The incorporation of hydroxyapatite (HAP) into poly-l-lactic acid (PLLA) matrix serving as bone scaffold is expected to exhibit bioactivity and osteoconductivity to those of the living bone. While ...too low degradation rate of HAP/PLLA scaffold hinders the activity because the embedded HAP in the PLLA matrix is difficult to contact and exchange ions with body fluid. In this study, biodegradable polymer poly (glycolic acid) (PGA) was blended into the HAP/PLLA scaffold fabricated by laser 3D printing to accelerate the degradation. The results indicated that the incorporation of PGA enhanced the degradation rate of scaffold as indicated by the weight loss increasing from 3.3% to 25.0% after immersion for 28 days, owing to the degradation of high hydrophilic PGA and the subsequent accelerated hydrolysis of PLLA chains. Moreover, a lot of pores produced by the degradation of the scaffold promoted the exposure of HAP from the matrix, which not only activated the deposition of bone like apatite on scaffold but also accelerated apatite growth. Cytocompatibility tests exhibited a good osteoblast adhesion, spreading and proliferation, suggesting the scaffold provided a suitable environment for cell cultivation. Furthermore, the scaffold displayed excellent bone defect repair capacity with the formation of abundant new bone tissue and blood vessel tissue, and both ends of defect region were bridged after 8 weeks of implantation.
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•PGA was blended into HAP/PLLA scaffold fabricated by laser 3D printing to accelerate degradation.•A lot of pores produced by scaffold degradation promoted the exposure of HAP from the matrix.•Scaffold provided a suitable environment for cell cultivation.•Scaffold displayed excellent bone repair capacity with the formation of abundant new bone tissue and blood vessel tissue.
Objectives/Hypothesis
Patients with unilateral vocal fold paralysis (UVFP) are commonly told to wait 12 months for spontaneous recovery. This study aims to 1) determine the time to vocal recovery in ...UVFP, 2) use that data to develop a neurophysiologically plausible model for recovery, and 3) use the model to generate meaningful predictions for patient counseling.
Study Design
Case series with de novo mathematical modeling.
Methods
Patients with UVFP who could pinpoint a discrete onset of vocal improvement were identified. The time‐to‐recovery data were modeled by assuming an “early” recovery group with neuropraxia and a “late” recovery group with more severe nerve injury. For the late group, a two‐stage model was developed to explain the time to recovery: regenerating axons must cross the site of injury in stage 1 (probabilistic), followed by unimpeded regrowth to the larynx in stage 2 (deterministic).
Results
Of 727 cases of UVFP over a 7‐year period, 44 reported spontaneous recovery with a discrete onset of vocal improvement. A hybrid distribution incorporating the two stages (exponentially modified Gaussian) accurately modeled the time‐to‐recovery data (R2 = 0.918). The model predicts 86% of patients with recoverable UVFP will recover within 6 months, with 96% recovering within 9 months. Earlier vocal recovery is associated with recovery of vocal fold motion and younger age.
Conclusions
Waiting 12 months for spontaneous recovery is probably too conservative. Repair across the site of injury, and not regrowth to larynx, is likely the rate‐determining step in reinnervation, consistent with other works on peripheral nerve regeneration.
Level of Evidence
4. Laryngoscope, 127:2585–2590, 2017
•Algorithms optimizing crystallization with temperature-dependent kinetics developed.•Optimal control theory is applied to develop the algorithms.•Algorithm based on an approximation is fast and ...introduces little error.•Pareto-optimal fronts for competing objective functions are plotted.•Methods could be applied for complex nucleation kinetics or online control.
Boundary value problems that arise when optimal control theory is applied to batch crystallization are complex and highly nonlinear, especially when crystallization kinetics are temperature-dependent, and conventional shooting methods sometimes fail to converge. In this work, three robust methods for solving such problems are presented and compared. The first method uses an approximation (neglecting the effect of the nucleated mass on the nucleation rate and the solution concentration) to simplify the problem. The second method uses a gradient-based algorithm to determine the optimal control input and the terminal constraints. The third method combines the first two, using the results from the approximation as an initial condition for the gradient-based algorithm. All three methods rely on a coordinate transformation of the population balance to enable explicit solutions to the population balance equations in the transformed domain and optimal control theory to provide the necessary condition of optimality.
The methods are applied to study the trade-off between competing objectives (minimizing the number and the volume of the nucleated crystals) by constructing Pareto-optimal fronts. The results show that the first method (utilizing an approximation) is most efficient and introduces little error. Furthermore, using the result of this method as an initial condition for the gradient-based method drastically reduces the computation time compared to the gradient-based method alone. The proposed algorithms can be used to study the effect of crystallization kinetics on optimal control policies or develop advanced process control technologies due to their high computational efficiency.
