bluuebunny/crossref_metadata_2025 huggingface dataset:
“I think I can; I think I can”
Authors: Neck Christopher P. , Neck Heidi M. , Manz Charles C. , Godwin Jeffrey
Published: July 2002

The concept of “Thought Self‐Leadership” involves individual self‐influence through cognitive strategies that focus on self‐dialogue, mental imagery, beliefs and assumptions, and thought patterns. A plethora of studies from various fields including management, counseling psychology, sports psychology, education, and communication, address the effect of these Thought Self‐Leadership cognitive strategies on cognitions and behaviors. This research provides consistent support for the relationship between constructive self‐leadership of these cognitive processes and enhanced performance. The application of these cognitive strategies to the entrepreneurship domain, however, is sparse. We propose that the application of these principles to the entrepreneurial process offers the potential to enhance individual performance and mental states for both practicing and aspiring entrepreneurs. Propositions derived from the proposed framework are developed to serve as catalysts for empirically testing the applicability of Thought Self‐Leadership to the entrepreneurship context.
National marketing strategies in international travel and tourism
Authors: Riege Andreas M. , Perry Chad
Published: July 2002

Focuses on how national travel and tourism authorities can market a country as a tourist destination, with particular reference to the marketing of Australia and New Zealand to target markets in Germany and the United Kingdom. These two nations in Europe are by far the most important tourist generating countries for Australia and New Zealand and there has been a recent substantial increase in the value of international travel and tourism revenues and promising future prospects. However, there is little research emphasising specific marketing and distribution strategies that may be applied by travel and tourism organisations, airlines and intermediaries to market a tourist destination successfully in overseas markets. This research collected data using in‐depth interviews with 41 experienced practitioners in Germany, the UK, Australia and New Zealand, and analysed the data with a rigorous case study methodology. The results of this research assist in clarifying the conceptual issues provided in the literature, linking theoretical marketing knowledge about strategies in the discipline of international travel and tourism marketing.
Employability in practice
Authors: Verhaar C.H.A. , Smulders H.R.M.
Published: July 2002

In this paper data referring to the salience of life long learning policies for employees are presented. These data are gathered from people working in Dutch horticulture and Dutch dairy industry. The study focuses on the points of view these employees have regarding the need to invest in their employability through training. The results emphasise the importance of training on the job for these employees, which according to many of them actually is sufficient to grow into a good worker. This is not in line with the emphasis laid on training and investing in human capital in general in the growing employability literature. Thus much needs to be done to communicate this need (assuming that it is real indeed) to the workforce. Therefore, the conclusion is drawn that employability policies do not relate to economic theory, such as the human capital approach, but rather to social theory
Non destructive evaluation in the time domain
Authors: Albanese R. , Rubinacci G. , Tamburrino A. , Villone F.
Published: July 2002

In this paper a method is presented for an efficient solution of the direct problem (find the scattered field for a given thin crack and driving field) in the time domain. This is a fundamental step in any non destructive evaluation problem. Two different approaches, one in the time domain and the other based on Fourier analysis, are used and compared with reference to a configuration for which some experimental results are available. The advantages and drawbacks of the two approaches are briefly discussed.
Feedback and Musical Resonance
Authors: Musès C.
Published: July 2002

Looks at the interrelationship between resonance, probability and feedback and describes how we can control and direct them – the very essence of cybernetics – by using musical science to explain their causes and effects.
Fast learning artificial neural networks for continuous input applications
Authors: Evans D.J. , Tay L.P.
Published: July 2002

A fast learning artificial neural network model (FLANN II) is developed to solve problems in the area of pattern classification for continuous input values. The operational aspects of the neural network are illustrated by two process control diagnostic problems.
Representations of logic functions
Authors: Lee Edward T.
Published: July 2002

Logic function representations play an important role in logic design and computer design, as well as VLSI design. There are many ways to represent a logic function. Presents and classifies 11 representation methods into “unique representation category” and “non‐unique representation category”. History of these methods is also briefly mentioned. There are three non‐unique representation methods: Boolean expression;sum of products; and product sums, and eight unique representation methods: truth table; canonical sum of products; canonical product of sums; sum of minterms; product of maxterms; Karnaugh map; Boolean lattice; and Venn diagram. A theorem is found which states that Boolean expression, sum of products, product of sums, sum of minterms, product of maxterms, and Karnaugh map, form a lattice structure. The results may have useful applications in knowledge representation, pictorial knowledge representation and other related areas.
Western joint ventures in Turkey: strategic motives and partner selection criteria
Authors: Tatoglu Ekrem
Published: July 2002

This paper considers two important aspects of joint venture (JV) activity between Western firms and local partner firms in Turkey. First, the strategic motivation for JV formation is investigated for a sample of Western partner firms. The relative importance of a set of strategic motives is identified and discussed with respect to the nationality of foreign partner. Second, the paper considers partner selection criteria for the sample using a typology that distinguishes between partner‐related and task‐related selection criteria and also examines the relationship between the relative importance of selection criteria and the nationality of foreign partner.
Grading the crease recovery with twisting of fabric by using image identification technique
Authors: Wang Xiaohong , Yao Mu
Published: July 2002

