bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genesis of Refractory Clay Near Guanajuato, Mexico
Authors: Hanson Robert F. , Keller W. D. 
Published: August 2006

AbstractRefractory clay, derived from hornblende chlorite schist that was hydrothermally altered along nearly vertical fractures and faults, occurs near Guanajuato, Mexico, a few kilometers south and east of the famous monument, El Cristo Rey. Part of the chlorite is expanding, i.e. probably mixed-layer vermiculitic chlorite or biotite. The most refractory clay is comprised chiefly of kaolinite, with variable amounts of finely crystalline quartz. Huge, thick “gossans” of silica have been deposited as surface-covers over the fractures; such silica gossans are fairly common over Mexican hydrothermal clay deposits and may be used as probable field guides to argillation.The trend of mineralogical and chemical changes (analyses tabulated in the paper) during argillation of the Guanajuato material is traced in overlapping sequence, as follows:(a)bleaching of green ferro-ferric silicates accompanied by oxidation of part of the iron to “limonite”.(b)leaching of alkali and alkaline earths accompanied by(c)partial desilication of parent silicate minerals yielding kaolinite whose flakes are commonly oriented parallel with the chlorite of the schist, mobile silica, and finely divided quartz intermixed with the kaolinite(d)refinement (“purification”) of the clay by further kaolinization and removal of silica minerals and some iron oxide.The final clay may run higher in silica than does its parent rock.
Quantitative Fabric of Wet Kaolinite
Authors: Martin R. Torrence 
Published: August 2006

AbstractA method is described for quantitatively expressing orientation of kaolinite particles in a wet clay mass. Wet clay is impregnated with a polyalcohol which permits grinding of a very flat surface (without disrupting the original fabric) for quantitative X-ray measurement. In the specific procedure discussed, a Norelco diffractometer equipped with a pole figure device and a Geiger detector was employed to measure by reflection the diffracted intensity of the 002 and 020 kaolinite reflections. The amplitude of the 002 peak to the amplitude of the 020 peak is called the peak ratio, PK, which quantitatively expresses particle orientation at any chosen angle to the specimen surface. Limits of orientation are random and maximum orientation. For the kaolinite tested, truly random orientation was achieved which gave a PR = 2.0. Maximum orientation found experimentally was PR = 200 for thoroughly dispersed slurry slowly dried on a glass slide. Vertical and lateral variations can be measured either continuously or in steps of any chosen size.
The Fabric of Mechanically Compacted Kaolin
Authors: Sloane Richard L. , Kell T. R. 
Published: August 2006

AbstractAn electron microscope study was made to determine the effect of mechanical compaction method on the fabric produced in a compacted commercial kaolin. Direct platinum-shadowed carbon replicas were made from horizontal and vertical fracture surfaces within the middle third of cylindrical specimens compacted by static load, impact, and kneading compaction at optimum moisture content and at 3% above and below optimum. Replicas were studied in the electron microscope to arrive at a qualitative evaluation of fabric. No oriented fabric or edge-to-face random fabric of individual particles, as postulated by others, was found. Regardless of compaction method the fabric was found to consist of parallel and random arrangements of packets of kaolin flakes. Both impact and kneading compaction produced essentially the same fabric consisting of trajectories of parallel packets, probably the result of shearing deformation during compaction, within essentially randomly oriented zones of packets. Static load compaction produced a fabric in which some tendency of the packets to orient normal to the direction of loading was apparent. For all compaction methods some increase in parallel packet orientation was noted with increase in molding water content. The mode of parallel orientation differed between static load compacted specimens and those produced by either impact or kneading compaction. Results of the study indicate that some revision of concepts regarding particle orientation due to mechanical compaction should be made.
The Fabric of Soil—Cement and Its Formation
Authors: Mitchell James K. , El Jack Sid Ahmed 
Published: August 2006

