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The common marmoset (Callithrix jacchus) is a small arboreal New World primate which has emerged as a promising model in auditory neuroscience. One potentially useful application of this model system is in the study of the neural mechanism underlying spatial hearing in primate species, as the marmoset’s visually occluded natural habitat in the forest would make sound localization an essential behavior for survival. However, interpretation of neurophysiological data on sound localization requires an understanding of perceptual abilities, and the sound localization behavior of marmosets has not been well studied. The present experiment measured sound localization acuity using an operant conditioning procedure in which marmosets were trained to discriminate changes in sound location in the horizontal (azimuth) or vertical (elevation) dimension. Our results showed that the minimum audible angle (MAA) for horizontal discrimination was on average 15° for band-passed Gaussian noise and 13° for Random Spectral Shape (RSS) stimuli, whereas the MAA for vertical locations was at 17° and 22° for band-passed Gaussian noises containing more and less high frequency energy, respectively.

SUMMARYNeural responses to sensory stimuli are markedly influenced by the context in which a stimulus is preceded or embedded. Cortical and subcortical neurons typically exhibit adaptation to repetitive auditory, visual, somatosensory, and olfactory stimulation. Here, we investigated single neuron responses to sequences of sounds either repeatedly delivered from a single spatial location or randomly delivered from multiple spatial locations in the auditory cortex of awake marmosets. Instead of inducing adaptation, repetitive stimulation from a target speaker evoked long-lasting, location-specific facilitation (LSF) in many neurons, irrespective of the visibility of the target speaker. The extent of LSF decreased with decreasing presentation probability of the target speaker. Intracellular recordings showed that repetitive sound stimulation evoked sustained membrane potential depolarization which gave rise to firing rate facilitation. Computational models suggest two distinct neural mechanisms underlying LSF. Our findings revealed a novel form of contextual modulation in the auditory cortex that may play a role in auditory streaming and predictive coding.

Sensory responses of the neocortex are strongly influenced by brain state changes. However, it remains unclear whether and how the sensory responses of the midbrain are affected. Here we addressed this issue by using in vivo two-photon calcium imaging to monitor the spontaneous and sound-evoked activities in the mouse inferior colliculus (IC). We developed a method enabling us to image the first layer of non-lemniscal IC (IC shell L1) in awake behaving mice. Compared with the awake state, spectral tuning selectivity of excitatory neurons was decreased during isoflurane anesthesia. Calcium imaging in behaving animals revealed that activities of inhibitory neurons were highly correlated with locomotion. Compared with stationary periods, spectral tuning selectivity of excitatory neurons was increased during locomotion. Taken together, our studies reveal that neuronal activities in the IC shell L1 are brain state dependent, whereas the brain state modulates the excitatory and inhibitory neurons differentially., Chenggang Chen and Sen Song report a new method for imaging the first layer of the non-lemniscal inferior colliculus in awake mice. They show that neuronal activity in the inferior colliculus shell L1 is brain-state dependent.

Triton Systems, Inc. and our academic partner University of Dayton Research Institute (UDRI) developed and demonstrated a lightweight, affordable composite heat shield sandwich panel for aerospace applications capable of protecting an underlying Polymer Matrix Composite (PMC) sandwich panel from 500℉ external impingement. Our design outperforms the incumbent heat shield, a bolt-on metallic sheet with an air gap, in both thermal protection (15% lower skin surface temperature) and weight (40% lighter) at an equivalent thickness (about 0.3”). Our panel has very low thermal conductivity (0.08 W/mK) but is also impact resistant, strong (~300 psi flatwise tensile strength), and tolerant to typical aerospace environmental conditions. Additionally, we demonstrated that our design could be produced as a curved panel configuration to match vehicle outer mold lines (OML’s). Now at Technology Readiness Level (TRL) 4, Triton’s panel design is ready to move to the next stage of development which we envision to be additional proof-of-concept testing including chemical and additional environmental exposure, cold exposure, thermal shock, and vibration as we scale up to a larger 4’x8’ panel. STEVE SCHOENHOLTZ

The primate cerebral cortex is organized into specialized areas representing different modalities and functions along a continuous surface. The functional maps across the cortex, however, are often investigated a single modality at a time (e.g., audition or vision). To advance our understanding of the complex landscape of primate cortical functions, here we develop a polarization-gated wide-field optical imaging method for measuring cortical functions through the un-thinned intact skull in awake marmoset monkeys (Callithrix jacchus), a primate species featuring a smooth cortex. Using this method, adjacent auditory, visual, and somatosensory cortices are noninvasively parcellated in individual subjects with detailed tonotopy, retinotopy, and somatotopy. An additional pure-tone-responsive tonotopic gradient is discovered in auditory cortex and a face-patch sensitive to motion in the lower-center visual field is localized near an auditory region representing frequencies of conspecific vocalizations. This through-skull landscape-mapping approach provides new opportunities for understanding how the primate cortex is organized and coordinated to enable real-world behaviors.

