bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of Clay Minerals During Low Temperature Experimental Alteration of Obsidian
Authors: Kawano Motoharu , Tomita Katsutoshi , Kamino Yoshitaka 
Published: August 2006

AbstractExperimental alteration of obsidian in distilled-deionized water at 150°, 175°, 200°, and 225°C was studied. The alteration products were examined by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX) to evaluate the formation process of clay minerals. The surface composition of obsidian before and after alteration was examined by X-ray photoelectron spectroscopy (XPS), and concentrations of released elements in solution were measured to elucidate alteration and dissolution processes. TEM clearly showed that allophane appeared as the first reaction product in each experiment. With increasing reaction length, noncrystalline straight fibrous material was formed in the aggregates of allophane particles as a metastable transitional phase, and tended to form curled or wavy bundles of fibers with longer reaction. The non-crystalline fibers were transformed into highly curled smectite exhibiting small circular forms less than 1.0 µm in diameter as reaction progressed. EDX confirmed that the smectite consisted mainly of Si, Al, and small amounts of Ca, K, and Fe. XPS revealed the formation of a dealkalized leached layer on the surface of obsidian during the reaction. The concentration of released elements suggested that nonstoichiometric dissolution proceeded during the reaction.
Some Colloidal Properties of Beidellite: Comparison with Low and High Charge Montmorillonites
Authors: Hetzel Frederic , Doner Harvey E. 
Published: August 2006

AbstractRecent evidence of the occurrence of beidellite in many soils around the world necessitates a better understanding of the role of charge location on the colloidal behavior of this smectite as compared to the more frequently studied montmorillonites. Clay suspension stability and sorption of an organic polymer, two properties sensitive to surface charge characteristics, were selected to examine the differences in colloidal behaviors of these smectites. The Otay montmorillonite was shown to have a higher charge than either the beidellite or the SWy-1 montmorillonite. Even though structural formulae resulted in a higher permanent charge for the beidellite as compared to the SWy-1, effective charge of these two smectites is the same. The pH dependency of the critical coagulation concentration of the smectites could not be explained based only on edge charge considerations, and it is proposed that tetrahedral charge location enhances the pH effect on the CCC. Decreased poly(vinyl) alcohol sorption with either increasing surface charge or tetrahedral charge location was observed. Both parameters affect the ease of replacement of water molecules by PVA on the surface of smectites.
Properties and Characterization of Al2O3 and SiO2-TiO2 Pillared Saponite
Authors: Malla P. B. , Komarneni S. 
Published: August 2006

AbstractA saponite pillared with a single (Al2O3) or a mixed (SiO2-TiO2) oxide exhibited basal spacings of 16–19 and 30–40Å, respectively. The pillared structures were found to be stable up to 700°C. Water, nitrogen, and high resolution argon adsorption were used to study the effect of thermal treatments on surface chemistry, pore structure, and surface area of these pillared clays. The pillared saponites exhibited a hydrophobic behavior at temperatures > 500°C, whereas such behavior was observed at ≥300°C for montmorillonite. Most of the micropores in the Al2O3 pillared clays were < 10 Å, whereas the SiO2-TiO2 pillared clays showed a broad distribution of pores in both micropore and mesopore regions. The SiO2-TiO2 pillared samples possessed higher surface area compared with Al2O3 pillared clays. The percent decrease in surface area was smaller for pillared saponites compared with pillared montmorillonites when calcined from 300° to 700°C, indicating a higher thermal stability of the former. The pillared clays were also characterized by solid state 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS/NMR) spectroscopy. There was no direct evidence of cross-linking (covalent bonding between the clay layer and pillar) in montmorillonite irrespective of the types of pillars. In saponite, however, a significant structural modification took place. 27Al spectra of Al2O3 pillared saponite heated at ≥300°C appear to indicate an increase in AlVI as a result, at least in part, of initiation of hydrolytic splitting of Si-O-Al bonds. The actual release of Al from the tetrahedral sheet probably occurred at a temperature > 500°C and completed around 700°C with the formation of Si-O-Si linkages. The decreased intensity of peak due to Si(1Al) in 29Si spectra of the sample heated at 700°C corroborates the 27Al MAS/NMR results. Additionally, the 29Si spectra indicated a cross-linking between SiO4 (clay sheet) with Al2O3 pillars, which could be achieved by inverting some silica tetrahedra into the interlayer. 27Al and 29Si spectra of SiO2TiO2 pillared saponite also showed the trend similar to that exhibited by Al2O3 pillared saponite, indicating that the crystal chemistry of the host may be more important than the nature of pillars in the structural modification and cross-linking behavior of thermally treated pillared clays.
Characterization of Hydroxy-Interlayered Vermiculite and Illite/Smectite Interstratified Minerals from the Weathering of Chlorite in a Cryorthod
Authors: Righi Dominique , Petit Sabine , Bouchet Alain 
Published: August 2006

