Single-beam velocimetry with dual frequency comb absorption spectroscopy.

Laser absorption Doppler velocimeters use a crossed-beam configuration to cancel errors due to laser frequency drift and absorption model uncertainty. This configuration complicates the spatial interpretation of the measurement since the two beams sample different volumes of gas. Here, we achieve single-beam velocimetry with a portable dual comb spectrometer (DCS) with high frequency accuracy and stability enabled by GPS-referencing, and a new high-temperature water vapor absorption database. We measure the inlet flow in a supersonic ramjet engine and demonstrate single-beam measurements that are on average within 19 m/s of concurrent crossed-beam measurements. We estimate that the DCS and the new database contribute 1.6 and 13 m/s to this difference respectively.

Thermometry and velocimetry in a ramjet using dual comb spectroscopy of the O2 A-band.

Dual comb spectroscopy (DCS) of near-infrared H2O absorption has been demonstrated in the past for low-uncertainty flow measurements in ground test ramjets. However, H2O is scarce at actual ramjet flight altitudes, so oxygen is a preferable absorption target. Here, we demonstrate DCS of the O2 A-band (13000-13200 cm-1) and fit temperature and velocity across different flow conditions in a ground-test ramjet, demonstrating precisions of 3-5% and 7-11% respectively in five minutes and total uncertainty estimates of 7-9% and 8-12% respectively. The DCS measurements and uncertainty estimates are compared to predicted values for the test facility.

Description of a COVID-19 Beta variant outbreak, Joint Base Lewis-McChord, WA, February-March 2021.

An outbreak of SARS CoV-2 infection occurred in an infantry battalion from Joint Base Lewis-McChord following participation in a field training exercise in the vicinity of Yakima, WA in February of 2021. Extreme weather during the exercise disrupted planned COVID-19 mitigation measures and caused 110 soldiers to be sheltered in a small aircraft hangar for several nights. The probable index case reported to sick call with symptoms compatible with COVID-19, but the soldier was not diagnosed with COVID-19, was returned to duty, and was allowed to remain in the enclosed hangar for 3 additional days. In total, 143 individuals with epidemiologic ties to the field training exercise tested positive for SARS-CoV-2 during the outbreak. Nine samples sent for sequencing were determined to be the SARS-CoV-2 Beta variant. This report illustrates important lessons learned whose implementation in the future will enable better protection of service members from COVID-19 and similar health risks associated with training.

Benefits of triple acoustic beamforming during speech-on-speech masking and sound localization for bilateral cochlear-implant users.

Bilateral cochlear-implant (CI) users struggle to understand speech in noisy environments despite receiving some spatial-hearing benefits. One potential solution is to provide acoustic beamforming. A headphone-based experiment was conducted to compare speech understanding under natural CI listening conditions and for two non-adaptive beamformers, one single beam and one binaural, called "triple beam," which provides an improved signal-to-noise ratio (beamforming benefit) and usable spatial cues by reintroducing interaural level differences. Speech reception thresholds (SRTs) for speech-on-speech masking were measured with target speech presented in front and two maskers in co-located or narrow/wide separations. Numerosity judgments and sound-localization performance also were measured. Natural spatial cues, single-beam, and triple-beam conditions were compared. For CI listeners, there was a negligible change in SRTs when comparing co-located to separated maskers for natural listening conditions. In contrast, there were 4.9- and 16.9-dB improvements in SRTs for the beamformer and 3.5- and 12.3-dB improvements for triple beam (narrow and wide separations). Similar results were found for normal-hearing listeners presented with vocoded stimuli. Single beam improved speech-on-speech masking performance but yielded poor sound localization. Triple beam improved speech-on-speech masking performance, albeit less than the single beam, and sound localization. Thus, triple beam was the most versatile across multiple spatial-hearing domains.

Anxiety during respirator use: comparison of two respirator types.

