bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ XAFS study at the Zr K-edge for SiO2/ZrO2 nano-sol
Authors: Choy Jin-Ho , Yoon Joo-Byoung , Park Joo-Hyoung
Published: July 2002

The structural characterisation of SiO2/ZrO2 nano-sol particles, prepared by mixing SiO2 sol and aqueous solution of ZrOCl2 8H2O, has been carried out by in-situ XAS measurement at the Zr K-edge during condensation reaction. The detailed XANES features at the Zr K-edge of the mixed sol of SiO2/ZrO2 are compared with those of other references such as ZrO2, ZrOCl2 8H2O, BaZrO3, and ZrSiO4, and it becomes obvious that the Zr4+ ions are stabilised in an octahedral symmetry. The EXAFS result also indicates that each Zr atom is coordinated with six oxygen ones as the first nearest neighbour, where two oxygen atoms are from the linkage of (Si-O-Zr) at short distance, and four ones are from water molecules at long distance. As the condensation reaction proceeds, it is found that the number of oxygen atoms due to the formation of (Si-O-Zr) bond at short distance and the second neighbour of silicon atoms increase simultaneously. From the above EXAFS and XANES results, the structural and gelating models could be proposed, which is based on the octahedrally coordinated but distorted zirconium species attaching on the SiO2 sol surface.
Local structure of Pb (II) ion catalysts anchored within zeolite cavities and their photocatalytic reactivity for the elimination of N2O
Authors: Ju Woo-Sung , Matsuoka Masaya , Yamashita Hiromi , Anpo Masakazu
Published: July 2002

The Pb2+/ZSM-5 catalyst was prepared by an ion-exchange method and its photocatalytic activity for the decomposition of N2O under UV irradiation was investigated. In-situ UV-Vis absorption spectroscopy and XAFS (XANES and FT-EXAFS) investigations revealed that the Pb2+ ions exist in a highly dispersed state within the pores of the zeolites. UV irradiation of the catalysts in the presence of N2O led to the photocatalytic decomposition of N2O into N2 at temperatures as low as 298K. The effective wavelength of the irradiated UV light indicated that the excited state of the Pb2+ ions included within the zeolite cavities plays a significant role in the photocatalytic decomposition of N2O molecules.
Determination of the local structure of the first and second shells in ordered and disordered Ni–Mn alloys
Authors: Ryazhkin A. V. , Babanov Yu. A. , Pilugin V. P. , Miyanaga T. , Okazaki T. , Crozier E. D. , Gordon R. A.
Published: July 2002

The coordination numbers and the interatomic distances for 50, 75 and 80 at.% Ni-Mn alloys in ordered and disordered states are presented. A new method for determining the first and second nearest neighbor coordination numbers in a binary alloy is applied. It is shown that magnetic properties of these alloys depend on short range order in atomic arrangement.
Double-channel excitation in the XAS spectra of divalent and trivalent iron complexes in water solution
Authors: Benfatto M. , Solera J. A. , García J. , Chaboy J.
Published: July 2002

We present a detailed analysis of XAS spectra of divalent and trivalent iron complexes in water solutions. The interpretation of the spectra has been provided by multi-channel multiple scattering approach. On this basis, good agreement between experimental data and theoretical calculations has been obtained in both cases including two excitation channels in the final state.
Has charge ordering actually been observed in manganites by resonant X-ray scattering?
Authors: García J. , Sánchez M. C. , Blasco J. , Subías G. , Proietti M. G.
Published: July 2002

The comparison between X-ray resonant scattering experiments and X-ray absorption data shows that no real Mn3+/Mn4+ charge ordering occurs in manganites with Mn3+/Mn4+ = 1 ratio. However, these experiments demonstrate the presence of two different types of manganese atoms with a different local geometrical structure. A structural model, which accounts for both X-ray absorption and resonant scattering experiments, is proposed.
Observation of the segregation and the dissolution of the Co and the Cu in CoCu metastable alloys
Authors: Fdez-Gubieda M. L. , Garcia Prieto A. , Garcia Arribas A. , Meneghini C. , Mobilio S.
Published: July 2002

Metastable Co
x
Cu100-x
(x = 5, 10, 15, 20) alloys have been annealed at increasing temperatures in order to study the evolution of the Co cluster and its relation with the magnetotransport properties. The structure was investigated by on the Co K-edge as a function of composition and annealing temperature. An anomalous trend in the structural evolution has been evidenced and related to the peculiar features observed in the magnetotransport properties.
O K and Cu L
III edge study of itinerant holes in I2-, HgI2- and HgBr2-intercalated BSCCO(2212) single crystals
Authors: Garg K. B. , Dalela B. , Dalela S. , Venkatesh S. , Choy J.-H. , Chaturvedi D. , Singhal R. K. , Garcia-Ruiz J.
Published: July 2002

Intercalation effect on BSCCO (2212) system, although it increases the interlayer distance and the c-axis remarkably, produces only a small change in the transition temperature. Thus, amongst other things, intercalation provides an effective method to investigate the influence of the inter-block coupling. Electrons are transferred from the host Cu-O2 layers to the guest lmolecules I2, HgBr2, HgI2 leading to evolution of the Tc. For this we have made high resolution XANES study on the O K and Cu L3 edges to estimate the density of the doping holes. We attempt on basis of our and earlier results the evolution of Tc in these as also the much larger decrease produced in Tc for I2-intercalation for which the increase in basal spacing is the smallest of the three halides.
Loyalty kiosks: making loyalty cards work
Authors: Rowley Jennifer
Published: July 2002

