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On the lack of Gaussian tail for rough line integrals along fractional Brownian paths
Get PDFWe show that the tail probability of the rough line integral \int_{0}^{1}\phi(X_{t})dY_{t}, where (X,Y) is a 2D fractional Brownian motion with Hurst parameter H\in(1/4,1/2) and \phi is a C_{b}^{\infty}-function satisfying a mild non-degeneracy condition on its derivative, cannot decay faster than a \gamma-Weibull tail with any exponent \gamma>2H+1. In particular, this produces a simple class of examples of differential equations driven by fBM, whose solutions fail to have Gaussian tail even though the underlying vector fields are assumed to be of class C_{b}^{\infty}. This also demonstrates that the well-known upper tail estimate proved by Cass-Litterer-Lyons in 2013 is essentially sharp
Mean curvature flow with generic initial data
No full textWe show that the mean curvature flow of generic closed surfaces in R3 avoids asymptotically conical and non-spherical compact singularities. We also show that the mean curvature flow of generic closed low-entropy hypersurfaces in R4 is smooth until it disappears in a round point. The main technical ingredient is a long-time existence and uniqueness result for ancient mean curvature flows that lie on one side of asymptotically conical or compact shrinking solitons
Understanding visible light and microbe-driven degradation mechanisms of polyurethane plastics : pathways, property changes, and product analysis
No full textThe accumulation of polyurethane plastics (PU-PS) in the environment is on the rise, posing potential risks to the health and function of ecosystems. However, little is known about the degradation behavior of PU-PS in the environment, especially water environment. To address this knowledge gap, we investigated and isolated a degrading strain of Streptomyces sp. B2 from the surface of polyurethane coatings. Subsequently, a photoreactor was employed to simulate the degradation process of bio-based polyurethane (BPU) and petroleum-based polyurethane (PPU) under three conditions, including single microorganism (SM), single light exposure (SL), and combined light exposure/microorganism action (ML) in aqueous solution. The results indicated that PU-PS mainly relies on biodegradation, with the highest degradation rate observed after 28 d under SM condition (BPU 5.69%; PPU 5.25%). SL inhibited microbial growth and degradation, with the least impact on plastic degradation. Microorganisms colonized the plastic surface, secreting relevant hydrolytic enzymes and organic acids into the culture medium, providing a negative charge. The carbon chains were broken and aged through hydrogen peroxide induction or attack by oxygen free radicals. This process promoted the formation of oxidized functional groups such as -OH and C=O, disrupting the polymer's structure. Consequently, localized fragmentation and erosion of the microstructure occurred, resulting in the generation of secondary microplastic (MPs) particles, weight loss of the original plastic, increased surface roughness, and enhanced hydrophilicity. Additionally, BPU exhibited greater degradability than PPU, as microorganisms could utilize the produced fatty acids, which promoted their reproduction. In contrast, PPU degradation generated a large amount of isocyanate, potentially toxic to cells and inhibiting biodegradation. This study unveils the significant role of microorganisms in plastic degradation and the underlying degradation mechanisms of BPU, providing a novel strategy for polyurethane degradation and valuable information for comprehensive assessment of the behavior and fate of MPs in the environment
Development of a high ductility DP steel using a segregation neutralization approach : benchmarked against a commercial dual phase steel
No full textCommercial dual-phase steels are typically synonymous with a banded distribution of martensite in their microstructures, which can degrade ductility and increase the anisotropy of mechanical properties. The concept of neutralizing the effect of Mn segregation is employed to change the distribution of martensite to a non-banded distribution. To this end, the ratio of austenite and ferrite stabilizer elements has been changed in the composition of dual-phase steel. Microstructural analysis has been carried out on both hot-rolled (ferrite + pearlite) and heat-treated (ferrite + martensite) microstructures by optical microscope and EBSD, respectively. The microstructural examinations have confirmed the non-banded distribution of second phase and more equiaxed ferrite grains in the segregated neutralized grade microstructures compared to a commercially benchmarked dual-phase steel. Tensile properties of two grades have also been assessed in hot-rolled and heat-treated conditions in RD, TD, and 45 deg tensile directions. In the case of heat-treated condition, total elongation in RD direction has been improved from 20.9 pct in benchmark dual-phase steel to 25.4 pct in segregated neutralized dual-phase steel. Tensile anisotropy results showed a significant difference in tensile strength by tensile direction in benchmark dual-phase steel in both hot-rolled (~ 85 MPa) and heat-treated conditions (~ 48 MPa), while the corresponding differences for the segregated neutralized grades were 14 and 15 MPa, respectively
Structures of wild-type and a constitutively closed mutant of connexin26 shed light on channel regulation by CO2
No full textConnexins allow intercellular communication by forming gap junction channels (GJCs) between juxtaposed cells. Connexin26 (Cx26) can be regulated directly by CO2. This is proposed to be mediated through carbamylation of K125. We show that mutating K125 to glutamate, mimicking the negative charge of carbamylation, causes Cx26 GJCs to be constitutively closed. Through cryo-EM we observe that the K125E mutation pushes a conformational equilibrium towards the channel having a constricted pore entrance, similar to effects seen on raising the partial pressure of CO2. In previous structures of connexins, the cytoplasmic loop, important in regulation and where K125 is located, is disordered. Through further cryo-EM studies we trap distinct states of Cx26 and observe density for the cytoplasmic loop. The interplay between the position of this loop, the conformations of the transmembrane helices and the position of the N-terminal helix, which controls the aperture to the pore, provides a mechanism for regulation
