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Selected AbstractsRhI -Catalyzed Cycloisomerization of Vinyl Bicyclopropyl Compounds to Azabicyclo[3.2.2]nona-2,8-dienesCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2010Young Kim Important class: Nitrogen-containing heterobicycles are an important structural motif ubiquitous in natural alkaloids. We found that azabicyclo[3.2.2]nona-2,8-dienes can be synthesized from vinyl bicyclopropropyl derivatives in the presence of a RhI catalyst (see scheme). Syntheses of such compounds and an investigation into the reaction mechanism through DFT calculations are presented. [source] Data partitioning-based parallel irregular reductionsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2-3 2004Eladio Gutiérrez Abstract Different parallelization methods for irregular reductions on shared memory multiprocessors have been proposed in the literature in recent years. We have classified all these methods and analyzed them in terms of a set of properties: data locality, memory overhead, exploited parallelism, and workload balancing. In this paper we propose several techniques to increase the amount of exploited parallelism and to introduce load balancing into an important class of these methods. Regarding parallelism, the proposed solution is based on the partial expansion of the reduction array. Load balancing is discussed in terms of two techniques. The first technique is a generic one, as it deals with any kind of load imbalance present in the problem domain. The second technique handles a special case of load imbalance which occurs whenever a large number of write operations are concentrated on small regions of the reduction arrays. Efficient implementations of the proposed optimizing solutions for a particular method are presented, experimentally tested on static and dynamic kernel codes, and compared with other parallel reduction methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] Through thick and thin: good and its determinatesDIALECTICA, Issue 2 2004Christine Tappolet What is the relation between the concept good and more specific or ,thick' concepts such as admirable or courageous? I argue that good or more precisely good pro tanto is a general concept, but that the relation between good pro tanto and the more specific concepts is not that of a genus to its species. The relation of an important class of specific evaluative concepts, which I call ,affective concepts', to good pro tanto is better understood as one between a determinable and its determinates, whereas concepts such as courageous can be analysed in terms of affective concepts and purely descriptive concepts. [source] Semi-analytic Approaches to Collateralized Debt Obligation ModellingECONOMIC NOTES, Issue 2 2004Christian Bluhm Collateralized debt obligations (CDOs) constitute an important class of asset-backed securities. Most major banks use CDOs as portfolio management tools for achieving regulatory capital relief, economic risk transfer and funding. On the other side, banks and other financial institutions invest in CDO tranches with a risk/return profile matching their risk appetite and investment policies. For both sides (risk selling and risk buying) of a CDO transaction, sound mathematical tools are required for an evaluation of the deal. In this paper, we investigate some techniques for CDO modelling, paying special attention to approaches based on semi-analytic approximations. [source] Partial Ordering of Unpredictable Mobility with Welfare ImplicationsECONOMICA, Issue 299 2008DANNY BEN-SHAHAR We propose a partial ordering of ,unpredictable mobility' in the spirit of Blackwell's ordering of information structures. The proposed ordering ranks mobility matrices according to the degree to which elements in a given set are likely to move from one state to another, independently of their origin. Furthermore, for an important class of transition structures, our proposed ordering implies ordering, thus carrying significant welfare implications. Moreover, whenever it exists, our partial ordering functions as a sufficient condition for a class of renowned mobility measures and thereby generates, for a subset of transition matrices, unanimous ranking among mobility indices that are not generally consistent with one another. [source] THEORIZING THE UNIVERSITY AS A CULTURAL SYSTEM: DISTINCTIONS, IDENTITIES, EMERGENCIESEDUCATIONAL THEORY, Issue 3 2006Mark Considine In this essay, Mark Considine argues that the prospect of such changes requires us to reflect carefully upon the theoretical and normative underpinnings of universities and to delineate the structures and processes through which they might seek to negotiate their identities. Considine re-theorizes the university as a higher education system composed by distinctions and networks acting through an important class of boundary objects. He moves beyond an environmental analysis, asserting that systems are best theorized as cultural practices based upon actors making and protecting important kinds of distinctions. Thus, the university system must be investigated as a knowledge-based binary for dividing