Gray Layer Research Articles

Wetland geomorphology and paleoecology near Akab Muclil, Rio Bravo floodplain of the Belize coastal plain

To understand wetland geomorphology and paleoecology, we collected a 2.6 m sediment core from a flooded swamp adjacent to the Maya archaeological site of Akab Muclil in the Maya Lowlands of northwestern Belize. The site of Akab Muclil has a known occupation that persisted from Early Maya Classic (1700–1350 BP) through the Terminal Maya Classic (1180–1050 BP) and into the Postclassic (1050–450 BP) and lies near a vast network of ancient Maya canal and field systems. We analyzed this core using a combination of paleoecological and geochemical techniques to determine the history of land use and natural change over time within this wetland. Accelerator Mass Spectrometry dating, pollen, charcoal analysis, micropaleontology, geochemical analysis, and magnetic susceptibility provide a suite of methods from which we interpret the geomorphic and ecological history of this wetland system. Four AMS dates from the length of the core provide us with an age model that runs from 1675 cal BP through the Maya Classic onward to the present. At the base of this system, soil composition and chemistry provide evidence that the system changed from a seasonally wet terrestrial soil to a perennially wet swamp, as the basal Mollisol soil lies buried by peats and calcareous sediments. This shift to a perennial wetland could be related to ancient Maya water management or a natural geomorphic change, though we suspect the former because of nearby ancient Maya large-scale geomorphic and hydrological manipulation in the form of intensive canalization and agriculture. Evidence of ancient Maya uses and impacts, including sedimentation, Zea mays pollen, and high charcoal counts occur from the lowest levels of the sequence through the Classic and into the Postclassic period. Above this level, the strata change to stable peats, laminated deposits of light gray/dark gray gypsum, authigenic carbonate, and layers of fibrist peat, with little evidence of human impact until recent increases in charcoal and phosphorous. This study, compared with other regional studies, indicates a later transition from terrestrial to wetland, later human impacts in the Postclassic, and a geomorphic impact record closely tied to the history of the adjacent site rather than broader land use trends.

Subsurface mapping and geochemical investigation of a marble deposit around Igarra, Southwestern Nigeria

Subsurface mapping of a marble deposit around Igarra and geochemical analysis of seven marble samples collected at different depths in four drill holes were carried out with the aim of determining the chemical compositions and economic viabilities of the deposit. Subsurface mapping and lithologic description revealed that snow-white and grey to dark grey marble layers occur in the four drill holes. Results of the geochemical analysis show that the CaO and MgO contents of the snow-white marble samples retrieved from depths between 10 m and 20 m (43.90-48.90 wt. % and 0.19-2.35 wt. % respectively) reflected calcitic to fairly dolomitic nature of the marble samples. This is confirmed by the high CaCO3 (91.65-95.75 wt. %) content of the samples. Grey to dark grey marble samples taken from depths between 30 m and 48 m have moderately high CaO contents (44.00-52.60 wt. %) and significantly high MgO contents (3.50-8.70 wt. %) which makes them highly dolomitic and impure. The pure, calcitic to fairly dolomitic marble is considered suitable as raw material for Portland cement production, flux in steel making and for paper production while the impure, dolomitic marble is suitable for making dimension stones and structural wares for landscaping purpose.

Complex layering of the Orange Mountain Basalt: New Jersey, USA

The Orange Mountain Basalt of New Jersey is a Mesozoic formation consisting of three units: a single lower inflated sheet lobe about 70 m thick (OMB1), a middle pillow basalt about 10 to 20 m thick (OMB2), and an upper compound pahoehoe flow about 20 to 40 m thick (OMB3). The Orange Mountain Basalt is part of the Central Atlantic Magmatic Province. Quarry and road-cut exposures of OMB1 near Paterson, New Jersey, display some unusual layering that is the focus of this study. OMB1 exposures displays the typical upper crust, core, and basal crust layers of sheet lobes but throughout the Patterson area also display distinct light gray layers of microvesicular basalt mineralized with albite directly over the basal crust and under the upper crust. The lower microvesicular layer is associated with mega-vesicular diapirs. We propose that the upper and lower microvesicular layers were composed of viscous crust that was suddenly quenched before it could devolatilize immediately before the solidification of the core. During initial cooling, the bottom of the basal layer was mineralized with high concentrations of calcite and albite during a high-temperature hydrothermal event. Subsequent albitization, as well as zeolite, prehnite, and calcite precipitation events, occurred during burial and circulation of basin brine heated by recurring Palisades magmatism below the Orange Mountain Basalt. Some of the events experienced by the Orange Mountain Basalt are unusual and place constraints on the fluid dynamics of thick flood basalt flows in general. The late penetration of vesicular diapirs through the entire thickness of the flow interior constrains its viscosity and solidification history.

