bluuebunny/crossref_metadata_2025 huggingface dataset:
Incentive-Elicited Brain Activation in Adolescents: Similarities and Differences from Young Adults
Authors: Bjork James M. , Knutson Brian , Fong Grace W. , Caggiano Daniel M. , Bennett Shannon M. , Hommer Daniel W.
Published: February 2004

Brain motivational circuitry in human adolescence is poorly characterized. One theory holds that risky behavior in adolescence results in part from a relatively overactive ventral striatal (VS) motivational circuit that readily energizes approach toward salient appetitive cues. However, other evidence fosters a theory that this circuit is developmentally underactive, in which adolescents approach more robust incentives (such as risk taking or drug experimentation) to recruit this circuitry. To help resolve this, we compared brain activation in 12 adolescents (12-17 years of age) and 12 young adults (22-28 years of age) while they anticipated the opportunity to respond to obtain monetary gains as well as to avoid monetary losses. In both age groups, anticipation of potential gain activated portions of the VS, right insula, dorsal thalamus, and dorsal midbrain, where the magnitude of VS activation was sensitive to gain amount. Notification of gain outcomes (in contrast with missed gains) activated the mesial frontal cortex (mFC). Across all subjects, signal increase in the right nucleus accumbens during anticipation of responding for large gains independently correlated with both age and self-rated excitement about the high gain cue. In direct comparison, adolescents evidenced less recruitment of the right VS and right-extended amygdala while anticipating responding for gains (in contrast with anticipation of nongains) compared with young adults. However, brain activation after gain outcomes did not appreciably differ between age groups. These results suggest that adolescents selectively show reduced recruitment of motivational but not consummatory components of reward-directed behavior.
A Rapid and Precise On-Response in Posterior Parietal Cortex
Authors: Bisley James W. , Krishna B. Suresh , Goldberg Michael E.
Published: February 2004

The activity of neurons in the lateral intraparietal area (LIP) of the monkey predicts the monkey's allocation of spatial attention. We show here that despite being relatively high within the visual hierarchy, neurons in LIP have extremely short and precise visual latencies. Mean latency was 45.2 msec; the timing precision of the onset response was usually better than 4 msec. The majority of neurons had a pause in response after an initial burst, followed by more sustained visual activity. Previous attention allocation had no effect on either the latency or magnitude of the initial burst, but produced clear effects on the magnitude of the later sustained activity. Together, these data indicate that the initial burst in LIP visual response reflects an uncontaminated sensory signal. Information about stimulus onset is transmitted rapidly through the visual system to LIP; the on-response has a higher speed and temporal precision than realized previously. This information could be used to orient attention to novel objects in the visual environment rapidly and reliably.
Distinct Roles of HippocampalDe NovoProtein Synthesis and Actin Rearrangement in Extinction of Contextual Fear
Authors: Fischer André , Sananbenesi Farahnaz , Schrick Christina , Spiess Joachim , Radulovic Jelena
Published: February 2004

It is believed thatde novoprotein synthesis is fundamentally linked to synaptic changes in neuronal circuits involved in acquisition and extinction of conditioned responses. Recent studies show that neuronal plasticity may be also altered by cytoskeletal rearrangement independently of protein synthesis. We investigated the role of these processes in the hippocampus during acquisition and extinction of context-dependent conditioned fear in mice. Intrahippocampal injections of the protein synthesis inhibitors anisomycin and puromycin, or of the actin rearrangement inhibitors cytochalasin D and latrunculin A, prevented the acquisition of context-dependent fear. Unexpectedly, anisomycin and puromycin enhanced extinction without erasing the fear memory. In contrast, cytochalasin D and latrunculin A prevented extinction of context-dependent freezing. On the basis of these findings, it is suggested that certain hippocampal mechanisms mediating extinction of conditioned contextual fear are inhibited by protein synthesis and involve actin rearrangement. Such mechanisms might predominantly elicit modifications of hippocampal circuits that store the conditioning memory.
Über einige lokal verallgemeinernde Speicher und ihre Weiterentwicklung, Teil 1: CMAC/AMS und MIAS (One some Locally Generalizing Storage Methods and their further Development, Part 1: CMAC/AMS and MIAS)
Authors: Tolle Henning
Published: February 2004

Bei der Modellierung, Steuerung und Regelung nichtlinearer Prozesse werden häufig zwei- bzw. mehrdimensionale Kennfelder eingesetzt. Sie können äußerst effektiv in lokal verallgemeinernden Speichern abgelegt werden. Der Beitrag stellt an Hand von drei Beispielen und ihren Weiterentwicklungen dar, dass sehr verschiedenartige Ansätze möglich sind und die Auswahl gemäß ihren inherenten Vor- und Nachteilen von der ins Auge gefassten Anwendung bestimmt werden sollte. Teil I behandelt mit 〟CMAC/AMS〞 ein neurobiologisch motiviertes und mit 〟MIAS〞 ein aus der grafischen Datenverarbeitung abgeleitetes Verfahren.
Benutzeranforderungen für den Einsatz von mobilen Endgeräten in der Industrieautomatisierung (User Requirements for the Use of Mobile Devices in the Industrial Automation)
Authors: Wittenberg Carsten
Published: February 2004

