Defence Science and Technology Laboratory

About: Defence Science and Technology Laboratory is a government organization based out in Salisbury, United Kingdom. It is known for research contribution in the topics: Burkholderia pseudomallei & Francisella tularensis. The organization has 926 authors who have published 1242 publications receiving 30091 citations. The organization is also known as: Dstl & [dstl].

Assurance in Reinforcement Learning Using Quantitative Verification

Abstract: Reinforcement learning (RL) agents converge to optimal solutions for sequential decision making problems. Although increasingly successful, RL cannot be used in applications where unpredictable agent behaviour may have significant unintended negative consequences. We address this limitation by introducing an assured reinforcement learning (ARL) method which uses quantitative verification (QV) to restrict the agent behaviour to areas that satisfy safety, reliability and performance constraints specified in probabilistic temporal logic. To this end, ARL builds an abstract Markov decision process (AMDP) that models the problem to solve at a high level, and uses QV to identify a set of Pareto-optimal AMDP policies that satisfy the constraints. These formally verified abstract policies define areas of the agent behaviour space where RL can occur without constraint violations. We show the effectiveness of our ARL method through two case studies: a benchmark flag-collection navigation task and an assisted-living planning system.

Influence of particle size on the pathology and efficacy of vaccination in a murine model of inhalational anthrax.

Abstract: Deposition of Bacillus anthracis endospores within either the lungs or nasal passages of A/J mice after aerosol exposure was influenced by different particle sized aerosols and resulted in different infection kinetics. The infection resulting from the inhalation of endospores within a 12 μm particle aerosol was prolonged compared to that from a 1 μm particle aerosol with a mean time-to-death of 161±16.1 h and 101.6±10.4 h, respectively. Inhalation of endospores within 1 μm or 12 μm particle aerosols resulted in a median lethal dose of 2432 and 7656 c.f.u., respectively. Initial involvement of the upper respiratory tract lymph nodes was observed in 75–83 % of mice exposed to either the 1 μm or 12 μm particle inhalational infections. Lung deposition was significantly greater after inhalation of the 1 μm particle aerosol with pronounced involvement of the mediastinal lymph node. Gastrointestinal involvement was observed only in mice exposed to 12 μm particle aerosols where bacteriological and histopathological analysis indicated primary gastritis (17 %), activation of the Peyer's patches (72 %) and colonization and necrosis of the mesenteric lymph nodes (67 %). Terminal disease was characterized by bacteraemia in both inhalational infections with preferential dissemination to spleen, liver, kidneys and thymus. Immunization with 1 μg recombinant protective antigen vaccine was equally efficacious against B. anthracis infections arising from the inhalation of 1 and 12 μm particle aerosols, providing 73–80 % survival under a suboptimum immunization schedule.

Advice from the Scientific Advisory Board of the Organisation for the Prohibition of Chemical Weapons on isotopically labelled chemicals and stereoisomers in relation to the Chemical Weapons Convention

Abstract: The Chemical Weapons Convention (CWC) is an international disarmament treaty that prohibits the development, stockpiling and use of chemical weapons This treaty has 193 States Parties (nations for which the treaty is binding) and entered into force in 1997 The CWC contains schedules of chemicals that have been associated with chemical warfare programmes These scheduled chemicals must be declared by the States that possess them and are subject to verification by the Organisation for the Prohibition of Chemical Weapons (OPCW, the implementing body of the CWC) Isotopically labelled and stereoisomeric variants of the scheduled chemicals have presented ambiguities for interpretation of the requirements of treaty implementation, and advice was sought from the OPCW's Scientific Advisory Board (SAB) in 2016 The SAB recommended that isotopically labelled compounds or stereoisomers related to the parent compound specified in a schedule should be interpreted as belonging to the same schedule This advice should benefit scientists and diplomats from the CWC's State Parties to help ensure a consistent approach to their declarations of scheduled chemicals (which in turn supports both the correctness and completeness of declarations under the CWC) Herein, isotopically labelled and stereoisomeric variants of CWC-scheduled chemicals are reviewed, and the impact of the SAB advice in influencing a change to national licensing in one of the State Parties is discussed This outcome, an update to national licensing governing compliance to an international treaty, serves as an example of the effectiveness of science diplomacy within an international disarmament treaty

Optimum detection and segmentation of oil-slicks with polarimetric SAR data

Abstract: A new polarimetric discriminator, derived by using the generalised likelihood approach, is proposed in this paper for the detection of slicks on the sea surface. A complete analytical expression of the detection performance is derived for the proposed detector and used to compare it to other conventional polarimetric detectors, showing its better performance. In particular, the improvement obtained by using the polarimetric images with respect to the best single channel image is demonstrated. Moreover it is shown that the ML discriminant outperforms conventional polarimetric detectors. The results achieved in the segmentation of the SIR-C/X-SAR image of the experimental set up in the German Bight confirm the results of the theoretical performance analysis.