Exact-exchange based quasiparticle energy calculations for the band gap, effective masses and deformation potentials of ScN

The band gaps, longitudinal and transverse effective masses, and deformation potentials of ScN in the rock-salt structure have been calculated employing G0W0-quasiparticle calculations using exact-exchange Kohn-Sham density functional theory one-particle wavefunctions and energies as input. Our quasiparticle gaps support recent experimental observations that ScN has a much lower indirect band gap than previously thought. The results are analyzed in terms of the influence of different approximations for exchange and correlation taken in the computational approach on the electronic structure of ScN.Comment: Comments: 9 pages including 5 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Theory of Doping and Defects in III-V Nitrides

Doping problems in GaN and in AlGaN alloys are addressed on the basis of state-of-the-art first-principles calculations. For n-type doping we find that nitrogen vacancies are too high in energy to be incorporated during growth, but silicon and oxygen readily form donors. The properties of oxygen, including DX-center formation, support it as the main cause of unintentional n-type conductivity. For p-type doping we find that the solubility of Mg is the main factor limiting the hole concentration in GaN. We discuss the beneficial effects of hydrogen during acceptor doping. Compensation of acceptors by nitrogen vacancies may occur, becoming increasingly severe as x increases in Al_x Ga_(1-x)N alloys.Comment: 7 pages, 2 figures. Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

Ab initio Description of Bond-Breaking in Large Electric Fields

Strong ($10^{10}$ V/m) electric fields capable of inducing atomic bond-breaking represent a powerful tool for surface chemistry. However, their exact effects are difficult to predict due to a lack of suitable tools to probe their associated atomic-scale mechanisms. Here we introduce a generalized dipole correction for charged repeated-slab models that controls the electric field on both sides of the slab, thereby enabling direct theoretical treatment of field-induced bond-breaking events. As a prototype application, we consider field evaporation from a kinked W surface. We reveal two qualitatively different desorption mechanisms that can be selected by the magnitude of the applied field

Growth process, characterization, and modeling of electronic properties of coupled InAsSbP nanostructures

Quaternary III-V InAsSbP quantum dots (QDs) have been grown in the form of cooperative InAsSb/InAsP structures using a modified version of the liquid phase epitaxy. High resolution scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectrometry were used to investigate these so-called nano-camomiles, mainly consisting of a central InAsSb QD surrounded by six InAsP-QDs, that shall be referred to as leaves in the following. The observed QDs average density ranges from 0.8 to 2 x 10(9) cm(-2), with heights and widths dimensions from 2 to 20 nm and 5 to 45 nm, respectively. The average density of the leaves is equal to (6-10) x 10(9) cm(-2) with dimensions of approx. 5 to 40 nm in width and depth. To achieve a first basic understanding of the electronic properties, we have modeled these novel nanostructures using second-order continuum elasticity theory and an eight-band k . p model to calculate the electronic structure. Our calculations found a clear localization of hole states in the central InAsSb dot. The localization of electron states, however, was found to be weak and might thus be easily influenced by external electric fields or strain. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3624621

Klinische, kontrollierte, prospektive Kohortenstudie zur Untersuchung der Effektivität einer azellulären dreidimensionalen Kollagenmatrix zur Verdickung der fazialen Mukosa nach Sofortimplantation

Connective tissue grafts have become a standard for compensating horizontal volume loss in immediate implant placement. The use of new biomaterials like acellular matrices may avoid the need to harvest autogenous grafts, yielding less postoperative morbidity. This randomized comparative study evaluated the clinical outcomes following extraction and immediate implant placement in conjunction with anorganic bovine bone mineral (ABBM) and the use of a porcine acellular dermal matrix (ADM) vs an autogenous connective tissue graft (CTG) in the anterior maxilla. Twenty patients (11 men, 9 women) with a mean age of 48.9 years (range: 21 to 72 years) were included in the study and randomly assigned to either the test (ADM) or control (CTG) group. They underwent tooth extraction and immediate implant placement together with ABBM for socket grafting and either ADM or CTG for soft tissue augmentation. Twelve months after implant placement, the cases were evaluated clinically and volumetrically. All implants achieved osseointegration and were restored. The average horizontal change of the ridge dimension at 1 year postsurgery was –0.55 ± 0.32 mm for the ADM group and –0.60 ± 0.49 mm for the CTG group. Patients of the ADM group reported significantly less postoperative pain. Using xenografts for hard and soft tissue augmentation in conjunction with immediate implant placement showed no difference in the volume change in comparison to an autogenous soft tissue graft, and showed significantly less postoperative morbidity. Int J Periodontics Restorative Dent 2022;42:381–390. doi: 10.11607/prd.563

