Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV

A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb(-1), from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling lambda ''(312) or lambda ''(323) and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the (t) over tilde -> qq' scenario.Peer reviewe

Removal of inorganic and trace organic contaminants by electrodialysis

With the continual concern over the presence of naturally occurring and anthropogenic inorganic and trace organic contaminants in the aquatic environment there is a growing need for the implementation of innovative treatment processes for the elimination of these contaminants from natural waters and wastewater effluents. While conventional treatment methods are ineffective in the removal of emerging contaminants such as steroidal hormones and pesticides, membrane technology, including electrodialysis (ED), has been highlighted as a potential treatment option. However, the clear lack of fundamental understanding of the behaviour of contaminants in ED is a current limitation for its extensive utilisation and is a critical issue that needs to be addressed. ED processing potentialities have not been fully exploited and more research is needed to account for all the key parameters such as contaminant physicochemical properties, solution chemistry and the presence of organic matter. The purpose of this study was to elucidate the mechanisms of inorganic and trace organic contaminant removal by ED. The inorganic contaminants fluoride, nitrate and boron were selected due to their ubiquitous nature in the environment and public health concerns resulting from longterm exposure. The hydrated radius and strength of hydration shells played a significant role in ionic transport, whereby nitrate with a smaller hydrated radius was removed more effectively (94.1 %) than fluoride (68.3 %) with a larger hydrated radius. While fluoride and nitrate removal was pH independent, the pH dependent speciation of boron enhanced its removal with increasing pH. Territorial binding and/or complexation of the inorganics with organic matter enhanced removal. The removal of a range of trace inorganics (e.g. arsenic, calcium, magnesium, uranium) from a brackish groundwater from a remote Australian community was investigated. Undissociated inorganics were not transported through the membranes, whereas dissociated inorganics were due to electrostatic attraction. At acidic-neutral conditions ionic transport was the dominant removal mechanism. At neutral to alkaline conditions insoluble carbonate species precipitated and deposited as a membrane scaling layer (60 μm). This has serious implications for the long-term practical applicability of ED to treat real waters as scaling increased ED stack resistance (pH 3: 27.5 4, pH 11: 50 4) and decreased total dissolved solids removal (pH 3: 99 %, pH 11: 89.5 %). While the treatment of trace organics by other membrane processes has been widely studied, their fate in ED and interaction with ED membranes is relatively unknown. Trace contaminant-membrane interaction studies were undertaken to quantify the partitioning of trace organics; namely steroidal hormones and the pesticide endosulfan, to ED membranes by measuring membrane-water partition coefficients (log KM). The extremely high sorption capacity of the membranes was attributed to hydrogen bonding between the trace organic and membrane functional groups. Hormone sorption during ED was influenced by solution pH and organic matter. In the case of estrone, membrane sorption decreased at pH 11 (487 μg/cm3) compared to pH 7 (591 μg/cm3) due to dissociation and membrane electrostatic repulsion .At pH 11, repulsion between dissociated estrone and HA coupled with membrane electrostatic attraction resulted in increased sorption. The findings from this study highlight that the transport of trace contaminants will depend largely on the characteristics of the membranes used in the ED process as well as the physicochemical characteristics of the contaminants, their interaction with the ED membranes and the presence of other inorganic and/or organic compounds. The knowledge gained has direct applications to current problems and uncertainties in water and wastewater treatment with regards to the fate and transport of contaminants.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Removal of inorganic and trace organic contaminants by electrodialysis

