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This paper presents a review of established and emerging methods for detecting and quantifying the intravenous anaesthetic propofol in solution. There is growing evidence of numerous advantages of total intravenous anaesthesia using propofol compared to conventional volatile-based anaesthesia, both in terms of patient outcomes and environmental impact. However, volatile-based anaesthesia still accounts for the vast majority of administered general anaesthetics, largely due to a lack of techniques for real-time monitoring of patient blood propofol concentration. Herein, propofol detection techniques that have been developed to date are reviewed alongside a discussion of remaining challenges.

We present a new method for epoxide polymerizations utilizing aluminum-based initiators, which leverage the chemical versatility of thiol compounds to control the polymer end group. The homo- and c...

Lignin has an enormous valorization potential as a sustainable raw material. The most common source of industrial lignin is black liquor, a byproduct from the kraft process. However, the variabilit...

Despite the growing evidence of improved patient outcomes and of a substantially reduced environmental impact of propofol-based total intravenous anesthesia when compared to volatile-based techniques, the vast majority of general anesthetics still use volatile agents for the maintenance phase. A significant reason for this is the lack of suitable point-of-care, real-time blood propofol measurement techniques. Here we present an enzyme-based electrochemical biosensor for the detection of propofol. Deactivated yeast cells expressing the enzyme cytochrome P450 2B6 are immobilized, alongside gold nanoparticles, within a chitosan film upon the surface of a screen printed electrode. In the presence of the cofactor NADPH, the enzyme converts propofol to a quinone/quinol redox pair that can be detected using simple electrochemistry. This approach avoids the issue of electrode fouling that commonly renders electrochemical propofol sensors impractical. The sensor has a limit of detection of 67 ± 7 ng/ml and a sensitivity of 4.2 ± 0.2 nA/ $\mu \text{g}$ /ml/mm $^{\mathbf {2}}$ . It has been successfully demonstrated in a serum-like solution and has shown a linear response across the therapeutic range of propofol (1 – $10~\mu \text{g}$ /ml). Additionally, the sensor has shown good specificity with regards to potential interfering compounds.

We describe the development of a new method for construction of highly substituted indole scaffolds through the strategic utilizing of the metathesis of Ar-X σ-bonds based on the dynamic nature of palladium-based oxidative addition/reductive elimination. A suitable and simple catalytic system has provided an appropriate platform for a productive ligand exchange and consecutive carbopalladation/C-H activation/amination of phosphine ligands with alkynes and aromatic/aliphatic amines for construction of structurally diverse indoles.

The microscopic origin of mechanical enhancement in polymer nanocomposite (PNC) melts is investigated through the combination of rheology and small-angle neutron scattering. It is shown that in the absence of an extensive particle network, the molecular deformation of polymer chains dominates the stress response on intermediate time scales. Quantitative analyses of small-angle neutron scattering spectra, however, reveal no enhanced structural anisotropy in the PNCs, compared with the pristine polymers under the same deformation conditions. These results demonstrate that the mechanical reinforcement of PNCs is not due to molecular overstraining, but instead a redistribution of strain field in the polymer matrix, akin to the classical picture of hydrodynamic effect of nanoparticles.

A mono(μ-oxo)bis(alkylaluminum) (MOB) catalyst and initiator for epoxide polymerization, [(H3C)2NCH2CH2(μ2-O)Al(iBu)2·Al(iBu)3] (1), produced a ca. 170-fold enhancement in epoxide polymerization rate over previously reported MOB initiators demonstrated with allyl glycidyl ether (AGE). This discovery reduces polymerization times to minutes. 1 exhibited an exponential dependence of polymerization rate on concentration, rather than an expected low integer order relationship. A proposed polymerization intermediate was identified via direct synthesis, isolation, kinetic comparison, and corroborating in situ spectroscopic evidence to be a symmetric bis((μ-alkoxo)dialkylaluminum) (BOD) with a characteristic R3N·AlR′3 (N–Al) adduct. The N–Al adduct on the BOD intermediate is proposed to act as a catalyst, whereas the aluminoxane ring is proposed to be the site of monomer enchainment on the basis of mass spectrometry and spectroscopic analysis of resultant polymer structure. The distinct catalytic and initiation/p...

Polysulfide-shuttle has been a critical concern for the advancement of lithium-sulfur (Li-S) batteries. Celgard membranes that are generally used in Li-S batteries exhibit a porous structure with a pore dimension generally on the micrometer scale. During cell operation, soluble lithium polysulfide species can easily migrate from the cathode through the porous separator and react with the lithium-metal anode. Such an unexpected chemical reaction induces a cascade of negative effects on the overall performance of Li-S batteries. Use of ion-selective membranes with reduced pore size provides a promising approach to suppress the migration of polysulfide species. In this study, a membrane based on a polymer with intrinsic nanoporosity (PIN) with a pore size of

A combined theoretical and experimental investigation into the structure and mechanism of the classical Vandenberg catalyst for the isoselective polymerization of epoxides has led to a consistent mechanistic proposal. The most likely reaction pathway was based on a bis(μ-oxo)di(aluminum) (BOD) resting state that proceeded through a mono(μ-oxo)di(aluminum) (MOD) transition state. The isoselectivity of the Vandenberg catalyst was derived from the rigidity of the BOD structure and its bonding to the ultimate and penultimate oxygen heteroatoms along the polyether backbone. The energetic driving force for isoselectivity was the loss of an energetically favorable secondary Al–O interaction during enchainment of oppositely configured epoxides, providing a ca. 2 kcal/mol driving force for the emergent isoselectivity. Experimental spectroscopic and kinetic evidence based on model BOD and MOD complexes support the new mechanistic framework developed using density functional theory calculations. A purposefully synth...

