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Selected AbstractsOrigins and Applications of London Dispersion Forces and Hamaker Constants in CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2000Roger H. French The London dispersion forces, along with the Debye and Keesom forces, constitute the long-range van der Waals forces. London's and Hamaker's work on the point-to-point dispersion interaction and Lifshitz's development of the continuum theory of dispersion are the foundations of our understanding of dispersion forces. Dispersion forces are present for all materials and are intrinsically related to the optical properties and the underlying interband electronic structures of materials. The force law scaling constant of the dispersion force, known as the Hamaker constant, can be determined from spectral or parametric optical properties of materials, combined with knowledge of the configuration of the materials. With recent access to new experimental and ab initio tools for determination of optical properties of materials, dispersion force research has new opportunities for detailed studies. Opportunities include development of improved index approximations and parametric representations of the optical properties for estimation of Hamaker constants. Expanded databases of London dispersion spectra of materials will permit accurate estimation of both nonretarded and retarded dispersion forces in complex configurations. Development of solutions for generalized multilayer configurations of materials are needed for the treatment of more-complex problems, such as graded interfaces. Dispersion forces can play a critical role in materials applications. Typically, they are a component with other forces in a force balance, and it is this balance that dictates the resulting behavior. The ubiquitous nature of the London dispersion forces makes them a factor in a wide spectrum of problems; they have been in evidence since the pioneering work of Young and Laplace on wetting, contact angles, and surface energies. Additional applications include the interparticle forces that can be measured by direct techniques, such as atomic force microscopy. London dispersion forces are important in both adhesion and in sintering, where the detailed shape at the crack tip and at the sintering neck can be controlled by the dispersion forces. Dispersion forces have an important role in the properties of numerous ceramics that contain intergranular films, and here the opportunity exists for the development of an integrated understanding of intergranular films that encompasses dispersion forces, segregation, multilayer adsorption, and structure. The intrinsic length scale at which there is a transition from the continuum perspective (dispersion forces) to the atomistic perspective (encompassing interatomic bonds) is critical in many materials problems, and the relationship of dispersion forces and intergranular films may represent an important opportunity to probe this topic. The London dispersion force is retarded at large separations, where the transit time of the electromagnetic interaction must be considered explicitly. Novel phenomena, such as equilibrium surficial films and bimodal wetting/dewetting, can result in materials systems when the characteristic wavelengths of the interatomic bonds and the physical interlayer thicknesses lead to a change in the sign of the dispersion force. Use of these novel phenomena in future materials applications provides interesting opportunities in materials design. [source] Role of dopamine transporter imaging in routine clinical practiceMOVEMENT DISORDERS, Issue 12 2003Vicky Marshall MRCP Abstract Functional imaging of the dopamine transporter (DAT) defines integrity of the dopaminergic system and has its main clinical application in patients with mild, incomplete, or uncertain parkinsonism. Imaging with specific single positron emission computerised tomography ligands for DAT (FP-CIT, ,-CIT, IPT, TRODAT) provides a marker for presynaptic neuronal degeneration. Striatal uptake correlates with disease severity, in particular bradykinesia and rigidity, and monitoring of progression assists in clinical trials of potential neuroprotective drugs. DAT imaging is abnormal in idiopathic Parkinson's disease, multiple system atrophy and progressive supranuclear palsy and does not distinguish between these disorders. Dopamine loss is seen even in the earliest clinical presentations of true parkinsonism; a normal scan suggests an alternative diagnosis such as essential tremor, vascular parkinsonism (unless there