Abstract Rising atmospheric CO 2 concentration ([CO 2 ]) enhances photosynthesis and reduces transpiration at the leaf, ecosystem, and global scale via the CO 2 fertilization effect. The CO 2 fertilization effect is among the most important processes for predicting the terrestrial carbon budget and future climate, yet it has been elusive to quantify. For evaluating the CO 2 fertilization effect on land photosynthesis and transpiration, we developed a technique that isolated this effect from other confounding effects, such as changes in climate, using a noisy time series of observed land-atmosphere CO 2 and water vapor exchange. Here, we evaluate the magnitude of this effect from 2000 to 2014 globally based on constraint optimization of gross primary productivity (GPP) and evapotranspiration in a canopy photosynthesis model over 104 global eddy-covariance stations. We found a consistent increase of GPP (0.138 ± 0.007% ppm −1 ; percentile per rising ppm of [CO 2 ]) and a concomitant decrease in transpiration (−0.073% ± 0.006% ppm −1 ) due to rising [CO 2 ]. Enhanced GPP from CO 2 fertilization after the baseline year 2000 is, on average, 1.2% of global GPP, 12.4 g C m −2 yr −1 or 1.8 Pg C yr −1 at the years from 2001 to 2014. Our result demonstrates that the current increase in [CO 2 ] could potentially explain the recent land CO 2 sink at the global scale.
Pronounced corrosion damage occurs in supercritical water oxidation reactors, and few materials are immune to attack. In this paper, we describe a phenomenological model for the corrosion process, and we discuss the effect of electrolyte dissociation and water density, as influenced by temperature and pressure, upon the kinetics of corrosion of metals and alloys in supercritical water. The corrosion process at near‐critical temperatures is believed to involve acid attack, with the concentration of H+ being a function of the dissociation constant of , which is a major product of the oxidation of chlorinated organic waste, and of the density of the solution. We show that the competing effects of temperature on the heterogeneous rate constant and on the concentrations of H+ and leads to a pressure (and hence density)‐dependent maximum in the corrosion rate in the vicinity of the critical temperature. This result is in general agreement with experimental data on corrosion in aqueous solutions at near‐critical temperatures.
The influence of dispersion on the interactions of H/sub 2/ and CO with Pd/SiO/sub 2/ has been investigated. The distribution of H/sub 2/ adstates changes with dispersion, due possibly to a change in the morphology of the Pd crystallites or in the coordination of adsorbed H atoms with the Pd atoms. The ratio of linearly held CO to bridge-bonded CO decreases with the dispersion, as does the ratio of Pd(100) to Pd(111) planes on the surfaces of the Pd crystallites. CO dissociation occurs preferentially from bridge sites and proceeds more readily with decreasing dispersion. Consistent with this, the turn-over frequency for methanation increases with decreasing dispersion. 34 references.
Two years have now passed since the publication of the first Thematic Series on gold catalysis for organic synthesis in the Beilstein Journal of Organic Chemistry. In the intervening time, the pace of progress and discovery in the field has continued unabated. Many of these advancements are exemplified in the more than twenty contributions that have been collected in this second Thematic Series. Many of the early examples of homogeneous gold-catalysis focused on the ability of cationic gold complexes to activate π-bonds towards attack of nucleophiles. This reactivity platform, examples of which can be found in this Thematic Series, continues to provide a fruitful basis for the discovery of important new transformations. This includes the development of a tandem or domino process that can be employed for the synthesis of complex polycyclic structures. These articles demonstrate the power of gold catalysis for the construction of complex structures, including the development of tandem processes, the expedient synthesis of heterocyclic structures, and applications to the synthesis of complex natural products. The field has also witnessed growth through the discovery of other modes of reactivity. For example, gold-catalyzed cycloaddition reactions, examples of which are found in this Thematic Series, have featured prominently. Additionally, enantioselective catalysis with gold has seen notable advancements and is highlighted in several articles. The remarkable breakthroughs in oxidative transformations catalyzed by gold complexes, including those employing N-oxides as stoichiometric oxidants, have featured prominently in many recent innovations. Taken together, these articles present an outstanding overview of the state of the field from many of its top practitioners. They foreshadow the many additional reactions, reactivity modes, and catalysts based on gold that remain to be uncovered. I am grateful to the authors for their excellent contribution and making this second Thematic Series as successful as the first. F. Dean Toste Berkeley, October 2013
Summary We assess the role of economic and security considerations in the currency composition of international reserves. We contrast the ‘Mercury hypothesis’ that currency choice is governed by pecuniary factors familiar to the literature, such as economic size and credibility of major reserve currency issuers, against the ‘Mars hypothesis’ that this depends on geopolitical factors. Using data on foreign reserves of 19 countries before World War I, for which the currency composition of reserves is known and security alliances proliferated, our results lend support to both hypotheses. We find that military alliances boost the share of a currency in the partner’s foreign reserve holdings by about 30 percentage points. These findings speak to the implications of possible US disengagement from global geopolitical affairs. In a hypothetical scenario where the United States withdraws from the world, our estimates suggest that long-term US interest rates could rise by as much as 80 basis points, assuming that the composition of global reserves changes but their level does not.
Thermal pressure and energy–volume coefficients are reported for several DMSO–water mixtures over the temperature range 13–55 °C. The energy–volume coefficient at 25 °C is found to pass through a maximum at 0.3–0.4 mole fraction DMSO and this observation is rationalized in terms of maximization of intercomponent interactions. The relationship between the energy–volume coefficient and the cohesive energy density of the binary liquid system is examined. The temperature dependence of the thermal pressure coefficient is discussed in terms of the effect of temperature on the susceptibility of the entropy of DMSO–water mixtures to isothermal expansion.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization of Organic SurfaceScott S. Perry and Gabor A. SomorjaiCite this: Anal. Chem. 1994, 66, 7, 403A–415APublication Date (Print):April 1, 1994Publication History Published online4 June 2012Published inissue 1 April 1994https://pubs.acs.org/doi/10.1021/ac00079a721https://doi.org/10.1021/ac00079a721research-articleACS PublicationsRequest reuse permissionsArticle Views108Altmetric-Citations3LEARN 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 optionsGet e-Alertsclose Get e-Alerts
