Search

A survey of the ant species in Kaufman County, Texas resulted in identification of 29 species in five subfamilies. Twenty-eight of the species were new records for the county. This brought the total number of species reported in the county to 32.

Collection of ants in Rockwall County, TX, resulted in three new records for the county: Aphaenogaster texana Wheeler, Tapinoma sessile Say, and Temnothorax schaumii Roger. Camponotus discolor was identified to species. This increased the number of documented species of ants in Rockwall County to 15.

A survey of 18 green spaces in Downtown Dallas, TX yielded 19 species of ants. A new record for Texas was collection of Nylanderia wojciki Trager at 13 sites. Other species collected included Paratrechina longicornis Latrielle, Pheidole lamia Wheeler, Hypoponera opacior Forrel, and Strumigenys louisianae Roger. The red imported fire ant, Solenopsis invicta Buren, was the only species collected at all sites.

Cosmic ray produced 10Be (half-life = 1.36 × 106 yr), 26Al (7.05 × 105 yr), and 36Cl (3.01 × 105 yr) were measured in a depth profile of 19 carefully-ground samples from the glass-coated lunar surface rock 64455. The solar cosmic ray (SCR) produced 26Al and 36Cl in this rock are present in high concentrations, which in combination with the low observed erosion rate

The writings of Sir Charles Oman provide the foundation for English-language readers' understanding of the tactical details of Napoleonic warfare. Oman explained British success against the French as the inevitable consequence of French tactical orthodoxy. Oman reduced tactics to a mathematical relationship between the number of effective marksmen in the French column versus the British line. This article demonstrates that Oman's understanding of French tactics was deeply flawed. Most importantly, it shows that Oman's "musket counting" analysis derived from a complete misapprehension about the 1806 Battle of Maida.

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at –42° latitude to about 40 grams per square centimeter at –77°. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 ± 15% of the layer by weight.

We present a general approach to the design, docking, and virtual screening of multiple combinatorial libraries against a family of proteins. The method consists of three main stages: docking the scaffold, selecting the best substituents at each site of diversity, and comparing the resultant molecules within and between the libraries. The core “divide-and-conquer” algorithm for side-chain selection, developed from an earlier version (Sun et al., J Comp Aided Mol Design 1998;12:597–604), provides a way to explore large lists of substituents with linear rather than combinatorial time dependence. We have applied our method to three combinatorial libraries and three serine proteases: trypsin, chymotrypsin, and elastase. We show that the scaffold docking procedure, in conjunction with a novel vector-based orientation filter, reproduces crystallographic binding modes. In addition, the free-energy-based scoring procedure (Zou et al., J Am Chem Soc 1999;121:8033–8043) is able to reproduce experimental binding data for P1 mutants of macromolecular protease inhibitors. Finally, we show that our method discriminates between a peptide library and virtual libraries built on benzodiazepine and tetrahydroisoquinolinone scaffolds. Implications of the docking results for library design are explored. Proteins 2001;42:296–318. © 2000 Wiley-Liss, Inc.

Systematic measurements of the concentrations of cosmogenic 41 Ca (half-life = 1.04 × 10 5 yr) in the Apollo 15 long core 15001–15006 were performed by accelerator mass spectroscopy. Earlier measurements of cosmogenic 10 Be, 14 C, 26 Al, 36 Cl, and 53 Mn in the same core have provided confirmation and improvement of theoretical models for predicting production profiles of nuclides by cosmic ray induced spallation in the Moon and large meteorites. Unlike these nuclides, 41 Ca in the lunar surface is produced mainly by thermal neutron capture reactions on 40 Ca. The maximum productions of 41 Ca, about 1 dpm/g Ca, was observed at a depth in the Moon of about 150 g/cm 2 . For depths below about 300 g/cm 2 , 41 Ca production falls off exponentially with an e-folding length of 175 g/cm 2 . Neutron production in the Moon was modeled with the Los Alamos High Energy Transport Code System, and yields of nuclei produced by low-energy thermal and epithermal neutrons were calculated with the Monte Carlo N-Particle code. The new theoretical calculations using these codes are in good agreement with our measured 41 Ca concentrations as well as with 60 Co and direct neutron fluence measurements in the Moon.