With the continual concern over the presence of naturally occurring and anthropogenic inorganic and trace organic contaminants in the aquatic environment there is a growing need for the implementation of innovative treatment processes for the elimination of these contaminants from natural waters and wastewater effluents. While conventional treatment methods are ineffective in the removal of emerging contaminants such as steroidal hormones and pesticides, membrane technology, including electrodialysis (ED), has been highlighted as a potential treatment option. However, the clear lack of fundamental understanding of the behaviour of contaminants in ED is a current limitation for its extensive utilisation and is a critical issue that needs to be addressed. ED processing potentialities have not been fully exploited and more research is needed to account for all the key parameters such as contaminant physicochemical properties, solution chemistry and the presence of organic matter. The purpose of this study was to elucidate the mechanisms of inorganic and trace organic contaminant removal by ED. The inorganic contaminants fluoride, nitrate and boron were selected due to their ubiquitous nature in the environment and public health concerns resulting from longterm exposure. The hydrated radius and strength of hydration shells played a significant role in ionic transport, whereby nitrate with a smaller hydrated radius was removed more effectively (94.1 %) than fluoride (68.3 %) with a larger hydrated radius. While fluoride and nitrate removal was pH independent, the pH dependent speciation of boron enhanced its removal with increasing pH. Territorial binding and/or complexation of the inorganics with organic matter enhanced removal. The removal of a range of trace inorganics (e.g. arsenic, calcium, magnesium, uranium) from a brackish groundwater from a remote Australian community was investigated. Undissociated inorganics were not transported through the membranes, whereas dissociated inorganics were due to electrostatic attraction. At acidic-neutral conditions ionic transport was the dominant removal mechanism. At neutral to alkaline conditions insoluble carbonate species precipitated and deposited as a membrane scaling layer (60 μm). This has serious implications for the long-term practical applicability of ED to treat real waters as scaling increased ED stack resistance (pH 3: 27.5 4, pH 11: 50 4) and decreased total dissolved solids removal (pH 3: 99 %, pH 11: 89.5 %). While the treatment of trace organics by other membrane processes has been widely studied, their fate in ED and interaction with ED membranes is relatively unknown. Trace contaminant-membrane interaction studies were undertaken to quantify the partitioning of trace organics; namely steroidal hormones and the pesticide endosulfan, to ED membranes by measuring membrane-water partition coefficients (log KM). The extremely high sorption capacity of the membranes was attributed to hydrogen bonding between the trace organic and membrane functional groups. Hormone sorption during ED was influenced by solution pH and organic matter. In the case of estrone, membrane sorption decreased at pH 11 (487 μg/cm3) compared to pH 7 (591 μg/cm3) due to dissociation and membrane electrostatic repulsion .At pH 11, repulsion between dissociated estrone and HA coupled with membrane electrostatic attraction resulted in increased sorption. The findings from this study highlight that the transport of trace contaminants will depend largely on the characteristics of the membranes used in the ED process as well as the physicochemical characteristics of the contaminants, their interaction with the ED membranes and the presence of other inorganic and/or organic compounds. The knowledge gained has direct applications to current problems and uncertainties in water and wastewater treatment with regards to the fate and transport of contaminants.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Removal of adsorbing estrogenic micropollutants by nanofiltration membranes in cross-flow : experiments and model development

