bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferred orientations and anisotropy in shales: Callovo-Oxfordian shale (France) and Opalinus Clay (Switzerland)
Authors: Wenk H.-R. , Voltolini M. , Mazurek M. , Van Loon L. R. , Vinsot A. 
Published: June 2008

AbstractAnisotropy in clay-rich sedimentary rocks is receiving increasing attention. Seismic anisotropy is essential in the prospecting for petroleum deposits. Anisotropy of diffusion has become relevant for environmental contaminants, including nuclear waste. In both cases, the orientation of component minerals is a critical ingredient and, largely because of small grain size and poor crystallinity, the orientation distribution of clay minerals has been difficult to quantify. A method is demonstrated that relies on hard synchrotron X-rays to obtain diffraction images of shales and applies the crystallographic Rietveld method to deconvolute the images and extract quantitative information about phase fractions and preferred orientation that can then be used to model macroscopic physical properties. The method is applied to shales from European studies which investigate the suitability of shales as potential nuclear waste repositories (Meuse/Haute-Marne Underground Research Laboratory near Bure, France, and Benken borehole and Mont Terri Rock Laboratory, Switzerland). A Callovo-Oxfordian shale from Meuse/Haute-Marne shows a relatively weak alignment of clay minerals and a random distribution for calcite. Opalinus shales from Benken and Mont Terri show strong alignment of illite-smectite, kaolinite, chlorite, and calcite. This intrinsic contribution to anisotropy is consistent with macroscopic physical properties where anisotropy is caused both by the orientation distribution of crystallites and high-aspect-ratio pores. Polycrystal elastic properties are obtained by averaging single crystal properties over the orientation distribution and polyphase properties by averaging over all phases. From elastic properties we obtain anisotropies for p waves ranging from 7 to 22%.
Hydrothermal synthesis, between 75 and 150°C, of High-charge, ferric nontronites
Authors: Decarreau Alain , Petit Sabine , Martin François , Farges François , Vieillard Philippe , Joussein Emmanuel 
Published: June 2008

AbstractHigh-charge nontronites were synthesized at 75, 90, 100, 110, 125, and 150°C from a silicoferrous starting gel with Si2FeNa2O6.nH2O composition. This gel was oxidized in contact with air and then hydrothermally treated, for a period of 4 weeks, under equilibrium water pressure. The synthesized nontronites were similar to each other, regardless of the synthesis temperature. Their structural formula, obtained from chemical analysis, X-ray diffraction (XRD), and Fourier transform infrared (FTIR), Mössbauer, and X-ray absorption fine structure spectroscopies is: (Si3.25Fe0.753+)Fe23+O10(OH)2Na0.75$\left( {{\rm{S}}{{\rm{i}}_{3.25}}{\rm{Fe}}_{0.75}^{3 + }} \right){\rm{Fe}}_2^{3 + }{{\rm{O}}_{10}}{\left( {{\rm{OH}}} \right)_2}{\rm{N}}{{\rm{a}}_{0.75}}$. A strictly ferric end-member of the nontronite series was therefore synthesized for the first time. The uncommon chemistry of the synthesized nontronites, notably the high level of Fe-for-Si substitution, induced particular XRD, FTIR, and differential thermal analysis-thermogravimetric analysis data. The ethylene glycol expandability of the synthetic nontronites was linked to their crystallinity and depended on the nature of the interlayer cation, moving from smectite to vermiculite-like behavior. As the synthesis temperature increased, the crystallinity of the synthesized clays increased. The nontronite obtained at 150°C had the ‘best crystallinity’, which cannot be improved by increasing synthesis time or temperature.
The pH of aqueous bentonite suspensions
Authors: Kaufhold Stephan , Dohrmann Reiner , Koch Dietrich , Houben Georg 
Published: June 2008

