Distal colonocytes targeted by C. rodentium recruit T-cell help for barrier defence.

Interleukin 22 (IL-22) has a non-redundant role in immune defence of the intestinal barrier1-3. T cells, but not innate lymphoid cells, have an indispensable role in sustaining the IL-22 signalling that is required for the protection of colonic crypts against invasion during infection by the enteropathogen Citrobacter rodentium4 (Cr). However, the intestinal epithelial cell (IEC) subsets targeted by T cell-derived IL-22, and how T cell-derived IL-22 sustains activation in IECs, remain undefined. Here we identify a subset of absorptive IECs in the mid-distal colon that are specifically targeted by Cr and are differentially responsive to IL-22 signalling. Major histocompatibility complex class II (MHCII) expression by these colonocytes was required to elicit sustained IL-22 signalling from Cr-specific T cells, which was required to restrain Cr invasion. Our findings explain the basis for the regionalization of the host response to Cr and demonstrate that epithelial cells must elicit MHCII-dependent help from IL-22-producing T cells to orchestrate immune protection in the intestine.

Optimizing non-Newtonian fluids for impact protection of laminates.

Non-Newtonian fluids can be used for the protection of flexible laminates. Understanding the coupling between the flow of the protecting fluid and the deformation of the protected solids is necessary in order to optimize this functionality. We present a scaling analysis of the problem based on a single coupling variable, the effective width of a squeeze flow between flat rigid plates, and predict that impact protection for laminates is optimized by using shear-thinning, and not shear-thickening, fluids. The prediction is verified experimentally by measuring the velocity and pressure in impact experiments. Our scaling analysis should be generically applicable for non-Newtonian fluid-solid interactions in diverse applications.

Spin current from sub-terahertz-generated antiferromagnetic magnons.

Spin dynamics in antiferromagnets has much shorter timescales than in ferromagnets, offering attractive properties for potential applications in ultrafast devices1-3. However, spin-current generation via antiferromagnetic resonance and simultaneous electrical detection by the inverse spin Hall effect in heavy metals have not yet been explicitly demonstrated4-6. Here we report sub-terahertz spin pumping in heterostructures of a uniaxial antiferromagnetic Cr2O3 crystal and a heavy metal (Pt or Ta in its ß phase). At 0.240 terahertz, the antiferromagnetic resonance in Cr2O3 occurs at about 2.7 tesla, which excites only right-handed magnons. In the spin-canting state, another resonance occurs at 10.5 tesla from the precession of induced magnetic moments. Both resonances generate pure spin currents in the heterostructures, which are detected by the heavy metal as peaks or dips in the open-circuit voltage. The pure-spin-current nature of the electrically detected signals is unambiguously confirmed by the reversal of the voltage polarity observed under two conditions: when switching the detector metal from Pt to Ta, reversing the sign of the spin Hall angle7-9, and when flipping the magnetic-field direction, reversing the magnon chirality4,5. The temperature dependence of the electrical signals at both resonances suggests that the spin current contains both coherent and incoherent magnon contributions, which is further confirmed by measurements of the spin Seebeck effect and is well described by a phenomenological theory. These findings reveal the unique characteristics of magnon excitations in antiferromagnets and their distinctive roles in spin-charge conversion in the high-frequency regime.

Enhanced spatial resolution in magnetic resonance imaging by dynamic nuclear polarization at 5 K.

Spatial resolution in MRI is ultimately limited by the signal detection sensitivity of NMR, since resolution equal to ρiso in all three dimensions requires the detection of NMR signals from a volume ρiso3. With inductively detected NMR at room temperature, it has therefore proven difficult to achieve isotropic resolution better than ρiso = 3.0 µm, even with radio-frequency microcoils, optimized samples, high magnetic fields, optimized pulse sequence methods, and data acquisition times around 60 h. Here we show that spatial resolution can be improved and data acquisition times can be reduced substantially by performing MRI measurements at 5 K and using dynamic nuclear polarization (DNP) to enhance sensitivity. We describe the experimental apparatus and methods, and we report images of test samples with ρiso = 2.6 µm and ρiso = 1.7 µm, with signal-to-noise ratios greater than 15, acquired in 31.5 and 81.6 h, respectively. Image resolutions are verified by quantitative comparisons with simulations. These results establish a promising direction for high-resolution MRI of small samples. With further improvements in the experimental apparatus and in paramagnetic dopants for DNP, DNP-enhanced low-temperature MRI with ρiso < 1.0 µm is likely to become feasible, potentially enabling informative studies of structures within typical eukaryotic cells, cell clusters, and tissue samples.

