Image-guided optical spectroscopy provides molecular-specific information in vivo: MRI-guided spectroscopy of breast cancer hemoglobin, water, and scatterer size

A multimodality instrument that integrated optical or near-infrared spectroscopy into a magnetic resonance imaging (MRI) breast coil was used to perform a pilot study of image-guided spectroscopy on cancerous breast tissue. These results are believed to be the first multiwavelength spectroscopic images of breast cancer using MRI-guided constraints, and they show the cancer tumor to have high hemoglobin and water values, decreased oxygen saturation, and increased subcellular granularity. The use of frequency-domain diffuse tomography methods at many wavelengths provides the spectroscopy required for recovering maps of absorbers and scattering spectra, but the integration with MRI allows these data to be recovered on an image field that preserves high resolution and fuses the two data sets together. Integration of molecular spectroscopy into standard clinical MRI can be achieved with this approach to spectral tomography.     

Numerical and experimental studies of gravity effect on the mechanism of lunar excavations

In this paper, the mechanism of soil excavation in partial gravity conditions is investigated by experimental model and numerical study. Experiments were conducted in a parabolic flight, which generated different gravity conditions, focusing on the bearing capacity problem using two soil samples: Toyoura sand and Japanese lunar soil simulant (FJS-1). Corresponding numerical studies were performed by the discrete element method (DEM) for reduced gravity conditions. Herein, the DEM method was modified to include the apparent cohesion that was found in the lunar soil simulant. Two case studies were investigated by the numerical simulations: bearing capacity and soil pushing (as by a bulldozer), and for the former case comparison was made with experiment. Results show that the gravity greatly affects the ultimate bearing capacity of the Toyoura sand; however, such effect becomes insignificant in the lunar soil when the gravity is small or the soil was densely packed. By using the numerical model, this paper suggests that the ultimate bearing capacity observed in the lunar soil simulant was dominated by the apparent cohesive component, rather than gravity or friction. However, gravity causes similar effects on both soil models in the soil pushing problem.     

Synthesis and characterization of (Me3Si)2AsCH2RCH2As(SiMe3)2 (R = CH2, SiME2) and

The synthesis and characterization of (Me₃Si)₂AsCH₂RCH₂As(SiMe₃)₂ [R = CH₂ ( 1 ), SiMe₂ ( 2 )] is described. Compound 1 reacts with four equivalents of Ph₂GaCl to produce (3), whose structure was deduced by use of ¹H and ¹³C{¹H} NMR spectroscopy.     

Application of nonresonance excitation to ion trap tandem mass spectrometry and selected ejection chemical ionization

Nonresonance excitation is a universal ion excitation and ejection method in which increased ion kinetic energy is achieved by the combination of an axial dc dipole and the rf trapping fields. The method does not require the applied excitation frequency to match with the secular frequency of the precursor ions to effect collision-induced dissociation (CID) for tandem mass spectrometry applications. Therefore, it is free of the effects of secular frequency changes caused by space-charge and simplifies the optimization of tandem mass spectrometry parameters when combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). Computer simulations show that in contrast to the resonance excitation process, the nonresonance excitation process is able to accelerate thermal ions to kinetic energies in excess of 40 eV in a few microseconds. Based on simulations, we expect that the rapid deposition of energy by this method may allow the study, in ion traps, of high energy decomposition channels of precursor ions with multiple decomposition channels. Furthermore, the method is able to simultaneously excite multiple precursor ions, for example, excite both analyte and its coeluting isotopically labeled internal standard for GC-MS/MS analysis. A GC-MS/MS analysis of 100 pg of n-butylbenzene is demonstrated with a signal-to-noise ratio of 3624, which is over an order of magnitude higher than the signal-to-noise ratio of 345 obtained by full scan gas chromatography-mass spectrometry. In addition, the nonresonance excitation method can be used as a low pass mass filter in the chemical ionization (CI) mode to eject undesired fragment ions that result from direct electron ionization. This new CI method, selected ejection chemical ionization, can produce a CI spectrum without contamination of sample fragment ions from electron ionization.     

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2‐propoxyethanol

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of 2‐propoxyethanol (2PEOH, CH₃CH₂CH₂OCH₂CH₂(OH)). 2PEOH reacts with OH with a bimolecular rate constant of (21.4 ± 6.0) × 10⁻¹² cm³molecule⁻¹s⁻¹ at 297 ± 3 K and 1 atm total pressure, which is a little larger than previously reported [1]. Assuming an average OH concentration of 1 × 10⁶ molecules cm⁻³, an atmospheric lifetime of 13 h is calculated for 2PEOH. In order to more clearly define this hydroxy ether's atmospheric reaction mechanism, an investigation into the OH + 2PEOH reaction products was also conducted. The OH + 2PEOH reaction products and yields observed were: propyl formate (PF, 47 ± 2%, CH₃CH₂CH₂OC(O)H), 2 propoxyethanal (CH₃CH₂CH₂OCH₂C(O)H 15 ± 1%), and 2‐ethyl‐1,3‐dioxolane (5.4 ± 0.4%). The 2PEOH reaction mechanism is discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground‐level ozone‐forming potential calculations (incremental reactivity) [2]. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 315–322, 1999     

The hydroxyl radical reaction rate constant and products of methyl isobutyrate

The relative rate technique has been used to measure the rate coefficient for the reaction of the hydroxyl radical (OH) with methyl isobutyrate (MIB, (CH₃)₂ CHC(O) O CH₃) to be (1.7 ± 0.4) × 10⁻¹²cm³molecule⁻¹s⁻¹ at 297 ± 3 K and 1 atmosphere total pressure. To more clearly define MIB's atmospheric degradation mechanism, the products of the OH + MIB reaction were also determined. The observed products and their yields were: acetone (97 ± 1%, (CH₃)₂C(O)) and methyl pyruvate (MP, 3.3 ± 0.3%, CH₃C(O)C(O) O CH₃). The products' formation pathways are discussed in light of current understanding of the atmospheric chemistry of oxygenated organic compounds. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 551–557, 1999     

Synthesis and characterization of [(Me3SiCH2)2GaP(SiMe3)2]2, an example of a gallium-phosphorus dimer obtainable only through an indirect reaction pathway

The dimeric gallium-phosphorus compound [(Me₃Si-CH₂)₂GaP(SiMe₃)₂]₂ ( 1 ) was prepared from the 1:1 mole ratio lithium-halide elimination reaction of (Me₃SiCH₂)₂GaP(SiMe₃)₂Ga(CH₂SiMe₃)₂Cl with LiP-(SiMe₃)₂ in benzene solution and has been characterized through multinuclear solution NMR, partial elemental analysis, and single-crystal X-ray analysis. Compound 1 could not be obtained from the direct reactions of (Me₃SiCH₂)₂GaCl with P(SiMe₃)₃ or LiP(SiMe₃)₂. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:147–150, 1998