207,565 research outputs found
Thermocapillary approaches to the deliberate patterning of polymers
No full textThe phenomenon of thermocapillarity, the response of fluids to thermal gradients due to thermal alteration of their surface tension, was first reported over a century ago. Since then, research has focused generally on either the fundamentals or mitigation of this effect during the processing of materials. Only in the past two decades has the deliberate use of thermocapillary forces for the patterning of polymers been actively pursued, either for the ordering of internal structure or the introduction of topographic features. This review seeks to highlight this work and further identify directions for further investigation. In particular, while thermocapillary forces are often inextricably bound to other mechanisms, there are emerging directions in the deliberate coupling of forces to improve the capabilities of each mechanism. Further, the applications of thermocapillary patterning to polymer-nanoparticle composites has recently provided another promising route to active architectures.Peer reviewed
Focused Laser-Induced Marangoni Dewetting for Patterning Polymer Thin Films
No full textHighly-localized focused laser spike (FLaSk) heating of polymer thin films is a resist- and developer-free alternative to 2D laser direct write for creating patterns on the single micron or, by exploiting overlap effects, submicron scale. The massive temporal and spatial thermal gradients and resulting thermal Marangoni stresses generated by FLaSk are an effective means for the directed dewetting and patterning of such films. Here, the general applicability of this technique to glassy amorphous polymer thin film systems is investigated through systematic investigation of film thickness, glass transition temperature, and polymer mobility. The results reveal that the important parameters are the film thickness (coupled to the optical heating effects through anti-reflection coating effects) and the high-temperature polymer melt mobility, allowing for generation of single features with linewidths of down to ~1 μm. Further, the introduction of spatial mobility variations by using polymer brushes, bilayers, and microphase separated block copolymers leads to additional profile manipulation effects (i.e. spontaneous 2D pattern generation and flattened top profiles).Peer reviewe
Determination of critical cooling rates in metallic glass forming alloy libraries through laser spike annealing
No full textThe glass forming ability (GFA) of metallic glasses (MGs) is quantified by the critical cooling rate (RC). Despite its key role in MG research, experimental challenges have limited measured RC to a minute fraction of known glass formers. We present a combinatorial approach to directly measure RC for large compositional ranges. This is realized through the use of compositionally-graded alloy libraries, which were photo-thermally heated by scanning laser spike annealing of an absorbing layer, then melted and cooled at various rates. Coupled with X-ray diffraction mapping, GFA is determined from direct RC measurements. We exemplify this technique for the Au-Cu-Si system, where we identify Au56Cu27Si17 as the alloy with the highest GFA. In general, this method enables measurements of RC over large compositional areas, which is powerful for materials discovery and, when correlating with chemistry and other properties, for a deeper understanding of MG formation.Peer reviewe
Multiscale Patterning of a Metallic Glass using Sacrificial Imprint Lithography
No full textBulk metallic glasses have been advanced as a means to achieve durable multiscale, nanotextured surfaces with desirable properties dictated by topography for a multitude of applications. One barrier to this achievement is the lack of a bridging technique between macroscale thermoplastic forming and nanoimprint lithography, which arises from the difficulty and cost of generating controlled nanostructures on complex geometries using conventional top-down approaches. This difficulty is compounded by the necessary destruction of any resulting reentrant structures during rigid demolding. We have developed a generalized method to overcome this limitation by sacrificial template imprinting using zinc oxide nanostructures. It is established that such structures can be grown inexpensively and quickly with tunable morphologies on a wide variety of substrates out of solution, which we exploit to generate the nanoscale portion of the multiscale pattern through this bottom-up approach. In this way, we achieve metallic structures that simultaneously demonstrate features from the macroscale down to the nanoscale, requiring only the top-down fabrication of macro/microstructured molds. Upon detachment of the formed part from the multiscale molds, the zinc oxide remains embedded in the surface and can be removed by etching in mild conditions to both regenerate the mold and render the surface of the bulk metallic glass nanoporous. The ability to pattern metallic surfaces in a single step on length scales from centimeters down to nanometers is a critical step toward fabricating devices with complex shapes that rely on multiscale topography for their intended functions, such as for biomedical and electrochemical applications.Peer reviewe
Thermocapillary Multidewetting of Thin Films
No full textThermocapillary dewetting of liquids and molten films has recently emerged as a viable alternative to conventional microprocessing methods. As this thermal gradient-induced mechanism is universal, it can be applied to any material. This work explores the sequential dewetting of materials with varying melting points, including polymers and metals, to create aligned morphologies. The variation in melting point allows for the dewetting of single layers at a time or mobility-limited simultaneous dewetting. As a result, a variety of multimaterial structures can be produced with built-in alignment, such as arrays of concentric circles, lines with periodic segmentation, or islands on holes. This approach employs photothermal methods to induce the necessary thermal gradient, manipulating several variables in order to influence the consequent structures. Adjusting laser power and light intensity allows for the control of temperature for selective dewetting of films; altering beam size and exposure time affects the extent of dewetting in terms of diameter size; overlap effects and simultaneous dewetting can result in complex architectures. This controlled writing of patterns also presents a technique to create both masks at low temperatures for conductive multilayers as well as templates for electrospray deposition.Peer reviewe
The Singer or the Song? Developments in Performers' Rights from the Perspective of a Cultural Economist
