Key points of development of motor skills in childhood embodied in gait parameters.

OBJECTIVE: To observe changes of correlations of gait parameters of four sets of body in children aged 3-6. DESIGN: A cross-sectional observational study. SETTING: Dong Gang kindergarten in Suzhou, China. PARTICIPANTS: A total of 89 children between 3 and 6 years old. MAIN OUTCOME MEASURES: A total of 37 three-dimensional (3-D) gait parameters assessed with a wearable gait analysis system in 2-min walking test, for 3 times. RESULTS: There were significant differences in gait speed, stride length and sagittal range of motion (ROM) of trunk among children of 3-6 years old (P < 0.05). The left and right toe out angle, sagittal ROM of waist, coronal ROM of trunk and arm swing velocity of male were significantly greater than those of female children (P < 0.05). Most gait parameters were symmetrical (P < 0.01). Canonical correlations of Upper Limbs Set vs. Trunk and Waist Sets increased by ages (P < 0.05). Canonical correlation of Trunk Set vs. Waist Set decreased by ages. Canonical correlations of Lower Limbs Set to any other sets were not significant (P > 0.05). CONCLUSIONS: Values and symmetry of gait parameters cannot reflect the development of motor skill during ages of 3-6. Proper trunk movement coordinating with upper limbs and isolating from waist is the key point of development of motor skill in walking. It is built during preschool period and girls develop better. Before the preschool period, lower limbs' isolating movements from the other segments have already developed well. These key points of motor skills in walking should be considered when motor tasks for segment isolation and coordination are given to children with motor dysfunction.

Transmissive Mode Laser Micro-Ablation Performance of Ammonium Dinitramide-Based Liquid Propellant for Laser Micro-Thruster.

The transmissive mode laser micro-ablation performance of near-infrared (NIR) dye-optimized ammonium dinitramide (ADN)-based liquid propellant was investigated in laser plasma propulsion using a pulse YAG laser with 5 ns pulse width and 1064 nm wavelength. Miniature fiber optic near-infrared spectrometer, differential scanning calorimeter (DSC) and high-speed camera were used to study laser energy deposition, thermal analysis of ADN-based liquid propellants and the flow field evolution process, respectively. Experimental results indicate that two important factors, laser energy deposition efficiency and heat release from energetic liquid propellants, obviously affect the ablation performance. The results showed that the best ablation effect of 0.4 mL ADN solution dissolved in 0.6 mL dye solution (40%-AAD) liquid propellant was obtained with the ADN liquid propellant content increasing in the combustion chamber. Furthermore, adding 2% ammonium perchlorate (AP) solid powder gave rise to variations in the ablation volume and energetic properties of propellants, which enhanced the propellant enthalpy variable and burn rate. Based on the AP optimized laser ablation, the optimal single-pulse impulse (I)~9.8 µN·s, specific impulse (Isp)~234.9 s, impulse coupling coefficient (Cm)~62.43 dyne/W and energy factor (η)~71.2% were obtained in 200 µm scale combustion chamber. This work would enable further improvements in the small volume and high integration of liquid propellant laser micro-thruster.

Liquid-solid phase regulating excited-state intramolecular proton transfer process of HBT-d-NO2: A QM/MM study.

The excited-state intramolecular proton transfer process of 2-(1,3-benzothiazol-2-yl)-4-[2-(4-nitrophenyl)ethynyl]phenol (HBT-d-NO2) in the different surrounding environment is investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The optimized molecular structure provides convincing evidence that the intramolecular hydrogen bond is strengthened in the first excited (S1) state. The frontier molecular orbitals observed the HBT-d-NO2 exists obvious intramolecular charge translate phenomenon. The results of the potential energy curve show that HBT-d-NO2 is difficult to undergo proton transfer in the ground (S0) state due to the high energy barrier, while it becomes easier in the S1 state in both liquid and solid phases. By comparison, the energy barrier of ESIPT in the solid phase is higher than that in the liquid phase. We can conclude that the solid phase effectively hinders the ESIPT process compared with that the liquid phase. In this work, we illustrate the influence of liquid and solid phases on the intramolecular proton transfer process, which could promote further developments in biomedical and fluorophore applications.

A Comparative Study on Microstructural Characterization of Thick High Strength Low Alloy Steel Weld by Arc Welding and Laser Welding.

Welding and the behavior of the weldments are important, since welding of high strength low alloy (HSLA) steels is a conventional method for manufacturing industrial parts. This work conducts a comparative investigation of microstructural characteristics and mechanical properties for joints of 16-mm-thick HSLA Q890 steel produced by multi-layer multi-pass shielded metal arc welding (SMAW) with filler wire and single-layer autogenous laser beam welding (LBW). The mechanical properties of the welded joints were assessed in terms of tensile and impact using butt joints. The results show that tensile failure occurred in the base metal during the tensile tests for most of the trials. The ultimate tensile strength and percent elongation of the LBW welded joint (973.5 MPa and 10%) are higher than those of the SMAW joint (951 MPa and 2.9%) due to the filler filling process of the SMAW process. The Charpy impact energy of the weld metal (16.4 J and 15.1 J) is lower than that of the heat-affected zone (18.5 J and 19.5 J) in the LBW joint and the SMAW joint.

