bluuebunny/crossref_metadata_2025 huggingface dataset:
A role for the transcription factor HEY1 in glioblastoma
Authors: Hulleman Esther , Quarto Micaela , Vernell Richard , Masserdotti Giacomo , Colli Elena , Kros Johan M. , Levi Daniel , Gaetani Paolo , Tunici Patrizia , Finocchiaro Gaetano , Baena Riccardo Rodriguez y , Capra Maria , Helin Kristian
Published: March 2008

Glioblastoma multiforme (GBM), the highest‐grade glioma, is the most frequent tumour of the brain with a very poor prognosis and limited therapeutic options. Although little is known about the molecular mechanisms that underlie glioblastoma formation, a number of signal transduction routes, such as the Notch and Ras signalling pathways, seem to play an important role in the formation of GBM. In the present study, we show by in situ hybridization on primary tumour material that the transcription factor HEY1, a target of the Notch signalling pathway, is specifically up‐regulated in glioma and that expression of HEY1 in GBM correlates with tumour‐grade and survival. In addition, we show by chromatin immunoprecipitations, luciferase assays and Northern blot experiments that HEY1 is a bona fide target of the E2F family of transcription factors, connecting the Ras and Notch signalling pathways. Finally, we show that ectopic expression of HEY1 induces cell proliferation in neural stem cells, while depletion of HEY1 by RNA interference reduces proliferation of glioblastoma cells in tissue culture. Together, these data imply a role for HEY1 in the progression of GBM, and therefore we propose that HEY1 may be a therapeutic target for glioblastoma patients. Moreover, HEY1 may represent a molecular marker to distinguish GBM patients with a longer survival prognosis from those at high risk.
A critically severe gingival bleeding following non‐surgical periodontal treatment in patients medicated with anti‐platelet
Authors: Elad Sharon , Chackartchi Tali , Shapira Lior , Findler Mordechai
Published: March 2008

Background: Only a few dental procedures have been reported to cause life‐threatening bleeding. All of these cases followed surgical intervention.

Material and Methods: In this paper, we report a case of severe bleeding following non‐surgical periodontal procedures in a patient treated with a dual anti‐platelet regimen post‐coronary stent insertion.

Results: Her medical history included ischaemic heart disease, hypertension and diabetes mellitus. Haemostasis was achieved at the conclusion of the non‐surgical periodontal treatment. However, several hours later, the patient arrived at the emergency room and was diagnosed with hypovolemic shock.

Conclusion: This case should raise the clinician's awareness of bleeding complications in non‐surgical procedures as well as the risk for bleeding when a dual anti‐platelet regimen is administered. The importance of patient monitoring and the use of local haemostatic agents is demonstrated in these cases.
Making sense of the porphyrias
Authors: Sarkany Robert P. E.
Published: March 2008

Patients with cutaneous porphyrias can be worrying for dermatologists. The diseases are rare enough to be unfamiliar, are associated with internal diseases, can have genetic implications, and are associated with incomprehensible biochemical pathways.

In this review, I will try to explain why porphyrias occur, why they present as they do in the clinic, and provide a checklist for treating patients with porphyria.
Does surface preparation alter ALA uptake in superficial non‐melanoma skin cancer in vivo?
Authors: Moseley Harry , Brancaleon Lorenzo , Lesar Andrea E. , Ferguson James , Ibbotson Sally H.
Published: March 2008

Background/purpose: Photodynamic therapy (PDT) using aminolaevulinic acid (ALA) is widely used in the treatment of non‐melanoma skin cancer. Surface preparation of the lesion is commonly performed before application of ALA but the extent of the preparation varies from centre to centre and there has been no study of its effects. The purpose of this study was to examine the effects of surface preparation on the local uptake of ALA by recording fluorescence from accumulated protoporphyrin IX (PPIX).

Methods: The study was performed on 16 lesions, either superficial basal cell carcinoma (BCC) or Bowen's disease (BD). Each half of the lesion was randomly assigned to (a) no surface preparation or (b) surface preparation (randomly allocated to gentle curettage or abrasion with a spatula). ALA was left for 4 h (BCC) or 6 h (BD). PPIX fluorescence was measured using an excitation wavelength of 405±5 nm and emission spectrum recorded using a photodiode array. Spectra were measured (a) before and (b) after surface preparation, (c) immediately before and (d) after laser irradiation at 630 nm.

Results: The ratio of fluorescence after incubation to that before incubation was 6.1±1.2 in the non‐prepared section. This increased slightly but not significantly to 6.8 ±1.8 in the prepared section (P<0.1). There was no significant difference between curettage and abrasion. There was also no significant difference in outcome after PDT.

Conclusions: The clinical assessment agrees with the fluorescence data as no significant difference was seen between prepared and unprepared halves of the lesion 12 months after PDT. Overall our data seem to suggest that for most BCC and BD lesions, surface preparation did not increase ALA uptake.
A normative sample of isotonic and isokinetic muscle strength measurements in children 7 to 12 years of age
Authors: Holm I , Fredriksen PM , Fosdahl M , Vøllestad N
Published: March 2008

Aim: To provide normative age‐ and gender‐associated values on muscular strength, power and endurance and to establish a reference database on healthy school children aged 7 to 12 years. In addition, associations between some simple functional tests and the more sophisticated isokinetic strength measures were investigated.

