Experiencing violence and other predictors of within-person same-day use of multiple substances in youth: a longitudinal study in emergency settings.

Background: Although experiencing violence is a risk factor for substance use among youth, its association with same-day use of multiple substances (a form of polysubstance use) and mitigating factors is less well understood.Objectives: To identify whether prosocial factors modified the effect of experiencing violence on the frequency of same-day use, and examine gender-specific risk/protective factors for same-day use.Methods: We analyzed longitudinal data from a cohort of youth who use drugs aged 14-24 (n = 599; 58% male) presenting to an urban emergency department between 2009-2011 and assessed biannually for two years. Using Poisson-generalized linear models with person-level fixed effects, we estimated within-person associations between self-reported experiencing violence and same-day use and analyzed gender and peer/parent support as effect modifiers. We adjusted for negative peer influence, parental drug and alcohol use, family conflict, anxiety and depression, and age.Results: Overall, positive parental support corresponded to lower rates of same-day use (rate ratio [RR]:0.93, 95% CI:0.87-0.99) and experiencing violence was associated with higher rates of same-day use (RR:1.25, 95% CI:1.10-1.41). Violence exposure was a risk factor among males (RR:1.42, 95% CI:1.21-1.66), while negative peer influences and parental substance use were risk factors among females (RR:1.63, 95% CI:1.36-1.97 and RR:1.58, 95% CI:1.35-1.83, respectively). Positive peer support reduced the association between violence exposure and same-day use among males (RR:0.69, 95% CI:0.57-0.84, p < .05).Conclusions: Tailored interventions may address gender differences in coping with experiencing violence - including interventions that promote parental support among males and reduce influence from parental substance use among females.

Predictors of middle school students' perceptions of automated writing evaluation.

This study examined middle school students' perceptions of an automated writing evaluation (AWE) system, MI Write. We summarize students' perceptions of MI Write's usability, usefulness, and desirability both quantitatively and qualitatively. We then estimate hierarchical entry regression models that account for district context, classroom climate, demographic factors (i.e., gender, special education status, limited English proficiency status, socioeconomic status, grade), students' writing-related beliefs and affect, and students' writing proficiency as predictors of students' perceptions. Controlling for districts, students reporting more optimal classroom climate also reported higher usability, usefulness, and desirability for MI Write. Also, model results revealed that eighth graders, students with limited English proficiency, and students of lower socioeconomic status perceived MI Write relatively more useable; students with lower socioeconomic status also perceived MI Write relatively more useful and desirable. Students who liked writing more and more strongly believed that writing is a recursive process viewed MI Write as more useable, useful, and desirable. Students with greater writing proficiency viewed MI Write as less useable and useful; writing proficiency was not related to desirability perceptions. We conclude with a discussion of implications and future directions.

Therapy-induced mutations drive the genomic landscape of relapsed acute lymphoblastic leukemia.

To study the mechanisms of relapse in acute lymphoblastic leukemia (ALL), we performed whole-genome sequencing of 103 diagnosis-relapse-germline trios and ultra-deep sequencing of 208 serial samples in 16 patients. Relapse-specific somatic alterations were enriched in 12 genes (NR3C1, NR3C2, TP53, NT5C2, FPGS, CREBBP, MSH2, MSH6, PMS2, WHSC1, PRPS1, and PRPS2) involved in drug response. Their prevalence was 17% in very early relapse (<9 months from diagnosis), 65% in early relapse (9-36 months), and 32% in late relapse (>36 months) groups. Convergent evolution, in which multiple subclones harbor mutations in the same drug resistance gene, was observed in 6 relapses and confirmed by single-cell sequencing in 1 case. Mathematical modeling and mutational signature analysis indicated that early relapse resistance acquisition was frequently a 2-step process in which a persistent clone survived initial therapy and later acquired bona fide resistance mutations during therapy. In contrast, very early relapses arose from preexisting resistant clone(s). Two novel relapse-specific mutational signatures, one of which was caused by thiopurine treatment based on in vitro drug exposure experiments, were identified in early and late relapses but were absent from 2540 pan-cancer diagnosis samples and 129 non-ALL relapses. The novel signatures were detected in 27% of relapsed ALLs and were responsible for 46% of acquired resistance mutations in NT5C2, PRPS1, NR3C1, and TP53. These results suggest that chemotherapy-induced drug resistance mutations facilitate a subset of pediatric ALL relapses.

