基于关节力传感器的并联六自由度机构标定方法

提出了一种基于关节力传感器的并联六自由度机构结构参数标定方法.从力学角度出发,通过测量并联六自由度机构各关节驱动力,利用并联六自由度机构自身的运动学和动力学模型构造相应的辨识模型,实现其结构参数的标定.通过标定仿真验证了该方法的实用性和有效性.     

Influence of the species and geographical location on volatile composition of Spanish oak wood (Quercus petraea Liebl. and Quercus robur L.)

The influence of the species and geographical origin on the volatile composition of wood samples from 80 Spanish oaks (55 Quercus petraea Liebl. and 25 Quercus robur L.) has been studied. Oak volatile components were isolated by simultaneous distillation-extraction and analyzed by gas chromatography-mass spectrometry. cis- and trans-beta-methyl-gamma-octalactones were the main constituents, the cis stereoisomer being predominant. Other important volatile components were furfural, 5-methylfurfural, guaiacol, eugenol, vanillin, or syringaldehyde. The main differences were established between species, Quercus petraea being significantly richer in volatile compounds than Quercus robur; however, the variability found among trees was high. Differences among geographical provenances were much less important than those found between species.     

Determination of volatile organic compound patterns characteristic of five unifloral honey by solid-phase microextraction-gas chromatography-mass spectrometry coupled to chemometrics

We report the evaluation of the floral origin of honey by analysis of its volatile organic compounds (VOCs) profile, joined with the use of combined pattern recognition techniques. Honey samples, from five floral origins, were analyzed by headspace solid-phase microextraction-gas chromatography-mass spectrometry, selecting 35 VOCs out of the entire profiles, which were analyzed by hierarchical cluster analysis (HCA), stepwise discriminant analysis (SDA), and K-nearest-neighbor (KNN). Both HCA and SDA were used as exploratory tools to select a group of VOCs representing similitude and differences among studied origins. Thus, six out of 35 VOCs were selected, verifying their discriminating power by KNN, which afforded 93% correct classification. Therefore, we drastically reduced the amount of compounds under consideration but kept a good differentiation between floral origins. Selected compounds were identified as octanal, benzeneacetaldehyde, 1-octanol, 2-methoxyphenol, nonanal, and 2-H-1-benzopyran-2-one. The analysis of VOC profiles, coupled to HCA, SDA, and KNN, provides a feasible alternative to evaluate the botanical source of honey.     

Seabird mortality at trawler warp cables and a proposed mitigation measure: A case of study in Golfo San Jorge, Patagonia, Argentina

We studied the interaction between seabirds and warp cables in the high-seas Argentine hake Merluccius hubbsi trawl fishery operating in Golfo San Jorge, Argentina, and tested the efficacy of a simple mitigation measure designed to reduce mortality at warp cables. Observations were made onboard hake trawlers during the height of the fishing season, between December 2004 and April 2005. Thirteen seabird species used food made available by fishing operations. The most frequent and abundant seabirds (% occurrence, mean maximum number per haul) were the Kelp gull Larus dominicanus (98.1%, 348.5) and the Black-browed albatross Thalassarche melanophrys (96.1%, 132.2). Contacts with warp cables were recorded for six species in 81.4% of hauls, with a mean number of contacts per haul of 14.4 ± 23.8 (range = 0-127). A total of 53 individuals were killed due to interactions with nets and cables, resulting in a total cable mortality rate of 0.14 birds/haul. Considering the fishery’s fishing effort, the estimated total number of birds killed during the study was 2703 (CV = 0.8), of which 306 (CV = 0.9) were killed due to contacts with warp cables (255 Kelp gulls and 51 Black-browed albatross). The tested device consisted of a plastic cone attached to each warp cable. In hauls with mitigation device, the number of contacts was reduced by 89% and no seabirds were killed. Mean distances between seabirds and cables were significantly larger in hauls with than without mitigation device (2.6 vs 0.9 m). The proposed device could be easily applied in this and other trawl fisheries operating in Argentine waters. Increased effort should be placed in implementing mitigation measures and the monitoring of cable related mortality associated to high-seas trawlers operating in the Argentine Continental Shelf.     

