bluuebunny/crossref_metadata_2025 huggingface dataset:
Pilots Strategically Compensate for Display Enlargements in Surveillance and Flight Control Tasks
Authors: Stelzer Emily Muthard , Wickens Christopher D.
Published: April 2006

Objective: Experiments were conducted to assess the impact of display size on flight control, airspace surveillance, and goal-directed target search. Background: Research of 3-D displays has shown that display scale compression influences the perception of flight path deviation, though less is known about the causes that drive this effect. In addition, research on attention-based tasks has shown that information displaced to significant eccentricities can amplify effort, but it is unclear whether the effect generates a performance difference in complex displays. Method: In Experiment 1, 16 pilots completed a low-fidelity flight control task under single- and dual-axis control. In Experiment 2, the control task from Experiment 1 was scaled up to a more realistic flight environment, and pilots performed hazard surveillance and target search tasks. Results: For flight control, pilots exhibited less path error and greater stick activity with a large display, which was attributed both to greater enhanced resolution and to the fact that larger depictions of error lead to greater urgency in correcting deviations. Size did not affect hazard surveillance or search, as pilots were adaptive in altering scanning patterns in response to the enlargement of the displays. Conclusion: Although pilots were adaptive to display changes in search and surveillance, display size reduction diminished estimates of flight path deviation and control performance because of lowered resolution and control urgency. Application: Care should be taken when manipulating display size, as size reduction can diminish control performance.
Compliance With Intended Use of Bar Code Medication Administration in Acute and Long-Term Care: An Observational Study
Authors: Patterson Emily S. , Rogers Michelle L. , Chapman Roger J. , Render Marta L.
Published: April 2006

Objective: To identify the types and extent of workaround strategies with the use of Bar Code Medication Administration (BCMA) in acute care and long-term care settings. Background: Medication errors are the most commonly documented cause of adverse events in hospital settings. Scanning of bar codes to verify patient and medication information may reduce medication errors. Method: A prospective ethnographic study was conducted using targeted observation. Fifteen acute care and 13 long-term care nurses were directly observed during medication administration at small, medium, and large Veterans Administration hospitals to detect workaround strategies. Results: Noncompliance with recommended practices was observed in all settings and facilities. A larger proportion of acute care nurses than long-term care nurses scanned bar-coded wristbands to identify patients (53% vs. 8%, p = .016). A larger proportion of acute care nurses than long-term care nurses administered barcoded medications immediately after scanning (93% vs. 23%, p < .001). Conclusion: Workaround strategies were employed with BCMA that increased efficiency but created new potential paths to adverse events. There was a significant difference in the rate of use of workaround strategies between acute and long-term care. Application: The extent of workaround strategies varied by care setting and facility. BCMA should be tailored to the long-term care setting, including increasing the efficiency of use. Hospitals implementing bar coding should facilitate the intended use through equipment procurement, implementation, and quality improvement strategies.
Stability Ball Versus Office Chair: Comparison of Muscle Activation and Lumbar Spine Posture During Prolonged Sitting
Authors: Gregory Diane E. , Dunk Nadine M. , Callaghan Jack P.
Published: April 2006

Objective: The objective of the study was to evaluate the differences between sitting on a stability ball and in an office chair in terms of trunk muscle activation and lumbar spine posture. Background: Stability balls have become increasingly popular as an alternative to office chairs to help reduce the prevalence of low back pain; however, little research has been conducted on their use as office chairs. Methods: The 14 participants (7 men, 7 women) were required to sit on both a stability ball and an office chair for 1 hour each while performing various computer workstation tasks throughout the sitting periods. The activation of eight muscles and lumbar spine posture were measured and analyzed. Results: Increased muscle activation in thoracic erector spinae (p = .0352), decreased pelvic tilt (p = .0114), and increased perceived discomfort (p < .0001) while sitting on the stability ball were observed. Conclusions: The small changes in biological responses when sitting on a stability ball as compared with an office chair, combined with the increased reported discomfort while on the ball, suggests its use for prolonged sitting may not be advantageous. Application: Prolonged sitting on a stability ball does not greatly alter the manner in which an individual sits, yet it appears to increase the level of discomfort. Therefore, it is important to fully explore a new chair design and consult scientific research before implementing its use.
Forearm Electromyographic Changes With the Use of a Haptic Force-Feedback Computer Mouse
Authors: Dennerlein Jack T. , DiMarino Maria-Helena J.
Published: April 2006

Objective: To examine changes in biomechanical and motor control associated with a force-feedback computer mouse. Background: Haptic computer mice can improve the movement times for point-and-click tasks; however, changes in upper extremity biomechanics and motor control are unknown. Method: Eighteen people (ages 22-37 years) performed a point-and-click task 80 times using a force-feedback computer mouse across three different conditions: (a) no force feedback, emulating a conventional mouse; (b) a single attractive force field at the desired target that pulls the mouse to the center of the target; and (c) an attractive force field at the desired target as well as others between the two possible targets, distracting the user from the intended target. Cursor kinematics, wrist posture, and electromyographic (EMG) forearm muscle activity were recorded. Results: The point-and-click movements were 30% faster with the addition of a single force field and 3% faster with the addition of multiple force fields. The Fitts' law index of performance metrics improved from 2.9 bits/response to 4.1 bits/response for multiple attractive fields and to 6.0 bits/response for a single force field. For the distracting force fields, the cursor maximum velocities were over 50% faster. EMG amplitude values were largest for the distracting force fields. These data suggest that the operator uses increased muscle activity to accelerate the mouse through the distracting force fields. Conclusion: When implementing attractive haptic force fields, one needs to consider how to reduce these observed effects of potential distracting force fields. Application: Applications include human-computer interface design for pointing devices extensively used for the graphical user interface.
The Right Picture Is Worth a Thousand Numbers: Data Displays in Anesthesia
Authors: Drews Frank A. , Westenskow Dwayne R.
Published: April 2006

