Academic Journals

Adipose derived stem cell transplantation is better than bone marrow mesenchymal stem cell transplantation in treating hindlimb ischemia in mice

The Behavior Analyst - Sun, 09/29/2019 - 00:00
Abstract Introduction:

Bone marrow derived MSCs (BM-MSCs) and adipose derived MSCs (AD-MSCs) are among the types of stem cells most commonly studied. Our study aims to compare the therapeutic efficacy of allograft AD-MSCs versus BM-MSCs in a mouse model of hindlimb ischemia.

Methods:

AD-MSCs were isolated from belly fat and BM-MSCs were isolated from femur bone marrow. They were used to treat mice with acute hindlimb ischemia. Treatment efficacy was compared among 4 groups: injected with BM-MSCs, injected with AD-MSCs, non-treated and injected with phosphate buffered saline. Mice in the groups were evaluated for the following: necrosis grade of leg, leg edema, blood flow, muscle cell restructure and new blood vessel formation.

Results:

Results showed that AD-MSC transplantation significantly recovered acute limb ischemia, with 76.5% of mice fully recovered, while the ratio was only 48.5% in BM-MSC transplanted group, and 0% in the non-treated and PBS groups. Evaluation of leg edema, blood flow, muscle cell restructure and new blood vessel formation also supported the observation that AD-MSC transplantation was superior over BM-MSC transplantation.

Conclusion:

Therefore, AD-MSCs may serve as the more suitable MSC for hindlimb ischemia treatment and angiogenesis therapy.

Categories: Academic Journals

Adipose derived stem cell transplantation is better than bone marrow mesenchymal stem cell transplantation in treating hindlimb ischemia in mice

The Psychological Record - Sun, 09/29/2019 - 00:00
Abstract Introduction:

Bone marrow derived MSCs (BM-MSCs) and adipose derived MSCs (AD-MSCs) are among the types of stem cells most commonly studied. Our study aims to compare the therapeutic efficacy of allograft AD-MSCs versus BM-MSCs in a mouse model of hindlimb ischemia.

Methods:

AD-MSCs were isolated from belly fat and BM-MSCs were isolated from femur bone marrow. They were used to treat mice with acute hindlimb ischemia. Treatment efficacy was compared among 4 groups: injected with BM-MSCs, injected with AD-MSCs, non-treated and injected with phosphate buffered saline. Mice in the groups were evaluated for the following: necrosis grade of leg, leg edema, blood flow, muscle cell restructure and new blood vessel formation.

Results:

Results showed that AD-MSC transplantation significantly recovered acute limb ischemia, with 76.5% of mice fully recovered, while the ratio was only 48.5% in BM-MSC transplanted group, and 0% in the non-treated and PBS groups. Evaluation of leg edema, blood flow, muscle cell restructure and new blood vessel formation also supported the observation that AD-MSC transplantation was superior over BM-MSC transplantation.

Conclusion:

Therefore, AD-MSCs may serve as the more suitable MSC for hindlimb ischemia treatment and angiogenesis therapy.

Categories: Academic Journals

Topological Fulde-Ferrell and Larkin-Ovchinnikov states in spin-orbit-coupled lattice system

The Psychological Record - Sun, 04/01/2018 - 00:00
Abstract

The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting (tSC) state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell (FF) state (having a phase-modulated order parameter with a uniform amplitude) and the Larkin-Ovchinnikov (LO) state (having a spatially varying order parameter amplitude). Here, we show that the topological FF state with Chern number (C = -1) (tFF1) and topological LO state with C= 2 (tLO2) can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 (tBCS1) far from half filling and C = 2 (tBCS2) near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-filling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.

Categories: Academic Journals

Topological Fulde-Ferrell and Larkin-Ovchinnikov states in spin-orbit-coupled lattice system

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting (tSC) state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell (FF) state (having a phase-modulated order parameter with a uniform amplitude) and the Larkin-Ovchinnikov (LO) state (having a spatially varying order parameter amplitude). Here, we show that the topological FF state with Chern number (C = -1) (tFF1) and topological LO state with C= 2 (tLO2) can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 (tBCS1) far from half filling and C = 2 (tBCS2) near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-filling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.

