bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning and Exit Behavior of New Entrant Discount Airlines from City-Pair Markets
Authors: Dixit Ashutosh , Chintagunta Pradeep K.
Published: March 2007

In this research, the authors investigate firms' exit behaviors. On the basis of extant literature in economics, strategy, and marketing, the authors identify market- and firm-specific factors that influence exit behavior. They account for firms' uncertainty about a market's true attractiveness after entry on the probability of exiting a market. To evaluate exit decisions, they propose a Bayesian belief-updating model of learning embedded in a logit model that incorporates market- and firm-specific factors. The estimated evolution of beliefs over time enables the authors to determine whether firms use market information to update their prior beliefs about market attractiveness. The authors empirically investigate the market exits of new entrant discount airlines from city-pair markets. The results suggest that a combination of several market and firm factors influences exit behavior. Airlines' prior beliefs about market attractiveness are not necessarily consistent with the market's intrinsic attractiveness, and firms learn about the true market attractiveness over time. The authors also provide model comparisons with extant approaches to studying market exit and find that the proposed approach provides a better fit and predictive ability.
Profiting from Partial Allowance of Ticket Resale
Authors: Geng Xianjun , Wu Ruhai , Whinston Andrew B.
Published: March 2007

For a seller that markets event tickets both in advance and on spot, a concern is that ticket resale may hurt its profitability. The conventional wisdom is for the seller to consider completely banning resale if possible. This article considers an alternative strategy in which resale is only partially restricted; specifically, resale is banned on spot but still allowed in advance. Using a two-period model in which buyers have discreet valuations, the authors show that it is possible for partial resale to outperform no resale (and also unrestricted resale at the other extreme) in terms of seller profitability when the following conditions hold: when the seller has limited capacity, when the number of high-valuation buyers is small enough, and when the number of early arrivers is not too large. An implication of this research is that when consumers conduct advance and spot resale in different channels, such as advance resale online and spot resale offline, the seller may be better off adopting different resale policies for different channels.
The Entry Strategy of Retail Firms into Transition Economies
Authors: Gielens Katrijn , Dekimpe Marnik G.
Published: March 2007

International entries into transition economies occur infrequently and involve considerable uncertainty. This raises the question whether managers, who have limited own experience, take their competitors' prior decisions into account when deciding on their own entry timing and size and whether there is value in doing so. To address these questions, the authors estimate a sequential hazard/Poisson regression model on the top 75 European grocery retailers' decisions to enter the Eastern European market. Indeed, firms pay close attention to prevailing practices in their industry. Prior entries first serve as legitimation but eventually become a deterring factor. Moreover, rather than just imitating the most popular or modal decision when determining the own entry timing and size, managers pay closer attention to the actions of their home competitors, react to prior entries of same-format competitors differently from those of different-format competitors, and adjust the observed industry practice for the specificity of their own resources. The authors show that managers are justified in taking the combined industry wisdom into account; deviations from prevailing industry practice, in terms of both timing and size, hurt the efficiency of their operations in subsequent years. Thus, attempts to develop own, distinct entry rules tend to be dysfunctional. Moreover, corrective actions are easier to implement along the size than along the time dimension; the detrimental effects of entering at a different time from the industry norm persist and even become amplified over time, whereas the negative impact of size deviations is temporary.
Volume and Lipid, Fatty Acid, and Amino Acid Composition of Golden Shiner Eggs during a Spawning Season
Authors: Lochmann S E , Goodwin K J , Lochmann R T , Stone N M , Clemment T
Published: March 2007

The Arkansas baitfish industry leads the nation in production of golden shiners Notemigonus crysoleucas. To determine nutritional requirements for golden shiner broodstock diets, we examined the volume and lipid, fatty acid, and amino acid composition of the eggs produced by a group of captive broodstock over a spawning season. Egg volume was 0.67 ± 0.117 mm3 (mean ± SD); egg volume declined during the spawning season. Total lipid was 15.67 ± 2.99 μg/egg, and triacylglyceride (TAG) concentration was 6.82 ± 1.81 μg/egg. Based on the stability of egg total lipid, the percent neutral lipid, the consistent contribution of TAG to neutral lipid, the consistent TAG concentration, and the stable fatty acid and amino acid profiles, we conclude that the lipid and amino acids in eggs from the experimental group were stable. The eggs should be equally sufficient for embryological development throughout the spawning season, but specific indices of egg and fry quality must be measured to confirm the links among egg size, biochemical composition, and egg and fry quality.
Captive Survival and Pearl Culture Potential of the Pink Heelsplitter Potamilus alatus
Authors: Hua Dan , Neves Richard J
Published: March 2007