Loyalty cards have become a popular strategy among retailers for collecting information about customer purchases and for offering “‘reward points” and other promotions. Many commentators have, however, been skeptical about the value of loyalty cars and, in particular, their ability to cultivate and promote the attitudes and behaviour associated with loyalty. This case study‐based article describes a new application of loyalty cards, which is being piloted in selected Sainsbury’s stores. Loyalty cards are swiped through a slot in a public access kiosk, located in store, to provide customer access to a range of selected benefits. These benefits include recipes, special reductions, information on videos, and other customer service options. The customer selects options by choosing from a simple touch screen. Special offer coupons or recipes are printed on small pieces of paper. Is this new application the basis for an enhanced role for loyalty cards? The article argues that this potential will only be realised if loyalty cards can become an integral part of the relationship with the customer, and cease to be no more than an “‘add‐on”.
Laying foundations for effective learning from commissioned projects in business education
Authors: Laughton David , Ottewill Roger
Published: July 2002

Examines the nature of commissioned projects in business education and the value they hold for key stakeholder groups: students, tutors and clients. Identifies the essence of commissioned projects as being a unique fusion of vocational and pedagogic (problem‐based learning) perspectives. Describes the structure of commissioned projects and argues that this is a necessary but not sufficient condition for their success. Argues that the key to their successful utilisation is the establishment of effective foundations. Identifies these as a strategy for curriculum support; a commitment to the integration of skills and knowledge; a negotiated approach to the specification of learning outcomes; a recognition of the importance of process issues; the development of a framework for applying learning; and an emphasis on the concept of reflective practice.
Analysis of the implementation of ISO 9000 quality assurance systems
Authors: Martínez Fuentes Clara , Balbastre Benavent Francisco , Angeles Escribá Moreno M. , González Cruz Tomás , Pardo del Val Manuela
Published: July 2002

Examines the literature relating to the implementation of quality assurance systems and then uses a questionnaire to a number of organisations and consultants to compare “practice” with “theory”. Analyses the implementation process for quality assurance systems designed to meet the requirements of the ISO 9000 standard to identify the role of the different “actors” to find out which factors facilitate the implementation or make it more difficult. Suggests that the primary motivation for introducing ISO 9000 systems is to improve image and reputation rather than processes.
Exploring the limits of Western leadership theory in East Asia and Africa
Authors: Blunt Peter , Jones Merrick L.
Published: July 2002

Contends that the vacuum left by the collapse of colonial empires has been filled by new forms of cultural and ideological imperialism conceived largely in the West. Signs of the new imperialism are to be found in many fields including human resource management. Explores this theme, focusing particularly on ideas about leadership. Examines leadership patterns in East Asia and Africa. Suggests that no single model of leadership can accommodate significant variations in societal culture and their influence on organizational behaviour.
“Scientists” and “amateurs”: mapping the bullying domain
Authors: Liefooghe Andy P.D. , Olafsson Ragnar
Published: July 2002

When a new field is explored, a variety of approaches can be used to clarify, identify and explain the phenomenon at hand. Traditional psychological research attributes a quasi‐physical quality to the bullying phenomenon, and attempts to capture it by rigorous measurement of a number of variables. We argue that, while this approach has considerable advantages, an investigation of the way “amateur scientists” explain “bullying” can aid a more detailed understanding. The use of the Critical Incident Technique in focus groups allowed participants to make their implicit thoughts and feelings about bullying explicit. Participants revealed a number of auxiliary or alternative frameworks to account for bullying‐related phenomena. It is suggested that these frameworks need closer scrutiny in terms of social representations. Implications of this approach are discussed in terms of their potential effect on policy development and implementation, highlighting the role organisational culture plays in this field.
Robotic fibre placement process planning and control
Authors: Shirinzadeh Bijan , Wei Foong Chee , Hui Tan Boon
Published: July 2002

The excellent material properties of fibre reinforced composites make them especially attractive for applications in the aerospace and automotive industries. Traditional methods of manufacturing composite structures have proven to be labour intensive and time‐consuming. Robotic fibre placement for fabrication of composite components has been proposed. This approach greatly reduces production cost and time. This paper briefly presents the overall strategy for the establishment of a robotic fibre placement facility. The methodology for development of process planning and programming, simulation, program generator and control is described. In addition, the algorithms for automatic fibre path generation for open and closed surfaces will also be discussed, as well as the control system architecture for the process.
Features Automated assembly and fixture planning at Sandia National Laboratories
Authors: Jones Rondall E. , Calton Terri L. , Peters Ralph R.
Published: July 2002

The Intelligent Systems and Robotics Center at Sandia National Laboratories supports several ongoing projects oriented towards enabling the creation of more automatic and effective robotic assembly systems, especially for small lot production. Two of these projects are Archimedes, which is an automatic assembly planning system, and HoldFast, which automatically designs optimal form‐closure fixtures. These technologies have application in many automated assembly contexts, whether robotic or not. Discusses the current state and applications of these two technologies. Both are based on use of a 3D CAD model, which currently must be converted to ACIS form for processing. Archimedes reasons about the liaisons between parts, then derives an assembly plan that is geometrically valid. This plan is improved by interaction with the user, who adds “constraints” to guide replanning. Facilities to define and search for a user’s “optimal” plan are under development. Given a workpiece shape, task constraints, and a description of a fixture kit, HoldFast finds the optimal fixture that can be made from the kit to hold the workpiece in form‐closure.
Institutional entrepreneurship ‐ A panacea for universities‐in‐transition?
Authors: Liu Sandra S. , Dubinsky Alan J.
Published: July 2002

