Satellite data confirm CFC link to ozone hole

Overview — Air Force policy on halons

Trichlorofluoromethane, commonly called CFC-11, is the primary blowing agent used in the production of polyurethane (PUR) or polyisocyanurate (PIR) rigid foams for laminate insulation. CFC-11 is also a member of a class of chlo rofluorocarbons called "hard CFC's," which are believed to contribute to the destruc tion of the earth's protective ozone layer located in the stratosphere above the Antarc tic. Two possible CFC-11 replacements for rigid laminate insulation production with lower ozone depletion potentials than CFC-11 have been identified. They are CF3CHCL2 (HCFC-123) and CCL2FCH3 (HCFH-141b). Many properties of the foam contribute to the overall effectiveness of the laminated insulation product when applied as part of a roof or in a sheathing application Some of these properties in clude foam density, compressive strength, dimensional stability, thermal conductiv ity, and performance in specified flammability tests (ASTM-E84 or UL-723). In order to be a viable replacement for CFC-11, utilizing current laminate chemistry and processing technology, HCFC-123 or HCFC-141b must produce foams that give equivalent or better values than CFC-11 blown foams for the properties listed above. Continuous laminate production evaluations of HCFC-123 abd HCFC-141b were conducted at the North Haven Laboratories of The Dow Chemical Company in a typical rigid laminate formulation to determine the viability of these chemicals as replacement blowing agents of CFC-11. These evaluations included a control run of 100% CFC-11 and blends of HCFC-123 or HCFC-141b with CFC-11. Analyses include reactivity profiles, physical property measurements, initial and aged thermal conductivities, and flammability performance as measured by the UL-723 Tunnel Test.

Accretion of gas and comets onto a nearby degenerate star

The treaty that worked

RETURN TO ISSUEPREVNewsNEXTCFC PRODUCTION: Du Pont seeks total phaseoutMARC REISCH and PAMELA ZURERView Author Information New York WashingtonCite this: Chem. Eng. News 1988, 66, 14, 4–5Publication Date (Print):April 4, 1988Publication History Published online8 November 2010Published inissue 4 April 1988https://pubs.acs.org/doi/10.1021/cen-v066n014.p004https://doi.org/10.1021/cen-v066n014.p004newsACS PublicationsCopyright © 1988 AMERICAN CHEMICAL SOCIETYArticle Views9Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options SUBJECTS:Chlorine,Electromagnetic radiation Get e-Alerts

