The Ring Dye Laser as a Source for Two-Photon Excited Fluorescence

ABSTRACT

The near-Gaussian beam profile, low pulse-to-pulse amplitude fluctuation and amenability to simple signal processing make synchronously-pumped dye lasers, both continuous and cavity-dumped, excellent sources for two-photon spectroscopy. In recent years attention has shifted from the more common standing wave configuration to a traveling wave ring laser of synchronous length. The continuous variant has proven to be a source with a detectivity for two-photon excited fluorescence equal to the cavity-dumped, standing wave laser but without the added optical and electronic complexity of the Bragg cell. However, cavity gain/loss, bandwidth and length changes influence pulse characteristics to a different extent than in standing wave lasers. These effects are discussed relative to both the two-color, two-photon experiment and overall instrumental design considerations.     

Social licence: power imbalances and levels of consciousness – two case studies

ABSTRACT

Social licence to operate (SLO) is a term that is finding increasing acceptance in a number of industries. Like all new terms, its precise meaning and implications are still being investigated. Using data from previous studies, this paper offers an analysis of the SLO of two case studies with each study being viewed separately through the grid of a distinct theoretical framework. Case study 1 looks at the development of differential social licence negotiated in the Hamlet of Cambridge Bay, Nunavut, as a result of an impact and benefit agreement negotiated between Tahera Diamond Corp. and the Kitikmeot Inuit Organisation in 2004. The study demonstrates that general acceptance of resource development can be uneven and reflect an unequal distribution of decision-making power. In case study 2, stakeholders of a failed mineral development project were queried across time about the specifics of the proposed mine development and were queried about resource development across different levels of consciousness. Perhaps, SLO is variable across different levels of consciousness. The paper concludes with observations about the variable nature of SLO acceptance across populations and across levels of consciousness within individuals. Perhaps, the concept of SLO is, in fact, complex, difficult to define and measure and, at this point, of limited utility as a measure of resource development acceptance.     

Automatic reconstruction of as-built building information models from laser-scanned point clouds: A review of related techniques

Building information models (BIMs) are maturing as a new paradigm for storing and exchanging knowledge about a facility. BIMs constructed from a CAD model do not generally capture details of a facility as it was actually built. Laser scanners can be used to capture dense 3D measurements of a facility's as-built condition and the resulting point cloud can be manually processed to create an as-built BIM — a time-consuming, subjective, and error-prone process that could benefit significantly from automation. This article surveys techniques developed in civil engineering and computer science that can be utilized to automate the process of creating as-built BIMs. We sub-divide the overall process into three core operations: geometric modeling, object recognition, and object relationship modeling. We survey the state-of-the-art methods for each operation and discuss their potential application to automated as-built BIM creation. We also outline the main methods used by these algorithms for representing knowledge about shape, identity, and relationships. In addition, we formalize the possible variations of the overall as-built BIM creation problem and outline performance evaluation measures for comparing as-built BIM creation algorithms and tracking progress of the field. Finally, we identify and discuss technology gaps that need to be addressed in future research.     

Performance of submillimeter square hollow waveguides

Propagation losses are determined for 100 microm x 100 microm square, hollow waveguides constructed from glass capillaries. The small size makes it possible to observe optical effects not easily seen with larger waveguides. The depletion of higher-order even modes creates a large, nonlinear loss. Over a distance of a meter the loss approaches the smaller, linear value expected for the fundamental mode. Additionally, the lowest two even modes beat to produce an oscillatory loss with a period of approximately 2 cm. Making the focal radius 0.35 the waveguide width minimizes these two effects. In a related study, 50-microm waveguides embossed in polydimethylsiloxane are shown to have losses similar to glass capillaries.     

Intraoperative echocardiography is indicated in high-risk coronary artery bypass grafting

BACKGROUND: Intraoperative echocardiography is a valuable monitoring and diagnostic technology used in cardiac surgery. This reports our clinical study of the usefulness of intraoperative echocardiography to both surgeons and anesthesiologists for high-risk coronary artery bypass grafting. METHODS: From March to November 1995, 82 consecutive high-risk patients undergoing coronary artery bypass grafting were studied in a four-stage protocol to determine the efficacy of intraoperative echocardiography in management planning. Alterations in surgical and anesthetic/hemodynamic management initiated by intraoperative echocardiography findings were documented in addition to perioperative morbidity and mortality. RESULTS: Intraoperative echocardiography initiated at least one major surgical management alteration in 27 patients (33%) and at least one major anesthetic/hemodynamic change in 42 (51%). Mortality and the rate of myocardial infarction in this consecutive high-risk study population using intraoperative echocardiography and in a similar group of patients without the use of intraoperative echocardiography was 1.2% versus 3.8% (not significant) and 1.2% versus 3.5% (not significant), respectively. CONCLUSIONS: We conclude that when all of the isolated diagnostic and monitoring applications of perioperative echocardiography are routinely and systematically performed together, it is a safe and viable tool that significantly affects the decision-making process in the intraoperative care of high-risk patients undergoing primary isolated coronary artery bypass grafting and may contribute to the optimal care of these patients.     

Inside Front Cover: Photonic Crystal Structures as a Basis for a Three‐Dimensionally Interpenetrating Electrochemical‐Cell System (Adv. Mater. 13/2006)

The inside cover shows an SEM image of a 3D‐interpenetrating electrochemical cell with submicrometer features, as reported by Stein and coworkers on p. 1750. The pores of an inverse‐opal carbon electrode are coated with a conformal layer of a polymer separator and infiltrated with vanadia to form the opposite electrode after lithiation. The idealized scheme illustrates lithium‐ion transport between the electrodes through the polymer membrane.     

Physiochemical characterization of five iron tubercles from a single drinking water distribution system: Possible new insights on their formation and growth

Physiochemical data were obtained for five iron tubercles from a single drinking water distribution system (DS). Texturally, there were two groups based on internal morphology: one with a core of soft brownish material marbled with veins of a hard black material, the other has a core consisting mostly of the hard, black material. Three iron mineral phases occur, α-FeOOH, γ-FeOOH, or Fe₃O₄. All three coexist in each tubercle but in widely varying proportions. These iron pipe tubercles exhibit a greater diversity within a single DS than previously thought. Because the chemical conditions for the formation of each material is different, water quality parameters may not be the main control of tubercle formation and growth.     

Detecting High-Contrast Seismic Anomalies Using Cross-Borehole Probing

Seismic probing between boreholes is useful for locating high-contrast geophysical anomalies such as an abandoned tunnel. Theoretical studies of continuous wave (CW) seismic wave interaction with a tunnel show that both the signal minima and the phase structure of the received signal can be used for locating the anomaly. The theoretical studies show that as the source and receiver are lowered in separate boreholes straddling the anomaly, the signal minima and the phase structure can be interpreted to yield both the lateral and vertical positions of the anomaly. Plane waves of compressional, horizontally polarized shear, and vertically polarized shear wave types incident on a cylindrical horizontal anomaly have been considered. The total seismic field has been calculated using an exact formulation. The variation of the response is studied as a function of the ratio of anomaly diameter to wavelength. The resulting fields in the receiver borehole are an effective diagnostic when a wavelength in the surrounding medium is less than or equal to the diameter of the anomaly. These results are analogous to the corresponding electromagnetic case which has been studied previously.