bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow and cavitation characteristics of a damping orifice in water hydraulics
Authors: Yinshui Liu , Bihai Zhu , Yuquan Zhu , Zhuangyun Li
Published: December 2006

The flow in damping orifices when using water as the working media is of high Reynolds number and cavitation is inevitable. In this article, experimental studies are made on the flow and cavitation characteristics of water hydraulic orifices and the coefficient formulae in previous documents are testified with the Reynolds number ranging from 104 to 105. All the orifices are made of transparent materials, so the flow and the occurrence process of the cavitation can be observed with the naked eye. The experiments for each orifice are carried out under the two cases with and without backpressure, respectively. Experimental results show that the flow coefficient with backpressure is larger than the case without it. The larger the aspect ratio, the less the flow characteristics are influenced by backpressure. The cavitation first occurs at the inlet of orifices and then shifts to the outlet gradually. When there is cavitation happening at the outlet, flow saturation emerges simultaneously.
Convenient polynomial approximation for calculating the onset of reverse flow in radial-flow centrifugal pump impellers having backward leaning blades
Authors: Visser F. C.
Published: December 2006

This article presents a sixth-order polynomial approximation for calculating the onset of reverse flow in centrifugal pump impellers having backward leaning blades. The polynomial approximation presented here is an easily computable alternative to the exact analytical formulation published in a previous study [1]. In this previous study, an exact analytical solution was given on the basis of potential-flow considerations. This exact solution was formulated in closed-form in terms of a Fourier series expansion, but the slow convergence of the series makes the expression rather inconvenient to evaluate for any given blade angle and/or number of blades. This situation is improved by the correlation presented in the current article. Moreover, it provides an extension to the empirical formulae commonly applied to predict the onset of suction and discharge flow recirculation in radial-flow centrifugal pump impellers [6–13]. The polynomial approximation can be used to calculate the reverse-flow onset capacity for any blade angle between 0 and 90°, with the number of blades varying from 2 to 12. The calculated result will approximate the exact analytical solution [1] with an error <0.5 per cent, and, as such, provides a theoretically sound and a practical engineering tool for evaluating new and existing impeller designs with regard to (avoidance of) reverse flow.
H∞ model reduction for polytopic systems with time-varying delay
Authors: Wang Q , Lam J , Xu S-Y , Zhou S-S
Published: December 2006

This paper addresses the H∞ model reduction problem for a polytopic system with time-varying delay. The delay-dependent sufficient conditions are presented to construct the reduced-order models such that the H∞ norm of the error system between the full-order model and the reduced-order one is less than a prescribed scalar. By employing a sequential convex optimization approach, two examples are employed to demonstrate the effectiveness of the proposed method.
Dynamic modelling of three-way catalysts using non-linear identification techniques
Authors: Soumelidis M. I. , Stobart R. K.
Published: December 2006

Automotive emissions are strictly regulated by environmental legislation. To maximize exhaust gas conversion efficiencies under transient conditions the dynamics of the three-way catalyst (TWC) need to be considered. Oxygen-storage-dominated models are conventionally used to describe the non-linear dynamic behaviour of TWCs. In this paper, a non-linear identification method is applied to model the system, based on measurements of the upstream and downstream air-fuel ratios. The performance of the obtained non-linear autoregressive with exogenous inputs (NARX) models is directly compared with that of an oxygen storage model. The results highlight some of the limitations of the latter, while demonstrating the advantages of non-linear modelling.
Global sliding mode control with chatter alleviation for robust eigenvalue assignment
Authors: Tai T. L. , Lu Y. S.
Published: December 2006

This paper proposes a global sliding mode control (GSMC) scheme that can guarantee a chattering-free performance for systems without external perturbations and ensure a chattering-alleviated performance under the perturbations of known bounds. The GSMC has been a remarkable control technique and is designed to achieve extremely robust performance. This perfectly robust control, however, suffers from the same problem as the conventional sliding mode control, i.e. the chattering problem due to switching control. In this paper, the GSMC scheme employs a smooth function for the switching device to alleviate the chattering phenomenon. Moreover, the proposed scheme uses an auxiliary compensator not only to establish the sliding condition for an ideal system but also to specify directly the dynamic characteristics of the sliding variable. According to Lyapunov's direct method, an explicit condition to ensure a stable attractor is derived. Experimental studies of designing a positioning system with a permanent magnet a.c. servomotor are conducted to illustrate further the feasibility and effectiveness of the proposed scheme.
System identification and microposition control of ionic polymer metal composite for three-finger gripper manipulation
Authors: Yun Kwansoo , Kim Won-Jong
Published: December 2006

Smart materials have been widely used for control actuation. A robotic hand can be equipped with artificial tendons and sensors for the operation of its various joints, mimicking human hand motions. The motors in the robotic hand could be replaced with novel electro-active polymer (EAP) actuators. In the three-finger gripper proposed in this paper, each finger can be actuated individually so that dexterous handling is possible, allowing precise manipulation. To develop model-based control laws, an approximated linear model representing the electromechanical behaviour of the gripper fingers is introduced. Several chirp voltage signal inputs were applied to excite the IPMC (ionic polymer metal composite) actuators in the interesting frequency range of (0.62 Hz, 5 Hz) for 30 s at a sampling frequency of 250 Hz. The linear Box-Jenkins (BJ) model was well matched with the model obtained using a stochastic power spectral method. With feedback control, the large overshoot, rise time, and settling time associated with the inherent material properties were reduced. The motions of the IPMC fingers in the microgripper would be coordinated to pick, move, and release a macro- or micro-part. The precise manipulation of this three-finger gripper was successfully demonstrated with experimental closed-loop responses.
Neural generalized prediction control with modified performance index
Authors: Rao D. N. , Murthy M. R. K. , Rao S. M. , Harshal D. N.
Published: December 2006