University administrators are facing increasingly difficult times as public funds are contracting and accountability for the use of such moneys is increasing. With these financial exigencies, universities must seek alternative means of generating revenues to support their mission. One such approach involves the use of institutional entrepreneurship. This paper describes how institutional entrepreneurship complements strategic marketing management and strategic management, how it can ultimately generate funds for universities‐in‐transition, and provides a case illustration of how universities have successfully employed entrepreneurial activities to their advantage.
Benchmarking employee skills: results from best practice firms in Greece
Authors: Papalexandris Nancy , Nikandrou Irene
Published: July 2002

The globalization of economic activity and the rapid technological developments require a more qualified workforce with multiple skills. As a result, rapid obsolescence of competences makes the capacity to update continuously and develop the required skills the key to competitiveness and growth. Moreover, under the pressure of competitive forces, developments in the HRM practices become increasingly important. The first part of this article draws from the findings of the Cranfield survey, in which Greece participated three times (in 1993, 1996 and 1999), in order to present an overall picture of HRM in Greece. The second part analyzes the results of a larger European Union project to study skills benchmarking in Europe, in which Greece participated along with eight European countries. The results from the Greek study do not show considerable deviations from the whole European sample. Some of the main conclusions of the study are: training can no longer be treated as a method to cure skills deficiencies, but rather as a continuous, life‐long learning process with considerable impact to the growth of the firms; acquiring human skills presents the greatest challenge for training; and adaptability and self‐learning are necessary elements that need to be incorporated in the educational system from its early stages.
American higher education system: consumerism versus professorialism
Authors: Michael Steve O.
Published: July 2002

Suggests that institutions of higher education in the USA encounter problems that are unique to the market environment. These problems include competition for resources, escalating costs, and resource constraints. In response to these problems, higher education systems within this kind of environment tend to borrow strategies from organizations operating under the most competitive environment ‐ the business sector. Discusses specific strategies adopted by institutions of higher education in North America. Examines how these strategies have affected the culture of higher education. Discusses the shift occurring between the consumerism‐ professorialism continuum. Calls for the need to understand the dual nature of higher education so that strategies can be selectively adapted.
Finite element analysis of heat transfer by natural convection in porous media in vertical enclosures
Authors: Satya Sai B.V.K. , Seetharamu K.N. , Aswathanarayana P.A.
Published: July 2002

Presents a numerical study on heat transfer by natural convection in porous media in vertical enclosures with side wall heating. The model for porous media includes inertia terms and also the Brinkman extension in addition to the Darcy resistance term. A semi‐implicit finite element scheme based on operator splitting method is adopted for solving the time‐dependent system of equations. The first half of the investigations is confined to the low permeability regime where Darcy law holds good. Presents the results for annular and rectangular cavities and proposes correlations for two types of boundary conditions, namely constant wall temperature case and uniform wall heat flux case. In the second half of the investigations, the scheme is applied in a high permeability regime, where the validity of Darcy law becomes questionable. Employs plane rectangular cavities with the two types of boundary conditions mentioned earlier. Highlights the influence of Rayleigh number (Ra) and Darcy number (Da) as separate parameters and proposes correlations for a square cavity for the first time in terms of Ra and Da as separate parameters. Discusses a qualitative study of the effect of aspect ratio on heat transfer as the permeability changes.
Print and Internet catalog shopping: assessing attitudes and intentions
Authors: Vijayasarathy Leo R. , Jones Joseph M.
Published: July 2002

The use of print catalogs for direct marketing has a long history of success. Today, telecommunication networks, such as the Internet, offer the potential to reach a larger market through the use of online catalogs that could be dynamic, flexible, and consumer‐responsive. This paper reports the results of an empirical study that compared individuals’ attitudes and intentions to shop using print and Internet catalogs. The findings suggest that individuals perceived differences between the two catalog media on the shopping factors of reliability, tangibility, and consumer risk. Further, product value, pre‐order information, post‐selection information, shopping experience, and consumer risk emerged as the factors that influenced attitudes and intentions to shop using print and Internet catalogs.
Direct slicing of CAD models for rapid prototyping
Authors: Jamieson Ron , Hacker Herbert
Published: July 2002

The 3D Systems stereolithography file format is a good workhorse for the rapid prototyping (RP) industry. It is supported by all major computer‐aided design (CAD) and RP manufacturers and there now exists a selection of third‐party software which supports this de facto standard and helps to make it work better. However, input to RP systems is sometimes best suited to the format of sliced contours. These may be produced from a three‐dimensional CAD model or via reverse engineering techniques such as laser scans and co‐ordinate measuring machines. Other sources include computed tomography and magnetic resonance imaging scans. Takes a brief look at both of the above methods, listing their advantages and disadvantages. Identifies several ways in which sliced data can be used to drive RP processes. Finally, presents in detail a methodology used to develop a direct and adaptive slicer from a commercial CAD system.
High‐resolution crystal structure of apolipoprotein(a) kringle IV type 7: Insights into ligand binding
Authors: Ye Qilu , Rahman Mona N. , Koschinsky Marlys L. , Jia Zongchao
Published: July 2002

