Enlightening the atomistic mechanisms driving self-diffusion of amorphous Si during annealing

We have analyzed the atomic rearrangements underlying self-diffusion in amorphous Si during annealing using tight-binding molecular dynamics simulations. Two types of amorphous samples with different structural features were used to analyze the influence of coordination defects. We have identified several types of atomic rearrangement mechanisms, and we have obtained an effective migration energy of around 1 eV. We found similar migration energies for both types of samples, but higher diffusivities in the one with a higher initial percentage of coordination defects.Comment: 9 pages, 4 figure

Pathological mandibular fracture after simple molar extraction in a patient with osteogenesis imperfecta treated with alendronate

Osteogenesis imperfecta (OI), is a heterogeneous group of inherited disorders of connective tissue characterized by bone fragility. Patients with this disease frequently suffer fractures, over 80% of the extremities due to the more intensive mechanical load. Fractures of the facial bones occur very infrequently. Several studies have proved that bisphosphonate therapy may be effective in reducing fracture risk in OI patients. We report here an unusual case of pathological mandibular fracture following simple molar extraction in an adult patient with OI type I and oral alendronic acid treatment. Extraction was atraumatical and without bone removal . Fracture was treated by internal fixation by plate osteosynthesis and additional mandibulomaxillary fixation (MMF). Bone healing after fracture treatment was completely normal and no clinical signs of osteoneocrosis were observed. To the best of our knowledge, this is an unusual complication even in this type of patients. Particular care is necessary is these patients during oral surgery, even when they have been treated and controlled

Molecular dynamics simulation of the regrowth of nanometric multigate Si devices

We use molecular dynamics (MD) simulation techniques to study the regrowth of nanometric multigate Si devices, such as fins and nanowires, surrounded by free surfaces and interfaces with amorphous material. Our results indicate that atoms in amorphous regions close to lateral free surfaces or interfaces rearrange at a slower rate compared to those in bulk due to the discontinuity of the lateral crystalline template. Consequently, the recrystallization front which advances faster in the device center than at the interfaces adopts new orientations. Regrowth then proceeds depending on the particular orientation of the new amorphous/crystal interfaces. In the particular case of (110) oriented fins, the new amorphous/crystal interfaces are aligned along the (111) direction, which produces frequent twining during further regrowth. Based on our simulation results, we propose alternatives to overcome this defected recrystallization in multigate structures: device orientation along (100) to prevent the formation of limiting {111} I amorphous/crystal interfaces and presence of a crystalline seed along the device body to favor regrowth perpendicular to the lateral surfaces/interfaces rather than parallel to them. (C) 2012 American Institute of Physics. [doi :10.1063/1.3679126

The use of pedicled buccal fat pad combined with sequestrectomy in bisphosphonate-related osteonecrosis of the maxilla

The use of pedicled buccal fat pad flap (BFP) has proved of value for the closure of oroantral and oronasal communications and is a well-established tool in oral and maxillofacial surgery. Otherwise, the perceived limitations of surgical therapy for bisphosphonate-related osteonecrosis of the jaws (BRONJ) have been widely discussed, and recommendations have largely been made to offer aggressive surgery only to stage 3 patients refractary to conservative management. Oroantral communication may be a common complication after sequestrectomy and bone debridement in upper maxillary BRONJ. We report a case series of stage 3 recalcitrant maxillary BRONJ surgically treated with extensive sequestrectomy and first reconstruction using pedicled BFP. All the cases presented an uneventful postoperative healing was uneventful without dehiscence, infection, necrosis or oroantral communication. We postulate that managing initially the site with BFP and primary closure may ensure a sufficient blood supply and adequate protection for an effective bone-healing response to occur. This technique may represent a mechanic protection and an abundant source of adipose-derived adult stem cells after debridement in upper maxillary BRONJ. We evaluate in this work results, advantages and indications of this technique. © Medicina Oral S. L

Self-trapping in B-doped amorphous Si: Intrinsic origin of low acceptor efficiency

We have used ab initio simulations to study the doping efficiency of amorphous semiconductors, in particular of B-doped amorphous Si. We have found that even in the optimum case of substitutional doping in dangling-bond free amorphous Si the holes provided by B atoms do not behave as free carriers. Instead, they are trapped into regions with locally distorted bond angles. Thus, the effective activation energy for hole conduction turns to be the hole binding energy to these traps. In the case of high B concentration, the trap states move deeper in the gap and the binding energy and spatial localization of holes increase. In addition, B atoms have lower energies for shorter bond lengths, configurations favored in the vicinity of these traps

The curious case of thin-body Ge crystallization

The authors investigate the templated crystallization of thin-body Ge fin structures with high aspect ratios. Experimental variables include fin thickness and thermal treatments, with fin structures oriented in the direction. Transmission electron microscopy determined that various crystal defects form during crystallization of amorphous Ge regions, most notably (111) stacking faults, twin boundaries, and small crystallites. In all cases, the nature of the defects is dependent on the fin thickness and thermal treatments applied. Using a standard 600 degrees C rapid-thermal-anneal, Ge structures with high aspect ratios crystallize with better crystal quality and fewer uncured defects than the equivalent Si case, which is a cause for optimism for thin-film Ge devices. (C) 2011 American Institute of Physics. (doi:10.1063/1.3643160

Alternative treatments for oral bisphosphonate-related osteonecrosis of the jaws: a pilot study comparing fibrin rich in growth factors and teriparatide