AbstractThe electron microscope has been used to study changes in particle size, shape, and arrangement that occur during the hydration of clay in soil—cement. Samples of kaolinite, of a mixture of silica flour and montmorillonite, and of a natural silty clay were mixed with sufficient portland cement to produce soft—cement. Specimens were cured at constant moisture content for periods up to 32 weeks after compaction at optimum moisture content for the mixture. At the end of the curing period surfaces of fresh fractures were replicated, and the replicas were studied using the electron microscope.All three mixtures showed similar behavior. Initially the fabric is one of separate portland cement grains distributed throughout the clay soil. As hydration of the cement proceeds, cement hydrate gel forms along the edges of groups of clay particles. Reaction between the soil and the cement is observed early in the hydration period. As hydration continues the soil grains are more and more broken down and the cement gel diffuses more extensively throughout the mass. Eventually, the breakdown of the soil minerals and the formation of hydration products reaches a point whore the soil and cement can no longer be distinguished as separate phases.
Suction Responses Due to Homogeneous Shear of Dilute Montmorillonite-Water Pastes
Authors: Ripple Charles D. , Day Paul R. 
Published: August 2006

AbstractA recently described phenomenon, the shear induced decrease of moisture suction in saturated clay—water systems and its subsequent recovery, has been investigated with the aid of a parallel plate shearing device. The apparatus allowed a more quantitative description of the phenomenon than was previously possible. In 4–6% Na-montmorillonite pastes it demonstrated a well defined suction response to shear oven for shear angles as small as one degree. The observed decrease in suction was rapid at first. It terminated within a few minutes and was followed by an approximately exponential, occasionally incomplete recovery. All the tests carried out exhibited the same general features of suction change.It is postulated that shear induces a displacement or change in configuration of particles and that subsequently they return to their original states due to thermal motion. The shapes of the recovery curves can be interpreted in terms of the relaxation spectrum functions encountered in linear viscoelasticity theory. By utilizing a characteristic relaxation time for these spectra, rate process theory has been employed to interpret the bonding mechanism in terms of the experimental activation free energy. The results suggest that the bonds which are re-established during the recovery are primarily of the Coulombic type.Shear induced suction changes should be considered when dealing with deformation theories and structural models of wet soils and clays. Indeed they provide a means of testing certain aspects of soil structure.
Statistical Distribution Patterns of Particle Size and Shape in the Georgia Kaolins
Authors: Conley Robert F. 
Published: August 2006

AbstractHigh resolution electron micrographic techniques have been employed for surveying the size and shape distributions of kaolinite particles, both plates and stacks, from well-crystallized Georgia deposits.Both size and shape follow typical, positively-skewed, frequency distributions. Particle thicknesses among plates appear quantized, dominantly as hoxalaminae and subordinately as trilaminae of the basic c-axis dimension in the unit cell. Specimens subjected to severe shear and attrition show intermediate values of thickness, i.e. 3n + 1 and 3n + 2. Profile studies on kaolinite stacks reval integral platelet units whose distribution in thickness corresponds to that of individual plates.Energy calculations for fracture (cleavage ‖ to c-axis) and delamination (cleavage ⊥c-axis) processes indicate that hydrokinetic cleavage in nature should result in particles having an aspect ratio distribution peaking near 6: 1. The dominance of stacks above 10 μ is suggestive of in situ weathering. Experimental shear measurements correlate well with these proposals.Sedimentation studies with clays of various shapes and distributions were performed in a variety of aqueous media, including sea water. Sediment volume data, microscopic observations, and theoretical packing calculations are compared with the several mechanisms proposed for plate-stack genesis.
Interrelationships of Physical and Chemical Properties of Kaolinites
Authors: Bundy W. M. , Johns W. D. , Murray H. H. 
Published: August 2006

AbstractRank-correlation coefficients are utilized to show relationships between physical and chemical properties of Georgia and English kaolins. Montmorillonite impurity in the Cretaceous kaolins shows high level correlations with magnesium, iron, silica-alumina ratio, CEC, water sorption, surface area, sediment volume, and Brookfield viscosity. Cation exchange capacity of these kaolins is believed to be related primarily to montmorillonite impurity. Low shear viscosity measurements show a strong correlation to properties indicative of montmorillonite. Correlations with viscosity are believed to be related primarily to surface area and particle packing. Packing volume exerts a dominant effect on high shear rheology. Differences in particle shape are not of sufficient magnitude to show a significant effect on rheology. A strong inverse relationship of vanadium with high shear viscosity indicates that the wetting effect of vanadium organic complexes or adsorption of (VO4)−3 tetrahedra at gibbsite edge faces may be mechanisms for viscosity reduction. Brightness and whiteness are related to titanium and iron-bearing impurities as well as the amount of particles having optimum diameters for light scattering. Well-crystallized kaolinites are believed to have been derived primarily from feldspar. Muscovite alteration may be retarded where well-crystallized kaolinites occur. To account for the inverse relation of vanadium with crystallinity, it is suggested that complex vanadium ions may act as growth poisons.
Collapse of Potassium Montmorillonite Clays Upon Heating—“Potassium Fixation”
Authors: van Olphen H. 
Published: August 2006

