UNDERSTANDING THE STRUCTURE-PROPERTY-PERFORMANCE RELATIONSHIP OF SILICON NEGATIVE ELECTRODES

Rechargeable lithium ion batteries (LIBs) have long been used to power not only portable devices, e.g., mobile phones and laptops, but also large scale systems, e.g., electrical grid and electric vehicles. To meet the ever increasing demand for renewable energy storage, tremendous efforts have been devoted to improving the energy/power density of LIBs. Known for its high theoretical capacity (4200 mAh/g), silicon has been considered as one of the most promising negative electrode materials for high-energy-density LIBs. However, diffusion-induced stresses can cause fracture and, consequently, rapid degradation in the electrochemical performance of Si-based negative electrodes. To mitigate the detrimental effects of the large volume change, several strategies have been proposed. This dissertation focuses on two promising approaches to make high performance and durable Si electrodes for high capacity LIBs. First, the effect of polymeric binders on the performance of Si-based electrodes is investigated. By studying two types of polymeric binders, polyvinylidene fluoride (PVDF) and sodium alginate (SA) using peel tests, SEM, XPS, and FTIR, I show that the high cohesive strength at the binder-silicon interface is responsible for the superior cell performance of the Si electrodes with SA as a binder. Hydrogen bonds formed between SA and Si is the main reason for the high cohesive strength since neither PVDF nor SA bonds covalently with Si. Second, the fabrication of high performance Si/polyacrylonitrile (PAN) composite electrode via oxidative pyrolysis is investigated. We show that high performance Si/polyacrylonitrile (PAN) composite negative electrodes can be fabricated by a robust heat treatment in air at a temperature between 250 and 400oC. Using Raman, SEM, XPS, TEM, TGA, and nanoindention, we established that oxidation, dehydration, aromatization, and intermolecular crosslinking take place in PAN during the heat treatment, resulting in a stable cyclized structure which functions as both a binder and a conductive agent in the Si/PAN composite electrodes. With a Si mass loading of 1 mg/cm2, a discharge capacity of ~1600 mAh/g at the 100th cycle is observed in the 400oC treated Si/PAN composite electrode when cycled at a rate of C/3. These studies on the structure-property-performance relations of Si based negative electrode may benefit the LIB community by providing (1) a guide for the design and optimization of binder materials for Si electrodes and (2) a facile method of synthesizing Si-based composite negative electrodes that can potentially be applied to other Si/polymer systems for further increasing the power/energy density and lower the cost of LIBs for electric vehicle applications and beyond

Scalable Multiuser Immersive Communications with Multi-numerology and Mini-slot

This paper studies multiuser immersive communications networks in which different user equipment may demand various extended reality (XR) services. In such heterogeneous networks, time-frequency resource allocation needs to be more adaptive since XR services are usually multi-modal and latency-sensitive. To this end, we develop a scalable time-frequency resource allocation method based on multi-numerology and mini-slot. To appropriately determining the discrete parameters of multi-numerology and mini-slot for multiuser immersive communications, the proposed method first presents a novel flexible time-frequency resource block configuration, then it leverages the deep reinforcement learning to maximize the total quality-of-experience (QoE) under different users' QoE constraints. The results confirm the efficiency and scalability of the proposed time-frequency resource allocation method

Orientation-specific RAG activity in chromosomal loop domains contributes to Tcrd V(D)J recombination during T cell development

T cell antigen receptor δ (Tcrd) variable region exons are assembled by RAG-initiated V(D)J recombination events in developing γδ thymocytes. Here, we use linear amplification–mediated high-throughput genome-wide translocation sequencing (LAM-HTGTS) to map hundreds of thousands of RAG-initiated Tcrd D segment (Trdd1 and Trdd2) rearrangements in CD4−CD8− double-negative thymocyte progenitors differentiated in vitro from bone marrow–derived hematopoietic stem cells. We find that Trdd2 joins directly to Trdv, Trdd1, and Trdj segments, whereas Trdd1 joining is ordered with joining to Trdd2, a prerequisite for further rearrangement. We also find frequent, previously unappreciated, Trdd1 and Trdd2 rearrangements that inactivate Tcrd, including sequential rearrangements from V(D)J recombination signal sequence fusions. Moreover, we find dozens of RAG off-target sequences that are generated via RAG tracking both upstream and downstream from the Trdd2 recombination center across the Tcrd loop domain that is bounded by the upstream INT1-2 and downstream TEA elements. Disruption of the upstream INT1-2 boundary of this loop domain allows spreading of RAG on- and off-target activity to the proximal Trdv domain and, correspondingly, shifts the Tcrd V(D)J recombination landscape by leading to predominant V(D)J joining to a proximal Trdv3 pseudogene that lies just upstream of the normal boundary

