Precise Control of Molecular Self-Diffusion in Isoreticular and Multivariate Metal-Organic Frameworks.

Understanding the factors that affect self-diffusion in isoreticular and multivariate (MTV) MOFs is key to their application in drug delivery, separations, and heterogeneous catalysis. Here, we measure the apparent self-diffusion of solvents saturated within the pores of large single crystals of MOF-5, IRMOF-3 (amino-functionalized MOF-5), and 17 MTV-MOF-5/IRMOF-3 materials at various mole fractions. We find that the apparent self-diffusion coefficient of N,N-dimethylformamide (DMF) may be tuned linearly between the diffusion coefficients of MOF-5 and IRMOF-3 as a function of the linker mole fraction. We compare a series of solvents at saturation in MOF-5 and IRMOF-3 to elucidate the mechanism by which the linker amino groups tune molecular diffusion. The ratio of the self-diffusion coefficients for solvents in MOF-5 to those in IRMOF-3 is similar across all solvents tested, regardless of solvent polarity. We conclude that average pore aperture, not solvent-linker chemical interactions, is the primary factor responsible for the different diffusion dynamics upon introduction of an amino group to the linker

An intensional implementation technique for functional languages

The potential of functional programming languages has not been widely accepted yet. The reason lies in the difficulties associated with their implementation. In this dissertation we propose a new implementation technique for functional languages by compiling them into 'Intensional Logic' of R. Montague and R. Carnap. Our technique is not limited to a particular hardware or to a particular evaluation strategy; nevertheless it lends itself directly to demand-driven tagged dataflow architecture. Even though our technique can handle conventional languages as well, our main interest is exclusively with functional languages in general and with Lucid-like dataflow languages in particular. We give a brief general account of intensional logic and then introduce the concept of intensional algebras as structures (models) for intensional logic. We, formally, show the computability requirements for such algebras. The target language of our compilation is the family of languages DE (definitional equations over intensional expressions). A program in DE is a linear (not structured) set of non-ambiguous equations defining nullary variable symbols. One of these variable symbols should be the symbol result. We introduce the compilation of Iswim (a first order variant of Landin's ISWIM) as an example of compiling functions into intensional expressions. A compilation algorithm is given. Iswim(A), for any algebra of data types A, is compiled into DE(Flo(A)) where Flo(A) is a uniquely defined intensional algebra over the tree of function calls. The approach is extended to compiling Luswim and Lucid. We describe the demand-driven tagged dataflow (the eduction) approach to evaluating the intensional family of target languages DE. Furthermore, for each intensional algebra, we introduce a collection of rewrite rules. A justification of correctness is given. These rules are the basis for evaluating programs in the target DE by reduction. Finally, we discuss possible refinements and extensions to our approach

Adsorption Mechanism and Uptake of Methane in Covalent Organic Frameworks: Theory and Experiment

We determined the methane (CH_4) uptake (at 298 K and 1 to 100 bar pressure) for a variety of covalent organic frameworks (COFs), including both two-dimensional (COF-1, COF-5, COF-6, COF-8, and COF-10) and three-dimensional (COF-102, COF-103, COF-105, and COF-108) systems. For all COFs, the CH_4 uptake was predicted from grand canonical Monte Carlo (GCMC) simulations based on force fields (FF) developed to fit accurate quantum mechanics (QM) [second order Møller−Plesset (MP2) perturbation theory using doubly polarized quadruple-ζ (QZVPP) basis sets]. This FF was validated by comparison with the equation of state for CH_4 and by comparison with the experimental uptake isotherms at 298 K (reported here for COF-5 and COF-8), which agrees well (within 2% for 1−100 bar) with the GCMC simulations. From our simulations we have been able to observe, for the first time, multilayer formation coexisting with a pore filling mechanism. The best COF in terms of total volume of CH_4 per unit volume COF absorbent is COF-1, which can store 195 v/v at 298 K and 30 bar, exceeding the U.S. Department of Energy target for CH_4 storage of 180 v/v at 298 K and 35 bar. The best COFs on a delivery amount basis (volume adsorbed from 5 to 100 bar) are COF-102 and COF-103 with values of 230 and 234 v(STP: 298 K, 1.01 bar)/v, respectively, making these promising materials for practical methane storage

