bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelial nitric oxide synthase (NOS3) knockout decreases NOS2 induction, limiting hyperoxygenation and conferring protection in the postischemic heart
Authors: Zhao Xue , Chen Yeong-Renn , He Guanglong , Zhang Aiwen , Druhan Lawrence J. , Strauch Arthur R. , Zweier Jay L.
Published: November 2006

Although it has been shown that endothelial nitric oxide synthase (eNOS)-derived nitric oxide downregulates mitochondrial oxygen consumption during early reperfusion, its effects on inducible NOS (iNOS) induction and myocardial injury during late reperfusion are unknown. Wild-type (WT) and eNOS−/− mice were subjected to 30 min of coronary ligation followed by reperfusion. Expression of iNOS mRNA and protein levels and peroxynitrite production were lower in postischemic myocardium of eNOS−/− mice than levels in WT mice 48 h postreperfusion. Significantly improved hemodynamics (±dP/d t, left ventricular systolic pressure, mean arterial pressure), increased rate pressure product, and reduced myocardial infarct size (18 ± 2.5% vs. 31 ± 4.6%) were found 48 h after reperfusion in eNOS−/− mice compared with WT mice. Myocardial infarct size was also significantly decreased in WT mice treated with the specific iNOS inhibitor 1400W (20.5 ± 3.4%) compared with WT mice treated with PBS (33.9 ± 5.3%). A marked reperfusion-induced hyperoxygenation state was observed by electron paramagnetic resonance oximetry in postischemic myocardium, but Po2 values were significantly lower from 1 to 72 h in eNOS−/− than in WT mice. Cytochrome c-oxidase activity and NADH dehydrogenase activity were significantly decreased in postischemic myocardium in WT and eNOS−/− mice compared with baseline control, respectively, and NADH dehydrogenase activity was significantly higher in eNOS−/− than in WT mice. Thus deficiency of eNOS exerted a sustained beneficial effect on postischemic myocardium 48 h after reperfusion with preserved mitochondrial function, which appears to be due to decreased iNOS induction and decreased iNOS-derived peroxynitrite in postischemic myocardium.
Ca2+ signaling in mouse mesenteric small arteries: myogenic tone and adrenergic vasoconstriction
Authors: Zacharia Joseph , Zhang Jin , Wier W. Gil
Published: November 2006

Arteries that have developed myogenic tone (MT) are in a markedly different physiological state compared with those that have not, with higher cytosolic [Ca2+] and altered activity of several signal transduction pathways. In this study, we sought to determine whether α1-adrenoceptor-induced Ca2+ signaling is different in pressurized arteries that have spontaneously developed MT (the presumptive physiological state) compared with those that have not (a common experimental state). At 32°C and intraluminal pressure of 70 mmHg, cytoplasmic [Ca2+] was steady in most smooth muscle cells (SMCs). In a minority of cells (34%), however, at least one propagating Ca2+ wave occurred. α1-Adrenoceptor activation (phenylephrine, PE; 0.1–10.0 μM) caused strong vasoconstriction and markedly increased the frequency of Ca2+ waves (in virtually all cells). However, when cytosolic [Ca2+] was elevated experimentally in these arteries ([K+] 20 mM), PE failed to elicit Ca2+ waves, although it did elevate [Ca2+] (F/F0) further and caused further vasoconstriction. During development of MT, the cytosolic [Ca2+] (F/F0) in individual SMCs increased, Ca2+ waves disappeared (from SMCs that had them), and small Ca2+ ripples (frequency ∼0.05 Hz) appeared in ∼13% of cells. PE elicited only spatially uniform increases in [Ca2+] and a smaller change in diameter (than in the absence of MT). Nevertheless, when cytosolic [Ca2+] and MT were decreased by nifedipine (1 μM), PE did elicit Ca2+ waves. Thus α1-adrenoceptor-mediated Ca2+ signaling is markedly different in arteries with and without MT, perhaps due to the elevated [Ca2+], and may have a different molecular basis. α1-Adrenoceptor-induced vasoconstriction may be supported either by Ca2+ waves or by steady elevation of cytoplasmic [Ca2+], depending on the amount of MT.
Magnesium attenuates isoproterenol-induced acute cardiac dysfunction and β-adrenergic desensitization
Authors: Jin Yin-Tie , Hasebe Naoyuki , Matsusaka Tomoyuki , Natori Shunsuke , Ohta Takafumi , Tsuji Shiro , Kikuchi Kenjiro
Published: November 2006

Sympathetic nervous activation is a crucial compensatory mechanism in heart failure. However, excess catecholamine may induce cardiac dysfunction and β-adrenergic desensitization. Although magnesium is known to be a cardioprotective agent, its beneficial effects on acute cardiac dysfunction remain to be elucidated. We examined the effects of magnesium on left ventricular (LV) dysfunction induced by a large dose of isoproterenol in dogs. Sixteen anesthetized dogs underwent a continuous infusion of isoproterenol (1 μg·kg−1·min−1) with or without a magnesium infusion (1 mg·kg−1·min−1). The dose response to small doses of isoproterenol (0.025–0.2 μg·kg−1·min−1) was tested hourly. A large dose of isoproterenol decreased LV systolic function, increased the time constant of LV isovolumic relaxation, and suppressed the dose response to small doses of isoproterenol in a time-dependent manner. Magnesium significantly attenuated isoproterenol-induced LV systolic and diastolic dysfunction and preserved the dose response to isoproterenol. Serum-ionized calcium significantly decreased with a large dose of isoproterenol but was fully maintained at baseline level with magnesium. A large dose of isoproterenol increased serum lipid peroxide levels and serological markers of myocardial damage, which were significantly suppressed by magnesium. In conclusion, magnesium significantly attenuated excess isoproterenol-induced acute cardiac dysfunction and β-adrenergic desensitization.
Deficiency of TNFR1 protects myocardium through SOCS3 and IL-6 but not p38 MAPK or IL-1β
Authors: Wang Meijing , Markel Troy , Crisostomo Paul , Herring Christine , Meldrum Kirstan K. , Lillemoe Keith D. , Meldrum Daniel R.
Published: November 2006

