bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning Electron Microscopic and X-ray Powder Diffraction Study of Manganiferous Bauxite, Kincsesbánya, Hungary
Authors: Bárdossy György , Csordás-Toth Anna , Klug Annamária
Published: September 2006

Manganiferous karst bauxites are rare on a worldwide scale. One such body, recently mined at Kincsesbánya, Hungary, has been studied by chemical, petrographic, X-ray powder diffraction, scanning electron microscopic, and energy dispersive X-ray analytical techniques. The bauxite deposits of Kinesesbánya are of Paleocene to Lower Eocene age; however, the enrichment of manganese in them was a much later, epigenetic process. Lithiophorite is the main Mn mineral in this bauxite and occurs chiefly in dusters of < 1-μm size crystallites. Well-developed crystallites, however, 5–10 μm in size, line the walls of many microfissures and voids.

The oxidation of pyritic bauxite and lignitic clays in the overlying beds apparently mobilized finely disseminated Mn and Fe. Downward-migrating acidic solutions were gradually neutralized, and Mn and Fe minerals precipitated. The manganiferous bauxite was found only along the eastern rim of heavily eroded Middle Eocene sedimentary rocks. Here, epigenetic oxidation and mobilization were optimum. Farther to the east, pyrite-rich overburden and bauxite were apparently eroded away before Fe and Mn could be mobilized.
Polytypism of Micas. III. X-Ray Diffraction Identification
Authors: Weiss Z. , Wiewióra A.
Published: September 2006

Classification and identification criteria of maximum-degree-of-order (MDO) polytypes of homo- and meso-octahedral micas based on the distribution of the intensities of 20l (13l) and 02l reflections are proposed. Calculated | F(20l) |2 and | F(02l) |2 values for single crystals of micas with different compositions are given for one-, two-, and three-layer polytypes. Transmission powder diffractometry is proposed as a suitable method for the identification of the different groups of mica polytypes from polycrystalline specimens. Calculated powder patterns and the characteristic properties of the diffraction patterns of random and highly oriented aggregates are employed for identification purposes. The individual MDO polytypes are designated by generalized Ramsdell symbols which also contain information about their position in the classification system.
Nature and Utility of Hexamethylenediamine-Produced Kaolin Floc Structure
Authors: Bundy Wayne M. , Harrison Jack L.
Published: September 2006

Kaolin floc structures of commercial utility are produced by adsorption of hexamethylenediamine. These flocs are largely face-to-face structures with small diameter platelets of colloidal kaolinite aggregated on larger platelets of kaolinite and muscovite. Because of its higher charge density, muscovite is more effective than kaolinite in scavenging colloidal particles.

Although earlier workers have been at odds as to where amines adsorb on kaolinite, the present work indicates that both edge and basal surfaces are involved. Evidence for this contention is two-fold: (1) Face-to-face and edge-to-face flocculation of hexamethylenediamine kaolins has been observed. (2) Polyesters have been observed adsorbed on basal and edge surfaces of ethylenediamine-treated kaolins.

The mechanism by which kaolinite particles are bonded together into floc structures is unclear. Bridging by hexamethylenediammonium ions is a probable mechanism up to satisfaction of the cation-exchange capacity; further amine addition continues to promote flocculation. From this observation it is inferred that, in addition to bridging, hydrogen bonding and, perhaps, van der Waals forces are instrumental in floc formation. Although rheologically inferior to the untreated equivalent, these chemically induced flocs of kaolinite provide loosely packed, randomly oriented structures in paper coatings. Improved brightness, opacity, and printability of paper coatings arise from this structure.
Microstructure in Mixed-Layer Illite/Smectite and Its Relationship to the Reaction of Smectite to Illite
Authors: Bell T. E.
Published: September 2006

The reaction of smectite to illite in shale from the COST 1 well in the south Texas Gulf Coast and from altered ash-fall tuffs from the Morrison Formation in New Mexico was investigated using X-ray powder diffraction in conjunction with transmission electron microscopy. In the COST 1 well, the bulk of the detrital clay was originally a K+-deficient mixed-layer illite/smectite (I/S). As the I/S adsorbed K+ released by the dissolution of K-feldspar during burial, the proportion of expandable layers decreased with depth from ~65% near the top of the well to ~25% at 4500 m depth. In contrast, the proportion of low-charged structural planes [<0.8 eq per (Al,Si)4O10 unit] in the I/S decreased gradually from ~40% near the top of the well to ~15% near the bottom. Authigenic smectite with 100% expandable layers from the Morrison Formation tuffs is an alteration product of vitric ash. Where these tuffs have been buried to ~ 1400 m the smectite has reacted to form I/S with ~ 15% expandable layers.

Direct lattice images of I/S crystallites from both locations reveal a correspondence between edge dislocations and the interface between illite layers and smectite layers. Al, Si, Fe, Ca, Mg, and Na were apparently mobile along these dislocations as the reaction of smectite to illite proceeded. Al was probably retained within the crystallite when illite layers replaced the smectite layers; however, some of the remaining cations were expelled. Lateral replacement of smectite layers by illite appears to have been the principal growth mechanism.
Transmission and Analytical Electron Microscopy of the Smectite-To-Illite Transition
Authors: Ahn Juno Ho , Peacor Donald R.
Published: September 2006

The smectite to illite reaction was studied by transmission and analytical electron microscopy (TEM/AEM) in argillaceous sediments from depths of 1750, 2450, and 5500 m in a Gulf Coast well. Smectite was texturally characterized as having wavy 10- to 13-Å layers with a high density of edge-dislocations, and illite, as having relatively defect-free straight 10-Å layers. The structures of smectite and illite were not continuous parallel to (001) at smectite-illite interfaces. AEM data showed that the smectite and illite were chemically distinct although smectite had a more variable composition. Illite formation appeared to have initiated with the growth of small packets of illite layers within subparallel layers of smectite matrix. With increasing depth, ubiquitous thin packets of illite layers increased in size until they coalesced.