Methods: Three hundred seventy‐six children, 191 girls and 185 boys, performed different muscle‐strength tests like knee flexion/extension, handgrip, back extension and vertical jump.

Results: There was a significant and linear increase in strength with no gender differences from 7 up to 11 years of age. There was a large variability within each age group, indicating that a normative sample of muscle‐strength measurements includes a wide range of values for each age group. The relationship between hand‐ grip strength and observed quadriceps strength was high (r = 0.84) and the correlation between vertical jump and relative quadriceps strength was moderate (r = 0.50).

Conclusion: All the different strength measures showed almost the same pattern, indicating increased absolute strength values with increasing age and no significant gender differences except for flexion at the age of 11 and 12 years . The association between grip strength, vertical jump and quadriceps strength measured isokinetically was moderate to strong. The back muscle endurance test (The Biering–Sørensen test) showed a great roof effect and should not be included in a test battery for school children.
Pyrimidine‐specific ribonucleoside hydrolase from the archaeon Sulfolobus solfataricus– biochemical characterization and homology modeling
Authors: Porcelli Marina , Concilio Luigi , Peluso Iolanda , Marabotti Anna , Facchiano Angelo , Cacciapuoti Giovanna
Published: March 2008

We report the characterization of the pyrimidine‐specific ribonucleoside hydrolase from the hyperthermophilic archaeon Sulfolobus solfataricus (SsCU‐NH). The gene SSO0505 encoding SsCU‐NH was cloned and expressed in Escherichia coli and the recombinant protein was purified to homogeneity. SsCU‐NH is a homotetramer of 140 kDa that recognizes uridine and cytidine as substrates. SsCU‐NH shares 34% sequence identity with pyrimidine‐specific nucleoside hydrolase from E. coli YeiK. The alignment of the amino acid sequences of SsCU‐NH with nucleoside hydrolases whose 3D structures have been solved indicates that the amino acid residues involved in the calcium‐ and ribose‐binding sites are preserved. SsCU‐NH is highly thermophilic with an optimum temperature of 100 °C and is characterized by extreme thermodynamic stability (Tm = 106 °C) and kinetic stability (100% residual activity after 1 h incubation at 90 °C). Limited proteolysis indicated that the only proteolytic cleavage site is localized in the C‐terminal region and that the C‐terminal peptide is necessary for the integrity of the active site. The structure of the enzyme determined by homology modeling provides insight into the proteolytic analyses as well as into mechanisms of thermal stability. This is the first nucleoside hydrolase from Archaea.
Development of a new method for isolation and long‐term culture of organ‐specific blood vascular and lymphatic endothelial cells of the mouse
Authors: Yamaguchi Takashi , Ichise Taeko , Iwata Osamu , Hori Akiko , Adachi Tomomi , Nakamura Masaru , Yoshida Nobuaki , Ichise Hirotake
Published: March 2008

Endothelial cells are indispensable components of the vascular system, and play pivotal roles during development and in health and disease. Their properties have been studied extensively by in vivo analysis of genetically modified mice. However, further analysis of the molecular and cellular phenotypes of endothelial cells and their heterogeneity at various developmental stages, in vascular beds and in various organs has often been hampered by difficulties in culturing mouse endothelial cells. In order to overcome these difficulties, we developed a new transgenic mouse line expressing the SV40 tsA58 large T antigen (tsA58T Ag) under the control of a binary expression system based on Cre/loxP recombination. tsA58T Ag‐positive endothelial cells in primary cultures of a variety of organs proliferate continuously at 33 °C without undergoing cell senescence. The resulting cell population consists of blood vascular and lymphatic endothelial cells, which could be separated by immunosorting. Even when cultured for two months, the cells maintained endothelial cell properties, as assessed by expression of endothelium‐specific markers and intracellular signaling through the vascular endothelial growth factor receptors VEGFR–2 and VEGFR‐3, as well as their physiological characteristics. In addition, lymphatic vessel endothelial hyaluronan receptor‐1 (Lyve‐1) expression in liver sinusoidal endothelial cells in vivo was retained in vitro, suggesting that an organ‐specific endothelial characteristic was maintained. These results show that our transgenic cell culture system is useful for culturing murine endothelial cells, and will provide an accessible method and applications for studying endothelial cell biology.
Early life history of the Mediterranean gorgonian Paramuricea clavata: implications for population dynamics
Authors: Linares Cristina , Coma Rafel , Mariani Simone , Díaz David , Hereu Bernat , Zabala Mikel
Published: March 2008

