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Exact results and instabilities in the harmonic approximation of active crystals
No full textCondensates of active particles, such as cells, form almost-crystalline lattices that play a central role in many biological systems. Typically, their properties have been determined merely by analogy to the rather trivial one-dimensional case, leaving a gap between experimentally accessible observables and suitable theoretical models. Within a harmonic approximation, we characterise analytically a two-dimensional triangular lattice of active particles that interact with their nearest
neighbours through a general pair potential, obtaining exact expressions for the correlators. We study this “active crystal” as a means of characterising active matter in the dense phase. Our treatment correctly approximates arbitrary pair potentials, rather than demanding an unphysical non-singular bilinear form. We retain “off-diagonal” terms that are routinely neglected despite quantifying the anisotropy of the particles’ local potential. From the exact expressions for the correlation
matrices, we derive exact results that shed light on the presence (or absence) of crystalline order. We further calculate the mean-squared particle separation, energy, entropy production rate and the onset of a pressure-induced instability resulting in the breakdown of the harmonic approximation. The entropy production rate is found to have a general form that is valid for generic active particles and lattice geometries, while resembling that of non-interacting “active modes”
Post-pancreatectomy clip migration: a two-stage management approach with pancreatography and pancreatoscopy
No full textClip migration is a rare complication occurring mostly after cholecystectomy. Upfront retrieval with endoscopic retrograde cholangiopancreatography (ERCP) is the standard treatment for post-cholecystectomy clip migration (PCCM [1]). However, performing invasive procedures during pancreatitis is associated with increased mortality. We report a safely managed post-pancreatectomy clip migration (PPCM) into the main pancreatic duct (MPD).
A 77-year-old man was recalled to the hospital 3 months after undergoing uncomplicated laparoscopic distal pancreatectomy for non-invasive intraductal papillary mucinous carcinoma of the pancreatic body because surveillance computed tomography revealed a clip lodged in the MPD causing obstructive pancreatitis ([Fig. 1]). Although he was asymptomatic with non-contributory physical examination, serum amylase (125 IU/L) and C-reactive protein (17.8 mg/dL) levels were elevated
Microscopic insight into the origin of super-cooled NCCDW state in 1T-TaS₂ nanocrystals
No full textTantalum disulfide (1T-TaS₂) is a quasi-two-dimensional transition metal dichalcogenide (TMD) that exhibits a series of charge density wave (CDW) transitions upon cooling and heating. These collective electronic phases can be tuned or disrupted by external stimuli such as pressure, electric fields, or illumination, leading to metastable or hidden metallic states. In nanoscale crystals of 1T-TaS₂, rapid cooling suppresses the insulating commensurate CDW (CCDW) phase and stabilizes a metastable metallic state, known as the supercooled nearly commensurate CDW (SC-NCCDW) phase. However, the atomic-scale structure and microscopic origin of this state remain elusive. Here, we combine electrical transport measurements with structural characterization to elucidate the nature of the SC-NCCDW phase in 1T-TaS₂ nanocrystals. Temperature-dependent X-ray diffraction reveals that, under gradual cooling, the NCCDW-to-CCDW transition is accompanied by lattice-volume expansion. In contrast, this anomaly is strongly suppressed upon rapid cooling, correlating with the stabilization of the SC-NCCDW state. Complementary high-resolution transmission electron microscopy (HR-TEM) shows that rapid cooling produces a mixed-phase configuration containing structural motifs of both NCCDW and CCDW phases, indicating that the SC-NCCDW represents an intermediate structural configuration frozen by kinetic constraints. These findings provide, to our knowledge, the first direct structural evidence of the SC-NCCDW state and offer a mechanistic understanding of cooling-rate-controlled metastability in layered correlated compounds such as 1T-TaS₂.
Keywords: 1T-TaS2, phase transitions, charge density waves (CDW), metastable phases, super-cooled NCCDW phase, structural characterization
Modelling cultivation and mechanical response of bacterial nanocellulose
No full textBacterial nanocellulose (BNC) is a material made of a network of nanocellulose fibres secreted by bacteria, most commonly Komagataeibacter xylinus. Both in its original wet pellicle form and dried nanopaper form, BNC receives considerable attention from the scientific community due to various desirable features such as high strength, porosity, and biocompatibility. Experimental studies were done about cultivation, refinement, and mechanical properties of this material, with a few simulation studies done to complement these. However, to this date, there was neither an agent-based simulation of BNC cultivation nor a mechanical simulation of 3-D BNC networks. This project is about constructing an agent-based simulation of BNC cultivation and using the resulting fibre networks for the mechanical simulation of wet BNC pellicles and compress-dried BNC nanopapers. The simulation provides a new method of analysing BNC materials and reveals new features of the material.
Cultivation simulation models oxygen and substrate diffusion as well as each individual cell’s movement, response to obstacles, entrapment by surrounding fibre network, growth, division, and metabolism. The simulation shows good agreement with experimental results. The simulation is employed to predict the sensitivity to various factors such as oxygen tension, pellicle vertical growth rate, cultivation vessel depth, and initial cell concentration.
Then, a model for chemotaxis of K. xylinus is added to the agent-based BNC cultivation simulation. Evolution simulations predict that chemotactic cells will outnumber non-chemotactic cells if they coexist in a cultivation.
