Agriculture, Population, Land and Water Scarcity in a Changing World – The Role of Irrigation

Fertile land and fresh water constitute two of the most fundamental resources for food production. These resources are affected by environmental, political, economic, and technical developments. Regional impacts may transmit to the world through increased trade. With a global forest and agricultural sector model, we quantify the impacts of increased demand for food due to population growth and economic development on potential land and water use. In particular, we investigate producer adaptation regarding crop and irrigation choice, agricultural market adjustments, and changes in the values of land and water.Irrigation, Food supply, Integrated assessment, Water use intensity, Agricultural adaptation, Land scarcity, Partial equilibrium model, Resource /Energy Economics and Policy,

Error-tolerant quantum convolutional neural networks for symmetry-protected topological phases

The analysis of noisy quantum states prepared on current quantum computers is getting beyond the capabilities of classical computing. Quantum neural networks based on parametrized quantum circuits, measurements and feed-forward can process large amounts of quantum data to reduce measurement and computational costs of detecting non-local quantum correlations. The tolerance of errors due to decoherence and gate infidelities is a key requirement for the application of quantum neural networks on near-term quantum computers. Here we construct quantum convolutional neural networks (QCNNs) that can, in the presence of incoherent errors, recognize different symmetry-protected topological phases of generalized cluster-Ising Hamiltonians from one another as well as from topologically trivial phases. Using matrix product state simulations, we show that the QCNN output is robust against symmetry-breaking errors below a threshold error probability and against all symmetry-preserving errors provided the error channel is invertible. This is in contrast to string order parameters and the output of previously designed QCNNs, which vanish in the presence of any symmetry-breaking errors. To facilitate the implementation of the QCNNs on near-term quantum computers, the QCNN circuits can be shortened from logarithmic to constant depth in system size by performing a large part of the computation in classical post-processing. These constant-depth QCNNs reduce sample complexity exponentially with system size in comparison to the direct sampling using local Pauli measurements.Comment: 24 pages, 12 figure

In-Season vs. Out-of-Season Academic Performance of College Student-Athletes

There is a commonly held belief within the intercollegiate athletics community that student-athletes perform better academically during their season of athletics competition than they do outside the season of competition. The thought is that the structured nature of the playing season leads to more structure in student-athletes’ academic lives and better academic performance. However, it is difficult to find empirical studies supporting this belief. A series of three studies was conducted to assess whether there is a difference in the grade-point average and credits earned of student-athletes in their season of competition vs. their off-season. These three studies are distinguished by NCAA membership division (Division I, Division II or Division III) and the specific nature of the data available in each of those divisions. The Division III study served as a pilot and examined over 3,000 student-athlete records at eight schools. The Division II study included nearly 12,000 student-athletes at 92 schools, and the Division I study involved analysis of a census of Division I student-athletes at over 325 colleges and universities followed term-by-term for up to four years. The separate divisional studies came to similar conclusions. Generally, the academic performance of student-athletes was shown to be better outside the season of competition than during the season—contrary to the conventional wisdom. The negative in-season effects were stronger in sports known to have high in-season time demands (e.g., Division I football, baseball and softball) and among student-athletes who entered college less well prepared academically

Global food efficiency of climate change mitigation in agriculture

Concerns exist regarding potential trade-offs between climate change mitigation in agriculture and food security. Against this background, the Global Biosphere Management Model (GLOBIOM) is applied to a range of scenarios of mitigation of emissions from agriculture to assess the implications of climate mitigation for agricultural production, prices and food availability. The “food efficiency of mitigation” (FEM) is introduced as a tool to make statements about how to attain desired levels of agricultural mitigation in the most efficient manner in terms of food security. It is applied to a range of policy scenarios which contrast a climate policy regime with full global collaboration to scenarios of fragmented climate policies that grant exemptions to selected developing country groups. Results indicate increasing marginal costs of abatement in terms of food calories and suggest that agricultural mitigation is most food efficient in a policy regime with global collaboration. Exemptions from this regime cause food efficiency losse

Combinatorics on words in information security: Unavoidable regularities in the construction of multicollision attacks on iterated hash functions

Classically in combinatorics on words one studies unavoidable regularities that appear in sufficiently long strings of symbols over a fixed size alphabet. In this paper we take another viewpoint and focus on combinatorial properties of long words in which the number of occurrences of any symbol is restritced by a fixed constant. We then demonstrate the connection of these properties to constructing multicollision attacks on so called generalized iterated hash functions.Comment: In Proceedings WORDS 2011, arXiv:1108.341

Sterically restricted tin phosphines, stabilized by weak intramolecular donor-acceptor interactions

Funding: Engineering and Physical Sciences Research Council (EPSRC)Four related sterically restricted pen-substituted acenaphthenes have been prepared containing mixed tin phosphorus moieties in the proximal 5,6-positions (Acenap[SnR3][(PPr2)-Pr-i]; Acenap = acenaphthene-5,6-diyl; R-3 = Ph-3 (1), Ph2Cl (2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P-Sn bonding within the series was investigated by X-ray crystallography, solution and solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM) calculations. All members of the series adopt a conformation such that the phosphorus lone pair is located directly opposite the tin center, promoting an intramolecular donor acceptor P -> Sn type interaction. The extent of covalent bonding between Sn and P is found to be much greater in triorganotin chlorides 2-4 in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atom naturally increases the Lewis acidity of the tin center, enhancing the Ip(P)-sigma*(Sn-Y) donor acceptor 3c-4e type interaction, as indicated by conspicuously short Sn-P peri distances and significant (1)J(P-31,Sn-119) spin spin coupling constants (SSCCs) in the range 740-754 Hz. Evidence supporting the presence of this interaction was also found in solid-state NMR spectra of some of the compounds which exhibit an indirect spin spin coupling on the same order of magnitude as observed in solution. DFT calculations confirm the increased covalent bonding between P and Sn in 2-4, with notable WBIs of ca. 0.35 obtained, in comparison to 0.1 in 1.PostprintPeer reviewe

Biospheric Monitoring and Ecological Forecasting

The latest generation of NASA Earth Observing System (EOS) satellites has brought a new dimension to monitoring the living part of the Earth system - the biosphere. EOS data can now measure weekly global productivity of plants and ocean chlorophyll and of related biophysical factors, such as changes to land cover and to the rate of snowmelt. However, the greatest economic impact would be realized by forecasting biosphere conditions. This predictive ability would be an advanced decision-making tool used to mitigate dangers or to exploit positive trends

Constrained phosphine chalcogenide selenoethers supported by peri-substitution

A series of phosphorus and selenium peri-substituted acenaphthene species with the phosphino group oxidized by O, S, and Se has been isolated and fully characterized, including by single-crystal X-ray diffraction. The P(V) and Se(II) systems showed fluxional behavior in solution due to the presence of two major rotamers, as evidenced with solution NMR spectroscopy. Using Variable-Temperature NMR (VT NMR) and supported by DFT (Density Functional Theory) calculations and solid-state NMR, the major rotamers in the solid and in solution were identified. All compounds showed a loss of the through-space JPSe coupling observed in the unoxidized P(III) and Se(II) systems due to the sequestration of the lone pair of the phosphine, which has been previously identified as the major contributor to the coupling pathway.Publisher PDFPeer reviewe