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Background: As many researchers have focused on promoting the graft-bone healing of artificial ligaments, even with numerous chemical coatings, identifying a biosafe, effective, and immediately usable method is still important clinically. Purpose: (1) To determine whether a low-intensity pulsed ultrasound system (LIPUS) promotes in vitro cell viability and osteogenic differentiation and (2) to assess the applicability and effectiveness of LIPUS in promoting the graft-bone healing of artificial ligaments in vivo. Study Design: Controlled laboratory study. Methods: Polyethylene terephthalate (PET) sheets and grafts were randomly assigned to control and LIPUS groups. MC3T3-E1 preosteoblasts were cultured on PET sheets. Cell viability and morphology were evaluated using a live/dead viability assay and scanning electron microscopy. Alkaline phosphatase activity, calcium nodule formation, and Western blot were evaluated for osteogenic differentiation. For in vivo experiments, the effect of LIPUS was evaluated via an extra-articular graft-bone healing model in 48 rabbits: the osteointegration and new bone formation were tested by micro–computed tomography and histological staining, and the graft-bone bonding was tested by biomechanical testing. Results: Cell viability was significantly higher in the LIPUS group as compared with control (living and dead compared between control and LIPUS groups, P = .0489 vs P = .0489). Better adherence of cells and greater development of extracellular matrix were observed in the LIPUS group. Furthermore, LIPUS promoted alkaline phosphatase activity, calcium nodule formation, and the protein expression of collagen 1 ( P = .0002) and osteocalcin ( P = .0006) in vitro. Micro–computed tomography revealed higher surrounding bone mass at 4 weeks and newly formed bone mass at 8 weeks in the LIPUS group ( P = .0014 and P = .0018). Histological analysis showed a narrower interface and direct graft-bone contact in the LIPUS group; the surrounding bone area at 4 weeks and the mass of newly formed bone at 4 and 8 weeks in the LIPUS group were also significantly higher as compared with control (surrounding bone, P < .0001; newly formed bone, P = .0016 at 4 weeks and P = .005 at 8 weeks). The ultimate failure load in the LIPUS group was significantly higher than in the control group ( P < .0001 at 4 weeks; P = .0008 at 8 weeks). Conclusion: LIPUS promoted the viability and osteogenic differentiation of MC3T3-E1 preosteoblasts in vitro and enhanced the graft-bone healing of PET artificial ligament in vivo. Clinical Relevance: LIPUS is an effective physical stimulation to enhance graft-bone healing after artificial ligament implantation.

Magnesium hydride (MgH2) was doped into PTFE/Al to improve the energy release characteristics of the material system and strive for better application in military engineering. Five types of PTFE/Al/MgH2 reactive materials with different MgH2 content were prepared by molding sintering method. The dynamic mechanical properties of the materials were studied by performing split-Hopkinson pressure bar (SHPB) tests and scanning electron microscope characterizations. The thermal behavior, reaction energy, reaction process and reaction mechanism were systematically investigated by conducting thermogravimetry-differential scanning calorimetry tests, oxygen bomb calorimeter measurements, X-ray diffraction and SHPB tests. The results show that MgH2 particles less than 10% content contribute to heightening the dynamic mechanical properties of PTFE/Al system. The product Mg generated by decomposition of MgH2 can not only react with gas phase C2F4+ but also undergo a Grignard-type reaction with condensed PTFE. The reaction energy and ignition threshold of PTFE/Al/MgH2 reactive materials enhance monotonously as MgH2 content rose. With the increase of MgH2 content from 0% to 20%, the reaction time is prolonged as well as the reaction intensity is enhanced dramatically arising from the massive water vapour produced by the reaction between O2 and H2. The gaseous products generated can form a high pressure shortly after the reaction, which helps to elevate the damage effect of the PTFE/Al system.

