Inference with progressively censored <Emphasis Type="Italic">k</Emphasis>-out-of-<Emphasis Type="Italic">n</Emphasis> system lifetime data

A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes.     

Inflammatory and cytotoxic responses of an alveolar-capillary coculture model to silica nanoparticles: Comparison with conventional monocultures

Background

Large production volumes of zinc oxide nanoparticles (ZnONP) might be anticipated to pose risks, of accidental inhalation in occupational and even in consumer settings. Herein, we further investigated the pathological changes induced by ZnONP and their possible mechanism of action.

Methods

Two doses of ZnONP (50 and 150 cm²/rat) were intratracheally instilled into the lungs of rats with assessments made at 24 h, 1 wk, and 4 wks after instillation to evaluate dose- and time-course responses. Assessments included bronchoalveolar lavage (BAL) fluid analysis, histological analysis, transmission electron microscopy, and IgE and IgA measurement in the serum and BAL fluid. To evaluate the mechanism, alternative ZnONP, ZnONP-free bronchoalveolar lavage exudate, and dissolved Zn²⁺ (92.5 μg/rat) were also instilled to rats. Acridine orange staining was utilized in macrophages in culture to evaluate the lysosomal membrane destabilization by NP.

Results

ZnONP induced eosinophilia, proliferation of airway epithelial cells, goblet cell hyperplasia, and pulmonary fibrosis. Bronchocentric interstitial pulmonary fibrosis at the chronic phase was associated with increased myofibroblast accumulation and transforming growth factor-β positivity. Serum IgE levels were up-regulated by ZnONP along with the eosinophilia whilst serum IgA levels were down-regulated by ZnONP. ZnONP are rapidly dissolved under acidic conditions (pH 4.5) whilst they remained intact around neutrality (pH 7.4). The instillation of dissolved Zn²⁺ into rat lungs showed similar pathologies (eg., eosinophilia, bronchocentric interstitial fibrosis) as were elicited by ZnONP. Lysosomal stability was decreased and cell death resulted following treatment of macrophages with ZnONP in vitro.

Conclusions

We hypothesise that rapid, pH-dependent dissolution of ZnONP inside of phagosomes is the main cause of ZnONP-induced diverse progressive severe lung injuries.     

On the mechanism of the esterification of a β-hydroxy alkylamide with a carboxylic acid

β-Hydroxy alkylamide reacts with carboxylic acid to form an ester much faster than with a normal alcohol. Many suggestions have been made to describe the mechanism of this reaction, but none of them have been proved. It is clear that this reaction cannot be seen as a normal esterification since it cannot be catalysed by acids or bases. We have prepared model compounds, for which calibration curves have been obtained by means of UV spectroscopy. A technique was developed for separating the starting materials and the expected reaction products by means of HPLC. In this way, quantitative and qualitative information about the reaction mixtures could be obtained as a function of time. This method revealed the existence of an intermediate oxazolinium cation. The formation of this compound plays a key role in the esterification. Apart from the expected ester and the intermediate, various other reaction products were determined. All the reaction products could be obtained in a pure state with the aid of preparative HPLC. The structures of the compounds were studied using ¹H NMR spectrometry. A reaction mechanism has been put forward to explain the experimental data.     

Leptomeningeal angiomatosis accompanied by hair follicle nevus

A 5-day-old male infant with leptomeningeal angiomatosis accompanied by hair follicle nevus and congenital alopecia is reported. Admitted for frequent left hemiconvulsions, he had three small papular lesions around his right eye and ipsilateral alopecia from the frontal to parietal areas. Histopathological examination of the papular lesions revealed crowding of hair follicles. There were no other skin lesions and no ophthalmic abnormalities. Ictal EEG showed a theta burst in the right parietal area. Computed tomography of the brain revealed cerebral atrophy and a slightly high intensity lesion in the right parietal and occipital lobes with calcification. Gyriform enhancement was demonstrated by contrast MRI in these areas. The pathogenesis is discussed. This case may represent a previously unknown neurocutaneous syndrome.     

