Lithium Intercalation into the Excitonic Insulator Candidate Ta2NiSe5.

A new reduced phase derived from the excitonic insulator candidate Ta2NiSe5 has been synthesized via the intercalation of lithium. LiTa2NiSe5 crystallizes in the orthorhombic space group Pmnb (no. 62) with lattice parameters a = 3.50247(3) Å, b = 13.4053(4) Å, c = 15.7396(2) Å, and Z = 4, with an increase of the unit cell volume by 5.44(1)% compared with Ta2NiSe5. Significant rearrangement of the Ta-Ni-Se layers is observed, in particular a very significant relative displacement of the layers compared to the parent phase, similar to that which occurs under hydrostatic pressure. Neutron powder diffraction experiments and computational analysis confirm that Li occupies a distorted triangular prismatic site formed by Se atoms of adjacent Ta2NiSe5 layers with an average Li-Se bond length of 2.724(2) Å. Li-NMR experiments show a single Li environment at ambient temperature. Intercalation suppresses the distortion to monoclinic symmetry that occurs in Ta2NiSe5 at 328 K and that is believed to be driven by the formation of an excitonic insulating state. Magnetometry data show that the reduced phase has a smaller net diamagnetic susceptibility than Ta2NiSe5 due to the enhancement of the temperature-independent Pauli paramagnetism caused by the increased density of states at the Fermi level evident also from the calculations, consistent with the injection of electrons during intercalation and formation of a metallic phase.

The role of copper in the thermal conductivity of thermoelectric oxychalcogenides: do lone pairs matter?

Understanding the underlying mechanisms that suppress thermal conduction in solids is of paramount importance for the targeted design of materials for thermal management and thermoelectric energy conversion applications. Bismuth copper oxychalcogenides, BiOCuQ (Q = Se, Te), are highly crystalline thermoelectric materials with an unusually low lattice thermal conductivity of ∼0.5 Wm(-1) K(-1), a value normally found in amorphous materials. Here we unveil the origin of the unusual thermal transport properties of these phases. First principles calculations of the vibrational properties combined with analysis of in-situ neutron diffraction data, demonstrate that weak bonding of copper atoms within the structure leads to an unexpected vibrational mode at low frequencies, which is likely to be a major contributor to the low thermal conductivity of these materials. In addition, we show that anharmonicity and the large Grüneisen parameter in these oxychalcogenides are mainly related to the low frequency copper vibrations, rather than to the Bi(3+) lone pairs.

Integrating health and environmental impact analysis.

Scientific investigations have progressively refined our understanding of the influence of the environment on human health, and the many adverse impacts that human activities exert on the environment, from the local to the planetary level. Nonetheless, throughout the modern public health era, health has been pursued as though our lives and lifestyles are disconnected from ecosystems and their component organisms. The inadequacy of the societal and public health response to obesity, health inequities, and especially global environmental and climate change now calls for an ecological approach which addresses human activity in all its social, economic and cultural complexity. The new approach must be integral to, and interactive, with the natural environment. We see the continuing failure to truly integrate human health and environmental impact analysis as deeply damaging, and we propose a new conceptual model, the ecosystems-enriched Drivers, Pressures, State, Exposure, Effects, Actions or 'eDPSEEA' model, to address this shortcoming. The model recognizes convergence between the concept of ecosystems services which provides a human health and well-being slant to the value of ecosystems while equally emphasizing the health of the environment, and the growing calls for 'ecological public health' as a response to global environmental concerns now suffusing the discourse in public health. More revolution than evolution, ecological public health will demand new perspectives regarding the interconnections among society, the economy, the environment and our health and well-being. Success must be built on collaborations between the disparate scientific communities of the environmental sciences and public health as well as interactions with social scientists, economists and the legal profession. It will require outreach to political and other stakeholders including a currently largely disengaged general public. The need for an effective and robust science-policy interface has never been more pressing. Conceptual models can facilitate this by providing theoretical frameworks and supporting stakeholder engagement process simplifications for inherently complex situations involving environment and human health and well-being. They can be tools to think with, to engage, to communicate and to help navigate in a sea of complexity. We believe models such as eDPSEEA can help frame many of the issues which have become the challenges of the new public health era and can provide the essential platforms necessary for progress.

Structural features of human immunoglobulin G that determine isotype-specific differences in complement activation.

