Fault-Tolerant Business Processes

Abstract. Service-oriented computing (SOC) paradigm promotes the idea of assembling application components into a network of loosely coupled services. Web services are the most promising SOC-based technology. A BPEL process definition represents a composite service that encapsulates some complex business logic including the invocation to other (external) web services. The complexity of a BPEL process together with the invocation of external services subject to network and computer failures requires countermeasures to tolerate this kind of failures. In this paper we present an overview of FT-BPEL, a fault-tolerant implementation of BPEL that copes both with failures of the machine running the BPEL process and network failures in a transparent way, that is, after a failure the system is able to resume the BPEL process consistently

The Polonnaruwa meteorite: oxygen isotope, crystalline and biological composition

Results of X-Ray Diffraction (XRD) analysis, Triple Oxygen Isotope analysis and Scanning Electron Microscopic (SEM) studies are presented for stone fragments recovered from the North Central Province of Sri Lanka following a witnessed fireball event on 29 December 2012. The existence of numerous nitrogen depleted highly carbonaceous fossilized biological structures fused into the rock matrix is inconsistent with recent terrestrial contamination. Oxygen isotope results compare well with those of CI and CI-like chondrites but are inconsistent with the fulgurite hypothesis.Comment: 7 pages, 7 figures, 4 table

Tractable Pathfinding for the Stochastic On-Time Arrival Problem

We present a new and more efficient technique for computing the route that maximizes the probability of on-time arrival in stochastic networks, also known as the path-based stochastic on-time arrival (SOTA) problem. Our primary contribution is a pathfinding algorithm that uses the solution to the policy-based SOTA problem---which is of pseudo-polynomial-time complexity in the time budget of the journey---as a search heuristic for the optimal path. In particular, we show that this heuristic can be exceptionally efficient in practice, effectively making it possible to solve the path-based SOTA problem as quickly as the policy-based SOTA problem. Our secondary contribution is the extension of policy-based preprocessing to path-based preprocessing for the SOTA problem. In the process, we also introduce Arc-Potentials, a more efficient generalization of Stochastic Arc-Flags that can be used for both policy- and path-based SOTA. After developing the pathfinding and preprocessing algorithms, we evaluate their performance on two different real-world networks. To the best of our knowledge, these techniques provide the most efficient computation strategy for the path-based SOTA problem for general probability distributions, both with and without preprocessing.Comment: Submission accepted by the International Symposium on Experimental Algorithms 2016 and published by Springer in the Lecture Notes in Computer Science series on June 1, 2016. Includes typographical corrections and modifications to pre-processing made after the initial submission to SODA'15 (July 7, 2014

Identification of differential pharyngeal cytokine profiles during HIV infection

Significantly higher pharyngeal shedding of Epstein-Barr virus (EBV) is observed during HIV infection. Increased EBV shedding in pharynx is not affected even during highly active antiretroviral theyrapy (HAART). EBV positive monocyte populations have been shown to carry EBV to pharyngeal mucosa. Human cytokine profiles are often altered to facilitate herpes virus infection. Thus pharyngeal cytokine profiles may influence EBV reactivation and shedding during HIV infection. Our objective was to compare 37 pharyngeal cytokine profiles of HIV-seropositive patients who were or were not receiving HAART therapy

Candida species exhibit differential in vitro hemolytic activities

A total of 80 Candida isolates representing 14 species were examined for their respective responses to an in vitro hemolytic test. A modification of a previously described plate assay system where the yeasts are incubated on glucose (3%)-enriched sheep blood agar in a carbon dioxide (5%)-rich environment for 48 h was used to evaluate the hemolytic activity. A group of eight Candida species which included Candida albicans (15 isolates), C. dubliniensis (2), C. kefyr (2), C. krusei (4), C. zeylanoides (1), C. glabrata (34), C. tropicalis (5), and C. lusitaniae (2) demonstrated both alpha and beta hemolysis at 48 h postinoculation. Only alpha hemolysis was detectable in four Candida species, viz., C. famata (3), C. guilliermondii (4), C. rugosa (1), and C. utilis (1), while C. parapsilosis (5) and C. pelliculosa (1) failed to demonstrate any hemolytic activity after incubation for 48 h or longer. This is the first study to demonstrate the variable expression profiles of hemolysins by different Candida species.published_or_final_versio

Staphylococcus aureus in the oral cavity: a three-year retrospective analysis of clinical laboratory data

