Imaging indicator for ESD safety testing.

This report describes the development of a new detection method for electrostatic discharge (ESD) testing of explosives, using a single-lens reflex (SLR) digital camera and a 200-mm macro lens. This method has demonstrated several distinct advantages to other current ESD detection methods, including the creation of a permanent record, an enlarged image for real-time viewing as well as extended periods of review, and ability to combine with most other Go/No-Go sensors. This report includes details of the method, including camera settings and position, and results with wellcharacterized explosives PETN and RDX, and two ESD-sensitive aluminum powders

Hydrogen effects in thermoplastics and elastomers in high-pressure and low- pressure cycling environments under ambient and cold temperature conditions

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Performance testing of aged hydrogen getters against criteria for interim safe storage of plutonium bearing materials.

Hydrogen getters were tested for use in storage of plutonium-bearing materials in accordance with DOE's Criteria for Interim Safe Storage of Plutonium Bearing Materials. The hydrogen getter HITOP was aged for 3 months at 70 C and tested under both recombination and hydrogenation conditions at 20 and 70 C; partially saturated and irradiated aged getter samples were also tested. The recombination reaction was found to be very fast and well above the required rate of 45 std. cc H2h. The gettering reaction, which is planned as the backup reaction in this deployment, is slower and may not meet the requirements alone. Pressure drop measurements and {sup 1}H NMR analyses support these conclusions. Although the experimental conditions do not exactly replicate the deployment conditions, the results of our conservative experiments are clear: the aged getter shows sufficient reactivity to maintain hydrogen concentrations below the flammability limit, between the minimum and maximum deployment temperatures, for three months. The flammability risk is further reduced by the removal of oxygen through the recombination reaction. Neither radiation exposure nor thermal aging sufficiently degrades the getter to be a concern. Future testing to evaluate performance for longer aging periods is in progress

Thermal characterization and model free kinetics of aged epoxies and foams using TGA and DSC methods.

Two classes of materials, poly(methylene diphenyl diisocyanate) or PMDI foam, and cross-linked epoxy resins, were characterized using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), to help understand the effects of aging and %E2%80%9Cbake-out%E2%80%9D. The materials were evaluated for mass loss and the onset of decomposition. In some experiments, volatile materials released during heating were analyzed via mass spectroscopy. In all, over twenty materials were evaluated to compare the mass loss and onset temperature for decomposition. Model free kinetic (MFK) measurements, acquired using variable heating rate TGA experiments, were used to calculate the apparent activation energy of thermal decomposition. From these compiled data the effects of aging, bake-out, and sample history on the thermal stability of materials were compared. No significant differences between aged and unaged materials were detected. Bake-out did slightly affect the onset temperature of decomposition but only at the highest bake-out temperatures. Finally, some recommendations for future handling are made

Savannah River Site/K Area Complex getter life extension report.

The K Area Complex (KAC) at the Savannah River Site (SRS) has been utilizing HiTop hydrogen getter material in 9975 Shipping Containers to prevent the development of flammable environments during storage of moisture-containing plutonium oxides. Previous testing and subsequent reports have been performed and produced by Sandia National Laboratories (SNL) to demonstrate the suitability and longevity of the getter during storage at bounding thermal conditions. To date, results have shown that after 18 months of continuous storage at 70 C, the getter is able to both recombine gaseous hydrogen and oxygen into water when oxygen is available, and irreversibly getter (i.e. scavenge) hydrogen from the vapor space when oxygen is not available, both under a CO{sub 2} environment. [Refs. 1-5] Both of these reactions are catalytically enhanced and thermodynamically favorable. The purpose of this paper is to establish the justification that maintaining the current efforts of biannual testing is no longer necessary due to the robust performance of the getter material, the very unlikely potential that the recombination reaction will fail during storage conditions in KAC, and the insignificant aging effects that have been seen in the testing to date

Imaging indicator for ESD safety testing.

