Multi-Objective Optimization Design through Machine Learning for Drop-on-Demand Bioprinting

Drop-on-demand (DOD) bioprinting has been widely used in tissue engineering due to its highthroughput efficiency and cost effectiveness. However, this type of bioprinting involves challenges such as satellite generation, too-large droplet generation, and too-low droplet speed. These challenges reduce the stability and precision of DOD printing, disorder cell arrays, and hence generate further structural errors. In this paper, a multi-objective optimization (MOO) design method for DOD printing parameters through fully connected neural networks (FCNNs) is proposed in order to solve these challenges. The MOO problem comprises two objective functions: to develop the satellite formation model with FCNNs;and to decrease droplet diameter and increase droplet speed. A hybrid multi-subgradient descent bundle method with an adaptive learning rate algorithm (HMSGDBA), which combines the multisubgradient descent bundle (MSGDB) method with Adam algorithm, is introduced in order to search for the Pareto-optimal set for the MOO problem. The superiority of HMSGDBA is demonstrated through comparative studies with the MSGDB method. The experimental results show that a single droplet can be printed stably and the droplet speed can be increased from 0.88 to 2.08 m·s^-1 after optimization with the proposed method. The proposed method can improve both printing precision and stability, and is useful in realizing precise cell arrays and complex biological functions. Furthermore, it can be used to obtain guidelines for the setup of cell-printing experimental platforms.

Mechanism from particle compaction to fluidization of liquid–solid two-phase flow

A new model of particle yield stress including cohesive strength is proposed,which considers the friction and cohesive strength between particles.A calculation method for the fluidization process of liquid–solid two-phase flow in compact packing state is given,and the simulation and experimental studies of fluidization process are carried out by taking the sand–water two-phase flow in the jet dredging system as an example,and the calculation method is verified.

Novel radioligands for imaging sigma-1 receptor in brain using positron emission tomography(PET)

The sigma-1 receptor(σ1R)is a unique intracellular protein.σ1R plays a major role in various pathological conditions in the central nervous system(CNS),implicated in several neuropsychiatric disorders.Imaging ofσ1R in the brain using positron emission tomography(PET)could serve as a noninvasively tool for enhancing the understanding of the disease’s pathophysiology.Moreover,σ1R PET tracers can be used for target validation and quantification in diagnosis.Herein,we describe the radiosynthesis,in vivo PET/CT imaging of novelσ1R11C-labeled radioligands based on 6-hydroxypyridazinone,[11C]HCC0923 and[11C]HCC0929.Two radioligands have high affinities toσ1R,with good selectivity.In mice PET/CT imaging,both radioligands showed appropriate kinetics and distributions.Additionally,the specific interactions of two radioligands were reduced by compounds 13 and 15(self-blocking).Ofthe two,[11C]HCC0929 was further investigated in positive ligands blocking studies,using classicσ1R agonist SA 4503 andσ1R antagonist PD 144418.Bothσ1R ligands could extensively decreased the uptake of[11C]HCC0929 in mice brain.Besides,the biodistribution of major brain regions and organs of mice were determined in vivo.These studies demonstrated that two radioligands,especially[11C]HCC0929,possessed ideal imaging properties and might be valuable tools for non-invasive quantification ofσ1R in brain.

Effects of operating conditions and pre-densification on the torrefaction products of sorghum straw

The effects of operating conditions and pre-densification on the torrefaction performance parameters and the properties of the torrefied sorghum straw were studied.A full-factor experiment was performed on a fixed tube furnace,in which sorghum straw powder and pellets were heated to 230℃,260℃,280℃ and 300℃ at 2.5℃/min,5℃/min and 7.5℃/min,respectively.The pyrolysis characteristics of the sorghum straw torrefied under various operating conditions were complemented by thermogravimetric analysis.It was observed that the high temperature led to the high calorific value of the torrefied sorghum straw with an acceptable mass and energy yield.The sorghum straw torrefied at a temperature above 280℃ had a higher heating value(HHV)that was comparable to that of the low rank coal while maintaining its energy yield above 85%.The results suggested that temperature was an important factor determining the properties of the torrefied products,and the heating rate would affect the internal temperature of the torrefied biomass by affecting the heat transfer during the torrefaction.The energy densification index of the pellets decreased uniformly as the heating rate increased proportionally,indicating that pre-densification can be used as a potential method to solve the heat transfer delay in the fixed reactors at high heating rates,especially for high temperatures.