AbstractThe lattice collapse and potassium fixation upon heating was studied for four expanding clay minerals in the potassium form by determining the change in X-ray patterns, and the decrease of both the cation exchange capacity and the total surface area derived from water vapour adsorption isotherms.In the literature, two factors promoting collapse have been considered: a high degree of tetrahedral substitution and a high potassium ion population in the unit layer surface. For the four minerals studied these two factors varied between wide limits, and the ease and degree of collapse were indeed found to correlate with these two factors. A third factor which has been considered previously is the degree of crystallinity of the mineral, which is determined by the origin of the clay. For the two bentonites which were investigated, one shows poor crystallinity, indicating its volcanic origin, the other shows a higher degree of crystallinity with boundary conformity in stacks of layers, indicating its formation by weathering of a micaceous mineral. The latter shows a higher degree of collapse.
Worrying in the Lab: Does Intolerance of Uncertainty Have Predictive Value?
Authors: de Bruin Gwendolijn Olivia , Rassin Eric , Muris Peter 
Published: August 2006

AbstractThe present article describes two experimental studies investigating whether individual differences in intolerance of uncertainty (IU) predict worry in response to uncertain situations. In both studies, undergraduate students completed the Intolerance of Uncertainty Scale (IUS; Freeston, Rheaume, Letarte, Dugas, & Ladouceur, 1994) and then completed an intelligence task, which was thought to elicit feelings of uncertainty. After completing the task, state worry was measured. Results of both studies showed that there were positive correlations between IUS scores and task-related state worry. Furthermore, Study 2 showed that individual differences in IU only were predictive of worry in a situation that elicits low to medium levels of uncertainty, and not in a situation high in uncertainty. Thus, only under certain conditions IU-related personality characteristics seem to be predictive of worrisome thoughts.
Bedeutung von Chrom, Kupfer, Selen und Zink bei Diabetes mellitus Typ 1 und Typ 2 mit Folgeerkrankungen / Importance of chromium, copper, selenium and zinc in diabetes mellitus type 1 and type 2 with late disease
Authors: Rükgauer Margarete , Schmitt York , Zeyfang Andrej 
Published: August 2006

Zusammenfassung

Chrom aktiviert die Wirkung von Insulin. Bei Typ-1- und Typ-2-Diabetikern reflektierten verminderte Chromgehalte in Leukozyten eine verminderte Chromversorgung. Je schlechter die Diabeteseinstellung, umso niedriger war der Chromstatus bei Typ-2-Diabetikern. Daher sollte bei diesen Patienten – besonders bei Typ-2-Diabetikern mit schlechter Einstellbarkeit – eine Chromsupplementation erwogen werden, wenn eine sichere Bestimmung der Chromversorgung nicht gewährleistet ist. Kupferionen besitzen anti- und auch prooxidative Eigenschaften. Hohe Kupferplasmawerte korrelieren mit der Entstehung einer Arteriosklerose. Die Kupferkonzentrationen im Plasma waren bei beiden Diabetikergruppen erhöht, weiter erhöhte Werte zeigten Typ-2-Diabetiker mit Hyperlipidämie oder diabetischen Folgeerkrankungen. Um das Risiko für Mikro- und Makroangiopathie oder Nephropathie zu vermindern, sollten Diabetiker eine hohe Kupferzufuhr vermeiden. Selen wirkt antioxidativ, immunstimulierend und antiatherogen. Der Selengehalt im Plasma reflektiert die Selenzufuhr. Die Selenplasmawerte waren bei beiden Diabetesgruppen geringfügig vermindert und auffällig vermindert bei Patienten mit Folgeerkrankungen. Eine selenreiche Ernährung oder Selengaben zur Prävention von Spätfolgen könnten bei Diabetikern daher sinnvoll sein. Patienten mit Nephropathie und eingeschränkter Zufuhr an tierischem, selen- und zinkreichem Protein profitieren möglicherweise von einer Selensupplementation. Zink ist an der Wundheilung, der Immunfunktion und der Aktivierung und Speicherung von Insulin beteiligt. Der Elementgehalt war bei Typ-1-Diabetikern in Leukozyten, dem bestem Indikator der Zinkversorgung, vermindert. Bei Patienten mit Nephropathie, Mikroangiopathie oder Neuropathie war das Zinkdefizit noch deutlicher ausgeprägt. Eine hochwertige, proteinreiche Ernährung könnte die Versorgungslage verbessern, auch eine Zinksupplementation wäre möglicherweise von Nutzen.
Diagnostik bei autoimmunen Schilddrüsenerkrankungen / Diagnostic testing for autoimmune thyroid diseases
Authors: Schott Matthias , Seißler Jochen , Scherbaum Werner A. 
Published: August 2006

