Robust Line Planning in case of Multiple Pools and Disruptions

We consider the line planning problem in public transportation, under a robustness perspective. We present a mechanism for robust line planning in the case of multiple line pools, when the line operators have a different utility function per pool. We conduct an experimental study of our mechanism on both synthetic and real-world data that shows fast convergence to the optimum. We also explore a wide range of scenarios, varying from an arbitrary initial state (to be solved) to small disruptions in a previously optimal solution (to be recovered). Our experiments with the latter scenario show that our mechanism can be used as an online recovery scheme causing the system to re-converge to its optimum extremely fast.Comment: To appear in TAPAS 201

Molecular detection of vector-borne bacterial pathogens in dromedary camels from Algeria

Background: In Algeria, little focus was placed on camels as hosts of tick-borne bacterial diseases. Recent studies showed a high prevalence of tick infestation in dromedaries. Transmission of various pathogenic micro organisms to camels by ticks imposes considerable economic losses to livestock and greatly impact on human and animal health. The aim of our study was to investigate the occurrence of vector-borne zoonotic bacteria in camels from Algeria. Methodology: Blood samples were collected from 80 randomly selected camels in Laghouat province, southern Algeria. The samples were screened for Anaplasma spp, Bartonella spp, Rickettsia spp and Coxiella burnetii by qPCR. All positive samples were confirmed by standard PCR followed by sequencing. Data on age, sex, tick infestation and location of the camels were analyzed using the SPSS version 17.0 and association of these with vector-borne bacterial pathogens was determined using Chi-square (χ2) test. P value lower than 0.05 wasconsidered as indicative of significance. Results: Twenty five of the 80 (31.3%) camels were positive to at least one vector-borne bacterial pathogen with Anaplasma phagocytophilum (22.5%, 18/80) being the most prevalent species, followed by Anaplasma platys (7.5%, 6/80) and Bartonella dromedarii (2.5%, 2/80). Only one camel was co-infected with two pathogens. All samples tested negative for Rickettsia spp and Coxiella burnetii. None of the factors (age, sex, tick infestation and study sites) was significantly associated with prevalence of vector-borne bacteria in the camels (p>0.05). Conclusion: The present study is the first report of anaplasmosis and bartonellosis in "Camelus dromedaries" from Algeria. Our results highlighted the need for further investigations on tickborne pathogens of camels

Microscopic investigation of the Johari-Goldstein relaxation in cumene:Insights on the mosaic structure in a van der Waals liquid

The Johari-Goldstein (βJG) relaxation anticipates in time, and is closely connected to, the structural relaxation in deeply supercooled liquids. Probing its microscopic properties is a crucial step for a complete understanding of the glass-transition. We here report the investigation of the van der Waals glass-former cumene using time-domain interferometry, a technique able to probe microscopic density fluctuations at the spatial and temporal scales relevant for the βJG-relaxation. We find that the molecules participating in it undergo a restricted motion, though sufficient to induce local, cage-breaking events at the characteristic time-scale for molecular re-orientations. A detailed characterization of the relaxation strength, i.e. the fraction of molecules involved in the relaxation process, shows that such molecules are connected in a percolating cluster which, above the glass-transition temperature, Tg, is weakly dependent on temperature. Our results confirm thus previous observations of a mosaic structure associated to the βJG-relaxation in the supercooled state, and provide additional information on its temperature evolution above the glass-transition temperature. We conclude that the observed microscopic properties of the βJG-relaxation, and thus of the associated mosaic structure, are generic and independent of the molecular interaction potential. In addition, we show that, while the dynamics within the percolating cluster becomes progressively slower on approaching Tg, the fraction of the molecules involved in cage-breaking events within the βJG-relaxation is not affected by temperature.</p

Lattice dynamics of endotaxial silicide nanowires

Self-organized silicide nanowires are considered as main building blocks of future nanoelectronics and have been intensively investigated. In nanostructures, the lattice vibrational waves (phonons) deviate drastically from those in bulk crystals, which gives rise to anomalies in thermodynamic, elastic, electronic, and magnetic properties. Hence, a thorough understanding of the physical properties of these materials requires a comprehensive investigation of the lattice dynamics as a function of the nanowire size. We performed a systematic lattice dynamics study of endotaxial FeSi$_2$ nanowires, forming the metastable, surface-stabilized $\alpha$-phase, which are in-plane embedded into the Si(110) surface. The average widths of the nanowires ranged from 24 to 3 nm, their lengths ranged from several $\mu$m to about 100 nm. The Fe-partial phonon density of states, obtained by nuclear inelastic scattering, exhibits a broadening of the spectral features with decreasing nanowire width. The experimental data obtained along and across the nanowires unveiled a pronounced vibrational anisotropy that originates from the specific orientation of the tetragonal $\alpha$-FeSi$_2$ unit cell on the Si(110) surface. The results from first-principles calculations are fully consistent with the experimental data and allow for a comprehensive understanding of the lattice dynamics of endotaxial silicide nanowires.Comment: 9 pages, 7 figures, 3 table

Thermoelectric performance of n-type Mg2Ge

Magnesium-based thermoelectric materials (Mg2X, X = Si, Ge, Sn) have received considerable attention due to their availability, low toxicity, and reasonably good thermoelectric performance. The synthesis of these materials with high purity is challenging, however, due to the reactive nature and high vapour pressure of magnesium. In the current study, high purity single phase n-type Mg2Ge has been fabricated through a one-step reaction of MgH2 and elemental Ge, using spark plasma sintering (SPS) to reduce the formation of magnesium oxides due to the liberation of hydrogen. We have found that Bi has a very limited solubility in Mg2Ge and results in the precipitation of Mg2Bi3. Bismuth doping increases the electrical conductivity of Mg2Ge up to its solubility limit, beyond which the variation is minimal. The main improvement in the thermoelectric performance is originated from the significant phonon scattering achieved by the Mg2Bi3 precipitates located mainly at grain boundaries. This reduces the lattice thermal conductivity by ~50% and increases the maximum zT for n-type Mg2Ge to 0.32, compared to previously reported maximum value of 0.2 for Sb-doped Mg2Ge

Spiral magnetism, spin flop, and pressure induced ferromagnetism in the negative charge transfer gap insulator Sr2FeO4

Iron IV oxides are strongly correlated materials with negative charge transfer energy negative Delta , and exhibit peculiar electronic and magnetic properties such as topological helical spin structures in themetallic cubic perovskite SrFeO3. Here, the spin structure of the layered negative Delta insulator Sr2FeO4 was studied by powder neutron diffraction in zero field and magnetic fields up to 6.5 T. Below TN 56K, Sr2FeO4 adopts an elliptical cycloidal spin structure with modulated magnetic moments between 1.9 and 3.5 amp; 956;B and a propagation vector k amp; 964;, amp; 964;, 0 with amp; 964; 0.137. With increasing magnetic field the spin structure undergoes a spin flop transition near 5 T. Synchrotron 57Fe Mössbauer spectroscopy reveals that the spin spiral transforms to a ferromagnetic structure at pressures between 5 and 8 GPa, just in the pressure range where a Raman active phonon nonintrinsic to the K2NiF4 type crystal structure vanishes. These results indicate an insulating ground state which is stabilized by a hidden structural distortion and differs from the charge disproportionation in other Fe IV oxide