A Comprehensive Analysis of Proportional Intensity-based Software Reliability Models with Covariates (New Developments on Mathematical Decision Making Under Uncertainty)

The black-box approach based on stochastic software reliability models is a simple methodology with only software fault data in order to describe the temporal behavior of fault-detection processes, but fails to incorporate some significant development metrics data observed in the development process. In this paper we develop proportional intensity-based software reliability models with time-dependent metrics, and propose a statistical framework to assess the software reliability with the timedependent covariate as well as the software fault data. The resulting models are similar to the usual proportional hazard model, but possess somewhat different covariate structure from the existing one. We compare these metricsbased software reliability models with eleven well-known non-homogeneous Poisson process models, which are the special cases of our models, and evaluate quantitatively the goodness-of-fit and prediction. As an important result, the accuracy on reliability assessment strongly depends on the kind of software metrics used for analysis and can be improved by incorporating the time-dependent metrics data in modeling

Discrete-time cost analysis for a telecommunication billing application with rejuvenation

AbstractSoftware rejuvenation is a proactive fault management technique that has been extensively studied in the recent literature. In this paper, we focus on an example for a telecommunication billing application considered in [1] and develop the discrete-time stochastic models to estimate the optimal software rejuvenation schedules. More precisely, two software cost models with rejuvenation are formulated via the discrete semi-Markov processes, and the optimal software rejuvenation schedules which minimize the expected costs per unit time in the steady state are derived analytically. Further, we develop statistically nonparametric algorithms to estimate the optimal software rejuvenation schedules, provided that the complete sample data of failure times are given. Then, a new statistical device, called discrete total time on test statistics, is introduced. Finally, we examine asymptotic properties for the statistical estimation algorithms proposed in this paper through a simulation experiment

A note on sensitivity analysis for PH approximation (New Developments on Mathematical Decision Making Under Uncertainty)

This paper presents the moment-based approximation for model depandability when the uncertainty of model parameters is considered. The propagation of uncertainty of model parameters can be estimated by regarding the model parameters as random variables. However, statistical model often involves the non-exponential distribution such as Weibull distribution, which leads to the high computation cost of uncertainty analysis. In this paper, we focus on the Phase-type(PH) distribution to overcome the difficulty of computation for model contains Weibull distribution

Pull-Type Security Patch Management in Intrusion Tolerant Systems: Modeling and Analysis

In this chapter, we introduce a stochastic framework to evaluate the system availability of an intrusion tolerant system (ITS), where the system undergoes patch management with a periodic vulnerability checking strategy, i.e., pull-type patch management. In particular, a composite stochastic reward net (SRN) is developed to capture the overall system behaviors, including vulnerability discovery, intrusion tolerance, and reactive maintenance operations. Furthermore, two kinds of availability criteria, the interval availability and the steady-state availability of the system, are formulated by applying the phase-type (PH) approximation to solve the Markov regenerative process (MRGP) model derived from the composite SRN. Numerical experiments are conducted to investigate the effects of the vulnerability checking interval on the system availability

Modes of Retrotransposition of Long Interspersed Element-1 by Environmental Factors

Approximately 42% of the human genome is composed of endogenous retroelements, and the major retroelement component, long interspersed element-1 (L1), comprises ∼17% of the total genome. A single human cell has more than 5 × 105 copies of L1, 80∼100 copies of which are competent for retrotransposition (RTP). Notably, L1 can induce RTP of other retroelements, such as Alu and SVA, and is believed to function as a driving force of evolution. Although L1-RTP during early embryogenesis has been highlighted in the literature, recent observations revealed that L1-RTP also occurs in somatic cells. However, little is known about how environmental factors induce L1-RTP. Here, we summarize our current understanding of the mechanism of L1-RTP in somatic cells. We have focused on the mode of L1-RTP that is dependent on the basic helix–loop–helix/per–arnt–sim (bHLH/PAS) family of transcription factors. Along with the proposed function of bHLH/PAS proteins in environmental adaptation, we discuss the functional linking of L1-RTP and bHLH/PAS proteins for environmental adaptation and evolution

CNOT1 regulates circadian behaviour through Per2 mRNA decay in a deadenylation-dependent manner

Circadian clocks are an endogenous internal timekeeping mechanism that drives the rhythmic expression of genes, controlling the 24 h oscillatory pattern in behaviour and physiology. It has been recently shown that post-transcriptional mechanisms are essential for controlling rhythmic gene expression. Controlling the stability of mRNA through poly(A) tail length modulation is one such mechanism. In this study, we show that Cnot1, encoding the scaffold protein of the CCR4-NOT deadenylase complex, is highly expressed in the suprachiasmatic nucleus, the master timekeeper. CNOT1 deficiency in mice results in circadian period lengthening and alterations in the mRNA and protein expression patterns of various clock genes, mainly Per2. Per2 mRNA exhibited a longer poly(A) tail and increased mRNA stability in Cnot1+/− mice. CNOT1 is recruited to Per2 mRNA through BRF1 (ZFP36L1), which itself oscillates in antiphase with Per2 mRNA. Upon Brf1 knockdown, Per2 mRNA is stabilized leading to increased PER2 expression levels. This suggests that CNOT1 plays a role in tuning and regulating the mammalian circadian clock.journal articl

Imaging analysis reveals mechanistic differences between first- and second-phase insulin exocytosis

The mechanism of glucose-induced biphasic insulin release is unknown. We used total internal reflection fluorescence (TIRF) imaging analysis to reveal the process of first- and second-phase insulin exocytosis in pancreatic β cells. This analysis showed that previously docked insulin granules fused at the site of syntaxin (Synt)1A clusters during the first phase; however, the newcomers fused during the second phase external to the Synt1A clusters. To reveal the function of Synt1A in phasic insulin exocytosis, we generated Synt1A-knockout (Synt1A−/−) mice. Synt1A−/− β cells showed fewer previously docked granules with no fusion during the first phase; second-phase fusion from newcomers was preserved. Rescue experiments restoring Synt1A expression demonstrated restoration of granule docking status and fusion events. Inhibition of other syntaxins, Synt3 and Synt4, did not affect second-phase insulin exocytosis. We conclude that the first phase is Synt1A dependent but the second phase is not. This indicates that the two phases of insulin exocytosis differ spatially and mechanistically