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.

Experimental Evidence for Millisecond-Timescale Structural Evolution Following the Microsecond-Timescale Folding of a Small Protein.

Prior work has shown that small proteins can fold (i.e., convert from unstructured to structured states) within 10 µs. Here we use time-resolved solid state nuclear magnetic resonance (ssNMR) methods to show that full folding of the 35-residue villin headpiece subdomain (HP35) requires a slow annealing process that has not been previously detected. ^{13}C ssNMR spectra of frozen HP35 solutions, acquired with a variable time τ_{e} at 30 °C after rapid cooling from 95 °C and before rapid freezing, show changes on the 3-10 ms timescale, attributable to slow rearrangements of protein sidechains during τ_{e}.

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.

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.

Ductile-to-brittle transition and yielding in soft amorphous materials: perspectives and open questions.

Soft amorphous materials are viscoelastic solids ubiquitously found around us, from clays and cementitious pastes to emulsions and physical gels encountered in food or biomedical engineering. Under an external deformation, these materials undergo a noteworthy transition from a solid to a liquid state that reshapes the material microstructure. This yielding transition was the main theme of a workshop held from January 9 to 13, 2023 at the Lorentz Center in Leiden. The manuscript presented here offers a critical perspective on the subject, synthesizing insights from the various brainstorming sessions and informal discussions that unfolded during this week of vibrant exchange of ideas. The result of these exchanges takes the form of a series of open questions that represent outstanding experimental, numerical, and theoretical challenges to be tackled in the near future.

From admissions to licensure: education data associations from a multi-centre undergraduate medical education collaboration.

This paper reports the findings of a Canada based multi-institutional study designed to investigate the relationships between admissions criteria, in-program assessments, and performance on licensing exams. The study's objective is to provide valuable insights for improving educational practices across different institutions. Data were gathered from six medical schools: McMaster University, the Northern Ontario School of Medicine University, Queen's University, University of Ottawa, University of Toronto, and Western University. The dataset includes graduates who undertook the Medical Council of Canada Qualifying Examination Part 1 (MCCQE1) between 2015 and 2017. The data were categorized into five distinct sections: demographic information as well as four matrices: admissions, course performance, objective structured clinical examination (OSCE), and clerkship performance. Common and unique variables were identified through an extensive consensus-building process. Hierarchical linear regression and a manual stepwise variable selection approach were used for analysis. Analyses were performed on data set encompassing graduates of all six medical schools as well as on individual data sets from each school. For the combined data set the final model estimated 32% of the variance in performance on licensing exams, highlighting variables such as Age at Admission, Sex, Biomedical Knowledge, the first post-clerkship OSCE, and a clerkship theta score. Individual school analysis explained 41-60% of the variance in MCCQE1 outcomes, with comparable variables to the analysis from of the combined data set identified as significant independent variables. Therefore, strongly emphasising the need for variety of high-quality assessment on the educational continuum. This study underscores the importance of sharing data to enable educational insights. This study also had its challenges when it came to the access and aggregation of data. As such we advocate for the establishment of a common framework for multi-institutional educational research, facilitating studies and evaluations across diverse institutions. This study demonstrates the scientific potential of collaborative data analysis in enhancing educational outcomes. It offers a deeper understanding of the factors influencing performance on licensure exams and emphasizes the need for addressing data gaps to advance multi-institutional research for educational improvements.

Lysine-Derived Charge-Altering Releasable Transporters: Targeted Delivery of mRNA and siRNA to the Lungs.

Targeted delivery of nucleic acid therapeutics to the lungs could transform treatment options for pulmonary disease. We have previously developed oligomeric charge-altering releasable transporters (CARTs) for in vivo mRNA transfection and demonstrated their efficacy for use in mRNA-based cancer vaccination and local immunomodulatory therapies against murine tumors. While our previously reported glycine-based CART-mRNA complexes (G-CARTs/mRNA) show selective protein expression in the spleen (mouse, >99%), here, we report a new lysine-derived CART-mRNA complex (K-CART/mRNA) that, without additives or targeting ligands, shows selective protein expression in the lungs (mouse, >90%) following systemic IV administration. We further show that by delivering siRNA using the K-CART, we can significantly decrease expression of a lung-localized reporter protein. Blood chemistry and organ pathology studies demonstrate that K-CARTs are safe and well-tolerated. We report on the new step economical, organocatalytic synthesis (two steps) of functionalized polyesters and oligo-carbonate-co-α-aminoester K-CARTs from simple amino acid and lipid-based monomers. The ability to direct protein expression selectively in the spleen or lungs by simple, modular changes to the CART structure opens fundamentally new opportunities in research and gene therapy.

