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Introduction: During recovery, stroke patients are at risk of developing psychological complications impacting their quality of life. Diets rich in fat negatively impact anxiety disorders; however, this relationship has not been explored among stroke survivors considering food insecurity status, a social determinant of health (SDOH). Methods: In a population-based cohort of 309 patients with acute stroke, we retrospectively assessed self-administered surveys to evaluate the association between dietary fat intake and anxiety in stroke survivors presenting for an initial visit at a University-based stroke clinic from January 2021-July 2021 in Houston, Texas. Anxiety was measured using the GAD-7 scoring system and dichotomized to either “None/Mild” or “Moderate/Severe.” Dietary fat intake was calculated using the quality frequency screener; food insecurity status, using the Hunger Vital sign screener. Results: Among this population, 15.46% reported food insecurity and 50.8% (N=157) had moderate to severe anxiety. The multivariable logistic regression model showed that total fat intake (Odds Ratio (OR)=1.01, 95% CI: 1.00, 1.03; P-value=0.016) and percent fat (OR=1.06, 95% CI: 1.01, 1.11; P-value=0.018) dietary intake had a statistically significant negative impact on anxiety, adjusting for covariates and an interaction term between food insecurity status and dietary fat intake. Conclusion: Although studies describe the role of a healthy diet in stroke, this is the first study that looks at dietary fat intake as it relates to stroke and anxiety, as well as, food insecurity among stroke survivors. SDOH including food access and affordability are associated with stroke risk and dietary fat outcomes. A better understanding of fat intake and associated factors in this population will provide an opportunity for developing interventions for those at highest risk. Access to healthy foods may prevent higher intake of fat in one’s diet and reduce the risk of stroke.

The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

Particle impact ignition has been the primary cause of numerous fires in oxygen systems. This ignition phenomenon is known to occur where particles are present in high-velocity gas, and where impact occurs on a flammable material. The particle impact ignition behavior of many metals has been widely studied, but the particle impact ignition behavior of polymeric materials is relatively unknown. Particle impact ignition in polymeric materials is a concern as these materials are commonly used in component seat and seal applications, where high-velocity particle impacts can occur. This study evaluates several polymeric materials and compares the minimum temperature required for ignition (threshold temperature) of these materials: Kel-F 81 (CTFE), Teflon (PTFE), PEEK, Vespel SP-21, and Nylon 6/6. The materials were configured as targets in the White Sands Test Facility high-velocity particle impact test system. Gaseous oxygen was flowed at 4000 psi and sonic velocity, and the targets were impacted with 2000-micron aluminum 2017 particles. This paper discusses the results of these tests and ranks the materials according to their threshold temperatures at these conditions.

The dimensional stability of polychlorotrifluoroethylene (PCTFE) valve seats used in oxygen regulator applications was determined by thermomechanical analysis (TMA). Two traceable grades of PCTFE were tested; Kel-F 81 and Neoflon CTFE M400H. For these particular resins, the effect of percent crystallinity, zero strength time (ZST) molecular weight, resin grade, process history (compression-molded versus extruded) on the dimensional stability and annealing behavior was determined. In addition to the traceable Kel-F 81 and Neoflon CTFE M400H grades, actual PCI'PH valve seats of differing geometry and design were tested by TMA. The PCTFE valve seats were of unspecified resin grade, although certain inferences about the grade could be drawn based on knowledge of the valve seat fabrication date. Results consistently revealed dimensional instability of varying magnitude at temperatures ranging from 40 to 70 degrees Celsius. Furthermore, some of the pre- 1 995 seats appeared to be more dimensionally stable than those fabricated after 1995. The TMA results are discussed in the context of several proposed ignition mechanisms; namely, particle impact, presence of contaminant oils and fibers, and localized heating by flow friction and/or resonance. The effect of metal constraint on the dimensional stability of PCTFE is also discussed. Finally, the effect of percent crystallinity, ZST molecular weight, resin grade, process history (compression-molded versus extruded) on the AIT, delta Hc and impact sensitivity of various types of Neoflon CTFE M400H was determined using Kel-F 81 as a control. Results show that the AIT, delta Hc and impact sensitivity were essentially independent of Neoflon CTFE process history and structure.

