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Successive Steps (successive + step)
Selected AbstractsEx vivo assessment of irrigant penetration and renewal during the cleaning and shaping of root canals: a digital subtraction radiographic studyINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2010F. Bronnec Bronnec F, Bouillaguet S, Machtou P.Ex vivo assessment of irrigant penetration and renewal during the cleaning and shaping of root canals: a digital subtraction radiographic study. International Endodontic Journal, 43, 275,282, 2010. Abstract Aim, To assess radiographically irrigant penetration in the root canal system of curved roots during root canal shaping procedures ex vivo. Methodology, Thirty extracted mandibular molar teeth with moderate to severe curvature were used. A special aiming device was used to guarantee that each successive radiograph was taken with the same positioning. The mesiolingual canal of each tooth was instrumented using the ProTaper system. For each step of the shaping procedure, two irrigation modalities were repeated in the same order. Active irrigation consisted of a 0.5-mL flush of sodium diatrizoate solution (Hypaque 50%) immediately followed by agitation with a size 08 K-file. Passive irrigation consisted of a 0.5-mL flush of sodium hypochlorite solution delivered with a syringe through a 27-gauge notched tip needle. A digital radiograph was taken after each modality and stored on computer for subsequent digital subtraction and measures of the depths of irrigant penetration. Comparisons were performed within an analysis-of-variance framework in a repeated-measures approach. Results, The penetration of irrigants was significantly greater for each successive step of the shaping procedure when the two modalities were analysed separately (P < 0.001). The difference between the two modalities was statistically significant for each step of the shaping procedure (P < 0.0001). Conclusions, Shaping root canals improved both penetration and exchange of irrigant inside the root canal system. Complete renewal of the solution was impossible to achieve with a conventional syringe delivery system and a limited volume of solution. Recapitulation with a K-file after flushing improved irrigant penetration. [source] The Polymerization of Tetrahydrofuran Initiated by Niobium(V) and Tantalum(V) HalidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Fabio Marchetti Abstract The halides MX5 (M = Nb, Ta, X = F, Cl, Br) (1) are effective in promoting the polymerization of tetrahydrofuran (thf). The polymerization reactions promoted by MCl5 and MBr5 proceed via the ionic species 3, which forms from MX5(thf) (2) by attack of the incoming monomer to the metal-bonded thf. The metal-bonded thf of 3 is not involved in the immediately successive steps of the reaction. The [TaF6], anion is not formed when the polymerization is initiated by TaF5. The activities of the promoters increase according to the series TaBr5 < NbCl5 < TaCl5 < TaF5. The latter possesses high activity and produces high molar mass poly(tetrahydrofuran) (67100 g/mol). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Silicon Microstructures: Detachment Lithography of Photosensitive Polymers: A Route to Fabricating Three-Dimensional Structures (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Mater. The scanning electron microscope image featured on the front cover shows a three-dimensional polydimethylsiloxane (PDMS) molded film bonded on a glass rod. Multilevel silicon structures used to mold the PDMS film were fabricated from successive steps of detachment lithography of photoresist films, which are patterned with lithography and reactive ion etching, as reported by J. Yeom and M. A. Shannon on page 289. The smallest feature on the pyramid is 2 µm in diameter. [source] Beyond control: wider implications for the management of biological invasionsJOURNAL OF APPLIED ECOLOGY, Issue 5 2006PHILIP E. HULME Summary 1Government departments, environmental managers and conservationists are all facing escalating pressure to address and resolve a diversity of invasive alien species (IAS) problems. Yet much research to date is primarily concerned with quantifying the scale of the problem rather than delivering robust solutions and has not adequately addressed all stages of the invasion process, and only a few studies embrace the ecosystem approach. 2Three successive steps, prevention, eradication and control, form the cornerstones of recommended best practices aimed at managing IAS. The goal of such actions is the restoration of ecosystems to preserve or re-establish native biodiversity and functions. 3Prevention is widely promoted as being a more environmentally desirable strategy than actions undertaken after IAS establishment, yet is hindered by the difficulty in separating invasive from non-invasive alien species. Furthermore, the high number of candidate IAS, the investment required in taxonomic support and inspection capacity, and the expense of individual risk assessments may act against the net benefits of prevention. More rewarding avenues may be found by pursuing neural networks to predict the potential composition of pest assemblages in different regions and/or model introduction pathways to identify likely invasion hubs. 4Rapid response should be consequent on early detection but, when IAS are rare, detection rates are compromised by low occurrence and limited power to discern significant changes in abundance. Power could be increased by developing composite indicators that track trends in a suite of IAS with similar life histories, shared pathways and/or habitat preferences. 5The assessment of management options will benefit from an ecosystem perspective that considers the manipulation of native competitors, consumers and mutualists, and reviews existing management practices as well as mitigates other environmental pressures. The ease with which an IAS can be targeted should not only address the direct management effects on population dynamics but also indirect effects on community diversity and structure. Where the goal is to safeguard native biodiversity, such activities should take into account the need to re-establish native species and/or restore ecosystem function in the previously affected area. 6Synthesis and applications. A comprehensive approach to IAS management should include consideration of the: (i) expected impacts; (ii) technical options available; (iii) ease with which the species can be targeted; (iv) risks associated with management; (v) likelihood of success; and (vi) extent of public concern and stakeholder interest. For each of these issues, in addition to targeting an individual species, the management of biological invasions must also incorporate an appreciation of other environmental pressures, the importance of landscape structure, and the role of existing management activities and restoration efforts. [source] Gas-phase ion chemistry in the ternary SiH4,C3H6,PH3 systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2002Stefania