The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation

Haumea-one of the four known trans-Neptunian dwarf planets-is a very elongated and rapidly rotating body. In contrast to other dwarf planets, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system, and the Centaur Chiron was later found to possess something similar to Chariklo's rings. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected.

Images of asteroid 21 Lutetia: a remnant planetesimal from the early Solar System

Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.

Beta endorphin concentrations in human milk

BACKGROUND

The source and regulatory mechanisms that elevate beta-endorphin (beta-EP) approximately twofold higher than circulating plasma levels in the colostrum of lactating mothers are still unknown, and no studies have examined beta-EP availability previously during maturation phases of human milk. Therefore, the aim of this study was to determine whether concentrations of beta-EP vary over time between colostrum, transitional, and mature breast-milk and to evaluate whether this depends on the method of delivery.

METHODS

Mothers of healthy full-term and pre-term newborn infants who planned to breast-feed their newborn infants were considered for this study. They were consecutively recruited in one of 3 groups of 14, according to delivery method: group 1, vaginal delivery at term (gestational age 40.2 +/- 0.3 weeks; birth weight, 3.48 +/- 0.09 kg); group 2, preterm vaginal delivery (gestational age, 35.6 +/- 0.3 weeks; birth weight, 2.49 +/- 0.08 kg); and group 3, at-term elective cesarean section (gestational age, 39.0 +/- 0.3 weeks; birth weight, 3.32 +/- 0.14 kg). Three consecutive breast milk samples were obtained on the fourth day after birth, before each mother's discharge, and thereafter on the 10th and 30th postpartum days, close to expression of the colostrum, transitional, and mature milk production phases, respectively, to test beta-EP concentrations (beta-Endorphin 125I RIA; INCSTAR Corporation, Stillwater, MN). Data are presented as mean +/- standard deviation. Statistical comparison of beta-EP concentration among the three lactating mother groups was performed using the Kruskal-Wallis nonparametric test. In addition, to test the hypothesis of a trend toward smaller values with time of beta-EP, the authors computed within each mother group a P value per trend (Kruskal-Wallis test) of beta-EP concentration averages on the 4th, 10th, and 30th days, respectively. Student's t test for independent samples was used for the analysis of the other data. The 0.05 significance level was used in the statistical analysis. All computations were made by computer.

RESULTS

Colostrum beta-EP concentrations on the fourth postpartum day of group 1 and group 2 mothers who were delivered of a neonate vaginally, at term, or prematurely were significantly higher (P < 0.01) than colostrum levels of group 3 mothers who underwent cesarean section. Group 2 mothers who were delivered of a neonate vaginally and prematurely presented the highest beta-EP concentrations (P < 0.05), lasting until the transitional milk phase (10th day). No significant differences were found across all 3 groups of lactating mothers in mature milk (30th day) beta-EP concentrations. In addition, the beta-EP trend toward smaller values with time within each of the three groups on days 4, 10, and 30 was statistically significant (P < 0.01 per trend).

CONCLUSIONS

It is hypothesized that elevated beta-EP concentrations in colostrum and transitional milk of mothers who were vaginally delivered of infants may contribute to postnatal fetal adaptation, to overcoming birth stress of natural labor and delivery, and at the same time to the postnatal development of several related biologic functions of breast-fed infants.

Effect of postpartum anxiety on the colostral milk beta-endorphin concentrations of breastfeeding mothers

Peripartal maternal apprehension and anxiety are associated with abnormal labour, dystocia and higher rates of fetal and maternal morbidity. Since colostral beta-endorphin (beta-EP) concentrations are twofold higher than circulating levels, we hypothesised that substantial maternal emotional distress in puerperium might induce consistent changes in colostral beta endorphin galactopoiesis. To test this hypothesis, we assessed the effects of postpartum maternal anxiety (State-Trait Anxiety Inventory-Y form, Spielberger CD, Palo Alto, CA, USA, 1983) on colostral milk beta-EP levels (beta-endorphin 125I RIA, INCSTAR Corporation-Stillwater, Minnesota, USA) in a population of healthy lactating mothers, on the fourth postpartum discharge day, 14 after at term vaginal delivery, 14 after premature (> or = 34 <37 gestational weeks) vaginal delivery, and 14 after elective cesarean section. The colostral milk beta-EP concentrations of mothers who vaginally delivered at term or prematurely were significantly higher on the fourth postpartum day (6.0+/-0.5 and 6.6+/-0.7 vs. 4.3+/-0.4 pmol/l, respectively; P <0.05) than colostral levels of mothers who underwent caesarean section. At the same time, while trait anxiety levels (T, age corrected values) were unaffected by route and mode of delivery, in mothers presenting increased colostral milk beta-EP galactopoiesis after vaginal delivery there was a statistically significant negative correlation (r-0.40; P <0.03) between colostral milk beta-EP concentrations and trait anxiety levels. These data indicate that the labour pain and the vaginal delivery process play a central role in increasing colostral opioid availability for the breastfed neonate; peripartal maternal anxiety is a negative psychobiological determinant in opioid galactopoiesis, and possibly in the postnatal development of several related biological functions of growing infants.

