Extensive water ice within Ceres' aqueously altered regolith: Evidence from nuclear spectroscopy.

The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA's Dawn mission, we determined the concentrations of elemental hydrogen, iron, and potassium on Ceres. The data show that surface materials were processed by the action of water within the interior. The non-icy portion of Ceres' carbon-bearing regolith contains similar amounts of hydrogen to those present in aqueously altered carbonaceous chondrites; however, the concentration of iron on Ceres is lower than in the aforementioned chondrites. This allows for the possibility that Ceres experienced modest ice-rock fractionation, resulting in differences between surface and bulk composition. At mid-to-high latitudes, the regolith contains high concentrations of hydrogen, consistent with broad expanses of water ice, confirming theoretical predictions that ice can survive for billions of years just beneath the surface.

Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres.

Studies of the dwarf planet (1) Ceres using ground-based and orbiting telescopes have concluded that its closest meteoritic analogues are the volatile-rich CI and CM carbonaceous chondrites. Water in clay minerals, ammoniated phyllosilicates, or a mixture of Mg(OH)2 (brucite), Mg2CO3 and iron-rich serpentine have all been proposed to exist on the surface. In particular, brucite has been suggested from analysis of the mid-infrared spectrum of Ceres. But the lack of spectral data across telluric absorption bands in the wavelength region 2.5 to 2.9 micrometres--where the OH stretching vibration and the H2O bending overtone are found--has precluded definitive identifications. In addition, water vapour around Ceres has recently been reported, possibly originating from localized sources. Here we report spectra of Ceres from 0.4 to 5 micrometres acquired at distances from ~82,000 to 4,300 kilometres from the surface. Our measurements indicate widespread ammoniated phyllosilicates across the surface, but no detectable water ice. Ammonia, accreted either as organic matter or as ice, may have reacted with phyllosilicates on Ceres during differentiation. This suggests that material from the outer Solar System was incorporated into Ceres, either during its formation at great heliocentric distance or by incorporation of material transported into the main asteroid belt.

Dawn at Vesta: testing the protoplanetary paradigm.

The Dawn spacecraft targeted 4 Vesta, believed to be a remnant intact protoplanet from the earliest epoch of solar system formation, based on analyses of howardite-eucrite-diogenite (HED) meteorites that indicate a differentiated parent body. Dawn observations reveal a giant basin at Vesta's south pole, whose excavation was sufficient to produce Vesta-family asteroids (Vestoids) and HED meteorites. The spatially resolved mineralogy of the surface reflects the composition of the HED meteorites, confirming the formation of Vesta's crust by melting of a chondritic parent body. Vesta's mass, volume, and gravitational field are consistent with a core having an average radius of 107 to 113 kilometers, indicating sufficient internal melting to segregate iron. Dawn's results confirm predictions that Vesta differentiated and support its identification as the parent body of the HEDs.

Global distribution of neutrons from Mars: results from Mars odyssey.

Global distributions of thermal, epithermal, and fast neutron fluxes have been mapped during late southern summer/northern winter using the Mars Odyssey Neutron Spectrometer. These fluxes are selectively sensitive to the vertical and lateral spatial distributions of H and CO2 in the uppermost meter of the martian surface. Poleward of +/-60 degrees latitude is terrain rich in hydrogen, probably H2O ice buried beneath tens of centimeter-thick hydrogen-poor soil. The central portion of the north polar cap is covered by a thick CO2 layer, as is the residual south polar cap. Portions of the low to middle latitudes indicate subsurface deposits of chemically and/or physically bound H2O and/or OH.

Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits.

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.

Physician and population determinants of rates of middle-ear surgery in Ontario.

CONTEXT: Small-area variations in surgical rates raise concerns about access to care, treatment appropriateness, and the quality and cost of care. OBJECTIVE: To measure small-area variations in rates of myringotomy with insertion of tympanostomy tubes (TTs) and to identify determinants of rate variation. DESIGN AND SETTING: Retrospective analyses using hospital discharge data for patients who had undergone a myringotomy with insertion of TT by county in Ontario between April 1, 1996, and March 31, 1999. Information on possible determinants was taken from a survey of otolaryngologists and primary care physicians in 1996 and from the 1996 Canadian census and physician demographic databases for 1996-1999. PARTICIPANTS: A total of 75 358 hospitalizations for TT placement of children and adolescents (aged

The role of adjuvant adenoidectomy and tonsillectomy in the outcome of the insertion of tympanostomy tubes.