Evaporation of Concentrated Polymer Solutions Is Insensitive to Relative Humidity.

A recent theory suggests that the evaporation kinetics of macromolecular solutions is insensitive to the ambient relative humidity (RH) due to the formation of a "polarization layer" of solutes at the air-solution interface. We confirm this insensitivity up to RH≈80% in the evaporation of polyvinyl alcohol solutions from open-ended capillaries. To explain the observed drop in evaporation rate at higher RH, we need to invoke compressive stresses due to interfacial polymer gelation. Moreover, RH-insensitive evaporation sets in earlier than theory predicts, suggesting a further role for a gelled "skin." We discuss the relevance of these observations for respiratory virus transmission via aerosols.

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.

The concurrent emergence and causes of double volcanic hotspot tracks on the Pacific plate.

Mantle plumes are buoyant upwellings of hot rock that transport heat from Earth's core to its surface, generating anomalous regions of volcanism that are not directly associated with plate tectonic processes. The best-studied example is the Hawaiian-Emperor chain, but the emergence of two sub-parallel volcanic tracks along this chain, Loa and Kea, and the systematic geochemical differences between them have remained unexplained. Here we argue that the emergence of these tracks coincides with the appearance of other double volcanic tracks on the Pacific plate and a recent azimuthal change in the motion of the plate. We propose a three-part model that explains the evolution of Hawaiian double-track volcanism: first, mantle flow beneath the rapidly moving Pacific plate strongly tilts the Hawaiian plume and leads to lateral separation between high- and low-pressure melt source regions; second, the recent azimuthal change in Pacific plate motion exposes high- and low-pressure melt products as geographically distinct volcanoes, explaining the simultaneous emergence of double-track volcanism across the Pacific; and finally, secondary pyroxenite, which is formed as eclogite melt reacts with peridotite, dominates the low-pressure melt region beneath Loa-track volcanism, yielding the systematic geochemical differences observed between Loa- and Kea-type lavas. Our results imply that the formation of double-track volcanism is transitory and can be used to identify and place temporal bounds on plate-motion changes.

The Physician Anesthesia Workforce in Canada From 1996 to 2018: A Longitudinal Analysis of Health Administrative Data.

BACKGROUND: A robust anesthesia workforce is essential to the provision of safe surgical, obstetrical, and critical care but information describing the physician anesthesia workforce and volume of clinical services delivered in Canada is limited. This study examines the Canadian physician anesthesia workforce, exploring trends in physician characteristics and activity levels over time. Practice patterns of specialist anesthesiologists and family physician anesthetists (FPAs) working in urban and rural communities were of particular interest. METHODS: Physicians who provided anesthesia care between 1996 and 2018 were identified using health administrative data from the Canadian Institute of Health Information (CIHI). In addition, data from the Canadian Post-MD Education Registry (CAPER) were used to characterize physicians pursuing postgraduate anesthesia training (1996-2019). Descriptive analyses of physician demographics, training, location, specialty designations, and volume of clinical services were undertaken. RESULTS: Between 1996 and 2018, the anesthesia workforce grew 1.8-fold to 3681 physicians, including 536 FPAs. Over the same time, nerve block services increased 7-fold, and payments for other anesthesia services increased 5-fold. The average age of the anesthesiology workforce increased by 2.3 years and the annual retirement rate was 3%. The workforce has become more gender balanced but remains predominantly male (73% in 2018). The proportion of physicians who were trained internationally (about 30%; 38% in rural areas) remained stable (and higher than that in the overall physician workforce). FPAs provided most anesthesia care in rural Canada and their attrition rate was generally 2- to 3-fold higher than specialists. Physicians in the rural anesthesia workforce provided anesthesia services more intensively over time. Relatively few FPAs who left the anesthesia workforce entered full retirement and they instead contributed other medical services to their communities. CONCLUSIONS: This study provides foundational information regarding anesthesia workforce capacity over a 22-year period, including insights into demographics, locations of practice, and clinical volumes. The results do not quantify the gap between service capacity and need; however, they support the need for a national workforce strategy to achieve equitable access to sustainable anesthesia services in Canada, particularly for rural communities.