No full textOver the last century, performers gradually acquired statutory protection of their economic and moral
rights. These rights are not copyright in the legal sense but neighboring rights and until recently, they
were mainly remuneration rights that are collectively administered. With the WPPT (WIPO
Performers and Phonograms Treaty), performers now have individual exclusive rights for digital
performances; this leads to the question: what has motivated this change – is it a change in the
perception of the value of performer or a change brought about by the changing technology of copying or,
indeed, a change that reflects different economic costs and benefits? The paper discusses the role of
copyright law as an incentive to performers and asks if the economic role of the performer is so different
from that of the author. The conclusion is that a complex interaction of the legal regulations, economic
conditions and institutional arrangements for administering these new rights will determine the outcome
A importância moral da dor e do sofrimento animal na ética de Peter Singer
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Humanas, Programa de Pós-Graduação em Filosofia, Florianópolis, 2012.O objetivo desta dissertação é defender a importância moral da consideração da dor e do sofrimento de animais não-humanos. Isso se dá através do principio da igual consideração de interesses desenvolvido por Peter Singer. A senciência possibilita os animais a terem interesses, no mínimo, o interesse evitar a dor e o sofrimento. É por essa razão que devem ser incluídos nas decisões morais. São reconstruídas e analisadas as objeções de Peter Harrison, Carl Cohen, R.G. Frey e Lawrence C. Becker direcionadas ao princípio de Singer, e que criticam os pressupostos básicos, quais sejam, a capacidade de sentirem dor/sofrimento e de terem interesses, sobre os quais se fundamenta a inclusão dos animais nas considerações morais. Cada uma dessas objeções é analisada e criticada de modo a demonstrar suas limitações e inconsistências, juntamente com as implicações morais geradas para seres humanos. Na análise dessas críticas, reforça-se a importância e a consideração moral que deve ser conferida à dor e ao sofrimento dos animais. Após essa discussão teórica, é analisado um caso de âmbito prático: a pesquisa científica sobre o câncer humano através do modelo animal. Verifica-se, a partir do princípio de Singer, a imoralidade de tal procedimento realizado em animais sencientes devido à violação de seus interesses. Com isso, a dissertação enfatiza a exigência ética de abolir o uso de animais nessa prática em razão da incapacidade preditiva dos animais, mas principalmente devido à dor e ao sofrimento causado neles e também aos seres humanos, que ficam sujeitos aos erros, prejuízos e sofrimentos originados pelo intenso uso animal nas pesquisas. Nessa conclusão, se constata que a insistência no uso de animais nos experimentos compromete o cientista a preferir usar seres humanos, uma vez que isso gera mais benefícios e resultados mais seguros. A recusa moral ao uso de humanos em pesquisas implica, por outro lado, na recusa moral do uso de animais, ou seja, sua abolição.Abstract : The aim of this dissertation is to defend the moral importance of considering pain and suffering of nonhuman animals. This is achieved through The Principle of Equal Consideration of Interests developed by Peter Singer. The sentience enables nonhuman animals to have interests, at least the interest of avoiding pain and suffering. That is why it should be included in moral decisions. The objections of Peter Harrison, Carl Cohen, RG Frey and Lawrence C. Becker directed to the principle of Singer are reconstructed and analyzed, as they are criticizing the basic assumptions, i.e., the ability to feel pain/suffering and have interests, upon which is based the inclusion of animals in moral considerations. Each of these objections is analyzed and criticized in order to demonstrate their limitations and inconsistencies, simultaneously with its moral implications for humans. In the analysis of these criticisms, it reinforces the moral importance and considerations that should be given to pain and suffering of animals. After this theoretical discussion, a case study of practical scope is analyzed: animal testing for scientific research on human cancer. It is verified from the Singer's principle that such procedures performed on sentient animals are a violation of their interests and, therefore, immoral. Thus, the dissertation emphasizes the ethical demand to abolish the use of nonhuman animals in this practice due to their predictive inability, but mainly due to the pain and suffering caused to them and also to humans, who are subject to errors, injuries and suffering originated by the intense use of nonhuman animals on research. The conclusion verifies that the insistence on the use of nonhuman animals in experiments moves the scientist to prefer using humans in experiments since it generates greater benefit and more reliable results. The moral refusal to using humans in research implies the moral rejection of the use of animals in experiments and consequently, its abolition
Powerful Trend Function Tests That are Robust to Strong Serial Correlation with an Application to the Prebisch Singer Hypothesis
Full text linkIn this paper we propose tests for hypothesis regarding the parameters of a the deterministic trend function of a univariate time series. The tests do not require knowledge of the form of serial correlation in the data and they are robust to strong serial correlation. The data can contain a unit root and the tests still have the correct size asymptotically. The tests we analyze are standard heteroskedasticity autocorrelation (HAC) robust tests based on nonparametric kernel variance estimators. We analyze these tests using the small-b asymptotic framework recently proposed by Kiefer and Vogelsang (2002). This analysis allows us to analyze the power properties of the tests with regards to bandwidth and kernel choices. Our analysis shows that among popular kernels, there are specific kernel and bandwidth choices that deliver tests with maximal power within a specific class of tests. We apply the recommended tests to the logarithm of a net barter terms of trade series and we find that this series has a statistically significant negative slope. This finding is consistent with the well known Prebisch-Singer hypothesis. Because our tests are robust to strong serial correlation or a unit root in the data, our results in support of the Prebisch-Singer hypothesis are relatively strong.Estimator, Fixed-b Asymptotics, Power Envelope, Unit Root, Nearly Integrated, Partial Sum, Deterministic Trend, Linear Trend.
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