Serum enzyme activities in premature infants with bronchopulmonary dysplasia

Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltranspeptidase (gamma-GT) and lactate dehydrogenase (LDH) activities were measured in 26 premature infants with bronchopulmonary dysplasia (BPD) (group 1), and in 24 premature controls, matched for gestational age and birth weight (group 2). Blood samples were taken serially on 3, 10, 20, 30 and 60 postpartum days. Group 1 and group 2 premature infants showed statistically higher LDH activities on the 3rd postpartum day. These differences disappeared later and LDH activities progressively decreased with time in both premature groups. Mean AST values of group 1 and group 2 premature infants were also significantly higher on the 3rd postpartum day. Subsequently, in all groups, AST showed a postpartal decrease, and a stabilization from the 10th day of life until the 2nd postnatal month. Mean ALT values were instead, comparable on the 3rd postnatal day and subsequently increased, although not significantly. Like the AST, gamma-GT of group 1 and group 2 premature infants were slightly more elevated on the 3rd postpartum day. The subsequent decrease was however transitory, and at 1 and 2 postnatal months a noticeable, significant progressive increase in mean values was found. It is concluded that serum ALT, AST, LDH and gamma-GT measurement of sick premature infants within the first 2 months of life are not significantly altered by the occurrence of BPD.

Risk factors of hypoglycemia in premature infants

Hypoglycemia is a frequent complication of preterm birth and may lead to later CNS damage. The hypoglycemia incidence and the relative risk factors for the affected preterm infants were assessed. We examined 1,500 preterm infants (<37 weeks of gestational age) consecutively admitted between January 1994 and December 1996 at the Department of Pediatrics of Padua University, and screened for hypoglycemia by Dextrostix within the first hour of life. Hypoglycemia was defined as blood glucose levels <40 mg% at Dextrostix. Among study prematures, 35% had hypoglycemia; while the incidence was 9% at levels of Dextrostix <20 mg%. The relative risk for hypoglycemia (odds ratio, OR) was computed assuming a 99% confidence interval (CI). We found 5 risk factors for hypoglycemia: cesarean section (OR 2.24, CI 1.66-3.03), intrauterine malnutrition (SGA) (OR 1.65, CI 1.08-2.53), NICU hospitalization (OR 1.45, CI 1. 09-1.93), gestational age between 30 and 33 weeks (OR 1.93, CI 1. 34-2.78), and twinning (OR 2.49, CI 1.77-3.56). At levels of Dextrostix <20 mg%, 3 more risk factors were found: cardiopulmonary resuscitation at birth (OR 4.06, CI 2.52-6.54), neonatal respiratory distress syndrome (OR 2.21, CI 1.34-3.36) and gestational age between 26 and 29 weeks (OR 2.16, CI 1.02-4.25). The identification of relative risk factors could be useful in improving the hypoglycemia prophylaxis, and in reducing related later CNS abnormalities.

Effect of prolonged dexamethasone on oxygen-dependency in infants with chronic lung disease

To determine the effect of prolonged dexamethasone therapy on oxygen-dependency clinical phase of prematures with bronchopulmonary dysplasia, we examined a consecutive group of 27 infants (birth weight, < 1500 g and gestational age, < 32 weeks), who remained with a static or deteriorating oxygen-dependency after weaning from the respirator [pre-treatment FiO2, mean +/- SEM over three days (31 +/- 2)%, range (27-73)%]. Twenty five out of 27 infants were weaned from supplemental oxygen during the 42-day steroid treatment period, with a mean (+/- SEM) duration of oxygen supplementation of 16 +/- 4 days. The distribution of the ratios of successive post-treatment FiO2 values with respect to pre-treatment FiO2 shows, on average, a progressive reduction with time. The percentage of the FiO2 decrease is statistically significant at a level of 2 and 3 SD after 3 days and 7 days, respectively and the average FiO2 fall, as function of time, follows an exponential law. It follows that the time spent in oxygen for a single patient may be determined, accounting for the individual severity of pre-treatment FiO2.

