Calculating NMR parameters in aluminophosphates : evaluation of dispersion correction schemes

Periodic density functional theory (DFT) calculations have recently emerged as a popular tool for assigning solid-state nuclear magnetic resonance (NMR) spectra. However, in order for the calculations to yield accurate results, accurate structural models are also required. In many cases the structural model (often derived from crystallographic diffraction) must be optimised (i.e., to an energy minimum) using DFT prior to the calculation of NMR parameters. However, DFT does not reproduce weak long-range "dispersion'' interactions well, and optimisation using some functionals can expand the crystallographic unit cell, particularly when dispersion interactions are important in defining the structure. Recently, dispersion-corrected DFT (DFT-D) has been extended to periodic calculations, to compensate for these missing interactions. Here, we investigate whether dispersion corrections are important for aluminophosphate zeolites (AlPOs) by comparing the structures optimised by DFT and DFT-D (using the PBE functional). For as-made AlPOs (containing cationic structure-directing agents (SDAs) and framework-bound anions) dispersion interactions appear to be important, with significant changes between the DFT and DFT-D unit cells. However, for calcined AlPOs, where the SDA-anion pairs are removed, dispersion interactions appear much less important, and the DFT and DFT-D unit cells are similar. We show that, while the different optimisation strategies yield similar calculated NMR parameters (providing that the atomic positions are optimised), the DFT-D optimisations provide structures in better agreement with the experimental diffraction measurements. Therefore, it appears that DFT-D calculations can, and should, be used for the optimisation of calcined and as-made AlPOs, in order to provide the closest agreement with all experimental measurements.PostprintPeer reviewe

Institutional Repositories, Open Access and Copyright: What Are the Practices and Implications?

A number of factors are driving open access to full-text journals: constantly rising prices of journal and database subscriptions, granting agencies requirements for recipients to submit their research publications into open access repositories, and pressure on libraries to create Institutional Repositories (IR) to promote the institutions’ reputations. Research proves that open access promotes the dissemination and use of scholarly works and citations for authors. This article examines the interactions among open access, institutional repositories, and copyright management. The research described herein investigates how institutional repositories are managing copyright and licensing issues that can interfere with open access

Institutional Repositories, Open Access and Copyright: What Are the Practices and Implications?

A number of factors are driving open access to full-text journals: constantly rising prices of journal and database subscriptions, granting agencies requirements for recipients to submit their research publications into open access repositories, and pressure on libraries to create Institutional Repositories (IR) to promote the institutions’ reputations. Research proves that open access promotes the dissemination and use of scholarly works and citations for authors. This article examines the interactions among open access, institutional repositories, and copyright management. The research described herein investigates how institutional repositories are managing copyright and licensing issues that can interfere with open access

Observational study on the palatability and tolerability of oral prednisolone and oral dexamethasone in children in Saudi Arabia and the UK

Background: Short-course oral corticosteroids are routinely used to treat acute asthma and croup. We evaluated their tolerability and palatability in Saudi Arabian (SA) and UK children. Methods: Prospective observational/interview study (three months in each country). Palatability was evaluated using a five-point facial scale and tolerability by direct questioning of patient/parents. Results: In SA, of 122 patients (2–10years) recruited: 52 received prednisolone base tablets; 37 prednisolone sodium phosphate syrup; 33 dexamethasone elixir. In the UK, of 133 patients (2–16years): 38 received prednisolone base tablets (mainly crushed and dispersed); 42 prednisolone sodium phosphate soluble tablets; 53 dexamethasone sodium phosphate oral solution. In both countries dexamethasone had the highest palatability scores (SA mean: 1.97; UK mean: 3) and prednisolone base tablets the lowest (SA mean: 1.12; UK mean: 1.39). Palatability scores improved for all formulations of prednisolone with each subsequent daily dose. In SA prednisolone base tablets were associated with more nausea (24 vs 7 patients) and vomiting (5 vs 0) than sodium phosphate syrup (P=0.008 and P=0.073 respectively). In the UK vomiting occurred more frequently with prednisolone base (8) than sodium phosphate soluble tablets (2) (P=0.041). In both centres dexamethasone was associated with less side effects. Vomiting (1 vs 0 patients), nausea (7 vs 3) and abdominal pain (10 vs 8) occurred more with dexamethasone sodium phosphate solution than dexamethasone elixir. Conclusions: Dexamethasone sodium phosphate solution was the most palatable preparation. Prednisolone base tablets were rated least palatable and were least well tolerated. Palatability scores improved with each dose taken

