bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuzzy systems and fuzzy expert control: An overview
Authors: Tzafestas Spyros G.
Published: July 2009

This paper presents an overview of fuzzy set theory and its application to the analysis and design of fuzzy expert control systems. Starting with a short account of the basic concepts and properties of fuzzy sets and fuzzy reasoning, a few fuzzy rule-based controllers, viz, basic single-input singleoutput fuzzy control, self-organizing fuzzy control, fuzzy PID supervisor, and the fuzzy PID incremental controller, are described in some detail. Then a survey of the theoretical results and applications is provided which gives a good picture of the current status of the field. This survey includes the work on neuro-fuzzy systems, and software systems for the representation and processing of fuzzy information. The paper closes with four application examples which show the type of results that must be expected from fuzzy expert control.
Artificial intellugence and knowledge based systems in molecular biology
Authors: Fox John , Rawlings Christopher J.
Published: July 2009

Over the last ten years, molecular biologists and computer scientists have experimented with various artificial intelligence techniques, notably knowledge based and expert systems, qualitative simulation, natural language processing and various machine learning techniques. These techniques have been applied to problems in molecular data analysis, construction of advanced databases and modelling of biological systems. Practical results are now being obtained, notably in the representation and recognition of genetically significant structures, the assembly of genetic maps and prediction of the structure of complex molecules such as proteins. The paper outlines the principal methods used, surveys the findings to date, and identifies promising trends and current limitations.
Case-based reasoning: A review
Authors: Watson Ian , Marir Farhi
Published: July 2009

Case-Based Reasoning (CBR) is a relatively recent problem solving technique that is attracting increasing attention. However, the number of people with first-hand theoretical or practical experience of CBR is still small. The main objective of this review is to provide a comprehensive overview of the subject to people new to CBR. The paper outlines the development of CBR in the US in the 1980s. It describes the fundamental techniques of CBR and contrasts its approach to that of model-based reasoning systems.1A critical review of currently available CBR software tools is followed by descriptions of CBR applications both from academic research and, in more detail, three CBR systems that are presently being used commercially. Each of the three commercial case studies highlights features that made CBR particularly suitable for the application. Moreover, the last case study describes a development methodology for implementing CBR systems. The paper concludes with a research agenda for CBR. A detailed categorized bibliography of CBR research is provided in a companion paper (Marir & Watson, 1994).
Case-based reasoning: a categorized bibliography
Authors: Marir Farhi , Watson Ian
Published: July 2009

Case-Based Reasoning (CBR) is a fresh reasoning paradigm for the design of expert systems in domains that may not be appropriate for other reasoning paradigms such as model-based reasoning. As a result of this, and because of its resemblance to human reasoning, CBR has attracted increasing interest both from those experienced in developing expert systems and from novices. Although CBR is a relatively new discipline, there are an increasing number of papers and books being published on the subject. In this context, this bibliographic categorization is an accompanying paper to a review of CBR by the same authors. The objective of this paper is to help researchers quickly identify relevant references.
Hybrid case-based reasoning
Authors: Hunt John , Miles Roger
Published: July 2009

This paper reviews a number of hybrid Case-Based Reasoning (CBR) systems. These systems are hybrid because the CBR components cooperate with one or more “co-reasoners” which employ a different type of reasoning strategy (e.g. qualitative simulation, constraint satisfaction, etc.). In this paper, we propose that CBR is in fact an inherently hybrid process. We review a number of systems and identify three classes of architecture which have been used for hybrid systems. We believe that to successfully exploit a co-reasoner within a CBR system it is necessary to analyse where, when, why and how the information provided by the co-reasoner will be used. We propose the KADS methodology as a suitable way of performing such an analysis and illustrate its use by example. We conclude by considering the control issues associated with the construction of hybrid CBR systems. We review the requirements of such systems and consider how well the two existing cooperation architectures match those requirements.
ECAl'94 Workshop on Formal Specification Methods for Knowledge-bassed Systems
Authors: Fensel Dieter
Published: July 2009

The Workshop on Formal Specification Methods for Knowledge-based Systems (KBS) took place in Amsterdam on August 8 1994 as part of the workshop program of the 11th European Conference on Artificial Intelligence (ECAI'94). It was the sixth workshop in a series concerned with the development and application of formal and executable specification languages for KBSs. Starting from the first familiarization workshop at GMD in Bonn 1992, where the different research groups met for the first time, further successor workshops were held at the University of Karlsruhe, the University of Amsterdam, and again at GMD in Bonn. Additionally, at ECAI'92 in Vienna, a workshop was held to compare different specification approaches for complex multi-layered KBSs.
Cognitive expertise research and knowledge engineering
Authors: Bolger Fergus
Published: July 2009

This paper is a review of research into cognitive expertise. The review is organized in terms of a simple model of the knowledge and cognitive processes that might be expected to be enhanced in experts relative to non-experts. This focus on cognitivecompetenceunderlying expert performance permits the identification of skills and knowledge that we might wish to capture and model in expert systems. The competence perspective also indicates areas of weakness in human experts. In these areas, we might wish to support or replace the expert with, for example, a normative system rather than attempting to model his or her knowledge.
A review of human linguistic probability processing: General principles and empirical evidence
Authors: Wallsten Thomas S. , Budescu David V.
Published: July 2009

