The structure and management of service level agreements innetworks

The paper proposes a structure for quality-of-service (QoS)-centered service level agreements (SLA), and a framework for their real-time management in multiservice packet networks. The SLA is structured to be fair to both parties, the service provider and their customer. The SLA considered here are for QoS assured delivery of aggregate bandwidth from ingress to egress nodes; however, the control and signaling is for the more granular flows or calls. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed, the results of a prior off-line design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes. The routing and resource management are based on virtual partitioning and its supporting mechanism of bandwidth protection. The effectiveness of SLA management is measured by the robustness in performance in the presence of substantial diversity in actual traffic conditions. A simulation testbed called D'ARTAGNAN has been built from which we report numerical results for a case study. The results show that the SLA management scheme is robust, fair and efficient over a broad range of traffic conditions     

Conservation en congélation et réfrigération de la viande hachée de boeuf et de porc: évolution de la flore microbienne et des propriétés physico-chimiques en cours de stockage

The minced meat market in Belgium is growing steadily; its share of the market has increased from 10 to 30% in three years. However, the mincing of meat can produce intense microbiol proliferation and thus cause food putrification.Any changes occurring in meat, especially minced meat, are essentially of microbial origin, hence refrigeration is particularly important. With chilling, minimum temperatures must be maintained (0±1°C), since only temperatures below +3°C avoid any health risk linked with the growth of pathogens and production of toxins. Under chilled conditions the storage use of minced meat is four to five days. With freezing, temperatures of about - 18°C are needed to avoid the growth of bacteria, yeasts and mould. At this temperature micro-organisms are progressively rendered inactive, but destruction is never total. The kinetics of reducing micro-organism populations depends on the nature of the micro-organisms, the storage temperature (reduction is more intense at − 12°C that at − 18°C or at − 30°C) and the freezing rate (micro-organisms are better able to resist rapid freezing than slow freezing). One years storage at − 18°C will destroy 90 to 99% of the micro-organisms which were initially present in the product. Nevertheless, the chilled storage (+4°C) of thawed minced meat must not exceed three days.The physico-chemical evolution of cold stored minced meat is explained. In chilled storage, the onset of flavour defects can be related to the measurement of volatile nitrogen. In frozen storage, the crystallisation of the water causes cellular breakdown. The role of packaging is important in avoiding superficial freeze-drying which is accompanied by browning. In addition, fatty matter can deteriorate by oxidation even at freezing temperatures. The degree of alteration of fats can be appreciated by the acidity index and peroxide index (showing that it is undesirable to store minced pork at − 18°C for more than nine months).Use of a partial vacuum or modified atmosphere in combination with impermeable packaging will prolong the storage life of minced meat provided that the initial contamination is as low as possible and the maintenance of the cold chain is strictly respected.

Résumé

Le marché de la viande hachée progresse en Europe, du fait de plusieurs facteurs socio-économiques. Le hachage diminue considérablement la durée de conservation de la viande; sa consommation peut être dangereuse.L'article analyse les points suivants: emballage, réfrigération et congélation (notamment vitesse de congélation), température et durée de conservation, atmosphères modifiées et leur influence sur les propriétés physico-chimiques de la viande et sur le comportement microbien.     

Lightpath Re-optimization in mesh optical networks

Intelligent mesh optical networks deployed today offer unparalleled capacity, flexibility, availability, and, inevitably, new challenges to master all these qualities in the most efficient and practical manner. More specifically, demands are routed according to the state of the network available at the moment. As the network and the traffic evolve, the lightpaths of the existing demands becomes sub-optimal. In this paper we study two algorithms to re-optimize lightpaths in resilient mesh optical networks. One is a complete re-optimization algorithm that re-routes both primary and backup paths, and the second is a partial re-optimization algorithm that re-routes the backup paths only. We show that on average, these algorithms allow bandwidth savings of 3% to 5% of the total capacity in scenarios where the backup path only is re-routed, and substantially larger bandwidth savings when both the working and backup paths are re-routed. We also prove that trying all possible demand permutations with an online algorithm does not guarantee optimality, and in certain cases does not achieve it, while for the same scenario optimality is achieved through re-optimization. This observation motivates the needs for a re-optimization approach that does not just simply look at different sequences, and we propose and experiment with such an approach. Re-optimization has actually been performed in a nationwide live optical mesh network and the resulting savings are reported in this paper, validating reality and the usefulness of re-optimization in real networks.     

Distributed computation of shared backup path in mesh optical networks using probabilistic methods

We assess the benefits of using statistical techniques to ascertain the shareability of protection channels when computing shared-mesh restored lightpaths in optical mesh networks. These optical networks support wavelength conversion everywhere as a byproduct of the electronic nature of the switching in the optical-electronic-optical optical cross connect used. Current deterministic approaches require a detailed level of information proportional to the number of active lightpaths. Although this is not an issue for good sized networks in the foreseeable future, these approaches are not practicable for distributed route computation involving larger networks. On the other hand, distributed approaches that do not make use of shareability information require a significant amount of additional capacity compared to a centralized approach with access to complete shareability information. With the proposed approach we show that even with less information, independent of the amount of traffic demand, it is possible to predict the shareability of protection channels with remarkable accuracy. In addition, we propose a local distributed channel assignment scheme that is used in conjunction with our distributed route computation proposal to assign shared channels when provisioning the backup path. This channel assignment scheme can also be used to further optimize capacity usage in individual links upon certain events or at regular intervals. Experiments are provided that demonstrate that our approach yields faster computation times with no significant penalty in terms of capacity usage than a centralized approach using complete information.     