Tumor necrosis factor-α (TNF-α) plays an important role in the development of heart failure. There is a direct correlation between myocardial function and myocardial TNF levels in humans. TNF may induce local inflammation to exert tissue injury. On the other hand, suppressors of cytokine signaling (SOCS) proteins have been shown to inhibit proinflammatory signaling. However, it is unknown whether TNF mediates myocardial inflammation via STAT3/SOCS3 signaling in the heart and, if so, whether this effect is through the type 1 55-kDa TNF receptor (TNFR1). We hypothesized that TNFR1 deficiency protects myocardial function and decreases myocardial IL-6 production via the STAT3/SOCS3 pathway in response to TNF. Isolated male mouse hearts ( n = 4/group) from wild-type (WT) and TNFR1 knockout (TNFR1KO) were subjected to direct TNF infusion (500 pg·ml−1·min−1 × 30 min) while left ventricular developed pressure and maximal positive and negative values of the first derivative of pressure were continuously recorded. Heart tissue was analyzed for active forms of STAT3, p38, SOCS3 and SOCS1 (Western blot analysis), as well as IL-1β and IL-6 (ELISA). Coronary effluent was analyzed for lactate dehydrogenase (LDH) activity. As a result, TNFR1KO had significantly better myocardial function, less myocardial LDH release, and greater expression of SOCS3 (percentage of SOCS3/GAPDH: 45 ± 4.5% vs. WT 22 ± 6.5%) after TNF infusion. TNFR1 deficiency decreased STAT3 activation (percentage of phospho-STAT3/STAT3: 29 ± 6.4% vs. WT 45 ± 8.8%). IL-6 was decreased in TNFR1KO (150.2 ± 3.65 pg/mg protein) versus WT (211.4 ± 26.08) mice. TNFR1 deficiency did not change expression of p38 and IL-1β following TNF infusion. These results suggest that deficiency of TNFR1 protects myocardium through SOCS3 and IL-6 but not p38 MAPK or IL-1β.
Soluble guanylate cyclase-dependent relaxation is reduced in the adult rat bronchial smooth muscle
Authors: Belik Jaques , Hehne Nadine , Pan Jingyi , Behrends Soenke
Published: November 2006

Cyclic nucleotides are relaxants of the airway smooth muscle, yet most of the available data were obtained in adult animals. The expression and activity of cyclases have been reported to be developmentally regulated in the lung, and little is known about the age-related changes in their bronchial muscle relaxation potential. We evaluated and compared the newborn and adult rat bronchial smooth muscle response to cyclic AMP- and GMP-dependent agonists in isometric mounted bronchial rings. In acetylcholine-precontracted bronchial muscle, the relaxant response to the cAMP agonist forskolin was not age dependent, but the relaxant response to the nitric oxide (NO) donor sodium nitroprusside (SNP) was significantly greater ( P < 0.01) in the newborn. To further evaluate the cGMP pathway, we stimulated the soluble guanylate cyclase (sGC) with the specific agonists BAY 41-2272 and YC-1. In keeping with the SNP dose-response curves, the sGC agonists significantly relaxed the newborn, but not the adult bronchial muscle. Protein expression of the sGC α1- and β1-subunits were significantly lower ( P < 0.01) in the adult compared with the newborn bronchial tissue. Consistent with these results, the NO-stimulated sGC activity was significantly greater in the newborn compared with the adult ( P < 0.01). In conclusion, the bronchial smooth muscle cGMP-, but not cAMP-dependent, relaxant response is developmentally regulated and significantly reduced in the adult rat.
I2 Imaging: Cancer Biology and the Tumor Microenvironment
Authors: Sloane Bonnie F. , Gillies Robert J. , Mohla Suresh , Sogn John A. , Menkens Anne E. , Sullivan Daniel C.
Published: November 2006

The use of imaging techniques to understand the role of the tumor microenvironment in cancer progression was the topic of a National Cancer Institute (NCI)–sponsored think tank entitled “I2 Imaging: Cancer Biology and the Tumor Microenvironment,” held in Alexandria, Virginia on June 8 to 10, 2006. Participants discussed both recent progress in the use of imaging to dissect cellular and molecular interactions within the tumor microenvironment and the challenges that remain. Recommendations made to the NCI included (a) holding an annual meeting at which biologists, clinicians, and imaging scientists could exchange data, facilitating new collaborations within this multidisciplinary field; (b) funding both research and training specifically designed to foster a cross-disciplinary focus; (c) creating and making available a variety of resources to interested investigators, such as a repository of stromal cells and extracellular matrix molecules; and (d) taking steps to encourage translation of the basic research findings into the clinic. (Cancer Res 2006; 66(23): 11097-9)
Patristic Biblical Quotations and Method: Four Changes to Lightfoot's Edition of Second Clement
Authors: Petersen William
Published: November 2006

