bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of Potent Antiretroviral Therapy on Progression of Human Immunodeficiency Virus: Bayesian Modelling and Model Checking via Counterfactual Replicates
Authors: Berzuini Carlo , Allemani Claudia
Published: September 2004

We analyse data from a seroincident cohort of 457 homosexual men who were infected with the human immunodeficiency virus, followed within the multicentre Italian Seroconversion Study. These data include onset times to acquired immune deficiency syndrome (AIDS), longitudinal measurements of CD4+ T-cell counts taken on each subject during the AIDS-free period of observation and the period of administration of a highly active antiretro- viral therapy (HAART), for the subset of individuals who received it. The aim of the study is to assess the effect of HAART on the course of the disease. We analyse the data by a Bayesian model in which the sequence of longitudinal CD4+ cell count observations and the associated time to AIDS are jointly modelled at an individual subject’s level as depending on the treatment. We discuss the inferences obtained about the efficacy of HAART, as well as modelling and computation difficulties that were encountered in the analysis. These latter motivate a model criticism stage of the analysis, in which the model specification of CD4+ cell count progression and of the effect of treatment are checked. Our approach to model criticism is based on the notion of a counterfactual replicate data set Zc. This is a data set with the same shape and size as the observed data, which we might have observed by rerunning the study in exactly the same conditions as the actual study if the treated patients had not been treated at all. We draw samples of Zc from a null model M0, which assumes absence of treatment effect, conditioning on data collected in each subject before initiation of treatment. Model checking is performed by comparing the observed data with a set of samples of Zc drawn from M0.
An Experimental Study on Particular Physical Properties of Several Interocclusal Recording Media. Part II: Linear Dimensional Change and Accompanying Weight Change
Authors: Michalakis Konstantinos X. , Pissiotis Argiris , Anastasiadou Vassiliki , Kapari Danai
Published: September 2004

Purpose: The purpose of this study was to evaluate the linear dimensional change and accompanying weight change of several elastomeric interocclusal recording media.

Materials and Methods: Ten 50 mm long, 8 mm wide, 3 mm deep Teflon molds and a stainless steel die were constructed for the purposes of this study. The die was made in order to produce standardized reference lines, which were used for the measurement of the linear change. After homogeneous mixing, each material was carried from the mixing pad or directly from the mixing tip to the Teflon mold. The mold was inverted onto the stainless steel die. The materials were allowed to set for the manufacturers' suggested setting time plus an additional 3 minutes to ensure polymerization of the material. An electronic scale (Galaxy 110, Ohaus, Pine Brook, NJ) was used for the measurement of the weight change of the specimens and a traveling micrometer microscope (Griffin Ltd., London, England) was used to measure the linear changes at 5 time intervals: 0, 1 hour, 24, 48, and 72 hours.

Results: Analysis of variance for a significance level of 5% revealed that there was a statistically significant effect of the “material” factor on the weight changes (F= 2229.98, p < 0.0005). There was also a statistically significant effect of the “time” factor on the weight changes (F= 2,332.04, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference Test revealed that the elastomeric material with the greatest weight changes is polyether (Ramitec).

Analysis of variance for a significance level of 5% revealed that there is a statistically significant effect of the “material” factor on the linear changes (F= 215.54, p < 0.0005). There is also a statistically significant effect of the “time” factor on the linear changes (F= 1,996.01, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference test revealed that the elastomeric material with the smallest linear changes is polyether (Ramitec).

Conclusions: Of all materials tested, Ramitec (polyether) presented the smallest linear change at all time intervals. Addition reaction silicones presented statistically significant differences in recordings of linear changes among them only at the 1st and the 24th hour. Linear changes did not seem to be associated with weight changes.
Forecast Dispersion and the Cross Section of Expected Returns
Authors: JOHNSON TIMOTHY C.
Published: September 2004

Recent work by Diether, Malloy, and Scherbina (2002) has established a negative relationship between stock returns and the dispersion of analysts' earnings forecasts. I offer a simple explanation for this phenomenon based on the interpretation of dispersion as a proxy for unpriced information risk arising when asset values are unobservable. The relationship then follows from a general options‐pricing result: For a levered firm, expected returns should always decrease with the level of idiosyncratic asset risk. This story is formalized with a straightforward model. Reasonable parameter values produce large effects, and the theory's main empirical prediction is supported in cross‐sectional tests.
The 52‐Week High and Momentum Investing
Authors: GEORGE THOMAS J. , HWANG CHUAN‐YANG
Published: September 2004

When coupled with a stock's current price, a readily available piece of information—the 52‐week high price–explains a large portion of the profits from momentum investing. Nearness to the 52‐week high dominates and improves upon the forecasting power of past returns (both individual and industry returns) for future returns. Future returns forecast using the 52‐week high do not reverse in the long run. These results indicate that short‐term momentum and long‐term reversals are largely separate phenomena, which presents a challenge to current theory that models these aspects of security returns as integrated components of the market's response to news.
Bond Insurance: What Is Special About Munis?
Authors: NANDA VIKRAM , SINGH RAJDEEP
Published: September 2004

Close to 50% of municipal bonds are prepackaged with insurance at the time of issue. We offer a tax‐based rationale for the emergence of third‐party insurance of tax‐exempt bonds. We argue that insurance adds value as it allows a third party to become, in a probabilistic sense, an issuer of tax‐exempt securities. Insurance however reduces value by eliminating the possibility of a capital tax loss. While the net benefit from insurance increases with bond maturity, the benefit may not increase monotonically with default risk. We also provide empirical evidence supportive of the model's predictions.
Evidence‐Based Practice and Research Utilization Activities Among Rural Nurses
Authors: Olade Rosaline A.
Published: September 2004

Purpose

: To identify the extent to which rural nurses utilize evidence‐based practice guidelines from scientific research in their practice; to describe both previous and current research utilization activities in which they have participated, and to identify the specific barriers they face in their practice settings.