Objective: To review the literature on data displays in anesthesia identifying issues and developing design recommendations. Background: Unexpected incidents are common in critical care medicine. Adverse outcomes are frequently the catastrophic endpoints of an “evolving” chain of subtle incidents. One strategy to reduce the likelihood of an adverse patient outcome during anesthesia is to improve the anesthesiologist's ability to detect, diagnose, and treat critical incidents. Method: A literature review and analysis of data displays. Results: Current numerical and waveform displays do not support anesthesiologists optimally. An alternative is graphical displays that functionally integrate variables into objects. In a well-designed graphic object, deviations from normal are shown by distortions in the object's symmetry. The emerging patterns that result from distorted symmetry facilitate the correct diagnosis. When treatment is effective, an object's shape is restored to normal. Graphical displays can be an effective tool in supporting anesthesiologists' situation awareness. Conclusion: Problems related to graphical displays have delayed their use in anesthesia, including the lack of conclusive clinical evidence of their value. However, currently more evidence is accumulating that graphical displays have the potential to improve clinical performance. The successful development of these graphical displays takes into account task requirements, a user's perceptual processes, and task-specific cognition. Application: This paper provides suggestions for the development of more effective displays in anesthesiology. Graphical displays can increase the anesthesiologist's situation awareness and improve clinical performance. Clinical use of these displays has the potential to significantly improve patient safety.
Describing Nurses' Work: Combining Quantitative and Qualitative Analysis
Authors: Wolf Laurie D. , Potter Patricia , Sledge Jennifer A. , Boxerman Stuart B. , Grayson Deborah , Evanoff Bradley
Published: April 2006

Objective: To better understand nursing activities and working conditions. Background: Nursing practice involves astute clinical decision making and the competent delivery of nursing care procedures. To complete nursing procedures, nurses must simultaneously organize and reorganize priorities and manage changing clinical information for multiple patients. Few researchers have examined the specific nature of nurses' activities and the effect of the environment on their work. Methods: Quantitative and qualitative methods were used to collect data on 7 nurses engaged in nursing activities. Examples of methods include link analysis, subject matter expert, task analysis, cognitive pathway, and “stacking.” Data collection focused on how nurses managed priorities, changing clinical information, and interruptions. Results: The “cognitive pathway” graphically depicts the nature of nurses' work. Specifically, it reveals the shifting of the nurse's attention from patient to patient and the occurrence of interruptions. “Stacking” shows the number of tasks a nurse must balance at any one time. On average, nurses had 10 or more activities waiting to be performed and experienced 3.4 interruptions/hr. Conclusion: These methods provide unique insight into the dynamic nature of patient care and nursing work. Application: Extension of the methods demonstrated here may be useful in guiding efforts to change the work of nursing to better provide quality care and less stressful work environments.
Ergonomic Guidelines for Traffic Sign Design Increase Sign Comprehension
Authors: Ben-Bassat Tamar , Shinar David
Published: April 2006

Objective: This research directly tests the relationship between comprehension probability of highway signs and the extent to which they comply with three ergonomic principles of design: sign-content compatibility, familiarity, and standardization. Background: A recent study that evaluated comprehension of traffic signs in four different countries showed that comprehension level varies widely and is apparently related to the extent that the sign's design incorporates ergonomic guidelines for good design (D. Shinar, R. E. Dewar, H. Summala, & L. Zakowska 2003). Method: Participants were presented with 30 signs and asked to describe each sign's meaning. They then evaluated each sign in terms of each of three ergonomic principles. In addition, a group of human factors/ergonomics experts evaluated each sign on its standardization and compatibility. Results: There were high correlations between the ratings of the students and the ratings of the experts on compatibility (rho = .94) and on standardization (rho = .84), validating the use of the students' evaluations of the signs on these variables. There was a great variability in signs' comprehension and high and statistically significant correlations between the comprehension level of each sign and the extent to which it complied with compatibility ( R = .76), familiarity ( R = .89), and standardization ( R = .88) principles. Conclusions: The more signs conform to universal ergonomic principles of good design, the more likely they are to be comprehended by drivers of different cultural backgrounds. Application: Sign design should be guided by established ergonomics principles to enhance comprehension, especially for drivers who have not had any prior encounters with specific signs.
The Potential of Training to Increase Acceptance and Use of Computerized Decision Support Systems for Medical Diagnosis
Authors: Lai Fuji , Macmillan Jean , Daudelin Denise H. , Kent David M.
Published: April 2006

Objective: The goals of this study were to understand the reasons underlying the limited use of medical decision-support tools and to explore the potential of a computerbased tutorial to mitigate barriers to use. Background: Medical decision-support tools such the Acute Cardiac Ischemia Time-Insensitive Predictive Instrument (ACITIPI) have demonstrated statistical validity and clinical impact for patient safety but have seen limited adoption and use. Methods: The study developed a brief Web-based “demystifying” ACI-TIPI tutorial employing case-based training and valuated the effectiveness of that tutorial in changing self-reported attitudes and behaviors. Results: Clinicians using the tutorial reported greater understanding of how to use the ACITIPI score appropriately and increased confidence in the score. Case studies in the tutorial that provided examples of how to use the score for actual cases were rated as especially helpful. Conclusion: This study suggests that a primary barrier to the use of statistical decision support tools for patient diagnosis is lack of training or experience in combining a population-based numerical risk score with other diagnostic information about the individual patient's case that is not considered in that score. The results of this study indicate that there is a potential for a relatively brief tutorial to increase acceptance and use of decision support tools for medical diagnosis. Application: These findings have the potential for the identification of methods to help clinicians learn how to use statistical and probabilistic information to better assess risk and to promote integration of decision support tools into medical decision making for improvement of patient safety.
Application of the Reference Temperature to the Evaluation of Cleavage Fracture in HSLA-100 Steel
Authors: Graham SM , Mercier GP , L'Heureux BP
Published: April 2006