Pink heelsplitter mussels Potamilus alatus were held at two bottom locations and suspended in pocket nets in a pond at the Freshwater Mollusk Conservation Center, Virginia Polytechnic Institute and State University, for 1 year to evaluate survival in captivity. Survival after 1 year differed significantly; the poorest survival (30.0%) was at the bottom of the deep end (2.5 m), and there was no difference in survival) at the shallow end (83.3%; 0.6 m) and in pocket nets (63.3%; 1–1.5 m). Monthly survival was inversely related to water temperature (R = −0.72); the lowest monthly survival occurred in summer, resulting in a significant difference among the three locations. Differences in the mean glycogen content of mussels among the three containment locations and wild-sampled pink heelsplitter mussels were significant (P = 0.001); the highest value was in mussels at the shallow end and the lowest value was in mussels at the deep end. We used pocket nets to hold surgically implanted mussels and measured glycogen reserves to monitor body condition and assess the potential of the pink heelsplitter mussel to produce nonnucleated and image pearls. Results of the pearl culture experiment in two ponds showed that nonnucleated pearls and image pearls with purple or purplish luster were successfully produced. There was no significant difference in pearl weight in mussels held in the two experimental ponds under different environmental conditions. Similarly, no differences in monthly survival rates of mussels were observed in either pond or among mussels with surgical implants and the no-surgery control mussels. Therefore, pink heelsplitter mussels can be considered a potentially suitable species for producing purple pearls in farm pond environments.
Seasonal Variation of Sperm Quality and the Relationship between Spermatocrit and Sperm Concentration in Yamú Brycon amazonicus
Authors: Cruz-Casallas Pablo E , Medina-Robles Víctor M , Velasco-Santamaría Yohana M
Published: March 2007

Osmolality, the concentrations of glucose, total cholesterol, and triglyceride, and the concentrations of ions such as Na+, Cl−, K+, and Mg2+ in the seminal plasma of yamú Brycon amazonicus were evaluated during one reproductive season. Semen quality and the relationship between spermatocrit and sperm concentration were examined over two reproductive seasons. Activation time, spermatocrit, and sperm concentration were significantly higher in 2003 than in 2004. Spermatocrit and sperm concentration showed a significant positive relationship (r  2 = 0.79). During the 2004 reproductive season, a significant variation was observed for spermatocrit and sperm concentration between the initial period (February 15th to March 14th) and the middle and final periods (March 15th to April 14th and April 15th to May 14th, respectively). Neither the ion concentrations nor the glucose and cholesterol concentrations varied between any periods of the reproductive season. Osmolality and triglyceride concentrations showed significant variations between periods during the reproductive season.
The evolution of a river modelling system
Authors: Evans E. P. , Wicks J. M. , Whitlow C. D. , Ramsbottom D. M.
Published: March 2007

This paper describes the development of the ISIS river modelling system. Solution methods are outlined and examples are provided to demonstrate applications to which practising engineers have applied the software. It is commonplace in much applied research that projects must be directed towards satisfying user needs, and that their benefits must be demonstrable and measurable. This philosophy, however, places limits by its very nature on the imagination of the researcher. This is not to say that the researcher should ignore user needs but rather that a creative dialogue is needed between the innovative idea and its potential users, against a background of advances and cross-fertilisation by ideas from other spheres. It is hoped that, as well as describing the development of the software, the paper will illustrate this point.
Aeration efficiency with nappe flow over stepped cascades
Authors: Baylar A. , Bagatur T. , Emiroglu M. E.
Published: March 2007

Hydraulic structures can increase dissolved oxygen levels by creating turbulent conditions where small air bubbles are carried into the bulk of the flow. Chute aeration is a particular instance of this. A chute is characterised by a steep bed slope associated with torrential flow. This chute flow may be either smooth or stepped. This paper investigates stepped chutes and how they affect the aeration efficiency. It is demonstrated that stepped chutes are very efficient at oxygen transfer because of the strong turbulent mixing associated with substantial air bubble entrainment and that this advantage becomes more pronounced in the nappe flow regime. In a nappe flow regime, the oxygen transfer on each step results from the flow aeration and mixing in the free-falling nappe, at the plunge point and possibly at the downstream hydraulic jump. An empirical correlation predicting aeration efficiency of one individual step for nappe flow regime was developed. A stepped chute design in terms of aeration efficiency can be optimised using this empirical correlation.
Digital Natives Come to Preschool: Implications for Early Childhood Practice
Authors: Zevenbergen Robyn
Published: March 2007

This article explores the implications of young learners' dispositions towards the use of digital technologies in contemporary early childhood settings. It is proposed that young learners have grown up in very different social conditions from previous generations, mainly through the saturation of digital technologies, in particular computers. This creates very different learners than previous generations. When educators fail to recognize such differences, there is potential for gaps in learning. This is particularly the case when equity dimensions are considered. It is proposed that early childhood settings need to reconceptualize pedagogy and learning opportunities for the new generation of learners. Drawing on Bourdieu's theoretical project, it is proposed that young learners come to early childhood settings with a digital habitus, which is differentially constructed in the home environment and needs to be considered in early childhood practice.
Richness or Rigour? A Discussion of Systematic Reviews and Evidence-Based Policy in Early Childhood
Authors: Penn Helen , Lloyd Eva
Published: March 2007

