Middle Depths Research Articles

Radial variations in xylem sap flux in a temperate red pine plantation forest

BackgroundScaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors. Previous studies have shown that much of this uncertainty is related to (i) measurement of sapwood area and (ii) variations in sap flow at different depths within the tree sapwood.ResultsThis study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine (Pinus resinosa) trees to more accurately estimate water-use at the tree- and stand-level in a plantation forest near Lake Erie in Southern Ontario, Canada. Results showed that most of the water transport (65%) occurred in the outermost sapwood, while only 26% and 9% of water was transported in the middle and innermost depths of sapwood, respectively.ConclusionsThese results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%, which may cause large uncertainties in water budgets at the ecosystem and catchment scale. This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.

Eo‐Variscan metamorphism in the Bohemian Massif: Thermodynamic modelling and monazite geochronology of gneisses and granulites of the Góry Sowie Massif, SW Poland

AbstractIn the Variscides of central Europe, the tectonothermal history of a few units jointly assigned to the Teplá‐Barrandian/Bohemian microplate had already terminated in the Devonian. One of these is the Góry Sowie Massif (GSM; Sudetes, SW Poland), mainly consisting of variably migmatitic gneisses with subordinate granulite and peridotite inserts. The eo‐Variscan evolution of the GSM was completed in five tectonothermal stages; however, the timing and pressure–temperature (P–T) conditions of the individual stages remain unclear because isotopic ages overlap within error, and previous P–T estimates have been determined without reference to these ages. Our thermodynamic modelling and LA–ICP–MS U–Pb and electron probe microanalysis (EPMA) U–Th–total Pb monazite geochronology provide new insights into the early Variscan multistage evolution of the GSM. The new P–T–time (t) data show that granulites were metamorphosed concurrently with gneisses but at different depths and temperatures. During subduction of Saxothuringia beneath Teplá‐Barrandia at 395–390 Ma, the granulites of crustal provenance experienced high‐P–high‐T conditions (740–750°C, 17–18 kbar) and came in contact with the overlying mantle. Slab break‐off gave rise to decompression from conditions of ~17 kbar/840°C to 11–12 kbar/850–860°C, which continued at 380–370 Ma when the granulites were sheared off and extruded as tectonic slices to lower–middle crustal depths, where gneisses were undergoing metamorphism and migmatization under amphibolite facies conditions. In the gneisses, the oldest monazite date of c. 390 Ma constrains the age of the early tectonometamorphic event D1. Two subsequent events (D2 and D3, sillimanite grade) occurred under conditions of 660–680°C and 5–9 kbar at 380–375 Ma, when, in various parts of the future massif, the gneisses were (re)folded and migmatized due to heat arising from underplated mantle. Isostatic exhumation was accompanied by pegmatite intrusions (D4) at 370 Ma and subsequent orogenic collapse (D5). Concurrently, high temperature conditions (~700°C) promoted a disturbance of the U–Pb system in monazite in some granulites.

Altitudinal Variation in Soil Properties with Reference to Forest Structure and Composition in Western Himalaya

The present study was carried out to determine the soil physical properties in relation to the forest structure and composition at different altitudes in Western Himalaya. The composite soil samples were obtained from three (viz. upper, middle and lower) depths. The average sand, silt and clay contents ranged between 62.87 to 79.19%; 2.09 to 5.82% and 17.58 to 31.20% respectively. The soils in the study area did not show much variation as far as the texture is concerned and only two textural classes (sandy clay loam and/or sandy loam) were found throughout the study area. The regression analysis indicated a decline in percentage of silt (r = - 0.71, P = 0.08) and clay (r = -0.67, P = 0.122) with altitude and a significant positive relationship between altitude and percentage of sand (r = 0.790, P = 0.05). Soil moisture showed significant positive correlations with community parameters like diversity of species (r = 0.961, P < 0.01); density of trees (r = 0.903, P < 0.01); TBC of trees (r = 0.786, P < 0.05); species richness (r = 0.971, P < 0.01) and canopy cover (r = 0.883, P < 0.05). Water holding capacity also exhibited similar correlations.

