A helium-burning white dwarf binary as a supersoft X-ray source.

Type Ia supernovae are cosmic distance indicators1,2, and the main source of iron in the Universe3,4, but their formation paths are still debated. Several dozen supersoft X-ray sources, in which a white dwarf accretes hydrogen-rich matter from a non-degenerate donor star, have been observed5 and suggested as Type Ia supernovae progenitors6-9. However, observational evidence for hydrogen, which is expected to be stripped off the donor star during the supernova explosion10, is lacking. Helium-accreting white dwarfs, which would circumvent this problem, have been predicted for more than 30 years (refs. 7,11,12), including their appearance as supersoft X-ray sources, but have so far escaped detection. Here we report a supersoft X-ray source with an accretion disk whose optical spectrum is completely dominated by helium, suggesting that the donor star is hydrogen-free. We interpret the luminous and supersoft X-rays as resulting from helium burning near the surface of the accreting white dwarf. The properties of our system provide evidence for extended pathways towards Chandrasekhar-mass explosions based on helium accretion, in particular for stable burning in white dwarfs at lower accretion rates than expected so far. This may allow us to recover the population of the sub-energetic so-called Type Iax supernovae, up to 30% of all Type Ia supernovae13, within this scenario.

An excess of massive stars in the local 30 Doradus starburst.

The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses ([Formula: see text]). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1 My. The IMF is densely sampled up to 200 [Formula: see text] and contains 32 ± 12% more stars above 30 [Formula: see text] than predicted by a standard Salpeter IMF. In the mass range of 15 to 200 [Formula: see text], the IMF power-law exponent is [Formula: see text], shallower than the Salpeter value of 2.35.

Binary interaction dominates the evolution of massive stars.

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

Effects of limb immobilization on brain plasticity.

OBJECTIVE: Little is known about the effects of reduced sensory input and motor output in the human brain. Therefore, we conducted a longitudinal study to investigate whether limb immobilization after unilateral arm injury is reflected in structural plastic changes in gray matter (cortical thickness) and white matter (fractional anisotropy [FA]). METHODS: We examined 10 right-handed subjects with injury of the right upper extremity that required at least 14 days of limb immobilization. Subjects underwent 2 MRI examinations, the first within 48 hours postinjury and the second after an average time interval of 16 days of immobilization. Based on the MRI scans, we measured cortical thickness of sensorimotor regions and FA of the corticospinal tracts. RESULTS: After immobilization, we revealed a decrease in cortical thickness in the left primary motor and somatosensory area as well as a decrease in FA in the left corticospinal tract. In addition, the motor skill of the left (noninjured) hand improved and is related to increased cortical thickness and FA in the right motor cortex. CONCLUSIONS: The present study illustrates that cortical thickness of the sensorimotor cortex and FA of the corticospinal tract changed during right arm immobilization and that these changes are associated with skill transfer from the right to the left hand. Thus, immobilization induces rapid reorganization of the sensorimotor system. Given that limb immobilization is a standard intervention technique in constraint-induced therapy, therapists should be aware of both the positive and negative effects of this intervention.

Is it possible to minimize overdrainage complications with gravitational units in patients with idiopathic normal pressure hydrocephalus? Protocol of the randomized controlled SVASONA Trial (ISRCTN51046698).

Overdrainage is a common complication observed after shunting patients with idiopathic normal-pressure hydrocephalus (iNPH), with an estimated incidence up to 25%. Gravitational units that counterbalance intracranial pressure changes were developed to overcome this problem. We will set out to investigate whether the combination of a programmable valve and a gravitational unit (proGAV, Aesculap/Miethke, Germany) is capable of reducing the incidence of overdrainage and improving patient-centered outcomes compared to a conventional programmable valve (Medos-Codman, Johnson & Johnson, Germany). SVASONA is a pragmatic randomized controlled trial conducted at seven centers in Germany. Patients with a high probability of iNPH (based on clinical signs and symptoms, lumbar infusion and/or tap test, cranial computed tomography [CCT]) and no contraindications for surgical drainage will randomly be assigned to receive (1) a shunt assistant valve (proGAV) or (2) a conventional, programmable shunt valve (programmable Medos-Codman).We will test the primary hypothesis that the experimental device reduces the rate of overdrainage from 25% to 10%. As secondary analyses, we will measure iNPH-specific outcomes (i.e., the Black grading scale and the NPH Recovery Rate), generic quality of life (Short Form 36), and complications and serious adverse events (SAE). One planned interim analysis for safety and efficacy will be performed halfway through the study. To detect the hypothesized difference in the incidence of overdrainage with a type I error of 5% and a type II error of 20%, correcting for multiple testing and an anticipated dropout rate of 10%, 200 patients will be enrolled.The presented trial is currently recruiting patients, with the first results predicted to be available in late 2008.

Serum cobalamin concentrations in healthy cats and cats with non-alimentary tract illness in Australia.

OBJECTIVE: To determine a reference range for serum cobalamin concentration in healthy cats in Australia using a chemiluminescent enzyme immunoassay and to prospectively investigate the prevalence of hypocobalaminaemia in cats with non-alimentary tract disease. DESIGN: Prospective study measuring serum cobalamin concentrations in clinically healthy cats and cats with non-alimentary tract illness. PROCEDURE: Blood was collected from 50 clinically healthy cats that were owned by staff and associates of Veterinary Specialist Services or were owned animals presented to Creek Road Cat Clinic for routine vaccination. Blood was collected from 47 cats with non-alimentary tract illness presented at either clinic. Serum cobalamin concentration was determined for each group using a chemiluminescent enzyme immunoassay. RESULTS: A reference range for Australian cats calculated using the central 95th percentile in the 50 clinically healthy cats was 345 to 3668 pg/mL. Median serum cobalamin concentration in 47 cats with non-alimentary tract illness (1186 pg/mL; range 117-3480) was not significantly different to the median serum cobalamin of the 50 healthy cats (1213 pg/mL, range 311-3688). Using the calculated reference range one sick cat with non-alimentary tract illness had a markedly low serum cobalamin concentration. CONCLUSION: Although hypocobalaminaemia is uncommon in sick cats with non-alimentary tract illness in Australia, its occurrence in this study warrants further investigation.

