bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orthodontic Attachments and Chlorhexidine-Containing Varnish Effects on Gingival Health
Authors: Paschos Ekaterini , Limbach Mirjam , Teichmann Marion , Huth Karin C. , Folwaczny Matthias , Hickel Reinhard , Rudzki-Janson Ingrid 
Published: February 2008

Abstract
Objective: To compare the severity of clinical inflammation parameters and the level of the inflammatory mediator interleukin (IL)–1β during orthodontic treatment by using brackets and bands. In addition, the effect of a chlorhexidine-containing varnish was investigated.
Materials and Methods: This prospective randomized controlled trial included 40 healthy children who required an orthodontic treatment of mild crowding. Either brackets or bands were randomly allocated to the premolars with a split-mouth design. Twenty of the children received a chlorhexidine-containing varnish during the treatment (0, 12, 24 weeks), while the remaining children served as a control group. Prior and until 24 weeks after the insertion, data were recorded regarding the pocket depth (PD), the gingival appearance (gingival index [GI]), and the plaque accumulation (plaque index [PI]). Gingival crevicular fluid was collected as well. A quantitative enzyme-linked immunoassay technique was used to detect differences in IL-1β.
Results: The PDs and the gingival index of teeth with brackets showed significantly lower values in comparison with teeth treated with bands (P = .0001). The IL-1β levels confirmed these findings. In contrast, the PI showed higher values for the teeth with brackets (P = .0001). The teeth that received a chlorhexidine-containing varnish showed significantly lower values in the follow-ups for most of the evaluated parameters (PDBand, PIBand, PIBracket, GIBand, GIBracket; P &lt; .015).
Conclusion: The clinically observed parameters as well as the IL-1β levels reflected the higher impact of bands on gingival health. These values showed a significant decrease after application of a chlorhexidine-containing varnish. However, the PI showed higher values for the teeth with brackets.
Soft-Tissue Facial Characteristics of Attractive and Normal Adolescent Boys and Girls
Authors: Sforza Chiarella , Laino Alberto , D'Alessio Raoul , Grandi Gaia , Tartaglia Gianluca Martino , Ferrario Virgilio Ferruccio 
Published: February 2008

Abstract
Objectives: To identify possible esthetic canons in facial size and shape of Italian adolescent boys and girls.
Materials and Methods: The three-dimensional coordinates of 50 facial landmarks (forehead, eyes, nose, cheeks, mouth, jaw, ears) were collected in 231 healthy, reference adolescents (10– 17 years old) and in 93 similar age group “attractive” adolescents selected by a commercial casting organization. Soft-tissue facial angles, distances, areas, and volumes were computed. Comparisons were made with analysis of variance.
Results: Attractive adolescents had wider, shorter, and less deep faces than reference adolescents, with a relatively larger forehead and maxilla, and a reduced mandible relative to the maxilla. Lips were larger and more prominent, and the nasolabial angle was reduced, but in older boys the effect was reversed. The prominence of the soft-tissue profile, and of the maxilla relative to the mandible, were larger in attractive boys, but smaller in attractive girls than in their reference peers. In the horizontal plane, attractive “young” adolescents had a flatter face, while the opposite pattern was observed in the “old” adolescents, with a relatively more prominent chin. Attractive adolescents had smaller noses than reference subjects of the same age and sex.
Conclusions: Overall, all the measurements appeared sufficiently homogenous, and the quantitative characteristics of an “attractive” face well defined. Esthetic reference values can be used to determine optimal timing and goals in orthodontic treatment.
Early Treatment with a Maxillary Lip Bumper-Bite Plateau Combination
Authors: Korn Marcel , Melsen Birte 
Published: February 2008