Design and Methods

: Data for this descriptive study were collected through questionnaires with open‐ended questions focused on (a) current utilization of nursing research findings, (b) previous involvement in nursing research activities, and (c) participation in medical research activities. The participants were 106 nurses from various practice areas in six rural counties of a southwestern state in the United States.

Findings

: Results revealed that only 20.8% of the participants stated they were currently involved in research utilization, and they were mostly nurses with bachelor's degrees. The two most common areas of current research utilization were pain management and pressure ulcer prevention and management. Barriers to research utilization, such as rural isolation and lack of nursing research consultants, were identified.

Conclusions

: The types of research utilization activities identified by these nurses indicate how much the facilities in which these nurses work in the rural areas are striving with the utilization of available scientific evidence. Rural nurses face unique barriers related to situational and geographic factors, with implications for nursing administrators, researchers, and educators.
Molecular Shaping of the Beak
Authors: Wu Ping , Jiang Ting-Xin , Suksaweang Sanong , Widelitz Randall Bruce , Chuong Cheng-Ming
Published: September 2004

Beak shape is a classic example of evolutionary diversification. Beak development in chicken and duck was used to examine morphological variations among avian species. There is only one proliferative zone in the frontonasal mass of chickens, but two in ducks. These growth zones are associated with bone morphogenetic protein 4 (BMP4) activity. By “tinkering” with BMP4 in beak prominences, the shapes of the chicken beak can be modulated.
A Small Molecule Smac Mimic Potentiates TRAIL- and TNFα-Mediated Cell Death
Authors: Li Lin , Thomas Ranny Mathew , Suzuki Hidetaka , De Brabander Jef K. , Wang Xiaodong , Harran Patrick G.
Published: September 2004

We describe the synthesis and properties of a small molecule mimic of Smac, a pro-apoptotic protein that functions by relieving inhibitor-of-apoptosis protein (IAP)–mediated suppression of caspase activity. The compound binds to X chromosome– encoded IAP (XIAP), cellular IAP 1 (cIAP-1), and cellular IAP 2 (cIAP-2) and synergizes with both tumor necrosis factor α (TNFα) and TNF-related apoptosis-inducing ligand (TRAIL) to potently induce caspase activation and apoptosis in human cancer cells. The molecule has allowed a temporal, unbiased evaluation of the roles that IAP proteins play during signaling from TRAIL and TNF receptors. The compound is also a lead structure for the development of IAP antagonists potentially useful as therapy for cancer and inflammatory diseases.
Activation of Apoptosis in Vivo by a Hydrocarbon-Stapled BH3 Helix
Authors: Walensky Loren D. , Kung Andrew L. , Escher Iris , Malia Thomas J. , Barbuto Scott , Wright Renee D. , Wagner Gerhard , Verdine Gregory L. , Korsmeyer Stanley J.
Published: September 2004

BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2 members is a prominent mechanism of control and is mediated through the amphipathic α-helical BH3 segment, an essential death domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties. The stapled peptides, called “stabilized alpha-helix of BCL-2 domains” (SAHBs), proved to be helical, protease-resistant, and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for experimental and therapeutic modulation of protein-protein interactions in many signaling pathways.
Assessment of Production Conditions for Efficient Use ofEscherichia coliin High-Yield Heterologous Recombinant Selenoprotein Synthesis
Authors: Rengby Olle , Johansson Linda , Carlson Lars A. , Serini Elena , Vlamis-Gardikas Alexios , Kårsnäs Per , Arnér Elias S. J.
Published: September 2004

The production of heterologous selenoproteins inEscherichia colinecessitates the design of a secondary structure in the mRNA forming a selenocysteine insertion sequence (SECIS) element compatible with SelB, the elongation factor for selenocysteine insertion at a predefined UGA codon. SelB competes with release factor 2 (RF2) catalyzing translational termination at UGA. Stoichiometry between mRNA, the SelB elongation factor, and RF2 is thereby important, whereas other expression conditions affecting the yield of recombinant selenoproteins have been poorly assessed. Here we expressed the rat selenoprotein thioredoxin reductase, with titrated levels of the selenoprotein mRNA under diverse growth conditions, with or without cotransformation of the accessory bacterialselA,selB, andselCgenes. Titration of the selenoprotein mRNA with a pBAD promoter was performed in both TOP10 and BW27783 cells, which unexpectedly could not improve yield or specific activity compared to that achieved in our prior studies. Guided by principal component analysis, we instead discovered that the most efficient bacterial selenoprotein production conditions were obtained with the high-transcription T7lac-driven pET vector system in presence of theselA,selB, andselCgenes, with induction of production at late exponential phase. About 40 mg of rat thioredoxin reductase with 50% selenocysteine content could thereby be produced per liter bacterial culture. These findings clearly illustrate the ability ofE. colito upregulate the selenocysteine incorporation machinery on demand and that this is furthermore strongly augmented in late exponential phase. This study also demonstrates thatE. colican indeed be utilized as cell factories for highly efficient production of heterologous selenoproteins such as rat thioredoxin reductase.
Integration of Microbial Ecology and Statistics: a Test To Compare Gene Libraries
Authors: Schloss Patrick D. , Larget Bret R. , Handelsman Jo
Published: September 2004