In this article, the authors report on the experiences of the Early Years Review Group, one of a number of education groups contracted to carry out systematic reviews for the Evidence for Policy and Practice Information and Coordinating (EPPI) Centre in the United Kingdom. The Early Years Review Group has carried out three systematic reviews: one on the impact of integration of care and education in the early years; one on providing support to young children affected by war and armed conflict; and one on the long-term cost benefits of early childhood interventions. Using the evidence from the third review, the authors address the issue of what constitutes useful evidence for policy makers in the field of early childhood and whether certain kinds of evidence are privileged. They conclude that the systematic review process is an independent and useful tool for analysing and critiquing existing studies.
Friendship Meeting or Blocking Circle? Identities in the Laminated Spaces of a Playground Conflict
Authors: Wohlwend Karen E.
Published: March 2007

Drawing from an incident that took place during a year-long investigation of children's play and peer culture on a school playground, the author argues that seemingly neutral child-centered techniques can maintain and even strengthen existing gender inequalities as teachers and children access laminated but contradictory identity positions surrounding agentic educational discourse. As children revisit the original conflict, they laminate time-spaces to discursively reconstruct events and position themselves advantageously. Critical discourse analysis problematizes the effects of a conflict resolution strategy based upon gendered notions of learner agency in a cultural model of teaching: developmentally appropriate practice (DAP). Although the focus of this article is a single event on one elementary school playground in the USA, the author suggest that the presence of the DAP cultural model internationally means that many early childhood teachers may experience similar ambiguity over gendered tensions that arise around issues of agency and authority as they attempt to resolve children's conflicts during play.
Distinguishing Undifferentiated Embryonal Sarcoma of the Liver from Biliary Tract Rhabdomyosarcoma: A Children's Oncology Group Study
Authors: Nicol Kathleen , Savell Van , Moore Julie , Teot Lisa , Spunt Sheri L. , Qualman Stephen ,   Children's Oncology Group, Soft Tissue Sarcoma Committee
Published: March 2007

Morphologically, the distinction between undifferentiated embryonal sarcoma of the liver (UESL) and biliary tract rhabdomyosarcoma (RMS) can be uncertain because of some shared pathologic similarities. Patients with UESL have been consistently but erroneously enrolled in Children's Oncology Group (COG) treatment protocols because UESL was equated with RMS, despite the differing primary treatment modalities of these entities. Review of COG pathology files yielded 20 cases of UESL that were compared to 25 cases of biliary tract RMS. Clinicopathologic features including immunohistochemical staining were examined. In the UESL cases, the male:female ratio was 1:1 and the median age was 10.5 years. Histologically, hyaline globules and diffuse anaplasia were consistently present. The cases of RMS had a male:female ratio of 1.8:1 with a median age of 3.4 years and routinely lacked diffuse anaplasia and hyaline globules. Polyclonal desmin and muscle-specific actin were variably immunoreactive in UESL and RMS; however, myogenin and myogenic regulatory protein D1 (MyoD1) were uniformly negative in UESL and routinely positive in the majority of biliary tract RMS. Myogenin, in particular, was highly significant ( P = 0.0003) in distinguishing RMS from UESL. With a median follow-up of 8 months, 11 of 18 patients with UESL were still alive. The estimated 5-year survival for biliary tract RMS was 66%. Establishing the correct diagnosis of these distinct clinical and pathologic entities is important, as surgery alone may be curative in UESL, whereas initial chemotherapy is often recommended for the treatment of biliary tract RMS.
Syngenta Professional Products Focuses Chemical Technology on New Applications to Enhance the Quality of Life
Authors: Sirchio Kris , Sutton Austen
Published: March 2007

Professional Products is an innovative and leading business sector of Syngenta comprising focus areas – Seed Care, Home Care and Lawn and Garden. It develops and markets specialty and branded professional products in the seed treatment, home care including public health, turf
management, floriculture and amenity sectors. Many countries have a reliable access to food – the production of which is our core competence – and now their populations demand an enhanced experience of their homes, local environment, leisure pursuits and aesthetic aspirations.
Syngenta Professional Products provides products and services to businesses that address these markets. Technology originally developed to support agricultural production is refined, improved and integrated into new packages with beneficial applications in urban environments. New, branded
products growing out of Syngenta's core competence in chemical innovation help our professional customers serve these new markets to fulfill people's lifestyle aspirations.
New Chemistry in the Digital Darkroom
Authors: Spuck Jochen
Published: March 2007

A state of the art and successful industrial application of nanoparticles, digital ink-jet photo paper, is presented. The new photo paper replaces the traditional barite papers in the reproduction of art and high-quality black and white prints. The patented process takes place at the
interface of chemistry and physics. Individual steps are briefly explained.
Fire, Colour, Sound and Light: Chemistry Show, ETH Hönggerberg, 17. Dec. 2006
Authors: Harvey Gillian
Published: March 2007

As part of the ETH Zürich project 'Treffpunkt Science City' aimed at making the ETH Hönggerberg more visible and accessible to the general public, Wolfram Uhlig and Bruno Rüttimann of the Laboratory of Inorganic Chemistry presented their chemistry show entitled 'Fire,
Colour, Sound and Light' to an enthusiastic audience.
Structural and Electronic Properties of the First Monolayers of Spin‐Cast Poly(fluorene)‐Based Conjugated‐ Polymer Films
Authors: Plank H. , Güntner R. , Scherf U. , List E. J. W.
Published: March 2007