The primate cerebral cortex is organized into specialized areas representing different functional modalities (e.g., vision, audition, touch) and their associations along a continuous surface. The functional maps of these areas, however, are often investigated in a single modality at a time. Here, we developed and applied to awake primates a polarization-enhanced wide-field optical imaging method for measuring cortical hemodynamics through the intact skull. Adjacent somatosensory, auditory, and visual cortices were noninvasively localized and rapidly parcellated in awake marmosets (Callithrix jacchus), a primate model featuring a smooth cortex. Detailed somatotopy, tonotopy, and retinotopy were also mapped out on an individual-subject basis, with a new pure-tone-responsive tonotopic gradient discovered outside the auditory core. Moreover, the motion-sensitive extent surrounding the primate-specific MT/V5 and the location of a face-sensitive patch were both revealed with respect to retinotopy. This approach provides a powerful tool for mapping the functional landscape across modalities in a single non-human primate subject, and thus opens new opportunities for probing how primate cortical system is organized to enable real-world behaviors.

The inferior colliculus (IC) is a critical integration center in the auditory pathway. However, because the inputs to the IC have typically been studied by the use of conventional anterograde and retrograde tracers, the neuronal organization and cell-type-specific connections in the IC are poorly understood. Here, we used monosynaptic rabies tracing andin situhybridization combined with excitatory and inhibitory Cre transgenic mouse lines of both sexes to characterize the brainwide and cell-type-specific inputs to specific neuron types within the lemniscal IC core and nonlemniscal IC shell. We observed that both excitatory and inhibitory neurons of the IC shell predominantly received ascending inputs rather than descending or core inputs. Correlation and clustering analyses revealed two groups of excitatory neurons in the shell: one received inputs from a combination of ascending nuclei, and the other received inputs from a combination of descending nuclei, neuromodulatory nuclei, and the contralateral IC. In contrast, inhibitory neurons in the core received inputs from the same combination of all nuclei. After normalizing the extrinsic inputs, we found that core inhibitory neurons received a higher proportion of inhibitory inputs from the ventral nucleus of the lateral lemniscus than excitatory neurons. Furthermore, the inhibitory neurons preferentially received inhibitory inputs from the contralateral IC shell. Because IC inhibitory neurons innervate the thalamus and contralateral IC, the inhibitory inputs we uncovered here suggest two long-range disinhibitory circuits. In summary, we found: (1) dominant ascending inputs to the shell, (2) two subpopulations of shell excitatory neurons, and (3) two disinhibitory circuits.SIGNIFICANCE STATEMENTSound undergoes extensive processing in the brainstem. The inferior colliculus (IC) core is classically viewed as the integration center for ascending auditory information, whereas the IC shell integrates descending feedback information. Here, we demonstrate that ascending inputs predominated in the IC shell but appeared to be separated from the descending inputs. The presence of inhibitory projection neurons is a unique feature of the auditory ascending pathways, but the connections of these neurons are poorly understood. Interestingly, we also found that inhibitory neurons in the IC core and shell preferentially received inhibitory inputs from ascending nuclei and contralateral IC, respectively. Therefore, our results suggest a bipartite domain in the IC shell and disinhibitory circuits in the IC.

Simulating nature to manufacture a self-powered device or motor has been an important goal in science and engineering. Conventional spontaneous motion has generally been achieved through the Marangoni flow of an organic liquid or water solution. Moreover, as a metallic material mercury has been developed as a beating heart, a kind of self-propulsion example. However, serious safety concerns about mercury restrict its extensive application. This study discovered an important mechanism to realize a GaIn alloy-based liquid metal beating heart by introducing a breathing mechanism in simulating living organisms. With the unique configuration of a semi-submerged liquid metal droplet partially immersed in alkaline solution, such a system produces a surface tension gradient perpendicular to the three-phase contact line which subsequently leads to the oscillation of the droplet and the surrounding solution. This finding suggests a feasible way to fabricate self-oscillating liquid metal motors without input of external electricity or fuels.

Commercial off-the-shelf (COTS) electronics are generally not specifically designed to perform in extremely transient high impact scenarios. This research focused on the development of a silver-decorated carbon black-based polymeric nanocomposite with properties such as high conductivity, flexibility, and shock absorbency. Polymeric rubber materials are generally very flexible and shock absorbing, however, most polymeric materials are electrical insulators. The dispersion of the silver-decorated carbon black into the polymeric matrix could significantly improve the electrical conductivity. The processing and fabrication of Ag-CB (silver-carbon black)/Epoxy (thermosetting epoxy polymer) and Ag-CB/TPU (thermoplastic polyurethane) will be reported. Both Ag-CB/Epoxy and Ag-CB/TPU mixtures with solvents showed the shear-thinning behavior, which was an important characteristic for direct printing of traces and Additive Manufacturing (AM). The mechanical properties of the nanocomposites were measured using Dynamic Mechanical Analysis (DMA) over a wide range of temperatures. These nanocomposite materials were also successfully used to print flexible circuits using a 3D-printing machine. The electrical resistance change for the Ag-CB/Epoxy on polydimethylsiloxane (PDMS) and Ag-CB/TPU on PDMS under strain was studied, and the results will be discussed.

