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Objectives The aim of this study was to define landmarks of the intermetatarsal channel of the dorsal pedal artery and to assess whether damage to the dorsal pedal artery during metatarsal screw placement in dogs undergoing pan- and partial-tarsal arthrodesis (PanTA/ParTA) could be a mechanism in the development of plantar necrosis. Study Design This study was divided in to two parts: (1) ex-vivo anatomical study: 19 canine cadavers, (2) retrospective clinical study: 39 dogs. Cadaveric dissection documented the mean intermetatarsal channel position. Metatarsal screw position was evaluated on postoperative radiographs of dogs after PanTA or ParTA. Screw position, arthrodesis type and surgical approach were assessed for their impact on complications, including plantar necrosis. Results The mean proximal and distal extent of the intermetatarsal channel lies between 4.3% ± 1.9 and 22.8% ± 2.9 the length of metatarsal III (MTIII) respectively. The intermetatarsal channel lies within the most proximal 25% of MTIII in 95% of cases. At least one screw risked damaging the mean intermetatarsal channel position in 92% of dogs; 8% of these dogs went on to develop plantar necrosis. The mean screw position did not differ between ParTA cases with or without plantar necrosis (p > 0.05). Conclusion Violation of the intermetatarsal channel is possible during metatarsal screw placement. Care should be taken when placing screws in the proximal 25% of the metatarsals, specifically avoiding exiting dorsally between MTII and MTIII and across the distal region of the intermetatarsal channel, where the perforating metatarsal artery passes interosseously, as damage may contribute to the aetiology of plantar necrosis.

Objective To determine the effects of low-level laser therapy (LLLT) on clinical outcomes in dogs with cranial cruciate ligament disease treated with tibial plateau leveling osteotomy (TPLO). Study design Randomized, placebo-controlled clinical trial. Owners and surgeons (care providers and assessors) were masked. Animals Ninety-five dogs were admitted for TPLO and assigned to 1 of 2 groups, laser group (LG; n = 51) or placebo group (PG; n = 44). Methods Three treatments (laser or placebo) were administered within a 4-day perioperative period. A fourth treatment was recommended and was accepted in 28.4% of cases (LG, n = 14; PG, n = 13). Dogs in the LG group received laser at wavelengths 660 nm red (100 mW) and at 800, 905 and 970 nm infrared (maximum 15 W continuous wave, 20 W peak pulsed wave), administered simultaneously. Dogs in the PG group received placebo laser (660 nm, 4 mW). Other treatments were identical. Outcomes were measured by difference in clinical metrology instruments (Liverpool Osteoarthritis in Dogs and adjusted Canine Orthopedic Index [COI]), osteotomy healing on a radiographic scale, time to cessation of nonsteroidal anti-inflammatory drug administration, and wound healing by owner questionnaire. Results The only difference detected between groups consisted of a greater improvement in the gait section of the adjusted COI (ACOI) in the LG group (median [interquartile range; IQR] = 6 [4-7.5]) compared with the PG group (median [IQR] = 4 [2-6]; P Conclusion The laser protocol used in this study was associated with a greater improvement in ACOI gait in dogs treated with TPLO but did not improve any other clinical metrology instrument scores or bone healing. Clinical significance This study provides some evidence that LLLT may improve the gait of dogs recovering from a TPLO, as assessed by owners.

Facies classification from well logs is an indispensable part of seismic interpretation and is important in the determination of sequence stratigraphy and ultimately reservoir characterization. Although there have been improvements in the tools used to perform this task, it remains laborious, subjective, and error-prone. Achieving a proper classification is complicated by increasing dataset sizes as well as the need for correlated multidisciplinary models. Recent developments in machine learning provide an opportunity to assist interpreters in accomplishing this task while also improving the accuracy of classification results. Applications of machine learning methods for automating facies classification from well logs have previously been explored, however these have largely focused on evaluations or comparisons of individual algorithms or of ensembles of homogeneous agents. The proposed method combines heterogeneous agents to enhance prediction accuracy. Specifically, supervised learning, which provides a direct mapping between the data domain and the solution domain while introducing bias to generalize the mapping, is combined with unsupervised learning, which does not depend on similar generalization bias or training data but also does not provide a direct mapping between the data and solution domains. The combination is accomplished via the joint probability density function (PDF) of the supervised classification, which is used to guide identification of clusters delineated by unsupervised learning. This multi-agent approach can reduce bias introduced during training and provides a basis for generating a probability distribution for each sample rather than a discrete classification. The distribution, in turn, can be used to more accurately model the continuous nature of well log signals, which reflects continuity in lithological regimes.