Apolipoprotein(a) [apo(a)] consists of a series of tandemly repeated modules known as kringles that are commonly found in many proteins involved in the fibrinolytic and coagulation cascades, such as plasminogen and thrombin, respectively. Specifically, apo(a) contains multiple tandem repeats of domains similar to plasminogen kringle IV (designated as KIV1 to KIV10) followed by sequences similar to the kringle V and protease domains of plasminogen. The KIV domains of apo(a) differ with respect to their ability to bind lysine or lysine analogs. KIV10 represents the high‐affinity lysine‐binding site (LBS) of apo(a); a weak LBS is predicted in each of KIV5–KIV8 and has been directly demonstrated in KIV7. The present study describes the first crystal structure of apo(a) KIV7, refined to a resolution of 1.45 Å, representing the highest resolution for a kringle structure determined to date. A critical substitution of Tyr‐62 in KIV7 for the corresponding Phe‐62 residue in KIV10, in conjunction with the presence of Arg‐35 in KIV7, results in the formation of a unique network of hydrogen bonds and electrostatic interactions between key LBS residues (Arg‐35, Tyr‐62, Asp‐54) and a peripheral tyrosine residue (Tyr‐40). These interactions restrain the flexibility of key LBS residues (Arg‐35, Asp‐54) and, in turn, reduce their adaptability in accommodating lysine and its analogs. Steric hindrance involving Tyr‐62, as well as the elimination of critical ligand‐stabilizing interactions within the LBS are also consequences of this interaction network. Thus, these subtle yet critical structural features are responsible for the weak lysine‐binding affinity exhibited by KIV7 relative to that of KIV10.
Dynamics of green fluorescent protein mutant2 in solution, on spin‐coated glasses, and encapsulated in wet silica gels
Authors: Chirico Giuseppe , Cannone Fabio , Beretta Sabrina , Diaspro Alberto , Campanini Barbara , Bettati Stefano , Ruotolo Roberta , Mozzarelli Andrea
Published: July 2002

Single‐molecule experiments are performed by investigating spectroscopic properties of molecules either diffusing in and out of the observation volume or fixed in space by different immobilization procedures. To evaluate the effect of immobilization methods on the structural and dynamic properties of proteins, a highly fluorescent mutant of the green fluorescent protein, GFPmut2, was spectroscopically characterized in bulk solutions, dispersed on etched glasses, and encapsulated in wet, nanoporous silica gels. The emission spectrum, the fluorescence lifetimes, the anisotropy, and the rotational correlation time of GFPmut2, encapsulated in silica gels, are very similar to those obtained in solution. This finding indicates that the gel matrix does not alter the protein conformation and dynamics. In contrast, the fluorescence lifetimes of GFPmut2 on glasses are two‐to fourfold higher and the fluorescence anisotropy decays yield almost no phase shifts. This indicates that the interaction of the protein with the bare glass surface induces a significant structural perturbation and severely restricts the rotational motion. Single molecules of GFPmut2 on glasses or in silica gels, identified by confocal image analysis, show a significant stability to illumination with bleaching times of the order of 90 and 60 sec, respectively. Overall, these data indicate that silica gels represent an ideal matrix for following biologically relevant events at a single molecule level.
Thermal unfolding of ribonuclease A in phosphate at neutral pH: Deviations from the two–state model
Authors: Stelea Simona D. , Pancoska Petr , Benight Albert S. , Keiderling Timothy A.
Published: July 2002

The thermal denaturation of ribonuclease A (RNase A) in the presence of phosphate at neutral pH was studied by differential scanning calorimetry (DSC) and a combination of optical spectroscopic techniques to probe the existence of intermediate states. Fourier transform infrared (FTIR) spectra of the amide I′ band and far‐uv circular dichroism (CD) spectra were used to monitor changes in the secondary structure. Changes in the tertiary structure were monitored by near‐uv CD. Spectral bandshape changes with change in temperature were analyzed using factor analysis. The global unfolding curves obtained from DSC confirmed that structural changes occur in the molecule before the main thermal denaturation transition. The analysis of the far‐uv CD and FTIR spectra showed that these lower temperature–induced modifications occur in the secondary structure. No pretransition changes in the tertiary structure (near‐uv CD) were observed. The initial changes observed in far‐uv CD were attributed to the fraying of the helical segments, which would explain the loss of spectral intensity with almost no modification of spectral bandshape. Separate analyses of different regions of the FTIR amide I′ band indicate that, in addition to α‐helix, part of the pretransitional change also occurs in the β‐strands.
Regulation of intracellular pH in Calu‐3 human airway cells
Authors: Inglis S. K. , Finlay L. , Ramminger S. J. , Richard K. , Ward M. R. , Wilson S. M. , Olver R. E.
Published: July 2002