Electromechanical, adhesion, and viscoelastic properties of polymers and polymer nanocomposites (PNCs) are of interest for additive manufacturing (AM) and flexible electronics. Development/optimization of inks for AM is complex, expensive, and substrate/interface dependent. This study investigates properties of free standing films of a thermoplastic polyurethane (TPU) polymer and an Ag–carbon black (Ag-CB) TPU PNC in a lightly loaded low strain compression contact as a rough measure of their suitability for AM. The TPU exhibited high hysteresis and a large viscoelastic response, and sufficient dwell time was needed for polymer chain relaxation and measurable adhesion. A new discovery is that large enough contact area is needed to allow longer time constant polymer ordering in the contact that led to higher adhesion and better performance/reliability. This has previously unknown implications for interface size relative to polymer chain length in AM design. The standard linear model was found to be a good fit for the viscoelastic behavior of the TPU. The PNC exhibited no adhesion (new result), low electrical resistance, and relatively small viscoelastic response. This implies potential for AM electrical trace as well as switch applications.

The erosive effect of ultraviolet radiation and atomic oxygen at the lower earth orbit space environment of the International Space Station on Epon 862 based epoxy composites with 12 and 100 nm silica particles was investigated. Although exposure to ultraviolet radiation had a small effect on surface erosion, restricted to 2 µm of the top surface, concurrent exposure to ultraviolet radiation and atomic oxygen resulted in significant erosion. Atomic oxygen erosion of nanocomposites with 1–5 wt% silica particles resulted in a carpet-like residual surface layer whose thickness and morphology were dependent on the size and concentration of the embedded silica particles. The eroded surface of the control epoxy had high surface roughness in the form of 10–40 µm long conical protrusions. With the addition of silica particles, the residual surface layer became fibrous and rich in silica particles, and its density increased with the weight fraction and size of the silica particles. The large and uneven erosion depth of samples exposed to atomic oxygen and ultraviolet radiation resulted in a surface damage layer with average thickness between 5 and 100 µm with significantly reduced mechanical properties compared to the surface of the as-fabricated nanocomposites. The erosion yield of the control epoxy due to atomic oxygen was 4.36 × 10−24 cm3/atom and the addition of silica nanoparticles reduced it significantly to 1.78 × 10−25 cm3/atom. In particular, silica nanoparticles of diameter 12 and 100 nm and weight fraction 5% reduced the erosion yield of the control epoxy by 90% and 96%, respectively.

The primary objective of the research was to evaluate the rheology and thermal properties of silylated apophyllite–filled epoxy nanocomposite. Several n-octyldimethylsiloxy-apophyllite with different grafting degrees were synthesized by controlling the ratio of the apophyllite and n-octyldimethylchlorosilane. The thermal studies of silylated apophyllite have shown that the onset decomposition temperature of silylated apophyllite far exceeds the onset temperature of conventional organoclays (~260 °C). Chemorheological measurements of 1.8 wt% silylated apophyllite–filled tetra functional epoxy (MY720) and difunctional epoxy (DER661) resin mixture showed that the addition of the silylated apophyllite does not dramatically affect the cure profile of the epoxy resin with the availability of 40 min of processing window after the addition of apophyllite. Wide angle X-ray diffraction and transmission electron microscopy results of the shear mixed and cured nanocomposite suggest that the apophyllite was well dispersed in the epoxy matrix. The thermal studies of epoxy nanocomposite showed an increase in the char yield on the addition of silylated apophyllite to the epoxy resin. In addition, an improvement in the onset decomposition temperature of the cyanopropyldimethylsiloxy-apophyllite epoxy nanocomposite was observed compared with that of pure epoxy resin. Copyright © 2011 John Wiley & Sons, Ltd.