Fusarium solani G6, a novel vitexin-producing endophytic fungus: characterization, yield improvement and osteoblastic proliferation activity.

The study aimed to characterize a novel vitexin-producing endophytic fungus Fusarium solani G6 from Cajanus cajan, improve its capability for producing vitexin and evaluate its osteoblastic proliferation activity. A total of 153 endophytic fungi, classified into 6 genera, were isolated from C. cajan. Among them, only one strain, endophyte G6 identified as Fusarium solani, was found to produce vitexin. After the optimization of fermentation conditions, the highest vitexin yield (18.72 mg/L) for the strain was observed in PDB liquid medium containing 20.54 g/L of glucose and 8.90 g/L of ammonium sulfate, at an initial medium pH of 5.1 and at 28 °C for 6 days of cultivation. Moreover, the fungal vitexin exhibited notable osteoblastic proliferation stimulating activity. A novel vitexin-producing endophytic fungus F. solani G6 was characterized from C. cajan for the first time. The findings highlighted its potential use for large-scale production of vitexin and might have a promising use as therapeutic agent for osteoporosis.

Connection Mechanism of Molten Pool during Laser Transmission Welding of T-Joint with Minor Gap Presence.

Laser welding of T-joint transmitting from the face plate to the core is commonly used in the sandwich structure preparation. Minor gaps between the face and the core plate are inevitably present after several beads on the sandwich structure welding due to the thermal deformation. The effects of gap presence on fluid flow from the face to the core plate are rather significant, where the gas can be easily entrapped into the pool and form the pores. To this end, three-dimensional transient simulations based on VOF (volume of fluid) method were conducted to explore and ascertain the effect of fluid flow inside the pool on the pore formation due to the gap presence. It was found that minor gap within 0.2 mm will not reduce the welding quality. Under the effects of gravity and surface tension, the fluid from the face sheet will drop down to the core, which removes all the air out of the gap and the laser goes through the fluid of the gap and then shines on the core, which prevents the air from being entrapped into the pool. While the laser goes though gap, the wall of keyhole opens and closes continuously. The vibrating time of keyhole is approximately 0.029 s. After finishing the vibration, the welding is stable, which is the same as common unfull penetration. Finally, the simulated results are well verified through observing the plasma oscillating frequency in the gap and comparing to the pore-free bead profile. This paper supplies evidence that minor gap presence during laser transmitting welding on sandwich structure has nothing to do with pore formation.

Effect of Temperature and Hold Time of Induction Brazing on Microstructure and Shear Strength of Martensitic Stainless Steel Joints.

1Cr12Mo martensitic stainless steel is widely used for intermediate and low-pressure steam turbine blades in fossil-fuel power plants. A nickel-based filler metal (SFA-5.8 BNi-2) was used to braze 1Cr12Mo in an Ar atmosphere. The influence of brazing temperature and hold time on the joints was studied. Microstructure of the joints brazed, element distribution and shear stress were evaluated at different brazing temperatures, ranging from 1050 °C to 1120 °C, with holding times of 10 s, 30 s, 50 s and 90 s. The results show that brazing joints mainly consist of the matrix of the braze alloy, the precipitation, and the diffusion affected zone. The filler metal elements diffusion is more active with increased brazing temperature and prolonged hold time. The shear strength of the brazed joints is greater than 250 MPa when the brazing temperature is 1080 °C and the hold time is 30 s.

The Microstructural Evolution of Vacuum Brazed 1Cr18Ni9Ti Using Various Filler Metals.

The microstructures and weldability of a brazed joint of 1Cr18Ni9Ti austenitic stainless steel with BNi-2, BNi82CrSiBFe and BMn50NiCuCrCo filler metals in vacuum were investigated. It can be observed that an interdiffusion region existed between the filler metal and the base metal for the brazed joint of Ni-based filler metals. The width of the interdiffusion region was about 10 µm, and the microstructure of the brazed joint of BNi-2 filler metal was dense and free of obvious defects. In the case of the brazed joint of BMn50NiCuCrCo filler metal, there were pits, pores and crack defects in the brazing joint due to insufficient wettability of the filler metal. Crack defects can also be observed in the brazed joint of BNi82CrSiBFe filler metal. Compared with BMn50NiCuCrCo and BNi82CrSiBFe filler metals, BNi-2 filler metal is the best material for 1Cr18Ni9Ti austenitic stainless steel vacuum brazing because of its distinct weldability.

Spatial distribution characteristics of plasma plume on attenuation of laser radiation under subatmospheric pressure.

The attenuation of a laser by plasma plume can be restrained for laser welding under subatmospheric pressure. Based on the experimental obtained spectra, the extinctions of a probe laser under different subatmospheric pressures and the spatial distribution of probe laser extinction were measured. The role of subatmospheric pressure on plasma plume was analyzed. The results show that, with decreasing ambient pressure, the extinction of a probe laser decreases, and the welding penetration depth increases. The maximum attainable value of extinction gets far away from the keyhole in the transversal and vertical directions. The attenuation of a fiber laser is about 10% under normal atmosphere, and it reaches only about 1% when the ambient pressure is reduced to 3 kPa.