PULSED-LASER DIRECT WRITING OF BIOLOGICAL MATERIALS

Laser direct writing, developed based on modified laser-induced forward transfer (LIFT), has been emerging as one of the most promising biofabrication techniques. While some studies have been conducted to investigate laser direct writing of biological materials, there are some key challenges such as mechanisms of bubble formation, droplet formation and process-induced cell injury that have not been well elucidated. The objective of this dissertation is to study laser-induced droplet formation dynamics and process-induced cell injury in pulsed-laser direct writing of biological materials, and improve the existing laser direct-write techniques. Phase explosion is identified as the dominant bubble formation mechanism in pulsed-laser direct writing. The phase explosion-induced bubble formation process is modeled using a homogenous nucleation theory. The proposed model can predict the formed bubble diameter and pressure in laser direct writing of glycerol-water solutions. Droplet formation mechanism is systematically studied through investigating the effects of laser fluence and material properties on the transferred droplet diameter. It is found that the transferred droplet diameter is linearly dependent on the laser fluence while there is no systematic dependence on the glycerol concentration. Process-induced cell injury in laser direct writing is systematically elucidated through investigating the effects of operating conditions on the post-transfer cell viability, proliferation and cell injury reversibility. It is found that the post-transfer cell viability decreases as the laser fluence increases and is not dependent on the cell density in direct writing of human colon cancer cells. Reversible process-induced cell injuries are observed in post-transfer yeast cells. An improved laser direct writing approach is proposed using a four-layer structure including an additional metallic foil between the laser transparent donor substrate and the coating to be transferred. It is found that the proposed approach is a promising fabrication technology for making encapsulated microspheres from highly viscous solutions and transferring mammalian cells with high post-transfer cell viability. It can eliminate the direct laser-cell interaction and possible contamination from residual sacrificial layer which may have using other conventional laser direct-write techniques. This dissertation provides a better understanding of the droplet formation dynamics and process-induced cell injury in laser direct writing. This work would help laser direct writing to be a viable biofabrication technology in cell printing and encapsulated microsphere fabrication

Design for Motor Controller in Hybrid Electric Vehicle Based on Vector Frequency Conversion Technology

Motor and its control technology are one of the main components of Hybrid Electric Vehicle (HEV). To meet HEV's fast torque response, vector control algorithm based on rotor flux-oriented and simulation model is concerned and modular designs for controller's hardware and software are presented in the paper in order to build a platform to achieve the vector control of asynchronous induction motor. Analyze the controller's electromagnetic compatibility, introduce the corresponding antijamming measures to assure the normal operation of the electromagnetic sensitive devices such as CAN bus; experiment proves that the measure is practical and feasible. On the basis of the control logic correct, such as improving CAN bus communication reliability, assuring power-on sequence and fault treatment, carry on the motor bench experiment, test its static properties, and adjust the controller parameters. The experimental results show that the designed driving system has the performance of low speed and high torque, a wide range of variable speed and high comprehensive efficiency

Optimization of Hybrid Electric Bus Driving System's Control Strategy

AbstractThe popularity of hybrid electric bus (HEB) is a most realistic way to solve emission and energy problem currently, so it's important to improve the HEB's fuel economy and efficiency. This paper optimizes the HEB's driving system to satisfy the conditions of this city. We applied the fuzzy logic control of modern control theory to the driving system's control of parallel-HEB, and optimized the driving system's control strategy of this city's hybrid bus based on this theory. We adopted the ADVISOR2002 for HEB's driving system's re-development, namely established the driving system's simulation model for this city's hybrid bus, then we tested the simulation model on the HEB urban driving cycle which had been developed in our preparatory work. The simulation results of our new control strategy and the simulation model proposed in this paper can further enhance the fuel economy and improve the driving system's efficiency, thus the results provided important reference for the upgrading of this type HEB's driving system

Understanding In-Context Learning from Repetitions

This paper explores the elusive mechanism underpinning in-context learning in Large Language Models (LLMs). Our work provides a novel perspective by examining in-context learning via the lens of surface repetitions. We quantitatively investigate the role of surface features in text generation, and empirically establish the existence of \emph{token co-occurrence reinforcement}, a principle that strengthens the relationship between two tokens based on their contextual co-occurrences. By investigating the dual impacts of these features, our research illuminates the internal workings of in-context learning and expounds on the reasons for its failures. This paper provides an essential contribution to the understanding of in-context learning and its potential limitations, providing a fresh perspective on this exciting capability

Synergistically activated dual-locked fluorescent probes to monitor H₂S-induced DNA damage

Naphthalimide-based fluorescent probes (NAN0-N3 and NAN6-N3) were developed with dual locked fluorescence. Here, ≥1.9 × 10−2 mM of H2S and ≥2.2 × 10−2 μg mL−1 of DNA could unlock a highly sensitive off-on fluorescence response through synergistic changes of the molecular structure and conformation. As such, the probes could monitor DNA damage induced by the overexpression of H2S, and were able to evaluate the degree of apoptosis of living cells mediated by H2S-induced mtDNA or nDNA damage.</p