Abstract. Knowledge about early stages of marine sessile invertebrates dispersing by means of free‐swimming propagules is fundamental toward understanding their population biology. In this study, we describe and quantify survivorship of early stages of the gorgonian Paramuricea clavata to contribute to the understanding of their implications on population dynamics of this emblematic species of the Mediterranean hard‐bottom communities. Spawning was recorded in June for the 3 years studied (2001–2003). High levels of fertilization rate were observed during the main spawning in 2001 and 2002 (62–69%). This appears to be related to the surface brooding mode of development, synchronous spawning, and high fecundity of the species. The timing of development of the blastulae was ∼24 h and the planulae appeared after 48–72 h. In the laboratory, metamorphosis into polyp started between 8 and 25 d, but this timing may have been delayed by lack of unknown appropriate cues for settlement. The behavior of first developed planulae exhibited a marked negative phototaxis that may be a strategy to avoid competition with fast‐growing algae on photophilous habitats. Despite the high fertilization rate in P. clavata, laboratory and field experiences indicate that survivorship through the planulae and polyp stages was very low, given that none of the settled polyps survived for >7 months in both experimental years. The low survival of the early stages may help explain the low recruitment rates observed in the field in addition to indicating major limitations for colonization of new areas and for persistence of the local population under disturbances.
Phylogenetic relationships of the Clavelinidae and Pycnoclavellidae (Ascidiacea) inferred from mtDNA data
Authors: Pérez‐Portela Rocío , Turon Xavier
Published: March 2008

Abstract.The phylogenetic relationships within the Order Aplousobranchiata (Ascidiacea) are largely unexplored. In this work, we study the phylogenetic status of the generaClavelinaandPycnoclavella.Traditionally, both genera had been included in the family Clavelinidae, until the new family Pycnoclavellidae was defined, removing the genusPycnoclavellafrom Clavelinidae. Not all authors accept the validity ofClavelinaandPycnoclavellaas distinct genera, let alone their belonging to different families. In addition, the assignment of species to these genera, as well as to the genusArchidistoma, has been controversial. We analyzed sequences of the mitochondrial gene cytochromecoxidase subunit I belonging to ten species ofPycnoclavella(including several formerly assigned toArchidistomaandClavelina), 11 species of Clavelinidae, and ten species of other aplousobranch genera belonging to seven families, plus two outgroups. Two different tree construction methods (maximum likelihood and Bayesian inference) showed similar results.PycnoclavellaandClavelinaappeared in distinct clades but formed a monophyletic group relative to representatives of the main families of the order Aplousobranchiata. Our phylogenetic results indicate that both genera are valid but should be included within a single family, with the name Clavelinidae having precedence. The monotypic clavelinid genusNephtheisbranches in our trees within the clade of the genusClavelina.Our results also confirm that some forms assigned toArchidistomaandClavelinahave been misplaced and belong to the genusPycnoclavella. Pycnoclavella martaen.sp. is described.
Histology and ultrastructure of the salivary glands in Bulla striata (Mollusca, Opisthobranchia)
Authors: Lobo‐da‐Cunha Alexandre , Calado Gonçalo
Published: March 2008

Abstract. The ribbon‐shaped salivary glands in Bulla striata were studied with light microscopy and transmission electron microscopy (TEM). Secretion is produced in tubules formed by two types of secretory cells, namely granular mucocytes and vacuolated cells, intercalated with ciliated cells. A central longitudinal duct lined by the same cell types collects the secretion and conducts it to the buccal cavity. In granular mucocytes, the nucleus is usually central and the secretory vesicles contain oval‐shaped granular masses attached to the vesicle membrane. Glycogen granules can be very abundant, filling the space around the secretory vesicles. These cells are strongly stained by PAS reaction for polysaccharides. Their secretory vesicles are also stained by Alcian blue, revealing acidic mucopolysaccharides, and the tetrazonium reaction detects proteins in minute spots at the edge of the vesicles, corresponding to the granular masses observed in TEM. Colloidal iron staining for acidic mucopolysaccharides in TEM reveals iron particles in the electron‐lucent region of the vesicles, while the granular masses are free of particles. In vacuolated cells, which are thinner and less abundant than the granular mucocytes, the nucleus is basal and the cytoplasm contains large electron‐lucent vesicles. These vesicles are very weakly colored by light microscopy techniques, but colloidal iron particles could be observed within them. The golf tee‐shaped ciliated cells contain some electron‐dense lysosomes in the apical region. In these cells, the elongated nucleus is subapically located, and bundles of microfibrils are common in the slender cytoplasmic stalk that reaches the basal lamina. The morphological, histochemical, and cytochemical data showed some similarities between salivary glands in B. striata and Aplysia depilans. These similarities could reflect the phylogenetic relationship between cephalaspidean and anaspidean opisthobranchs or result from a convergent adaptation to an identical herbivorous diet.
Fractures of the distal phalanx in horses
Authors: YOVICH J. V. , HILBERT B. J. , McGILL C. A.
Published: March 2008

Summary. Nineteen cases of fracture of the distal phalanx in horses are reviewed. This represented 1.1% of the total number of horses seen at Murdoch University Veterinary Hospital (MUVH) over a 32‐month period. All horses were managed conservatively. Eight horses made a complete recovery. Three are being trained again and are not lame. Four horses made a limited recovery. Two horses are still resting and one horse was killed humanely when it still showed lameness after 2 years. One horse was killed humanely after the fracture was first diagnosed.
The comparative tuberculin test in guinea pigs using PPD extracts prepared from mycobacteria killed with phenol
Authors: CHOI C. S. , FROST A. J. , FRANCIS J.
Published: March 2008

Summary. Purified‐protein‐derivative (PPD) extracts were prepared from Mycobacterium tuberculosis (PPD‐S), M. bovis (PPD‐BS), M. avium (PPD‐A) and M. kansasii (PPD‐K), after killing the cultures with phenol. The reactions were assessed in guinea pigs sensitised to a range of mycobacteria, with a view to selecting a suitable pairing of the extracts to distinguish sensitivity due to M. tuberculosis or M. bovis from that due to other mycobacteria.

