Transgressive overyielding in mixed compared with pure stands of Norway spruce and European beech in Central Europe: evidence on stand level and explanation on individual tree level   总被引：2，自引：1，他引：1  

Hans Pretzsch  Gerhard Schütze 《European Journal of Forest Research》2009,128(2):183-204

  相似文献   

Development of high-performance strand boards: engineering design and experimental investigations   总被引：1，自引：0，他引：1  

Reinhard Stürzenbecher  Karin Hofstetter  Thomas Bogensperger  Gerhard Schickhofer  Josef Eberhardsteiner 《Wood Science and Technology》2010,44(1):13-29

Strand-based engineered wood products such as oriented strand boards enjoy great popularity in structural engineering and are widely used for a variety of applications. To strengthen their competitiveness and to enlarge their range of utilization particularly in the load-bearing sector, the mechanical properties of these products need to be improved. This motivated the research efforts to use large-area, slender veneer strands for the production of strand boards with increased stiffness and strength. Target-oriented development of these products requires comprehending the effects of the relevant (micro-)characteristics, such as wood quality, strand geometry, and strand orientation and compaction during the production process, as well as layer assembly and density profile, on the mechanical properties of the finished strand boards. Comprehensive test series, in which these effects on tension, bending and shear properties of the boards have been studied individually, are presented in this paper. The obtained results provided insight into the microstructural load-carrying mechanisms and, thus, yielded valuable knowledge for product optimization and further improvement of custom-designed strand-based engineered wood products.  相似文献   

Evaluation of Erysiphe graminis f sp tritici field isolates for resistance to strobilurin fungicides with different SNP detection systems     

Bäumler S  Sierotzki H  Gisi U  Mohler V  Felsenstein FG  Schwarz G 《Pest management science》2003,59(3):310-314

A single nucleotide polymorphism (snp) in the cytochrome b gene confers resistance to strobilurin fungicides in Erysiphe graminis DC fsp tritici Marchal. On the basis of this point mutation three different types of molecular markers have been developed. Cleaved amplified polymorphic sequences and allele-specific PCR were used to score resistant and sensitive isolates from specifically selected regional populations across Europe. The results of molecular tests were in total agreement with the resistance phenotypes revealed by in vivo tests. Serial dilutions of mixed samples (resistant/sensitive) delimited the detection for strobilurin-resistant alleles to a range of 10-50% for both marker classes. Due to these detection limits no mixture of mitochondria within individual isolates was found. Denaturing high performance chromatography was used to increase the detection sensitivity for the mutant allele. Although the detection limit was lowered to 5-10%, there was no evidence for the existence of mixed mitochondrial genotypes.  相似文献   

Synthesis of anthelmintically active N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A     

Jeschke P  Harder A  von Samson-Himmelstjerna G  Etzel W  Gau W  Thielking G  Bonse G 《Pest management science》2002,58(12):1205-1215

The N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A represent novel derivatives with activity against Trichinella spiralis Owen and Nippostrongylus brasiliensis Lane in vitro and against parasitic nematodes in mice and sheep. Some of them show better activity against Hymenolepis nana Siebold, Heterakis spumosa Schneider and Heligmosomoides polygyrus Dujardin in mice than the natural product PF1022A. In particular an improved efficacy against Haemonchus contortus Rudolphi and Trichostrongylus colubriformis Giles in sheep compared to the potent cyclic octadepsipeptide PF1022A and its mono-thionated derivative has been observed. Here we report on a specific modification at the N-methyl amide linkage by using the mono-thionated PF1022A, resulting in novel anthelmintically active backbone analogues of PF 1022A.  相似文献   

Effects of leucocyte extract, levamisole and sulphadimidine on natural coccidial infections (Eimeria spp.) in young lambs     