The purpose of this study was to evaluate the fracture behavior of HSLA-100 steel at a temperature of −40°C (−40°F). Tests were conducted on three different compositions and two orientations of HSLA-100. HY-100 was also tested to provide a baseline for comparison. Various fracture-related tests were conducted, including traditional test methods, such as the Charpy V-notch and the Dynamic Tear, and more recent methods, such as ductile crack growth initiation (JIc) and the reference temperature. Transition temperatures from the Charpy tests were all very similar, falling around −129°C (−200°F), although the upper shelf Charpy energy for the HY-100 was lower than the HSLA-100 steels. Dynamic tear energies at −40°C for the four steels ranged from 800 to 1800 J. The average reference temperature of all four steels, measured according to ASTM E 1921, was around −151°C (−240°F), with one composition of HSLA-100 coming in as low as −179°C (−290°F) and another as high as −123°C (−190°F). Fracture toughness tests were conducted according to E 1820 at temperatures of −40, −29, and −18°C. These temperatures were more than 83°C above the highest of the reference temperatures, so cleavage fracture was not expected to occur. The HY-100 specimens exhibited an average initiation toughness of 227 kJ/m2 (1296 lb/in.) and crack growth remained ductile throughout the tests. Even though the HSLA-100 exhibited initiation toughnesses more than twice as high as the HY-100, many of the tests terminated in cleavage fracture after amounts of ductile crack growth varying from 0 to 1.85 mm (0.073 in.). This was an unexpected result based on good Charpy and dynamic tear energies at −40°C, and low reference temperatures. The higher initiation toughness and tearing resistance of HSLA-100 allowed very high stresses to develop in the fracture process zone. As ductile crack growth occurred, the fracture process zone swept through an increasing volume of metal, which increased the probability of cleavage fracture. It is shown that the load required to reach these levels of crack driving force may be above gross section yielding of a typical structure. In this case failure by gross section yielding would occur before fracture. This is demonstrated with the aid of a failure assessment diagram.
Explanation of the Origin of Distortion and Residual Stress in Water Quenched Cylinders Using Computer Simulation
Authors: Arimoto K , Horino T , Ikuta F , Jin C , Tamura S , Narazaki M
Published: April 2006

Measurements of quench distortion and internal residual stresses in quenched cylinders have been performed for many years. Distortion and stress distribution patterns have been identified in the typical steels and cooling conditions. Pioneers of the heat treatment simulation compared their simulated results with experimental data obtained and reported in the 1970s and 1980s. However, these early researchers did not fully explain the mechanism of distortion and residual stress generation based on their simulated results. Although there were several reports on distribution changes of stress, similar reports relating to strains were rarely reported. In this research, water quenched steel cylinders were simulated and an origin of distortion and residual stress generations was explained using the simulated stress and strain distribution changes.
Device Harmonization to Determine Smoothness Specification for Asphalt Pavements
Authors: Chen J-S , Chang M-K , Lin K-Y
Published: April 2006

Pavement smoothness is a key factor in determining highway user satisfaction. Because of technical limitations of traditional equipment and measurement procedures, the adequacy of a straightedge in characterizing roughness and having it relate to user response has come to question. One barrier to more widespread implementation of a new smoothness standard is the lack of objective, verifiable correlation methods for use in establishing specification limits. The purpose of this study was to (1) develop statistical approaches to harmonize two different measurement devices, i.e., a 3-m straightedge and an inertial profiler; and (2) determine the specification for flexible pavements. The device harmonization requires the development of procedures for statistically testing through comparisons to reference measurements. Data collected from 85 pavement sections on newly constructed and resurfaced highways were examined to demonstrate the device's ability to measure specific smoothness properties. Smoothness data are shown to be normally distributed according to the chi-squared test. Test results obtained from straightedge are found to be significantly different from those from profiler. Smoothness specifications applied for straightedge cannot be directly used to those for profiler. A conversion equation is developed to help contractors convert smoothness measurements between these two devices based on the same acceptance level. The International Roughness Index (IRI) obtained from the profiler appears to provide better measures of smoothness and better correlation with user response. Four following ranges are proposed for the smoothness specification according to the acceptance smoothness level: bonus, full pay, penalty, and correction. As the acceptance probability sets at 20%, the bonus threshold value should be less than 1.20 mm and 2.55 m/km for straightedge and profiler, respectively. The acceptance level is found to be below 2.60 mm and 3.60 m/km for straightedge and profiler, respectively. The demarcation line between penalty and correction is drawn at 95% of the acceptance probability with corresponding values of 3.35 mm and 4.10 m/km for straightedge and profiler, respectively. This research effort has developed a series of relationships between IRI and straightedge that can assist highway agencies in transitioning to IRI smoothness specification for pavements.
Numerische Methoden zur passivitätserhaltenden Modellreduktion (Numerical Methods for Passivity Preserving Model Reduction)
Authors: Faßbender Heike , Benner Peter
Published: April 2006

