Structure Discovery in Atomic Force Microscopy Imaging of Ice.

The interaction of water with surfaces is crucially important in a wide range of natural and technological settings. In particular, at low temperatures, unveiling the atomistic structure of adsorbed water clusters would provide valuable data for understanding the ice nucleation process. Using high-resolution atomic force microscopy (AFM) and scanning tunneling microscopy, several studies have demonstrated the presence of water pentamers, hexamers, and heptamers (and of their combinations) on a variety of metallic surfaces, as well as the initial stages of 2D ice growth on an insulating surface. However, in all of these cases, the observed structures were completely flat, providing a relatively straightforward path to interpretation. Here, we present high-resolution AFM measurements of several water clusters on Au(111) and Cu(111), whose understanding presents significant challenges due to both their highly 3D configuration and their large size. For each of them, we use a combination of machine learning, atomistic modeling with neural network potentials, and statistical sampling to propose an underlying atomic structure, finally comparing its AFM simulated images to the experimental ones. These results provide insights into the early phases of ice formation, which is a ubiquitous phenomenon ranging from biology to astrophysics.

Association of blood pressure and outcomes differs upon cerebral perfusion post-thrombectomy in patients with acute ischemic stroke.

BACKGROUND: The relationship between post-endovascular thrombectomy (EVT) blood pressure (BP) and outcomes in patients with acute ischemic stroke (AIS) remains contentious. We aimed to explore whether this association differs with different cerebral perfusion statuses post-EVT. METHODS: In a multicenter observational study of patients with AIS with large vessel occlusion who underwent EVT, we enrolled those who accepted CT perfusion (CTP) imaging within 24 hours post-EVT. We recorded post-EVT systolic (SBP) and diastolic BP. Patients were stratified into favorable perfusion and unfavorable perfusion groups based on the hypoperfusion intensity ratio (HIR) on CTP. The primary outcome was good functional outcome (90-day modified Rankin Scale score of ≤3). Secondary outcomes included early neurological deterioration, infarct size growth, and symptomatic intracranial hemorrhage. RESULTS: Of the 415 patients studied (mean age 62 years, 75% male), 233 (56%) achieved good functional outcomes. Logistic regression showed that post-EVT HIR and 24-hour mean SBP were significantly associated with functional outcomes. Among the 326 (79%) patients with favorable perfusion, SBP <140 mmHg was associated with a higher percentage of good functional outcomes compared with SBP ≥140 mmHg (68% vs 52%; aOR 1.70 (95% CI 1.00 to 2.89), P=0.04). However, no significant difference was observed between SBP and functional outcomes in the unfavorable perfusion group. There was also no discernible difference between SBP and secondary outcomes across the different perfusion groups. CONCLUSIONS: In patients with favorable perfusion post-EVT, SBP <140 mmHg was associated with good functional outcomes, which underscores the need for further investigations with larger sample sizes or a more individualized BP management strategy. CLINICAL TRIAL REGISTRATION: ChiCTR1900022154.