B Gjerde  O Helle 《Acta veterinaria Scandinavica》1987,28(1):33-45

The efficacy of leucocyte extract (LE) and sulphadimidine in preventing coccidiosis in naturally infected lambs on pasture was evaluated in 3 separate experiments, whereas the prophylactic effect of levamisole was studied in 1 of the experiments. LE prepared from ewes immune to coccidia (Eimeria spp.) was administered either intravenously or intraperitoneally to young lambs 7, 5, or 2 days before they were turned out on pastures contaminated with coccidia. In all experiments, LE failed to transfer protective immunity to the lambs against the first coccidial infection on pasture. The LE preparations used apparently had an immunosuppressive effect, which resulted in more severe clinical signs of coccidiosis in the recipients. The lambs given LE showed a higher incidence of diarrhoea, a poorer weight gain, a higher mortality, and a higher oocyst output than the untreated control lambs. In lambs treated with sulphadimidine at 200 mg/kg on days 12, 13, and 14 after turnout there was a reduced severity of the coccidial infections in all experiments. The sulphadimidine-treated lambs had better weight gains and passed fewer oocysts than the controls during the third and fourth week after turnout, but some of them developed diarrhoea. Lambs treated with levamisole at 2 mg/kg 2 days before turnout, at turnout, and 2 days after turnout were more severely affected by the first coccidial infection on pasture than the controls.To study the lambs’ immunity against a heavy challenge infection with coccidia as compared with their immunity against the natural reinfection on pasture, some of the lambs from the original groups (untreated, sulphadimidine-treated, LE-treated) were each inoculated with 2 mill. Eimeria spp. oocysts about 6 weeks after turnout. The oocyst counts of the challenged lambs, except the LE-treated lambs, increased to a new peak 19–20 days after challenge. The challenge infection caused a softening of the faeces and a marked depression in weight gain in all challenged groups of lambs, mainly between days 10 and 17 after challenge. The lambs were thus only partially immune to coccidia after the first coccidial infection on pasture. The lambs treated with either LE or sulphadimidine in connection with the first coccidial infection on pasture were not appreciably more susceptible to the challenge infection than the untreated lambs.  相似文献   

Characterisation of three equine influenza A H3N8 viruses from Germany (2000 and 2002): evidence for frozen evolution     

Borchers K  Daly J  Stiens G  Kreling K  Kreling I  Ludwig H 《Veterinary microbiology》2005,107(1-2):13-21

Reported here are the results of antigenic and genetic characterisation of equine influenza strains causing local outbreaks reported to the Equine Diagnostic Centre in Berlin, Germany. In 2000, equine influenza virus was detected in a nasal swab from a non-vaccinated horse using a rapid diagnostic kit, but was not successfully isolated. Partial direct sequencing of the haemagglutinin (HA1) gene, indicated that the virus was a European lineage H3N8 subtype strain representative of strains isolated in several European countries during 2000. In 2002, two equine influenza viruses were isolated from nasal swabs both taken from unvaccinated horses with acute respiratory symptoms housed at the same stables. Antigenic characterisation using a panel of ferret antisera suggested that these isolates also belonged to the European lineage of H3N8 viruses. Analysis of deduced HA1 amino acid sequences confirmed that the HA1 of both isolates were identical and belonged to the European lineage. However, from phylogenetic analysis, both strains appeared to be more closely related to viruses isolated between 1989 and 1995 than to viruses isolated more recently in Europe. These results suggested that viruses with fewer changes than those on the main evolutionary lineage may continue to circulate. The importance of expanding current equine influenza surveillance efforts is emphasised.  相似文献   

Amphidial structure of ivermectin-resistant and susceptible laboratory and field strains of Haemonchus contortus   总被引：3，自引：0，他引：3  

Freeman AS  Nghiem C  Li J  Ashton FT  Guerrero J  Shoop WL  Schad GA 《Veterinary parasitology》2003,110(3-4):217-226

The development of anthelmintic resistance by nematode parasites is a growing problem for veterinarians, pet owners, and producers. The intensive use of the macrocyclic lactones for the treatment of a variety of parasitic diseases has hastened the development of resistance to this family of parasiticides. As a result, resistance to ivermectin, moxidectin, nemadectin, and doramectin by Haemonchus contortus has been documented throughout the world.

Sensory neurons located in the cephalic end of nematodes are in close contact with the external environment. Through these neurons, important chemical and thermal cues are gathered by the parasite. Examination of serial electron micrographs of ivermectin-susceptible and ivermectin-resistant H. contortus allows for comparison of neuronal structure, arrangement of neurons within the amphidial channel, and distance of the tip of the dendritic processes to the amphidial pore. The latter of these characteristics provides a useful means by which to compare the association between the neurons and the external environment of the worm.

