Jesse L. Beauchamp

Bio: Jesse L. Beauchamp is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Ion cyclotron resonance & Ion. The author has an hindex of 55, co-authored 275 publications receiving 10971 citations. Previous affiliations of Jesse L. Beauchamp include Varian Associates & KAIST.

Ion Cyclotron Resonance Spectroscopy

Abstract: Ion cyclotron resonance spectroscopy has met with such wide acceptance that research groups utilizing this relatively new experimental technique now likely outnumber research groups which have used more traditional techniques, such as high pressure mass spectrometry, for the study of ion-molecule reactions. Since the previous review of ion-molecule reactions in Volume 1 9 o f the Annual Review of Physical Chemistry (1) there has been considerable development in the field. This development has been distributed among studies conducted with ion cyclotron resonance spectroscopy, drift tubes, high pressure mass spectrometry, flowing afterglows, tandem mass spectrometry, and beam experiments. Chemical applications of these techniques have been the subject of numerous recent reviews and monographs authored by principals in these investigations. In the present review an attempt will be made to chron­ icle the development of ion cyclotron resonance spectroscopy. Since this is the first review of the subject to appear in these volumes, the present article purports to be not only a review but an introduction as well. Sufficient back­ ground is developed to allow for a critical review of current experimentation in this field of endeavor. Ion cyclotron resonance spectroscopy is finding applications to the study of an increasing number of problems of general chemical interest. Recent developments promise an even wider range of applications. The technique is well suited for the routine study of ion-molecule reactions, which are readily identified using double resonance experiments (2). The identification of an ion-molecule reaction in a double resonance experiment provides useful information relating to the thermochemical properties of both ions and neu­ trals [including acidities (3-8) and basicities (9, 10) determined in the absence of complicating solvation phenomena], the identification of isomeric ion structures (1 1-16), and information concerning reaction mechanisms (17-23). Ion ejection techniques (11, 24) allow for the determination of product ion distributions in ion-molecule reactions even when other processes, such as

Particle phase acidity and oligomer formation in secondary organic aerosol.

Abstract: A series of controlled laboratory experiments are carried out in dual Teflon chambers to examine the presence of oligomers in secondary organic aerosols (SOA) from hydrocarbon ozonolysis as well as to explore the effect of particle phase acidity on SOA formation. In all seven hydrocarbon systems studied (i.e., α-pinene, cyclohexene, 1-methyl cyclopentene, cycloheptene, 1-methyl cyclohexene, cyclooctene, and terpinolene), oligomers with MW from 250 to 1600 are present in the SOA formed, both in the absence and presence of seed particles and regardless of the seed particle acidity. These oligomers are comparable to, and in some cases, exceed the low molecular weight species (MW < 250) in ion intensities in the ion trap mass spectra, suggesting they may comprise a substantial fraction of the total aerosol mass. It is possible that oligomers are widely present in atmospheric organic aerosols, formed through acid- or base-catalyzed heterogeneous reactions. In addition, as the seed particle acidity increases, larger oligomers are formed more abundantly in the SOA; consequently, the overall SOA yield also increases. This explicit effect of particle phase acidity on the composition and yield of SOA may have important climatic consequences and need to be considered in relevant models.

The chemistry of atomic transition-metal ions: insight into fundamental aspects of organometallic chemistry

Abstract: For species as simple as atomic transition-metal ions, organometallic transformations usually involve multistep processes. These transformations have been studied with the entire arsenal of experimental techniques developed for the study of ion-molecule chemistry: conventional tandem mass spectrometry, flowing afterglow (FA) techniques, and ion cyclotron resonance (ICR) mass spectrometry and its Fourier transform adaptation (FT-ICR). In this Account, the authors limit ourselves to those methods in which motion along the reaction coordinate is the key dynamic variable that can be controlled as reactants approach and measured as the products recede. In our laboratories, guided ion beam techniques have been developed and highly refined for studies of the variation of reaction probabilities with E{sub T}. Complementing this work are measurements of product kinetic energy release distributions (KERDs).

Electronic structure considerations for methane activation by third-row transition-metal ions

Abstract: Methane is spontaneously dehydrogenated in the gas phase by many metal ions of the 5d transition series. In most cases, the MCH{sub 2}{sup +} produced undergoes further reactions, leading eventually to products such as WC{sub 8}H{sub 16}{sup +}. The reactivity of the third-row transition-metal ions, both bare and with simple ligands, may be explained in terms of electronic structure considerations. Promotion energy, exchange energy, and the relative and absolute sizes of the valence s and d orbitals all appear to be important.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Efficient diffuse function‐augmented basis sets for anion calculations. III. The 3‐21+G basis set for first‐row elements, Li–F

Abstract: The relatively small diffuse function-augmented basis set, 3-21+G, is shown to describe anion geometries and proton affinities adequately. The diffuse sp orbital exponents are recommended for general use to augment larger basis sets.

Microfluidics: Fluid physics at the nanoliter scale

Abstract: Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

The formation, properties and impact of secondary organic aerosol: current and emerging issues

Abstract: Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.