On-line Formation Research Articles

Effects of accuracy motivation and need to evaluate on mode of attitude formation and attitude–behavior consistency

This study investigates the effects of accuracy motivation and need to evaluate on online vs. memory-based attitude formation and attitude–behavior consistency. Results show that online attitude formation is more likely when accuracy motivation or the need to evaluate is high. However, cognitive load disrupts online attitude formation even when accuracy motivation is high. Additionally, attitude relevance increases the likelihood of online attitude formation, but attitude accessibility does not. Furthermore, online (vs. memory-based) attitudes are more predictive of subsequent non-hypothetical choice.

High Throughput Automated Determination of Glutathione Based on the Formation of a UV-Absorbing Thioacrylate Derivative

Sequential injection analysis (SIA) has been employed as the platform for the development of a high throughput automated assay for glutathione (GSH) in nutrition supplements. The proposed assay is based on the on-line formation of a UV-absorbing thioacrylate derivative (lambda(max) = 285 nm) upon reaction of thiol with the new reagent ethyl-propiolate (EP). This is the very first application of this reagent for the determination of GSH either in batch or continuous flow modes and the first SI method for the determination of GSH in pharmaceutical supplements. The various variables that typically affect such a protocol were studied, while thorough validation experiments according to established standards proved the reliability of the assay for the intended applications. As many as 100 sample injections were enabled per hour.

Nanoparticle-Based Sandwich Electrochemical Immunoassay for Carbohydrate Antigen 125 with Signal Enhancement Using Enzyme-Coated Nanometer-Sized Enzyme-Doped Silica Beads

A novel nanoparticle-based electrochemical immunoassay of carbohydrate antigen 125 (CA125) as a model was designed to couple with a microfluidic strategy using anti-CA125-functionalized magnetic beads as immunosensing probes. To construct the immunoassay, thionine-horseradish peroxidase conjugation (TH-HRP) was initially doped into nanosilica particles using the reverse micelle method, and then HRP-labeled anti-CA125 antibodies (HRP-anti-CA125) were bound onto the surface of the synthesized nanoparticles, which were used as recognition elements. Different from conventional nanoparticle-based electrochemical immunoassays, the recognition elements of the immunoassay simultaneously contained electron mediator and enzyme labels and simplified the electrochemical measurement process. The sandwich-type immunoassay format was used for the online formation of the immunocomplex in an incubation cell and captured in the detection cell with an external magnet. The electrochemical signals derived from the carried HRP toward the reduction of H(2)O(2) using the doped thionine as electron mediator. Under optimal conditions, the electrochemical immunoassay exhibited a wide working range from 0.1 to 450 U/mL with a detection limit of 0.1 U/mL CA125. The precision, reproducibility, and stability of the immunoassay were acceptable. The assay was evaluated for clinical serum samples, receiving in excellent accordance with results obtained from the standard enzyme-linked immunosorbent assay (ELISA) method. Concluding, the nanoparticle-based assay format provides a promising approach in clinical application and thus represents a versatile detection method.

Do animals and furniture items elicit different brain responses in human infants?

One of the earliest categorical distinctions to be made by preverbal infants is the animate–inanimate distinction. To explore the neural basis for this distinction in 7–8-month-olds, an equal number of animal and furniture pictures was presented in an ERP-paradigm. The total of 118 pictures, all looking different from each other, were presented in a semi-randomized order for 1000 ms each. Infants’ brain responses to exemplars from both categories differed systematically regarding the negative central component (Nc: 400–600 ms) at anterior channels. More specifically, the Nc was enhanced for animals in one subgroup of infants, and for furniture items in another subgroup of infants. Explorative analyses related to categorical priming further revealed category-specific differences in brain responses in the late time window (650–1550 ms) at right frontal channels: Unprimed stimuli (preceded by a different-category item) elicited a more positive response as compared to primed stimuli (preceded by a same-category item). In sum, these findings suggest that the infant’s brain discriminates exemplars from both global domains. Given the design of our task, we conclude that processes of category identification are more likely to account for our findings than processes of on-line category formation during the experimental session.