Traditionally, the grade of fabric’s crease recovery with twisting is decided by comparing the processed sample fabric with standard sample photograph under some conditions. This method is completely reliant on subjective appraisal, so it is easy to lead to some subjective error and affect the conclusion. In this paper, we use image processing and texture analysis technique to calculate a few of the parameters which describe the fabric’s crease recovery properties. At the same time, we use the Fuzzy priority similarity comparison method to assess the fabric’s crease recovery properties synthetically.
Mechanical stability of fused textile systems
Authors: Gutauskas M. , Masteikaite V.
Published: July 2002

Presents the results of tests to determine the mechanical stability of textile fusing systems using two instruments: pulser ERDT‐3 and rotary‐rolls set‐up ARRV. The pulser ERDT‐3 allows textile systems in different testing conditions to be fatigued; one‐sided and double‐sided loading. Using instrument ARRV the specimen is not only fatigued in repeated one‐axed loading, but at the same time, its surface is abraded. Determines the relations between fusing conditions, fabric properties and glue line texture under different mechanical treatments. Proves that pressure increase allows a comparatively sufficient initial bond strength of textile systems forum, but this bond proves unstable under mechanical treatment.
Guilty or not: the impact and effects of site‐based management on schools
Authors: Dempster Neil
Published: July 2002

This paper examines the impact and effects of site‐based management on schools using a framework developed by Canadian researchers, Sackney and Dibski. It draws on research literature from the UK, New Zealand and Australia and includes results from three studies in which the author has been engaged. The Sackney and Dibski framework is used to lay seven “charges” against site‐based management – that site‐based management leads to greater decision‐making flexibility, changes the work role and increases the workload of principals, improves student learning outcomes, increases innovation, increases competition, results in reduced funding and affects the standing of the public education system. The analysis of the literature selected suggests that site‐based management is guilty of some and not of others.
The influence of school architecture on academic achievement
Authors: Tanner C. Kenneth
Published: July 2002

Limited, dated information is available to school administrators concerning the influence that the built learning environment has on academic achievement. Given the population increases, volatile standardized test scores, demand for new schools, and deplorable conditions of school facilities in the United States, it is timely to investigate this neglected aspect of educational research. In the face of radical technological changes and curriculum innovations, much of the new public school architectural design is tied firmly to past and outdated practices. Currently reform advocates push for program change to occur, while voicing minimal concern for the often obsolete and shabby physical environments of the schools where the program improvement is to evolve. With these problems representing the educational need, the specific purpose of this study was to determine how school architectural design factors might influence student achievement scores in elementary schools. A total of seven design factors were found to correlate with student learning outcomes.
A re‐appraisal of the role of the head of department in UK secondary schools
Authors: Brown Marie , Rutherford Desmond
Published: July 2002

In this paper we review current thinking on the role of the head of department in secondary schools which emphasises that theirs is the critical agency in school improvement. We go on to describe a two‐fold strategy for developing successful schools which requires departments to improve: their teaching and their pupils’ learning; their capacity to both make and implement policy and so to facilitate the progress of change. We suggest that improving teaching and learning is best addressed at the departmental level by an evolutionary approach that emphasises vision, commitment, planning, action and review, rather than grandiose aims, statements, over elaborate policies and detailed, long‐term plans. In addition, we suggest that a department’s capacity to implement change depends on seven essential processes but that the leadership of heads of department is the key to developing successful departments and successful schools.
Diffusion theory and practice
Authors: Kautz Karlheinz , Åby Larsen Even
Published: July 2002

This article analyzes a European‐wide dissemination project which aimed at spreading quality management and software process improvement approaches among organizations in the IT sector and beyond to organizations which produce software as part of their primary product. The research presented investigates to what extent that mission has been accomplished and what lessons can be learned for similar actions in the future. For the analysis Rogers’ well‐known model of the diffusion of innovations is used. A secondary outcome of the study therefore is an appraisal of the suitability of the model to plan and perform large‐scale diffusion actions.
From arms‐length to collaborative relationships in the supply chain
Authors: Hoyt James , Huq Faizul
Published: July 2002

Buyer‐supplier relationships play an important role in an organization’s ability to respond to dynamic and unpredictable change. If the relationship is too restrictive, flexibility will be difficult to achieve and, if it is too lenient the risk of opportunism will be present. This paper provides a framework for understanding how buyer‐supplier relationships have evolved over the past two decades from transaction processes based on arms‐length agreements to collaborative processes based on trust and information sharing. To achieve this objective, buyer‐supplier relationships are reviewed from the perspectives of transaction cost theory, strategy‐structure theory and resource‐based theory of the firm. Findings from early supply chain research are contrasted with the findings of more current research to provide a better understanding of how these relationships have changed. Current theory is extended by offering two proposals that test the influence of trust and information sharing and a third proposal that rejects the notion that supply chain alliances lead to monopolistic practices.
Nurses’ access to higher education: a quality product
Authors: Hill Yvonne , MacGregor Janet , Dewar Kate
Published: July 2002

