Function Of Experimental Conditions Research Articles

First principles studies of proton conduction in KTaO3.

KTaO3 (KTO) is a useful prototypical perovskite for examining the mechanisms of proton transport in perovskites. Previously, Gomez et al. [J. Chem. Phys. 126, 194701 (2007)] reported density functional theory (DFT) calculations describing proton hopping in defect-free KTO. We use DFT calculations to extend that work in two directions, namely, understanding isotope effects in low and high temperature proton transport and the role of native point defects in KTO. At cryogenic temperatures, quantum tunneling plays a vital role in the net hopping of protons in KTO. At the elevated temperature characteristic of applications involving proton-conducting perovskites, tunneling is negligible but zero point energy effects still lead to non-negligible isotope effects for H(+), D(+), and T(+). We also use DFT to characterize the populations of relevant point defects in KTO as a function of experimental conditions, and to examine the migration of protons that are close in proximity to these defects. This information gives useful insight into the overall transport rates of protons through KTO under a variety of external environments. We also assess the overall diffusivity of protons in KTO at various ranges of oxygen vacancy concentrations by performing kinetic Monte Carlo simulations.

Sorption of solutions complicated by the crystallization of a polymer sorbent

The sorption of a liquid polymer solution have been studied as a function of experimental conditions, and the experimental results are discussed taking into account the chemical nature of the sorbate and the sorbent and the structure of the polymer. An algorithm of successive actions is given; it shows the effect of the structure of aqueous organic solutions on their sorption by semicrystalline polyethylene terephthalate.

Modeling the Photocatalytic Process of Variation in Chemical Oxygen Demand via Stochastic Differential Equations

Several papers in the literature on Advanced Oxidation Processes (AOPs) confirm the process as a viable alternative for the treatment of a variety of industrial effluents. In many of these works, modeling the variations of Chemical Oxygen Demand (COD) as a function of different experimental conditions was performed by techniques such as Design of Experiments, Artificial Neural Networks and Multivariate Analysis. These techniques require both a large number of parameters and a large quantity of experimental data for a systematic study of the model parameters as a function of experimental conditions. On the other hand, the study of Stochastic Differential Equations (SDE) is presently well developed with several practical applications noted in the literature. This paper presents a new approach in studying the variations of COD in AOPs via SDE. Specifically, two effluents, from the manufacture of paints and textiles were studied by combined treatment of the photo-Fenton process and catalytic ozonization.

Synthesis and optimization of colloidal silica nanoparticles and their functionalization with methacrylic acid

The synthesis of colloidal SiO2 nanoparticles was achieved via the base-catalyzed hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) in an alcoholic medium with the careful variation of the concentrations of water, ammonia and TEOS. In this study, we investigated the influence of experimental parameters on the average size of nanoparticles by means of a multivariate statistical analysis using a factorial design to create one model to predict particle size in function of experimental conditions. This model predicted that it is possible to synthesize silica nanoparticles with size in the range from 17 to 333nm, according to the chosen condition for the amount of water, ammonia and TEOS. It was observed that only the molar amount of NH3, the molar amount of H2O and the effect from interaction between molar amount of TEOS and H2O were significant. Subsequently, surface modification of the colloidal silica was performed in situ using the coupling agent 3(trimethoxysilyl)propyl methacrylate (TMSPM).

“Healthy,” “diet,” or “hedonic”. How nutrition claims affect food-related perceptions and intake?

The main purpose of this study was to investigate the impact of nutrition claims on food perceptions and intake among adult men and women, during ad libitum snacks. In a three (healthy vs. diet vs. hedonic) by two (normal-weight vs. overweight/obese) by two (unrestrained vs. restrained eaters) factorial design, 164 men and 188 women were invited to taste and rate oatmeal-raisin cookies. Despite the fact that the cookies were the same in all conditions, they were perceived as being healthier in the “healthy” condition than in the “diet” and “hedonic” conditions. The caloric content was estimated as higher by participants in the “hedonic” than in the “healthy” condition, by women than by men, and by restrained than by unrestrained eaters. Although measured ad libitum cookie intake did not differ as a function of experimental condition, overweight restrained men ate more than did women from each BMI and restraint category. Conversely, overweight restrained women ate less than did men from each BMI and restraint category. In conclusion, our manipulations of healthiness and “fatteningness” of food were effective in changing perceptions, but were not in changing behavior.

