1,666 research outputs found

    A longitudinal project of new venture teamwork and outcomes

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    This chapter present a research project dedicated to better understand how new venture teams work together to achieve desired outcomes. Teams, as opposed to an individual, start a majority of all innovative new ventures. Yet, little research or theory exists in new venture settings about how members interact with each other over time—teamwork—to produce innovative technologies, products, and services. We believe a systematic study of social and psychological processes that underlie new venture teamwork and venture outcomes is timely and important. Unique features of our research project include: (1) a team level focus on social and psychological processes, to assess relations to proximal (e.g., innovation, first sales and team satisfaction), and distal value creation outcomes (e.g., sales growth, raised capital and profits). (2) Combined qualitative and quantitative research methodologies to provide both theory building and theory testing for the relations of interest. (3) A time-sequential design with data collection every three months over one year to allow us to investigate the relations of interest for new ventures

    Tropospheric methane retrieved from ground-based near-IR solar absorption spectra

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    High-resolution near-infrared solar absorption spectra recorded between 1977 and 1995 at the Kitt Peak National Solar Observatory are analyzed to retrieve column abundances of methane (CH_4), hydrogen fluoride (HF), and oxygen (O_2). Employing a stratospheric “slope equilibrium” relationship between CH_4 and HF, the varying contribution of stratospheric CH_4 to the total column is inferred. Variations in the CH_4 column due to changes in surface pressure are determined from the O_2 column abundances. By this technique, CH_4 tropospheric volume mixing ratios are determined with a precision of ∼0.5%. These display behavior similar to Mauna Loa in situ surface measurements, with a seasonal peak-to-peak amplitude of approximately 30 ppbv and a nearly linear increase between 1977 and 1983 of 18.0 ± 0.8 ppbv yr^(−1), slowing significantly after 1990

    Emission factors for open and domestic biomass burning for use in atmospheric models

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    Biomass burning (BB) is the second largest source of trace gases and the largest source of primary fine carbonaceous particles in the global troposphere. Many recent BB studies have provided new emission factor (EF) measurements. This is especially true for non-methane organic compounds (NMOC), which influence secondary organic aerosol (SOA) and ozone formation. New EF should improve regional to global BB emissions estimates and therefore, the input for atmospheric models. In this work we present an up-to-date, comprehensive tabulation of EF for known pyrogenic species based on measurements made in smoke that has cooled to ambient temperature, but not yet undergone significant photochemical processing. All EFs are converted to one standard form (g compound emitted per kg dry biomass burned) using the carbon mass balance method and they are categorized into 14 fuel or vegetation types. Biomass burning terminology is defined to promote consistency. We compile a large number of measurements of biomass consumption per unit area for important fire types and summarize several recent estimates of global biomass consumption by the major types of biomass burning. Post emission processes are discussed to provide a context for the emission factor concept within overall atmospheric chemistry and also highlight the potential for rapid changes relative to the scale of some models or remote sensing products. Recent work shows that individual biomass fires emit significantly more gas-phase NMOC than previously thought and that including additional NMOC can improve photochemical model performance. A detailed global estimate suggests that BB emits at least 400 Tg yr^(−1) of gas-phase NMOC, which is almost 3 times larger than most previous estimates. Selected recent results (e.g. measurements of HONO and the BB tracers HCN and CH_3CN) are highlighted and key areas requiring future research are briefly discussed

    An analysis of fast photochemistry over high northern latitudes during spring and summer using in-situ observations from ARCTAS and TOPSE

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    Observations of chemical constituents and meteorological quantities obtained during the two Arctic phases of the airborne campaign ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) are analyzed using an observationally constrained steady state box model. Measurements of OH and HO_2 from the Penn State ATHOS instrument are compared to model predictions. Forty percent of OH measurements below 2 km are at the limit of detection during the spring phase (ARCTAS-A). While the median observed-to-calculated ratio is near one, both the scatter of observations and the model uncertainty for OH are at the magnitude of ambient values. During the summer phase (ARCTAS-B), model predictions of OH are biased low relative to observations and demonstrate a high sensitivity to the level of uncertainty in NO observations. Predictions of HO_2 using observed CH_2O and H_2O_2 as model constraints are up to a factor of two larger than observed. A temperature-dependent terminal loss rate of HO_2 to aerosol recently proposed in the literature is shown to be insufficient to reconcile these differences. A comparison of ARCTAS-A to the high latitude springtime portion of the 2000 TOPSE campaign (Tropospheric Ozone Production about the Spring Equinox) shows similar meteorological and chemical environments with the exception of peroxides; observations of H_2O_2 during ARCTAS-A were 2.5 to 3 times larger than those during TOPSE. The cause of this difference in peroxides remains unresolved and has important implications for the Arctic HO_x budget. Unconstrained model predictions for both phases indicate photochemistry alone is unable to simultaneously sustain observed levels of CH_2O and H_2O_2; however when the model is constrained with observed CH_2O, H_2O_2 predictions from a range of rainout parameterizations bracket its observations. A mechanism suitable to explain observed concentrations of CH_2O is uncertain. Free tropospheric observations of acetaldehyde (CH_3CHO) are 2–3 times larger than its predictions, though constraint of the model to those observations is sufficient to account for less than half of the deficit in predicted CH_2O. The box model calculates gross O_3 formation during spring to maximize from 1–4 km at 0.8 ppbv d^(−1), in agreement with estimates from TOPSE, and a gross production of 2–4 ppbv d^(−1) in the boundary layer and upper troposphere during summer. Use of the lower observed levels of HO_2 in place of model predictions decreases the gross production by 25–50%. Net O_3 production is near zero throughout the ARCTAS-A troposphere, and is 1–2 ppbv in the boundary layer and upper altitudes during ARCTAS-B

    Balloon borne in-situ detection of OH in the stratosphere from 37 to 23 km

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    The OH number density in the stratosphere has been measured over the altitude interval of 37 to 23 km at midday via a balloon-borne gondola launched from Palestine, Texas on July 6, 1988. OH radicals are detected with a laser induced fluorescence instrument employing a 17 kHz repetition rate copper vapor laser pumped dye laser optically coupled to an enclosed flow, in-situ sampling chamber. OH abundances ranged from 88±31 pptv (1.1 ± 0.4 × 10^7 molec cm^(−3)) in the 36 to 35 km interval to 0.9 ± 0.8 pptv (8.7 ± 7.7 × 10^5 molec cm^(−3)) in the 24 to 23 km interval. The stated uncertainty (±1σ) includes that from both measurement precision and accuracy. Simultaneous detection of ozone and water vapor densities was carried out with separate on-board instruments
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