bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric properties of oxydianiline‐based polyimide thin films according to the water uptake
Authors: Lee Choonkeun , Shul Yonggun , Han Haksoo
Published: September 2002

For polyimide thin films, the dielectric properties were investigated with the capacitance and optical methods. The dielectric constants of the 4,4′‐oxydianiline (ODA)‐based polyimide thin films varied from 2.49 to 3.10 and were in the following decreasing order: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)–ODA > 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA)–ODA > 4,4′‐hexafluoroisopropylidene diphthalic dianhydride (6FDA)–ODA. According to the absorption of water, the diffusion coefficients in the films varied from 4.8 × 10−10 to 7.2 × 10−10 cm2/s and were in the following increasing order: BPDA–ODA < PMDA–ODA < 6FDA–ODA. The dielectric constants and diffusion coefficients of the polyimides were affected by the morphological structures, including the molecular packing order. However, because of the water uptake, the changes in the dielectric constants in the polyimide thin films varied from 0.49 to 1.01 and were in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. Surprisingly, 6FDA–ODA with bulky hexafluoroisopropylidene groups showed less of a change in its dielectric constant than PMDA–ODA. The total water uptake for the polyimide thin films varied from 1.43 to 3.19 wt % and was in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. This means that the changes in the dielectric constants in the polyimide thin films were significantly related to the morphological structure and hydrophobicity of hexafluoroisopropylidene groups. Therefore, the morphological structure and chemical affinity in the polyimide thin films were important factors in controlling the dielectric properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2190–2198, 2002
Studies on the phase structure of ethylene‐vinyl acetate copolymers by solid‐state 1H and 13C NMR
Authors: Zhang Qiujin , Lin Weixin , Yang Guang , Chen Qun
Published: September 2002

The phase structure of a series of ethylene‐vinyl acetate copolymers has been investigated by solid‐state wide‐line 1H NMR and solid‐state high‐resolution 13C NMR spectroscopy. Not only the degree of crystallinity but the relative contents of the monoclinic and orthorhombic crystals within the crystalline region varied with the vinyl acetate (VA) content. Biexponential 13C NMR spin–lattice relaxation behavior was observed for the crystalline region of all samples. The component with longer 13C NMR spin–lattice relaxation time (T1) was attributed to the internal part of the crystalline region, whereas the component with shorter 13C NMR T1 to the mobile crystalline component was located between the noncrystalline region and the internal part of the crystalline region. The content of the mobile crystalline component relative to the internal part of the crystalline region increased with the VA content, showing that the 13C NMR spin–lattice relaxation behavior is closely related to the crystalline structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2199–2207, 2002
Sulfobetaine zwitterionomers based on n‐butyl acrylate and 2‐ethoxyethyl acrylate: Physical properties
Authors: Gauthier Mario , Carrozzella Tony , Snell Greg
Published: September 2002

New materials with potential applications for adhesives and coatings, based on copolymers containing zwitterionic pendent groups, were investigated. n‐Butyl acrylate and 2‐ethoxyethyl acrylate were copolymerized with a series of five zwitterionic sulfobetaine monomers (SBMs). The structures of the SBMs were varied systematically in terms of (1) intercharge spacing in the zwitterionic moiety and (2) substituent bulkiness at the quaternary ammonium functionality. The effect of varying the sulfobetaine content and structure in the copolymers was investigated, with an emphasis on ion aggregation behavior and physical properties, with dynamic mechanical analysis. The zwitterionomers exhibited the expected biphasic morphology, with the appearance of an ion‐rich glass‐transition temperature. An increase in the storage modulus was observed with increasing SBM content in the rubbery and terminal regions, suggesting an increased degree of ionic crosslinking in the rubbery region and decreased chain mobility in the flow region. Intercharge spacing variation in the sulfobetaine moiety did not have a significant effect on the modulus–temperature curves, contrary to our expectations. Increases in the modulus were much less pronounced for the bulkier SBMs than for the other monomers, possibly because of hindered aggregation of the sulfobetaine moieties. Likewise, matrix polarity had a greater influence on the physical properties of these materials than intercharge separation in the SBMs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2303–2312, 2002
Effect of benzenesulfonamide plasticizers on the glass‐transition temperature of semicrystalline polydodecamide
Authors: De Groote Ph. , Devaux J. , Godard P.
Published: September 2002

The effect of various benzenesulfonamide (BSA) plasticizers on the amorphous phase of semicrystalline polydodecamide (PA‐12) has been investigated. MonoBSAs appear as efficient glass‐transition temperature (Tg) depressors because of their miscibility with the host polyamide (PA), low glass transition, and small molecule size. PA‐12's Tg shifts from 50 to about 0 °C at 20 mol % of the most efficient molecules. Comparatively, the more bulky bisBSAs appear to induce less important absolute Tg decreases (30 K at 20 mol %), although these appear as more important when considering the polymer Tg to plasticizer Tg difference. This unexpected observation could be ascribed to both the amide‐sulfonamide interactions and the sterically generated disorder within the polyamide because of the plasticizer molecule's size. Phase‐separation behavior of BSA plasticizers within the host PA has also been investigated. Crystalline phenyl‐SO2NH2, for instance, dephased beyond 20 mol % in PA‐12, forming distinct 1–2 micrometer wide crystalline domains as a result of its high propensity to crystallize upon cooling from the melt. By contrast, slow crystallizing N,N‐dimethylBSA, which lacks any specific interaction for PA‐12, remained nevertheless dispersed at a molecular level (metastable state, no phase separation) when vitrification of the host PA‐12 amorphous phase occurred on cooling. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2208–2218, 2002
Nafion®/(organically modified silicate) nanocomposites via polymer in situ sol–gel reactions: Mechanical tensile properties
Authors: Young S. K. , Mauritz K. A.
Published: September 2002

