Oxidation-reduction potential and its influence on Cheddar cheese quality

Oxidation-reduction (redox) potential is a fundamental physicochemical parameter that affects the growth of microorganisms in dairy products and contributes to a balanced flavour development in cheese. Even though redox potential has an important impact on the quality of dairy products, it is not usually monitored in dairy industry. The aims of this thesis were to develop practical methods for measuring redox potential in cheese, to provide detailed information on changes in redox potential during the cheesemaking and cheese ripening and how this parameter is influenced by starter systems and to understand the relationship between redox potential and cheese quality. Methods were developed for monitoring redox potential during cheesemaking and early in ripening. Changes in redox potential during laboratory scale manufacture of Cheddar, Gouda, Emmental, and Camembert cheeses were determined. Distinctive kinetics of reduction in redox potential during cheesemakings were observed, and depended on the cheese technology and starter culture utilised. Redox potential was also measured early in ripening by embedding electrodes into Cheddar cheese at moulding together with the salted curd pieces. Using this approach it was possible to monitor redox potential during the pressing stage. The redox potential of Emmental cheese was also monitored during ripening. Moreover, since bacterial growth drives the reduction in redox potential during cheese manufacture and ripening, the ability of Lactococcus lactis strains to affect redox potential was studied. Redox potential of a Cheddar cheese extract was altered by bacterial growth and there were strain-specific differences in the nature of the redox potential/time curves obtained. Besides, strategies to control redox potential during cheesemaking and ripening were developed. Oxidizing or reducing agents were added to the salted curd before pressing and results confirmed that a negative redox potential is essential for the development of sulfur compounds in Cheddar cheese. Overall, the studies described in this thesis gave an evidence of the importance of the redox potential on the quality of dairy products. Redox potential could become an additional parameter used to select microorganisms candidate as starters in fermented dairy products. Moreover, it has been demonstrated that the redox potential influences the development of flavour component. Thus, measuring continuously changes in redox potential of a product and controlling, and adjusting if necessary, the redox potential values during manufacture and ripening could be important in the future of the dairy industry.

Reminders, Refugees, and Ramadan: Characterizing Missed Immunization Appointments among Palestinian Refugees in Jordan

There are currently over two million Palestinian refugees residing in Jordan, 370,000 of whom reside in refugee camps. Due to conflict-affiliated disease outbreaks among children in the region, the UN Relief and Works Agency for Palestine Refugees (UNRWA) has identified incomplete vaccination as a critical public health issue and has invested in the development and implementation of a text message reminder service for preventing loss-to-follow-up. Childhood immunization rates in UNRWA catchment regions are generally high, yet little is known about risk factors for missed appointments, which impose a substantial administrative burden due to the need to contact patients for rescheduling. Stronger user characterization is necessary for improved targeting and minimized cost as we develop a more robust SMS system capable of scaling across all health facilities.

This mixed-methods study prospectively recorded 6 months of immunization history among a cohort of children born in June 2014 at Taybeh Health Center in Amman. Demographic information was collected at the time of birth, and caregivers of cohort members were invited to participate in interviews that assessed immunization knowledge, preferences, decision-making, and experience with the SMS reminder system. Patients were more likely to significantly delay appointments during the Ramadan holiday and for doses further from the child date of birth. Future policies that might bridge these gaps include targeting pre-appointment SMS reminders to high-risk patients, implementing holiday shifts in clinic hours, and regularly updating patient contact information.

Accurate ground-state potential energy surfaces of the C2H2–Kr and C2H2–Xe van der Waals complexes