This article reviews research on how people use and understand linguistic expressions of uncertainty, with a view toward the needs of researchers and others interested in artificial intelligence systems. We discuss and present empirical results within an inductively developed theoretical framework consisting of two background assumptions and six principles describing the underlying cognitive processes.
Information processing and the management of uncertainty
Authors: Parsons Simon , saffiotti Alessandro
Published: July 2009

The First International Conference on Information Processing and the Management of Uncertainty (IPMU) was held in 1986 at a time of great debate about the necessity of modelling uncertainty in intelligent systems (which at that time largely meant rule-based expert systems) and the best way of doing so. Whereas the founders of the Conference on Uncertainty in Artificial Intelligence (UAI) in the United States set out with the aim of promoting the use of probability, the organisers of IPMU chose a diametrically opposed course. Though there were a few papers on probability at IPMU '86, the main focus was on alternative methods, primarily those based upon fuzzy sets. Though subsequent conferences have seen greater mix of papers, IPMU remains largely non-probabilistic with the result that the bulk of the participants come from Europe rather than the United States (despite the large amount of work on uncertainty, and especially probability, that is carried out in the US) making IPMU something of a counterpoint to UAT. The difference in participation is exacerbated by the location—whilst the UAI remains in North America, IPMU alternates between Paris and other cities in Europe, including Urbino in 1988 and Palma in 1992.
The Legal Applications of Logic Programming Workshop at the ICLP 94 Conference
Authors: Tiscornia Daniela
Published: July 2009

The representation of parts of legislation in logic, successively implemented in the language oflogic programmingand managed by Prolog interpreters, has by now existed for more than ten years. The first and most well-known projects were those by theLogic Programming Groupof Imperial College of London which, in 1985, formalized theBritish Nationality Act(Sergot et al., 1986; Sergot, 1990). Other projects followed, for the most part European, including the Italian project, Esplex, developed in Florence (Biagioli et al., 1987), the Dutch project,Prolex, (Walker et al., 1990), the German project born of the collaboration between IBM and the University of Tubingen (Alschwee, Grundrnann, 1986), and the Japanese project,Les-2(Yoshino, 1986).
Verification and validation of knowledge-based systems with formal specifications
Authors: Meseguer Pedro , Preece Alun D.
Published: July 2009

This paper examines how formal specification techniques can support the verification and validation (V&V) of knowledge-based systems. Formal specification techniques provide levels of description which support both verification and validation, and V&V techniques feed back to assist the development of the specifications. Developing a formal specification for a system requires the prior construction of a conceptual model for the intended system. Many elements of this conceptual model can be effectively used to support V&V. Using these elements, the V&V process becomes deeper and more elaborate, and it produces results of a better quality compared with the V&V activities which can be performed on systems developed without conceptual models. However, we note that there are concerns in using formal specification techniques for V&V, not least being the effort involved in creating the specifications.
Formal specification languages in knowledge and software engineering
Authors: Fensel Dieter
Published: July 2009

During the last few years, a number of formal specification languages for knowledge-based systems (KBS) have been developed. Characteristics of such systems are a complex knowledge base and an inference engine which uses this knowledge to solve a given problem. Languages for KBS have to cover both these aspects. They have to provide a means to specify a complex and large amount of knowledge and they have to provide a means to specify the dynamic reasoning behaviour of a KBS. Nevertheless, KBS are just a specific type of software system. Therefore, it seems quite natural to compare formal languages for specifying KBS with formal languages which were developed by the software community for specifying software systems. That is the subject of this paper.
An introduction to executable temporal logics
Authors: Fisher Michael
Published: July 2009

In recent years a number of programming languages based upon the direct execution of temporal logic formulae have been developed. The use of such logics provides a powerful basis for the representation and implementation of a range of dynamic behaviours. Though many of these languages are still experimental, they are beginning to be applied, not only in computer science and AI, but also in less obvious areas such as user interfaces, process control and social modelling. This article provides an introduction to some of the basic concepts of executable temporal logics, together with an overview of the main approaches being pursued.
An integrated approach for different attribute types in nearest neighbour classification
Authors: Liu W. Z.
Published: July 2009

The basic nearest neighbour algorithm works by storing the training instances and classifying a new case by predicting that it has the same class as its nearest stored instance. To measure the distance between instances, some distance metric needs to be used. In situations when all attributes have numeric values, the conventional nearest neighbour method treats examples as points in feature spaces and uses Euclidean distance as the distance metric. In tasks with only nominal attributes, the simple “over-lap” metric is usually used. To handle classification tasks that have mixed types of attributes, the twodifferentmetrics are simply combined. Work by researchers in the machine learning field has shown that this approach performs poorly. This paper attempts to study a more recently developed distance metric and show that this metric is capable of measuring the importance of different attributes. With the use of discretisation for numeric-valued attributes, this method provides an integrated way in dealing with problem domains with mixtures of attribute types. Through detailed analyses, this paper tries to provide further insights into the understanding of nearest neighbour classification techniques and promote further use of this type of classification algorithm.
Third international workshop on deontic logic in computer science
Authors: Brown Mark A. , Carno Jose
Published: July 2009

