bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission Electron Microscopy Evidence for Experimental Illitization of Smectite in K-Enriched Seawater Solution at 50°C and Basic pH
Authors: Drief A. , Martinez-Ruiz F. , Nieto F. , Velilla Sanchez N. 
Published: February 2003

AbstractExperimental illitization of smectite was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Experiments were performed on the <2 µm fraction consisting entirely of smectite separated from a soil formed on subvolcanic rock located in the External Zone of the Betic Cordilleras (southern Spain). Amounts of 0.25 g were added to different solutions: seawater, and three K-enriched seawater solutions prepared by adding KOH to seawater whose final [K] values were 0.1, 0.5 and 1 M, respectively. The experiments were performed at 50°C over a period of 30 days. The XRD patterns showed no mineralogical changes in residues from seawater or from the 0.1 M [K] solution. With increasing pH and K molarity, the smectite peak, initially at 1.4 nm, became broader. This change in the smectite peak was more significant in the residue from the 1 M [K] solution. The appearance of a small shoulder at 1.0 nm in the residue from a 0.5 M [K] solution showed the beginning of illite formation. However, its appearance was clearer in XRD patterns of the residue corresponding to the 1 M [K] solution. The XRD data from air-dried, glycolated, and heated samples from the 1 M [K] solution indicated the presence of smectite, disordered interstratified illite-smectite (I-S) and illite.The TEM/AEM studies were performed on the residue corresponding to the 1 M [K] experiment. The HRTEM images revealed that smectite and illite occurred as separated packets with a ferroan lizardite, as a by-product of the smectite-to-illite reaction, interstratified and intergrown with illite. Smectite occurs both as ‘rims’ on the illite packet and in its core. The presence of smectite in the core of illite packet indicates that the lateral transition from smectite to illite was incomplete, taking place by direct replacement of smectite layers as a whole through a dissolution-precipitation mechanism. The experimental study shows that smectite may transform in a wide range of geological and artificial environments involving high-pH K-rich solutions.
Chemical Disaggregation of Kaolinitic Claystones (Tonsteins and Flint Clays)
Authors: Triplehorn Don M. , Bohor Bruce F. , Betterton William J. 
Published: February 2003

AbstractThe coarse, non-clay fraction of many flint-like kaolinitic claystones often contains mineral grains diagnostic of the claystone's origin and, in the case of tonsteins (altered volcanic ashes), may also provide minerals suitable for radiometric dating. Separation of the non-clay mineral fraction is often difficult because flint clays and flint-like clays resist slaking in water and thus are difficult to disaggregate. Chemical disaggregation of resistant kaolinitic claystones may be achieved by immersion in either hydrazine monohydrate or DMSO for periods ranging from one day to several weeks. Generally, hydrazine monohydrate works more quickly and efficiently than DMSO to disaggregate most kaolinitic claystones and flint clays.
Formation of Sepiolite-Palygorskite and Related Minerals from Solution
Authors: Birsoy Rezan 
Published: February 2003

AbstractMost of the world's sepiolite-palyg orskite precipitates in lacustrine and perimarine environments. Although these minerals can transform from precursor minerals, the most common formation mechanism involves crystallization from solution. In this study, equilibrium activity diagrams are calculated for sepiolite-palygorskite in the seven component system MgO-CaO-Al2O3-SiO2-H2O-CO2-HCl, employing available thermodynamic data for related minerals, aqueous species and water. Stability fields are illustrated graphically on plots of log [aMg2+/(aH+)2]vs. log [aH4SiO4o], using the activities for log [aAl3+/(aH+)3] defined by an arbitrarily chosen value and the approximate saturation limits of pyrophyllite + amorphous silica, kaolinite + amorphous silica, kaolinite + pyrophyllite, pyrophyllite + quartz and gibbsite. The formation of sepiolite-palygorskite from solution is more favored in the presence of amorphous silica than quartz. Lower aqueous aluminum activities favor the non-aluminum phases sepiolite and kerolite relative to the aluminum-containing phases palygorskite and saponite. The stability ranges of worldwide associations of magnesite and dolomite with sepiolite and palygorskite are also illustrated as a function of aluminum activity.
Transmission and Analytical Electron Microscopy Evidence for High Mg Contents of 1M Illite: Absence of 1M Polytypism in Normal Prograde Diagenetic Sequences of Pelitic Rocks
Authors: Peacor Donald R. , Bauluz Blanca , Dong Hailiang , Tillick David , Yan Yonghong 
Published: February 2003

