bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of mold surface conditions on flow length in injection molding process
Authors: Otsuka Masaki , Oyabe Aya , Ito Hiroshi 
Published: March 2011

AbstractIn this study, to clarify the influence of a mold on thin‐wall molding, the effect of different mold surface conditions on the flow length and mobility (i.e., ease with, which melted plastics can be filled into the mold) in an injection molding process was investigated. Three different coatings were used for the mold surface. Several degrees of roughness were also selected for the mold surface. The results were evaluated by comparing flow length with interfacial tensions, which were derived from Young's formula. Although the interfacial tension exhibited different values, the influence on flow length was generally found to be small. On the other hand, in the mold that gives surface roughness, though the change of interfacial tension was small compared with coatings, the flow length increased linearly with the surface roughness when the roughness exceeded a certain level roughness. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Castor oil‐based polyurethanes containing cellulose nanocrystals
Authors: Wik V.M. , Aranguren M.I. , Mosiewicki M.A. 
Published: March 2011

AbstractPartially foamed and nanocellulose‐reinforced polyurethanes (PU) based on castor oil (CO) were prepared and their different properties were measured and related to their structures. A castor oil‐based polyol (COPO) was obtained by alcoholysis of CO with triethanolamine. The COPO was used in the preparation of partially foamed and solid PU. Cellulose nanofibrils (NC) in the range of the rheological percolation content were incorporated to the materials and the final mechanical properties of these nanocomposites were analyzed. The incorporated NC considerably affected the rheology of the suspensions, which presented solid‐like behavior under frequency sweep tests with the addition of only 0.5 wt% of NC. By increasing the NC concentration the dispersion becomes increasingly difficult. The properties of the solid PU were also affected by the incorporation of NC and a significant increase of the tensile modulus was observed for the 0.5 wt% NC composite, compared to the unfilled solid PU. This behavior was associated to the incorporation of the rigid particle reinforcement and the interfacial bonding. As expected, the partially foamed PU showed lower modulus than the corresponding solid PU. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Encapsulation of hydrophobic drugs in a copolymer: Glass transition behavior and miscibility evaluation
Authors: Babu R. Jayachandra , Brostow Witold , Fasina Oladiran , Kalogeras Ioannis M. , Sathigari Sateeshkumar , Vassilikou‐Dova Aglaia 
Published: March 2011

AbstractThe knowledge of glass transition temperatures Tg in drug + polymer systems is indispensable for drug encapsulation. Tg values as a function of composition make possible the determination whether a given polymer is miscible or compatible with the drug and whether the polymer will provide release of the drug into organism within an acceptable rate range. We have used differential scanning calorimetry and Fourier‐transform infrared spectroscopy to evaluate miscibility in solid dispersions of the drugs carvedilol, itraconazole, nevirapine, and nimodipine in the pharmaceutical grade copolymer poly(vinyl pyrrolidone‐co‐vinyl acetate) (PLS‐630 Copovidone). Successful drug encapsulation is discussed in terms of thermophysical behavior (suppression of crystallization, negative excess volumes of mixing) and intermolecular interactions (concentrations of proton donating/accepting groups) in drug + polymer systems. Several equations were applied to the complex s‐shaped Tg(ϕ) patterns obtained (ϕ being the mass fraction of the drug). The best agreement of calculations with experiment is achieved using a recently proposed three‐parameter equation, symmetric with respect to the equal concentration of both components. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Extrusion of linear polypropylene–clay nanocomposite foams
Authors: Chaudhary Amit Kumar , Jayaraman Krishnamurthy 
Published: March 2011

AbstractThis work presents new results on using organoclay with an appropriate polymeric compatibilizer as rheology‐modifying additives for extrusion foaming of a linear polypropylene (PP), which by itself does not display strain hardening in extensional flow of the melt. The uniaxial melt‐extensional viscosity behavior of several nanocomposites prepared with varying ratio of bound maleic anhydride to clay as well as varying compatibilizer molecular weight was investigated. A chemical‐blowing agent was used at a fixed concentration for foaming these nanocomposites in a single‐screw extruder. Among nanocomposites with similar levels of clay dispersion or intercalation, the ones that displayed significant strain hardening in the melt state along with slower crystallization led to extruded PP nanocomposite foams with smaller cell sizes and greater cell density by reducing cell coalescence. This was achieved with as little as 3 wt% organoclay and a high‐molecular weight PP‐g‐MA compatibilizer in linear PP. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Highly reversible and repeatable PTCR characteristics of PMMA/Ag‐coated glass bead composites based on CTE mismatch phenomena
Authors: Kar Prativa , Khatua Bhanu B. 
Published: March 2011

