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Airborne respiratory aerosol particle transmission of pathogens such as severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), influenza, or rhinoviruses plays a major role in the spread of infectious diseases. The infection risk is increased during indoor exercise, as aerosol particle emission can increase by more than 100-fold from rest to maximal exercise. Earlier studies have investigated the effect of factors such as age, sex, and body mass index (BMI), but only at rest and without taking ventilation into account. Here, we report that during both rest and exercise, subjects aged 60 to 76 y emit on average more than twice as many aerosol particles per minute than subjects aged 20 to 39 y. In terms of volume, older subjects emit on average five times as much dry volume (i.e., the residue of dried aerosol particles) than younger subjects. There was no statistically significant effect of sex or BMI within the test group. Together, this suggests that aging of the lung and respiratory tract is associated with an increased generation of aerosol particles irrespective of ventilation. Our findings demonstrate that age and exercise increase aerosol particle emission. In contrast, sex or BMI only have minor effects.

INTRODUCTION: Pathogens such as severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), influenza, and rhinoviruses are transmitted by airborne aerosol respiratory particles that are exhaled by infectious subjects. We have previously reported that the emission of aerosol particles increases on average 132-fold from rest to maximal endurance exercise [1]. The aims of this study are to first measure aerosol particle emission during an isokinetic resistance exercise at 80% of the maximal voluntary contraction until exhaustion, second to compare aerosol particle emission during a typical spinning class session versus a three-set resistance training session. Finally, we then used this data to calculate the risk of infection during endurance and resistance exercise sessions with different mitigation strategies. METHODS: We recruited 24 healthy participants (age: 21 to 37 years): eight of them for the endurance training session, eight for a resistance training, and eight for an isokinetic resistance training. In each training setting, we included four women and four men. The BMI of the participants ranged between 20.7 kg/m2 and 37 kg/m2 in the resistance exercise groups due to high muscle mass. In the endurance exercise group, the BMI ranged from 20.7 kg/m2 to 26.5 kg/m2. To measure ventilation and particle emission we coupled a spiroergometry device (Metalyzer; Cortex Medical™) with a particle counter (Palas Promo 3000 with Welas 2300 sensor, Palas GmbH) in a closed system. All measurements were performed in a clean air tent with reduced aerosol particle concentration (<150 particles/L compared to >30,000 particles/L in the ambient air). The airspace in the tent was flooded with cleaned air (H14 filter quality), and subjects directly inhale filtered air. RESULTS: During a set of isokinetic resistance exercise, aerosol particle emission increased 10-fold from 5,400 ± 1,200 particles/min at rest to 59,000 ± 69,900 particles/min during a set of resistance exercise

Astigmatism Particle Tracking Velocimetry (APTV) is a three-dimensional flow measurement technique. It requires only a single camera and is therefore best suited for measurement domains with limited optical access, such as compressor and combustion research. The z-component of the spatial particle position is coded in the geometry of its particle image. In order to prove the feasibility of APTV to measure macroscopic air flows, an accuracy analysis using a pinhole matrix is carried out. Two different optical setups with different measurement depths (20-100 mm) are investigated. The relative measurement error lies in the range of 0.34-0.46 % of the measurement depth. Altogether APTV allows for accurate volumetric velocity measurements in macroscopic air flows.

Acute lymphoblastic leukemia (ALL) is the major pediatric cancer. At diagnosis, the developmental timing of mutations contributing critically to clonal diversification and selection can be buried in the leukemia's covert natural history. Concordance of ALL in monozygotic, monochorionic twins is a consequence of intraplacental spread of an initiated preleukemic clone. Studying monozygotic twins with ALL provides a unique means of uncovering the timeline of mutations contributing to clonal evolution, pre- and postnatally. We sequenced the whole genomes of leukemic cells from two twin pairs with ALL to comprehensively characterize acquired somatic mutations in ALL, elucidating the developmental timing of all genetic lesions. Shared, prenatal, coding-region single-nucleotide variants were limited to the putative initiating lesions. All other nonsynonymous single-nucleotide variants were distinct between tumors and, therefore, secondary and postnatal. These changes occurred in a background of noncoding mutational changes that were almost entirely discordant in twin pairs and likely passenger mutations acquired during leukemic cell proliferation.