Simulation Analysis of CO2-EOR Process and Feasibility of CO2 Storage during EOR

In this study, oil production and retention were observed and compared in 72 reservoir simulation cases, after which an economic analysis for various CO2 and oil prices was performed. Reservoir simulation cases comprise different combinations of water alternating gas (WAG) ratios, permeabilities, and well distances. These models were set at three different depths; thus different pressure and temperature conditions, to see the impact of miscibility on oil production and CO2 sequestration. Those reservoir conditions affect oil production and CO2 retention differently. The retention trend dependence on depth was not monotonic—optimal retention relative to the amount of injected CO2 could be achieved at middle depths and mediocre permeability as well. Results reflecting different reservoir conditions and injection strategies are shown, and analysis including the utilization factor and the net present value was conducted to examine the feasibility of different scenarios. The analysis presented in this paper can serve as a guideline for multiparameter analysis and optimization of CO2-enhanced oil recovery (EOR) with a WAG injection strategy.

Upper crustal shear wave velocity and radial anisotropy beneath Jeju Island volcanoes from ambient noise tomography

SUMMARYJeju Island offshore of the southern Korean Peninsula is an isolated intraplate volcano formed by multiple basaltic eruptions from the Pleistocene (∼1.8 Ma) to the Holocene (∼3.7 ka). Due to the lack of available seismic data, magma structures at upper crustal depths of the island have not been clearly revealed. In this study, we imaged upper crustal isotropic and radial anisotropic structures beneath the island using ambient noise data from a temporary seismic network. A series of transdimensional hierarchical Bayesian inversions were performed to construct upper crustal (1–10 km) isotropic and anisotropic structures. Surface wave (Rayleigh and Love wave) group and phase velocity dispersion data were jointly inverted for 2–15 s. The results show that layers of negative anisotropy (VSH < VSV) are predominant at shallower (<2 km) and deeper (>5 km) depths, which was interpreted as reflecting dyke swarms responsible for the more than 400 cinder cones at the surface and the vertical plumbing systems supplying magma from deeper sources, respectively. Additionally, a layer with significantly positive radial anisotropy (VSH > VSV, up to 5 per cent) was found at middle depths (2–5 km), and was interpreted as horizontally aligned magma plumbing systems (e.g. sills) through comparisons with several other volcanoes worldwide. In comparison with the isotropic structure, the positive anisotropic layer was separated into upper and lower layers with locally neutral to slightly fast and slower shear wave velocities, respectively, beneath the largest central crater (Mt Halla). Such a structure indicates that the cooled upper part of the magma plumbing systems formed within the horizontally developed sill complex, and is underlain by still-warm sill structures, potentially with a small fraction of melting. With dykes predominant above and below, the island-wide sill layer and locally high-temperature body at the centre explain the evolution of the Jeju Island volcanoes by island-forming surface lava flows and central volcanic eruptions before and after the eruptions of cinder cones.

Ultra-high field fMRI reveals origins of feedforward and feedback activity within laminae of human ocular dominance columns

Ultra-high field MRI can functionally image the cerebral cortex of human subjects at the submillimeter scale of cortical columns and laminae. Here, we investigate both in concert, by imaging ocular dominance columns (ODCs) in primary visual cortex (V1) across different cortical depths. We ensured that putative ODC patterns in V1 (a) are stable across runs, sessions, and scanners located in different continents, (b) have a width (~1.3 mm) expected from post-mortem and animal work and (c) are absent at the retinotopic location of the blind spot. We then dissociated the effects of bottom-up thalamo-cortical input and attentional feedback processes on activity in V1 across cortical depth. Importantly, the separation of bottom-up information flows into ODCs allowed us to validly compare attentional conditions while keeping the stimulus identical throughout the experiment. We find that, when correcting for draining vein effects and using both model-based and model-free approaches, the effect of monocular stimulation is largest at deep and middle cortical depths. Conversely, spatial attention influences BOLD activity exclusively near the pial surface. Our findings show that simultaneous interrogation of columnar and laminar dimensions of the cortical fold can dissociate thalamocortical inputs from top-down processing, and allow the investigation of their interactions without any stimulus manipulation.

