The stochastic separatrix and the reaction coordinate for complex systems

We present a new approach to the identification of degrees of freedom which comprise a reaction coordinate in a complex system. The method begins with the generation of an ensemble of reactive trajectories. Each trajectory is analyzed for its equicommittor position or transition state; then the transition state ensemble is identified as the stochastic separatrix. Numerical analysis of the points along the separatrix for variability of coordinate location correctly identifies the components of the reaction coordinate in a test system of a double well coupled to a promoting vibration and a bath of linearly coupled oscillators.

Annealing of nanoindentation-induced high pressure crystalline phases created in crystalline and amorphous silicon

Thermally induced phase transformation of Si-III/Si-XII zones formed by nanoindentation has been studied during low temperature (200<T<300 °C) thermal annealing by Raman microspectroscopy and transmission electron microscopy. Two sizes of spherical indenter tips have been used to create substantially different volumes of phase transformed zones in both crystalline (c-Si) and amorphous silicon (a-Si) to study the zone size and starting matrix effects. The overall transformation is from Si-III/XII to poly- or nanocrystalline Si-I through intermediate phases of Si-XIII and Si-IV. Attempts have been made to determine the exact transformation pathways. Two scenarios are possible: either Si-XII first transforms to Si-III before transforming to Si-I through the intermediate phases or that Si-XII goes through the intermediate phases while Si-III transforms directly to Si-I. Finally, the phase transformations are slower in the larger indents and the starting matrix (crystalline or amorphous) has a substantial effe...

TIGER2: An improved algorithm for temperature intervals with global exchange of replicas

Electromagnetic source transformations using superellipse equations

Transformation optics can be used to design media with unique properties that alter the behavior of electromagnetic waves in passive space and recently in space containing source distributions. We present source transformations where current from a linear radiator is spread over a cylindrical shell with various cross sections. The semianalytic transformations are based on superellipse equations. Finite-element full-wave simulations of transformations from a dipole to a cylinder, diamond-shaped cylinder, and flattened cylinder are presented. The radiation pattern of the dipole seen by an outside observer is replicated in all cases demonstrating the potential applicability of source transformations to conformal antenna design. © 2009 American Institute of Physics. DOI: 10.1063/1.3130182

Quantum metrology with Bose-Einstein condensates

We show how a generalized quantum metrology protocol can be implemented in a two-mode Bose-Einstein condensate of n atoms, achieving a sensitivity that scales better than 1/n and approaches 1/n^(3/2) for appropriate design of the condensate.

Quantum metrology from an information theory perspective

Questions about quantum limits on measurement precision were once viewed from the perspective of how to reduce or avoid the effects of quantum noise. With the advent of quantum information science came a paradigm shift to proving rigorous bounds on measurement precision. These bounds have been interpreted as saying, first, that the best achievable sensitivity scales as 1/n, where n is the number of particles one has available for a measurement and, second, that the only way to achieve this Heisenberg-limited sensitivity is to use quantum entanglement. We review these results and show that using quadratic couplings of n particles to a parameter to be estimated, one can achieve sensitivities that scale as 1/n^2 if one uses entanglement, but even in the absence of any entanglement at any time during the measurement protocol, one can achieve a super-Heisenberg scaling of 1/n^(3/2)

Time-Resolved Spectroscopy of RHESSI GRBs

Field Air Sampling and Simultaneous Chemical and Sensory Analysis of Livestock Odorants with Sorbent Tube GC-MS∕Olfactometry

Characterization and quantification of livestock odorants is one of the most challenging analytical tasks because odor-causing gases are very reactive, polar and often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this research was to develop a novel analytical method for characterization of the livestock odorants including their odor character, odor intensity, and hedonic tone and to apply this method for quantitative analysis of the key odorants responsible for livestock odor. Sorbent tubes packed with Tenax TA were used for field sampling. The automated one-step thermal desorption module coupled with multidimensional gas chromatography-mass spectrometry/olfactometry system was used for simultaneous chemical and odor analysis. Fifteen odorous VOCs and semi-VOCs identified from different livestock species operations were quantified. Method detection limits ranges from 40 pg for skatole to 3590 pg for acetic acid. In addition, odor character, odor intensity and hedonic tone associated with each of the target odorants are also analyzed simultaneously. We found that the mass of each VOCs in the sample correlates well with the log stimulus intensity. All of the correlation coefficients (R2) are greater than 0.74, and the top 10 correlation coefficients were greater than 0.90. © 2009 American Institute of Physics.

Field Air Sampling with SPME for Ranking and Prioritization of Downwind Livestock Odors with MDGC-MS-Olfactometry

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is due to low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds and other gases. Many of these gases are odorous. Relatively little is known about the link between specific VOCs/gases and specifically, about the impact of specific odorants downwind from sources. In this research, solid phase microextraction (SPME) was used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranged from 20 min to 1 hr. Samples were analyzed using a commercial GC‐MS‐Olfactometry system. Odor profiling efforts were directed at odorant prioritization with respect to distance from the source. The results indicated the odor downwind was increasingly defined by a smaller number of high priority odorants. These ‘character defining’ odorants appear...

Analysis of Odor-Causing VOCs and Semi-VOCs Associated with Particulate Matter in Swine Barns Using SPME-GC-MS-Olfactometry

Swine operations can affect air quality by emissions of odor, volatile organic compounds (VOCs) and other gases, and particulate matter (PM). Particulate matter has been proposed to be an important pathway for carrying odor. However, little is known about the odor‐VOCs‐PM interactions. In this research, continuous PM sampling was conducted simultaneously with three collocated TEOM analyzers inside a 1000‐head swine finish barn located in central Iowa. Each TEOM (tapered element oscillating microbalance) was fitted with total suspended particulate (TSP), PM‐10, PM‐2.5 and PM‐1 preseparators. Used filters were stored in 40 mL vials and transported to the laboratory. VOCs adsorbed/absorbed to dust were allowed to equilibrate with vial headspace. Solid‐phase microextraction (SPME) Carboxen/polydimethylsiloxane(PDMS) 85 μm fibers were used to extract VOCs. Simultaneous chemical and olfactometry analyses of VOCs and odor associated with swine PM were completed using a gas chromatography‐mass‐olfactometry (GC‐MS...