Field ion microscopic studies of the CO oxidation on platinum: Field ion imaging and titration reactions

NASA Astrophysics Data System (ADS)

Gorodetskii, V.; Drachsel, W.; Block, J. H.

1994-05-01

Elementary steps of the CO oxidation—which are important for understanding the oscillatory behavior of this catalytic reaction—are investigated simultaneously on different Pt-single crystal surfaces by field ion microscopy. Due to preferential ionization probabilities of oxygen as imaging gas on those surface sites, which are adsorbed with oxygen, these sites can be imaged in a lateral resolution on the atomic scale. In the titration reaction a COad-precovered field emitter surface reacts with gaseous oxygen adsorbed from the gas phase or, vice versa, the Oad-precovered surface with carbon monoxide adsorbed from the gas phase. The competition of the manifold of single crystal planes exposed to the titration reaction at the field emitter tip is studied. The surface specificity can be documented in the specific reaction delay times of the different planes and in the propagation rates of the reaction-diffusion wave fronts measured on these individual planes during the titration reaction with a time resolution of 40 ms. At 300 K the COad-precovered surfaces display the {011} regions, precisely the {331} planes as the most active, followed by {012}, {122}, {001}, and finally by {111}. Reaction wave fronts move with a velocity of 8 Å/s at {012}, with ≊0.8 Å/s at {111}, and have a very fast ``switch-on'' reaction at the (001) plane with 500 Å/s. At higher temperature, T=350 K, an acceleration of reaction rates is combined with shorter delay times. The titration reaction of a precovered Oad surface with COgas at T=373 K shows the formation of CO islands starting in the {011} regions with a quickly moving reaction front into the other surface areas without showing particular delay times for different surface symmetries. The two reverse titration reactions have a largely different character. The titration of COad with oxygen adsorbed from the gas phase consists of three different steps, (i) the induction times, (ii) the highly surface specific reaction, and (iii) different rates of wave front propagation. The reaction of COgas with a precovered Oad layer on the other hand starts with nucleating islands around the {011} planes from where the whole emitter surface is populated with COad without pronounced surface specifity.

On the Implications of a Sex Difference in the Reaction Times of Sprinters at the Beijing Olympics

PubMed Central

Lipps, David B.; Galecki, Andrzej T.; Ashton-Miller, James A.

2011-01-01

Elite sprinters offer insights into the fastest whole body auditory reaction times. When, however, is a reaction so fast that it represents a false start? Currently, a false start is awarded if an athlete increases the force on their starting block above a given threshold before 100 ms has elapsed after the starting gun. To test the hypothesis that the fastest valid reaction times of sprinters really is 100 ms and that no sex difference exists in that time, we analyzed the fastest reaction times achieved by each of the 425 male and female sprinters who competed at the 2008 Beijing Olympics. After power transformation of the skewed data, a fixed effects ANOVA was used to analyze the effects of sex, race, round and lane position. The lower bounds of the 95, 99 and 99.9% confidence intervals were then calculated and back transformed. The mean fastest reaction time recorded by men was significantly faster than women (p<0.001). At the 99.9% confidence level, neither men nor women can react in 100 ms, but they can react in as little as 109 ms and 121 ms, respectively. However, that sex difference in reaction time is likely an artifact caused by using the same force threshold in women as men, and it permits a woman to false start by up to 21 ms without penalty. We estimate that female sprinters would have similar reaction times to male sprinters if the force threshold used at Beijing was lowered by 22% in order to account for their lesser muscle strength. PMID:22039438

A comparative study on visual choice reaction time for different colors in females.

PubMed

Balakrishnan, Grrishma; Uppinakudru, Gurunandan; Girwar Singh, Gaur; Bangera, Shobith; Dutt Raghavendra, Aswini; Thangavel, Dinesh

2014-01-01

Reaction time is one of the important methods to study a person's central information processing speed and coordinated peripheral movement response. Visual choice reaction time is a type of reaction time and is very important for drivers, pilots, security guards, and so forth. Previous studies were mainly on simple reaction time and there are very few studies on visual choice reaction time. The aim of our study was to compare the visual choice reaction time for red, green, and yellow colors of 60 healthy undergraduate female volunteers. After giving adequate practice, visual choice reaction time was recorded for red, green, and yellow colors using reaction time machine (RTM 608, Medicaid, Chandigarh). Repeated measures of ANOVA and Bonferroni multiple comparison were used for analysis and P < 0.05 was considered statistically significant. The results showed that both red and green had significantly less choice visual choice reaction (P values <0.0001 and 0.0002) when compared with yellow. This could be because individual color mental processing time for yellow color is more than red and green.

Generalizing Over Conditions by Combining the Multitrait Multimethod Matrix and the Representative Design of Experiments,

DTIC Science & Technology

1986-01-01

by Anderson (1985) was reported in an article by Posner (1969) in which the difference in reaction time to an 1 "identity match" and a "name match...shorter reaction time) for the identity match but after a two-second [inter-stimulus) interval this * * advantage has almost completely disappeared. This...of critical sentences in a story. It is similar, however, in that reaction time was also used to evaluate differences between response categories that

Effects of reaction time variability and age on brain activity during Stroop task performance.

PubMed

Tam, Angela; Luedke, Angela C; Walsh, Jeremy J; Fernandez-Ruiz, Juan; Garcia, Angeles

2015-09-01

Variability in reaction time during task performance may reflect fluctuations in attention and cause reduced performance in goal-directed tasks, yet it is unclear whether the mechanisms behind this phenomenon change with age. Using fMRI, we tested young and cognitively healthy older adults with the Stroop task to determine whether aging affects the neural mechanisms underlying intra-individual reaction time variability. We found significant between-group differences in BOLD activity modulated by reaction time. In older adults, longer reaction times were associated with greater activity in frontoparietal attentional areas, while in younger adults longer reaction times were associated with greater activity in default mode network areas. Our results suggest that the neural correlates of reaction time variability change with healthy aging, reinforcing the concept of functional plasticity to maintain high cognitive function throughout the lifespan.

A free, easy-to-use, computer-based simple and four-choice reaction time programme: the Deary-Liewald reaction time task.

PubMed

Deary, Ian J; Liewald, David; Nissan, Jack

2011-03-01

Reaction time tasks are used widely in basic and applied psychology. There is a need for an easy-to-use, freely available programme that can run simple and choice reaction time tasks with no special software. We report the development of, and make available, the Deary-Liewald reaction time task. It is initially tested here on 150 participants, aged from 18 to 80, alongside another widely used reaction time device and tests of fluid and crystallised intelligence and processing speed. The new task's parameters perform as expected with respect to age and intelligence differences. The new task's parameters are reliable, and have very high correlations with the existing task. We also provide instructions for downloading and using the new reaction time programme, and we encourage other researchers to use it.

The Role of Gender in Neuropsychological Assessment in Healthy Adolescents.

PubMed

Mormile, Megan Elizabeth Evelyn; Langdon, Jody L; Hunt, Tamerah Nicole

2018-01-01

Research in college athletes has revealed significant gender differences in areas of verbal memory, visual memory, and reaction time. Additionally, research has focused on differences in neuropsychological components and gender in college populations; however, such differences in gender have not been documented in healthy adolescent populations. To identify potential differences between males and females using different components of a common computerized neuropsychological test. A computerized neuropsychological test battery (ImPACT®) was administered to 662 high-school age adolescent athletes (male: n = 451 female: n = 262). Differences between genders were calculated using a 1-way ANOVA. All statistical analyses were conducted using SPSS 23.0. Significance levels were set a priori at P < .05. A 1-way ANOVA revealed statistically significant differences between males and females for composite reaction time (F 1,660  = 10.68, P = .001) and total symptom score (F 1,660  = 81.20, P < .001). However, no statistically significant differences were found between males and females in composite verbal memory, visual memory, visual motor, or impulse control (P > .05). Significant differences between males and females were discovered for composite reaction time and total symptom scores, with females reporting more symptoms and slower reaction times at a baseline assessment. Increased symptom reporting by females may be attributed to both hormonal differences and increased honesty. Quicker reaction times in males may support theories that repetition of activities and quicker muscle contraction are gender dependent. However, additional research is necessary to understand gender differences in adolescent athletes during periods of cognitive and physical maturation.

Multichannel quench-flow microreactor chip for parallel reaction monitoring.

PubMed

Bula, Wojciech P; Verboom, Willem; Reinhoudt, David N; Gardeniers, Han J G E

2007-12-01

This paper describes a multichannel silicon-glass microreactor which has been utilized to investigate the kinetics of a Knoevenagel condensation reaction under different reaction conditions. The reaction is performed on the chip in four parallel channels under identical conditions but with different residence times. A special topology of the reaction coils overcomes the common problem arising from the difference in pressure drop of parallel channels having different length. The parallelization of reaction coils combined with chemical quenching at specific locations results in a considerable reduction in experimental effort and cost. The system was tested and showed good reproducibility in flow properties and reaction kinetic data generation.

The sound of a mobile phone ringing affects the complex reaction time of its owner

PubMed Central

Zajdel, Justyna; Zwolińska, Anna; Śmigielski, Janusz; Beling, Piotr; Cegliński, Tomasz; Nowak, Dariusz

2012-01-01

Introduction Mobile phone conversation decreases the ability to concentrate and impairs the attention necessary to perform complex activities, such as driving a car. Does the ringing sound of a mobile phone affect the driver's ability to perform complex sensory-motor activities? We compared a subject's reaction time while performing a test either with a mobile phone ringing or without. Material and methods The examination was performed on a PC-based reaction time self-constructed system Reactor. The study group consisted of 42 healthy students. The protocol included instruction, control without phone and a proper session with subject's mobile phone ringing. The terms of the study were standardised. Results There were significant differences (p < 0.001) in reaction time in control (597 ms), mobile (633 ms) and instruction session (673 ms). The differences in female subpopulation were also significant (p < 0.01). Women revealed the longest reaction time in instruction session (707 ms), were significantly quicker in mobile (657 ms, p < 0.01) and in control session (612 ms, p < 0.001). In men, the significant difference was recorded only between instruction (622 ms) and control session (573 ms, p < 0.01). The other differences were not significant (p > 0.08). Men proofed to complete significantly quicker than women in instruction (p < 0.01) and in mobile session (p < 0.05). Differences amongst the genders in control session was not significant (p > 0.05). Conclusions The results obtained proofed the ringing of a phone exerts a significant influence on complex reaction time and quality of performed task. PMID:23185201

Time-Frequency Cross Mutual Information Analysis of the Brain Functional Networks Underlying Multiclass Motor Imagery.

PubMed

Gong, Anmin; Liu, Jianping; Chen, Si; Fu, Yunfa

2018-01-01

To study the physiologic mechanism of the brain during different motor imagery (MI) tasks, the authors employed a method of brain-network modeling based on time-frequency cross mutual information obtained from 4-class (left hand, right hand, feet, and tongue) MI tasks recorded as brain-computer interface (BCI) electroencephalography data. The authors explored the brain network revealed by these MI tasks using statistical analysis and the analysis of topologic characteristics, and observed significant differences in the reaction level, reaction time, and activated target during 4-class MI tasks. There was a great difference in the reaction level between the execution and resting states during different tasks: the reaction level of the left-hand MI task was the greatest, followed by that of the right-hand, feet, and tongue MI tasks. The reaction time required to perform the tasks also differed: during the left-hand and right-hand MI tasks, the brain networks of subjects reacted promptly and strongly, but there was a delay during the feet and tongue MI task. Statistical analysis and the analysis of network topology revealed the target regions of the brain network during different MI processes. In conclusion, our findings suggest a new way to explain the neural mechanism behind MI.

Microwave-Assisted Rapid Enzymatic Synthesis of Nucleic Acids.

PubMed

Hari Das, Rakha; Ahirwar, Rajesh; Kumar, Saroj; Nahar, Pradip

2016-07-02

Herein we report microwave-induced enhancement of the reactions catalyzed by Escherichia coli DNA polymerase I and avian myeloblastosis virus-reverse transcriptase. The reactions induced by microwaves result in a highly selective synthesis of nucleic acids in 10-50 seconds. In contrast, same reactions failed to give desired reaction products when carried out in the same time periods, but without microwave irradiation. Each of the reactions was carried out for different duration of microwave exposure time to find the optimum reaction time. The products produced by the respective enzyme upon microwave irradiation of the reaction mixtures were identical to that produced by the conventional procedures. As the microwave-assisted reactions are rapid, microwave could be a useful alternative to the conventional and time consuming procedures of enzymatic synthesis of nucleic acids.

Age-Related Differences in Reaction Time Task Performance in Young Children

ERIC Educational Resources Information Center

Kiselev, Sergey; Espy, Kimberlay Andrews; Sheffield, Tiffany

2009-01-01

Performance of reaction time (RT) tasks was investigated in young children and adults to test the hypothesis that age-related differences in processing speed supersede a "global" mechanism and are a function of specific differences in task demands and processing requirements. The sample consisted of 54 4-year-olds, 53 5-year-olds, 59…

On the Meaning of Cross-Cultural Differences in Simple Cognitive Measures

ERIC Educational Resources Information Center

van de Vijver, Fons J. R.

2008-01-01

A set of 5 reaction time tests of increasing cognitive complexity were administered to 35 secondary school pupils in Zimbabwe and The Netherlands at 4 consecutive school days in order to explore the existence and nature of cross-cultural differences on reaction time tests measuring basic cognitive operations. No cross-cultural differences were…

A Time-Dependent Quantum Dynamics Study of the H2 + CH3 yields H + CH4 Reaction

NASA Technical Reports Server (NTRS)

Wang, Dunyou; Kwak, Dochan (Technical Monitor)

2002-01-01

We present a time-dependent wave-packet propagation calculation for the H2 + CH3 yields H + CH4 reaction in six degrees of freedom and for zero total angular momentum. Initial state selected reaction probability for different initial rotational-vibrational states are presented in this study. The cumulative reaction probability (CRP) is obtained by summing over initial-state-selected reaction probability. The energy-shift approximation to account for the contribution of degrees of freedom missing in the 6D calculation is employed to obtain an approximate full-dimensional CRP. Thermal rate constant is compared with different experiment results.

Individual differences in implicit motor learning: task specificity in sensorimotor adaptation and sequence learning

PubMed Central

Raza, Meher; Ivry, Richard B.

2016-01-01

In standard taxonomies, motor skills are typically treated as representative of implicit or procedural memory. We examined two emblematic tasks of implicit motor learning, sensorimotor adaptation and sequence learning, asking whether individual differences in learning are correlated between these tasks, as well as how individual differences within each task are related to different performance variables. As a prerequisite, it was essential to establish the reliability of learning measures for each task. Participants were tested twice on a visuomotor adaptation task and on a sequence learning task, either the serial reaction time task or the alternating reaction time task. Learning was evident in all tasks at the group level and reliable at the individual level in visuomotor adaptation and the alternating reaction time task but not in the serial reaction time task. Performance variability was predictive of learning in both domains, yet the relationship was in the opposite direction for adaptation and sequence learning. For the former, faster learning was associated with lower variability, consistent with models of sensorimotor adaptation in which learning rates are sensitive to noise. For the latter, greater learning was associated with higher variability and slower reaction times, factors that may facilitate the spread of activation required to form predictive, sequential associations. Interestingly, learning measures of the different tasks were not correlated. Together, these results oppose a shared process for implicit learning in sensorimotor adaptation and sequence learning and provide insight into the factors that account for individual differences in learning within each task domain. NEW & NOTEWORTHY We investigated individual differences in the ability to implicitly learn motor skills. As a prerequisite, we assessed whether individual differences were reliable across test sessions. We found that two commonly used tasks of implicit learning, visuomotor adaptation and the alternating serial reaction time task, exhibited good test-retest reliability in measures of learning and performance. However, the learning measures did not correlate between the two tasks, arguing against a shared process for implicit motor learning. PMID:27832611

The Eschenmoser coupling reaction under continuous-flow conditions

PubMed Central

Singh, Sukhdeep; Köhler, J Michael; Schober, Andreas

2011-01-01

Summary The Eschenmoser coupling is a useful carbon–carbon bond forming reaction which has been used in various different synthesis strategies. The reaction proceeds smoothly if S-alkylated ternary thioamides or thiolactames are used. In the case of S-alkylated secondary thioamides or thiolactames, the Eschenmoser coupling needs prolonged reaction times and elevated temperatures to deliver valuable yields. We have used a flow chemistry system to promote the Eschenmoser coupling under enhanced reaction conditions in order to convert the demanding precursors such as S-alkylated secondary thioamides and thiolactames in an efficient way. Under pressurized reaction conditions at about 220 °C, the desired Eschenmoser coupling products were obtained within 70 s residence time. The reaction kinetics was investigated and 15 examples of different building block combinations are given. PMID:21915222

High luminescent L-cysteine capped CdTe quantum dots prepared at different reaction times

NASA Astrophysics Data System (ADS)

Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.

2018-04-01

This paper reports a facile synthesis route of high luminescent L-cysteine capped CdTe quantum dots (QDs). The effect of reaction time on the growth mechanism, optical and physical properties of the CdTe QDs was investigated in order to find the suitability of them towards optical and medical applications. The representative high-resolution transmission microscopy (HRTEM) analysis showed that the as-obtained CdTe QDs appeared as spherical particles with excellent monodispersity. The images exhibited clear lattice fringes which are indicative of good crystallinity. The X-ray diffraction (XRD) pattern displayed polycrystalline nature of the QDs which correspond well to zinc blende phase of bulk CdTe. The crystallite sizes calculated from the Scherrer equation were less than 10 nm for different reaction times which were in close agreement with the values estimated from HRTEM. An increase in reaction time improved crystallinity of the sample as explained by highest peak intensity of the XRD supported by the photoluminescence emission spectra which showed high intensity at a longer growth time. It was observed that for prolonged growth time the emission bands were red shifted from about 517-557 nm for 5-180 min of reaction time due to increase in particle sizes. Ultraviolet and visible analysis displayed well-resolved absorption bands which were red shifted upon an increase in reaction time. There was an inverse relation between the band gap and reaction time. Optical band gap decreases from 3.98 to 2.59 eV with the increase in reaction time from 15 to 180 min.

Study on The Application of Composed TiO2-diatomite in The Removal of Phenol in Water

NASA Astrophysics Data System (ADS)

Liu, S.; Li, J.

2017-10-01

As an environmentally friendly pollution control technology, TiO2 photocatalytic technology has a broad prospect in the field of environmental protection. In this paper, composed nano-TiO2-diatomite were prepared by depositing TiO2 nanoparticles on the surface of diatomite microparticles. The nano-TiO2/diatomite composed photocatalyst is used to remove phenol in water in a specific designed reaction box under 4 different operation factors such as different reaction time, different pollutant concentration, different UV light powers and different amount of catalytic powder. The experimental results indicate that the phenol removal percentages are influenced by the reaction time most significantly, the second is the phenol concentration, the next one is the photocatalyst amount and the UV light powers’ effect is quite limited. Tthe degradation of phenol typically slows down at the reaction time about 30 or 60 minutes. Besides that, the phenol removal kinetic removal rates were also investigated.

Psychological differences between influence of temperament with the hemishere asymmetry of a brain on size of sensorymotor reactions of male and female cosmonauts

NASA Astrophysics Data System (ADS)

Prisniakova, Lyudmila; Prisniakov, Volodymyr; Volkov, D. S.

The purpose of research was definition and comparison of relative parameters of sensorimotor reactions with a choice depending on a level of lateral asymmetry of hemispheres of a brain at representatives of various types of temperament OF male and female cosmonauts . These parameters were by the bases for verification of theoretical dependence for the latent period of reaction in conditions of weightlessness and overloads. The hypothesis about influence of functional asymmetry on parameters of psychomotor in sensory-motor reactions was laid in a basis of experiment. Techniques of definition of individual characters of the sensori-motor asymmetries were used, and G. Ajzenk's questionnaire EPQ adapted by Prisniakova L. Time of sensorimotor reaction has significant distinctions between representatives of different types of temperament with a various level interchemishere asymmetry OF male and female cosmonauts. With increase in expressiveness of the right hemisphere time of reaction tends to reduction at representatives of all types of temperament, the number of erroneous reactions as a whole increases also a level of achievement tends to reduction. Results of time of sensorimotor reaction correspond with parameter L. Prisniakova which characterizes individual - psychological features. .Earlier the received experimental data of constant time of processing of the information in memory at a period of a sensorimotor reactions of the man and new results for women were used for calculation of these time constants for overloads distinct from terrestrial. These data enable to predict dynamics of behavior of cosmonauts with differing sex in conditions of flight in view of their individual characteristics connected with the hemisphere asymmetry of a brain and with by a various degree of lateralization.

Comparative efficacy of microwave, visible light and ultrasound irradiation for green synthesis of dihydropyrimidinones in fruit juice medium

NASA Astrophysics Data System (ADS)

Pramanik, Tanay; Padan, Simarjit Kaur; Gupta, Richa; Bedi, Pooja; Singh, Gurinderpal

2017-07-01

Dihydropyrimidinones (DHPM) were synthesized via multi component condensation reaction employing urea, ethyl acetoacetate and aromatic aldehydes as reactants. Apple, pomegranate, grape juice were used individually as biodegradable, eco friendly, and green reaction medium whereas microwave, visible light and ultrasound irradiation were applied individually as green source of energy for carrying out the aforesaid reactions. It was observed that the reactions under microwave irradiation were taking minimum time to go for completion whereas the reactions under ultrasound and visible light irradiation were taking approximately same time duration to form products. This is the first of its kind study where the three different reaction methodologies based on three different sources of green energies were compared with each other for their effectiveness and efficiency towards multi component condensation reactions.

Influence of rotating shift work on visual reaction time and visual evoked potential.

PubMed

R V, Hemamalini; N, Krishnamurthy; A, Saravanan

2014-10-01

The present day life style is changing the circadian rhythm of the body especially in rotating night shift workers. The impact of this prolongs their reaction time. Night shift also interferes with the circadian variation of pupil size which may affect the visual evoked potential. To compare the visual reaction time, visual evoked potential (VEP) in rotating night shift workers & day workers and also to correlate the changes in visual reaction time with visual evoked potential. Forty healthy male security guards & staff (25 - 35 y) who did rotating night shifts at least for six months & 40 d workers (25 - 35 y) who did not do night shift in last two years were involved in the study. Visual reaction time and the latency & amplitude of VEP were recorded. Kolmogorov- Smirnov test for normalcy showed the latencies & amplitude of VEP to be normally distributed. Student's unpaired t test showed significant difference (p<0.05) in the visual time and in the latencies of VEP between night shift & day workers. There was no significant difference in the amplitude of VEP. Night shift workers who are prone to circadian rhythm alteration will have prolonged visual reaction time & visual evoked potential abnormalities. Implementation of Bright Light Therapy would be beneficial to the night shift worker.

The Persistence of "Solid" and "Liquid" Naive Conceptions: A Reaction Time Study

ERIC Educational Resources Information Center

Babai, Reuven; Amsterdamer, Anat

2008-01-01

The study explores whether the naive concepts of "solid" and "liquid" persist in adolescence. Accuracy of responses and reaction times where measured while 41 ninth graders classified different solids (rigid, non-rigid and powders) and different liquids (runny, dense) into solid or liquid. The results show that these naive conceptions affect…

Relating Derived Relations as a Model of Analogical Reasoning: Reaction Times and Event-Related Potentials

ERIC Educational Resources Information Center

Barnes-Holmes, Dermot; Regan, Donal; Barnes-Holmes, Yvonne; Commins, Sean; Walsh, Derek; Stewart, Ian; Smeets, Paul M.; Whelan, Robert; Dymond, Simon

2005-01-01

The current study aimed to test a Relational Frame Theory (RFT) model of analogical reasoning based on the relating of derived same and derived difference relations. Experiment 1 recorded reaction time measures of similar-similar (e.g., "apple is to orange as dog is to cat") versus different-different (e.g., "he is to his brother as…

Organocatalytic aza-Michael/retro-aza-Michael reaction: pronounced chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction.

PubMed

Cai, Yong-Feng; Li, Li; Luo, Meng-Xian; Yang, Ke-Fang; Lai, Guo-Qiao; Jiang, Jian-Xiong; Xu, Li-Wen

2011-05-01

A detailed experimental investigation of an aza-Michael reaction of aniline and chalcone is presented. A series of Cinchona alkaloid-derived organocatalysts with different functional groups were prepared and used in the aza-Michael and retro-aza-Michael reaction. There was an interesting finding that a complete reversal of stereoselectivity when a benzoyl group was introduced to the cinchonine and cinchonidine. The chirality amplification vs. time proceeds in the quinine-derived organocatalyst containing silicon-based bulky group, QN-TBS, -catalyzed aza-Michael reaction under solvent-free conditions. In addition, we have demonstrated for the first time that racemization was occurred in suitable solvents under mild conditions due to retro-aza-Michael reaction of the Michael adduct of aniline with chalcone. These indicate the equilibrium of retro-aza-Michael reaction and aza-Michael reaction produce the happening of chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction under different conditions, which would be beneficial to the development of novel chiral catalysts for the aza-Michael reactions. Copyright © 2011 Wiley-Liss, Inc.

Iris Pigmentation and Fractionated Reaction and Reflex Time.

ERIC Educational Resources Information Center

Hale, Bruce D.; And Others

Behavioral measures, fractionated reaction and reflex times by means of electromyography, were used to determine if the eye color differences are found in the central or peripheral regions of the nervous system. The purpose of this research was to determine the truth of the hypothesis that dark-eyed individuals have faster reflex and reaction time…

The effects of arm movement on reaction time in patients with latent and active upper trapezius myofascial trigger point.

PubMed

Yassin, Marzieh; Talebian, Saeed; Ebrahimi Takamjani, Ismail; Maroufi, Nader; Ahmadi, Amir; Sarrafzadeh, Javad; Emrani, Anita

2015-01-01

Myofascial pain syndrome is a significant source of mechanical pain. The aim of this study was to investigate the effects of arm movement on reaction time in females with latent and active upper trapezius myofascial trigger point. In this interventional study, a convenience sample of fifteen women with one active MTP, fifteen women with one latent MTP in the upper trapezius, and fifteen normal healthy women were participated. Participants were asked to stand for 10 seconds in an erect standing position. Muscle reaction times were recorded including anterior deltoid (AD), cervical paraspinal (CP) lumbar paraspinal (LP), both of upper trapezius (UT), sternocleidomastoid (SCM) and medial head of gastrocnemius (GcM). Participants were asked to flex their arms in response to a sound stimulus preceded by a warning sound stimulus. Data were analyzed using one-way ANOVA Test. There was significant differences in motor time and reaction time between active and control groups (p< 0.05) except for GcM. There was no significant difference in motor time between active and passive groups except for UT without MTP and SCM (p< 0.05). Also, there were no significant differences in motor times between latent MTP and control groups. Furthermore, there was no significant difference in premotor times between the three groups. The present study shows that patients with active MTP need more time to react to stimulus, but patients with latent MTP are similar to healthy subjects in the reaction time. Patients with active MTP had less compatibility with environmental stimulations, and they responded to a specific stimulation with variability in Surface Electromyography (SEMG).

Diastereoselective Synthesis of Symmetrical and Unsymmetrical Tetrahydropyridines Catalyzed by Bi(III) Immobilized on Triazine Dendrimer Stabilized Magnetic Nanoparticles.

PubMed

Asadi, Beheshteh; Landarani-Isfahani, Amir; Mohammadpoor-Baltork, Iraj; Tangestaninejad, Shahram; Moghadam, Majid; Mirkhani, Valiollah; Amiri Rudbari, Hadi

2017-06-12

Unsymmetrical 1,2,5,6-tetrahydropyridine-3-carboxylates were obtained for the first time from a five-component Fe 3 O 4 @TDSN-Bi(III)-catalyzed reaction of aryl aldehydes, aryl amines, and ethyl acetoacetate. This magnetically separable catalyst enabled the selective incorporation of two different aryl amines or two different aryl aldehydes into the product, and provided excellent yields, short reaction times, mild reaction conditions, satisfactory catalyst recyclability, and low catalyst loading.

Reaction time norms as measured by ruler drop method in school-going South Asian children: A cross-sectional study.

PubMed

Aranha, V P; Saxena, S; Moitra, M; Narkeesh, K; Arumugam, N; Samuel, A J

2017-01-01

This study aimed to estimate normative range for reaction time using ruler drop method for school-going South Asian children between 6 and 12 years of age. A cross-sectional study was used to evaluate the reaction time for 204 children. Normal values for each age group were obtained. The results of multiple linear regressions showed a decrease in the reaction time values with age, and a significant change occurring between six and eight years of age. No difference in reaction time was obtained between boys and girls. Ruler drop method is an easy to use test and the results of this study provide a normative data for age groups 6-12 years ranging from 214.2ms to 248.8ms. These values can serve as a reference to screen children with delayed reaction time. Copyright © 2016 Elsevier GmbH. All rights reserved.

The Effect of Lateral Ankle Ligament Repair in Muscle Reaction Time in Patients with Mechanical Ankle Instability.

PubMed

Li, H-Y; Zheng, J-J; Zhang, J; Hua, Y-H; Chen, S-Y

2015-11-01

Studies have shown that functional ankle instability can result in prolonged muscle reaction time. However, the deficit in muscle reaction time in patients with mechanical ankle instability (MAI) and the effect of lateral ankle ligament repair on muscle reaction time are unclear. The purpose of this study was to identify the deficit in muscle reaction time, and to evaluate the role of lateral ligament repair in improving muscle reaction time in MAI patients. Sixteen MAI patients diagnosed with lateral ankle ligament tears by ultrasonography and magnetic resonance imaging underwent arthroscopic debridement and open lateral ankle ligament repair with a modified Broström procedure. One day before the operation, reaction times of the tibialis anterior and peroneus longus muscles were recorded following sudden inversion perturbation while walking on a custom walkway, and anterior drawer test (ADT) and American Orthopaedic Foot and Ankle Society (AOFAS) scale score were evaluated. Six months postoperatively, muscle reaction time, ADT and AOFAS scale score were reevaluated, and muscle reaction times in 15 healthy controls were also recorded. Preoperatively, the affected ankles in the MAI group had significantly delayed tibialis anterior and peroneus longus muscles reaction times compared with controls. Six months after the operation, median AOFAS scale scores were significantly greater than preoperatively, and ADT was negative in the MAI group. However, the affected ankles in the MAI group showed no difference in muscle reaction time compared with preoperative values. MAI patients had prolonged muscle reaction time. The modified Broström procedure produced satisfactory clinical outcomes in MAI patients, but did not shorten reaction times of the tibialis anterior and peroneus longus muscles. © Georg Thieme Verlag KG Stuttgart · New York.

Definition of simulated driving tests for the evaluation of drivers' reactions and responses.

PubMed

Bartolozzi, Riccardo; Frendo, Francesco

2014-01-01

This article aims at identifying the most significant measures in 2 perception-response (PR) tests performed at a driving simulator: a braking test and a lateral skid test, which were developed in this work. Forty-eight subjects (26 females and 22 males) with a mean age of 24.9 ± 3.0 years were enrolled for this study. They were asked to perform a drive on the driving simulator at the University of Pisa (Italy) following a specific test protocol, including 8-10 braking tests and 8-10 lateral skid tests. Driver input signals and vehicle model signals were recorded during the drives and analyzed to extract measures such as the reaction time, first response time, etc. Following a statistical procedure (based on analysis of variance [ANOVA] and post hoc tests), all test measures (3 for the braking test and 8 for the lateral skid test) were analyzed in terms of statistically significant differences among different drivers. The presented procedure allows evaluation of the capability of a given test to distinguish among different drivers. In the braking test, the reaction time showed a high dispersion among single drivers, leading to just 4.8 percent of statistically significant driver pairs (using the Games-Howell post hoc test), whereas the pedal transition time scored 31.9 percent. In the lateral skid test, 28.5 percent of the 2 × 2 comparisons showed significantly different reaction times, 19.5 percent had different response times, 35.2 percent had a different second peak of the steering wheel signal, and 33 percent showed different values of the integral of the steering wheel signal. For the braking test, which has been widely employed in similar forms in the literature, it was shown how the reaction time, with respect to the pedal transition time, can have a higher dispersion due to the influence of external factors. For the lateral skid test, the following measures were identified as the most significant for application studies: the reaction time for the reaction phase, the second peak of the steering wheel angle for the first instinctive response, and the integral of the steering wheel angle for the complete response. The methodology used to analyze the test measures was founded on statistically based and objective evaluation criteria and could be applied to other tests. Even if obtained with a fixed-base simulator, the obtained results represent useful information for applications of the presented PR tests in experimental campaigns with driving simulators.