Der vorliegende Artikel beschreibt, wie unter frühzeitiger Einbeziehung potentieller Endnutzer Anforderungen für ein geeignetes User Interface Konzept für mobile Endgeräte im Bereich der industriellen Automatisierungstechnik aufgenommen wurden. Als ein Ergebnis der Anforderungsanalyse wird ein besonderer Vorteil des Einsatzes von mobilen Geräten im Service- und Wartungsbereich erkannt. Eine Usability Testreihe mit unterschiedlichen Benutzergruppen hat gezeigt, dass durch die Umsetzung der Anforderungen in einen Prototyp ein User Interface entsteht, welches Wartungstechniker bei ihren täglichen Aufgaben in industriellen automatisierten Produktionssystemen unterstützt.
Bestimmung der Messunsicherheit bei Durchflussmessungen (Determination of the Uncertainty of Flow Measurements)
Authors: Adunka Franz
Published: February 2004

Die Bestimmung der Messunsicherheit bei Durchflussmessungen unterscheidet sich prinzipiell nicht von jener anderer Messungen. Im Folgenden werden daher die Grundkonzepte des GUM vorausgesetzt und jene Fragen diskutiert, die typisch für den Problemkreis Durchflussmessungen sind. Aus dem großen Gebiet der Durchflussmesstechnik sollen hier vorwiegend Strömungen flüssiger Medien in Rohrleitungen betrachtet werden, aber nicht in Kanälen oder offenen Gerinnen. Die Vorgehensweise bei der Gasmessung wird in einem Beispiel angeschnitten.
Messunsicherheitsbetrachtung bei der Oszilloskopkalibrierung (Evaluation of Measurement Uncertainty in Calibrating Oscilloscopes)
Authors: Berg Klaus-Peter
Published: February 2004

Die Messunsicherheitsbetrachtung bei der Kalibrierung von Oszilloskopen hat sich bisher als ausgesprochen schwierig erwiesen, weil entsprechende Kalibrierrichtlinien nicht zur Verfügung standen, und weil auch in den Kalibrieranweisungen der Hersteller nicht auf dieses Thema eingegangen wird. Mit der VDI/VDE/DGQ/DKD-Richtlinienreihe 2622 „Kalibrieren von Messmitteln für elektrische Größen“ hat sich die Situation grundlegend geändert. Der vorliegende Beitrag beschreibt die Ermittlung der Messunsicherheit bei der Kalibrierung von Oszilloskopen auf der Grundlage dieser Richtlinie.
Praxisgerechtes Bestimmen der Messunsicherheit nach GUM (Practical Determination of the Measurement Uncertainty under GUM)
Authors: Sommer Klaus-Dieter , Siebert Bernd R. L.
Published: February 2004

Der von der ISO im Auftrag mehrerer internationaler Organisationen herausgegebene „Guide to the Expression of Uncertainty in Measurement“, kurz GUM genannt, ist in den letzten Jahren ein weltweit akzeptierter Standard für die Bewertung und Angabe der Messunsicherheit geworden. Die entscheidenden Aufgaben der Messunsicherheitsbewertung nach GUM sind die Beschreibung der Messaufgabe, die Einschätzung der beteiligten Größen mithilfe von Wahrscheinlichkeitsverteilungen und das Aufstellen der Modellgleichung. Alle weiteren Verfahrensschritte folgen festen mathematischen Regeln und lassen sich daher rechnergestützt ausführen. Das Hauptproblem für den Praktiker ist das Aufstellen der Modellgleichung. Dafür wird im Beitrag ein GUM-konsistentes Verfahren gezeigt, das leicht an konkrete Messaufgaben angepasst werden kann. Damit lässt sich das GUM-Verfahren durchgängig als praxisgerechte, schrittweise abarbeitbare Prozedur darstellen und anwenden.
Weiterentwicklung des GUM und Monte-Carlo-Techniken (New Developments of the GUM and Monte Carlo Techniques)
Authors: Siebert Bernd R. L. , Sommer Klaus-Dieter
Published: February 2004

Der „Leitfaden zur Angabe der Unsicherheit beim Messen“ (GUM) wird von ISO, DIN und anderen Institutionen als das grundlegende Dokument für die Ermittlung der Messunsicherheit angesehen. Er wurde vor etwa 10 Jahren veröffentlicht. Vermutlich schon im Jahr 2004 werden Ergänzungen erscheinen, die Weiterentwicklungen präsentieren. Eine dieser Ergänzungen betrifft Messprobleme mit mehr als einer Ausgangsgröße und eine andere wird, insbesondere für nichtlineare Modelle zur Auswertung der Messunsicherheit, Monte-Carlo-Techniken empfehlen, in die dieser Bericht einführt.
Werkstückeinflüsse in der Koordinatenmesstechnik (Workpiece Influence in Coordinate Metrology)
Authors: Keck Christian , Franke Matthias , Schwenke Heinrich
Published: February 2004

Dieser Beitrag gibt einen Überblick über die Einflüsse, die bei taktilen Koordinatenmessungen vom Werkstück ausgehen. Er beschreibt ihre Entstehung und macht Vorschläge, wie sie bei der Planung, Durchführung und Auswertung von Koordinatenmessungen sowie bei der Ermittlung der Messunsicherheit berücksichtigt werden können.
Messunsicherheitsbestimmung in der Nanotechnologie am Beispiel eines Nanoclusters (Determining Measurement Uncertainty in Nanometrology with the example of Nanoclusters)
Authors: Weckenmann Albert , Wiedenhöfer Thomas , Sommer Klaus-Dieter
Published: February 2004