A series of Nafion®/[organically modified silicate (ORMOSIL)] hybrid materials have been created by in situ sol–gel copolymerizations of tetraethylorthosilicate and semiorganic silicon alkoxide monomers. The trends in the mechanical tensile properties of these hybrid materials were largely rationalized in terms of the entrapment of the long sulfonic acid side chains in silicate or ORMOSIL structures. There is a significant increase in the mechanical strength relative to that of unfilled Nafion®, except in one case. Young's modulus is enhanced relative to that of unfilled acid form Nafion® in a number of cases, although the degree of ductility is reduced relative to that of unfilled Nafion®. The filler fractions are beneath a critical value that would reflect percolation of a glassy, direct load‐bearing silicate phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2237–2247, 2002
Modeling the failure of an adhesive layer in a peel test
Authors: Lin Y. Y. , Hui C. Y. , Wang Y. C.
Published: September 2002

The failure of an adhesive layer in a 180° peel test is analyzed by the modeling of the peel as an elastica. The adhesive is assumed to fail by a process of cavitation and fibrillation. The resistance of the fibrillated material to deformation gives rise to a rate‐dependent peel force F. Governing equations, which take into account the large deformation of the fibrillated materials, are derived. Numerical solutions are obtained for the special case of a linear, viscous adhesive. Assuming a critical strain failure criterion for the fibrils, we show that the peel rate is inversely proportional to the square root of the adhesive thickness and directly proportional to F3/4. The connection between the peel test and the tack test is also discussed. The maximum traction on the peel arm is found to be directly proportional to the peel force and inversely proportional to the adhesive thickness. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2277–2291, 2002
Influence of a mixing solvent with tetrahydrofuran and N,N‐dimethylformamide on electrospun poly(vinyl chloride) nonwoven mats
Authors: Lee Keun Hyung , Kim Hak Yong , La Young Min , Lee Douk Rae , Sung Nak Hyun
Published: September 2002

We evaluated the effects of the solvent composition with respect to the solution concentration, applied electric field, and tip‐to‐collector distance on the morphology of electrospun poly(vinyl chloride) (PVC) fibers. The solvent volume ratio was strongly correlated with the diameter of the electrospun fibers with respect to the other processing parameters. Electrospun PVC fibers dissolved in tetrahydrofuran (THF) had diameters ranging from 500 nm to 6 μm; those dissolved in N,N‐dimethylformamide (DMF) had an average diameter of 200 nm. The diameters of the electrospun fibers were obtained from narrow to broad distributions with the solvent composition. Also, the diameters of fibers electrospun from a mixed solvent of THF and DMF were less than 1 μm. The mechanical properties of electrospun PVC nonwoven mats depended on the fiber orientation and linear velocity of the drum surface. With increasing linear velocity of the drum surface, electrospun PVC fibers were arranged toward the machine direction, and the dimensions of the spiral path were shorter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2259–2268, 2002
Mechatronics design of stiffness enhancement for direct‐drive motor system using ER variable damper
Authors: Su Y. X. , Duan B. Y. , Zheng C. H.
Published: September 2002

Direct‐drive (DD) motors have the characteristics of simple structure and high controllability without reduction gears or ball screws. However, DD motors are more sensitive to the disturbance torque and parameter variation than other motor systems, which have reduction gears. Enhancement of DD motor stiffness by increasing the gain is one of the effective methods to reduce this influence, but large gain will lead to instability and even vibration. Viewed from mechatronics design, an ER variable damper with a damping coefficient that can be changed depending on how the applicable voltage is designed, and directly attached to the shaft of the DD motor to achieve high servo stiffness. The structure and the damping coefficient model of the proposed ER variable damper are developed. The validation of this mechatronics design is demonstrated by a position PD (proportional derivative) control DD motor system with numerical simulations, which achieved both high stiffness and good stability for the controlled DD motor system. © 2002 Wiley Periodicals, Inc.
Handling uncertainties of robot manipulators and active vision by constraint propagation
Authors: Yang Christopher C. , Ciarallo Frank W. , Marefat Michael M.
Published: September 2002