AbstractThe pH of aqueous bentonite suspensions is known to be influenced by carbonates present even in minor amounts. On the other hand, at high solid:liquid ratios (at standard pH measurement conditions: 2% w/w suspension), the type of exchangeable cation in the smectite is also known to determine pH (particularly Na+ or Ca2+). By cation-exchange tests we proved that exchanging the Ca2+ for Na+ results in an increase in the pH. However, this increase in pH was only found if excess salts were removed from the system (by washing or dialysis, respectively). The effect of the type of exchangeable cation can, at least partially, be explained by hydrolysis of Ca2+. On the other hand, a pronounced alkalinity of Na bentonites is observed which can, at least partially, be attributed to the hydrolysis of montmorillonite (Na+ is exchanged for H+ of water). The increase in the volume of the Stern layer, caused by increasing the degree of delamination, is also suggested to play a role. H+ and Na+ are concentrated in the Stern layer. Hence, increasing the Stern layer volume decreases the amount of H+ and Na+ in solution and thus increases pH. Unfortunately, both processes, montmorillonite hydrolysis and delamination, depend on the ionic strength. Distinguishing the processes quantitatively, therefore, is an analytical challenge, and impossible based on the data presented here.To model the pore-water chemistry of clays and clay stones, all of the above-mentioned processes have to be considered. It is possible that other reactions, not identified in the present work, contribute toward the pH values of aqueous bentonite suspensions.
The behavior of Fe in ground and acid-treated vermiculite from Santa Olalla, Spain
Authors: Maqueda Celia , Romero Agua Santas , Morillo Esmeralda , Pérez-Rodríguez José L. , Lerf Anton , Wagner Friedrich Ernst 
Published: June 2008

AbstractThe preparation of porous materials from clay minerals by selective leaching is of interest because it yields residues with large specific surface areas that can be used as adsorbents of contaminants or as catalysts. Grinding produces surface modifications and therefore may significantly influence the leaching behavior. The aim of this paper is to study the effect of grinding and leaching on the structure of the vermiculite from Santa Olalla, Spain, using 57Fe Mössbauer spectroscopy, X-ray diffraction, infrared spectroscopy, and specific surface area (SBET) measurements. The study shows that grinding destroys the long range order of the vermiculite, but leaves the local structure in the environment of the Fe atoms intact, at least up to a grinding time of 10 min. The Mössbauer study shows that there is no Fe3+ in the tetrahedral sheets and that grinding does not lead to a significant oxidation of the structural Fe. Vermiculite ground for 4 min and leached with 1 M HCl solution at 80°C over a 24 h period was decomposed to X-ray amorphous silica with a very large specific surface area (SBET = 720 m2g−1) and with total pore volume of 0.586 cm3 g−1, whereas an unground sample leached with the same acid concentration yielded a specific surface area of only 504 m2 g−1. Most of the Mg2+ and Al3+ are removed from the ground sample after leaching with 1 M HCl, while large percentages of Fe2O3 remain with the X-ray amorphous silica. In unground vermiculite leached with 1 M HCl, a considerable amount of vermiculite remains in the residue. A sample ground for 4 min and treated with 0.25 M HCl also shows the typical vermiculite Mössbauer spectrum with an Fe2+/Fe3+ ratio similar to that of the unground vermiculite. The samples ground for 2 or 4 min and treated with 1 M HCl solution have an orange color and, according to the Mössbauer spectra, only Fe3+ remains. Mössbauer spectra of these samples taken at 4.2 K reveal the presence of akaganéite.
An evaluation of the bioavailability and aquatic toxicity attributed to ambient copper concentrations in surface waters from several parts of the world
Authors: Van Genderen Eric , Adams William , Cardwell Rick , van Sprang Patrick , Arnold Ray , Santore Robert , Rodriguez Patricio 
Published: July 2008

