bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and testing of the European Heart Failure Self‐Care Behaviour Scale
Authors: Jaarsma T. , Strömberg A. , Mårtensson J. , Dracup K. 
Published: February 2003

AbstractBackground:Improvement of self‐care behaviour is an aim of several non‐pharmacological nurse‐led management programmes for patients with heart failure. These programmes are often evaluated based on their effects on readmission, costs and quality of life. It is, however, also important to know how patients changed their self‐care behaviour as a result of such a programme. Therefore a comprehensive, reliable and valid measure of the self‐care behaviour of HF patients is needed.Objectives:To develop a scale measuring the behaviour that heart failure patients perform to maintain life, healthy functioning, and well‐being.Method:The European Heart Failure Self‐Care Behaviour Scale (EHFScBS) was developed in three phases: (1) concept analysis and first construction; (2) revision of items and response and scoring format; and (3) testing of the new scale for validity and reliability.Results:The European Heart Failure Self‐Care Behaviour Scale is a 12‐item, self‐administered questionnaire that covers items concerning self‐care behaviour of patients with heart failure. Face‐validity and concurrent validity was established and the internal consistency of the scale was tested using pooled data of 442 patients from two centres in Sweden, three in the Netherlands and one in Italy. Cronbachs's alpha was 0.81.Conclusion:The instrument is a valid, reliable and practical scale to measure the self‐reported self‐care behaviour of heart failure patients. It is ready to use by investigators evaluating the outcome of heart failure management programmes that target changes in patients’ self‐care practices.
Smectite-Type Clay Minerals as Nanomaterials
Authors: Schoonheydt Robert A. 
Published: February 2003

AbstractDilute aqueous smectite suspensions are well suited to convert into functional nanofilms. The functionalization is performed by ion exchange of amphiphilic molecules carrying the desired functionality. A functionalized clay mineral nanofilm is obtained by the organization of the molecules at the clay surface and by the organization of the elementary clay platelets in the film. Two techniques are presented: self-assembling and Langmuir-Blodgett (LB). Self-assembling is a very simple experiment, but the organizational order of the clay mineral particles is low. Nevertheless, films with nonlinear optical properties which are able to generate frequency-doubled light have been produced. The drawback of disorder of the clay platelets in the film can be largely overcome with the LB technique. Well organized films are obtained. In the presence of amphiphilic ruthenium(II)-bipyridine complexes, nonlinear optical properties are measured. In the presence of two dyes, oxacarbocyanine and rhodamine B, simultaneously adsorbed, efficient energy transfer between the donor (oxacarbocyanine) and the acceptor (rhodamine B) is measured. Fundamental research into the organization of molecules at clay mineral platelets is necessary to optimize the materials for specific applications.
Benzene Vapor Sorption by Organobentonites From Ambient Air
Authors: Zhu Lizhong , Su Yuhong 
Published: February 2003

AbstractA number of organobentonites were synthesized by exchanging the metal ions in bentonite with the cationic surfactant, cetyltrimethylammonium bromide. Samples of natural bentonite and organobentonites were analyzed for their organic carbon contents, examined by X-ray diffraction (XRD) for interlayer spacings, and viewed using a scanning electron microscope (SEM) for surface morphology. The sorption isotherm of benzene vapor from ambient air (relative humidity (RH) = 45 ± 5%) on natural bentonite was nonlinear; however, the isotherms of benzene from ambient air onto organobentonites were virtually linear over a large range of relative vapor concentrations. The sorption capacities of air-dried organobentonites were far greater than that of the natural bentonite. For air-dried organobentonites, the sorption coefficients correlated positively with the sample organic carbon contents and negatively with the sample BET-N2 surface areas. The heats of benzene vapor sorption onto air-dried organobentonites were less exothermic than the heat of benzene-vapor condensation. These findings suggest that benzene vapor sorption by air-dried organobentonites occurs essentially by vapor partition into the sample organic-matter fractions. This offers a potential application of organobentonites for the removal of organic vapors from flue gases and for assessing the efficiency of vapor removal.
Genesis, Mineralogy and Geochemistry of Kaolin Deposits of the Jari River, Amapá State, Brazil
Authors: Montes Célia R. , Melfi Adolpho J. , Carvalho Adilson , Vieira-Coelho Antonio C. , Formoso Milton L. L. 
Published: February 2003