[Quality of life by limited vision in old age: the example of age-related macula degeneration]. / Lebensqualität bei Seheinschränkung im Alter: Das Beispiel altersabhängige Makuladegeneration.

Age-related macula degeneration (AMD) is accompanied by considerable consequences regarding the psychosocial quality of life. A considerable body of research literature now indicates, for instance, an increased rate of depression and substantial loss of everyday capabilities in AMD patients. However, inter-individual differences are large and part of the explanation lies in differences in the ability to cope with and detach oneself from aims in life. The negative impact of AMD on the qualify of life is associated with a need for psychosocial support, but this need is barely met at present. A series of studies nevertheless supports the view that successful intervention is possible even with very old patients. In this respect the problems at present have less to do with recognition than with application and implementation.

Protothecosis in 17 Australian dogs and a review of the canine literature.

Systemic protothecosis was diagnosed in 17 Australian dogs between 1988 and 2005. There was a preponderance of young-adult (median 4 years), medium- to large-breed dogs. Females (12/17 cases) and Boxer dogs (7 cases, including 6 purebreds and one Boxer cross) were over-represented. Sixteen of 17 dogs died, with a median survival of four months. A disproportionate number of cases were from coastal Queensland. In most patients, first signs were referable to colitis (11/17 cases), which varied in severity, and was often present for many months before other symptoms developed. Subsequent to dissemination, signs were mostly ocular (12 cases) and/or neurologic (8 cases). Two dogs had signs due to bony lesions. Once dissemination was evident, death or euthanasia transpired quickly. Prototheca organisms had a tropism for the eye, central nervous system (CNS), bone, kidneys and myocardium, tissues with a good blood supply. Microscopic examination and culture of urine (5 cases), cerebrospinal fluid (CSF;1 case), rectal scrapings (4 cases), aspirates or biopsies of eyes (5 cases) and histology of colonic biopsies (6 cases) as well as skin and lymph nodes (2 cases) helped secure a diagnosis. Of the cases where culture was successful, P wickerhamii was isolated from two patients, while P zopfii was isolated from five. P zopfii infections had a more aggressive course. Treatment was not attempted in most cases. Combination therapy with amphotericin B and itraconazole proved effective in two cases, although in one of these treatment should have been for a longer duration. One surviving dog is currently still receiving itraconazole. Protothecosis should be considered in all dogs with refractory colitis, especially in female Boxers.

[Intraoperative ultrasound of intra- and extramedullary tumours]. / Wertigkeit des intraoperativen Ultraschalls bei intra- und extramedullären Tumoren.

AIM: Spinal tumours can be diagnosed precisely by magnetic resonance imaging (MRI). Planning the surgical procedure of intradural tumours, intraoperative ultrasound (IOUS) has been used to evaluate its diagnostic potential. METHOD: From 1997 to 9/2002 32 patients with the diagnosis of an ependymoma (n = 9), astrocytoma (n = 5), haemangioblastoma (n = 5), neurinoma (n = 4), meningeoma (n = 4) and filum terminale ependymoma (n = 5) were investigated by intraoperative transdural sonography. The sonographic results were correlated to the preoperative MRI-findings and histopathological work-up. RESULTS: Intramedullary tumours characteristically present with a heterogenous morphology, sometimes carrying intralesional or perilesional cysts. The tumour margins are frequently poorly defined, and there is a perifocal oedema. Extramedullary tumours frequently display a homogenous signal intensity, well defined tumour margins and the abscence of perifocal oedema. Haemangioblastomas turned out to be a specific sonographic entity among intramedullary tumours, as they most often contain only a cystic part with a small tumour nodule. IOUS influenced the surgical approach as laminotomy has to be extended in 7/32 cases to reach the tips of the tumour. CONCLUSION: The precision of surgical exposure of intradural spinal lesions can be optimised by IOUS which shows a high correlation with MRI characterizing extra- and intramedullary tumours. Using IOUS, the exact position of the laminectomy/laminotomy can be adapted to the true extent of the tumour, thus avoiding the necessity of further bone work in the case of the frequently oedematous spinal cord protruding through the opening in the dura. Overall, IOUS guidance can help to reduce postoperative morbidity in surgery for all spinal intradural lesions.

Comparison of pregnancy mood profiles in gestational diabetes and preexisting diabetes.

PURPOSE: This study sought to answer the following questions: How does intensified diabetes management affect the patient's mood profile? Is there a relationship between levels of glycemic control and emotional profile? Which factors distinguish the emotional profile of women with pregestational diabetes from women with newly diagnosed gestational diabetes? METHODS: A secondary analysis was conducted of women with newly diagnosed gestational diabetes (GDM), pregestational diabetes (PGDM), and nondiabetic controls. Those with diabetes were treated with an intensified approach. All participants responded to a questionnaire measuring bipolar subjective mood states. The relation between diabetes types, glucose characteristics during pregnancy, and mood were analyzed. RESULTS: The mood profile was significantly associated with level of glycemic control in GDM women (comparable to controls). PGDM women were not affected by either level of glycemic control or diabetes class categories. The number of glucose determinations, marital status, and maternal age were related to mood profile for GDM women. CONCLUSIONS: Because women with GDM and PGDM present different mood profiles in pregnancy, customized medical/behavioral goals may be needed to enhance compliance and optimize perinatal outcome.