On the Maximal Excess Charge of the Chandrasekhar-Coulomb Hamiltonian in Two Dimensions

We show that for the straightforward quantized relativistic Coulomb Hamiltonian of a two-dimensional atom -- or the corresponding magnetic quantum dot -- the maximal number of electrons does not exceed twice the nuclear charge. It result is then generalized to the presence of external magnetic fields and atomic Hamiltonians. This is based on the positivity of |\bx| T(\bp) + T(\bp) |\bx| which -- in two dimensions -- is false for the non-relativistic case T(\bp) = \bp^2, but is proven in this paper for T(\bp) = |\bp|, i.e., the ultra-relativistic kinetic energy

Photophysics, Molecular Reorientation in Solution and X-Ray Structure of a New Fluorescent Probe 1,7-Diazaperylene

A new fluorescent molecule 1,7-diazaperylene (DP) has been investigated by means of time-resolved and steady-state polarized fluorescence spectroscopy, as well as X-ray spectroscopy. Absorption and fluorescence spectra of DP in solution are similar to those of perylene. However, absorption and fluorescence spectra of 2,8-dimethoxy DP and 2,8-dipentyloxy DP in solution are red-shifted by ca. 55 nm relative to perylene. The fluorescence decay of DP is exponential with a lifetime of 5.1 ns in ethanol, 4.9 ns in glycerol and 4.3 ns in paraffin oil. The radiative lifetime in ethanol was calculated to be 6.3 ns for DP, 8.0 ns for 2,8-dimethoxy DP and 7.6 ns for 2,8-dipentyloxy DP. The calculated fluorescence quantum yields of 0.8 for DP and its alkoxy derivatives in ethanol, are in good agreement with those obtained from measurements. The calculated Förster radius is 37.2 ± 1 Å for DP and 41.9 ± 1 Å for its alkoxy derivatives in ethanol. Examining the S0 S1 transition, we obtain a limiting fluorescence anisotropy of r0 0.38 for DP and its alkoxy derivatives. The rotational rates of DP in paraffin oil and glycerol were compared to that of perylene. In paraffin oil both molecules show an almost identical biexponential decay of the fluorescence anisotropy, which is compatible with a rotational motion like an oblate ellipsoid. The fluorescence anisotropy is monoexponential for DP in glycerol, and DP appears to rotate like a spherical particle while perylene in glycerol appears to rotate like an oblate ellipsoid. Moreover, the rotational diffusion constant, corresponding to rotation about an axis in the aromatic plane (D), is the same for both DP and perylene in glycerol

Stability of Relativistic Matter With Magnetic Fields

Stability of matter with Coulomb forces has been proved for non-relativistic dynamics, including arbitrarily large magnetic fields, and for relativistic dynamics without magnetic fields. In both cases stability requires that the fine structure constant alpha be not too large. It was unclear what would happen for both relativistic dynamics and magnetic fields, or even how to formulate the problem clearly. We show that the use of the Dirac operator allows both effects, provided the filled negative energy `sea' is defined properly. The use of the free Dirac operator to define the negative levels leads to catastrophe for any alpha, but the use of the Dirac operator with magnetic field leads to stability.Comment: This is an announcement of the work in cond-mat/9610195 (LaTeX

Limited Effect of Dopaminergic Medication on Straight Walking and Turning in Early-to-Moderate Parkinson’s Disease during Single and Dual Tasking

Background: In Parkinson’s disease (PD), the effects of dopaminergic medication on straight walking and turning were mainly investigated under single tasking (ST) conditions. However, multitasking situations are considered more daily relevant.Methods: Thirty-nine early to moderate PD patients performed the following standarized ST and dual tasks (DT) as fast as possible for one minute during On- and Off-medication while wearing inertial sensors: straight walking and turning, checking boxes, and subtracting serial 7s. Quantitative gait parameters, as well as velocity of the secondary tasks were analyzed.Results: The following parameters improved significantly in On-medication during ST: gait velocity during straight walking (p=0.03); step duration (p=0.048) and peak velocity (p=0.04) during turning; velocity of checking boxes during ST (p=0.04) and DT (p=0.04). Velocity of checking boxes was the only parameter that also improved during DT.Conclusion: These results suggest that dopaminergic medication does not relevantly influence straight walking and turning in early to moderate PD during DT

Launching of Conical Winds and Axial Jets from the Disk-Magnetosphere Boundary: Axisymmetric and 3D Simulations

We investigate the launching of outflows from the disk-magnetosphere boundary of slowly and rapidly rotating magnetized stars using axisymmetric and exploratory 3D magnetohydrodynamic (MHD) simulations. We find long-lasting outflows in both cases. (1) In the case of slowly rotating stars, a new type of outflow, a conical wind, is found and studied in simulations. The conical winds appear in cases where the magnetic flux of the star is bunched up by the disk into an X-type configuration. The winds have the shape of a thin conical shell with a half-opening angle 30-40 degrees. The conical winds may be responsible for episodic as well as long-lasting outflows in different types of stars. (2) In the case of rapidly rotating stars (the "propeller regime"), a two-component outflow is observed. One component is similar to the conical winds. A significant fraction of the disk matter may be ejected into the winds. A second component is a high-velocity, low-density magnetically dominated axial jet where matter flows along the opened polar field lines of the star. The jet has a mass flux about 10% that of the conical wind, but its energy flux (dominantly magnetic) can be larger than the energy flux of the conical wind. The jet's angular momentum flux (also dominantly magnetic) causes the star to spin-down rapidly. Propeller-driven outflows may be responsible for the jets in protostars and for their rapid spin-down. The jet is collimated by the magnetic force while the conical winds are only weakly collimated in the simulation region.Comment: 29 pages and 29 figures. This version has a major expansion after comments by a referee. The 1-st version is correct but mainly describes the conical wind. This version describes in greater detail both the conical winds and the propeller regime. Accepted to the MNRA

