Showing papers by "General Dynamics published in 2017"

Predictors of Employment Outcomes in Veterans With Traumatic Brain Injury: A VA Traumatic Brain Injury Model Systems Study.

Abstract: Objectives To examine the length of time to return to work (RTW) among service members and veterans (SM/V) with traumatic brain injury (TBI) and to identify variables predictive of RTW. Setting Department of Veterans Affairs Polytrauma Rehabilitation Centers (VA PRC). Participants SM/V enrolled in the VA PRC Traumatic Brain Injury Model Systems database who were of 18 to 60 years of age and admitted with the diagnosis of TBI. Design Prospective observational cohort study. Main outcome measures Employment status at 1-year postinjury follow-up; Time to Employment (ie, number of days it took to RTW) as documented during 1-year postinjury follow-up. Results The final sample (n = 293) included male (96%) SM/V with severe TBI (69%). Approximately 21% of the sample participants were employed at 1 year postinjury. Younger individuals who self-identified as nonminority returned to work sooner. Significant associations were observed for time to employment for cause of injury and injury severity. Conclusions Few SM/V with moderate to severe TBI returned to work at 1 year postinjury. Predictors such as younger age at the time of injury, minority status, and severity of TBI affected time to and probability of RTW. Findings from this study have important implications for rehabilitation planning and service delivery across the continuum of recovery.

Two-Photon Spectroscopy of a Series of Platinum Acetylides: Conformation-Induced Ground-State Symmetry Breaking

Abstract: With the goal of elucidating electronic and conformational effects on structure–spectroscopic property relationships in platinum acetylides, we synthesized a series of nominally centrosymmetric chromophores trans-Pt(PBu3)2(C≡C-Phenyl-X)2, where X = diphenylamino (DPA), NH2, OCH3, t-Bu, CH3, H, F, benzothiazole (BTH), CF3, CN, and NO2. We collected one- and two-photon absorption spectra and also performed density functional theory (DFT) and time-dependent (TD) DFT calculations on the ground- and excited-state properties of these compounds. The DFT calculations revealed facile rotation between the two ligands, suggesting that the compounds exhibit nonplanar ground-state conformations in solution. TDDFT calculation of the S1 state energy and transition dipole moment for a nonplanar conformation gave good agreement with experiment. Two-photon absorption spectra obtained from these compounds allowed estimation of the change of permanent electric dipole moment upon vertical excitation from ground state to S1 st...

nsPEF-induced PIP2 depletion, PLC activity and actin cytoskeletal cortex remodeling are responsible for post-exposure cellular swelling and blebbing.

Abstract: Cell swelling and blebbing has been commonly observed following nanosecond pulsed electric field (nsPEF) exposure. The hypothesized origin of these effects is nanoporation of the plasma membrane (PM) followed by transmembrane diffusion of extracellular fluid and disassembly of cortical actin structures. This investigation will provide evidence that shows passive movement of fluid into the cell through nanopores and increase of intracellular osmotic pressure are not solely responsible for this observed phenomena. We demonstrate that phosphatidylinositol-4,5-bisphosphate (PIP2) depletion and hydrolysis are critical steps in the chain reaction leading to cellular blebbing and swelling. PIP2 is heavily involved in osmoregulation by modulation of ion channels and also serves as an intracellular membrane anchor to cortical actin and phospholipase C (PLC). Given the rather critical role that PIP2 depletion appears to play in the response of cells to nsPEF exposure, it remains unclear how its downstream effects and, specifically, ion channel regulation may contribute to cellular swelling, blebbing, and unknown mechanisms of the lasting "permeabilization" of the PM.

Product Line Engineering Meets Model Based Engineering in the Defense and Automotive Industries

Abstract: Product line engineering and model based engineering are two powerful engineering approaches that each bring significant advantages to system engineering projects. This paper explores how three companies - Raytheon, General Dynamics, and General Motors - are combining these two paradigms in unique and innovative ways in very challenging application domains to achieve engineering goals of critical importance to them.

