bluuebunny/crossref_metadata_2025 huggingface dataset:
Feature Discovery by Competitive Learning*
Authors: Rumelhart David E. , Zipser David
Published: July 2005

This paper reports the results of our studies with an unsupervised learning paradigm which we have called “Competitive Learning.” We have examined competitive learning using both computer simulation and formal analysis and have found that when it is applied to parallel networks of neuron‐like elements, many potentially useful learning tasks can be accomplished. We were attracted to competitive learning because it seems to provide a way to discover the salient, general features which can be used to classify a set of patterns. We show how a very simply competitive mechanism can discover a set of feature detectors which capture important aspects of the set of stimulus input patterns. We also show how these feature detectors can form the basis of a multilayer system that can serve to learn categorizations of stimulus sets which are not linearly separable. We show how the use of correlated stimuli con serve as a kind of “teaching” input to the system to allow the development of feature detectors which would not develop otherwise. Although we find the competitive learning mechanism a very interesting and powerful learning principle, we do not, of course, imagine thot it is the only learning principle. Competitive learning is an essentially nonassociative statistical learning scheme. We certainly imagine that other kinds of learning mechanisms will be involved in the building of associations among patterns of activation in a more complete neural network. We offer this analysis of these competitive learning mechanisms to further our understanding of how simple adaptive networks can discover features important in the description of the stimulus environment in which the system finds itself.
A Learning Algorithm for Boltzmann Machines*
Authors: Ackley David H. , Hinton Geoffrey E. , Sejnowski Terrence J.
Published: July 2005

The computational power of massively parallel networks of simple processing elements resides in the communication bandwidth provided by the hardware connections between elements. These connections can allow a significant fraction of the knowledge of the system to be applied to an instance of a problem in a very short time. One kind of computation for which massively parallel networks appear to be well suited is large constraint satisfaction searches, but to use the connections efficiently two conditions must be met: First, a search technique that is suitable for parallel networks must be found. Second, there must be some way of choosing internal representations which allow the preexisting hardware connections to be used efficiently for encoding the constraints in the domain being searched. We describe a general parallel search method, based on statistical mechanics, and we show how it leads to a general learning rule for modifying the connection strengths so as to incorporate knowledge about a task domain in an efficient way. We describe some simple examples in which the learning algorithm creates internal representations that are demonstrably the most efficient way of using the preexisting connectivity structure.
Learning to Search: From Weak Methods to Domain‐Specific Heuristics*
Authors: Langley Pat
Published: July 2005

Learning from experience involves three distinct components—generating behavior, assigning credit, and modifying behavior. We discuss these components in the context of learning search heuristics, along with the types of learning that can occur. We then focus on SAGE, a system that improves its search strategies with practice. The program is implemented as a production system, and learns by creating and strengthening rules for proposing moves. SAGE incorporates five different heuristics for assigning credit and blame, and employs a discrimination process to direct its search through the space of rules. The system has shown its generality by learning heuristics for directing search in six different task domains. In addition to improving its search behavior on practice problems, SAGE is able to transfer its expertise to scaled‐up versions of a task, and in one case, transfers its acquired search strategy to problems with different initial and goal states.
Languages and Designs for Probability Judgment*
Authors: Shafer Glenn , Tversky Amos
Published: July 2005

Theories of subjective probability are viewed as formal languages for analyzing evidence and expressing degrees of belief. This article focuses on two probability langauges, the Bayesian language and the language of belief functions (Shafer, 1976). We describe and compare the semantics (i.e., the meaning of the scale) and the syntax (i.e., the formal calculus) of these languages. We also investigate some of the designs for probability judgment afforded by the two languages.
The More Things Change…: Metamorphoses and Conceptual Structure*
Authors: Kelly Michael H. , Keil Frank C.
Published: July 2005

Given that mythmakers must construct stories that are comprehensible to their audience, it is reasonable to expect stories to be conceptually natural even when their topics deal with the supernatural. Thus, as stories are adapted to human conceptual structure, they should reflect characteristics of that structure. An examination of the types of magical transformations in Ovid's Metamorphoses and Grimms' Fairy Tales suggests that this is the case. It was possible to predict the patterns of transformations on the basis of structural properties of ontological knowledge, which is knowledge of the basic categories of existence (e.g., conscious beings, animals, plants, events). Other characteristics of the transformations seem to reflect the conceptual distinction between animates and inanimates as well as the relative prototypicality of various taxonomic classes of animals. It appears that aspects of conceptual structure can constrain patterns of thinking even during “the willing suspension of disbelief.”
Comparing Natural and Abstract Categories: A Case Study from Computer Science
Authors: Adelson Beth
Published: July 2005

In order to address the issue of whether abstract and concrete objects are categorized similarly, this paper looks at how computer scientists categorize the common concepts of their field. Using the methodology of Rosch, Mervis, Gray, Johnson, and Boyes‐Braem (1976) and of Rosch and Mervis (1975) to identify the categorizations used by computer scientists, this study found that the categorization phenomena reported for concrete objects are quite general, operating over a wider range than was previously thought.
The Development of Children's Problem Solving in a Gears Task: A Problem Space Perspective
Authors: Metz Kathleen E.
Published: July 2005

