Chemometric analysis of multiple species of Bacillus bacterial endospores using infrared spectroscopy: Discrimination to the strain level

Previous work using infrared spectroscopy has shown potential for rapid discrimination between bacteria in either their sporulated or vegetative states, as well as between bacteria and other common interferents. For species within one physiological state, however, distinction is far more challenging, and requires chemometrics. In the current study, we have narrowed the field of study by eliminating the confounding issues of vegetative cells as well as growth media and focused on using IR spectra to distinguish only between different species all in the sporulated state. Using principal component analysis (PCA) and a classification method based upon similarity measurements, we demonstrate a successful identification rate to the species level of 85% for Bacillus spores grown and sporulated in a glucose broth medium.     

A multispectrum analysis of the ν2 band of HCN: Part I. Intensities, broadening, and shift coefficients

Absolute intensities, self- and air-broadening coefficients, self- and air-induced shift coefficients and their temperature dependences have been determined for lines belonging to the P- and R-branches of the ν₂ band of H¹²C¹⁴N centered near 712 cm⁻¹. Infrared spectra of HCN in the 14-μm region were obtained at high resolution (0.002-0.008 cm⁻¹) using two different Fourier transform spectrometers (FTS), the McMath-Pierce FTS at the National Solar Observatory on Kitt Peak and the Bruker IFS 120HR FTS at the Pacific Northwest National Laboratory. Spectra were recorded with 99.8% pure HCN as well as lean mixtures of HCN in air at various temperatures ranging between +26 and −60 °C. A multispectrum nonlinear least squares technique was used to fit selected intervals of 36 spectra simultaneously to obtain the line positions, intensities, broadening, and shift parameters. The measured line intensities were analyzed to determine the vibrational band intensity and the Herman-Wallis coefficients. The measured self-broadening coefficients vary between 0.2 and 1.2 cm⁻¹ atm⁻¹ at 296 K, and the air-broadening coefficients range from 0.08 to 0.14 cm⁻¹ atm⁻¹ at 296 K. The temperature dependence exponents of self-broadening range from 1.46 to −0.12 while the corresponding exponents for air broadening vary between 0.58 and 0.86. The present measurements are the first known determination of negative values for the temperature dependence exponents of HCN-broadening coefficients. We were able to support our self-broadening measurements with appropriate theoretical calculations. Our present measurements are compared, where possible, with previous measurements for this and other HCN bands, as well as the parameters that are included in the 2000 and 2004 editions of the high-resolution transmission (HITRAN) database.     

Self-absorption effects on alpha-induced atmospheric nitrogen fluorescence yield

Nitrogen fluorescence induced by radiation can be used to detect the presence of radioactive contamination in the environment. Contamination quantification from the fluorescence signal requires: the source’s effective alpha spectrum; the specific radiation quantum fluorescence efficiency; optical attenuation length in air of the fluorescence signal; the absolute throughput and quantum efficiency of the optical instrumentation; calibration of the instrumentation; and radiation transport modeling of the “effective” array exposure rate given the alpha particle spectrum. Field testing conducted on optical instrumentation measured the nitrogen fluorescence yield generated by ²⁴¹Am alpha emissions. Laboratory studies of ²⁴¹Am via alpha spectrometry determined whether the presence of solids on source surfaces produced sufficient self-absorption to decrease fluorescence. Results from the laboratory studies provided correction to the effective alpha-source activity values in a model of the earlier optical-sensor field measurements, and determined the air fluorescence efficiency of alpha particles generated by the ²⁴¹Am sources used in the field experiments.     

