Mixed Zone Research Articles

Mercury in dated sediment cores from coastal ponds of St Thomas, USVI

We collected seven cores from five coastal ponds in St Thomas, USVI, dated them via 210Pb, and measured their Hg profiles. Levels ranged from 20 to 100ngg−1 and always increased upward to the surface or a shallow mixed zone. Taking into account differences in sediment accumulation rates and the presence or absence of a mixed zone, all sites revealed similar deposition histories. Mercury levels were at low, possibly pristine, values until the early to mid-20th century. Then they then doubled or quadrupled steadily until about 1990, after which Hg became relatively constant. We conclude that Hg in the sediments of these ponds came from long range deposition directly to the ponds and to their watersheds. Constant levels in recent years may be caused by transfer from watersheds, a pathway that is delayed compared to direct deposition from the atmosphere.

Patterns of Acute Ischemic Strokes After Carotid Endarterectomy and Therapeutic Implications.

Acute ischemic strokes following surgical treatment of carotid stenosis lead to substantial disability and mortality, and vascular mechanisms underlying their development are not fully elucidated. The goal of this study was to analyze the topographic patterns of acute ischemic stroke following carotid endarterectomy (CEA) on diffusion-weighted and perfusion-weighted magnetic resonance imaging (MRI). Data were retrospectively collected from consecutive patients who underwent CEA and developed postoperative acute ischemic stroke. Based on the MRI data sets, the lesion patterns of acute stoke were characterized. Morphology of the circle of Willis, the 3-D time-of-flight (3D-TOF) of the cerebral arteries, and status of the carotid circulation were also analyzed in order to determine the vascular mechanisms involved in stroke development. Between January 2008 and May 2015, 821 patients were treated surgically for a symptomatic or asymptomatic carotid stenosis at the University Hospital of Nice. Nineteen (2.3%) patients had an acute ischemic stroke after surgery. Among them, 11 (57.9%) patients had a territorial infarction and 8 (42.1%) patients had an internal watershed infarction, cortical watershed infarction, or mixed border zone infarction. According to imaging data sets, embolic mechanism of stroke was reported for 12 (63.2%) patients, hemodynamic mechanism for 2 (10.5%) patients, and mixed mechanism for 5 (26.3%) patients. An asymmetry on 3D-TOF was observed in 60% and 50% of patients with hemodynamic and mixed stroke and in 25% of patients with embolic stroke. The latter 2 patients with embolic stroke underwent successful mechanical thrombectomy using stent-retriever devices. In this cohort, embolic mechanism leading to postoperative stroke was more frequently observed than hemodynamic mechanism. Immediate characterization of the cerebral lesion by postoperative brain MRI is of utmost importance because it may rapidly identify patients eligible for treatments such as mechanical thrombectomy.

Metals in 1–0.25 mm grain-size fraction in the soils of the mixed forest zone of the Russian plain

For an improved understanding of metal behavior in soils, studies on geochemical changes occurring in a specific grain-size fraction during pedogenesis and lateral translocation of soil material are needed. In the present research we analyzed the concentrations and vertical distributions of Fe, Mn, Cu, Ni, Co, Cr, Zn, Pb, Ti, Zr in coarse and medium sand fraction of the major soil types of the middle Protva basin, situated in the mixed forest zone of European Russia, and described patterns of downslope (lateral) distribution of metals in the humus horizons along two catenas and two types of small erosional systems. The observed concentrations for all metals in the fraction 1–0.25mm, except of Mn, conform to the natural geogenic concentrations reported previously in literature. The majority of the metals exhibit high natural variability in concentrations in the sand fraction. Higher metal concentrations are found either in the topsoil horizons or in parent material and underlying stratum. Studying lateral aspects of metal distribution in the sand fraction of humus horizons revealed a decrease in Mn, Zn, Pb, Co, Ti and an increase in Fe, Cr and Ni levels of the lower sections of the slopes. The similarity of metal concentrations in the sand fraction in these positions across two catenas implies the importance of the geochemical convergence processes operating in downslope direction. The small erosional landforms, a gully and a dry U-shaped valley, show similar patterns in lateral distribution of Fe, Cu, Ni, Cr, Zr, Zn, but they differ in terms of Pb, Co and Mn behavior across their elementary units: adjacent areas, slopes and bottom. The results imply that the features of vertical (within the soil profiles) and lateral (along catenas and small erosional systems) distributions of metals are significantly controlled by the provenance of the sand fraction, although at the same time some variations in metal contents seem are attributed to chemical transformations of the sand fraction due to pedogenic processes and during downslope translocation of soil material.

