Robustness against Consistency Models with Atomic Visibility

To achieve scalability, modern Internet services often rely on distributed databases with consistency models for transactions weaker than serializability. At present, application programmers often lack techniques to ensure that the weakness of these consistency models does not violate application correctness. We present criteria to check whether applications that rely on a database providing only weak consistency are robust, i.e., behave as if they used a database providing serializability. When this is the case, the application programmer can reap the scalability benefits of weak consistency while being able to easily check the desired correctness properties. Our results handle systematically and uniformly several recently proposed weak consistency models, as well as a mechanism for strengthening consistency in parts of an application

Using higher-order contracts to model session types ⋆

Abstract. Session types are used to describe and structure interactions between independent processes in distributed systems. Higher-order types are needed in order to properly structure delegation of responsibility between processes. In this paper we show that higher-order web-service contracts can be used to provide a fully-abstract model of recursive higher-order session types. The model is settheoretic, in the sense that the denotation of a contract is given by the set of contracts with which it complies; we use a novel notion of peer compliance. A crucial step in the proof of full-abstraction is showing that every contract has a non-empty denotation.

Agri-Food Traceability Management using a RFID System with Privacy Protection

In this paper an agri-food traceability system based on public key cryptography and Radio Frequency Identification (RFID) technology is proposed. In order to guarantee safety in food, an efficient tracking and tracing system is required. RFID devices allow recording all useful information for traceability directly on the commodity. The security issues are discussed and two different methods based on public cryptography are proposed and evaluated. The first algorithm uses a nested RSA based structure to improve security, while the second also provides authenticity of data. An experimental analysis demonstrated that the proposed system is well suitable on PDAs to

A Framework for Transactional Consistency Models with Atomic Visibility

Modern distributed systems often rely on databases that achieve scalability by providing only weak guarantees about the consistency of distributed transaction processing. The semantics of programs interacting with such a database depends on its consistency model, defining these guarantees. Unfortunately, consistency models are usually stated informally or using disparate formalisms, often tied to the database internals. To deal with this problem, we propose a framework for specifying a variety of consistency models for transactions uniformly and declaratively. Our specifications are given in the style of weak memory models, using structures of events and relations on them. The specifications are particularly concise because they exploit the property of atomic visibility guaranteed by many consistency models: either all or none of the updates by a transaction can be visible to another one. This allows the specifications to abstract from individual events inside transactions. We illustrate the use of our framework by specifying several existing consistency models. To validate our specifications, we prove that they are equivalent to alternative operational ones, given as algorithms closer to actual implementations. Our work provides a rigorous foundation for developing the metatheory of the novel form of concurrency arising in weakly consistent large-scale databases

Long-term impact risk for (101955) 1999 RQ36

The potentially hazardous asteroid (101955) 1999 RQ36 has the possibility of collision with the Earth in the latter half of the 22nd century, well beyond the traditional 100-year time horizon for routine impact monitoring. The probabilities accumulate to a total impact probability of approximately 10E-3, with a pair of closely related routes to impact in 2182 comprising more than half of the total. The analysis of impact possibilities so far in the future is strongly dependent on the action of the Yarkovsky effect, which raises new challenges in the careful assessment of longer term impact hazards. Even for asteroids with very precisely determined orbits, a future close approach to Earth can scatter the possible trajectories to the point that the problem becomes like that of a newly discovered asteroid with a weakly determined orbit. If the scattering takes place late enough so that the target plane uncertainty is dominated by Yarkovsky accelerations then the thermal properties of the asteroid,which are typically unknown, play a major role in the impact assessment. In contrast, if the strong planetary interaction takes place sooner, while the Yarkovsky dispersion is still relatively small compared to that derived from the measurements, then precise modeling of the nongravitational acceleration may be unnecessary.Comment: Reviewed figures and some text change

Effects of gradual discontinuation of selective serotonin reuptake inhibitors in panic disorder with agoraphobia.

