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Papers by Allen Thomas

Research paper thumbnail of Multivariate analysis in weed science research

Research paper thumbnail of The potential of using laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOF-MS) in the forensic analysis of micro debris

Talanta, 2005

The majority of crimes result in the generation of some form of physical evidence, which is avail... more The majority of crimes result in the generation of some form of physical evidence, which is available for collection by crime scene investigators or police. However, this debris is often limited in amount as modern criminals become more aware of its potential value to forensic scientists. The requirement to obtain robust evidence from increasingly smaller sized samples has required refinement and modification of old analytical techniques and the development of new ones. This paper describes a new method for the analysis of oxy-acetylene debris, left behind at a crime scene, and the establishment of its co-provenance with single particles of equivalent debris found on the clothing of persons of interest (POI).

Research paper thumbnail of Analysis of diamonds and indicator minerals for diamond exploration by laser ablation?inductively coupled plasma mass spectrometry

Analyst, 1995

A method has been developed, using laser ablation–inductively coupled plasma mass spectrometry (L... more A method has been developed, using laser ablation–inductively coupled plasma mass spectrometry (LA–ICP-MS), for the semiquantitative determination of 43 elements in diamonds, chromites and garnets. Samples of diamonds from five countries have been ...

Research paper thumbnail of The Catalytic Asymmetric Aminohydroxylation of Unsaturated Phosphonates

Journal of Organic Chemistry, 1999

The solvents, CH 3 CN for sulfonamides and n-PrOH for carbamates, were not interchangeable. Use o... more The solvents, CH 3 CN for sulfonamides and n-PrOH for carbamates, were not interchangeable. Use of n-PrOH resulted in higher ee's in both sulfonamide and carbamate AA products (eg, 2a was generated in 90% ee using n-PrOH). However, utilization of n-PrOH ...

Research paper thumbnail of Isotope effects and the distinction between synchronous, asynchronous, and stepwise Diels–Alder reactions

Tetrahedron, 2001

A variety of symmetrical or nearly symmetrical Diels–Alder reactions are studied by a combination... more A variety of symmetrical or nearly symmetrical Diels–Alder reactions are studied by a combination of experimental isotope effects, theoretical calculations, and rate observations. Becke3LYP calculations predicted highly asynchronous transition structures for Diels–Alder reactions of bis(boryl)acetylenes, dialkyl acetylenedicarboxylates, triazolinediones, and dialkyl maleates. Rate observations and kinetic isotope effects are consistent with these predictions, though the experimental support for the calculated structures is notably ambiguous in some cases. A concerted mechanism is supported for the retro-Diels–Alder reaction of norbornene. Overall, Diels–Alder reactions appear to be only very weakly biased toward synchronous transition states.Graphic

Research paper thumbnail of Experimental and Theoretical Kinetic Isotope Effects for Asymmetric Dihydroxylation. Evidence Supporting a Rate-Limiting “(3 + 2)” Cycloaddition

Journal of The American Chemical Society, 1997

... Mehmet Ali Celik, Robin Haunschild and Gernot Frenking. Organometallics 2010 29 (7), 1560-156... more ... Mehmet Ali Celik, Robin Haunschild and Gernot Frenking. Organometallics 2010 29 (7), 1560-1568. ... K. Barry Sharpless, Willi Amberg, Youssef L. Bennani, Gerard A. Crispino, Jens Hartung, Kyu Sung Jeong, Hoi Lun Kwong, Kouhei Morikawa, Zhi Min Wang,. ...

