Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FIRS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2000

Steam pretreatment of Douglas-fir wood chips. Can conditions for optimum hemicellulose recovery still provide adequate access for efficient enzymatic hydrolysis?

Douglas-fir sapwood and heartwood were impregnated with SO2 and steam exploded at three severity levels, and the cellulose-rich, water-insoluble component was enzymatically hydrolyzed. The high-severity conditions resulted in near complete solubilization and some degradation of hemicelluloses and a significant improvement in the efficiency of enzymatic digestibility of the cellulose component. At lower severity, some of the hemicellulose remained unhydrolyzed, and the cellulose present in the pretreated solids was not readily hydrolyzed. The medium-severity pretreatment conditions proved to be a good compromise because they improved the enzymatic hydrolyzability of the solids and resulted in the recovery of the majority of hemicellulose in a monomeric form within the water-soluble stream. Sapwood-derived wood chips exhibited a higher susceptibility to both pretreatment and hydrolysis and, on steam explosion, formed smaller particles as compared to heartwood-derived wood chips.

Cellulase↗
PubMedDate not supplied

Foliar and cortex oleoresin variability of silver fir (Abies alba Mill.) in Albania.

Terpene composition of needle and cortical oleoresin from lateral shoots were analyzed by GC/MS for four Silver fir (Abies alba Mill.) populations scattered in natural species range in Albania. More than sixty compounds were detected in the needle oleoresin, which was characterized by a high content of alpha-pinene, camphene, beta-pinene, limonene and bornyl acetate. Three monoterpenes, alpha-pinene, beta-pinene and limonene, and two sesquiterpenes, beta-caryophyllene and germacrene D, comprised the majority of cortical oleoresin. The terpene composition differences among the populations that led to the recognition of two chemotypes. The needle oleoresin from the provinces of Puka, Bulqiza and Llogara were characterised by high amounts of beta-pinene, camphene and alpha-pinene and low amounts of limonene, while that from Drenova had high amounts of beta-pinene and limonene. A similar pattern was found in the cortical oleoresin with the exception of camphene that was a minor contributor. Geographical and seasonal variation between the populations was, also, investigated. Multivariate analysis of both needle and cortical oleoresin separated Drenova (southeastern population) from the other sites. When both major monoterpenes and sesquiterpenes were considered four chemical profiles could be attributed. Based on their chemical profiles, the populations can be divided into two groups: Populations with high content of beta-pinene and alpha-pinene but a low content of limonene (Puka, Bulqiza and Llogara), typical of most of A. alba populations in all its distribution range. Population with a high content of limonene and a moderate content of beta-pinene and alpha-pinene (Drenova).

Albania↗
PubMed2005

Nucleotide diversity and linkage disequilibrium in cold-hardiness- and wood quality-related candidate genes in Douglas fir.

Nuclear sequence variation and linkage disequilibrium (LD) were studied in 15 cold-hardiness- and 3 wood quality-related candidate genes in Douglas fir [Pseudotsuga menziesii (Mirb.) Franco]. This set of genes was selected on the basis of its function in other plants and collocation with cold-hardiness-related quantitative trait loci (QTL). The single-nucleotide polymorphism (SNP) discovery panel represented 24 different trees from six regions in Washington and Oregon plus parents of a segregating population used in the QTL study. The frequency of SNPs was one SNP per 46 bp across coding and noncoding regions on average. Haplotype and nucleotide diversities were also moderately high with H(d) = 0.827 +/- 0.043 and pi = 0.00655 +/- 0.00082 on average, respectively. The nonsynonymous (replacement) nucleotide substitutions were almost five times less frequent than synonymous ones and substitutions in noncoding regions. LD decayed relatively slowly but steadily within genes. Haploblock analysis was used to define haplotype tag SNPs (htSNPs). These data will help to select SNPs for association mapping, which is already in progress.

Adaptation, Physiological↗
PubMed2004

Bacillus thuringiensis subsp. kurstaki aerial spray prescriptions for balsam fir stand protection against spruce budworm (Lepidoptera: Tortricidae).

