Product design: Formulation of a screen-printable sintering-type conductive paste

Due to the complexity of the screen-printing operation and the rheological behaviors of the screen-printable paste, such a paste is usually formulated by trial-and-error. In this report, a systematic procedure, based on heuristics and mechanistic models, for the design of a screen-printable paste is developed. The procedure is demonstrated by a case study of the formulation of a conductive paste of copper particles.     

An adaptable luminescence resonance energy transfer assay for measuring and screening protein-protein interactions and their inhibition

Protein-protein interactions (PPIs) are central to biological processes and represent an important class of therapeutic targets. Here we show that the interaction between FK506-binding protein 12 fused to green fluorescent protein (GFP-FKBP) and the rapamycin-binding domain of mTor fused to Escherichia coli dihydrofolate reductase (FRB-eDHFR) can be sensitively detected (signal-to-background ratio (S/B)>100) and accurately quantified within an impure cell lysate matrix using a luminescence resonance energy transfer (LRET) assay. Ascomycin-mediated inhibition of GFP-FKBP-rapamycin-FRB-eDHFR complex formation was also detected at high S/B ratio (>80) and Z'-factor (0.89). The method leverages the selective, stable binding of trimethoprim (TMP)-terbium complex conjugates to eDHFR, and time-resolved, background-free detection of the long-lifetime (～ms) terbium-to-GFP LRET signal that indicates target binding. TMP-eDHFR labeling can be adapted to develop high-throughput screening assays and complementary, quantitative counter-screens for a wide variety of PPI targets with a broad range of affinities that may not be amenable to purification.     

Response to walnut olfactory and visual cues by the parasitic wasp Diachasmimorpha juglandis

Diachasmimorpha juglandis is a specialist parasitoid attacking fly larvae in the genus Rhagoletis that feed exclusively on walnut fruit husks. In a free-foraging assay comparing response to uninfested, infested, and mechanically damaged fruits, we first determined that D. juglandis use host feeding damage on the fruit as a cue for host presence. In another free-foraging assay that used artificial walnut models and wind tunnel experiments, D. juglandis distinguished infested from uninfested fruits by using either olfactory or visual cues separately. However, the response rate of wasps in the wind tunnel was raised considerably when visual cues were also available. We analyzed the volatile compounds emitted by cohorts of uninfested, mechanically damaged, and infested fruits 1, 3, 5, 8, and 10 days after oviposition by flies into the infested fruits. Total volatile emissions did not differ significantly among treatments, but quantitative changes in volatiles distinguished infested fruits from uninfested and damaged fruits. The fact that parasitoids did not distinguish between infested and damaged fruits in assays where damage was visible indicates that they rely on visual cues when those are available.     

Combustion characteristics of candles made from hydrogenated soybean oil

Hydrogenated soybean oil, referred to as soywax by candle makers, is a renewable and biodegradable alternative to paraffin wax in candle manufacturing. Soywax was investigated for its tendency to produce soot as well as potentially harmful organic volatiles (acrolein, formaldehyde, and acetaldehyde) during combustion. Beeswax and paraffin candles were used as references. A considerable amount of soot was produced from the combustion of paraffin candles, but little or none was observed from soywax candles. Compared to paraffin candles, soywax candles burned at a significantly slower rate and required less air. Small amounts of formaldehyde were detected and quantified in the fumes of burning paraffin candles. However, formaldehyde, peaks found in the chromatograms of soy- and beeswax candles were similar to or slightly higher than that of the blank. Since soywax candles exhibited burning properties similar to those of beeswax candles, soywax shows promise in candle applications.     