knowledge from other things. This approach, in turn, produces an identity-centering (cultural) model of the system that assumes universities must perform two different acts of distinction to exist: first, they must distinguish themselves from other systems (such as the economy, organized religion, and the labor market), and, second, they must operate successfully in a chosen resource environment. Ultimately, Considine argues that while environmental problems (such as cuts in government grants) may generate periodic crises, threats within identities produce emergencies generating a radical kind of problematic for actor networks. [source] Affinity Biosensors Based on Electropolymerized FilmsELECTROANALYSIS, Issue 19 2005Serge Cosnier Abstract This review gives an overview on different types of affinity biosensors based on electropolymerized polymer films that are becoming an important class of analytical tools. These affinity biosensors may be classified according to the strategy used for their fabrication, namely entrapment within polymers during their electrochemical growth, simple adsorption onto electropolymerized films, chemical coupling or affinity interactions between bioreceptors and electropolymerized films or direct electrochemical polymerization of the bioreceptor itself. Recently opened perspectives and potential research directions are also discussed. [source] Determination of amino acids in rat vitreous perfusates by capillary electrophoresisELECTROPHORESIS, Issue 17 2004Kongthong Thongkhao-On Abstract In vivo determinations of amino acids are important for improving our understanding of physiological states of biological tissue function and dysfunction. However, the chemically complex matrix of different biological fluids complicates the assay of this important class of molecules. We introduce a method for characterizing the amino acid composition of submicroliter volumes of vitreous humor perfusates. Low-flow push-pull perfusion sampling is compatible with collecting small volume samples in a complicated matrix that are potentially difficult to separate. An efficient, sensitive, and rapid analysis of amino acids from in vivo perfusates of the vitreous is presented with 3-(4-carboxybenzoyl)-2-quinoline-carboxaldehyde (CBQCA) derivatitation and capillary electrophoresis (CE) separation with laser-induced fluorescence detection (LIF). Derivatization with CBQCA for up to 2 h provided high sensitivity and low detection limits at the nM level. Seventeen amino acids including D -serine (D -Ser) and D -aspartate (D -Asp) were resolved in less than 10 min. Importantly, D -Ser is separated from its enantiomeric pair. Characterization of vitreal amino acids with this assay technique will be useful for understanding ocular diseases and physiological mechanisms in vision. [source] Mutagenic repair of DNA interstrand crosslinksENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 6 2010Xi Shen Abstract Formation of DNA interstrand crosslinks (ICLs) in chromosomal DNA imposes acute obstruction of all essential DNA functions. For over 70 years bifunctional alkylators, also known as DNA crosslinkers, have been an important class of cancer chemotherapeutic regimens. The mechanisms of ICL repair remains largely elusive. Here, we review a eukaryotic mutagenic ICL repair pathway discovered by work from several laboratories. This repair pathway, alternatively termed recombination-independent ICL repair, involves the incision activities of the nucleotide excision repair (NER) mechanism and lesion bypass polymerase(s). Repair of the ICL is initiated by dual incisions flanking the ICL on one strand of the double helix; the resulting gap is filled in by lesion bypass polymerases. The remaining lesion is subsequently removed by a second round of NER reaction. The mutagenic repair of ICL likely interacts with other cellular mechanisms such as the Fanconi anemia pathway and recombinational repair of ICLs. These aspects will also be discussed. Environ. Mol. Mutagen., 2010. © 2010 Wiley-Liss, Inc. [source] Uptake and accumulation of sediment-associated 4-nonylphenol in a benthic invertebrate (Lumbriculus variegatus, freshwater oligochaete)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Valeria Croce Abstract In the present work, the oligochaete Lumbriculus variegatus was exposed for 56 d to lake sediment spiked with 4-nonylphenol (4-NP), which is a breakdown product of alkylphenol polyethoxylates, an important class of nonionic surfactants. During the exposure period, the content of 4-NP was determined in the oligochaetes, sediment, overlying water, and pore water in order to monitor the distribution of the 4-NP in the compartments of the test system. Concentration of 4-NP in L. variegatus increased linearly over the course of the test, with an uptake rate coefficient of 1.9 × 10,2 (± 0.2 × 10,2; [g carbon/(g lipid-h)]). No steady state was reached at the end of the exposure period, suggesting that the elimination of 4-NP by the organism was negligible. Ingested sediments played an important role in the accumulation of 4-NP in L. variegatus, which may achieve very high 4-NP body