添加玉米和水稻秸秆对淹水土壤pH、二氧化碳及交换态铵的影响

通过温室土壤培养试验,研究了不同添加量玉米和水稻秸秆对淹水土壤pH、CO₂及交换态铵的影响.结果表明：在接近中性的土壤中加入秸秆可使土壤pH值降低,4 g·kg^-1玉米和水稻秸秆处理的土壤pH值均与对照差异显著（P＜0.05）,而1 g·kg^-1玉米和水稻秸秆处理与对照差异不显著（P＞0.05）.土壤溶液中的CO₂含量随秸秆添加量的增加而增大,1 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为35.9％和31.9％（v/v）,与对照（25.8％）差异达显著水平（P＜0.05）,但两者间差异不显著（P＞0.05）;4 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为54.2％和41.8％（v/v）,与对照差异极显著（P＜0.01）,两者间差异也达显著水平（P＜0.05）.在不施氮肥的情况下,添加秸秆可降低土壤铵态氮浓度,且铵态氮浓度随秸秆添加量的增加而降低,不同添加量处理间差异显著（P＜0.05）;在施入氮肥的情况下,1 g·kg^-1玉米和水稻秸秆处理提高了土壤铵态氮浓度,而4 g·kg^-1玉米和水稻秸秆处理降低了土壤铵态氮浓度.无论是否施入氮肥,玉米和水稻秸秆处理的土壤铵态氮浓度差异不显著（P＞0.05）.     

Alkane composition diversity among populations of dwarf forms of Juniperus communis L.: comparison between western Europe and northern American populations

The cuticular wax composition of leaves has been analysed in three western European populations (Corsica, central Pyrenees, northern Alps) of Juniperus communis var. saxatilis Pall. (=  J. nana Willd., nom illeg.) and in one population of J. communis L. var. depressa Pursh. from North America (Sierra Nevada). Gas chromatography shows the presence of 13 alkanes in all samples ranging from C₂₃ to C₃₅ with important intraspecific polymorphism in alkane content. The dominant alkanes range from C₃₃ to C₃₅. Alkanes C₂₁ and C₂₂ were found only in Corsica and Sierra Nevada populations. Canonical discriminant analysis separated the J. communis L. var. depressa Pursh. of the population of Sierra Nevada from other populations of J. communis var. saxatilis Pall. on the basis of their higher C₃₁ content and the constant presence of C₂₁ and C₂₂ alkanes. J. communis var. saxatilis Pall. populations from the Pyrenees are close to northern Alps populations characterized by high concentrations of C₃₃, C₃₄ and C₃₅ alkanes. This paper confirms the existence of Juniperus var. saxatilis Pall. in the Pyrenees (France).  © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 165–168.     

Simulation of a cross-flow shrinking-bed reactor for the hydrolysis of lignocellulosics.

An idealized model is developed for the case in which biomass slurry is conveyed through an annulus, with water or steam entering through an inner porous wall and liquid product leaving through an outer porous wall. It is assumed that the ratio of occluded liquid to solid in the slurry is a constant, Rws, and that non-occluded water is immediately removed from the reactor. The goal of > 90% sugar yield with > 10% sugar in the product is almost reached (88% glucose yield, 91% xylose yield, 47 g/l glucose and 45 g/l xylose) at 240 degrees C, 1% acid. Rws = 1 and a radial wash water flow of three times the initial mass flow of solids to the reactor per meter of reactor length per g/l of sugar concentration in the occluded water. If Rws is limited to 3, the yield falls to 85% and the total sugar concentration to 61 g/l. Even without cross-flow wash, the yields can be increased by about 16 percentage points, compared to plug flow, by extracting excess liquid through the outer wall as it is formed. At 200 degrees C, where one might prefer to operate for ease of control and concern about the possibility of making fermentation inhibitors at higher temperatures, the maximum glucose yield in a plug-flow reactor is low (12-13%) whereas in a cross-flow reactor, at a high cross-flow wash rate, it can still be quite high (60-83%) but at a very low concentration (0.57-1.47%). In these simulations it is assumed that one-half of the inerts is solubilized. The formation of oligomers is neglected.     

