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Robert Wagner

Publications and source records attributed to Robert Wagner.

At least 19 recordsLinked to original sources

Physics Driven Image Simulation from Commercial Satellite Imagery

Physics driven image simulation allows for the modeling and creation of realistic imagery beyond what is afforded by typical rendering pipelines. We aim to automatically generate a physically realistic scene for simulation of a given region using satellite imagery to model the scene geometry, drive material estimates, and populate the scene with dynamic elements. We present automated techniques to utilize satellite imagery throughout the simulated scene to expedite scene construction and decrease manual overhead. Our technique does not use lidar, enabling simulations that could not be constructed previously. To develop a 3D scene, we model the various components of the real location, addressing the terrain, modelling man-made structures, and populating the scene with smaller elements such as vegetation and vehicles. To create the scene we begin with a Digital Surface Model, which serves as the basis for scene geometry, and allows us to reason about the real location in a common 3D frame of reference. These simulated scenes can provide increased fidelity with less manual intervention for novel locations on earth, and can facilitate algorithm development, and processing pipelines for imagery ranging from UV to LWIR $(200nm-20μm)$.

cs.CV

Semantic Information Management in Low-Temperature Plasma Science and Technology with VIVO

Digital research data management is increasingly integrated across universities and research institutions, addressing the handling of research data throughout its lifecycle according to the FAIR data principles (Findable, Accessible, Interoperable, Reusable). Recent emphasis on the semantic and interlinking aspects of research data, e.g., by using ontologies and knowledge graphs further enhances findability and reusability. This work presents a framework for creating and maintaining a knowledge graph specifically for low-temperature plasma (LTP) science and technology. The framework leverages a domain-specific ontology called Plasma-O, along with the VIVO software as a platform for semantic information management in LTP research. While some research fields are already prepared to use ontologies and knowledge graphs for information management, their application in LTP research is nascent. This work aims to bridge this gap by providing a framework that not only improves research data management but also fosters community participation in building the domain-specific ontology and knowledge graph based on the published materials. The results may also support other research fields in the practical use of knowledge graphs for semantic information management.

physics.plasm-ph

Glucodensity Functional Profiles Outperform Traditional Continuous Glucose Monitoring Metrics

Continuous glucose monitoring (CGM) data has revolutionized the management of type 1 diabetes, particularly when integrated with insulin pumps to mitigate clinical events such as hypoglycemia. Recently, there has been growing interest in utilizing CGM devices in clinical studies involving healthy and diabetes populations. However, efficiently exploiting the high temporal resolution of CGM profiles remains a significant challenge. Numerous indices -- such as time-in-range metrics and glucose variability measures -- have been proposed, but evidence suggests these metrics overlook critical aspects of glucose dynamic homeostasis. As an alternative method, this paper explores the clinical value of glucodensity metrics in capturing glucose dynamics -- specifically the speed and acceleration of CGM time series -- as new biomarkers for predicting long-term glucose outcomes. Our results demonstrate significant information gains, exceeding 20\% in terms of adjusted $R^2$, in forecasting glycosylated hemoglobin (HbA1c) and fasting plasma glucose (FPG) at five and eight years from baseline AEGIS data, compared to traditional non-CGM and CGM glucose biomarkers. These findings underscore the importance of incorporating more complex CGM functional metrics, such as the glucodensity approach, to fully capture continuous glucose fluctuations across different time-scale resolutions.

stat.AP

Thermal Behavior of Astrophysical Amorphous Molecular Ices

Ice is a major component of astrophysical environment - from interstellar molecular clouds through protoplanetary disks to evolved solar systems. Ice and complex organic matter coexist in these environments as well, and it is thought primordial ice brought the molecules of life to Earth four billion years ago, which could have kickstarted the origin of life on Earth. To understand the journey of ice and organics from their origins to becoming a part of evolved planetary systems, it is important to complement high spatial and spectral resolution telescopes such as JWST with laboratory experimental studies that provide deeper insight into the processes that occur in these astrophysical environments. Our laboratory studies are aimed at providing this knowledge. In this article we present simultaneous mass spectrometric and infrared spectroscopic investigation on how molecular ice mixtures behave at different temperatures and how this information is critical to interpret observational data from protoplanetary disks as well as comets. We find that amorphous to crystalline water ice transformation is the most critical phenomenon that differentiates between outgassing of trapped volatiles such as CO2 vs. outgassing of pure molecular ice domains of the same in a mixed molecular ice. Crystalline water ice is found to trap only a small fraction of other volatiles (<5%), indicating ice grain composition in astrophysical and planetary environments must be different depending on whether the ice is in amorphous phase or transformed into crystalline phase, even if the crystalline ice undergoes radiation-induced amorphization subsequently. Crystallization of water ice is a key differentiator for many ices in astronomical environments as well as in our Solar System.