The Third International Workshop on Deontic Logic in Computer Science (ΔEON'96) took place in Sesimbra, Portugal, from 11–13 January 1996. It consisted of 12 refereed technical presentations and four invited talks. The invited speakers were Nuel Belnap (Pittsburgh University, USA), Andrew Jones (Oslo University, Norway), Krister Segerberg (Uppsala University, Sweden) and Marek Sergot (Imperial College, UK).
International workshop on Advanced Visual Interfaces: AVI '96 Gubbio, Italy
Authors: Levialdi Stefano
Published: July 2009

It is well known that a program—to accomplish any task—is welcomed by new users as long as it is easy to use, to understand, to learn. In the recent past, programs were written first and a nice adhoc interface was added later. The look and feel of this interface gradually became the convincing part of the whole system (program plus interface): in fact the way in which the screen presented the available commands, the possibility of on-line help, of undo operations, etc. were firstly greeted and then requested by the new users of complex programs.
Declarative specifications
Authors: Fuchs Norbert E. , Robertson David
Published: July 2009

Deriving formal specifications from informal requirements is extremely difficult since one has to overcome the conceptual gap between an application domain and the domain of formal specification methods. To reduce this gap we introduce application-specific specification languages, i.e., graphical and textual notations that can be unambiguously mapped to formal specifications in a logic language. We describe a number of realised approaches based on this idea, and evaluate them with respect to their domain specificity vs. generality.
Logic engineering in medicine
Authors: Lucas Peter J. F.
Published: July 2009

The safety-critical nature of the application of knowledge-based systems to the field of medicine requires the adoption of reliable engineering principles with a solid foundation for their construction. Logical languages with their inherent, precise notions of consistency, soundness and completeness provide such a foundation, thus promoting scrupulous engineering of medical knowledge. Moreover, logic techniques provide a powerful means for getting insight into the structure and meaning of medical knowledge used in medical problem solving. Unfortunately, logic is currently only used on a small scale for building practical medical knowledge-based systems. In this paper, the various approaches proposed in the literature are reviewed, and related to the various types of knowledge and problem solving employed in the medical field. The appropriateness of logic for building medical knowledge-based expert systems is further motivated.
Provenance and post-depositional low-temperature evolution of the James Ross Basin sedimentary rocks (Antarctic Peninsula) based on fission track analysis
Authors: Svojtka Martin , Nývlt Daniel , Murakami Masaki , Vávrová Jitka , Filip Jiří , Mixa Petr
Published: July 2009

Zircon and apatite fission track (AFT) thermochronology was applied to the James Ross Basin sedimentary rocks from James Ross and Seymour islands. The probable sources of these sediments were generated in Carboniferous to Early Paleogene times (∼315 to 60 Ma). The total depths of individual James Ross Basin formations are discussed. The AFT data were modelled, and the thermal history model was reconstructed for samples from Seymour Island. The first stage after a period of total thermal annealing (when the samples were above 120°C) involved Late Triassic cooling (∼230 to 200 Ma) and is followed by a period of steady cooling through the whole apatite partial annealing zone (PAZ, 60–120°C) to minimum temperature in Paleocene/Early Eocene. The next stage was the maximum burial of sedimentary rocks in the Eocene (∼35 Ma, 1.1–1.8 km) and the final cooling and uplift of Seymour Island sedimentary rocks at ∼35 to 20 Ma.
A unifying perspective on personality pathology across the life span: Developmental considerations for the fifth edition of theDiagnostic and Statistical Manual of Mental Disorders
Authors: Tackett Jennifer L. , Balsis Steve , Oltmanns Thomas F. , Krueger Robert F.
Published: July 2009

Proposed changes in the fifth edition of theDiagnostic and Statistical Manual of Mental Disorders(DSM-V) include replacing current personality disorder (PD) categories on Axis II with a taxonomy of dimensional maladaptive personality traits. Most of the work on dimensional models of personality pathology, and on personality disorders per se, has been conducted on young and middle-aged adult populations. Numerous questions remain regarding the applicability and limitations of applying various PD models to early and later life. In the present paper, we provide an overview of such dimensional models and review current proposals for conceptualizing PDs inDSM-V. Next, we extensively review existing evidence on the development, measurement, and manifestation of personality pathology in early and later life focusing on those issues deemed most relevant for informingDSM-V. Finally, we present overall conclusions regarding the need to incorporate developmental issues in conceptualizing PDs inDSM-Vand highlight the advantages of a dimensional model in unifying PD perspectives across the life span.
Predictors of withdrawal: Possible precursors of avoidant personality disorder
Authors: Eggum Natalie D. , Eisenberg Nancy , Spinrad Tracy L. , Valiente Carlos , Edwards Alison , Kupfer Anne S. , Reiser Mark
Published: July 2009

