Fabrication of a quantum well heterostructure based on plasma polymerized aniline and its characterization using STM/STS

Two-dimensional electronic systems play a crucial role in modern electronics and offer a multitude of opportunities to study the fundamental phenomena at low dimensional physics. A quantum well heterostructure based on polyaniline (P) and iodine doped polyaniline (I) thin films were fabricated using radio frequency plasma polymerization on indium tin oxide coated glass plate. Scanning probe microscopy and scanning electron microscopy studies were employed to study the morphology and roughness of the polymer thin films. Local electronic density of states (LDOS) of the P–I–P heterostructures is probed using scanning tunnelling spectroscopy (STS). A step like LDOS is observed in the P–I–P heterostructure and is attributed to the quantum well confinement of electrons in the polymer heterostructure.

Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

Commercial samples of Magnetite with size ranging from 25–30nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed

Contact potential induced enhancement of magnetization in polyaniline coated nanomagnetic iron oxides by plasma polymerization

The present work derives motivation from the so called surface/interfacial magnetism in core shell structures and commercial samples of Fe3O4 and c Fe2O3 with sizes ranging from 20 to 30 nm were coated with polyaniline using plasma polymerization and studied. The High Resolution Transmission Electron Microscopy images indicate a core shell structure after polyaniline coating and exhibited an increase in saturation magnetization by 2 emu/g. For confirmation, plasma polymerization was performed on maghemite nanoparticles which also exhibited an increase in saturation magnetization. This enhanced magnetization is rather surprising and the reason is found to be an interfacial phenomenon resulting from a contact potential.

Plasma Assisted Deposition Technique for Synthesis of low Dielectric Constant Polyanisidine Thin Films

Plasma Science, 2002. ICOPS 2002. IEEE Conference Record-Abstracts. The 29th IEEE International Conference on

Lithography-free micro- and nanostructuring based on conventional plasma etching

In now-a-days semiconductor and MEMS technologies the photolithography is the working horse for fabrication of functional devices. The conventional way (so called Top-Down approach) of microstructuring starts with photolithography, followed by patterning the structures using etching, especially dry etching. The requirements for smaller and hence faster devices lead to decrease of the feature size to the range of several nanometers. However, the production of devices in this scale range needs photolithography equipment, which must overcome the diffraction limit. Therefore, new photolithography techniques have been recently developed, but they are rather expensive and restricted to plane surfaces. Recently a new route has been presented - so-called Bottom-Up approach - where from a single atom or a molecule it is possible to obtain functional devices. This creates new field - Nanotechnology - where one speaks about structures with dimensions 1 - 100 nm, and which has the possibility to replace the conventional photolithography concerning its integral part - the self-assembly. However, this technique requires additional and special equipment and therefore is not yet widely applicable. This work presents a general scheme for the fabrication of silicon and silicon dioxide structures with lateral dimensions of less than 100 nm that avoids high-resolution photolithography processes. For the self-aligned formation of extremely small openings in silicon dioxide layers at in depth sharpened surface structures, the angle dependent etching rate distribution of silicon dioxide against plasma etching with a fluorocarbon gas (CHF3) was exploited. Subsequent anisotropic plasma etching of the silicon substrate material through the perforated silicon dioxide masking layer results in high aspect ratio trenches of approximately the same lateral dimensions. The latter can be reduced and precisely adjusted between 0 and 200 nm by thermal oxidation of the silicon structures owing to the volume expansion of silicon during the oxidation. On the basis of this a technology for the fabrication of SNOM calibration standards is presented. Additionally so-formed trenches were used as a template for CVD deposition of diamond resulting in high aspect ratio diamond knife. A lithography-free method for production of periodic and nonperiodic surface structures using the angular dependence of the etching rate is also presented. It combines the self-assembly of masking particles with the conventional plasma etching techniques known from microelectromechanical system technology. The method is generally applicable to bulk as well as layered materials. In this work, layers of glass spheres of different diameters were assembled on the sample surface forming a mask against plasma etching. Silicon surface structures with periodicity of 500 nm and feature dimensions of 20 nm were produced in this way. Thermal oxidation of the so structured silicon substrate offers the capability to vary the fill factor of the periodic structure owing to the volume expansion during oxidation but also to define silicon dioxide surface structures by selective plasma etching. Similar structures can be simply obtained by structuring silicon dioxide layers on silicon. The method offers a simple route for bridging the Nano- and Microtechnology and moreover, an uncomplicated way for photonic crystal fabrication.