Die Zuordnung der Messunsicherheit zu einem Messergebnis im Bereich der Nanomesstechnik ist eine neue Herausforderung für die angewandten Wissenschaften. Es mangelt bisher an Modellen und Vorgehensweisen zur Analyse und Interpretation der Messaufgaben und Einflüsse. Auch die zu Grunde liegenden technologischen Mechanismen sind häufig nur unzureichend bekannt. Anhand von Nanoclustern wird versucht, eine Messunsicherheitsbetrachtung in diesem Bereich zu erläutern. Typische Einflüsse werden gemäß ISO-„Guideline to the Expression of Uncertainty in Measurement“ (GUM) modelliert, Unsicherheitsbeiträge quantifiziert und zugehörige Unsicherheitsbereiche festgelegt, bevor das vollständige Messergebnis, bestehend aus Erwartungswert und beigeordneter Messunsicherheit berechnet, sowie das resultierende Messunsicherheitsbudget analysiert wird.
Hydrogel Nanoparticle Dispersions with Inverse Thermoreversible Gelation
Authors: Hu Z. , Xia X.
Published: February 2004

A novel aqueous solution of hydrogel nanoparticles with interpenetrating polymer networks of poly(isopropylacrylamide) and poly(acrylic acid) has been synthesized. This hydrogel can form a physically bonded nanoparticle network above a certain gelation temperature. The system exhibits a very rich phase behavior, including a colloidal crystalline phase, in which the system displays iridescent colors (for examples, see Figure).
High‐Performance Organic Light‐Emitting Diodes Using ITO Anodes Grown on Plastic by Room‐ Temperature Ion‐Assisted Deposition
Authors: Yang Y. , Huang Q. , Metz A. W. , Ni J. , Jin S. , Marks T. J. , Madsen M. E. , DiVenere A. , Ho S.‐T.
Published: February 2004

Ion‐assisted deposition (IAD) was used to deposit smooth, adherent, and electrically/optically high‐quality indium tin oxide (ITO) films on glass and plastic substrates at room temperature. These films afforded organic light‐emitting diode performance comparable to devices with commercial ITO/glass anodes, indicating that IAD is an attractive technique for low‐temperature ITO deposition, especially on plastics (see Figure).
Assembly of Gold Nanoparticles into Fibrous Aggregates Using Thiol‐Terminated Gelators
Authors: Kimura M. , Kobayashi S. , Kuroda T. , Hanabusa K. , Shirai H.
Published: February 2004

Gold nanoparticles are organized into a three‐dimensional network structure using a newly designed thiol‐terminated organic gelator. Gold nanoparticles have been covalently linked with supramolecular nanoscopic fibers, in which the gelators have been assembled by intermolecular hydrogen bonding. The Figure shows fibrous aggregates of Au nanoparticles in the presence of the new gelator (see also the front cover).
“Non‐Fouling” Oligo(ethylene glycol)‐ Functionalized Polymer Brushes Synthesized by Surface‐Initiated Atom Transfer Radical Polymerization
Authors: Ma H. , Hyun J. , Stiller P. , Chilkoti A.
Published: February 2004

The in‐situ synthesis of oligo(ethylene glycol)‐functionalized polymer brushes from a self‐assembled monolayer of an alkanethiol on gold that presents a tethered initiator by surface‐initiated atom transfer radical polymerization is reported. These polymer brushes exhibit no detectable adsorption of proteins, and are cell‐resistant for up to a month under typical cell culture conditions. The synthesis method is compatible with a range of patterning techniques from the nano‐ to the microscale, and enables the patterning of cells in a biologically relevant milieu over extended periods of time. Images of the brushes are shown on the inside front cover.
Transparent Organic Thin‐Film Transistor with a Laterally Grown Non‐Planar Phthalocyanine Channel
Authors: Ohta H. , Kambayashi T. , Nomura K. , Hirano M. , Ishikawa K. , Takezoe H. , Hosono H.
Published: February 2004

An improved‐performance transparent organic thin‐film transistor (OTFT) is described, which has a vanadyl‐phthalocyanine (VOPc) film as an active p‐channel, lattice‐matched (Sc0.7Y0.3)2O3 film as a high‐k gate dielectric, and atomically flat indium tin oxide (ITO) film as the bottom contact (see Figure). These features—lattice matching and atomic flatness—are expected to lead to further improvements in transparent OTFTs.
Well‐Aligned “Nano‐Box‐Beams” of SnO2
Authors: Liu Y. , Dong J. , Liu M.
Published: February 2004

A new nanostructure, a “nano‐box‐beam”, of tin dioxide has been synthesized using a vapor deposition process in open atmosphere (see Figure). Each as‐grown SnO2 nanotube is a single crystal with four {110} peripheral surfaces and [001] growth direction. The new nanostructure could be used in devices such as nanobatteries, nanoscale fuel cells, and nanosensors.
Dramatic Enhancement of Photorefractive Properties by Controlling Electron Trap Density in a Monolithic Material
Authors: You W. , Hou Z. , Yu L.
Published: February 2004

Serving as the electron‐trapping center in photorefractive (PR) materials, the molecule M1, having a more electron‐deficient core, M, was doped with a monolithic PR material M0 (see Figure). Typical PR properties were dramatically improved with only 0.05 wt.‐% M1 with M0. An optical gain of 235 cm–1 at a field of 35 V μm–1 and diffraction efficiency of 77.5 % at a low field of 23 V μm–1 can be obtained.
Electrospinning Nanofibers as Uniaxially Aligned Arrays and Layer‐by‐Layer Stacked Films
Authors: Li D. , Wang Y. , Xia Y.
Published: February 2004

