A multicentre serosurvey on diphtheria immunity in a French population of 1004 subjects

Syncope is a common medical problem with multiple potential causes and it is very frequent in pediatric population . Neurocardiogenic syncope has been increasingly recognized with the introduction of head-up tilt test (HUTT). The study investigates the clinical utility of HUTT in the evaluation and management of children with recurrent syncope and structurally normal heart. Two-hundred-forty-three consecutive young patients with recurrent unexplained syncope, 100 males and 143 females (mean age 11.4 years, range 5 to 20) underwent HUTT using a 60 degree tilt for 45 min. The test was considered positive when it provoked symptoms of syncope with hypotension and/or bradycardia. Twenty-six patients (10.7%) were positive for neurocardiogenic syncope. Of the 26 patients with the positive tilt, 5 (19.2%) had cardioinhibitory response, 5 (19.2%) mixed response and 16(61.6%) vasodepressive response. Nineteen of 143 females (13.3%) and 7 of 100 males (7%) resulted positive (NS). Among patients < 10 years of age 3/41 (9.8%) were positive and among > 10 years 22/202 patients (10.9%) resulted positive (NS). The cardioinhibitory response is more frequent in males (p = 0.01), and the vasodepressive in females (p = 0.05). In our study, concerning a non selected pediatric population a positive test resulted in a lower percentage than previously reported; moreover, the tilt test has appeared a promising method of identifying patients requiring pharmacotherapy. Additional randomized controlled studies are necessary to better define the prognosis and treatment of neurocardiogenic syncope in children and adolescents with positive tilt test. Finally, an assessment of the outcome of young patients with syncope and a negative tilt test is needed.     

Organolithium route to poly(arylsilane)s

Various poly(arylsilane)s The poly(carbosilane)s prepared in this way are of higher molecular weight than when prepared by the Wurtz-type condensation route previously reported. TG shows 40–50% overll weight loss attained at 500–600°C.     

Morphological,Electrical, and Chemical Changes in Cyclically Contacting Polycrystalline Silicon Surfaces Coated with Perfluoroalkylsilane Self-Assembled Monolayer

The evolution of morphology, electrical properties, and chemical composition has been studied in cyclically contacting polycrystalline silicon (polysilicon) surfaces coated with perfluoroalkylsilane self-assembled monolayer (SAM). The microinstrument used is a MEMS cantilever that is repeatedly actuated out-of-plane to impact a landing pad and is then moved in-plane to enable nondestructive in situ inspection of the impacted area. Analyses show that a device with a monolayer coating exhibits signs of surface degradation after a much higher number of cycles than its uncoated counterpart. A sharp increase in contact resistance between the cantilever and landing pad is observed at ~10 billion cycles for a coated device, versus ~25 million cycles for an uncoated device. Likewise, the onset of grain fracture in the landing pad occurs at ~25 billion cycles for the SAM-coated device, versus ~3 billion cycles for its uncoated counterpart. The effectiveness of the monolayer coating diminishes after more than 100 billion contact cycles as the SAM layer is removed, and the polysilicon substrate becomes susceptible to adhesive wear.     

Declining sperm counts in the United States? A critical review

PURPOSE: Recent reports suggest declining sperm counts in the United States. These reports did not include all available data and did not account for geographic variations noted in prior studies. We examined all available data on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. MATERIALS AND METHODS: We reviewed all 29 U.S. studies from 1938 to 1996 reporting manually counted semen analyses of 9,612 fertile or presumably fertile men. We determined mean sperm concentrations by geographic location with weighted analysis of variance, and assessed any changes with time by linear regression analysis. RESULTS: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, respectively, p = 0.006). There has been no statistically significant change with time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separating by location revealed a decline (p = 0.047). CONCLUSIONS: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm counts in the U.S. during the last 60 years. Further studies addressing the causes of geographic variations are needed.