is focal basal ganglia infarction), drug-induced parkinsonism, or psychogenic parkinsonism. Congruence between working clinical diagnosis and DAT imaging increases over time in favour of baseline DAT imaging results. Additional applications are characterising dementia with parkinsonian features (abnormal results in dementia with Lewy bodies, normal in Alzheimer's disease); and differentiating juvenile-onset Parkinson's disease (abnormal DAT) from dopa-responsive dystonia (normal DAT). © 2003 Movement Disorder Society [source] Phase determination via Sayre-type equations with anomalous-scattering dataACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2001Jeffrey Roach The necessary background for the analysis of complex-valued electron-density maps is established. Various systems of structure-factor equations of convolutional type akin to Sayre's squaring method equations are tested for agreement on the real and imaginary parts of the electron density as well as approximations thereof. A system of convolutional structure-factor equations holding in a complex-valued electron density generated by two atom types is developed. The scope of application of these equations is determined and it is shown that the equations provide a method of extrapolating high-resolution phases from a low-resolution base phase set without introducing further model bias. Additional applications to phase refinement are explored. [source] Structurating Activity Theory: An Integrative Approach to Policy KnowledgeCOMMUNICATION THEORY, Issue 1 2010Heather E. Canary This article presents a theoretical framework for investigating the communicative construction of policy knowledge. Research regarding public policy and organizational knowledge demonstrates the importance of these areas for organizational communication scholars. In light of this research, structurating activity theory is offered as an integration of structuration theory and cultural-historical activity theory (CHAT). Four theoretical constructs are discussed: (a) structuration through activity, (b) mediation of social activity, (c) contradictions as generative mechanisms, and (d) intersections of activity systems. Six propositions offer the explanatory significance of each construct, and then the theory is applied to a case study of the construction of special education policy knowledge. Additional applications of structurating activity theory are proposed and suggestions for future research directions are offered. La thÈorie de l'activitÈ structurante,: une approche intÈgrative aux connaissances sur les politiques RÈsumÈ Cet article prÈsente un cadre thÈorique pour l'Ètude de la construction communicationnelle des connaissances sur les politiques. La recherche au sujet des politiques publiques et des connaissances organisationnelles dÈmontre l'importance de ces domaines pour les chercheurs en communication organisationnelle. ¿ la lumiËre de cette littÈrature, nous proposons une thÈorie de l'activitÈ structurante qui intËgre la thÈorie de la structuration et la thÈorie de l'activitÈ historico-culturelle. Quatre concepts sont discutÈs,: 1) la structuration par l'activitÈ, 2) la mÈdiation de l'activitÈ sociale, 3) les contradictions comme mÈcanismes gÈnÈratifs et 4) les intersections de systËmes d'activitÈs. Six propositions suggËrent l'importance explicative de chaque concept. La thÈorie est ensuite appliquÈe , une Ètude de cas de la construction des connaissances sur les politiques de l'Èducation spÈcialisÈe. D'autres applications de la thÈorie de l'activitÈ structurante sont proposÈes et des suggestions d'avenues de recherche sont offertes. Die Strukturation der Aktivitätstheorie: Ein integrativer Ansatz zu Politikwissen In diesem Artikel legen wir ein theoretisches Bezugssystem zur Untersuchung der kommunikativen Konstruktion von Politikwissen dar. Die aktuellen Forschungsaktivitäten im Bereich von Public Policy und Organisationswissen verdeutlichen die Bedeutung dieser Felder für Organisationskommunikationswissenschaftler. Im Lichte dieser Forschung stellen wir die Strukturation der Aktivitätstheorie als eine Integration von Strukturationstheorie und kulturhistorischer Aktivitätstheorie vor. Vier theoretische Konstrukte werden diskutiert: (1) Strukturation durch Aktivität; (2) Mediation von sozialer Aktivität; (3) Widersprüche als generative Mechanismen und (4) Überschneidungen der Aktivitätssysteme. Sechs Propositionen erklären jedes einzelne Konstrukt. Anschließend wird die Theorie anhand eines Fallbeispiels zur Konstruktion von Politikwissen in der Förderpädagogik angewendet. Weitere