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Evaluation of a method to assess digitally recorded surgical skills of novice veterinary students
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54.
Effects of semi-isostatic densification of wood on the variation in strength properties with density
The variation in strength properties with density was compared between semi-isostatically densified and non-densified wood.
Strength properties were compared with published data from earlier studies using other methods for densification. Small clear
specimens of eight species were analysed for compression strength in axial, radial and tangential direction, three-point bending
and Brinell hardness. After densification, all tested strength properties increased with density, but especially strength
perpendicular to grain became lower than expected from the density of non-densified wood. Strength of densified wood relative
to what could be expected for non-densified wood of similar density was denoted as ‘strength potential index’. For axial compression
strength and bending strength, strength potential index of individual wood species varied between 0.7 and 1.0, i.e. densified
wood is slightly weaker than what could be expected from its density. Strength potential index was lower for properties much
determined by strength perpendicular to grain. In radial direction, densified wood was rubbery with low modulus of elasticity
and nearly no proportional limit or modulus of rupture. Generally, wood was apparently weakened in proportion to the degree
of compression in respective direction. Strength potential index also increased with increasing original density of the species. 相似文献
55.
Jonas Blomberg 《Journal of Wood Science》2005,51(4):401-404
Quarter-sawn and plain-sawn specimens of Scots pine were semi-isostatically compressed at 5, 15, 50, and 140 MPa in a Quintus press. Elastic strain was measured using a telescope device that was pushed together when wood was compressed and remained in this position at release of pressure. Delayed elastic and plastic strains were assessed through repeated callipering during 5 years after densification. At 140 MPa, wood reached an almost compact structure (ρ ≈ 1450 kg/m3) but as a result of elastic springback the density decreased to just below 1000 kg/m3. At 140 MPa, the elastic and delayed elastic strains were 14.6% and 1.8%, respectively, in quarter-sawn specimens, and were 13.1% and 0.8%, respectively, in plain-sawn specimens. The higher elastic strains in quarter-sawn specimens can be attributed to elastic springback in the tangentially deformed latewood bands. 相似文献
56.
成熟期短时渍水胁迫对烤烟碳氮代谢关键酶及主要碳、氮化合物含量的影响 总被引:2,自引:0,他引:2
以烤烟云烟97为材料,采用田间试验研究了成熟期短时渍水处理对烤烟碳氮代谢关键酶活性及主要碳、氮化合物含量的影响。结果表明,在烤烟成熟期渍水处理3 d,中部叶片硝酸还原酶活性低于对照,降幅为20.39%;转化酶和淀粉酶活性高于对照,增幅分别为33.14%,56.70%;烟叶淀粉、总氮和烟碱含量有降低趋势,分别下降了2.9,0.74,0.77个百分点,而总糖和还原糖含量有增加趋势,分别上升了1.33,0.46个百分点。说明渍水胁迫使叶片生理代谢紊乱,氮代谢减弱,碳水化合物积累减少。研究结果有助于从生理生化角度揭示成熟期渍水胁迫对烤烟生长和品质形成影响的机制。 相似文献
57.
LA Quintela AI Peña MD Vega J Gullón C Prieto M Barrio JJ Becerra PG Herradón 《Reproduction in domestic animals》2009,44(5):829-833
This study was aimed to evaluate the reproductive performance of rabbit does artificially inseminated (AI) with a GnRH analogue [des‐Gly10, d ‐Ala6]‐LHRH. ethylamide to induce ovulation by intravaginal administration, delivered in the seminal dose. In a preliminary experiment, 39 does were divided into three groups (n = 13) that, at the time of AI, received the following ovulation induction treatments: (i) control group: 20 μg of gonadorelin administered intramuscularly; (ii) 25 μg of the GnRH analogue added to the seminal dose; (iii) 30 μg of the GnRH analogue added to the seminal dose. Fertility did not differ between the three groups (control: 80.6%, group 2: 82.8%, group 3: 73.3%). In a second experiment, a large‐scale field trial was conducted to test the use of 25 μg of the GnRH analogue [des‐Gly10, d ‐Ala6]‐LHRH ethylamide delivered in the seminal dose (n = 270) against 20 μg of gonadorelin administered intramuscularly. Fertility was higher (p < 0.05) when ovulation was induced by intravaginal administration of the GnRH agonist (91.1% vs 85.6%). Prolificacy or mortality at birth was never affected by the ovulation induction treatments. In a third experiment, two groups of does [control group (n = 39): ovulation was induced using 20 μg of gonadorelin administered intramuscularly; treatment group (n = 40): ovulation was induced using 25 μg of [(des‐Gly10, d ‐Ala6)‐LHRH ethylamide added to the seminal dose] were inseminated at 42‐day intervals for five successive AI cycles, to test the response to the GnRH agonist after repeated intravaginal administration to the same animals. Fertility and prolificacy were not influenced by the ovulation induction treatment neither there was an interaction between treatment and parity. The last experiment was aimed to determine whether it could be possible to add the GnRH agonist to the semen in the AI Center, just after semen collection and dilution, or it would have to be added in the farm, immediately before AI. Kindling rates did not significantly differ when ovulation was induced by intramuscular injection of gonadorelin (84.5%) or when the GnRH agonist was added to the seminal dose just at the moment (93.8 %) or 24 h before AI (90.4 %), but it was significantly lower when the hormone was added to the semen 32 h before AI (76.3 %). Prolificacy, however, was not influenced by the ovulation induction treatment. 相似文献
58.
