Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As

We report on a theoretical study of dc transport coefficients in (Ga,Mn)As diluted magnetic semiconductor ferromagnets that accounts for quasiparticle scattering from ionized Mn$^{2+}$ acceptors with a local moment $S=5/2$ and from non-magnetic compensating defects. In metallic samples Boltzmann transport theory with Golden rule scattering rates accounts for the principle trends of the measured difference between resistances for magnetizations parallel and perpendicular to the current. We predict that the sign and magnitude of the anisotropic magnetoresistance can be changed by strain engineering or by altering chemical composition.Comment: 4 pages, 2 figure

Propagating Waves Transverse to the Magnetic Field in a Solar Prominence

We report an unusual set of observations of waves in a large prominence pillar which consist of pulses propagating perpendicular to the prominence magnetic field. We observe a huge quiescent prominence with the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) in EUV on 2012 October 10 and only a part of it, the pillar, which is a foot or barb of the prominence, with the Hinode Solar Optical Telescope (SOT) (in Ca II and H\alpha lines), Sac Peak (in H\alpha, H\beta\ and Na-D lines), THEMIS ("T\'elescope H\'eliographique pour l' Etude du Magn\'etisme et des Instabilit\'es Solaires") with the MTR (MulTi-Raies) spectropolarimeter (in He D_3 line). The THEMIS/MTR data indicates that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features on a much smaller scale than the pillar as a whole. The data is consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and Sac Peak data over the 4 hour observing period show vertical oscillations appearing as wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along thin quasi-vertical columns in the much broader pillar. The pulses have a velocity of propagation of about 10 km/s, a period about 300 sec, and a wavelength around 2000 km. We interpret these waves in terms of fast magneto-sonic waves and discuss possible wave drivers.Comment: Accepted for publication in The Astrophysical Journa

Unhappiness, health and cognitive ability in old age

Background To test whether scores on depression inventories on entry to a longitudinal study predict mental ability over the next 4–16 years. Method Associations between scores on the Beck Depression Inventory and on tests of intelligence, vocabulary and memory were analysed in 5070 volunteers aged 49–93 years after differences in prescribed drug consumption, death and drop-out, sex, socio-economic advantage and recruitment cohort effects had also been considered. Results On all cognitive tasks Beck scores on entry, even in the range 0–7 indicating differences in above average contentment, affected overall levels of cognitive performance but not rates of age-related cognitive decline suggesting effects of differences in life satisfaction rather than in depression. Conclusions A new finding is that, in old age, increments in life satisfaction are associated with better cognitive performance. Implications for interpreting associations between depression inventory scores and cognitive performance in elderly samples are discussed

A dynamic global model for planktonic foraminifera

International audienceSeasonal changes in the flux of planktonic foraminifera have to be understood to interpret corresponding proxy-based reconstructions. To study the seasonal cycle of planktonic foraminifera species we developed a numerical model of species concentration (PLAFOM). This model is forced with a global hydrographic dataset (e.g. temperature, mixed layer depth) and with biological information taken from an ecosystem model (e.g. "food type", zooplankton abundance) to predict monthly concentrations of the most common planktonic foraminifera species used for proxies: N. pachyderma (sinistral and dextral varieties), G. bulloides, G. ruber (white variety) and G. sacculifer. The sensitivity of each species with respect to temperature (optimal temperature and range of tolerance) is derived from sediment-trap studies. Overall, the spatial distribution patterns of most of the species are comparable to core-top data. N. pachyderma (sin.) is limited to polar regions, N. pachyderma (dex.) and G. bulloides are the most common species in high productivity zones like upwelling areas, while G. ruber and G. sacculifer are more abundant in tropical and subtropical oligotrophic waters. Modeled seasonal variation match well with sediment-trap records in most of the locations for N. pachyderma (sin), N. pachyderma (dex.) and G. bulloides. G. ruber and G. sacculifer show, in general, lower concentrations and less seasonal variability in all sites. The lower variability is reflected in the model output, but the small scale variations are not reproduced by the model in several locations. Due to the fact that the model is forced by climatological data, it can not capture interannual variations. The sensitivity experiments we carried out show that, inside the temperature tolerance range, food availability is the main parameter which controls the abundance of some species. The here presented model represents a powerful tool to explore the response of planktonic foraminifera to different boundary conditions, and to quantify the seasonal bias in foraminifera-based proxy records

