Children and the experience of violence: contrasting cultures of punishment in northern Nigeria

Arising out of debates over ‘children at risk’ and the ‘rights of the child’, the article compares two contrasting childhoods within a single large society—the Hausa‐speaking peoples of northern Nigeria. One segment of this society—the non‐Muslim Maguzawa—refuse to allow their children to be beaten; the other segment, the Muslim Hausa, tolerate corporal punishment both at home and especially in Qur'anic schools. Why the difference? Economic as well as political reasons are offered as reasons for the rejection of corporal punishment while it is argued that, in the eyes of Muslim society in the cities, the threat of punishment is essential for both educating and ‘civilising’ the young by imposing the necessary degree of discipline and self‐control that are considered the hallmark of a good Muslim. In short, ‘cultures of punishment’ arise out of specific historical conditions, with wide variations in the degree and frequency with which children actually suffer punishment, and at whose hands. Finally the question is raised whether the violence experienced in schooling has sanctioned in the community at large a greater tolerance of violence‐as‐‘punishment’

Surface plasma resonance in small rare gas clusters by mixing IR and VUV laser pulses

The ionization dynamics of a Xenon cluster with 40 atoms is analyzed under a pum p probe scenario of laser pulses where an infrared laser pulse of 50 fs length follows with a well defined time delay a VUV pulse of the same length and peak intensity. The mechanism of resonant energy absorption due to the coinc idence of the IR laser frequency with the frequency of collective motion of quasi free electrons in the cluster is mapped out by varying the time delay between the pulses

A family of Schr\"odinger operators whose spectrum is an interval

By approximation, I show that the spectrum of the Schr\"odinger operator with potential $V(n) = f(n\rho \pmod 1)$ for f continuous and $\rho > 0$, $\rho \notin \N$ is an interval.Comment: Comm. Math. Phys. (to appear

Optimization of nanostructured permalloy electrodes for a lateral hybrid spin-valve structure

Ferromagnetic electrodes of a lateral semiconductor-based spin-valve structure are designed to provide a maximum of spin-polarized injection current. A single-domain state in remanence is a prerequisite obtained by nanostructuring Permalloy thin film electrodes. Three regimes of aspect ratios $m$ are identified by room temperature magnetic force microscopy: (i) high-aspect ratios of $m \ge 20$ provide the favored remanent single-domain magnetization states, (ii) medium-aspect ratios $m \sim 3$ to $m \sim 20$ yield highly remanent states with closure domains and (iii) low-aspect ratios of $m \le 3$ lead to multi-domain structures. Lateral kinks, introduced to bridge the gap between micro- and macroscale, disturb the uniform magnetization of electrodes with high- and medium-aspect ratios. However, vertical flanks help to maintain a uniformly magnetized state at the ferromagnet-semiconcuctor contact by domain wall pinning.Comment: revised version, major structural changes, figures reorganized,6 pages, 8 figures, revte

Paleohydrology, Sedimentology, and Geochemistry of Two Meromictic Saline Lakes in Southern Saskatchewan