Abstract
Objective: To evaluate the intra-arch displacements of the molars and the change in molar relationship following the use of a maxillary lip bumper combined with a bite plate.
Materials and Methods: The material comprised study casts taken before and after the treatment of 40 consecutive patients with mixed dentition. The sagittal and transversal displacements were evaluated by a three-dimensional digitizer using the palatal rugae as an indirect fixed reference. The displacements were expressed as translation mesiodistally and buccolingually and rotation around the long axis and tipping mesiodistally. The change in molar relationship was measured to the nearest millimeter at the level of the occlusal plane.
Results: The tooth movements were predominantly of distal rotation (mean, 9.7°; range, 6.5° to 26°) and distal tipping (mean, 5°; range, 5.8° to 18°). The distal displacement was a modest mean (mean, 0.3 mm; SD, 1.6 mm) and more pronounced to the buccal (mean 1.6 mm; SD, 1.5 mm). The molar relationship improved in all but four sites, and a full Class I was obtained in 65 of 80 sites.
Conclusions: The early treatment with the lip bumper and bite plate can be recommended from a cost-benefit point of view.
The Dynamic Apparent Viscosity of Polymer Melts During Pulsatile Extrusion Flow with Vibration Force Field
Authors: He G.-J. , Yin X.-C. , Qu J.-P. 
Published: February 2008

Abstract
The dynamic apparent viscosity of polymer melts during pulsatile extruding flow with a vibration force field was studied on a self-made dynamic capillary rheometer (DCR). A theory that could reflect the vibration influence on the dynamic apparent viscosity was proposed. Due to the superposition of the vibration force field upon the steady shear flow, the phase difference between the shear stress and the shear rate could be chosen as a parameter to reflect the effect of vibration on the dynamic apparent viscosity. According to this theory, the average shear rate during pulsatile extrusion increased because of the existence of the phase difference, which caused the decrease of the dynamic apparent viscosity. The experimental results proved that the phase difference was reduced with the increase of vibration frequency, which resulted in a decrease in the dynamic apparent viscosity during the pulsatile extrusion.
Influence of Uniaxial Extension on the Mechanical Properties of PET and PEN Films
Authors: Wang J. H. , Kim J. H. , Kang H. J. , Talke F. E. 
Published: February 2008

Abstract
The modulus and hardness of poly(ethylene terephthalate)-(PET) and poly(ethylene naphthalate)(PEN) films are studied as a function of the uniaxial draw ratio using nanoindentation and macro-scale tensile testing equipment. Nanoindentation tests were conducted in the machine-transverse plane, the transvers-normal plane, and the machine-normal plane of the PET and PEN films to determine mechanical properties (hardness and modulus of elasticity) of the uniaxially stretched films at the nano-scale. The films were then re-tested using a tensile tester to determine the modulus on the macro-scale. The results from the two methods show large differences. Birefringence measurements indicate that the macro-scale and nano-scale moduli are strongly influenced by the chain orientation after uniaxial stretching. In addition, the influence of chain orientation is found to be much larger on the macro-scale than on the nano-scale.
Non-Isothermal Simulation of the Film Blowing Process Using Multi-Mode Extended Pom-Pom Model
Authors: Sarafrazi S. , Sharif F. 
Published: February 2008

Abstract
Plastic films are largely produced using the film blowing process. Branched polymers such as LDPE are commonly used in this process to produce a variety of plastic films. In this study, recently developed eXtended Pom-Pom (XPP) model, which focuses on describing rheological behavior of branched polymers, is employed to analyze the non-isothermal flow in the film blowing process. Furthermore, the Nakamura equation for crystallization kinetics is employed to consider crystallization effects and improve prediction of the state of the stress in the film. Results of the numerical analysis show good agreement with the experimental values reported by Tas (1994) for the bubble shape and film velocity of the LDPE films. Predictions for the strain rates in machine and hoop directions which are critical for the estimation of the stress are also compared with the reported data and showed reasonably good agreement.
Flow Analysis of Flat Spiral Dies and Comparison with Cylindrical Spiral Mandrel Dies
Authors: Malekzadeh M. , Goharpey F. , Foudazi R. 
Published: February 2008