On Learning Monotone DNF Formulae under Uniform Distributions

AbstractWe show how to learn in polynomial time monotone d-term DNF formulae (formulae in disjunctive normal form with at most d terms) using positive examples drawn from a distribution that is a generalization of the uniform distribution

Observations of ozone production in a dissipating tropical convective cell during TC4

From 13 July–9 August 2007, 25 ozonesondes were launched from Las Tablas, Panama as part of the Tropical Composition, Cloud, and Climate Coupling (TC4) mission. On 5 August, a strong convective cell formed in the Gulf of Panama. World Wide Lightning Location Network (WWLLN) data indicated 563 flashes (09:00–17:00 UTC) in the Gulf. NO2 data from the Ozone Monitoring Instrument (OMI) show enhancements, suggesting lightning production of NOx. At 15:05 UTC, an ozonesonde ascended into the southern edge of the now dissipating convective cell as it moved west across the Azuero Peninsula. The balloon oscillated from 2.5–5.1 km five times (15:12–17:00 UTC), providing a unique examination of ozone (O3) photochemistry on the edge of a convective cell. Ozone increased at a rate of 1.6–4.6 ppbv/hr between the first and last ascent, resulting cell wide in an increase of (2.1–2.5)×106 moles of O3. This estimate agrees to within a factor of two of our estimates of photochemical lightning O3 production from the WWLLN flashes, from the radar-inferred lightning flash data, and from the OMI NO2 data (1.2, 1.0, and 1.7×106 moles, respectively), though all estimates have large uncertainties. Examination of DC-8 in situ and lidar O3 data gathered around the Gulf that day suggests 70–97% of the O3 change occurred in 2.5–5.1 km layer. A photochemical box model initialized with nearby TC4 aircraft trace gas data suggests these O3 production rates are possible with our present understanding of photochemistry

Deformation pattern in vibrating microtubule: Structural mechanics study based on an atomistic approach

The mechanical properties of microtubules are of great importance for understanding their biological function and for applications in artificial devices. Although microtubule mechanics has been extensively studied both theoretically and experimentally, the relation to its molecular structure is understood only partially. Here, we report on the structural analysis of microtubule vibration modes calculated by an atomistic approach. Molecular dynamics was applied to refine the atomic structure of a microtubule and a C α elastic network model was analyzed for its normal modes. We mapped fluctuations and local deformations up to the level of individual aminoacid residues. The deformation is mode-shape dependent and principally different in α-tubulins and β-tubulins. Parts of the tubulin dimer sequence responding specifically to longitudinal and radial stress are identified. We show that substantial strain within a microtubule is located both in the regions of contact between adjacent dimers and in the body of tubulins. Our results provide supportive evidence for the generally accepted assumption that the mechanics of microtubules, including its anisotropy, is determined by the bonds between tubulins

Elektronische Geruchsuntersuchung von Hölzern

Zusammenfassung: Ber Hoizgeruch wurde bisiang bei der Bestimmung der Holzart und Beschreibung des Holzzustandes nur marginal berücksichtigt. Mit Hilfe einer Anlage mit einer neuen Kombination von Gassensorarrays (Serien von gasempfindlichen Metallhalbleitern), verbunden mit neuronalen Netzen, wurden einheimische Nadel- und Laubhölzer sowie tropische Laubhölzer auf ihre Unterscheidbarkeit getestet. Eine gezielte Datenbearbeitung ermöglicht es, auch bisher schwer zu unterscheidende Arten über den Geruch zu trennen. Neben der Abhängigkeit des Geruches von der Holzart und weiterer Faktoren (mit dem Ort der Probenentnahme im Baum zusammenhängend) werden auch allgemeine Anwendungsmöglichkeiten des Systems kurz diskutier