Relations of avoidant personality disorder (AvPD) with shyness and inhibition suggest that a precursor of AvPD is withdrawal. Using a sample of 4.5- to 7-year-olds studied four times, 2 years apart, four and three classes of children differing in trajectories of mother- and teacher-reported withdrawal, respectively, were identified. Mothers and teachers generally did not agree on children's trajectories but the pattern of findings in the two contexts did not differ markedly. The mother-identified high and declining withdrawal class, in comparison with less withdrawn classes, and the teacher-identified high and declining class compared with low withdrawal classes, were associated with relatively high levels of anger and low levels of attentional control and resiliency. The mother-identified moderate and increasing withdrawal class was distinguished from less problematic withdrawal classes by higher anger, lower resiliency, and sometimes, lower attentional control. The teacher-identified low and increasing withdrawal class was distinguished from less problematic withdrawal classes by lower resiliency and lower attentional control. Findings are discussed in terms of the developmental precursors to social withdrawal and avoidant behavior.
Childhood personality pathology: Dimensional stability and change
Authors: de Clercq Barbara , van Leeuwen Karla , van den Noortgate Wim , de Bolle Marleen , de Fruyt Filip
Published: July 2009

Studies on the developmental course of personality disorders have suggested that adult personality disorders enclose both features with a natural plasticity over time, as well as stable components represented by underlying trait dimensions. The current study broadens this dimensional stability perspective toward an earlier developmental stage, and describes with different indices of stability the longitudinal behavior of basic childhood maladaptive trait dimensions in a community sample of 477 Flemish children. The results underscore structural, rank-order, and within-person stability for the disagreeableness, emotional instability, introversion, and compulsivity dimensions and suggest a similar maturation principle as has been proposed for adults. Individual growth curve analyses indicate that children's maladaptive trait scores generally decrease as they grow older, with a smaller decline for high-scoring individuals. Childhood maladaptive traits and general psychopathology dimensions show similar longitudinal patterns in terms of shape and change over time, supporting a spectrum conceptualization of Axis I related pathology and personality disorder precursors at young age. The implications of these findings for a developmental perspective on dimensional conceptualizations of personality disorders are discussed.
Child maltreatment and trajectories of personality and behavioral functioning: Implications for the development of personality disorder
Authors: Kim Jungmeen , Cicchetti Dante , Rogosch Fred A. , Manly Jody Todd
Published: July 2009

This study investigated the longitudinal impact of maltreatment parameters on personality processes and maladjustment and prospective relationships between personality trajectory classes and subsequent maladjustment outcomes. The sample involved maltreated (n= 249) and nonmaltreated (n= 200) children followed longitudinally between ages 6 and 10. Growth mixture modeling indicated multifinality in personality development depending on the risk status (i.e., maltreated vs. nonmaltreated). Two trajectory classes of ego resiliency were identified for maltreated children: those who showed a declining trajectory exhibited greater maladjustment. In contrast, three trajectory classes of ego control were identified for nonmaltreated children; the subgroups showing increases in ego undercontrol or dramatic changes from high ego undercontrol to high ego overcontrol exhibited poor adjustment. Experiencing multiple maltreatment subtypes and physical/sexual abuse were related to higher levels of ego undercontrol and externalizing symptomatology, whereas early onset of maltreatment was associated with the low and decreasing trajectory of ego resiliency and higher levels of internalizing symptomatology. The findings suggest that ego resiliency and ego control, personality processes related to self-regulation, may be important factors in identifying distinct pathways to later personality disorders as well as pathways to resilient functioning.
Neighborhoods and genes and everything in between: Understanding adolescent aggression in social and biological contexts
Authors: Hart Daniel , Marmorstein Naomi R.
Published: July 2009

Adolescent aggression was explored in relation to neighborhood and genetic characteristics. Child saturation (the proportion of the population consisting of children under the age of 15), ethnic heterogeneity, poverty, and urbanicity of neighborhoods were examined in relation to adolescent aggression in 12,098 adolescents followed longitudinally for 1 year. Longitudinal analyses indicated that child saturation was positively associated with increases in aggression, with this finding emerging among those living in the same neighborhood at both testing times and those who moved between testing times. In a subsample of males for whom genetic data were available, the relation of child saturation to adolescent aggression was moderated by the monoamine oxidase A (MAOA) gene. The regression of aggression on child saturation was steeper for those with the low activity version of the MAOA allele than among those with the high activity version of the allele. The implications of the results for an understanding of the origins and ontogeny of aggression and personality disorders are discussed.
Self-heating phenomena in high-power III-N transistors and new thermal characterization methods developed within EU project TARGET
Authors: Kuzmik Jan , Bychikhin Sergey , Pichonat Emmanuelle , Gaquière Christophe , Morvan Erwan , Kohn Erhard , Teyssier Jean-Pierre , Pogany Dionyz
Published: July 2009

