Browsing by Author "Physics, School of Science"
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Item 3D Printing of Human Ossicle Models for the Biofabrication of Personalized Middle Ear Prostheses(MDPI, 2022-10-31) Dairaghi, Jacob; Rogozea, Dan; Cadle, Rachel; Bustamante, Joseph; Moldovan, Leni; Petrache, Horia I.; Moldovan, Nicanor I.; Physics, School of ScienceThe middle ear bones (‘ossicles’) may become severely damaged due to accidents or to diseases. In these situations, the most common current treatments include replacing them with cadaver-derived ossicles, using a metal (usually titanium) prosthesis, or introducing bridges made of biocompatible ceramics. Neither of these solutions is ideal, due to the difficulty in finding or producing shape-matching replacements. However, the advent of additive manufacturing applications to biomedical problems has created the possibility of 3D-printing anatomically correct, shape- and size-personalized ossicle prostheses. To demonstrate this concept, we generated and printed several models of ossicles, as solid, porous, or soft material structures. These models were first printed with a plottable calcium phosphate/hydroxyapatite paste by extrusion on a solid support or embedded in a Carbopol hydrogel bath, followed by temperature-induced hardening. We then also printed an ossicle model with this ceramic in a porous format, followed by loading and crosslinking an alginate hydrogel within the pores, which was validated by microCT imaging. Finally, ossicle models were printed using alginate as well as a cell-containing nanocellulose-based bioink, within the supporting hydrogel bath. In selected cases, the devised workflow and the printouts were tested for repeatability. In conclusion, we demonstrate that moving beyond simplistic geometric bridges to anatomically realistic constructs is possible by 3D printing with various biocompatible materials and hydrogels, thus opening the way towards the in vitro generation of personalized middle ear prostheses for implantation.Item A High Sensitivity Custom-Built Vibrating Sample Magnetometer(MDPI, 2022-08) Phillips, Jared Paul; Yazdani, Saeed; Highland, Wyatt; Cheng, Ruihua; Physics, School of ScienceThis work details the construction and optimization of a fully automated, custom-built, remote controlled vibrating sample magnetometer for use in spintronics related research and teaching. Following calibration by a standard 6 mm diameter Ni disc sample with known magnetic moment, hysteresis measurements of Nd-Fe-B thin films acquired by this built vibrating sample magnetometer were compared to the data taken using a commercial superconducting quantum interference device and showed very similar results. In plane and out of plane magnetic hysteresis data acquired for 25 nm Fe thin films are also presented. The developed vibrating sample magnetometer is able to achieve a sensitivity approaching 1 × 10−5 emu. Further alterations to the design that may improve beyond this limit are also discussed.Item A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands(IOP, 2024-01) Pope, I.; Mori, K.; Abdelmaguid, M.; Gelfand, J. D.; Reynolds, S. P.; Safi-Harb, S.; Hailey, C. J.; An, H.; (NuSTAR Collaboration); Bangale, P.; Batista, P.; Benbow, W.; Buckley, J. H.; Capasso, M.; Christiansen, J. L.; Chromey, A. J.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Gallagher, G.; Hanlon, W. F.; Hanna, D.; Hervet, O.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McGrath, C. E.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O'Brien, S.; Ong, R. A.; Park, N.; Patel, S. R.; Pfrang, K.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Roache, E.; Sadeh, I.; Saha, L.; Sembroski, G. H.; Tak, D.; Tucci, J. V.; Weinstein, A.; Williams, D. A.; Woo, J.; (VERITAS Collaboration); Physics, School of ScienceG106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" and "tail") regions in the radio band. A discovery of very-high-energy gamma-ray emission (Eγ > 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission (Eγ > 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100'' around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B-field (B ∼ 3 μG) and larger distance (d ∼ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ∼1000 yr ago. In this case, the head region should be formed by GeV–TeV electrons injected earlier by the pulsar propagating into the low-density environment.Item A VERITAS/Breakthrough Listen Search for Optical Technosignatures(IOP, 2023-09) Acharyya, A.; Adams, C. B.; Archer, A.; Bangale, P.; Batista, P.; Benbow, W.; Brill, A.; Capasso, M.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Griffin, S.; Hanlon, W.; Hanna, D.; Hervet, O.; Hinrichs, C. E.; Hoang, J.; Holder, J.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kherlakian, M.; Kieda, D.; Kleiner, T. K.; Korzoun, N.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; McGrath, C. E.; Millard, M. J.; Miller, H. R.; Millis, J.; Mooney, C. L.; Moriarty, P.; Mukherjee, R.; O'Brien, S.; Ong, R. A.