Publications

Refine Results

(Filters Applied) Clear All

Monitoring of hemorrhage and whole blood resuscitation in non-human primates

September 16, 2025
  |
Journal Article
Author:
Saaid Arshad
…
Topic:
health
R&D group:

Summary

Massive hemorrhage remains the primary cause of potentially preventable death in traumatic injuries. Monitoring hemorrhage and resuscitation accurately can improve outcomes but continues to be challenging since traditional vital signs are highly compensated by the body. Previous work has developed physiologically interpretable algorithms to assess volume status in simulated models of hemorrhage and resuscitation. In this paper, we further develop these algorithms to assess volume status in a nonhuman primate model of controlled blood loss and subsequent whole-blood resuscitation. We acquired arterial blood pressure (ABP) waveform data on 12 adult male baboons during a step-and-hold protocol for hemorrhage and a constant resuscitation rate. A gradient-boosted regression tree model trained on only the ejected-wave pulse area (EWPA) feature yielded a 19% root-mean-square-error (RMSE), 0.71 R2, and an area under the receiver operating characteristic curve of ≥ 0.9 for key operating points of volume status. The performance of this model with a single feature compares well to results reported previously from single-feature machine-learning (ML) models as well as more complex machine learning models that are difficult to interpret and computationally intensive. This study is the first investigation of these physiologically interpretable models on invasively measured ABP waveforms.
READ LESS

Summary

Massive hemorrhage remains the primary cause of potentially preventable death in traumatic injuries. Monitoring hemorrhage and resuscitation accurately can improve outcomes but continues to be challenging since traditional vital signs are highly compensated by the body. Previous work has developed physiologically interpretable algorithms to assess volume status in simulated models...

READ MORE
Monitoring of hemorrhage and whole blood resuscitation in non-human primates

Estimating visceral adiposity from wrist-worn accelerometry

September 16, 2025
  |
Journal Article
Author:
Jim R. Williamson
…
Topic:
health
R&D group:

Summary

Visceral adipose tissue (VAT) is a key marker of both metabolic health and habitual physical activity (PA). Excess VAT is highly correlated with type 2 diabetes and insulin resistance. The mechanistic basis for this pathophysiology relates to overloading the liver with fatty acids. VAT is also a highly labile fat depot, with increased turnover stimulated by catecholamines during exercise. VAT can be measured with sophisticated imaging technologies, but can also be inferred directly from PA.We tested this relationship using National Health and Nutrition Examination Survey (NHANES) data from 2011-2014, for individuals aged 20-60 years with 7 days of accelerometry data (n=2,456 men; 2,427 women) [1]. Two approaches were used for estimating VAT from activity. The first used engineered features based on movements during gait and sleep, and then ridge regression to map summary statistics of these features into a VAT estimate. The second approach used deep neural networks trained on 24 hours of continuous accelerometry. A foundation model first mapped each 10 s frame into a high-dimensional feature vector. A transformer model then mapped each day's feature vector time series into a VAT estimate, which were averaged over multiple days. For both approaches, the most accurate estimates were obtained with the addition of covariate information about subject demographics and body measurements. The best performance was obtained by combining the two approaches, resulting in VAT estimates with correlations of r=0.86. These findings demonstrate a strong relationship between PA and VAT and, by extension, between PA and metabolic health risks.
READ LESS

Summary

Visceral adipose tissue (VAT) is a key marker of both metabolic health and habitual physical activity (PA). Excess VAT is highly correlated with type 2 diabetes and insulin resistance. The mechanistic basis for this pathophysiology relates to overloading the liver with fatty acids. VAT is also a highly labile fat...

READ MORE
Estimating visceral adiposity from wrist-worn accelerometry

TAU: Trust via Asynchronous Updates for satellite network resiliency

June 23, 2025
  |
Conference Paper
Author:
Quincy Bayer
…
Topic:
cyber security
R&D group:

Summary

Satellite networks are key enablers to many applications, including world-wide sensing and communications. Unlike their terrestrial counterparts, satellites are able to provide coverage in remote and hard-to-reach areas, including areas with regional conflicts. However, they are also susceptible to multiple security threats and potential failures. In addition to commonly used security techniques, it is essential to have algorithms that assess the trustworthiness of satellites as they operate, without limiting the satellites' abilities to perform their intended tasks. In this paper we focus on trust assessment methods that analyze the behavior of satellites to detect attacks and identify failed or compromised nodes in constellation networks. In this work, we (1) present a satellite threat model and enumerate possible attacks, (2) compare several existing trust assessment models when applied to low earth orbit satellite constellations, and (3) propose Trust via Asynchronous Updates (TAU), a novel trust algorithm model that is applicable to all modern satellite constellation networks. Model TAU uses finite state machines and asynchronous updates to track node behavior. Our custom simulator evaluates the performance of our algorithm in comparison to several previously proposed trust models. We consider two well-known attacks, the kinetic and black hole attacks, and show that the proposed Model TAU accurately identifies malicious satellites, with low false positive rate, in time comparable to previously proposed trust models while achieving lower computational complexity and communication overhead.
READ LESS

Summary

Satellite networks are key enablers to many applications, including world-wide sensing and communications. Unlike their terrestrial counterparts, satellites are able to provide coverage in remote and hard-to-reach areas, including areas with regional conflicts. However, they are also susceptible to multiple security threats and potential failures. In addition to commonly used...