BACKGROUND: Otitis media is the most common medical problem in young children. The usual surgical treatment is myringotomy with insertion of tympanostomy tubes. There is debate about the usefulness of concomitant adenoidectomy or adenotonsillectomy. We examined the effects of these adjuvant procedures on the rates of reinsertion of tympanostomy tubes and rehospitalization for conditions related to otitis media. METHODS: Using hospital discharge records for the period 1995 through 1997, we examined the results of surgery for all 37,316 children (defined as persons 19 years of age or younger) in Ontario, Canada, who received tympanostomy tubes as their first surgical treatment for otitis media. We determined the time to the first readmission for conditions related to otitis media and the time to the first reinsertion of tympanostomy tubes. RESULTS: As compared with treatment involving the insertion of tympanostomy tubes alone, adjuvant adenoidectomy was associated with a reduction in the likelihood of reinsertion of tympanostomy tubes (relative risk, 0.5; 95 percent confidence interval, 0.5 to 0.6; P<0.001) and the likelihood of readmission for conditions related to otitis media (relative risk, 0.5; 95 percent confidence interval, 0.5 to 0.6; P<0.001). The risk of these outcomes was further reduced if an adjuvant adenotonsillectomy was performed. The effect was age-related. Children as young as one year appeared to benefit from adjuvant adenotonsillectomy; the benefit of an adjuvant adenoidectomy was apparent in two-year-olds and was greatest for children three years of age or older. CONCLUSIONS: Performing an adenoidectomy at the time of the initial insertion of tympanostomy tubes substantially reduces the likelihood of additional hospitalizations and operations related to otitis media among children two years of age or older.

Assessing the efficacy of a school-based asthma education program for children: a pilot study.

BACKGROUND: Asthma diminishes the health-related quality of life for many school-aged children. This study sought to explore the effect of a School-Based Asthma Education Program (SBAEP) on quality of life. METHODS: Children with asthma who attended grades 1-5 at two selected schools were requested to participate in this pilot study. Participants at one school were provided with a SBAEP, those at another school (control group) were provided with written educational material about asthma. The children completed the Paediatric Asthma Quality of Life Questionnaire (PAQLQ) before and one month after the educational interventions. RESULTS: There were clinically important improvements in the SBAEP group in quality of life, specifically in the symptom subdomain. CONCLUSIONS: The "Air Force" SBAEP appears to result in a favourable trend in quality of life for children. A larger scale trial is required following revisions to the program.

Referral of children with otitis media. Do family physicians and pediatricians agree?

OBJECTIVE: To determine factors influencing family physicians' and pediatricians' decisions to refer children with recurrent acute otitis media (RAOM) and otitis media with effusion (OME) to otolaryngologists for an opinion about tympanostomy tube insertion. DESIGN: Mailed survey. SETTING: Physicians' practices in Ontario. PARTICIPANTS: Random sample of 1459 family physicians and all 775 pediatricians in the province. MAIN OUTCOME MEASURES: Physicians' reports of the influence of 17 factors on decisions to refer (more likely, no influence, less likely to refer) and number of episodes of otitis media, months with effusion, level of hearing loss, or months of continuous antibiotics without improvement prompting referral. RESULTS: Physicians agreed (> 80% concordance) on six out of 17 factors as indications for referring children with RAOM or OME. Opinions about the importance of other factors varied widely. Family physicians would refer children with otitis media after fewer episodes of illness, fewer months of effusion, lower levels of hearing loss, and fewer months of prophylactic antibiotic therapy than pediatricians (all P < .001). Pediatricians would prescribe continuous antibiotics longer (11.8 weeks) than family physicians (8.9 weeks, P < .0001), which correlated with lower referral thresholds for family physicians. CONCLUSION: Family physicians' and pediatricians' self-reported referral practices for surgical opinions on children with otitis media varied considerably. These observations raise questions about the consistency of care for children with otitis media and whether revised clinical guidelines would be helpful.

