Reducing contaminating noise effects when calculating low-boom loudness levels.

During NASA X-59 quiet supersonic aircraft community response tests, low-boom recordings will contain contaminating noise from instrumentation and ambient acoustical sources. This noise can inflate sonic boom perception metrics by several decibels. This paper discusses the development and comparison of robust lowpass filtering techniques for removing contaminating noise effects from low-boom recordings. The two filters are a time-domain Butterworth-magnitude filter and a frequency-domain Brick Wall filter. Both filters successfully reduce noise contamination in metric calculations for simulated data with real-world contaminating noise and demonstrate comparable performance to a modified ISO 11204 correction. The Brick Wall filter's success indicates that further attempts to match boom spectrum high-frequency roll-off beyond the contaminating noise floor are unnecessary and have marginal improvements on final metric calculations. Additionally, the Butterworth filter removes statistical correlation between ambient and boom levels for a real-world flight campaign, adding evidence that these techniques also work on other boom shapes. Overall, both filters can produce accurate metric calculations with only a few hundred hertz of positive signal-to-noise ratio. This work describes methods for accurate metric calculations in the presence of moderate noise contamination that should benefit X-59 and future low-boom supersonic aircraft testing.

Gut Microbiome in Progressive Multiple Sclerosis.

OBJECTIVE: This study was undertaken to investigate the gut microbiome in progressive multiple sclerosis (MS) and how it relates to clinical disease. METHODS: We sequenced the microbiota from healthy controls and relapsing-remitting MS (RRMS) and progressive MS patients and correlated the levels of bacteria with clinical features of disease, including Expanded Disability Status Scale (EDSS), quality of life, and brain magnetic resonance imaging lesions/atrophy. We colonized mice with MS-derived Akkermansia and induced experimental autoimmune encephalomyelitis (EAE). RESULTS: Microbiota ß-diversity differed between MS patients and controls but did not differ between RRMS and progressive MS or differ based on disease-modifying therapies. Disease status had the greatest effect on the microbiome ß-diversity, followed by body mass index, race, and sex. In both progressive MS and RRMS, we found increased Clostridium bolteae, Ruthenibacterium lactatiformans, and Akkermansia and decreased Blautia wexlerae, Dorea formicigenerans, and Erysipelotrichaceae CCMM. Unique to progressive MS, we found elevated Enterobacteriaceae and Clostridium g24 FCEY and decreased Blautia and Agathobaculum. Several Clostridium species were associated with higher EDSS and fatigue scores. Contrary to the view that elevated Akkermansia in MS has a detrimental role, we found that Akkermansia was linked to lower disability, suggesting a beneficial role. Consistent with this, we found that Akkermansia isolated from MS patients ameliorated EAE, which was linked to a reduction in RORγt+ and IL-17-producing γδ T cells. INTERPRETATION: Whereas some microbiota alterations are shared in relapsing and progressive MS, we identified unique bacteria associated with progressive MS and clinical measures of disease. Furthermore, elevated Akkermansia in MS may be a compensatory beneficial response in the MS microbiome. ANN NEUROL 2021;89:1195-1211.

Saturn-V sound levels: A letter to the Redditor.

The Saturn V is a monument to one of mankind's greatest achievements: the human Moon landings. However, online claims about this vehicle's impressive acoustics by well-meaning individuals are often based on misunderstood or incorrect data. This article, intended for both educators and enthusiasts, discusses topics related to rocket acoustics and documents what is known about the Saturn V's levels: overall power, maximum overall sound pressure, and peak pressure. The overall power level was approximately 204 dB re 1 pW, whereas its lesser sound pressure levels were impacted by source size, directivity, and propagation effects. As this article is part of a special issue on Education in Acoustics in The Journal of the Acoustical Society of America, supplementary Saturn V-related homework problems are included.

Using multiple imputation to efficiently correct cerebral MRI whole brain lesion and atrophy data in patients with multiple sclerosis.