Determination of Trace Inorganic Mercury in Mineral Water by Flow Injection On-line Sorption Preconcentration-Cold Vapor Atomic Fluorescence Spectrometry

Abstract Flow injection on-line sorption preconcentration and separation in a knotted reactor (KR) was coupled to cold vapor atomic fluorescence spectrometry for the determination of trace mercury in mineral water. Mercury was preconcentrated by on-line formation of mercury diethyldithiocarbamate complex (Hg-DDTC) and absorption of the resulting neutral complex on the inner walls of a knotted reactor. A 20% (v/v) HNO 3 solution heated by Electromagnetic induction heating technique was used as eluent to remove the absorbed Hg-DDTC from the KR, and then the vapor mercury generated by mixing the resulting solution and KBH 4 was determined on-line by cold vapor atomic fluorescence spectrometry. The 20% HNO 3 was used as both the efficient eluent and the required acidic medium for subsequent mercury vapor generation. Using 20% HNO 3 instead of conventional organic solvent as eluent, the proposed method is simple, easy operational and environmental friendly. Under the optimal experimental conditions, the sample throughput was approximately 30 per hour with the enhancement factor of 35. The detection limit of mercury was 2.0 ng l −1 . The precision (RSD, n = 11) was 2.2% at the 0.1 μg l −1 Hg 2+ level.

Determination of arsenic in foods by flow injection on-line sorption pre-concentration with hydride generation atomic fluorescence spectrometry

A method was developed for the determination of total arsenic in foods using flow injection on-line sorption coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) using a cigarette filter as the sorbent material. After reducing As(V) to As(III) by using L-cysteine, the determination of total arsenic was achieved through on-line formation and retention of the pyrrolidine dithiocarbamate arsenic complex (As(III)–PDC) on the cigarette filter, which was packed in the pre-concentration column and total arsenic was determined by HG-AFS. The analytes were eluted with 1.68 mol l−1 HCl from the sorbent material. With consumption of 22 ml of the sample solution, an enrichment factor of 25.6 was obtained at a sample throughput of 11.6 h−1. The detection limits (3 standard deviations) and the precision (relative standard deviation) in foods ranged from 2.5 to 9.9 ng g−1 and from 1.1 to 2.2%, respectively. The method was used to determine arsenic in carrot, mushroom, chicken tissue, cod fish, rice, common carp and shrimp.

Flow-injection iodimetric determination of captopril in pharmaceutical preparations

A simple, fast and low cost procedure for spectrophotometric determination of captopril in pharmaceutical preparations is described. The procedure is based on a flow-injection system exploiting the on-line formation of the triiodide reagent, which is consumed in the presence of the analyte generating a transient signal. Linear response was observed up to 200 µmol L-1 with a detection limit of 1.0 µmol L-1 (99.7% confidence level). The coefficient of variation (n = 20) and the sampling rate were estimated as 1.2% and 72 determinations per hour, respectively. The main excipients found in pharmaceutical preparations did not affect the captopril determination. The zone sampling approach was exploited to implement on-line dilutions, aiming direct analysis of sample extracts. Results of the analysis of commercial samples agreed with the obtained by the titrimetric reference procedure described in the US-Pharmacopeia at the 95% confidence level. The reagent consumption was estimated as 18 µg of KMnO4 and 10 mg of KI per determination, with a cost of US$ 2.50 per 1000 determinations.

Flow injection on-line displacement/solid phase extraction system coupled with flame atomic absorption spectrometry for selective trace silver determination in water samples

A novel flow injection (FI) on-line displacement solid phase extraction preconcentration and/or separation method coupled with FAAS in order to minimize interference from other metals was developed for trace silver determination. The proposed method involved the on-line formation and subsequently pre-sorption of lead diethyldithiocarbamate (Pb-DDTC) into a column packed with PTFE-turnings. The preconcentration and/or separation of the Ag(I) took place through a displacement reaction between Ag(I) and Pb(II) of the pre-sorbed Pb-DDTC. Finally, the retained analyte was eluted with isobutyl methyl ketone (IBMK) and delivered directly to nebulizer for measuring. Interference from co-existing ions with lower DDTC complex stability in comparison with Pb-DDTC, was eliminated without need for any masking reagent. With 120 s of preconcentration time at a sample flow rate of 7.6 mL min−1, an enhancement factor of 110 and a detection limit (3 s) of 0.2 μg L−1 were obtained. The precision (RSD, n = 10) was 3.1% at the 10 μg L−1 level. The developed method was successfully applied to trace silver determination in a variety of environmental water samples and certified reference material.