Responding to government initiatives which demand that quality in education be identified in a measurable way, nursing, in its move to professionalization, has sought to gain academic parity with other professions allied to medicine and has entered higher education (HE) institutions. In setting up new courses, it is now necessary to work within an identified model of quality and use it as the basis for evaluation. Describes how the authors set up an access module for nurses who had never studied within HE but had come from a traditional “training” background. In the early planning stage it became evident that no established framework for quality was suitable for this module. As a result, a model was designed based on the work of several authors (Donabedian, 1966; Holzemer, 1992 and Maxwell, 1984). The major categories within this model were identified as context, process and outcome. These were chosen from the literature as they reflect key concepts in nursing practice familiar to all nursing practitioners. Within each category, several sub‐components were later identified. Having used this model to plan, implement and evaluate several modules over a two‐year period, it appears to be a useful tool in recognizing and measuring appropriate quality issues for access courses for nursing. Although it was constructed specifically for this purpose, it could be of use in a wider education arena for mature students returning to study.
Trust in Web‐based electronic commerce security
Authors: Ratnasingham Pauline
Published: July 2002

Electronic commerce is about business. Businesses are built on relationships and relationships are built on trust, especially in today’s virtual competitive world. Trust is an essential ingredient for electronic commerce in creating loyal and very satisfied customers. This paper discusses the concept of trust and its importance for secure electronic commerce.
Australian academic use of the Internet: implications for university administrators
Authors: Applebee Ann , Clayton Peter , Pascoe Celina , Bruce Harry
Published: July 2002

Reports on the first‐ever nationwide quantitative survey of academic staff use of the Internet. After briefly noting reasons for adopting a mailed‐out survey, the article discusses some of the results obtained. These include daily use of e‐mail, access to the Internet via remote dial‐in services and technical support provided to academics. More than one‐third of respondents seem in need of more training in Net use and time limitations and lack of training are typical barriers to effective use. The study concludes with opportunities for further research at both national and international levels and discusses possible implications for university administrators. The full report of the study is published as Academics Online (Auslib Press, Adelaide, 1998). The research team also included Edna Sharpe of the Australian Quarantine and Inspection Service.
Rapid tooling for sand casting using laminated object manufacturing process
Authors: Wang Wanlong , Conley James G. , Stoll Henry W.
Published: July 2002

It is now possible to generate tooling for near net shape manufacturing processes directly from a CAD database by using computer numerical control (CNC) machining or a variety of rapid prototyping (RP) processes. These methods are widely referred to as rapid tooling processes because the tool geometry is created in a relatively short time. In particular, the use of RP processes has proved to be a cost‐effective and time‐efficient approach for producing patterns and core boxes for sand casting. However, the suitability of this approach depends on a variety of geometry and process related considerations. Investigates the use of the laminated object manufacturing (LOM) based rapid tooling process in sand casting. Issues discussed include geometry considerations, error sources and propagation, and shrinkage effects. A case study illustrating time and cost savings using the LOM approach is also presented.
Environmental preferences of homeowners
Authors: Bender André , Din Allan , Hoesli Martin , Brocher Séverin
Published: July 2002

A comparative study of perceptions concerning the environmental quality of residential real estate in Switzerland based on empirical data collected in three different linguistic regions is presented. Responses by homeowners in the Geneva, Zurich and Lugano areas to questionnaires involving pairwise preference criteria are analysed in the framework of the analytic hierarchy process (AHP). Eight different environmental quality criteria are used and responses are categorised in terms of indicators concerning the personal situation of the homeowner. The results show that environmental preference levels across the three cities are in the 7‐18 per cent range. It appears that perceptions are similar for four of the eight criteria, whereas notable differences exist for the other criteria. Some possible interpretations of these results are given. Finally, possible extensions to this study are discussed, in particular how the approach could be integrated in a more detailed spatial analysis of socio‐economic data in the framework of geographic information systems.
Molecular confinement influences protein structure and enhances thermal protein stability
Authors: Eggers Daryl K. , Valentine Joan S.
Published: July 2002

The sol‐gel method of encapsulating proteins in a silica matrix was investigated as a potential experimental system for testing the effects of molecular confinement on the structure and stability of proteins. We demonstrate that silica entrapment (1) is fully compatible with structure analysis by circular dichroism, (2) allows conformational studies in contact with solvents that would otherwise promote aggregation in solution, and (3) generally enhances thermal protein stability. Lysozyme, α‐lactalbumin, and metmyoglobin retained native‐like solution structures following sol‐gel encapsulation, but apomyoglobin was found to be largely unfolded within the silica matrix under control buffer conditions. The secondary structure of encapsulated apomyoglobin was unaltered by changes in pH and ionic strength of KCl. Intriguingly, the addition of other neutral salts resulted in an increase in the α‐helical content of encapsulated apomyoglobin in accordance with the Hofmeister ion series. We hypothesize that protein conformation is influenced directly by the properties of confined water in the pores of the silica. Further work is needed to differentiate the steric effects of the silica matrix from the solvent effects of confined water on protein structure and to determine the extent to which this experimental system mimics the effects of crowding and confinement on the function of macromolecules in vivo.
Role of individual disulfide bonds in hen lysozyme early folding steps
Authors: Guez Valérie , Roux Pascale , Navon Amiel , Goldberg Michel E.
Published: July 2002