The residual stress that arises from processing and the mismatch of coefficient of the thermal expansion (CTE) between polymer and carbon fiber (or metal) could cause a crack initiation and de-lamination in the aircraft structural applications. In this study, bismaleimide composites with zirconium tungstate (−8.8 ppm/K) were successfully fabricated. A synergetic effect led to a significant improvement of the thermal stability of the composites due to the formation of the integrated structure in the zirconium tungstate (ZrW2O8)/Matrimid 5292 (Huntsman, the Woodlands, TX) composite at high temperature, which prevented and/or slowed the escape of the thermal decomposition by-products. The addition of zirconium tungstate into the Matrimid 5292 could also increase the storage modulus while keeping the glass transition temperature unchanged. The CTE of a 20 vol.% ZrW2O8/Matrimid 5292composite material can be reduced by 40% compared with that of the pure Matrimid 5292. The extent of reduction in the CTE is much greater than predicted from the rule of mixture. Micromechanical modeling shows that the Christensen model and the Schapery upper limit model gave a good prediction of CTEs for ZrW2O8/Matrimid 5292 composite. Published 2011. This article is a US Government work and is in the public domain in the USA.

Previous research has shown that the inclusion of the spherical silica (SiO 2 ) nanoparticles into epoxy resin can achieve simultaneous improvement of fracture toughness and modulus. However, the glass transition temperature of the nanocomposite was significantly decreased when loading the nanosilica was higher than 5 wt.%. This perhaps was caused by utilization of the ultrasonication probe in the processing of these materials. In this paper, milder processing procedures were applied to make spherical silica epoxy nanocomposites while investigating if the homogeneous dispersion and morphology of the individual silica nanoparticle dispersed in the epoxy matrix could still be achieved. The results show that even at high loading of the silica nanoparticle, such as 30 wt.% silica, the perfect morphology of the nanocomposite could still be achieved with these milder processing conditions which indicates that ultrasonication is not needed. With the use of milder processing conditions, the glass transition temperature of the nanocomposite of 5 wt.% silica loading did not change, and the drop in the T g was minimal for silica loading up to 15%, but some effects of self-polymerization of the epoxy were noted on T g up to 30 wt.% loading of silica. Thermal analysis and flammability testing of the resulting materials suggest that nanosilica has only an inert filler effect (dilution of fuel) on flammability reduction and char yield increase, not a synergistic decrease in heat release as is often observed for clays and carbon nanotubes/nanofibers. So the mild and easy processing procedure only achieved uniform nanoscale morphology with excellent dispersion in the final nanocomposite, but also the effect on the change in the T g can be minimized as nanosilica loading was increased.

An experimental investigation of the composite and local mechanical and fracture behavior of an EPON based epoxy with 12 nm (primary) and 100 nm (secondary) fumed silica particles was carried out. The secondary particles promoted matrix stiffening at small weight fractions, which decreased at larger weight fractions and converged to that of the primary nanoparticles. The elastic modulus of the composites with 12-nm silica particles increased by as much as 30% for 15 wt.% silica loading. Atomic Force Microscopy coupled with Digital Image correlation (AFM/DIC) full-field strain measurements showed matrix strain localization in the vicinity of 100-nm fillers, which controlled the overall composite stiffness. In composites with 5 wt.% secondary particles, neighboring particles located at small proximities to each other behaved as single large particles or resulted in local matrix strain shielding. The tensile strength of all composites was independent of particle size and weight fraction, which was attributed to strong particle bonding and failure initiation in the matrix. The critical mode I stress intensity factor of 12-nm silica composites increased with silica weight fraction, by as much as 35% for 15 wt.% silica. SEM fractographs showed enhanced matrix yielding for 15 wt.% silica compared to significant roughening of the fracture plane and void formation at smaller weight fractions.

Epoxy–nanocomposite resins filled with 12-nm spherical silica particles were investigated for their thermal and mechanical properties as a function of silica loading. The nanoparticles were easily dispersed with minimal aggregation for loadings up to 25 wt% as determined using transmission electron microscopy (TEM) and ultra-small-angle X-ray scattering (USAXS). A proportional decrease in cure temperatures and glass transition temperature (for loadings of 10 wt% and above) was observed with increased silica loading. The morphology determined by USAXS is consistent with a zone around the silica particles from which neighboring particles are excluded. The “exclusion zone” extends to 10× the particle diameter. For samples with loadings less than 10 wt%, increases of 25% in tensile modulus and 30% in fracture toughness were obtained. More highly loaded samples continued to increase in modulus, but decreased in strength and fracture toughness. Overall, the addition of nanosilica is shown as a promising method for property enhancement of aerospace epoxy composite resins.