This study is an extended investigation on the formation of the first few monolayers of conjugated poly(fluorene)‐based polymer films prepared from solution on defined polar and nonpolar surfaces. In particular, a symmetrical A–B–A triblock copolymer consisting of poly(2‐alkylaniline) as A blocks and poly(9,9‐dialkylfluorene) as B blocks and a poly(9,9‐dialkylfluorene) homopolymer is used for this study. The dependence on drying conditions by means of solvent selection, the influence of a subsequent heat treatment, and the influence of the substrate polarity are investigated for ultrathin films as well as the transition from the first monolayers to the bulk polymer. The study is performed with optical absorption and photoluminescence spectroscopy, and atomic force microscopy to obtain complementary information of optical properties and morphological details. We find that ultrathin films (ca. 1–2 nm) prepared on mica from various solvents form highly defined, flat monolayers at the interface without lateral regularities indicating a dipole–dipole interaction between conjugated‐polymer segments and mica surface dipoles. This is further confirmed by bathochromic photoluminescence shifts observed for the ultrathin layers compared to the bulk polymer. Complementary experiments on nonpolar surfaces, highly oriented pyrolytic graphite (HOPG), show a total absence of defined flat films supporting the assumption of a dipole–dipole assisted formation on mica. For increased film thickness on mica (5 nm and more) the homopolymer does not form any regular structures or ordered layers on top of the monolayer. In contrast, the triblock copolymer, shorter in length, revealed a tendency to form a less‐defined layer‐type growth (3–3.5 nm thick) above the monolayer that was of higher order for higher‐boiling‐point solvents, indicating that the polymers are found in a different conformation. Moreover, one finds that some solvents that show partial immiscibility with the polymer strongly alter the formation of the film. The observations made for the two different types of polymers allow for an assignment of film‐formation driving forces to individual polymer segments and allow for the formulation of a growth model that explains the observed results and indicates the importance of appropriate substrate selection for organic electronic/optoelectronic devices.
Soft Lithography of Ceramic Patterns
Authors: Göbel O. F. , Nedelcu M. , Steiner U.
Published: March 2007

Polymer‐based precursor solutions are patterned using a soft‐lithographic patterning technique to yield sub‐micrometer‐sized ceramic patterns. By using a polymer–metal‐nitrate solution as a lithographic resist, we demonstrate a micromolding procedure using a simple rubber stamp that yields a patterned precursor layer. A subsequent high‐temperature annealing step degrades the polymer giving rise to a patterned metal oxide film. This procedure is demonstrated for three different ceramic materials: Al2O3, ZnO, and PbTiO3. Al2O3 initially forms an amorphous phase that is subsequently converted into a polycrystalline material upon electron irradiation. The formed ZnO and PbTiO3 are polycrystalline. PbTiO3 exhibits epitaxial alignment when cast onto a SrTiO3(001) surface that matches its lattice periodicity. This epitaxial alignment is maintained when the PbTiO3 phase is patterned by micromolding, giving rise to epitaxially grown PbTiO3 patterns with feature sizes down to 300 nm.
Dysregulation of X‐linked gene expression in Klinefelter's syndrome and association with verbal cognition
Authors: Vawter Marquis P. , Harvey Philip D. , DeLisi Lynn E.
Published: March 2007

Klinefelter's Syndrome (KS) is a chromosomal karyotype with one or more extra X chromosomes. KS individuals often show language impairment and the phenotype might be due to overexpression of genes on the extra X chromosome(s). We profiled mRNA derived from lymphoblastoid cell lines from males with documented KS and control males using the Affymetrix U133P microarray platform. There were 129 differentially expressed genes (DEGs) in KS group compared with controls after Benjamini–Hochberg false discovery adjustment. The DEGs included 14 X chromosome genes which were significantly over‐represented. The Y chromosome had zero DEGs. In exploratory analysis of gene expression–cognition relationships, 12 DEGs showed significant correlation of expression with measures of verbal cognition in KS. Overexpression of one pseudoautosomal gene, GTPBP6 (GTP binding protein 6, putative) was inversely correlated with verbal IQ (r = −0.86, P < 0.001) and four other measures of verbal ability. Overexpression of XIST was found in KS compared to XY controls suggesting that silencing of many genes on the X chromosome might occur in KS similar to XX females. The microarray findings for eight DEGs were validated by quantitative PCR. The 14 X chromosome DEGs were not differentially expressed in prior studies comparing female and male brains suggesting a dysregulation profile unique to KS. Examination of X‐linked DEGs, such as GTPBP6, TAF9L, and CXORF21, that show verbal cognition–gene expression correlations may establish a causal link between these genes, neurodevelopment, and language function. A screen of candidate genes may serve as biomarkers of KS for early diagnosis. © 2007 Wiley‐Liss, Inc.
Facile exfoliation of rectorite nanoplatelets in soy protein matrix and reinforced bionanocomposites thereof
Authors: Yu Jiahui , Cui Guojuan , Wei Ming , Huang Jin
Published: March 2007

