Notes on implementation of sparsely distributed memory

The Sparsely Distributed Memory (SDM) developed by Kanerva is an unconventional memory design with very interesting and desirable properties. The memory works in a manner that is closely related to modern theories of human memory. The SDM model is discussed in terms of its implementation in hardware. Two appendices discuss the unconventional approaches of the SDM: Appendix A treats a resistive circuit for fast, parallel address decoding; and Appendix B treats a systolic array for high throughput read and write operations

Naive Noncommutative Blowing Up

Let B(X,L,s) be the twisted homogeneous coordinate ring of an irreducible variety X over an algebraically closed field k with dim X > 1. Assume that c in X and s in Aut(X) are in sufficiently general position. We show that if one follows the commutative prescription for blowing up X at c, but in this noncommutative setting, one obtains a noncommutative ring R=R(X,c,L,s) with surprising properties. In particular: (1) R is always noetherian but never strongly noetherian. (2) If R is generated in degree one then the images of the R-point modules in qgr(R) are naturally in (1-1) correspondence with the closed points of X. However, both in qgr(R) and in gr(R), the R-point modules are not parametrized by a projective scheme. (3) qgr R has finite cohomological dimension yet H^1(R) is infinite dimensional. This gives a more geometric approach to results of the second author who proved similar results for X=P^n by algebraic methods.Comment: Latex, 42 page

β\beta-NMR of Isolated 8^{8}Li+^{+} Implanted into a Thin Copper Film

Depth-controlled $\beta$-NMR was used to study highly spin-polarized $^8$Li in a Cu film of thickness 100 nm deposited onto a MgO substrate. The positive Knight Shifts and spin relaxation data show that $^8$Li occupies two sites at low temperatures, assigned to be the substitutional ($S$) and octahedral ($O$) interstitial sites. Between 50 to 100 K, there is a site change from $O$ to $S$. The temperature dependence of the Knight shifts and spin-lattice relaxation rates at high temperatures, i.e. when all the Li are in the $S$ site, is consistent with the Korringa Law for a simple metal.Comment: Accepted for publication in Phys. Rev.

Hyperfine Fields in an Ag/Fe Multilayer Film Investigated with 8Li beta-Detected Nuclear Magnetic Resonance

Low energy $\beta$-detected nuclear magnetic resonance ($\beta$-NMR) was used to investigate the spatial dependence of the hyperfine magnetic fields induced by Fe in the nonmagnetic Ag of an Au(40 \AA)/Ag(200 \AA)/Fe(140 \AA) (001) magnetic multilayer (MML) grown on GaAs. The resonance lineshape in the Ag layer shows dramatic broadening compared to intrinsic Ag. This broadening is attributed to large induced magnetic fields in this layer by the magnetic Fe layer. We find that the induced hyperfine field in the Ag follows a power law decay away from the Ag/Fe interface with power $-1.93(8)$, and a field extrapolated to $0.23(5)$ T at the interface.Comment: 5 pages, 4 figure. To be published in Phys. Rev.

Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets

We present longitudinal field muon spin relaxation ($\mu$SR) measurements in the unilluminated state of the photo-sensitive molecular magnetic Co-Fe Prussian blue analogues M$_{1-2x}$Co$_{1+x}$[Fe(CN)$_6$]$\cdot z$ H$_2$O, where M=K and Rb with $x=0.4$ and $\simeq 0.17$, respectively. These results are compared to those obtained in the $x=0.5$ stoichiometric limit, Co$_{1.5}$[Fe(CN)$_6$]$\cdot 6$ H$_2$O, which is not photo-sensitive. We find evidence for correlation between the range of magnetic ordering and the value of $x$ in the unilluminated state which can be explained using a site percolation model.Comment: 7 pages, 12 figure

‘An almost continuous picture of sordid vice’: The Keeler Affair, the Profumo Scandal and ‘Political’ Film Censorship in the 1960s

In 1963, the Profumo affair brought Christine Keeler to public attention and transformed her, briefly, into one of the most talked about women in the world. Seeking to exploit her notoriety, Topaz Films entered into an agreement with Keeler to make a cinematic version of her life story, The Keeler Affair. This article explores some of the controversies surrounding The Keeler Affair, especially in terms of the way in which the British Board of Film Censors dealt with the film. The Keeler Affair was submitted to the BBFC on two occasions – once when it was completed and then again in 1969 when Keeler's memoirs were serialised in the News of the World – and was rejected both times. On the second occasion, The Keeler Affair was also submitted to, and rejected by, the Greater London Council. The article seeks to establish some of the political factors that shaped the BBFC's and the GLC's attitudes towards politically contentious films, and demonstrates that the decisions made by the censors were guided not simply by the content of The Keeler Affair, but also by personal relationships, shared Establishment attitudes, concerns about public perceptions of the film industry and a desire not to be drawn into political controversies. Consequently, the article serves to reinforce the idea that censorship is best understood as a dynamic process shaped by a host of determining factors, many of which might best be described as extra- or para-cinematic

Isolation, purification, and full NMR assignments of cyclopamine from Veratrum californicum

The Hedgehog signaling pathway is essential for embryogenesis and for tissue homeostasis in the adult. However, it may induce malignancies in a number of tissues when constitutively activated, and it may also have a role in other forms of normal and maladaptive growth. Cyclopamine, a naturally occurring steroidal alkaloid, specifically inhibits the Hedgehog pathway by binding directly to Smoothened, an important Hedgehog response element. To use cyclopamine as a tool to explore and/or inhibit the Hedgehog pathway in vivo, a substantial quantity is required, and as a practical matter cyclopamine has been effectively unavailable for usage in animals larger than mice

Kinks Dynamics in One-Dimensional Coupled Map Lattices

We examine the problem of the dynamics of interfaces in a one-dimensional space-time discrete dynamical system. Two different regimes are studied : the non-propagating and the propagating one. In the first case, after proving the existence of such solutions, we show how they can be described using Taylor expansions. The second situation deals with the assumption of a travelling wave to follow the kink propagation. Then a comparison with the corresponding continuous model is proposed. We find that these methods are useful in simple dynamical situations but their application to complex dynamical behaviour is not yet understood.Comment: 17pages, LaTex,3 fig available on cpt.univ-mrs.fr directory pub/preprints/94/dynamical-systems/94-P.307