Polymer/layered-silicate nanocomposites have unique and hierarchical structures that can provide improvements to the properties of polymeric materials. Controlling the dispersion of the nanomaterials through processing greatly influences the resulting morphology and the resulting properties of the nanocomposite. In this article, the dispersion behavior of organic layered silicates (OLS) as a function of the processing procedure is reported. The behavior of the OLS in all stages of processing—in the solvent, the epoxy prepolymer, and in the epoxy through cure—is discussed. On the basis of understanding of the dispersion behavior of the OLS in the epoxy resin at each stage of processing, a different processing procedure can be designed and used so that the morphology of the epoxy/layered-silicate nanocomposite can be regulated. Mild low-shear processing resulted in an intercalated nanocomposite with large-size aggregates (> 10 μm), and high-shear processing resulted in an intercalated nanocomposite with relatively small-size aggregates (0.5–3 μm), whereas the high-shear and ultrasonication processing procedures gave rise to an exfoliated nanocomposite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

This research demonstrates that an epoxy nanocomposite can be made through electron beam (e-beam) curing. The nanofillers can be two-dimensional (layered-silicate) and zero-dimensional (spherical silica). Both the spherical silica epoxy nanocomposite and the layered-silicate epoxy nanocomposite can be cured to a high degree of curing. The transmission electron microscopy (TEM) and small-angle X-ray scattering of the e-beam-cured layered-silicate epoxy nanocomposites demonstrate the intercalated nanostructure or combination of exfoliated and intercalated nanostructure. The TEM images show that the spherical silica epoxy nanocomposite has the morphology of homogeneous dispersion of aggregates of silica nanoparticles. The aggregate size is ∼ 100 nm. The dynamic mechanical analysis shows that the storage modulus of the spherical silica nanocomposite has been improved, and the glass transition temperature can be very high (∼ 175°C). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The objective of this study is to prepare layered organosilicates with enhanced thermal stability that can be used to formulate high-temperature polymer nanocomposites. Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), and thermal gravimetric analysis (TGA) characterization results of the modified silicates indicate that the organic pendant group has been chemically grafted on to the backbone of layered silicate and the organically modified apophyllite is thermally stable up to approximately 430°C. The organically modified apophyllite was mixed along with vinyl ester resin and styrene diluent in a sonic dismembrator and the mixture cured to form a nanocomposite specimen. Transmission electron microscopy (TEM) results of the nanocomposites showed mixed morphology with predominant fraction of organosilicates exhibiting an intercalated structure. Tapping mode atomic force microscopy (TMAFM) observation of the nanocomposite showed striated layered silicates dispersed in the resin matrix. The nanocomposites formulated with organosilicates containing reactive terminal pendant group were found to have a higher tensile strain than the nanocomposites formulated with organosilicates containing inert pendant group. Copyright © 2007 John Wiley & Sons, Ltd.

Fully exfoliated layered silicate epoxy nanocomposites are reported in this article. The processing route that resulted in these fully exfoliated layered silicate epoxies is based on a combination of high-shear mixing in the presence of acetone and ultrasonication. Homomogeneous and random dispersion of the individual silicate nanolayers in the epoxy is confirmed through transmission electron microscopy images spanning low to high magnification as well as by X-ray diffraction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3981–3986, 2004

Polymer layered-silicate nanocomposites have attracted a lot of attention because of impressive enhancements of polymeric properties. In this research, both commercially available and synthesized organolayered silicates, which are compatible with the epoxy resins, were used to make epoxy nanocomposites. The epoxy resin used in this research includes Epon 862/curing agent W (the aerospace epoxy resin), the Epon 828/Epi-Cure curing agent 8290-Y-60 (used as the primer layer for corrosion prevention in aircraft coating), and Epon 828/Jeffamine D400. The morphology of the nanocomposites was characterized using wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The morphology development for the aerospace epoxy-organoclay nanocomposite was monitored through in situ SAXS and analyzed. The solvent absorption of the exfoliated aerospace epoxy-organoclay nanocomposite in acetone was examined, and the diffusion coefficients of solvent in the nanocomposites were reduced. The organoclay/Epon 828/Y-60 and organoclay/Epon 828/D400 nanocomposite were used to make coatings on an Al surface. The anticorrosion properties of the nanocomposite coating were evaluated and discussed.

Polymer-layered silicate nanocomposites are new hybrid polymeric materials with nanometre thick layered silicates that generally show improvement over the properties of polymeric materials. This paper reports that synthesized organolayered silicates can be used to make epoxy nanocomposites. The nanocomposites were characterized by wide-angle x-ray diffraction, small-angle x-ray scattering (SAXS) and transmission electron microscopy. The studies on in situ SAXS and differential scanning calorimetry were carried out to gain an understanding of the morphological development of a nanocomposite during processing. The storage and glass transition temperature of the nanocomposite were also studied by dynamic mechanical analysis.

Research on nanocomposites attracted a lot of attention because of their unique nanostructure and interesting properties. Layered-Silicate epoxy nanocomposites cured by traditional thermal cure processing were prepared, and the morphology was confirmed by the wide-angle x-ray diffraction, small-angle x-ray scattering and transmission electron microscopy. Layered-Silicate epoxy nanocomposites could also be cured through e-beam curing. The small-angle x-ray scattering and transmission electron microscopy indicated that the e-beam-cured nanocomposites showed intercalated nanostructure. Dynamic mechanical analysis showed some improvement of the Storage modulus for the nanocomposites with high Tg.