The objective of this paper is to improve the dynamic response and reduction in sluggishness in neural generalized predictive control (NGPC) with a modified performance index. A comparative study has been made between NGPC and a modified NGPC. The simulation results show that there is further significant improvement in the dynamic response using the modified NGPC.
A Biomimetic Approach for Hierarchically Structured Inorganic Crystals through Self-Organization
Authors: Imai Hiroaki , Oaki Yuya , Kotachi Akiko
Published: December 2006

Here, we describe a biomimetic pathway for the synthesis of hierarchically structured inorganic crystals. In artificial systems mimicking biomineralization, versatile morphogenesis was achieved with the construction of bridged nanocrystals through self-organization by controlling growth with polymeric molecules such as a gel matrix and soluble anionic polymers. The self-organized formation of bridged crystals in hierarchical architectures is a possible new paradigm for advanced materials processing which could afford new inorganic–organic nanocomposites for use as novel functional materials.
syn-Selective Direct Catalytic Asymmetric Mannich-Type Reactions of Aromatic and Heteroaromatic Hydroxy Ketones Promoted by Y[N(SiMe3)2]3/Linked-BINOL Complexes
Authors: Matsunaga Shigeki , Sugita Mari , Yamagiwa Noriyuki , Handa Shinya , Yamaguchi Akitake , Shibasaki Masakatsu
Published: December 2006

Full details of syn-selective catalytic asymmetric direct Mannich-type reactions of aromatic and heteroaromatic hydroxy ketones promoted by Y[N(SiMe3)2]3/linked-BINOL complexes are described. From a screening of various rare-earth metals and linked-BINOL derivatives, a Y[N(SiMe3)2]3/TMS-linked-BINOL (1.7/1) complex was determined to be the most effective. Mannich-type reactions of aromatic and heteroaromatic hydroxy ketones with aryl and alkenyl N-diphenylphosphinoylimines, catalyzed by 0.1 molar amount of Y[N(SiMe3)2]3 and 0.059 molar amount of TMS-linked-BINOL, afforded syn-β-amino-α-hydroxy ketones in good yields (78–98%), high diastereoselectivity (syn/anti = 81/19–96/4), and high enantioselectivity (86–98% ee).
SRP RNA provides the physiologically essential GTPase activation function in cotranslational protein targeting
Authors: Siu Fai Y. , Spanggord Richard J. , Doudna Jennifer A.
Published: December 2006

The signal recognition particle (SRP) cotranslationally targets proteins to cell membranes by coordinated binding and release of ribosome-associated nascent polypeptides and a membrane-associated SRP receptor. GTP uptake and hydrolysis by the SRP-receptor complex govern this targeting cycle. Because no GTPase-activating proteins (GAPs) are known for the SRP and SRP receptor GTPases, however, it has been unclear whether and how GTP hydrolysis is stimulated during protein trafficking in vivo. Using both biochemical and genetic experiments, we show here that SRP RNA enhances GTPase activity of the SRP–receptor complex above a critical threshold required for cell viability. Furthermore, this stimulation is a property of the SRP RNA tetraloop. SRP RNA tetraloop mutants that confer defective growth phenotypes can assemble into SRP–receptor complexes, but fail to stimulate GTP hydrolysis in these complexes in vitro. Tethered hydroxyl radical probing data reveal that specific positioning of the RNA tetraloop within the SRP–receptor complex is required to stimulate GTPase activity to a level sufficient to support cell growth. These results explain why no external GAP is needed and why the phylogenetically conserved SRP RNA tetraloop is required in vivo.
An asymmetric underlying rule in the assignment of codons: Possible clue to a quick early evolution of the genetic code via successive binary choices
Authors: Delarue Marc
Published: December 2006

Aminoacyl-tRNA synthetases (aaRSs) are responsible for creating the pool of correctly charged aminoacyl-tRNAs that are necessary for the translation of genetic information (mRNA) by the ribosome. Each aaRS belongs to either one of only two classes with two different mechanisms of aminoacylation, making use of either the 2′OH (Class I) or the 3′OH (Class II) of the terminal A76 of the tRNA and approaching the tRNA either from the minor groove (2′OH) or the major groove (3′OH). Here, an asymmetric pattern typical of differentiation is uncovered in the partition of the codon repertoire, as defined by the mechanism of aminoacylation of each corresponding tRNA. This pattern can be reproduced in a unique cascade of successive binary decisions that progressively reduces codon ambiguity. The deduced order of differentiation is manifestly driven by the reduction of translation errors. A simple rule can be defined, decoding each codon sequence in its binary class, thereby providing both the code and the key to decode it. Assuming that the partition into two mechanisms of tRNA aminoacylation is a relic that dates back to the invention of the genetic code in the RNA World, a model for the assignment of amino acids in the codon table can be derived. The model implies that the stop codon was always there, as the codon whose tRNA cannot be charged with any amino acid, and makes the prediction of an ultimate differentiation step, which is found to correspond to the codon assignment of the 22nd amino acid pyrrolysine in archaebacteria.
An allosteric-feedback mechanism for protein-assisted group I intron splicing
Authors: Caprara Mark G. , Chatterjee Piyali , Solem Amanda , Brady-Passerini Kristina L. , Kaspar Benjamin J.
Published: December 2006