Energy and natural resources are crucial to the sustainability of worldwide economies, security, and overall well-being. However, the future workforce in the energy and natural-resources sector is at risk, and meeting the challenges of this dwindling workforce requires well-educated geoscientists in exploration and applied geophysics and related geoscience and technology disciplines. Programs such as geophysical field courses that are supported by SEG and industry, in partnership with academic institutions and government laboratories, are important approaches to maintaining and enhancing expertise in exploration geophysics. One example of a geophysical field course devoted to educating our future workforce is the Summer of Applied Geophysical Experience (SAGE), a four-week program based in Santa Fe, New Mexico, designed to actively engage students in all phases of applied geophysical research. SAGE is a unique educational experience that combines teaching and research as a partnership among universities, industry, government agencies, and professional societies. SAGE teaches the principles and applications of refraction and reflection seismology, magnetics, gravity, GPS, heat flow, several electromagnetic (EM) methods, and ground-penetrating radar (GPR) in a field-based, hands-on setting. More than 850 students and qualified professionals have attended SAGE, many of whom have gone on to become leaders in academia, industry, and government. SAGE students are exposed to the exciting challenges that face earth scientists today, and they develop skills that are necessary to address the world's growing energy demands. Examples of SAGE research projects include mapping archaeological sites and tectonic structure and investigating water and geothermal resources in the Rio Grande rift.

The Sobolev gradient steepest descent provides a numerically efficient iterative bending algorithm for two-point ray tracing. This new algorithm has advantages in its relative ease of numerical implementation, its ability to provide accurate solutions in discontinuous velocity fields (including head wave solutions), and its ability, when smooth velocity fields are used, to provide accurate solutions while using relatively few ray segments. The algorithm owes its advantages to its implicit nature, which it inherits from the Sobolev gradient solution method. For most models, the algorithm can be implemented such that at convergence, the norm of the gradient approaches zero. Thus, convergence implies a stationary point of the traveltime integral, guaranteeing that the rays found satisfy Fermat’s principle.

Pharmaceutical and personal care products (PPCPs) discharged with wastewater treatment plant (WWTP) effluents are an emerging surface water quality concern. Biological transformation has been identified as an important removal mechanism during wastewater treatment. The aim of this research was the identification of bacteria with characteristics for potential bioaugmentation to enhance PPCP removal. We report here the cultivation and characterization of bacteria capable of degrading PPCPs to ng/L concentrations. An isolation approach was developed using serial enrichment in mineral medium containing 1 mg/L of an individual PPCP as the sole organic carbon source available to heterotrophs until the original activated sludge inocula was diluted to ~10(-8) of its initial concentration, followed by colony growth on solid R2A agar. Eleven bacteria were isolated, eight that could remove triclosan, bisphenol A, ibuprofen, or 17β-estradiol to below 10 ng/L, one that could remove gemfibrozil to below 60 ng/L, and two that could remove triclosan or E2, but not to ng/L concentrations. Most bacterial isolates degraded contaminants during early growth when grown utilizing rich carbon sources and were only able to degrade the PPCPs on which they were isolated. Seven of the bacterial isolates were sphingomonads, including all the triclosan and bisphenol A degraders and the ibuprofen degrader. The study results indicate that the isolated bacteria may have a positive influence on removal in WWTPs if present at sufficient concentrations and may be useful for bioaugmentation.

Recent interest in carbon-neutral biofuels has revived interest in co-digestion for methane generation. At wastewater treatment facilities, organic wastes may be co-digested with sludge using established anaerobic digesters. However, changes to organic loadings may induce digester instability, particularly for thermophilic digesters. To examine this problem, thermophilic (55 degrees C) co-digestion was studied for two food-industry wastes in semi-continuous laboratory digesters; in addition, the wastes' biochemical methane potentials were tested. Wastes with high chemical oxygen demand (COD) content were selected as feedstocks allowing increased input of potential energy to reactors without substantially altering volumetric loadings. Methane generation increased while reactor pH and volatile solids remained stable. Lag periods observed prior to methane stimulation suggested that acclimation of the microbial community may be critical to performance during co-digestion. Chemical oxygen demand mass balances in the experimental and control reactors indicated that all of the food industry waste COD was converted to methane.

As you receive this issue of The Leading Edge the Summer of Applied Geophysical Experience (SAGE) will be starting our 30th field season. SAGE is a unique educational program that combines teaching and research as a partnership between universities, industry, government agencies and professional societies. SAGE includes a four-week period based in Santa Fe, New Mexico and one-week workshop in the following January for undergraduates, at San Diego State University, which allows us to enhance their research experience. We teach the principles and applications of refraction and reflection seismics, magnetics, gravity, GPS, several electromagnetic (EM) methods and ground-penetrating radar (GPR) in a field-based, hands-on setting. The central research activity of SAGE is the acquisition and interpretation of geophysical field data. Students learn geophysics by doing geophysics—a discovery oriented approach.

