Correction: Sizing multimodal suspensions with differential dynamic microscopy.

Correction for 'Sizing multimodal suspensions with differential dynamic microscopy' by Joe J. Bradley et al., Soft Matter, 2023, 19, 8179-8192, https://doi.org/10.1039/D3SM00593C.

Characterization and Control of the Run-and-Tumble Dynamics of Escherichia Coli.

We characterize the full spatiotemporal gait of populations of swimming Escherichia coli using renewal processes to analyze the measurements of intermediate scattering functions. This allows us to demonstrate quantitatively how the persistence length of an engineered strain can be controlled by a chemical inducer and to report a controlled transition from perpetual tumbling to smooth swimming. For wild-type E. coli, we measure simultaneously the microscopic motility parameters and the large-scale effective diffusivity, hence quantitatively bridging for the first time small-scale directed swimming and macroscopic diffusion.

Quantitative characterization of run-and-tumble statistics in bulk bacterial suspensions.

We introduce a numerical method to extract the parameters of run-and-tumble dynamics from experimental measurements of the intermediate scattering function. We show that proceeding in Laplace space is unpractical and employ instead renewal processes to work directly in real time. We first validate our approach against data produced using agent-based simulations. This allows us to identify the length and time scales required for an accurate measurement of the motility parameters, including tumbling frequency and swim speed. We compare different models for the run-and-tumble dynamics by accounting for speed variability at the single-cell and population level, respectively. Finally, we apply our approach to experimental data on wild-type Escherichia coli obtained using differential dynamic microscopy.

Sizing multimodal suspensions with differential dynamic microscopy.

Differential dynamic microscopy (DDM) can be used to extract the mean particle size from videos of suspensions. However, many suspensions have multimodal particle size distributions, for which a single 'mean' is not a sufficient description. After clarifying how different particle sizes contribute to the signal in DDM, we show that standard DDM analysis can extract the mean sizes of two populations in a bimodal suspension given prior knowledge of the sample's bimodality. Further, the use of the CONTIN algorithm obviates the need for such prior knowledge. Finally, we show that by selectively analysing portions of the DDM images, we can size a trimodal suspension where the large particles would otherwise dominate the signal, again without prior knowledge of the trimodality.

Muscle Thickness, Echo-Intensity, Peak Force, Time Under Tension, Total Load Lifted, and Perception of Effort Comparisons Between Two Abdominal Crunch Resistance Training Protocols in Recreationally-Trained Participants.

The primary purpose of this study was to evaluate acute dose response of different intensities with total volume equalized during the abdominal crunch exercise on muscle thickness, echo-intensity, peak force, time under tension, total load lifted, and perception of effort in recreationally-trained participants. Fifteen resistance-trained participants (23 ± 3 years) performed the abdominal crunch exercise in one of two different resistance training (RT) protocols in a randomized order: RT4×10RM (4 sets of 10RM / 1-min rest) or RT1×40RM (1 set of 40RM). Muscle thickness (MT), echo-intensity (EI), peak force (PF), time under tension (TUT), total load lifted (TLL), and session rating of perceived exertion (sRPE) were measured pre-test and post-test (0-min and 15-min). Two-way repeated-measures ANOVAs (2 × 3) were used to test differences between RT protocols (RT4×10RM and RT1×40RM) and time (pre-test, post-0, and post-15) for MT, EI, and PF. Paired t-test was used to compare RT protocols for sRPE, TLL, and TUT. For MT, there were significant differences for RT4×10RM between pre-x post-0 (p = 0.011), pre-x post-15 (p < 0.001), and post-0 × post-15 (p = 0.02); and for RT1×40RM between pre-x post-0 (p < 0.001) and pre-x post-15 (p = 0.003). For EI, there was a significant difference for RT4×10RM between pre-x post-0 (p = 0.002). For sRPE, there was no significant difference between RT protocols. For TLL and TUT, there were significant differences between RT protocols (p < 0.05). In conclusion, both RT protocols (RT4×10RM and RT1×40RM) induced similar increases in MT but not for EI. TLL and TUT were higher for RT4×10RM. PF and sRPE were similar between RT protocols.

Metaheuristic for Optimal Dynamic K-Coloring Application on Band Sharing for Automotive Radars.