Nanofiltration (NF) can be used in water and wastewater treatment as well as water recycling applications, removing micropollutants such as hormones. Due to their potential health risk it is vital to understand their removal mechanisms by NF membranes aiming at improving and developing more effective and efficient treatment processes. Although NF should be effective and efficient in removing small molecular sized compounds such as hormones, the occurrence of adsorption onto polymeric membranes results in performances difficult to predict and with reduced effectiveness and efficiency. This study aims firstly at defining, understanding and quantifying the relevant filtration operation parameters and, secondly, in identifying the physical mechanisms of momentum and mass transfer controlling the adsorption and transport of hormones onto polymeric NF membranes in cross-flow mode. The hormones estrone (E1) and 17-b-estradiol (E2) were chosen as they have very high endocrine disrupting potency. The NF membranes used and tested were the NF 270, NF 90, BW30, TFC-SR2 and TFC-SR3 since they have a wide span of pore sizes. The first step is to experimentally acquire the knowledge of how fluid flow hydrodynamics and mass transfer close to the membrane affect hormone adsorption. The focus will be particularly on the effect of operating pressure, circulating Reynolds numbers (based on channel height, Reh) and hormone feed concentration. These hydrodynamic parameters play an important role in concentration polarisation development at the membrane surface. A Reh increase from 400 to 1400 for the NF 270 membrane caused the total mass adsorbed of E1 and E2 to decrease from 1.5 to 1.3 ng.cm-2 and 0.7 to 0.5 ng.cm-2, respectively. In contrast, a pressure increase from 5 to 15 bar yielded an increase in the adsorbed mass of E1 and E2 from 1.0 to 1.8 ng.cm-2 and 0.5 to 0.7 ng.cm-2, respectively. Moreover, increasing hormone feed concentration caused an increase in the mass adsorbed for both hormones. These observations led to the conclusion that adsorption is governed by the initial concentration at the membrane surface which, in turn, depends on the hormone feed concentration, operating Reh and pressure. Membrane retention, however, depends on the initial polarisation modulus, defined as the ratio between the initial concentration at the membrane surface and the initial feed concentration. The same trends were obtained for the TFC-SR2 membrane. However, this membrane has a much lower permeability compared to the NF 270 one (7.2 vs 17 L.h-1.m-2.bar-1, respectively) and concentration polarisation is less severe. The experimental variations in mass adsorbed and retention as a function of the operating filtration parameters (Reh and pressure) were therefore lower. Based on these experimental results, a sorption model was developed. This model predicts well both feed and permeate transient concentrations for both hormones and membranes (NF 270 and TFC-SR2) in the common range of operating pressures and Reh of spiral-wound membrane modules. The model was further applied for E2 in the presence of background electrolyte, yielding good predictions. These findings are an important advancement in determining which membrane would be more suitable to effectively remove hormones with a substantial reduction of experimental work. The above-mentioned developed model does not give insight into the phenomena occurring inside the membrane since it focuses on the feed conditions. However, membrane characteristics, such as material and pore radius were found to have an impact in adsorption and retention of hormones. It was found experimentally that polyamide, from which the active layer of the NF membranes is made, adsorbs three times more mass of hormone than any other polymers constituting the membranes. Since this active layer is the membrane selective barrier of the membrane that is in contact with the largest hormone concentration (due to concentration polarization in the feed solution) it is concluded that the active layer adsorbs most of the hormones. Further experimental work carried out in this thesis showed that increasing the pore radius from 0.32 nm to 0.52 nm increased the E2 mass adsorbed from 0.17 ng.cm-2 to 1.1 ng.cm-2 and decreased the retention from 88% to 34%. These results show that the wider the pore, the larger the quantity of hormone that penetrates (i.e. partitions) inside the membrane and, therefore, the more the membrane adsorbs the hormone. For membranes of similar pore radius, the membrane with larger internal surface area was found to adsorb more. All the previous results led to the establishment of a new model for the hormone transport inside the membrane pore taking convection, diffusion and adsorption into account. Since the differential equation describing the transport with adsorption inside the pore has no analytical solution, a numerical model based on the finite-difference approach was applied. With such a model, its validation against experiments and parametric studies it was possible to understand the transport mechanisms of adsorbing hormones through NF membranes. The results show that for low pressures the hormone transport is diffusion dominated. In contrast, for higher pressures (above 11 bar) the transport is convection dominated, showing that a purely diffusion transport model does not describe well the actual transport phenomena of hormones in NF membranes. Furthermore, it was found that two similar molecules can behave very differently in terms of adsorption on the membrane. E1, which adsorbs 20% more than E2 in static mode, being slightly smaller than E2, partitions more inside the membrane pore and adsorbs double under filtration conditions. This study contributes to illuminating the adsorption mechanisms of hormones onto NF membranes by understanding what parameters control adsorption such as hydrodynamics, materials, structure, etc. This not only identifies a potential problem in large scale applications, but it also provides an understanding of the mechanisms involved in the removal of these hormones and a tool that can be used to design future membranes for the improvement of micropollutant removal.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Influence of solute-solute interactions on membrane filtration