The formation of lead dioxide PbO(2), an important corrosion product in drinking water distribution systems with lead-bearing plumbing materials, has been hypothesized to involve Pb(III) intermediates, but their nature and formation mechanisms remain unexplored. This study employed the electrochemical (EC) method of rotating ring disk electrode (RRDE) and quantum chemical (QC) simulations to examine the generation of intermediates produced during the oxidation of Pb(II) to PbO(2). RRDE data demonstrate that PbO(2) deposition and reduction involves at least two intermediates. One of them is a soluble Pb(III) species that undergoes further transformations to yield immobilized PbO(2) nanoparticles. The formation of this intermediate in EC system is mediated by hydroxyl radicals (OH(•)), as was evidenced by the suppression of intermediates formation in the presence of the OH(•) scavenger para-chlorobenzoic acid. QC simulations confirmed that the oxidation of Pb(II) by OH(•) proceeds via Pb(III) species. These results show that Pb(III) intermediates play an important role in the reactions determining transitions between Pb(II) and Pb(IV) species and could impact lead release in drinking water.

This study examined effects of desalinated water on the corrosion of and metal release from copper and lead-containing materials. A jar test protocol was employed to examine metal release from copper and lead–tin coupons exposed to water chemistries with varying blending ratios of desalinated water, alkalinities, pHs and orthophosphate levels. Increasing fractions of desalinated water in the blends resulted in non-monotonic changes of copper and lead release, with generally lower metal concentrations in the presence of desalinated water, especially when its contribution increased from 80% to 100%. SEM examination showed that the increased fractions of desalinated water were associated with pronounced changes of the morphology of the corrosion scales, likely due to the influence of natural organic matter. This hypothesis was corroborated by the existence of correlations between changes of the ζ-potential of representative minerals (malachite and hydrocerussite) and metal release. For practical applications, maintaining pH at 7.8 and adding 1 mg/L orthophosphate as PO4 were concluded to be adequate to decrease copper and lead release. Lower alkalinity of desalinated water was beneficial for blends containing 50% or more desalinated water.

Canine osteoarthritis (OA) commonly occurs in association with articular diseases, such as hip dysplasia (HD), elbow dysplasia (ED), or cranial cruciate ligament rupture (CCLR). We hypothesized that a common genomic risk for the development of canine joint disease and canine OA would be identified by evaluating the allele frequencies of candidate gene single nucleotide polymorphisms (SNPs) in dogs with OA associated with different articular diseases when compared with a general population of breed-matched dogs. DNA was extracted from blood samples obtained from Labrador Retrievers and Golden Retrievers surgically treated for ED, HD, and CCLR and confirmed to have radiographic evidence of OA. One hundred and thirteen SNPs in 20 candidate genes were genotyped. No significant associations were identified for SNPs or haplotypes in the candidate genes for the diseases evaluated. The candidate gene approach for the study of genetic association is unlikely to be successful for complex canine diseases such as OA without prior trait mapping evaluation.

The 4D microgravity method is becoming a mature technology. A project to develop practical measurement and interpretation techniques was conducted at Prudhoe Bay, Alaska, from 1994 through 2002. Beginning in 2003 these techniques have been systematically applied to monitor a waterflood in the gas cap of the Prudhoe Bay reservoir. Approximately 300 stations in a [Formula: see text] area are reoccupied in each survey year with sub-[Formula: see text] precision absolute gravity and centimeter precision Global Positioning System (GPS) geodetic measurements. The 4D gravity measured over epochs 2005–2003, 2006–2003, and 2007–2003 has been successfully modeled to track the mass of water injected since late in 2002. A new and improved version of the A-10 field-portable absolute gravity meter was developed in conjunction with this project and has proven to be a key element in the success of the 4D methodology. The use of an absolute gravity meter in a field survey of this magnitude is unprecedented. There are substantial differences between a 4D absolute microgravity survey and a conventional gravity survey in terms of station occupation procedures, GPS techniques, and the 4D elevation correction. We estimate that the overall precision of the 4D gravity signal in each epoch is less than [Formula: see text].

Between March 2003 and March 2007, four high-precision 4D absolute microgravity surveys were performed at Prudhoe Bay, Alaska. These surveys are part of an ongoing effort to monitor the progress of a very large water-injection project in the gas cap of the Prudhoe Bay reservoir at a depth of [Formula: see text]. These carefully acquired gravity data must be modeled and interpreted in terms of water movement within the reservoir. A constrained linear inversion scheme was tested on reservoir simulations during the planning and development phase of this project (preinjection). The inver-sion methodology has been applied to data for three epochs (2005–2003, 2006–2003, and 2007–2003), and mass-distribution models have been produced for the reservoir. The time evolution of the water-mass distribution in the reservoir is visualized from these three snapshot models. The waterflood is expanding into the gas cap at the expected rate but is exhibiting nonsymmetric behavior that is consistent with a greater degree of structural control than expected. The waterflood seems to be restrained episodically and guided by fault barriers. These barriers are overcome and fault-bounded blocks filled with water in stages.

The increasing world demand and record-high costs for energy and mineral resources, along with the attendant environmental and climate concerns, have escalated the need for trained geophysicists to unprecedented levels. This is not only a national need; it's a critical global need. As Earth scientists and educators we must seriously ask if our geophysics pipeline can adequately address this crisis. One program that has helped to answer this question in the affirmative for 25 years is SAGE (Summer of Applied Geophysical Experience). SAGE continues to develop with new faculty, new collaborations, and additional ways to support student participation during and after SAGE.

