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Selected AbstractsParallel isoelectric focusing IIELECTROPHORESIS, Issue 21-22 2004Gleb V. Zilberstein Abstract A miniature electrophoretic device is developed on the basis of a new isoelectric focusing (IEF) method, namely parallel isoelectric focusing. We report here the theory and the results of operation of a new parallel isoelectric device (PID). The main advantages and limitations of the method are discussed for miniaturization purposes. It is shown that the method guarantees the fast and complete separation of any complex protein mixtures under acceptable conditions, such as voltage source, temperature, size of the device, and separation process duration. It is shown that the main problem of PID miniaturization is the buffer design, and the relation between Immobiline buffer capacity and solution buffer capacity. The main experimental limitation of PID resolution is protein sensitivity to pH changes. [source] Mate Choice for Genetic Benefits: Time to Put the Pieces TogetherETHOLOGY, Issue 1 2010Attila Hettyey It is thought that mate choice allows individuals to obtain genetic benefits for their offspring, and although many studies have found some support for this hypothesis, several critical questions remain unresolved. One main problem is that empirical studies on mate choice and genetic benefits have been rather piecemeal. Some studies (1) aimed to test how mate choice affects offspring fitness, but have not examined whether the benefits are because of genetic effects. Other studies tested whether mate choice provides (2) additive or (3) non-additive genetic benefits and only a few studies (4) considered these genetic effects together. Finally, some studies (5) examined whether the potential benefits that might be gained from mate choice are due to additive genetic effects vs. non-additive effects, and although they found evidence for both, they did not examine whether mate choice is relevant. Furthermore, previous studies have usually not controlled for non-genetic sources of variation in offspring fitness. Thus, there remain gaping holes in our understanding, and it is the connections among the research approaches that now need more attention. We suggest that studies are needed that measure non-genetic effects, the potential benefits from both additive and non-additive genetic effects, and also determine whether mate choice exploits these potential benefits. Such integrative studies are necessary to put the pieces together and clarify the role of genetic benefits in the evolution of mate choice. [source] Comparison of electromagnetic field for two different lightning pulse current modelsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2001A. Andreotti In this paper the electromagnetic field produced by a lightning current analytically described by the so called double exponential model is compared with the field produced by the same current (same peak, rise and decay time) analytically described by the model proposed by Heidler. The exponential model has been widely used in literature for its simplicity and its relatively good accuracy. The Heidler model is more complex, but removes the main problem shown by the double exponential: the non-zero derivative at the beginning of the lightning pulse in contrast with the physical phenomenon. In the lightning electromagnetic pulse (LEMP) simulations both models are now used. In the paper we aim to make a comparison between the two. In particular we show that the two models are fairly equivalent in the frequency range up to 2 MHz, namely the range of interest of typical lightning phenomena. In addition, the double exponential model is shown to be conservative for higher frequencies. [source] Applying aggregation operators for information access systems: An application in digital librariesINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 12 2008Enrique Herrera-Viedma Nowadays, the information access on the Web is a main problem in the computer science community. Any major advance in the field of information access on the Web requires the collaboration of different methodologies and research areas. In this paper, the concept of aggregation operator playing a role for information access on the Web is analyzed. We present some Web methodologies, as search engines, recommender systems, and Web quality evaluation models and analyze the way aggregation operators help toward the success of their activities. We also show an application of the aggregation operators in digital libraries. In particular, we introduce a Web information system to analyze the quality of digital libraries that implements an important panel of aggregation operators to obtain the quality assessments. © 2008 Wiley Periodicals, Inc. [source] One-Pot Conversion of Cephalosporin C to 7-Aminocephalosporanic Acid in the Absence of Hydrogen PeroxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005Fernando Lopez-Gallego Abstract The main drawback in the production of 7-aminocephalosporanic acid (7-ACA) at the industrial level is the inactivation of the enzymes implicated in the process