The wide diversity of structurally similar wine proteins

In the present work, single grape variety wines, Moscatel and Arinto, were used. Analysis by denaturing polyacrylamide gel electrophoresis of the wine proteins revealed the presence of only a few polypeptides ranging in molecular mass from 15 to 30 kDa. However, a more detailed examination of the whole protein fraction, by a combination of techniques, showed that these wines contain a very large number (many tens and, possibly, many more) of distinct polypeptides, exhibiting similar molecular masses but different electrical charges. The results obtained using highly specific antibodies and N-terminal sequencing indicate that there is structural similarity among most of the wine polypeptides. These observations can be explained by the existence of a common precursor to most or all of the wine proteins, which could generate all of the detected polypeptides by limited proteolysis. Comparison of the N-terminal sequences of the polypeptides isolated from Moscatel wine with proteins from other sources revealed a high degree of homology to pathogenesis-related proteins.     

Silvopastoral systems improve carbon stocks at livestock ranches in Tabasco,Mexico

Silvopastoral systems have great potential for storing carbon because of carbon assimilation in tree woody biomass, carbon input through litterfall and below-ground carbon turnover. In this study, we quantified and compared the carbon stocks at livestock ranches in Tabasco, Mexico, containing either scattered trees in grazing pastures (STP) or grass monocultures. Sampling plots were randomly established at each ranch where the above- and below-ground carbon stocks, carbon input from litterfall, grass production and arboreal biomass growth were measured. We found that silvopastoral systems stored an average of 257.45 Mg ha⁻¹ of soil organic carbon (SOC) compared to 119.17 Mg SOC ha⁻¹ at grass monoculture ranches (to 30 cm depth); silvopastoral systems also stored 44.64 Mg C ha⁻¹ in wood biomass; and, grass monocultures had greater cumulative grass biomass production. Overall, it is concluded that livestock ranches in Tabasco, Mexico, with scattered trees in grazing pastures stored 58.8% more carbon than those grass monocultures, with carbon stocks of 327.01 Mg C ha⁻¹and 134.47 Mg C ha⁻¹, respectively. The results are useful for land management decision making for sustainable livestock systems framed in the Sustainable Development Goals (SDGs).     

High frequency somatic embryogenesis with a pampeana-derived genotype of alfalfa (Medicago sativa L.)

Summary Somatic embryos of genotype R11 of the alfalfa variety Pampeana were produced from embryogenic calli derived from leaf sections. They were induced by an auxin shock and its development was attempted on six different media. The best condition for somatic embryo production was inducing callus on MS medium plus 10 M 2,4-D and 4,6 M KIN and transferring them, after the auxin shock, to MS with 10–20 mM NH₄ ⁺ and 30 mM proline. More than 500 somatic embryos per plate were produced. Embryos were grown to plants on MS or half strength MS media and all regenerated plants resembled the original R11 genotype. This technique could be useful in alfalfa Pampeana improvement using genetic modification.     

Evaluation of nonpolar metabolites in plant extracts by 13C NMR spectroscopy

(13)C nuclear magnetic resonance (NMR) spectroscopy was explored as a simple and efficient technique for the quantitative analysis of nonpolar metabolites in plants. The method was first optimized with a mixture of known metabolites and then applied to the nonpolar leaf extracts of plants harvested in the Valencian community (eastern Spain) belonging to three different genera: Euphorbia (Euphorbiaceae), Araujia (Apocynaceae), and Morus (Moraceae). Furthermore, an exhaustive analysis of Euphorbia characias leaf and stem extracts from different geographic locations allowed that quantitative (13)C NMR spectroscopy is a suitable tool for metabolic profiling purpose.