Determination of As(III) and As(V) in water samples by flow injection online sorption preconcentration coupled to hydride generation atomic fluorescence spectrometry

A method was developed for the determination of arsenite [As(III)] and arsenate [As(V)] in water samples using flow injection online sorption coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) using a cigarette filter as the sorbent. Selective determination of As(III) was achieved through online formation and retention of the pyrrolidine dithiocarbamate arsenic complex on the cigarette filter, but As(V) which did not form complexes was discarded. After reducing As(V) to As(III) using L-cysteine, total arsenic was determined by HG-AFS. The concentration of As(V) was calculated by the difference between As(III) and total arsenic. The analytes were eluted from the sorbent using 1.68 mol L−1 HCl. With consumption of 22 mL of the sample solution, the enrichment factor of As(III) was 25.6. The detection limits (3σ/k) and the relative standard deviation for 11 replicate determinations of 1.0 ng mL−1 As(III) were found to be 7.4 pg mL−1 and 2.6%, respectively.

Computer simulation of sub-micron-scale precision truing of a metal-bonded diamond grinding wheel

A new simulation mode of wheel profile generation was proposed in precision truing of a metal-bonded diamond grinding wheel by considering the mutual wear of grinding wheel and truer in sub-micron scale. The aim is to understand how truing parameters influence truing accuracy and truing efficiency, namely wheel profile flatness and truing number. In order to assure the sub-micron-scale accuracy of a trued wheel profile, dry electro-contact discharge was employed in arc envelope truing. First, an arc-shaped truing profile replicated on wheel profile was defined and analyzed theoretically and then identified by truing experiment; second, the micro-truing ratio describing the mutual wear of a grinding wheel and truer related to the depth of cut was investigated by micro-truing experiment; then the simulation mode of the truing grinding wheel was established by using dispersed profile coordinates of the grinding wheel and truer with reference to the micro-truing ratio; finally, simulation analysis was conducted to trace on-line formation of the trued wheel profile in truing process. It is confirmed that this simulation method is valid and applicable to visualize the sub-micron-scale truing process. It is also found that by decreasing the depth of cut or plunge truing number wheel profile flatness decreases but truing number increases. It is concluded that there exist minimum wheel profile flatness and minimum truing number in a truing process, which can be used to optimize truing parameters for efficient precision truing.

A Fast and Simple Analysis of Glyphosate in Tea Beverages by Capillary Electrophoresis with On-Line Copper(II)-Glyphosate Complex Formation

Glyphosate is an herbicide used for many plants that can be toxic to humans in high doses. Current methods for measuring glyphosate are slow and expensive. Here we describe a fast and simple method for measuring glyphosate in tea beverages by capillary electrophoresis with on-line formation of copper(II)-glyphosate complex. The optimum running conditions were found to be 40 mM acetate buffer (pH 5.0) containing 5 mM CuSO4 with an effective voltage of +15 kV using a sulfonated capillary (FunCap-CE Type S) and direct UV detection at 250 nm. Linearity (r2>0.999) was demonstrated in the range 5-1000 mg/l of glyphosate. Good reproducibilities of peak area (relative standard deviation <1.2%) and migration time (relative standard deviation <0.2%) were obtained. Recovery of glyphosate was between 98 and 100%. With this method, a tea beverage that was mixed with a glyphosate formulation was successfully analyzed.

Measuring the Unmeasurable? Toward Operationalizing On-line and Memory-Based Political Judgments in Surveys

The article presents the development and validation of measuring online and memory-based judgment formation. The on-line model holds that judgments are formed when the information is encountered while the memory-based model affirms that judgments are formed based on the information people can recall from memory at a time a judgment is needed. In a correlation analysis, there is lower response latency, higher judgmental confidence and attitude extremity when the judgment is formed on-line. In construct validation, people who have formed memory-based judgments need more time to report their attitudes.

Theta synchronization networks emerge during human object???place memory encoding

Recent rodent hippocampus studies have suggested that theta rhythm-dependent neural dynamics ('theta phase precession') is essential for an on-line memory formation. A computational study indicated that the phase precession enables a human object-place association memory with voluntary eye movements, although it is still an open question whether the human brain uses the dynamics. Here we elucidated subsequent memory-correlated activities in human scalp electroencephalography in an object-place association memory designed according the former computational study. Our results successfully demonstrated that subsequent memory recall is characterized by an increase in theta power and coherence, and further, that multiple theta synchronization networks emerge. These findings suggest the human theta dynamics in common with rodents in episodic memory formation.