Epoxy nanocomposites were prepared from the different organoclays with aerospace epoxy resin. A series of organoclays treated with alkylammonium chloride with different alkyl groups of different carbon chains were prepared, including SC4, SC6, SC8, SC10, SC12, SC16, SC18, and NC8, NC12, NC18. All of these organoclays, except for SC4, are very compatible with the aerospace Epon 862/curing agent W. The characterization from wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) confirms the exfoliated nanostructure. The six-carbon chain length of the ammonium cation is enough to wet the surface of the clay gallery to make the organoclay compatible with epoxy resin. The clay with lower cation exchange capacity is more favorable for the polymer penetration inside the gallery and is dispersed better in the polymer matrix. The structural evolution of the aerospace epoxy nanocomposite was monitored by in situ SAXS. The 3% SC18/Epon 862/W, 3 and 6% SC8/Epon 862/W showed exfoliated nanostructure, while there is no exfoliation taking place for 3% S30B/Epon 862/W and 3%S25A/Epon 862/W up to 200°C. The acidity from the pendent group in SC18 and SC8 has a catalytic effect for the polymerization inside the gallery, while the organic pendent group of S30B and S25A does not. The faster reaction of the intragallery epoxy resin produced extra thermal heat inside the gallery to expand the gallery and is favorable for the migration of epoxy resin outside the gallery into the gallery where exfoliation took place. The exothermal heat of curing inside the gallery is an important factor for nanosheets exfoliation. Although exfoliation took place for both 3% SC18/Epon 862/W and 3% SC8/Epon 862/W, the detailed morphology development during the curing is different. For 3% SC8/Epon 862/W, the interplanar spacing between the layers is increased gradually, while 3% SC18/Epon 862/W experienced the disappearance of the ordered structure of the layered silicate in the beginning of the curing process and reappearance of the ordered structure of the silicate later. The glassy and rubbery moduli of the polymer-silicate nanocomposites were found to be greater than the unmodified resin because of the high aspect ratio and high stiffness of the layered silicate filler. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2276–2287, 2003

Nanoscale dispersion of only a few weight percentage of layered silicate (montmorillonite) in nylon 6 and epoxy results in the formation of a uniform passivating and self-healing inorganic surface region upon exposure to oxygen plasma. The enrichment of inorganic is compositionally graded with respect to the surface and is due to the preferential oxidation of the polymer from the nanocomposite and the corresponding enhancement of the nanoscale layered silicate on the surface. The structure of the inorganic region is turbostratic, with an average distance between layered silicates of 1−4 nm. This ceramic-like silicate layer provides an overcoat to the nanocomposite and can significantly retard the penetration of oxygen plasma. Thus, layered silicate containing nanocomposites may enhance the survivability of polymeric materials in aggressive oxidative environments, such as atomic oxygen in low earth orbit (LEO). The formed inorganic region was characterized chemically and morphologically by X-ray photoelect...

The advantages of thermoelectric energy conversion technologies are briefly summarized. Recent material advances are discussed, with the focus on one-dimensional (1-D) self-assembled molecular materials as building blocks for new thermoelectric materials. The preparation, doping, and thermal characterization of phthalocyanine based materials are presented. The thermal conductivity of the doped material is lower than the undoped material even though the electrical conductivity of the doped material is orders of magnitude higher than the undoped material. This is counter intuitive against the backdrop of the Wiedemann-Franz treatment of thermal conductivity in electrical conductors from which one would expect thermal and electrical conductivity to both increase with introduction of additional charge carriers. These unusual results can be understood as a competition between the generation of an increased number of charge carriers and enhanced phonon scattering resulting from the introduction of chemical dopants. The thermal conductivity of the undoped phthalocyanines has been found to be small and only modestly temperature dependent in the 50-300 C range, but it is larger than a previous, indirect measurement.

The advantages of thermoelectric energy conversion technologies are briefly summarized. Recent material advances are discussed, with the focus on one-dimensional (1-D) self-assembled molecular materials as building blocks for new thermoelectric materials. The preparation, doping, and thermal characterization of phthalocyanine based materials are presented. The thermal conductivity of the doped material is orders of magnitude higher than the undoped material. This is counter intuitive against the backdrop of the Wiedemann-Franz treatment of thermal conductivity in electrical conductors from which one would expect thermal and electrical conductivity to both increase with introduction of additional charge carriers. These unusual results can be understood as a competition between the generation of an increased number of charge carriers and enhanced phonon scattering resulting from the introduction of chemical dopants.