Otolaryngologists' perceptions of the indications for tympanostomy tube insertion in children.

BACKGROUND: Bilateral myringotomy with insertion of tympanostomy tubes is the most common operation that children in Canada undergo. Area variations in surgical rates for this procedure have raised questions about indications used to decide about surgery. The objective of this study was to describe the factors that influence otolaryngologists to recommend tympanostomy tube insertion in children with otitis media and their level of agreement about indications for surgery. METHODS: A survey was sent to all 227 otolaryngologists in Ontario in the fall of 1996. The influence of 17 clinical and social factors on recommendations to insert tympanostomy tubes were assessed. Case vignettes were used to determine the effect of multiple factors in decisions about the need for surgical management. RESULTS: Surveys were returned by 138 (68.3%) of the 202 eligible otolaryngologists. There was agreement (more than 90% of respondents) about 6 indications for surgery: persistent effusion, a lack of improvement after 3 months of antibiotic therapy, a history of persistent effusion for 3 or more months per episode of otitis media, more than 7 episodes of otitis media in 6 months, a bilateral conductive hearing loss of 20 dB or more and a persistently abnormal tympanic membrane. Some respondents were more likely to recommend tube insertion if there were parental concerns about hearing problems or the frequency or severity of episodes of otitis media. Otolaryngologists agreed about the role of tympanostomy tubes in 1 of 4 case vignettes but disagreed about whether adenoidectomy should also be performed in that instance. Most viewed tympanostomy tube insertion as beneficial, with few adverse effects. INTERPRETATION: There is a lack of consensus among practising otolaryngologists in Ontario as to which children with recurrent otitis media or persistent effusion should undergo bilateral myringotomy with tympanostomy tube insertion. These findings suggest the need to revisit clinical guidelines for this procedure.

Accuracy of clinical assessment of heart murmurs by office based (general practice) paediatricians.

AIM: To determine the diagnostic accuracy of physical examination by office based (general practice) paediatricians in the evaluation of heart murmurs. DESIGN: Each of 30 office based paediatricians blindly examined a random sample of children with murmurs (43% of which were pathological). Sensitivity and specificity were calculated and were related to paediatricians' characteristics. RESULTS: Mean (SD) sensitivity was 82 (24)% with a mean specificity of 72 (24)% in differentiating pathological from innocent murmurs, with further investigations requested for 54% of assessments. The addition of a referral strategy would have increased mean sensitivity to 87 (20)% and specificity to 98 (8)%. Diagnostic accuracy was not significantly related to the paediatricians' age, education or practice characteristics, but was related to referral practices and confidence in assessment. CONCLUSIONS: Diagnostic accuracy of clinical assessment of heart murmurs by office based paediatricians is suboptimal, and educational strategies are needed to improve accuracy and reduce unnecessary referrals and misdiagnosis.

Periodic health examination, 1999 update: 1. Detection, prevention and treatment of obesity. Canadian Task Force on Preventive Health Care.

