Design issues for VREs: can richer records of meetings enhance collaboration?

Technologies for collaboration have advanced significantly in the past ten years. Through tools such as the Access Grid (AG), it is now possible to conduct multi-site meetings involving large numbers of participants interacting using high quality and video and sharing data. Virtual Venues within the AG toolkit store data, documents, applications and services which can be accessed across multiple sites. These documents might include records of the meetings themselves. We discuss ways in which such records can be made navigable and re-usable so that collaborators can achieve a shared understanding of meetings’ work

Queen of Spades

Semblance—or parody—is, of course, the operative word when considering a text that strives to be subversive of both form (the “anti-realism” of minor literature) and social function. Regarding the latter, as stated before, my goal in the text is the reverse of the traditional moral fable’s: implanting a desire in readers to experience firsthand the world of risk as a means to live in a more vital way, outside the text, whether through gambling or another form of chance-taking. Uncertainty is troubling, unsettling, but it is also mysterious and enlivening—this is what gamblers, acolytes at the altar of luck, understand in the final analysis

Horizontal Mergers of Online Firms: Structural Estimation and Competitive Effects

This paper (1) presents a general model of online price competition, (2) shows how to structurally estimate the underlying parameters of the model when the number of competing firms is unknown or in dispute, (3) estimates these parameters based on UK data for personal digital assistants, and (4) uses these estimates to simulate the competitive effects of horizontal mergers. Our results suggest that competitive effects in this online market are more closely aligned with the simple homogeneous product Bertrand model than might be expected given the observed price dispersion and number of firms. Our estimates indicate that so long as two firms remain in the market post merger, the average transaction price is roughly unaffected by horizontal mergers. However, there are potential distributional effects; our estimates indicate that a three-to-two merger raises the average transaction price paid by price sensitive "shoppers" by 2.88 percent, while lowering the average transaction price paid by consumers "loyal" to a particular firm by 1.37 percent.

Measurement of a topological edge invariant in a microwave network

We report on the measurement of topological invariants in an electromagnetic topological insulator analog formed by a microwave network, consisting of the winding numbers of scattering matrix eigenvalues. The experiment can be regarded as a variant of a topological pump, with non-zero winding implying the existence of topological edge states. In microwave networks, unlike most other systems exhibiting topological insulator physics, the winding can be directly observed. The effects of loss on the experimental results, and on the topological edge states, is discussed.Comment: 10 pages, 10 figure

Coastal Altimetry and Applications

This report was prepared by Dr. Michael Anzenhofer of the Geo-Forschungs-Zentrum (GFZ) Potsdam, Germany, while visiting the Department of Civil and Environmental Engineering and Geodetic Science (CEEGS), Ohio State University, during 1997-1998. The visit was hosted by Prof. C.K. Shum of the Department of Civil and Environmental Engineering and Geodetic Science.This work was partially supported by NASA Grant No.735366, Improved Ocean Radar Altimeter and Scatterometer Data Products for Global Change Studies and Coastal Application, and by a grant from GFZ, Prof. Christoph Reigber, Director

Test-Retest Reliability of Simulated Driving Performance: A Pilot Study

Twenty-seven volunteers completed three simulated driving tests to determine test-retest reliability of performance on a low-cost, fixed-base computerized driving simulator. One retest was completed a few hours after the initial drive, and the final retest was completed 7 days following the initial test drive. Driving performance was compared using measures of vehicle control, speed, and reaction time to critical events. A measure of participants’ ability to inhibit a pre-potent response was also assessed using an inhibition task during each drive, with the number of incorrect inhibition responses recorded. Practice effects were evident for measures of vehicle control (deviation of lane position and number of line crossings) and participants’ ability to withhold responses to inhibition tasks. Good test-retest reliability was observed for measures of vehicle control, speed, reaction time, and variability measures. Poor test-retest reliability was observed for the number of stopping failures observed during driving. The findings from this study suggest that the driving scenario used provides reliable assessment tasks that could be used to track the effects of pharmacological treatments on driving performance. However, an additional familiarization drive should be included as part of future study protocols employing this driving scenario to reduce learning effects during trials. Care should also be taken when interpreting results from tasks with low test-retest reliabilit

Developing a Complex Independent Component Analysis (CICA) technique to extract non-stationary patterns from geophysical time series

