scholarly journals Interpretative optimization of the isocratic ion chromatographic separation of anions

2016 ◽  
Vol 81 (6) ◽  
pp. 661-672
Author(s):  
Zaklina Todorovic ◽  
Ljubinka Rajakovic ◽  
Antonije Onjia
Keyword(s):  
Experimental Design ◽  
Ion Exchange ◽  
Retention Data ◽  
Optimal Conditions ◽  
Peak Resolution ◽  
Total Analysis ◽  
Multiple Species ◽  
Ph Range ◽  
The Individual ◽  
Good Agreement

Interpretive retention modeling was utilized to optimize the isocratic ion chromatographic (IC) separation of the nine anions (formate, fluoride, chloride, nitrite, bromide, nitrate, phosphate, sulfate, oxalate). The carbonate-bicarbonate eluent was used and separation was done on a Dionex AS14 ion-exchange column. The influence of combined effects of two mobile phase factors, the total eluent concentration (2 - 6 mM) and the carbonate/bicaronate ratio from 1:9 to 9:1 (which corespondent to pH range 9.35 - 11.27), on the IC separation was studied. The multiple species analyte/eluent model that takes into account ion-exchange equilibria of the eluent and sample anions was used. In order to estimate the parameters in the model, a non-linear fitting of the retention data, obtained at two-factor three-level experimental design, was applied. To find the optimal conditions in the experimental design, the normalized resolution product as a chromatographic objective function was employed. This criterion includes both the individual peak resolution and the total analysis time. A good agreement between experimental and simulated chromatograms was obtained.

Equilibria of the Simultaneously Existing Multiple Species in the Copper(II)–L-Histidine System

1973 ◽  
Vol 51 (21) ◽  
pp. 3549-3554 ◽  
Author(s):  
Theo P. A. Kruck ◽  
Bibudhendra Sarkar
Keyword(s):  
Statistical Analysis ◽  
Standard Deviation ◽  
Stability Constants ◽  
Individual Values ◽  
Complex Species ◽  
Molar Ratios ◽  
Multiple Species ◽  
The Stability ◽  
Ph Range ◽  
The Individual

The complete species distribution and the stability constants of the complex species in the Cu(II)–L-histidine system have been worked out for the pH range 2–11. The method of "analytical potentiometry" has been applied successfully to this system having excess ligand with respect to Cu(II) ion. The equilibria of three systems of Cu(II) (M) and L-histidine (H3A) in molar ratios of 1:2, 1:4, and 1:8 were investigated by this technique in 0.15 M NaCl at 25°. The following species were detected in this system: MHA, MA, MH2A2, MHA2, MA2, MH−1A2, MH−1A, and M2H−2A2. Statistical analysis on the numerical results has been performed and is given as standard deviation together with the individual values for the stability constants.

Structure of the Species in the Copper (II)–L-Histidine System

1973 ◽  
Vol 51 (21) ◽  
pp. 3563-3571 ◽  
Author(s):  
Theo P. A. Kruck ◽  
Bibudhendra Sarkar
Keyword(s):  
Species Distribution ◽  
Equilibrium Mixture ◽  
The Other ◽  
Individual Species ◽  
Complex Species ◽  
System A ◽  
Multiple Species ◽  
Ph Range ◽  
The Individual ◽  
Total Absorbance

The presence of simultaneously existing multiple species were taken into account in interpreting the structures of the complex species in the Cu(II)–L-histidine system. A refined proton displacement technique was utilized for structure elucidation of the species in solution. The absorbance and the molar extinction of the individual species were computed from the total absorbance and the species distribution over the pH range studied. The i.r. spectra of L-histidine and Cu(II)–L-histidine in D2O were obtained as a function of pD. They were interpreted in view of the species detected in a given pH range. The results of the species distribution as a function of pH, proton displacement, visible spectra of the individual species, and infrared data, were all combined to make structural interpretations. The following modes of metal coordination were proposed for the major species in the Cu(II)–L-histidine system: MHA, O(carboxyl) and N(imidazole); MH2A2, O(carboxyl) and N(amino) in both L-histidines; MA, O(carboxyl), N(imidazole), and N(amino); MHA2O(carboxyl), N(imidazole), and N(amino) in one L-histidine and O(carboxyl) and N(amino) in the other; MA2, O(carboxyl). N(imidazole), and N(amino) in both L-histidines, or O(carboxyl), N(imidazole), and N(amino) in one L-histidine and N(amino) and N(imidazole) in the other or an equilibrium mixture of both structures.