Anwendungen der Strukturations-Aktivitätstheorie werden dargelegt, ergänzt durch Vorschläge für weiterführenden Forschung. La Teoría de Estructuración de la Actividad: Una Aproximación Integradora al Conocimiento sobre las Políticas Resumen Este artículo presenta un marco teórico para la investigación de la construcción comunicativa del conocimiento sobre las políticas. La investigación sobre las políticas públicas y el conocimiento organizacional demuestra la importancia de estas áreas para los estudiosos de la comunicación organizacional. A la luz de esta investigación, la teoría de la actividad de estructuración es ofrecida como una integración de la teoría de estructuración y la teoría de la actividad cultural-histórica (CHAT). Cuatro constructos teóricos son discutidos: (1) la estructuración a través de la actividad; (2) la mediación de la actividad social; (3) las contradicciones como mecanismos generativos; y (4) las intersecciones de los sistemas de actividad. Seis proposiciones ofrecen la significancia explicativa de cada constructo y luego la teoría es aplicada a un estudio de caso de la construcción de conocimiento de políticas sobre la educación especial. Aplicaciones adicionales de la teoría de la actividad de estructuración son propuestas y sugerencias para las direcciones de la investigación futuras son ofrecidas. [source] A clinical study evaluating the treatment of supra-alveolar-type defects with access flap surgery with and without an enamel matrix protein derivative: a pilot studyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 8 2008Holger Jentsch Abstract Aim: There is evidence that regenerative treatment of intra-bony and mandibular class II furcation defects with access flap and an application of an enamel matrix protein derivative (EMD) can result in a clinical benefit compared with access flap alone. The aim of this pilot study was to check if the results of access flap surgery in suprabony defects are improved by additional application of EMD. Material and Methods: Thirty-nine adult subjects with supra-alveolar-type defects were randomly assigned to a test (n=25) and a control group (n=14). Seventy teeth were treated with EMD; 28 teeth were treated by access flap. Probing depth (PD), clinical attachment level and bleeding on probing were evaluated at baseline and after 12 months. Results: PD of the operated teeth was improved in both groups (p<0.001 to p=0.041) but always better in the test group. The attachment gain was 2.72±1.80 mm at sites with an initial PD 7 mm in the test group and 0.78±0.62 mm in the control group (p=0.004). In the test group the mean attachment gain was 0.97±0.92 mm (p<0.001); the mean reduction of PD was 1.55±0.90 mm (p<0.001). Conclusions: The data suggest a significant clinical benefit of supplementary application of EMD during surgical treatment of periodontitis of supra-alveolar pockets, especially in deeper pockets. [source] Continuous arterial spin labeling at the human common carotid artery: the influence of transit timesNMR IN BIOMEDICINE, Issue 1 2005Toralf Mildner Abstract In evaluating the sensitivity of arterial spin labeling (CASL) and for quantification of perfusion, knowledge of the transit time from the labeling plane to the imaging slice is crucial. The purpose of the current study was to obtain estimates of transit times relevant under the specific experimental conditions of CASL in human subjects using a separate local labeling coil at the neck. Specifically, the post-label delay (PLD), i.e. the time between the end of the labeling period and the image acquisition, was varied either with or without additional application of crusher gradients to suppress intravascular signal contributions. The overall sensitivity change for varying the PLD between 1000 and 1700,ms was low. A tissue transit time from the neck to an axial supraventricular section through Broca's knee was obtained by fitting the PLD dependence to a two-compartment model. Averaging over subjects yielded 1930,±,110,ms for the tissue transit time, and 73,±,5,ml,min,1 100,g,1 for the cerebral blood flow. Small areas that exhibited a very high signal change upon labeling were indicative of regional variation in cerebral blood flow related to vascular anatomy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Role of heat treatment in childhood cancers: Distinct resistance profiles of solid tumor cell lines towards combined thermochemotherapyPEDIATRIC BLOOD & CANCER, Issue 5 2005Anette Debes PhD Abstract Background Since information on the efficacy of hyperthermia in combination with