astro-ph.EP

On the investigation of the closure relations for Gamma-Ray Bursts observed by Swift in the post-plateau phase and the GRB fundamental plane

Gamma-Ray Bursts (GRBs) are the most explosive phenomena in the Universe after the Big Bang. A large fraction of GRB lightcurves (LCs) shows X-ray plateaus. We perform the most comprehensive analysis of all GRBs (with known and unknown redshifts) with plateau emission observed by The Neil Gehrels Swift Observatory from its launch until August 2019. We fit 455 LCs showing a plateau and explore whether these LCs follow closure relations, relations between the temporal and spectral indices of the afterglow, corresponding to 2 distinct astrophysical environments and cooling regimes within the external forward shock (ES) model, and find that the ES model works for the majority of cases. The most favored environments are a constant density interstellar or wind medium with slow cooling. We also confirm the existence of the fundamental plane relation between the rest-frame time and luminosity at the end of the plateau emission and the peak prompt luminosity for this enlarged sample, and test this relation on groups corresponding to the astrophysical environments of our known redshift sample. The plane becomes a crucial discriminant corresponding to these environments in terms of the best fitting parameters and dispersions. Most GRBs for which the closure relations are fulfilled with respect to astrophysical environments have an intrinsic scatter sigma compatible within 1 sigma of that of the Gold GRBs, a subset of long GRBs with relatively flat plateaus. We also find that GRBs satisfying closure relations indicating a fast cooling regime have a lower sigma than ever previously found in literature.

astro-ph.HE

Pointing System for the Large Size Telescopes Prototype of the Cherenkov Telescope Array

The pointing system of the prototype of the Large Size Telescope (LST-1) for the Cherenkov Telescope Array observatory, should ensure mapping of the gamma-ray image of a point-like source in the Cherenkov camera to the sky coordinates with a precision better than 14 arcseconds. Detailed studies of the telescope deformations are performed in order to disentangle different deformations and quantify their contributions to the miss-pointing, to learn how to correct for them, and finally how to design the system for offline and online pointing corrections. The LST-1 pointing precision system consist of several devices mounted at the center of the dish: Starguider Camera (SG), Camera Displacement Monitor (CDM), two inclinometers, four distance meters, and an Optical Axis Reference Laser (OARL), working together with the LEDs mounted in a circle around the Cherenkov camera. The online pointing corrections are based on a bending model as currently done by existing IACTs. The offline corrections will be performed combining measurements done by the SG and CDM cameras. SG will provide the position of the Cherenkov camera center with respect to the sky coordinates with a precision of 5 arcseconds, while CDM will provide the deviation of the telescope optical axis defined by the OARL spots with respect to the Cherenkov camera center with a precision better than 5 arcseconds. Laboratory measurements on dedicated test benches showed that the required pointing precision can be achieved for SG, CDM and inclinometer.

astro-ph.IM

4-D Scene Alignment in Surveillance Video

Designing robust activity detectors for fixed camera surveillance video requires knowledge of the 3-D scene. This paper presents an automatic camera calibration process that provides a mechanism to reason about the spatial proximity between objects at different times. It combines a CNN-based camera pose estimator with a vertical scale provided by pedestrian observations to establish the 4-D scene geometry. Unlike some previous methods, the people do not need to be tracked nor do the head and feet need to be explicitly detected. It is robust to individual height variations and camera parameter estimation errors.