The fabrication of lightweight mirror assemblages via a replication technique offers great potential for eliminating the high cost and schedule associated with the grinding and polishing steps needed for conventional glass or SiC mirrors. A replication mandrel is polished to an inverse figure shape and to the desired finish quality. It is then, coated with a release layer, the appropriate reflective layer, and followed by a laminate for coefficient of thermal expansion (CTE) tailorability and strength. This optical membrane is adhered to a mirror structural substrate with a low shrinkage, CTE tailored adhesive. Afterwards, the whole assembly is separated from the mandrel. The mandrel is then cleaned and reused for the next replication run. The ultimate goal of replication is to preserve the surface finish and figure of the optical membrane upon its release from the mandrel. Successful replication requires a minimization of the residual stresses within the optical coating stack, the curing stresses from the adhesive and the thermal stress resulting from CTE mismatch between the structural substrate, the adhesive, and the optical membrane. In this paper, the results on replicated trials using both metal/metal and ceramic/ceramic laminates adhered to light weighted structural substrates made from syntactic foams (both inorganic and organic) will be discussed.

[Cu 2 (ClO 4 ) 4 (C 4 H 13 N 3 ) 2 (C 4 H 4 N 2 )] cristallise dans P1 avec a=7,204, b=7,814, c=12,612A, α=87,90, β=89,08, γ=76,54°, Z=1; affinement jusqu'a R=0,052. La geometrie de la coordination de l'atome de Cu II est un octaedre quadratique allonge. Les cycles du coordinat diethylene triamine adoptent une conformation δλ. Le cycle pyrazine forme un angle diedre de 58,8° avec le plan equatorial de la coordination de l'atome Cu II et peut ainsi intervenir dans les interactions de superechanges magnetiques entre deux atomes Cu II

Polymer nanocomposites draw great interest due to their unique nanostructures and improved properties [1–2]. Epoxy is a widely-used thermosetting material. The research on the epoxy layered-silicate epoxy nanocomposite has exploded in the last decade [3–9]. The morphology of nanocomposites is the key to making high-performance nanocomposites. In this presentation, the factors influencing the morphology development behavior of epoxy nanocomposites will be discussed. The factors to be investigated include organoclay, epoxide, and curing agent. In this study, the aliphatic diamine (Jeffamines) with different molecular weights and aromatic diamine were selected as the curing agents, S30B (quaternary onium-montmorillonite) and SC18 (primary oniummont-morillonite) as the organoclays, and Epon 862 and Epon 828 as epoxides. In situ small-angle x-ray scattering (SAXS) was utilized to study the morphology development of the epoxy nanocomposite.

The paper describes a multiscale experimental investigation of the mechanical behavior of polymer nanocomposites with nanoscale fused silica inclusions with the objective to shed light into the effect of the hard nanoparticles on the quasistatic mechanical behavior of epoxy matrix and the implications of the latter to the effective composite properties. The main variable in this study was the nanofiller volume fraction while the particle size was either 15 nm or 100 nm. Local strain measurements indicated strain field localization in the vicinity of the nanofillers at strains that macroscopically fall in the linearly elastic regime. The matrix strains were as high as three times the applied far field strain at applied effective strains of ∼ 1%. At larger stresses the local strain fields evolved to maxima that were considerably higher than the applied strain, and they were affected by local particle density and distribution. In composites with the largest particle volume fraction, 5 vol.%, 100 nm fillers, neighboring particles located in small proximities behaved as single large particles and often resulted in matrix strain shielding thus decreasing the benefit of the large surface-to-volume ratio and the associated efficiency in load transfer. On the other hand the 15 nm fillers resulted in more uniformly distributed deformation compared to composites with 100 nm particles.

Polymer layered-silicate nanocomposites have attracted great attention due to their unique nanostructure and properties. The property of the nanocomposite is determined by the morphology of the nanocomposite. The typical morphologies of the nanocomposite are the intercalated and exfoliated nanostructures. In this study, the layered-silicate epoxy nanocomposite with different morphology can be controlled and achieved. The different morphology could include the intercalated nanostructure with the 15 Å increase of the interplanar spacing, the intercalated one with ∼150 Å increase of the gallery and fully exfoliated nanostructure.

Epoxy nanocomposites were prepared from the montmorillonite after organic treatment with a high Tg epoxy resin (Shell Epon 862 and curing agent W). Investigation of the rheological characteristics showed that the addition of clay to the resin did not significantly alter the viscosity or cure kinetics and that the modified resin would still be suitable for liquid composite molding techniques such as resin transfer molding. DSC was performed to study the kinetics of the curing reactions in the modified resin. An in situ small-angle x-ray scattering (SAXS) experiment was used to try to understand the structural development during cure. Based on the in situ SAXS data, structural changes were monitored in real time during cure and analyzed. Results from wide-angle x-ray diffraction, SAXS, and transmission electron microscopy of the polymer-silicate nanocomposites were used to characterize the morphology of the layered silicate in the epoxy resin matrix. The glassy and rubbery moduli of the polymer-silicate nanocomposites were found to be greater than the unmodified resin due to the high aspect ratio and high stiffness of the layered silicate filler. The solvent absorption in methanol was also slower for the polymer-silicate nanocomposites.

