bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation Mechanism of Aluminum Hydroxide Polymorphs
Authors: Violante A. , Huang P. M. 
Published: August 2006

AbstractSubstantial studies have been carried out to investigate the mechanism of the formation of Al(OH)3 polymorphs. The influence of the nature of Al precipitation products on the formation of Al(OH)3 polymorphs still remains obscure. In this study, X-ray diffraction, infrared and thermal analyses, and electron microscopic observations of the Al precipitates formed at the initial pH 8.2 and at a citric acid/Al molar ratio of 0.01 and aged for 3 hr to 60 days revealed that the transformation from the initially formed noncrystalline materials to pseudoboehmite occurred through the formation of intermediate materials with various degrees of ordering and sizes of particles that apparently had a wide range of solubility. By increasing the pH of the suspension of precipitation products of Al to 10.0 after 3 hr and 3, 11, 31, and 60 days or longer, the crystalline precipitation products were hayerite, nordstrandite and bayerite, nordstrandite and pseudoboehmite, pseudoboehmite and gibbsite, and pseudoboehmite, respectively. This work shows evidence that, as the nature of the starting Al precipitates changed, the rate of their dissolution apparently changed, and various Al(OH)3 polymorphs consequently formed. Therefore, the data substantiate the hypothesis that the mechanism of the formation of an Al(OH)3 polymorph is determined by the rate of its nucleation, which is, in turn, influenced by the rate of dissolution of the noncrystalline or poorly ordered Al-oxides initially formed.
The Effect of Mechanical Treatment on the Crystal Structure and Thermal Behavior of Kaolinite
Authors: Kristóf Éva , Juhász A. Zoltán , Vassányi István 
Published: August 2006

AbstractThe destruction of the crystal structure of kaolinite caused by mechanical forces was investigated by X-ray diffraction, thermal analysis, infrared spectroscopy, and specific surface area determination. Attention was also directed to the change of thermal reactions of milled kaolinite. Grinding experiments for 5 min, 10 min, and 1, 2, 4, 6, and 10 h were carried out in an AGO I planetary mill. After 1 h of grinding, the crystalline order of kaolin is destroyed; but the amorphization continues in the course of prolonged grinding. Grinding for 1 h produces a favorable state for forming mullite-type crystals after heating even at 1000°C.
Kaolinite Particle Sizes in the <2 µm Range Using Laser Scattering
Authors: Mackinnon Ian D. R. , Uwins Philippa J. R. , Yago Anya , Page David 
Published: August 2006

AbstractThe Clay Minerals Society Source Clay kaolinites, Georgia KGa-1 and KGa-2, have been subjected to particle size determinations by 1) conventional sedimentation methods, 2) electron microscopy and image analysis, and 3) laser scattering using improved algorithms for the interaction of light with small particles. Particle shape, size distribution, and crystallinity vary considerably for each kaolinite. Replicate analyses of separated size fractions showed that in the <2 µm range, the sedimentation/centrifugation method of Tanner and Jackson (1947) is reproducible for different kaolinite types and that the calculated size ranges are in reasonable agreement with the size bins estimated from laser scattering. Particle sizes determined by laser scattering must be calculated using Mie theory when the dominant particle size is less than ∼5 µm. Based on this study of two well-known and structurally different kaolinites, laser scattering, with improved data reduction algorithms that include Mie theory, should be considered an internally consistent and rapid technique for clay particle sizing.
The Chemical Form of Vanadium (IV) in Kaolinite
Authors: Gehring A. U. , Fry I. V. , Luster J. , Sposito Garrison 
Published: August 2006

AbstractA combined application of electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) spectroscopies with thermal methods was used to determine the chemical form of V(IV) in a Georgia kaolinite (KGa-I). Precise values of the EPR spectroscopic g-values and hyperfine coupling constants were obtained for an untreated sample (g∥ = 1.940, A∦ = 18.71 mT; g⊥ = 1.966, A⊥ = 7.63 mT). Heating the sample to 1000°C in steps while monitoring phase changes with EPR and FTIR spectra led to the following structural interpretations: 1) Vanadium (IV) occurs almost entirely as an isomorphically substituted species in the octahedral sheet of KGa-1 kaolinite; 2) during the dehydroxylation of kaolinite at about 500°C and the subsequent formation of metakaolinite, V(IV)-substituted octahedral sites are readily converted into truncated octahedra exhibiting fourfold coordination; and 3) in these highly distorted four-coordinated sites, V(IV) is metastable, being completely oxidized at about 800°C.
A Chemical, XRD, and 27Al MAS NMR Investigation of Miocene Gulf Coast Shales with Application to Understanding Illite/Smectite Crystal-Chemistry
Authors: Schroeder Paul A. 
Published: August 2006

