Search results for " phantom"

2015

Background Accurate evaluation of immunostained histological images is required for reproducible research in many different areas and forms the basis of many clinical decisions. The quality and efficiency of histopathological evaluation is limited by the information content of a histological image, which is primarily encoded as perceivable contrast differences between objects in the image. However, the colors of chromogen and counterstain used for histological samples are not always optimally distinguishable, even under optimal conditions. Methods and Results In this study, we present a method to extract the bivariate color map inherent in a given histological image and to retrospectively o…

Staggered magnetic nanowire devices for effective domain-wall pinning in racetrack memory

2019

Domain-wall memory devices, in which the information is stored in nanowires, are expected to replace hard disk drives. A problem that remains to be solved in domain-wall memory is to pin the domain walls in a controllable manner at the nanometer scale using simple fabrication. We demonstrate the possibility to stabilize domain walls by making staggered nanowires. Controllable domain-wall movement is exhibited in permalloy nanowires using magnetic fields where the pinning field is about 10 mT. The pinning field and stability of the domain walls can be increased by adjusting the offset dimensions of the staggered nanowires. Domain-wall velocities of about 200 m/s are computed for the experime…

Quantum size effects in solitary wires of bismuth

2007

We have performed four-probe electrical transport measurements on solitary highly crystalline wires of semimetallic bismuth with aspect ratios up to 60 at room and at cryogenic temperatures. By proper choice of the substrate material and the film deposition parameters, lithographic wires with lateral dimensions of down to one single grain, $\sim 250$ nm, were fabricated. The electrical resistance of each wire was measured against its thickness through successive reactive ion etching of the self-same wire. Quantum size effects revealed themselves as regular oscillations in the electrical resistance. Some evidence for the semimetal-to-semiconductor phase transition has been detected. The meas…

Selective Excitation of Guided Waves into Bone Phantoms by a Time-Delayed Laser Diode Array

2012

We excite selectively the Ao and So plate mode into an acrylic bone phantom using a laser diode array. This is done by controlling the time delay between the signals driving the array elements. Selective mode generation is important because it can potentially increase the sensitivity of in vivo osteoporosis screening.

Optical pulling and pushing forces in bilayer PT-symmetric structures

2018

Photons are massless, yet can exert force on small particles. This $r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n$ $p\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e$, though discussed by Kepler, still needs investigation for modern systems. This study reveals that the optical force exerted on a parity-time-symmetric bilayer with balanced gain and loss can be $a\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0…

Phantom size in brachytherapy source dosimetric studies

2004

An important point to consider in a brachytherapy dosimetry study is the phantom size involved in calculations or experimental measurements. As pointed out by Williamson [Med. Phys. 18, 776-786 (1991)] this topic has a relevant influence on final dosimetric results. Presently, one-dimensional (1-D) algorithms and newly-developed 3-D correction algorithms are based on physics data that are obtained under full scatter conditions, i.e., assumed infinite phantom size. One can then assume that reference dose distributions in source dosimetry for photon brachytherapy should use an unbounded phantom size rather than phantom-like dimensions. Our aim in this paper is to study the effect of phantom s…

Sensitivity recovery for the AX-PET prototype using inter-crystal scattering events

2014

The development of novel detection devices and systems such as the AX-positron emission tomography (PET) demonstrator often introduce or increase the measurement of atypical coincidence events such as inter-crystal scattering (ICS). In more standard systems, ICS events often go undetected and the small measured fraction may be ignored. As the measured quantity of such events in the data increases, so too does the importance of considering them during image reconstruction. Generally, treatment of ICS events will attempt to determine which of the possible candidate lines of response (LoRs) correctly determine the annihilation photon trajectory. However, methods of assessment often have low su…

2021-$H_0$ Odyssey: Closed, Phantom and Interacting Dark Energy Cosmologies

2021

Up-to-date cosmological data analyses have shown that \textit{(a)} a closed universe is preferred by the Planck data at more than $99\%$ CL, and \textit{(b)} interacting scenarios offer a very compelling solution to the Hubble constant tension. In light of these two recent appealing scenarios, we consider here an interacting dark matter-dark energy model with a non-zero spatial curvature component and a freely varying dark energy equation of state in both the quintessential and phantom regimes. When considering Cosmic Microwave Background data only, a phantom and closed universe can perfectly alleviate the Hubble tension, without the necessity of a coupling among the dark sectors. Accountin…

Experiments on the Parallel Hall Effect in Three-Dimensional Metamaterials

2017

The usual Hall effect in a semiconductor leads to a voltage perpendicular to an applied static magnetic field. The authors significantly extend their recent work and demonstrate $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ that not only the sign but also the direction of the Hall field can be tailored by a metamaterial's microstructure. They show that, with judicious engineering, the Hall voltage can be $p\phantom{\rule{0}{0…

Transit dose comparisons for60Co and192Ir HDR sources

2016

The goal of this study is to evaluate the ambient dose due to the transit of high dose rate (HDR) 60Co sources along a transfer tube as compared to 192Ir ones in a realistic clinical scenario. This goal is accomplished by evaluating air-kerma differences with Monte Carlo calculations using PENELOPE2011. Scatter from both the afterloader and the patient was not taken into account. Two sources, mHDR-v2 and Flexisource Co-60, (Elekta Brachytherapy, Veenendaal, the Netherlands) have been considered. These sources were simulated within a standard transfer tube located in an infinite air phantom. The movement of the source was included by displacing their positions along the connecting tube from …