10,000 publications from this institution
Carrier distribution and dynamics in semiconductor materials often govern their physical properties that are critical to functionalities and performance in industrial applications. The continued miniaturization of electronic and photonic devices calls for tools to probe carrier behavior in semiconductors simultaneously at the picosecond time and nanometer length scales. Here, we report pump-probe optical nanoscopy in the visible-near-infrared spectral region to characterize the carrier dynamics in silicon nanostructures. By coupling experiments with the point-dipole model, we resolve the size-dependent photoexcited carrier lifetime in individual silicon nanowires. We further demonstrate local carrier decay time mapping in silicon nanostructures with a sub-50 nm spatial resolution. Our study enables the nanoimaging of ultrafast carrier kinetics, which will find promising applications in the future design of a broad range of electronic, photonic, and optoelectronic devices.
En Castigar a los pobres, mostré que el ascenso del Estado Penal en los Estados Unidos y otras sociedades avanzadas en el último cuarto de siglo es una respuesta a la creciente inseguridad social y no a la inseguridad criminal, que los cambios en la asistencia social y las políticas judiciales están vinculados entre sí, el tan restrictivo workfare y el tan expansivo prisonfare se unen en un artefacto único de organización para la disciplina de las fracciones precarizadas de la clase trabajadora en la era post-industrial, y que un sistema carcelario diligente no es una desviación, sino un elemento constitutivo del Leviatán neoliberal. En este artículo, extraigo las consecuencias teóricas de ese diagnóstico respecto al gobierno emergente de la inseguridad social. Utilizo el concepto de campo burocrático de Bourdieu para revisar la tesis clásica de Piven y Cloward sobre la regulación de la pobreza a través de la asistencia público, y contrastar el modelo de penalización como técnica para la gestión de la marginalidad urbana con la visión de Michel Foucault sobre la sociedad disciplinaria, las consideraciones de David Garlad sobre la cultura del control y la caracterización de David Harvey acerca de la política neoliberal. Contra la concepción estrecha del neoliberalismo como una regla del mercado, se propone una especificación de mayor densidad sociológica que implica prestaciones sociales de supervisión, un estado penal proactivo y el tropo cultural de la responsabilidad individual. Esto sugiere que es necesario teorizar, no respecto a la prisión como una técnica práctica para aplicar la ley, sino como un núcleo cuya capacidad política selectiva y agresiva descargada sobre las regiones inferiores del espacio social viola los ideales de la ciudadanía democrática.<br>In Punishing the Poor, I show that the ascent of the penal state in the United States and other advanced societies over the past quarter-century is a response to rising social insecurity, not criminal insecurity; that changes in welfare and justice policies are interlinked, as restrictive ''workfare'' and expansive ''prisonfare'' are coupled into a single organizational contraption to discipline the precarious fractions of the postindustrial working class; and that a diligent carceral system is not a deviation from, but a constituent component of, the neoliberal Leviathan. In this article, I draw out the theoretical implications of this diagnosis of the emerging government of social insecurity. I deploy Bourdieu's concept of ''bureaucratic field'' to revise Piven and Cloward's classic thesis on the regulation of poverty via public assistance, and contrast the model of penalization as technique for the management of urban marginality to Michel Foucault's vision of the ''disciplinary society,'' David Garland's account of the ''culture of control,'' and David Harvey's characterization of neoliberal politics. Against the thin economic conception of neoliberalism as market rule, I propose a thick sociological specification entailing supervisory workfare, a proactive penal state, and the cultural trope of ''individual responsibility.'' This suggests that we must theorize the prison not as a technical implement for law enforcement, but as a core political capacity whose selective and aggressive deployment in the lower regions of social space violates the ideals of democratic citizenship.