To probe the role of individual disulfide bonds in the folding kinetics of hen lysozyme, the variants with two mutations, C30A,C115A, C64A,C80A, and C76A,C94A, were constructed. The corresponding proteins, each lacking one disulfide bond, were produced in Escherichia coli as inclusion bodies and solubilized, purified, and renatured/oxidized using original protocols. Their enzymatic, spectral, and hydrodynamic characteristics confirmed that their conformations were very similar to that of native wild‐type (WT) lysozyme. Stopped‐flow studies on the renaturation of these guanidine‐unfolded proteins with their three disulfides intact showed that, for the three variants, the native far‐UV ellipticity was regained in a burst phase within the 4‐ms instrument dead‐time. The transient overshoots of far‐UV ellipticity and tryptophan fluorescence that follow the burst phase, as well as the kinetics of transient 8‐anilino‐1‐naphthalene‐sulfonic acid (ANS) binding, were diversely affected depending on the variant. Together with previous reports on the folding kinetics of WT lysozyme carboxymethylated on cysteines 6 and 127, detailed analysis of the kinetics showed that (1) none of the disulfide bonds were indispensable for the rapid formation (<4 ms) of the native‐like secondary structure; (2) the two intra‐α‐domain disulfides (C6‐C127 and C30‐C115) must be simultaneously present to generate the trapped intermediate responsible for the slow folding population observed in WT lysozyme; and (3) the intra‐β‐domain (C64‐C80) and the inter‐αβ‐domains (C76‐C94) disulfides do not affect the kinetics of formation of the trapped intermediate but are involved in its stability.
The X‐ray structure determination of bovine carbonmonoxy hemoglobin at 2.1 Å resoultion and its relationship to the quaternary structures of other hemoglobin crystal forms
Authors: Safo Martin K. , Abraham Donald J.
Published: July 2002

Crystallographic studies of the intermediate states between unliganded and fully liganded hemoglobin (Hb) have revealed a large range of subtle but functionally important structural differences. Only one T state has been reported, whereas three other quaternary states (the R state, B state, and R2 or Y state) for liganded Hb have been characterized; other studies have defined liganded Hbs that are intermediate between the T and R states. The high‐salt crystal structure of bovine carbonmonoxy (CO bovine) Hb has been determined at a resolution of 2.1 Å and is described here. A detailed comparison with other crystallographically solved Hb forms (T, R, R2 or Y) shows that the quaternary structure of CO bovine Hb closely resembles R state Hb. However, our analysis of these structures has identified several important differences between CO bovine Hb and R state Hb. Compared with the R state structures, the β‐subunit N‐terminal region has shifted closer to the central water cavity in CO bovine Hb. In addition, both the α‐ and β‐subunits in CO bovine Hb have more constrained heme environments that appear to be intermediate between the T and R states. Moreover, the distal pocket of the β‐subunit heme in CO bovine Hb shows significantly closer interaction between the bound CO ligand and the Hb distal residues Val 63(E11) and His 63(E7). The constrained heme groups and the increased steric contact involving the CO ligand and the distal heme residues relative to human Hb may explain in part the low intrinsic oxygen affinity of bovine Hb.
Delayed and prolonged effects of a near threshold EPSP on the firing time of human α‐motoneurones
Authors: Mattei Benjamin , Schmied Annie
Published: July 2002

In order to investigate the effects of near‐threshold excitatory inputs on the precise timing of the action potentials during the tonic discharge of human motoneurones, the activity of single motor units was recorded in the extensor carpi radialis muscles while tendon taps (indentation, 0.1 mm; duration, 1 ms) were being delivered irregularly at a mean rate of 0.8 s−1. New methods of analysis, such as the phase response function, were used to study the relative changes in the interspike interval (ISI1) during which the stimulus was being delivered and in the three subsequent intervals (ISI2, ISI3, ISI4) as a percentage of the pre‐stimulus interspike interval (ISI0). The consistency of the effects of the actual stimulus as regards the spontaneous variability was assessed by comparing the data with those obtained with virtual stimulation. When the stimulus occurred at the end of ISI1, and triggered a spike, ISI1 and ISI3 were generally shortened, whereas ISI2 was lengthened, probably due to the negative correlation induced by the summation of the after‐hyperpolarisations (AHPs). When the stimulus occurred in the middle of ISI1 without triggering a spike, ISI1, ISI2 and more rarely ISI3 were shortened. Lastly, when the stimulus occurred during the AHP scoop in ISI1, ISI2 was shortened although ISI1 remained unchanged. ISI4 was not consistently affected in any of these cases. The present results show that the tendon tap‐induced inputs (probably from muscle spindle primary endings) mediated delayed and prolonged shortening effects of the ISIs on most of the α‐motoneurones tested (n= 16). These effects undetected in classic peri‐stimulus histogram analysis may involve long‐lasting conductance changes although the contribution of polysynaptic pathways cannot be excluded. The changes in ISI were quite moderate (< 15 % of ISI) but highly consistent. Their functional involvement in the synchronisation or desynchronisation processes and/or the mechanisms of optimisation of muscle contraction still remains to be explored.
The role of guanylyl cyclases in the permeability response to inflammatory mediators in pial venular capillaries in the rat
Authors: Sarker M. H. , Fraser P. A.
Published: July 2002