Libraries of 16S rRNA genes provide insight into the membership of microbial communities. Statistical methods help to determine whether differences in library composition are artifacts of sampling or are due to underlying differences in the communities from which they are derived. To contribute to a growing statistical framework for comparing 16S rRNA libraries, we present a computer program, ∫-LIBSHUFF, which calculates the integral form of the Cramér-von Mises statistic. This implementation builds upon the LIBSHUFF program, which uses an approximation of the statistic and makes a number of modifications that improve precision and accuracy. Once ∫-LIBSHUFF calculates thePvalues, when pairwise comparisons are tested at the 0.05 level, the probability of falsely identifying a significantPvalue is 0.098 for a study with two libraries, 0.265 for three libraries, and 0.460 for four libraries. The potential negative effects of making the multiple pairwise comparisons necessitate correcting for the increased likelihood that differences between treatments are due to chance and do not reflect biological differences. Using ∫-LIBSHUFF, we found that previously published 16S rRNA gene libraries constructed from Scottish and Wisconsin soils contained different bacterial lineages. We also analyzed the published libraries constructed for the zebrafish gut microflora and found statistically significant changes in the community during development of the host. These analyses illustrate the power of ∫-LIBSHUFF to detect differences between communities, providing the basis for ecological inference about the association of soil productivity or host gene expression and microbial community composition.
Large-Scale Population Structure of Human Commensal
Escherichia coli
Isolates
Authors: Escobar-Páramo Patricia , Grenet Karine , Le Menac'h Arnaud , Rode Luc , Salgado Emmanuelle , Amorin Christine , Gouriou Stéphanie , Picard Bertrand , Rahimy Mohamed Chérif , Andremont Antoine , Denamur Erick , Ruimy Raymond
Published: September 2004

The study of several
Escherichia coli
intestinal commensal isolates per individual in 265 healthy human subjects belonging to seven populations distributed worldwide showed that the
E. coli
population is highly structured, with major differences between the tropical and temperate populations.
Effects of acute creatine kinase inhibition on metabolism and tension development in isolated single myocytes
Authors: Kindig Casey A. , Howlett Richard A. , Stary Creed M. , Walsh Brandon , Hogan Michael C.
Published: August 2004

This study investigated the effects of acute creatine kinase (CK) inhibition (CKi) on contractile performance, cytosolic Ca2+concentration ([Ca2+]c), and intracellular Po2(Pi[Formula: see text]) in Xenopus laevis isolated myocytes during a 2-min bout of isometric tetanic contractions (0.33-Hz frequency). Peak tension was similar between trials during the first contraction but was significantly ( P < 0.05) attenuated for all subsequent contractions in CKivs. control (Con). The fall in Pi[Formula: see text](ΔPi[Formula: see text]) from resting values was significantly greater in Con (26.0 ± 2.2 Torr) compared with CKi(17.8 ± 1.8 Torr). However, the ratios of Con to CKiend-peak tension (1.53 ± 0.11) and ΔPi[Formula: see text](1.49 ± 0.11) were similar, suggesting an unaltered aerobic cost of contractions. Additionally, the mean response time (MRT) of ΔPi[Formula: see text]was significantly faster in CKivs. Con during both the onset (31.8 ± 5.5 vs. 49.3 ± 5.7 s; P < 0.05) and cessation (21.2 ± 4.1 vs. 68.0 ± 3.2 s; P < 0.001) of contractions. These data demonstrate that initial phosphocreatine hydrolysis in single skeletal muscle fibers is crucial for maintenance of sarcoplasmic reticulum Ca2+release and peak tension during a bout of repetitive tetanic contractions. Furthermore, as Pi[Formula: see text]fell more rapidly at contraction onset in CKicompared with Con, these data suggest that CK activity temporally buffers the initial ATP-to-ADP concentration ratio at the transition to an augmented energetic demand, thereby slowing the initial mitochondrial activation by mitigating the energetic control signal (i.e., ADP concentration, phosphorylation potential, etc.) between sites of ATP supply and demand.
A high-fat, refined-carbohydrate diet induces endothelial dysfunction and oxidant/antioxidant imbalance and depresses NOS protein expression
Authors: Roberts Christian K. , Barnard R. James , Sindhu Ram K. , Jurczak Michael , Ehdaie Ashkan , Vaziri Nosratola D.
Published: August 2004

