bluuebunny/crossref_metadata_2025_split huggingface dataset:
NULLCLINES AND NULLCLINE INTERSECTIONS
Authors: THOMAS RENÉ 
Published: December 2006

One purpose of this paper is to document the fact that, in dynamical systems described by ordinary differential equations, the trajectories can be organized not only around fixed points (steady states), but also around lines. In 2D, these lines are the nullclines themselves, in 3D, the intersections of the nullclines two by two, etc.We precise the concepts of "partial steady states" (i.e. steady states in a subsystem that consists of sections of phase space by planes normal to one of the axes) and of "partial multistationarity" (multistationarity in such a subsystem).Steady states, nullclines or their intersections are revisited in terms of circuits, defined from nonzero elements of the Jacobian matrix. It is shown how the mere examination of the Jacobian matrix and the sign patterns of its circuits can help interpreting (and often predicting) aspects of the dynamics of systems.The results reinforce the idea that chaotic dynamics requires both a positive circuit, to provide (if only partial) multistationarity, and a negative circuit, to provide sustained oscillations. As shown elsewhere, a single circuit may suffice if it is ambiguous (i.e. positive or negative depending on the location in phase space).The description in terms of circuits is by no means exclusive of the classical description. In many cases, a fruitful approach involves repeated feedback between the two viewpoints.
Cholesterol Enrichment of Human Monocyte/Macrophages Induces Surface Exposure of Phosphatidylserine and the Release of Biologically-Active Tissue Factor–Positive Microvesicles
Authors: Liu Ming-Lin , Reilly Michael P. , Casasanto Peter , McKenzie Steven E. , Williams Kevin Jon 
Published: December 2006

Objective—Biologically significant amounts of two procoagulant molecules, phosphatidylserine (PS) and tissue factor (TF), are transported by monocyte/macrophage-derived microvesicles (MVs). Because cellular cholesterol accumulation is an important feature of atherosclerotic vascular disease, we now examined effects of cholesterol enrichment on MV release from human monocytes and macrophages.Methods and Results—Cholesterol enrichment of human THP-1 monocytes, alone or in combination with lipopolysaccharide (LPS), tripled their total MV generation, as quantified by flow cytometry based on particle size and PS exposure. The subset of these MVs that were also TF-positive was likewise increased by cellular cholesterol enrichment, and these TF-positive MVs exhibited a striking 10-fold increase in procoagulant activity. Moreover, cholesterol enrichment of primary human monocyte-derived macrophages also increased their total as well as TF-positive MV release, and these TF-positive MVs exhibited a similar 10-fold increase in procoagulant activity. To explore the mechanisms of enhanced MV release, we found that cholesterol enrichment of monocytes caused PS exposure on the cell surface by as early as 2 hours and genomic DNA fragmentation in a minority of cells by 20 hours. Addition of a caspase inhibitor at the beginning of these incubations blunted both cholesterol-induced apoptosis and MV release.Conclusions—Cholesterol enrichment of human monocyte/macrophages induces the generation of highly biologically active, PS-positive MVs, at least in part through induction of apoptosis. Cholesterol-induced monocyte/macrophage MVs, both TF-positive and TF-negative, may be novel contributors to atherothrombosis.
The Sphingosine-1-Phosphate Analogue FTY720 Reduces Atherosclerosis in Apolipoprotein E–Deficient Mice
Authors: Keul Petra , Tölle Markus , Lucke Susann , von Wnuck Lipinski Karin , Heusch Gerd , Schuchardt Mirjam , van der Giet Markus , Levkau Bodo 
Published: December 2006