Fiber-Matrix Interfacial Adhesion Improvement in Carbon Fiber-Bisphenol-A Polycarbonate Composites by Polymer Grafting

Fiber-matrix interfacial adhesion in thermoplastic composites is generally poor due to the lack of formation of strong covalent and/or ionic bonds between the generally inert thermoplastic resins and the surface of the reinforcing fiber. Adhesion can be improved by forming covalent linkages between the fiber and the matrix by grafting a polymer of appropriate compatibility, molecular weight, and sufficient density onto the surface of the fiber. We have grafted low molecular weight polycarbonate and polymethyl methacrylates onto the surface of carbon fibers and measured an improvement in the level of adhesion ranging from 25% to100% over the ungrafted composites. It was also observed that the level of improvement in adhesion appears to be independent of the molecular weight of the grafted polymer. Examination of the fracture surface of these composites reveals that the failure is cohesive in the matrix for the polymer grafted fiber composites, while it is adhesive for the ungrafted composites.     

Modelling collisions of soft agglomerates at the continuum length scale

Growth and breakdown mechanisms in granulation processes may involve collisions between soft plastically deforming agglomerates. It has been established previously that the flow stress in such collisions increases with the strain rate, which is dependent on the impact velocity and the size of the agglomerates. In the current paper, a scaling model is described that is based on a continuum constitutive relationship and formulated in terms of accessible experimental parameters. It is an extension of an existing contact mechanics model for elastoplastic nonadhesive collisions and therefore limited to deformations in which the contact radius is less than about 40% of the agglomerate radius. In addition, it is assumed that the elastic strains are small compared to the maximum value. Finite element simulations were carried out for a range of impact velocities and material parameters associated with an elastoviscoplastic constitutive relationship of the type used in the scaling model. The results were employed to validate the scaling model. Within the specified limits of applicability, it was found that the coefficient of restitution, contact area, loading and unloading curves and also the time evolution of the compressive displacement could be calculated with relatively high accuracy. Moreover, it was found that for a viscoplastic material the rate of decrease of the coefficient of restitution with increasing impact velocity is greater than for plastic deformation. The model should prove useful in understanding collision processes in granulation systems, particularly those occurring at relatively high impact velocities when the main energy dissipation process arises from viscoplastic deformation. Under this circumstance, the influence of adhesion is negligible and coalescence may be taken to occur when the coefficient of restitution is small.     

Electrophilic Aromatic Functionalization of Phenolic Photoresist Polymers

Summary Functionalization of both linear poly(4-hydroxystyrene) (PHS) and branched poly(4-hydroxystyrene) (PHS-B) was accomplished via a Reimer-Tiemann electrophilic aromatic substitution reaction. Linear and branched poly(4-hydroxystyrene-co-5-vinylsalicylaldehyde) (pHS/5VSA and pHS-B/5VSA) copolymers were observed to undergo acid-catalyzed, novolac type self-crosslinking. Both the pHS/5VSA and pHS-B/5VSA copolymer systems possessed a lower deep ultra violet microlithographic sensitivity compared to linear PHS when formulated in negative photoresists. The sluggishness of the negative photoresists containing 5-vinylsalicylaldehyde functionalized copolymers was attributed to a combination of resonance stabilization and steric hindrance effects.     

First Identification of a Putative Sex Pheromone in a Praying Mantid

Praying mantids are models for a wide variety of behavioral, physiological, and ecological studies, and sex pheromones have been assumed to be important components of their biology. However, no mantid pheromone has ever been identified. We collected volatiles emitted by females of the mantid, Sphodromantis lineola, via solid phase microextraction (SPME). Mass spectral analysis revealed the collected volatiles to be a mixture of pentadecanal and tetradecanal. We prepared a synthetic mixture of these compounds, and found that males were both attracted to this mixture and stimulated to exhibit typical precopulatory behavior. We then examined male antennae with scanning electron microscopy, and confirmed the presence of porous antennal sensilla typical of insect pheromone receptors, i.e., that male mantids are equipped with the appropriate morphological apparatus to receive volatile chemical signals. Pheromones, in conjunction with visual and tactile cues, are thus an important feature of the reproductive biology of this, and undoubtedly other species of mantids. In addition to adding a crucial aspect of behavioral biology to our knowledge of this group, identification and synthesis of mantid pheromones may be a first step in attracting and aggregating these generalist predators for use in pest control.