Background-Aortic root rupture is a major concern with balloon-expandable transcatheter aortic valve replacement (TAVR). We sought to identify predictors of aortic root rupture during balloon-expandable TAVR by using multidetector computed tomography. Methods and Results-Thirty-one consecutive patients who experienced left ventricular outflow tract (LVOT)/annular/ aortic contained/noncontained rupture during TAVR were collected from 16 centers. A caliper-matched sample of 31 consecutive patients without annular rupture, who underwent pre-TAVR multidetector computed tomography served as a control group. Multidetector computed tomography assessment included short-and long-axis diameters and crosssectional area of the sinotubular junction, annulus, and LVOT, and the presence, location, and extent of calcification of the LVOT, as well. There were no significant differences between the 2 groups in any preoperative clinical and echocardiographic variables. Aortic root rupture was identified in 20 patients and periaortic hematoma in 11. Patients with root rupture had a higher degree of subannular/LVOT calcification quantified by the Agatston score (

A fundamental requirement for the development of advanced electronic device architectures based on graphene nanoribbon (GNR) technology is the ability to modulate the band structure and charge carrier concentration by substituting specific carbon atoms in the hexagonal graphene lattice with p- or n-type dopant heteroatoms. Here we report the atomically precise introduction of group III dopant atoms into bottom-up fabricated semiconducting armchair GNRs (AGNRs). Trigonal-planar B atoms along the backbone of the GNR share an empty p-orbital with the extended π-band for dopant functionality. Scanning tunneling microscopy (STM) topography reveals a characteristic modulation of the local density of states along the backbone of the GNR that is superimposable with the expected position and concentration of dopant B atoms. First-principles calculations support the experimental findings and provide additional insight into the band structure of B-doped 7-AGNRs.

The implementation of an MDCT annulus area sizing algorithm for TAVR reduces PAR. Three-dimensional aortic annular assessment and annular area sizing should be considered for TAVR.

TitleAtomically precise graphene nanoribbon heterojunctions from a single molecular precursor AbstractThe rational bottom-up synthesis of atomically defined graphene nanoribbon (GNR)heterojunctions represents a key enabling technology for the design of nanoscale electronic devices. Synthetic strategies have thus far relied on the random copolymerization of two electronically distinctive molecular precursors to yield a segmented band structure within a GNR. Here we report the fabrication and electronic characterization of atomically precise GNR heterojunctions prepared through a late-stage functionalization of chevron GNRs obtained from a single precursor that features fluorenone substituents along the convex edges. Excitation of the GNR induces cleavage of sacrificial carbonyl groups at the GNR edge, thus giving rise to atomically well-defined heterojunctions comprised of segments of fluorenone GNR and unfunctionalized chevron GNR. The structure of fluorenone/unfunctionalized GNR heterojunctions was characterized using bond-resolved STM (BRSTM) which enables chemical bonds to be imaged via STM at T = 4.5 K. Scanning tunneling spectroscopy (STS) reveals that the band alignment across the interface yields a staggered gap Type II heterojunction and is consistent with first-principles calculations. Detailed spectroscopic and theoretical studies reveal that the band realignment at the interface between fluorenone and unfunctionalized chevron GNRs proceeds over a distance less than 1nm, leading to extremely large effective fields.

In clinically indicated chest CT examinations, ASIR images had better image quality and less image noise at a lower radiation dose than images acquired with a conventional FBP reconstruction algorithm.

NATMs). [1,3,[7][8][9][10][11][12][13][14][15][16][17][18] Such NATMs with extremely high permeance and selectivity [3,4,7,8,[12][13][14][15][16][17][18][19][20] are expected to offer significant advances over current state-of-the-art polymer membranes, specifically for diffusion-based separation processes such as dialysis. [9] However, i) large-area membrane quality graphene synthesis [1,21,22] and transfer to suitable porous supports (without polymer residue or other contamination from transfer), [1,9,21,[23][24][25][26] ii) mitigation of nonselective leakage by plugging tears/ damages to graphene from transfer and subsequent processing during membrane fabrication, [1,9,13,26] and most importantly iii) the formation of nanopores with a high density and narrow size distribution using cost-effective, scalable processes [1,9,13,27,28] are some of the major challenges that need to be collectively addressed to realize NATMs for practical applications. [22,29] Here, we note that large-area monolayer graphene synthesis has been demonstrated via roll-to-roll chemical vapor deposition (CVD) processes. [22,30] Further, graphene transfer at large scale has also been shown [30,31] (although complete elimination of polymer residue remains nontrivial) [17,32,33] and widely used scalable membrane manufacturing techniques such as interfacial polymerization have been adapted to effectively plug leakage across tears/damage in graphene. [13] However, facile, cost-effective processes to form nanoscale defects in Direct synthesis of graphene with well-defined nanoscale pores over large areas can transform the fabrication of nanoporous atomically thin membranes (NATMs) and greatly enhance their potential for practical applications. However, scalable bottom-up synthesis of continuous sheets of nanoporous graphene that maintain integrity over large areas has not been demonstrated. Here, it is shown that a simple reduction in temperature during chemical vapor deposition (CVD) on Cu induces in-situ formation of nanoscale defects (≤2-3 nm) in the graphene lattice, enabling direct and scalable synthesis of nanoporous monolayer graphene. By solution-casting of hierarchically porous polyether sulfone supports on the as-grown nanoporous CVD graphene, large-area (>5 cm2 ) NATMs for dialysis applications are demonstrated. The synthesized NATMs show size-selective diffusive transport and effective separation of small molecules and salts from a model protein, with ≈2-100× increase in permeance along with selectivity better than or comparable to state-of-the-art commercially available polymeric dialysis membranes. The membranes constitute the largest fully functional NATMs fabricated via bottom-up nanopore formation, and can be easily scaled up to larger sizes permitted by CVD synthesis. The results highlight synergistic benefits in blending traditional membrane casting with bottom-up pore creation during graphene CVD for advancing NATMs toward practical applications.

Substitutional doping of graphene nanoribbons (GNRs) with heteroatoms is a principal strategy to fine-tune the electronic structure of GNRs for future device applications.Here we report the fabrication and nanoscale characterization of atomically-precise N=13 armchair graphene nanoribbons featuring regioregular edge-doping with sulfur atoms (S-13-AGNRs) on a Au(111) surface. Scanning tunneling spectroscopy and first principle calculations reveal modification of the electronic structure of S-13-AGNRs when compared to undoped N=13 AGNRs.

Two-dimensional materials such as layered transition-metal dichalcogenides (TMDs) are ideal platforms for studying defect behaviors, an essential step towards defect engineering for novel material functions. Here, we image the 3D lattice locations of selenium-vacancy V_{Se} defects and manipulate them using a scanning tunneling microscope (STM) near the surface of PdSe_{2}, a recently discovered pentagonal layered TMD. The V_{Se} show a characterisitc charging ring in a spatially resolved conductance map, based on which we can determine its subsurface lattice location precisely. Using the STM tip, not only can we reversibly switch the defect states between charge neutral and charge negative, but also trigger migrations of V_{Se} defects. This allows a demonstration of direct "writing" and "erasing" of atomic defects and tracing the diffusion pathways. First-principles calculations reveal a small diffusion barrier of V_{Se} in PdSe_{2}, which is much lower than S vacancy in MoS_{2} or an O vacancy in TiO_{2}. This finding opens an opportunity of defect engineering in PdSe_{2} for such as controlled phase transformations and resistive-switching memory device application.