Crystallization of a Mos1 transposase-inverted-repeat DNA complex: biochemical and preliminary crystallographic analyses

A complex formed between Mos1 transposase and its inverted-repeat DNA has been crystallized. The crystals diffract to 3.25 Å resolution and exhibit monoclinic (P2(1)) symmetry, with unit-cell parameters a = 120.8, b = 85.1, c = 131.6 Å, β = 99.3°. The X-ray diffraction data display noncrystallographic twofold symmetry and characteristic dsDNA diffraction at ∼3.3 Å. Biochemical analyses confirmed the presence of DNA and full-length protein in the crystals. The relationship between the axis of noncrystallographic symmetry, the unit-cell axes and the DNA diffraction pattern are discussed. The data are consistent with the previously proposed model of the paired-ends complex containing a dimer of the transposase

Two mechanisms for optic flow and scale change processing of looming

Published in final edited form as: J Vis. ; 11(3): . doi:10.1167/11.3.5.The detection of looming, the motion of objects in depth, underlies many behavioral tasks, including the perception of self-motion and time-to-collision. A number of studies have demonstrated that one of the most important cues for looming detection is optic flow, the pattern of motion across the retina. Schrater et al. have suggested that changes in spatial frequency over time, or scale changes, may also support looming detection in the absence of optic flow (P. R. Schrater, D. C. Knill, & E. P. Simoncelli, 2001). Here we used an adaptation paradigm to determine whether the perception of looming from optic flow and scale changes is mediated by single or separate mechanisms. We show first that when the adaptation and test stimuli were the same (both optic flow or both scale change), observer performance was significantly impaired compared to a dynamic (non-motion, non-scale change) null adaptation control. Second, we found no evidence of cross-cue adaptation, either from optic flow to scale change, or vice versa. Taken together, our data suggest that optic flow and scale changes are processed by separate mechanisms, providing multiple pathways for the detection of looming.We thank Jonathan Victor and the anonymous reviewers of the paper for feedback and suggestions regarding the stimuli used here. This work was supported by NIH grant R01NS064100 to LMV. (R01NS064100 - NIH)Accepted manuscrip

TiB_2 and ZrB_2 diffusion barriers in GaAs Ohmic contact technology

The transition metal diboride compounds, ZrB_2 and TiB_2, interposed between Ni/Ge/Au Ohmic contact metallization on n‐type GaAs wafers and an overlying thick Au contact layer, have been investigated to evaluate their effectiveness in stabilizing the Ohmic contact by limiting the in‐diffusion of Au. All of the metal layers were e‐beam deposited except the ZrB_2 which was rf‐diode sputtered. The barrier layer thicknesses were 50 and 100 nm for the TiB_2 and the ZrB_2, respectively. Postdeposition alloying of the contacts was performed at 400, 425, or 450 °C. Auger electron spectroscopy depth profiling of the resultant Ohmic contacts demonstrates that the barrier layers effectively preclude penetration of Au to the Ohmic contact structure. Specific contact resistivities for such contacts are in the low 10^(−7) Ω cm^2 range; although some degradation of the contact resistivity is observed after long term annealing, the values of resistivities do not exceed 1.5×10^(−6) Ω cm^2 after 92 h at 350 °C

Open vs.Closed standards for ambient intelligence: an exploratory study of adoption

Emerging forms of structurally complex information systems, such as Ambient Intelligence (AmI), requires the integration of a range of technologies. To enable such systems’ development there is a reliance on interoperability standards. However, due to their inherent characteristics, the adoption of open or closed standards by technology vendors can have impacts the later stages of the adoption and diffusion of systems. This paper reports on research-in-progress which explores the adoption of open and closed standards by technology vendors engaged in AmI development. Existing models of innovation adoption and diffusion fail to adequately account for adoption in more complex technological contexts. In order to address such deficiencies, current perspectives on standards are discussed, before a conceptual framework for structuring the research is proposed which integrates both existing adoption theory and standards-oriented research. The use of the European Consumer Electronics sector as a unit of analysis is discussed, before concluding with an overview of how the study will progress

A two-fluid model describing the finite-collisionality, stationary Alfvén wave in anisotropic plasma

The stationary inertial Alfvén (StIA) wave (Knudsen, 1996) was predicted for cold, collisionless plasma. The model was generalized (Finnegan et al., 2008) to include nonzero values of electron and ion collisional resistivity and thermal pressure. Here, the two-fluid model is further generalized to include anisotropic thermal pressure. A bounded range of values of parallel electron drift velocity is found that excludes periodic stationary Alfvén wave solutions. This exclusion region depends on the value of the local Alfvén speed VA, plasma beta perpendicular to the magnetic field β⊥ and electron temperature anisotropy

Curiosity-driven search for novel nonequilibrium behaviors

Exploring the full spectrum of novel behaviors that a system can produce can be an intensive task. Sampling techniques developed in response to this exploration challenge often require a predefined metric, such as distance in a space of known order parameters. However, order parameters are rarely known for nonequilibrium systems, especially in the absence of a diverse set of example behaviors, creating a chicken-and-egg problem. Here, we combine active and unsupervised learning for automated exploration of nonequilibrium systems with unknown order parameters. We iteratively use active learning based on current order parameters to expand the library of behaviors and relearn order parameters based on this expanded library. We demonstrate the utility of this approach in Kuramoto models of increasing complexity. In addition to reproducing known phases, we reveal previously unknown behavior and related order parameters, and we demonstrate how to align search with human intuition

A computational study of whole-brain connectivity in resting state and task fMRI

Background: We compared the functional brain connectivity produced during resting-state in which subjects were not actively engaged in a task with that produced while they actively performed a visual motion task (task-state). Material/Methods In this paper we employed graph-theoretical measures and network statistics in novel ways to compare, in the same group of human subjects, functional brain connectivity during resting-state fMRI with brain connectivity during performance of a high level visual task. We performed a whole-brain connectivity analysis to compare network statistics in resting and task states among anatomically defined Brodmann areas to investigate how brain networks spanning the cortex changed when subjects were engaged in task performance. Results: In the resting state, we found strong connectivity among the posterior cingulate cortex (PCC), precuneus, medial prefrontal cortex (MPFC), lateral parietal cortex, and hippocampal formation, consistent with previous reports of the default mode network (DMN). The connections among these areas were strengthened while subjects actively performed an event-related visual motion task, indicating a continued and strong engagement of the DMN during task processing. Regional measures such as degree (number of connections) and betweenness centrality (number of shortest paths), showed that task performance induces stronger inter-regional connections, leading to a denser processing network, but that this does not imply a more efficient system as shown by the integration measures such as path length and global efficiency, and from global measures such as small-worldness. Conclusions: In spite of the maintenance of connectivity and the “hub-like” behavior of areas, our results suggest that the network paths may be rerouted when performing the task condition