Chemotaxis and Motility of Spongospora subterranea Zoospores in Response to Potato Root Exudate Constituents and pH.

Spongospora subterranea f. sp. subterranea is an important pathogen of potato responsible for major losses in most potato growing regions of the world. Infection is initiated by biflagellated motile zoospores released from long-lived resting spores. Zoospore chemotaxis to the host plant root is widely believed to be stimulated by host root exudate compounds, although direct evidence is lacking. This study refined the traditional chemotaxis capillary assay, with which we provided the first empirical evidence of S. subterranea zoospore chemotaxis. Individual potato root exudate metabolites were either taxis neutral, inhibitory, or attractant to the zoospores. L-Glutamine was the strongest chemoattractant, while spermine was the most inhibitory. Zoospore motility and chemotaxis were constrained by strongly acidic or alkaline solutions of pH < 5.3 and >8.5, respectively. Beyond pH, ionic constituents of the test solution affected zoospore motility as Sorensen's phosphate buffer stalled zoospore motility, but HEPES buffer at the same concentration and pH had little or no negative motility effect. Zoospore motility, as characterized by several parameters, influenced chemotaxis. Among the parameters measured, total distance traveled was the best predictor of zoospore chemotaxis. The characterization of environmental and ecological effects on zoospore motility and chemotaxis highlights useful targets for S. subterranea disease control through manipulation of zoospore taxis or selection of host resistance traits.

The anesthesia workforce in Canada: a methodology to identify physician anesthesia providers using health administrative data.

BACKGROUND: Safe and timely anesthesia services are an integral component of modern health care systems. There are, however, increasing concerns about the availability of anesthesia services in Canada. Thus, a comprehensive approach to assess the capacity of the anesthesia workforce to provide service is a critical need. Data regarding the anesthesia services provided by specialists and family physicians are available through the Canadian Institute for Health Information (CIHI) but collating the data across delivery jurisdictions has proven challenging. As a result, information related to the activity of physician anesthesia providers is routinely excluded from annual physician workforce reports. Our goal was to develop a novel approach to identifying and characterizing the anesthesia workforce on a pan-Canadian scale. METHODS: The study was approved by the University of Ottawa Office of Research Ethics and Integrity. We developed a methodology to identify physicians who provided anesthesia services in Canada between 1996 and 2018 using data elements from the CIHI National Physician Database. We iteratively consulted with expert advisors and compared the results with Scott's Medical Database, the Canadian Medical Association (CMA) Masterfile, and the College of Family Physicians of Canada membership database. RESULTS: The methodology identified providers of anesthesia services using data elements from the CIHI National Physician Database, including categories of the National Grouping System, specialty designations, activity levels and participation thresholds. Physicians who provided anesthesia services only sporadically and medical residents-in-training were excluded. This methodology produced estimates of anesthesia providers that aligned with other sources. The process we followed was sequential, transparent, and intuitive, and was strengthened by collaboration and iterative consultation with experts and stakeholders. CONCLUSIONS: Using physician activity patterns, this novel methodology allows stakeholders to identify which physician provide anesthesia services in Canada. It is an essential step in developing a pan-Canadian anesthesia workforce strategy that can be used to examine patterns and trends related to the workforce and support evidence-informed workforce decision-making. It also establishes a foundation for assessing the effectiveness of a variety of interventions aimed at optimizing physician anesthesia services in Canada.

Effectiveness of telehealth in preventive care: a study protocol for a randomised controlled trial of tele-exercise programme involving older people with possible sarcopenia or at risk of fall.