Objectives: The aim of this study is to describe and compare the evolution of recurrent bisphosphonate-related osteonecrosis of the jaws (BRONJ) in patients treated with plasma rich in growth factors or teriparatide. Material and Methods: Two different types of treatments were applied in patients diagnosed of recurrent BRONJ in a referral hospital for 1.100.000 inhabitants. In the group A, plasma rich in growth factors was applied dur - ing the surgery. In the group B, the treatment consisted in the subcutaneous administration of teriparatide. All the cases of BRONJ should meet the following conditions: recurrent BRONJ, impossibility of surgery in stage 3 Ruggiero classification and absence of diagnosed neoplastic disease. Clinical and radiographic evolution of the patients from both groups was observed. Results: Nine patients were included, 5 in group A and 4 in group B. All the patients were women on oral bis- phosphonate therapy for primary osteoporosis (5 patients) or osteoporosis-related to the use of corticosteroids (4 patients). Alendronate was the most common oral bisphosphonate associated with BRONJ in our study (four patients in group A and two in group B). The mean age was 72,8 years in the group A and 73,5 years in the group B. All the patients from group A showed a complete resolution of their BRONJ. Only one patient in the group B showed the same evolution. Conclusions: In our series, the plasma rich in growth factors showed better results than the teriparatide in the treatment of recurrent BRONJ

Radiation-Induced Sarcomas of the Head and Neck : A Systematic Review

Introduction As a result of the increased use of radiotherapy (RT) and improved long-term overall survival of patients with cancers of the head and neck (HN), the frequency of radiation-induced sarcomas of the head and neck (RISHN) may be increasing. The main objective of this systematic review was to determine the existing evidence on the frequency, treatment, and outcome of RISHN. Methods Using PRISMA guidelines we conducted a systematic review of the literature published from 2000 to 2020. Results Our review includes data of 560 patients from 64 articles. The total frequency of RISHNs among the reviewed series was 0.15%. The most frequent location of the primary tumor treated by RT was the nasopharynx. The mean RT dose used was 62 Gy, mean latency interval between irradiation and occurrence of RISHN was 11.1 years, and the most common RISHN location was the sinonasal region. Osteosarcoma was the principal histology, followed by fibrosarcoma. Surgery was the most frequently applied treatment modality. Of all patients with RISHN, 40.7% died of this disease after a mean interval of 13.9 months. Conclusions Notwithstanding the increased use of RT, the number of reported RISHNs has not increased substantially during the past two decades. Surgery with wide margins forms the best therapeutic option for these cases, but the outcome remains poor.Peer reviewe

Trends in the Management of Non-Vestibular Skull Base and Intracranial Schwannomas

The aim of this review is to analyze the latest trends in the management of nonvestibular skull base and intracranial schwannomas in order to optimize tumor control and quality of life. Non-vestibular cranial nerve schwannomas are rare lesions, representing 5-10% of cranial nerve schwannomas. Management decisions should be individualized depending on tumor size, location and associated functional deficits. Generally, large sized schwannomas exerting significant mass effect with increased intracranial pressure are treated surgically. In some cases, even after optimal skull base resection, it is not possible to achieve a gross total resection because tumor location and extent and/or to reduce morbidity. Thus, subtotal resection followed by stereotactic radiosurgery or fractioned radiotherapy offers an alternative approach. In certain cases, stereotactic radiosurgery or radiotherapy alone achieves good tumor control rates and less morbidity to gross total resection. Finally, given the slow growth rate of most of these tumors, observation with periodic radiographic follow-up approach is also a reasonable alternative for small tumors with few, if any, symptoms.Peer reviewe

Quantitative uptake of colloidal particles by cell cultures

The use of nanotechnologies involving nano- and microparticles has increased tremendously in the recent past. There are various beneficial characteristics that make particles attractive for a wide range of technologies. However, colloidal particles on the other hand can potentially be harmful for humans and environment. Today, complete understanding of the interaction of colloidal particles with biological systems still remains a challenge. Indeed, their uptake, effects, and final cell cycle including their life span fate and degradation in biological systems are not fully understood. This is mainly due to the complexity of multiple parameters which need to be taken in consideration to perform the nanosafety research. Therefore, we will provide an overview of the common denominators and ideas to achieve universal metrics to assess their safety. The review discusses aspects including how biological media could change the physicochemical properties of colloids, how colloids are endocytosed by cells, how to distinguish between internalized versus membrane-attached colloids, possible correlation of cellular uptake of colloids with their physicochemical properties, and how the colloidal stability of colloids may vary upon cell internalization. In conclusion three main statements are given. First, in typically exposure scenarios only part of the colloids associated with cells are internalized while a significant part remain outside cells attached to their membrane. For quantitative uptake studies false positive counts in the form of only adherent but not internalized colloids have to be avoided. pH sensitive fluorophores attached to the colloids, which can discriminate between acidic endosomal/lysosomal and neutral extracellular environment around colloids offer a possible solution. Second, the metrics selected for uptake studies is of utmost importance. Counting the internalized colloids by number or by volume may lead to significantly different results. Third, colloids may change their physicochemical properties along their life cycle, and appropriate characterization is required during the different stages.This work was supported by the European Commission (grant FutureNanoNeeds) grant agreement no. 604602 to WJP. NF acknowledges funding from the Lars Hiertas Minne Fundation (Sweden), SA, BP and IC acknowledge a fellowship from the Alexander von Humboldt Fundation (Germany). AE acknowledges Junta de Andalucía (Spain) for a Talentia Postdoc Fellowship, co-financed by the European Union Seventh Framework Programme, grant agreement no 267226. AHS acknowledges the Egyptian government (Ministry of Higher Education, Mission). The project was also supported by the Dr. Dorka-Stiftung (Germany) to PJ