Investigating FAM-N pulses for signal enhancement in MQMAS NMR of quadrupolar nuclei

The authors would like to thank EPSRC (EP/K503162/1) for the award of a studentship to HFC and the ERC (EU FP7 Consolidator Grant 614290 “EXONMR”) for support. SEA would also like to thank the Royal Society and Wolfson Foundation for a merit award. The UK 850 MHz solid-state NMR Facility used in this research was funded by EPSRC and BBSRC (contract reference PR140003), as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). Financial support from the TGIR-RMN-THC Fr3050 CNRS to access the 800 MHz spectrometer (Lille) is gratefully acknowledged.Although a popular choice for obtaining high-resolution solid-state NMR spectra of quadrupolar nuclei, the inherently low sensitivity of the multiple-quantum magic-angle spinning (MQMAS) experiment has limited its application for nuclei with low receptivity or when the available sample volume is limited. A number of methods have been introduced in the literature to attempt to address this problem. Recently, we have introduced an alternative, automated approach, based on numerical simulations, for generating amplitude-modulated pulses (termed FAM-N pulses) to enhance the efficiency of the triple- to single-quantum conversion step within MQMAS. This results in efficient pulses that can be used without experimental reoptimisation, ensuring that this method is particularly suitable for challenging nuclei and systems. In this work, we investigate the applicability of FAM-N pulses to a wider variety of systems, and their robustness under more challenging experimental conditions. These include experiments performed under fast MAS, nuclei with higher spin quantum numbers, samples with multiple distinct sites, low-γ nuclei and nuclei subject to large quadrupolar interactions.Publisher PDFPeer reviewe

VCU-UNITE: Identifying Recognition Mechanisms for University-Community Engagement

The aims of the project were to determine what process would be appropriate to recognize significant contributions of university and community partners to joint community engagement projects. Our view was that several different award ceremonies exist in VCU, none of which are well attended and suggesting that this form of recognition may not be a high priority for participants. Thus, we sought to determine the awareness and extent of involvement of VCU faculty, staff and students in community engagement projects, and to find out what format of recognition process would be appealing to both university and community participants. We gathered this information through surveys and focus groups, analyzed the data and determined that university and community partners had differing views on what types of recognition would be desirous. Next, we designed a web portal through which nominations could be made by members of the university and by the community. We propose a streamlined nomination and online review process, leading to a quarterly award consisting of a letter of thanks from the Division of Community Engagement, and a photograph and narrative placed on the VCU website. Recipients of quarterly awards would automatically compete for an annual award, such as P&T credit or additional community leave time (university), or a scholarship, a plaque, or recognition at a VCU event (community)

Local Collections in Discovery Services: An Inquiry

Many libraries subscribed to discovery services in the hope of boosting the use of their local collections such as print materials, DVDs, or even subscribed ejournals and ebooks that are separate from licensed databases. However, anecdotal evidence shows that the implementation of a discovery service will increase the usage of the vendors’ electronic resources instead. This study aims to find out how well local collections are promoted through EBSCO Discovery Service (EDS), Primo, Summon, and WorldCat Discovery Services (WorldCat) by comparing results of queries in the discovery services versus the number of actual listings from these libraries’ traditional catalogs. Authors conducted three searches based on real-life student assignments in science, history, and sociology in each of the four discovery services. To offset the bias of location configuration, ten libraries with the same discovery tool were selected for each search and total results are averaged. ANOVA and Tukey Honest Significant Difference statistical analyses show differences among the four discovery services investigated. Discovery tools promote local collections in different ways. Some tools provide the possibility to list libraries’ local collections before listing the vendor’s database items, but others are less inclined to do so.