concentrations. The 56-d biota sediment accumulation factor (BSAF) was 24 ± 7 g carbon/g lipid. L. variegatus also was exposed to 4-NP-contaminated field sediment, and field oligochaetes and sediments were collected for 4-NP pollution assessment in aquatic ecosystem. The 4-NP uptake with natural sediment was in accordance with that measured with spiked sediments, suggesting that the bioavailability of sediment-associated 4-NP for L. variegatus was not affected by 4-NP sediment concentration and abiotic sediment characteristics. The BSAFs measured in field oligochaetes, ranging from 39 to 55 g carbon/g lipid, was relatively higher than the bioaccumulation factor measured in laboratory tests. The results suggest that 4-NP concentration can reach high levels in benthic oligochaetes; this can be an important way of exposure for their pelagic predators. [source] A Sex-Specific Affiliative Contact Behavior in Indian Ocean Bottlenose Dolphins, Tursiops sp.ETHOLOGY, Issue 7 2006Richard Connor A variety of signals are employed by animals to establish, mediate and advertise social bonds. Gentle contact behaviors, such as grooming in primates, are an important class of affiliative signals that may provide direct benefits (e.g. stress reduction, parasite removal) in addition to their signal information. Unlike other kinds of signals (e.g. male displays) examples of affiliative contact behaviors restricted to one sex are rare. Here we describe a strongly sex-biased affiliative behavior ,contact swimming', in female bottlenose dolphins in Shark Bay, Western Australia. Females were more likely to be observed contact swimming than males and the presence of males likely influenced this behavior. This is surprising given that female relationships have been characterized as weak. Female dolphins are sometimes herded and harassed by males and contact swimming occurs most often between females in male-biased groups. Contact swimming may serve as a signal of cooperation between females. Possible direct benefits include stress reduction and assisted locomotion. [source] Role of angiotensin receptor blockers in the prevention and management of ischaemic strokeEUROPEAN JOURNAL OF NEUROLOGY, Issue 11 2007G. Mathur Angiotensin receptor blockers (ARB's) are an important class of antihypertensive agents and appear to have a role in the prevention and management of ischaemic stroke. We present a discussion of the data on ARB's in this important condition. [source] Theoretical Description of Substituent Effects in Electrophilic Aromatic Substitution ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2008Tobias Schwabe Abstract The ability of the current Kohn,Sham density functional theory (DFT) to compute the change of the proton affinity (PA) of phenol derivatives due to substitution is investigated. These systems can be used as models to predict reactivities in electrophilic aromatic substitution reactions. The complexity of the problem is increased systematically by introducing successively up to four substituents in five typical cases (methyl, cyano, fluorine, chlorine, and bromine). Our investigation can be regarded as representative for an important class of problems consistently encountered in the DFT modeling of organic reactions. High-level theoretical reference data from CCSD(T) and SCS-MP2 wave-function calculations are presented, and the PAs are compared to those obtained by a series of density functionals (DFs). It is shown that not all DFs are capable of quantitatively reproducing the substituent effects. These can be simply linear in the number of substituents or show more complicated patterns. Especially for halogens, some DFs even fail completely. In these cases, linearly increasing errors with the number of groups are observed. Reliable results are obtained with hybrid DFs or the even more accurate double-hybrid DF approach. The errors are attributed to the common self-interaction (over-delocalization) error in part of the DFs. Comparison with Hartree,Fock results shows that a reliable account of electron correlation is necessary to compute the PA of unsaturated and highly substituted molecules with chemical accuracy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Novel 4-Aminoquinolines through Microwave-Assisted SNAr Reactions: a Practical Route to Antimalarial AgentsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2007Sergio Melato Abstract 4-Aminoquinolines have recently been indicated to be an important class of chemotherapeutic agents for artemisinin-based antimalarial combination therapy. A rapid, cheap, possibly clean and scalable route to 4-aminoquinolines endowed with multiple diversity is therefore badly needed. Classically, they have been prepared by means of SNAr reactions, requiring hazardous or costly reagents and conditions and complex purification procedures. In this paper, microwave flash-heating chemistry is shown to allow the efficient conversion of the available 4,7-dichloroquinoline into a library of aminoquinolines in high yields and purities, with no need for further purification steps and requiring very short reaction times. Some of the compounds in this library were active against chloroquine-sensitive and chloroquine-resistant parasite strains.