due to the presence of hydrogen peroxide during the reaction. As an alternative, we have developed the conversion of cephalosporin C to 7-ACA in a single reactor without the presence of hydrogen peroxide during the reaction, achieving more than 80% yield. In order to develop this process, D -amino acid oxidase (DAAO) was co-immobilized with catalase (CAT), which is able to fully eliminate in situ the hydrogen peroxide formed by the neighbouring DAAO molecules. Thus, the product of the reaction is only ,-ketoadipyl-7-ACA. This system prevents the inactivation of the oxidase by hydrogen peroxide, solving the main problem of the enzymatic process. Moreover, we have found that ,-ketoadipyl-7-ACA is recognized as a substrate by glutaryl acylase (GAC) and hydrolyzed as long as glutaric acid is absent from the reaction medium (because it is able to inhibit the hydrolysis). The low stability of ,-ketoadipyl-7-ACA justifies the use of a single reactor, in which glutaryl acylase is already present when this substrate is generated. Thus, the whole process may (and must) be performed in a single step, and in the absence of hydrogen peroxide that could affect the stabilities of the involved enzymes. [source] Forecasting volatility by means of threshold modelsJOURNAL OF FORECASTING, Issue 5 2007M. Pilar Muńoz Abstract The aim of this paper is to compare the forecasting performance of competing threshold models, in order to capture the asymmetric effect in the volatility. We focus on examining the relative out-of-sample forecasting ability of the SETAR-Threshold GARCH (SETAR-TGARCH) and the SETAR-Threshold Stochastic Volatility (SETAR-THSV) models compared to the GARCH model and Stochastic Volatility (SV) model. However, the main problem in evaluating the predictive ability of volatility models is that the ,true' underlying volatility process is not observable and thus a proxy must be defined for the unobservable volatility. For the class of nonlinear state space models (SETAR-THSV and SV), a modified version of the SIR algorithm has been used to estimate the unknown parameters. The forecasting performance of competing models has been compared for two return time series: IBEX 35 and S&P 500. We explore whether the increase in the complexity of the model implies that its forecasting ability improves. Copyright © 2007 John Wiley & Sons, Ltd. [source] Green Energy or Organic Food?: A Life-Cycle Assessment Comparing Two Uses of Set-Aside LandJOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2001Richard van den Broek Summary Bioenergy has a large worldwide potential in future climate change abatement, although its application may become limited by demands for land for other functions. The aim of this study was to make an environmental assessment of the use of energy crops in the Netherlands in a context that incorporates scarcity of land. A base case system was defined, consisting of conventional winter wheat production, set-aside land (1 hectare, together), and the production of coal-based electricity. Using life-cycle assessment, we compared this system with (1) a green energy system in which willow is cultivated on the set-aside land to replace the coal-based electricity and (2) an organic agriculture system in which the full hectare produces wheat under the Dutch EKO organic agriculture standard. In this way, the functional unit and the amount of land used is the same in each system. The final system comparison was based on normalized scores per environmental theme. The green energy system scored the best with respect to acidification, climate change, and energy carrier depletion. The organic food system scored best on terrestrial eco-toxicity and slightly better on the mutually related themes of seawater and seawater sediment eco-toxicity. The base case system performed slightly better with regard to eutrophication. Preferences, from an environmental point of view, for one of the systems should be determined by environmental policy priorities and the severity of local environmental problems. The case studied here shows that when climate change, energy carrier depletion, and acidification are the main drivers behind environmental policy, one should focus not on the extensification of agriculture, but rather dedicate more land to energy crops. Extensification of agriculture would be the preferred system when toxicity from pesticides is considered the main problem. [source] Optimum acquisition of Raman spectra in pigment analysis with IR laser diode and pulsed UV irradiationJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2006Alejandro López-Gil Abstract Fluorescence, due to the binding media, is the main problem that one encounters in the molecular analysis of artistic pigments using Raman spectroscopy. With the object of minimizing this problem, we propose the use of a semiconductor IR laser in Raman spectral acquisition and the application of local irradiation with a pulsed UV laser on the analysis zone. The Raman analysis with an IR source shows advantages compared to that with visible lasers, such as the reduction of fluorescence and its shot noise, although a