Quantum Dynamical Simulation of a Transversal Stern–Gerlach Interferometer

Originally conceived as a thought experiment, an apparatus consisting of two Stern–Gerlach apparatuses joined in an inverted manner touched on the fundamental question of the reversibility of evolution in quantum mechanics. Theoretical analysis showed that uniting the two partial beams requires an extreme level of experimental control, making the proposal in its original form unrealizable in practice. In this work, we revisit the above question in a numerical study concerning the possibility of partial-beam recombination in a spin-coherent manner. Using the Suzuki–Trotter numerical method of wave propagation and a configurable, approximation-free magnetic field, a simulation of a transversal Stern–Gerlach interferometer under ideal conditions is performed. The result confirms what has long been hinted at by theoretical analyses: the transversal Stern–Gerlach interferometer quantum dynamics is fundamentally irreversible even when perfect control of the associated magnetic fields and beams is assumed.

Design of 3D-printed Cable Driven Humanoid Hand Based on Bidirectional Elastomeric Passive Transmission

Motion control of the human hand is the most complex part of the human body. It has always been a challenge for a good balance between the cost, weight, responding speed, grasping force, finger extension, and dexterity of prosthetic hand. To solve these issues, a 3D-printed cable driven humanoid hand based on bidirectional elastomeric passive transmission (BEPT) is designed in this paper. A semi-static model of BEPT is investigated based on energy conservation law to analyze the mechanical properties of BEPT and a dynamical simulation of finger grasping is conducted. For a good imitation of human hand and an excellent grasping performance, specific BEPT is selected according to human finger grasping experiments. The advantage of BEPT based humanoid hand is that a good balance between the price and performance of the humanoid hand is achieved. Experiments proved that the designed prosthetic hand’s single fingertip force can reach 33 N and the fastest fingertip grasping speed realized 0.6 s/180°. It also has a good force compliance effect with only 430g’s weight. It can not only grab fragile objects like raw eggs and paper cup, but also achieve strong grasping force to damage metal cans. This humanoid hand has considerable application prospects in artificial prosthesis, human-computer interaction, and robot operation.

Cargo surface fluidity reduces inter-motor interference, promotes load-sharing and enhances run-lengths in an ATP dependent manner

In cells, multiple molecular motors work together to carry membranous cargoes including vesicles and organelles along a network of cytoskeletal filaments. The fluidity of the cargo surface has been potentially associated with both positive and negative effects in transport, but the physical mechanisms, at the motor and cargo level that might be responsible, are not clear. To explore these mechanisms, we developed a 3D dynamical simulation of cargo transport along microtubules by teams of canonically non-cooperative kinesin-1 motors that accounts for membrane fluidity by explicitly simulating the Brownian dynamics of motors on the cargo surface. Our results suggest that cargo surface fluidity reduces inter-motor interference and promotes load-sharing thereby decreasing off-rates, allows the adaptive recruitment of motors and a co-operative increase in on-rates resulting from the 3D geometry. These effects altogether result in enhanced cargo run-lengths, most significantly at low ATP concentrations with implications for transport in vivo and artificial cargo design.

ExoSim: the Exoplanet Observation Simulator

A new generation of exoplanet research beckons and with it the need for simulation tools that accurately predict signal and noise in transit spectroscopy observations. We developed ExoSim: an end-to-end simulator that models noise and systematics in a dynamical simulation. ExoSim improves on previous simulators in the complexity of its simulation, versatility of use and its ability to be generically applied to different instruments. It performs a dynamical simulation that can capture temporal effects such as correlated noise and systematics on the light curve. It has also been extensively validated, including against real results from the Hubble WFC3 instrument. We find ExoSim is accurate to within 5% in most comparisons. ExoSim can interact with other models which simulate specific time-dependent processes. A dedicated star spot simulator allows ExoSim to produce simulated observations that include spot and facula contamination. ExoSim has been used extensively in the Phase A and B design studies of the ARIEL mission, and has many potential applications in the field of transit spectroscopy.

Relaxation behaviors of star polymers in the grid model

The tube theory has made a detailed description for the linear polymer entangled system, while the behavior of entangled star polymers is still determined by a qualitative prediction. In this paper, the dynamical simulation of a three-arms star polymer in the grid model is presented. We record the diffusion coefficient [Formula: see text], the relaxation time for the arms of star polymer [Formula: see text] and some other parameters corresponding to different branch length. Therefore, results that are inconsistent with the theoretical begin to emerge.