The number of vehicles equipped with radars on the road has been increasing for years and is expected to reach 50% of cars by 2030. This rapid rise in radars will likely increase the risk of harmful interference, especially since radar specifications from standardization bodies (e.g., ETSI) provide requirements in terms of maximum transmit power but do no mandate specific radar waveform parameters nor channel access scheme policies. Techniques for interference mitigation are thus becoming very important to ensure the long-term correct operation of radars and upper-layer ADAS systems that depend on them in this complex environment. In our previous work, we have shown that organizing the radar band into time-frequency resources that do not interfere with each other vastly reduces the amount of interference by facilitating band sharing. In this paper, a metaheuristic is presented to find the optimal resource sharing between radars, knowing their relative positions and thereby the line-of-sight and non-line-of-sight interference risks during a realistic scenario. The metaheuristic aims at optimally minimizing interference while minimizing the number of resource changes that radars have to make. It is a centralized approach where everything about the system is known (e.g., the past and future positions of the vehicles). This and the high computational load induce that this algorithm is not meant to be used in real-time. However, the metaheuristic approach can be extremely useful for finding near optimal solutions in simulations, allowing for the extraction of efficient patterns, or as data generation for machine learning.

Distinct types of multicellular aggregates in Pseudomonas aeruginosa liquid cultures.

Pseudomonas aeruginosa forms suspended multicellular aggregates when cultured in liquid media. These aggregates may be important in disease, and/or as a pathway to biofilm formation. The polysaccharide Psl and extracellular DNA (eDNA) have both been implicated in aggregation, but previous results depend strongly on the experimental conditions. Here we develop a quantitative microscopy-based method for assessing changes in the size distribution of suspended aggregates over time in growing cultures. For exponentially growing cultures of P. aeruginosa PAO1, we find that aggregation is mediated by cell-associated Psl, rather than by either eDNA or secreted Psl. These aggregates arise de novo within the culture via a growth process that involves both collisions and clonal growth, and Psl non-producing cells do not aggregate with producers. In contrast, we find that stationary phase (overnight) cultures contain a different type of multicellular aggregate, in which both eDNA and Psl mediate cohesion. Our findings suggest that the physical and biological properties of multicellular aggregates may be very different in early-stage vs late-stage bacterial cultures.

Analysis of Co-Channel Coexistence Mitigation Methods Applied to IEEE 802.11p and 5G NR-V2X Sidelink.

Direct communication between vehicles and surrounding objects, called vehicle-to-everything (V2X), is ready for the market and promises to raise the level of safety and comfort while driving. To this aim, specific bands have been reserved in some countries worldwide and different wireless technologies have been developed; however, these are not interoperable. Recently, the issue of co-channel coexistence has been raised, leading the European Telecommunications Standards Institute (ETSI) to propose a number of solutions, called mitigation methods, for the coexistence of the IEEE 802.11p based ITS-G5 and the 3GPP fourth generation (4G) long term evolution (LTE)-V2X sidelink. In this work, several of the envisioned alternatives are investigated when adapted to the coexistence of the IEEE 802.11p with its enhancement IEEE 802.11bd and the latest 3GPP standards, i.e., the fifth generation (5G) new radio (NR)-V2X. The results, obtained through an open-source simulator that is shared with the research community for the evaluation of additional proposals, show that the methods called A and C, which require modifications to the standards, improve the transmission range of one or both systems without affecting the other, at least in low-density scenarios.

Deep Tissue Penetration of Bottle-Brush Polymers via Cell Capture Evasion and Fast Diffusion.

Drug nanocarriers (NCs) capable of crossing the vascular endothelium and deeply penetrating into dense tissues of the CNS could potentially transform the management of neurological diseases. In the present study, we investigated the interaction of bottle-brush (BB) polymers with different biological barriers in vitro and in vivo and compared it to nanospheres of similar composition. In vitro internalization and permeability assays revealed that BB polymers are not internalized by brain-associated cell lines and translocate much faster across a blood-brain barrier model compared to nanospheres of similar hydrodynamic diameter. These observations performed under static, no-flow conditions were complemented by dynamic assays performed in microvessel arrays on chip and confirmed that BB polymers can escape the vasculature compartment via a paracellular route. BB polymers injected in mice and zebrafish larvae exhibit higher penetration in brain tissues and faster extravasation of microvessels located in the brain compared to nanospheres of similar sizes. The superior diffusivity of BBs in extracellular matrix-like gels combined with their ability to efficiently cross endothelial barriers via a paracellular route position them as promising drug carriers to translocate across the blood-brain barrier and penetrate dense tissue such as the brain, two unmet challenges and ultimate frontiers in nanomedicine.