We present data for the cosmogenic nuclides Be-10 and A-26 in a suite of 24 extraterrestrial spherules, collected from Antarctic moraines and deep sea sediments. All of the 10 large spherules collected in glacial till at Lewis Cliff are extraterrestrial. As in earlier work, the great majority of particles show prominent solar cosmic-ray (SCR) production of Al-26, indicating bombardment ages on the order of 106 years or even longer. These long ages are in direct contradiction to model ages for small particles in the inner Solar System and may require reconsideration of models of small particle lifetimes. A small fraction of the particles so far measured (6/42) possess cosmogenic radionuclide patterns consistent with predictions for meteoroid spall droplets. We believe that most of the spherules were bombarded in space primarily as bodies not much larger than their present size. The content of in situ produced Be-10 and Al-26 in quartz pebbles in the same moraine suggests that these spherules may have on average a significant terrestrial age.

Targets of silicon and silicon dioxide were irradiated with spallation neutrons to simulate the production of long-lived radionuclides in the surface of the Earth. Gamma-ray spectroscopy was used to measure Be-7 and Na-22, and accelerator mass spectrometry was used to measure Be-10, C-14, and Al-26. The measured ratios of these nuclides are compared with calculated ratios and with ratios from other simulations and agree well with ratios inferred from terrestrial samples.

The central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings. In the light of these general models, we discuss the information that can be derived about geomorphic processes, utilizing concentrations of in situ produced cosmogenic radionuclides 10Be (half-life=1·5 ma) and 26A1 (half-life=0·7 ma) in a variety of geomorphic contexts: glacial polish and tills; meteorite impact craters; alluvial fans; paleo-beach ridges; marine terraces; sand dunes; and bedrock slopes. We also compare 10Be-26Al data with results obtained by other dating methods. We conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time-scales in a wide range of geomorphological problems.

Cosmic-ray produced 59Ni (t12 = 76000 years) was detected in meteoritic and lunar material by AMS with fully stripped ions. At 641 MeV beam energy, a clean separation of 59Ni28+ ions from 59Co27+ background was achieved with a magnetic spectrograph. A background limit of 59Ni/Ni < 7 × 10−14 was determined with a blank Ni sample. A 59Ni/Ni ratio of (2.3 ± 0.4) × 10−11 was measured in a sample from the Admire stony-iron (pallasite) meteorite, corresponding to a specific activity of 280±50dpm/kg meteorite. In a surface layer of Apollo 16 lunar rock 68815, a 59Ni/Ni ratio of (8.8 ± 3.3) × 10−13 was measured (diluted with Ni carrier), corresponding to a specific activity of 4.1 ± 1.5 dpm/kg rock. This result compares well with values calculated by Reedy from the 56Fe(α, n)59Ni reaction induced by solar cosmic ray alpha particles. Methodological aspects of the full-stripping technique and future possibilities of 59Ni measurements in lunar materials are discussed.

In this work we examine ways to improve the sensitivity of the analysis procedure for gamma ray spectra with respect to small differences in the continuum (Compton) spectra. The method developed is applied to analyze gamma ray spectra obtained from planetary mapping by the Mars Observer spacecraft launched in September 1992. Calculated Mars simulation spectra and actual thick target bombardment spectra have been taken as test cases. The principle of the method rests on the extraction of continuum information from Fourier transforms of the spectra. We study how a better estimate of the spectrum from larger regions of the Mars surface will improve the analysis for smaller regions with poorer statistics. Estimation of signal within the continuum is done in the frequency domain which enables efficient and sensitive discrimination of subtle differences between two spectra. The process is compared to other methods for the extraction of information from the continuum. Finally we explore briefly the possible uses of this technique in other applications of continuum spectra.

The cosmogenic radionuclides Ca-41, Cl-36, Al-26, and Be-10 in the Allan Hills 81005, MacAlpine Hills 88104, MacAlpine Hills 88105, and Yamato 791197 meteorites were measured by accelerator mass spectrometry. Mn-53 in Allan Hills 81005 and Yamato 791197 was measured by neutron activation. These four lunar meteorites experienced similar histories. They were ejected from near the surface of the moon ranging in depth down to 400 g/sq cm and had very short transition times (less than 0.1 Ma) from the moon to the earth. A comparison of the cosmogenic nuclide concentrations in MacAlpine Hills 88104 and MacAlpine Hills 88105 clearly indicates that they are a pair from the same fall.