WILLIAM M. ADAMS MIRIAM M. KLEITER DONALD E. THRALL JULIA M. KLAUER LISA J. FORREST TRACY A. LA DUE THOMAS C. HAVIGHURST 《Veterinary radiology & ultrasound》2009,50(3):330-335
Prognostic significance of tumor histology and four computed tomography (CT) staging methods was tested retrospectively in dogs from three treatment centers that underwent intent-to-cure-radiotherapy for intranasal neoplasia. Disease-free and overall survival times were available for 94 dogs. A grouping of anaplastic, squamous cell, and undifferentiated carcinomas had a significantly shorter median disease-free survival (4.4 mo) than a grouping of all sarcomas (10.6 months). Disease-free survivals were not significantly different, when all carcinomas were compared with all sarcomas. The published original and modified WHO staging methods did not significantly relate to either survival endpoint. A modified human maxillary tumor staging system previously applied to canine nasal tumors was prognostically significant for both survival endpoints; a further modified version of that CT-based staging system resulted in improved significance for both survival endpoints. Dogs with unilateral intranasal involvement without bone destruction beyond the turbinates on CT, had longest median survival (23.4 months); CT evidence of cribriform plate involvement was associated with shortest median survival (6.7 months). Combining CT and histology statistically improved prognostic significance for both survival endpoints over the proposed CT staging method alone. Significance was lost when CT stages were collapsed to 相似文献
59.
A growth experiment on agar medium and a hydroponics experiment were carried out to study the nitrogen (N) metabolism of a low-N tolerant mutant (lnt1) of Arabidopsis thaliana under different N levels as compared with the wildtype (WT) Arabidopsis. On the agar medium, no apparent growth differences were observed between the lnt1 and WT plants under a normal N level of 9 mmol L-1 NO3-. However, under a low N level of 0. 18 mmol L-1 NO3-, the growth of the WT plants was greatly retarded, while the lnt1 plants were not affected by low-N stress and showed similar growth with those grown under a normal N level. In the hydroponics experiment, the lnt1 mutant had higher activities of glutamine synthetase (GS) and NADH-dependent glutamate synthase (NADH-GOGAT) in both leaves and roots under N-deficient conditions. Moreover, they accumulated less ammonium (NH4+) but more free amino acids in leaves compared with the WT plants. These observations suggest that better N assimilation might contribute to the low-N tolerant phenotype of the lnt1 mutant. 相似文献
60.
西藏玛旁雍错流域湖泊面积变化及成因分析 总被引:5,自引:0,他引:5
利用1975年地形图、1990年、1999-2009年TM卫星遥感影像和近35 a(1975-2009年)气温、降水、积雪日数、蒸发量等气候资料,分析研究了位于西藏阿里地区南部普兰县境内玛旁雍错、拉昂错湖泊面积变化对气候变化的响应。结果表明:在过去35 a里玛旁雍错、拉昂错面积先减少后增加,总体呈减小趋势,到2009年玛旁雍错面积为415.44 km2,拉昂错面积为261.36 km2。与1975年相比2个湖泊面积分别减少了1.56 km2和11.01 km2;受气候变暖的影响,流域附近的冰川面积也在加速退缩。对1975-2009年普兰县气象资料统计分析可知,降水量减少是导致湖泊面积缩小的主要原因,蒸发量不显著的增加及雪冰消融也是近几年湖泊面积波动变化的原因之一。 相似文献