bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of thermal exposure on the microstructure and hardness of as-cast Mg–Zn–Al alloys with Sn addition
Authors: Jihua Chen , Zhenhua Chen , Hongge Yan , Suqiong Li , Peiyun Xia
Published: February 2009

Microstructural evolution and hardness changes of as-cast Mg-6Zn-2Al alloys with Sn addition during prolonged thermal exposure to 150 °C and 200 °C were studied using optical microscopy, X-ray diffraction, scanning electron microscopy and hardness tests. Neither obvious grain growth nor new phases were detected in these alloys during thermal exposure. There were initial precipitation hardening peaks followed by long-term hardness stability during thermal exposure to 150 °C, indicating that all the alloys exhibited excellent microstructural stability. There were two peaks in the hardness vs. annealing time curves of these alloys during thermal exposure to 200 °C, which corresponded to the precipitation of MgZn and Mg2Sn. The overall hardness of these alloys decreased with prolonged time, resulting from the aggregation and coarsening of Mg2Sn.
Suitability of maraging steel weld cladding for repair of die casting tooling
Authors: Klobčar Damjan , Tušek Janez , Taljat Boštjan , Kosec Ladislav , Muhič Mitja
Published: February 2009

This study was done to evaluate precipitation annealing of 18 % Ni maraging steel repair welds during aluminium alloy die casting and to predict the prolonged in-service tool life. The emphasis of this study was the influence of post-weld precipitation annealing heat treatment and aluminium die casting thermal cycling on metallurgical and mechanical properties. A series of specimens of 1.2344 tool steel was prepared to which 1.6356 maraging steel was gas tungsten arc weld clad. Analysis of weld microstructure and hardness was made in order to understand the metallurgical processes during heat treatment at elevated temperatures and at prolonged time. The Response Surface model for prediction of hardness after heat treatment was developed. The edges of immersion test specimens are gas tungsten arc weld clad with 1.6356 maraging steel and machined to the final edge geometry. Two specimens were tested in as-welded condition and two in optimally aged condition. Testing was performed on specially developed immersion test apparatus, which enables the simulation of thermal fatigue during aluminium alloy die casting. After completion of a particular number of thermal fatigue cycles the weld microstructure and hardness were evaluated. A hypothetical model for prediction of precipitation annealing time during aluminium alloy die casting was proposed. The results showed that tool heating lasts 30 % of molten metal injection time, preparing conditions for precipitation annealing at 10 % of injection time, and precipitation annealing at 60 % of injection time. These results, together with a finite element model for prediction of tool temperature and response surface model for prediction of hardness after precipitation annealing, enable accurate prediction of maraging steel tool hardness after any particular number of die casting cycles and consequently in-service tool life. The thermal fatigue resistance of maraging steel welds was compared to AISI H13 tool steel. The results showed superior thermal fatique resistance for AISI H13.
STAU – a review of the Karlsruhe weakest link finite element postprocessor with extensive capabilities
Authors: Riesch-Oppermann Heinz , Härtelt Martin , Kraft Oliver
Published: February 2009

The inherent brittleness of ceramics led to a probabilistic approach for designing with ceramic materials. For tackling this issue, numerous research projects led to the generation and continuous development of the weakest link postprocessor STAU over the last twenty years. Compared to other similar tools, STAU is unique in its comprehensive capabilities addressing spontaneous fracture, sub-critical crack propagation under transient loading, including a temperature-dependent fracture stress, and crack propagation parameters and analysis of strong stress gradients allowing for solving general thermo-mechanical problems including thermal shock and contact loading. Remarkably, the stress analysis, using commercial finite element codes, does not require a separate meshing with respect to the subsequent probabilistic analysis. Within the framework of a collaborative research effort (SFB 483) ceramics are qualified with respect to friction and wear for highly demanding applications. Here, uncertainty analysis methods for STAU were developed and led to an important extension of STAU for several technological applications. In this paper, the main features of STAU as well as the physical background are revisited and some application cases are shown.
Effect of phase stability and composition on hydrogen diffusion in the binary systems Ti–Mo and Ti–V and related Ti-base alloys
Authors: Schmidt Peter , Christ Hans-Jürgen
Published: February 2009

Hydrogen diffusion coefficients DH were determined in various commercial β titanium alloys and binary titanium alloys of the Ti – Mo and Ti – V systems, since molybdenum and vanadium are the most important β-stabilizing alloying elements. For this purpose, hydrogen concentration step profiles were established in long thin titanium rod samples via electrochemical hydrogenation. Subsequent diffusion annealing at various temperatures led to hydrogen diffusion inside the samples. The hydrogen concentration profiles established were evaluated either numerically by means of a finite-difference application or analytically by applying the Matano technique and the hydrogen diffusion coefficients were calculated. The results show that the DH-values increase with increasing β stability, obey an Arrhenius-type temperature dependence and are not affected by hydrogen concentration.
A transmission electron microscopy procedure for in-situ straining of miniature pseudoelastic NiTi specimens
Authors: Olbricht J. , Wagner M. F.-X. , Condó A. , Dlouhy A. , Großmann Ch. , Kröger A. , Somsen Ch. , Eggeler G.
Published: February 2009