THz Plasma Waves in Field-Effect-Transistors: A Monte Carlo Study

Sensing with electromagnetic waves having frequencies in the Terahertz-range is a very attractive investigative method with applications in fundamental research and industrial settings. Up to now, a lot of sources and detectors are available. However, most of these systems are bulky and have to be used in controllable environments such as laboratories. In 1993 Dyakonov and Shur suggested that plasma waves developing in field-effect-transistors can be used to emit and detect THz-radiation. Later on, it was shown that these plasma waves lead to rectification and allows for building efficient detectors. In contrast to the prediction that these plasma waves lead to new promising solid-state sources, only a few weak sources are known up to now. This work studies THz plasma waves in semiconductor devices using the Monte Carlo method in order to resolve this issue. A fast Monte Carlo solver was developed implementing a nonparabolic bandstructure representation of the used semiconductors. By investigating simplified field-effect-transistors it was found that the plasma frequency follows under equilibrium conditions the analytical predictions. However, no current oscillations were found at room temperature or with a current flowing in the channel. For more complex structures, consisting of ungated and gated regions, it was found that the plasma frequency does not follow the value predicted by the dispersion relation of the gated nor the ungated device.

Site Controller: A System for Computer-Aided Civil Engineering and Construction

A revolution\0\0\0 in earthmoving, a $100 billion industry, can be achieved with three components: the GPS location system, sensors and computers in bulldozers, and SITE CONTROLLER, a central computer system that maintains design data and directs operations. The first two components are widely available; I built SITE CONTROLLER to complete the triangle and describe it here. SITE CONTROLLER assists civil engineers in the design, estimation, and construction of earthworks, including hazardous waste site remediation. The core of SITE CONTROLLER is a site modelling system that represents existing and prospective terrain shapes, roads, hydrology, etc. Around this core are analysis, simulation, and vehicle control tools. Integrating these modules into one program enables civil engineers and contractors to use a single interface and database throughout the life of a project.

Plasma polymerization of C[subscript 4]F[subscript 8] thin film on high aspect ratio silicon molds

High aspect ratio polymeric micro-patterns are ubiquitous in many fields ranging from sensors, actuators, optics, fluidics and medical. Second generation PDMS molds are replicated against first generation silicon molds created by deep reactive ion etching. In order to ensure successful demolding, the silicon molds are coated with a thin layer of C[subscript 4]F[subscript 8] plasma polymer to reduce the adhesion force. Peel force and demolding status are used to determine if delamination is successful. Response surface method is employed to provide insights on how changes in coil power, passivating time and gas flow conditions affect plasma polymerization of C[subscript 4]F[subscript 8].

Factores asociados al desarrollo de eventos adversos con transfusión de plasma fresco congelado en la Fundación Cardioinfantil-Instituto de Cardiología

Objetivo: Determinar los factores asociados con reacciones adversas transfusionales al Plasma Fresco Congelado en la FCI-IC durante los años 2008-2010. Metodología: Estudio de Casos y Controles, en relación 1:3. Pacientes mayores de 18 años transfundidos con plasma fresco congelado en la FCI-IC durante los años 2008-2010. Se definieron como casos pacientes identificados a partir del registro de eventos adversos transfusionales de la FCI que presentaron una reacción adversa transfusional a Plasma Fresco Congelado de los siguientes tipos: alérgica, febril, edema pulmonar no cardiogénico, sobrecarga volumen, CID o PTT. Los controles se definieron como personas que recibieron transfusión de plasma fresco congelado y cumpliendo los criterios de selección, no presentaron reacción adversa transfusional. Resultados: La edad de los casos fue significativamente menor (52,4 vs. 60,5 p=0,001). Para las reacciones alérgicas, el número de unidades de plasma provenientes de una unidad externa (0,7 vs. 0,0 p=0,003), de una donante de sexo femenino (2,5 vs. 1,4 p=0,11) y la paridad de dichas donantes (4,0 vs. 2,6 p=0,04), fueron en promedio mayor que para los controles. La presencia de sépsis (OR:0.01, IC95%:0,01-0,87, p=0,015) y de diabetes (OR:0.9, IC95%:0,01-0,54, p=0,003) se comportaron como factores protectores para el desarrollo de una reacción alérgica. Discusión y Conclusiones: Los resultados de este trabajo son compatibles con el hecho de que las reacciones adversas transfusionales están relacionadas con plasma provenientes de un banco de sangre externo, de donantes mujeres y de mujeres con un mayor número de gestaciones.