Design of a micro-AUV for autonomy development and multi-vehicle systems

Abstract: This paper presents the Bluefin SandShark micro Autonomous Underwater Vehicle (AUV), a low-logistics platform designed to encourage broader use of AUVs and reduce the timeline for new technology development. The AUV architecture includes a standardized tail section containing the necessary hardware and software for basic functionality, while reserving over half of its available volume for a user-defined payload in the forward section. Payload development is encouraged via open interfaces and a software architecture designed for the developer. The micro-AUV is also suited to multi-vehicle missions, and use-cases requiring a low-cost or expendable AUV.

Perceived quality of life among caregivers of children with a childhood-onset dystrophinopathy: a double ABCX model of caregiver stressors and perceived resources

Abstract: Duchenne and Becker muscular dystrophies, collectively referred to as dystrophinopathies, are recessive X-linked disorders characterized by progressive muscle weakness and ultimately cardiac and respiratory failure. Immediate family members are often primary caregivers of individuals with a dystrophinopathy. We explored the impact of this role by inviting primary caregivers (n = 209) of males diagnosed with childhood-onset dystrophinopathy who were identified by the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) to complete a mailed questionnaire measuring perceived social support and stress, spirituality, and family quality of life (FQoL). Bivariate and multivariate analyses examined associations between study variables using the Double ABCX model as an analytic framework. Higher stressor pile-up was associated with lower perceived social support (r = -0.29, p 0.05). FQoL was positively associated with all support measures (correlations ranged from: 0.25 to 0.58, p-values 0.01–0.001) and negatively associated with perceived stress and control (r = -0.49, p < .001). The association between stressor pile-up and FQoL was completely mediated through global perceived social support, supportive family relationships, and perceived stress and control; supportive non-family relationships did not remain statistically significant after controlling for other mediators. Findings suggest caregiver adaptation to a dystrophinopathy diagnosis can be optimized by increased perceived control, supporting family resources, and creation of a healthy family identity. Our findings will help identify areas for family intervention and guide clinicians in identifying resources that minimize stress and maximize family adaptation.

Noninvasive techniques for the determination of burn severity in real time

Abstract: Visual diagnosis of second-degree burns has proven inadequate for determining the appropriate treatment regimen. Although multiple noninvasive imaging techniques have shown promise for providing information about burn wound severity, the ideal technology to aid burn wound excision would provide real-time readouts. Herein, the authors examine a high-resolution infrared (IR) camera (thermography) and a multiprobe adapter system (MPAS-6; transepidermal evaporative water loss, colorimetry) to assess their usefulness in predicting burn severity. Contact burn wounds of increasing severity were created in a porcine model. Wounds were assessed for 4 days with an IR camera and MPAS-6. In addition, each day, the burn wounds were biopsied for histological analysis to determine burn depth for correlation with noninvasive measures. Surface temperatures decreased with increasing burn severity, which was associated with increasing transepidermal evaporative water loss. Melanin content correlated with the depth of collagen coagulation and was bimodal, with superficial and full-thickness burns having higher values than deep partial thickness wounds. Erythema content was highest in superficial burns and negatively correlated with necrosis (high-mobility group box protein 1 expression). Importantly, surface temperature taken on every single day after injury was predictive of all histologically determined measurements of burn depth (ie, collagen coagulation, apoptosis, necrosis, vascular occlusion). The results indicate that IR imaging and skin quality probes can be used to support the diagnosis of burn severity. Most importantly, IR measurements gave insight into both the zone of coagulation and the zone of stasis on every postburn day studied.

The Benefits and Risks of Energy Drinks in Young Adults and Military Service Members.