I examined two contexts of development in children's problem solving: (1) the macro‐context of different age cohorts (8–9 vs 11–12 years of age); and (2) the micro‐context of an approximately one‐hour experimental session. Twenty subjects (even divided across sexes and these two age groups) were individually presented a collection of variously sized gears, a board onto which these gears could be easily attached and rotated, and a knob. Each subject was asked to find all solutions, in which two marked gears were turning the same way, and to represent these solutions graphically. Subjects applied four different problem spaces to the task: the Euclidean, the Kinematic, the Dynamic, and the Topological. The Arithmetic Modifier could be applied to any of these problem spaces, resulting in a numerical characterization of the gear constructions and/or production strategies. The 11–12's tended to shift problem spaces adaptively; the 8–9's seldom did so. Analysis of the pathways of transition between the problem spaces revealed a complex picture of partial or complete incorporation, and substitution.
Approximate Semantic Transference: A Computational Theory of Metaphors and Analogies
Authors: Indurkhya Bipin
Published: July 2005

In this paper we start from the assumption that in a metaphor, or an analogy, some terms belonging to one domain (source domain) are used to refer to objects other than their conventional referents belonging to a possibly different domain (target domain). We describe a formalism, which is based on the First Order Predicate Calculus, for representing the knowledge structure associated with a domain and then develop a theory of Constrained Semantic Transference [CST] which allows the terms and the structural relationships of the source domain to be transferred coherently across to the target domain. We show how metaphors and analogies can be characterized in CST in such a way that many of their cognitive properties con be explained.

We then propose a theory of Approximate Semantic Transference [AST] which is a computational version of CST and is derived from it by replacing the coherency requirement with approximate coherency. We show how AST can be used as a basis for designing models of cognitive processes involved in comprehending metaphors and analogies.
Dual Space Search During Scientific Reasoning
Authors: Klahr David , Dunbar Kevin
Published: July 2005

The purpose of the two studies reported here was to develop an integrated model of the scientific reasoning process. Subjects were placed in a simulated scientific discovery context by first teaching them how to use an electronic device and then asking them to discover how a hitherto unencountered function worked. To do this task, subjects had to formulate hypotheses based on their prior knowledge, conduct experiments, and evaluate the results of their experiments. In the first study, using 20 adult subjects, we identified two main strategies that subjects used to generate new hypotheses. One strategy was to search memory and the other was to generalize from the results of previous experiments. We described the former group as searching an hypothesis space, and the latter as searching an experiment space. In a second study, with 10 adults, we investigated how subjects search the hypothesis space by instructing them to state all the hypotheses that they could think of prior to conducting any experiments. Following this phase, subjects were then allowed to conduct experiments. Subjects who could not think of the correct rule in the hypothesis generation phase discovered the correct rule only by generalizing from the results of experiments in the experimental phase.

Both studies provide support for the view that scientific reasoning can be characterized as search in two problem spaces. By extending Simon and Lea's (1974) Generalized Rule Inducer, we present a general model of Scientific Discovery as Dual Search (SDDS) that shows how search in two problem spaces (an hypothesis space and an experiment space) shapes hypothesis generation, experimental design, and the evaluation of hypotheses. The model also shows how these processes interact with each other. Finally, we interpret earlier findings about the psychology of scientific reasoning in terms of the SDDS model.
FERMI: A Flexible Expert Reasoner with Multi‐Domain Inferencing
Authors: Larkin Jill H. , Reif Frederick , Carbonell Jaime , Gugliotta Angela
Published: July 2005

Expert reasoning combines voluminous domain‐specific knowledge with more general factual and strategic knowledge. Whereas expert system builders have recognized the need for specificity and problem‐solving researchers the need for generality, few attempts have been made to develop expert reasoning engines combining different kinds of knowledge at different levels of generality. This paper reports on the FERMI project, a computer‐implemented expert reasoner in the natural sciences that encodes factual and strategic knowledge in separate semantic hierarchies. The principled decomposition of knowledge according to type and level of specificity yields both power and cross‐doman generality, as demonstrated in FERMI's ability to apply the same principles of invariance and decomposition to solve problems in fluid statics, DC‐circuits, and centroid location. Hierarchical knowledge representation and problem‐solving principles are discussed, and illustrative problem‐solving traces are presented.
Critical Decisions under Uncertainty: Representation and Structure
Authors: Kuipers Benjamin , Moskowitz Alan J. , Kassirer Jerome P.
Published: July 2005

How do people make difficult decisions in situations involving substantial risk and uncertainty? In this study, we presented a difficult medical decision to three expert physicians in a combined “thinking aloud” and “cross examination” experiment. Verbatim transcripts were analyzed using script analysis to observe the process of constructing and making the decision, and using referring phrase analysis to determine the representation of knowledge of likelihoods. These analyses are compared with a formal decision analysis of the same problem to highlight similarities and differences. The process of making the decision resembles an incremental, sequential‐refinement planning algorithm, where a complex decision is broken into a sequence of choices to be made with a simplified description of the alternatives. This strategy results in certain kinds of relevant information being underweighted in the final decision. Knowledge of likelihood appears to be represented as symbolic descriptions capturing categorical and ordinal relations with “landrhark” likelihoods, only some of which are described numerically. Numerical probabilities, capable of being combined and compared arithmetically, were not observed. These observations suggest an explanation for the heuristics and biases in human decision making under uncertainty in terms of the processes that manipulate symbolic descriptions of likelihoods and construct plans of action for situations involving risk and uncertainty.
Adaptive Planning
Authors: Alterman Richard
Published: July 2005

