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排序方式: 共有41条查询结果,搜索用时 31 毫秒
31.
Tiainen M Pusenius J Julkunen-Tiitto R Roininen H 《Journal of chemical ecology》2006,32(10):2287-2301
We studied the effects of the intensity of intraspecific competition, as indicated by seedling density, and competitive success within populations, as indicated by seedling size, on the secondary chemistry of the stems of silver birch seedlings and their palatability to field voles. We found that the size of seedlings and their total phenolic concentrations were inversely related to stand density. Voles, however, did not discriminate between seedlings grown at the densities studied. Variation in competitive success was associated with several phenomena. Seedling size was positively related to the concentrations of several secondary compounds and to vole preferences, but negatively related to nitrogen concentration. We suggest that the ecological consequences of variation in seedling size cannot be predicted without knowledge of the mechanism behind the variation. 相似文献
32.
Fatty acids of lipid fractions in extracellular polymeric substances of activated sludge flocs 总被引:1,自引:0,他引:1
Conrad A Suutari MK Keinänen MM Cadoret A Faure P Mansuy-Huault L Block JC 《Lipids》2003,38(10):1093-1105
Phospholipid (PL), glycolipid (GL), and neutral lipid (NL) FA, and the lipopolysaccharide 2- and 3-hydroxy (LPS 2-OH and 3-OH) FA of activated sludges and extracted extracellular polymeric substances (EPS) were determined on samples collected from two wastewater treatment plants. EPS extracted from sludges by means of sonication and cation exchange contained proteins (43.4%), humic-like substances (11.5%), nucleic acids (10.9%), carbohydrates (9.9%), and lipid-bound FA (1.8%). The lipids associated with EPS were composed of GL, PL, NL, and LPS acids in proportions of 61, 21, 16, and 2%, respectively. The profiles of lipid-bound FA in activated sludges and EPS were similar (around 85 separate FA were identified). The FA signatures observed can be attributed to the likely presence of yeasts, fungi, sulfate-reducing bacteria, gram-positive and gram-negative bacteria, and, in lesser quantities, mycobacteria. Comparison of data from the dates of sampling (January and September) showed that there were more unsaturated PLFA in the EPS extracted from the activated sludges sampled in January. This observation could be partly related to microorganism adaptation to temperature variations. The comparison between two wastewater treatment plants showed that the FA profiles were similar, although differences in microbial community structure were also seen. Most of the FA in sludges had an even number of carbons. 相似文献
33.
The non-parametric k-nearest neighbour (k-NN) multi-source estimation method is commonly employed in forest inventories that use satellite images and field data. The method presumes the selection of a few estimation parameters. An important decision is the choice of the pixel-dependent geographical area from which the nearest field plots in the spectral space for each pixel are selected, the problem being that one spectral vector may correspond to several different ground data vectors. The weighting of different spectral components is an obvious problem when defining the distance metric in the spectral space.The paper presents a new method. The first innovation is that the large-scale variation of forest variables is used as ancillary data that are added to the variables of the multi-source k-NN estimation. These data are assigned weights in a way similar to the spectral information of satellite images when defining the applied distance metric. The second innovation is that “optimal” weights for spectral data, as well as ancillary data, are computed by means of a genetic algorithm. Tests with practical forest inventory data show that the method performs noticeably better than other applications of k-NN estimation methods in forest inventories, and that the problem of biases in the species volume predictions can for example, almost completely be overcome with this new approach. 相似文献
34.
Tape casting system for ULTCCs to fabricate multilayer and multimaterial 3D electronic packages with embedded electrodes
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Mei‐Yu Chen Timo Vahera Chi‐Shiung Hsi Maciej Sobocinski Merja Teirikangas Jani Peräntie Jari Juuti Heli Jantunen 《Journal of the American Ceramic Society》2017,100(4):1257-1260
A 3D multilayer structure built by two ultra‐low temperature co‐fired ceramic (ULTCC) compositions with silver embedded electrodes are co‐fired at a temperature of 450°C. The 3D multilayer module is prepared by laminating the ULTCC green tapes with a new binder system, which organics can be completely burned out at temperature of 250°C before the sintering of the ULTCC 3D modulus. High‐density microstructures are achieved for the sintered module. In this study, the ULTCC feasible binder system is introduced. Also, ULTCC multilayers and multimaterial structures with surface and embedded silver electrodes are fabricated. This research opens up a new horizon for fabrication of electroceramic devices with embedded electrodes in multimaterial devices. 相似文献
35.
