Unusual underwater flowering of Utricularia australis populations: a botanical enigma?

The free-floating aquatic plant Utricularia australis has typically subsurface shoots and subaerial showy in- florescences. To find it growing with large populations among benthic Chara stands at 4–6 m depth in two Central Italian lakes, is a phenomenon that was never previously reported. Production of showy chasmogamous flowers at this depth makes such finding yet increasingly intriguing. Here we make quantitative-qualitative comparisons of morphological characters among subaerial and underwater flowers taken from diverse sites in Central Italy. Environmental data were used to delineate differences between superficial and underwater habitats where flowering U. australis populations were found, and to help explain these extraordinary findings. Although similar, the subaerial and underwater flowers did show some differences, the most important being the length of the floral scape. Underwater scapes were around three times longer than those emerged. This might be a typical phototropic-response or a failed attempt to get flowers above water surface for allowing entomophilous polli- nation, or a redundant morpho-physiological trait as a result of a recent ecological move. Underwater flowers were generally smaller, but they did have longer styles, nectar signalling was less obvious, thinner petals, mucous-coated pollen (subaerial pollen is dry and grainy). Both types of flower were sterile, producing abortive fruits. Possibility of underwater ecological conditions causing stress-induced flowering is also proposed. A lack of water movement is an important ecological requirement for U. australis growth and could explain why large populations have been found in deep water far from its typical habitat

Unusual underwater flowering of Utricularia australis populations: a botanical enigma?

The free-floating aquatic plant Utricularia australis has typically subsurface shoots and subaerial showy inflorescences. To find it growing with large populations among benthic Chara stands at 4–6 m depth in two Central Italian lakes, is a phenomenon that was never previously reported. Production of showy chasmogamous flowers at this depth makes such finding yet increasingly intriguing. Here we make quantitative-qualitative comparisons of morphological characters among subaerial and underwater flowers taken from diverse sites in Central Italy. Environmental data were used to delineate differences between superficial and underwater habitats where flowering U. australis populations were found, and to help explain these extraordinary findings. Although similar, the subaerial and underwater flowers did show some differences, the most important being the length of the floral scape. Underwater scapes were around three times longer than those emerged. This might be a typical phototropic-response or a failed attempt to get flowers above water surface for allowing entomophilous pollination, or a redundant morpho-physiological trait as a result of a recent ecological move. Underwater flowers were generally smaller, but they did have longer styles, nectar signalling was less obvious, thinner petals, mucous-coated pollen (subaerial pollen is dry and grainy). Both types of flower were sterile, producing abortive fruits. Possibility of underwater ecological conditions causing stress-induced flowering is also proposed. A lack of water movement is an important ecological requirement for U. australis growth and could explain why large populations have been found in deep water far from its typical habitat

Field Emission from Graphene Layers

We report the field emission characterization of graphene flakes deposited on SiO2/Si substrates. Electrical measurements are performed inside a scanning electron microscope provided of nano-manipulated metallic probes exploited as electrodes either to contact the flakes or as anode to collect electrons in field emission configuration. We demonstrate that local electric field as high as few hundreds V/µm allows to extract a current from the top of the flake. We also demonstrate a horizontal field emission device in which the electrons are extracted from the edge of the flake

Characterization of InSb nanopillars for field emission applications

A piezoelectrically driven metallic nanoprobe is installed inside a scanning electron microscope to perform local characterization of the field emission properties of InSb nanopillars. The tip-shaped anode can be precisely positioned at sub-micron distances from the emitters to collect electrons from areas as small as 1μm2 under the application of an external bias up to 100 V. Current-voltage characteristics are measured for cathode-anode separation down to 500 nm and are analyzed in the framework of the Fowler-Nordheim theory. We give estimation of performance parameters such as the field enhancement factor and the turn-on field and their dependence on the cathode-anode separation distance. We demonstrate the time stability of the emitted current for several minutes. Finally, we perform a finite element electrostatic simulation to calculate the electric field in proximity of the nanopillars and we evaluate the effective emitting area as well as the screening effect due to presence of other pillars in close vicinity. We show that InSb nanopillars are very stable emitters that allow current density as high as 104 A/cm2 and excellent time stability, crucial characteristics to envisage device exploitation

PtSe2 phototransistors with negative photoconductivity

Platinum diselenide (PtSe2) is one of the most studied materials of the emerging group-10 transition-metal dichalcogenides. We investigate the electrical conduction and the photoconduction of PtSe2 ultrathin films exploited as the channel of back-gated field-effect transistors. The channel resistance decreases with the rising temperature and shows that the films have semiconducting behaviour. The gate modulation confirms a p-type conductivity with field-effect mobility up to 30 cm2/(Vs). Under exposure to the radiation from a super-continuous white light source, a reduction of the PtSe2 electrical conductivity (negative photoconductivity) is observed in low vacuum, while a positive photoconductivity emerges only under high-power illumination conditions. Although, the positive photoconductivity arises from conventional photoconductive effect, the negative photoconductivity can be explained as the combination of the photogating effect caused by charge accumulation in the SiO2 dielectric and the photo-induced desorption of adsorbates

