Arbitrage Bounds for Prices of Weighted Variance Swaps

We develop robust pricing and hedging of a weighted variance swap when market prices for a finite number of co--maturing put options are given. We assume the given prices do not admit arbitrage and deduce no-arbitrage bounds on the weighted variance swap along with super- and sub- replicating strategies which enforce them. We find that market quotes for variance swaps are surprisingly close to the model-free lower bounds we determine. We solve the problem by transforming it into an analogous question for a European option with a convex payoff. The lower bound becomes a problem in semi-infinite linear programming which we solve in detail. The upper bound is explicit. We work in a model-independent and probability-free setup. In particular we use and extend F\"ollmer's pathwise stochastic calculus. Appropriate notions of arbitrage and admissibility are introduced. This allows us to establish the usual hedging relation between the variance swap and the 'log contract' and similar connections for weighted variance swaps. Our results take form of a FTAP: we show that the absence of (weak) arbitrage is equivalent to the existence of a classical model which reproduces the observed prices via risk-neutral expectations of discounted payoffs.Comment: 25 pages, 4 figure

Rotating dust solutions of Einstein's equations with 3-dimensional symmetry groups; Part 1: Two Killing fields spanned on u^{\alpha} and w^{\alpha }

For a rotating dust with a 3-dimensional symmetry group all possible metric forms can be classified and, within each class, explicitly written out. This is made possible by the formalism of Pleba\'nski based on the Darboux theorem. In the resulting coordinates, the Killing vector fields (if any exist) assume a special form. Each Killing vector field may be either spanned on the fields of velocity and rotation or linearly independent of them. By considering all such cases one arrives at the classification. With respect to the structures of the groups, this is just the Bianchi classification, but with all possible orientations of the orbits taken into account. In this paper, which is part 1 of a 3-part series, all solutions are considered for which two Killing fields are spanned on velocity and rotation. The solutions of Lanczos and G\"{o}del are identified as special cases, and their new invariant definitions are provided. In addition, a new invariant definition is given of the Ozsvath class III solution.Comment: 23 pages, LaTe

Integrating AIS Course Content Using Concept Maps

This paper introduces the use of a concept mapping technique to suggest an approach to teaching accounting information systems.  The concept mapping technique has been successfully used elsewhere in the field of education, and has characteristics suited to the instruction of accounting information systems.  Included in the paper are illustrations of the use of concept mapping technique to show how students’ knowledge of accounting can be leveraged to logically integrate in their education the information systems view of accounting

Successful thrombolysis of aortic prosthetic valve thrombosis during first trimester of pregnancy

Prosthetic heart valve thrombosis during pregnancy is life-threatening. Standard surgical treatment using cardiopulmonary bypass carries high maternal and fetal complications. Here we report a case of an antenatal female in first trimester with aortic prosthetic valve thrombosis (PVT), who was successfully thrombolysed with streptokinase with no complication to mother or fetus. The aim was to justify the usefulness of thrombolysis as a treatment option for prosthetic valve thrombosis in antenatal patients. A 35-year-old female patient presented in the first trimester of pregnancy with PVT at aortic position. After due consent, thrombolysis was undertaken with streptokinase. During the hospital course, she was followed clinically and with echocardiography. She symptomatically improved with thrombolysis. Transthoracic echocardiography showed complete resolution of thrombus. Peak trans-aortic velocity improved from 5.5 m/s to 3.7 m/s. She delivered a normal baby uneventfully in follow up at full term of pregnancy with no complications. Fibrinolytic therapy for mechanical valve thrombosis is a reasonable alternative to surgery in first trimester of pregnancy.KEY WORDS: Prosthetic valve thrombosis; Echocardiography; Streptokinase; Thrombolysis; Fetu

Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells with Improved Efficiency

Sun is the continuous source of renewable energy, from where we can get abundant of solar energy. Concept of conversionof solar energy into heat was used back in 200 B.C. since then, the solar cells have been developed which can convert solar energy into theelectrical energy and these systems have been produced commercially. The technologies to enhance the power conversion efficiency (PCE)have been continuously improved. Different technologies used for developing solar cells can be categorized either on the basis of materialused or techniques of technology development which is further termed as ‘first generation' (e.g. crystalline silicon), ‘second generation'(thin films of Amorphous silicon, Copper indium gallium selenide, Cadmium telluride), ‘Third generation' (Concentrated, Organic and Dyesensitize solar cell). These technologies give PCE up to 25% depending on the technology and the materials used. Nanotechnology enablesthe use of nanomaterial whose size is below 100 nm with extraordinary properties which has the capability to enhance the PCE to greaterextent. Various nanomaterials like Quantum Dots, Quantum well, carbon nanotubes, Nanowire and graphene have been used to makeefficient and economical solar cells, which not only provide high conversion efficiency economically but also are easy to produce. Today,by using nanotechnology, conversion efficiency up to 44.7 % has been achieved by Fraunhofer Institute at Germany. In this review article,we have reviewed the literature including various patents and publications, summarized the history of solar cell development, developmentof different technologies and rationale of their development highlighting the advantages and challenges involved in their development forcommercial purpose. We have also included the recent developments in solar cell research where different nanomaterials have beendesigned and used successfully to prove their superiority over conventional systems