Studying Reaction Intermediates Formed at Graphenic Surfaces

NASA Astrophysics Data System (ADS)

Sarkar, Depanjan; Sen Gupta, Soujit; Narayanan, Rahul; Pradeep, Thalappil

2014-03-01

We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate.

Individual differences in implicit motor learning: task specificity in sensorimotor adaptation and sequence learning.

PubMed

Stark-Inbar, Alit; Raza, Meher; Taylor, Jordan A; Ivry, Richard B

2017-01-01

In standard taxonomies, motor skills are typically treated as representative of implicit or procedural memory. We examined two emblematic tasks of implicit motor learning, sensorimotor adaptation and sequence learning, asking whether individual differences in learning are correlated between these tasks, as well as how individual differences within each task are related to different performance variables. As a prerequisite, it was essential to establish the reliability of learning measures for each task. Participants were tested twice on a visuomotor adaptation task and on a sequence learning task, either the serial reaction time task or the alternating reaction time task. Learning was evident in all tasks at the group level and reliable at the individual level in visuomotor adaptation and the alternating reaction time task but not in the serial reaction time task. Performance variability was predictive of learning in both domains, yet the relationship was in the opposite direction for adaptation and sequence learning. For the former, faster learning was associated with lower variability, consistent with models of sensorimotor adaptation in which learning rates are sensitive to noise. For the latter, greater learning was associated with higher variability and slower reaction times, factors that may facilitate the spread of activation required to form predictive, sequential associations. Interestingly, learning measures of the different tasks were not correlated. Together, these results oppose a shared process for implicit learning in sensorimotor adaptation and sequence learning and provide insight into the factors that account for individual differences in learning within each task domain. We investigated individual differences in the ability to implicitly learn motor skills. As a prerequisite, we assessed whether individual differences were reliable across test sessions. We found that two commonly used tasks of implicit learning, visuomotor adaptation and the alternating serial reaction time task, exhibited good test-retest reliability in measures of learning and performance. However, the learning measures did not correlate between the two tasks, arguing against a shared process for implicit motor learning. Copyright © 2017 the American Physiological Society.

Reaction Dynamics of Proton-Coupled Electron Transfer from Reduced ZnO Nanocrystals.

PubMed

Braten, Miles N; Gamelin, Daniel R; Mayer, James M

2015-10-27

The creation of systems that efficiently interconvert chemical and electrical energies will be aided by understanding proton-coupled electron transfers at solution-semiconductor interfaces. Steps in developing that understanding are described here through kinetic studies of reactions of photoreduced colloidal zinc oxide (ZnO) nanocrystals (NCs) with the nitroxyl radical TEMPO. These reactions proceed by proton-coupled electron transfer (PCET) to give the hydroxylamine TEMPOH. They occur on the submillisecond to seconds time scale, as monitored by stopped-flow optical spectroscopy. Under conditions of excess TEMPO, the reactions are multiexponential in character. One of the contributors to this multiexponential kinetics may be a distribution of reactive proton sites. A graphical overlay method shows the reaction to be first order in [TEMPO]. Different electron concentrations in otherwise identical NC samples were achieved by three different methods: differing photolysis times, premixing with an unphotolyzed sample, or prereaction with TEMPO. The reaction velocities were consistently higher for NCs with higher numbers of electrons. For instance, NCs with an average of 2.6 e(-)/NC reacted faster than otherwise identical samples containing ≤1 e(-)/NC. Surprisingly, NC samples with the same average number of electrons but prepared in different ways often had different reaction profiles. These results show that properties beyond electron content determine PCET reactivity of the particles.

In Site Analysis of a High Temperature Cure Reaction in Real Time Using Modulated Fiber-Optic FT-Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Cooper, John; Aust, Jeffrey F.; Wise, Kent L.; Jensen, Brian J.

1999-01-01

The vibrational spectrum of a high temperature (330 C) polymerization reaction was successfully monitored in real time using a modulated fiber-optic FT-Raman spectrometer. A phenylethynyl terminated monomer was cured, and spectral evidence for two different reaction products was acquired. The products are a conjugated polyene chain and a cyclized trimer. This is the first report describing the use of FT-Raman spectroscopy to monitor a high temperature (greater than 250 C) reaction in real time.

In Situ Analysis of a High-Temperature Cure Reaction in Real Time Using Modulated Fiber-Optic FT-Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Aust, Jeffrey F.; Cooper, John B.; Wise, Kent L.; Jensen, Brian J.

1999-01-01

The vibrational spectrum of a high-temperature (330 C) polymerization reaction was successfully monitored in real time with the use of a modulated fiber-optic Fourier transform (FT)-Raman spectrometer. A phenylethynyl-terminated monomer was cured, and spectral evidence for two different reaction products was acquired. The products are a conjugated polyene chain and a cyclized trimer. This is the first report describing the use of FT-Raman spectroscopy to monitor a high temperature (greater than 250 C) reaction in real time.

Effect of fatigue on reaction time, response time, performance time, and kick impact in taekwondo roundhouse kick.

PubMed

Sant'Ana, Jader; Franchini, Emerson; da Silva, Vinicius; Diefenthaeler, Fernando

2017-06-01

Reaction time and response time are considered important abilities and can potentially affect combat performance. This study investigated the effect of a specific fatigue protocol on reaction time, response time, performance time, and kick impact. Seven male athletes reported to the laboratory on two different days. During day one, athletes performed a specific progressive taekwondo test, and on day two, a protocol for determining reaction time, response time, performance time, and kick impact before and after a time to exhaustion test at an intensity level corresponding to the maximal kick frequency obtained during the specific progressive taekwondo test. Muscle activation from rectus femoris and kick impact of the preferred limb were assessed. No differences were observed for response time and performance time. However, kick impact decreased (43 ± 27 to 13 ± 10 g, p < 0.01) while reaction time increased (145 ± 51 to 223 ± 133 ms, p < 0.05). Moderate correlation was observed between kick impact and response time (r = 0.565; p < 0.01), and kick impact and performance time (r = 0.494; p < 0.05). Results indicate that coaches and athletes may use taekwondo training programmes on coordination-based exercises leading to improve response time and to reduce fatigue effects in order to improve technique effectiveness and enhance the possibilities of scoring in a competitive situation.

Poststimulation time interval-dependent effects of motor cortex anodal tDCS on reaction-time task performance.

PubMed

Molero-Chamizo, Andrés; Alameda Bailén, José R; Garrido Béjar, Tamara; García López, Macarena; Jaén Rodríguez, Inmaculada; Gutiérrez Lérida, Carolina; Pérez Panal, Silvia; González Ángel, Gloria; Lemus Corchero, Laura; Ruiz Vega, María J; Nitsche, Michael A; Rivera-Urbina, Guadalupe N

2018-02-01

Anodal transcranial direct current stimulation (tDCS) induces long-term potentiation-like plasticity, which is associated with long-lasting effects on different cognitive, emotional, and motor performances. Specifically, tDCS applied over the motor cortex is considered to improve reaction time in simple and complex tasks. The timing of tDCS relative to task performance could determine the efficacy of tDCS to modulate performance. The aim of this study was to compare the effects of a single session of anodal tDCS (1.5 mA, for 15 min) applied over the left primary motor cortex (M1) versus sham stimulation on performance of a go/no-go simple reaction-time task carried out at three different time points after tDCS-namely, 0, 30, or 60 min after stimulation. Performance zero min after anodal tDCS was improved during the whole course of the task. Performance 30 min after anodal tDCS was improved only in the last block of the reaction-time task. Performance 60 min after anodal tDCS was not significantly different throughout the entire task. These findings suggest that the motor cortex excitability changes induced by tDCS can improve motor responses, and these effects critically depend on the time interval between stimulation and task performance.

How Changes in White Matter Might Underlie Improved Reaction Time Due to Practice1

PubMed Central

Voelker, Pascale; Piscopo, Denise; Weible, Aldis; Lynch, Gary; Rothbart, Mary K.; Posner, Michael I.; Niell, Cristopher M.

2017-01-01

Why does training on a task reduce the reaction time for performing it? New research points to changes in white matter pathways as one likely mechanism. These pathways connect remote brain areas involved in performing the task. Genetic variations may be involved in individual differences in the extent of this improvement. If white matter change is involved in improved reaction time with training, it may point the way toward understanding where and how generalization occurs. We examine the hypothesis that brain pathways shared by different tasks may result in improved performance of cognitive tasks remote from the training. PMID:27064751

Test analysis and research on static choice reaction ability of commercial vehicle drivers

NASA Astrophysics Data System (ADS)

Zhang, Lingchao; Wei, Lang; Qiao, Jie; Tian, Shun; Wang, Shengchang

2017-03-01

Drivers' choice reaction ability has a certain relation with safe driving. It has important significance to research its influence on traffic safety. Firstly, the paper uses a choice reaction detector developed by research group to detect drivers' choice reaction ability of commercial vehicles, and gets 2641 effective samples. Then by using mathematical statistics method, the paper founds that average reaction time from accident group has no difference with non-accident group, and then introduces a variance rate of reaction time as a new index to replace it. The result shows that the test index choice reaction errors and variance rate of reaction time have positive correlations with accidents. Finally, according to testing results of the detector, the paper formulates a detection threshold with four levels for helping transportation companies to assess commercial vehicles drivers.

The Effect of Road Traffic Noise on Reaction Time.

PubMed

Alimohammadi, Iraj; Zokaei, Mojtaba; Sandrock, Stephan

2015-01-01

Traffic noise is one of the main important sources in urban noise pollution, which causes various physiological and psychological effects that can cause disturbs in performance, sleep disturbances, hearing loss and impact on job performance. This study was conducted to verify the impact of road traffic noise on reaction time in terms of extraversion and sex. Traffic noise was measured and recorded in 10 arterial streets in Tehran, and then the recorded noise was emitted towards participants in an acoustic room. The participants were 80 (40 cases and 40 controls) students. Personality type was determined by Eysenck Personality Inventory (EPI) questioner. Reaction time before and after exposure to traffic noise was measured. Reaction time before exposure to traffic noise did not differ (P=0.437) significantly between introverts and extraverts. However, it was increased significantly in both groups after exposure to traffic noise (P<0.01). Introvert's reaction time was more increased than that of extraverts. Traffic noise augmented reaction time of both males and females. This study also revealed that exposure to traffic noise leads to increase in reaction time.

Impact of reaction conditions on grafting acrylamide onto starch

USDA-ARS?s Scientific Manuscript database

We have explored the radical initiated graft polymerization reaction of acrylamide onto starch where the solvent, concentration, temperature and reaction times were varied. We have found that the morphology of the resulting grafted polymer is dramatically different and is dependent on the reaction c...

Hydrothermal replacement of calcite by Mg-carbonates

NASA Astrophysics Data System (ADS)

Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

2014-05-01

The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product phases increases with increasing distance from the unreacted calcite core, countered by a decrease of Ca incorporated. Both the coexistence of two different product phases and the distinct compositional gradient within the forming reaction rim are unequivocal signs of a chemical zonation of Ca and Mg in the fluid phase which mediates the element exchange between the reaction interface and the bulk solution. Atomic adsorption spectroscopy revealed that the Ca/Mg ratio in the reacted fluid increases as a function of time, reflecting the progressive exchange of Mg and Ca between the fluid and the solid phase. The time-dependence of the evolving Ca/Mg ratio can be fitted with a square root of time relation that indicates a transport controlled reaction. We interpret the hydrothermal replacement of calcite to operate via a dissolution/re-precipitation mechanism, whereas the reaction progress is controlled by the transport of the structure forming elements through the developing reaction rim.

Development of various reaction abilities and their relationships with favorite play activities in preschool children.

PubMed

Miyaguchi, Kazuyoshi; Demura, Shinich; Sugiura, Hiroki; Uchiyama, Masanobu; Noda, Masahiro

2013-10-01

This study examines the development of various reaction movements in preschool children and the relationship between reaction times and favorite play activities. The subjects were 167 healthy preschool children aged 4-6 (96 boys and 71 girls). This study focused on the reaction times of the upper limbs (reaction 1: release; reaction 2: press) and the whole body (reaction 3: forward jump). The activities frequently played in preschools are largely divided into dynamic play activities (tag, soccer, gymnastics set, dodge ball, and jump rope) and static play activities (drawing, playing house, reading, playing with sand, and building blocks). The subjects chose 3 of 10 cards picturing their favorite play activities, depicting 10 different activities. All intraclass correlation coefficients of measured reaction times were high (0.73-0.79). In addition, each reaction time shortened with age. Reaction 1 showed a significant and low correlation with reaction 3 (r = 0.37). The effect size of the whole body reaction time was the largest. Whole body reaction movement, which is largely affected by the exercise output function, develops remarkably in childhood. Children who liked "tag" were faster in all reaction times. The children who chose "soccer" were faster in reactions 2 and 3. In contrast, children who liked "playing house" tended to have slower reaction times. Dynamic activities, such as tag and soccer, promote development of reaction speed and agility in movements involving the whole body. Preschool teachers and physical educators should re-examine the effect of tag and use it periodically as one of the exercise programs to avoid unexpected falls and injuries in everyday life.

Haptic Search for Hard and Soft Spheres

PubMed Central

van Polanen, Vonne; Bergmann Tiest, Wouter M.; Kappers, Astrid M. L.

2012-01-01

In this study the saliency of hardness and softness were investigated in an active haptic search task. Two experiments were performed to explore these properties in different contexts. In Experiment 1, blindfolded participants had to grasp a bundle of spheres and determine the presence of a hard target among soft distractors or vice versa. If the difference in compliance between target and distractors was small, reaction times increased with the number of items for both features; a serial strategy was found to be used. When the difference in compliance was large, the reaction times were independent of the number of items, indicating a parallel strategy. In Experiment 2, blindfolded participants pressed their hand on a display filled with hard and soft items. In the search for a soft target, increasing reaction times with the number of items were found, but the location of target and distractors appeared to have a large influence on the search difficulty. In the search for a hard target, reaction times did not depend on the number of items. In sum, this showed that both hardness and softness are salient features. PMID:23056197

Haptic search for hard and soft spheres.

PubMed

van Polanen, Vonne; Bergmann Tiest, Wouter M; Kappers, Astrid M L

2012-01-01

In this study the saliency of hardness and softness were investigated in an active haptic search task. Two experiments were performed to explore these properties in different contexts. In Experiment 1, blindfolded participants had to grasp a bundle of spheres and determine the presence of a hard target among soft distractors or vice versa. If the difference in compliance between target and distractors was small, reaction times increased with the number of items for both features; a serial strategy was found to be used. When the difference in compliance was large, the reaction times were independent of the number of items, indicating a parallel strategy. In Experiment 2, blindfolded participants pressed their hand on a display filled with hard and soft items. In the search for a soft target, increasing reaction times with the number of items were found, but the location of target and distractors appeared to have a large influence on the search difficulty. In the search for a hard target, reaction times did not depend on the number of items. In sum, this showed that both hardness and softness are salient features.

Discussion of the Investigation Method on the Reaction Kinetics of Metallurgical Reaction Engineering

NASA Astrophysics Data System (ADS)

Du, Ruiling; Wu, Keng; Zhang, Jiazhi; Zhao, Yong

Reaction kinetics of metallurgical physical chemistry which was successfully applied in metallurgy (as ferrous metallurgy, non-ferrous metallurgy) became an important theoretical foundation for subject system of traditional metallurgy. Not only the research methods were very perfect, but also the independent structures and systems of it had been formed. One of the important tasks of metallurgical reaction engineering was the simulation of metallurgical process. And then, the mechanism of reaction process and the conversion time points of different control links should be obtained accurately. Therefore, the research methods and results of reaction kinetics in metallurgical physical chemistry were not very suitable for metallurgical reaction engineering. In order to provide the definite conditions of transmission, reaction kinetics parameters and the conversion time points of different control links for solving the transmission and reaction equations in metallurgical reaction engineering, a new method for researching kinetics mechanisms in metallurgical reaction engineering was proposed, which was named stepwise attempt method. Then the comparison of results between the two methods and the further development of stepwise attempt method were discussed in this paper. As a new research method for reaction kinetics in metallurgical reaction engineering, stepwise attempt method could not only satisfy the development of metallurgical reaction engineering, but also provide necessary guarantees for establishing its independent subject system.

Reaction time for processing visual stimulus in a computer-assisted rehabilitation environment.

PubMed

Sanchez, Yerly; Pinzon, David; Zheng, Bin

2017-10-01

To examine the reaction time when human subjects process information presented in the visual channel under both a direct vision and a virtual rehabilitation environment when walking was performed. Visual stimulus included eight math problems displayed on the peripheral vision to seven healthy human subjects in a virtual rehabilitation training (computer-assisted rehabilitation environment (CAREN)) and a direct vision environment. Subjects were required to verbally report the results of these math calculations in a short period of time. Reaction time measured by Tobii Eye tracker and calculation accuracy were recorded and compared between the direct vision and virtual rehabilitation environment. Performance outcomes measured for both groups included reaction time, reading time, answering time and the verbal answer score. A significant difference between the groups was only found for the reaction time (p = .004). Participants had more difficulty recognizing the first equation of the virtual environment. Participants reaction time was faster in the direct vision environment. This reaction time delay should be kept in mind when designing skill training scenarios in virtual environments. This was a pilot project to a series of studies assessing cognition ability of stroke patients who are undertaking a rehabilitation program with a virtual training environment. Implications for rehabilitation Eye tracking is a reliable tool that can be employed in rehabilitation virtual environments. Reaction time changes between direct vision and virtual environment.

Chemical Continuous Time Random Walks

NASA Astrophysics Data System (ADS)

Aquino, T.; Dentz, M.

2017-12-01

Traditional methods for modeling solute transport through heterogeneous media employ Eulerian schemes to solve for solute concentration. More recently, Lagrangian methods have removed the need for spatial discretization through the use of Monte Carlo implementations of Langevin equations for solute particle motions. While there have been recent advances in modeling chemically reactive transport with recourse to Lagrangian methods, these remain less developed than their Eulerian counterparts, and many open problems such as efficient convergence and reconstruction of the concentration field remain. We explore a different avenue and consider the question: In heterogeneous chemically reactive systems, is it possible to describe the evolution of macroscopic reactant concentrations without explicitly resolving the spatial transport? Traditional Kinetic Monte Carlo methods, such as the Gillespie algorithm, model chemical reactions as random walks in particle number space, without the introduction of spatial coordinates. The inter-reaction times are exponentially distributed under the assumption that the system is well mixed. In real systems, transport limitations lead to incomplete mixing and decreased reaction efficiency. We introduce an arbitrary inter-reaction time distribution, which may account for the impact of incomplete mixing. This process defines an inhomogeneous continuous time random walk in particle number space, from which we derive a generalized chemical Master equation and formulate a generalized Gillespie algorithm. We then determine the modified chemical rate laws for different inter-reaction time distributions. We trace Michaelis-Menten-type kinetics back to finite-mean delay times, and predict time-nonlocal macroscopic reaction kinetics as a consequence of broadly distributed delays. Non-Markovian kinetics exhibit weak ergodicity breaking and show key features of reactions under local non-equilibrium.

Does listening to music with an audio ski helmet impair reaction time to peripheral stimuli?

PubMed

Ruedl, G; Pocecco, E; Wolf, M; Schöpf, S; Burtscher, M; Kopp, M

2012-12-01

With the recent worldwide increase in ski helmet use, new market trends are developing, including audio helmets for listening to music while skiing or snowboarding. The aim of this study was to evaluate whether listening to music with an audio ski helmet impairs reaction time to peripheral stimuli. A within-subjects design study using the Compensatory-Tracking-Test was performed on 65 subjects (36 males and 29 females) who had a mean age of 23.3 ± 3.9 years. Using repeated measures analysis of variance, we found significant differences in reaction times between the 4 test conditions (p=0.039). The lowest mean reaction time (± SE) was measured for helmet use while listening to music (507.9 ± 13.2 ms), which was not different from helmet use alone (514.6 ± 12.5 ms) (p=0.528). However, compared to helmet use while listening to music, reaction time was significantly longer for helmet and ski goggles used together (535.8 ± 14.2 ms, p=0.005), with a similar trend for helmet and ski goggles used together while listening to music (526.9 ± 13.8 ms) (p=0.094). In conclusion, listening to music with an audio ski helmet did not increase mean reaction time to peripheral stimuli in a laboratory setting. © Georg Thieme Verlag KG Stuttgart · New York.

Systematic derivation of reaction-diffusion equations with distributed delays and relations to fractional reaction-diffusion equations and hyperbolic transport equations: application to the theory of Neolithic transition.

PubMed

Vlad, Marcel Ovidiu; Ross, John

2002-12-01

We introduce a general method for the systematic derivation of nonlinear reaction-diffusion equations with distributed delays. We study the interactions among different types of moving individuals (atoms, molecules, quasiparticles, biological organisms, etc). The motion of each species is described by the continuous time random walk theory, analyzed in the literature for transport problems, whereas the interactions among the species are described by a set of transformation rates, which are nonlinear functions of the local concentrations of the different types of individuals. We use the time interval between two jumps (the transition time) as an additional state variable and obtain a set of evolution equations, which are local in time. In order to make a connection with the transport models used in the literature, we make transformations which eliminate the transition time and derive a set of nonlocal equations which are nonlinear generalizations of the so-called generalized master equations. The method leads under different specified conditions to various types of nonlocal transport equations including a nonlinear generalization of fractional diffusion equations, hyperbolic reaction-diffusion equations, and delay-differential reaction-diffusion equations. Thus in the analysis of a given problem we can fit to the data the type of reaction-diffusion equation and the corresponding physical and kinetic parameters. The method is illustrated, as a test case, by the study of the neolithic transition. We introduce a set of assumptions which makes it possible to describe the transition from hunting and gathering to agriculture economics by a differential delay reaction-diffusion equation for the population density. We derive a delay evolution equation for the rate of advance of agriculture, which illustrates an application of our analysis.

Anomalous dielectric relaxation with linear reaction dynamics in space-dependent force fields.

PubMed

Hong, Tao; Tang, Zhengming; Zhu, Huacheng

2016-12-28

The anomalous dielectric relaxation of disordered reaction with linear reaction dynamics is studied via the continuous time random walk model in the presence of space-dependent electric field. Two kinds of modified reaction-subdiffusion equations are derived for different linear reaction processes by the master equation, including the instantaneous annihilation reaction and the noninstantaneous annihilation reaction. If a constant proportion of walkers is added or removed instantaneously at the end of each step, there will be a modified reaction-subdiffusion equation with a fractional order temporal derivative operating on both the standard diffusion term and a linear reaction kinetics term. If the walkers are added or removed at a constant per capita rate during the waiting time between steps, there will be a standard linear reaction kinetics term but a fractional order temporal derivative operating on an anomalous diffusion term. The dielectric polarization is analyzed based on the Legendre polynomials and the dielectric properties of both reactions can be expressed by the effective rotational diffusion function and component concentration function, which is similar to the standard reaction-diffusion process. The results show that the effective permittivity can be used to describe the dielectric properties in these reactions if the chemical reaction time is much longer than the relaxation time.

Single-digit Arabic numbers do not automatically activate magnitude representations in adults or in children: Evidence from the symbolic same–different task☆

PubMed Central

Wong, Becky; Szücs, Dénes

2013-01-01

We investigated whether the mere presentation of single-digit Arabic numbers activates their magnitude representations using a visually-presented symbolic same–different task for 20 adults and 15 children. Participants saw two single-digit Arabic numbers on a screen and judged whether the numbers were the same or different. We examined whether reaction time in this task was primarily driven by (objective or subjective) perceptual similarity, or by the numerical difference between the two digits. We reasoned that, if Arabic numbers automatically activate magnitude representations, a numerical function would best predict reaction time; but if Arabic numbers do not automatically activate magnitude representations, a perceptual function would best predict reaction time. Linear regressions revealed that a perceptual function, specifically, subjective visual similarity, was the best and only significant predictor of reaction time in adults and in children. These data strongly suggest that, in this task, single-digit Arabic numbers do not necessarily automatically activate magnitude representations in adults or in children. As the first study to date to explicitly study the developmental importance of perceptual factors in the symbolic same–different task, we found no significant differences between adults and children in their reliance on perceptual information in this task. Based on our findings, we propose that visual properties may play a key role in symbolic number judgements. PMID:24076332

Five different tests of reaction time evaluated in HIV seropositive men.

PubMed

Dunlop, O; Bjørklund, R A; Abdelnoor, M; Myrvang, B

1992-09-01

In an attempt to develop a short neuropsychological test battery five different tests of reaction time were assessed according to their ability to discriminate between HIV seropositive men and healthy controls. In all tests a patient group with clinical symptoms was slower than the control group. In the complex reaction time test, which has a large cognitive aspect, even a clinically "asymptomatic" group was slower than the control group. The movement test, a new test with a large motor component, identified most slow responders, defining approximately half of the patients with clinical symptoms and one third of the "asymptomatic" patients as such. A test battery consisting of three tests is suggested for serial assessment and screening.

Utilizing the dynamic stark shift as a probe for dielectric relaxation in photosynthetic reaction centers during charge separation.

PubMed

Guo, Zhi; Lin, Su; Woodbury, Neal W

2013-09-26

In photosynthetic reaction centers, the electric field generated by light-induced charge separation produces electrochromic shifts in the transitions of reaction center pigments. The extent of this Stark shift indirectly reflects the effective field strength at a particular cofactor in the complex. The dynamics of the effective field strength near the two monomeric bacteriochlorophylls (BA and BB) in purple photosynthetic bacterial reaction centers has been explored near physiological temperature by monitoring the time-dependent Stark shift during charge separation (dynamic Stark shift). This dynamic Stark shift was determined through analysis of femtosecond time-resolved absorbance change spectra recorded in wild type reaction centers and in four mutants at position M210. In both wild type and the mutants, the kinetics of the dynamic Stark shift differ from those of electron transfer, though not in the same way. In wild type, the initial electron transfer and the increase in the effective field strength near the active-side monomer bacteriochlorophyll (BA) occur in synchrony, but the two signals diverge on the time scale of electron transfer to the quinone. In contrast, when tyrosine is replaced by aspartic acid at M210, the kinetics of the BA Stark shift and the initial electron transfer differ, but transfer to the quinone coincides with the decay of the Stark shift. This is interpreted in terms of differences in the dynamics of the local dielectric environment between the mutants and the wild type. In wild type, comparison of the Stark shifts associated with BA and BB on the two quasi-symmetric halves of the reaction center structure confirm that the effective dielectric constants near these cofactors are quite different when the reaction center is in the state P(+)QA(-), as previously determined by Steffen et al. at 1.5 K (Steffen, M. A.; et al. Science 1994, 264, 810-816). However, it is not possible to determine from static, low-temperature measurments if the difference in the effective dielectric constant between the two sides of the reaction center is manifest on the time scale of initial electron transfer. By comparing directly the Stark shift dynamics of the ground-state spectra of the two monomer bacteriochlorophylls, it is evident that there is, in fact, a large dielectric difference between protein environments of the two quasi-symmetric electron-transfer branches on the time scale of initial electron transfer and that the effective dielectric constant in the region continues to evolve on a time scale of hundreds of picoseconds.

Serial measurement of serum cytokines, cytokine receptors and neopterin in leprosy patients with reversal reactions.

PubMed

Faber, W R; Iyer, A M; Fajardo, T T; Dekker, T; Villahermosa, L G; Abalos, R M; Das, P K

2004-09-01

Serum levels of cytokines (IL-4, IL-5, IFN-gamma, TNF-alpha), cytokine receptors (TNFR I and II) and one monokine (neopterin) were estimated in seven leprosy patients to establish disease associated markers for reversal reactions (RR). Sera were collected at diagnosis of leprosy, at the onset of reversal reaction and at different time points during and at the end of prednisone treatment of reactions. It was expected that the serum cytokine and monokine profile before and at different time points during reactions would provide guidelines for the diagnosis and monitoring of reversal reactions in leprosy. The cytokines and cytokine receptors were measured by ELISA, whereas a radioimmunoassay was used for neopterin measurement. Six of the seven patients showed increased levels of neopterin either at the onset of RR or 1 month thereafter, and levels declined on prednisone treatment to that seen at the time of diagnosis without reactions. No consistent disease associated cytokine profile was observed in these patients. Interestingly, serum TNF-alpha levels were increased in the same patients even after completion of prednisone treatment, indicating ongoing immune activity. In conclusion, this study demonstrates that despite cytokines levels in leprosy serum being inconsistent in relation to reversal reactions, serum neopterin measurement appears to be an useful biomarker in monitoring RR patients during corticosteroid therapy.

The effects of reward and punishment on reaction times and autonomic activity in hyperactive and normal children.

PubMed

Firestone, P; Douglas, V

1975-01-01

The performance of hyperactive and control children was compared on a delayed reaction time task under three reinforcement conditions: reward, punishment, and reward plus punishment. Hyperactives had slower and more variable reaction times, suggesting an attentional deficit. Although each of the three reinforcement conditons was successful in improving reaction times for both subject groups, reward led to a significant increase in impulsive responses in the hyperactive children. Autonomic data revealed that reward also increased arousal to a greater extent than punishment or reward plus punishment. Although resting skin conductance was not different in the two groups of subjects, hyperactives produced fewer specific autonomic responses to signal stimuli.

Influence of sleep deprivation and auditory intensity on reaction time and response force.

PubMed

Włodarczyk, Dariusz; Jaśkowski, Piotr; Nowik, Agnieszka

2002-06-01

Arousal and activation are two variables supposed to underlie change in response force. This study was undertaken to explain these roles, specifically, for strong auditory stimuli and sleep deficit. Loud auditory stimuli can evoke phasic overarousal whereas sleep deficit leads to general underarousal. Moreover, Van der Molen and Keuss (1979, 1981) showed that paradoxically long reaction times occurred with extremely strong auditory stimuli when the task was difficult, e.g., choice reaction or Simon paradigm. It was argued that this paradoxical behavior related to reaction time is due to active disconnecting of the coupling between arousal and activation to prevent false responses. If so, we predicted that for extremely loud stimuli and for difficult tasks, the lengthening of reaction time should be associated with reduction of response force. The effects of loudness and sleep deficit on response time and force were investigated in three different tasks: simple response, choice response, and Simon paradigm. According to our expectation, we found a detrimental effect of sleep deficit on reaction time and on response force. In contrast to Van der Molen and Keuss, we found no increase in reaction time for loud stimuli (up to 110 dB) even on the Simon task.

Contrasting effect of prepulse signals on performance of Toxoplasma-infected and Toxoplasma-free subjects in an acoustic reaction times test.

PubMed

Příplatová, Lenka; Sebánková, Blanka; Flegr, Jaroslav

2014-01-01

About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive. We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis. Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis.

