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31.
Drought Stress Alters the Concentration of Wood Terpenoids in Scots Pine and Norway Spruce Seedlings 总被引:10,自引:0,他引:10
Drought is known to have an impact on the resistance of conifers to various pests, for example, by affecting resin flow in trees. Little is known, however, about the quantitative and qualitative changes in resin when trees are growing in low moisture conditions. We exposed Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings to medium and severe drought stress for two growing seasons and analyzed the monoterpenes and resin acids in the main stem wood after two years of treatment. In addition to secondary chemistry, we measured the level of nutrients in the needles and the growth response of seedlings. After the first year of treatment, drought stress did not affect the growth of seedlings, but in the second year, shoot growth was retarded, especially in Scots pine. In both conifer species, severe drought increased the concentrations of several individual monoterpenes and resin acids. Total monoterpenes and resin acids were 39 and 32% higher in severe drought-treated Scots pine seedlings than in the controls, and 35 and 45% higher in Norway spruce seedlings. In Scots pine needles, the concentrations of nitrogen and phosphorus increased, while magnesium and calcium decreased compared to controls. In Norway spruce needles, nutrient concentrations were not affected. The results suggest that drought stress substantially affects both the growth of conifers and the chemical quality of the wood. We discuss the potential trade-off in growth and defense of small conifer seedlings. 相似文献
32.
33.
Hakala KS Laitinen L Kaukonen AM Hirvonen J Kostiainen R Kotiaho T 《Analytical chemistry》2003,75(21):5969-5977
Good reliability of Caco-2 permeability studies requires competent sampling and analytical methods to ensure the comparability of day-to-day experiments. In this work, two n-in-one LC/MS/MS methods based on two different ionization techniques were developed and validated for a group of reference compounds; eight of them are recommended by the Food and Drug Administration (FDA) for the evaluation of oral drug permeability. The performance of a new ionization technique, atmospheric pressure photoionization (APPI), as an interface for quantitative LC/MS analysis was evaluated in comparison to the electrospray ionization (ESI). Generally, the validation parameters, including sensitivity, accuracy, and repeatability, were comparable for the APPI and ESI methods. The main difference was that the linear quantitative range of APPI was 3-4 orders of magnitude (r(2) >/= 0.998) whereas in ESI it was typically 2-3 orders of magnitude (r(2) >/= 0.990). By the APPI and ESI methods, the simultaneous analysis of nine highly heterogeneous compounds was achieved within 5.5-7 min, which leads to significant savings in time and cost of the analyses. The successful validation data indicate the usefulness of both the methods for the rapid and sensitive (LOD values typically =5 nM) testing of drug transport across the Caco-2 monolayers, and after case-specific modification, the methods enable the permeability screening of new drug candidates. The applicability and reliability of both methods was demonstrated with a real batch of Caco-2 samples, each providing similar values of apparent permeability (P(app)). In addition, the individual permeabilities of the compounds in the cocktail experiments correlated closely to the ones obtained from single-compound experiments. 相似文献
34.
This paper introduces a generalized design method for polynomial-based interpolation filters. These filters can be implemented
by using a modified Farrow structure, where the fixed finite impulse response (FIR) sub-filters possess either symmetrical
or anti-symmetrical impulse responses. In the proposed approach, the piecewise polynomial impulse response of the interpolation
filter is optimized directly in the frequency domain using either the minimax or least mean square criterion subject to the
given time domain constraints. The length of the impulse response and the degree of the approximating polynomial in polynomial
intervals can be arbitrarily selected. The optimization in the frequency domain makes the proposed design scheme more suitable
for various digital signal processing applications and enables one to synthesize interpolation filters for arbitrary desired
and weighting functions. Most importantly, the interpolation filters can be optimized in a manner similar to that of conventional
linear-phase FIR filters. 相似文献
35.