Personal computers of the past were limited to running computational fluid dynamics codes in serial mode. With the advent of multicore technology and suitable compilers, personal computers nowadays can execute codes in a parallel fashion similar to that of supercomputers and cluster computer systems. This article investigated what performance can be achieved when executing an aerodynamic code on an Intel quad core based personal computer with an OpenMP compiler in a Windows environment. The code solved the Euler equations to find the flowfield around a NACA0012 aerofoil on an O-type boundary fitted structured grid system. A speedup of up to 350% was obtainable in double precision accuracy. The reduced computation time means that, for small scale problems, more accurate Euler codes can replace commonly used transonic small disturbance codes. For larger problems, this information serves as a reference for developers of hybrid MPI/OpenMP algorithms for cluster computer systems. References Advanced Micro Devices (AMD), AMD FireStream 9170: Industry's First GPU with Double-Precision Floating Point, 2007, http://ati.amd.com/products/streamprocessor/specs.html Allmaras, S. R., Venkatakrishnan, V., and Johnson, F. T., Farfield Boundary Conditions for 2-D Airfoils, AIAA Paper 2005-4711, AIAA, 2005. Bailey, D., Barszcz, E., Barton, J., Browning, D., Carter, R., Dagum, L., Fatoohi, R., Fineberg, S., Frederickson, P., Lasinski, T., Schreiber, R., Simon, H., Venkatakrishnan, V., and Weeratunga, S., The NAS Parallel Benchmarks, National Aeronautics and Space Administration (NASA), Contractor Report 203186, USA, 1994, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970014936_1997021577.pdf Dong, S., and Karniadakis, G. E., Dual-Level Parallelism for High-Order CFD Methods, Parallel Computing, 30, Jan. 2004, pp. 1--20. Hirsch, C., Numerical Computation of Internal and External Flows (Volume 2): Computational Methods for Inviscid and Viscous Flows, John Wiley and Sons, Great Britain, 1992. Hoffmann, K. A., Computational Fluid Dynamics for Engineers, Engineering Educational System, Texas, USA, 1989. Intel, Tera-scale Computing Research Program, c.2007, http://www.intel.com/research/platform/terascale/ Jin, H., Frumkin, M., and Yan, J., The OpenMP Implementation of NAS Parallel Benchmarks and its Performance, National Aeronautics and Space Administration (NASA), Technical Report NAS-99-011, Moffett Field, USA, 1999. Liu, Y., and Vinokur, M., Nonequilibrium Flow Computations 1: An Analysis of Numerical Formulations of Conservation Laws, National Aeronautics and Space Administration (NASA), Contractor Report 177489, California, USA, 1988, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880021000_1988021000.pdf Lock, R. C., Test Cases for Numerical Methods in Two-Dimensional Transonic Flows, Advisory Group for Aerospace Research and Development (AGARD), Report Number 575, 1970. Ly, E., Improved Approximate Factorisation Algorithm for the Steady Subsonic and Transonic Flow over an Aircraft Wing, Proceedings of the 21st Congress of the International Council of the Aeronautical Sciences (ICAS98), ICAS and AIAA, Melbourne, Australia, 1998, Paper A98-31699. Ly, E., and Gear, J. A., Time-Linearized Transonic Computations Including Shock Wave Motion Effects, Journal of Aircraft, 39, 6, Nov/Dec. 2002, pp. 964--972. Ly, E., and Nakamichi, J., Time-Linearised Transonic Computations Including Entropy, Vorticity and Shock Wave Motion Effects, The Aeronautical Journal, Nov. 2003, pp. 687--695. Ly, E., and Norrison, D., Automatic Elliptic Grid Generation by an Approximate Factorisation Algorithm, ANZIAM Journal, 48 (CTAC2006), pp. C188--C202, July 2007, http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/48. Ly, E., and Norrison, D., Generating Elliptic Grids in Three Dimensions by a Method of False Transients, ANZIAM Journal, 49 (EMAC2007), pp. C170--C183, Nov. 2007, http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/313. Nvidia, The Era of the Personal Supercomputer, 2007, http://www.nvidia.com/content/events/siggraph_2007/supercomputing.html Pope, S. B., A Perspective on Turbulence Modeling, Modeling Complex Turbulent Flows, Kluwer Academic Publishers, The Netherlands, 1999. Pulliam, T., Kutler, P., and Rossow, V., Harvard Lomax: His Quiet Legacy to Computational Fluid Dynamics, 14th AIAA Computational Fluid Dynamics Conference, Norfolk, VA, 28 June-1 July, 1999, http://people.nas.nasa.gov/ pulliam/mypapers/lomax_la.ps Steger, J. L., and Warming, R. F., Flux Vector Splitting of the Inviscid Gasdynamic Equations with Application to Finite Difference Methods, National Aeronautics and Space Administration (NASA) Technical Memorandum 78605, California, USA, 1979, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790020779_1979020779.pdf Thompson, J. R., Warsi, Z. U. A., and Mastin, C. W., Numerical Grid Generation: Foundations and Applications, Elsevier Science Publishing Co. Inc., New York, USA, 1985. Van Leer, B., Flux-Vector Splitting for the Euler Equations, Proceedings of the 8th International Conference on Numerical Methods in Fluid Dynamics, Aachen, West Germany, 1982.