Study on Pure Aqueous Extraction Method of PHB/Ectoine Co-Products Based on Osmotic Downshock

2014 ◽  
Vol 955-959 ◽  
pp. 3377-3380 ◽  
Author(s):  
Qing Chen ◽  
Te Wang ◽  
Jin Dan Zhao ◽  
Fu Hui Kang ◽  
Yi Ming Zhang ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Hollow Fiber ◽  
Extraction Method ◽  
Pure Water ◽  
Aqueous Extraction ◽  
Extraction Rate ◽  
Extraction Temperature ◽  
Optimal Conditions ◽  
Pressure Extraction ◽  
Osmotic Downshock

The simultaneously co-production of Poly-β-hydroxybutyrate (PHB) and ectoine in a process (PHB/Ect co-production) and co-products extraction have great significant for reducing the manufacture cost and promoting industrialization of PHB and ectoine. The pure aqueous extraction method based on osmotic downshock was used for the extraction of PHB/Ect co-products byH. salina. The effects of osmotic pressure, extraction temperature and extraction time on the extraction rate of PHB were investigated. The ectoine was extracted and purified by the techniques of hollow fiber and ion exchange. The optimal conditions for PHB extraction were osmotic downshock in pure water, extraction temperature at 60 °C and extraction for 4 h. The extraction rate of PHB was 87.5%. The extraction rate of ectoine was 84.2%.

Expressions for the effective diffusivity in materials with interphase boundaries

2004 ◽  
Vol 819 ◽  
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Polycrystalline Material ◽  
Effective Diffusivity ◽  
Poor Agreement ◽  
Two Phase ◽  
Interphase Boundaries ◽  
Long Time ◽  
Simulation Results ◽  
The Individual ◽  
Individual Grains ◽  
Good Agreement

AbstractWe address the problem of calculating the long-time-limit effective diffusivity in stable two- phase polycrystalline material. A phenomenological model is used where the high diffusivity interphase boundaries are treated as connected “coatings” of the individual grains. Derivation of expressions for the effective diffusivity with segregation is made along Maxwell lines. Monte Carlo simulation using lattice-based random walks is used to test the validity of the expressions. It is shown that for the case analysed the derived expressions for the effective diffusivity are in very good agreement with simulation results. The equivalent of the Hart equation is also derived. It is shown to be in poor agreement with simulation results.

scholarly journals TEMPO-Functionalized Nanoporous Au Nanocomposite for the Electrochemical Detection of H2O2

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Dongxiao Wen ◽  
Qianrui Liu ◽  
Ying Cui ◽  
Huaixia Yang ◽  
Jinming Kong
Keyword(s):  
Electrochemical Detection ◽  
Nanoporous Gold ◽  
Carboxyl Groups ◽  
Time Interval ◽  
Optimal Conditions ◽  
Sem Images ◽  
One Step ◽  
Ph Range ◽  
Synthesis Approach ◽  
Higher Sensitivity

A novel nanocomposite of nanoporous gold nanoparticles (np-AuNPs) functionalized with 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO) was prepared; assembled carboxyl groups on gold nanoporous nanoparticles surface were combined with TEMPO by the “bridge” of carboxylate-zirconium-carboxylate chemistry. SEM images and UV-Vis spectroscopies of np-AuNPs indicated that a safe, sustainable, and simplified one-step dealloying synthesis approach is successful. The TEMPO-np-AuNPs exhibited a good performance for the electrochemical detection of H2O2 due to its higher number of electrochemical activity sites and surface area of 7.49 m2g-1 for load bigger amount of TEMPO radicals. The TEMPO-functionalized np-AuNPs have a broad pH range and shorter response time for H2O2 catalysis verified by the response of amperometric signal under different pH and time interval. A wide linear range with a detection limit of 7.8 × 10-7 M and a higher sensitivity of 110.403 μA mM-1cm-2 were obtained for detecting H2O2 at optimal conditions.

