Regge's space-time skeletons and the quantization of 2d gravity

Regge's method for regularizing euclidean quantum gravity is applied to two dimensional gravity. Using topologies with genus zero and two and a scale invariant measure, we show that the Regge method fails to reproduce the values of the string susceptibilities of the continuum model.Comment: 3 pages, contribution to Lattice'94, 3 ps figs. (uuencoded

Combustion and emissions characteristics of a compression-ignition engine using ammonia-DME mixtures

In this study operating characteristics of a compression-ignition engine using mixtures of ammonia and dimethyl ether (DME) are investigated. Ammonia can be regarded as a carbon-free fuel that can help mitigate greenhouse gas emissions. Ammonia is one of the world\u27s most synthesized chemicals and its infrastructure is well established. Recent technological advances also show that ammonia can be produced from renewable resources, making it an attractive energy carrier. In the present study, a high-pressure mixing system is developed to blending liquid ammonia with DME that serves to initiate combustion. The engine uses a modified injection system without fuel return to prevent fuel mixture from vaporizing in the return line. Results using different mixture quantities of ammonia and DME show that ammonia causes longer ignition delays and limits the engine load conditions due to its high autoignition temperature and low flame speed. The inclusion of ammonia in the fuel mixture also decreases combustion temperature, resulting in higher CO and HC emissions. NOx emissions increase due to the formation of fuel NOx when ammonia is used. However, improvements for the same operating conditions were made by increasing the injection pressure using 40%NH3-60%DME. Exhaust ammonia emissions is on the order of hundreds of ppm under the conditions tested. Soot emissions are extremely low for all cases. Double injection schemes using 20%NH3-80%DME are also employed and found not to extend engine performance. Its effects on the exhaust emissions vary with operating conditions

Price structures in the market for long-distance voice telephony in Germany

This paper analyses price structures in the liberalized German market for long-distance telecommunications services. Theoretically deduced patterns are backed-up by empirical observations. The market is exceptionally competitive; entry is taking place on a large scale and prices are falling sharply. The product is strongly homogeneous and search costs are extremely low. Propositions included in the assessment concern the necessary absence of systematic price discrimination, the probability of cut-throat competition, and the necessary presence of a demand-compatible peak-load structure. With respect to the latter there is an observable move of the price structure, which can be explained by regulatory failure

On the Reliability of LTE Random Access: Performance Bounds for Machine-to-Machine Burst Resolution Time

Random Access Channel (RACH) has been identified as one of the major bottlenecks for accommodating massive number of machine-to-machine (M2M) users in LTE networks, especially for the case of burst arrival of connection requests. As a consequence, the burst resolution problem has sparked a large number of works in the area, analyzing and optimizing the average performance of RACH. However, the understanding of what are the probabilistic performance limits of RACH is still missing. To address this limitation, in the paper, we investigate the reliability of RACH with access class barring (ACB). We model RACH as a queuing system, and apply stochastic network calculus to derive probabilistic performance bounds for burst resolution time, i.e., the worst case time it takes to connect a burst of M2M devices to the base station. We illustrate the accuracy of the proposed methodology and its potential applications in performance assessment and system dimensioning.Comment: Presented at IEEE International Conference on Communications (ICC), 201

Indications for Criticality at Zero Curvature in a 4d Regge Model of Euclidean Quantum Gravity

We re-examine the approach to four-dimensional Euclidean quantum gravity based on the Regge calculus. A cut-off on the link lengths is introduced and consequently the gravitational coupling and the cosmological constant become independent parameters. We determine the zero curvature, $=0$, line in the coupling constant plane by numerical simulations. When crossing this line we find a strong, probably first order, phase transition line with indications of a second order endpoint. Beyond the endpoint the transition through the $=0$ line appears to be a crossover. Previous investigations, using the Regge or the Dynamical Triangulation approach, dealt with a limit in which the first order transition prevails.Comment: Contribution to the lattice 2003 Tsukuba symposiu

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

A common approach to generate tailored materials and nanoparticles (NPs) is the formation of molecular monolayers by chemisorption of bifunctional anchor molecules. This approach depends critically on the choice of a suitable anchor group. Recently, bifunctional catecholates, inspired by mussel-adhesive proteins (MAPs) and bacterial siderophores, have received considerable interest as anchor groups for biomedically relevant metal surfaces and nanoparticles. We report here the synthesis of new tripodal catecholates as multivalent anchor molecules for immobilization on metal surfaces and nanoparticles. The tripodal catecholates have been conjugated to various effector molecules such as PEG, a sulfobetaine and an adamantyl group. The potential of these conjugates has been demonstrated with the immobilization of tripodal catecholates on ZnO NPs. The results confirmed a high loading of tripodal PEG-catecholates on the particles and the formation of stable PEG layers in aqueous solution

Stable isochronal synchronization of mutually coupled chaotic lasers

The dynamics of two mutually coupled chaotic diode lasers are investigated experimentally and numerically. By adding self feedback to each laser, stable isochronal synchronization is established. This stability, which can be achieved for symmetric operation, is essential for constructing an optical public-channel cryptographic system. The experimental results on diode lasers are well described by rate equations of coupled single mode lasers

Conditions in subjects with rheumatic diseases: pulmonary manifestations of vasculitides

Pulmonary involvement is a common complication of vasculitides, especially small vessel vasculitides. This review provides an overview of vasculitic manifestations of the lung as well as of other organs involved in vasculitides. Furthermore, it provides the diagnostic procedures required to asses a patient with vasculitic lung involvement and gives an overview of current treatment strategies