In recent decades, decomposition techniques have enabled increasingly more applications for dimension reduction, as well as extraction of additional information from geophysical time series. Traditionally, the principal component analysis (PCA)/empirical orthogonal function (EOF) method and more recently the independent component analysis (ICA) have been applied to extract, statistical orthogonal (uncorrelated), and independent modes that represent the maximum variance of time series, respectively. PCA and ICA can be classified as stationary signal decomposition techniques since they are based on decomposing the autocovariance matrix and diagonalizing higher (than two) order statistical tensors from centered time series, respectively. However, the stationarity assumption in these techniques is not justified for many geophysical and climate variables even after removing cyclic components, e.g., the commonly removed dominant seasonal cycles. In this paper, we present a novel decomposition method, the complex independent component analysis (CICA), which can be applied to extract non-stationary (changing in space and time) patterns from geophysical time series. Here, CICA is derived as an extension of real-valued ICA, where (a) we first define a new complex dataset that contains the observed time series in its real part, and their Hilbert transformed series as its imaginary part, (b) an ICA algorithm based on diagonalization of fourth-order cumulants is then applied to decompose the new complex dataset in (a), and finally, (c) the dominant independent complex modes are extracted and used to represent the dominant space and time amplitudes and associated phase propagation patterns. The performance of CICA is examined by analyzing synthetic data constructed from multiple physically meaningful modes in a simulation framework, with known truth. Next, global terrestrial water storage (TWS) data from the Gravity Recovery And Climate Experiment (GRACE) gravimetry mission (2003–2016), and satellite radiometric sea surface temperature (SST) data (1982–2016) over the Atlantic and Pacific Oceans are used with the aim of demonstrating signal separations of the North Atlantic Oscillation (NAO) from the Atlantic Multi-decadal Oscillation (AMO), and the El Niño Southern Oscillation (ENSO) from the Pacific Decadal Oscillation (PDO). CICA results indicate that ENSO-related patterns can be extracted from the Gravity Recovery And Climate Experiment Terrestrial Water Storage (GRACE TWS) with an accuracy of 0.5–1 cm in terms of equivalent water height (EWH). The magnitude of errors in extracting NAO or AMO from SST data using the complex EOF (CEOF) approach reaches up to ~50% of the signal itself, while it is reduced to ~16% when applying CICA. Larger errors with magnitudes of ~100% and ~30% of the signal itself are found while separating ENSO from PDO using CEOF and CICA, respectively. We thus conclude that the CICA is more effective than CEOF in separating non-stationary patterns

Identification and Estimation of Online Price Competition With an Unknown Number of Firms

This paper considers identification and estimation of a general model for online price competition. We show that when the number of competing firms is unknown the underlying parameters of the model can still be identified and estimated employing recently developed results on measurement errors. We illustrate our methodology using UK data for personal digital assistants and employ the estimates to simulate competitive effects. Our results reveal that heightened competition has differential effects on the prices paid by different consumer segments

NEDD9 regulates 3D migratory activity independent of the Rac1 morphology switch in glioma and neuroblastoma.

Metastasizing tumor cells must transmigrate the dense extracellular matrix that surrounds most organs. The use of three-dimensional (3D) collagen gels has revealed that many cancer cells can switch between different modes of invasion that are characterized by distinct morphologies (e.g., rounded vs. elongated). The adhesion protein NEDD9 has the potential to regulate the switch between elongated and rounded morphologies; therefore, its role was interrogated in the invasion switch of glioblastoma and neuroblastoma tumors that similarly derive from populations of neural crest cells. Interestingly, siRNA-mediated depletion of NEDD9 failed to induce cell rounding in glioma or neuroblastoma cells, contrasting the effects that have been described in other tumor model systems. Given that Rac1 GTPase has been suggested to mediate the switch between elongated and rounded invasion, the functionality of the Rac1 morphology switch was evaluated in the glioma and neuroblastoma cells. Using both dominant-negative Rac1 and Rac1-specific siRNA, the presence of this morphologic switch was confirmed in the neuroblastoma, but not in the glioma cells. However, in the absence of a morphologic change following NEDD9 depletion, a significant decrease in the cellular migration rate was observed. Thus, the data reveal that NEDD9 can regulate 3D migration speed independent of the Rac1 morphology switch. IMPLICATIONS: NEDD9 targeting is therapeutically viable as it does not stimulate adaptive changes in glioma and neuroblastoma invasion.National Health and Medical Research Council (NHMRC) grant 63251