price has to be paid in the form of the small intensity of the obtained spectra with the same acquisition time. Also, in this paper we demonstrate that controlled levels of pulsed UV radiation over the analyzed painting (pigment + binding media) can improve even more the Raman spectral quality obtained with the IR laser, which leads us to conclude that the local use of a pulsed UV laser, prior to Raman analysis with the IR source, can bring optimum quality results in pigment identification. The spectral quality of these experimental results for different pigments has been measured by calculating in each case the signal-to-noise ratio (SNR) of the corresponding spectra. From a quantitative point of view, in some practical cases (chromium yellow and ultramarine blue) an SNR improvement of 16 dB is achieved when pulsed UV irradiation and IR laser Raman analysis are used instead of a simple Raman analysis with a visible laser. Copyright © 2006 John Wiley & Sons, Ltd. [source] New approach to 3D time-resolved angiographyMAGNETIC RESONANCE IN MEDICINE, Issue 5 2002Bruno Madore Abstract TRICKS is an acquisition and reconstruction method capable of generating 3D time-resolved angiograms. Arguably, the main problem with TRICKS is the way it handles the outer regions of the k -space matrix, leading to artifacts at the edges of blood vessels. An alternative to the data- processing stage of TRICKS, designed to better represent edges and small vessels, is presented here. A weakness of the new approach is an increased sensitivity to motion compared to TRICKS. Since this method can use the same data as TRICKS, a hybrid reconstruction method could conceivably be developed where the advantages of both approaches are combined. Magn Reson Med 47:1022,1025, 2002. © 2002 Wiley-Liss, Inc. [source] Clinical and prognostic features of plasmacytomas: A multicenter study of Turkish Oncology Group-Sarcoma Working PartyAMERICAN JOURNAL OF HEMATOLOGY, Issue 9 2008Sevil Kilciksiz To identify the outcomes of prognostic factors of solitary plasmacytoma mainly treated with local radiotherapy (RT). The data were collected from 80 patients with solitary plasmacytoma (SP). Forty patients (50.0%) received radiotherapy (RT) alone while 38 of them (47.5%) were treated with surgery (S) and RT. The median radiation dose was 46 Gy (range 30,64). The median follow up was 2.41 years (range 0.33,12.33). Ten-year overall survival (OS) and local relapse-free survival (LRFS) were 73% and 94%, respectively. The median progression-free survival (PFS) and multiple myeloma-free survival (MMFS) were 3.5 years and 4.8 years, respectively. On multivariate analyses, the favorable factors were radiotherapy dose of ,50 Gy and RT + S for PFS and younger age for MMFS. For the patients with medullary plasmacytoma, the favorable factor was younger age for MMFS. RT at ,50 Gy and RT + S may be favorable prognostic factors on PFS. Younger patients, especially with head-neck lesion and without pre-RT macroscopic tumor, seem to have the best outcome when treated with RT ± S. Progression to MM remains as the main problem especially for older patients. Am. J. Hematol., 2008. © 2008 Wiley-Liss, Inc. [source] Frontal polymerization of acrylic monomers for the consolidation of stonePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2005Silvia Vicini Abstract Polymeric products are largely used for consolidation of stone in the field of cultural heritage. Nevertheless, the main problem of polymeric compounds is related to their macromolecular nature, it being difficult for a polymer to penetrate inside the pores which may have a very small diameter. These considerations are the starting points for in situ polymerization. According to this technique, not the pre-formed polymer, but the monomer is introduced into the stone and it is polymerized in situ in a subsequent step. Frontal polymerization (FP) is a particular technique in which the heat released by the exothermal reaction of monomer to polymer conversion is exploited to promote the formation of a hot traveling front able to propagate and self-sustain the reaction. In the present work, FP is performed inside the pores of the stone and the results lead to the conclusion that the hot front is still active in the presence of an inorganic material which dissipates partially the heat released during the polymerization. In addition some recent applications of FP are discussed in comparison with the traditional polymerization for the in situ consolidation and protection of stones. Copyright © 2005 John Wiley & Sons, Ltd. [source] Deficiency of oncoretrovirally transduced hematopoietic stem cells and correction through ex vivo expansionTHE JOURNAL OF GENE MEDICINE, Issue 2 2005David Bryder Abstract Background Extensive efforts to develop hematopoietic stem cell (HSC) based gene therapy have been hampered by low gene marking. Major emphasis has so far been directed at improving gene transfer efficiency, but low gene marking in transplanted recipients might equally well reflect compromised repopulating activity of transduced cells, competing for reconstitution with endogenous and