scholarly journals Stable silver isotope fractionation in the natural transformation process of silver nanoparticles

2016 ◽  
Vol 11 (8) ◽  
pp. 682-686 ◽  
Author(s):  
Dawei Lu ◽  
Qian Liu ◽  
Tuoya Zhang ◽  
Yong Cai ◽  
Yongguang Yin ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Isotope Fractionation ◽  
Natural Transformation ◽  
Transformation Process ◽  
Silver Isotope

Building amorphous calcium carbonate into geochemical biomineralisation models

2020 ◽  
Author(s):  
David Evans ◽  
William Gray ◽  
James Rae ◽  
Rosanna Greenop ◽  
Paul Webb ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Isotope Fractionation ◽  
Planktonic Foraminifera ◽  
Transformation Process ◽  
Geochemical Data ◽  
Amorphous Calcium Carbonate ◽  
Carbonate System ◽  
Precursor Phase ◽  
Shell Geochemistry

<p>Amorphous calcium carbonate (ACC) has been observed, or inferred to exist, in the majority of the major phyla of marine calcifying organisms. The CaCO<sub>3</sub> produced by these organisms represents one of the largest long-term carbon sinks on Earth’s surface, such that identifying how calcification will respond to anthropogenic climate change is an urgent priority. A substantial portion of our knowledge of the biomineralisation process of these organisms is derived from inferences based on skeletal geochemical data, yet such models typically do not include an ACC component because little is known about trace element and isotope fractionation into ACC. In order to address this, we present, to our knowledge, the first structural and geochemical data of ACC precipitated from seawater under varying carbonate system conditions, seawater Mg/Ca ratios, and in the presence of three of the most common intracrystalline amino acids (aspartic acid, glutamic acid, and glycine). Based on these data we identify the carbonate system conditions necessary to produce ACC from seawater [Evans <em>et al</em>., 2019], and identify the dominant controls on ACC geochemistry. As an example, we utilise these data to build a simple biomineralisation model for the low-Mg (e.g. planktonic) foraminifera, based on precipitation of low-Mg calcite through an ACC precursor phase in a semi-enclosed pool. This exercise demonstrates that the observed shell geochemistry of this group of organisms can be fully reconciled with a model that includes an ACC component, and moreover that constraints can be placed on the degree of ACC utilisation and the ACC-calcite transformation process. More broadly, the exercise demonstrates that knowledge of the characteristics and geochemistry of ACC is important in the development of a process-based understanding of marine calcification.</p><p>Evans, D., Webb, P., Penkman, K. Kröger, R., & Allison, N. [2019] The Characteristics and Biological Relevance of Inorganic Amorphous Calcium Carbonate (ACC) Precipitated from Seawater. <em>Crystal Growth & Design</em> <strong>19</strong>: 4300.</p>

scholarly journals Revealing ancient gold parting with silver and copper isotopes: implications from cementation experiments and for the analysis of gold artefacts

2021 ◽  
Vol 13 (9) ◽  
Author(s):  
Daniel Berger ◽  
Michael Brauns ◽  
Gerhard Brügmann ◽  
Ernst Pernicka ◽  
Nicole Lockhoff
Keyword(s):  
Trace Element ◽  
Isotope Fractionation ◽  
Copper Alloys ◽  
Pure Gold ◽  
Copper Isotopes ◽  
Gold Silver ◽  
Analytical Proof ◽  
Gold Refining ◽  
Isotope Systematics ◽  
Silver Isotope

AbstractGold parting enabled the production of very pure gold for various purposes from the sixth century BC onwards, but analytical proof of this pyrotechnical process is difficult. We describe a new analytical approach for the identification of purified gold combining silver and copper isotopic with trace element analyses. Parting experiments were performed with gold-silver-copper alloys using the classical salt cementation process to investigate potential silver and copper isotope fractionation and changes in trace element concentrations. In addition, we provide the first comprehensive dataset of silver isotope ratios of archaeological gold objects from the Mediterranean and Central Europe to test whether or not gold refining can be identified on the basis of isotope systematics. The results show that very heavy silver and copper isotopic compositions are clear evidence for parted gold, but that the application of copper isotopes might be limited.

scholarly journals Accurate and Precise Determination of Silver Isotope Fractionation in Environmental Samples by Multicollector-ICPMS

2010 ◽  
Vol 82 (9) ◽  
pp. 3922-3928 ◽  
Author(s):  
Yan Luo ◽  
Ewa Dabek-Zlotorzynska ◽  
Valbona Celo ◽  
Derek C. G. Muir ◽  
Lu Yang
Keyword(s):  
Environmental Samples ◽  
Isotope Fractionation ◽  
Precise Determination ◽  
Silver Isotope

scholarly journals Natural Transformation of Zinc Oxide Nanoparticles and Their Cytotoxicity and Mutagenicity

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Mei M. Wang ◽  
Juan Wang ◽  
Rui Cao ◽  
Si Y. Wang ◽  
Hua Du
Keyword(s):  
Zinc Oxide Nanoparticles ◽  
Natural Transformation ◽  
Rapid Development ◽  
Transformation Process ◽  
Oxide Nanoparticles ◽  
Zinc Hydroxide ◽  
Zno Nps ◽  
Cellular Toxicity ◽  
X Ray ◽  
Mutation Assay

