Who is afraid of constructivism? (¿Quién tiene miedo del constructivismo?)

Both generative and constructivist researchers agree that children are able to form abstractions and produce novel grammatically patterned utterances. Both approaches are able to explain such abilities, and hence their existence does not entail an innate Universal Grammar. However, generativists and constructivists differ in their views on the nature of early generalisations: while generative researchers assume that adult-like linguistic representations are present from the very beginning, constructivists argue that children begin with relatively specific, low level schemas and gradually extract more abstract patterns. There is considerable empirical evidence for the latter position. Moreover, constructivist theories provide a better explanation for principled behaviour -not just the observed patterns, but also the absence of certain constructions in children's early productions and various developmental asynchronies. Tanto los investigadores generativistas como constructivistas coinciden en que los niños son capaces de formar abstracciones y de producir emisiones novedosas gramaticalmente estructuradas. Ambos enfoques son capaces de explicar tales habilidades, y por eso su existencia no implica una Gramática Universal innata. Sin embargo, los investigadores generativistas y constructivistas difieren en su visión sobre la naturaleza de las generalizaciones tempranas: mientras que los investigadores generativistas asumen que las representaciones lingüísticas parecidas a las adultas están presentes desde edades tempranas, los constructivistas argumentan que los niños comienzan con esquemas de bajo nivel, relativamente específicos, y que gradualmente extraen esquemas más abstractos. Existe considerable evidencia empírica en apoyo de esta segunda posición. Además, las teorías constructivistas proporcionan una mejor explicación de las conductas basadas en reglas; no sólo de los patrones observados, sino también de la ausencia de ciertas construcciones en las producciones verbales tempranas de los niños y de diversas asincronías evolutivas

The space-time budget method in criminological research

This article reviews the Space-Time Budget method developed by Wikström and colleagues and particularly discusses its relevance for criminological research. The Space-Time Budget method is a data collection instrument aimed at recording, retrospectively, on an hour-by-hour basis, the whereabouts and activities of respondents during four days in the week before the interview. The method includes items about criminologically relevant events, such as offending and victimization. We demonstrate that the method can be very useful in criminology, because it enables the study of situational causes of crime and victimization, because it enables detailed measurement of theoretical concepts such as individual lifestyles and individual routine activities, and because it enables the study of adolescents’ whereabouts, which extends the traditional focus on residential neighborhoods. The present article provides the historical background of the method, explains how the method can be applied, presents validation results based on data from 843 secondary school students in the Netherlands and describes the methods’ strengths and weaknesses. Two case studies are summarized to illustrate the usefulness of the method in criminological research. The article concludes with some anticipated future developments and recommendations on further readings

Nanoscale Electrostatic Control of Oxide Interfaces

We develop a robust and versatile platform to define nanostructures at oxide interfaces via patterned top gates. Using LaAlO$_3$/SrTiO$_3$ as a model system, we demonstrate controllable electrostatic confinement of electrons to nanoscale regions in the conducting interface. The excellent gate response, ultra-low leakage currents, and long term stability of these gates allow us to perform a variety of studies in different device geometries from room temperature down to 50 mK. Using a split-gate device we demonstrate the formation of a narrow conducting channel whose width can be controllably reduced via the application of appropriate gate voltages. We also show that a single narrow gate can be used to induce locally a superconducting to insulating transition. Furthermore, in the superconducting regime we see indications of a gate-voltage controlled Josephson effect.Comment: Version after peer review; includes additional data on superconductivit

Two- versus three-dimensional connectivity testing of first-order queries to semi-algebraic sets

This paper addresses the question whether one can determine the connectivity of a semi-algebraic set in three dimensions by testing the connectivity of a finite number of two-dimensional ``samples'' of the set, where these samples are defined by first-order queries. The question is answered negatively for two classes of first-order queries: cartesian-product-free, and positive one-pass.Comment: corrected minor confusion in Proof of Theorem

Fast Long-Distance Control of Spin Qubits by Photon Assisted Cotunneling

We investigate theoretically the long-distance coupling and spin exchange in an array of quantum dot spin qubits in the presence of microwaves. We find that photon assisted cotunneling is boosted at resonances between photon and energies of virtually occupied excited states and show how to make it spin selective. We identify configurations that enable fast switching and spin echo sequences for efficient and non-local manipulation of spin qubits. We devise configurations in which the near-resonantly boosted cotunneling provides non-local coupling which, up to certain limit, does not diminish with distance between the manipulated dots before it decays weakly with inverse distance.Comment: 17 pages (including 8 pages of Appendices), 2 figure

Nuclear Spin Dynamics in Double Quantum Dots: Multi-Stability, Dynamical Polarization, Criticality and Entanglement

We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically-defined double quantum dot (DQD) in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections.Comment: 35 pages, 19 figures. This article provides the full analysis of a scheme proposed in Phys. Rev. Lett. 111, 246802 (2013). v2: version as publishe

Electrostatic confinement of electrons in graphene nano-ribbons

Coulomb blockade is observed in a graphene nanoribbon device with a top gate. When two pn junctions are formed via the back gate and the local top gate, electrons are confined between the pn junctions which act as the barriers. When no pn junctions are induced by the gate voltages, electrons are still confined, as a result of strong disorder, but in a larger area. Measurements on five other devices with different dimensions yield consistent results.Comment: 4 figures, 1 table, 4.4page