The in-situ transmission electron microscopy technique allows direct observations of formation and growth of stress-induced martensite in pseudoelastic NiTi shape memory alloys. The present paper reports on the development of a miniature test procedure for in-situ straining experiments with specimens taken from small components. The deformation of an ultra-fine grained NiTi specimen is characterised by transmission electron microscopy (at early loading stages) and by optical microscopy (at larger strains). A complementary finite element analysis of the complex strain state in the specimen rationalises why the stress-induced martensitic transformation first occurs in the thin foil region of the specimen before spreading towards the outer rim of the specimen.
Development of multifunctional thin films using high-throughput experimentation methods
Authors: Ludwig Alfred , Zarnetta Robert , Hamann Sven , Savan Alan , Thienhaus Sigurd
Published: February 2009

This paper describes the use of thin film high-throughput experimentation methods for the efficient development of multifunctional materials, using Ni – Ti – X and ferromagnetic shape memory alloys as examples. The thin films were fabricated in the form of binary, ternary, and quaternary materials libraries by special magnetron sputter deposition processes. These materials libraries were subsequently processed and characterized by high-throughput experimentation methods in order to relate compositional information with structural and functional properties. For this, appropriate visualization of the data is necessary. Results show that the martensitically transforming regions in ternary thin films are generally larger than was known from literature. Within these regions, the variation of the functional properties can be mapped with respect to the composition and microstructure, and thus the most suitable materials for applications can be effectively selected.
“Evolution” of microstructure in materials
Authors: Hornbogen Erhard
Published: February 2009

The term “evolution” is used in both biology and materials science. There are however large differences in what is meant by it. It will be shown that one difference is the probability of single or multi step nucleation. Biological structures are too complex to be recreatable by nucleation. They originate by a very rare event. Consequently they are prone to extinction, if they had no chance to multiply and modify in particular environments (populations, generations).

Formation of various dispersoid microstructures in Al – Cu alloy is shown as an example of nucleation controlled evolution in materials science.
Mechanical properties of a single gecko seta
Authors: Huber Gerrit , Orso Steffen , Spolenak Ralph , Wegst Ulrike G. K. , Enders Susan , Gorb Stanislav N. , Arzt Eduard
Published: February 2009

Measurements of the stress – strain response of hairlike gecko setae are presented. These setae have diameters in the micron range and are part of the attachment organs that enable lizards to cling to surfaces. Three test methods were employed: (a) applying tension with a piezoresistive cantilever inside a focused ion beam microscope under vacuum conditions, (b) three-point bending in air using an atomic force microscope, and (c) nanoindentation tests on the circumference of the seta. Elastic moduli were found to depend strongly on the method of testing: Tensile testing in vacuum yielded an elastic modulus of 7.3 ± 1.0 GPa which was roughly five to six times higher than in bending and in nanoindentation tests at ambient conditions. The results are discussed in terms of the anisotropic nanostructure of the setae and humidity effects. They constitute valuable input parameters for optimizing the performance of artificial attachment devices.
A model to calculate the viscosity of silicate melts
Authors: Grundy A. Nicholas , Liu Honqin , Jung In-Ho , Decterov Sergei A. , Pelton Arthur D.
Published: February 2009

A model has been developed that links the viscosities of silicate melts to their thermodynamic properties. Over the past several years, through critical evaluation of all available thermodynamic and phase equilibrium data, we have developed a quantitative thermodynamic description of multicomponent silicate melts using the Modified Quasichemical Model for short-range ordering. The local structure of the liquid, in terms of the bridging behavior of oxygen, calculated using our thermodynamic model allows us to characterize the structure of the liquid semi-quantitatively using the concepts of Q-species and connectivity of Q-species. The viscosity is modeled by optimizing viscosity parameters that are related to the structure of the liquid. The viscosity of pure liquid silica is modeled using four model parameters and every other unary liquid is modeled using two. The viscosity of all binary liquids is reproduced within experimental accuracy by optimizing one or at most two binary viscosity parameters for each system. In the present article the equations for the viscosity model are derived and analyses for the experimentally well-established systems CaO – SiO2MgO – SiO2, NaO0.5– SiO2, KO0.5– SiO2and AlO1.5– SiO2are presented. This is the first step in the development of a predictive model for the viscosity of multicomponent silicate melts that will be presented in part II.
A note on the application of the phase rule
Authors: Chen Shuang-Lin , Schmid-Fetzer Rainer , Chou Kuo-Chih , Chang Y. Austin , Oates William A.
Published: February 2009

When an equilibrium state contains degenerate phases, the number of independent phases must be considered in applying Gibbs' Phase Rule. This number can be derived from the rank of the matrix containing the coefficients of the Gibbs – Duhem equations. This provides a quantitative determination of the degrees of freedom even under such conditions of degeneracy.
Thermodynamic properties of liquid silver–indium–tin alloys determined from emf measurements
Authors: Jendrzejczyk-Handzlik Dominika , Gierlotka Wojciech , Fitzner Krzysztof
Published: February 2009

The thermodynamic properties of liquid Ag – Sn – In alloys were determined using solid oxide galvanic cells with zirconia electrolyte. The following galvanic cells were employed:

Re + kanthal, Ag
x
– In
y
– Sn(1−x−y
),(In2O3)s.s//ZrO2 + (Y2O3)//NiO, Ni, Pt(I)

in the temperature range from 973 to 1273 K, and in the range of indium mole fraction from 0.3 to 0.8.

This limitation was imposed by the side reaction between tin in the liquid alloy and solid In2O3. It was also found that the liquid is in equilibrium with the solid solution of oxides. Calorimetric measurements of the heat of mixing were also carried out at constant temperature 1003 K and along one isopleth with XAg/XSn = 1/1.

