Large area Czochralski silicon

The overall cost effectiveness of the Czochralski process for producing large-area silicon was determined. The feasibility of growing several 12 cm diameter crystals sequentially at 12 cm/h during a furnace run and the subsequent slicing of the ingot using a multiblade slurry saw were investigated. The goal of the wafering process was a slice thickness of 0.25 mm with minimal kerf. A slice + kerf of 0.56 mm was achieved on 12 cm crystal using both 400 grit B4C and SiC abrasive slurries. Crystal growth experiments were performed at 12 cm diameter in a commercially available puller with both 10 and 12 kg melts. Several modifications to the puller hoz zone were required to achieve stable crystal growth over the entire crystal length and to prevent crystallinity loss a few centimeters down the crystal. The maximum practical growth rate for 12 cm crystal in this puller design was 10 cm/h, with 12 to 14 cm/h being the absolute maximum range at which melt freeze occurred

The Spectral Evolution of Transient Anomalous X-ray Pulsar XTE J1810--197

(Abridged) We present a multi-epoch spectral study of the Transient Anomalous X-ray Pulsar XTE J1810-197 obtained with the XMM X-ray telescope. Four observations taken over the course of a year reveal strong spectral evolution as the source fades from outburst. The origin of this is traced to the individual decay rates of the pulsar's spectral components. A 2-T fit at each epoch requires nearly constant temperatures of kT=0.25 & 0.67 keV while the component luminosities decrease exponentially with tau=900 & 300d, respectively. One possible interpretation is that the slowly decaying cooler component is the radiation from a deep heating event that affected a large fraction of the crust, while the hotter component is powered by external surface heating at the foot-points of twisted magnetic field lines, by magnetospheric currents that are decaying more rapidly. The energy-dependent pulse profile of XTE J1810-197 is well modeled at all epochs by the sum of a sine and triangle function. These profiles peak at the same phase, suggesting a concentric surface emission geometry. The spectral and pulse evolution together argue against the presence of a significant ``power-law'' contribution to the X-ray spectrum below 8 keV. The extrapolated flux is projected to return to the historic quiescent level, characterized by an even cooler blackbody spectrum, by the year 2007.Comment: 12 pages, 6 Figures, Latex, emulateapj. To appear in the Astrophysical Journa

Optical Observations of PSR J0205+6449 - the next optical pulsar?

PSR J0205+6449 is a young ({\approx} 5400 years), Crab-like pulsar detected in radio and at X and {\gamma}-ray energies and has the third largest spin-down flux among known rotation powered pulsars. It also powers a bright synchrotron nebula detected in the optical and X-rays. At a distance of {\approx} 3.2 kpc and with an extinction comparable to the Crab, PSR J0205+6449 is an obvious target for optical observations. We observed PSR J0205+6449 with several optical facilities, including 8m class ground-based telescopes, such as the Gemini and the Gran Telescopio Canarias. We detected a point source, at a significance of 5.5{\sigma}, of magnitude i {\approx} 25.5, at the centre of the optical synchrotron nebula, coincident with the very accurate Chandra and radio positions of the pulsar. Thus, we discovered a candidate optical counterpart to PSR J0205+6449. The pulsar candidate counterpart is also detected in the g ({\approx}27.4) band and weakly in the r ({\approx}26.2) band. Its optical spectrum is fit by a power law with photon index {\Gamma}0 = 1.9{\pm}0.5, proving that the optical emission if of non-thermal origin, is as expected for a young pulsar. The optical photon index is similar to the X-ray one ({\Gamma}X = 1.77{\pm}0.03), although the optical fluxes are below the extrapolation of the X-ray power spectrum. This would indicate the presence of a double spectral break between the X-ray and optical energy range, at variance with what is observed for the Crab and Vela pulsars, but similar to the Large Magellanic Cloud pulsar PSR B0540-69.Comment: 13 Pages, 4 Tables, 7 Figures, Accepted for publication in MNRA

Long term hard X-ray variability of the anomalous X-ray pulsar 1RXS J170849.0-400910 discovered with INTEGRAL

We report on a multi-band high-energy observing campaign aimed at studying the long term spectral variability of the Anomalous X-ray Pulsar (AXP) 1RXS J170849.0-400910, one of the magnetar candidates. We observed 1RXS J170849.0-400910 in Fall 2006 and Spring 2007 simultaneously with Swift/XRT, in the 0.1-10 keV energy range, and with INTEGRAL/IBIS, in the 20-200 keV energy range. Furthermore, we also reanalyzed, using the latest calibration and software, all the publicly available INTEGRAL data since 2002, and the soft X-ray data starting from 1999 taken using BeppoSAX, Chandra, XMM, and Swift/XRT, in order to study the soft and hard X-ray spectral variability of 1RXS J170849.0-400910. We find a long-term variability of the hard X-ray flux, extending the hardness-intensity correlation proposed for this source over 2 orders of magnitude in energy.Comment: 5 pages, 2 figures, accepted for publication in Astronomy & Astrophysics main journa

VLT observations of the magnetar CXO J164710.2-455216 and the detection of a candidate infrared counterpart