Joint errors are inevitable in robot manipulation. These uncertainties propagate to give rise to translational and orientational errors in the position and orientation of the robot end‐effector. The displacement of the active vision head mounted on the robot end‐effector produces distortion of the projected object on the image. Upon active visual inspection, the observed dimension of a mechanical part is given dimension by the measurement on the projected edge segment on the image. The difference between the observed dimension and the actual dimension is the displacement error in active vision. For different motion of the active vision head, the resulting displacement errors are different. Given the uncertainties of the robot manipulator's joint errors, constraint propagation can be employed to assign the motion of the active sensor in order to satisfy the tolerance of the displacement errors for inspection. In this article, we define the constraint consistency and network satisfaction in the constraint network for the problem of displacement errors in active vision. A constraint network is a network where the nodes represent variables, or constraints, and the arcs represent the relationships between the output variables and the input variables of the constraints. In the displacement errors problem, the tolerance of the displacement errors and the translational and orientational errors of robot manipulators have interval values while the sensor motion has real values. Constraint propagation is developed to propagate the tolerance of displacement errors in the hierarchical interval constraint network in order to find the feasible robot motion. © 2002 Wiley Periodicals, Inc.
Extended Jacobian inverse kinematics algorithms for mobile manipulators
Authors: Tchoń Krzysztof , Jakubiak Janusz
Published: September 2002

We consider the inverse kinematic problem for mobile manipulators consisting of a nonholonomic mobile platform and a holonomic manipulator on board the platform. The kinematics of a mobile manipulator are represented by a driftless control system with outputs together with the associated variational control system. The output reachability map of the driftless control system determines the instantaneous kinematics, while the output reachability map of the variational system plays the role of the analytic Jacobian of the mobile manipulator. Relying on a formal analogy between the kinematics of stationary and mobile manipulators we exploit the extended Jacobian construction in order to design a collection of extended Jacobian inverse kinematics algorithms for mobile manipulators. It has been proved mathematically and confirmed in computer simulations that these algorithms are capable of efficiently solving the inverse kinematic problem. Moreover, a choice of the Jacobian extension may lay down some guidelines for the platform‐manipulator motion coordination. © 2002 Wiley Periodicals, Inc.
Science centers and scientific literacy: Promoting a relationship with science
Authors: Rennie Léonie J. , Williams Gina F.
Published: September 2002

This research explores the perceptions, ideas, and understanding about science of the staff and adult visitors to an interactive science center. Data were collected from 63 staff and 102 visitors through interviews and a survey designed for the study. Visitors' perceptions about science were more limited than those of the Center staff, especially in terms of the nature of science. For example, after their visit, visitors were more likely to think that scientists always agree with each other, that scientific explanations are definite, and that science has the answers to all problems. Staff were more skeptical than visitors about scientists' ability to communicate their work clearly and that scientific knowledge would not be misused. Staff were more positive and confident about their own use of science than were visitors. The research suggests that visitors to the science center have a positive experience, most of them recognize a change in the way they think about science, and this change represents not just learning new knowledge, but a step toward a change in their relationship with science. This outcome is consistent with one of the major roles the staff saw for the Center: that visitors should become more aware of and interested in science, and leave feeling more comfortable with it. Although the staff were very enthusiastic about what they saw as a positive impact on visitors' science‐related experience, many also felt there was room for improvement, especially in terms of how the nature of science was portrayed, and the representation of controversial aspects of science. © 2002 Wiley Periodicals, Inc. Sci Ed 86:706–726, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10030
Longitudinal impact of an inquiry‐based science program on middle school students' attitudes toward science
Authors: Gibson Helen L. , Chase Christopher
Published: September 2002

This study examined the long‐term impact of the Summer Science Exploration Program (SSEP), a 2‐week inquiry‐based science camp, conducted at Hampshire College Amherst, MA from 1992 to 1994. The goal of the program was to stimulate greater interest in science and scientific careers among middle‐school students. One hundred fifty‐eight students were selected from a pool of applicants to attend the program using stratified random sampling procedures. In 1996, 22 participants were selected to participate in follow‐up interviews using stratified random sampling procedures. Two quantitative surveys, the Science Opinion Survey and the Career Decision‐Making Revised Surveys, were administered to 79 SSEP students and 35 students who applied but were not accepted (the control group). Pretest and posttest scores were analyzed for any significant change over time. Additionally, a cohort of over 500 students who were enrolled in the same grades and public schools that SSEP students attended completed the two surveys in both 1992–1994 and 1996–1997. The interviews and surveys suggested that SSEP students maintained a more positive attitude towards science and a higher interest in science careers than students who applied to the program but were not selected. © 2002 Wiley Periodicals, Inc. Sci Ed 86:693–705, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10039
Strata of comprehending ecology: Looking through the prism of feeding relations
Authors: Eilam Billie
Published: September 2002

The present paper focuses on ninth graders' difficulties in learning ecology. Three dimensions, in addition to the macrolevel dimension, were identified as basic obstacles that might hinder students' meaningful learning of ecology: the microlevel dimension, relating to the molecular and micro processes of matter and energy transfer in ecosystems; the spatial dimension of ecosystems, regarding simultaneous occurrences in space and the multiple roles of their biotic elements; and the time dimension, relating to long‐term evolutionary forces acting in ecosystems. These four dimensions were examined in students' understanding of the concept of food chains in ecosystems. Four ninth grade classrooms participated in the study. Two of the classes studied ecology in the traditional mode and served as a control. Two classes were exposed to a novel, specifically designed learning context for ecology study, which integrated several elements known to influence learning, including a special curriculum to guide students' active involvement in a self‐regulated process of inquiry. A qualitative analysis of students' written responses and recorded verbal interactions was used, as well as simple quantitative methods. © 2002 Wiley Periodicals, Inc. Sci Ed 86:645–671, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10041
Automating the management of software maintenance workflows in a large software enterprise: a case study
Authors: Aversano Lerina , Canfora Gerardo , De Lucia Andrea , Stefanucci Silvio
Published: September 2002

