Investigations of failure mechanisms at Ta and TaO diffusion barriers by secondary neutral mass spectrometry

One of the most important processes in Cu metallization for highly integrated circuits is to fabricate reliable diffusion barriers. Recently, thin films made of refractory metals and their compounds have been widely used in solid-state electronics as barriers because of their good electric properties, favourable thermal properties and chemical stability. Thermal stability of Tantalum (Ta) and Tantalum-oxide (TaO_x) layers as a diffusion barrier in Si/Ta/Cu, Si/TaO_x/Cu and Si/Ta-TaO_x/Cu systems have been investigated. Si/Ta (10 nm)/Cu (25 nm)/W (10 nm), Si/TaO_x (10 nm)/Cu (25 nm)/W (10 nm) and Si/Ta (5 nm)TaO_x (5 nm)/Cu (25 nm)/W (10 nm) thin layers were prepared by DC magnetron sputtering. A tungsten cap layer was applied to prevent the oxidation of the samples during the annealing process. The samples were annealed at various temperatures (473 K-973 K) in vacuum. Transmission Electron Microscopy, X-ray diffraction, X-Ray Photoelectron Spectroscopy and Secondary Neutral Mass Spectrometry were used to characterize the microstructure and diffusion properties of the thin films. Our results show that at the beginning phase of the degradation of the Si/Ta/Cu system Ta atoms migrate through the copper film to the W/Cu interface. In the Si/TaO_x/Cu system the crystallization of TaO and the diffusion of Si through the barrier determine the thermal stability. The Ta-TaO bilayer proved to be an excellent barrier layer between the Si and Cu films up to 1023 K. The observed outstanding performance of the combined film is explained by the continuous oxidation of Ta film in the TaO_x-Ta bilayer.     

Drosophila Rab39 Attenuates Lysosomal Degradation

Lysosomal degradation, the common destination of autophagy and endocytosis, is one of the most important elements of eukaryotic metabolism. The small GTPases Rab39A and B are potential new effectors of this pathway, as their malfunction is implicated in severe human diseases like cancer and neurodegeneration. In this study, the lysosomal regulatory role of the single Drosophila Rab39 ortholog was characterized, providing valuable insight into the potential cell biological mechanisms mediated by these proteins. Using a de novo CRISPR-generated rab39 mutant, we found no failure in the early steps of endocytosis and autophagy. On the contrary, we found that Rab39 mutant nephrocytes internalize and degrade endocytic cargo at a higher rate compared to control cells. In addition, Rab39 mutant fat body cells contain small yet functional autolysosomes without lysosomal fusion defect. Our data identify Drosophila Rab39 as a negative regulator of lysosomal clearance during both endocytosis and autophagy.     

Investigation of thickness and density dependence of thermal conductivity of expanded polystyrene insulation materials

Analysis of thermal conductivity of different insulation materials is very important in applications for passive and nearly zero houses. This paper presents the measurements results of the thermal conductivities of expanded polystyrene (EPS) insulation materials, with different thicknesses and air pore content. The measurements were achieved on pure (white) as well as graphite-enhanced (grey) EPS slabs, with a Holometrix type 2000 series heat flow meter after desiccating them in a Venticell 111 type drying apparatus to changeless weight. The densities of the white samples were varied from 10 to 26 kg/m³ (EPS types 30–200 and grey), furthermore both the white ones and the grey (14 kg/m³) samples with three different thicknesses (5, 8, 10 cm) were tested. In addition, experimental results for the density dependence of thermal conductivity at low densities are given. Thermal conductivity measurements of different white slabs in combination with grey slabs were executed also and the changes in the thermal conductivity values are presented.     

The representation of auditory source characteristics: simple geometric form

Two experiments examined listeners' ability to discriminate the geometric shape of simple resonating bodies on the basis of their corresponding auditory attributes. In cross-modal matching tasks, subjects listened to recordings of pairs of metal bars (Experiment 1) or wooden bars (Experiment 2) struck in sequence and then selected a visual depiction of the bar cross sections that correctly represented their relative widths and heights from two opposing pairs presented on a computer screen. Multidimensional scaling solutions derived from matching scores for metal and wooden bars indicated that subjects' performance varied directly with increasing differences in the width/height (W/H) ratios of both sets of bars. Subsequent acoustic analyses revealed that the frequency components from torsional vibrational modes and the ratios of frequencies of transverse bending modes in the bars correlated strongly with both the bars' W/H ratios and bar coordinates in the multidimensional configurations. The results suggest that listeners can encode the auditory properties of sound sources by extracting certain invariant physical characteristics of their gross geometric properties from their acoustic behavior.     

Population balance model of heat transfer in gas–solid particulate systems

A population balance model is derived for heat transfer processes in gas–solid systems with intensive motion of particles in order to describe the temperature distribution of particulate phase. The model involves collisional particle–particle and particle–wall heat transfers, and continuous gas–particle, gas–wall and wall–liquid environment heat transfer processes. Collisional heat transfers are characterised by collision frequencies and random heat exchange parameters with general probability distributions with support [0, 1], describing the heat transfer efficiency between the colliding solid bodies. An infinite hierarchy of moment equations, describing the time evolution of moments of the temperature of particle population is derived from the population balance equation, which can be closed at any order of moments. The properties of the model and the effects of parameters are examined by numerical experiments using the second order moment equation model of a spatially homogeneous fluidized bed.