The thermodynamic properties of the liquid phase were described by the Redlich – Kister – Muggianu formula and the phase relations in the ternary system were calculated. The results of calculations were compared with the experimental data which are available from different literature sources.
Elastic properties of braided ceramic matrix composites
Authors: Tushtev Kamen , Koch Dietmar , Grathwohl Georg
Published: February 2009

Fibre reinforced ceramic components are most efficiently produced by the braiding technique. Since the braiding angle can be adjusted during the preform fabrication process in a wide range as required by the loading situation of the composite, the evaluation and prediction of the elastic properties as a function of variable braiding angles is of high importance. Based on the classical laminate theory an inverse method for the determination of the elastic properties of an equivalent unidirectional ply is elaborated and applied to predict the effect of variable braiding angles. Orthogonal and non-orthogonal braided carbon/carbon composites were tested under in-plane tensile and shear loading in order to validate the analytical concept. A very good correlation between theoretical and experimental results was obtained.
Hardfacing behavior of Cr–Ni stainless steel with Co-based super alloys
Authors: Nursoy Mustafa , Yaz Mehmet , Celik Halis
Published: February 2009

In this study, the hardfacing behavior of Cr – Ni stainless steel was studied by depositing of Stellite 1, Stellite 6, and Stellite 12 superalloys on Cr – Ni stainless steel specimens using electric arc welding and tungsten inert gas welding. The cobalt base alloys were hardfaced on stainless steel plates as a single layer. The samples taken from the hardfaced materials were studied by optical microscopy, scanning electron microscopy, X-ray diffraction, and microhardness measurements. The hardness and wear resistance values of the layer obtained after the hardfacing processes are satisfactory and the process seem to be suitable for application.
Development of SMD 32.768 kHz tuning fork-type crystals
Authors: Lee Sungkyu , Moon Yangho , Ahn Jae-Hwan , Chung Hyungsik
Published: February 2009

Taguchi' design of experiment method and statistical F-test were used to optimize design of tuning forks for use in Qualcomm® mobile station modem (MSM)-3000TM series central processing unit chips of code division multiple access, personal communication system, and global system for mobile communication systems. Design parameters for motional capacitance C1 was further optimized after much trial and error so that as-fabricated resonance frequency values of a tuning fork blank remain almost the same prior to final frequency adjustment plating of the mounted crystals, regardless of packaging pressure change from ambient to designated 6 × 10– 5 Torr. Finite element method modeling was used in conjunction with Taguchi' design of experiment method and, after much trial and error, this enabled selection of essential design parameters to effectively manufacture tuning fork test samples using photolithography with subsequent photoresist spray coating. The tuning fork test samples thus fabricated were characterized and analyzed using Taguchi' method and statistical F-test to evaluate sensitivity of motional capacitance C1 and as-fabricated resonance frequency for various design parameters at ambient to designated packaging pressure of 6 × 10– 5 Torr. Motional capacitance C1 is most sensitive to tine width and tine surface electrode width. Unlike as-fabricated resonance frequency values, motional capacitance values do change with vacuum level of the package. However, tine width asymmetry, electrode thickness and tine tip electrode thickness could be freely adjusted for crystal impedance level without affecting resonance frequency and motional capacitance value. Other design parameters could be adjusted to best suit the manufacturing process.
Quantification of ∊-martensite after thermocycling in Fe-(17∼25)Mn alloys
Authors: Murasov Mykhaylo , Duprez Lode , Van Humbeeck Jan
Published: February 2009

Fe-(17∼25)Mn alloys have been systematically investigated by means of X-ray diffraction, optical microscopy, differential scanning calorimetry and dilatometry. Such parameters of martensitic transformation as transformation temperatures, enthalpy, phase composition and microstructural changes are discussed taking into account the effect of thermocycling. A special focus is laid on the incompleteness of the γ → ∊ transformation that is attributed mainly to the antiferromagnetic → paramagnetic transition of austenite. The volume fraction of epsilon martensite has been determined using the results from X-ray diffraction and dilatometry tests.
Far infrared spectroscopy of Pb0.85Sn0.15Te alloy doped with Ni
Authors: Nikolić Pantelija M. , Vujatović Stevan S. , Golić Danijela Lukovic , Labus Nebojša J. , Paraskevopoulos Konstantinos M. , Zorbas Kostas T. , Nikolić Maria Vesna , Bojičić Aleksandar , Blagojević Vladimir , König Wolfgang
Published: February 2009

Far infrared reflectivity spectra of single crystal Pb0.85Sn0.15Te doped with Ni were measured in the temperature range between 10 K and 300 K. Analysis of the experimental spectra was made using a fitting procedure based on the modified model of plasmon-phonon interactions and the optical parameters were calculated. Two local modes were observed and their origin was discussed.
Experimental study on gallium activity in the liquid Ga-Bi-Sn alloys using the EMF method with zirconia solid electrolyte
Authors: Katayama Iwao , Živković Dragana , Novaković Rada , Yamashita Hiromi
Published: February 2009

