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81.
The methanol extractives from western red cedar mechanical pulps were found to be radically different in composition to the
extractives obtained from the heartwood. The major heartwood extractive components, the tropolones and lignans, were not present
in the extractives from the pulps. However, the proportion of a brown polymer doubled. The low and high molecular weight methanol
extractives components from the pulps were separated using methyl tert-butyl ether. The low molecular fraction contained mostly
guaiacyl-based compounds with dihydroquercetin, thujic acid, 3-hydroxy-1-(4′-hydroxy-3′-methoxyphenyl)-2-oxopropane and 4-ethyl-2-methoxy-6-hydroxyphenol
being positively identified. The brown polymeric portion had molecular weights ranging from 1,000 to 10,000. Infrared analysis
indicated that the polymers were formed from lignans. Examination of the changes in diffuse reflectance UV-visible and infra
red spectra of the pulps on extraction with methanol, suggested that the colour resides in insoluble polymers formed from
plicatic acid/plicatin during refining.
Received 18 December 1998 相似文献
82.
M. Giacometti J. Nicolet K.E. Johansson T. Naglic M.P. Degiorgis J. Frey 《Zoonoses and public health》1999,46(3):173-180
A specific PCR assay based on unique sequences of the rrs genes (16S rRNA) of Mycoplasma conjunctivae was developed for direct detection and identification of this pathogen from clinical material. DNA from eye swabs was amplified after a simple lysis step by either a single PCR with the M. conjunctivae specific primer pair McoR1 and McoF1, or by a nested PCR with the Mycoplasma genus specific primer pair MOLIGEN1-L and 16UNI-R in the first step and McoR1 and McoF1 in the second step. The specificity of the primer pair McoR1 and McoF1 was verified with purified DNA from the type strain, from 17 field isolates of M. conjunctivae and from several Mollicutes which are phylogenetically related to M. conjunctivae or which can be isolated from the same host animals. This method identified mycoplasma isolates from goat, sheep, ibex and chamois originating from different countries as M. conjunctivae. No cross amplifications with other mycoplasmas which are related to M. conjunctivae were observed. Eye swab samples containing known numbers of M. conjunctivae cells were analysed after direct lysis of the material. The detection level was estimated to be 20 cells per swab when the nested PCR procedure was used and 2 × 105 by the single PCR method. In an experimental infection model of sheep, the nested PCR method for detection of M. conjunctivae gave results which were comparable to mycoplasmal culture. These are the implications for diagnostic purposes: M. conjunctivae isolates can be identified by the one-step PCR method, whereas for detection and identification of M. conjunctivae in clinical material the two-step method should be used (higher sensitivity). 相似文献
83.
Mechanical fiber separation under torsional stress 总被引:1,自引:1,他引:0
Summary Spruce wood (Picea abies) samples were pretreated at different temperatures and, in some cases, with sodium sulfite solution under normal conditions
for the chemimechanical pulping of wood chips. The pretreated samples were simultaneously subjected to torsion and compression
stresses at temperatures ranging from 20 to 90 °C. The load-deformation relationship was analyzed at each temperature. The
failure zones were studied using the scanning electron microscope technique.
The results showed that the maximum torque decreased with increasing temperature under the deformation conditions applied.
Sulfonation of the samples gave a similar effect, although to a smaller extent. The elastoplasticity of the samples, as viewed
in terms of the twist angle at failure, was also affected by the pretreatment. While axial compression had a major effect,
sulfonation only caused a marginal change.
Microscopic studies of the failure zone showed that when the temperature increased, the fracture plane traveled around fibers
instead of through them, thus causing less fiber damage. Sulfonation improved fiber separation and decreased fiber damage.
The separation of ray cells from the fiber tracheids was improved, particularly by sulfonation. Increasing temperature and
sulfonation changed the fracture plane from the secondary wall of fibers towards the more lignin enriched primary wall and
middle lamella.
Received 29 January 1997 相似文献
84.
Self-oriented regular arrays of carbon nanotubes and their field emission properties 总被引:4,自引:0,他引:4
S Fan MG Chapline NR Franklin TW Tombler AM Cassell H Dai 《Science (New York, N.Y.)》1999,283(5401):512-514
The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology. 相似文献
85.
Detection and identification of Mycoplasma conjunctivae in infectious keratoconjunctivitis by PCR based on the 16S rRNA gene. 总被引:2,自引:0,他引:2
M Giacometti J Nicolet K E Johansson T Naglic M P Degiorgis J Frey 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1999,46(3):173-180
A specific PCR assay based on unique sequences of the rrs genes (16S rRNA) of Mycoplasma conjunctivae was developed for direct detection and identification of this pathogen from clinical material. DNA from eye swabs was amplified after a simple lysis step by either a single PCR with the M. conjunctivae specific primer pair McoR1 and McoF1, or by a nested PCR with the Mycoplasma genus specific primer pair MOLIGEN1-L and 16UNI-R in the first step and McoR1 and McoF1 in the second step. The specificity of the primer pair McoR1 and McoF1 was verified with purified DNA from the type strain, from 17 field isolates of M. conjunctivae and from several Mollicutes which are phylogenetically related to M. conjunctivae or which can be isolated from the same host animals. This method identified mycoplasma isolates from goat, sheep, ibex and chamois originating from different countries as M. conjunctivae. No cross amplifications with other mycoplasmas which are related to M. conjunctivae were observed. Eye swab samples containing known numbers of M. conjunctivae cells were analysed after direct lysis of the material. The detection level was estimated to be 20 cells per swab when the nested PCR procedure was used and 2 x 10(5) by the single PCR method. In an experimental infection model of sheep, the nested PCR method for detection of M. conjunctivae gave results which were comparable to mycoplasmal culture. These are the implications for diagnostic purposes: M. conjunctivae isolates can be identified by the one-step PCR method, whereas for detection and identification of M. conjunctivae in clinical material the two-step method should be used (higher sensitivity). 相似文献
86.
