arXiv subjects

James Green

Publications and source records attributed to James Green.

At least 19 recordsLinked to original sources

arXiv2026

Infant Care Video Dataset for Classification of Interventions Using Transformers

Healthcare documentation in the neonatal intensive care unit (NICU) presents significant challenges, with nurses spending approximately 25\% of their time on record-keeping, while up to 60\% of interventions remain undocumented. Motivated by the need to detect interventions from video automatically, we present the Infant Care Video Dataset (ICVD), a collection of 4,144 videos spanning 12 simulated intervention classes designed for developing automated documentation systems. Our manikin-based approach systematically varies conditions, such as camera angle and clinician skin tone, while ensuring privacy compliance. Using video transformer architectures (TimeSformer and MotionFormer), we establish strong baseline performance (93.97\% and 93.17\% top-1 accuracy) among the 12 infant care classes. Our ablation study comparing temporal models with a framewise approach (23.17\% accuracy) demonstrates a 70.80\% performance gap, validating the need for temporal modeling. The ICVD provides a foundation for developing automated documentation systems to reduce clinical burden in neonatal care environments and improve existing practices.

cs.CV↗

arXiv2025

The Exospace Weather Frontier

Space weather is among the most powerful and least understood forces shaping planetary atmospheres. In our Solar System, we observe its effects directly: atmospheric escape, chemical disruption, and spectacular auroral displays. Yet for exoplanets, we lack the tools and data to comprehensively assess the impacts of space weather, especially invisible elements like stellar winds, coronal mass ejections, energetic particles, and variable interplanetary magnetic fields. This problem lies at the intersection of four key fields: heliophysics, planetary science, astrobiology, and astrophysics. In 2023--2025, experts from these four fields convened at the W. M. Keck Institute for Space Studies to explore pathways for advancing the study of exospace weather. Organizing the subject into five core themes -- planets and their stellar particle environments, stellar magnetism and space weather modeling, quasi-steady stellar winds, transient events, and programmatic pathways -- our team synthesized concepts from across relevant fields and identified a wide array of opportunities for progress. This report is the product of that effort. It assembles cross-disciplinary knowledge; highlights outstanding theoretical challenges; explores promising innovations in observation, modeling, methodology, and instrumentation; and makes recommendations for accelerating community-wide progress. Together, these lay out a path to transforming the challenging, yet tractable problem of exospace weather into a foundational element of our understanding exoplanetary systems, and our own Solar System, in their entirety.

astro-ph.IM↗

arXiv2025

Sleep Stage Classification using Multimodal Embedding Fusion from EOG and PSM

Accurate sleep stage classification is essential for diagnosing sleep disorders, particularly in aging populations. While traditional polysomnography (PSG) relies on electroencephalography (EEG) as the gold standard, its complexity and need for specialized equipment make home-based sleep monitoring challenging. To address this limitation, we investigate the use of electrooculography (EOG) and pressure-sensitive mats (PSM) as less obtrusive alternatives for five-stage sleep-wake classification. This study introduces a novel approach that leverages ImageBind, a multimodal embedding deep learning model, to integrate PSM data with dual-channel EOG signals for sleep stage classification. Our method is the first reported approach that fuses PSM and EOG data for sleep stage classification with ImageBind. Our results demonstrate that fine-tuning ImageBind significantly improves classification accuracy, outperforming existing models based on single-channel EOG (DeepSleepNet), exclusively PSM data (ViViT), and other multimodal deep learning approaches (MBT). Notably, the model also achieved strong performance without fine-tuning, highlighting its adaptability to specific tasks with limited labeled data, making it particularly advantageous for medical applications. We evaluated our method using 85 nights of patient recordings from a sleep clinic. Our findings suggest that pre-trained multimodal embedding models, even those originally developed for non-medical domains, can be effectively adapted for sleep staging, with accuracies approaching systems that require complex EEG data.

cs.CV↗

arXiv2025

Sleep Position Classification using Transfer Learning for Bed-based Pressure Sensors

Bed-based pressure-sensitive mats (PSMs) offer a non-intrusive way of monitoring patients during sleep. We focus on four-way sleep position classification using data collected from a PSM placed under a mattress in a sleep clinic. Sleep positions can affect sleep quality and the prevalence of sleep disorders, such as apnea. Measurements were performed on patients with suspected sleep disorders referred for assessments at a sleep clinic. Training deep learning models can be challenging in clinical settings due to the need for large amounts of labeled data. To overcome the shortage of labeled training data, we utilize transfer learning to adapt pre-trained deep learning models to accurately estimate sleep positions from a low-resolution PSM dataset collected in a polysomnography sleep lab. Our approach leverages Vision Transformer models pre-trained on ImageNet using masked autoencoding (ViTMAE) and a pre-trained model for human pose estimation (ViTPose). These approaches outperform previous work from PSM-based sleep pose classification using deep learning (TCN) as well as traditional machine learning models (SVM, XGBoost, Random Forest) that use engineered features. We evaluate the performance of sleep position classification from 112 nights of patient recordings and validate it on a higher resolution 13-patient dataset. Despite the challenges of differentiating between sleep positions from low-resolution PSM data, our approach shows promise for real-world deployment in clinical settings