A model for the transition requires that the structure of smectite was largely disrupted at the illite-smectite interface and reconstituted as illite, with concomitant changes in the chemistry of octahedral and tetrahedral sites. At least partial Na-K exchange of smectite preceded illite formation. Transport of reactants (K, Al) and products (Na, Si, Fe, Mg, H20) through the surrounding smectite matrix may have taken place along dislocations.

The smectite-to-illite conversion process for the studied samples does not necessarily appear to have required mixed-layer illite/smectite as an intermediate phase, and TEM and AEM data from unexpanded samples were found to be incompatible with the existence of mixed-layer illite/smectite in specimens whose XRD patterns indicated its presence.
The Polymer Model of Thermochemical Clay Mineral Stability
Authors: Sposito Garrison
Published: September 2006

The Nriagu polymer model of 2:1 layer type clay minerals develops from the premise that clay minerals are condensation copolymers of solid hydroxides. In the Mattigod-Sposito formulation of the model, standard state chemical potentials (standard Gibbs energies of formation from the elements) of 2:1 clay minerals are predicted quantitatively with a linear correlation equation relating the standard Gibbs energy of the polymerization reaction (ΔGor) to the half-cell layer charge of the clay mineral and to the valence and ionic radius of the exchangeable cation. It is now shown that this correlation equation can be derived from two basic assumptions: (1) that the standard Gibbs energy change for the transfer of a cation in a pure hydroxide solid to a hydroxide component in the tetrahedral or octahedral sheet of a 2:1 clay mineral is independent of the nature of the cation and (2) that the difference between ΔGor for the polymerization reaction to form a 2:1 clay mineral and ΔGor for the same reaction to form the zero layer-charge analog of the clay mineral is proportional to the number of interlayer exchangeable cations per unit cell of the clay mineral and to the radius of its exchangeable cation. Both of these assumptions can be tested experimentally, independent of the polymer model.
Quantitative Determination of Aluminum-Substituted Goethite-Hematite Mixtures By Mössbauer Spectroscopy
Authors: Amarasiriwardena D. D. , DeGrave E. , Bowen L. H. , Weed S. B.
Published: September 2006

Mixtures of synthetic Al-substituted goethite (α-Fe0.814Al0.186OOH) and hematite (α-Fe1.658Al0.342O3) (75, 50, 25, 3% hematite by weight) were studied by Mössbauer spectroscopy to evaluate the use of that technique for quantitative analysis. Mössbauer spectra for these mixtures, obtained in the temperature range 12–130 K, were better fitted by a distribution of magnetic fields than by two magnetic sextets. Spectra at 80 K were equally as good as those from lower temperature to determine the hematitegoethite ratio. The recoil-free fractions of the individual components were about equal at any fixed temperature, but thickness effects caused as much as 30% error in the determination of the ratio of components in mixtures.
Textural Variation and Composition of Bentonite Derived from Basaltic Ash
Authors: Konta Jiri
Published: September 2006

The Rokle bentonite deposit is part of an accumulation of argillized volcanoclastic rocks in the Tertiary stratovolcanic complex of the Doupovské Mountains east of Karlovy Vary (Carlsbad), about 100 km westnorthwest of Prague, Czechoslovakia. The arenite basalt ash was originally composed of hyaloclasts and subordinate biotite. The following types of montmorillonite aggregates were produced during the alteration of the ash in a stagnant, lacustrine environment: (1) extremely fine-grained micro-crystalline aggregates that have honeycomb textures and that replace the original hyaloclasts, and (2) coarse crystalline aggregates that have more open honeycomb textures and that fill pores and cracks in altered hyaloclasts and in pumice vesicles. Both types of aggregates have the same chemical composition according to energy dispersive X-ray analysis.

Montmorillonite, separated as the <1-¼m size fraction from olive gray bentonite, has the following crystallochemical formula: (K0.09Na0.02Ca0.29Mg0.10) (Al2.43Fe3+1.05Fe2+0.005Mn2+0.005Mg0.50) (Si7.62Al0.38) O20(OH)4. Biotite was apparently stable during the alteration of the hyaloclasts. Anatase and possible accessory heulandite-clinoptilolite were also formed in small amounts, but were not observed by scanning electron microscopy. Goethite is the youngest oxidation product in some parts of the bentonite. Minute fragments of sodium-rich plagioclase, potassium feldspar, quartz, and muscovite are ubiquitous accessories of the original hyaloclasts. Together with kaolinite, they formed from the underlying fresh or kaolinized orthogneiss.
57Fe Mössbauer Spectroscopy of Montmorillonites: A New Interpretation
Authors: Cardile C. M. , Johnston J. H.
Published: September 2006