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Ryan, J. L.; Sadeh, I.; Saha, L.; Santander, M.; Sembroski, G. H.; Shang, R.; Tak, D.; Talluri, A. K.; Tucci, J. V.; Vazquez, N.; Williams, D. A.; Wong, S. L.; Woo, J.; VERITAS Collaboration; DeBoer, D.; Isaacson, H.; de Pater, I.; Price, D. C.; Siemion, A.; Physics, School of ScienceThe Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) Collaboration joined this program in 2018 and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds in duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof of principle.Item Absolute sensitivity of phase measurement in an SU(1,1) type interferometer(OSA, 2018) Du, Wei; Jia, Jun; Chen, J. F.; Ou, Z. Y.; Zhang, Weiping; Physics, School of ScienceAbsolute sensitivity is measured for the phase measurement in an SU(1,1) type interferometer, and the results are compared to that of a Mach–Zehnder interferometer operated under the condition of the same intra-interferometer intensity. The interferometer is phase locked to a point with the largest quantum noise cancellation, and a simulated phase modulation is added in one arm of the SU(1,1) interferometer. Both the signal and noise level are estimated at the same frequency range, and we obtained 3 dB improvement in sensitivity for the SU(1,1) interferometer over the Mach–Zehnder interferometer. Our results demonstrate a direct phase estimation and may pave the way for practical applications of a nonlinear interferometer.Item Accessible precisions for estimating two conjugate parameters using Gaussian probes(American Physical Society, 2020-05) Assad, Syed M.; Li, Jiamin; Liu, Yuhong; Zhao, Ningbo; Zhao, Wen; Lam, Ping Koy; Ou, Z. Y.; Li, Xiaoying; Physics, School of ScienceWe analyze the precision limits for a simultaneous estimation of a pair of conjugate parameters in a displacement channel using Gaussian probes. Having a set of squeezed states as an initial resource, we compute the Holevo Cramér-Rao bound to investigate the best achievable estimation precisions if only passive linear operations are allowed to be performed on the resource prior to probing the channel. The analysis reveals the optimal measurement scheme and allows us to quantify the best precision for one parameter when the precision of the second conjugate parameter is fixed. To estimate the conjugate parameter pair with equal precision, our analysis shows that the optimal probe is obtained by combining two squeezed states with orthogonal squeezing quadratures on a 50:50 beam splitter. If different importance is attached to each parameter, then the optimal mixing ratio is no longer 50:50. Instead, it follows a simple function of the available squeezing and the relative importance between the two parameters.Item Active learning pedagogy: Structuring the pre-instruction assignment(IOP, 2019) Novak, G.; Physics, School of ScienceEducation research is changing the way teachers teach and students learn. In contrast with the lecture-based approach to instruction, centered on the teacher as "performer", teaching and learning activities now place equal emphasis on in-class and out-of-class work. Much of the interaction between at-home activity and classroom experience and is mediated by information technology tools. Students are technology savvy, comfortable in the world of on-line delivery of information and social media interactions. To be an effective player in this world, instructional design has to follow the students. Contrary to the opinion that the introduction of technology into the teaching and learning process will diminish the role of the teacher, we believe that the opposite could be the case. Communication technology can enable all students to be exposed to the best and most charismatic lecturers. Electronically enabled social media forums can give rise to much more individualized interactions between students and instructors and students and students than what was ever possible. In this paper, we focus on some pedagogical approaches that allow the students to prepare themselves for interactive classroom engagement. The techniques we describe are labelled Just-in-Time Teaching and Worked-Examples. These involve carefully crafted assignments that students complete before going to class. The results of these assignments, completed just before class-time and available to the instructor, prepare the both for a more productive in-class experience.Item All n-3 PUFA are not the same: MD simulations reveal differences in membrane organization for EPA, DHA and DPA(Elsevier, 2018) Leng, Xiaoling; Kinnun, Jacob J.; Cavazos, Andres T.; Canner, Samuel W.; Shaikh, Saame Raza; Feller, Scott E.; Wassall, Stephen R.; Physics, School of ScienceEicosapentaenoic (EPA, 20:5), docosahexaenoic (DHA, 22:6) and docosapentaenoic (DPA, 22:5) acids are omega-3 polyunsaturated fatty acids (n-3 PUFA) obtained from dietary consumption of fish oils that potentially alleviate the symptoms of a range of chronic diseases. We focus here on the plasma membrane as a site of action