The EMF of galvanic cells with zirconia solid electrolytes was measured to determine the activity of gallium in liquid Ga-Bi-Sn alloys in the temperature range of 1000–1250 K along three pseudo-binary lines of (Bi
y
, Sn1−y)-Ga where y = 0.25, 0.50 and 0.75. A mixture of Ga and Ga203 was used as a reference electrode. The activity curves of Ga show positive deviations from ideality in the whole composition range. The excess free energies of mixing for Ga-Bi-Sn alloys have been calculated using the general solution model in the same temperature range and along same pseudo-binary lines. The gallium activities obtained by the EMF method and calculated using the general solution model at 1100 K were compared with literature data.
Achieving ultra-fine grains in AZ61 Mg alloy by friction stir processing
Authors: Du Xinghao , Zhang Erlin , Wu Baolin
Published: February 2009

In order to obtain fine-microstructure magnesium alloys with superior mechanical properties, AZ61 alloy is processed by friction stir processing combined with rapid heat sinking in this study. Ultrafine-grain microstructure with average size less than 300 nm was observed in the resultant AZ61 alloy. The mean microhardness of the ultrafine-grain region reached 120 ∼ 130 HV, twice that of the AZ61 substrate. All these results demonstrate clearly that under a cooling rate high enough, ultrafine-grain structure in AZ 61 alloy with superior mechanical properties can be produced by one pass friction stir processing via dynamic re-crystallization.
The role of solidification conditions on the microstructural features of AA6111 aluminum strips cast on a horizontal single belt caster
Authors: Shabestari S. G. , Li D. , Isac M. , Guthrie R. I. L.
Published: February 2009

The effect of the thickness of strips and cooling rates on the macro- and micro-structural features such as grain size, secondary dendrite arm spacing, and intermetallic phases, were studied for AA6111 aluminum alloy cast on a simulator of a horizontal single belt strip casting process. Different strips were investigated. As strip thickness decreased from 2.49 mm to 0.55 mm, the grain size decreased about 56 % and secondary dendrite arm spacing decreased about 56.7 %. An equation was developed based on the results obtained via thermal analysis which relates secondary dendrite arm spacing to cooling rate in this process. The formation and behavior of various complex intermetallic compounds in AA6111 were studied using scanning electron microscopy. The compositions of the precipitates were analyzed using electron probe microanalysis and their most likely stoichiometries determined.
Thermographic analysis of AlSi12 during crystallisation as a function of cooling rate
Authors: Wulf Eric , Krause Christian , Bormann Dirk , Schaper Mirko , Becker Jörg August , Becker Verena , Bach Friedrich-Wilhelm
Published: February 2009

At the Institute of Materials Science of the Leibniz University of Hannover, investigations were carried out to better understand the crystallisation processes of the cast alloy AlSi12. Here, the influence of different cooling rates was investigated in-situ and ex-situ. The temperatures of the geometric specimens were determined during the experiment with the aid of a near-infrared camera and thermocouples. The aim was to both determine a function between the specimen' cooling rate and the speed of the solid – liquid interface as well as establish a relationship between the thermographic images and the solidification' morphology.
Correlation between heat treatment, microstructure and mechanical properties of a hot-work tool steel
Authors: Mayer Svea , Scheu Christina , Leitner Harald , Siller Ingo , Clemens Helmut
Published: February 2009

The mechanical properties of the hot-worked and tempered tool steel grade X37CrMoV5-1 were studied as a function of the heat treatment and, thus, microstructure. Based on the continuous cooling transformation diagram, different hardening processes had been chosen to achieve fully martensitic and mixed martensitic-bainitic microstructures with different amounts of bainite. Mechanical tests demonstrate that the fully martensitic microstructure exhibits the highest toughness and ductility over the entire temperature range, whereas the strength remains constant. Microstructural investigations, performed using scanning and transmission electron microscopy, show that the degraded mechanical properties are related to the presence of the bainitic microstructure as well as carbides at former austenite grain boundaries.
A combined microtensile testing and nanoindentation study of the mechanical behavior of nanocrystalline LIGA Ni–Fe
Authors: Schwaiger Ruth , Reszat Jan-Thorsten , Bade Klaus , Aktaa Jarir , Kraft Oliver
Published: February 2009

In this work, we studied nanocrystalline LIGA Ni-2.6 at.% Fe and Ni-5.6 at.% Fe with an average grain size of 10 nm. Microtensile samples were produced by the LIGA process including direct current electrodeposition. Microstructures and mechanical properties were investigated in the as-deposited state as well as after annealing at different temperatures. Results from tensile testing were compared to nanoindentation experiments with a particular emphasis on the strain rate sensitivity of the alloys. The Ni – Fe alloys were confirmed to be suitable LIGA materials for applications that require high hardness combined with microstructural stability and low internal stresses. For both alloys with 10 nm grain size, tensile yield strength and corresponding hardness values of the order of 2 GPa and 6 GPa, respectively, were found. After annealing at moderate temperatures (200 °C), strength and hardness increased although some grain growth was observed.
Microstructure evolution during a liquid–liquid decomposition under the common action of the nucleation, growth and Ostwald ripening of droplets
Authors: Zhao J. Z. , Li H. L. , Zhang X. F. , He J. , Ratke L.
Published: February 2009

The kinetic details of the microstructure evolution during a liquid – liquid phase transformation under the common action of the nucleation, diffusional growth and Ostwald ripening of the minority phase droplets are investigated numerically. The results demonstrate that the cooling rate during the nucleation period of the minority phase droplets has an overwhelmingly strong effect on the microstructure formation compared with the cooling rate after the nucleation period. Generally, the effect of the Ostwald ripening of the minority phase droplets is weak in an alloy cooled continuously all through the miscibility gap and the average radius of the minority phase particles shows an inverse square root dependence on cooling rate. An obvious coarsening of the minority phase droplets occurs and the exponential varies towards – 1/3 only when the cooling rate decreases by more than two orders of magnitude after the nucleation of the precipitated droplets.
Bainite orientation in plastically deformed austenite
Authors: Shirzadi A. A. , Abreu H. , Pocock L. , Klobčuar D. , Withers P. J. , Bhadeshia H. K. D. H.
Published: February 2009