Categories: Academic Journals

Stable periodic orbits for spacecraft around minor celestial bodies

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

We are interested in stable periodic orbits for spacecraft in the gravitational field of minor celestial bodies. The stable periodic orbits around minor celestial bodies are useful not only for the mission design of the deep space exploration, but also for studying the long-time stability of small satellites in the large-size-ratio binary asteroids. The irregular shapes and gravitational fields of the minor celestial bodies are modeled by the polyhedral model. Using the topological classifications of periodic orbits and the grid search method, the stable periodic orbits can be calculated and the topological cases can be determined. Furthermore, we find five different types of stable periodic orbits around minor celestial bodies: (1) stable periodic orbits generated from the stable equilibrium points outside the minor celestial body; (2) stable periodic orbits continued from the unstable periodic orbits around the unstable equilibrium points; (3) retrograde and nearly circular periodic orbits with zero-inclination around minor celestial bodies; (4) resonance periodic orbits; (5) near-surface inclined periodic orbits. We take asteroids 243 Ida, 433 Eros, 6489 Golevka, 101955 Bennu, and the comet 1P/Halley for examples.

Categories: Academic Journals

Calibration of atmospheric density model using two-line element data

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

For satellites in orbits, most perturbations can be well modeled, however the inaccuracy of the atmospheric density model remains the biggest error source in orbit determination and prediction. The commonly used empirical atmospheric density models, such as Jacchia, NRLMSISE, DTM, and Russian GOST, still have a relative error of about 10%–30%. Because of the uncertainty in the atmospheric density distribution, high accuracy estimation of the atmospheric density cannot be achieved using a deterministic model. A better way to improve the accuracy is to calibrate the model with updated measurements. Twoline element (TLE) sets provide accessible orbital data, which can be used in the model calibration. In this paper, an algorithm for calibrating the atmospheric density model is developed. First, the density distribution of the atmosphere is represented by a power series expansion whose coefficients are denoted by the spherical harmonic expansions. Then, the useful historical TLE data are selected. The ballistic coefficients of the objects are estimated using the BSTAR data in TLEs, and the parameterized model is calibrated by solving a nonlinear least squares problem. Simulation results show that the prediction error is reduced using the proposed calibration algorithm.

Categories: Academic Journals

A note on the full two-body problem and related restricted full three-body problem

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

Truncating at the second order of the mutual potential between two rigid bodies, time-explicit first order solutions to the rotations and the orbital motion of the two bodies in the planar full two-body problem (F2BP) are constructed. Based on this analytical solution, equations of motion (EOMs) for the related restricted full three-body problem are given. In the case of the synchronous or double synchronous states for the full two-body problem, EOMs for the related restricted full three-body problem (RF3BP) are also given. At last, one example—the “collinear libration point” in the binary asteroid system—is given.

Categories: Academic Journals

Stabilization of coupled orbit–attitude dynamics about an asteroid utilizing Hamiltonian structure

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

The gravitationally coupled orbit–attitude dynamics, also called the full dynamics, in which the spacecraft is modeled as a rigid body, is a high-precision model for the motion in the close proximity of an asteroid. A feedback control law is proposed to stabilize relative equilibria of the coupled orbit–attitude motion in a uniformly rotating second degree and order gravity field by utilizing the Hamiltonian structure. The feedback control law is consisted of potential shaping and energy dissipation. The potential shaping makes the relative equilibrium a minimum of the modified Hamiltonian by modifying the potential artificially. With the energy-Casimir method, it is theoretically proved that an unstable relative equilibrium can always be stabilized in the Lyapunov sense by the potential shaping with sufficiently large feedback gains. Then, the energy dissipation leads the motion to converge to the relative equilibrium. The proposed stabilization control law has a simple form and is easy to implement autonomously, which can be attributed to the utilization of natural dynamical behaviors in the controller design.

Categories: Academic Journals

Optimization of observing sequence based on nominal trajectories of symmetric observing configuration

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

This paper presents the crucial method for obtaining our team’s results in the 8th Global Trajectory Optimization Competition (GTOC8). Because the positions and velocities of spacecraft cannot be completely determined by one observation on one radio source, the branch and bound method for sequence optimization of multi-asteroid exploration cannot be directly applied here. To overcome this difficulty, an optimization method for searching the observing sequence based on nominal low-thrust trajectories of the symmetric observing configuration is proposed. With the symmetric observing configuration, the normal vector of the triangle plane formed by the three spacecraft rotates in the ecliptic plane periodically and approximately points to the radio sources which are close to the ecliptic plane. All possible observing opportunities are selected and ranked according to the nominal trajectories designed by the symmetric observing configuration. First, the branch and bound method is employed to find the optimal sequence of the radio source with thrice observations. Second, this method is also used to find the optimal sequence of the left radio sources. The nominal trajectories are then corrected for accurate observations. The performance index of our result is 128,286,317.0 km which ranks the second place in GTOC8.

