Biodegradation of 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol

Call number: LD2668 .T4 CHE 1987 S56Master of ScienceChemical Engineerin

5-micron photometry of late-type dwarfs

We present narrowband-M photometry of nine low-mass dwarfs with spectral types ranging from M2.5 to L0.5. Combining the (L'-M') colours derived from our observations with data from the literature, we find colours consistent with a Rayleigh-Jeans flux distribution for spectral types earlier than M5, but enhanced F_3.8/F_4.7 flux ratios (negative (L'-M') colours) at later spectral types. This probably reflects increased absorption at M' due to the CO fundamental band. We compare our results against recent model predictions and briefly discuss the implications.Comment: accepted for the Astronomical Journa

A test for the search for life on extrasolar planets: Looking for the terrestrial vegetation signature in the Earthshine spectrum

We report spectroscopic observations (400 to 800nm, R = approx 100) of Earthshine in June, July and October 2001 from which normalised Earth albedo spectra have been derived. The resulting spectra clearly show the blue colour of the Earth due to Rayleigh diffusion in its atmosphere. They also show the signatures of oxygen, ozone and water vapour. We tried to extract from these spectra the signature of Earth vegetation. A variable signal (4 to 10 +/-3%) around 700nm has been measured in the Earth albedo. It is interpreted as being due to the vegetation red edge, expected to be between 2 to 10% of the Earth albedo at 700nm, depending on models. We discuss the primary goal of the present observations: their application to the detection of vegetation-like biosignatures on extrasolar planets.Comment: 7 pages, 7 figures. A&A, accepted 6 May 200

Voltage gated inter-cation selective ion channels from graphene nanopores

With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we demonstrate that nanopores introduced into graphene membranes, as large as 50 nm in diameter, exhibit inter-cation selectivity with a ~20x preference for K+ over divalent cations and can be modulated by an applied gate voltage. Liquid atomic force microscopy of the graphene devices reveals surface nanobubbles near the pore to be responsible for the observed selective behavior. Molecular dynamics simulations indicate that translocation of ions across the pore likely occurs via a thin water layer at the edge of the pore and the nanobubble. Our results demonstrate a significant improvement in the inter-cation selectivity displayed by a solid-state nanopore device and by utilizing the pores in a de-wetted state, offers an approach to fabricating selective graphene membranes that does not rely on the fabrication of sub-nm pores

1994 Northern Goshawk inventory on portions of Los Alamos National Laboratory, Los Alamos, NM

Northern goshawks (Accipiter gentilis) (hereafter referred to as goshawk) are large forest dwelling hawks. They are the largest species of the Accipiter genus which also includes sharp-shinned hawks (A. striatus) and the Cooper`s hawk (A. cooperii). Goshawks are holarctic in distribution and nest in coniferous, deciduous, and mixed species forests. In the southwest they primarily nest in ponderosa pine (Pinus ponderosa), mixed species, and spruce-fir forests. Goshawks may be declining in population and reproduction in the southwestern United States. In 1982 the USDA-Forest Service listed the goshawk as a {open_quotes}sensitive species{close_quotes} and in 1992 the U.S. Fish and Wildlife Service listed the goshawk as a {open_quotes}Category 2 species{close_quotes} in accordance with the Endangered Species Act. Reasons for the possible decline in goshawk populations include timber harvesting resulting in the loss of nesting habitat, toxic chemicals, and the effects of drought, fire, and disease. Thus, there is a need to determine their population status and assess impacts of management activities in potential goshawk habitat. Goshawk inventory was conducted during the 1993 nesting season with no adult goshawk responses detected within the LANL survey area. As noted by Sinton and Kennedy, these results may be interpreted in several ways: (1) no goshawk territory(ies) occur in the inventoried area; (2) goshawk territory(ies) exist but have failed prior to the survey and thus were not detected; or (3) territory(ies) exist and were successful but the goshawks did not respond to tapes or their responses were undetected by the observer. For those reasons, a goshawk inventory was conducted in 1994. This report summarizes the results of this inventory

Recovering the state sequence of hidden Markov models using mean-field approximations

Inferring the sequence of states from observations is one of the most fundamental problems in Hidden Markov Models. In statistical physics language, this problem is equivalent to computing the marginals of a one-dimensional model with a random external field. While this task can be accomplished through transfer matrix methods, it becomes quickly intractable when the underlying state space is large. This paper develops several low-complexity approximate algorithms to address this inference problem when the state space becomes large. The new algorithms are based on various mean-field approximations of the transfer matrix. Their performances are studied in detail on a simple realistic model for DNA pyrosequencing.Comment: 43 pages, 41 figure

24. GEOMAGNETIC-FIELD VARIATIONS RECORDED WITHIN DRILL PIPE AT SITE 865: IMPLICATIONS FOR PALEOMAGNETIC STUDIES 1

ABSTRACT In this study, we measured the magnetic field within the drill string with a wireline magnetometer log and estimated the effect that this magnetic-field might have on paleomagnetic core samples. Sharp decreases in the vertical magnetic-field component and sharp increases in the horizontal component were observed at approximately 10-m intervals, corresponding to the pipe joints. Induced magnetization by the greater thicknesses of iron at these connection points apparently causes the magnetic-field variations. The bottom-hole assembly of the drill string was dominated by induced magnetization and possibly was affected by permanent magnetization. In general, the magnetic-field throughout most of the drill pipe and bottom-hole assembly is only two to five times greater than the Earth's magnetic field at Site 865 and so is not likely to affect paleomagnetic samples. However, the magnetometers vertical sensor became saturated in a downward direction between 344 and 356 m below the rig floor at Site 865, suggesting negative inclination of a strong permanent magnetization of two pipes within this zone. Such a strong magnetic field is a likely cause of remagnetization of core samples

28. STRUCTURAL IMPLICATIONS OF GRAVITY ANOMALIES, RESOLUTION AND HEEZEN GUYOTS, MID-PACIFIC MOUNTAINS 1

ABSTRACT Drilling showed that carbonate rocks make up most of Resolution Guyot, located in the western Mid-Pacific Mountains. Density data from Hole 866A, in the top of the guyot, were used to calculate a forward model of the gravity anomaly caused by the guyot's topography. After this anomaly was subtracted from the observed free-air anomaly, a significant positive residual, 35 mGal in amplitude, remained. The same densities were used for nearby Heezen Guyot, which yielded a similar, 45 mGal residual. Inverse models of the Resolution Guyot residual indicate that most of the mass excess can be attributed to the contrast between surrounding sediments and the dolomites at the bottom of the guyot's limestone section and the basalt pedestal beneath the guyot. Nevertheless, models with a central mass concentration fit the residual significantly better than those without, suggesting that there may be either a buried, conical, seamount remanent in the center of the guyot or a central conduit with dense intrusive rocks. The latter seems more plausible because seismic reflection profiles show no evidence of a buried conical structure. In addition, models with bottoms below the predicted top of the underlying basaltic plateau give more plausible density contrasts, suggesting that either a dense zone exists within the plateau beneath the guyot or that the extrapolated depth to the plateau top is incorrect by 500 m to 1000 m. The Resolution Guyot models imply that the carbonate bank buried a small seamount or igneous pedestal and retained nearly the same shape and width. Although the Heezen Guyot residual anomaly was not explicitly modeled, it is similar to that of Resolution Guyot and implies an analogous subsurface structure. In contrast, the Heezen Guyot residual is located to the west side of that edifice and does not have the same elongated shape as the guyot. Thus, it appears that the carbonate bank of Heezen Guyot expanded eastward from its pedestal