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of Benzomorphan Analogues by Intramolecular Buchwald,Hartwig CyclizationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2007Anton S. Khartulyari Abstract A new strategy toward the important class of benzomorphans is described. The key bond formation is based on an intramolecular Buchwald,Hartwig enolate arylation reaction. Thus, alkylation of piperidones with ortho -bromobenzyl bromides provides the necessary substrates. In the presence of a palladium catalyst, a sterically hindered phosphane ligand, and a base, carbon,carbon bond formation to tricyclic benzomorphan derivatives takes place. After removal of the N -protecting group, derivatization reactions are possible. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Novel Pyrazines from the Myxobacterium Chondromyces crocatus and Marine BacteriaEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2005Jeroen S. Dickschat Abstract The volatiles released by two strains of the myxobacterium Chondromyces crocatus and seven strains of marine Alphaproteobacteria from the North Sea were collected using the CLSA or SPME headspace methods and analysed by GC-MS. In the extracts of C. crocatus 27 pyrazines were identified, belonging to different classes. 2,5-Dialkylpyrazines and related 3-methoxy-2,5-dialkylpyrazines dominated. Several pyrazines like 2-(1-methylethenyl)-5-(1-methylethyl)pyrazine (7) and 3-methoxy-2,5-dialkylpyrazines with methyl, isopropyl, isobutyl or sec -butyl side-chains were obtained from natural sources for the first time. It was essential for the identification to rely on synthetic reference materials, which were obtained using Fürstner's iron-catalysed coupling of chloropyrazines with Grignard reagents or condensation of azido ketones as key steps. The synthetic material allowed the identification of two previously unknown attractants of bacterial origin for the pineapple beetle Carpophilus humeralis, namely 3-methoxy-2-(1-methylpropyl)-5-(2-methylpropyl)pyrazine (17) and 3-methoxy-2,5-bis(1-methylpropyl)pyrazine (52). Several 2,5-dialkylpyrazines were identified in the extracts of the marine Alphaproteobacteria. The unique 2,5-dimethyl-3-(methylsulfanyl)pyrazine (67) represents a new type of natural pyrazine. Our results, together with literature reports, show that pyrazines are an important class of bacterial volatiles which might be more widespread than previously thought. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Intrinsic Surface Dipoles Control the Energy Levels of Conjugated PolymersADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Georg Heimel Abstract Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3-hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of , -conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first-principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the , -electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design. [source] Chemistry of phosphorus ylides 21 new route for the synthesis of azetidinones.HETEROATOM CHEMISTRY, Issue 6 2005Reaction of phosphonium ylides with benzil-, o -naphthoquinone-, triketonemonoanils Active vinylidenetriphenylphosphoranes are nucleophilic reagents which can be con- sidered as versatile synthons for the synthesis of new heterocycles. The active phosphacumulene ylides, namely N -phenylimino- 2a, 2-oxo- 2b or 2-thioxo-vinylidenetriphenylphosphoranes (2c), react with benzil- (1a,b), o -naphthoquinone- (8), or triketone-monoanils (11), to give the corresponding phenylimino- (3a, d, 9a, 12a), oxo- (3b, e, 9b, 12b), or thioxoazetidinones (3c, f, 9c, 12c), respectively, which constitute an important class of organic compounds with medicinal and biological importance. On the other hand, quinone monoanils 1a, 8, 11 can be converted by reaction with the stabilized alkylidenephosphoranes (5a,d), namely acetylmethylene- 5a, methoxycarbonylmethylene- 5b, ethoxycarbonylmethylene- 5c, and benzoylmethylene-triphenylphosphorane 5d, into the phosphoranylidenes (7a,d, 10a,d, 13a,d). No reaction was observed between iminophosphorane (14) and the monoanil (11). The structures of the new products were assigned according to consistent analytical and spectroscopic data. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:476,483, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20144 [source] On integration of a cyclic soil plasticity modelINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2001Majid T. Manzari Abstract Performance of three classes of explicit and implicit time-stepping integrators is assessed for a cyclic plasticity constitutive model for sands. The model is representative of an important class of cyclic plasticity models for soils and includes both isotropic and nonlinear kinematic hardening. The implicit algorithm is based on the closest point projection method and the explicit algorithm follows a cutting-plane integration procedure. A sub-stepping technique was also implemented. The performance of these algorithms is assessed through a series of numerical simulations