The High-Flux Backscattering Spectrometer at the NIST Center for Neutron Research

We describe the design and current performance of the high-flux backscattering spectrometer located at the NIST Center for Neutron Research. The design incorporates several state-of-the-art neutron optical devices to achieve the highest flux on sample possible while maintaining an energy resolution of less than 1mueV. Foremost among these is a novel phase-space transformation chopper that significantly reduces the mismatch between the beam divergences of the primary and secondary parts of the instrument. This resolves a long-standing problem of backscattering spectrometers, and produces a relative gain in neutron flux of 4.2. A high-speed Doppler-driven monochromator system has been built that is capable of achieving energy transfers of up to +-50mueV, thereby extending the dynamic range of this type of spectrometer by more than a factor of two over that of other reactor-based backscattering instruments

Discovery of a Low-mass Companion Around HR 3549

We report the discovery of a low-mass companion to HR 3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 μm (10σ significance). We imaged HR 3549 B in the L band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in 2015 January. The companion is at a projected separation of ≃80 AU and position angle of ≃157°, so it is orbiting well beyond the warm disk inner edge of r > 10 AU. Our age estimate for this system corresponds to a companion mass in the range 15–80 M_J, spanning the brown dwarf regime, and so HR 3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR 3549 provides interesting empirical constraints on models of the formation of substellar companions

Effects of aspect ratio on the mode couplings of thin-film bulk acoustic wave resonators

We studied mode couplings in thin film bulk acoustic wave resonators of a piezoelectric film on a dielectric layer operating with the fundamental thickness-extensional mode. A system of plate equations derived in our previous paper was used which includes the couplings to the unwanted in-plane extension, flexure, fundamental and second-order thickness shear modes. It was shown that the couplings depend strongly on the plate length/thickness ratio. For a relatively clean operating mode with weak couplings to unwanted modes, a series of discrete values of the plate length/thickness ratio should be avoided and these values were determined in the present paper. The results can be of great significance to the design and optimization of film bulk acoustic wave resonators

Improving the Information Security Model by using TFI

In the context of information systems and information technology, information security is a concept that is becoming widely used. The European Network of Excellence INTEROP classifies information security as a nonfunctional aspect of interoperability and as such it is an integral part of the design process for interoperable systems. In the last decade, academics and practitioners have shown their interest in information security, for example by developing security models for evaluating products and setting up security specifications in order to safeguard the confidentiality, integrity, availability and accountability of data. Earlier research has shown that measures to achieve information security in the administrative or organisational level are missing or inadequate. Therefore, there is a need to improve information security models by including vital elements of information security. In this paper, we introduce a holistic view of information security based on a Swedish model combined with a literature survey. Furthermore we suggest extending this model using concepts based on semiotic theory and adopting the view of an information system as constituted of the technical, formal and informal (TFI) parts. The aim is to increase the understanding of the information security domain in order to develop a well-founded theoretical framework, which can be used both in the analysis and the design phase of interoperable systems. Finally, we describe and apply the Information Security (InfoSec) model to the results of three different case studies in the healthcare domain. Limits of the model will be highlighted and an extension will be proposed.In the context of information systems and information technology, information security is a concept that is becoming widely used. The European Network of Excellence INTEROP classifies information security as a nonfunctional aspect of interoperability and as such it is an integral part of the design process for interoperable systems. In the last decade, academics and practitioners have shown their interest in information security, for example by developing security models for evaluating products and setting up security specifications in order to safeguard the confidentiality, integrity, availability and accountability of data. Earlier research has shown that measures to achieve information security in the administrative or organisational level are missing or inadequate. Therefore, there is a need to improve information security models by including vital elements of information security. In this paper, we introduce a holistic view of information security based on a Swedish model combined with a literature survey. Furthermore we suggest extending this model using concepts based on semiotic theory and adopting the view of an information system as constituted of the technical, formal and informal (TFI) parts. The aim is to increase the understanding of the information security domain in order to develop a well-founded theoretical framework, which can be used both in the analysis and the design phase of interoperable systems. Finally, we describe and apply the Information Security (InfoSec) model to the results of three different case studies in the healthcare domain. Limits of the model will be highlighted and an extension will be proposed.Monograph's chapter

Comparative analysis of the diffuse radio emission in the galaxy clusters A1835, A2029, and Ophiuchus

