A microscopic 2D lattice model of dimer granular compaction with friction

We study by Monte Carlo simulation the compaction dynamics of hard dimers in 2D under the action of gravity, subjected to vertical and horizontal shaking, considering also the case in which a friction force acts for horizontal displacements of the dimers. These forces are modeled by introducing effective probabilities for all kinds of moves of the particles. We analyze the dynamics for different values of the time $\tau$ during which the shaking is applied to the system and for different intensities of the forces. It turns out that the density evolution in time follows a stretched exponential behavior if $\tau$ is not very large, while a power law tail develops for larger values of $\tau$. Moreover, in the absence of friction, a critical value $\tau^*$ exists which signals the crossover between two different regimes: for $\tau < \tau^*$ the asymptotic density scales with a power law of $\tau$, while for $\tau > \tau^*$ it reaches logarithmically a maximal saturation value. Such behavior smears out when a finite friction force is present. In this situation the dynamics is slower and lower asymptotic densities are attained. In particular, for significant friction forces, the final density decreases linearly with the friction coefficient. We also compare the frictionless single tap dynamics to the sequential tapping dynamics, observing in the latter case an inverse logarithmic behavior of the density evolution, as found in the experiments.Comment: 10 pages, 15 figures, to be published in Phys. Rev.

Convection in colloidal suspensions with particle-concentration-dependent viscosity

The onset of thermal convection in a horizontal layer of a colloidal suspension is investigated in terms of a continuum model for binary-fluid mixtures where the viscosity depends on the local concentration of colloidal particles. With an increasing difference between the viscosity at the warmer and the colder boundary the threshold of convection is reduced in the range of positive values of the separation ratio psi with the onset of stationary convection as well as in the range of negative values of psi with an oscillatory Hopf bifurcation. Additionally the convection rolls are shifted downwards with respect to the center of the horizontal layer for stationary convection (psi>0) and upwards for the Hopf bifurcation (psi<0).Comment: 8 pages, 6 figures, submitted to European Physical Journal

Compaction of Rods: Relaxation and Ordering in Vibrated, Anisotropic Granular Material

We report on experiments to measure the temporal and spatial evolution of packing arrangements of anisotropic, cylindrical granular material, using high-resolution capacitive monitoring. In these experiments, the particle configurations start from an initially disordered, low-packing-fraction state and under vertical vibrations evolve to a dense, highly ordered, nematic state in which the long particle axes align with the vertical tube walls. We find that the orientational ordering process is reflected in a characteristic, steep rise in the local packing fraction. At any given height inside the packing, the ordering is initiated at the container walls and proceeds inward. We explore the evolution of the local as well as the height-averaged packing fraction as a function of vibration parameters and compare our results to relaxation experiments conducted on spherically shaped granular materials.Comment: 9 pages incl. 7 figure

Risk thresholds for total and beverage-specific alcohol consumption and incident atrial fibrillation

OnlinePubl.Abstract not available.Samuel J. Tu, Celine Gallagher, Adrian D. Elliott, Dominik Linz, Bradley M. Pitman, Jeroen M.L. Hendriks, Dennis H. Lau, Prashanthan Sanders, Christopher X. Won

Alcohol intake and bradyarrhythmia risk: a cohort study of 407 948 individuals

Online publish-ahead-of-print 17 February 2022Aims: There is a paucity of epidemiological evidence on alcohol and the risk of bradyarrhythmias. We thus characterized associations of total and beverage-specific alcohol consumption with incident bradyarrhythmias using data from the UK Biobank. Methods and results: Alcohol consumption reported at baseline was calculated as UK standard drinks (8 g alcohol)/week. Bradyarrhythmia events were defined as sinus node dysfunction (SND), high-level atrioventricular block (AVB), and permanent pacemaker implantations. Outcomes were assessed through hospitalization and death records, and dose–response associations were characterized using Cox regression models with correction for regression dilution bias. We studied 407 948 middle-aged individuals (52.4% female). Over a median follow-up time of 11.5 years, a total of 8 344 incident bradyarrhythmia events occurred. Increasing total alcohol consumption was not associated with an increased risk of bradyarrhythmias. Beer and cider intake were associated with increased bradyarrhythmia risk up to 12 drinks/week; however, no significant associations were observed with red wine, white wine, or spirit intake. When bradyarrhythmia outcomes were analysed separately, a negative curvilinear was observed for total alcohol consumption and risk of SND, but no clear association with AVB was observed. Conclusion: In this predominantly White British cohort, increasing total alcohol consumption was not associated with an increased risk of bradyarrhythmias. Associations appeared to vary according to the type of alcoholic beverage and between different types of bradyarrhythmias. Further epidemiological and experimental studies are required to clarify these findings.Samuel J. Tu, Celine Gallagher, Adrian D. Elliott, Dominik Linz, Bradley M. Pitman, Jeroen M.L. Hendriks, Dennis H. Lau, Prashanthan Sanders and Christopher X. Won

Alcohol consumption and risk of ventricular arrhythmias and sudden cardiac death: an observational study of 408,712 individuals

Abstract not available.Samuel J. Tu Celine Gallagher, Adrian D. Elliott, Dominik Linz, Bradley M. Pitman, Jeroen M.L. Hendriks, Dennis H. Lau, Prashanthan Sanders, Christopher X. Won

Associations of dietary patterns, ultra-processed food and nutrient intake with incident atrial fibrillation.