The conventional procedure for electrospinning has been modified to generate nanofibers as uniaxially aligned arrays over large areas. The key to the success of this method was the use of a collector composed of two conductive strips separated by an insulating gap of variable width. Directed by electrostatic interactions, the charged nanofibers were stretched to span across the gap and became uniaxially aligned arrays. Two types of gaps have been demonstrated: void gaps and gaps made of a highly insulating material. When a void gap was used, the nanofibers could readily be transferred onto the surfaces of other substrates for various applications. When an insulating substrate was involved, the electrodes could be patterned in various designs on the solid insulator. In both cases, the nanofibers could be conveniently stacked into multi‐layered architectures with controllable hierarchical structures. This new version of electrospinning has already been successfully applied to a range of different materials that include organic polymers, carbon, ceramics, and composites.
Facile Creation of a Super‐Amphiphobic Coating Surface with Bionic Microstructure
Authors: Xie Q. , Xu J. , Feng L. , Jiang L. , Tang W. , Luo X. , Han C. C.
Published: February 2004

A super‐amphiphobic polymeric coating, i.e., one that shows both water‐ and oil‐repellent properties, produced by a simple, one‐step casting process from two common polymers, is described. The micro–nano binary structure of the film has similarities to that of a lotus leaf. The Figure shows a water droplet on the coating surface, demonstrating a contact angle (CA) of 166 °C.
Discrete simulation of gas‐liquid bubble columns and gas‐liquid‐solid fluidized beds
Authors: Chen Caixia , Fan Liang‐Shih
Published: February 2004

A computational scheme for three‐dimensional (3‐D), discrete simulation of bubble dynamics in gas‐liquid bubble columns and gas‐liquid‐solid fluidized beds is presented. This scheme describes the motion of the gas, liquid, and solid phases, respectively, based on the level‐set interface tracking method, the locally averaged time‐dependent Navier‐Stokes equations coupled with the Smagorinsky Sub‐Grid Scale stress model, and the Lagrangian particle motion equations. Various gas, liquid, and solid interactive forces are considered, which include those due to drag, added mass, interfacial tension, bubble‐particle collision and particle‐particle collision. The accuracy and validity of the simulation based on this scheme is examined through computational experiments on some well‐known bubbling phenomena including the rise behavior of a single gas bubble in liquids and the bubble formation process from an orifice embedded in liquids. The computed bubble rise velocity, bubble shapes and their fluctuations, and bubble formation behavior in liquids show a good agreement with existing theories and experimental findings. The simulation is extended to investigate the effects of solids concentration on bubble formation and rise behavior. It is found that the bubbles are less coalesced in a fluidized bed with a higher solids concentration. A circulatory motion of particles with an upward flow in the center region and a downward flow near the wall, and a lateral solids concentration distribution in a gas‐liquid‐solid fluidized bed can also be predicted. The bubble formation and rise behavior in a multi‐nozzle bubble column are simulated, and the limitation of the Smagorinsky Sub‐Grid Scale stress model is discussed. © 2004 American Institute of Chemical Engineers AIChE J, 50: 288–301, 2004
Hybrid membrane materials comprising organic polymers with rigid dispersed phases
Authors: Moore Theodore T. , Mahajan Rajiv , Vu De Q. , Koros William J.
Published: February 2004

Dispersing highly selective rigid “inserts” such as zeolites and carbons into polymers can produce novel membrane materials with improved gas mixture permselectivity. Rigid inserts frequently cause the permeability in an “interphase” surrounding individual inserts to differ markedly from the intrinsic permeability of the matrix polymer. While existing theoretical models describe permselectivity reasonably well, they fail to predict the absolute permeabilities for individual components in such hybrid media. In fact, the degree of deviation from the simple model predictions provides insight into the detailed properties of the interphase, which has been neglected in previous analyses of these hybrid materials. Extension of an existing model provides a framework to analyze gas permeation properties of model systems with rigid molecular sieve inserts in glassy matrices. Inhibited segmental motion due to surface attachment and matrix contraction at the interface during preparation of these materials is hypothesized as the key cause of the observed behavior. © 2004 American Institute of Chemical Engineers AIChE J, 50: 311–321, 2004
Advanced rate‐based simulation tool for reactive distillation
Authors: Kenig E. Y. , Górak A. , Pyhälahti A. , Jakobsson K. , Aittamaa J. , Sundmacher K.
Published: February 2004

A rigorous rate‐based modeling approach to reactive distillation equipment is presented in detail. This approach has succeeded from the three‐year project “Reactive Distillation” initiated by SUSTECH and supported by the EU in the frame of the BRITE‐EURAM program. As a result, a steady‐state rate‐based simulator DESIGNER has been created and tested with industrially important reactive distillations. First, a thorough description of the model development, including process hydrodynamics and kinetics, is given. The general structure of DESIGNER is highlighted. Furthermore, numerical problems, simulation issues, and validation of the developed simulator are discussed, whereas several industrially important applications are demonstrated. The main advantages of DESIGNER are the direct account of mass and heat transport (rate‐based approach), multicomponent mass‐transport description via the Maxwell‐Stefan equations, consideration of a large spectrum of reactions (homogeneous and heterogeneous; slow, moderate, and fast; equilibrium and kinetically controlled), reaction account in both bulk and film phases, availability of different hydrodynamic models, and a large choice of hydrodynamic and mass‐transfer correlations for various types of column internals (trays, random and structured packings, catalytic packings). Particular attention is devoted to the mass‐transfer model, including the reaction in the film region, to the catalyst efficiency determination based on the mass transfer inside the catalyst and to the hydrodynamic models for reactive trays. © 2004 American Institute of Chemical Engineers AIChE J, 50:322–342, 2004
Water‐in‐oil coalescence in micro‐nanofiber composite filters
Authors: Shin C. , Chase G. G.
Published: February 2004