AbstractThis study assesses the distribution of Al and Fe in mixed-layer illite/smectites (I/S) in shales undergoing burial diagenetic changes, using evidence from 27Al NMR, XRD, and chemical analyses. Samples studied include a sequence of mixed-layer I/S (ranging from 40% to 68% illite layers) in shales from a well located in the Caillou Island Oil Field, Terrebonne Parish, Louisiana, as well as synthetic mica-montmorillonite (Syn-1), Silver Hill illite (IMt-1), K-benonite (ISMt-1), an Fe-bearing muscovite, phengitic muscovite, and a randomly interstratified mixed-layer I/S with 50% illite layers. Using a simplified model, where Fe3+ isomorphously substitutes randomly for [6]Al in the dioctahedral 2:1 structure, the 27Al NMR signal intensities are examined with regard to the paramagnetic deshielding effect of the Fe3+. The rapid decrease in paramagnetic deshielding with distance allows for a spherical “wipeout” model with a radius of 6 Å, over which there is complete effective paramagnetic line broadening (i.e., Al within the sphere is not “seen”). Using the average dimensions of a dioctahedral mica, the expected relative intensities of the octahedral and tetrahedral Al signal are determined as a function of Fe2O3 content.Observed 27Al signals, normalized per unit weight of Al2O3 and relative to the lowest Fe-bearing phase, show a clear trend of decreasing intensity with increasing Fe2O3 content. Normative fitting of oxide data to structural formulae reveals a similar trend of decreasing 27Al intensity with increasing fraction of dioctahedral site occupied by Fe3+. Agreement between the observed 27Al intensities of low Fe-bearing 2:1 phyllosilicates and 27Al intensities predicted using the wipeout model indicate regular ordering of Fe and Al within the low Fe-bearing phases. However, observed 27Al intensities for the I/S specimens fall into a region where the amount of Al seen is in excess for the given XFe, thus indicating segregation of Al and Fe domains.The second order quadrupole effect for the [6]Al site in the I/S fraction of shales decreases very slightly with increasing depth and percent of illite in the I/S, but not enough to effect site quantitation. Quantitative apportionment of elements into the I/S phase of the <0.2 µm fraction using NMR constraints shows directly a trend of increasing number of [4]Al sites and no change in the number of [6]Al sites with increasing degree of illitization for samples from the Gulf Coast diagenetic environment. Stoichiometry indicates an approximate 1:1 substitution of tetrahedral Al for Si over the 40–68% range of illite in I/S examined.
The Effect of Dissolved Ligands upon the Sorption of Cu(II) by Ca-Montmorillonite
Authors: Stadler Markus , Schindler Paul W. 
Published: August 2006

AbstractThe effect of three organic ligands on the adsorption of Cu on Ca-montmorillonite was studied. The results indicate that these effects include three different processes:1)Enhanced uptake of positively charged Cu-ligand complexes by ion-exchange.2)Formation of ternary surface complexes involving surface aluminol groups.3)Inhibited uptake due to competition between the surface ligands and the dissolved ligands for dissolved copper.Ethylenediamine promotes Cu uptake by ion-exchange at low pH but tends to suppress adsorption at aluminol groups by ligand competition at high pH. The same mechanisms are operative for β-alanine; however, the uptake of Cu(β-ala)+ by ion-exchange is not promoted by the attached ligand. The influence of malonate includes both ligand competition and formation of ternary complexes. A quantitative interpretation based on the surface complexation model using the least-square programs FITEQL (Westall, 1982) and GRFIT (Ludwig, 1992) is presented. The obtained equilibrium constants are listed in Tables 2b and 3.
Hydroxy-Chromium Smectite
Authors: Volzone C. , Cesio A. M. , Sánchez R. M. Torres , Pereira E. 
Published: August 2006

AbstractHydroxy-chromium solutions were prepared from chromium nitrate solutions by adding NaOH with OH/Cr = 2.The solutions were treated at 20°C and 60°C. The hydrolysis times were from 1 to 100 days. Polymeric species in hydrolyzed chromium solutions were followed by visible absorption spectra within the range 325–800 nm and by pH measurement. OH-Cr-smectite with high d(001) spacing (2.07 nm) was obtained when hydroxy-chromium solution was prepared at 60°C and with 1-day hydrolysis. When this sample was heated up to 350°C the basal spacing collapsed at 1.8 nm.The samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherms.
Kaolinite: NMF Intercalates
Authors: Uwins Philippa J. R. , Mackinnon Ian D. R. , Thompson John G. , Yago Anya J. E. 
Published: August 2006