The Calu‐3 human cell line exhibits features of submucosal gland serous cells and secretes HCO3−. The aim of this study was to identify the HCO3− transporters present in these cells by studying their role in the regulation of intracellular pH (pHi). Calu‐3 cells were grown on coverslips, loaded with the pH‐sensitive fluorescent dye BCECF, and their fluorescence intensity monitored as an indication of pHi. Cells were acidified with NH4Cl (25 mm, 1 min) and pHi recovery recorded. In the absence of HCO3−, initial recovery was 0.208 ± 0.016 pH units min−1(n = 37). This was almost abolished by removal of extracellular Na+ and by amiloride (1 mm), consistent with the activity of a Na+‐H+ exchanger (NHE). In the presence of HCO3− and CO2, recovery (0.156 ± 0.018 pH units min−1) was abolished (reduced by 91.8 ± 6.7 %, n = 7) by removal of Na+ but only attenuated (by 63.3 ± 5.8 %, n = 9) by amiloride. 4,4‐Dinitrostilbene‐2,2‐disulfonic acid (DNDS) inhibited recovery by 45.8 ± 5.0 % (n = 7). The amiloride‐insensitive recovery was insensitive to changes in membrane potential, as confirmed by direct microelectrode measurements, brought about by changing extracellular [K+] in the presence of either valinomycin or the K+ channel opener 1‐EBIO. In addition, forskolin (10 μm), which activates the cystic fibrosis transmembrane conductance regulator Cl− conductance in these cells and depolarises the cell membrane, had no effect on recovery. Removal of extracellular Cl− trebled pHi recovery rates, suggesting that an electroneutral, DNDS‐sensitive, Cl−‐HCO3− exchanger together with a NHE may be involved in pHi regulation and HCO3− secretion in these cells. RT‐PCR detected the expression of the electrogenic Na+‐HCO3− cotransporter NBC1 and the Cl−‐HCO3− exchanger (AE2) but not the electroneutral Na+‐HCO3− cotransporter NBCn1.
Relaxation by vasoactive intestinal polypeptide in the gastric fundus of nitric oxide synthase‐deficient mice
Authors: Dick Joëlle M. C. , Van Molle Wim , Brouckaert Peter , Lefebvre Romain A.
Published: July 2002

In many gastrointestinal tissues nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) both play a role as inhibitory non‐adrenergic non‐cholinergic neurotransmitters. As the mode of interaction between NO and VIP remains controversial, the aim of this study was to investigate the interplay between NO and VIP in the mouse gastric fundus and to evaluate the nitric oxide synthase (NOS) isoform involved in VIP‐induced relaxation by using inducible NOS (iNOS), endothelial NOS (eNOS) and neuronal NOS (nNOS) knockout mice. The influence of NOS inhibitors on the relaxant effect of VIP was determined in isolated smooth muscle cells and smooth muscle strips of wild‐type and knockout mice. In isolated smooth muscle cells from wild‐type, eNOS knockout and nNOS knockout mice, the relaxation induced by VIP (10−9m) was inhibited by approximately 70–95 % by both the non‐selective NOS inhibitor NG‐nitro‐l‐arginine (l‐NA; 10−4m) and the selective inducible NOS inhibitor N‐(3‐(aminomethyl)‐benzyl)acetamidine (1400W; 10−6m). In cells isolated from iNOS knockout mice, VIP still induced full relaxation but it was not influenced by l‐NA or 1400W. In smooth muscle strips from wild‐type and knockout mice, the concentration‐dependent relaxation by VIP (10−9 to 3 × 10−7m) was not influenced by l‐NA or 1400W. These results suggest that the experimental method determines the influence of NOS inhibitors on the relaxant effect of VIP. iNOS, probably induced by the isolation procedure, might be involved in the relaxant effect of VIP in isolated smooth muscle cells but not in classic smooth muscle strips.
Identification and function of ryanodine receptor subtype 3 in non‐pregnant mouse myometrial cells
Authors: Mironneau J. , Macrez N. , Morel J.L. , Sorrentino V. , Mironneau C.
Published: July 2002

Subtype 3 of the ryanodine receptor (RYR3) is a ubiquitous Ca2+ release channel which is predominantly expressed in smooth muscle tissues and certain regions of the brain. We show by reverse transcription‐polymerase chain reaction (RT‐PCR) that non‐pregnant mouse myometrial cells expressed only RYR3 and therefore could be a good model for studying the role of endogenous RYR3. Expression of RYR3 was confirmed by Western blotting and immunostaining. Confocal Ca2+ measurements revealed that in 1.7 mm extracellular Ca2+, neither caffeine nor photolysis of caged Ca2+ were able to trigger any Ca2+ responses, whereas in the same cells oxytocin activated propagated Ca2+ waves. However, under conditions of increased sarcoplasmic reticulum (SR) Ca2+ loading, brought about by superfusing myometrial cells in 10 mm extracellular Ca2+, all the myometrial cells responded to caffeine and photolysis of caged Ca2+, indicating that it was possible to activate RYR3. The caffeine‐induced Ca2+ responses were inhibited by intracellular application of an anti‐RYR3‐specific antibody. Immunodetection of RYR3 with the same antibody revealed a rather homogeneous distribution of fluorescence in confocal cell sections. In agreement with these observations, spontaneous or triggered Ca2+ sparks were not detected. In conclusion, our results suggest that under conditions of increased SR Ca2+ loading, endogenous RYR3 may contribute to the Ca2+ responses of myometrial cells.
Feedback inhibition in the inner plexiform layer underlies the surround‐mediated responses of AII amacrine cells in the mammalian retina
Authors: Völgyi Béla , Xin Daiyan , Bloomfield Stewart A.
Published: July 2002

