bluuebunny/crossref_metadata_2025 huggingface dataset:
Small Organic Molecules for Electrically Re-writable Non-volatile Polymer Memory Devices
Authors: Salaoru Iulia , Paul Shashi
Published: August 2010

The usage of organic materials in the manufacture of electronic polymer memory devices is on the rise. Polymer memory devices are fabricated by depositing a blend (an admixture of organic polymer, small molecules and nanoparticles) between two metal electrodes. The primary aim is to produce devices that exhibit two distinct electrical conductance states when a voltage is applied. These two states can be viewed as the realisation of non-volatile memory. This is an interesting development; however, there are a number of theories that have been proposed to explain the observed electrical behaviour. We have proposed a model that is based on electric dipole formation in the polymer matrix. Here, we investigate further the proposed model by deliberately creating electric dipoles in a polymer matrix using electron donors (8-Hydroxyquinoline, Tetrathiafulvalene and Bis(ethylenedithio)tetrathiafulvalene) and electron acceptors (7,7,8,8-Tetracyanoquinodimethane, Tetracyanoethylene and Fullerene) small molecules.

Two types of structures were investigated (i) a metal/blend of polymer and small molecules/metal (MOM), device and (ii) a metal/insulator/blend of small molecules and polymer/semiconductor (MIS) architecture. A blend of polymer and small organic molecules was prepared in methanol and spin-coated onto a glass substrate marked with thin aluminium (Al) tracks; a top Al contact was then evaporated onto the blend after drying - this resulted in a metal-organic-metal structure. The MIS structures consisted of an ohmic bottom Al contact, p-type Si, a polymer blend (two small organic molecules and insulating polymer), followed by polyvinyl acetate and finally a top, circular Al electrode. In-depth FTIR studies were carried out to understand the observed electrical behaviour. An electrical analysis of these structures was performed using an HP4140B picoammeter and an HP 4192A impedance analyser at a frequency of 1 MHz.
High-temperature Process Endurance of Oxide/Electrode Stacking Structure for Resistance Random Access Memory
Authors: Shima Hisashi , Nakano Takashi , Akinaga Hiro
Published: August 2010

The systematic investigation on the thermal stability of the CoO layer was carried out for various electrode materials. When Pt with higher oxygen potential (Gibbs free energy change of the oxidation reaction) compared to Co is used as electrodes, the resistance of the Pt/CoO/Pt devise was severely decreased by the post deposition annealing (PDA) process and the resistance switching into the high resistance state was observed in the first voltage sweep. This indicants that the reducing Ar ambient induces the quite local reduction of CoO. The reduction of the CoO layer is also expected even with the Co electrode, which is reasonably attributed to the oxygen concentration gradient at the Co/CoO interface in the Co/CoO/Pt device. With the Ti electrode having a much lower oxygen potential than Co, the reduction of CoO by Ti is also indicated electrically in the Pt/CoO/Ti device. On the other hands, W electrodes which is thought to have the solid-solution oxygen can stabilize the CoO layer during PDA although W is more affinitive with oxygen compared with Co. It can be pointed out the oxygen delivery at the electrode/oxide layer interface is a critical factor in designing the thermally stable stacking structure for resistance random access memory.
Electrical Characteristics of Crystalline Gd2O3 Film on Si (111): Impacts of Growth Temperature and Post Deposition Annealing
Authors: Niu Gang , Vilquin Bertrand , Baboux Nicolas , Saint-Girons Guillaume , Plossu Carole , Hollinger Guy
Published: August 2010

This work reports on the epitaxial growth of crystalline high-k Gd2O3 on Si (111) by Molecular Beam Epitaxy (MBE) for CMOS gate application. Epitaxial Gd2O3 films of different thicknesses have been deposited on Si (111) between 650°C~750°C. Electrical characterizations reveal that the sample grown at the optimal temperature (700°C) presents an equivalent oxide thickness (EOT) of 0.73nm with a leakage current density of 3.6×10-2 A/cm2 at |Vg-VFB|=1V. Different Post deposition Annealing (PDA) treatments have been performed for the samples grown under optimal condition. The Gd2O3 films exhibit good stability and the PDA process can effectively reduce the defect density in the oxide layer, which results in higher performances of the Gd2O3/Si (111) capacitor.
Study of Tunability of BST With Different Structures for Microwave Applications
Authors: El-Shaarawy Heba Badr El-Din , Pacchini Sebastien , Ouagague Badreddine , Payan Sandrine , Rousseau Anthony , Maglione Mario , Plana Robert
Published: August 2010

This paper addresses the characterization of the ferroelectric Ba0.6Sr0.4TiO3 on different substrates using three different microwave components. First, at low frequencies, metal-insulator-metal (MIM) capacitors are used to investigate the variation of the BST dielectric constant and loss tangent for different biasing voltages. BST shows a variation for the dielectric constant from 380 to 130, recording a tunability range of 66 %, and loss tangent of 0.027 to 0.005. In the range of frequency from 1 to 40 GHz, coplanar waveguides (CPW) are used to investigate the effective dielectric constant of BST on four different substrates, HR silicon substrates covered by silicon dioxide, silicon covered by silicon dioxide and silicon nitride, magnesium oxide (MgO (100)), and R-plane sapphire (Al2O3) substrate, all covered with 350 nm BST layer. The effective dielectric constant over silicon substrates covered by silica and BST is 7.2, 6.3 for Al2O3 substrates and 5.8 for MgO; and for the loss tangent, Al2O3 and MgO give about 0.03, while silicon substrates suffer higher values of 0.08 to 0.25. Finally, to study the tunability of microwave structures on the investigated substrates, interdigital capacitors (IDC) are fabricated and measured for different biasing voltages ranging from 0 to 55 V. IDCs over MgO show a tunability of 8.3%, while IDCs over sapphire show 20%.
Percolation Conduction of Nanoclusters Films for Nano-devices
Authors: Kang Il-Suk , Ahn Chi Won
Published: August 2010

