Parameters controlling the incorporation of Cu in calcite

2020 ◽  
Author(s):  
Jean-Michel Brazier ◽  
Katja Götschl ◽  
Martin Dietzel ◽  
Vasileios Mavromatis
Keyword(s):  
Growth Rate ◽  
Natural Waters ◽  
Fluid Composition ◽  
Partitioning Coefficient ◽  
Mineral Growth ◽  
Chemical Signatures ◽  
Fundamental Understanding ◽  
First Results ◽  
Ph Conditions ◽  
Co Precipitation

<p>Carbonate minerals record, through their chemical and isotopic composition, the environmental conditions occurring at the time of their formation. Thus, the incorporation of traces/impurities in CaCO<sub>3</sub> minerals calcite and aragonite, have been widely studied over the last five decades in order to provide the fundamental knowledge needed for the use of these traces in paleoenvironmental reconstructions. The processes controlling the uptake of traces in natural samples, however, are manifold and hard to distinguish from each other. Thus, experimental co-precipitation studies on synthetic material under strictly controlled abiotic conditions can provide fundamental understanding on the effect of each process involved in the chemical signatures of natural carbonates. In this study, we explore the incorporation of Cu in calcite and its potential as proxy of reactive fluid composition. This transition metal commonly occurs complexed with organic ligands in natural waters, however, it exhibits very high affinity for calcite. Our experiments were performed at pH 6.3 and 8.3, with varying growth rate ranging between 10<sup>-8.5</sup> and 10<sup>-7.6</sup> (mol/m<sup>2</sup>/s). Our first results highlight that the partitioning coefficient of Cu is positively correlated to the calcite growth rate at both pH conditions, indicating an increase of Cu entrapment at higher growth rate. These new preliminary findings could bring fundamental understanding of Cu incorporation in calcite and highlight the potential of Cu partitioning coefficient as a proxy of mineral growth rate.</p>

Controls of Li incorporation in aragonite

2020 ◽  
Author(s):  
Vasileios Mavromatis ◽  
Jean-Michel Brazier ◽  
Katja Goetschl
Keyword(s):  
Growth Rate ◽  
Experimental Studies ◽  
Chemical Properties ◽  
Elemental Ratios ◽  
Mineral Growth ◽  
Chemical Signatures ◽  
Physico Chemical ◽  
Geological Past ◽  
Temperature Proxy ◽  
Li Content

<p>The cation-to-Ca ratio in natural carbonate minerals is routinely used by the geoscientific community in order to reveal information about the conditions occurred during mineral formation in the geological past. Environmental reconstruction, however, relies on our understanding on the mechanisms controlling mineral growth but also on the physico-chemical properties of cations. In this respect experimental studies and laboratory calibrations of elemental ratios in synthetic carbonates provide important insights on the interpretation of the chemical signatures in natural samples. This holds especially truth for the chemical and isotopic signals of carbonates forming in continental environments that are characterized by the absence of bio-induced precipitation, low concentration of solutes in the forming fluid and slow growth rates (e.g. speleothems). In this study, we examine the incorporation of Li in aragonite, owing to its use as a temperature proxy and its importance in paleo-weathering reconstruction. Our preliminary results suggest that aragonite growth rate is likely the most important parameter controlling Li content in the forming phase. This finding comes in excellent agreement with the recent study by Füger et al. (2019). In addition, the experimental work suggest that temperature is also affecting the distribution of Li in aragonite but to a lesser extent than growth rate. It is anticipated that once completed this work will provide the fundamental knowledge needed for adequate interpretation of Li partitioning in aragonite and significantly improve our ability to interpret Li signatures in natural carbonates.</p><p> </p><p>References: Füger et al. 2019. Effect of growth rate and pH on lithium incorporation in calcite, Geochim. Cosmochim. Acta., 248, 14-24.</p>

scholarly journals Incompressible variable-density turbulence in an external acceleration field