This study examines the putative New Testament parallels in Second Clement, especially as found in the enormously influential edition of J. B. Lightfoot. Such putative parallels are important not just for the Patristic text itself, but also for the establishment of the text of the New Testament. Additionally, they shed light on the probable date and provenance of the document. Close textual examination suggests there are four places where the text of Lightfoot's edition should be changed (three of these instances apply to all later editions, as well). Investigating how Lightfoot (and later editors) came to their textual decisions exposes serious flaws in their commonly-employed methodology, which we label "normative." The "normative" method is based on the anachronistic use of texts, flawed logic, and special pleading. An alternative to this "normative" method will be presented; it avoids these pitfalls, and produces more reliable results. We label this alternative method "non-normative." The implications for the editing of Patristic and apocryphal texts, as well as for producing critical editions of the New Testament, are significant.
Mechanisms of Anterior Cruciate Ligament Injury in Basketball
Authors: Krosshaug Tron , Nakamae Atsuo , Boden Barry P. , Engebretsen Lars , Smith Gerald , Slauterbeck James R. , Hewett Timothy E. , Bahr Roald
Published: November 2006

Background

The mechanisms of anterior cruciate ligament injury in basketball are not well defined.

Purpose

To describe the mechanisms of anterior cruciate ligament injury in basketball based on videos of injury situations.

Study Design

Case series; Level of evidence, 4.

Methods

Six international experts performed visual inspection analyses of 39 videos (17 male and 22 female players) of anterior cruciate ligament injury situations from high school, college, and professional basketball games. Two predefined time points were analyzed: initial ground contact and 50 milliseconds later. The analysts were asked to assess the playing situation, player behavior, and joint kinematics.

Results

There was contact at the assumed time of injury in 11 of the 39 cases (5 male and 6 female players). Four of these cases were direct blows to the knee, all in men. Eleven of the 22 female cases were collisions, or the player was pushed by an opponent before the time of injury. The estimated time of injury, based on the group median, ranged from 17 to 50 milliseconds after initial ground contact. The mean knee flexion angle was higher in female than in male players, both at initial contact (15° vs 9°, P = .034) and at 50 milliseconds later (27° vs 19°, P = .042). Valgus knee collapse occurred more frequently in female players than in male players (relative risk, 5.3; P = .002).

Conclusion

Female players landed with significantly more knee and hip flexion and had a 5.3 times higher relative risk of sustaining a valgus collapse than did male players. Movement patterns were frequently perturbed by opponents.

Clinical Relevance

Preventive programs to enhance knee control should focus on avoiding valgus motion and include distractions resembling those seen in match situations.
Epidemiology of 1.6 Million Pediatric Soccer-Related Injuries Presenting to US Emergency Departments from 1990 to 2003
Authors: Leininger Robert E. , Knox Christy L. , Comstock R. Dawn
Published: November 2006

Background

As soccer participation in the United States increases, so does the number of children at risk for injury.

Purpose

To examine pediatric soccer-related injuries presenting to US emergency departments from 1990 to 2003.

Study Design

Descriptive epidemiology study.

Methods

A descriptive analysis of nationally representative, pediatric, soccer-related injury data from the US Consumer Product Safety Commission's National Electronic Injury Surveillance System.

Results

Among those 2 to 18 years of age, a nationally estimated 1 597 528 soccer-related injuries presented to US emergency departments from 1990 to 2003. Mean age was 13.2 years (range, 2-18 years); 58.6% were male. From 1990 to 2003, there was an increase in the absolute number of injuries among girls (P < .0001). The wrist/finger/hand (20.3%), ankle (18.2%), and knee (11.4%) were the most commonly injured body parts. The most common diagnoses were sprain/strain (35.9%), contusion/abrasion (24.1%), and fracture (23.2%). Boys were more likely to have face and head/neck injuries (17.7%; relative risk, 1.40; 95% confidence interval, 1.32-1.49; P < .01) and lacerations/punctures (7.5%; relative risk, 3.31; 95% confidence interval, 2.93-3.74; P < .01) than were girls (12.7% and 2.3%, respectively). Girls were more likely to have ankle injuries (21.8%; relative risk, 1.38; 95% confidence interval, 1.33-1.45; P < .01) and knee injuries (12.9%; relative risk, 1.25; 95% confidence interval, 1.15-1.35; P < .01) than were boys (15.7% and 10.4%, respectively). Girls were more likely to have sprains or strains (42.4%) than were boys (31.3%; relative risk, 1.36; 95% confidence interval, 1.31-1.40; P < .01). Children 2 to 4 years old sustained a higher proportion of face and head/neck injuries (41.0%) than did older children (15.5%; relative risk, 2.65; 95% confidence interval, 2.09-3.36; P < .01).

Conclusion

When comparing these data to available national statistics that estimate participation in youth soccer, true injury rates may actually be decreasing for boys and girls. Young children should be closely supervised because of risk of head injuries and rate of hospitalization. The establishment of a national database of soccer participation and injury data is needed to better identify injury risks.
Significance of the Arthroscopic Meniscal Flounce Sign
Authors: Wright Rick W. , Boyer Dory S.
Published: November 2006

Background

The meniscal flounce sign is a fold in the free, nonanchored inner edge of the medial meniscus that can be noted during routine arthroscopy of the knee.

Hypothesis

The meniscal flounce sign can be a significant indicator of the presence or absence of medial meniscus injury.

Study Design

Cohort study (diagnosis); Level of evidence, 4.