Analysis of the difference in depths and variation in slope steepness of the Sunda Trench, Indonesia, east Indian Ocean

The paper discusses geomorphology of the Sunda Trench, an oceanic trench located in eastern Indian Ocean along the Sumatra and Java Islands of the Indonesian archipelago. In particular, it analysis the difference in depths and variation in slope steepness between the two segments of the trench: the southern Java transect (coordinates 108.8°E 10.10°S to 113.0°E 10.75°S) and the northern Sumatra transect (97.5°E 1.1°S to 101.0°E 5.5°S). The thematic maps and geomorphological modelling were plotted using Generic Mapping Tools (GMT). The materials include high-resolution data on topography, geology and geophysics: GEBCO 15 arc-minute resolution grid, EGM2008 2.5 minute Earth Gravitation Model of 2008, GlobSed global 5‐arc‐minute total sediment thickness and vector geological datasets. In addition to the GEBCO-based bathymetric data, geological, topographic and geophysical maps, the results include enlarged transects for the Java and Sumatra segments, their slope gradients and cross-section profiles, derived from the bathymetric GEBCO dataset. The geomorphology framework of the Sunda Trench is largely controlled by the subduction of the Australian plate underneath the Sunda microplate. The geological processes take place in basin of the Indian Ocean at different stages of its evolution and influence the nature of the submarine geomorphology and geometric shape of the trench. Sunda Trench is seismically active part of the Pacific Ring of Fire. A large number of the catastrophic earthquakes are recorded around the trench. The histograms shows variation in depths along the segments of the Sumatra and Java. The Java segment has a bell-shaped data distribution in contrast to the Sumatra with bimodal pattern. The Java segment has the most repetitive depths at -2,500 to -5,200 m. The Sumatra transect has two peaks: 1) a classic bell-shaped peak at depths -4,500 m to -5,500 m; 2) shelf area with a peak from 0 to -1,750 m. The data at middle depths (-1,750 to -4,500 m) have a frequency <300 samples. The most frequent bathymetry for the Sumatra segment corresponds to the -4,750 m to -5,000 m (2,151 samples). Comparing to the Sumatra segment, the Java segment is deeper. For the depths >-6,000 m, there are only 138 samples for the Sumatra while 547 samples for Java. Furthermore, Java segment has more symmetrical geometric shape while Sumatra segment is asymmetric, one-sided. The Sumatra segment has a steepness of 57.86° on its eastern side (facing Sumatra Island) and a contrasting 14.58° on the western part. The Java segment has a steepness of 64.34° on its northern side (facing Java Island) and 24.95° on the southern part (facing Indian Ocean). The paper contributes to the studies of the submarine geomorphology in Indonesia.

Optimal processing sequence and method combination of linear resampling and spectral shaping in swept-source optical coherence tomography

There are many methods employed for the linear resampling and spectral shaping, the most important and complex signal processing procedures in swept-source optical coherence tomography. In this study, commonly used 4 interpolation methods (IMs) and 4 shaping methods (SMs) were used as an example to study the processing sequences (PSs) and method combinations of the two procedures. The acquired interference spectra at different optical path-length differences, corresponding to the shallow, middle, and deep depths in sample, were processed with all the combinations of the IMs and SMs with the current (the resampling followed by the shaping) and exchanged (the shaping followed by the resampling) PSs, respectively. The amplitude, signal-to-noise ratio, and full width at half maximum of axial point spread function, were used for performance evaluation. The exchanged PS was verified to be also correct and had improved performance compared with the current PS. The found optimal method combination with the exchanged PS can improve the performance compared with the current methods, especially for middle and deep regions.

Evolution of the Southwest Australian Rifted Continental Margin During Breakup of East Gondwana: Results From International Ocean Discovery Program Expedition 369