Summary The world's first 4D surface-gravity surveillance of a1 waterflood has been implemented at Prudhoe Bay, Alaska. This monitoring technique is an essential component of the surveillance program for the Gas Cap Water Injection (GCWI) project. A major factor in the approval process for the waterflood was to show that we could monitor water movement economically where a very limited number of wells penetrated the waterflood area. The drilling of numerous surveillence wells to monitor water movement adequately would have been cost-prohibitive. Field surveys now show conclusively that density changes associated with water replacing gas are being detected readily with high-resolution surface-gravity measurements. The gravity methods used to monitor the water-flood include time-lapse (4D) measurement of surface gravity over the reservoir followed by inversion of the 4D signal for mass-balance calculation and flood-front detection. This paper will focus on field results of time-lapse surface-gravity surveys. Differences in the gravity field over time reflect changes in the reservoir-fluid density. The inversion procedure was formulated and coded to allow for various constraints on model parameters such as density, total mass, and moment of inertia. The gravity survey was designed to permit the inversion for reservoir mass distribution, with resolution on the order of hundreds of meters in the presence of uncorrelated noise of reasonable magnitude (12-μGal standard deviation). Time-differenced gravity-survey results clearly show an increase in surface gravity that is a result of the injected-water mass. Density-change maps deduced from measured gravity change show that water movement is reasonably similar to the reservoir simulations and to the water detected in observation wells. The overall ultimate gravity signal is predicted to increase to approximately 250 μGal, ultimately resulting in accurate maps of the water movement.

San Marcos Pueblo site (LA 98), located in the Galisteo Basin south of Santa Fe, New Mexico, encompasses the remains of 43 identified room blocks, a Spanish mission and 20 middens. As part of ongoing field investigations at San Marcos, students and faculty from the Summer of Applied Geophysical Experience (SAGE) field programme are using multiple geophysical techniques to non-invasively investigate the site. Modelling of the underlying Quaternary stream terrace geology and the detection of subsurface Pueblo-era features were accomplished through the integrated interpretation of data from seismic refraction and reflection, electromagnetic, magnetic and ground-penetrating radar methods. Although to date only a targeted spatially small extent of the site has been explored using these methods, the SAGE field programme has been able detect a variety of anthropogenic structures and debris. The SAGE field programme validated the presence of excavations in the natural stream terrace sequence over areas believed to contain kivas, mapped the geometry of walls over a closed room block, and detected an area of magnetized debris associated with smelting operations. Collectively, the data from the SAGE field programme demonstrate the value of using multiple, complementary, geophysical methods for archaeological prospection. Copyright © 2008 John Wiley & Sons, Ltd.

Reactions of representative lead (II) solid phases (hydrocerussite, cerussite) with chlorine were examined in this study. Chlorine consumption profiles for these solids exhibited a lag phase, during which little consumption of chlorine occurred, and an ensuing rapid reaction phase. The durations of these phases were affected by the pH, carbonate, and chlorine concentrations. SEM and XRD data showed that hydrocerussite started to be transformed into cerussite during the lag phase. Kinetic analysis indicated that only the protonated form of HClO drives the autocatalytic oxidation step, which is mediated by dispersed PbO2 crystals. The rate of the noncatalytic oxidation decreased with the increase of carbonate due to the formation of unreactive surface carbonate Pb(II) complexes.

Geophysical techniques can be used for non-invasive surveys at archaeological sites. One under-utilized technique, seismic refraction, has many potential applications. It is an inexpensive, efficient way to characterize subsurface deposits, especially at sites with shallow accumulations over bedrock. Archaeologists and geophysicists participating in the Summer of Applied Geophysics Experience from Los Alamos National Laboratory and Bandelier National Monument on the Pajarito Plateau in northern New Mexico characterized Ancestral Puebloan sites (A.D. 1200–1450) using this technique. We provide an overview of how seismic refraction works and demonstrate the applicability of seismic refraction for identifying buried archaeological features such as communal structures and walls.

Between 1994 and 2002, a series of experiments was conducted at Prudhoe Bay, Alaska, aimed at the development of an effective 4D (or time-lapse) gravity technique. Theoretical investigations had pointed out the potential for monitoring water injection in the [Formula: see text]-deep reservoir, but it was not clear that gravity measurements of sufficient accuracy could be made in the arctic environment. During the course of these experiments, new techniques and instrumentation were introduced and perfected for both gravity and position measurements. Gravity stations are located using high-precision global positioning system (GPS) techniques without permanent monuments. Robust methods for meter drift control have improved noise resistance in relative gravimeter surveys. Absolute gravity measurements with a field-portable instrument maintain absolute gravity levels among surveys. A 4D gravity-difference noise of [Formula: see text] standard deviation has been established at Prudhoe Bay for GPS-controlled relative gravimeter surveys. The lessons learned are now being applied to full-scale waterflood monitoring at Prudhoe Bay. The basic technique is applicable to microgravity surveys and 4D microgravity surveys for any purpose.

