Robust Hyperproperty Preservation for Secure Compilation (Extended Abstract)

We map the space of soundness criteria for secure compilation based on the preservation of hyperproperties in arbitrary adversarial contexts, which we call robust hyperproperty preservation. For this, we study the preservation of several classes of hyperproperties and for each class we propose an equivalent "property-free" characterization of secure compilation that is generally better tailored for proofs. Even the strongest of our soundness criteria, the robust preservation of all hyperproperties, seems achievable for simple transformations and provable using context back-translation techniques previously developed for showing fully abstract compilation. While proving the robust preservation of hyperproperties that are not safety requires such powerful context back-translation techniques, for preserving safety hyperproperties robustly, translating each finite trace prefix back to a source context seems to suffice

Carboxymethyl guar gum nanoparticles for drug delivery applications: preparation and preliminary in-vitro investigations

Abstract Carboxymethyl guar gum (CMGG) synthesised from commercially available polysaccharide was formulated into nanoparticles via ionic gelation using trisodium trimetaphosphate (STMP) as cross-linking agent. Characterisation using a range of analytical techniques (FTIR, NMR, GPC, TGA and DLS) confirmed the CMGG structure and revealed the effect of the CMGG and STMP concentration on the main characteristics of the obtained nanoformulations. The average nanoparticle diameter was found to be around 208 nm, as determined by dynamic light scattering (DLS) and confirmed by scanning electron microscopy (SEM) and nanoparticle tracking analysis (NTA). Experiments using simulated gastric and intestinal fluids evidenced significant pH-dependent drug release behaviour of the nanoformulations loaded with Rhodamine B (RhB) as a model drug (loading capacity in excess of 83%), as monitored by UV-Vis. While dose-dependent cytotoxicity was observed, the nanoformulations appeared completely non-toxic at concentrations below 0.3 mg/mL. Results obtained so far suggest that carboxymethylated guar gum nanoparticles formulated with STMP warrant further investigations as polysaccharide based biocompatible drug nanocarriers

Magnetic chitosan grafted (alkyl acrylate) composite particles: Synthesis, characterization and evaluation as adsorbents

An efficient process for preparing a series of magnetic chitosan grafted (alkyl acrylate) composite particles as novel adsorbent materials has been proposed. Magnetite nanoparticles (Fe3O4) were produced by co-precipitation. Modified chitosan (CSg) bearing surface vinyl groups was synthesized by glycidyl methacrylate coupling in acidic aqueous solution through an epoxide ring opening mechanism. The magnetic chitosan grafted (alkyl acrylate) composites were prepared by radical copolymerization of butyl acrylate (BA), butyl methacrylate (BMA) or hexyl acrylate (HA) with ethylene glycol dimethacrylate (EGDMA) onto the modified chitosan vinyl groups, with addition of magnetite nanoparticles in suspension. The prepared particles were characterized by TEM, SEM, XRD, VSM and FTIR. Adsorption batch experiments on the newly synthesized composites were conducted using Ni(II) ions in aqueous solutions. The variables that influence the sorption capacity, namely the solution pH, initial metal ion concentration, sorbent mass, adsorption time and temperature have been investigated. The adsorption kinetics was analyzed by fitting the data into the following models: pseudo-first-order, pseudo-second-order and intraparticle diffusion. The Langmuir, Freundlich and Dubinin–Radushkevich models were used to fit the adsorption isotherms. The proven high stability and recovery capacity of the composite particles suggest their potential use for Ni(II) ions removal from wastewater by using magnetically aided adsorption technology. Keywords: Composite particles, Chitosan, Magnetite, Acrylates, Ni(II) ions, Adsorption isotherm

Semantic subtyping with an SMT solver

We study a first-order functional language with the novel combination of the ideas of refinement type (the subset of a type to satisfy a Boolean expression) and type-test (a Boolean expression testing whether a value belongs to a type). Our core calculus can express a rich variety of typing idioms; for example, intersection, union, negation, singleton, nullable, variant, and algebraic types are all derivable. We formulate a semantics in which expressions denote terms, and types are interpreted as first-order logic formulas. Subtyping is defined as valid implication between the semantics of types. The formulas are interpreted in a specific model that we axiomatize using standard first-order theories. On this basis, we present a novel type-checking algorithm able to eliminate many dynamic tests and to detect many errors statically. The key idea is to rely on an SMT solver to compute subtyping efficiently. Moreover, interpreting types as formulas allows us to call the SMT solver at run-time to compute instances of types