Accurate ab initio intermolecular potential energy surfaces (IPES) have been obtained for the first time for the ground electronic state of the C 2H2-Kr and C2H2-Xe van der Waals complexes. Extensive tests, including complete basis set and all-electron scalar relativistic results, support their calculation at the CCSD(T) level of theory, using small-core relativistic pseudopotentials for the rare-gas atoms and aug-cc-pVQZ basis sets extended with a set of 3s3p2d1f1g mid-bond functions. All results are corrected for the basis set superposition error. The importance of the scalar relativistic and rare-gas outer-core (n.1)d correlation effects is investigated. The calculated IPES, adjusted to analytical functions, are characterized by global minima corresponding to skew T-shaped geometries, in which the Jacobi vector positioning the rare-gas atom with respect to the center of mass of the C2H2 moiety corresponds to distances of 4.064 and 4.229Å, and angles of 65.22° and 68.67° for C 2H2-Kr and C2H2-Xe, respectively. The interaction energy of both complexes is estimated to be -151.88 (1.817 kJ mol-1) and -182.76 cm-1 (2.186 kJ mol-1), respectively. The evolution of the topology of the IPES as a function of the rare-gas atom, from He to Xe, is also discussed. © 2012 Taylor and Francis.

Computational modeling of mold filling and related free-surface flows in shape casting: an overview of the challenges involved

Accurate representation of the coupled effects between turbulent fluid flow with a free surface, heat transfer, solidification, and mold deformation has been shown to be necessary for the realistic prediction of several defects in castings and also for determining the final crystalline structure. A core component of the computational modeling of casting processes involves mold filling, which is the most computationally intensive aspect of casting simulation at the continuum level. Considering the complex geometries involved in shape casting, the evolution of the free surface, gas entrapment, and the entrainment of oxide layers into the casting make this a very challenging task in every respect. Despite well over 30 years of effort in developing algorithms, this is by no means a closed subject. In this article, we will review the full range of computational methods used, from unstructured finite-element (FE) and finite-volume (FV) methods through fully structured and block-structured approaches utilizing the cut-cell family of techniques to capture the geometric complexity inherent in shape casting. This discussion will include the challenges of generating rapid solutions on high-performance parallel cluster technology and how mold filling links in with the full spectrum of physics involved in shape casting. Finally, some indications as to novel techniques emerging now that can address genuinely arbitrarily complex geometries are briefly outlined and their advantages and disadvantages are discussed.

Study of the rheological behaviour of Sn-Ag-Cu solder pastes and their correlation with printing performance

Solder paste plays an important role in the electronic assembly process by providing electrical, mechanical and thermal bonding between the components and the substrate. The rheological characterisation of pastes is an important step in the design and development of new paste formulations. With the ever increasing trend of miniaturisation of electronic products, the study of the rheological properties of solder pastes is becoming an integral part in the R&D of new paste formulations and in the quality monitoring and control during paste manufacture and electronic assembly process. This research work outlines some of the novel techniques which can be successfully used to investigate the rheology of leadfree solder pastes. The report also presents the results of the correlation of rheological properties with solder paste printing performance. Four different solder paste samples (namely paste P1, P2, P3 and P4) with different flux vehicle systems and particle size distributions were investigated in the study. As expected, all the paste samples showed shear thinning behaviour. Although the samples displayed similar flow behaviour at high shear rates, differences were observed at low shear rates. In the stencil printing trials, round deposits showed better results than rectangular deposits in terms of paste heights and aperture filling. Our results demonstrate a good correlation between higher paste viscosity and good printing performance. The results of the oscillatory and thixotropy tests were also successfully correlated to the printing behaviour of solder paste.

Synthesis and enzymatic evaluation of the guanosine analogue 2-amino-6-mercapto-7-methylpurine ribonucleoside (MESG): insights into the phosphorolysis reaction mechanism based on the blueprint transition state: SN1 or SN2?

A modified experimental procedure for the synthesis of MESG (2-amino-6-mercapto-7-methylpurine ribonucleoside) 1 has been successfully performed and its full characterization is presented. High resolution ESI(+)-MSMS indicates both the nucleoside bond cleavage as the main fragmentation in the gas phase and a possible SN1 mechanism. Ab initio transition state calculations based on the blue print transition state support this mechanistic rationale and discard an alternative SN2 mechanism. Assays using purine nucleoside phosphorylase (PNP) enzyme (human and M. tuberculosis sources) indicate its efficiency in the phosphorolysis of MESG and allow the quantitative determination of inorganic phosphate in real time assay.