Scaled Experimental and Simulation Study of Segregation in Water-Above-Gas Injection

Summary The water-above-gas injection has been introduced as a modified injection strategy for simultaneous or alternating water/gas injection to improve the recovery factor. This can be achieved through maximizing the size of the mixed zone and extending the complete-segregation distance. Verifying this approach in the laboratory needs special experimental design in which the effect of capillary force is eliminated or strongly reduced, and viscous and gravity forces are active. In this study, an experimental setup has been prepared and implemented to verify the advantages of the water-above-gas injection. Key parameters in this experiment have been scaled to reservoir conditions. This was possible through choosing correct porous media and fluid system. The porous media should have high porosity and permeability, and the fluid system should have very low interfacial tension (IFT) between phases. Supplementary experiments have been conducted to prove the reliability of the model before the main experiment. In addition to the investigation of different injection rates and water/gas injection ratios in this process, the effect of stepwise injection also has been investigated to verify the practical approach, which results in maximized sweep efficiency. Finally, a simulation study has been conducted, and by comparing its results to experimental results, the applicability of numerical simulation in designing reservoir-scale water-above-gas injection is confirmed.

Factors influencing the productivity and efficiency of wheat farmers in Punjab, Pakistan

PurposeScientists in Pakistan are currently developing biofortified wheat varieties to address widespread zinc deficiency, especially among women and children in poorer rural households. The purpose of this paper is to understand how the productivity and efficiency of small-scale and marginal wheat farmers can be improved so that their households may benefit from zinc-fortified varieties.Design/methodology/approachThe authors estimate a stochastic frontier production function model with data from a survey of wheat farmers conducted in Punjab, Pakistan in 2011.FindingsThe productivities of the newer varieties of wheat were significantly greater than the older varieties, as expected. Farmers growing wheat in the rice-wheat and cotton-wheat zones tend to be more efficient than farmers from the mixed zone. Farmers who wait to adopt a leading variety are not less efficient than earlier adopters, but the longer the time until they switch varieties again, the more inefficient is their wheat production. Older farmers tend to be more technically inefficient than younger farmers, but the effect of education is not statistically significant. Wheat farmers with access to extension advice are more efficient. Farmers whose land suffered from severe salinity or severe toxicity are less productive and less efficient than others.Research limitations/implicationsThe authors find no differences in technical inefficiency effects associated with growing the four most popular varieties, either grown alone or with other varieties – suggesting that no single leading variety should be targeted for biofortification. In contrast to some earlier studies, the authors find that small-scale farmers tend to be less technically efficient. This result underscores the need to specifically target this group in promotional programs, and also to complement these with reinforcement of agronomic recommendations.Originality/valueThis project is part of the HarvestPlus program to determine the appropriate variety or varieties to biofortify with zinc so that Pakistan’s population can have better health and well-being. Further, the results show that there it is desirable to undertake further studies to improve the productivity and efficiency of wheat farmers in the Punjab, Pakistan to increase the health and well-being of the population in general.

