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Giant piezoelectricity on Si for hyperactive MEMS 总被引：1，自引：0，他引：1
Baek SH Park J Kim DM Aksyuk VA Das RR Bu SD Felker DA Lettieri J Vaithyanathan V Bharadwaja SS Bassiri-Gharb N Chen YB Sun HP Folkman CM Jang HW Kreft DJ Streiffer SK Ramesh R Pan XQ Trolier-McKinstry S Schlom DG Rzchowski MS Blick RH Eom CB 《Science (New York, N.Y.)》2011,334(6058):958-961
Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO(3) template layer with superior piezoelectric coefficients (e(31,f) = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting. 相似文献
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Krzysztof Dziedzic Danuta Górecka Artur Szwengiel Hanna Sulewska Ivan Kreft Elżbieta Gujska Jarosław Walkowiak 《Plant foods for human nutrition (Dordrecht, Netherlands)》2018,73(1):82-88
In this report, we presented the profile of polyphenolic substances in flowers, leaves, stalk and roots of Fagopyrum tataricum estimated by using RP–UHPLC–ESI-MS equipment (reversed-phase ultra-high-performance liquid chromatography electrospray ionisation mass spectrometry). The neutral detergent fibre, acid detergent fibre, acid detergent lignin, cellulose and hemicellulose were also determined. Flowers, leaves, stalk and roots showed varying levels of dietary fibre and polyphenols. The highest content of neutral and acid detergent fibre were found in the roots (63.92 and 45.45% d.m., respectively) while the most rich in phenolic compounds were flowers (4.8 mg/1 g d.m.). Root and stalk contained the highest level of cellulose, 38.70 and 25.57% d.m., respectively. Among the investigated polyphenolic substances such as: 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 4-hydrobenzoic acid, caffeic acid, catechin, chlorogenic acid, fagopyrin, ferulic acid, myricetin, gallic acid, isovanilic acid, isovitexin, kaempferol, luteolin, p-coumaric acid, procyanidin B2, quercetin, quercetin 3-D galactoside, rutin, syringic acid and vitexin, we observed that the contents of rutin and chlorogenic acid were the highest. We found some correlation between dietary fibre fractions and individual phenolic substances. The levels of acid detergent fibre (ADF), cellulose and hemicellulose were negatively correlated with isovitexin, kaempferol, vitexin, fagopyrin, caffeic acid and procyanidin B2 content. In this investigation, two solvents (water and methanol) were estimated regarding their extraction efficiency of phenolic compounds. Taking these results into consideration, we recommend using methanol as the extractor to isolate chlorogenic acid, fagopyrin, kaempferol, procyanidin B2, quercetin, quercetin 3-D-galactoside, rutin, vitexin, and water for other investigated polyphenolic substances obtained from Fagopyrum tataricum. 相似文献
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Buckwheat is a pseudocereal with a strong characteristic aroma. Compounds responsible for the aroma of buckwheat groats were recently identified, but the distribution of aromatic compounds between different fractions of the buckwheat kernel (flour, bran, and husk) is not yet known. In this study, the composition of aromatic compounds in buckwheat seed fractions was investigated and compared to the composition of aromatic compounds in groats produced from the same batch of buckwheat seeds. Volatiles from each sample were extracted with simultaneous distillation/extraction with a Likens‐Nickerson apparatus. Extracts were analyzed by gas chromatography coupled with mass spectrometry (GC‐MS) with electron ionization. Apart from the aroma molecules present in all fractions, compounds that are present only in flour or bran, but not in groats, were also found. Furthermore, some compounds were identified only in buckwheat groats but not in buckwheat flour or bran [octanal, (E,E)‐2,4‐heptadienal, (E)‐2‐decenal, and (E,E)‐2,4‐decadienal], others were identified only in husks [(E)‐2‐hexenal, heptanal, (E,E)‐2,4‐hexadienal, phenylacetaldehyde, and alpha‐bisabolol]. 相似文献
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An experiment was made to test the possibility of the quantitative analysis of chlorides in biological material by the modern potentiometric method using an ion-selective electrode. The results were compared with the current practical methods--polarography and photometry. The results demonstrate the suitability and benefits of the use of the ion-selective electrode, mainly in the series determination of Cl- ion concentration in biological material. The expediency of the tested analytical method and its well-reproducible results demonstrate the advantages of the ion-selective method in the analysis of chlorides in biological material, as compared with the polarographic and photometric methods. 相似文献
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The effects of selenium (Se) (VI) soil fertilization with 2 μg Se L?1 or foliar spraying twice with 20 mg Se L?1 in the form of sodium (Na) selenate on the physiological and biochemical characteristics of cabbage plants were studied. The ability of the plants to take up Se and translocate it to different parts of the plants was also studied. Despite the high concentration of Se in the foliar solution, there was no effect on photosynthesis, transpiration rate, photochemical efficiency of PSII, or electron transport system activity. The amount of chlorophyll and anthocyanins were unchanged. At harvest, the concentration of Se in control plants was lower than 100 ng Se g?1 dry weight (DW), while plants treated with 20 mg Se L?1 contained 5500 ng Se g?1. Selenium enriched cabbage could be used in human nutrition. The tolerance of cabbage to Se could be explained by the formation of insoluble compounds that are not available for the plant. 相似文献