Although very similar in sequence, the four subclasses of human immunoglobulin G (IgG) differ markedly in their ability to activate complement. Glu318-Lys320-Lys322 has been identified as a key binding motif for the first component of complement, C1q, and is present in all isotypes of Ig capable of activating complement. This motif, however, is present in all subclasses of human IgG, including those that show little (IgG2) or even no (IgG4) complement activity. Using point mutants of chimeric antibodies, we have identified specific residues responsible for the differing ability of the IgG subclasses to fix complement. In particular, we show that Ser at position 331 in gamma 4 is critical for determining the inability of that isotype to bind C1q and activate complement. Additionally, we provide further evidence that levels of C1q binding do not necessarily correlate with levels of complement activity, and that C1q binding alone is not sufficient for complement activation.

Effects of nitrogen enrichment on phosphatase activity and nitrogen : phosphorus relationships in Cladonia portentosa.

*Relationships between nitrogen deposition in the UK and phosphomonoesterase (PME) activity and nitrogen (N) and phosphorus (P) concentrations in Cladonia portentosa were quantified to understand factors limiting lichen growth and to further develop biomarkers for N pollution. *Lichen was collected from sites differing either in rates of wet N (NH(4)(+) + NO(3)(-)) deposition or in annual mean N concentration in rainfall based on both measured and modelled data sets. The PME activity, and total N and P concentrations were measured in specific horizontal strata in lichen mats and PME activity in the thallus was located using an enzyme-labelled fluorescent phosphatase substrate. *With an increase in modelled N deposition from 4.1 to 32.8 kg N ha(-1) yr(-1), PME activity, thallus N and N : P ratio increased by factors of 2.3, 1.4 and 1.8, respectively. Correlations with modelled data were generally stronger than with measured data and those with N deposition were stronger than those with N concentration in rainfall. The PME activity was located solely in the lichen fungus in outer regions of the thallus. *Nitrogen enrichment changes lichen N : P ratios from values typical of N limitation (for example, 10) to those indicative of P limitation (for example, 26) driving upregulation of PME activity.

Ammonia absorption in calcium graphite intercalation compound: in situ neutron diffraction, Raman spectroscopy and magnetization.

The structure and superconducting properties of ammoniated calcium-graphite intercalation compound (Ca-GIC) have been investigated using in situ time-of-flight neutron diffraction, Raman spectroscopy and magnetization studies. Ammonia absorption has been carried out by exposing preformed Ca-GIC to ammonia vapour at various pressures. Our in situ neutron diffraction data reveal a complex ammonia pressure dependent structural transformation, in which the growth of secondary ammoniated Ca-GIC phases are observed at the expense of the pristine CaC(6) and graphite. The ammonia absorption is irreversible in nature, and degassing the sample at elevated temperature leads to the formation of calcium amide and hydrogen. The Raman spectroscopy and magnetization studies show that the ammonia absorption not only leads to a large stacking disorder, but it also reduces the superconducting CaC(6) phase fraction. Finally, we propose a molecular stacking model which accounts for the observed ammonia absorption and concomitant structural phase transitions.

The upgraded Polaris powder diffractometer at the ISIS neutron source.

This paper describes the design and operation of the Polaris time-of-flight powder neutron diffractometer at the ISIS pulsed spallation neutron source, Rutherford Appleton Laboratory, UK. Following a major upgrade to the diffractometer in 2010-2011, its detector provision now comprises five large ZnS scintillator-based banks, covering an angular range of 6° ≤ 2θ ≤ 168°, with only minimal gaps between each bank. These detectors have a substantially increased solid angle coverage (Ω âˆ¼ 5.67 sr) compared to the previous instrument (Ω âˆ¼ 0.82 sr), resulting in increases in count rate of between 2× and 10×, depending on 2θ angle. The benefits arising from the high count rates achieved are illustrated using selected examples of experiments studying small sample volumes and performing rapid, time-resolved investigations. In addition, the enhanced capabilities of the diffractometer in the areas of in situ studies (which are facilitated by the installation of a novel design of radial collimator around the sample position and by a complementary programme of advanced sample environment developments) and in total scattering studies (to probe the nature of short-range atomic correlations within disordered crystalline solids) are demonstrated.

Investigation of the changes in hydrogen bonding accompanying the structural reorganization at 103†K in ammonium iodate.

Neutron powder diffraction has been used to observe the changes in hydrogen bonding that occur as a function of temperature in ND4IO3 and, thus, determine the structural features that occur during the low-temperature (103 K) phase transition. It is shown that in the deuterated material the change is not a phase change per se but rather a structural reorganization in which the hydrogen bonding becomes firmly locked in at the phase transition temperature, and stays in this configuration upon further cooling to 4.2 K. In addition, both the differences and changes in the axial thermal expansion coefficients in the region 100-290 K can be explained by the changes involving both the hydrogen bonding and the secondary I...O halogen bonds.

