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The term "beef' describes bedding-parallel calcite veins found commonly in the organic-rich matrix of unconventional resource plays. Although some authors have interpreted beef to be an early diagenetic feature, these calcite veins are commonly attributed to precipitation at high temperatures and localized overpressure during hydrocarbon generation. The temperature at which the beef formed is thus crucial to ascertain the process of beef genesis. We use the novel methodology of clumped isotope analysis to constrain both the temperature at which beef forms and the isotopic composition of fluids present during formation. For this study, we use beef from basinal sections of the Vaca Muerta Formation in the Neuquen Basin, where veins are commonly up to approximately 10 cm (~4 in.) thick and are laterally continuous over 1 km (0.6 mi). The calcite veins occur in isolation or in association with concretions and ash layers. Sequence stratigraphic boundaries have little influence on distribution, and only a low correlation between beef and total organic content or beef and ash layers exists. The internal crystal structure of beef varies largely, suggesting both syntaxial and antitaxial growth forms. The δ18O values of beef range from approximately -- 12%o to -9%o, and the δ13C values vary between approximately -l%o and l%o. The surrounding mudstone and concretion fracture fills (calcite) show little difference isotopically when compared to the beef itself. The δ18O values of nearby concretions range from approximately -3.5%o to l°/oo, and the δ13C values vary between approximately 6%o and 1 l%o. Clumped isotope analysis of beef in the Vaca Muerta Formation indicates temperatures between approximately 140°C and 195°C, whereas the surrounding mudstones vary from approximately 120°C to 150°C. The corresponding formation fluid δ18OW values range from 8.5 to 14.5%o. These temperature data are higher than the maximum temperatures suggested by published studies modeling the basin's thermal and burial histories. If these models are correct, the clumped isotope data indicate that the growth of beef in the Vaca Muerta Formation required the input of hydrothermal fluids from greater depths. Alternatively, the geothermal gradient or burial depth was underestimated in these models. [ABSTRACT FROM AUTHOR]

Aviation safety relies on maintaining adequate spacing between aircraft. While uncertainties are common, this study employs approaches that account for small uncertainties and deviations in aircraft positions. The objective is to assess the likelihood of airborne collision risks using data from the Aviation Risk Identification and Assessment (ARIA) developed by MITRE. To achieve this, we utilize a model that integrates probability density functions (PDFs), convolution integrals, and engineering dynamics. The study validates results from the convolution approach using a logit model for binary outcome data, where 1 indicates a collision event if the spacing is less than or equal to λxy, and 0 otherwise. Predictions from both the convolution and logit models show similarities in the horizontal dimension, with parameters derived exclusively from data-driven methods. Total collision risks are calculated by multiplying probabilities across horizontal, vertical, and time intervention dimensions. Notably, vertical spacing data exhibit considerable volatility, leading to a wider probability range and discussions on threshold crossings. Reliability theory is also applied to analyze the impact of timely interventions. This study highlights the correlation between collision probabilities and ARIA scores, while Bayesian Monte Carlo simulations reveal underlying data patterns. Additionally, the research addresses the strengths and limitations of the analytical models. For instance, navigation system errors and deviations in paired aircraft positions are often dynamic and unknown, and ARIA data may not fully capture the complexities of potential collisions. These factors underscore the need for further data-driven efforts to obtain more accurate estimates of uncertainties and overlap probabilities.

San Francisco is now widely considered to be the most important city in the world for the location of new technology start-up firms, especially high valuation “unicorns,” and is increasingly seen as both a locational and metaphorical extension of Silicon Valley. In this paper, I trace some of the political strategies and tensions that have accompanied the city’s prominence in this area, and in particular the distinctive role of technology and venture capital in the political economy of urban development. The paper has four empirical sections. It describes (1) the political machinations surrounding the 2011 and 2015 municipal elections, which saw the election of Ed Lee as Mayor with significant support from individual technology investors such as Ron Conway and Marc Benioff, and accompanied by various “tech-friendly” policy shifts; (2) the foundation of the “tech chamber of commerce” sf.citi as a means of enhancing the policy influence of the tech industry in San Francisco; (3) the introduction of a low taxation regime in the city’s Central Market area that has attracted technology companies such as Twitter as tenants; and (4) the urban policy tensions associated with the evolution of new “sharing economy” firms such as Uber and Airbnb, which have aggressively challenged municipal regulations in the taxi and property rental fields. Throughout these machinations, we can see a reshaping of capital fractions, with venture and angel capital increasingly involved in reengineering the labor, housing, and public transport markets of the city in order to circumvent the accumulation problems that tech investors had suffered in the earlier dot.com failures.

Abstract

AbstractInterpreting the inscription of ‘Chineseness’ in cities beyond China is a challenging process. This article reflects upon some recent architectural and urban design issues in what is known as Sydney’s ‘Chinatown’. Drawing on some of the insights provided in Li Shiqao’s recent book, Understanding the Chinese City (2014), it provides a commentary on some of the challenges facing architects and urban designers in their attempts to rearticulate Sydney’s Chinatown. This comes at a time when development processes in central Sydney are seen as being driven by apparently contradictory forces of supertall apartment building design and fine-grain, low-rise ‘heritage’ streetscapes.