We report a new class of organoaluminum-based initiator for anionic ring-opening polymerization of epoxides that is simple to synthesize from readily available precursors. The resultant organometallic initiator was the triethylaluminum adduct of (2-dibenzylamino)ethoxydiethylaluminum (TAxEDA) [(AlEt3)·(O(AlEt2)CH2CH2N(Bn)2)], which was isolated by direct crystallization from the reaction medium and then compositionally and structurally characterized by NMR spectroscopy and XRD. We studied the reactivity and versatility of the new initiator through the polymerization of propylene oxide, butylene oxide, epichlorohydrin, and allyl glycidyl ether into homopolymer, statistical copolymer, and block copolymer architectures with heterobifunctional end-groups consisting of dibenzylamine and hydroxyl functionalities. The TAxEDA-initiated polymerizations were consistent with a controlled, living, anionic mechanism that was tolerant of chemical functionality and exhibited no chain transfer to monomer that limits the ...

We present an improvement in the rate, utility, and mechanistic understanding of mono-μ-oxo-dialuminum initiators for epoxide ring-opening polymerization based on investigation of a homologous series of trialkylaluminum adducts of (2-dibenzylamino)ethoxy-dialkylaluminum (TAxEDA) [(AlR3)·(O(AlR2)CH2CH2N(Bn)2), with R = Me, Et, iBu]. Using in situ FTIR spectroscopy of neat AGE polymerizations, we determined that the isobutyl-substituted TAxEDA (iBu-TAxEDA) exhibited a propagation rate constant (kp) of 1.100 ± 0.022 × 10−3 M−1 s−1, which was twice that of the methyl-functional TAxEDA (Me-TAxEDA) (kp = 0.500 ± 0.011 × 10−3 M−1 s−1) and four times that of ethyl-functional TAxEDA (Et-TAxEDA) (kp = 0.270 ± 0.003 × 10−3 M−1 s−1). The dative R3Al–O bond length in the mono-μ-oxo-dialuminum was longest for the iBu-TAxEDA (1.93 A) and shortest for the Et-TAxEDA (1.88 A). Consistent with a previously proposed mechanism for TAxEDA-initiated polymerization, the increased Al–O bond length may accommodate more-facile coordination and enchainment of the monomer by separation of the Al–O interaction leading to an increased polymerization rate. The generality of the improved iBu-TAxEDA was supported by polymerization of a range of monomer substrates such as propylene oxide (PO), butylene oxide (BO), epichlorohydrin (ECH), allyl glycidyl ether (AGE), propargyl glycidyl ether (PGE), and adamantylmethyl glycidyl ether (AMGE). In all cases investigated, the triisobutyl-functional TAxEDA (iBu-TAxEDA) represented an improved initiator for epoxide polymerization.

The Galloway region of south-west Scotland has historically been subject to long-term deposition of acidic precipitation which has resulted in acidification of soils and surface waters and subsequent damage to aquatic ecology. Since the end of the 1970s, however, acidic deposition has decreased substantially. The general pattern is for a rapid decline in non-marine sulphate in rainwater over the period 1978-1988 followed by stable concentrations to the mid-1990s. Concentrations of nitrate and ammonium in deposition have remained constant between 1980 and 1998. Seven water quality surveys of 48 lochs in the Galloway region have been conducted between 1979 and 1998. During the first 10 years, from 1979, there was a major decline in regional sulphate concentrations in the lochs, which was expected to have produced a decline in base cations and an increase in the acid neutralising capacity. But sea-salt levels (as indicated by chloride concentrations) were approximately 25% higher in 1988 than in 1979 and thus short-term acidification due to sea-salts offset much of the long-term recovery trend expected in the lochs. During the next 10 years, however, the chloride concentrations returned to 1979 levels and the lochs showed large increases in acid neutralising capacity despite little change in sulphate concentrations. From the observed decline in sulphate deposition and concentrations of sulphate in the lochs, it appears that approximately 75% of the possible improvement in acid neutralising capacity has already occurred over the 20-year period (1979-1998). The role of acid deposition as a driving factor for change in water chemistry in the Galloway lochs is confounded by concurrent changes in other driving variables, most notably, factors related to episodic and year-to-year variations in climate. In addition to inputs of sea-salts, climate probably also influences other chemical signals such as peaks in regional nitrate concentrations and the sharp increase in dissolved organic carbon during the 1990s. Keywords: acidification, recovery, Galloway, sulphur, nitrogen