Zusammenfassung
Die Autoimmunthyreoiditis (AIT) ist die häufigste Autoimmunerkrankung des Menschen. Die Klinik ist sehr variabel und reicht von Hypo- bis zu Hyperthyreose-Symptomen. Das Schilddrüsenparenchym stellt sich dabei typischerweise inhomogen und diffus echoarm dar. Es besteht eine positive Korrelation zwischen den Titern von Antikörpern gegen die Thyreoperoxidase (TPO) und der Wahrscheinlichkeit für das Auftreten einer Hypothyreose. Diese Korrelation kann derzeit jedoch nur unzureichend quantifiziert werden. Eine generelle Empfehlung zur Bestimmung der Antikörper gegen TPO in der Allgemeinbevölkerung kann nicht gemacht werden. Bei Nachweis eines erhöht gemessenen TSH-Wertes ist diese Bestimmung allerdings angezeigt.
Die Immunhyperthyreose ist die einzige Autoimmunerkrankung, bei der es zu einer Stimulation des Zielgewebes und primär nicht zu dessen Destruktion kommt. Neben der Hyperthyreose kann es zu extrathyreoidalen Manifestationen wie der endokrinen Orbitopathie kommen. In der Sonographie bzw. Duplex-Sonographie sieht man häufig eine diffuse Echoarmut und verstärkte Durchblutung des Organs. Zur Diagnosesicherung des Morbus Basedow sollten die TSH-Rezeptor-Autoantikörper (TRAK) bestimmt werden. Aufgrund der höheren Sensitivität und Spezifität ist der Assay der zweiten Generation (Einheiten in IU/L) gegenüber demjenigen der ersten Generation (Einheiten in U/L) vorzuziehen. Eine Prognoseabschätzung des Morbus Basedow gelingt durch eine Bestimmung der TRAK sechs Monate nach Erstdiagnose, wobei Werte >10 IU/L eine Remission weitgehend ausschließen, so dass eine definitive Therapie schon zu diesem Zeitpunkt angestrebt werden kann. Für niedrigere Werte oder auch Abnahmezeitpunkte nach kürzerer Krankheitsdauer kann derzeit noch keine zuverlässige Aussage gemacht werden. Mittels der TRAK-Bestimmung auf der Basis eines Assays der zweiten Generation kann auch das Risiko für eine Verschlechterung einer endokrinen Orbitopathie abgeschätzt werden. Die Bestimmung der Thyreoglobulin-Antikörper (Thyreoglobulin-AK) ist für beide Erkrankungsentitäten entbehrlich.
Characterization of Neutron Fields Using MCNP in the Experimental Fast Reactor JOYO
Authors: Maeda S , Wootan DW , Sekine T 
Published: August 2006

Abstract
An extensive set of neutron dosimeters ranging from the core center to beyond the reactor vessel were irradiated during the first two operating cycles of the MK-III core to allow a detailed characterization of the neutron spectra and flux distributions for this new core configuration. New analysis methods for predicting the reaction rates for comparison with the dosimetry measurements based on the MCNP code were developed. Analysis of previous MK-II cycle 34-35 dosimetry tests was used to verify the methods. Core models were developed for the different types and locations of dosimetry test subassemblies and biasing schemes were developed. MCNP optimization techniques and the C/E differences were explored. Most of the important parameters that affect the reaction rate calculations and measurements were investigated. In most cases, MCNP provides more accurate estimations of reaction rates and neutron flux than DORT. This indicates that treatment of heterogeneous structure is needed in the predictions for the irradiation test subassembly with no fuel and the irradiation field with large flux gradients.
Quantifying the Influence of Specimen Geometry on the Results of the Restrained Ring Test
Authors: Moon J-H , Rajabipour F , Pease B , Weiss J 
Published: August 2006