Methods

One hundred sixty-eight patients were prospectively evaluated at the time of the arthroscopy for the presence or absence of the arthroscopic meniscal flounce sign. These results were then correlated with the presence of medial meniscus tears.

Results

The presence of the meniscal flounce sign has a positive predictive value of a normal meniscus of 0.97 (63/65). The absence of the meniscal flounce sign has a positive predictive value of an abnormal meniscus of 0.98 (101/103). Specificity is 98%, and sensitivity is 97%.

Conclusion

The absence of the arthroscopic meniscal flounce sign is a sensitive and specific predictor of the presence of medial meniscus tears that should alert the surgeon to probe carefully for an occult medial meniscus tear.
Personal Involvement of Young People in HIV Prevention Campaign Messages: The Role of Message Format, Culture, and Gender
Authors: Geary Cynthia Waszak , Burke Holly M. , Johnson Laura , Liku Jennifer , Castelnau Laure , Neupane Shailes , Niang Cheikh
Published: November 2006

To examine young people's reactions to and understanding of HIV prevention messages developed for MTV's global HIV prevention campaign Staying Alive, videotaped campaign materials were shown to focus group discussion (FGD) participants living in urban areas of Brazil, Kenya, Nepal, and Senegal. Responses related to “personal involvement” with the message were identified in the data from these FGDs and were examined in relationship to the emerging message themes, the message format (public service announcements [PSAs] vs. documentary), cultural context (site), and participant gender. Across groups, greater personal involvement (measured by personal connections, emotional reactions, and lessons learned) was found in responses about the documentary format compared to the PSA format. Exceptions were found for specific PSAs that were considered more relevant within specific gender or cultural contexts. Implications of findings for global campaigns were considered.
Randomized Trials on Consider This, a Tailored, Internet-Delivered Smoking Prevention Program for Adolescents
Authors: Buller David B. , Borland Ron , Woodall W. Gill , Hall John R. , Hines Joan M. , Burris-Woodall Patricia , Cutter Gary R. , Miller Caroline , Balmford James , Starling Randall , Ax Bryan , Saba Laura
Published: November 2006

The Internet may be an effective medium for delivering smoking prevention to children. Consider This, an Internet-based program, was hypothesized to reduce expectations concerning smoking and smoking prevalence. Group-randomized pretest-posttest controlled trials were conducted in Australia ( n = 2,077) and the United States ( n = 1,234) in schools containing Grades 6 through 9. Australian children using Consider This reported reduced 30-day smoking prevalence. This reduction was mediated by decreased subjective norms. The amount of program exposure was low in many classes, but program use displayed a dose-response relationship with reduced smoking prevalence. American children only reported lower expectations for smoking in the future. Intervening to prevent smoking is a challenge, and this data suggest small benefits from an Internet-based program that are unlikely to be of practical significance unless increased by improved implementation. Implementation remains the major challenge to delivering interventions via the Internet, both for health educators and researchers.
A Socioecological Approach to Improving Mammography Rates in a Tribal Community
Authors: English Kevin C. , Fairbanks Jo , Finster Carolyn E. , Rafelito Alvin , Luna Jolene , Kennedy Marianna
Published: November 2006

This article highlights the processes and intermediate outcomes of a pilot project to increase mammography rates of women in an American Indian tribe in New Mexico. Using a socioecological framework and principles of community-based participatory research, a community coalition was able to (a) bolster local infrastructure to increase access to mammography services; (b) build public health knowledge and skills among tribal health providers; (c) identify community-specific knowledge, attitudes, and beliefs related to breast cancer; (d) establish interdependent partnerships among community health programs and between the tribe and outside organizations; and (e) adopt local policy initiatives to bolster tribal cancer control. These findings demonstrate the value of targeting a combination of individual, community, and environmental factors, which affect community breast cancer screening rates and incorporating cultural strengths and resources into all facets of a tribal health promotion intervention.
High speed fusion weld bead defects
Authors: Nguyen T. C. , Weckman D. C. , Johnson D. A. , Kerr H. W.
Published: November 2006

A comprehensive survey of high speed weld bead defects is presented with strong emphasis on the formation of humping and undercutting in autogenous and non-autogenous fusion welding processes. Blowhole and overlap weld defects are also discussed. Although experimental results from previous studies are informative, they do not always reveal the physical mechanisms responsible for the formation of these high speed weld bead defects. In addition, these experimental results do not reveal the complex relationships between welding process parameters and the onset of high speed weld bead defects. Various phenomenological models of humping and undercutting have been proposed that were based on observations of events in different regions within the weld pool or the final weld bead profile. The ability of these models to predict the onset of humping or undercutting has not been satisfactorily demonstrated. Furthermore, the proposed formation mechanisms of these high speed weld bead defects are still being questioned. Recent welding techniques and processes have, however, been shown to be very effective in suppressing humping and undercutting by slowing the backward flow of molten metal in the weld pool. This backward flow of molten weld metal may be the principal physical phenomenon responsible for the formation of humping and undercutting during high speed fusion welding.
Prediction of dilution in GMA and UGMA stainless steel single layer cladding using response surface methodology
Authors: Shahi A. S. , Pandey S.
Published: November 2006