Inflammatory mediators have a role in the formation of cerebral oedema and there is evidence that cGMP is an important signal in vascular permeability increase. We have investigated the role and the source of cGMP in mediating the permeability response to acutely applied bradykinin and the histamine H2 agonist dimaprit on single cerebral venular capillaries, by using the single vessel occlusion technique. We found that 8‐bromo‐cGMP applied acutely resulted in a small and reversible permeability increase with a log EC50−7.2 ± 0.15 m. KT 5823, the inhibitor of cGMP‐dependent protein kinase, abolished the permeability responses to both bradykinin and dimaprit, while zaprinast, an inhibitor of type 5 phosphodiesterase, potentiated the response to bradykinin. On the other hand, l‐NMMA blocked the response to dimaprit, but not that to bradykinin. Inhibitors of soluble guanylyl cyclase, LY 85353 and methylene blue, also inhibited the permeability response to dimaprit, but not bradykinin. The permeability responses to the natriuretic peptides ANP and CNP were of similar magnitude to that of bradykinin with log EC50−10.0 ± 0.33 m and −8.7 ± 0.23 m, respectively. The natriuretic peptide receptor antagonist HS‐142–1 blocked permeability responses to bradykinin as well as to ANP, and leukotriene D4 blocked the responses to CNP and bradykinin, but not to dimaprit. In conclusion, the histamine H2 receptor appears to signal via cGMP that is generated by a NO and soluble guanylyl cyclase, while bradykinin B2 receptor also signals via cGMP but through particulate guanylyl cyclase.
An inward rectifier K+ channel at the basolateral membrane of the mouse distal convoluted tubule: similarities with Kir4‐Kir5.1 heteromeric channels
Authors: Lourdel Stéphane , Paulais Marc , Cluzeaud Françoise , Bens Marcelle , Tanemoto Masayuki , Kurachi Yoshihisa , Vandewalle Alain , Teulon Jacques
Published: July 2002

In this study, K+ channels present in the basolateral membrane of the distal convoluted tubule (DCT) were investigated using patch‐clamp methods. In addition, Kir4.1, Kir4.2 and Kir5.1 inward rectifier channels were investigated using RT‐PCR and immunohistochemistry (Kir4.1). DCTs were microdissected from collagenase‐treated mouse kidneys. One type of K+ channel was detected in about 50 % of cell‐attached patches from the DCT basolateral membrane; this channel was inwardly rectifying and had an inward conductance (gin) of ∼40 pS at an external [K+] of 145 mm. The current‐voltage relationship was linear when inside‐out patches were exposed to a Mg2+‐free medium. Mg2+ at a concentration of 1.2 mm considerably reduced the outward conductance (gout), yielding a gin/gout ratio of ∼4.7. The polycation spermine (5 × 10−7m) reduced the open probability (Po) by 50 %. Channel activity was dependent upon the intracellular pH, with acid pH decreasing, and basic pH increasing, Po. Internal ATP (2 mm) and Ca2+ (up to 10−3m) had no effect. Channel activity declined irreversibly when the inner side of the patch was exposed to Mg2+. Kir4.1, Kir4.2 and Kir5.1 mRNAs were all detected in the DCT. The Kir4.1 protein co‐localised with the Na+‐Cl− cotransporter, which is specific to the DCT, and was located on basolateral membranes. The DCT K+ channel differs from other functionally identified renal K+ channels with regard to its inhibition by spermine and insensitivity to internal ATP and Ca2+. At the current state of knowledge, the channel is similar to Kir4.1‐Kir5.1 and Kir4.2‐Kir5.1 heteromeric channels, but not to Kir4.1 or Kir4.2 homomeric channels.
Non‐linear, high‐gain and sustained‐to‐transient signal transmission from rods to amacrine cells in dark‐adapted retina of Ambystoma
Authors: Yang Xiong‐Li , Gao Fan , Wu Samuel M.
Published: July 2002