Objective—The sphingosine-1-phosphate (S1P) analogue FTY720 is a potent immunosuppressive agent currently in Phase III clinical trials for kidney transplantation. FTY720 traps lymphocytes in secondary lymphoid organs thereby preventing their migration to inflammatory sites. Previously, we have identified FTY720 as a potent activator of eNOS. As both inhibition of immune responses and stimulation of eNOS may attenuate atherosclerosis, we administered FTY720 to apolipoprotein E−/−mice fed a high-cholesterol diet.Methods and Results—FTY720 dramatically reduced atherosclerotic lesion volume (62.5%), macrophage (41.8%), and collagen content (63.5%) after 20 weeks of high-cholesterol diet. In isolated aortic segments and cultured vascular smooth muscle cell, FTY720 potently inhibited thrombin-induced release of monocyte chemoattractant protein-1. This effect was mediated by the S1P3sphingolipid receptor as FTY720 had no effect on thrombin-induced monocyte chemoattractant protein-1 release in S1P3−/−mice. In contrast to S1P receptors on lymphocytes, FTY720 did not desensitize vascular S1P receptors as arteries from FTY720-treated mice retained their vasodilator response to FTY720-phosphate.Conclusions—We suggest that FTY720 inhibits atherosclerosis by suppressing the machinery involved in monocyte/macrophage emigration to atherosclerotic lesions. As vascular S1P receptors remained functional under FTY720 treatment, S1P agonists that selectively target the vasculature and not the immune system may be promising new drugs against atherosclerosis.
An Analytical Hydrological Model for the Study of Scaling Issues in Land Surface Modeling
Authors: Ren Diandong , Henderson-Sellers Ann 
Published: December 2006

Abstract
Besides the atmospheric forcing such as solar radiation input and precipitation, the heterogeneity of the surface cover also plays an important role, especially in the distribution characteristics of the latent heat flux (LE). In this study, scaling issues are discussed based on an analytical hydrological model that describes the transpiration and diffusion processes of soil water.
The solution of this analytical model is composed of a transient part that depends primarily on initial conditions and a steady part that depends on the boundary conditions. To know how sensitive the different averaging approaches are to the initial conditions, three initial profiles are chosen that cover the prevailing soil moisture regimes. After analyzing its solution, the study shows that 1) upon reaching the steady state, directly taking an average of soil properties will cause systematic overestimation in the calculation of area-averaged LE. For an initially very dry condition, averaging of a sandy soil and a clay soil can cause a percentage error as large as 40%. 2) For vegetation growing on sandy soils, a direct averaging of the transpiration rate results in persistent overestimation of LE. For vegetation growing on clay soil, however, even after reaching the steady state, averaging of two water extraction weights can be either an overestimation or an underestimation, depending on which two vegetation types are involved. 3) During the interim stage of drying down, averaging of the soil/vegetation properties can lead to either an overestimation or an underestimation, depending on the evolving stage of the soil moisture profile. 4) The initial soil moisture condition matters during the transient stage of drying down. Different initial soil moisture conditions yield different scenarios of underestimation and overestimation patterns and a differing severity of errors.
The simplicity of the analytical model and the heuristic initial soil profiles make the generalization easier than using sophisticated numerical models and make the causality mechanism clearer for physical interpretations.
Chemical dissolution techniques in the study of soil clays: Part I
Authors: Follett E. A. C. , McHardy W. J. , Mitchell B. D. , Smith B.F.L. 
Published: December 2006

AbstractThe mineralogy of the clay fractions of two soil profiles representing the end-members of a catena developed on a glacial till derived from basic lavas has been determined. Particular attention has been given to the assessment of the nature of the amorphous inorganic material in the clay fraction of these soils. Chemical dissolution techniques were used and their effects on the clay fraction were followed by X-ray diffraction, differential thermal, infrared absorption, electron-optical and surface area measurements. The principal conclusion is that the soil clays are a continuum from completely disordered, through poorly ordered to well crystallized material.
Argillization of basic hornfelses from the Land's End granite aureole, Cornwall
Authors: Floyd P. A. 
Published: December 2006

AbstractMineralogical and chemical variation in a 24 ft wide argillized zone in basic hornfelses from Gwavas quarry, Cornwall, is described and compared with variation in unaltered wall rock hornfelses.Hydrothermal minerals developed are well-ordered kaolinite, sericite, chlorite, quartz, and limonite. Biotite has replaced hornblende as the dominant mafic constituent in the argillized zone. With increasing argillization kaolinite progressively replaces plagioclase, biotite, chloritized biotite, quartz, and finally Fe ore. No montmorillonite is present.From the argillized zone, Si, Na, Ca, Mg, and Fe were extensively leached, although an approximate equivalent of H was added to compensate for the loss. Al and K are relatively constant throughout the zone. F was expelled from the most heavily argillized areas and is now concentrated in the biotite of the zone's margin as a marked ‘fluorine front’.Two tenuous kaolinite-sericite zones are observed which are thought to be due to local variation in a single hydrothermal pulse with time.Hydrothermal alteration of the hornfelses was effected in two stages (1) K+ metasomatism (biotitization) and (2) H+ metasomatism (kaolinization and sericitization).
A high-aluminous chlorite-swelling chlorite regular mixed-layer clay mineral
Authors: Heckroodt R. O. , Roering C. 
Published: December 2006

