Smooth Wilson Loops in N=4 Non-Chiral Superspace

We consider a supersymmetric Wilson loop operator for 4d N=4 super Yang-Mills theory which is the natural object dual to the AdS_5 x S^5 superstring in the AdS/CFT correspondence. It generalizes the traditional bosonic 1/2 BPS Maldacena-Wilson loop operator and completes recent constructions in the literature to smooth (non-light-like) loops in the full N=4 non-chiral superspace. This Wilson loop operator enjoys global superconformal and local kappa-symmetry of which a detailed discussion is given. Moreover, the finiteness of its vacuum expectation value is proven at leading order in perturbation theory. We determine the leading vacuum expectation value for general paths both at the component field level up to quartic order in anti-commuting coordinates and in the full non-chiral superspace in suitable gauges. Finally, we discuss loops built from quadric splines joined in such a way that the path derivatives are continuous at the intersection.Comment: 44 pages. v2 Added some clarifying comments. Matches the published versio

Do hybrid compressed air energy storage (HCAES) systems offer a viable alternative solution to energy storage requirements for small to medium size renewable energy systems?

With the increased international pressure to make use of more renewable energy technologies, the intermittent nature of renewable resources requires some kind of energy storage in order to ensure energy is available when needed. Most conventional storage solutions for small to medium size applications are based on chemical batteries which are hazardous, not easily recycled and can have a negative environmental effect. Thus renewed interest is being given to clean and environmentally friendly storage technologies such as compressed air, a technology more than a century old, and still being used in flammable and explosive industrial environments. New, improved compressors, air motors and advanced technologies and materials that can withstand large fluctuations in temperature have become available, and have been used by some innovative manufacturers to produce Hybrid Compressed Air Energy Storage (HCAES) Systems, which claim to have high turn around efficiencies. In this research, the available literature on compressed air systems, and new HCAES systems are evaluated in order to compare them to conventional storage technologies. Furthermore, an evaluation was conducted to determine if it would be possible to design a HCAES system with off the shelf air equipment and if this HCAES system could possibly be a viable alternative to conventional or new chemical battery storage technologies. During the research it was found that there is very little literature on the subject of HCEAS systems, and that the manufacturers do not give much information or proof on actual efficiencies of their systems. What was found is that there are several academic institutions working on combining compressed air with technologies such as diesel engines, oil pneumatics, wind, water, super capacitors and flywheels in order to improve current hybrid systems’ effectiveness and efficiency in energy storage and supply applications and to reduce the environmental footprint of such systems. From literature, research and manufacturer specifications it was found that although theoretical efficiencies of close to 100% can be realised, available HCAES systems do not offer such an effective or efficient solution as chemical battery systems. In addition off the shelf compressors and motors that can be used to design a HCAES system have been manufactured to give high performance and torque with low efficiencies. The efficiency is further drastically reduced as the storage pressure is increased, which is necessary to decrease storage vessel requirements

Sedimentpetrologie van het dekgebergte in Limburg

Hoofdstuk 1. Eenige principieele vraagstukken betreffende de zware-mineralenanalyse worden hier opnieuw naar voren gebracht. Uitgaande van waarschijnlijkheidskrommen wordt aangegeven, hoe groot de waarschijnlijkheid is, dat bepaalde afwijkingen van het "werkelijke" percentage zullen optreden, als men de mineraalverhoudingen niet in het geheele preparaat, doch slechts in een steekproef van 100 of 500 korrels bepaalt." ... Zie: Samenvattin

The impact of cognitive load on operatic singers' timing performance

In the present paper, we report the results of an empirical study on the effects of cognitive load on operatic singing. The main aim of the study was to investigate to what extent a working memory task affected the timing of operatic singers' performance. Thereby, we focused on singers' tendency to speed up, or slow down their performance of musical phrases and pauses. Twelve professional operatic singers were asked to perform an operatic aria three times; once without an additional working memory task, once with a concurrent working memory task (counting shapes on a computer screen), and once with a relatively more difficult working memory task (more shapes to be counted appearing one after another). The results show that, in general, singers speeded up their performance under heightened cognitive load. Interestingly, this effect was more pronounced in pauses-more in particular longer pauses-compared to musical phrases. We discuss the role of sensorimotor control and feedback processes in musical timing to explain these findings