This paper describes the use of a variant of GMAW process named as UGMAW (universal gas metal arc welding) process for single layer stainless steel cladding, which makes use of a specially designed torch to preheat the filler wire, using an auxiliary welding power source, before its emergence from the torch. The experimental work undertaken was that of single layer cladding of 12 mm thick low carbon steel with the austenitic stainless steel 316L solid filler wire of 1·14 mm diameter. Dependence of dilution was investigated using four factor five level central composite rotatable design to develop relationship for predicting dilution, which enables to quantify the direct and interactive effects of four numerical factors, namely, wire feed rate, open circuit voltage (OCV), welding speed, electrode stickout and one categorical factor, preheat current. External preheating of the filler wire in UGMAW process resulted in greater contribution of arc energy by resistive heating owing to which significant drop in the main welding current and hence low dilution values were observed. Numerical optimisation was carried out and the optimal solutions generated indicate that for same levels of dilution, higher deposition rates are achievable in UGMAW process, thus making it a good choice for low cost surfacing applications.
Evaluation of 2D, 3D and applied plastic strain methods for predicting buckling welding distortion and residual stress
Authors: Michaleris P. , Zhang L. , Bhide S. R. , Marugabandhu P.
Published: November 2006

Welding induces residual stresses which in thin section structures may cause buckling distortion. The magnitude of longitudinal residual stress is critical in the prediction of buckling distortion, which affects numerous welding applications in the ship building, railroad and other industries. The objectives of this paper are to overview and evaluate modelling procedures for bucking distortion. Moving source two-dimensional (2D), three-dimensional (3D) small deformation, 3D large deformation, and 2D–3D applied plastic strain analyses are evaluated by comparing computed residual stress and distortion against experimental measurements. Guidelines for modelling welding distortion are developed along with an assessment of the efficiency and limitations of the various analysis methods.
Experimental examination of welding nozzle jet flow at cold flow conditions
Authors: Johnson D. A. , Orakwe P. , Weckman E.
Published: November 2006

A fundamental study of welding nozzle flow under cold flow conditions is presented. The aim is to examine the shielding gas flow characteristics for several gas metal arc welding (GMAW) flow conditions. Experimental investigations are used to predict the flow behaviour of the gas shielding the weld pool. Results are presented for generic GMAW nozzle configurations at typical welding situations under cold flow. Flow visualisation and particle image velocimetry (PIV) gas velocity measurements reveal the various flow characteristics that are crucial to understanding of weld pool protection by the shielding gas. Results may be used to assist in understanding shield gas delivery and the effect of flow and geometry variables on shield gas coverage.
Experimental investigation on resistance spot welding of galvannealed HSLA steel
Authors: Nieto J. , Guerrero-Mata M. P. , Colás R. , Maní A.
Published: November 2006

A systematic variation of the parameters involved in the spot welding by electrical resistance of galvannealed strips was carried out on samples from a 2 mm thickness galvannealed high strength low alloy steel strip used for automotive applications. The varied parameters in the present study were welding current, welding time, holding time after welding and number of welding pulses, while the dimensions and characteristics of the electrodes and the applied force during welding were kept constant. The wear of the electrodes is important, however it was not the aim of the present study, therefore it was not taken into account. The experimental results were analysed to evaluate the influence of the various parameters on diverse characteristics of the welded bead. It was possible to determine the optimal operational conditions for this particular type of material.
3D rigid viscoplastic FE modelling of continuous drive friction welding process
Authors: Zhang Q. Z. , Zhang L. W. , Liu W. W. , Zhang X. G. , Zhu W. H. , Qu S.
Published: November 2006

With torsional friction being introduced into the calculation of heat generation and deformation, a 3D rigid viscoplastic FE (finite element) model was established to describe the continuous drive friction welding process. In this model, the workpiece was treated as a deformable body with rigid viscoplastic incompressible material. The friction stress was calculated using Coulomb friction law and shear friction law at different stages of friction welding process respectively. The model simulated two continuous drive friction welding cases by performing coupled thermal and mechanical analyses. Simulations successfully predict the thermal history of the joint as well as deformation rate and final geometries. Meanwhile, the possibility of defect occurrence is also obtained. Experiments on continuous drive friction welding of GH4169 superalloy rod were carried out. The temperature history and the final geometry of the welded joint were measured and compared with the calculated results, which show a good agreement between them.
Organo-bentonites with quaternary alkylammonium ions
Authors: Favre H. , Lagaly G.
Published: November 2006

Three bentonites, from Bavaria, Wyoming and Brazil, were separated into various fractions. The layer charge was determined by alkylammonium ion exchange and increases with particle size from 0·25 Eq/(Si, Al)4O10 (<0·06 µm) to 0·28 Eq/(Si, Al)4O10 (1–10 µm). The charge density corresponds to an interlayer cation density of 0·75–0·80 mEq/g silicate. Total amounts of 0·90–1·0 mEq of different surfactant cations (dimethyl dioctadecylammonium, trimethyl tetradecylammonium, alkylammonium ions) are bound per gram silicate. The difference between the total and the interlayer amount of surfactant ions decreases with increasing particle size. The amounts exceeding the interlayer CEC are bound at the edges. Tetramethylammonium (TM) ions restrict the interlayer adsorption of long-chain quaternary alkylammonium ions such as trimethyl tetradecylammonium (TMTD) ions, and only monolayers of flat-lying surfactants are formed. A ratio of TMTD and TM is attained which leads to densely packed monolayers of organic ions. The collapsing effect is smaller for tetraethylammonium ions so that considerable amounts of TMTD ions are adsorbed in bilayers. When bentonites are reacted with quaternary alkylammonium ions of technical quality some selectivity is observed according to particle size and layer charge. Smaller particles with lower charge density preferentially bind the longer chain compounds, whereas large particles with higher charge density select smaller sized surfactants.
Preparation of porous materials by chemical activation of the Llano vermiculite
Authors: Suquet H. , Chevalier S. , Marcilly C. , Barthomeuf D.
Published: November 2006