Behavioral and Neural Sustained Attention Deficits in Disruptive Mood Dysregulation Disorder and Attention-Deficit/Hyperactivity Disorder

PubMed Central

Pagliaccio, David; Wiggins, Jillian Lee; Adleman, Nancy E.; Curhan, Alexa; Zhang, Susan; Towbin, Kenneth E.; Brotman, Melissa A.; Pine, Daniel S.; Leibenluft, Ellen

2017-01-01

Objective Disruptive mood dysregulation disorder (DMDD), characterized by severe irritability, and attention-deficit/hyperactivity disorder (ADHD) are highly comorbid. This is the first study to characterize neural and behavioral similarities and differences in attentional functioning across these disorders. Method Twenty-seven healthy volunteers, 31 patients with DMDD, and 25 patients with ADHD (8–18-year-olds) completed a functional magnetic resonance imaging (fMRI) attention task. Group differences in intra-subject variability in reaction time (ISVRT) were examined. The current fMRI analytic approach precisely quantified trial-wise associations between reaction time and brain activity. Results Group differences manifested in the relationship between reaction time and brain activity (all regions: p<.01, F>2.54, ηp2>0.06). Patients with DMDD showed specific alterations in the right paracentral lobule, superior parietal lobule, fusiform gyrus, and cerebellar culmen. In contrast, both patients with DMDD and ADHD exhibited blunted compensatory increases in activity on long reaction time trials. Additionally, youth with DMDD exhibited increased activity in the postcentral gyrus, medial frontal gyrus, and cerebellar tonsil and declive (all regions: p<.05, F>2.46, ηp2>0.06). The groups in the imaging sample did not differ significantly in ISVRT (F[2,79]=2.664, p=.076, ηp2=0.063), though ISVRT was significantly elevated among youth with DMDD and ADHD when including those not meeting strict motion and accuracy criteria for the imaging analysis (F[2,96]=4.283, p=.017, ηp2=0.083). Conclusion Patients with DMDD exhibited specific alterations in the relationship between pre-stimulus brain activity and reaction time. Both patients with DMDD and ADHD exhibited similar blunting of compensatory neural activity in frontal, parietal, and other regions. Additionally, patients with DMDD demonstrated elevated reaction time variability relative to healthy youth. This work is the first to identify common and unique behavioral and neural signatures of DMDD and ADHD. PMID:28433092

Design Factors Affecting the Reaction Time for Identifying Toilet Signs: A Preliminary Study.

PubMed

Chen, Yi-Lang; Sie, Cai-Cin

2016-04-01

This study focused on the manner in which design factors affect the reaction time for identifying toilet signs. Taiwanese university students and staff members (50 men, 50 women; M age = 23.5 year, SD = 5.7) participated in the study. The 36 toilet signs were modified on three factors (six presenting styles, two figure-ground exchanges, and three colors), and the reaction time data of all participants were collected when the signs were presented in a simulation onscreen. Participants were quickest when reading Chinese text, followed by graphics and English texts. The findings also showed that men and women had different reaction times across various design combinations. These findings can serve as a reference for practically designing toilet signs, since design factors can lead to difficulties with comprehension based on reaction time measurements. © The Author(s) 2016.

Impact of virtual reality games on psychological well-being and upper limb performance in adults with physical disabilities: A pilot study.

PubMed

Singh, D K A; Rahman, N N A; Seffiyah, R; Chang, S Y; Zainura, A K; Aida, S R; Rajwinder, K H S

2017-04-01

There is limited information regarding the effects of interactive virtual reality (VR) games on psychological and physical well-being among adults with physical disabilities. We aimed to examine the impact of VR games on psychological well-being, upper limb motor function and reaction time in adults with physical disabilities. Fifteen participants completed the intervention using Wii VR games in this pilot study. Depressive, Anxiety and Stress Scales (DASS) and Capabilities of Upper Extremity (CUE) questionnaires were used to measure psychological well-being and upper limb motor function respectively. Upper limb reaction time was measured using reaction time test. Results showed that there was a significant difference (p<0.05) in DASS questionnaire and average reaction time score after intervention. There is a potential for using interactive VR games as an exercise tool to improve psychological wellbeing and upper limb reaction time among adults with disabilities.

Sex differences in the Kimchi-Palmer task revisited: Global reaction times, but not number of global choices differ between adult men and women.

PubMed

Scheuringer, Andrea; Pletzer, Belinda

2016-10-15

Research, directly assessing sex-dependent differences in global versus local processing is sparse, but predominantly suggesting that men show a stronger global processing bias than women. Utilizing the Kimchi-Palmer task however, sex differences in the number of global choices can only be found in children, but not in adults. In the current study 52 men and 46 women completed a computerized version of the Kimchi Palmer task, in order to investigate whether sex-differences in global-local processing in the Kimchi-Palmer task are reflected in choice reaction times rather than choices per se. While no sex differences were found in the number of global choices, we found that especially women are faster in making local choices than men, while men are faster in making global choices than women. We did not find support for the assumption that this sex difference was modulated by menstrual cycle phase of women, since the difference between reaction times to global and local choices was consistent across the menstrual cycle of women. Accordingly there was no relationship between progesterone and global-local processing in the Kimchi-Palmer task. However, like in studies utilizing the Navon task, testosterone was positively related to the number of global choices in both men and women. To our knowledge, this is the first study including reaction times as outcome measure in a Kimchi Palmer paradigm and also the first study demonstrating sex differences in the Kimchi Palmer task in adults. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Spontaneous Fluctuations in Sensory Processing Predict Within-Subject Reaction Time Variability.

PubMed

Ribeiro, Maria J; Paiva, Joana S; Castelo-Branco, Miguel

2016-01-01

When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset, just after the onset of the N1 peak. Interestingly, single trial N1 latency correlated significantly with reaction time, while N1 amplitude did not. In conclusion, our findings suggest that inter-trial variability in the timing of extrastriate visual processing contributes to reaction time variability.

Spontaneous Fluctuations in Sensory Processing Predict Within-Subject Reaction Time Variability

PubMed Central

Ribeiro, Maria J.; Paiva, Joana S.; Castelo-Branco, Miguel

2016-01-01

When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset, just after the onset of the N1 peak. Interestingly, single trial N1 latency correlated significantly with reaction time, while N1 amplitude did not. In conclusion, our findings suggest that inter-trial variability in the timing of extrastriate visual processing contributes to reaction time variability. PMID:27242470

Independence of reaction time and response force control during isometric leg extension.

PubMed

Fukushi, Tamami; Ohtsuki, Tatsuyuki

2004-04-01

In this study, we examined the relative control of reaction time and force in responses of the lower limb. Fourteen female participants (age 21.2 +/- 1.0 years, height 1.62 +/- 0.05 m, body mass 54.1 +/- 6.1 kg; mean +/- s) were instructed to exert their maximal isometric one-leg extension force as quickly as possible in response to an auditory stimulus presented after one of 13 foreperiod durations, ranging from 0.5 to 10.0 s. In the 'irregular condition' each foreperiod was presented in random order, while in the 'regular condition' each foreperiod was repeated consecutively. A significant interactive effect of foreperiod duration and regularity on reaction time was observed (P < 0.001 in two-way ANOVA with repeated measures). In the irregular condition the shorter foreperiod induced a longer reaction time, while in the regular condition the shorter foreperiod induced a shorter reaction time. Peak amplitude of isometric force was affected only by the regularity of foreperiod and there was a significant variation of changes in peak force across participants; nine participants were shown to significantly increase peak force for the regular condition (P < 0.001), three to decrease it (P < 0.05) and two showed no difference. These results indicate the independence of reaction time and response force control in the lower limb motor system. Variation of changes in peak force across participants may be due to the different attention to the bipolar nature of the task requirements such as maximal force and maximal speed.

Effect of Substrate Concentration and Reaction Time of Aquilaria subintegra Leaves Extract on Inhibition of Pancreatic Lipase

NASA Astrophysics Data System (ADS)

Zainal, S.; Musa, M.; Idris, J.; Hamid, K. H. Ku

2018-05-01

The purpose of this research are to recovery of pancreatic lipase inhibitor and to study the effect of using different concentration of substrate and reaction time on pancreatic lipase inhibitor. In this research, Aquilaria subintegra mature and fresh leaves was used as a sample. The research was conducted by using hydro-distillation with different concentrations, which are 100 µM, 200 µM and 300 µM and reaction times from 20, 40 and 60 minutes were studied. Based on the results obtained for the samples of phenol, flavonoid, gallic acid and quercetin were 49.30 µg/ml, 314.33 µg/ml, 12.94 µg/ml, and 5.15 µg/ml, respectively.

Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thanh, Vo Hong, E-mail: vo@cosbi.eu; Priami, Corrado, E-mail: priami@cosbi.eu; Department of Mathematics, University of Trento, Trento

We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reactionmore » rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.« less

Single-digit Arabic numbers do not automatically activate magnitude representations in adults or in children: evidence from the symbolic same-different task.

PubMed

Wong, Becky; Szücs, Dénes

2013-11-01

We investigated whether the mere presentation of single-digit Arabic numbers activates their magnitude representations using a visually-presented symbolic same-different task for 20 adults and 15 children. Participants saw two single-digit Arabic numbers on a screen and judged whether the numbers were the same or different. We examined whether reaction time in this task was primarily driven by (objective or subjective) perceptual similarity, or by the numerical difference between the two digits. We reasoned that, if Arabic numbers automatically activate magnitude representations, a numerical function would best predict reaction time; but if Arabic numbers do not automatically activate magnitude representations, a perceptual function would best predict reaction time. Linear regressions revealed that a perceptual function, specifically, subjective visual similarity, was the best and only significant predictor of reaction time in adults and in children. These data strongly suggest that, in this task, single-digit Arabic numbers do not necessarily automatically activate magnitude representations in adults or in children. As the first study to date to explicitly study the developmental importance of perceptual factors in the symbolic same-different task, we found no significant differences between adults and children in their reliance on perceptual information in this task. Based on our findings, we propose that visual properties may play a key role in symbolic number judgements. © 2013. Published by Elsevier B.V. All rights reserved.

Exploration of kinetic and multiple-ion-fluids effects in D3He and T3He gas-filled ICF implosions using multiple nuclear reaction histories

NASA Astrophysics Data System (ADS)

Sio, Hong; Rinderknecht, Hans; Rosenberg, Michael; Zylstra, Alex; Séguin, Fredrick; Gatu Johnson, Maria; Li, Chikang; Petrasso, Richard; Hoffman, Nelson; Kagan, Krigory; Molvig, Kim; Amendt, Peter; Bellei, Claudio; Wilks, Scott; Stoeckl, Christian; Glebov, Vladimir; Betti, Riccardo; Sangster, Thomas; Katz, Joseph

2014-10-01

To explore kinetic and multi-ion-fluid effects in D3He and T3He gas-filled shock-driven implosions, multiple nuclear reaction histories were measured using the upgraded Particle Temporal Diagnostic (PTD) on OMEGA. For D3He gas-filled implosions, the relative timing of the DD and D3He reaction histories were measured with 20 ps precision. For T3He gas-filled implosions (with 1-2% deuterium), the relative timing of the DT and D3He reaction histories were measured with 10 ps precision. The observed differences between the reaction histories on these two OMEGA experiments are contrasted to 1-D single-ion hydro simulations for different gas-fill pressure and gas mixture. This work is supported in part by the U.S. DOE, LLNL, LLE, and NNSA SSGF.

Effects of pallidal deep brain stimulation and levodopa treatment on reaction-time performance in Parkinson's disease.

PubMed

Schubert, T; Volkmann, J; Müller, U; Sturm, V; Voges, J; Freund, H-J; Von Cramon, D Y

2002-05-01

Basal ganglia-thalamocortical circuits play an important role in movement preparation and execution. Tracer, single-cell, and lesion studies in monkeys suggest the existence of topologically segregated motor and nonmotor basal ganglia cortical circuits. In this study we used deep brain stimulation (DBS) of the posteroventrolateral globus pallidus internus (GPi) in patients with Parkinson's disease to elucidate the function of the GPi in human sensorimotor behavior. This question was investigated by comparing the influence of DBS on patients' performance in various reaction-time tasks that differed with respect to cognitive but not motor requirements. As a main result, DBS improved performance on the different tasks independently of the complexity of the involved cognitive processing functions. Furthermore, the observed effects did not depend on the modality of the processed information. These results suggest that the functional state of the posteroventrolateral GPi selectively affects the motor stage in simple sensorimotor acts, because this stage was the only stage involved in all investigated tasks. In addition to DBS, we manipulated the levodopa medication state of the PD patients. In contrast to DBS, levodopa effects on reaction times were less consistent. Levodopa improved reaction times in choice reaction tasks significantly, while affecting reaction times in a simple reaction task to a lesser extent. Error analysis revealed that the medication-dependent reaction-time improvement in the choice reaction tasks was accompanied by an increase in errors, suggesting a shift of the speed-accuracy criteria of the patients. A similar pattern of results was not observed for the DBS effects. Taken together, our data are in agreement with recent findings in monkeys that indicate a topological organization of the GPi in which motor functions are localized in posterolateral regions apart from cognitive regions. Furthermore, our data show a way to uncover the subcortical-cortical circuitry serving human sensorimotor behavior.

Vasovagal reactions in whole blood donors at 3 REDS-II blood centers in Brazil

PubMed Central

Goncalez, T. T.; Sabino, E. C.; Schlumpf, K.S.; Wright, D.J.; Leao, S.; Sampaio, D.; Takecian, P. L.; Carneiro-Proietti, AB; Murphy, E.; Busch, M.; Custer, B.

2013-01-01

Background In Brazil little is known about adverse reactions during donation and the donor characteristics that may be associated with such events. Donors are offered snacks and fluids prior to donating and are required to consume a light meal after donation. For these reasons the frequency of reactions may be different than those observed in other countries. Methods A cross-sectional study was conducted of eligible whole blood donors at three large blood centers located in Brazil between July 2007 and December 2009. Vasovagal reactions (VVRs) along with donor demographic and biometric data were collected. Reactions were defined as any presyncopal or syncopal event during the donation process. Multivariable logistic regression was performed to identify predictors of VVRs. Results Of 724,861 donor presentations, 16,129 (2.2%) VVRs were recorded. Rates varied substantially between the three centers: 53, 290 and 381 per 10,000 donations in Recife, São Paulo and Belo Horizonte, respectively. Although the reaction rates varied, the donor characteristics associated with VVRs were similar [younger age (18–29), replacement donors, first time donors, low estimated blood volume (EBV)]. In multivariable analysis controlling for differences between the donor populations in each city younger age, first-time donor status and lower EBV were the factors most associated with reactions. Conclusion Factors associated with VVRs in other locations are also evident in Brazil. The difference in VVR rates between the three centers might be due to different procedures for identifying and reporting the reactions. Potential interventions to reduce the risk of reactions in Brazil should be considered. PMID:22073941

Effective Analysis of Reaction Time Data

ERIC Educational Resources Information Center

Whelan, Robert

2008-01-01

Most analyses of reaction time (RT) data are conducted by using the statistical techniques with which psychologists are most familiar, such as analysis of variance on the sample mean. Unfortunately, these methods are usually inappropriate for RT data, because they have little power to detect genuine differences in RT between conditions. In…

Sentence Processing in High Proficient Kannada--English Bilinguals: A Reaction Time Study

ERIC Educational Resources Information Center

Ravi, Sunil Kumar; Chengappa, Shyamala K.

2015-01-01

The present study aimed at exploring the semantic and syntactic processing differences between native and second languages in 20 early high proficient Kannada--English bilingual adults through accuracy and reaction time (RT) measurements. Subjects participated in a semantic judgement task (using 50 semantically correct and 50 semantically…

Reactivity, stability, and strength performance capacity in motor sports.

PubMed

Baur, H; Müller, S; Hirschmüller, A; Huber, G; Mayer, F

2006-11-01

Racing drivers require multifaceted cognitive and physical abilities in a multitasking situation. A knowledge of their physical capacities may help to improve fitness and performance. To compare reaction time, stability performance capacity, and strength performance capacity of élite racing drivers with those of age-matched, physically active controls. Eight élite racing drivers and 10 physically active controls matched for age and weight were tested in a reaction and determination test requiring upper and lower extremity responses to visual and audio cues. Further tests comprised evaluation of one-leg postural stability on a two-dimensional moveable platform, measures of maximum strength performance capacity of the extensors of the leg on a leg press, and a test of force capacity of the arms in a sitting position at a steering wheel. An additional arm endurance test consisted of isometric work at the steering wheel at +30 degrees and -30 degrees where an eccentric threshold load of 30 N.m was applied. Subjects had to hold the end positions above this threshold until exhaustion. Univariate one way analysis of variance (alpha = 0.05) including a Bonferroni adjustment was used to detect group differences between the drivers and controls. The reaction time of the racing drivers was significantly faster than the controls (p = 0.004). The following motor reaction time and reaction times in the multiple determination test did not differ between the groups. No significant differences (p>0.05) were found for postural stability, leg extensor strength, or arm strength and endurance. Racing drivers have faster reaction times than age-matched physically active controls. Further development of motor sport-specific test protocols is suggested. According to the requirements of motor racing, strength and sensorimotor performance capacity can potentially be improved.

Transfer effects of manipulating temporal constraints on learning a two-choice reaction time task with low stimulus-response compatibility.

PubMed

Chen, David D; Pei, Laura; Chan, John S Y; Yan, Jin H

2012-10-01

Recent research using deliberate amplification of spatial errors to increase motor learning leads to the question of whether amplifying temporal errors may also facilitate learning. We investigated transfer effects caused by manipulating temporal constraints on learning a two-choice reaction time (CRT) task with varying degrees of stimulus-response compatibility. Thirty-four participants were randomly assigned to one of the three groups and completed 120 trials during acquisition. For every fourth trial, one group was instructed to decrease CRT by 50 msec. relative to the previous trial and a second group was instructed to increase CRT by 50 msec. The third group (the control) was told not to change their responses. After a 5-min. break, participants completed a 40-trial no-feedback transfer test. A 40-trial delayed transfer test was administered 24 hours later. During acquisition, the Decreased Reaction Time group responded faster than the two other groups, but this group also made more errors than the other two groups. In the 5-min. delayed test (immediate transfer), the Decreased Reaction Time group had faster reaction times than the other two groups, while for the 24-hr. delayed test (delayed transfer), both the Decreased Reaction Time group and Increased Reaction Time group had significantly faster reaction times than the control. For delayed transfer, both Decreased and Increased Reaction Time groups reacted significantly faster than the control group. Analyses of error scores in the transfer tests indicated revealed no significant group differences. Results were discussed with regard to the notion of practice variability and goal-setting benefits.

The effect of milling frequency on a mechanochemical organic reaction monitored by in situ Raman spectroscopy

PubMed Central

Julien, Patrick A; Malvestiti, Ivani

2017-01-01

We provide the first in situ and real-time study of the effect of milling frequency on the course of a mechanochemical organic reaction conducted using a vibratory shaker (mixer) ball mill. The use of in situ Raman spectroscopy for real-time monitoring of the mechanochemical synthesis of a 2,3-diphenylquinoxaline derivative revealed a pronounced dependence of chemical reactivity on small variations in milling frequency. In particular, in situ measurements revealed the establishment of two different regimes of reaction kinetics at different frequencies, providing tentative insight into processes of mechanical activation in organic mechanochemical synthesis. PMID:29114323

QRTEngine: An easy solution for running online reaction time experiments using Qualtrics.

PubMed

Barnhoorn, Jonathan S; Haasnoot, Erwin; Bocanegra, Bruno R; van Steenbergen, Henk

2015-12-01

Performing online behavioral research is gaining increased popularity among researchers in psychological and cognitive science. However, the currently available methods for conducting online reaction time experiments are often complicated and typically require advanced technical skills. In this article, we introduce the Qualtrics Reaction Time Engine (QRTEngine), an open-source JavaScript engine that can be embedded in the online survey development environment Qualtrics. The QRTEngine can be used to easily develop browser-based online reaction time experiments with accurate timing within current browser capabilities, and it requires only minimal programming skills. After introducing the QRTEngine, we briefly discuss how to create and distribute a Stroop task. Next, we describe a study in which we investigated the timing accuracy of the engine under different processor loads using external chronometry. Finally, we show that the QRTEngine can be used to reproduce classic behavioral effects in three reaction time paradigms: a Stroop task, an attentional blink task, and a masked-priming task. These findings demonstrate that QRTEngine can be used as a tool for conducting online behavioral research even when this requires accurate stimulus presentation times.

Copper(I)/TEMPO Catalyzed Aerobic Oxidation of Primary Alcohols to Aldehydes with Ambient Air

PubMed Central

Hoover, Jessica M.; Steves, Janelle E.; Stahl, Shannon S.

2012-01-01

This protocol describes a practical laboratory-scale method for aerobic oxidation of primary alcohols to aldehydes, using a chemoselective CuI/TEMPO catalyst system. The catalyst is prepared in situ from commercially available reagents, and the reactions are performed in a common organic solvent (acetonitrile) with ambient air as the oxidant. Three different reaction conditions and three procedures for the isolation and purification of the aldehyde product are presented. The oxidations of eight different alcohols, described here, include representative examples of each reaction condition and purification method. Reaction times vary from 20 min to 24 h, depending on the alcohol, while the purification methods each take about 2 h. The total time necessary for the complete protocol ranges from 3 – 26 h. PMID:22635108

Combined effect of whole-body vibration and ambient lighting on human discomfort, heart rate, and reaction time.

PubMed

Monazzam, Mohammad Reza; Shoja, Esmaeil; Zakerian, Seyed Abolfazl; Foroushani, Abbas Rahimi; Shoja, Mohsen; Gharaee, Masoumeh; Asgari, Amin

2018-07-01

This study aimed to investigate the effect of whole-body vibration and ambient lighting, as well as their combined effect on human discomfort, heart rate, and reaction time in laboratory conditions. 44 men were recruited with an average age of 25.4 ± 1.9 years. Each participant was subjected to 12 experimental steps, each step lasting five minutes for four different vibration accelerations in X, Y, and Z axes at a fixed frequency; three different lighting intensities of 50, 500, and 1000 lx were also considered. At each step, a visual computerized reaction test was taken from subjects and their heart rate recorded by pulse oximeter. In addition, the discomfort rate of subjects was measured using Borg scale. Increasing vibration acceleration significantly increased the discomfort rate and heart beat but not the reaction time. Lack of lighting caused more discomfort in the subjects, but there was no significant correlation between lighting intensity with heart rate and reaction time. The results also showed that the combined effect of vibration and lighting had no significant effect on any of the discomfort, heart rate, and reaction time variables. Whole-body vibration is an important factor in the development of human subjective and physiological reactions compared to lighting. Therefore, consideration of the level of vibration to which an individual is exposed in workplaces subject to vibration plays an important role in reducing the level of human discomfort, but its interaction with ambient lighting does not have a significant effect on human subjective and physiological responses.

A Novel Assessment of Braking Reaction Time Following THA Using a New Fully Interactive Driving Simulator.

PubMed

Ruel, Allison V; Lee, Yuo-Yu; Boles, John; Boettner, Friedrich; Su, Edwin; Westrich, Geoffrey H

2015-07-01

After total hip replacement surgery, patients are eager to resume the activities of daily life, particularly driving. Most surgeons recommend waiting 6 weeks after surgery to resume driving; however, there is no evidence to indicate that patients cannot resume driving earlier. Our purpose was to evaluate when in the recovery period following THA that patients regain or improve upon their preoperative braking reaction time, allowing them to safely resume driving. We measured and compared pre- and postoperative braking reaction times of 90 patients from 3 different surgeons using a Fully Interactive Driving Simulator (Simulator Systems International, Tulsa, OK). We defined a return to safe braking reaction time as a return to a time value that is either equal to or less than the preoperative braking reaction time. Patients tested at 2 and 3 weeks after surgery had slower braking reaction times than preoperative times by an average of 0.069 and 0.009 s, respectively. At 4 weeks after surgery, however, patients improved their reaction times by 0.035 s (p = 0.0398). In addition, at 2, 3, and 4 weeks postoperatively, the results also demonstrated that patient less than 70 years of age recovered faster. Based upon the results of this study, most patients should be allowed to return to driving 4 weeks following minimally invasive primary total hip arthroplasty.

Placing Inspection Time, Reaction Time, and Perceptual Speed in the Broader Context of Cognitive Ability: The VPR Model in the Lothian Birth Cohort 1936

ERIC Educational Resources Information Center

Johnson, Wendy; Deary, Ian J.

2011-01-01

The idea that information processing speed is related to cognitive ability has a long history. Much evidence has been amassed in its support, with respect to both individual differences in general intelligence and developmental trajectories. Two so-called elementary cognitive tasks, reaction time and inspection time, have been used to compile this…

Evaluation of the Combined Effects of Heat and Lighting on the Level of Attention and Reaction Time: Climate Chamber Experiments in Iran.

PubMed

Mohebian, Zohreh; Farhang Dehghan, Somayeh; Dehghan, Habiballah

2018-01-01

Heat exposure and unsuitable lighting are two physical hazardous agents in many workplaces for which there are some evidences regarding their mental effects. The purpose of this study was to assess the combined effect of heat exposure and different lighting levels on the attention rate and reaction time in a climatic chamber. This study was conducted on 33 healthy students (17 M/16 F) with a mean (±SD) age of 22.1 ± 2.3 years. The attention and reaction time test were done by continuous performance test and the RT meter, respectively, in different exposure conditions including the dry temperatures (22°C and 37°C) and lighting levels (200, 500, and 1500 lux). Findings demonstrated that increase in heat and lighting level caused a decrease in average attention percentage and correct responses and increase in commission error, omission error, and response time ( P < 0.05). The average of simple, diagnostic, two-color selective, and two-sound selective reaction times increased after combined exposure to heat and lighting ( P < 0.05). The results of this study indicated that, in job task which requires using cognitive functions like attention, vigilance, concentration, cautiousness, and reaction time, the work environment must be optimized in terms of heat and lighting level.

Probing Aluminum Reactions in Combustion and Explosion Via the Kinetic Isotope Effect

NASA Astrophysics Data System (ADS)

Tappan, Bryce

2015-06-01

The mechanism that controls the reaction speed of aluminum in explosion and combustion is poorly understood, and experimentally difficult to measure. Recently, work in our laboratory has demonstrated that during the combustion of nanoparticulate aluminum with H2O or D2O, different reaction rates due to the kinetic isotope effect are observed. This result is the first-ever observed kinetic isotope effect in a metal combustion reaction and verifies that chemical reaction kinetics play a major role in determining the global burning rate. During or shortly after a detonation, however, the reaction rates are dramatically faster and the physical mechanism controlling Al reaction is likely different than during combustion events. To utilize the kinetic isotope effect to probe Al reactions in detonation, formulations were produced that contain powdered Al in deuterated high explosives and high-fidelity detonation velocity were determined along with PDV measurements to observe early wall velocity expansion measurements. The JWL equation of state was solved to determine temperature, pressure and energies at specific time periods, in addition of Gurney energies, which enables the elucidation of Al reaction extent. By comparison of the Al oxidation with LiF, data indicate that Al oxidation occurs on an extremely fast time scale and isotope effects in both the HE detonation and post-detonation Al reactions are discussed.

Design of experiments for zeroth and first-order reaction rates.

PubMed

Amo-Salas, Mariano; Martín-Martín, Raúl; Rodríguez-Aragón, Licesio J

2014-09-01

This work presents optimum designs for reaction rates experiments. In these experiments, time at which observations are to be made and temperatures at which reactions are to be run need to be designed. Observations are performed along time under isothermal conditions. Each experiment needs a fixed temperature and so the reaction can be measured at the designed times. For these observations under isothermal conditions over the same reaction a correlation structure has been considered. D-optimum designs are the aim of our work for zeroth and first-order reaction rates. Temperatures for the isothermal experiments and observation times, to obtain the most accurate estimates of the unknown parameters, are provided in these designs. D-optimum designs for a single observation in each isothermal experiment or for several correlated observations have been obtained. Robustness of the optimum designs for ranges of the correlation parameter and comparisons of the information gathered by different designs are also shown. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sex differences in cardiovascular and subjective stress reactions: prospective evidence in a realistic military setting.

PubMed

Taylor, Marcus K; Larson, Gerald E; Hiller Lauby, Melissa D; Padilla, Genieleah A; Wilson, Ingrid E; Schmied, Emily A; Highfill-McRoy, Robyn M; Morgan, Charles A

2014-01-01

Evidence points to heightened physiological arousal in response to acute stress exposure as both a prospective indicator and a core characteristic of posttraumatic stress disorder (PTSD). Because females may be at higher risk for PTSD development, it is important to evaluate sex differences in acute stress reactions. This study characterized sex differences in cardiovascular and subjective stress reactions among military survival trainees. One hundred and eighty-five military members (78% males) were studied before, during, and 24 h after stressful mock captivity. Cardiovascular (heart rate [HR], systolic blood pressure [SBP], diastolic blood pressure [DBP]) and dissociative states were measured at all three time points. Psychological impact of mock captivity was assessed during recovery. General linear modeling with repeated measures evaluated sex differences for each cardiovascular endpoint, and causal steps modeling was used to explore interrelationships among sex, cardiovascular reactions and psychological impact of mock captivity. Although females had lower SBP than males at all three time points, the difference was most pronounced at baseline and during stress. Accordingly, females showed greater residual elevation in SBP during recovery. Females had lower DBP at all three time points. In addition, females reported greater psychological impact of mock captivity than males. Exploratory causal steps modeling suggested that stress-induced HR may partially mediate the effect of sex on psychological impact of mock captivity. In conclusion, this study demonstrated sex-specific cardiovascular stress reactions in military personnel, along with greater psychological impact of stress exposure in females. This research may elucidate sex differences in PTSD development.

Enhancement of force patterns classification based on Gaussian distributions.

PubMed

Ertelt, Thomas; Solomonovs, Ilja; Gronwald, Thomas

2018-01-23

Description of the patterns of ground reaction force is a standard method in areas such as medicine, biomechanics and robotics. The fundamental parameter is the time course of the force, which is classified visually in particular in the field of clinical diagnostics. Here, the knowledge and experience of the diagnostician is relevant for its assessment. For an objective and valid discrimination of the ground reaction force pattern, a generic method, especially in the medical field, is absolutely necessary to describe the qualities of the time-course. The aim of the presented method was to combine the approaches of two existing procedures from the fields of machine learning and the Gauss approximation in order to take advantages of both methods for the classification of ground reaction force patterns. The current limitations of both methods could be eliminated by an overarching method. Twenty-nine male athletes from different sports were examined. Each participant was given the task of performing a one-legged stopping maneuver on a force plate from the maximum possible starting speed. The individual time course of the ground reaction force of each subject was registered and approximated on the basis of eight Gaussian distributions. The descriptive coefficients were then classified using Bayesian regulated neural networks. The different sports served as the distinguishing feature. Although the athletes were all given the same task, all sports referred to a different quality in the time course of ground reaction force. Meanwhile within each sport, the athletes were homogeneous. With an overall prediction (R = 0.938) all subjects/sports were classified correctly with 94.29% accuracy. The combination of the two methods: the mathematical description of the time course of ground reaction forces on the basis of Gaussian distributions and their classification by means of Bayesian regulated neural networks, seems an adequate and promising method to discriminate the ground reaction forces without any loss of information. Copyright © 2017 Elsevier Ltd. All rights reserved.

Negativization rates of IgE radioimmunoassay and basophil activation test in immediate reactions to penicillins.