In order to improve the energy density of polytetrafluoroethylene/aluminum (PTFE/Al), titanium hydride (TiH2) was added as a high-energy additive, and thermogravimetry–differential scanning calorimetry (TG-DSC), quasi-static compression and Split-Hopkinson pressure bar (SHPB) tests were conducted to investigate the chemical reaction mechanism and mechanical response of PTFE/Al/TiH2. The results of TG-DSC indicate that TiH2 first decomposes to form titanium and hydrogen, and titanium reacts with PTFE to produce TiF3, and then with the temperature rising, titanium reacts with carbon and excessive aluminum to generate TiC and Al3Ti. Under quasi-static compression, the strength of PTFE/Al/TiH2 specimens can reach 108.8 Mpa, 14.2% higher than that of PTFE/Al, the special burning flames during the reaction and XRD patterns of the reaction residues consistently indicate that TiH2 has participated in the reaction and react completely, achieving its purpose as a high-energy additive. Under dynamic compression tests, PTFE/Al/TiH2 composites show obvious strain hardening and strain rate hardening effects, and the yield strength and compressive strength are sensitive to strain rates; the established Johnson-Cook (JC) constitutive model can describe the mechanical response of PTFE/Al/TiH2 material well. In addition, the ignition threshold of PTFE/Al/TiH2 drops to 22.78 m/s, less than that of PTFE/Al (23.74 m/s), and the ignition delay time is advanced from 650-700 to 100-150 μs as the impact velocity increase.

To explore the effect of potassium perchlorate (KClO4) on Al nanoparticles/MnO2-nanorods nanothermite systems, in this paper, Al/MnO2 nanothermites with different mass fraction of KClO4 were prepared by electrospray. The samples were characterized by XRD, SEM, TG-DSC analysis. According to the results of TG-DSC, the addition of KClO4 seemed to cause no direct improvement on their exothermic reactions. But the results of activation energy calculations showed that KClO4 could remarkably reduce the activation energy of nanothermite systems by up to 48.8%. The XRD results indicated that residues consisted mainly of Mn3O4. The reasons why KClO4 has little effect on thermal properties but makes a great difference on kinetics were analyzed and discussed. Finally, onset combustion tests were carried out. The results and findings provide a useful approach to decrease the activation energy and combustion rate of nanothermites, which may facilitate practical and combustible applications.

Micron-MnO2 powder has unique thermal decomposition process compared with other metal oxides, and the different characteristics of components in thermite could affect the thermal performance of the whole system directly. In this work, the Al powder with different three particle sizes was combined with micron-MnO2 to prepare the Al-MnO2 thermite system, and the effect of Al powder particle sizes on the whole thermal behavior was studied. Firstly, the thermal decomposition process of micron-MnO2 and purity of Al powder are tested by TG-DSC. By using ultrasonic dispersion method, the fuel-rich thermite samples were prepared and characterized by SEM and TG-DSC at different heating rates. The Kissinger method was also employed to calculate the activation energy for the first exothermic peak. It was found that the thermal decomposition process of MnO2 in the thermite system can be significantly disturbed by different Al particles size. In other words, the effect of Al particle sizes on the thermite can be magnified due to the unique decomposition properties of micron-MnO2 instead of onset temperature of exothermic reaction changing simply. The activation energy of thermite system decreased with the reduction of Al particle sizes in micron-level, while in nanolevel the activation energy markedly increased. Finally, the possible reasons for phenomenon were discussed.

To explore the effect of potassium perchlorate (KClO

When the Al/Ta/PTFE reactive material was sintered at 360 &deg, C in a vacuum sintering furnace, it was found that the material reacted to form a soft fluffy white substance and carbon black. To explore the reaction process further, powder samples of pure PTFE, Al/PTFE, Ta/PTFE and Al/Ta/PTFE, and molded cylindrical specimens were prepared. A TG-DSC test was carried out on the thermal reaction of four reactive materials, and XRD phase analysis was conducted on the white product, formed by the sintering reaction and the residue of the TG-DSC test sample, based on which of the pyrolysis processes and reaction mechanisms were analyzed. The results show that Ta and PTFE could have a chemical reaction at sintering temperature (360 &deg, C) to form soft and fluffy white material TaF3 and carbon black, which can overflow the surface of the specimen and cause cracking of the specimen, which is tightly pressed. Since no obvious exothermic peak showed up on the TG-DSC curve, the composition of the residue of TG-DSC sample at different temperatures was tested and TaF3 was detected in the residue at 350 &deg, C and 360 &deg, C, indicating that Ta began to react with PTFE at a temperature range of 340&ndash, 350 &deg, C. According to the chemical properties and product formation of Ta, it could be speculated that the reaction mechanism between Ta and PTFE involves the PTFE decomposing first, then the fluorine-containing gas product reacting with metal Ta. According to the temperature range of the reaction, it is estimated that PTFE starts to decompose before 500 &deg, C, but it is not detected effectively by TG-DSC, and the introduction of Ta could also affect the decomposition process of PTFE.