unmanipulated stem cells. Methods The autologous settings of clinical gene therapy protocols preclude evaluation of changes in repopulating ability following transduction; however, using a congenic mouse model, allowing for direct evaluation of gene marking of lympho-myeloid progeny, we show here that these issues can be accurately addressed. Results We demonstrate that conditions supporting in vitro stem cell self-renewal efficiently promote oncoretroviral-mediated gene transfer to multipotent adult bone marrow stem cells, without prior in vivo conditioning. Despite using optimized culture conditions, transduction resulted in striking losses of repopulating activity, translating into low numbers of gene marked cells in competitively repopulated mice. Subjecting transduced HSCs to an ex vivo expansion protocol following the transduction procedure could partially reverse this loss. Conclusions These studies suggest that loss of repopulating ability of transduced HSCs rather than low gene transfer efficiency might be the main problem in clinical gene therapy protocols, and that a clinically feasible ex vivo expansion approach post-transduction can markedly improve reconstitution with gene marked stem cells. Copyright © 2004 John Wiley & Sons, Ltd. [source] Teaching Mass Casualty Triage Skills Using Immersive Three-dimensional Virtual RealityACADEMIC EMERGENCY MEDICINE, Issue 11 2008Dale S. Vincent MD Abstract Objectives:, Virtual reality (VR) environments offer potential advantages over traditional paper methods, manikin simulation, and live drills for mass casualty training and assessment. The authors measured the acquisition of triage skills by novice learners after exposing them to three sequential scenarios (A, B, and C) of five simulated patients each in a fully immersed three-dimensional VR environment. The hypothesis was that learners would improve in speed, accuracy, and self-efficacy. Methods:, Twenty-four medical students were taught principles of mass casualty triage using three short podcasts, followed by an immersive VR exercise in which learners donned a head-mounted display (HMD) and three motion tracking sensors, one for their head and one for each hand. They used a gesture-based command system to interact with multiple VR casualties. For triage score, one point was awarded for each correctly identified main problem, required intervention, and triage category. For intervention score, one point was awarded for each correct VR intervention. Scores were analyzed using one-way analysis of variance (ANOVA) for each student. Before and after surveys were used to measure self-efficacy and reaction to the training. Results:, Four students were excluded from analysis due to participation in a recent triage research program. Results from 20 students were analyzed. Triage scores and intervention scores improved significantly during Scenario B (p < 0.001). Time to complete each scenario decreased significantly from A (8:10 minutes) to B (5:14 minutes; p < 0.001) and from B to C (3:58 minutes; p < 0.001). Self-efficacy improved significantly in the areas of prioritizing treatment, prioritizing resources, identifying high-risk patients, and beliefs about learning to be an effective first responder. Conclusions:, Novice learners demonstrated improved triage and intervention scores, speed, and self-efficacy during an iterative, fully immersed VR triage experience. [source] Effect of obesity and morbid obesity on the growth hormone (GH) secretion elicited by the combined GHRH + GHRP-6 testCLINICAL ENDOCRINOLOGY, Issue 6 2006Fahrettin Kelestimur Summary Objective, Obesity is characterized by low basal levels of growth hormone (GH) and impeded GH release. However, the main problem arises in the diagnosis of GH deficiency in adults, as all accepted cut-offs in the diagnostic tests of GH reserve are no longer valid in obese subjects. In this work, the role of obesity in the GH response elicited by the GHRH + GHRP-6 test was assessed in a large population of obese and nonobese subjects. Patients, GHRH + GHRP-6-induced GH peaks were evaluated in 542 subjects. One hundred and five were healthy obese, 50 were morbid obese, and 261 were nonobese (both normal weight and overweight). One hundred and seventy-six GH-deficient patients (obese and nonobese) were also studied. Results, A regression analysis of the 366 subjects with normal pituitary function indicated that adiposity had a negative effect on the elicited GH peak (r = ,0·503, P < 0·0001). A receiver operating characteristic (ROC) curve analysis showed that in subjects with a BMI 35, the currently accepted cut-offs of the GHRH + GHRP-6 test (GH peaks 20 µg/l: normal secretion; GH peaks 10 µg/l: GH deficiency), were fully operative. However, in subjects with a BMI > 35, normality was indicated by GH peaks 15 µg/l and GH deficiency by peaks 5 µg/l (1 µg/l = 2·6 mU/l). Conclusions, This study confirms: (a) that the combined provocative test is adequate to separate normal and GH-deficient subjects; (b) the negative effect of obesity on GH secretion; (c) that obesity accounts for 25% of the reduction of GH release; and (d) that