PHARMACISTS’ KNOWLEDGE AND PERCEPTION REGARDING DIETARY SUPPLEMENTS IN PALESTINE: DESCRIPTIVE STUDY

Objective: To assess pharmacists’ knowledge with regards registered dietary supplements DS and their perception toward DS registration by the ministry of health MOH Methods: A questionnaire was designed to assess pharmacists’ knowledge about newly registered food supplements (registered after 2012) and to assess their view about the current measures followed by MOH in registering these supplements. The questionnaire was distributed to pharmacists in West Bank–Palestine during the period from December 2017 to March 2018. Data collected were analyzed using the Statistical Package for Social Sciences program (SPSS) version 10. Results: Pharmacists’ knowledge with regards to registered DS was high with approximately 86% have recorded the right answers. Their perception about the current increasing registration of DS, pharmacists (67%) thinks that ‘what available DS in the market’ is enough and there is no need for more DS to be registered. Almost half of the pharmacists (48%) think that the information provided regarding dietary supplements is inadequate and almost 30% think is adequate. More than 70% of the pharmacists they never or rarely access the MOH web site to access for information about DS. Conclusion: This study highlighted the importance of controlling DS registration by the MOH and the necessity to effectively update pharmacists about these DS for effective counseling

Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water Harvester.

Sorbent-assisted water harvesting from air represents an attractive way to address water scarcity in arid climates. Hitherto, sorbents developed for this technology have exclusively been designed to perform one water harvesting cycle (WHC) per day, but the productivities attained with this approach cannot reasonably meet the rising demand for drinking water. This work shows that a microporous aluminum-based metal-organic framework, MOF-303, can perform an adsorption-desorption cycle within minutes under a mild temperature swing, which opens the way for high-productivity water harvesting through rapid, continuous WHCs. Additionally, the favorable dynamic water sorption properties of MOF-303 allow it to outperform other commercial sorbents displaying excellent steady-state characteristics under similar experimental conditions. Finally, these findings are implemented in a new water harvester capable of generating 1.3 L kgMOF -1 day-1 in an indoor arid environment (32% relative humidity, 27 °C) and 0.7 L kgMOF -1 day-1 in the Mojave Desert (in conditions as extreme as 10% RH, 27 °C), representing an improvement by 1 order of magnitude over previously reported devices. This study demonstrates that creating sorbents capable of rapid water sorption dynamics, rather than merely focusing on high water capacities, is crucial to reach water production on a scale matching human consumption

Finite element thermal analysis of the fusion welding of a P92 steel pipe

Fusion welding is common in steel pipeline construction in fossil-fuel power generation plants. Steel pipes in service carry steam at high temperature and pressure, undergoing creep during years of service; their integrity is critical for the safe operation of a plant. The high-grade martensitic P92 steel is suitable for plant pipes for its enhanced creep strength. P92 steel pipes are usually joined together with a similar weld metal. Martensitic pipes are sometimes joined to austenitic steel pipes using nickel based weld consumables. Welding involves severe thermal cycles, inducing residual stresses in the welded structure, which, without post weld heat treatment (PWHT), can be detrimental to the integrity of the pipes. Welding residual stresses can be numerically simulated by applying the finite element (FE) method in Abaqus. The simulation consists of a thermal analysis, determining the temperature history of the FE model, followed by a sequentially-coupled structural analysis, predicting residual stresses from the temperature history. <br><br> In this paper, the FE thermal analysis of the arc welding of a typical P92 pipe is presented. The two parts of the P92 steel pipe are joined together using a dissimilar material, made of Inconel weld consumables, producing a multi-pass butt weld from 36 circumferential weld beads. Following the generation of the FE model, the FE mesh is controlled using Model Change in Abaqus to activate the weld elements for each bead at a time corresponding to weld deposition. The thermal analysis is simulated by applying a distributed heat flux to the model, the accuracy of which is judged by considering the fusion zones in both the parent pipe as well as the deposited weld metal. For realistic fusion zones, the heat flux must be prescribed in the deposited weld pass and also the adjacent pipe elements. The FE thermal results are validated by comparing experimental temperatures measured by five thermocouples on the pipe outside surface with the FE temperature history at corresponding nodal points