In darkness, On‐Off amacrine cells (ACs) of the tiger salamander retina exhibited large spontaneous transient depolarizing potentials (sTDPs) with average peak amplitude of 5.05 ± 2.5 mV and average frequency of 0.42 ± 0.25 s−1. Under voltage‐clamp conditions the cell displayed large spontaneous postsynaptic currents (sPSCs) with average peak amplitude of 98 ± 39 pA and average frequency of 0.45 ± 0.22 s−1. To a light step, ACs gave rise to a transient ‘On’ response at the light onset and a transient ‘Off’ response at light offset, followed by a train of TDPs (‘After’ response). Near the response threshold (0.3 activated rhodopsin molecules per rod per second), light‐evoked TDPs (leTDPs) of similar amplitude and kinetics as the large sTDPs observed in darkness were seen, and about half of these leTDPs elicited a regenerative potential (RP). Brighter light steps gave rise to more leTDPs and higher rates of RPs in the On, Off and After responses. Within the linear response range of the rods, the AC response was non‐linear, with the highest gain (676 ± 429) near the dark potential. The amplitude of Off responses increased with the duration of the light step, and ACs may use this to encode speeds of moving stimuli: the faster the light object moves, the smaller the AC Off response. Moreover, the number of leTDPs in the AC After response increased with light intensity, and the onset of the After response coincides with bipolar cell tail response recovery. One possible origin of the large sTDPs and leTDPs is the spontaneous and depolarization‐induced regenerative calcium potentials (RCaPs) in bipolar cell synaptic terminals. RCaPs in bipolar cell synaptic terminals cause transient glutamate release that results in the sTDPs in darkness, and leTDPs in On, Off and After responses in ACs.
Rho and rho kinase modulation of barrier properties: cultured endothelial cells and intact microvessels of rats and mice
Authors: Adamson R. H. , Curry F. E. , Adamson G. , Liu B. , Jiang Y. , Aktories K. , Barth H. , Daigeler A. , Golenhofen N. , Ness W. , Drenckhahn D.
Published: July 2002

Previous experiments using cultured endothelial monolayers indicate that Rho‐family small GTPases are involved in modulation of endothelial monolayer permeability by regulating assembly of the cellular actin filament scaffold, activity of myosin‐based contractility and junctional distribution of the Ca2+‐dependent endothelial cell adhesion molecule, VE‐cadherin. We investigated these mechanisms using both cultured endothelial cells (from porcine pulmonary artery and mouse heart) and vascular endothelium in situ (mouse aorta, and individually perfused venular microvessels of mouse and rat mesentery). Exposure to Clostridium difficile toxin B (100 ng ml−1) inactivated 50–90 % of all endothelial Rho proteins within 60–90 min. This was accompanied by considerable reduction of actin filament stress fibres and junctional F‐actin in cultured endothelial monolayers and in mouse aortic endothelium in situ. Also, VE‐cadherin became discontinuous along endothelial junctions. Inhibition of Rho kinase with Y‐27632 (30 μm) for 90–120 min induced F‐actin reduction both in vitro and in situ but did not cause redistribution or reduction of VE‐cadherin staining. Perfusion of microvessels with toxin B increased basal hydraulic permeability (Lp) but did not attenuate the transient increase in Lp of microvessels exposed to bradykinin. Perfusion of microvessels with Y‐27632 (30 μm) for up to 100 min reduced basal Lp but did not attenuate the permeability increase induced by platelet activating factor (PAF) or bradykinin. These results show that toxin B‐mediated reduction of endothelial barrier properties is due to inactivation of small GTPases other than RhoA. Rho proteins as well as RhoA‐mediated contractile mechanisms are not involved in bradykinin‐ or PAF‐induced hyperpermeability of intact microvessels.
Basolateral PAR‐2 receptors mediate KCl secretion and inhibition of Na+ absorption in the mouse distal colon
Authors: Cuffe John E. , Bertog Marko , Velázquez‐Rocha Sara , Dery Olivier , Bunnett Nigel , Korbmacher Christoph
Published: July 2002

Proteinase‐activated receptor‐2 (PAR‐2) may participate in epithelial ion transport regulation. Here we examined the effect of mouse activating peptide (mAP), a specific activator of PAR‐2, on electrogenic transport of mouse distal colon using short‐circuit current (ISC) measurements. Under steady‐state conditions, apical application of amiloride (100 μm) revealed a positive ISC component of 74.3 ± 6.8 μA cm−2 indicating the presence of Na+ absorption, while apical Ba2+ (10 mm) identified a negative ISC component of 26.2 ± 1.8 μA cm−2 consistent with K+ secretion. Baseline Cl− secretion was minimal. Basolateral addition of 20 μm mAP produced a biphasic ISC response with an initial transient peak increase of 11.2 ± 0.9 μA cm−2, followed by a sustained fall to a level 31.2 ± 2.6 μA cm−2 (n= 43) below resting ISC. The peak response was due to Cl− secretion as it was preserved in the presence of amiloride but was largely reduced in the presence of basolateral bumetanide (20 μm) or in the absence of extracellular Cl−. The secondary decline of ISC was also attenuated by bumetanide and by Ba2+, indicating that it is partly due to a stimulation of K+ secretion. In addition, the amiloride‐sensitive ISC was slightly reduced by mAP, suggesting that inhibition of Na+ absorption also contributes to the ISC decline. Expression of PAR‐2 in mouse distal colon was confirmed using RT‐PCR and immunocytochemistry. We conclude that functional basolateral PAR‐2 is present in mouse distal colon and that its activation stimulates Cl− and K+ secretion while inhibiting baseline Na+ absorption.
Slow excitatory synaptic potentials evoked by distension in myenteric descending interneurones of guinea‐pig ileum
Authors: Thornton P. D. J. , Bornstein J. C.
Published: July 2002

