The First Record of Calvolia summersi (Mostafa, 1970) (Acari: Winterschmidtiidae) from the Oriental Region and a new record of host association with Xylocopa (Ctenoxylocopa) fenestrata (Fabricius, 1798) with a review on Xylocopa-mite associations in India

Mites have long been associated with bees, often showing a close relationship with particular taxa, probably due to a co-evolutionary process. The present study is the first confirmation on the occurrence of the mite species Calvolia summersi (Mostafa, 1970) in India and its association with Xylocopa fenestrata (Fabricius, 1798), a large carpenter bee species. The mite species was previously reported from Brazil in association with Zethus, a neotropical potter wasp genus. C. summersi is isolated and studied from different populations of X. fenestrata in Sagar Islands, West Bengal, the biggest island of mangrove Sundarban deltaic complex. A literature-based review of the Xylocopa-mite associations from India is provided herewith to understand the diversity and pattern of mite species on Xylocopa host selection in the country. Instigating a baseline study of Xylocopa-mite association is recommended to demark the status of dynamism for better conservation and protection

Mixed A-Cation Perovskites for Solar Cells:Atomic-Scale Insights into Structural Distortion, Hydrogen Bonding, and Electronic Properties

Hybrid lead halide perovskites containing a mixture of A-site cations such as the formamidinium (CH­(NH₂)₂⁺, FA) and the smaller cesium (Cs⁺) cations have attracted considerable interest due to their improved stability and solar cell performance. However, the structural changes at the atomic scale and modifications to the optoelectronic properties of these mixed cation perovskites are not fully understood. Here, we investigate the FA_1–<i>x</i>Cs_<i>x</i>PbI₃ (<i>x</i> ≤ 0.25) system using a combination of static and dynamic <i>ab initio</i> computational methods. We find that the incorporation of Cs⁺ cations into the parent FAPbI₃ structure induces a chemical pressure or lattice strain effect through Cs/FA ion size mismatch resulting in structural distortion and stronger FA-iodide (N–H···I) hydrogen bonding interactions. The dynamic tilting of PbI₆ octahedra and the rotational motion of FA cations are also suppressed, which leads to symmetry-breaking of the lattice. Such symmetry-breaking distortions of the Pb/I lattice give rise to a Rashba-type effect, which spin-splits the frontier electronic bands making the band gap indirect. Our results suggest that the direct–indirect band gap transition may be a factor in the reduced charge-carrier recombination rate in these mixed cation perovskites

Good Vibrations:Locking of Octahedral Tilting in Mixed-Cation Iodide Perovskites for Solar Cells

Metal halide perovskite solar cells have rapidly emerged as leading contenders in photovoltaic technology. Compositions with a mixture of cation species on the A-site show the best performance and have higher stability. However, the underlying fundamentals of such an enhancement are not fully understood. Here, we investigate the local structures and dynamics of mixed A-cation compositions. We show that substitution of low concentrations of smaller cations on the A-site in formamidimium lead iodide (CH­(NH₂)₂PbI₃) results in a global “locking” of the PbI₆ octahedra tilting. In the locked structure the octahedra tilt at a larger angle but undergo a much reduced amplitude of rocking motion. A key impact of this feature is that the rotational or tumbling motion of the CH­(NH₂)₂⁺ molecular ion in a locked cage is severely restricted. We discuss the impact of locking on the photovoltaic performance and stability

Lead-Free Perovskite Semiconductors Based on Germanium-Tin Solid Solutions:Structural and Optoelectronic Properties

Solar cells and optoelectronics based on lead halide perovskites are generating considerable interest but face challenges with the use of toxic lead. In this study, we fabricate and characterize lead-free perovskites based on germanium and tin solid solutions, CH₃NH₃Sn_{(1–<i>x</i>)}Ge_<i>x</i>I₃ (0 ≤ <i>x</i> ≤ 1). We show that these perovskite compounds possess band gaps from 1.3 to 2.0 eV, which are suitable for a range of optoelectronic applications, from single junction devices and top cells for tandems to light-emitting layers. Their thermodynamic stability and electronic properties are calculated for all compositions and agree well with our experimental measurements. Our findings demonstrate an attractive family of lead-free perovskite semiconductors with a favorable band-gap range for efficient single-junction solar cells

