Maximum Cell Loss Research Articles

Multicasting flow control for hybrid wired/wireless ATM networks

Multipoint communication has been an increasingly focused topic in computer communication networks, including the Internet, the ATM, and the wireless/mobile networks. The major challenges of designing multicast flow control protocols for a combined wired/wireless network are the varying transmission characteristics (bandwidth, error, reliability, and propagation delay) of the wireless and wired media, and the irregular, different, possibly conflicting flow control requests from multiple receivers in the point-to-multipoint (branching) setting, or from multiple senders in the multipoint-to-point (merging) setting. To address these issues, in this paper we design, analyze, and evaluate both branch-point and merge-point algorithms; we also provide a comparison on the major issues and solutions of the two multicasting scenarios. On point-to-multipoint ABR flow control, we examine an existing max–min fair branch-point algorithm proposed by Siu and Tzeng, and formally analyze its maximum cell loss. A new algorithm is then proposed. Both the maximum cell loss and max–min fairness of new algorithm are analyzed. With extensive simulation, we compare three branch-point algorithms (including a third one proposed by Fahmy, Jain et al.). On multipoint-to-point flow control, we extend the “essential fairness” concept, which was first proposed by Wang and Schwartz to flow control of multicast and unicast TCP traffic in the Internet to the multipoint-to-point ABR flow control. We design a general switch algorithm, which provides essential fairness to the multipoint-to-point ABR flow control. Three major variations of the algorithm, each of them guarantees different fairness (of favor) to unicast or multicast sessions, are then presented. These three schemes are evaluated by simulation. The significance of our approach is illustrated by the formal analysis of cell loss, feedback delay and max–min fairness properties, the generalized fairness definition for multicasting flow control, and the comparisons we made for (1) point-to-multipoint vs. multipoint-to-point scenarios, (2) three branch-point algorithms, and (3) three fairness definitions and mechanisms of multipoint-to-point multicasting. The work may be applied to multicast services in various high speed networks, such as supporting differentiated multicast service over IP, supporting flexible billing schemes, and providing QoS services over hybrid networks.

Achieving minimum slice loss for real time MPEG 2 based video networking in a flow-oriented input-queued ATM switching router system

Since the slice is the basic reconstruction unit at the display device, the MPEG-2-based video traffic in an ATM network is treated as many slice flows. For a real-time MPEG-2-based video service, the most important restriction is that all cells in a slice flow must be transmitted to their destination node completely before the deadline; otherwise, they should be dropped totally. The main purpose of this article is to propose a flow-oriented input-queued ATM switching router architecture with a scheduling strategy, MCL-MSL, taking advantage of the above characteristics to achieve higher-quality video services and more efficient utilization of network bandwidth. If the needed bandwidth for transmitting slice flows exceeds the available network bandwidth, MCL-MSL selects the slice flow with minimum slice loss for transmission. Furthermore, if multiple choices exist, it selects the one with maximum cell loss among them to achieve the most efficient bandwidth utilization.

Dopamine depletion protects striatal neurons from heatstroke-induced ischemia and cell death in rats.

To explore the importance of brain dopamine in the heatstroke-induced striatal ischemia and neuronal injury, we compared the temporal profile of the heatstroke-induced striatal extracellular dopamine release, striatal blood flow, and striatal neuronal loss in rats with or without striatal dopamine depletion produced by 6-hydroxydopamine. In vivo voltammetry was used in rats to measure changes in extracellular concentrations of dopamine in the corpus striatum. Striatal neuronal damage was rated on a scale from zero to three (0, no damage; 3, maximum cell loss). The autoradiographic diffusible tracer technique was used for the measurement of striatal blood flow. After the onset of heatstroke, the heatstroke rats without brain dopamine depletion displayed hyperthermia, decreased mean arterial pressure, increased intracranial pressure, decreased cerebral perfusion pressure, decreased striatal blood flow, increased striatal dopamine release, and increased score of striatal neuronal damage as compared with those of normothermic controls. However, when the striatal dopamine system was destroyed by 6-hydroxydopamine, the heatstroke-induced arterial hypotension, intracranial hypertension, ischemic damage to the striatum, and elevated striatal dopamine release were reduced. In addition, the survival time of the heatstroke rats was prolonged after depleting striatal dopamine. Thus it appears that dopamine depletion protects striatal neurons from heatstroke-induced ischemia and cell death.

Simulation Technique For Evaluating Cell-Loss Rate in ATM Networks

Asynchronous transfer mode (ATM) is the transmission and switching system that has been adopted for next generation multimedia networks. It is based on statistical multiplexing techniques and the performance of an ATM based network is quantified by the quality of service, QoS, delivered to the network users. QoS is defined in terms of the maximum cell loss rate and the delay/jitter allowable for a given network service connection. Normally, network performance is evaluated through the use of either mathematical or computer simulation modelling. The two model types differ in their individual limitations and the extent to which they can represent the real system. In this application, a computer simulation model has the advantage of flexibility and accuracy but is limited by the extent to which cell loss rate can be calculated. For video services, for example, a cell loss rate of 1 E-11 is specified which would require an unacceptably high amount of computer simulation time to investigate. In order to investigate such issues, therefore, this paper describes an approach which integrates both mathematical and computer simulation modelling. Simulation results are presented to prove the validity of the proposed approach, which is applicable for use in other application environments involving rare-event occurrences.