Adaptive Planning is an approach to planning in the commonsense domain. An adaptive planner takes advantage of the habitual nature of many of the planning situations for which it plans by bosing its activities on a memory of pre‐stored plans. A critical issue, and the subject of this paper, is the question of flexibility: How does an adaptive planner refit an old plan in order to meet the demands of some new planning situation? An adaptive planner refits prestored plans by constructing an interpretation of the situation in which it is engaged. Key elements in the theory of adaptive planning are its treatment of specific plans and a notion of situation matching. The theory of adaptive planning has been modeled by a computer program called PLEXUS.
A Distributed Connectionist Production System
Authors: Touretzky David S. , Hinton Geoffrey E.
Published: July 2005

DCPS is a connectionist production system interpreter that uses distributed representations. As a connectionist model it consists of many simple, richly interconnected neuron‐like computing units that cooperate to solve problems in parallel. One motivation for constructing DCPS was to demonstrate that connectionist models are capable of representing and using explicit rules. A second motivation was to show how “coarse coding” or “distributed representations” can be used to construct a working memory that requires far fewer units than the number of different facts that can potentially be stored. The simulation we present is intended as a detailed demonstration of the feasibility of certain ideas and should not be viewed as a full implementation of production systems. Our current model only has a few of the many interesting emergent properties that we eventually hope to demonstrate: It is damage‐resistant, it performs matching and variable binding by massively parallel constraint satisfaction, and the capacity of its working memory is dependent on the similarity of the items being stored.
Observed Methods for Generating Analogies in Scientific Problem Solving
Authors: Clement John
Published: July 2005

Evidence from videotapes of experts thinking aloud is presented which documents the spontaneous use of analogies in scientific problem solving. Four processes appear to be important in using an analogy: (1) generating the analogy; (2) establishing confidence in the validity of the analogy relation; (3) understanding the analogous case; and (4) applying findings to the original problem. This study concentrates on process (1). Evidence was found for three different methods of analogy generation: generation via a principle (1 case), generation via an association (8 cases), and generation via a transformation (18 cases). Although the mechanism underlying analogy generation is usually described as an association process, transformation processes, where the subject modifies or transforms some aspect of the original problem, may be just as important if not more important. In contrast to the usual view of an analogous case as already residing in memory, several of the analogous cases were quite novel, indicating that they were newly invented Gedanken experiments. The usefulness of some analogies appears to lie in a “provocative” function of activating additional knowledge schemas that is different from the commonly cited “direct transfer” function where established knowledge is transferred fairly directly from the analogous to the original case.
Studies of Diagnosis and Remediation with High School Algebra Students
Authors: Sleeman D. , Kelly A.E. , Martinak R. , Ward R.D. , Moore J.L.
Published: July 2005

Despite extensive discussion in the literature about the diagnosis and subsequent remediation of students' errors, few studies have compared the effects of different styles of error‐based remediation. Swan (1983) found that a conflict approach (pointing out errors made by students and demonstrating their consequences) was more effective than simple reteaching, but Bunderson & Olsen (1983) found no difference between error‐specific remediation and reteaching. More studies are needed in order to understand the factors which lead to successful remediation. The three studies discussed in this article compared error‐specific or model‐based remediation (MBR) with reteaching in algebra. MBR bases its remediation on the model inferred for an individual student before reteaching the correct procedure. Reteaching simply shows students the correct procedure without addressing specific errors. The results show that MBR and reteaching are both more effective than no tutoring; however, MBR is not clearly more effective than reteaching. The results are discussed in terms of stability of errors, their relevance to educational practice and to intelligent tutoring systems (ITS). Although the studies were carried out using human tutors, the results suggest that for the purpose of remediation in the algebra domain, when taught procedurally, “classical” computer‐assisted instruction (CAI) would be as effective as an ITS.
Case‐Based Planning: A Framework for Planning from Experience
Authors: Hammond Kristian J.
Published: July 2005

This article presents a view of planning as a task supported by a dynamic memory. This view attempts to ingegrate models of memory, learning, and planning into a single system that learns about planning by creating new plans and analyzing how they interact with the world. We call this view of planning case‐based planning.

A case‐based planner makes use of its own past experience in developing new plans. It relies on its memory of observed effects, rather than a set of causal rules, to create and modify new plans. Memories of past successes are accessed and modified to create new plans. Memories of past failures are used to warn the planner of impending problems, and memories of past repairs are called upon to tell the planner how to deal with them.

This view of planning from experience supports and is supported by a learning system that incorporates new experiences into the planner's episodic memory. This learning algorithm gains from the planner's failures as well as its successes. Successful plans are stored in memory, indexed by the goals they satisfy and the problems they avoid. Failures are also stored and indexed by the features in the world that predict them. By storing failures as well as successes, the planner is able to anticipate and avoid future plan failures.