Sensitisation induced by M. bovis was best distinguished from others using PPD‐S and PPD‐A; for sensitisation by atypical mycobacteria, PPD‐BS was better than PPD‐S, used with either PPD‐K or PPD‐A, PPD‐BS was more specific than PPD‐S.

Using PPD‐BS, PPD‐A and PPD‐K in a comparative test, 3 groups were recognised: those sensitive to M. bovis or M. tuberculosis (greatest reaction was to PPD‐BS); those sensitive to M. avium, M. Intracellulare and M. scrofulaceum (greatest reaction was to PPD‐A); those sensitive to M. kansasii, M. marium, M. gordonae and M. fortuitum (greatest reaction was to PPD‐K).
BOOK REVIEWS
Authors: Canfield P. J. , Halnan C. , Beh K. J. , Sabine M.
Published: March 2008

Laboratory Profiles of Small Animal Diseases: a Guide to Laboratory Diagnosis. Charles Sodikoff, ed Paul W. Pratt. Santa Barbara Veterinary Publications 1981. pp 215.

The Future of Beef Production in the European Community, Vol. 5, in current topics in Veterinary Medicine and Animal Science Seminar EEC Program of Co‐ordination of Research on Beef Production and Land Use, Italy, 1978. Ed J. C. Bowman and P. Susmel.

Introduction to Veterinary Immunology. I. R. Tizard, W. B. Saunders, 1979. pp 367 $27.50.

Viral Diseases of Farm Livestock. W. I. B. Beveridge (Animal Health in Australia, Vol. 1). Australian Bureau of Animal Health, Australian Government Publishing Service, Canberra 1981 pp 197.
A multidisciplinary dental program for community‐living adults with chronic mental illness
Authors: Chalmers Jane M. , Smith Dell Kingsford , Carter Knute D.
Published: March 2008

Only recently have reports described specialized large‐scale dental programs for community‐living adults with chronic mental illness. In response to requests from community mental health center case managers, a multidisciplinary team from Central Sydney Area Health Service dentistry, mental health, and transport services joined together to develop a pilot dental program. The aim was to profile the dental needs of community‐living clients with chronic mental illness and to improve clients' utilization of inner Sydney public dental services. A review of clients' dental problems and access is presented, together with a description of the pilot program developed by the multidisciplinary team. A profile of the initial dental needs of the participants, and information on the participants' utilization of the pilot dental program is documented. This multidisciplinary approach was successful in developing a program to profile dental needs of clients, and improved the access to public dental services for the majority of clients. There was a subgroup of clients who did not utilize the program, and further follow‐up of these clients is needed. This multi‐disciplinary approach could be useful in the development and funding of other special care dental programs.
Disposal options for infectious medical waste generated during home‐based dental care
Authors: Stark Alan M.
Published: March 2008

The number of dentists providing mobile care is increasing. One of the challenges the mobile dentist faces is proper handling and disposal of infectious medical waste generated during patient care. Mobile dentists must concern themselves with meeting Federal, state, and local regulations. Federal agencies that have jurisdiction over this issue are the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA). EPA guidelines are summarized and clarified with respect to pre‐transportation and transportation issues. Compliance with OSHA standards are addressed through presentation of a sample protocol for handling infectious medical waste. It is beyond the scope of this paper to discuss in detail the policies of each municipality, and practitioners are advised to consult with state and local authorities regarding proper handling and transportation of this material. Using the information presented in this paper, the mobile dentist can approach this complex issue in an organized manner.
Politics of municipal property taxes: implications for decision‐making
Authors: Kennedy William , McAllister Mary Louise
Published: March 2008

Abstract: Property taxes are one of the few, important mechanisms through which municipal governments can exercise a measure of autonomy and determine policies that shape their local communities. Property taxes account for almost half of a municipality's own‐source revenues. Ideally, decisions surrounding property‐tax assessments could be based on criteria related to such things as equity, efficiency and stability. A closer examination of property‐tax assessments between property classes in Northern British Columbian municipalities, however, suggests that the setting of tax rates appears to be an incremental, rather than systematic, process that builds on past experiences, current demands, and observation of the practices of nearby municipalities. These findings suggest that property‐tax policy development is a poorly understood process that can have significant implications for the economic health of local municipalities.