The origin of chondrules at jovian resonances

Isotopic dating indicates that chondrules were produced a few million years after the solar nebula formed. This timing is incompatible with dynamical lifetimes of small particles in the nebula and short time scales for the formation of planetesimals. Temporal and dynamical constraints can be reconciled if chondrules were produced by heating of debris from disrupted first-generation planetesimals. Jovian resonances can excite planetesimal eccentricities enough to cause collisional disruption and melting of dust by bow shocks in the nebular gas. The ages of chondrules may indicate the times of Jupiter's formation and dissipation of gas from the asteroidal region.

Factors associated with neonatal hypoglycemia in premature twins and singletons

Twin gestation is associated with higher rate of neonatal hypoglycemia than do singletons. We examined the role of specific risk factors associated with neonatal hypoglycemia of 216 premature twins and 1284 premature singletons, consecutively born in the years 1994-1996 in the Department of Pediatrics of Padua University, Italy. Significantly higher risk of hypoglycemia (Dextrostix < 40 and < 20 mg%) was found in twins vs singletons (54% vs 32%, OR 2.49, CI 1.77-3.56; 19% vs 8%, OR 2.65, CI 1.59-4.19, respectively). Gestational age of 34-37 weeks increased hypoglycemia risk for the premature twins (77% vs 51%, OR 3.20 CI 1.49-6.88). Twin deliveries statistically differed from those of singletons in several perinatal characteristics. More twins were born by cesarean section (85% vs 55%, OR 4.15, CI 2.48-6.95), and the birth weight of twins was much lower related to prematures with BW < 1.0 kg (12% vs 6%, OR 2.06, CI 1.11-3.82) and SGA (20% vs 10%, OR 2.41, CI 1.46-3.98). The risk of twin deliveries was increased at 30-33 weeks gestational age (25% vs 15%, OR 1.84; CI 1.17-2.90). Twins were found to have higher rates of hospitalization (50% vs 40%, OR 1.52, CI 1.04-2.23) and showed an increased risk of cardiorespiratory resuscitation (51% vs 31%, OR 2.36, CI 1.61-3.47), hypothermia (11% vs 4%, OR 3.02, CI 2.33-3.91), BPD (25% vs 19%, OR 2.55, CI 1.10-5.91), and PVL (4% vs 1%, OR 4.08, CI 1.23-13.5). Mortality was found more often (not significant) in premature twins. The risk for intrapartum and early neonatal morbidity was however, mostly reduced in hypoglycemic twins, while it was comparable between smaller or smaller weight discordant twins and larger twins. Similarly, SGA twins, and smaller or smaller weight-discordant twins did not show increased hypoglycemia risk. In conclusion, our findings suggest that the multiple gestation per se is the single most important relative risk factor of hypoglycemia in premature twins.

Gravitational scattering as a possible origin for giant planets at small stellar distances

The recent discoveries of massive planetary companions orbiting several solar-type stars pose a conundrum. Conventional models for the formation of giant planets (such as Jupiter and Saturn) place such objects at distances of several astronomical units from the parent star, whereas all but one of the new objects are on orbits well inside 1 AU; these planets must therefore have originated at larger distances and subsequently migrated inwards. One suggested migration mechanism invokes tidal interactions between the planet and the evolving circumstellar disk. Such a mechanism results in planets with small, essentially circular orbits, which appears to be the case for many of the new planets. But two of the objects have substantial orbital eccentricities, which are difficult to reconcile with a tidal-linkage model. Here we describe an alternative model for planetary migration that can account for these large orbital eccentricities. If a system of three or more giant planets form about a star, their orbits may become unstable as they gain mass by accreting gas from the circumstellar disk; subsequent gravitational encounters among these planets can eject one from the system while placing the others into highly eccentric orbits both closer and farther from the star.