PubMed

Fernández, T D; Torres, M J; Blanca-López, N; Rodríguez-Bada, J L; Gomez, E; Canto, G; Mayorga, C; Blanca, M

2009-02-01

Skin test sensitivity in patients with immediate allergy to penicillins tends to decrease over time, but no information is available concerning in vitro tests. We analysed the negativization rates of two in vitro methods that determine specific immunoglobulin E (IgE) antibodies, the basophil activation test using flow cytometry (BAT) and the radioallergosorbent test (RAST), in immediate allergic reactions to penicillins. Forty-one patients with immediate allergic reactions to amoxicillin were followed up over a 4-year period. BAT and RAST were performed at 6-month intervals. Patients were randomized into groups: Group I, skin tests carried out at regular intervals; Group II, skin tests made only at the beginning of the study. Differences were observed between RAST and BAT (P < 0.01), the latter showing earlier negativization. Considering different haptens, significant differences for the rate of negativization were only found for amoxicillin (P < 0.05). Comparisons between Groups I (n = 10) and II (n = 31) showed a tendency to become negative later in Group I with RAST. Levels of specific IgE antibodies tended to decrease over time in patients with immediate allergic reactions to amoxicillin. Conversion to negative took longer for the RAST assay, although the differences were only detected with the amoxicillin hapten. Skin testing influenced the rate of negativization of the RAST assay, contributing to maintenance of in vitro sensitivity. Because of the loss of sensitivity over time, the determination of specific IgE antibodies to penicillins in patients with immediate allergic reactions must be done as soon as possible after the reaction.

Changes in Choice Reaction Time During and After 8 Days Exhaustive Cycling Are Not Related to Changes in Physical Performance.

PubMed

Ten Haaf, Twan; van Staveren, Selma; Iannetta, Danilo; Roelands, Bart; Meeusen, Romain; Piacentini, Maria F; Foster, Carl; Koenderman, Leo; Daanen, Hein A M; de Koning, Jos J

2018-04-01

Reaction time has been proposed as a training monitoring tool, but to date, results are equivocal. Therefore, it was investigated whether reaction time can be used as a monitoring tool to establish overreaching. The study included 30 subjects (11 females and 19 males, age: 40.8 [10.8] years, VO 2max : 51.8 [6.3] mL/kg/min) who participated in an 8-day cycling event. The external exercise load increased approximately 900% compared with the preparation period. Performance was measured before and after the event using a maximal incremental cycling test. Subjects with decreased performance after the event were classified as functionally overreached (FOR) and others as acutely fatigued (AF). A choice reaction time test was performed 2 weeks before (pre), 1 week after (post), and 5 weeks after (follow-up), as well as at the start and end of the event. A total of 14 subjects were classified as AF and 14 as FOR (2 subjects were excluded). During the event, reaction time at the end was 68 ms (95% confidence interval, 46-89) faster than at the start. Reaction time post event was 41 ms (95% confidence interval, 12-71) faster than pre event and follow-up was 55 ms faster (95% confidence interval, 26-83). The time by class interaction was not significant during (P = .26) and after (P = .43) the event. Correlations between physical performance and reaction time were not significant (all Ps > .30). No differences in choice reaction time between AF and FOR subjects were observed. It is suggested that choice reaction time is not valid for early detection of overreaching in the field.

Errors in Postural Preparation Lead to Increased Choice Reaction Times for Step Initiation in Older Adults

PubMed Central

Nutt, John G.; Horak, Fay B.

2011-01-01

Background. This study asked whether older adults were more likely than younger adults to err in the initial direction of their anticipatory postural adjustment (APA) prior to a step (indicating a motor program error), whether initial motor program errors accounted for reaction time differences for step initiation, and whether initial motor program errors were linked to inhibitory failure. Methods. In a stepping task with choice reaction time and simple reaction time conditions, we measured forces under the feet to quantify APA onset and step latency and we used body kinematics to quantify forward movement of center of mass and length of first step. Results. Trials with APA errors were almost three times as common for older adults as for younger adults, and they were nine times more likely in choice reaction time trials than in simple reaction time trials. In trials with APA errors, step latency was delayed, correlation between APA onset and step latency was diminished, and forward motion of the center of mass prior to the step was increased. Participants with more APA errors tended to have worse Stroop interference scores, regardless of age. Conclusions. The results support the hypothesis that findings of slow choice reaction time step initiation in older adults are attributable to inclusion of trials with incorrect initial motor preparation and that these errors are caused by deficits in response inhibition. By extension, the results also suggest that mixing of trials with correct and incorrect initial motor preparation might explain apparent choice reaction time slowing with age in upper limb tasks. PMID:21498431

A coupled theory for chemically active and deformable solids with mass diffusion and heat conduction

NASA Astrophysics Data System (ADS)

Zhang, Xiaolong; Zhong, Zheng

2017-10-01

To analyse the frequently encountered thermo-chemo-mechanical problems in chemically active material applications, we develop a thermodynamically-consistent continuum theory of coupled deformation, mass diffusion, heat conduction and chemical reaction. Basic balance equations of force, mass and energy are presented at first, and then fully coupled constitutive laws interpreting multi-field interactions and evolving equations governing irreversible fluxes are constructed according to the energy dissipation inequality and the chemical kinetics. To consider the essential distinction between mass diffusion and chemical reactions in affecting free energy and dissipations of a highly coupled system, we regard both the concentrations of diffusive species and the extent of reaction as independent state variables. This new formulation then distinguishes between the energy contribution from the diffusive species entering the solid and that from the subsequent chemical reactions occurring among these species and the host solid, which not only interact with stresses or strains in different manners and on different time scales, but also induce different variations of solid microstructures and material properties. Taking advantage of this new description, we further establish a specialized isothermal model to predict precisely the transient chemo-mechanical response of a swelling solid with a proposed volumetric constraint that accounts for material incompressibility. Coupled kinetics is incorporated to capture the volumetric swelling of the solid caused by imbibition of external species and the simultaneous dilation arised from chemical reactions between the diffusing species and the solid. The model is then exemplified with two numerical examples of transient swelling accompanied by chemical reaction. Various ratios of characteristic times of diffusion and chemical reaction are taken into account to shed light on the dependency on kinetic time scales of evolution patterns for a diffusion-reaction controlled deformable solid.

The Importance of Reaction Times for Developmental Science: What a Difference Milliseconds Make

ERIC Educational Resources Information Center

Lange-Küttner, Christiane

2012-01-01

Reaction times are still rarely reported in developmental psychology although they are an indicator of the neural maturity of children's information processing system. Competence and capacity are confounded in development, where children may be able to reason, or remember, but are unable to cope with information processing load. Furthermore, there…

More Symmetrical Children Have Faster and More Consistent Choice Reaction Times

ERIC Educational Resources Information Center

Hope, David; Bates, Timothy C.; Dykiert, Dominika; Der, Geoff; Deary, Ian J.

2015-01-01

Greater cognitive ability in childhood is associated with increased longevity, and speedier reaction time (RT) might account for much of this linkage. Greater bodily symmetry is linked to both higher cognitive test scores and faster RTs. It is possible, then, that differences in bodily system integrity indexed by symmetry may underlie the…

Testing a potential alternative to traditional identification procedures: Reaction time-based concealed information test does not work for lineups with cooperative witnesses.

PubMed

Sauerland, Melanie; Wolfs, Andrea C F; Crans, Samantha; Verschuere, Bruno

2017-11-27

Direct eyewitness identification is widely used, but prone to error. We tested the validity of indirect eyewitness identification decisions using the reaction time-based concealed information test (CIT) for assessing cooperative eyewitnesses' face memory as an alternative to traditional lineup procedures. In a series of five experiments, a total of 401 mock eyewitnesses watched one of 11 different stimulus events that depicted a breach of law. Eyewitness identifications in the CIT were derived from longer reaction times as compared to well-matched foil faces not encountered before. Across the five experiments, the weighted mean effect size d was 0.14 (95% CI 0.08-0.19). The reaction time-based CIT seems unsuited for testing cooperative eyewitnesses' memory for faces. The careful matching of the faces required for a fair lineup or the lack of intent to deceive may have hampered the diagnosticity of the reaction time-based CIT.

Missense Gamma-Aminobutyric Acid Receptor Polymorphisms Are Associated with Reaction Time, Motor Time, and Ethanol Effects in Vivo.

PubMed

García-Martín, Elena; Ramos, María I; Cornejo-García, José A; Galván, Segismundo; Perkins, James R; Rodríguez-Santos, Laura; Alonso-Navarro, Hortensia; Jiménez-Jiménez, Félix J; Agúndez, José A G

2018-01-01

Background: The Gamma-aminobutyric acid type A receptor (GABA-A receptor) is affected by ethanol concentrations equivalent to those reached during social drinking. At these concentrations, ethanol usually causes impairment in reaction and motor times in most, but not all, individuals. Objectives: To study the effect of GABA-A receptor variability in motor and reaction times, and the effect of low ethanol doses. Methods: Two hundred and fifty healthy subjects received one single dose of 0.5 g/Kg ethanol per os . Reaction and motor times were determined before ethanol challenge (basal), and when participants reached peak ethanol concentrations. We analyzed all common missense polymorphisms described in the 19 genes coding for the GABA-A receptor subunits by using TaqMan probes. Results: The GABRA6 rs4454083 T/C polymorphisms were related to motor times, with individuals carrying the C/C genotype having faster motor times, both, at basal and at peak ethanol concentrations. The GABRA4 rs2229940 T/T genotype was associated to faster reaction times and with lower ethanol effects, determined as the difference between basal reaction time and reaction time at peak concentrations. All these associations remained significant after correction for multiple comparisons. No significant associations were observed for the common missense SNPs GABRB3 rs12910925, GABRG2 rs211035, GABRE rs1139916, GABRP rs1063310, GABRQ rs3810651, GABRR1 rs12200969 or rs1186902, GABRR2 rs282129, and GABRR3 rs832032. Conclusions: This study provides novel information supporting a role of missense GABA-A receptor polymorphisms in reaction time, motor time and effects of low ethanol doses in vivo .

Long-term mass transfer and mixing-controlled reactions of a DNAPL plume from persistent residuals

NASA Astrophysics Data System (ADS)

Liu, Yuan; Illangasekare, Tissa H.; Kitanidis, Peter K.

2014-02-01

Understanding and being able to predict the long-term behavior of DNAPL (i.e., PCE and TCE) residuals after active remediation has ceased have become increasingly important as attention at many sites turns from aggressive remediation to monitored natural attenuation and long-term stewardship. However, plume behavior due to mass loading and reactions during these later phases is less studied as they involve large spatial and temporal scales. We apply both theoretical analysis and pore-scale simulations to investigate mass transfer from DNAPL residuals and subsequent reactions within the generated plume, and, in particular, to show the differences between early- and late-time behaviors of the plume. In the zone of entry of the DNAPL entrapment zone where the concentration boundary layer in the flowing groundwater has not fully developed, the pore-scale simulations confirm the past findings based on laboratory studies that the mass transfer increases as a power-law function of the Peclét number, and is enhanced due to reactions in the plume. Away from the entry zone and further down gradient, the long-term reactions are limited by the available additive and mixing in the porous medium, thereby behave considerably differently from the entry zone. For the reaction between the contaminant and an additive with intrinsic second-order bimolecular kinetics, the late-time reaction demonstrates a first-order decay macroscopically with respect to the mass of the limiting additive, not with respect to that of the contaminant. The late-time decay rate only depends on the intrinsic reaction rate and the solubility of the entrapped DNAPL. At the intermediate time, the additive decays exponentially with the square of time (t2), instead of time (t). Moreover, the intermediate decay rate also depends on the initial conditions, the spatial distribution of DNAPL residuals, and the effective dispersion coefficient.

Moderate anxiety modifies the electromyographic activity of a forearm muscle during a time-reaction task in women.

PubMed

Langlet, C; Hainaut, J P; Bolmont, B

2017-03-16

Arousal anxiety has a great impact on reaction time, physiological parameters and motor performance. Numerous studies have focused on the influence of anxiety on muscular activity during simple non ecologic task. We investigate the impact of a moderate state-anxiety (arousal stressor) on the specific component of a complex multi-joint ecologic movement during a reaction time task of auditory stimulus-response. Our objective is to know if central and peripheral voluntary motor processes were modulated in the same way by an arousal stressor. Eighteen women volunteers performed simple reaction time tasks of auditory stimulus-response. Video-recorded Stroop test with interferences was used to induced moderate state-anxiety. Electromyographic activity of the wrist extensor was recorded in order to analyse the two components of the reaction time: the premotor and motor time. In anxiogenic condition, an acceleration and an increase of muscular activity of the reaction time was obtained. This increase was due to a stronger muscle activity during the premotor time in the anxiogenic condition. Arousal anxiety has a different impact on central and peripheral voluntary motor processes. The modifications observed could be related to an increase in arousal related to a higher anxiety in order to prepare the body to act. Copyright © 2017 Elsevier B.V. All rights reserved.

Lack of correlation between reaction speed and analytical sensitivity in isothermal amplification reveals the value of digital methods for optimization: validation using digital real-time RT-LAMP

PubMed Central

Khorosheva, Eugenia M.; Karymov, Mikhail A.; Selck, David A.; Ismagilov, Rustem F.

2016-01-01

In this paper, we asked if it is possible to identify the best primers and reaction conditions based on improvements in reaction speed when optimizing isothermal reactions. We used digital single-molecule, real-time analyses of both speed and efficiency of isothermal amplification reactions, which revealed that improvements in the speed of isothermal amplification reactions did not always correlate with improvements in digital efficiency (the fraction of molecules that amplify) or with analytical sensitivity. However, we observed that the speeds of amplification for single-molecule (in a digital device) and multi-molecule (e.g. in a PCR well plate) formats always correlated for the same conditions. Also, digital efficiency correlated with the analytical sensitivity of the same reaction performed in a multi-molecule format. Our finding was supported experimentally with examples of primer design, the use or exclusion of loop primers in different combinations, and the use of different enzyme mixtures in one-step reverse-transcription loop-mediated amplification (RT-LAMP). Our results show that measuring the digital efficiency of amplification of single-template molecules allows quick, reliable comparisons of the analytical sensitivity of reactions under any two tested conditions, independent of the speeds of the isothermal amplification reactions. PMID:26358811

Effect of residence time on two-step liquefaction of rice straw in a CO2 atmosphere: Differences between subcritical water and supercritical ethanol.

PubMed

Yang, Tianhua; Wang, Jian; Li, Bingshuo; Kai, Xingping; Li, Rundong

2017-04-01

This study investigated the influence of temperature and residence time on liquefaction of rice straw in subcritical CO 2 -subcritical water (subCO 2 -subH 2 O) and in subcritical CO 2 -supercritical ethanol (subCO 2 -scEtOH), considering the final reaction temperatures (270-345°C) and residence times (15 and 30min). Residence time was identified as a crucial parameter in the subCO 2 -subH 2 O liquefaction, whereas residence time had a marginal influence on subCO 2 -scEtOH liquefaction. When reaction conditions were 320°C and 15min, solvents have weak impact on the quality of bio-oil, HHV 28.57MJ/kg and 28.62MJ/kg, respectively. There was an obvious difference between the subCO 2 -subH 2 O and subCO 2 -scEtOH liquefaction mechanisms. In subCO 2 -subH 2 O, CO 2 promoted the carbonyl reaction. In subCO 2 -scEtOH, supercritical ethanol have the function of donating hydrogen and promoting the reaction of hydroxyl-alkylation. Copyright © 2017 Elsevier Ltd. All rights reserved.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-01

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 107 and the detection limit can reach 10-10M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

A monolayer of hierarchical silver hemi-mesoparticles with tunable surface topographies for highly sensitive surface-enhanced Raman spectroscopy.

PubMed

Zhu, Shuangmei; Fan, Chunzhen; Mao, Yanchao; Wang, Junqiao; He, Jinna; Liang, Erjun; Chao, Mingju

2016-02-21

We proposed a facile green synthesis system to synthesize large-scale Ag hemi-mesoparticles monolayer on Cu foil. Ag hemi-mesoparticles have different surface morphologies on their surfaces, including ridge-like, meatball-like, and fluffy-like shapes. In the reaction, silver nitrate was reduced by copper at room temperature in dimethyl sulfoxide via the galvanic displacement reaction. The different surface morphologies of the Ag hemi-mesoparticles were adjusted by changing the reaction time, and the hemi-mesoparticle surface formed fluffy-spherical nanoprotrusions at longer reaction time. At the same time, we explored the growth mechanism of silver hemi-mesoparticles with different surface morphologies. With 4-mercaptobenzoic acid as Raman probe molecules, the fluffy-like silver hemi-mesoparticles monolayer with the best activity of surface enhanced Raman scattering (SERS), the enhancement factor is up to 7.33 × 10(7) and the detection limit can reach 10(-10)M. SERS measurements demonstrate that these Ag hemi-mesoparticles can serve as sensitive SERS substrates. At the same time, using finite element method, the distribution of the localized electromagnetic field near the particle surface was simulated to verify the enhanced mechanism. This study helps us to understand the relationship between morphology Ag hemi-mesoparicles and the properties of SERS.

Immediate effects of different treatments for the wrist joints of subdominant hands, using electromechanical reaction time.

PubMed

Hu, Chunying; Huang, Qiuchen; Yu, Lili; Zhou, Yue; Gu, Rui; Cui, Yao; Ge, Meng; Xu, Yanfeng; Liu, Jianfeng

2016-08-01

[Purpose] The aim of this study was to examine the immediate effects of muscle strength training and neuromuscular joint facilitation distal resistance training on wrist joints by using electromechanical reaction time. [Subjects and Methods] The subjects were 12 healthy young people (24.2 ± 3.1 years, 169.7 ± 6.5 cm, 65.3 ± 12.6 kg). Two kinds of isotonic contraction techniques were applied on the wrist joint: the wrist joint extension muscle strength training and the wrist joint extension pattern of neuromuscular joint facilitation. The electromechanical reaction time, premotor time, and motor time of the left upper limb were measured before and after each intervention session of muscle strength training and neuromuscular joint facilitation. [Results] The neuromuscular joint facilitation group showed significant shortening of the electromechanical reaction time and motor time after the intervention. [Conclusion] These results suggest that the electromechanical reaction time and motor time of the wrist joint can be improved by neuromuscular joint facilitation together with proximal resistance training, which can be used as a new form of exercise for improving the functions of subdominant hand wrist joints.

Using scattering theory to compute invariant manifolds and numerical results for the laser-driven Hénon-Heiles system.

PubMed

Blazevski, Daniel; Franklin, Jennifer

2012-12-01

Scattering theory is a convenient way to describe systems that are subject to time-dependent perturbations which are localized in time. Using scattering theory, one can compute time-dependent invariant objects for the perturbed system knowing the invariant objects of the unperturbed system. In this paper, we use scattering theory to give numerical computations of invariant manifolds appearing in laser-driven reactions. In this setting, invariant manifolds separate regions of phase space that lead to different outcomes of the reaction and can be used to compute reaction rates.

A Novel Computational Method to Reduce Leaky Reaction in DNA Strand Displacement.

PubMed

Li, Xin; Wang, Xun; Song, Tao; Lu, Wei; Chen, Zhihua; Shi, Xiaolong

2015-01-01

DNA strand displacement technique is widely used in DNA programming, DNA biosensors, and gene analysis. In DNA strand displacement, leaky reactions can cause DNA signals decay and detecting DNA signals fails. The mostly used method to avoid leakage is cleaning up after upstream leaky reactions, and it remains a challenge to develop reliable DNA strand displacement technique with low leakage. In this work, we address the challenge by experimentally evaluating the basic factors, including reaction time, ratio of reactants, and ion concentration to the leakage in DNA strand displacement. Specifically, fluorescent probes and a hairpin structure reporting DNA strand are designed to detect the output of DNA strand displacement, and thus can evaluate the leakage of DNA strand displacement reactions with different reaction time, ratios of reactants, and ion concentrations. From the obtained data, mathematical models for evaluating leakage are achieved by curve derivation. As a result, it is obtained that long time incubation, high concentration of fuel strand, and inappropriate amount of ion concentration can weaken leaky reactions. This contributes to a method to set proper reaction conditions to reduce leakage in DNA strand displacement.

HPLC method for rapidly following biodiesel fuel transesterification reaction progress using a core-shell column.

PubMed

Allen, Samuel J; Ott, Lisa S

2012-07-01

There are a wide and growing variety of feedstocks for biodiesel fuel. Most commonly, these feedstocks contain triglycerides which are transesterified into the fatty acid alkyl esters (FAAEs) which comprise biodiesel fuel. While the tranesterification reaction itself is simple, monitoring the reaction progress and reaction products is not. Gas chromatography-mass spectrometry is useful for assessing the FAAE products, but does not directly address either the tri-, di-, or monoglycerides present from incomplete transesterification or the free fatty acids which may also be present. Analysis of the biodiesel reaction mixture is complicated by the solubility and physical property differences among the components of the tranesterification reaction mixture. In this contribution, we present a simple, rapid HPLC method which allows for monitoring all of the main components in a biodiesel fuel transesterification reaction, with specific emphasis on the ability to monitor the reaction as a function of time. The utilization of a relatively new, core-shell stationary phase for the HPLC column allows for efficient separation of peaks with short elution times, saving both time and solvent.

Comparison of sulfuric and hydrochloric acids as catalysts in hydrolysis of Kappaphycus alvarezii (cottonii).

PubMed

Meinita, Maria Dyah Nur; Hong, Yong-Ki; Jeong, Gwi-Taek

2012-01-01

In this study, hydrolysis of marine algal biomass Kappaphhycus alvarezii using two different acid catalysts was examined with the goal of identifying optimal reaction conditions for the formation of sugars and by-products. K. alvarezii were hydrolyzed by autoclave using sulfuric acid or hydrochloric acid as catalyst with different acid concentrations (0.1-1.0 M), substrate concentrations (1.0-13.5%), hydrolysis time (10-90 min) and hydrolysis temperatures (100-130 (°)C). A difference in galactose, glucose, reducing sugar and total sugar content was observed under the different hydrolysis conditions. Different by-product compounds such as 5-hydroxymethylfurfural and levulinic acid were also observed under the different reaction conditions. The optimal conditions for hydrolysis were achieved at a sulfuric acid concentration, temperature and reaction time of 0.2 M, 130 °C and 15 min, respectively. These results may provide useful information for the development of more efficient systems for biofuel production from marine biomass.

Determination of detonation parameters for liquid High Explosives

NASA Astrophysics Data System (ADS)

Mochalova, Valentina; Utkin, Alexander

2011-06-01

The experimental investigation of detonation parameters and reaction zone structure in liquid HE (bis-(2-fluoro-2,2-dinitroethyl)formal (FEFO), tetranitromethane (TNM), nitromethane (NM)) was conducted. Detonation front in TNM and NM was stable while the instability of detonation in FEFO was observed. Von Neumann spike was recorded for these HE and its parameters were determined. The different methods for C-J point determination were used for each HE. For FEFO reaction time τ was found from experiments with different charge diameters (τ is approximately equal to 300 ns); for TNM - at fixed diameter and different lengths of charges (τ ~ 200 ns); for NM - at fixed diameter and length of charges, but detonation initiation was carried out by different explosive charges (τ ~ 50 ns). It was found that in TNM the detonation velocity depends on charge diameter. Maximum value of reaction rate in investigated liquid HE was observed after shock jump and induction time was not recorded.

R/S analysis of reaction time in Neuron Type Test for human activity in civil aviation

NASA Astrophysics Data System (ADS)

Zhang, Hong-Yan; Kang, Ming-Cui; Li, Jing-Qiang; Liu, Hai-Tao

2017-03-01

Human factors become the most serious problem leading to accidents of civil aviation, which stimulates the design and analysis of Neuron Type Test (NTT) system to explore the intrinsic properties and patterns behind the behaviors of professionals and students in civil aviation. In the experiment, normal practitioners' reaction time sequences, collected from NTT, exhibit log-normal distribution approximately. We apply the χ2 test to compute the goodness-of-fit by transforming the time sequence with Box-Cox transformation to cluster practitioners. The long-term correlation of different individual practitioner's time sequence is represented by the Hurst exponent via Rescaled Range Analysis, also named by Range/Standard deviation (R/S) Analysis. The different Hurst exponent suggests the existence of different collective behavior and different intrinsic patterns of human factors in civil aviation.

The Immediate Effect of Neuromuscular Joint Facilitation (NJF) Treatment on Electromechanical Reaction Times of Hip Flexion.

PubMed

Huo, Ming; Wang, Hongzhao; Ge, Meng; Huang, Qiuchen; Li, Desheng; Maruyama, Hitoshi

2013-11-01

[Purpose] The aim of this study was to investigate the change in electromechanical reaction times (EMG-RT) of hip flexion of younger persons after neuromuscular joint facilitation (NJF) treatment. [Subjects] The subjects were 39 healthy young people, who were divided into two groups: a NJF group and a proprioceptive neuromuscular facilitation (PNF) group. The NJF group consisted of 16 subjects (7 males, 9 females), and the PNF group consisted of 23 subjects (10 males, 13 females). [Methods] Participants in the NJF group received NJF treatment. We measured the EMG-RT, the premotor time (PMT) and the motor time (MT) during hip flexion movement before and after the intervention in both groups. [Results] There were no significant differences among the results of the PNF group. For the NJF group, there were significant differences in PMT and EMG-RT after NJF treatment. [Conclusion] These results suggest that there is an immediate effect of NJF intervention on electromechanical reaction times of hip flexion.

The Immediate Effect of Neuromuscular Joint Facilitation (NJF) Treatment on Electromechanical Reaction Times of Hip Flexion

PubMed Central

Huo, Ming; Wang, Hongzhao; Ge, Meng; Huang, Qiuchen; Li, Desheng; Maruyama, Hitoshi

2013-01-01

[Purpose] The aim of this study was to investigate the change in electromechanical reaction times (EMG-RT) of hip flexion of younger persons after neuromuscular joint facilitation (NJF) treatment. [Subjects] The subjects were 39 healthy young people, who were divided into two groups: a NJF group and a proprioceptive neuromuscular facilitation (PNF) group. The NJF group consisted of 16 subjects (7 males, 9 females), and the PNF group consisted of 23 subjects (10 males, 13 females). [Methods] Participants in the NJF group received NJF treatment. We measured the EMG-RT, the premotor time (PMT) and the motor time (MT) during hip flexion movement before and after the intervention in both groups. [Results] There were no significant differences among the results of the PNF group. For the NJF group, there were significant differences in PMT and EMG-RT after NJF treatment. [Conclusion] These results suggest that there is an immediate effect of NJF intervention on electromechanical reaction times of hip flexion. PMID:24396211

The relation between face-emotion recognition and social function in adolescents with autism spectrum disorders: A case control study.

PubMed

Høyland, Anne Lise; Nærland, Terje; Engstrøm, Morten; Lydersen, Stian; Andreassen, Ole Andreas

2017-01-01

An altered processing of emotions may contribute to a reduced ability for social interaction and communication in autism spectrum disorder, ASD. We investigated how face-emotion recognition in ASD is different from typically developing across adolescent age groups. Fifty adolescents diagnosed with ASD and 49 typically developing (age 12-21 years) were included. The ASD diagnosis was underpinned by parent-rated Social Communication Questionnaire. We used a cued GO/ NOGO task with pictures of facial expressions and recorded reaction time, intra-individual variability of reaction time and omissions/commissions. The Social Responsiveness Scale was used as a measure of social function. Analyses were conducted for the whole group and for young (< 16 years) and old (≥ 16 years) age groups. We found no significant differences in any task measures between the whole group of typically developing and ASD and no significant correlations with the Social Responsiveness Scale. However, there was a non-significant tendency for longer reaction time in the young group with ASD (p = 0.099). The Social Responsiveness Scale correlated positively with reaction time (r = 0.30, p = 0.032) and intra-individual variability in reaction time (r = 0.29, p = 0.037) in the young group and in contrast, negatively in the old group (r = -0.23, p = 0.13; r = -0.38, p = 0.011, respectively) giving significant age group interactions for both reaction time (p = 0.008) and intra-individual variability in reaction time (p = 0.001). Our findings suggest an age-dependent association between emotion recognition and severity of social problems indicating a delayed development of emotional understanding in ASD. It also points towards alterations in top-down attention control in the ASD group. This suggests novel disease-related features that should be investigated in more details in experimental settings.

Human short-term exposure to electromagnetic fields emitted by mobile phones decreases computer-assisted visual reaction time.

PubMed

Mortazavi, S M J; Rouintan, M S; Taeb, S; Dehghan, N; Ghaffarpanah, A A; Sadeghi, Z; Ghafouri, F

2012-06-01

The worldwide dramatic increase in mobile phone use has generated great concerns about the detrimental effects of microwave radiations emitted by these communication devices. Reaction time plays a critical role in performing tasks necessary to avoid hazards. As far as we know, this study is the first survey that reports decreased reaction time after exposure to electromagnetic fields generated by a high specific absorption rate mobile phone. It is also the first study in which previous history of mobile phone use is taken into account. The aim of this study was to assess both the acute and chronic effects of electromagnetic fields emitted by mobile phones on reaction time in university students. Visual reaction time (VRT) of young university students was recorded with a simple blind computer-assisted-VRT test, before and after a 10 min real/sham exposure to electromagnetic fields of mobile phones. Participants were 160 right-handed university students aged 18-31. To assess the effect of chronic exposures, the reaction time in sham-exposed phases were compared among low level, moderate and frequent users of mobile phones. The mean ± SD reaction time after real exposure and sham exposure were 286.78 ± 31.35 ms and 295.86 ± 32.17 ms (P < 0.001), respectively. The age of students did not significantly alter the reaction time either in talk or in standby mode. The reaction time either in talk or in standby mode was shorter in male students. The students' VRT was significantly affected by exposure to electromagnetic fields emitted by a mobile phone. It can be concluded that these exposures cause decreased reaction time, which may lead to a better response to different hazards. In this light, this phenomenon might decrease the chances of human errors and fatal accidents.

Autonomous Vehicles: Disengagements, Accidents and Reaction Times.

PubMed

Dixit, Vinayak V; Chand, Sai; Nair, Divya J

2016-01-01

Autonomous vehicles are being viewed with scepticism in their ability to improve safety and the driving experience. A critical issue with automated driving at this stage of its development is that it is not yet reliable and safe. When automated driving fails, or is limited, the autonomous mode disengages and the drivers are expected to resume manual driving. For this transition to occur safely, it is imperative that drivers react in an appropriate and timely manner. Recent data released from the California trials provide compelling insights into the current factors influencing disengagements of autonomous mode. Here we show that the number of accidents observed has a significantly high correlation with the autonomous miles travelled. The reaction times to take control of the vehicle in the event of a disengagement was found to have a stable distribution across different companies at 0.83 seconds on average. However, there were differences observed in reaction times based on the type of disengagements, type of roadway and autonomous miles travelled. Lack of trust caused by the exposure to automated disengagements was found to increase the likelihood to take control of the vehicle manually. Further, with increased vehicle miles travelled the reaction times were found to increase, which suggests an increased level of trust with more vehicle miles travelled. We believe that this research would provide insurers, planners, traffic management officials and engineers fundamental insights into trust and reaction times that would help them design and engineer their systems.

Autonomous Vehicles: Disengagements, Accidents and Reaction Times

PubMed Central

Dixit, Vinayak V.; Chand, Sai; Nair, Divya J.

2016-01-01

Autonomous vehicles are being viewed with scepticism in their ability to improve safety and the driving experience. A critical issue with automated driving at this stage of its development is that it is not yet reliable and safe. When automated driving fails, or is limited, the autonomous mode disengages and the drivers are expected to resume manual driving. For this transition to occur safely, it is imperative that drivers react in an appropriate and timely manner. Recent data released from the California trials provide compelling insights into the current factors influencing disengagements of autonomous mode. Here we show that the number of accidents observed has a significantly high correlation with the autonomous miles travelled. The reaction times to take control of the vehicle in the event of a disengagement was found to have a stable distribution across different companies at 0.83 seconds on average. However, there were differences observed in reaction times based on the type of disengagements, type of roadway and autonomous miles travelled. Lack of trust caused by the exposure to automated disengagements was found to increase the likelihood to take control of the vehicle manually. Further, with increased vehicle miles travelled the reaction times were found to increase, which suggests an increased level of trust with more vehicle miles travelled. We believe that this research would provide insurers, planners, traffic management officials and engineers fundamental insights into trust and reaction times that would help them design and engineer their systems. PMID:27997566

How we can measure the non-driving-task engagement in automated driving: Comparing flow experience and workload.