Experimental demonstration of linear and spinning Janus dipoles for polarisation and wavelength selective near-field coupling

The electromagnetic field scattered by nano-objects contains a broad range of wave vectors and can be efficiently coupled to waveguided modes. The dominant contribution to scattering from subwavelength dielectric and plasmonic nanoparticles is determined by electric and magnetic dipolar responses. Here, we experimentally demonstrate spectral and phase selective excitation of Janus dipoles, sources with electric and magnetic dipoles oscillating out of phase, in order to control near-field interference and directional coupling to waveguides. We show that by controlling the polarisation state of the dipolar excitations and the excitation wavelength to adjust their relative contributions, directionality and coupling strength can be fully tuned. Furthermore, we introduce a novel spinning Janus dipole featuring cylindrical symmetry in the near and far field, which results in either omnidirectional coupling or noncoupling. Controlling the propagation of guided light waves via fast and robust near-field interference between polarisation components of a source is required in many applications in nanophotonics and quantum optics

Peri-implant soft-tissue esthetic outcome after immediate implant placement in conjunction with xenogeneic acellular dermal matrix or connective tissue graft: A randomized controlled clinical study

Objectives This randomized comparative study evaluated the clinical esthetic outcome of the peri-implant mucosa following extraction and immediate implant placement in conjunction with anorganic bovine bone mineral (ABBM) and the use of a porcine acellular dermal matrix (pADM) versus an autogenous connective tissue graft (CTG) in the anterior maxilla. Materials and methods Twenty patients (11 men, 9 women) with a mean age of 48,9 years (range 21-72) were included in the study and randomly assigned to either the test (pADM) or control group (CTG). They underwent extraction and immediate implant placement together with ABBM for socket grafting and either pADM or CTG for soft tissue augmentation. Twelve months after implant placement color measurements of the peri-implant mucosa and a reference tooth were performed using a spectophotometer and the color difference (Delta E) was calculated. The overall esthetic appearance of the peri-implant soft tissue was evaluated using the Pink Esthetic Score (PES). Statistical analysis was performed using Student's T-Test, the alpha was set to 0.05. Results All implants received osseointegration and were restored. The mean color difference of the peri-implant mucosa 1 year after surgery amounted Delta E 4.06 +/- 1.6 for the test group (pADM) and Delta E 3.58 +/- 1.36 mm for the control group (CTG), showing no statistically significant difference (p = 0.47). The mean PES of the pADM group was 11.4 +/- 1.4 and for the CTG group 10.7 +/- 1.5, showing no statistically significant difference (p = 0.29). Conclusion Twelve months after surgery, a porcine acellular dermal matrix for soft tissue augmentation in conjunction with immediate implant placement showed no difference in the overall esthetic appearance regarding color match and Pink Esthetic Score in comparison to autogenous soft tissue graft. Clinical Significance Connective tissue grafts have become a standard in order to enhance the soft tissue quality and esthetic appearance in immediate implant placement. The use of new biomaterials like porcine acellular dermal matrices may avoid the need to harvest autogenous grafts resulting in simplified treatment and less postoperative morbidity

Technical aspects and indications for distration osteogenesis

With the introduction of distraction osteogenesis in oral and maxillofacial surgery in the mid 1990s, especially for the treatment of congenital malformations, there was initially a rapid development in the vertical alveolar distraction procedures based on the TRACK (Tissue Regeneration by Alveolar Callus distraction) distractors, which were seen as a preimplantologic grafting procedure. Because the treatment requires high surgical skill and intensive patient care in the postoperative follow-up, the procedure is now used selectively for particular indications. With precise indications, especially in the case of multiple previous surgeries, this method is superior to the other augmentation techniques in terms of complications and the possible vertical defect height reconstruction