Nanoscale lattice dynamics in hexagonal boron nitride moiré superlattices

Twisted two-dimensional van der Waals (vdW) heterostructures have unlocked a new means for manipulating the properties of quantum materials. The resulting mesoscopic moiré superlattices are accessible to a wide variety of scanning probes. To date, spatially-resolved techniques have prioritized electronic structure visualization, with lattice response experiments only in their infancy. Here, we therefore investigate lattice dynamics in twisted layers of hexagonal boron nitride (hBN), formed by a minute twist angle between two hBN monolayers assembled on a graphite substrate. Nano-infrared (nano-IR) spectroscopy reveals systematic variations of the in-plane optical phonon frequencies amongst the triangular domains and domain walls in the hBN moiré superlattices. Our first-principles calculations unveil a local and stacking-dependent interaction with the underlying graphite, prompting symmetry-breaking between the otherwise identical neighboring moiré domains of twisted hBN.

Here, the authors investigate the lattice dynamics of twisted hexagonal boron nitride layers via nano-infrared spectroscopy, showing local and stacking-dependent variations of the optical phonon frequencies associated to the interaction with the graphite substrate.

Intrathoracic biopsies, pulmonary wedge excision, and management of pleural disease: is video-assisted closed chest surgery the approach of choice?

Few studies define differences between video-assisted thoracic surgery (VATS) over conventional posterolateral thoracotomy (PLT) for limited procedures. We propose that length of hospital stay (LOS), the days of requirement for narcotic analgesia (DNA) by epidural, intravenous, intramuscular, or oral administration, operating time (OT), return to pre-operative functional status (RT), and the achievement of a therapeutic objective are not dependent on the approach taken (VATS or PLT) for selected diagnostic and therapeutic procedures for pleural, pulmonary, or mediastinal disease. A total of 102 consecutive patients (52 males, 50 females, age 48 +/- 16 years) were eligible to undergo (VATS) for diagnosis and/or treatment of lung lesions, pleural disease, persistent pneumothorax or mediastinal lesions. Seventy-two underwent VATS only and 21, conventional posterolateral thoracotomy (PLT). Nine VATS patients were converted to PLT, for completion of lobectomies after VATS staging of resectable malignancy (6), extensive decortication (2), and giant bullectomy (1). VATS and PLT were compared according to OT, LOS, DNA, RT, achievement of diagnostic and/or therapeutic objective, and morbidity and mortality. After VATS only and PLT only, LOS was 4.8 +/- 2.7 and 7.8 +/- 4.6 days, respectively (P < .03). DNA was 3.4 +/- 2.1 and 6.1 +/- 3.6 days after surgery, respectively (P < .01). RT was 12.0 +/- 11.2 and 21.4 +/- 9.5 days, respectively (P < .01). OT was 80 +/- 34 and 95 +/- 32 minutes, respectively (P = ns). Among 9 conversions from VATS to PLT LOS was 11.4 +/- 5.5, DNA 6.9 +/- 4.4 and RT 20.1 +/- 6.0 days.(ABSTRACT TRUNCATED AT 250 WORDS)