An understanding of solute-solute interactions is essential for aquatic systems as this can affect the fate and behaviour of micropollutants in the environment and engineered systems. Despite the importance of solute-solute interactions there is a general lack of understanding which may be attributed to the fact that many engineering models overlook solute-solute interactions and that the quantification of such interactions is inherently difficult. When solute-solute interactions are considered, they are often studied at unrepresentative concentrations and do not consider the influence of organic matter type or solution chemistry. Steroidal hormones, such as estradiol and estrone, were selected as model micropollutants as they are ubiquitous in the aquatic environment due to constant introduction of wastewater effluent, and can have implications for growth and development of organisms including impaired fertility and behavioural abnormalities. The purpose of this study was to develop a methodology to quantify solute-solute interactions at environmental concentrations, and to determine the implications of such interactions in membrane filtration. A solid-phase microextraction (SPME) technique was developed to quantify solutesolute interactions at environmental (low) concentrations. Using SPME, organic matter-water partition coefficients (log KOM) were measured for a range of steroidal hormones including estradiol, estrone, progesterone and testosterone with different organic matter types such as humic acid. The dominant mechanism of hormoneorganic matter interactions was identified as hydrogen bonding. In the case of estrone and progesterone the log KOM values were significantly influenced by organic matter type and concentration, as well as solution chemistry. No difference was observed for estradiol and testosterone due to generally weaker sorption to organic matter. Previous studies have indicated that the presence of organic matter can alter micropollutant retention in membrane filtration. Much of the current literature focuses on solute-membrane interactions, as the influence of solute-solute interactions are typically difficult to determine in membrane filtration. Therefore, hormone-organic matter interactions were studied to determine if this interaction had an influence on hormone removal by ultrafiltration (UF) using a range of molecular weight cut-off (MWCO) membranes. The results indicated increased retention of estrone in the presence of humic acid, while organic matter concentration and solution chemistry influenced retention by affecting solute-solute interactions. The findings of this study indicate the importance of solute-solute interactions in membrane filtration and experimental log KOM results were used to quantify the findings and elucidate the influences of 1) membrane sorption, 2) solute-solute interactions and 3) solute-foulant interactions. Further, the removal of steroidal hormones using a magnetic ion exchange (MIEX®) resin with a range of MWCO UF membranes was studied as such sorbents can be used to improve micropollutant removal in wastewater treatment. Greater removal with IX-UF was observed compared to UF alone and the main hormone removal mechanisms were sorption to MIEX® and solute-fouling interactions. The findings of this study indicate that it is indeed possible to quantify solute-solute interactions at environmental concentrations using SPME, with hydrogen bonding being the main mechanism of interaction for steroidal hormones and organic matter. Further, micropollutant retention by membrane filtration can be influenced by solutesolute interactions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Quantification of Hormone–Humic Acid Interactions in Nanofiltration

The influence of solute–solute interactions on hormone retention during nanofiltration (NF) was quantified and mechanisms underlying retention identified. A new approach to predict both the mass of hormone sorbed to organic matter and the retention of hormone influenced by solute–solute interactions was applied. Laboratory-scale experiments were carried out in a cross-flow filtration system examining organic matter concentration, solution pH, and hormone type. Solute–solute interactions between HA and estrone improved estrone retention while decreasing estrone adsorption to membranes. HA concentration determined the amount of estrone bound to HA and hence affected estrone retention based on the mechanism of size exclusion. The solution pH influenced both solute–solute as well as solute–membrane interactions. Solute–solute interactions were most important below the p<i>K</i>_a of estrone, whereas charge repulsion between estrone and negative functional groups of the membrane dominated estrone retention above the p<i>K</i>_a. Of the four hormones studied, progesterone had the greatest affinity for both HA and NF membrane, which was attributed to hydrogen bonding ability. Using partition coefficients <i>K_OM</i> from solid-phase microextraction (SPME) resulted in very good agreement between predicted and experimental retention

Experimental Energy Barriers to Anions Transporting through Nanofiltration Membranes