AbstractX-ray diffraction, FTIR, and chemical analyses were performed on clay fractions (1–2 µm, <0.1 µm), separated by means of size fractionations and high-gradient magnetic separation techniques, from a Cryorthod developed in a chlorite-mica schist saprolite. Weathering of large phyllosilicates pre-existing in the saprolite involves physical fragmentation and mineralogical transformations. Chloritic minerals in the coarse fractions were the most affected by physical breakdown, while micas were generally preserved. As a consequence, a concentration of mica layers occurred in the coarse clay fraction, while chloritic residues accumulated in the fine clays. These residues exhibited the typical XRD pattern of hydroxy-interlayered intergrade minerals, but the interlayered contaminants were found to be mainly hydroxy-Mg cations. Further mineralogical transformations of the intergrade minerals involved the progressive removal of the hydroxide interlayered sheet and dissolution of chloritic layers. Illite/smectite mixed-layers were formed in the surface horizon of the soil profile. These processes were associated with a strong decrease in Fe and Mg contents in the clay fractions.
The Al Pillaring of Clays. Part I. Pillaring with Dilute and Concentrated Al Solutions
Authors: Schoonheydt Robert A. , van den Eynde J. , Tubbax H. , Leeman H. , Stuyckens M. , Lenotte I. , Stone W. E. E. 
Published: August 2006

AbstractSaponite, hectorite, and laponite have been pillared with cationic Al clusters, and special attention has been given to the solution chemistry or Al. Pillared saponite is obtained after exchange with refluxed Al solutions; while for hectorite, Al solutions treated with ammonium acetate give a pillared product with 1.8–1.9 nm spacing and thermal stability up to 873 K. In both types of solutions, the Keggin ion Al cluster is a minority species or totally absent. The typical 1.8–1.9 nm spacing is only obtained after washing. The quality of the pillared material can be judged from its thermal stability, its surface area, and the width of the d001 line before and after pillaring. The width should not exceed 0.3 nm before calcination and 0.5 nm after calcination. The latter criterion reflects the importance of the crystallinity of the parent clay for successful pillaring. Pillaring in concentrated conditions occurs by a combination of ion exchange and precipitation of Al and gives materials that exhibit poor thermal stability.
Weathering of Spodumene to Smectite in a Lateritic Environment
Authors: Singh Balbir , Gilkes R. J. 
Published: August 2006

AbstractWeathering of spodumene in a lateritized pegmatite in Western Australia was studied by investigating in situ samples by electron-beam techniques. The spodumene had mostly altered to smectite. However, some non-crystalline material adjacent to smectite and intermixed with smectite was also observed. No crystallographic orientation between spodumene and smectite was observed by high resolution techniques. The spodumene dissolved to produce etch pits similar to those observed on hornblende grains. The etch pits were almost completely filled with smectite. Most of the Li in the spodumene was lost during its weathering to smectite.
Synthesis of Smectite from Volcanic Glass at Low Temperature
Authors: Tomita Katsutoshi , Yamane Hisanori , Kawano Motoharu 
Published: August 2006