Ionothermal synthesis and characterization of CoAPO-34 molecular sieve

The cobalt-doped aluminophosphate molecular sieve, CoAPO-34 (with the chabazite-type topology) was prepared under ionothermal conditions using 1-ethyl-3-methylimidazolium bromide (EMIMBr) ionic liquid in presence of 1,6-hexanediamine (HDA). The HDA is not incorporated in CoAPO-34, but is required to mediate the availability of Co2+ during the synthesis. The material was characterized using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and solid-state NMR spectroscopy. Wideline 31P NMR spectroscopy showed broad signals (∼5000–10000 ppm wide), confirming that paramagnetic cobalt ions are successfully incorporated within the framework of the materials.PostprintPeer reviewe

The ambient hydration of the aluminophosphate JDF-2 to AlPO-53(A):insights from NMR crystallography

The aluminophosphate (AlPO) JDF-2 is prepared hydro­thermally with methyl­ammonium hydroxide (MAH+·HO-, MAH+ = CH3NH3+), giving rise to a microporous AEN-type framework with occluded MAH+ cations and extra-framework (Al-bound) HO- anions. Despite the presence of these species within its pores, JDF-2 can hydrate upon exposure to atmospheric moisture to give AlPO-53(A), an isostructural material whose crystal structure contains one mol­ecule of H2O per formula unit. This hydration can be reversed by mild heating (such as the frictional heating from magic angle spinning). Previous work has shown good agreement between the NMR parameters obtained experimentally and those calculated from the (optimized) crystal structure of JDF-2. However, several discrepancies are apparent between the experimental NMR parameters for AlPO-53(A) and those calculated from the (optimized) crystal structure (e.g. four 13C resonances are observed, rather than the expected two). The unexpected resonances appear and disappear reversibly with the respective addition and removal of H2O, so clearly arise from AlPO-53(A). We investigate the ambient hydration of JDF-2 using qu­anti­tative 31P MAS NMR to follow the transformation over the course of 3 months. The structures of JDF-2 and AlPO-53(A) are also investigated using a combination of multinuclear solid-state NMR spectroscopy to characterize the samples, and first-principles density functional theory (DFT) calculations to evaluate a range of possible structural models in terms of calculated NMR parameters and energetics. The published structure of JDF-2 is shown to be a good representation of the dehydrated material, but modification of the published structure of AlPO-53(A) is required to provide calculated NMR parameters that are in better agreement with experiment. This modification includes reorientation of all the MAH+ cations and partial occupancy of the H2O sites

Radiation Tolerance of Fully-Depleted P-Channel CCDs Designed for the SNAP Satellite

Thick, fully depleted p-channel charge-coupled devices (CCDs) have been developed at the Lawrence Berkeley National Laboratory (LBNL). These CCDs have several advantages over conventional thin, n-channel CCDs, including enhanced quantum efficiency and reduced fringing at near-infrared wavelengths and improved radiation tolerance. Here we report results from the irradiation of CCDs with 12.5 and 55 MeV protons at the LBNL 88-Inch Cyclotron and with 0.1-1 MeV electrons at the LBNL Co60 source. These studies indicate that the LBNL CCDs perform well after irradiation, even in the parameters in which significant degradation is observed in other CCDs: charge transfer efficiency, dark current, and isolated hot pixels. Modeling the radiation exposure over a six-year mission lifetime with no annealing, we expect an increase in dark current of 20 e/pixel/hr, and a degradation of charge transfer efficiency in the parallel direction of 3e-6 and 1e-6 in the serial direction. The dark current is observed to improve with an annealing cycle, while the parallel CTE is relatively unaffected and the serial CTE is somewhat degraded. As expected, the radiation tolerance of the p-channel LBNL CCDs is significantly improved over the conventional n-channel CCDs that are currently employed in space-based telescopes such as the Hubble Space Telescope.Comment: 11 pages, 10 figures, submitted to IEEE Transaction