To better understand the thermal decomposition and reaction process of a fluorine-containing powdery thermite, PTFE/Al/MnO2, reactions at different temperatures were investigated by the TG/DSC-MS technique. The corresponding reaction products were characterized with XRD phase analysis. Another three thermite materials, i.e., PTFE/Al, Al/MnO2, and PTFE/MnO2, were also prepared for comparison. Results showed that PTFE behaved as both oxidizer and reducer in PTFE/Al/MnO2 fluorinated thermite. The thermal decomposition and reaction process of as-fabricated ternary thermite could be divided into two stages&mdash, the mutual reaction between each of PTFE, Al, and MnO2 and the subsequent reaction produced between Al and Mn2O3/Mn3O4/MnF2. Compared with the three control systems, the specially designed ternary system possessed a shorter reaction time, a faster energy release rate, and a better heat release performance.

PTFE is a semi-crystalline polymer which can undergo two phase transitions at 19°Ϲ and 30°Ϲ. To investigate influence of temperature-induced phase transition of PTFE on the mechanical behavior and impact-induced initiation characteristics of Al/PTFE, the dynamic mechanical analysis, split Hopkinson pressure bar test and drop-weight test were conducted at different temperatures. The correlation between fracture modes and ignition mechanism were analyzed associated with microstructures and reaction phenomena. The results show that with the temperature elevated, the mechanical behavior and reactive characteristics of Al/PTFE manifested a bilinear temperature dependence. Al/PTFE went through a gradual transition from brittleness to ductility. The ignition energy declined, explosion flare enhanced and reaction time prolonged consistent with the change of mechanical properties. The shock pressure and ignition time under drop-weight tests were far from the requirement of shock-induced reaction, indicating that it is fracture-induced reaction dominates the ignition of Al/PTFE at low strain rate.

The performance of energetic materials is mainly reflected in two aspects, thermal performance and combustion performance. To figure out the differences in reaction performance, in this paper, thermal and combustion properties of Al/CuO, Al/Fe2O3 and Al/MnO2 nanothermites were studied respectively by thermal analysis and fast heating wire experiments. According to the thermal analysis, the exothermic peak temperature points of Al/MnO2, Al/CuO, Al/Fe2O3 nanothermites were 552.1 °C, 563.1 °C and 565.3 °C, respectively, while the sequence of activation energy calculated from low to high was Al/Fe2O3, Al/CuO, Al/MnO2 nanothermites. By the way, the values of Al/CuO and Al/Fe2O3 nanothermites showed little difference in temperature and activation energy. The ignition energy characterized by direct current had little difference among them, and the sequence from low to high was Al/MnO2, Al/Fe2O3, Al/CuO nanothermites, corresponding to 1.169 A, 1.214 A and 1.221 A, respectively. As for burning rate, Al/CuO burnt the fastest clearly while the Al/Fe2O3 burnt the longest. In terms of combustion performance, Al/CuO and Al/MnO2 were basically the same, with little splash of sparks, and the concentrations of combustion energy were better. The combustion phenomenon of Al/Fe2O3 nanothermite was quite unique with a large number of scattered sparks and poor energy concentration. Finally, the intrinsic reasons for above different phenomena of these three nanothermites were analyzed and discussed.