Comparison of parental laboratory strains of ivermectin-susceptible strains of H. contortus with related selected, ivermectin-resistant strains and with a wild-type ivermectin-susceptible field strain of H. contortus from Louisiana reveal that the ivermectin-resistant worms examined have markedly shorter sensory cilia than their ivermectin-susceptible parental counterparts. Additionally, the amphidial neurons of ivermectin-resistant worms are characterized by generalized degeneration and loss of detail, whereas other neurons outside of the channels, such as the labial and cephalic neurons, are normal in structure. These findings raise a number of questions regarding the relationship between amphidial structure and ivermectin resistance as well as the role of amphids as a means of entry for ivermectin. While shortened amphidial sensilla are associated with ivermectin resistance, it remains unclear if such a structural modification facilitates survival of nematodes exposed to macrocyclic lactones.  相似文献   

Mortality of purebred and mixed-breed dogs in Denmark     

Proschowsky HF  Rugbjerg H  Ersbøll AK 《Preventive veterinary medicine》2003,58(1-2):63-74

Causes of death and age at death of 2928 dogs are reported from a questionnaire study among members of the Danish Kennel Club (DKC) in 1997. The dogs represented 20 breeds, 15 breed-groups and a group of mixed-breed dogs. The median age at death for all dogs in the study was 10.0 years. Mixed-breed dogs had a higher median age at death (11.0 years) than the entire population, but breeds like Shetland Sheepdog, Poodle and Dachshund exceeded this age (12 years). The Bernese Mountaindog, the group of Molossian types and the Sighthounds had the shortest life span with a median age at death of 7.0 years. Old age was the most frequent reported cause of death (20.8%) followed by cancer (14.5%), behavioural problems (6.4%) accidents (6.1%), hip dysplasia (4.6%), heart diseases (4.6%) and spinal diseases (3.9%). Breed-specific proportional mortalities with 95% confidence limits are given for the six most prevalent specific causes of death.  相似文献   

Antibody titer against bovine viral diarrhea virus (BVDV) in bulk milk samples from Bavaria     

Meier N  Meier B  Banzhaf K  Wittkowski G  Schmitt D  Truyen U 《Berliner und Münchener tier?rztliche Wochenschrift》2003,116(5-6):240-243

A total of 5204 bulk milk samples were tested for antibodies against bovine viral diarrhea virus (BVDV) classified according to the scheme after Alenius. Forty-five percent of the samples from 2002 were classified as class 0 and class 1, 55% as class 2 and 3. 6420 bulk milk samples from 1997 were classified in an independent study in 65.6% class 0 and 1 and 34.4% in class 2 and 3. In class 0 and class 1 farms only very rarely persistent viremic animals have been found, whereas in class 2 and 3 their presence is highly likely. Our studies with non-selected sera defined the serological screening of bulk milk samples as a promising tool for a possible BVDV eradication program in Bavaria.  相似文献   

The new classification system for slaughter-pig herds in the Danish Salmonella surveillance-and-control program   总被引：3，自引：0，他引：3  

Alban L  Stege H  Dahl J 《Preventive veterinary medicine》2002,53(1-2):133-146

The Danish surveillance-and-control program for Salmonella in slaughter pigs was introduced in 1995. The key element of the program is a quick and correct identification of herds with high seroprevalence. After 5 years, the classification scheme was evaluated--and a revision was made. Data from two Salmonella screenings including a total of 1902 slaughter pig herds were used. For each herd, information was available on Salmonella status based on both microbiology and serology. Based on analyses of these data, suitable changes in the scheme were identified and their effect estimated by use of data from the Danish Salmonella Database including all herds in 2000. The classification scheme has been adjusted on the following points. (1) The sampling has been simplified into 60, 75, or 100 samples per herd per year depending on herd size. This means more-precise estimates for the seroprevalence among smaller herds. (2) Herds with an annual kill or=index 40, and the limit between Levels 2 and 3 to >or=index 70. If the Danish swine producers are interested, a Level 0 may be introduced (consisting of seronegative herds as an indication of a negligible Salmonella prevalence). The classification scheme was introduced in August 2001.  相似文献