The 57Fe Mössbauer spectra of several montmorillonites, measured at room temperature and 453 K, showed a considerably broadened Fe3+ resonance which can be computer-fitted with a similarly broadened Fe3+ doublet. In some spectra, particularly if all linewidths were constrained to be equal, this broadened Fe3+ resonance was further resolved into overlapping inner and outer Fe3+ doublets, also having broad linewidths. In accordance with recent electron diffraction evidence, the assignment by previous workers of the inner doublet to Fe3+ in the octahedral sites having the cis-arrangement of OH groups and the outer doublet to the octahedral site having the trans-arrangement of OH groups is incorrect. Instead, the Fe3+ was found to be located largely in the trans-octahedral sites. Because of the relatively low iron content of the montmorillonite examined, the next and more distant neighboring-cation environment varied considerably about the octahedral Fe3+ ions. This variation produced a broadened experimental resonance, and the resulting two-doublet computer fits probably represent the mean extremes of a continuum of slightly different Fe3+ resonances arising from the variable nature of the environment surrounding these such trans-sites, rather than distinct cis- and trans-sites. In addition, a small resonance indicating the substitution of Fe3+ into the tetrahedral sites was observed. The interlayer species probably influenced the Mössbauer resonance of Fe3+ in the tetrahedral and octahedral sites.
Hydroxy-Cu-Vermiculite Formed By the Weathering of Fe-Biotites at Salobo, Carajas, Brazil
Authors: Ildefonse Philippe , Manceau Alain , Prost Dominique , Groke Maria Christina Toledo
Published: September 2006

Weathering of a copper stratiform deposit (schist) at Salobo, Brazil, has produced two distinct Cu-bearing minerals from a biotite parent: vermiculite and a manganese oxide containing as much as 13% and 25% CuO, respectively. Manganiferous products were formed as the result of an interhorizon transfer of solutions through a fissure system. Thus, the structural orientation of the schists was a major factor in controlling the supergene concentration of Cu. The Cu-vermiculite formed by the weathering of Fe-biotite, although the unweathered biotites in the parent rocks were found to contain no copper, suggesting that Cu was supplied by weathering solutions. X-ray powder diffraction (XRD) and cationexchange capacity data for the Cu-vermiculite differ from those of typical Mg-vermiculite and are similar to those of hydroxy- Al-vermiculite. A comparison of the XRD pattern of the Cu-vermiculite with that of a Cu-free vermiculite indicates that Cu atoms are located in interlayer sites. Cu probably occurs in a brucite-like layer. The position and structure of the Cu K-absorption spectrum suggest that the Cu is divalent and exists in 6-fold coordination.
Chemistry of Illite/Smectite and End-Member Illite
Authors: Środoń Jan , Morgan David J. , Eslinger Eric V. , Eberl Dennis D. , Karlinger Michael R.
Published: September 2006

Chemical data from three different series of diagenetic illite/smectites (I/S), analyzed statistically by two regresion techniques, indicate that the content of fixed-K per illite layer is not constant, but ranges from ~0.55 per O10(OH)2 for illite layers in randomly interstratified I/S (R=0; >50% smectite layers) to ~ 1.0 per O10(OH)2 for illite layers formed in ordered I/S (R>0; <50% smectite layers). By extrapolation of the experimental data, the following chemical characteristics were obtained for end-member illite derived from the alteration of smectite in bentonite: average fixed-K per illite layer = 0.75 per O10(OH)2; total charge = about -0.8; cation-exchange capacity = 15 meq/100 g; surface area (EGME) = 150 m2/g.
Chemical and Physical Properties of Paleozoic Potassium Bentonites from Kinnekulle, Sweden
Authors: Brusewitz Ann Marie
Published: September 2006

The < 1-μm fraction of 17 bentonite samples from Kinnekulle, southwest Sweden, were studied by chemical analysis, X-ray powder diffraction, and cation-exchange capacity. The bentonites are interbedded with undeformed, flat-laying Ordovician and Silurian sediments and were formed by the transformation of volcanic ash (dated at about 450 Ma) into smectite, which later converted to mixed-layer illite/smectite (I/S). The reaction, possibly driven by heat from an overlaying diabase intrusion (about 300 Ma), stopped at different stages of conversion, as evidenced by the I/S which ranges in composition from 60 to 10% smectite layers. A 2-m-thick bed shows zonation, with decreasing smectite proportions towards the upper contact. The zonation is not symmetrical towards the lower contact. In thin beds the illite proportion is higher and the regularity of ordering is inversely proportional to the thickness of the bed. K:Sr and K:Rb ratios follow the illite pattern; the ratios are highest at the contact and in thin beds. The inhibiting effect of Ca and Mg on the smectite-to-illite conversion probably was the cause of less-reacted smectite in the center of the thick bed.
Infrared Spectroscopic Study of the Formamide-Na-Montmorillonite Complex. Conversion of s-Triazine to Formamide
Authors: Nguyen T. T.
Published: September 2006

The adsorption and degradation on montmorillonite of s-triazine, the parent compound of a major group of triazine-based herbicides, were studied by Fourier-transform infrared spectroscopy. The original s-triazine appeared to hydrolyze with residual bound water in montmorillonite at 20°C to produce formamide, which formed an intercalate with the clay. A mechanism for the conversion of s-triazine to formamide was proposed which does not support earlier reports that formic acid and ammonia are the reaction products. The infrared spectrum of the formamide-Na-montmorillonite intercalate suggests that formamide reacted with the exchangeable Na cation and that the NH2 group hydrogen bonded with the clay. Assuming the intercalated formamide molecule to be planar, the molecular plane was found to be inclined at ~33° with respect to the plane of the silicate sheet. C-N and C-O bonds were also found to be tilted at the same angle with respect to the clay surface. The proposed orientation is in good agreement with the measured value of d(001) for the formamide-Na-montmorillonite complex. The proposed model of the formamide-montmorillonite complex serves as a basis for comparison of other clay-amide complexes that are important in protein-clay interactions.
Reduction of the Cation-Exchange Capacity of Montmorillonite by Take-Up of Hydroxy-Al Polymers
Authors: Keren R.
Published: September 2006