Anxiety may interfere with proper respirator use. This study directly compares the effect of two types of respirators--elastomeric half-face mask with dual-cartridges (HFM) and N95 filtering facepiece--on anxiety levels. Twelve volunteers with normal or mildly impaired respiratory conditions performed a series of simulated work tasks using the HFM and N95 on different days. The State-Trait Anxiety Inventory (STAI) measured state anxiety (SA) before and during respirator use. STAI also measured trait anxiety (TA), a stable personal characteristic. The effect of the respirator was measured as the difference between SA pre-use and during use. Work with HFM was associated with an increase in SA (2.92 units, p < .01), whereas work with the N95 had no observed effect. Anxiety should be considered in the selection of the best respirator for a user. Impact on anxiety should be considered for respirator design and certification purposes, particularly if the device is to be widely used in workplace and community settings.

Respirator impact on work task performance.

OBJECTIVE: Respirators are used to maintain work performance and protect against inhaled toxins. The study compared the effects of two commonly used respirator classes--dual cartridge half face mask (HFM) and filtering face piece (N95)--upon work productivity. METHODS: 107 volunteers performed eight simulated work tasks when using the HFM and N95 respirators. Tasks included several body positions, exertion levels, and concentration requirements. Objective measures of accuracy and speed were developed for each task. Scores for each task were based on the subject's rank among all subjects. RESULTS: All subjects were capable of performing the tasks. There were no statistically significant differences between respirator types in either task performance metric. CONCLUSIONS: Productivity impact can be measured effectively and should be considered as part of respirator design testing and when selecting the optimal respirator for a worker.

Subjective response to respirator type: effect of disease status and gender.

OBJECTIVE: To assess the effect of respirator type and user characteristics (eg, health status) on the subjective response to respirator use. METHODS: The subjective responses for multiple domains were evaluated in 104 volunteers performing work tasks in a simulated work environment. Each used a dual cartridge half face mask and a filtering facepiece (N95) respirator. The study population was recruited to include four groups (normal respiratory status, mild asthma, chronic obstructive pulmonary disease, or chronic rhinitis). Mixed model regression analyses determined the effects of respirator type, disease, gender, and age. RESULTS: Half face mask produced more adverse subjective response than the N95 for most scales. There were significant interactions such that disease status modified the effect of respirator type. In general, women reported greater adverse ratings than did men. CONCLUSIONS: The effect of respirator type depends on disease status. Respirator design evaluation panels should include persons with mild respiratory disease.

Respirator physiologic impact in persons with mild respiratory disease.

OBJECTIVE: To assess whether mild respiratory disease affects physiologic adaptation to respirator use. METHODS: The study compared the respiratory effects of dual cartridge half face mask and filtering facepeice (N95) respirators while performing simulated-work tasks. Subjects with mild chronic obstructive pulmonary disease (n = 14), asthma (n = 42), chronic rhinitis (n = 17), and normal respiratory status (n = 24) were studied. Mixed model regression analyses determined the effects of respirator type, disease status, and the respirator-disease interactions. RESULTS: Respirator type significantly affected several physiologic measures. Respirator type effects differed among disease categories as shown by statistically significant interaction terms. Respiratory timing parameters were more affected than ventilatory volumes. In general, persons with asthma showed greater respirator-disease interactions than chronic obstructive pulmonary disease, rhinitis, or healthy subjects. CONCLUSIONS: The effects of respirator type differ according to the category of respiratory disease.

Multidomain subjective response to respirator use during simulated work.

OBJECTIVE: : Evaluate subjective tolerance to respirator use outside of traditional industrial settings by users including persons with mild respiratory impairment. METHODS: : The response to respirator use (half face mask dual cartridge and N95) was measured during eight types of work activities as well as in an exercise laboratory setting. The 43 research subjects included persons with mild respiratory impairments. Multiple domains of subjective response were evaluated. RESULTS: : Mixed model regression analyses assessing the effect of respirator type and task type showed: 1) most tolerated respirator use well; 2) half face mask respirators typically had greater adverse impact than N95 types; 3) multiple subjective outcomes, rather than only comfort/breathing impact, should be measured; and 4) rated subjective impact during work activities is less than in exercise laboratory settings. CONCLUSIONS: : The results suggest that respirator use may be feasible on a widespread basis if necessary in the face of epidemic or terror concerns.