Coalescence filtration is very effective for the separation of secondary emulsions that contain water droplets with diameters less than 50 μm. The factors that control the performance of coalescer filter media are fiber size and wettability. High wettability materials for water‐in‐oil dispersion promote coalescence. New experimental results investigating the performance of nonwoven filter media glass fiber augmented with polymer nanofiber are presented in relation to the relevant parameters (wettability, filter depth, flow velocity, and filter materials). A decrease in fiber size improves the overall separation efficiency of the process. However, the nanofibers cause a significant increase in the pressure drop through the filter. © 2004 American Institute of Chemical Engineers AIChE J, 50: 343–350, 2004
Prediction of binary gas diffusion in carbon molecular sieves at high pressure
Authors: Qinglin Huang , Farooq S. , Karimi I. A.
Published: February 2004

A dual‐resistance model, in which a barrier resistance confined at the micropore mouth is assumed to act in series with pore diffusional resistance distributed in the micropore interior, has been proposed for multicomponent transport of gases in carbon molecular sieves (CMS). Excellent predictive power of the model has been thoroughly validated by means of extensive unary/binary integral uptake and breakthrough measurements involving large pressure steps on Takeda and Bergbau Forschung (BF) CMS samples. Quantitative agreement between the experimental and predicted results is truly remarkable considering the fact that all the predictions are strictly based on independently measured single‐component equilibrium and kinetic parameters. Impact of two mixture isotherms, namely ideal adsorbed solution (IAS) theory and extended Langmuir (E‐L) model, on mixture uptakes has also been investigated. This study undeniably establishes the following: (1) effectiveness of a dual‐resistance approach for gas transport in CMS micropores, and (2) much stronger concentration dependence of the transport parameters than that predicted from the use of a chemical potential gradient as the driving force for diffusion with constant intrinsic mobility. © 2004 American Institute of Chemical Engineers AIChE J, 50: 351–367, 2004
A ceramic microfiltration tube membrane dispersion extractor
Authors: Chen G. G. , Luo G. S. , Sun Y. , Xu J. H. , Wang J. D.
Published: February 2004

Although the phase‐free membrane extraction process has shown many advantages over the traditional extraction, the process is still at the experimental stage. On the other hand, in a new extractor a microfiltration membrane is used as a dispersion medium. The mass‐transfer performance of the new extractor was tested with 30% TBP (in kerosene)–nitric acid–H2O as an experimental system. The overall mass‐transfer coefficient and the equipment efficiency were calculated with the concentrations of the inlet and outlet. The extractor was designed and constructed with two special inner elements for improving the performance further. The effects of the transmembrane pressure, the continuous‐phase flow rate, and the geometric parameters of the inner elements on the mass‐transfer performance, as well as on the flux of the dispersion phase, are discussed. The experimental results showed that very higher efficiency was reached. The inner elements could improve the mass‐transfer performance greatly by changing the two‐phase contact status. The results suggested that the mass‐transfer process could be completed quickly while the drop size was in the range of micrometers. In addition, the flux of the dispersed phase was mainly influenced by the transmembrane pressure, not by the equipment structures, inner elements, and the continuous‐phase flow rate. The new extractor can be operated with very higher efficiency and higher flux, and the efficiency can be predicted with a cubic polynomial. © 2004 American Institute of Chemical Engineers AIChE J, 50: 382–387, 2004
PCA‐based fault diagnosis in the presence of control and dynamics
Authors: Gertler Janos , Cao Jin
Published: February 2004

In PCA‐model‐based fault diagnosis, using the isolation enhancement approaches of analytical redundancy, mis‐isolation of some sensor and actuator faults may arise if the training data is collected under constant control. A detailed analysis is provided of how control actions affect PCA‐model‐based diagnosis. Ratio and feedback control in linear static and discrete dynamic systems, with full and partial PCA models is investigated. It is shown that all that it takes to eliminate the adverse effects is to vary the control set point (in feedback control) or the ratio coefficient (in ratio control) in the course of collecting the training data. © 2004 American Institute of Chemical Engineers AIChE J, 50: 388–402, 2004
Scheduling intermediate storage multipurpose batch plants using the S‐graph
Authors: Romero Javier , Puigjaner Luis , Holczinger Tibor , Friedler Ferenc
Published: February 2004

A graph theoretical approach is proposed for the optimal scheduling of multipurpose batch plants when constraints on intermediate storage allocation are met. The novel S‐graph representation is extended and combined with a set of rationales to consider intermediate storage policy in production scheduling. This set of rationales accelerates the optimization procedure, reducing the searching tree from the very beginning, without losing optimality. It is assumed that the storage units can be commonly used throughout the plant to achieve maximum plant flexibility. Therefore, the problem solved suggests the more general batch‐process transfer strategy, common intermediate storage policy (CIS). This policy is suggested for more flexible use of intermediate storage units. The accuracy of this proposed algorithm is tested with an exhaustive B&B search algorithm. The methodology is compared with other CIS algorithms and is applied to solve several case studies. The benefits of considering this kind of storage coupled with the use of the proposed algorithm are discussed through motivating examples. © 2004 American Institute of Chemical Engineers AIChE J, 50: 403–417, 2004
Characterization of flow distribution in microchannel reactors
Authors: Pfeifer P. , Wenka A. , Schubert K. , Liauw M. A. , Emig G.
Published: February 2004

The applicability of thermal anemometry with constant wire temperature for characterization of the flow distribution in microchannel reactors was first proven by a comparison of simulation and experimental results using uncoated microchannels. The anemometry was then applied for structured reactor foils with different nanoparticle washcoats. Homogeneity of the coatings observed by scanning electron microscopy showed good correlation to the results of the anemometry. © 2004 American Institute of Chemical Engineers AIChE J, 418–425, 2004
Effect of resins and DBSA on asphaltene precipitation from petroleum fluids
Authors: Goual Lamia , Firoozabadi Abbas
Published: February 2004

