Polarization-dependence of anomalous scattering in brominated DNA and RNA molecules, and importance of crystal orientation in single- and multiple-wavelength anomalous diffraction phasing

In this paper the anisotropy of anomalous scattering at the Br K-absorption edge in brominated nucleotides is investigated, and it is shown that this effect can give rise to a marked directional dependence of the anomalous signal strength in X-ray diffraction data. This implies that choosing the correct orientation for crystals of such molecules can be a crucial determinant of success or failure when using single- and multiple-wavelength anomalous diffraction (SAD or MAD) methods to solve their structure. In particular, polarized absorption spectra on an oriented crystal of a brominated DNA molecule were measured, and were used to determine the orientation that yields a maximum anomalous signal in the diffraction data. Out of several SAD data sets, only those collected at or near that optimal orientation allowed interpretable electron density maps to be obtained. The findings of this study have implications for instrumental choices in experimental stations at synchrotron beamlines, as well as for the development of data collection strategy programs

Transition-metal-free homologative cross-coupling of aldehydes and ketones with geminal bis(boron) compounds

We report a transition-metal-free coupling of aldehydes and ketones with geminal bis(boron) building blocks which provides the coupled, homologated carbonyl compound upon oxidation. This reaction not only extends an alkyl chain containing a carbonyl group, it also simultaneously introduces a new carbonyl substituent. We demonstrate that enantiopure aldehydes with an enolizable stereogenic center undergo this reaction with complete retention of stereochemistry

Making connections and promoting the profession: social media use by World Federation of Occupational Therapy member organisations

BACKGROUND: World Federation of Occupational Therapists (WFOT) member organisations comprise 77 national occupational therapy organisations across the world. Each national organisation interacts with its members and the public using diverse methods. Increasingly, national organisations are broadening their communication methods. OBJECTIVE: The objective of this study was to examine if and how occupational therapy organisations are using social media for communication, and if so, the types of concerns or barriers they experience and what role they anticipate social media might play in the near future. METHODS: An online survey was developed; 57 of 77 WFOT member organisations responded. FINDINGS: This study identified that WFOT national organisations are using social media, to varying degrees, with or without an individual formally assigned to manage social media. Respondents reported that they used social media to: communicate with members, promote the organisation and promote the profession. Commonly expressed needs included assistance with guide- lines for ethical social media use, developing technical expertise, and recognition of limits of time and competing priorities. Recommendations arising from this research are at the global, national, local and individual levels and incorporate active dissemination and pure diffusion approaches. Taking steps to increase the use of social media could indirectly impact occu- pational therapy practice through enhancing organisations’ abilities to support practitioners to enhance their practice. LIMITATIONS AND RECOMENDATIONS FOR FURTHER RESEARCH: Although 57% of WFOT member organisations returned usable responses, there may be some additional perspectives that were not captured. It would be helpful to contact non-responding organisations to explore their social media use and plans. Further research could examine how future initiatives put in place by WFOT impact social media use by member organisations.Published versio

Cooperative Jahn-Teller Distortion in PrO2

We report neutron diffraction data on single crystal PrO2 which reveal a cooperative Jahn-Teller distortion at TD = 120 +/- 2 K. Below this temperature an internal distortion of the oxygen sublattice causes the unit cell of the crystallographic structure to become doubled along one crystal axis. We discuss several possible models for this structure. The antiferromagnetic structure below TN = 13.5 K is found to consist of two components, one of which shares the same doubled unit cell as the distorted crystallographic structure. We also present measurements of the magnetic susceptibility, the specific heat capacity and the electrical conductivity of PrO2. The susceptibility data show an anomaly at a temperature close to TD. From the specific heat capacity data we deduce that the ground state is doubly degenerate, consistent with a distortion of the cubic local symmetry. We discuss possible mechanisms for this. The conductivity shows an activated behaviour with an activation energy Ea = 0.262 +/- 0.003 eV.Comment: 12 pages, 14 figures, 2 tables. Additional suggested structure in v

Equation-oriented modeling, simulation, and optimization of integrated and intensified process and energy systems