AbstractBulk and size-fractionated kaolinites from seven localities in Australia as well as the Clay Minerals Society Source Clays Georgia KGa-1 and KGa-2 have been studied by X-ray diffraction (XRD), laser scattering, and electron microscopy in order to understand the variation of particle characteristics across a range of environments and to correlate specific particle characteristics with intercalation behavior. All kaolinites have been intercalated with N-methyl (NMF) after pretreatment with hydrazine hydrate, and the relative efficiency of intercalation has been determined using XRD. Intercalate yields of kaolinite: NMF are consistently low for bulk samples that have a high proportion of small-sized particles (i.e., <0.5 µm) and for biphased kaolinites with a high percentage (>60%) of low-defect phase. In general, particle size appears to be a more significant controlling factor than defect distribution in determining the relative yield of kaolinite: NMF intercalate.
Brønsted Acidification Observed during Hydrothermal Treatment of a Calcium Montmorillonite
Authors: Heimann Robert B. 
Published: August 2006

AbstractAn aluminous Ca-montmorillonite from southern Manitoba, Canada, has been shown to generate very low pH values in clay/groundwater slurries over a range of ionic strength of the groundwater (fresh and saline) and temperatures from 25°–90°C. Dialysis experiments as well as results of X-ray diffraction and FTIR vibration spectroscopy point to an acidification mechanism that involves hydrolysis of exchangeable Al3+ ions, thus releasing protons, and the subsequent intercalation of gibbsite-like hydroxy-Al complexes into the smectite lattice forming a non-expandable “Al”-montmorillonite.
Clay Mineralogy and Illite Crystallinity of the Atoka Formation, Arkoma Basin, and Frontal Ouachita Mountains
Authors: Spötl Christoph , Houseknecht David W. , Jaques Robert 
Published: August 2006

AbstractClay mineralogy (including illite crystallinity) was studied in Pennsylvanian synorogenic sediments (Atoka Formation) in the subsurface of the Arkoma Basin and the adjacent Ouachita thrust belt. Vitrinite reflectance values range from ≥0.8% at the surface up to as high as 4.7% Roat the base of the Atoka Formation. The mineralogy of the <2µm fraction of the mudrocks is fairly monotonous and composed of illite (<10% interstratified smectite), Fe-chlorite, kaolinite, quartz, and traces of feldspars. Kaolinite is common at shallow levels and “disappears” in most wells at a thermal maturity of 1.9–2.1% Ro, suggesting its possible use as an independent paleothermal indicator in this basin. Illite crystallinity (IC) values are fairly high (0.3–0.5° 2θ) and show little variation throughout the entire maturity range. In addition, no relation was observed between vitrinite reflectance and illite crystallinity, indicating that IC is not a useful paleothermal indicator in these rocks. Illite is almost exclusively of the 2M1polytype, suggesting a predominantly detrital origin. Incipient metamorphic and low-grade metamorphic mudrocks in the Ouachita thrust belt to the east of the Arkoma Basin are regarded as the source rocks for the clays of the Atoka Formation. Rapid transportation and deposition by turbidity currents probably played a key role in protecting these unweathered micas from pervasive alteration in the terrestrial environment.
Relationships of Serum Ferritin, Transferrin Saturation, and HFE Mutations and Self-Reported Diabetes in the Hemochromatosis and Iron Overload Screening (HEIRS) Study
Authors: Acton Ronald T. , Barton James C. , Passmore Leah V. , Adams Paul C. , Speechley Mark R. , Dawkins Fitzroy W. , Sholinsky Phyliss , Reboussin David M. , McLaren Gordon D. , Harris Emily L. , Bent Thomas C. , Vogt Thomas M. , Castro Oswaldo 
Published: August 2006