Abstract
Ambient concentrations of metals in surface waters have become an important consideration when establishing water quality criteria and conducting risk assessments. This study sought to estimate amounts of copper that may be released into fresh and estuarine waters considering ambient concentrations, toxicity thresholds, and bioavailability. Cumulative distribution functions of ambient copper concentrations were compared statistically for individual sites within 14 surface waters of North America and Europe to identify differences among mean distribution variables (e.g., slopes, intercepts, and inflection points). Results illustrated that the majority of distributions among sites differed significantly. These differences illustrate the variability in ambient copper concentrations in surface waters due to geographic location, regional geology, and anthropogenic influence. Additionally, surface water quality data were used for streams and lakes in Chile, Europe, and North America (including 1 saltwater estuary) to estimate bioavailable copper concentrations in ambient surface waters (based on predictions using biotic ligand models). The amount of dissolved metal that could be added to surface waters without exceeding toxicity thresholds was calculated by subtracting ambient surface water concentrations from chronic (reproduction) no-observable-effect concentrations (NOEC) for Daphnia magna using the freshwater data and 48-h median-effect (normal shell development) concentrations (EC50) for Mytilus edulis using that for saltwater. Because ambient dissolved copper concentrations were, on average, only a small fraction (18%) of predicted effects threshold, an average of 14 ± 17 μg/L (±SD) of copper could be added before exceeding the D. magna chronic NOEC or the M. edulis EC50. However, several sites were identified as having ambient copper concentrations in excess of these toxicity thresholds. The risks posed by copper to sensitive indicator species in surface waters can now be readily computed to facilitate site-specific consideration of point and nonpoint sources of metal.
Simulation-Based Technology for Rapid Assessment of Redevelopment Potential in Marginal Gas Fields—Technology Advances and Validation in Garden Plains Field, Western Canada Sedimentary Basin
Authors: Cheng Y. , McVay D. A. , Wang J. , Ayers W. B. 
Published: July 2008

SummaryIt is often difficult to quantify the redevelopment potential of marginal oil and gas fields because of a wide range of depositional environments, variability in reservoir properties, a large number of wells, and limited reservoir information. Evaluation of infill potential in these fields with traditional simulation methods is timeconsuming, labor-intensive, and frequently cost-prohibitive. Without adequate assessment technology, some unprofitable infill campaigns may be initiated, while other promising infill campaigns may be terminated prematurely because of disappointing early results.In this paper, we present a simulation-based regression technique to assess infill-drilling potential in marginal gas fields. With limited, basic reservoir information, this technique first estimates the spatial distribution of subsurface reservoir properties by rapid history matching of well production data. We implemented a sequential regression algorithm to estimate, from available flowrate measurements, not only the permeability distribution, but also the pore-volume distribution. Future production is forecasted and infill-drilling potential is determined using the estimated permeability and pore-volume distributions. Because the method uses an approximate reservoir description, it identifies regions of the field with promising infill potential rather than individual-infill-well locations.The proposed technique provides rapid, reliable, and cost-effective assessment of redevelopment potential in marginal gas fields. In this paper, we first validate our approach using synthetic reservoir data. We then apply the approach to the Second White Specks formation, Garden Plains field, Western Canada Sedimentary Basin. The prediction of infill potential in this gas field, which has more than 700 wells, demonstrates the power and utility of the proposed technique.
Drainage and Imbibition Relative Permeability Relationships for Supercritical CO2/Brine and H2S/Brine Systems in Intergranular Sandstone, Carbonate, Shale, and Anhydrite Rocks
Authors: Bennion D. Brant , Bachu Stefan 
Published: July 2008

Summary
Disposal of acid gas, composed of carbon dioxide (CO2) and hydrogen sulfide (H2S), in deep underground formations is a means for reducing atmospheric emissions of toxic and greenhouse gases produced from sour-gas reservoirs that has been practiced for 18 years in North America and is currently being considered in other regions, such as the Middle East and central Asia. Acid-gas-injection operations constitute a commercial-scale analog to CO2injection in geological media as a climate-change mitigation measure. Deep saline aquifers provide a very large capacity for the sequestration of acid and greenhouse gases, being found in all sedimentary basins around the world. Proper understanding of the relative permeability-displacement character of such systems is essential in ascertaining gas injectivity and migration, and in assessing the suitability, containment, and safety of prospective injection sites.
Pure CO2 and H2S represent the compositional end members of acid and greenhouse gases, hence the interest in measuring their displacement properties. This paper presents the detailed experimental equipment and protocols along with the results of a series of relative permeability measurements conducted at full reservoir conditions using supercritical pure CO2 and H2S on samples of intercrystalline sandstone, carbonate, shale, and anhydrite rocks from the Wabamun and Zama areas in Alberta, Canada, where large CO2 sources and several acid-gas-injection operations exist. Results of the relative permeability measurements are presented for each fluid and rock type. The results provide a valuable data set for the evaluation and simulation of acid-gas disposal and CO2-sequestration projects.
Controllability of the discrete-spectrum Schrödinger equation driven by an external field
Authors: Chambrion Thomas , Mason Paolo , Sigalotti Mario , Boscain Ugo 
Published: June 2008