On the use of MTBDDs for performability analysis and verification of stochastic systems

This paper describes how to employ multi-terminal binary decision diagrams (MTBDDs) for the construction and analysis of a general class of models that exhibit stochastic, probabilistic and non-deterministic behaviour. It is shown how the notorious problem of state space explosion can be circumvented by compositionally constructing symbolic (i.e. MTBDD-based) representations of complex systems from small-scale components. We emphasise, however, that compactness of the representation can only be achieved if heuristics are applied with insight into the structure of the system under investigation. We report on our experiences concerning compact representation, performance analysis and verification of performability properties.     

Plastic‐film displays with NanoBlock IC drivers integrated by a fluidic self‐assembly process

Abstract— High‐performance compact plastic displays have been built by integrating high‐quality crystalline‐Si NanoBlock IC drivers into plastic films using a fluidic self‐assembly (FSA) process. Plastic‐film‐based liquid‐crystal displays, only 500 μm thick, were integrated into smartcards using NanoBlock IC voltage drivers. In an additional demonstration, polymer‐LED displays were constructed using NanoBlock IC current drivers. FSA technology provides a cost‐effective means of packaging integrated circuits within plastic film, enabling high‐performance backplanes that can be combined with a variety of display media.     

A tool for model-checking Markov chains

Markov chains are widely used in the context of the performance and reliability modeling of various systems. Model checking of such chains with respect to a given (branching) temporal logic formula has been proposed for both discrete [34, 10] and continuous time settings [7, 12]. In this paper, we describe a prototype model checker for discrete and continuous-time Markov chains, the Erlangen–Twente Markov Chain Checker E⊢MC², where properties are expressed in appropriate extensions of CTL. We illustrate the general benefits of this approach and discuss the structure of the tool. Furthermore, we report on successful applications of the tool to some examples, highlighting lessons learned during the development and application of E⊢MC². Published online: 19 November 2002 Correspondence to: Holger Hermanns     

Model-checking algorithms for continuous-time Markov chains

Continuous-time Markov chains (CTMCs) have been widely used to determine system performance and dependability characteristics. Their analysis most often concerns the computation of steady-state and transient-state probabilities. This paper introduces a branching temporal logic for expressing real-time probabilistic properties on CTMCs and presents approximate model checking algorithms for this logic. The logic, an extension of the continuous stochastic logic CSL of Aziz et al. (1995, 2000), contains a time-bounded until operator to express probabilistic timing properties over paths as well as an operator to express steady-state probabilities. We show that the model checking problem for this logic reduces to a system of linear equations (for unbounded until and the steady-state operator) and a Volterra integral equation system (for time-bounded until). We then show that the problem of model-checking time-bounded until properties can be reduced to the problem of computing transient state probabilities for CTMCs. This allows the verification of probabilistic timing properties by efficient techniques for transient analysis for CTMCs such as uniformization. Finally, we show that a variant of lumping equivalence (bisimulation), a well-known notion for aggregating CTMCs, preserves the validity of all formulas in the logic.     

Synthesis and stochastic assessment of cost-optimal schedules

We treat the problem of generating cost-optimal schedules for orders with individual due dates and cost functions based on earliness/tardiness. Orders can run in parallel in a resource-constrained manufacturing environment, where resources are subject to stochastic breakdowns. The goal is to generate schedules while minimizing the expected costs. First, we estimate the distribution of each order type by simulation (assuming a reasonable machine/load model) and derive from the cost-function an optimal offset from the due date of each individual order. Second, these optimal offsets are then used to guide the generation of schedules which are responsible to resolve resource conflicts. Third, we evaluate the generated schedules by simulation. The approach is demonstrated by means of a non-trivial case-study from lacquer production. Optimal offsets are derived with the Modest/Möbius tool, schedules are generated using Uppaal Cora. The experimental results show that our approach achieves good results in all considered scenarios, and better results than an approach based on adding slack to processing times.