Removal of disinfection by-product precursors by coagulation and an innovative suspended ion exchange process

This investigation aimed to compare the disinfection by-product formation potentials (DBPFPs) of three UK surface waters (1 upland reservoir and 2 lowland rivers) with differing characteristics treated by (a) a full scale conventional process and (b) pilot scale processes using a novel suspended ion exchange (SIX) process and inline coagulation (ILCA) followed by ceramic membrane filtration (CMF). Liquid chromatography-organic carbon detection analysis highlighted clear differences between the organic fractions removed by coagulation and suspended ion exchange. Pretreatments which combined SIX and coagulation resulted in significant reductions in dissolved organic carbon (DOC), UV absorbance (UVA), trihalomethane and haloacetic acid formation potential (THMFP, HAAFP), in comparison with the SIX or coagulation process alone. Further experiments showed that in addition to greater overall DOC removal, the processes also reduced the concentration of brominated DBPs and selectively removed organic compounds with high DBPFP. The SIX/ILCA/CMF process resulted in additional removals of DOC, UVA, THMFP, HAAFP and brominated DBPs of 50, 62, 62, 62% and 47% respectively compared with conventional treatment

Ullmann coupling reactions on Ag(111) and Ag(110); substrate influence on the formation of covalently coupled products and intermediate metal-organic structures Metal-Organic Structures

On-surface reactions based on Ullmann coupling are known to proceed on coinage-metal substrates (e.g. Au, Ag, Cu), with the chemistry of the surface strongly influencing the reaction progression. In addition, the topography of the surface may be expected to affect the local adsorption geometry of the reactants as well as the intermediate and final structures. Here, we investigate the effect of two different surface facets of silver, Ag(111) and Ag(110) on the formation of organometallic and covalent structures for Ullmann-type coupling reactions. Deposition of 4,4”-diiodo-m-terphenyl molecules onto either Ag(111) or Ag(110) surfaces leads to the scission of C-I bonds followed by the formation of organometalic zigzag structures, consisting of molecules connected by coordination bonds to Ag adatoms. The covalently coupled product is formed by annealing each surface, leading to the removal of Ag atoms and the formation of covalently bonded zigzag poly(m-phenylene) structures. Comparisons of the adsorption model of molecules on each surface before and after annealing reveal that on Ag(111), structures rearrange by rotation and elongation of bonds in order to become commensurate with the surface, whereas for the Ag(110) surface, the similarity in adsorption geometry of the intermediate and final states means that no rotation is required

What Next-Generation 21 cm Power Spectrum Measurements Can Teach Us About the Epoch of Reionization

A number of experiments are currently working towards a measurement of the 21 cm signal from the Epoch of Reionization. Whether or not these experiments deliver a detection of cosmological emission, their limited sensitivity will prevent them from providing detailed information about the astrophysics of reionization. In this work, we consider what types of measurements will be enabled by a next-generation of larger 21 cm EoR telescopes. To calculate the type of constraints that will be possible with such arrays, we use simple models for the instrument, foreground emission, and the reionization history. We focus primarily on an instrument modeled after the $\sim 0.1~\rm{km}^2$ collecting area Hydrogen Epoch of Reionization Array (HERA) concept design, and parameterize the uncertainties with regard to foreground emission by considering different limits to the recently described "wedge" footprint in k-space. Uncertainties in the reionization history are accounted for using a series of simulations which vary the ionizing efficiency and minimum virial temperature of the galaxies responsible for reionization, as well as the mean free path of ionizing photons through the IGM. Given various combinations of models, we consider the significance of the possible power spectrum detections, the ability to trace the power spectrum evolution versus redshift, the detectability of salient power spectrum features, and the achievable level of quantitative constraints on astrophysical parameters. Ultimately, we find that $0.1~\rm{km}^2$ of collecting area is enough to ensure a very high significance ($\gtrsim30\sigma$) detection of the reionization power spectrum in even the most pessimistic scenarios. This sensitivity should allow for meaningful constraints on the reionization history and astrophysical parameters, especially if foreground subtraction techniques can be improved and successfully implemented.Comment: 27 pages, 18 figures, updated SKA numbers in appendi

Ullmann coupling reactions on Ag(111) and Ag(110); substrate influence on the formation of covalently coupled products and intermediate metal-organic structures Metal-Organic Structures

On-surface reactions based on Ullmann coupling are known to proceed on coinage-metal substrates (e.g. Au, Ag, Cu), with the chemistry of the surface strongly influencing the reaction progression. In addition, the topography of the surface may be expected to affect the local adsorption geometry of the reactants as well as the intermediate and final structures. Here, we investigate the effect of two different surface facets of silver, Ag(111) and Ag(110) on the formation of organometallic and covalent structures for Ullmann-type coupling reactions. Deposition of 4,4”-diiodo-m-terphenyl molecules onto either Ag(111) or Ag(110) surfaces leads to the scission of C-I bonds followed by the formation of organometalic zigzag structures, consisting of molecules connected by coordination bonds to Ag adatoms. The covalently coupled product is formed by annealing each surface, leading to the removal of Ag atoms and the formation of covalently bonded zigzag poly(m-phenylene) structures. Comparisons of the adsorption model of molecules on each surface before and after annealing reveal that on Ag(111), structures rearrange by rotation and elongation of bonds in order to become commensurate with the surface, whereas for the Ag(110) surface, the similarity in adsorption geometry of the intermediate and final states means that no rotation is required

