Complete description of polarization effects in emission of a photon by an electron in the field of a strong laser wave

We consider emission of a photon by an electron in the field of a strong laser wave. Polarization effects in this process are important for a number of physical problems. A probability of this process for circularly or linearly polarized laser photons and for arbitrary polarization of all other particles is calculated. We obtain the complete set of functions which describe such a probability in a compact invariant form. Besides, we discuss in some detail the polarization effects in the kinematics relevant to the problem of electron to photon conversion at photon-photon and photon-electron colliders.Comment: 18 pages, minor changes, published versio

Adiponectin Deficiency Impairs Maternal Metabolic Adaptation to Pregnancy in Mice.

Hypoadiponectinemia has been widely observed in patients with gestational diabetes mellitus (GDM). To investigate the causal role of hypoadiponectinemia in GDM, adiponectin gene knockout (Adipoq-/- ) and wild-type (WT) mice were crossed to produce pregnant mouse models with or without adiponectin deficiency. Adenoviral vector-mediated in vivo transduction was used to reconstitute adiponectin during late pregnancy. Results showed that Adipoq-/- dams developed glucose intolerance and hyperlipidemia in late pregnancy. Increased fetal body weight was detected in Adipoq-/- dams. Adiponectin reconstitution abolished these metabolic defects in Adipoq-/- dams. Hepatic glucose and triglyceride production rates of Adipoq-/- dams were significantly higher than those of WT dams. Robustly enhanced lipolysis was found in gonadal fat of Adipoq-/- dams. Interestingly, similar levels of insulin-induced glucose disposal and insulin signaling in metabolically active tissues in Adipoq-/- and WT dams indicated that maternal adiponectin deficiency does not reduce insulin sensitivity. However, remarkably decreased serum insulin concentrations were observed in Adipoq-/- dams. Furthermore, β-cell mass, but not glucose-stimulated insulin release, in Adipoq-/- dams was significantly reduced compared with WT dams. Together, these results demonstrate that adiponectin plays an important role in controlling maternal metabolic adaptation to pregnancy

Singular Cross Sections in Muon Colliders

We address the problem that the cross section for the collisions of unstable particles diverges, if calculated by standard methods. This problem is considered for beams much smaller than the decay length of the unstable particle, much larger than the decay length and finally also for pancake- shaped beams. We find that in all cases this problem can be solved by taking into account the production/propagation of the unstable particle and/or the width of the incoming wave packets in momentum space.Comment: 12 pages, 3 figures. References corrected. Removed one sentence about a fact that was known. Added explaination why one of our graphs is different as compared to one of the references. Clearified explaination in sec. 3.

Dams

The construction of large dams is one of the most costly and controversial forms of public infrastructure investment in developing countries, but little is known about their impact. This paper studies the productivity and distributional effects of large dams in India. To account for endogenous placement of dams we use GIS data and the fact that river gradient affects a district's suitability for dams to provide instrumental variable estimates of their impact. We find that, in a district where a dam is built, agricultural production does not increase but poverty does. In contrast, districts located downstream from the dam benefit from increased irrigation and see agricultural production increase and poverty fall. Overall, our estimates suggest that large dam construction in India is a marginally cost-effective investment with significant distributional implications, and has, in aggregate, increased poverty.

Dams

The construction of large dams is one of the most costly and controversial forms of public infrastructure investment in developing countries, but little is known about their impact. This paper studies the productivity and distributional effects of large dams in India. To account for endogenous placement of dams we use GIS data and the fact that river gradient affects a district's suitability for dams to provide instrumental variable estimates of their impact. We find that, in a district where a dam is built, agricultural production does not increase but poverty does. In contrast, districts located downstream from the dam benefit from increased irrigation and see agricultural production increase and poverty fall. Overall, our estimates suggest that large dam construction in India is a marginally cost-effective investment with significant distributional implications, and has, in aggregate, increased poverty.Dams, Development Planning, Program Evaluation, India

The Electroweak Standard Model in the Axial Gauge

We derive the Feynman rules of the standard model in the axial gauge. After this we prove that the fields $\phi_W$ and $\phi_Z$ do not correspond to physical particles. As a consequence, these fields cannot appear as incoming or outgoing lines in Feynman graphs. We then calculate the contribution of these fields in the case of a particular decay mode of the top quark.Comment: 16 pages, no figures. Added derivation of polarization su

A Risky Climate for Southern African Hydro

This in-depth study of the hydrological risks to hydropower dams on the Zambezi River gives an early warning about what Southern Africa could be facing as it contemplates plans for more large hydropower dams in a time of climate change.Currently, 13,000 megawatts of new large-dam hydro is proposed for the Zambezi and its tributaries. The report finds that existing and proposed hydropower dams are not being properly evaluated for the risks from natural hydrological variability (which is extremely high in the Zambezi), much less the risks posed by climate change.Overall, Africa's fourth-largest river will experience worse droughts and more extreme floods. Dams being proposed and built now will be negatively affected, yet energy planning in the basin is not taking serious steps to address these huge hydrological uncertainties. The result could be dams that are uneconomic, disruptive to the energy sector, and possibly even dangerous.The report recommends a series of steps to address the coming storm of hydrological changes, including changes to how dams are planned and operated

Jamming-Resistant Learning in Wireless Networks

We consider capacity maximization in wireless networks under adversarial interference conditions. There are n links, each consisting of a sender and a receiver, which repeatedly try to perform a successful transmission. In each time step, the success of attempted transmissions depends on interference conditions, which are captured by an interference model (e.g. the SINR model). Additionally, an adversarial jammer can render a (1-delta)-fraction of time steps unsuccessful. For this scenario, we analyze a framework for distributed learning algorithms to maximize the number of successful transmissions. Our main result is an algorithm based on no-regret learning converging to an O(1/delta)-approximation. It provides even a constant-factor approximation when the jammer exactly blocks a (1-delta)-fraction of time steps. In addition, we consider a stochastic jammer, for which we obtain a constant-factor approximation after a polynomial number of time steps. We also consider more general settings, in which links arrive and depart dynamically, and where each sender tries to reach multiple receivers. Our algorithms perform favorably in simulations.Comment: 22 pages, 2 figures, typos remove

Should we build more large dams? The actual costs of hydropower megaproject development

A brisk building boom of hydropower mega-dams is underway from China to Brazil. Whether benefits of new dams will outweigh costs remains unresolved despite contentious debates. We investigate this question with the "outside view" or "reference class forecasting" based on literature on decision-making under uncertainty in psychology. We find overwhelming evidence that budgets are systematically biased below actual costs of large hydropower dams - excluding inflation, substantial debt servicing, environmental, and social costs. Using the largest and most reliable reference data of its kind and multilevel statistical techniques applied to large dams for the first time, we were successful in fitting parsimonious models to predict cost and schedule overruns. The outside view suggests that in most countries large hydropower dams will be too costly in absolute terms and take too long to build to deliver a positive risk-adjusted return unless suitable risk management measures outlined in this paper can be affordably provided. Policymakers, particularly in developing countries, are advised to prefer agile energy alternatives that can be built over shorter time horizons to energy megaprojects