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When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating thermal convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely distributed vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being proportional (≈ 30%) to the cluster length. Such long-range correlation leads to the counterintuitive collective outward motion of warm vortices. Our study brings insights into the vortex dynamics that are widely present in nature. Ding et al. study the collective motion of densely packed vortices in rotating thermal convection. They uncover the counterintuitive effect of warmer and thus lighter vortices moving outward from the central axis of rotation, driven by long range, scale-free vortex correlations. [ABSTRACT FROM AUTHOR]

Background: The concurrent presence of liver cirrhosis and hepatocellular carcinoma (HCC) poses a challenge for laparoscopic surgeons to establish a routine practice. The aim of this study was to gather evidence and produce recommendations on the safe and effective practice of laparoscopic hepatectomy for patients with solitary HCC (≤ 5 cm) and liver cirrhosis. Methods: Between October 2013 and October 2014, 356 curative hepatectomies were performed for patients pathologically diagnosed with solitary HCC (≤ 5 cm) accompanied by cirrhosis (stage 4 fibrosis). To overcome selection bias, a 1:2 match using propensity score matching analysis was conducted between laparoscopic and open hepatectomy. Perioperative outcomes were compared between the groups, including hospitalization, operation time, blood loss, and surgical complications. Perioperative inflammation-based markers, including systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR) were collected from medical records and analyzed. Results: There were 43 and 77 patients in the laparoscopic and open groups, respectively. The laparoscopic group had less hepatic inflow occlusion (16.3% vs. 61%; P < 0.001), shorter operation time (155 vs. 170 min; P = 0.004), and shorter postoperative hospital stay (4 vs. 7 days; P < 0.001). Although the difference was not significant (P = 0.154), the rate of postoperative complications tended to be lower in the laparoscopic group (2.3%) compared with the open group (9.1%). The increase in postoperative SII, NLR, and LMR for laparoscopic hepatectomy were significantly lower than for open hepatectomy. NLR < 5.8 on postoperative day 3 was significantly correlated with shorter hospital stay (P < 0.001). Conclusions: Compared with open hepatectomy, laparoscopic hepatectomy for selected HCC patients, even in the presence of cirrhosis, might result in better perioperative outcomes and postoperative inflammatory response attenuation, and ultimately promote faster recovery. This provides evidence for considering routine laparoscopic hepatectomy through careful selection of patients with HCC. [ABSTRACT FROM AUTHOR]