In-vivo quantitative structural imaging of the human midbrain and the superior colliculus at 9.4T

We explored anatomical details of the superior colliculus (SC) by in vivo magnetic resonance imaging (MRI) at 9.4T. The high signal-to-noise ratio allowed the acquisition of high resolution, multi-modal images with voxel sizes ranging between 176 × 132 × 600 μm and (800)3μm. Quantitative mapping of the longitudinal relaxation rate R1, the effective transverse relaxation rate R2*, and the magnetic susceptibility QSM was performed in 14 healthy volunteers. The images were analyzed in native space as well as after normalization to a common brain space (MNI). The coefficient-of-variation (CoV) across subjects was evaluated in prominent regions of the midbrain, reaching the best reproducibility (CoV of 5%) in the R2* maps of the SC in MNI space, while the CoV in the QSM maps remained high regardless of brain-space. To investigate whether more complex neurobiological architectural features could be detected, depth profiles through the SC layers towards the red nucleus (RN) were evaluated at different levels of the SC along the rostro-caudal axis. This analysis revealed alterations of the quantitative MRI parameters concordant with previous post mortem histology studies of the cyto- and myeloarchitecture of the SC. In general, the R1 maps were hyperintense in areas characterized by the presence of abundant myelinated fibers, and likely enabled detection of the deep white layer VII of the SC adjacent to the periaqueductal gray. While R1 maps failed to reveal finer details, possibly due to the relatively coarse spatial sampling used for this modality, these could be recovered in R2* maps and in QSM. In the central part of the SC along its rostro-caudal axis, increased R2* values and decreased susceptibility values were observed 2 mm below the SC surface, likely reflecting the myelinated fibers in the superficial optic layer (layer III). Towards the deeper layers, a second increase in R2* was paralleled by a paramagnetic shift in QSM suggesting the presence of an iron-rich layer about 3 mm below the surface of the SC, attributed to the intermediate gray layer (IV) composed of multipolar neurons. These results dovetail observations in histological specimens and animal studies and demonstrate that high-resolution multi-modal MRI at 9.4T can reveal several microstructural features of the SC in vivo.

Implications of Color and Lightness Characteristics for Lithostratigraphy of Bottom Sediments from the Chukchi Plateau, Arctic Ocean

Marine sediment cores from the Chukchi Plateau are used to demonstrate the efficiency of digital photographic determination of sediment color and lightness, supplemented with the statistically processed data on sediment composition, for lithostratigraphy and paleoreconstructions. Several clusters were established that correspond to brown and gray sediment layers, carbonate-rich beige interlayers and specific segments of unclear lamination and/or lens-like intercalation of brownish and grayish beds. Correlation of the studied cores with other sediment cores from the region with well-established stratigraphy revealed good correspondence (though with certain specific features) to the conventional model of the Late Pleistocene–Holocene sediment accumulation in the offshore Arctic Ocean beyond shelf areas with clearly defined glacial–interglacial cyclicity. It was shown that enhanced red-color component corresponds to the enrichment of the interglacial brown sediment layers with manganese and accompanying elements. Glacial gray layers with enhanced green-color component are enriched in iron, as well as rubidium, vanadium, titanium and yttrium and bear evidence for considerable diagenetic transformations. Blue-color component is related to the high calcium content (carbonate rock fragments) in the carbonate-rich interlayers accumulated during the periods of active disintegration of continental ice sheets and iceberg-rafting of terrigenous lithic fragments. Intermediate values of the studied parameters are likely indicative of specific sedimentation environments.