cs.CV↗

arXiv2024

Permanent Capture into the Solar System

In this note, an interesting region about the Sun in phase space is described where the permanent capture of an object, $P$, of small mass from interstellar space can occur, under the gravitational perturbation of the resultant mass of the Galaxy. $P$ is never ejected back into interstellar space and won't collide with the Sun. It cycles about the Sun for all time, asymptotically approaching the capture set. In addition to being permanently captured, $P$ is also weakly captured. A recent result in \cite{Belbruno:2024} describes this region in general. It has a fractal structure. This is applied to the permanent capture of rogue planets and other objects from interstellar space

astro-ph.EP↗

arXiv2022

The Possible Cause of the 40 SpaceX Starlink Satellite Losses in February 2022: Prompt Penetrating Electric Fields and the Dayside Equatorial and Midlatitude Ionospheric Convective Uplift

On ~1613 UT, 3 February 2022 SpaceX launched 49 Starlink satellites from Cape Kennedy, Florida into ~210 km altitude orbits where they were to receive subsequent boosts. We assume that 9 satellites received subsequent boosts and succeeded in obtaining stable orbits. Several of the Starlink satellites reentered the atmosphere in the early morning hours of 7 February. Two magnetic storms occurred one with a peak SYM-H intensity of -80 nT at ~1056 UT on 3 February and a second with a SYM-H peak intensity of -71 nT on ~2059 UT 4 February. The ESA polar orbiting Swarm B satellite data show that enhanced storm-time air mass densities occurred in dayside equatorial and midlatitudes at ~500 km altitude with a density peak increase of ~50% higher than quiet time daytime values. The nightside density peak increase was ~100-190% compared to quiet time nighttime values. Prompt penetration electric fields causing ExB uplift of the dayside F-region O+ ions and the downward convection of the nightside O+ ions can explain the Swarm B day-night asymmetry during the magnetic storm main phases and are the probable cause of the losses of the Starlink satellites. Our scenario for the 40 Starlink satellite losses is different from Dang et al. (2022) who assumed that the Starlink satellites received no boosts at 210 km altitude.

physics.space-ph↗

arXiv2022

When Leaving the Solar System: Dark Matter Makes a Difference

A resultant gravitational force due to the current estimates of the virial mass of the Milky Way galaxy, dominated by dark matter, is estimated near the Sun and is described in two different analytical models yielding consistent results. One is a two-step Hernquist model, the other is a Navarro-Frenk-White model. The effect of this force is estimated on trajectories for spacecraft sufficiently far from the Sun. The difficulty of detecting this force is studied. It is concluded that its effect should be considered for certain spacecraft missions. Its effect on the Pioneer and New Horizons spacecrafts is discussed. A future mission is discussed that may be able to detect this force. Implications of this force are discussed with its impact for problems in planetary astronomy and astrophysics.

astro-ph.GA↗

arXiv2021

Call for a Framework for Reporting Evidence for Life Beyond Earth

Ours could realistically be the generation to discover evidence of life beyond Earth. With this privileged potential comes responsibility. The magnitude of the question, "are we alone?", and the public interest therein, opens the possibility that results may be taken to imply more than the observations support, or than the observers intend. As life detection objectives become increasingly prominent in space sciences, it is essential to open a community dialog about how to convey information in a subject matter that is diverse, complicated, and has high potential to be sensationalized. Establishing best practices for communicating about life detection can serve to set reasonable expectations on the early stages of a hugely challenging endeavor, attach value to incremental steps along the path, and build public trust by making clear that "false starts" and "dead ends" are an expected and potentially productive part of the scientific process. Here, we endeavor to motivate and seed the discussion with basic considerations and offer an example of how such considerations might be incorporated and applied in a proof-of-concept-level framework. Everything mentioned herein, including the name of the confidence scale, is intended not as a prescription, but simply as the beginning of an important dialogue.

