Capillary wrinkling of floating thin polymer films     

Huang J  Juszkiewicz M  de Jeu WH  Cerda E  Emrick T  Menon N  Russell TP 《Science (New York, N.Y.)》2007,317(5838):650-653

A freely floating polymer film, tens of nanometers in thickness, wrinkles under the capillary force exerted by a drop of water placed on its surface. The wrinkling pattern is characterized by the number and length of the wrinkles. The dependence of the number of wrinkles on the elastic properties of the film and on the capillary force exerted by the drop confirms recent theoretical predictions on the selection of a pattern with a well-defined length scale in the wrinkling instability. We combined scaling relations that were developed for the length of the wrinkles with those for the number of wrinkles to construct a metrology for measuring the elasticity and thickness of ultrathin films that relies on no more than a dish of fluid and a low-magnification microscope. We validated this method on polymer films modified by plasticizer. The relaxation of the wrinkles affords a simple method to study the viscoelastic response of ultrathin films.  相似文献   

Plant sciences. Promiscuous maize chromosomes     

Martinez-Perez E  Moore G 《Science (New York, N.Y.)》2004,303(5654):49-50

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Early Cretaceous spider web with its prey     

Peñalver E  Grimaldi DA  Delclòs X 《Science (New York, N.Y.)》2006,312(5781):1761

The orb web is a spectacular evolutionary innovation that enables spiders to catch flying prey. This elegant, geometric structure is woven with silk fibers that are renowned for their superior mechanical properties. We used silk gland expression libraries to address a long-standing controversy concerning the evolution of the orb-web architecture. Contrary to the view that the orb-web design evolved multiple times, we found that the distribution and phylogeny of silk proteins support a single, ancient origin of the orb web at least 136 million years ago. Furthermore, we substantially expanded the repository of silk sequences that can be used for the synthesis of high-performance biomaterials.  相似文献   

Transient expression of pepper Bs2 gene in Citrus limon as an approach to evaluate its utility for management of citrus canker disease     

L. N. Sendín  M. P. Filippone  I. G. Orce  L. Rigano  R. Enrique  L. Peña  A. A. Vojnov  M. R. Marano  A. P. Castagnaro 《Plant pathology》2012,61(4):648-657

The pepper Bs2 gene confers resistance to Xanthomonas campestris pv. vesicatoria (Xcv) pathogenic strains containing the avrBs2 avirulence gene in susceptible pepper and tomato. The avrBs2 gene is highly conserved in the Xanthomonas genus and when bacteria lack this gene their growth in a susceptible host is diminished, indicating that the avrBs2 gene product could confer an adaptive advantage to the pathogen. The avrBs2 of Xanthomonas citri subsp. citri (Xcc), cause of citrus canker, shares 96% homology with avrBs2 of Xcv. To evaluate if Bs2 could recognize avrBs2 of Xcc in citrus plants and thereby activate plant defence mechanisms to increase resistance to canker, transient expression experiments were conducted using Agrobacterium tumefaciens in lemon plants subsequently challenged with wildtype Xcc. The results showed that transient expression of Bs2 reduced canker formation in lemon and induced plant defence mechanisms, as shown by callose deposition and PR‐1 expression. Moreover, when an avrBs2 mutant of Xcc was used, no decrease in disease symptoms was observed. This work shows that the Bs2 gene from Solanaceae is functional in lemon, a member of the Rutaceae family. Therefore, Bs2 is a potential candidate gene for stable expression in transgenic citrus plants in order to improve resistance to canker disease.  相似文献   

Enzymatic treatment to improve extraction of capsaicinoids and carotenoids from chili (Capsicum annuum) fruits     

Salgado-Roman M  Botello-Alvarez E  Rico-Martínez R  Jiménez-Islas H  Cárdenas-Manríquez M  Navarrete-Bolaños JL 《Journal of agricultural and food chemistry》2008,56(21):10012-10018

Enzymatic treatments using noncommercial enzymes as a means to the improve the extraction of carotenoids and capsaicinoids from chili fruits are explored in this study. The results show that it is possible to obtain chili fruit powder with a higher concentration of both capsaicinoids and carotenoids than previously reported for similar processes. Furthermore, extraction yields above 96% for carotenoids and 85% for capsaicinoids as separate fractions can be achieved using a sequential and selective two-stage extraction. Evidence is presented demonstrating that the content and extraction yield depend directly on the extent of the enzymatic hydrolysis of chili cell walls, and higher yields are obtained when the sample is completely hydrolyzed. The enzymatic treatment described here is a promising alternative to current industrial practices, and it improves the extraction of carotenoids and capsaicinoids from chili fruits.  相似文献   

Modifications to atrazine degradation pathways in a loamy soil after addition of organic amendments   总被引：4，自引：0，他引：4  

Sabine Houot  Enrique Barriuso  Valérie Bergheaud 《Soil biology & biochemistry》1998,30(14):2147-2157

The effects of two organic amendments, a municipal solid waste compost and a composted straw, on [U-ring- ]atrazine degradation pathways in a loamy soil (Grignon, Yvelines, France) were studied during laboratory incubations under controlled conditions. Three month conditionings were conducted under sterile or non-sterile conditions, with soil plus atrazine, organic amendment plus atrazine, or soil plus organic amendment. Then either an organic amendment or soil or atrazine was added, respectively, to these three treatments and incubated for an additional 3 months under non-sterile conditions. Both organic amendments modified the behaviour of atrazine in soil but via different processes. The addition of municipal compost increased atrazine sorption and decreased its availability for degradation by soil microorganisms. The effect of the composted straw was mainly related to its high enzymatic activity, which appeared to be responsible for the production of large amounts of hydroxyatrazine. This hydroxylation favoured the opening of the triazine ring and its subsequent mineralization in the soil. At the end of the incubations, less atrazine was mineralized in the presence of the two types of organic amendment, which both increased the formation of non-extractable residues of atrazine. The addition of municipal compost preserved larger amounts of extractable atrazine, while the addition of composted straw enhanced hydroxyatrazine production. In all cases, the greatest effects were found when atrazine was directly in contact with the organic amendment during conditioning.  相似文献   

Effect of emerged shipment on the physiological condition of the adductor muscle in adult giant lion's paw scallop Nodipecten subnodosus (Sowerby 1835)     

Victor Manuel Ocaño‐Higuera  Alfonso Nivardo Maeda‐Martínez  María Elena Lugo‐Sánchez  Gillermina García‐Sánchez  Enrique Márquez‐Ríos  Silvia Gómez‐Jimenez  Ramón Pacheco‐Aguilar 《Aquaculture Research》2011,42(8):1087-1095

Currently, there is an increasing interest in shipping live adult scallops to markets and broodstock to hatcheries; nevertheless, information about the shipping effect on live scallops physiology is very scarce. In a previous study, a method in emersion was developed to ship scallop seed out of water, but it was not known whether this method is useful to transport adult organisms. As a consequence, the purpose of this study was to evaluate the effects of transportation by the emersion method on the physiological status of the adductor muscle of adult giant lion's paw scallop. Live specimens were packaged in a container and transported in emersion for 11 h. Six scallops were frozen in a farm and a similar number were frozen as soon as they arrived to the laboratory. Physiological indices were determined in each lot and the survival was estimated 24 h after re‐immersion. As a result of the transportation, a significant loss (P<0.05) of total carbohydrates, glycogen, adenosine 5′‐triphosphate and adenilated energetic charge, and a significant increase (P<0.05) in the free amino acids concentration were observed. Eighty‐eight per cent survival was achieved; therefore, we conclude that this method is appropriate for shipping live adult scallops of Nodipecten subnodosus.  相似文献   

Influence of Compost Addition to Soil on the Behaviour of Herbicides     

Enrique Barriuso  Sabine Houot  Claire Serra-Wittling 《Pest management science》1997,49(1):65-75

The transformations of eight herbicides (atrazine, simazine, terbutryn, pendimethalin, carbetamide, 2,4-D, metsulfuron-methyl and dimefuron) in soil after compost addition were monitored during long-term laboratory incubations. The herbicides were applied to soil, compost and soil-compost mixtures. Herbicide sorption, their kinetics of mineralisation and the extractability of residues were compared in the different treatments. Compost addition to soil generally decreased herbicide mineralisation and favoured the stabilisation of herbicide residues. A fraction of the stabilised residues remained extractable and potentially available. However, most of them were unextractable and formed bound residues. Sorption could be at the origin of a kinetically limited biodegradation, mainly for the most highly-sorbed herbicides (atrazine, simazine, terbutryn, pendimethalin and dimefuron). Compost addition had little effects on the less sorbed herbicides (carbetamide, 2,4-D and metsulfuron- methyl). © 1997 SCI.  相似文献   

Substrate selection and effect of different substrates on survival and growth of juveniles of the freshwater crayfish <Emphasis Type="Italic">Cherax quadricarinatus</Emphasis> (von Martens 1868) (Decapoda,Parastacidae)     

Verónica E. Viau  Enrique M. Rodríguez 《Aquaculture International》2010,18(5):717-724

Survival and growth of juveniles of the Australian freshwater crayfish Cherax quadricarinatus were evaluated in aquaria with four different substrates covering their bottom. The four substrates were plastic mesh, small stones, fine sand and bare glass without cover (control group). Two size classes of juveniles were evaluated: recently hatched or early (~0.02 g of body weight) and pre-fattening or advanced (~1 g of body weight). A group of twelve early or ten advanced juveniles were placed in each of the 24 aquaria. Each substrate had a total of six aquaria, three containing early juveniles and the other three containing advanced juveniles groups. Each aquarium had an excess small PVC pipes that served as shelters. After 12 weeks, early juveniles raised in small stones or fine sand had a statistically significant heavier body mass than the control group while the advanced juveniles did not show statistically significant differences in body weight. In a second experiment, ten early and ten advanced juveniles were individually placed in a circular glass aquarium divided into four sections each containing one of the same substrates used in the first experiment. Each individual was filmed for 24 h, and the time spent in each compartment was registered. Both sizes of juveniles showed a marked preference for the small stones. This experiment was repeated with animals used in the first experiment and observed the same selection pattern indicating that substrate selection is independent of body mass or previous acclimation to the different substrates.  相似文献   

Protein lipid ratio for the growth and survival of juvenile crayfish Procambarus acanthophorus (Hobbs 1972) reared under controlled conditions     

Enrique Cervantes‐Santiago  Martha P. Hernández‐Vergara  Carlos I. Pérez‐Rostro  Miguel A. Olvera‐Novoa 《Aquaculture Research》2010,41(9):e62-e71

The influence of dietary protein/lipid levels on growth and survival in juvenile crayfish (Procambarus acanthophorus) was evaluated during a 12‐week nutritional trial. Twenty experimental diets were formulated containing different protein (200, 250, 300, 350 and 400 g kg^?1) and lipid (60, 80, 100 and 120 g kg^?1) levels. A bifactorial model (5 × 4) was used with three replicates and 15 crayfish (0.014±0.006 g) per replicate, in a recirculation system with 60–15 L rectangular tanks and a biological filter, the culture conditions were a photoperiod of 12:12 h L:D and temperature 24.7±1.0 °C. Total survival ranged from 66.6% to 86.6%, with no differences attributed to treatments. Dietary protein levels had a significant effect on growth gain and nutritional efficiency; in contrast, lipid levels had no effect on juvenile performance. The 250/120 (protein/lipid) treatment promoted the most efficient growth (final weight: 3.09 g, weight gain: 21 995%, specific growth rate: 3.35% day^?1); the less efficient growth was observed in juveniles fed with 400 g kg^?1 protein diets. The quadratic regression model indicated 279 g kg^?1 as the optimal protein level for crayfish growth, while levels between 211 and 232 g kg^?1 could minimize the feeding costs without affecting growth.  相似文献