Cu(C10H8N2)(CI0H8N2)(C104)2) , Mr = 574.5, orthorhombic, Pbcn, a=12.413(3), b = 14.645 (3), c = 12.287 (2) , V = 2233.6 (8) A 3, Z = 4, Dx = 1.708 g cm -3, A(Mo Kte) = 0.71069 ,~, /z = 13.12 cm- 1, F(000) = 1164, room temperature, R = 0.050 and wR = 0.049 for 1498 observed reflections. The coordination around Cu n is an elongated dis- torted octahedron. Two N atoms of 2,2'-bipyridyl and two N atoms from two 4,4'-bipyridyls form the equatorial coordination plane, and two perchlorate ions occupy the axial sites. The 4,4'-bipyridyl ligand bridges neighbouring Cu n atoms to form polymeric chains along the c axis in the crystal. The rings of 4,4'-bipyridyl are coplanar and make a dihedral angle of 114 ° with the equatorial coordination plane; the 4,4'-bipyridyl may provide a pathway for mag- netic superexchange interaction between the adjacent Cu ~I atoms. Introduction. In the last decade, a number of binu- clear transition-metal complexes bridged by hetero- cyclic aromatic diamines have been investigated as * To whom correspondence should be addressed.

Spherical nanoscale particles were incorporated into an aerospace epoxy resin. When properly dispersed with a combination of mechanical and ultrasonic mixing, the fracture toughness could be made twice that of the control resin. Spherical nanoparticles were added as a suspension which tended to agglomerate, dry fumed powders which were easiest to disperse and were formed in situ from silanes. The spherical particles had little effect on the flexural properties of the resin. Layered silicates were not observed to change the fracture toughness of the resin but did double the flexural properties in some formulations.

Reaction of chlorosilanes with sheet silicates, such as the naturally occurring apophyllite, [Ca4Si8O2O(F, OH).8H2O] results in the formation of sheet organofunctional siloxane polymers. Similarly, reaction of chlorosilanes with the tube silicate K2CuSi4O10results in the formation of tube organofunctional siloxane polymers. Representative polymers have been characterized by XRD, KR, XPS and solid state 29Si NMR. The interlayer spacing of the sheet polymers varies with the type of the group pendent on the sheet. When the organofunctional pendent groups of the sheet polymers contain reactive sites, further reactivity can be demonstrated with heterogeneous reactions such as hydrosilation. The sheet polymers behave as very effective thickeners of siloxane fluids. Dispersions of them in siloxane fluids exhibit thixotropic properties. The organosilicon polymers have the potential to show useful chemical, thermal, rheological and mechanical properties

Alkylcobalt(III) Schiff base B(12) model complexes with secondary alkyls or a bulky diamine in the equatorial position were synthesized and characterized. Structures have been first determined by X-ray diffraction analysis for i-C(4)H(9)Co(salen)(gamma-pic) (I), n-C(3)H(7)Co(salen)(gamma-pic) (II) and C(2)H(5)Co(SB) (III), where salen = N,N'-ethylenebis(salicylideneamine) dianion; SB = 1,1,2,2-tetramethyl-N,N'-ethylenebis(salicylideneamine) dianion, gamma-pic = gamma-picoline. Crystal data for I (CoC(26)N(3)O(2)H(30)): space group P2(1)/c with a = 6.661(5) Å, b = 18.612(2) Å, c = 19.533(3) Å, beta = 98.93(1) degrees, V = 2392.10 Å(3), D(calcd) = 1.320 g.cm(-3), Z = 4, and R = 0.048 for 4469 measured reflections. Crystal data for II (CoC(25)N(3)O(2)H(28)): space group P2(1)/c, a = 9.609(6) Å, b = 19.169(8) Å, c = 12.995(9) Å, beta = 106.9(7) degrees, V = 2290.4 Å(3), D(calcd) = 1.332 g.cm(-1), Z = 4, and R = 0.048 for 4358 measured reflections. Crystal data for III (CoC(22)N(2)O(2)H(27)): space group P2(1)/c, a = 8.318(3) Å, b = 21.579(2) Å, c = 11.572(2) Å, beta = 93.35(1) degrees, V = 2073.7 Å(3), D(calcd) = 1.314 g.cm(-1), Z = 4, and R = 0.060 for 3954 measured reflections. The crystal structure data reveal that complexes I and II display six-coordinate octahedral geometry; their Co-C, Co-N bond lengths, as well as the Co-C-C angles, are very close to those in 5'-deoxyadenosylcobalamin. Complex III is one of the very few compounds having five-coordinate square pyramidal geometry and observed instability of the Co-C bond.