Bei der Modellierung dynamischer Systeme entstehen heutzutage häufig Systeme hoher Ordnung (d.h. mit 10000 und mehr Gleichungen). Um eine numerische Simulation mit akzeptablem zeitlichem Umfang zu gewährleisten, reduziert man das gegebene dynamische System von Gleichungen zu einem System derselben Form, welches eine Lösung mit stark verkürzter Rechenzeit erlaubt. Häufig wird gefordert, dass das reduzierte System die selben Eigenschaften wie das unreduzierte Modell aufweist; wichtige Eigenschaften sind in diesem Zusammenhang insbesondere Stabilität und Passivität. Dieser Beitrag gibt einen Überblick über numerische Verfahren zur passivitätserhaltenden Modellreduktion.
Ordnungsreduktion linearer zeitinvarianter Finite-Elemente-Modelle mit multivariater polynomieller Parametrierung (Model Order Reduction of Linear Finite Element Models Parameterized by Polynomials in Several Variables)
Authors: Farle Ortwin , Hill Volker , Ingelström Pär , Dyczij-Edlinger Romanus
Published: April 2006

Der vorliegende Beitrag stellt ein Verfahren zur Ordnungsreduktion linearer Gleichungssysteme vor, die durch Polynome in mehreren Variablen parametriert sind und aus der Finite-Elemente-Methode hervorgehen. Der vorgeschlagene Ansatz beruht auf multivariaten Krylov-Unterräumen und erweitert bestehende Verfahren in zweierlei Hinsicht: Erstens beinhaltet er einen neuen Algorithmus zur Berechnung einer stabilen Basis für das reduzierte System, und zweitens verallgemeinert er das Konzept der Krylov-Unterräume höherer Ordnung auf Mehrparametersysteme.
Modellreduktion in elastischen Mehrkörpersystemen (Model Reduction in Flexible Multibody Systems)
Authors: Lehner Michael , Eberhard Peter
Published: April 2006

In dieser Arbeit wird die Verwendung von Krylov-Unterraummethoden zur Reduktion flexibler Körper in elastischen Mehrkörpersystemen vorgeschlagen. Mit diesen Verfahren können reduzierte Modelle sehr gut auf den zu untersuchenden Frequenzbereich und die wirkenden Kräfte abgestimmt werden. Dadurch ist es möglich, für bestimmte Problemklassen bessere Approximationen zu erzeugen als bei Verwendung der in diesem Anwendungsbereich üblichen Verfahren auf Basis der modalen Reduktion.
Zur zeitdiskreten Implementierung nichtlinearer Regelgesetze (On the Discrete-time Implementation of Nonlinear Control Laws)
Authors: Holl Johann , Schlacher Kurt
Published: April 2006

Basierend auf wohlbekannten Entwurfsmethoden der nichtlinearen Regelungstheorie wird für die Klasse der zeitkontinuierlichen dynamischen Systeme ein Zugang zur modellbasierten zeitdiskreten Regelung vorgestellt. Die Berechnung der Stellfolge erfolgt durch die Forderung nach Äquivalenz der Trajektorien des betrachteten dynamischen Systems und denen des durch zeitkontinuierliche Regelung resultierenden geschlossenen Kreises zu diskreten Zeitschritten. Der dazu benötigte Fluss des nichtlinearen zeitkontinuierlichen Systems wird hierfür auf dem Intervall zweier aufeinander folgender Abtastzeitpunkte durch eine Lie-Reihe oder numerische Integration approximiert. In diesem Beitrag werden insbesondere die Methoden der exakten Linearisierung, Regelgesetze basierend auf differentieller Flachheit sowie ein passivitätsbasierter Reglerentwurf hinsichtlich ihrer zeitdiskreten Implementierung untersucht. Erörtert wird auch, dass die Trajektorienfolgeregelung keine Neuplanung der gewünschten Trajektorie erfordert. Schließlich wird die vorgeschlagene Methode anhand der Regelung eines stufenlosen Getriebes illustriert.
EDA — Eine Voraussetzung für die Nanoelektronik (EDA — a Precondition for Nanoelectronics)
Authors: Treytnar Dieter , Popp Ralf
Published: April 2006

Der fehlerfreie und effiziente Entwurf von hochkomplexen Chips mit oft mehr als 100 Millionen Transistoren ist heute eine der größten Herausforderungen beim Chip-Design. Ohne Entwurfsautomatisierung (Electronic Design Automation, EDA) ist sie nicht zu bewältigen. Um die hierzu notwendigen intensiven Forschungsarbeiten voranzutreiben, fördert das BMBF diesen Bereich in hohem Maße und hilft damit deutsche Kernkompetenzen wie Automotive und Telekommunikation voranzutreiben.
Effiziente Selbstkonfiguration mobiler Ad-hoc-Netze (Efficient Self-Configuration of Mobile ad hoc Networks)
Authors: Weniger Kilian Alexander
Published: April 2006