The rectorite (REC), a form of layered silicate, was facilely intercalated and even exfoliated in soy protein isolate (SPI) matrix. Furthermore, the reinforced biodegradable nanocomposite sheets were produced, in which the exfoliated REC lamellae plays a key role. After solution‐mixing, XRD patterns showed that the REC lamellae were intercalated and even completely exfoliated for 4 wt % REC added, but the expanded gallery gradually became narrower with increasing REC content. FT‐IR also verified the molecular‐level associations between SPI molecules and REC lamellae by vibration variances of hydrogen bonding. The compression‐molding further promoted intercalation and exfoliation, namely the 8 wt % REC can also be almost dispersed as exfoliated lamellae, while the interlayer of RECs also further separated for nanocomposites with higher REC content. TEM images visualized the transfer from exfoliation to intercalation and the decrease of interlayer distance with increasing REC content. The thicker and longer exfoliated REC lamellae resulted in high load and easy‐to‐yield of material. The maximum strength of nanocomposite sheets occurred at the addition of 12 wt % REC. Thereafter, the SPI chain can move more easily because of weak interaction between free negative‐charge rich domain of SPI and REC surface in gallery, which did not favor enhancing mechanical performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Construction of a choline biosensor through enzyme immobilization on a poly(2‐hydroxyethyl methacrylate)‐grafted Teflon film
Authors: Yucel Deniz , Ozer Nazmi , Hasirci Vasif
Published: March 2007

An amperometric choline biosensor was constructed by immobilizing choline oxidase (ChO) on poly(2‐hydroxyethyl methacrylate) (PHEMA)‐grafted Teflon (polytetrafluoroethylene, PTFE) film. Grafting was achieved by γ irradiation. PHEMA‐grafted Teflon films were activated with epichlorohydrin or glutaraldehyde to achieve covalent immobilization of enzyme onto the film. To decrease the diffusional barrier caused by the enzyme‐immobilized film, the film was stretched directly on the electrode. The PHEMA‐grafted Teflon film, therefore, had to have appropriate mechanical properties. Glucose oxidase (GOD) was used in the determination of optimum immobilization conditions, then these were applied to ChO. With GOD, the effect of activation type and film position in electrode on enzyme activity was studied and the highest catalytic activity was obtained when the enzyme was immobilized using glutaraldehyde and the film was stretched over the electrode surface. Further studies revealed that the films activated with glutaraldehyde, immobilized in 2 mg/mL ChO concentration, and stretched directly on the electrode were suitable (specific activity, 0.427 ± 0.068 U mg−1) for use in the choline biosensor. The linear working range of this biosensor was found to be 52–348 μM, with a 40 ± 5 μM minimum detection limit. The response of the sensor, however, decreased linearly upon repeated use. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Melting, crystallization behaviors, and nonisothermal crystallization kinetics of PET/PTT/PBT ternary blends
Authors: Run Mingtao , Song Aijun , Wang Yingjin , Yao Chenguang
Published: March 2007

The melting, crystallization behaviors, and nonisothermal crystallization kinetics of the ternary blends composed of poly(ethylene terephthalate), poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate) (PBT) were studied with differential scanning calorimeter (DSC). PBT content in all ternary blends was settled invariably to be one‐third, which improved the melt‐crystallization temperature of the ternary blends. All of the blend compositions in amorphous state were miscible as evidenced by a single, composition‐dependent glass transition temperature (Tg) observed in DSC curves. DSC melting thermograms of different blends showed different multiple melting and crystallization peaks because of their various polymer contents. During melt‐crystallization process, three components in blends crystallized simultaneously to form mixed crystals or separated crystals depending upon their content ratio. The Avrami equation modified by Jeziorny and the Ozawa theory were employed to describe the nonisothermal crystallization process of two selected ternary blends. The results spoke that the Avrami equation was successful in describing the nonisothermal crystallization process of the ternary blends. The values of the t1/2 and the parameters Zc showed that the crystallization rate of the ternary blends with more poly(ethylene terephthalate) content was faster than that with the lesser one at a given cooling rate. The crystal morphology of the five ternary blends investigated by polarized optical microscopy (POM) showed different size and distortional Maltese crosses or light spots when the PTT or poly(ethylene terephthalate) component varied, suggesting that the more the PTT content, the larger crystallites formed in ternary blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Electrorheological properties of kaolinite, polyindole, and polyindole/kaolinite composite suspensions
Authors: Arslan Yasin , Ibrahim Unal Halil , Yilmaz Hasim , Sari Bekir
Published: March 2007

In this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl3 as an initiator. Average particle sizes (d50) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Haptoglobin‐stimulated bone resorption in neonatal mouse calvarial bones in vitro
Authors: Lerner Ulf H. , Fröhlander Nils
Published: March 2007

Objective. To study the in vitro effects of human haptoglobin (Hp) on bone resorption and prostanoid formation.

Methods. Parietal bones were dissected out from neonatal mice that had been injected with 45Ca, and were cultured in chemically defined medium with or without test substances. Bone resorption was assessed by analysis of 45Ca release. Prostanoid formation was quantified by analysis of the amount of prostaglandin E2 (PGE2) in culture medium.