Respirator physiological effects under simulated work conditions.

This study compared the physiological impacts of two respirator types in simulated work conditions. Fifty-six subjects included normal volunteers and persons with mild respiratory impairments (chronic rhinitis, mild COPD, and mild asthma). Respiratory parameters and electrocardiogram were measured using respiratory inductive plethysmography while performing eight work tasks involving low to moderate exertion using two respirators: (1) a dual cartridge half face mask (HFM) respirator, and (2) the N95. Mixed model regression analyses evaluating the effect of task and respirator type showed that task affected tidal volume, minute ventilation, breathing frequency and heart rate; all were greater in heavier tasks. Although respirator type did not affect respiratory volume parameters and flow rates, the HFM led to increase in the inspiratory time, reduction of the expiratory time, and increase in the duty cycle in comparison with the N95. The magnitude of differences was relatively small. The results suggest that most individuals, including persons with mild respiratory impairments, will physiologically tolerate either type of respirator at low to moderate exertion tasks. However, because effective protection depends on proper use, differences in subjective effect may have greater impact than physiological differences. Using respirators may be feasible on a widespread basis if necessary for maintaining essential services in the face of widespread concern about an infectious or terrorist threat.

Localization of primary prostate cancer with dual-phase 18F-fluorocholine PET.

UNLABELLED: This study compared 18F-fluorocholine uptake in malignant and benign areas of the prostate at 2 time points to determine the suitability of delayed or dual-phase 18F-fluorocholine PET for localizing malignancy in the prostate gland. METHODS: Twenty-six men (15 newly diagnosed with prostate cancer, 2 with recurrent prostate cancer, 6 with no evidence of prostate cancer recurrence after treatment, and 3 with no history of prostate cancer) underwent dual-phase PET consisting of initial whole-body PET starting 7 min after injection of 3.3-4 MBq/kg of 18F-fluorocholine followed by 1-h delayed PET of the pelvis. Tracer uptake in the prostate on the initial and delayed images was measured on a sextant basis. Prostate biopsy or whole-prostate histologic examination after radical prostatectomy was used to classify a prostate sextant as a dominant malignant region or probable benign region. For each sextant, a retention index based on the measured maximum standardized uptake value (SUVmax) was calculated on the initial and delayed images. In 15 prostates with both benign and malignant sextants on histologic examination, a malignant-to-benign ratio of SUVmax was also calculated for each time point. RESULTS: A dominant malignant region was found in 17 subjects, and a probable benign region was found in 24 subjects. The mean SUVmax for dominant malignant regions increased significantly between initial and delayed scans, from 7.6 to 8.6 (mean retention index, +14%; 95% confidence interval, 6%-22%; P = 0.002). The mean SUVmax for probable benign regions decreased significantly between initial and delayed scans, from 4.8 to 3.9 (mean retention index, -17%; 95% confidence interval, -10% to -23%, P < 0.001). The mean malignant-to-benign ratio increased significantly, from 1.4 on the initial scan to 1.8 on the delayed scan (P = 0.003). The areas under the receiver operating characteristic curves for distinguishing dominant malignant regions from probable benign regions based on initial SUVmax, delayed SUVmax, and retention index were 0.81, 0.92, and 0.93, respectively. CONCLUSION: On dual-phase PET of the prostate, areas of malignancy consistently demonstrated stable or increasing 18F-fluorocholine uptake, whereas most areas containing benign tissue demonstrated decreasing uptake. Delayed or dual-phase imaging after injection of 18F-fluorocholine may improve the performance of 18F-fluorocholine PET for localizing malignant areas of the prostate.