In the framework of the Top Amplifier Research Groups in a European Team (TARGET) project, we developed a new electrical method for the temperature measurement of HEMTs and performed several unique studies on the self-heating effects in AlGaN/GaN HEMTs. This method, in combination with transient interferometric mapping (TIM), provides a fundamental understanding of the heat propagation in a transient state of HEMTs. The AlGaN/GaN/Si HEMT thermal resistance was determined to be ~70 K/W after 400 ns from the start of a pulse, and the heating time constant was ~200 ns. Our experimental methods were further applied on multifinger high-power AlGaN/GaN/sapphire HEMTs. The TIM method indicates that the airbridge structure serves as a cooler, removing approximately 10% of the heat energy. In the next study we used TIM and the micro-Raman technique to quantify thermal boundary resistance (TBR) between different wafer materials and GaN epi-structure. We found TBR to be ~7 × 10−8 m2K/W for GaN/Si and ~1.2 × 10−7 m2K/W for GaN/SiC interfaces. The role of TBR at the GaN/sapphire interface was found to be less important.
Three‐way validation of the Rankin Inlet PolarDARN radar velocity measurements
Authors: Koustov A. V. , St.‐Maurice J.‐P. , Sofko G. J. , Andre D. , MacDougall J. W. , Hairston M. R. , Fiori R. A. , Kadochnikov E. E.
Published: July 2009

The newly installed Rankin Inlet HF radar is very similar to other SuperDARN radars but uses a new type of antennae with its back lobe overlooking the auroral zone where ionospheric irregularities occur very frequently. Despite the fact that a special screen has been installed, there is a chance to receive echoes from the back/side lobe, which can affect the observed velocities. In this study, Rankin Inlet HF radar (RKN) velocities are compared with measurements from three independent instruments: the HF radar in Saskatoon, the CADI ionosonde at Resolute Bay, and drift meters on board DMSP satellites passing the RKN field of view. Although data spread and the degree of agreement vary from one comparison to another, the overall conclusion is that even if echoes are received from the back/side lobe, their effect is statistically insignificant. RKN velocities were found to be comparable to those inferred from other instrument outputs; the slope of the best fit line and the correlation coefficient can be as high as 0.7 and 0.8, respectively. The majority of inconsistencies are related to the difference in the spatial and temporal resolutions of the instruments involved in the comparison.
Stress evolution of the San Andreas fault system: Recurrence interval versus locking depth
Authors: Smith‐Konter Bridget , Sandwell David
Published: July 2009

Major ruptures along the San Andreas Fault System (SAFS) are driven by stress that has accumulated in the upper locked portion of the crust. The present‐day stress accumulation rate on any given fault segment is fairly well resolved by current geodetic measurements. Model stress accumulation rates vary between 0.5 and 7 MPa per century and are inversely proportional to earthquake recurrence intervals. In contrast, the total accumulated stress on a given fault segment is poorly resolved since it depends on the uncertain rupture history of each fault over the past few thousand years. We simulate accumulated stress at crustal depths for both past and present‐day conditions by assuming complete release of accumulated slip deficit during major ruptures. These speculative results indicate that the southern San Andreas, which has not ruptured in a major earthquake in over 300 years, is currently approaching a threshold stress level.
Toward linking weather and climate in the interactive ensemble NCAR climate model
Authors: Kirtman Ben P. , Straus David M. , Min Dughong , Schneider Edwin K. , Siqueira Leo
Published: July 2009

Diagnosing how much low frequency climate variability is due to intrinsic coupled (i.e., interactions among the components of the climate system) modes and how much is stochastically forced by internal dynamics (e.g., weather noise forcing ocean variability or ocean dynamics associated with western boundary current forcing atmospheric variability) remains a challenge in climate research. Here we present a methodology for separating the intrinsic coupled modes from the stochastically forced variability that can be applied at the air‐sea, air‐land, air‐ice or ice‐ocean interface. In the results presented here, we focus on the air‐sea interface and apply the approach to the National Center for Atmospheric Research Community Climate System Model. We find that coupled ocean‐atmosphere feedbacks contribute to a significant fraction of the sea surface temperature variability worldwide with increasing importance in the tropics. One of the by‐products of the experiments presented here is an improved diagnostic tool for understanding atmospheric teleconnections. In this regard, we find that the mid‐latitude atmospheric response to tropical forcing is not simply a function of the magnitude of the forcing.
Estimating biomass consumed from fire using MODIS FRE
Authors: Ellicott Evan , Vermote Eric , Giglio Louis , Roberts Gareth
Published: July 2009

Biomass burning is an important global phenomenon impacting atmospheric composition. Application of satellite based measures of fire radiative energy (FRE) has been shown to be effective for estimating biomass consumed, which can then be used to estimate gas and aerosol emissions. However, application of FRE has been limited in both temporal and spatial scale. In this paper we offer a methodology to estimate FRE globally for 2001–2007 at monthly time steps using MODIS. Accuracy assessment shows that our FRE estimates are precise (R2 = 0.85), but may be underestimated. Global estimates of FRE show that Africa and South America dominate biomass burning, accounting for nearly 70% of the annual FRE generated. Applying FRE‐based combustion factors to Africa yields an annual average biomass burned of 716–881 Tg of dry matter (DM). Comparison with the GFEDv2 biomass burned estimates shows large annual differences suggesting significant uncertainty remains in emission estimates.
Particle‐size dependent bipolar charging of Martian regolith simulant
Authors: Forward Keith M. , Lacks Daniel J. , Sankaran R. Mohan
Published: July 2009