This case study presents the results from a pilot project aimed at introducing workflow management technologies and a Web‐based software tool in a large software enterprise. In particular, we analyzed and modeled the workflows and documents at the site of the ordinary maintenance process and implemented a prototype for the management of the process using a commercial‐Web‐based workflow management system. This paper reports on the experience gained from a 10‐month project, which included the experimental use at a single site of the workflow prototype for 4 months in an industrial setting involving more than 800 maintenance service requests on a large software system. Copyright © 2002 John Wiley & Sons, Ltd.
State‐of‐the‐art: software inspections after 25 years
Authors: Aurum Aybuke , Petersson Håkan , Wohlin Claes
Published: September 2002

Software inspections, which were originally developed by Michael Fagan in 1976, are an important means to verify and achieve sufficient quality in many software projects today. Since Fagan's initial work, the importance of software inspections has been long recognized by software developers and many organizations. Various proposals have been made by researchers in the hope of improving Fagan's inspection method. The proposals include structural changes to the process and several types of support for the inspection process. Most of the proposals have been empirically investigated in different studies.

This is a review paper focusing on the software inspection process in the light of Fagan's inspection method and it summarizes and reviews other types of software inspection processes that have emerged in the last 25 years. This paper also addresses important issues related to the inspection process and examines experimental studies and their findings that are of interest with the purpose of identifying future avenues of research in software inspection. Copyright © 2002 John Wiley & Sons, Ltd.
An empirical evaluation of six methods to detect faults in software
Authors: So Sun Sup , Cha Sung Deok , Shimeall Timothy J. , Kwon Yong Rae
Published: September 2002

Although numerous empirical studies have been conducted to measure the fault detection capability of software analysis methods, few studies have been conducted using programs of similar size and characteristics. Therefore, it is difficult to derive meaningful conclusions on the relative detection ability and cost‐effectiveness of various fault detection methods. In order to compare fault detection capability objectively, experiments must be conducted using the same set of programs to evaluate all methods and must involve participants who possess comparable levels of technical expertise. One such experiment was ‘Conflict1’, which compared voting, a testing method, self‐checks, code reading by stepwise refinement and data‐flow analysis methods on eight versions of a battle simulation program. Since an inspection method was not included in the comparison, the authors conducted a follow‐up experiment ‘Conflict2’, in which five of the eight versions from Conflict1 were subjected to Fagan inspection. Conflict2 examined not only the number and types of faults detected by each method, but also the cost‐effectiveness of each method, by comparing the average amount of effort expended in detecting faults. The primary findings of the Conflict2 experiment are the following. First, voting detected the largest number of faults, followed by the testing method, Fagan inspection, self‐checks, code reading and data‐flow analysis. Second, the voting, testing and inspection methods were largely complementary to each other in the types of faults detected. Third, inspection was far more cost‐effective than the testing method studied. Copyright © 2002 John Wiley & Sons, Ltd.
DNA‐PK inhibitor wortmannin enhances DNA damage induced by bleomycin in V79 Chinese hamster cells
Authors: Oliveira Nuno G. , Castro Matilde , Rodrigues António S. , Gil Octávia M. , Toscano‐Rico José M. , Rueff José
Published: September 2002

The fungal metabolite wortmannin (WM) is a potent and irreversible inhibitor of the enzyme DNA‐dependent protein kinase (DNA‐PK), a nuclear serine‐threonine kinase, member of the phosphaditylinositol‐3 kinase related kinase family. WM has been used in the last few years as a promising radiosensitizer mainly throughout cell survival experiments. However, few studies have addressed the role of DNA‐PK inhibition in the repair of DNA lesions generated by antitumor agents. Bleomycin (BLM) is an antitumor agent used in the treatment of various neoplasia with a unique genotoxicity profile that mimics the ionizing radiation effects. In this study, we evaluated the effect of different concentrations of WM on the DNA damage induced by BLM. The cytokinesis‐block micronucleus assay (CBMN) in V79 Chinese hamster cells was used as the end‐point. WM significantly increased the frequency of micronucleated cells (%MNBN) by about 2.2‐fold, the number of micronuclei per binucleated cell (MN/BN) by about 2.4‐fold, and also changed the pattern of the distribution of micronuclei induced by BLM. The frequency of micronucleated cells with 2 MN per cell and with ≥3 MN per cell increased, whereas the frequency of micronucleated cells with 1 MN per cell decreased. WM was not genotoxic but decreased cell proliferation as assessed by the frequency of binucleated cells. Our results show that WM clearly enhances the efficacy of BLM in terms of DNA damage inflicted and therefore reinforces its use as a chemosensitizer. Teratogenesis Carcinog. Mutagen. 22:343–351, 2002. © 2002 Wiley‐Liss, Inc.
Inhibitory effects of ascorbic acid and folinic acid on chromosome aberrations induced by pyrimethamine in vitro
Authors: Egel Çiĝdem , Bilaloĝlu Rahmi , Aydemir Nilüfer
Published: September 2002