AbstractPositive temperature coefficient of resistivity (PTCR) behavior of poly(methyl methacrylate) PMMA/silver (Ag)‐coated glass bead composites has been investigated with reference to the conventional PMMA/carbon black (CB) composites. The PMMA/CB composites showed a sudden rise in resistivity (PTC trip) at 115°C, close to the glass transition temperature (T
g, 113°C) of the PMMA. However, the PTC trip temperature (92°C) of PMMA/Ag‐coated glass bead composites was appeared well below the T
g of PMMA. The room temperature resistivity and PTC trip temperature of the composites were also very much stable upon thermal cycling. Addition of 1 phr of nanoclay increased the PTC trip temperature of PMMA/CB composites to 120°C, close to the T
g (118°C) of PMMA/clay nanocomposites, while PMMA/clay/Ag‐coated glass bead nanocomposites showed the PTC trip at 98°C. We proposed that the mismatch in coefficient of thermal expansion (CTE) between PMMA and glass beads played a key role that led to a disruption in continuous network structure of Ag‐coated glass beads even at a temperature well below the T
g of PMMA. The decrease in dielectric permittivity of PMMA/Ag‐coated glass bead composites on increasing frequency indicated possible use of the PTC composites as dielectric material. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
One‐dimensional photogeneration profiles in silicon solar cells with pyramidal texture
Authors: Baker‐Finch Simeon C. , McIntosh Keith R. 
Published: March 2011

ABSTRACTThe key metric of surface texturing is the short‐circuit current Jsc. It depends on front surface transmittance, light trapping and the spatial profiles of photogeneration G and collection efficiency ηc. To take advantage of a one‐dimensional profile of ηc(ζ), where ζ is the shortest distance to the p–n junction, we determine G(ζ) via ray tracing. This permits rigorous optical assessment of common pyramidal textures for various cell designs. When ζ is small, G(ζ) is largest beneath regular inverted pyramids, upright pyramids (regular or random) and planar surfaces, respectively. This higher G(ζ) results in superior collection of generated carriers in front‐junction cells. In simulations of a conventional screen‐print cell, 92.0% of generated carriers are collected for inverted pyramids, compared to 91.4% for upright pyramids, and 90.0% for a planar surface. Higher efficiency and rear junction devices are analysed in the paper. Despite differences in G(ζ) beneath textures, inverted pyramids achieve the highest Jsc for all cell designs examined (marginally so for high‐efficiency rear‐contact cells) due to superior front surface transmittance and light trapping. We assess a common one‐dimensional model for photogeneration beneath textured surfaces. This model underestimates G(ζ) when ζ is small, and overestimates G(ζ) when ζ is large. As a result, the generation current determined is inaccurate for thin substrates. It can be computed to within 3% error for 250 µm thick substrates. However, errors in G(ζ) can lead to 7.5% inaccuracy in calculations of Jsc. Errors are largest for lower efficiency designs, in which collection efficiency varies through the substrate. Copyright © 2011 John Wiley & Sons, Ltd.
Analysis and Modeling of Gas‐Phase Processes in a CHF3/Ar Discharge
Authors: Barz Jakob P. , Oehr Christian , Lunk Achim 
Published: March 2011