This paper explores the nature of the contemporary political identity of the European Union through an engagement with the literature on globalized cities and relational geographies. Taking London as its centrepoint, the paper begins by considering the contradictory position of cities within European space, and examines what an urbanist, rather than nationalist, vision of Europe might entail. Engaging with spatio-temporal conceptualizations of European urbanism, the paper suggests that speed, mobility, or financial transactions (rather than citizenship, unity, and particularist cultural integration) are the fundamental tenets of contemporary European identity. These structures, embedded in the Single European Act and Maastricht Treaty, may have a more significant impact than idealizations of European identity such as the hotly debated European Constitution. The paper examines several aspects of London’s entanglement with Europe: it considers the attitudes embedded in recent urban regeneration projects which link into a ‘fast’ geography of integration with a European high-speed rail and air network, and the anxiety surrounding a deregulated financial landscape of currency trading and business services involving New York and Tokyo as much as Frankfurt and Paris. The two unstable spatial signifiers of ‘city’ and ‘Europe’ are thus unpacked and explored.

• Anesthetic management and dosage schedules of vasodilators have not been standardized in many studies of aortic cross clamping (CCL). For this reason, 25 consecutive patients with arteriosclerotic disease of the aorta were studied, all having received the same anesthetic management. Six patients who received nitroglycerin during the cross clamp period, at a dosage of 0.25 μg/kg/min, were compared with 19 who underwent CCL without the drug. Contractility was maintained in the nitroglycerin group, but not in the other group. Despite a low cardiac index in both groups, peripheral blood flow was adequate only in the nitroglycerin group. Intrapulmonary shunt was higher in the nitroglycerin group, but it did not significantly decrease the Pao2. Nitroglycerin infusion seems to be helpful in maintaining pre-CCL contractility and adequacy of peripheral blood flow.(Arch Surg 1982;117:1285-1288)

New foraminiferal evidence from two boreholes on the paleoshelf and slope of western Great Bahama Bank has wide-ranging implications for understanding formation and evolution of carbonate-platform margins. The new data, abundant well-preserved planktic foraminifera, were obtained by disaggregating samples from intercalated pelagic layers and selected parts of thick hemipelagic limestone. Earlier efforts to obtain biostratigraphic ages identified six biostratigraphic units in each borehole, provided biozonal age alternatives for both holes, and resulted in different Pliocene biozones between them. The new data define six units in one hole and seven in the other, bracket the biozones present and their ages, indicate different sedimentation rates, and show that within the limits of biostratigraphic resolution the biozones are correlative between the holes. Most importantly, the revised ages show that the paleoshelf borehole probably penetrated the late Miocene rather than middle Miocene.

The Political Economy of Regionalism.Michael Keating and John Loughlin (Eds), 1997. London/Portland: Frank Cass. 491 pp.; £22.50 paperback. ISBN 0 7146 4187 1From Here to Free Trade: Essays in the Post‐Uruguay Round Trade Strategy.E. H. Preeg, 1998. Chicago: The University of Chicago Press. 165 pp.; £14.50 paperback. ISBN 0 226 67962 4Population Migration in the European Union.P. Rees, J. Stillwell, A. Convey and M. Kupiszewski (Eds), 1996. Chichester: Wiley and Sons. 410 pp.; £65.00 hardback. ISBN 0 471 949 68 X

1. A report is presented of the perinatal mortality associated with cesarean section, with a review of 944 cesarean sections with respect to the factors accounting for the infant loss.

Our experience with small intestinal neoplasms at the Medical College of Virginia has been reviewed. There were 78 benign and malignant neoplasms observed in our surgical pathology laboratory over a 20-year period. There were 34 benign small-bowel tumors, but the majority of these lesions were asymptomatic incidental findings at the time of surgery for other conditions. There were 21 patients with malignant neoplasms of the small bowel and 23 patients with carcinoid, a potentially malignant lesion. Clinical observations and the results of treatment are reviewed.

Members of the Tequesta, a pre/proto-historic indigenous group of South Florida, cut thousands of postholes into the shallow limestone bedrock of the Metropolitan Square site, located in present-day Miami. Calcrete (limestone soil crust) formations found in and around these postholes serve as a geochemical repository attesting to various human and natural processes at the site. We present here the results of petrographic, total organic carbon (TOC), X-ray diffraction (XRD), X-ray fluorescence (XRF), and stable-isotope analysis, which were used in an attempt to relatively date posthole excavation and to identify patterns of changing site use. Ultimately, the combination of these methods yielded useful insights into paleoenvironment and proposed changes in site use, while failing to provide desired information on chronology. A combined geochemical approach such as that employed here would seem to hold potential for future study of sites located in calcareous/karstic contexts.