Relating magnetic reconnection to coronal heating.

It is clear that the solar corona is being heated and that coronal magnetic fields undergo reconnection all the time. Here we attempt to show that these two facts are related--i.e. coronal reconnection generates heat. This attempt must address the fact that topological change of field lines does not automatically generate heat. We present one case of flux emergence where we have measured the rate of coronal magnetic reconnection and the rate of energy dissipation in the corona. The ratio of these two, [Formula: see text], is a current comparable to the amount of current expected to flow along the boundary separating the emerged flux from the pre-existing flux overlying it. We can generalize this relation to the overall corona in quiet Sun or in active regions. Doing so yields estimates for the contribution to coronal heating from magnetic reconnection. These estimated rates are comparable to the amount required to maintain the corona at its observed temperature.

Have the boundaries of the 'grey zone' of perinatal resuscitation changed for extremely preterm infants over 20 years?

AIM: To determine the boundaries of the grey zone of discretionary resuscitation over the past 20 years. BACKGROUND: As the likelihood of survival improves over time, the BW- and GA-specific boundaries of discretionary nonresuscitation should fall. HYPOTHESIS: Between 1988 and 2008 reductions in BW- and GA-specific mortality would drive a parallel reduction in BW and GA boundaries of discretionary resuscitation. METHODS: We determined the likelihood of resuscitation and survival to NICU discharge for all infants born <700 g or <26 gestational weeks from 1988 to 2008. In addition, for 1988, 1993, 1998, 2003 and 2008, we determined the BW and GA for the 10 smallest infants who were resuscitated, and the 10 largest infants who were not resuscitated. We excluded any infant born with congenital anomaly. RESULTS: Mortality fell from 80% in 1988 to 28% in 2008, and as expected, the percentage who were resuscitated rose from 63% in 1988-93 to 95% in 2004-2008. However, unexpectedly, over the 20-year study period, the smallest infants who were resuscitated despite extreme immaturity did not change (450-550 g and 23-24 weeks) and the largest infants not resuscitated did not change (600-700 g and 23-24 weeks. CONCLUSION: Neither the BW nor GA boundaries of the grey zone of discretionary resuscitation have fallen over the past 20 years. Factors guiding resuscitation at the border of viability are complex and incompletely understood.

Effect of heat treatment on microcrack healing behavior of a machinable dental ceramic.

The purpose of this study was to evaluate the effect of annealing in air on the crack healing behavior of a machinable dental ceramic (Vita Mark II). The glass transition temperature and the softening point were determined by dilatometry. Polished Vita Mark II blocks (n = 12) were indented with a Vickers indenter under a 9.8 N load. Optical micrographs were taken immediately after indentation, and the crack lengths were measured. The specimens were annealed at 900 degrees C for either 30 min, 1 h, or 2 h. One group was indented and heat treated at 400 degrees C for 2 h as control. The ratio of crack length after annealing to crack length before annealing treatment was calculated for each indentation. Scanning electron microscopy was performed before and after annealing at 900 degrees C for 1 h. Scanning electron microscopy revealed shortening and blunting of the cracks after annealing. Annealing in air at 900 degrees C for either 30 min, 1 or 2 h significantly reduced the mean crack length of an indented machinable dental ceramic compared to the control group. However, the mean biaxial flexural strength was not significantly affected by an annealing treatment.

Using utilization review information to improve hospital efficiency.

Hospitals are currently under great pressure to improve the efficiency of internal operations without sacrificing quality of care. In the rush to do this, they often overlook an extremely useful source of information that already exists--data routinely collected as part of the utilization review (UR) process. This article describes a system using UR data for management purposes that was developed in a large urban teaching hospital. The components described are: (1) data collected systematically by trained reviewers applying the Appropriateness Evaluation Protocol; (2) software for data collection using inexpensive, highly portable computers; and (3) formats for reporting UR findings to hospital administrators and physicians. Information derived from UR in the study hospital is discussed, as well as factors to be considered in adapting some or all of the system's components in other hospitals.