The aim of this investigation was to explore the prevalence and features of discontinuation syndromes ensuing with gradual tapering of selective serotonin reuptake inhibitors (SSRIs), in optimal clinical conditions in patients with panic disorder and agoraphobia. Twenty-six consecutive outpatients met the DSM-IV criteria for panic disorder and agoraphobia while taking SSRIs. Twenty remitted upon behavioural treatment. Antidepressant drugs were then tapered at the slowest possible pace and with appropriate patient education. Patients were assessed with the Discontinuation-Emergent Signs and Symptoms (DESS) checklist 2 wk, 1 month and 1 yr after discontinuation. Nine of the 20 patients (45%) experienced a discontinuation syndrome, which subsided within a month in all but three patients who had been taking paroxetine for a long time. Discontinuation syndromes appeared to be fairly common even when performed with slow tapering and during clinical remission. In some cases disturbances persisted for months after discontinuation

Cell-Based Therapies for Diabetic Complications

In recent years, accumulating experimental evidence supports the notion that diabetic patients may greatly benefit from cell-based therapies, which include the use of adult stem and/or progenitor cells. In particular, mesenchymal stem cells and the circulating pool of endothelial progenitor cells have so far been the most studied populations of cells proposed for the treatment of vascular complications affecting diabetic patients. We review the evidence supporting their use in this setting, the therapeutic benefits that these cells have shown so far as well as the challenges that cell-based therapies in diabetic complications put out

Late Breaking Abstract - An exercise training program improves endothelial function in COPD patients

COPD is associated with increased cardiovascular (CV) mortality. An early manifestation in the pathogenesis of CV diseases is the endothelial dysfunction; the gold standard for its measurement is the flow-mediated dilatation (FMD). It is known that an active lifestyle has a favorable effect on FMD also in COPD (retrospective studies), however no prospective study has evaluated the effect of an exercise training program (ET) on FMD. Aim: to evaluate the impact of a supervised endurance ET on FMD in COPD. Methods: 11 COPD patients (4F/7M) were recruited. Patients who agreed to participate at ET were assigned to the training group (Ex, n=6) and the others to the control group (C, n=5). The Ex exercised on a treadmill 50 min, twice a week for 8 weeks. At the beginning (T0) patients performed spirometry, 6MWD, measurement of physical activity (SenseWear Armband) and FMD. At the end of the program (T1) FMD and spirometry were repeated. Furthermore, Ex performed an incremental cycling test at T0 and T1 to assess VO2max. Results: No differences in age (Ex:66±10, C:69±8yr), BMI (Ex:30±3, C:28±4kg/m2), pulmonary function [FEV1(%) Ex:54±14, C:60±16] and 6MWD (Ex:356±90, C:406±49m) were found between the groups at T0; C were a little more active than Ex (1.3±0.2 vs 1.1±0.1 METs respectively;p=0.03). No difference was found in FMD at T0 after adjustment for physical activity (Ex:4.2±0.54, C:4.05±0.62%). FMD improved significantly in the Ex (+2.74±1.33%, p=0.004) but not in the C (-0.09±0.21, p>0.05); t test between groups p=0.0001. Conclusion: These preliminary data show that after 8 weeks of ET a significant improvement in FMD was found in trained COPD and can be considered another positive effect of pulmonary rehabilitatio

Efficiency of a wide-area survey in achieving short- and long-term warning for small impactors

We consider a network of telescopes capable of scanning all the observable sky each night and targeting Near-Earth objects (NEOs) in the size range of the Tunguska-like asteroids, from 160 m down to 10 m. We measure the performance of this telescope network in terms of the time needed to discover at least 50% of the impactors in the considered population with a warning time large enough to undertake proper mitigation actions. The warning times are described by a trimodal distribution and the telescope network has a 50% probability of discovering an impactor of the Tunguska class with at least one week of advance already in the first 10 yr of operations of the survey. These results suggest that the studied survey would be a significant addition to the current NEO discovery efforts