READ MORE
TAU: Trust via Asynchronous Updates for satellite network resiliency

In-grown diamond color centers with narrow inhomogeneous spectral distributions

June 1, 2025
  |
Conference Paper
Author:
Zachary Zitzewitz
…
Topic:
quantum
R&D group:

Summary

We characterize silicon vacancies in a bulk diamond sample grown at MIT Lincoln Laboratory. The measured narrow, inhomogeneous spectral distribution indicates that they will be useful for implementing scalable quantum networks.
READ LESS

Summary

We characterize silicon vacancies in a bulk diamond sample grown at MIT Lincoln Laboratory. The measured narrow, inhomogeneous spectral distribution indicates that they will be useful for implementing scalable quantum networks.

READ MORE
In-grown diamond color centers with narrow inhomogeneous spectral distributions

Impact of interconnected architectures on near-term quantum algorithms

June 1, 2025
  |
Conference Paper
Author:
Eric Bersin
…
Topic:
quantum
R&D area:
R&D group:

Summary

Scaling quantum computers requires interconnected processors; however, the interconnected architecture's effect on computing performance is not well quantified. We assess the impact of architectures on algorithm performance and identify performance benefits relative to interconnect-free architectures.
READ LESS

Summary

Scaling quantum computers requires interconnected processors; however, the interconnected architecture's effect on computing performance is not well quantified. We assess the impact of architectures on algorithm performance and identify performance benefits relative to interconnect-free architectures.

READ MORE
Impact of interconnected architectures on near-term quantum algorithms

It is time to standardize principles and practices for software memory safety

February 1, 2025
  |
Journal Article
Author:
Robert N. M. Watson
…
Topic:
cyber security
R&D group:

Summary

For many decades, endemic memory-safety vulnerabilities in software trusted computing bases (TCBs) have enabled the spread of malware and devastating targeted attacks on critical infrastructure, national-security targets, companies, and individuals around the world. During the last two years, the information-technology industry has seen increasing calls for the adoption of memory-safety technologies, frames as part of a broader initiative for Secure by Design, from government, academia, and within the industry itself. These calls are grounded in extensive evidence that memory-safety vulnerabilities have persistently made up the majority of critical security vulnerabilities for multiple decades, and have affected all mainstream software ecosystems and products--and also the growing awareness that these problems are almost entirely avoidable by using recent advances in strong and scalable memory-safety technology. In this Inside Risks column, we explore memory-safety standardization, which we argue is an essential step to promoting universal strong memory safety in government and industry, and in turn, to ensure access to more secure software for all. During the last two decades, a set of research technologies for strong memory safety--memory-safe languages, hardware and software inventory protection, formal approaches, and software compartmentalization--have reached sufficient maturity to see early deployment in security-critical use cases. However, there remains no shared, technology-neutral terminology or framework with which to specify memory-safety requirements. This is needed to enable reliable specification, design, implementation, auditing, and procurement of strongly memory-safe systems. Failure to speak in a common language makes it difficult to understand the possibilities or communicate accurately with each other, limiting perceived benefits and hence actual demand. The lack of such a framework also acts as an impediment to potential future policy interventions, and as an impediment to stating requirements to address observed market failures preventing adoption of these technologies. Standardization would also play a critical role in improving industrial best practice, another key aspect of adoption. This Inside Risks column is derived from a longer technical report published by the same authors, which includes further case studies and applications, as well as considering the potential implications of various events and interventions on potential candidate adoption timelines.
READ LESS

Summary

For many decades, endemic memory-safety vulnerabilities in software trusted computing bases (TCBs) have enabled the spread of malware and devastating targeted attacks on critical infrastructure, national-security targets, companies, and individuals around the world. During the last two years, the information-technology industry has seen increasing calls for the adoption of memory-safety...

READ MORE
It is time to standardize principles and practices for software memory safety

Capacity-based analysis of physical-layer and link-layer techniques for reliable communication over free-space optical fading channels

January 23, 2025
  |
Conference Paper
Author:
Curt M. Schieler
…
Topic:
laser communications
R&D area:
R&D group:

Summary

Free-space optical communication links can experience signal power fluctuations due to channel effects such as turbulence and pointing jitter. Systems can ensure reliable, error-free communication over fading channels by using physical-layer techniques (e.g., forward error correction with codeword interleaving) and link-layer techniques (e.g., erasure coding or ARQ). In this work, Shannon capacity analysis is used to compare the fundamental performance of different coding architectures in a variety of link conditions. For systems using coherent receivers we find that, in channels with benign to moderate fade statistics, there can be a ~3 dB link budget advantage to using physical-layer interleaving instead of deferring fade mitigation to the link layer. On the other hand, in very strong fluctuations or when system robustness is paramount, it can be advantageous to use link layer codes.
READ LESS

Summary

Free-space optical communication links can experience signal power fluctuations due to channel effects such as turbulence and pointing jitter. Systems can ensure reliable, error-free communication over fading channels by using physical-layer techniques (e.g., forward error correction with codeword interleaving) and link-layer techniques (e.g., erasure coding or ARQ). In this work...