A posteriori error estimate and adaptivity for QM/MM models of crystalline defects
No full textHybrid quantum mechanics/molecular mechanics (QM/MM) models play a pivotal role in molecular simulations. These models provide a balance between accuracy, surpassing pure MM models, and computational efficiency, offering advantages over pure QM models. Adaptive approaches have been developed to further improve this balance by allowing on-the-fly selection of the QM and MM subsystems as necessary. We propose a novel and robust adaptive QM/MM method for practical material defect simulations. To ensure mathematical consistency with the QM reference model, we employ machine-learning interatomic potentials (MLIPs) as the MM models (Chen et al., 2022 and Grigorev et al., 2023). Our adaptive QM/MM method utilizes a residual-based error estimator that provides both upper and lower bounds for the approximation error, thus indicating its reliability and efficiency. Furthermore, we introduce a novel adaptive algorithm capable of anisotropically updating the QM/MM partitions. This update is based on the proposed residual-based error estimator and involves solving a free interface motion problem, which is efficiently achieved using the fast marching method. We demonstrate the robustness of our approach via numerical tests on a range of crystalline defects comprising edge dislocations, cracks and di-interstitials
Extreme mortality during a historical measles outbreak on Rotuma is consistent with measles immunosuppression
No full textUntil the early twentieth century, populations on many Pacific Islands had never experienced measles. As travel to the Pacific Islands by Europeans became more common, the arrival of measles and other pathogens had devastating consequences. In 1911, Rotuma in Fiji was hit by a measles epidemic, which killed 13% of the island population. Detailed records show two mortality peaks, with individuals reported as dying solely from measles in the first and from measles and diarrhoea in the second. Measles is known to disrupt immune system function. Here, we investigate whether the pattern of mortality on Rotuma in 1911 was a consequence of the immunosuppressive effects of measles. We use a compartmental model to simulate measles infection and immunosuppression. Whilst immunosuppressed, we assume that individuals are vulnerable to dysfunctional reactions triggered by either (i) a newly introduced infectious agent arriving at the same time as measles or (ii) microbes already present in the population in a pre-existing equilibrium state. We show that both forms of the immunosuppression model provide a plausible fit to the data and that the inclusion of immunosuppression in the model leads to more realistic estimates of measles epidemiological parameters than when immunosuppression is not included
MCDGait : multimodal co-learning distillation network with spatial-temporal graph reasoning for gait recognition in the wild
No full textExperiences and challenges of people living with multiple long-term conditions in managing their care in primary care settings in Kerala, India : a qualitative study
No full textBackground: Multimorbidity or multiple long-term conditions (MLTCs), the coexistence of two or more chronic conditions within an individual, presents a growing concern for healthcare systems and individuals’ well-being. However, we know little about the experiences of those living with MLTCs in low- and middle-income countries (LMICs) such as India. We explore how people living with MLTCs describe their illness, their engagements with healthcare services, and challenges they face within primary care settings in Kerala, India. Methods: We designed a qualitative descriptive study and conducted in-depth, semi-structured interviews with 31 people (16 males and 15 females) from family health centres (FHCs) in Kerala. Interview data were recorded, transcribed, and thematic analysis using the Framework Method was undertaken. Findings: Two main themes and three sub-themes each were identified; (1) Illness impacts on life (a)physical issues (b) psychological difficulties (c) challenges of self-management and (2) Care-coordination maze (a)fragmentation and poor continuity of care (b) medication management; an uphill battle and (c) primary care falling short. All participants reported physical and psychological challenges associated with their MLTCs. Younger participants reported difficulties in their professional lives, while older participants found household activities challenging. Emotional struggles encompassed feelings of hopelessness and fear rooted in concerns about chronic illness and physical limitations. Older participants, adhering to Kerala’s familial support norms, often found themselves emotionally distressed by the notion of burdening their children. Challenges in self-management, such as dietary restrictions, medication adherence, and physical activity engagement, were common. The study highlighted difficulties in coordinating care, primarily related to traveling to multiple healthcare facilities, and patients’ perceptions of FHCs as fit for diabetes and hypertension management rather than their multiple conditions. Additionally, participants struggled to manage the task of remembering and consistently taking multiple medications, which was compounded by confusion and memory-related issues. Conclusion: This study offers an in-depth view of the experiences of individuals living with MLTCs from Kerala, India. It emphasizes the need for tailored and patient-centred approaches that enhance continuity and coordination of care to manage complex MLTCs in India and similar LMICs