Results. Hp phenotype 2–1, in quantities ≥0.17 mg/ml, stimulated the release of 45Ca and the biosynthesis of PGE2, in a time‐ and dose‐dependent manner. Hp‐induced PGE2 formation was abolished by indomethacin and flurbiprofen, whereas the stimulation of 45Ca release was only partially reduced.

Conclusion. These observations suggest that the acute‐phase reactant Hp may contribute, by a humoral mechanism, to the bone resorption seen in chronic inflammatory processes.
The news of science, a colloquium‐style course designed to promote lifelong scientific awareness
Authors: Mathews Christopher K.
Published: March 2007

It is generally agreed that informed citizens in a republic such as the United States should maintain broad awareness of current developments in science and technology. This paper describes a colloquium‐style course, The News of Science, designed to stimulate in undergraduate students a desire for such awareness, and to present a convenient means for doing so. The course, which has been offered since 2000 at Oregon State University, requires students to read Science magazine and to present oral reports on articles of their choosing. Each student in the course is required to read all of the articles selected for oral presentation, and to contribute toward discussion of each talk.
HPLC determination of caffeine and paraxanthine in urine: An assay for cytochrome P450 1A2 activity
Authors: Furge Laura Lowe , Fletke Kyle J.
Published: March 2007

Cytochrome P450 enzymes are a family of heme‐containing proteins located throughout the body with roles in metabolism of endogenous and exogenous compounds. Among exogenous compounds, clinically relevant pharmaceutical agents are nearly all metabolized by P450 enzymes. However, the activity of the different cytochrome P450 enzymes varies among individuals and, therefore, so does drug efficacy as well as susceptibility to side effects and toxicity. Thus, assessing P450 activity is of great interest in drug development and clinical pharmacology. This study investigates the phenotyping of a single P450 activity by analyzing urine samples using isocratic reverse‐phase HPLC. Specifically, the activity of human P450 1A2, which converts caffeine into paraxanthine, can be investigated by measuring the change in caffeine and paraxanthine concentrations in urine over time following a single dose of caffeine. There is an observable relationship between caffeine intake and paraxanthine formation that varies among individuals. This laboratory exercise provides a means for simple assessment of P450 1A2 metabolic activity using an HPLC method without additional extraction or purification steps and introduces students to the complexities of individualized medicine as well as the basic biochemical techniques of sample preparation and quantitative HPLC. Furthermore, students may design and test their own hypothesis using these methods.
Reversible ligand binding reactions: Why do biochemistry students have trouble connecting the dots?
Authors: Sears Duane W. , Thompson Scott E. , Saxon S. Robin
Published: March 2007

Adaptive chemical behavior is essential for an organism's function and survival, and it is no surprise that biological systems are capable of responding both rapidly and selectively to chemical changes in the environment. To elucidate an organism's biochemistry, its chemical reactions need to be characterized in ways that reflect the normal physiology in vivo. This is a challenging experimental problem because biological systems are inherently complex with myriads of interlinked chemical networks orchestrating processes that are mostly irreversible in nature. One successful approach for simplifying the study of biochemical reactions is to analyze them under controlled reversible equilibrium conditions in vitro that approximate the range of physiological conditions found in vivo. Because this approach has helped elucidate some of the chemical mysteries of complex biological systems, many topics presented in modern biochemistry courses are essentially rooted in the chemistry of reversible equilibrium reactions. Since most undergraduate biochemistry courses typically require students to complete year‐long general and organic chemistry courses, biochemistry instructors may assume that entering students have sufficient understanding of basic reversible equilibrium chemistry to move forward into more advanced biochemical topics. However, this assumption is at odds with our experience in that many entering students seem confused by the conventions, language, symbolic formalism, and/or mathematical tools normally use to describe reversible equilibrium reactions. Part of the problem here may stem from how certain basic chemical concepts are taught (or are not taught) in their prerequisite chemistry courses. Here, we identify some conceptual barriers that many students seem to confront and we discuss instructional strategies designed to help students “connect the dots,” so to speak, and better understand how dynamic biological processes can be analyzed in terms of reversible equilibrium chemistry.
Teaching the role of mitochondrial transport in energy metabolism
Authors: Passarella Salvatore , Atlante Anna
Published: March 2007

Studies from our laboratories over recent years have uncovered the existence, and established the properties of a variety of mitochondrial transporters. The properties of these transporters throw light on a variety of biochemical phenomena that were previously poorly understood. In particular the role of mitochondrial transport in energy metabolism has been investigated under a variety of physio‐pathological conditions. Consistently we describe the procedure to investigate mitochondrial traffic in isolated mitochondria as a model system for students to learn. Here we report some observations that contribute to novel knowledge of the role of mitochondria in glycolysis, urea and purine nucleotide cycle, and nitrogen metabolism with particular reference to the malate/oxaloacetate shuttle and fumarate, glutamine, and lactate metabolism.
Analysis of the cell cycle by flow cytometry
Authors: Szeberenyl Jozsef
Published: March 2007