Electrical conduction of metal nanoclusters by percolation is a very interesting area in nano-device. For more functional nano-sensors consisting of multiple nanocluster blending film, various metals, such as Cu and Ni nanocluster films were fabricated using inert-gas condensation method. The percolation threshold of the films was measured. In addition, for the operation of sensors using these nanocluster films in air, aging experiments of the percolated films in air were carried out. While the percolation threshold was in connection not with the material species but with the area coverage of nanocluster films, the conductive characteristics according to the aging temperature depended on the material species. Reversible and irreversible conduction behaviors of nanocluster films were investigated with nanoscale microstructures using electron microscopes.
Multifunctional Nanoparticles for Targeted Imaging and Therapy of Cancer
Authors: Koo Lee Yong-Eun , Kopelman Raoul
Published: August 2010

The idea of making biocompatible multifunctional nanoparticles, combining therapy, imaging and targeting, was aimed at cancer from the start a dozen years ago. This presentation will emphasize targeted theranostic nanoparticles, where “theranostic” literally means combining therapy and diagnostics, but more generally may mean a combination of imaging/visualization with therapy/surgery. Specific examples will cover (1) imaging (MRI, CT and optical methods), (2) therapy (chemo, photodynamic, radiation) and (3) guided surgery (using intra-operative imaging and therapy). Progress on brain and on head and neck cancer will be reported.
Realization of silicon nanopillar arrays with controllable sidewall profiles by holography lithography and a novel single-step deep reactive ion etching
Authors: Hung Yung-Jr , Lee San-Liang , Thibeault Brian J. , Coldren Larry A.
Published: August 2010

A simple and efficient approach for fabricating silicon nanopillar arrays with a high aspect ratio and controllable sidewall profiles has been developed by using holographic lithography and a novel single-step deep reactive ion etching. During the etching process, scalloping of the sidewalls can be avoided while reserving the high mask selectivity and high etching rate. Besides, the sidewall angle of resultant patterns can be adjusted by tuning the composition of the gas mixture of single-step DRIE process. We further fabricate a tapered silicon nanopillar array and observe its photonic bandgap property. We believe that the good optical performance of this tapered silicon nanopillar array realized by the proposed approach shows the promising of this process for various applications.
EFM Study on Ge Island: Carrier Charge and Storage Effect
Authors: Lin Zhen , Brunkov Pavel , Ma Xueying , Bassani Franck , Bremond Georges
Published: August 2010

In this paper, individual Ge nano island on top of a silicon dioxide layer of thermally grown on a n+ type doped silicon (001) substrate have been studied. The charging ability of an individual Ge island was evaluated by EFM two-pass lift mode measurement. Such Ge nano island becomes an iso-potential and behaves as a conductive material after being charged. These charges were directly injected and were trapped homogenous in the isolated Ge island. It is also shown that the dominant charge decay mechanism during discharging of nc-Ge is related to the leakage of these trapped charges. Further more, the retention time of these trapped charges was evaluated and the electrostatic force was also studied by using different tip bias during scan. Such a study should be very useful to the Ge-nc in memory applications.
Ultrahigh-pressure study on the magnetic state of iron hydride using an energy domain synchrotron radiation 57Fe Mössbauer spectrometer
Authors: Mitsui Takaya , Hirao Naohisa
Published: August 2010

Pressure induced magnetic phase transition of iron hydride was investigated with an in-situ Mössbauer spectrometer using synchrotron radiation (SR). The spectrometer is composed of a high resolution monochromator, an X-ray focusing device, a variable frequency nuclear monochromator and a diamond anvil cell. The optical system, advantages of the spectrometer and the observed high pressure magnetic phases of iron hydride are described.
Study of Nano-cluster Formation in Fe-18Cr ODS Ferritic Steel by Atom Probe Tomography
Authors: Kalokhtina Olena , Radiguet Bertrand , de Carlan Yann , Pareige Philippe
Published: August 2010

A high chromium ferritic Oxide Dispersion Strengthened steel was produced by mechanical alloying of Fe-18Cr-1W-0.3Ti-0.3Ni-0.15Si and 0.5% Y2O3 (wt.%) powders in industrial attritor, followed by hot extrusion at 1100°C. The material was characterized by Atom Probe Tomography on each step of manufacturing process: as-milled powder and in final hot extruded state. In addition, to get information on clustering kinetics the powder was also characterized after annealing at 850°C during 1 hour. Atom Probe Tomography revealed that the oxide dispersion strengthened steel Fe-18Cr contains nanometer scale yttrium- and oxygen-enriched nanoclusters in as-milled state. Their evolution is shown after subsequent annealing and hot extrusion. More well defined nanophases also enriched in Ti are observed. A mechanism of their formation is proposed. Mechanical alloying results in supersaturated solid solution with presence of small Y- and O-enriched clusters. Subsequent annealing stimulates incorporation of Ti to the nucleii that were previously formed during mechanical alloying.
Probing the isothermal δ→α' martensitic transformation in Pu-Ga with in situ x-ray diffraction
Authors: Jeffries Jason R. , Blobaum Kerri J.M. , Schwartz Adam J. , Cynn Hyunchae , Yang Wenge , Evans William J.
Published: August 2010