AbstractThe normal prograde diagenetic and low-grade metamorphic sequence of dioctahedral clay minerals including illite-rich I-S and illite, as observed by TEM, proceeds from a partially disordered 1Md stacking sequence to 2M1; i.e. 1M does not normally occur as an intermediate polytype. Examples of 1M illite stacking sequences have been studied, however, from the Golden Cross gold deposit, New Zealand, the Broadlands-Ohaaki geothermal system, New Zealand, the Potsdam Sandstone, New York, and the Silverton Caldera, Colorado. Specific clay-mineral packets identified by TEM techniques as 1M illite were found to have anomalously high Mg contents. The Broadlands illite provides the most definitive data, as separate packets of 1M and 2M1 illite coexist. Average compositions for 1M and 2M1 illite are (K1.66Ca0.04)Σ1.70(Al3.32Fe0.31Mg0.57Mn0.06)Σ4.26(Si6.43Al1.57)Σ8O20(OH)4 and (K1.57Na0.31Ca0.03)Σ1.91(Al3.58Fe0.05Mg0.29Mn0.01)Σ3.93(Si6.70Al1.30)Σ8O20(OH)4, respectively. In addition, 1Mdillite, which is the polytype occurring in the common 1Mdto 2M1 prograde sequence, is relatively Mg poor, but coexists with Mg-rich illite in the Silverton Caldera sample.These data confirm that 1M stacking is caused by compositional anomalies, and thus explain the lack of the 1M stacking sequence in normal diagenetic sequences in pelitic rocks, as most illite in such environments has a relatively small phengitic component. The parameter Δz, a measure of the corrugation of the oxygen sheets, may be the key parameter reflecting the polytypic state of dioctahedral and trioctahedral micaceous minerals. Such composition-determined relations may be related to the occurrence of 1M polytypism in glauconite and celadonite, both dioctahedral 2:1 clay minerals having large Mg or Fe octahedral-cation components, and in trioctahedral micas. Insofar as the 1M stacking sequence does not have the same composition as 2M1 material, these data confirm that the different varieties of illite are not polytypes, sensu stricto.
Diagenesis and Rheology of a Recent-Pleistocene Volcanogenic Sedimentary Sequence, Mexican Basin
Authors: de Pablo-Galán Liberto , de Pablo Juan J. , de Lourdes Chávez-García M. 
Published: February 2003

AbstractDiagenesis of the Holocene-Pleistocene volcanogenic sediments of the Mexican Basin produced, in strata of gravel and sand, 1H2O- and 2H2O-smectite, kaolinite, R3-2H2O-smectite (0.75)-kaolinite, R1-2H2O-smectite (0.75)-kaolinite, R3-kaolinite (0.75)-2H2O-smectite and R1-1H2O-smectite (0.75)-kaolinite. Smectite platelets were formed from volcanic glass by loss of Si4+. Partially-formed platelets have Si4+ between 4.55−4.10 a.p.f.u., Mg+Mn and the interlayer charge are relatively uniform while VIAl+Fe3++Ti varies between 0.98 and 1.63 a.p.f.u. Almost fully transformed platelets have Si4+ of 4.08−4.04 a.p.f.u.; Mg+Mn and the interlayer charge decrease proportionally to increasing VIAl+Fe3++Ti. Smectite-kaolinite mixed layers have octahedral occupancies of 2.01–2.15 a.p.f.u., IVAl3+ 0.09–0.55 a.p.f.u. and interlayer charges about half that of smectite; structural formulae corresponding to smectite (0.75–0.80)-kaolinite indicate octahedral occupancy of 2.50 a.p.f.u., tetrahedral replacement 0–0.31 a.p.f.u., and interlayer charge 0.24–0.51 equivalents, some indicating interstratifications of beidellite. Kaolinite is presumed to have formed from K-feldspar; smectite-kaolinite interstratifications sustain the transformation of kaolinite to smectite in an increasingly siliceous high-cation environment. In the mudstones of low-hydraulic conductivity and practically stagnant alkaline fluids, glass was transformed to 2H2O-smectite lamellae of IVAl between 0 and 0.47 a.p.f.u., octahedral occupancy 1.70–2.00 a.p.f.u. and interlayer charge of 0.23–1.21 equivalents, some corresponding to beidellite. The interlayer charge increases with IVAl and decreasing occupancy of the octahedral sheet; the abundance of Mg+Mn is inverse to that of VIAl+Fe3++Ti.Clay suspensions containing 1H2O- and 2H2O-smectite, kaolinite and R3-2H2O-smectite (0.75)-kaolinite lead to low-energy edge-to-edge particle associations, non-Newtonian pseudoplastic behavior, and maximum apparent viscosity of 180 Pa s at 0.008 s−1 followed by rapid descent. Clay fractions with slightly larger 2H2O-smectite contents and smaller kaolinite contents reach maximum viscosity of 3611 Pa s at a shear rate of 0.0018 s−1 and of 3300 Pa s at 0.0024 s−1. They denote two high-energy face-to-face particle associations, followed by slow descent of the apparent viscosity under viscous flow. Suspensions change from elastic to viscous behavior at shear stresses of 1.03 and 5.91 Pa, respectively. Clay suspension vibrated at a frequency of 1 Hz develops a shear storage dynamic modulus greater than the shear dynamic loss modulus or the energy is preferentially stored, whereas at 5 Hz more energy is dissipated than stored.
Risk factors for hysterectomy among Mexican‐American women in the U.S. southwest
Authors: Hautaniemi Susan I. , Leidy Sievert Lynnette 
Published: January 2003