Enucleation Induces Parvalbumin and Glial Fibrillary Acidic Protein, but Not Calbindin D28k Protein Expression in Superior Colliculus of Wistar Rats

Background: It is known that eye enucleation causes various morphological and functional alterations in the central nervous system (CNS). The purpose of this study was to examine the sub-chronic effects of monocular enucleation on the distribution of the calcium binding proteins calbindin D28k (CB) and parvalbumin (PV) as well as the glial fibrillary acidic protein (GFAP) immunoreactivity in the superior colliculus (SC) of Wistar rats.Materials and Methods: Thirty young adult (8 weeks) male Wistar rats from SLC (Shizuoka, Japan), weighing 200-250 grams, were housed in separate cages under controlled conditions with a constant temperature kept in 12:12 light/dark cycle and ad libitum water and food. In this study the rats were divided into two groups, a control and an enucleated groups. The experimental group received unilateral eye enucleation and was allowed 1, 4 or 12 weeks recovery before sacrificed.Results: Unilateral enucleation over a period of 1 week or more caused a decrease in the number CB-immunoreactive (CBIR) neurons. This loss was associated with an increase in GFAP-IR astrocytes in the superficial gray layer and the optic layer of the SC with contralateral side predominance. In addition, the CB-IR neurons illustrated a smaller soma and poor dendritic arborization. Conversely, the GFAP-IR astrocytes were hypertrophied with longer foot processes on the contralateral side of enucleation. Interestingly, the number of PV-IR neurons was elevated for up to 4 weeks in enucleated rats versus shamoperated rats.Conclusion: This study demonstrates the importance of calcium-binding protein homeostasis and reversible glial response for maintaining variability of neuronal function in sub-cortical visual centers following optic nerve deafferentation.Keywords: enucleation, superior colliculus, calbindin D28k, parvalbumin, glial fibrillary acidic protein

Surface-based characteristics of the cerebellar cortex visualized with ultra-high field MRI

Although having a relatively homogeneous cytoarchitectonic organization, the cerebellar cortex is a heterogeneous region characterized by different amounts of myelin, iron and protein expression profiles. In this study, we used quantitative T1 and T2* mapping at ultra-high field (7T) MRI to investigate the tissue characteristics of the cerebellar gray matter surface and its layers. Detailed subject-specific surfaces were generated at three different cortical depths and averaged across subjects to create averaged T1- and T2*-maps on the cerebellar surface. T1 surfaces showed an alternation of lower and higher T1 values when going from the median to the lateral part of the cerebellar hemispheres. In addition, longer T1 values were observed in the more superficial gray matter layers. T2*-maps showed a similar longitudinal pattern, but no change related to the cortical depths. These patterns are possibly due to variations in the level of myelination, iron and zebrin protein expression.

Cobalt(ii) liquid metal salts for high current density electrodeposition of cobalt.

Cobalt(ii)-containing ionic liquids were synthesized using N,N-dimethylformamide, N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMAc), pyridine-N-oxide (py-O), 1,10-phenanthroline (phen), ethylenediamine (en) and dimethylimidazolidinone (DMI) as ligands. The weakly coordinating bis(trifluoromethylsulfonyl)imide (Tf2N-) was used as a counter anion. Several compounds had a melting temperature below 100 °C, and the compound [Co(DMAc)6][Tf2N]2 was liquid at room temperature, with a viscosity of only 18 mPa s at 80 °C. Several compounds were recrystallized to give high quality single crystals and their crystal structures were determined. EXAFS measurements were performed on [Co(DMAc)6][Tf2N]2 at different temperatures and it was observed that the [Co(DMAc)6]2+ ion partially dissociated at higher temperatures, which explains the temperature-dependent color change (thermochromism). The electrochemical properties of the compounds with the lowest melting points were also investigated. Adherent, crack-free metallic cobalt layers could be electrodeposited from [Co(DMAc)6][Tf2N]2, [Co(DMI)6][Tf2N]2 and [Co(NMP)6][Tf2N]2. From the first two, black deposits consisting of micrometer-sized needles were obtained, whereas the latter resulted in a dull grey cobalt layer consisting of micrometer-sized cobalt spheres. The Co(iii)/Co(ii) redox couple was not found to occur in any compound with an O-donor ligand, but the Co(iii)/Co(ii) redox couple was found to be quasi-reversible for [Co(phen)3][Tf2N]2 dissolved in [BMP][Tf2N].