Intracellular recordings were made from narrow‐field, bistratified AII amacrine cells in the isolated, superfused retina‐eyecup of the rabbit. Pharmacological agents were applied to neurons to dissect the synaptic pathways subserving AII cells so as to determine the circuitry generating their off‐surround responses. Application of the GABA antagonists, picrotoxin, bicuculline and 1,2,5,6‐tetrahydropyridine‐4‐yl methylphosphinic acid (TPMPA) all increased the on‐centre responses of AII amacrine cells, but attenuated the off‐surround activity. At equal concentrations, picrotoxin was approximately twice as effective as bicuculline or TPMPA in modifying the response activity of AII amacrine cells. These results indicate that the mechanism underlying surround inhibition of AII amacrine cells includes activation of both GABAA and GABAC receptors in an approximately equal ratio. Application of the GABA antagonists also increased the size of on‐centre receptive fields of AII amacrine cells. Again, picrotoxin was most effective, producing, on average, a 54 % increase in the size of the receptive field, whereas bicuculline and TPMPA produced comparable 34 and 33 % increases, respectfully. Application of the voltage‐gated sodium channel blocker TTX produced effects on AII amacrine cells qualitatively similar to those of the GABA blockers. Intracellular application of the chloride channel blocker 4,4′‐dinitro‐stilbene‐2,2′‐disulphonic acid (DNDS) abolished the direct effects of GABA on AII amacrine cells. Moreover, DNDS increased the amplitude of both the on‐centre and off‐surround responses. The failure of DNDS to block the off‐surround activity indicates that it is not mediated by direct GABAergic inhibition. Taken together, our results suggest that surround receptive fields of AII amacrine cells are generated indirectly by the GABAergic, reciprocal feedback synapses from S1/S2 amacrine cells to the axon terminals of rod bipolar cells.
Ca2+‐activated Cl− current in rabbit sinoatrial node cells
Authors: Verkerk Arie O. , Wilders Ronald , Zegers Jan G. , van Borren Marcel M. G. J. , Ravesloot Jan H. , Verheijck E. Etienne
Published: July 2002

The Ca2+‐activated Cl− current (ICl(Ca)) has been identified in atrial, Purkinje and ventricular cells, where it plays a substantial role in phase‐1 repolarization and delayed after‐depolarizations. In sinoatrial (SA) node cells, however, the presence and functional role of ICl(Ca) is unknown. In the present study we address this issue using perforated patch‐clamp methodology and computer simulations. Single SA node cells were enzymatically isolated from rabbit hearts. ICl(Ca) was measured, using the perforated patch‐clamp technique, as the current sensitive to the anion blocker 4,4′‐diisothiocyanostilbene‐2,2′‐disulphonic acid (DIDS). Voltage clamp experiments demonstrate the presence of ICl(Ca) in one third of the spontaneously active SA node cells. The current was transient outward with a bell‐shaped current‐voltage relationship. Adrenoceptor stimulation with 1 μm noradrenaline doubled the ICl(Ca) density. Action potential clamp measurements demonstrate that ICl(Ca) is activate late during the action potential upstroke. Current clamp experiments show, both in the absence and presence of 1 μm noradrenaline, that blockade of ICl(Ca) increases the action potential overshoot and duration, measured at 20 % repolarization. However, intrinsic interbeat interval, upstroke velocity, diastolic depolarization rate and the action potential duration measured at 50 and 90 % repolarization were not affected. Our experimental data are supported by computer simulations, which additionally demonstrate that ICl(Ca) has a limited role in pacemaker synchronization or action potential conduction. In conclusion, ICl(Ca) is present in one third of SA node cells and is activated during the pacemaker cycle. However, ICl(Ca) does not modulate intrinsic interbeat interval, pacemaker synchronization or action potential conduction.
The effects of temperature on vesicular supply and release in autaptic cultures of rat and mouse hippocampal neurons
Authors: Pyott Sonja J. , Rosenmund Christian
Published: July 2002

Membrane fusion plays a central role in the synaptic vesicle cycle. While many of the pre‐ and postfusion events have been investigated at room temperature, few researchers have investigated these processes at more physiologically relevant temperatures. We have used autaptic cultures of hippocampal neurons to investigate changes in the size and refilling rate of the readily releasable pool (RRP) of synaptic vesicles brought about by an increase in temperature from 25 to 35 °C. We have also examined temperature‐dependent changes in spontaneous and action potential (AP)‐evoked release as well as the fraction of the RRP that is released during an AP. Although we found a threefold increase in the refilling rate of the RRP at the higher temperature, there was no apparent change in the size of the RRP with increased temperature. Moreover, we observed a slight but significant decrease in the quanta released during an AP. This increased refilling rate and decreased release probability resulted in a reduction of both the degree and time course of synaptic depression during high frequency stimulation at the higher temperature. This reduction in synaptic depression was accompanied by an increased maintenance of the synchronous component of release during high frequency stimulation. These findings indicate that the dynamics of vesicular supply and release in hippocampal neurons at room temperature are significantly different at near physiological temperatures and could affect our present understanding of the way in which individual neurons and networks of neurons process information.
Activation of group I mGluRs elicits different responses in murine CA1 and CA3 pyramidal cells
Authors: Chuang Shih‐Chieh , Zhao Wangfa , Young Steven R. , Conquet François , Bianchi Riccardo , Wong Robert K. S.
Published: July 2002