Abstract: Introduction: Energy drinks (EDs) have become an integral part of the young adult, athletic, and military culture. Many athletes are convinced that EDs enhance performance, and service members as well as college students frequently use EDs as stimulants to counter sleep deprivation, or to improve academic performance. However, concerns have been raised by some military leaders about potential adverse effects of EDs. Materials and Methods: A needs assessment survey of a convenience sample of military health care providers was conducted and identified EDs as a top knowledge need for those providers working in the area of traumatic brain injury (TBI). The instrument demonstrated high interitem consistency (Cronbach's α > .80). To further explore the state of knowledge on EDs, and to prompt further discussion of ED use and how it may related to military treatment protocols and supporting educational products, we conducted a literature review of English language publications listed in the National Lib...

Computational modeling of blast exposure associated with recoilless weapons combat training

Abstract: Military personnel are exposed to blast as part of routine combat training with shoulder-fired recoilless rifles. These weapons fire large-caliber ammunitions capable of disabling structures and uparmored vehicles (e.g., tanks). Scientific, medical, and military leaders are beginning to recognize the blast overpressure from these shoulder-fired weapons may result in acute and even long-term physiological effects to military personnel. However, the back blast generated from the Carl Gustav and Shoulder-launched Multipurpose Assault Weapon (SMAW) shoulder-fired weapons on the weapon operator has not been quantified. By quantifying and modeling the full-body blast exposure from these weapons, better injury correlations can be constructed. Blast exposure data from the Carl Gustav and SMAW were used to calibrate a propellant burn source term for computational simulations of blast exposure on operators of these shoulder-mounted weapon systems. A propellant burn model provided the source term for each weapon to capture blast effects. Blast data from personnel-mounted gauges during weapon firing were used to create initial, high-fidelity 3D computational fluid dynamic simulations using SHAMRC (Second-order Hydrodynamic Automatic Mesh Refinement Code). These models were then improved upon using data collected from static blast sensors positioned around the military personnel while weapons were utilized in actual combat training. The final simulation models for both the Carl Gustav and SMAW were in good agreement with the data collected from the personnel-mounted and static pressure gauges. Using the final simulation results, contour maps were created for peak overpressure and peak overpressure impulse experienced by military personnel firing the weapon as well as those assisting with firing of those weapons. Reconstruction of the full-body blast loading enables a more accurate assessment of the cause of potential mechanisms of injury due to air blast even for subjects not wearing blast gauges themselves. By accurately understanding the blast exposure and its variations across an individual, more meaningful correlations with physiologic response including potential TBI spectrum physiology associated with sub-concussive blast exposure can be established. As blast injury thresholds become better defined, results from these reconstructions can provide important insights into approaches for reducing possible risk of injury to personnel operating shoulder-launched weapons.

High strain rate testing and modeling of a woven E-glass–vinylester composite in dry and saturated conditions:

Abstract: The behavior of a woven E-glass–Vinylester composite in dry and seawater-saturated conditions was investigated for strain rates in the range of 0.001–100 s−1. Reliable data were obtained by conduct...

Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants

Abstract: The influence of two selected bistetrazoles, 5,5′-bis(1H-tetrazolyl)-amine (BTA) and 5,5′-hydrazinebistetrazole (HBT), on the combustion behavior of a typical triple-base propellant was investigated. Seven propellant formulations, one reference and six others incorporating 5 %, 15 %, and 25 % of either HBT or BTA compounds, respectively, were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93 % higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT-containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25 % HBT. The thermal behavior of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen-rich materials, indicating that the two compounds probably react readily with the −ONO2 groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds.

Ryanodine and IP 3 receptor-mediated calcium signaling play a pivotal role in neurological infrared laser modulation.