The I-AniI maturase facilitates self-splicing of a mitochondrial group I intron inAspergillus nidulans. Binding occurs in at least two steps: first, a specific but labile encounter complex rapidly forms and then this intermediate is slowly resolved into a native, catalytically active RNA/protein complex. Here we probe the structure of the RNA throughout the assembly pathway. Although inherently unstable, the intron core, when bound by I-AniI, undergoes rapid folding to a near-native state in the encounter complex. The next transition includes the slow destabilization and docking into the core of the peripheral stacked helix that contains the 5′ splice site. Mutational analyses confirm that both transitions are important for native complex formation. We propose that protein-driven destabilization and docking of the peripheral stacked helix lead to subtle changes in the I-AniI binding site that facilitate native complex formation. These results support an allosteric-feedback mechanism of RNA–protein recognition in which proteins engaged in an intermediate complex can influence RNA structure far from their binding sites. The linkage of these changes to stable binding ensures that the protein and RNA do not get sequestered in nonfunctional complexes.
Autoregulation of GLD-2 cytoplasmic poly(A) polymerase
Authors: Rouhana Labib , Wickens Marvin
Published: December 2006

Cytoplasmic polyadenylation regulates mRNA stability and translation and is required for early development and synaptic plasticity. The GLD-2 poly(A) polymerase catalyzes cytoplasmic polyadenylation in the germline of metazoa. Among vertebrates, the enzyme is encoded by two isoforms of mRNA that differ only in the length of their 3′-UTRs. Here we focus on regulation of vertebrate GLD-2 mRNA. We show that the 3′-UTR of GLD-2 mRNA elicits its own polyadenylation and translational activation during frog oocyte maturation. We identify the sequence elements responsible for repression and activation, and demonstrate that CPEB and PUF proteins likely mediate repression in the resting oocyte. Regulated polyadenylation of GLD-2 mRNA is conserved, as are the key regulatory elements. Poly(A) tails of GLD-2 mRNA increase in length in the brain in response to neuronal stimulation, suggesting that a comparable system exists in that tissue. We propose a positive feedback circuit in which translation of GLD-2 mRNA is stimulated by its polyadenylation, thereby reinforcing the switch to polyadenylate and activate batteries of mRNAs.
Optimal Dynamic Advertising Policy for New Products
Authors: Krishnan Trichy V. , Jain Dipak C.
Published: December 2006

Advertising is one of the key marketing tools managers have at their disposal to influence their customers into purchasing a new product. The overall objective of new product advertising is to inform and persuade customers. Drawing up an advertising plan for a new product that is under the influence of diffusion phenomenon is not an easy task. Hence, research in this area is very limited. In our research, we use an empirically proven diffusion demand function that explicitly incorporates the advertising component. Our results suggest that optimal advertising is determined by the advertising effectiveness, discount rate, and the ratio of advertisement to profits. Depending upon the interplay among these factors, the optimal advertising takes decrease-increase, increase-decrease, monotonically increasing or monotonically decreasing shape.
Sitaxsentan for Treatment of Pulmonary Hypertension
Authors: Wittbrodt Eric T , Abubakar Amina
Published: December 2006

Objective:

To review the literature pertinent to the efficacy and safety of sitaxsentan, a selective endothelin (ET)-A receptor antagonist under evaluation for the treatment of pulmonary arterial hypertension (PAH).

Data Sources:

Articles were identified through searches of the MEDLINE (1966–November 2006) and International Pharmaceutical Abstracts (1970–November 2006) databases, using the key words endothelin antagonist, pulmonary arterial hypertension, pulmonary hypertension, sitaxsentan, and TBC11251. Searches were limited to articles published in English.

Study Selection And Data Extraction:

Due to the limited number of articles on sitaxsentan, all studies captured in the search results were evaluated.

Data Synthesis:

Four studies of sitaxsentan in humans with PAH have been published to date. An uncontrolled open-label study and a randomized placebo-controlled study (STRIDE-1; Sitaxsentan to Relieve Impaired Exercise-1) showed sitaxsentan to improve exercise tolerance in patients with PAH, as evidenced by significant increases in the distance walked in 6 minutes. Significant hepatotoxicity developed in patients receiving sitaxsentan 300 mg. The benefits of sitaxsentan with respect to exercise tolerance and hemodynamics were sustained in a one year extension of the placebo-controlled study. The results of a multicenter, randomized, placebo-controlled trial of 2 doses of sitaxsentan with an open-label bosentan arm (STRIDE-2) suggested that only the 100 mg dose provided superior benefit in exercise tolerance and improvement in functional class. Treatment-related adverse effects were similar for all groups.