The functional significance of the slow excitatory synaptic potentials (EPSPs) in myenteric neurones is unknown. We investigated this using intracellular recording from myenteric neurones in guinea‐pig ileum, in vitro. In all, 121 neurones responded with fast EPSPs to distension of the intestine oral to the recording site. In 28 of these neurones, distension also evoked depolarizations similar to the slow EPSPs evoked by electrical stimulation in the same neurones. Intracellular injection of biocytin and immunohistochemistry revealed that neurones responding to distension with slow EPSPs were descending interneurones, which were immunoreactive for nitric oxide synthase (NOS). Other neurones, including inhibitory motor neurones and interneurones lacking NOS, did not respond to distension with slow EPSPs, but many had slow EPSPs evoked electrically. Slow EPSPs evoked electrically or by distension in NOS‐immunoreactive descending interneurones were resistant to blockade of NK1 or NK3 tachykinin receptors (SR 140333, 100 nm; SR 142801, 100 nm, respectively) and group I metabotropic glutamate receptors (PHCCC, 10–30 μm), when the antagonists were applied in the recording chamber of a two‐chambered organ bath. However, slow EPSPs evoked electrically in inhibitory motor neurones were substantially depressed by SR 140333 (100 nm). Blockade of synaptic transmission in the stimulation chamber of the organ bath abolished slow EPSPs evoked by distension, indicating that they arose from activity in interneurones, and not from anally directed, intrinsic sensory neurones. Thus, distension evokes slow EPSPs in a subset of myenteric neurones, which may be important for intestinal motility.
Influence of afferent synaptic innervation on the discharge variability of cat abducens motoneurones
Authors: González‐Forero David , Álvarez Francisco J. , de la Cruz Rosa R. , Delgado‐García José María , Pastor Ángel M.
Published: July 2002

The discharge variability of abducens motoneurones was studied after blocking inhibitory synaptic inputs or both excitatory and inhibitory inputs by means of an intramuscular (lateral rectus) injection of either a low (0.5 ng kg−1) or a high dose (5 ng kg−1) of tetanus neurotoxin (TeNT), respectively. Motoneuronal firing increased after low‐dose TeNT. High‐dose treatment, however, produced a firing depression, and in some cells, a total lack of modulation in relation to eye movements. Firing became increasingly more regular with larger TeNT doses as shown by significant reductions in the coefficient of variation after low‐ and high‐dose treatments. Similarly, autocorrelation histograms of interspike intervals increased the number of resolvable peaks twofold in low‐dose‐treated motoneurones and sevenfold in high‐dose‐treated motoneurones. The plots of standard deviation versus the mean instantaneous firing frequency showed an upward deflexion with low firing frequencies. The upward deflexion occurred in controls at 39.9 ± 4.9 ms, an interval similar to the mean afterhyperpolarisation (AHP) duration (48.4 ± 8.8 ms). Low‐dose TeNT treatment shifted the deflexion point to 20.9 ± 3.9 ms, whereas the high dose increased it to 60.7 ± 6.1 ms, in spite of the fact that no differences in AHP parameters between groups were found. The density of synaptophysin‐immunoreactive boutons decreased by 14 % after the low‐dose treatment and 40.5 % after the high‐dose treatment, indicating that protracted synaptic blockade produces elimination of synaptic boutons. It is concluded that abducens motoneurone spike variability during spontaneous ocular fixations depends largely on the balance between inhibitory and excitatory synaptic innervation.
Long lasting effects of rTMS and associated peripheral sensory input on MEPs, SEPs and transcortical reflex excitability in humans
Authors: Tsuji Tetsuya , Rothwell John C.
Published: July 2002

We tested the effect of repetitive transcranial magnetic stimulation (rTMS) over the motor cortex on the size of transcortical stretch and mixed nerve reflexes. Fourteen healthy subjects were investigated using either 25 min of 1 Hz rTMS or 30 min of 0.1 Hz rTMS paired with electrical stimulation of the motor point of the first dorsal interosseous muscle (FDI). Following treatment, we measured the effect on the size of: (1) EMG responses evoked in FDI by transcranial magnetic stimulation (MEPs), (2) somatosensory evoked potentials (SEPs) evoked by ulnar nerve stimulation, and (3) transcortical stretch or electrically elicited reflexes. rTMS at 1 Hz reduced the amplitude of both MEPs and long latency reflexes by 20–30 % for about 10 min after the end of stimulation. Short latency reflexes were unaffected. SEPs were not studied, as it has been shown previously that they are also suppressed. rTMS at 0.1 Hz paired with motor point stimulation (interstimulus interval of 25 ms) increased the amplitude of the MEP and the cortical components of the SEP (N20/P25 and later peaks) for up to 10 min. Long latency reflexes were facilitated with the same time course. We conclude that rTMS over the motor cortex either alone or in conjunction with peripheral inputs can decrease or increase the excitability of the sensory and motor cortex for short periods after the end of stimulation. These changes affect not only MEPs and SEPs but also EMG responses to more ‘natural’ inputs involved in transcortical stretch reflexes.
Molecular determinants of the inhibition of human Kv1.5 potassium currents by external protons and Zn2+
Authors: Kehl Steven J. , Eduljee Cyrus , Kwan Daniel C. H. , Zhang Shetuan , Fedida David
Published: July 2002

