How many herbarium specimens are needed to detect threatened species?

The distribution, ecology and conservation status of the majority of plant species are poorly known. One of the challenges ahead is to address this knowledge gap and give more emphasis to this important group of species that represents a critical component of earth’s biodiversity. Full conservation assessments require expert knowledge of the group concerned, but for the majority of plant species, especially those from the tropics, the best source of knowledge is specimens housed within herbaria. Digitisation projects are underway to render information from this important global biodiversity resource more accessible; the next step is to assemble and utilise these data to make better informed conservation decisions. One crucial question is: how many herbarium specimens are needed to detect threatened species? Such information would inform and help to prioritise digitisation efforts. Using 11,461 herbarium records we assessed species geographic range to determine a preliminary conservation status of 661 endemic species of Leguminosae and Orchidaceae from Madagascar, following the IUCN criteria. By capturing 15 georeferenced specimens per species we produced range estimates for use in conservation assessments consistent with estimates based on all known specimens, for more than 95% of species. None of the threatened species were misclassified as not threatened, and less than 3% of species would receive conservation support as a result of being falsely identified as threatened. This approach can therefore help progress towards the Global Strategy for Plant Conservation target of a conservation assessment for each plant species, while reducing digitisation effort by up to half.     

树鼩驯化中应激综合征的防治

本文分析了树鼩应激发生机制和影响,即生长受阻、采食量下降、能量消耗增加、繁殖率下降、抗病力低下,总结了树露鼩驯化中应激的综合防治措施,为树鼩驯化提供参考。     

Experimental infection in calves with a specific subtype of verocytotoxin-producing Escherichia coli O157:H7 of bovine origin

Background

In Sweden, a particular subtype of verocytotoxin-producing Escherichia coli (VTEC) O157:H7, originally defined as being of phage type 4, and carrying two vtx₂ genes, has been found to cause the majority of reported human infections during the past 15 years, including both sporadic cases and outbreaks. One plausible explanation for this could be that this particular subtype is better adapted to colonise cattle, and thereby may be excreted in greater concentrations and for longer periods than other VTEC O157:H7 subtypes.

Methods

In an experimental study, 4 calves were inoculated with 10⁹ colony forming units (cfu) of strain CCUG 53931, representative of the subtype VTEC O157:H7 (PT4;vtx₂;vtx_2c). Two un-inoculated calves were co-housed with the inoculated calves. Initially, the VTEC O157:H7 strain had been isolated from a dairy herd with naturally occurring infection and the farm had previously also been linked to human infection with the same strain. Faecal samples were collected over up to a 2-month period and analysed for VTEC O157 by immuno-magnetic separation (IMS), and IMS positive samples were further analysed by direct plating to elucidate the shedding pattern. Samples were also collected from the pharynx.

Results

All inoculated calves proved culture-positive in faeces within 24 hours after inoculation and the un-inoculated calves similarly on days 1 and 3 post-inoculation. One calf was persistently culture-positive for 43 days; in the remainder, the VTEC O157:H7 count in faeces decreased over the first 2 weeks. All pharyngeal samples were culture-negative for VTEC O157:H7.

Conclusion

This study contributes with information concerning the dynamics of a specific subtype of VTEC O157:H7 colonisation in dairy calves. This subtype, VTEC O157:H7 (PT4;vtx_2;vtx_2c), is frequently isolated from Swedish cattle and has also been found to cause the majority of reported human infections in Sweden during the past 15 years. In most calves, inoculated with a representative strain of this specific subtype, the numbers of shed bacteria declined over the first two weeks. One calf could possibly be classified as a high-shedder, excreting high levels of the bacterium for a prolonged period.     

Determination of diquat residues in rape seeds

A method for the determination of diquat residues in rape seeds has been developed. It is based on the original procedure of Calderbank, Morgan and Yuen¹ as modified by Kirsten² for diquat residues in potato tubers, which includes acid hydrolysis, ion exchange clean-up, colour formation and spectrophotometry. When applied to rape seeds the background was too high. Ion pair extraction with bromthymol blue in dichloromethane removed most interfering substances. Measurement of absorbance at three wavelengths 10 nm apart increased the specificity further. Because of varying recoveries from rape seeds (range 35-60%) in the procedure isotope dilution analysis was applied to each sample. The limit of detectability at 40-50 % recovery in a 20 g sample is 0.07 mg/kg and in a 50 g sample 0.03 mg/kg. The application to field trials is illustrated.     

