El Roque de Los Muchachos Site Characteristics. III. Analysis of Atmospheric Dust and Aerosol Extinction

Canary Islands are normally interested by dominant North-East winds that, in some meteorological conditions, can transport sand at high altitude from the Sahara desert. The dust may affect the efficiency of the telescopes and decreases the transparency of the sky. In order to maximize the scientific return of the telescopes located at the ORM, we present an analysis of the atmospheric dust content and its effects on astronomical observations. B, V and I dust aerosol astronomical extinction are derived. Using a 5 years series database of data taken from the four channel TNG dust monitor, we compute a mean hourly and daily values of the dust content. We have detected particles having size 0.3, 0.5, 1.0 and 5.0 um. Using a power law we have derived the content of 10.0 um particles. We found a typical local dust concentration ranging from 3x10^6 particles per cubic meter at 0.3 um, to 10^3 at 5.0 um and 10 at 10.0 um, increasing up to 3 order of magnitudes during the dust storms, with a relative higher increase of 1.0, 5.0 and 10.0 um particles. The number of local dust storm events is the same in winter- and summertime, but, the average background and storm-related increases in the dust concentration in summer are significantly higher than in winter. In a uniform approximation, during the dust storms, an average height of the dust layer of 2.5 km above the telescope is inferred. During the sand storms La Palma Island is affected by an almost uniform layer extending up to 5 km above the sea level, down, at least the height of the telescope. The visible extinction is dominated by particles at 1.0, 5.0 and 10.0 um. In agreement with the results from Carlsberg Automatic Meridian Circle (CAMC) we find a typical extinction during dust storms of about 0.2 mag/airmass.Comment: Accepted for publication in A&A. 9 pages, 11 figures. This work is the continuation of a series of papers concerning a detailed study of the Astroclimatology at ORM. The two previous papers (both Lombardi et al.) have reference PASP.2006.118.1198-1204 and PASP.2007.119.292-30

El Roque de Los Muchachos Site Characteristics. II. Analysis of Wind, Relative Humidity and Air Pressure

In this paper we present an analysis of wind speed, wind direction, relative humidity and air pressure taken at TNG, CAMC and NOT at Observatorio del Roque de Los Muchachos, in the Canary Islands. Data are compared in order to check local variations and both long term and short term trends of the microclimate. Furthermore, influence of wind speed on the astronomical seeing is estimated to the aim to better understand the influence of wide scale parameters on local meteorological data. The three telescopes show different prevailing wind direction, wind speed, relative humidity and air pressure confirming differences in local microclimate. We found that seeing deteriorates when wind speed is lower than 3.3 m/s. Comparison in terms of wind speed and high relative humidity (> 90%) shows that TNG seems to have optimal observational conditions with respect to CAMC and NOT. Air pressure analysis shows that ORM is dominated by high pressure. Short time variations of pressure anticipate temperature variations tipically by 2-3 hours, this property vanishes in time scales higher than some hours and disappear in longer time scales.Comment: 10 pages, 9 figures, accepted for publication in PAS

Epstein-Barr Virus, Cytomegalovirus, and Other Viral Infections in Children After Liver Transplantatlon

We studied 51 consecutive pediatric patients for the frequency and morbidity of viral infections after liver transplantation. The incidence of primary (67%) and reactivation (48%) Epstein-Barr virus (EBV) infections and reactivation (88%) cytomegalovirus (CMV) infection was comparable to that seen in adult transplant recipients. However, fewer pediatric than adult transplant recipients experienced primary CMV infection (P `.01). Five (38%) of 13CMV infections were symptomatic and included hepatitis, pneumonitis, enteritis, and mononucleosis. Tho of 14 patients with primary EBV infection subsequently developed, at two months and two years after initial infection, an EBV-associated lymphoproliferative syndrome, and one of 10 patients with reactivated EBV infection developed a possible EBV-associated febrile encephalopathy. Other viruses causing infection in these children included herpes simplex virus, varicella-zoster virus, adenovirus, parainfluenza virus, respiratory syncytial virus, and rotavirus. © 1987 by The University of Chicago

El Roque de Los Muchachos site characteristics, I.Temperature analysis

In this paper we present an analysis of temperature taken at two telescopes located at the Observatorio del Roque de Los Muchachos in the Canary Islands. More than 20 years of measurements at CAMC are included. The analysis of the data from TNG and CAMC are compared in order to check local variations and long term trends. Furthermore, the temperatures at different heights are correlated to the quality of astronomical seeing. We considered the correlation of NAO Index and annual downtime with mean annual temperatures. The final aim of this work is to better understand the influence of wide scale parameters on local meteorological data. The analysis is done using a statistical approach. From each long series of data we compute the hourly averages and than the monthly averages in order to reduce the short time fluctuations due to the day/night cycle. A particular care is used to minimize any effect due to biases in case of lacking of data. Finally, we compute the annual average from the monthly ones. The two telescopes show similar trends. There is an increase of temperatures of about 1.0 deg/10yrs from the annual means and a more rapid increase of the annual minimums then the maximums. We found that positive NAO Index reduces the increase of temperatures, and accelerates the decrease. Moreover, there is no evidence that positive NAO Index corresponds to a lower number of non-observable nights. Finally, seeing deteriorates when the gradient of temperatures between 2 and 10 m above the ground is greater than -0.6 deg.Comment: 8 pages, 9 figures, accepted by PAS

Do Quasars Lens Quasars?