A catchment-scale mass-balance model of linked carbon and nitrogen cycling in ecosystems has been developed for simulating leaching losses of inorganic nitrogen. The model (MERLIN) considers linked biotic and abiotic processes affecting the cycling and storage of nitrogen. The model is aggregated in space and time and contains compartments intended to be observable and/or interpretable at the plot or catchment scale. The structure of the model includes the inorganic soil, a plant compartment and two soil organic compartments. Fluxes in and out of the ecosystem and between compartments are regulated by atmospheric deposition, hydrological discharge, plant uptake, litter production, wood production, microbial immobilization, mineralization, nitrification, and denitrification. Nitrogen fluxes are controlled by carbon productivity, the C:N ratios of organic compartments and inorganic nitrogen in soil solution. Inputs required are: 1) temporal sequences of carbon fluxes and pools- 2) time series of hydrological discharge through the soils, 3) historical and current external sources of inorganic nitrogen; 4) current amounts of nitrogen in the plant and soil organic compartments; 5) constants specifying the nitrogen uptake and immobilization characteristics of the plant and soil organic compartments; and 6) soil characteristics such as depth, porosity, bulk density, and anion/cation exchange constants. Outputs include: 1) concentrations and fluxes of NO3 and NH4 in soil solution and runoff; 2) total nitrogen contents of the organic and inorganic compartments; 3) C:N ratios of the aggregated plant and soil organic compartments; and 4) rates of nitrogen uptake and immobilization and nitrogen mineralization. The behaviour of the model is assessed for a combination of land-use change and nitrogen deposition scenarios in a series of speculative simulations. The results of the simulations are in broad agreement with observed and hypothesized behaviour of nitrogen dynamics in growing forests receiving nitrogen deposition.

We investigate, both experimentally and through hybrid particle/self-consistent field theoretic (hSCFT) calculations, the dispersion state of gold nanorods (AuNRs) grafted with homopolymer, bidispersed, or mixed polymer brushes. AuNRs are grafted with 11.5 kg/mol PS (HNRs), 11.5 kg/mol PS, and 5.3 kg/mol PS (BNRs) or 11.5 kg/mol PS and 5K poly(methyl methacrylate) (PMMA) (MBNRs) and cast in PS or PMMA films consisting of short to very long chains compared to the grafted brush. We further investigated the MBNR systems by varying the length of the PS brush. Overall, we find that the MBNRs dispersed markedly better than the other brush types (HNRs or BNRs) in PS matrices. We utilize hSCFT calculations, in particular potential of mean force (PMF) and brush profile calculations, to elucidate the thermodynamics of these systems. The PMFs and brush profiles exhibit similar trends for the BNRs and MBNRs where the short grafted chain forces the longer grafted chain away from the AuNR surface and promotes wetting b...

International audience; A novel nanohybrid assembly consisting of gold nanorods (AuNRs) and organic semiconductors (OSCs) to tune optical properties is presented. OSCs are bound to specific areas of the AUNRs (e.g., end or side) by controlling the surface Chemistry of the AuNRs. AuNRs anisotropically fiinctionalized with cetrimonium bromide (CTAB) cysteine, poly(ethylene oxide) (PEO), and/or DNA. Rhodamine B (RhB) 5(6)-carboxyfluorescein (CF), or c-yanine3 (Cy3) are incubated with the anisotropically functionalized AuNRs. The resulting optical properties of the dispersed AuNRs are characterized via steady-state UVvis absorption and photoluminescence (PL) Spectroscopies as a function Of OSC concentration. We found that CF and RhB adsorb to the AuNR differently depending on the AuNR surface chemistry, which results in unique optical properties of the assembly. The distinctive spectra were used to dotermine the interaction between the OSC and the AuNIL Finally, we found that attaching Cy3 specifically to the ends of the AuNR via a DNA tether results in a larger emission quenching process than when Cy3 is not attached. This method of nanohybrid assembly can be extended to :other metal nanostructures and OSCs. Its generic nature qualifies it as new methodology to precisely assemble nano- and molecular objects with controlled (opto)electronic properties.

In this work, we develop a novel, in situ characterization method to measure the orientation order parameter and investigate the reorientation and reshaping dynamics of polymer grafted gold nanorods (AuNRs) in polymer nanocomposite (PNC) thin films. The long aspect-ratio of AuNRs results in two well-defined plasmon resonance modes, allowing the optical properties of the PNC to be tuned over a wide spectral range. The alignment of the AuNRs in a particular direction can also be used to further tune these optical properties. We utilize variable angle spectroscopic ellipsometry as a unique technique to measure the optical properties of PNC films containing AuNRs at various angles of incidence, and use effective index of refraction analysis of the PNC to relate the birefringence in the film due to changes of the plasmon coupling to the orientation order parameter of AuNRs. Polymer thin films (ca. 70 nm) of either polystyrene (PS) or poly(methyl methacrylate) (PMMA) containing PS grafted AuNRs are probed with ellipsometry, and the resulting extinction coefficient spectra compare favorably with more traditional analytical techniques, electron microscopy (EM) and optical absorbance (vis-NIR) spectroscopy. Furthermore, variable angle spectroscopic ellipsometry measures optical birefringence, which allows us to determine the in- and out-of plane order of the AuNRs, a property that is not easily accessible using other measurement techniques. Additionally, this technique is applied in situ to demonstrate that AuNRs undergo a rapid (ca. 1-5 hours) reorientation before undergoing a slower (ca. 24 hours) rod to sphere shape transition. The reorientation behavior is different depending on the polymer matrix used. In the athermal case (i.e. PS matrix), the AuNRs reorient isotropically, while in PMMA the AuNRs do not become isotropic, which we hypothesize is due to PMMA preferentially wetting the silica substrate, leaving less vertical space for the AuNRs to reorient.