We tested whether consumption of a high-fat, high-sucrose (HFS) diet can affect endothelium-dependent relaxation, whether this precedes the development of diet-induced hypertension previously noted in this model, and whether it is mediated, in part, by changes in nitric oxide synthase (NOS) and/or NOS regulatory proteins. Female Fischer rats were fed either a HFS diet or standard low-fat, complex-carbohydrate chow starting at 2 mo of age for 7 mo. Vasoconstrictive response to KCl and phenylephrine was similar in both groups. Vasorelaxation to acetylcholine was significantly impaired in the HFS animals, and there were no differences in relaxation to sodium nitroprusside, suggesting that the endothelial dysfunction is due, at least in part, to nitric oxide deficiency. HFS consumption decreased protein expression of endothelial NOS in aorta, renal, and heart tissues, neuronal NOS in kidney, heart, aorta, and brain, and inducible NOS in heart and aorta. Caveolin-1 and soluble guanylate cyclase protein expression did not change, but AKT protein expression decreased in heart and aorta and increased in kidney tissue. Consumption of HFS diet raised brain carbonyl content and plasma hydrogen peroxide concentration and diminished plasma total antioxidant capacity. Because blood pressure, which is known to eventually rise in this model, was not as yet significantly elevated, the present data suggest that endothelial dysfunction precedes the onset of diet-induced hypertension. The lack of a quantitative change in caveolin-1 and soluble guanylate cyclase protein content indicates that alteration in these proteins is not responsible for the endothelial dysfunction. Thus nitric oxide deficiency combined with antioxidant/oxidant imbalance, appears to be a primary factor in the development of endothelial dysfunction in this model.
Active and passive components in the length-dependent stiffness of tracheal smooth muscle during isotonic shortening
Authors: Meiss Richard A. , Pidaparti Ramana M.
Published: August 2004

Contraction of smooth muscle tissue involves interactions between active and passive structures within the cells and in the extracellular matrix. This study focused on a defined mechanical behavior (shortening-dependent stiffness) of canine tracheal smooth muscle tissues to evaluate active and passive contributions to tissue behavior. Two approaches were used. In one, mechanical measurements were made over a range of temperatures to identify those functions whose temperature sensitivity (Q10) identified them as either active or passive. Isotonic shortening velocity and rate of isometric force development had high Q10 values (2.54 and 2.13, respectively); isometric stiffness showed Q10 values near unity. The shape of the curve relating stiffness to isotonic shortening lengths was unchanged by temperature. In the other approach, muscle contractility was reduced by applying a sudden shortening step during the rise of isometric tension. Control contractions began with the muscle at the stepped length so that properties were measured over comparable length ranges. Under isometric conditions, redeveloped isometric force was reduced, but the ratio between force and stiffness did not change. Under isotonic conditions beginning during force redevelopment at the stepped length, initial shortening velocity and the extent of shortening were reduced, whereas the rate of relaxation was increased. The shape of the curve relating stiffness to isotonic shortening lengths was unchanged, despite the step-induced changes in muscle contractility. Both sets of findings were analyzed in the context of a quasi-structural model describing the shortening-dependent stiffness of lightly loaded tracheal muscle strips.
Changes in inorganic phosphate and force production in human skeletal muscle after cast immobilization
Authors: Pathare Neeti , Walter Glenn A. , Stevens Jennifer E. , Yang Zhaohui , Okerke Enyi , Gibbs John D. , Esterhai John L. , Scarborough Mark T. , Gibbs C. Parker , Sweeney H. Lee , Vandenborne Krista
Published: August 2004

Cast immobilization is associated with decreases in muscle contractile area, specific force, and functional ability. The pathophysiological processes underlying the loss of specific force production as well as the role of metabolic alterations are not well understood. The aim of this study was to quantify changes in the resting energy-rich phosphate content and specific force production after immobilization.31P-magnetic resonance spectroscopy, three-dimensional magnetic resonance imaging, and isometric strength testing were performed in healthy subjects and patients with an ankle fracture after 7 wk of immobilization and during rehabilitation. Muscle biopsies were obtained in a subset of patients. After immobilization, there was a significant decrease in the specific plantar flexor torque and a significant increase in the inorganic phosphate (Pi) concentration ( P < 0.001) and the Pi-to-phosphocreatine (PCr) ratio ( P < 0.001). No significant change in the PCr content or basal pH was noted. During rehabilitation, both the Picontent and the Pi-to-PCr ratio decreased and specific torque increased, approaching control values after 10 wk of rehabilitation. Regression analysis showed an inverse relationship between the in vivo Piconcentration and specific torque ( r = 0.65, P < 0.01). In vitro force mechanics performed on skinned human muscle fibers demonstrated that varying the Pilevels within the ranges observed across individuals in vivo (4–10 mM) changed force production by ∼16%. In summary, our findings clearly depict a change in the resting energy-rich phosphate content of skeletal muscle with immobilization, which may negatively impact its force generation.
Inspiratory flow in the nose: a model coupling flow and vasoerectile tissue distensibility
Authors: Fodil Redouane , Brugel-Ribere Lydia , Croce Céline , Sbirlea-Apiou Gabriela , Larger Christian , Papon Jean-François , Delclaux Christophe , Coste André , Isabey Daniel , Louis Bruno
Published: August 2004

