Reproducibility Distinguishability and Correlation of Fireball and Shockwave Dynamics in Explosive Munitions Detonations

The classification of battlespace detonations, specifically the determination of munitions type and size using temporal and spectral features of infrared emissions, is a particularly challenging problem. The intense infrared radiation produced by the detonation of high explosives is largely unstudied. Furthermore, the time-varying fireball imagery and spectra are driven by many factors including the type, size and age of the chemical explosive, method of detonation, interaction with the environment, and the casing used to enclose the explosive. To distinguish between conventional military munitions and improvised or enhanced explosives, the current study investigates fireball expansion dynamics using high speed, multi-band imagery. Instruments were deployed to three field tests involving improvised explosives in howitzer shells, simulated surface-to-air missiles, and small caliber muzzle flashes. The rate of shockwave expansion for the improvised explosives was determined from apparent index of refraction variations in the visible imagery. Fits of the data to existing drag and explosive models found in the literature, as well as modifications to these models, showed agreement in the near- and mid-fields (correlation coefficient, r2 \u3e 0.985 for t \u3c 50 msec); the modified models typically predicted the time for the shockwave to arrive a kilometer away to better than 10%; and fit parameters typically had an uncertainty of less than 20%. The shockwave was distinctive (Fisher Ratio, FR \u3e 1) within the first 2-10 milliseconds after detonation, then it decayed to an indistinguishable acoustic wave (coefficient of variation, CV \u3c 0.05). The area profiles of the fireballs were also examined and found to be highly variable, especially after 10 milliseconds (CV \u3e 0.5), regardless of munitions type. Scaling relationships between properties of the explosive (mass, specific energies, and theoretical energies) and detonation areas, characteristic times, and properties of the shockwave were assessed for distinguishing weights and types: Efficiency decreased with mass (FR \u3e 19); early-time Mach number and overpressure were primarily dependent on energy release (FR ~ 1.5-10); fireball area increased cubically with specific energies (r2 ~ 0.3-0.76) but its time of occurrence decreased cubically (r2 ~ 0.4-0.67). The relationship between fireball and shockwave features was fairly independent of variability (r2 ~ 0.5-0.9), indicating that both fireball and shockwave features scale similarly with variability in detonations

Characterization and Discrimination of Large Caliber Gun Blast and Flash Signatures

Two hundred and one firings of three 152 mm howitzer munitions were observed to characterize firing signatures of a large caliber gun. Muzzle blast expansion was observed with high-speed (1600 Hz) optical imagery. The trajectory of the blast front was well approximated by a modified point-blast model described by constant rate of energy deposition. Visible and near-infrared (450 - 850 nm) spectra of secondary combustion were acquired at 0.75 nm spectral resolution and depict strong contaminant emissions including Li, Na, K, Cu, and Ca. The O2 (X-b) absorption band is evident in the blue wing of the potassium D lines and was used for monocular passive ranging accurate to within 4 - 9%. Time-resolved midwave infrared (1800 - 6000 cm-1) spectra were collected at 100 Hz and 32 cm-1 resolution. A low dimensional radiative transfer model was used to characterize plume emissions in terms of area, temperature, soot emissivity, and species concentrations. Combustion emissions have 100 ms duration, 1200 - 1600 K temperature, and are dominated by H2O and CO2. Noncombusting plume emissions last 20 ms, are 850 - 1050 K, and show significant continuum (emissivity 0.36) and CO structure. Munitions were discriminated with 92 - 96% classification accuracy using only 1 - 3 firing signature features

Arrhenius Rate Chemistry-informed Inter-phase Source Terms (ARCIIST)

Currently, in macro-scale hydrocodes designed to simulate explosive material undergoing shock-induced ignition, the state of the art is to use one of numerous reaction burn rate models. These burn models are designed to estimate the bulk chemical reaction rate. Unfortunately, these burn rate models are largely based on empirical data and must be recalibrated for every new material being simulated. We propose that the use of Arrhenius Rate Chemistry-Informed Interphase Source Terms (ARCIIST) in place of empirically derived burn models will improve the accuracy for these computational codes. A reacting chemistry model of this form was developed for the cyclic nitramine RDX by the Naval Research Laboratory (NRL). Initial implementation of ARCIIST has been conducted using the Air Force Research Laboratory’s (AFRL) MPEXS multi-phase continuum hydrocode. In its present form, the bulk reaction rate is based on the destruction rate of RDX from NRL’s chemistry model. Early results using ARCIIST show promise in capturing deflagration to detonation features more accurately in continuum hydrocodes than what was previously achieved using empirically derived burn models

Deterministic Global 3D Fractal Cloud Model for Synthetic Scene Generation

This paper describes the creation of a fast, deterministic, 3D fractal cloud renderer for the AFIT Sensor and Scene Emulation Tool (ASSET). The renderer generates 3D clouds by ray marching through a volume and sampling the level-set of a fractal function. The fractal function is distorted by a displacement map, which is generated using horizontal wind data from a Global Forecast System (GFS) weather file. The vertical windspeed and relative humidity are used to mask the creation of clouds to match realistic large-scale weather patterns over the Earth. Small-scale detail is provided by the fractal functions which are tuned to match natural cloud shapes. This model is intended to run quickly, and it can run in about 700 ms per cloud type. This model generates clouds that appear to match large-scale satellite imagery, and it reproduces natural small-scale shapes. This should enable future versions of ASSET to generate scenarios where the same scene is consistently viewed from both GEO and LEO satellites from multiple perspectives

2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the American Thyroid Association's (ATA's) guidelines for the management of these disorders were revised in 2009, significant scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid nodules and differentiated thyroid cancer

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Adapting and testing measures of organizational context in primary care clinics in KwaZulu-Natal, South Africa

BackgroundImplementation science frameworks situate intervention implementation and sustainment within the context of the implementing organization and system. Aspects of organizational context such as leadership have been defined and measured largely within US health care settings characterized by decentralization and individual autonomy. The relevance of these constructs in other settings may be limited by differences like collectivist orientation, resource constraints, and hierarchical power structures. We aimed to adapt measures of organizational context in South African primary care clinics.MethodsWe convened a panel of South African experts in social science and HIV care delivery and presented implementation domains informed by existing frameworks and prior work in South Africa. Based on panel input, we selected contextual domains and adapted candidate items. We conducted cognitive interviews with 25 providers in KwaZulu-Natal Province to refine measures. We then conducted a cross-sectional survey of 16 clinics with 5-20 providers per clinic (N = 186). We assessed reliability using Cronbach's alpha and calculated interrater agreement (awg) and intraclass correlation coefficient (ICC) at the clinic level. Within clinics with moderate agreement, we calculated correlation of clinic-level measures with each other and with hypothesized predictors - staff continuity and infrastructure - and a clinical outcome, patient retention on antiretroviral therapy.ResultsPanelists emphasized contextual factors; we therefore focused on elements of clinic leadership, stress, cohesion, and collective problem solving (critical consciousness). Cognitive interviews confirmed salience of the domains and improved item clarity. After excluding items related to leaders' coordination abilities due to missingness and low agreement, all other scales demonstrated individual-level reliability and at least moderate interrater agreement in most facilities. ICC was low for most leadership measures and moderate for others. Measures tended to correlate within facility, and higher stress was significantly correlated with lower staff continuity. Organizational context was generally more positively rated in facilities that showed consistent agreement.ConclusionsAs theorized, organizational context is important in understanding program implementation within the South African health system. Most adapted measures show good reliability at individual and clinic levels. Additional revision of existing frameworks to suit this context and further testing in high and low performing clinics is warranted