AbstractInternational Ocean Discovery Program Expedition 369 drilled four sites on the southwestern Australian continental margin, in the deep water Mentelle Basin (MB) and on the neighboring Naturaliste Plateau (NP). The drillsites are located on continental crust that continued rifting after seafloor spreading began further north on the Perth Abyssal Plain (PAP) between magnetochrons M11r and M11n (133–132 Ma), ending when spreading began west of the NP between chrons M5n and M3n (126–124 Ma). Drilling recovered the first in situ samples of basalt flows overlying the breakup unconformity on the NP, establishing a magnetostratigraphically constrained eruption age of >131–133 Ma, and confirming a minimal late Valanginian age for the breakup unconformity (coeval with the onset of PAP seafloor spreading). Petrogenetic modeling indicates the basalts were generated by 25% melting at 1.5 GPa and a potential temperature of 1380°C–1410°C, consistent with proximity of the Kerguelen plume during breakup. Benthic foraminiferal fossils indicate that the NP remained at upper bathyal or shallower depths during the last 6 Myr of rifting and for 3–5 Myr after breakup between India and Australia. The limited subsidence is attributed to heat from the nearby Kerguelen plume and PAP spreading ridge. The margin subsided to middle bathyal depths by Albian time and to lower bathyal (NP) or greater (MB) depths by late Paleogene time. Periods of rapid sedimentation accompanied a westward jump of the PAP spreading ridge (108 Ma), rifting on the southern margin (100–84 Ma), and opening of the southern seaway between Australia and Antarctica (60–47 Ma).

Early Cambrian multiple-sourced plutonism in the Eastern Sierras Pampeanas, Córdoba, Argentina: Implications for the evolution of the early Paleozoic Gondwana margin

Four major igneous suites with different geochemical characteristics are identified in the accretionary complex of the Pampean orogeny from the southern Sierras de Córdoba, Argentina. Crystallization ages of gabbroic and trondhjemitic plutonic rocks are Early to Middle Cambrian. The plutonic suites include mafic to intermediate alkaline OIB-like rocks, mafic tholeiitic N-MORB rocks, transitional mafic rocks, and minor trondhjemitic rocks with adakitic geochemical signature. The multiple igneous suites are spatially and temporally related to what reveals simultaneous tapping of distinct source reservoirs with their respective melts remaining distinctive from extraction to emplacement at middle crustal depths. The alkaline mafic-intermediate rocks with OIB-like geochemistry were generated by the partial melting of an enriched or metasomatized mantle source. By contrast, tholeiitic mafic rocks with N-MORB geochemical signature came out from a depleted mantle source. Trace element abundances of the transitional mafic magmas reflect variable mixtures between OIB-like and MORB-type magmas. Trondhjemitic rocks exhibit geochemical features highlighting their parent melts formed by low degree melting of a metasomatized subducting oceanic crust. The most reliable setting to generate all these diverse magmatic suites at the same time is a convergent margin where the opening of a slab window followed ridge-trench interaction. A corollary is that widespread mafic magmatism enhanced heat advection and gave rise to extensive intra-crustal anatexis in an accretionary complex of crustal extension.

Effect of cyclic jacking on sand-pile interface shear behaviour

Pile jacking is a kind of competitive method for pile installation due to its less noise and vibration pollution. In this paper, the pile jacking process has been numerically simulated by considering the friction fatigue, and the characteristics of sand-pile interface shear paths at different depths were thoroughly investigated. It is found that during the cyclic jacking process, the interface shear path at a specified depth tends to transform from one-way shear to two-way shear, especially for the shallow to middle depth. But for the deep soil layer, one-way cyclic shear is still the dominated loading mode. Focusing the effects of different paths on the sand-pile interface shear behaviours, a series of cyclic interface shear tests have been conducted, in which two types of sands and four typical shear paths were adopted. It has been revealed that during continuous jacking process, the sample volume response changes significantly with different interface shear paths. The previous shear path also plays a key role in the cyclic degradation of interface strength with CNS (constant normal stiffness) condition. If the sample contraction is small during jacking process, the cyclic degradation of interface strength is obvious. But, when the sample contraction during jacking process is significant, the interface strength degradation is largely suppressed. This is mainly because the abundant broken fine particles along the pile shaft will fill into the voids and make the sand sample near the interface much denser. It is shown that the changes of pile-soil interface characteristics will affect the pile responses.