We have developed a discrete multisegmental model describing the coupling between inspiratory flow and nasal wall distensibility. This model is composed of 14 individualized compliant elements, each with its own relationship between cross-sectional area and transmural pressure. Conceptually, this model is based on flow limitation induced by the narrowing of duct due to collapsing pressure. For a given inspiratory pressure and for a given compliance distribution, this model predicts the area profile and inspiratory flow. Acoustic rhinometry and posterior rhinomanometry were used to determine the initial geometric area and mechanical characteristics of each element. The proposed model, used under steady-state conditions, is able to simulate the pressure-flow relationship observed in vivo under normal conditions (4 subjects) and under pathological conditions (4 vasomotor rhinitis and 3 valve syndrome subjects). Our results suggest that nasal wall compliance is an essential parameter to understand the nasal inspiratory flow limitation phenomenon and the associated increase of resistance that is well known to physiologists. By predicting the functional pressure-flow relationship, this model could be a useful tool for the clinician to evaluate the potential effects of treatments.
Inducible Mouse Models for Inherited Skin Diseases: Implications for Skin Gene Therapy
Authors: Arin Meral J. , Roop Dennis R.
Published: September 2004

Stem cells are crucial for the formation and maintenance of tissues and organs. To understand the role of stem cells in the pathogenesis of mosaic skin disorders, we generated inducible mouse models for two autosomal dominant keratin disorders, epidermolytic hyperkeratosis (EHK) and epidermolysis bullosa simplex (EBS), that enable activation of the respective mutation in epidermal stem cells in a spatially and temporally controlled manner using a ligand-inducible Cre recombinase. Whereas mosaic forms have been reported for EHK, which is caused by mutations in the suprabasal keratins K1 or K10, this has never been reported for EBS, which is due to mutations in the basal keratins K5 or K14. When we induced the phenotype in these models by topical application of the inducer, we found phenotypic areas in the EHK model that persisted for the life of the mouse. On the contrary, the induced blisters in the EBS model healed within a few weeks by migration of surrounding non-phenotypic stem cells into the wound bed. Our results indicate that lack of selective pressure against certain mutations in epidermal stem cells could explain why mosaic forms exist for EHK, but not for EBS. These findings have important implications for the development of new strategies for somatic gene therapy of dominant genodermatoses, and we are currently using these inducible mouse models to test gene therapy approaches.
Randomized Comparison of Burch Urethropexy Procedures Concomitant with Gynecologic Operations
Authors: Üstün Yusuf , Engin-Üstün Yaprak , Güngör Mete , Tezcan Sevgi
Published: September 2004

Objective: We compared the success of laparoscopic Burch colposuspension with the laparotomic Burch colposuspension for the treatment of genuine stress incontinence (GSI) concomitant with gynecologic operations. Materials and Methods: Fifty-two women with symptoms of GSI, also requiring additional gynecologic operations, were randomly assigned to undergo laparoscopic (n = 26) or laparotomic (n = 26) Burch colposuspension. For all patients complete histories were taken and physical examination, urinalysis, urine culture, multi-channel urodynamics with cystometry, uroflowmetry, and measurement of Valsalva leak-point pressure were performed. Variables analyzed included: age, surgical time, length of catheterization, number of days in hospital, and complications. Results: Both groups were similar in age, parity and menopausal status. Valsalva leak-point pressure significantly increased in the laparoscopy group after the operation. There were no statistical differences in other urodynamics in both groups. The mean operating time in the laparoscopy group was longer than in the laparotomy group. The laparoscopy group required a significantly shorter hospitalization and catheterization than the laparotomy group. The success and complication rates did not differ significantly for both groups. Conclusion: The laparoscopic approach for the treatment of GSI in patients requiring additional gynecologic procedures is associated with a shorter duration of hospital stay compared with the abdominal approach.
Heart Valve Development
Authors: Armstrong Ehrin J. , Bischoff Joyce
Published: September 2004

During the past decade, single gene disruption in mice and large-scale mutagenesis screens in zebrafish have elucidated many fundamental genetic pathways that govern early heart patterning and differentiation. Specifically, a number of genes have been revealed serendipitously to play important and selective roles in cardiac valve development. These initially surprising results have now converged on a finite number of signaling pathways that regulate endothelial proliferation and differentiation in developing and postnatal heart valves. This review highlights the roles of the most well-established ligands and signaling pathways, including VEGF, NFATc1, Notch, Wnt/β-catenin, BMP/TGF-β, ErbB, and NF1/Ras. Based on the interactions among and relative timing of these pathways, a signaling network model for heart valve development is proposed.
Spatial Behavior in San Francisco’s Plazas
Authors: Zacharias John , Stathopoulos Ted , Wu Hanqing
Published: September 2004

This observational study of plaza-user behavior in San Francisco is intended first to determine whether behavior is invariant across different microclimatic regimes. Statistical behaviors in the present study are indistinguishable from those observed in a previous study, holding constant the microclimatic conditions in the two cases. Certain social behaviors are examined in relation to response to microclimatic conditions. The presence of smokers had no effect on the distribution of users and activities. However, when preferred environmental conditions were in limited supply, users accepted slightly higher levels of crowding in the preferred condition. When a threshold density of persons was reached, users opted for less ideal conditions, moving into the preferred condition when space became available. The provision of seating had no impact on use level, whereas a redesign to provide sheltered seating had a modest positive impact. In this study, environmental design had minor effects in relation to microclimate.
Legibility, Mystery, and Visual Access as Predictors of Preference and Perceived Danger in Forest Settings without Pathways
Authors: Herzog Thomas R. , Kropscott Laura S.
Published: September 2004