chemotherapy on pediatric tumors is limited, we performed a systematic analysis on the synergistic effects of a combined application of heat and chemotherapy on 20 tumor cell lines derived from patients with neuroblastomas, Ewing tumors, germ cell tumors (GCT), and osteosarcomas. Methods Cisplatin (cDDP), a cross-linking agent, and etoposide (VP-16), a topoisomerase II inhibitor, were examined either alone or in combination with heat (42°C, 43°C) by using the XTT-assay 1. Results Our data demonstrate that heat stress at 43°C for 1 hr, but not at 42°C, leads to a notable cytotoxic effect on the different tumor cells. The comparison of mean survival fractions reveals values between 62% for neuroblastoma cells and 76% for Ewing tumor cells. Analyzing the sensitivity to chemotherapy alone, our results show that cDDP (5 ,g/ml) reduces cell growth to 47% in Ewing tumor cells, to 61% in neuroblastoma cells, to 75% in GCT cells, and to 76% in osteosarcoma cells. Treatment with VP-16 (10 ,g/ml) decreases cell survival to mean values between 58% (neuroblastomas) and 77% (osteosarcomas). Simultaneous application of heat and chemotherapy enhances synergistically cDDP cytotoxicity in all tumor types tested, whereas the efficacy of VP-16 is only slightly influenced by additional application of hyperthermia. The cytotoxicity of cDDP (5 ,g/ml) can be increased by a factor of between 1.5 and 2.5 at 42°C and from 2.6 to 14.0 at 43°C. Furthermore, the results show that the sensitivity to heat (43°C) as well as the sensitivity to chemotherapy and combined thermochemotherapy varies considerably between cell lines of the same tumor group. Conclusions Simultaneous application of hyperthermia synergistically enhances the cytotoxicity of the alkylating agent cDDP, but not of the topoisomerase II inhibitor VP-16, in a defined spectrum of cell lines from different pediatric tumor entities. © 2005 Wiley-Liss, Inc. [source] SHORT COMMUNICATION: CD3, CD56+ CD16+ Natural Killer Cells and Improvement of Pregnancy Outcome in IVF/ICSI Failure After Additional IVIG-TreatmentAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 3 2010Lothar Heilmann Citation Heilmann L, Schorsch M, Hahn T. CD3, CD56+ CD16+ Natural killer cells and improvement of pregnancy outcome in IVF/ICSI failure after additional IVIG-treatment. Am J Reprod Immunol 2010; 63: 263,265 Problem, The purpose of this retrospective, observational study was to investigate whether additional treatment with intravenous immunglobulin (IVIG) increased the rate of successful pregnancies after repeated implantation failure (RIF). The retrospective data were compared with data of patients without IVIG-therapy from the meta-analysis of Clark et al. Method of study, A total of 188 women with 226 treatment cycles between 2007 and 2009 were evaluated for IVIG therapy. The percentage of NK cells was measured two times before a new embryo transfer (only women with NK cell percentages >12% were included) and after embryo transfer at a positive pregnancy test. Results, In comparison with the meta-analysis of Clark et al., we observed a pregnancy rate of 50.5%, an implantation rate of 21% and a miscarriage rate of 16.8%. In 42%/IVIG- patient or 34.9%/embryo transfer, we observed a live born baby. The live born rate per embryo was 16.6%. In accordance with the study of Kwak et al., we indicate a decrease in the NK cells in patients with improved pregnancy outcome. Conclusion, In a subgroup of RIF-patients with high level of CD56+ CD16+ NK-cells the additional application of IVIG leads to a favourable pregnancy outcome. [source] Neuromyelitis optica: Pathogenicity of patient immunoglobulin in vivo,ANNALS OF NEUROLOGY, Issue 5 2009Monika Bradl PhD Objective Severe inflammation and astrocyte loss with profound demyelination in spinal cord and optic nerves are typical pathological features of neuromyelitis optica (NMO). A diagnostic hallmark of this disease is the presence of serum autoantibodies against the water channel aquaporin-4 (AQP-4) on astrocytes. Methods We induced acute T-cell,mediated experimental autoimmune encephalomyelitis in Lewis rats and confronted the animals with an additional application of immunoglobulins from AQP-4 antibody,positive and ,negative NMO patients, multiple sclerosis patients, and control subjects. Results The immunoglobulins from AQP-4 antibody,positive NMO patients are pathogenic. When they reach serum titers in experimental animals comparable with those seen in NMO patients, they augment clinical disease and induce lesions in the central nervous system that are similar in structure and