In this study, the anticlastogenic effects of ascorbic acid and the protective effect of folinic acid against the formation of chromosomal aberrations in humans by pyrimethamine were investigated. Pyrimethamine is a folic acid antagonist used for the treatment of malaria and toxoplasmosis. In this study, 18 different healthy people, who do not drink alcohol and are non‐smokers, were chosen as an experimental group; 0.025 mg/ml pyrimethamine was given to the lymphocyte culture, which had been prepared with the peripheral blood taken from this group. After that each of the following doses were given to the same culture: 20, 40, and 80 mM of ascorbic acid and 25, 50, and 100 mM of folinic acid. The results of the cytogenetic evaluation showed that the aberrations due to pyrimethamine in the chromosomes were reduced by ascorbic acid and folinic acid significantly, depending on the given dose. Teratogenesis Carcinog. Mutagen. 22:353–362, 2002. © 2002 Wiley‐Liss, Inc.
Genetic polymorphisms in the cytochrome P450 1A1, glutathione S‐transferase M1 and T1, and susceptibility to colon cancer
Authors: Ye Zheng , Parry James M.
Published: September 2002

Several polymorphic cytochrome P‐450 and glutathione S‐transferase (GST) enzymes are involved in the activation and detoxification of many potential carcinogens and may therefore be important in susceptibility to cancer induction. CYP1A1 MspI, GSTM1, and GSTT1 are polymorphic enzymes and some alleles have been correlated with an increased risk of developing some cancers. In the present study, we examined possible associations between genetic polymorphisms of CYP1A1 MspI, GSTM1, and GSTT1 and colon cancer in a United Kingdom population. An excess of CYP1A1 MspI, and GSTM1 null genotypes was observed amongst colon cancer patients, although this did not reach the level of statistical significance. We found no significant increase in the risk of colon cancer for either CYP1A1 MspI (OR = 1.39; 95%CI: 0.46–4.21) or GSTM1 null (OR = 1.41; 95%CI: 0.76–3.01) genotypes. Individuals with GSTT1 null genotype had no association with colon cancer (OR = 0.42; 95%CI: 0.09–2.02). No significant association was observed in the site of colon cancer (proximal vs. distal). This study suggests that the polymorphisms of CYP1A1 MspI, GSTM1, and GSTT1 are not associated with a significant risk of developing colon cancer in a United Kingdom population. Teratogenesis Carcinog. Mutagen. 22:385–392, 2002. © 2002 Wiley‐Liss, Inc.
Brazil and Mexico—Partners in sowing a free trade area of the Americas
Authors: Gouvea Raul
Published: September 2002

The second half of 2000 brought renewed interest to the Free Trade Agreement of the Americas (FTAA).

This hemispheric economic integration initiative presents numerous opportunities and challenges for each of the

34 countries involved in unifying markets across the Americas. The North American Free Trade Agreement

(NAFTA) and Mercosur, the region's two largest trading blocs, play a vital role in any attempt to

integrate Latin American markets. Integration under Mercosur has strengthened the position of member

countries—especially Brazil, which is a choice location for foreign direct investment and has realized a

significant growth in extra‐Mercosur trade. The newly elected Mexican president, Vicente Fox, has

demonstrated a strong desire to bring Mexico to the forefront of hemispheric trade negotiations and brings a new

dynamic to integration of Latin American markets and to the FTAA initiative. This article elaborates on the role

of the two largest Latin American economies and the United States in the creation and solidification of a

hemispheric trading bloc in the Americas. © 2002 Wiley Periodicals, Inc.
The relationship between Arab values and work beliefs: An exploratory examination
Authors: Robertson Christopher J. , Al‐Khatib Jamal A. , Al‐Habib Mohammed
Published: September 2002

In this study, 365 employees from three Middle Eastern countries (Saudi Arabia, Kuwait, and Oman) are

queried about their cultural values and work‐related beliefs. This analysis is unique both in its sample

and its focus on the relationship between individual cultural values and beliefs about work. Results suggest that

the cultural value dimensions individualism (p < .001) and masculinity (p < .001) are

related to both an individual's beliefs about organizational commitment and work ethic. Additional findings

reveal patterns between cultural values and humanistic and political beliefs. Future research directions and

managerial implications are also discussed. © 2002 Wiley Periodicals, Inc.
A single FKS homologue in Yarrowia lipolytica is essential for viability
Authors: León Maela , Sentandreu Rafael , Zueco Jesús
Published: September 2002

The synthesis of β‐1,3‐glucan, the structural component of the yeast cell wall which gives shape to the cell, occurs at the plasma membrane and is the result of the activity of at least a two‐component complex. Fks1p is the catalytic subunit directly responsible for the synthesis of β‐1,3‐glucan, whilst the second subunit, Rho1p, has a GTP‐dependent regulatory role. FKS1 has been characterized in Saccharomyces cerevisiae, where its function is at least partially redundant with that of FKS2/GSC2. FKS homologues have also been identified in several other fungal species, including Candida albicans, Schizosaccharomyces pombe, Aspergillus nidulans, Cryptococcus neoformans and Paracoccidiodes brasiliensis. In this work, we have used degenerate oligonucleotides derived from the conserved regions of Fks1ps to isolate the possible FKS homologue genes of the strictly aerobic non‐conventional yeast Yarrowia lipolytica. Using this approach, we have isolated a single FKS homologue which we have named YlFKS1; this codes a 1961 amino acid protein that shows a high degree of homology with other Fksps. Expression analysis of YlFKS1 under different conditions affecting the cell wall did not reveal significant differences. Finally, attempts to obtain a Y. lipolytica strain containing a disrupted YlFKS1 allele failed, despite having used two different techniques. Taken together, these results suggest that, unlike S. cerevisiae, YlFKS1 is the only FKS1 homologue in Y. lipolytica and is essential for growth. Copyright © 2002 John Wiley & Sons, Ltd.
HXT5 expression is determined by growth rates in Saccharomyces cerevisiae
Authors: Verwaal René , Paalman Johannes W. G. , Hogenkamp Astrid , Verkleij Arie J. , Verrips C. Theo , Boonstra Johannes
Published: September 2002