PubMed

Ko, Sang Min; Ji, Yong Gu

2018-02-01

In automated driving, a driver can completely concentrate on non-driving-related tasks (NDRTs). This study investigated the flow experience of a driver who concentrated on NDRTs and tasks that induce mental workload under conditional automation. Participants performed NDRTs under different demand levels: a balanced demand-skill level (fit condition) to induce flow, low-demand level to induce boredom, and high-demand level to induce anxiety. In addition, they performed the additional N-Back task, which artificially induces mental workload. The results showed participants had the longest reaction time when they indicated the highest flow score, and had the longest gaze-on time, road-fixation time, hands-on time, and take-over time under the fit condition. Significant differences were not observed in the driver reaction times in the fit condition and the additional N-Back task, indicating that performing NDRTs that induce a high flow experience could influence driver reaction time similar to performing tasks with a high mental workload. Copyright © 2017. Published by Elsevier Ltd.

Peripheral Nerve Conduction Velocity, Reaction Time, and Intelligence: An Attempt to Replicate Vernon and Mori.

ERIC Educational Resources Information Center

Wickett, John C.; Vernon, Philip A.

1994-01-01

In a study involving 38 adult females, nerve conduction velocity (NCV) did not correlate with intelligence or reaction time. A reanalysis of the Vernon and Mori data showed a possible sex difference in relation to NCV and intelligence, with the correlation between these variables much smaller in females than males. (SLD)

Age and Sex Differences in Intra-Individual Variability in a Simple Reaction Time Task

ERIC Educational Resources Information Center

Ghisletta, Paolo; Renaud, Olivier; Fagot, Delphine; Lecerf, Thierry; de Ribaupierre, Anik

2018-01-01

While age effects in reaction time (RT) tasks across the lifespan are well established for level of performance, analogous findings have started appearing also for indicators of intra-individual variability (IIV). Children are not only slower, but also display more variability than younger adults in RT. Yet, little is known about potential…

Effects of Sparring Load on Reaction Speed and Punch Force During the Precompetition and Competition Periods in Boxing.

PubMed

Hukkanen, Esa; Häkkinen, Keijo

2017-06-01

Seven, male, national-level boxers (age, 20.3 ± 2.7 years; height, 1.80 ± 0.06 m; mass, 73.8 ± 11.1 kg) participated in this study to investigate the effects of sparring on reaction time and punch force of straight punches measured during the precompetition and competition periods. Heart rate and blood lactate concentrations were also monitored. Sparring load was chosen in accordance with the current rules: 3 × 3-minute bouts with 1-minute break in between. Reaction time of rear straight lengthened (p < 0.01) during the sparring load of the precompetition period after the third round (to 390 milliseconds) in comparison to the competition period (to 310 milliseconds). Reaction time of lead straight lengthened (p ≤ 0.05) between the first and third round during the precompetition with no differences during the competition period. Both rear and lead straight punch forces were greater at all measurement points during the precompetition compared with the competition period. Punch forces increased for both rear and lead straight between the first and third rounds with the highest forces after third round during the precompetition (rear straight, 209 kg) and competition (rear straight, 176 kg) periods. Blood lactate levels increased after every round during both periods being at its greatest after the third round (17 mmol·L during the precompetition and 13 mmol·L during the competition period). The present sparring-induced differences in reaction time and punch forces of straight punches during the precompetition compared with the competition period may be the result of different volume and intensity of training with different goals in boxing-specific and explosive strength training.

a Direct Probe for Chemical Potentials Difference Between Neutron and Protons in Heavy-Ion Collisions

NASA Astrophysics Data System (ADS)

Ma, Chun-Wang; Zhang, Yan-Li; Wang, Shan-Shan

We briefly introduce the newly proposed probe to the neutron and proton chemical potential (and density) difference, which is called as the isobaric yield ratio difference (IBD). The IBD probe is related to the chemical potential difference of neutrons and protons between two reactions, at the same time, the nuclear density difference between two reactions. The relationship between the IBD probe and the isoscaling method has also been discussed.

Driver compliance to take-over requests with different auditory outputs in conditional automation.

PubMed

Forster, Yannick; Naujoks, Frederik; Neukum, Alexandra; Huestegge, Lynn

2017-12-01

Conditionally automated driving (CAD) systems are expected to improve traffic safety. Whenever the CAD system exceeds its limit of operation, designers of the system need to ensure a safe and timely enough transition from automated to manual mode. An existing visual Human-Machine Interface (HMI) was supplemented by different auditory outputs. The present work compares the effects of different auditory outputs in form of (1) a generic warning tone and (2) additional semantic speech output on driver behavior for the announcement of an upcoming take-over request (TOR). We expect the information carried by means of speech output to lead to faster reactions and better subjective evaluations by the drivers compared to generic auditory output. To test this assumption, N=17 drivers completed two simulator drives, once with a generic warning tone ('Generic') and once with additional speech output ('Speech+generic'), while they were working on a non-driving related task (NDRT; i.e., reading a magazine). Each drive incorporated one transition from automated to manual mode when yellow secondary lanes emerged. Different reaction time measures, relevant for the take-over process, were assessed. Furthermore, drivers evaluated the complete HMI regarding usefulness, ease of use and perceived visual workload just after experiencing the take-over. They gave comparative ratings on usability and acceptance at the end of the experiment. Results revealed that reaction times, reflecting information processing time (i.e., hands on the steering wheel, termination of NDRT), were shorter for 'Speech+generic' compared to 'Generic' while reaction time, reflecting allocation of attention (i.e., first glance ahead), did not show this difference. Subjective ratings were in favor of the system with additional speech output. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reaction time inconsistency in a spatial stroop task: age-related differences through childhood and adulthood.

PubMed

Williams, Benjamin R; Strauss, Esther H; Hultsch, David F; Hunter, Michael A

2007-07-01

Age-related differences in inconsistency of reaction time (RT) across the life span were examined on a task with differing levels of demand on executive control. A total of 546 participants, aged 5 to 76 years, completed a spatial Stroop task that permitted observations under three conditions (congruent, incongruent, and neutral) according to the correspondence between the required response (based on stimulus direction) and stimulus location. An interference effect was observed across all ages. Analyses of neutral condition data replicated previous research demonstrating RT inconsistency follows a U-shaped developmental curve across the life span. The relationship between age and inconsistency, however, depended on condition: inconsistency in the congruent condition was higher than inconsistency in both the neutral and incongruent conditions across middle-aged groups. Reaction time inconsistency may reflect processing efficiency that is maximal in young adulthood and may also be sensitive to fluctuations in performance that reflect momentarily highly efficient responding.

Perturbation theory in the catalytic rate constant of the Henri-Michaelis-Menten enzymatic reaction.

PubMed

Bakalis, Evangelos; Kosmas, Marios; Papamichael, Emmanouel M

2012-11-01

The Henry-Michaelis-Menten (HMM) mechanism of enzymatic reaction is studied by means of perturbation theory in the reaction rate constant k (2) of product formation. We present analytical solutions that provide the concentrations of the enzyme (E), the substrate (S), as well as those of the enzyme-substrate complex (C), and the product (P) as functions of time. For k (2) small compared to k (-1), we properly describe the entire enzymatic activity from the beginning of the reaction up to longer times without imposing extra conditions on the initial concentrations E ( o ) and S ( o ), which can be comparable or much different.

Ab initio molecular dynamics study of thermite reaction at Al and CuO nano-interfaces at different temperatures

NASA Astrophysics Data System (ADS)

Tang, Cui-Ming; Chen, Xiao-Xu; Cheng, Xin-Lu; Zhang, Chao-Yang; Lu, Zhi-Peng

2018-05-01

The thermite reaction at Al/CuO nano-interfaces is investigated with ab initio molecular dynamics calculations in canonical ensemble at 500 K, 800 K, 1200 K and 1500 K, respectively. The reaction process and reaction products are analyzed in terms of chemical bonds, average charge, time constants and total potential energy. The activity of the reactants enhances with increasing temperature, which induces a faster thermite reaction. The alloy reaction obviously expands outward at Cu-rich interface of Al/CuO system, and the reaction between Al and O atoms obviously expands outward at O-rich interface as temperature increases. Different reaction products are found at the outermost layer of different interfaces in the Al/CuO system. In generally, the average charge of the outer layer aluminum atoms (i.e., Al1, Al2, Al5 and Al6) increases with temperature. The potential energy of Al/CuO system decreases significantly, which indicates that drastic exothermic reaction occurs at the Al/CuO system. This research enhances fundamental understanding in temperature effect on the thermite reaction at atomic level, which can potentially open new possibilities for its industrial application.

MESOSCOPIC MODELING OF STOCHASTIC REACTION-DIFFUSION KINETICS IN THE SUBDIFFUSIVE REGIME

PubMed Central

BLANC, EMILIE; ENGBLOM, STEFAN; HELLANDER, ANDREAS; LÖTSTEDT, PER

2017-01-01

Subdiffusion has been proposed as an explanation of various kinetic phenomena inside living cells. In order to fascilitate large-scale computational studies of subdiffusive chemical processes, we extend a recently suggested mesoscopic model of subdiffusion into an accurate and consistent reaction-subdiffusion computational framework. Two different possible models of chemical reaction are revealed and some basic dynamic properties are derived. In certain cases those mesoscopic models have a direct interpretation at the macroscopic level as fractional partial differential equations in a bounded time interval. Through analysis and numerical experiments we estimate the macroscopic effects of reactions under subdiffusive mixing. The models display properties observed also in experiments: for a short time interval the behavior of the diffusion and the reaction is ordinary, in an intermediate interval the behavior is anomalous, and at long times the behavior is ordinary again. PMID:29046618

Efficient reactive Brownian dynamics

DOE PAGES

Donev, Aleksandar; Yang, Chiao-Yu; Kim, Changho

2018-01-21

We develop a Split Reactive Brownian Dynamics (SRBD) algorithm for particle simulations of reaction-diffusion systems based on the Doi or volume reactivity model, in which pairs of particles react with a specified Poisson rate if they are closer than a chosen reactive distance. In our Doi model, we ensure that the microscopic reaction rules for various association and dissociation reactions are consistent with detailed balance (time reversibility) at thermodynamic equilibrium. The SRBD algorithm uses Strang splitting in time to separate reaction and diffusion and solves both the diffusion-only and reaction-only subproblems exactly, even at high packing densities. To efficiently processmore » reactions without uncontrolled approximations, SRBD employs an event-driven algorithm that processes reactions in a time-ordered sequence over the duration of the time step. A grid of cells with size larger than all of the reactive distances is used to schedule and process the reactions, but unlike traditional grid-based methods such as reaction-diffusion master equation algorithms, the results of SRBD are statistically independent of the size of the grid used to accelerate the processing of reactions. We use the SRBD algorithm to compute the effective macroscopic reaction rate for both reaction-limited and diffusion-limited irreversible association in three dimensions and compare to existing theoretical predictions at low and moderate densities. We also study long-time tails in the time correlation functions for reversible association at thermodynamic equilibrium and compare to recent theoretical predictions. Finally, we compare different particle and continuum methods on a model exhibiting a Turing-like instability and pattern formation. Our studies reinforce the common finding that microscopic mechanisms and correlations matter for diffusion-limited systems, making continuum and even mesoscopic modeling of such systems difficult or impossible. We also find that for models in which particles diffuse off lattice, such as the Doi model, reactions lead to a spurious enhancement of the effective diffusion coefficients.« less

Efficient reactive Brownian dynamics

NASA Astrophysics Data System (ADS)

Donev, Aleksandar; Yang, Chiao-Yu; Kim, Changho

2018-01-01

We develop a Split Reactive Brownian Dynamics (SRBD) algorithm for particle simulations of reaction-diffusion systems based on the Doi or volume reactivity model, in which pairs of particles react with a specified Poisson rate if they are closer than a chosen reactive distance. In our Doi model, we ensure that the microscopic reaction rules for various association and dissociation reactions are consistent with detailed balance (time reversibility) at thermodynamic equilibrium. The SRBD algorithm uses Strang splitting in time to separate reaction and diffusion and solves both the diffusion-only and reaction-only subproblems exactly, even at high packing densities. To efficiently process reactions without uncontrolled approximations, SRBD employs an event-driven algorithm that processes reactions in a time-ordered sequence over the duration of the time step. A grid of cells with size larger than all of the reactive distances is used to schedule and process the reactions, but unlike traditional grid-based methods such as reaction-diffusion master equation algorithms, the results of SRBD are statistically independent of the size of the grid used to accelerate the processing of reactions. We use the SRBD algorithm to compute the effective macroscopic reaction rate for both reaction-limited and diffusion-limited irreversible association in three dimensions and compare to existing theoretical predictions at low and moderate densities. We also study long-time tails in the time correlation functions for reversible association at thermodynamic equilibrium and compare to recent theoretical predictions. Finally, we compare different particle and continuum methods on a model exhibiting a Turing-like instability and pattern formation. Our studies reinforce the common finding that microscopic mechanisms and correlations matter for diffusion-limited systems, making continuum and even mesoscopic modeling of such systems difficult or impossible. We also find that for models in which particles diffuse off lattice, such as the Doi model, reactions lead to a spurious enhancement of the effective diffusion coefficients.

Efficient reactive Brownian dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donev, Aleksandar; Yang, Chiao-Yu; Kim, Changho

We develop a Split Reactive Brownian Dynamics (SRBD) algorithm for particle simulations of reaction-diffusion systems based on the Doi or volume reactivity model, in which pairs of particles react with a specified Poisson rate if they are closer than a chosen reactive distance. In our Doi model, we ensure that the microscopic reaction rules for various association and dissociation reactions are consistent with detailed balance (time reversibility) at thermodynamic equilibrium. The SRBD algorithm uses Strang splitting in time to separate reaction and diffusion and solves both the diffusion-only and reaction-only subproblems exactly, even at high packing densities. To efficiently processmore » reactions without uncontrolled approximations, SRBD employs an event-driven algorithm that processes reactions in a time-ordered sequence over the duration of the time step. A grid of cells with size larger than all of the reactive distances is used to schedule and process the reactions, but unlike traditional grid-based methods such as reaction-diffusion master equation algorithms, the results of SRBD are statistically independent of the size of the grid used to accelerate the processing of reactions. We use the SRBD algorithm to compute the effective macroscopic reaction rate for both reaction-limited and diffusion-limited irreversible association in three dimensions and compare to existing theoretical predictions at low and moderate densities. We also study long-time tails in the time correlation functions for reversible association at thermodynamic equilibrium and compare to recent theoretical predictions. Finally, we compare different particle and continuum methods on a model exhibiting a Turing-like instability and pattern formation. Our studies reinforce the common finding that microscopic mechanisms and correlations matter for diffusion-limited systems, making continuum and even mesoscopic modeling of such systems difficult or impossible. We also find that for models in which particles diffuse off lattice, such as the Doi model, reactions lead to a spurious enhancement of the effective diffusion coefficients.« less

Arginine in the salt-induced peptide formation reaction: enantioselectivity facilitated by glycine, L- and D-histidine.

PubMed

Li, Feng; Fitz, Daniel; Fraser, Donald G; Rode, Bernd M

2010-07-01

The salt-induced peptide formation reaction has been proposed as a conceivable preliminary to the prebiotic evolution of peptides. In the present paper, the behaviour of arginine is reported for this reaction together with a discussion of the catalytic effects of glycine, and L- and D-histidine. Importantly, the behaviour of the two histidine enantiomers is different. Both histidine enantiomers perform better than glycine in enhancing the yields of arginine dipeptide with L-histidine being more effective than D-histidine. Yields in the presence of histidine are up to 70 times greater than for arginine solutions alone. This compares with 4.2 times higher in the presence of glycine. This difference is most pronounced in the most concentrated (containing 80 mM arginine) reaction solution where arginine has the lowest reactivity. A distinct preference for dimerisation of L-arginine also appears in the 80 mM cases for catalyses of other amino acids. This phenomenon is different from the behaviour of aliphatic amino acids, which display obvious inherent enantioselectivity for the L-stereomers in the SIPF reaction on their own rather than when catalysed by glycine or histidine.

Development of a chemiluminescent and bioluminescent system for the detection of bacteria in wastewater effluent

NASA Technical Reports Server (NTRS)

Thomas, R. R.

1975-01-01

Automated chemiluminescent and bioluminescent sensors were developed for continuous monitoring of microbial levels in wastewater effluent. Development of the chemiluminescent system included optimization of reagent concentrations as well as two new techniques which will allow for increased sensitivity and specificity. The optimal reagent concentrations are 0.0025 M luminol and 0.0125 M sodium perborate in 0.75N sodium hydroxide before addition of sample. The methods developed to increase specificity include (1) extraction of porphyrins from bacteria collected in a filter using 0.1N NaOH - 50 percent Ethanol, and (2) use of the specific reaction rate characteristics for the different luminol catalysts. Since reaction times are different for each catalyst, the reaction can be made specific for bacteria by measuring only the light emission from the particular reaction time zone specific for bacteria. Developments of the bioluminescent firefly luciferase system were in the area of flow system design.

Impact of physical exercise on reaction time in patients with Parkinson's disease-data from the Berlin BIG Study.

PubMed

Ebersbach, Georg; Ebersbach, Almut; Gandor, Florin; Wegner, Brigitte; Wissel, Jörg; Kupsch, Andreas

2014-05-01

To determine whether physical activity may affect cognitive performance in patients with Parkinson's disease by measuring reaction times in patients participating in the Berlin BIG study. Randomized controlled trial, rater-blinded. Ambulatory care. Patients with mild to moderate Parkinson's disease (N=60) were randomly allocated to 3 treatment arms. Outcome was measured at the termination of training and at follow-up 16 weeks after baseline in 58 patients (completers). Patients received 16 hours of individual Lee Silverman Voice Treatment-BIG training (BIG; duration of treatment, 4wk), 16 hours of group training with Nordic Walking (WALK; duration of treatment, 8wk), or nonsupervised domestic exercise (HOME; duration of instruction, 1hr). Cued reaction time (cRT) and noncued reaction time (nRT). Differences between treatment groups in improvement in reaction times from baseline to intermediate and baseline to follow-up assessments were observed for cRT but not for nRT. Pairwise t test comparisons revealed differences in change in cRT at both measurements between BIG and HOME groups (intermediate: -52ms; 95% confidence interval [CI], -84/-20; P=.002; follow-up: 55ms; CI, -105/-6; P=.030) and between WALK and HOME groups (intermediate: -61ms; CI, -120/-2; P=.042; follow-up: -78ms; CI, -136/-20; P=.010). There was no difference between BIG and WALK groups (intermediate: 9ms; CI, -49/67; P=.742; follow-up: 23ms; CI, -27/72; P=.361). Supervised physical exercise with Lee Silverman Voice Treatment-BIG or Nordic Walking is associated with improvement in cognitive aspects of movement preparation. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Pump-shaped dump optimal control reveals the nuclear reaction pathway of isomerization of a photoexcited cyanine dye.

PubMed

Dietzek, Benjamin; Brüggemann, Ben; Pascher, Torbjörn; Yartsev, Arkady

2007-10-31

Using optimal control as a spectroscopic tool we decipher the details of the molecular dynamics of the essential multidimensional excited-state photoisomerization - a fundamental chemical reaction of key importance in biology. Two distinct nuclear motions are identified in addition to the overall bond-twisting motion: Initially, the reaction is dominated by motion perpendicular to the torsion coordinate. At later times, a second optically active vibration drives the system along the reaction path to the bottom of the excited-state potential. The time scales of the wavepacket motion on a different part of the excited-state potential are detailed by pump-shaped dump optimal control. This technique offers new means to control a chemical reaction far from the Franck-Condon point of absorption and to map details of excited-state reaction pathways revealing unique insights into the underlying reaction mechanism.

In Reaction to Columbine, "Times" Focuses on Culture of Violence.

ERIC Educational Resources Information Center

Donofrio, Leana; Richards, Megan

1999-01-01

Describes how "The Lakewood Times" (Lakewood, Ohio) covered the shootings at Columbine High School. Suggests that the newspaper covered the story differently than other media by taking many different angles to the story. (RS)

Lack of correlation between reaction speed and analytical sensitivity in isothermal amplification reveals the value of digital methods for optimization: validation using digital real-time RT-LAMP.

PubMed

Khorosheva, Eugenia M; Karymov, Mikhail A; Selck, David A; Ismagilov, Rustem F

2016-01-29

In this paper, we asked if it is possible to identify the best primers and reaction conditions based on improvements in reaction speed when optimizing isothermal reactions. We used digital single-molecule, real-time analyses of both speed and efficiency of isothermal amplification reactions, which revealed that improvements in the speed of isothermal amplification reactions did not always correlate with improvements in digital efficiency (the fraction of molecules that amplify) or with analytical sensitivity. However, we observed that the speeds of amplification for single-molecule (in a digital device) and multi-molecule (e.g. in a PCR well plate) formats always correlated for the same conditions. Also, digital efficiency correlated with the analytical sensitivity of the same reaction performed in a multi-molecule format. Our finding was supported experimentally with examples of primer design, the use or exclusion of loop primers in different combinations, and the use of different enzyme mixtures in one-step reverse-transcription loop-mediated amplification (RT-LAMP). Our results show that measuring the digital efficiency of amplification of single-template molecules allows quick, reliable comparisons of the analytical sensitivity of reactions under any two tested conditions, independent of the speeds of the isothermal amplification reactions. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Persistence of the Intuitive Conception That Heavier Objects Sink More: A Reaction Time Study with Different Levels of Interference

ERIC Educational Resources Information Center

Potvin, Patrice; Masson, Steve; Lafortune, Stéphanie; Cyr, Guillaume

2015-01-01

Recent research efforts have argued for the "persistence" of some of students' frequent scientific misconceptions, even after correct answers are produced. Some of these studies, based on the analysis of reaction times, have recorded latencies for counter-intuitive or incongruent stimuli compared to intuitive or congruent ones. The…

Evaluation of different embryonating bird eggs and cell cultures for isolation efficiency of avian influenza A virus and avian paramyxovirus serotype 1 from real-time reverse transcription polymerase chain reaction--positive

USDA-ARS?s Scientific Manuscript database

Two hundred samples collected from Anseriformes, Charadriiformes, Gruiformes, and Galliformes were assayed using real-time reverse transcriptase polymerase chain reaction (RRT-PCR) for presence of avian influenza virus and avian paramyxovirus-1. Virus isolation using embryonating chicken eggs, embr...

Atomic Force Microscopy Nanomechanical Mapping Visualizes Interfacial Broadening between Networks Due to Chemical Exchange Reactions.

PubMed

He, Changfei; Shi, Shaowei; Wu, Xuefei; Russell, Thomas P; Wang, Dong

2018-06-06

The interfacial broadening between two different epoxy networks having different moduli was nanomechanically mapped. The interfacial broadening of the two networks produced an interfacial zone having a gradient in the concentration and, hence, properties of the original two networks. This interfacial broadening of the networks leads to the generation of a new network with a segmental composition corresponding to a mixture of the original two network segments. The intermixing of the two, by nature of the exchange reactions, was on the segmental level. By mapping the time dependence of the variation in the modulus at different temperatures, the kinetics of the exchange reaction was measured and, by varying the temperature, the activation energy of the exchange reaction was determined.

Degradation pathway of the naphthalene azo dye intermediate 1-diazo-2- naphthol-4-sulfonic acid using Fenton's reagent.

PubMed

Zhu, Nanwen; Gu, Lin; Yuan, Haiping; Lou, Ziyang; Wang, Liang; Zhang, Xin

2012-08-01

Degradation of naphthalene dye intermediate 1-diazo-2- naphthol-4-sulfonic acid (1,2,4-Acid) by Fenton process has been studied in depth for the purpose of learning more about the reactions involved in the oxidation of 1,2,4-Acid. During 1,2,4-Acid oxidation, the solution color initially takes on a dark red, then to dark black associated with the formation of quinodial-type structures, and then goes to dark brown and gradually disappears, indicating a fast degradation of azo group. The observed color changes of the solution are a result of main reaction intermediates, which can be an indicator of the level of oxidization reached. Nevertheless, complete TOC removal is not accomplished, in accordance with the presence of resistant carboxylic acids at the end of the reaction. The intermediates generated along the reaction time have been identified and quantified. UPLC-(ESI)-TOF-HRMS analysis allows the detection of 19 aromatic compounds of different size and complexity. Some of them share the same accurate mass but appear at different retention time, evidencing their different molecular structures. Heteroatom oxidation products like SO(4)(2-) have also been quantified and explanations of their release are proposed. Short-chain carboxylic acids are detected at long reaction time, as a previous step to complete the process of dye mineralization. Finally, considering all the findings of the present study and previous related works, the evolution from the original 1,2,4-Acid to the final products is proposed in a general reaction scheme. Copyright © 2012 Elsevier Ltd. All rights reserved.

Level of neurotic disorders among drivers causing traffic accidents.

PubMed

Durić, Predrag; Filipović, Danka

2007-01-01

Different aspects of driver personality may affect traffic safety. Extended driver reaction time causes deceleration of the reflexes, which is a major cause of traffic accidents. Cornell index was used in 30 drivers responsible for traffic accidents, with the aim to measure their level of neurotic disorder and compare them with results of controls (drivers not responsible for traffic accidents). Reaction time was maesured and compared among subjects with normal results of Cornell test and those with pathological findings. Drivers causing traffic accidents showed significantly higher Cornell index scores than drivers not responsible for traffic accidents. Drivers with pathological results of Cornell index showed a significantly longer reaction time.

Time-resolved serial crystallography captures high-resolution intermediates of photoactive yellow protein

DOE PAGES

Tenboer, Jason; Basu, Shibom; Zatsepin, Nadia; ...

2014-12-05

We report that serial femtosecond crystallography using ultrashort pulses from X-ray Free Electron Lasers (XFELs) offers the possibility to study light-triggered dynamics of biomolecules. Using microcrystals of the blue light photoreceptor, photoactive yellow protein, as a model system, we present high resolution, time-resolved difference electron density maps of excellent quality with strong features, which allow the determination of structures of reaction intermediates to 1.6 Å resolution. These results open the way to the study of reversible and non-reversible biological reactions on time scales as short as femtoseconds under conditions which maximize the extent of reaction initiation throughout the crystal.

The chemistry of subcritical water reactions of a hardwood derived lignin and lignin model compounds with nitrogen, hydrogen, carbon monoxide and carbon dioxide

NASA Astrophysics Data System (ADS)

Hill Bembenic, Meredith A.

Biofuels, like cellulosic ethanol, may only be cost effective if the lignin byproduct is upgraded to value-added products. However, lignin's inherent aromatic structure and interunit crosslinkages hinder effective conversion. High temperature H2O is considered for lignin conversion, because H2O exhibits unusual properties at higher temperatures (particularly at its supercritical point of 374°C and 3205 psi) including a decreased ion product and a decreased static dielectric constant (similar to those of polar organic solvents at room temperature) such that there is a high solubility for organic compounds, like lignin. Much of the research concerning lignin and supercritical H2O has focused on further decomposition to gases (e.g., H2, CH4, and CO2) where nearly no char formation is expected in the presence of a catalyst. However, the conditions required for supercritical H2O are difficult to maintain, catalysts can be expensive, and gases are not favorable to the current liquid fuel infrastructure. Reactions using Organosolv lignin, subcritical H2O (365°C) and various industrial gases (N2, H2, CO, and CO2 at an initial pressure of 500 psi) for 30 min. were examined to determine both lignin's potential to generate value-added products (e.g., monomer compounds and methanol) and the role (if any) of the H2O and the gases during the reactions. The behavior of H2O at reaction temperature and pressure is expected to be similar to the behavior of supercritical H 2O without the need to maintain supercritical conditions. Different characterization techniques were used for the products collected including primarily GC/FID-TCD of the evolved gases, GC/MS analysis of the organic liquids, solid phase microextraction analysis of the water, and solid state 13C-NMR analysis of the residues. The reactor pressure at temperature was shown to influence the reactivity of the H2O and lignin, and the highest conversions (≈54--62%) were obtained when adding a gas. However, the collected solids from the CO reactions appeared to be the most reacted (i.e., the most changed from the unreacted lignin) according to solid state 13C-NMR analysis, and the widest variety of products (methoxy-substituted phenolic compounds) were obtained when using CO according to GC/MS analysis. Therefore, reactions with CO were completed that varied the initial reaction pressure (300, 500 and 800 psi) in order to elucidate the effects of CO pressure. Similar conversion (≈54--58%) and DCM-soluble liquid product yields (≈53--62%) were obtained for the different pressure reactions, but the reactions with an initial pressure of 500 psi had the greatest change in aromaticity from the unreacted lignin. Additional reactions between Organosolv lignin and H2O with CO (initial pressure of 500 psi) were conducted where the reaction time was varied (15, 30 and 60 min.) to determine the effect of reaction time. Longer reaction time (60 min.) appeared to inhibit conversion to low molecular weight compounds (i.e., conversion and DCM-soluble yields were lower at ≈53% and ≈28%, respectively). Solid state 13C-NMR of collected residues also showed that there are losses in carbons representative of both guaiacyl and syringyl components as reaction time increases, which may indicate that methoxy groups are being cleaved or the products are reacting with each other (i.e., repolymerization) to form high molecular weight compounds as reaction time is increased. The role of H2O and the gases during the baseline reactions and the expanded CO reactions is not intuitive based on the results, so reactions with lignin model compounds (i.e., aromatic aldehydes represented by vanillin and syringaldehyde, aromatic ketones represented by acetovanillone and acetosyringone, and aromatic ethers represented by dibenzyl ether and 2-phenethyl phenyl ether) were completed to study this. From these results, the suggested reaction pathway of Organosolv lignin reactions in subcritical H2O with and without added pressure is: 1) cleavage of ethers (via hydrolysis) to form smaller methoxy-substituted phenolic monomers with aldehyde- or ketone-substituents representative of lignin monomers; 2) cleavage of the methoxy-, aldehyde- and/or ketone-substituents to form primarily methoxy-substituted phenolic monomers; 3) rearrangement of these phenolic monomers due to the enhanced pressure at reaction temperature; 4) formation of oligomers due to interaction amongst the methoxy-substituted phenolic monomers, which is also due to the enhanced pressure at reaction temperature; and 5) repolymerization of the monomers and oligomers to form high molecular weight compounds (i.e., longer reactions times or different pressures seemed to enhance these reactions). Under these conditions, depolymerization seems to be the dominant reaction pathway versus repolymerization. Reactions with lignin and H2O at 365°C have not been previously reported nor has the reaction chemistry for lignin depolymerization at these conditions been established. The results with lignin (or lignin model compounds), subcritical H2O and CO also show that the desired product slate can be modified with different pressure and time conditions. In particular, increasing reaction time (from 15 to 60 min.) caused lignin conversion to decrease, and the products appeared to be reacting with each other. However, the longer reaction time also showed that more methanol is generated (along with more solids).

Increased reaction times and reduced response preparation already starts at middle age

PubMed Central

Wolkorte, Ria; Kamphuis, Janine; Zijdewind, Inge

2014-01-01

Generalized slowing characterizes aging and there is some evidence to suggest that this slowing already starts at midlife. This study aims to assess reaction time changes while performing a concurrent low-force and high-force motor task in young and middle-aged subjects. The high-force motor task is designed to induce muscle fatigue and thereby progressively increase the attentional demands. Twenty-five young (20–30 years, 12 males) and 16 middle-aged (35–55 years, 9 males) adults performed an auditory two-choice reaction time task (CRT) with and without a concurrent low- or high-force motor task. The CRT required subjects to respond to two different stimuli that occurred with a probability of 70 or 30%. The motor task consisted of index finger abduction, at either 10% (10%-dual-task) or 30% (30%-dual-task) of maximal voluntary force. Cognitive task performance was measured as percentage of correct responses and reaction times. Middle-aged subjects responded slower on the frequent but more accurately on the infrequent stimuli of CRT than young subjects. Both young and middle-aged subjects showed increased errors and reaction times while performing under dual-task conditions and both outcome measures increased further under fatiguing conditions. Only under 30%-dual-task demands, an age-effect on dual-task performance was present. Both single- and dual-task conditions showed that already at mid-life response preparation is seriously declined and that subjects implement different strategies to perform a CRT task. PMID:24808862

Unconscious and conscious processing of negative emotions examined through affective priming.