As a novel energetic material with quite a high energy density, titanium hydride (TiH2) was introduced into a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material system for the first time. The effects of TiH2 on the reaction energy, dynamic mechanical responses, and reaction properties of the composites were investigated through adiabatic bomb calorimeter, split-Hopkinson pressure bar, and drop-weight experiments. The results show that the reaction heat of the composites improved significantly as the content of TiH2 increased. Under dynamic compression, these composites show obvious strain hardening and strain rate hardening effects. Besides, a certain amount of TiH2 granules helps to improve the material&rsquo, s compressive strength, and the maximum would even reach 173.2 MPa with 5% TiH2 percentage, 10.1% higher than that of PTFE/Al. Mesoscale images of the samples after dynamic compression indicate that interface debonding between the particles and PTFE matrix and the fracture of the PTFE matrix are the two major mechanisms resulting in the material&rsquo, s failure. In addition, the drop-weight experiments indicate that the material&rsquo, s impact sensitivities are sensitive to the content of TiH2, which would be increased to within 20% of the content of TiH2 compared with PTFE/Al, and the reaction degree is also improved to within 10% of the content of TiH2. The retrieved reaction residues after drop-weight experiments imply that the reaction is initiated at the edges of the samples, indicating a shear-induced initiation mechanism of this kind of reactive material.

Polytetrafluoroethylene/aluminum/molybdenum oxide (PTFE/Al/MoO3) reactive composites of a volume ratio of 60:16:24 were studied in this research. Quasi-static compression, dynamic compression and drop-weight experiments were performed to explore the mechanical response and the shear-induced initiation properties of the composites. Mesoscale images of the specimens after sintering demonstrate that PTFE, Al and MoO3 powders were evenly mixed and no chemical reaction occurred after the materials were stirred, pressed and sintered. The yield stress and compressive strength of PTFE/Al/MoO3 specimens are sensitive to strain rate within the range of 10&minus, 3~3 &times, 103 s&minus, 1, and the yield stress shows a bilinear dependence on the logarithm values of strain rate. The established Johnson-Cook constitutive model based on the experimental data can describe the mechanical response of PTFE/Al/MoO3 material well. Drop-weight tests show that the PTFE/Al/MoO3 specimens can react violently when impacted, with the characteristic drop height (H50) calculated as 51.57 cm. The recovered specimens show that the reaction started from the outer edge of the specimen with the largest shear force and the most concentrated shear deformation, indicating a shear-induced initiation mechanism. The reaction products of PTFE/Al/MoO3 specimens were AlF3, Al2O3, Mo and C, demonstrating that redox reaction occurred between PTFE and Al, and between Al and MoO3.

To study the impact sensitivity and damage effect of PTFE-matrix energetic materials, PTFE-matrix specimens and liners were prepared by molding-vacuum sintering to carry out drop-hammer and impact experiments. The results show that the two metal additives contributed to reducing the impact sensitivity of Al/PTFE. The energy release level of Al/Ni/PTFE and Al/W/PTFE with the same metal content was different at different drop heights. In addition, the collision process, black burning marks and carbon indicate that the energetic liner reacted during the impact process. All perforations were petal-shaped holes because of better radial expansion effect of products. The seven groups of energetic liners can penetrate 3 mm steel plate. The Al/W/PTFE liner with volume fraction of 5% W had the strongest reaming capacity due to its higher strength and density than Al/PTFE liner. The 3 mm steel plate with low strength failed prematurely and the impact energy did not initiate the Ni-Al intermetallic reaction because of low sensitivity of Al/Ni/PTFE. Therefore, the energy release of Al/Ni/PTFE was lower than that of Al/W/PTFE. Only Al/Ni/PTFE liner with volume fraction of 15% Ni can penetrate 10 mm steel plate due to its higher strength and density compared with Al/PTFE and other Al/Ni/PTFE liners. But different with Al/W/PTFE liners, the energy released by the reaction of Al/PTFE initiated the Ni-Al combination, which greatly increased the energy release of the Al/Ni/PTFE and provided better damage effect. The damage effect of reactive materials on target is affected by its strength, density and energy release.

