No abstract

Most T cells recognize antigen through the T-cell antigen receptor (TCR)alpha beta-CD3 complex on the T-cell surface. A small percentage of T cells, however, do not express alpha beta but a second type of TCR complex designated gamma delta (ref. 2). Unlike alpha beta+ lymphocytes, gamma delta+ lymphocytes do not generally express CD4 or CD8 molecules, and the nature of antigen recognition by these cells is unknown. To study antigen recognition by gamma delta+ lymphocytes we raised a gamma delta+ alpha beta- -CD4-CD8- line from an individual immune to PPD (purified protein derivative). This line showed a specific proliferative response to PPD and to a recombinant mycobacterial heat-shock protein (HSP) of relative molecular mass 65,000 (65K). The gamma delta+ line was shown to exhibit a major response to HSP in the presence of autologous antigen-presenting cells (APCs). Minor responses occurred, however, with APCs matched for some HLA class I or II antigens, whereas no response occurred with HLA-mismatched APCs. These findings, therefore, document the requirement of HSP-reactive gamma delta+ lymphocytes for histocompatible APCs.

ABSTRACT

This work focuses on the mechanisms of interfacial processes at the surface of amorphous silicon thin-film electrodes in organic carbonate electrolytes to unveil the origins of the inherent non-passivating behavior of silicon anodes in Li-ion batteries. Attenuated total reflection Fouriertransform infrared spectroscopy (ATR-FTIR), X-ray absorption spectroscopy (XAS), and infrared near-field scanning optical microscopy (IR aNSOM) were used to investigate the formation, evolution and chemical composition of the surface layer formed on Si upon cycling. We found that the chemical composition and thickness of the solid/electrolyte interphase layer (SEI) continuously change during the charging/discharging cycles. This SEI layer "breathing" effect is directly related

In situ diffuse reflectance infrared Fourier‐transformed spectroscopy (DRIFTS) investigations have been made to examine solid‐electrolyte interphase (SEI) formation on lithium‐rich Li1.2Ni0.2Mn0.6O2 (LLNMO) and LiCoO2 cathodes during first‐ and second‐cycle charging and discharging. This DRIFTS technique allows us to clarify SEI formation with different charging voltages. Both cathodes revealed the formation of the same surface species during first‐cycle charging, initially including ethylene carbonate (EC) adsorption, and SEI species, for example, ROCOF, RCOOR, Li2CO3, ROCO2Li, and PFx, are formed above the onset potential, namely 4.0 and 4.5 V for LiCoO2 and LLNMO, respectively. The onset potentials correspond to the upper limit of the reversible redox potential range for transition‐metal couples (e.g. Co3+/Co4+ in LiCoO2 and Ni2+/Ni4+ in LLNMO), which account for the intrinsic instability of these cathode materials. Such results suggest the participation of intermediate reactive oxygen species in SEI formation. SEI species continue to form during the discharge process when the potential is scanned cathodically below 3.6 and 4.0 V for LiCoO2 and LLNMO, respectively. Similar SEI species are also observed during the second cycle charge–discharge over LLNMO, where additional oxidized species such as carboxylate (−COO−) and CO2 are also found during charging. With the exception of PFx, all of the observed SEI species can be attributed to the oxidative decomposition of the organic solvent, EC. Finally, possible reaction mechanisms related to the oxidative decomposition of EC are discussed.

Trace water content in the electrolyte causes the degradation of LiPF, and the decomposed products further react with water to produce HF, which alters the surface of anode and cathode. As a result, the reaction of HF and the deposition of decomposed products on electrode surface cause significant capacity fading of cells. Avoiding these phenomena is crucial for lithium ion batteries. Considering the Lewis-base feature of the N-Si bond, 1-(trimethylsilyl)imidazole (1-TMSI) is proposed as a novel water scavenging electrolyte additive to suppress LiPF decomposition. The scavenging ability of 1-TMSI and beneficiary interfacial chemistry between the MCMB electrode and electrolyte are studied through a combination of experiments and density functional theory (DFT) calculations. NMR analysis indicated that LiPF decomposition by water was effectively suppressed in the presence of 0.2 vol % 1-TMSI. XPS surface analysis of MCMB electrode showed that the presence of 1-TMSI reduced deposition of ionic insulating products caused by LiPF decomposition. The results showed that the cells with 1-TMSI additive have better performance than the cell without 1-TMSI by facilitating the formation of solid-electrolyte interphase (SEI) layer with better ionic conductivity. It is hoped that the work can contribute to the understanding of SEI and the development of electrolyte additives for prolonged cycle life with improved performance.

No abstract

Based on responses of ordering physicians, the CCP report adds meaningful new information to risk assessment for localized prostate cancer patients. Test results led to changes in treatment with reductions and increases in interventional treatment that were directionally aligned with prostate cancer risk specified by the test.