Abstract
Cylindrical Spiral Mandrel Dies (SMD) and Flat Spiral Dies (FSD) are widely used in blown film co-extrusion processes. Although in recent years the use of stackable (flat) spiral dies in the blown film extrusion has been continuously growing, a phenomenological study on designing parameters of this type of dies, and comparison of their flow distribution with SMD has not been made yet. In this work, the flow of a viscous power law fluid in a typical flat spiral die, based on Rauwendaal's method (1987) for analyzing cylindrical spiral mandrel dies, has been investigated. Validation of this method for flat spiral dies was confirmed by comparison with the results reported using the finite element method. The effects of some design parameters, such as number of grooves, initial flight clearance, initial groove depth, on pressure gradient, flow distribution and other operational variables have also been studied. It has been found that the flow distribution becomes more uniform with increasing number of grooves, initial groove depth and coefficient of Archimedes type flat spiral. Moreover, the results have shown that the increment of the clearance angle between two die plates, as well as the initial clearance, have an optimum value in which the flow distribution is the most uniform. Finally, flow variations in FSD and SMD have been compared for different design parameters. The results demonstrated that the melt flow distribution at the outlet of the cylindrical spiral mandrel die is more uniform, while the pressure loss of the flat spiral die is lower.
Development of Polymer Blend Morphology along an Extruder with Different Screw Geometries
Authors: Huang H.-X. , Jiang G. , Li X.-J. 
Published: February 2008

Abstract
The morphology development of an immiscible polymer blend along a single screw extruder was investigated, concentrating on the effect of screw geometry. Three different screw geometries were evaluated: one with conventional screw elements; the other two with a fluted and Pineapple mixing element, respectively. The experiments were conducted using a polypropylene/polyamide-6 (PP/PA 6) blend. The blend samples were collected from four different positions using specially designed sampling device along the extruder online during blending and were then examined using scanning electron microscopy. The experimentally observed morphology evolution was evaluated both qualitatively, in terms of spatial distribution of dispersed phase, as well as quantitatively, by analysis for the size of the dispersed phase. The morphology development was interpreted with the aid of the flow fields occurring along screw elements. The results showed that the screw with conventional screw elements produce the coarsest and most non-uniform morphology whereas the screw with a fluted mixing element appears to produce the finest and most uniform morphology at the end of the extruder. The Pineapple mixing element, with a characteristic of chaotic mixing, facilitates to form thinner laminar layers of dispersed phase. The experimentally observed morphology difference between the conventional and fluted mixing element was demonstrated by the simulation.
Melting Mechanism of Thermoplastic Elastomers and Comparison to Polyolefin Thermoplastic Melting Studies in a Single Screw Extruder
Authors: Lu W.-J. , Bumm S. H. , White J. L. 
Published: February 2008

Abstract
An experimental investigation of the mechanisms of melting of various thermoplastics elastomers (TPEs) in single screw extruder was carried out under different operating conditions. The TPEs included three polypropylene vulcanized EPDM (TPV) thermoplastic elastomers and two styrene-hydrogenated butadiene block copolymer. The results were compared to new and earlier experimental investigations of the melting of polyethylene and polypropylene. We also characterized the shear viscosity of all polymer melts studied. The TPEs all exhibited yield values in shear flows. To characterize the melting process in a single screw extruder, we used a flow marker procedure which consists of introducing pigments with the neat pellets. This is a technique originally developed by Maddock (1959). At the steady state, we abruptly stopped the extruder operation, cooled the barrel and pushed the screw from the barrel. The polymer carcasses were stripped from the screws and slices cross-sectioned every turn from the hopper to die were photographed and evaluated, and the melting mechanism was determined. The results for the TPEs exhibit significant differences from the crystalline polyolefin.
Shrinkage Analysis on Convex Shellby Injection Molding
Authors: Chen C.-C. A. , Chang S.-W. 
Published: February 2008

