U. G. Jørgensen

Operative versus nonoperative treatment of Achilles tendon rupture A prospective randomized study and review of the literature

One hundred eleven patients with acute rupture of the Achilles tendon were included in a prospective trial and randomly assigned to groups for operative (56 patients) or nonoperative (55 patients) treatment. All of the patients were followed with clinic evalua tions at 4 months and 1 year after the rupture. The major complications in the operative treatment group were three reruptures and two deep infections as com pared with seven reruptures, one second rerupture, and one extreme residual lengthening of the tendon in the nonoperative group. There were fewer minor com plications in the nonoperative group than in the opera tive group. The operatively treated patients had a significantly higher rate of resuming sports activities at the same level, a lesser degree of calf atrophy, better ankle movement, and fewer complaints 1 year after the ac cident. The conclusion we reached through this randomized prospective study is that operative treatment of rup tured Achilles tendons is preferable, but nonoperative treatment is an acceptable alternative.

Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing

In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M⊕) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (au), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptunes mass or less have not hitherto been detected at separations of more than 0.15 au from normal stars. Here we report the discovery of a 5.5+5.5-2.7 M⊕ planetary companion at a separation of 2.6+1.5-0.6 au from a 0.22+0.21-0.11 M[circdot] M-dwarf star, where M[circdot] refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.

No supernovae associated with two long-duration gamma-ray bursts.

It is now accepted that long-duration γ-ray bursts (GRBs) are produced during the collapse of a massive star1,2. The standard ‘collapsar’ model3 predicts that a broad-lined and luminous type Ic core-collapse supernova accompanies every long-duration GRB4. This association has been confirmed in observations of several nearby GRBs5–9. Here we report that GRB 060505 (ref. 10) and GRB 060614 (ref. 11) were not accompanied by supernova emission down to limits hundreds of times fainter than the archetypal supernova SN 1998bw that accompanied GRB 980425, and fainter than any type Ic supernova ever observed12. Multi-band observations of the early afterglows, as well as spectroscopy of the host galaxies, exclude the possibility of significant dust obscuration and show that the bursts originated in actively star-forming regions. The absence of a supernova to such deep limits is qualitatively different from all previous nearby long-duration GRBs and suggests a new phenomenological type of massive stellar death.

One or more bound planets per Milky Way star from microlensing observations

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17–30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002–07) that reveals the fraction of bound planets 0.5–10 au (Sun–Earth distance) from their stars. We find that of stars host Jupiter-mass planets (0.3–10 MJ, where MJ = 318 M⊕ and M⊕ is Earth’s mass). Cool Neptunes (10–30 M⊕) and super-Earths (5–10 M⊕) are even more common: their respective abundances per star are and . We conclude that stars are orbited by planets as a rule, rather than the exception.

The optical afterglow of the short |[gamma]|-ray burst GRB 050709

It has long been known that there are two classes of γ-ray bursts (GRBs), mainly distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (those lasting more than ∼2 s), which ultimately linked them with energetic type Ic supernovae, came from the discovery of their long-lived X-ray and optical ‘afterglows’, when precise and rapid localizations of the sources could finally be obtained. X-ray localizations have recently become available for short (duration <2 s) GRBs, which have evaded optical detection for more than 30 years. Here we report the first discovery of transient optical emission (R-band magnitude ∼23) associated with a short burst: GRB 050709. The optical afterglow was localized with subarcsecond accuracy, and lies in the outskirts of a blue dwarf galaxy. The optical and X-ray afterglow properties 34 h after the GRB are reminiscent of the afterglows of long GRBs, which are attributable to synchrotron emission from ultrarelativistic ejecta. We did not, however, detect a supernova, as found in most nearby long GRB afterglows, which suggests a different origin for the short GRBs.