If the unexpectedly high frequency of quasar pairs with very different component redshifts is due to the lensing of a population of background quasars by the foreground quasar, typical lens masses must be \sim10^{12}M_{\sun} and the sum of all such quasar lenses would have to contain $\sim0.005$ times the closure density of the Universe. It then seems plausible that a very high fraction of all \sim10^{12} M_{\sun} gravitational lenses with redshifts $z\sim1$ contain quasars. Here I propose that these systems have evolved to form the present population of massive galaxies with M$_{\rm B}\leq-22$ and M >5\times10^{11} M_{\sun}.Comment: 6 pages, aas style, ams symbols, ApJL (accepted

Pediatric liver transplantation from neonatal donors

Sixteen recipients of neonatal liver grafts were compared with 114 contemporaneous pediatric recipients of grafts from older donors. Graft and patient survival were worse in the neonatal group although the differences were not statistically significant. Patients with neonatal livers who had no technical complications required a longer time postoperatively to correct jaundice and a prolonged prothrombin time. These functional differences were limited to the 1st postoperative month and the end result was the same as with liver transplantation from older donors. © 1992 Springer-Verlag

Dynamics of high-energy multimode Raman solitons

The dynamics of high-energy Raman solitons in graded-index multimode fibers is both numerically and experimentally investigated. The propagation of high-power pulses produces nonlinear losses, that quench up to 80% of the fiber transmission. In such a regime, several solitons arising from the fission of ultra-short femtosecond pulses manifest unique features: pulse width, Raman self-frequency shift and soliton order remain nearly constant over a broad range of energies

Calorimetry of photon gases in nonlinear multimode optical fibers

Because of their massless nature, photons do not interact in linear optical media. However, light beam propagation in nonlinear media permits to break this paradigm, and makes it possible to observe photon-photon interactions. Based on this principle, a beam of light propagating in a nonlinear multimode optical system can be described as a gas of interacting particles. As a consequence, the spatio-temporal evolution of this photon gas is expressed in terms of macroscopic thermodynamic variables, e.g., temperature and chemical potential. Moreover, the gas evolution is subject to experiencing typical thermodynamic phenomena, such as thermalization. The meaning of thermodynamic variables associated with the photon gas must not be confused with their classical counterparts, e.g., the gas temperature cannot be measured by means of standard thermometers. Although the thermodynamic parameters of a multimode photon gas result from a rigorous mathematical derivation, their physical meaning is still unclear. In this work, we report on optical calorimetric measurements, which exploit nonlinear beam propagation in multimode optical fibers. Our results show that, indeed, heat only flows from a hot to a cold photon gas subsystem. This provides an unequivocal demonstration that nonlinear multimode wave propagation phenomena are governed by the second law of thermodynamics. In addition to be fundamental, our findings provide a new approach to light-by-light activated management of laser beams

NICMOS Imaging of the Host Galaxies of z ~ 2 - 3 Radio-Quiet Quasars

We have made a deep NICMOS imaging study of a sample of 5 z ~ 2 - 3 radio-quiet quasars with low absolute nuclear luminosities, and we have detected apparent host galaxies in all of these. Most of the hosts have luminosities approximately equal to present-day L*, with a range from 0.2 L* to about 4 L*. These host galaxies have magnitudes and sizes consistent with those of the Lyman break galaxies at similar redshifts and at similar rest wavelengths, but are about two magnitudes fainter than high-z powerful radio galaxies. The hosts of our high-z sample are comparable to or less luminous than the hosts of the low-z RQQs with similar nuclear absolute magnitudes. However, the high z galaxies are more compact than the hosts of the low z quasars, and probably have only 10 - 20% of the stellar mass of their low-z counterparts. Application of the M(bulge)/M(BH) relation found for present-day spheroids to the stellar masses implied for the high z host galaxies would indicate that they contain black holes with masses around 10^8 Msolar. Comparison to their nuclear magnitudes implies accretion rates that are near or at the Eddington limit. Although these high z hosts already contain supermassive black holes, the galaxies will need to grow significantly to evolve into present-day L* galaxies. These results are basically consistent with theoretical predictions for the hierarchical buildup of the galaxy host and its relation to the central supermassive black hole.Comment: 25 pages, 13 figures, accepted for publication in Ap

High energy pulse dynamics in multimode GRIN fibers

High energy, ultra-short multimode soliton pulse fission is observed and numerically studied in multimode GRIN fibers, showing complex dynamics bringing to multiple fundamental solitons that do not entirely follow standard single mode soliton perturbation theory predictions