Phase-field simulations of Te-precipitate morphology and evolution kinetics in Te-rich CdTe crystals

Te precipitates are one of principal defects that form during cooling of melt-grown CdTe or CZT crystals when grown Te-rich. Many factors such as the kinetic properties of intrinsic point defects (vacancy, interstitial, and antisite defects); stresses associated with the lattice mismatch between precipitate and matrix; temperature gradients and extended defects (dislocations, twin and grain boundaries); non-stoichiometric composition; thermal treatment history all affect the formation and growth/dissolution of Te precipitates in CdTe. A good understanding of these effects on Te precipitate evolution kinetics is technically important in order to optimize material processing and obtain high-quality crystals. This research develops a phase-field model capable of investigating the evolution of coherent Te precipitates in a Te-rich CdTe crystal undergoing cooling from the melt. Cd vacancies and Te interstitials are assumed to be the dominant diffusing species in the system, which is in two-phase equilibrium (matrix CdTe and liquid Te inclusion) at high temperatures and three-phase equilibrium (matrix CdTe, Te precipitate, and void) at low temperatures. Using available thermodynamic and kinetic data from experimental phase diagrams and thermodynamic calculations, the effects of Te interstitial and Cd vacancy mobility, cooling rates and stresses on Te precipitate, and void evolution kinetics are investigated.     

Online Bounded Coloring of Permutation and Overlap Graphs

We consider a track assignment problem in a train depot leading to an online bounded coloring problem on permutation graphs or on overlap graphs. For permutation graphs we study the competitiveness of a First Fit-based algorithm and we show it matches the competitive ratio of the problem. For overlap graphs, even the unbounded case does not admit a constant competitive ratio.     

Recent developments in and applications of resonance ionization mass spectrometry

Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 10⁶ atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. ^236–244Pu, ^89,90Sr and ⁹⁹Tc in environmental samples are described, and the application of RIMS to the ultrarare long-lived radioisotope ⁴¹Ca for cosmochemical, radiodating and medical purposes are presented. Received: 17 December 1998 / Revised: 11 February 1999/Accepted: 18 February 1999     

Screening of potential sites for undeclared nuclear facilities in environmental monitoring for nuclear proliferation

The sensitivity of environmental sampling and analysis for the estimated atmospheric concentrations of radionuclides in effluents from clandestine nuclear facilities may require many sampling sites and exorbitant costs to monitor such large areas. An assessment has been made of the key factors necessary to support the operation of a nuclear facility, e.g., the existence of a nearby transportation network, main electrical power supply, and population centers. Screening, the subject of this paper, evaluates how cartographic data and satellite imagery can be used to identify areas most capable of supporting undeclared nuclear operations. As a result, large geographical areas can be eliminated from environmental monitoring and sampling. This leads to reduced costs, a reduction in the number of sampling sites required, and a reduction in the overall level of effort required to accomplish effective environmental monitoring. The screening methodology and techniques are described and examples given.     

First Measurement of the Nuclear Charge Radii of Short-Lived Lithium Isotopes

A novel method for the determination of nuclear charge radii of lithium isotopes is presented. Precise laser spectroscopic measurements of the isotope shift in the lithium 2s → 3s transition are combined with highly accurate atomic physics calculation of the mass dependent isotope shift to extract the charge-distribution-sensitive information. This approach has been used to determine the charge radii of ^8,9Li for the first time.     

Magnetic coupling mechanism in A-site ordered perovskite YMn3Al4O12: Extended (Mn–O)–(O–Mn) superexchange

A-site ordered double perovskites hold promise for potential device applications, where how their magnetic objects actually interact is known to influence functionality. Here, we investigate, by first-principles calculations, electronic and magnetic properties of YMn₃Al₄O₁₂, and demonstrate that it is an antiferromagnetic insulator. Our calculations reveal the extended (Mn–O)–(O–Mn) superexchange as a primary magnetic coupling mechanism in YMn₃Al₄O₁₂, and further identify the O–O bonds as a key factor to dominate coupling strength. We suggest that this superexchange mode is the origin of antiferromagnetic behavior, opening an additional avenue to understand magnetic coupling in A-site ordered double perovskites.     

Analysis of realistic rough surface for its globally dominant parameters using continuous wavelets

Continuous Morlet and Mexican hat wavelets are used to analyze a highly irregular rough surface replicated from real turbine blades which are roughened by deposi-tion of foreign materials. The globally dominant aspect ratio, length scale, and orientation of the roughness elements are determined. These parameters extracted from this highly irregular rough surface are important for the future studies of their effects on turbulent flows over this kind of rough surfaces encountered in Washington aerospace and power generating industries.