Abstract: Pulsed infrared (IR) laser energy has been shown to modulate neurological activity through both stimulation and inhibition of action potentials. While the mechanism(s) behind this phenomenon is (are) not completely understood, certain hypotheses suggest that the rise in temperature from IR exposure could activate temperature- or pressure-sensitive ion channels or create pores in the cellular outer membrane, allowing an influx of typically plasma-membrane-impermeant ions. Studies using fluorescent intensity-based calcium ion ([Formula: see text]) sensitive dyes show changes in [Formula: see text] levels after various IR stimulation parameters, which suggests that [Formula: see text] may originate from the external solution. However, activation of intracellular signaling pathways has also been demonstrated, indicating a more complex mechanism of increasing intracellular [Formula: see text] concentration. We quantified the [Formula: see text] mobilization in terms of influx from the external solution and efflux from intracellular organelles using Fura-2 and a high-speed ratiometric imaging system that rapidly alternates the dye excitation wavelengths. Using nonexcitable Chinese hamster ovarian ([Formula: see text]) cells and neuroblastoma-glioma (NG108) cells, we demonstrate that intracellular [Formula: see text] receptors play an important role in the IR-induced [Formula: see text], with the [Formula: see text] response augmented by ryanodine receptors in excitable cells.

A View-Dependent Adaptive Matched Filter for LADAR-Based Vehicle Tracking

Abstract: LADARs mounted on mobile platforms produce a wealth of precise range data on the surrounding objects and vehicles. The challenge we address is to infer from these raw LADAR data the location and orientation of nearby vehicles. We propose a novel view-dependent adaptive matched filter for obtaining fast and precise measurements of target vehicle pose. We derive an analytic expression for the matching function which we optimize to obtain target pose and size. Our algorithm is fast, robust and simple to implement compared to other methods. When used as the measurement component of a tracker on an autonomous ground vehicle, we are able to track in excess of 50 targets at 10 Hz. Once targets are aligned using our matched filter, we use a support vector-based discriminator to distinguish vehicles from other objects. This tracker provides a key sensing component for our autonomous ground vehicles which have accumulated hundreds of miles of on-road and off-road autonomous driving.

Short infrared laser pulses increase cell membrane fluidity

Abstract: Short infrared laser pulses induce a variety of effects in cells and tissues, including neural stimulation and inhibition. However, the mechanism behind these physiological effects is poorly understood. It is known that the fast thermal gradient induced by the infrared light is necessary for these biological effects. Therefore, this study tests the hypothesis that the fast thermal gradient induced in a cell by infrared light exposure causes a change in the membrane fluidity. To test this hypothesis, we used the membrane fluidity dye, di-4-ANEPPDHQ, to investigate membrane fluidity changes following infrared light exposure. Di-4-ANEPPDHQ fluorescence was imaged on a wide-field fluorescence imaging system with dual channel emission detection. The dual channel imaging allowed imaging of emitted fluorescence at wavelengths longer and shorter than 647 nm for ratiometric assessment and computation of a membrane generalized polarization (GP) value. Results in CHO cells show increased membrane fluidity with infrared light pulse exposure and this increased fluidity scales with infrared irradiance. Full recovery of pre-infrared exposure membrane fluidity was observed. Altogether, these results demonstrate that infrared light induces a thermal gradient in cells that changes membrane fluidity.

System and methods for automatic solar panel recognition and defect detection using infrared imaging

Abstract: Methods and systems are provided for detecting a defect in a solar panel The method includes initially imaging, via an infrared camera, a group of solar panels Then, identifying, via a computer system configured for solar panel defect detection, the individual solar panels in the group of solar panels Finally, identifying, via evaluation of an infrared image obtained by the infrared camera, a defect in at least one of the group of solar panels

In-Hospital Mortality Following Traumatic Brain Injury Among Older Medicare Beneficiaries, Comparing Statin Users With Nonusers

Abstract: Background: Traumatic brain injury (TBI) is a significant public health concern for older adults. Small-scale human studies have suggested pre-TBI statin use is associated with decreased in-hospita...

Qualitative Behavior of the Low-Frequency Vibrational Dynamics of Microtubules and the Surrounding Water.