Experiments have been conducted to see whether specific crystallographic variants of bainite form in polycrystalline steel when transformation occurs from plastically deformed austenite which is otherwise free from externally applied stress. It is demonstrated by studying both overall and microtexture that there is no perceptible variant selection as bainite forms. Indeed, the texture is found to weaken on transformation.
Oxidation behaviour of experimental Co–Re-base alloys in laboratory air at 1000°C
Authors: Klauke Michael , Mukherji Debashis , Gorr Bronislava , da Trindade Filho Vicente Braz , Rösler Joachim , Christ Hans-Jürgen
Published: February 2009

The oxidation behaviour of experimental Co – Re-based alloy at 1000 °C was studied. A set of binary, ternary and quaternary alloys from the Co – Re – Cr – C system was used as model alloys to understand the role each alloying element plays on oxidation. The morphology and composition of the oxide scale that formed was analysed by X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. It was found that the present Co – Re alloys with 23 at.% and 30 at.% Cr additions behaved very similarly to Co – Cr binary alloys with equivalent Cr content. The oxide scale was multilayered, consisting of a dense CoO outer layer, a porous mixed oxide layer containing Co-oxide and Co – Cr spinel, and a discontinuous and non-protective Cr3O2 layer. The binary Co – Re alloy behaved differently in oxidation, and it formed only a monolithic CoO scale. However, Re in combination with Cr promotes Cr – Re-rich phase formation, which oxidises preferentially compared to the Co matrix. Carbon ties up part of the Cr to form Cr23C6 type carbides. However, these carbides are not stable at 1000 °C and dissolved with time, therefore C had only a minor role in the oxidation behaviour. In general, increasing Cr content in the alloy improved oxidation resistance.
High-speed Melt Spinning of Nanoparticle-filled High Molecular Weight Poly(ethylene terephthalate)
Authors: Jang K. H. , Kim B. C. , Hahm W. G. , Kikutani T.
Published: February 2009

High molecular weight poly(ethylene terephthalate) (HMW-PET) (intrinsic viscosity of 0.809 dL/g) and its nanocomposites with 1 wt.% organoclay C12PPh-Cl− and 1 and 2 wt.% trisilanol isobutyl-poly(hedral oligomeric silsesquioxane) (POSS) were high-speed melt spun over the range of take-up speeds 1 to 4.5 km/min, and the effects of nanoparticle type on the fiber properties were investigated. The clay and POSS nanocomposites exhibited quite different melt spinning behaviors. The neat PET and PET/POSS nanocomposites showed a neck-like deformation distinctly from the take-up speed of 3.5 and 3 km/min while PET/clay nanocomposites did not show any neck-like deformation over the entire spinning speed range. In comparison with nanocomposite chips clay gave rise to re-aggregation of nanoparticles whereas POSS made little change in dispersion. Clay suppressed the crystallization of PET during high-speed spinning although it had more effective nucleation effects at the static state than POSS. Clay nanocomposite fibers gave lower modulus and higher elongation at break than PET fibers. On the other hand, the mechanical properties of POSS nanocomposite fibers were almost equal or slightly better than PET fibers.
Investigation of the Effects of Formulation and Processing Parameters on Properties of PA 6 Nanocomposites using Taguchi Method of Experimental Design
Authors: Moghri M. , Garmabi H.
Published: February 2009

In this work, the effect of processing conditions and nanoclay (NC) content on formation and various properties of polyamide 6 (PA 6) nanocomposites was studied by means of Taguchi method of experimental design. PA 6/organoclay nanocomposites were prepared by melt mixing of PA 6 at different organoclay loadings using a co-rotating twin-screw extruder. In order to investigate the effects of both processing conditions and organoclay content on silicate dispersion (exfoliation) and thermal and mechanical properties of the nanocomposites, different extrusion rates, processing temperatures and feeding rates at various NC loadings were used. X-ray diffraction (XRD) was used to characterize the formation of nanostructure and clay dispersion. The thermal properties of PA 6 nanocomposites were studied through TMA tests. XRD results revealed the formation of nanocomposite and evidenced that the samples exhibit mixed intercalated / exfoliated morphology and verified that, the extent of exfoliation increases with both clay content and extrusion rate used. The mechanical properties of PA 6 nanocomposites were studied using tensile tests. The strength and modulus of PA 6 nanocomposites were improved significantly by increasing the clay concentration and shear rate level.
A Two-level Decomposition Method for Cooling System Optimization in Injection Molding
Authors: Yu D. , Wang X. , Wang Y.
Published: February 2009

The cooling system of a plastic injection mold plays a crucial role in determining both the productivity of the injection molding process and part quality. The cooling process is an important phase of injection molding, which could account for more than three-fourths of the total molding cycle time. Thus, an efficient cooling will significantly improve productivity by reducing the cooling time, and uniformity and balanced cooling can ensure part quality by preventing sink marks, different shrinkage, internal thermal residual stress and warpage.