AbstractThe present work deals with the diagnostics of fluorocarbon plasmas by different experimental methods and complementary numerical analysis of the plasma. The plasma diagnostics were performed with non‐invasive methods. In this paper, we present results obtained by laser‐induced fluorescence and UV absorption measurements. The complementary numerical simulations accounted for the electron–neutral interactions, discharge dynamics, and chemical reactions. Several insights were obtained from the combined experimental and numerical approaches, especially concerning the conclusiveness of the results and previous observations from the literature. As important initial neutral species, CF3 and H originate from electron collisions with CHF3. The atomic hydrogen is responsible for fluorine abstraction reactions which result in the formation of hydrofluoric acid as well as in unsaturated carbon bonds. It was found from the simulations that in the examined discharges, this reaction is the most important channel for the high‐rate production of the CF molecule in the gas phase via ${\rm CF}_{2} + {\rm H}\to {\rm CF} + {\rm HF}$. For this molecule, no anisotropy in the density was found and the production solely occurs in the gas phase. Contrary to that, the production of CF2 via the abstraction of fluorine from CF3 in the gas phase was found to be of less importance for the overall concentration of this molecule. Instead, chemical reactions at the chamber walls which release CF2 were identified experimentally as major sources. According to the simulations, the unsaturated fluorocarbon molecules react to oligomers, such that the net reaction can be roughly described by $n{\rm CHF}_{3} \to {\rm (CF}_{{\rm 2}} {\rm )}_{n} + n{\rm HF}$. A good agreement between the simulated and the experimentally observed densities and rates was obtained, which confirms the interpretation of the ongoing plasma‐chemical processes as well as the underlying physical discharge parameters consistently. magnified image
Functionalization of Fluropolymers and Polyolefins via Grafting of Polyelectrolyte Brushes From Atmospheric‐Pressure Plasma Activated Surfaces
Authors: Neuhaus Sonja , Padeste Celestino , Spencer Nicholas D. 
Published: March 2011

AbstractETFE, PE, and PP surfaces were functionalized by a procedure involving the activation of the substrates with cold, atmospheric‐pressure helium plasma, formation of surface‐bound peroxides in air, and subsequent grafting of polymer brushes from these initiators by means of free‐radical polymerization. Strategies for obtaining weak and strong polyelectrolyte brushes are presented and the applicability of the method to the different polymer substrates is evaluated. The wettability of the modified surfaces was found to be increased on all three polymers, resulting in a decrease of contact angle from 100° in the unmodified state to about 10° after modification with the most hydrophilic brushes. Examples of surfaces with strong wettability contrast or with reversibly switchable wettability are shown. magnified image
Signature of n→π* interactions in α‐helices
Authors: Choudhary Amit , Raines Ronald T. 
Published: March 2011

AbstractThe oxygen of a peptide bond has two lone pairs of electrons. One of these lone pairs is poised to interact with the electron‐deficient carbon of the subsequent peptide bond in the chain. Any partial covalency that results from this n→π* interaction should induce pyramidalization of the carbon (C′i) toward the oxygen (Oi−1). We searched for such pyramidalization in 14 peptides that contain both α‐ and β‐amino acid residues and that assume a helical structure. We found that the α‐amino acid residues, which adopt the main chain dihedral angles of an α‐helix, display dramatic pyramidalization but the β‐amino acid residues do not. Thus, we conclude that Oi−1 and C′i are linked by a partial covalent bond in α‐helices. This finding has important ramifications for the folding and conformational stability of α‐helices in isolation and in proteins.
Computational protein design with a generalized born solvent model: Application to asparaginyl‐tRNA synthetase
Authors: Polydorides Savvas , Amara Najette , Aubard Caroline , Plateau Pierre , Simonson Thomas , Archontis Georgios 
Published: March 2011

AbstractComputational Protein Design (CPD) is a promising method for high throughput protein and ligand mutagenesis. Recently, we developed a CPD method that used a polar‐hydrogen energy function for protein interactions and a Coulomb/Accessible Surface Area (CASA) model for solvent effects. We applied this method to engineer aspartyl‐adenylate (AspAMP) specificity into Asparaginyl‐tRNA synthetase (AsnRS), whose substrate is asparaginyl‐adenylate (AsnAMP). Here, we implement a more accurate function, with an all‐atom energy for protein interactions and a residue‐pairwise generalized Born model for solvent effects. As a first test, we compute aminoacid affinities for several point mutants of Aspartyl‐tRNA synthetase (AspRS) and Tyrosyl‐tRNA synthetase and stability changes for three helical peptides and compare with experiment. As a second test, we readdress the problem of AsnRS aminoacid engineering. We compare three design criteria, which optimize the folding free‐energy, the absolute AspAMP affinity, and the relative (AspAMP‐AsnAMP) affinity. The sequences and conformations are improved with respect to our previous, polar‐hydrogen/CASA study: For several designed complexes, the AspAMP carboxylate forms three interactions with a conserved arginine and a designed lysine, as in the active site of the AspRS:AspAMP complex. The conformations and interactions are well maintained in molecular dynamics simulations and the sequences have an inverted specificity, favoring AspAMP over AsnAMP. The method is not fully successful, since experimental measurements with the seven most promising sequences show that they do not catalyze at a detectable level the adenylation of Asp (or Asn) with ATP. This may be due to weak AspAMP binding and/or disruption of transition‐state stabilization. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Pool fire extinction by remotely controlled application of liquid nitrogen
Authors: Levendis Yiannis A. , Delichatsios Michael A. 
Published: March 2011