AbstractOne of the alteration products of a deuteric altered beryl is a high-aluminous chlorite-swelling chlorite regular mixed-layer clay mineral. An attempt was made to calculate the structural formula, and the results of X-ray, differential thermal and electron diffraction analyses are given.
Clay-organic studies. X. Complexes of primary amines with montmorillonite and vermiculite
Authors: Brindley G. W. 
Published: December 2006

AbstractBasal spacing data for neutral amine complexes with montmorillonite and vermiculite are explained on the basis of two layers of fully extended amine molecules inclined at about 65° to (001) with the NH2 groups closely associated with pairs of silicate oxygen atoms. The molecular orientation is shown to be favourable for good intermolecular packing and for possible NH..O bonding, but the results do not constitute proof of such bonding. Packing of the molecules on the silicate surfaces and with respect to each other may explain the formation of double layer complexes. The amine data are correlated with corresponding data for the low-temperature (or below melting point) series of alcohol-montmorillonite complexes and it is suggested that the molecular layers may have some solid-like characteristics.
The mineralogy of some Upper Chalk samples from the Arundel area, Sussex
Authors: Weir A. H. , Catt J. A. 
Published: December 2006

AbstractSeven samples, representative of all zones of the Upper Chalk in the Arundel area of Sussex, were treated with acetic acid and the residues analysed to determine their mechanical and mineralogical compositions. The sand and silt fractions of the residues consist mainly of flint and opaline silica, collophane, limonite, and quartz, and the clay fractions consist of montmorillonite, mica, quartz, and apatite. Authigenic apatite and quartz occur in the clay and silt and authigenic alkali feldspar in the silt. The montmorillonite may also be authigenic.
Urea complexes with montmorillonite : an infrared absorption study
Authors: Mortland M.M. 
Published: December 2006

AbstractUrea was observed to become protonated in H-, Fe-, and Al-montmorillonite films and to form hemisalts when urea was present in excess of the number of available protons. The fully protonated urea disappeared upon dehydration, then the original protonated condition was re-established by rehydration. This completely reversible reaction indicates the importance of water in the protonated form. Indications were that urea will coordinate through the carbonyl group to the metal ion in Cu (II), Mn (II), and Ni (II) montmorillonite. Urea may be bonded to the metal ion in Mg-, Ca-, Li-, Na-, and K-montmorillonite by coordination and possibly by ionization of the N-H bond. The importance of ion-dipole interaction in urea complexes with montmorillonite is suggested. Decomposition of urea to ammonium ions was observed mainly in the Cumontmorillonite system.
Organo-metallic clay complexes
Authors: Bodenheimer W. , Heller L. , Yariv S. 
Published: December 2006

AbstractDifferential thermal analysis curves were obtained for a series of diamine and glycol complexes with natural and copper substituted montmorillonite, in air and in an inert atmosphere. Thermobalance curves of the diamine-clay systems were also determined. The exothermic peaks observed in air are characteristic for any particular system and reflect the nature and binding of the interlamellar material; no direct correlation was, however, observed with pyrolysis and oxidation processes in the clay. Organic matter is frequently liberated from the clay before oxidation, which then occurs within the reaction cell but outside the clay phase. The extent to which oxidation is completed at any particular temperature depends upon the supply of oxygen and the amount of organic material present.
Experimental studies of fine-grained micas
Authors: Rouxhet P. G. , Brindley G. W. 
Published: December 2006

AbstractThe surface properties of wet-ground muscovite were studied by thermodynamics of water adsorption. The surface appears to be covered by contaminating material, probably organic, which is strongly held; it was not removed at 350° C and under a vacuum of 10−4 torr. Attention is directed to the difficulty of maintaining freshly made silicate surfaces without contamination and to the importance of surface conditions in the interpretation of silicate properties which involve surface phenomena.
Vermiculite, hydrobiotite, and biotite in the Rainy Creek igneous complex near Libby, Montana
Authors: Boettcher A. L. 
Published: December 2006