The permeation resistance of chlorinated polyethylene (CPE) used in totally encapsulating chemical protective suits against the aerospace fuels hydrazine, monomethylhydrazine, and uns-dimethylhydrazine was determined by measuring the breakthrough time (BT) and time-averaged vapor transmission rate (VTR) using procedures consistent with ASTM F 739 and ASTM F 1383. Two exposure scenarios were simulated: a 2 hour (h) fuel vapor exposure, and a liquid fuel "splash" followed by a 2 h vapor exposure. To simulate internal suit pressure during operation, a positive differential pressure of 0.3 in. water (75 Pa) on the collection side of the permeation apparatus was used. Using the available data, a model was developed to estimate propellant concentrations inside an air-line fed, totally encapsulating chemical protective suit. Concentrations were calculated under simulated conditions of fixed vapor transmission rate, variable breathing air flow rate, and variable splash exposure area. Calculations showed that the maximum allowable permeation rates of hydrazine fuels through CPE were of the order of 0.05 to 0.08 ng/sq cm min for encapsulating suits with low breathing air flow rates (of the order of 5 scfm or 140 L min-1). Above these permeation rates, the 10 parts-per-billion (ppb) threshold limit value time-weighted average could be exceeded. To evaluate suit performance at 10 ppb threshold-limiting value/time-weighted average level concentrations, use of a sensitive analytical method such as cation exchange high performance liquid chromatography with amperometric detection was found to be essential. The analytical detection limit determines the lowest measurable VTR, which in turn governed the lowest per meant concentration that could be calculated inside the totally encapsulating chemical protective suit.

When a helicopter main rotor blade is ballistically damaged, an imbalance is created in the rotor, causing the rotor disk to execute unwanted motions, which are detrimental to performance. The normally smooth-flying helicopter develops new vibrations that can be physiologically annoying or debilitating to the pilot, can exceed structural fatigue endurance limits, can cause aeromechanical instabilities, and can reduce helicopter performance ability. This report examines the effect of the loss of the outboard section of one rotating blade of a rotor set of four blades on the fixed-system (nonrotating) rotor disk motion. The report shows, beginning with the rotor blade forcing, how a damaged blades response changes, and how this change feeds into the rotor's fixed-system disk motion (the disk referring to the blades acting in concert as a whole entity). With a normally undamaged rotor (referring to all the blades), there exists within the rotor itself the capability of motion canceling of certain frequencies depending on the number of rotor blades in the rotor. This study tracks each individual harmonic (integer multiples of the rotor speed) frequency, one at a time, in order to obtain a first-principles understanding of the phenomena involved with rotor imbalance.

The objective of this work was to obtain a validated equation of state for hydrazine and monomethylhydrazine (MMH) and use this equation to calculate thermodynamic properties. The approach was based on using both reliable critical property values and a value of the acentric factor in the Soave Redlich Kwong and the Peng Robinson model equations of state. These equations were validated by comparing calculated molar volumes for phase equilibrium with published experimental values and comparing calculated vapor pressures with published experimental values over the temperature range appropriate for the corresponding state equations. The equation of state giving the best results was used to calculate enthalpy and entropy departure functions and fugacity values. Additional thermodynamic property calculations were performed to produce partial Mollier diagrams and thermodynamic properties containing internal energy, enthalpy, and entropy values for hydrazine and MMH. The analyses of systems in which either adiabatic or near-adiabatic compression of liquid or vapor hydrazine or low velocity detonations occur require a validated equation of state for representing occurring molar volumes and for energy calculations. Other calculations for thermodynamic properties of hydrazine are available, but the values are for a strict ideal gas state. This work characterized destructive events using hydrazine by calculating for isentropic compression temperatures. The final temperatures were calculated and compared using the ideal and real gas fluid equations of state.

This report presents a generic first-principles helicopter trim analysis for use on a personal work station. Working from the helicopter's physical properties, it calculates the main rotor blade's collective, longitudinal cyclic, body pitch, and stabilator pitch angles to maintain a trimmed flight condition over a complete forward-speed range. The computer program automatically sweeps through a forward-speed range, varying the collective, longitudinal cyclic, and stabilator pitch angles to satisfy the trimmed condition. It is an improvement over earlier work where the analyst had to vary these parameters at the keyboard. It presents an example of the usage with an AH-64A helicopter, and the program's source code is included.