AbstractThis article presents a technique for effective remote‐controlled application of liquid nitrogen to fires. Application of the cryogen from a distance, by spraying through a nozzle, proved challenging as evaporation along the trajectory path of the jet reduces the quantity of the liquid reaching the fire. To the contrary, use of a remotely guided unmanned robotic vehicle to carry the hose to the fire and discharge the cryogen in the fire proved to be more effective. Upon contact with a pyrolyzing/burning surface or the ground, abrupt vaporization of the cryogen generated cold vapors that spread by gravity and blanketed the burning area. The pyrolyzing gases were inerted, the surface was cooled, air was separated from the fuel, and the fire was extinguished. To demonstrate this technique, experiments were conducted with pool fires of isopropanol. Fire extinction in these feasibility tests was fast and effective. © 2011 American Institute of Chemical Engineers Process Saf Prog 2011
Dealing with midair collisions in dense collective aerial systems
Authors: Leven Severin , Zufferey Jean‐Christophe , Floreano Dario 
Published: March 2011

AbstractThe idea of creating collective aerial systems is appealing because several rather simple flying vehicles could join forces to cover a large area in little time in applications such as monitoring, mapping, search and rescue, or airborne communication relays. In most of these scenarios, a fleet of cooperating vehicles is dispatched to a confined airspace area and requested to fly close to a nominal altitude. Moreover, depending on the task each vehicle is assigned to, individual flight trajectories in this essentially two‐dimensional space may interfere, resulting in disastrous collisions. This paper begins by introducing a probabilistic model to predict the rate of midair collisions that would occur if nothing is done to prevent them. In a second step, a control strategy for midair collision avoidance is proposed, which is interesting because it requires only local communication and information about flight altitudes. The proposed strategy is systematically analyzed in theory and simulation as well as in experiments with five physical aerial vehicles. A significant reduction in collision rates can be achieved. Statistically, values close to zero are possible when the swarm's density is below an application‐dependent threshold. Such low collision rates warrant an acceptable level of confidence in collision‐free operation of a physical swarm. © 2011 Wiley Periodicals, Inc.
It really does matter how you normalize the branch distance in search‐based software testing
Authors: Arcuri Andrea 
Published: March 2011

SUMMARYThe use of search algorithms for test data generation has seen many successful results. For structural criteria like branch coverage, heuristics have been designed to help the search. The most common heuristic is the use of approach level (usually represented with an integer) to reward test cases whose executions get close (in the control flow graph) to the target branch. To solve the constraints of the predicates in the control flow graph, the branch distance is commonly employed. These two measures are linearly combined. Since the approach level is more important, the branch distance is normalized, often in the range [0, 1]. In this paper, different types of normalizing functions are analyzed. The analyses show that the one that is usually employed in the literature has several flaws. The paper presents a different normalizing function that is very simple and does not suffer from these limitations. Empirical and analytical analyses are carried out to compare these two functions. In particular, their effect is studied on commonly used search algorithms, such as Hill Climbing, Simulated Annealing and Genetic Algorithms. Copyright © 2011 John Wiley & Sons, Ltd.
Energy‐efficient human probes for high‐resolution sensing in urban environments
Authors: Thepvilojanapong Niwat , Konomi Shin'ichi , Tobe Yoshito 
Published: March 2011

AbstractPortable sensory devices carried by humans—which are referred to as Human Probes—facilitate easy‐to‐use sensing and monitoring of urban areas. However, when each Human Probe individually senses and transmits information, the sensing activity is inefficient in terms of energy consumption. In this paper, we propose Aquiba protocol in which the sensing activities carried out by the Human Probes are adjusted autonomously under different conditions. Aquiba involves cooperative sensing that helps in efficiently maintaining the desired sensing resolution, while minimizing overall energy consumption. To validate Aquiba protocol, we have conducted comprehensive simulations by including small‐scale and large‐scale scenarios along with applying three movement patterns of human. The simulation results demonstrate that Aquiba protocol is capable of providing high sensing resolution and reducing energy consumption substantially. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Is PIXE still a useful technique for the analysis of atmospheric aerosols? The LABEC experience
Authors: Lucarelli F. , Nava S. , Calzolai G. , Chiari M. , Udisti R. , Marino F. 
Published: March 2011