Assessing the environmental consequences of CO2 leakage from geological CCS: Generating evidence to support environmental risk assessment

At the start of the industrial revolution (circa 1750) the atmospheric concentration of carbon dioxide (CO2) was around 280 ppm. Since that time the burning of fossil fuel, together with other industrial processes such as cement manufacture and changing land use, has increased this value to 400 ppm, for the first time in over 3 million years. With CO2 being a potent greenhouse gas, the consequence of this rise for global temperatures has been dramatic, and not only for air temperatures. Global Sea Surface Temperature (SST) has warmed by 0.4–0.8 °C during the last century, although regional differences are evident (IPCC, 2007). This rise in atmospheric CO2 levels and the resulting global warming to some extent has been ameliorated by the oceanic uptake of around one quarter of the anthropogenic CO2 emissions (Sabine et al., 2004). Initially this was thought to be having little or no impact on ocean chemistry due to the capacity of the ocean’s carbonate buffering system to neutralise the acidity caused when CO2 dissolves in seawater. However, this assumption was challenged by Caldeira and Wickett (2005) who used model predictions to show that the rate at which carbonate buffering can act was far too slow to moderate significant changes to oceanic chemistry over the next few centuries. Their model predicted that since pre-industrial times, ocean surface water pH had fallen by 0.1 pH unit, indicating a 30% increase in the concentration of H+ ions. Their model also showed that the pH of surface waters could fall by up to 0.4 units before 2100, driven by continued and unabated utilisation of fossil fuels. Alongside increasing levels of dissolved CO2 and H+ (reduced pH) an increase in bicarbonate ions together with a decrease in carbonate ions occurs. These chemical changes are now collectively recognised as “ocean acidification”. Concern now stems from the knowledge that concentrations of H+, CO2, bicarbonate and carbonate ions impact upon many important physiological processes vital to maintaining health and function in marine organisms. Additionally, species have evolved under conditions where the carbonate system has remained relatively stable for millions of years, rendering them with potentially reduced capacity to adapt to this rapid change. Evidence suggests that, whilst the impact of ocean acidification is complex, when considered alongside ocean warming the net effect on the health and productivity of the oceans will be detrimental.

Progress in satellite remote sensing for studying physical processes at the ocean surface and its borders with the atmosphere and sea-ice

Physical oceanography is the study of physical conditions, processes and variables within the ocean, including temperature-salinity distributions, mixing of the water column, waves, tides, currents, and air-sea interaction processes. Here we provide a critical review of how satellite sensors are being used to study physical oceanography processes at the ocean surface and its borders with the atmosphere and sea-ice. The paper begins by describing the main sensor types that are used to observe the oceans (visible, thermal infrared and microwave) and the specific observations that each of these sensor types can provide. We then present a critical review of how these sensors and observations are being used to study i) ocean surface currents, ii) storm surges, iii) sea-ice, iv) atmosphere-ocean gas exchange and v) surface heat fluxes via phytoplankton. Exciting advances include the use of multiple sensors in synergy to observe temporally varying Arctic sea-ice volume, atmosphere- ocean gas fluxes, and the potential for 4 dimensional water circulation observations. For each of these applications we explain their relevance to society, review recent advances and capability, and provide a forward look at future prospects and opportunities. We then more generally discuss future opportunities for oceanography-focussed remote-sensing, which includes the unique European Union Copernicus programme, the potential of the International Space Station and commercial miniature satellites. The increasing availability of global satellite remote-sensing observations means that we are now entering an exciting period for oceanography. The easy access to these high quality data and the continued development of novel platforms is likely to drive further advances in remote sensing of the ocean and atmospheric systems.

An investigation of the thermal stability and sulphur tolerance of Ag/Y-Al2O3 catalysts for the SCR of NOx with hydrocarbons and hydrogen