BACKGROUND: Continuous loss of muscle mass and strength are the consequences of the ageing process, which increase the risk of falls among older people. Falls can lead to severe consequences such as bone fractures and hampered physical and psychological well-being. Regular exercise is the key to reversing muscle atrophy and relieving sarcopenia. However, the frailty of older people and the recent COVID-19 pandemic may affect their confidence to leave home to attend classes in the community. A feasible and effective alternative should be explored. METHODS: The primary objective is to evaluate the effectiveness of tele-exercise (TE) in relation to physical functioning and exercise adherence among community-dwelling older people at risk of falls in comparison with a community-based group (CB). The secondary objective includes evaluating older people's experience with tele-exercise, emphasizing their psychological welfare, social well-being, and acceptance of the telehealth approach. The design, conduct, and report follow the SPIRIT guidelines (Standard Protocol Items: recommended items to address in a Clinical Trial Protocol and Related Documents). Older people will be recruited from 10 local community centres in Hong Kong and randomly allocated into two groups. All participants will attend the exercise training 3 days per week for 3 months but the mode of delivery will differ, either online as the tele-exercise group (TE) or face-to-face as the community-based group (CB). The outcome measures include muscle strength, physical function, exercise adherence and dropout rate, psychological and social well-being will be assessed at the baseline, and the 3rd, 6th and 12th month. Some participants will be invited to attend focus group interviews to evaluate their overall experience of the tele-exercise training. DISCUSSION: Tele-exercise reduces the barriers to exercise, such as time constraints, inaccessibility to facilities, and the fear of frail older people leaving their homes. Promoting an online home-based exercise programme for older people can encourage them to engage in regular physical activity and increase their exercise adherence even when remaining at home. The use of telehealth can potentially result in savings in cost and time. The final findings will provide insights on delivering exercise via telehealth to older people and propose an exercise delivery and maintenance model for future practice. TRIAL REGISTRATION: Chinese Clinical Trial Registry ( https://www.chictr.org.cn/hvshowprojectEN.html?id=219002&v=1.1 ), registration number: ChiCTR2200063370. Registered on 5 September 2022.

A combined rheometry and imaging study of viscosity reduction in bacterial suspensions.

Suspending self-propelled "pushers" in a liquid lowers its viscosity. We study how this phenomenon depends on system size in bacterial suspensions using bulk rheometry and particle-tracking rheoimaging. Above the critical bacterial volume fraction needed to decrease the viscosity to zero, [Formula: see text], large-scale collective motion emerges in the quiescent state, and the flow becomes nonlinear. We confirm a theoretical prediction that such instability should be suppressed by confinement. Our results also show that a recent application of active liquid-crystal theory to such systems is untenable.

Low early complication rates after arthroscopic meniscus repair and meniscectomy.

PURPOSE: To evaluate the 30-day complication rates after arthroscopic meniscus repair and meniscectomy using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, with subgroup analysis of patients aged > 40 years. METHODS: NSQIP registries between 2006 and 2019 were queried using Current Procedural Terminology codes to identify patients undergoing arthroscopic meniscus repair (CPT 29882, 29883) and meniscectomy (29880, 29881). The following 30-day complications were assessed: pulmonary embolism (PE), venous thromboembolism (VTE), surgical site infection (SSI), reoperation, and readmission. Complications rates between treatment groups were compared using multivariate logistic regression analyses adjusted for sex, age, steroid use, and smoking/dyspnoea/COPD. A subgroup analysis was performed for patients aged > 40 years. RESULTS: A total 6354 meniscus repairs and 99,372 meniscectomies were identified. Complication rates were < 1% for both meniscus repair and meniscectomy. Meniscus repair was associated with significantly higher rates of PE, VTE, and readmission compared to meniscectomy: PE (0.2% vs 0.1%, p < 0.001), VTE (0.8% vs 0.4%, p < 0.001), superficial SSI (0.1% vs 0.2%, n.s), deep SSI (0.07% vs 0.1%, n.s), reoperation (0.5% vs 0.4%, n.s), and readmission (0.9% vs 0.8%, p = 0.003). Among patients aged > 40 years, complication rates were < 1.3% for both meniscus repair and meniscectomy. Similar trends and rates were found in patients aged > 40 years undergoing meniscus repair versus meniscectomy: PE (0.38% vs 0.12%, p < 0.001), VTE (1.07% vs 0.46%, p < 0.001), superficial SSI (0.03% vs 0.19%, n.s), deep SSI (0.1% vs 0.06%, n.s), reoperation (0.48% vs 0.43%, n.s), and readmission (1.2% vs 0.85%, p = 0.01). CONCLUSION: Arthroscopic meniscus repair and meniscectomy are both low-risk procedures with 30-day complication rates < 1% overall and < 1.3% among patients aged > 40 years. These findings support meniscus repair whenever feasible in the setting of preserved articular cartilage. Understanding of the short-term complication rates after arthroscopic meniscus repair and meniscectomy can aid surgeons in providing comprehensive preoperative counselling to patients considering such treatments, specifically when discussing the risks and benefits of meniscus repair. LEVEL OF EVIDENCE: III.