Spatial aliasing is unavoidable in some seismic data and has serious effects on the performance of multichannel data processing and migration. Antialias filtering produces distortion of the signal through the removal of high-frequency information. In contrast, dealiasing produces an unaliased estimate of the signal at all frequencies present in the original time series. A new dealiasing algorithm is developed by exploiting the properties of seismic wavefields in the wavelet-Radon transform domain, specifically the overlap of information between wavelet scales at the same frequency. The effectiveness of the wavelet-Radon dealiasing algorithm is demonstrated through the processing of both synthetic and field seismic data.

Properties of solid phases formed during the oxidation of EDTA by permanganate in a high-pH, high-ionic strength solution, and the retention of Cu2+, Ni2+, and Zn2+ by them were examined. Morphologically, the solids were agglomerates of particles with sizes100 nm. X-ray absorption spectroscopy (XAS) analysis indicated that these particles were birnessite. Its precipitation was accompanied by the removal of Zn2+ and Cu2+ released as a result of the breakdown of their complexes with EDTA. However, Ni2+ was not removed from the supernatant. Cu2+ was strongly bound by birnessite and exhibited little mobility in the pH range from 3 to 14. Zn2+ was more mobile, especially at pH12. XAS showed that Cu2+ binding sites were located within MnO6 octahedra-comprised sheets that constitute birnessite while Zn2+ was positioned between them.

The ADM1 was employed to assess the effect of variations in solids hydrolysis and acetoclastic methanogen process characterizations on municipal digester stability relating to excess acetate utilization capacity. First-order single- and dual-pathway hydrolysis rate functions and single and competitive acetoclastic methanogen rate functions were implemented in the ADM1. The acetate capacity number (ACN), defined as the ratio between the maximum acetate utilization rate and the average acetate production rate, was used to index digester instability. Simulations of a single CSTR at steady state indicate a similar ACN can be obtained with a 12-day SRT digester dominated by Methanosarcina sp and a 24-day SRT digester dominated by Methanosaeta sp. An increase in ACN with a decrease in SRT representing Methanosarcina sp. selection was observed for particulate feed loadings from 40 g COD/L to 90 g COD/L. Feeding frequency and dual-pathway hydrolysis were found to have less effect on the ACN than the competitive acetoclastic model structure.

Methanosarcina species with a high maximum specific growth rate (mumax) and high half-saturation coefficient (KS) and Methanosaeta species with a low mumax and low KS are the only known aceticlastic methanogens. Because of Methanosaeta's low KS, the low acetate concentrations in conventional, mesophilic anaerobic digestion yield Methanosaeta dominance. However, Methanosarcina absorbs increases in acetate more efficiently and thus promotes more stable digestion. This paper tests the hypothesis that decreasing digester feeding frequencies can increase Methanosarcina predominance. Two acetate-fed reactors were established at a 17-day solids retention time. One reactor was fed hourly, and one was fed once daily. Microscopic and molecular methods were used to verify that the hourly fed reactor enriched for Methanosaeta, while the daily fed reactor enriched for Methanosarcina. Growth and substrate-use kinetics were measured for each reactor. A digester overload condition was simulated, and the Methanosarcina-enriched reactor was found to perform better than the Methanosaeta-enriched reactor. These findings indicate that Methanosarcina dominance can be achieved with infrequent feedings, leading to more stable digestion.

Influence of natural organic matter (NOM) on the morphology of lead surfaces exposed to drinking water and on the properties of lead-containing colloidal particles was explored based on the data of scanning electron microscopy, sequential filtrations, measurements of particle size distributions and electrophoretic potential. It was demonstrated that NOM prevented the formation of cerussite and hindered the growth of hydrocerussite crystals. Measurements of zeta-potential showed that the surface activity was highest for unaltered NOM, while ozonation and chlorination decreased it. The concentrations of soluble lead and tin increased several fold in the presence of NOM, while large colloidal particles of lead and solder corrosion products tended to break down to form smaller fragments. It is suggested that these phenomena are important for understanding of lead release mechanisms in drinking water.

The stability, capacity, and solids destruction efficiency of single versus two-stage anaerobic digestion was studied in bench-scale reactors using combined waste activated and primary sludge. Laboratory staged mesophilic digesters showed an improved volatile solids and volatile suspended solids destruction efficiency over a single-stage system (at the same total solids retention time [SRT]) of approximately 3.2 and 5.8 percentage points, respectively. To quantify stability and capacity, a new digester monitoring method was introduced that measured the digester maximum acetate utilization capacity, V(max,ac), and was used to investigate the potential for digester instability at different transient loadings. The ratio of the V(max,ac) value to the estimated acetate production rate for a given digester loading was termed the acetate capacity number (ACN). Values greater than 1.0 indicate excess acetate utilization capacity. The first stage of the laboratory two-stage mesophilic system (10-day SRT for each stage) had an ACN number of 1.3 compared with a value of 1.8 for the single-stage 20-day SRT digester. Thus, while a staged mesophilic system can improve solids destruction efficiency, it demonstrates a lower capacity for metabolizing highly variable loads.