distribution to those seen in NMO patients, consisting of AQP-4 and astrocyte loss, granulocytic infiltrates, T cells and activated macrophages/microglia cells, and an extensive immunoglobulin and complement deposition on astrocyte processes of the perivascular and superficial glia limitans. AQP-4 antibody containing NMO immunoglobulin injected into naïve rats, young rats with leaky blood,brain barrier, or after transfer of a nonencephalitogenic T-cell line did not induce disease or neuropathological alterations in the central nervous system. Absorption of NMO immunoglobulins with AQP-4,transfected cells, but not with mock-transfected control cells, reduced the AQP-4 antibody titers and was associated with a reduction of astrocyte pathology after transfer. Interpretation Human anti,AQP-4 antibodies are not only important in the diagnosis of NMO but also augment disease and induce NMO-like lesions in animals with T-cell,mediated brain inflammation. Ann Neurol 2009;66:630,643 [source] Effects of functionalized and nonfunctionalized single-walled carbon nanotubes on root elongation of select crop species,,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2008Jaclyn E. Cañas Abstract Single-walled carbon nanotubes have many potential beneficial uses, with additional applications constantly being investigated. Their unique properties, however, create a potential concern regarding toxicity, not only in humans and animals but also in plants. To help develop protocols to determine the effects of nanotubes on plants, we conducted a pilot study on the effects of functionalized and nonfunctionalized single-walled carbon nanotubes on root elongation of six crop species (cabbage, carrot, cucumber, lettuce, onion, and tomato) routinely used in phytotoxicity testing. Nanotubes were functionalized with poly-3-aminoben-zenesulfonic acid. Root growth was measured at 0, 24, and 48 h following exposure. Scanning-electron microscopy was used to evaluate potential uptake of carbon nanotubes and to observe the interaction of nanotubes with the root surface. In general, nonfunctionalized carbon nanotubes affected root length more than functionalized nanotubes. Nonfunctionalized nanotubes inhibited root elongation in tomato and enhanced root elongation in onion and cucumber. Functionalized nanotubes inhibited root elongation in lettuce. Cabbage and carrots were not affected by either form of nanotubes. Effects observed following exposure to carbon nanotubes tended to be more pronounced at 24 h than at 48 h. Microscopy images showed the presence of nanotube sheets on the root surfaces, but no visible uptake of nanotubes was observed. [source] Hollow, pH-sensitive calcium,alginate/poly(acrylic acid) hydrogel beads as drug carriers for vancomycin releaseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Hong-Ru Lin Abstract In this study, hollow calcium,alginate/poly(acrylic acid) (PAA) hydrogel beads were prepared by UV polymerization for use as drug carriers. The hollow structure of the beads was fortified by the incorporation of PAA. The beads exhibited different swelling ratios when immersed in media at different pH values; this demonstrated that the prepared hydrogel beads were pH sensitive. A small amount (<9%) of vancomycin that had been incorporated into the beads was released in simulated gastric fluid, whereas a large amount (,67%) was released in a sustained manner in simulated intestinal fluid. The observed drug-release profiles demonstrated that the prepared hydrogel beads are ideal candidate carriers for vancomycin delivery into the gastrointestinal tract. Furthermore, the biological response of cells to these hydrogel beads indicated that they exhibited good biological safety and may have additional applications in tissue engineering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] ANTIMICROBIAL, PHYSICAL AND MECHANICAL PROPERTIES OF CHITOSAN-BASED FILMS INCORPORATED WITH THYME, CLOVE AND CINNAMON ESSENTIAL OILSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2009M.H. HOSSEINI ABSTRACT Chitosan-based films containing thyme, clove and cinnamon essential oils at 0.5, 1 and 1.5% v/v were prepared to examine their antibacterial, physical and mechanical properties. Scanning electron microscopy was carried out to explain structure,property relationships. Films containing thyme essential oil revealed larger inhibition zones than those containing clove and cinnamon essential oils against gram-positive and gram-negative bacteria tested. Films were more effective against gram-positive bacteria than gram-negative. Incorporating thyme