2 Abstract: Two contrasting experimental descriptions of P1 plasmid replication during the cell cycle of Escherichia coli have been described. One set of results led to the proposal that replication of P1 plasmid occurs at a specific time during the cell cycle over a wide range of growth rates and follows rules similar to that governing bacterial chromosome replication. Experiments supporting this proposal utilized membrane-elution experiments, radioactive double-labeling of DNA and scintillation counting of purified plasmids. An alternative experimental description of P1 plasmid replication during the cell cycle, also based on membrane-elut ion methodology but measuring radioactivity incorporated into plasmid DNA by autoradiograp hy and scanning of films, proposed that P1 plasmid replicates at all stages of the cell cycle in rapidly growing cells, but with a slight periodicity or increase in P1 replication probability within the cell cycle of slower growing cells. These discordant experimental results are analyzed. It is concluded that the direct double-label counting approach is to be preferred, as the results are consistent with a large number of experiments, are supported by theoretical considerations and yield a unified view of plasmid replication over a wide range of growth rates. Theoretical ramifications of each view of P1 plasmid replication-cycle-dependent and cycle-independent are compared. An analysis of P1 plasmid segregation is also presented.
The richness and versatility of biological systems make them ideally suited to solve some of the world's most significant challenges, such as converting cheap, renewable resources into energy-rich molecules; producing high-quality, inexpensive drugs to fight disease; and remediating polluted sites. Over the years, significant strides have been made in engineering microorganisms to produce fuels, bulk chemicals, and valuable drugs from inexpensive starting materials; to detect and degrade nerve agents as well as less toxic organic pollutants; and to accumulate metals and reduce radionuclides. The components needed to engineer the chemistry inside a microbial cell are significantly different from those commonly used to overproduce pharmaceutical proteins. Synthetic biology has had and will continue to have a significant impact on the development of these components to engineer cellular metabolism and microbial chassis to host the chemistry. The ready availability of more well-characterized gene expression components and hosts for chemical synthesis, standards for the connection of these components to make larger functioning devices, computer-aided design software, and debugging tools for biological designs will decrease both the time and the support needed to construct these designs. Some of the most important tools for engineering bacterial metabolism and their use for production of the antimalarial drug artemisinin are reviewed.
Dicobalt(II) cofacial bisporphyrins anchored by dibenzofuran (DPD) and xanthene (DPX) are efficient electrocatalysts for the four-electron reduction of oxygen to water despite their ca. 4 Å difference in metal–metal distances, suggesting that the considerable longitudinal Pac-Man flexibility of the pillared platforms is the origin for the similar catalytic reactivity of these structurally disparate systems.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An important component of the drive towards intelligent vehicles is the ability to maintain a fixed distance from a lead vehicle using feedback provided by range sensors. We are investigating the possibility of using stereo vision to provide the range information, in conjunction with a scanning laser radar sensor. The vision algorithms build on fixation and reconstruction algorithms designed for active vision systems, and combine stereo and motion cues. We shall present preliminary results comparing the quality of range measurements provided by a vision system with the laser radar system, using data obtained off-line. Later we will implement the tracker in real time on a network of C40 DSPs, and combine the laser and vision sensing in a cooperative manner.
Pour explorer les changements institutionnels qui ont augmente l'etendue de la polarisation sociale et economique dans les dernieres decennies, l'A. explore quatre differentes logiques de polarisation : macrosociale, economique, politique et spatiale. Puis il en trace les consequences pour la pauperisation croissante des plus pauvres, ce qui en fait le groupe le plus souvent decrit comme underclass. Mais, comme Ingham, il souligne qu'une polarisation implique deux poles et ne doit pas etre vue en relation avec le seul groupe des pauvres. En depit d'une experience similaire de croissance des inegalites depuis la fin des annees 1970, (et, dans le cas britannique, depuis l'application des politiques neoliberales) l'A. estime qu'un parallele direct ne peut etre dresse entre les experiences americaines et europeennes, en particulier en ce qui concerne la criminalisation de la pauvrete aux Etats-Unis. Il evalue les differentes strategies qui ont ete proposees pour stopper la polarisation sociale et ses effets negatifs, soutenant que la solution a la deterioration des chances sociales des groupes situes au bas de l'echelle sociale reside dans l'instauration d'une forme de revenu minimum qui effectue une redistribution des revenus depuis les classes privilegiees