Abstract
Injection molding of a convex shell has induced divergent flow front directions and therefore the shrinkage of a convex shell is difficult to controll. In some optical applications, such as ophthalmic devices of soft contact lens, that can be cast molded with a set of two convex shells made by injection molding there is a demand in maintaining dimensional stability. This research investigates the optimization of injection molding parameters for the minimum shrinkage of a convex shell of polypropylene (PP). The MPI 5.0 software is used first to simulate the filling stage of the convex shell and find the feasible operational ranges of parameters. Experiments were performed by an electric injection machine. Short shot experiments have been tested to compare with results of mold flow simulation. Taguchi's method is then used to find the optimal parameters for the minimum shrinkage of convex shell. Four parameters or factors, including mold temperature, injection temperature, holding pressure, and cooling time are considered in this study. An ANOVA table has been obtained for checking the significance of parameters. Results of simulation and experiments have been compared and the holding or packing pressure is found as the most significant parameter for the minimum shrinkage of a convex shell. Cooling time and injection temperature have been found as the second and third most significant parameters in this study. The optimal parameters have been established and then verified by the optimal injection molding experiment and the minimum shrinkage of convex shell was obtained as 72 μm.
Thermal Degradation of Meta- and Para-Aramid Fibers in Different Atmospheres
Authors: Wang X.-W. , Hu Z.-M. , Liu Z.-F. 
Published: February 2008

Abstract
The thermal degradation behavior of meta- and para-aramid fibers (PMIA and PPTA) in different atmospheres was studied by thermogravimetric analysis coupled with mass spectrometry (TGA-DTA/MS). The process of mass loss in the degradation of PMIA was divided into three steps in both argon and air. The mass loss of PPTA was greater than that of PMIA in argon when the temperature reached 1000°C. Simultaneous TG/DTA measurements showed that the thermal degradation was endothermic in argon and exothermic in air for both fibers. Mass spectra of volatiles were obtained, and PMIA and PPTA gave similar mass signals. The temperatures of maximum abundances in ion currents corresponded to the temperatures of mass loss peaks in the DTG curves. The relative values of ion currents were compared at various temperatures. The yield of CO2 was the largest fraction in ion currents of all the volatiles, and the abundances of ion currents of phenyl compounds were low. The elemental analyses of decomposed PMIA and PPTA fibers provided direct information of chemical and morphological changes. A synthetic kinetic model was introduced, and the analyses of kinetic parameters were used to explain the degradation progresses.
Experimental Studies on Screw Characteristics in Closely Intermeshing Counter-rotating Twin Screw Extruder
Authors: Hong M.-H. , Jiang Q. , White J. L. 
Published: February 2008

Abstract
Experimental studies were carried out to characterize the screw pumping behavior of various screw elements for a closely intermeshing counter-rotating twin screw extruder. The pumping capacity of the screw elements was compared to earlier flow simulations by some the authors of this type of twin screw extruder.
Experimental Analysis of Heat Transfer in Rotational Molding Process
Authors: Sobotka V. , Perot E. , Maazouz A. , Delaunay D. 
Published: February 2008

Abstract
Rotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This process is relatively simple in a technical point of view but it involves very complex physical phenomena. Constant quality in technical parts requires the mastery of the process by controlling on line these phenomena. One of these of first importance is heat transfer. This paper concerns the experimental analysis of heat transfer in rotational molding process with semi-crystalline polymer. By using an instrumented mold associated with an original radio transmission data acquisition system, we demonstrate that the rotational nature of the process implies complex heat transfer evolutions in the mold. The crystallization of the material is modeled with accuracy by coupling heat transfer equation to a kinetic model determined by calorimetry. It appears that thermal contact resistance evolution is a key point of heat transfer during the solidification of the polymer.
Experimental Study and Modeling of Flow Behavior and Orientation Kinetics of Layered Silicate/Polypropylene Nanocomposites in Start-up of Shear Flows
Authors: Rajabian M. , Naderi G. , Beheshty M. H. , Lafleur P. G. , Dubois C. , Carreau P. J. 
Published: February 2008