A semantic context model for managing privacy on smartphones

In this work we describe an approach to protecting the privacy and security of user data on mobile devices using a richer semantic model of a user's context. Mobile OS frameworks like Android always lacked mechanisms for dynamic privacy control, while recent advances in context modeling, tracking and collaborative localization has led to the emergence of a new class of smartphone applications that can access and share embedded sensor data. Existing literature on context based privacy and security has predominantly focused on device user's context for probing privacy vulnerability and enforcing security at runtime. We bring into picture the most important component of privacy vulnerability on smartphones, the resident applications themselves and we introduce the novel idea of application provenance. Our context model is realized as a dynamic knowledge base of RDF [67] triples grounded in an ontology in the semantic web language OWL. Policies in the form of rules over this knowledge base monitor and control application access to sensitive information and sensor data. The policies filter data flowing from sensor resources to applications to reduce disclosure by generalizing or obfuscating data. Our ontology includes the ability to represent application provenance and other metadata that can be used by the policies. The resulting system provides fine-grained, context-dependent control to sensitive user data

Early Modern London Theatres (EMLoT)

This is a review of Early Modern London Theatres (EMLoT)

A semantic context model for managing privacy on smartphones

In this work we describe an approach to protecting the privacy and security of user data on mobile devices using a richer semantic model of a user's context. Mobile OS frameworks like Android always lacked mechanisms for dynamic privacy control, while recent advances in context modeling, tracking and collaborative localization has led to the emergence of a new class of smartphone applications that can access and share embedded sensor data. Existing literature on context based privacy and security has predominantly focused on device user's context for probing privacy vulnerability and enforcing security at runtime. We bring into picture the most important component of privacy vulnerability on smartphones, the resident applications themselves and we introduce the novel idea of application provenance. Our context model is realized as a dynamic knowledge base of RDF [67] triples grounded in an ontology in the semantic web language OWL. Policies in the form of rules over this knowledge base monitor and control application access to sensitive information and sensor data. The policies filter data flowing from sensor resources to applications to reduce disclosure by generalizing or obfuscating data. Our ontology includes the ability to represent application provenance and other metadata that can be used by the policies. The resulting system provides fine-grained, context-dependent control to sensitive user data

Spin-State Switching of Manganese Porphyrin by Conformational Modification

Controlled spin-state switching in small molecules is of great interest for recent molecular spintronic and spin-caloritronic applications. The 3d transition metal incorporated porphyrin molecules with stable paramagnetic states are one of the most explored classes of molecules for this purpose where adsorption and desorption of small gaseous molecules (e.g., CO, NO, O-2) on the transition metal center show efficient control over the spin states of metalloporphyrins. However, in the present study, using on-site Coulomb interaction incorporated density functional theory (DFT + U), we demonstrate reversible spin-state switching of NO-adsorbed manganese porphyrin (MnP) on top of a gold (111) surface by inducing conformational change in the molecular geometry. In this approach, mechanical manipulation by a scanning tunneling microscope (STM) tip can reversibly interchange the binding mode of the Mn-NO bond between ground-state linear and metastable bent conformations. And this modification leads to spin-state switching between the low-spin state (S = 0) of the linear geometry and intermediate spin (S = 1) of the bent conformer. Further, nonequilibrium Green's function based studies reveal that, in a two-terminal device architecture, spin polarized electronic transport through this MnP-based molecular junction can efficiently be switched off/on upon the conformational change. Thermally induced current and thermopower can also be modified distinctly when we introduce temperature bias in this nanodevice. Interestingly, precise tuning of the Fermi level of the device results in generation of pure spin thermopower, which is highly demanding for potential spin-caloritronic application