Case‐based planning is aimed at improving planning behavior in three areas: failure avoidance, plan repair, and plan reuse. It also attempts gains over current learning systems, in that the learning is driven by the functional needs of a planner.
Prediction of the Modal Characteristics of the Human Spine at Resonant Frequency Using Finite Element Models
Authors: Guo Li-Xin , Teo Ee-Chon
Published: July 2005

To understand the dynamic characteristics of the human spine, a detailed three-dimensional finite element model of the lower thorax to pelvis segment, T12-pelvis, was developed based on actual vertebral geometry. After modal analysis, the resonant frequencies of different spinal segments were obtained. The vibration mode of T12-pelvis shows that the human upper body mainly performs the vertical motion during whole-body vibration and the lumbar spine segment conducts translation and rotation in the sagittal plane. The lower segments of the lumbar spine move in flexion and the upper lumbar segments move in extension. This investigation may be helpful in understanding further the biomechanical behaviour of the human spine under the condition of whole-body vibration and to offer potential references for spinal disease treatments and product design in industry.
Near-surface damage - a persistent problem in crowns obtained by computer-aided design and manufacturing
Authors: Rekow D , Thompson V P
Published: July 2005

Robust dental systems obtained by computer-aided design and manufacture (CAD/CAM) have been introduced and, in parallel, the strength of the ceramic materials used in fabricating dental crowns has improved. Yet all-ceramic crowns suffer from near-surface damage, limiting their clinical success, especially on posterior teeth. Factors directly associated with CAD/CAM fabrication that contribute to the degree of damage include material selection and machining parameters and strategies. However, a number of additional factors also either create new damage modes or exacerbate subcritical damage, potentially leading to catastrophic failure of the crown. Such factors include post-fabrication manipulations in the laboratory or by the clinician, fatigue associated with natural occlusal function, and stress fields created by compliance or distortion within the supporting tooth structure and/or adhesive material holding the crown to the tooth. Any damage reduces the strength of a crown, increasing the probability of catastrophic failure. The challenge is to understand and manage the combination of competing damage initiation sites and mechanisms, limitations imposed by the demand for aesthetics, and biologically related constraints.
“Syn Effect” in the 1,4-Eliminative Ring Opening of [3-Substituted (E)-1-Propenyl]oxiranes to the Corresponding 2,4-Dienyl Alcohols
Authors: Takeda Naohiro , Chayama Takuya , Takenaka Hiroyuki , Ukaji Yutaka , Inomata Katsuhiko
Published: July 2005

Stereochemistry of the 1,4-eliminative ring opening of [3-substituted (E)-1-propenyl]oxiranes to the corresponding 2,4-dienyl alcohols by LDA was investigated. The Z/E ratios of the resulting 2,4-dienyl alcohols varied with the substituents at 3-position of the propenyl group. This phenomenon was discussed based on the concept of a “syn-effect,” which is most primarily rationalized by a σ → π* interaction. Furthermore, in the case of δ-benzyloxy-substituted vinyloxirane, [1,2]-Wittig rearrangement proceeded following the initial 1,4-eliminative ring opening to give a (E,Z)-2,4-dienyl 1,6-diol in a completely stereoselective manner.
Dipyrrin–Porphyrin Hybrids: Potential π-Conjugated Platform to Fabricate Coordination Oligomers
Authors: Maeda Hiromitsu , Ito Miki
Published: July 2005

Bis-dipyrrin-appended porphyrin derivatives, potential building blocks for supramolecular coordination architectures, were synthesized and exhibited complexation at the two dipyrrin sites with BF2 and Rh(CO)2.
Silver-catalyzed Alkyl–Alkyl Homo-coupling of Grignard Reagents
Authors: Nagano Takashi , Hayashi Tamio
Published: July 2005

Oxidative homo-coupling of alkyl Grignard reagents possessing β-hydrogens proceeded with high selectivity in the presence of silver tosylate (AgOTs) as a catalyst (1 mol %) and 1,2-dibromoethane as a reoxidant.
Research Note: A Dynamic Programming Approach to Customer Relationship Pricing
Authors: Lewis Michael
Published: July 2005

The practice of offering discounts to prospective customers represents a rudimentary form of using transaction history measures to customize the marketing mix. Furthermore, the proliferation of powerful customer relationship management (CRM) systems is providing the data and the communications channels necessary to extend this type of pricing strategy into true dynamic marketing policies that adjust pricing as customer relationships evolve. In this paper, we describe a dynamic programming–based approach to creating optimal relationship pricing policies. The methodology has two main components. The first component is a latent class logit model that is used to model customer buying behavior. The second component is a dynamic optimization procedure that computes profit-maximizing price paths. The methodology is illustrated using subscriber data provided by a large metropolitan newspaper.

