Essential Oil Composition of Norwegian Peppermint (Mentha × piperita L.) and Sachalinmint [Mentha sachalinensis (Briq.) Kudô]     

Jens Rohloff  Else Berit Skagen  Albert Håkon Steen  Tor Beisvåg  Tor-Henning Iversen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):161-168

Production of varieties of the medicinal plants Mentha  相似文献   

Flowering in six clones of the Andean root crop arracacha (Arracacia xanthorrhiza Bancroft)     

Steen Randers Knudsen  Michael Hermann  Marten Srensen 《The Journal of Horticultural Science and Biotechnology》2013,88(4):454-458

Summary

The effect of dehydration on arracacha (Arracacia xanthorrhiza Bancroft) cormels was investigated and found to have a positive effect on flowering for some accessions and a negative or negligible effect on others. The clear difference in flowering response between accessions is attributed to genetic variation and suboptimal growth conditions. The unclear results indicate that the treatments used were suboptimal and that factors other than drought stress are involved in flower induction. However, the dehydration treatments had a positive effect on the production of hermaphrodite flowers in all accessions, and dehydration is therefore considered an important factor in the flower-inducing treatment. The high temperatures and low humidity during the current experiment had a negative effect on pollen release and thus seed production, indicating that a moderate temperature is needed during the arracacha growth period. There are clear morphological differences between the accessions, with ABS 5516 as the most vigorous and with the highest measured values in all variables except percentage of hermaphrodite flowers.  相似文献   

Foundations of mathematics: unsolvable problems     

Steen LA 《Science (New York, N.Y.)》1975,189(4198):209-210

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Maternal influence mediated by litter size during the suckling period on reproduction traits in pigs     

H.A.M. Van Der Steen 《Livestock Production Science》1985,13(2):147-158

Maternal effects might affect the response to selection for litter size. An experiment was carried out to determine the effect of the size of litter in which a gilt was raised on its production and reproduction characteristics. Gilts raised in large litters (12 piglets) produced smaller litters (?0.48 piglets) compared to those raised in small litters (six piglets). Results obtained suggest that a low standardization level positively affects weaning weight and development of the uterus. Lower weight at weaning, in combination with a larger pool of primordial follicles, might explain the positive effect on litter size.  相似文献   

Mathematics education: a predictor of scientific competitiveness     

Steen LA 《Science (New York, N.Y.)》1987,237(4812):251-302

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Model-calibrated k-nearest neighbor estimators     

Steen Magnussen  Erkki Tomppo 《Scandinavian Journal of Forest Research》2016,31(2):183-193

A generalized difference, a model-calibrated (MC), and a pseudo-empirical likelihood (PEMLE) kNN estimator of a population mean and its sampling variance was assessed with simulated simple random (SRS) and one-stage cluster sampling (CLU) from three artificial and one actual multivariate populations. The number of nearest neighbors (k) for imputing values of a target variable varied from one to eight. The design-based MC estimator had the lowest bias, but bias varied among populations and target variables. In terms of root mean squared errors (RMSEs), the estimators had similar performance, yet RMSEs of MC and PEMLE were less variable. Results were uneven across populations and target variables. The value of k had little effect on RMSE suggesting an advantage of choosing a low value that retains most of the attribute variance in a map. Nominal confidence intervals computed from MC estimators of variance achieved overall the best coverage rate. Rankings of the estimators in SRS and CLU designs were similar. We recommend MC for practical kNN applications in forest inventories for pixel-level predictions and derived estimates.  相似文献   

The effects of wilting grass before ensiling on silage intake     

Dawson  Ferris  Steen  Gordon  & Kilpatrick 《Grass and Forage Science》1999,54(3):237-247

