IPACK2007-33026 THERMAL CONDUCTIVITY AND CONTACT RESISTANCE MEASUREMENTS FOR ADHESIVES

ABSTRACT Thermal adhesives that contain large concentrations of high thermal conductivity filler materials, such as ceramics or metals, are widely used by the electronics industries in a variety of applications. The thermal properties of these materials, such as the thermal contact resistance across a bonded joint and the thermal conductivity of the bulk material, are critical to the selection of the "best" material. A method is presented for the measurement of these thermal properties using a steady-state, guarded heat flux meter test apparatus based on the welldocumented and familiar ASTM test standard D-5470. Five different adhesive materials are tested and a linear fit of the resulting resistance versus thickness data are used to determine the bulk thermal conductivity and contact resistance values. Four of the five materials tested had conductivity values of less than 1 W/mK, and the data demonstrates that a small but significant thermal contact resistance exists between the adhesive and the substrate for each of the adhesives. NOMENCLATUR

Stranded and equilibrated assemblages of late feldspars in two granitic pegmatites in the Pampean Ranges, Argentina

Late primary K-feldspar in two granitic pegmatites from the Pampean pegmatite province in Argentina shows similar patterns of growth and exsolution, but different structural states and mineral associations. (i) In El Criollo, a beryl - columbite - phosphate pegmatite in the Punilla pegmatite field, a single miarolitic cavity in the blocky zone is lined with pale rusty crystals of veinperthitic K-feldspar and quartz. The Kfs host, Or89.7 Ab7.8 Rbf0.3 LEf(? 1.1 (□Si4O8)1.2 (∼88 vol.%), corresponds to optically and XRD-monoclinic, but highly (Al,Si -ordered orthoclase (2t1 = 0.82), with only a slight incipient conversion to intermediate grid-twinned microcline along contacts with exsolved low albite, Ab98.1 An1.2 Or0.9 (∼12 vol.%). The homogeneous precursor of the perthite contained ∼22 mole % Abss. The perthitic orthoclase is overgrown, mainly on the {010} faces, by nonperthitic, gemmy, pale grey to beige orthoclase, Or91.6 Ab6.1 Rbf0.5 Cno.2 Srf0.1 LEf(?)0.2 (□Si4O8)1.5, with 2t1 equal to 0.84. Small tabular crystals of white low albite, Ab99.5 Or0.7, elongate parallel to c, are situated on the {010} faces of the orthoclase in epitactic orientation. (ii) In San Luis II, a spodumene pegmatite in El Totoral pegmatite field, crystals of coarsely perthitic K-feldspar and quartz line cavities in the core-margin zone. The mottled-grey euhedral K-feldspar, Or92.3 Ab4.1 Rbf1.1 Csf0.1 Cn0.1 Srf0.1 LEf(?)1.5 (□Si4O8)0.8 (∼92 vol.%), locally altered to muscovite and clay minerals, is very close to end-member low microcline with vein-shaped exsolution lamellae of low albite. Ab99.1 An0.1 Or0.4 Cn0.1 Srf0.1 (∼8 vol.%). The homogeneous precursor of the perthite contained ∼13 mole % Abss. All faces of the perthite crystals have an even overgrowth of pale grey, nonperthitic low microcline, Or92.8 Ab4.8 Rbf0.2 Srf0.1 LEf(? 1.8(□Si4O8)0.3. The cavity space among the crystals of the K-feldspar and primary quartz is largely filled by microcrystalline secondary quartz, "chalcedony", opal and goethite. Different subsolidus histories of the two host vugs explain the conspicuous contrast between the structural states of their cavity-lining K-feldspar. In El Criollo pegmatite, the cavity probably quickly lost residual aqueous fluid, as the orthoclase of both the primary perthitic crystals and particularly of the gemmy overgrowth show only stranded, coherent domain-scale order and twinning, and very limited alteration. In the San Luis II pegmatite, the cavity-lining K-feldspar shows considerable alteration and overgrowth by low-temperature phases, indicative of substantial hydrothermal activity, which promoted (Al,Si)-ordering to give tartan-twinned low microcline in both the primary perthitic crystals and the norperthitic overgrowths.Le feldspath potassique primaire qui s’est formé tardivement dans deux pegmatites granitiques de la province pegmatitique de Pampea, en Argentine, montre des points communs en termes de croissance et d’exsolution, mais des différences marquées en termes du degré d’ordre et d’associations minérales. (i) A El Criollo, une pegmatite à béryl – columbite – phosphate du champ pegmatitique de Punilla, une seule cavité miarolitique de la zone à cristaux polyédriques est tapissée de cristaux pâles de couleur rouille de feldspath potassique, perthitique à veines, avec quartz. L’hôte dans cette perthite, Or89.7 Ab7.8 Rbf0.3 LEf(?)1.1 (Si4O8)1.2 (~88% en volume), correspond optiquement et en diffraction X à une phase monoclinique (orthose) fortement ordonnée, avec 2t1 = 0.82, et un début de conversion à la microcline intermédiaire avec maclage quadrillé le long des contacts avec l’albite ordonnée exsolvée, Ab98.1 An1.2 Or0.9 (~12% en volume). Le précurseur homogène de la perthite contenait ~22% Abss (base molaire). L’orthose perthitique est recouverte, surtout sur les faces {010}, d’une surcroissance d’orthose non perthitique, gemme, gris pâle à beige, Or91.6 Ab6.1 Rbf0.5 Cn0.2 Srf0.1 LEf(?)0.2 (Si4O8)1.5, avec 2t1 egal à 0.84. De petits cristaux tabulaires blancs d’albite ordonnée, Ab99.5 Or0.7, allongés parallèles à c, recouvrent les faces {110} de l’orthose, en relation épitactique. (ii) A San Luis II, une pegmatite à spodumène du champ de El Totoral, des cristaux grossiers et perthitiques de feldspath potassique et de quartz tapissent les cavités de la zone externe du coeur du massif. Les cristaux idiomorphes de feldspath potassique sont gris nuagé, Or92.3 Ab4.1 Rbf1.1 Csf0.1 Cn0.1 Srf0.1 LEf(?)1.5 (Si4O8)0.8 (~92% en volume), localement transformés en muscovite et en argiles; ils sont très près du pôle microcline ordonné, avec des lamelles exsolvées en veines d’albite ordonnée, Ab99.1 An0.1 Or0.4 Cn0.1 Srf0.1 (~8% en volume). Le précurseur homogène de la perthite contenait ~13% d’albite Abss (base molaire). Toutes les faces des cristaux de perthite sont recouvertes d’une surcroissance uniforme gris pâle de microline ordonné non perthitique, Or92.8 Ab4.8 Rbf0.2 Srf0.1 LEf(?)1.8(Si4O8)0.3. Les espaces entre les cristaux de feldspath potassique et de quartz sont surtout remplis de quartz microcristallin secondaire, “calcédoine”, opale et goethite. Des différences dans l’évolution subsolidus des deux cavités hôtes expliquent le contraste frappant en termes du degré d’ordre du feldspath potassique sur les parois. Dans la pegmatite de El Criollo, la cavité a probablement perdu la phase fluide résiduelle rapidement; l’orthose des cristaux primaires devenus perthitiques et de la surcroissance gemme ne contient que des domaines ordonnés cohérents et maclés, conservés de façon métastable, et très peu d’altération. Dans la pegmatite de San Luis II, les cristaux de feldspath potassique le long des parois montrent des signes importants d’altération et de surcroissances de phases de basse température, indications d’une activité hydrothermale substantielle, qui a favorisé la mise en ordre (Al,Si) du feldpath pour mener à la forme à maclage quadrillé du microcline ordonné, aussi bien dans les cristaux perthitiques que dans les surcroissances non perthitiques.Fil: Cerny, Petr. University of Manitoba; CanadáFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico. Instituto Antártico Argentino. Instituto Antártico Argentino - Sede Cricyt (Mendoza); ArgentinaFil: Oyarzabal, Julio C.. Universidad Nacional de San Luis; ArgentinaFil: Teertstra, David K.. University of Manitoba; CanadáFil: Chapman, Ron. University of Manitoba; CanadáFil: MacBride, Lyndsey. University of Manitoba; CanadáFil: Ferreira, Karen. University of Manitoba; Canad