Research paper thumbnail of High-Precision Simultaneous Determination of Multiple Small Kinetic Isotope Effects at Natural Abundance

Journal of The American Chemical Society, 1995

Research paper thumbnail of How to Build a System that Manages Bioinformatics Content

We discuss how to build systems with sophisticated features based on a core set of bioinformatics... more We discuss how to build systems with sophisticated features based on a core set of bioinformatics tool s. Beside from being the front-end server to the core analyses, such a system can manage users, bioinform atics content and shared data. Using tools available in the open-source community, we show how to build a syste m with such sophisticated features with

Research paper thumbnail of Multivariate analysis in weed science research

Research paper thumbnail of The potential of using laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOF-MS) in the forensic analysis of micro debris

Talanta, 2005

The majority of crimes result in the generation of some form of physical evidence, which is avail... more The majority of crimes result in the generation of some form of physical evidence, which is available for collection by crime scene investigators or police. However, this debris is often limited in amount as modern criminals become more aware of its potential value to forensic scientists. The requirement to obtain robust evidence from increasingly smaller sized samples has required refinement and modification of old analytical techniques and the development of new ones. This paper describes a new method for the analysis of oxy-acetylene debris, left behind at a crime scene, and the establishment of its co-provenance with single particles of equivalent debris found on the clothing of persons of interest (POI).

Research paper thumbnail of Analysis of diamonds and indicator minerals for diamond exploration by laser ablation?inductively coupled plasma mass spectrometry

Analyst, 1995

A method has been developed, using laser ablation–inductively coupled plasma mass spectrometry (L... more A method has been developed, using laser ablation–inductively coupled plasma mass spectrometry (LA–ICP-MS), for the semiquantitative determination of 43 elements in diamonds, chromites and garnets. Samples of diamonds from five countries have been ...

Research paper thumbnail of The Catalytic Asymmetric Aminohydroxylation of Unsaturated Phosphonates

Journal of Organic Chemistry, 1999

The solvents, CH 3 CN for sulfonamides and n-PrOH for carbamates, were not interchangeable. Use o... more The solvents, CH 3 CN for sulfonamides and n-PrOH for carbamates, were not interchangeable. Use of n-PrOH resulted in higher ee's in both sulfonamide and carbamate AA products (eg, 2a was generated in 90% ee using n-PrOH). However, utilization of n-PrOH ...

Research paper thumbnail of Isotope effects and the distinction between synchronous, asynchronous, and stepwise Diels–Alder reactions

Tetrahedron, 2001

A variety of symmetrical or nearly symmetrical Diels–Alder reactions are studied by a combination... more A variety of symmetrical or nearly symmetrical Diels–Alder reactions are studied by a combination of experimental isotope effects, theoretical calculations, and rate observations. Becke3LYP calculations predicted highly asynchronous transition structures for Diels–Alder reactions of bis(boryl)acetylenes, dialkyl acetylenedicarboxylates, triazolinediones, and dialkyl maleates. Rate observations and kinetic isotope effects are consistent with these predictions, though the experimental support for the calculated structures is notably ambiguous in some cases. A concerted mechanism is supported for the retro-Diels–Alder reaction of norbornene. Overall, Diels–Alder reactions appear to be only very weakly biased toward synchronous transition states.Graphic

Research paper thumbnail of Experimental and Theoretical Kinetic Isotope Effects for Asymmetric Dihydroxylation. Evidence Supporting a Rate-Limiting “(3 + 2)” Cycloaddition

Journal of The American Chemical Society, 1997

... Mehmet Ali Celik, Robin Haunschild and Gernot Frenking. Organometallics 2010 29 (7), 1560-156... more ... Mehmet Ali Celik, Robin Haunschild and Gernot Frenking. Organometallics 2010 29 (7), 1560-1568. ... K. Barry Sharpless, Willi Amberg, Youssef L. Bennani, Gerard A. Crispino, Jens Hartung, Kyu Sung Jeong, Hoi Lun Kwong, Kouhei Morikawa, Zhi Min Wang,. ...

Research paper thumbnail of High-Precision Simultaneous Determination of Multiple Small Kinetic Isotope Effects at Natural Abundance

Journal of The American Chemical Society, 1995

Research paper thumbnail of How to Build a System that Manages Bioinformatics Content

We discuss how to build systems with sophisticated features based on a core set of bioinformatics... more We discuss how to build systems with sophisticated features based on a core set of bioinformatics tool s. Beside from being the front-end server to the core analyses, such a system can manage users, bioinform atics content and shared data. Using tools available in the open-source community, we show how to build a syste m with such sophisticated features with

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