The group I metabotropic glutamate receptor agonist DHPG has been shown to produce two major effects on CA3 pyramidal cells at rest: a reduction in the background conductance and an activation of a voltage‐gated inward current (ImGluR(V)). Both effects contribute to depolarising CA3 pyramidal cells and the latter has been implicated in eliciting prolonged epileptiform population bursts. We observed that DHPG‐induced depolarisation was smaller in CA1 pyramidal cells than in CA3 cells. Voltage clamp studies revealed that while DHPG elicited ImGluR(V) in CA3 pyramidal cells, such a response was absent in CA1 pyramidal cells. Both mGluR1 and mGluR5 have been localised in CA3 pyramidal cells, whereas only mGluR5 has been detected in CA1 pyramidal cells. Using mGluR1 knockout mice, we evaluated whether the absence of an ImGluR(V) response can be correlated with the absence of mGluR1. In these experiments, DHPG failed to elicit ImGluR(V) in CA3 pyramidal cells. This suggests that the smaller depolarising effects of DHPG on wild‐type CA1 pyramidal cells is caused, at least in part, by the absence of ImGluR(V) in these cells and that the difference in the responses of CA1 and CA3 cells may be attributable to the lack of mGluR1 in CA1 pyramidal cells.
MgATP counteracts intracellular proton inhibition of the sodium‐calcium exchanger in dialysed squid axons
Authors: DiPolo Reinaldo , Beaugé Luis
Published: July 2002

Intracellular Na+ and H+ inhibit Na+‐Ca2+ exchange. ATP regulates exchange activity by altering kinetic parameters for Ca2+i, Na+i and Na+o. The role of the Ca2+i regulatory site on Na+i‐H+i‐ATP interactions was explored by measuring the Na+o‐dependent 45Ca2+ efflux (Na+o‐Ca2+i exchange) and Ca2+i‐dependent 22Na+ efflux (Na+o‐Na+i exchange) in intracellular‐dialysed squid axons. Our results show that: (1) without ATP, inhibition by Na+i is strongly dependent on H+i. Lowering the pHi by 0.4 units from its physiological value of 7.3 causes 80 % inhibition of Na+o‐Ca2+i exchange; (2) in the presence of MgATP, H+i and Na+i inhibition is markedly diminished; and (3) experiments on Na+o‐Na+i exchange indicate that the drastic changes in the Na+i‐H+i‐ATP interactions take place at the Ca2+i regulatory site. The increase in Ca2+i affinity induced by ATP at acid pH (6.9) can be mimicked by a rise in pHi from 6.9 to 7.3 in the absence of the nucleotide. We conclude that ATP modulation of the Na+‐Ca2+ exchange occurs by protection from intracellular proton and sodium inhibition. These findings are predicted by a model where: (i) the binding of Ca2+ to the regulatory site is essential for translocation but not for the binding of Na+i or Ca2+i to the transporting site; (ii) H+i competes with Ca2+i for the same form of the exchanger without an effect on the Ca2+i transporting site; (iii) protonation of the carrier increases the apparent affinity and changes the cooperativity for Na+i binding; and (iv) ATP prevents both H+i and Na+i effects. The relief of H+ and Na+ inhibition induced by ATP could be important in cardiac ischaemia, in which a combination of acidosis and rise in [Na+]i occurs.
Heterogeneous expression of KChIP2 isoforms in the ferret heart
Authors: Patel Sangita P. , Campbell Donald L. , Morales Michael J. , Strauss Harold C.
Published: July 2002

Kv4 channels are believed to underlie the rapidly recovering cardiac transient outward current (Ito) phenotype. However, heterologously expressed Kv4 channels fail to fully reconstitute the native current. Kv channel interacting proteins (KChIPs) have been shown to modulate Kv4 channel function. To determine the potential involvement of KChIPs in the rapidly recovering Ito, we cloned three KChIP2 isoforms (designated fKChIP2, 2a and 2b) from the ferret heart. Based upon immunoblot data suggesting the presence of a potential endogenous KChIP‐like protein in HEK 293, CHO and COS cells but absence in Xenopus oocytes, we coexpressed Kv4.3 and the fKChIP2 isoforms in Xenopus oocytes. Functional analysis showed that while all fKChIP2 isoforms produced a fourfold acceleration of recovery kinetics compared to Kv4.3 expressed alone, only fKChIP2a produced large depolarizing shifts in the V1/2 of steady‐state activation and inactivation as seen for the native rapidly recovering Ito. Analysis of RNA and protein expression of the three fKChIP2 isoforms in ferret ventricles showed that fKChIP2b was most abundant and was expressed in a gradient paralleling the rapidly recovering Ito distribution. Ferret KChIP2 and 2a were expressed at very low levels. The ventricular expression distribution suggests that fKChIP2 isoforms are involved in modulation of the rapidly recovering Ito; however, additional regulatory factors are also likely to be involved in generating the native current.
Cortical sensory suppression during arousal is due to the activity‐dependent depression of thalamocortical synapses
Authors: Castro‐Alamancos Manuel A. , Oldford Elizabeth
Published: July 2002