Automated segmentation of brain MRI scans into tissue classes is commonly used for the assessment of multiple sclerosis (MS). However, manual correction of the resulting brain tissue label maps by an expert reader remains necessary in many cases. Since automated segmentation data awaiting manual correction are "missing", we proposed to use multiple imputation (MI) to fill-in the missing manually-corrected MRI data for measures of normalized whole brain volume (brain parenchymal fraction-BPF) and T2 hyperintense lesion volume (T2LV). Automated and manually corrected MRI measures from 1300 patients enrolled in the Comprehensive Longitudinal Investigation of Multiple Sclerosis at the Brigham and Women's Hospital (CLIMB) were identified. Simulation studies were conducted to assess the performance of MI with missing data both missing completely at random and missing at random. An imputation model including the concurrent automated data as well as clinical and demographic variables explained a high proportion of the variance in the manually corrected BPF (R(2)=0.97) and T2LV (R(2)=0.89), demonstrating the potential to accurately impute the missing data. Further, our results demonstrate that MI allows for the accurate estimation of group differences with little to no bias and with similar precision compared to an analysis with no missing data. We believe that our findings provide important insights for efficient correction of automated MRI measures to obviate the need to perform manual correction on all cases.

Space Launch System acoustics: Far-field noise measurements of the Artemis-I launch.

To improve understanding of super heavy-lift rocket acoustics, this letter documents initial findings from noise measurements during liftoff of the Space Launch System's Artemis-I mission. Overall sound pressure levels, waveform characteristics, and spectra are described at distances ranging from 1.5 to 5.2 km. Significant results include: (a) the solid rocket boosters' ignition overpressure is particularly intense in the direction of the pad flame trench exit; (b) post-liftoff maximum overall levels range from 127 to 136 dB, greater than pre-launch predictions; and (c) the average maximum one-third-octave spectral peak occurred at 20 Hz, causing significant deviation between flat and A-weighted levels.

Ascorbate deficiency increases progression of shigellosis in guinea pigs and mice infection models.

Shigella spp. are the causative agents of bacterial dysentery and shigellosis, mainly in children living in developing countries. The study of Shigella entire life cycle in vivo and the evaluation of vaccine candidates' protective efficacy have been hampered by the lack of a suitable animal model of infection. None of the studies evaluated so far (rabbit, guinea pig, mouse) allowed the recapitulation of full shigellosis symptoms upon Shigella oral challenge. Historical reports have suggested that dysentery and scurvy are both metabolic diseases associated with ascorbate deficiency. Mammals, which are susceptible to Shigella infection (humans, non-human primates and guinea pigs) are among the few species unable to synthesize ascorbate. We optimized a low-ascorbate diet to induce moderate ascorbate deficiency, but not scurvy, in guinea pigs to investigate whether poor vitamin C status increases the progression of shigellosis. Moderate ascorbate deficiency increased shigellosis symptom severity during an extended period of time (up to 48 h) in all strains tested (Shigella sonnei, Shigella flexneri 5a, and 2a). At late time points, an important influx of neutrophils was observed both within the disrupted colonic mucosa and in the luminal compartment, although Shigella was able to disseminate deep into the organ to reach the sub-mucosal layer and the bloodstream. Moreover, we found that ascorbate deficiency also increased Shigella penetration into the colon epithelium layer in a Gulo-/- mouse infection model. The use of these new rodent models of shigellosis opens new doors for the study of both Shigella infection strategies and immune responses to Shigella infection.

Sonic boom measurements: Practical implications considering ground effects, microphone installation, and weather hardening.

Sonic boom measurements from recent flight tests have provided an opportunity to investigate effects of microphone installation on sonic boom waveforms, spectra, and metric levels in support of NASA X-59 flight test planning. While those flight tests used N-wave aircraft (F-18s), modeling studies were also conducted using source characteristics for a shaped low-boom aircraft. Of particular interest were the effects of receiver height on boom waveforms and metrics at elevated receiver positions, microphone installation, and local ground cover type. Reductions of more than 2 dB in A-weighted sound exposure level and perceived level were shown for 1.6 ft (0.48 m) microphone heights for 35º ray elevation angle. Measured and modeled results are described in this letter.

The MUB40 Peptide for Use in Detecting Neutrophil-Mediated Inflammation Events.