We propose a Kirchhoff‐style algorithm that migrates coefficients obtained by wavelet decomposition of seismic traces over time. Wavelet‐based prestack multiscale Kirchhoff migration involves four steps: wavelet decomposition of the seismic data, thresholding of the resulting wavelet coefficients, multiscale Kirchhoff migration, and image reconstruction from the multiscale images. The migration procedure applied to each wavelet scale is the same as conventional Kirchhoff migration but operates on wavelet coefficients. Since only the wavelet coefficients are migrated, the cost of wavelet‐based migration is reduced compared to that of conventional Kirchhoff migration. Kirchhoff migration of wavelet‐decomposed data, followed by wavelet reconstruction, is kinematically equivalent to and yields similar migrated signal shapes and amplitudes as conventional Kirchhoff migration when data at all wavelet scales are included.The decimation in the conventional discrete pyramid wavelet decomposition introduces a translation‐variant phase distortion in the wavelet domain. This phase distortion is overcome by using a stationary wavelet‐transform rather than the conventional discrete wavelet‐transform of the data to be migrated.A wavelet reconstruction operator produces a single composite broadband migrated space‐domain image from multiscale images. Multiscale images correspond to responses in different frequency windows, and migrating the data at each scale has a different cost. Migrating some, or only one, of the individual scale data sets considerably reduces the computational cost of the migration. Successful 2D tests are shown for migrations of synthetic data for a point‐diffractor model, a multilayer model, and the Marmousi model.

Recuperative thickening of anaerobic digester sludge (thickening with solids return) yields increased digester capacity. Common thickening methods cause oxygen exposure to the digester sludge. This study evaluated the effects of various levels of oxygen exposure on the acetoclastic methanogens. Gravity belt thickening had no detrimental effect on the acetoclastic activity. From a 7-day batch test with continuous oxygen exposure of digester sludge, a 12% loss in acetoclastic activity was predicted for a digester with a 20-day solids retention time (SRT) and 100% recycle with recuperative thickening via dissolved air flotation thickening. However, a greater loss (27%) was found from a long-term, bench-scale digester operated under similar conditions. This loss did not affect the digester performance, as measured by volatile solids destruction. This research suggests that recuperative thickening may not affect digester performance at a long SRT with constant operation, but may change the reserve capacity of the anaerobic community.

The steady-state performance of thermophilic (55 degrees C) and mesophilic (35 degrees C) anaerobic digestion as a function of solids retention time (SRT) was evaluated in laboratory digesters at SRTs ranging from 4 to 15 days, and in pilot-plant digesters at a 20-day SRT. All of the digesters were fed the same source of municipal combined primary and secondary waste sludge. The destruction efficiency of volatile solids increased from 53% to 66% as the SRT was increased from 6 days to 20 days. The average destruction efficiency of volatile solids was 3 percentage points higher for the thermophilic digester at the 6-day SRT and approximately 1 percentage point higher for the higher SRTs, but the difference was only statistically significant at the 15-day SRT. Based on volatile suspended solids measurements, the thermophilic solids destruction efficiency was approximately 4 percentage points higher at the 10- and 15-day SRTs. At a 4-day SRT, methanogenic activity could only be maintained in the thermophilic digester. The pH, alkalinity, ammonia, volatile fatty acid, and soluble chemical oxygen demand concentrations were higher for the thermophilic digester at each SRT. At SRTs of 10 days and less, the thermophilic digester had a much higher propionate and slightly higher butyrate concentration. Carbohydrates were readily degraded by both digesters, protein was the major component in the sludge at the long SRTs, and lipid degradation increased with increasing SRT.

The precision with which the elevation of a feature, such as a terrace, can be measured depends on the characterization of the noise contaminating the measurement. A method for identification and extraction of terrace feature elevations is presented and the topographic noise, due to erosion, as well as measurement error, is quantified. High-resolution digital elevation models (DEM) are acquired at six wave-cut, volcanic bedrock terrace sites from around the highstand of paleo-Lake Lahontan in the western Great Basin. Local DEMs, which are tied to regional geodetic control, were acquired using conventional total station, rapid postprocessed and real-time kinematic Global Positioning System methods. The topographic signal is processed with derivative filters for geomorphic feature recognition and averaging for noise reduction. Results indicate that noise levels for identifiable features such as riser crest, knickpoint, and slope inflection point are statistically equivalent and on the order of 0.5 m standard deviation. Averaging within topographic bins spanning ∼50 m along terrace strike yields feature elevation estimates with standard errors on the order of 0.12 m. The mean bench window elevation (between the riser crest and knickpoint) has the lowest standard error and is systematically related to water level. Propagation of surveying, geoid estimation, and terrace feature elevation estimation errors indicates that displacements on the order of 0.5 m may be resolved using these methods. Elevation estimate interpretation involves terrace development, degradation, and neotectonics, but this new methodology has significant advantages in studies of neotectonic or geomorphic processes using local terrace elevation measurements.