Changes in the atmospheric deposition of acidifying compounds in the UK between 1986 and 2001.

Emissions of a precursor of acidity in precipitation, sulphur dioxide (SO2), declined in the UK and the EU (15) by 71% and 72%, respectively, between 1986 and 2001, while nitrous oxide emissions declined by about 40%. Acidity in UK precipitation and the deposition of sulphate in precipitation halved during this period, but reductions were larger in the English Midlands than at the west coast and in high rainfall areas (>2000 mm). There is evidence that the smaller reductions in sulphur deposition in the west and south are due in part to shipping sources of SO2. Reductions in sulphur dry deposition (74%) are larger than in wet deposition (45%), due to changes in the canopy resistance to dry deposition. For reduced nitrogen, there has been a small (10%) reduction in emissions and deposition, while for oxidized nitrogen, a substantial reduction in emissions (40%) occurred but wet deposition of nitrate changed by less than 10%.

New insights into the phase diagram of a magnetic perovskite, LaCo1/3Mn2/3O3.

We report the crystal structure of the orthorhombic perovskite LaCo1/3Mn2/3O3 as determined by neutron diffraction from 5-300 K. A high-temperature x-ray diffraction study is also reported from 290-900 K. At temperatures above 570 K, LaCo1/3Mn2/3O3 transforms to a rhombohedral structure with space group R3̄c. This rhombohedral phase is also observed in the material at high pressure and the crystal structure has been determined by in situ neutron diffraction at 4.7 GPa. Finally, the ferromagnetic behaviour has been determined by magnetometry and the magnetic structure has been determined using low temperature neutron diffraction at ambient pressure.

Visible foliar injury of red spruce seedlings subjected to simulated acid mist.

Two-year-old red spruce seedlings [Picea rubens Sarg. syn. P. rubra (Du Roi) Link] were subjected to 6 simulated acid mist treatments (pH 2.5, 2.7, 3.0, 3.5, 4.0, 5.0) in a replicated experiment using open-top chambers. Acid mist solutions containing equimolar (NH4 )2 SO4 , and HNO3 were applied twice weekly for 22 weeks, each application being equivalent to 2 mm of precipitation. Visible symptoms of foliar damage were observed on the 3 most acidic mist treatments (pH 2.5, 2.7, 3.0). The inputs of nitrogen, sulphur and acidity in the most acidic treatment were 55, 42, 1,3 kg ha-1 , respectively, over a 10 week period. The plants subjected to the pH 2.5 treatment were found to be most severely damaged with approximately 40% foliar necrosis after 10 weeks of treatment. On approximately 80% of seedlings, necrosis was confined to current year needles only. These damaged needles were initially light brown or light orange in colour turning a deeper red 3 to 5 weeks after initial necrosis. Percentage foliar damage was linearly related to concentration (of NH4 + , NO3 - , SO4 2- and H+ ) with 62% foliar damage in the pH 2.5 treatment after a 22-week period. Spray application stopped in December 1987. Observations during the following spring showed that the pH 2.5 and pH 3 treatments induced earlier Hushing, requiring 60 day °C less thermal time than the pH 5-0 treatment. In 1988, this decrease in thermal requirement was equivalent to flushing 11 days earlier. There was no evidence of acid mist treatments inducing bud mortality.

Effects of acid mist on the frost hardiness of red spruce seedlings.

Seedlings of red spruce [Picea rubens Sarg. syn. P. rubra (Du Roi) Link] were exposed to mists containing equimolar (NH4 , SO4 and HNO3 at pHs of 2.5, 2.7, 3.0, 35, 4.0 or 5.0. The mists were applied twice each week, amounting to 2 mm precipitation equivalent on each occasion, between July and December, to open-top chambers supplied with charcoal-filtered air. Frost hardiness of shoots excised from seedlings was determined on 6 occasions starting on 21 September, and was found to be strongly influenced by acid mist treatments, seedlings subject to the most acidic mists being the least frost hardy. On 21 September when the first sample was taken the lethal temperature for killing 50% of shoots (LT50 ) was - 11 °C for the least acidic (pH 5.0) mist and - 7 °C for the most acidic (pH 2.5). By 19 October, the LT50 s of pH 5.0 and pH 2.5 mists were -27 and -15 °C respectively. All intermediate treatments ranked according to treatment concentration, with the smaller concentrations causing lower LT.50 values. The treatment at pH 30 provided S and N inputs to the seedlings similar to those experienced by red spruce at elevations of about 1000 m in the southern Appalachians. At pH 3.0, the frost hardiness LT10 during October was typically 8 °C higher than the pH 5.0 treatment, leading to a significant increase in the probability of frost damage at the LT10 level in an average October. The proximity of minimum night temperatures during September to December to the LT10 temperatures of red spruce shoots receiving large inputs of SO4 2- , NO3 - , NH4 + and H+ suggests that decreases in frost hardiness caused by intercepted cloud water containing large concentrations of these ions may play a significant part in the observed decline at mountain-top locations.