We prove approximate controllability of the bilinear Schrödinger equation in the case in which the uncontrolled Hamiltonian has discrete non-resonant spectrum. The results that are obtained apply both to bounded or unbounded domains and to the case in which the control potential is bounded or unbounded. The method relies on finite-dimensional techniques applied to the Galerkin approximations and permits, in addition, to get some controllability properties for the density matrix. Two examples are presented: the harmonic oscillator and the 3D well of potential, both controlled by suitable potentials.RésuméNous montrons la contrôlabilité approchée de l'équation de Schrödinger bilinéaire dans le cas où l'hamiltonien non contrôlé a un spectre discret et non-résonnant. Les résultats obtenus sont valables que le domaine soit borné ou non, et que le potentiel de contrôle soit borné ou non. La preuve repose sur des méthodes de dimension finie appliquées aux approximations de Galerkyn du système. Ces méthodes permettent en plus d'obtenir des résultats de contrôlabilité des matrices de densité. Deux exemples sont présentés, l'oscillateur harmonique et le puits de potentiel en dimension trois, munis de potentiels de contrôle adéquats.
Neurodevelopmental markers in different psychopathological dimensions of first episode psychosis: The ESPIGAS Study
Authors: Ruiz-Veguilla Miguel , Cervilla Jorge A. , Barrigón Maria Luisa , Ferrín Maite , Gutiérrez Blanca , Gordo Estibaliz , Anguita Manuel , Brañas Antía , Fernández-Logroño Jesús , Gurpegui Manuel 
Published: June 2008

AbstractObjectiveThe main aim of this study was to explore whether specific groups of patients with first episode non-affective psychosis could be identified on a psychopathological basis and, then, whether such identified groups could be validated by exploring their correlation with a variety of neurodevelopmental markers.MethodEighty-seven patients with a first episode of non-affective psychotic disorder were consecutively recruited. We assessed psychopathology and neurological soft signs using the PANSS and the Neurological Evaluation Scale, respectively. We collected information on obstetric complications, premorbid adjustment and family history.ResultsAll PANSS symptoms were analysed using principal component analysis and four factors were obtained (negative, disorganization, positive and paranoid). Subsequently, the four factors were subjected to a cluster analysis where three groups emerged: “paranoid” (n = 40), “low score” (n = 29) and “negative” (n = 18) subtype. After adjusting by sex and age, we found that the “negative group” had poorer social premorbid adjustment, worse verbal fluency and higher prevalence of both obstetric complications and neurological soft signs, when compared with the “low score” group. Similarly, the “negative group” showed significantly poorer social premorbid adjustment and higher number of neurological soft signs than the “paranoid group”.ConclusionsOur results support that, among non-affective first onset psychotic patients, those with predominant negative symptoms are more likely to correlate with higher presence of neurodevelopmental markers.
Risk factors for well‐differentiated thyroid carcinoma in patients with thyroid nodular disease
Authors: Raza S. Naweed , Shah Manish D. , Palme Carsten E. , Hall Francis T. , Eski Spiro , Freeman Jeremy L. 
Published: June 2008