2017 ◽  
Vol 827 ◽  
pp. 506-535 ◽  
Author(s):  
Ilana Gat ◽  
Georgios Matheou ◽  
Daniel Chung ◽  
Paul E. Dimotakis
Keyword(s):  
Growth Rate ◽  
Turbulent Flow ◽  
Shear Layers ◽  
Variable Density ◽  
Fluid Composition ◽  
Turbulent Regime ◽  
Low Density ◽  
Acceleration Field ◽  
Density Ratios ◽  
Mixed Fluid

Dynamics and mixing of a variable-density turbulent flow subject to an externally imposed acceleration field in the zero-Mach-number limit are studied in a series of direct numerical simulations. The flow configuration studied consists of alternating slabs of high- and low-density fluid in a triply periodic domain. Density ratios in the range of $1.05\leqslant R\equiv \unicode[STIX]{x1D70C}_{1}/\unicode[STIX]{x1D70C}_{2}\leqslant 10$ are investigated. The flow produces temporally evolving shear layers. A perpendicular density–pressure gradient is maintained in the mean as the flow evolves, with multi-scale baroclinic torques generated in the turbulent flow that ensues. For all density ratios studied, the simulations attain Reynolds numbers at the beginning of the fully developed turbulence regime. An empirical relation for the convection velocity predicts the observed entrainment-ratio and dominant mixed-fluid composition statistics. Two mixing-layer temporal evolution regimes are identified: an initial diffusion-dominated regime with a growth rate ${\sim}t^{1/2}$ followed by a turbulence-dominated regime with a growth rate ${\sim}t^{3}$. In the turbulent regime, composition probability density functions within the shear layers exhibit a slightly tilted (‘non-marching’) hump, corresponding to the most probable mole fraction. The shear layers preferentially entrain low-density fluid by volume at all density ratios, which is reflected in the mixed-fluid composition.

scholarly journals Aquaculture potential of Bohai Red and its hybrid with Agropecten irradians concentricus in southern China

2019 ◽  
Author(s):  
Gaoyou Yao ◽  
Jianqiang Li ◽  
Yuyuan Wu ◽  
Xiaoying Su ◽  
Jie Tan ◽  
...  
Keyword(s):  
Growth Rate ◽  
Natural Waters ◽  
Southern China ◽  
Fertilization Rate ◽  
Temperature Tolerance ◽  
Hatching Rate ◽  
Poor Growth ◽  
The North ◽  
High Temperature Tolerance ◽  
New Varieties

AbstractArgopecten irradians concentricus (Say), one of four geographic subspecies of the bay scallop, has become the major cultured species in southern China since its introduction in 1995. However, its population has been significantly reduced due to high mortality.Also, poor growth rate has been observed following decades of culture.Therefore, the introduction or creation of new varieties is an urgent need. This study describes the first introduction of the new strain, Bohai Red, from the north to southern China. Hybridization trials were conducted between the recently introduced new strain and the local specie, A. irradians concentricus (Say). The success of hybridization was confirmed by SSR maker.The adult and juvenile Bohai Red cannot tolerate high temperatures compared to A. irradians concentricus (Say), whether in natural waters or under laboratory conditions. Fertilization rate for A. irradians concentricus (Say) × Bohai Red exceeded 80%, and hatching rate was 70%. The hybrids exhibit heterosis in survival rate, growth rate, and high-temperature tolerance, demonstrating substantial potential to replace A. irradians concentricus (Say) in southern China.

scholarly journals Mg-Al-Cr2O7 Hydrotalcite-Like Catalysts Synthesized at Different pH Values for Styrene Oxidation

2020 ◽  
pp. 13-21
Author(s):  
Le Huy Tran ◽  
Thi Ngoc Mai Tran ◽  
Tuan Vu Anh ◽  
Pham Quoc Khanh ◽  
Thi Minh Thu Nguyen ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
Styrene Oxidation ◽  
Preparation Conditions ◽  
Physico Chemical ◽  
Ph Conditions ◽  
Dichromate Anions ◽  
Co Precipitation ◽  
Styrene Conversion