The time-temperature-transformation (TTT) curve for the δ → α′ isothermal martensitic transformation in a Pu-1.9 at. % Ga alloy exhibits an anomalous double-C curve. Recent work suggests that an ambient temperature conditioning treatment enables the lower-C curve. However, the mechanisms responsible for the double-C are still not fully understood. When the δ → α′ transformation is induced by pressure, an intermediate γ′ phase is observed in some alloys. It has been suggested that transformation at upper-C temperatures may proceed via this intermediate phase, while lower-C transformation progresses directly from δ to α′. To investigate the possibility of thermally induced transformation via the intermediate γ′ phase, in situ x-ray diffraction at the Advanced Photon Source was performed. Using transmission x-ray diffraction, the δ → α′ transformation was observed as a function of time and temperature in samples as thin as 30 μm. The intermediate γ′ phase was not observed at -120°C (upper-C curve) or -155 °C (lower-C curve). Results indicate that the bulk of the α′ phase forms relatively rapidly at -120 and -155 °C.
Probing Radiation Damage in Plutonium Alloys with Multiple Measurement Techniques
Authors: McCall Scott K. , Fluss Mike , Chung Brandon W.
Published: August 2010

A material subjected to radiation damage will usually experience changes in its physical properties. Measuring these changes in the physical properties provides a basis to study radiation damage in a material which is important for a variety of real world applications from reactor materials to semiconducting devices. When investigating radiation damage, the relative sensitivity of any given property can vary considerably based on the concentration and type of damage present as well as external parameters such as the temperature and starting material composition. By measuring multiple physical properties, these differing sensitivities can be leveraged to provide greater insight into the different aspects of radiation damage accumulation, thereby providing a broader understanding of the mechanisms involved. In this report, self-damage from α-particle decay in Pu is investigated by measuring two different properties: magnetic susceptibility and resistivity. The results suggest that while the first annealing stage obeys second order chemical kinetics, the primary mechanism is not the recombination of vacancy-interstitial close pairs.
Electronic Structure, Photoemission and Superconductivity in PuCoGa5
Authors: Shick Alexander , Khmelevskyi Sergii , Havela Ladislav
Published: August 2010

We study theoretically the electronic structure and photoemission spectra of PuCoGa5 making use of the LDA+Hubbard I approximation implemented in the full-potential LAPW basis, including self-consistency over the charge density. The calculations show relative reduction of the f-states spectral weight at the Fermi energy. There is fairly good agreement between calculated photoemission spectra and experimental results. We demonstrate that an account of Pu f-electron Coulomb correlations does not modify significantly the Fermi surface topologies but leads to substantial reduction of the f-character for the electronic states at the Fermi energy. These findings can be important for the theory of superconductivity in PuCoGa5 and related compounds.
Geo-descriptive Modeling of Water Conducting Features Characterized in Sedimentary Formations in Horonobe Area of Japan
Authors: Hatanaka Koichiro , Doo-hyun Lim , Ishii Eiichi
Published: August 2010

A three-dimensional (3-D) discrete fracture network (DFN) geo-descriptive model is developed for water conducting features (WCFs) in the sedimentary formations of Horonobe underground research laboratory (URL) in Japan. Fracturing and faulting system in/around the URL area, which is the main investigation area of the Horonobe URL project, is characterized by taking into account borehole geophysical logging data, regional geologic/structural data, and fracture/fault data (orientation, intensity, size) obtained from the surface-based investigations. Volumetric fracture intensity potential is estimated by the correlation and the multi-linear regression analysis of observed data, and is used as one of controls for 3-D DFN model. A regional scale 3-D geo-descriptive DFN model is constructed based on the analyzed fracturing system identified for the WCFs. The current 3-D geo-descriptive model could be utilized explicitly to derive performance assessment (PA) parameters for the hypothetical repository of the high-level radioactive wastes in Japan, and to assist optimization of the safe repository design.
Determination of Crevice Corrosion Susceptibility of Alloy 22 Using Different Electrochemical Techniques
Authors: Rincon Ortiz Mauricio , Rodríguez Martín A. , Carranza Ricardo M. , Rebak Raul B.
Published: August 2010

Alloy 22 belongs to the Ni-Cr-Mo family and it is highly resistant to general and localized corrosion. It may suffer crevice corrosion in aggressive environmental conditions. This alloy has been considered as a corrosion-resistant barrier for high-level nuclear waste containers. It is assumed that localized corrosion may occurs when the corrosion potential (ECORR) is equal or higher than the crevice corrosion repassivation potential (ER,CREV). The latter is measured by means of different electrochemical techniques using artificially creviced specimens. These techniques include cyclic potentiodynamic polarization (CPP) curves, Tsujikawa-Hisamatsu electrochemical (THE) method or other non-standard methods, such as the PD-GS-PD technique.

The aim of the present work was to determine reliable critical or protection potentials for crevice corrosion of Alloy 22 in pure chloride solutions at 90°C. Conservative methodologies (which include extended potentiostatic steps) were applied for determining protection potentials below which crevice corrosion cannot initiate and propagate. Results from PD-GS-PD technique were compared with those from these methodologies in order to assess their reliability. Results from the CPP and the THE methods were also considered for comparison. The repassivation potential resulting from the PD-GS-PD technique was conservative and reproducible, and it did not depend on the amount of previous crevice corrosion propagation.
Portable Power Thermoelectric Generator – Design and Characterization
Authors: Koripella Ramesh , Bell Lon E , Crane Doug
Published: August 2010