B Tufvesson M Tufvesson K Lillpers K Johansson M Wilhelmson 《British poultry science》1999,40(2):209-216
1. Divergent selection for comb shape (SH, the way that the cockerel bears the comb) was performed in 2 White Leghorn lines in a study aimed at assessing possibilities for improving SH. 2. Line A, selected for large comb size (CS) at 29 weeks of age, had great SH problems whereas Line H, selected for high hyaluronic acid concentration in the comb (HA), had minor SH problems. Multivariate analyses were used to estimate genetic parameters for SH, CS and HA in lines A and H and in a control line (C). 3. Significant direct selection responses for SH were achieved in both lines. There were significant unfavourable correlated responses for CS in both lines. 4. The correlated responses for HA were not significant and were unfavourable in Line A and favourable in Line H. 5. Heritabilities for SH and CS were high in both lines and relatively low for HA. Most of the genetic correlations were in agreement with the correlated responses obtained. 相似文献
87.
G Medeiros-Ribeiro AM Bratkovski TI Kamins DAA Ohlberg RS Williams 《Science (New York, N.Y.)》1998,279(5349):353-355
Chemical vapor deposition of germanium onto the silicon (001) surface at atmospheric pressure and 600 degrees Celsius has previously been shown to produce distinct families of smaller (up to 6 nanometers high) and larger (all approximately 15 nanometers high) nanocrystals. Under ultrahigh-vacuum conditions, physical vapor deposition at approximately the same substrate temperature and growth rate produced a similar bimodal size distribution. In situ scanning tunneling microscopy revealed that the smaller square-based pyramids transform abruptly during growth to significantly larger multifaceted domes, and that few structures with intermediate size and shape remain. Both nanocrystal shapes have size-dependent energy minima that result from the interplay between strain relaxation at the facets and stress concentration at the edges. A thermodynamic model similar to a phase transition accounts for this abrupt morphology change. 相似文献
88.
Anna M. Johansson Maulik Upadhyay Erling Strandberg Susanne Eriksson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2020,69(1-2):39-46
ABSTRACTThe Swedish Mountain (Fjäll) cattle and the subpopulation Fjällnära originates from northern Sweden. They are differentiated from both traditional and commercial cattle from southern Sweden. We analysed data from the GGP HD150k SNP array and investigated genetic diversity and differences between Fjäll and Fjällnära, and between different groups of Fjällnära. We found that the Fjällnära can be divided into four groups, which are differentiated from each other and from the other Fjäll cattle. We also compared allele frequencies between different groups of Fjäll and Fjällnära for some of the functional SNPs included in the SNP array. Interestingly, the B allele of Beta lactoglobulin has a very high frequency (94%) in the Fjällnära cattle, which is significantly different from the frequency in the Fjäll cattle (60%). Comparing older samples of Fjäll cattle with more recent samples, we found a significant increase in the frequency of the B allele in Fjäll cattle. 相似文献
89.
An enzyme-linked immunosorbent assay (ELISA) was developed to measure total antibody to Toxoplasma gondii in serum samples from macropods. The validity of the assay was established by comparing parasite isolation in mice for 17 Tasmanian pademelons (Thylogale billardierii) and 17 Bennett's wallabies (Macropus rufogriseus rufogriseus). The ELISA was then used to detect antibody against T. gondii in serum from 236 macropods, collected from 21 locations in Tasmania, including Flinders Island. Antibody against T. gondii was detected in 20 animals (15 T. billardierii and 5 M. rufogriseus). There was a significant (p less than 0.01) difference in possession of T. gondii antibodies between adult (greater than or equal to 1 year of age) Tasmanian pademelons and Bennett's wallabies. 相似文献
90.
SE RIDGE JT HARKIN† ‡ RT BADMAN† AM MELLOR§ JWA LARSEN¶ 《Australian veterinary journal》1995,72(4):150-153
SUMMARY: Johne's disease was diagnosed in 10 alpacas ( Lama pacos ) in Australia between February 1993 and May 1994. Eight of the animals were between 12 and 24 months of age, one was a 6-year-old female, and one was a 4-year-old male. Five, including the 6-year-old and the 4-year-old alpacas, showed weight loss and diarrhoea before death or slaughter. The other cases showed no clinical signs of Johne's disease but 4 gave a positive result on faecal culture and one gave a positive result on testing with the caprine ACID assay and had acid-fast organisms in its faeces. At necropsy, all cases had grossly enlarged mesenteric lymph nodes. Johne's disease was diagnosed after histological examination of the lymph nodes with conventional culture and polymerase chain reaction testing of tissue samples. This report outlines the clinical, epidemiological, and pathological findings in these cases. 相似文献