Hind limb malformations in free-living northern leopard frogs (Rana pipiens) from Maine, Minnesota, and Vermont suggest multiple etiologies

BACKGROUND: Reports of malformed frogs have increased throughout the North American continent in recent years. Most of the observed malformations have involved the hind limbs. The goal of this study was to accurately characterize the hind limb malformations in wild frogs as an important step toward understanding the possible etiologies. METHODS: During 1997 and 1998, 182 recently metamorphosed northern leopard frogs (Rana pipiens) were collected from Minnesota, Vermont, and Maine. Malformed hind limbs were present in 157 (86%) of these frogs, which underwent necropsy and radiographic evaluation at the National Wildlife Health Center. These malformations are described in detail and classified into four major categories: (1) no limb (amelia); (2) multiple limbs or limb elements (polymelia, polydactyly, polyphalangy); (3) reduced limb segments or elements (phocomelia, ectromelia, ectrodactyly, and brachydactyly; and (4) distally complete but malformed limb (bone rotations, bridging, skin webbing, and micromelia). RESULTS: Amelia and reduced segments and/or elements were the most common finding. Frogs with bilateral hind limb malformations were not common, and in only eight of these 22 frogs were the malformations symmetrical. Malformations of a given type tended to occur in frogs collected from the same site, but the types of malformations varied widely among all three states, and between study sites within Minnesota. CONCLUSIONS: Clustering of malformation type suggests that developmental events may produce a variety of phenotypes depending on the timing, sequence, and severity of the environmental insult. Hind limb malformations in free-living frogs transcend current mechanistic explanations of tetrapod limb development.     

Combined prime-boost vaccination against tick-borne encephalitis (TBE) using a recombinant vaccinia virus and a bacterial plasmid both expressing TBE virus non-structural NS1 protein

Background  

Heterologous prime-boost immunization protocols using different gene expression systems have proven to be successful tools in protecting against various diseases in experimental animal models. The main reason for using this approach is to exploit the ability of expression cassettes to prime or boost the immune system in different ways during vaccination procedures. The purpose of the project was to study the ability of recombinant vaccinia virus (VV) and bacterial plasmid, both carrying the NS1 gene from tick-borne encephalitis (TBE) virus under the control of different promoters, to protect mice against lethal challenge using a heterologous prime-boost vaccination protocol.     

A protein secretion pathway critical for Mycobacterium tuberculosis virulence is conserved and functional in Mycobacterium smegmatis

The Snm protein secretion system is a critical determinant of Mycobacterium tuberculosis virulence. However, genes encoding components of this pathway are conserved among all mycobacteria, including the nonpathogenic saprophyte Mycobacterium smegmatis. We show that the Snm system is operational in M. smegmatis and that secretion of its homologous ESAT-6 and CFP-10 substrates is regulated by growth conditions. Importantly, we show that Snm secretion in M. smegmatis requires genes that are homologous to those required for secretion in M. tuberculosis. Using a gene knockout strategy in M. smegmatis, we have also discovered four new gene products that are essential for Snm secretion, including the serine protease mycosin 1. Despite the evolutionary distance between M. smegmatis and M. tuberculosis, the M. smegmatis Snm system can secrete the M. tuberculosis ESAT-6 and CFP-10 proteins, suggesting that substrate recognition is also conserved between the two species. M. smegmatis, therefore, represents a powerful system to study the multicomponent Snm secretory machine and to understand the role of this conserved system in mycobacterial biology.     

SEGMENTATION APPROACHES THAT DIFFERENTIATE CONSUMPTION FREQUENCY FROM SENSORY PREFERENCE1

People can eat a food without having a strong preference for it, and people can prefer a food without eating it. Given this seeming disconnect between attitude and behavior, which type of measure or segment can best be used to profile or identify loyal consumer segments of a food, such as soy? This research compares a usage‐based method (heavy‐light‐nonusers) with a new attitude‐based method (seeker‐neutral‐avoider), and finds that the attitude‐based method differentiates purchase‐related intentions better than the usage‐based method. Implications for profiling consumer taste patterns and consumer segments are provided.     

Characterization and molecular genetic complementation of mutants affecting dimorphism in the fungus ustilago maydis

Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a unicellular, nonpathogenic yeast-like form and a dikaryotic, pathogenic filamentous form. Previously, a constitutively filamentous haploid mutant was obtained. Complementation of this mutant led to the isolation of the gene encoding adenylate cyclase, uac1. Secondary mutagenesis of a uac1 disruption strain allowed the isolation of a large number of suppressor mutants, termed ubc, for Ustilago bypass of cyclase, lacking the filamentous phenotype. Analysis of one of these suppressor mutants previously led to the identification of the ubc1 gene, encoding the regulatory subunit of cAMP-dependent protein kinase. In this report we describe the isolation of cosmids containing three new ubc genes, termed ubc2, ubc3, and ubc4. We also describe the morphology of the ubc2, ubc3, and ubc4 mutants in a uac1- background as well as in a background with a functional uac1 gene. In addition, we describe several mutant strains not complemented with any of the genes currently in hand and that are thus presumed to possess mutations in additional ubc genes. Copyright 1998 Academic Press.