Abstract: The dynamics of the low-frequency vibrational modes of microtubules play a key role in many theoretical models regarding their biological function. We analyze these dynamics through large scale, classical molecular dynamics simulations of a microtubule composed of 42 tubulin heterodimers to provide insights into the qualitative nature of the vibrational energy absorption and dissipation mechanisms. The computed microtubule absorption spectra and vibrational density of states in the terahertz regime are presented, along with an analysis of the vibrational dephasing rates of the tubulin monomer center of mass dynamics, which are shown to be overdamped. Additionally, the presence of the microtubule modifies the dynamical properties of the solvation shell structure within roughly 10 A of the protein. These vibrational properties are similar to those seen in other globular proteins and indicate microtubules are unlikely candidates for any large scale collective vibrational processes in the terahertz regime suc...

Susceptibility-Based Neuroimaging: Standard Methods, Clinical Applications, and Future Directions.

Abstract: The evaluation of neuropathologies using MRI methods that leverage tissue susceptibility have become standard practice, especially to detect blood products or mineralization. Additionally, emerging MRI techniques have the ability to provide new information based on tissue susceptibility properties in a robust and quantitative manner. This paper discusses these advanced susceptibility imaging techniques and their clinical applications.

Photodriven Oxygen Removal via Chromophore-Mediated Singlet Oxygen Sensitization and Chemical Capture

Abstract: We report a general, photochemical method for the rapid deoxygenation of organic solvents and aqueous solutions via visible light excitation of transition metal chromophores (TMCs) in the presence of singlet oxygen scavenging substrates. Either 2,5-dimethylfuran or an amino acid (histidine or tryptophan methyl ester) was used as the substrate in conjunction with an iridium or ruthenium TMC in toluene, acetonitrile, or water. This behavior is described for solutions with chromophore concentrations that are pertinent for both luminescence and transient absorption spectroscopies. These results consistently produce TMC lifetimes comparable to those measured using traditional inert gas sparging and freeze–pump–thaw techniques. This method has the added benefits of providing long-term stability (days to months); economical preparation due to use of inexpensive, commercially available oxygen scrubbing substrates; and negligible size and weight footprints compared to traditional methods. Furthermore, attainment o...

LADAR-Based Vehicle Tracking and Trajectory Estimation for Urban Driving

Abstract: Safe mobility for unmanned ground vehicles requires reliable detection of other vehicles, along with precise estimates of their locations and trajectories. Here we describe the algorithms and system we have developed for accurate trajectory estimation of nearby vehicles using an onboard scanning LADAR. We introduce a variable-axis Ackerman steering model and compare this to an independent steering model. Then for robust tracking we propose a multi-hypothesis tracker that combines these kinematic models to leverage the strengths of each. When trajectories estimated with our techniques are input into a planner, they enable an unmanned vehicle to negotiate traffic in urban environments. Results have been evaluated running in real time on a moving vehicle with a scanning LADAR.

Thermal Wake Studies During the August 21st 2017 Total Solar Eclipse

Abstract: A thermal wake occurs when a high altitude balloon (HAB) influences and changes the surrounding ambient atmospheric temperature of the air through which it passes. This effect warms the air below the balloon to greater than the ambient temperatures during daytime flights, and cooler than ambient temperatures during nighttime flights. The total solar eclipse of August 21st, 2017, provided us with an opportunity to study these balloon induced temperature transitions from daytime, to eclipsed induced night conditions over the scale of a single flight. To measure these transitions, St. Catherine University and the University of Minnesota, Morris, flew over 40 temperature sensors suspended beneath weather balloons ascending within the path of totality. Stratospheric temperature data collected during the eclipse show evidence of both daytime and nighttime wake temperature profiles.