The sulphur tolerance and thermal stability of a 2 wt% Ag/gamma-Al2O3 catalyst was investigated for the H-2-promoted SCR of NO, with octane and toluene. The aged catalyst was characterised by XRD and EXAFS analysis. It was found that the effect of ageing was a function of the gas mix and temperature of ageing. At high temperatures (800 degrees C) the catalyst deactivated regardless of the reaction mix. EXAFS analysis showed that this was associated with the Ag particles on the surface of the catalyst becoming more ordered. At 600 and 700 degrees C, the deactivating effect of ageing was much less pronounced for the catalyst in the H-2-promoted octane-SCR reaction and ageing at 600 degrees C resulted in an enhancement in activity for the reaction in the absence of H-2. For the toluene + H-2-SCR reaction the catalyst deactivated at each ageing temperature. The effect of addition of low levels of sulphur (1 ppm SO2) to the feed was very much dependent on the reaction temperature. There was little deactivation of the catalyst at low temperatures ( 500 degrees C). The results can be explained by the activity of the catalyst for the oxidation Of SO2 to SO3 and the relative stability of silver and aluminium sulphates. The catalyst could be almost fully regenerated by a combination of heating and the presence of hydrogen in the regeneration mix. The catalyst could not be regenerated in the absence of hydrogen. (c) 2006 Published by Elsevier B.V.

A survey of [ D2CO] /[ H2CO] and [ N2D^+] /[ N2H^+] ratios towards protostellar cores

Aims.We use observations and models of molecular D/H ratios to probe the physical conditions and chemical history of the gas and to differentiate between gas-phase and grain-surface chemical processing in star forming regions. Methods: As a follow up to previous observations of HDCO/H2CO and DCN/HCN ratios in a selection of low-mass protostellar cores, we have measured D2CO/H2CO and N2D^+/N2H+ ratios in these same sources. For comparison, we have also measured N2D^+/N2H+ ratios towards several starless cores and have searched for N2D+ and deuterated formaldehyde towards hot molecular cores (HMCs) associated with high mass star formation. We compare our results with predictions from detailed chemical models, and to other observations made in these sources. Results: Towards the starless cores and low-mass protostellar sources we have found very high N2D+ fractionation, which suggests that the bulk of the gas in these regions is cold and heavily depleted. The non-detections of N2D+ in the HMCs indicate higher temperatures. We did detect HDCO towards two of the HMCs, with abundances 1-3% of H2CO. These are the first detections of deuterated formaldehyde in high mass sources since Turner (1990) measured HDCO/H2CO and D2CO/H2CO towards the Orion Compact Ridge. Figures 1-5 are only available in electronic form at http://www.aanda.org

Comparison between fluid simulations and experiments in inductively coupled argon/chlorine plasmas

Comparisons of 2D fluid simulations with experimental measurements of Ar/Cl-2 plasmas in a low-pressure inductively coupled reactor are reported. Simulations show that the wall recombination coefficient of Cl atom (gamma) is a crucial parameter of the model and that neutral densities are very sensitive to its variations. The best agreement between model and experiment is obtained for gamma = 0.02, which is much lower than the value predicted for stainless steel walls (gamma = 0.6). This is consistent with reactor wall contaminations classically observed in such discharges. The electron density, negative ion fraction and Cl atom density have been investigated under various conditions of chlorine and argon concentrations, gas pressure and applied rf input power. The plasma electronegativity decreases with rf power and increases with chlorine concentration. At high pressure, the power absorption and distribution of charged particles become more localized below the quartz window. Although the experimental trends are well reproduced by the simulations, the calculated charged particle densities are systematically overestimated by a factor of 3-5. The reasons for this discrepancy are discussed in the paper.

Au on (111) and (110) surfaces of CeO2: A density-functional theory study

The atomic structures of gold supported on (111) and (110) surfaces of CeO2 have been studied using density-functional theory calculations. A single Au atom is placed on three adsorption sites on the surfaces; the stoichiometric surfaces, an oxygen vacancy and a Ce-vacancy. It is found that (i) the Au adsorption energies are in the following order: E-ad(Ce-vacancy) > E-ad(O-vacancy) > E-ad(stoichiometric surface); and (ii) the Au atom adsorption on the Ce-vacancy activates O atoms nearby. One 0 atom is less stable than that in O-2 in the gas phase and another O atom is much easier to remove compared to that of the stoichiometric surfaces. These results suggest that the Au adsorption on Ce-vacancies not only creates an O-vacancy but also activates an O atom nearby. This provides a piece of direct evidence that Au adsorption on a Ce-vacancy may be responsible for some unique catalytic properties of Au/CeO2. (C) 2008 Elsevier B.V. All rights reserved.

