Wealth Of Theoretical Work Research Articles

State-dependent geometry of population activity in rat auditory cortex.

The accuracy of the neural code depends on the relative embedding of signal and noise in the activity of neural populations. Despite a wealth of theoretical work on population codes, there are few empirical characterizations of the high-dimensional signal and noise subspaces. We studied the geometry of population codes in the rat auditory cortex across brain states along the activation-inactivation continuum, using sounds varying in difference and mean level across the ears. As the cortex becomes more activated, single-hemisphere populations go from preferring contralateral loud sounds to a symmetric preference across lateralizations and intensities, gain-modulation effectively disappears, and the signal and noise subspaces become approximately orthogonal to each other and to the direction corresponding to global activity modulations. Level-invariant decoding of sound lateralization also becomes possible in the active state. Our results provide an empirical foundation for the geometry and state-dependence of cortical population codes.

Attosecond streaking metrology with isolated nanotargets

The development of attosecond metrology has enabled time-resolved studies on atoms, molecules, and (nanostructured) solids. Despite a wealth of theoretical work, attosecond experiments on isolated nanotargets, such as nanoparticles, clusters, and droplets have been lacking. Only recently, attosecond streaking metrology could be extended to isolated silica nanospheres, enabling real-time measurements of the inelastic scattering time in dielectric materials. Here, we revisit these experiments and describe the single-shot analysis of velocity-map images, which permits to evaluate the recorded number of electrons. Modeling of the recorded electron histograms allows deriving the irradiated nanoparticle statistics. Theoretically, we analyze the influence of the nanoparticle size on the field-induced delay, which is one of the terms contributing to the measured streaking delay. The obtained new insight into attosecond streaking experiments on nanoparticles is expected to guide wider implementation of the approach on other types of nanoparticles, clusters, and droplets.

On the Evaluation of Semantic Web Service Frameworks

In recent years, a huge amount of research effort and funding has been devoted to the area of Semantic Web services (SWS). This has resulted in the proposal of numerous competing approaches to facilitate the automation of mediation, choreography, and discovery for Web services using semantic annotations. However, despite a wealth of theoretical work, too little effort has been spent toward the comparative experimental evaluation of the competing approaches so far. Progress in scientific development and industrial adoption is thereby hindered. An established evaluation methodology and standard benchmarks that allow the comparative evaluation of different frameworks are thus needed for the further advancement of the field. To this end, a criteria model for SWS evaluation is presented, and the existing approaches toward SWS evaluation are comprehensively analyzed. Their shortcomings are discussed in order to identify the fundamental issues of SWS evaluation. Based on this discussion, a research agenda toward agreed upon evaluation methodologies is proposed.

An experimental look into subelectron charge flow.

The prediction and measurement of charge distribution among interacting chemical entities in complex environments is a major challenge for modern chemistry. It encompasses information concerning fundamental quantities such as the electronic chemical potential and hardness of molecular fragments as well as their interactions with the surroundings. Although a wealth of theoretical work has been accumulated from the days of Pauling to the present, a specific molecular model system that allows quantitative and direct measurement of these properties has not yet been reported. Because atomic charges are not quantum mechanical observables, they cannot be derived from first principles, but rather they rely on the availability of high-precision experimental data and the interpretation of related experimental observables. Here, we demonstrate, for the first time, that a fragmental charge flow between a chelated metal center and reversibly bound molecules can be accurately monitored experimentally.

Gender and leadership in work groups: Six alternative models

Interest in understanding the dynamics of gender and leadership has blossomed in recent years as occupations and organizations have become less sex-segregated. Much of the work in this area has failed to draw on the wealth of theoretical work that addresses the dynamics of gender in social interaction. The aim of this article is to review several theoretical traditions within the gender literature that have social psychological implications for emergent status structures for groups of varying sex compositions over time. Six models are developed with competing predictions for leadership emergence and status structures, and existing evidence is compared with model predictions. The article concludes by noting that greater understanding can be reached by performing competitive tests of a variety of models, such as the ones presented in this article, and doing so by studying groups over time.