AbstractVermiculite and hydrobiotite both occur as alteration products of biotite pyroxenite near Libby, Montana. Hydrothermal and weathering studies and new chemical analyses by C. O. Ingamells suggest that the vermiculite is a product of leaching of biotite by ground waters; the hydrobiotite may be a higher temperature alteration product.
Hysteresis in the crystalline swelling of montmorillonite
Authors: Laffer B. G. , Posner A. M. , Quirk J. P. 
Published: December 2006

AbstractThe crystalline swelling of sodium and potassium montmorillonites immersed respectively in solutions of sodium and potassium chloride of different concentration exhibits hysteresis in the swelling-contraction cycles. The position and extent of the hysteresis can be varied by altering the method of preparation of the clays; in all cases the hysteresis loops for potassium montmorillonite were more extensive than those for sodium montmorillonite.The results have been explained in terms of a structural rigidity of montmorillonite crystals, where the crystals consist of five to ten aluminosilicate sheets (lamellae). The extent of hysteresis depends on this rigidity, which varies in a co-operative manner with the spacing between the lamellae in the crystal.Electrical interactions between pairs of lamellae are also considered in analysing the swelling behaviour.
X-ray diffraction study of orientation of the micaceous minerals in slate
Authors: Fayed Laila A. 
Published: December 2006

AbstractAn X-ray diffraction technique has been used to determine the orientation pattern of the (001) planes of 10 Å micaceous minerals in slate. The guiding principle of this technique is the direct measurement of the diffracted radiation from the pre-selected family of crystallographic planes as a function of the orientation of the specimen.Results obtained indicated that the basal planes of these minerals are mostly oriented in a direction parallel to the cleavage planes and the possibility of another orientation was considered to be slight.
Ionic composition of a disordered kaolinite
Authors: Worrall W. E. , Cooper A. E. 
Published: December 2006

AbstractA white-burning, highly-plastic clay from Jamaica, containing mainly disordered kaolinite, was examined recently. It was unusual in that it was practically free from fine mica, and therefore could be purified readily by standard sedimentation techniques.The cation exchange capacity was abnormally high, and the purified clay mineral, on analysis and calculation of the ionic composition, was found to be deficient in aluminium, but contained magnesium and iron.The results confirmed the view, previously expressed, that disorder in kaolinites is associated with a high cation exchange capacity and a substituted lattice.
Clay-organic studies
Authors: Brindley G. W. , Thompson T. D. 
Published: December 2006

AbstractComplexes are formed between a Ca-saturated fluorhectorite and organic molecules derived from propane by substituting benzene, pyridine, and piperidine rings in the 1,3 positions. The complexes are mainly of the A- and B-types described earlier by Greene-Kelly. Only one of the substances studied forms long-spacing complexes; in this case, the organic molecule is terminated at one end by a benzene ring and at the other by an active =NH group. Neutral forms of this molecule develop double-layer complexes, cationic forms develop single-layer complexes. The results are consistent with data for alcohols, alkyl chlorides and bromides, and alkyl amines.
Chemisorption of methylene blue by kaolinite
Authors: Faruqi F. A. , Okuda Susumu , Williamson W. O. 
Published: December 2006

AbstractThe chemisorption of methylene blue by kaolinite crystals increased as the aqueous suspensions changed from acid to alkaline because, at high pH values, not only the basal pinacoids but the edge-faces were negatively charged. The inability to calculate acceptable specific surfaces or cation exchange capacities from the chemisorption data is discussed, with special reference to the orientation of adsorbed dye cations, the covering of more than one exchange site by a monomer or polymer, the different concentrations of exchange sites on the basal pinacoids and edge-faces respectively, the possibility that such sites occur on the tetrahedral rather than on the octahedral basal pinacoid, and the incomplete replacement of inorganic cations.
Energy changes in dehydration processes of clay minerals
Authors: Sudo Toshio , Shimoda Susumu , Nishigaki Shigeru , Aoki Masaharu 
Published: December 2006