Improvements in perceptual and cognitive performance linked to baseline iron status and consumption of a double‐fortified salt

Iron deficiency (ID) has numerous effects on individual functioning, including perception and cognition. Research has documented substantial deficits with ID and improvements with iron repletion. However, a weakness of this work has been its lack of specificity in measuring these changes. The present study considered the effects of ID and repletion in 248 female tea‐pickers of reproductive age (18–55 y) in West Bengal, India. Six measures of perceptual and cognitive performance‐‐‐simple reaction time, 2 measures of visual detection, 2 measures of attention, and recognition memory‐‐‐were selected for their ability to selectively examine perceptual and cognitive functioning relative to iron status. The measures were used in a randomized controlled double‐blind intervention involving salt double‐fortified with iodine and iron (DFS). Measures were taken before and after a 10‐month intervention. We previously reported substantial improvements as a function of experimental condition. We here link improvements in specific aspects of perceptual and cognitive performance to baseline iron status and total amount of DFS consumed. Support: Mathile Institute, Micronutrient Initiative, and NSF.

Spontaneous deposition of Pd onto Fe–Cr–Al alloys

The spontaneous deposition of Pd onto Fecralloy sheets and foams was studied. Pd deposits were obtained by immersion of Fecralloy samples in mildly acid, deaerated PdCl2 solutions, at open circuit. Pd displaced all alloy elements and deposited onto the alloy which was initially coated by an oxides film and underwent transpassive dissolution. The Pd loading and the Pd surface area were determined as a function of experimental conditions, like the nature of the Fecralloy sample (sheets or foams of variable grade), the concentration of the PdCl2 solution and the duration of the deposition. The results were compared to those obtained by depositing Pd onto Ni foams, with the same procedure. The Pd deposition rates were not much different on Fecralloy and Ni, but the Pd surface area per unit Pd mass was significantly higher for Ni than for Fecralloy. The Pd deposit morphology was influenced by the presence of passive oxides on the Fecralloy surface. The catalytic activity in methanol anodic oxidation depended only on the Pd surface area, irrespective of the nature of the support (Ni or Fecralloy).

Green synthesis of xylan hemicellulose esters

The esterification of xylan type hemicelluloses, isolated from birchwood, was carried out firstly in homogeneous conditions using N, N-dimethylformamide (DMF) and lithium chloride (LiCl) in the presence of 4-dimethylaminipyridine (DMAP). The degree of substitution (DS) of xylan acetates ranged between 0.9 and 2.0 as a function of experimental conditions. Due to the problems of toxicity and recycling of DMF, an alternative method of esterification is reported in the second part of this work, performing in the absence of organic solvent and using DMAP or methanesulfonic acid (MSA) as catalysts. Acetylation reaction catalyzed by MSA was developed through an experimental design in order to achieve the highest DS under the mildest conditions. The significant factors and their interactions were identified. The optimization of reaction parameters allowed to obtain a high DS (1.6) and maximal yield (85%). Moreover, the reactivity of propionic and hexanoic anhydrides was evaluated and hydrophobic xylan esters with low degrees of substitution were obtained.

Dynamics of Cryptococcus neoformans-Macrophage Interactions Reveal that Fungal Background Influences Outcome during Cryptococcal Meningoencephalitis in Humans

ABSTRACTCryptococcosis is a multifaceted fungal infection with variable clinical presentation and outcome. As in many infectious diseases, this variability is commonly assigned to host factors. To investigate whether the diversity of Cryptococcus neoformans clinical (ClinCn) isolates influences the interaction with host cells and the clinical outcome, we developed and validated new quantitative assays using flow cytometry and J774 macrophages. The phenotype of ClinCn-macrophage interactions was determined for 54 ClinCn isolates recovered from cerebrospinal fluids (CSF) from 54 unrelated patients, based on phagocytic index (PI) and 2-h and 48-h intracellular proliferation indexes (IPH2 and IPH48, respectively). Their phenotypes were highly variable. Isolates harboring low PI/low IPH2 and high PI/high IPH2 values were associated with nonsterilization of CSF at week 2 and death at month 3, respectively. A subset of 9 ClinCn isolates with different phenotypes exhibited variable virulence in mice and displayed intramacrophagic expression levels of the LAC1, APP1, VAD1, IPC1, PLB1, and COX1 genes that were highly variable among the isolates and correlated with IPH48. Variation in the expression of virulence factors is thus shown here to depend on not only experimental conditions but also fungal background. These results suggest that, in addition to host factors, the patient’s outcome can be related to fungal determinants. Deciphering the molecular events involved in C. neoformans fate inside host cells is crucial for our understanding of cryptococcosis pathogenesis.

