Spatio-temporal second-order quantum correlations of surface plasmon polaritons

We present an experimental methodology to observe spatio-temporal second-order quantum coherence of surface plasmon polaritons which are emitted by nitrogen vacancy color centers attached at the apex of an optical tip. The approach relies on leakage radiation microscopy in the Fourier space and we use this approach to test wave-particle duality for surface plasmon polaritons

The Phylogeny and Biogeography of the Monito del Monte (Dromiciops Gliroides) and its Relatives

Marsupials are a group of mammals that give birth to young that are not fully developed. These offspring must complete the remainder of their development outside of the womb attached to their mother’s teat. Marsupials only occur in South America and Australasia, with one species extending into North America. The marsupial known as the monito del monte, which is Spanish for ‘little monkey of the mountain,’ (Dromiciops gliroides) is a South American marsupial; however, it shares a key morphological feature of ankle bone morphology with Australasian marsupials. This shared, derived trait is what defines the cohort Australidelphia, to which the four Australasian orders of marsupials and the monito del monte belong. Because of this placement, the monito del monte appears to be a link between the South American and Australasian marsupials. By reviewing phylogenetic studies on marsupials, fossil evidence, biogeography, and extinct and extant marsupial and placental mammals of Australasia and South America, it is anticipated that the evolutionary history of marsupials will be better understood. The role of the monito del monte is pivotal in this story. The close relationship between the monito del monte and the Australasian marsupials was strongly supported by molecular, biogeographic, and fossil evidence, in addition to morphology. This thesis hypothesized that an ancient American marsupial dispersed across the supercontinent Gondwana and gave rise to the Australidelphians. Subsequently, dispersal is what brought the monito del monte to South America. Therefore, the Australidelphians, including the monito del monte, originated in Australasia

A survey of laser lightning rod techniques

The work done to create a laser lightning rod (LLR) is discussed. Some ongoing research which has the potential for achieving an operational laser lightning rod for use in the protection of missile launch sites, launch vehicles, and other property is discussed. Because of the ease with which a laser beam can be steered into any cloud overhead, an LLR could be used to ascertain if there exists enough charge in the clouds to discharge to the ground as triggered lightning. This leads to the possibility of using LLRs to test clouds prior to launching missiles through the clouds or prior to flying aircraft through the clouds. LLRs could also be used to probe and discharge clouds before or during any hazardous ground operations. Thus, an operational LLR may be able to both detect such sub-critical electrical fields and effectively neutralize them

Creating Harmony from Diversity: What Confucianism Reveals about the True Value of Liberal Education for the 21st Century

This paper takes inspiration from Confucius’s teachings on social harmony to suggest that the most salient defense of a liberal education is that it is the indispensible means by which to parlay our increasingly diverse student populations into a more harmonious global society for the 21st century and beyond. Given the ever-increasing diversity of local communities and the globality of our social and professional lives as the significance of political boundaries and local citizenship fades, traditional defenses of a liberal education on the grounds that it prepares students for meaningful participation in local democracies or that it abstractly enhances life satisfaction, while valid, are no longer sufficient. Realizing that Confucius understood diversity on many levels as essential to cultivating social and universal harmony may help to reveal greater contemporary relevance of his teachings and bolster advocacy for a liberal education

Prediction of Fretting-fatigue Crack Nucleation Using a Surface Shear - Sliding Size Crack Analog Parameter

AbstractFretting fatigue is a critical load that appears on many structures, such as the blade/disk contact of aircraft engines, train wheel assemblies, etc. Predicting crack nucleation risk is essential for safety, but is particularly complex. Fretting contact stress is multiaxial, with severe stress gradients. To palliate this difficulty, a common approach consists in computing multiaxial fatigue at a critical distance, thus correcting the stress gradient effect and achieving stable pertinent predictions. However, this strategy is very costly in FEM computation due to very fine FEM mesh size, which may be <10μm, and application needs to be limited in large 3D industrial contacts. Investigating the partial slip fretting crack nucleation boundaries of 35NCD16 steel (plane) fretted against 52100 steel cylinders, a new semi-empirical contact loading parameter was introduced, defined as the maximum shear stress generated in the interface (qmax) multiplied by the square-root of the sliding size (s) of the partial slip interface (i.e., ϕ = qmax ×√s). Using this very simple parameter inspired by “crack analog strategy”, it was found that all the crack nucleation data obtained for a wide spectrum of contact pressures and cylinder radii were aligned along a single master curve. Scatter was very low, even less than for the costly “fatigue-critical distance method”. The approach was extended to various fretting-fatigue loading conditions, confirming stability of prediction