A successful transition to global clean energy hinges on meeting the world’s growing demand for power, while at the same time reducing greenhouse gas emissions. Achieving this will require significant growth in electricity generation from clean and carbon-free energy sources. Several energy providers (Acar and Dincer, 2019, “Review and Evaluation of Hydrogen Production Options for Better Environment,” J. Cleaner Prod., 218, pp. 835–849 and Nagashima, M., 2024, “Japan’s Hydrogen Strategy and Its Economic and Geopolitical Implications,” Afficher la page d’accueil du site) have already begun the transition from traditional carbon-based fuels to cleaner alternatives, such as hydrogen (H2) and hydrogen-enriched natural gas (HENG). However, there are still many technical questions/challenges that must be addressed when applying these fuels in gas turbines. The application of H2 or H2/natural gas (NG) blends to advanced-class gas turbines, which have higher operating pressures and temperatures, has raised concerns about the potential for leakages or fuel sequencing operations where flammable mixtures of fuel and air could auto-ignite. Public information on the auto-ignition of H2 in the air at atmospheric pressure shows an auto-ignition temperature (AIT) between 520 and 585 °C (U.S. Department of Energy, 2024, “U.S. Department of Energy Hydrogen Program Plan,” U.S. Department of Energy, Washington, DC; Georgia Power, 2022, “Georgia Power, Mitsubishi Power, EPRI Complete World’s Largest Hydrogen Fuel Blending at Plant McDonough-Atkinson,” Georgia Power, Atlanta, GA; and gepower-v2, 2024, “New York Power Authority: GE Vernova,” gepower-v2, Cambridge, MA). Such data show AIT of H2 is ∼100 °C lower than that of methane (CH4) which has a minimum AIT of around 600 °C (Huth, M., and Heilos, A., 2013, “Fuel Flexibility in Gas Turbine Systems: Impact on Burner Design and Performance,” Modern Gas Turbine Systems, Sawston, UK, pp. 635–684). Studies also show that as pressure increases, methane’s AIT decreases significantly to around 390 °C (Loving, C., Mastantuono, G., Terracciano, A. C., Vasu, S. S., Pigon, T., Hernandez, A., and Cloyd, S., 2023, “Auto-Ignition Test Results of Hydrogen and Natural Gas Fuels at Atmospheric and Elevated Pressures for Gas Turbine Safety,” ASME Paper No. GT2023-102674). However, there was insufficient information in the published literature to characterize the influence of pressure on the AIT of H2 and HENG fuels. At atmospheric conditions, H2 has a wider flammability range of equivalence ratios that ignition can occur compared to methane. H2’s flammability ranges from 4% to 75% molar (volume) fuel concentration, which is an equivalence ratio range of 0.137–2.57. Methane’s flammability limit ranges from 5% to 15% molar (volume) or an equivalence ratio between 0.53 and 1.58 (National Aeronautics and Space Administration, 1997, Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation, National Aeronautics and Space Administration, Office of Safety and Mission Assurance; National Technical Information Service, Distributor, Washington, DC, Springfield, VA). Previous research has also been done to determine the effect of longer hydrocarbons present in natural gas mixtures. The presence of ethane (C2H6) and propane (C3H8) has been shown to reduce the AIT of natural gas, especially at elevated pressures (The Association, 1994, NFPA 49: Hazardous Chemicals Data, The Association, Quincy, MA). These longer hydrocarbons also tend to promote ignition in richer conditions, whereas methane tends to ignite easier in slightly lean conditions (National Aeronautics and Space Administration, 1997, Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation, National Aeronautics and Space Administration, Office of Safety and Mission Assurance; National Technical Information Service, Distributor, Washington, DC, Springfield, VA). Numerous variables besides the pressure, fuel, and equivalence ratio can affect the AIT including chamber volume size, chamber materials, presence of diluents, and other factors (Standards Australia International, 2000, Electrical Apparatus for Explosive Gas Atmospheres. Part 20, Data for Flammable Gases and Vapours, Relating to the Use of Electrical Apparatus, Standards Australia International; Standards New Zealand, Strathfield, NSW, Wellington, NZ). This study describes the test methodology used to evaluate conditions where auto-ignition occurs for various fuel–air mixtures operating at different pressures (1–30 atm) and temperatures. Testing was completed with 100% H2 and multiple H2/NG blends at various equivalence ratios (ER) between 0.2 and 2.5. Testing was similarly performed for 100% NG to validate the test and data collection methods cited in prior published literature. Results indicate that, at atmospheric pressures, an increase in H2 concentration results in a reduced AIT. However, at 30 atm, the increased presence of H2 increased the AIT. At elevated pressures above 10 atm, increased equivalence ratio resulted in reduced AIT for all mixtures with NG having the greatest sensitivity to equivalence ratio. Variations of auto-ignition delay times (AIDT) were also observed during the testing and are compared to modeling predictions, providing insight into auto-ignition characteristics.