and clove essential oils into chitosan-based films increased moisture content (from 17.80,28.38%), solubility in water (25.97,30.62%), water vapor transmission rate (0.00233,0.00571 g/s/m2) and elongation at break (25.31,42.70%) of films. Cinnamon-enriched films had opposite changes such as increase in tensile strength (from 12.2,21.35 MPa) and decrease in moisture content (17.80,9.36%) and solubility in water (25.9,14.21%) of films. PRACTICAL APPLICATIONS Microbial growth on food surfaces is a major cause of food spoilage. Combining antimicrobial agents such as plant essential oils directly into a food packaging polymer is a form of active packaging. These films possess the potential for improving microbial stability of foods by acting on the food surface upon contact. Because of the effect of direct addition of plant essential oils to food on sensory characteristics of packaged food, incorporation of essential oils into films may have additional applications in food packaging. [source] The economics of soil productivity: local, national and global perspectivesLAND DEGRADATION AND DEVELOPMENT, Issue 6 2004D. J. Knowler Abstract Soil degradation is a mounting problem on many smallholder lands in developing countries. Economic analysis has been an important tool in addressing this problem, beginning with assessments of the financial attractiveness of investing in soil conservation works. Data compiled from 67 studies of the financial attractiveness of conservation technologies suggest that many can provide positive net returns at the farm level (64·2,per,cent). While such studies have made a valuable contribution, economists have been exploring additional applications of economics to the problem, such as the development of new perspectives under the guise of ecological economics. As a result, this paper argues it is an opportune time to assess progress in the field of economic analysis of soil degradation and to consider the policy ramifications of this research. Key issues are grouped into farm-level considerations, national policy linkages and global issues. A number of policy implications emerge. Clearly, devising effective incentives at the farm or community (collective action) level must be a priority. As part of this effort, even more attention should be paid to the influence of macroeconomic and sectoral policies on soil productivity. Since soil degradation is also a problem with global ramifications, there is a clear rationale for intervention at the international level via mechanisms such as international transfers. Copyright © 2004 John Wiley & Sons, Ltd. [source] Embedding 3D models of biological specimens in PDF publicationsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 11 2008Bernhard Ruthensteiner Abstract By providing two examples, the option for embedding 3D models in electronic versions of life science publications is presented. These examples, presumably representing the first such models published, are developmental stages of an evertebrate (Patella caerulea, Mollusca) and a vertebrate species (Psetta maxima, Teleostei) obtained from histological section series reconstruction processed with the software package Amira. These surface rendering models are particularly suitable for a PDF file because they can easily be transformed to a file format required and components may be conveniently combined and hierarchically arranged. All methodological steps starting from specimen preparation until embedding of resulting models in PDF files with emphasis on conversion of Amira data to the appropriate 3D file format are explained. Usability of 3D models in PDF documents is exemplified and advantages over 2D illustrations are discussed, including better explanation capabilities for spatial arrangements, higher information contents, and limiting options for disguising results by authors. Possibilities for additional applications reaching far beyond the examples presented are suggested. Problems such as long-term compatibility of file format and hardware plus software, editing and embedding of files, file size and differences in information contents between printed and electronic version will likely be overcome by technical development and increasing tendency toward electronic at the cost of printed publications. Since 3D visualization plays an increasing role in manifold disciplines of science and appropriate tools for the popular PDF format are readily available, we propose routine application of this way of illustration in electronic life science papers. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||