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.

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.

Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 ± 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo p(V) = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm(-3) is inferred from the data.

A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation.

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1 AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163 ± 6 kilometres, density 2.52 ± 0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ∼1 nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.

Charon's size and an upper limit on its atmosphere from a stellar occultation.

Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600 km for the satellite's radius, which was later refined to 601.5 km (ref. 4). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, R(C) = 603.6 +/- 1.4 km (1sigma), and a density of rho = 1.71 +/- 0.08 g cm(-3). This occultation also provides upper limits of 110 and 15 (3sigma) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.

Using oligochaeta assemblages as an indicator of environmental changes.

We designed a field survey (the entire river length; not dammed: First and Second plateaus; dammed: Third Plateau) to test the hypothesis that the cascade of reservoirs promoted a reduction in species richness and changed the composition of Oligochaeta assemblage along the Iguaçu River. Changes in environmental variables and in richness and composition of Oligochaeta were summarized by Canonic Correspondence Analysis. Along the Iguaçu River, conductivity, and altitude decreased, whereas temperature increased. Oligochaeta composition showed a significant spatial variation, with higher abundances of the family Tubificidae and the genus Dero (Naididae) occurring in the First Plateau. In the Second and Third plateaus, few species were dominant, with increases in the presence of species of Naididae below dams. We found a clear decrease in species richness along the Iguaçu River. Moreover, we found that Oligochaeta assemblage was influenced by some environmental variables such as altitude, conductivity, substrate type and temperature, and by anthropogenic activities (human occupation and damming). The results supported the use of Oligochaeta as surrogate taxa to predict environmental changes along impacted (dammed and eutrophic) rivers. The validity of this was indicated by the strong and significant gradient registered, from the headwater to mouth of the Iguaçu River.

Eight years of monitoring aquatic Oligochaeta from the Baía and Ivinhema Rivers.

The aim of this study was to analyze the factors that influence spatial and temporal variations of the Oligochaeta assemblage in the Baía and Ivinhema Rivers, located in the Upper Paraná River floodplain (Mato Grosso do Sul State, Brazil). Samples of Oligochaeta were collected between February 2000 and November 2007. A total of 27 Oligochaeta species were identified. A Principal Component Analysis (PCA) of the physical and chemical variables was used to summarize the total variation in the data and to identify major environmental gradients. Detrended Correspondence Analysis (DCA) was conducted to verify possible spatial and temporal gradients in the Oligochaeta species distribution. The highest Oligochaeta species densities and richness values were recorded during limnophases. The intensity and amplitude of the potamophase influenced the density, richness and composition of Oligochaeta since many species were transported by high water current velocities and/or died due to the low oxygen levels that are characteristic of this phase. L. hoffmeisteri, P. descolei and A. pigueti were recorded in the potamophase and in the limnophase and we concluded that they are adapted to different conditions of rivers (lotic and lentic) due to the presence of these species during the entire study period in both rivers. Nevertheless, these species were dominant in the potamophase periods of these rivers as they have body adaptations to survive in these conditions.

[Ultrasonographic diagnosis in inflammatory-rheumatic changes of the shoulder joint]. / Sonographische Diagnostik bei entzündlich-rheumatischen Veränderungen am Schultergelenk.

Inflammatory rheumatoid changes of the shoulder joint are often diagnosed rather late, so therapy is largely directed towards pain reduction and less towards maintenance of full joint function. When considering the mutilating type of chronic polyarthritis, it becomes evident how important the role of the shoulder joint is in the patients performance of basic everyday activities. In this paper the important structures of the shoulder joint that can be visualized by ultrasound are described as to their rheumatological significance, and pathological findings are discussed along with the appropriate therapy.

[Methods of surface measurements in idiopathic scoliosis]. / Oberflächenvermessungsmethoden bei der idiopathischen Skoliose.

The radiologic evaluation of scoliotic spines is a well established, exact method. In long follow-up histories these patients aquire a remarcable radiation exposure. Measurement of additional clinical parameters intends since decades to minimize this exposure. Documentation of surface deformities follows the presumption of a correlation between these and the radiologic angles. The analysis of 714 completely documented untreated idiopathic scoliotic curves showed a good overall correlation between surface deformity and Cobb angle, but single measurements varied too widely to make the used surface documentation a real alternative to x-rays. Treated scoliosis patients pose additional problems in the evaluation, a any treatment - brace and operation - further diminish the correlation. Obviously the usual clinical surface evaluation can only document the cosmetic appearance. Regular radiologic follow-up stays inevitable especially in treated scoliotic patients.

[Sonographic assessment of typical lesions in shoulder dislocation]. / Sonographische Beurteilung typischer Läsionen bei der Schulterluxation.

The traumatic dislocation of the shoulder joint is the most often joint luxation. The involved patients are often sporting and between the age of 20 to 40 years. The therapeutic and prognostic point of interest is to recognize and reconstruct injured structures. Among the soft tissue injuries the Bankart lesions, among the osseous injuries the Hill-Sachs defect are numeric well to the fore. Hitherto existing diagnostic methods for these injuries are either invasive or with X-rays. Its is demonstrated, that dynamic ultrasonography examination of the shoulder joint can visualize besides the rotator cuff abnormalities of the labrum glenoidale and the caput humeri outline.

Intraarticular hip treatment with triamcinolonehexacetonide in juvenile chronic arthritis.