A mild acid attack of the Llano vermiculite produces porous materials suitable for use as cracking catalysts and/or catalysts supports. After HCl attack at 80°C (1 m), the number of acid sites measured by the Hammett indicator method is ∼0·50/nm2, and the specific surfaces are 245 m2/g after calcination at 550°C (4 h), and 55 m2/g after steaming at 750°C (4 h). The performance of leached (1 m HCl) vermiculite has been compared with another hydrocarbon cracking catalyst—γ-Al2O3. The leached vermiculite produces a definite higher conversion and higher C3, C4 and gasoline yields, but much lower coke production. By electron microscopy, infrared spectroscopy, X-ray powder diffraction and thermal analysis, it has been shown that the leached vermiculite samples are composed of more or less attacked layers retaining their original platy morphology, and non-crystalline hydrated silica. Chemical analyses indicate that octahedral cations are dissolved first.
Smectites in the montmorillonite-beidellite series
Authors: Yamada H. , Nakazawa H. , Yoshioka K. , Fujita T.
Published: November 2006

Smectites in the montmorillonite-beidellite pseudo-binary system were synthesized from glass at the hydrothermal conditions 100 MPa and 250–500°C. Products were analysed by X-ray powder diffraction for randomly oriented and glycolated samples, and also according to the Greene-Kelly test. A new mixed-layer mineral consisting of regularly interstratified montmorillonite-beidellite was found below 400°C for M50B50 composition, where M and B denote the compositions of ideal Na-montmorillonite and Na-beidellite, respectively. Montmorillonite was obtained as a single phase below 375°C in the composition range from M100B0 to M78B22. Above 375°C, montmorillonite decomposed into an assemblage of beidellite, saponite and a silica mineral. Beidellite as a single phase was synthesized below 400°C for M0B100 composition. Above 450°C, Na-rectorite (regularly interstratified paragonite-beidellite), Mg-free dioctahedral smectite and/or Mg-rich trioctahedral smectite appeared together with silica minerals. These smectites showed the same swelling behaviour as that of montmorillonite. Phase relations in the montmorillonite-beidellite pseudo-binary system indicate no complete solid-solution series.
Diagenesis of the Central Basque-Cantabrian Basin (Iberian Peninsula) based on illite-smectite distribution
Authors: Aróstegui J. , Zuluaga M. C. , Velasco F. , Ortega-Huertas M. , Nieto F.
Published: November 2006

X-ray diffraction was used to analyse the distribution of clay minerals in the <2 µm fraction of the lutitic and marly facies from the centre of the Basque-Cantabrian Basin (Basque Arc), where the sedimentary section is 2000 to 10,000 m thick. Most of the deposits were laid down during the Cretaceous and Paleogene and were related to the opening and closing of the Bay of Biscay. The most noteworthy variations are in kaolinite, smectite and mixed-layered (R = 0, R = 1 and R ≥ 3) illite-smectite, which can be ascribed both to provenance and to diagenesis. A general diminution in expandability is related to the gradual transformation of smectite to illite from south to north, and with depth. Temperature, residence time and chemical activity during diagenesis are the factors that had greatest influence on the changes in the original mineral assemblages inherited from the source area. On the basis of the clay minerals and the Kübler index, a general scheme is proposed for the diagenetic evolution of the area from the initial stages to anchimetamorphism.
Improved evaluation of layer charge of n-alkylammonium-treated fine soil clays by Lorentz- and polarization-correction and curve-fitting
Authors: Stanjek H. , Niederbudde E. A. , Häusler W.
Published: November 2006

The clay mineralogy of K-fixing soils from southern Germany was investigated using the alkylammonium method. Conventional X-ray diffraction chart recordings of glycerol-saturated <0·1 µm samples showed peaks at 18 Å that were initially interpreted as smectites. However, step-scanning combined with the Lorentz- and polarization-correction and curve-fitting, revealed the presence of low- and high-charge smectites and of low- and high-charge vermiculites. The severe overlap of the 001 basal reflections of the high-charge vermiculites with the broad and intensive peaks of smectites sensu stricto prevented visual evaluation at the alkylchains nc = 5–9, but this problem was overcome by curve-fitting. The 002 peaks of high-charge vermiculites (nc = 8 and nc = 10) in the fraction 0·1–0·2 µm could furthermore be clearly resolved from the 001 peaks of illite by curve-fitting. In one example, 003 (at nc = 17) could be resolved from 001 of illite.
Abundance of halloysite neoformation in soils developed from crystalline rocks. Contribution of transmission electron microscopy
Authors: Romero R. , Robert M. , Elsass F. , Garcia C.
Published: November 2006

The soils developed from crystalline and metamorphic rocks in Galicia (NW Spain), are characterized by high concentrations of 1 : 1 phyllosilicates and gels. Thermal analyses, X-ray diffraction after formamide treatment, and IR spectroscopy in the OH vibration range have been performed on the clay fractions, but do not discriminate clearly between the different associated mineralogical phases. HRTEM studies linked with microdiffraction and microanalyses have led to the identification of several types of gel which transform into goethite, gibbsite, clay precursors, and/ or halloysite according to their composition (Fe, Al or Si-Al). Halloysite-like minerals are the main constituents and they have a great variety of morphologies: lamellar, spheroidal, tubular, platy or poikilitic. In general, halloysite and gel formation on crystalline rocks is related to the bioclimatic conditions, involving high hydrolysis in the presence of organic matter. This halloysite seems to be a metastable mineral which would evolve into kaolinite with increasing weathering time.
Adsorption of methylene blue on sepiolite gels: spectroscopic and rheological studies
Authors: Aznar A. J. , Casal B. , Ruiz-Hitzky E. , Lopez-Arbeloa I. , Lopez-Arbeloa F. , Santaren J. , Alvarez A.
Published: November 2006