A Methodology for Abstracting the Physical Layer of Direct V2X Communications Technologies.

Recent advancements in vehicle-to-everything (V2X) communications have greatly increased the flexibility of the physical (PHY) and medium access control (MAC) layers. This increases the complexity when investigating the system from a network perspective to evaluate the performance of the supported applications. Such flexibility, in fact, needs to be taken into account through a cross-layer approach, which might lead to challenging evaluation processes. As an accurate simulation of the signals appears unfeasible, a typical solution is to rely on simple models for incorporating the PHY layer of the supported technologies based on off-line measurements or accurate link-level simulations. Such data are, however, limited to a subset of possible configurations, and extending them to others is costly when not even impossible. The goal of this paper is to develop a new approach for modeling the PHY layer of V2X communications that can be extended to a wide range of configurations without leading to extensive measurement or simulation campaigns at the link layer. In particular, given a scenario and starting from results in terms of the packet error rate (PER) vs. signal-to-interference-plus-noise ratio (SINR) related to a subset of possible configurations, we first approximated the curves with step functions characterized by a given SINR threshold, and we then derived one parameter, called implementation loss, that was used to obtain the SINR threshold and evaluate the network performance under any configuration in the same scenario. The proposed methodology, leading to a good trade-off among the complexity, generality, and accuracy of the performance evaluation process, was validated through extensive simulations with both IEEE 802.11p and LTE-V2X sidelink technologies in various scenarios. The results first show that the curves can be effectively approximated by using an SINR threshold, with a value corresponding to 0.5 PER, and then demonstrate that the network-level outputs derived from the proposed approach are very close to those obtained with complete curves, despite not being restricted to a few possible configurations.

Encapsulated bacteria deform lipid vesicles into flagellated swimmers.

We study a synthetic system of motile Escherichia coli bacteria encapsulated inside giant lipid vesicles. Forces exerted by the bacteria on the inner side of the membrane are sufficient to extrude membrane tubes filled with one or several bacteria. We show that a physical coupling between the membrane tube and the flagella of the enclosed cells transforms the tube into an effective helical flagellum propelling the vesicle. We develop a simple theoretical model to estimate the propulsive force from the speed of the vesicles and demonstrate the good efficiency of this coupling mechanism. Together, these results point to design principles for conferring motility to synthetic cells.

Run-to-Tumble Variability Controls the Surface Residence Times of E. coli Bacteria.

Motile bacteria are known to accumulate at surfaces, eventually leading to changes in bacterial motility and biofilm formation. We use a novel two-color, three-dimensional Lagrangian tracking technique to follow simultaneously the body and the flagella of a wild-type Escherichia coli. We observe long surface residence times and surface escape corresponding mostly to immediately antecedent tumbling. A motility model accounting for a large behavioral variability in run-time duration reproduces all experimental findings and gives new insights into surface trapping efficiency.

In Situ Characterization of the Protein Corona of Nanoparticles In Vitro and In Vivo.

A new theoretical framework that enables the use of differential dynamic microscopy (DDM) in fluorescence imaging mode to quantify in situ protein adsorption onto nanoparticles (NP) while simultaneously monitoring for NP aggregation is proposed. This methodology is used to elucidate the thermodynamic and kinetic properties of the protein corona (PC) in vitro and in vivo. The results show that protein adsorption triggers particle aggregation over a wide concentration range and that the formed aggregate structures can be quantified using the proposed methodology. Protein affinity for polystyrene (PS) NPs is observed to be dependent on particle concentration. For complex protein mixtures, this methodology identifies that the PC composition changes with the dilution of serum proteins, demonstrating a Vroman effect never quantitatively assessed in situ on NPs. Finally, DDM allows monitoring of the evolution of the PC in vivo. This results show that the PC composition evolves significantly over time in zebrafish larvae, confirming the inherently dynamic nature of the PC. The performance of the developed methodology allows to obtain quantitative insights into nano-bio interactions in a vast array of physiologically relevant conditions that will serve to further improve the design of nanomedicine.