Mobile Ad-hoc-Netze (MANET) ermöglichen die Datenkommunikation vollkommen unabhängig von einer Kommunikationsinfrastruktur und eröffnen dadurch zahlreiche neue Möglichkeiten der mobilen Kommunikation. Auf Grund der speziellen Randbedingungen in diesen Netzen, wie die Notwendigkeit zur Selbstorganisation, die hochdynamische Netztopologie und die beschränkte Bandbreite und Energie, entstehen jedoch neue Anforderungen an Systemkonzepte und Protokolle. Eine essentielle, bisher aber nicht zufriedenstellend gelöste Problemstellung in diesem Zusammenhang ist die effiziente und zuverlässige Selbstkonfiguration solcher Netze, auch Autokonfiguration genannt. Wichtigster Konfigurationsparameter im Zusammenhang mit IP ist eine netzweite eindeutige IP-Adresse der Netzwerkschnittstelle. Dieser Artikel gibt einen Überblick über einige Ergebnisse der Dissertation mit dem Titel “IP-Autokonfiguration in mobilen Ad-hoc-Netzwerken”, in der mögliche Ansätze analysiert und eine sehr effiziente und zuverlässige Lösung zur dezentralen und automatischen IP-Adresszuweisung in MANETs vorgeschlagen wird.
Von Wissensportalen zu Wissensinfrastrukturen – Gestaltung von IT für die Wissensarbeit mit dem Konzept der Wissenslage (From Knowledge Portals to Knowledge Infrastructures – Designing IT for Knowledge Work with the Concept of Knowledge Stance)
Authors: Maier Ronald
Published: April 2006

Wissensintensive Arbeit stellt einen zunehmenden Anteil der Tätigkeiten in Unternehmen und Organisationen dar. Die Steigerung ihrer Produktivität verlangt nach einer gleichermaßen organisatorischen wie informations- und kommunikationstechnischen Unterstützung durch Instrumente des Wissensmanagements. Entsprechend gestaltete Wissensportale bieten geeignete Plattformen für deren Implementierung. Bei der Entwicklung von Wissensportalen werden weit reichende Anforderungen an Angebot, Zugang und Integration von Daten, Dokumenten und Diensten gestellt. Deren konsequente Umsetzung bedeutet den Aufbau einer unternehmensweiten Wissensinfrastruktur.
Virtuelle Portale – Mandantenfähigkeit für Websphere Portal Server (Virtual Portal – Multiple Tenant Capabilities for Websphere Portal)
Authors: Stober Thomas
Published: April 2006

Websphere.® Portal 5.1 unterstützt ein Konzept von virtuellen Portalen, die ohne wiederholtes Durchführen des Installationsprozesses auf sehr komfortable Weise angelegt werden können. Derartige virtuelle Portale entstehen durch Partitionieren einer existierenden Installation in mehrere logische Server. Endanwender bemerken dabei keinerlei Unterschied, ob ihre Anfrage von einer Vollinstallation oder einem virtuellen Portal bedient wird. Dieser Beitrag beschreibt die Konzepte, die dieser Lösung zugrunde liegen. Außerdem wird auf Anwendungsszenarien eingegangen, in denen virtuelle Portale genutzt werden, um die Mandantenfähigkeit von Websphere Portal zu erreichen.
Wirtschaftlichkeit von Unternehmensportalen (Economic Valuation of Enterprise Portals)
Authors: Okujava Shota , Remus Ulrich
Published: April 2006

Mittlerweile erkennen immer mehr Unternehmen, dass Portalprojekte enorm komplex, zeit- und kostenintensiv sind. Kosten und Nutzen, um ein Unternehmensportal aufzubauen und zu betreiben, sollten daher sorgfältig abgewägt werden. Häufig fehlen jedoch genaue Kennzahlen, die detailliert die Wirtschaftlichkeit einer Portalinvestition darstellen. Ziel des Artikels ist daher die Analyse der relevanten Faktoren, die Gegenstand einer Wirtschaftlichkeitsbetrachtung von Unternehmensportalen sind. Dazu werden Vorgehen zur Wirtschaftlichkeitsanalyse, sowie wesentliche Faktoren bzgl. des Nutzens, der Kosten und des Risikos bei der Implementierung eines Unternehmensportals, strukturiert nach den wesentlichen Portaltypen B2E und B2C diskutiert.
Enumeration of closest-packings by the space group: a simple approach
Authors: Iglesias Juan E.
Published: April 2006

The problem of enumerating the possible closest-packings of equal spheres having a period P for each of the possible space groups is solved by systematic exploitation of the properties of the two-color symmetry group of the cyclotomic representation of the Zhdanov symbol. No sophisticated combinatorial or group-theoretical techniques are required, and for some space groups, non-recursive, simple analytical expressions are obtained through the use of Möbius Inversion Formula. A corollary to Möbius theorem, used in the derivation, has been proved.
Uranyl oxalate hydrates: structures and IR spectra
Authors: Giesting Paul A. , Porter Nathan J. , Burns Peter Carman
Published: April 2006

The novel compound (UO2)2C2O4(OH)2(H2O)2 (UrOx2A) and the previously studied compound UO2C2O4(H2O)3 (UrOx3) have been synthesized by mild hydrothermal methods. Single crystal diffraction data collected at 125 K using MoK
α radiation and a CCD-based area detector were used to solve and refine the crystal structures by full-matrix least-squares techniques to agreement indices (UrOx2A, UrOx3) wR
2 = 0.037, 0.049 for all data, and R1 = 0.015, 0.024 calculated for 1285, 2194 unique reflections respectively. The compound UrOx2A is triclinic, space group P-1, Z = 1, a = 5.5353(4), b = 6.0866(4), c = 7.7686(6) Å, α = 85.6410(10)°, β = 89.7740(10)°, γ = 82.5090(10)°, V = 258.74(3) Å3. The compound UrOx3 is monoclinic, space group P21/c, Z = 4, a = 5.5921(4), b = 16.9931(13), c = 9.3594(7) Å, β = 99.5330(10)°, V = 877.11(11) Å3. The structures consist of chains of uranyl pentagonal bipyramids connected by oxalate groups and, in UrOx2A, hydroxyl groups; UrOx2A is also notable for its high (2 : 1) ratio of uranyl to oxalate groups, higher than any observed in other published structures of uranyl oxalates. The structure determined for UrOx3, previously studied by Jayadevan and Chackraburtty (1972); Mikhailov et al. (1999) is in agreement with the previous results; however, the increased precision of the present low-temperature structure refinement allows for the assignment of H atom positions based on the difference Fourier map of electron density. The infrared spectra of these two materials collected at room temperature are also presented and compared with previous work on uranyl oxalate systems.
The crystal structure of ZSM-10, a powder X-ray and electron diffraction study
Authors: Dorset Douglas L.
Published: April 2006