In the yeast Saccharomyces cerevisiae, hexose transporter (Hxt) proteins transport glucose across the plasma membrane. The Hxt proteins are encoded by a multigene family with 20 members, of which Hxt1–4p and Hxt6–7p are the major hexose transporters. The remaining Hxt proteins have other or unknown functions. In this study, expression of HXT5 under different experimental set‐ups is determined. In glucose‐grown batch cultures, HXT5 is expressed prior to glucose depletion. Independent of the carbon source used in batch cultures, HXT5 is expressed after 24 h of growth and during growth on ethanol or glycerol, which indicates that growth on glucose is not necessary for expression of HXT5. Increasing the temperature or osmolarity of the growth medium also induces expression of HXT5. In fed‐batch cultures, expression of HXT5 is only observed at low glucose consumption rates, independent of the extracellular glucose concentration. The only common parameter in these experiments is that an increase of HXT5 expression is accompanied by a decrease of the growth rate of cells. To determine whether HXT5 expression is determined by the growth rate, cells were grown in a nitrogen‐limited continuous culture, which enables modulation of only the growth rate of cells. Indeed, HXT5 is expressed only at low dilution rates. Therefore, our results indicate that expression of HXT5 is regulated by growth rates of cells, rather than by extracellular glucose concentrations, as is the case for the major HXTs. A possible function for Hxt5p and factors responsible for increased expression of HXT5 upon low growth rates is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
ADP‐sensitive purinoceptors induce steroidogenesis via adenylyl cyclase activation in bovine adrenocortical fasciculata cells
Authors: Nishi Haruhisa , Kato Fusao , Masaki Eiji , Kawamura Masahiro
Published: September 2002

The role of P2Y receptors in the production of cAMP and the activation of protein kinase A (PKA) was studied with respect to the regulation of the steroidogenesis in primary cultures of bovine adrenocortical fasciculata cells (BAFCs).

ADP and ATP stimulated cAMP production with EC50 values of 23.7±6.8 μM and 40.1±5.5 μM, respectively. In contrast, the EC50 of BzATP for cAMP production was 153.0±37.4 μM. Adenosine and AMP (0.1–1000 μM) were much less effective than ADP and ATP. 2MeSADP and UTP did not exert detectable effects. ADP (10 and 100 μM) significantly stimulated steroidogenesis; the process was blocked by an adenylyl cyclase inhibitor SQ22536 (100 μM) but not by the P2Y1 receptor antagonist MRS2179 (100 μM).

Real‐time imaging of the PKA activity with the dye ARII, which became less fluorescent upon phosphorylation, revealed that ADP (100 μM) immediately activated PKA. These effects could be mimicked by forskolin (100 μM) and were blocked by the PKA inhibitor H89 (50 μM). UTP (100 μM) did not activate PKA.

The cytoplasm harvested from morphologically and electrophysiologically identified single BAFCs contained mRNA for P2Y2 but not for P2Y1, P2Y4, P2Y11 or P2Y12 receptors, as confirmed by single‐cell RT–PCR amplification (50 cycles).

These results suggest an expression of an ADP‐sensitive Gs‐coupled purinoceptor in BAFCs. We propose that this not yet described type of P2Y receptor might mediate the extracellular purine‐activated steroidogenesis via cAMP/PKA‐mediated pathways, independently from the pathways involving InsP3 production and consequent intracellular Ca2+ increase.

British Journal of Pharmacology (2002) 137, 177–184. doi:10.1038/sj.bjp.0704847
Effects of mutations of a glutamine residue in loop D of the α7 nicotinic acetylcholine receptor on agonist profiles for neonicotinoid insecticides and related ligands
Authors: Shimomura Masaru , Okuda Hiroshi , Matsuda Kazuhiko , Komai Koichiro , Akamatsu Miki , Sattelle David B
Published: September 2002

Neonicotinoid insecticides are agonists of insect nicotinic acetylcholine receptors (AChRs) and show selective toxicity for insects over vertebrates. To elucidate the molecular basis of the selectivity, amino acid residues influencing neonicotinoid sensitivity were investigated by site‐directed mutagenesis of the chicken α7 nicotinic AChR subunit, based on the crystal structure of an ACh binding protein (AChBP).

In the ligand binding site of AChBP, Q55 in loop D is close to Y164 in loop F that corresponds to G189 of the α7 nicotinic receptor. Since Q55 of AChBP is preserved as Q79 in the α7 nicotinic receptor and the G189D and G189E mutations have been found to reduce the neonicotinoid sensitivity, we investigated effects of Q79E, Q79K and Q79R mutations on the neonicotinoid sensitivity of the α7 receptor expressed in Xenopus laevis oocytes to evaluate contributions of the glutamine residue to nicotinic AChR–neonicotinoid interactions.