Sommaire: Les taxes fanciers ne sont que l'un des quelques rares et impotents mécanismes au moyen desquels les Governments municipaux prevent exercer une certain autonomic et determiner les propitious qui faqonnent leurs communautés locales. Les taxes foncières représentent près de la moitié des recettes d'une munici‐palité. En principe, les décisions entourant les évaluations de taxes foncières pour‐raient reposer sur des critères se rapportant à des facteurs comme l'équité, l'efficience et la stabilité. Un examen plus attentif d'évaluations des taxes foncières de différentes catégories dans les municipalités du Nord de la Colombie‐Britannique laisse entendre que l'établissement des taux de taxes semble être un processus pro‐gressif plutôt que systématique, reposant sur les expériences passées, les demandes actuelles et l'observation des pratiques des municipalités environnantes. Ces résul‐tats donnent à penser que l'élaboration d'une politique en matière de taxes foncières est un processus mal compris qui pourrait avoir d'importantes répercussions sur la santééconomique des municipalités locales.
Limitations to developing virtual communities in the public sector: A local government case study
Authors: Stefanick Lorna , LeSage Edward
Published: March 2008

Abstract: This article explores how new information and communication technologies affect public administration practice. It examines efforts by the University of Alberta to develop a web‐based “meeting place,” an on‐line community of practice in the local government sector that was to be a forum for practice‐building discourse and a resource for professional development courses. While the MuniMall project was not an unequivocal success, it does provide important lessons for others who are contemplating similar projects. There are important differences between “open” and “closed” virtual communities, as well as differences among professional groups with respect to their receptivity to engaging in discourse in an open forum. For virtual communities targeted towards a specific professional community, critical factors for ensuring success include the readiness of site architecture upon rollout, as well as the culture, capacity and readiness of the audience.

Sommaire: Le présent article approfondit la maniére dont les nouvelles technologies de I'information et de la communication influent sur I'exercice de l'administration public. I1 examine les efforts déployés par 1'Université de l'Alberta pour mettre en place un « lieu de rencontre » sur Internet, réseau en ligne d'échanges de pratiques dans le secteur de l'administration municipale qui devait être un forum de discussions sur le renforcement des pratiques et une resource pour les cours de perfection‐nement professionnel. Alors que le project « MuniMall » n'a pas été un succès sans équivoque, il foumit des leçons importantes à ceux qui envisagent des projects simi‐laires. I1 existe de grandes différences entre les communautés virtuelles « ouvertes » et « fermées », ainsi que des différences parmi les groupes professionnels en ce qui conceme leur réceptivitéà s'engager dans un discours au sein d'un forum ouvert. Pour les communautés virtuelles visant une communauté professionnelle particulière, les facers critiques de succès comprennent l'état de preparation de l'architcc‐ture ciu site dès sa mise en place, ainsi que la culture, la capacité et l'état de préparation de l'audience.
Enduring, ephemeral and emerging issues in public administration in Canada: Trends in Canadian Public Administration over fifty years (1958–2007)
Authors: Carroll Barbara Wake , Kpessa Michael Whyte
Published: March 2008

Abstract: This issue of Canadian Public Administration marks two landmarks. It is the 50th anniversary issue of the Journal, and it is the last issue to be published by the Institute of Public Administration of Canada. For this issue, we have not produced a “special issue” in the sense of commissioning particular articles. Instead, we have brought together a number of articles that were already in the “pipeline” but that the editors thought made a particular contribution to public administration in Canada. This introductory article, or editor's review, is a retrospective analysis of the content of the Journal. It would appear that while there has been a slight shift towards public policy and a greater concern with provincial and local administration, cpa has maintained an enduring interest in its core areas of administrative theory and political and legal institutions. The content is also compared with findings of the content of other journals and also other analyses of cpa. This review is followed by commentaries by former editors and associate editors on their experiences with the Journal.
Linear Feedback Control of Position and Contact Force for a Nonlinear Constrained Mechanism
Authors: McClamroch H. , Wang D.
Published: March 2008

A feedback control problem for a constrained mechanism is formulated and solved. The mechanism is controlled by forces applied to the mechanism which are to be adjusted according to a linear control law, based on feedback of the positions and velocities of the mechanism and feedback of the constraint force on the mechanism. The control objective is to achieve accurate and robust local regulation of the motion of the mechanism and of the constraint force on the mechanism. Derivation of a suitable control law is significantly complicated by the nonclassical nature of the differential-algebraic model of the constrained system and by the nonlinear characteristics of the model. The control design approach involves use of a certain nonlinear transformation which leads to a set of decoupled differential-algebraic equations; classical control design methodology can be applied to these latter equations. An example of a planar mechanism is studied in some detail, for two different regulation objectives. Specific control laws are developed using the described methodology. Comparisons are made with a closed loop system, where the control law is derived without proper consideration of the constraint force. Computer simulations are presented to demonstrate the several closed-loop properties.
The Dynamic Analysis and Design of a High-Speed Insertion Hand Using the Generalized Centroid and Virtual Mass
Authors: Asada H. , Kakumoto Y.
Published: March 2008