The empirical results provide support for the common managerial practice of offering discounts to new customers. However, in contrast to current practice, the results suggest the use of a series of decreasing discounts based on the length of customer tenure rather than a single steep discount for first-time purchasers. The dynamic programming (DP) methodology also represents an important approach to calculating customer value (CV). Specifically, the DP framework allows the calculation of CV to be an explicit function of marketing policies and customer status. As such, this method for calculating CV accounts for the value of managerial flexibility and improves upon existing methods that do not model revenue and attrition rates as functions of marketing variables.
Harvest Scheduling Subject to Maximum Area Restrictions: Exploring Exact Approaches
Authors: Goycoolea Marcos , Murray Alan T. , Barahona Francisco , Epstein Rafael , Weintraub Andrés
Published: July 2005

We consider a spatial problem arising in forest harvesting. For regulatory reasons, blocks harvested should not exceed a certain total area, typically 49 hectares. Traditionally, this problem, called the adjacency problem, has been approached by forming a priori blocks from basic cells of 5 to 25 hectares and solving the resulting mixed-integer program. Superior solutions can be obtained by including the construction of blocks in the decision process. The resulting problem is far more complex combinatorially. We present an exact algorithmic approach that has yielded good results in computational tests. This solution approach is based on determining a strong formulation of the linear programming problem through a clique representation of a projected problem.
A Note on Convexity of the Expected Delay Cost in Single-Server Queues
Authors: Fridgeirsdottir Kristin , Chiu Sam
Published: July 2005

In this note, we show that the expected delay cost for a G/G/1 queue is not necessarily convex in the arrival rate as sometimes claimed in the literature. We can prove, however, that the total expected delay cost rate is convex in the arrival rate. This cost rate is often of interest when designing queueing systems.
Anisogamy, Expenditure of Reproductive Effort, and the Optimality of Having Two Sexes
Authors: Epelman Marina A. , Pollock Stephen , Netter Brian , Low Bobbi S.
Published: July 2005

No good formal arguments exist for a central question in biology: Why, in species that have sexual reproduction, are there usually only “males” and “females”? We present a nonlinear optimization model that supports the conclusion that having only two sexes maximizes long-run viability.
Optimal Protein Structure Alignment Using Maximum Cliques
Authors: Strickland Dawn M. , Barnes Earl , Sokol Joel S.
Published: July 2005

In biology, the protein structure alignment problem answers the question of how similar two proteins are. Proteins with strong physical similarities in their tertiary (folded) structure often have similar functions, so understanding physical similarity could be a key to developing protein-based medical treatments. One of the models for protein structure alignment is the maximum contact map overlap (CMO) model. The CMO model of protein structure alignment can be cast as a maximum clique problem on an appropriately defined graph. We exploit properties of these protein-based maximum clique problems to develop specialized preprocessing techniques and show how they can be used to more quickly solve contact map overlap instances to optimality.
Throughput Maximization for Tandem Lines with Two Stations and Flexible Servers
Authors: Andradóttir Sigrún , Ayhan Hayriye
Published: July 2005

For a Markovian queueing network with two stations in tandem, finite intermediate buffer, and M flexible servers, we study how the servers should be assigned dynamically to stations to obtain optimal long-run average throughput. We assume that each server can work on only one job at a time, that several servers can work together on a single job, and that the travel times between stations are negligible. Under these assumptions, we completely characterize the optimal policy for systems with three servers. We also provide a conjecture for the structure of the optimal policy for systems with four or more servers that is supported by extensive numerical evidence. Finally, we develop heuristic server-assignment policies for systems with three or more servers that are easy to implement, robust with respect to the server capabilities, and generally appear to yield near-optimal long-run average throughput.
Menopausal Status, Moderate-Intensity Walking, and Symptoms in Midlife Women
Authors: Wilbur JoEllen , Miller Arlene Michaels , McDevitt Judith , Wang Edward , Miller Josephine
Published: July 2005

The purpose of this randomized clinical trial study was to determine the effectiveness of a 24-week, home-based, moderate-intensity, walking intervention in improving symptoms (vasomotor, uro-genital/sexual, sleep, psychological, cognitive, physical) experienced by midlife women. One hundred and seventy-three Caucasian and African American women aged 45 to 65 who were not on hormone therapy, had no major signs or symptoms of cardiovascular disease, and were sedentary in their leisure activity were randomly assigned to the moderate-intensity walking group or the nonexercise control group. The exercise prescription was walking at a frequency of 4 times a week for a duration of 20 to 30 minutes. The symptom impact inventory included the frequency, intensity, and bothersomeness of 33 symptoms collected at baseline and 24 weeks. Adherence was measured with a heart rate monitor and exercise log. Average adherence to frequency of walking was 71.6% of the expected walks. After 24 weeks, there were no differences between the walking and control group on change in symptoms. However, multiple regression revealed that frequency of adherence to walking along with change in physical symptoms and menopausal status were significant predictors of change in sleep symptoms. While walking did not improve most symptoms experienced by midlife women, frequency of walking may improve sleep.
Coalescence of immiscible polymer blends in chaotic mixers
Authors: Perilla Jairo E. , Jana Sadhan C.
Published: July 2005

The study evaluated if excellent mixing conditions prevailing in chaotic mixers also promote droplet coalescence in the mixing of immiscible polymers. A combined approach of experiments and simplified modeling was used to understand the effects of the degree of chaotic mixing, shear rate, and viscosity ratio on coalescence rates. It was found experimentally that the extent of coalescence was substantially reduced when the bulk of the fluid in the mixer experienced chaotic mixing. In addition, coalescence was subdued at higher rates of shear and for higher viscosity ratio droplets. Pseudo‐steady state droplet size distributions were reached faster with higher droplet volume fractions and for higher viscosity ratio droplets. © 2005 American Institute of Chemical Engineers AIChE J, 2005
Modelling the structural behaviour of a dam affected by alkali–silica reaction
Authors: Fairbairn Eduardo M. R. , Ribeiro Fernando L. B. , Lopes Luciana E. , Toledo‐Filho Romildo D. , Silvoso Marcos M.
Published: July 2005