We recently performed a study of a sample of relaxed, cooling core galaxy clusters with deep Very Large Array observations at 1.4 GHz. We find that in the central regions of A1835, A2029, and Ophiuchus the dominant radio galaxy is surrounded by a diffuse low-brightness radio emission that takes the form of a mini-halo. Here we present the results of the analysis of the extended diffuse radio emission in these mini-halos. In order to investigate the morphological properties of the diffuse radio emission in clusters of galaxies we propose to fit their azimuthally averaged brightness profile with an exponential, obtaining the central brightness and the e-folding radius from which the radio emissivity can be calculated. We investigate the radio properties of the mini-halos in A1835, A2029, and Ophiuchus in comparison with the radio properties of a representative sample of mini-halos and halos already known in the literature. We find that radio halos can have quite different length-scales but their emissivity is remarkably similar from one halo to the other. In contrast, mini-halos span a wide range of radio emissivity. Some of them, like the Perseus mini-halos, are characterized by a radio emissivity which is more than 100 times greater than that of radio halos. On the other hand, the new mini-halos in cooling core clusters analyzed in this work, namely A2029, Ophiuchus, and A1835, have a radio emissivity which is much more typical of halos in merging clusters rather than similar to that of the other mini-halos previously known.Comment: 17 pages, 11 figures, A&A in press. For a version with high quality figures, see http://erg.ca.astro.it/preprints/mini_halo_2

Salmon at River\u27s End: The Role of the Estuary in the Decline and Recovery of Columbia River salmon

The continued decline of Columbia River salmon (Oncorhynchus spp.) populations has long focused concerns on habitat changes upriver, particularly the effects of large hydroelectric dams. Increasing evidence that ocean conditions strongly influence salmon production, however, has raised questions about the importance of the estuarine environment to salmon and whether the hydropower system has affected estuarine-rearing habitats. In response to Northwest Power Planning Council recommendations, we initiated a review of what is known about the effects of the hydroelectric system on the hydrology, habitats, and ecology of the Columbia River estuary. Our goal was to develop recommendations for improving estuarine conditions or to identify research that may be needed before appropriate salmon-management changes can be defined. Our review and analyses addressed four major questions: (1) What habitats and processes support native salmon populations during the estuarine phase of their life cycle? (2) Have changes to the estuary had a significant role in salmon decline? (3) What have been the impacts of flow regulation on the hydrology, habitat, and biological interactions in the estuarine ecosystem? (4) What estuarine conditions are necessary to maintain salmonid diversity in the Columbia River basin

Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy

An important technique for discovering and characterizing planets beyond our solar system relies upon measurement of weak Doppler shifts in the spectra of host stars induced by the influence of orbiting planets. A recent advance has been the introduction of optical frequency combs as frequency references. Frequency combs produce a series of equally spaced reference frequencies and they offer extreme accuracy and spectral grasp that can potentially revolutionize exoplanet detection. Here we demonstrate a laser frequency comb using an alternate comb generation method based on electro-optical modulation, with the comb centre wavelength stabilized to a molecular or atomic reference. In contrast to mode-locked combs, the line spacing is readily resolvable using typical astronomical grating spectrographs. Built using commercial off-the-shelf components, the instrument is relatively simple and reliable. Proof of concept experiments operated at near-infrared wavelengths were carried out at the NASA Infrared Telescope Facility and the Keck-II telescope

Development of in-situ trap characterisation techniques for EMCCDs

The "trap pumping" technique has seen considerable use over recent years as a means to probe the intrinsic properties of silicon defects that can impact charge transfer performance within CCD-based technologies. While the theory behind the technique is reasonably well understood, it has to date only been applied to relatively simple pixel designs where the motion of charge between pixel phases is fairly easy to predict. For some devices, the intrinsic pixel architecture is more complex and can consist of unequal phase sizes and additional implants that deform the electronic potential. Here, we present the implementation of the trap pumping technique for the CCD201-20, a 2-phase Teledyne e2v EMCCD. Clocking schemes are presented that can provide the location of silicon defects to sub-micron resolution. Experimental techniques that allow determination of trap energy levels and emission cross sections are presented. These are then implemented on an irradiated CCD201-20 to determine the energy level and emission cross section for defects thought to be the double acceptor state of the silicon divacancy (VV--) and carbon-phosphorus (CiPs) pairs. An improvement in charge transfer performance through optimised parallel clock delay is demonstrated and found to correlate with the properties of defects found using the trap pumping technique

Comparing the development of cortex-wide gene expression patterns between two species in a common reference frame

Advances in sequencing techniques have made comparative studies of gene expression a current focus for understanding evolutionary and developmental processes. However, insights into the spatial expression of genes have been limited by a lack of robust methodology. To overcome this obstacle, we developed methods and software tools for quantifying and comparing tissue-wide spatial patterns of gene expression within and between species. Here, we compare cortex-wide expression of RZRβ and Id2 mRNA across early postnatal development in mice and voles. We show that patterns of RZRβ expression in neocortical layer 4 are highly conserved between species but develop rapidly in voles and much more gradually in mice, who show a marked expansion in the relative size of the putative primary visual area across the first postnatal week. Patterns of Id2 expression, by contrast, emerge in a dynamic and layer-specific sequence that is consistent between the two species. We suggest that these differences in the development of neocortical patterning reflect the independent evolution of brains, bodies, and sensory systems in the 35 million years since their last common ancestor