University of Bath

About: University of Bath is a education organization based out in Bath, Bath and North East Somerset, United Kingdom. It is known for research contribution in the topics: Population & Photonic-crystal fiber. The organization has 15830 authors who have published 39608 publications receiving 1358769 citations. The organization is also known as: Bath University.

Thermodynamic Origin of Photoinstability in the CH3NH3Pb(I1-xBrx)3 Hybrid Halide Perovskite Alloy.

Abstract: The formation of solid-solutions of iodide, bromide, and chloride provides the means to control the structure, band gap, and stability of hybrid halide perovskite semiconductors for photovoltaic applications. We report a computational investigation of the CH3NH3PbI3/CH3NH3PbBr3 alloy from density functional theory with a thermodynamic analysis performed within the generalized quasi-chemical approximation. We construct the phase diagram and identify a large miscibility gap, with a critical temperature of 343 K. The observed photoinstability in some mixed-halide solar cells is explained by the thermodynamics of alloy formation, where an initially homogeneous solution is subject to spinodal decomposition with I and Br-rich phases, which is further complicated by a wide metastable region defined by the binodal line.

Welfare regimes and the welfare mix

Abstract: We present a different approach to appraising welfare regimes, stressing differ- ent dimensions, variables and techniques to those used by Esping-Andersen in his path- breaking work entitled The Three Worlds of Welfare Capitalism .F irst, instead of focusing on social rights, we construct an alternative path to identifying welfare regimes starting from the welfare mix. Second, we incorporate active labour market policies (ALMP) as a key variable of the welfare mix. Third, we use hierarchical and k-means cluster analysis to iden- tify welfare regimes in the data. Fourth, we compare regimes over time. Nevertheless, despite these different approaches, we conclude, like Esping-Andersen, that there are three clusters or worlds of welfare capitalism. We also find that the clustering of welfare regimes was sharper in the mid-1990s as compared to the mid-1980s, but that comparing welfare regimes in the 1980s with the 1990s indicates strong path-dependence. Faced with high and persistent levels of unemployment in the 1990s, OECD countries have adopted policies, including ALMP, which reinforce their welfare mix.

Post-synthetic modification of tagged metal-organic frameworks

Abstract: Metal–organic frameworks (MOFs) are currently attracting considerable attention, largely because of their potential for porosity, and their consequent use in applications as diverse as gas storage, catalysis, separations, and drug delivery. The first generation of MOFs were formed by linking together metal centers with simple, commercially available bridging ligands, such as 1,4-benzenedicarboxylate (bdc), but there has since been an increasing shift towards more complex structures and increased functionality. For example, MOFs in which the pores contain accessible hydrogenbonding groups, unsaturated metal centers, or chirality have been reported and studied, and the preparation of dynamic porous materials, capable of undergoing guestinduced transformations or reformations, has been explored. Another approach to forming functionalized networks is to undertake reactions on preformed MOFs, converting one solid state material into another. The incorporation of an additional functional group, a “tag”, into a linking ligand offers the opportunity to form structures in which this group is preserved during the MOF synthesis, allowing it to project into the pores or channels of the network structure. We define a “tag” as a group or functionality that is stable and innocent (that is, non-structure-defining) during MOF formation, but that can be transformed by a post-synthetic modification. This approach is shown schematically in Figure 1. A similar concept of tagging has also recently been applied in medicinal chemistry. Post-synthetic modification allows the pores in a preformed MOF to be tailored for a specific purpose, which offers the possibility of fine-tuning for selective adsorption and catalysis. The strategy also facilitates the incorporation into a MOF of functional groups that would not survive the conditions of the MOF synthesis (e.g., temperature and pH) and of functional groups that might compete with the donor groups on the bridging ligands. Given these advantages, it is surprising that there has been very little focus on postsynthetic modification of MOFs. Kim and co-workers showed that the pendant pyridyl groups in a chiral zinc network could be methylated and, very recently, Wang and Cohen, and Gamez and co-workers have both demonstrated that the amino groups in 2-amino-1,4-benzenedicarboxylate MOFs can be converted into amides or urethanes. Rosseinsky and co-workers have converted these amines into salicylidenes, and then used these to coordinate vanadium. Fujita and co-workers have shown that guest molecules can undergo similar transformations within the pores of a MOF. Herein, we report our endeavors to prepare tagged MOFs suitable for post-synthetic modification, starting from an aldehyde-modified dicarboxylate. Following seminal work from Yaghi and co-workers, it is now well-established that the octahedral zinc secondary building unit (SBU) Zn4O(O2CR)6 forms an isoreticular series of MOFs containing the same framework topology with linear dicarboxylates, such as bdc and 4,4’-biphenyldicarboxylate (bpdc). We have prepared the aldehyde-tagged dicarboxylic acid H2L 1 (2-formylbiphenyl-4,4’-dicarboxylic acid, Scheme 1), and used it in MOF synthesis. The coordinated L ligand is suitable for Figure 1. Schematic representation of the post-synthetic modification strategy for MOFs.

Assessment and analysis of damage in L’Aquila historic city centre after 6th April 2009

Abstract: The paper describes the output of a survey carried out in the district of L’Aquila, Italy, in May 2009 after the April earthquake and later in January 2010, and the consequent vulnerability assessment completed by the authors. Observations collected on site regard masonry buildings of the historic centre of L’Aquila and the towns of Paganica and Onna; particular focus was given to a number of buildings of interest, which better represent two locally recurrent building typologies: the mansion and the common dwelling. A description of the main structural features and their influence on damage mechanism is provided, stressing the importance of elements such as wall lay-out, quality of masonry and strengthening interventions. The gathered information is used as input for the application of the FaMIVE method (D’Ayala and Speranza in Earthq Spectra 19(3):479–509, 2003), whereby feasible collapse mechanisms and the associate failure load factors can be identified. The procedure is briefly outlined and results are discussed from the point of view of the performance point: push-over curves produced by statistical elaboration of FaMIVE’s output are compared both with the demand spectra obtained from EC8 and the response spectrum for the main shock as recorded by the closest station to the town. Conclusions are drawn on the reliability of the FaMIVE method with respect to its capability of predicting the damage mechanism identified on site.