A new approach to the design of an assembly end effector for the high-speed insertion of a peg into a chamfered hole is presented. The peg is supported by a special mechanical hand that allows it to be guided along the chamfer surface without bouncing on it, even when bumping against the chamfer at a high speed. The dynamic process of the peg insertion is analyzed, and mass properties of the hand mechanism for successful insertion are derived by using the theory of generalized centroid and virtual mass. Namely, for successful high-speed insertion, the generalized centroid must be put near the tip of the peg, and the virtual mass in the horizontal direction must be minimized. Following this, a hand that meets the mass property conditions is designed, built and tested. It is demonstrated that this hand accomplishes a high approach-speed of over 2 m/s.
Dynamic Stability Analysis of a Two-Link Force-Controlled Flexible Manipulator
Authors: Chiou B. C. , Shahinpoor M.
Published: March 2008

This study investigates the effect of link flexibility on the dynamic stability of a two-link force-controlled robot manipulator. The nonlinear open-loop equations for the compliant motion are derived first. By employing the hybrid force/position control law, the closed-loop dynamic equations are then explicitly derived. The nonlinear closed-loop equations are linearized about some equilibrium configurations. Stability analyses are carried out by computing the eigenvalues of the linearized system equations. Results are verified by the numerical simulations using the complete nonlinear dynamic equations. The effect of the wrist force sensor stiffness on the dynamic stability is also investigated. Results show that the link flexibility is indeed an important source of dynamic instability in the motion of force-controlled manipulators. Moreover, the system stability is dominated by the effect of the distributed flexibility of the first link.
Precise Point-to-Point Positioning Control of Flexible Structures
Authors: Bhat S. P. , Miu D. K.
Published: March 2008

Control strategies to accomplish precise point-to-point positioning of flexible structures are discussed. First, the problem is formulated and solved in closed form using a linear quadratic optimal control technique for a simple system with only one rigid and one flexible mode; the resulting analytical solutions are examined in both the time and frequency domain. In addition, the necessary and sufficient condition for zero residual vibration is derived which simply states that the Laplace transform of the time bounded control input must vanish at the system poles. This criteria is then used to highlight the common features of existing techniques and to outline an alternative design procedure for precise position control of more complicated structures having multiple flexible modes.
Accurate Position Control of a Pneumatic Actuator
Authors: Lai Jiing-Yih , Menq Chia-Hsiang , Singh Rajendra
Published: March 2008

We propose a new control strategy for on-off valve controlled pneumatic actuators and robots with focus on the position accuracy. A mathematical model incorporating pneumatic process nonlinearities and nonlinear mechanical friction has been developed to characterize the actuator dynamics; this model with a few simplifications is then used to design the controller. In our control scheme, one valve is held open and the other is operated under the pulse width modulation mode to simulate the proportional control. An inner loop utilizing proportional-plus-integral control is formed to control the actuator pressure, and an outer loop with displacement and velocity feedbacks is used to control the load displacement. Also, a two staged feedforward force is implemented to reduce the steady state error due to the nonlinear mechanical friction. Experimental results on a single-degree-of-freedom pneumatic robot indicate that the proposed control system is better than the conventional on-off control strategy as it is effective in achieving the desired position accuracy without using any mechanical stops in the actuator.
A Linear Time Varying Model for On-Off Valve Controlled Pneumatic Actuators
Authors: Kunt C. , Singh R.
Published: March 2008

A new linear time varing (LTV) model has been developed for open loop, on-off valve controlled pneumatic actuation systems. This formulation is based on a periodic profile description for variable operating points and directional control valve flow variations. The dynamic behavior of the example case, a single acting cylinder controlled by a two way-two port rotary valve, under the cyclic pressure loading is obtained using the proposed LTV model. Experimental evidence and digital simulation predictions based on the nonlinear mathematical equations validate the analytical formulation. The proposed LTV model is found to be better and more applicable than linear time invariant (LTI) models used previously by many investigators.
The Effect of Some Operating Conditions on the Performance of a Two-Stage Controller-Pump Combination
Authors: Akers A. , Lin S. J.
Published: March 2008

A previous investigation into a two-stage controller with a stand-alone first stage showed that the modeled results for the real-time responses of the swashplate angle and for Bode plots agreed well with experiment (Lin and Akers, 1988). The current investigation shows the separate effects of feedback ratio and supply pressure on the pump’s dynamic behavior.
On-Board Real-Time Failure Detection and Diagnosis of Automotive Systems
Authors: de Benito C. D.
Published: March 2008

This paper presents a failure detection and diagnosis (FDD) technique for on-board vehicle applications. Failures are represented by abrupt changes in the characteristic parameters of a system that occur at random instants of time. This representation facilitates the formulation of the FDD problem as a combined state and parameter estimation problem of a system with uncertain parameters. This nonlinear estimation problem is solved using a Bayesian approach and implementing a suboptimal algorithm. The performance of the FDD system is demonstrated in simulations of an active suspension subjected to sensor failures. In the simulations, the system detected and diagnosed the failures correctly within .05 seconds from their occurrence.
Model-Based Discrete Linear State Estimator for Nonlinearizable Systems With State-Dependent Noise
Authors: Chang R. J.
Published: March 2008