READ MORE
Capacity-based analysis of physical-layer and link-layer techniques for reliable communication over free-space optical fading channels

High-fidelity control of a strongly coupled electro-nuclear spin-photon interface [e-print]

January 21, 2025
  |
Journal Article
Author:
Isaac B. Harris
…
Topic:
quantum
R&D group:

Summary

Long distance quantum networking requires combining efficient spin-photon interfaces with long-lived local memories. Group-IV color centers in diamond (SiV–, GeV–, and SnV–) are promising candidates for this application, containing an electronic spin-photon interface and dopant nuclear spin memory. Recent work has demonstrated state-of-the-art performance in spin-photon coupling and spin-spin entanglement. However, coupling between the electron and nuclear spins introduces a phase kickback during optical excitation that limits the utility of the nuclear memory. Here, we propose using the large hyperfine coupling of 117SnV– to operate the device at zero magnetic field in a regime where the memory is insensitive to optical excitation. We further demonstrate ground state spin control of a 117SnV– color center integrated in a photonic integrated circuit, showing 97.8% gate fidelity and 2.5 ms coherence time for the memory spin level. This shows the viability of the zero-field protocol for high fidelity operation, and lays the groundwork for building quantum network nodes with 117SnV– devices.
READ LESS

Summary

Long distance quantum networking requires combining efficient spin-photon interfaces with long-lived local memories. Group-IV color centers in diamond (SiV–, GeV–, and SnV–) are promising candidates for this application, containing an electronic spin-photon interface and dopant nuclear spin memory. Recent work has demonstrated state-of-the-art performance in spin-photon coupling and spin-spin entanglement...

READ MORE
High-fidelity control of a strongly coupled electro-nuclear spin-photon interface [e-print]

Design and performance of a 40W uplink laser transmitter for NASA's O2O laser communications mission

January 14, 2025
  |
Conference Paper
Author:
Katia Shtyrkova
…
Topic:
laser communications
R&D group:

Summary

NASA's Orion Artemis II Optical Communications System (O2O) will provide operational laser communications between the ground and lunar orbit for the Artemis II crewed mission. In this work we describe a 40 W ground-based laser transmitter for the O2O system. The uplink transmitter operates in the optical C-band and uses an energy-efficient 32- PPM modulation format. Four spatial diversity channels are time-aligned and combined in the far field. Each channel produces up to 10 W of output power and contains both the communications signal and the 7 kHz modulated beacon signal required for acquisition. The transmitter delivers data at 10 Mbits/s and 20 Mbits/s channel rates, corresponding to the 250 MHz and 500 MHz slot rates respectively.
READ LESS

Summary

NASA's Orion Artemis II Optical Communications System (O2O) will provide operational laser communications between the ground and lunar orbit for the Artemis II crewed mission. In this work we describe a 40 W ground-based laser transmitter for the O2O system. The uplink transmitter operates in the optical C-band and uses...

READ MORE
Design and performance of a 40W uplink laser transmitter for NASA's O2O laser communications mission

Endovascular localization of aortic injury in a porcine model

January 1, 2025
  |
Journal Article
Author:
Saaid Arshad
…
Topic:
health
R&D group:

Summary

Goal: Non-compressible torso hemorrhage represents a category of lethal injuries in both civilian and military traumatically injured populations that with proper intervention, training, or technological advancements are survivable. Endovascular localization of active bleeding in the pre-hospital setting can allow faster, less invasive, and more accurate applications of life-saving interventions. In this paper, we report initial in vivo and in silico experimental results to test the feasibility of endovascular localization of hemorrhage. Methods: Endovascular pressure waveforms were acquired on five pigs with an induced aortic injury via a custom intra-aortic catheter instrumented with four pressure sensors. Pressure and velocity data were then simulated on an in silico human aortic model with the same kind of injury. Results: A decrease in pulse pressure across the injury (proximal to distal) reliably indicated the injury location to within a few centimeters. The simulated model showed a similar decrease in pulse pressure as well as an increase in velocity. Conclusions: With additional refinement, localization accuracy may be sufficient for application of a modern covered stent to stop bleeding. The simulated model results indicate relevance for humans and provide guidance for future experiments.
READ LESS

Summary

Goal: Non-compressible torso hemorrhage represents a category of lethal injuries in both civilian and military traumatically injured populations that with proper intervention, training, or technological advancements are survivable. Endovascular localization of active bleeding in the pre-hospital setting can allow faster, less invasive, and more accurate applications of life-saving interventions. In...

READ MORE
Endovascular localization of aortic injury in a porcine model
1-10 of 2318