Extrusion-based 3D printing is the manufacturing technology which shapes the material layer by layer. This deposition mode results in a weak interface between layers, which seriously deteriorates the ...mechanical performance of printed objects. It is well-known that bonding strength of layer interface is fundamentally controlled by the deposition process (time interval, interfacial humidity, etc.) and properties of printing material. In this paper, XCT/SEM image processing was introduced to analyze interfacial pore structure at different scales, while nano-indentation was utilized for characterizing the interface micromechanical performance. The results indicated that layer interface generates a dual hierarchical structure, where deformation ability of rough layer surface contributes to the macro-interface and hydrates structure dominates the micro-interface. The influences of such factors including material rheological properties, deposition time interval and interfacial humidity can be integrated in this dual hierarchical structure. Finally, an empirical model was proposed to combine dual hierarchical structure with bonding strength of layer interface in 3D printed concrete.
A deconstructive oxygenation of unstrained primary cycloalkanamines has been developed for the first time using an auto‐oxidative aromatization promoted C(sp3)−C(sp3) bond cleavage strategy. This ...metal‐free method involves the substitution reaction of cycloalkanamines with hydrazonyl chlorides and subsequent auto‐oxidative annulation to in situ generate pre‐aromatics, followed by N‐radical‐promoted ring‐opening and further oxygenation by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) and m‐cholorperoxybenzoic acid (mCPBA). Consequently, a series of 1,2,4‐triazole‐containing acyclic carbonyl compounds were efficiently produced. This protocol features a one‐pot operation, mild reaction conditions, high regioselectivity and ring‐opening efficiency, broad substrate scope, and is compatible with alkaloids, osamines, and peptides, as well as steroids.
Opening up: A regioselective deconstructive oxygenation of unstrained cycloalkanamines has been developed for the first time. This metal‐free method involves the substitution reaction of cycloalkanamines with hydrazonyl chlorides and subsequent auto‐oxidative annulation to in situ generate pre‐aromatics, followed by N‐radical‐promoted aromatizative ring‐opening and further oxygenation by (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and m‐chloroperoxybenzoic acid (mCPBA).
Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has ...been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.
A block-centered finite difference scheme is introduced to solve the nonlinear Darcy-Forchheimer equation, in which the velocity and pressure can be approximated simultaneously. The second-order ...error estimates for both pressure and velocity are established on a nonuniform rectangular grid. Numerical experiments using the scheme show the consistency of the convergence rates of our method with the theoretical analysis.
Dense and crack-free Al-6Zn-2Mg (wt%) alloys with 1 wt% (Sc + Zr) addition were additively manufactured by laser powder bed fusion (LPBF) using gas atomized powders. As-built microstructure consisted ...of small equiaxed grains near the melt pool boundary and columnar grains between adjacent melt pools. Alloying of Sc + Zr promoted the formation of Al3(Sc,Zr) particles, which contributed to the grain refinement. The alloy exhibited outstanding tensile properties (i.e., 418 ± 3 MPa yield strength, 436 ± 3 MPa tensile strength and 11 ± 1% elongation) after heat treatment. The results demonstrate that high strength aluminum alloy can be fabricated by LPBF through alloy design and microstructural control.
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Cardiac hypertrophy is an adaptive response of the myocardium to pressure or volume overload. Recent evidences indicate that allicin can prevent cardiac hypertrophy. However, it is not clear whether ...allicin alleviates cardiac hypertrophy by inhibiting autophagy.
We aimed to investigate the effects of allicin on pressure overload-induced cardiac hypertrophy, and further to clarify the related mechanism.
Cardiac hypertrophy was successfully established by abdominal aortic constriction (AAC) in rats, and cardiomyocytes hypertrophy was simulated by angiotensin II (Ang II) in vitro. Hemodynamic parameters were monitored by organism function experiment system in vivo. The changes of cell surface area were observed using HE and immunofluorescence staining in vivoand in vitro, respectively. The expressions of cardiac hypertrophy relative protein (BNP and β-MHC), autophagy marker protein (LC3-II and Beclin-1), Akt, PI3K and ERK were detected by western blot.
Allicin could improve cardiac function, and reduce cardiomyocytes size, and decrease BNP and β-MHC protein expressions. Further results showed that allicin could lower LC3-II and Beclin-1 protein expressions both in vivo and in vitro experiments. And pharmacological inhibitor of mTOR, rapamycin could antagonize the effects of allicin on Ang II-induced cardiac hypertrophy and autophagy. Simultaneously, allicin could promote the expressions of p-Akt, p-PI3K and p-ERK protein.
These findings reveal a novel mechanism of allicin attenuating cardiac hypertrophy which allicin could inhibit excessive autophagy via activating PI3K/Akt/mTOR and MAPK/ERK/mTOR signaling pathways.
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Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, ...lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm
, together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.
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