present cut-off values are applicable to normal weight, overweight and grade I obesity subjects, whereas in obese subjects with a BMI exceeding 35, all the normative limits of the GHRH-GHRP +6 test must be reduced by 5 µg/l. [source] Reengineering Academic Teams Toward a Network Organizational Structure,DECISION SCIENCES JOURNAL OF INNOVATIVE EDUCATION, Issue 2 2007Emmanouil Kaldis ABSTRACT This article examines student teamwork in the academic field from a structural perspective. Student teams are often prearranged and then left to organize themselves and get on with their work, without any further structural support; this, however, can become a negative experience on teamwork. A varied contribution among team members often occurs and unavoidably leads to friction and reduced performance. The aim of this project is to explore the main problems in academic teamwork and investigate tools that provide relevant solutions. We present the concept of network organizational structure and discuss how this can improve collaboration and communication. The main tools to achieve a structural transformation from the more traditional form of team organization to the fairer network form, and their implications are discussed. [source] A CHINESE PERSPECTIVE ON THE CHINA-AUSTRALIA FREE TRADE AGREEMENT AND POLICY SUGGESTIONSECONOMIC PAPERS: A JOURNAL OF APPLIED ECONOMICS AND POLICY, Issue 1 2008DAWEI CHENG This article provides an analysis of the potential economic effects of the China,Australia free trade agreement, and provides a set of policy recommendations regarding such an agreement. The article begins with a review of China,Australia trade relations, showing the widening gap in the importance of one country relative to the other. Next, the article examines the competitive advantages of China and Australia in trade by way of local revealed comparative advantage (RCA) and finds that trade between China and Australia is predicated on differences in their factor endowments. The study then investigates the main problems in the negotiations for the China,Australia Free Trade Agreement and concludes with a set of policy suggestions. [source] Separation of proteins in a multicompartment electrolyzer with chambers defined by a bed of gel beadsELECTROPHORESIS, Issue 4 2003Marina Cretich Abstract Multicompartment electrolyzers (MEs) with isoelectric membranes were introduced in 1989 for purifying proteins in an electric field. At the basis of ME technology there are membranes consisting of cross-linked copolymers of acrylamide and acrylamido monomers bearing protolytic groups. The technology employed for casting the membranes is an extension of the isoelectric focusing in immobilized pH gradient technique for which specific acrylamido monomers, known with the trade name of Immobiline, have been developed. However, the use of continuous membranes presents several disadvantages. Due to the mechanical characteristics of polyacrylamide, the gel must physically adhere onto a rigid support, which prevents it from collapsing. The support must have a highly porous structure in order to be permeable to proteins. The mechanical fragility of the membranes is one of the main problems that hinders the industrial scale application of ME separators. In order to overcome this problem, we propose to substitute the continuous membranes with a bed of gel beads of identical comonomer composition, obtained by an inverse emulsion polymerization process. [source] Mechanical preparation of root canals: shaping goals, techniques and meansENDODONTIC TOPICS, Issue 1 2005Michael Hülsmann Preparation of root canal systems includes both enlargement and shaping of the complex endodontic space together with its disinfection. A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Although many reports on root canal preparation can be found in the literature, definitive scientific evidence on the quality and clinical appropriateness of different instruments and techniques remains elusive. To a large extent this is because of methodological problems, making comparisons among different investigations difficult if not impossible. The first section of this paper discusses the main problems with the methodology of research relating to root canal preparation while the remaining section critically reviews current endodontic instruments and shaping techniques. [source] Dental undergraduate expectations and opinions of Web-based courseware to supplement traditional teaching methodsEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 3 2003R. Eynon The rapid growth of Internet for the delivery of information has enabled teaching materials to be placed on websites allowing student access to course material. It is the aim of this paper to evaluate a cohort of dental undergraduate students who have used Web-based courseware in prosthetic dentistry for a semester. A questionnaire was distributed to clinical undergraduate students prior to the use of the prosthetics course to determine their experience of using the World Wide Web (WWW) and their expectations of an online course. A second questionnaire was distributed at the end