PubMed

Okubo, Chisa; Ogawa, Toshiki

2013-04-01

This study investigated unconscious and conscious processes by which negative emotions arise. Participants (26 men, 47 women; M age = 20.3 yr.) evaluated target words that were primed with subliminally or supraliminally presented emotional pictures. Stimulus onset asynchrony was either 200 or 800 msec. With subliminal presentations, reaction times to negative targets were longer than reaction times to positive targets after negative primes for the 200-msec. stimulus onset asynchrony. Reaction times to positive targets after negative or positive primes were shorter when the stimulus onset asynchrony was 800 msec. For supraliminal presentations, reaction times were longer when evaluating targets that followed emotionally opposite primes. When emotional stimuli were consciously distinguished, the evoked emotional states might lead to emotional conflicts, although the qualitatively different effects might be caused when subliminally presented emotion evoking stimulus was appraised unconsciously; that possibility was discussed.

Monitoring biodiesel reactions of soybean oil and sunflower oil using ultrasonic parameters

NASA Astrophysics Data System (ADS)

Figueiredo, M. K. K.; Silva, C. E. R.; Alvarenga, A. V.; Costa-Félix, R. P. B.

2015-01-01

Biodiesel is an innovation that attempts to substitute diesel oil with biomass. The aim of this paper is to show the development of a real-time method to monitor transesterification reactions by using low-power ultrasound and pulse/echo techniques. The results showed that it is possible to identify different events during the transesterification process by using the proposed parameters, showing that the proposed method is a feasible way to monitor the reactions of biodiesel during its fabrication, in real time, and with relatively low- cost equipment.

Particle velocity measurements of the reaction zone in nitromethane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheffield, S. A.; Engelke, R. P.; Alcon, R. R.

2002-01-01

The detonation reaction-zone length in neat, deuterated, and chemically sensitized nitromethane (NM) has been measured by using several different laser-based velocity interferometry systems. The experiments involved measuring the particle velocity history at a NM/PMMA (polymethylmethacrylate) window interface during the time a detonation in the NM interacted with the interface. Initially, Fabry-Perot interferometry was used, but, because of low time resolution (>5 ns), several different configurations of VISAR interferometry were subsequently used. Early work was done with VISARs with a time resolution of about 3 ns. By making changes to the recording system, we were able to improve this to {approx}1more » ns. Profiles measured at the NM/PMMA interface agree with the ZND theory, in that a spike ({approx}2.45 mm/{micro}s) is measured that is consistent with an extrapolated reactant NM Hugoniot matched to the PMMA window. The spike is rather sharp, followed by a rapid drop in particle velocity over a time of 5 to 10 ns; this is evidence of early fast reactions. Over about 50 ns, a much slower particle velocity decrease occurs to the assumed CJ condition - indicating a total reaction zone length of {approx}300 {micro}m. When the NM is chemically changed, such as replacing the hydrogen atoms with deuterium or chemically sensitizing with a base, some changes are observed in the early part of the reaction zone.« less

A Novel Computational Method to Reduce Leaky Reaction in DNA Strand Displacement

PubMed Central

Li, Xin; Wang, Xun; Song, Tao; Lu, Wei; Chen, Zhihua; Shi, Xiaolong

2015-01-01

DNA strand displacement technique is widely used in DNA programming, DNA biosensors, and gene analysis. In DNA strand displacement, leaky reactions can cause DNA signals decay and detecting DNA signals fails. The mostly used method to avoid leakage is cleaning up after upstream leaky reactions, and it remains a challenge to develop reliable DNA strand displacement technique with low leakage. In this work, we address the challenge by experimentally evaluating the basic factors, including reaction time, ratio of reactants, and ion concentration to the leakage in DNA strand displacement. Specifically, fluorescent probes and a hairpin structure reporting DNA strand are designed to detect the output of DNA strand displacement, and thus can evaluate the leakage of DNA strand displacement reactions with different reaction time, ratios of reactants, and ion concentrations. From the obtained data, mathematical models for evaluating leakage are achieved by curve derivation. As a result, it is obtained that long time incubation, high concentration of fuel strand, and inappropriate amount of ion concentration can weaken leaky reactions. This contributes to a method to set proper reaction conditions to reduce leakage in DNA strand displacement. PMID:26491602

Human Performance: Sex Differences and the Influence of the Menstrual Cycle (A Selected Bibliography)

DTIC Science & Technology

1978-05-01

22 C. Vigilance/ Attention .. .... ......... .......... 23 D. Reaction Time .. ... ......... ......... .... 24 E. Time Estimation...24 F. Cognitive Skills/Intelligence. .. ....... ........ .... 25 G. Memory .. ........ ........ ......... .. 26 H. Problem...Sex Differences in Cognitive Abilities. ..... .... 30 IV. SEX DIFFERENCES IN PERSONALITY .. ..... ........ .... 33 A. Emotional ity/Adaptive Styles

Excitation wavelength dependence of excited state intramolecular proton transfer reaction of 4'-N,N-diethylamino-3-hydroxyflavone in room temperature ionic liquids studied by optical Kerr gate fluorescence measurement.

PubMed

Suda, Kayo; Terazima, Masahide; Sato, Hirofumi; Kimura, Yoshifumi

2013-10-17

Excited state intramolecular proton transfer reactions (ESIPT) of 4'-N,N-diethylamino-3-hydroxyflavone (DEAHF) in ionic liquids have been studied by steady-state and time-resolved fluorescence measurements at different excitation wavelengths. Steady-state measurements show the relative yield of the tautomeric form to the normal form of DEAHF decreases as excitation wavelength is increased from 380 to 450 nm. The decrease in yield is significant in ionic liquids that have cations with long alkyl chains. The extent of the decrease is correlated with the number of carbon atoms in the alkyl chains. Time-resolved fluorescence measurements using optical Kerr gate spectroscopy show that ESIPT rate has a strong excitation wavelength dependence. There is a large difference between the spectra at a 200 ps delay from different excitation wavelengths in each ionic liquid. The difference is pronounced in ionic liquids having a long alkyl chain. The equilibrium constant in the electronic excited state obtained at a 200 ps delay and the average reaction rate are also correlated with the alkyl chain length. Considering the results of the steady-state fluorescence and time-resolved measurements, the excitation wavelength dependence of ESIPT is explained by state selective excitation due to the difference of the solvation, and the number of alkyl chain carbon atoms is found to be a good indicator of the effect of inhomogeneity for this reaction.

Coding the Assembly of Polyoxotungstates with a Programmable Reaction System.

PubMed

Ruiz de la Oliva, Andreu; Sans, Victor; Miras, Haralampos N; Long, De-Liang; Cronin, Leroy

2017-05-01

Chemical transformations are normally conducted in batch or flow mode, thereby allowing the chemistry to be temporally or spatially controlled, but these approaches are not normally combined dynamically. However, the investigation of the underlying chemistry masked by the self-assembly processes that often occur in one-pot reactions and exploitation of the potential of complex chemical systems requires control in both time and space. Additionally, maintaining the intermediate constituents of a self-assembled system "off equilibrium" and utilizing them dynamically at specific time intervals provide access to building blocks that cannot coexist under one-pot conditions and ultimately to the formation of new clusters. Herein, we implement the concept of a programmable networked reaction system, allowing us to connect discrete "one-pot" reactions that produce the building block{W 11 O 38 } ≡ {W 11 } under different conditions and control, in real time, the assembly of a series of polyoxometalate clusters {W 12 O 42 } ≡ {W 12 }, {W 22 O 74 } ≡ {W 22 } 1a, {W 34 O 116 } ≡ {W 34 } 2a, and {W 36 O 120 } ≡ {W 36 } 3a, using pH and ultraviolet-visible monitoring. The programmable networked reaction system reveals that is possible to assemble a range of different clusters using {W 11 }-based building blocks, demonstrating the relationship between the clusters within the family of iso-polyoxotungstates, with the final structural motif being entirely dependent on the building block libraries generated in each separate reaction space within the network. In total, this approach led to the isolation of five distinct inorganic clusters using a "fixed" set of reagents and using a fully automated sequence code, rather than five entirely different reaction protocols. As such, this approach allows us to discover, record, and implement complex one-pot reaction syntheses in a more general way, increasing the yield and reproducibility and potentially giving access to nonspecialists.

Coding the Assembly of Polyoxotungstates with a Programmable Reaction System

PubMed Central

2017-01-01

Chemical transformations are normally conducted in batch or flow mode, thereby allowing the chemistry to be temporally or spatially controlled, but these approaches are not normally combined dynamically. However, the investigation of the underlying chemistry masked by the self-assembly processes that often occur in one-pot reactions and exploitation of the potential of complex chemical systems requires control in both time and space. Additionally, maintaining the intermediate constituents of a self-assembled system “off equilibrium” and utilizing them dynamically at specific time intervals provide access to building blocks that cannot coexist under one-pot conditions and ultimately to the formation of new clusters. Herein, we implement the concept of a programmable networked reaction system, allowing us to connect discrete “one-pot” reactions that produce the building block{W11O38} ≡ {W11} under different conditions and control, in real time, the assembly of a series of polyoxometalate clusters {W12O42} ≡ {W12}, {W22O74} ≡ {W22} 1a, {W34O116} ≡ {W34} 2a, and {W36O120} ≡ {W36} 3a, using pH and ultraviolet–visible monitoring. The programmable networked reaction system reveals that is possible to assemble a range of different clusters using {W11}-based building blocks, demonstrating the relationship between the clusters within the family of iso-polyoxotungstates, with the final structural motif being entirely dependent on the building block libraries generated in each separate reaction space within the network. In total, this approach led to the isolation of five distinct inorganic clusters using a “fixed” set of reagents and using a fully automated sequence code, rather than five entirely different reaction protocols. As such, this approach allows us to discover, record, and implement complex one-pot reaction syntheses in a more general way, increasing the yield and reproducibility and potentially giving access to nonspecialists. PMID:28414229

Monitoring single coffee bean roasting by direct volatile compound analysis with proton transfer reaction time-of-flight mass spectrometry.

PubMed

Yener, Sine; Navarini, Luciano; Lonzarich, Valentina; Cappellin, Luca; Märk, Tilmann D; Bonn, Günther K; Biasioli, Franco

2016-09-01

This study applies proton transfer reaction time-of-flight mass spectrometry for the rapid analysis of volatile compounds released from single coffee beans. The headspace volatile profiles of single coffee beans (Coffeea arabica) from different geographical origins (Brazil, Guatemala and Ethiopia) were analyzed via offline profiling at different stages of roasting. The effect of coffee geographical origin was reflected on volatile compound formation that was supported by one-way ANOVA. Clear origin signatures were observed in the formation of different coffee odorants. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Simple reaction time to the onset of time-varying sounds.

PubMed

Schlittenlacher, Josef; Ellermeier, Wolfgang

2015-10-01

Although auditory simple reaction time (RT) is usually defined as the time elapsing between the onset of a stimulus and a recorded reaction, a sound cannot be specified by a single point in time. Therefore, the present work investigates how the period of time immediately after onset affects RT. By varying the stimulus duration between 10 and 500 msec, this critical duration was determined to fall between 32 and 40 milliseconds for a 1-kHz pure tone at 70 dB SPL. In a second experiment, the role of the buildup was further investigated by varying the rise time and its shape. The increment in RT for extending the rise time by a factor of ten was about 7 to 8 msec. There was no statistically significant difference in RT between a Gaussian and linear rise shape. A third experiment varied the modulation frequency and point of onset of amplitude-modulated tones, producing onsets at different initial levels with differently rapid increase or decrease immediately afterwards. The results of all three experiments results were explained very well by a straightforward extension of the parallel grains model (Miller and Ulrich Cogn. Psychol. 46, 101-151, 2003), a probabilistic race model employing many parallel channels. The extension of the model to time-varying sounds made the activation of such a grain depend on intensity as a function of time rather than a constant level. A second approach by mechanisms known from loudness produced less accurate predictions.

Reaction Rates Of Olivine Carbonation - An Experimental Study Using Synthetic Fluid Inclusions As Micro-Reactors

NASA Astrophysics Data System (ADS)

Sendula, E.; Lamadrid, H. M.; Bodnar, R. J.

2017-12-01

Ultramafic and mafic rocks (e.g. peridotites, serpentinites and basalts) are being considered as possible targets for CO2 sequestration via mineral carbonation. The determination of reaction kinetics and the factors that control mineralization are important in order to understand and predict fluid-rock reactions between the injected CO2 and the host rocks. Here we present results of experiments focused on determining the reaction rates of carbonation of olivine as a function of initial CO2 concentration (20 mol% and 11 mol%) in the aqueous solution and temperature (100°C and 50°C). We used a recently developed experimental method (Lamadrid et al., 2017) that uses synthetic fluid inclusions as micro-reactors. The micro-reactor technique coupled with non-destructive Raman spectroscopy allows us to monitor the reaction progress in situ and in real time, by quantifying the amount of CO2 consumed in the reaction as a function of time. Results show a measurable decrease of CO2 density in the fluid inclusions as a result of the reaction between the CO2-bearing aqueous phase and olivine. Magnesite formation begins within several hours at 100°C and most of the CO2 was consumed within two days. At 50°C, however, magnesite nucleation and precipitation required weeks to months to begin, and the reaction rates were about an order of magnitude slower than in the experiments at 100°C. No significant differences were observed in the reaction rates as a function of initial CO2 concentration. The application of the synthetic fluid inclusion technique as micro-reactors coupled with non-destructive analytical techniques is a promising tool to monitor rates of fluid-rock reactions in situ and in real time, allowing detailed micron-scale investigations. The technique can be applied to a wide variety of chemical systems, host minerals, reaction products, fluid densities, temperatures, and different starting fluid compositions.

Single-molecule stochastic times in a reversible bimolecular reaction

NASA Astrophysics Data System (ADS)

Keller, Peter; Valleriani, Angelo

2012-08-01

In this work, we consider the reversible reaction between reactants of species A and B to form the product C. We consider this reaction as a prototype of many pseudobiomolecular reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.

Organisational Pattern Driven Recovery Mechanisms

NASA Astrophysics Data System (ADS)

Giacomo, Valentina Di; Presenza, Domenico; Riccucci, Carlo

The process of reaction to system failures and security attacks is strongly influenced by its infrastructural, procedural and organisational settings. Analysis of reaction procedures and practices from different domains (Air Traffic Management, Response to Computer Security Incident, Response to emergencies, recovery in Chemical Process Industry) highlight three key requirements for this activity: smooth collaboration and coordination among responders, accurate monitoring and management of resources and ability to adapt pre-established reaction plans to the actual context. The SERENITY Reaction Mechanisms (SRM) is the subsystem of the SERENITY Run-time Framework aimed to provide SERENITY aware AmI settings (i.e. socio-technical systems with highly distributed dynamic services) with functionalities to implement applications specific reaction strategies. The SRM uses SERENITY Organisational S&D Patterns as run-time models to drive these three key functionalities.

Increased Intra-Individual Reaction Time Variability in Attention-Deficit/Hyperactivity Disorder across Response Inhibition Tasks with Different Cognitive Demands

ERIC Educational Resources Information Center

Vaurio, Rebecca G.; Simmonds, Daniel J.; Mostofsky, Stewart H.

2009-01-01

One of the most consistent findings in children with ADHD is increased moment-to-moment variability in reaction time (RT). The source of increased RT variability can be examined using ex-Gaussian analyses that divide variability into normal and exponential components and Fast Fourier transform (FFT) that allow for detailed examination of the…

Sustained attention to response task (SART) shows impaired vigilance in a spectrum of disorders of excessive daytime sleepiness.

PubMed

Van Schie, Mojca K M; Thijs, Roland D; Fronczek, Rolf; Middelkoop, Huub A M; Lammers, Gert Jan; Van Dijk, J Gert

2012-08-01

The sustained attention to response task comprises withholding key presses to one in nine of 225 target stimuli; it proved to be a sensitive measure of vigilance in a small group of narcoleptics. We studied sustained attention to response task results in 96 patients from a tertiary narcolepsy referral centre. Diagnoses according to ICSD-2 criteria were narcolepsy with (n=42) and without cataplexy (n=5), idiopathic hypersomnia without long sleep time (n=37), and obstructive sleep apnoea syndrome (n=12). The sustained attention to response task was administered prior to each of five multiple sleep latency test sessions. Analysis concerned error rates, mean reaction time, reaction time variability and post-error slowing, as well as the correlation of sustained attention to response task results with mean latency of the multiple sleep latency test and possible time of day influences. Median sustained attention to response task error scores ranged from 8.4 to 11.1, and mean reaction times from 332 to 366ms. Sustained attention to response task error score and mean reaction time did not differ significantly between patient groups. Sustained attention to response task error score did not correlate with multiple sleep latency test sleep latency. Reaction time was more variable as the error score was higher. Sustained attention to response task error score was highest for the first session. We conclude that a high sustained attention to response task error rate reflects vigilance impairment in excessive daytime sleepiness irrespective of its cause. The sustained attention to response task and the multiple sleep latency test reflect different aspects of sleep/wakefulness and are complementary. © 2011 European Sleep Research Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shepherd, James; Fairweather, Michael; Hanson, Bruce C.

The oxidation of spent uranium carbide fuel, a candidate fuel for Generation IV nuclear reactors, is an important process in its potential reprocessing cycle. However, the oxidation of uranium carbide in air is highly exothermic. A model has therefore been developed to predict the temperature rise, as well as other useful information such as reaction completion times, under different reaction conditions in order to help in deriving safe oxidation conditions. Finite difference-methods are used to model the heat and mass transfer processes occurring during the reaction in two dimensions and are coupled to kinetics found in the literature.

Are there gender differences in cognitive function, chronic stress, and neurobehavioral symptoms after mild-to-moderate traumatic brain injury?

PubMed

Covassin, Tracey; Bay, Esther

2012-06-01

Research is inconclusive on whether gender differences exist in cognitive function in persons who sustain a mild-to-moderate traumatic brain injury (TBI). Furthermore, it is also unclear whether there is a relationship between chronic stress and cognitive function in these persons. The purpose of this integrative review is to determine whether gender differences exist in cognitive function, neurobehavioral symptoms, and chronic stress levels after a mild-to-moderate TBI. Participants (n = 72) were recruited from eight outpatient rehabilitation centers. Participants completed the demographic questions, the Immediate Postconcussion Assessment Cognitive Testing neurocognitive test battery, the Perceived Stress Scale-14, and the Neurobehavioral Functioning Inventory (NFI). Gender differences were present on verbal memory composite scores (p = .033), with women performing worse than men. There were no other between-gender differences on cognitive tasks, neurobehavioral symptoms, or chronic stress. Higher chronic stress levels result in a decrease in verbal memory (p = .015) and motor processing speed (p = .006) and slower reaction time (p = .007) for women. As male NFI cognition scores increased, motor processing speed scores decreased (p = .012) and reaction time got slower (p = .019), whereas women exhibited decreased verbal memory (p = .017) and slower reaction time (p = .034). As NFI motor symptoms increased, men exhibited decreased verbal memory (p = .005), visual memory (p = .002), and motor processing speed (p = .002) and slower reaction time (p = .002). Overall, this study only found gender differences on verbal memory composite scores, whereas the remaining cognitive tasks, neurobehavioral symptoms, and chronic stress did not indicate gender differences. Correlations between chronic stress, neurobehavioral symptoms, and cognitive function differed in both men and women with TBI. Persons in the chronic phase of recovery from a TBI may benefit from training in compensatory strategies for verbal memory deficits and stress management.

Auditory and visual interhemispheric communication in musicians and non-musicians.

PubMed

Woelfle, Rebecca; Grahn, Jessica A

2013-01-01

The corpus callosum (CC) is a brain structure composed of axon fibres linking the right and left hemispheres. Musical training is associated with larger midsagittal cross-sectional area of the CC, suggesting that interhemispheric communication may be faster in musicians. Here we compared interhemispheric transmission times (ITTs) for musicians and non-musicians. ITT was measured by comparing simple reaction times to stimuli presented to the same hemisphere that controlled a button-press response (uncrossed reaction time), or to the contralateral hemisphere (crossed reaction time). Both visual and auditory stimuli were tested. We predicted that the crossed-uncrossed difference (CUD) for musicians would be smaller than for non-musicians as a result of faster interhemispheric transfer times. We did not expect a difference in CUDs between the visual and auditory modalities for either musicians or non-musicians, as previous work indicates that interhemispheric transfer may happen through the genu of the CC, which contains motor fibres rather than sensory fibres. There were no significant differences in CUDs between musicians and non-musicians. However, auditory CUDs were significantly smaller than visual CUDs. Although this auditory-visual difference was larger in musicians than non-musicians, the interaction between modality and musical training was not significant. Therefore, although musical training does not significantly affect ITT, the crossing of auditory information between hemispheres appears to be faster than visual information, perhaps because subcortical pathways play a greater role for auditory interhemispheric transfer.

Bereavement experiences of mothers and fathers over time after the death of a child due to cancer.

PubMed

Alam, Rifat; Barrera, Maru; D'Agostino, Norma; Nicholas, David B; Schneiderman, Gerald

2012-01-01

The authors investigated longitudinally bereavement in mothers and fathers whose children died of cancer. Thirty-one parents were interviewed 6 and 18 months post-death. Analyses revealed parental differences and changes over time: (a) employment--fathers were more work-focused; (b) grief reactions--mothers expressed more intense grief reactions that lessened over time; (c) coping--mothers were more child-focused, fathers more task-focused; (d) relationship with bereaved siblings-mothers actively nurtured relationship with child; (e) spousal relationship--parents reported diversity in their relationship over time; and (f) relationship with extended family--mothers maintained contact with extended family more. Findings illustrate parental differences in bereavement over time that might be partly socially determined. These findings emphasize the need for tailoring bereavement support services in the family.

Assessing the temporal aspects of attention and its correlates in aging and chronic stroke patients.

PubMed

Shalev, Nir; Humphreys, Glyn; Demeyere, Nele

2016-11-01

Temporal dynamics of attention have been in the spotlight of research since the earliest days of cognitive psychology. Typically, researchers describe two different aspects of the temporal fluctuations of attention: one is in intervals of milliseconds (phasic alertness), and the other over minutes or even hours (tonic alertness or sustained attention). In order to evaluate individual capacities for sustained attention and phasic alertness, most studies rely on variations of the Continuous Performance Task (CPT). Indices of sustained attention and phasic alertness are typically based on reaction times to targets; phasic alertness is related to the change in reaction times following a cue, and sustained attention is related to variability of reaction times during the task. In the following study, we attempted to establish a new approach for studying sustained attention and phasic alertness, not reliant solely on reaction time measures. We developed a new variation of the CPT with conjunctive feature targets and forward and backward masking to induce a higher variability in accuracy. This allowed us to assess an individual's ability to maintain the same level of sensitivity to targets (d-prime) across a ten minute period on the task as an index for sustained attention. We also assessed reaction times as a function of previous trial type, and suggest previous trial RT benefit might be a marker for an individual's phasic alertness. We demonstrated the use of this task with healthy aging controls and stroke survivors. As a demonstration of external validity of the novel paradigm, we present a correlation between how individual performance drops over time and individual reports of distractibility in everyday life on the Cognitive Failures Questionnaire. In addition, we found significant differences between the patient and control groups in our proposed marker of phasic alertness. We discuss the implications of our study for current assessment tools, as well as general differences in phasic alertness between clinical and neurologically unimpaired groups. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of phosphorus fertilizer soil reactions by Raman and synchrotron infrared microspectroscopy.

PubMed

Vogel, Christian; Adam, Christian; Sekine, Ryo; Schiller, Tara; Lipiec, Ewelina; McNaughton, Don

2013-10-01

The reaction mechanisms of phosphate-bearing mineral phases from sewage sludge ash-based fertilizers in soil were determined by Raman and synchrotron infrared microspectroscopy. Different reaction mechanisms in wet soil were found for calcium and magnesium (pyro-) phosphates. Calcium orthophosphates were converted over time to hydroxyapatite. Conversely, different magnesium phosphates were transformed to trimagnesium phosphate. Since the magnesium phosphates are unable to form an apatite structure, the plant-available phosphorus remains in the soil, leading to better growth results observed in agricultural pot experiments. The pyrophosphates also reacted very differently. Calcium pyrophosphate is unreactive in soil. In contrast, magnesium pyrophosphate quickly formed plant-available dimagnesium phosphate.

A two-dimensional, finite-difference model of the oxidation of a uranium carbide fuel pellet

NASA Astrophysics Data System (ADS)

Shepherd, James; Fairweather, Michael; Hanson, Bruce C.; Heggs, Peter J.

2015-12-01

The oxidation of spent uranium carbide fuel, a candidate fuel for Generation IV nuclear reactors, is an important process in its potential reprocessing cycle. However, the oxidation of uranium carbide in air is highly exothermic. A model has therefore been developed to predict the temperature rise, as well as other useful information such as reaction completion times, under different reaction conditions in order to help in deriving safe oxidation conditions. Finite difference-methods are used to model the heat and mass transfer processes occurring during the reaction in two dimensions and are coupled to kinetics found in the literature.

Time management problems and discounted utility.

PubMed

König, Cornelius J; Kleinmann, Martin

2007-05-01

The lens of behavioral decision theory offers a new perspective for research on time management. The basic idea of this approach is that people discount future consequences of their time management decisions, meaning that they work on tasks with smaller but sooner outcomes rather than on tasks with larger but later outcomes. The authors performed 2 experimental studies to test whether people are sensitive to differences in the discounted utility of time management decisions. In Experiment 1, they used vignettes of typical time management situations; Experiment 2 was a laboratory simulation (an in-basket task that was part of a training assessment). Participants in both studies were German students. As expected, manipulating the discounted utility of options resulted in different time management decisions. In Experiment 1, reactions to time management situations were judged as less likely if the reactions had lower discounted utilities. In Experiment 2, people spent less time on an interruption.

Rate variations of a hetero-Diels--Alder reaction in supercritical fluid CO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, R.L.; Glaeser, R.; Bush, D.

1999-11-01

The hetero-Diels-Alder reaction between anthracene and excess 4-phenyl-1,2,4-triazoline-3,5-dione has been investigated in supercritical CO{sub 2} at 40 C and pressures between 75 and 216 bar. Biomolecular reaction rate constants have been measured via fluorescence spectroscopy by following the decrease in anthracene concentration with reaction time. The reaction rate is elevated in the vicinity of the critical pressure. This difference is consistent with local composition enhancement and can be modeled with the Peng-Robinson equation of state.

A numerical solution for a variable-order reaction-diffusion model by using fractional derivatives with non-local and non-singular kernel

NASA Astrophysics Data System (ADS)

Coronel-Escamilla, A.; Gómez-Aguilar, J. F.; Torres, L.; Escobar-Jiménez, R. F.

2018-02-01

A reaction-diffusion system can be represented by the Gray-Scott model. The reaction-diffusion dynamic is described by a pair of time and space dependent Partial Differential Equations (PDEs). In this paper, a generalization of the Gray-Scott model by using variable-order fractional differential equations is proposed. The variable-orders were set as smooth functions bounded in (0 , 1 ] and, specifically, the Liouville-Caputo and the Atangana-Baleanu-Caputo fractional derivatives were used to express the time differentiation. In order to find a numerical solution of the proposed model, the finite difference method together with the Adams method were applied. The simulations results showed the chaotic behavior of the proposed model when different variable-orders are applied.

Real-Time Reverse Transcription–Polymerase Chain Reaction Assay for SARS-associated Coronavirus

PubMed Central

Emery, Shannon L.; Bowen, Michael D.; Newton, Bruce R.; Winchell, Jonas M.; Meyer, Richard F.; Tong, Suxiang; Cook, Byron T.; Holloway, Brian P.; McCaustland, Karen A.; Rota, Paul A.; Bankamp, Bettina; Lowe, Luis E.; Ksiazek, Tom G.; Bellini, William J.; Anderson, Larry J.

2004-01-01

A real-time reverse transcription–polymerase chain reaction (RT-PCR) assay was developed to rapidly detect the severe acute respiratory syndrome–associated coronavirus (SARS-CoV). The assay, based on multiple primer and probe sets located in different regions of the SARS-CoV genome, could discriminate SARS-CoV from other human and animal coronaviruses with a potential detection limit of <10 genomic copies per reaction. The real-time RT-PCR assay was more sensitive than a conventional RT-PCR assay or culture isolation and proved suitable to detect SARS-CoV in clinical specimens. Application of this assay will aid in diagnosing SARS-CoV infection. PMID:15030703

Predictors of chronic ankle instability: Analysis of peroneal reaction time, dynamic balance and isokinetic strength.

PubMed

Sierra-Guzmán, Rafael; Jiménez, Fernando; Abián-Vicén, Javier

2018-05-01

Previous studies have reported the factors contributing to chronic ankle instability, which could lead to more effective treatments. However, factors such as the reflex response and ankle muscle strength have not been taken into account in previous investigations. Fifty recreational athletes with chronic ankle instability and 55 healthy controls were recruited. Peroneal reaction time in response to sudden inversion, isokinetic evertor muscle strength and dynamic balance with the Star Excursion Balance Test and the Biodex Stability System were measured. The relationship between the Cumberland Ankle Instability Tool score and performance on each test was assessed and a backward multiple linear regression analysis was conducted. Participants with chronic ankle instability showed prolonged peroneal reaction time, poor performance in the Biodex Stability System and decreased reach distance in the Star Excursion Balance Test. No significant differences were found in eversion and inversion peak torque. Moderate correlations were found between the Cumberland Ankle Instability Tool score and the peroneal reaction time and performance on the Star Excursion Balance Test. Peroneus brevis reaction time and the posteromedial and lateral directions of the Star Excursion Balance Test accounted for 36% of the variance in the Cumberland Ankle Instability Tool. Dynamic balance deficits and delayed peroneal reaction time are present in participants with chronic ankle instability. Peroneus brevis reaction time and the posteromedial and lateral directions of the Star Excursion Balance Test were the main contributing factors to the Cumberland Ankle Instability Tool score. No clear strength impairments were reported in unstable ankles. Copyright © 2018 Elsevier Ltd. All rights reserved.

Reaction Time is a Marker of Early Cognitive and Behavioral Alterations in Pure Cerebral Small Vessel Disease.

PubMed

Jouvent, Eric; Reyes, Sonia; De Guio, François; Chabriat, Hugues

2015-01-01

The assessment of early and subtle cognitive and behavioral effects of cerebral small vessel disease (SVD) requires specific and long-lasting evaluations performed by experienced neuropsychologists. Simpler tools would be helpful for daily clinical practice. To determine whether a simple reaction time task that lasts 5 minutes and can be performed without external supervision on any tablet or laptop can be used as a proxy of early cognitive and behavioral alterations in CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy), a monogenic form of pure SVD related to NOTCH3 mutations. Twenty-two genetically confirmed patients with CADASIL having preserved global cognitive abilities and without disability (MMSE >24 and modified Rankin's scale ≤1) were compared to 29 age-and-gender matched controls to determine group differences according to: 1) conventional neuropsychological and behavioral testing; 2) a computerized battery evaluating reaction time, processing speed, and executive functions. In a second step, correlations between reaction time and cognitive and behavioral alterations detected using both conventional and computerized testing were tested in patients. Reaction time was significantly higher in patients than in controls (mean in patients: 283 ms - in controls: 254 ms, p = 0.03). In patients, reaction time was significantly associated with conventional and chronometric tests of executive functions, working memory, and apathy. Reaction time obtained using a very simple task may serve as a proxy of early cognitive and behavioral alterations in SVD and could be easily used in daily clinical practice.

