Ultrafast electron diffraction using an ultracold source

We present diffraction patterns from micron-sized areas of mono-crystalline graphite obtained with an ultracold and ultrafast electron source. We show that high spatial coherence is manifest in the visibility of the patterns even for picosecond bunches of appreciable charge, enabled by the extremely low source temperature (~ 10 K). For a larger, ~ 100 um spot size on the sample, spatial coherence lengths > 10 nm result, sufficient to resolve diffraction patterns of complex protein crystals. This makes the source ideal for ultrafast electron diffraction of complex macromolecular structures such as membrane proteins, in a regime unattainable by conventional photocathode sources. By further reducing the source size, sub-um spot sizes on the sample become possible with spatial coherence lengths exceeding 1 nm, enabling ultrafast nano-diffraction for material science.Comment: 5 pages, 4 figure

Smart Search in Newspaper Archives Using Topic Maps

The OmniPaper project has implemented three information retrieval prototypes in the area of electronic news publishing. One prototype uses SOAP as communication protocol between the central system and a number of distributed news archives. The second prototype uses an RDF metadata database, enabling direct metadata queries to the central system. Finally the Topic Map prototype uses query expansion and semantic linking for smart metadata search. The Topic Map prototype enhances thesearch experience by implementing a knowledge layer that combines the semantic content of a lexical database, consisting of concepts and keywords, with a metadata-set of newspaper articles. The linking between both is currently implemented at the level of keywords but will be developed at the level of concepts in the final prototype. The knowledge layer has been designed from a Topic Map point of view, although the XTM syntax has not been used to avoid performance issues. The consortium’s adopted view on information publishing and retrieval considers querying and navigation as two very related actions that can both be captured under the name “search for relevant information”. Navigation forces the user to followpredefined paths whereas querying enables the user to look freely for a suitable starting point. The query and navigation functionality is provided through a web engine and is build on top of the information structure of the knowledge layer

NDM-526: INVESTIGATION OF STABLE AND UNSTABLE FIBER-REINFORCED ELASTOMERIC ISOLATORS

Fiber-reinforced elastomeric isolators (FREIs) are a potentially low-cost alternative to conventional steel-reinforced elastomeric isolators. FREIs can exhibit a non-linear horizontal force-displacement relationship characterized by a softening and stiffening phase, similar to other adaptive isolation devices such as the triple friction pendulum. This non-linear relationship is a consequence of unique deformations that occur during horizontal displacement denoted as rollover, which causes softening, and full rollover, which causes stiffening. The magnitude of the softening due to rollover is primarily governed by the width-to-total height aspect ratio of the FREI. If the aspect ratio is low, below about 2.5, the isolator may be susceptible to horizontal instability where the tangential stiffness becomes negative before increasing due to full rollover. Design codes prevent the use of an isolation system susceptible to horizontal instability within the design displacement. In this paper, experimental testing is used to calibrate a numerical model of a base isolated structure using horizontally unstable and stable FREIs. The performance of the structure is evaluated based on peak displacement of the isolation layer and peak acceleration of the base isolated structure. For the isolators considered, it is shown that the horizontal instability does not have a negative impact on the performance of the structure. It is postulated that some level of horizontal instability may be allowed in the design of unbonded FREIs

Minimizing gravitational lensing contributions to the primordial bispectrum covariance

The next generation of ground-based cosmic microwave background (CMB) experiments aim to measure temperature and polarization fluctuations up to ℓmax≈5000 over half of the sky. Combined with Planck data on large scales, this will provide improved constraints on primordial non-Gaussianity. However, the impressive resolution of these experiments will come at a price. Besides signal confusion from galactic foregrounds, extragalactic foregrounds, and late-time gravitational effects, gravitational lensing will introduce large non-Gaussianity that can become the leading contribution to the bispectrum covariance through the connected four-point function. Here, we compute this effect analytically for the first time on the full sky for both temperature and polarization. We compare our analytical results with those obtained directly from map-based simulations of the CMB sky for several levels of instrumental noise. Of the standard shapes considered in the literature, the local shape is most affected, resulting in a 35% increase of the estimator standard deviation for an experiment such as the Simons Observatory (SO) and a 110% increase for a cosmic-variance limited experiment, including both temperature and polarization modes up to ℓmax=3800. Because of the nature of the lensing four-point function, the impact on other shapes is reduced while still non-negligible for the orthogonal shape. Two possible avenues to reduce the non-Gaussian contribution to the covariance are proposed: First by marginalizing over lensing contributions, such as the Integrated Sachs Wolfe (ISW)-lensing three-point function in temperature, and second by delensing the CMB. We show the latter method can remove almost all extra covariance, reducing the effect to below <5% for local bispectra. At the same time, delensing would remove signal biases from secondaries induced by lensing, such as ISW lensing. We aim to apply both techniques directly to the forthcoming SO data when searching for primordial non-Gaussianity