A 9000-year flood history for Southern California: A revised stratigraphy of varved sediments in Santa Barbara Basin

The center of Santa Barbara Basin (SBB) preserves annual laminations through most of the Holocene providing an important locality for high-resolution late Quaternary paleoclimate and paleoceanography reconstructions. An accurate chronology is necessary for these sediment-based records and enables comparisons with more distal data time-series of similar quality. Here we present an improved high-resolution radiocarbon chronology for the last 9000yrs. based on 89 accelerator mass spectrometric (AMS) 14C dates of mixed planktonic foraminiferal carbonate from three sediment cores collected in SBB (MV0811-14JC, SPR0901-06KC and ODP Hole 893A). Accurate core-to-core correlation is demonstrated using prominent gray flood and olive turbidite layers identified in SBB and dated in multiple cores. Gray layer deposits were found more frequently in wetter intervals as determined by multi-proxy hydroclimate records in Southern California (e.g., lake deposits and tree rings). Mass accumulation rates (MARs) calculated for the SBB depocenter using the improved radiocarbon age model indicate high MARs are associated with these gray layers that have been associated with floods. Thus sediment accumulation in SBB is largely controlled by sediment delivery via river runoff following precipitation events although MARs may also be influenced by other factors that enhance erosion in river catchments. Folded sediment is observed within the basal core section of MV0811-14JC which stratigraphically correlates with 14C age reversals in ODP Hole 893A. We associate this sediment slump feature with the large Goleta submarine slide complex in Santa Barbara Channel and estimate the submarine slide event occurred at ~ 9000±200yrs. BP. Furthermore, small olive turbidite layers identified and dated in SBB can be temporally linked with large earthquakes along San Andreas Fault and can therefore potentially reconstruct earthquake history in Southern California.

Connections between the zona incerta and superior colliculus in the monkey and squirrel.

The zona incerta contains GABAergic neurons that project to the superior colliculus in the cat and rat, suggesting that it plays a role in gaze changes. However, whether this incertal connection represents a general mammalian pattern remains to be determined. We used neuronal tracers to examine the zona incerta connections with the midbrain tectum in the gray squirrel and macaque monkey. Collicular injections in both species revealed that most incertotectal neurons lay in the ventral layer, but anterogradely labeled tectoincertal terminals were found in both the dorsal and ventral layers. In the monkey, injections of the pretectum also produced retrograde labeling, but mainly in the dorsal layer. The dendritic fields of incertotectal and incertopretectal cells were generally contained within the layer inhabited by their somata. The macaque, but not the squirrel, zona incerta extended dorsolaterally, within the external medullary lamina. Zona incerta injections produced retrogradely labeled neurons in the superior colliculus of both species. In the squirrel, most cells inhabited the lower sublamina of the intermediate gray layer, but in the monkey, they were scattered throughout the deeper layers. Labeled cells were present among the pretectal nuclei in both species. Labeled terminals were concentrated in the lower sublamina of the intermediate gray layer of both species, but were dispersed among the pretectal nuclei. In summary, an incertal projection that is concentrated on the collicular motor output layers and that originates in the ventral layer of the ipsilateral zona incerta is a common mammalian feature, suggesting an important role in collicular function.

Structural and optical properties of electrochemically etched p+-type GaAs surfaces: influence of HF presence in the etching electrolyte

Porous GaAs layers have been prepared by electrochemical etching of p +-type GaAs (10 0) surfaces in two different solutions; HCl: H2O2: H2O (HF free electrolyte) and HCl: H2O2: H2O: HF: C2H5OH (HF electrolyte). Under the same equivalent etching condition, naked eyes observations reveal the formation of a white color layer on the top of the sample formed in the HF electrolyte, while the sample in the HF free electrolyte exhibited the ordinary gray color layer of porous GaAs. Scanning electron microscope (SEM) observation revealed the impact of presence of HF in the electrolyte on surface topography of the layer. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and micro-Raman scattering investigations demonstrate that the use of HF electrolyte leads to formation of GaF3 *3H2O and enhances the formation of As2O3 (arsenolite) in the layer. This is found to result in a remarkable improvement in the intensity of the room temperature photoluminescence (PL). The intensity of “green” PL band of the layer formed in the HF electrolyte is found to be about 40 times higher than that formed in the HF free electrolyte.