We present deep observations of the field of the magnetar CXOJ164710.2-455216 in the star cluster Westerlund 1, obtained in the near-infrared with the adaptive optics camera NACO@VLT. We detected a possible candidate counterpart at the {\em Chandra} position of the magnetar, of magnitudes $\mathrm{J} = 23.5 \pm 0.2$, $\mathrm{H} = 21.0 \pm 0.1$, and $\mathrm{K}_\mathrm{S} = 20.4 \pm 0.1$. The K$_{\rm S}$-band measurements available for two epochs (2006 and 2013) do not show significant signs of variability but only a marginal indication that the flux varied (at the 2 $\sigma$ level), consistent with the fact that the observations were taken when CXOJ164710.2-455216 was in quiescence. At the same time, we also present colour--magnitude and colour--colour diagrams in the J, H, and K$_{\rm S}$ bands from the 2006 epoch only, the only one with observations in all three bands, showing that the candidate counterpart lies in the main bulk of objects describing a relatively well--defined sequence. Therefore, based on its colours and lack of variability, we cannot yet associate the candidate counterpart to CXOJ164710.2-455216. Future near-infrared observations of the field, following-up a source outburst, would be crucial to confirm the association from the detection of near-infrared variability and colour evolution.Comment: 5 pages, 3 figures, accepted for publication in MNRA

Heartbreak, Spirit, and Hope: Leading a School in the Throes and Aftermath of a School Crisis.

Ed.D. Thesis. University of Hawaiʻi at Mānoa 2017

Hybrid Inspection Robot for Indoor and Outdoor Surveys

In this paper, simulation and experimental tests are reported for a hybrid robot being used for indoor and outdoor inspections. Automatic or tele-operated surveys can be performed by mobile robots, which represent the most efficient solution in terms of power consumption, control, robustness, and overall costs. In the context of structures and infrastructure inspection, robots must be able to move on horizontal or sloped surfaces and overpass obstacles. In this paper, the mechatronic design, simulations, and experimental activity are proposed for a hybrid robot being used for indoor and outdoor inspections, when the environmental conditions do not allow autonomous navigation. In particular, the hybrid robot is equipped with external and internal sensors to acquire information on the main structural elements, avoiding the need for experienced personnel being directly inside the inspection site, taking information from the environment and aiding the pilot to understand the best maneuvers/decisions to take. Given the current state of research and shortcomings worldwide, this paper discusses inspection robots taking into account the main issues in their use, functionality and standard systems, and how internal sensors can be set in order to improve inspection robots’ performances. On this basis, an illustrative study case is proposed

Design and Development of an Inspection Robotic System for Indoor Applications

The inspection and monitoring of industrial sites, structures, and infrastructure are important issues for their sustainability and further maintenance. Although these tasks are repetitive and time consuming, and some of these environments may be characterized by dust, humidity, or absence of natural light, classical approach relies on large human activities. Automatic or robotic solutions can be considered useful tools for inspection because they can be effective in exploring dangerous or inaccessible sites, at relatively low-cost and reducing the time required for the relief. The development of a paradigmatic system called Inspection Robotic System (IRS) is the main objective of this paper to demonstrate the feasibility of mechatronic solutions for inspection of industrial sites. The development of such systems will be exploited in the form of a tool kit to be flexible and installed on a mobile system, in order to be used for inspection and monitoring, possibly introducing high efficiency, quality and repetitiveness in the related sector. The interoperability of sensors with wireless communication may form a smart sensors tool kit and a smart sensor network with powerful functions to be effectively used for inspection purposes. Moreover, it may constitute a solution for a broad range of scenarios spacing from industrial sites, brownfields, historical sites or sites dangerous or difficult to access by operators. First experimental tests are reported to show the engineering feasibility of the system and interoperability of the mobile hybrid robot equipped with sensors that allow real-time multiple acquisition and storage

Cholesterol metabolism in the endoplasmic reticulum of rat liver

In work directed towards the purification of a liver microsomal cytochrome P-450 species capable of supporting cholesterol 7a-hydroxylase activity in a reconstituted system, the use of the detergent Renex 690 for the solubilisation of microsomal protein resulted in an unacceptable inhibition of cholesterol 7ct-hydroxylation. This confirmed previous work, showing that Nonidet P42 is the optimum choice of solubilising agent for this purpose. DEAE-cellulose chromatography of microsomal protein solubilised with Nonidet P42 was confirmed to be a suitable first step in the purification of liver microsomal cytochrome P-450, since there is a good separation of this species from NADPH cytochrome c reductase activity. However, the recovery and purification of total cytochrome P-450 was low. Dithiothreitol, 4-phenyl-imidazole, diethyldithiocarbamate and glycerol, by themselves or in combination with each other, were shown to be useful agents in liver microsomal cytochrome P-450 purification. It was further demonstrated that increasing the recovery of cytochrome P-450 gave a concomitant improvement in its purification. Chromatography on quaternary aminoethyl-Sephadex or on carboxymethylcellulose did not result in any purification of cytochrome P-450. Hydroxyapatite chromatography of cytochrome P-450 - containing fractions from the DEAE-cellulose eluate gave a further small purification of cytochrome P-450. The use of chemical donors of "active oxygen" in the reconstitution of cholesterol 7a-hydroxylase activity with liver microsomal cytochrome P-450 was shown to be limited by the rapid destruction of the cytochrome by these agents

Development of a mechatronic system for the mirror therapy

This paper fits into the field of research concerning robotic systems for rehabilitation. Robotic systems are going to be increasingly used to assist fragile persons and to perform rehabilitation tasks for persons affected by motion injuries. Among the recovery therapies, the mirror therapy was shown to be effective for the functional recovery of an arm after stroke. In this paper we present a master/slave robotic device based on the mirror therapy paradigm for wrist rehabilitation. The device is designed to orient the affected wrist in real time according to the imposed motion of the healthy wrist. The paper shows the kinematic analysis of the system, the numerical simulations, an experimental mechatronic set-up, and a built 3D-printed prototype