Calderan Abstract Propene,phosphine and the silane,propene,phosphine gaseous mixtures were studied by ion trap mass spectrometry. For the binary mixture the variation of ion abundances under different partial pressures and the mechanisms of ion,molecule reactions are reported. Moreover, the rate constants of the main processes were measured and compared with the collisional rate constants to determine the reaction efficiencies. In the ternary silane,propene,phosphine mixture the mechanisms of formation of ion clusters were elucidated, but the complexity of the system and the low abundances of the ions usually isolated by successive steps prevented the determination of rate constants. The hydrogenated ternary ions are mainly formed by reactions of ions with propene, whereas a minor contribution comes from reactions of ions with phosphine. The ions show very low reactivity with silane. The formation processes of these species are discussed in relation to their possible role as precursors of amorphous silicon carbides doped with phosphorus obtained by deposition from properly activated silane,propene,phosphine mixtures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Rapid and Precise Release from Nano-Tracted Poly(N -isopropylacrylamide) Hydrogels Containing Linear Poly(acrylic acid)MACROMOLECULAR BIOSCIENCE, Issue 11 2006Taka-aki Asoh Abstract Summary: We investigated the rapid and precise molecular release from hydrogels in response to dual stimuli. To achieve precise on/off drug release using thermoresponsive poly(N -isopropylacrylamide) hydrogels, we prepared nano-structured semi-IPNs, which consisted of thermosensitive PNIPAAm networks penetrated by pH-responsive poly(acrylic acid) (PAAc) linear chains and perforated to create nano-tracts as a molecular pathway. The present nano-tracted semi-IPNs show a rapid deswelling response to both temperature and pH. Model drug releases were investigated when simultaneous changes in temperature and pH were applied. We observed that the cationic drug was rapidly released and then abruptly discontinued from the nano-tracted semi-IPNs in response to the dual stimuli, and clear release and stopping cycles were repeatedly observed on successive steps. Moreover, the release rates and amount of drug released were controllable by the deswelling speed of the gels and the PAAc content inside the gels. This novel release system using the nano-tracted semi-IPNs may be useful for the high performance, pulsed release of molecules. Release profiles of MB from semi-IPNs at pH,=,5.5, 20,°C (white region) and pH,=,2, 40,°C (gray region). [source] Prevalence of tic disorder in two schools in the Basque country: Results and methodological caveatsMOVEMENT DISORDERS, Issue 12 2006Gurutz Linazasoro Abstract Different studies have shown that the prevalence of tic disorder is highly variable, depending on the methodology employed. The aim of this study was to determine the prevalence of tic disorder among children of two schools. The study was conducted in three successive steps: information to parents and teachers by way of speeches and projection of videotapes; anonymous fulfilling of an ad hoc questionnaire by teachers and parents and identification of children as "possible tic disorder" according to the questionnaire; and confirmation of the presence of tics by direct observation of children at school (20 minutes in each classroom). Eight hundred sixty-seven children were included. Age ranged from 4 to 16 years. Ninety percent of parents and 99% of teachers fulfilled the questionnaire. Seventy-one children had tics according to parents' and 50 according to teachers' opinion (both coincided in 23 cases). Fifty-seven cases were identified after direct observation in the classroom (prevalence of 6.5%). The vast majority of tics were mild in severity and duration. Prevalence obtained in this study was comparable with data reported in studies using a similar methodology, which is higher than results shown in early studies addressed with less rigid methodology. Most of identified cases were quite mild, not leading to major functional disability. In spite of the methodology employed, it is possible that some cases were lost. © 2006 Movement Disorder Society [source] Diaquadichloridobis(1H -imidazole)manganese(II) at 100 KACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2009Barbara Hachu The mononuclear title complex, [MnCl2(C3H4N2)2(H2O)2], is located on a crystallographic inversion center. The MnII ion is coordinated by two imidazole ligands [Mn,N = 2.2080,(9),Å], two Cl atoms [Mn,Cl = 2.5747,(3),Å] and two water molecules [Mn,O = 2.2064,(8),Å]. These six monodentate ligands define an octahedron with almost ideal angles: the adjacent N,Mn,O, N,Mn,Cl and O,Mn,Cl angles are 90.56,(3), 92.04,(2) and 90.21,(2)°, respectively. Hydrogen bonds between the coordinated water molecules and Cl atoms form a two-dimensional network parallel to (100) involving R42(8) rings. The two-dimensional networks link into a three-dimensional framework through weaker N,H...Cl interactions. Thermogravimetric analysis results are in accordance with the water-coordinated character of the substance and its dehydration in two successive steps. [source] Towards an inert diet for first-feeding gilthead seabream Sparus aurata L. larvaeAQUACULTURE NUTRITION, Issue 3 2000Yúfera The development of an inert food to replace live prey during the early stages of marine fish larvae requires research in different fields and therefore a precise work strategy. Our research on this subject has been carried out in successive steps using the gilthead seabream Sparus aurata. The first step was the design of a food particle that would be well accepted and ingested by free-swimming marine larval fish during the first developmental stages. We chose microencapsulation by polymerization of the dietary protein as the most appropriate method for making the particles; different types of microcapsules were made using a basic diet containing only the major dietary components. In the second step, our aim was to keep the larvae alive in a routine rearing system in 300-L tanks, using exclusively this kind of food, long enough to detect any changes in growth, survival, or anatomical and histological status of the larvae, in order to verify whether the technological changes were positive. The third step focused on diet formulation and searching for clues to inefficient assimilation and growth. The use of ,in vitro' digestibility techniques allowed us to detect the inhibitory effect of some diet ingredients on larval proteases and to determine more suitable sources of protein. We now have a microcapsule able to efficiently support growth and development of S. aurata larvae, at least during the first 2 weeks of life, although the larvae still need to feed on rotifers during the first 2,4 days of exogenous feeding. This microcapsule will make it possible to make advances in determining the specific nutritional requirements of larval fish. 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