Field dependent anisotropy change in a supramolecular Mn(II)-[3x3] grid

The magnetic anisotropy of a novel Mn(II)-[3x3] grid complex was investigated by means of high-field torque magnetometry. Torque vs. field curves at low temperatures demonstrate a ground state with S > 0 and exhibit a torque step due to a field induced level-crossing at B* \approx 7.5 T, accompanied by an abrupt change of magnetic anisotropy from easy-axis to hard-axis type. These observations are discussed in terms of a spin Hamiltonian formalism.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let

Ferromagnetic coupling and magnetic anisotropy in molecular Ni(II) squares

We investigated the magnetic properties of two isostructural Ni(II) metal complexes [Ni4Lb8] and [Ni4Lc8]. In each molecule the four Ni(II) centers form almost perfect regular squares. Magnetic coupling and anisotropy of single crystals were examined by magnetization measurements and in particular by high-field torque magnetometry at low temperatures. The data were analyzed in terms of an effective spin Hamiltonian appropriate for Ni(II) centers. For both compounds, we found a weak intramolecular ferromagnetic coupling of the four Ni(II) spins and sizable single-ion anisotropies of the easy-axis type. The coupling strengths are roughly identical for both compounds, whereas the zero-field-splitting parameters are significantly different. Possible reasons for this observation are discussed.Comment: 7 pages, 7 figure

Dreaming of atmospheres

Here we introduce the RobERt (Robotic Exoplanet Recognition) algorithm for the classification of exoplanetary emission spectra. Spectral retrievals of exoplanetary atmospheres frequently requires the preselection of molecular/atomic opacities to be defined by the user. In the era of open-source, automated and self-sufficient retrieval algorithms, manual input should be avoided. User dependent input could, in worst case scenarios, lead to incomplete models and biases in the retrieval. The RobERt algorithm is based on deep belief neural (DBN) networks trained to accurately recognise molecular signatures for a wide range of planets, atmospheric thermal profiles and compositions. Reconstructions of the learned features, also referred to as `dreams' of the network, indicate good convergence and an accurate representation of molecular features in the DBN. Using these deep neural networks, we work towards retrieval algorithms that themselves understand the nature of the observed spectra, are able to learn from current and past data and make sensible qualitative preselections of atmospheric opacities to be used for the quantitative stage of the retrieval process.Comment: ApJ accepte

Locally Noncommutative Space-Times

Localized noncommutative structures for manifolds with connection are constructed based on the use of vertical star products. The model's main feature is that two points that are far away from each other will not be subject to a deviation from classical geometry while space-time becomes noncommutative for pairs of points that are close to one another.Comment: 28 pages, 7 figure

Electron Spectroscopy and Density-Functional Study of "Ferric Wheel" Molecules

The Li-centered "ferric wheel" molecules with six oxo-bridged iron atoms form molecular crystals. We probed their electronic structure by X-ray photoelectron (XPS) and soft X-ray emission spectroscopy (XES), having calculated in parallel the electronic structure of a single "ferric wheel" molecule from first-principles by tools of the density-functional theory, using, specifically, the Siesta method. The Fe local moments were found to be 4 mu_B, irrespective of their mutual orientation. Neighbouring atoms, primarily oxygen, exhibit a noticeable magnetic polarization, yielding effective spin S=5/2 per iron atom, that can get inverted as a "rigid" one in magnetic transitions. Corresponding energy preferences can be mapped onto the Heisenberg model with effective exchange parameter J of about -80 K.Comment: 8 pages with 3 embedded postscript figures; uses elsart.cls; contribution at the E-MRS 2003 Spring Meeting (Strasbourg, June 2003

Further Perspectives on Corporate Wrongdoing, In Pari Delicto, and Auditor Malpractice

In recent years, instant messaging (IM) has started to replace short message service (SMS) in communication. IM offers more functionality but there is a great downside. IM demands more power and drains the mobile device battery faster. This paper shows the energy consumption of  IM when the user is not using the application and how the consumption  can be reduced by enabling mobile sensors and sending fewer packets by the application. We began by investigating the various sensors that are supported by mobile devices. With the retrieved vendor information, we evaluated the different sensors and chose two sensors, light sensor and proximity sensor in order to study their use for reduction of energy in  an instant messaging scenario. These two sensors can together estimate if the mobile device is placed in the pocket of the user. The development of a simple IM application was completed and sensors were used to create an extension to the application. The extension would lengthen the interval between the updates of the automatic update function when the mobile was inactive, reducing the energy consumption. Two types of tests were performed. The first test evaluated if the extension would correctly deduce that the mobile device was placed inside a pocket. The mobile device with the pocket-aware application was used in different common situations and the tests showed that the extension made a correct computation in seven of nine situations. The faulty situations were when the mobile device is placed with the screen faced down to a surface. The second test compared the energy consumed by a pocket-aware application compared to a mobile device without our extension. Based on the results that we retrieved, we estimated that during a one minute period the pocket-aware application with an update interval of ten seconds could save on average 12% and could save on average 62% when the update interval was increased to fifteen seconds