Categories: Academic Journals

Overview of China’s 2020 Mars mission design and navigation

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

Scheduled for an Earth-to-Mars launch opportunity in 2020, the China’s Mars probe will arrive on Mars in 2021 with the primary objective of injecting an orbiter and placing a lander and a rover on the surface of the Red Planet. For China’s 2020 Mars exploration mission to achieve success, many key technologies must be realized. In this paper, China’s 2020 Mars mission and the spacecraft architecture are first introduced. Then, the preliminary launch opportunity, Earth–Mars transfer, Mars capture, and mission orbits are described. Finally, the main navigation schemes are summarized.

Categories: Academic Journals

Stable periodic orbits for spacecraft around minor celestial bodies

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

We are interested in stable periodic orbits for spacecraft in the gravitational field of minor celestial bodies. The stable periodic orbits around minor celestial bodies are useful not only for the mission design of the deep space exploration, but also for studying the long-time stability of small satellites in the large-size-ratio binary asteroids. The irregular shapes and gravitational fields of the minor celestial bodies are modeled by the polyhedral model. Using the topological classifications of periodic orbits and the grid search method, the stable periodic orbits can be calculated and the topological cases can be determined. Furthermore, we find five different types of stable periodic orbits around minor celestial bodies: (1) stable periodic orbits generated from the stable equilibrium points outside the minor celestial body; (2) stable periodic orbits continued from the unstable periodic orbits around the unstable equilibrium points; (3) retrograde and nearly circular periodic orbits with zero-inclination around minor celestial bodies; (4) resonance periodic orbits; (5) near-surface inclined periodic orbits. We take asteroids 243 Ida, 433 Eros, 6489 Golevka, 101955 Bennu, and the comet 1P/Halley for examples.

Categories: Academic Journals

Calibration of atmospheric density model using two-line element data

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

For satellites in orbits, most perturbations can be well modeled, however the inaccuracy of the atmospheric density model remains the biggest error source in orbit determination and prediction. The commonly used empirical atmospheric density models, such as Jacchia, NRLMSISE, DTM, and Russian GOST, still have a relative error of about 10%–30%. Because of the uncertainty in the atmospheric density distribution, high accuracy estimation of the atmospheric density cannot be achieved using a deterministic model. A better way to improve the accuracy is to calibrate the model with updated measurements. Twoline element (TLE) sets provide accessible orbital data, which can be used in the model calibration. In this paper, an algorithm for calibrating the atmospheric density model is developed. First, the density distribution of the atmosphere is represented by a power series expansion whose coefficients are denoted by the spherical harmonic expansions. Then, the useful historical TLE data are selected. The ballistic coefficients of the objects are estimated using the BSTAR data in TLEs, and the parameterized model is calibrated by solving a nonlinear least squares problem. Simulation results show that the prediction error is reduced using the proposed calibration algorithm.

Categories: Academic Journals

A note on the full two-body problem and related restricted full three-body problem

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

Truncating at the second order of the mutual potential between two rigid bodies, time-explicit first order solutions to the rotations and the orbital motion of the two bodies in the planar full two-body problem (F2BP) are constructed. Based on this analytical solution, equations of motion (EOMs) for the related restricted full three-body problem are given. In the case of the synchronous or double synchronous states for the full two-body problem, EOMs for the related restricted full three-body problem (RF3BP) are also given. At last, one example—the “collinear libration point” in the binary asteroid system—is given.

Categories: Academic Journals

Stabilization of coupled orbit–attitude dynamics about an asteroid utilizing Hamiltonian structure

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

The gravitationally coupled orbit–attitude dynamics, also called the full dynamics, in which the spacecraft is modeled as a rigid body, is a high-precision model for the motion in the close proximity of an asteroid. A feedback control law is proposed to stabilize relative equilibria of the coupled orbit–attitude motion in a uniformly rotating second degree and order gravity field by utilizing the Hamiltonian structure. The feedback control law is consisted of potential shaping and energy dissipation. The potential shaping makes the relative equilibrium a minimum of the modified Hamiltonian by modifying the potential artificially. With the energy-Casimir method, it is theoretically proved that an unstable relative equilibrium can always be stabilized in the Lyapunov sense by the potential shaping with sufficiently large feedback gains. Then, the energy dissipation leads the motion to converge to the relative equilibrium. The proposed stabilization control law has a simple form and is easy to implement autonomously, which can be attributed to the utilization of natural dynamical behaviors in the controller design.