Conclusions:

Sitaxsentan appears to be superior to placebo in improving exercise tolerance in patients with PAH but may produce therapeutic outcomes similar to those of bosentan, a comparator agent. The optimal dose of sitaxsentan appears to be 100 mg once daily. Information about the use of sitaxsentan in a greater number of patients with PAH for longer periods is necessary to further define its place in the treatment of PAH.
Perioral Numbness Associated with Intravenous Pentamidine Administration
Authors: Milligan Karen S , Phillips Debra L
Published: December 2006

Objective:

To report a case of perioral numbness associated with intravenous pentamidine.

Case Summary:

A 56-year-old female with acute myelogenous leukemia in remission developed Pneumocystis carinii infection. Treatment was initiated with trimethoprim/sulfamethoxazole (TMP/SMX), but the patient subsequently developed a rash on day 10 of treatment. TMP/SMX was discontinued and intravenous pentamidine was started in order to complete a 21 day treatment course for P. carinii pneumonia (PCP). However, on day 3 of pentamidine treatment, the patient reported perioral numbness during the infusion. The numbness disappeared soon after completion of the infusion but recurred with all subsequent pentamidine infusions.

Discussion:

Paresthesias in general and facial area numbness in particular have been reported with pentamidine administration. While it is possible such adverse events may be a result of pentamidine's effect on serum electrolytes and glucose, especially hypocalcemia and hypoglycemia, these laboratory values were not grossly affected by pentamidine in our patient. The Naranjo probability scale revealed a probable adverse reaction of perioral numbness associated with intravenous pentamidine.

Conclusions:

Pentamidine is considered an alternative agent to TMP/SMX in the treatment of PCP. Although they do not commonly occur, paresthesias have been reported with pentamidine therapy. Healthcare practitioners should be aware of this type of event in association with pentamidine administration, especially as it may not be associated with overt serum glucose or electrolyte disturbances.
Individual values, learning routines and academic procrastination
Authors: Dietz Franziska. , Hofer Manfred. , Fries Stefan.
Published: December 2006

Background. Academic procrastination, the tendency to postpone learning activities, is regarded as a consequence of postmodern values that are prominent in post‐industrialized societies. When students strive for leisure goals and have no structured routines for academic tasks, delaying strenuous learning activities becomes probable.

Aims. The model tested in this study posits that postmodern value orientations are positively related to procrastination and to a lack of daily routines concerning the performance of academic activities. In contrast, modern values are negatively related to procrastination and positively to learning routines. Academic procrastination, in‐turn, should be associated with the tendency to prefer leisure activities to schoolwork in case of conflicts between these two life domains.

Sample. Seven hundred and four students from 6th and 8th grade with a mean age of 13.5 years participated in the study. The sample included students from all tracks of the German educational system.

Method. Students completed a questionnaire containing two value prototypes as well as scales on learning routines and procrastination. Decisions in motivational conflicts were measured using two vignettes.

Results and Conclusions. Results from structural equation modelling supported the proposed model for the whole sample as well as for each school track. A planned course of the day can prevent procrastination and foster decisions for academic tasks in case of conflicts. Students' learning takes place within a societal context and reflects the values held in the respective culture.
Getting Marketers to Invest in Firm-Specific Capital
Authors: Griffith David A. , Lusch Robert F.
Published: December 2006

Firms gain competitive advantage by employing marketing professionals that have developed firm-specific capital. This study argues that marketers’ perceptions of the governance structure employed by the firm to protect marketer capital influence marketers’ job outcomes of organizational commitment, organizational trust, job satisfaction, and intention to turnover, which in turn influence the accumulation of capital more specific to the firm. The results demonstrate (1) that a protective governance structure in which marketers are able to obtain greater rewards internally than externally on more specific or less easily transferable capital does not enhance positive job outcomes and (2) that it is through the governance structures’ influence on job outcomes, not through the governance structure itself, that marketing professionals are motivated to invest in the accumulation of capital specific to the firm. These results provide insights for senior marketing managers charged with developing a governance mechanism to both retain current marketing talent and develop a more effective marketing group.
Increase in and clearance of cell-free plasma DNA in hemodialysis quantified by real-time PCR
Authors: García Moreira Vanessa , de la Cera Martínez Tamara , Gago González Emilio , Prieto García Belén , Alvarez Menéndez Francisco V.
Published: December 2006

Clin Chem Lab Med 2006;44:1410–5.
Analytical performance and clinical utility of the INNOTEST® PHOSPHO-TAU(181P) assay for discrimination between Alzheimer's disease and dementia with Lewy bodies
Authors: Vanderstichele Hugo , De Vreese Karen , Blennow Kaj , Andreasen Niels , Sindic Christian , Ivanoiu Adrian , Hampel Harald , Bürger Katharina , Parnetti Lucilla , Lanari Alessia , Padovani Allesandro , DiLuca Monica , Bläser Miriam , Ohrfelt Olsson Annika , Pottel Hans , Hulstaert Frank , Vanmechelen Eugeen
Published: December 2006

Clin Chem Lab Med 2006;44:1472–80.
Improvement in HPLC separation of porphyrin isomers and application to biochemical diagnosis of porphyrias
Authors: Macours Pascale , Cotton Frédéric
Published: December 2006