The intense dust devils and dust storms on Mars are believed to generate large electrostatic fields that significantly alter geophysical and geochemical processes on the planet. The existence of such fields must be related to a mechanism by which charged dust separates by polarity; it has been widely hypothesized that this separation originates from a particle‐size dependence of the charge polarity, but this effect has never been demonstrated. To address this issue, we carry out experiments on the triboelectric charging of Martian regolith simulant (JSC‐1 Mars), using a fluid flow apparatus wherein only particle‐particle interactions occur, as is the case in Martian dust events. Our experiments show direct evidence that smaller particles tend to charge negatively and larger particles tend to charge positively, which provides a mechanism for the charge separation that creates electric fields in Martian dust events.
Evaluation of the relationship between hyperinsulinaemia and myocardial ischaemia/reperfusion injury in a rat model of depression
Authors: Solskov Lasse , Løfgren Bo , Pold Rasmus , Kristiansen Steen B. , Nielsen Torsten T. , Overstreet David H. , Schmitz Ole , Bøtker Hans Erik , Lund Sten , Wegener Gregers
Published: July 2009

Major depression is associated with medical co-morbidity, such as ischaemic heart disease and diabetes, but the underlying pathophysiological mechanisms remain unclear. The FSL (Flinders Sensitive Line) rat is a genetic animal model of depression exhibiting features similar to those of depressed individuals. The aim of the present study was to compare the myocardial responsiveness to I/R (ischaemia/reperfusion) injury and the effects of IPC (ischaemic preconditioning) in hearts from FSL rats using SD (Sprague–Dawley) rats as controls and to characterize differences in glucose metabolism and insulin sensitivity between FSL and SD rats. Hearts were perfused in a Langendorff model and were subjected or not to IPC before 40 min of global ischaemia, followed by 120 min of reperfusion. Myocardial infarct size was found to be significantly larger in the FSL rats than in the SD rats following I/R injury (62.4±4.2 compared with 46.9±2.9%; P<0.05). IPC reduced the infarct size (P<0.01) and improved haemodynamic function (P<0.01) in both FSL and SD rats. No significant difference was found in blood glucose levels between the two groups measured after 12 h of fasting, but fasting plasma insulin (70.1±8.9 compared with 40.9±4.7 pmol/l; P<0.05) and the HOMA (homoeostatic model assessment) index (P<0.01) were significantly higher in FSL rats compared with SD rats. In conclusion, FSL rats had larger infarct sizes following I/R injury and were found to be hyperinsulinaemic compared with SD rats, but appeared to have a maintained cardioprotective mechanism against I/R injury, as IPC reduced infarct size in these rats. This animal model may be useful in future studies when examining the mechanisms that contribute to the cardiovascular complications associated with depression.
Energetics and electronic structure of aluminum point defects in HfO2: A first-principles study
Authors: Hou Z. F. , Gong X. G. , Li Quan
Published: July 2009

Using the plane-wave pseudopotential method within the generalized gradient approximation, we studied the atomic structure, energetics, and electronic structure of the interstitial and substitutional point defect of dopant aluminum in monoclinic HfO2. Our results show that the doped Al atom energetically prefers to substitute for the Hf atom under the oxygen-rich condition. Substitution of Al for Hf creates a shallow acceptor level near the valence band maximum, whereas both substitution of Al for O and interstitial Al introduce deep levels in the band gap of HfO2. We also discussed the possible effect of Al doping on the electronic properties of HfO2.
Computational study of nanometer-scale self-propulsion enabled by asymmetric chemical catalysis
Authors: Shi Yunfeng , Huang Liping , Brenner Donald W.
Published: July 2009

We present a detailed analysis of the self-propulsion of a model nanometer-scale motor by reactive molecular dynamics simulations. The nanomotor is decorated with catalysts on only one side that promotes exothermic reactions of the surrounding fuel. Unidirectional drift of the nanomotor is observed that is superimposed on its Brownian motion. The motor response upon the application of external loads is also investigated and the thermodynamic efficiency is calculated. It is shown that the propulsion of our nanomotor can be understood by a momentum transfer model which is akin to rocket propulsion.
Single-photon and resonance-enhanced multiphoton threshold ionization of the allyl radical
Authors: Gasser Michael , Schulenburg Anna M. , Dietiker Peter M. , Bach Andreas , Merkt Frédéric , Chen Peter
Published: July 2009

Pulsed-field-ionization zero-kinetic-energy photoelectron spectra of jet-cooled allyl radical (C3H5) have been recorded following single-photon and resonant multiphoton excitation. Simulations based on an orbital ionization model and rovibronic photoionization selection rules reliably describe the observed intensity distributions in the photoelectron spectra obtained from single-photon excitation from the ground state and resonant multiphoton excitation via the 3s and the 3p Rydberg states. More than 30 transitions to vibrational levels of the cation were identified and assigned on the basis of predictions from ab initio calculations.
Equilibrium paradigm for field-reversed configurations and application to experiments
Authors: Steinhauer Loren C. , Intrator T. P.
Published: July 2009