A new method of dating the surface exposure of rocks from in situ production of 10Be and 26Al has been applied to determine the age of Meteor Crater, Arizona. A lower bound on the crater age of 49,200 ± 1,700 years has been obtained by this method.

The problem of environmental contamination is a serious impediment to the development or redevelopment of real property. The cost of cleanup can easily render a proposed redevelopment project economically infeasible. This paper describes how sites known to be contaminated can be profitably and successfully redeveloped. Statutes establishing the ground rules for environmental obligations are reviewed. The environmental investigation process, including environmental reviews and sampling and testing plans, is discussed. Alternative treatment methods for soil and ground‐water contamination are also discussed. A site mitigation flowchart is presented to show how remediation alternatives can be developed for each environmental risk. Development alternatives can then be developed for each remediation alternative, and, based upon benefit/cost considerations, can be used to produce a remediation and development plan for the redevelopment of contaminated property. A hypothetical example of the redevelopment of a co...

Cosmic-ray produced Be-10 and Al-26 were measured in purified quartz fractions of selected rock samples from Antarctic mountains. From these data, mean erosion rates were calculated for the limiting case of steady-state surface exposure to cosmic rays, and minimum exposure ages, for the limiting case of no erosion. Calculated mean erosion rates are very low, on the order of a few times 0.00001 cm/yr; the sampling is believed to be sufficient to generalize this result to exposed bedrock in Antarctica. In favorable cases it is possible to distinguish between the limiting cases; steady-state erosion seems a better description in such cases. Most samaples, including some taken a few meters above the present ice level, seem to have been exposed for millions of years, without major episodes of burial or abrasion by ice.

Accelerator mass spectrometry is utilized to determine the half-life of Ca-41 from the decrease of its concentration with terrestrial age in five Antarctic meteorites and a recent fall. The meteorites were selected on the basis of their Cl-36 concentrations, which showed a span of terrestrial ages of about 600 ka, and on the basis of other cosmogenic nuclide concentrations which indicated that the meteorites had small preatmospheric sizes, and sufficiently long irradiation times in space that the concentrations of Ca-41 and Cl-36 were in secular equilibrium prior to the meteorites' fall to earth. The half-life of Ca-41 is determined at 103 + or - 7 ka. Topics discussed include the effects of undersaturation (short exposure time in space), shielding (the samples are from the interior of a large meteorite), and weathering on the cosmogenic nuclide concentrations in meteorites.

It is important to minimize the background for gamma ray remote sensing experiments. It becomes more important with the advent of high-resolution gamma ray spectroscopy, as one wishes to study smaller regions and lower elemental concentrations. Here, we describe our procedure to minimize the background due to γ-radioactivity in the local mass around the gamma ray spectrometer (GRS). We have used low-level counting systems, a GeLi and a high-purity Ge detector for material screening. Although most commercially available materials are found clean down to a few ppm for 232 Th and 238 U, the worst-case analysis has been limited occasionally due to statistical error in counting data, self-absorption of gamma rays or due to nonavailability of larger samples.

[1] We report maps of the concentrations of H, Si, Cl, K, Fe, and Th as determined by the Gamma Ray Spectrometer (GRS) on board the 2001 Mars Odyssey Mission for ±∼45° latitudes. The procedures by which the spectra are processed to yield quantitative concentrations are described in detail. The concentrations of elements determined over the locations of the various Mars landers generally agree well with the lander values except for Fe, although the mean of the GRS Fe data agrees well with that of Martian meteorites. The water-equivalent concentration of hydrogen by mass varies from about 1.5% to 7.5% (by mass) with the most enriched areas being near Apollinaris Patera and Arabia Terra. Cl shows a distribution similar to H over the surface except that the Cl content over Medusae Fossae is much greater than elsewhere. The map of Fe shows enrichment in the northern lowlands versus the southern highlands. Silicon shows only very modest variation over the surface with mass fractions ranging from 19% to 22% over most of the planet, though a significant depletion in Si is noted in a region west of Tharsis Montes and Olympus Mons where the Si content is as low as 18%. K and Th show a very similar pattern with depletions associated with young volcanic deposits and enrichments associated with the TES Surface Type-2 material. It is noted that there appears to be no evidence of significant globally distributed thick dust deposits of uniform composition.

