C^sub 4^ grasses form the foundation of warm-climate grasslands and savannas and provide important food crops such as corn, but their Neogene rise to dominance is still not fully understood. Carbon ...isotope ratios of tooth enamel, soil carbonate, carbonate cements, and plant lipids indicate a late Miocene-Pliocene (8-2 Ma) transition from C^sub 3^ vegetation to dominantly C^sub 4^ grasses at many sites around the world. However, these isotopic proxies cannot identify whether the C^sub 4^ grasses replaced woody vegetation (trees and shrubs) or C^sub 3^ grasses. Here we propose a method for reconstructing the carbon isotope ratio of Neogene grasses using the carbon isotope ratio of organic matter trapped in plant silica bodies (phytoliths). Although a wide range of plants produce phytoliths, we hypothesize that in grass-dominated ecosystems the majority of phytoliths will be derived from grasses, and will yield a grass carbon isotope signature. Phytolith extracts can be contaminated by non-phytolith silica (e.g., volcanic ash). To test the feasibility of the method given these potential problems, we examined sample purity (phytolith versus non-phytolith silica), abundance of grass versus non-grass phytoliths, and carbon isotope ratios of phytolith extracts from late Miocene-Pliocene paleosols of the central Great Plains. Isotope results from the purest samples are compared with phytolith assemblage analysis of these same extracts. The dual record spans the interval of focus (ca. 12-2 Ma), allowing us, for the first time, to investigate how isotopic shifts correlate with floral change. We found that many samples contained high abundances of non-biogenic silica; therefore, only a small subset of "pure" samples (>50% of phytoliths by volume) with good preservation were considered to provide reliable carbon isotope ratios. All phytolith assemblages contained high proportions (on average 85%) of grass phytoliths, supporting our hypothesis for grass-dominated communities. Therefore, the carbon isotope ratio of pure, well-preserved samples that are dominated by grass biosilica is considered a reliable measure of the proportion of C^sub 3^ and C^sub 4^ grasses in the Neogene. The carbon isotope ratios of the pure fossil phytolith samples indicate a transition from predominantly C^sub 3^ grasses to mixed C^sub 3^-C^sub 4^ grasses by 5.5 Ma and then a shift to more than 80% C^sub 4^ grasses by 3-2 Ma. With the exception of the Pliocene sample, these isotopie data are broadly concordant with phytolith assemblages that show a general increase in C^sub 4^ grasses in the late Miocene. However, phytolith assemblage analysis indicates lower relative abundance of C^sub 4^ grasses in overall vegetation than do the carbon isotopes from the same phytolith assemblages. The discrepancy may relate to either (1) incomplete identification of (C^sub 4^) PACMAD phytoliths, (2) higher production of non-diagnostic phytoliths in C^sub 4^ grasses compared to C^sub 3^ grasses, or (3) biases in the isotope record toward grasses rather than overall vegetation. The impact of potential incomplete characterization of (C^sub 4^) PACMAD phytoliths on assemblage estimates of proportion of C^sub 4^, though important, cannot reconcile discrepancies between the methods. We explore hypothesis (2) by analyzing a previously published data set of silica content in grasses and a small data set of modern grass leaf assemblage composition using analysis of variance, independent contrasts, and sign tests. These tests suggest that C^sub 4^ grasses do not have more silica than C^sub 3^ grasses; there is also no difference with regard to production of non-diagnostic phytoliths. Thus, it is most likely that the discrepancy between phytolith assemblages and isotope ratios is a consequence of hypothesis (3), that the isotope signature is influenced by the contribution of non-diagnostic grass phytoliths, whereas the assemblage composition is not. Assemblage-based estimates of % C^sub 4^ within grasses, rather than overall vegetation, are in considerably better agreement with the isotope-based estimates. These results support the idea that, in grass-dominated assemblages, the phytolith carbon isotope method predominantly records shifts in dominant photosynthetic pathways among grasses, whereas phytolith assemblage analysis detects changes in overall vegetation. Carbon isotope ratios of fossil phytoliths in conjunction with phytolith assemblage analysis suggest that the late Neogene expansion of C^sub 4^ grasses was largely at the expense of C^sub 3^ grasses rather than C^sub 3^ shrubs/trees. Stable isotopic analysis of phytoliths can therefore provide unique information about grass community changes during the Neogene, as well as help test how grass phytolith morphology relates to photosynthetic pathway. PUBLICATION ABSTRACT