The Q79E mutation markedly reduced neonicotinoid sensitivity of the α7 nicotinic AChR whereas the Q79K and Q79R mutations increased sensitivity, suggesting electronic interactions of the neonicotinoids with the added residues.

By contrast, the Q79E mutation scarcely influenced responses of the α7 nicotinic receptor to ACh, (−)‐nicotine and desnitro–imidacloprid (DN–IMI), an imidacloprid derivative lacking the nitro group, whereas the Q79K and Q79R mutations reduced the sensitivity to these ligands. The results indicate that the glutamine residue of the α7 nicotinic receptor is likely to be located close to the nitro group of the insecticides in the nicotinic receptor–insecticide complex.

British Journal of Pharmacology (2002) 137, 162–169. doi:10.1038/sj.bjp.0704848
Role of Rho kinase signalling in healthy and varicose human saphenous veins
Authors: Cario‐Toumaniantz Chrystelle , Evellin Sandrine , Maury Séverine , Baron Olivier , Pacaud Pierre , Loirand Gervaise
Published: September 2002

The present study was performed to determine the role of Rho‐Rho kinase signalling pathway in smooth muscle cells from both healthy and varicose human saphenous vein.

The Rho kinase inhibitor Y‐27632 inhibited the noradrenaline (NA)‐induced contraction in human saphenous veins with IC50 corresponding to 0.5 μM and 10.9 μM in control and varicose veins, respectively. The maximal amplitude of the NA‐induced contraction was smaller in varicose vein compared to control (1263±172 mg versus 1974±245 mg, P<0.05).

In β‐escin permeabilized strips, GTPγS induced a rise in tension that was inhibited by Y‐27632. The amplitude of the GTPγS‐induced contraction was smaller in varicose compared to control veins (23.1±2.4% versus 41.3±2.2%, P<0.002).

In smooth muscle cells, Y‐27632 induced disassembly of both actin cytoskeleton and extracellular fibronectin matrix. In comparison to control cells, varicose vein smooth muscle cells show decreased actin cytoskeleton organization and reduction of fibronectin matrix deposition.

The Rho proteins Rnd1 and RhoA, and Rho kinase 1 are expressed in human saphenous veins. A 2.6 fold reduction of Rho kinase expression was found in varicose veins.

These results indicate that RhoA‐Rho kinase mediated Ca2+ sensitization of the contraction and regulated actin cytoskeleton and extracellular fibronectin matrix assembly in human saphenous smooth muscle. The decrease of Rho kinase expression and Rho kinase‐dependent functions detected in smooth muscle from varicose veins supports a role of this signalling pathway in the functional alterations of the vein wall occurring in the course of the disease.

British Journal of Pharmacology (2002) 137, 205–212. doi:10.1038/sj.bjp.0704849
Different mechanism of LPS‐induced vasodilation in resistance and conductance arteries from SHR and normotensive rats
Authors: Farias Nelson C , Borelli‐Montigny Gisele L , Fauaz Grasiele , Feres Teresa , Borges Antonio C R , Paiva Therezinha B
Published: September 2002

The direct and endothelium‐dependent effects of lipopolysaccharide (LPS) were investigated on resistance and conductance arteries from normotensive Wistar (NWR) and spontaneously hypertensive (SHR) rats.

In both NWR and SHR, LPS induced dose‐dependent relaxations of the mesenteric vascular bed, which were inhibited by L‐NNA in SHR but not in NWR. Iberiotoxin (IBTX) inhibited the responses to LPS in both groups, indicating the participation of high conductance Ca2+‐dependent K+ channels.

In mesenteric artery rings, the resting membrane potentials and the hyperpolarizing responses of NWR to LPS did not differ in endothelized and denuded preparations but L‐NNA inhibited the responses only in endothelized rings. These responses were reduced by bosentan, suggesting that endothelin release may mask a possible hyperpolarizing response to LPS. The hyperpolarizing responses to LPS were blocked by IBTX in both endothelized and de‐endothelized NWR rings. In the SHR only intact rings showed hyperpolarization to LPS, which was inhibited by IBTX and byL‐NNA.

In SHR aortic endothelized or denuded rings, LPS induced hyperpolarizing responses which, in endothelized rings, were partially blocked by L‐NNA, by IBTX or by glibenclamide, but totally abolished by IBTX plus glibenclamide. No response to LPS was observed in NWR aortic rings.

Our results indicate that LPS activates large conductance Ca2+‐sensitive K+ channels located in the smooth muscle cell membrane both directly and indirectly, through NO release from the endothelium in NWR, whereas NO is the major mediator of the LPS responses in SHR resistance vessels.

British Journal of Pharmacology (2002) 137, 213–220. doi:10.1038/sj.bjp.0704850
Analgesic effect of intrathecally administered orexin‐A in the rat formalin test and in the rat hot plate test
Authors: Yamamoto Tatsuo , Nozaki‐Taguchi Natsuko , Chiba Tanemichi
Published: September 2002

Orexin‐A and orexin‐B (also known as hypocretin‐1 and hypocretin‐2) are hypothalamic peptides and regulate feeding behaviour, energy metabolism and the sleep‐wake cycle. Orexin‐A binds equally to both orexin‐1 and orexin‐2 receptors, while orexin‐B has a preferential affinity for orexin‐2 receptors.

