Performance modeling tools with applications

This paper deals with the role of performance modeling tools. It introduces 3 major tool development centers and shows how a given tool can be applied to investigate the performance of a finite-source retrial queueing system

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

On a Pitman-Yor problem

We answer the question posed by Pitman and Yor (Canad. J. Math. 55 (2003) 292-330) about the existence of probability distributions which solve distributional equation of a special type. In the "typical" case we study the tail behaviour of these distributions. Two new explicit examples are given.Perpetuity Fixed points Shot noise transform Shot noise distribution Infinite divisibility Tail behaviour

J. ROSZIK et al.: RETRIAL QUEUES IN THE PERFORMANCE MODELING OF... RETRIAL QUEUES IN THE PERFORMANCE MODELING OF CELLULAR MOBILE NETWORKS USING MOSEL

Abstract: This paper investigates a multiserver infinite-source retrial queueing system for the performance modeling of cellular mobile communication networks. The objective is to demonstrate how performance tool MOSEL (Modeling, Specification and Evaluation Language) can be efficiently used in the modeling of cell based networks. In our analysis the blocked and dropped users are treated separately, that is they redial with different probabilities and different rates, with reducing the state space by maximizing the number of redialing customers with appropriately large values (i. e. when the ignored probability mass can be neglected). The guard channel scheme is included in the model, too. The novelty of our analysis is that not only the active but also both types of redialing customers are allowed to depart to other cells, which was not the case in the previous works. The model description is translated step by step into the description language of MOSEL, and then it is automatically converted into the other tool-specific system descriptions and analyzed by the appropriate tools. As the benefit of the tool the effects of various system parameters on the fresh call blocking probability, on the handoff call dropping probability and on the grade of service are displayed and analyzed graphically