In this work we present an alkali–silica reaction (ASR) thermo‐chemo‐mechanical expansion model, whose main feature is to represent the stress‐induced anisotropy by means of a classical smeared cracking model. This model considers the influence of temperature and humidity in the development of ASR. Since cracking occurs generally at the beginning of the swelling process, it is suggested that the assessment of the reaction characteristics in free expansion tests could be attained considering a cracked specimen. Hence, an inverse analysis is used to determine ASR parameters. The model was applied to the 3D simulation of alkali–silica expansion in a real gravity dam. We computed the displacements at the crest of the block comparing it with measures taken in situ for the last 25 years. The good correlation between experimental and numerical data displays the accuracy of the model, indicating its potentialities for engineering applications. Copyright © 2005 John Wiley & Sons, Ltd.
Ultrafast Fluorescence Depolarisation in the Yellow Fluorescent Protein due to Its Dimerisation
Authors: Jung Gregor , Ma Yingzhong , Prall Bradley S. , Fleming Graham R.
Published: July 2005

Transient absorption spectroscopy with sub‐100 fs time resolution was performed to investigate the oligomerisation behaviour of eYFP in solution. A single time constant τAD=2.2±0.15 ps is sufficient to describe the time‐resolved anisotropy decay up to at least 200 ps. The close contact of two protein barrels is deduced as the exclusive aggregation state in solution. From the final anisotropy r∞=0.28±0.02, the underlying quaternary structure can be traced back to the somewhat distorted structure of the dimers of wt‐GFP. The use of autofluorescent proteins as rulers in Förster resonance energy transfer (FRET) measurements may demand polarisation‐sensitive detection of the fluorescence with high time resolution.
Structural Colors in Nature: The Role of Regularity and Irregularity in the Structure
Authors: Kinoshita Shuichi , Yoshioka Shinya
Published: July 2005

Coloring in nature mostly comes from the inherent colors of materials, but it sometimes has a purely physical origin, such as diffraction or interference of light. The latter, called structural color or iridescence, has long been a problem of scientific interest. Recently, structural colors have attracted great interest because their applications have been rapidly progressing in many fields related to vision, such as the paint, automobile, cosmetics, and textile industries. As the research progresses, however, it has become clear that these colors are due to the presence of surprisingly minute microstructures, which are hardly attainable even by ultramodern nanotechnology. Fundamentally, most of the structural colors originate from basic optical processes represented by thin‐film interference, multilayer interference, a diffraction grating effect, photonic crystals, light scattering, and so on. However, to enhance the perception of the eyes, natural creatures have produced various designs, in the course of evolution, to fulfill simultaneously high reflectivity in a specific wavelength range and the generation of diffusive light in a wide angular range. At a glance, these two characteristics seem to contradict each other in the usual optical sense, but these seemingly conflicting requirements are realized by combining appropriate amounts of regularity and irregularity of the structure. In this Review, we first explain the fundamental optical properties underlying the structural colors, and then survey these mysteries of nature from the viewpoint of regularity and irregularity of the structure. Finally, we propose a general principle of structural colors based on structural hierarchy and show their up‐to‐date applications.
Paradoxical Solvent Effects on the Absorption and Emission Spectra of Amino‐Substituted Perylene Monoimides
Authors: Zoon Peter D. , Brouwer Albert M.
Published: July 2005

In N‐(2,5‐di‐tert‐butylphenyl)‐9‐pyrrolidinoperylene‐3,4‐dicarboximide (5PI) the absorption and emission spectra display large solvatochromic shifts, but, remarkably, the Stokes shift is practically independent of solvent polarity. This unique behavior is caused by the extraordinarily large ground‐state dipole moment of 5PI, which further increases upon increasing the solvent polarity, whereas the excited‐state dipole moment is less solvent dependent. In the corresponding piperidine compound, 6PI, this effect is much less important owing to the weaker coupling between the amino group and the aromatic imide moiety, and in the corresponding naphthalimide, 5NI, it is absent. The latter shows the conventional solvatochromic behavior of a push–pull substituted conjugated system, that is, minor shifts in absorption and a larger change in the emission energy with solvent polarity.
Bis[di(2,2,2‐trifluoroethyl)dithiocarbamato]CuII: A Volatile Precursor for the Efficient Growth of Cuprous Sulfide Films by MOCVD
Authors: McCain M. N. , Metz A. W. , Yang Y. , Stern C. L. , Marks T. J.
Published: July 2005

The air‐stable, highly volatile precursor bis[di(2,2,2‐trifluoroethyl) dithiocarbamato]copper(II)(see Figure) has been fully characterized by single‐crystal XRD and thermogravimetric analysis, and shown to be a highly effective single‐source precursor for the deposition of high‐quality p‐type cuprous sulfide films by MOCVD. As‐deposited films are phase‐pure and polycrystalline, as indicated by XRD and X‐ray photoelectron spectroscopy.
A Multiscale Simulation Approach for the MOCVD of GaN Using a Single‐Molecule Precursor in a Vertical Stagnation Flow Reactor
Authors: Mukinovic M. , Brenner G. , Khanderi J. , Spöllmann S. , Fischer R. A. , Tafipolsky M. , Cadenbach T. , Schmid R.
Published: July 2005