Integrating biological and chemical information is one key task in drug discovery, and one approach to attaining this goal is via three-dimensional pharmacophore descriptors derived from protein binding sites. The SitePrint program generates, aligns, scores, and classifies three-dimensional pharmacophore descriptors, active site grids, and ligand surfaces. The descriptors are formed from molecular fragments that have been docked, minimized, filtered, and clustered in protein active sites. The descriptors have geometric coordinates derived from the fragment positions, and they capture the shape, electrostatics, locations, and angles of entry into pockets of the recognition sites: they also provide a direct link to databases of organic molecules. The descriptors have been shown to be robust with respect to small changes in protein structure observed when multiple compounds are cocrystallized in a protein. Five aligned thrombin cocrystals with an average core alpha-carbon RMSD of 0.7 A gave three-dimensional pharmacophore descriptors with an average RMSD of 1.1 A. On a larger test set, alignment and scoring of the descriptors using clique-based alignment, and a best first search strategy with an adapted forward-looking Ullmann heuristic was able to select the global minimum three-dimensional alignment in twenty-nine out of thirty cases in less than one CPU second on a workstation. A protein family based analysis was then performed to demonstrate the usefulness of the method in producing a correlation of active site pharmacophore descriptors to protein function. Each protein in a test set of thirty was assigned membership to a family based on computed active site similarity to the following families: kinases, nuclear receptors, the aspartyl, cysteine, serine, and metallo proteases. This method of classifying proteins is complementary to approaches based on sequence or fold homology. The values within protein families for correctly assigning membership of a protein to a family ranged from 25% to 80%.

When Galileo first turned his telescope toward the sky, he made two major discoveries. One, the four large moons of Jupiter, is justly famous. The other, less familiar, is perhaps more important historically. He saw the Moon with enough resolution to conclude that it is not a ‘heavenly body’ as that term was understood, made of perfect and everlasting heavenly stuff, but a rough, cratered object more like the Earth — a real world rather than a figment of the human imagination. Its study moved from the field of theology to that of natural philosophy, now called science.

We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.

Like other scientific advances, radiocarbon dating did not happen in a moment. The fortieth anniversary could have been celebrated as early as 1986 — since, as we shall see, the idea was certainly in Willard Libby’s mind in 1946 — or as late as 1991, since the first date list of unknowns appeared in Science in 1951 (Arnold & Libby 1951). In fact, what is surprising in retrospect is not that it took so long, but that it was accomplished so quickly. In this age of team research, centers and consortia, it is remarkable how much of the accomplishment was due to one man.

Cosmogenic Be-10 and Al-26 were measured in a suite of stony cosmic spherules derived from deep-sea sediments and the Greenland ice cap. These spherules show clear evidence of exposure to galactic cosmic ray and solar cosmic ray bombardment on time scales from a few times 100,000 years up to as much as 10 to the 7th years. The exposure took place in the inner solar system, not in highly eccentric orbits. When they reached the earth, the particles were not much larger than their present size, but it is not excluded that most of their cosmic ray exposure took place very close to the surface of an asteroidal body.

Stratospheric particles were collected between 34 and 36 km, using a combination of cascade impactors and filters lofted by a large helium balloon, and the particle concentration, size distribution, and bulk elemental composition were determined using SEM and proton-induced X-ray emission (PEXE) instrument. In addition, datailed particle morphology, elemental analysis, and electron diffraction data were obtained on 23 particles using a TEM. The concentration of particles between 0.045 and 1.0 micron in radius was found to be orders of magnitude above the concentrations predicted by the model of Hunten et al. (1980), but was consistent with balloon and satellite observations. Elemental composition analysis showed the presence of Cl, S, Ti, Fe, Br, Ni, Zr, Zn, Sr, and Cu in decreasing order of concentration. The 23 particles analyzed by TEM ranged from Al-rich silicates to almost pure Fe to one containing almost exclusively Ba and S. None were definitely chondritic in composition.