Quantitative interpretation of carbonate reservoir rock using wireline logs: a case study from Central Luconia, offshore Sarawak, Malaysia

The current study focuses on the quantitative evaluation of petrophysical parameters of selected wells using wireline log data in Central Luconia, offshore Sarawak. Based on the relatively high resistivity and, low-neutron/-density log responses, three major zones are identified. These include gas-bearing zones (Zone-1 and Zone-3) and mixed zone (Zone-2). The gamma ray, neutron and density logs confirmed that Well A was composed of carbonate rocks ranging from limestone to dolomite. Zone-1 and Zone-3 consist of limestone, whereas Zone-2 contains dolomite. The average porosity of these zones (Zone-1, Zone-2 and Zone-3) are 15.7, 4.3 and 13.7%, whereas gas saturation is 83, 41 and 93%, respectively. The permeability values are 543 mD (Zone-1), 47.7 mD (Zone-2) and 601.5 mD (Zone-3). The water saturation value in Zone-2 is very high, up to 66% compared to Zone-1 and Zone-3 which are 17 and 7%, respectively. It is pertinent to mention that Zone-1 and Zone-3 contain movable gas (i.e., HC movability index is less than 0.7). Furthermore, bulk volume water values in three zones (0.012, 0.0083 and 0.009) indicate the presence of irreducible water. In contrast, pore-filled dolomite cement is mostly from Zone-2, indicating high water, low gas saturation, low porosity and less movability index values, which indicate the presence of high microporosity. Additionally, bulk volume water suggests that these micropores are saturated with irreducible water. High microporosity affects the wireline log response in Zone-2 and therefore provides misleading information.

Insight into electric field-induced rupture mechanism of water-in-toluene emulsion films from a model system.

This paper presents a model, which we have designed to get insight into the development of electro-induced instability of a thin toluene emulsion film in contact with the saline aqueous phase. Molecular dynamics (MD) simulations demonstrate the role of charge accumulation in the toluene-film rupture induced by a DC electric field. Two ensembles-NVT and NPT-are used to determine the critical value of the external field at which the film ruptures, the charge distribution and capacitance of the thin film, number densities, and the film structure. The rupture mechanism as seen from this model is the following: in both NVT and NPT ensembles, condenser plates, where the charge density is maximal, are situated at the very border between the bulk aqueous (water) phase and the mixed layer. No ion penetration is observed within the toluene core, thus leaving all the distribution of charges within the mixed zone and the bulk phase that could be attributed to the formation of hydration shells. When the critical electric field is reached within a certain time after the field application, electric discharge occurs indicating the beginning of the rupturing process. The MD simulations indicate that the NPT ensemble predicts a value of the critical field that is closer to the experimental finding.

Influence of substrate temperature on morphology and behavior under cyclic thermal load of gas flow sputtered zirconia coatings

The aim of this work is to gain an understanding of the influence of substrate temperature during deposition on the resulting microstructure and crystallographic properties of gas flow sputtered (GFS) partially yttria stabilized zirconia coatings (PSZ).PSZ coatings were deposited on a FeCrAl-Alloy substrate, varying the substrate temperature between 500°C and 800°C. Regardless of the substrate temperature, all coatings were columnar, but varied in their morphology. Four different groups of sub-microstructures, each defined by a substrate temperature range, were identified based on morphology and X-ray diffraction (XRD) pattern.The two low-temperature groups exhibit a novel microstructure characterized by three dense ridges at intervals of 120° converging at the column center. Supported by these ridges small stacked plates lead to a featherlike porosity. The XRD pattern revealed a monoclinic fraction, besides the tetragonal and/or cubic one, and a 〈111〉 growth direction. Higher temperatures diminish the monoclinic fraction until it vanishes at 800°C accompanied by a change in growth direction to 〈100〉.Thermal cycling experiments were conducted between 1050°C and 100°C. Macroscopic spallation occurred for one group while the other samples were intact after the end of the experiment at 1300cycles. Microscopic delaminations were found between a pure alumina scale and a mixed oxide zone, consisting of zirconia particles embedded into an alumina matrix. A hypothesis was proposed explaining the observed failure mode.