Screening for Oxidative Stress Elicited by Engineered Nanomaterials: Evaluation of Acellular DCFH Assay.

The DCFH assay is commonly used for measuring free radicals generated by engineered nanomaterials (ENM), a well-established mechanism of ENM toxicity. Concerns exist over susceptibility of the DCFH assay to: assay conditions, adsorption of DCFH onto ENM, fluorescence quenching and light scattering. These effects vary in magnitude depending on ENM physiochemical properties and concentration. A rigorous evaluation of this method is still lacking. The objective was to evaluate performance of the DCFH assay for measuring ENM-induced free radicals. A series of diverse and well-characterized ENM were tested in the acellular DCFH assay. We investigated the effect of sonication conditions, dispersion media, ENM concentration, and the use of horseradish peroxidase (HRP) on the DCFH results. The acellular DCFH assay suffers from high background signals resulting from dye auto-oxidation and lacks sensitivity and robustness. DCFH oxidation is further enhanced by HRP. The number of positive ENM in the assay and their relative ranking changed as a function of experimental conditions. An inverse dose relationship was observed for several Carbon-based ENM. Overall, these findings indicate the importance of having standardized assays for evaluating ENM toxicity and highlights limitations of the DCFH assay for measuring ENM-induced free radicals.

Formation of Gas-Phase Bromine from Interaction of Ozone with Frozen and Liquid NaCl/NaBr Solutions: Quantitative Separation of Surficial Chemistry from Bulk-Phase Reaction

The formation kinetics of gas-phase bromine (Br(2)) from interaction of gas-phase ozone (O(3)) with frozen and liquid solutions of NaCl (0.55 M) and NaBr (largely from 1.7 to 8.5 mM) have been studied from -40 to 0 °C in a coated-wall flow tube coupled to a chemical ionization mass spectrometer. The reactive uptake coefficient for O(3) is deduced from the product formation rate and then studied as a function of experimental conditions. In particular, for both the liquid and frozen solutions, we find that the uptake coefficient is inversely dependent on the gas-phase O(3) concentration in a manner that is quantitatively consistent with both surface- and bulk-phase kinetics. The reaction is fastest on acidic media (pH of the starting solution down to 2) but also proceeds at an appreciable rate on neutral substrates. Above 253 K, the uptake coefficient increases with increasing temperature on frozen solutions, consistent with an increasing brine content. The similarity of the absolute magnitude and form of the kinetics on the frozen and liquid substrates suggests that the reaction on the frozen solution is occurring with the associated brine, and not with the ice bulk or a quasi-liquid layer existing on the ice. The implications of these results to bromine activation in the tropospheric boundary layer are made.

Long-range correlation properties in motor timing are individual and task specific

1/f (β) noise represents a specific form of (long-range) correlations in a time series that is pervasive across many sensorimotor variables. Recent studies have shown that the precise properties of the correlations demonstrated by a group of test participants may vary as a function of experimental conditions or factors characterizing the group. Our purpose in the present study was to clarify whether long-range correlations affect sensorimotor performance generally or in a task-specific manner and whether each individual produces characteristic long-range correlations that are reliable across several runs of the same task. We analyzed the series of time intervals produced by 43 participants in two timing tasks: unimanual rhythmic tapping and circle drawing. We found that a participant's 1/f (β) properties in tapping were not related to the 1/f (β) properties in circle drawing. However, within each task, individual differences were reliable, and a Cronbach's alpha of .59 showed a high degree of within-subjects reproducibility of the long-range correlations. Thus, long-range correlations represent a consistent and distinctive characteristic of individuals performing a particular task, rather than a ubiquitous generic property of sensorimotor time series. The implications of these results are discussed from both a theoretical and a methodological perspective.

