Implications of land use change in tropical Northern Africa under global warming

A major link between climate and humans in Northern Africa, and the Sahel in particular, is land use and associated land cover change, mainly where subsistence farming prevails. Here we assess possible feedbacks between the type of land use and harvest intensity and climate by analyzing a series of idealized GCM experiments using the MPI-ESM. The base line for these experiments is a simulation forced by the RCP8.5 scenario which includes strong greenhouse gas emissions and anthropogenic land cover changes. The anthropogenic land cover changes in the RCP8.5 scenario include a mixture of pasture and agriculture. In subsequent simulations, we replace the entire area affected by anthropogenic land cover change in the region between the Sahara in the North and the Guinean Coast in the South (4 to 20° N) by either pasture or agriculture, respectively. In a second setup we vary the amount of harvest in case of agriculture. The RCP8.5 base line simulation reveals strong changes in mean agriculture and monsoon rainfall. In comparison with these changes, any variation of the type of land use in the study area leads to very small, mostly insignificantly small, additional differences in mean temperature and annual precipitation change in this region. Within the uncertainty of the representation of land use in current ESMs, our study suggests marginal feedback between land use changes and climate changes triggered by strong greenhouse gas emissions. Hence as a good approximation, climate change can be considered as external driver in models of land-use – conflict dynamics when seasonal or mean values are used as external driver

A new Method for Computing One-Loop Integrals

We present a new program package for calculating one-loop Feynman integrals, based on a new method avoiding Feynman parametrization and the contraction due to Passarino and Veltman. The package is calculating one-, two- and three-point functions both algebraically and numerically to all tensor cases. This program is written as a package for Maple. An additional Mathematica version is planned later.Comment: 12 pages Late

The European storm Kyrill in January 2007: synoptic evolution, meteorological impacts and some considerations with respect to climate change

The synoptic evolution and some meteorological impacts of the European winter storm Kyrill that swept across Western, Central, and Eastern Europe between 17 and 19 January 2007 are investigated. The intensity and large storm damage associated with Kyrill is explained based on synoptic and mesoscale environmental storm features, as well as on comparisons to previous storms. Kyrill appeared on weather maps over the US state of Arkansas about four days before it hit Europe. It underwent an explosive intensification over the Western North Atlantic Ocean while crossing a very intense zonal polar jet stream. A superposition of several favourable meteorological conditions west of the British Isles caused a further deepening of the storm when it started to affect Western Europe. Evidence is provided that a favourable alignment of three polar jet streaks and a dry air intrusion over the occlusion and cold fronts were causal factors in maintaining Kyrill's low pressure very far into Eastern Europe. Kyrill, like many other strong European winter storms, was embedded in a pre-existing, anomalously wide, north-south mean sea-level pressure (MSLP) gradient field. In addition to the range of gusts that might be expected from the synoptic-scale pressure field, mesoscale features associated with convective overturning at the cold front are suggested as the likely causes for the extremely damaging peak gusts observed at many lowland stations during the passage of Kyrill's cold front. Compared to other storms, Kyrill was by far not the most intense system in terms of core pressure and circulation anomaly. However, the system moved into a pre-existing strong MSLP gradient located over Central Europe which extended into Eastern Europe. This fact is considered determinant for the anomalously large area affected by Kyrill. Additionally, considerations of windiness in climate change simulations using two state-of-the-art regional climate models driven by ECHAM5 indicate that not only Central, but also Eastern Central Europe may be affected by higher surface wind speeds at the end of the 21st century. These changes are partially associated with the increased pressure gradient over Europe which is identified in the ECHAM5 simulations. Thus, with respect to the area affected, as well as to the synoptic and mesoscale storm features, it is proposed that Kyrill may serve as an interesting study case to assess future storm impacts