Opposite effects of two zinc(II) dithiocarbamates on NF-kB pathway

Inhibiting nuclear factor-kappaB (NF-kB) activation in anticancer and antiinflammatory therapy is of topical interest. Current research in molecular biology has dramatically advanced in the understanding of the cellular events involved in NF-kB induction. Dithiocarbamates, in particular diethyldithiocarbamate and pyrrolidinedithiocarbamate, have been known and widely used as strong inhibitors of NF-kB signaling pathway for more than ten years. Their activity is frequently thought to be due to chelating of zinc or copper present in serum supplemented in the culture medium. Zinc(II) diethyldithiocarbamate (Et2Zn) and zinc(II) dibenzyldithiocarbamate (Bz2Zn) were prepared by direct synthesis in aqueous millieu. They were structurally characterized by X-ray analysis (solid phase) and mass spectrometry (aqueous conditions). Et2Zn and Bz2Zn both in 20 micromolar concentration were applied to HeLa cells. The status of NF-kB signaling was assessed as nuclear translocation of p65 subunit. Surprisingly, Et2Zn activated NF-kB pathway, while TNF-dependent activation of NF-kB was inhibited by Bz2Zn. Our results are preliminary

The Law of International Trade: copyright law related aspects of the use of the internet from a German perspective in comparison to South African Legislation and jurisdiction

Today, the Internet cannot be described any more as a new technology, even though it is still growing and new features are constantly invented and added. The Internet is now in constant daily use by millions of users all over the world. However, as it could be observed many times before, legal developments find it difficult to hold pace with the technical development. That is especially true in regard to copyright law and the use of the Internet. Although computer programs and their specific requirements are now renown internationally by many legal system, so far there are little regulations which deal with the specific demands of the Internet use. However, efforts in that direction are undertaken, but the outcome is still uncertain. In Germany, first serious efforts to tackle the legal problems of the Internet could be observed in 1996, but only in the recent two years a large number of publications dealing with different problems in that regard were made available to the public. The situation in South Africa is somewhat different. Only little publication in that regard could so far be found. Often, for whatever reason, problems are actually more pointed out than an effort is made to provide an answer. Still though, one will actually find, that many problems can be discussed in an international context regardless to the exact provisions of a certain legal order. The following work will therefore compare the German and South African legislation and jurisdiction in regard to copyright related aspects of the Internet. Although one will observe that more room is given to the German point of view, it is to hope that this will at the same time serve as a source of inspiration to the South African lawyer. The final aim, however, should be to harmonise internationally rules in that regard, so that no legal order is to prevail or, to put it into other words, the aim is to make the law as 'international' as the Internet itself

Polynomial time ultrapowers and the consistency of circuit lower bounds

A polynomial time ultrapower is a structure given by the set of polynomial time computable functions modulo some ultrafilter. They model the universal theory ∀PV of all polynomial time functions. Generalizing a theorem of Hirschfeld (Israel J Math 20(2):111–126, 1975), we show that every countable model of ∀PV is isomorphic to an existentially closed substructure of a polynomial time ultrapower. Moreover, one can take a substructure of a special form, namely a limit polynomial time ultrapower in the classical sense of Keisler (in: Bergelson, V., Blass, A., Di Nasso, M., Jin, R. (eds.) Ultrafilters across mathematics, contemporary mathematics vol 530, pp 163–179. AMS, New York, 1963). Using a polynomial time ultrapower over a nonstandard Herbrand saturated model of ∀PV we show that ∀PV is consistent with a formal statement of a polynomial size circuit lower bound for a polynomial time computable function. This improves upon a recent result of Krajíček and Oliveira (Logical methods in computer science 13 (1:4), 2017).Peer ReviewedPostprint (author's final draft