Specific biases for identifying facial expression of emotion in children and adolescents with conversion disorders.

PubMed

Kozlowska, Kasia; Brown, Kerri J; Palmer, Donna M; Williams, Lea M

2013-04-01

This study aimed to assess how children and adolescents with conversion disorders identify universal facial expressions of emotion and to determine whether identification of emotion in faces relates to subjective emotional distress. Fifty-seven participants (41 girls and 16 boys) aged 8.5 to 18 years with conversion disorders and 57 age- and sex-matched healthy controls completed a computerized task in which their accuracy and reaction times for identifying facial expressions were recorded. To isolate the effect of individual emotional expressions, participants' reaction times for each emotion (fear, anger, sadness, disgust, and happiness) were subtracted from their reaction times for the neutral control face. Participants also completed self-report measures of subjective emotional distress. Children/Adolescents with conversion disorders showed faster reaction times for identifying expressions of sadness (t(112) = -2.2, p = .03; 444 [609] versus 713 [695], p = .03) and slower reactions times for happy expressions (t(99.3) = 2.28, p ≤ .024; -33 [35] versus 174 [51], p = .024), compared with controls (F(33.75, 419.81) = 3.76, p < .001). There were no significant correlations (at the corrected p value of .01) between reaction times and subjective reports of perceived distress (r values ranged from 092 to 0.221; p > .018). There were also no differences in identification accuracy for any emotion (p > .82). The observation of faster reaction times to sad faces in children and adolescents with conversion disorders suggests increased vigilance and motor readiness to emotional signals that are potential threats to self or to close others. These effects may occur before conscious processing.

Bradykinesia and bradyphrenia revisited: patterns of subclinical deficit in motor speed and cognitive functioning in head-injured patients with good recovery.

PubMed

Gray, C; Cantagallo, A; Della Sala, S; Basaglia, N

1998-05-01

Twenty-four patients, showing a good clinical recovery from coma-inducing injury and coping well with the activities of everyday living, were tested, at least 1 year after trauma, on motor speed and reaction time, and given a neuropsychological examination. While the patients generally performed within the normal range on the neuropsychological tests, their motor speeds and reaction times--both simple (SRT) and complex (CRT)--were significantly slower than those of matched controls. This points to a subclinical bradykinesia. The patients' motor speed scores did not correlate significantly with any of the neuropsychological tests; nor did SRT or CRT. While the difference between simple and complex reaction time was significantly greater in the patient group, the percentage difference was not significantly different between the two groups. Collectively, these results suggest that bradykinesia and bradyphrenia do not necessarily overlap. Finally, there was no significant correlation between motor performance and severity of original injury, whether the latter was measured by number and size of lesions or by duration of post-traumatic amnesia.

Individual differences in the recognition of facial expressions: an event-related potentials study.

PubMed

Tamamiya, Yoshiyuki; Hiraki, Kazuo

2013-01-01

Previous studies have shown that early posterior components of event-related potentials (ERPs) are modulated by facial expressions. The goal of the current study was to investigate individual differences in the recognition of facial expressions by examining the relationship between ERP components and the discrimination of facial expressions. Pictures of 3 facial expressions (angry, happy, and neutral) were presented to 36 young adults during ERP recording. Participants were asked to respond with a button press as soon as they recognized the expression depicted. A multiple regression analysis, where ERP components were set as predictor variables, assessed hits and reaction times in response to the facial expressions as dependent variables. The N170 amplitudes significantly predicted for accuracy of angry and happy expressions, and the N170 latencies were predictive for accuracy of neutral expressions. The P2 amplitudes significantly predicted reaction time. The P2 latencies significantly predicted reaction times only for neutral faces. These results suggest that individual differences in the recognition of facial expressions emerge from early components in visual processing.

Liquid phase products and solid deposit formation from thermally stressed model jet fuels

NASA Technical Reports Server (NTRS)

Kim, W. S.; Bittker, D. A.

1984-01-01

The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given.

Time-delayed reaction-diffusion fronts

NASA Astrophysics Data System (ADS)

Isern, Neus; Fort, Joaquim

2009-11-01

A time-delayed second-order approximation for the front speed in reaction-dispersion systems was obtained by Fort and Méndez [Phys. Rev. Lett. 82, 867 (1999)]. Here we show that taking proper care of the effect of the time delay on the reactive process yields a different evolution equation and, therefore, an alternate equation for the front speed. We apply the new equation to the Neolithic transition. For this application the new equation yields speeds about 10% slower than the previous one.

Improved synthesis of fine zinc borate particles using seed crystals

NASA Astrophysics Data System (ADS)

Gürhan, Deniz; Çakal, Gaye Ö.; Eroğlu, İnci; Özkar, Saim

2009-03-01

Zinc borate is a flame retardant additive used in polymers, wood applications and textile products. There are different types of zinc borate having different chemical compositions and structures. In this study, the production of zinc borate having the molecular formula of 2ZnO·3B 2O 3·3.5H 2O was reexamined by studying the effects of reaction parameters on the properties of product as well as the reaction kinetics. Production of zinc borate from the reaction of boric acid and zinc oxide in the presence of seed crystals was performed in a continuously stirred, temperature-controlled batch reactor having a volume of 1.5 L. Samples taken in regular time intervals during the experiments were analyzed for the concentration of zinc oxide and boron oxide in the solid as well as for the conversion of zinc oxide to zinc borate versus time. The zinc borate production reaction was fit to the logistic model. The reaction rate, reaction completion time, composition and particle size distribution of zinc borate product were determined by varying the following parameters: the boric acid to zinc oxide ratio (H 3BO 3:ZnO=3:1, 3.5:1, 5:1 and 7:1), the particle size of zinc oxide (10 and 25 μm), stirring rate (275, 400, 800 and 1600 rpm), temperature (75, 85 and 95 °C) and the size of seed crystals (10 and 2 μm). The products were also analyzed for particle size distribution. The experimental results showed that the reaction rate increases with the increase in H 3BO 3:ZnO ratio, particle size of zinc oxide, stirring rate and temperature. Concomitantly, the reaction completion time is decreased by increasing the H 3BO 3:ZnO ratio, stirring rate and temperature. The average particle sizes of the zinc borate products are in the range 4.3-16.6 μm (wet dispersion analysis).

Temporal properties of material categorization and material rating: visual vs non-visual material features.

PubMed

Nagai, Takehiro; Matsushima, Toshiki; Koida, Kowa; Tani, Yusuke; Kitazaki, Michiteru; Nakauchi, Shigeki

2015-10-01

Humans can visually recognize material categories of objects, such as glass, stone, and plastic, easily. However, little is known about the kinds of surface quality features that contribute to such material class recognition. In this paper, we examine the relationship between perceptual surface features and material category discrimination performance for pictures of materials, focusing on temporal aspects, including reaction time and effects of stimulus duration. The stimuli were pictures of objects with an identical shape but made of different materials that could be categorized into seven classes (glass, plastic, metal, stone, wood, leather, and fabric). In a pre-experiment, observers rated the pictures on nine surface features, including visual (e.g., glossiness and transparency) and non-visual features (e.g., heaviness and warmness), on a 7-point scale. In the main experiments, observers judged whether two simultaneously presented pictures were classified as the same or different material category. Reaction times and effects of stimulus duration were measured. The results showed that visual feature ratings were correlated with material discrimination performance for short reaction times or short stimulus durations, while non-visual feature ratings were correlated only with performance for long reaction times or long stimulus durations. These results suggest that the mechanisms underlying visual and non-visual feature processing may differ in terms of processing time, although the cause is unclear. Visual surface features may mainly contribute to material recognition in daily life, while non-visual features may contribute only weakly, if at all. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Impact of Hypnotic Suggestions on Reaction Times in Continuous Performance Test in Adults with ADHD and Healthy Controls

PubMed Central

Virta, Maarit; Hiltunen, Seppo; Mattsson, Markus; Kallio, Sakari

2015-01-01

Attention is one of the key factors in both hypnotic processes and patients with ADHD. In addition, the brain areas associated with hypnosis and ADHD overlap in many respects. However, the use of hypnosis in ADHD patients has still received only minor attention in research. The main purpose of the present work was to investigate whether hypnosis and hypnotic suggestions influence the performance of adult ADHD (n = 27) and control participants (n = 31) in the continuous performance test (CPT). The hypnotic susceptibility of the participants was measured by the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:A) and the attentional task was a three minute long auditory version of the CPT. The CPT task was administered four times: before hypnosis (CPT1), after a hypnotic induction (CPT2), after suggestions about speed and accuracy (CPT3), and after the termination of hypnosis (CPT4). The susceptibility of the groups measured by HGSHS:A did not differ. There was a statistically significant decrease in reaction times in both ADHD and control groups between CPT2 and CPT3. The differences between CPT1 and CPT2, even though non-significant, were different in the two groups: in the ADHD group reaction times decreased whereas in the control group they increased. Both groups made very few errors in the short CPT. This study indicates that hypnotic suggestions have an effect on reaction times in the sustained attention task both in adult ADHD patients and control subjects. The theoretical and clinical implications are discussed. PMID:25962151

Cumulative Significance of Hyporheic Exchange and Biogeochemical Processing in River Networks

NASA Astrophysics Data System (ADS)

Harvey, J. W.; Gomez-Velez, J. D.

2014-12-01

Biogeochemical reactions in rivers that decrease excessive loads of nutrients, metals, organic compounds, etc. are enhanced by hydrologic interactions with microbially and geochemically active sediments of the hyporheic zone. The significance of reactions in individual hyporheic flow paths has been shown to be controlled by the contact time between river water and sediment and the intrinsic reaction rate in the sediment. However, little is known about how the cumulative effects of hyporheic processing in large river basins. We used the river network model NEXSS (Gomez-Velez and Harvey, submitted) to simulate hyporheic exchange through synthetic river networks based on the best available models of network topology, hydraulic geometry and scaling of geomorphic features, grain size, hydraulic conductivity, and intrinsic reaction rates of nutrients and metals in river sediment. The dimensionless reaction significance factor, RSF (Harvey et al., 2013) was used to quantify the cumulative removal fraction of a reactive solute by hyporheic processing. SF scales reaction progress in a single pass through the hyporheic zone with the proportion of stream discharge passing through the hyporheic zone for a specified distance. Reaction progress is optimal where the intrinsic reaction timescale in sediment matches the residence time of hyporheic flow and is less efficient in longer residence time hyporheic flow as a result of the decreasing proportion of river flow that is processed by longer residence time hyporheic flow paths. In contrast, higher fluxes through short residence time hyporheic flow paths may be inefficient because of the repeated surface-subsurface exchanges required to complete the reaction. Using NEXSS we found that reaction efficiency may be high in both small streams and large rivers, although for different reasons. In small streams reaction progress generally is dominated by faster pathways of vertical exchange beneath submerged bedforms. Slower exchange beneath meandering river banks mainly has importance only in large rivers. For solutes entering networks in proportion to water inputs it is the lower order streams that tend to dominate cumulative reaction progress.

Prismatic displacement effect of progressive multifocal glasses on reaction time and accuracy in elderly people.

PubMed

Ellison, Ashton C; Campbell, A John; Robertson, M Clare; Sanderson, Gordon F

2014-01-01

Multifocal glasses (bifocals, trifocals, and progressives) increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1) map the prismatic displacement of a progressive lens, and 2) test whether this displacement impaired reaction time and accuracy. The reaction times of healthy ≥75-year-olds (31 participants) were measured when grasping for a bar and touching a black line. Participants performed each test twice, wearing their progressives and new, matched single vision (distance) glasses in random order. The line and bar targets were positioned according to the maximum and minimum prismatic displacement effect through the progressive lens, mapped using a focimeter. Progressive spectacle lenses have large areas of prismatic displacement in the central visual axis and edges. Reaction time was faster for progressives compared with single vision glasses with a centrally-placed horizontal grab bar (mean difference 101 ms, P=0.011 [repeated measures analysis]) and a horizontal black line placed 300 mm below center (mean difference 80 ms, P=0.007). There was no difference in accuracy between the two types of glasses. Older people appear to adapt to the false projection of progressives in the central visual axis. This adaptation means that swapping to new glasses or a large change in prescription may lead to a fall. Frequently updating glasses may be more beneficial.

Longer reaction time of the fibularis longus muscle and reduced postural control in basketball players with functional ankle instability: A pilot study.

PubMed

Méndez-Rebolledo, Guillermo; Guzmán-Muñoz, Eduardo; Gatica-Rojas, Valeska; Zbinden-Foncea, Hermann

2015-08-01

Motor control evaluation in subjects with functional ankle instability is questionable when both ankles of the same subject are compared (affected vs non-affected). To compare the postural control and reaction time of ankle muscles among: basketball players with FAI (instability group), basketball players without FAI (non-instability group) and healthy non-basketball-playing participants (control group). Case-control study. Laboratory. Instability (n = 10), non-instability (n = 10), and control groups (n = 11). Centre of pressure variables (area, velocity and sway) were measured with a force platform. Reaction time of ankle muscles was measured via electromyography. A one-way ANOVA demonstrated that there were significant differences between the instability and non-instability groups in the fibularis longus (p < 0.001), fibularis brevis (p = 0.031) and tibialis anterior (p = 0.049) muscles. Repeated-measures ANOVA and post hoc analysis determined significant differences for the area between the instability and non-instability groups (p = 0.001). Basketball players with FAI have reduced postural control and longer reaction time of the fibularis and tibialis anterior muscles. Copyright © 2014 Elsevier Ltd. All rights reserved.

Exposure-time based modeling of nonlinear reactive transport in porous media subject to physical and geochemical heterogeneity.

PubMed

Sanz-Prat, Alicia; Lu, Chuanhe; Amos, Richard T; Finkel, Michael; Blowes, David W; Cirpka, Olaf A

2016-09-01

Transport of reactive solutes in groundwater is affected by physical and chemical heterogeneity of the porous medium, leading to complex spatio-temporal patterns of concentrations and reaction rates. For certain cases of bioreactive transport, it could be shown that the concentrations of reactive constituents in multi-dimensional domains are approximately aligned with isochrones, that is, lines of identical travel time, provided that the chemical properties of the matrix are uniform. We extend this concept to combined physical and chemical heterogeneity by additionally considering the time that a water parcel has been exposed to reactive materials, the so-called exposure time. We simulate bioreactive transport in a one-dimensional domain as function of time and exposure time, rather than space. Subsequently, we map the concentrations to multi-dimensional heterogeneous domains by means of the mean exposure time at each location in the multi-dimensional domain. Differences in travel and exposure time at a given location are accounted for as time difference. This approximation simplifies reactive-transport simulations significantly under conditions of steady-state flow when reactions are restricted to specific locations. It is not expected to be exact in realistic applications because the underlying assumption, such as neglecting transverse mixing altogether, may not hold. We quantify the error introduced by the approximation for the hypothetical case of a two-dimensional, binary aquifer made of highly-permeable, non-reactive and low-permeable, reactive materials releasing dissolved organic matter acting as electron donor for aerobic respiration and denitrification. The kinetically controlled reactions are catalyzed by two non-competitive bacteria populations, enabling microbial growth. Even though the initial biomass concentrations were uniform, the interplay between transport, non-uniform electron-donor supply, and bio-reactions led to distinct spatial patterns of the two types of biomass at late times. Results obtained by mapping the exposure-time based results to the two-dimensional domain are compared with simulations based on the two-dimensional, spatially explicit advection-dispersion-reaction equation. Once quasi-steady state has been reached, we find a good agreement in terms of the chemical-compound concentrations between the two approaches inside the reactive zones, whereas the exposure-time based model is not able to capture reactions occurring in the zones with zero electron-donor release. We conclude that exposure-time models provide good approximations of nonlinear bio-reactive transport when transverse mixing is not the overall controlling process and all reactions are essentially restricted to distinct reactive zones. Copyright © 2016 Elsevier B.V. All rights reserved.

Vaccine allergy.

PubMed

Caubet, Jean-Christoph; Ponvert, Claude

2014-08-01

Overdiagnosis of vaccine allergy is considered a major public health problem. This article discusses the different types of allergic reactions after immunization based on the timing (immediate vs nonimmediate) and the extent of the reaction (local vs systemic). The vaccine components potentially responsible for an allergic reaction are discussed, as well as the management of patients with a history of reaction to a specific vaccine and those with a history of allergy to one of the vaccine components. Copyright © 2014 Elsevier Inc. All rights reserved.

Production of biodiesel fuel by transesterification of different vegetable oils with methanol using Al₂O₃ modified MgZnO catalyst.

PubMed

Olutoye, M A; Hameed, B H

2013-03-01

An active heterogeneous Al2O3 modified MgZnO (MgZnAlO) catalyst was prepared and the catalytic activity was investigated for the transesterification of different vegetable oils (refined palm oil, waste cooking palm oil, palm kernel oil and coconut oil) with methanol to produce biodiesel. The catalyst was characterized by using X-ray diffraction, Fourier transform infrared spectra, thermo gravimetric and differential thermal analysis to ascertain its versatility. Effects of important reaction parameters such as methanol to oil molar ratio, catalyst dosage, reaction temperature and reaction time on oil conversion were examined. Within the range of studied variability, the suitable transesterification conditions (methanol/oil ratio 16:1, catalyst loading 3.32 wt.%, reaction time 6h, temperature 182°C), the oil conversion of 98% could be achieved with reference to coconut oil in a single stage. The catalyst can be easily recovered and reused for five cycles without significant deactivation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Reaction front barriers in time aperiodic fluid flows

NASA Astrophysics Data System (ADS)

Locke, Rory; Mitchell, Kevin

2016-11-01

Many chemical and biological systems can be characterized by the propagation of a front that separates different phases or species. One approach to formalizing a general theory is to apply frameworks developed in nonlinear dynamics. It has been shown that invariant manifolds form barriers to passive transport in time-dependent or time-periodic fluid flows. More recently, analogous manifolds termed burning- invariant-manifolds (BIMs), have been shown to form one-sided barriers to reaction fronts in advection-reaction-diffusion (ARD) systems. To model more realistic time-aperiodic systems, recent theoretical work has suggested that similar one-sided barriers, termed burning Lagrangian coherent structures (bLCSs), exist for fluid velocity data prescribed over a finite time interval. In this presentation, we use a stochastic "wind" to generate time dependence in a double-vortex channel flow and demonstrate the (locally) most attracting or repelling curves are the bLCSs.

Optofluidic UV-Vis spectrophotometer for online monitoring of photocatalytic reactions

NASA Astrophysics Data System (ADS)

Wang, Ning; Tan, Furui; Zhao, Yu; Tsoi, Chi Chung; Fan, Xudong; Yu, Weixing; Zhang, Xuming

2016-06-01

On-chip integration of optical detection units into the microfluidic systems for online monitoring is highly desirable for many applications and is also well in line with the spirit of optofluidics technology-fusion of optics and microfluidics for advanced functionalities. This paper reports the construction of a UV-Vis spectrophotometer on a microreactor, and demonstrates the online monitoring of the photocatalytic degradations of methylene blue and methyl orange under different flow rates and different pH values by detecting the intensity change and/or the peak shift. The integrated device consists of a TiO2-coated glass substrate, a PDMS micro-sized reaction chamber and two flow cells. By comparing with the results of commercial equipment, we have found that the measuring range and the sensitivity are acceptable, especially when the transmittance is in the range of 0.01-0.9. This integrated optofluidic device can significantly cut down the test time and the sample volume, and would provide a versatile platform for real-time characterization of photochemical performance. Moreover, its online monitoring capability may enable to access the usually hidden information in biochemical reactions like intermediate products, time-dependent processes and reaction kinetics.

Optofluidic UV-Vis spectrophotometer for online monitoring of photocatalytic reactions

PubMed Central

Wang, Ning; Tan, Furui; Zhao, Yu; Tsoi, Chi Chung; Fan, Xudong; Yu, Weixing; Zhang, Xuming

2016-01-01

On-chip integration of optical detection units into the microfluidic systems for online monitoring is highly desirable for many applications and is also well in line with the spirit of optofluidics technology–fusion of optics and microfluidics for advanced functionalities. This paper reports the construction of a UV-Vis spectrophotometer on a microreactor, and demonstrates the online monitoring of the photocatalytic degradations of methylene blue and methyl orange under different flow rates and different pH values by detecting the intensity change and/or the peak shift. The integrated device consists of a TiO2-coated glass substrate, a PDMS micro-sized reaction chamber and two flow cells. By comparing with the results of commercial equipment, we have found that the measuring range and the sensitivity are acceptable, especially when the transmittance is in the range of 0.01–0.9. This integrated optofluidic device can significantly cut down the test time and the sample volume, and would provide a versatile platform for real-time characterization of photochemical performance. Moreover, its online monitoring capability may enable to access the usually hidden information in biochemical reactions like intermediate products, time-dependent processes and reaction kinetics. PMID:27352840

Optofluidic UV-Vis spectrophotometer for online monitoring of photocatalytic reactions.

PubMed

Wang, Ning; Tan, Furui; Zhao, Yu; Tsoi, Chi Chung; Fan, Xudong; Yu, Weixing; Zhang, Xuming

2016-06-29

On-chip integration of optical detection units into the microfluidic systems for online monitoring is highly desirable for many applications and is also well in line with the spirit of optofluidics technology-fusion of optics and microfluidics for advanced functionalities. This paper reports the construction of a UV-Vis spectrophotometer on a microreactor, and demonstrates the online monitoring of the photocatalytic degradations of methylene blue and methyl orange under different flow rates and different pH values by detecting the intensity change and/or the peak shift. The integrated device consists of a TiO2-coated glass substrate, a PDMS micro-sized reaction chamber and two flow cells. By comparing with the results of commercial equipment, we have found that the measuring range and the sensitivity are acceptable, especially when the transmittance is in the range of 0.01-0.9. This integrated optofluidic device can significantly cut down the test time and the sample volume, and would provide a versatile platform for real-time characterization of photochemical performance. Moreover, its online monitoring capability may enable to access the usually hidden information in biochemical reactions like intermediate products, time-dependent processes and reaction kinetics.

Systemic effect of mineral aggregate-based cements: histopathological analysis in rats.

PubMed

Garcia, Lucas da Fonseca Roberti; Huck, Claudia; Magalhães, Fernando Augusto Cintra; Souza, Pedro Paulo Chaves de; Souza Costa, Carlos Alberto de

2017-01-01

Several studies reported the local tissue reaction caused by mineral aggregate-based cements. However, few studies have investigated the systemic effects promoted by these cements on liver and kidney when directly applied to connective tissue. The purpose of this in vivo study was to investigate the systemic effect of mineral aggregate-based cements on the livers and kidneys of rats. Samples of Mineral Trioxide Aggregate (MTA) and a calcium aluminate-based cement (EndoBinder) containing different radiopacifiers were implanted into the dorsum of 40 rats. After 7 and 30 d, samples of subcutaneous, liver and kidney tissues were submitted to histopathological analysis. A score (0-3) was used to grade the inflammatory reaction. Blood samples were collected to evaluate changes in hepatic and renal functions of animals. The moderate inflammatory reaction (2) observed for 7 d in the subcutaneous tissue decreased with time for all cements. The thickness of inflammatory capsules also presented a significant decrease with time (P<.05). Systemically, all cements caused adverse inflammatory reactions in the liver and kidney, being more evident for MTA, persisting until the end of the analysis. Liver functions increased significantly for MTA during 30 d (P<.05). The different cements induced to a locally limited inflammatory reaction. However, from the systemic point of view, the cements promoted significant inflammatory reactions in the liver and kidney. For MTA, the reactions were more accentuated.

Effect of Maillard reaction products on the physical and antimicrobial properties of edible films based on ε-polylysine and chitosan.

PubMed

Wang, Yingying; Liu, Fuguo; Liang, Chunxuan; Yuan, Fang; Gao, Yanxiang

2014-11-01

Edible films based on Maillard reaction products (MRPs) of ε-polylysine and chitosan, without the use of any plasticiser, were prepared by solution casting. The effect of Maillard reaction parameters (reaction time and the ratio of polylysine/chitosan) of ε-polylysine and chitosan on the structure, moisture content, water solubility, total colour difference and mechanical properties of edible films formed by MRPs were systematically evaluated. Scanning electron microscopy confirmed that edible films prepared by the MRPs of ε-polylysine and chitosan through the Maillard reaction exhibited a more compact and dense structure than those from the mixture of biopolymers without the presence of MRPs. The tensile strength and % elongation values of films from the mixture were decreased significantly with the rise of ε-polylysine (P < 0.05). The moisture content of the films was not significantly affected by Maillard reaction, whereas water solubility was decreased and total colour difference was increased significantly (P < 0.05) with the extension of Maillard reaction time. In addition, antimicrobial activity of chitosan films against E. coli and S. aureus. could be achieved by incorporating ε-polylysine into chitosan. These films can ensure food quality and safety, especially for coating highly perishable foods, such as meat products. © 2014 Society of Chemical Industry. © 2014 Society of Chemical Industry.

Associations Between Physical Fitness Indices and Working Memory in Breast Cancer Survivors and Age-Matched Controls

PubMed Central

Mackenzie, Michael J.; Zuniga, Krystle E.; Raine, Lauren B.; Awick, Elizabeth A.; Hillman, Charles H.; Kramer, Arthur F.

2016-01-01

Abstract Background: This study examined the effects of cardiorespiratory fitness, heart rate recovery, and physical activity on working memory in breast cancer survivors and age-matched controls. Method: Using a case-control design, 32 women who had received a breast cancer diagnosis and completed primary treatment within the past 36-months (11 radiation only; 21 chemotherapy) and 30 age-matched women with no previous cancer diagnosis completed a n-back continuous performance task commonly used as an assessment of working memory. In addition, cardiorespiratory fitness and heart rate recovery were measured during a submaximal graded exercise test and physical activity was measured using 7-days of accelerometer monitoring. Results: Breast cancer survivors who had received chemotherapy had poorer heart rate recovery (p = .010) and engaged in less physical activity than women who had received radiation only (p = .004) or non-cancer controls (p = .029). Cancer treatment (radiation; chemotherapy) predicted differences in reaction times on the 1-back working memory task (p = .029). However, more rapid heart rate recovery predicted shorter reaction times on the 1-back task in the age-matched control group (p = .002). All participants with greater cardiorespiratory fitness displayed greater accuracy independent of disease status on the 1-back task (p = .017). No significant group differences in reaction times were observed for 2-back target trials between breast cancer survivors and controls. However, greater total physical activity predicted shorter reaction times in breast cancer survivors (radiation, chemotherapy) on the 2-back task (p = .014). In addition, all participants who exhibited more rapid heart rate recovery demonstrated better greater accuracy regardless of disease status (p = .013). Conclusion: These findings support differences in physical activty participation, heart rate recovery, and 1- and 2-back working memory reaction times between breast cancer survivors and age-matched controls. Greater cardiorespiratory fitness, heart rate recovery, and physical activity were positively associated with better working memory performance across conditions. PMID:26418463

Functional network mediates age-related differences in reaction time: a replication and extension study

PubMed Central

Gazes, Yunglin; Habeck, Christian; O'Shea, Deirdre; Razlighi, Qolamreza R; Steffener, Jason; Stern, Yaakov

2015-01-01

Introduction A functional activation (i.e., ordinal trend) pattern was previously identified in both young and older adults during task-switching performance, the expression of which correlated with reaction time. The current study aimed to (1) replicate this functional activation pattern in a new group of fMRI activation data, and (2) extend the previous study by specifically examining whether the effect of aging on reaction time can be explained by differences in the activation of the functional activation pattern. Method A total of 47 young and 50 older participants were included in the extension analysis. Participants performed task-switching as the activation task and were cued by the color of the stimulus for the task to be performed in each block. To test for replication, two approaches were implemented. The first approach tested the replicability of the predictive power of the previously identified functional activation pattern by forward applying the pattern to the Study II data and the second approach was rederivation of the activation pattern in the Study II data. Results Both approaches showed successful replication in the new data set. Using mediation analysis, expression of the pattern from the first approach was found to partially mediate age-related effects on reaction time such that older age was associated with greater activation of the brain pattern and longer reaction time, suggesting that brain activation efficiency (defined as “the rate of activation increase with increasing task difficulty” in Neuropsychologia 47, 2009, 2015) of the regions in the Ordinal trend pattern directly accounts for age-related differences in task performance. Discussion The successful replication of the functional activation pattern demonstrates the versatility of the Ordinal Trend Canonical Variates Analysis, and the ability to summarize each participant's brain activation map into one number provides a useful metric in multimodal analysis as well as cross-study comparisons. PMID:25874162

Traumatic reactions as predictors of posttraumatic stress six months after the Oklahoma City bombing.

PubMed

Tucker, P; Dickson, W; Pfefferbaum, B; McDonald, N B; Allen, G

1997-09-01

This study attempted to identify remembered reactions of Oklahoma City residents at the time of the April 1995 terrorist bombing that predicted later development of posttraumatic stress symptoms. Eighty-six adults who sought help for distress related to the bombing six months after it occurred completed a survey about demographic characteristics, level of exposure to the event, symptoms of grief, retrospective reports of reactions at the time of the trauma, current posttraumatic stress symptoms, and coping strategies. To identify immediate bombing reactions predictive of later distress, retrospective reports of reactions to the trauma were correlated with current posttraumatic stress symptoms. Multiple regression analysis was used to determine which reactions predicted the emergence of posttraumatic stress symptoms. Reactions of being nervous and being upset by how other people acted when the bombing occurred accounted for about one-third of the total variation in posttraumatic stress symptom scores and thus were major predictors of posttraumatic stress. These results differ from those of other studies in which peritraumatic dissociation, or dissociation at the time of the event, was more predictive than anxiety for developing later distress. The results suggest that persons who experience significant anxiety at the time of the traumatic event may continue to experience distress. Those who are overly concerned about others' actions may be showing diminished interpersonal trust, evidence of terrorism's ability to erode social harmony.

A simple route to shape controlled CdS nanoparticles

NASA Astrophysics Data System (ADS)

Nejo, Ayorinde O.; Nejo, Adeola A.; Pullabhotla, Rajasekhar V. S. R.; Revaprasadu, Neerish

2013-02-01

We report the synthesis of CdS nanoparticles in the form of spheres, triangles and wire-like structures. The method involves the reaction of reduced sulfur with a cadmium salt followed by thermolysis in hexadecylamine (HDA). The different shapes were obtained by variation of reaction conditions such as reaction time, temperature and cadmium source. The optical studies show the particles to be quantum confined and luminescent at room temperature.

Overlap of movement planning and movement execution reduces reaction time.

PubMed

Orban de Xivry, Jean-Jacques; Legrain, Valéry; Lefèvre, Philippe

2017-01-01

Motor planning is the process of preparing the appropriate motor commands in order to achieve a goal. This process has largely been thought to occur before movement onset and traditionally has been associated with reaction time. However, in a virtual line bisection task we observed an overlap between movement planning and execution. In this task performed with a robotic manipulandum, we observed that participants (n = 30) made straight movements when the line was in front of them (near target) but often made curved movements when the same target was moved sideways (far target, which had the same orientation) in such a way that they crossed the line perpendicular to its orientation. Unexpectedly, movements to the far targets had shorter reaction times than movements to the near targets (mean difference: 32 ms, SE: 5 ms, max: 104 ms). In addition, the curvature of the movement modulated reaction time. A larger increase in movement curvature from the near to the far target was associated with a larger reduction in reaction time. These highly curved movements started with a transport phase during which accuracy demands were not taken into account. We conclude that an accuracy demand imposes a reaction time penalty if processed before movement onset. This penalty is reduced if the start of the movement consists of a transport phase and if the movement plan can be refined with respect to accuracy demands later in the movement, hence demonstrating an overlap between movement planning and execution. In the planning of a movement, the brain has the opportunity to delay the incorporation of accuracy requirements of the motor plan in order to reduce the reaction time by up to 100 ms (average: 32 ms). Such shortening of reaction time is observed here when the first phase of the movement consists of a transport phase. This forces us to reconsider the hypothesis that motor plans are fully defined before movement onset. Copyright © 2017 the American Physiological Society.