SUMMARY An indirect boundary element method has been used to compute seismic wavefields in layered media. The advantages of this technique over numerical grid methods are that it satisfies radiation conditions, incorporates free surface effects, solves viscoelastic problems and can handle arbitrary source types. The technique is more appropriate for models with high aspect ratios and a limited number of layers. The computational cost increases with the number of layers and frequency content. Examples are presented in this study to illustrate some of the features of the technique. Seismograms are computed for SH and P‐SV line sources in 2-D earth models. Finite-difference and the Cagniard‐ de Hoop methods are used to test the accuracy of the technique. Even though the computation time for the method is several times greater than finite differences, the technique becomes cost effective as the number of computed shot-gathers increases. The technique also allows computation of constant offset gathers at a small additional cost which is very expensive to do by using finite differences. Numerical grid methods (e.g. finite differences, finite elements and pseudospectral methods) have become the standard tool for seismic modelling. These techniques are extremely versatile in terms of model complexity that can be treated, although grid generation may still be problematic. These methods are also very demanding of computation time. They involve discretization of the entire model volume, at a grid spacing which is generally much shorter than the smallest wavelength present in the solution. The finite aperture of the grid also imposes difficulties in the approximation of radiation conditions on the solutions and thus the grid may need to be made much larger than the modelled region. A third set of difficulties is associated with the approximation of the solution in the vicinity of boundaries (both internal and free surface). All of the grid methods involve some smoothing of the solution that may be objectionable for some modelling purposes, but may in fact be an advantage in imaging or migration. Boundary methods, boundary integrals (BIM) and boundary elements (BEM) have emerged as alternatives to the grid methods in cases where better accuracy is required near boundaries and sources or where the domain is infinite in extent (Cruse 1980). Boundary methods discretize the model only on boundary surfaces, rather than throughout the model volume, so that advantages may be obtained for models with large aspect ratio

Dechlorination studies were conducted using microbial cultures developed in a fluidized-bed reactor (FBR) that dechlorinates pentachlorophenol (PCP) to 3,4-dichlorophenol (3,4-DCP) and 4-monochlorophenol (4-MCP). Electron donor experiments demonstrated that lactate, propionate, and H2 can serve as electron donors for chlorophenol (CP) dechlorination in mixed, anaerobic, PCP-enriched cultures. Dechlorination did not proceed in the absence of an electron donor. Acetate, which resulted in little H2 production, was a poor electron donor. The results of inhibition studies using vancomycin and 2-bromoethanesulfonic acid implicate members of the domain bacteria in the dechlorination of CPs, whereas methanogens do not appear to be involved in dechlorination. Brief heat treatment (80°C for 90 min) of the FBR enrichment cultures implicated endospore formers in the dechlorination of CPs, primarily at the ortho position, where PCP was dechlorinated to 3,4,5-trichlorophenol (3,4,5-TCP) (the sole TCP detected) and subs...

Combine the bold landscape of northern New Mexico (Figure 1) with a unique educational program that blends teaching and research as a partnership among universities, industry, and federal laboratories and you have SAGE (Summer of Applied Geophysical Experience). SAGE was conceived from a vision that something special would come from pooling the resources and talents of diverse groups. It enables undergraduate and graduate students from large and small schools alike to share the excitement of hands-on, modern field geophysical research and learning. Much more than a summer geophysics field camp, SAGE is an immersion in geophysics, an educational experience that many students say is the most satisfying in their lives. Students participate in every phase of the field program: They collect data with modern equipment; they process, model, and interpret the data with workstations and PCs; and they present their results in both oral and written form. The program is not just about using equipment; it's about unde...

Microbial degradation kinetics of carbon tetrachloride (CT) under reducing conditions were investigated for different cultures, fed with 1,2-propanediol, dextrose, propionaldehyde, or acetate and nitrate, in the anaerobic step of an anaerobic/aerobic operation sequence. Methanogenesis was inhibited due to the aerobic step. CT biodegradation rates followed first-order kinetics with respect to CT concentration and biomass and were not affected by the presence of growth substrate. CT degradation rates increased linearly with higher intracellular vitamin B12 content. The culture fed 1,2-propanediol had the highest vitamin B12 content, which was 3.8, 4.7, and 16 times that of the propionaldehyde-, dextrose-, and acetate-fed cultures, respectively, and its first-order degradation rate constant was 2.8, 4.5, 6.0 times that for those cultures, respectively. No CT degradation occurred with culture liquid, suggesting that intracellular factors were responsible for CT degradation. The propanediol culture was able to...