physics.soc-ph↗

arXiv2020

Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection

Characterizing habitable exoplanets and/or their moons is of paramount importance. Here we show the results of our magnetic field topological modeling which demonstrate that terrestrial exoplanet-exomoon coupled magnetospheres work together to protect the early atmospheres of both the exoplanet and the exomoon. When exomoon magnetospheres are within the exoplanet's magnetospheric cavity, the exomoon magnetosphere acts like a protective magnetic bubble providing an additional magnetopause confronting the stellar winds when the moon is on the dayside. In addition, magnetic reconnection would create a critical pathway for the atmosphere exchange between the early exoplanet and exomoon. When the exomoon's magnetosphere is outside of the exoplanet's magnetosphere it then becomes the first line of defense against strong stellar winds, reducing the exoplanet's atmospheric loss to space. A brief discussion is given on how this type of exomoon would modify radio emissions from magnetized exoplanets.

astro-ph.EP↗

arXiv2020

Reconstructing the Grassmannian of lines from Kapranov's tilting bundle

Let $E$ be the tilting bundle on the Grassmannian $\text{Gr}(n,r)$ of $r$-dimensional quotients of $\Bbbk^n$ constructed by Kapranov. Buchweitz, Leuschke and Van den Bergh introduced a quiver $Q$ and a surjective $\Bbbk$-algebra homomorphism $Φ\colon\Bbbk Q\rightarrow A=\text{End}(E)$, together with a recipe on how the kernel may be computed. In this paper, for the case $r=2$ we give a new, direct proof that $Φ$ is surjective and then complete the picture by calculating the ideal of relations explicitly. As an application, we then use this presentation to show that $\text{Gr}(n,2)$ is isomorphic to a fine moduli space of certain stable $A$-modules, just as $\mathbb{P}^n$ can be recovered from the endomorphism algebra of Beilinson's tilting bundle $\bigoplus_{0\leq i\leq n}\mathcal{O}_{\mathbb{P}^n}(i)$.

math.AG↗

arXiv2017

Reconstructing toric quiver flag varieties from a tilting bundle

We prove that every toric quiver flag variety $Y$ is isomorphic to a fine moduli space of cyclic modules over the algebra $\text{End}(T)$ for some tilting bundle $T$ on $Y$. This generalises the well known fact that $\mathbb{P}^n$ can be recovered from the endomorphism algebra of $\bigoplus_{0\leq i\leq n} \mathcal{O}_{\mathbb{P}^n}(i)$.

math.AG↗

arXiv2016

Heter-LP: A heterogeneous label propagation algorithm and its application in drug repositioning

Drug repositioning offers an effective solution to drug discovery, saving both time and resources by finding new indications for existing drugs. Typically, a drug takes effect via its protein targets in the cell. As a result, it is necessary for drug development studies to conduct an investigation into the interrelationships of drugs, protein targets, and diseases. Although previous studies have made a strong case for the effectiveness of integrative network-based methods for predicting these interrelationships, little progress has been achieved in this regard within drug repositioning research. Moreover, the interactions of new drugs and targets (lacking any known targets and drugs, respectively) cannot be accurately predicted by most established methods. In this paper, we propose a novel semi-supervised heterogeneous label propagation algorithm named Heter-LP, which applies both local as well as global network features for data integration. To predict drug-target, disease-target, and drug-disease associations, we use information about drugs, diseases, and targets as collected from multiple sources at different levels. Our algorithm integrates these various types of data into a heterogeneous network and implements a label propagation algorithm to find new interactions. Statistical analyses of 10-fold cross-validation results and experimental analysis support the effectiveness of the proposed algorithm.

q-bio.QM↗

arXiv2016

The re-flight of the Colorado high-resolution Echelle stellar spectrograph (CHESS): improvements, calibrations, and post-flight results

In this proceeding, we describe the scientific motivation and technical development of the Colorado High-resolution Echelle Stellar Spectrograph (CHESS), focusing on the hardware advancements and testing supporting the second flight of the payload (CHESS-2). CHESS is a far ultraviolet (FUV) rocket-borne instrument designed to study the atomic-to-molecular transitions within translucent cloud regions in the interstellar medium (ISM). CHESS is an objective f/12.4 echelle spectrograph with resolving power $>$ 100,000 over the band pass 1000 $-$ 1600 Å. The spectrograph was designed to employ an R2 echelle grating with "low" line density. We compare the FUV performance of experimental echelle etching processes (lithographically by LightSmyth, Inc. and etching via electron-beam technology by JPL Microdevices Laboratory) with traditional, mechanically-ruled gratings (Bach Research, Inc. and Richardson Gratings). The cross-dispersing grating, developed and ruled by Horiba Jobin-Yvon, is a holographically-ruled, "low" line density, powered optic with a toroidal surface curvature. Both gratings were coated with aluminum and lithium fluoride (Al+LiF) at Goddard Space Flight Center (GSFC). Results from final efficiency and reflectivity measurements for the optical components of CHESS-2 are presented. CHESS-2 utilizes a 40mm-diameter cross-strip anode readout microchannel plate (MCP) detector fabricated by Sensor Sciences, Inc., to achieve high spatial resolution with high count rate capabilities (global rates $>$ 1 MHz). We present pre-flight laboratory spectra and calibration results. CHESS-2 launched on 21 February 2016 aboard NASA/CU sounding rocket mission 36.297 UG. We observed the intervening ISM material along the sightline to $ε$ Per and present initial characterization of the column densities, temperature, and kinematics of atomic and molecular species in the observation.