Hypervolemic hemodilution may protect the rat's striatal neurons from ischemic injury by reducing the extracellular dopamine

In vivo voltammetry (IVV) was used in rats with transient brain ischemia to measure changes in extracellular concentrations of dopamine (DA) and its metabolites in the corpus striatum. Striatal neuronal damage were also rated on a scale of 0–3 (0 = no damage; 3 = maximum cell loss). The striatal extracellular levels of DA and its metabolites increased by 12-fold during the 30 min of brain ischemia and returned to control values at 30 min after reperfusion. In another group treated with 4–5 ml of 10% human albumin intravenously infused 30 min before brain ischemia, both augmented striatal DA (and its metabolites) levels and striatal neuronal damages were reduced as compared to the ischemic control group ( P < 0.05, unpaired Student's t-test). These results suggest that hypervolemic hemodilution protects the striatal neurons from ischemic injury by reducing the extracellular striatal DA release in rats.

Dimensioning of an ATM switch with shared buffer and threshold priority

A number of recent studies have addressed the use of priority mechanisms in Asynchronous Transfer Mode (ATM) switches. This investigation concerns the performance evaluation and dimensioning of a shared-buffer switching element with a threshold priority mechanism (partial buffer sharing). It assumes that incoming ATM ceils are distinguished by a space priority assignment, i.e., loss of a high priority cell should be less likely than loss of a low priority cell. The evaluation method is analytic, based on an approximate discrete-time, finite-state Markov model of a switch and its incoming traffic. The development focuses on the formulation of steady-state loss probabilities for each priority class. Evaluation of delay measures for each class is also supported by the model; results concerning the latter are illustrated without development. The analysis of loss probabilities is then used to dimension the buffer capacity and threshold level such that required maximum cell loss probabilities are just satisfied for each cell type. Moreover, when so dimensioned with respect to relatively stringent loss requirements, i.e., probabilities of 10 10 and 10 s for high and low priority cells, respectively, we find that both loss performance and resource utilization are appreciably improved over a comparable switch without such a mechanism.

Evaluation of the effect of ototopical neomycin on spiral ganglion cell density in the guinea pig

The development of a reproducible unilateral deafness animal model was the primary objective of this study. Because of its importance in the function of cochlear prostheses, the status of the VIIIth nerve was used as the measure of deafness. The effect of a concentrated neomycin solution applied locally to the middle ear of the guinea pig was evaluated. Spiral ganglion cell survival was quantitated at 1, 2, 4, 6 and 10 weeks after exposure. Although the intermediate time periods showed moderate inter-animal variability, by ten weeks, consistent spiral ganglion cell loss was seen with maximum cell loss at the extreme apex (18.8% of control) and base (30.3% of control) and maximum cell survival in the lower middle turns of the cochlear spiral (53% of control).

Long-Term Effects of Iron Particle (HZE) Irradiation on Mouse Spermatogonia

High-energy (HZE) cosmic ray particles in space present an environmental hazard, especially to long-duration high altitude space travel. The energy released when these particles slow down and stop in living tissue causes deleterious biological effects, including death of cells. In order to study and quantitate the effects of this radiation, a number of cell systems could be used. The spermatogonial cell population in mouse testes has a rapidly dividing cell population, can be examined three days after irradiation, and is one of the most sensitive tissues to radiation. Therefore, it is ideally suited for quantitative studies of radiation effects. Previous work has shown that the various types of spermatogonial cells differ in their radiation sensitivity and that this can be very easily evaluated with the light/electron microscope. Using the system of staging established by Oak-berg and Huckins, the mixed or single cell population can be evaluated. Our work, using this method, has revealed cell sensitivity at doses as low as one rad. In these experiments, the animals were sacrificed three days post-irradiation because this is the time when maximum cell loss can be viewed. However, we are now reporting long term results of HZE particles using iron irradiation.

Endothelial cell loss following phacoemulsification in the pupillary plane

Endothelial cell loss following posterior chamber phacoemulsification with and without posterior chamber lens implantation was studied. Postoperative cell counts were taken four months after surgery. Three surgeons participated in this study. Posterior chamber phacoemulsification alone (30 patients) resulted in a mean cell loss of 9%, with a maximum cell loss of 22% in one patient. Posterior chamber phacoemulsification with posterior chamber lens implantation (30 patients) resulted in a mean cell loss of 8% with a maximum cell loss of 26% in one patient. Statistical analysis shows no difference in postoperative cell loss between these two groups.

Cytokinetics of Regeneration in β-Irradiated Guinea-Pig Epidermis

We studied the time course of depopulation and repopulation of epidermal cells in guinea-pig skin after β irradiation from a ${}^{90}{\rm Sr}-{}^{90}{\rm Y}$ sealed source. Immediately after clipping, one site on each flank was locally irradiated with 1000, 2200, 3000, or 5000 rad (six sites per animal). The changes in number of basal cells, labeling index (LI), and the appearance of clusters of ${}^{3}{\rm H}\text{-thymidine-labeled}$ basal cells (two or more pulse-labeled cells in direct contact) were observed. Maximum cell loss of recognizable basal cells of 20% on Day 8, 60% on Day 12, and 75% on Day 15 occurred after irradiation with 1000, 2200, and 3000 rad, respectively. The data for 5000 rad was similar to that in 3000-rad-irradiated epidermis. Repopulation (as evidenced by increase in LI and clusters of labeled cells) at all doses began on about the day of maximal cell loss. Regeneration occurred from survivors within the irradiated area after 1000 and 2200 rad, and was completed in 5 days (i.e.,...