A novel, solution-based method is presented to prepare bifunctional gold nanorods (B-NRs), assemble B-NRs end-to-end in various solvents, and disperse linked B-NRs in a polymer matrix. The B-NRs have poly(ethylene glycol) grafted along its long axis and cysteine adsorbed to its ends. By controlling cysteine coverage, bifunctional ligands or polymer can be end-grafted to the AuNRs. Here, two dithiol ligands (C6DT and C9DT) are used to link the B-NRs in organic solvents. With increasing incubation time, the nanorod chain length increases linearly as the longitudinal surface plasmon resonance shifts toward lower adsorption wavelengths (i.e., red shift). Analogous to step-growth polymerization, the polydispersity in chain length also increases. Upon adding poly(ethylene glycol) or poly(methyl methacrylate) to chloroform solution with linked B-NR, the nanorod chains are shown to retain end-to-end linking upon spin-casting into PEO or PMMA films. Using quartz crystal microbalance with dissipation (QCM-D), the mechanism of nanorod linking is investigated on planar gold surfaces. At submonolayer coverage of cysteine, C6DT molecules can insert between cysteines and reach an areal density of 3.4 molecules per nm(2). To mimic the linking of Au NRs, this planar surface is exposed to cysteine-coated Au nanoparticles, which graft at 7 NPs per μm(2). This solution-based method to prepare, assemble, and disperse Au nanorods is applicable to other nanorod systems (e.g., CdSe) and presents a new strategy to assemble anisotropic particles in organic solvents and polymer coatings.

Top-selective surface modification has been widely used for the synthesis of Janus nanoparticles (NPs). Herein we demonstrate that polymer single crystals can serve as generic substrates to immobilize NPs and the resultant NPs are Janus in nature. This technique is generic because various NPs as well as polymer single crystal substrates can be used. Single crystals of poly(ethylene oxide), polycaprolactone, and polyethylene-block-poly(ethylene oxide) have been successfully used to immobilize gold, magnetic, and semiconducting NPs. Subsequent dissolution of the single crystals led to various types of Janus NPs and NP clusters with different polymer brushes.

This study investigates the parameters that affect the dispersion of polymer grafted mesoscopic iron-oxide rods (FeMRs) in polymer matrices. FeMRs (212 nm long by 36 nm in diameter) are grafted with poly(methyl methacrylate) (PMMA) at three different brush molecular weights: 3.7 kg mol(-1), 32 kg mol(-1), and 160 kg mol(-1). Each FeMR sample was cast in a polymer thin film consisting of either PMMA or poly(ethylene oxide) (PEO) each at a molecular weight much higher or much lower than the brush molecular weight. We find that the FeMRs with 160 kg mol(-1) brush disperse in all matrices while the FeMRs with 32 kg mol(-1) and 3.7 kg mol(-1) brushes aggregate in all matrices. We perform simple free energy calculations, taking into account steric repulsion from the brush and van der Waals attraction between FeMRs. We find that there is a barrier for aggregation for the FeMRs with the largest brush, while there is no barrier for the other FeMRs. Therefore, for these mesoscopic particles, the brush size is the main factor that determines the dispersion state of FeMRs in polymer matrices with athermal or weakly attractive brush-matrix interactions. These studies provide new insight into the mechanisms that affect dispersion in polymer matrices of mesoscopic particles and therefore guide the design of composite films with well-dispersed mesoscopic particles.

This study examines the seasonal variability in levels of nitrogen (N) leaching and acidity in four acid impacted upland regions of the UK: the South Pennines, Snowdonia, Galloway and the Mourne Mountains. All regions are acidified, with median pH values of

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to evaluate tumor permeability, yet measurements have not been directly validated in brain tumors. Our purpose was to compare estimates of forward leakage K trans derived from DCE-MRI to the estimates K obtained using [ 14 C]aminoisobutyric acid quantitative autoradiography ([ 14 C]AIB OAR), an established method of evaluating blood-tumor barrier permeability. Both DCE-MRI and [ 14 C]AIB OAR were performed in five rats 9 to 11 days following tumor implantation. K trans in the tumor was estimated from DCE-MRI using the threeparameter general kinetic model and a measured vascular input function. K i was estimated from OAR data using regions of interest (ROI) closely corresponding to those used to estimate K trans . K trans and K i correlated with each other for two independent sets of central tumor ROI ( R = 0.905, P = .035; R = 0.933, P = .021). In an additional six rats, K trans was estimated on two occasions to show reproducibility (intraclass coefficient = 0.9993; coefficient of variance = 6.07%). In vivo blood-tumor permeability parameters derived from DCE-MRI are reproducible and correlate with the gold standard for quantifying blood tumor barrier permeability, [ 14 C]AIB OAR.