Abstract
Over the last decade, the restrained ring test has trequently been used to assess the cracking susceptibility of a concrete mixture when it is restrained from shrinking treely. Despite the trequent use of the ring test, limited analysis has been performed to understand how the specimen geometry influences the results of the test. This paper discusses the influence of specimen geometry on the results of the ring test considering three conditions: (1) uniform shrinkage of the concrete ring, (2) shrinkage caused by drying from the top and bottom surfaces of the concrete ring, and (3) shrinkage caused by drying from the outer circumference of the concrete ring. The role of moisture gradients, thickness of the concrete and the restraining (i.e., steel) rings, and the stiffness of concrete are considered in a series of numerical simulations. Results from these simulations can enable better selection of test specimen geometries and interpretation of the results from the ring test. Analytical expressions are provided to use for determining the geometry of the ring specimen that better simulates specific field conditions while providing the most useful information from the test.
The Effects of Construction Variability on the Superpave Simple Performance Test
Authors: Robinette CJ , Williams RC 
Published: August 2006

Abstract
The Superpave Simple Performance Test is quickly coming into the mainstream of practice for research purposes and implementation by owner/agencies. The research presented in this paper focuses on understanding the nuances of the testing procedure and building libraries of values for future reference. This project examined both 12.5-mm and 19.0-mm mixtures from the State of Wisconsin which included various traffic volumes. Of particular importance was construction variability in terms of air voids and asphalt binder content and their impact on performance with the flow number test. Plant produced mix was sampled for the jobs as well as the asphalt binder. Specimens were compacted to 4.0, 7.0, and 10.0% air voids at the sampled asphalt binder content. Additionally, specimens were further mixed with +0.3 % asphalt binder content and compacted to 7.0% air voids. The air voids and asphalt binder content changes were based on the tolerances set by typical construction variability and Wisconsin Department of Transportation specifications, respectively. The testing found that the flow number was greatly affected by air voids, but was rather insensitive to changes in asphalt content and nominal maximum aggregate size. It was determined that the accumulated microstrain at tertiary flow would be a good measure for comparing performance within a specific mixture in terms of changes in air voids and asphalt binder content. The flow number was found to be the best measure for comparing between different mixtures.
Flachheitsbasierte Regelung und Zustandsschätzung für einen Fedbatch-Bioprozess (Flatness Based Control and State Estimation for a Fed-Batch Biological Reactor)
Authors: Rothfuß R. , Riek A. , Reuss M. 
Published: August 2006

Für einen im Fedbatch-Verfahren betriebenen Bioreaktor, der zur Herstellung des Antibiotikums Penicillin~G eingesetzt wird, wird eine flachheitsbasierte Folgeregelung mit einem neuen Verfahren zur Zustandsschätzung entworfen. Bei der betrachteten Fermentation handelt es sich um einen instationären Prozess, bei dem die eingesetzten Mikroorganismen während eines exponentiellen Wachstums über verschiedene Zwischenstufen das gewünschte Produkt, Penicillin G, produzieren. Dieser Prozess kann durch nichtlineare Differentialgleichungen beschrieben werden. Ziel des eingesetzten Regelungskonzepts ist es, die Produktion von Penicillin G einem vorgegebenen Sollverlauf nachzuführen. Zur Lösung dieses Trajektorienfolgeproblems kann durch Zufütterung von zwei verschiedenen Substraten das Wachstum der Mikroorganismen, der Stoffwechsel und die Produktbildung beeinflusst werden. Neben der Trajektorienfolge soll das System gegen Störungen, Parameteränderungen durch Alterungsprozesse und Modellfehler stabilisiert werden.
Es wird gezeigt, dass der Bioreaktor ein flaches System ist. Die Flachheitseigenschaft erlaubt eine elegante Lösung des Trajektorienfolgeproblems. Durch die Vorgabe geeigneter Trajektorien für die Penicillinmasse und eine Substratmasse kann das System aufgrund der Flachheit durch eine statische Zustandsrückführung gegen Störungen und Modellfehler stabilisiert werden. Darüber hinaus erlaubt die Flachheitseigenschaft den Entwurf eines neuartigen nichtlinearen Folgefilters auf der Basis des erweiterten Kalman-Filters zur Realisierung der Zustandsrückführung und zur Schätzung zeitveränderlicher Parameter. Die Leistungsfähigkeit des Regelungskonzepts wird in der Simulation gezeigt und im Experiment bestätigt.