To evaluate the effect and tolerance of intraarticular Triamcinolonehexacetonide (TCH) in the course of chronic coxitis in juvenile chronic arthritis (JCA) in an open uncontrolled study. Since 1990 we treated patients < 16 years of age suffering from chronic coxitis with 1 mg/TCH/KG body weight. The patients were checked again 4-8 weeks after the treatment. Clinical and ultrasound courses were recorded with the help of ultrasound and joint scores. The evaluation took place 6, 12, 24 and 36 months after the treatment. At that time we give a report on the 12 months follow-up of 37 hip joints and the 24 months follow-up of 20 hip joints. The immediate effect of TCH influencing mobility, pain sensitivity and joint effusions of the patients is impressing. The long term effect of TCH has to be evaluated by regular check ups for at least 2 years. An individual comparison with the not treated contralateral joint would be desired if ethically justifiable. Most patients suffering from polyarticular diseases with a long course of coxitis needed more than one injection of TCH (mean reinjection time 5.8 months). Any avascular necrosis of the femoral heads or other complications were not observed.

[Spontaneous liver rupture in eclampsia]. / Die spontane Leberruptur bei Eklampsie.

We report on a case of a 34-year old nullipara who suffered from rupture of the liver during eclampsia and survived despite most serious complications. Most cases of rupture of a non-traumatic subcapsular haematoma of the liver during pregnancy are associated with symptoms of pre-eclampsia. The pathogenesis of this severe complication as well as diagnostic imaging and surgical treatment are discussed. The classical trias of pre-eclampsia, epigastric pain and sudden circulary collapse may vary considerably. Since early diagnosis is crucial for maternal and foetal outcome, a subcapsular haematoma of the liver should be considered in women during pregnancy and childbed presenting with pre-eclampsia and upper abdominal pain. Here ultrasonographic imaging is a valuable and readily available diagnostic tool for the obstetrician.

[Early experiences with the total mini hip-joint endoprosthesis (St. George Mini model) in dysplasia coxarthrosis]. / Früherfahrungen mit der Mini-Hüftgelenkstotalendoprothese (Modell "St. Georg-Mini") bei Dysplasie-Coxarthrose.

The results of 106 patients with osteoarthritis secondary to severe congenital hip dysplasia and dislocations of the hip operated at the Endo-Klinik were evaluated after an average follow up of 21 months. 142 "St. Georg-Mini" total hips were implanted employing Refobacin-Palacos R. The clinical results were graded as "combined performance" which considered hip pain, walking distance, hip mobility and walking aids. In 93% of the cases "combined performance" was improved at follow up and 91.7% of the patients were satisfied with the result. The early (during hospitalization) and late (after discharge from hospital) complication rate which had an influence on the result at follow up was 2.1% (n = 3) and 3.5% (n = 4) respectively. There were no deep infections. An extended indication for total hip arthroplasty also for younger patients with severe osteoarthritis secondary to hip dysplasia is discussed and can be advocated.

Eight years of monitoring aquatic Oligochaeta from the Baía and Ivinhema Rivers / Oito anos de monitoramento de Oligochaeta aquáticas nos Rios Baía e Ivinhema

The aim of this study was to analyze the factors that influence spatial and temporal variations of the Oligochaeta assemblage in the Baía and Ivinhema Rivers, located in the Upper Paraná River floodplain (Mato Grosso do Sul State, Brazil). Samples of Oligochaeta were collected between February 2000 and November 2007. A total of 27 Oligochaeta species were identified. A Principal Component Analysis (PCA) of the physical and chemical variables was used to summarize the total variation in the data and to identify major environmental gradients. Detrended Correspondence Analysis (DCA) was conducted to verify possible spatial and temporal gradients in the Oligochaeta species distribution. The highest Oligochaeta species densities and richness values were recorded during limnophases. The intensity and amplitude of the potamophase influenced the density, richness and composition of Oligochaeta since many species were transported by high water current velocities and/or died due to the low oxygen levels that are characteristic of this phase. L. hoffmeisteri, P. descolei and A. pigueti were recorded in the potamophase and in the limnophase and we concluded that they are adapted to different conditions of rivers (lotic and lentic) due to the presence of these species during the entire study period in both rivers. Nevertheless, these species were dominant in the potamophase periods of these rivers as they have body adaptations to survive in these conditions.

O objetivo do estudo foi analisar os fatores que influenciam as variações espaciais e temporais da assembléia de Oligochaeta nos Rios Baía e Ivinhema, localizados na planície de inundação do Alto Rio Paraná. (Estado do Mato Grosso do Sul, Brasil). As amostras de Oligochaeta foram coletadas de fevereiro de 2000 a novembro de 2007. Um total de 27 espécies foi identificado. Análise de Componentes Principais (PCA) das variáveis físicas e químicas foi usada para sumarizar a variação total nos dados e identificar os principais gradientes ambientais. Para verificar possíveis gradientes espaciais e temporais na distribuição das espécies de Oligochaeta foi realizada uma Análise de Correspondência Dendrítica com remoção do efeito de arco (DCA). As maiores densidades e riqueza de espécies de Oligochaeta foram registradas nos períodos de águas baixas. A intensidade e amplitude da potamofase influenciaram a riqueza, densidade e composição de espécies, uma vez que muitas das espécies foram carreadas pela alta velocidade de corrente de água e/ou mortas devido aos baixos níveis de oxigênio que foram característicos dessa fase. L. hoffmeisteri, P. descolei and A. pigueti foram registradas nos períodos de potamofase e limnofase e nós concluímos que são adaptadas a diferentes condições de rios (lótico e lêntico) devido a preseça dessas espécies durante todo período estudado em ambos os rios. Contudo, essas espécies foram dominantes nos períodos de potamofase desses rios uma vez que elas apresentam adaptações corporais para sobreviver nessas condições.