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Reducing Cr<sup>6+</sup> emissions from gas tungsten arc welding using a silica precursor
Topham, Nate,Kalivoda, Mark,Hsu, Yu-Mei,Wu, Chang-Yu,Oh, Sewon,Cho, Kuk Elsevier 2010 Journal of aerosol science Vol.41 No.3
<P><B>Abstract</B></P><P>Hexavalent chromium (Cr<SUP>6+</SUP>) emission from stainless steel welding operations poses a serious threat to worker safety and ambient air quality. In this study, tetraethyloxysilane (TEOS) was used as a silica precursor additive to welding shield gas during gas tungsten arc welding (GTAW) operations to determine the feasibility of using these chemicals for Cr<SUP>6+</SUP> exposure reduction. Fume aerosol samples were analyzed for Cr<SUP>6+</SUP> concentration using ion chromatography (IC) and for total Cr by inductively coupled plasma with atomic emission spectroscopy (ICP-AES).</P><P>At high temperature, silica precursors are pyrolyzed to form amorphous silica (SiO<SUB>2</SUB>) which can condense on the existing metal aerosols. The inert silica layer surrounding the aerosols can prevent further chromium oxidation by insulating chromium aerosols. Experimental results showed approximately 45% Cr<SUP>6+</SUP> reductions when 3.0% TEOS was added to the shield gas. Nitrate concentration also decreased by 53%, indicating that reactive oxygen species were also reduced. Transmission electron microscopy (TEM) images of collected fume aerosols showed SiO<SUB>2</SUB> coating on metal particles, verifying the proposed mechanism.</P>
Decreasing biotoxicity of fume particles produced in welding process
Yu, Kuei-Min,Topham, Nathan,Wang, Jun,Kalivoda, Mark,Tseng, Yiider,Wu, Chang-Yu,Lee, Wen-Jhy,Cho, Kuk Elsevier 2011 Journal of hazardous materials Vol.185 No.2
<P><B>Abstract</B></P><P>Welding fumes contain heavy metals, such as chromium, manganese, and nickel, which cause respiratory diseases and cancer. In this study, a SiO<SUB>2</SUB> precursor was evaluated as an additive to the shielding gas in an arc welding process to reduce the biotoxicity caused by welding fume particles. Transmission electron micrographic images show that SiO<SUB>2</SUB> coats on the surface of welding fume particles and promotes particle agglomeration. Energy dispersive X-ray spectroscopy further shows that the relative amount of silicon in these SiO<SUB>2</SUB>-coated agglomerates is higher than in baseline agglomerates. In addition, <I>Escherichia coli</I> (<I>E. coli</I>) exposed to different concentrations of pure SiO<SUB>2</SUB> particles generated from the arc welding process exhibits similar responses, suggesting that SiO<SUB>2</SUB> does not contribute to welding fume particle toxicity. The trend of <I>E. coli</I> growth in different concentrations of baseline welding fume particle shows the most significant inhibition occurs in higher exposure concentrations. The 50% lethal logarithmic concentrations for <I>E. coli</I> in arc welding particles of baseline, 2%, and 4.2% SiO<SUB>2</SUB> precursor additives were 823, 1605, and 1800mg/L, respectively. Taken together, these results suggest that using SiO<SUB>2</SUB> precursors as an additive to arc welding shielding gas can effectively reduce the biotoxicity of welding fume.</P>
Synaptic removal of diacylglycerol by DGKzeta and PSD-95 regulates dendritic spine maintenance.
Kim, Karam,Yang, Jinhee,Zhong, Xiao-Ping,Kim, Myoung-Hwan,Kim, Yun Sook,Lee, Hyun Woo,Han, Seungnam,Choi, Jeonghoon,Han, Kihoon,Seo, Jinsoo,Prescott, Stephen M,Topham, Matthew K,Bae, Yong Chul,Koretzk Published for the European Molecular Biology Organ 2009 The EMBO journal Vol.28 No.8
<P>Diacylglycerol (DAG) is an important lipid signalling molecule that exerts an effect on various effector proteins including protein kinase C. A main mechanism for DAG removal is to convert it to phosphatidic acid (PA) by DAG kinases (DGKs). However, it is not well understood how DGKs are targeted to specific subcellular sites and tightly regulates DAG levels. The neuronal synapse is a prominent site of DAG production. Here, we show that DGKzeta is targeted to excitatory synapses through its direct interaction with the postsynaptic PDZ scaffold PSD-95. Overexpression of DGKzeta in cultured neurons increases the number of dendritic spines, which receive the majority of excitatory synaptic inputs, in a manner requiring its catalytic activity and PSD-95 binding. Conversely, DGKzeta knockdown reduces spine density. Mice deficient in DGKzeta expression show reduced spine density and excitatory synaptic transmission. Time-lapse imaging indicates that DGKzeta is required for spine maintenance but not formation. We propose that PSD-95 targets DGKzeta to synaptic DAG-producing receptors to tightly couple synaptic DAG production to its conversion to PA for the maintenance of spine density.</P>
Efremova, Olga A.,Brylev, Konstantin A.,Vorotnikov, Yuri A.,Vejsadová,, Lucie,Shestopalov, Michael A.,Chimonides, Gwen F.,Mikes, Petr,Topham, Paul D.,Kim, Sung-Jin,Kitamura, Noboru,Sutherland, A The Royal Society of Chemistry 2016 Journal of Materials Chemistry C Vol.4 No.3
<▼1><P>Transparent yet photoluminescent, materials with facile processability are key in many applications.</P></▼1><▼2><P>Materials that combine photoluminescence, optical transparency and facile processability are of high importance in many applications. This article reports on the development of photoluminescent poly(methyl methacrylate) materials based on novel highly emissive anionic molybdenum cluster complex [{Mo6I8}(OTs)6]<SUP>2−</SUP> (where OTs<SUP>−</SUP> is the <I>p</I>-toluenesulfonate ion). The materials were obtained by both solution and bulk copolymerisation of methyl methacrylate and (dMDAEMA)2[{Mo6I8}(OTs)6], where dMDAEMA<SUP>+</SUP> is the polymerisable cation [2-(methacryloyloxy)ethyl]dimethyl-dodecylammonium. Evaluation of the resultant hybrid materials showed that one could combine the excellent photoluminescent properties of the cluster complex with the transparency and processability of PMMA.</P></▼2>