On-line Formation, Separation, and Estrogen Receptor Affinity Screening of Cytochrome P450-Derived Metabolites of Selective Estrogen Receptor Modulators

We have developed a fully automated bioreactor coupled to an on-line receptor affinity detection system. This analytical system provides detailed information on pharmacologically active metabolites of selective estrogen receptor modulators (SERMs) generated by cytochromes P450 (P450s). We demonstrated this novel concept by investigating the metabolic activation of tamoxifen and raloxifene by P450-containing pig and rat liver microsomes. The high resolution screening (HRS) system is based on the coupling of a P450-bioreactor to an HPLC-based estrogen receptor alpha (ERalpha) affinity assay. P450-derived metabolites of the SERMs were generated in the bioreactor, subsequently trapped on-line with solid phase extraction, and finally separated with gradient HPLC. Upon elution, the metabolites were screened on affinity for ERalpha with an on-line HRS assay. With this HRS system, we were able to follow, in a time-dependent manner, the formation of ERalpha-binding metabolites of tamoxifen and raloxifene. By analyzing the bioaffinity chromatograms with liquid chromatography-tandem mass spectrometry, structural information of the pharmacologically active metabolites was obtained as well. For tamoxifen, 15 active and 6 nonactive metabolites were observed, of which 5 were of primary, 10 of secondary, and 6 of an as yet unknown order of metabolism. Raloxifene was biotransformed in three primary and three secondary metabolites. MS/MS analysis revealed that three of the observed active metabolites of raloxifene were not described before. The present automated on-line HRS system coupled to a P450-containing bioreactor and an ERalpha-affinity detector proved very efficient, sensitive, and selective in metabolic profiling of SERMs.

Determination of arsenic(III) by flow injection solid phase extraction coupled with on-line hydride generation atomic absorption spectrometry using a PTFE turnings-packed micro-column

A novel flow injection (FI) solid phase extraction method for the determination of arsenic(III) at trace levels was developed, using on-line hydride generation atomic absorption spectrometry (HG-AAS). Selective determination of As(III) was achieved by on-line formation and retention of the pyrrolidine dithiocarbamate arsenic complex As(III)–PDC on the PTFE turnings which are packed in the preconcentration micro-column. The retained complex was eluted by 2 ml 2 mol l −1 HCl and subsequently introduced on-line into the integrated reaction chamber/gas–liquid separator (RC–GLS). A 1.5% (m/v) NaBH 4 solution was used for arsine generation, while a gas stream of N 2 was employed for flash release and transportation towards the atomic absorption flow through cell (AAC) for atomization and measurement. The excellent performance of PTFE turnings as sorbent material and the compact design of the RC–GLS result to high sensitivity, selectivity and sampling frequency. For 60 s preconcentration time and sample consumption 10.4 ml a sampling frequency of 25 h −1 and a detection limit of c L = 0.02 μg l −1 were obtained. The repeatability, expressed as relative standard deviation (R.S.D.), at 1.0 μg l −1 As(III), was s r = 2.8%. The proposed method was successfully applied to the selective determination of As(III) in natural waters and total arsenic determination in certified reference material.

On-line emulsion formation and multi-element analysis of edible oils by inductively coupled plasma atomic emission spectrometry

A novel simple on-line emulsion formation system for multi-element analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) was developed. A laboratory made magnetic-stirring micro-chamber was used for continuous edible emulsification with Triton X-100 and for subsequent introduction of the emulsion into ICP-AES. The optimum concentration of oil in emulsion for maximum sensitivity was 50% (v/v). The performance of the system was demonstrated for Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb, Tl and Zn determination in olive, sunflower and corn oil. Good agreement was found between calibration curves for oil emulsion and aqueous ones for the most of the investigated spectral lines. The calibration curves for each element were linear at least up to 1.0 mg l −1 and the correlation coefficients were ranged between 0.991 and 0.999. The proposed method was applied to the analysis of olive oil sample and compared with ETAAS-wet digestion method. No significant differences were observed between the two methods.

On-line slurry formation and nebulization for inductively coupled plasma atomic emission spectrometry. Multi-element analysis of cocoa and coffee powder samples

A simple on-line slurry formation and direct nebulization system for inductively coupled plasma atomic emission spectrometric multi-element analysis was developed. A laboratory made micro-chamber with a magnetic-stirrer was used for on-line stable slurry formation in a dispersant solution of 0.5% v/v Triton X-100 and 1% v/v HNO3. A Babington-type nebulizer combined with cyclonic-type spray chamber was adopted for on-line slurry nebulization and atomization. All critical parameters were studied and optimized. The performance of the system was demonstrated for Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Ni, and Zn determination in cocoa and coffee powder samples. The recommended particle size was <70 μm and the slurry concentration was 0.6% m/v, while the working slurry concentration could be ranged from 0.3 to 3.3% m/v with proportional sensitivity. Excellent agreement was found between the standard addition calibration procedure and the calibration curves using simple aqueous standard solutions for almost all of the investigated elements. The reliability of the proposed method was confirmed by comparing it with FAAS and ETAAS wet digestion methods for the analysis of cocoa and coffee samples. No significant differences were observed between the two methods.