AbstractKaolin samples from the Jari deposit (Amazon region) were studied using various techniques to characterize its structural and crystallochemical aspects, and to establish its origin and evolution. A profile 60 m thick was selected in a kaolin mine (Morro do Felipe) located at the banks of the Jari river. Despite the great thickness of the deposit and the variety of kaolin types, the mineralogical composition is rather homogeneous and is mainly kaolinite associated with gibbsite and small amounts of quartz, anatase, goethite and hematite. The field observations and the morphological analysis indicate the existence of sedimentary features throughout the whole profile except for the upper aluminous clayey layer (Belterra Clay). This is evidence that the Rio Jari kaolin deposit originated from sedimentary material, the Alter do Chão Formation. The presence of alternating clay and sandy layers is explained by sedimentation processes with great depositional energy variation. Thus, the accumulation of thick clay layers was related to a low-energy phase, and during the high-energy phases, the deposition process led to the accumulation of sandy materials, constituted essentially of quartz and showing strong textural and structural variation. Later on, periods of hydromorphy were responsible for iron removal and consequently for the bleaching of the sedimentary formation. The crystallinity data show an increase of the structural disorder toward the surface associated with an increase in the amount of structural Fe in the kaolinite. The Rio Jari kaolin deposits should be considered as having originated from kaolinitic clay sediments of the Alter do Chão formation (protore) that was submitted to intensive lateritic weathering processes.
Kerolite in Carbonate-Rich Speleothems and Microbial Deposits From Basaltic Caves, Kauai, Hawaii
Authors: Léveillé Richard J. , Longstaffe Fred J. , Fyfe William S. 
Published: February 2003

AbstractThe occurrence of kerolite in association with various secondary Ca-Mg carbonate mineral deposits (speleothems) was identified in basaltic sea caves on the island of Kauai, Hawaii. Kerolite is the dominant clay mineral in the deposits. X-ray diffraction (XRD) peaks of the kerolite are characteristically broadened indicating its extremely poor crystallinity. Few changes were observed in the XRD patterns of this kerolite when it was subjected to various humidity, temperature and ethylene-glycol treatments. The crystals appear as flaky masses with irregular or jagged edges in scanning (SEM) and transmission electron microscopy (TEM). Electron probe and energy dispersive X-ray (EDX) microanalysis show that the clay material is dominated by Mg-Si-O, with minor amounts of Al and Ca in some samples. The chemical composition, thermal analysis and TEM observations suggest that smaller amounts of an amorphous serpentine-like phase are mixed with the kerolite. Kerolite is often the only mineral associated with poorly mineralized, actively-growing microbial mats in these caves and it is common in completely lithified microbial mats. The latter commonly have microstromatolitic structures with kerolite as a dominant phase. These features suggest that kerolite formation is at least in part a result of microbial activity. The abundant extracellular polymers of the mat-forming bacteria bind and concentrate ions (Mg2+, silica) from solution and serve as nucleation sites for kerolite precipitation. Conditions within the mats also probably lead to formation of Mg-Si-gels, amorphous Mg-silicate precursors and ultimately kerolite. Evaporation of the cave solutions may also contribute to kerolite formation.
Thickness Distribution of Illite Crystals in Shales. I: X-Ray Diffraction vs. High-Resolution Transmission Electron Microscopy Measurements
Authors: Dudek Teresa , Środoń Jan , Eberl Dennis D. , Elsass Françoise , Uhlik Peter 
Published: February 2003

AbstractTwo independent methods of crystal-size distribution analysis were compared: the Bertaut-Warren-Averbach XRD technique (MudMaster computer program) and high-resolution transmission electron microscopy (HRTEM). These techniques were used to measure thickness distributions of illite crystals (fundamental particles) from sets of illite-smectites from shales and bentonites that had expandabilities ranging from 86%S to 6%S. The illite-smectites were treated with a polymer (polyvinylopyrolidone, PVP) to separate them into fundamental particles for XRD and HRTEM investigations.A systematic difference between XRD and HRTEM results was observed: XRD (area-weighted distributions) detected a larger fraction of thick (>4 nm) and a smaller fraction of thin crystals as compared to HRTEM (number-weighted distributions). As a result, XRD-determined distributions have larger mean thickness values and larger distribution parameters (α and β2). The measurements performed by the two techniques were verified by modeling XRD patterns of the PVP-illites, using the measured distributions as inputs. The modeling indicated that the XRD-determined distributions are very accurate. Selecting broader thickness distributions in MudMaster further improved the modeling results. The HRTEM measurements underestimate the proportion of coarse particles, in particular in shale samples, and this inaccuracy is attributed to the effect of using number-weighted (rather than area-weighted) distributions and to inaccurate counting statistics for thick crystals.
The Stability of Fe-Mg Chlorites in Hydrothermal Solutions: Ii. Thermodynamic Properties
Authors: Aja Stephen U. 
Published: February 2003