Clin Chem Lab Med 2006;44:1433–40.
Prevalence-dependent decision limits for the early detection of type 2 diabetes mellitus in venous blood, venous plasma and capillary blood during glucose challenge
Authors: Haeckel Rainer , Raber Rüdiger , Wosniok Werner
Published: December 2006

Clin Chem Lab Med 2006;44:1462–71.
Lipoprotein lipase gene polymorphism at the PvuII locus and serum lipid levels in Guangxi Hei Yi Zhuang and Han populations
Authors: Yin Ruixing , Wang Yong , Chen Guangqin , Lin Weixiong , Yang Dezhai , Pan Shangling
Published: December 2006

Clin Chem Lab Med 2006;44:1416–21.
Approved IFCC recommendation on reporting results for blood glucose: International Federation of Clinical Chemistry and Laboratory Medicine Scientific Division, Working Group on Selective Electrodes and Point-of-Care Testing (IFCC-SD-WG-SEPOCT)
Authors: D'Orazio Paul , Burnett Robert W. , Fogh-Andersen Niels , Jacobs Ellis , Kuwa Katsuhiko , Külpmann Wolf R. , Larsson Lasse , Lewenstam Andrzej , Maas Anton H.J. , Mager Gerhard , Naskalski Jerzy W. , Okorodudu Anthony O.
Published: December 2006

In current clinical practice, plasma and blood glucose are used interchangeably with a consequent risk of clinical misinterpretation. In human blood, glucose is distributed, like water, between erythrocytes and plasma. The molality of glucose (amount of glucose per unit water mass) is the same throughout the sample, but the concentration is higher in plasma, because the concentration of water and therefore glucose is higher in plasma than in erythrocytes. Different devices for the measurement of glucose may detect and report fundamentally different quantities. Different water concentrations in the calibrator, plasma, and erythrocyte fluid can explain some of the differences. Results for glucose measurements depend on the sample type and on whether the method requires sample dilution or uses biosensors in undiluted samples. If the results are mixed up or used indiscriminately, the differences may exceed the maximum allowable error for glucose determinations for diagnosing and monitoring diabetes mellitus, thus complicating patient treatment. The goal of the International Federation of Clinical Chemistry and Laboratory Medicine, Scientific Division, Working Group on Selective Electrodes and Point of Care Testing (IFCC-SD-WG-SEPOCT) is to reach a global consensus on reporting results. The document recommends reporting the concentration of glucose in plasma (in the unit mmol/L), irrespective of sample type or measurement technique. A constant factor of 1.11 is used to convert concentration in whole blood to the equivalent concentration in plasma. The conversion will provide harmonized results, facilitating the classification and care of patients and leading to fewer therapeutic misjudgments.

Clin Chem Lab Med 2006;44:1486–90.
Quantification of Wrist Motions during Scanning
Authors: Marras William S. , Marklin Richard W. , Greenspan Gerald J. , Lehman Katherine R.
Published: December 2006

A laboratory study was performed to help assess the risk of cumulative trauma disorders (CTDs) associated with the use of scanners in the grocery store environment. In this study experienced and inexperienced cashiers scanned a set of 12 standard grocery items using 19 different combinations of scanners, scanner orientations, and check stands. The motion characteristics of both wrists in three-dimensional space were documented and used as dependent measures of performance. These motions were compared with wrist motion benchmarks of high-and low-risk wrist accelerations. It was found that, in general, scanning motions are of sufficient magnitude to contribute to CTDs of the wrist. It was also found that wrist motion characteristics were greatly influenced by the different combinations of scanners, scanner orientations, and check stand designs. It was concluded that the "front-style" check stand minimizes potentially injurious wrist motions because it permits the checker to split the scanning task between the two hands. The type of scanner and scanner orientation that minimized potentially injurious wrist motions was much more unique to the individual workstation condition. Additionally, it appears that scanners perceived by the checkers as needing fewer wrist deviations, such as those with slanted windows, also minimize wrist motions. The implications of these findings for the ergonomic design of the workplace are discussed.
Social and Cognitive Processes in Interpersonal Communication: Implications for Advanced Telecommunications Technologies
Authors: Fussell Susan R.
Published: December 2006

Interactive multimedia conferencing systems, in which two or more remotely located people can work on cooperative tasks through shared audio, video, and data, appear to be the wave of the future. However, because of great advances in the underlying technology of multimedia conferencing systems, many design decisions have been driven by what is technically feasible as opposed to what will best suit the needs of the users. In this paper we provide a framework for the design and evaluation of features in advanced telecommunications products and services which is derived from empirical research on interpersonal communication. We also discuss implications of this research for the development and use of advanced telecommunications technologies.
The Out-of-the-Loop Performance Problem and Level of Control in Automation
Authors: Endsley Mica R. , Kiris Esin O.
Published: December 2006