Terms to be familiar with before you start to solve the test: Cell cycle, flow cytometry, cell culture, fluorescent DNA dye, diploid and tetraploid cells, mitosis, phases of the cell cycle, growth factors, microtubules, apoptosis, DNA synthesis, proteasome, [3H]thymidine, pulse labeling, histones, protein phosphorylation, M‐phase promoting factor (MPF), cyclins, cyclin‐dependent kinases (Cdks), synchronized culture.
Students' ability to organize biochemical and biochemistry‐related terms correlates with their performance in a biochemical examination
Authors: Nagata Ryoichi
Published: March 2007

Organization is believed to be related to understanding and memory. Whether this belief was applicable in biochemical education was examined about two years after students had experienced biochemistry classes in their first year. The ability of organizing information in biochemistry was judged from the number of correct links of 886 biochemical and biochemistry‐related terms to 14 headings, and the level of understanding and memory on biochemical material was determined from the number of correct answers to biochemical items. The result showed a statistically significant positive correlation between the ability of organization and the level of understanding and memory. Thus, biochemistry teachers need to show the organization of what they teach for the help of the students who have a low level of understanding and memory.
Interplay Between Kinetically Slow Thermal Spin‐Crossover and Metastable High‐Spin State Relaxation in an Iron(II) Complex with Similar T1/2 and T(LIESST)
Authors: Money Victoria A. , Carbonera Chiara , Elhaïk Jérôme , Halcrow Malcolm A. , Howard Judith A. K. , Létard Jean‐François
Published: March 2007

This paper describes the first material to show the well‐known light‐induced excited spin‐state trapping (LIESST) effect, the metastable excited state of which relaxes at a temperature approaching its thermal spin‐crossover. Cooling polycrystalline [FeL2][BF4]2⋅x H2O (L=2,6‐bis{3‐methylpyrazol‐1‐yl}pyridine; x=0–1/3) at 1 K min−1 leads to a cooperative spin transition, taking place in two steps centered at 147 and 105 K, that is only 54 % complete by magnetic susceptibility. Annealing the sample at 100 K for 2 h results in a slow decrease in χMT to zero, showing that the remainder of the spin‐crossover can proceed, but is kinetically slow. The crystalline high‐ and fully low‐spin phases of [FeL2][BF4]2⋅x H2O are isostructural (C2/c, Z=8), but the spin‐crossover proceeds via a mixed‐spin intermediate phase that has a triple unit cell (C2/c, Z=24). The water content of the crystals is slowly lost on exposure to air without causing decomposition. However, the high‐spin/mixed‐spin transition in the crystal proceeds at 110±20 K when x=1/3 and 155±5 K when x=0, which correspond to the two spin‐crossover steps seen in the bulk material. The high‐spin state of the compound is generated quantitatively by irradiation of the low‐spin or the mixed‐spin phase at 10 K, and in approximately 70 % yield by rapidly quenching the sample to 10 K. This metastable high‐spin state relaxes back to the low‐spin ground state at 87±1 K in one, not two, steps, and without passing through the intermediate phase. This implies that thermal spin‐crossover and thermally activated high‐spin–low‐spin relaxation in this material become decoupled, thus avoiding the physical impossibility of T(LIESST) being greater than T1/2.
Molecule‐Responsive Block Copolymer Micelles
Authors: Ishihara Yoshihiro , Bazzi Hassan S. , Toader Violeta , Godin François , Sleiman Hanadi F.
Published: March 2007

Ring‐opening metathesis polymerization was used to generate an ABC triblock copolymer, containing complementary diamidopyridine (DAP) and thymine (THY) outer blocks, which assembles into spherical aggregates held together by DAP–THY noncovalent interactions. Addition of THY‐containing small guest molecules results in complete opening and deaggregation of the block copolymer micelle. This molecular recognition and macroscopic response shows high selectivity to the guest structure, and tolerates only a small amount of conformational mobility in the THY guest. On the other hand, addition of a small DAP‐containing guest does not break the aggregates, but instead, results in new micelles which show a different selectivity profile from the parent morphology. We have examined the effect of a number of structural features in the block copolymers, on both the extent and selectivity of their macroscopic response to guests (that is, opening of the micelle). This study has resulted in a set of structural guidelines, which help in the design of effective molecule‐responsive micelles for applications in selective drug delivery, sensing, and surface patterning.
Preparative chiral chromatography and chiroptical characterization of enantiomers of omeprazole and related benzimidazoles
Authors: Andersson Shalini , Nelander Hanna , Öhlén Kristina
Published: March 2007

To chiroptically characterize the enantiomers of omeprazole and some structurally related benzimidazoles with circular dichroism (CD), preparative chiral liquid chromatography was utilized for the isolation of the pure enantiomers. A limited analytical column screen was performed identifying Kromasil‐CHI‐TBB and the amylose‐based phases Chiralpak AD and AS as possible chiral stationary phases (CSPs) for the preparative scale separation of the enantiomers of the different benzimidazoles. Optimization of the chromatographic conditions with respect to retention, enantioseparation, and resolution was achieved by variation of the mobile phase constituents as well as of temperature. Because of the lability of the compound in slightly acidic media, supercritical fluid chromatography (SFC) could not be applied for a preparative scale separation of the enantiomers. The separation of omeprazole was optimized to give high throughput (2.6 kg racemate/kg CSP/day) and high enantiomeric excess of the obtained isomers. The absolute configurations of the pure enantiomers of rabeprazole, lansoprazole, and pantoprazole were determined from the strong correlation to the CD spectrum of (+)‐(R)‐omeprazole. For all the compounds, the (+)‐enantiomers displayed similar chiroptical features as (+)‐(R)‐omeprazole and were thus assigned the (R)‐ configuration. Elution order of the optical isomers was monitored by injecting racemic solutions spiked with one of the isomers and also by an on‐line laser polarimeter. Both the type of CSP and also the mobile phase constituents had a strong effect on elution order of the enantiomers. Chirality, 2007. © 2007 Wiley‐Liss, Inc.
Update on the molecular biology of malignant mesothelioma
Authors: Lee Amie Y. , Raz Dan J. , He Biao , Jablons David M.
Published: March 2007