The Global Analysis of DEER Data

Previously, global analysis has been successfully used to analyze both continuous wave and saturation transfer EPR data1-3. In this work, algorithms have been developed for the global analysis of DEER data. Applications include the analysis of DEER data collected at multiple frequencies or multiple timescales. Analysis of DEER data from the soluble protein CDB3 (MW ≈ 90 kD) has shown that the background DEER signal is not well-fit by an exponential decay due to the large size of the CDB3 dimer. As a result, background correction with an exponential decay prior to analysis results in a poor fit to the data. An algorithm has been developed which explicitly fits the background signal with the radius of the molecule (assuming it is spherical) and the spin concentration as parameters. Using this approach, excellent fits to DEER data can be obtained without prior background correction. Also, DEER data can be globally analyzed to determine changes in the relative populations of components of the distance distribution as a function of experimental conditions. For example, DEER has been previously used to study the structural effects of a proline to arginine mutation at residue 327 of CDB3. Intradimer distances in spin-labelled wild type CDB3 can be fit using a single component distance distribution4. The same measurements on P327R CDB3 indicate the mutation induces a second more disordered component in the distance distribution5. The global analysis of DEER data collected for multiple spin-labelling sites in both the WT and P327R background is being used to further test this two-component model. Supported by NIH GM 080513. 1. Hustedt and Beth, BJ 69:1409–1423 (1995). 2. Hustedt et al., BJ 64:614–621 (1993). 3. Hustedt et al., BJ 72:1861–1877 (1997). 4. Zhou et al., Biochemistry 44:15115–15128 (2005). 5. Zhou et al., BJ 90:528A (2006).

Preparation of rib channel waveguides on polymer in electric field

Micro-sized patterns were created on oligomer (Su-8) films by the effect of external electric field, perpendicular to the film surface. Structures with varying parameters were prepared and the growth of continuous or dot-like structures was observed. The mechanism dominating the structure growth was examined and found to be a function of experimental conditions. The dependence of the form and the size of the created patterns on the intensity of the electric field, exposure time and initial distance between mask and polymer surface was investigated. Waveguiding properties of the linear pattern, produced by the above technique, were examined and the following parameters were obtained: propagation loss — 2–3 dB/cm, effective refractive index — 1.6276, number of supported modes — 30).

The role of demonstrator familiarity and language cues on infant imitation from television

An imitation procedure was used to investigate the impact of demonstrator familiarity and language cues on infant learning from television. Eighteen-month-old infants watched two pre-recorded videos showing an adult demonstrating a sequence of actions with two sets of stimuli. Infants’ familiarity with the demonstrator and the language used during the demonstration varied as a function of experimental condition. Immediately after watching each video, infants’ ability to reproduce the target actions was assessed. A highly familiar demonstrator did not enhance infants’ performance. However, the addition of a narrative, developed from mothers’ naturalistic description of the event, facilitated learning from an unfamiliar demonstrator. We propose that the differential effect of demonstrator familiarity and language cues may reflect the infants’ ability to distinguish between important and less important aspects in a learning situation.

Ab initio thermodynamic evaluation of Pd atom interaction with CeO2 surfaces

Palladium supported on ceria is an effective catalytic material for three-way automotive catalysis, catalytic combustion, and solid-oxide fuel cell (SOFC) anodes. The morphology, oxidation state, and particle size of Pd on ceria affect catalytic activity and are a function of experimental conditions. This work utilizes ab initio thermodynamics using density functional theory (DFT) (DFT+U) methods to evaluate the stability of Pd atoms, PdO(x) species, and small Pd particles in varying configurations on CeO(2) (111), (110), and (100) single crystal surfaces. Over specific oxygen partial pressure and temperature ranges, palladium incorporation to form a mixed surface oxide is thermodynamically favorable versus other single Pd atom states on each ceria surface. For example, Pd atoms may incorporate into Ce fluorite lattice positions in a Pd(4+) oxidation state on the CeO(2) (111) surface. The ceria support shifts the transition between formal Pd oxidation states (Pd(0), Pd(2+), Pd(4+)) relative to bulk palladium and stabilizes certain oxidized palladium species on each surface. We show that temperature, oxygen pressure, and cell potential in a SOFC can influence the stable states of palladium supported on ceria surfaces, providing insight into structural stability during catalytic operation.

