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A shear-induced limit on bacterial surface adhesion in fluid flow
No full textControlling bacterial surface adhesion and subsequent biofilm formation in fluidsystems is crucial for the safety and efficacy of medical and industrial processes. Here,we theoretically examine the transport of bacteria close to surfaces, isolating how thekey processes of bacterial motility and fluid flow interact and alter surface adhesion.We exploit the disparity between the fluid velocity and the swimming velocity ofcommon motile bacteria and, using a hybrid asymptotic-computational approach,we systematically derive the coarse-grained bacterial diffusivity close to surfaces asa function of swimming speed, rotational diffusivity, and shape. We calculate ananalytical upper bound for the bacterial adhesion rate by considering the scenario inwhich bacteria adhere irreversibly to the surface on first contact. Our theory predictsthat maximal adhesion occurs at intermediate flow rates: At lower flow rates, increasingflow increases surface adhesion, while at higher flow rates, adhesion is decreased byshear-induced cell reorientation
The distinctive psychopathology of NMDAR-antibody encephalitis compared with primary psychoses: an international, multicentre, retrospective phenotypic analysis
No full textSharp error bounds for approximate eigenvalues and singular values from subspace methods
No full textSubspace methods are commonly used for finding approximate eigenvalues and singular values of large-scale matrices. Once a subspace is found, the Rayleigh–Ritz method (for symmetric eigenvalue problems) and Petrov–Galerkin projection (for singular values) are the de facto method for extraction of eigenvalues and singular values. In this work we derive quadratic error bounds for approximate eigenvalues of symmetric matrices obtained via the Rayleigh–Ritz process. Our bounds take advantage of the fact that extremal eigenpairs tend to converge faster than the rest, hence having smaller residuals , where is a Ritz pair (approximate eigenpair). The proof uses the structure of the perturbation matrix underlying the Rayleigh–Ritz method to bound the components of its eigenvectors. In this way, we obtain a bound of the form , where is roughly the gap between the th Ritz value and the eigenvalues that are not approximated by the Ritz process, and is a modest scalar. Our bound is adapted to each Ritz value and is robust to clustered Ritz values, which is a key improvement over existing results. We further show that the bound is asymptotically sharp, and generalize it to singular values of arbitrary real matrices. Finally, we apply these bounds to several methods for computing eigenvalues and singular values, and illustrate the sharpness of our bounds in a number of computational settings, including Krylov methods and randomized algorithms
Effective permeability conditions for diffusive transport through impermeable membranes with gaps
No full textMembranes regulate transport in a wide variety of industrial and biological applications. The microscale geometry of the membrane can significantly affect overall transport through the membrane, but the precise nature of this multiscale coupling is not well characterised in general. Motivated by the application of transport across a bacterial membrane, we use formal multiscale analysis to derive explicit effective coupling conditions for macroscale transport across a two-dimensional impermeable membrane with periodically spaced gaps, and validate these with numerical simulations. We derive analytic expressions for macroscale membrane quantities, such as the effective permeability, in terms of the microscale geometry. Our results generalise the classic constitutive membrane coupling conditions to a wider range of membrane geometries and time-varying scenarios e.g. we demonstrate that the unsteady conditions can gain a memory property and depend on the system history. By applying our effective conditions to small-molecule transport through gaps in bacterial membranes called porins, we predict that membrane permeability here is primarily dominated by membrane thickness. Furthermore, we predict how alterations to membrane microstructure, e.g. via changes to porin expression, might affect overall transport. These results will apply to other physical applications with similar membrane structures, from medical and industrial filtration to carbon capture
Cognitive behavioural therapy for a specific phobia of vomiting during pregnancy: a case study
Get PDFSpecific phobia of vomiting (SPOV) is a persistent, excessive fear of vomiting that is more prevalent in females, often begins in childhood and typically lasts 25 years before treatment is sought. It is a relatively neglected area of research, with most evidence consisting of single case studies. There are implications for the perinatal period, in particular the experience of pregnancy which for many involves symptoms of nausea and vomiting. However, there is a paucity of research on the experience of SPOV during pregnancy and currently no published treatment research. This study aimed to extend the existing literature by applying Veale’s (2009) protocol for SPOV to a pregnant client in her twenties. The intervention comprised 12 one-hour face-to-face sessions and was effective in significantly reducing anxiety (GAD-7 reduced from 7 to 0), depression (PHQ-9 reduced from 6 to 1), impaired functioning (WSAS reduced from 20 to 4) and vomiting phobia (SPOVI reduced from 40 to 0)
Helicity-preserving finite element discretization for magnetic relaxation
No full textThe Parker conjecture, which explores whether magnetic fields in perfectly conducting plasmas can develop tangential discontinuities during magnetic relaxation, remains an open question in astrophysics. Helicity conservation provides a topological barrier during relaxation, preventing topologically nontrivial initial data relaxing to trivial solutions; preserving this mechanism discretely over long time periods is therefore crucial for numerical simulation. This work presents an energy- and helicity-preserving finite element discretization for the magneto-frictional system for investigating the Parker conjecture. The algorithm preserves a discrete version of the topological barrier and a discrete Arnold inequality. We also propose extensions of the notion of helicity and the Arnold inequality to certain kinds of topologically nontrivial domains. Numerical experiments demonstrate that helicity preservation is crucial in obtaining physically meaningful simulations of magnetic relaxation, providing an example where structure-preserving schemes are necessary