Inter- and intra-species heterogeneity in germination of Aspergillus conidia

Aspergilli are among the most abundant fungi worldwide. They degrade organic material and can be pathogens of plants and animals. Aspergilli spread by forming high numbers of conidia. Germination of these stress resistant asexual spores is characterized by a swelling and a germ tube stage. Here, we show that conidia of Aspergillusniger,Aspergillusoryzae,Aspergillusclavatus, Aspergillusnidulans and Aspergillusterreus show different swelling and germ tube formation dynamics in pure water or in water supplemented with (in)organic nutrients. Apart from inter-species heterogeneity, intra-species heterogeneity was observed within spore populations of the aspergilli except for A.terreus. Sub-populations of conidia differing in size and/or contrast showed different swelling and germ tube formation dynamics. Together, data imply that aspergilli differ in their competitive potential depending on the substrate. Moreover, results suggest that intra-species heterogeneity provides a bet hedging mechanism to optimize survival of aspergilli

Host defence peptides identified in human apolipoprotein B as promising antifungal agents

Therapeutic options to treat invasive fungal infections are still limited. This makes the development of novel antifungal agents highly desirable. Naturally occurring antifungal peptides represent valid candidates, since they are not harmful for human cells and are endowed with a wide range of activities and their mechanism of action is different from that of conventional antifungal drugs. Here, we characterized for the first time the antifungal properties of novel peptides identified in human apolipoprotein B. ApoB-derived peptides, here named r(P)ApoBLPro, r(P)ApoBLAla and r(P)ApoBSPro, were found to have significant fungicidal activity towards Candida albicans (C. albicans) cells. Peptides were also found to be able to slow down metabolic activity of Aspergillus niger (A. niger) spores. In addition, experiments were carried out to clarify the mechanism of fungicidal activity of ApoB-derived peptides. Peptides immediately interacted with C. albicans cell surfaces, as indicated by fluorescence live cell imaging analyses, and induced severe membrane damage, as indicated by propidium iodide uptake induced upon treatment of C. albicans cells with ApoB-derived peptides. ApoB-derived peptides were also tested on A. niger swollen spores, initial hyphae and branched mycelium. The effects of peptides were found to be more severe on swollen spores and initial hyphae compared to mycelium. Fluorescence live cell imaging analyses confirmed peptide internalization into swollen spores with a consequent accumulation into hyphae. Altogether, these findings open interesting perspectives to the application of ApoB-derived peptides as effective antifungal agents