Effect of dietary supplementation of organic or inorganic zinc on carbonic anhydrase activity in eggshell formation and quality of aged laying hens

This study evaluated the effects of different dietary levels and sources of zinc (Zn) on performance and carbonic anhydrase (CA) activity in eggshell formation and quality in aged laying hens. A total of 504 Hy-line Grey layers aged 59 wk were fed a basal diet (Zn, 28.4 mg/kg) for 4 wks, then randomly allocated to 7 groups that were fed a basal diet or a basal diet supplemented with inorganic (ZnSO4·H2 O) or organic (amino acid metals, 9.58%) Zn at 35, 70, or 140 mg Zn per kg of feed for 6 weeks. Each group had 6 replicates of 12 hens. Results showed that egg weight decreased linearly with the supplemental level of organic Zn (P < 0.05). Dietary Zn supplementation had linear and quadratic effects on the CA activity in plasma (P < 0.05), and it was higher in the organic Zn-added groups at wks 2 and 4 (P < 0.05). Dietary Zn supplementation had a quadratic effect on the CA activity in the eggshell gland (P < 0.05). Shell thickness was greater in the organic Zn-added groups (P < 0.05), and its relationship with the supplemental level of Zn showed linearly and quadratically, increasing with the organic Zn and with the inorganic Zn at wk 4, while linearly increasing with the inorganic Zn at wk 6 (P < 0.05). At wk 4, the supplemental level of inorganic Zn had a linear effect on shell weight, and linear and quadratic effects on shell index and ratio (P < 0.05), while shell weight, the index, and ratio increased linearly and quadratically with the organic Zn level in the diet (P < 0.05), with more obvious effects in the organic Zn-added groups (P < 0.05). Overall, dietary Zn supplementation, up to 140 mg/kg feed, could increase eggshell thickness by enhancing CA activity in the plasma and eggshell gland of aged layers; thicker eggshells were found in the organic Zn-added groups, but the breaking strength did not increase despite the eggshell thickness increasing.

Transient deep-water oxygenation in the early Cambrian Nanhua Basin, South China

Many late Neoproterozoic to early Cambrian fossils of multicellular eukaryotes, including those of benthic animals, are found preserved under anoxic and even euxinic bottom-water conditions, which is contradictory to the consensus that oxygen is essential to eukaryotes. To investigate this conundrum, we conducted an integrated study of iron speciation, redox-sensitive trace elements, and Mo isotopes (δ98Mo) on the black shale interval of the lower Cambrian Hetang Formation (∼535–521Ma) at Lantian, South China, in which benthic sponge fossils are abundant in the lower member (LM) but absent in the upper member (UM). Iron speciation data point to uniformly anoxic-ferruginous conditions in the LM and euxinic conditions in the UM, whereas the trace-element and δ98Mo data show greater secular variation in redox conditions. The LM shows higher mean trace element concentrations (Mo: 108ppm, U: 36ppm, V: 791ppm) and lower and more variable δ98Mo (+0.13 to +1.76‰) relative to the UM (Mo: 45ppm, U: 18ppm, V: 265ppm, δ98Mo: +1.59 to +1.67‰), and ratios of redox-sensitive trace element concentrations to total organic carbon are significantly more variable and higher on average in the LM relative to the UM. The appearance of sponge fossils and lower δ98Mo values correlate strongly with gray (i.e., lighter-colored) layers in the LM. These patterns can best be interpreted as recording mainly euxinic conditions throughout deposition of the study units, with more intense background euxinia in the LM relative to the UM, but also with frequent transient oxygenation events in the LM that do not appear in the UM. The transient oxygenation events of the LM led to the initial colonization of the deep Nanhua Basin by sponges, and the termination of these events in the UM caused sponge faunas to disappear until a general rise in O2 levels later in the Cambrian permitted their return to deeper-water habitats. Our study also illustrates that multiple geochemical and paleobiological proxies exhibit different responses in ‘poikiloredox’ environments (i.e., characterized by small-scale spatial and high-frequency temporal variations), which can lead to apparent contradictions between metazoan fossil occurrences and their inferred watermass redox conditions.

A precise optical transmission spectrum of the inflated exoplanet WASP-52b

We have measured a precise optical transmission spectrum for WASP-52b, a highly inflated hot Jupiter with an equilibrium temperature of 1300 K. Two transits of the planet were observed spectroscopically at low resolution with the auxiliary-port camera (ACAM) on the William Herschel Telescope (WHT), covering a wide range of 4000-8750 \AA. We use a Gaussian process approach to model the correlated noise in the multi-wavelength light curves, resulting in a high precision relative transmission spectrum with errors on the order of a pressure scale height. We attempted to fit a variety of different representative model atmospheres to the transmission spectrum, but did not find a satisfactory match to the entire spectral range. For the majority of the covered wavelength range (4000-7750 \AA) the spectrum is flat, and can be explained by an optically thick and grey cloud layer at 0.1 mbar, but this is inconsistent with a slightly deeper transit at wavelengths $> 7750$ \AA. We were not able to find an obvious systematic source for this feature, so this opacity may be the result of an additional unknown absorber.