Boundedness and stability of a 2-D parabolic-elliptic system arising in biological transport networks
Get PDFThis paper is concerned with the Dirichlet initial-boundary value problem of a 2-D parabolic-elliptic system of the following form
{mt − κ∆m + |m| 2(γ−1) m = (m · ∇p)∇p, − ∇ · [(I + m ⊗ m)∇p] = S,
which was proposed to model the formation of biological transport networks. Even if global weak solutions for this system are known to exist, how to improve the regularity of weak solutions is a challenging problem due to the peculiar cubic nonlinearity and the possible elliptic singularity of the system. Global-in-time existence of classical solutions has recently been established, showing that finite time singularities cannot emerge in this problem. However, whether or not singularities in infinite time can be precluded was still pending. In this work, we show that classical solutions of the initial-boundary value problem are uniformly bounded in time as long as γ ⩾ 1 and κ is suitably large, closing this gap in the literature. Moreover, the uniqueness of classical solutions is also achieved based on the uniform-in-time bounds. Furthermore, it is shown that the corresponding stationary problem possesses a unique classical stationary solution which is semi-trivial, and that is globally exponentially stable, i.e., all solutions of the time-dependent problem converge exponentially fast to the semi-trivial steady state for κ large enough
Finger-prick transcriptomic profiling in northern Nigeria reveals a muted maternal systemic response in stillbirth
Get PDFInflammation is implicated in placental dysfunction leading to stillbirth, yet evidence of a systemic immune response during parturition remains unclear. Here, we present the first transcriptomic analysis of maternal systemic responses associated with stillbirth, using a minimally invasive finger-prick method for whole blood collection in labouring women in northern Nigeria. This approach facilitated participant recruitment with minimal disruption to care and provided high-quality RNA for transcriptomic profiling. Contrary to expectations, no major differences were observed in systemic immune states between propensity-matched live births and stillbirths. These findings suggest several possibilities, including the dominance of a parturition response masking an underlying immune state, physical protective barriers, or placental tolerance mechanisms. This study offers novel insights into maternal systemic immune health during stillbirth and highlights the need for further research. It also contributes to the broader “Stillbirths in Kano” initiative, aimed at reducing stillbirth rates through enhanced prenatal care
A transdiagnostic perspective on the measurement, assessment, and treatment of cognitive impairment in neuropsychiatric disorders
Get PDFCognitive impairment is a core feature of numerous neuropsychiatric disorders yet remains under-addressed in routine clinical care. This PhD thesis adopts a transdiagnostic perspective to explore the measurement, assessment, and treatment of cognitive impairment across diagnostic boundaries. First, brain-derived neurotrophic factor (BDNF) and metabolic syndrome were evaluated for their potential as biomarkers in clinical settings. While both showed associations with cognitive function, neither proved specific or reliable enough for routine use due to measurement limitations and high dependence on external factors. Second, the development and real-world application of the Transdiagnostic Global Impression – Psychopathology scale (TGI-P), a brief tool assessing ten transdiagnostic symptom domains, including cognition was described. In a small inpatient sample, TGI-P scores correlated well with established scales such as the PANSS, particularly for positive and manic symptoms. Cognitive and depressive symptoms were less strongly correlated but still measurable, suggesting the scale’s promise for integrating measurement-based care in psychiatry. Third, the cognitive effects of cariprazine, a third-generation antipsychotic was evaluated. A systematic review and meta-analysis indicated the potential of cariprazine as a transdiagnostic treatment for cognitive symptoms. This was further supported by findings from a 12-week observational study in patients with Huntington’s and Parkinson’s disease, where cariprazine showed promising effects on cognitive and affective symptoms. Overall, this thesis highlights the importance and challenges of addressing cognitive impairment independent from clinical diagnosis. While robust biomarkers are still lacking, practical tools like the TGI-P and emerging treatments like cariprazine may support better recognition and management of cognitive impairment in clinical practice
The fragmented landscape of shrimp life cycle assessments: uncovering methodological dependence and analytical blind spots
Get PDFLife Cycle Assessment (LCA) of shrimp aquaculture is hampered by widely divergent results, with reported impacts varying by more than fiftyfold across key categories. This systematic review of 16 peer-reviewed LCAs provides quantitative evidence that much of this divergence is driven by analytical choices rather than on-farm performance: In this case study covering 37 farming cycles, methodological differences in shrimp LCAs induced larger changes in global warming estimates for identical farm data compared to different farming practices. This issue is compounded by a lack of transparency, with only five of the 16 studies providing sufficient data for full reproducibility. We find that this methodological dominance is amplified by analytical blind spots, as most studies neglect critical environmental pressures such as land use change, biodiversity loss, and antibiotic use. To build a robust and comparable evidence base, we recommend representative studies, specific methodological harmonisation, mandatory inclusion of neglected impact categories, and improved reporting transparency. These improvements are essential for LCA to accurately guiding the sector towards more sustainability