On the impact of capillarity for strength at the nanoscale

The interior of nanoscale crystals experiences stress that compensates the capillary forces and that can be large, in the order of 1 GPa. Various studies have speculated on whether and how this surface-induced stress affects the stability and plasticity of small crystals. Yet, experiments have so far failed to discriminate between the surface contribution and other, bulk-related size effects. In order to clarify the issue, we study the variation of the flow stress of a nanomaterial while distinctly different variations of the two capillary parameters surface tension and surface stress are imposed under control of an applied electric potential. Our theory qualifies the suggested impact of $\textit{surface stress}$ as not forceful and instead predicts a significant contribution of the surface energy, as measured by the $\textit{surface tension}$. The predictions for the combined potential- and size dependence of the flow stress are quantitatively supported by the experiment. Previous suggestions, favoring the surface stress as the relevant capillary parameter, are not consistent with the experiment

The Shakespearean Sonnet

This unit presents the poetic structure of the Shakespearean Sonnet and its importance and place in the world of poetry. The unit focuses on familiarizing students with the structural elements of a sonnet (e.g., iambs, iambic pentameter, rhyme schemes, turns, stanzas, quatrains, and couplets) as well as using the writing comprehension process to write an original sonnet that uses the conventions of poetry in hand with imagery and figurative language. Students will also analyze and interpret sonnets, connecting them to modern forms of media including songs, raps, movies and music videos. Students will understand that writers construct personal, creative poems to express their encompassing world views. The unit will end with a performance assessment of students constructing their own “Hollywood Sonnet” (following appropriate structural criteria) to display in a Gallery Walk for students to evaluate and discuss

Switchable Imbibition in Nanoporous Gold

Spontaneous imbibition enables the elegant propelling of nano-flows because of the dominance of capillarity at small length scales. The imbibition kinetics are, however, solely determined by the static geometry of the porous host, the capillarity, and the fluidity of the imbibed liquid. This makes active control particularly challenging. Here, we show for aqueous electrolyte imbibition in nanoporous gold that the fluid flow can be reversibly switched on and off through electric potential control of the solid-liquid interfacial tension, i.e. we can accelerate the imbibition front, stop it, and have it proceed at will. Simultaneous measurements of the mass flux and the electrical current allow us to document simple scaling laws for the imbibition kinetics, and to explore the charge flow dynamics in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for ionic and/or fluid transport render nanoporous elemental gold a versatile, accurately controllable electro-capillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages.Comment: 12 pages, 5 figure

Educación y movimientos migratorios: los casos comparados de Chile y Francia

El comparatismo es, en las Ciencias Sociales, una herramienta más para ayudarnos en la tarea de comprender -y, si es posible, explicar- aquellos fenómenos sociales que incumben a nuestros campos de investigación. Sin embargo, hay que tener presente las dificultades que este conlleva. Como ya lo indica la sabiduría popular, "solo se puede comparar lo comparable", y la comparación tiene sus límites que hay que respetar, en la medida en que dos países (en el caso presente) tienen en alguna medida aspectos que pueden ser comparados (con mucha precaución) y otros no.  

O papel do dialeto no desempenho de alunos na prova de proficiência Deutsches Sprachdiplom I

This paper investigates the role of Hunsrückisch, a dialect spoken by German descendents in South Brazil, in regard to the performance of high school students in the proficiency exam Deutsches Sprachdiplom (DSD-I). The article will first discuss the concept of bilinguism and then analyzes the performance of bilingual students (Portuguese/German) from the Instituo de Educação Ivoti in DSD-I exams over the last 5 years

Diffraction microstrain in nanocrystalline solids under load - heterogeneous medium approach

This is an account of the computation of X-ray microstrain in a polycrystal with anisotropic elasticity under uniaxial external load. The results have been published in the article "Microstrain in nanocrystalline solids under load by virtual diffraction", at Europhysics Letters 89, 66002 (2010). The present information was submitted to Europhysics Letters as part of the manuscript package, and was available to the reviewers who recommended the paper for publication.Comment: Supporting online material for J. Markmann, D. Bachurin, L.-H. Shao, P. Gumbsch, J. Weissm\"uller, Microstrain in nanocrystalline solids under load by virtual diffraction, Europhys. Lett. 89, 66002 (2010

Anomalous compliance and early yielding of nanoporous gold

We present a study of the elastic and plastic behavior of nanoporous gold in compression, focusing on molecular dynamics simulation and inspecting experimental data for verification. Both approaches agree on an anomalously high elastic compliance in the early stages of deformation, along with a quasi immediate onset of plastic yielding even at the smallest load. Already before the first loading, the material undergoes spontaneous plastic deformation under the action of the capillary forces, requiring no external load. Plastic deformation under compressive load is accompanied by dislocation storage and dislocation interaction, along with strong strain hardening. Dislocation-starvation scenarios are not supported by our results. The stiffness increases during deformation, but never approaches the prediction by the relevant Gibson-Ashby scaling law. Microstructural disorder affects the plastic deformation behavior and surface excess elasticity might modify elastic response, yet we relate the anomalous compliance and the immediate yield onset to an atomistic origin: the large surface-induced prestress induces elastic shear that brings some regions in the material close to the shear instability of the generalized stacking fault energy curve. These regions are elastically highly compliant and plastically weak

Declarative Specialization for Object-Oriented-Program Specialization

The use of partial evaluation for specializing programs written in im- perative languages such as C and Java is hampered by the di-culty of controlling the specialization process. We have developed a simple, declar- ative language for controlling the specialization of Java programs, and in- terfaced this language with the JSpec partial evaluator for Java. This lan- guage, named Pesto, allows declarative specialization of programs written in an object-oriented style of programming. The Pesto compiler auto- matically generates the context information needed for specializing Java programs, and automatically generates guards that enable the specialized code in the right context

Bank liquidity management through the issuance of bonds in the aftermath of the global financial crisis

Next to deposits, European banks have historically largely used bank obligations such as covered bonds (CB). Their US counterparties, on the contrary, heavily rely on securitization to fund mortgages. We assess how banks’ liquidity and funding position during and after the Global Financial Crisis (GFC) affects the decision to issue (private label) mortgage backed securities (MBS), covered bonds or senior unsecured bonds. Since the decisions to issue either instrument are not necessarily independent from each other, we estimate conditional probit and tobit models in order to account for the simultaneous nature of the issuances. We see that neither instrument plays any role in liquidity management during the GFC. In the post-GFC period, banks reach out to issuing MBS when facing short-term illiquidity. Banks could issue MBS as a way to comply with Basel III liquidity regulations. In turn, a bank’s decision to issue CB is not affected by bank’s liquidity and liquidity management occurs instead through managing the amount of CB. The issuance of SUB is also not affected by liquidity. Overall, the paper shows that only MBS have actively been issued as a response to liquidity shortages of banks’ balance sheets and shows that MBS and CB which often are seen as alternative instruments serve different purposes