OBJECTIVES: (1) To evaluate the evidence relating to the effectiveness of methods to prevent and treat obesity, and (2) to provide recommendations for the prevention and treatment of obesity in adults aged 18 to 65 years and for the measurement of the body mass index (BMI) as part of a periodic health examination. OPTIONS: In adults with obesity (BMI greater than 27) management options include weight reduction, prevention of further weight gain or no intervention. OUTCOMES: The long-term (more than 2 years) effectiveness of (a) methods to prevent obesity and (b) methods to treat obesity. EVIDENCE: MEDLINE was searched for articles published from 1966 to April 1998 that related to the prevention and treatment of obesity; additional articles were identified from the bibliographies of review articles and the listings of Current Contents. Selection criteria were used to limit the analysis to prospective studies with at least 2 years' follow-up. BENEFITS, HARM AND COSTS: Health benefits of weight reduction were evaluated in terms of alleviation of symptoms, improved management of obesity-related diseases and a reduction in major clinical outcomes. The health risk of weight-reduction methods were briefly evaluated in terms of increased mortality and morbidity. VALUES: The recommendations of this report reflect the commitment of the Canadian Task Force on Preventive Health Care to provide a structured, evidence-based appraisal of whether a manoeuvre should be part of a periodic health examination. RECOMMENDATIONS: (1) PREVENTION: There is insufficient evidence to recommend in favour of or against community-based obesity prevention programs; however, because of considerable health risks associated with obesity and the limited long-term effectiveness of weight-reduction methods, the prevention of obesity should be a high priority for health care providers (grade C recommendation). (2) TREATMENT: (a) For obese adults without obesity-related diseases, there is insufficient evidence to recommend in favour of or against weight-reduction therapy because of a lack of evidence supporting the long-term effectiveness of weight-reduction methods (grade C recommendation); (b) for obese adults with obesity-related diseases (e.g., diabetes mellitus, hypertension), weight reduction is recommended because it can alleviate symptoms and reduce drug therapy requirements, at least in the short term (grade B recommendation). (3) Detection: (a) for people without obesity-related diseases, there is insufficient evidence to recommend the inclusion or exclusion of BMI measurement as part of a periodic health examination, and therefore BMI measurement is left to the discretion of individual health care providers (grade C recommendation); (b) for people with obesity-related diseases, BMI measurement is recommended because weight reduction should be considered with a BMI of more than 27 (grade B recommendation). VALIDATION: The findings of this analysis were reviewed through an iterative process by the members of the Canadian Task Force on Preventive Health Care. SPONSORS: The Canadian Task Force on Preventive Health Care is funded through a partnership between the Provincial and Territorial Ministries of Health and Health Canada.

Cohort study on circumcision of newborn boys and subsequent risk of urinary-tract infection.

BACKGROUND: A decrease in risk of urinary-tract infection is one of the most commonly given reasons for circumcision of newborn boys. Previous studies have reported rates of UTI to be 10-20 times higher in uncircumcised than in circumcised boys. This population-based cohort study followed neonates in Ontario, Canada, prospectively to study the relation between circumcision and subsequent UTI risk. METHODS: Eligible boys were born to residents of Ontario between April 1, 1993, and March 31, 1994. We used hospital discharge data to follow up boys until March 31, 1996. FINDINGS: Of 69,100 eligible boys, 30,105 (43.6%) were circumcised and 38,995 (56.4%) uncircumcised. 888 boys circumcised after the first month of life were excluded. 29,217 uncircumcised boys were matched to the remaining circumcised boys by date of birth. The 1-year probabilities of hospital admission for UTI were 1.88 per 1000 person-years of observation (83 cases up to end of follow-up) in the circumcised cohort and 7.02 per 1000 person-years (247 cases up to end of follow-up) in the uncircumcised cohort (p<0.0001). The estimated relative risk of admission for UTI by first-year follow-up indicated a significantly higher risk for uncircumcised boys than for circumcised boys (3.7 [2.8-4.9]). 195 circumcisions would be needed to prevent one hospital admission for UTI in the first year of life. INTERPRETATION: Although our findings support the notion that circumcision may protect boys from UTI, the magnitude of this effect may be less than previously estimated.

PIP: A prospective population-based cohort study assessed the association between male circumcision and subsequent urinary tract infection (UTI) in children born in Ontario, Canada, in a 12-month period in 1993-94. Of the 69,100 eligible infants, 30,105 (43.6%) were circumcised in the first month of life. 29,217 uncircumcised boys were matched to circumcised boys by date of birth and followed for 24-36 months. Information on UTIs was extracted from the Canadian Institute for Health Information computerized database on hospital discharges. There were 83 UTI cases in the circumcised cohort (1.88/1000 person-years of observation) and 247 in the uncircumcised group (7.02/1000 person-years) (p 0.0001). The relative risk of UTI in uncircumcised compared to circumcised boys was 4.5 (95% CI, 2.4-8.4) in the first month of life and 3.7 (95% CI, 2.8-4.9) in the year after the procedure. Calculation of the attributable risk indicated 195 circumcisions would be necessary to prevent one admission for UTI in the first year of life. Previous studies have recorded UTI rates 10-20 times higher in uncircumcised than circumcised boys. These findings support the hypothesis that circumcision protects boys from UTI, but the magnitude of this effect may be less than previously estimated.