Validation of a turbulence numerical 3D model for an open channel with strong tidal currents

Abstract Turbulence characteristics of tidal currents, essential to predict the performance of tidal stream energy converters, present a significant spatial and temporal variability. Spatial fluctuations can occur within an area of the order of m2, mainly due to the geomorphologic characteristics of the area. Temporally due to ebb-flood asymmetries and also the effect of meteorological agents such as wind and waves, especially at shallower depths. This paper introduces an FVCOM (Finite Volume Community Ocean Model) numerical model validated with current velocity and turbulent kinetic energy data from three measuring devices installed in the Tanoura and Naru Straits (Goto Islands), one of them covering different vertical layers of the water column, confirming its capacity to estimate turbulence conditions at various depths when these are mostly generated by tidal currents. Correlation coefficients obtained under these conditions at the three locations are higher than 0.84 and 0.8 for current velocity and turbulent kinetic energy, respectively. Results from the validated model show that at deeper layers, TKE is primarily determined by the bathymetry characteristics of the area, while for middle and shallower depths the coastline shape is more important.

Layer-dependent multiplicative effects of spatial attention on contrast responses in human early visual cortex.

Attention mechanisms at different cortical layers of human visual cortex remain poorly understood. Using submillimeter-resolution fMRI at 7 Tesla, we investigated the effects of top-down spatial attention on the contrast responses across different cortical depths in human early visual cortex. Gradient echo (GE) T2* weighted BOLD signal showed an additive effect of attention on contrast responses across cortical depths. Compared to the middle cortical depth, attention modulation was stronger in the superficial and deep depths of V1, and also stronger in the superficial depth of V2 and V3. Using ultra-high resolution (0.3 mm in-plane) balanced steady-state free precession (bSSFP) fMRI, a multiplicative scaling effect of attention was found in the superficial and deep layers, but not in the middle layer of V1. Attention modulation of low contrast response was strongest in the middle cortical depths, indicating baseline enhancement or contrast gain of attention modulation on feedforward input. Finally, the additive vs. scaling effect of attention from GE-EPI and bSSFP signals can be explained by stronger nonlinearity of BOLD signals from large than small blood vessels, suggesting multiplicative effect of attention on neural activity. These findings support that top-down spatial attention mainly operates through feedback connections from higher order cortical areas, and a distinct mechanism of attention may also be associated with feedforward input through subcortical pathway.

3D facial morphometry in Italian patients affected by Aicardi syndrome

Aicardi syndrome (AIC) is a rare congenital neurodevelopmental disorder of unknown etiology, that affects almost exclusively females, originally characterized by corpus callosum agenesis, chorioretinal lacunae, and infantile spasms. The current diagnostic criteria also include qualitative facial features (prominent premaxilla, upturned nasal tip, decreased nasal bridge angle, sparse lateral eyebrows, and microphthalmia) that still need quantification. A three-dimensional (3D) photogrammetric assessment of 11 Italian females, age 7-32 years, who satisfied AIC criteria, was performed. Linear distances and angles were computed from soft-tissue facial landmarks coordinates. The z-score values were calculated using data of 850 healthy reference females matched for age and compared by Mann-Whitney test (p < .01). Patients showed a shorter philtrum and right side orbital height (mean z-scores: -1.7, -0.9), shorter superior, middle, and inferior facial depths (mean z-scores: -1.3, -2.2, -2.3), and a smaller length of mandibular ramus (mean z-score: -2.1); conversely, they showed larger nasal and lower facial widths, and lower facial convexity (mean z-scores: 1.7, 1.4, 2.4). The inclinations of the orbit versus the true horizontal were increased bilaterally (mean z-scores: 1.8, 1.1). Some common facial abnormalities were quantified in AIC patients using a noninvasive instrument. They may help clinicians in performing a definite AIC diagnosis in atypical or doubt cases.

Growth, Gut Morphology and Microflora of African Catfish Clarias gariepinus Fed Mushroom (Pleurotus pulmonarius) Stalk Meal Supplemented Diets