An Empirical Study of Catastrophic Forgetting in Large Language Models During Continual Fine-tuning

Catastrophic forgetting (CF) is a phenomenon that occurs in machine learning when a model forgets previously learned information as it learns new information. As large language models (LLMs) have shown excellent performance, it is interesting to uncover whether CF exists in the continual fine-tuning of LLMs. In this study, we empirically evaluate the forgetting phenomenon in LLMs' knowledge, from the perspectives of domain knowledge, reasoning, and reading comprehension. The experiments demonstrate that catastrophic forgetting is generally observed in LLMs ranging from 1b to 7b. Furthermore, as the scale increases, the severity of forgetting also intensifies. Comparing the decoder-only model BLOOMZ with the encoder-decoder model mT0, BLOOMZ suffers less forgetting and maintains more knowledge. We also observe that LLMs can mitigate language bias (e.g. gender bias) during continual fine-tuning. Moreover, we find that ALPACA can maintain more knowledge and capacity compared with LLAMA during the continual fine-tuning, which implies that general instruction tuning can help mitigate the forgetting phenomenon of LLMs in the further fine-tuning process

mtDNA-Specific Ultrasensitive Near-Infrared Fluorescent Probe Enables the Differentiation of Healthy and Apoptotic Cells

Mitochondrial DNA (mtDNA) as a class of important genetic material is easily damaged, which can result in a series of metabolic diseases, hereditary disease, and so on. mtDNA is an ultrasensitive indicator for the health of living cells due to the extremely short physiological response time of mtDNA toward damage (ca. 5.0 min). Therefore, the development of specific ultrasensitive fluorescent probes that can in real-time monitor mtDNA in vivo are of great value. With this research, we developed a near-infrared twisted intramolecular charge transfer (TICT) fluorescent probe YON. YON is a thread-like molecule with an A-π-D-π-A structure, based on the dicyanoisophorone fluorophore. The molecular design of YON enabled the specific binding with dsDNA (binding constant (K) = 8.5 × 105 M-1) within 1.3 min. And the appropriate water-oil amphiphilicity makes YON significantly accumulate in the mitochondria, enabling the specific binding to mtDNA. The fluorescence intensity at 640 nm of YON enhanced linearly with increasing concentrations of mtDNA. Dicyanoisophorone as the strong electron-withdrawing group that was introduced into both ends of the molecule resulted in YON being a classic quadrupole, so it could ultrasensitively detect trace mtDNA. The minimum detection limit was 71 ng/mL. Moreover, the large Stokes shift (λex = 435 nm, λem = 640 nm) makes YON suitable for "interference-free"imaging of mtDNA. Therefore, YON was used to monitor trace changes of mtDNA in living cells; more importantly, it could be used to evaluate the health of cells by monitoring microchanges of mtDNA, enabling the ultrasensitive evaluation of apoptosis. </p

Changes of Spoilage Bacteria on the Surface of Broiler Carcasses during the Efficient Slaughtering Process of Yellow Feather Chicken

To analyze the changes of spoilage bacteria on the carcasses of broiler during the slaughtering of yellow feather broiler, the diversity of spoilage bacteria in the processing environment and on the carcass surface during the efficient slaughter of yellow feather broiler was determined by the plate pouring method and Illumina MiSeq high-throughput sequencing. The results showed that the main contamination procedure for the growth of bacteria of yellow feather broilers was eviscerating, pre-cooling and grading procedure, and the grading scale, in which the grading scale, workers' gloves from grading workshop, pre-cooling tank and workers' gloves from eviscerating manual gloves were contamination sources in the three processes aforementioned. Moreover, grading scale and workers' gloves in the decomposition workshop were the main source of contaminated flora of yellow feather broilers carcasses. The growth rate of total viable counts (TVC) and Pseudomonas on the surface of yellow feather broilers carcasses was as high as 24.13% and 41.27%, respectively. The TVC of yellow feather broilers increased to 4.63 lg(CFU/g) after grading scale and grading workshop worker's hands (P<0.05). Streptococcus, Escherichia and Aeromonas were the main dominant bacteria in yellow feather broilers carcasses after plucking (DM), evisceration (JH) and disinfection (CH). The abundance of Aeromonas increased substantially in yellow feather broilers after pre-cooling, followed by Streptococcus. After the grading scale, Acinetobacter was the dominant bacterium in the yellow feather broilers carcasses, followed by Macrococcus. As the abundance of Aeromonas and Streptococcus decreased significantly on the carcasses of yellow feather broilers treated with slightly acidic electrolyzed water (SAEW), it indicated that the disinfecting effect of SAEW was obvious. The results of the present investigation could provide data support and theoretical reference for environmental control, product quality maintenance and shelf-life extension in yellow feather broilers slaughterhouse by analyzing the microbial distribution during the slaughter of yellow feather broilers