High energy density and power density are two important considerations in the design of a portable power source. High efficiency of energy conversion is one of the important factors in achieving high energy density. We report on the design, fabrication and characterization of a high efficiency and power density thermoelectric generator. Segmented thermoelectric elements with a high temperature-weighted average zT are used in the fabrication of the generator to achieve high energy conversion efficiency. A comprehensive model of the generator has been developed that includes temperature dependent thermoelectric properties for the segmented thermoelectric element design, and system level thermal and electrical losses. These models are used to guide the design of a high efficiency thermoelectric generator. A 14W size portable thermoelectric generator was built and its performance for converting thermal energy into electrical energy was characterized and compared to the model predictions. The magnitude of individual loss mechanisms and their effect on overall system efficiency are presented. The evolution of the device design and critical design parameters that have been incorporated or modified to minimize performance losses and improved device robustness are discussed. Important future design optimizations that can further reduce losses for improved performance were identified.
Temperature and Size Effects on the Extremely Low Thermal Conductivity of Self-assembled Germanium Quantum-dot Supercrystals in Silicon
Authors: Gillet Jean-Numa
Published: August 2010

Design of semiconducting nanomaterials with an indirect electronic bandgap is currently one of the major areas of research to obtain a high thermoelectric yield by lowering their lattice thermal conductivity. Intensive investigations on superlattices were performed to achieve this goal. However, like one-dimensional nanowires, they decrease heat transport in only one propagation direction of the phonons. Moreover, they often lead to dislocations since they are composed of layered materials with a lattice mismatch. Design of superlattices with a thermoelectric figure of merit ZT higher than unity is therefore hazardous. Self-assembly of epitaxial layers on silicon has been used for bottom-up synthesis of three-dimensional (3D) Ge quantum-dot (QD) arrays in Si for quantum-device and solar-energy applications. Using the atomic-scale 3D phononic crystal model, it is predicted that high-density 3D arrays of self-assembled Ge QDs in Si can as well show an extreme reduction of the thermal transport. 3D supercrystals of Ge QDs in Si present a thermal conductivity that can be as tiny as that of air. These extremely low values of the thermal conductivity are computed for a number of Ge filling ratios and size parameters of the 3D Si-Ge supercrystal. Owing to incoherent phonon scattering with predominant near-field effects, the same conclusion holds for supercrystals with moderate QD disordering. As a result, design of highly-efficient CMOS-compatible thermoelectric devices with ZT possibly much higher than unity might be possible. In this theoretical study, simultaneous evolution of both temperature and average distance between the Ge QDs is analyzed for a non-variable Ge filling ratio to obtain thermal-conductivity values as low as that of air (+/- 0.025 W/m/K).
Thermoelectric Properties of Composite PbTe – PbSnS2 Materials
Authors: Girard Steven N , He Jiaqing , Dravid Vinayak P , Kanatzidis Mercouri
Published: August 2010

The thermoelectric (Pb1-mSnmTe)1-x(PbS)x where m = 0.05 and x = 0.08 has been shown to produce PbS nanostructures that effectively scatter phonons, enhancing ZT. As Sn substitution is increased, a new phase of PbSnS2 precipitates. We find that incorporation of PbSnS2 in PbTe results in a significant reduction in lattice thermal conductivity around 0.6 W/mK at room temperature. We present preliminary characterization and thermoelectric properties.
The Effect of Rh and Sr Substitution on the Thermoelectric Performance of LaCoO3
Authors: Kwong Kyei-Sing , Smith Andrew E , Subramanian Mas
Published: August 2010

A series of LaCo1-xRhxO3 (x=0-1) samples and La1-ySryCo1-xRhxO3 (y = 0.05, 0.15 and x = 0.1-0.3) samples were prepared to study the effect of Rh substituion for Co in the four component system and Sr substitution for La in the five component system on the crystal structure and thermoelectric performance of the LaCoO3. At Rh substitution for Co of x=0.2 greater, the crystal structure shifts from rhombohederal (LaCoO3) to orthorhombic (LaRhO3). Thermoelectric evaluation revealed that Rh doped samples (0.3 <x <1) show large positive seebeck coefficients indicating a P-type conduction in the temperature range of the tests (273 to 775K). Rh substitution for Co decreases thermal conductivity, increases Seebeck coefficient and consequently increases the theroelectric figure of merit ZT. Sr substitution for La increases thermal and electrical conductivity and consquenently negligiblely decreases the seebeck coefficient. A thermoelectric figure-of-merit (ZT) around 0.075 has been achieved for LaCo0.5Rh0.5O3 at 775 K, and is expected to be above 0.1 at 1000 K. Sr substitution improved the TE properties throughout the lower temperature range with a ZT =0.045 observed for La0.95Sr0.05Co0.9Rh0.1O3 at 425 K and ZT = 0.05 for La0.85Sr0.15Co0.5Rh0.5O3 at 775 K. These findings provide new insight into thermoelectric perovskite oxides containing rhodium and strontium.
Direct Measurement of the Absolute Seebeck Coefficient for Pb and Cu at 300 K to 450 K
Authors: Garrity Patrick L. , Stokes Kevin L.
Published: August 2010