Postretinal Structure and Function in Severe Congenital Photoreceptor Blindness Caused by Mutations in the GUCY2D Gene.

PurposeTo examine how severe congenital blindness resulting from mutations of the GUCY2D gene alters brain structure and function, and to relate these findings to the notable preservation of retinal architecture in this form of Leber congenital amaurosis (LCA).MethodsSix GUCY2D-LCA patients (ages 20–46) were studied with optical coherence tomography of the retina and multimodal magnetic resonance imaging (MRI) of the brain. Measurements from this group were compared to those obtained from populations of normally sighted controls and people with congenital blindness of a variety of causes.ResultsPatients with GUCY2D-LCA had preservation of the photoreceptors, ganglion cells, and nerve fiber layer. Despite this, visual function in these patients ranged from 20/160 acuity to no light perception, and functional MRI responses to light stimulation were attenuated and restricted. This severe visual impairment was reflected in substantial thickening of the gray matter layer of area V1, accompanied by an alteration of resting-state correlations within the occipital lobe, similar to a comparison group of congenitally blind people with structural damage to the retina. In contrast to the comparison blind population, however, the GUCY2D-LCA group had preservation of the size of the optic chiasm, and the fractional anisotropy of the optic radiations as measured with diffusion tensor imaging was also normal.ConclusionsThese results identify dissociable effects of blindness upon the visual pathway. Further, the relatively intact postgeniculate white matter pathway in GUCY2D-LCA is encouraging for the prospect of recovery of visual function with gene augmentation therapy.

Compositions of foraminifera-rich turbidite sediments from the Shenhu area on the northern slope of the South China Sea: Implication for the presence of deep water bottom currents

The sediments in gravity core DH-1, collected from Shenhu area on the northern slope of the South China Sea, are composed of two dark grey clay silt layers (A1 and A3) and two foraminifera-rich layers (A2 and A4) (A1 is the top layer and A4 is the bottom layer). Major and trace metal contents, along with grain size and mineralogic data suggest that these silt layers represent background hemipelagic sedimentation. Unlike silt layers, the intervening foraminifera-rich layerA4 exhibits a fining-upward trend, is distal turbidite. Grain size CM diagram and the sharp contacts between the foraminifera-rich layer A2 and the upper and lower layers suggest layer A2 is the result of depositional interaction between turbidite and bottom currents. AMS 14C dating of planktonic foraminifera indicate the age of the turbidite in A2 is between15.3ka and 22.6ka. We hypothesize that turbidite formation in this period was related to the increase supply of terrigenous matter since the LastGlacialMaximum. The rapid deposition of each turbidite led to reduced rates of oxygen diffusion into the sediment, allowing anoxic conditions develop in sediments and fostering U enrichment (>3.1μg/g) in foraminifera-rich layer A4b. In contrast, decrease concentration of U and U/Mo ratios in foraminifera-rich layerA2, which is possibly due to U remobilization as a consequence of downward penetration of the oxidation front from the oxygen rich bottom currents. These new data suggest that authigenic U was quite sensitive to the inflow of bottom currents, and U/Mo ratios may indicate the depositional environmental change in relation to the bottom current action on the turbidite.

Neutral Molten Salt-Bath Carburizing of Ti6Al4V Alloy with Nanocrystalline Surface Layer at Low Temperature Assisted by Surface Mechanical Attrition Treatment

Nanocrystalline surface layer about 10~15μm thick was fabricated on the surface of Ti6Al4V sheet by means of the surface mechanical attrition treatment (SMAT). The average grain size was about 10nm and the grain characteristic presented equiaxed morphology. The nanocrystalline surface layer could be perfectly maintained below 550°C in the following thermal stability analysis. Neutral salt mixture was about 21% NaCl, 31% BaCl2 and 48% CaCl2 and additionally 5% Na2CO3 of total was utilized. After carburizing process, a continuous charcoal grey carburized layer was composed of TiC and carbon supersaturated solid solution, the hardening layer was about 10~15μm thick. The hardness of the outermost surface reached 1000HV, which was much higher than its coarse-grained counterpart in the same carburizing condition. The experimental result indicated that the carburizing kinetics was obviously enhanced by nanocrystalline surface layer assistance. Furthermore, the neutral molten salt-bath carburizing was verified that it could be performed in a relatively low temperature of 650°C.

