Frozen capillary waves on glass surfaces: an AFM study

Using atomic force microscopy on silica and float glass surfaces, we give evidence that the roughness of melted glass surfaces can be quantitatively accounted for by frozen capillary waves. In this framework the height spatial correlations are shown to obey a logarithmic scaling law; the identification of this behaviour allows to estimate the ratio $kT\_F/\pi\gamma$ where $k$ is the Boltzmann constant, $\gamma$ the interface tension and $T\_F$ the temperature corresponding to the ``freezing'' of the capillary waves. Variations of interface tension and (to a lesser extent) temperatures of annealing treatments are shown to be directly measurable from a statistical analysis of the roughness spectrum of the glass surfaces

Demonstration of a heterogeneously integrated III-V/SOI single wavelength tunable laser

A heterogeneously integrated III-V-on-silicon laser is reported, integrating a III-V gain section, a silicon ring resonator for wavelength selection and two silicon Bragg grating reflectors as back and front mirrors. Single wavelength operation with a side mode suppression ratio higher than 45 dB is obtained. An output power up to 10 mW at 20 °C and a thermo-optic wavelength tuning range of 8 nm are achieved. The laser linewidth is found to be 1.7 MHz

Quantitative AFM analysis of phase separated borosilicate glass surfaces

Phase separated borosilicate glass samples were prepared by applying various heat treatments. Using selective chemical etching we performed AFM measurement on the phase separated glass surfaces. A quantitative roughness analysis allowed us to measure precisely the dependence of the characteristic size of the phase domains on heating time and temperature. The experimental measurements are very well described by the theoretically expected scaling laws. Interdiffusion coefficients and activation energy are estimated from this analysis and are consistent with literature data

Apatite fission track thermochronology applied to igneous basement and sedimentary rocks from Amazonas Basin, in Itaituba region PA, Brazil

Com o intuito de contribuir para o entendimento da história termotectônica da borda sul da Bacia do Amazonas, foi aplicado o método Traços de Fissão em Apatita (TFA) em rochas ígneas paleoproterozoicas (~1,88 Ga), pertencentes ao embasamento, situadas na região de Itaituba (PA), bem como em uma amostra do arenito da sequência Pensilvaniano-Permiana. As idades TFA obtidas e a modelagem dos dados TFA revelaram para as rochas do embasamento, a existência de dois episódios de resfriamento separados por um período de aquecimento.O episódio de resfriamento mais antigo ocorrido na faixa de 280- 306 Ma pode revelar a exumação relacionada à aglutinação do Pangéia (320-270 Ma) e a deglaciação do Gondwana (~300 Ma). O segundo evento de resfriamento (117-98 Ma) pode estar relacionado à exuma- ção decorrente da reconhecida deformação das rochas da porção sudoeste da Bacia do Amazonas durante o Eocretáceo. A etapa intermediária de aquecimento pode estar relacionada ao magmatismo Penatecaua (~200 Ma) registrado na bacia, e associado à ruptura do Pangéia e formação do Atlântico Central. A rocha sedimentar da Bacia do Amazonas registrou o evento de soerguimento do Eocretáceo e revelou ainda a aceleração desse soerguimento/exumação a partir do início do Paleógeno.The apatite fission track thermochronology was used to investigate the thermotectonic evolution of the Amazonas Basin in the region of Itaituba (PA). The apatite fission track (AFT) data are mainly from the Paleoproterozoic igneous rocks of the basement (~1.88 Ga), as well as a sample of the sandstone sequence Pennsylvanian-Permian. The fission track ages and mathematical modeling data of the basement samples suggested two cooling/uplift events and a heating event between them. The older cooling/uplift event, starting between 306 and 280 Ma, may be associated with the Pangea amalgamation (320-270 Ma) and with the deglaciation of Gondwana (~300 Ma). The second cooling/uplift event, which started between 117 and 98 Ma may be related to the deformation (anticlines and inverse faults) in the rocks of the Amazonas Basin that occurred during the Upper Cretaceous. The heating event that occurred in between is associated with the widespread mafic magmatism related to break up of Pangea (~200 Ma) and formation of the Central Atlantic Ocean, known as Penatecaua magmatism in the Amazonas Basin. The ATF data for the sedimentary rock of the basin recorded the Upper Cretaceous uplift event and suggested a higher rate of exhumation in the beginning of the Paleogene

Spectral density of random graphs with topological constraints

The spectral density of random graphs with topological constraints is analysed using the replica method. We consider graph ensembles featuring generalised degree-degree correlations, as well as those with a community structure. In each case an exact solution is found for the spectral density in the form of consistency equations depending on the statistical properties of the graph ensemble in question. We highlight the effect of these topological constraints on the resulting spectral density.Comment: 24 pages, 6 figure

An analysis of 1.55 mu m InAs/InP quantum dash lasers

Calculations show that electron states are not confined in the dashes in 1.55 mu m InAs/InP quantum dash-in-a-well laser structures. The combination of strain and three-dimensional confinement reduces the calculated density of states (DOS) near the valence band maximum, with the conduction and valence DOS then almost equal close to the band edges. Calculations and photoabsorption measurements show strongly polarized spontaneous emission and gain spectra. Experimental analysis shows the room temperature threshold current is dominated by nonradiative current paths. (C) 2008 American Institute of Physics. (DOI: 10.1063/1.2952194

Probabilistic Reconstruction in Compressed Sensing: Algorithms, Phase Diagrams, and Threshold Achieving Matrices

Compressed sensing is a signal processing method that acquires data directly in a compressed form. This allows one to make less measurements than what was considered necessary to record a signal, enabling faster or more precise measurement protocols in a wide range of applications. Using an interdisciplinary approach, we have recently proposed in [arXiv:1109.4424] a strategy that allows compressed sensing to be performed at acquisition rates approaching to the theoretical optimal limits. In this paper, we give a more thorough presentation of our approach, and introduce many new results. We present the probabilistic approach to reconstruction and discuss its optimality and robustness. We detail the derivation of the message passing algorithm for reconstruction and expectation max- imization learning of signal-model parameters. We further develop the asymptotic analysis of the corresponding phase diagrams with and without measurement noise, for different distribution of signals, and discuss the best possible reconstruction performances regardless of the algorithm. We also present new efficient seeding matrices, test them on synthetic data and analyze their performance asymptotically.Comment: 42 pages, 37 figures, 3 appendixe