In this paper, the geometric parameters (i. e., radius and location of each cooling channel) and process parameters (i. e., inlet coolant temperature, volumetric flow rate of each cooling channel, packing time, and cooling time, etc.) are considered systematically in the cooling system design of injection molding. A two-level decomposition method for the cooling system optimization is proposed. The optimization problem is divided into two subproblems (cooling channel design and process design) on the basis of the different effects on refrigerant behaviour of different kinds of design variables. By combining the Kriging model and CAE technology, a mold cooling system for a 15-inch display was optimized. The results show that the method can efficiently improve the temperature distribution and the part quality.
Capillary Extrusion Studies of LLDPE/LDPE Blends: Effects of Manufacturing Technology of LLDPE and Long Chain Branching
Authors: Delgadillo-Velázquez O. , Hatzikiriakos S. G.
Published: February 2009

The processing behavior of a number of LLDPE/LDPE blends with emphasis on the effects of manufacturing technology of LLDPE and long chain branching is presented. A single low-density polyethylene was blended with two Ziegler-Natta linear-low-density polyethylenes LLDPE's and two metallocene-LLDPE's having distinctly different molecular structures. The weight fractions of the LDPEs used in the blends were 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, 50 wt.% and 75 wt.%. Capillary extrusion reveals that the onset of sharkskin and gross melt fracture are slightly influenced with the addition of LDPE into LLDPE. However, the amplitude of the oscillations in the stick-slip flow regime was found to scale well with the weight fraction of LDPE even at amounts as low as 1 wt.%. Furthermore, it was observed that the onset of this flow regime was shifted to higher shear rates with increase of LDPE content. Shear rheology was found to be insensitive to detect small levels of LDPE. On the other hand, extensional rheology was found to be capable of detecting levels of LDPE as low as 1 wt.% at high Hencky strain rates (typically greater than 5 s−1) although only for certain blends.
Crystallization of PLA/Thermoplastic Starch Blends
Authors: Li H. , Huneault M. A.
Published: February 2009

In this paper, the crystallization of PLA in PLA/thermoplastic starch (TPS) blends was investigated. The TPS was used as the minor component at a concentration varying between 0 and 42 %. The effect of interfacial area was studied by compatibilizing the blend using maleic anhydride grafted PLA. To further enhance the crystallization rate in PLA/TPS blends, the addition of talc and acetyl triethyl citrate, as nucleating agent and plasticizer respectively, was also studied. The crystallization rate was monitored using DSC analysis under both isothermal and non- isothermal conditions. The isothermal data was used to determine the crystallization half-life and to determine the optimum crystallization temperature. The crystallization half-time of PLA was decreased significantly in presence of the TPS phase and this effect was strengthened by the blends interfacial modification. By applying proper plasticization and nucleation strategy, crystallinity in excess of 50 % was achieved even at cooling rates as high as 80°C/min. Fully crystallized PLA/TPS samples were obtained by injection molding in a hot mold (80°C). Crystallized parts showed improved thermal resistance at temperatures above PLA's glass transition.
Euclidean Quantum Mechanics and Universal Nonlinear Filtering
Authors: Balaji Bhashyam
Published: February 2009

An important problem in applied science is the continuous nonlinear filtering problem, i.e., the estimation of a Langevin state that is observed indirectly. In this paper, it is shown that Euclidean quantum mechanics is closely related to the continuous nonlinear filtering problem. The key is the configuration space Feynman path integral representation of the fundamental solution of a Fokker-Planck type of equation termed the Yau Equation of continuous-continuous filtering. A corollary is the equivalence between nonlinear filtering problem and a time-varying Schr¨odinger equation.
Total Syntheses of (±)-Gusanlung A, (±)-Gusanlung D and 8-Oxyberberrubine and the Uncertainty Concerning the Structures of (-)-Gusanlung A, (-)-Gusanlung D and 8-Oxyberberrubine
Authors: Nimgirawath Surachai , Udomputtimekakul Phansuang , Apornpisarn Thitima , Wanbanjob Asawin , Taechowisan Thongchai
Published: February 2009

(±)-Gusanlung A, 8-oxyberberrubine and (±)-gusanlung D have been synthesized by radical cyclisation of the corresponding 2-aroyl-1-methylenetetra- hydroisoquinolines. The 1H and 13C spectra of (-)-gusanlung D were found to be different from those of synthetic (±)-gusanlung D. Careful analyses of the 13C spectra of (–)-gusanlung A and natural 8-oxyberberrubine also cast doubt on the correctness of the structures previously assigned to these two compounds. (±)-Gusanlung A and (±)-gusanlung D were inactive against Staphylococcus aureus ATCC25932, Escherichia coli ATCC10536 and Candida albicans ATCC90028.
How long do the short‐term violent video game effects last?
Authors: Barlett Christopher , Branch Omar , Rodeheffer Christopher , Harris Richard
Published: February 2009

How long do the effects of the initial short‐term increase in aggression and physiological arousal last after violent video game play? Study 1 (N=91) had participants complete pre‐ and postvideo game measures of aggressive thoughts, aggressive feelings, and heart rate. Then, participants completed Time 3 measures after 4 min or 9 min of delay. Study 2 employed a similar procedure, but had participants (N=91) complete the hot sauce paradigm to assess aggressive behavior after a 0, 5, or 10 min delay. First, results indicated that aggressive feelings, aggressive thoughts, aggressive behavior, and heart rate initially increased after violent video game play. Second, results of the delay condition revealed that the increase in aggressive feelings and aggressive thoughts lasted less than 4 min, whereas heart rate and aggressive behavior lasted 4–9 min. Aggr. Behav. 35:225–236, 2009. © 2009 Wiley‐Liss, Inc.
How accurately can older adults evaluate the quality of their text recall? The effect of providing standards on judgment accuracy
Authors: Baker Julie M. C. , Dunlosky John , Hertzog Christopher
Published: February 2009