AbstractUsing the adiabatic calorimeter which has been developed by Nagasaki & Takagi (1948) and manufactured by the Rigaku Denki Company, the energy changes associated with the dehydration and dehydroxylation processes of clay minerals were measured at room pressure. The samples studied were mont-morillonite, chlorite (trioctahedral type), and three kinds of interstratified minerals with component layers such as mica, dioctahedral chlorite, and montmorillonite. ΔH-values due to the dehydration of the interlayer region were 9·8 kcal/H2O mole for montmorillonite and 12·4–13·4 kcal/H2O mole for interstratified minerals mica-montmoriIlonite and dioctahedral chlorite-montmorillonite. The values due to dehydroxylation of the silicate layer were 17·7 kcal/H2O mole for montmorillonite, 16·8–17·5 kcal/H2O mole for the interstratified mica- montmorillonite, and 19·3 kcal/H2O mole for chlorite. The value for the dehydroxylation of the hydroxyl layer of chlorite was 19·3 kcal/H2O mole. For the sake of comparison, the heat of transition α↔β of quartz was found to be 140 cal/mole. The reproducibility of these values was in the range of ±5%.
Hydration states of an expanded phlogopite in relation to interlayer cations
Authors: Thompson T. D. , Wentworth Sally A. , Brindley G. W. 
Published: December 2006

AbstractA 2–20 µ fraction of phlogopite has been converted to the sodium form by use of sodium tetraphenylboron-NaCl solutions. The cation exchange capacity of the treated material increases to a maximum of about 212 m-eq/100 g, which agrees well with the K2O + Na2O content of the initial mineral. Li-, Na-, Ca-, and Mg-saturated forms have been prepared and examined by X-ray diffraction and by thernogravimetric measurements in air, in vacuo, and at progressively elevated temperatures. Hydration states corresponding to double water layers are observed for the Mg- and Ca- forms, and to single water layers for the Mg-, Ca-, Na-, and Li- forms. The numbers of water molecules per unit cell and per interlayer cation are considered for the various hydration states.
A study of hydroxyl groups in kaolin minerals utilizing selective deuteration and infrared spectroscopy
Authors: Wada Koji 
Published: December 2006

AbstractThe OH-OD exchange of kaolin minerals through contact with D2O introduced into interlayer space via intersalation resulted in a partial shift of the OH absorption bands. The total decrease in OH absorbance upon deuteralion was 52, 56, and 47% for the kaolinite, dickite-nacrite, and halloysite respectively, but the percentage decrease differed for the different absorption maxima of any one mineral. A secondary OH—OD exchange in the deuterated specimens was also observed upon heating to 350 and 400° C. These data together with the lack of deuteration in montmorillonite, and available orientation data on the kaolin OH groups by infrared spectroscopy, suggest that only two-thirds of the inner-surface OH groups form the interlayer OH—O bonds.
Quantitative X-ray diffraction analysis using clay mineral standards extracted from the samples to be analysed
Authors: Gibbs Ronald J. 
Published: December 2006

AbstractIn the quantitative X-ray diffraction analysis of a series of samples, the problems arising from the variable compositions and degrees of crystallinity of clay minerals were overcome to a great extent by the use of standards extracted from the samples. Procedures are given for separation of the montmorillonite standard by differential settling of Na-montmorillonite solvated in an ethanol solution and for isolation of the kaolinite, mica, and chlorite standards by density separation of their Na-forms in thallous formate.Calibration curves were prepared from the X-ray diffractograms obtained for series of known mixtures of Ca-forms of the standards and the internal standard boehmite using both powder and smear-oriented mounting techniques.
The argillation of sub-marine tufts from the Mount Carmel, Israel
Authors: Singer Arieh 
Published: December 2006

AbsractThe alteration products of five sub-marine tuffs from the Mount Carmel were analysed chemically, by X-ray, D.T.A. and I.T.A. techniques and their mineralogical composition determined. Smectites are dominant in all the samples. In the less altered tuffs the smectite seems to consist of a mixture of saponite with a smectite from the beidellite-nontronite series. In the more intensely altered tuffs the saponite disappears and a swelling chlorite appears. The formation of the swelling chlorite is attributed to the degradation of the saponite. These mineralogical changes are accompanied by the loss of a large part of the alkali and alkaline earth cations.