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Rates and mechanisms of uranyl oxyhydroxide mineral dissolution
Reinoso-Maset, Estela,Steefel, Carl I.,Um, Wooyong,Chorover, Jon,O'Day, Peggy A. Pergamon Press 2017 Geochimica et cosmochimica acta Vol.207 No.-
<P><B>Abstract</B></P> <P>Uranyl oxyhydroxide minerals are important weathering products in uranium-contaminated surface and subsurface environments that regulate dissolved uranium (U) concentrations. However, dissolution rates for this class of minerals and associated dissolution mechanisms have not been previously reported for circumneutral pH conditions, particularly for the case of flow through porous media. In this work, the dissolution rates of K- and Na-compreignacite (K<SUB>2</SUB>(UO<SUB>2</SUB>)<SUB>6</SUB>O<SUB>4</SUB>(OH)<SUB>6</SUB>·8H<SUB>2</SUB>O and Na<SUB>2</SUB>(UO<SUB>2</SUB>)<SUB>6</SUB>O<SUB>4</SUB>(OH)<SUB>6</SUB>·8H<SUB>2</SUB>O, respectively) were measured using flow-through columns reacted with two simulated background porewater (BPW) solutions of low and high dissolved carbonate concentration (ca. 0.2 and 2.8mmolL<SUP>−1</SUP>). Column materials were characterized before and after reaction with electron microscopy, bulk chemistry, and EXAFS to identify structural and chemical changes during dissolution and to obtain insight into molecular-scale processes. The reactive transport code CrunchFlow was used to calculate overall dissolution rates while accounting for fluid transport and changes in mineral volume and reactive surface area, and results were compared to steady-state dissolution rate calculations. In low carbonate BPW systems, interlayer K and Na were initially leached from both minerals, and in Na-compreignacite, K and minor divalent cations from the input solution were incorporated into the mineral structure. Results of characterization analyses suggested that after reaction both K- and Na-compreignacite resembled a disordered K-compreignacite with altered surfaces. A 10-fold increase in dissolved carbonate concentration and corresponding increase in pH (from 6.65 to 8.40) resulted in a net removal of 58–87% of total U mass from the columns, compared to <1% net loss in low carbonate BPW systems. Steady-state release of dissolved U was not observed with high carbonate solutions and post-reaction characterizations indicated a lack of development of leached or altered surfaces. Dissolution rates (normalized to specific surface area) were 2.5–3 orders-of-magnitude faster in high versus low carbonate BPW systems, with Na-compreignacite dissolving more rapidly than K-compreignacite under both BPW conditions, possibly due to greater ion exchange (1.57·10<SUP>−10</SUP> vs. 1.28·10<SUP>−13</SUP> molm<SUP>−2</SUP> s<SUP>−1</SUP> [log <I>R</I> =−9.81 and −12.89] and 5.79·10<SUP>−10</SUP> vs. 3.71·10<SUP>−13</SUP> molm<SUP>−2</SUP> s<SUP>−1</SUP> [log <I>R</I> =−9.24 and −12.43] for K- and Na-compreignacite, respectively). Experimental and spectroscopic results suggest that the dissolution rate is controlled by bond breaking of a uranyl group and detachment from polyhedral layers of the mineral structure. With higher dissolved carbonate concentrations, this rate-determining step is accelerated by the formation of Ca-uranyl carbonate complexes (dominant species under these conditions), which resulted in an increase of the dissolution rates. Optimization of both dissolution rate and mineral volume fraction in the reactive transport model to account for U mass removal during dissolution more accurately reproduced effluent data in high carbonate systems, and resulted in faster overall rates compared with a steady-state dissolution assumption. This study highlights the importance of coupling reaction and transport processes during the quantification of mineral dissolution rates to accurately predict the fate of contaminants such as U in porous geomedia.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Compreignacite dissolution rates vary with the interlayer cation (Na>K). </LI> <LI> Detachment of uranyl groups from polyhedral layers is the rate-determining step. </LI> <LI> I