Firearm safety counseling among caregivers of high-school age teens: Results from a National Survey.

Firearms are the leading cause of death for high-school age teens. To inform prevention efforts, we characterize the prevalence of healthcare provider (HCP) counseling of caregivers of teens around firearm safety, safety conversation elements, and caregiver receptivity towards counseling. A cross-sectional web survey (6/24/2020-7/22/2020) was conducted among caregivers (n = 2924) of teens (age:14-18). Weights were applied to generate nationally representative estimates. Bivariate analyses and multivariate regressions were examined. Among respondents, 56.0% were women, 75.1% were non-Hispanic White, and mean (SD) age was 47.4. Firearm safety was the least discussed topic among caregivers reporting their teen received HCP preventative counseling (14.9%). For caregivers receiving counseling, the most common issues discussed were household firearms screening (75.7%); storing firearms locked (66.8%); and storing firearms unloaded (53.0%). Only 24.6% of caregivers indicated firearm safety was an important issue for teen HCPs to discuss and only 21.9% trusted teen HCPs to counsel about firearm safety. Female caregivers (aOR = 1.86;95%CI = 1.25-2.78), those trusting their teen's HCP to counsel on firearm safety (aOR = 9.63;95%CI = 6.37-14.56), and those who received teen HCP firearm safety counseling (aOR = 5.14;95%CI = 3.02-8.72) were more likely to favor firearm safety counseling. Caregivers of teens with prior firearm safety training (aOR = 0.50;95%CI = 0.31-0.80) were less likely to agree that firearm safety was an important preventative health topic. In conclusion, few caregivers receive preventive counseling on firearm safety from their teen's HCP, with trust a key barrier to effective intervention delivery. Future research, in addition to understanding barriers and establishing effective strategies to increase safety practices, should focus on increasing provider counseling competency.

Factors associated with naloxone availability and dispensing through Michigan's pharmacy standing order.

Background: Pharmacy standing order policies allow pharmacists to dispense naloxone, thereby increasing access to naloxone. Objectives: To describe pharmacy standing order participation and associations of pharmacy and community characteristics that predict naloxone availability and dispensing across eight counties in Michigan. Methods: We conducted a telephone survey of 662 standing order pharmacies with a response rate of 81% (n = 539). Pharmacies were linked with census tract-level demographics, overdose fatality rates, and dispensing data. County maps were created to visualize pharmacy locations relative to fatality rates. Regression models analyzed associations between pharmacy type, neighborhood characteristics, fatality rates, and these outcomes: naloxone availability, having ever dispensed naloxone, and counts of naloxone dispensed. Results: The prevalence of standing order pharmacies was 54% (n = 662/1231). Maps revealed areas with higher fatality rates had fewer pharmacies participating in the standing order or lacked any pharmacy access. Among standing order pharmacies surveyed, 85% (n = 458/539) had naloxone available and 82% had ever dispensed (n = 333/406). The mean out-of-pocket cost of Narcan® was $127.77 (SD: 23.93). National chains were more likely than regional chains to stock naloxone (AOR = 3.75, 95%CI = 1.77, 7.93) and to have ever dispensed naloxone (AOR 3.02, 95%CI = 1.21,7.57). Higher volume of naloxone dispensed was associated in neighborhoods with greater proportions of public health insurance (IRR = 1.38, 95%CI = 1.21, 1.58) and populations under 44 years old (IRR = 1.24, 95%CI = 1.04, 1.48). There was no association with neighborhood overdose fatality rates or race in regression models. Conclusion: As deaths from the opioid epidemic continue to escalate, efforts to expand naloxone access through greater standing order pharmacy participation are warranted.