OBJECTIVE—We evaluated the associations of self-reported diabetes with serum ferritin concentration, transferrin saturation (TfSat), and HFE C282Y and H63D mutations in six racial/ethnic groups recruited at five field centers in the Hemochromatosis and Iron Overload Screening (HEIRS) study.
RESEARCH DESIGN AND METHODS—Analyses were conducted on 97,470 participants. Participants who reported a previous diagnosis of diabetes and/or hemochromatosis or iron overload were compared with participants who did not report a previous diagnosis.
RESULTS—The overall prevalence of diabetes was 13.8%; the highest prevalence was in Pacific Islanders (20.1%). Of all participants with diabetes, 2.0% reported that they also had hemochromatosis or iron overload. The mean serum ferritin concentration was significantly greater in women with diabetes in all racial/ethnic groups and in Native-American men with diabetes than in those without diabetes. The mean serum ferritin concentration was significantly lower in Asian men with diabetes than in those without diabetes. Mean TfSat was lower in participants with diabetes from all racial/ethnic groups except Native-American women than in those without diabetes. There was no significant association of diabetes with HFE genotype. The mean serum ferritin concentration was greater (P &lt; 0.0001) in women with diabetes than in those without diabetes for HFE genotypes except C282Y/C282Y and C282Y/H63D. Log serum ferritin concentration was significantly associated with diabetes in a logistic regression analysis after adjusting for age, sex, racial/ethnic group, HFE genotype, and field center.
CONCLUSIONS—Serum ferritin concentration is associated with diabetes, even at levels below those typically associated with hemochromatosis or iron overload.
Disparities in HbA1c Levels Between African-American and Non-Hispanic White Adults With Diabetes
Authors: Kirk Julienne K. , D’Agostino Ralph B. , Bell Ronny A. , Passmore Leah V. , Bonds Denise E. , Karter Andrew J. , Narayan K.M. Venkat 
Published: August 2006

OBJECTIVE—Among individuals with diabetes, a comparison of HbA1c (A1C) levels between African Americans and non-Hispanic whites was evaluated. Data sources included PubMed, Web of Science, the Cumulative Index to Nursing and Allied Health, the Cochrane Library, the Combined Health Information Database, and the Education Resources Information Center.
RESEARCH DESIGN AND METHODS—We executed a search for articles published between 1993 and 2005. Data on sample size, age, sex, A1C, geographical location, and study design were extracted. Cross-sectional data and baseline data from clinical trials and cohort studies for African Americans and non-Hispanic whites with diabetes were included. Diabetic subjects aged &lt;18 years and those with pre-diabetes or gestational diabetes were excluded. We conducted a meta-analysis to estimate the difference in the mean values of A1C for African Americans and non-Hispanic whites.
RESULTS—A total of 391 studies were reviewed, of which 78 contained A1C data. Eleven had data on A1C for African Americans and non-Hispanic whites and met selection criteria. A meta-analysis revealed the standard effect to be 0.31 (95% CI 0.39–0.25). This standard effect correlates to an A1C difference between groups of ∼0.65%, indicating a higher A1C across studies for African Americans. Grouping studies by study type (cross-sectional or cohort), method of data collection for A1C (chart review or blood draw), and insurance status (managed care or nonmanaged care) showed similar results.
CONCLUSIONS—The higher A1C observed in this meta-analysis among African Americans compared with non-Hispanic whites may contribute to disparity in diabetes morbidity and mortality in this population.
Glomerular Filtration Rate, Cardiorenal End Points, and All-Cause Mortality in Type 2 Diabetic Patients
Authors: So Wing Yee , Kong Alice P.S. , Ma Ronald C.W. , Ozaki Risa , Szeto Cheuk Chun , Chan Norman N. , Ng Vanessa , Ho Chung Shun , Lam Christopher W.K. , Chow Chun Chung , Cockram Clive S. , Chan Juliana C.N. , Tong Peter C.Y. 
Published: August 2006

OBJECTIVE—Chronic kidney disease (CKD) predicts cardiovascular disease (CVD) in the general population. We investigated the effects of stages of renal function using the estimated glomerular filtration rate (eGFR) on all-cause mortality and cardiovascular end points in a prospective cohort of Chinese type 2 diabetic patients.RESEARCH DESIGN AND METHODS—Between 1995 and 2000, 4,421 patients without macrovascular disease or end-stage renal disease were recruited. Renal function was assessed by eGFR, as calculated by the abbreviated Modification of Diet in Renal Disease Study Group formula. Clinical end points included all-cause mortality, cardiovascular end point (cardiovascular death, new admissions due to angina, myocardial infarction, stroke, revascularization, or heart failure), and renal end point (reduction in eGFR by &gt;50%, progression of eGFR to stage 5, or dialysis or renal death).RESULTS—After a median follow-up period of 39.4 months (interquartile range 20.3–55), all-cause mortality rate increased from 1.2% (95% CI 0.8–1.7) to 18.3% (9.1–27.5) (P for trend &lt;0.001) as renal function deteriorated from stage 1 (eGFR ≥90 ml/min per 1.73 m2) to stage 4 (15–29 ml/min per 1.73 m2). The respective rate of new cardiovascular end points also increased from 2.6% (2.0–3.3) to 25.3% (15.0–35.7) (P for trend &lt;0.001). After adjustment for covariates (age, sex, albuminuria, use of renin-angiotensin-aldosterone system [RAAS] inhibitors, lipids, blood pressure, and glycemic control), hazard ratios across different stages of eGFR (≥90, 60–89, 30–59, and 15–29 ml/min per 1.73 m2) for all-cause mortality were 1.00, 1.27, 2.34, and 9.82 (P for trend &lt;0.001), for cardiovascular end points were 1.00, 1.04, 1.05, and 3.23 (P for trend &lt;0.001), and for renal end points were 1.00, 1.36, 3.34, and 27.3 (P for trend &lt;0.001), respectively.CONCLUSIONS—Chinese type 2 diabetic patients with reduced eGFR were at high risk of developing cardiovascular end points and all-cause mortality, independent of albuminuria and metabolic control.
Ethnic Differences in Perinatal Outcome of Gestational Diabetes Mellitus
Authors: Silva Jana Kaida , Kaholokula Joseph Keawe‘aimoku , Ratner Robert , Mau Marjorie 
Published: August 2006

