Dynamical Models of Elliptical Galaxies in z=0.5 Clusters: II. Mass-to-Light Ratio Evolution without Fundamental Plane Assumptions

We study M/L evolution of early-type galaxies using dynamical modeling of resolved internal kinematics. This makes fewer assumptions than Fundamental Plane (FP) studies and provides a powerful new approach for studying galaxy evolution. We focus on the sample of 25 galaxies in clusters at z=0.5 modeled in Paper I. For comparison we compile and homogenize M/L literature data for 60 nearby galaxies that were modeled in comparable detail. The nearby sample obeys log(M/L)_B = Z + S log(sigma_eff/[200 km/s]), with Z = 0.896 +/- 0.010, S = 0.992 +/- 0.054, and sigma_eff the effective velocity dispersion. The z=0.5 sample follows a similar relation but with lower zeropoint. The implied M/L evolution is Delta log(M/L) / Delta z = -0.457 +/- 0.046(random) +/- 0.078(systematic), consistent with passive evolution following high-redshift formation. This agrees with the FP results for this sample by van Dokkum & van der Marel. This confirms that FP evolution tracks M/L evolution, which is an important verification of the assumptions that underly FP studies. However, while we find more FP evolution for galaxies of low sigma_eff (or low mass), the dynamical M/L evolution instead shows little trend with sigma_eff. We argue that this difference can be plausibly attributed to a combination of two effects: (a) evolution in structural galaxy properties other than M/L; and (b) the neglect of rotational support in studies of FP evolution. The results leave the question open whether the low-mass galaxies in the sample have younger population ages than the high-mass galaxies. This highlights the general importance in the study of population ages for complementing dynamical measurements with broad-band colors or spectroscopic population diagnostics.Comment: ApJ, submitted; 17 pages formatted with emulateap

The fate of quasiparticles in the superconducting state

Quasiparticle properties in the superconducting state are masked by the superfluid and are not directly accessible to infrared spectroscopy. We show how one can use a Kramers--Kronig transformation to separate the quasiparticle from superfluid response and extract intrinsic quasiparticle properties in the superconducting state. We also address the issue of a narrow quasiparticle peak observed in microwave measurements, and demonstrate how it can be combined with infrared measurements to obtain unified picture of electrodynamic properties of cuprate superconductors

Interface superconductivity in LaAlO3_{3}-SrTiO3_{3} heterostructures

The interface superconductivity in LaAlO$_{3}$-SrTiO$_{3}$ heterostructures reveals a non-monotonic behavior of the critical temperature as a function of the two-dimensional density of charge carriers. We develop a theoretical description of interface superconductivity in strongly polar heterostructures, based on the dielectric function formalism. The density dependence of the critical temperature is calculated accounting for all phonon branches including different types of optical (interface and half-space) and acoustic phonons. The LO- and acoustic-phonon-mediated electron-electron interaction is shown to be the dominating mechanism governing the superconducting phase transition in the heterostructure.Comment: 7 pages, 2 figures, accepted in Physical Review

Microscopic mechanisms for the Fermi-liquid behavior of Nb-doped strontium titanate

The relaxation rate in Nb-doped strontium titanate involving different scattering channels is investigated theoretically. It is demonstrated that the total relaxation rate in SrTiO_{3} is provided mainly by two mechanisms. The Baber electron-electron scattering with participation of both Coulomb and phonon-mediated electron-electron interactions provides the T^{2}-dependence of the relaxation rate. The scattering on the potential landscape caused by impurities is responsible for the residual relaxation rate at low temperatures. A good agreement with experiment is achieved accounting for all phonon branches in strontium titanate, both the optical and acoustic phonons. It is shown that the effective electron-electron interaction can be attractive in strontium titanate, and provides superconductivity at low temperatures and Fermi-liquid response in a wide range of temperatures. Thus our microscopic model supports the notion that superconductivity and Fermi-liquid properties of n-type SrTiO_{3} have a common origin.Comment: 22 pages, 6 figures, 1 tabl

Comment on ''Phase Diagram of La2−x_{2-x}Srx_xCuO4_4 Probed in the Infrared: Imprints of Charge Stripe Excitations''

Recently Lucarelli {\it et al.} have reported\cite{lucarelli} temperature-dependence of the in-plane optical reflectivity of La$_{2-x}$Sr$_x$CuO$_4$ over a wide doping range, focusing on the infrared peaks at 30 cm$^{-1}$ (for $x$=0.12), 250 cm$^{-1}$ and 510 cm$^{-1}$. They interpreted the first peak (30 cm$^{-1}$) as a signature of charge stripe ordering, while the latter two (250 cm$^{-1}$ and 510 cm$^{-1}$) are attributed to the polaronic charge excitations. However, careful readers would notice that the reported spectra are largely different from those so far measured on the same system. As we illustrate below, all these peaks are caused by an uncontrolled leakage of the c-axis reflectivity into the measured spectra.Comment: 1 page, 1 figure, accepted for publication in Phys. Rev. Lett 91 (2003