The cation-exchange capacity (CEC) of Na-Al- and Ca-Al-montmorillonite after neutralization with NaOH or Ca(OH)2 was studied at three Al levels: 10, 25, and 50% of the CEC. Hydroxy-Al polymers were effective in reducing the CEC of Na-montmorillonite (by more than 46%), the exact effectiveness being dependent on the hydroxy-Al content. The hydroxy-Al polymers were less effective in reducing the CEC of Ca-montmorillonite (less than 26%). The CEC reduction was equal to or larger than the amount of the untitrated Al. The electrostatic charges of the clay which were blocked by the hydroxy-Al polymers were compensated for by both the positive charge of the hydroxy-Al polymers and the trapped cations on the clay surfaces. These cations remained on the clay even after extensive washing with 0.1 M KCl.
Transformation of Synthetic Birnessite to Cryptomelane: An Electron Microscopic Study
Authors: Chen Cy-Chain , Golden D. C. , Dixon J. B.
Published: September 2006

Na-saturated bimessite was synthesized by oxidizing an alkaline MnCl2 solution with gaseous O2. Transmission electron microscopy (TEM) showed no morphological change upon K-saturation of the bimessite, but selected-area diffraction (SAD) revealed structural disorder. Stepwise heating of the K-birnessite to 800°C yielded cryptomelane, as indicated by X-ray powder diffraction (XRD). Various degrees of transformation to the final cryptomelane product were observed by TEM and SAD, but not by XRD. Unaltered bimessite formed chiefly as thin, platy crystals of apparent hexagonal outline. The cryptomelane crystals that formed by heating the K-saturated bimessite were acicular. Bimessite crystals, partially transformed to cryptomelane and displaying non-integral diffraction spots, formed plates having linear striations and rods twinned at 60° to each other. These intermediate products commonly retained some of the original hexagonal appearance of the parent bimessite. Structural disorder was detected in the partially transformed crystals by SAD. TEM revealed 6.8- and 4.8-Å spacings of the (110) and (200) planes of cryptomelane, respectively. The basal planes of bimessite layers (001) appeared to correspond topotactically to the (110) plane of cryptomelane during these transformations.
Molecular Motions, Surface Interactions, and Stacking Disorder in Kaolinite Intercalates
Authors: Lipsicas M. , Raythatha R. , Giese R. F. , Costanzo P. M.
Published: September 2006

Intercalates of Georgia well-crystallized kaolinite with formamide, N-methylformamide (NMF), and dimethylsulfoxide (DMSO) were prepared at room temperature by dispersing the clay in the organic liquid. Several physical and chemical properties of the intercalated organic molecules and the clay, while intercalated and after de-intercalation, were examined using nuclear magnetic resonance (NMR), infrared (IR), and electron paramagnetic resonance spectroscopy (EPR), and specific heat (Cp) measurements. The chemical bonding between the inner-surface hydroxyls and the organic molecules, as indicated by IR, was strongest for DMSO and weakest for formamide. The distortion of the kaolinite layer, as shown by EPR, also was greatest for DMSO and least for formamide. NMR T1 measurements indicated a relatively strong DMSO-kaolinite surface interaction that slowed down the methyl group reorientation comparable to that in bulk solid DMSO. T1 measurements indicated a weaker interaction for NMF. De-intercalation by mild heating did not return the kaolinite to its original structural state as shown by EPR and Cp. The greatest disorder was found for the DMSO de-intercalate and the least for the formamide de-intercalate. These experiments show that for sufficiently strong bonding between the clay inner surface and the intercalating molecule, the structure of the clay is capable of distortion, which is partly temporary and partly permanent. The permanent changes probably involve the introduction of stacking faults.
Distribution of Pancreatic Endocrine Cells Including IAPP-expressing Cells in Non-diabetic and Type 2 Diabetic Cases
Authors: Iki Katsumichi , Pour Parviz M.
Published: September 2006

There is a lack of agreement on the distribution of islet amyloid polypeptide (IAPP) in the pancreases of healthy and diabetic subjects. Therefore, a detailed morphometrical and immunohistochemical study was performed to obtain information on the distribution of cells expressing insulin, glucagon, somatostatin, pancreatic polypeptide (PP), and IAPP in the pancreases of non-diabetic ( n=4) and diabetic individuals ( n=6). In the non-diabetic cases, β-cells contributed to ∼64%, α-cells to 26%, δ-cells to 8%, PP cells to 0.3%, and IAPP cells to 34% of the islet cell population. The ratio of IAPP/insulin was ∼1:2. In diabetic cases, β-cells were decreased by 24%, and IAPP was decreased by 57%. The α- and δ-cells were increased by 40% and 58%, respectively. IAPP/insulin ratio was decreased by 41%. Thus, only 50% of the β-cells in non-diabetics and only 30% in diabetics coexpressed IAPP. In diabetics, more δ-cells coexpressed IAPP than in non-diabetics. The results seem to argue against the notion that the secretion of IAPP is increased in diabetics. It is possible that an increase in somatostatin and glucagon plays a greater role in diabetes than IAPP.
Endothelial Proliferation and Increased Blood–Brain Barrier Permeability in the Basal Ganglia in a Rat Model of 3,4-Dihydroxyphenyl-l-Alanine-Induced Dyskinesia
Authors: Westin Jenny E. , Lindgren Hanna S. , Gardi Jonathan , Nyengaard Jens Randel , Brundin Patrik , Mohapel Paul , Cenci M. Angela
Published: September 2006