Adults have difficulties accurately judging how well they have learned text materials; unfortunately, such low levels of accuracy may obscure age‐related deficits. Higher levels of accuracy have been obtained when younger adults make postdictions about which test questions they answered correctly. Accordingly, we focus on the accuracy of postdictive judgments to evaluate whether age deficits would emerge with higher levels of accuracy and whether people's postdictive accuracy would benefit from providing an appropriate standard of evaluation. Participants read texts with definitions embedded in them, attempted to recall each definition, and then made a postdictive judgment about the quality of their recall. When making these judgments, participants either received no standard or were presented the correct definition as a standard for evaluation. Age‐related equivalence was found in the relative accuracy of these term‐specific judgments, and older adults' absolute accuracy benefited from providing standards to the same degree as did younger adults. Copyright © 2009 John Wiley & Sons, Ltd.
Influence of maternal stature, pregnancy age, and infant birth weight on growth during childhood in Yucatan, Mexico: A test of the intergenerational effects hypothesis
Authors: Varela‐Silva Maria Inês , Azcorra Hugo , Dickinson Federico , Bogin Barry , Frisancho A. R.
Published: February 2009

In developing nations, obesity has increased dramatically in the last decade, but a high prevalence of stunting still coexists. The intergenerational influences hypothesis (IIH) is one explanation for this. We test the IIH regarding variation in maternal stature, mother's age at pregnancy, and infant birth weight in relation to risk for overweight and stunting in 206 Maya children (4–6 years old) from Mérida, Yucatan, Mexico. The Maya children are compared with growth references (Frisancho 2008: Anthropometric Standards: An Interactive Nutritional Reference of Body Size and Body Composition for Children and Adults. Ann Arbor, MI: The University of Michigan Press. 335 pp) for height, weight, and body mass index (BMI). Almost 70% of the mothers are shorter than 150 cm. Mothers' height and child's birth weight predict overweight. Children with a mother shorter than 150 cm are less than half as likely (OR = 0.44) to be overweight compared to children whose mothers are equal to or taller than 150 cm. Children with birth weights below 3,000 g are only a third as likely to be overweight (OR = 0.28) than their peers within the range of normal birth weight (3,000–3,500 g). Sex of the child, mother's height, and birth weight predict stunting. Girls are only 40% as likely as boys to be stunted. Children with a mother below 150 cm are 3.6 times more likely of being stunted. Children with birth weights below 3000 g are over 3 times more likely to be stunted relative to children with birth weights within the normal range. Mother's age at pregnancy is not a predictor of overweight or stunting. Our findings conform the IIH and with similar studies of populations undergoing nutritional/epidemiological transitions from traditional to globalized lifestyles. Am. J. Hum. Biol., 2009. © 2009 Wiley‐Liss, Inc.
Male‐to‐male transmission of Costello syndrome: G12S HRAS germline mutation inherited from a father with somatic mosaicism
Authors: Sol‐Church Katia , Stabley Deborah L. , Demmer Laurie A. , Agbulos Abigail , Lin Angela E. , Smoot Leslie , Nicholson Linda , Gripp Karen W.
Published: February 2009

Costello syndrome is a rare congenital anomaly syndrome associated with mental retardation and predisposition to benign and malignant tumors, caused by heterozygous missense mutations in the HRAS oncogene. Previously, all molecularly analyzed mutations appeared de novo, and most arose in the paternal germline. A single patient with somatic mosaicism for a Costello syndrome causing HRAS mutation has been reported. Here we describe the first documented transmission of an HRAS mutation from a parent with somatic mosaicism to a child with typical Costello syndrome. Prior to the identification of the underlying gene mutation in Costello syndrome, this family had been identified clinically. The proband was subsequently found to carry a G12S HRAS germline mutation. Testing of the parents for parental origin identified his father as mosaic for the same HRAS mutation. The mother was found not to carry an HRAS mutation. The causative familial mutation is identified as a c.34G > A, which is the most common mutation in the HRAS gene in patients with Costello syndrome. The father carries the mutation in 7–8% of his alleles. This is the second case of mosaicism observed in Costello syndrome and the first direct molecular evidence of father‐to‐son transmission of the disease‐causing mutation. Our observation underlines the importance of parental evaluation, and may have implications for genetic counseling and clinical practice. © 2009 Wiley‐Liss, Inc.
A missense mutation, p.V132G, in the X‐linked spermine synthase gene (SMS) causes Snyder–Robinson syndrome
Authors: Becerra‐Solano L.E. , Butler J. , Castañeda‐Cisneros G. , McCloskey D.E. , Wang X. , Pegg A.E. , Schwartz C.E. , Sánchez‐Corona J. , García‐Ortiz J.E.
Published: February 2009