The authors attempt to address some unresolved issues within the Kaplans’ preference-matrix model of environmental preference. These issues involve the relation between legibility and preference and the relations among preference, danger, and mystery. Participants rated 70 within-forest settings containing no visible pathways for preference, danger, or one of seven predictor variables. Legibility and coherence were found to be independent, positive predictors of preference. Likewise, landmarks and visual access were independent positive predictors of legibility. Legibility fully mediated the positive relation between landmarks and preference. Visual access interacted with legibility in predicting preference: The relation between preference and either predictor was strongest and positive at low values of the other predictor. Preference and danger were negatively correlated, and there was some tendency for each of them to have a different pattern of relations with predictors. Mystery was negatively correlated with both preference and visual access, an unusual finding.
Transmission electron microscopy of hexadecyltrimethylammonium-exchanged smectite
Authors: Lee Seung Yeop , Kim Soo Jin
Published: August 2004

The morphological and structural changes in smectite caused by hexadecyltrimethylammonium (HDTMA) treatment were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The HDTMA-exchanged smectite shows not only morphological features such as irregular, wavy surface with curled edges, but also structural features such as larged-spacings (20 – 26 Å ) and lattice distortions. The surface morphological heterogeneity is assumed to be related to the inhomogeneous intercalation of HDTMA cations into the interlayer of smectite.
The effect of maturation upon the mineralogical and physicochemical properties of illitic-smectitic clays for pelotherapy
Authors: Sánchez C. J . , Parras J . , Carretero M. I .
Published: August 2004

Illitic-smectitic clays were matured with a ferruginous, bicarbonate-rich and sulphate-rich water for different periods of time (7, 15, 30, 60 and 90 days), and subjected to discontinuous stirring, to test their use in pelotherapy. A progressive degradation of the clay minerals was observed during the maturation process, with a reduction in the illite and smectite crystallinity, in the percentage of smectites and in the phyllosilicate content. The percentage of <2 μm particles also decreased. These modifications caused changes in the clays’ physicochemical properties, which are evident in an increase in their plasticity index and in slower cooling of the peloid, both of which improved the clays’ effect in pelotherapy.
Structural insights from the study of Cs-exchanged smectites submitted to wetting-and-drying cycles
Authors: Cuadros J .
Published: August 2004

Six smectites of different tetrahedral and octahedral compositions (SAz-1, Chambers, Belle Fourche, two subsamples of nontronite 33B and SWy-1) were Cs-exchanged and submitted to 70 wetting-and-drying cycles. X-ray diffraction (XRD) of oriented and glycolated mounts of the resultant material showed non-expandable layer proportions ranging from 15 to 60%. They were also analysed by powder XRD at 200°C in vacuum. These patterns showed that 15 – 40% of the layers were not rotated relative to each other and the rest were randomly rotated (no rotations of the 60°and 120°types). All layers had ad-spacing of 11 Å, corresponding to collapsed layers with Cs in the cavities created by the hexagonal rings of the tetrahedral sheets. Analysis of the number of cavities available in relation to the layer rotation shows that the rotation angle must be close to 30°or its multiples 90, 150, 210, 270 and 330°. X-ray diffraction and thermal analysis detected the same proportion ofcis-andtrans-vacant sites in the smectites. The idealbdimensions of the tetrahedral and octahedral sheets (the sheets are considered independently, without deformation) were calculated for the samples used in this work and for others from the literature, using the tetrahedral and octahedral compositions. These idealbdimensions have a strong positive correlation. Thecis/transvacant character of the smectites is related to the relative lateral dimensions of the ideal tetrahedral and octahedral sheets. A possible explanation of this fact is offered, in which the different configurations of hydroxyls and oxide ions incis- andtrans-vacant structures can affect octahedralsheet dimension.
Identification of halloysite (7 Å) by ethylene glycol solvation: the ‘MacEwan effect’
Authors: Hillier S. , Ryan P. C.
Published: August 2004

X-ray powder diffraction patterns of halloysite (7 Å) are characteristically altered following solvation with ethylene glycol. Some effect was first noted in the classic work of MacEwan but its value in the unequivocal identification of halloysite (7 Å ) seems to have been overlooked subsequently. The response to ethylene glycol solvation involves a decrease in the intensity (peak height) of the peak at ∼7.2 Å and an increase in the intensity (peak height) of the peak at ∼3.58 Å thus narrowing the 7.2 Å /3.58 Å peak height intensity ratio. For pure samples of halloysite, this ratio is narrowed by an average of ∼50%. This distinctive change is related to the interstratified nature of halloysite (7 Å), specifically the presence of ‘residual’ interlayer water, i.e. halloysite (10 Å), which can be replaced with ethylene glycol so forming 10.9 Å layers, a spacing that is almost exactly one and a half times the thickness of dehydrated (7.2 Å) layers which do not imbibe ethylene glycol. Thus the separation between the 001 peaks in the 7.2 Å /10.9 Å interstratification is increased and the 0027.2(3.58 Å) and 00310.9(3.63 Å) peaks become more or less coincident, compared to the 7.2 Å /10 Å interstratification, i.e. the partially hydrated state. The widespread use of ethylene glycol solvation in clay mineral studies makes it a particularly useful and simple test to determine the presence of halloysite. Pure halloysites should be readily identifiable and experiments indicate a ‘routine’ sensitivity of ∼20% halloysite in mixtures with kaolinite, although this will depend on factors such as ‘crystallinity’ and could be improved with careful attention to intensity measurements. It is proposed to call this phenomenon the ‘MacEwan effect’ in honour of its discoverer Douglas Maclean Clark MacEwan.
Tritium accumulation in structures of clay minerals
Authors: Kalinichenko E. A. , Pushkarova R. A. , Fenoll Hach-Alí P. , López-Galindo A.
Published: August 2004