This work examines the effect of various resins and dodecyl benzene sulfonic acid (DBSA) amphiphile on asphaltene precipitation from different petroleum fluids. Various resins are added to three different petroleum fluids to measure precipitation with n‐pentane. Results show that the dipole moment of resins (which is a measure of polarity) has a strong effect on precipitation. Resins with a high dipole moment are more effective than resins with a low dipole moment. The effectiveness is defined in terms of the increase in the onset point of precipitation. However, addition of resins to a petroleum fluid increases the amount of precipitated asphaltenes. This is the first report of such a behavior in the literature; the increase is less pronounced with the most polar resins. Addition of asphaltenes to a petroleum fluid results in a high amount of precipitation. As expected, the onset point of precipitation from asphaltene addition to a petroleum fluid is different from that of resins. When the DBSA amphiphile is mixed with the petroleum fluid at different concentrations, we observe a retrograde phenomenon. The amount of precipitated asphaltene increases first with increasing DBSA concentration. Beyond a certain concentration, there is a decrease in precipitation. At higher concentrations, DBSA proves to be very effective to move the onset point of precipitation. The data show the complex interactions between various species in petroleum fluids. © 2004 American Institute of Chemical Engineers AIChE J, 50: 470–479, 2004
Effect of aqueous PEG or PPG solvents on reaction selectivity and Gibbs energies
Authors: Leininger Neil F. , Gainer John L. , Kirwan Donald J.
Published: February 2004

Low molecular weight polyethylene glycol (PEG 300), polypropylene glycol (PPG 425), and their aqueous solutions are investigated for use as novel, nonvolatile, environmentally friendly reaction solvents. The kinetics and selectivities of a SN1 and a Diels‐Alder reaction (reactions commonly used in pharmaceutical synthesis) in the polyglycol‐H2O solutions are reported. Reaction rate constants and product selectivities in the polyglycol‐H2O solvents were comparable to those observed in the traditional organic solvents used with these reactions. Gibbs free energy calculations show that the reactants and reaction transition states for the SN1 and Diels‐Alder reactions are stabilized in the presence of the polyglycol‐H2O solvents. © 2004 American Institute of Chemical Engineers AIChE J, 50:511–517, 2004)
Two‐step formation of methane–propane mixed gas hydrates in a batch‐type reactor
Authors: Uchida Tsutomu , Moriwaki Minoru , Takeya Satoshi , Ikeda Ikuko Y. , Ohmura Ryo , Nagao Jiro , Minagawa Hideki , Ebinuma Takao , Narita Hideo , Gohara Kazutoshi , Mae Shinji
Published: February 2004

Vapor compositions of methane and propane mixed gas in a batch‐type reactor were measured by gas chromatography during hydrate crystallization at 274 K with molar ratios of propane below 10 vol %. The volume ratio of propane in the vapor decreased as the hydrate crystallization progressed. When the initial propane concentration was between 4 and 8 vol %, rapid gas consumption occurred for about 1 h, causing an initial pressure drop, and after a temporary stabilization of the pressure, a second pressure drop occurred; that is, hydrate crystallization occurred in two steps. X‐Ray diffraction and Raman spectroscopic analyses on samples taken from the reactor during each step revealed that the structure II methane–propane mixed gas hydrates crystallized in the first step, and structure I methane hydrates in the second step. This process was observed only when the partial pressure of methane was above the equilibrium pressure of methane hydrate at the end of the first step. © 2004 American Institute of Chemical Engineers AIChE J, 50: 518–523, 2004
Conversion of SO2 into elemental sulfur by using the RF plasma technique
Authors: Tsai Cheng‐Hsien , Lee Wen‐Jhy , Shih Minliang , Chen Chuh‐Yung , Tsai Perng‐Jy
Published: February 2004

This study demonstrates a new approach for converting SO2 into elemental sulfur by adding CH4 in a radio‐frequency (RF) plasma reactor. With the applied power (P) of the RF reactor specified at 90 W and operating pressure set at 4000 N/m2, it was found that as the CH4/SO2 ratio (R) was increased from 0.3 to 1.0, most sulfur‐containing products were in the form of elemental sulfur. While R was increased from 1 to 2, the content of elemental sulfur was decreased significantly, but CS2 was increased dramatically. While R was increased from 2 to 3, both elemental sulfur and CS2 contents became quite comparable. Nevertheless, it was found that both H2 and CO (that is, syngas) were the main nonsulfur‐containing products under all testing conditions. These results indicate that the use of the RF plasma technique was not only beneficial to convert SO2, but also was able to convert CH4 into useful materials. For R = 0 (that is, no CH4 was introduced), it was found that the SO2 conversion (i.e., η) = 0.084, indicating that the RF plasma process was inadequate to convert pure SO2 without adding CH4 as a reducing agent. While R was increased to 2, it was found that η was improved significantly to 0.968 accompanied with η = 0.999. But as R was increased from 2 to 3, both η and η were slightly decreased. Both η and η also were sensitive to the applied power (P). As P was increased from 15 W to 90 W at R = 2, it was found that both η and η were increased dramatically from 0.247 and 0.320 to 0.968 and 0.999, respectively. But as P was increased from 90 W to 120 W, the increase on both η and η became very limited. Based on these, this study suggests that the operating condition of R = 2 and P = 90 W would be the most appropriate combination for SO2 conversion. © 2004 American Institute of Chemical Engineers AIChE J, 50: 524–529, 2004
Raymond Pearl's Legacy: The proper measure of man
Authors: Sokal Robert R.
Published: February 2004