Kinematic distributions from an inclusive sample of 1.41×106 charged-current νμ interactions on iron, obtained using the MINOS near detector exposed to a wide-band beam with peak flux at 3 GeV, are ...compared to a conventional treatment of neutrino scattering within a Fermi gas nucleus. Results are also used to guide the selection of a subsample enriched in quasielastic νμFe interactions, containing an estimated 123,000 quasielastic events of incident energies 1 < Eν < 8 GeV, with < Eν > = 2.79 GeV. Four additional subsamples representing topological and kinematic sideband regions to quasielastic scattering are also selected for the purpose of evaluating backgrounds. Comparisons using subsample distributions in four-momentum transfer Q2 show the Monte Carlo model to be inadequate at low Q2. Its shortcomings are remedied via inclusion of a Q2-dependent suppression function for baryon resonance production, developed from the data. A chi-square fit of the resulting Monte Carlo simulation to the shape of the Q2 distribution for the quasielastic-enriched sample is carried out with the axial-vector mass MA of the dipole axial-vector form factor of the neutron as a free parameter. Furthermore, the effective MA which best describes the data is 1.23+0.13-0.09(fit)+0.12-0.15(syst) GeV.
Careers, stress, and mental health in the twenty-first century Organizations and people in the twenty-first century face challenges that arise from ever increasing complexity and dynamics resulting ...from fierce competition on the industrial battlefield (Nelson and Quick, 2006). As individuals' skills become obsolete, they strive to "de-learn and re-learn" in order to add continuing value to organizations. This continuous process of upgrading skills and abilities, along with other career challenges such as career deadlocks and career plateaus, contributes to a significant rise in stress and anxiety for people at work. These forces can affect the state of mental health of employees at all organizational levels. Mental health has a significant relevance for people's career and, conversely, their career can have an impact on their mental health. This special issue of Career Development International focuses attention on the complex, intertwined set of issues around careers, stress, and mental health. The special issue is particularly concerned with two issues. The first issue is the emerging area of careers within the changing work context. No longer do individuals begin and follow a single career path over several decades, let alone follow one within a single company for an extended period of time. It is much more common for an individual to engage in anywhere from five to seven careers in a career cycle. In the same vein, professionals and especially managers no longer work in the same country. Career mobility is becoming a global phenomenon and companies are struggling to find out ways and means of increasing the likelihood of success for the international assigned managers. Executives and their families who do not adopt to the new culture, become highly stressed and the repercussions are devastating for them and for their respective organizations;
both mental health and performance (i.e. organizational health) can be affected. Thus, the paper on emotional intelligence as predictor of international managers' success can be understood within the context of improving the selection model and thereby enhancing cultural adaptation and success. The second issue concerns the implications of these career changes for individual physical and psychological health. Various career and mental health themes such as emotions at work, misfit between personalities and career choices, promotion policies, career and stress are relevant here. While Quick et al. (1997) previously focused on career issues and the preventive management of stress and other chronic mental health risks in organizations, there has been a shift in the psychological community to a more positive orientation. Peterson and Seligman (2004) represent this shift with a focus on character strengths and virtues in the larger domain of positive health psychology. This is in alignment with the current leadership challenge in organizations for healthy, happy, productive work. Some scholars even propose a new agenda for leaders of the twenty-first century organizations consisting of reengineering the culture to increase the possibilities for individuals not only to add economic values but also to find the workplace playful and exciting (Dolan and Garcia, 2002; Dolan and Richley, 2005). Other leaders liked Major General James Childress of the United States Air Force, who brought in a senior USAF psychologist to oversee the mental health of a 13,000 person workforce during a major process of realignment and industrial restructuring, are needed through civilian, military, and governmental organizations (Quick and Quick, 2004). In sum, career management in the twenty-first century has been overshadowed by the urgency of day-to-day pressures that in turn
incur serious costs in terms of quality, performance, employee morale and commitment, absenteeism and even work accidents. With a heightened awareness of career management in the workplace, organizations can seek ways and means to implement strategies that align business objectives with individual visions of career success on the one hand, but avoiding the catastrophic stress and mental health consequences on the other hand. If such alignment is successful, an organizational career development program can accelerate workforce adaptation to change, improve cost-effectiveness of human resource decisions, increase retention of the organization top achievers, and enhance the overall well being of the organization. Shimon L. Dolan James Campbell Quick Guest Editors Previously published in: Career Development International, Volume 10, Number 5, 2005.