3,4-Dihydroxyphenyl-l-alanine (l-DOPA)-induced dyskinesia is associated with molecular and synaptic plasticity in the basal ganglia, but the occurrence of structural remodeling through cell genesis has not been explored. In this study, rats with 6-hydroxydopamine lesions received injections of the thymidine analog 5-bromo-2′-deoxyuridine (BrdU) concomitantly withl-DOPA for 2 weeks. A large number of BrdU-positive cells were found in the striatum and its output structures (globus pallidus, entopeduncular nucleus, and substantia nigra pars reticulata) inl-DOPA-treated rats that had developed dyskinesia. The vast majority (60–80%) of the newborn cells stained positively for endothelial markers. This endothelial proliferation was associated with an upregulation of immature endothelial markers (nestin) and a downregulation of endothelial barrier antigen on blood vessel walls. In addition, dyskinetic rats exhibited a significant increase in total blood vessel length and a visible extravasation of serum albumin in the two structures in which endothelial proliferation was most pronounced (substantia nigra pars reticulata and entopeduncular nucleus). The present study provides the first evidence of angiogenesis and blood–brain barrier dysfunction in an experimental model ofl-DOPA-induced dyskinesia. These microvascular changes are likely to affect the kinetics ofl-DOPA entry into the brain, favoring the occurrence of motor complications.
Macaque V2 Neurons, But Not V1 Neurons, Show Choice-Related Activity
Authors: Nienborg Hendrikje , Cumming Bruce G.
Published: September 2006

In the macaque extrastriate cortex, robust correlations between perceptual choice and neuronal response have been demonstrated, frequently quantified as choice probabilities (CPs). Such correlations are modest in early visual cortex, suggesting that CPs may depend on the position of a neuron in the hierarchy of visual processing. However, previous studies have not compared neurons with similar precision in equivalent tasks.

We investigated the role of cortical hierarchy on CP using a task for which significant CPs have been described previously for middle temporal area (MT). We measured CPs in disparity-selective neurons from both V1 and V2. The stimulus was a dynamic random dot stereogram, presented with a near or a far disparity, masked by varying numbers of binocularly uncorrelated dots. Two macaque monkeys reported whether they perceived a circular patch in front or behind a surrounding annulus in a forced choice task.

For V2 (n= 69), CP was on average 0.56, the first demonstration of systematic CPs in a visual area as early as V2. In V1 (n= 74), average CP was at chance level (0.51). The pattern was similar in a subgroup of neurons selected such that the statistical precision in the task was on average identical to that reported for MT (mean CP, 0.51 for V1,n= 33; 0.58 for V2,n= 54). This difference between V1 and V2 could not be explained by eye movements, stimulus size relative to the receptive field, or differences in disparity tuning. Rather, it seems to reflect a functional difference (at least in disparity processing) between striate and extrastriate cortex.
Paradoxical Facilitation of Object Recognition Memory after Infusion of Scopolamine into Perirhinal Cortex: Implications for Cholinergic System Function
Authors: Winters Boyer D. , Saksida Lisa M. , Bussey Timothy J.
Published: September 2006

The cholinergic system has long been implicated in learning and memory, yet its specific function remains unclear. In the present study, we investigated the role of cortical acetylcholine in a rodent model of declarative memory by infusing the cholinergic muscarinic receptor antagonist scopolamine into the rat perirhinal cortex during different stages (encoding, storage/consolidation, and retrieval) of the spontaneous object recognition task. Presample infusions of scopolamine significantly impaired object recognition compared with performance of the same group of rats on saline trials; this result is consistent with previous reports supporting a role for perirhinal acetylcholine in object information acquisition. Scopolamine infusions directly before the retrieval stage had no discernible effect on object recognition. However, postsample infusions of scopolamine with sample-to-infusion delays of up to 20 h significantly facilitated performance relative to postsample saline infusion trials. Additional analysis suggested that the infusion episode could cause retroactive or proactive interference with the sample object trace and that scopolamine blocked the acquisition of this interfering information, thereby facilitating recognition memory. This is, to our knowledge, the first example of improved recognition memory after administration of scopolamine. The overall pattern of results is inconsistent with a direct role for cortical acetylcholine in declarative memory consolidation or retrieval. Rather, the cholinergic input to the perirhinal cortex may facilitate acquisition by enhancing the cortical processing of incoming stimulus information.
DARPP-32 Involvement in the Photic Pathway of the Circadian System
Authors: Yan Lily , Bobula Jessica M. , Svenningsson Per , Greengard Paul , Silver Rae
Published: September 2006