Injection into and extraction from single fungal cells.

The direct delivery of molecules and the sampling of endogenous compounds into and from living cells provide powerful means to modulate and study cellular functions. Intracellular injection and extraction remain challenging for fungal cells that possess a cell wall. The most common methods for intracellular delivery into fungi rely on the initial degradation of the cell wall to generate protoplasts, a step that represents a major bottleneck in terms of time, efficiency, standardization, and cell viability. Here, we show that fluidic force microscopy enables the injection of solutions and cytoplasmic fluid extraction into and out of individual fungal cells, including unicellular model yeasts and multicellular filamentous fungi. The approach is strain- and cargo-independent and opens new opportunities for manipulating and analyzing fungi. We also perturb individual hyphal compartments within intact mycelial networks to study the cellular response at the single cell level.

Scratching the Surface of the Protein Corona: Challenging Measurements and Controversies.

This Review aims to provide a systematic analysis of the literature regarding ongoing debates in protein corona research. Our goal is to portray the current understanding of two fundamental and debated characteristics of the protein corona, namely, the formation of mono- or multilayers of proteins and their binding (ir)reversibility. The statistical analysis we perform reveals that these characterisitics are strongly correlated to some physicochemical factors of the NP-protein system (particle size, bulk material, protein type), whereas the technique of investigation or the type of measurement (in situ or ex situ) do not impact the results, unlike commonly assumed. Regarding the binding reversibility, the experimental design (either dilution or competition experiments) is also shown to be a key factor, probably due to nontrivial protein binding mechanisms, which could explain the paradoxical phenomena reported in the literature. Overall, we suggest that to truly predict and control the protein corona, future efforts should be directed toward the mechanistic aspects of protein adsorption.

Probing the dynamics of turbid colloidal suspensions using differential dynamic microscopy.

Few techniques can reliably measure the dynamics of colloidal suspensions or other soft materials over a wide range of turbidities. Here we systematically investigate the capability of Differential Dynamic Microscopy (DDM) to characterise particle dynamics in turbid colloidal suspensions based on brightfield optical microscopy. We measure the Intermediate Scattering Function (ISF) of polystyrene microspheres suspended in water over a range of concentrations, turbidities, and up to 4 orders of magnitude in time-scales. These DDM results are compared to data obtained from both Dynamic Light Scattering (DLS) and Two-colour Dynamic Light Scattering (TCDLS). The latter allows for suppression of multiple scattering for moderately turbid suspensions. We find that DDM can obtain reliable diffusion coefficients at up to 10 and 1000 times higher particle concentrations than TCDLS and standard DLS, respectively. Additionally, we investigate the roles of the four length-scales relevant when imaging a suspension: the sample thickness L, the imaging depth z, the imaging depth of field DoF, and the photon mean free path . More detailed experiments and analysis reveal the appearance of a short-time process as turbidity is increased, which we associate with multiple scattering events within the imaging depth of the field. The long-time process corresponds to the particle dynamics from which particle-size can be estimated in the case of non-interacting particles. Finally, we provide a simple theoretical framework, ms-DDM, for turbid samples, which accounts for multiple scattering.

Characterising shear-induced dynamics in flowing complex fluids using differential dynamic microscopy.

Microscopic dynamics reveal the origin of the bulk rheological response in complex fluids. In model systems particle motion can be tracked, but for industrially relevant samples this is often impossible. Here we adapt differential dynamic microscopy (DDM) to study flowing highly-concentrated samples without particle resolution. By combining an investigation of oscillatory flow, using a novel "echo-DDM" analysis, and steady shear, through flow-DDM, we characterise the yielding of a silicone oil emulsion on both the microscopic and bulk level. Through measuring the rate of shear-induced droplet rearrangements and the flow velocity, the transition from a solid-like to liquid-like state is shown to occur in two steps: with droplet mobilisation marking the limit of linear visco-elasticity, followed by the development of shear localisation and macroscopic yielding. Using this suite of techniques, such insight could be developed for a wide variety of challenging complex fluids.

Particle sizing for flowing colloidal suspensions using flow-differential dynamic microscopy.