A CONSISTENT RETRIEVAL ANALYSIS OF 10 HOT JUPITERS OBSERVED IN TRANSMISSION

We present a consistent optimal estimation retrieval analysis of ten hot Jupiter exoplanets, each with transmission spectral data spanning the visible to near-infrared wavelength range. Using the NEMESIS radiative transfer and retrieval tool, we calculate a range of possible atmospheric states for WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HD 189733b, HD 209458b, HAT-P-1b and HAT-P-12b. We find that the spectra of all ten planets are consistent with the presence of some atmospheric aerosol; WASP-6b, WASP-12b, WASP-17b, WASP-19b, HD 189733b and HAT-P-12b are all fit best by Rayleigh scattering aerosols, whereas WASP-31b, WASP-39b and HD 209458b are better represented by a grey cloud model. HAT-P-1b has solutions that fall into both categories. WASP-6b, HAT-P-12b, HD 189733b and WASP-12b must have aerosol extending to low atmospheric pressures (below 0.1 mbar). In general, planets with equilibrium temperatures between 1300 and 1700 K are best represented by deeper, grey cloud layers, whereas cooler or hotter planets are better fit using high Rayleigh scattering aerosol. We find little evidence for the presence of molecular absorbers other than H$_2$O. Retrieval methods can provide a consistent picture across a range of hot Jupiter atmospheres with existing data, and will be a powerful tool for the interpretation of James Webb Space Telescope observations.

Distribution patterns of contaminants in the Mogale Gold tailing dam: a case study from South Africa

This study evaluates the geochemical and mineralogical characterisation of weathering layers associated with the Mogale tailing dam in the Randfontein Cluster—Witwatersrand Basin, South Africa. In the tailing dam, it is observed that high hematite/Fe2O3 contents separate the ferruginous from the rest layers. Also, the oxidised layers with high quartz/SiO2 contents compositionally differ from the underlying (capillary zone) grey and ferruginous layers. Likewise, a combination of gypsum contents (MnO, CaO, tot S) versus pyrophyllite/muscovite (Al2O3 and K2O) distinguishes the lower grey from the upper grey layer, which corresponds to the saturated and capillary zones, respectively.Similarly, the amount of REE and most trace elements depleted in the oxidised layers is compared to the underlying layers. Factor analysis of this variation in layers related element distribution to the spatial patterns of pyrite, gypsum, hematite, and jarosite. Furthermore, analysis of the mass balance revealed an estimated net loss of between 23 and 123 ppm for uranium, zinc, nickel, and arsenic right from the inception of the tailing dam 50 years ago. A loss of between 1.5–1.8 and 2.8–2.9 % is also estimated for total sulphur and aluminium, respectively. These results underpin the sources and patterns of mobilisation of elements in the weathering zones as a major step towards the development of a predictive model for mitigation of AMD in the region.

Evaluation of Moringa oleifera leaf in laying hens: effects on laying performance, egg quality, plasma biochemistry and organ histopathological indices

This experiment was conducted to evaluate the effects of supplementary Moringa oleifera leaf (MOL) on performance, egg quality, plasma parameters and organ histopathological indices of layers. A total of 360 27-week-old Hy-Line Grey commercial layers were randomly allotted to four groups. Each group consisted of six replicates with 15 birds and 3 birds were placed in one cage. The control group was fed a corn-soybean meal based diet and the experimental groups were fed on control diet supplemented with 5%, 10% or 15% MOL (MOL5, MOL10 and MOL15 group). The experiment lasted for 8 weeks. No significant differences were observed in egg weight or feed intake among all groups (p > .05). The birds in MOL15 group had higher feed conversation ratio and lower egg production compared with those in control group (p < .05). Layers in MOL5 had a deeper yolk colour than those in control group (p < .05). The albumen height and Haugh unit increased with increasing level of MOL when eggs were stored at 4 °C and 28 °C for 4 weeks (p < .05). Layers in MOL15 group had higher aspartate aminotransferase activity and lower uric acid concentration than other groups (p < .05). Layers in MOL10 and MOL15 groups had higher malondialdehyde content than those in control group (p < .05). Supplementary MOL increased the activity of glutathione peroxidase (p < .05). In conclusion, dietary supplementation with 5% MOL could improve yolk colour value and protein absorption without adverse effects on laying performance and egg quality.