Characterization of Polyphenoloxidase from 2 Peach (Prunus persica L.) Varieties Grown in Argentina
Adriana Garro,Estela Gasull 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.3
Polyphenoloxidase was extracted from September peach (SEPPO) and Summerset peach (SUPPO) and its physicochemical characteristics were analyzed. The optimum pH was 6.5 for SEPPO and 5.5 for SUPPO. The optimum temperature was 35℃ for SEPPO and 39.4℃ for SUPPO. Activation energy (Ea) from thermal activation was 41.5 kJ/mol for SEPPO and 37.5 kJ/mol for SUPPO. Heating at 60℃ by 5 min, SUPPO was denatured whereas SEPPO retained 2.6% of activity. Activation enthalpy (ΔH#)and activation entropy (ΔS#) for SEPPO heat-inactivation were 69.9 J/mol and −83.5 kJ/mol·K for SUPPO, ΔH# was 91.8 J/mol while ΔS# was −21.0 kJ/mol·K. Substrate specificity (Vmax/KM) was 4-methylcatechol>catechol>pyrogallol for SEPPO and 4-mehtylcatechol>pyrogallol>catechol for SUPPO. For both enzymes, the order of inhibition effectiveness using reductor agents was metabisulphite>ascorbic acid. Benzaldehyde, 4-hydroxybenzaldehyde, and DL-dopa were competitive inhibitors, and their KI values were 38.86, 8.43, and 2.08 mM, respectively.
Isolation and Molecular Characterization of Xylella fastidiosa from Coffee Plants in Costa Rica
Mauricio Montero-Astua,Carlos Chacon-Diaz,Estela Aguilar,Carlos Mario Rodriguez,Laura Garita,William Villalobos,Lisela Moreira,John S. Hartung,Carmen Rivera 한국미생물학회 2008 The journal of microbiology Vol.46 No.5
Coffee plants exhibiting a range of symptoms including mild to severe curling of leaf margins, chlorosis and deformation of leaves, stunting of plants, shortening of internodes, and dieback of branches have been reported since 1995 in several regions of Costa Rica’s Central Valley. The symptoms are referred to by coffee producers in Costa Rica as “crespera” disease and have been associated with the presence of the bacterium Xylella fastidiosa. Coffee plants determined to be infected by the bacterium by enzyme linked immunosorbent assay (ELISA), were used for both transmission electron microscopy (TEM) and for isolation of the bacterium in PW broth or agar. Petioles examined by TEM contained rod-shaped bacteria inside the xylem vessels. The bacteria measured 0.3 to 0.5 μm in width and 1.5 to 3.0 μm in length, and had rippled cell walls 10 to 40 nm in thickness, typical of X. fastidiosa. Small, circular, dome-shaped colonies were observed 7 to 26 days after plating of plant extracts on PW agar. The colonies were comprised of Gram-negative rods of variable length and a characteristic slight longitudinal bending. TEM of the isolated bacteria showed characteristic rippled cell walls, similar to those observed in plant tissue. ELISA and PCR with specific primer pairs 272-1-int/272-2-int and RST31/RST33 confirmed the identity of the isolated bacteria as X. fastidiosa. RFLP analysis of the amplification products revealed diversity within X. fastidiosa strains from Costa Rica and suggest closer genetic proximity to strains from the United States of America than to other coffee or citrus strains from Brazil.