Eficacia del plasma rico en plaquetas en procedimientos médicos estéticos faciales . Evaluación en contorno de ojos.

Introducción: En la actualidad se están implementando nuevas técnicas, para el tratamiento de líneas de expresión facial. El Plasma Rico en Plaquetas (PRP) utiliza factores de crecimiento humano autólogos con fines médicos estéticos. El objetivo de este trabajo fue evaluar el tratamiento con plasma rico en plaquetas en el manejo del rejuvenecimiento periocular. Materiales y métodos: Estudio descriptivo retrospectivo en una cohorte de 27 pacientes entre 30 a 70 años de ambos sexos,tratados con PRP sin tratamientos médicos estéticos previos . Se compararon fotografías del sistema VISIA®, previo y posterior el PRP, para determinar los cambios del área periocular. Con análisis comparativo de medias utilizando pruebas t de student. Resultados: De 27 historias clínicas revisadas 96,3% eran mujeres, la edad promedio fue de 52.67 años. Se observaron cambios clínicos satisfactorios en el manejo del foto envejecimiento periocular con mejoría estadísticamente significativa entre el promedio inicial y el post tratamiento en arrugas, textura y porfirinas (p: 0.000). No se observaron diferencias estadísticamente significativas entre los grupos de edad (p = 0,62). Los pacientes analizados posterior al tratamiento se encuentran en mejor estado que el 63,78% de la población de su mismo sexo, edad y fototipo de piel. Los eventos adversos fueron disminuyendo en su frecuencia en cada una de las sesiones siguientes. Discusión: El PRP proporciona una mejoría global en los parámetros de envejecimiento periocular lo cual se correlaciono con los estudios previos in vitro. Conclusiones: El PRP es seguro y eficaz en contorno de ojos.

Corticosterone plasma concentrations in Carioca High- and Low-Conditioned freezing rats after a fear conditioned task

Our group in the Psychology Department at Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio) developed a rat genetic model of extreme freezing in response to contextual cues in an experimental chamber previously associated with footshock. One of the lines, Carioca High Freezing (CHF), exhibits an enhanced conditioned freezing response, whereas the other line, Carioca Low Freezing (CLF), shows the opposite response. The present study investigated corticosterone concentration between these two lines of animals and a random (RND) line of rats both under basal conditions and test condition after an emotional challenge using a contextual fear conditioning protocol. Comparisons between basal and test plasma corticosterone concentrations suggested differential basal and fear-induced differences between the two lines. The differences between basal conditions is an important and relevant aspect to be considered in behavioral experiments using or assessing stress and could help to understand variability in naïve populations.

Proyecto Plasma "Metodología de análisis entre Monopolio y Monopsonio"

muestra las opciones de negociación que tienen un Monopolio y un Monopsonio, donde los agentes se encuentran obligados a variar completamente el curso de sus estrategias.

Blackbody emission under laser excitation of silicon nanopowder produced by plasma-enhanced chemical-vapor deposition

Previous results concerning radiative emission under laser irradiation of silicon nanopowder are reinterpreted in terms of thermal emission. A model is developed that considers the particles in the powder as independent, so under vacuum the only dissipation mechanism is thermal radiation. The supralinear dependence observed between the intensity of the emitted radiation and laser power is predicted by the model, as is the exponential quenching when the gas pressure around the sample increases. The analysis allows us to determine the sample temperature. The local heating of the sample has been assessed independently by the position of the transverse optical Raman mode. Finally, it is suggested that the photoluminescence observed in porous silicon and similar materials could, in some cases, be blackbody radiation

Gas collisions and pressure quenching of the photoluminescence of silicon nanopowder grown by plasma-enhanced chemical vapor deposition

The quenching of the photoluminescence of Si nanopowder grown by plasma-enhanced chemical vapor deposition due to pressure was measured for various gases ( H2, O2, N2, He, Ne, Ar, and Kr) and at different temperatures. The characteristic pressure, P0, of the general dependence I(P)=I0exp(-P/P0) is gas and temperature dependent. However, when the number of gas collisions is taken as the variable instead of pressure, then the quenching is the same within a gas family (mono- or diatomic) and it is temperature independent. So it is concluded that the effect depends on the number of gas collisions irrespective of the nature of the gas or its temperature