The multifunctional regulator of protein kinases and phosphatases dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) is an important molecular target of the dopamine signaling pathway. In the present study, we investigated the possible involvement of DARPP-32 regulation in the circadian system using DARPP-32 knock-out (KO) mice. These mice showed normal entrainment to a 12 h light/dark cycle and free run in constant darkness with a period similar to that of wild-type controls. After light exposure, however, the behavioral phase-delay response and the expression of light-induced clock genemPer2were attenuated in the DARPP-32 KO mice. Attenuated phase delays were also seen in animals bearing a point mutation in DARPP-32 at the PKA (Thr34) but not at the casein kinase I (Ser130) phosphorylation site. We next examined DARPP-32 expression in the retina and intergeniculate leaflet (IGL), both of which convey light information to the suprachiasmatic nucleus (SCN), the locus of a master circadian clock, and in the SCN itself. DARPP-32 was expressed in the retina but not in the IGL or the SCN. The results indicate that DARPP-32 is involved in the retinal pathway transmitting photic information that resets the circadian clock.
Random Walk
Authors: Butler Mary Odell
Published: September 2006

This article traces the development of a career in applied anthropology that began in the early days of the feminist movement and in the antiwar movement of the 1960s and 1970s. The story begins with the early marriage and childbearing prescribed during the 1950s, continues to a traditional four‐field education in anthropology, and concludes with a leadership position in a largely male corporate environment. The repeated revision of expectations for women's roles, pressure on academic jobs, and an expanding scope of anthropology in the world at large yielded both challenges and opportunities. This story of one woman's career shares many essential elements with the stories of other female anthropologists from this generation.
Anthropology in Pursuit of Public Policy and Practical Knowledge
Authors: Fiske Shirley J.
Published: September 2006

When I look backward, it seems easy to see the threads of continuity in my life. When I look forward, it is not that easy to see a plan, which makes me wonder whether this chapter is a convenient fabrication of hindsight. Practicing anthropologists have a particular challenge to create coherent careers because there is no one path or career for using anthropology to generate practical knowledge and action. All of the women in this Bulletin have forged lives that come in part from inner sources of strength and knowledge, sometimes good fortune, and sometimes desperation. But we share the belief that anthropological knowledge is valuable and good for something, and we share the common experience of trying to apply it. In this chapter, I identify what I think are the key values, circumstances, people, and events that made me choose to be a practicing anthropologist. Although we originally were to focus on gender and how that influenced our lives, this Bulletin has become a much broader look at our lives. I follow the key circumstances, values, and decisions that led me to practicing anthropology, including my family background, educational choices and degree programs, and my first academic appointment. I describe my transition to the federal government and experience in the executive branch as a program manager encouraging and integrating anthropology into program missions for the National Oceanic and Atmospheric Administration and the National Sea Grant College Program. My most recent work with the U.S. Senate as a legislative aide for environment and energy to a Democratic Senator is the latest addition to this story, but I do not think this is finished. As with all the chapters, I end with practical advice.
Analysis of doubly loaded end blocks in FRP-prestressed concrete
Authors: Gale L. , Ibell T. J. , Williams C.
Published: September 2006

Corrosion in conventional steel-reinforced and prestressed concrete bridges is a major durability concern. Fibre-reinforced polymer (FRP) materials have received widespread interest as an alternative material to steel. Owing to the low stiffness of these materials compared with steel, it could be argued that concrete bridges containing FRP should be prestressed. In doing so, this removes much of the strain capacity in the FRP, so that serviceability of the bridge is ensured and efficient use is made of all materials. Although relevant research into FRP-prestressed concrete is well established, the area of post-tensioned anchorage zones has received very little attention. The current paper concentrates on the analysis (and the design) of post-tensioned anchorage zones subject to multiple anchors, with the feasibility of adopting FRP bars as equilibrium reinforcement. Using an elasticity-based model, both the position and load at first cracking have been predicted with good accuracy compared with the experimental results. Further, a plasticity-based model has been developed, in which equilibrium of the failing wedge formed underneath the bearing plates at ultimate load is considered, and which has also shown good correlation compared with test results. It is concluded that both the serviceability and ultimate limit state behaviours of post-tensioned FRP-reinforced anchorage zones subject to multiple anchors are predictable. The pre-cracking behaviour can be predicted using an elastic finite difference method, while a plasticity-based analytical solution can be used to predict the ultimate capacity.
Gravel-Pack-Placement Limits In Extended Horizontal Offshore Wells
Authors: de Magalhães J. V. M. , Calderon A. , Martins A. L.
Published: September 2006

Long horizontal-section wells are economical requirements for heavy-oil fields in deepwater environments. This article discusses the operational limits for gravel-pack placement in such wells in consideration of the maximization of the horizontal-section extension in low fracture-gradient scenarios. A parametric study on the variables governing the gravel-pack operations indicates that careful hydraulic design and detailed operational procedures can guarantee a successful job. Alternative strategies are proposed to extended hydraulic limits in critical conditions.
3D Porosity Modeling of a Carbonate Reservoir Using Continuous Multiple-Point Statistics Simulation
Authors: Zhang T. , Bombarde S. , Strebelle S. , Oatney E.
Published: September 2006

Training images are numerical representations of geological conceptual models that provide prior information on reservoir architecture. A new emerging geostatistical approach named multiple-point statistics (MPS) simulation allows extracting multiple-point structures from such training images and anchoring these structures to the data actually observed in the reservoir. By reproducing multiple-point statistics inferred from training images, MPS enables the modeling of complex curvilinear structures (e.g., sinuous channels) in a much more geologically realistic way than traditional two-point statistics (variogram-based) techniques. However, in the original MPS implementation, all MPS moments computed from the training image are exported to the reservoir model without processing, which allows simulating only categorical or discretized variables. This implementation is appropriate with clastic reservoirs for which, typically, depositional facies are simulated first using MPS, then porosity and permeability are distributed within each simulated facies using traditional variogram-based techniques. But for reservoirs, in particular in carbonate environments, where porosity and permeability trends/cycles are not closely tied to any facies distribution, simulating porosity/permeability directly using corresponding continuous training images appears to be a more suitable approach.