The adsorption isotherm of methylene blue (MB) on sepiolite gels is of the Langmuir type, indicating a great affinity of the MB towards the sepiolite; the adsorption is quantitative up to adsorption of MB of 0·1 mmol/g sepiolite. The differences observed in the absorption spectrum in the region 500–650 nm for different MB loadings are interpreted in terms of aggregation of MB molecules on the sepiolite surface with the formation of MB dimers, trimers and higher aggregates. The progressive coverage of the sepiolite surface by MB produces a sharp decrease in the viscosity of the gels, and the suspension becomes peptized for an MB loading of 0·21 mmol/g which corresponds to the adsorption of MB dimers. These results indicate that MB avoids particle-to-particle interactions. The viscosity decrease is parallel to the perturbation of the Si-OH groups on the sepiolite surface as observed by IR spectroscopy, suggesting that these silanol groups can also play an important role in the rheological behaviour of aqueous sepiolite dispersions.
The conversion of montmorillonite to interstratified halloysite-smectite by weathering in the Omi acid clay deposit, Japan
Authors: Watanabe T. , Sawada Y. , Russell J. D. , McHardy W. J. , Wilson M. J.
Published: November 2006

The weathering of montmorillonite in the acid clay deposit at Itoigawa, Japan has been investigated by X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). In the lower, least weathered part of the deposit, weathering has occurred by the formation of minor amounts of halloysite with concomitant precipitation of a silica phase identified as opal C-T. A relatively rapid transition occurs to the most weathered, upper part of the deposit where the mineralogy is dominated by interstratified halloysite-smectite. Computer simulations of XRD profiles indicate that the interstratified arrangement is random with a probable composition of 70% halloysite and 30% smectite, a composition supported by the 75–85% and 15–25% of the phases, respectively, calculated from the IR spectra.
Weathering of biotite to vermiculite in Quaternary lahars from Monti Ernici, Central Italy
Authors: Pozzuoli A. , Vila E. , Franco E. , Ruiz-Amil A. , De La Calle C.
Published: November 2006

The weathering of biotite in Quaternary lahars from Monti Ernici (Central Italy) via interstratification stages has been studied by X-ray diffraction of both the interstratified minerals and the initial (biotite) and final (vermiculite) end-members. The structure of the biotite and vermiculite is described by means of monodimensional Fourier series. The interstratified phases have been studied using the INTER program which permits an analysis of two interstratified components by Fourier transform methods. It is shown that in the alteration range for biotite to vermiculite even small samples have different spatial concentrations of biotite, vermiculite and an intermediate biotite-vermiculite-type phase. Hydrobiotite and a rare biotite-hydrobiotite with a tendency to regularity have also been documented. Chemically, the process involves considerable oxidation of Fe2+ and the removal of most of the elements, corresponding to a 34% loss in matter. The sequence of the element losses is: K+ > Fe2+ > F− > Mn2+ > Si4+ > Mg2+ > Al3+ > Ti4+. There are also some gains in the order: H+ > Ca2+ > Fe3+ > Na+.
Volcanoclastic minerals of some Czechoslovakian tonsteins and their alteration
Authors: Weiss Z. , Baronnet A. , Chmielova M.
Published: November 2006

In the Czechoslovak part of the Upper Silesian Coal Basin (Ostrava-Karvina Coal Basin), only part of the Upper Carboniferous (Namurian A, B, C and Westphalian A) is well developed, and tonsteins, which are clayey rocks or claystones, occur as thin, clayey interlayers in the coal seams. Two types of primary volcanic mineral assemblages were identified in four tonstein samples from different coal seams; the first type is characterized by the presence of biotite and sanidine, and the second by the presence of biotite, bytownite and Ca-amphibole. All tonsteins studied contained kaolinite minerals, volcanic quartz grains, crystals of zircon and apatite. Separated biotite flakes with an admixture of kaolinite layers were identified as 1M polytype. The flakes without kaolinite minerals were identified as epitactic overgrowth of 1M and complex polytypes, and twinned crystals of 2M1 polytype. Kaolinization of biotite flakes was observed in all tonstein samples studied. Kaolinite single layers (7 Å) as well as two-layer polytype of kaolinite minerals (14 Å) sandwiched between biotite layers (10 Å) were identified by HRTEM imaging.
Allophane in weathered zones of barite ore deposits (Vide de Alba and San Blas, Zamora, Spain): mineralogy and genesis
Authors: Perez del Villar L. , Moro M. C. , Cembranos M. L.
Published: November 2006

The allophane studied occurs in the weathered zones of the barite-sulphide-bearing dolomitic levels, interbedded in the barite ore deposits of Vide de Alba and San Bias (Province of Zamora). These ore deposits are interstratified in the Silurian-Devonian sulphide bearing volcano sedimentary materials of the Alcañices Synform. The allophanic samples have been studied by polarizing microscopy, SEM, XRD, DTA, TG, IRS, EMA and chemical analyses, the last after dissolving the samples by acid (HF + HNO3 + 3HCl + H3BO3) and alkaline digestion (0·5 m NaOH). It is suggested that allophane originates from the reaction of acid solutions released during the weathering of sulphides with acid volcanoclastic rocks. Silica-alumina gels were deposited in holes formed during earlier dissolution of the dolomite associated with the barite ores. Later processes of desilication partially transform allophane to gibbsite.
Aluminium activity in soil solution and mineral stability in soils from Galicia (NW Spain)
Authors: Calvo R. , Alvarez E.
Published: November 2006