Global elemental maps of the moon: the Lunar Prospector gamma-Ray spectrometer.

Lunar Prospector gamma-ray spectrometer spectra along with counting rate maps of thorium, potassium, and iron delineate large compositional variations over the lunar surface. Thorium and potassium are highly concentrated in and around the nearside western maria and less so in the South Pole-Aitken basin. Counting rate maps of iron gamma-rays show a surface iron distribution that is in general agreement with other measurements from Clementine and the Lunar Prospector neutron detectors.

Fluxes of fast and epithermal neutrons from Lunar Prospector: evidence for water ice at the lunar poles.

Maps of epithermal- and fast-neutron fluxes measured by Lunar Prospector were used to search for deposits enriched in hydrogen at both lunar poles. Depressions in epithermal fluxes were observed close to permanently shaded areas at both poles. The peak depression at the North Pole is 4.6 percent below the average epithermal flux intensity at lower latitudes, and that at the South Pole is 3.0 percent below the low-latitude average. No measurable depression in fast neutrons is seen at either pole. These data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles.

Is bone marrow aspiration needed in acute childhood idiopathic thrombocytopenic purpura to rule out leukemia?

OBJECTIVE: To assess the prevalence of leukemia in a series of bone marrow aspiration (BMA) samples collected to confirm provisional diagnoses of acute idiopathic thrombocytopenic purpura (ITP) in children. DESIGN: A retrospective cohort. SETTING: All BMA reports at The Hospital for Sick Children, Toronto, Ontario (a tertiary care pediatric hospital), from January 1, 1984, to May 31, 1996, were reviewed. PATIENTS: Included were BMAs performed to confirm provisional diagnoses of ITP in children (6 months to 18 years of age) with "typical" contemporaneous hematologic features of ITP (platelet count, < or =50 x 10(9)/L; hemoglobin level, > or =100 g/L [6-12 months of age] or > or =110 g/L [> 1 year of age]; white blood cell count, > or =5 x 10(9)/L [6 months to 6 years of age] or > or =4 x 10(9)/L [> 6 years of age]; and neutrophil count, > or =1.5 x 10(9)/L [6 months to 6 years of age] or > or =2 x 10(9)/L [> 6 years of age]). Children with chronic ITP, thrombocytopenia-related chronic conditions, or leukemic blasts on peripheral smears were excluded. MAIN OUTCOME MEASURE: The finding of leukemia in the BMA report was chosen a priori as the primary outcome for the yield of BMA. RESULTS: Four hundred eighty-four BMAs were performed to confirm provisional diagnoses of acute childhood ITP. No diagnoses of leukemia were revealed in the 332 children with typical hematologic features of ITP. The risk of missing the diagnosis of leukemia in this setting is less than 1%. CONCLUSIONS: The yield of BMA for leukemia in this setting is low. Routine BMA is not necessary for children with typical acute ITP.

The economic impact of high-risk pregnancies.

To compare the costs of prenatal care, labor and delivery, and postnatal care of 775 high-risk (HR) pregnancies with costs of 2,825 low-risk pregnancies, data were collected from retrospective chart review and computerized financial records of infants and mothers. Claims paid to providers, hospitals, and ancillary services were the direct medical costs of care for Sentara Health Plan. The total prenatal, labor and delivery, and postnatal costs were more than 6 million dollars and 3.5 million dollars for premature and term babies, respectively. Postnatal and total costs were related inversely to gestational ages and birth weights and directly related to length of stay. The data indicate the substantially increased cost of identified HR pregnancies. The gestational age and birth weight correlate with postnatal and total costs.