To analyze the mechanical properties and reaction characteristics of Al-ZrH2-PTFE (aluminum-zirconium hydride-polytetrafluoroethylene) composites under quasi-static compression, five types of specimens with different ZrH2 contents (0%, 5%, 10%, 20% and 30%) were prepared by molding-vacuum sintering. The true stress-strain curves and reaction rates of the different specimens were measured using quasi-static compression. The specific reaction processes were recorded by a high-speed camera. The corresponding reaction products were characterized by the XRD phase analysis, the calorific value was tested by a Calorimeter, and the reaction mechanism was analyzed. According to the results, the strength of the composites increased first and then decreased with the increase in the content of ZrH2. It reached a maximum of 101.01 MPa at 5%. Violent reaction occurred, and special flames were observed during the reaction of the specimens with 5% ZrH2. With the increase in the content of ZrH2, the chemical reaction was hard to induce due to the reduction in strength and toughness of composites. The reaction mechanism of Al/ZrH2/PTFE reveals that high temperatures at crack tip induced the reaction of Al and PTFE. Subsequently, ZrH2 decomposed to release hydrogen and generate ZrC. Calorimetric experiment shows that the calorific value of Al/ZrH2/PTFE with 20% ZrH2 is higher than that of Al/PTFE. The findings verify the potential of ZrH2 as an energetic additive for the enhancement of strength and release of the energy of the composites.

ATP-sensitive K+ (KATP) channels couple the intracellular metabolic state to electrical activity, which is important in the control of neuronal excitability and seizure propagation. In this study, we investigated the changes in the gene and protein expression of KATP channel subunits in the brain of picrotoxin (PTX)-kindled rats, which were daily administered with a subconvulsant dose of PTX for 20 days. At 14 days after the last administration of PTX, kindled rats were retreated with PTX and killed by decapitation at 12 h, 1 and 3 days, as well as retreated with vehicle and killed at 0 h after starting the retreatment. The abundance of Kir6.1, Kir6.2, SUR1 and SUR2A/B mRNAs was evaluated by reverse transcription polymerase chain reaction (RT-PCR) using endogenous gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal control, and the level of Kir6.2 and SUR1 proteins was measured by Western blot. At 0 h, the brain showed decreasing expression of various subunit mRNAs, with the exception of the SUR2A mRNA. In contrast, from 12 h to 3 days, the amount of various subunit mRNAs was up-regulated dynamically, but SUR2A of which was not changed significantly both from cortical and hippocampal samples. Furthermore, we demonstrated that the levels of Kir6.1, Kir6.2, SUR1 and SUR2B mRNAs at 12 h and 3 days (excepting SUR1 at 3 days) from hippocampal samples, as well as Kir6.1 at 1 day and SUR1 at 3 days from cortical samples, were significantly higher than that detected at 0 h. In addition, low levels of Kir6.2 and SUR1 proteins were observed both from cortical and hippocampal samples at 0 h and also, from 12 h to 3 days, a marked up-modulation of Kir6.2 and SUR1 protein expressions especially from hippocampal samples was found. These results suggest that the PTX-induced changes in the KATP channels may play a key role in the induction and maintenance of kindling and the PTX-induced seizures might be important for the acute changes of KATP channels observed in kindled rat brain.

This paper presents an advanced dynamic model and computer simulator for underbalanced drilling. The model is formulated based on the theory of multiphase transient flow referring to the drilling mud, water, oil, gas and solid particles. All the important factors affecting underbalanced drilling have been taken into account comprehensively in the model, including IPR relation, physical properties and mass transfer behavior of fluids, flow regime and phase migration features, geometry and deviation of wellbore as well as the different operating modes which may be carried out in practical underbalanced drilling. A specific numerical approach is adopted for solution of the theoretical models and on the basis, an advanced computer simulator is developed for undertaking simulation, study and planning of underbalanced drilling operations. The computer simulator differs from existing simulators because it is fully dynamical and interactive with users. Researchers and users can change different operating modes according to their will at any time during simulating process just as they are really performing an underbalanced drilling operation. The simulator can track all the complicated and complex conditions in underbalanced drilling process, and all the related parameters and profiles of parameter distribution along wellbore at any time can be shown dynamically. Through a number of simulating computations, tests and verifications, it is shown that the model and simulator are valid and in accordance with actual drilling practice under different and complicated conditions. It is of great importance for consummating underbalanced drilling theory and on the spot application. A typical simulation result and case study are also presented in the paper.