A multiscale simulation approach, including atomistic quantum mechanical calculations on the molecular scale and physical continuum mechanical process simulations on the macroscopic scale, has been used to study the initial gas‐phase decomposition of a single‐molecule precursor. The compound bisazido(dimethylaminopropyl)gallium (BAZIGA), that forms gallium nitride in the absence of other nitrogen sources, is proposed to decompose by a multistep reaction mechanism to the key intermediate, GaN3. The reaction rates for the effective overall reaction were derived on the basis of transition state theory in an ab initio fashion from the results of density functional theory‐type calculations. Methods to accurately approximate the entropic contributions to the free energies of activation for the elementary steps were developed and employed. The calculated rates were fit to an Arrhenius type rate law with an apparent energy of activation of Ea = 321 kJ mol–1 (A = 9.90×1020 s–1). Process simulations were performed for a real vertical stagnation flow test reactor. The inclusion of radiative heat transfer was found to be crucial to reproduce the experimentally determined temperature distribution on the reactor wall. By inclusion of the gas phase decomposition to GaN3 in terms of an effective one‐step reaction, only the intermediate GaN3 was found to contribute to film growth. It is concluded that all parent precursor molecules decompose in the hot zone above the substrate and do not reach the surface under the given conditions.
MOCVD of YF3 and Y1–xErxF3 Thin Films from Precursors Synthesized In Situ
Authors: Condorelli G. G. , Anastasi G. , Fragalà I. L.
Published: July 2005

RE(hfac)3 precursors (RE = Y, Er and Hhfac=1,1,1,5,5,5‐hexafluoroacetylacetonate) have been obtained in‐situ in a metal‐organic (MO) CVD reactor by vapor‐solid reaction between Hhfac and powders of suitable mixtures of RE2O3 oxides. YF3 and Y1–xErxF3 (x ≈ 0.2) ultra‐thin films have been deposited over glass substrates under Ar/O2 environments. Fourier‐transform infrared (FTIR) in‐situ measurements have been used to identify the nature of the precursor species in the gas phase, as well as to investigate decomposition mechanisms which accompany the film growth. Deposition involves the breakdown of the metal–ligand bond, thus leading to free Hhfac ligands and fluorinated ketones. Films have been characterized by energy dispersive X‐ray (EDX) microanalysis, grazing incidence X‐ray diffraction (GIXRD), X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).
Metal‐Organic CVD of Conductive and Crystalline Hafnium Nitride Films
Authors: Kim Y. , Baunemann A. , Parala H. , Devi A. , Fischer R. A.
Published: July 2005

HfN films have been deposited on Si, SiO2, and Al2O3 substrates by MOCVD using Hf(NMe2)4 and Me2NNH2 (DMHy) in the deposition temperature range 600–800 °C. The resistivity and morphology of the films strongly depends on the deposition temperature. A cubic polycrystalline and conductive HfN film deposited at 800 °C shows the lowest resistivity, of approximately 1020 μΩ·cm. The HfN film was slightly nitrogen‐rich and the film density was 12.9 g cm–3. It was found that DMHy and the high deposition temperature were important factors for the growth of good‐quality HfN films.
CVD of Titanium Oxide Thin Films from the Reaction of Tetrakis(dimethylamido)‐ titanium with Oxygen
Authors: Woods J. B. , Beach D. B. , Nygren C. L. , Xue Z.‐L.
Published: July 2005

TiO2 thin films on silicon wafers have been prepared from the reaction of Ti(NMe2)4 with O2 at 250–300 °C by CVD processes. These films, which are carbon free and contain no TiN or TiOxNy species, are amorphous before annealing but crystalline anatase after annealing at 600 °C in air. The average dielectric constant (κ) of the annealed films is 50(5), with an average leakage current of 5(3)×10–5 A cm–2, and breakdown strength of 1.8(0.3) MV cm–1.
Laser‐Assisted Atomic Layer Deposition of Boron Nitride Thin Films
Authors: Olander J. , Ottosson L. M. , Heszler P. , Carlsson J.‐O. , Larsson K. M. E.
Published: July 2005

Boron nitride thin films have been grown by both laser‐assisted, and conventional atomic layer deposition (LALD/ALD) at temperatures in the range 250–750 °C. Both the NH3 and BBr3 precursors were appreciably dissociated by the ArF excimer laser, and up to 600 °C, the growth rate was 100 % higher for the LALD process than for ALD. The films consisted of hydrogen‐terminated turbostratic BN grains. H2 was theoretically found to bind as strongly as BBrX and NHX (X = 0–2) to hBN(100) edges. The fresh films were stoichiometric with respect to B and N, and contained low degrees of contamination, but oxidized easily in air.
Deposition of Thin Films of SiOxCyH in a Surfatron Microwave Plasma Reactor with Hexamethyldisiloxane as Precursor
Authors: Walkiewicz‐Pietrzykowska A. , Cotrino J. , González‐Elipe A. R.
Published: July 2005

