Green Roofs Support a Wide Diversity of Collembola in Urban Portland, Oregon

Green roofs can help address habitat loss in urban areas by supporting plant and animal communities. To determine whether green roofs can support collembola biodiversity, we collected pitfall samples from April-June 2015 on two extensive and two intensive green roofs in urban Portland, Oregon. Twenty morphospecies were found across the roofs, indicating that green roofs support a diversity of collembola taxa. The intensive roofs were more biodiverse than the extensive, though roof type may not be the most significant factor affecting collembolan biodiversity. Each of the four green roofs were characterized by a different and unique most dominant morphospecies, and, indeed, each roof possessed a different set of top-three abundant collembola taxa. While green roofs support moderate collembola diversity, preserving natural habitat is important to maintain species richness

Startup failures: the research on the major factors causing the startup failures

The research is focused on finding out what are the major reasons for start up failures. To accomplish that, the survey on the founders of start ups that failed was conducted. The results were split into the general presentation and divided by the characteristics of companies such as a stage of development, number of founders, industry, type of financing, and business model. The critical factors of start up failures turned out to be Poor sales and marketing, Business model not viable, Not the right team, Other market problems (not enough traction, too niche market), Lack of financing. The results differ in the start ups with different characteristics

SXSAQCT and XSAQCT: XML Queryable Compressors

Recently, there has been a growing interest in queryable XML compressors, which can be used to query compressed data with minimal decompression, or even without any decompression. At the same time, there are very few such projects, which have been made available for testing and comparisons. In this paper, we report our current work on two novel queryable XML compressors; a schema-based compressor, SXSAQCT, and a schema-free compressor, XSAQCT. While the work on both compressors is in its early stage, our experiments (reported here) show that our approach may be successfully competing with other known queryable compressors

Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate

Nano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry

Comparative Laser Spectroscopy Diagnostics for Ancient Metallic Artefacts Exposed to Environmental Pollution

Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are recovered from excavation sites, as well as artefacts exposed to polluted air. Stabilization of the conservation state of these objects needs precise diagnostics of the accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. This paper presents analyses of the chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy. The discussion of the results is supported by material studies (SEM-EDS, XRF, ion-analyses). The tests were performed on several samples taken from original objects, including copper roofing from Wilanów Palace in Warsaw and Karol Poznański Palace in ŁódŸ, bronze decorative figures from the Wilanów Palace gardens, and four archaeological examples of old jewellery (different copper alloys). Work has been performed as a part of the MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu) and the results enable the comparison of the methodology and to elaborate the joint diagnostic procedures of the three project partner independent laboratories

Enhanced generation of VUV radiation by four-wave mixing in mercury using pulsed laser vaporization

The efficiency of a coherent VUV source at 125 nm, based on 2-photon resonant four-wave mixing in mercury vapor, has been enhanced by up to 2 orders of magnitude. This enhancement was obtained by locally heating a liquid Hg surface with a pulsed excimer laser, resulting in a high density vapor plume in which the nonlinear interaction occurred. Energies up to 5 μJ (1 kW peak power) have been achieved while keeping the overall Hg cell at room temperature, avoiding the use of a complex heat pipe. We have observed a strong saturation of the VUV yield when peak power densities of the fundamental beams exceed the GW/cm2 range, as well as a large intensity-dependant broadening (up to ~30 cm-1) of the two-photon resonance. The source has potential applications for high resolution interference lithography and photochemistry

Tuning the Reactivity of Nanoenergetic Gas Generators Based on Bismuth and Iodine oxidizers

There is a growing interest on novel energetic materials called Nanoenergetic Gas- Generators (NGGs) which are potential alternatives to traditional energetic materials including pyrotechnics, propellants, primers and solid rocket fuels. NGGs are formulations that utilize metal powders as a fuel and oxides or hydroxides as oxidizers that can rapidly release large amount of heat and gaseous products to generate shock waves. The heat and pressure discharge, impact sensitivity, long term stability and other critical properties depend on the particle size and shape, as well as assembling procedure and intermixing degree between the components. The extremely high energy density and the ability to tune the dynamic properties of the energetic system makes NGGs ideal candidates to dilute or replace traditional energetic materials for emerging applications. In terms of energy density, performance and controllability of dynamic properties, the energetic materials based on bismuth and iodine compounds are exceptional among the NGGs. The thermodynamic calculations and experimental study confirm that NGGs based on iodine and bismuth compounds mixed with aluminum nanoparticles are the most powerful formulations to date and can be used potentially in microthrusters technology with high thrust-to-weight ratio with controlled combustion and exhaust velocity for space applications. The resulting nano thermites generated significant value of pressure discharge up to 14.8 kPa m3/g. They can also be integrated with carbon nanotubes to form laminar composite yarns with high power actuation of up to 4700 W/kg, or be used in other emerging applications such as biocidal agents to effectively destroy harmful bacteria in seconds, with 22 mg/m2 minimal content over infected area

Determination of absolute H atom concentrations in low-pressure flames by two-photon laser-excited fluorescence

Bittner J, Kohse-Höinghaus K, Meier U, Kelm S, Just T. Determination of absolute H atom concentrations in low-pressure flames by two-photon laser-excited fluorescence. Combustion and Flame. 1988;71(1):41-50.A calibration technique is demonstrated which allows the determination of absolute atom concentrations in flames: two-photon laser-excited fluorescence signals from known atom concentrations generated in a discharge flow reactor are related to the fluorescence signals in a flame under identical excitation and detection conditions. With this method, absolute H atom profiles in several low-pressure hydrogen-oxygen flames have been obtained. For the same flame conditions, local temperature and absolute OH concentration profiles have been determined using laser-induced fluorescence (LIF). The experimental results are compared to the predictions of a one-dimensional flame model. The application of the new calibration technique to the atom detection in hydrocarbon flames is discussed

Ultrafast Laser-Based Spectroscopy and Sensing: Applications in LIBS, CARS, and THz Spectroscopy

Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), coherent Raman spectroscopy, and terahertz (THz) spectroscopy. Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications

Reseña sobre espectroscopia de rompimiento inducida por láser

Se presenta una reseña sobre la espectroscopia de rompimiento inducida por láser (LIBS). Asimismo, se presenta un recuento histórico sobre dicha técnica, su funcionamiento e instrumentación y una descripción de su configuración experimental en general. LIBS ha crecido significativamente convirtiéndose en una técnica rápida, fiable y adecuada para la detección y análisis espectral de los elementos constituyentes de la materia. El análisis de los elementos se puede hacer de manera simultánea e incluso en tiempo real de forma independiente de la naturaleza, origen y estado de agregación de las muestras. Se discuten los alcances y limitaciones de la técnica, así como sus potenciales aplicaciones en diversos campos tales como física, química, análisis de materiales, biomedicina, biotecnología, genómica, entre otros