Fresh insights on field-reversed configurations (FRCs) are incorporated in a new paradigm for equilibria. In particular four new or unappreciated properties are accounted for: an empirically based scrape-off layer thickness; a new, more accurate axial force balance relation; viscous force regularity at the O-point; and the broken-surface effect. The new paradigm corrects glaring defects of previous models (rigid rotor, Hill’s vortex). Further, the new paradigm is simple enough to be easily used as an interpretive tool despite the limited data suite in most experiments. It is applied to the newly enhanced FRC data compendium, a database of 69 records from 15 facilities. Several important observations and corrections on the previous understanding of FRCs follow, three of which stand out. (1) The traditional axial force balance (“average-β” relation) gives an inaccurate scaling with the separatrix-to-wall radius ratio. (2) The improved equilibrium paradigm yields separatrix particle transport rates of 3–5 m2/s for “best confinement” examples; this is a factor of three lower than crude “bulk” estimates commonly used. (3) The transport compared to the Bohm rate shows a great deal of scatter (40% scatter/mean ratio), i.e., “Bohm” is not a useful representation for transport scaling.
A five-dimensional potential-energy surface for the rotational excitation of SO2 by H2 at low temperatures
Authors: Spielfiedel A. , Senent M.-L. , Dayou F. , Balança C. , Cressiot-Vincent L. , Faure A. , Wiesenfeld L. , Feautrier N.
Published: July 2009

The SO2 molecule is detected in a large variety of astronomical objects, notably molecular clouds and star-forming regions. An accurate modeling of the observations needs a very good knowledge of the collisional excitation rates with H2 because of competition between collisional and radiative processes that excite and quench the different rotational levels of SO2. We report here a five-dimensional, rigid-body, interaction potential for SO2–H2. As a first application, we present rate constants for excitation/de-excitation of the 31 first levels of SO2 by para-H2 at low temperatures. Propensity rules are discussed.
High temperature properties of BiScO3–PbTiO3 piezoelectric ceramics
Authors: Sehirlioglu Alp , Sayir Ali , Dynys Fred
Published: July 2009

Smart actuators and intelligent structures are sought after for aeronautical applications. As a result of high Curie temperature (430 °C) and piezoelectric coefficient (>200 pC/N), BiScO3–PbTiO3 (BS-PT) ceramics are prospective materials for high temperature actuators. This paper reports on the temperature dependent electrical, ferroelectric, and electromechanical properties of liquid phase sintered BS-PT ceramics. Compared to solid state sintered BS-PT, liquid phase sintered BS-PT with Bi2O3 showed improved electrical performance: (1) threefold reduction in loss tangent at elevated temperatures, (2) fivefold increase in dc resistivity at high electrical fields, and (3) 15% increase in high field piezoelectric coefficient. Hysteresis loops of the highly resistive ceramics were saturated and showed no major dependence on the magnitude and the frequency of the applied field. BS-PT ceramics exhibit depoling behavior at temperatures below (>350 °C) the Curie temperature (430 °C). Liquid phase sintering using excess Bi2O3 is shown to be a promising approach to produce superior BS-PT ceramics for high temperature actuators.
Structural, electrical, and magnetic properties of chemical solution deposited BiFe1−xTixO3 and BiFe0.9Ti0.05Co0.05O3 thin films
Authors: Murari N. M. , Thomas R. , Melgarejo R. E. , Pavunny S. P. , Katiyar R. S.
Published: July 2009

BiFeO 3 (BFO), BiFe1−xTixO3, and BiFe0.9Ti0.05Co0.05O3 thin films were deposited on Pt/TiO2/SiO2/Si substrates by chemical solution deposition. BFO film has distorted rhombohedral R3c structure and in BiFe1−xTixO3 (104)/(110) reflections broadened suggesting limited grain growth with Ti substitution. The surface roughness (rms) decreased in the case of Ti substituted BFO. Up to 5% Ti in the lattice reduces the leakage current substantially. For BiFe1−xTixO3, the leakage current qualitatively followed the same trend and the behavior resembles to space charge limited current conduction. The magnetic properties were completely lost by Ti substitution and slightly recovered upon cosubstitution with magnetically active Co. The disappearance of ferromagnetic hysteresis of BFO with Ti substitution and its reappearance with Co is suggestive of the origin of magnetic properties consequential from the BFO lattice itself and hence support it as an intrinsic property of BFO. Capacitance-voltage characteristics of BFO, BiFe0.95Ti0.05O3, and BiFe0.9Ti0.05Co0.05O3 showed butterfly loop indicating ferroelectric property at room temperature as well as at low temperature. However, saturated polarization-voltage hysteresis was not observed in all cases and BiFe0.9Ti0.05Co0.05O3 films showed very poor ferroelectricity compared to BFO and BiFe0.95Ti0.05O3.
Effects of target bias voltage in magnetic tunnel junctions grown by ion beam deposition
Authors: Chen Wei , Nam Dao N. H. , Lu Jiwei , West Kevin G. , Wolf Stuart A.
Published: July 2009