Dichromate anions were intercalated between two consecutive hydroxide layers of [Mg0.6Al0.4(OH)2]0.40+ via co-precipitation at different pH conditions. The physico-chemical properties of the obtained solids were examined by physical methods such as X-ray diffraction (XRD), Infrared (IR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and Energy-Dispersive Spectroscopy (EDS). The experimental results indicated that the amount of dichromate anions in the catalysts varies with the pH media. Also, the morphology, structure and chemical composition of the materials depends strongly on the preparation conditions. The Mg-Al-Cr2O7 hydrotalcite-like compounds are used as heterogeneous catalysts for the styrene oxidation with H2O2 at mild conditions. The styrene conversion is about 20-50% while styrene selectivity remains rather high.

scholarly journals Growth of duckweed upon exposure to aluminum and atrazine in the laboratory conditions

2018 ◽  
Vol 9 (2) ◽  
pp. 106-111
Author(s):  
Thi My Chi Vo ◽  
Minh Phap Dao ◽  
Thanh Son Dao
Keyword(s):  
Growth Rate ◽  
Aquatic Ecosystems ◽  
Natural Waters ◽  
Lemna Minor ◽  
Viet Nam ◽  
Combined Effects ◽  
Ecological Health ◽  
Negative Effects ◽  
Antagonistic Effects ◽  
Guideline Values

The trace metals and pesticides are commonly found in surface water receiving industrial and agricultural effluents. However, the potential negative effects of these compounds on aquatic ecosystems have not been deeply studied. Hence, the aim of this study is to assess the single and combined effects of aluminum (Al) and atrazine on the development and growth rate of duckweed, Lemna minor L. The single exposures were implemented with either Al or atrazine at the concentration of 5, 50 and 500 µg L-1 and a binary exposure was conducted with 50 µg L-1 of Al and 5 µg L-1 of atrazine for two weeks. The results revealed that both Al and atrazine at the concentration of 500 µg L-1 strongly inhibited the development and growth rate of the duckweed. On the contrary, the mixture of Al and atrazine showed antagonistic effects on the plant. To our knowledge, this is the first report on the combined effects of these two contaminants on the duckweed. Therefore, our results could be useful for environmental managers in setting up and adjusting the safe guideline values in Vietnam for Al and atrazine in natural waters in term of ecological health protection. Kim loại nặng và thuốc trừ sâu thường được tìm thấy trong các nguồn nước mặt, nơi tiếp nhận nước thải công nghiệp và nông nghiệp. Tuy nhiên, những ảnh hưởng tiềm tàng mang tính tiêu cực của những hợp chất này đối với hệ sinh thái thủy vực chưa được nghiên cứu đầy đủ. Do đó, mục tiêu của nghiên cứu này nhằm đánh giá những ảnh hưởng riêng lẻ và kết hợp của nhôm (Al) và atrazine lên sự phát triển và tốc độ sinh trưởng của bèo tấm, Lemma minor L. Sự phơi nhiễm riêng lẻ với Al hoặc atrazine được thực hiện ở các nồng độ 5, 50 và 500 µg L-1, trong khi đó, quá trình phơi nhiễm kết hợp được tiến hành với Al tại nồng độ 50 µg L-1 và atrazine tại nồng độ 5 µg L-1 trong hai tuần. Kết quả cho thấy cả Al và atrazine ở nồng độ phơi nhiễm 500 µg L-1 kìm hãm mạnh mẽ sự phát triển và tốc độ sinh trưởng của bèo tấm. Ngược lại, sự kết hợp Al và atrazine dẫn kết tác động triệt tiêu trên bèo tấm. Theo sự hiểu biết của chúng tôi, đây là ghi nhận đầu tiên về những ảnh hưởng kết hợp của hai chất gây ô nhiễm này lên bèo tấm. Vì vậy, những kết quả này có thể hữu ích cho các nhà quản lý môi trường tại Việt Nam trong việc thiết lập và điều chỉnh các giá trị an toàn đối với Al và Atrazie trong môi trường nước tự nhiên về khía cạnh bảo vệ sức khỏe sinh thái.  