The crystal structure of the aluminosilicate, ZSM-10 (T108O216, where T = Si, Al), has been determined from electron diffraction and powder X-ray diffraction data. The material crystallizes in space group P6/mmm, where a = 31.390(2), c = 7.5147(8) Å. The framework [001] projection was determined independently with 300 kV precession electron diffraction amplitudes by direct methods. T-site positions in this projection were consistent with two models proposed in 1996 by Higgins and Schmitt. Subsequent Rietveld refinement favors their model A, comprising stacked cancrinite cages and hexagonal prisms. The framework density is 16.6 T sites/1000 Å3, similar to zeolite framework LTL. However, the refinement against synchrotron data from a dehydrated sample (R
wp = 0.1600, R(F
2) = 0.1418) finds no extra-framework species, despite the detection of some K+ in the material.
The structure of the red-brown form of [Fe2(η5-C5H4Me)2(CO)(CN)(μ-CO)(μ-CNMe2)] and its confirmation as a cis isomer
Authors: Boss Kevin , Manning Anthony R. , Müller-Bunz Helge
Published: April 2006

The crystal and molecular structure of the red brown form of [Fe2(η5-C5H4Me)2(CO)(CN)(μ-CO) · (μ-CNMe2)] has been determined by X-ray crystallography. It crystallises with one molecule per asymmetric unit (P21/c) and CO/CN disorder among the terminal ligands. It is a cis isomer with a non-planar Fe2(μ-C)2 bridge having a dihedral angle of 154° between the two Fe2C planes. The Fe—C distances to the 2-electron donor ligands (CO, CN, μ-CO and μ-CNMe2
+) can be rationalised on the basis of their σ donor and π acceptor abilities.
Crystal structure of silver salicylate C7H5AgO3 solved by reverse Monte-Carlo method from X-ray powder diffraction data and confirmed on single crystal
Authors: Wolcyrz Marek , Paściak Marek , Kowalczyk Jerzy , Maciejewski Marcin
Published: April 2006

The crystal structure of silver salicylate C7H5AgO3 has been solved originally on powder sample by molecular modeling and reverse Monte-Carlo (RMC) algorithm and then confirmed by X-ray diffraction single crystal structure solution and refinement. C7H5AgO3 crystallizes in the monoclinic symmetry (space group P21/n) with the lattice parameters: a = 10.9868(15) Å, b = 8.8190(18) Å, c = 7.398(2) Å, β = 112.27(3)° (data from single crystal). The structure consists of [C6H4(OH)COOAg— AgOOCC6H4(OH)] dimers and is stabilized by weak intermolecular interactions of the C—H···O type. The comparison of the two independent structure solutions confirmed the effectiveness of the RMC procedure based on powder data to solve the unknown organic structures of the mediocre complexity even using the laboratory X-ray sources.
Synthesis, crystal structure and magnetic behaviourof a mononuclear Fe(III) — Schiff base metal complex
Authors: Nazir Hasan , Akben Nimet Sapmaz , Ateş Meltem Bürke , Sözeri Hüseyin , Ercan Ismail , Atakol Orhan , Ercan Filiz
Published: April 2006

A complex from Fe(II) and a hexa-dentate linear ligand containing O2N4 donor atoms were prepared and the structure enlightened with X-ray diffraction. The Fe(II) ion in the complex was seen to be oxidized to form a Fe(III) complex, [C20H24Cl3N4O2]Fe and the three chloride ions were situated at a distance of Fe…Cl(1) 3.976(5), Fe…Cl(2) 4.479(3) and Fe…Cl(3) 7.509(4) Å outside the coordination sphere. The Fe(III) ion has an octahedral coordination sphere and as expected the two oxygen donor atoms are coordinated in a -cis position. The Fe—O, Fe—Nimin and Fe—Namine distances are 1.880(3) Å, 1.931(4) Å and 2.004(4) Å, respectively.
The molecular structure of 2-phenylbenzimidazole: a new example of incommensurate modulated intramolecular torsion
Authors: Zúñiga F. Javier , Palatinus Lukáš , Cabildo Pilar , Claramunt Rosa M. , Elguero José
Published: April 2006

Molecular crystals of 2-phenylbenzimidazole, C13H10N2, exhibit a one-dimensional incommensurate structure. The structure has been solved by charge flipping and refined using the superspace formalism in the (3 + 1) D superspace group C2/c(0b0) s0 with modulation wave-vector q = 0.368b*. The unit cell contains 8 molecules, each one disorderly occupying two configurations related by inversion center. The refinement based on a molecular model with two rigid-body parts per molecule includes up to second order Fourier amplitudes for the modulation. The displacive modulation involves a significant intra-molecular twist between the phenyl and the benzimidazole parts.
Non-linear optical properties and absolute structure of metastable 4-methyl benzophenone
Authors: Kaminsky Werner , Weckert Edgar , Kutzke Hartmut , Glazer A. Michael , Klapper Helmut
Published: April 2006

Metastable 4-methyl benzophenone (4-MBP, C14H12O) crystallizes in the polar (pyroelectric) and enantiomorphic space groups (SG) P31 and P32. The optical rotation tensor has been measured for 670 nm and the material was tested for evidence of phase-matchability. The absolute structure was determined via three-beam diffraction, showing that the structural right-hand screw 31 is combined with positive (right-handed, i.e. clockwise when looking towards the light source) optical rotation, for both tensor components ρ
11 = ρ
22 = 26(5)°/mm, ρ
33 = 8.3(5)°/mm (contrary to low-quartz which shows negative optical rotation for ρ
33 and positive rotation for ρ
11 in right-hand SG P312).

