A Direct Upper Limit on the Density of Cosmological Dust from the Absence of an X-ray Scattering Halo around the z=4.3 QSO 1508+5714

We report on the results of a search for an intergalactic X-ray dust scattering halo in a deep observation of the bright, high-redshift quasar QSO 1508+5714 with the Chandra X-ray Observatory. We do not detect such a halo. Our result implies an upper limit on the density of diffuse, large-grained intergalactic dust of Omega_ dust < 2 x 10^-6, assuming a characteristic grain size of 1micron. The result demonstrates the sensitivity of this technique for detecting very small amounts of intergalactic dust which are very hard to detect otherwise. This will allow us to put important constraints on systematic effects induced by extinction on the interpretation of the SN Ia Hubble Diagram, as well as on the amount and properties of cosmological dust being expelled into the intergalactic medium at early z~2 times.Comment: 14 pages, 2 figures. to appear in ApJ, vol. 651, Nov. 200

Amniotic Membrane Transplantation for Ocular Surface Reconstruction

The purpose of this study is to analyze the clinical experience and the effect of human amniotic membrane transplantation on pterygium excision and bullous keratopathy. From January 1999 to January 2001 at University Hospital »Sestre milosrdnice« amniotic membrane transplantation was performed consecutively in 21 eyes: 11 eyes with bullous keratopathy and 10 with recurrent pterygia. In the group with bullous keratopathy epithelization took place in 19.6 days in 72.7% and the reduction of pain was satisfactory. Recurrence rate in group with recurrent pterygia was 20%. Based on the presented results it could be concluded that amniotic membrane transplantation can be considered as an effective alternative for treating severe ocular surface diseases and as an alternative for penetrating keratoplasty if there is a lack of graft

Glaucoma Triple Procedure: A One-site vs. a Two-site Approach

The purpose of this study is to describe and evaluate the success rate of combined glaucoma and small cataract surgery by means of a one-site versus two-site approach. Fifty-eight eyes of fifty-five patients undergoing combined surgery were operated: thirtyone eyes underwent two-site approach and twenty-seven eyes underwent one-site approach. Short term and long term mean intraocular pressure (IOP) was similar in both groups. There was no significant difference in postoperative inflammation and complication rates between two groups. There is no significant difference in the postoperative results in those two different approaches to perform combined operations of cataract and glaucoma

Sensitive observations at 1.4 and 250 GHz of z > 5 QSOs

We present 1.4 and 5 GHz observations taken with the Very Large Array (VLA), and observations at 250 GHz obtained with the Max-Planck millimeter bolometer (MAMBO) at the IRAM 30~m telescope, of ten optically selected Quasi-stellar Objects (QSOs) at 5.0 < z < 6.28. Four sources are detected at 1.4 GHz two of which are radio loud and are also detected at 5 GHz. These results are roughly consistent with there being no evolution of the radio-loud QSO fraction out to z~6. Three sources have been detected at 250 GHz or 350 GHz at much higher levels than their 1.4 GHz flux densities suggesting that the observed mm emission is likely thermal emission from warm dust, although more exotic possibilities cannot be precluded. The highest redshift source in our sample (J1030+0524 at z=6.28) is not detected at 1.4 or 250 GHz, but four fairly bright radio sources (flux density at 1.4GHz > 0.2 mJy) are detected in a 2' field centered on the QSO, including an edge-brightened ('FRII') double radio source with an extent of about 1'. A similar over-density of radio sources is seen in the field of the highest redshift QSO J1148+5251. We speculate that these over-densities of radio sources may indicate clusters along the lines-of-sight, in which case gravitational lensing by the cluster could magnify the QSO emission by a factor 2 or so without giving rise to arcsecond-scale distortions in the optical images of the QSOs.Comment: 25 pages, 12 figures. accepted by A

Redox Reactions on Anodised or Passivated Metals

The simple redox reactions on anodised or passivated metal (Al, Fe, Zn) were investigated by the current-potential method. The redox systems were chosen so that the electrochemical reaction was practically under the control of the diffusion in the electrolyte in case of unhindered charge transfer in the solid phase and on the contact electrode/electrolyte. Measurements were performed in a wider potential range, but on the previously anodised or passivated metal, in which case the potential range investigated was within the limits corresponding to low equivalent corrosion currents for the pure supporting electrolyte. In all the investigated cases the phenomena were observed, showing that the electron structure of the solid phase and possible potential barriers of the metal/phase layer/solution system had a predominant influence