Covalent Organic Frameworks as Exceptional Hydrogen Storage Materials

We report the H_2 uptake properties of six covalent organic frameworks (COFs) from first-principles-based grand canonical Monte-Carlo simulations. The predicted H_2 adsorption isotherm is in excellent agreement with the only available experimental result (3.3 vs 3.4 wt % at 50 bar and 77 K for COF-5), also reported here, validating the predictions. We predict that COF-105 and COF-108 lead to a reversible excess H_2 uptake of 10.0 wt % at 77 K, making them the best known storage materials for molecular hydrogen at 77 K. We predict that the total H_2 uptake for COF-108 is 18.9 wt % at 77 K. COF-102 shows the best volumetric performance, storing 40.4 g/L of H_2 at 77 K. These results indicate that the COF systems are most promising candidates for practical hydrogen storage

Moderating effects of performance measurement use on the relationship between organizational performance, measurement diversity and product innovation

This study sets'out to address the question of whether the effect of organizational' performance measurement diversity on product innovation will differ depending on how organizational performance measures are used. There is strong empirical evidence that many companies who are successful today are less likely to be successful in the future because they fail to innovate. It is surprisingly then, that when everyone stresses the importance of innovation, there are many organizations adopting performance measurement systems, which may constrain their innovativeness. Currently, there are three differing perspectives on the effect of measurement on a firm's propensity to innovate. Moreover, each of these has empirical evidence to support its argument. The first perspective views measurement as constraining innovation because it impedes creativity, experimentation, and search in firms. The second perspective views measurement as helping innovation because it triggers search, facilitates decision-making, and increases risk-taking. The third perspective views measurement as having insignificant or little impact on innovation because it is used primarily for signalling. A possible explanation of the contradiction in the empirical findings of these studies is that they generally ignore how measurement is used. Therefore, using the behavioural theory of innovation, I argue that one possible way of resolving the contradictory findings is by incorporating measurement use as a moderating variable. Using data from a cross-sectional, large-scale, probability sample survey of 145 UK manufacturing firms, I show that organizational performance measurement diversity interacts with performance measurement use to determine product innovation. My findings suggest that the extent to which a firm offers new products will be more positively (negatively) associated with performancemeasurement diversity when diagnostic use is high (low) holding interactive use constant and will be more negatively (positively) associated with performance measurement diversity when interactive use is high (low) holding, diagnostic use constant.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Reticular Synthesis of Multinary Covalent Organic Frameworks.

Hexagonal hexaminophenyl benzene, tetragonal tetrakis(4-aminophenyl) ethane, and trigonal 1,3,5-tris(p-formylphenyl)benzene were all joined together by imine linkages to yield a 2D porous covalent organic framework with unprecedented tth topology, termed COF-346. Unlike the 5 simple existing 2D topologies reported in COFs, COF-346 has 3 kinds of vertices and 2 kinds of edges and is constructed with linkers of 3 kinds of connectivity, and thus represents a higher degree of complexity in COF structures. The success in crystallizing COF-346 was based on precisely chosen geometry and metrics of the linkers and error correction offered by dynamic imine formation. We also report two additional related COFs: a crystalline, porous COF, termed COF-360 with a rare kgd topology, as well as the first crystalline, porous COF with defected tth topology, termed COF-340