Particle size is a key variable in understanding the behaviour of the particulate products that underpin much of our modern lives. Typically obtained from suspensions at rest, measuring the particle size under flowing conditions would enable advances for in-line testing during manufacture and high-throughput testing during development. However, samples are often turbid, multiply scattering light and preventing the direct use of common sizing techniques. Differential dynamic microscopy (DDM) is a powerful technique for analysing video microscopy of such samples, measuring diffusion and hence particle size without the need to resolve individual particles while free of substantial user input. However, when applying DDM to a flowing sample, diffusive dynamics are rapidly dominated by flow effects, preventing particle sizing. Here, we develop "flow-DDM", a novel analysis scheme that combines optimised imaging conditions, a drift-velocity correction and modelling of the impact of flow. Flow-DDM allows a decoupling of flow from diffusive motion that facilitates successful particle size measurements at flow speeds an order of magnitude higher than for DDM. We demonstrate the generality of the technique by applying flow-DDM to two separate microscopy methods and flow geometries.

Exercise Variability Did Not Affect Muscle Thickness and Peak Force for Elbow Flexors After a Resistance Training Session in Recreationally-Trained Subjects.

The purpose of this study is to measure the acute effects of exercise variability on muscle thickness and physical performance after two resistance training (RT) protocols using the same or different exercises in recreationally-trained subjects. Fifteen resistance-trained men (23.1 ± 2.6 years, 83.4 ± 16.6 kg, 173.5 ± 8.3cm) performed one of two RT protocols: SINGLE: six sets of 10RM/two-minutes rest of the unilateral biceps curl exercise using cables or MIX: six sets of 10RM/two-minutes rest for the unilateral biceps curl exercises (cable: three sets and dumbbells: three sets, randomly). Muscle thickness (MT) and peak force (PF) were measured ten-minutes before (control), pre-RT session, and post-RT (immediately after and 15-minutes after). All acute RT variables were measured during both RT protocols: the maximal number of repetitions (MNR), the total number of repetitions (TNR), time under tension (TUT), and rating of perceived exertion (RPE). Two-way ANOVA (2 x 4) was used to test differences between RT protocol (SINGLE and MIX) and time (control, pre-test, post0, and post15) for MT and PF. Two-way ANOVAs (2 x 6) were used to test differences between RT protocol (SINGLE and MIX) and sets for MNR, RPEset, and TUT. For PF and MT, there were significant differences in time for both RT protocols (p < 0.05), however, there were not statistical differences between RT protocols. For MNR, RPEset, and TUT, there were significant differences in time (p < 0.05), however, there were not statistical differences between RT protocols. In conclusion, both RT protocols induced a similar increase in MT for elbow flexors and a reduction in peak force.

Different Barbell Height Positions Affect Maximal Isometric Deadlift Force and Subsequent Squat Jump Performance in Recreationally-Trained Men.

The primary purpose of this study is to examine the effect of two different deadlift barbell height positions on maximal isometric force and subsequent maximal squat jump performance in recreationally-trained men. Fifteen young, healthy, recreationally-trained men (age: 24.7 ± 3.5years, height: 177.1 ± 7.9cm, and total body mass: 81.2 ± 9.8kg) volunteered to participate. All participants performed maximal squat jumps (MSJ) at 90° of knee flexion before (pre-test) and after 4-min (post-test) performing the deadlift exercise using maximal isometric force (MIF) and MIF normalized by body mass (ratioMIF) in two barbell height positions (25% and 75% of the lower limb height, LLH) in a randomized and counterbalanced order. A paired-sample t-test was used to test differences in MIF and ratioMIF between 25% LLH and 75% LLH. Two-way ANOVAs were used for positions (25% LLH and 75% LLH) and time (pre- and post-test) for all dependent variables with an alpha of 5%. Differences were found for MIF and ratioMIF during the deadlift between 25% LLH and 75% LLH (p < 0.001). There was observed an increase in impulse between pre- and post-test only at 75% LLH (p < 0.001), decrease in time to peak force between pre- and post-test only at 75% LLH (p < 0.001), and increase in peak force between pre- and post-test at 75% LLH (p = 0.029). The present results showed that the maximal isometric deadlift exercise at 75% LLH (midthigh) improves subsequent jump performance of the squat jump recreationally-trained men.