Order, disorder, and metalation of tetraphenylporphyrin (2H-TPP) on Au(111)

A thermally induced order–disorder transition of tetraphenylporphyrin (2H-TPP) on Au(111) is characterised by scanning probe microscopy and X-ray photoelectron spectroscopy-based techniques. We observed that a transition from an ordered close-packed phase to a disordered diffuse phase is correlated with an on-surface cyclodehydrogenation reaction, and that additional heating of this diffuse phase gives rise to a single distinct nitrogen environment indicative of the formation of a Au–TPP species

Molecular quantum rings formed from a π-conjugated macrocycle

The electronic structure of a molecular quantum ring (stacks of 40-unit cyclic porphyrin polymers) is characterised via scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS). Our measurements access the energetic and spatial distribution of the electronic states and, utilising a combination of density functional theory and tight binding calculations, we interpret the experimentally obtained electronic structure in terms of coherent quantum states confined around the circumference of the π-conjugated macrocycle. These findings demonstrate that large (53 nm circumference) cyclic porphyrin polymers have the potential to act as molecular quantum rings

Conservative management versus open reduction and internal fixation for mid-shaft clavicle fractures in adults - The Clavicle Trial: Study protocol for a multicentre randomized controlled trial

Background: Clavicle fractures account for around 4% of all fractures and up to 44% of fractures of the shoulder girdle. Fractures of the middle third (or mid-shaft) account for approximately 80% of all clavicle fractures. Management of this group of fractures is often challenging and the outcome can be unsatisfactory. In particular it is not clear whether surgery produces better outcomes than non-surgical management. Currently there is much variation in the use of surgery and a lack of good quality evidence to inform our decision.Methods/Design: We aim to undertake a multicentre randomised controlled trial evaluating the effectiveness and safety of conservative management versus open reduction and internal fixation for displaced mid-shaft clavicle fractures in adults. Surgical treatment will be performed using the Acumed clavicle fixation system. Conservative management will consist of immobilisation in a sling at the side in internal rotation for 6 weeks or until clinical or radiological union. We aim to recruit 300 patients. These patients will be followed-up for at least 9 months. The primary endpoint will be the rate of non-union at 3 months following treatment. Secondary endpoints will be limb function measured using the Constant-Murley Score and the Disabilities of the Arm, Shoulder and Hand (DASH) Score at 3 and 9 months post-operatively.Discussion: This article presents the protocol for a multicentre randomised controlled trial. It gives extensive details of, and the basis for, the chosen methods, and describes the key measures taken to avoid bias and to ensure validity.Trial Registration: United Kingdom Clinical Research Network ID: 8665. The date of registration of the trial is 07/09/2006. The date the first patient was recruited is 18/12/2007. © 2011 Longo et al; licensee BioMed Central Ltd

Structural characterisation of molecular conformation and the incorporation of adatoms in an on-surface Ullmann-type reaction

© 2020, The Author(s). The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects. The transition from a three-dimensional reaction volume to quasi-two-dimensional confinement, as is the case for on-surface synthesis, has the potential to facilitate alternative reaction pathways to those available in solution. Ullmann-type reactions, where the surface plays a role in the coupling of aryl-halide functionalised species, has been shown to facilitate extended one- and two-dimensional structures. Here we employ a combination of scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and X-ray standing wave (XSW) analysis to perform a chemical and structural characterisation of the Ullmann-type coupling of two iodine functionalised species on a Ag(111) surface held under ultra-high vacuum (UHV) conditions. Our results allow characterisation of molecular conformations and adsorption geometries within an on-surface reaction and provide insight into the incorporation of metal adatoms within the intermediate structures of the reaction

Field Deployment of Prototype Antenna Tiles for the Mileura Widefield Array--Low Frequency Demonstrator

Experiments were performed with prototype antenna tiles for the Mileura Widefield Array--Low Frequency Demonstrator (MWA-LFD) to better understand the widefield, wideband properties of their design and to characterize the radio frequency interference (RFI) between 80 and 300 MHz at the site in Western Australia. Observations acquired during the six month deployment confirmed the predicted sensitivity of the antennas, sky-noise dominated system temperatures, and phase-coherent interferometric measurements. The radio spectrum is remarkably free of strong terrestrial signals, with the exception of two narrow frequency bands allocated to satellite downlinks and rare bursts due to ground-based transmissions being scattered from aircraft and meteor trails. Results indicate the potential of the MWA-LFD to make significant achievements in its three key science objectives: epoch of reionziation science, heliospheric science, and radio transient detection.Comment: Accepted by AJ. 17 pages with figure

Hydrogen Epoch of Reionization Array (HERA)

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and to explore earlier epochs of our Cosmic Dawn ($z\sim30$). During these epochs, early stars and black holes heated and ionized the IGM, introducing fluctuations in 21 cm emission. HERA is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. The full HERA instrument will be a 350-element interferometer in South Africa consisting of 14-m parabolic dishes observing from 50 to 250 MHz. Currently, 19 dishes have been deployed on site and the next 18 are under construction. HERA has been designated as an SKA Precursor instrument. In this paper, we summarize HERA's scientific context and provide forecasts for its key science results. After reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the HERA instrument. Next, we present the HERA instrument design, along with the subsystem specifications that ensure that HERA meets its performance requirements. Finally, we summarize the schedule and status of the project. We conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. HERA is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. The result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology.Comment: 26 pages, 24 figures, 2 table