Orexins are also known to be concentrated in superficial laminae of the spinal dorsal horn, and orexin‐A and orexin‐1 receptors are found in the dorsal root ganglion cells.

In the present study, the authors examined the effect of intrathecal injection of either orexin‐A or orexin‐B in the rat formalin test (a model of inflammatory pain) and in the rat hot plate test. The paw formalin injection induces biphasic flinching (phase 1: 0–6 min; phase 2: 10–60 min) of the injected paw.

Intrathecal injection of orexin‐A, but not orexin‐B, decreased the sum of flinches in phases 1 and 2 in the formalin test and increased the hot plate latency. These effects of orexin‐A were completely antagonized by pre‐treatment with SB‐334867, a selective orexin‐1 receptor antagonist. Intrathecal injection of SB‐334867 alone had no effect in the formalin test or in the hot plate test.

Intrathecal injection of orexin‐A suppressed the expression of Fos‐like immunoreactivity (Fos‐LI), induced by paw formalin injection, in laminae I‐II of L4–5 of the spinal cord.

These data suggest that the spinal orexin‐1 receptor is involved in the nociceptive transmission and that the activation of the spinal orexin‐1 receptor produces analgesic effects in the rat formalin test and in the rat hot plate test.

British Journal of Pharmacology (2002) 137, 170–176. doi:10.1038/sj.bjp.0704851
Accumulation of platelets in the lung and liver and their degranulation following antigen‐challenge in sensitized mice
Authors: Yoshida Atsushi , Ohba Mami , Wu Xia , Sasano Takashi , Nakamura Masanori , Endo Yasuo
Published: September 2002

Mast cells and basophils are believed to trigger allergic reactions and anaphylaxis. They rapidly release histamine (H), a typical mediator of inflammation, in response to antigens. In the mouse, platelets contain much 5‐hydroxytryptamine (5HT), an additional inflammatory mediator, while human platelets contain both H and 5HT. Here, we examined the response of platelets in sensitized mice to antigen challenge.

Platelets accumulated in the lung and liver almost immediately after intravenous injection of ovalbumin (OVA), in mice sensitized to it, and platelet degranulation occurred during these reactions.

These responses of platelets preceded H release from mast cells and/or basophils, occurred at doses of OVA lower than those inducing H release, and contributed to the signs of shock.

We reported previously that intravenous injection into mice of LPS (a membrane constituent of gram‐negative bacteria) induces a similar platelet response (accumulation of platelets in the lung and liver) and shock.

Blood that has passed through the body (other than the digestive tract) passes first to the lungs before being recirculated by the heart, and blood that has passed through the digestive tract passes next to the liver. Thus, our findings suggest that in addition to their role in haemostasis, platelets, tiny anuclear cytoplasts, may be important in both innate and acquired immunity, and that the lung and liver may be the fronts at which platelets wage war on pathogens.

British Journal of Pharmacology (2002) 137, 146–152. doi:10.1038/sj.bjp.0704852
Ligands for histamine H3 receptors modulate cell proliferation and migration in rat oxyntic mucosa
Authors: Morini Giuseppina , Grandi Daniela , Schunack Walter
Published: September 2002

(R)‐α‐methylhistamine, a selective agonist of histamine H3 receptors, promotes mucus secretion and increases the number and volume of mucus‐secreting cells. The hypothesis that the increased number of mucous cells could reside in an alteration of homeostasis in the gastric epithelium was investigated.

(R)‐α‐methylhistamine was administered to rats 1 h (10–100 mg kg−1 by intragastric and by intraperitoneal route) and 24 h (100 mg kg−1 by intragastric route) prior to killing. The (S)‐isomer of α‐methylhistamine (55.4 mg kg−1), 100 times less potent than the (R)‐isomer at H3 receptors, and the H3‐receptor agonist FUB 407 (9.14–91.35 mg kg−1) were intragrastically administered 1 h prior to killing. The H1‐receptor antagonist mepyramine (30 mg kg−1), the H2‐receptor antagonist famotidine (3 mg kg−1), and the H3‐receptor antagonists ciproxifan (3 mg kg−1) and clobenpropit (30 mg kg−1) were intragastrically administered 30 min before (R)‐α‐methylhistamine. Gastric tissue was processed for histology and immunohistochemistry.

Within 1 h, (R)‐α‐methylhistamine and FUB 407 dose‐dependently increased the number of BrdU‐positive cells and of apoptotic cells. (S)‐α‐methylhistamine failed to modify proliferation and apoptosis. The increase in proliferation by (R)‐α‐methylhistamine was reversed by ciproxifan and clobenpropit, but not by mepyramine and famotidine.

(R)‐α‐methylhistamine accelerated the differentiation towards pit cells and their outward migration 24 h after its administration. These effects were counteracted by ciproxifan. The apoptosis rate was unaffected at 24 h.

These findings reveal a primary role of histamine H3‐receptor ligands in modulating cell proliferation and migration in rat fundic mucosa.

British Journal of Pharmacology (2002) 137, 237–244. doi:10.1038/sj.bjp.0704853