Upscaling methane emission hotspots in boreal peatlands

Upscaling the properties and the effects of small-scale surface heterogeneities to larger scales is a challenging issue in land surface modeling. We developed a novel approach to upscale local methane emissions in a boreal peatland from the micro-topographic scale to the landscape-scale. We based this new parameterization on the analysis of the water table pattern generated by the Hummock–Hollow model, a micro-topography resolving model for peatland hydrology. We introduce this parameterization of methane hotspots in a global model-like version of the Hummock–Hollow model, that underestimates methane emissions. We tested the robustness of the parameterization by simulating methane emissions for the next century forcing the model with three different RCP scenarios. The Hotspot parameterization, despite being calibrated for the 1976–2005 climatology, mimics the output of the micro-topography resolving model for all the simulated scenarios. The new approach bridges the scale gap of methane emissions between this version of the model and the configuration explicitly resolving micro-topography

Influence of anharmonicity on the negative thermal expansion of α−Sn\alpha-Sn

The lattice vibrational properties of $\alpha-Sn$ (gray tin) were investigated experimentally by temperature-dependent x-ray diffraction and theoretically by density functional theory calculations. Similar to the other elements of group IV, $\alpha-Sn$ exhibits a lattice anomaly at low temperatures and negative thermal expansion, with a minimum at $\sim 27K$ and a magnitude three times larger than in Si. The influence of anharmonic effects up to fourth-order potential terms on the phonon dispersion relations, the lattice parameters, and the thermal expansion coefficient have been tested. The performed analysis gives an excellent agreement with experiment when quartic potential terms are included in the theory. We point out that negative thermal expansion in $\alpha-Sn$ is not driven by the anharmonicity of the interatomic potential. This resolves the long-standing puzzle in the thermal behavior of $\alpha-Sn$

Electroweak Corrections to the Top Quark Decay

We have calculated the one-loop electroweak corrections to the decay t-> bW+, including the counterterm for the CKM matrix elements V(tb). Previous calculations used an incorrect delta V(tb) that led to a gauge dependent amplitude. However, since the contribution stemming from delta V(tb) is small, those calculations only underestimate the width by roughly one part in 10^5.Comment: 7 pages, 2 figure

The predictive value of molecular markers (p53, EGFR, ATM, CHK2) in multimodally treated squamous cell carcinoma of the oesophagus

Pretherapeutic identification of oesophageal squamous cell carcinomas that will respond to neoadjuvant chemoradiotherapy is an important attempt for improvement of patient's prognosis. In the current study, pretherapeutic biopsies from 94 oesophageal squamous cell carcinomas (cT3, cN0/+, cM0) in patients who underwent neoadjuvant chemoradiotherapy (RCTx: 45 Gy plus cisplatin and 5-fluorouracil) and subsequent oesophagectomy in the setting of a single-centre prospective treatment trial were investigated by means of immunohistochemistry. Expression of proteins involved in DNA repair and/or cell-cycle regulation, that is p53, p53 (phosphorylated at Ser15), EGFR, ATM protein kinase (phosphorylated at Ser1981) and checkpoint kinase 2 (CHK2) (phosphorylated at Thr68) was correlated with the response to RCTx and with overall survival. Tumours that were positive for CHK2 expression more frequently showed clinically determined regression after RCTx (69.4%) than tumours that were negative for CHK2 expression (32.1%; P=0.0011), whereas other parameters did not correlate with tumour regression. Expression of ATM correlated with expression of CHK2 (P=0.0061) and p53-phospho (P=0.0064). Expression of p53 correlated with expression of p53-phospho (P<0.0001). In contrast to clinical and histopathological response evaluation, none of the molecular parameters under investigation correlated with overall survival. In conclusion, expression analysis of p53, EGFR CHK2 and ATM has no predictive value in multimodally treated oesophageal squamous cell carcinoma

How to Integrate Divergent Integrals: a Pure Numerical Approach to Complex Loop Calculations

Loop calculations involve the evaluation of divergent integrals. Usually [1] one computes them in a number of dimensions different than four where the integral is convergent and then one performs the analytical continuation and considers the Laurent expansion in powers of epsilon =n-4. In this paper we discuss a method to extract directly all coefficients of this expansion by means of concrete and well defined integrals in a five dimensional space. We by-pass the formal and symbolic procedure of analytic continuation; instead we can numerically compute the integrals to extract directly both the coefficient of the pole 1/epsilon and the finite part.Comment: 13 pages, 1 Postscript figur