AbstractThe purpose of this study was to assess risk factors associated with a history of hysterectomy among Mexican‐American women living in the United States Southwest. Mexican‐American women ages 20–74 at time of interview were defined as a subpopulation among adults in the Hispanic Health and Nutrition Examination Survey (HHANES), 1982–1984. Language preference, reproductive history, level of education, poverty status, generation of immigration, marital status, and insurance coverage were examined in relation to risk of hysterectomy using weighted tabulation and logistic regression for data resulting from complex survey designs. Heretofore, language preference has not been a variable considered in relation to risk of hysterectomy. In the HHANES, over 60% of women who spoke English most often rather than Spanish reported a history of hysterectomy. Women who had previously been pregnant were almost four times as likely (odds ratio 3.972) to have had a hysterectomy compared to women who had never been pregnant. Women who expressed any preference for English were twice as likely (odds ratio 2.050) to have had a hysterectomy than were those who responded that they exclusively preferred Spanish. Age, higher levels of education, and higher economic status also increased the risk of hysterectomy. In contrast, reproductive history, marital status, prior tubal ligation, generation of immigration, and health insurance did not have substantial effects on the risk of hysterectomy. This study suggests that, in the future, the effect of language preference should not be overlooked when considering risk factors for hysterectomy. Am. J. Hum. Biol. 15:38–47, 2003. © 2002 Wiley‐Liss, Inc.
Potential association between endogenous leptin and sympatho‐vagal activities in young obese Japanese women
Authors: Matsumoto Tamaki , Miyatsuji Aya , Miyawaki Takashi , Yanagimoto Yukio , Moritani Toshio 
Published: January 2003

AbstractLeptin is an adipocyte‐derived hormone that decreases food intake and increases energy expenditure through the activation of the sympathetic nervous system (SNS). Notwithstanding recent intensive research, the underlying physiological mechanism of leptin as well as the etiology of obesity in humans remains elusive. The present study attempted to investigate the potential association between endogenous circulating leptin and sympatho‐vagal activities in age‐ and height‐matched obese and nonobese healthy young women. Plasma leptin concentrations were measured by radioimmunoassay. The autonomic nervous system activity was assessed during the resting condition by means of a recently devised power spectral analysis of heart rate variability, which serves to identify three separate frequency components, very low (VLO), low (LO), and high (HI). Plasma leptin concentrations were greater in the obese than in the control group (45.7 ± 5.89 vs. 11.2 ± 1.10 ng · ml−1, P < 0.01). As to the contribution of endogenous leptin to SNS activity, both the ratios of the VLO frequency component reflecting thermoregulatory sympathetic function and the global SNS index [(VLO + LO)/HI] to plasma leptin concentration were markedly reduced in the obese compared to the control group (VLO per leptin: 5.9 ± 1.39 vs. 37.8 ± 8.1 ms2 · ml · ng−1, P < 0.01; SNS index per leptin: 0.04 ± 0.008 vs. 0.33 ± 0.01 ml ċ· ng−1, P < 0.01). Additionally, a nonlinear regression analysis revealed that these ratios exponentially decreased as a function of body fat content (VLO per leptin r2 = 0.57, P < 0.01; SNS index per leptin r2 = 0.53, P < 0.01). Our data suggest that reduced sympathetic responsiveness to endogenous leptin production, implying peripheral leptin resistance, might be a pathophysiological feature of obesity in otherwise healthy young women. The findings regarding the association of leptin, body fat content, and SNS activity further indicate that the 30% of total body fat, which has been used as a criterion of obesity, might be a critical point at which leptin resistance is induced. Am. J. Hum. Biol. 15:8–15, 2003. © 2002 Wiley‐Liss, Inc.
Age differences in growth and physical abilities in trained and untrained girls 10–17 years of age
Authors: Loko J. , Aule R. , Sikkut T. , Ereline J. , Viru A. 
Published: January 2003