OBJECTIVE— Despite the high rates of gestational diabetes mellitus (GDM) among certain Pacific Islander and Asian ethnic groups in the U.S., little is known about the risk for adverse perinatal outcomes in these populations. We sought to examine ethnic differences in perinatal outcome among Asian and Pacific-Islander women with GDM.
RESEARCH DESIGN AND METHODS— A retrospective review of all women referred to the largest outpatient GDM program in the state of Hawai‘i from 1995 to 2005 was conducted. Patients of Native-Hawaiian/Pacific-Islander, Japanese, Chinese, Filipino, and Caucasian ethnicity were included (n = 2,155). Treatment of all patients consisted of an outpatient education class, dietary management, self-monitoring of blood glucose, and insulin instruction (if indicated). Demographics, maternal and neonatal characteristics, and delivery information were evaluated.
RESULTS— Neonates born to Native-Hawaiian/Pacific-Islander mothers and Filipino mothers had 4 and 2 times the prevalence of macrosomia, respectively, compared with neonates born to Japanese, Chinese, and Caucasian mothers. These differences persisted after adjustment for other statistically significant maternal and fetal characteristics. Ethnic differences were not observed for other neonatal or maternal complications associated with GDM, with the exception of neonatal hypoglycemia and hyperbilirubinemia.
CONCLUSIONS— Significant ethnic differences in perinatal outcomes exist across Asian and Pacific-Islander women with GDM. This finding emphasizes the need to better understand ethnic-specific factors in GDM management and the importance of developing ethnic-tailored GDM interventions to address these disparities.
New-Onset Diabetes and Risk of All-Cause and Cardiovascular Mortality
Authors: Smith Nicholas L. , Barzilay Joshua I. , Kronmal Richard , Lumley Thomas , Enquobahrie Daniel , Psaty Bruce M. 
Published: August 2006

OBJECTIVE—Cardiovascular risk associated with new-onset diabetes is not well characterized. We hypothesized that risk of all-cause and cardiovascular mortality would be similar among participants with and without new-onset diabetes in the first years of follow-up and rise over time for new-onset diabetes.
RESEARCH DESIGN AND METHODS—The Cardiovascular Health Study (CHS) is a longitudinal study of cardiovascular risk factors in adults aged ≥65 years. We used CHS participants to define a cohort (n = 282) with new-onset diabetes during 11 years of follow-up. New-onset diabetes was defined by initiation of antidiabetes medication or by fasting plasma glucose &gt;125 mg/dl among CHS participants without diabetes at study entry. Three CHS participants without diabetes were matched for age, sex, and race to each participant with new-onset diabetes at the time of diabetes identification (n = 837). Survival analysis provided adjusted hazard ratios (HRs) for all-cause and cardiovascular mortality.
RESULTS—During a median of 5.9 years of follow-up, there were 352 deaths, of which 41% were cardiovascular. In adjusted analyses, new-onset diabetes was associated with an HR of 1.9 (95% CI 1.4–2.5) for all-cause and 2.2 (1.4–3.4) for cardiovascular mortality compared with no diabetes. Mortality risks were elevated within 2 years of onset, especially cardiovascular risk (4.3 [95% CI 1.7–10.8]), and did not increase over time.
CONCLUSIONS—Our findings indicate that there may be a mortality differential soon after diabetes onset in older adults and suggest that long-term macrovascular damage from atherosclerosis may not be primarily responsible for increased risk.