Du Pont plans to end all production of ozone-depleting chlorofluorocarbons (CFCs) in developed countries by the end of 1994, one year earlier than required by the latest revisions to the Montreal protocol. The company's decision was prompted by the continuing deterioration of the ozone layer and the growing availability of alternatives. Coincidentally, the World Meteorological Organization (WMO) reported on March 5 that for the second winter in a row substantially less ozone than normal was measured over some regions of the Northern Hemisphere. WMO's observation follows the National Aeronautics & Space Administration's earlier finding that the 1992 Antarctic ozone hole was the largest and longest lasting ever observed. The 1992 Copenhagen amendments to the Montreal Protocol on Substances That Deplete the Ozone Layer require that CFC production be cut back to 75% of 1986 levels by Jan. 1, 1994, then phased out completely by Jan. 1, 1996. Du Pont s decision to halt production by the ...

Metal oxide modified MCM-41 on simultaneous removal of HF and HCl: Experimental and theoretical studies

HE ownership of resulting from T government financed research and development constitutes a very controversial problem. The federal government mainly the Department of Defense (DOD) has permitted industrial firms to obtain the patent rights to most of the inventions emerging from its contract research, under the so-called with the government acquiring royaltyfree licenses on the inventions. Our task here is an empirical investigation of one of the issues in the controversy over federal patent policy, namely, the concentration of resulting from the operation of the license policy. One of the strongest objections to the license policy rests on the belief that it causes undue concentration of economic power. The objection has been raised repeatedly by attorneys general, by legislators, and by economists who favor the so-called ' under which the government retains ownership of resulting from its contract research. From records of the United States Patent Office, we have compiled data for the period 1946 to 1962 on the numbers of assigned to business firms that have been the research and development (R and D) for the Atomic Energy Commission (AEC), the Department of Defense, and the National Aeronautics and Space Administration (NASA). The data are neither estimates nor samples; they are complete counts. The three agencies account for nearly all of the issued under the license policy to contractors. Henceforth, we shall refer to these as license-policy patents. We also have data on the private patents resulting from the company financed R and D of the same contractors. The major R and D contractors are 177 business firms that were among the first 100 of DOD in any fiscal year from 1955 to 1962, or who had contract awards of $2 million or more from the AEC or from NASA.2 Of these 177 firms, 40 are among the first 100 in Fortune's list for 1962. Another 49 are among Fortune's 500 companies. A further 36 have been officially stamped as small businesses. With the exception of a few of the bigger chemical and oil companies that have done little or no research for the federal government, the names of nearly all the Schumpeterian giants of American industry are on our list. By treating each firm and its subsidiaries as a unit, we overstate patent concen* The research underlying this article was supported by a grant (NsG 425) from the National Aeronautics and Space Administration to The George Washington University. 1 Department of Justice, Investigations of Government Patent Practices and Policies: Report and Recommendations of the Attorney General to the President 1 (Washington, D.C.: U.S. Government Printing Office, 1947), 37; Report of the Attorney General Pursuant to Section 708 (e) of the Defense Production Act of 1950, as Amended (Nov. 9, 1956, mimeo.); Clair Wilcox, Public Policies Toward Business (Homewood, Ill.: Richard D. Irwin, 1960), 191; Walter Adams and Horace M. Gray, Monopoly in America: The Government as Promotor (New York: Macmillan, 1955), 47, 94, and 148-152. Testimony against the license policy and in favor of the title policy was given to a Senate subcommittee in 1963 by Horace M. Gray, Robert F. Lanzillotti, Wassily W. Leontief, Richard R. Nelson, and Lee E. Preston. See Aspects of Government Patent Policies, Hearings before a Subcommittee of the Select Committee on Small Business, United States Senate, 88th Congress, First Session, Impact of Government Patent Policies on Economic Growth, Scientific and Technological Progress, Competition, and Opportunities for Small Business, March 7, 8, 13, and 14, 1963 (Washington, D.C.: U.S. Government Printing Office, 1963). Only Leontief (p. 236), however, addressed himself specifically to the question of concentration. 2 Department of Defense, 500 Contractors Listed According to Net Value of Military Prime Contract Awards for Experimental, Development Test and Research Work (Fiscal years 1955 through 1962, mimeo.); and Files of the Atomic Energy Commission and published reports of the National Aeronautics and Space Administration. 'Usually, government employees are required to assign title to the government. However, if a government employee, with his own resources, produces an invention that his agency wants, the government frequently files the patent application in exchange for a royalty-free license. Also, if an agency does not want a government financed invention made by an employee, the employee often is permitted to acquire title. Regulations governing employees were tightened in 1950. This fact and the relative growth of contract research are the causes of the decline in the number of licenses from employees after 1950.