AN INVESTIGATION OF RELATIONSHIP BETWEEN PHASE SEPARATION AND CRYSTALLIZATION OF ZnO-Al2O3-SiO2 GLASSES

Les résultats de la microscopie électronique, le l'ATD et de la diffraction des rayons X montrent qu'il y a une assez forte tendance de la séparation de phase dans les verres de système ZnO-Al2O3-SiO2 (ZAS). Pendant le processus de cristallisation, la solution solide de β-quartz pourra être obtenue comme phase primaire métastable, si le degré de séparation de phase est petit dans le verre. La solution solide de β-quartz et celle de β-Willemite seront obtenues si la séparation de phase est assez complète. Non seulement, la séparation de phase dans le verre influence la composition des phases cristallines primaires, mais encore accélère la cristallisation du verre ZAS.TEM, DTA, X-ray diffraction results reveal that there is a strong tendency to phase separation into two immiscible liquid phases in the ZnO-Al2O3- SiO2 (ZAS) glasses. β-quartz solid solution would precipitate as metastable initial crystalline phase, when the degree of phase separation of the original glass is low, whereas β-quartz solid solution and β-Willemite solid solution would both be precipitate when the degree of phase separation is more complete. It was found that degree of phase separation not only determines the initial crystalline phase, but also accelerates the crystallization of the ZAS glasses

Acylsulfonamides and processes for producing the same

The present disclosure relates to acylsulfonamides and processes for their preparation. The processes involve a target-guided synthesis approach, whereby a thioacid and a sulfonyl azide are reacted in the presence of a biological target protein, a Bcl-2 family protein, to form the acylsulfonamide

Impact of Ni Content on the Electrochemical Performance of the Co-Free, Li and Mn-Rich Layered Cathode Materials

Li and Mn-rich layered cathode (LLC) materials show great potential as the next generation cathode materials because of their high, practical and achievable specific capacity of ~250 mAh/g, thermal stability and lower raw material cost. However, LLC materials suffer from degradation of specific capacity, voltage fading due to phase transformation upon cycling and transition-metal dissolution, which presents a significant barrier for commercialization. Here, we report the effects of Ni content on the electrochemical performance, structural and thermal stability of a series of Co-free, LLC materials (Li1.2NixMn0.8-xO2, x = 0.12, 0.18, 0.24, 0.30 and 0.36) synthesized via a sol-gel method. Our study shows that the structure of the material as well as the electrochemical and thermal stability properties of the LLC materials are strongly dependent on the Ni or Mn content. An increase in the Ni to Mn ratio results in an increase in the average discharge voltage and capacity, as well as improved structural stability but decreased thermal stability

Dietary conjugated linoleic acid supplementation alleviates high lipid-induced intestinal damage in grass carp (Ctenopharyngodon idella)

High lipid diet has been shown to increase the intestinal permeability and inflammatory properties in mammals, and the conjugated linoleic acid (CLA) could alleviate the symptoms caused by high lipid diet. However, the information about the impact of high lipid diet on the intestine of fish was limited, and the effect of CLA on intestinal changes induced by high lipid diet in fish is still unknown. Therefore, an 8-week feeding trial was conducted to investigate CLA's potential effects against high lipid diet-induced intestinal physical and immune barrier damage in grass carp (Ctenopharyngodon idella). Three isonitrogenous diets, including fish meal-control diet, control diet supplemented with 3.5% soybean oil as high lipid diet (HL), and HL replaced with a 2.5% CLA diet (CLA) formulated. Compared to the control group, HL significantly increased the expression of pro-inflammation genes (TNF-α, IL-8, IL-1β, NF-κB p65, IκBα, IKKα, IKKβ, and IKKγ) and down-regulated the gene expression of anti-inflammation cytokine (IL-10). The expression of intestinal tight junction proteins (ZO-1, occludin, claudin c, and claudin b) in fish fed with high lipid diets was lower than those fed with control diets. In the CLA group, the gene expression of pro-inflammation cytokines was decreased, and the expression level of the anti-inflammation cytokine was increased, compared with those in HL group. Moreover, feeding with high lipid diets induced fish intestine and dietary CLA damage could alleviate the symptom as shown by HE staining. In conclusion, this research revealed that CLA could mitigate high lipid diet-induced inflammation and permeability in the intestine of grass carp

Effect of Si and Holding Time on Ti₂Al₂₀La Phase in Al-Ti-La Intermediate Alloy

The effects of holding time and Si on the content, shape size and structure of Ti2Al20La phase in Al-Ti-La intermediate alloy were investigated by an X-ray diffractometer, scanning electron microscope and transmission electron microscope. The results show that the volume fraction and aspect ratio of Ti2Al20La phase in Al-Ti-La intermediate alloy decrease significantly, from 21% and 2.3 without Si addition to 4% and 2.0 with the addition of 2.3 wt.% Si at a holding time of 15 min at 750 °C, respectively. The Si element will attach to the Ti2Al20La phase and form La-Si binary phase at the grain boundary of α-Al. With the increase of holding time from 15 min to 60 min, the content of Ti2Al20La phase in the alloy gradually decreases and the size decreases significantly. Meanwhile, Al11La3 will dissolve and disappear, while the content of La-Si binary phase increases, and part of Ti2Al20La phase transforms into Ti2(Al20−x,Six)La phase