Pacific Northwest National Laboratory

About: Pacific Northwest National Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Catalysis & Aerosol. The organization has 11581 authors who have published 27934 publications receiving 1120489 citations. The organization is also known as: PNL & PNNL.

Recommendations for reporting ion mobility Mass Spectrometry measurements

Abstract: Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method‐dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so.

A framework for benchmarking land models

Abstract: Land models, which have been developed by the modeling community in the past few decades to predict fu- ture states of ecosystems and climate, have to be critically evaluated for their performance skills of simulating ecosys- tem responses and feedback to climate change. Benchmark- ing is an emerging procedure to measure performance of models against a set of defined standards. This paper pro- poses a benchmarking framework for evaluation of land model performances and, meanwhile, highlights major chal- lenges at this infant stage of benchmark analysis. The frame- work includes (1) targeted aspects of model performance

Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

Abstract: Ambient ionization imaging mass spectrometry is uniquely suited for detailed spatially resolved chemical characterization of biological samples in their native environment. However, the spatial resolution attainable using existing approaches is limited by the ion transfer efficiency from the ionization region into the mass spectrometer. Here, we present a first study of ambient imaging of biological samples using nanospray desorption ionization (nano-DESI). Nano-DESI is a new ambient pressure ionization technique that uses minute amounts of solvent confined between two capillaries comprising the nano-DESI probe and the solid analyte for controlled desorption of molecules present on the substrate followed by ionization through self-aspirating nanospray. We demonstrate highly sensitive spatially resolved analysis of tissue samples without sample preparation. Our first proof-of-principle experiments indicate the potential of nano-DESI for ambient imaging with a spatial resolution of better than 12 μm. The si...

Variational Transition State Theory with Multidimensional Tunneling

Abstract: This review describes the application of variational transition state theory (VTST) to the calculation of chemical reaction rates In 1985 two of us, together with Alan D Isaacson, wrote a book chapter on this subject entitled “Generalized Transition State Theory” for the multi-volume series entitled Theory of Chemical Reaction Dynamics1 Since that time, variational transition state theory has undergone important improvements due mainly to the ability of this theory to adapt to more challenging problems For instance, the 1985 chapter mainly describes the application of VTST to bimolecular reactions involving 3–6 atoms, which were the state-of-the-art at that moment The study of those reactions by VTST dynamics depended on the construction of an analytical potential energy surface (PES) Nowadays, thanks to the development of more efficient algorithms and more powerful computers, the situation is completely different, and most rate calculations are based on “on the fly” electronic structure calculations, which together with hybrid approaches, like combined quantum mechanical molecular mechanical methods (QM/MM), allow researchers to apply VTST to systems with hundreds or even tens of thousands of atoms Three other major advances since 1985 are that transition state dividing surfaces can now be defined much more realistically, more accurate methodsmore » have been developed to include multidimensional quantum mechanical tunneling into VTST, and the theory has also been extended to reactions in condensed phases« less