H. J. Junes H. Alles M. S. Manninen A. Y. Parshin I. A. Todoshchenko 《Journal of Low Temperature Physics》2008,153(5-6):244-249
Recently observed non-classical rotational inertial (NCRI) in solid 4He is most probably related to defects which appear during the sample preparation. We have measured the energy of the stacking fault (SF) in an hcp 4He crystal at 0.2 K. The SF creates a groove with a dihedral angle of 155±5° on the crystal surface in a quasi-equilibrium with the liquid. The obtained value for the SF energy is (0.07±0.02) mJ/m2, which is ~0.4 of the surface tension of the liquid–solid interface of 4He. Our findings suggest that the phenomenon of burst-like creation of new atomic layers might be accompanied by the creation of SFs. 相似文献
36.
T. Petäjä G. Mordas H. Manninen P. P. Aalto K. Hämeri M. Kulmala 《Aerosol science and technology》2013,47(12):1090-1097
In this article we present observations on the detection efficiency of a recently developed TSI 3785 Water Condensation Particle Counter (WCPC). The instrument relies on activation of sampled particles by water condensation. The supersaturation is generated by directing a saturated airflow into a “growth tube,” in which the mass transfer of water vapor is faster than heat transfer. This results in supersaturated conditions with respect to water vapor in the centerline of a “growth tube.” In this study, the cut-off diameter, that is, the size, where 50% of the sampled particles are successfully activated, varied from 4 to 14 nm for silver particles as a function of temperature difference between the saturator and the growth tube. The solubility of the sampled particles to water played an important role in the detection efficiency. Cut-off diameters for ammonium sulphate and sodium chloride particles were 5.1 and 3.6–3.8 nm, respectively at nominal operation conditions. Corresponding cut-off diameter for hydrophobic silver particles was 5.8 nm. 相似文献
37.
Rönnholm Mats R. Hernández Carucci José R. Arve Kalle Eränen Kari Salmi Tapio 《Topics in Catalysis》2007,42(1-4):195-198
A silver/alumina catalyst was tested for its NO
x
reduction activity during oxygen-rich conditions and during variation in the input parameters (nitric oxide, octane and oxygen).
The experimental data using the microreactor was investigated by means of artificial neural networks (ANN). 相似文献
38.
Identification of milk fat triacylglycerols was accomplished by capillary supercritical fluid chromatography (SFC) combined
with atmospheric pressure chemical ionization mass spectrometry [(APCI)MS]. Supercritical carbon dioxide was the carrier fluid
in SFC. Ionization was achieved by introducing vapor of ammonia in methanol into the ionization chamber, which resulted in
the formation of abundant [M+18]+ and [M-RCOO]+ ions of triacylglycerols. These ions defined both the molecular weight and the fatty acid constituents of a triacylglycerol,
respectively. SFC on a nonpolar stationary phase provided an efficient separation of triacylglycerols according to the combined
number of carbon atoms in the acyl chains of a molecule. In addition to the identification of the major chromatographic peaks
representing molecules with 26–54 acyl carbons, minor peaks representing triacylglycerols with an odd number of acyl carbons
were separated and identified. Furthermore, compositional information on partially separated isobaric triacylglycerols, which
differed substantially in the chain length of the fatty acyl residues, was achieved within some of the peaks. A new finding
of the present study was the formation of abundant [M+18]+ ions of saturated triacylglycerols in addition to diagnostic fragment ions, being of primary importance in structure elucidation.
This extends the applicability of capillary SFC-(APCI)MS in the analysis of both saturated and unsaturated triacylglycerols. 相似文献
39.
Heidi Markus Päivi Mäki-Arvela Narendra Kumar Natalya V. Kul’kova Patrik Eklund Rainer Sjöholm Bjarne Holmbom Tapio Salmi Dmitry Yu. Murzin 《Catalysis Letters》2005,103(1-2):125-131
The natural lignan hydroxymatairesinol was hydrogenolysed to a potential anticarcinogenic substance matairesinol over different carbon-supported palladium catalysts. The reaction was conducted in 2-propanol at 70 °C under hydrogen flow in a stirred glass reactor. The catalysts were characterised by N2-physisorption, CO pulse chemisorption and pH measurement of aqueous catalyst slurries. The most active catalyst (Degussa-Hüls) gave yields of matairesinol over 90% in 4 h. It was concluded that the acidity of the catalyst had a profound influence on the reaction rate. 相似文献
40.