Technique for detecting warm-hot intergalactic gas in quasar UV spectra

The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~ 1200 A. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being intrinsic to quasars. We consider the possibility that the steepening may result from a tenuous absorption component that is anticorrelated with large mass overdensities. UV sensitive satellites, whose detectors can extend down to 1000 A, can set a useful limit to such an absorption component through the search of a flux increase in the window 1050-1190 A (observer frame) with respect to an extrapolation of the continuum above 1230 A. Since the recent FUSE or HST-STIS data do not show any obvious discontinuity in this region, this effectively rules out the possibility that intergalactic HI absorption is very important, and it is concluded that most if not all of the steepening is intrinsic to quasars. A smaller flux discontinuity of order 1% cannot, however, be ruled out yet and would still be consistent with the warm-hot intergalactic component if it amounts to 30% of the baryonic mass, as predicted by some models of large scale structure formation, provided its temperature lies around 10^{5.5} K.Comment: 13 pages, 5 figures and 1 table, accepted for publication in Astrophysical Journal, typos corrected and correction for the faulty scaling of variable n_H^0 with redshif

The Effect of Disorder in an Orbitally Ordered Jahn-Teller Insulator

We study a two dimensional, two-band double-exchange model for $e_g$ electrons coupled to Jahn-Teller distortions in the presence of quenched disorder using a recently developed Monte-Carlo technique. In the absence of disorder the half-filled system at low temperatures is an orbitally ordered ferromagnetic insulator with a staggered pattern of Jahn-Teller distortions. We examine the finite temperature transition to the orbitally disordered phase and uncover a qualitative difference between the intermediate and strongly coupled systems, including a thermally driven insulator to metal crossover in the former case. Long range orbital order is suppressed in the presence of disorder and the system displays a tendency towards metastable states consisting of orbitally disordered stripe-like structures enclosing orbitally ordered domains.Comment: 10 pages, 9 figure

Controllable direction of liquid jets generated by thermocavitation within a droplet.

A high-velocity fluid stream ejected from an orifice or nozzle is a common mechanism to produce liquid jets in inkjet printers or to produce sprays among other applications. In the present research, we show the generation of liquid jets of controllable direction produced within a sessile water droplet by thermocavitation. The jets are driven by an acoustic shock wave emitted by the collapse of a hemispherical vapor bubble at the liquid-solid/substrate interface. The generated shock wave is reflected at the liquid-air interface due to acoustic impedance mismatch generating multiple reflections inside the droplet. During each reflection, a force is exerted on the interface driving the jets. Depending on the position of the generation of the bubble within the droplet, the mechanical energy of the shock wave is focused on different regions at the liquid-air interface, ejecting cylindrical liquid jets at different angles. The ejected jet angle dependence is explained by a simple ray tracing model of the propagation of the acoustic shock wave inside the droplet

Magnetic transitions in Pr2NiO4 single crystal

The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a first‐order character and involves both the out‐of‐plane and the in‐plane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a first‐order character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the out‐of‐phase component of χac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two field‐induced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the high‐field anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4

Incisivo lateral superior con dos raíces y dos conductos. Caso Clínico.

Las anomalías en la morfología del incisivo lateral superior son de muy baja frecuencia. Las anomalías de desarrollo radicular pueden presentarse como alteraciones tanto en el número de conductos, como en el número de raíces, así como en ambas regiones a la vez. En el presente trabajo, se reporta el caso de un paciente que se presenta a la consulta con malestar en el incisivo lateral superior izquierdo. En la radiografía preoperatoria se detectó la presencia de dos conductos y dos raíces, sin anomalía morfológica de su corona clínica, con requerimiento de tratamiento endodóntico. Concluimos que una correcta interpretación de las imágenes radiográficas preoperatorias es esencial, para poder detectar estas variantes y tomar las consideraciones necesarias para el adecuado tratamiento endodóntico.Fil: Martinez, P.. Universidad de Buenos Aires. Facultad de Odontología; Argentina;Fil: Boldo, M.. Universidad de Buenos Aires. Facultad de Odontología; Argentina;Fil: Corominola, P.. Universidad de Buenos Aires. Facultad de Odontología; Argentina;Fil: Sierra, L.. Universidad de Buenos Aires. Facultad de Odontología; Argentina;Fil: Lenarduzzi, A.. Universidad de Buenos Aires. Facultad de Odontología; Argentina;Fil: Fernández Solari, Jose Javier. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Fisiología; Argentina;Fil: Rodriguez, P.. Universidad de Buenos Aires. Facultad de Odontología; Argentina

For which infants with viral bronchiolitis could it be deemed appropriate to use albuterol, at least on a therapeutic trial basis?

Although there is increasing evidence showing that infants with viral bronchiolitis exhibit a high degree of heterogeneity, a core uncertainty shared by many clinicians is with regard to understanding which patients are most likely to benefit from bronchodilators such as albuterol. Based on our review, we concluded that older infants with rhinovirus (RV) bronchiolitis, especially those with a nasopharyngeal microbiome dominated by Haemophilus influenzae; those affected during nonpeak months or during non-respiratory syncytial virus (RSV) predominant months; those with wheezing at presentation; those with clinical characteristics such as atopic dermatitis or a family history of asthma in a first-degree relative; and those infants infected with RSV genotypes ON1 and BA, have the greatest likelihood of benefiting from albuterol. Presently, this patient profile could serve as the basis for rational albuterol administration in patients with viral bronchiolitis, at least on a therapeutic trial basis, and it could also be the starting point for future targeted randomized clinical trials (RCTs) on the use of albuterol among a subset of infants with bronchiolitis