A randomized prospective study was performed to compare the efficacy and toxicity of high-dose intravenous bolus interleukin-2 (IL-2) and a lower-dose intravenous bolus regimen for the treatment of ...metastatic renal cell carcinoma (RCC).
Between March 1991 and April 1993, 125 patients with metastatic RCC were randomized to receive IL-2 by intravenous bolus every 8 hours at either 720,000 IU/kg (high-dose) or 72,000 IU/kg (low-dose) to the maximum-tolerated number of doses (or a maximum of 15 doses). After approximately 7 to 10 days, both treatment groups were re-treated with a second identical cycle of therapy. Those patients who were stable or responding to treatment 5 to 6 weeks later went on to receive re-treatment with another course (two cycles) of therapy. Response rates and toxicity were determined for the two treatment arms.
One hundred twenty-five patients received a total of 208 courses of therapy. Sixty patients were randomized to receive low-dose, and 65 to receive high-dose IL-2. There were no treatment-related deaths in either arm. There was a greater incidence of grade III or IV thrombocytopenia, malaise, and hypotension in patients who received high-dose IL-2, while patients who received low-dose IL-2 had significantly more infections. Three percent of treatment courses with low-dose IL-2 required vasopressor support, compared with 52% of courses with high-dose IL-2. Patients who received low-dose IL-2 had a 7% complete response (CR) and an 8% partial response (PR) rate, and patients who received high-dose IL-2 had a 3% CR and a 17% PR rate.
Low-dose intravenous bolus IL-2 represents an effective regimen for the treatment of metastatic RCC, with preliminary results comparable to those observed with high-dose IL-2. Low-dose IL-2 can be administered with significantly fewer complications, reduced use of vasopressor support, and fewer admissions to an intensive care unit (ICU).
Questions About Orrorin Femur/Response Ohman, James C; C Owen Lovejoy; White, Tim D ...
Science (American Association for the Advancement of Science),
02/2005, Letnik:
307, Številka:
5711
Journal Article
As a consequence of the aims of this project, this thesis is divided into two distinct sections. Initially, the computationally efficient phase-screen forward modelling technique is extended to allow ...investigation of non-normal ray paths. The code is developed to accommodate all diffracted and converted phases up to critical angle, building on a geometrical construction method previously developed with a narrow-angle approximation. The new approach relies upon pre-scanning the model space to assess the complexity of each screen. The propagating wavefields are then divided as a function of horizontal wavenumber, and each subset is transformed to the spatial domain separately, carrying with it angular information. This allows both locally accurate 3D phase corrections and Zoeppritz reflection and transmission coefficients to be applied. The phase-screen code is further developed to handle simple anisotropic media. During phase-screen modelling, propagation is undertaken in the wavenumber domain where exact expressions for anisotropic phase velocities are incorporated. Extensive testing of the enhanced phase-screen technique includes simple analytical models to justify the inclusion of multiple energy alongside synthetic examples from models commonly used to test numerical modelling techniques. Additionally the code is tested with real models from a producing field in a marine sedimentary location where an exhaustive range of geophysical techniques were used to constrain the VTI parameters. Secondly within this thesis, the narrow angle version of the phase-screen method is used to generate a comprehensive pre-stack seismic reflection dataset for our industrial partners. Current exploration within the European oil and gas community is heavily focused on regions where the targets for production are positioned beneath plateau basalts oh the north west European margin. These environments produce a complex seismic response due to the scattering generated by the internal composition of the basalt flows. This study generates a large subsurface volume, derived from geological mapping projects in the Hold-with-Hope region of north east Greenland, and synthetically acquires a realistic 3-D reflection study across it. The basalt is uniquely generated as a single random volume with distinct correlation lengths in each orthogonal direction and a novel approach to determine seismic attenuation through basalts is developed. Initial results from this data set are presented after careful optimisation of the modelling code and parameters.