The thalamus serves as a gate that regulates the flow of sensory inputs to the neocortex, and this gate is controlled by neuromodulators from the brainstem reticular formation that are released during arousal. Here we show in rats that sensory‐evoked responses were suppressed in the neocortex by activating the brainstem reticular formation and during natural arousal. Sensory suppression occurred at the thalamocortical connection and was a consequence of the activity‐dependent depression of thalamocortical synapses caused by increased thalamocortical tonic firing during arousal. Thalamocortical suppression may serve as a mechanism to focus sensory inputs to their appropriate representations in neocortex, which is helpful for the spatial processing of sensory information.
Mechanics of Machining With Chamfered Tools
Authors: Ren H. , Altintas Y.
Published: July 2002

Chamfered cutting tools are used in high speed machining of hardened steels due to their wedge strength. An analytic model is proposed to investigate the influence of chamfer angle and cutting conditions on the cutting forces and temperature. The model is based on the tool geometry, cutting conditions, steady state temperature in the shear and chip-rake face contact zones, strain, strain rate, and the corresponding flow stress of the work material. With the aid of a slip line field model, the cutting and friction energy in the primary, secondary and chamfer zones are evaluated. By applying the minimum energy principle to total energy, the shear angle in the primary deformation zone is estimated. The corresponding shear strain, strain rate and flow stresses are identified. The model leads to the prediction of cutting forces and temperature produced in three deformation zones. The model is experimentally verified by high-speed orthogonal cutting tests applied to P20 mold steel using ISO S10 carbide and CBN cutting tools. It is shown that the analytic model is quite useful in selecting optimal chamfer angle and cutting speed which gives the minimum tool wear and relatively lower cutting forces. [S1087-1357(00)00204-5]
Performance of a Semi-Active Damper for Heavy Vehicles
Authors: Kitching K. J. , Cole D. J. , Cebon D.
Published: July 2002

This paper describes the development, modeling, and testing of a prototype, continuously variable semi-active damper for heavy vehicles. A simple proportional valve is used to generate the variable damping coefficient and the detrimental effects of the oil flow forces acting on the valve spool are studied. The force tracking performance of the damper is then examined under simple input conditions. The compliance of the hydraulic fluid is found to have a strong influence on the response of the damper. The performance of the prototype damper is investigated under realistic operating conditions using a Hardware-in-the-Loop (HiL) test rig, with a single wheel station vehicle model. The prototype damper displays a time lag of approximately 20 ms between the demanded and achieved damping force. The semi-active suspension is found to be most effective in reducing the vehicle body motion relative to the performance of an optimum passive suspension. [S0022-0434(00)00903-5]
A Simulation-Based Correlation of the Density and Thermal Conductivity of Objects Produced by Laser Sintering of Polymer Powders
Authors: Kandis M. , Bergman T. L.
Published: July 2002

Numerical simulation of the laser-induced formation of shapes from polymer powders is achieved using an extension of a previously developed model of nonisothermal powder sintering. The extended model mimics the Selective Laser Sintering process which is used to produce a multiple layer part via laser irradiation. Model predictions of the physical features and effective thermophysical properties (porosity and thermal conductivity) of the object demonstrate sensitivity to several thermal processing parameters. Predicted values of the effective thermal conductivity and average porosity of the processed item are reported and correlated. [S1087-1357(00)00904-7]
A Microstructural Model of Elastostatic Properties of Articular Cartilage in Confined Compression
Authors: Bursac´ Predrag , McGrath C. Victoria , Eisenberg Solomon R. , Stamenovic´ Dimitrije
Published: July 2002

A microstructural model of cartilage was developed to investigate the relative contribution of tissue matrix components to its elastostatic properties. Cartilage was depicted as a tensed collagen lattice pressurized by the Donnan osmotic swelling pressure of proteoglycans. As a first step in modeling the collagen lattice, two-dimensional networks of tensed, elastic, interconnected cables were studied as conceptual models. The models were subjected to the boundary conditions of confined compression and stress–strain curves and elastic moduli were obtained as a function of a two-dimensional equivalent of swelling pressure. Model predictions were compared to equilibrium confined compression moduli of calf cartilage obtained at different bath concentrations ranging from 0.01 to 0.50 M NaCl. It was found that a triangular cable network provided the most consistent correspondence to the experimental data. The model showed that the cartilage collagen network remained tensed under large confined compression strains and could therefore support shear stress. The model also predicted that the elastic moduli increased with increasing swelling pressure in a manner qualitatively similar to experimental observations. Although the model did not preclude potential contributions of other tissue components and mechanisms, the consistency of model predictions with experimental observations suggests that the cartilage collagen network, prestressed by proteoglycan swelling pressure, plays an important role in supporting compression. [S0148-0731(00)00704-4]
Model-Based Machining Force Control
Authors: Landers Robert G. , Ulsoy A. Galip
Published: July 2002

Regulating machining forces provides significant economic benefits by increasing operation productivity and improving part quality. Machining force regulation is a challenging problem since the force process varies significantly under normal operating conditions. Since fixed-gain controllers cannot guarantee system performance and stability as the force process varies, a substantial research effort has been invested in the development of adaptive force controllers. However, adaptive controllers can be difficult to develop, analyze, implement, and maintain due to their inherent complexity. Consequently, adaptive machining force controllers have found little application in industry. In this paper, a model-based machining force control approach, which incorporates detailed force process models, is introduced. The proposed design has a simple structure and explicitly accounts for the changes in the force process to maintain system performance and stability. Two model-based machining force controllers are implemented in face milling operations. The stability robustness of the closed-loop system with respect to model parameter uncertainties is analyzed, and the analysis is verified via simulation and experimental studies. [S0022-0434(00)02303-0]