variation in matter density and Hubble rate can have the same effect on redshift as acceleration in a perfectly homogeneous universe. As a consequence, a simple spatial variation in the Hubble rate can account for the distant supernova data in a dust universe without any dark energy. I also review various attempts towards a semirealistic description of the universe based on the LTB model.Comment: Invited Review for a special Gen. Rel. Grav. issue on Dark Energy. 17 pages, 3 figure

The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies

We review a sample of the early literature in which the reality of the expansion is discussed, explain Hubble's reticence to accept the expansion as real, and contrast the Tolman surface brightness test with three other modern tests. We search for the Tolman surface brightness depression with redshift using the Hubble Space Telescope (HST) data from Paper III for 34 early-type galaxies from the three clusters Cl 1324+3011 (z=0.76), Cl 1604+4304 (z=0.90), and Cl 1604+4321 (z=0.92). Depressions of the surface brightness relative to the zero-redshift fiducial lines in the mean surface brightness, log linear radius diagrams of Paper I are found for all three clusters. Expressed as the exponent, n, in 2.5 log (1 + z)^n mag, the value of n for all three clusters is n = 2.59 +/- 0.17 in the R band and 3.37 +/- 0.13 in the I band for a q_o = 1/2 model. The sensitivity of the result to the assumed value of q_o is shown to be less than 23% between q_o = 0 and +1. For a true Tolman signal with n = 4, the luminosity evolution in the look-back time, expressed as the exponent in 2.5 log (1+z)^(4-n) mag, must then be between 1.72 to 1.19 in the R band and 0.94 to 0.45 in the I band. We show that this is precisely the range expected from the evolutionary models of Bruzual & Charlot. We conclude that the Tolman surface brightness test is consistent with the reality of the expansion. We have also used the high-redshift HST data to test the ``tired light'' speculation for a non-expansion model for the redshift. The HST data rule out the ``tired light'' model at a significance level of better than 10 sigma.Comment: 36 pages, 6 figures; accepted for publication in the Astronomical Journa

Testing The Friedmann Equation: The Expansion of the Universe During Big-Bang Nucleosynthesis

In conventional general relativity, the expansion rate H of a Robertson-Walker universe is related to the energy density by the Friedmann equation. Aside from the present day, the only epoch at which we can constrain the expansion history in a model-independent way is during Big-Bang Nucleosynthesis (BBN). We consider a simple two-parameter characterization of the behavior of H during BBN and derive constraints on this parameter space, finding that the allowed region of parameter space is essentially one-dimensional. We also study the effects of a large neutrino asymmetry within this framework. Our results provide a simple way to compare an alternative cosmology to the observational requirement of matching the primordial abundances of the light elements.Comment: 18 pages, Final version to be published in Phys. Rev.

GMRT HI observations of the Eridanus group of galaxies

The GMRT HI 21cm-line observations of galaxies in the Eridanus group are presented. The Eridanus group, at a distance of ~23 Mpc, is a loose group of \~200 galaxies. The group extends more than 10 Mpc in projection. The velocity dispersion of the galaxies in the group is ~240 km/s. The galaxies are clustered into different sub-groups. The overall population mix of the group is 30% (E+S0) and 70% (Sp+Irr). The observations of 57 Eridanus galaxies were carried out with the GMRT for ~200 hour. HI emission was detected from 31 galaxies. The channel rms of ~1.0 mJy beam^{-1} was achieved for most of the image-cubes made with 4 hour of data. The corresponding HI column density sensitivity (3-sigma) is ~1x10^{20} cm^{-2} for a velocity-width of ~13.4 km/s. The 3-sigma detection limit of HI mass is ~1.2x10^{7} M_sun for a line-width of 50 km/s. Total HI images, HI velocity fields, global HI line profiles, HI mass surface densities, HI disk parameters and HI rotation curves are presented. The velocity fields are analysed separately for the approaching and the receding sides of the galaxies. This data will be used to study the HI and the radio continuum properties, the Tully-Fisher relations, the dark matter halos, and the kinematical and HI lopsidedness in galaxies.Comment: 75 pages including HI atlas; Accepted for publication in Journal of Astroph. & Astron. March, 200

The isolated interacting galaxy pair NGC 5426/27 (Arp 271)

We present H alpha observations of the isolated interacting galaxy pair NGC 5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. The FWHM map and the residual velocities map were also computed to study the role of non-circular motions of the gas. Most of these motions can be associated with the presence of spiral arms and structure such as central bars. We found a small bar-like structure in NGC 5426, a distorted velocity field for NGC 5427 and a bridge-like feature between both galaxies which seems to be associated with NGC 5426. Using the observed rotation curves, a range of possible masses was computed for each galaxy. These were compared with the orbital mass of the pair derived from the relative motion of the participants. The rotation curve of each galaxy was also used to fit different mass distribution models considering the most common theoretical dark halo models. An analysis of the interaction process is presented and a possible 3D scenario for this encounter is also suggested.Comment: 27 pages, 15 figures, to be published in Astronomy & Astrophysic