Interface-dependent phononic and optical properties of GeO/MoSO heterostructures.

The interface-dependent electronic, vibrational, piezoelectric, and optical properties of van der Waals heterobilayers, formed by buckled GeO (b-GeO) and Janus MoSO structures, are investigated by means of first-principles calculations. The electronic band dispersions show that O/Ge and S/O interface formations result in a type-II band alignment with direct and indirect band gaps, respectively. In contrast, O/O and S/Ge interfaces give rise to the formation of a type-I band alignment with an indirect band gap. By considering the Bethe-Salpeter equation (BSE) on top of G0W0 approximation, it is shown that different interfaces can be distinguished from each other by means of the optical absorption spectra as a consequence of the band alignments. Additionally, the low- and high-frequency regimes of the Raman spectra are also different for each interface type. The alignment of the individual dipoles, which is interface-dependent, either weakens or strengthens the net dipole of the heterobilayers and results in tunable piezoelectric coefficients. The results indicate that the possible heterobilayers of b-GeO/MoSO asymmetric structures possess various electronic, optical, and piezoelectric properties arising from the different interface formations and can be distinguished by means of various spectroscopic techniques.

Vibrational and optical identification of GeO2 and GeO single layers: a first-principles study.

In the present work, the identification of two hexagonal phases of germanium oxides (namely GeO2 and GeO) through the vibrational and optical properties is reported using density functional theory calculations. While structural optimizations show that single-layer GeO2 and GeO crystallize in 1T and buckled phases, phonon band dispersions reveal the dynamical stability of each structure. First-order off-resonant Raman spectral predictions demonstrate that each free-standing single-layer possesses characteristic peaks that are representative for the identification of the germanium oxide phase. On the other hand, electronic band dispersion analysis shows the insulating and large-gap semiconducting nature of single-layer GeO2 and GeO, respectively. Moreover, optical absorption, reflectance, and transmittance spectra obtained by means of G0W0-BSE calculations reveal the existence of tightly bound excitons in each phase, displaying strong optical absorption. Furthermore, the excitonic gaps are found to be at deep UV and visible portions of the spectrum, for GeO2 and GeO crystals, with energies of 6.24 and 3.10 eV, respectively. In addition, at the prominent excitonic resonances, single-layers display high reflectivity with a zero transmittance, which is another indication of the strong light-matter interaction inside the crystal medium.

Arthroscopic diagnosis and treatment of an acetabular labrum bucket handle tear: a case report.

The acetabular labrum is a fibrocartilaginous structure attached to the acetabular rim. It increases the surface area of acetabulum and stabilizes joint. Acetabular labral tears are an important cause of intractable hip pain in adults. We report a cause of an acetabular bucket handle tear of the right hip, caused by femoroacetabular impingement that was diagnosed and treated successfully with hip arthroscopy.

A 2-staged method for treatment of deep osteochondral lesions of the knee joint.

We performed a 2-staged arthroscopic-assisted surgical procedure to treat a patient with a large osteochondral lesion of the knee joint. The osteochondral lesion was too comminuted to reattach; in addition, the underlying bony defect was too deep. In the first stage, autogenous cortical bone was used for grafting the bony defect along with screw fixation. The second stage consisted of screw removal and transplantation of autogenous osteochondral graft overlying the chondral defect. The osteochondral grafts were taken from the non-weight bearing areas of the same knee.