AbstractThe hydrothermal stabilities of a low-Fe clinochlore and a high-Mg chamosite, in the presence of kaolinite, were investigated recently at T ⩽ 200°C and Pv=PH2O (Aja and Small, 1999; Aja and Dyar, 2002). Standard state thermodynamic properties (S2980, ΔfH1,2980 and ΔfG1,2980) have been obtained for the two chlorites whose structural formulae are (Al2.33Fe1.002+Fe0.143+Ca0.02Mn0.01Ni0.02Cr0.01Mg8.40α0.07) (Si5.66Al2.34)O20(OH)16 and (Fe0.603+Fe5.432+Mg2.30Al2.98Mn0.05Ca0.03Zn0.01α0.60)(Si5.63Al2.37)O20(OH)16. For the low-Fe clinochlore, the respective thermochemical properties are 430 J mol−1 K−1, −8770.64±35.24 kJ mol−1, and −8120.54±32.63 kJ mol−1. ΔfH1,2980, ΔfG1,2980 and S2980, similarly obtained for the Windsor chamosite are −7851.29±23.14 kJ mol−1, −7271.01±21.43 kJ mol−1 and 668±5 J mol−1K−1, respectively. Ideal site-mixing models of chlorite composition, along the chamosite-clinochlore binary, fail to model satisfactorily these chlorite-fluid equilibria only at lower temperatures (T <175°C). The magnitudes of the excess thermodynamic properties calculated for these chlorites, within the ternary clinochlore-daphnite-sudoite system, suggest significant deviations from ideality.
Refinement of the Crystal Structure of Cronstedtite-2H2
Authors: Hybler Jiří , Petříček Václav , Fábry Jan , Ďurovič Slavomil 
Published: February 2003

AbstractThe crystal structure of cronstedtite-2H2 was refined in a hexagonal cell, space group P63, Z = 2, using two acicular crystals from Wheal Maudlin, Cornwall, England, and from Pribram, Czech Republic. The Wheal Maudlin sample has the chemical composition (Fe2.2912+Fe0.7093+)(Si1.298Fe0.7073+Al0.004)O5(OH)4 and the Příbram sample has the composition (Fe2.2692+Fe0.7313+)(Si1.271Fe0.7243+Al0.005)O5(OH)4. The results of refinements are as follows: a = 5.500(1), c = 14.163(2) Å, V = 371.08(8) Å3, R = 3.83%, from 381 independent reflections, and a = 5.4927(1), c = 14.1481(2) Å, V = 369.70(4) Å3, R = 4.77%, from 1088 independent reflections for the Wheal Maudlin and Příbram samples, respectively. The best Fovs.Fc agreement was achieved when the structure was interpreted as merohedral twin; several possible twinning laws are discussed. The cronstedtite layer consists of one tetrahedral sheet and one octahedral sheet. There is one octahedral (M1) position, occupied by Fe only, and two tetrahedral (T1, T2) positions in the structure. Refinement of occupancy of tetrahedral sites led to values Si:Fe = 0.45:0.55(1) (Wheal Maudlin) and 0.432:0.568(8) (Příbram) in T1, and Si: Fe = 0.99:0.01(1) (Wheal Maudlin) and 0.888:0.112(7) (Příbram) in 72. Whereas the size of T1 is reasonable (average dT1-O = 1.693 Å (Wheal Maudlin), 1.691 Å (Příbram)), T2 is unusually large: (dT2-O= 1.740 Å (Wheal Maudlin), 1.737 Å (Příbram)) with respect to the small or almost zero Fe content. As an explanation, an alternative structure model comprising a certain amount of vacancies in T2 is presented. The tetrahedral rotation angle α is highly positive (+12.1° and +12.5° for the Wheal Maudlin and Příbram samples, respectively), and the layer belongs to the Franzini type A. Distortion parameters of octahedra and tetrahedra are given for both samples. One hydrogen atom engaged in the hydrogen bond was located in the Wheal Maudlin sample.
Effect of Acid and Alkali Treatments on Surface-Charge Properties of Selected Minerals
Authors: Jozefaciuk Grzegorz 
Published: February 2003

AbstractBentonite, biotite, illite, kaolin, vermiculite and zeolite were treated with 0.1, 1.0 and 5.0 mol. dm−3 HCl or NaOH. Suspensions of Na homoionic forms of the initial and the treated minerals were back titrated with 0.1 mol. dm−3 NaOH. From back-titration data variable surface charge, QV, vs. pH dependencies and apparent surface dissociation constant distribution functions were estimated. Variable charge vs. pH curves were scaled against cation exchange capacity at pH 7.2 to obtain actual charge, QA, vs. pH plots. In general both treatments led to an increase of QV, while the QA value increased and decreased depending on the mineral and the treatment. Products of 5 mol dm−3 NaOH action on zeolite and of 1 and 5 mol. dm−3 NaOH on kaolin apparently developed a positive surface charge below pH ∼3.7 and below ∼4.3, respectively.The heterogeneity of charge-generating surface groups was observed in natural minerals. During acid treatment, the number of weakly-acidic surface functional groups increased while the number of groups of stronger acidic character decreased. The opposite was found for alkaline treatment: the number of surface groups of intermediate acidity increased and that of low acidity decreased.
Stability of Magadiite Between 20 and 100°C
Authors: Dietzel Martin , Letofsky-Papst Ilse 
Published: February 2003

AbstractNew experimental data with respect to the solubility of natural and synthesized magadiite at elevated temperatures and in alkaline solutions are presented. The results show that the solubility of magadiite increases according to the expression ln(Kmag) = −8146·T(K)−1 − 5.71 from 20 to 100°C ((ΔGR0(Kmag)=19.6±0.3 and ΔHR0(Kmag)=16.2±0.4kcalmol−1). The experimental results and the related data from the literature suggest that the formation of magadiite may be favored by a decrease of temperature and pH (pH >9) as well by large amounts of Na+ ions and low ionic strength. These effects are related to the value of ΔHR0(Kmag), the distribution of dissolved silica species, the stoichiometry of magadiite, and the occurrence of negatively-charged species, respectively.
Preparation and Porous Properties of Materials Prepared by Selective Leaching of Phlogopite
Authors: Okada Kiyoshi , Nakazawa Noriyuki , Kameshima Yoshikazu , Yasumori Atsuo , Temuujin Jadambaa , MacKenzie Kenneth J. D. , Smith Mark E. 
Published: February 2003

AbstractPorous silica products obtained by selective leaching of phlogopite using an acid solution were investigated by XRD, MAS NMR, SEM, TEM, DTA/TG, and N2 and Ar gas adsorptions. The phlogopite powder was leached by a nitric acid solution at various concentrations (0.01–10 M) at 5–150°C for 10 min–480 h. Selective leaching of the phlogopite powder became extensive when the concentration of nitric acid was >1 M. Only SiO2 remained after the treatment, the other components (MgO, Al2O3, K2O and Fe2O3) being selectively leached from the product. At higher leaching temperatures, the leaching rate became faster and the resulting maximum specific surface area of the porous silica product became larger at each leaching temperature. The porous silica products were found by SEM and TEM, to maintain their original platy particle shape even after the selective leaching. The 29Si MAS NMR spectra of the products, however, revealed that the linkage structure of SiO4 tetrahedra converted to a framework type from a layered type in the original phlogopite. The porous silica product with the maximum specific surface area (532 m2/g) was obtained by leaching in a nitric acid solution with concentration of 5 M at 90°C for 15 min. The pore-size distribution of the porous silica product was bimodal with micropores of ∼0.7 nm and mesopores of ∼4 nm. The pore size of the products changed from 0.7 nm to 4 nm and further to 6 nm with increased leaching time. The present results are discussed in relation to those reported for phlogopite by other workers.
Vibrational Analysis of Palygorskite and Sepiolite
Authors: McKeown David A. , Post Jeffrey E. , Etz Edgar S. 
Published: February 2003

AbstractLattice dynamic calculations for the sepiolite and palygorskite structures using polarized Raman and FTIR spectra provide a fundamental basis for interpreting spectral features by assigning vibrational modes. The Si-O stretch and O-Si-O bond bending force constants determined for palygorskite are similar to equivalent values calculated previously for other phyllosilicates. The Mg-O bond stretch values, on the other hand, are about half of those determined for the equivalent Al-O and Mg-O bond stretch environments in other phyllosilicates, suggesting that the bonding within the octahedral ribbons in palygorskite and sepiolite is weaker than that in the continuous octahedral sheets in micas. The weaker bonding allows more flexible octahedral environments in palygorskite and sepiolite, giving rise to higher probabilities for cation substitutions and vacancies relative to the micas. Above ∼700 cm−1 in the IR and 750 cm−1 in the Raman spectra, the eigenmodes are dominated by atomic displacements within the silicate sheets. Below 700 cm−1 the eigenmodes become mixed with motions among the Mg octahedra and the silicate sheets; the eigenmodes assigned to the most prominent peaks in the Raman spectra (near 700 cm−1) belong to this group. As mode frequencies decrease, the corresponding eigenmodes evolve from more localized Mg-O stretch, O-Mg-O bend and O-Si-O bend motions to longer-range motions such as silicate sheet deformations caused by silicate tetrahedra rotation and silicate sheet shearing around the Mg-octahedral sheets.
Hydrothermal Synthesis of Zn-Smectites
Authors: Higashi Shoji , Miki Kazuhiko , Komarneni Sridhar 
Published: February 2003