精准扶贫下首都农业科技对口支援实践与思考

对口支援作为"精准扶贫"的重要措施,一直以来也是北京的重点工作之一。然而在当前扶贫开发的关键时期,受援地区农牧业发展水平仍较低,亟需提档升级。该研究选取北京对口支援的7个地区,开展实地调研,分析受援地区发展困境及需求,从工作机制及成效方面具体分析北京发挥科技优势开展对口援助的实践,并结合存在的问题,提出完善首都农业科技对口支援工作的几点思考。为对口支援工作及其他地区扶贫工作提供借鉴。     

Preparation and Characterization of Starch Particles for Use in Pickering Emulsions

Particle‐stabilized emulsions, called Pickering emulsions, can be produced by using starch particles. In this work we studied how the properties of the starch particles affect the droplet size and creaming of such emulsions. In the study, various sizes of starch particles were generated by two different methods and used to stabilize Pickering emulsions. Sedimentation according to Stokes’ law was used to separate small and large starch granules. Acid hydrolysis was another method used to obtain smaller particles. All samples were modified with octenyl succinic anhydride (OSA) to increase their hydrophobicity with a level of OSA substitution between 1.8 and 3.1%. The size of starch particles was the main factor influencing emulsion droplet sizes. Furthermore, the droplet size decreased as the starch concentration increased. Using small starch particles with sizes <10 μm produced stable emulsions with smaller droplet size compared with larger sizes of starch particles, >10 μm. When subjected to acid hydrolysis, smaller starch particles were generally obtained, which could subsequently create smaller emulsion droplets. The emulsion index increased for the acid‐hydrolyzed starch owing to the size reduction of starch particles. The shape of the starch seemed to have a minor impact on the droplet size and the creaming of Pickering emulsions.     

Transmission electron microscopy of mozzarella cheeses made from microfluidized milk.

The nanostructure of Mozzarella cheeses prepared from microfluidized milk was compared with that of control cheeses made from untreated milk. Milk heated to 10 or 54 degrees C and containing 1.0 or 3.2% fat was homogenized by microfluidization at 34 or 172 MPa prior to cheesemaking. The effects on the casein particles and fat globules in the cheese were determined by transmission electron microscopy after 1 day and 6 weeks of storage at 4 degrees C. The micrographs showed that electron-dense regions theorized to be casein submicelles rearranged from a homogeneous configuration to a pattern of clusters during the storage period. The nanostructure of the cheeses made from milk processed under the mildest conditions resembled the controls, but otherwise the fat droplets decreased in size and increased in number as the pressure and temperature were increased. The results indicate that both homogenization temperature and pressure affect the nanostructure of Mozzarella cheese.     

Surface of venus: evidence of diverse landforms from radar observations

Recent radar images of the surface of Venus reveal a complex and varied terrain. By applying a set of simplifying assumptions about the nature of the surfaces returning the radar signal, it is possible to make a number of plausible interpretations. In one region on Venus, several circular features have the gross morphology of degraded impact craters. If they are indeed of impact origin, these features suggest that there exist on Venus areas which are ancient and where erosion or resurfacing has not been as intense or as pervasive as on the earth. In other regions there are intriguing features that may evidence active internal processes. One is a large trough-like depression (0 degrees , 76 degrees W; measuring 1400 by 150 by 2 kilometers) planimetrically suggestive of both the Valles Marineris on Mars and the East African Rift on the earth. Another feature, about 250 kilometers in diameter and of positive relief, includes an 80-kilometer-diameter circular depression at its summit, suggestive of a large volcanic construct. A third region, near 0 degrees , 10 degrees E, contains roughly parallel ranges of mountains separated by valley-like features, with relief varying from small isolated hills several hundred meters high to low ranges on the order of 1000 meters to large mountains approaching 2 kilometers in height. If Venus has a mobile crust similar to the earth's, these mountains may have been produced by compressional tectonics. These interpretations of the radar data indicate that Venus has been a geologically active planet which has developed diverse landforms and therefore is an exciting candidate for future exploration.     

Evidence for persistent flow and aqueous sedimentation on early Mars

Landforms representative of sedimentary processes and environments that occurred early in martian history have been recognized in Mars Global Surveyor Mars Orbiter Camera and Mars Odyssey Thermal Emission Imaging System images. Evidence of distributary, channelized flow (in particular, flow that lasted long enough to foster meandering) and the resulting deposition of a fan-shaped apron of debris indicate persistent flow conditions and formation of at least some large intracrater layered sedimentary sequences within fluvial, and potentially lacustrine, environments.