Photorefractive two-wave mixing phase coupling measurement in a self-stabilized recording regime

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigation of the corrosion behaviour of AA 2024-T3 in low concentrated chloride media

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photorefractive phase coupling measurement using self-stabilized recording technique

The measurement of the phase shift φ between the transmited and difracted beams interfering along the same direction behind the hologram recorded in a photorefractive crystal is directly and accurately measured using a self-stabilized recording technique. The measured phase shift as a function of the applied electric field allows computing the Debye screening lenght and the effectively applied field coefficient of an undoped Bi 12TiO 20 crystal. The result is in good agreement with the already available information about this sample. © 2008 American Institute of Physics.

The role of coarse intermetallics in the localized corrosion behaviour of AA 2024-T3 in low concentrated chloride media

Aluminium alloy (AA) 2024-T3 is an important engineering material due to its widespread use in the aerospace industry. However, it is very prone to localized corrosion attack in chloride containing media, which has been mainly associated to the presence of coarse intermetallics (IMs). In this work the corrosion behaviour of aluminium alloy 2024-T3 in low concentrated chloride media was investigated using microscopy and electrochemical methods. SEM observations have shown that intermetallics with the same nominal composition present heterogeneous reaction rates, and that both types of coarse IMs normally found in the AA 2024-T3 microstructure corrode. Moreover, EDS analyses have shown important compositional changes in the corroded IMs, evidencing the selective corrosion of their more active constituents and the onset of an intense oxygen peak, irrespective to the IM nature. TEM/EDS observations on non-corroded samples have evidenced the heterogeneous composition within the IMs. On the other hand, the results of the electrochemical investigations, in accordance with the SEM/EDS observations, have evidenced that IMs corrosion dominates the electrochemical response of the alloy during the first hours of immersion in the test electrolyte. © 2009 by NACE International.

Aniline-1,4-benzoquinone as a model system for the characterization of products from aniline oligomerization in low acidic media

Increase in the pH medium of aniline polymerization is used for giving products of different morphologies, which are often wrongly attributed to PANI chains. Infrared and Raman spectroscopic data, supported by quantum chemical calculations, show that aniline-1,4-benzoquinone (AnBzq) is a model system for the characterization of the products of aniline oligomerization in low acidic media. The Raman spectra excited at different laser lines reveal the bichromophoric nature of AnBzq, whose absorption bands at 550 nm and 440 nm can be attributed to pi-pi* transitions of the delocalized benzoquinone and amino-phenyl moieties, respectively. (C) 2012 Elsevier B.V. All rights reserved.

Self-Immolation In Tibet: Beyond The Lens Of The Western Media

This thesis provides a critique of Western media articles concerning self-immolation in Tibet. I begin by illustrating how the Western media provides reductionist accounts of Tibetan self-immolation by depicting the act solely as a form of political protest in response to Chinese occupation. I argue that these limited portrayals of self-immolation can be attributed to the Shangri-La imagery that characterizes much of the Western conceptions of Tibet. Through Shangri-La imagery, both Tibetans and their Buddhist religion are portrayed as utopic, peaceful, and able to provide the antidote to solving Western problems relating to modernization and consumerism. After illustrating the ways in which Shangri-La imagery influences Western media portrayals of Tibetan self-immolation, this thesis explores the commonly disregarded Buddhist dimensions of the act. Looking to Buddhist doctrine, scripture, and history, this thesis establishes a clear relationship between self-immolation and Buddhism, which situates the act as being more complicated than mere political protest. I argue that these limited portrayals given by the Western media are problematic because they overlook a fundamental aspect of self-immolation, thus potentially misrepresenting Tibetans. This thesis explores the Buddhist dimensions of self-immolation as a possible way to further understand what has led more than one hundred Tibetans to perform this act during the time of political crisis.

The use of social media to communicate child health information to low-income parents: A formative study

The Internet, and specifically web 2.0 social media applications, offers an innovative method for communicating child health information to low-income parents. The main objective of this study was to use qualitative data to determine the value of using social media to reach low-income parents with child health information. A qualitative formative evaluation employing focus groups was used to determine the value of using social media for dissemination of child health information. Inclusion criteria included: (1) a parent with a child that attends a school in a designated Central Texas school district; and (2) English-speaking. The students who attend these schools are generally economically disadvantaged and are predominately Hispanic. The classic analysis strategy was used for data analysis. Focus group participants (n=19) were female (95%); White (53%), Hispanic (42%) or African American (5%); and received government assistance (63%). Most had access to the Internet (74%) and were likely to have low health literacy (53%). The most preferred source of child health information was the family pediatrician or general practitioner. Many participants were familiar with social media applications and had profiles on popular social networking sites, but used them infrequently. Objections to social media sites as sources of child health information included lack of credibility and parent time. Social media has excellent potential for reaching low-income parents when used as part of a multi-channel communication campaign. Further research should focus on the most effective type and format of messages that can promote behavior change in this population, such as story-telling. ^

Media Influence on Youth: Scientific Evidence, Policy Considerations, and the History of Media Self-Regulation

This invited commentary reviews the survey research described in "Examining the Relationship between Media use and Aggression, Sexuality, and Body Image" and situates this research within the recent history of entertainment media regulation.