Vinorelbine and ifosfamide for unresectable non-small cell lung cancer

OBJECTIVE: The diagnostic value of cine magnetic resonance imaging (CMRI) that visualizes fluid and tissue movement was evaluated in patients with spinal intradural arachnoid cysts, a rare but increasingly detected cause of spinal cord dysfunction. METHODS: Four patients with thoracic spinal intradural arachnoid cysts were investigated with conventional T1- and T2-weighted and cardiac-gated CMRI. Four normal volunteers also underwent CMRI for comparison. RESULTS: Sagittal T1- and T2-weighted imaging showed lesions as an abnormal widening of the posterior spinal subarachnoid space, but mixed high- and low-signal intensities on T2-weighted imaging suggested cystic lesions. CMRI, using 16 to 20 sagittal gradient echo images during the cardiac cycle of normal volunteers, indicated synchronous signal changes along the subarachnoid space, suggesting a smooth cerebrospinal fluid flow. CMRI of patients detected that the caudal or cranial direction of the high-signal propagation suddenly reversed at some locations (as if rebounding) in an asynchronous fashion along the lesion (asynchronous rebound phenomenon), which was well demonstrated by the closed-loop video mode. Cystectomy revealed that the cysts consisted of multiple lobules and that the asynchronous rebound phenomenon corresponded with some boundaries of cyst lobules. CMRI also visualized dynamic spinal cord compression by the cyst. CONCLUSION: CMRI can demonstrate abnormal fluid flow and spinal cord compression caused by a spinal intradural arachnoid cyst.     

Treatment of low back pain and sciatica by intradiskal injection of chymopapain

Single injections of 50 mug estradiol-17beta (E2beta) into overiectomized sheep caused biphasic changes in plasma luteinizing hormone (LH). An initial 8-h period of LH inhibition was followed by a period (12-20 h after E2beta) of facilitated LH release. Pituitary LH responsiveness to small dosages of synthetic gonadotropin-releasing hormone (GnRH) was tested repeatedly at 2-h intervals during the time periods when plasma LH was inhibited and when it was facilitated. Reduced sensitivity to GnRH (91% decrease) characterized only the initial 4 h of the inhibitory period, suggesting that E2beta suppressed endogenous LH-releasing factor (LRF) during the latter part of the inhibitory period. Hypersensitivity (2-fold increase) to GnRH was briefly observed at the beginning of the period of E2beta-facilitated LH release. This transient and modest hypersensitivity does not completely account for the very large E2beta-induced increases in plasma LH. Therefore, E2beta probably increased endogenous LRF during the period of facilitated LH release.     

Invited: Routing Strategies for Capacity-Efficient and Fast-Restorable Mesh Optical Networks

Wavelength division multiplexed (WDM)-based mesh network infrastructures that route optical connections using intelligent optical cross-connects (OXCs) are emerging as the technology of choice to implement the next generation core optical networks. In these architectures a single OXC is capable of switching tens of terabits of traffic per second. With such data transfer rates at stake, it becomes increasingly challenging for carriers to (1) efficiently and cost-effectively operate and manage their infrastructure, and (2) cope with network failures while guaranteeing prescribed service level agreements (SLAs) to their customers. Proper routing of primary and backup paths is a critical component of the routing and restoration architecture required to meeting these challenges. In this paper we review some of the various strategies and approaches proposed so far to intelligently route connections while at the same time providing guaranteed protection against various types of network failures. We explore the tradeoffs associated with these approaches, and investigate in particular different, sometimes competing aspects, such as cost/capacity required, level of protection (link vs. node failure), restoration time, and complexity of route computation.     

An accurate, repeatable, and well characterized measurement of laser damage density of optical materials

Known for more than 40 years, laser damage phenomena have not been measured reproducibly up to now. Laser resistance of optical components is decreased by the presence of material defects, the distribution of which can initiate a distribution of damage sites. A raster scan test procedure has been used for several years in order to determine laser damage density of large aperture UV fused silica optics. This procedure was improved in terms of accuracy and repeatability. We describe the equipment, test procedure, and data analysis to perform this damage test of large aperture optics with small beams. The originality of the refined procedure is that a shot to shot correlation is performed between the damage occurrence and the corresponding fluence by recording beam parameters of hundreds of thousands of shots during the test at 10 Hz. We characterize the distribution of damaging defects by the fluence at which they cause damage. Because tests are realized with small Gaussian beams (about 1 mm at 1e), beam overlap and beam shape are two key parameters which have to be taken into account in order to determine damage density. After complete data analysis and treatment, we reached a repeatable metrology of laser damage performance. The measurement is destructive for the sample. However, the consideration of error bars on defect distributions in a series of parts allows us to compare data with other installations. This will permit to look for reproducibility, a necessary condition in order to test theoretical predictions.