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991.
Small white aggregates frequently observed in peat have been studied using scanning electron microscopy and infrared absorption spectrometry. It has been shown that they are fibrous, consisting of paraffin wax and associated carbohydrate and secondary amide, and are secreted by the aphid Colopha compressa, which colonizes the roots of Eriophorum spp. growing on peat. This is the first report of the occurrence of this aphid species in Scotland.  相似文献   
992.
The LDL receptor gene: a mosaic of exons shared with different proteins   总被引:112,自引:0,他引:112  
The multifunctional nature of coated pit receptors predicts that these proteins will contain multiple domains. To establish the genetic basis for these domains (LDL) receptor. This gene is more than 45 kilobases in length and contains 18 exons, most of which correlate with functional domains previously defined at the protein level. Thirteen of the 18 exons encode protein sequences that are homologous to sequences in other proteins: five of these exons encode a sequence similar to one in the C9 component of complement; three exons encode a sequence similar to a repeat sequence in the precursor for epidermal growth factor (EGF) and in three proteins of the blood clotting system (factor IX, factor X, and protein C); and five other exons encode nonrepeated sequences that are shared only with the EGF precursor. The LDL receptor appears to be a mosaic protein built up of exons shared with different proteins, and it therefore belongs to several supergene families.  相似文献   
993.
994.
A new magnetic material with appreciable optical transmission in the visible region at room temperature has been isolated as a gamma-Fe(2)O(3)/polymer nanocomposite. The synthesis is carried out in an ion-exchange resin at 60 degrees C. Magnetization and susceptibility data demonstrate loading-dependent saturation moments as high as 46 electromagnetic units per gram and superparamagnetism for lower loadings where particle sizes are less than 100 angstroms. Optical absorption studies show that the small-particle form of gamma-Fe(2)O(3) is considerably more transparent to visible light than the single-crystal form. The difference in absorption ranges from nearly an order of magnitude in the "red" spectral region to a factor of 3 at 5400 angstroms. The magnetization of the nanocomposite is greater by more than an order of magnitude than those of the strongest room-temperature transparent magnets, FeBO(3) and FeF(3).  相似文献   
995.
Summary Three different laboratory earthworm protocols for assessing the potential toxicity of environmental samples were evaluated using Eisenia fetida. The 48-h Contact Test (CT) is a short test and may indicate the presence of water-soluble chemicals. The 14-day Soil Test (ST) is best suited to assess chemical impacts of either known or unknown chemicals in soils. The Giant Axon Conduction Velocity protocol (GACVT) used with either the CT or the ST can detect sublethal neurotoxic effects in shorter periods of time and at lower chemical concentrations than mortality tests. The use of these tests is suggested as an estimate of potential toxicity of environmental soil samples.  相似文献   
996.
The magnetic field signature obtained by Cassini during its first close encounter with Titan on 26 October 2004 is presented and explained in terms of an advanced model. Titan was inside the saturnian magnetosphere. A magnetic field minimum before closest approach marked Cassini's entry into the magnetic ionopause layer. Cassini then left the northern and entered the southern magnetic tail lobe. The magnetic field before and after the encounter was approximately constant for approximately 20 Titan radii, but the field orientation changed exactly at the location of Titan's orbit. No evidence of an internal magnetic field at Titan was detected.  相似文献   
997.
998.
It is shown that whistler mode waves from the ionosheath of Venus are absorbed by Landau damping at the dayside ionosphere boundary. This process heats the ionospheric electrons and it may provide an important energy input into the dayside ionosphere. Cyclotron damping of the waves does not occur in the same region. However, Landau damping of ionosheath waves is apparently not an important energy source in the nightside ionosphere. Impulsive events in the nightside ionosphere seem to fall into two classes: (i) lightning signals (near periapsis) and (ii) noise, which may be caused by gradient or current instabilities.  相似文献   
999.
Developed for carrying out risk assessments under the European Commission (EC) Council Regulation No 708/2007 concerning the use of alien and locally absent species in aquaculture (ASR), the European Non‐native Species in Aquaculture Risk Assessment Scheme (ENSARS) is briefly summarised, and the ‘Organism’ module is applied to the 24 species listed in ASR's Annex IV. Four other ENSARS modules (Infectious Agent, Facility, Pathway, and Socio‐economic) were used to assess two case study species (European catfish Silurus glanis L. and red swamp crayfish Procambarus clarkii Girard). No Annex IV species was categorised as low risk, 10 as moderately low risk, 12 as medium risk, two as moderately high risk and none as high risk. The results are discussed and recommendations are made on further development of the scheme as well as the need to have multiple assessors of multidisciplinary expertise from the Member States concerned carry out the assessments using an approach similar to that carried out by EU Reference Laboratory proficiency tests.  相似文献   
1000.
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