Identifying tumor clones in sparse single-cell mutation data.

MOTIVATION: Recent single-cell DNA sequencing technologies enable whole-genome sequencing of hundreds to thousands of individual cells. However, these technologies have ultra-low sequencing coverage (<0.5× per cell) which has limited their use to the analysis of large copy-number aberrations (CNAs) in individual cells. While CNAs are useful markers in cancer studies, single-nucleotide mutations are equally important, both in cancer studies and in other applications. However, ultra-low coverage sequencing yields single-nucleotide mutation data that are too sparse for current single-cell analysis methods. RESULTS: We introduce SBMClone, a method to infer clusters of cells, or clones, that share groups of somatic single-nucleotide mutations. SBMClone uses a stochastic block model to overcome sparsity in ultra-low coverage single-cell sequencing data, and we show that SBMClone accurately infers the true clonal composition on simulated datasets with coverage at low as 0.2×. We applied SBMClone to single-cell whole-genome sequencing data from two breast cancer patients obtained using two different sequencing technologies. On the first patient, sequenced using the 10X Genomics CNV solution with sequencing coverage ≈0.03×, SBMClone recovers the major clonal composition when incorporating a small amount of additional information. On the second patient, where pre- and post-treatment tumor samples were sequenced using DOP-PCR with sequencing coverage ≈0.5×, SBMClone shows that tumor cells are present in the post-treatment sample, contrary to published analysis of this dataset. AVAILABILITY AND IMPLEMENTATION: SBMClone is available on the GitHub repository https://github.com/raphael-group/SBMClone. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Differences in management of isolated spinal fractures between neurosurgery and orthopaedics: a 6-year retrospective study.

INTRODUCTION: The acute management of spinal fractures is traditionally split between neurosurgeons and orthopaedic surgeons and the specialities have varying approaches to management. This study investigates differences between neurosurgeons and spinal orthopaedic surgeons in the management of spinal fractures at a single trauma centre in the United Kingdom. METHODS: A retrospective study at a single trauma centre of patients identified using the Trauma Audit and Research Network (TARN). Case notes and radiological investigations were reviewed for demographics, fracture classification, clinical management and outcomes. Polytrauma cases and patients managed by non-neurosurgical/orthopaedic specialties were excluded. RESULTS: A total of 465 patients were included in this study (neurosurgery n = 266, orthopaedics n = 199). There were no significant differences between groups for age, gender, Charlson co-morbidity score or distribution of fractures using the AO spine classification. Patients admitted and managed under the orthopaedic surgeons were more likely to undergo a surgical procedure when compared to those admitted under the neurosurgeons (n = 71; 35.7% vs n = 71; 26.8%, p = 0.042, OR 1.56 95%CI 1.056 to 2.31). The median overall length of stay was 8 days and there was no significant difference between teams; however, the neurosurgical cohort were more likely to be admitted to an intensive care unit (24.3% vs 16.2%, p = 0.04). CONCLUSION: This study is the first in the United Kingdom to compare neurosurgical and orthopaedic teams in their management of spinal fractures. It demonstrates that differences may exist both in operating rates and outcomes.

In Vitro Leakage Testing of Tissue Containment Bags When Subjected to Power Morcellation Forces.

