用扫描电镜分析表征大气气溶胶单颗粒

1　IntroductionAtmosphericaerosolsarecomplexmixture,originatedfromavarietyofsources.Mostoftheanalyticaltechniquesusedforitscharacterizationarebulkmethodsthatgenerateonesetofdatapersample,describingtheoverallcompositionofthesample .Toworkoutusefulinformationonpollu tionsources,itrequiresdataofagreatnumberofsamplesandmultivariatedataanalysismethodsusuallyareneeded .Ontheotherhand ,scanningelectronmicroscope energydispersiveX rayanaly sissystem (SEM EDX)isabletoprovideanalyticaldataforeachsing…     

Genetically informed captive breeding of hybrids of an extinct species of Galapagos tortoise

Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive-breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward-in-time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive-bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic-based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation.     

Umbilical cord pseudocyst in trisomy 18

Prenatal diagnosis of cord defects by means of ultrasound examination is possible and highly accurate. Although this is a rare pathological finding, we report two cases in which umbilical cord pseudocysts were associated with trisomy 18. These observations underscore the need of umbilical blood sampling for establishing the karyotype in fetuses with such umbilical cord anomalies and the importance of careful examination of placentas and infants born with such defects.     

Correlation structure between inflation and oil futures returns: An equilibrium approach

We use an equilibrium model of a monetary economy to understand the economics behind the correlation between inflation and oil futures returns. We find that some of the positive correlation found in empirical studies is due to the fact that oil is in the consumption basket; however, this accounts only for a minor part of it. There exist other important sources of correlation related to monetary shocks and output shocks. In particular, we find that the correlation is extremely sensitive to the reaction of the central bank to output shocks, while the reaction to inflation changes is less significant. We estimate our model using maximum likelihood with the following data sets: crude oil futures prices, nominal interest rates, inflation rates and money supply growth rates. Our estimates suggest that the monetary authority overreacts to output shocks by increasing the money supply in a more than necessary amount, generating a significant source of positive correlation. From a practical perspective, We find that it is a good strategy to use as a hedge, the futures whose maturity is closer to the hedging horizon. This is particularly true for short-term hedging.     

History of Bioengineering Techniques for Erosion Control in Rivers in Western Europe

Living plants have been used for a very long time throughout the world in structures against soil erosion, as traces have been found dating back to the first century BC. Widely practiced in Western Europe during the eighteenth and nineteenth centuries, bioengineering was somewhat abandoned in the middle of the twentieth century, before seeing a resurgence in recent times. Based on an extensive bibliography, this article examines the different forms of bioengineering techniques used in the past to manage rivers and riverbanks, mainly in Europe. We compare techniques using living material according to their strength of protection against erosion. Many techniques are described, both singly and in combination, ranging from tree planting or sowing seeds on riverbanks to dams made of fascine or wattle fences. The recent appearance of new materials has led to the development of new techniques, associated with an evolution in the perception of riverbanks. This study was part of a research project on river bioengineering funded by the French Ministère de l’Ecologie, de l’Energie, du Développement Durable et de l’Aménagement du Territoire, Direction Générale de la Prévention des Risques.     

Twin–twin transfusion syndrome—possible roles for doppler ultrasound and amniocentesis

A 29-year-old woman was referred for suspicion of twin-twin transfusion syndrome (TTTS). Several ultrasonographic and neonatal criteria of TTTS were encountered in this twin pregnancy. The peculiar observations in this case were, firstly, the demonstration of superficial anastomosis by Doppler ultrasound and, secondly, that one single therapeutic amniocentesis could have been sufficient to partially correct the progression of the syndrome, as after amniocentesis it was no longer possible to demonstrate the vascular communication. This observation suggests that superficial anastomoses could also have a role in the genesis of TTTS. Their effect could be monitored by Doppler ultrasound and could be more easily corrected by therapeutic amniocentesis.