Visualizing sound emission of elephant vocalizations: evidence for two rumble production types

Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species'

Accretion, Outflows, and Winds of Magnetized Stars

Many types of stars have strong magnetic fields that can dynamically influence the flow of circumstellar matter. In stars with accretion disks, the stellar magnetic field can truncate the inner disk and determine the paths that matter can take to flow onto the star. These paths are different in stars with different magnetospheres and periods of rotation. External field lines of the magnetosphere may inflate and produce favorable conditions for outflows from the disk-magnetosphere boundary. Outflows can be particularly strong in the propeller regime, wherein a star rotates more rapidly than the inner disk. Outflows may also form at the disk-magnetosphere boundary of slowly rotating stars, if the magnetosphere is compressed by the accreting matter. In isolated, strongly magnetized stars, the magnetic field can influence formation and/or propagation of stellar wind outflows. Winds from low-mass, solar-type stars may be either thermally or magnetically driven, while winds from massive, luminous O and B type stars are radiatively driven. In all of these cases, the magnetic field influences matter flow from the stars and determines many observational properties. In this chapter we review recent studies of accretion, outflows, and winds of magnetized stars with a focus on three main topics: (1) accretion onto magnetized stars; (2) outflows from the disk-magnetosphere boundary; and (3) winds from isolated massive magnetized stars. We show results obtained from global magnetohydrodynamic simulations and, in a number of cases compare global simulations with observations.Comment: 60 pages, 44 figure

Testing of drift reducing maize sowing machines

Die meisten der heutzutage eingesetzten Maiseinzelkornsägeräte arbeiten mit Unterdruck. Im Süden Deutschlands sind insbesondere Monosem-Geräte aber auch Kuhn-, Amazone- und Gaspardo-Geräte im Einsatz. Das Hauptproblem der mit Unterdruck arbeitenden Geräte besteht darin, dass Staubabrieb hohe Mengen an Beizmittel enthält, der durch die Gebläseabluft an die Umgebung abgegeben wird und durch Abdrift auf nahe gelegene blühende Bestände gelangt (teilweise auch auf entferntere Bestände). Das Julius Kühn-Institut (JKI) hat in Abstimmung mit den Herstellern ein Abdriftmessverfahren erarbeitet, um modifizierte Maiseinzelkornsägeräte im Vergleich zu Standard-Sägeräten prüfen zu können. Im Herbst 2008 wurden die Sägeräte namhafter Hersteller vom Institut für Anwendungstechnik im Pflanzenschutz des JKI getestet und diejenigen, die eine Abdriftminderung von mindestens 90 % erreichten, in die JKI-Liste abdriftmindernder Maiseinzelkornsägeräte eingetragen. In der Zwischenzeit wurden die gesetzlichen Regelungen geändert, um eine höhere Beizqualität und eine Driftreduktion sicherzustellen. Die Aufhebung des Ruhens der Zulassung von Mesurol ist an die Bedingung geknüpft, dass mit Mesurol gebeiztes Maissaatgut nicht mit Unterdruck arbeitenden Sägeräten ausgebracht werden darf, es sei denn, diese Sägeräte sind modernisiert und erreichen eine Abdriftminderung von mehr als 90 %. Einzelkornsägeräte, die in der JKI-Liste „abdriftmindernde Maissägeräte“ eingetragen sind, erfüllen diese Anforderung. Diese Anforderungen sind nicht relevant für mechanisch oder mit Überdruck arbeitende Sägeräte. Maiseinzelkornsägeräte, die bereits im praktischen Einsatz sind, können mit diesen vom JKI geprüften und eingetragenen Nachrüstsätzen ausgestattet werden. Einzelkornsägeräte, für die es keine geprüften / gelisteten Nachrüstsätze gibt, können nicht mehr eingesetzt werden. Ein Umbau der Maiseinzelkornsägeräte durch den Landwirt selbst ist nicht erlaubt.The sowing machines used today are mostly precision airplanters with vacuum singling. In southern Germany, Monosem sowing machines are widespread but Kuhn, Amazone and Gaspardo are also used. The main problem with all sowing machines with vacuum singling is that abrasion dust which contains a lot of seed treatment products is blown through the fan outlet into the air and drifts to flowering plants nearby (but sometimes also further afield). Together with the manufacturers Julius Kühn-Institute (JKI) has established a drift test where modified sowing machines are tested against standard machines with high drift. In autumn 2008 the sowing machines of all well known manufacturers were tested by the Institute for Application Techniques in Plant Protection and those which proved a drift reduction of at least 90 % were registered in the JKI-list “drift reducing maize sowing machines“. In the meantime the legal regulations have been modified resulting in both a higher quality of seed coating as well as drift reduction. The first re-registration of an insecticide for maize seed shows that maize seed treated with Mesurol may not be sown by precision airplanters with vacuum singling unless they have been modernised so that a drift reduction of more than 90 % is guaranteed. Precision airplanters registered in the JKI-list “drift reducing maize sowing machines” fulfil these demands. This requirement is not relevant for precision airplanters with mechanical or overpressure singling. Precision airplanters for maize already used by farmers can be equipped with drift reduction kits tested and registered by the JKI. Precision airplanters, for which drift reduction kits have not been tested or listed, cannot be used any more. A modification of the sowing machines by the farmer himself is not allowed