Optimal conditions for induction of competence in nitrogen-fixing Azotobacter vinelandii

1982 ◽  
Vol 28 (4) ◽  
pp. 389-397 ◽  
Author(s):  
William J. Page
Keyword(s):  
Dissolved Oxygen ◽  
Sodium Acetate ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Cell Mass ◽  
Apparent Competition ◽  
Competence Development ◽  
Optimal Conditions ◽  
Nitrogen Fixing ◽  
Ph Range

Competence development in nitrogen-fixing Azotobacter vinelandii cells was optimal at pH 7.2–7.4 which necessitated additional buffering of the iron-limited nitrogen-free competence medium or the addition of a suitable organic acid salt, e.g., sodium acetate. An autolysin was active in this pH range and competent cells were more susceptible to autolysis than the general cell population. Competence development also required restricted aeration of the culture, and only those cultures that attained zero dissolved oxygen became competent. Restricted aeration served to protect the iron-limited cell nitrogenase from oxygen inactivation thus allowing the culture to reach zero dissolved oxygen. The inclusion of additional sources of reductant, e.g., malate, in buffered competence medium resulted in increased respiration and protection of nitrogenase, increased cell mass, and poly-β-hydroxybutyrate synthesis, but decreased competence. A possible explanation for the apparent competition between competence development and nitrogenase activity is discussed.

scholarly journals Accuracy of Wind Observations from Open-Ocean Buoys: Correction for Flow Distortion

2020 ◽  
Vol 37 (4) ◽  
pp. 687-703 ◽  
Author(s):  
Michael Schlundt ◽  
J. Thomas Farrar ◽  
Sebastien P. Bigorre ◽  
Albert J. Plueddemann ◽  
Robert A. Weller
Keyword(s):  
Flow Distortion ◽  
Error Sources ◽  
Neutral Winds ◽  
Flow Simulations ◽  
Temporal Sampling ◽  
Empirical Correction ◽  
The Individual ◽  
Wind Vane ◽  
Subsequent Comparison ◽  
Good Agreement

AbstractThe comparison of equivalent neutral winds obtained from (i) four WHOI buoys in the subtropics and (ii) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56–0.76 m s−1. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because 1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and 2) 1-min sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy–scatterometer comparisons. The interanemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the interanemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement.

scholarly journals Influence of hydrotalcite preparation conditions on its physico-chemical properties

2019 ◽  
Vol 12 (1) ◽  
pp. 119-126
Author(s):  
Miroslava Mališová ◽  
Michal Horňáček ◽  
Pavol Hudec ◽  
Jozef Mikulec ◽  
Vladimír Jorík ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Chemical Properties ◽  
Synthesis Temperature ◽  
Optimal Synthesis ◽  
Preparation Process ◽  
Optimal Conditions ◽  
Temperature Range ◽  
Preparation Conditions ◽  
Physico Chemical ◽  
Ph Range

Abstract The aim of the research was to prepare and characterize hydrotalcite synthesized under different preparation conditions. The most common hydrotalcite preparation is the co-precipiaton method. The preparation process strongly influences the catalytic properties of hydrotalcite; therefore, optimal conditions have to be determined. During the study, seven samples of the catalyst were prepared in the pH range from 8 to 12 and the synthesis temperature range from 25 to 55 °C. Based on several catalyst properties, optimal synthesis pH 10 was found. Ideal temperature of the preparation was determined to be 35 °C, but the temperature does not have a significant effect on the catalyst properties.

