Experimental studies of the internal Goos-Hanchen shift for self-collimated beams in two-dimensional microwave photonic crystals

We study experimentally the Goos-Hanchen effect observed at the reflection of a self-collimated beam from the surface of a two-dimensional photonic crystal and describe a method for controlling the beam reflection through surface engineering. The microwave photonic crystal, fabricated from alumina rods, allows control of the output position of a reflected beam undergoing an internal Goos-Hanchen shift by changing the rod diameter at the reflection surface. The experimental data is in good agreement with the results of the finite-difference time-domain numerical calculations.Comment: 3 pages 4 figures, submitted to AP

MESAS: Measuring the Emission of Stellar Atmospheres at Submm/mm wavelengths

In the early stages of planet formation, small dust grains grow to become mm sized particles in debris disks around stars. These disks can in principle be characterized by their emission at submillimeter and millimeter wavelengths. Determining both the occurrence and abundance of debris in unresolved circumstellar disks of A-type main-sequence stars requires that the stellar photospheric emission be accurately modeled. To better constrain the photospheric emission for such systems, we present observations of Sirius A, an A-type star with no known debris, from the JCMT, SMA, and VLA at 0.45, 0.85, 0.88, 1.3, 6.7, and 9.0 mm. We use these observations to inform a PHOENIX model of Sirius A's atmosphere. We find the model provides a good match to these data and can be used as a template for the submm/mm emission of other early A-type stars where unresolved debris may be present. The observations are part of an ongoing observational campaign entitled Measuring the Emission of Stellar Atmospheres at Submm/mm wavelengths (MESAS)Comment: 17 pages, 1 figure, Accepted to AJ on April 25th 201

Indigenous perspectives on integrating learning technologies in a tertiary enabling program

The Centre for Aboriginal Studies at Curtin University offers an Indigenous Tertiary Enabling Course designed to equip Indigenous students for entry into mainstream university degree programs. While the program is highly regarded, it is argued that opportunities offered by incorporating contemporary learning technologies to allow more effective student engagement can deliver more successful outcomes. With this in mind the Centre has undertaken to introduce the use of tablet devices (iPad) and notebook computers (MacBook Air), which will enable a strategic shift towards a more student-centred, technology, integrated model of student engagement with anticipated enhanced outcomes. The Centre has undertaken to trial the use of online teaching and learning strategies in semester 1, 2014. At this pre-tertiary level, it is anticipated the advantages of a student-centred experience will become evident as the trial moves through the year. This paper describes the current conditions and staff perceptions after the first year of implementation as well as comparing outcomes from the most recent ITEC cohort

North American Genetic Counselors\u27 Approach to Collecting and Using Ancestry in Clinical Practice

Current guidelines from the National Society of Genetic Counselors (NSGC) recommend that patients\u27 ancestry be obtained when taking a family history. However, no study has explored how consistently genetic counselors obtain or utilize this information. The goals of this study included assessing how genetic counselors collect their patients\u27 ancestry, what factors influence this decision, and how they view the utility of this information. Genetic counselors working in a direct patient care setting in the US or Canada were recruited to participate in an anonymous survey via an NSGC email blast. Most participants (n = 115) obtain information about their patients\u27 ancestry (96.5%), with the most common methods being directly asking the patient (91%) and utilizing intake forms (43.2%). Of participants who ask about ancestry directly, 50.5% always ask about the presence of Ashkenazi Jewish ancestry and 70.3% always ask about additional ancestries, suggesting that for most genetic counselors’ collection of ancestry is standard practice. However, the clinical utility of ancestry information is highly variable, with the impact on genetic testing choice being particularly low. A slight majority of participants support a reevaluation of current ancestry guidelines (51.3%), with many participants suggesting that the varying utility of ancestry in different clinical indications/specialties should be incorporated into guidelines. Despite being standard practice for most genetic counselors, no unified approach or standard for how ancestral information should be used in genetic counseling practice was identified

Visualizing Spacetime Curvature via Frame-Drag Vortexes and Tidal Tendexes II. Stationary Black Holes