scholarly journals An Internally Consistent Approach To Common Stock Valuation

2011 ◽  
Vol 1 (3) ◽  
Author(s):  
Larry Gorman
Keyword(s):  
Growth Rate ◽  
Traditional Approach ◽  
Stock Valuation ◽  
Second Stage ◽  
Pricing Errors ◽  
Multi Stage ◽  
Fundamental Understanding ◽  
Distinct Stage ◽  
The One ◽  
Dividend Growth

A modern corporate finance curriculum typically extends the one-stage Gordon (1962) dividend discount model into a multi-stage environment. In such instances, each regime of constant dividend growth defines a distinct stage. The rate of sustainable dividend growth in each stage is typically determined by specifying the firms return on asset (ROA) and plowback (PB) ratios in each stage, and then computing the implied dividend growth rate as g = ROAPB.In a two-stage problem, current convention typically advocates that the first dividend in the second stage should equal the last dividend in the first stage, multiplied by 1 + g2, where g2 is the growth rate of dividends in the second stage. We show that the dividend stream generated with this methodology is inconsistent with the ROA and plowback assumptions used previously to compute g2. The implication is that the conventional pricing methodology results in stock valuations that are inconsistent with ROA and PB assumptions. For a common textbook problem, we demonstrate pricing errors on the order of 30%. In order to address the issue, we provide an alternative pricing methodology that results in valuations that are consistent with underlying assumptions.Pedagogically, when the proposed approach is contrasted with the traditional approach, the student is forced to develop a deeper fundamental understanding of how stock valuation relates to (i) operational efficiency, (ii) dividend policy, and (iii) the economic environment in which the firm competes.

Crystallization via non-classical pathways: Nanoscale imaging of mineral surfaces 

2021 ◽  
Author(s):  
Christine V. Putnis ◽  
Lijun Wang ◽  
Encarnación Ruiz-Agudo ◽  
Cristina Ruiz-Agudo ◽  
François Renard
Keyword(s):  
Crystal Growth ◽  
Imaging Techniques ◽  
Parent Phase ◽  
Aqueous Fluid ◽  
New Mineral ◽  
Fluid Composition ◽  
Mineral Surfaces ◽  
Fluid Interface ◽  
Mineral Growth ◽  
Sem And Tem

<p>The advancement in analytical imaging techniques, including atomic force microscopy (AFM) and scanning and transmission electron microscopies (SEM and TEM), has allowed us to observe processes occurring at mineral surfaces in situ at a nanoscale in real space and time and hence giving the possibility to elucidate reaction mechanisms. Classical crystal growth theories have been established for well over 100 years and while they can still be applied to explain crystal growth in many growth scenarios, we now know that these models are not always an accurate description of the mechanism of all crystal/mineral growth processes, especially where nanoparticle formation is observed. Consequently there is a current challenge at the forefront of understanding crystal/mineral growth mechanisms. This work describes experimental observations of non-classical crystallization processes at the nanoscale. Using AFM as well as SEM and TEM imaging, we demonstrate that many minerals commonly grow by the attachment of nanoparticles on an existing mineral surface, often resulting from the coupling of dissolution of a parent phase and the precipitation of a new product mineral. Through varied examples of crystal/mineral growth, including calcite and other carbonates, barite, brucite, and apatite, we define the importance of the mineral-fluid interface and the aqueous fluid interfacial (boundary) layer in the control of crystal growth. Whether a crystal will grow by classical monomer attachment resulting in step advancement or by the formation, aggregation and merging of nanoparticles, will be controlled by the aqueous fluid composition at the mineral-fluid interface. The processes described also allow for the development of porosity within the new mineral and hence have important consequences for fluid movement and element mobility within the Earth. Additionally an understanding of natural mineral growth has implications for geomimetic applications for the manufacture of functional engineered materials.</p>

scholarly journals The chemical signatures of the Large Magellanic Cloud globular clusters

2008 ◽  
Vol 4 (S256) ◽  
pp. 299-304
Author(s):  
Alessio Mucciarelli
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Chemical Enrichment ◽  
Chemical Signatures ◽  
First Results ◽  
History Of ◽  
Crucial Information