Abstract Effects of dietary supplementation of Pleurotus pulmonarius stalk meal on growth, gut microflora and intestinal morphology of Clarias gariepinus were assessed in this study. The stalk meal was incorporated at 0.0 g/100 g (Control), 2.5 g/100 g (PSM 2), 5.0 g/100 g (PSM 3), 7.5 g/100 g (PSM 4) and 10.0 g/100 g (PSM 5). Clarias gariepinus (n=375), with an initial weight of 10.84±0.04 g, were allotted at 25 fish/60 litres of water in a completely randomised design for each diet treatment in triplicate. Feeding trial was conducted for eight weeks. Weight gain, specific growth rate, survival rate, feed intake and feed conversion ratio were not significantly different across all diet treatments. However, the production performance index of the fish and protein efficiency ratio were higher in fish fed PSM 3 diet than other treatments. Total viable bacteria count in the gut ranged from 7.56 (PSM 2) to 8.34 log10 cfu/g (PSM 4), while lactic acid bacteria count was between 5.00 (control) and 7.03 log10 cfu/g (PSM 3). Escherichia coli were identified in the gut of the control group but were not detected in those fed supplemented diets. More colonies of Salmonella and Vibrio species were observed in the control but fewer colonies in the diets supplemented groups. The proximal, middle and distal villus length, proximal, middle and distal cryptal depth, proximal and distal absorption area of fish fed supplemented diet were higher than those of the control. Conversely, proximal, middle and distal villus width and middle absorption area were not significantly different. In spite of observable favourable gut microflora and gut histomorphology of fish fed supplemental P. pulmonarius stalk meal diet, these attributes did not manifest in growth performance indices.

Spatial-temporal Distribution of Nutrients in Hanfeng Lake After Official Operation

The hydrograph of Hanfeng Lake, which is the largest pre-dam of theThree Gorges Reservoir, varied between the fluvial stage and lake stage after the lake was officially operated, resulting in large shifts in the aquatic biogeochemical processes. To explore the spatial-temporal distribution of nitrogen and phosphorus concentrations and identify their influencing factors in Hanfeng Lake, seven sampling sites were set up to monitor the changes of nutrients and other water indicators at different water depths monthly from January to December 2018. The results showed that completely vertical mixing across water profiles was observed. The nutrient concentrations were not significantly different between the top, middle, and bottom water depths (P>0.05). Total nitrogen concentration decreased from January to September but gradually increased from October to December, with a monthly average concentration of 1.52 mg·L-1. NO2--N concentration decreased in the first four months, increased sharply from May to June, and decreased from July to December with a monthly average concentration of 0.05 mg·L-1. NO3--N concentration gradually decreased from January to June, and gradually increased from July to December. NH4+-N concentration was the highest in July, with a concentration of 0.44 mg·L-1, and the change in other months was not notable, with a monthly average concentration of 0.09 mg·L-1. The concentrations of total phosphorus (TP), dissolved phosphorus, and soluble reactive phosphorus showed insignificant changes in trends throughout the year, with monthly average concentrations of 0.17 mg·L-1, 0.11 mg·L-1, and 0.05 mg·L-1, respectively. The phosphate concentration was mainly sourced from the upstream Nan River and Taoxi River, and gradually decreased from upper Zhendong to the downstream regulating dam. Of these nutrients, TP was the key factor in the growth of algae in Hanfeng Lake.

Wave motion over stratified porous absorber combined with seaward vertical barrier

The oblique wave reflection by horizontally stratified porous absorber having two horizontal porous bars of different porosities and friction factors placed on step-type bottom is studied using eigenfunction expansion method based on linearised wave theory. The present study examines several structural configurations such as porous absorber consisting of finite and semi-infinite thickness with/without seaward vertical barrier. The present study derived the direct analytical relations to determine wave reflection by each of the structural configuration for plane-wave assumption using potential flow theory. Initially, the porous absorber considering uniform porosity and friction factor is examined and validated with available numerical results, and the direct analytical relations are also validated with available relations of possible structural configurations. In addition, the present study reported wave reflection performance of submerged single-layer and double-layer porous absorbers with/without seaward vertical barrier. The effect of bottom rigid bar, surface porous bar, middle porous bar depth, multiple porosities, friction factors, incident wave angle and porous effect parameter on wave reflection coefficient is presented in detail for various structural configurations. The significance of seaward vertical barrier on wave reflection and wave trapping is reported. The point of wave trapping, critical angle of impinging, resonating peaks and troughs due to various structural configurations are presented against structural thickness.