ObjectivesEvaluate current accepted risk factors for well‐differentiated thyroid carcinoma, and develop a predictive model to determine one's risk of malignancy given a thyroid nodule.Study DesignRetrospective analysis of 600 patients.Subjects and MethodsPatients with benign thyroid nodular disease and with well‐differentiated thyroid cancer were randomly selected. Patient, clinical, and investigational data were compared by means of univariate and multivariate regression analyses.ResultsAge, regional lymphadenopathy, ipsilateral vocal cord palsy, solid and/or calcified nodules, and an aspiration biopsy being malignant or suspicious predicted for cancer (P < 0.05). Regional lymphadenopathy and vocal cord palsy are perfect predictors of malignancy. Multivariate analysis indicated age, solid and/or calcified nodules, and all fine‐needle aspiration biopsy results to be significant in assessing risk (P < 0.05).ConclusionTaking individual risk factors in isolation is not always reliable. Using a predictive model, one can anticipate a patient's risk of malignancy when the diagnosis is unclear.
Intralesional steroid injection for the management of otohematoma
Authors: Im Gi Jung , Chae Sung Won , Choi Jun , Kim Yang Soo , Kim Woo Joo , Jung Hak Hyun 
Published: June 2008

ObjectivesTo compare the therapeutic efficacies of aspiration plus intralesional steroid injection and aspiration plus pressure dressing for the management of otohematoma.Study Design and SettingFifteen patients with otohematoma were treated by aspiration plus pressure dressing (the pressure dressing group) and 34 patients were treated with intralesional steroid injections followed by simple aspiration (the steroid injection group).ResultsOtohematoma resolved within four weeks in all 15 patients in the pressure dressing group, but eight of the 15 showed perichondrial thickening. The duration of treatment was shorter in the steroid injection group than in the pressure dressing group; 14 (41.2%) of the 34 recovered after the first injections and another 15 (44.1%) after the second, and the remaining 5 (14.7%) after the third without any complications. However, multiple steroid injections are needed due to a high early recurrence rate.ConclusionIntralesional steroid injection is the treatment of choice for the management of otohematoma. The correction of causative use of a hard pillow, a helmet, and headphones is essential to prevent late recurrence.
Laser myringoplasty for tympanic membrane atelectasis
Authors: Brawner J. Travis , Saunders James E. , Berryhill Wayne E. 
Published: June 2008

ObjectiveTo review our experience with laser myringoplasty using a potassium‐titanyl‐phosphate (KTP) laser for pars tensa atelectasis.Study DesignRetrospective review.MethodsA pulsed diode KTP laser (532 nm) was used to tighten the tympanic membrane after lysis of middle ear adhesions through a myringotomy. A tympanostomy tube was then placed. Operative reports and clinic notes were reviewed.ResultsWe reviewed 34 procedures performed on 31 ears in 29 patients. The average time of follow‐up was 10.5 months with a range of 1 to 30 months. Seventeen of 34 tubes (50%) extruded during the follow‐up period. Eleven cases had follow‐up with the tube extruded and TM intact. Two (18%) of those had progression of atelectasis. Two (6%) cases had operative perforations and both healed spontaneously.ConclusionLaser myringoplasty using a KTP laser for pars tensa atelectasis appears to be beneficial in selected patients. Patients should be followed closely for early tube extrusion and recurrent disease.
Accelerating functional recovery after rat facial nerve injury: Effects of gonadal steroids and electrical stimulation
Authors: Hetzler Laura E. T. , Sharma Nijee , Tanzer Lisa , Wurster Robert D. , Leonetti John , Marzo Sam J. , Jones Kathryn J. , Foecking Eileen M. 
Published: June 2008

ObjectiveWe investigated the combined effects of electrical stimulation and testosterone propionate on overall recovery time in rats with extracranial crush injuries to the facial nerve.Study DesignMale rats underwent castration 3 to 5 days prior to right facial nerve crush injury and electrode implantation. Rats were randomly assigned to two groups: crush injury + testosterone or crush injury with electrical stimulation + testosterone. Recovery was assessed by daily subjective examination documenting vibrissae orientation/movement, semi‐eye blink, and full eye blink.ResultsMilestones of early recovery were noted to be significantly earlier in the groups with electrical stimulation, with/without testosterone. The addition of testosterone to electrical stimulation showed significant earlier return of late recovery parameters and complete overall recovery.ConclusionElectrical stimulation may decrease cell death or promote sprouting to accelerate early recovery. Testosterone may affect the actual rate of axonal regeneration and produce acceleration in functional recovery. By targeting different stages of neural regeneration, the synergy of electrical stimulation and testosterone appears to have promise as a neurotherapeutic strategy for facial nerve injury.