The Northern Great Plains of western Canada contain numerous saline and hypersaline lakes. Most of these lakes are shallow (< 3 m) and exhibit playa characteristics. Some, however, are relatively deep, permanent water bodies. The sediment records of these deep perennial saline lakes offer an excellent opportunity to evaluate key paleohydrologic and hydrochemical parameters. Variations in these parameters may, in turn, be interpreted with respect to climatic fluctuations in the region. Waldsea and Deadmoose lakes, located in south-central Saskatchewan, are both presently meromictic, with saline Mg-Na-SO4-CI waters overlying denser hypersaline brines of similar composition. The modern sediments of the lakes consist of a mixture of organic matter, finegrained detrital elastics (mainly clay minerals, carbonate minerals, quartz, and feldspars), and finely crystalline endogenic/authigenic precipitates (aragonite, gypsum, calcite, pyrite, and mirabilite). Variations in mineralogy and chemistry of sediment cores from the morphologically simple Waldsea basin show that the lake was much shallower and more saline about 4000 years ago. Although water levels have since generally increased in the basin giving rise to higher organic productivity and greater inorganic carbonate precipitation, there is also evidence of several hydrologie reversals during the last 2000 years. The stratigraphy preserved in nearby Deadmoose Lake is much more complex because of the irregular basin morphology. Lower water levels about 1000 years ago created several isolated but still relatively deep lakes in the Deadmoose basin.Les grandes plaines du nord de l'ouest du Canada contiennent de nombreux lacs salés et hypersalés. La plupart de ces lacs sont peu profonds (< 3 m) et offrent les caractéristiques des playas. D'autres, par contre, sont des plans d'eau permanents relativement profonds. Les données sédimentologiques de ces derniers permettent d'évaluer certains paramètres clés de paléohydrologie et d'hydrochimie. Les variations qu'offrent ces paramètres peuvent à leur tour être interprétées en fonction des fluctuations climatiques qu'a connues la région. Les lacs Waldsea et Deadmoose, dans le centre-sud de la Saskatchewan, sont méromictiques et leurs eaux composées de Mg-Na-So4-Cl recouvrent une saumure hypersaline plus dense, mais de composition semblable. Les sédiments actuels de ces lacs consistent en un mélange de matière organique, de roches détritiques à grains fins (surtout des minéraux argileux et carbonates ainsi que des quartz et des feldspaths) et de calcaires de précipitation cristallins à grains fins endogènes et authigènes (aragonite, gypse, calcite, pyrite et mirabilite). La minéralogie et la chimie des sédiments contenus dans les carottes recueillies dans le bassin du lac Waldsea, de morphologie simple, montrent des variations qui indiquent que le lac était beaucoup moins profond et plus salé il y a 4000 ans. Bien que, de façon générale, les niveaux lacustres se soient haussés depuis, ce qui a donné lieu à une production accrue de matière organique et à une plus forte précipitation des carbonates inorganiques, on trouve les témoins de plusieurs inversions de nature hydrologique depuis les 2000 dernières années. Non loin, au lac Deadmoose, la stratigraphie est beaucoup plus complexe en raison de la morphologie irrégulière du bassin. Il y a 1000 ans environ, les bas niveaux lacustres ont été à l'origine de la formation de plusieurs lacs isolés et relativement profonds dans le bassin Deadmoose.den nôrdlichen groBen Ebenen von West-Kanada gibt es zahlreiche salzhaltige und hypersalzhaltige Seen. Die meisten dieser Seen sind seicht (< 3 m) und zeigen Pfannen Charakteristika. Einige hingegen sind relativ tiefe permanente Wasserspiegel. Die Sediment-Belege dieser tiefen, bestândigen Salz-Seen bieten eine ausgezeichnete Gelegenheit, die paleohydrologischen und hydrochemischen Schlùssel-Parameter zu bewerten. Variationen dieser Parameter kônnen ihrerseits interpretiert werden in Bezug auf die klimatischen Fluktuationen in dieser Region. Die Seen Waldsea und Deadmoose, die im sùdlichen Zentrum von Saskatchewan liegen, sind gegenwârtig beide meromiktisch, mit salinen Mg-Na-SO4-Cl Wassern, welche dichtere, hypersaline Salzlaken âhnlicher Zusammensetzung ùberlagern. Die gegenwàrtigen Sedimente dieser Seen bestehen aus einer Mischung von organischem Material, feinkôrnigen Trùmmergesteinen (hauptsàchlich Lehm-Minerale, Karbonat-Minerale, Quartz und Feldspate), und fein kristallinen endogenen/ authigenen Niederschlàgen (Aragonit, Gipsstein, Kalkspat, Pyrit und Mirabilit). Variationen in der Minéralogie und Chemie der Sediment-Keme von dem morphologisch einfachen Waldsea-Becken zeigen, dafî der See vor etwa 4000 Jahren viel seichter und saliner war. Obwohl die Wasserspiegel seitdem im Allgemeinen in dem Becken angestiegen sind, was zu hôherer organischer Produktivitàt und vestârktem inorganischem Karbonat-Niederschlag fùhrte, findet man auch Belege fur einige hydrologische Umschwùnge wâhrend der letzten 2000 Jahre. Die im nahegelegenen Deadmoose-See erhaltene Stratigraphie ist viel komplexer auf Grund der unregelmàfîigen Morphologie des Beckens. Niedrigere Wasserspiegel vor ungefâhr 1000 Jahren fùhrten zu einigen isolierten, aber immer noch relativ tiefen Seen im Deadmoose-Becken

Going the distance in Canada

Athabasca University; University College of the Fraser Valle

Singular Continuous Spectrum for the Laplacian on Certain Sparse Trees

We present examples of rooted tree graphs for which the Laplacian has singular continuous spectral measures. For some of these examples we further establish fractional Hausdorff dimensions. The singular continuous components, in these models, have an interesting multiplicity structure. The results are obtained via a decomposition of the Laplacian into a direct sum of Jacobi matrices

Enhanced ionization in small rare gas clusters

A detailed theoretical investigation of rare gas atom clusters under intense short laser pulses reveals that the mechanism of energy absorption is akin to {\it enhanced ionization} first discovered for diatomic molecules. The phenomenon is robust under changes of the atomic element (neon, argon, krypton, xenon), the number of atoms in the cluster (16 to 30 atoms have been studied) and the fluency of the laser pulse. In contrast to molecules it does not dissappear for circular polarization. We develop an analytical model relating the pulse length for maximum ionization to characteristic parameters of the cluster

Double butterfly spectrum for two interacting particles in the Harper model

We study the effect of interparticle interaction $U$ on the spectrum of the Harper model and show that it leads to a pure-point component arising from the multifractal spectrum of non interacting problem. Our numerical studies allow to understand the global structure of the spectrum. Analytical approach developed permits to understand the origin of localized states in the limit of strong interaction $U$ and fine spectral structure for small $U$.Comment: revtex, 4 pages, 5 figure

Bloch electron in a magnetic field and the Ising model

The spectral determinant det(H-\epsilon I) of the Azbel-Hofstadter Hamiltonian H is related to Onsager's partition function of the 2D Ising model for any value of magnetic flux \Phi=2\pi P/Q through an elementary cell, where P and Q are coprime integers. The band edges of H correspond to the critical temperature of the Ising model; the spectral determinant at these (and other points defined in a certain similar way) is independent of P. A connection of the mean of Lyapunov exponents to the asymptotic (large Q) bandwidth is indicated.Comment: 4 pages, 1 figure, REVTE