The Cairngorms in north-east Scotland is remote from pollutant sources although it currently receives ca. 10 kg ha1 yr1 S and ca. 11 kg ha1 yr1 N deposition from the atmosphere.In 1955, 15 lochs (lakes) at a range of altitudes were sampled and analysed for major ion concentrations. A new survey of these and an additional 23 lochs and their catchment soils was conducted in 1999 to determine the impact of acid deposition, and the changes in loch chemistry since the 1955 survey. The bedrock geology of this region has a strong influence on the loch chemistry. Surface waters were generally more acidic in high altitude areas due to predominantly poorly buffered, thin alpine soils developed on granitic parent material (mean acid neutralising capacity (ANC) for 23 lochs = 30 μeq L1). At lower altitudes where the geology is dominated by Dalradian metamorphic rocks surface waters are comparatively base rich and have higher ANC (mean ANC for 15 lochs = 157 μeq L1). Surface water nitrate concentrations show a negative relationship with soil C:N status, in that higher nitrate only occurs at low soil C:N ratios. A comparison of data for 1955 and 1999 shows that sulphate concentrations are significantly lower (67.8 and 47.5 μeq L1, respectively), and pH has improved (pH 5.6 and 5.9) in response to decreased S deposition since the mid 1970s. However, mean nitrate concentrations were found to increase from 2.48 μ>eq L1 in 1955 to 5.65 μeq L1 in 1999. Differences in the sampling and laboratory methods from 1955 and 1999 are acknowledged in the interpretation of data.

Controls on nitrate leaching from upland moorland catchments are not yet fully understood and yet, despite agreements on emission reductions, increased surface water nitrate concentrations may affect significantly the acidity status of these waters in the future. At Lochnagar, an upland moorland catchment in N.E. Scotland, 12 years of surface water chemistry observations have identified a steady increase in nitrate concentration despite no measured change in inorganic nitrogen deposition. The MAGIC model has been applied to simulate a "best case" situation assuming nitrate in surface water represents "hydrological" contributions (direct run-off) and a ‘worst case’ assuming a nitrogen saturation mechanism in the catchment soil. Only the ‘saturation’ model is capable of matching the 12 years of observation for nitrate but both model structures match the pH and acid neutralising capacity record. Future predictions to 2040, in response to the agreed emission reductions under the Gothenburg Protocol, are markedly different. The worst case predicts continued surface water acidification whilst the best case predicts a steady recovery. Keywords: nitrogen saturation, modelling, Lochnagar, Gothenburg Protocol

The Harmonised Monitoring Scheme (HMS) was initiated in 1974 and represents the best-organised source of temporal and spatial data describing water quality for the major mainland rivers of Scotland, England and Wales. This paper presents the first detailed analysis of HMS data for Scotland, and identifies temporal changes in water quality from 1974 to 1995. From a concomitant analysis of catchment land cover characteristics, water quality indices have been linked with potential ‘drivers’ of change, influencing both point and diffuse sources. Nitrate concentrations between rivers are highly correlated with the amount of arable land, and relationships exist between grassland cover, orthphosphate-P and suspended solids concentrations. Similarly, urban catchments are highly correlated with ammonium-N, orthophosphate-P and suspended solids. Spatial and temporal trends in water quality for the rivers of Scotland are discussed.

A conceptual model of the combined effects of acid deposition and land-use, Model of Acidification of Groundwater In Catchments (MAGIC), was applied to 21 upland sites in the UK Acid Waters Monitoring Network (AWMN) to assess the likely future recovery in response to the latest international agreements controlling anthropogenic sulphur emissions throughout Europe. Future estimates of sulphur deposition were generated by the Hull Acid Rain Model (HARM), based on the agreed reductions outlined in the Second Sulphur Protocol. The results indicate only a limited degree of recovery in surface-water chemistry at all sites over the next 50 years; moreover, a continuing decline in soil base status is predicted to occur at 70% of sites, resulting in longer term reacidification of surface-water at 38% of sites. However, compared with a ‘business as usual’ scenario the recovery is pronounced, although acidified sites will require further reductions in acidic deposition if recovery to pre-industrial chemical conditions are to be achieved. Furthermore, land-use scenarios at afforested sites suggest that replanting of felled forest will lead to a further increase in acidification. This strengthens the argument that plantation forestry should be avoided in areas considered geologically sensitive to acidic deposition.

MAGIC-WAND (Model of Acidification of Groundwaters In Catchments—With Aggregated Nitrogen Dynamics) has been specifically developed for wide application and scenario assessment. It maintains the sulphur driven acid/base chemistry dynamics of MAGIC, and considers in addition the impacts of changes in nitrogen deposition from the atmosphere and changes in nitrogen utilisation within the catchment. The model uses estimates of nitrification, mineralisation, N fixation and denitrification and changes in these soil processes through time. Plant uptake is nonlinear and dependant upon inorganic nitrogen concentrations in soil solution. Calibration of the model requires specification of values for the soil N fluxes and for the parameters which describe the hyperbolic uptake function. Literature data can provide ranges for these values but specific catchment related values are not obtainable since the model is conceptual. Selection of uptake parameters must reflect current catchment vegetation and vegetation change through time, and this has been investigated at a catchment in SW Scotland. Changes in soil processes through time are also important to model functioning, but are not considered in this study. The model has been applied to 25 acid sensitive (Acid Neutralising Capacity (ANC) −1 ) lochs in SW Scotland to examine the interaction of afforestation and changes in nitrogen deposition, assuming recently agreed reductions in sulphur deposition. The model results suggest that a 50% reduction in nitrogen deposition coupled with agreed sulphur reductions is not sufficient to promote reversibility of acidification at the most sensitive sites within 15 years. Increased nitrogen deposition in conjunction with agreed sulphur reductions will most likely cause continued acidification at afforested lochs in the region.

