Full Crystallographic Imaging of Hexagonal Boron Nitride Monolayers with Phonon-Enhanced Sum-Frequency Microscopy

Hexagonal boron nitride (hBN) is an important 2D material for van der Waals heterostructures, single photon emitters, and infrared nanophotonics. The optical characterization of mono- and few-layer samples of hBN however remains a challenge as the material is almost invisible optically. Here we introduce phase-resolved sum-frequency microscopy as a technique for imaging monolayers of hBN grown by chemical vapor deposition (CVD) and visualize their crystal orientation. A combination of femtosecond mid-infrared (IR) and visible laser pulses is used for sum-frequency generation (SFG), which is imaged in a wide-field optical microscope. The IR laser resonantly excites a phonon of hBN that leads to an ~800-fold enhancement of the SFG intensity, making it possible to image large 100x100 µm2 sample areas in less than 1 s. Implementing heterodyne detection in combination with azimuthal rotation of the sample further provides full crystallographic information. Through combined knowledge of topography and crystal orientation, we find that triangular domains of CVD-grown monolayer hBN have nitrogen-terminated zigzag edges. Overall, SFG microscopy can be used as an ultra-sensitive tool to image crystal structure, strain, stacking sequences, and twist angles, and is applicable to the wide range of van der Waals structures, where location and identification of monolayer regions and interfaces with broken inversion symmetry is of paramount importance

Clinical outcomes of pediatric kidney replacement therapy after childhood cancer—An ESPN/ERA Registry study

Cancer and its treatment may lead to kidney injury and the need for kidney replacement therapy (KRT). We identified 287 pediatric KRT patients with a history of malignancy from the European Society for Paediatric Nephrology/European Renal Association Registry. Of these, 197 had cancer as a primary cause of KRT (group 1) and 90 had a malignancy diagnosis before KRT (group 2). Two matched controls without malignancy were randomly selected for each patient. Data were complemented with a questionnaire. Median time to kidney transplantation (KT) from KRT initiation was 2.4 (IQR: 1.5-4.7), 1.5 (IQR: 0.4-3.3), 3.6 (IQR: 1.3 to Q3 not reached), and 1.1 (IQR: 0.3-3.6) years for group 1, their controls, group 2, and their controls, respectively. Overall 10-year mortality for those on KRT was higher among cancer patients vs controls in group 1: 16% vs 9% (adjusted hazard ratio 2.02, 95% CI: 1.21-3.37) and in group 2: 23% vs 14% (adjusted hazard ratio 2.32, 95% CI: 1.11-4.85). In contrast, 10-year patient survival after the first KT was comparable to controls (93% vs 96%; 100% vs 94%, in groups 1 and 2, respectively). In summary, childhood cancer survivors’ KT was delayed, and their overall mortality when on KRT was increased, but once transplanted, their long-term outcome was similar to other KT recipients

Reproducibility of electromagnetic field simulations of local radiofrequency transmit elements tailored for 7 T MRI

The literature reports on radiofrequency (RF) transmit (Tx) elements tailored for ultrahigh-field (UHF) magnetic resonance imaging (MRI) showed confounded reproducibility due to variations in simulation tools, modeling assumptions, and meshing techniques. This study proposes a standardized methodology to improve reproducibility and consistency across research sites (testers) and simulation tools (testing conditions). The methodology includes detailed simulation workflow and performance metrics for RF Tx elements. The impact of the used mesh setting is assessed. Following the methodology, a reproducibility study was conducted using CST Microwave Studio Suite, HFSS, and Sim4Life. The methodology and simulations were ultimately validated through 7 T MRI phantom experiments. The reproducibility study showed consistent performance with less than 6% standard deviation for B(1)(+) fields and 12% for peak SAR averaged over 10 g tissue (pSAR10g). The SAR efficiency metric (|B(1)(+)|/√pSAR(10g)) was particularly robust (<5%). The simulated and experimental |B(1)(+)| maps showed good qualitative agreement. This study demonstrates the feasibility of a standardized methodology for achieving reproducible RF Tx element electromagnetic field simulations. By following the FAIR principles including making the framework publicly available, we promote transparency and collaboration within the MRI community, supporting the advancement of technological innovation and improving patient safety in UHF-MRI

Current views on the role of Notch signaling and the pathogenesis of human leukemia

The Notch signaling pathway is highly conserved from Drosophila to humans and plays an important role in the regulation of cellular proliferation, differentiation and apoptosis

Hydrodynamic Self-Righting in Manicina Areolata, A Strategy with Palaeoecolgical Significance

The scleractinian Manicina areolata is a common coral on Caribbean hard and soft substrata and was studied at Lee Stocking Island (Exuma Cays, Bahamas). It is not only found on reefs but also on bioclastic sand with seagrasses. Investigated corolla ranged in size from 2 to 10 cm, growth form varied from conical with round to oval cross-section to turbinate forms with few meanders and flat oval cross-section. The conical morphotype was usually attached to hard substratum, while the turbinate morphotype was usually unattached and upright, in soft substratum. In infratidal areas, both attached and unattached turbinate forms were found in close vicinity, however, conical attached forms were rare. Habitats with sandy softgrounds, where free-living turbinate morphotypes were common, were influenced by strong tidal currents with concurrent danger of burial or “disorientation” of the corolla. Investigations in the flume channel showed that the colony shape itself led to passive cleaning and self-righting, which was achieved by the flat-turbinate morphology, with a concave side and a flat to slightly convex opposite side, under high current speeds. The concave side, and particularly the median lobes formed by many meandroid coralla, were the critical morphological factors. Grooves formed in between the lobes channeled currents in a way that scour underneath the coral and drag produced by the lobes allowed passive self-righting. This could be used to explain ecological strategies in similar-shaped fossil solitary corals