Sulfur-tolerant NOx storage traps: an infrared and thermodynamic study of the reactions of alkali and alkaline-earth metal sulfates

The sulfur tolerance of a barium-containing NOx storage/reduction trap was investigated using infrared analysis. It was confirmed that barium carbonate could be replaced by barium sulfate by reaction with low concentrations of sulfur dioxide (50 ppm) in the presence of large concentrations of carbon dioxide (10%) at temperatures up to 700 degreesC. These sulfates could at least be partially removed by switching to hydrogen-rich conditions at elevated temperatures. Thermodynamic calculations were used to evaluate the effects of gas composition and temperature on the various reactions of barium sulfate and carbonate under oxidizing and reducing conditions. These calculations clearly showed that if, under a hydrogen-rich atmosphere, carbon dioxide is included as a reactant and barium carbonate as a product then barium sulfate can be removed by reaction with carbon dioxide at a much lower temperature than is possible by decomposition to barium oxide. It was also found that if hydrogen sulfide was included as a product of decomposition of barium sulfate instead of sulfur dioxide then the temperature of reaction could be significantly lowered. Similar calculations were conducted using a selection of other alkaline-earth and alkali metals. In this case calculations were simulated in a gas mixture containing carbon monoxide, hydrogen and carbon dioxide with partial pressures similar to those encountered in real exhausts during switches to rich conditions. The results indicated that there are metals such as lithium and strontium with less stable sulfates than barium, which may also possess sufficient NOx storage capacity to give sulfur-tolerant NOx traps.

Effect of the incorporation of hydroxy-terminated liquid silicones on the cure characteristics, morphology, and release of a model protein from silicone elastomer-covered rods

Silicone elastomer systems have previously been shown to offer potential for the sustained release of protein therapeutics. However, the general requirement for the incorporation of large amounts of release enhancing solid excipients to achieve therapeutically effective release rates from these otherwise hydrophobic polymer systems can detrimentally affect the viscosity of the precure silicone elastomer mixture and its curing characteristics. The increase in viscosity necessitates the use of higher operating pressures in manufacture, resulting in higher shear stresses that are often detrimental to the structural integrity of the incorporated protein. The addition of liquid silicones increases the initial tan delta value and the tan delta values in the early stages of curing by increasing the liquid character (G '') of the silicone elastomer system and reducing its elastic character (G'), thereby reducing the shear stress placed on the formulation during manufacture and minimizing the potential for protein degradation. However, SEM analysis has demonstrated that if the liquid character of the silicone elastomer is too high, the formulation will be unable to fill the mold during manufacture. This study demonstrates that incorporation of liquid hydroxy-terminated polydimethylsiloxanes into addition-cure silicone elastomer-covered rod formulations can both effectively lower the viscosity of the precured silicone elastomer and enhance the release rate of the model therapeutic protein bovine serum albumin. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Geophysical and geochemical survey of a large marine pockmark on the Malin Shelf, Ireland

Marine pockmarks are a specific type of seabed geological setting resembling craters or pits and are considered seabed surface expressions of fluid flow in the subsurface. A large composite pockmark on the Malin Shelf, off the northern coast of Ireland was surveyed and ground truthed to assess its activity and investigate fluid related processes in the subsurface. Geophysical (including acoustic and electromagnetic) data confirmed the subsurface presence of signatures typical of fluids within the sediment. Shallow seismic profiling revealed a large shallow gas pocket and typical gas related indicators such as acoustic blanking and enhanced reflectors present underneath and around the large pockmark. Sulphate profiles indicate that gas from the shallow reservoir has been migrating upwards, at least recently. However, there are no chimney structures observed in the sub-bottom data and the migration pathways are not apparent. Electromagnetic data show slightly elevated electrical conductivity on the edges of the pockmarks and a drop below regional levels within the confines of the pockmark, suggesting changes in physical properties of the sediment. Nuclear Magnetic Resonance (NMR) experiments were employed to characterize the organic component of sediments from selected depths. Very strong microbial signatures were evident in all NMR spectra but microbes outside the pockmark appear to be much more active than inside. These observations coincide with spikes in conductivity and the lateral gas bearing body suggesting that there is an increase in microbial activity and biomass when gas is present.