A new model for simulating nitrogen leaching fromforested ecosystems has been applied to data from anexperimentally manipulated 30-year-old Sitka sprucestand. The manipulation experiment (at Aber, in north-western Wales, UK) was part of the European NITREXproject and involved five years of additions ofinorganic nitrogen to the spruce stand. The model(MERLIN) is a catchment-scale, mass-balance model thatsimulates both biotic and abiotic processes affectingnitrogen in ecosystems.

In laboratory adsorption experiments, the comparison of podzol Bs horizons from coastal and inland moderately-impacted catchments with those from a severely-acidified inland region has demonstrated the effect of marine inputs on SO 4 2- -retention. Moderate sea-salt inputs and low acid deposition leads to the retention of most of the SO 4 2- and the release of soluble Mg 2+ ; increasing the marine salt loading causes the development of a selectivity towards retention of acidic SO 4 2- and the retention of Mg 2+ . In the highly-impacted soil, the marine input caused a decrease in SO 4 2- retention in open moorland soils. The opposite occurred under forest, due to the ion-exchange of marine Mg 2+ for soil Al 3+ , increasing soil acidity towards the pH 0 (Gillman and Uehara, 1980), which is depressed below that of its moorland equivalent

In this work, we describe a simple method to prepare hybrid nanogels consisting of a biocompatible core-shell polymer host containing silver nanoparticles. First, the nanogels (NG, ~160 nm) containing a lysozyme rich core and a dextran rich shell, are prepared via Maillard and heat-gelation reactions. Second, silver nanoparticles (Ag NPs, ~5nm) are synthesized in situ in the NG solution without requiring additional reducing agents. This approach leads to stable Ag NPs located in the NG. Furthermore, we demonstrate that the amount of Ag NPs in the NG can be tuned by varying silver precursor concentration. Hybrid nanogels with silver nanoparticles have potential in antimicrobial, optical and therapeutic applications.

An acidification experiment was conducted on a small stream in the Loch Ard area of central Scotland. The stream was chosen because of its large, flow related, variation in pH (5.9-4.0). Two acid additions were made to approximately pH 3.5–3.7. The results indicated a strong correlation between labile aluminium and hydrogen, and a noticeable hysteresis in the response of calcium and hydrogen. It is hypothesised that divalent cation response is a result of ion-exchange mechanisms involving the streambed vegetation, with aluminium release resulting primarily from exchange reactions with streambed sediment stores. Data from a program of stream spot sampling have been analysed in an attempt to elucidate the contribution of different sources of aluminium under different flow conditions. Streambed sources of aluminium contribute significantly under low flow conditions; however, at high flow, additional sources of aluminium must contribute to match observed streamwater chemistry.

A comparison between two analytical techniques commonly used for the determination of sulphur concentrations in natural water samples is reported. Significant differences in the sulphur values obtained using inductively coupled plasma atomic emission spectrometry and ion chromatography are described. The contribution of a sulphur fraction (presumed to be organic S) not detected by ion chromatography is identified.

Recent environmental controversy has focused on the role of forestry practices in stream acidification, with conflicting claims regarding interception mechanisms, altered site hydrology, etc. While it is generally accepted that there are strong correlations between some parameters, for example aluminium in stream water and coniferous afforestation, there is less consensus on the reaction of trees to pollutants with consequences on the crucial production and mobility of anions, especially sulphate. Examination of data from Scottish studies has shown that Sitka spruce is capable of intercepting atmospheric SO 2 , leading to accumulations of excess sulphate in tree foliage. This sulphate is readily soluble and when leached by rainfall produces increases in tree throughfall sulphate concentrations in Sitka spruce compared with other species.

The similarity in the physical and chemical parameters of the soil profiles located at Loch Chon (central Scotland) and Hoylandet (mid Norway) enabled the comparison of soil sulphate adsorption and accumulation under two different levels of sulphate deposition. The Loch Chon site, due to its proximity to the industrialized central belt in Scotland, has received a history of anthropogenic sulphur loadings, while the Hoylandet site is situated in an area of Norway subjected to precipitation generated from unpolluted air masses originating over the North Atlantic ocean. Both soils show accumulation of water-soluble sulphate in the organic horizons (45 mg S kg −1 at Chon and 65 mg S kg −1 at Hoylandet), with low levels (0–5 mg S kg −1 ) being found in the mineral horizons. The iron podzol from the pristine (unpolluted) site at Hoylandet had levels of adsorbed sulphate in the range of 0–17 mg S kg −1 , which may have arisen through microbial mineralization of translocated organic matter and dead root tissue. In contrast, the humus iron podzol from Loch Chon, which had similar levels of mineralizable sulphate, showed a build-up of high levels of adsorbed sulphate throughout the profile (15–90 mg S kg −1 ). This additional sulphate may reflect a history of high anthropogenic sulphate deposition in this area, as laboratory based adsorption isotherm studies indicated that both soils were capable of adsorbing sulphate. Regression analysis indicated that adsorbed sulphate was correlated (5% level) with dithionite-soluble aluminium in the Loch Chon soil, but with the similar iron fraction in the Hoylandet soil.