AbstractTwo varieties of Zn-smectite were synthesized hydrothermally: sauconite, with an ideal composition of Na0.4Zn3(Si3.6Al0.4)O10(OH)2·nH2O; and a Zn equivalent of hectorite, with an ideal composition of Na0.4 (Li0.4Zn2.6)Si4O10(OH)2·nH2O (referred to here as Zn-hectorite). For comparison, hydrothermal synthesis of the related trioctahedral smectites of hectorite, Na0.4(Li0.4Mg2.6)Si4O10(OH)2·nH2O and hectorites containing Cu, Co or Ni in the octahedral sheets instead of Mg were also attempted. The results showed that sauconite, Zn-hectorite and hectorite could be synthesized in the temperature range 100–125°C but hectorites containing Cu, Co or Ni in the octahedral sheet, under the same conditions or even at a temperature of 150°C, could not.
Infrared Evidence of Dioctahedral-Trioctahedral Site Occupancy in Palygorskite
Authors: Chahi A. , Petit S. , Decarreau A. 
Published: February 2003

AbstractA Mg-rich palygorskite sample from phosphorite deposits of Ganntour (Morocco) with the structural formula Si8(Mg2.6Al1.19Fe0.33III□0.88)Ca0.056Na0.024K0.104O20(OH)2(OH2)4⋅4H2O, was studied by FTIR spectroscopy. In both OH-stretching and OH-bending regions, there is evidence of dioctahedral Al2□OH, AlFe□OH and trioctahedral Mg3OH features, leading to a di-trioctahedral crystallochemical model of octahedral site occupancies in ribbons of Ganntour palygorskite.This model, established through the IR spectroscopy study of a Mg-rich palygorskite, seems to be appropriate for many other palygorskites with lower Mg content in the octahedral sheet.
In Situ Characterization and Differentiation of Kaolinites in Lateritic Weathering Profiles Using Infrared Microspectroscopy
Authors: Beauvais Anicet , Bertaux Jacques 
Published: February 2003

AbstractLateritic weathering kaolinites have been characterized in situ and differentiated for the first time by means of infrared microspectroscopy (IRMS). Four classical OH-stretching bands have been observed in the Fourier transform infrared (FTIR) spectra, at 3695, 3668, 3650 and 3620 cm−1, denoted ν1, ν2, ν3 and ν4, respectively, plus a band at 3595 cm−1 associated with the octahedral substitution of Fe3+ for Al3+. Infrared microspectroscopy of thin-sections of lateritic weathering profiles provides useful information on the types of kaolinite present in different horizons of the profile. The spectra obtained from large well-ordered kaolinite crystals look like those obtained by diffuse reflectance in that, compared with the KBr disk spectra of <2 µm powders, bands at 3668 and 3650 cm−1 are enhanced, and the strong absorption of KBr disks at 3695 cm−1 is replaced by a broad weaker band from 3700–3680 cm−1. In laterites, these large well-ordered kaolinites often exhibit a band at 3595 cm−1 indicative of significant Fe3+ substitution for Al3+ in the structure. The IR microspectra obtained from regions of small, more poorly-ordered kaolinites do not differ so markedly from that of KBr disks. All show enhanced absorption around 3650 cm−1 compared with well-ordered kaolinites, indicating that the disorder is due, at least in part, to domains of dickite-like and/or nacrite-like stacking in their structure. The 3595 cm−1 band is always weaker than that of the well-ordered kaolinite in the same profile. The IRMS data from well-characterized reference kaolinites show that the ratio Aν2/Aν3 is a pertinent IR order index for kaolinites. The larger this index, the larger is the area of the 3595 cm−1 band, and the larger and the more ordered is the kaolinite sample. It is suggested that the diversity of FTIR spectra observed reflects intergrowths of kaolinite-dickite polymorphs, or at least mixtures of high- and low-defect kaolinites which are frequently encountered in the lateritic geosphere rather than pure kaolinitic phases. The largest kaolinites having secondary crystallized in voids are the most ordered and the most ferruginous and have been considered as useful mineralogical tracers of the recent evolution of old lateritic terrains.