Herbage, predominantly perennial ryegrass (Lolium perenne) grown in Northern Ireland, was harvested at four dates from June to October 1996 (H1, H2, H3 and H4). At each harvest approximately one-fifth of the grass harvested was artificially dried and pelleted (G). The remainder of the grass was either wilted for 28–52 h (W), depending on the weather conditions, or ensiled directly, i.e. unwilted (UW). Within the W and UW treatments an inoculant or formic acid additive was applied to the herbage before ensiling. After a minimum ensiling period of 10 weeks, sixty steers, mean initial live weight 432 (s.d. 37) kg, were offered the twenty forages in a four-period partially balanced changeover design experiment. Each period was of 2 weeks’ duration. Dry-matter (DM) intakes were recorded daily, with intakes in the second week of each period used in the statistical analysis of the data. The digestibility of each of the forages was also determined in vivo using four castrated male sheep per silage. Wilting increased the DM content of the silage and the pH, the largest increase in DM content occurring at the second harvest. On average, wilting proportionally increased silage DM intake by 0·21 compared with the unwilted silage (P < 0·001), but the intake of the wilted silage was not significantly different from that of the artificially dried and pelleted grass (P > 0·05). The intake of the wilted silage was higher than that of the unwilted silage at each harvest, the proportional increases being 0·22 (P < 0·001), 0·41 (P < 0·001), 0·19 (P < 0·001) and 0·05 (P > 0·05) at harvests H1, H2, H3 and H4 respectively. Treatment of the grass with formic acid before ensiling resulted in a proportional increase in silage intake of 0·08 compared with the inoculant-treated silage (P < 0·05). Compared with the inoculant-treated silage, formic acid increased silage intake by 0·08, 0·02, 0·14 and 0·10 at harvests H1 (P > 0·05), H2 (P > 0·05), H3 (P < 0·01) and H4 (P < 0·05). The results of this study indicate that the effect of wilting on silage intake varies across different harvests and additive treatments. The difference in response to wilting across different harvests is mainly a result of the prevailing weather conditions during wilting.  相似文献   

Secular trends in diet among elderly Swedes -- cohort comparisons over three decades     

Eiben G  Andersson CS  Rothenberg E  Sundh V  Steen B  Lissner L 《Public health nutrition》2004,7(5):637-644

OBJECTIVE: The purpose of this study was to compare dietary practices among different birth cohorts of 70-year-old Swedes, who were examined between 1971 and 2000. SETTING: G?teborg, Sweden. DESIGN: Four population-based samples of 1360 70-year-olds, born in 1901, 1911, 1922 and 1930, have undergone health examinations and dietary assessments over a period of almost three decades. One-hour diet history (DH) interviews were conducted in 1971, 1981, 1992 and 2000 with a total of 758 women and 602 women. The formats and contents of the dietary examinations were similar over the years. Statistical analysis of linear trends was conducted, using year of examination as the independent variable, to detect secular trends in food and nutrient intakes across cohorts. RESULTS: At the 2000 examination, the majority of 70-year-olds consumed nutritionally adequate diets. Later-born cohorts consumed more yoghurt, breakfast cereals, fruit, vegetables, chicken, rice and pasta than earlier-born cohorts. Consumption of low-fat spread and milk also increased, along with that of wine, light beer and candy. In contrast, potatoes, cakes and sugar were consumed less in 2000 than in 1971. The ratio of reported energy intake to estimated basal metabolic rate did not show any systematic trend over time in women, but showed a significant upward trend in men. CONCLUSIONS: The diet history method has captured changes in food selections in the elderly without changing in general format over three decades. Dietary quality has improved in a number of ways, and these findings in the elderly are consistent with national food consumption trends in the general population.  相似文献   

Aggressive behavior of sows at parturition   总被引：7，自引：0，他引：7  

H A van der Steen  L R Schaeffer  H de Jong  P N de Groot 《Journal of animal science》1988,66(2):271-279

Sows, especially primiparous, may show aggressive behavior at parturition against their own piglets, resulting in wounding or death of the piglets. Frequency, environmental influences and heritability of aggressive behavior were studied in two data sets. The first (923 first litters) was collected at an experimental farm and the other (925 first litters) came from a pig breeding organization. Frequency of aggressiveness ranged, depending on its definition, from 7 to 12%. Fixed effects of year, season and feeding level of the gilt during the rearing period did not affect the frequency of aggressiveness. A regression of aggression on postpartum sow weight was found, suggesting that low weight at first farrowing might predispose sows to aggressive behavior. Coefficients for backfat and litter size were positive but nonsignificant. Heritability of aggressiveness on the underlying normal scale, estimated from the paternal half-sib component of variance, averaged .12 for the first data set, and .25 for data set II. Estimates from daughter-dam regression were .49 and .87 for the two data sets, respectively. A simulation study indicated that this difference might be due to maternal effects. A simple application would be to select boars and gilts from non-aggressive sows only. Response to selection would be rather slow if the frequency of aggressive behavior is low. At frequencies that are too high from an economic point of view, estimation of breeding values, combining own performance and(or) data from relatives, is required.  相似文献   

Quantitative determination of tyrosinase activity using paper discs and a recording densitometer     

M. L. Weaver  H. A. Steen 《American Journal of Potato Research》1967,44(11):387-392

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