Malignant mesothelioma (MM) is a highly aggressive tumor with a very poor prognosis. The disease is largely unresponsive to conventional chemotherapy or radiotherapy, and most patients die within 10–17 months of the first symptoms. Novel, more effective therapeutic strategies are needed for this inexorably fatal disease. Improvement in our understanding of the molecular biology of MM has identified promising new candidates for targeted treatments. In this review the key molecular signaling pathways, including vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), Wnt, and the cell cycle control genes p53, pRb, and bcl‐2 that appear to play an important role in the pathogenesis of MM are explored. Cancer 2007. © 2007 American Cancer Society.
Immunohistochemical localization of cocaine‐ and amphetamine‐regulated transcript peptide in the brain of the catfish, Clarias batrachus (Linn.)
Authors: Singru Praful S. , Mazumdar Minakshi , Sakharkar Amul J. , Lechan Ronald M. , Thim Lars , Clausen Jes Thorn , Subhedar Nishikant K.
Published: March 2007

The organization of cocaine‐ and amphetamine‐regulated transcript peptide (CARTp, 54–102) immunoreactivity was investigated in the brain of the catfish, Clarias batrachus. CARTp‐immunoreactivity was observed in several granule cells of the olfactory bulbs, in dot‐like terminals around mitral cells, and in the fibers of the medial olfactory tracts. While several groups of discrete cells in the telencephalon showed CARTp‐immunoreactivity, the immunostained fibers were widely distributed in the area dorsalis and ventralis telencephali. Immunoreactivity was seen in several periventricular and a few magnocellular neurons, and in a dense fiber network throughout the preoptic area. Varying degrees of immunoreactive fibers were seen in the periventricular region in the thalamus, hypothalamus, and pituitary. Some neurons in the nucleus preglomerulosus medialis and lateralis, central nucleus of the inferior lobes, nucleus lobobulbaris of the posterior tuberculum, and nucleus recessus posterioris showed distinct CARTp‐immunoreactivity. Considerable immunoreactivity was seen in the optic tectum, rostral torus semicircularis, central pretectal area, and granule cells of the cerebellum. While only isolated immunoreactive cells were seen at three distinct sites in the metencephalon, a fiber network was seen in the facial and vagal lobes and periventricular and ventral regions of the medulla oblongata. The pattern of the CARTp distribution in the brain of C. batrachus suggests that it may play an important role in the processing of sensory information, the regulation of hormone secretion by hypophysial cell types, and motor and vegetative function. Finally, as in other animal species, CARTp seems to play a role in the processing of gustatory information. J. Comp. Neurol. 502:215–235, 2007. © 2007 Wiley‐Liss, Inc.
Clustering, migration, and neurite formation of neural precursor cells in the adult rat hippocampus
Authors: Seki Tatsunori , Namba Takashi , Mochizuki Hideki , Onodera Masafumi
Published: March 2007

Adult neurogenesis occurs in the subgranular zone and innermost part of the dentate granule cell layer. To examine how neural precursor cells proliferate, migrate, and extend their neurites, we performed BrdU‐ and improved retrovirus‐green fluorescence protein (GFP)‐labeling analyses. Soon after labeling the majority of BrdU+ cells and GFP+ cells expressed Ki67, a cell cycle marker, and formed clusters together with PSA+ neuroblasts. Most of the Ki67+ proliferating cells expressed Hu, an immature and mature neuronal marker, and the subpopulation expressed both Hu+ and GFAP+. In the clusters, Ki67+ and PSA+ cells strongly expressed β‐catenin and N‐cadherin, but PSA+ cells outside the clusters did not. Therefore, it was mainly Hu+ neuronal precursor cells that proliferated within clusters in which the cluster cells are closely associated via cell adhesion molecules, such as N‐cadherin/β‐cateninIn and PSA. The newly generated cells appeared to stay in the clusters for a few days and then disperse around the clusters. The findings of this in vivo analysis and in vitro time‐lapse imaging of early postnatal hippocampal slices support the notion that most postmitotic neuroblasts migrate tangentially from clusters, extending tangentially oriented processes, one of which often retains close contact with the clusters, and finally extend radial processes, or prospective apical dendrites. These results suggest that the clustering cells and tangentially migrating cells have a systematic cellular arrangement and intercellular interaction. J. Comp. Neurol. 502:275–290, 2007. © 2007 Wiley‐Liss, Inc.