Finally, mechanical simulations of BNC networks reveal the structure-property relationships for wet and compress-dried BNC networks. Fail stress of wet pellicle is shown to depend on crosslink density and average fibre cross-section area while fail strain is shown to depend on average segment length. Crosslink formation, hence strength of network, is shown to mainly depend on cells joining to/separating from previously laid BNC fibres
A novel time-varying Wiener process for adaptive RUL prediction under multiple uncertainties
No full textThe file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Remaining useful life (RUL) prediction for high-reliability complex systems is often challenged by scarce real degradation data and noise-contaminated simulated data, limiting the ability of existing methods to handle multiple uncertainties and time-varying characteristics, which in turn constrains the robustness and interpretability of predictions. This study proposes a time-varying Wiener process (TVWP) degradation model that incorporates the quantification of multiple uncertainties. First, a TVWP model is developed to characterize dynamic degradation patterns, taking into full account unit-to-unit variability and time-varying degradation behaviors. Second, a normal cloud model-based Bayesian parameter estimation method is designed to achieve adaptive updating of time-varying parameters and dynamic quantification of epistemic uncertainty. Finally, the probability distribution of the RUL is derived analytically, enabling adaptive prediction while simultaneously achieving real-time quantification of prediction errors and uncertainty. The proposed method is validated on a small-sample gyroscope drift dataset and the large-scale C-MAPSS benchmark. Results demonstrate its strong adaptability to different data volumes and significant superiority over conventional Wiener process models and state-of-the-art approaches in both prediction accuracy and robustness
Diabetes mellitus and the risk of vulvar and vaginal cancer: results from a large cohort study
No full textBackground: Although diabetes mellitus has been associated with increased risk of several cancers, evidence in relation to vulvar and vaginal cancers has been limited and inconsistent. We investigated the association between diabetes and diabetes complications and the risk of vulvar and vaginal cancer risk in a nationwide cohort of 2.8 million women in Taiwan.
Methods: A retrospective cohort study of 2.8 million women with and without diabetes mellitus aged 18-90 years was conducted. Multivariable proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between diabetes diagnosis and the risk of vulvar and vaginal cancer.
Results: During 7.8 years follow-up, 553 vulvar and 506 vaginal cancer cases occurred. A history of diabetes mellitus was associated with higher risk of vulvar cancer with a HR (95% CIs) of 1.34 (1.12-1.60), but not vaginal cancer (1.09, 0.91-1.31). The HR was 1.97 (0.95-4.11) for early-onset and 1.34 (1.12-1.61) for later-onset vulvar cancer and 1.81 (0.76-4.32) for early-onset and 1.09 (0.90-1.31) for later-onset vaginal cancer. The associations were similar when restricted to type 2 diabetes cases, and when excluding the first 5 years of follow-up.
Conclusion: These findings suggest diabetes mellitus is associated with increased risk of vulvar, but not vaginal cancer. Further studies are needed to clarify these findings
What Incentive Structures Do to Political Philosophy: Epistemic Pathologies and Institutional Design
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UGAE: Unified Geometry and Attribute Enhancement for G-PCC Compressed Point Clouds
No full textThe file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Lossy compression of point clouds reduces storage and transmission costs; however, it inevitably leads to irreversible distortion in geometry structure and attribute information. To address these issues, we propose a unified geometry and attribute enhancement (UGAE) framework, which consists of three core components: post-geometry enhancement (PoGE), pre-attribute enhancement (PAE), and post-attribute enhancement (PoAE). In PoGE, a Transformer-based sparse convolutional U-Net is used to reconstruct the geometry structure with high precision by predicting voxel occupancy probabilities. Building on the refined geometry structure, PAE introduces an innovative enhanced geometry-guided recoloring strategy, which uses a detail-aware K-Nearest Neighbors (DA-KNN) method to achieve accurate recoloring and effectively preserve high-frequency details before attribute compression. Finally, at the decoder side, PoAE uses an attribute residual prediction network with a weighted mean squared error (W-MSE) loss to enhance the quality of high-frequency regions while maintaining the fidelity of low-frequency regions. UGAE significantly outperformed existing methods on three benchmark datasets: 8iVFB, Owlii, and MVUB. Compared to the latest G-PCC test model (TMC13v29), in terms of total bitrate setting, UGAE achieved an average BD-PSNR gain of 9.98 dB and -90.54% BD-bitrate for geometry under the D1 metric, as well as a 3.34 dB BD-PSNR improvement with -55.53% BD-bitrate for attributes. Additionally, it improved perceptual quality significantly. Our source code will be released on GitHub at: https://github.com/yuanhui0325/UGA
Excessive shear rate, not shear stress, influences cell mechanical damage in small-bore needle injections
No full textPurpose: Cell therapies and 3D bioprinting often require suspended cells to be delivered through needles of 20-gauge and smaller. This often damages cells, affecting their short and long-term viability. Most researchers have attributed this to excessive viscous stresses encountered entering or within the needle, but the experimental evidence contradicts that, as higher viscosity suspension fluids generally yield higher cell viabilities when injected at the same flow rate. We therefore sought to determine the most relevant fluid flow parameter influencing cell mechanical damage.
Methods: A combination of reprocessing published results and cell injection experiments were conducted. Human umbilical vein endothelial cells were suspended in Newtonian fluids of varying viscosities and injected through 30-gauge syringe needles in experiments that controlled for either shear stress or shear rate (a kinematic quantity expressing relative velocity of adjacent fluid layers).
Results: Based on evidence from injection experiments using a variety of fluids, it is shown that increasing shear rate better explains reductions in cell viability than increasing shear stress.
Conclusion: Knowledge that shear rate is a more relevant fluid mechanical parameter governing mechanical damage provides a rational basis for designing injection protocols (injectors and suspension fluid rheological properties) to maximize cell viability
Building the evidence base for regional water planning
No full textThis briefing explores the case for taking a more holistic approach to water planning and proposes some concrete steps towards making that a reality. More specifically, while holistic approaches can encompass many important dimensions, including stakeholder engagement, water governance, institutional coordination and decision-making processes, this briefing focuses on the evidence needed to support proposed Regional Water Planning