Categories: Academic Journals

Optimization of observing sequence based on nominal trajectories of symmetric observing configuration

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

This paper presents the crucial method for obtaining our team’s results in the 8th Global Trajectory Optimization Competition (GTOC8). Because the positions and velocities of spacecraft cannot be completely determined by one observation on one radio source, the branch and bound method for sequence optimization of multi-asteroid exploration cannot be directly applied here. To overcome this difficulty, an optimization method for searching the observing sequence based on nominal low-thrust trajectories of the symmetric observing configuration is proposed. With the symmetric observing configuration, the normal vector of the triangle plane formed by the three spacecraft rotates in the ecliptic plane periodically and approximately points to the radio sources which are close to the ecliptic plane. All possible observing opportunities are selected and ranked according to the nominal trajectories designed by the symmetric observing configuration. First, the branch and bound method is employed to find the optimal sequence of the radio source with thrice observations. Second, this method is also used to find the optimal sequence of the left radio sources. The nominal trajectories are then corrected for accurate observations. The performance index of our result is 128,286,317.0 km which ranks the second place in GTOC8.

Categories: Academic Journals

Overview of China’s 2020 Mars mission design and navigation

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

Scheduled for an Earth-to-Mars launch opportunity in 2020, the China’s Mars probe will arrive on Mars in 2021 with the primary objective of injecting an orbiter and placing a lander and a rover on the surface of the Red Planet. For China’s 2020 Mars exploration mission to achieve success, many key technologies must be realized. In this paper, China’s 2020 Mars mission and the spacecraft architecture are first introduced. Then, the preliminary launch opportunity, Earth–Mars transfer, Mars capture, and mission orbits are described. Finally, the main navigation schemes are summarized.

Categories: Academic Journals

Optimal sidewall functionalization for the growth of ultrathin TiO 2 nanotubes via atomic layer deposition

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

One of the most suitable approaches for the production of inorganic nanotubes is by means of carbon nanotube (CNT) templates coated by atomic layer deposition (ALD). This approach is attractive because it has the potential of controlling the wall thickness down to the Angstroms level. However, it is a recognized fact that the chemistry of the substrate surface can delay the full coverage at the initial stages of the ALD coating process, mainly due to nucleation issues. This is an important issue that might restrict laying down homogeneous coatings within the ultrathin range, which is the foundation for producing self-supported inorganic nanotubes. Here, we explore the early stage of the TiO2 nucleation on CNT templates systematically functionalized with different chemical groups (COOH, OH) or N-doped. The effects of the functionalization on the nucleation process from tetrakis (dimethylamino) titanium and water were meticulously studied by means of transmission electron microscopy. Observations revealed grain-like growth of TiO2 over pristine, purified and –OH-functionalized CNTs. In contrast, COOH functionalization yielded good conformality, which was improved on N-doped CNTs. Results were confirmed by X-rays photoelectron spectroscopy analysis. We recommend either COOH or N-doped CNTs for the production of ultrathin TiO2 nanotubes.

Categories: Academic Journals

Helical gold nanotube film as stretchable micro/nanoscale strain sensor

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

A micro/nanoscale strain sensor based on helical gold nanotube films (GNTFs) is proposed, which is prepared by magnetron sputtering using carbon nanocoils (CNCs) as templates. The gauge factor of the sensor reaches 5, while the stretch of it can achieve more than 10% owing to the helical geometries. The resistance increase of GNTFs with temperature decreasing from 300 to 4 K indicates a thermal activation tunneling model for electron transport. With thicknesses increasing from 16 to 32 nm, the GNTFs show a structural transition from discontinuous to quasi-continuous film. In this transition region, the conductive path of GNTFs increases rapidly, resulting in a rapid resistance decrease of CNC–GNTF composite structure. When a helical GNTF is stretched, the resistance is increased. The helical GNTFs in the transition region exhibit the highest response sensitivity, which owes to the special torsion-dominated strains of this helical structure to some extent. The unique helical morphology gives the sensor great stretchability and special electrical response. Choosing appropriate CNCs and GNTFs with suitable thickness, the helical GNTFs can be used as micro/nanostretchable strain sensors, stretchable electrodes or connects, resonators in micro/nanoelectromechanical system.

Categories: Academic Journals

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