A3MMM3R2

Obiettivo è valorizzare i quattro ambiti dʼintervento – Stupinigi, interramento ferrovia, sponda Sangone, ex Viberti – collocandoli in un sistema di relazioni spazio-funzionali di livello territoriale ed eliminando le barriere esistenti – ferrovia, autostrada e, in modo diverso, fiume. I quattro ambiti sono sub-sistemi di un sistema territoriale comunale (e oltre) che si offre quale volano di uno sviluppo armonico e sostenibile dellʼintero territorio comunale di Nichelino e, soprattutto, della sua comunità di uomini e donne. Lo sviluppo sostenibile è considerato nelle tre dimensioni ambientale, sociale ed economica. La proposta è di intervenire nei quattro ambiti attraverso un progetto unitario di sviluppo sostenibile territoriale che consideri lʼambiente, la società, lʼeconomia di Nichelino e del suo comprensorio. La strategia è mettere a sistema gli interventi previsti. La tutela ambientale è interpretata attraverso due canali. Il primo riguarda lʼimpatto sullʼambiente naturale di tutti gli interventi previsti. Il secondo è relativo alIa valorizzazione del Parco di Stupinigi, delle sponde del fiume Sangone e di tutte le altre aree verdi esistenti e che si realizzeranno. La promozione sociale è interpretata in termini di fruizione di luoghi, nuovi o rinnovati, che si offrono alla comunità dei cittadini per favorire gli incontri, lʼaggregazione, lʼinclusione e il godimento del patrimonio naturale e culturale di Nichelino. La crescita economica è interpretata come produzione di ricchezza attraverso interventi il cui ritorno sia superiore alle risorse investite per la capacità di mettere in moto attività produttive in campo turistico, artigianale, agricolo, culturale e commerciale. Lʼidea-progetto è il collegamento fisico, funzionale e simbolico dei quattro ambiti attraverso soluzioni osmotiche che realizzino il passaggio da un ambito allʼaltro. Il collegamento fisico si esplica nella possibilità di spostarsi agevolmente tra gli ambiti a piedi, in bicicletta e con piccoli bus elettrici dedicati. Per lʼinterramento della ferrovia e la ricucitura: la sistemazione della nuova area di sedime, il ponte piastra con i nuovi edifici soprastanti, lʼhousing sociale e i servizi pertinenti, il parcheggio multipiano e il polo per lo spettacolo e il pubblico intrattenimento, la nuova stazione e il polo di scambio intermodale, il recupero della vecchia stazione, i percorsi attrezzati con pensiline, il miglio solare con la passeggiate e i pannelli fotovoltaici, le aree verdi e gli spazi pubblici. Per lʼarea dismessa della ex fabbrica Viberti: lʼarea si proietta verso il parco di Stupinigi e verso lʼinterramento della ferrovia segnando il territorio, il taglio della tangenziale è ricomposto dal ponte piastra, le nuove funzioni dialogano con gli altri ambiti, con la città di Nichelino e il territorio, il recupero degli edifici esistenti con le funzioni innovative, le nuove costruzioni con le pertinenze, gli impianti a rete e la centrale fotovoltaica, la nuova viabilità, gli spazi pubblici e le aree verdi. Per il Parco di Stupinigi e i Poderi Juvarriani: la rinnovata fruizione del parco a piedi e in bicicletta, parcheggi di interscambio con i minibus elettrici, il recupero degli edifici storici e le nuove funzioni, il viale dellʼarte, le cascine della memoria, il borgo creativo, le cascine per la coltivazione, lʼosservatorio e cabina di regia, la costruzione dei nuovi parcheggi in duna, lʼadeguamento paesaggistico-funzionale dei vecchi parcheggi, lʼadeguamento delle strade e la riorganizzazione della mobilità, la pedonalizzazione del parco e del nuovo viale dellʼarte, la rinaturalizzazione del parco. Per lʼarea sensibile del torrente Sangone: la tutela dellʼecosistema, la valorizzazione ecologica, la fruizione sostenibile, le aree attrezzate, il nuovo elemento ponte che proietta il verde di Nichelino verso il territorio al di là del fiume, la trasformazione del torrente Sangone da elemento di divisione in raccordo tra le due sponde, la sistemazione delle rive e del canale fluviale, la costruzione del ponte bio-architettonico, gli interventi di rinaturalizzazione, la costruzione degli ingressi al Boschetto con i parcheggi di attestamento, le aree ludiche e per lo sport

Germanium arsenide nanosheets applied as two-dimensional field emitters

The IV–V groups binary compound germanium arsenide (GeAs) is a semiconductor that can be easily exfoliated in very thin nanosheets and is characterized by a band gap ranging from 0.6 eV (bulk form) up to 2.1 eV (monolayer). We investigate the field emission characteristics of exfoliated multilayer GeAs nanosheets by means of a tip-anode setup, where a nanomanipulatio W-tip is positioned in front of the GeAs emitting layer at nanometric distance, all controlled inside a scanning electron microscope. We demonstrate that GeAs multilayers are suitable to develop electron sources, with turn-on field of the order of 102 Vµm-1 , and field enhancement factor of about 70

Temperature Dependence of Electrical Resistance in Graphite Films Deposited on Glass and Low-Density Polyethylene by Spray Technology

Graphite lacquer was simply sprayed on glass and low-density polyethylene (LDPE) substrates to obtain large area films. Scanning Electron Microscopy (SEM) images, Raman spectra, X Ray Diffraction (XRD) spectra and current-voltage characteristics show that at room temperature, the as-deposited films on different substrates have similar morphological, structural and electrical properties. The morphological characterization reveals that the films are made of overlapped graphite platelets (GP), each composed of nanoplatelets with average sizes of a few tens of nanometers and about forty graphene layers. The thermoresistive properties of the GP films deposited on the different substrates and investigated in the temperature range from 20 to 120 °C show very different behaviors. For glass substrate, the resistance of the film decreases monotonically as a function of temperature by 7%; for LDPE substrate, the film resistance firstly increases more than one order of magnitude in the 20–100 °C range, then suddenly decreases to a temperature between 105 and 115 °C. These trends are related to the thermal expansion properties of the substrates and, for LDPE, also to the phase transitions occurring in the investigated temperature range, as evidenced by differential scanning calorimetry measurements