cs.CV

Characteristics of fast timing MCP-PMTs in magnetic fields

The motivation of this paper is to explore the parameters that affect the performance of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) in magnetic fields with the goal to guide their design to achieve a high magnetic field tolerance. MCP-PMTs based on two different designs were tested.The magnetic field tolerance of MCP-PMT based on a design providing independently biased voltages showed a significant improvement (up to 0.7 T) compared to the one utilizing an internal resistor chain design (up to 0.1 T), indicating the importance of individually adjustable voltages. The effects of the rotation angle of the MCP-PMT relative to the magnetic field direction and of the bias voltage between the photocathode and the top MCP were extensively investigated using the MCP-PMT based on the independently biased voltage design. It was found that the signal amplitude of the MCP-PMT exhibits an enhanced performance at a tilt angle of $\pm$8$^{\circ}$, due to the 8$^{\circ}$ bias angle of the MCP pores. The maximum signal amplitude was observed at different bias voltages depending on the magnetic field strength.

physics.ins-det

Rate capability and magnetic field tolerance measurements of fast timing microchannel plate photodetectors

Microchannel plate photodetectors provide both picosecond time resolution and sub-millimeter position resolution, making them attractive photosensors for particle identification detectors of a future U.S. Electron Ion Collider. We have tested the rate capability and magnetic field tolerance of 6$\times$6 cm$^{2}$ microchannel plate photodetectors fabricated at Argonne National Laboratory. The microchannel plate photodetector is designed as a low-cost all-glass vacuum package with a chevron pair stack of next-generation microchannel plates functionalized by atomic layer deposition. The rate capability test was performed using Fermilab's 120 GeV primary proton beam, and the magnetic field tolerance test was performed using a solenoid magnetic with tunable magnetic field strength up to 4 Tesla. The measured gain of the microchannel plate photodetector is stable up to 75 kHz/cm$^{2}$, and varies depending on the applied magnetic field strength and the rotation angle relative to the magnetic field direction.

physics.ins-det

Development and testing of cost-effective, 6 cm x 6 cm MCP-based photodetectors for fast timing applications

Micro-channel plate (MCP)-based photodetectors are capable of picosecond level time resolution and sub-mm level position resolution, which makes them a perfect candidate for the next generation large area photodetectors. The large-area picosecond photodetector (LAPPD) collaboration is developing new techniques for making large-area photodetectors based on new MCP fabrication and functionalization methods. A small single tube processing system (SmSTPS) was constructed at Argonne National Laboratory (ANL) for developing scalable, cost-effective, glass-body, 6 cm x 6 cm, picosecond photodetectors based on MCPs functionalized by Atomic Layer Deposition (ALD). Recently, a number of fully processed and hermitically sealed prototypes made of MCPs with 20 micron pores have been fabricated. This is a significant milestone for the LAPPD project. These prototypes were characterized with a pulsed laser test facility. Without optimization, the prototypes have shown excellent results: The time resolution is ~57 ps for single photoelectron mode and ~15 ps for multi-photoelectron mode; the best position resolution is < 0.8 mm for large pulses. In this paper, the tube processing system, the detector assembly, experimental setup, data analysis and the key performance will be presented.

physics.ins-det

MCP-based Photodetectors for Cryogenic Applications

The Argonne MCP-based photo detector is an offshoot of the Large Area Pico-second Photo Detector (LAPPD) project, wherein 6 cm x 6 cm sized detectors are made at Argonne National Laboratory. We have successfully built and tested our first detectors for pico-second timing and few mm spatial resolution. We discuss our efforts to customize these detectors to operate in a cryogenic environment. Initial plans aim to operate in liquid argon. We are also exploring ways to mitigate wave length shifting requirements and also developing bare-MCP photodetectors to operate in a gaseous cryogenic environment.

physics.ins-det

High Performance Photocathodes based on Molecular Beam Epitaxy Deposition for Next Generation Photo Detectors and Light Sources

The development of high-performance photocathodes is a key challenge for future accelerator and particle physics applications. In this paper photocathode growth through molecular beam epitaxy is introduced as a promising technique to obtain robust, highly efficient alkali-antimonide based photocathodes. Recent research shows that the quantum efficiency of photocathodes can be significantly enhanced through control of the photocathode crystallinity. Molecular beam epitaxy allows for cost-effective growth of large-area photocathodes with excellent control of the stoichiometry and crystallinity, making photocathodes with peak quantum efficiencies exceeding 35% routine.