Metformin ameliorates the mitochondrial damage induced by C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia-related poly-GR

Objective·To investigate the effect of C9ORF72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD)-related poly-glycine-arginine (poly-GR) on mitochondrial morphology and function, and analyze the rescue effect of metformin on mitochondrial damage induced by poly-GR and its underlying mechanism.Methods·SK-N-SH cells stably overexpressing 50 repeated glycine-arginine sequences [(GR)50] or green fluorescent protein (GFP) were constructed by lentivirus infection, which were respectively named as (GR)50-SK cell line and GFP CTRL-SK cell line. (GR)50 expression in (GR)50-SK cells was verified by Western blotting. GFP expression in GFP GTRL-SK cells was observed by fluorescence microscope. Propidium iodide (PI) staining was used to detect the apoptosis levels of (GR)50-SK and GFP CTRL-SK cells. Immunofluorescence (IF) staining was performed to determine the subcellular location of (GR)50. Reactive oxygen species (ROS) level of mitochondria was evaluated by staining cells with MitoSOX Red followed by observing the intensity of red fluorescence under fluorescence microscope. The mitochondrial morphology of (GR)50-SK and GFP CTRL-SK cells was observed by transmission electron microscopy. Western blotting was used to detect protein kinase B (PKB, also known as AKT) and its phosphorylation levels in (GR)50-SK and GFP CTRL-SK cells. SC79 was used to activate AKT in (GR)50-SK cells, and MitoSOX Red staining and PI staining were used to analyze mitochondrial ROS and apoptosis levels after phosphorylated AKT increased. Metformin was used to treat (GR)50-SK and GFP CTRL-SK cells, respectively, and the apoptosis levels, mitochondrial ROS levels, mitochondrial morphology, AKT and its phosphorylation levels, and ATP concentrations of the two cells were detected by the above methods and ATP detection kit, respectively.Results·Western blotting showed that the construction of (GR)50-SK cells was successful, and fluorescence microscopy showed that the construction of GFP CTRL-SK cells was also successful. PI staining results showed that the apoptosis level of (GR)50-SK cells was higher than that of the GFP CTRL-SK cells (P=0.016). IF staining results showed that there was partial co-localization of (GR)50 in the mitochondria of (GR)50-SK cells. Compared with GFP CTRL-SK cells, the mitochondrial morphology and structure of (GR)50-SK cells were significant abnormalities, with a significantly increased ROS levels. The AKT levels in (GR)50-SK cells were similar to those in the GFP CTRL-SK cells, but there was a significant decrease in phosphorylated AKT levels. After (GR)50-SK cells were treated with SC79, the AKT phosphorylation level was significantly upregulated, and ROS level and apoptosis level were significantly downregulated. Metformin could significantly up-regulate the phosphorylated AKT levels in (GR)50-SK cells, but had no effect on AKT levels; it could reshape the morphology and structure of some mitochondria, reduce ROS levels, increase ATP production (P=0.000), and down-regulate the level of cell apoptosis (P=0.000).Conclusion·(GR)50 can cause mitochondrial morphology and function abnormalities by down-regulating AKT phosphorylation, and promote cell apoptosis. Metformin can effectively reduce the occurrence of the above pathological events induced by (GR)50

The complete mitochondrial genome of Xizicus (Haploxizicus) maculatus revealed by Next-Generation Sequencing and phylogenetic implication (Orthoptera, Meconematinae)

Xizicus Gorochov, 1993, the quiet-calling katydid, is a diverse genus with 68 species in world, which includes more than 45 species in China, has undergone numerous taxonomic revisions with contradicting conclusions. In this study the complete mitochondrial genome of Xizicus (Haploxizicus) maculatus collected from Hainan for the first time was sequenced using the Next-Generation Sequencing (NGS) technology. The length of whole mitogenome is 16,358 bp and contains the typical gene arrangement, base composition, and codon usage found in other related species. The overall base composition of the mitochondrial genome is 37.0 % A, 32.2 % T, 20.2 % C, and 10.6 % G. All 13 protein-coding genes (PCGs) began with typical ATN initiation codon. Nine of the 13 PCGs have a complete termination codon, but the remaining four genes (COI, COIII, ND5, and ND4) terminate with an incomplete T. Phylogenetic analyses are carried out based on the concatenated dataset of 13 PCGs and two rRNAs of Tettigoniidae species available in GenBank. Both Bayesian inference and Maximum Likelihood analyses recovered each subfamily as a monophyletic group. Regardless of the position of Lipotactinae, the relationships among the subfamilies of Tettigoniidae were as follows: ((((Tettigoniinae, Bradyporinae) Meconematinae) Conocephalinae) Hexacentrinae). The topological structure of the phylogeny trees showed that the Xizicus (Haploxizicus) maculatus is closer to Xizicus (Xizicus) fascipes than Xizicus (Eoxizicus) howardi