Cristiane T. Citadin,Mirella P. Santos,Estela R. Andrade,Thaís M. Cipriano,Francisco J. L. Aragão 한국육종학회 2022 Plant Breeding and Biotechnology Vol.10 No.2
The detection of the presence and expression of transgenes in genetically modified plants is a key step in the process ofselecting promising lines. We adapted two methods developed for detecting tolerance to the herbicide imazapyr for selection oftransgenic lines expressing the mutated acetohydroxyacid synthase enzyme (AHAS) from Arabidopsis thaliana (Atahas gene). Thiswas achieved using transgenic events from cotton, cowpea, soybean and common bean, which have previously been transformed toexpress the mutated Atahas gene. In the first method, a colorimetric assay was developed that detects acetoin, an intermediate in thebiosynthetic pathway of branched chain amino acids, which is accumulated in the presence of cyclopropanedicarboxylic acid (CPCA),an inhibitor of ketoacid reductoisomerase (KARI). In the presence of the herbicide, it was possible to distinguish non-transgenic fromtransgenic plants. Qualitative analysis of acetoin formed during the AHAS inhibition allowed to indirectly determine the Atahastransgene expression. The second method measured the kinetics of chlorophyll fluorescence emission. Leaf discs pre-treated withimazapyr for 24 hours were evaluated using the modulated fluorimeter for maximum quantum efficiency of Photosystem II (PSII)(Fv/Fm) and relative electron transport rate (ETR). Results showed that almost all species analyzed presented a marked decrease inFv/Fm after treatment with imazapyr. In addition, the ETR was significantly reduced in transgenic plants treated with the herbicide. Collectively, our results showed that it is possible to identify transgenic plants expressing Atahas gene and infer their levels of toleranceto imazapyr at a very early stage after transformation.
Acupuncture Points and Their Relationship with Multireceptive Fields of Neurons
Salvador Quiroz-Gonzalez,Sergio Torres-Castillo,Rosa Estela Lopez-Gomez,Ismael Jimenez Estrada 사단법인약침학회 2017 Journal of Acupuncture & Meridian Studies Vol.10 No.2
In Traditional Chinese Medicine, acupuncture points (APs) have been emphasized as key elements that generate the therapeutic effects of acupuncture. At the spinal cord or supraspinal level, sensory neurons located in the dorsal horn receive an extensive supply of sensory information from skin and muscle receptors through peripheral afferent nerves. The stimulated skin area that influences the activity of a spinal sensory neuron is known as the peripheral receptive field (RF) of that neuron. By considering that a particular AP location involves the activation of one or various RFs, it can be assumed that several sensory central neurons are the site of convergence of the peripheral input generated by acupuncture stimulation. However, stimulation on nonacupoint sites could also activate skin areas with RFs that have been sensitized, and they could be involved in the generation of nonspecific effects of acupuncture, as seen in clinical practice. From the latter, it is suggested that effective APs, and even nonacupoints, are associated with a particular arrangement of RFs, and their study will be useful for understanding the intrinsic mechanisms of acupuncture and for the development and identification of more efficient sites and modes of acupuncture stimulation to evoke optimal therapeutic actions.
Edgar Cano-Europa,Rocio Ortiz-Butron,Estela Melendez Camargo,Maria Miriam Esteves-Carmona,Rosa Maria Oliart-Ros,Vanessa Blas-Valdivia,Margarita Franco-Colin 한국식품영양과학회 2016 Journal of medicinal food Vol.19 No.11
We investigated the effect of a canola oil-supplemented diet on the metabolic state and diabetic renal function of a type I diabetes experimental model. Male Sprague-Dawley rats were randomly divided into four groups: (1) normoglycemic+chow diet, (2) normoglycemic+a canola oil-supplemented chow diet, (3) diabetic+chow diet, and (4) diabetic+a canola oil-supplemented chow diet. For 15 weeks, animals were fed a diet of Purina rat chow alone or supplemented with 30% canola oil. Energetic intake, water intake, body weight, and adipose tissue fat pad were measured; renal function, electrolyte balance, glomerular filtration rate, and the plasmatic concentration of free fatty acids, cholesterol, triglycerides, and glucose were evaluated. The mesenteric, retroperitoneal, and epididymal fat pads were dissected and weighed. The kidneys were used for lipid peroxidation (LP) and reactive oxygen species (ROS) quantifications. Diabetic rats fed with a canola oilsupplemented diet had higher body weights, were less hyperphagic, and their mesenteric, retroperitoneal, and epididymal fat pads weighed more than diabetic rats on an unsupplemented diet. The canola oil-supplemented diet decreased plasmatic concentrations of free fatty acids, triglycerides, and cholesterol; showed improved osmolarity, water clearances, and creatinine depuration; and had decreased LP and ROS. A canola oil-supplemented diet decreases hyperphagia and prevents lipotoxicity and renal dysfunction in a type I diabetes mellitus model.