Heat-Affected Zone Formation in Electrospark-Deposition Additive Manufacturing on Ultrahigh-Strength Steel

Electrospark deposition (ESD), an additive microweld-surfacing process, is typically used as a new or repair technology to enhance wear and corrosion resistance for build-up and special surface modifications. ESD employs short-duration, high-current electrical pulses that result in a fused metallurgical bond to the substrate. The pulse microsecond duration splat transfer produces micro- and nanostructures and a very narrow heat-affected zone. The limited corrosion and hydrogen-induced cracking resistance of conventional ultrahigh strength 4340 type steel, greater than 1500-MPa yield strength, led to the development of precipitation-hardened, corrosion-resistant, ultrahigh-strength steel alloys such as Custom 465 and Ferrium S53. Additive surface repair technologies of these alloys in the heat-treated condition are very limited. Preheating requirements, distortion, heat-affected zones, and post-additive heat-treatment requirements prevent surface treatments in the heat-treated condition. This paper characterizes ESD applied to ultrahigh-strength steel with respect to the heat-affected zone and the deposit–substrate mixed zone through micro- and nanohardness measurements and through microstructural and microchemical characterization. The additive alloy was Stellite 21, a cobalt-based, high-chromium alloy capable of developing high hardness and high corrosion resistance. Results show that, properly applied, the heat-affected zone width ranged from 8 to 15 μm. Microhardness analysis revealed a drop in hardness within this zone. The weld dilution zone width in the deposit is on the order of 8 to 10 μm within the first two deposit layers.

Effect of stratification on current hydrodynamics over Louisiana shelf during Hurricane Katrina

Numerical experiments were conducted using the finite volume community ocean model (FVCOM) to study the impact of the initial density stratification on simulated currents over the Louisiana shelf during Hurricane Katrina. Model results for two simulation scenarios, including an initially stratified shelf and an initially non-stratified shelf, were examined. Comparison of two simulations for two-dimensional (2D) currents, the time series of current speed, and variations of cross-shore currents across different sections showed that the smallest differences between simulated currents for these two scenarios occurred over highly mixed regions within 1 radius of maximum wind (RMW) under the hurricane. For areas farther from the mixed zone, differences increased, reaching the maximum values off Terrebonne Bay. These large discrepancies correspond to significant differences between calculated vertical eddy viscosities for the two scenarios. The differences were addressed based on the contradictory behavior of turbulence in a stratified fluid, as compared to a non-stratified fluid. Incorporation of this behavior in the Mellor-Yamada turbulent closure model established a Richardson number-based stability function that was used for estimation of the vertical eddy viscosity from the turbulent energy and macroscale. The results of this study demonstrate the necessity for inclusion of shelf stratification when circulation modeling is conducted using three-dimensional (3D) baroclinic models. To achieve high-accuracy currents, the parameters associated with the turbulence closures should be calibrated with field measurements of currents at different depths.

Peculiarities of Population Structure and Hybridization of the Genus Carassius (Cypriniformes, Cyprinidae) in Polyssia (Northern Ukraine)

Abstract Study of population structure of crucian carps in the mixed forests zone of Northern Ukraine (characterized by ample diversity of unregulated aquatic systems) showed the presence of diploid C. carassius and C. auratus, triploid C. gibelio (represented by a series of clones), C. auratus × C. carassius diploid hybrids, and tetraploid hybrids between C. carassius and C. gibelio. The crucian carps of the region compared with those of more southern zones of Ukraine are characterized by numerical prevalence of unisexual form of C. gibelio, and relatively restricted hybridization of C. carassius and C. auratus.