An X-ray jet discovered by Chandra in the z=4.3 radio-selected quasar GB 1508+5714

We report the Chandra discovery of an X-ray jet associated with the redshift 4.3 radio-loud quasar GB 1508+5714. The jet X-ray emission peaks ~2 arcsec to the South-West of the quasar core. We present archival HST WFPC2 data of the quasar field which shows no optical emission at the location of the X-ray jet. We discuss possible emission mechanisms and give constraints to the magnetic field and energy densities for synchrotron radiation or for Compton scattering of the Cosmic Microwave Background radiation as the jet X-ray emission process.Comment: 5 pages, 4 figures, submitted to ApJ. Letters on Aug.13, accepted for publication in ApJ Letters on Oct.

A sample of radio-loud QSOs at redshift ~ 4

We obtained spectra of 60 red, starlike objects (E< 18.8) identified with FIRST radio sources, S_{1.4GHz} > 1 mJy. Eight are QSOs with redshift z> 3.6.Combined with our pilot search (Benn et al 2002), our sample of 121 candidates yields a total of 18 z > 3.6 QSOs (10 of these with z > 4.0). 8% of candidates with S_{1.4GHz} 10 mJy are QSOs with z > 3.6. The surface density of E 1mJy, z> 4 QSOs is 0.003 deg^{-2}. This is currently the only well-defined sample of radio-loud QSOs at z ~ 4 selected independently of radio spectral index. The QSOs are highly luminous in the optical (8 have M_B < -28, q_0 = 0.5, H_0 = 50 kms^{-1}Mpc^{-1}). The SEDs are as varied as those seen in optical searches for high-redshift QSOs, but the fraction of objects with weak (strongly self-absorbed) Ly alpha emission is marginally higher (3 out of 18) than for high-redshift QSOs from SDSS (5 out of 96).Comment: Accepted for publication in MNRAS, 9 pages, Latex, 5 postscript figures, 1 landscape table (postscript

Amniotic Membrane Transplantation for Ocular Surface Reconstruction in Neurotrophic Corneal Ulcera

The purpose of this study is to analyze clinical experience about the effects of human amniotic membrane transplantation in eyes with neurotrophic ulcers. In 11 eyes the application of amniotic membrane was performed since January 1999 because of neurotrophic ulcers. The follow up period was longer than 12 months: 19.76.0 months. The average healing period after the surgery was 1.60.6 weeks. All corneas were fluorescein negative even 12 months after operation. Visual acuity after the transplantation was similar to the one before the surgery in 8 eyes. In 3 eyes the visual acuity after the surgery was better than before. Amniotic membrane transplantation can be considered an effective alternative for treating persistent epithelial defects such as neurotrophic ulcers. It has some advantages over corneal transplantation: a relatively simple procedure, no allograft rejection and it could be particularly beneficial in countries where cornea shortage is apparent

In vivo electrophysiological characterization of TASK-1 deficient mice

Background/Aims: TASK-1 is a potassium channel predominantly expressed in heart and brain. We have previously shown that anesthetized TASK-1(-/-) mice have prolonged QT intervals in surface electrocardiograms (ECGs). In addition, heart rate variability quantified by time and frequency domain parameters was significantly altered in TASK-1(-/-) mice with a sympathetic preponderance. Aims of the present study were the analysis of QT intervals by telemetric ECGs, to determine potential influences of anesthesia and beta-adrenergic stimulation on repolarization in surface ECGs, to investigate in vivo electrophysiological parameters by intracardiac electrical stimulation and to quantify heart rate turbulence after ischemia/reperfusion or ventricular pacing in TASK-1(+/+) and TASK-1(-/-) mice. Methods: Rate corrected QT intervals (QTc) were recorded in conscious mice by telemetry and in surface ECGs following administration of various anesthetics (tribromoethanol (Avertin (R)), pentobarbital and isoflurane). TASK-1(+/+) and TASK-1(-/-) mice were characterized by programmed electrical stimulation using an intracardiac octapolar catheter. The baroreceptor reflex was analyzed by heart rate turbulence (turbulence onset and slope) after ischemia/reperfusion and by stimulated premature ventricular contractions