and investigate how they affect molecular organization when taken up into a phospholipid. All atom MD simulations were performed to compare 1-stearoyl-2-eicosapentaenoylphosphatylcholine (EPA-PC, 18:0–20:5PC), 1-stearoyl-2-docosahexaenoylphosphatylcholine (DHA-PC, 18:0–22:6PC), 1-stearoyl-2-docosapentaenoylphosphatylcholine (DPA-PC, 18:0–22:5PC) and, as a monounsaturated control, 1-stearoyl-2-oleoylphosphatidylcholine (OA-PC, 18:0–18:1PC) bilayers. They were run in the absence and presence of 20 mol% cholesterol. Multiple double bonds confer high disorder on all three n-3 PUFA. The different number of double bonds and chain length for each n-3 PUFA moderates the reduction in membrane order exerted (compared to OA-PC, 𝑆̅𝐶𝐷 = 0.152). EPA-PC (𝑆̅𝐶𝐷 = 0.131) is most disordered, while DPA-PC ( 𝑆̅𝐶𝐷 = 0.140) is least disordered. DHA-PC (𝑆̅𝐶𝐷 = 0.139) is, within uncertainty, the same as DPA-PC. Following the addition of cholesterol, order in EPA-PC (𝑆̅𝐶𝐷 = 0.169), DHA-PC (𝑆̅𝐶𝐷 = 0.178) and DPA-PC (𝑆̅𝐶𝐷 = 0.182) is increased less than in OA-PC (𝑆̅𝐶𝐷 = 0.214). The high disorder of n-3 PUFA is responsible, preventing the n-3 PUFA-containing phospholipids from packing as close to the rigid sterol as the monounsaturated control. Our findings establish that EPA, DHA and DPA are not equivalent in their interactions within membranes, which possibly contributes to differences in clinical efficacy.Item Annihilation and Control of Chiral Domain Walls with Magnetic Fields(ACS, 2021-02-10) Karna, Sunil K.; Marshall, Madalynn; Xie, Weiwei; DeBeer-Schmitt, Lisa; Young, David P.; Vekhter, Ilya; Shelton, William A.; Kovács, Andras; Charilaou, Michalis; DiTusa, John F.; Physics, School of ScienceThe control of domain walls is central to nearly all magnetic technologies, particularly for information storage and spintronics. Creative attempts to increase storage density need to overcome volatility due to thermal fluctuations of nanoscopic domains and heating limitations. Topological defects, such as solitons, skyrmions, and merons, may be much less susceptible to fluctuations, owing to topological constraints, while also being controllable with low current densities. Here, we present the first evidence for soliton/soliton and soliton/antisoliton domain walls in the hexagonal chiral magnet Mn1/3NbS2 that respond asymmetrically to magnetic fields and exhibit pair-annihilation. This is important because it suggests the possibility of controlling the occurrence of soliton pairs and the use of small fields or small currents to control nanoscopic magnetic domains. Specifically, our data suggest that either soliton/soliton or soliton/antisoliton pairs can be stabilized by tuning the balance between intrinsic exchange interactions and long-range magnetostatics in restricted geometries.Item Automated Fovea Detection Based on Unsupervised Retinal Vessel Segmentation Method(IEEE, 2017-10) Tavakoli, Meysam; Kelley, Patrick; Nazar, Mahdieh; Kalantari, Faraz; Physics, School of ScienceThe Computer Assisted Diagnosis systems could save workloads and give objective diagnostic to ophthalmologists. At first level of automated screening of systems feature extraction is the fundamental step. One of these retinal features is the fovea. The fovea is a small fossa on the fundus, which is represented by a deep-red or red-brown color in color retinal images. By observing retinal images, it appears that the main vessels diverge from the optic nerve head and follow a specific course that can be geometrically modeled as a parabola, with a common vertex inside the optic nerve head and the fovea located along the apex of this parabola curve. Therefore, based on this assumption, the main retinal blood vessels are segmented and fitted to a parabolic model. With respect to the core vascular structure, we can thus detect fovea in the fundus images. For the vessel segmentation, our algorithm addresses the image locally where homogeneity of features is more likely to occur. The algorithm is composed of 4 steps: multi-overlapping windows, local Radon transform, vessel validation, and parabolic fitting. In order to extract blood vessels, sub-vessels should be extracted in local windows. The high contrast between blood vessels and image background in the images cause the vessels to be associated with peaks in the Radon space. The largest vessels, using a high threshold of the Radon transform, determines the main course or overall configuration of the blood vessels which when fitted to a parabola, leads to the future localization of the fovea. In effect, with an accurate fit, the fovea normally lies along the slope joining the vertex and the focus. The darkest region along this line is the indicative of the fovea. To evaluate our method, we used 220 fundus images from a rural database (MUMS-DB) and one public one (DRIVE). The results show that, among 20 images of the first public database (DRIVE) we detected fovea in 85% of them. Also for the MUMS-DB database among 200 images we detect fovea correctly in 83% on them.