Tritium accumulation in clay minerals (kaolinite, montmorillonite, palygorskite) was studied experimentally over a one year contact with tritiated water (initial activity 1.676x109 Bq/m3) under room conditions, and was compared to theoretical calculations. The amounts of tritium ions in bound water and structural hydroxyls were measured by the activity of water fractions released at characteristic temperatures determined on the basis of the mineral DTA patterns. Experiments showed that after a 400 day contact with tritiated water, tritium exchange rates (θ) were highest in palygorskite (θa = 0.42 in bound water and θs = 0.51 in the structure) compared to montmorillonite (θa = 0.15 and θs = 0.11, respectively) and kaolinite (θa = 0.34 and θs = 0.02, respectively). This could be due to different tritium concentrations in the solution near the bound-water layers, and also to certain features of the mineral structures, most of the kaolinite structural hydroxyls not interacting directly with bound HTO molecules.

Tritium accumulation in these minerals, under room conditions, can be described by a relatively simple two-stage isotope exchange model in which tritium ions first migrate from the solution to the bound layers and then substitute the protons of the structural hydroxyls. Rate constants for both stages of this isotope exchange were calculated on the basis of the experimental data.
Fe-rich smectites from Gafsa (Tunisia): characterization and pillaring behaviour
Authors: Letaïef S. , Casal B. , Kbir-ariguib N. , Trabelsi–Ayadi M. , Ruiz-hitzky E.
Published: August 2004

Three raw samples of Fe-rich smectites from Gafsa (Jebels Shemsi and Hammadi, Tunisia) have been characterized by different techniques which indicate that they contain (15 – 20%) illite, probably interstratified and to a lesser extent they also contain kaolinite, calcite, quartz and Fe oxides. These samples present a relatively high Fe content (∼9%) in the <2 μm fraction. From EPR and Mössbauer spectroscopy it is deduced that Fe is mainly present as Fe(III) in the octahedral environment of smectites and also in Fe-oxyhydroxides associated with the clays. Aluminium-pillared clays have been prepared from the Na+-purified samples, and their thermal stability and acidity have been studied.
Adsorption and discrimination of alanine and alanyl-alanine enantiomers by allophane
Authors: Hashizume H. , Theng B. K. G. , Yamagishi A.
Published: August 2004

We have investigated the adsorption of D- and L-alanine, and their respective dimers, by three allophanes with different Al/Si ratios. The Kanuma (Al/Si = 1.2) and Kitakami (Al/ Si = 1.5) allophanes were from Japan whereas the Te Kuiti (Al/Si = 1.6) sample came from New Zealand. The three allophanes differed in their capacity for adsorbing alanine but none of the samples showed a clear preference for either the D- or the L-form. In the case of alanyl-alanine both Kanuma and Kitakami allophanes gave a hint of preferring the L- to the D-enantiomer. On the other hand, the allophane sample from Te Kuiti showed a clear preference for L-alanyl-L-alanine. In keeping with this observation, circular dichroic spectrometry indicated that solutions of a racemic mixture of alanyl-alanine, after equilibration with Te Kuiti allophane, became relatively enriched in the Denantiomer. The size, intra-molecular charge separation, and surface orientation, of L-alanyl-Lalanine zwitterions apparently combine to confer ‘structural chirality’ to the complex (adduct) with Te Kuiti allophane. As a result, the mineral-organic complex develops a preference for the L-form of alanyl-alanine. This finding points to a possible role of certain allophanes in the origin of biochirality.
Synthetic allophane from highconcentration solutions: nanoengineering of the porous solid
Authors: Ohashi F. , Wada S.-I . , Suzuki M. , Maeda M. , Tomura S.
Published: August 2004

The amorphous aluminosilicate allophane was synthesized by rapid mixing of inorganic solutions with high initial concentrations (10 – 100 mmol/l) followed by hydrothermal treatment. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed homogeneous products having a hollow spherical amorphous structure with a particle diameter of 3 – 5 nm. The amorphous products had a high BET specific surface area (490 – 552 m2/g) in comparison with natural allophane and had a narrow pore-size distribution (2 – 5 nm in diameter). The results of water vapour adsorption isotherm studies showed a gradual increase over the range of relative water vapour pressure of 0.6 – 0.9 and reached a maximum of ∼85 wt.%. The synthetic allophane shows promise as an adsorbent material because of its high adsorption-desorption capacity and its unique structure.
Clay mineralogy and geochemistry of early Jurassic sedimentary rocks from the Moezian Platform, northern Bulgaria
Authors: Hrischeva E. , Gier S.
Published: August 2004

Clay minerals in early Jurassic sequences of shales, siltstones and sandstones deposited in non-marine, transitional and shallow marine environments have been examined by X-ray diffraction, electron microscopy and chemical analysis to study the relationship between clay minerals, their environment of deposition and subsequent diagenetic modifications.