Tumour thickness in oral cancer using an intra-oral ultrasound probe

To investigate tumour-thickness measurement with an intra-operative ultrasound (US) probe. A retrospective data analysis was undertaken for a total of 65 patients with a T1-2 oral cavity cancer, who were seen at a tertiary referral centre between 2004 and 2010. The correspondence between tumour thickness measured by ultrasonography and histopathology was assessed by Pearson's correlation coefficient, and also between tumour thickness and the development of neck metastasis. In 11 cases, intra-oral measurement was not optimal due to limited mouth opening (n = 2) or impossibility to depict the lesion (n = 9). Tumour thickness measured by US correlated well with histopathology (n = 23, R = 0.93). Tumour thickness of a parts per thousand currency sign7 mm carries a risk of lymph node metastasis of 12%, whereas in tumours exceeding 7 mm this risk is 57% (p = 0.001). Twenty-five percent developed neck metastasis and 19% had local recurrence. Tumour thickness is an important predictive marker for lymph node metastases. As such, it can help in decision-making with regard to management of the primary tumour and neck. Based upon our findings, a wait-and-see policy is only warranted for superficial lesions with tumour thickness of less than 7 mm, but only if regular follow-up using US-guided aspiration of the neck is ensure

Impact of maturation and growth temperature on cell-size distribution, heat-resistance, compatible solute composition and transcription profiles of Penicillium roqueforti conidia

Penicillium roqueforti is a major cause of fungal food spoilage. Its conidia are the main dispersal structures of this fungus and therefore the main cause of food contamination. These stress resistant asexual spores can be killed by preservation methods such as heat treatment. Here, the effects of cultivation time and temperature on thermal resistance of P. roqueforti conidia were studied. To this end, cultures were grown for 3, 5, 7 and 10 days at 25 °C or for 7 days at 15, 25 and 30 °C. Conidia of 3- and 10-day-old cultures that had been grown at 25 °C had D56-values of 1.99 ± 0.15 min and 5.31 ± 1.04 min, respectively. The effect of cultivation temperature was most pronounced between P. roqueforti conidia cultured for 7 days at 15 °C and 30 °C, where D56-values of 1.12 ± 0.05 min and 4.19 ± 0.11 min were found, respectively. Notably, D56-values were not higher when increasing both cultivation time and temperature by growing for 10 days at 30 °C. A correlation was found between heat resistance of conidia and levels of trehalose and arabitol, while this was not found for glycerol, mannitol and erythritol. RNA-sequencing showed that the expression profiles of conidia of 3- to 10-day-old cultures that had been grown at 25 °C were distinct from conidia that had been formed at 15 °C and 30 °C for 7 days. Only 33 genes were upregulated at both prolonged incubation time and increased growth temperature. Their encoded proteins as well as trehalose and arabitol may form the core of heat resistance of P. roqueforti conidia.</p

Heterogeneity in liquid shaken cultures of Aspergillus niger inoculated with melanised conidia or conidia of pigmentation mutants

AbstractBlack pigmented conidia of Aspergillus niger give rise to micro-colonies when incubated in liquid shaken medium. These micro-colonies are heterogeneous with respect to gene expression and size. We here studied the biophysical properties of the conidia of a control strain and of strains in which the fwnA, olvA or brnA gene is inactivated. These strains form fawn-, olive-, and brown-coloured conidia, respectively. The ΔolvA strain produced larger conidia (3.8 μm) when compared to the other strains (3.2–3.3 μm). Moreover, the conidia of the ΔolvA strain were highly hydrophilic, whereas those of the other strains were hydrophobic. The zeta potential of the ΔolvA conidia in medium was also more negative when compared to the control strain. This was accompanied by the near absence of a rodlet layer of hydrophobins. Using the Complex Object Parametric Analyzer and Sorter it was shown that the ratio of individual hyphae and micro-colonies in liquid shaken cultures of the deletion strains was lower when compared to the control strain. The average size of the micro-colonies of the control strain was also smaller (628 μm) than that of the deletion strains (790–858 μm). The size distribution of the micro-colonies of the ΔfwnA strain was normally distributed, while that of the other strains could be explained by assuming a population of small and a population of large micro-colonies. In the last set of experiments it was shown that relative expression levels of gpdA, and AmyR and XlnR regulated genes correlate in individual hyphae at the periphery of micro-colonies. This indicates the existence of transcriptionally and translationally highly active and lowly active hyphae as was previously shown in macro-colonies. However, the existence of distinct populations of hyphae with high and low transcriptional and translational activity seems to be less robust when compared to macro-colonies grown on solid medium