Monitoring of the Chemical Species in a Liquid-Phase Claus Reaction

Although the Claus-reaction-based processes are widely used in industry to recover sulfur from sour gas or crude oil, the precise mechanism of this reaction remains unclear and controversial. The aim of this study was to determine the chemical species of the Claus reaction in an organic liquid phase [using polyethylene glycol 400 (PEG) as solvent] at 125−130 °C. A combined UV−vis and Raman spectroscopic approach is developed to monitor the sulfur speciation. In addition, ab initio molecular-modeling techniques lead to an exhaustive mapping of the Raman spectral properties of molecules. Several intermediate sulfur-containing species have also been identified, as a function of experimental conditions. These analytical results are required as preliminary data to describe the chemistry of the Claus reaction in the organic liquid phase. These data are helpful to improve the kinetic model for the subdew point Claus tail gas treatment, used in the refining and natural gas treatment industries.

Spatial point pattern analysis applied to bubble nucleation in silicate melts

Experimental bubble nucleation studies are used for determining the nucleation mechanism as a function of experimental conditions, the resulting bubble number density, and can also yield estimates of the melt-vapor surface tension. This provides important information on gas exsolution in silicate melts, which can be applied towards understanding magmatic degassing in volcanic conduits. At present, determination of nucleation processes in tiny experimental samples relies upon visual observations. To improve the characterization of the spatial distribution of bubbles, we present a new application of spatial point pattern analysis. This technique allows the quantitative description of the spatial distribution of nucleation sites and has the potential to distinguish between homogeneous, heterogeneous, and multiple nucleation events. Since point pattern analysis highlights clustering or spatial regularity among objects, it may improve our understanding of the melt structure underlying the spatial distribution of nucleation sites, as well as interactions between bubble populations resulting from different nucleation pulses within a single experimental sample.

One-way avoidance acquisition and cellular density in the basolateral amygdala: Strain differences in Roman high- and low-avoidance rats

The goal of the present experiment was to study the performance of inbred Roman high- (RHA-I) and low- (RLA-I) avoidance rats in one-way avoidance learning and to relate the behaviour of the animals to cellular density in the basolateral amygdala (BLA), a brain region related to fear and anxiety. Thus, females from both strains were exposed either to 30 s or 1 s in the safe place as a function of experimental condition, until they reached five consecutive avoidance responses. Thereafter, the rats were perfused, and their brains sectioned in 40 μm coronal sections, stained with cresyl violet. The area (percentage of field) corresponding to the BLA structures was quantified by computerized-assisted image analysis. The results indicated that RLA-I showed a significantly poorer acquisition of the one-way avoidance task than did RHA-I rats, but only when safe time was the shortest (1 s). In addition, the number of trials needed to reach the behavioural acquisition criterion was negatively correlated with BLA cellular density in RLA-I rats. These data suggest the possibility of relating behavioural and neuro-anatomical indexes, enabling exploration of the biological basis of fear/anxiety behaviours.

A resolution study for electrostatic force microscopy on bimetallic samples using theboundary element method

Electrostatic force microscopy (EFM) is a special design of non-contact atomic forcemicroscopy used for detecting electrostatic interactions between the probe tip and thesample. Its resolution is limited by the finite probe size and the long-range characteristicsof electrostatic forces. Therefore, quantitative analysis is crucial to understanding therelationship between the actual local surface potential distribution and the quantitiesobtained from EFM measurements. To study EFM measurements on bimetallic sampleswith surface potential inhomogeneities as a special case, we have simulated suchmeasurements using the boundary element method and calculated the force component andforce gradient component that would be measured by amplitude modulation (AM) EFMand frequency modulation (FM) EFM, respectively. Such analyses have been performed forinhomogeneities of various shapes and sizes, for different tip–sample separationsand tip geometries, for different applied voltages, and for different media (e.g.,vacuum or water) in which the experiment is performed. For a sample with asurface potential discontinuity, the FM-EFM resolution expression agrees with theliterature; however, the simulation for AM-EFM suggests the existence of an optimaltip radius of curvature in terms of resolution. On the other hand, for sampleswith strip- and disk-shaped surface potential inhomogeneities, we have obtainedquantitative expressions for the detectability size requirements as a function ofexperimental conditions for both AM- and FM-EFMs, which suggest that a largertip radius of curvature is moderately favored for detecting the presence of suchinhomogeneities.