The out-of-the-loop performance problem, a major potential consequence of automation, leaves operators of automated systems handicapped in their ability to take over manual operations in the event of automation failure. This is attributed to a possible loss of skills and of situation awareness (SA) arising from vigilance and complacency problems, a shift from active to passive information processing, and change in feedback provided to the operator. We studied the automation of a navigation task using an expert system and demonstrated that low SA corresponded with out-of-the-loop performance decrements in decision time following a failure of the expert system. Level of operator control in interacting with automation is a major factor in moderating this loss of SA. Results indicated that the shift from active to passive processing was most likely responsible for decreased SA under automated conditions.
Telepresence in Videocommunications: A Study on Stereoscopy and Individual Eye Contact
Authors: Muhlbach Lothar , Bocker Martin , Prussog Angela
Published: December 2006

We conducted two experiments to investigate how stereoscopy and technologies that allow individual eye contact affect the impression of telepresence in videoconferencing. Telepresence is defined as the degree to which participants of a telemeeting get the impression of sharing space with the remote site. Results revealed, among other things, that stereoscopy increases telepresence and makes videoconferencing more attractive. In addition, we found that reduced eye contact angles enhance the recognizability of individually addressed nonverbal signals. However, a setup that eliminates horizontal and vertical eye contact angles seems to be advantageous only in conferences with more than two persons per site.
Using Natural Language Conventions in the User Interface Design of Automatic Speech Recognition Systems
Authors: Brems Douglas J. , Rabin Michael D. , Waggett Jill L.
Published: December 2006

Four experiments were performed to examine how natural language conventions might be used to improve the user interface for systems using automatic speech recognition (ASR). Two new technological developments offered us this opportunity: word spotting permits recognition of key words embedded in extraneous speech; barge in permits the user to speak to the system while it plays instructional prompts. Our goal was to take advantage of natural language conventions to design an optimal prompting arrangement that would accommodate both novice and expert users. The conversational conventions we focused on included people's readiness to speak in response to a direct question and during an appropriately timed conversational pause. We studied these conventions in the context of an automated operator service. Our results indicated that a prompt-arranged as a leading question, followed by a brief pause and then a list of key words-met our goals for both the initial prompt and, if ASR failed. a subsequent reprompt. This approach resulted in fast, accurate responding, a user interface that received high user acceptance ratings, and an interface that was usable by both novice and expert users.
Cell-Surface Actin Binds Plasminogen and Modulates Neurotransmitter Release from Catecholaminergic Cells
Authors: Miles Lindsey A. , Andronicos Nicholas M. , Baik Nagyung , Parmer Robert J.
Published: December 2006

An emerging area of research has documented a novel role for the plasminogen activation system in the regulation of neurotransmitter release. Prohormones, secreted by cells within the sympathoadrenal system, are processed by plasmin to bioactive peptides that feed back to inhibit secretagogue-stimulated release. Catecholaminergic cells of the sympathoadrenal system are prototypic prohormone-secreting cells. Processing of prohormones by plasmin is enhanced in the presence of catecholaminergic cells, and the enhancement requires binding of plasmin(ogen) to cellular receptors. Consequently, modulation of the local cellular fibrinolytic system of catecholaminergic cells results in substantial changes in catecholamine release. However, mechanisms for enhancing prohormone processing and cell-surface molecules mediating the enhancement on catecholaminergic cells have not been investigated. Here we show that plasminogen activation was enhanced >6.5-fold on catecholaminergic cells. Carboxypeptidase B treatment decreased cell-dependent plasminogen activation by ∼90%, suggesting that the binding of plasminogen to proteins exposing C-terminal lysines on the cell surface is required to promote plasminogen activation. We identified catecholaminergic plasminogen receptors required for enhancing plasminogen activation, using a novel strategy combining targeted specific proteolysis using carboxypeptidase B with a proteomics approach using two-dimensional gel electrophoresis, radioligand blotting, and tandem mass spectrometry. Two major plasminogen-binding proteins that exposed C-terminal lysines on the cell surface contained amino acid sequences corresponding to β/γ-actin. An anti-actin monoclonal antibody inhibited cell-dependent plasminogen activation and also enhanced nicotine-dependent catecholamine release. Our results suggest that cell-surface-expressed forms of actin bind plasminogen, thereby promoting plasminogen activation and increased prohormone processing leading to inhibition of neurotransmitter release.
Imaging of cAMP Levels and Protein Kinase A Activity Reveals That Retinal Waves Drive Oscillations in Second-Messenger Cascades
Authors: Dunn Timothy A. , Wang Chih-Tien , Colicos Michael A. , Zaccolo Manuela , DiPilato Lisa M. , Zhang Jin , Tsien Roger Y. , Feller Marla B.
Published: December 2006