Pia Michler Anne Schedel Martha Witschas Ulrike Anne Friedrich Rabea Wagener Juha Mehtonen Triantafyllia Brozou Maria Menzel Carolin Walter Dalileh Nabi Glen Pearce Miriam Erlacher Gudrun Ghring Martin Dugas Merja Heinniemi Arndt Borkhardt Friedrich Stlzel Julia Hauer Franziska Auer 《International journal of molecular sciences》2021,22(21)
While the shelterin complex guards and coordinates the mechanism of telomere regulation, deregulation of this process is tightly linked to malignant transformation and cancer. Here, we present the novel finding of a germline stop-gain variant (p.Q199*) in the shelterin complex gene POT1, which was identified in a child with acute myeloid leukemia. We show that the cells overexpressing the mutated POT1 display increased DNA damage and chromosomal instabilities compared to the wildtype counterpart. Protein and mRNA expression analyses in the primary patient cells further confirm that, physiologically, the variant leads to a nonfunctional POT1 allele in the patient. Subsequent telomere length measurements in the primary cells carrying heterozygous POT1 p.Q199* as well as POT1 knockdown AML cells revealed telomeric elongation as the main functional effect. These results show a connection between POT1 p.Q199* and telomeric dysregulation and highlight POT1 germline deficiency as a predisposition to myeloid malignancies in childhood. 相似文献
36.
Tarl W. Prow Xianfeng Chen Natalie A. Prow Germain J. P. Fernando Cindy S. E. Tan Anthony P. Raphael David Chang Merja P. Ruutu Derek W. K. Jenkins Alyssa Pyke Michael L. Crichton Kristin Raphaelli Lucas Y. H. Goh Ian H. Frazer Michael S. Roberts Joy Gardner Alexander A. Khromykh Andreas Suhrbier Roy A. Hall Mark A. F. Kendall 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(16):1776-1784
The ‘Nanopatch’ (NP) comprises arrays of densely packed projections with a defined geometry and distribution designed to physically target vaccines directly to thousands of epidermal and dermal antigen presenting cells (APCs). These miniaturized arrays are two orders of magnitude smaller than standard needles—which deliver most vaccines—and are also much smaller than current microneedle arrays. The NP is dry‐coated with antigen, adjuvant, and/or DNA payloads. After the NP was pressed onto mouse skin, a protein payload co‐localized with 91.4 ± 4.1 APC mm−2 (or 2925 in total) representing 52% of the delivery sites within the NP contact area, agreeing well with a probability‐based model used to guide the device design; it then substantially increases as the antigen diffuses in the skin to many more cells. APC co‐localizing with protein payloads rapidly disappears from the application area, suggesting APC migration. The NP also delivers DNA payloads leading to cutaneous expression of encoded proteins within 24 h. The efficiency of NP immunization is demonstrated using an inactivated whole chikungunya virus vaccine and a DNA‐delivered attenuated West Nile virus vaccine. The NP thus offers a needle‐free, versatile, highly effective vaccine delivery system that is potentially inexpensive and simple to use. 相似文献
37.
Kärhä P Heikkilä A Ruokolainen K Kaunismaa M 《The Review of scientific instruments》2011,82(2):023107
A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter. Radiation at the wavelength range 250-500 nm is dispersed onto the sample plane of 1.5 cm in height and 21 cm in width. The optical performance of the device has been characterized by radiometric measurements. Using the facility, test samples prepared of regular newspaper have been irradiated from 1 to 8 h. Color changes on the different locations of the aged samples have been quantified by color measurements. Yellowness indices computed from the color measurements demonstrate the capability of the facility in revealing wavelength dependencies of the material property changes in reasonable time frames. 相似文献
38.
Transesterification of trimethylolpropane and rapeseed oil methyl ester to environmentally acceptable lubricants 总被引:7,自引:0,他引:7
Esa Uosukainen Yu-Yen Linko Merja Lämsä Tommi Tervakangas Pekka Linko 《Journal of the American Oil Chemists' Society》1998,75(11):1557-1563
Biodegradable trimethylolpropane [2-ethyl-2-(hydroxymethyl)-1,3-propanediol] esters of rapeseed oil fatty acids were synthesized
by transesterification with rapeseed oil methyl ester both by enzymatic and chemical means, both in bench and pilot scales.
Nearly complete conversions were obtained with both techniques. A reduced pressure of about 2 to 5 kPa, to remove the methanol
formed during transesterification, was critical for a high product yield. The quantity of added water was also critical in
the biocatalysis. Candida rugosa lipase was used as biocatalyst and an alkaline catalyst in chemical transesterifications. In biocatalysis the maximum total
conversion to trimethylolpropane esters of up to 98% was obtained at 42°C, 5.3 kPa, and 15% added water. The maximum conversion
of about 70% to the tri-ester was obtained at the slightly higher temperature of 47°C. The reaction time was longer in the
biocatalysis, but considerably higher temperatures were required in chemical synthesis. In the chemical synthesis tri-ester
yields increased when the temperature was first held at 85 to 110°C for 2.5 h and subsequently increased to up to 120°C for
8 h. The trimethylolpropane esters obtained were tested as biodegradable hydraulic fluids and compared to commercially available
hydraulic oils. The hydraulic fluids based on trimethylolpropane esters of rapeseed oil had good cold stability, friction
and wear characteristics, and resistance against oxidation at elevated temperatures. 相似文献
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