Environmentally relevant contaminants fluoride, chloride, nitrate, and nitrite face Arrhenius energy barriers during transport through nanofiltration (NF) membranes. The energy barriers were quantified using crossflow filtration experiments and were in the range of 7–17 kcal·mol^–1, according to ion type and membrane type (Filmtec NF90 and NF270). Fluoride faced a comparatively high energy barrier for both membranes. This can be explained by the strong hydration energy of fluoride rather than other ion properties such as bare ion radius, fully hydrated radius, Stokes radius, diffusion coefficient, or ion charge. The energy barrier for fluoride decreased with pressure, indicating an impact of directional force on energy barriers. The influence of temperature-induced pore radius variability and viscosity on energy barriers was considered. The novel link between energy barriers and ion properties emphasizes the importance of ion hydration and/or partial dehydration mechanisms in determining transport in NF

Integrated Workflow for Structural Proteomics Studies Based on Cross-Linking/Mass Spectrometry with an MS/MS Cleavable Cross-Linker

Cross-linking combined with mass spectrometry (MS) has evolved as an alternative strategy in structural biology for characterizing three-dimensional structures of protein assemblies and for mapping protein–protein interactions. Here, we describe an integrated workflow for an automated identification of cross-linked products that is based on the use of a tandem mass spectrometry (MS/MS) cleavable cross-linker (containing a 1,3-bis-(4-oxo-butyl)-urea group, BuUrBu) generating characteristic doublet patterns upon fragmentation. We evaluate different fragmentation methods available on an Orbitrap Fusion mass spectrometer for three proteins and an <i>E. coli</i> cell lysate. An updated version of the dedicated software tool MeroX was employed for a fully automated identification of cross-links. The strength of our cleavable cross-linker is that characteristic patterns of the cross-linker as well as backbone fragments of the connected peptides are already observed at the MS/MS level, eliminating the need for conducting MS³ or sequential CID (collision-induced dissociation)- and ETD (electron transfer dissociation)-MS/MS experiments. This makes our strategy applicable to a broad range of mass spectrometers with MS/MS capabilities. For purified proteins and protein complexes, our workflow using CID-MS/MS acquisition performs with high confidence, scoring cross-links at 0.5% false discovery rate (FDR). The cross-links provide structural insights into the intrinsically disordered tetrameric tumor suppressor protein p53. As a time-consuming manual inspection of cross-linking data is not required, our workflow will pave the way for making the cross-linking/MS approach a routine technique for structural proteomics studies

Integrated Workflow for Structural Proteomics Studies Based on Cross-Linking/Mass Spectrometry with an MS/MS Cleavable Cross-Linker

Cross-linking combined with mass spectrometry (MS) has evolved as an alternative strategy in structural biology for characterizing three-dimensional structures of protein assemblies and for mapping protein–protein interactions. Here, we describe an integrated workflow for an automated identification of cross-linked products that is based on the use of a tandem mass spectrometry (MS/MS) cleavable cross-linker (containing a 1,3-bis-(4-oxo-butyl)-urea group, BuUrBu) generating characteristic doublet patterns upon fragmentation. We evaluate different fragmentation methods available on an Orbitrap Fusion mass spectrometer for three proteins and an <i>E. coli</i> cell lysate. An updated version of the dedicated software tool MeroX was employed for a fully automated identification of cross-links. The strength of our cleavable cross-linker is that characteristic patterns of the cross-linker as well as backbone fragments of the connected peptides are already observed at the MS/MS level, eliminating the need for conducting MS³ or sequential CID (collision-induced dissociation)- and ETD (electron transfer dissociation)-MS/MS experiments. This makes our strategy applicable to a broad range of mass spectrometers with MS/MS capabilities. For purified proteins and protein complexes, our workflow using CID-MS/MS acquisition performs with high confidence, scoring cross-links at 0.5% false discovery rate (FDR). The cross-links provide structural insights into the intrinsically disordered tetrameric tumor suppressor protein p53. As a time-consuming manual inspection of cross-linking data is not required, our workflow will pave the way for making the cross-linking/MS approach a routine technique for structural proteomics studies