On the generative equations of fractal self-similarity in granular media and the related PSD models

The physical appearance of granular media suggests the existence of geometrical scale invariance. The paper discuss how this physico-empirical property can be mathematically encoded leading to different generative models: a smooth one encoded by a differential equation and another encoded by an equation coming from a measure theoretical property.

New instruction media: self instruction, guided instruction, and the role of the teacher.

Mode of access: Internet.

Autochthonous heritage languages and social media:writing and bilingual practices in Low German on Facebook

This article analyses how speakers of an autochthonous heritage language (AHL) make use of digital media, through the example of Low German, a regional language used by a decreasing number of speakers mainly in northern Germany. The focus of the analysis is on Web 2.0 and its interactive potential for individual speakers. The study therefore examines linguistic practices on the social network site Facebook, with special emphasis on language choice, bilingual practices and writing in the autochthonous heritage language. The findings suggest that social network sites such as Facebook have the potential to provide new mediatized spaces for speakers of an AHL that can instigate sociolinguistic change.

Low frequency peculiarities of the photorefractive response in sillenites

We investigate experimentally and theoretically the dependence of the amplitude of the spatial fundamental grating, created by a pair of coherent light beams while using the running grating technique [M.P. Petrov, S.I. Stepanov and A.V. Khomenko, Photorefractive Crystals in Coherent Optical Systems, Springer Series in Optical Sciences (Springer, 1991); P. Refregier, L. Solymar, H. Rajbenbach and J.P. Huignard, J. Appl. Phys. 58 (1985) 45], as a function of detuning frequency and beam ratio ß in photorefractive Bi12SiO20. It is shown that for ß > 0.05, in addition to the main peak in the frequency dependence of the amplitude, there is an additional peak of lower frequency which, as a rule, dominates the main peak. The position of the main peak depends on ß. The experimental results are in good agreement with the theoretical analysis and the general ideas about excitation and nonlinear interaction of weakly damped space-charge waves.

Low frequency peculiarities of the photorefractive response in sillenites

We investigate experimentally and theoretically the dependence of the amplitude of the spatial fundamental grating, created by a pair of coherent light beams while using the running grating technique [M.P. Petrov, S.I. Stepanov and A.V. Khomenko, Photorefractive Crystals in Coherent Optical Systems, Springer Series in Optical Sciences (Springer, 1991); P. Refregier, L. Solymar, H. Rajbenbach and J.P. Huignard, J. Appl. Phys. 58 (1985) 45], as a function of detuning frequency and beam ratio ß in photorefractive Bi12SiO20. It is shown that for ß > 0.05, in addition to the main peak in the frequency dependence of the amplitude, there is an additional peak of lower frequency which, as a rule, dominates the main peak. The position of the main peak depends on ß. The experimental results are in good agreement with the theoretical analysis and the general ideas about excitation and nonlinear interaction of weakly damped space-charge waves.

Step and flash imprint lithography: Fabrication of patterned media for extremely high density magnetic data storage devices

Currently the data storage industry is facing huge challenges with respect to the conventional method of recording data known as longitudinal magnetic recording. This technology is fast approaching a fundamental physical limit, known as the superparamagnetic limit. A unique way of deferring the superparamagnetic limit incorporates the patterning of magnetic media. This method exploits the use of lithography tools to predetermine the areal density. Various nanofabrication schemes are employed to pattern the magnetic material are Focus Ion Beam (FIB), E-beam Lithography (EBL), UV-Optical Lithography (UVL), Self-assembled Media Synthesis and Nanoimprint Lithography (NIL). Although there are many challenges to manufacturing patterned media, the large potential gains offered in terms of areal density make it one of the most promising new technologies on the horizon for future hard disk drives. Thus, this dissertation contributes to the development of future alternative data storage devices and deferring the superparamagnetic limit by designing and characterizing patterned magnetic media using a novel nanoimprint replication process called "Step and Flash Imprint lithography". As opposed to hot embossing and other high temperature-low pressure processes, SFIL can be performed at low pressure and room temperature. Initial experiments carried out, consisted of process flow design for the patterned structures on sputtered Ni-Fe thin films. The main one being the defectivity analysis for the SFIL process conducted by fabricating and testing devices of varying feature sizes (50 nm to 1 μm) and inspecting them optically as well as testing them electrically. Once the SFIL process was optimized, a number of Ni-Fe coated wafers were imprinted with a template having the patterned topography. A minimum feature size of 40 nm was obtained with varying pitch (1:1, 1:1.5, 1:2, and 1:3). The Characterization steps involved extensive SEM study at each processing step as well as Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM) analysis.