The inherited clay mineral composition of the fine-grained sediments reflects the influence of climate, relief, source rocks and depositional processes. Inhomogeneous clay mineral assemblages, comprising abundant kaolinite and varying proportions of illite, I-S, chlorite and vermiculite, characterize fine-grained sediments from the non-marine and transitional environments. In shallow marine depositional environments clay mineral assemblages are more uniform, dominated by illite+I-S with minor kaolinite and chlorite.

The principal diagenetic process affecting fine-grained sedimentary rocks is the smectite–illite transformation. In sandstones, the authigenic formation of kaolinite, chlorite and illite appears to have been primarily determined by the environment of deposition.
Review of the mineralogy of the Cretaceous-Tertiary boundary clay: evidence supporting a major extraterrestrial catastrophic event
Authors: Ortega-Huertas M. , Martí Nez-Ruiz F. , Palomo I . , Chamley H.
Published: August 2004

The proposed impact event at the end of the Cretaceous resulted in mass extinctions and subsequently significant variations in the geochemical and mineralogical composition of the sediments marking the K/T boundary. The impact-generated material derived from target rocks produced the ejecta layer deposits around Chicxulub crater, which were subsequently diagenetically altered to mainly smectite in marine sections and to kaolinite in continental sections. The fireball layer represents the cosmic dust dispersed and deposited globally and contains smectite derived from the alteration of microkrystites and the finest fraction. The lowermost Danian clay layer, recognized in marine sections, resulted from the sudden decrease in ocean productivity and represents a reduced sedimentation deposit. Its clay mineral associations depend on local environmental conditions and diagenetic processes. Overall, the diagenetic alteration of the boundary materials resulted in a significant modification of original signatures. The composition of the clay mineral phases can, however, still be evidence of the nature of the precursor materials providing evidence for an extraterrestrial impact event.
The structure and diagenetic transformation of illite-smectite and chlorite-smectite from North Sea Cretaceous-Tertiary chalk
Authors: Lindgreen H. , Drits V. A. , Sakharov B. A. , Jakobsen H. J . , Salyn A. L. , Dainyak L. G. , Krøyer H.
Published: August 2004

Illite-smectite (I-S) mixed-layer minerals from North Sea oil fields and a Danish outcrop were investigated to determine the detailed structure and the diagenetic clay transformation. Clay layers in the chalk and residues obtained by dissolution of the chalk matrix at pH 5 were investigated. The phase compositions and layer sequences were determined by X-ray diffraction (XRD) including simulation with a multicomponent program. The structural formulae were determined from chemical analysis, infrared (IR) and27Al NMR spectroscopies and XRD, and the particle shape by atomic force microscopy (AFM). A high-smectitic (HS) I-S phase and a lowsmectitic (LS) illite-smectite-chlorite (I-S-Ch) phase, both dioctahedral, together constitute 80 – 90% of each sample. However, two samples contain significant amounts of tosudite and of Ch-Serpentine (Sr), respectively. Most of the clay layers have probably formed by dissolution of the chalk, but one Campanian and one Santonian clay layer in well Baron 2 may have a sedimentary origin. The HS and LS minerals are probably of detrital origin. Early diagenesis has taken place through a fixation of Mg in brucite interlayers in the LS phase, this solid-state process forming di-trioctahedral chlorite layers. During later diagenesis involving dissolution of the HS phase, neoformation of a tosudite or of a random mixed-layer trioctahedral chlorite-berthierine took place. In the tosudite, brucite-like sheets are regularly interstratified with smectite interlayers between dioctahedral 2:1 layers, resulting in ditrioctahedral chlorite layers.
Surface heterogeneity of kanemite, magadiite and kenyaite: a high-resolution gas adsorption study
Authors: Eypert-Blaison C. , Villiéras F. , Michot L. J . , Pelletier M. , Humbert B. , Ghanbaja J . , Yvon J .
Published: August 2004

The surface properties of various synthetic layered silicates, Na-kanemite, Nakenyaite and magadiite, exchanged with H, K and Ca, were examined using high-resolution nitrogen and argon adsorption and the data were treated using the Derivative Isotherm Summation method. Using argon as an adsorbate, the aspect ratio of platelets can be determined. In the case of magadiite exchanged with various cations, the stacking of particles is influenced by the nature of the exchangeable cations, thicker platelets being observed for ions with low polarizability. Highresolution argon adsorption data also confirm some structural information previously deduced from Raman spectroscopy experiments concerning the existence of rather open six-membered rings at the surfaces of both magadiite and kenyaite. Furthermore, in the low-energy domain of the isotherms, argon forms a very organized film on basal planes, suggesting a commensurate relationship between silica framework and argon atoms for both magadiite and kenyaite, contrary to what is observed for kanemite. Nitrogen adsorption results reveal the presence of polar sites on the surface of all the investigated minerals but does not allow us to propose an unequivocal assignment for such sites.