In this paper, a new filter-based implementation of MPS, named filtersim, is proposed to reproduce features from continuous variable training images. First, a set of general filters is applied to the training image to transform (summarize) each training pattern into a set of scores accounting for different aspects of the pattern, such as north-south and east-west gradients and curvatures. The training patterns are classified in the score space and grouped into a small number of similarity classes. The simulation consists then of visiting each grid node along a random path, identifying the similarity class that best fits to the local conditioning data, and patching a pattern drawn from that selected similarity class. In our study, this new approach was applied to model the 3D porosity distribution of a carbonate reservoir in Kazakhstan. First, the original "categorical" MPS program snesim was used to model the two main reservoir regions, platform and slope, where the spatial porosity distribution is characterized by significantly different features. Interpreted well markers and seismic data were used to condition the modeling of these two regions. Then porosity was distributed in the platform region using the "continuous" filter-based MPS program filtersim, as described previously. The 3D training images used in that second step displayed porosity trends/cycles controlled by the type of geological sedimentation process believed to have occurred in the reservoir.
High-Precision Relative Depth and Subsidence Mapping From Seafloor Water-Pressure Measurements
Authors: Stenvold T. , Eiken O. , Zumberge M. A. , Sasagawa G. S. , Nooner S. L.
Published: September 2006

A method to accurately measure seafloor subsidence away from platform locations is presented. The method is based on seafloor water pressure, which is measured on top of predeployed benchmarks visited one after another using a remotely operated vehicle (ROV) and is at the same time measured continuously throughout the survey at one or more reference locations. Because no significant subsidence is expected during a few days of data acquisition, high-precision relative depths representative for the average time of the survey can be obtained. Accurate subsidence estimates between seafloor surveys are found assuming negligible subsidence at benchmarks located outside the field.

Results from six seafloor surveys performed at two gas fields in the North Sea are presented. For an area of 1 km2 at 80 m water depth, single-measurement relative depth precision (standard deviation) of 0.4 cm was obtained. Correspondingly, for an area of 700 km2 at 295 to 345 m water depth, 0.6 cm was obtained. Single-station subsidence accuracy down to 1 cm is achieved from the two most recent pressure surveys at the large field. A subsidence signal is seen for this difference, and it is compared with modeled subsidence. Error budgets for depth precision and subsidence, incorporating instrumental and environmental errors, are discussed.
A Prototype Four-Dimensional Galerkin-Type Integral
Authors: Lyness J. N.
Published: September 2006

An error functional expansion is constructed for a four-dimensional integral over [0, 1]4 whose integrand function has a singularity structure of a type that occurs in integrals in the Galerkin boundary element method. We show with an example how extrapolation may be used to evaluate this integral.
Numerical Integration of Functions with Endpoint Singularities and/or Complex Poles in 3D Galerkin Boundary Element Methods
Authors: Monegato Giovanni , Scuderi Letizia
Published: September 2006

In this paper we propose special strategies to compute 1D integrals of functions having weakly or strong singularities at the endpoints of the interval of integration or complex poles close to the domain of integration. As application of the proposed strategies, we compute a four dimensional integral arising from 3D Galerkin boundary element methods (BEM) applied to hypersingular boundary integral equations.
Discovery of the Double Exponential Transformation and Its Developments
Authors: Mori Masatake
Published: September 2006

This article is mainly concerned how the double exponential formula for numerical integration was discovered and how it has been developed thereafter. For evaluation of

I = \int_{-1}^1 f(x)dx

, H. Takahasi and M. Mori took advantage of the optimality of the trapezoidal formula over

(−∞, ∞)

with an equal mesh size and proposed in 1974

x = \phi(t) = \tanh(\frac{π}{2} \sinh t)

as an optimal choice of variable transformation which transforms the original integral to

I = \int^∞_{−∞} f(\phi(t))\phi' (t) dt

. If the trapezoidal formula is applied to the transformed integral and the resulting inﬁnite summation is properly truncated a quadrature formula

I ≈ h ∑^n_{k=−n}f_(\phi(kh))\phi'(kh)

is obtained. Its error is expressed as

O(\exp(−CN/ \log\, N_))

as a function of the number

N

(

= 2n + 1

) of function evaluations. Since the integrand decays double exponentially after the transformation it is called the double exponential (DE) formula. It is also shown that the formula is optimal in the sense that there is no quadrature formula obtained by variable transformation whose error decays faster than

O(\exp(−CN/ \log\, N))

as

N

becomes large. Since the paper by Takahasi and Mori was published the DE formula has gradually come to be used widely in various ﬁelds of science and engineering. In fact we can ﬁnd papers in which the DE formula is successfully used in the ﬁelds of molecular physics, ﬂuid dynamics, statistics, civil engineering, ﬁnancial engineering, in particular in the ﬁeld of the boundary element method, and so on. The DE transformation has turned out to be also useful for evaluation of indeﬁnite integrals, for solution of integral equations and for solution of ordinary diﬀerential equations, so that the scope of its applications is expected to spread also in the future.
A Numerical Integration Formula Based on the Bessel Functions
Authors: Ogata Hidenori
Published: September 2006

In this paper, we discuss the properties of a quadrature formula with the zeros of the Bessel functions as nodes for integrals