physics.ins-det

Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics

Very-high energy (VHE) gamma quanta contribute only a minuscule fraction - below one per million - to the flux of cosmic rays. Nevertheless, being neutral particles they are currently the best "messengers" of processes from the relativistic/ultra-relativistic Universe because they can be extrapolated back to their origin. The window of VHE gamma rays was opened only in 1989 by the Whipple collaboration, reporting the observation of TeV gamma rays from the Crab nebula. After a slow start, this new field of research is now rapidly expanding with the discovery of more than 150 VHE gamma-ray emitting sources. Progress is intimately related with the steady improvement of detectors and rapidly increasing computing power. We give an overview of the early attempts before and around 1989 and the progress after the pioneering work of the Whipple collaboration. The main focus of this article is on the development of experimental techniques for Earth-bound gamma-ray detectors; consequently, more emphasis is given to those experiments that made an initial breakthrough rather than to the successors which often had and have a similar (sometimes even higher) scientific output as the pioneering experiments. The considered energy threshold is about 30 GeV. At lower energies, observations can presently only be performed with balloon or satellite-borne detectors. Irrespective of the stormy experimental progress, the success story could not have been called a success story without a broad scientific output. Therefore we conclude this article with a summary of the scientific rationales and main results achieved over the last two decades.

physics.hist-ph

Nonuniform current density and spin accumulation in a 1 μm thick n-GaAs channel

The spin accumulation in an n-GaAs channel produced by spin extraction into a (Ga,Mn)As contact is measured by cross-sectional imaging of the spin polarization in GaAs. The spin polarization is observed in a 1 \mum thick n-GaAs channel with the maximum polarization near the contact edge opposite to the maximum current density. The one-dimensional model of electron drift and spin diffusion frequently used cannot explain this observation. It also leads to incorrect spin lifetimes from Hanle curves with a strong bias and distance dependence. Numerical simulations based on a two-dimensional drift-diffusion model, however, reproduce the observed spin distribution quite well and lead to realistic spin lifetimes.

cond-mat.mtrl-sci

Monitoring of bright, nearby Active Galactic Nuclei with the MAGIC telescopes

Observations and detections of Active Galactic Nuclei (AGN) by Cherenkov telescopes are often triggered by information about high flux states in other wavelength bands. To overcome this bias, the VHE gamma-ray telescope MAGIC has conducted dedicated monitoring observations of nearby AGN since 2006. Three well established, TeV-bright blazars were selected to be observed regularly: Mrk 421, Mrk 501, and 1ES1959+650. The goals of these observations are to obtain an unbiased distribution of flux states shedding light on the duty cycle of AGN, to investigate potential spectral changes during periods of different source activity, and to correlate the results with multiwavelength observations. Also clues on a potential periodic behavior of the sources might be drawn from a study of the obtained lightcurves. By testing predictions of theoretical models, like, e.g., the correlation between the TeV flux level and the peak frequency predicted in SSC models, monitoring deepens our knowledge about the acceleration and emission processes in AGN. The status and results of the MAGIC AGN monitoring program will be presented.

astro-ph.HE

Studies of the Influence of Moonlight on Observations with the MAGIC Telescope

The ground-based imaging atmospheric Cherenkov technique is currently the most powerful observation method for very high energy gamma rays. With its specially designed camera and readout system, the MAGIC Telescope is capable of observing also during nights with a comparatively high level of night-sky background light. This allows to extend the MAGIC duty cycle by 30% compared to dark-night observations without moon. Here we investigate the impact of increased background light on single-pixel level and show the performance of observations in the presence of moonlight conditions to be consistent with dark night observations.

astro-ph.IM

MAGIC observations of Mkn 421 in 2008, and related optical/X-ray/TeV MWL study

The HBL-type blazar Markarian 421 is one of the brightest TeV gamma-ray sources of the Northern sky. From December 2007 until June 2008 it was intensively observed in the VHE (E>100 GeV) band by the MAGIC gamma-ray telescope. The source showed intense and prolonged activity during the whole period. In some nights the integral flux rose up to 3.6 Crab units (E>200 GeV). Intra-night rapid flux variations were observed. We compared the optical (KVA) and X-ray (RXTE-ASM, Swift-XRT) data with the MAGIC VHE data, investigating the correlations between different energy bands.

astro-ph.HE