When one splits spacetime into space plus time, the Weyl curvature tensor (which equals the Riemann tensor in vacuum) splits into two spatial, symmetric, traceless tensors: the tidal field $E$, which produces tidal forces, and the frame-drag field $B$, which produces differential frame dragging. In recent papers, we and colleagues have introduced ways to visualize these two fields: tidal tendex lines (integral curves of the three eigenvector fields of $E$) and their tendicities (eigenvalues of these eigenvector fields); and the corresponding entities for the frame-drag field: frame-drag vortex lines and their vorticities. These entities fully characterize the vacuum Riemann tensor. In this paper, we compute and depict the tendex and vortex lines, and their tendicities and vorticities, outside the horizons of stationary (Schwarzschild and Kerr) black holes; and we introduce and depict the black holes' horizon tendicity and vorticity (the normal-normal components of $E$ and $B$ on the horizon). For Schwarzschild and Kerr black holes, the horizon tendicity is proportional to the horizon's intrinsic scalar curvature, and the horizon vorticity is proportional to an extrinsic scalar curvature. We show that, for horizon-penetrating time slices, all these entities ($E$, $B$, the tendex lines and vortex lines, the lines' tendicities and vorticities, and the horizon tendicities and vorticities) are affected only weakly by changes of slicing and changes of spatial coordinates, within those slicing and coordinate choices that are commonly used for black holes. [Abstract is abbreviated.]Comment: 19 pages, 7 figures, v2: Changed to reflect published version (changes made to color scales in Figs 5, 6, and 7 for consistent conventions). v3: Fixed Ref

The First Scattered Light Image of the Debris Disk around the Sco-Cen target HD 129590

We present the first scattered light image of the debris disk around HD 129590, a ~1.3 M$_\odot$ G1V member of the Scorpius Centaurus association with age ~10-16 Myr. The debris disk is imaged with the high contrast imaging instrument SPHERE at the Very Large Telescope, and is revealed by both the IRDIS and IFS subsytems, operating in the H and YJ bands respectively. The disk has a high infrared luminosity of $L_{\textrm{IR}}/L_{\textrm{star}}$~5$\times$10$^{-3}$, and has been resolved in other studies using ALMA. We detect a nearly edge on ring, with evidence of an inner clearing. We fit the debris disk using a model characterized by a single bright ring, with radius ~60-70 AU, in broad agreement with previous analysis of the target SED. The disk is vertically thin, and has an inclination angle of ~75$^\circ$. Along with other previously imaged edge-on disks in the Sco-Cen association such as HD 110058, HD 115600, and HD 111520, this disk image will allow of the structure and morphology of very young debris disks, shortly after the epoch of planet formation has ceased.Comment: 8 pages, 4 figures. Accepted for publication in ApJ

Frame-Dragging Vortexes and Tidal Tendexes Attached to Colliding Black Holes: Visualizing the Curvature of Spacetime

When one splits spacetime into space plus time, the spacetime curvature (Weyl tensor) gets split into an "electric" part E_{jk} that describes tidal gravity and a "magnetic" part B_{jk} that describes differential dragging of inertial frames. We introduce tools for visualizing B_{jk} (frame-drag vortex lines, their vorticity, and vortexes) and E_{jk} (tidal tendex lines, their tendicity, and tendexes), and also visualizations of a black-hole horizon's (scalar) vorticity and tendicity. We use these tools to elucidate the nonlinear dynamics of curved spacetime in merging black-hole binaries.Comment: 4 pages, 5 figure

Visualizing Spacetime Curvature via Frame-Drag Vortexes and Tidal Tendexes III. Quasinormal Pulsations of Schwarzschild and Kerr Black Holes

In recent papers, we and colleagues have introduced a way to visualize the full vacuum Riemann curvature tensor using frame-drag vortex lines and their vorticities, and tidal tendex lines and their tendicities. We have also introduced the concepts of horizon vortexes and tendexes and 3-D vortexes and tendexes (regions where vorticities or tendicities are large). Using these concepts, we discover a number of previously unknown features of quasinormal modes of Schwarzschild and Kerr black holes. These modes can be classified by mode indexes (n,l,m), and parity, which can be electric [(-1)^l] or magnetic [(-1)^(l+1)]. Among our discoveries are these: (i) There is a near duality between modes of the same (n,l,m): a duality in which the tendex and vortex structures of electric-parity modes are interchanged with the vortex and tendex structures (respectively) of magnetic-parity modes. (ii) This near duality is perfect for the modes' complex eigenfrequencies (which are well known to be identical) and perfect on the horizon; it is slightly broken in the equatorial plane of a non-spinning hole, and the breaking becomes greater out of the equatorial plane, and greater as the hole is spun up; but even out of the plane for fast-spinning holes, the duality is surprisingly good. (iii) Electric-parity modes can be regarded as generated by 3-D tendexes that stick radially out of the horizon. As these "longitudinal," near-zone tendexes rotate or oscillate, they generate longitudinal-transverse near-zone vortexes and tendexes, and outgoing and ingoing gravitational waves. The ingoing waves act back on the longitudinal tendexes, driving them to slide off the horizon, which results in decay of the mode's strength. (iv) By duality, magnetic-parity modes are driven in this same manner by longitudinal, near-zone vortexes that stick out of the horizon. [Abstract abridged.]Comment: 53 pages with an overview of major results in the first 11 pages, 26 figures. v2: Very minor changes to reflect published version. v3: Fixed Ref