Dynamic model atmospheres of AGB stars - III. Effects of frequency-dependent radiative transfer

We present a new generation of model atmospheres for AGB stars which combine time-dependent dynamics and frequency-dependent radiative transfer. This allows us to take both the effects of pulsation (shock waves, stellar winds) and the complex influence of molecular opacities into account. In the case of C-rich stars, the models also include a self-consistent time-dependent description of dust formation. We investigate the influence of frequency-dependent radiative transfer on the energy and momentum balance of the atmosphere and compare our new models to existing grey dynamical models as well as to classical hydrostatic model atmospheres. We stress the importance of non-grey radiative transfer for obtaining realistic density-temperature structures even in highly dynamical models, discussing both the resulting observable properties and the wind characteristics. Presenting synthetic spectra, we argue that the current dynamical models represent an important step in a process leading from a qualitative to a quantitative description of atmospheres and winds of pulsating AGB stars.

Spectra of carbon-rich asymptotic giant branch stars between 0.5 and 2.5

We present a hydrostatic analysis of ve carbon rich stars, BH Cru, T Cae, S Cen, RU Pup and Y Hya in the wavelength range between 0.5 and 2.5m. All except BH Cru, which is a Mira star, show only modest variability. We identify the absorption features of the molecules CO, CN and C2. The overall energy distribution, which is very sensitive to the eective temperature in the investigated wavelength range, as well as the bands of these molecules put strict limits on the possible values of eective temperature and C/O. We show that our model atmospheres and corresponding synthetic spectra are able to reproduce the observed spectra quite accurately from about 0.7 to 2.5m. The discrepancies are mainly due to uncertainties in the molecular input data. We discuss briefly why the variations of the molecular features are small and why dynamic phenomena do not play a very important role in this wavelength range. We identify colour indices based on commonly available lters and potentially suitable for the empirical determination of fundamental parameters of carbon stars.

\mu

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur—that is, one of a class of small objects orbiting primarily between Jupiter and Neptune—with an equivalent radius of 124  9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

m: Theory meets observation

During the 1993–1994 volleyball season, injuries to players in the two Danish elite divisions were registered by means of a questionnaire survey. Eighty per cent of the players returned the questionnaire. A total of 70 female players reported 79 injuries and 67 male players reported 98 injuries, representing an overall incidence of 3.8 injuries per player per 1000 volleyball hours played. The injury incidence was the same for female and male players. Most injuries occurred in spiking (32%) and in blocking (28%). The injuries were predominantly either acute injuries to fingers (21%) and ankles (18%) or overuse injuries to shoulders (15%) and knees (16%). Shoulder injuries seemed to be a more serious problem in females. During the past 10 years the rate of overuse injuries has increased from 16% to 47% in male elite volleyball, corresponding to a significant increase in the incidence of these injuries from 0.5 to 1.8 injuries per player per 1000 played hours (P<0.001). A possible explanation for this could be a 50% increase in training activity during this period.

A ring system detected around the Centaur (10199) Chariklo

Abstract The majority of previous studies on partial ruptures of the anterior cruciate ligament (ACL) include a relatively large proportion of knees with associated intra-articular injury or collateral ligament tear that contributes to an increase in the symptoms of instability and further deterioration of knee function. In the present study only patients with isolated, partial ruptures of the ACL were evaluated. Fifty-six patients with one injured knee were examined after a median of 5.3 (range 2.0–12.7) years using the IKDC evaluation form, Lysholm knee function score and Tegner activity score. Of the 56 knees, 6 underwent autologous reconstruction due to early progression to complete rupture. Of 34 knees evaluated for laxity, 25 had a negative Lachman test and 7 a positive (+) Lachman. In 2 knees a Lachman ++ result and a positive pivot shift were found. With instrumented laxity testing 24 knees had 2 mm or less difference in laxity compared with the contralateral uninjured knee. The largest side-to-side difference in knee laxity was 4.5 mm. Lysholm score was median 86 (range 52–100) points, and 62% had good or excellent knee function. A significant decline in activity was seen. Only 10 patients (30%) resumed their preinjury activities. We find that the majority of patients with an isolated, partial rupture of the ACL have an acceptable knee function and a stable knee after a median 5 years follow-up. There is, however, a marked reduction in activity.