This report describes the development of a new detection method for electrostatic discharge (ESD) testing of explosives, using a single-lens reflex (SLR) digital camera and a 200-mm macro lens. This method has demonstrated several distinct advantages to other current ESD detection methods, including the creation of a permanent record, an enlarged image for real-time viewing as well as extended periods of review, and ability to combine with most other Go/No-Go sensors. This report includes details of the method, including camera settings and position, and results with wellcharacterized explosives PETN and RDX, and two ESD-sensitive aluminum powders

Etching of Surfactant from Solution-Processed, Type-Separated Carbon Nanotubes and Impact on Device Behavior

Semiconducting single-walled carbon nanotubes (SWCNTs) have great potential for use in electronic and optoelectronic devices. However, methods for synthesizing SWCNTs produce a mixture of metallic and semiconducting materials, which require additional processing to separate by electronic type. Purification and enrichment of the semiconducting fraction is readily achieved by using the centrifugation of aqueous suspensions of SWCNTs with the help of surfactants, but this leaves residual surfactant on the SWCNT surface that can impact their electronic and optical properties. Here, we present a detailed study of the sodium taurodeoxycholate (STDC) surfactant removal process during vacuum annealing, showing that it occurs through fragmentation of the surfactant, and that complete removal requires exceedingly high temperatures, which indicates strong binding to the SWCNTs. We then present an approach based on air oxidation and mild annealing to completely remove the surfactant while maintaining the SWCNT properties. Using this approach, we compare single SWCNT electronic devices with and without STDC and show that, despite the very strong surfactant binding, it does not affect device performance substantially

Continuous Cerebral Blood Flow Autoregulation Monitoring in Patients Undergoing Liver Transplantation

BACKGROUND: Clinical monitoring of cerebral blood flow (CBF) autoregulation in patients undergoing liver transplantation may provide a means for optimizing blood pressure to reduce the risk of brain injury. The purpose of this pilot project is to test the feasibility of autoregulation monitoring with transcranial Doppler (TCD) and near infrared spectroscopy (NIRS) in patients undergoing liver transplantation and to assess changes that may occur perioperatively. METHODS: We performed a prospective observational study in 9 consecutive patients undergoing orthotopic liver transplantation. Patients were monitored with TCD and NIRS. A continuous Pearson’s correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity and between MAP and NIRS data, rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Both Mx and COx were averaged and compared during the dissection phase, anhepatic phase, first 30 mins of reperfusion, and remaining reperfusion phase. Impaired autoregulation was defined as Mx ≥ 0.4. RESULTS: Autoregulation was impaired in one patient during all phases of surgery, in two patients during the anhepatic phase, and in one patient during reperfusion. Impaired autoregulation was associated with a MELD score > 15 (p=0.015) and postoperative seizures or stroke (p<0.0001). Analysis of Mx categorized in 5-mmHg bins revealed that MAP at the lower limit of autoregulation (MAP when Mx increased to ≥ 0.4) ranged between 40 and 85 mmHg. Average Mx and average COx were significantly correlated (p=0.0029). The relationship between COx and Mx remained when only patients with bilirubin > 1.2 mg/dL were evaluated (p=0.0419). There was no correlation between COx and baseline bilirubin (p=0.2562) but MELD score and COx were correlated (p=0.0458). Average COx was higher for patients with a MELD score > 15 (p=0.073) and for patients with a neurologic complication than for patients without neurologic complications (p=0.0245). CONCLUSIONS: These results suggest that autoregulation is impaired in patients undergoing liver transplantation, even in the absence of acute, fulminant liver failure. Identification of patients at risk for neurologic complications after surgery may allow for prompt neuroprotective interventions, including directed pressure management

High Asymptomatic Carriage With the Omicron Variant in South Africa

We report a 23% asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) Omicron carriage rate in participants being enrolled into a clinical trial in South Africa, 15-fold higher than in trials before Omicron. We also found lower CD4 + T-cell counts in persons with human immunodeficiency virus (HIV) strongly correlated with increased odds of being SARS-CoV-2 polymerase chain reaction (PCR) positive