Back-to-back Schottky diodes: the generalization of the diode theory in analysis and extraction of electrical parameters of nanodevices

We report on the analysis of nonlinear current-voltage characteristics exhibited by a set of blocking metal/SnO(2)/metal. Schottky barrier heights in both interfaces were independently extracted and their dependence on the metal work function was analyzed. The disorder-induced interface states effectively pinned the Fermi level at the SnO(2) surface, leading to the observed Schottky barriers. The model is useful for any two-terminal device which cannot be described by a conventional diode configuration.     

Escape and transport for an open bouncer: Stretched exponential decays

We consider time-dependence of dynamical transport, following a recent study of the stadium billiard in which classical transmission and reflection probabilities were shown to exhibit exponential or algebraic decays depending on the choice of the lead or “hole”, raising the question of whether this feature is due to special properties of the stadium. The system considered here is much more general, having a generic mixed phase space structure, time-dependence of the dynamics, and Fermi acceleration (trajectories with unbounded velocity). We propose an efficient numerical scheme for this model, observe escape and transport effects including similar asymmetry, and also clear stretched exponential decays.     

Phase Transformation in Titania Nanocrystals by the Oriented Attachment Mechanism: The Role of the pH Value

The oriented attachment (OA) mechanism has been investigated as an important process in the formation of anisotropic nanostructures such as depicted. The results showed that the control of a desired phase in this system may be attained by the control of OA mechanism through pH value, obtaining several morphologies.

     

Calorimetry studies for interaction in solid/liquid interface between the modified cellulose and divalent cation

Cellulose (Cel) was initially modified with thionyl chloride in order to increase its reactivity. In another step, chlorinated cellulose (CelCl) was reacted with ethylenediamine (CelEn) molecule. The last reaction step was reacting CelEn with ethylene sulfide molecule, yielding the solid named CelEnEs. The two last steps occur in free solvent conditions. Elemental analysis showed the incorporation of an enormous amount of chlorine in the CelCl structure, the nitrogen entrance from the ethylenediamine molecule, as well as the huge amount of sulfur that was added due to entry of the ethylene sulfide molecule. Infrared spectroscopy, thermogravimetry, and ¹³C NMR in the solid state demonstrated the effectiveness of the reaction, in which the last one has shown signals at 30 and 32 ppm for CelEnEs due to the change in the methylene group environment. Divalent metal uptake by chemically modified biopolymer gave the order Ni²⁺ > Co²⁺ > Cu²⁺ > Zn²⁺, reflecting the corresponding acidity of these cations in bonding to the sulfur and the basic nitrogen atoms available on the pendant chains. The equilibrium data were fitted to Langmuir model. The maximum monolayer adsorption capacity for the cations was found to be 5.561 ± 0.017, 4.694 ± 0.013, 1.944 ± 0.062, and 1.733 ± 0.020 mmol g^?1 for Ni²⁺, Co²⁺, Cu²⁺, and Zn²⁺, respectively. Through calorimetric titrations thermodynamic parameters could be obtained, and the results proved the favor of the interactions between cations and basic centers of modified cellulose. This new synthesized biopolymer can be used as a material for cation removal from aqueous solution.     

Biosynthesis of Bromoroquefortines in a High Saline Medium by Penicillium chrysogenum,a Terrestrial Endophyte Collected from Coffea arabica

Roquefortine C ( 1 ) and 11‐bromoroquefortine C ( 4 ) were isolated from Penicillium chrysogenum, an endophyte obtained from green leaves of Coffea arabica, during induction experiments by adding halide salts to the culture media. In our studies, 11‐bromoroquefortine D and 11‐bromo‐17‐hydroxybromoroquefortine C were identified by LC/HR‐MS. It is the first time that bromoroquefortine C and D are described as halogenated natural products. These halo alkaloids were shown to be biosynthesized from brominated tryptophan as the biosynthetic precursor. Cytotoxic and antibiotic assays using roquefortine C and 11‐bromoroquefortine C showed that the presence of the 11‐Br substituent impairs some biological activities of this alkaloid.     

Bioactive coating on titanium implants modified by Nd:YVO4 laser

Apatite coating was applied on titanium surfaces modified by Nd:YVO₄ laser ablations with different energy densities (fluency) at ambient pressure and atmosphere. The apatites were deposited by biomimetic method using a simulated body fluid solution that simulates the salt concentration of bodily fluids. The titanium surfaces submitted to the fast melting and solidification processes (ablation) were immersed in the simulated body fluid solution for four days. The samples were divided into two groups, one underwent heat treatment at 600 °C and the other dried at 37 °C. For the samples treated thermally the diffractograms showed the formation of a phase mixture, with the presence of the hydroxyapatite, tricalcium phosphate, calcium deficient hydroxyapatite, carbonated hydroxyapatite and octacalcium phosphate phases. For the samples dried only the formation of the octacalcium phosphate and hydroxyapatite phases was verified. The infrared spectra show bands relative to chemical bonds confirmed by the diffraction analyses. The coating of both the samples with and without heat treatment present dense morphology and made up of a clustering of spherical particles ranging from 5 to 20 μm. Based on the results we infer that the modification of implant surfaces employing laser ablations leads to the formation of oxides that help the formation of hydroxyapatite without the need of a heat treatment.     

Synchronization structure of evolving epileptic networks using cross-entropy

In this paper we present connectivity patterns of evolving large scale epileptic networks. We employed a cross-entropy measure in the frequency domain on EEG signals to infer the networks, before and during episodes of epileptic seizures. This measure allowed us to make a richer portrait about the node interactions on the graph and to identify emergent structures associated with the synchronization of brain activity. Our results points to a more complex scenario of network organization than the synchronized/unsynchronized dichotomy, with two main results: first, showing regions with unsynchronized (or independent) behavior, even during absence seizures, contradicting the concept of hypersynchrony. Furthermore, we explore the cross-entropy fluctuations along the seizure: a group of nodes became more similar over time while another group became more different, showing a complementary behaviour and different local brain activities. These results bring new questions about the spreading and the sustenance of the epileptic seizures and others synchronization phenomena in living systems.     

Okra as a drag reducer for high Reynolds numbers water flows

The capability of a mixture of okra fiber and mucilage as drag reducer in high Reynolds number flows through a pipeline, in which the flux is maintained by a centrifugal pump with controlled rotation, is analyzed. A DR close to the maximum drag reduction asymptote, which is obtained for polymeric additives, was achieved when concentrations around 1600 ppm were used. The loss of efficiency of the solution over the number of passes through the system was almost the same of that observed for rigid materials like Xanthan Gum and Guar Gum, which suggest that the main cause of a decreasing drag reduction is the de-aggregation instead of mechanical degradation, commonly observed in flexible polymers. As expected, the material degrades biologically, but it seems that it is not a great problem for open systems, since such a degradation is perceptible only after 24 h. We strongly believe that this new bio-drag reducer can be an alternative to synthetic polymers or other biopolymers, since it is extremely cheap and easy to be obtained.