scholarly journals A Radiomics nomogram for preoperative predicting recurrence of low grade gliomas based on multiparametric MRI

2021 ◽  
Author(s):  
Zhenhua Wang ◽  
Xinlan Xiao ◽  
Zhaotao Zhang ◽  
Keng He ◽  
Peipei Pang ◽  
...  
Keyword(s):  
Multivariate Logistic Regression Analysis ◽  
Low Grade ◽  
Training Set ◽  
Decision Curve Analysis ◽  
Logistic Analysis ◽  
Contrast Enhanced ◽  
Fluid Attenuated Inversion Recovery ◽  
Validation Set ◽  
The Individual ◽  
Good Agreement

Abstract Objective To develop a radiomics nomogram to predict the recurrence of Low grade glioma(LGG) after their first surgery; Methods A retrospective analysis of pathological, clinical and Magnetic resonance image(MRI) of LGG patients who underwent surgery and had a recurrence between 2017 and 2020 in our hospital was performed. After a rigorous selection,64 patients were eligible and enrolled in the study(22 cases were with recurrent gliomas),which was randomly assigned in a 7:3 ratio to either the training set and validation set; T1WI,T2WI fluid-attenuated-inversion-recovery(T2WI-FLAIR) and contrast-enhanced T1-weighted(T1CE) sequences, 396 radiomics features were extracted from each image sequence, minimum-redundancy maximum-relevancy(mRMR) alone or combining with univariate logistic analysis were used for features screening, the screened features were performed by multivariate logistic regression analysis and developed a predictive model both in training set and validation set; Receiver operating characteristic(ROC) curve, calibration curve, and decision curve analysis(DCA) were used to assess the performance of each model. Results The radiomics nomogram derived from three MRI sequence yielded an ideal performance than the individual ones, the AUC in the training set and validation set were 0.966 and 0.93 respectively, 95% confidence interval(95%CI) were 0.949-0.99 and 0.905-0.973 respectively; the calibration curves indicated good agreement between the predictive and the actual probability. The DCA demonstrated that a combination of three sequences had more favorable clinical predictive value than single sequence imaging. Conclusion Our multiparametric radiomics nomogram could be an efficient and accurate tool for predicting the recurrence of LGG after its first resection.

Cognitive Processes and Creative Lateral Thinking in Students of the Naval School of Peru

2021 ◽  
Vol 19 (5) ◽  
pp. 10-17
Author(s):  
Hector Santa Maria Relaiza ◽  
Doris Fuster-Guillen ◽  
Yolvi Ocana-Fernandez ◽  
Patricia Edith Guillen Aparicio ◽  
Freddy Antonio Ochoa Tataje
Keyword(s):  
High School ◽  
High School Students ◽  
Experimental Design ◽  
Data Collection ◽  
Cognitive Processes ◽  
School Students ◽  
Cross Sectional ◽  
Probabilistic Sampling ◽  
The Individual ◽  
Lateral Thinking

The present research focused on identifying the influence of cognitive processes in the creative lateral thinking of high school students. The work was developed under the positivist paradigm; it was classified as basic, of explanatory level, with quantitative approach, non-experimental design and cross-sectional. The sample, calculated through probabilistic sampling, consisted of 221 students. Two data collection instruments were used: the cognitive processes questionnaire and the lateral thinking questionnaire, which were subjected to content validity by expert judgment and reliability and internal consistency analysis by Cronbach's alpha, reaching values of 0.908 and 0.802, respectively. The analysis of verification by Spearman's rho obtained was 0.762, which determined the significant influence between cognitive processes and lateral thinking. It was concluded that, if procedures and actions that lead to the acquisition of knowledge in a constructive way and by discovery are practiced, creative and perceptive lateral thinking would be developed; then the individual would exhibit imagination and creative behaviors.

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