of 6 months which asked about their usage and opinions of the prosthetics Web-based courseware. The main concerns raised at the beginning of the course were related to computer access, the ability to use computers, the time involved and their conception that the e-course would be an additional burden. The main potential benefits were perceived to be convenience, availability of information and the ability to reinforce or catch up on aspects of the module they did not understand or had missed. Feedback at the end of the year showed that most students had accessed the Web-based courseware site at least once a month and, generally, their comments were favourable, dispelling some of the initial perceived fears. They felt that the website was a quick and convenient way to access information and was a good additional resource. Access to the site and printing information were the main problems raised by the students who had to use a shared cluster. In conclusion, Web-based courseware was felt to be a useful additional resource for students. However, this research showed that sufficient computers and printers must be available for such a resource to become an integrated part of the dental course. [source] Microwave Hybrid Post-Heat Treatment of Reaction Sintered Alumina/Lanthanum Hexaaluminate Composite Ceramics,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Zahra Negahdari One of the main problems in development of in situ reaction sintered alumina/lanthanum hexaaluminate composite ceramics is achievement of simultaneous densification and in situ formation of lanthanum hexaaluminate (LHA) platelets inside the matrix. Microwave hybrid post-sintering was investigated as a method to enhance the solid-state reaction of LHA formation and the densification of composite ceramics with 2.8,80 vol% LHA. Comparison of the conventionally and microwave assisted sintered alumina/lanthanum hexaaluminate composite ceramics revealed that utilization of microwave heating in second stage of sintering could enhance the solid-state reaction, the densification, and the anisotropic grain growth of the LHA platelets in ceramics containing more than 20 vol% LHA and for heat treatment at 1500,°C. [source] Raw materials: the importance of quality and safety.FLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2010A review. Abstract Aromatic plants and spices are used throughout the world for flavouring food and beverages, as well as for food supplements, novel foods and as a source of essential oils and aromatic extracts. The non-availability or inadequacy of standards for checking and assuring the quality of aromatic plants and spices is one of the main problems that arise for industry when using such raw materials. As many aromatic plants are harvested from the wild, standardization to assure their quality is important for their safe and effective utilization in food and beverage industries. On the other hand, there are numerous parameters that influence the chemical composition of plants, which play an important role in the final quality of the product and possibly in any risk arising to the consumer. Also, from a safety point of view, aromatic plants and spices should be free of undeclared contaminants and adulterants, such as toxic botanicals, pathogenic microorganisms and excessive levels of microbial toxins, pesticides or fumigation agents. We focus on these aspects and examine ways to assure their appropriate utilization from the quality and safety standpoint. The regulatory situation of medicinal and aromatic plants (MAPs) is very complicated; several differences in standards and regulations between countries can be found, a situation that can result in more health risks arising for consumers. To clarify some of the existing problems, the major regulations of the USA and the European Union (EU) and the borderlines between food supplements and medicines and other international standards, are briefly described and discussed. Copyright © 2010 John Wiley & Sons, Ltd. [source] A majority model in group decision making using QMA,OWA operatorsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 2 2006J.I. Peláez Group decision-making problems are situations where a number of experts work in a decision process to obtain a final value that is representative of the global opinion. One of the main problems in this context is to design aggregation operators that take into account the individual opinions of the decision makers. One of the most important operators used for synthesizing the individual opinions in a representative value of majority in the OWA operator, where the majority concept used aggregation processes, is modeled using fuzzy logic and linguistic quantifiers. In this work the semantic of majority used in OWA operators is analyzed, and it is shown how its application in group decision-making problems does not produce representative results of the concept expressed by the quantifier. To solve this type of problem, two aggregation operators, QMA,OWA, are proposed that use two quantification strategies and a quantified normalization process to model the semantic of the linguistic quantifiers in the group decision-making process. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 193,208, 2006. [source] A comparison of three closest fit approaches to missing attribute values in preterm birth dataINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 2 2002Jerzy W. Grzymala-Busse One of the main problems of data mining is imperfection of input data. Such data may be uncertain, vague, and incomplete. In our data set, describing preterm birth, many attribute values were missing, that is, the input data set was incomplete. The main approach to solving the missing attribute value problem was based on a closest fit: a missing attribute value in a case was replaced by the existing attribute value in the best candidate, a case that fits as closely as possible (resembles the most) the case with the missing attribute value. We experimented with three methods based on the idea of the closest fit: looking for the best candidate among the set of all cases, among the cases that belong to the same concept (cases within the same class as the case with missing attribute values), and a special method, where the set of all attributes was restricted to a single attribute with the missing attribute value. In the last method, the missing attribute value was replaced by the most common value within the concept for symbolic attributes, and by the average value of all attribute values of the same concept for numerical attributes. © 2002 John Wiley & Sons, Inc. [source] Merging databases: Problems and examplesINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 10 2001Laurence Cholvy This paper focuses on databases merging, which is one particular case of data fusion. Databases merging is the process which consists of integrating, physically or virtually, the data provided by several databases. With examples throughout the paper, we stress the main problems raised by databases merging and we present, not exhaustively, some solutions. The topics receiving deepest study are: cases matching, inconsistency handling and summarizing data. © 2001 John Wiley & Sons, Inc. [source] A Pragmatic Guide to Qualitative Historical Analysis in the Study of International RelationsINTERNATIONAL STUDIES PERSPECTIVES, Issue 4 2002Cameron G. Thies Researchers using qualitative methods, including case studies and comparative case studies, are becoming more self,conscious in enhancing the rigor of their research designs so as to maximize their explanatory leverage with a small number of cases. One aspect of qualitative research that has not received as much attention is the use of primary and secondary source material as data or evidence. This essay explores the potential problems encountered by political scientists as they conduct archival research or rely on secondary source material produced by historians. The essay also suggests guidelines for researchers to minimize the main problems associated with qualitative historical research, namely, investigator bias and unwarranted selectivity in the use of historical source materials. These guidelines should enable advanced undergraduates and graduate students to enhance the quality of their historically minded political science scholarship. [source] Stabilization of biomass-derived pyrolysis oilsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2010R.H. Venderbosch Abstract BACKGROUND: Biomass is the only renewable feedstock containing carbon, and therefore the only alternative to fossil-derived crude oil derivatives. However, the main problems concerning the application of biomass for biofuels and bio-based chemicals are related to transport and handling, the limited scale of the conversion process and the competition with the food industry. To overcome such problems, an integral processing route for the conversion of (non-feed) biomass (residues) to transportation fuels is proposed. It includes a pretreatment process by fast pyrolysis, followed by upgrading to produce a crude-oil-like product, and finally co-refining in traditional refineries. RESULTS: This paper contributes to the understanding of pyrolysis oil upgrading. The processes include a thermal treatment step and/or direct hydroprocessing. At temperatures up to 250 °C (in the presence of H2 and catalyst) parallel reactions take place including re-polymerization (water production), decarboxylation (limited CO2 production) and hydrotreating. Water is produced in small quantities (approx. 