Narrow Results

We introduce a method to isolate the contribution of parity-violating modes to the peak constrained correlation function. This method can be used as a local estimate of polarization rotation. We test this method using simulations and by applying it to Planck maps [P. A. R. Ade et al., arXiv:1502.01589 astro.ph.co]. We obtain a constraint on the monopole of the polarization rotation angle $\alpha =0.31\pm 0.23$.

Bioglasses are promising alternatives as biomedical materials to repair or replace damaged parts of bones because of its good bioactivity and biocompatibility. It is possible to combine the bone-bonding ability of the bioglass surface with the high mechanical properties of the metallic substrate though the coating of metallic implants with bioglass. The principles and characteristics of some coating techniques, including sintering, plasma spray, sol-gel, electrophoresis deposition, ion beam assisted deposition and pulsed laser deposition, are introduced. Their current applications in preparing bioglass coatings are reviewed in detail. The future application trends are also reviewed.

Ground-based long-baseline astronomical interferometry operates in a regime where short integration exposures are demanded by working in the presence of a turbulent atmosphere. To reduce piston noise to less than one radian per aperture, these exposure times are on order 10 milliseconds or less in the visible. It has long been recognized that, in the low signal-to-noise ratio (SNR) regime, the visibility SNR is improved by co-adding frames, each rotated by an estimate of its phase. However, implementation of this technique is challenging. Where it is most needed, on low SNR baselines and when combining multiple phases to estimate the phase for a lower SNR baseline, phase errors reduce the amplitude by a large amount and in a way that has proven difficult to calibrate. In this paper, an improved coherent integration algorithm is presented. A parameterized model for the phase as a function of time and wavelength is fit to the entire data set. This framework is used to build a performance model which can be used in two ways. First, it can be used to test the algorithm; by comparing its performance to theory, one can test how well the parameter fitting has worked. Also, when designing future systems, this model provides a simple way to predict performance and compare it to alternative techniques such as hierarchical fringe tracking. This technique has been applied to both simulated and stellar data.

We introduce an observational tool based on visibility nulls in optical spectro-interferometry fringe data to probe the structure of stellar atmospheres. In a preliminary demonstration, we use both Navy Precision Optical Interferometer (NPOI) data and stellar atmosphere models to show that this tool can be used, for example, to investigate limb darkening.

Using bootstrapping with either multiple linked baselines or multiple wavelengths in optical and infrared spectro-interferometric observations of stars makes it possible to measure the spatial frequency $u_0$ at which the real part of the fringe visibility $\mathrm{\text{Re}}(V)$ vanishes. That spatial frequency is determined by $u_0=B_{\perp }/{\lambda }_0$, where $B_{\perp }$ is the projected baseline length, and ${\lambda }_0$ is the wavelength at which the null is observed. Since $B_{\perp }$ changes with the Earth’s rotation, ${\lambda }_0$ also changes. If $u_0$ is constant with wavelength, ${\lambda }_0$ varies in direct proportion to $B_{\perp }$. Any departure from that proportionality indicates that the brightness distribution across the stellar disk varies with wavelength via variations in limb darkening, in the angular size of the disk, or both.

In this paper, we introduce the use of variations of $u_0$ with $\lambda$ as a means of probing the structure of stellar atmospheres. Using the equivalent uniform disk diameter ${\theta }_{\mathrm{\text{UD}},0}({\lambda }_0)$, given by ${\theta }_{\mathrm{\text{UD}},0}=1.22/u_0({\lambda }_0)$, as a convenient and intuitive parameterization of $u_0({\lambda }_0)$, we demonstrate this concept by using model atmospheres to calculate the brightness distribution for $\nu$ Ophiuchi and to predict ${\theta }_{\mathrm{\text{UD}},0}({\lambda }_0)$, and then comparing the predictions to coherently averaged data from observations taken with the NPOI.

Distance measurement is crucial to astronomy. Here, we suggest a new conceptual method to measure the distance by using a local instrument. By engaging the double-slit interference and by considering the phase information of the light, the position of the intensity maximum is related to the distance of the source. Consequently, the precise measurement of the position can be used to measure the distance of the remote source.

The Mexican Array Radio Telescope (MEXART), located in the state of Michoacan in Mexico, has been operating in an analog fashion, utilizing a Butler Matrix to generate fixed beams on the sky, since its inception. Calibrating this instrument has proved difficult, leading to loss in sensitivity. It was also a rigid setup, requiring manual intervention and tuning for different observation requirements. The Radio Frequency (RF) system has now been replaced with a digital one. This digital backend is a hybrid system utilizing both FPGA-based technology and GPU acceleration, and is capable of automatically calibrating the different rows of the array, as well as generating a configurable number of frequency-domain synthesized beams to towards selected locations on the sky. A monitoring and control system, together with a full-featured web-based front-end, has also been developed, greatly simplifying the interaction with the instrument. This paper presents the design, implementation and deployment of the new digital backend, including preliminary analysis of system performance and stability.

Professional futurologists have turned their speculative ideas and theories into concepts that are well worth considering by educational planners and professionals in the fields of education to create a new field of professional concern — educational futurism. We must become more receptive to it, while also considering the futuristic thought that indicates an increasing awareness among the general public of the need for serious thinking about the future. The necessity of preparing people for the future requires that we exercise considerable imagination and insight in speculating as to what the future will bring, what skills will be necessary, what jobs and occupations will be in demand, and what sort of lives the majority of people will lead in the following years.

Modern gait analysis results in large quantities of correlated data. A current challenge in the field is the development of appropriate data analysis techniques for the representation and interpretation of these data. Knee osteoarthritis is a common debilitating disease of the musculoskeletal system that has been the focus of many gait studies in recent years. Various data analysis techniques have been used to extract pathological information from gait data in these studies. The following review discusses the successes and limitations of many of these analysis techniques in the attempt to understand the biomechanics of knee osteoarthritis.