ranging from simulations of laboratory tests (such as triaxial and bi-axial compression, direct shear, and cyclic triaxial tests) to the analysis of a typical boundary value problem of geotechnical earthquake engineering. These simulations show that the closest point projection algorithm remains stable and accurate for relatively large strain increments and for cases where the mean effective stress in a soil element reaches very small values leading to a liquefaction state. It is also shown that while the cutting plane (CP) and sub-stepping (SS) algorithms provide high efficiency and good accuracy for small to medium size strain increments, their accuracy and efficiency deteriorate faster than the closest point projection method for large strain increments. The CP and SS algorithms also face convergence difficulties in the liquefaction analysis when the soil approaches very small mean effective stresses. Copyright © 2001 John Wiley & Sons, Ltd. [source] Identification and adaptive control of some stochastic distributed parameter systemsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2001B. Pasik-Duncan Abstract An important class of controlled linear stochastic distributed parameter systems is that with boundary or point control. A survey of some existing adaptive control problems with their solutions for the boundary or the point control of a partially known linear stochastic distributed parameter systems is presented. The distributed parameter system is described by an analytic semigroup with cylindrical white noise and a control that occurs only on the boundary or at discrete points. The unknown parameters in the model appear affinely in both the infinitesimal generator of the semigroup and the linear transformation of the control. The noise in the system is a cylindrical white Gaussian noise. Strong consistency is verified for a family of least-squares estimates of the unknown parameters. For a quadratic cost functional of the state and the control, the certainty equivalence control is self-optimizing, that is the family of average costs converges to the optimal ergodic cost. Copyright © 2001 John Wiley & Sons, Ltd. [source] The Development of Light-Emitting Dendrimers for Displays,ADVANCED MATERIALS, Issue 13 2007L. Burn Abstract Dendrimers are now an important class of light-emitting material for use in organic light-emitting diodes (OLEDs). Dendrimers are branched macromolecules that consist of a core, one or more dendrons, and surface groups. The different parts of the macromolecule can be selected to give the desired optoelectronic and processing properties. The first light-emitting dendrimers were fluorescent but more recently highly efficient phosphorescent dendrimers have been developed. OLEDs containing light-emitting dendrimers have been reported to have external quantum efficiencies of up to 16,%. The solubility of the dendrimers opens the way for simple processing and a new class of flat-panel displays. In this Review we show how the structure of the light-emitting dendrimers controls key features such as intermolecular interactions and charge transport, which are important for all OLED materials. The advantages of the dendrimer architecture for phosphorescent emitters and the way the structure can be varied to enhance materials performance and device design are illustrated. [source] Discontinuous feedbacks, discontinuous optimal controls, and continuous-time model predictive controlINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 3-4 2003Fernando A. C. C. Fontes Abstract It is known that there is a class of nonlinear systems that cannot be stabilized by a continuous time-invariant feedback. This class includes systems with interest in practice, such as nonholonomic systems, frequently appearing in robotics and other areas. Yet, most continuous-time model predictive control (MPC) frameworks had to assume continuity of the resulting feedback law, being unable to address an important class of nonlinear systems. It is also known that the open-loop optimal control problems that are solved in MPC algorithms may not have, in general, a continuous solution. Again, most continuous-time MPC frameworks had to artificially assume continuity of the optimal controls or, alternatively, impose some demanding assumptions on the data of the optimal control problem to achieve the desired continuity. In this work we analyse the reasons why traditional MPC approaches had to impose the continuity assumptions, the difficulties in relaxing these assumptions, and how the concept of ,sampling feedbacks' combines naturally with MPC to overcome these difficulties. A continuous-time MPC framework using a strictly positive inter-sampling time is argued to be appropriate to use with discontinuous optimal controls and discontinuous feedbacks. The essential features for the stability of such MPC framework are reviewed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Recent Advances in the Synthesis of 2-Imidazolines and Their Applications in Homogeneous CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Han Liu Abstract As an important class of heterocyclic scaffolds, 2-imidazolines have attracted the attention from the chemists interested in natural products, pharmaceutical chemistry, synthetic organic chemistry, coordination chemistry, and homogeneous catalysis. To fulfill the demand of structural diversity, many efficient methods towards 2-imidazolines, as well as modifications of traditional methods, have been reported in the past two decades. 