OnlinePublOBJECTIVE: To examine the associations between specific dietary patterns and incident atrial fibrillation (AF). METHODS: Using data from the UK Biobank, dietary intakes were calculated from 24-hour diet recall questionnaires. Indices representing adherence to dietary patterns (Mediterranean-style, Dietary Approaches to Stop Hypertension (DASH) and plant-based diets) were scored, and ultra-processed food consumption was studied as a percentage of total food mass consumed. Incident AF hospitalisations were assessed in Cox regression models. RESULTS: A total of 121 300 individuals were included, with 4 579 incident AF cases over a median follow-up of 8.8 years. Adherence to Mediterranean-style or DASH diets was associated with a lower incidence of AF in minimally adjusted analyses (HR for highest vs lowest quintile 0.87 (95% CI 0.80-0.96) and HR 0.78 (95% CI 0.71-0.86), respectively). However, associations were no longer significant after accounting for lifestyle factors (HR 0.95 (95% CI 0.87-1.04) and 0.94 (95% CI 0.86-1.04) respectively), with adjustment for body mass index responsible for approximately three-quarters of the effect size attenuation. Plant-based diets were not associated with AF risk in any models. Greatest ultra-processed food consumption was associated with a significant increase in AF risk even in fully adjusted models (HR 1.13 (95% CI 1.02-1.24)), and a 10% increase in absolute intake of ultra-processed food was associated with a 5% increase in AF risk (HR 1.05 (95% CI 1.01-1.08)). CONCLUSION: With the possible exception of reducing ultra-processed food consumption, these findings suggest that attention to other modifiable risk factors, particularly obesity, may be more important than specific dietary patterns for the primary prevention of AF.Samuel J Tu, Celine Gallagher, Adrian D Elliott, Kathryn E Bradbury, Gregory M Marcus, Dominik Linz, Bradley M Pitman, Melissa E Middeldorp, Jeroen M Hendriks, Dennis H Lau, Prashanthan Sanders, Christopher X Won

Associations of anaemia with stroke, bleeding, and mortality in atrial fibrillation: a systematic review and meta-analysis

BACKGROUND: Anaemia frequently co-exists with atrial fibrillation (AF) and has been variably associated with worse outcomes. We performed a systematic review and meta-analysis to comprehensively assess the effect of anaemia on mortality, stroke/systemic thromboembolism and bleeding events in patients with AF. METHODS: MEDLINE and Embase were searched from inception until May 2020. Studies examining associations of anaemia with the above outcomes in AF patients were included, and maximally adjusted hazard ratios (HRs) meta-analysed. PROSPERO registration number CRD42020171113. RESULTS: Twenty-eight studies involving 365,484 patients (41% female, mean age 74.7 years) were included. The average study follow-up ranged from 0.2 to 4.0 years, and prevalence of anaemia was 16%. Anaemia was associated with a 78% increase in all-cause mortality (HR 1.78, 95% CI 1.44-2.20), 60% increase in cardiovascular mortality (HR 1.60, 95% CI 1.17-2.19), 134% increase in non-cardiovascular mortality (HR 2.34, 95% CI 1.58-3.47) 15% increase in stroke/systemic thromboembolism (HR 1.15, 95% CI 1.01-1.31), 78% increase in major bleeding (HR 1.78, 95% CI 1.54-2.05), and 77% increase in gastrointestinal bleeding (HR 1.77, 95% CI 1.23-2.55). Sensitivity analyses including studies that reported odds ratios did not result in any material change. CONCLUSION: Anaemia is a frequently observed comorbidity in patients with AF, and is associated with an increased risk of all-cause, cardiovascular and non-cardiovascular mortality, stroke/systemic thromboembolism, and major and gastrointestinal bleeding. Future studies are required to explore the causes of anaemia in AF, and whether investigation and treatment may be clinically beneficial in affected individuals. This article is protected by copyright. All rights reserved.Samuel J. Tu, Nicole Hanna‐Rivero, Adrian D. Elliott, Nicholas Clarke, Sonia Huang, Bradley M. Pitman … et al