The non-linear optical tensors for optical rotation, d-coefficients, electro-optic effect and electrogyration have been calculated using a set of electronic polarizabilities as input parameters for a dipole-dipole interaction model that reproduces the experimental refractive indices and optical rotation. Unusually high polarizability volumes are needed for hydrogen atom bonding to aromatic carbons in order to model the optical tensors. The non-linear optical coefficients are of medium size.
Electroless, Electrolytic and Galvanic Copper Deposition with the Scanning Electrochemical Microscope (SECM)
Authors: Radtke Valentin , Heß Christian , Souto Ricardo M. , Heinze Jürgen
Published: April 2006

The Scanning Electrochemical Microscope (SECM) can be used with different techniques of microstructured copper deposition. A first approach involves the electrolytic copper deposition on noble metals, whereby copper ions are released from a complex by a suitable tip reaction and then reduced on the polarised conducting surface to form a copper microstructure. The second approach is very similar to the first, but does not involve polarising the substrate. It generates a tip-induced microgalvanic cell, the positive electromotoric force of which is constituted by two electrochemical reactions at different areas of the substrate. Finally the electroless copper deposition is performed on nonconducting surfaces like glass or semiconducting surfaces like silicon. This involves locally reducing a suitable precursor film whose surface has been previously immobilised.
Amphiphilic Block Copolymers that Form Micelles but Are not Surface Active and Bind Normal Surfactants
Authors: Eghbali Elham , Hoffmann Heinz
Published: April 2006

The phase diagram and the properties of the aqueous phases of the AB block copolymer poly-n-butylacrylate-block-polyacrylic acid (nBuA100-b-AA150) has been studied as a function of the neutralisation degree α with NaOH. Aqueous solutions of the block copolymer with α < 0.1 are turbid and separate into two phases while solutions with α > 0.1 are transparent and single phase. The viscosities of such solutions increase with α and pass over a maximum at α = 0.5. Solutions with a concentration of Cp ≥ 1% and at α = 0.5 are highly viscoelastic and have a yield stress value. Cryo-TEM micrographs show that globular micelles are present in the viscoelastic solutions. The micelles have a polydisperse size distribution. The radius of the hydrophobic core varies from about 100 Å to 200 Å what is the length of the fully stretched hydrophobic block.

The rheological properties of the solutions are explained on the basis of the globular core–shell micelles where the polyelectrolyte chains form a corona around the hydrophobic block. Most of the counter ions are in the condensed and free state inside the corona. Some of the counter ions are outside of the corona and form an electrical double layer whose thickness depends on α. The viscoelastic properties of the solutions are thus given by the dense packing of the charged globular micelles. The decrease of the viscosity for α > 0.5 comes about by the shrinkage of the thickness of the electrical double layer. With increase of excess salt the double layer and the corona also shrink and the viscoelastic properties break down. With adsorption of zwitterionic surfactants the viscoelastic properties also disappear. Cryo-TEM micrographs of the block copolymers at α = 0.5 with adsorbed zwitterionic surfactants show that the polyelectrolyte chains of the block copolymers are wrapped around small globular micelles of the zwitterionic surfactants. The supra-molecular structures look like raspberry-like micelles.

The block copolymers show a very unusual amphiphilic behavior. For a neutralisation degree of α > 0.1 the compounds do not seem to adsorb at the water surface even though the compounds form micelles in the bulk solution. The micellar solutions have the same surface tension of water. The acidic form of the compound however is surface active.
Activation Parameters of the Eu3+/Eu2+ Electrode Reaction in Mixed Solvents
Authors: Kisova L. , Komenda J.
Published: April 2006

The rate constants for the electrochemical reduction of Eu3+ in water–acetone and water–dimethylformamide solvent mixtures with different parts of the organic component were measured in the temperature range 15°C–40°C. The activation parameters for this reaction were evaluated. While the activation enthalpy does not depend on the composition of the solvent, the activation entropy changes follows the changes of reaction rates.

The entropy contribution (responsible for the form of dependence of rate constants on the composition of the solvent) is obviously related to structure changes of the resolvatated particle.
An Empirical Approach to Modeling Ion Size Effects in Diffuse Double Layer Theory
Authors: Smagala Thomas G. , Fawcett W. Ronald
Published: April 2006

A novel empirical model for the diffuse double layer is found by generalizing the simple analytical equations of Gouy–Chapman theory. Two adjustable parameters are introduced into the Boltzmann equation for the exponential dependence of the ion–wall correlation functions on the diffuse layer potential. Optimal parameter values and model validation for 1:1 and 2:1 electrolytes are provided by Monte Carlo simulations. Simple relationships are obtained between these empirical parameters and those commonly associated with the mean-spherical approximation. The new empiricism accurately models diffuse layer potential profiles and ion–wall correlation functions for a restricted 1:1 electrolyte in a primitive solvent.
Novel Insight into the Protonation–Deprotonation Equilibria of Tetracycline, Sancycline and 10-Propoxy-Sancycline in Aqueous Solution. I. Analysis of the pH-Dependent UV/vis Absorption Spectra by the SVD Technique
Authors: Schmitt Matthias O. , Schneider Siegfried
Published: April 2006

