The sub-energetic gamma-ray burst GRB 031203 as a cosmic analogue to the nearby GRB 980425.

Over the six years since the discovery of the gamma-ray burst GRB 980425, which was associated with the nearby (distance approximately 40 Mpc) supernova 1998bw, astronomers have debated fiercely the nature of this event. Relative to bursts located at cosmological distance (redshift z approximately 1), GRB 980425 was under-luminous in gamma-rays by three orders of magnitude. Radio calorimetry showed that the explosion was sub-energetic by a factor of 10. Here we report observations of the radio and X-ray afterglow of the recent GRB 031203 (refs 5-7), which has a redshift of z = 0.105. We demonstrate that it too is sub-energetic which, when taken together with the low gamma-ray luminosity, suggests that GRB 031203 is the first cosmic analogue to GRB 980425. We find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows. We expect intensive follow-up of faint bursts with smooth gamma-ray light curves (common to both GRB 031203 and 980425) to reveal a large population of such events.

Computer simulations of the belousov-zhabotinsky reaction.

Morphological features of the two-dimensional Belousov-Zhabotinsky reaction were modeled with an algorithm involving only two simple parameters, one describing the productivity of the reaction on a local scale length and the other characterizing the delay or quiescent time after the localized reaction. Self-organizing wavelike structures, including single-and multiarmed spirals, were most easily generated.

A retrospective review of the efficacy and safety of prostaglandin E2 with premature rupture of the membranes at term.

OBJECTIVE: The purpose of this study was to assess rates of endometritis, clinical chorioamnionitis, cesarean delivery, and neonatal sepsis from the records of patients with premature rupture of the membranes (PROM) and an unfavorable cervix treated with vaginal prostaglandin (PG) E2 in comparison with those in the literature. METHODS: Using a computer data base at Denver General Hospital, we identified 146 women with PROM and cervical dilatation of 2 cm or less at term who were treated with PGE2 gel or suppositories. The records were reviewed to identify rates of maternal and neonatal infection and complications, as well as cesarean delivery. RESULTS: The cesarean rate was 12%. Chorioamnionitis developed in 6.8% of the study group and endometritis in 2%. Neonatal complications were limited to two with low Apgar scores (less than 7 at 5 minutes), one with microbiologically confirmed sepsis, and two with positive urine counterimmunoelectrophoresis for group B streptococcus. The only instance of neonatal sepsis occurred in a patient with rupture of membranes longer than 24 hours. CONCLUSIONS: The use of vaginal PGE2 suppositories for induction of labor and cervical ripening in term patients with PROM was accompanied by a high rate of vaginal delivery and a low rate of maternal and neonatal complications in a city hospital setting.

Experience in a series of fimbriectomies.

In a series of 247 consecutive sterilizations by fimbriectomy performed at the Denver General Hospital, a failure rate of 2.4% was found. The literature is reviewed, and these results are compared with results of other series. In several of the fimbriectomy series with more successful outcome, modifications of the technique originally described were used. The difficulties associated with the Kroener technique are discussed. The fimbriectomy failures were caused by either lack of resection of all of the fimbriae or the presence of tuboperitoneal fistulas, both congenital and acquired. Fimbriectomy should not be regarded as the method of choice for sterilization unless one can ensure adequate surgical exposure and complete removal of the fibria, including the fimbria ovarica.

Microsurgical anastomosis of the rabbit oviduct using 9-0 monofilament polyglycolic acid suture.

As part of a larger study to determine which factors are important in fallopian tube reconstruction, 9-0 monofilament polyglycolic acid suture on a 145 micron-needle was used for rabbit oviduct microsurgical anastomosis. A 100% pregnancy rate in five rabbits with no disruption of the endosalpingial or muscular layers was noted. Of special note, the suture was totally resorbed, and no suture residuum or surrounging reaction was noted. The suture material appears to fulfill the criteria for an ideal suture described at the beginning of the paper. This is the first report of the use of a 9-0 monofilament polyglycolic acid suture.

The neonate with unexpected acidemia.

We attempted to determine the etiology and clinical significance of unexpected acidemia in otherwise healthy neonates. A retrospective review was performed of the umbilical cord pH in 11,203 deliveries performed at Denver General Hospital, with an umbilical artery pH < 7.13 (3 SD below the mean) selected as the definition of neonatal acidemia. Among those neonates weighing > 2.5 kg with umbilical artery pH < 7.13, 76 were expected to have acidemia because of signs of severe fetal distress. There were 59 neonates with unexpected acidemia, having umbilical artery pH < 7.13, with no definite etiology found. In 96% of cases of unexpected acidemia, the neonates were discharged with their mothers, while 84% of the expected cases went home with their mothers. In excess of $880,000 was spent performing routine umbilical blood pH determinations without any apparent clinical or legal benefit. Routine umbilical blood gas studies on all neonates does not appear to be indicated for either clinical or legal reasons.

Measuring cosmological parameters.