The influence of depth and season on the benthic communities of a Macrocystis pyrifera forest in the Falkland Islands

Information on the ecology of invertebrate communities populating Macrocystis pyrifera forests in the Falkland Islands is scarce. Indeed, the factors influencing diversity, distribution and community structure have never been studied here. Benthic photoquadrats were collected along three permanent 20 m transects at three depth strata (shallow 5–10 m; middle 10–15 m; deep 15–20 m) off the coast of Kidney Island, Falkland Islands from Austral summer 2009 to Austral spring 2010. 146 taxa comprising 10 phyla and 21 classes were recorded during the surveys, with the most abundant sessile and vagile taxa being Spirorbinid worms and the hermit crab Pagurus comptus, respectively. Community structure was influenced by depth, with highest species richness in the middle depth stratum, and strong contrasts between the communities in the shallow and deep depth strata. Influence of season on community structure was evident, though not as strong a factor as depth. Spring and summer months were most species rich, demonstrating a difference between the shallow subtidal regions of Patagonia where species richness was reported to be highest in Austral autumn and winter. The effect of substrate and depth was also investigated for the abundance of individual taxa. This study provides the first description of the fauna and flora of shallow rocky reefs in the Falkland Islands, describing how these communities change over small spatial and temporal scales. The outcomes of this investigation contribute to better understanding ecological patterns of the Falklands shallow benthic environments and adds knowledge to the biogeography of the South Atlantic.

Potential risk and source distribution of groundwater contamination by mercury in district Swabi, Pakistan: Application of multivariate study

This study identified mercury (Hg) concentration in groundwater of District Swabi, Pakistan. The objective of the study was to find geochemistry, health risk and source distribution pattern. Therefore, groundwater (n = 38) were collected from three hydrological environments, viz. shallower (10–20) m, middle depth (25–45) m and deeper depth (50–90) m aquifers. The water samples were tested for Hg, and results showed in the form of lowest concentration (0.16 µg/L) and highest concentration (2.0 µg/L) were recorded in deeper and shallower aquifers. Thus, shallower aquifer has been more contaminated than deeper aquifer. Most groundwater samples (68.4%) exceeded the guidelines of Hg (1.0 µg/L) recommended by WHO. The results of Hg exceeded WHO recommended level of 1.0 µg/L. Similarly, the PLI and GRQ also showed moderate pollution of Hg in the groundwater samples. The study showed that the inhabitants of the area may be exposed to several health problems. The GRQ technique revealed that the drinking groundwater sources with relatively high concentration of Hg are extremely unfit for drinking purposes.

A technique for spatial resolution improvement in helium-beam radiography.

Ion-beam radiography exhibits a significantly lower spatial resolution (SR) compared to x-ray radiography. This is mostly due the multiple Coulomb scattering (MCS) that the ions undergo in the imaged object. In this work, a novel technique to improve the spatial resolution in helium-beam radiography was developed. Increasing helium-beam energies were exploited in order to decrease the MCS, and therefore increase the SR. The experimental investigation was carried out with a dedicated ion-tracking imaging system fully composed of thin, pixelated silicon detectors (Timepix). Four helium beams with increasing energies (from 168.8 to 220.5MeV/u) were used to image a homogeneous 160mm PMMA phantom with a 2mm air gap at middle depth. An energy degrader (ED) was placed between the rear tracking system and the energy-deposition detector to compensate for the longer range associated with more energetic ions. The SR was measured for each beam energy. To take into account the overall impact on the image quality, the contrast-to-noise ratio (CNR), the single-ion water equivalent thickness (WET) precision and the absorbed dose in the phantom were also evaluated as a function of the initial beam energy. FLUKA Monte Carlo simulations were used to support the conceptual design of the experimental setup and for dose estimation. In the investigated energy interval, a total SR increase by around 30% was measured with increasing beam energy, reaching a maximum value of 0.69lp/mm. For radiographs generated with 350μGy of absorbed dose and 220μm pixel size, a CNR decrease of 32% was found as the beam energy increases. For 1mm pixel size, the CNR decreases only by 22%. The CNR of the images was always above 6. The single-ion WET precision was found to be in a range between 1.2% and 1.5%. We have experimentally shown and quantified the possibility of improving SR in helium-beam radiography by using increasing beam energies in combination with an ED. A significant SR increase was measured with an acceptable decrease of CNR. Furthermore, we have shown that an ED can be a valuable tool to exploit increasing beam energies to generate energy-deposition radiographs.