AbstractThe purpose of the present study was to assess the age differences in growth characteristics and physical abilities of physically active adolescent girls and to compare them to corresponding data for girls nonactive in sport. The cross‐sectional study was carried out on 643 Estonian girls, 10–17 years of age, who were regularly training track and field, and 902 nonactive girls. The organized physical activity of the studied girls consisted of lessons in the school curriculum (2 × 45 minutes per week) for both groups and special track and field training for the first group. Height, weight, and the body mass index (BMI) were used to characterize growth status. Physical ability was assessed with the 30‐m dash, standing long jump, medicine ball throw (2 kg), standing quintuplet jump, isometric strength of back extensor muscles, and 1‐minute ergocycling at the highest possible rate. Girls active in track and field were taller in all the age groups (P < 0.05–0.001) and lighter except at 17 years, when they were heavier (P > 0.05), but the differences at 12 and 13 years were not significant. BMI was also significantly lower in active girls (P < 0.05–0.001) in all age groups, except at 17 (P > 0.05). The actively training girls had higher physical abilities at all ages from 10–17. The annual differences in performance scores were significant (P < 0.05–0.001) up to 15 years except for the standing long jump. Differences in mean scores of most motor abilities were minimal or reduced significantly at 13–14 years in nonactive girls, but were significant in active girls. Am. J. Hum. Biol. 15:72–77, 2003. © 2002 Wiley‐Liss, Inc.
Allometric scaling of strength in an independently living population age 55–86 years
Authors: Amara Catherine E. , Rice Charles L. , Koval John J. , Paterson Donald H. , Winter Edward M. , Cunningham David A. 
Published: January 2003

AbstractMost physiological functions vary allometrically with body size; however, few investigators have examined the relationship between strength and body size with allometric scaling. Thus, we hypothesized that allometric analysis would reveal that both the amount and quality of muscle are significant determinants of strength in the elderly. Allometric analyses were used to determine the influence of limb cross‐sectional area (CSA), physical activity, demispan (distance between index‐middle finger web and the sternal notch), leg length, and sex on grip and plantar flexor strength in men (n = 188) and women (n = 205) age 55–86 years. Physical activity was measured using a self‐reporting questionnaire (Taylor et al. [1978] J Chron Dis 31:741–755). Forearm and leg CSA was estimated from anthropometry. There was an age‐related decline in grip strength, independent of forearm CSA, demispan, and sex, equal to ≈12% per decade, whereas plantar flexor strength adjusted for leg CSA, physical activity, and sex was reduced at a rate of ≈15% per decade. The allometric models explained 71.4% (r = 0.845) and 38.8% (r = 0.623) of the variance in grip and plantar flexor strength, respectively. Model parameters were identified using multiple linear regression (P < 0.05). Thus, grip strength = forearm CSA0.435 · demispan0.161 · exp(3.905 − 0.012 age + 0.413 sex) and plantar flexor strength = leg CSA0.223 · physical activity 0.115 · exp(5.867 − 0.015 age + 0.366 sex). These findings indicate that age‐related reductions in muscle CSA do not fully account for strength declines with age. Physical activity is also important and partially explains these reductions. Am. J. Hum. Biol. 15:48–60, 2003. © 2002 Wiley‐Liss, Inc.
Genetic structure of seven Mexican indigenous populations based on five polymarker loci
Authors: Buentello‐Malo Leonora , Peñaloza‐Espinosa Rosenda I. , Loeza Francisco , Salamanca‐Gomez Fabio , Cerda‐Flores Ricardo M. 
Published: January 2003

AbstractThis descriptive study investigates the genetic structure of seven Mexican indigenous populations (Mixteca Alta, Mixteca Baja, Otomies, Purepecha, Nahuas‐Guerrero, Nahuas‐Xochimilco, and Tzeltales) on the basis of five PCR‐based polymorphic DNA loci: LDLR, GYPA, HBGG, D7S8, and GC. Genetic distance and diversity analyses indicate that these Mexican indigenous are similar and that more than 96% of the total gene diversity (HT) can be attributed to individual variation within populations. Mixteca‐Alta, Mixteca‐Baja, and Nahuas‐Xochimilco show indications of higher admixture with European‐derived persons. The demonstration of a relative genetic homogeneity of Mexican Indians for the markers studied suggests that this population is suitable for studying disease‐marker associations in the search for candidate genes of complex diseases. Am. J. Hum. Biol. 15:23–28, 2003. © 2002 Wiley‐Liss, Inc.
Physical activity, body fat, and serum c‐reactive protein in postmenopausal women with and without hormone replacement
Authors: Manns Patricia J. , Williams Daniel P. , Snow Christine M. , Wander Rosemary C. 
Published: January 2003