Thin films of SiOxCyH have been prepared by plasma enhanced (PE)CVD in a surface‐wave, microwave reactor. The films were deposited in direct mode by using hexamethyldisiloxane (HMDSO) as the precursor, and mixtures of oxygen/argon as the plasma gas. Analysis of the plasma by optical emission spectroscopy (OES) showed that, under reaction conditions, the molecules of the precursor are not greatly fragmented in the plasma. This suggests that polymerization occurs after adsorption of the precursor species on the surface of the growing films. The chemical structure and composition of the films were examined by Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). A strong correlation is found between the composition and bonding structure of the thin films and the oxygen:HMDSO ratio in the plasma gas. Raising the oxygen concentration leads to an increase in the growth rate and to the removal of the organic groups from the films that, for O2:HMDSO ratios greater than 0.8, reach a composition close to silicon dioxide. It has been shown that the Auger parameter of silicon determined by XPS depends on the composition of the films (e.g., 1714.5 for O2:HMDSO = 0, and 1712.3 for O2:HMDSO = 0.75). It is shown that this parameter can be taken as a measurement of the polarizability of the films. It is concluded that surfatron launchers are a versatile set‐up for an efficient control of the composition and properties of thin films of SiOxCyH prepared by PECVD.
Deposition of HfO2 Films by Liquid Injection MOCVD Using a New Monomeric Alkoxide Precursor, [Hf(dmop)4]
Authors: Loo Y. F. , O'Kane R. , Jones A. C. , Aspinall H. C. , Potter R. J. , Chalker P. R. , Bickley J. F. , Taylor S. , Smith L. M.
Published: July 2005

Thin films of HfO2 have been deposited by liquid injection metal‐organic (MO)CVD using the new alkoxide precursor [Hf(dmop)4] (dmop = 2‐(4,4‐dimethyloxazolinyl)‐propanolate). The crystal structure of [Hf(dmop)4] has been determined, and shows it to be a six‐coordinate monomeric complex. [Hf(dmop)4] is volatile and is significantly less reactive to air and moisture than simple Hf alkoxide complexes such as [Hf(OtBu)4]. The HfO2 thin films were deposited over substrate temperatures ranging from 350 °C to 650 °C. Analysis by X‐ray diffraction (XRD) shows that the films are amorphous at deposition temperatures of 400 °C and below. At substrate temperatures above 450 °C, the films adopt a monoclinic (α‐HfO2) phase with a fiber texture dependent upon growth temperature. Analysis by Auger electron spectroscopy (AES) shows that the films are non‐stoichiometric and contain residual carbon (2.1 – 11.6 at.‐%) and nitrogen (0.4 – 1.9 at.‐%).
Editorial: 10 Years of CVD
Authors: Hitchman M. L.
Published: July 2005

It has been said that ‘the ultimate function of prophecy is not to tell the future, but to make it.’ To celebrate the 10th anniversary of CVD, the Editor, Michael Hitchman, looks back at the predictions made at the launch of the journal to see just how well CVD has succeeded in making its own future over the past ten years, and to prove that the prophet might indeed not be without honor, even in his own land...
Supramolecular Cations of (S)‐, (R)‐, and (RS)‐Indan‐1‐aminium(dibenzo[18]crown‐6) in Magnetic [Ni(dmit)2]– Salts
Authors: Akutagawa Tomoyuki , Matsuura Kazumasa , Nishihara Sadafumi , Noro Shin‐ichiro , Nakamura Takayoshi
Published: July 2005

Magnetic crystals were formed using supramolecular cation structures that consist of (S)‐AIH+(dibenzo[18]crown‐6), (R)‐AIH+(dibenzo[18]crown‐6), or (RS)‐AIH+(dibenzo[18]crown‐6) (AIH+ = indan‐1‐aminium) as the counter cation to [Ni(dmit)2]– ions (dmit2– = 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate), which bear one S = 1/2 spin. The resulting salts, (S)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (1), (R)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (2), and (RS)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (3), feature supramolecular cations that are formed through the inclusion of the ammonium moiety of AIH+ into the cavity of dibenzo[18]crown‐6 through N–H···O hydrogen bonds. Salts 1, 2, and 3 possess space groups of P21, P21, and P2/m, respectively, and possess similar molecular packings. Chiral cations (S)‐AIH+ (salt 1) and (R)‐AIH+ (salt 2) yielded chiral crystals, whereas racemic (RS)‐AIH+ (salt 3) afforded a racemic crystal with a mirror plane. Within the crystals, alternating layers of [Ni(dmit)2]– ions and(AIH+)(dibenzo[18]crown‐6) cations formed a layered structure along the b axis. Since the 21 axis of salts 1 and 2 were observed along the b axis, effective chiral magnetic interactions between the [Ni(dmit)2]– ions were not observed. In the ac plane, weak interactions among the [Ni(dmit)2]– ions formed a two‐dimensional layer. Temperature‐dependent magnetic susceptibilities of salts 1, 2, and 3 exhibited aCurie–Weiss‐type behavior, which shows weak antiferromagnetic interactions between the [Ni(dmit)2]– ions, with Weiss temperatures of –2.9, –2.9, and –4.2 K, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)