Turkey-Russia Relations After The Cold War Era And The Middle East Policies

Ottoman Empire- Tsarist Empire, Turkey-Soviet Union and Turkey- Russia’s politic conflict dates back past to present. Tsarist Empire or Soviet Union or Russia Federation’s goal, which is “desire to gain access to the warm waters”, in other words “Panslavizm” still continues. The ideal for them is that Turkey constituted a threat of all time. Turkey and Soviet Union’s relationship alternates between tense and cold. Turkey is allied NATO due to its self-border security. It has regarded Soviet Union as a threat and their relationship are exceedingly tense owing to politic conflict of interest. In the same way, with the world power USSR. Turkey is a threat to NATO for the World power USSR’s regional politic factors. However, the relationship between Turkey and Russia has been very improved in time. Today Russia is in the top 10 of the countries that Turkey exports. That is to say, Turkey and Russia’s political relationship are more advanced comparing with the past. Although their relations are “warmer” than the past, the two countries’ remarks does not match in the Middle East politics. These issues are North Iraq and Kurdish State, PKK and terror Issues, Turkoman, Energy Issues, and the Syria Crisis… This issues especially concern Turkey but Russia follows different politics thus this obstruct constituting ‘trust’ issue between two countries. Russia really fell down in the Soviet Union’s period of regression but it recuperates today. Old foreign affairs minister and the Middle East expert Yevgeni Primakov and ongoing period Putin government has been building “trust” and showing “stability” in a sort of way again and it works for gaining their old power today. Russia has understood that it needs to gather themselves up; by trying to get support from Muslim state for Chechen problem that leads Russia to play an active role in the Middle East and Syria Crisis. At the same time Putin government is planning arms sale which will be a significant economic resource for the mixed zone. Turkey is in the opposite of the Russia in terms of policy as it follows its own which protects its zone’s stability. Today the detrimental effects of the conflict reached its peak and there is a war in zone. Besides that, Turkey wants to take the advantage of the power and the authority vacuum in the region in order to be effective power in the zone. Because of this entire situation, Turkey and Russia conflict in terms of politics.

Diversity and Spatial-Temporal Distribution of Soil Macrofauna Communities Along Elevation in the Changbai Mountain, China.

The understanding of patterns of vertical variation and diversity of flora and fauna along elevational change has been well established over the past century. However, it is unclear whether there is an elevational distribution pattern for soil fauna. This study revealed the diversity and spatial-temporal distribution of soil macrofauna communities in different vegetation zones from forest to alpine tundra along elevation of the Changbai Mountain, China. The abundance, richness, and Shannon-Wiener diversity index of soil macrofauna communities were compared in four distinguished vegetation zones including the coniferous and broadleaved mixed forest zone, the coniferous forest zone, the subalpine dwarf birch (Betula ermanii) forest zone, and the alpine tundra zone. Soil macrofauna were extracted in May, July, and September of 2009. In each season, the abundance and richness of the soil macrofauna decreased with the ascending elevation. The Shannon-Wiener diversity indices of the soil macrofauna were higher in the vegetation zones of lower elevation than of higher elevation. Significant differences were observed in the abundance, richness, and Shannon-Wiener diversity index for the studied vegetation zones. Soil macrofauna congregated mainly to the litter layer in the low-elevation areas and in the 0-5 cm soil layer of the higher elevation areas. The results emphasized that the diversity of soil macrofauna communities decreased as the elevation increased and possess the distinct characteristics of zonation in the mountain ecosystem. The diversity and distribution of soil macrofauna communities were influenced by mean annual precipitation, altitude, annual radiation quantity, and mean annual temperature.

Ca. 820–640 Ma SIMS U-Pb age signal in the peripheral Vijayan Complex, Sri Lanka: Identifying magmatic pulses in the assembly of Gondwana