Item Information in the Rasch Model

Fisher's information measure for the item difficulty parameter in the Rasch model and its marginal and conditional formulations are investigated. It is shown that expected item information in the unconditional model equals information in the marginal model, provided the assumption of sampling examinees from an ability distribution is made. For the logistic ability distribution considered in this paper, item information in the two models can be expressed in a closed form. Also, it is shown that for a random examinee expected item information in the conditional model is always less than that in the other two models, albeit the difference quickly decreases with an increase in test length. If the distribution of the item difficulties in the test deviates more and more from the ability distribution, item information in all three models takes smaller and smaller values. Results from a simulation study of tests with 5 and 20 items demonstrate these features numerically. Six tables present the results of the simulation study, and one graph illustrates item information in the marginal model

CMB B -mode non-Gaussianity

We study the degree to which the cosmic microwave background (CMB) can be used to constrain primordial non-Gaussianity involving one tensor and two scalar fluctuations, focusing on the correlation of one polarization B mode with two temperature modes. In the simplest models of inflation, the tensor-scalar-scalar primordial bispectrum is nonvanishing and is of the same order in slow-roll parameters as the scalar-scalar-scalar bispectrumr. We calculate the {BTT} correlation arising from a primordial tensor-scalar-scalar bispectrum, and show that constraints from an experiment like CMB-Stage IV using this observable are more than an order of magnitude better than those on the same primordial coupling obtained from temperature measurements alone. We argue that B-mode non-Gaussianity opens up an as-yet-unexplored window into the early Universe, demonstrating that significant information on primordial physics remains to be harvested from CMB anisotropies

Joint mapping of genes and conditions via multidimensional unfolding analysis

<p>Abstract</p> <p>Background</p> <p>Microarray compendia profile the expression of genes in a number of experimental conditions. Such data compendia are useful not only to group genes and conditions based on their similarity in overall expression over profiles but also to gain information on more subtle relations between genes and conditions. Getting a clear visual overview of all these patterns in a single easy-to-grasp representation is a useful preliminary analysis step: We propose to use for this purpose an advanced exploratory method, called multidimensional unfolding.</p> <p>Results</p> <p>We present a novel algorithm for multidimensional unfolding that overcomes both general problems and problems that are specific for the analysis of gene expression data sets. Applying the algorithm to two publicly available microarray compendia illustrates its power as a tool for exploratory data analysis: The unfolding analysis of a first data set resulted in a two-dimensional representation which clearly reveals temporal regulation patterns for the genes and a meaningful structure for the time points, while the analysis of a second data set showed the algorithm's ability to go beyond a mere identification of those genes that discriminate between different patient or tissue types.</p> <p>Conclusion</p> <p>Multidimensional unfolding offers a useful tool for preliminary explorations of microarray data: By relying on an easy-to-grasp low-dimensional geometric framework, relations among genes, among conditions and between genes and conditions are simultaneously represented in an accessible way which may reveal interesting patterns in the data. An additional advantage of the method is that it can be applied to the raw data without necessitating the choice of suitable genewise transformations of the data.</p

Delayed life-threatening subdural hematoma after minor head injury in a patient with severe coagulopathy: a case report

Minor head injury is a frequent cause for neurologic consultation and imaging. Most patients with minor head injury will make an uneventful recovery, but in a very small proportion of these patients life threatening intracranial complications occur. We describe a patient on oral anticoagulation therapy, and severely impaired coagulation, with normal head computed tomography on admission, who developed a subdural hematoma requiring surgery 12 hours later. Current guidelines and literature for the management of minor head injury are discussed