STUDY OBJECTIVE: To determine the ability of tissue containment systems to prevent leakage of cancer cell surrogates when subjected to forces encountered during power morcellation procedures. DESIGN: In vitro study. SETTING: Medical device research laboratory. INTERVENTIONS: Samples from 7 different legally marketed tissue containment bags (1 of which is indicated for power morcellation) were subjected to dye and bacteriophage penetration tests at pressures ranging from 0.5 to 50 times the insufflation pressure. The minimum pressure required to cause bag leakage was measured. Subsequently, the morcellation leakage safety factor for each bag was determined as the ratio of the minimum leakage pressure of the bag to the total pressure contributed from insufflation pressure and mechanical forces acting during the power morcellation procedure. MEASUREMENT AND MAIN RESULTS: The leakage performance of the bags varied markedly from brand to brand. No correlation was found between leakage pressure and the bag material or the total bag thickness. The leakage pressures ranged from 26 mmHg to >1293 mmHg for the 7 bags, and safety factors ranged from 1 to 50 when only the insufflation pressure was considered. However, if the morcellation forces were included in the calculation, the safety factor dropped by 6-fold for all brands and dropped below 1, indicating likelihood of leakage, for 2 of the 7 brands. CONCLUSION: This study provides a mechanism for more realistically simulating the conditions experienced by containment bags during morcellation and quantifying the level of safety provided by the bags.

Impact of Design Changes in Gastrostomy Tube (G-tube) Devices for Patients Who Rely on Home-Based Blenderized Diets for Enteral Nutrition.

OBJECTIVE: Blenderized diets are gaining increasing popularity among enteral tube users. Connectors in gastrostomy tubes (G-tubes) are undergoing standardization to reduce misconnections. These standardized G-tubes are referred to as ENFit G-tubes. This study was performed to quantify the in vitro performance of existing (legacy) G-tubes and compare them with ENFit G-tubes for blenderized diets. METHOD: Patient blenderized diet recipes and practices were obtained through patient advocacy groups. Different blenders and blending times were studied. Five legacy G-tube brands and three corresponding ENFit brands, sized between 14 Fr and 24 Fr, were studied under gravity and push modes of feeding. RESULTS: Considering both thin and thick blenderized gravity mode diets, an average increase in feeding time from 20 minutes to 32 ± 18 minutes in transitioning from legacy to ENFit was observed with standard G-tubes, compared to 22 ± 3.5 minutes for low profiles. For push-mode diets, a 60-second push with standard ENFit G-tubes was easier compared to standard legacy G-tubes (61% ± 21% as much force), but faster 5-second pushes required considerably more effort for ENFit standard G-tubes (167% ± 96%). Low-profile ENFit G-tubes required slightly less effort compared to low-profile legacies for both 60-second and 5-second pushes (72% ± 22% and 90% ± 19%, respectively). Clogging was common in both legacy and ENFit devices, particularly under gravity mode. CONCLUSIONS: For a push mode of feeding, patients will largely be unimpacted after the transition to ENFit. For a gravity mode of feeding, some ENFit users may need higher-powered blenders and should expect increased feeding times.

Modeling the Effectiveness of Respiratory Protective Devices in Reducing Influenza Outbreak.

Outbreaks of influenza represent an important health concern worldwide. In many cases, vaccines are only partially successful in reducing the infection rate, and respiratory protective devices (RPDs) are used as a complementary countermeasure. In devising a protection strategy against influenza for a given population, estimates of the level of protection afforded by different RPDs is valuable. In this article, a risk assessment model previously developed in general form was used to estimate the effectiveness of different types of protective equipment in reducing the rate of infection in an influenza outbreak. It was found that a 50% compliance in donning the device resulted in a significant (at least 50% prevalence and 20% cumulative incidence) reduction in risk for fitted and unfitted N95 respirators, high-filtration surgical masks, and both low-filtration and high-filtration pediatric masks. An 80% compliance rate essentially eliminated the influenza outbreak. The results of the present study, as well as the application of the model to related influenza scenarios, are potentially useful to public health officials in decisions involving resource allocation or education strategies.

Comparison of Heat Transfer Enhancement Between Magnetic and Gold Nanoparticles During HIFU Sonication.