AbstractAt the 3‐MV Tandetron accelerator of LABEC (INFN) an external beam facility is fully dedicated to particle‐induced X‐ray emission (PIXE) and particle‐induced γ‐ray emission (PIGE) measurements of atmospheric aerosol elemental composition. All the elements with Z > 10 are simultaneously detected by PIXE in a few minutes and an automatic system for positioning, changing and scanning of the samples allows the analysis of the aerosol collected by different kinds of devices: long series of daily PMX samples can be measured in short times, as well as size‐segregated and high time‐resolution aerosol samples. Thanks to the capability of detecting all the crustal elements, PIXE‐PIGE analyses are unrivalled in the study of mineral dust: as a consequence, they are very effective in the study of natural aerosols, like, for example, mineral dust archived in polar ice cores (for environmental and paleoclimatic studies) and Saharan‐dust intrusions. Among the detectable elements, there are also important markers of anthropogenic sources, which allow effective source apportionment studies in polluted urban environments. Examples regarding recent monitoring campaigns, performed in urban and remote areas, both on a daily basis and with high‐time resolution (hourly samples), are presented to evidence how PIXE can still provide unique information in aerosol studies or can play a complementary role to X‐ray fluorescence or induced coupled plasma mass spectroscopy analysis. Copyright © 2011 John Wiley & Sons, Ltd.
New Tungsten Chloride Cluster Compounds Containing Iron or Cobalt: MW2Cl10 and MW6Cl14 (M = Fe, Co)
Authors: Ströbele Markus , Meyer H.‐Jürgen 
Published: March 2011

AbstractThe reduction of tungsten hexachloride with iron powder or cobalt powder resulted in the formation of MW2Cl10 (M = Fe and Co) in fused silica tubes at 250 °C and 225 °C, respectively. Crystal structures of the new compounds were refined isotypically from X‐ray powder diffraction patterns [C2/c, Z = 4, a = 6.1226(1) Å, b = 16.7943(1) Å, c = 12.3737(1) Å, and β = 108.99(1)° for FeW2Cl10, and a = 6.111(1) Å, b = 16.696(1) Å, c = 12.384(1) Å, and β = 108.97(1)° for CoW2Cl10]. The structures of Fe1/5W2/5Cl2 and Co1/5W2/5Cl2 can be considered as a cation‐deficient CdI2‐type structure, in which bioctahedral [W2Cl10]n– anions with n ≈︁ 2 introduce significant distortions. The compounds MW6Cl14 (M = Fe and Co) were prepared following the same procedure at 475 °C. Their crystal structures were refined isotypically [Pn3, Z = 4, a = 12.567(1) Å for FeW6Cl14, and 12.525(1) Å for CoW6Cl14] to the structure of PbMo6Cl14 from X‐ray powder diffraction patterns.
Epoxidizable Fatty Amide–Phenol Conjugates
Authors: Zerkowski Jonathan A. , Haas Michael J. 
Published: March 2011

AbstractThis paper reports the synthesis of a series of novel compounds where carboxylic acids have been linked to a phenol through amidomethyl units. For instance, one, two, or three fatty acids have been selectively appended to the phenol in yields above 75%. The fatty acid used was oleic acid, which was subsequently epoxidized. Other functional groups, such as amino acids, can be incorporated in these compounds. Examples of monomers that are suitable for polymerization were also prepared: one acrylamide, one styrene derivative, and two types of AB2 diamino acids, all of which contain oleic units that are sites for epoxidation and crosslinking. Fatty acid aryl ethers were prepared using hydroxy fatty acids. These molecules are intended to serve as augmented analogues of epoxidized vegetable oil. Their amide groups should lead to intermolecular aggregation through hydrogen bonding, and the option to covalently include other functional groups may permit tuning of the macroscopic materials properties of films, coatings, or solids constructed from them.