Recent evidence demonstrates that low-frequency oscillations of intracellular calcium on timescales of seconds to minutes drive distinct aspects of neuronal development, but the mechanisms by which these calcium transients are coupled to signaling cascades are not well understood. Here we test the hypothesis that spontaneous electrical activity activates protein kinase A (PKA). We use live-cell indicators to observe spontaneous and evoked changes in cAMP levels and PKA activity in developing retinal neurons. Expression of cAMP and PKA indicators in neonatal rat retinal explants reveals spontaneous oscillations in PKA activity that are temporally correlated with spontaneous depolarizations associated with retinal waves. In response to short applications of forskolin, dopamine, or high-potassium concentration, we image an increase in cAMP levels and PKA activity, indicating that this second-messenger pathway can be activated quickly by neural activity. Depolarization-evoked increases in PKA activity were blocked by the removal of extracellular calcium, indicating that they are mediated by a calcium-dependent mechanism. These findings demonstrate for the first time that spontaneous activity in developing circuits is correlated with activation of the cAMP/PKA pathway and that PKA activity is turned on and off on the timescale of tens of seconds. These results show a link between neural activity and an intracellular biochemical cascade associated with plasticity, axon guidance, and neural differentiation.
Bim and Noxa Are Candidates to Mediate the Deleterious Effect of the NF-κB Subunit RelA in Cerebral Ischemia
Authors: Inta Ioana , Paxian Stephan , Maegele Ira , Zhang Wen , Pizzi Marina , Spano PierFranco , Sarnico Ilenia , Muhammad Sajjad , Herrmann Oliver , Inta Dragos , Baumann Bernd , Liou Hsiou-Chi , Schmid Roland M. , Schwaninger Markus
Published: December 2006

The transcription factor nuclear factor κB (NF-κB) is well known for its antiapoptotic action. However, in some disorders, such as cerebral ischemia, a proapoptotic function of NF-κB has been demonstrated. To analyze which subunit of NF-κB is functional in cerebral ischemia, we induced focal cerebral ischemia in mice with a germline deletion of thep52orc-Relgene or with a conditional deletion of RelA in the brain. Only RelA deficiency reduced infarct size. Interestingly, expression of the proapoptotic BH3 (Bcl-2 homology domain 3)-only genesBimandNoxain cerebral ischemia depended on RelA and the upstream kinase IKK (IκB kinase). RelA stimulated Bim and Noxa gene transcription in primary cortical neurons and bound to the promoter of both genes. Thus, the deleterious function in cerebral ischemia is specific for the NF-κB subunit RelA and may be mediated through Bim and Noxa.
Learning-Induced Plasticity in Deep Cerebellar Nucleus
Authors: Ohyama Tatsuya , Nores William L. , Medina Javier F. , Riusech Frank A. , Mauk Michael D.
Published: December 2006

Evidence that cerebellar learning involves more than one site of plasticity comes from, in part, pavlovian eyelid conditioning, where disconnecting the cerebellar cortex abolishes one component of learning, response timing, but spares the expression of abnormally timed short-latency responses (SLRs). Here, we provide evidence that SLRs unmasked by cerebellar cortex lesions are mediated by an associative form of learning-induced plasticity in the anterior interpositus nucleus (AIN) of the cerebellum. We used pharmacological inactivation and/or electrical microstimulation of various sites afferent and efferent to the AIN to systematically eliminate alternative candidate sites of plasticity upstream or downstream from this structure. Collectively, the results suggest that cerebellar learning is mediated in part by plasticity in target nuclei downstream of the cerebellar cortex. These data demonstrate an instance in which an aspect of associative learning, SLRs, can be used as an index of plasticity at a specific site in the brain.
GODZ-Mediated Palmitoylation of GABAAReceptors Is Required for Normal Assembly and Function of GABAergic Inhibitory Synapses
Authors: Fang Cheng , Deng Lunbin , Keller Cheryl A. , Fukata Masaki , Fukata Yuko , Chen Gong , Lüscher Bernhard
Published: December 2006

Golgi-specific DHHC (Asp-His-His-Cys) zinc finger protein (GODZ) is a DHHC family palmitoyl acyltransferase that is implicated in palmitoylation and regulated trafficking of diverse substrates that function either at inhibitory or excitatory synapses. Of particular interest is the γ2 subunit of GABAAreceptors, which is required for targeting these receptors to inhibitory synapses. Here, we report that GODZ and, to a lesser extent, its close paralog sertoli cell gene with a zinc finger domain-β (SERZ-β) are the main members of the DHHC family of enzymes that are able to palmitoylate the γ2 subunit in heterologous cells. Yeast two-hybrid and colocalization assays in human embryonic kidney 293T (HEK293T) cells indicate that GODZ and SERZ-β show indistinguishable palmitoylation-dependent interaction with the γ2 subunit. After coexpression in HEK293T cells, they form homomultimers and heteromultimers, as shown by coimmunoprecipitation andin vivocross-linking experiments. Analyses in neurons transfected with dominant-negative GODZ (GODZC157S) or plasmid-based GODZ-specific RNAi indicate that GODZ is required for normal accumulation of GABAAreceptors at synapses, for normal whole-cell and synaptic GABAergic inhibitory function and, indirectly, for GABAergic innervation. Unexpectedly, GODZ was found to be dispensable for normal postsynaptic AMPA receptor-mediated glutamatergic transmission. We conclude that GODZ-mediated palmitoylation of GABAAreceptors and possibly other substrates contributes selectively to the formation and normal function of GABAergic inhibitory synapses.
The Molecular Gatekeeper Dexras1 Sculpts the Photic Responsiveness of the Mammalian Circadian Clock
Authors: Cheng Hai-Ying M. , Dziema Heather , Papp Joseph , Mathur Daniel P. , Koletar Margaret , Ralph Martin R. , Penninger Josef M. , Obrietan Karl
Published: December 2006

