Optical Monitoring of the Seyfert Galaxy NGC 4151 and Possible Periodicities in the Historical Light Curve

We report B, V, and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0-m telescope at Weihai Observatory of Shandong University and the 1.56-m telescope at Shanghai Astronomical Observatory from 2005 December to 2013 February. Combining all available data from literature, we have constructed a historical light curve from 1910 to 2013 to study the periodicity of the source using three different methods (the Jurkevich method, the Lomb-Scargle periodogram method and the Discrete Correlation Function method). We find possible periods of P_1=4\pm0.1, P_2=7.5\pm0.3 and P_3=15.9\pm0.3 yr.Comment: 8 pages, 5 figures, Accepted by Research in Astronomy and Astrophysic

Stress equivalence principle for saturated porous media

The stress equivalence principle for saturated porous media is studied in the plastic domain using a homogenization approach. The skeleton is composed of a micro-isotropic and micro-homogeneous material. The stress localization law in saturated porous media is first obtained. This makes it possible to define an appropriate effective stress tensor in the sense of the stress equivalence principle. The form of the effective stress tensor is examined for two particular yield functions of skeleton material

Premedication with dexmedetomidine in pediatric patients: a systematic review and meta-analysis

Premedication is important in pediatric anesthesia. This meta-analysis aimed to investigate the role of dexmedetomidine as a premedicant for pediatric patients. A systematic literature search was conducted to identify randomized controlled trials comparing dexmedetomidine premedication with midazolam or ketamine premedication or placebo in children. Two reviewers independently performed the study selection, quality assessment and data extraction. The original data were pooled for the meta-analysis with Review Manager 5. The main parameters investigated included satisfactory separation from parents, satisfactory mask induction, postoperative rescue analgesia, emergence agitation and postoperative nausea and vomiting. Thirteen randomized controlled trials involving 1190 patients were included. When compared with midazolam, premedication with dexmedetomidine resulted in an increase in satisfactory separation from parents (RD = 0.18, 95% CI: 0.06 to 0.30, p = 0.003) and a decrease in the use of postoperative rescue analgesia (RD = -0.19, 95% CI: -0.29 to -0.09, p = 0.0003). Children treated with dexmedetomidine had a lower heart rate before induction. The incidence of satisfactory mask induction, emergence agitation and PONV did not differ between the groups. Dexmedetomidine was superior in providing satisfactory intravenous cannulation compared to placebo. This meta-analysis suggests that dexmedetomidine is superior to midazolam premedication because it resulted in enhanced preoperative sedation and decreased postoperative pain. Additional studies are needed to evaluate the dosing schemes and long-term outcomes of dexmedetomidine premedication in pediatric anesthesia

Realization of Zero-Refractive-Index Lens with Ultralow Spherical Aberration

Optical complex materials offer unprecedented opportunity to engineer fundamental band dispersion which enables novel optoelectronic functionality and devices. Exploration of photonic Dirac cone at the center of momentum space has inspired an exceptional characteristic of zero-index, which is similar to zero effective mass in fermionic Dirac systems. Such all-dielectric zero-index photonic crystals provide an in-plane mechanism such that the energy of the propagating waves can be well confined along the chip direction. A straightforward example is to achieve the anomalous focusing effect without longitudinal spherical aberration, when the size of zero-index lens is large enough. Here, we designed and fabricated a prototype of zero-refractive-index lens by comprising large-area silicon nanopillar array with plane-concave profile. Near-zero refractive index was quantitatively measured near 1.55 um through anomalous focusing effect, predictable by effective medium theory. The zero-index lens was also demonstrated to perform ultralow longitudinal spherical aberration. Such IC compatible device provides a new route to integrate all-silicon zero-index materials into optical communication, sensing, and modulation, and to study fundamental physics on the emergent fields of topological photonics and valley photonics.Comment: 14 pages, 4 figure

Possible approach to improve sensitivity of a Michelson interferometer

We propose a possible approach to achieve an 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems might be lower than the quantum approaches and the sensitivity improvement is frequency independent in all detection band.Comment: 8 pages, 3 figures, new versio

Effet de resaturation sur le comportement mécanique de mortier

Le présent travail s'intéresse à l'effet de resaturation sur le comportement mécanique d'un mortier normal mature. Aussi, des essais de compression uniaxiale et triaxiale déviatorique ont-ils été réalisés en fonction de l'état de saturation (saturé, séché à 60°C jusqu'à poids constant, resaturé à différents degrés). Il a été observé que les résistances à la compression uniaxiale et triaxiale déviatorique diminuent avec la resaturation après une première augmentation due au séchage. Les éprouvettes resaturées sous vide ont une résistance plus faible que les éprouvettes saturées à cause de la microfissuration induite par séchage notamment, mais cette chute est moins prononcée dans le cas de la compression déviatorique du fait de la présence d'un confinement. Une diminution du module d'Young, venant s'ajouter à celle due au séchage, a également été constatée après resaturation sous vide mais uniquement en compression uniaxiale. Par ailleurs, la contrainte de limite élastique dépend du degré de resaturation. L'ensemble des résultats obtenus montre ainsi la nécessité de prendre en compte les effets de séchage et de resaturation dans l'évaluation de la durabilité des matériaux à matrice cimentaire

Caractérisation des propriétés mécaniques des roches par micro-indentation

Cette étude est consacrée à la détermination des propriétés mécaniques des roches isotropes, et isotropes transverse à l’aide de la technique de micro indentation. Après avoir présenté le principe de la micro indentation, nous rappelons le cadre théorique permettant le dépouillement des résultats (courbe force-déplacement de l’indenteur) ainsi que la détermination des propriétés élastiques dans un contexte isotrope, et isotrope transverse. Nous présentons ensuite l’exploitation de l’essai pour identifier l’endommagement isotrope dû à des sollicitations thermiques (cas du grès de Fontainebleau). Enfin, on étudie l’influence de l’humidité relative sur les paramètres mécaniques de l’argilite du Callovo Oxfordien qui est une roche isotrope transverse