Stream water at the 18.7 ha pristine Ingabekken catchment, on granitic bedrock, in mid-Norway has been studied for 2 years, including intensive episode studies in the spring and autumn. The pH varied from over 7 at base flow to 5 or slightly below at high flow, while inorganic monomeric Al was

Humic substances were isolated from the vegetation throughfall, soil drainage waters and adjacent stream waters at two forested sites in the Central Region of Scotland. Fractionation on XAD-8 hydrophobic resin gave three humic substance components and one hydrophilic acid fraction. Norway spruce generally gave 2–3 times more dissolved organic carbon in the litter drainage compared with Sitka spruce, although there was little qualitative difference in organic acidity between the two litterflows. The humic substances in the drainage at ca. 1 m depth (BC horizon) showed considerable differences between sites, reflecting the types of soils and sources of soil water. Phenolic acids released on hydrolysis confirm the differences between sites and may indicate the sources of subsoil water and their relationships with the stream outputs.

Efficacy and safety of an alpha-tocopherol-enriched emulsion incorporating soybean, coconut, olive, and fish oils (SMOF) are compared in terms of biologic parameters to those of soybean oil-based emulsion (LIPOVEN).Twenty stressed patients were randomly assigned in a double-blind study to receive at least a 5-day course of total parenteral nutrition. Plasma activities of liver enzymes, C-reactive protein, antioxidant capacity, alpha-tocopherol, retinol, and low density lipoprotein (LDL)-alpha-tocopherol levels were determined. LDL-lipid oxidation is measured after incubation of the LDL in the presence of a prooxidant.The plasma activities of liver enzymes and the phospholipids/apo A1 ratio were increased in both groups. However, in the SMOF group the increases were lower than in the LIPOVEN group and non-significant for the CRP plasma level and the alanineamino-transferase activity. Before parenteral nutrition, the plasma antioxidant status was markedly reduced in both groups. After parenteral nutrition discontinuation, the antioxidant capacity and the amount of LDL-derived oxidation by-products formed were comparable in both groups. There was a significant improvement in plasma lipophilic antioxidant vitamins and LDL-alpha-tocopherol levels only in the SMOF group.The lower increase of plasma liver enzymes and phospholipids/apo A1 ratio in the SMOF group suggest a better liver function than in the LIPOVEN group. This beneficial effect results in a higher liver mobilization and plasma levels of lipophilic antioxidants. They could, together with higher delivery of omega-3 fatty acids to peripheral tissues, contribute positively to survival rate of stressed patients.

The MAGIC model of the responses of catchments to acidic deposition has been applied and tested extensively over a 15 year period at many sites and in many regions around the world. Overall, the model has proven to be robust, reliable and useful in a variety of scientific and managerial activities. Over the years, several refinements and additions to MAGIC have been proposed and/or implemented for particular applications. These adjustments to the model structure have all been included in a new version of the model (MAGIC7). The log aluminium – pH relationship now does not have to be fixed to aluminium trihydroxide solubility. Buffering by organic acids using a triprotic analog is now included. Dynamics of nitrogen retention and loss in catchments can now be linked to soil nitrogen and carbon pools. Simulation of short-term episodic response by mixing fractions of different water types is also possible. This paper presents a review of the conceptual structure of MAGIC7 relating to long-term simulation of acidification and recovery, describes the conceptual basis of the new nitrogen dynamics and provides a comprehensive update of the equations, variables, parameters and inputs for the model. Keywords: process-based model, acid deposition, recovery

Publisher Summary From recent research it is clear that the old idea of brain noradrenergic neurons subserving a predominantly sympathoinhibitory role is no longer tenable. The substantial increase in brain norepinephrine (NE) turnover following trimethaphan presumably results from a compensatory response in sympathoexcitatory forebrain noradrenergic neurons in the face of interruption of sympathetic neural traffic and reduction in arterial blood pressure, while the reduction in central nervous system (CNS) NE turnover in response to intravenous clonidine administration underlies the blood pressure-lowering action of the drug. Following the characterization of NE as the sympathetic neurotransmitter and the subsequent finding of a direct relationship between rates of sympathetic nerve firing and neurotransmitter release, the potential to use NE washout, or spillover to plasma, as an index of sympathetic nervous function is well established. Recent research extends this reasoning to CNS neurons and suggests the utility of using direct internal jugular vein blood sampling techniques in the assessment of central nervous system neuronal activity, by demonstrating a reduction in 3-methoxy-4-hydroxyphenylglycol (MHPG) jugular venous overflow from the brain of stump-tailed monkeys following clonidine administration. The clinical application of such methodology, however, is in line with current advancement.

We applied transmitter washout methodology, sampling internal jugular venous plasma via a percutaneously placed catheter, to study CNS norepinephrine release in humans and its relation to peripheral sympathetic activity. Norepinephrine overflows into the venous drainage of the brain, as do its precursor, DOPA, and metabolites DHPG and MHPG, indicating that the blood-brain barrier provides an incomplete impediment to their outward flux from the brain. Pharmacological testing with two drugs which altered CNS norepinephrine turnover, the tricyclic antidepressant desipramine and the ganglionic blocker, trimethaphan, demonstrated a direct relation existed between CNS norepinephrine release and sympathetic nerve firing rates. In essential hypertension, the sympathetic activation commonly present was associated with, and possibly caused by increased CNS release of norepinephrine, manifested in elevated overflow of norepinephrine, MHPG and DHPG from the brain. Bilateral jugular sampling, coupled with a cerebral venous sinus scan to delineate the drainage pattern, demonstrated that this increased norepinephrine release was confined to subcortical forebrain regions.