Sri Lanka comprises three roughly north-south trending amphibolite- to granulite-facies lithotectonic complexes, from west to east the Highland Complex, the Wanni Complex, and the Vijayan Complex. These terranes were correlated with other East Gondwana continental terranes with similar lithologies forming at similar ages. The Wanni Complex and the Vijayan Complex have been interpreted as volcanic arc terranes brought together by a double-sided subduction. The Highland Complex represents the metamorphosed accretionary prism within the suture when the Wanni and Vijayan Complexes were juxtaposing against each other. In contrast to the Wanni and Highland Complexes, the Vijayan Complex has yielded only a few geochronological data with satisfactory precision. Previous studies suggested that the Vijayan Complex comprises ∼1100–924Ma granitic gneisses, which were metamorphosed during ∼590–456Ma. More recently, ∼772–617Ma mafic intrusions have been identified. This study divides the Vijayan granitic gneisses and the associated melt products geochemically into a low-Nb series and a more primitive high-Nb series. Our SIMS U-Pb zircon data suggested that both series have protolith magmatic ages of ∼1062–935Ma, and metamorphic ages of ∼580–521Ma, which is consistent with previous work. However, some of the Vijayan granitic gneisses and granitic anatectic melt products at the Highland-Vijayan tectonic mixed zone preserve an additional Tonian-Cryogenian (∼820–630Ma) age signal. This age signal suggested that felsic magmatism also occurred when mafic granulites were emplaced along the Highland-Vijayan boundary, which is broadly coeval with to the bimodal magmatism occurring along the Highland-Wanni boundary. This study also suggests that charnockitisation in the Vijayan Complex occurred at 562±6Ma during the Neoproterozoic regional metamorphism. The Tonian-Cryogenian signal preserved in the Highland-Vijayan tectonic mixed zone can also be found in the alkaline intrusion hosted by the Namuno Terrane and the Lurio Belt in Mozambique. This indicates a relationship between the Vijayan granitic gneisses and the Lurio foreland metagranitic basement, while the Namuno Terrane and the Lurio Belt are correlated with the Highland-Vijayan tectonic mixed zone. The ages and the isotope signatures of these granitic bodies further suggest a genetic relationship of these granitic bodies with various magmatic intrusions in East Antarctica.

Safe Zone of Posterior Screw Insertion for Talar Neck Fractures on 3-Dimensional Reconstruction Model.

To investigate the optimal posterior screw placement and the geometry of safe zones for screw insertion in the talar neck. Computed tomography data for 15 normal feet were imported into Mimics 10.01 software for 3-dimensional reconstruction; 4.0-mm-diameter screws were simulated from the lateral tubercle of the posterior process of the talus to the talar head. The range of screw paths trajectories and screw lengths at nine locations that did not breach the cortex of the talus were evaluated. In addition, the farthest (point a) and nearest point (point b) of the safe zone to the subtalar joint at each location, the anteversion angle (angle A), which is parallel to the sagittal plane, and the horizontal angle (angle B), which is perpendicular to the sagittal plane, were measured. The safe zone was mainly between the 30% location and the 60% location; the width of each safe zone was 13.6° ± 1.4°; the maximum height of each safe zone was 7.8° ± 1.2°. The height of the safe zone was lowest at the 30% location (4.5°) and highest at the 50% location (7.3°). The mixed safe zone of all tali was between the 50% location and the 60% location. When a screw was inserted at point a, the safe entry distance (screw length) ranged from 48.8 to 49.5 mm, and when inserted to point b, the distance ranged from 48.2 to 48.9 mm. And inserting a 48.7 mm screw, 5.6° laterally and 7.4° superiorly, from the lateral tubercle of the posterior process of the talus towards the talar head is safest. The safe zone of posterior screw fixation have been defined applying to most talus, assuming the fractures are well reduced, this may strengthen the stability, shorten the operation time and reduce the incidence of surgical complications.

