Nylon 46-polytetramethylene oxide segmented block copolymers

Block copolymers were synthesized from amine-terminated polytetramethylene oxide (PMTO) (Mw 800 and 1130) and polyamide 4,6 salt. First prepolymers were prepared at 200–210°C in the presence of a solvent (pyrrolidone). The prepolymers were postcondensed at 255°C (where possible in the solid state) to a high molecular weight. In the materials the endgroups were analysed, and the inherent viscosities and ethanol extraction values measured. The thermal properties were determined with d.s.c. and d.m.a. With ethanol, polyether could be extracted. Thus it seems that not all the polyether is present as part of the block copolymer. Melt phasing seems to have taken place and occurs even more with the higher molecular weight PTMO. With d.m.a. two glass transitions were observed; one of the polyether phase and one of the polyamide-rich phase. The melting temperatures of these polyamide 4,6 block copolymers are high (200–270°C), and the torsion modulus remained fairly constant up to these high melting temperatures

‘Giant’ magnetoresistance in obliquely co-evaporated Co-Ag films

Magnetoresistance (MR) measurements at room temperature have been performed on obliquely (co-) evaporated Ag-Co films deposited at room- and elevated-temperatures. The ‘giant’ magnetoresistance ratio (max. 13% for a composition of about Co35Ag65) over a wide range of compositions has been measured. The films are polycrystalline and grown in a columnar morphology. The columnar diameter depends on the thickness and is < 20 nm at 400 nm thickness. From XRD, NMR and saturation magnetization (Ms) vs. at% Ag, one can conclude that the films consist of Co-Co and Ag-Ag clusters. The coercivity depends on the thickness of the films (100–700 nm) and varies from 5 to 15 kA/m

Neutron reflectometry on Co-Cr layers

Polarized neutron reflection experiments were performed on a thin in-plane magnetized Co-Cr layer deposited on a quartz substrate. Data taken at a low magnetic field ( 0.1 T) clearly indicate the existence of an initial layer at the substrate side, whereas data at saturation ( 0.7 T) are consistent with a rather homogeneous magnetization

Giant magnetoresistance in Co/Cu multilayers sputtered with Kr

This paper presents some results of magnetoresistance measurements on Kr-sputter-deposited Co/Cu multilayers. We find that Co/Cu MLs sputtered with Kr gas show a larger GMR effect than those sputtered with Ar gas

Restricted Power - Computational Complexity Results for Strategic Defense Games

We study the game Greedy Spiders, a two-player strategic defense game, on planar graphs and show PSPACE-completeness for the problem of deciding whether one player has a winning strategy for a given instance of the game. We also generalize our results in metatheorems, which consider a large set of strategic defense games. We achieve more detailed complexity results by restricting the possible strategies of one of the players, which leads us to Sigma^p_2- and Pi^p_2-hardness results

Domain wall theory and exchange stiffness in Co/Pd multilayers

The stripe model of domain structure in multilayers is studied by micromagnetic simulation. The results indicate a strong reduction of the effective domain wall energy (by dipolar effects). Domain width measurements on sputtered Co/Pd multilayers are compared with the theory. The estimated exchange stiffness is comparable with that of bulk Co. The effects of interface roughness and of interlayer exchange are discussed

DC modeling of composite MOS transistors

Mixed-signal circuit design on sea-of-gates arrays requires the use of composite MOSTs, combinations of in-series and in-parallel connected unit MOSTs. To avoid an increase in circuit simulation complexity these are in general replaced by artificial single MOSTs. The analysis in this paper shows that a straightforward replacement will lead to incorrect results. Series MOSTs (in-series connected unit MOSTs) are essentially different from single MOSTs due to the presence of diffusion areas interrupting the channel at regular distances. The influence of lateral diffusion, charge sharing, and series resistance needs to be reconsidered. The theoretical results are confirmed by measurements on an experimental IC. Parameter decks of existing MOST models for circuit level simulation can be modified easily to reflect the length dependences of composite MOST parameters

Reading maps in the dark. Route planning for development geography in a post-ist world

The symposium on "Land Management and Sustainable Development in Rural and Urban Environments of the Third World" at the 1996 International Geographical Congress in The Hague focused on geographical research in land society relationships. The range of papers provided a variety of case studies of local land management in terms of livelihood strategies and the wider politico-socio-economic and ecological context in which they operate. They also highlighted the contradictions and tensions between different systems of knowledge about the environment, and the ways in which one may be privileged over others. These are implicit in most of the papers - in some, modernising knowledge is promoted for the solution of the problems of a modernising economy (for example, managing urban pollution in Malaysia), while in others institutional, political and technical knowledge is undergoing profound change, whereby the local continues to resist, adapt to, or be replaced by the forces of globalisation . Most papers in this collection make implicit distinctions between the familiar, and some would say, stereo-typical characterisations of different knowledges (scientific, western and modern on the one hand and indigenous and traditional on the other), although it is a much debated point whether it is useful to make a distinction between them at all (Agrawal 1996)