The effects of bioaugmentation with a pentachlorophenol (PCP)-adapted consortium and biostimulation with glucose as a carbon source on anaerobic bioremediation of PCP-contaminated soil were investigated in terms of the initial PCP removal rate and the extent of PCP dechlorination and mineralization. Samples from two PCP-contaminated sites were prepared, put into a series of Hungate tubes, inoculated, and fed under different conditions. Chlorophenols in the tubes were monitored over a 4-month period to measure PCP transformation in the soil. In less contaminated soil (10 mg PCP/kg soil), it was found that biostimulation with glucose at 1 g/kg soil or bioaugmentation at 0.14 g volatile suspended solids (VSS)/kg soil could greatly improve PCP degradation. The best PCP degradation was obtained when both bioaugmentation and biostimulation were applied, but higher levels of glucose (2 g/kg soil) or inoculum (0.56 g VSS/kg soil) had little additional effect. The highest initial PCP-removal rate reached ...

Natural organic matter (NOM) affects the rate of metal leaching from the surface of leaded brass and the morphology of lead-containing corrosion products. SEM data indicate that lead forms a separate phase on the surface of the alloy. In organic-free water, hexagonal thin plates of hydrocerussite Pb 3 (OH) 2 (CO 3 ) 2 accumulate on and near corroding lead islets. NOM inhibits the growth of the crystals of hydrocerussite and promotes the formation of an amorphous hydrated surface film. The galvanic coupling of the surface lead phase with the rest of the alloy accelerates its oxidation. The share of lead in the oxidized metal leached from or accumulated on the surface, substantially exceeds that in the bulk alloy both in organic free-water and in the presence of NOM. NOM increases both short- and long-term lead leaching. Its effects are most noticeable in the range of dissolved carbon concentrations 0–2 mg/l.

The reductive dechlorination of chlorophenols was studied in three fluidized-bed reactors (FBRs) with respect to enrichment, pathways, complete dechlorination, and overall performance. The methanogenic consortia, developed by previous researchers in our laboratory, have been further enriched by reducing the ratio of substrate to pentachlorophenol (PCP) and increasing the PCP loading. The performance of the consortia was improved, and complete dechlorination at high PCP loading rates was observed, reaching a PCP loading of 1227 µmol/L d with 99% chlorophenol removal. The dechlorination rates in the reactors for chlorophenol (CP) congeners were obtained and were used to evaluate the performance of the three consortia and to quantitatively estimate the fates of these chlorophenols in the reactors. The consortium with the best performance was further investigated in bottle tests by treatment with heat and metabolic inhibitors to examine chlorophenol degradation and to characterize the CP degraders. The degrad...

The fate and dechlorination kinetics of PCP and its intermediates were studied in two fluidized-bed reactors (FBRs) with methanogenic enrichments. The two FBRs were operated at a 1-day hydraulic retention time and fed lactate at 400 mg/L and pentachlorophenol (PCP) at 5 mg/L (18.8 μmol/L). PCP was meta-dechlorinated to 2,3,4,6-tetrachlorophenol (2346-TeCP). Approximately 75% of the 2346-TeCP was meta-dechlorinated to 2,4,6-trichlorophenol (246-TCP), followed by sequential o-chlorine removals to 4-monochlorophenol (4-MCP); the remaining 2346-TeCP was ortho-dechlorinated via 245-TCP to 3,4-dichlorophenol (34-DCP). Neither 34-DCP nor 4-MCP were dechlorinated throughout the 18-month testing period. In mixed-CP batch tests, CPs competed with each other, resulting in reduced dechlorination rates; competition was position-specific with respect to ortho- and meta-dechlorination reactions. Michaelis−Menten dechlorination kinetic coefficients and linear solid−liquid partition coefficients were determined for PCP, 2...

The goal of this research was to determine conditions that could promote or inhibit pathogen growth during storage or application of pasteurized digester solids. Growth of enterobacteriaceae and Salmonella after pasteurization (70 °C for 30 minutes) of mesophilic anaerobic digester solids was reported for numerous facilities in Switzerland but the cause was not known. However, our work found no growth of indigenous Salmonella or fecal coliform in well-mixed pasteurized samples in bench-scale conditions. Salmonella typhimurium was then added in batch tests to determine growth or die-off at 20 and 35 °C incubation temperatures. In addition, pasteurized digester solids were fed for 3 months to a laboratory 6-day solids retention time (SRT) secondary mesophilic digester to determine if pathogen growth could occur. Fecal coliform die-off occurred in inoculated pasteurized solids under all conditions, but Salmonella growth readily occurred within 5 days and died off within 30 days of incubation. The Salmonella grew better at 20 than at 35 °C, and substrate addition did not improve growth. When the pasteurized solids were mixed and oxygenated, Salmonella die-off instead of growth occurred. Experiments at 35 °C with both batch bottles and the secondary digester showed that the presence of other active anaerobic bacteria apparently caused Salmonella die-off instead of growth. Pathogen growth can be prevented and Class A biosolids can be ensured by storing pasteurized digester solids in a secondary mesophilic digester with a 6-day SRT.