10% extra), likely caused by repolymerization. This repolymerization takes place faster (order of minutes) than the hydrotreating reactions (order of tens of minutes, hours). CONCLUSIONS: In hydroprocessing of bio-oils, a pathway is followed by which pyrolysis oils are further polymerized if H2 and/or catalyst is absent, eventually to char components, or, with H2/catalyst, to stabilized components that can be further upgraded. Results of the experiments suggest that specifically the cellulose-derived fraction of the oil needs to be transformed first, preferably into alcohols in a ,mild hydrogenation' step. This subsequently allows further dehydration and hydrogenation. Copyright © 2010 Society of Chemical Industry [source] Constructing Rotating Item Pools for Constrained Adaptive TestingJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 4 2004Adelaide Ariel Preventing items in adaptive testing from being over- or underexposed is one of the main problems in computerized adaptive testing. Though the problem of overexposed items can be solved using a probabilistic item-exposure control method, such methods are unable to deal with the problem of underexposed items. Using a system of rotating item pools, on the other hand, is a method that potentially solves both problems. In this method, a master pool is divided into (possibly overlapping) smaller item pools, which are required to have similar distributions of content and statistical attributes. These pools are rotated among the testing sites to realize desirable exposure rates for the items. A test assembly model, motivated by Gulliksen's matched random subtests method, was explored to help solve the problem of dividing a master pool into a set of smaller pools. Different methods to solve the model are proposed. An item pool from the Law School Admission Test was used to evaluate the performances of computerized adaptive tests from systems of rotating item pools constructed using these methods. [source] Experimental and thermal analysis of washing the packed ice bed in wash columnsAICHE JOURNAL, Issue 11 2009Frank G. F. Qin Abstract In the process of freeze concentration (FC), the main problems in operating the counter-current wash column used for separating ice from ice slurries are channeling and viscous fingering. These phenomena lead to the mixing of pure water and mother liquid, as well as entrainment of mother liquid within the removed ice. Experimental and thermal analysis of the wash front interface in this research relates ice melting and wash front breakthrough with the operating conditions (such as the wash water temperature, ice bed temperature and porosity). Criteria for wash front stability are proposed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Normative decision making with multiattribute performance targetsJOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 3-4 2009Ali E. Abbas Abstract Many companies set multiple performance targets for their managers and reward them on meeting a threshold value for each target or goal. Examples of such incentive structures abide in the managerial literature and in organizational settings. We show that this incentive structure, while popular, has two main problems: (i) it can induce managers who try to maximize the probability of meeting their performance targets to make decisions that are not compatible with expected utility maximizing decisions, and (ii) it may lead to trade-offs among the performance objectives that are inconsistent with the corporate value function. In this paper, we propose a method to remedy these two problems, while retaining a target-based incentive scheme. We define a multiattribute target as a deterministic region in the space of multiattribute outcomes that has two properties: (1) the probability that the outcome of a multiattribute lottery lies within the target region is equal to the expected utility of the lottery, and (2) all outcomes within the target region are preferred to all outcomes outside it. These two properties lead to a new quantity; which we call the ,value aspiration equivalent' that leads managers who maximize the probability of meeting their targets to simultaneously maximize the expected utility, and it also induces trade-offs that are consistent with the decision maker's value function. Copyright © 2009 John Wiley & Sons, Ltd. [source] Students' levels of explanations, models, and misconceptions in basic quantum chemistry: A phenomenographic studyJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 5 2009Christina Stefani We investigated students' knowledge constructions of basic quantum chemistry concepts, namely atomic orbitals, the Schrödinger equation, molecular orbitals, hybridization, and chemical bonding. Ausubel's theory of meaningful learning provided the theoretical framework and phenomenography the method of analysis. The semi-structured interview with 19 second-year chemistry students supplied the data. We identified four levels of explanations in the students' answers. In addition, the scientific knowledge claims reflected three main levels of models. By combining levels of explanations with levels of models, we derived four categories. Two of the categories are shades of variation in the rote-learning part of a continuum, while the other two categories are in the meaningful-learning part. All students possessed alternative conceptions some of which occurred within certain categories, while others spanned more categories. The insistence on the deterministic models of the atom, the misinterpretation of models, and the poor understanding of the current quantum concepts are main problems in the learning of the basic quantum chemistry concepts. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 46: 520,536, 2009 [source] | |||||||||||||||||||||||||||||||||||||