\int^∞_{−∞} |x|^{2ν+1} f(x) dx

, where

ν

is a real constant greater than

−1

and

f(x)

is a function analytic on the real axis

(−∞, +∞)

. We show from theoretical error analysis that (i) the quadrature formula converges exponentially, (ii) it is as accurate as the trapezoidal formula over

(−∞, +∞)

and (iii) the accuracy of the quadrature formula doubles that of an interpolation formula with the same nodes. Numerical examples support the above theoretical results. We also apply the quadrature formula to the numerical integration of integral involving the Bessel function.
Vector Measure Orthonormal Systems and Self-weighted Functions Approximation
Authors: García-Raffi Luis M. , Ginestar Damián , Sánchez Pérez Enrique A.
Published: September 2006

If λ is a positive vector measure on _l_2, the notion of λ-orthonormal system of functions leads to a natural generalization of the relation between orthogonality and best approximation in Hilbert spaces for spaces _L_2(λ) of square integrable functions with respect to λ. We provide a vector orthogonality criterion that induces the deﬁnition of a particular projection on a subspace of _L_2(λ) that we call the selfweighted approximation. As an application, we show a new extrapolation technique.
Sum Relations for Multiple Zeta Values and Connection Formulas for the Gauss Hypergeometric Functions
Authors: Aoki Takashi , Ohno Yasuo
Published: September 2006

We give an explicit representation for the sums of multiple zeta-star values of ﬁxed weight and height in terms of Riemann zeta values.
Eigenvalue Asymptotics for the Maass Hamiltonian with Decreasing Electric Potentials
Authors: Shirai Shin-ichi
Published: September 2006

We study the eigenvalue distribution in the spectral gaps of the Maass Hamiltonian with electric potential

V

. For a real constant

B

, the (unperturbed) Maass Hamiltonian is given by

H(0) = y^2 \Big( \frac 1 {\sqrt{-1} } \frac ∂ {∂x} - \frac B y \Big)^2 - y^2 \frac{∂^2}{∂y^2},

where

\mathbf H= \{(x, y)|x \in \mathbf R, y > 0\}

is the hyperbolic plane. The spectrum of the Maass Hamiltonian consists of the two disjoint parts: the continuous part and the discrete Landau levels (a ﬁnite number of eigenvalues of inﬁnite multiplicity) if

|B| > 1/2

. Following the argument as in Raikov, G. D. and Warzel, S. [“Quasi-classical versus non-classical spectral asymptotics for magnetic Schrödinger operators with decreasing potentials”, Rev. Math. Phys., vol. 14, no. 10, (2002), 1051–1072], we obtain the asymptotic distribution of the number of discrete spectrum of

H(V) = H(0) + V

near each discrete Landau level when

V

is real-valued, asymptotically spherically symmetric and satisﬁes some decay estimates near inﬁnity, or

V

is compactly supported.
The Damped Oscillator: A Locally Convex Formulation
Authors: Dubin Daniel A. , Hennings Mark A.
Published: September 2006

We formulate the quantum system of an oscillator driven by a quantum Wiener process, in the locally convex setting based on the rigged triple

\mathcal S(ℝ) ⊂ L^2(ℝ) ⊂ \mathcal S'(ℝ)

. The generalized observables are taken to be the elements of

\mathcal L(\mathcal S(ℝ), \mathcal S'(ℝ))

. Pulling the dynamics back to phase space by means of the inverse of Weyl quantization, we prove that the time translations semigroup is equicontinuous of class

C_0

. Moreover, it is differentiable, and its generator is an extension to

\mathcal L(\mathcal S(ℝ), \mathcal S'(ℝ))

of the known result for bounded operators.
Spectral and Scattering Theory for Schrödinger Operators with Cartesian Anisotropy
Authors: Richard Serge
Published: September 2006

We study the spectral and scattering theory of some
n
-dimensional anisotropic Schrödinger operators. The characteristic of the potentials is that they admit limits at inﬁnity separately for each variable. We give a detailed analysis of the spectrum: the essential spectrum, the thresholds, a Mourre estimate, a limiting absorption principle and the absence of singularly continuous spectrum. Then the asymptotic completeness is proved and a precise description of the asymptotic states is obtained in terms of a suitable family of asymptotic operators.
Polyhedra Dual to the Weyl Chamber Decomposition: A Précis
Authors: Saito Kyoji
Published: September 2006

Let

V_ℝ

be a real vector space with an irreducible action of a ﬁnite reﬂection group

W

. We study the semi-algebraic geometry of the

W

-quotient affine variety

V//W

with the discriminant divisor

D_W

in it and the

τ

-quotient affine variety

V//W//τ

with the bifurcation set

BW

in it, where

τ

is the

\mathbb G_a

-action on

V//W

obtained by the integration of the primitive vector ﬁeld

D

on

V//W

and

B_W

is the discriminant divisor of the induced projection :

D_W → V//W//τ

.

Our goal is the construction of a
one-parameter family of the semi-algebraic polyhedra

K_W(λ)

in

V_ℝ

which are dual to the Weyl chamber decomposition of

V_ℝ

.

As an application, we obtain two
geometric descriptions of generators for

π_1((V//W)_ℂ^{\text{reg}})

,
satisfying the Artin braid relations
.

The key of the construction of the polyhedra

K_W(λ)

is a theorem on a linearization of the tube domain in

(V//W)_ℝ

over the simplicial cone

E_W

in

T_{W,ℝ}

.