AbstractSmectite and zeolites were formed from a volcanic glass as the products of reaction with NaOH solution at 90°C and 100°C under atmospheric pressure. Formation conditions of smectite and various zeolites were determined by the ratio of the amounts of volcanic glass (g) to NaOH (g) in the solution. Smectite was formed under the condition that the values of weight of volcanic glass (g)/(NaOH(g)/40) are between 0.5 and 6. Fe was an important constituent of the octahedral layer of smectite.
Rietveld Refinement of the Kaolinite Structure at 1.5 K
Authors: Bish David L. 
Published: August 2006

AbstractThe crystal structure of Keokuk kaolinite, including all H atoms, was refined in space group C1 using low-temperature (1.5 K) neutron powder diffraction data (λ = 1.9102 Å) and Rietveld refinement/difference-Fourier methods to Rwp = 1.78%, reduced χ2 = 3.32. Unit-cell parameters are: a = 5.1535(3) Å, b = 8.9419(5) Å, c = 7.3906(4) Å, α = 91.926(2)°, β = 105.046(2)°, γ = 89.797(2)°, and V = 328.70(5) Å3. Unit-cell parameters show that most of the thermal contraction occurred along the [001] direction, apparently due to a decrease in the interlayer distance. The non-H structure is very similar to published C1 structures, considering the low temperature of data collection, but the H atom positions are distinct. The inner OH group is essentially in the plane of the layers, and the inner-surface OH groups make angles of 60°–73° with the (001) plane. Difference-Fourier maps show minor anisotropy of the inner-OH group in the [001] direction, but the inner-surface OH groups appear to have their largest vibrational (or positional disorder) component parallel to the layers. Although no data indicate a split position of any of the H sites in kaolinite, there is support for limited random positional disorder of the H atoms. However, these data provided no support for a space group symmetry lower than C1.
A Prospective Analysis of the Prognostic Value of Biomarkers (FibroTest) in Patients with Chronic Hepatitis C
Authors: Ngo Yen , Munteanu Mona , Messous Djamila , Charlotte Frederic , Imbert-Bismut Françoise , Thabut Dominique , Lebray Pascal , Thibault Vincent , Benhamou Yves , Moussalli Joseph , Ratziu Vlad , Poynard Thierry 
Published: August 2006

AbstractBackground: FibroTest, a noninvasive method of measuring biomarkers of liver fibrosis, is an alternative to liver biopsy for determining the severity of chronic hepatitis C virus (HCV) infection. We compared the 5-year prognostic value of the FibroTest with biopsy staging for predicting cirrhosis decompensation and survival in patients with chronic HCV infection.Methods: Fibrosis stage was assessed on the same day by FibroTest and biopsy in a prospective cohort of 537 patients. Disease classification at baseline was 157 patients with severe fibrosis (FibroTest &gt;0.58), 137 with moderate fibrosis (FibroTest 0.32–0.58), and 243 with no or minimal fibrosis (FibroTest &lt;0.32).Results: In 64 untreated patients with severe fibrosis, survival without HCV complications was 73% [95% confidence interval (CI), 59%–086%; 13 complications], and survival without HCV-related death was 85% (95% CI, 73%–96%; 7 HCV deaths). Survival rates were higher in patients with moderate fibrosis, [99% (95% CI, 97%–100%; 1 complication; P &lt;0.001) and 100% (no HCV death; P &lt;0.001) for patients with and without HCV-related complications, respectively], and in patients with minimal fibrosis [100% (no complication; P &lt;0.001 vs severe) and 100% (no HCV death; P &lt;0.001 vs severe), respectively]. FibroTest was a better predictor than biopsy staging for HCV complications, with area under the ROC curves (AUROC) = 0.96 (95% CI, 0.93%–0.97%) vs 0.91 (95% CI, 0.85%–0.94%; P = 0.01), respectively; it was also a better predictor for HCV deaths: AUROC = 0.96 (95% CI, 0.93%–0.98%) vs 0.87 (95% CI, 0.70%–0.94%; P = 0.046), respectively. The prognostic value of FibroTest was still significant (P &lt;0.001) in multivariate analyses after taking into account histology, treatment, alcohol consumption, and HIV coinfection.Conclusion: The FibroTest measurement of HCV biomarkers has a 5-year prognostic value similar to that of liver biopsy.
Gestational Diabetes Mellitus Increases the Risk of Cardiovascular Disease in Women With a Family History of Type 2 Diabetes
Authors: Carr Darcy B. , Utzschneider Kristina M. , Hull Rebecca L. , Tong Jenny , Wallace Tara M. , Kodama Keiichi , Shofer Jane B. , Heckbert Susan R. , Boyko Edward J. , Fujimoto Wilfred Y. , Kahn Steven E. ,   the American Diabetes Association GENNID Study Group
Published: August 2006