Although commercial formulations of Bacillus thuringiensis subsp. kurstaki (Btk) are being widely used in forest protection against lepidopteran defoliators, optimal application prescriptions have often yet to be worked out in detail. We conducted field experiments over a 6-yr period (1996-2001) in southwestern Québec to determine application prescriptions for optimal protection of balsam fir, Abies balsamea (L.), healthy stands against the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae). At moderate larval densities (<30 larvae per 45-cm branch tip), similar foliage protection was achieved with one or two Btk applications of 30 billion international units per hectare (BIU/ha). When larval densities exceeded 30 larvae per branch tip, two successive applications of 30 BIU/ha significantly increased foliage protection. Whether the second application took place 5 or 10 d after the first spray did not affect treatment efficacy. Increasing the application dosage from 30 to 50 BIU/ha did not lead to better foliage protection against high larval densities, but the current standard dosage of 30 BIU/ha saved more foliage than 15 BIU/ha against moderate populations. The recommended dosage of 30 BIU can be applied in lower application volumes (1.5 liters/ha) by using a high-potency product (20 BIU/liter), because we did not observe a reduction in efficacy compared with the application of a lower potency product (12.7 BIU/liter) in 2.37 liters/ha. We also demonstrated that Btk can be applied much earlier in the season without compromising spray efficacy: there was no difference in treatment efficacy of double applications at 30 BIU/ha when the first spray was timed for early third, peak third, or early fourth instars.

Abies↗
PubMedDate not supplied

Copper, zinc, and arsenic in soil surrounding Douglas-fir poles treated with ammoniacal copper zinc arsenate (ACZA).

The levels of copper, zinc, and arsenic in soil surrounding Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] utility poles treated with ammoniacal copper zinc arsenate (ACZA) were investigated at sites in Florida, Virginia, and New York. Copper levels were elevated near the poles and declined with both horizontal distance away from the pole and depth beneath the soil surface. Zinc levels were also elevated next to the poles, but the levels declined more slowly than did those of copper. Arsenic levels were elevated in soil immediately next to the poles but declined to near background levels farther away. The results indicate that metals can leach from ACZA-treated poles, but do not migrate far in the soil, and thus the levels decline sharply with distance from the poles.

Arsenates↗
PubMed2000

Carbon and nitrogen allocation to male and female reproduction in Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca, Pinaceae).

We measured carbon (respiration, photosynthesis, and production) and nitrogen allocation to male and female cones of Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca) to quantify gender-specific: (1) resource allocation to reproduction, and (2) contribution to carbon costs of reproduction via photosynthesis. We also measured foliar photosynthesis and nitrogen concentration ([N]) near and far from female cones to examine the relationship between reproduction and foliar physiology. Over one growing season, male cones required only 8% of all carbon allocated to reproduction, with females consuming the remaining 92%. Female cones, however, had maximum instantaneous refixation rates of 54%, which, integrated over the season, offset 6% of their total carbon requirements, while male cones were completely dependent on vegetative tissues for carbon. Male cones received 22% of all nitrogen allocated to reproduction and female cones received the remaining 78%. Foliage near female cones had elevated photosynthesis during the early stages of cone development and consistently lower [N] than foliage far from cones. Although female cones may photosynthesize, the annual sum of carbon fixed by reproductive structures is minor in comparison to the total carbon allocated to production and respiration.

Journal Article↗
PubMed2000

[Decomposition process of Chinese fir stump roots and changes of nutrient concentration].

With space as a substitute for time, the changes of the density of stump sapwoods and heartwoods, and the releasing process of major nutrients during the decomposition of Chinese fir stump roots were investigated. The yearly loss rate of the densities of sapwoods and heartwoods was 2.767 x 10(-2) and 2.255 x 10(-2) respectively during decomposition. The contents of N and P in sapwoods and roots decreased continually, while those in heartwoods increased during the first stage of decomposition, and then decreased. The K concentration in stump roots decreased remarkably during first two years, and the content of organic substances decreased during the whole decomposition process. The N, P and K concentrations in roots, were higher than those in stump sapwoods and heartwoods at the beginning of decomposition, but bet content of organic substance was opposite.

Abies↗
PubMedDate not supplied

[Genetic control of Silver fir isozymes (Abies alba Mill.) of the Ukrainian Carpathian Mountains].

Genetic control of GOT, GDH, DIA, MDH, ME, SOD, FDH, ADH, ACP, LAP enzymes has been studied in the seed megagametophytes of Silver fir (Abies alba Mill.) from four natural populations of the Ukrainian Carpathian mountains. The distinct electrophoretic division has been obtained for the 21 loci products. The analysis of allele segregation in the heterozygous trees confirms monogenic inheritance of the revealed variants.

Abies↗
PubMed2001

[Assignments of FIR-LMR spectra of CF X 2Pi (nu = 1) and MIR-LMR spectra of NO X 2Pi (nu = 1<--0)].