Long procedure times and collateral damage remain challenges in high-intensity focused ultrasound (HIFU) medical procedures. Magnetic nanoparticles (mNPs) and gold nanoparticles (gNPs) have the potential to reduce the acoustic intensity and/or exposure time required in these procedures. In this research, we investigated relative advantages of using gNPs and mNPs during HIFU thermal-ablation procedures. Tissue-mimicking phantoms containing embedded thermocouples (TCs) and physiologically acceptable concentrations (0.0625% and 0.125%) of gNPs were sonicated at acoustic powers of 5.2 W, 9.2 W, and 14.5 W, for 30 s. It was observed that when the concentration of gNPs was doubled from 0.0625% to 0.125%, the temperature rise increased by 80% for a power of 5.2 W. For a fixed concentration (0.0625%), the energy absorption was 1.7 times greater for mNPs than gNPs for a power of 5.2 W. Also, for the power of 14.5 W, the sonication time required to generate a lesion volume of 50 mm3 decreased by 1.4 times using mNPs, compared with gNPs, at a concentration of 0.0625%. We conclude that mNPs are more likely than gNPs to produce a thermal enhancement in HIFU ablation procedures.

The Wessex modified Richmond Sedation Scale as a novel tool for monitoring patients at risk of malignant MCA syndrome.

BACKGROUND: The Wessex Modified Richmond Sedation Scale (WMRSS) has been developed with the aim of improving the early identification of patients requiring decompressive hemicraniectomy for malignant middle cerebral artery syndrome (MMS). The objective of this study was to evaluate the WMRSS against the Glasgow Coma Scale (GCS). METHODS: A retrospective study was conducted of patients admitted to our unit for observation of MMS. Data were obtained on WMRSS and GCS recordings from admission up to 120-h post-ictus. Patients' meeting inclusion criteria were recommended for theatre based on subsequent deteriorations in consciousness on either WMRSS or GCS from a 6-h post-stroke baseline, after ruling out non-neurological causes. RESULTS: Approximately, 60% of those eligible for monitoring were not recommended for theatre, and none died; however, these patients continued to demonstrate some variability in recorded conscious level. Patients requiring surgical intervention showed earlier drops in WMRSS compared to GCS. Neither the GCS nor the WMRSS on admission predicted the subsequent need for decompressive surgery. There was no increase in mortality with the introduction of WMRSS. CONCLUSIONS: WMRSS adds value to monitoring MMS by indicating need for surgery prior to GCS. Early reduction in consciousness may not be sufficient for proceeding to surgical intervention, but subsequent reduction in consciousness may be a more appropriate criterion for surgery.

Thermal analysis of ultrasound-powered miniaturized implants: A tissue-phantom study.

Neurological implants that harvest ultrasound power have the potential to provide long-term stimulation without complications associated with battery power. An important safety question associated with long-term operation of the implant involves the heat generated by the interaction of the device with the ultrasound field. A study was performed in which the temperature rise generated by this interaction was measured. Informed by temperature data from thermocouples outside the ultrasound beam, a mathematical inverse method was used to determine the volume heat source generated by ultrasound absorption within the implant as well as the surface heat source generated within the viscous boundary layer on the surface of the implant. For the test implant used, it was determined that most of the heat was generated in the boundary layer, giving a maximum temperature rise ∼5 times that for absorption in an equivalent volume of soft tissue. This result illustrates that thermal safety guidelines based solely on ultrasound absorption of tissue alone are not sufficient. The method presented represents an alternative approach for quantifying ultrasound thermal effects in the presence of implants. The analysis shows a steady temperature rise of about 0.2 °C for every 100 mW/cm2 for the presented test implant.

Assessment of Gold Nanoparticle-Mediated-Enhanced Hyperthermia Using MR-Guided High-Intensity Focused Ultrasound Ablation Procedure.