OBJECTIVE: A retrospective analysis of laboratory data to investigate the isolation of Staphylococcus aureus from the oral cavity and facial area in specimens submitted to a regional diagnostic oral microbiology laboratory. METHODS: A hand search of laboratory records for a three-year period (1998-2000) was performed for specimens submitted to the regional diagnostic oral microbiology laboratory based at Glasgow Dental Hospital and School. Data were collected from forms where S. aureus was isolated. These data included demographics, referral source, specimen type, methicillin susceptibility and clinical details. RESULTS: For the period 1998-2000, there were 5,005 specimens submitted to the laboratory. S. aureus was isolated from 1,017 specimens, of which 967 (95%) were sensitive to methicillin (MSSA) and 50 (5%) were resistant to methicillin (MRSA). The 1,017 specimens were provided from 615 patients. MRSA was isolated from 37 (6%) of patients. There was an increasing incidence of S. aureus with age, particularly in the greater than 70 years age group. The most common specimen from which MSSA was isolated was an oral rinse (38%) whilst for MRSA isolates this was a tongue swab (28%). The clinical condition most commonly reported for MSSA isolates was angular cheilitis (22%). Erythema, swelling, pain or burning of the oral mucosa was the clinical condition most commonly reported for MRSA isolates (16%). Patients from whom the MSSA isolates were recovered were most commonly (55%) seen in the oral medicine clinic at the dental hospital, whilst patients with MRSA were more commonly seen in primary care settings such as nursing homes, hospices and general dental practice (51%). CONCLUSION: In line with more recent surveys, this retrospective study suggests that S. aureus may be a more frequent isolate from the oral cavity than hitherto suspected. A small proportion of the S. aureus isolates were MRSA. There were insufficient data available to determine whether the S. aureus isolates were colonising or infecting the oral cavity. However, the role of S. aureus in several diseases of the oral mucosa merits further investigation

Fluconazole resistance in Candida albicans is induced by Pseudomonas aeruginosa quorum sensing

Microorganisms employ quorum sensing (QS) mechanisms to communicate with each other within microbial ecosystems. Emerging evidence suggests that intraspecies and interspecies QS plays an important role in antimicrobial resistance in microbial communities. However, the relationship between interkingdom QS and antimicrobial resistance is largely unknown. Here, we demonstrate that interkingdom QS interactions between a bacterium, Pseudomonas aeruginosa and a yeast, Candida albicans, induce the resistance of the latter to a widely used antifungal fluconazole. Phenotypic, transcriptomic, and proteomic analyses reveal that P. aeruginosa’s main QS molecule, N-(3-Oxododecanoyl)-L-homoserine lactone, induces candidal resistance to fluconazole by reversing the antifungal’s effect on the ergosterol biosynthesis pathway. Accessory resistance mechanisms including upregulation of C. albicans drug-efflux, regulation of oxidative stress response, and maintenance of cell membrane integrity, further confirm this phenomenon. These findings demonstrate that P. aeruginosa QS molecules may confer protection to neighboring yeasts against azoles, in turn strengthening their co-existence in hostile polymicrobial infection sites

The role of secreted aspartyl proteinases in Candida tropicalis invasion and damage of oral mucosa

Candida virulence attributes include the ability to colonize and invade host tissues, and the secretion of hydrolytic enzymes. Although Candida albicans is regarded as the principal fungi causing infections in humans, other species, particularly Candida tropicalis, are increasingly being recognized as human pathogens. Relatively little is known, however, about the virulence attributes associated with C. tropicalis. The present study aimed to investigate epithelial infection by C. tropicalis using a reconstituted human oral epithelium (RHOE) together with confocal laser scanning microscopy and real-time PCR. A comparison of clinical strains was made in terms of tissue colonization, invasion and C. tropicalis secreted aspartyl proteinase (SAPT) gene expression. All C. tropicalis strains were able to colonize RHOE in a strain-dependent manner. After 12 h of infection, C. tropicalis was found to be highly invasive, with extensive tissue damage occurring after 24 h. Real-time PCR of C. tropicalis SAPT1-4 genes showed that expression was strain-dependent, with SAPT2-4 transcripts being frequently detected and SAPT1 rarely detected. Tissue invasion and damage was not inhibited by the presence of pepstatin A. Accordingly, and given that an increase in infection time was not accompanied with an increase in SAPT gene expression, it can be suggested that the proteinases are not involved in invasion and damage of RHOE by C. tropicalis. In summary, C. tropicalis can be considered as highly invasive with the ability to induce significant tissue damage. These features, however, do not appear to be related to specific SAPT gene expression.We would like to thank Mrs Kath Allsopp for processing and sectioning the tissue samples. This work was supported by grant SFRH/BD/28341/2006 from 'Fundacao para a Ciencia e Tecnologia' (FCT), Portugal