What if pulsars are born as strange stars?

The possibility and the implications of the idea, that pulsars are born as strange stars, are explored. Strange stars are very likely to have atmospheres with typical mass of $\sim 5\times 10^{-15}M_\odot$ but bare polar caps almost throughout their lifetimes, if they are produced during supernova explosions. A direct consequence of the bare polar cap is that the binding energies of both positively and negatively charged particles at the bare quark surface are nearly infinity, so that the vacuum polar gap sparking scenario as proposed by Ruderman & Sutherland should operate above the cap, regardless of the sense of the magnetic pole with respect to the rotational pole. Heat can not accumulate on the polar cap region due to the large thermal conductivity on the bare quark surface. We test this ``bare polar cap strange star'' (BPCSS) idea with the present broad band emission data of pulsars, and propose several possible criteria to distinguish BPCSSs from neutron stars.Comment: 31 pages in Latex. Accepted by AstroParticle Physic

The flux of carbonyl sulfide and carbon disulfide between the atmosphere and a spruce forest

Turbulent fluxes of carbonyl sulfide (COS) and carbon disulfide (CS₂) were measured over a spruce forest in Central Germany using the relaxed eddy accumulation (REA) technique. A REA sampler was developed and validated using simultaneous measurements of CO₂ fluxes by REA and by eddy correlation. REA measurements were conducted during six campaigns covering spring, summer, and fall between 1997 and 1999. Both uptake and emission of COS and CS₂ by the forest were observed, with deposition occurring mainly during the sunlit period and emission mainly during the dark period. On the average, however, the forest acts as a sink for both gases. The average fluxes for COS and CS₂ are&nbsp; -93 ± 11.7 pmol m^-2 s^-1 and&nbsp; -18 ± 7.6 pmol m^-2 s^-1, respectively. The fluxes of both gases appear to be correlated to photosynthetically active radiation and to the CO₂ and chem{H_2O} fluxes, supporting the idea that the air-vegetation exchange of both gases is controlled by stomata. An uptake ratio COS/CO₂ of 10 ± 1.7 pmol <font face='Symbol'>m</font> mol^-1 has been derived from the regression line for the correlation between the COS and CO₂ fluxes. This uptake ratio, if representative for the global terrestrial net primary production, would correspond to a sink of 2.3 ± 0.5 Tg COS yr^-1

Association Between Air Pollution and Low Birth Weight: A Community-Based Study

The relationship between maternal exposure to air pollution during periods of pregnancy (entire and specific periods) and birth weight was investigated in a well-defined cohort. Between 1988 and 1991, all pregnant women living in four residential areas of Beijing were registered and followed from early pregnancy until delivery. Information on individual mothers and infants was collected. Daily air pollution data were obtained independently. The sample for analysis included 74,671 first-parity live births were gestational age 37-44 weeks. Multiple linear regression and logistic regression were used to estimate the effects of air pollution on birth weight and low birth weight (< 2,500 g), adjusting for gestational age, residence, year of birth, maternal age, and infant gender. There was a significant exposure-response relationship between maternal exposures to sulfur dioxide (SO2) and total suspended particles (TSP) during the third trimester of pregnancy and infant birth weight. The adjusted odds ratio for low birth weight was 1.11 (95% CI, 1.06-1.16) for each 100 micrograms/m3 increase in SO2 and 1.10 (95% CI, 1.05-1.14) for each 100 micrograms/m3 increase in TSP. The estimated reduction in birth weight was 7.3 g and 6.9 g for each 100 micrograms/m3 increase in SO2 and in TSP, respectively. The birth weight distribution of the high-exposure group was more skewed toward the left tail (i.e., with higher proportion of births < 2,500 g) than that of the low-exposure group. Although the effects of other unmeasured risk factors cannot be excluded with certainty, our data suggests that TSP and SO2, or a more complex pollution mixture associated with these pollutants, contribute to an excess risk of low birth weight in the Beijing population.National Institute of Environmental Health Sciences (ES05947, ES08337); National Institute of Child Health & Human Development (R01 HD32505); Department of Health and Human Services (MCJ-259501, HRSA 5 T32 PE10014