LMC Self-lensing from a new perspective

We present a new analysis on the issue of the location of the observed microlensing events in direction of the Large Magellanic Cloud (LMC). This is carried out starting from a recently drawn coherent picture of the geometrical structure and dynamics of the LMC disk and by considering different configurations for the LMC bar. In this framework it clearly emerges that the spatial distribution of the events observed so far shows a near--far asymmetry. This turns out to be compatible with the optical depth calculated for the LMC halo objects. In this perspective, our main conclusion, supported by a statistical analysis on the outcome of an evaluation of the microlensing rate, is that self lensing can not account for all the observed events. Finally we propose a general inequality to calculate quickly an upper limit to the optical depth along a line of view through the LMC center.Comment: revised version (minor changes) Accepted for publication in A&

Gene and cell therapy based treatment strategies for inflammatory bowel diseases

Gene and cell therapy based treatment strategies for inflammatory bowel diseases Inflammatoire darmziekten (IBD) Hoofdstuk 1 van dit proefschrift geeft een algemeen overzicht van de huidige stand van zaken in het onderzoek naar gen, en celtherapeutisch behandelingen in IBD. Het onderzoek naar gentherapie in IBD bevindt zich in een experimentele fase en er is nog geen onderzoek gedaan bij pati_nten. Voor celtherapie is er, voor het gebruik van mesenchymale stamcellen in de behandeling van IBD wel mensgebonden onderzoek verricht, al valt dit celtype buiten het bereik van dit proefschrift. Deel I van dit proefschrift richt zich op de ontwikkeling van een celtherapeutisch behandeling voor IBD en Deel II op de ontwikkeling van een gentherapeutisch behandeling voor IBD. Hoofdstuk 2 en 3 beschrijven de ontwikkeling van een nieuwe methode die het maken van regulatoire T cellen in het laboratorium mogelijk maakt. Hoe deze cellen succesvol konden worden ingezet om ontsteking van de darm te verminderen in een experimenteel model van IBD informeert Hoofdstuk 3. Hoofdstuk 4, beschrijft we een studie naar het voorkomen van antilichamen tegen de adeno-geassocieerde virussen (AAV) in een groep van IBD pati_nten en gezonde vrijwilligers. Dit onderzoek was van belang, omdat in kaart wordt gebracht, welke type AAV het beste gebruikt kan worden voor de verdere ontwikkeling van een gentherapeutische behandeling voor IBD. Met behulp van deze kennis is een type AAV gekozen dat gebruikt is om genetisch materiaal over te brengen in een experimenteel model van IBD. Dit genetische materiaal zorgt ervoor dat er een eiwit wordt aangemaakt dat het immuunsysteem kan onderdrukken. Hoofdstuk 5 beschrijft dat met deze AAV vector de ontsteking in de darm in dit model minder wordt. Verder wordt aangetoond dat in dit experimentele systeem de vermindering van deze ontsteking gepaard gaat met een toename van het aantal regulatoire T cellen. Hoofdstuk 6 en 7 beschrijven in meer detail het belang van antilichamen tegen de AAV vector. Deze antilichamen zouden, mogelijkerwijs gentherapie met de AAV minder effici_nt kunnen maken. Daarom werd (Hoofdstuk 6) een experimenteel model ontwikkeld waarmee de invloed van deze antilichamen kan worden bestudeerd. Er wordt aangetoond dat in de muis, antilichamen tegen de AAV, al in hele lage concentraties een negatieve invloed hebben op de behandeling met AAV. Hoofdstuk 7 beschrijft een strategie om de aanmaak van deze antilichamen te verminderen. Dit kon bewerkstelligd worden met een medicament, te weten Bortezomib, wat zeer specifiek antilichaam producerende cellen in het lichaam onschadelijk maakt. Echter, deze aanpak was niet voldoende om deze antilichamen geheel te verwijderen en daarom dient er in de toekomst verder onderzoek te worden gedaan. Dit onderwerp komt terug in Hoofdstuk 8, de algemene discussie van dit proefschrift. Verder wordt in dit hoofdstuk commentaar gegeven op noodzaak op vooruitgang in het IBD onderzoeksveld dat voor de toekomst gen, en celtherapie mogelijk moet kunnen maken.The printing of this thesis was financially supported by: Abbvie, Dr. Falk Pharma Benelux BV, Ferring, Nederlandse Vereniging voor Gastro-Enterologie, Pfizer, Tramedico, uniQure, Vifor Pharma BV, Zambon Nederland BV.UBL - phd migration 201

Transverse optical plasmons in layered superconductors

We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Josephson couplings. We show that our model is in quantitative agreement with the recent experimental observation by a number of groups of a peak at the Josephson plasma frequency in the optical conductivity of La$_{1.85}$Sr$_{0.15}$CuO$_4$Comment: Proceedings of LT21, in press, 4 pages, Latex with LTpaper.sty and epsfig.sty, 2 postscript figure