The mammalian master clock, located in the suprachiasmatic nucleus (SCN), is exquisitely sensitive to photic timing cues, but the key molecular events that sculpt both the phasing and magnitude of responsiveness are not understood. Here, we show that the Ras-like G-protein Dexras1 is a critical factor in these processes.Dexras1-deficient mice (dexras1−/−) exhibit a restructured nighttime phase response curve and a loss of gating to photic resetting during the day. Dexras1 affects the photic sensitivity by repressing or activating time-of-day-specific signaling pathways that regulate extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK). During the late night, Dexras1 limits the capacity of pituitary adenylate cyclase (PAC) activating peptide (PACAP)/PAC1 to affect ERK/MAPK, and in the early night, light-induced phase delays, which are mediated predominantly by NMDA receptors, are reduced as reported previously. Daytime photic phase advances are mediated by a novel signaling pathway that does not affect the SCN core but rather stimulates ERK/MAPK in the SCN shell and triggers downregulation of clock protein expression.
Regional Differentiation of the Medial Prefrontal Cortex in Regulating Adaptive Responses to Acute Emotional Stress
Authors: Radley Jason J. , Arias Carlos M. , Sawchenko Paul E.
Published: December 2006

The medial prefrontal cortex (mPFC) is an important neural substrate for integrating cognitive-affective information and regulating the hypothalamo–pituitary–adrenal (HPA) axis response to emotional stress. mPFC modulation of stress responses is effected in part via the paraventricular hypothalamic nucleus (PVH), which houses both autonomic (sympathoadrenal) and neuroendocrine (HPA) effector mechanisms. Although the weight of evidence suggests that mPFC influences on stress-related PVH outputs are inhibitory, discordant findings have been reported, and such work has tended to treat this cortical region as a unitary structure. Here we compared the effects of lesions of the dorsal versus ventral aspects of mPFC, centered in the prelimbic and infralimbic fields, respectively, on acute restraint stress-induced activation of PVH cell groups mediating autonomic and neuroendocrine responses. Lesions to the dorsal mPFC enhanced restraint-induced Fos and corticotropin-releasing factor (CRF) mRNA expression in the neurosecretory region of PVH. Ablation of the ventral mPFC decreased stress-induced Fos protein and CRF mRNA expression in this compartment but increased Fos induction in PVH regions involved in central autonomic control. Repetition of the experiments in rats bearing retrograde tracer deposits to label PVH-autonomic projections confirmed that ventral mPFC lesions selectively increased stress-induced Fos expression in identified preautonomic neurons. Finally, hormonal indices of HPA activation in response to acute stress were augmented after dorsal mPFC lesions and attenuated after ventral mPFC lesions. These results suggest that dorsal and ventral aspects of the mPFC differentially regulate neuroendocrine and autonomic PVH outputs in response to emotional stress.
A Neurovascular Niche for Neurogenesis after Stroke
Authors: Ohab John J. , Fleming Sheila , Blesch Armin , Carmichael S. Thomas
Published: December 2006

Stroke causes cell death but also birth and migration of new neurons within sites of ischemic damage. The cellular environment that induces neuronal regeneration and migration after stroke has not been defined. We have used a model of long-distance migration of newly born neurons from the subventricular zone to cortex after stroke to define the cellular cues that induce neuronal regeneration after CNS injury. Mitotic, genetic, and viral labeling and chemokine/growth factor gain- and loss-of-function studies show that stroke induces neurogenesis from a GFAP-expressing progenitor cell in the subventricular zone and migration of newly born neurons into a unique neurovascular niche in peri-infarct cortex. Within this neurovascular niche, newly born, immature neurons closely associate with the remodeling vasculature. Neurogenesis and angiogenesis are causally linked through vascular production of stromal-derived factor 1 (SDF1) and angiopoietin 1 (Ang1). Furthermore, SDF1 and Ang1 promote post-stroke neuroblast migration and behavioral recovery. These experiments define a novel brain environment for neuronal regeneration after stroke and identify molecular mechanisms that are shared between angiogenesis and neurogenesis during functional recovery from brain injury.
Mettius Fufetius in Livy
Authors: Noonan J. D.
Published: December 2006

Abstract This essay makes the case that Livy's version of the tale of Mettius Fufetius transmits certain facts that relate to inherited ritual practices (horse-sacrifice among them) along with formulas used in early law and diplomacy. Although the author may not be fully aware of the original meaning of all he is handing down (e.g., the etymology of mitis) because he has simply taken materials from his sources without much critical investigation, the traditional elements are important to him because they seem to authenticate this legend about the reign of Tullus Hostilius. For the moralizing historian that Livy certainly is, the treason of Mettius Fufetius and his execution at the command of the Roman king comprise the starting point of a remarkable sequence of episodes in his narrative that demonstrate the dishonorable behavior of Rome's chief rivals in Italy. The legend of Mettius Fufetius thus embodies a kind of “original sin” in the political realm, and becomes the paradigm for Rome's harsh dealing with faithless allies over the next five centuries. The essay concludes that this story typifies many Roman fabulae, insofar as they were often composed on the basis of outdated or unfamiliar idionyms, toponyms, ceremonial words and phrases, and ancient legal terms. In such fabulae characters like Tullus Hostilius and Mettius Fufetius, perhaps mere names in annals and king-lists, become the performers whose ceremonial acts turn into the foundational moments of Rome's public life.