Near-field microscopy with a scanning nitrogen-vacancy color center in a diamond nanocrystal: A brief review

We review our recent developments of near-field scanning optical microscopy (NSOM) that uses an active tip made of a single fluorescent nanodiamond (ND) grafted onto the apex of a substrate fiber tip. The ND hosting a limited number of nitrogen-vacancy (NV) color centers, such a tip is a scanning quantum source of light. The method for preparing the ND-based tips and their basic properties are summarized. Then we discuss theoretically the concept of spatial resolution that is achievable in this special NSOM configuration and find it to be only limited by the scan height over the imaged system, in contrast with the standard aperture-tip NSOM whose resolution depends critically on both the scan height and aperture diameter. Finally, we describe a scheme we have introduced recently for high-resolution imaging of nanoplasmonic structures with ND-based tips that is capable of approaching the ultimate resolution anticipated by theory.Comment: AD, AC, OM, MB and SH wish to dedicate this brief review article to their co-author and colleague Yannick Sonnefraud who passed away in September 2014. Yannick initiated this research in 200

Photophysics of single nitrogen-vacancy centers in diamond nanocrystals

A study of the photophysical properties of nitrogen-vacancy (NV) color centers in diamond nanocrystals of size of 50~nm or below is carried out by means of second-order time-intensity photon correlation and cross-correlation measurements as a function of the excitation power for both pure charge states, neutral and negatively charged, as well as for the photochromic state, where the center switches between both states at any power. A dedicated three-level model implying a shelving level is developed to extract the relevant photophysical parameters coupling all three levels. Our analysis confirms the very existence of the shelving level for the neutral NV center. It is found that it plays a negligible role on the photophysics of this center, whereas it is responsible for an increasing photon bunching behavior of the negative NV center with increasing power. From the photophysical parameters, we infer a quantum efficiency for both centers, showing that it remains close to unity for the neutral center over the entire power range, whereas it drops with increasing power from near unity to approximately 0.5 for the negative center. The photophysics of the photochromic center reveals a rich phenomenology that is to a large extent dominated by that of the negative state, in agreement with the excess charge release of the negative center being much slower than the photon emission process

From uni- to multi-axial fretting-fatigue crack nucleation: Development of a stress-gradient-dependent critical distance approach

International audienceFretting fatigue is characterized by combined high stress gradients induced by contact loading and more homogeneous stress gradients induced by bulk fatigue stressing. The stress gradients computed at the "hot-spot" located on the surface at the trailing contact border are very high, usually above 10 GPa/mm. For such uncommon stressing conditions, prediction of cracking risk becomes very complex and non-local fatigue approaches must be adopted. The purpose of the present study was to investigate how non-local strategies, such as "critical distance", developed for medium stress gradient conditions such as "notch" configurations, were transposed to predict fretting cracking risk. Elastic crack nucleation conditions of a 35 Ni Cr Mo 16 low alloyed steel at 10E6 cycles have been identified for various cylinder pad radius, contact pressure and fatigue stress conditions. The experimental crack nucleation conditions were then compared to predictions from analytical simulations coupling uni-axial and Crossland's multiaxial fatigue descriptions. The local "hot-spot" analysis systematically overestimated cracking risk and induced more than 30% error with respect to the experimental values. The non-local "critical distance method" based on a constant length scale value still displayed more than 10% dispersion suggesting that a non-constant "critical distance" approach must be considered. By expressing the critical distance evolution as a function of the hydrostatic stress gradient operating next to the stress hot-spot, dispersion was reduced below 5%. Established for the Crossland's stress invariant formulation, this tendency is confirmed by comparing McDiarmid and MWCM critical plane fatigue approaches