암반구간의 슬러리 쉴드 TBM의 버력운송 파이프 마모에 관한 연구

본 연구에서는 광산이나 오일샌드 등의 분야에서 적용되고 있는 슬러리 파이프 마모량 측정 방법과 슬러리 파이프의 마모량 예측에 관련된 이론식들을 문헌연구를 통해 살펴보고, 실제 싱가포르 슬러리 쉴드 TBM 현장에서 주기적으로 측정한 직선부 슬러리 파이프의 두께 측정 자료로부터 평균 일일 마모율과 굴착거리당 마모율을 산정하였다. Bukit Timah Granite의 풍화등급에 따른 마모율을 구하였는데, 풍화토에 가까운 G (V) 등급 지반 및 G (III)/G (V)의 복합지반에서의 마모율이 G(I)~G (IV)의 암반 등급지반에 비해서 1.5배 높게 나타났다. 슬러리 파이프 마모율은 슬러리 운송속도에 비례하여 증가하는 경향을 보였다. 향후 지반특성 별 파이프 마모율과 합리적인 관리두께 선정을 통하여 보다 최적화된 슬러리 파이프의 교체 및 회전 주기를 산정할 수 있을 것으로 판단된다. In this study, we investigated the wear measurement methods for slurry pipe applied in the field of mining and oil sand industry and theoretical equations related to the prediction of wear in slurry pipe through literature review. Average daily wear rate and wear rate per excavated distance were determined from slurry discharge pipe thickness measurement data periodically measured at the actual slurry shield TBM site in Singapore. The wear rate of slurry pipe for Bukit Timah Granite was obtained. The wear rates for G (V) grade and mixed zone were 1.5 times higher than that of G (I) to G (IV) grade. Slurry pipe wear rate tends to increase in proportion to the slurry discharge velocity. The optimal slurry pipe replacement or rotation frequency can be estimated through the selection of the pipe wear rate considering geological condition and the reasonable pipe management thickness.

Changes in Stoichiometry, Cellular RNA, and Alkaline Phosphatase Activity of Chlamydomonas in Response to Temperature and Nutrients.

Phytoplankton may respond both to elevated temperatures and reduced nutrients by changing their cellular stoichiometry and cell sizes. Since increased temperatures often cause increased thermal stratification and reduced vertical flux of nutrients into the mixed zone, it is difficult to disentangle these drivers in nature. In this study, we used a factorial design with high and low levels of phosphorus (P) and high and low temperature to assess responses in cellular stoichiometry, levels of RNA, and alkaline phosphatase activity (APA) in the chlorophyte Chlamydomonas reinhardtii. Growth rate, C:P, C:N, N:P, RNA, and APA all responded primarily to P treatment, but except for N:P and APA, also temperature contributed significantly. For RNA, the contribution from temperature was particularly strong with higher cellular levels of RNA at low temperatures, suggesting a compensatory allocation to ribosomes to maintain protein synthesis and growth. These experiments suggest that although P-limitation is the major determinant of growth rate and cellular stoichiometry, there are pronounced effects of temperature also via interaction with P. At the ecosystem level, nutrients and temperature will thus interact, but temperatures would likely exert a stronger impact on these phytoplankton traits indirectly via its force on stratification regimes and vertical nutrient fluxes.

Persistence and productivity of phalaris (Phalaris aquatica) germplasm in dry marginal rainfall environments of south-eastern Australia

Perennial grasses have production and environmental benefits in areas of southern Australia typified by the mixed farming zone of southern New South Wales (NSW). The perennial grass phalaris (Phalaris aquatica L.) is widely used in southern Australia; however, it would find more use in the mixed farming zone if its persistence in marginal rainfall areas (450–500 mm average annual rainfall) were improved. We evaluated a range of germplasm (n = 29) including wild accessions, lines bred from these, and existing cultivars for persistence and production at three sites in a summer-dry area of southern NSW with 430–460-mm average annual rainfall. Two sites were used over 4 years and the third site over 5 years. Summer dormancy, maturity time and seedling growth were also assessed. Analysis of genotype × environment interaction employing factor analytic models and accounting for spatial and temporal correlations indicated that changes in persistence occurred mainly over time rather than between sites. Ranking changes occurred in the dry establishment phase of the experiment and during a severe final summer drought, with few changes occurring in the intervening high-rainfall years. Lines that survived the establishment phase best had vigorous seedlings and earlier maturity, whereas those surviving the final summer best were earlier maturing and higher in summer dormancy with high winter-growth activity. Some later maturing lines within the higher summer dormancy group were less persistent. Some accessions from North Africa were the most persistent; also, populations bred from these and other more persistent accessions generally persisted and produced better than cultivars used presently. However, present cultivars were capable of high yield in the higher rainfall years. We suggest that persistence of higher summer dormancy cultivars over very dry years could be improved by selecting for earlier maturity time.