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Aleksandra Golob Vekoslava Stibilj Ivan Kreft Katarina Vogel-Mikuš Alenka Gaberščik Mateja Germ 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(1):5-15
Ambient UV radiation is recognised as an important environmental factor in the regulation of plant growth and development, and selenium (Se) as a beneficial nutrient that can increase plant tolerance to different environmental constraints. The effects on hybrid buckwheat plants of full (+UV) and reduced (?UV) ambient UV radiation without (?Se) and with (+Se) foliar Se treatment (10?mg?L?1 sodium selenate) provided the four conditions of Se?UV–, Se–+UV, +Se?UV and +Se+UV. Plant morphological, biochemical and physiological properties were examined, along with leaf elemental composition and content, efficiency of Se enrichment, and production parameters. Leaf anatomical parameters under all conditions were mainly affected by UV radiation, and less so by Se. +Se+UV plants showed a trade-off between primary and secondary metabolism, which resulted in high levels of protective substances (e.g. anthocyanins, UV absorbing compounds), and low levels of photosynthetic pigments. All +UV plants were significantly shorter in comparison to those under the reduced ?UV, while biomass production was highest for ?Se+UV plants and lowest for +Se+UV plants. +Se plants accumulated ～20-fold greater Se content compared to ?Se plants, and full ambient UV radiation partly reduced this effect. +UV plants showed increased phosphorus content in leaves, independent of Se status, while +Se plants showed increased K content. Si content was increased by Se treatment and decreased by the full UV exposure. Se treatment and the ambient UV radiation, separately have positive effects on growth and production of this hybrid buckwheat, while the combination of the Se treatment and ambient UV resulted in lower yields. However, under these conditions (+Se+UV), the buckwheat plants established good protection against the different environmental constraints that are becoming more and more frequent due to changes to our climate. 相似文献
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Effect of Se on selenoprotein activity and thyroid hormone metabolism in beef and dairy cows and calves 总被引：2，自引：0，他引：2
Rowntree JE Hill GM Hawkins DR Link JE Rincker MJ Bednar GW Kreft RA 《Journal of animal science》2004,82(10):2995-3005
Although Se is essential for antioxidant and thyroid hormone function, factors influencing its requirement are not well understood. A survey and two experiments were conducted to determine the influence of cattle breed and age on selenoprotein activity and the effect of maternal Se supplementation on cow and calf selenoprotein activity and neonatal thyroid hormone production. In our survey, four cowherds of different ages representing three breeds were bled to determine the influence of breed and age on erythrocyte glutathione peroxidase activity (RBC GPX-1). All females were nonlactating, pregnant, and consumed total mixed diets (Holstein) or grazed pasture (Angus and Hereford). In our survey of beef breeds, yearlings had greater average RBC GPX-1 activity than mature cows. In Exp. 1, neonatal Holstein heifers (n = 8) were bled daily from 0 to 6 d of age to determine thyroid hormone profile. An injection of Se and vitamin E (BO-SE) was given after the initial bleeding. Thyroxine (T4) and triiodothyronine (T3) concentrations were greatest on d 0 and decreased (P < 0.05) continuously until d 5 postpartum (156.13 to 65.88 and 6.69 to 1.95 nmol/L, d 0 to 5 for T4 and T3, respectively). Reverse T3 concentrations were 3.1 nmol/L on d 0 and decreased (P < 0.05) to 0.52 nmol/ L by d 5. In Exp. 2, multiparous Hereford cows were drenched weekly with either a placebo containing 10 mL of double-deionized H2O (n = 14) or 20 mg of Se as sodium selenite (n = 13). After 2 mo of treatment, Se-drenched cows had greater (P < 0.01) plasma concentrations than control cows (84.92 vs. 67.08 ng/mL), and at parturition, they had plasma Se concentrations twofold greater than (P < 0.05) control cows (95.51 vs. 47.14 ng Se/mL). After 4 mo, cows receiving Se had greater (P < 0.05) RBC GPX-1 activity than controls; this trend continued until parturition. Colostrum Se concentration was twofold greater (P < 0.05) in Se-drenched cows than control cows (169.97 vs. 87.00 ng/mL). Calves born to cows drenched with Se had greater (P < 0.05) plasma Se concentration, RBC GPX-1, and plasma glutathione peroxidase activity on d 0 compared with calves born to control cows. By d 7, no differences in plasma glutathione peroxidase activity in calves were observed. Maternal Se supplementation did not influence calf thyroid hormone concentrations. Selenium provided by salt and forages is not adequate for cattle in Se-deficient states. 相似文献