AbstractThe objective was to determine whether higher physical activity is associated with lower serum C‐reactive protein (CRP), independent of oral hormone replacement therapy (HRT) status and body fatness, in 133 postmenopausal women using a cross‐sectional exploratory design at a university research laboratory. The subjects were 133 postmenopausal women, age 50–73 years, with no evidence of coronary artery disease or diabetes. The main outcome measures were: serum CRP, physical activity as measured by Stanford 7‐day activity recall, body fat (both total and regional) as measured by dual energy X‐ray absorptiometry (DXA), and anthropometry (waist and hip circumference). Secondary outcome measures included fasting plasma glucose and insulin as well as fasting serum triglycerides, total cholesterol, high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol. Higher physical activity energy expenditures were significantly associated with lower serum CRP levels (r = −0.18, P = 0.041), independent of oral HRT use, age, smoking behavior, alcohol consumption, aspirin use, and statin use. However, in the complete multivariate model, which included body fat, older ages (P = 0.047), greater trunk fat masses (P < 0.001), any oral HRT use (P < 0.001), and unopposed oral estrogen use (P = 0.012) were the sole independent predictors of higher serum CRP levels. The complete multivariate model accounted for 58% of the variance in serum CRP. We conclude that the association between higher physical activity and lower serum CRP levels is dependent on the lower body fat of the more active women, yet independent of oral HRT use. Future intervention trials should determine whether diet‐ and exercise‐related reductions in body fat may be effective ways to diminish the proinflammatory effects of oral HRT in postmenopausal women. Am. J. Hum. Biol. 15:91–100, 2003. © 2002 Wiley‐Liss, Inc.
Behavior of loci D1S1656 and D12S391 in a sample from Maracaibo, Venezuela
Authors: Bernal Lennie Pineda , Rodríguez‐Larralde Alvaro , Lareu María V. , Carracedo Angel , Borjas‐Fajardo Lisbeth 
Published: January 2003

AbstractTwo recently reported short tandem repeat polymorphisms characterized by PCR, D1S1656 and D12S391, were investigated in a sample from Maracaibo, an admixed population of Venezuela, in order to evaluate their application in forensic and population genetics studies. The unbiased heterozygosities were 0.9011 and 0.8444 for locus D1S1656 and D12S391, respectively. The joint discrimination power and joint probability of exclusion were 0.99972 and 0.93287. When allele frequencies of locus D1S1656 from Maracaibo were compared with eight other populations, our group clustered with the European or European‐derived samples, mainly from Spain. In the comparison of locus D12S391 with 16 populations, Maracaibo clustered with 3 Asian samples. The high heterozygosity and discrimination power make these two loci important candidates to be considered for STR packages for forensic and population genetic purposes. Am. J. Hum. Biol. 15:68–71, 2003. © 2002 Wiley‐Liss, Inc.
Effect of husbands' education on fatness of wives
Authors: Lipowicz Anna 
Published: January 2003

AbstractThe aim of the study was to examine the relationship between social position of females achieved by marriage and level of fatness and relative fat distribution. The data of 588 healthy, occupationally active, married women, age 21–62 years, with 12 years of education (completed secondary school) were used. The body mass index (BMI, kg/m2 ), triceps and subscapular skinfold thicknesses, and summed skinfold thicknesses were used as indicators of fatness. The waist–hip ratio, the waist–thigh ratio, and waist, hip, and thigh circumferences were used as indicators of fat distribution. According to the educational level of husbands, women were grouped as 1) moving up the social scale (spouse with complete university education), 2) stable (equal level of education), and 3) moving down the social scale (spouse who never passed beyond the level of basic vocational school, i.e., skilled and unskilled manual workers). The two opposite groups were analyzed, i.e., moving up and moving down. Women with secondary schooling who married up were consistently leaner than women who married down. A similar pattern was observed for fat distribution. Women marrying down had more abdominal body fat compared to women marrying up. Am. J. Hum. Biol. 15:1–7, 2003. © 2002 Wiley‐Liss, Inc.