During much of his academic career, Raymond Pearl advocated the employment of quantitative and statistical methods in biology and applied them in his own voluminous research output, much of it in various aspects of human biology. If he were to return today, he would be pleased to note the fruits of his advocacy—the widespread quantification of biological and anthropological research. He would undoubtedly be impressed with the tremendous progress in statistical analysis in the 63 years since he ceased his work and with that amazing tool, the personal computer. But he would also note the dangers inherent in applying these powerful methods without sufficient regard for the experimental or observational designs they require and for their basic assumptions. Among the errors Pearl would note are: 1) the use of canned computer programs in ignorance of or inattention to their implied assumptions; 2) testing many contrasts in one dataset without making allowances for the lack of independence of these tests; 3) ignoring the effects of lack of independence (autocorrelation) when working with spatially, temporally, or phylogenetically related data; 4) presenting distorted ordination plots; and 5) using an unrealistic null distribution in computation or simulation, as when employing sample sizes too small to test the hypotheses the investigator is interested in. All of these errors are common not only in publications on physical anthropology and human biology, but also in the wider biological literature. Am. J. Hum. Biol. 16:113–124, 2004. © 2004 Wiley‐Liss, Inc.
Percentiles of body composition from bioelectrical impedance and body measurements in U.S. adolescents 8–17 years old: Project HeartBeat!
Authors: Mueller William H. , Harrist Ronald B. , Doyle Suzanne R. , Labarthe Darwin R.
Published: February 2004

Reference percentiles (5th, 10th, 50th, 85th, 90th, and 95th) of black and nonblack children ages 8–17 years from Project HeartBeat! (n = 678) are presented for body mass index (BMI), percent body fat (PBF), fat‐free mass (FFM), and fat mass (FM) derived from bioelectrical impedance. Project HeartBeat! is a mixed longitudinal study in which three cohorts of children (seen initially at age 8, 11, or 14 years) were followed for 4 years and measured thrice‐yearly from 1991 through 1995. Weight, height, and BMI of Project HeartBeat! children are similar in central tendency and variability to those of nationally representative samples for nonblack children but not black children, for whom there is an excess of children at or above the 95th percentile for weight and BMI. Values of PBF above which cardiovascular risk variables increase (as suggested in the literature) are located at the 85th percentile of the Project HeartBeat! distributions. This percentile of PBF may be tentatively considered as a cutoff point with epidemiological significance for children. Am. J. Hum. Biol. 16:135–150, 2004. © 2004 Wiley‐Liss, Inc.
Patterns of joint distribution in hand osteoarthritis: Contribution of age, sex, and handedness
Authors: Kalichman Leonid , Cohen Zvi , Kobyliansky Eugene , Livshits Gregory
Published: February 2004

The most frequent site of osteoarthritis (OA) is the hands, but the pattern of hand OA development remains controversial. Understanding these patterns may assist in evaluating biological aging, determining etiology, and proposing ways of preventing hand OA. We investigated the pattern distribution of OA in hands and the influences of age, sex, and handedness on its development. The study population was comprised of Chuvashians (660 males age 18–89 years and 585 females age 18–90 years). OA development was evaluated for 15 joints of each hand according to the Kellgren and Lawrence grading scheme. Statistical analyses included Pearson correlation, cluster analysis, MANCOVA, and linear and polynomial regression. OA changes first appeared in subjects <30 years of age. Metacarpophalangeal (MP) joints underwent the first OA changes until the sixth decade, when the row of distal interphalangeal (DIP) joints became most affected. Cluster analysis showed that symmetry was the most common pattern of interrelationship between rows of joints. The best‐fitting and most parsimonious model of age‐related pattern of hand OA was the polynomial two‐interval linear model. It showed a higher rate of OA development during the relatively young ages, 32–34 years than later on. We found statistically significant differences between sexes only for the DIP (P = 0.019) and PIP (P = 0.011) rows of joints. Handedness had no influence on hand OA development. Am. J. Hum. Biol. 16:125–134, 2004. © 2004 Wiley‐Liss, Inc.
Methodologic issues in the use of workers' compensation databases for the study of work injuries with days away from work. I. Sensitivity of case ascertainment
Authors: Oleinick Arthur , Zaidman Brian
Published: February 2004

Background

Case ascertainment costs vary substantially between primary and secondary data sources. This review summarizes information on the sensitivity of state administrative databases in workers' compensation systems for the ascertainment of days‐away‐from‐work (DAFW) work injuries for use in modeling studies.

Methods

Review of the literature supplemented by data from governmental or organizational reports or produced for this report.

Results

Employers currently appear to provide workers' compensation insurance coverage for 98.9% of wage and salary workers. Wage and salary jobs account for approximately 90% of jobs in the United States. In industries such as manufacturing, the fraction of covered jobs is probably closer to 98%. In Minnesota, the number of DAFW cases ascertained by the Bureau of Labor Statistics' annual survey of occupational injuries and illnesses is approximately 92–97% concordant with the number of wage compensation claims for injuries producing DAFW over the period 1992–2000, once adjustments are made to permit direct comparisons of the numbers. The workers' compensation databases provide information for more than 95% of the total DAFW resulting from work injuries. Covariate estimates are unaffected by this less than 5% loss because effects appear dependent on time from injury.

Conclusions

Statewide workers' compensation administrative databases can have substantial utility for epidemiologic study of work injuries with DAFW because of their size, using high sensitivity for case ascertainment as the evaluative criterion. Am. J. Ind. Med. 45:260–274, 2004. © 2004 Wiley‐Liss, Inc.
Criteria for skin notation in different countries
Authors: Nielsen Jesper B. , Grandjean Philippe
Published: February 2004

Background

Skin notation criteria was introduced almost 50 years ago as a qualitative indicator of a hazard related to dermal absorption at work. However, risk is not a qualitative term, but needs a quantitative measure to be useful for prevention. For this reason, some countries have developed alternative criteria for assigning skin notations to industrial chemicals.