Snyder–Robinson syndrome (SRS, OMIM 309583) is a rare X‐linked syndrome characterized by mental retardation, marfanoid habitus, skeletal defects, osteoporosis, and facial asymmetry. Linkage analysis localized the related gene to Xp21.3–p22.12, and a G‐to‐A transition at point +5 of intron 4 of the spermine synthase gene, which caused truncation of the SMS protein and loss of enzyme activity, was identified in the original family. Here we describe another family with Snyder–Robinson syndrome in two Mexican brothers and a novel mutation (c.496T>G) in the exon 5 of the SMS gene confirming its involvement in this rare X‐linked mental retardation syndrome. © 2009 Wiley‐Liss, Inc.
The R402Q tyrosinase variant does not cause autosomal recessive ocular albinism
Authors: Oetting William S. , Pietsch Jacy , Brott Marcia J. , Savage Sarah , Fryer James P. , Summers C. Gail , King Richard A.
Published: February 2009

Mutations in the gene for tyrosinase, the key enzyme in melanin synthesis, are responsible for oculocutaneous albinism type 1, and more than 100 mutations of this gene have been identified. The c.1205G > A variant of the tyrosinase gene (rs1126809) predicts p.R402Q and expression studies show thermolabile enzyme activity for the variant protein. The Q402 allele has been associated with autosomal recessive ocular albinism when it is in trans with a tyrosinase gene mutation associated with oculocutaneous albinism type 1. We have identified 12 families with oculocutaneous albinism type 1 that exhibit segregation of the c.1205G > A variant with a known pathologic mutation on the homologous chromosome, and demonstrate no genetic association between autosomal recessive oculocutaneous albinism and the Q402 variant. We conclude that the codon 402 variant of the tyrosinase gene is not associated with albinism. © 2009 Wiley‐Liss, Inc.
A locus for ophthalmo‐acromelic syndrome mapped to 10p11.23
Authors: Hamanoue Haruka , Megarbane Andre , Tohma Takaya , Nishimura Akira , Mizuguchi Takeshi , Saitsu Hirotomo , Sakai Haruya , Miura Shoko , Toda Tatsushi , Miyake Noriko , Niikawa Norio , Yoshiura Koichiro , Hirahara Fumiki , Matsumoto Naomichi
Published: February 2009

Ophthalmo‐acromelic syndrome (OAS, OMIM %206920) is a rare autosomal recessive disease, presenting with clinical anophthalmia and limb anomalies. We recruited three OAS families including a Japanese family with two affected patients and two consanguineous Lebanese families each having an affected. Homozygosity mapping was performed using the 50K SNP chip and additional informative markers. A locus for OAS was mapped to the 422‐kb region at 10q11.23, based on the results from the two consanguineous families as well as the consistent data from the Japanese non‐consanguineous family. The 422‐kb region only contained one gene, MPP7. Although we could not detect any pathological mutations in OAS families analyzed, MPP7 could remain a candidate as aberrant changes might exist beyond our mutation detection methods. Further families are needed to confirm this candidate locus. © 2009 Wiley‐Liss, Inc.
Pallister–Killian syndrome caused by mosaicism for a supernumerary ring chromosome 12p
Authors: Yeung Alison , Francis David , Giouzeppos Olivia , Amor David J.
Published: February 2009

Pallister–Killian syndrome (PKS) is a rare but distinctive chromosomal syndrome distinguished by severe intellectual impairment, characteristic facial features, and variable structural anomalies. The characteristic cytogenetic abnormality in PKS is a supernumerary isochromosome 12p that confers mosaic tetrasomy. We describe a female child with PKS in whom tetrasomy 12p resulted from a supernumerary ring chromosome containing two copies of chromosome 12cen → p13, a novel cytogenetic finding. The ring chromosome exhibited tissue‐limited mosaicism, being absent in blood but detected in 38% of buccal mucosa cells and 41% of skin fibroblasts. Our patient demonstrated the typical dysmorphic characteristics of PKS, but her development was relatively advanced in comparison to children with isochromosome PKS. Her milder developmental phenotype may be attributable to differences in the mosaic distribution or the genomic content of the ring chromosome compared to mosaic isochromosome 12p. © 2009 Wiley‐Liss, Inc.
First record of tool use by wild populations of the yellow‐breasted capuchin monkey (Cebus xanthosternos) and new records for the bearded capuchin (Cebus libidinosus)
Authors: Canale Gustavo Rodrigues , Guidorizzi Carlos Eduardo , Kierulff Maria Cecília Martins , Gatto Cassiano Augusto Ferreira Rodrigues
Published: February 2009

Reports on use of stones as hammers and anvils to open hard nuts by wild capuchin monkeys are scarce and limited toCebus libidinosus. Here, we report for the first time data on tool use—stones as hammer and anvils to open nuts—in wildC. xanthosternosand a description of new tool using sites forC. libidinosus. Our records were made by visiting anvil sites and by information obtained from local residents. We surveyed three different biomes:Caatinga(dry forest and thorn scrub),Cerrado(Brazilian bush savannah), and Atlantic forest (wet forest), all records of tool use were fromCaatingaor transitional areas between habitats. The behavior is suggested to be routinely performed and widespread among several populations. The fruits of six plant species in different localities were opened with hammer stones byC. xanthosternos.Hammer stones were of similar weigh as those described in other studies ofC. libidinosus. Conditions found inCaatinga, such as a more frequent use of the ground by the monkeys and/or food scarcity, may play an important role in the acquisition of nut‐cracking behavior. The absence of more reports of nut cracking and other forms of tool use in other species of wildCebusis likely to result from a lack of surveys in very dry and food limited habitats or intrinsic characteristics of otherCebusspecies. Am. J. Primatol. 71:366–372, 2009. © 2009 Wiley‐Liss, Inc.