The utilization of thermal fluctuations or Johnson/Nyquist noise as a spectroscopic technique to experimentally measure transport properties is applied to Pb and Cu metal films. Through cross-correlation and autocorrelation functions obtained from power spectral density measurements, multiple transport coefficients are obtained through the Green-Kubo formalism. Supported rigorously by the underlying fluctuation-dissipation theory, this new experimental technique provides a direct measurement of absolute thermoelectric coefficients in addition to the electrical resistivity, electronic contribution to thermal conductivity, Lorentz number and various diffusion coefficients. This work reports the validation results of the experiment accomplished through the use of materials with thermoelectric properties widely accepted by the thermoelectric community, Pb and Cu. Further validation of the data was accomplished by comparing resistivity results to standard collinear four-probe resistivity measurements. Thermal fluctuation data for Pb at 300 K resulted in 5.9% and 2.02% agreement with the published Seebeck and four-probe resistivity data respectively. The Cu thermal fluctuation measurements at 300 K showed agreement within 3.76% and 6.14% for the published Seebeck and four-probe data respectively thus lending further credibility to the experimental method and underlying theory.
Surface Characterization of Poly(acrylic acid) Grafted to Photo-oxidized Perfluorosulfonic Acid Membrane Used in Fuel Cells
Authors: Bailey Alla , Lu Fei , Khot Ameya , Hussain Shahida , Rugg Kyle W. , Leong G. J. , Debies Thomas , Takacs Gerald Alan
Published: August 2010

Perfluorosulfonic acid membrane (Nafion®-117) was first surface modified with atmospheric pressure UV photo-oxidation or low-pressure vacuum UV photo-oxidation downstream from an Ar microwave plasma, and then graft polymerized with acrylic acid. X-ray photoelectron spectroscopy (XPS) was used to analyze the modified Nafion surface and poly(acrylic acid) grafted to the modified surface.
Evaporative Deposition of Bacteria and Microspheres on Mica from a Sessile Drop: The Use of Surface Conditioning in a Laboratory Atmosphere to Control Drop Spreading and Particle Deposition Patterns
Authors: Curry Joan E , Maier Raina M. , Norris Theresa A. , Baughman Kyle Fisher
Published: August 2010

Evaporative deposition from a sessile drop is an appealing way to deposit materials on a surface due to the simplicity of the technique. In this work we deposit aqueous solutions of two types of colloidal particles, namely bacteria and microspheres, on mica. We show that by controlling the extent of initial drop spreading through subtle changes in surface conditioning caused by exposure to the laboratory atmosphere in a laminar flow hood it is possible to systematically vary the particle deposition patterns. On freshly cleaved mica the contact angle of water is < 5°. Drops of bacterial and microsphere solutions deposited on freshly cleaved mica spread to cover a large surface area. Drying occurs through pinning and depinning events leaving a series of colloidal particle rings. We found in our laboratory that the contact angle of water on mica exposed to a constant flow of filtered laboratory air in a laminar flow hood gradually increases with time. For drops of both bacterial and microsphere solutions there is a corresponding decrease in the extent of drop spreading with increasing exposure of the mica surface to laboratory air. This results in a profound change in the colloidal particle deposition pattern. Short exposures of minutes to hours are enough to decrease spreading and affect the resulting deposition pattern. For our longest mica surface exposure times (months to 1 year) the contact angle of water reaches values near 20°. Spreading of the bacterial and microsphere drops is substantially decreased. A portion of the colloidal particles are deposited in an outer deposition ring which marks the extent of drop spreading and the remainder of the particles are deposited in the drop interior as a honeycomb or cellular film. The fraction of the drop residue covered with the cellular film increases with particle concentration as well as the length of time the mica is exposed to the laboratory atmosphere. This work shows that evaporative deposition on mica is very sensitive to surface conditioning through atmospheric exposure and also suggests that particle deposition patterns can be tuned by small changes in drop spreading.
Quantitative approaches for characterising fibrillar protein nanostructures
Authors: Knowles Tuomas P. J. , White Duncan A. , Dobson Christopher M. , Welland Mark E.
Published: August 2010

Polypeptide sequences have an inherent tendency to self-assemble into filamentous nanostructures commonly known as amyloid fibrils. Such self-assembly is used in nature to generate a variety of functional materials ranging from protective coatings in bacteria to catalytic scaffolds in mammals. The aberrant self-assembly of misfolded peptides and proteins is also, however, implicated in a range of disease states including neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. It is increasingly evident that the intrinsic material properties of these structures are crucial for understanding the thermodynamics and kinetics of the pathological deposition of proteins, particularly as the mechanical fragmentation of aggregates enhances the rate of protein deposition by exposing new fibril ends which can promote further growth. We discuss here recent advances in physical techniques that are able to characterise the hierarchical self-assembly of misfolded protein molecules and define their properties.
Computational multiscale studies of collagen tissues in the context of brittle bone diseaseosteogenesis imperfecta
Authors: Vesentini Simone , Gautieri Alfonso , Redaelli Alberto , Buehler Markus J.
Published: August 2010

Osteogenesis imperfecta(abbreviated as OI) is a genetic disorder in collagen characterized by mechanically weakened tendon, fragile bones, skeletal deformities and in severe cases prenatal death. Even though many studies have attempted to associate specific mutation types with phenotypic severity, the molecular and mesoscale mechanisms by which a single point mutation influences the mechanical behavior of tissues at multiple length-scales remain unknown. Here we review results of a hierarchy of full atomistic and mesoscale simulations that demonstrated that OI mutations severely compromise the mechanical properties of collagenous tissues at multiple scales, from single molecules to collagen fibrils. Notably, mutations that lead to the most severe OI phenotype correlate with the strongest effects, leading to weakened intermolecular adhesion, increased intermolecular spacing, reduced stiffness, as well as a reduced failure strength of collagen fibrils (Gautieriet al., Biophys. J., 2009). Our study explains how single point mutations can control the breakdown of tissue at much larger length-scales, a question of great relevance for a broad class of genetic diseases. Furthermore, by extending the MARTINI coarse-grained force field, we provide a new modeling tool to study collagen molecules and fibrils at much larger scales than accessible to existing full atomistic models, while incorporating key chemical and mechanical features and thereby presents a powerful approach to computational materiomics (Gautieri et al., Journal of Chemical Theory and Computation, 2010). We describe the coarse-graining approach and present preliminary findings based on this model in applying it to large-scale models of molecular assemblies into fibrils.
Intestinal permeability assessed by 51Cr-EDTA in rats with CCl4 - induced cirrhosis
Authors: Ramos Ana Regina L. , Matte Ursula , Goldani Helena Ayako Sueno , Oliveira Osmar L. M. , Vieira Sandra Maria Gonçalves , Silveira Themis Reverbel da
Published: August 2010

CONTEXT: The straight relationship between cirrhosis and impaired intestinal barrier has not been elucidated yet. OBJECTIVES: To verify 51Cr-EDTA-intestinal permeability in rats with CCl4-induced cirrhosis and controls. METHOD: Fifty male Wistar rats weighing 150-180 g were separated in three groups: 25 animals received CCl4 0.25 mL/kg with olive oil by gavage with 12 g/rat/day food restriction for 10 weeks (CCl4-induced cirrhosis); 12 received the same food restriction for 10 weeks (CCl4-non exposed). Other 13 rats received indomethacin 15 mg/kg by gavage as positive control of intestinal inflammation. RESULTS: The median (25-75 interquartile range) 51Cr-EDTA-IP values of cirrhotic and CCl4-non exposed rats were 0.90% (0.63-1.79) and 0.90% (0.60-1.52) respectively, without significant difference (P = 0.65). Animals from indomethacin group showed 51Cr-EDTA-IP, median 7.3% (5.1-14.7), significantly higher than cirrhotic and CCl4-non exposed rats (P<0.001). CONCLUSION: This study showed the lack of difference between 51Cr-EDTA-intestinal permeability in rats with and without cirrhosis. Further studies are necessary to better clarify the relationship between intestinal permeability and cirrhosis.
O efeito do consumo crônico de etanol na absorção duodenal de ferro em camundongos
Authors: Sabino Kelly Renata , Petroianu Andy , Alberti Luiz Ronaldo , Machado Adriana Nunes
Published: August 2010

CONTEXTO: Os indivíduos alcoolistas apresentam aumento da concentração hepática de ferro e os mecanismos responsáveis por essa deposição são ainda desconhecidos. Apesar da extensa literatura existente sobre a absorção de ferro nos diferentes estados patológicos, os efeitos do consumo prolongado do etanol não estão totalmente esclarecidos. OBJETIVOS: Determinar a absorção de ferro no duodeno de camundongos após consumo prolongado de etanol, com relação ao controle de camundongos normais. MÉTODOS: Foram utilizados 10 camundongos machos da raça Swiss, distribuídos em dois grupos: grupo 1 (n = 5) - controle e grupo 2 (n = 5) - consumo de água com etanol, como única fonte de água ofertada. Os animais foram acompanhados durante 120 dias. Decorrido esse período, isolou-se o duodeno e pela parte oral de cada alça, infundiu-se solução salina contendo ascorbato de ferro II na concentração de 0,016 mg de ferro elemento. O efluente foi coletado nos tempos 20, 40, 60, 80, 100 e 120 minutos. Os resultados foram analisados pelo teste Mann-Whitney e Kruskal-Wallis, com significância para P<0,05. RESULTADOS: Não houve diferença entre a absorção duodenal de ferro dos grupos 1 e 2, assim como na curva de absorção. CONCLUSÕES: Conclui-se que, nas condições deste experimento, o consumo prolongado de etanol não alterou a absorção de ferro.
Variabilidade genética de búfalos em rebanho-núcleo com base na análise de pedigree
Authors: Marcondes C.R. , Vozzi P.A. , Cunha B.R.N. , Lôbo R.B. , Araújo C.V. , Marques J.R.F.
Published: August 2010

Parâmetros baseados na probabilidade de origem do gene foram usados para descrever a variabilidade em uma população de búfalos da Embrapa Amazônia Oriental. A magnitude dos resultados foi de média a baixa (por volta de 20 animais), sugerindo que poucos fundadores contribuiriam para a formação da população. Dentre os 20 ancestrais que mais aportam genes aos machos - representando ao todo 71% dos alelos -, 39%, 26% e 5%, respectivamente, são as contribuições marginais das raças Murrah e Mediterrâneo e seus mestiços. Para as fêmeas, em que os 20 ancestrais aportam 67,5% dos genes, 42% e 26%, respectivamente, são as contribuições marginais das raças Murrah e Mediterrâneo.
Testes bioquímico (albumina e proteína de ligação da vitamina D) e molecular (gene KIT) para detecção de marcadores genéticos para pelagem tobiana em cavalos Pampa e Paint
Authors: Coelho E.G.A. , Oliveira D.A.A. , Teixeira C.S.
Published: August 2010

Foram utilizados 159 cavalos Pampa, registrados na Associação Brasileira dos Criadores de Cavalo Pampa, e um grupo-controle, de 32 cavalos da raça Paint, ambos os grupos provenientes de plantéis de diferentes regiões brasileiras, com o objetivo de comparar os testes bioquímico e molecular para detecção de marcadores genéticos para pelagem tobiana em cavalos Pampa. Houve diferença significativa (P<0,001) entre os testes bioquímico e molecular, nos cavalos Pampa, mas o mesmo fato não ocorreu com os da raça Paint. Os resultados mostraram que o marcador molecular (KIT) foi mais eficiente na identificação dos prováveis cavalos homozigotos do que os marcadores bioquímicos albumina (Al) e proteína de ligação da vitamina D (Gc), em ambas as raças.
Crescimento inicial de Dimorphandra wilsonii (Fabaceae - Caesalpinioideae) em diferentes condições de fertilidade em solo de cerrado
Authors: Fonseca Márcia Bacelar , França Marcel Giovanni Costa , Zonta Everaldo , Giorni Victor
Published: August 2010

Dimorphandra wilsonii Rizz. é uma espécie arbórea criticamente ameaçada de extinção. Foi descrita para áreas de maior fertilidade no Domínio do cerrado; entretanto, atualmente ocorre em áreas isoladas e de baixa fertilidade natural. Com o objetivo de avaliar a adaptação desta espécie a condições de oligotrofia, plantas foram cultivadas em casa de vegetação em solo destas áreas oligotróficas, mas com diferentes níveis de fertilidade. A partir da análise de fertilidade do solo foram definidas as doses de macronutrientes (NPK) e a dose de calcário a serem utilizadas nos tratamentos que se constituíram de dois níveis de calagem e três níveis de adubação. Após 220 dias do plantio, os tratamentos que aumentaram significativamente o crescimento foram aqueles que receberam adubação com a dose indicada de NPK em solo não corrigido pela calagem e aquele que teve o solo calado e adubado com duas vezes a dose indicada de NPK. A calagem por si só não promoveu maior crescimento, mas propiciou respostas crescentes de crescimento a níveis crescentes de disponibilidade de nutrientes. Foram encontrados nódulos radiculares em todos os tratamentos, e os resultados permitiram concluir que a espécie apresenta requerimento nutricional coerente com sua área de origem no Domínio do Cerrado. Também foi possível ressaltar a fixação biológica de nitrogênio, incomum em Caesalpinioideae, como estratégia adaptativa para crescimento em áreas com baixa oferta de nutrientes.
A família Aristolochiaceae Juss. no estado do Paraná, Brasil
Authors: Nascimento Dilma Silva do , Cervi Armando Carlos , Guimarães Olavo Araújo
Published: August 2010

O presente trabalho trata do estudo taxonômico das espécies de Aristolochiaceae ocorrentes no Estado do Paraná. Por meio de estudos de levantamento em herbários, coletas e observações, foram constatados dez táxons pertencentes ao gênero Aristolochia L.: A. chamissonis (Klotzsch) Duch., A. elegans Mast., A. fimbriata Cham. & Schltdl., A. gigantea Mart. & Zucc., A. melastoma Silva Manso ex Duch., A. odoratissima L., A. paulistana Hoehne, A. triangularis Cham., A. trilobata L. e A. wendeliana Hoehne. A. fimbriata é citada pela primeira vez para o Estado do Paraná. Chaves de identificação, descrições e ilustrações são também incluídas neste trabalho.
Wissadula Medik. (Malvaceae) no Brasil: novas espécies e combinação
Authors: Bovini Massimo G.
Published: August 2010

Duas novas espécies e uma nova combinação são apresentadas para o gênero Wissadula (Malvaceae): Wissadula delicata Bovini, W. krapovickasiana Bovini e Wissadula caribea (DC.) Bovini, respectivamente, além de novos sinônimos. Para as espécies apresentadas, são fornecidas descrições, ilustrações e chaves de reconhecimento para distingui-las das espécies relacionadas.
Comparison of seedling growth among three co-occurring varieties of Araucaria angustifolia (Bertol.) Kuntze under greenhouse conditions
Authors: Coutinho André Luiz , Dillenburg Lúcia Rebello
Published: August 2010

Araucaria angustifolia (Bertol.) Kuntze is a tall, long-lived tree species, which grows as an emergent tree in the araucaria forests of southern Brazil. Four varieties have been described for this species, and three of them were selected for this study: "angustifolia" (the type variety), "caiova" and "indehiscens". These are co-occurring varieties that differ in external seed color and timing of seed maturation. The purpose of this study was to compare the initial growth of plants originated from seeds of these three varieties, in order to test the hypothesis that these varieties also differ in the initial growth of their seedlings. Seeds were collected from a single forest location, and 60 plants per variety were grown in pots for a period of 244 days. The "angustifolia" variety accumulated significantly more mass (both in shoot and root) than the other two, but the three varieties did not differ in mass allocation between shoot and root and between lateral roots and the main root. The greater growth of the type variety may help explain its greater natural abundance, since attaining a larger size will have positive effects on seedling recruitment and survival.
Trabalho e produção de saúde: práticas de liberdade e formas de governamentalidade
Authors: Bernardes Anita Guazzelli , Pelliccioli Eduardo Cavalheiro , Guareschi Neuza Maria de Fátima
Published: August 2010

Este texto tem como objetivo analisar o conceito de produção de saúde, no campo da Saúde Coletiva, como o nó de uma rede de cuidados. Nó porque a produção de saúde costura a noção de sujeito na saúde com os cuidados na saúde em um campo de estranhamento. Para fazer essa discussão, este texto partirá do trabalho na saúde como um conjunto de práticas de governamentalidade que encontram na produção de saúde a conformação de práticas de liberdade. As ferramentas conceituais utilizadas para essa discussão partem da proposição foucaultiana sobre uma ontologia do presente: subjetividade, poder e verdade. Esses operadores conceituais serão articulados às ideias de trabalho afetivo e potência de vida. Como exercícios do pensamento, tomam-se, então, as discussões no campo da Saúde Coletiva: integralidade, produção de saúde, cidadania e trabalho na saúde.
Juventude e afetividade: tecendo projetos de vida pela construção dos mapas afetivos
Authors: Furlani Daniela Dias , Bomfim Zulmira Áurea Cruz
Published: August 2010

A pesquisa teve como objetivo analisar projetos de vida de jovens de ambientes rural e urbano no Ceará, a partir da afetividade em relação ao ambiente do qual fazem parte. Participaram da pesquisa 38 jovens de ambos os sexos. Para apreensão dos afetos, utilizou-se o método dos mapas afetivos e para questões relacionadas ao projeto de vida foram utilizadas entrevistas. A análise dos dados qualitativos foi realizada por meio da análise de conteúdo e de uma análise estatística complementar. O fato de alguns jovens morarem em ambiente rural e outros em ambiente urbano não diferiu completamente seus projetos de vida. Jovens do ambiente rural tendem a buscar mais cedo trabalho. Jovens do ambiente urbano apresentaram queixa em relação à violência urbana. Conclui-se como sendo necessária a disseminação de práticas sociais que visem um posicionamento crítico do sujeito diante das questões sociais.
O desafio colocado pelas pessoas em medida de segurança no âmbito do Sistema Único de Saúde: a experiência do PAILI-GO
Authors: Silva Martinho Braga Batista e
Published: August 2010

No contexto da consolidação da Reforma Psiquiátrica Brasileira e do Plano Nacional de Saúde no Sistema Penitenciário, as pessoas em medida de segurança e os Hospitais de Custódia e Tratamento Psiquiátrico apontam para um desafio à efetivação dos princípios e diretrizes do Sistema Único de Saúde. A descrição e análise do Programa de Atenção Integral ao Louco Infrator (PAILI-GO) são uma estratégia para delinear os limites e possibilidades de construir ações e serviços de saúde para essa população vulnerável. Uma visita a esse programa permitiu notar a potencialidade de multiplicação dessa experiência governamental em âmbito estadual, capaz de extinguir a medida de segurança de uma parcela de seus participantes, contribuindo assim para um processo de reinserção social imerso em ações intersetoriais.
Contabilidade de custos vs. contabilidade de ganhos: respostas às exigências da produção enxuta
Authors: Queiroz José Antonio de , Rentes Antonio Freitas
Published: August 2010

A produção enxuta tem provocado mudanças significativas nas empresas, mudanças estas que não vêm sendo acompanhadas pelos sistemas de gestão econômica, desenvolvidos sobre pressupostos equivocados da produção em massa que defendem que as otimizações locais isoladas resultam na otimização global da empresa. Deste modo, pode-se afirmar que a contabilidade de custos não é capaz de prover as informações necessárias à correta tomada de decisão nas empresas enxutas. Por outro lado, constata-se uma coerência entre os princípios da produção enxuta e os pressupostos que sustentam a contabilidade de ganhos da Teoria das Restrições. Sendo assim, o objetivo deste artigo é apresentar argumentos que respaldem estas afirmações, bem como justifiquem a necessidade da utilização da contabilidade de ganhos como base teórica para a proposta de um método de gestão econômica para a produção enxuta.
"Remar o próprio barco": a centralidade do trabalho no mundo das mulheres "sós"
Authors: Gonçalves Eliane
Published: August 2010

Várias das noções atribuídas às mulheres "solteiras" presentes na teoria social e no senso comum remetem a algumas idéias proclamadas pelo feminismo. Educação, trabalho qualificado e remunerado são considerados a via privilegiada para a conquista da "autonomia" que, ampliada, possibilitaria a um conjunto de mulheres, sobretudo das camadas médias urbanas, maiores chances de realizar escolhas, decidir por si mesmas e até mesmo romper com os estereótipos clássicos da "solteirona". Compreender como se entrelaçam as noções associadas à idéia de "mulher independente" e seus paradoxos requer revisitar algumas idéias que marcaram a emergência e a consolidação do feminismo como um movimento político da "modernidade" em sua expansão a partir dos anos 1960. Neste artigo, examino os nexos entre educação e profissionalização e o não casamento na contemporaneidade, a partir da análise de algumas narrativas de mulheres "solteiras" de camadas médias urbanas, sem filhos e que moram sozinhas.
Transposição do enxerto vascularizado da fíbula pro fêmur diafisário sem microanastomoses
Authors: Torres Luciano Ruiz , Paganotti Fernanda Bogdanovics , Gaiarsa Guilherme Pelosini , Teng Hsiang Wei , Soro Neto Francisco Perez , Viola Dan Carai Maia , Souza Fabiano Inácio de , Yuhara Clécio Seiji , Mattar Júnior Rames , Gaia Leonardo Franco Pinheiro
Published: August 2010

OBJETIVO: O estudo descreve uma maneira nova e simples de transplantar o enxerto ósseo vascularizado da fíbula pro fêmur diafisário sem necessidade de microcirurgia, demonstra o caso clínico operado com bom resultado quanto a vascularização e consolidação óssea e, por último, especula sobre possíveis outras aplicações dentro da cirurgia reconstrutiva. MÉTODOS: A fíbula vascularizada é transportada até o fêmur sem necessidade de microcirurgia, alcançando até sua metáfise proximal através das comunicações das perfurantes do músculo gêmeo lateral com as septais fibulares via retalho de pele póstero-lateral da perna que intersecciona os dois sistemas. RESULTADOS: O paciente operado evoluiu sem infecção. Cintilografia esquelética precoce demonstrou vascularização óssea. CONCLUSÃO: O retalho gêmeo fibular é nova arma no arsenal do cirurgião. Sua técnica é factível, reprodutível, seu tempo cirúrgico reduzido e o princípio de construção com ponte através de ilhas de pele e perfurantes poderá ser aplicado na construção de novos retalhos.