According to the theories of Zeeman effect and the principle of laser magnetic resonance (LMR), a method and model for the analysis of the laser magnetic resonance spectra were developed and successfully employed to assign the FIR-LMR spectra of CF X2 Pi (nu = 1) and the MIR-LMR spectra of NO X 2Pi (nu = 1<--0). This work provided an efficient and accurate approach for primary analysis of the LMR spectra of novel radicals.

English Abstract↗
PubMed2005

[Effects of different ground clearance on soil fertility of Chinese fir stands].

The study on the soil physical properties, nutrient contents, microbial amounts and enzyme activities of clear cutting and controlled burning Chinese fir stands showed that in comparing with the control, soil non-capillary porosity of clear cutting stand increased by 23%, whereas soil natural water capacity and capillary moisture capacity decreased by 25%. In controlled burning stand, soil bulk density increased by 10%, while soil non-capillary porosity, natural water capacity and capillary moisture capacity decreased by 61%, 48% and 26%, respectively. The contents of soil organic matter, total N, total P and total K in clear cutting stand decreased by 14%, 14%, 35% and 22%, and in controlled burning stand, they decreased by 37%, 37%, 47% and 7%, respectively. Soil alkalized N and available K in clear cutting stand increased by 24% and 31%, respectively, but soil available P decreased by 15%. The contents of soil alkalized N, available P and available K in controlled burning stand decreased by 25%, 43% and 40%, respectively. In clear cutting stand, the amounts of soil bacteria, fungi and actinomyces increased by 1.4, 11.3 and 0.8 times, respectively, but in controlled burning stand, the amounts of soil bacteria decreased by 24%, while those of soil fungi and actinomyces increased by 5.0 and 0.5 times, respectively. The activities of soil urease, catalase and cellulase in clear cutting stand increased by 1.9, 1.6 and 2.1 times, and in controlled burning land, they were 35%, 90% and 106% of the control, respectively. Damp soil had higher contents of organic matter, total N and total P, whereas porous soil was favorable for the accumulation of alkalized N, available P and available K and for the increase of soil urease activity. The amount of soil fungi decreased with increasing soil capillary porosity. Aerated soil was favorable for the increase of soil catalase activity.

Catalase↗
PubMed2006

[Structural and property characteristics of Chinese fir wood charcoal prepared under various conditions].

By techniques of one-step and two-step carbonization, and capped and uncapped carbonization, the pyrolysis on the thinning wood of Chinese fir, one of the fastest growing tree species in south China, was carried out. With special focus on the variation of Raman spectra and X-ray diffraction analysis of carbonized materials under different carbonization conditions, comprehensive analyses of charcoals were conducted. Results show that, with temperature rising, the graphite-like microcrystal and carbon atoms at the edge of graphite-like microcrystal increase rapidly. As a result, the hexagon carbon plane structure in carbonized material keeps growing. Moreover, the experiments reveal that carbonization condition has great effects on the property and structure of carbonized material, and 700 degrees C is the critical temperature at which the qualitative change of carbonized material occurs. Furthermore, formation and growth of graphite-like microcrystal in carbonized material, two-step method is more beneficial than one-step method, uncapped container carbonization method is better than the capped one, and using air as atmosphere gas is better than using N2. Samples with longer holding time in the process of carbonization enjoy higher graphitization extent.

English Abstract↗
PubMed2000

Variational Evaluation of the HSSH FIR Transitions: The Anomalous K-Doubling.

The roto-torsional energy levels of HSSH and DSSD up to J = 20 are evaluated variationally with a Hamiltonian expressed in terms of internal coordinates. The kinetic and potential parameters are derived from ab initio calculations with full optimization of the geometry. The calculated levels are employed for the determination of the centrifugal distortion constants. HSSH is a near-prolate symmetric rotor. The most stable C(2) conformer, calculated with MP4(SDQ)/cc-pVQZ, exhibits a 90.55 degrees dihedral angle. For J = 0, the lowest energies of HSSH and DSSD are 413.4876 cm(-1) (n = 1), 798.0304 cm(-1) (n = 2) and 1151.5773 cm(-1) (n = 3), and 304.3185 cm(-1) (n = 1), 594.2919 cm(-1) (n = 2), and 869.3508 cm(-1) (n = 3), respectively. For J = 60, the ab initio calculations allow the reproduction of the anomalous type-K doubling predicted with perturbation theory. Copyright 2000 Academic Press.

Journal Article↗