Solutions obtained from soils in the Galicia Region of NW Spain had considerably lower activities of Al3+ when obtained by a speciation procedure (fractionation with an ionic column and application of specific software) than when obtained from concentrations of reactive Al (colorimetry with pyrocatechol violet) by a calculation that only considers simple hydroxylated species. Using the speciation method, many of the solutions obtained from surface horizons are unsaturated for most minerals, especially in granitic areas.
Illite-smectite from the North Sea investigated by scanning tunnelling microscopy
Authors: Lindgreen H. , Garnaes J. , Besenbacher F. , Laegsgaard E. , Stensgaard I.
Published: November 2006

Two samples of illite-smectite (I-S) isolated from Upper Jurassic clays in well 2/7-3 (3365 m) and well 2/11-1 (4548 m) have been investigated by scanning tunnelling microscopy (STM), and the particle shape and dimensions have been correlated to results from transmission electron microscopy (TEM) on shadowed specimens and results from atomic-force microscopy (AFM). By STM, lath-like and equant particles were observed in both samples, some of the particles having sharp edges. In the I-S from well 2/11-1, spiral-shaped particles were also seen. For both samples, the most frequent particle diameter was 100–200 Å. Particle-thickness distributions from STM and TEM were similar for the I-S from well 2/7-3, being dominated by 10 Å thick particles. For I-S from 2/11-1, the STM particle-thickness distribution has a predominance of 20 Å thick particles, but the TEM particle-thickness distribution is broad, with about equal amounts of 20, 30, 40, 50 and 60 Å thick particles. The AFM particle-thickness distribution for this I-S resembles the TEM thickness distribution. It is concluded that mainly thin (10 and 20 Å) particles are seen by STM. Failure of AFM to show sharp particle edges (seen in STM and TEM) might be attributed to the AFM tip movement or tip shape. In STM, I-S particles from well 2/7-3 have peaks along edges, whereas I-S particles from well 2/11-1 have rims. These rims are also seen in AFM and are therefore real geometrical features, probably a result of two-dimensional growth, whereas the spirals in the I-S from well 2/11-1 demonstrate three-dimensional growth. The minimum thickness of most particles is 10 Å.
Electron spin resonance study of donor-acceptor sites in Zr-montmorillonite
Authors: Zanchetta J. V. , Matrod-Bashi A. , Figueras F.
Published: November 2006

The charge transfer process that occurs in two samples of Wyoming montmorillonite of different grain size pillared with Zr by interaction with perylene (Pe) and tetracyanoethylene (TCNE) has been studied. These smectites are strongly affected by the exchange of Zr and appear to be strong electron acceptors and weak donors. The ESR results show that their ability to form charge transfer radicals is related to the details of preparation, which most probably control the accessibility of Pe and TCNE to the internal surface.
Use of bentonite for isolation of radioactive waste products
Authors: Pusch R.
Published: November 2006

Sodium smectite clay, commercially available in the form of bentonite powder, serves as a very effective water flow barrier and cation exchanger. At bulk densities between 1·9 and 2·2 g/cm3 after water uptake to reach complete saturation, the hydraulic conductivity is of the order of 10−14 to 10−13 m/s. The swelling potential produces a tight contact with confining structures, which makes bentonite ideal as overpack of rock-deposited radioactive canisters and for borehole and shaft sealing. At bulk densities between 1·1 and 1·3 g/cm3, the hydraulic conductivity of smectite gels is still sufficiently low to make them useful as effective grouts for sealing rock fractures. The longevity in a granite environment is very significant and the ultimate transformation residue—hydrous mica (“illite”)—preserves some of the excellent sealing properties of smectites.
Possible confusion between so-called ferrihydrites and hisingerites
Authors: Farmer V. C.
Published: November 2006

The term ferrihydrite, originally defined as a poorly ordered hydrous ferric oxide exhibiting five or more distinctive X-ray diffraction maxima, has come to be extended to include species that exhibit only 4, 3 or 2 of these maxima. It is pointed out here that hisingerites may exhibit a similar 2-line diffraction pattern. The laboratory synthesis of hisingerites show that they can form under soil conditions. Acid oxalate buffer of pH 3, a reagent considered a fairly specific solvent for ferrihydrite, extracts the iron content of these synthetic hisingerites quantitatively.
The effect of dry heating on the chemistry, surface area, and oxalate solubility of synthetic 2-line and 6-line ferrihydrites
Authors: Stanjek H. , Weidler P. G.
Published: November 2006

Synthetic 2-line and 6-line ferrihydrites were heated to 400 K, 500 K and 600 K, under dry conditions. Heating to 400 K lowered the ratios of structural OH to Fe2O3 without a phase transformation. The lowest ratios observed at 400 K were 1·23 (2-line) and 0·85 (6-line ferrihydrite) after 1150 h. For 6-line ferrihydrites heated to 400 K, the solubility in oxalate and the BET surface areas decreased with increasing heating time, whereas the unit-cell parameters, the relative peak intensities and the mean coherence lengths did not change significantly. Heating the 2-line ferrihydrites to 400 K produced microporosity.