Modelling the comparative growth, water use and productivity of the perennial legumes, tedera (Bituminaria bituminosa var. albomarginata) and lucerne (Medicago sativa) in dryland mixed farming systems

Tedera (Bituminaria bituminosa var. albomarginata) has been proposed as an alternative perennial forage legume to lucerne in the mixed farming zone of Australia. Simulation of growth and production of tedera would be a useful tool for assessing its integration into Australian farming systems and agronomic and management options. This paper describes the development and testing of a model of the growth and development of tedera in Agricultural Production Systems Simulator (APSIM). The existing APSIM-Lucerne was modified to develop APSIM-Tedera. The key physiological parameters for tedera were obtained from the literature or by measuring and comparing the phenology and growth characteristics of tedera and lucerne in glasshouse experiments and partially from field experiments. The model was tested using data from a diverse range of soil and climatic conditions. Using the modelling approach, the production of tedera and lucerne was also assessed with long-term (1951–2015) weather data at Arthur River, Western Australia. Biomass simulations of tedera (n = 26, observed mean = 510 kg dry mass ha–1) explained 66% of the observed variation in field experiments (root mean square deviation = 212 kg dry mass ha–1). Long-term simulations of a 4-year pasture phase showed that more total annual biomass (5600 kg ha–1) would be obtained from lucerne than tedera if the pasture forage was harvested four times a year. Less biomass (400 kg ha–1) was also simulated for tedera in summer under this management. When the pasture forage was harvested when biomass was more than 2000 kg ha–1, tedera and lucerne produced similar accumulated biomass in the second (8000 kg ha–1), third (12 000 kg ha–1) and fourth (15 000 kg ha–1) years, but much less in the first 2 years for tedera. The model can be used for assessing tedera production, agronomic and management options in the Mediterranean climate of Australia. The present preliminary study indicates that tedera is not as effective as lucerne for total biomass production, but it may provide useful feed in situations where the summer-autumn feed gap is a major constraint to production. Further research is also necessary to determine the potential role of tedera in areas where lucerne is not well adapted.

Eruption and emplacement dynamics of a thick trachytic lava flow of the Sancy volcano (France)

A 70-m-thick, 2200-m-long (51 × 106 m3) trachytic lava flow unit underlies the Puy de Cliergue (Mt. Dore, France). Excellent exposure along a 400-m-long and 60- to 85-m-high section allows the flow interior to be accessed on two sides of a glacial valley that cuts through the unit. We completed an integrated morphological, structural, textural, and chemical analysis of the unit to gain insights into eruption and flow processes during emplacement of this thick silicic lava flow, so as to elucidate the chamber and flow dynamic processed that operate during the emplacement of such systems. The unit is characterized by an inverse chemical stratification, where there is primitive lava beneath the evolved lava. The interior is plug dominated with a thin basal shear zone overlying a thick basal breccia, with ramping affecting the entire flow thickness. To understand these characteristics, we propose an eruption model that first involves processes operating in the magma chamber whereby a primitive melt is injected into an evolved magma to create a mixed zone at the chamber base. The eruption triggered by this event first emplaced a trachytic dome, into which banded lava from the chamber base was injected. Subsequent endogenous dome growth led to flow down the shallow slope to the east on which the highly viscous (1012 Pa s) coulee was emplaced. The flow likely moved extremely slowly, being emplaced over a period of 4–10 years in a glacial manner, where a thick (>60-m) plug slid over a thin (5-m-thick) basal shear zone. Excellent exposure means that the Puy de Cliergue complex can be viewed as a case type location for understanding and defining the eruption and emplacement of thick, high-viscosity, silicic lava flow systems.