@article{holmes_hawari_2014, title={Generation of an S(alpha, beta) Covariance Matrix by Monte Carlo Sampling of the Phonon Frequency Spectrum}, volume={118}, ISSN={["1095-9904"]}, DOI={10.1016/j.nds.2014.04.089}, abstractNote={Formats and procedures are currently established for representing covariances in the ENDF library for many reaction types. However, no standard exists for thermal neutron inelastic scattering cross section covariance data. These cross sections depend on the material's dynamic structure factor, or S ( α , β ) . The structure factor is a function of the phonon density of states (DOS). Published ENDF thermal neutron scattering libraries are commonly produced by modeling codes, such as NJOY/LEAPR, which utilize the DOS as the fundamental input and directly output the S ( α , β ) matrix. To calculate covariances for the computed S ( α , β ) data, information about uncertainties in the DOS is required. The DOS may be viewed as a probability distribution function of available atomic vibrational energy states in a solid. In this work, density functional theory and lattice dynamics in the harmonic approximation were used to simulate the structure of silicon dioxide ( α -quartz) to produce the DOS. A range for the variation in the partial DOS for silicon in α -quartz was established based on limits of variation in the crystal lattice parameters. Uncertainty in an experimentally derived DOS may also be incorporated with the same methodology. A description of possible variation in the DOS allowed Monte Carlo generation of a set of perturbed DOS spectra which were sampled to produce the S ( α , β ) covariance matrix for scattering with silicon in α -quartz. With appropriate sensitivity matrices, it is shown that the S ( α , β ) covariance matrix can be propagated to generate covariance matrices for integrated cross sections, secondary energy distributions, and coupled energy-angle distributions.}, journal={NUCLEAR DATA SHEETS}, author={Holmes, J. C. and Hawari, A. I.}, year={2014}, month={Apr}, pages={392–395} }
 @article{blair_leithold_ford_peeler_holmes_perkey_2003, title={The persistence of memory: The fate of ancient sedimentary organic carbon in a modern sedimentary system}, volume={67}, ISSN={["1872-9533"]}, DOI={10.1016/S0016-7037(02)01043-8}, abstractNote={The cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales. The burial of organic carbon occurs predominantly at sea in association with clay-sized particles derived from the erosion of uplifted continental rocks. It follows that the history of the fine-grained particles on land may bear on the nature of the organic carbon buried. In this study, the evolution of clay-associated organic matter was followed from bedrock source to the seabed in the Eel River sedimentary system of northern California using natural abundance 13C and 14C tracers. Approximately half of the fine-grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted Mesozoic-Tertiary Franciscan Complex of the watershed. The short residence time of friable soils on steep hill slopes, coupled with rapid sediment accumulation rates on the shelf-slope, act to preserve the ancient organic carbon. A comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope. The bimodal mixture of ancient and modern C in soils and sediments may be characteristic of many short, mountainous rivers. If the Eel River chemistry is typical of such rivers, more than 40 Tg of ancient organic C may be delivered to the world’s oceans each year. A flux of that magnitude would have a significant influence on marine and global C-cycles.}, number={1}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Blair, NE and Leithold, EL and Ford, ST and Peeler, KA and Holmes, JC and Perkey, DW}, year={2003}, month={Jan}, pages={63–73} }