Here, we provide a protocol involving the use of MUB40, a synthesized peptide with the ability to bind glycosylated lactoferrin stored at high concentrations in specific and tertiary granules of neutrophils. This protocol details how MUB40 conjugated directly to a fluorophore can be used to stain neutrophils in fixed/permeabilized tissues as well as how this can be used in live-cell imaging to assay for neutrophil activation and de-granulation. Neutrophil detection methods are limited to species-specific monoclonal antibodies, which are not always suitable for certain applications. MUB40 does not penetrate the cell membrane and is thus excluded from lactoferrin stored in non-activated/non-permeabilized neutrophils. MUB40 has the added benefit of recognizing lactoferrin from a broad host range, making it especially useful for comparing results in studies involving multiple research models, reducing the number of duplicate reagents, and simplifying protocols through single-step staining.

MUB40 Binds to Lactoferrin and Stands as a Specific Neutrophil Marker.

Neutrophils represent the most abundant immune cells recruited to inflamed tissues. A lack of dedicated tools has hampered their detection and study. We show that a synthesized peptide, MUB40, binds to lactoferrin, the most abundant protein stored in neutrophil-specific and tertiary granules. Lactoferrin is specifically produced by neutrophils among other leukocytes, making MUB40 a specific neutrophil marker. Naive mammalian neutrophils (human, guinea pig, mouse, rabbit) were labeled by fluorescent MUB40 conjugates (-Cy5, Dylight405). A peptidase-resistant retro-inverso MUB40 (RI-MUB40) was synthesized and its lactoferrin-binding property validated. Neutrophil lactoferrin secretion during in vitro Shigella infection was assessed with RI-MUB40-Cy5 using live cell microscopy. Systemically administered RI-MUB40-Cy5 accumulated at sites of inflammation in a mouse arthritis inflammation model in vivo and showed usefulness as a potential tool for inflammation detection using non-invasive imaging. Improving neutrophil detection with the universal and specific MUB40 marker will aid the study of broad ranges of inflammatory diseases.

Shigella sonnei Encodes a Functional T6SS Used for Interbacterial Competition and Niche Occupancy.

Shigella is a leading cause of dysentery worldwide, with the majority of infections caused by two subgroups, S. flexneri and S. sonnei. Although S. flexneri has been highly prevalent in low-income countries, global development has brought an increase in S. sonnei at the expense of S. flexneri. However, the mechanisms behind this shift are not understood. Here we report that S. sonnei, but not S. flexneri, encodes a type VI secretion system (T6SS) that provides a competitive advantage in the gut. S. sonnei competes against E. coli and S. flexneri in mixed cultures, but this advantage is reduced in T6SS mutant strains. In addition, S. sonnei can persist as well as outcompete E. coli and S. flexneri in mice in a T6SS-dependent manner. These findings suggest that S. sonnei has a competitive advantage over S. flexneri and potentially explain the increasing global prevalence of S. sonnei.

Handling changes in MRI acquisition parameters in modeling whole brain lesion volume and atrophy data in multiple sclerosis subjects: Comparison of linear mixed-effect models.

Magnetic resonance imaging (MRI) of the brain provides important outcome measures in the longitudinal evaluation of disease activity and progression in MS subjects. Two common measures derived from brain MRI scans are the brain parenchymal fraction (BPF) and T2 hyperintense lesion volume (T2LV), and these measures are routinely assessed longitudinally in clinical trials and observational studies. When measuring each outcome longitudinally, observed changes may be potentially confounded by variability in MRI acquisition parameters between scans. In order to accurately model longitudinal change, the acquisition parameters should thus be considered in statistical models. In this paper, several models for including protocol as well as individual MRI acquisition parameters in linear mixed models were compared using a large dataset of 3453 longitudinal MRI scans from 1341 subjects enrolled in the CLIMB study, and model fit indices were compared across the models. The model that best explained the variance in BPF data was a random intercept and random slope with protocol specific residual variance along with the following fixed-effects: baseline age, baseline disease duration, protocol and study time. The model that best explained the variance in T2LV was a random intercept and random slope along with the following fixed-effects: baseline age, baseline disease duration, protocol and study time. In light of these findings, future studies pertaining to BPF and T2LV outcomes should carefully account for the protocol factors within longitudinal models to ensure that the disease trajectory of MS subjects can be assessed more accurately.