astro-ph.IM↗

arXiv2013

12.2-GHz methanol maser MMB follow-up catalogue - III. Longitude range 10 to 20 degrees

We present the third instalment of a series of catalogues presenting 12.2-GHz methanol maser observations made towards each of the 6.7-GHz methanol masers detected in the Methanol Multibeam (MMB) Survey. The current portion of the catalogue includes the Galactic longitude region 10 to 20 degrees, where we detect 47 12.2-GHz methanol masers towards 99 6.7-GHz targets. We compare the occurrence of 12.2-GHz methanol masers with water maser emission, for which all 6.7-GHz methanol masers in the 6 to 20 degrees longitude range have now been searched. We suggest that the water masers follow a more complicated evolutionary scenario than has been found for the methanol and OH masers, likely due to their different pumping mechanisms. Comparisons of the 6.7-GHz methanol to OH maser peak flux density ratio and the luminosity of the associated 12.2-GHz sources suggests that the 12.2-GHz maser luminosity begins to decline around the time that an OH maser becomes detectable.

astro-ph.GA↗

arXiv2013

WFIRST Science with a Probe Class Mission

WFIRST is the highest priority space mission of the Decadal review, however, it is unlikely to begin in this decade primarily due to a anticipated NASA budget that is unlikely to have sufficient resources to fund such a mission. For this reason we present a lower cost mission that accomplishes all of the WFIRST science as described in the Design Reference Mission 1 with a probe class design. This is effort is motivated by a desire to begin WFIRST in a timely manner and within a budget that can fit within the assets available to NASA on a realistic basis. The design utilizes dichroics to form four focal planes all having the same field of view to use the majority of available photons from a 1.2 meter telescope.

astro-ph.IM↗

arXiv2013

Confirmation of the exclusive association between 6.7-GHz methanol masers and high-mass star formation regions

Recently, a comparison between the locations of 6.7-GHz methanol masers and dust continuum emission has renewed speculation that these masers can be associated with evolved stars. The implication of such a scenario would be profound, especially for the interpretation of large surveys for 6.7-GHz masers, individual studies where high-mass star formation has been inferred from the presence of 6.7-GHz methanol masers, and for the pumping mechanisms of these masers. We have investigated the two instances where 6.7-GHz methanol masers have been explicitly suggested to be associated with evolved stars, and we find the first to be associated with a standard high-mass star formation region, and the second to be a spurious detection. We also find no evidence to suggest that the methanol maser action can be supported in the environments of evolved stars. We thereby confirm their exclusive association with high-mass star formation regions.

astro-ph.GA↗

arXiv2012

Unique Astrophysics in the Lyman Ultraviolet

There is unique and groundbreaking science to be done with a new generation of UV spectrographs that cover wavelengths in the "Lyman Ultraviolet" (LUV; 912 - 1216 Ang). There is no astrophysical basis for truncating spectroscopic wavelength coverage anywhere between the atmospheric cutoff (3100 Ang) and the Lyman limit (912 Ang); the usual reasons this happens are all technical. The unique science available in the LUV includes critical problems in astrophysics ranging from the habitability of exoplanets to the reionization of the IGM. Crucially, the local Universe (z <= 0.1) is entirely closed to many key physical diagnostics without access to the LUV. These compelling scientific problems require overcoming these technical barriers so that future UV spectrographs can extend coverage to the Lyman limit at 912 Ang.

astro-ph.IM↗

arXiv2012

12.2-GHz methanol maser MMB follow-up catalogue - II. Longitude range 186 to 330 degrees

We present the second portion of a catalogue of 12.2-GHz methanol masers detected towards 6.7-GHz methanol masers observed in the unbiased Methanol Multibeam (MMB) Survey. Using the Parkes radio telescope we have targeted all 207 6.7-GHz methanol masers in the longitude range 186 to 330 degrees for 12.2-GHz counterparts. We report the detection of 83 12.2-GHz methanol masers, and one additional source which we suspect is thermal emission, equating to a detection rate of 40 per cent. Of the 83 maser detections, 39 are reported here for the first time. We discuss source properties, including variability and highlight a number of unusual sources. We present a list of 45 candidates that are likely to harbor methanol masers in the 107.0-GHz transition.

astro-ph.GA↗