As a consequence of the aims of this project, this thesis is divided into two distinct sections. Initially, the computationally efficient phase-screen forward modelling technique is extended to allow ...investigation of non-normal ray paths. The code is developed to accommodate all diffracted and converted phases up to critical angle, building on a geometrical construction method previously developed with a narrow-angle approximation. The new approach relies upon pre-scanning the model space to assess the complexity of each screen. The propagating wavefields are then divided as a function of horizontal wavenumber, and each subset is transformed to the spatial domain separately, carrying with it angular information. This allows both locally accurate 3D phase corrections and Zoeppritz reflection and transmission coefficients to be applied. The phase-screen code is further developed to handle simple anisotropic media. During phase-screen modelling, propagation is undertaken in the wavenumber domain where exact expressions for anisotropic phase velocities are incorporated. Extensive testing of the enhanced phase-screen technique includes simple analytical models to justify the inclusion of multiple energy alongside synthetic examples from models commonly used to test numerical modelling techniques. Additionally the code is tested with real models from a producing field in a marine sedimentary location where an exhaustive range of geophysical techniques were used to constrain the VTI parameters. Secondly within this thesis, the narrow angle version of the phase-screen method is used to generate a comprehensive pre-stack seismic reflection dataset for our industrial partners. Current exploration within the European oil and gas community is heavily focused on regions where the targets for production are positioned beneath plateau basalts oh the north west European margin. These environments produce a complex seismic response due to the scattering generated by the internal composition of the basalt flows. This study generates a large subsurface volume, derived from geological mapping projects in the Hold-with-Hope region of north east Greenland, and synthetically acquires a realistic 3-D reflection study across it. The basalt is uniquely generated as a single random volume with distinct correlation lengths in each orthogonal direction and a novel approach to determine seismic attenuation through basalts is developed. Initial results from this data set are presented after careful optimisation of the modelling code and parameters.
A high positive correlation is found between the isotopic composition of atmospheric water vapor and both the specific and relative humidities at Palisades, New York, during the growing season. This ...relationship is explained in terms of the meteorological setting. In general, the lowest δD values occur when cool, dry Canadian air that is stable aloft moves southeastward, while much higher values occur in hot, more humid air that is unstable aloft. The highest δD values approach the local groundwater value and occur when the surface air is stably stratified.
We have developed an extraction system to analyze isotopes of carbon monoxide (CO). We then analyzed CO isotopes for two years at Indianapolis, IN, USA. These measurements were done at three towers, ...one of which measured incoming, background air into the city. We quantitatively removed the background signal and determined the urban CO mole fraction and isotopic enhancements. During the winter months, we constrained the isotopic signature and concluded that the majority of CO produced during the winter was produced by fossil fuel combustion. We found that the Indianapolis fossil fuel signature differed from that of studies done in Europe. Further, we performed a limited traffic study to look at CO isotopes from traffic. While this was not conclusive, it did support our hypothesis that a larger fraction of the Indianapolis vehicle fleet may have malfunctioning catalytic systems, which biases the isotopic results, particularly for δ18O. We used the wintertime fossil fuel isotopic signature to help constrain the summertime budget. It was hypothesized that a second source of CO was significant during the summer months. Oxidation of biogenically produced volatile organic compounds (BVOC’s) was one possible source. Oxidized BVOC’s were consistent with the changes between our winter and summer isotopic source signatures. We then used the isotopic signatures to determine that between zero and sixty percent of the summertime CO budget was produced from oxidized VOC’s. This provided the first direct evidence of a larger percentage of urban CO being produced by oxidized VOC’s.
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