Low-radio-frequency eclipses of the redback pulsar J2215+5135 observed in the image plane with LOFAR.

The eclipses of certain types of binary millisecond pulsars (i.e. 'black widows' and 'redbacks') are often studied using high-time-resolution, 'beamformed' radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of two weeks - six months, we find preliminary evidence that the eclipse duration is frequency dependent (∝ν-0.4), such that the pulsar is eclipsed for longer at lower frequencies, in broad agreement with beamformed studies of other similar sources. Furthermore, the detection of the eclipses in imaging data suggests an eclipsing medium that absorbs the pulsed emission, rather than scattering it. Our study is also a demonstration of the prospects of finding pulsars in wide-field imaging surveys with the current generation of low-frequency radio telescopes.

A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations.

Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers--cascades of secondary particles in the atmosphere-and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 10(17)-10(17.5) electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 10(17.5) electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 10(17)-10(17.5) electronvolt range.

Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

Population-based survival estimates for childhood cancer in Australia during the period 1997-2006.

BACKGROUND: This study provides the latest available relative survival data for Australian childhood cancer patients. METHODS: Data from the population-based Australian Paediatric Cancer Registry were used to describe relative survival outcomes using the period method for 11,903 children diagnosed with cancer between 1983 and 2006 and prevalent at any time between 1997 and 2006. RESULTS: The overall relative survival was 90.4% after 1 year, 79.5% after 5 years and 74.7% after 20 years. Where information onstage at diagnosis was available (lymphomas, neuroblastoma, renal tumours and rhabdomyosarcomas), survival was significantly poorer for more-advanced stage. Survival was lower among infants compared with other children for those diagnosed with leukaemia, tumours of the central nervous system and renal tumours but higher for neuroblastoma. Recent improvements in overall childhood cancer survival over time are mainly because of improvements among leukaemia patients. CONCLUSION: The high and improving survival prognosis for children diagnosed with cancer in Australia is consistent with various international estimates. However, a 5-year survival estimate of 79% still means that many children who are diagnosed with cancer will die within 5 years, whereas others have long-term health morbidities and complications associated with their treatments. It is hoped that continued developments in treatment protocols will result in further improvements in survival.

Trends in incidence of childhood cancer in Australia, 1983-2006.

BACKGROUND: There are few population-based childhood cancer registries in the world containing stage and treatment data. METHODS: Data from the population-based Australian Paediatric Cancer Registry were used to calculate incidence rates during the most recent 10-year period (1997-2006) and trends in incidence between 1983 and 2006 for the 12 major diagnostic groups of the International Classification of Childhood Cancer. RESULTS: In the period 1997-2006, there were 6184 childhood cancer (at 0-14 years) cases in Australia (157 cases per million children). The commonest cancers were leukaemia (34%), that of the central nervous system (23%) and lymphomas (10%), with incidence the highest at 0-4 years (223 cases per million). Trend analyses showed that incidence among boys for all cancers combined increased by 1.6% per year from 1983 to 1994 but have remained stable since. Incidence rates for girls consistently increased by 0.9% per year. Since 1983, there have been significant increases among boys and girls for leukaemia, and hepatic and germ-cell tumours, whereas for boys, incidence of neuroblastomas and malignant epithelial tumours has recently decreased. For all cancers and for both sexes combined, there was a consistent increase (+0.7% per year, 1983-2006) at age 0-4 years, a slight non-significant increase at 5-9 years, and at 10-14 years, an initial increase (2.7% per year, 1983-1996) followed by a slight non-significant decrease. CONCLUSION: Although there is some evidence of a recent plateau in cancer incidence rates in Australia for boys and older children, interpretation is difficult without a better understanding of what underlies the changes reported.

Viridans streptococcus bacteremia in children on chemotherapy for cancer: an underestimated problem.

The authors discuss the morbidity associated with viridans streptococcus bacteremia, and its implications on the choice of antibiotics used as prophylaxis and treatment. They retrospectively studied the case notes of 38 children who were being treated for various malignant conditions in their unit and developed 40 episodes of bacteremia with viridans streptococci between October 1995 and January 1999. Viridans streptococci were the third commonest blood culture isolate during this period, after coagulase-negative staphylococci and Staphylococcus aureus. The majority of the isolates were Streptococcus mitis (55%). Others were S. sanguis (25%), S. oralis (12.5%), S. salivarius (5%), and S. acidominimus (2.5%). Twenty-five percent of the patients had been treated with regimens that included cytosine arabinoside, 60% were receiving prophylactic co-trimoxazole, and 87.5% were neutropenic. Thirty percent of patients had abnormal chest X-rays, and 15% were hypotensive; 2 patients required admission to the intensive care unit. Initial antibiotic therapy was changed because of failure of clinical response in 60% of cases, despite the infecting organism being sensitive in vitro. This study confirms the importance of viridans streptococci as a cause of bacteremia in pediatric hematology and oncology patients, leading to significant morbidity. Further work is required to establish the optimal treatment for viridans streptococcus bacteremia.

A physician's guide to information available from the FDA about new drug approvals. The ACG Committee on FDA-related matters. American College of Gastroenterology.

The Freedom of Information Act established the right of any individual to have access to records maintained by federal agencies, within limits provided by exemptions in the Act. Most of the records of the FDA pertaining to the review and approval of drug products are available, at least in part, under the provisions of this Act.

Effects of simulated facility-design changes on outpatient pharmacy efficiency.

The potential effects of using the Baker drug counter or the Systamodule pharmacy fixture, or both, on the efficiency of the current outpatient pharmacy system at the National Institutes of Health were evaluated by computer simulation. It was hypothesized that the use of these two devices would reduce (1) the prescription-filling time (RxFT) and (2) the distance traveled (DT) by pharmacists in filling individual prescriptions. The sample used was 20% of two weeks' prescriptions, randomly selected. All theoretical estimations of RxFT were done by a computer program; DT was calculated based on measurements from the architect's schematic drawings. The effect of the application of the Baker drug counter alone, the Systamodule pharmacy fixture alone, and the Baker drug counter in combination with the Systamodule pharmacy fixture was to reduce the prescription-filling time by 0.123, 0.159, and 0.280 minutes per prescription, respectively. The average DT per prescription, 102 feet, was identical in the current NIH pharmacy and with use of the Baker counter. It was reduced by 86.3% (to 14 feet) with use of the Systamodule feature, both alone and in combination with the Baker counter. The use of the Baker drug counter and the Systamodule together promises improved efficiency of the prescription dispensing operation.