High-intensity focused ultrasound (HIFU) has gained increasing popularity as a noninvasive therapeutic procedure to treat solid tumors. However, collateral damage due to the use of high acoustic powers during HIFU procedures remains a challenge. The objective of this study is to assess the utility of using gold nanoparticles (gNPs) during HIFU procedures to locally enhance heating at low powers, thereby reducing the likelihood of collateral damage. Phantoms containing tissue-mimicking material (TMM) and physiologically relevant concentrations (0%, 0.0625%, and 0.125%) of gNPs were fabricated. Sonications at acoustic powers of 10, 15, and 20 W were performed for a duration of 16 s using an MR-HIFU system. Temperature rises and lesion volumes were calculated and compared for phantoms with and without gNPs. For an acoustic power of 10 W, the maximum temperature rise increased by 32% and 43% for gNPs concentrations of 0.0625% and 0.125%, respectively, when compared to the 0% gNPs concentration. For the power of 15 W, a lesion volume of 0, 44.5 ± 7, and 63.4 ± 32 mm3 was calculated for the gNPs concentration of 0%, 0.0625%, and 0.125%, respectively. For a power of 20 W, it was found that the lesion volume doubled and tripled for concentrations of 0.0625% and 0.125% gNPs, respectively, when compared to the concentration of 0% gNPs. We conclude that gNPs have the potential to locally enhance the heating and reduce damage to healthy tissue during tumor ablation using HIFU.

The Effect of Pressure and Temperature on Mid-Infrared Sensing of Dissolved Hydrocarbons in Water.

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy using a polymer coated internal reflection element/waveguide is an established sensor platform for the detection of a range of organic and hydrocarbon molecules dissolved in water. The polymer coating serves two purposes: to concentrate hydrocarbons from the aqueous phase and to exclude water along with other interfering molecules from the surface of the internal reflection element. Crucial to reliable quantification and analytical performance is the calibration of the ATR-FTIR sensor which is commonly performed in water under mild ambient conditions (i.e., 25 °C and 1 atm). However, there is a pressing need to monitor environmental and industrial processes/events that may occur at high pressures and temperatures where this calibration approach is unsuitable. Using a ruggedized optical fiber probe with a diamond-based ATR, we have conducted mid-infrared sensor experiments to understand the influence of high pressure (up to 207 bar) and temperature (up to 80 °C) on the detection of toluene and naphthalene dissolved in water. Using a poly(isobutylene) film, we have shown that the IR spectroscopic response is relatively unaffected by changes in pressure; however, a diminished response was observed with increasing temperature. We reveal that changes in the refractive index of the polymer film with temperature have only a minor effect on sensitivity. A more plausible explanation for the observed significant change in sensor response with temperature is that the partitioning process is exothermic and becomes less favorable with increasing temperature. This Article shows that the sensitivity is relatively invariant to pressure; however, the thermal variations are significant and need to be considered when quantifying the concentration of hydrocarbons in water.

Genetic dissection of sorghum grain quality traits using diverse and segregating populations.

KEY MESSAGE: Coordinated association and linkage mapping identified 25 grain quality QTLs in multiple environments, and fine mapping of the Wx locus supports the use of high-density genetic markers in linkage mapping. There is a wide range of end-use products made from cereal grains, and these products often demand different grain characteristics. Fortunately, cereal crop species including sorghum [Sorghum bicolor (L.) Moench] contain high phenotypic variation for traits influencing grain quality. Identifying genetic variants underlying this phenotypic variation allows plant breeders to develop genotypes with grain attributes optimized for their intended usage. Multiple sorghum mapping populations were rigorously phenotyped across two environments (SC Coastal Plain and Central TX) in 2 years for five major grain quality traits: amylose, starch, crude protein, crude fat, and gross energy. Coordinated association and linkage mapping revealed several robust QTLs that make prime targets to improve grain quality for food, feed, and fuel products. Although the amylose QTL interval spanned many megabases, the marker with greatest significance was located just 12 kb from waxy (Wx), the primary gene regulating amylose production in cereal grains. This suggests higher resolution mapping in recombinant inbred line (RIL) populations can be obtained when genotyped at a high marker density. The major QTL for crude fat content, identified in both a RIL population and grain sorghum diversity panel, encompassed the DGAT1 locus, a critical gene involved in maize lipid biosynthesis. Another QTL on chromosome 1 was consistently mapped in both RIL populations for multiple grain quality traits including starch, crude protein, and gross energy. Collectively, these genetic regions offer excellent opportunities to manipulate grain composition and set up future studies for gene validation.

Mitochondria Initiate and Regulate Sarcopenia.

We present the hypothesis that an accumulation of dysfunctional mitochondria initiates a signaling cascade leading to motor neuron and muscle fiber death and culminating in sarcopenia. Interactions between neural and muscle cells that contain dysfunctional mitochondria exacerbate sarcopenia. Preventing sarcopenia will require identifying mitochondrial sources of dysfunction that are reversible.

Quantification of leakage of sub-micron aerosols through surgical masks and facemasks for pediatric use.

Surgical respirators, surgical masks (SMs), and facemasks for pediatric use (FPUs) are routinely used in the U.S. healthcare industry as personal protective equipment (PPE) against infectious diseases. While N95s including surgical respirators have been routinely studied, SMs and FPUs have not received as much attention, particularly in the context of aerosolized threats. This is because SMs and PFUs are not designed to protect against sub-micron aerosols. However, with the possibility of new or re-emerging airborne diseases or bio-aerosol weapons lingering, combined with the limited availability of respirators and logistical issues associated with fit-testing millions, the general adult and pediatric populations may elect to wear SMs and FPUs, respectively, in the case of a pandemic or a bio-terrorist attack. When a person dons a PPE, gaps are created between the wearer's face and the PPE, and aerosols leaking through these gaps can be an important contributor to the risk of infection compared to filtered aerosols. To understand and quantify the contribution of leakage of aerosols through gaps, with particular emphasis on SMs and FPUs, this study investigated leakage of charge-neutralized, polydispersed, dried sodium-chloride aerosols across different brands of PPE. Different breathing rates, aerosol particle sizes, and gap sizes were considered. A few major findings of this study were: (a) leakage, is not a strong function of sub-micron aerosol size; (b) for the same gap size, leakage of aerosols through surgical respirators can often be higher than in SMs and FPUs; and (c) as the gap size increases, the increase in leakage through surgical respirators is higher compared for SMs and FPUs, implying that some SMs and FPUs that possess electret layers may be preferable to N95s that have not been fit-tested. The results obtained can also be used to explain conflicting findings from clinical studies on the effectiveness of SMs when compared to N95s and can be input into risk-assessment models to determine the increase in infection rate resulting from deployment of PPE under less-than-ideal conditions.

Experimental validation of a nonlinear derating technique based upon Gaussian-modal representation of focused ultrasound beams.

A technique useful for performing derating at acoustic powers where significant harmonic generation occurs is illustrated and validated with experimental measurements. The technique was previously presented using data from simulations. The method is based upon a Gaussian representation of the propagation modes, resulting in simple expressions for the modal quantities, but a Gaussian source is not required. The nonlinear interaction of modes within tissue is estimated from the nonlinear interaction in water, using appropriate amounts of source reduction and focal-point reduction derived from numerical simulations. An important feature of this nonlinear derating method is that focal temperatures can be estimated with little additional effort beyond that required to determine the focal pressure waveforms. Hydrophone measurements made in water were used to inform the derating algorithm, and the resulting pressure waveforms and increases in temperature were compared with values directly measured in tissue phantoms. For a 1.05 MHz focused transducer operated at 80 W and 128 W, the derated pressures (peak positive, peak negative) agreed with the directly measured values to within 11%. Focal temperature rises determined by the derating method agreed with values measured using a remote thermocouple technique with a difference of 17%.