Methods

The present analysis compares the current use of skin notations on lists of exposure limits for industrial chemicals in six countries.

Results

Up to one‐third of industrial chemicals listed now have a skin notation. The criteria for assigning skin notation differ but cannot explain the substantial discrepancies between countries that otherwise have very comparable occupational exposure limits (OELs).

Conclusions

The increasing number of chemicals with a skin notation requires a new approach to differentiating between degrees of risk. The first step will be to address the problems related to criteria for assigning skin notations, and the effect of penetration enhancers and mixtures. Am. J. Ind. Med. 45:275–280, 2004. © 2004 Wiley‐Liss, Inc.
Asbestos‐related pleural diseases: Dimensional criteria are not appropriate to differentiate diffuse pleural thickening from pleural plaques
Authors: Ameille Jacques , Matrat Mireille , Paris Christophe , Joly Nathalie , Raffaelli Claude , Brochard Patrick , Iwatsubo Yuriko , Pairon Jean Claude , Letourneux Marc
Published: February 2004

Background

In the literature, the criteria used to define pleural plaques (PP) and diffuse pleural thickening (DPT) are very heterogeneous and often imprecise. A multicenter restropective study was conducted to assess the relevance of two radiographic definitions of DPT.

Methods

The study population consisted of 287 subjects with asbestos‐related pleural thickening. Two definitions were used to characterize DPT on postero‐anterior chest radiographs: definition 1: pleural thickening associated with obliteration of the costophrenic angle; definition 2: pleural thickening at least 5 mm wide, extending for more than one quarter of the chest wall. Prevalence of respiratory symptoms and pulmonary function tests were compared in the DPT and PP groups resulting from the two definitions of DPT.

Results

According to definition 1, 34 patients (11.8%) were classified in the DPT group. Prevalence of chronic sputum, dyspnea, and chest pain was significantly higher in this group than in the PP group. FEV1, FVC, and TLC were significantly lower. The differences persisted after adjustment for confounding factors. According to definition 2,102 patients (36.6%) were classified in the DPT group. DPT and PP groups did not differ in terms of prevalence of respiratory symptoms, or pulmonary function tests. Agreement between readers was significantly better when using definition 1.

Conclusions

Obliteration of costophrenic angle is a much more reliable sign than dimensional criteria to characterize DPT. Am. J. Ind. Med. 45:289–296, 2004. © 2004 Wiley‐Liss, Inc.
Occupational exposures to acid mists and gases and ulcerative lesions of the oral mucosa
Authors: Vianna Maria Isabel Pereira , Santana Vilma Sousa , Loomis Dana
Published: February 2004

Background

This study examines the hypothesis that acid mist or mixtures of acid mists and acid gases are associated with ulcerative lesions of the oral mucosa.

Methods

All 665 active male workers of a metal processing factory were the study population. Semi‐quantitative measures of exposure were estimated from a job exposure matrix constructed with industrial hygienist scoring and job titles. Ulcerative lesions of the oral mucosa were identified with standardized clinical dental exams.

Results

Past exposure to acid mists were positively associated with ulcerative lesions of the oral mucosa but only among workers without lip sealing (age‐ and alcohol consumption‐adjusted prevalence ratio (PR), PRadjusted = 3.40; 90% CI: 1.48–7.85). Also in this worker group, the mixture of acid mists and acid gases was associated with ulcerative lesions of the oral mucosa limited to exposure in the past (PRadjusted = 2.83; 90% CI: 1.12–7.17).

Conclusions

There is a positive association between acid mist or mixtures of acid mists and acid gases and ulcerative lesions of the oral mucosa only in the absence of lip sealing. The evidence of a chronic rather than acute irritative process suggests a possible step on the etiology of oral malignancies, which needs investigation. Am. J. Ind. Med. 45:238–245, 2004. © 2004 Wiley‐Liss, Inc.
Prevalence of respiratory symptoms among wheat flour mill workers in Ibadan, Nigeria
Authors: Ijadunola K.T. , Erhabor G.E. , Onayade A.A. , Ijadunola M.Y. , Fatusi A.O. , Asuzu M.C.
Published: February 2004

Background

While investigations into occupational health problems of various groups of workers have been conducted in Nigeria, so far, very little attention has been paid to the health status of workers in the grain industry. The prevalence of respiratory symptoms among wheat flour mill workers and control groups in a medium size industrial setting in Nigeria was studied.

Methods

The study employed a cross‐sectional analytical design. Data were collected using structured interviews, work‐site observations, and physical examination. Respondents consisted of 91 flour‐millers, 30 matched internal controls from the maintenance unit of the same flour mill factory, and 121 matched external controls.

Results

Fifty‐four percent of the flour‐millers reported at least one respiratory symptom compared with 30% of the internal controls (P < 0.05) and 19% of the external controls (P < 0.001). Most symptoms were significantly more prevalent among the flour‐millers compared with control subjects, and this trend was more evident amongst non‐smokers than ex‐smokers.

Conclusions

The study concluded that wheat flour mill workers in Nigeria, like grain workers elsewhere, were at an increased risk of developing both pulmonary and non‐pulmonary symptoms compared with control subjects. The result has implications for improved dust control measures in the grain industry in Nigeria. Am. J. Ind. Med. 45:251–259, 2004. © 2004 Wiley‐Liss, Inc.