Pricing of insurance policies against cloud storage price rises

When a company migrates to cloud storage, the way back is neither easy nor cheap. The company is then locked up in the storage contract and exposed to upward market prices, which reduce the company's profit and may even bring it below zero. We propose a protection means based on an insurance contract, by which the cloud purchaser is indemnified when the current storage price exceeds a pre-defined threshold. By applying the financial options theory, we provide a formula for the insurance price (the premium). By using historical data on market prices for disks, we apply the formula in realistic scenarios. We show that the premium grows nearly quadratically with the length of the coverage period as long as this is below one year, but grows more slowly, though faster than linearly, over longer coverage periods

An abstract domain for objects in dynamic programming languages

Dynamic languages, such as JavaScript, PHP, Python or Ruby, provide a memory model for objects data structures allowing programmers to dynamically create, manipulate, and delete objects’ properties. Moreover, in dynamic languages it is possible to access and update properties by using strings: this represents a hard challenge for static analysis. In this paper, we exploit the finite state automata abstract domain, approximating strings, in order to define a novel abstract domain for objects. We design an abstract interpreter useful to analyze objects in a toy language, inspired by real-word dynamic programming languages. We then show, by means of minimal yet expressive examples, the precision of the proposed abstract domain

Completeness of string analysis for dynamic languages

In Abstract Interpretation, completeness ensures that the analysis does not lose information with respect to the property of interest. In particular, for dynamic languages like JavaScript, completeness of string analysis is a key security issue, as poorly managed string manipulation code may easily lead to significant security flaws. In this paper, we provide a systematic and constructive approach for generating the completion of string domains for dynamic languages, and we apply it to the refinement of existing string abstractions. We also provide an effective procedure to measure the precision improvement obtained when lifting the analysis to complete domains

On topologies for (hyper)properties

Usually, systems properties are defined in terms of the infinite executions which satisfy it. In this work we explore what happens if we allow finite executions in properties de-nitions. In particular, we give a topological interpretation of the safety/liveness classification in the do-mains of: only finite, only infinite and mixed executions. Then we extend our reasoning to hyperproperties, namely sets of sets of executions (or sets of properties). Also in this case we give a topological interpretation of the hypersafety/hyperliveness classification in the three domains

The effects of vaccination and immunity on bacterial infection dynamics in vivo.

Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body.This work was supported by the Biotechnology and Biological Sciences Research Council [grant number BB/I002189/1].This is the published manuscript. It was originally published by PLOS One here: http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1004359

Quantification of the effects of antibodies on the extra- and intracellular dynamics of Salmonella enterica.

Antibodies are known to be essential in controlling Salmonella infection, but their exact role remains elusive. We recently developed an in vitro model to investigate the relative efficiency of four different human immunoglobulin G (IgG) subclasses in modulating the interaction of the bacteria with human phagocytes. Our results indicated that different IgG subclasses affect the efficacy of Salmonella uptake by human phagocytes. In this study, we aim to quantify the effects of IgG on intracellular dynamics of infection by combining distributions of bacterial numbers per phagocyte observed by fluorescence microscopy with a mathematical model that simulates the in vitro dynamics. We then use maximum likelihood to estimate the model parameters and compare them across IgG subclasses. The analysis reveals heterogeneity in the division rates of the bacteria, strongly suggesting that a subpopulation of intracellular Salmonella, while visible under the microscope, is not dividing. Clear differences in the observed distributions among the four IgG subclasses are best explained by variations in phagocytosis and intracellular dynamics. We propose and compare potential factors affecting the replication and death of bacteria within phagocytes, and we discuss these results in the light of recent findings on dormancy of Salmonella.This work was funded by grants from the Wellcome Trust and from the Medical Research Council to PM. O.R. is supported by the Royal Society through a University Research Fellowship. M.P. is supported by a studentship from the Wellcome Trust

Statically Analyzing Information Flows - An Abstract Interpretation-based Hyperanalysis for Non-Interference.

In the context of systems security, information flows play a central role. Unhandled information flows potentially leave the door open to very dangerous types of attacks, such as code injection or sen- sitive information leakage. Information flows verification is based on the definition of Non-Interference [8], which is known to be an hyperproperty [7], i.e., a property of sets of executions. The sound verification of hyperproperties is not trivial [3, 16]: It is not easy to adapt classic verification methods, used for trace properties, in order to deal with hyperproperties. In the present work, we design an abstract interpretation-based static analyzer soundly checking Non-Interference. In particular, we define an hyper abstract do- main, able to approximate the information flows occurring in the analyzed programs

Epigenetic regulation of adult neural stem cells: implications for Alzheimer's disease.

Published onlineJournal ArticleResearch Support, Non-U.S. Gov'tReviewExperimental evidence has demonstrated that several aspects of adult neural stem cells (NSCs), including their quiescence, proliferation, fate specification and differentiation, are regulated by epigenetic mechanisms. These control the expression of specific sets of genes, often including those encoding for small non-coding RNAs, indicating a complex interplay between various epigenetic factors and cellular functions.Previous studies had indicated that in addition to the neuropathology in Alzheimer's disease (AD), plasticity-related changes are observed in brain areas with ongoing neurogenesis, like the hippocampus and subventricular zone. Given the role of stem cells e.g. in hippocampal functions like cognition, and given their potential for brain repair, we here review the epigenetic mechanisms relevant for NSCs and AD etiology. Understanding the molecular mechanisms involved in the epigenetic regulation of adult NSCs will advance our knowledge on the role of adult neurogenesis in degeneration and possibly regeneration in the AD brain.Internationale Stichting Alzheimer Onderzoek (ISAO)Netherlands Organization for Scientific Research (NWO)Maastricht University Medical Centre