AbstractWe present the first results of a long-term project based on the analysis of high-resolution optical spectra for a sample of Large Magellanic Cloud globular clusters. The final aim is to build a new, reliable metallicity scale for this cluster system and shed some light on the role played by the different chemical contributors (AGB, SN II and SN Ia), in order to understand the chemical enrichment history of the Large Magellanic Cloud. The analysis of 6 young and intermediate-age clusters and 11 field stars, observed with the UVES@FLAMES spectrograph, provides crucial information about the chemical composition of the dominant stellar population of the LMC. All these stars are metal-rich ([Fe/H]~ −0.4 dex), with solar-scaled [α/Fe] ratios, that point toward an enrichment from SN Ia. Moreover, we observed a general depletion for the [Al/Fe] ratio (indication of a chemical enrichment by metal-poor SN II) and a strong enhancement of the [Ba/Y] ratio (likely due to the enrichment by metal-poor AGB stars).

Hybridization with Domesticated Rainbow Trout (Oncorhynchus mykiss) Reduces Seasonal Variation in Growth of Steelhead Trout (O. mykiss)

1993 ◽  
Vol 50 (3) ◽  
pp. 480-487 ◽  
Author(s):  
Jörgen I. Johnsson ◽  
W. Craig Clarke ◽  
Ruth E. Withler
Keyword(s):  
Growth Rate ◽  
Seasonal Variation ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Natural Waters ◽  
Salt Water ◽  
Feeding Activity ◽  
Steelhead Trout ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Winter Conditions

We tested the hypothesis that hybridization with domesticated rainbow trout (Oncorhynchus mykiss) reduces the seasonal variation in growth in both fresh and salt water in anadromous steelhead trout (O. mykiss). The seasonal variation in freshwater growth was more pronounced in the steelhead trout than in the hybrid and domesticated trout. Consequently, differences in growth rate among groups were considerably higher during winter than in fall or spring. We suggest that high feeding activity during unfavourable winter conditions in natural waters is maladaptive, but is not selected against in protected hatchery environments with a continuous food supply. This may lead to genetic divergence in feeding physiology and/or behaviour between steelhead trout and domesticated rainbow trout. Growth rates in experimental groups transferred to seawater in December relative to groups transferred in April were faster in rainbow and hybrid trout than in steelhead trout. The results support the hypothesis that seasonal variation in seawater growth in steelhead trout is reduced by crossing with domesticated rainbow trout.

scholarly journals MALTE – model to predict new aerosol formation in the lower troposphere

2006 ◽  
Vol 6 (12) ◽  
pp. 4499-4517 ◽  
Author(s):  
M. Boy ◽  
O. Hellmuth ◽  
H. Korhonen ◽  
E. D. Nilsson ◽  
D. ReVelle ◽  
...  
Keyword(s):  
Growth Rate ◽  
Organic Molecules ◽  
Particle Diameter ◽  
Lower Troposphere ◽  
Aerosol Formation ◽  
Aerosol Model ◽  
Aerosol Dynamics ◽  
Model Code ◽  
Responsible Mechanism ◽  
First Results

Abstract. The manuscript presents a detailed description of the meteorological and chemical code of Malte – a model to predict new aerosol formation in the lower troposphere. The aerosol dynamics are achieved by the new developed UHMA (University of Helsinki Multicomponent Aerosol Model) code with kinetic limited nucleation as responsible mechanism to form new clusters. First results indicate that the model is able to predict the on- and offset of new particle formation as well as the total aerosol number concentrations that were in good agreement with the observations. Further, comparison of predicted and measured H2SO4 concentrations showed a satisfactory agreement. The simulation results indicated that at a certain transitional particle diameter (2–7 nm), organic molecules can begin to contribute significantly to the growth rate compared to sulphuric acid. At even larger particle sizes, organic molecules can dominate the growth rate on days with significant monoterpene concentrations. The intraday vertical evolution of newly formed clusters and particles in two different size ranges resulted in two maxima at the ground. These particles grow around noon to the detectable size range and agree well with measured vertical profiles.

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