OBJECTIVE— We sought to determine whether a history of gestational diabetes mellitus (GDM) further increases the risk of cardiovascular disease (CVD) in parous women with first-degree relatives with type 2 diabetes.
RESEARCH DESIGN AND METHODS— Women with (n = 332) and without (n = 663) a history of GDM were compared regarding 1) the revised National Cholesterol Education Program Adult Treatment Panel III metabolic syndrome criteria, 2) the prevalence of type 2 diabetes, and 3) self-reported CVD.
RESULTS— Women with prior GDM were younger (48.6 ± 0.7 vs. 52.4 ± 0.6 years [means ± SE];P &lt; 0.001) and less likely to be postmenopausal (48.3 vs. 57.9%; P &lt; 0.005). Although both groups were obese (BMI 34.4 ± 1.2 vs. 33.7 ± 0.6 kg/m2), women with prior GDM were more likely to have metabolic syndrome (86.6 vs. 73.5%; P &lt; 0.001) and type 2 diabetes (93.4 vs. 63.3%; P &lt; 0.001). Moreover, they had a higher prevalence of CVD (15.5 vs. 12.4%; adjusted odds ratio 1.85 [95% CI 1.21–2.82];P = 0.005) that occurred at a younger age (45.5 ± 2.2 vs. 52.5 ± 1.9 years;P = 0.02) and was independent of metabolic syndrome (1.74 [1.10–2.76]; P = 0.02) and type 2 diabetes (1.56 [1.002–2.43];P &lt; 0.05).
CONCLUSIONS— Among women with a family history of type 2 diabetes, those with prior GDM were even more likely to not only have CVD risk factors, including metabolic syndrome and type 2 diabetes, but also to have experienced CVD events, which occurred at a younger age. Thus, women with both a family history of type 2 diabetes and personal history of GDM may be especially suitable for early interventions aimed at preventing or reducing their risk of CVD and diabetes.
Treating Postprandial Hyperglycemia Does Not Appear to Delay Progression of Early Type 2 Diabetes
Authors: Kirkman M. Sue , Shankar R. Ravi , Shankar Sudha , Shen Changyu , Brizendine Edward , Baron Alain , McGill Janet 
Published: August 2006

OBJECTIVE—Postprandial hyperglycemia characterizes early type 2 diabetes. We investigated whether ameliorating postprandial hyperglycemia with acarbose would prevent or delay progression of diabetes, defined as progression to frank fasting hyperglycemia, in subjects with early diabetes (fasting plasma glucose [FPG] &lt;140 mg/dl and 2-h plasma glucose ≥200 mg/dl).
RESEARCH DESIGN AND METHODS—Two hundred nineteen subjects with early diabetes were randomly assigned to 100 mg acarbose t.i.d. or identical placebo and followed for 5 years or until they reached the primary outcome (two consecutive quarterly FPG measurements of ≥140 mg/dl). Secondary outcomes included measures of glycemia (meal tolerance tests, HbA1c, annual oral glucose tolerance tests [OGTTs]), measures of insulin resistance (homeostasis model assessment [HOMA] of insulin resistance and insulin sensitivity index from hyperglycemic clamps), and secondary measures of β-cell function (HOMA-β, early- and late-phase insulin secretion, and proinsulin-to-insulin ratio).
RESULTS—Acarbose significantly reduced postprandial hyperglycemia. However, there was no difference in the cumulative rate of frank fasting hyperglycemia (29% with acarbose and 34% with placebo; P = 0.65 for survival analysis). There were no significant differences between groups in OGTT values, measures of insulin resistance, or secondary measures of β-cell function. In a post hoc analysis of subjects with initial FPG &lt;126 mg/dl, acarbose reduced the rate of development of FPG ≥126 mg/dl (27 vs. 50%; P = 0.04).
CONCLUSIONS—Ameliorating postprandial hyperglycemia did not appear to delay progression of early type 2 diabetes. Factors other than postprandial hyperglycemia may be greater determinants of progression of diabetes. Alternatively, once FPG exceeds 126 mg/dl, β-cell failure may no longer be remediable.
Diabetes Does Not Influence Treatment Decisions Regarding Revascularization in Patients With Stable Coronary Artery Disease
Authors: Breeman Arno , Bertrand Michel E. , Ottervanger Jan Paul , Hoeks Sanne , Lenzen Mattie , Sechtem Udo , Legrand Victor , de Boer Menko-Jan , Wijns William , Boersma Eric ,   on behalf of the investigators of the Euro Heart Survey on Coronary Revascularization
Published: August 2006