Magnetic tunnel junctions (MTJs) with an AlOx barrier were fabricated by a biased target ion beam deposition (BTIBD) sputtering technique using a low energy ion source (0–50 eV) and voltage biased targets. The BTIBD system applies a bias voltage directly onto the desired targets, providing enough sputtering energy and avoiding overspill contamination during film deposition. The successful deposition of AlOx-MTJs demonstrated the capability of the BTIBD to make multilayer structures with good film quality. MTJ thin film surface roughness and intermixing between layers are among the key problems leading to low tunneling magnetoresistance (TMR) performance. Here we study the effects of bias voltage on MTJ properties via the measurements of the Néel coupling field and TMR. We suggest that a lower bias voltage reduces the intermixing that occurs when a top CoFe free layer is deposited on an AlOx barrier, but produces relatively high surface roughness. On the other hand, higher energy deposition enhances both interlayer mixing and surface flattening. Such understanding of the bias voltage effects on film properties could be used to optimize MTJ performance.
Electron tunneling in conductor-insulator composites with spherical fillers
Authors: Ambrosetti G. , Johner N. , Grimaldi C. , Maeder T. , Ryser P. , Danani A.
Published: July 2009

We report on our Monte Carlo calculations of the conductivity of monosized and conducting spherical particles dispersed in a homogeneous matrix, with interparticle transport mechanism given by electron tunneling. We show that our numerical results can be reproduced by a simple formula based on a critical path analysis and which gives also a practical way to estimate the characteristic tunneling length ξ in real composites. We find that ξ is about 1 nm for several low structure carbon black polymer composites, in agreement with the expected order of magnitude.
Thermoelectric properties of nanoporous Ge
Authors: Lee Joo-Hyoung , Grossman Jeffrey C.
Published: July 2009

We computed thermoelectric properties of nanoporous Ge (np-Ge) with aligned pores along the [001] direction through a combined classical molecular dynamics and first-principles electronic structure approach. A significant reduction in the lattice thermal conductivity of np-Ge leads to a 30-fold increase in the thermoelectric figure-of-merit (ZT) compared to that of bulk. Detailed comparisons with the recently proposed np-Si show that although the maximum ZT (ZTmax) of Ge is nine times larger than that of Si in the bulk phase, ZTmax of np-Ge is twice as large as that of np-Si due to the similarity in lattice thermal conductivity of the two np systems. Moreover, ZTmax is found to occur at a carrier concentration two orders of magnitude lower than that for with np-Si due to the dissimilarities in their electronic structure.
Top-down lithographic method for inducing strain in carbon nanotubes
Authors: Kumar Rajay , Aykol Mehmet , Ryu Koungmin , Zhou Chongwu , Cronin Stephen B.
Published: July 2009

We demonstrate a method for inducing strain in carbon nanotubes using standard lithographic techniques. In this work, aligned nanotubes are partially suspended over trenches made by chemical etching. Strain-induced downshifts as high as 31 cm−1 are observed in the Raman spectra, roughly corresponding to 1.1% strain. We also observe significant shifts in the resonant transition energy Eii and an irreversible increase in the D band Raman intensity. The strains demonstrated using this technique are capable of creating significant bandgaps in metallic nanotubes, greater than kBT at room temperature, thereby making it possible to convert metallic nanotubes into semiconductors.
Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides
Authors: Ramzan M. , Ahuja R.
Published: July 2009

Light weight complex metal hydrides, sodium hydride (NaH), and lithium hydride (LiH) are the last step materials during hydrogen release process of alanates and borates, which are promising candidates for hydrogen storage. We report ab initio molecular dynamics (MD) calculations based on density functional theory to study the hydrogen-deuterium exchange in NaH and LiH. We predict the single hydrogen-deuterium exchange in NaH and LiH and calculate the self-diffusion constants, ⟨D⟩NaH≈1.46×10−9 m2 s−1 of deuterium in NaH at 420 K and ⟨D⟩LiH≈1.49×10−9 m2 s−1 of deuterium in LiH at 550 K, which are in good agreement with the experimental values.
Design and development of a portable gamma radiation monitor
Authors: Munir M. , Ahmad N. , Sohail S. , Naveed R. A. , Rafiq M. Q. , Khalid M.
Published: July 2009

A portable gamma radiation monitor has been designed and developed. The monitor can be used effectively in the dose range from 0.07 to 500 mGy/h due to gamma rays of energy greater than 65 keV. The monitor overestimated radiation doses and the uncertainty in the measured dose rate has been found to be ≤30%. The response of the monitor can be considered isotropic within an acceptable error of ±30%. Provision has also been added to use the monitor as an installed radiation monitor. In installed mode, it can be operated from a remote location up to 1 km and the timing history can be stored on a personal computer.
Modeling of high-order many-mode terms in the expansion of multidimensional potential energy surfaces: Application to vibrational spectra
Authors: Rauhut Guntram , Hartke Bernd
Published: July 2009

High-order many-mode terms in the expansion of multidimensional potential energy surfaces were modeled by a fully automated molecule-specific fitting of parameters within semiempirical molecular orbital theory to low-order grid representations of high-level ab initio potentials. Analytical derivatives of the total energy with respect to the fitting parameters in combination with global and local optimization procedures allow for an efficient and accurate estimation of such terms. The accuracy of this approach was tested on the basis of vibrational SCF and configuration interaction calculations for the fundamental modes of a set of test molecules. Deviations with respect to reference calculations were found to be very small. Speedups in computation time by about three orders of magnitude relative to conventional calculations were achieved.