Air pollution statistics in policy applications.

This review of the role of air pollution statistics in environmental policy sets the UK current controls of sulfur emissions for health and environmental effects in a historical context. The use of critical loads and levels is discussed. The role of air pollution monitoring data in assessing achievement of a health effects air quality standard or predicting exceedance of a critical level or critical load on a national basis is reviewed with the level of monitoring and the interpolation of concentration data identified as important issues. The problems of spatial scale, the scarcity of data for model validation and the use of trends to identify model inadequacy are illustrated. The current statistical challenges in understanding air pollution processes and defining appropriate policies include quantification of uncertainty within complex models, problems of spatial scale and model validation, and development of monitoring strategies which balance the spatial (more sites) and temporal (better process understanding) aspects of the science alongside the balance between policy desire and monitoring practicality. An appropriate statistical goal is development of methodology to ensure appropriate derived data with sufficient accuracy are used for measuring policy achievement.

Ozone dose mapping and the utility of models.

In Europe the monitoring of ozone doses to growing crops is based on measurement of AOT40, the annual accumulated excess ozone concentration over a threshold of 40 ppb, aggregated over the growing season. To show the extent of ozone pollution it is desirable to construct maps of AOT40. However, data are limited and there is large inter-annual variation, so what is to be mapped is very variable, and our knowledge of it is limited. This paper describes a spatially referenced random effects model which appears able to describe many features of the data and our uncertainty about them. The problem of translating this or similar models into a map faithfully representing our knowledge is considered, as are some questions it raises about decision-makers' and the public's need for and use of technical models.

Vascular plants as bioindicators of regional warming in Antarctica.

Monitoring selected populations of the only two native Antarctic vascular plant species (Colobanthus quitensis andDeschampsia antarctica) over a 27-year period has revealed a significant and relatively rapid increase in numbers of individuals and populations at two widely separated localities in the maritime Antarctic. There is strong evidence that this increase is a response to a warming trend in summer air temperatures, which has been evident throughout the region since the late 1940s, enhancing seed maturation, germination and seedling survival. This study provides the only known long-term monitoring data for any terrestrial organisms in Antarc-tica. Because their response to ameliorating conditions is more rapid than that of the dominant cryptogamic groups, Antarctic phanerogams may be useful bioindicators of climate change in West Antarctica.

Influence of nutrient application rate on growth and rooting potential of the West African hardwood Triplochiton scleroxylon.

Effects of stock plant nutrition on growth and subsequent rooting of leafy stem cuttings of the commercially important west African tree Triplochiton scleroxylon K. Schum. were investigated to identify the primary morphological variables influencing adventitious root formation. Potted plants were watered as required with one of four balanced nutrient solutions (0, 15, 63 or 125 mg N l(-1)). Increasing the nutrient supply to stock plants increased growth rate and rate of adventitious root production of subsequently harvested cuttings, but an optimum nutrient regime was not identified. Rooting percentage increased from 27% in cuttings harvested from stock plants receiving a low nutrient supply to 64% for cuttings harvested from stock plants receiving eight times the amount of nutrients extractable from plants under typical field conditions in West Africa. The ability of a cutting to retain its leaf during propagation and the length of the cutting were the primary measured characteristics associated with rooting and accounted for 43% of the variance fitted in the model. The length of the new shoot, total leaf area and within-shoot position (node position) were also significantly associated with rooting. After these characteristics were fitted to the model, the genetic origin (clone) was not statistically significant. We conclude that genetic variation in rooting potential is mediated through variations in morphological and physiological traits, rather than through genetic variation in cell differentiation or related aspects of root initiation.

Exchanges of sodium and chloride at low salinities by Nereis diversicolor (Annelida, Polychaeta).

