Mapping curie point depth of the west African Craton from satellite magnetic data and its implication for diamond exploration

The main objective of this work is to map the Curie depth of the West African Craton (WAC) using satellite magnetic data with the aim to provide first order evaluation, within this vast territory, for the spatial association between Curie-depth surface and known kimberlite locations. Taking into account Clifford's rule, the first and foremost exploration guideline for diamond exploration is the existence of a sufficiently thick lithosphere that expected to have a low surface heat flow. The Curie depth is closely related to the surface heat-flow conditions and lithosphere thickness. In actual fact, the only few regions that have sufficient density of surface heat flow measurements corroborate the association of these conditions with the diamond resources. To better explore in an efficient way the spatial relationship between the Curie depth and known diamondiferous primary sources within the WAC, we used GIS-based weights of evidence method to provide a quantitative analysi

The structures and dipole moments of Ar–PF3 and Kr–PF3

The complexes of PF3 with Ar and Kr, were studied by Fourier transform microwave spectroscopy. The force constants and amplitudes of vibration for the van der Waals modes of the complexes and the average moments of inertia and structural parameters were estimated from the centrifugal distortion constants. The distance (Rc.m. )ave between the rare‐gas atom and the center of mass of PF3 is 3.959 Å for the Ar complex and 4.077 Å for Kr while the angle (θc.m. )ave between the Rc.m. vector and the C3 axis of the PF3 is 69.30° and 67.25°, respectively. The dipole moments of both complexes and of free PF3 were determined. The induced dipole components estimated for the rare gas using electric fields from ab initio calculations of PF3 agree with the experimental values for a conformation with the rare gas over a PF2 face. The PF2 face conformation is also consistent with the observed and ab initio estimates of the 83 Kr nuclear quadrupole coupling constant for the 83 Kr–PF3 species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70747/2/JCPSA6-90-12-6949-1.pd

Local Optical Probe of Motion and Stress in a multilayer graphene NEMS

Nanoelectromechanical systems (NEMSs) are emerging nanoscale elements at the crossroads between mechanics, optics and electronics, with significant potential for actuation and sensing applications. The reduction of dimensions compared to their micronic counterparts brings new effects including sensitivity to very low mass, resonant frequencies in the radiofrequency range, mechanical non-linearities and observation of quantum mechanical effects. An important issue of NEMS is the understanding of fundamental physical properties conditioning dissipation mechanisms, known to limit mechanical quality factors and to induce aging due to material degradation. There is a need for detection methods tailored for these systems which allow probing motion and stress at the nanometer scale. Here, we show a non-invasive local optical probe for the quantitative measurement of motion and stress within a multilayer graphene NEMS provided by a combination of Fizeau interferences, Raman spectroscopy and electrostatically actuated mirror. Interferometry provides a calibrated measurement of the motion, resulting from an actuation ranging from a quasi-static load up to the mechanical resonance while Raman spectroscopy allows a purely spectral detection of mechanical resonance at the nanoscale. Such spectroscopic detection reveals the coupling between a strained nano-resonator and the energy of an inelastically scattered photon, and thus offers a new approach for optomechanics

Weakly Trapped, Charged, and Free Excitons in Single-Layer MoS2 in the Presence of Defects, Strain, and Charged Impurities

Few- and single-layer MoS2 host substantial densities of defects. They are thought to influence the doping level, the crystal structure, and the binding of electron-hole pairs. We disentangle the concomitant spectroscopic expression of all three effects and identify to what extent they are intrinsic to the material or extrinsic to it, i.e., related to its local environment. We do so by using different sources of MoS2 - a natural one and one prepared at high pressure and high temperature - and different substrates bringing varying amounts of charged impurities and by separating the contributions of internal strain and doping in Raman spectra. Photoluminescence unveils various optically active excitonic complexes. We discover a defect-bound state having a low binding energy of 20 meV that does not appear sensitive to strain and doping, unlike charged excitons. Conversely, the defect does not significantly dope or strain MoS2. Scanning tunneling microscopy and density functional theory simulations point to substitutional atoms, presumably individual nitrogen atoms at the sulfur site. Our work shows the way to a systematic understanding of the effect of external and internal fields on the optical properties of two-dimensional materials

UNSUPERVISED CLASSIFICATION BASED NEGATIVE SELECTION ALGORITHM

In  the  last decade, artificial  life has been considered as a promising area  for  rising challenges  to unresolved computational problems. Inspired by natural phenomena, its study focuses on the exploration of complex systems. Neuronal networks, genetic algorithms  and more  recently  artificial  immune  systems  are  examples. Artificial  Immune  Systems  (AIS)  are  one  type  of intelligent algorithms  inspired by  the principles and processes of  the human  immune system. Emulating  the discrimination mechanism of the natural system, negative selection algorithm of AIS has been successfully applied on change and anomaly detection.  This paper describes  initial  investigations  in applying negative  selection algorithm on pixel classification by maintaining a population of detectors that remove undesired patterns. Its purpose is to find several detectors which do not match to self in the population. We make use of an Euclidian space with an Euclidian performance measure on color images. The experimental show promising results. The obtained classifier is effective and feasible