OBJECTIVE—To evaluate whether in stable angina preference for coronary revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG) is influenced by diabetes status and whether this has prognostic implications.
RESEARCH DESIGN AND METHODS—A total of 2,928 consecutive patients with stable angina who were enrolled in the prospective Euro Heart Survey on Coronary Revascularization were studied. Multivariable analyses were applied to evaluate the relation between diabetes, treatment decision, and 1-year outcome.
RESULTS—Diabetes was documented in 587 patients (20%) who had more extensive coronary disease. Revascularization was intended in 74% of patients with diabetes and in 77% of those without diabetes. In patients selected for revascularization, CABG was intended in 35% of diabetic and in 33% of nondiabetic patients. Multivariable analyses did not change these findings, but in some subgroups diabetes influenced treatment decisions. For example, diabetic subjects with mild heart failure had more often intended revascularization (91%) than those without diabetes (67%, P &lt; 0.001). Treatment decisions in patients with more extensive (left main, multivessel, or proximal left anterior descending artery) disease were not influenced by diabetes status. Diabetes was not associated with an increased incidence of all-cause death, nonfatal cerebrovascular accident, or nonfatal myocardial infarction at 1 year, regardless of preferred treatment. The incidence of the combined end points was 7.3% in diabetic and 6.8% in nondiabetic patients (adjusted hazard ratio 1.0 [95% CI 0.7–1.4]).
CONCLUSIONS—In stable angina, treatment decisions regarding revascularization or the choice for CABG or PCI were not influenced by the presence of diabetes. Diabetes was not associated with a poor prognosis.
Natural History and Risk Factors for Microalbuminuria in Adolescents With Type 1 Diabetes
Authors: Stone Monique L. , Craig Maria E. , Chan Albert K. , Lee Jenny W. , Verge Charles F. , Donaghue Kim C. 
Published: August 2006

OBJECTIVE— To describe the natural history and risk factors for persistent microalbuminuria in children and adolescents with type 1 diabetes followed for up to 15 years.
RESEARCH DESIGN AND METHODS— This study contained a longitudinal cohort of 972 patients; analysis of baseline risk factors was performed using logistic regression and predictors over time using survival analysis. Albumin excretion rate was measured on three consecutive timed overnight urine collections on at least two occasions. Normoalbuminuria was defined as a median albumin excretion rate &lt;7.5 μg/min, borderline microalbuminuria as 7.5–20 μg/min, and microalbuminuria as 20–200 μg/min. Microalbuminuria was further classified as persistent if its duration was &gt;12 months. Median age was 12.7 years (interquartile range 11.5–14.4) and diabetes duration 6.5 years (4.1–9.3) at first assessment, and median follow-up was 6.2 years (range 1–15.3).
RESULTS— The incidence of persistent microalbuminuria was 4.6 (95% CI 3.3–6.1) per 1,000 patient-years. Predictors of persistent microalbuminuria from the first assessment using multiple logistic regression were high cholesterol (odds ratio 2.2 [95% CI 1.2–4.0]) and borderline microalbuminuria (2.5 [1.2–5.2]). Predictors using Cox regression were HbA1c (hazard ratio 1.4 [95% CI 1.1–1.7]), age at diagnosis (1.2 [1.1–1.3]), obesity (3.6 [0.8–15.5]), and insulin dose (2.7 [1.0–7.5]).
CONCLUSIONS— Children and adolescents with type 1 diabetes who have borderline microalbuminuria are more than twice as likely to develop persistent microalbuminuria. In addition to poor glycemic control, clinical markers of insulin resistance were associated with an increased risk of microalbuminuria.
Synthesis, structure and biological activity studies of 2‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1‐aryl)‐3‐ferrocenyl prop‐2‐en‐1‐one derivatives
Authors: Liu Jianbing , Liu Tao , Dai Hong , Jin Zhong , Fang Jianxin 
Published: August 2006

AbstractFifteen new ferrocene derivatives containing 1H‐1,2,4‐triazole moiety were synthesized in various yields by the condensation of ferrocenecarboxaldehyde with 1‐aryl‐3‐(1H‐1,2,4‐triazo‐1‐yl)‐propen‐1‐ones in toluene. Their structures have been confirmed by 1H NMR, IR, MS and elemental analysis. In addition, the crystal structure of 4l was determined. The antifungal and plant growth regulatory activities of the title compounds are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Interpenetrating Coordination Polymers from CuI or AgI and Flexible Ligands: 2D Polyrotaxanes and Interpenetrating Grids
Authors: Kasai Kayoko , Sato Mariko 
Published: August 2006

AbstractThe reaction of [Cu(CH3CN)4]NO3 or AgNO3 with flexible ligands 1,4‐bis(4‐pyridylmethyl)‐2,3,5,6‐tetrafluorobenzene (bpf) or 4,4′‐bis(4‐pyridylmethyl)‐2,2′,3,3′,5,5′,6,6′‐octafluorobiphenyl (bpfb) afforded two types of interpenetrating coordination polymers. The structures of [Cu2(bpf)3(NO3)2]n and [Ag2(bpf)3‐(NO3)2]n are 2D polyrotaxane networks in which 1D polymeric chains are aligned in a grid. The structure of {[Cu(bpfb)2]NO3}n is a 2D grid polymer with two‐fold parallel interpenetration.
Linking Chiral Clusters with Molybdate Building Blocks: From Homochiral Helical Supramolecular Arrays to Coordination Helices
Authors: Long De‐Liang , Kögerler Paul , Farrugia Louis J. , Cronin Leroy 
Published: August 2006

AbstractThe synthesis of four new oxo‐centered Fe clusters (1 a–c, 2) of the form [FeIII3(μ3‐O)(CH2=CHCOO)6] with acrylate as the bridging ligand gives rise to potentially intrinsically chiral oxo‐centered {M3} trimers that show a tendency to spontaneously resolve upon crystallization. For instance, 1 a, [FeIII3(μ3‐O)(CH2=CHCOO)6‐(H2O)3]+, crystallizes in the chiral space group P31 as a chloride salt. Crystallization of 1 b, [Fe3(μ3‐O)(C2H3CO2)6(H2O)3]NO3⋅4.5H2O, from aqueous solution followed by recrystallization from acetonitrile also gives rise to spontaneous resolution to yield the homochiral salt [Fe3(μ3‐O)(C2H3CO2)6‐(H2O)3]NO3⋅CH3CN of 1 c (space group P212121). Furthermore, the reaction of 1 a with hexamolybdate in acetonitrile gives the helical coordination polymer {[(Fe3(μ3‐O)L6(H2O))(MoO4)‐(Fe3(μ3‐O)L6(H2O)2)]⋅2CH3CN⋅H2O}∞ 2 (L: H2CCHCOO), which crystallizes in the space group P21. The nature of the ligand geometry allows the formation of atropisomers in both the discrete (1 a–c) and linked {Fe3} clusters (2), which is described along with a magnetic analysis of 1 a and 2.