CA-ARBAC: privacy preserving using context-aware role-based access control on Android permission system

Existing mobile platforms are based on manual way of granting and revoking permissions to applications. Once the user grants a given permission to an application, the application can use it without limit, unless the user manually revokes the permission. This has become the reason for many privacy problems because of the fact that a permission that is harmless at some occasion may be very dangerous at another condition. One of the promising solutions for this problem is context-aware access control at permission level that allows dynamic granting and denying of permissions based on some predefined context. However, dealing with policy configuration at permission level becomes very complex for the user as the number of policies to configure will become very large. For instance, if there are A applications, P permissions, and C contexts, the user may have to deal with A × P × C number of policy configurations. Therefore, we propose a context-aware role-based access control model that can provide dynamic permission granting and revoking while keeping the number of policies as small as possible. Although our model can be used for all mobile platforms, we use Android platform to demonstrate our system. In our model, Android applications are assigned roles where roles contain a set of permissions and contexts are associated with permissions. Permissions are activated and deactivated for the containing role based on the associated contexts. Our approach is unique in that our system associates contexts with permissions as opposed to existing similar works that associate contexts with roles. As a proof of concept, we have developed a prototype application called context-aware Android role-based access control. We have also performed various tests using our application, and the result shows that our model is working as desired

Synthesis, Structure, Luminescence, and Magnetic Properties of a Single-Ion Magnet “<i>mer</i>”‑[Tris(<i>N</i>‑[(imidazol-4-yl)-methylidene]-dl-phenylalaninato)terbium(III) and Related “<i>fac</i>”-dl-Alaninato Derivative

Two Tb^III complexes with the same N₆O₃ donor atoms but different coordination geometries, “<i>fac</i>”-[Tb^III(HL^dl‑ala)₃]·7H₂O (<b>1</b>) and “<i>mer</i>”-[Tb^III(HL^dl‑phe)₃]·7H₂O (<b>2</b>), were synthesized, where H₂L^dl‑ala and H₂L^dl‑phe are <i>N</i>-[(imidazol-4-yl)­methylidene]-dl-alanine and -dl-phenylalanine, respectively. Each Tb^III ion is coordinated by three electronically mononegative NNO tridentate ligands to form a coordination geometry of a tricapped trigonal prism. Compound <b>1</b> consists of enantiomers “<i>fac</i>”-[Tb^III(HL^d‑ala)₃] and “<i>fac</i>”-[Tb^III(HL^l‑ala)₃], while <b>2</b> consists of “<i>mer</i>”-[Tb^III(HL^d‑phe)₂(HL^l‑phe)] and “<i>mer</i>”-[Tb^III(HL^d‑phe)­(HL^l‑phe)₂]. Magnetic data were analyzed by a spin Hamiltonian including the crystal field effect on the Tb^III ion (4f⁸, <i>J</i> = 6, <i>S</i> = 3, <i>L</i> = 3, <i>g</i>_<i>J</i> = 3/2, ⁷F₆). The Stark splitting of the ground state ⁷F₆ was evaluated from magnetic analysis, and the energy diagram pattern indicated easy-plane and easy-axis (Ising type) magnetic anisotropies for <b>1</b> and <b>2</b>, respectively. Highly efficient luminescences with Φ = 0.50 and 0.61 for <b>1</b> and <b>2</b>, respectively, were observed, and the luminescence fine structure due to the ⁵D₄ → ⁷F₆ transition is in good accordance with the energy diagram determined from magnetic analysis. The energy diagram of <b>1</b> shows an approximate single-well potential curve, whereas that of <b>2</b> shows a double- or quadruple-well potential within the ⁷F₆ multiplets. Complex <b>2</b> displayed an onset of the out-of-phase signal in alternating current (ac) susceptibility at a direct current bias field of 1000 Oe on cooling down to 1.9 K. A slight frequency dependence was recorded around 2 K. On the other hand, <b>1</b> did not show any meaningful out-of-phase ac susceptibility. Pulsed-field magnetizations of <b>1</b> and <b>2</b> were measured below 1.6 K, and only <b>2</b> exhibited magnetic hysteresis. This finding agrees well with the energy diagram pattern from crystal field calculation on <b>1</b> and <b>2</b>. DFT calculation allowed us to estimate the negative charge distribution around the Tb^III ion, giving a rationale to the different magnetic anisotropies of <b>1</b> and <b>2</b>

Synthesis, Structure, Luminescence, and Magnetic Properties of a Single-Ion Magnet “<i>mer</i>”‑[Tris(<i>N</i>‑[(imidazol-4-yl)-methylidene]-dl-phenylalaninato)terbium(III) and Related “<i>fac</i>”-dl-Alaninato Derivative

Two Tb^III complexes with the same N₆O₃ donor atoms but different coordination geometries, “<i>fac</i>”-[Tb^III(HL^dl‑ala)₃]·7H₂O (<b>1</b>) and “<i>mer</i>”-[Tb^III(HL^dl‑phe)₃]·7H₂O (<b>2</b>), were synthesized, where H₂L^dl‑ala and H₂L^dl‑phe are <i>N</i>-[(imidazol-4-yl)­methylidene]-dl-alanine and -dl-phenylalanine, respectively. Each Tb^III ion is coordinated by three electronically mononegative NNO tridentate ligands to form a coordination geometry of a tricapped trigonal prism. Compound <b>1</b> consists of enantiomers “<i>fac</i>”-[Tb^III(HL^d‑ala)₃] and “<i>fac</i>”-[Tb^III(HL^l‑ala)₃], while <b>2</b> consists of “<i>mer</i>”-[Tb^III(HL^d‑phe)₂(HL^l‑phe)] and “<i>mer</i>”-[Tb^III(HL^d‑phe)­(HL^l‑phe)₂]. Magnetic data were analyzed by a spin Hamiltonian including the crystal field effect on the Tb^III ion (4f⁸, <i>J</i> = 6, <i>S</i> = 3, <i>L</i> = 3, <i>g</i>_<i>J</i> = 3/2, ⁷F₆). The Stark splitting of the ground state ⁷F₆ was evaluated from magnetic analysis, and the energy diagram pattern indicated easy-plane and easy-axis (Ising type) magnetic anisotropies for <b>1</b> and <b>2</b>, respectively. Highly efficient luminescences with Φ = 0.50 and 0.61 for <b>1</b> and <b>2</b>, respectively, were observed, and the luminescence fine structure due to the ⁵D₄ → ⁷F₆ transition is in good accordance with the energy diagram determined from magnetic analysis. The energy diagram of <b>1</b> shows an approximate single-well potential curve, whereas that of <b>2</b> shows a double- or quadruple-well potential within the ⁷F₆ multiplets. Complex <b>2</b> displayed an onset of the out-of-phase signal in alternating current (ac) susceptibility at a direct current bias field of 1000 Oe on cooling down to 1.9 K. A slight frequency dependence was recorded around 2 K. On the other hand, <b>1</b> did not show any meaningful out-of-phase ac susceptibility. Pulsed-field magnetizations of <b>1</b> and <b>2</b> were measured below 1.6 K, and only <b>2</b> exhibited magnetic hysteresis. This finding agrees well with the energy diagram pattern from crystal field calculation on <b>1</b> and <b>2</b>. DFT calculation allowed us to estimate the negative charge distribution around the Tb^III ion, giving a rationale to the different magnetic anisotropies of <b>1</b> and <b>2</b>