The UV/vis absorption spectra recorded during titration experiments (pH2 ↔ pH11, ΔpH ∼ 0.33) were subjected to a principal component analysis. The aim was to determine by means of the program SPECFIT the number of significant components and to reduce the noise in the spectra. The attempt to achieve a global fit of the “noise-reduced” data was in general successful if 5 or more independent species were considered. The necessity to include a larger number of species than the 4 occuring within the simple protonation-deprotonation scheme of a triprotic acid provides strong evidence for conformational heterogeneity at various levels of protonation. Only if this heterogeneity is taken into account, the analysis yields the correct pK
a-values. For tetracycline, slow conformational changes are suggested to occur in the neutral state. Consequently, tetracycline adopts conformation 2 in alkaline solution if the pH is raised slowly up to pH11, whereas if it is dissolved directly in buffer solution at pH2 or pH11 it adopts conformation 1 (like in the crystal). In this conformation, tetracycline degrades rapidly in a methanol–water mixture around pH11 probably by methylation of the 11,12-β-carbonyl group. Sancycline and 10-propoxy-sancycline are stable at any pH, the conformational changes are proposed to occur preferentially in the anionic state. Because of these conformational changes, the pK
a-values derived from forward and backward titration can differ up to 0.4 pH units. In addition, there is evidence that C10-OH does not dissociate at pH less than 11.

In contrast to a widely accepted hypothesis, 4-epi-tetracycline also changes its conformation in the anionic form. This shows that CD spectra are not suited to draw conclusions on molecular geometry if the total net charge changes.
UV and Visible Light Acrylate Photopolymerisation Initiated by Nitrogen- or Carbon-Doped Titanium Dioxide
Authors: Damm C. , Sakthivel S. , Kisch H.
Published: April 2006

Nitrogen and carbon doped titania powders initiate acrylate polymerisation upon UV excitation. Time resolved photovoltage measurements afford surface charge carrier lifetimes of 7–8 ms for undoped and N-doped titania, whereas 12 ms are observed for the C-doped semiconductor. These values correlate with the observation that the polymerisation rate constants are similar for titania or N-doped titania but about two times larger for the C-doped material. Wavelength dependent polymerisation experiments indicate that visible light polymerisation is possible only with carbon-doped titania. This suggests that hole relaxation to dopant-centered surface states is much more efficient in nitrogen-doped titania. These experimental findings are in accord with the assumption that polymerisation is initiated by hole oxidation of the acrylate.
Cyclic Voltammetry of N,N-Dimethyl-p-Phenylenediamine and its HCl-Salt in Acetonitrile with Pyridine as Proton Acceptor
Authors: Nickel Ulrich , Garcia-Angel Maria de Gracia , Ramminger Ute , Weidinger Birgit
Published: April 2006

The redox behaviour of N,N-dimethyl-p-phenylenediamine (PPD) and N,N-dimethyl-p-phenylenediamine · 2HCl (PPD · 2HCl) in acetonitrile was studied by means of cyclic voltammetry – both in the absence and in the presence of proton accepting pyridine. The oxidation occurs in two separate steps yielding first N,N-dimethyl-p-semiquinonediimine (SQDI+) and subsequently N,N-dimethyl-p-quinonediimine (QDI2+ or QDI+(H+)). In case of N,N-dimethyl-p-phenylenediamine the 1st oxidation step is fully reversible, while the 2nd oxidation step is slightly quasi-reversible. At 10°C the formal redox potentials of the PPD/SQDI+ and SQDI+/QDI2+ redox couples are −0.200 ± 0.005 V and 0.380 ± 0.010 V (versus Fc/Fc+), respectively. The synproportionation constant K
syn = [SQDI+]2/[PPD][QDI2+] is 2.1 × 1010. Adding pyridine to the reaction mixture leads to a shift of the 2nd anodic wave to less positive potentials. This shift is primarily due to proton transfer from QDI2+ to pyridine to form QDI+, which overall renders the oxidation easier. The corresponding cathodic peak, on the other hand, disappears as the reduction of QDI+ necessitates a proton. The formal oxidation potential of the redox couple SQDI+/QDI+(H+) is about 0.190 V and, therefore, the synproportionation constant K
syn = 1.7 × 106. N,N-dimethyl-p-phenylenediamine · 2HCl lacks completely the 1st anodic peak. The position of the anodic peak is given by the direct oxidation of PPDH+ to QDI2+(H+) and is similar to that of the SQDI+/QDI2+ redox couple. Upon adding pyridine the 2nd anodic peak shifts notably to less positive potentials and the redox process attributable to the PPD/SQDI+ redox couple is seen. As pyridine influences the potential of the Ag pseudo-reference electrode a reference electrode based on the ferrocene/ferrocenium redox couple was used.
Rational Design of Cation Hosts – Prediction of Cation Selectivity by Quantum Chemical Calculations
Authors: Galle Michael , Puchta Ralph , van Eikema Hommes Nico J. R. , van Eldik Rudi
Published: April 2006

Structures of [M ⊂ 2.2.2]n+ obtained with MNDO, AM1, PM3, PM3/SPASS, and PM5, are evaluated against X-ray and DFT (B3LYP/LANL2DZp) geometries. DFT and X-ray structures agree well, followed by PM3/SPASS. The ion selectivity calculated with DFT and PM3/SPASS for a simple model reaction, agrees satisfactorily with the available complex-formation constants (log K
S). The applied theoretical treatment has a good predictive potential.