A practical technique to derive a discrete-time linear state estimator for estimating the states of a nonlinearizable stochastic system involving both state-dependent and external noises through a linear noisy measurement system is presented. The present technique for synthesizing a discrete-time linear state estimator is first to construct an equivalent reference linear model for the nonlinearizable system such that the equivalent model will provide the same stationary covariance response as that of the nonlinear system. From the linear continuous model, a discrete-time state estimator can be directly derived from the corresponding discrete-time model. The synthesizing technique and filtering performance are illustrated and simulated by selecting linear, linearizable, and nonlinearizable systems with state-dependent noise.
The Extended Bond Graph Notation
Authors: Ingrim M. E. , Masada G. Y.
Published: March 2008

The extended bond graph notion was developed to overcome significant limitations in the standard bond graph notation for modeling systems described by vector and tensor-valued quantities. A brief introduction to this extended notation is given including the definition of a set of primitive extended elements and a discussion of extended power and energy concepts.
The Influence of Tire Damping in Quarter Car Active Suspension Models
Authors: Levitt J. A. , Zorka N. G.
Published: March 2008

Setting tire damping to zero when modeling automotive active suspension systems compels the misleading conclusions that, at the wheelhop frequency, no matter what forces are exerted between sprung and unsprung masses, their motion are uncoupled, and the vertical acceleration of the sprung mass will be unaffected. Alternatively, taking tire damping to be small but nonzero, the motions of the sprung and unsprung masses are coupled at all frequencies, and control forces can be used to reduce the sprung mass vertical acceleration at the wheelhop frequency. The effect of introducing tire damping can be quite large. In the case of a force law chosen to enhance ride along a straight smooth road, where road holding is not a major concern, setting the tire damping ratio to 0.02 reduces rms body acceleration by 30 percent.
Dissipative Modal Approximation of Fluid Transmission Lines Using Linear Friction Model
Authors: Yang W. C. , Tobler W. E.
Published: March 2008

For both hydraulic and pneumatic transmission lines, analytical dissipative modal approximation techniques, which take into account the frequency dependent viscosity and heat transfer effects, are developed by introducing frequency dependent damping and natural frequency modification factors to the quadratic modes obtained analytically from linear friction model. The main advantage over the existing dissipative modal approximations is that the modal parameters of the resulting modal transfer function matrices and modal state space equations can be determined analytically rather than determined by table and/or numerical computer calculations. This introduces modeling flexibilities and greatly alleviates the difficulties of modeling complex fluid networks but still maintaining the modal accuracy and complexities. Unit step response comparisons are made with quasi-method of characteristics showing good agreements for both hydraulic and pneumatic lines.
Dynamic Analysis of a Flapper-Nozzle Valve
Authors: Lin S. J. , Akers A.
Published: March 2008

A previous analysis into the dynamic behavior of the flapper-nozzle component of the electrohydraulic servovalve was performed after linearization of the equations relating to control piston flow (Lin and Akers, 1989a). This paper reports results for first-stage gain and for dynamic behavior when linearization has not been performed. Good agreement has been achieved between results calculated from the nonlinear theory presented and experimental results.
Experimental Evidence for Chaotic Response in a Feedback System
Authors: Golnaraghi M. F. , Moon F. C.
Published: March 2008

In this paper, the dynamics of a one-degree-of-freedom mechanical positioning device with nonlinear stiffness and linear feedback are described. Experimental results show that chaotic dynamics can result due to an increase in control gain or shuttle frequency. Adding sufficient damping through velocity feedback gain, however, eliminated the chaos. In some chaotic motions, a one-dimensional delay map was obtained from the experimental time samples. The map was modeled by a piecewise linear function, which suggested that the third-order system might be modeled by a lower dimensional equation.
Frequency-Domain Vibration Control of Distributed Gyroscopic Systems
Authors: Yang B. , Mote C. D.
Published: March 2008

A new method is presented for vibration control of distributed gyroscopic systems. The control is formulated in the Laplace transform domain. The transfer function of a closed-loop system, consisting of the plant, a feedback control law and the dynamics of the sensing and actuation devices, is derived. Stability analyses of the closed-loop system use both the root locus method and the generalized Nyquist criterion. Two stability criteria are obtained. Design of stabilizing controllers is carried out for both colocation and noncolocation of the sensor and actuator. The effects of time-delay and noncolocation of the sensor and actuator on the system stability are analyzed. In addition, the relationship between the root locus method and the generalized Nyquist criterion is discussed.
On the Modeling, and Open-Loop Control of a Rotating Thin Flexible Beam
Authors: Choura S. , Jayasuriya S. , Medick M. A.
Published: March 2008

A set of governing differential equations is derived for the inplane motion of a rotating thin flexible beam. The beam is assumed to be linearly elastic and is connected to a rigid hub driven by a torque motor. Both flexural and extensional effects are included in the derivation. This coupling due to flexure and extension is usually neglected in studies dealing with the control of such a system. Models for typical control studies are often derived by utilizing an assumed mode approach where the mode shapes are obtained by solving the Euler-Bernoulli beam equation for flexural vibrations, with clamped-free or pinned-free boundary conditions. The coupled equations developed in this paper are used to demonstrate that typical models in control studies give satisfactory results up to a critical rotational speed. For the case where these coupled equations are specialized to simple flexure only, valid for low angular speeds, a unique feedforward control strategy can be derived. This is an open-loop control strategy that enables total elimination of an a priori specified vibratory mode from the gross motion in a finite critical time.
Dynamic Modeling of an Axially Moving Beam in Rotation: Simulation and Experiment
Authors: Yuh J. , Young T.
Published: March 2008