2-Imidazolines have been developed as ligands in homogeneous catalysis, for the substitution on the nitrogen atom that provides an opportunity for fine-tuning of the electronic effect. This review summarizes recent advances in the synthesis of 2-imidazolines and their applications in homogeneous catalysis. [source] Oxycellulose: Significant characteristics in relation to its pharmaceutical and medical applicationsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009Bajerová Martina Abstract As a biomaterial, cellulose can be converted into a wide range of derivatives with desired properties for a variety of medical, biomedical, and pharmaceutical applications. The oxidation of cellulose yields oxidized cellulose (OC, oxycellulose, 6-carboxycellulose). OC represents an important class of biocompatible and bioresorbable polymers. In vivo bioabsorption of OC occurs via chemical depolymerization and enzymatic hydrolysis. Despite the fact OC is well established as a hemostatic agent and is widely used in a clinical practice, it still attracts a great interest and its new applications, especially pharmaceutical, are investigated. The present review is focused on characterization of OC's physical and chemical properties. Its synthesis and mechanisms involved in its in vivo and in vitro biodegradation are discussed. Medical and biomedical applications of OC are summarized, and especially its hemostatic, enterosorbent, and wound-healing properties are described. In addition to these applications, OC could be used as a pharmaceutical excipient in solid (e.g., tablets, microparticles), semisolid (e.g., gels), as well as liquid (e.g., suspensions) dosage forms. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:199,208, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20161 [source] Charles Darwin, embryology, evolution and skeletal plasticityJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2010B. K. Hall Summary Darwin provided us with the theory of evolutionary change through natural selection. Just as important to the science of biology was Darwin's recognition that all organisms could be classified and were related to one another because they arose from a single common universal ancestor , what we know as the universal tree of life (UtoL). All the features of the skeletal biology of fish therefore can be explained, both in an evolutionary framework (ultimate causation) and in the framework of development, growth and physiology (proximate causation). Neither approach is complete without the other. I will outline the elements of Darwin's theories on evolution and classification and, as importantly, discuss what was missing from Darwin's theories. An important class of evidence for evolution used by Darwin came from embryology, both comparative embryology and the existence of vestiges and atavisms. After discussing this evidence I examine some fundamental features of skeletal development and evolution These include: the presence of four skeletal systems in all vertebrates; the existence of two skeletons, one based on cartilage, the other on bone and dentine; the modular nature of skeletal development and evolution; and the plasticity of the skeleton in response to either genetic or environmental changes. [source] Quantum chemical modeling of enzymatic reactions: The case of histone lysine methyltransferaseJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2010Polina Georgieva Abstract Quantum chemical cluster models of enzyme active sites are today an important and powerful tool in the study of various aspects of enzymatic reactivity. This methodology has been applied to a wide spectrum of reactions and many important mechanistic problems have been solved. Herein, we report a systematic study of the reaction mechanism of the histone lysine methyltransferase (HKMT) SET7/9 enzyme, which catalyzes the methylation of the N-terminal histone tail of the chromatin structure. In this study, HKMT SET7/9 serves as a representative case to examine the modeling approach for the important class of methyl transfer enzymes. Active site models of different sizes are used to evaluate the methodology. In particular, the dependence of the calculated energies on the model size, the influence of the dielectric medium, and the particular choice of the dielectric constant are discussed. In addition, we examine the validity of some technical aspects, such as geometry optimization in solvent or with a large basis set, and the use of different density functional methods. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Ab initio calculations of intramolecular parameters for a class of arylamide polymersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2006Satyavani Vemparala Abstract Using DFT methods, we have determined intramolecular parameters for an important class of arylamide polymers displaying antimicrobial and anticoagulant inhibitory properties. A strong link has been established between these functions and the conformation that the polymers adopt in solution and at lipid bilayer interfaces. Thus, it is imperative for molecular dynamics simulations designed to probe the conformational behavior of these systems to accurately describe the torsional degrees of freedom. Standard force fields were shown to be deficient in this respect. Therefore, we have computed the relevant torsional energy profiles using a series of constrained geometry optimizations. We have also determined electrostatic parameters using our results in combination with standard RESP charge optimization. Force constants for bond and angle potentials were calculated by iteratively matching quantum and classical normal modes via a Monte Carlo scheme. The resulting new set of parameters accurately described the conformation and dynamical behavior of the arylamide polymers. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 693,700, 2006 [source] Evidence of an Interaction Involving Complexity and Coupling as Predicted by Normal Accident TheoryJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 3 2007Frederick Wolf This paper describes a test of the principle hypothesis of Normal Accident Theory. It posits and tests for the existence of an interaction involving interactive complexity and coupling associated with in an important class of manufacturing organizations. Ninety four (n=94) petroleum refineries located in the United States during the five-year period 1993,97 were examined. The dependent variable in this test was the ratio of Reportable Quantity accidental hazardous chemical releases per unit of production. Refinery capacity and age were included as control variables. This study identified a statistically significant interaction involving interactive complexity and coupling, as predicted by Normal Accident Theory. The interaction appears to be consistent with an important core hypothesis of normal accident theory over a significant portion of its domain. The nature of this interaction and its potential relevance to organizational sense making is discussed. Additional opportunities for quantitative research involving Normal Accident Theory are identified. [source] Measuring the Benefits of Examinee-Selected QuestionsJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2005Nancy L. Allen Allowing students to choose the question(s) that they will answer from among several possible alternatives is often viewed as a mechanism for increasing fairness in certain types of assessments. The fairness of optional topic choice is not a universally accepted fact, however, and various studies have been done to assess this question. We examine an important class of experiments that we call C1-A, "choose one, answer all," designs, and point out an important problem that they face. We suggest two analytical methods that can be used to circumvent this problem. We illustrate our ideas using the data from Bridgeman et al. (1997). Our reanalysis of these data show: (a) that differential topic difficulty exists in real choice data, (b) that it affects naďve analyses of such data and masks the effects, positive or negative, of examinee choice, (c) that in this study there is a measurable and positive effect of examinee choice that follows predicted patterns in most but not all cases, (d) that the beneficial strength of examinee choice varies from case to case, and (e) that while the benefits of choice in terms of average points scored on the essays are usually positive, there is a substantial amount of variation around these averages and it is not uncommon for "incorrect" choices to be associated with higher test performance. [source] What's in a Standard Form Contract?JOURNAL OF EMPIRICAL LEGAL STUDIES, Issue 4 2007An Empirical Analysis of Software License Agreements The vast majority of commercial transactions are governed by standard form contracts, but little is known about their actual content and the determinants of that content. This article provides a comprehensive empirical analysis of an important class of modern standard form contracts,software license agreements. In a sample of 647 licenses for software from various markets, I document the prevalence of terms relating to license acceptance, license scope, limitations on transfer, warranties, limitations on liability, maintenance and support, and conflict resolution. I find that almost all licenses display a net bias, relative to relevant default rules, in favor of the software company (the contract writer). I also investigate firm- and buyer-type determinants of the net bias. Larger and (controlling for size) younger firms offer more one-sided terms. Firms offer similar terms to both business buyers and members of the general public. In addition to providing new insight about the nature of standard form contracts, the results may inform efforts to draft new default rules to govern software transactions. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||