Process intensification, defined as unconventional design and/or operation of processes that results in substantial performance improvements, represents a promising route toward reducing capital and operating expenses in the chemical/petrochemical process industry, while simultaneously achieving improved safety and environmental performance. In this dissertation, intensification is approached from three different angles: reactor design and control, process flowsheet design and optimization, and production scheduling and control. In the first part of the dissertation, three novel concepts for improving the controllability of intensified microchannel reactors are introduced. The first concept is a latent energy storage-based temperature controller, where a phase change material is confined within the walls of an autothermal reactor to improve local temperature control. The second concept is a segmented catalyst layer which modulates the rate of heat generation and consumption along the length of an autothermal reactor. Finally, the third concept is a thermally actuated valve, which uses small-scale bimetallic strips to modulate flow in a microchannel reactor in response to temperature changes. The second part of the dissertation introduces a novel framework for equation-oriented flowsheet modeling, simulation and optimization. The framework consists of a pseudo-transient reformulation of the steady-state material and energy balance equations of process unit operations as differential-algebraic equation (DAE) systems that are statically equivalent to the original model. I show that these pseudo-transient models improve the convergence properties of equation-oriented process flowsheet simulations by expanding the convergence basin in comparison to conventional steady state equation-oriented simulators. A library of pseudo-transient unit operation models is developed, and several case studies are presented. Models for more complex unit operations such as a pseudo-transient multistream heat exchanger and a dividing-wall distillation column are later introduced, and can easily be included in the flowsheet optimization framework. In the final part of the dissertation, a paradigm for calculating the optimal production schedule in a fast changing market situation is introduced. This is accomplished by including a model of the dynamics of a process and its control system into production scheduling calculations. The scheduling-relevant dynamic models are constructed to be of lower order than a detailed dynamic process model, while capturing the closed-loop behavior of a set of scheduling-relevant variables. Additionally, a method is given for carrying out these production scheduling calculations online and in "closed scheduling loop,"' i.e., recalculating scheduling decisions upon the advent of scheduling-relevant process or market events. An air separation unit operating in a demand response scenario is used as a representative case study.Chemical Engineerin

Facile Pyrolytic Synthesis of Silicon Nanowires

One-dimensional nanostructures such as silicon nanowires (SiNW) are attractive candidates for low power density electronic and optoelectronic devices including sensors. A new simple method for SiNW bulk synthesis[1, 2] is demonstrated in this work, which is inexpensive and uses low toxicity materials, thereby offering a safe, energy efficient and green approach. The method uses low flammability liquid phenylsilanes, offering a safer avenue for SiNW growth compared with using silane gas. A novel, duo-chamber glass vessel is used to create a low-pressure environment where SiNWs are grown through vapor-liquid-solid mechanism using gold nanoparticles as a catalyst. The catalyst decomposes silicon precursor vapors of diphenylsilane and triphenylsilane and precipitates single crystal SiNWs, which appear to grow parallel to the substrate surface. This opens up possibilities for synthesizing nano-junctions amongst wires which is important for the grid architecture of nanoelectronics proposed by Likharev[3]. Even bulk synthesis of SiNW is feasible using sacrificial substrates such as CaCO(3) that can be dissolved post-synthesis. Furthermore, by dissolving appropriate dopants in liquid diphenylsilane, a controlled doping of the nanowires is realized without the use of toxic gases and expensive mass flow controllers. Upon boron doping, we observe a characteristic red shift in photoluminescence spectra. In summary, an inexpensive and versatile method for SiNW is presented that makes these exotic materials available to any lab at low cost

Estimating fuel channel bore from fuel grab load trace data

Detailed measurements of the graphite core fuel channels are made by specialist inspection equipment during planned outages, typically every 18 months to 3 years. The bores of the graphite fuel bricks are obtained during these inspections and are used to provide important information about the health of the core. Additionally, less detailed online monitoring data is obtained much more frequently during refuelling events, called the fuel grab load trace (FGLT), which can be also used to infer the health of the graphite core. This paper describes the process of creating a model which isolates a component of the refuelling data and maps it directly to dimensional measurements of fuel channel bore. The model is created from a combination of the theoretical understanding of the physical interactions of the fuel stringer during refuelling events and several years of refuelling and inspection data to estimate suitable model parameters. Initially the model created was a coarse estimation of FGLT to fuel bore dimension but through refinements a much more accurate model has been created. An application of this model is shown through a case study of a recent outage where estimations were made on refuelling data and were compared to previously unseen inspection data

Cimetidine, C10H16N6S, formC: crystal structure and modelling of polytypes using suoperspace approach

An efficient method for modelling a polytypic family is presented with the example of cimetidine in the form C polymorph. The method exploits the (3 + 1)-dimensional superspace model, which is a powerful tool for the description, prediction and understanding of polytype modifications in small-molecule crystallography, as illustrated with this pharmaceutical example