Rime ice deposition and snow chemistry has been determined over a 4-year period on the summit of Cairngorm Mountain, NE Scotland. The direction of ice deposition reflected the dominant air mass movement over the summit. Sea salt concentrations in the rime ice were approximately 2.5 times greater than in snow deposited over the same period. Excess sulphate concentrations were double, and those of nitrate nearly four times higher. The direction of deposition influenced concentrations of excess sulphate and nitrogen species (nitrate and ammonium) in rime ice. The same directional effect was found in the snow chemistry indicating increased entrapment of pollutants, or a more polluted air mass, when it prevailed from a Southerly or Easterly direction. The potential surface reactions involving gaseous species of S and N may increase the ionic loading to the rime and reflect natural ionic enrichment of the rimed snowpack surface. Because of such phenomena, rime ice is proposed as a further indicator of winter air quality revealing important information on ionic interactions and total deposition flux measurement, especially at high altitudes.

SUMMARY In normal man the sympathetic nervous system could exert an inhibitory influence on aldosterone responsiveness to angiotensin II. The possible role of alpha-1 adrenoceptors in the modulation of aldosterone response was assessed by studying the changes of plasma aldosterone during infusion of angiotensin II at the doses of 1, 2, 5 and 10 ng/kg.min or after 1–24corticotrophin injection, 0.25 mg, in 9 normal subjects before and after treatment with the selective alpha-1 adrenoceptor antagonist, prazosin. Prazosin, given during 3 weeks, did not modify supine arterial pressure, heart rate and the plasma levels of angiotensin II, renin, aldosterone or adrenaline but caused a significant (P < 005) increase of plasma noradrenaline. The correlation relating plasma aldosterone to plasma angiotensin II levels before and during angiotensin II infusion and the response of plasma aldosterone to corticotrophin was not modified by prazosin. These findings suggest that in normal man there is no inhibitory influence of the noradrenergic system on aldosterone responsiveness to angiotensin II mediated by an alpha-1 dependent mechanism.

1. We compared the baseline phosphorus (P) concentrations inferred by diatom-P transfer functions and export coefficient models at 62 lakes in Great Britain to assess whether the techniques produce similar estimates of historical nutrient status.2. There was a strong linear relationship between the two sets of values over the whole total P (TP) gradient (2-200 mu g TP L-1). However, a systematic bias was observed with the diatom model producing the higher values in 46 lakes (of which values differed by more than 10 mu g TP L-1 in 21). The export coefficient model gave the higher values in 10 lakes (of which the values differed by more than 10 mu g TP L-1 in only 4).3. The difference between baseline and present-day TP concentrations was calculated to compare the extent of eutrophication inferred by the two sets of model output. There was generally poor agreement between the amounts of change estimated by the two approaches. The discrepancy in both the baseline values and the degree of change inferred by the models was greatest in the shallow and more productive sites.4. Both approaches were applied to two lakes in the English Lake District where long-term P data exist, to assess how well the models track measured P concentrations since approximately 1850. There was good agreement between the pre-enrichment TP concentrations generated by the models. The diatom model paralleled the steeper rise in maximum soluble reactive P (SRP) more closely than the gradual increase in annual mean TP in both lakes. The export coefficient model produced a closer fit to observed annual mean TP concentrations for both sites, tracking the changes in total external nutrient loading.5. A combined approach is recommended, with the diatom model employed to reflect the nature and timing of the in-lake response to changes in nutrient loading, and the export coefficient model used to establish the origins and extent of changes in the external load and to assess potential reduction in loading under different management scenarios.6. However, caution must be exercised when applying these models to shallow lakes where the export coefficient model TP estimate will not include internal P loading from lake sediments and where the diatom TP inferences may over-estimate TP concentrations because of the high abundance of benthic taxa, many of which are poor indicators of trophic state.

Hydrochemical and catchment data from 80 upland moorland sites in four regions with contrasting climate, soils, geology and geomorphology have been analysed to assess the key catchment attributes that influence enhanced leaching of soluble nitrogen to surface waters. The regions are the South Pennines of northern England, the Snowdonia National Park in north Wales, the Galloway region of south-west Scotland and the Mourne Mountains in Northern Ireland, all highly acidified, with median pH values of 3−), ammonium (NH4+), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) were expressed as functions of catchment attributes. Nitrate concentrations in waters draining catchments dominated by peaty soils (large C pool) were much less than those in catchments dominated by mineral soils (small C pool). Hence, if future N deposition levels are maintained or increase, high-altitude catchments with small carbon pools are potentially more susceptible to NO3− leaching. All N species exhibit seasonality; this is most marked in Galloway and least marked in the South Pennines, which implies that the South Pennines have reached an advanced stage of N saturation. Surface water inorganic N concentrations and the ratio of dissolved organic carbon (DOC) to dissolved organic N (DON) can be related to deposition inputs, although relationships differ throughout the year. If the DOC/DON ratio is indicative of catchment N saturation, levels of N retention are at least partially determined by deposition levels. This study identifies N deposition as a major inter-regional control on the degree of catchment N saturation and on N leaching to surface waters; it stresses the importance of catchment factors in modifying the relationship between N deposition and leaching in acid sensitive UK upland catchments.