Online formation of a hierarchical cognitive map for object–place association by theta phase coding

Object-place associative memory, the storage of object and place conjunctions based on a one-time experience, is hippocampal-dependent in humans. Theta phase precession, a type of neural dynamics observed in the rat hippocampus, has recently been suggested to serve a role in instantaneous memory formation based on a one-time experience, while its functional role in associating distinct types of information (object and place information) is unclear. In this study, we hypothesize that theta phase encoding with theta phase precession contributes to the storage of object-place associations. To examine this hypothesis, we propose a neural network model of the corticohippocampal system, including central-peripheral visual pathways and theta phase coding in the hippocampus. Memory storage computer experiments demonstrate that the hippocampal network successfully stores the object-place associations of a one-time experience. Interestingly, it is also found that a random visual input sequence results in a robust formation of asymmetric connections between objects and scenes instantaneously after a single trial. Furthermore, it is found that scene-object connections and scene-scene connections form a hierarchical network representing the spatial alignment of scenes and objects in the environment. Our findings indicate that the theta phase coding, as observed in the rat hippocampus, can facilitate the online memory storage of complex environments in humans as a hierarchical cognitive map.

Effects of a group stereotype on memory for behaviors performed by a group member

Participants were provided with a group impression prior to receiving behavioral information pertaining to a group member. The group impression conveyed a below average level of intelligence or an above average level of intelligence. In addition, the distribution of intelligence scores within the group was unimodal in one condition and bimodal in another condition. The behavioral information pertaining to the individual group member was predominantly intelligent or predominantly unintelligent, thereby affording the on-line formation of an intelligent or unintelligent personal impression regarding the group member. After receiving the behavioral information, participants recalled the behaviors and rated the group member along the intelligence dimension. Recall and judgment data revealed that the group impression functioned as the dominant expectancy that influenced processing of the behavioral information. Moreover, the effect of the group expectancy was substantially greater in the unimodal condition than in the bimodal condition. Presence of a group impression appears to reduce the tendency for participants to derive a personal impression on-line, and reduce the tendency for participants to rely on a derived personal expectancy when encoding behaviors performed by a group member. Potential moderators of this effect are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

Selective Quantification of Trace Palladium in Road Dusts and Roadside Soils by Displacement Solid-Phase Extraction Online Coupled with Electrothermal Atomic Absorption Spectrometry

There is a growing concern about the effect of palladium on human health because of the toxicity and increasing occurrence of palladium as a result of its extensive use in automotive catalytic converters. Development of reliable analytical methodologies for the determination of palladium in environmental materials is of great importance for critical evaluation of the possible risks for human health. In this work, a displacement solid-phase extraction technique was developed and online coupled to electrothermal atomic absorption spectrometry (ETAAS) for selective and sensitive determination of trace palladium in environmental samples without need of any special selective complexing agents, selective sorbents, and masking agents. The developed methodology involved the online formation of copper pyrrolidine dithiocarbamate (Cu-PDC), and the resultant Cu-PDC was extracted onto a microcolumn packed with the sorbent from a cigarette filter. Trace Pd(II) was selectively preconcentrated through loading the sample solution onto the microcolumn by online displacement reaction between Pd(II) and the extracted Cu-PDC on the microcolumn. The retained analyte was subsequently eluted with 40 microL of ethanol for online ETAAS determination. Interferences from coexisting heavy metal ions with lower stability of their PDC complexes relative to Cu-PDC were minimized. The tolerable concentrations of Cd-(II), Fe(III), Co(II), Mn(II), Cr(III), and Zn(II) were up to 2, 6, 40, 2, 1.5, and at least 100 mg L(-1), respectively. Compared with conventional solid-phase extraction methodology, the developed displacement solid-phase extraction protocol gave 2-4 orders of magnitude improvement in the maximum tolerable concentrations of coexisting heavy metal ions. With the consumption of only 2.8 mL of sample solution, an enhancement factor of 52 and a detection limit (3sigma) of 18 ng L(-1) were achieved at a sample throughput of 30 samples h(-1). The precision (RSD, n = 13) was 2.5% at the 1 microg L(-1) level. The present methodology was successfully applied to selective determination of trace palladium in local road dusts and roadside soils.