Using human Kv1.5 channels expressed in HEK293 cells we assessed the ability of H+o to mimic the previously reported action of Zn2+ to inhibit macroscopic hKv1.5 currents, and using site‐directed mutagenesis, we addressed the mechanistic basis for the inhibitory effects of H+o and Zn2+. As with Zn2+, H+o caused a concentration‐dependent, K+o‐sensitive and reversible reduction of the maximum conductance (gmax). With zero, 5 and 140 mm K+o the pKH for this decrease of gmax was 6.8, 6.2 and 6.0, respectively. The concentration dependence of the block relief caused by increasing [K+]o was well fitted by a non‐competitive interaction between H+o and K+o, for which the KD for the K+ binding site was 0.5‐1.0 mm. Additionally, gating current analysis in the non‐conducting mutant hKv1.5 W472F showed that changing from pH 7.4 to pH 5.4 did not affect Qmax and that charge immobilization, presumed to be due to C‐type inactivation, was preserved at pH 5.4. Inhibition of hKv1.5 currents by H+o or Zn2+ was substantially reduced by a mutation either in the channel turret (H463Q) or near the pore mouth (R487V). In light of the requirement for R487, the homologue of Shaker T449, as well as the block‐relieving action of K+o, we propose that H+ or Zn2+ binding to histidine residues in the pore turret stabilizes a channel conformation that is most likely an inactivated state.
Analytical Stability Analysis of Variable Spindle Speed Machining
Authors: Jayaram S. , Kapoor S. G. , DeVor R. E.
Published: July 2002

A new analytical model to predict the chatter stability of variable spindle speed machining is presented. This model is based on transforming the linear differential equations with time varying delay to the solution of an infinite order characteristic equation. The model has been validated using the results of numerical time domain simulations and through experimentation. The analytical model employs normalized parameters which permits its use in studying the stability of variable spindle speed machining systems with a wide range of parameters without having to solve the complex system of differential equations. The analytical model is also used to design optimal variable spindle speed machining parameters in the presence of known fixed or varying machining dynamics. [S1087-1357(00)01402-7]
Suppression of Performance Curve Instability of a Mixed Flow Pump by Use of J-groove
Authors: Saha Sankar L. , Kurokawa Junichi , Matsui Jun , Imamura Hiroshi
Published: July 2002

In order to control and suppress performance curve instability characterized by the positive slope of head-capacity curve of a mixed flow pump, a very simple passive method utilizing shallow grooves mounted on a casing wall parallel to the pressure gradient (J-groove) is proposed. The optimum groove dimension and location for suppressing such an instability are determined experimentally. Results show that shallow grooves of adequate dimension and proper location can suppress such instability perfectly without decreasing the pump maximum efficiency. The remarkable effect of shallow grooves is to decrease both the swirl strength and the propagation of reverse flow at the impeller inlet region, through angular momentum absorption owing to mixing of groove reverse flow and swirl flow, yielding recovery of impeller theoretical head. [S0098-2202(00)02603-1]
Constitutive Dynamic-Order Model for Nonlinear Contact Phenomena
Authors: Ingman D. , Suzdalnitsky J. , Zeifman M.
Published: July 2002

A dynamic integro-differential operator of variable order is suggested for a more adequate description of processes, which involve state dependent measures of elastic and inelastic material features. For any negative constant order this operator coincides with the well-known operator of fractional integration. The suggested operator is especially effective in cases with strong dependence of the behavior of the material on its present state—i.e., with pronounced nonlinearity. Its efficiency is demonstrated for cases of viscoelastic and elastoplastic spherical indentation into such materials (aluminum, vinyl) and into an elastic material (steel) used as a reference. Peculiarities in the behavior of the order function are observed in these applications, demonstrating the “physicality” of this function which characterizes the material state. Mathematical generalization of the fractional-order integration-differentiation in the sense of variability of the operator order, as well as definitions and techniques, are discussed. [S0021-8936(00)02102-4]
The Top With a Blunted Vertex Slipping With Light Friction at a High Rate of Spin
Authors: Paris, P. C. , Zhang, and L. , Tada H.
Published: July 2002

The problem of determining the motion of a top is a classic example of a complex analysis in analytical dynamics. Adding a blunt tip to the top and setting it spinning on a surface with sliding friction might be thought to render it intractable for simple analysis. However, if it is set in motion with a high rate of spin it is possible to find a simple approximate solution for the case of approximate steady precession. For this pseudo-steady motion it will be noted that the rate of diminution of the nutation will also be almost constant. Further, the ratio of these rates (latter over former) will be equal to the negative of the coefficient of friction for the top slipping on the surface. As a consequence the mass center of the top will tend to proceed around a steady circle above the plane. These results will first be observed by writing the full Lagrange’s equations for the problem and reducing them prior to integration by observing appropriate approximations by deleting relatively smaller terms. The above results will then follow directly. Further, the full Lagrange’s equations will be numerically integrated to show that the analytically developed approximate results are appropriate. Once these results are known, it is observed that a subsequent intuitive analysis based on time rate of change of angular momentum leads to the same results, if only the angular momentum about the spin axis is considered with other relevant assumptions. [S0021-8936(00)00203-8]