A mass spectrometric method for in-depth profiling of phosphoinositide regioisomers and their disease-associated regulation

Phosphoinositides are a family of membrane lipids essential for many biological and pathological processes. Due to the existence of multiple phosphoinositide regioisomers and their low intracellular concentrations, profiling these lipids and linking a specific acyl variant to a change in biological state have been difficult. To enable the comprehensive analysis of phosphoinositide phosphorylation status and acyl chain identity, we develop PRMC-MS (Phosphoinositide Regioisomer Measurement by Chiral column chromatography and Mass Spectrometry). Using this method, we reveal a severe skewing in acyl chains in phosphoinositides in Pten-deficient prostate cancer tissues, extracellular mobilization of phosphoinositides upon expression of oncogenic PIK3CA, and a unique profile for exosomal phosphoinositides. Thus, our approach allows characterizing the dynamics of phosphoinositide acyl variants in intracellular and extracellular milieus.

Handheld LIBS for Li Exploration: An Example from the Carolina Tin-Spodumene Belt, USA

Laser-induced breakdown spectroscopy (LIBS), which has recently emerged as tool for geochemical analysis outside the traditional laboratory setting, is an ideal tool for Li exploration because it is the only technique that can measure Li in minerals, rocks, soils, and brines in-situ in the field. In addition to being used in many products essential to modern life, Li is a necessary element for a reduced carbon future and Li–Cs–Ta (LCT) granitic pegmatites are an important source of Li. Such pegmatites can have varying degrees of enrichment in Li, Rb, Cs, Be, Sn, Ga, Ta>Nb, B, P, and F. We focus here on the LCT pegmatites of the Carolina Tin-Spodumene Belt (CTSB) situated in the Kings Mountain Shear Zone, which extends from South Carolina into North Carolina. The CTSB hosts both barren and fertile pegmatites, with Li-enriched pegmatites containing spodumene, K-feldspar, albite, quartz, muscovite, and beryl. We illustrate how handheld LIBS analysis can be used for real-time Li analysis in the field at a historically important CTSB pegmatite locality in Gaston County, N.C. in four contexts: (i) elemental detection and identification; (ii) microchemical mapping; (iii) depth profiling; and (iv) elemental quantitative analysis. Finally, as an example of a practical exploration application, we describe how handheld LIBS can be used to measure K/Rb ratios and Li contents of muscovite and rapidly determine the degree of pegmatite fractionation. This study demonstrates the potential of handheld LIBS to drastically reduce the time necessary to acquire geochemical data relevant to acquiring compositional information for pegmatites during a Li pegmatite exploration program.

Considerations in Applying Neutron Depth Profiling (NDP) to Li-Ion Battery Research

Li distribution within micron-scale battery electrode materials is quantified with neutron depth profiling (NDP). This method allows the determination of intra- and inter-electrode parameters such as lithiation efficiency, electrode morphology...

Influence of Different Ester Side Groups in Polymers on the Vapor Phase Infiltration with Trimethyl Aluminum

The vapor phase infiltration (VPI) process of trimethyl aluminum (TMA) into poly(4-acetoxystyrene) (POAcSt), poly(nonyl methacrylate) (PNMA) and poly(tert-butyl methacrylate) (PtBMA) is reported. Depth-profiling X-ray photoelectron spectroscopy (XPS) measurements are used...

Comprehensive physical and electrical characterizations of NO nitrided SiO2/4H-SiC(1120) interfaces

Nitridation of SiO2/4H-SiC(1120) interfaces with post-oxidation annealing in an NO ambient (NO-POA) and its impact on the electrical properties were investigated. Sub-nm-resolution nitrogen depth profiling at the interfaces was conducted by using a scanning x-ray photoelectron spectroscopy microprobe. The results showed that nitrogen atoms were incorporated just at the interface and that interface nitridation proceeded much faster than at SiO2/SiC(0001) interfaces, resulting in a 2.3 times higher nitrogen concentration. Electrical characterizations of metal-oxide-semiconductor capacitors were conducted through capacitance-voltage (C–V) measurements in the dark and under illumination with ultraviolet light to evaluate the electrical defects near the conduction and valence band edges and those causing hysteresis and shifting of the C–V curves. While all of these defects were passivated with the progress of the interface nitridation, excessive nitridation resulted in degradation of the MOS capacitors. The optimal conditions for NO-POA are discussed on the basis of these experimental findings.

Stabilizing effects of Ag doping on structure and thermal stability of FeN thin films

In this work, we investigated the effect of Ag doping (2-20 at.%) on the phase formation of iron mononitride (FeN) thin films. Together with deposition of FeN using reactive dc magnetron sputtering, Ag was also co-sputtered at various doping levels between 2-20 at.%. We found that doping of Ag around 5 at.% is optimum to not only improve the thermal stability of FeN but also to reduce intrinsic defects that are invariably present in (even in epitaxial) FeN. Conversion electron Mössbauer spectroscopy and N K-edge x-ray near edge absorption measurements clearly reveal a reduction of defects in Ag doped FeN samples. Moreover, Fe self-diffusion measurements carried out using secondary ion mass spectroscopy depth-profiling and polarized neutron reflectivity in 57Fe enriched samples exhibit an appreciable reduction in Fe self-diffusion in Ag doped FeN samples. Ag being immiscible with Fe and non-reactive with N, occupies grain-boundary positions as nanoparticles and prohibits the fast Fe self-diffusion in FeN.