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The Montreal Protocol and its amendments (MPA) have been a major success in preventing serious health damage from the destruction of the stratospheric ozone layer by chlorofluorocarbons (CFCs). Additionally, unabated CFC emissions would have significantly accelerated global warming and affected large-scale tropospheric circulation. CFC-induced ozone depletion would have contributed to global climate change through reduced absorption of UV radiation, resulting in weaker stratospheric circulation, affecting the dynamical coupling to the troposphere. With the Earth System Model SOCOLv4, we study an extreme condition where the MPA is absent to disentangle the radiative and chemical (i.e., ozone-mediated) effects of CFCs and their impacts on stratosphere-troposphere coupling. Our results show that at the end of the 21st century, unabated CFC emissions would have largely destroyed the global ozone layer, which would have strongly affected the large-scale stratospheric and tropospheric circulation. In the stratosphere, contrary to historical ozone destruction, the polar vortices severely weaken due to low-latitude ozone depletion. In the Northern Hemisphere (NH), the weakening of the vortex leads to a pronounced negative phase of the North Atlantic Oscillation (NAO) in boreal winter and spring due to the chemical CFC effect. Similarly, the stratosphere also affects the Southern Annular Mode (SAM) to be in a more negative phase in austral winter and spring. However, tropospheric warming from CFCs largely dominates the overall SAM response to be in a more positive phase, whereas in the NH it compensates for the NAO negative phase. Additionally to the circulation changes, uncontrolled CFC emissions would have led to around 2.5 K additional global surface warming, being partially compensated by a cooling of around 0.6 K due to ozone depletion, leading to an overall warming of around 1.9 K. Our study strongly emphasizes the importance of the MPA for our climate and its mitigation of stratospheric circulation changes and their effects on tropospheric variability.

Rats developed benign testicular tumors in long-term toxicity tests of a projected major substitute for ozonedepleting chlorofluorocarbons (CFCs), according to results released last week by the Program for Alternative Fluorocarbon Toxicity Testing (PAFT). The program is sponsored by an international consortium of companies producing CFCs and CFC substitutes. However, the tumors show up only at massive doses unlikely to be encountered by people using hydrofluorocarbon-134a (HFC-134a, CH 2 FCF 3 ). HFC-134a is the most likely replacement for CFC-12 (CH 2 F 2 ) in many airconditioning and refrigeration applications—especially auto air-conditioning (C&EN, June 22, page 7)—and is already used in some car models. Because it contains no chlorine, it has zero potential for depleting Earth's stratospheric ozone layer. Earlier short-term tests on HFC-134a found no toxicity problems. The benign tumors appeared only at the end of a two-year study that exposed rats over their entire lifetime to air containing 50,000 p...

Preliminary data from an airborne mission to the yearly ozone hole over Antarctica show the lowest ozone levels yet recorded over that continent, it was announced at a news conference September 30, 1987. Measurements made by two NASA (National Aeronautics and Space Administration) aircraft flying through the zone of ozone depletion, as well as satellite a n d balloon‐based data, indicate a 15% mid‐September decrease in ozone between 14 and 23 km altitude over the mid‐ September levels of 1985, the lowest previous measurements. Chemical and meteorological mechanisms appear to play an interactive role in the hole's development.In situ sampling and remote sensing of chlorine from NASA's ER‐2 and DC‐8 aircraft showed concentrations of u p to 100 times the amount found at mid‐latitudes at the same altitudes. The documentation of this perturbed chlorine chemistry provides further support for theories linking the hole to the destruction of ozone by chlorine species like the CIO radical.

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