Abstract
Effects of organoclay contents on the startup flow properties of layered nano-scale particles in the simple shear mode are investigated. The addition of small amounts of nanoclays to polypropylene melts was found to dramatically change the flow characteristics and creates stress overshoots at large shear rates. A rheological model, initially developed for studying the motion of a group of symmetric ellipsoid particles in viscoelastic fluids was used to describe the orientation state of the uniformly dispersed suspensions of layered silicate in polypropylene melts. The effects of shear, particle loadings, particle interactions, flow reversal and rest time after cession of shear are studied and discussed according to our experimental observations and model predictions. It is shown that another diffusion term in the governing equation for the particles can be used to predict the properties by applying the rest time which was found to change the orientation of particles and shifts it to more isotropic microstructures. The experimental results of the startup viscosity are reasonably well predicted by the model at the three shear rates tested.
Grazing as a factor structuring grasslands in the Pyrenees
Authors: Sebastià Maria‐Teresa , de Bello Francesco , Puig Laura , Taull Marc 
Published: February 2008

Questions: What are the relative roles of abiotic and grazing management factors on plant community distribution in landscapes? How are livestock type and stocking rate related to changes in vegetation structure and composition?Location: Sub‐alpine grasslands in the central and eastern Pyrenees.Methods: Multivariate analysis and variance partitioning methods were used to evaluate the relative roles of environmental factors in structuring vegetation composition and diversity patterns in three surveys on differently managed grasslands.Results: Vegetation composition within a region was affected by environmental factors hierarchically, changing first according to abiotic factors and then to grazing management. At landscape scales, abiotic factors explained two‐fold more variation in vegetation composition than grazing factors. Within landscape units, cattle grazing increased vegetation heterogeneity at landscape and patch scales, while sheep grazing favoured the presence of a specific set of species with high conservation value. Species composition was highly responsive to management variables compared to diversity components.Conclusions: The combination of sheep and cattle grazing at various stocking rates is an effective tool to preserve the diversity of plant species and communities within a region with a long tradition of livestock management, through the scaling up of effects by local processes occurring in patches at smaller scales.
Strong shifts in plant diversity and vegetation composition in grassland shortly after climatic change
Authors: Sebastià Maria‐Teresa , Kirwan Laura , Connolly John 
Published: February 2008

AbstractQuestions:Is plant diversity in mesic grassland ecosystems vulnerable in the short‐term to extreme climate change events? How rapidly can responses in vegetation composition occur in perennial grasslands? Are the expected compositional changes related to rare species losses or to shifts in the relative abundance of the dominants?Location:Subalpine mesic grasslands on limestone in the Pyrenees.Methods:Transplanting turves from the upland, with cold‐temperate climate, to a lowland location, with continental Mediterranean climate.Results:Transplanting led to decreased biodiversity and strong shifts in vegetation composition. Results from both permutation tests and traditional multivariate analysis suggested different trajectories of vegetation depending on the initial species pool. Vegetation showed a tendency to converge in composition in the lowland over time, independently of initial differences. Estimated changes in relative biomass of the five most abundant species between the upland and the lowland ranged from ‐89 to +96 %. The ensemble of all other species was reduced by 80%. The most dominant species in the upland, Festuca nigrescens, reduced its abundance in the lowland, shifting from having mainly positive to mainly negative associations with other species.Conclusions:Mesic grassland ecosystems in the Pyrenees showed strong shifts in plant diversity and composition after a short period of warming and drought, as a consequence of acute vulnerability of some dominant grasses, losses of rare species, and aggregate and trigger effects of originally uncommon forb species.
Optimal and self‐tuning fusion Kalman filters for discrete‐time stochastic singular systems
Authors: Sun Shu‐Li , Ma Jing , Lv Nan 
Published: February 2008

AbstractBased on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd.