Ultrahigh-density nanowire lattices and circuits

We describe a general method for producing ultrahigh-density arrays of aligned metal and semiconductor nanowires and nanowire circuits. The technique is based on translating thin film growth thickness control into planar wire arrays. Nanowires were fabricated with diameters and pitches (center-to-center distances) as small as 8 nanometers and 16 nanometers, respectively. The nanowires have high aspect ratios (up to 10(6)), and the process can be carried out multiple times to produce simple circuits of crossed nanowires with a nanowire junction density in excess of 10(11) per square centimeter. The nanowires can also be used in nanomechanical devices; a high-frequency nanomechanical resonator is demonstrated.     

Polymer gate dielectric surface viscoelasticity modulates pentacene transistor performance

Nanoscopically confined polymer films are known to exhibit substantially depressed glass transition temperatures (Lg's) as compared to the corresponding bulk materials. We report here that pentacene thin films grown on polymer gate dielectrics at temperatures well below their bulk Tg's exhibit distinctive and abrupt morphological and microstructural transitions and thin-film transistor (TFT) performance discontinuities at well-defined growth temperatures. The changes reflect the higher chain mobility of the dielectric in its rubbery state and are independent of dielectric film thickness. Optimization of organic TFT performance must recognize this fundamental buried interface viscoelasticity effect, which is detectable in the current-voltage response.     

Extracellular DNA plays a key role in deep-sea ecosystem functioning

The ecological role and biogeochemical relevance of extracellular DNA in the oceanic sediments are unknown. Our global estimates indicate that up to 0.45 gigatons of extracellular DNA are present in the top 10 centimeters of deep-sea sediments, representing the largest reservoir of DNA in the world oceans. We demonstrate that extracellular DNA accounts for about one fifth of the total organic phosphorus regeneration and provides almost half of the prokaryotic demand for organic phosphorus. It therefore plays a key role in deep-sea ecosystem functioning on a global scale.     

The Miller volcanic spark discharge experiment

Miller's 1950s experiments used, besides the apparatus known in textbooks, one that generated a hot water mist in the spark flask, simulating a water vapor-rich volcanic eruption. We found the original extracts of this experiment in Miller's material and reanalyzed them. The volcanic apparatus produced a wider variety of amino acids than the classic one. Release of reduced gases in volcanic eruptions accompanied by lightning could have been common on the early Earth. Prebiotic compounds synthesized in these environments could have locally accumulated, where they could have undergone further processing.     

Multielement fingerprinting as a tool in origin authentication of PGI food products: Tropea red onion

Tropea red onion ( Allium cepa L. var. Tropea) is among the most highly appreciated Italian products. It is cultivated in specific areas of Calabria and, due to its characteristics, was recently awarded with the protected geographical indications (PGI) certification from the European Union. A reliable classification of onion samples in groups corresponding to "Tropea" and "non-Tropea" categories is now available to the producers. This important goal has been achieved through the evaluation of three supervised chemometric approaches. Onion samples with PGI brand (120) and onion samples not cultivated following the production regulations (80) were digested by a closed-vessel microwave oven system. ICP-MS equipped with a dynamic reaction cell was used to determine the concentrations of 25 elements (Al, Ba, Ca, Cd, Ce, Cr, Dy, Eu, Fe, Ga, Gd, Ho, La, Mg, Mn, Na, Nd, Ni, Pr, Rb, Sm, Sr, Tl, Y, and Zn). The multielement fingerprint was processed using linear discriminant analysis (LDA) (standard and stepwise), soft independent modeling of class analogy (SIMCA), and back-propagation artificial neural network (BP-ANN). The cross-validation procedure has shown good results in terms of the prediction ability for all of the chemometric models: standard LDA, 94.0%; stepwise LDA, 94.5%; SIMCA, 95.5%; and BP-ANN, 91.5%.     

Comparison of a rebound and an applanation tonometer for measuring intraocular pressure in normal rabbits

Objective To compare intraocular pressure (IOP) measurements made on healthy adult rabbits without the effect of tranquilizers using the new applanation tonometer, Tono‐Pen Avia^®, and the rebound tonometer Tonovet^®. Methods Intraocular pressure was measured throughout the day (6:00, 9:00, 12:00, 15:00, and 18:00 h) in 38 adult New Zealand White rabbits (76 eyes). The animals were 20 males and 18 females, with a mean weight of 3.5 kg and an average age of 6 months. A complete ocular exam (including Schirmer tear test, fluorescein staining, slit‐lamp biomicroscopy, and direct ophthalmoscopy) was performed on all animals at the beginning of the trial. Rebound tonometry was performed, and after 10 min, anesthetic drops were instilled and applanation tonometry was carried out. IOP values obtained using the two techniques were analyzed statistically. Results The mean IOP was 9.51 ± 2.62 mmHg with Tonovet^®, and 15.44 ± 2.16 mmHg with the Tono‐Pen Avia^®. Significant differences between measurements with the two tonometers were observed (P < 0.001). The linear regression equation describing the relationship between the two tonometers was y = 0.4923x + 10.754 (y = Tonovet^® and x = Tono‐Pen Avia^®). High IOPs were recorded in the early measurements (6:00), but the average IOPs from both devices were statistically similar throughout the day (P = 0.086). The correlation coefficient was r² = 0.357. No significant difference in IOP regarding gender was observed. Conclusion The Tono‐Pen Avia^® recorded higher levels of IOP compared with the Tonovet^®. Early in the day, the IOP of rabbits was higher than later in the day, regardless of the tonometer used.     

sunTILL: a TILLING resource for gene function analysis in sunflower

Background

Cultivated sunflower (Helianthus annus L.) is a globally important oilseed crop, subjected to intensive genetic and genomic studies. Although classical mutagenesis has successfully been applied to Helianthus genus in the past, we have developed the first sunflower TILLING resource.

Results

To balance the maximum mutation density with an acceptable plant survival rate, a 'kill curve' analysis was first conducted with different ethylmethanesulfonate (EMS) dosages and different exposure times. According to the germination rate, a treatment with 0.7% EMS for 6 h was chosen. An M₂ progeny of 3,651 fertile plants was obtained. Totally, 4.79% of the whole population showed clear aberrant phenotypes. A microsatellite analysis on a representative sample of the original seed stock and mutant lines confirmed the uniformity of the genetic background of plant material. The TILLING procedure was successfully applied to sunflower genome, initially by a CelI-nuclease mismatch cleavage assay coupled with a DNA-pooling level test. To investigate the efficiency of the mutagenic treatment, a pilot screening was carried out on 1,152 M₂ lines focusing on four genes, three involved in the fatty acid biosynthetic pathway and one for downy mildew resistance. A total of 9 mutant lines were identified and confirmed by sequencing; thereby, the estimated overall mutation frequency for the pilot assay resulted to be 1/475 kb.

Conclusion

A first TILLING population for a high throughput identification of EMS-induced point mutations in sunflower genome has been successfully obtained. This represents a powerful tool to a better understanding of gene function in sunflower.     

Partial replacement of Fe(o,o‐EDDHA) by humic substances for Fe nutrition and fruit quality of citrus

The most widely used Iron (Fe) fertilizer in calcareous soils is the synthetic chelate Fe(o,o‐EDDHA). However, humic substances are occasionally combined with Fe chelates in drip irrigation systems in order to lower costs. We investigated the effect of various mixtures of Fe(o,o‐EDDHA) and a commercially available humic substance on Fe availability in a calcareous soil from Murcia, Spain (in vitro experiment) and on leaf Fe content and fruit‐quality attributes of Citrus macrophylla (field experiment). In the in vitro experiment, a calcareous soil was incubated for 15 d with solutions of sole Fe(o,o‐EDDHA) and humic substance and of a mixture of humic substance and Fe(o,o‐EDDHA) to determine the dynamics of available Fe. While the mixture did not significantly increase the available soil Fe, it did decrease the rate of Fe retention in the surface soil compared to sole Fe(o,o‐EDDHA). In the field experiment, the substitution in the application solution of 67% of Fe(o,o‐EDDHA) by commercial humic substance increased leaf P in lemon trees from 0.19% with sole Fe(o,o‐EDDHA) to 0.30% and leaf Fe from 94 mg kg^–1 to 115 mg kg^–1. Some quality parameters like vitamin C content and peel thickness were also improved with a partial substitution of Fe(o,o‐EDDHA) by humic substances. We conclude that a partial substitution of commercial Fe chelates by humic substance can improve crop Fe uptake and may thus be economically attractive. The underlying physiological mechanisms and ecological implications require further studies.     

The origin of Manihot esculenta Crantz (Euphorbiaceae)

Summary Contrary to views that cassava (Manihot esculenta) is only known in cultivation an argument is made that wild accessions of the species grow over much of the American neotropics, in Brazil, Bolivia, Peru, Venezuela, Guyana, and Surinam. Three subspecies are recognized. M. esculenta subsp. esculenta is the domesticate and includes all cultivars known in cultivation. The wild M. esculenta subsp. peruviana occurs in eastern Peru and western Brazil. The wild M. esculenta subsp. flabellifolia shows a wider distribution and ranges from the central Brazilian state of Goiás northward to Venezuelan Amazonia. The large area of distribution of the two wild subspecies makes it difficult to assign a place of initial domestication.