LADAR-based vehicle tracking and trajectory estimation for urban driving

Abstract: Safe mobility for unmanned ground vehicles requires reliable detection of other vehicles, along with precise estimates of their locations and trajectories. Here we describe the algorithms and system we have developed for accurate trajectory estimation of nearby vehicles using an onboard scanning LADAR. We introduce a variable-axis Ackerman steering model and compare this to an independent steering model. Then for robust tracking we propose a multi-hypothesis tracker that combines these kinematic models to leverage the strengths of each. When trajectories estimated with our techniques are input into a planner, they enable an unmanned vehicle to negotiate traffic in urban environments. Results have been evaluated running in real time on a moving vehicle with a scanning LADAR.

Fluorescence lifetime imaging of calcium flux in neurons in response to pulsed infrared light

Abstract: Pulsed infrared light can excite action potentials in neurons; yet, the fundamental mechanism underlying this phenomenon is unknown. Previous work has observed a rise in intracellular calcium concentration following infrared exposure, but the source of the calcium and mechanism of release is unknown. Here, we used fluorescence lifetime imaging of Oregon Green BAPTA-1 to study intracellular calcium dynamics in primary rat hippocampal neurons in response to infrared light exposure. The fluorescence lifetime of Oregon Green BAPTA-1 is longer when bound to calcium, and allows robust measurement of intracellular free calcium concentrations. First, a fluorescence lifetime calcium calibration curve for Oregon Green BAPTA-1 was determined in solutions. The normalized amplitude of the short and long lifetimes was calibrated to calcium concentration. Then, neurons were incubated in Oregon Green BAPTA-1 and exposed to pulses of infrared light (0-1 J/cm2; 0-5 ms; 1869 nm). Fluorescence lifetime images were acquired prior to, during, and after the infrared exposure. Fluorescence lifetime images, 64x64 pixels, were acquired at 12 or 24 ms for frame rates of 83 and 42 Hz, respectively. Accurate α1 approximations were achieved in images with low photon counts by computing an α1 index value from the relative probability of the observed decay events. Results show infrared light exposure increases intracellular calcium in neurons. Altogether, this study demonstrates accurate fluorescence lifetime component analysis from low-photon count data for improved imaging speed.

Quality of Life and Medication Adherence of Independently Living Older Adults Enrolled in a Pharmacist-Based Medication Management Program

Abstract: This study sought to understand the medication adherence and quality of life (QOL) of recipients of a pharmacist-based medication management program among independently living older adults. Using a cross-sectional, quasi-experimental study design, we compared older adults enrolled in the program to older adults not enrolled in the program. Data were collected via face-to-face interviews in independent-living facilities and in participants’ homes. Independently living older adults who were enrolled in the medication management program (n = 38) were compared to older adults not enrolled in the program (control group (n = 41)). All participants were asked to complete questionnaires on health-related quality of life (QOL, using the SF-36) and medication adherence (using the four-item Morisky scale). The medication management program recipients reported significantly more prescribed medications (p < 0.0001) and were more likely to report living alone (p = 0.01) than the control group. The medication management program recipients had a significantly lower SF-36 physical functioning score (p = 0.03) compared to the control group, although other SF-36 domains and self-reported medication adherence were similar between the groups. Despite taking more medications and more commonly living alone, independent living older adults enrolled in a pharmacist-based medication management program had similar QOL and self-reported medication adherence when compared to older adults not enrolled in the program. This study provides initial evidence for the characteristics of older adults receiving a pharmacist-based medication management program, which may contribute to prolonged independent living and positive health outcomes.

Systems and methods for a firearm conversion kit with slaved ejector

Abstract: A slide for a weapon conversion kit of the type used in conjunction with a firearm having a stock ejector and configured to fire ammunition is provided. The slide includes a slide body and a slaved ejector member rotatably coupled to the slide body. The slaved ejector member has a first portion and a second portion, the second portion including a contact region. The slaved ejector member is configured to contact the stock ejector when the slide body slides rearward in response to firing of the firearm and thereby causes the contact region of the second portion of the slaved ejector member to eject a cartridge case of the ammunition.