In this paper, we consider a beam which has a rotational and translational motion. A time-varying partial differential equation and the boundary conditions are derived to describe the lateral deflection of the beam. For multivariable control, an approximated model is also derived by using the assumed mode method. The validity of the approximated model is investigated by the experiment. For different repositional motions, response of the beam is further investigated by computer simulation. Application of the beam to flexible robotic manipulators is discussed with simulation results.
Automated Robotic Deburring of Parts Using Compliance Control
Authors: Her M. G. , Kazerooni H.
Published: March 2008

This work presents a method for robotic deburring of two-dimensional planar parts with unknown geometry. Robotic deburring requires “compliancy” and “stiffness” in the robot in the directions tangent and normal to the part, respectively. Compliancy in the tangential direction allows robotic accommodation of tangential cutting forces, while stiffness in the normal direction impedes a robotic response to normal cutting forces. But, to track the part contour, the robot requires compliancy in the normal direction. These conflicting requirements are addressed in this article as two problems: control of the metal removal process and tracking of the part contour. In general, these two problems are coupled; however, here they are separated into a hardware problem and a control problem. A tracking mechanism has been designed and built which incorporates a roller bearing mounted on a force sensor at the robot endpoint. This force sensor is located directly below the cutter and measures the contact forces which are the input to the tracking controller. These contact forces are used not only to calculate the normal vector to the part surface, but also to generate compliancy in the robot. However, the deburring algorithm uses another set of forces (cutting forces generated by the cutter) to produce a stable metal removal process. This deburring control method guarantees compliancy and stiffness in the robot in response to the tangential and normal cutting forces, respectively. Experimental results are given to show the effectiveness of this method for deburring of two-dimensional parts with unknown geometry.
Adaptive Pneumatic Force Actuation and Position Control
Authors: Bobrow J. E. , Jabbari F.
Published: March 2008

In this paper an implementation of an adaptive control law for a pneumatic actuator is presented. Pneumatic actuators are of particular interest for robotic applications because of their large force output per unit weight, and their low cost. Stabilization of a pneumatic actuator is difficult if a high bandwidth closed-loop system is desired. This is because of the compressibility of air, and of the nonlinear characteristics of air flowing through a variable area orifice. Further complications arise from the geometry of the mechanism because the equations of motion are highly nonlinear. The order of the dominant dynamics is shown to vary with the position of the mechanicsm.
A Class of Transfer Functions With Non-Negative Impulse Response
Authors: Jayasuriya S. , Franchek M. A.
Published: March 2008

Presented in this note is a class of stable, minimum phase transfer functions whose impulse response is non-negative. A simple sufficiency criterion based on the relative locations of the poles and zeros characterizes the class. When the transfer function is in a factored form the sign of its impulse response may either be obtained by inspection or is inconclusive. A need for identifying such transfer functions was recently established by Jayasuriya (1989) who showed that a controller designed on the basis of maximizing a step input disturbance will reject a persistent disturbance bounded by the size of the maximized step if and only if the closed-loop system’s impulse response is of one sign.
A Bound on the Impulse Response of Stable Rational Plants
Authors: MacCluer C. R.
Published: March 2008

The magnitude of the impulse response of a strictly proper stable rational plant at time t is estimated to be of order 0(1/t) where the implied constant is explicitly given in terms of the spectral energy and the real parts of the zeros and poles. When exact location of poles and zeros is uncertain, this estimate can usefully replace the actual but uncertain exponential decay.
Robust Computed Torque Schemes for Mechanical Manipulators: Nonadaptive Versus Adaptive
Authors: Chen Y. H.
Published: March 2008

We consider the tracking control problem of mechanical manipulators in the presence of uncertainty. Two classes of control algorithms are proposed. If the possible bound of the uncertainty is known, a class of nonadaptive robust computed torque control schemes is used. The control guarantees the tracking error to be confined within a specified region after a finite time. If the bound of uncertainty is unknown, a class of adaptive robust computed torque control schemes is used. The control guarantees the tracking error to converge to zero. Both classes of controls are continuous. No statistical information on the uncertainty is ever assumed.
Fault Diagnosis With Process Uncertainty
Authors: Danai Kourosh , Chin Hsinyung
Published: March 2008

A nonparametric pattern classification method is introduced for fault diagnosis of complex systems. This method represents the fault signatures by the columns of a multi-valued influence matrix (MVIM), and uses adaptation to cope with fault signature variability. In this method, the measurements are monitored on-line and flagged upon the detection of an abnormality. Fault diagnosis is performed by matching this vector of flagged measurements against the columns of the influence matrix. The MVIM method has the capability to assess the diagnosability of the system, and use that as the basis for sensor selection and optimization. It also uses diagnostic error feedback for adaptation, which enables it to estimate its diagnostic model based upon a small number of measurement-fault data.