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Fracture treatment in children needs new implant materials to overcome disadvantages associated with removal surgery. Magnesium-based implants constitute a biocompatible and ...bioresorbable alternative. In adults and especially in children, implant safety needs to be evaluated. In children the bone turnover rate is higher and implant material might influence growth capacity, and the long-term effect of accumulated particles or ions is more critical due to the host’s prolonged post-surgery lifespan. In this study we aimed to investigate the degradation behavior of ZX00 (Mg-0.45Zn-0.45Ca; in wt.%) in a small and a large animal model to find out whether there is a difference between the two models (i) in degradation rate and (ii) in bone formation and in-growth. Our results 6, 12 and 24 weeks after ZX00 implantation showed no negative effects on bone formation and in-growth, and no adverse effects such as fibrotic or sclerotic encapsulation. The degradation rate did not significantly differ between the two growing-animal models, and both showed slow and homogeneous degradation performance. Our conclusion is that small animal models may be sufficient to investigate degradation rates and provide preliminary evidence on bone formation and in-growth of implant materials in a growing-animal model.
The safety of implant material is of the utmost importance, especially in children, who have enhanced bone turnover, more growth capacity and longer postoperative lifespans. Magnesium (Mg)-based implants have long been of great interest in pediatric orthopedic and trauma surgery, due to their good biocompatibility, biodegradability and biomechanics. In the study documented in this manuscript we investigated Mg–Zn–Ca implant material without rare-earth elements, and compared its outcome in a small and a large growing-animal model. In both models we observed bone formation and in-growth which featured no adverse effects such as fibrotic or sclerotic encapsulation, and slow homogeneous degradation performance of the Mg-based implant material.
This study is a prospective, non-randomized trial for the treatment of fractures of the medial malleolus using lean, bioabsorbable, rare-earth element (REE)-free, magnesium (Mg)-based biodegradable ...screws in the adult skeleton.
A total of 20 patients with isolated, bimalleolar, or trimalleolar ankle fractures were recruited between July 2018 and October 2019. Fracture reduction was achieved through bioabsorbable Mg-based screws composed of pure Mg alloyed with zinc (Zn) and calcium (Ca) ( Mg-Zn0.45-Ca0.45, in wt.%; ZX00). Visual analogue scale (VAS) and the presence of complications (adverse events) during follow-up (12 weeks) were used to evaluate the clinical outcomes. The functional outcomes were analyzed through the range of motion (ROM) of the ankle joint and the American Orthopaedic Foot and Ankle Society (AOFAS) score. Fracture reduction and gas formation were assessed using several plane radiographs.
The follow-up was performed after at least 12 weeks. The mean difference in ROM of the talocrural joint between the treated and the non-treated sites decreased from 39° (SD 12°) after two weeks to 8° (SD 11°) after 12 weeks (p ≤ 0.05). After 12 weeks, the mean AOFAS score was 92.5 points (SD 4.1). Blood analysis revealed that Mg and Ca were within a physiologically normal range. All ankle fractures were reduced and stabilized sufficiently by two Mg screws. A complete consolidation of all fractures was achieved. No loosening or breakage of screws was observed.
This first prospective clinical investigation of fracture reduction and fixation using lean, bioabsorbable, REE-free ZX00 screws showed excellent clinical and functional outcomes.Cite this article:
2020;9(8):477-483.
A wave-optical approach to electron transport in devices containing a finite number of scatterers based on a direct solution of the Schroedinger equation and exploiting the similarity with wave ...optics is suggested. Being a first-principles one, it allows at the same time a transparent physical picture illuminating in particular some details that may be hidden within more formalized approaches like those involving random matrices. It is shown that existing experimental data concerning “non-universal” conductance fluctuations can be explained as a result of “combined” interference involving a trajectory backscattered to the contact in the vicinity of the contact and a “remote” one backscattered by scatterers situated at distances of the order of the electron mean free path.
Controlled transfer of single charge carriers Urbina, C.; Pothier, H.; Lafarge, P. ...
IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers); (United States),
03/1991, Letnik:
27, Številka:
2
Journal Article, Conference Proceeding
Two devices that allow the coherent transfer of single electrons are described. They are based on the electrostatic control of tunnel processes across ultrasmall normal tunnel junctions. When ...appropriate AC signals are applied to gates a current I=e*f is forced to flow through the devices. There are, however, fundamental differences in their principles which make the pump the only suitable candidate for the controlled transfer of cooper pairs. Although in these experiments the I=e*f relation was verified with only a 1% accuracy, more elaborate versions of these devices could be promising candidates for a current standard.
Conductance fluctuations of microfabricated silver point contacts, which operate in the ballistic electron-transport regime, are studied. The correlation energy E sub c of the conductance ...fluctuations has been determined from the voltage correlation of the fluctuations, and from the temperature and modulation voltage dependence of the fluctuation amplitude. For all the devices investigated E sub c approx = 1 meV. This value is in good agreement with a model where the conductance fluctuations are due to quantum interference of electrons backscattered by a few impurities at a distance of the order of the elastic mean free path from the constriction. For temperatures higher than E sub c /k sub B or the ac modulation voltages exceeding E sub c /e, a decrease of the fluctuation amplitude is observed, in agreement with averaging over uncorrelated fluctuation patterns. However, for dc bias voltages larger than E sub c /e the amplitude of fluctuations of the differential conductance remains unchanged for voltages up to V approx = 8 mV. This behavior is in strong contrast to observations and theoretical descriptions of conductance fluctuations in diffusive metallic samples.
The electrical properties of microfabricated nanobridges of Cu, Ag, and Au with contact diameters in the range 4-32 nm have been studied. High-quality point-contact spectra are evidence that electron ...transport is ballistic in these nanobridges. A comparison of the spectra with spectra from mechanical point contacts shows that microfabricated nanobridges are at least as good as mechanical point contacts for study of the electron--phonon interaction. Further, in Au nanobridges defect motion induced two-level resistance fluctuations (TLFs) were observed. An expression is derived for the voltage dependence of the temperature T sub d of a defect in a nanobridge at low lattice temperatures. Using this expression for T sub d , the experimental voltage dependence of the TLFs is successfully described by a thermal-activation model for the fluctuation rates, in which the voltage dependence of the activation energy and defect temperature is included. The values for the attempt time, activation energy, and electomigration parameter are as expected for defects in metals. An analysis of the two TLFs studied, showing a striking difference in both voltage dependence and magnitude of the duty cycle, suggests that rearrangement of complex defects is the mechanism behind the TLF behavior.
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