With rapid development of the nanoindustry, studies focusing on the transformation of nanoparticles (NPs) are required to understand their stability and toxicity after being released into the environment. Here, we characterized the physicochemical properties of ZnO NPs and found that they are naturally alkalized in the presence of air (without the addition of exogenous alkaline substances). Energy dispersive X-ray/X-ray powder diffraction/Fourier transform infrared (EDX/XRD/FTIR)/Raman spectroscopy gave evidence for the formation of hydrozincite (Zn5(CO3)2(OH)6) and zinc hydroxide (Zn(OH)2). Further, we comparatively evaluated the cellular toxicity of pristine and alkalized ZnO NPs. Cell viability testing (colony formation) showed that alkalization time-dependently decreased cytotoxicity. Alkalized NPs exhibited mutagenicity at multiple concentrations, as shown by a CD59 gene loci mutation assay. Variations in toxicity were associated with the chemical transformation of ZnO NPs, and Zn2+ played a key role in the mutagenicity of alkalized NPs. These results indicate that NPs are chemically transformed in the environment. These transformations result in obvious variations in toxicity, suggesting that the NP transformation process should be considered more thoroughly when evaluating toxicity.

scholarly journals CrfP, a fratricide protein, contributes to natural transformation in Streptococcus suis

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Yinchu Zhu ◽  
Jiale Ma ◽  
Yue Zhang ◽  
Xiaojun Zhong ◽  
Qiankun Bai ◽  
...  
Keyword(s):  
Natural Transformation ◽  
Potential Effect ◽  
Transformation Process ◽  
Transformation Rate ◽  
Bacterial Cells ◽  
Exogenous Dna ◽  
Src Homology 3 ◽  
Src Homology ◽  
Natural Genetic Transformation

AbstractStreptococcussuis (S.suis) is an important zoonotic pathogen that causes septicaemia, meningitis and streptococcal toxic shock-like syndrome in its host, and recent studies have shown that S.suis could be competent for natural genetic transformation. Transformation is an important mechanism for the horizontal transfer of DNA, but some elements that affect the transformation process need to be further explored. Upon entering the competent state, Streptococcus species stimulate the transcription of competence-related genes that are responsible for exogenous DNA binding, uptake and processing. In this study, we performed conserved promoter motif and qRT-PCR analyses and identified CrfP as a novel murein hydrolase that is widespread in S.suis and stimulated with a peptide pheromone in the competent state through a process controlled by ComX. A bioinformatics analysis revealed that CrfP consists of a CHAP hydrolase domain and two bacterial Src homology 3-binding (SH3b) domains. Further characterization showed that CrfP could be exported to extracellular bacterial cells and lytic S.suis strains of different serotypes, and this finding was verified by TEM and a turbidity assay. To investigate the potential effect of CrfP in vivo, a gene-deletion mutant (ΔcrfP) was constructed. Instead of stopping the natural transformation process, the inactivation of CrfP clearly reduced the effective transformation rate. Overall, these findings provide evidence showing that CrfP is important for S.suis serovar 2 competence.

Structure of a new orthorhombic phase in NiTi: Mn shape memory alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 1000-1001
Author(s):  
Jenö Beyer ◽  
Lajos Tóth
Keyword(s):  
Martensitic Transformation ◽  
Structural Changes ◽  
High Vacuum ◽  
Intermetallic Phase ◽  
Orthorhombic Phase ◽  
Transformation Process ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Crystallographic Structures ◽  
Ternary Additions

The structural changes during reversible martensitic transformation of near-equiatomic NiTi alloys can best be studied in TEM at around room temperature. Ternary additions like Mn offer this possibility by suppressing the Ms temperature below RT. Besides the stable intermetallic phases (Ti2Ni, TiNi, TiNi3) several metastable phases with various crystallographic structures (rhombohedral, hexagonal, monoclinic, cubic) have also been reported to precipitate due to suitable annealing procedures.TiNi:Mn samples with 0.9 and 1.3 at% Mn were arc melted in argon atmosphere and homogenized at 948 °C for 72 hours in high vacuum in an infrared furnace. After spark cutting slices of 0.2 mm, TEM specimens were prepared by electrochemical polishing with the twin-jet technique in methanol - perchloric acid electrolyte. The TEM study was carried out in a JEOL 200 CX analytical electron microscope.In this paper a new intermetallic phase is reported which has been observed in both samples by TEM during the martensitic transformation process.

Got the Results, Now What Do You Do?

2012 ◽  
Vol 2 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Michaela Heese
Keyword(s):  
Safety Culture ◽  
Success Factors ◽  
Service Providers ◽  
Transformation Process ◽  
Driving Safety ◽  
Critical Success ◽  
Culture Transformation ◽  
Survey Results ◽  
Air Navigation Services ◽  
Navigation Service

Members of the Civil Air Navigation Services Organisation have committed themselves to measure and improve safety culture within their organizations by 2013 ( CANSO, 2010 ). This paper attempts to offer support to air navigation service providers that have already implemented a standardized safety culture survey approach, in the process of transforming their safety culture based on existing survey results. First, an overview of the state of the art with respect to safety culture is presented. Then the application of the CANSO safety culture model from theory into practice is demonstrated based on four selected case studies. Finally, a summary of practical examples for driving safety culture change is provided, and critical success factors supporting the safety culture transformation process are discussed.

Sign in / Sign up

Export Citation Format

Share Document