Ring-Opening-Induced Toughening of a Low-Permittivity Polymer-Metal Interface

Integrating low dielectric permittivity (low-k) polymers to metals is an exacting fundamental challenge because poor bonding between low-polarizability moieties and metals precludes good interfacial adhesion. Conventional adhesion-enhancing methods such as using intermediary layers are unsuitable for engineering polymer/metal interfaces for many applications because of the collateral increase in dielectric permittivity. Here, we demonstrate a completely new approach without surface treatments or intermediary layers to obtain an excellent interfacial fracture toughness of > 13 J/m(2) in a model system comprising copper. and a cross-linked polycarbosilane with k similar to 2.7 obtained by curing a cyclolinear polycarbosilane in air.Our results suggest that interfacial oxygen catalyzed molecularring-opening and anchoring of the opened ring moieties of the polymer to copper is the main toughening mechanism. This novel approach of realizing adherent low-k polymer/metal structures without intermediary layers by activating metal-anchoring polymer moieties at the interface could be adapted for applications such as device wiring and packaging, and laminates and composites.

Insulator-metal transition

A theory of the insulator-metal transition in transition-metal compounds is developed in terms of the collapse of the effective energy gap which is a function of the thermally excited electron-hole pairs. This dependence is shown to arise from the hole-lattice interaction. The reaction of the lattice is found to be equivalent to generating an internal positive pressure (strain). Estimates show that the observed typical behaviour of the conductivity jump and the change of volume at the transition temperature can be explained by the present theory.

Ultra-violet bands of mercury iodide

The ultraviolet bands of mercury iodide have been excited in uncondensed discharge and photographed with a quartz Littrow spectrograph. The bands in the region λ 2658 to 2530 Å have been analysed into two systems which may form the two components of a2Π-2∑ electronic transition with a2Π interval equal to 858·9 cm-1. These systems and the systems in the region λ 3095 to 2647 Å have the same lower state.

Studies on the hydrolysis of metal ions - Part II-Nickel

A detailed investigation of the hydrolysis of nickel in the lower concentration range has been made. The results have been analysed on the basis of 'Core + links' theory and on the assumption of the formation of one predominant complex. Evidence is obtained for the formation of Ni2 (OH)62- and its stability constant is calculated to be 1038.78

Phase change on transmission of microwaves through metal disc delay dielectrics

Expressions for the phase change Φ suffered by microwaves when transmitted through an artificial dielectric composed of metallic discs arranged in a three-dimensional array have been derived with different approaches as follows (i) molecular theory, (ii) electromagnetic theory and (iii) transmission line theory. The phase change depends on the distance t that the wave traverses inside the dielectric and also the spacing d between centre to centre of any two adjacent discs in the three principal directions. Molecular theory indicates Φ as an increasing function of t, whereas, the other two theories indicate Φ as an oscillatory function of t. The transmission line theory also exhibits Φ to be real or imaginary depending on t. Experimental values of Φ as a function of t have been obtained with the help of a microwave (3·2 cms wavelength) interferometer for two dielectrics having d as 1·91 cms and 2·22 cms respectively.

Analysis of multiple crystal forms of Bacillus subtilis BacB suggests a role for a metal ion as a nucleant for crystallization

Bacillus subtilis BacB is an oxidase that is involved in the production of the antibiotic bacilysin. This protein contains two double-stranded beta-helix (cupin) domains fused in a compact arrangement. BacB crystallizes in three crystal forms under similar crystallization conditions. An interesting observation was that a slight perturbation of the crystallization droplet resulted in the nucleation of a different crystal form. An X-ray absorption scan of BacB suggested the presence of cobalt and iron in the crystal. Here, a comparative analysis of the different crystal forms of BacB is presented in an effort to identify the basis for the different lattices. It is noted that metal ions mediating interactions across the asymmetric unit dominate the different packing arrangements. Furthermore, a normalized B-factor analysis of all the crystal structures suggests that the solvent-exposed metal ions decrease the flexibility of a loop segment, perhaps influencing the choice of crystal form. The residues coordinating the surface metal ion are similar in the triclinic and monoclinic crystal forms. The coordinating ligands for the corresponding metal ion in the tetragonal crystal form are different, leading to a tighter packing arrangement. Although BacB is a monomer in solution, a dimer of BacB serves as a template on which higher order symmetrical arrangements are formed. The different crystal forms of BacB thus provide experimental evidence for metal-ion-mediated lattice formation and crystal packing.

Positional dependence of material flow in friction stir welding: analysis of joint line remnant and its relevance to dissimilar metal welding

Understanding material flow in friction stir welding is important for production of sound dissimilar metal welding that control the intermixing of two alloys being welded and consequent formation of new constituents which influences the weld properties. In the present experimental investigation material flow patterns are visualised using dissimilar and similar aluminium alloys using a simple innovative ,experiment. The experimental results reveal that only a portion of material transported from the leading edge undergoes chaotic flow and the remaining is deposited systematically in the trailing edge of the weld. Using this information it is shown that the formation of a friction stir welding defect, joint line remnant, does not occur only when the weld interface is on the advancing side. The material flow visualisation study has been utilised to analyse the mechanism of weld formation and its usefulness in improving fatigue properties and for dissimilar metal welds.

Druvan - Den personalekonomiska nyttan av mångdimensionell företagshälsovårds- och personalutvecklingsverksamhet baserad på Metal Age-konceptet i Dragsfjärds kommun (2002-2005)

Under åren 2002-2005 förverkligades Druvan-projektet i Dragsfjärds kommun, vilket innebar en dramatisk ökning av företagshälsovårdsinsatserna. Företagshälsovårdsutgifterna ökade från 20 € per anställd till över 400 €. Den totala satsningen på personalens hälsa ökade ännu mer. Innehållet i Druvan baserade sig på den s.k. Metal Age-metoden. Metoden går ut på att arbetsgemenskapen tillsammans identifierar utvecklingsbehov och –åtgärder. Projektet ledde till en stor mängd utvecklingsåtgärder och därpå följande effekter på personalens hälsa, trivsel och samarbete. Som en del av åtgärderna utarbetade kommunen en personalrapport för de aktuella åren. Under projekttiden utvecklades personalens arbetsförmåga betydligt gynnsammare än förväntat. Den ekonomiska analysen visade att det investerade kapitalet gav en avkastning på 46%. Nyttan uppkom som resultat av minskad sjukfrånvaro och färre förtidspensioneringar. Druvan-projektet stöder de tidigare bedömningarna, enligt vilka det finns ett klart utrymme för att öka satsningarna på företagshälsovård i vårt land. Detta gäller speciellt arbetsplatser vars satsningar på företagshälsovård är betydligt under genomsnittet. Dragsfjärds kommun har beslutat göra Druvan till en bestående struktur inom kommunen. Guy Ahonen är professor i Knowledge Management, speciellt personalekonomi vid institutionen för företagsledning och organisation vid Hanken. Ove Näsman är ledande företagsläkare vid Dalmed OyAb i Dalsbruk i sydvästra Finland. Båda har forskat i årtionden kring effekterna av ökat välbefinnande i arbetet.