1. Experiments to compare the exchange (total influx) of sodium and chloride in the polychaete Nereis diversicolor in steady-state adaptation to very low salinities are reported. 2. The Na-uptake mechanism shows a high affinity for sodium, reaching half the maximal uptake rate at an external Na-concentration of 8-10 mM/liter (ca. 2% SW), and becomes "saturated" or reaches a plateau of uptake at concentrations of 40-50 mM/liter (ca. 10% SW) up to ca. 350 mM/liter (75% SW), above which Na-exchange is proportional to the external concentration. 3. The Cl-uptake curve differs from the Na-uptake curve in showing a relative depression at very low salinities before reaching "saturation" at Cl-concentrations of 50-60 mM/liter (ca. 10% SW). Cl-uptake becomes proportional to external concentration in salinities of 50% SW or greater, suggestive of passive diffusion in the ionic and osmotic conforming range. 4. It is shown that the permeability of the body wall, both to Na and to Cl, is reduced at very low salinities, thus destroying one of the assumptions upon which a previously-presented balance-sheet for chloride exchanges in N. diversicolor was based (Smith, 1970a). 5. Attempts to demonstrate an activation of the Na-uptake mechanism at very low salinities were inconclusive; reduction of body-wall permeability to sodium masks any possible activation. 6. It is suggested that the inside-negative body-wall potential is related to the depression of the Cl-uptake curve in salinities below 10% SW.

An investigation of the impact of afforestation on stream-water chemistry in the Loch Dee catchment, SW Scotland.

The impact of conifer afforestation on stream-water chemistry was investigated in the acidified catchment of Loch Dee, SW Scotland. Long-term trends in stream-water chemistry were evaluated during a period of forest growth from age 6 to 17 years. A significant increase was observed for pH (0.2 units) and a significant decline for aluminium (0.05 mg litre(-1)), sulphate (1.2 mg litre(-1)) and nitrate (0.02 mg litre(-1)) concentrations. The long-term decrease in stream-water acidity was ascribed to the marked reductions in sulphur depositions during the 1970s and early 1980s. There was no evidence that this response had been attenuated by afforestation, the improvements in stream-water chemistry being of a similar magnitude to those recorded in nearby moorland lochs and exceeding that in an adjacent moorland-catchment stream. The lack of a clear forest acidification effect is consistent with deposition-model estimates which show the increased scavenging of occult and dry deposition by the growing forest to be small at this site (

Stem growth reduction in mature Sitka spruce trees exposed to acid mist.

An eighteen-year-old clone of Sitka spruce (Picea sitchensis (Bong.) Carr) growing in the field was used to evaluate the whole tree response of 'mature' Sitka spruce to acid mist treatment. The mist, an equimolar mixture of H(2)SO(4) and NH(4)NO(3) at pH 2.5 with or without particles (soda glass ballotini < 20 microm diameter), was applied twice weekly (equivalent to 4 mm precipitation week(-1)) throughout the growing season, May-November 1990-1992. The annual dose of S, N, H applied as mist (at 51, 48 and 3.3 kg ha(-1), respectively) was 2.5 times that measured in the Scottish uplands. Throughout the experiment there was no evidence of visible injury symptoms, yet there was a highly significant reduction (p < 0.02) in the stem-area increment relative to the stem area at the start, measured using vernier dendrometer bands. There was no significant difference between the (acid mist + particle) and the acid mist only treatments. The mean relative stem-area increment over two complete growing seasons (1991-1992) was 65% for control trees, but only 53% for acid-misted trees.

Modelling photochemical oxidant formation, transport, deposition and exposure of terrestrial ecosystems.

The chemical processes responsible for production of photochemical oxidants within the troposphere have been the subject of laboratory and field study throughout the last three decades. During the same period, models to simulate the atmospheric chemistry, transport and deposition of ozone (O(3)) from individual urban sources and from regions have been developed. The models differ greatly in the complexity of chemical schemes, in the underlying meteorology and in spatial and temporal resolution. Input information from land use, spatial and temporally disaggregated emission inventories and meteorology have all improved considerably in recent years and are not fully implemented in current models. The development of control strategies in both North America and Europe to close the gaps between current exceedances of environmental limits, guide values, critical levels or loads and full compliance with these limits provides the focus for policy makers and the support agencies for the research. The models represent the only method of testing a range of control options in advance of implementation. This paper describes currently applied models of photochemical oxidant production and transport at global and regional scales and their ability to simulate individual episodes as well as photochemical oxidant climatology. The success of current models in quantifying the exposure of terrestrial surfaces and the population to potentially damaging O(3) concentrations (and dose) is examined. The analysis shows the degree to which the underlying processes and their application within the models limit the quality of the model products.