In this review, the status of measurements of the matter density (Omegam), the vacuum energy density or cosmological constant (OmegaLambda), the Hubble constant (H0), and the ages of the oldest measured objects (t0) are summarized. Three independent types of methods for measuring the Hubble constant are considered: the measurement of time delays in multiply imaged quasars, the Sunyaev-Zel'dovich effect in clusters, and Cepheid-based extragalactic distances. Many recent independent dynamical measurements are yielding a low value for the matter density (Omegam approximately 0.2-0.3). A wide range of Hubble constant measurements appear to be converging in the range of 60-80 km/sec per megaparsec. Areas where future improvements are likely to be made soon are highlighted-in particular, measurements of anisotropies in the cosmic microwave background. Particular attention is paid to sources of systematic error and the assumptions that underlie many of the measurement methods.

Determination of the Hubble constant.

Establishing accurate extragalactic distances has provided an immense challenge to astronomers since the 1920s. The situation has improved dramatically as better detectors have become available, and as several new, promising techniques have been developed. For the first time in the history of this difficult field, relative distances to galaxies are being compared on a case-by-case basis, and their quantitative agreement is being established. New instrumentation, the development of new techniques for measuring distances, and recent measurements with the Hubble Space telescope all have resulted in new distances to galaxies with precision at the +/-5-20% level. The current statistical uncertainty in some methods for measuring H(0) is now only a few percent; with systematic errors, the total uncertainty is approaching +/-10%. Hence, the historical factor-of-two uncertainty in the value of the H(0) is now behind us.

Comparison of umbilical artery pH and 5-minute Apgar score in the low-birth-weight and very-low-birth-weight infant.

The division between "normal" and low Apgar scores is based largely on data obtained from term newborns and may not apply to the premature infant. Umbilical artery pH has been suggested as a better indicator of intrapartum asphyxia. We examined the charts of 558 infants with birth weights less than or equal to 2500 gm with respect to umbilical artery pH, 5-minute Apgar scores, and birth weight percentiles. A positive correlation between birth weight and 5-minute Apgar score was noted. No such relationship existed between birth weight and umbilical artery pH. Within birth weight groups, small-for-gestational-age infants have higher Apgar scores and lower umbilical artery pH values than their appropriate-for-gestational age counterparts.

Clinical evaluation of a low lint surgical sponge.

To evaluate a new low lint, nonwoven surgical sponge material, a prospective, stratified, randomized, single blind study of 232 patients was carried out. Patients studied underwent thoracic, upper abdominal or lower abdominal operations. The new material, in the form of laparotomy pads and sponges, was compared with cotton gauze. Safety of the material was evaluated by a battery of biochemical and hematologic tests. No clinically significant differences were seen. Effectiveness was evaluated by measuring fluid absorption. The new material was significantly more effective than cotton gauze in both configurations studied. Since this article was completed, the sponge material has been refabricated into laparotomy pads which are appreciably softer and more comformable than the study pads. The newest revision has been cleared by the Food and Drug Administration for clinical use.

The association of maternal low birthweight and infant low birthweight in a racially mixed population.

The association between maternal low birthweight (LBW) and infant low birthweight has been explored in previous studies in mainly middle and upper income, Caucasian populations. This study investigated whether the association found in these populations is true in a racially mixed, low socio-economic group. A case-control methodology was used and estimates of association were derived by means of logistic regression analyses. Data were gathered for 167 LBW infant-mother dyads and 338 adequate weight infant-mother controls matched on race and parity. The odds of a LBW infant having a LBW mother were 80% more likely than for adequate weight infants (OR = 1.80, 95% CI 1.14-2.84). This association was stronger for Hispanic women and their infants than for Black or non-Hispanic White women and their infants. Women who were both preterm and LBW had the higher estimate of risk for infant LBW than women who were LBW due to intrauterine growth retardation (IUGR). As found in previous research, the estimate of association between maternal LBW and infant LBW was greater for those infants who were LBW due to IUGR than those who were LBW due to being premature. The question of whether maternal LBW is also associated with increased risk of neonatal mortality and morbidity is as yet left unanswered.

A distance to the galaxy NGC4258 from observations of Cepheid variable stars.

Cepheid variable stars pulsate in a way that is correlated with their intrinsic luminosity, making them useful as 'standard candles' for determining distances to galaxies; the potential systematic uncertainties in the resulting distances have been estimated to be only 8-10%. They have played a crucial role in establishing the extragalactic distance scale and hence the value of the Hubble constant. Here we report observations of Cepheids in the nearby galaxy NGC4258; the distance calculated from the Cepheids is 8.1 +/- 0.4 Mpc, where the uncertainty does not include possible systematic errors. There is an independently determined geometric distance to this galaxy of 7.2 +/- 0.5 Mpc, based on the observed proper motions of water masers orbiting the central black hole; the distances differ by 1.3sigma. If the maser-based distance is adopted and the Cepheid distance scale revised accordingly, the derived value of the Hubble constant would increase by 12 +/- 9%, while the expansion age of the Universe would decrease by the same amount.