Overlap of movement planning and movement execution reduces reaction time

PubMed Central

Legrain, Valéry; Lefèvre, Philippe

2016-01-01

Motor planning is the process of preparing the appropriate motor commands in order to achieve a goal. This process has largely been thought to occur before movement onset and traditionally has been associated with reaction time. However, in a virtual line bisection task we observed an overlap between movement planning and execution. In this task performed with a robotic manipulandum, we observed that participants (n = 30) made straight movements when the line was in front of them (near target) but often made curved movements when the same target was moved sideways (far target, which had the same orientation) in such a way that they crossed the line perpendicular to its orientation. Unexpectedly, movements to the far targets had shorter reaction times than movements to the near targets (mean difference: 32 ms, SE: 5 ms, max: 104 ms). In addition, the curvature of the movement modulated reaction time. A larger increase in movement curvature from the near to the far target was associated with a larger reduction in reaction time. These highly curved movements started with a transport phase during which accuracy demands were not taken into account. We conclude that an accuracy demand imposes a reaction time penalty if processed before movement onset. This penalty is reduced if the start of the movement consists of a transport phase and if the movement plan can be refined with respect to accuracy demands later in the movement, hence demonstrating an overlap between movement planning and execution. NEW & NOTEWORTHY In the planning of a movement, the brain has the opportunity to delay the incorporation of accuracy requirements of the motor plan in order to reduce the reaction time by up to 100 ms (average: 32 ms). Such shortening of reaction time is observed here when the first phase of the movement consists of a transport phase. This forces us to reconsider the hypothesis that motor plans are fully defined before movement onset. PMID:27733598

Auditory and Visual Interhemispheric Communication in Musicians and Non-Musicians

PubMed Central

Woelfle, Rebecca; Grahn, Jessica A.

2013-01-01

The corpus callosum (CC) is a brain structure composed of axon fibres linking the right and left hemispheres. Musical training is associated with larger midsagittal cross-sectional area of the CC, suggesting that interhemispheric communication may be faster in musicians. Here we compared interhemispheric transmission times (ITTs) for musicians and non-musicians. ITT was measured by comparing simple reaction times to stimuli presented to the same hemisphere that controlled a button-press response (uncrossed reaction time), or to the contralateral hemisphere (crossed reaction time). Both visual and auditory stimuli were tested. We predicted that the crossed-uncrossed difference (CUD) for musicians would be smaller than for non-musicians as a result of faster interhemispheric transfer times. We did not expect a difference in CUDs between the visual and auditory modalities for either musicians or non-musicians, as previous work indicates that interhemispheric transfer may happen through the genu of the CC, which contains motor fibres rather than sensory fibres. There were no significant differences in CUDs between musicians and non-musicians. However, auditory CUDs were significantly smaller than visual CUDs. Although this auditory-visual difference was larger in musicians than non-musicians, the interaction between modality and musical training was not significant. Therefore, although musical training does not significantly affect ITT, the crossing of auditory information between hemispheres appears to be faster than visual information, perhaps because subcortical pathways play a greater role for auditory interhemispheric transfer. PMID:24386382

Response preparation and intra-individual reaction time variability in schizophrenia.

PubMed

Dankinas, Denisas; Mėlynytė, Sigita; Šiurkutė, Aldona; Dapšys, Kastytis

2016-01-01

Background. It is important to prepare response in advance to increase the efficiency of its execution. The process of response preparation is usually studied using the precueing paradigm. In this paradigm subjects have to employ the preceding information about further imperative stimulus to perform proper response preparation, which shortens the reaction time of subsequent response execution. Previous studies detected the impairment of response preparation in schizophrenia only with the help of electroencephalographic parameters, but not with the assessing of reaction time. Therefore, in this study we attempted to find a behavioural parameter that could detect impairment in response preparation of schizophrenia patients. It was recently found that appropriate response preparation not only shortens the reaction time but also increases its stability, which is measured with the intra-individual reaction time variability. It was also revealed that response stability could better find cognitive dysfunction in some studies of schizophrenia disorder than classical behavioural parameters. Hence, the main goal of this study was to verify if intra-individual reaction time variability could detect the impairment of response preparation in schizophrenia patients. Materials and methods. In order to achieve the main purpose, we carried out a study with 14 schizophrenia patients and 14 control group subjects. We used precueing paradigm in our research, in which participants had to employ information about stimulus probability for the proper response preparation. Results. Our main result showed that despite the responses of schizophrenia patients were faster to the high-probability stimulus than to the low-probability one ( F (1, 13) = 30.9, p < 0.001), intra-individual reaction time variability did not differ in this group between the responses to more and less probable stimuli ( F (1, 13) = 0.64, p = 0.44). Conclusions. Results of the study suggest that people with schizophrenia were able to use precueing probabilistic information only to shorten their reaction time, but not to increase response stability. Therefore, it was found that intra-individual reaction time variability parameter could detect response preparation impairment in schizophrenia, and could be used in clinical purposes.

Hydrothermal pre-treatment of oil palm empty fruit bunch into fermentable sugars

NASA Astrophysics Data System (ADS)

Muhd Ali, M. D.; Tamunaidu, P.; Nor Aslan, A. K. H.; Morad, N. A.; Sugiura, N.; Goto, M.; Zhang, Z.

2016-06-01

Presently oil palm empty fruit bunch (OPEFB) is one of the solid waste which is produced daily whereby it is usually left at plantation site to act as organic fertilizer for the plants to ensure the sustainability of fresh fruit bunch. The major drawback in biomass conversion technology is the difficulty of degrading the material in a short period of time. A pre-treatment step is required to break the lignocellulosic biomass to easily accessible carbon sources for further use in the production of fuels and fine chemicals. Therefore, this study investigated the effect of hydrothermal pre-treatment under different reaction temperatures (100 - 250°C), reaction time (10 - 40 min), solid to solvent ratio of (1:10 - 1:20 w/v) and particle size (0.15 - 1.00 mm) on the solubilization of OPEFB to produce soluble fermentable sugars. The maximum soluble sugars of 68.18 mg glucose per gram of OPEFB were achieved at 175°C of reaction temperature, 20 min of reaction time, 1:15 w/v of solid to solvent ratio for 30 mm of particle size. Results suggest that reaction temperature, reaction time, the amount of solid to solvent ratio and size of the particle are crucial parameters for hydrothermal pretreatment, in achieving a high yield of soluble fermentable sugars.

Interfacing supercritical fluid reaction apparatus with on-line liquid chromatography: monitoring the progress of a synthetic organic reaction performed in supercritical fluid solution.

PubMed

Ramsey, Edward D; Li, Ben; Guo, Wei; Liu, Jing Y

2015-04-03

An interface has been developed that connects a supercritical fluid reaction (SFR) vessel directly on-line to a liquid chromatograph. The combined SFR-LC system has enabled the progress of the esterification reaction between phenol and benzoyl chloride to synthesize phenyl benzoate in supercritical fluid carbon dioxide solution to be dynamically monitored. This was achieved by the periodic SFR-LC analysis of samples directly withdrawn from the esterification reaction mixture. Using the series of SFR-LC analysis results obtained for individual esterification reactions, the reaction progress profile for each esterification reaction was obtained by expressing the measured yield of phenyl benzoate as a function of reaction time. With reaction temperature fixed at 75°C, four sets (n=3) of SFR-LC reaction progress profiles were obtained at four different SFR pressures ranging from 13.79 to 27.58 MPa. The maximum SFR yield obtained for phenyl benzoate using a standard set of reactant concentrations was 85.2% (R.S.D. 4.2%) when the reaction was performed at 13.79 MPa for 90 min. In comparison, a phenyl benzoate yield of less than 0.3% was obtained using the same standard reactant concentrations after 90 min reaction time at 75°C using either: heptane, ethyl acetate or acetonitrile as conventional organic reaction solvents. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaluation of Photopolymerization Kinetics by Means of Transmittance Measurements

NASA Astrophysics Data System (ADS)

Bovesecchi, G.; Coppa, P.; Armellin, E.; Cerroni, L.

2018-04-01

Polymeric resins are widely used for dental reconstruction, and most resins use camphorquinone as activator of the polymerization reaction, through the absorption of light at a defined wavelength range (from 400 nm to 460 nm). During the photopolymerization curing, transparency of these resins changes and transmittance variation can be detected by photodiode and bolometer measurements. This change can be used as an index of the reaction rate, and the kinetic parameter k (reaction rate) can be evaluated from transmittance data by means of nonlinear regression. The relation between k and the light intensity impinging on the resin sample can thus be obtained. In the present work, tests were carried out using the resin Enamel Plus HFO GE2. Results reveal the presence of two different polymerization reactions at two different intensity ranges. The obtained k values were used to predict the most suited curing times for different light intensities. The proposed methodology can be applied to different dental reconstruction materials, provided that the material is partially transparent and that its transparency changes during the polymerization reaction.

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface.

PubMed

den Boer, Duncan; Li, Min; Habets, Thomas; Iavicoli, Patrizia; Rowan, Alan E; Nolte, Roeland J M; Speller, Sylvia; Amabilino, David B; De Feyter, Steven; Elemans, Johannes A A W

2013-07-01

Manganese porphyrins have been extensively investigated as model systems for the natural enzyme cytochrome P450 and as synthetic oxidation catalysts. Here, we report single-molecule studies of the multistep reaction of manganese porphyrins with molecular oxygen at a solid/liquid interface, using a scanning tunnelling microscope (STM) under environmental control. The high lateral resolution of the STM, in combination with its sensitivity to subtle differences in the electronic properties of molecules, allowed the detection of at least four distinct reaction species. Real-space and real-time imaging of reaction dynamics enabled the observation of active sites, immobile on the experimental timescale. Conversions between the different species could be tuned by the composition of the atmosphere (argon, air or oxygen) and the surface bias voltage. By means of extensive comparison of the results to those obtained by analogous solution-based chemistry, we assigned the observed species to the starting compound, reaction intermediates and products.

Postural stability, clicker reaction time and bow draw force predict performance in elite recurve archery.

PubMed

Spratford, Wayne; Campbell, Rhiannon

2017-06-01

Recurve archery is an Olympic sport that requires extreme precision, upper body strength and endurance. The purpose of this research was to quantify how postural stability variables both pre- and post-arrow release, draw force, flight time, arrow length and clicker reaction time, collectively, impacted on the performance or scoring outcomes in elite recurve archery athletes. Thirty-nine elite-level recurve archers (23 male and 16 female; mean age = 24.7 ± 7.3 years) from four different countries volunteered to participate in this study prior to competing at a World Cup event. An AMTI force platform (1000Hz) was used to obtain centre of pressure (COP) measurements 1s prior to arrow release and 0.5s post-arrow release. High-speed footage (200Hz) allowed for calculation of arrow flight time and score. Results identified clicker reaction time, draw force and maximum sway speed as the variables that best predicted shot performance. Specifically, reduced clicker reaction time, greater bow draw force and reduced postural sway speed post-arrow release were predictors of higher scoring shots. It is suggested that future research should focus on investigating shoulder muscle tremors at full draw in relation to clicker reaction time, and the effect of upper body strength interventions (specifically targeting the musculature around the shoulder girdle) on performance in recurve archers.

Impaired motor inhibition in adults who stutter - evidence from speech-free stop-signal reaction time tasks.

PubMed

Markett, Sebastian; Bleek, Benjamin; Reuter, Martin; Prüss, Holger; Richardt, Kirsten; Müller, Thilo; Yaruss, J Scott; Montag, Christian

2016-10-01

Idiopathic stuttering is a fluency disorder characterized by impairments during speech production. Deficits in the motor control circuits of the basal ganglia have been implicated in idiopathic stuttering but it is unclear how these impairments relate to the disorder. Previous work has indicated a possible deficiency in motor inhibition in children who stutter. To extend these findings to adults, we designed two experiments to probe executive motor control in people who stutter using manual reaction time tasks that do not rely on speech production. We used two versions of the stop-signal reaction time task, a measure for inhibitory motor control that has been shown to rely on the basal ganglia circuits. We show increased stop-signal reaction times in two independent samples of adults who stutter compared to age- and sex-matched control groups. Additional measures involved simple reaction time measurements and a task-switching task where no group difference was detected. Results indicate a deficiency in inhibitory motor control in people who stutter in a task that does not rely on overt speech production and cannot be explained by general deficits in executive control or speeded motor execution. This finding establishes the stop-signal reaction time as a possible target for future experimental and neuroimaging studies on fluency disorders and is a further step towards unraveling the contribution of motor control deficits to idiopathic stuttering. Copyright © 2016 Elsevier Ltd. All rights reserved.

Probabilistic motor sequence learning in a virtual reality serial reaction time task.

PubMed

Sense, Florian; van Rijn, Hedderik

2018-01-01

The serial reaction time task is widely used to study learning and memory. The task is traditionally administered by showing target positions on a computer screen and collecting responses using a button box or keyboard. By comparing response times to random or sequenced items or by using different transition probabilities, various forms of learning can be studied. However, this traditional laboratory setting limits the number of possible experimental manipulations. Here, we present a virtual reality version of the serial reaction time task and show that learning effects emerge as expected despite the novel way in which responses are collected. We also show that response times are distributed as expected. The current experiment was conducted in a blank virtual reality room to verify these basic principles. For future applications, the technology can be used to modify the virtual reality environment in any conceivable way, permitting a wide range of previously impossible experimental manipulations.

Patients with breakthrough reactions to iodinated contrast media have low incidence of positive skin tests.

PubMed

Berti, A; Della-Torre, E; Yacoub, Mr; Tombetti, E; Canti, V; Sabbadini, M G; Colombo, G

2016-07-01

The term "breakthrough reactions" designates repeated hypersensitivity reactions to iodinated contrast media (ICM) despite premedication with glucocorticoids and antihistamines. We aimed to retrospectively evaluate the rate of positive skin test (STs) in our cohort of patients with previous breakthrough reactions to different ICMs. A series of 35 patients, who experienced at least one breakthrough reaction to ICM and who underwent STs within 6 months from the reaction were studied, and results were compared to a control group of patients with a first hypersensitivity reaction occurred without premedication. Skin prick tests (SPT), intradermal tests (IDT) and patch tests (PT) at different dilutions, with a set of three to four ICM were performed. Of the 35 patients with prior breakthrough reactions, 57% had an immediate reaction (IR) and 43% had a non-immediate reaction (NIR). Patients who experienced the first hypersensitivity IR or NIR, later had one or more breakthrough IR or NIR, respectively. Overall, 29% (10/35) of patients with prior breakthrough reactions resulted positive to STs compared to 57% (16/28) of the control group (p < 0.05). No significant difference in allergy history, age, sex, other clinical / demographic features nor chronic use of ACE-inhibitor, beta-blockers or NSAIDs was observed. This preliminary finding suggests that patients with prior breakthrough reactions have significantly lower immunologically proven ICM reactions (positive STs) if compared to non-breakthrough patients. According to that, a considerable number of breakthrough reactions seems to be non-allergic hypersensitivity reactions or reactions which could be mostly prevented by a proper, well-timed skin testing. Larger prospective studies are needed to confirm these results, with a more careful analysis of patients' risk factors, a laboratory assessment that includes an in vitro allergy diagnostics, and hopefully a drug provocation test for selected cases.

Quantum chemistry and TST study of the mechanism and kinetics of the butadiene and isoprene reactions with mercapto radicals

NASA Astrophysics Data System (ADS)

Francisco-Márquez, Misaela; Alvarez-Idaboy, J. Raul; Galano, Annia; Vivier-Bunge, Annik

2008-03-01

The reactions of isoprene and butadiene with SH rad radicals have been investigated by density functional theory and ab initio molecular orbital theories. We report the thermodynamics and kinetics of four different pathways, involving addition of SH rad radicals to all double-bonded carbon atoms. Calculations have been performed on all stationary points using BHandHLYP functional, Moller-Plesset perturbation theory to second-order (MP2) and the composite CBS-QB3 method at the MP2 optimized geometries and frequencies. Pre-reactive complexes have been identified. The apparent activation energies are negative for SH rad addition at the terminal carbon atoms and are slightly smaller than those for OH rad addition at the same positions. The calculated overall rate coefficient for butadiene + SH rad reaction at 298 K is in excellent agreement with the only available experimentally measured value. Activation energies and overall rate coefficients at different temperatures are predicted for the first time for butadiene + SH rad and isoprene + SH rad reactions. The reactions of butadiene and isoprene with SH rad radicals were found to be about four times faster than with OH rad radicals.

Ethanesulfonic acid-based esterification of industrial acidic crude palm oil for biodiesel production.

PubMed

Hayyan, Adeeb; Mjalli, Farouq S; Hashim, Mohd Ali; Hayyan, Maan; AlNashef, Inas M; Al-Zahrani, Saeed M; Al-Saadi, Mohammed A

2011-10-01

An industrial grade acidic crude palm oil (ACPO) pre-treatment process was carried out using ethanesulfonic acid (ESA) as a catalyst in the esterification reaction. ESA was used in different dosages to reduce free fatty acid (FFA) to a minimum level for the second stage of biodiesel production via alkaline transesterification reaction. Different process operating conditions were optimized such as ESA dosage (0.25-3.5% wt/wt), methanol to ACPO molar ratio (1:1-20:1), reaction temperature (40-70 °C), and reaction time (3-150 min). This study revealed the potential use of abundant quantities of ACPO from oil palm mills for biodiesel production. The lab scale results showed the effectiveness of the pre-treatment process using ESA catalyst. Three consecutive catalyst recycling runs were achieved without significant degradation in its performance. Second and third reuse runs needed more reaction time to achieve the target level of FFA content. Esterification and transesterification using ESA and KOH respectively is proposed for biodiesel industrial scale production. The produced biodiesel meets the international standards specifications for biodiesel fuel (EN 14214 and ASTM D6751). Copyright © 2011 Elsevier Ltd. All rights reserved.

Individual differences influence two-digit number processing, but not their analog magnitude processing: a large-scale online study.

PubMed

Huber, Stefan; Nuerk, Hans-Christoph; Reips, Ulf-Dietrich; Soltanlou, Mojtaba

2017-12-23

Symbolic magnitude comparison is one of the most well-studied cognitive processes in research on numerical cognition. However, while the cognitive mechanisms of symbolic magnitude processing have been intensively studied, previous studies have paid less attention to individual differences influencing symbolic magnitude comparison. Employing a two-digit number comparison task in an online setting, we replicated previous effects, including the distance effect, the unit-decade compatibility effect, and the effect of cognitive control on the adaptation to filler items, in a large-scale study in 452 adults. Additionally, we observed that the most influential individual differences were participants' first language, time spent playing computer games and gender, followed by reported alcohol consumption, age and mathematical ability. Participants who used a first language with a left-to-right reading/writing direction were faster than those who read and wrote in the right-to-left direction. Reported playing time for computer games was correlated with faster reaction times. Female participants showed slower reaction times and a larger unit-decade compatibility effect than male participants. Participants who reported never consuming alcohol showed overall slower response times than others. Older participants were slower, but more accurate. Finally, higher grades in mathematics were associated with faster reaction times. We conclude that typical experiments on numerical cognition that employ a keyboard as an input device can also be run in an online setting. Moreover, while individual differences have no influence on domain-specific magnitude processing-apart from age, which increases the decade distance effect-they generally influence performance on a two-digit number comparison task.

Discovery of a Significant Acetone•Hydroperoxy Adduct Chaperone Effect and Its Impact on the Determination of Room Temperature Rate Constants for Acetonylperoxy/Hydroperoxy Self-Reactions and Cross Reaction Via Infrared Kinetic Spectroscopy.

NASA Astrophysics Data System (ADS)

Grieman, F. J.; Hui, A. O.; Okumura, M.; Sander, S. P.

2017-12-01

In order to model the upper troposphere/lower stratosphere in regions containing acetone properly, the kinetics of the acetonylperoxy/hydroperoxy self-reactions and cross reaction have been studied over a wide temperature range using Infrared Kinetic Spectroscopy. We report here the determination of different rate constants for the acetonylperoxy chemistry that we obtained at 298 K compared to currently accepted values. A considerable increase in the observed HO2 self-reaction rate constant due to rate enhancement via the chaperone effect from the reaction between HO2 and the (CH3)2CO•HO2 hydrogen-bonded adduct, even at room temperature, was discovered that was previously ignored. Correct determination of the acetonylperoxy and hydroperoxy kinetics must include this dependence of the HO2 self-reaction rate on acetone concentration. Via excimer laser flash photolysis to create the radical reactants, HO2 absorption was monitored in the infrared by diode laser wavelength modulation detection simultaneously with CH3C(O)CH2O2absorption monitored in the ultraviolet at 300 nm as a function of time. Resulting decay curves were fit concurrently first over a short time scale to obtain the rate constants minimizing subsequent product reactions. Modeling/fitting with a complete reaction scheme was then performed to refine the rate constants and test their veracity. Experiments were carried out over a variety of concentrations of acetone and methanol. Although no effect due to methanol concentration was found at room temperature, the rate constant for the hydroperoxy self-reaction was found to increase linearly with acetone concentration which is interpreted as the adduct being formed and resulting in a chaperone mechanism that enhances the self-reaction rate: (CH3)2CO·HO2 + HO2 → H2O2 + O2 + (CH3)2CO Including this effect, the resulting room temperature rate constants for the cross reaction and the acetonylperoxy self-reaction were found to be 2-3 times smaller than previously reported. This complex formation/chaperone mechanism is similar to that found for methanol, but different in that it occurs at room temperature. No precursor concentration dependence was found for the acetonylperoxy radical reactions. The equilibrium constant for the complex formation will also be presented.

Isoprene/methyl acrylate Diels-Alder reaction in supercritical carbon dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, B.; Akgerman, A.

1999-12-01

The Diels-Alder reaction between isoprene and methyl acrylate was carried out in supercritical carbon dioxide in the temperature range 110--140 C and the pressure range 95.2--176.9 atm in a 300 cm{sup 3} autoclave. The high-pressure phase behavior of the reaction mixture in the vicinity of its critical region was determined in a mixed vessel with a sight window to ensure that all the experiments were performed in the supercritical single-phase region. Kinetic data were obtained at different temperatures, pressures, and reaction times. It was observed that in the vicinity of the critical point the reaction rate constant decreases with increasingmore » pressure. It was also determined that the reaction selectivity does not change with operating conditions. Transition-state theory was used to explain the effect of pressure on reaction rate and product selectivity. Additional experiments were conducted at constant temperature but different phase behaviors (two-phase region, liquid phase, supercritical phase) by adjusting the initial composition and pressure. It was shown that the highest reaction rate is in the supercritical region.« less

The effect of a non-steroidal anti-inflammatory drug on two important predictors for accidental falls: postural balance and manual reaction time. A randomized, controlled pilot study.

PubMed

Hegeman, Judith; Nienhuis, Bart; van den Bemt, Bart; Weerdesteyn, Vivian; van Limbeek, Jacques; Duysens, Jacques

2011-04-01

Accidental falls in older individuals are a major health and research topic. Increased reaction time and impaired postural balance have been determined as reliable predictors for those at risk of falling and are important functions of the central nervous system (CNS). An essential risk factor for falls is medication exposure. Amongst the medications related to accidental falls are the non-steroidal anti-inflammatory drugs (NSAIDs). About 1-10% of all users experience CNS side effects. These side effects, such as dizziness, headaches, drowsiness, mood alteration, and confusion, seem to be more common during treatment with indomethacin. Hence, it is possible that maintenance of (static) postural balance and swift reactions to stimuli are affected by exposure to NSAIDs, indomethacin in particular, consequently putting older individuals at a greater risk for accidental falls. The present study investigated the effect of a high indomethacin dose in healthy middle-aged individuals on two important predictors of falls: postural balance and reaction time. Twenty-two healthy middle-aged individuals (59.5 ± 4.7 years) participated in this double-blind, placebo-controlled, randomized crossover trial. Three measurements were conducted with a week interval each. A measurement consisted of postural balance as a single task and while concurrently performing a secondary cognitive task and reaction time tasks. For the first measurement indomethacin 75 mg (slow-release) or a visually identical placebo was randomly assigned. In total, five capsules were taken orally in the 2.5 days preceding assessment. The second measurement was without intervention, for the final one the first placebo group got indomethacin and vice versa. Repeated measures GLM revealed no significant differences between indomethacin, placebo, and baseline in any of the balance tasks. No differences in postural balance were found between the single and dual task conditions, or on the performance of the dual task itself. Similarly, no differences were found on the manual reaction time tasks. The present study showed that a high indomethacin dose does not negatively affect postural balance and manual reaction time in this healthy middle-aged population. Although the relatively small and young sample limits the direct ability to generalize the results to a population at risk of falling, the results indicate that indomethacin alone is not likely to increase fall risk, as far as this risk is related to above mentioned important functions of the CNS, and not affected by comorbidities. Copyright © 2010 Elsevier B.V. All rights reserved.

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

PubMed

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Hydroxyacetone production from C 3 Criegee intermediates

DOE PAGES

Taatjes, Craig A.; Liu, Fang; Rotavera, Brandon; ...

2016-12-21

Hydroxyacetone (CH 3C(O)CH 2OH) is observed as a stable end product from reactions of the (CH 3) 2COO Criegee intermediate, acetone oxide, in a flow tube coupled with multiplexed photoionization mass spectrometer detection. In the experiment, the isomers at m/z = 74 are distinguished by their different photoionization spectra and reaction times. Hydroxyacetone is observed as a persistent signal at longer reaction times at a higher photoionization threshold of ca. 9.7 eV than Criegee intermediate and definitively identified by comparison with the known photoionization spectrum. Complementary electronic structure calculations reveal multiple possible reaction pathways for hydroxyacetone formation, including unimolecular isomerizationmore » via hydrogen atom transfer and –OH group migration as well as self-reaction of Criegee intermediates. Varying the concentration of Criegee intermediates suggests contributions from both unimolecular and self-reaction pathways to hydroxyacetone. As a result, the hydroxyacetone end product can provide an effective, stable marker for the production of transient Criegee intermediates in future studies of alkene ozonolysis.« less

Effects of bright and blue light on acoustic reaction time and maximum handgrip strength in male athletes: a randomized controlled trial.

PubMed

Knaier, Raphael; Schäfer, Juliane; Rossmeissl, Anja; Klenk, Christopher; Hanssen, Henner; Höchsmann, Christoph; Cajochen, Christian; Schmidt-Trucksäss, Arno

2017-08-01

To assess which type of evening light exposure has the greatest effect on reaction time and maximum handgrip strength. These were pre-specified secondary outcomes in a trial which primarily investigated the influence of light on cycling performance. Seventy-four male athletes were allocated at random to either bright light (BRIGHT), monochromatic blue light (BLUE), or a control condition (CONTROL). Light exposure lasted for 60 min and started 17 h after the individual midpoint of sleep. Reaction time, handgrip strength, and melatonin levels were measured before and after the light exposure. We used analysis of covariance to compare the groups with respect to the investigated outcomes. Two participants had to be excluded retrospectively. The remaining 72 participants had a median age of 23 years. The adjusted difference in reaction time was -1 ms [95% confidence interval (CI) -8, 6] for participants in BRIGHT and 2 ms (95% CI -5, 9) for participants in BLUE, both relative to participants in CONTROL. The adjusted difference in handgrip strength was 0.9 kg (95% CI -1.5, 3.3) for participants in BRIGHT and -0.3 kg (95% CI -2.7, 2.0) for participants in BLUE, both relative to participants in CONTROL. After the light exposure, 17% of participants in BRIGHT, 22% in BLUE, and 29% in CONTROL showed melatonin concentrations of 2 pg/ml or higher. The results suggest that bright light might reduce melatonin levels but neither bright nor blue light exposure in the evening seem to improve reaction time or handgrip strength in athletes.

Behavioral and Neural Sustained Attention Deficits in Bipolar Disorder and Familial Risk of Bipolar Disorder.

PubMed

Pagliaccio, David; Wiggins, Jillian Lee; Adleman, Nancy E; Harkins, Elizabeth; Curhan, Alexa; Towbin, Kenneth E; Brotman, Melissa A; Pine, Daniel S; Leibenluft, Ellen

2017-11-01

Few neuroimaging studies compare individuals affected with bipolar disorder (BP), at high familial risk of BP, and at low risk to identify endophenotypes for BP. None have examined variability in attention, despite promising behavioral work in this area. We used functional magnetic resonance imaging (fMRI) methods uniquely powered to compare the neural correlates of attention variability in these three groups. The present study examined 8- to 25-year-old individuals (n = 106) who completed an fMRI attention task: 24 with BP, 29 at risk based on a first-degree relative with BP, and 53 healthy, low-risk individuals. Group differences in intrasubject variability in reaction time were examined, and a sophisticated fMRI analytic approach was used to quantify precisely trialwise associations between reaction time and brain activity. The latter has not been examined previously in BP or risk of BP. Relative to healthy individuals, those with BP or at risk for BP exhibited increased reaction time variability (F 2,102 = 4.26, p = .02, η p 2 = .08). Importantly, we identified blunted relationships between trialwise variation in reaction time and brain activity in the inferior and middle frontal gyri, precuneus, cingulate cortex, caudate, and postcentral gyrus (all regions: p < .001, η p 2 > .06) in both at-risk and BP individuals compared with healthy, low-risk individuals. This blunting partially mediated group differences in reaction time variability (β = .010, 95% confidence interval 0.002 to 0.020, Sobel Z = 2.08, p = .038). Blunting in key frontal, cingulate, and striatal areas was evident in unaffected, at-risk individuals and in euthymic BP patients. Elucidating such novel neural endophenotypes can facilitate new approaches to BP prediction, diagnosis, and prevention. Published by Elsevier Inc.

Does Occupational Exposure of Shahid Dastghieb International Airport Workers to Radiofrequency Radiation Affect Their Short Term Memory and Reaction Time?

PubMed

Jarideh, S; Taeb, S; Pishva, S M; Haghani, M; Sina, S; Mortazavi, S A R; Hosseini, M A; Nematollahi, S; Shokrpour, N; Hassan Shahi, M; Mortazavi, S M J

2015-09-01

Airport workers are continuously exposed to different levels of radiofrequency microwave (RF/MW) radiation emitted by radar equipments. Radars are extensively used in military and aviation industries. Over the past several years, our lab has focused on the health effects of exposure to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons and MRI. The main goal of this study was to investigate if occupational exposure of Shahid Dastghieb international airport workers to radiofrequency radiation affects their short term memory and reaction time. Thirty two airport workers involved in duties at control and approach tower (21 males and 11 females), with the age range of 27-67 years old (mean age of 37.38), participated voluntary in this study. On the other hand, 29 workers (13 males, and 16 females) whose offices were in the city with no exposure history to radar systems were also participated in this study as the control group. The employees' reaction time and short term memory were analyzed using a standard visual reaction time (VRT) test software and the modified Wechsler memory scale test, respectively. The mean± SD values for the reaction times of the airport employees (N=32) and the control group (N=29) were 0.45±0.12 sec and 0.46±0.17 sec, respectively.  Moreover, in the four subset tests; i.e. paired words, forward digit span, backward digit span and word recognition, the following points were obtained for the airport employees and the control group, respectively: (i) pair words test: 28.00±13.13 and 32.07±11.65, (ii) forward digit span: 8.38±1.40 and 9.03±1.32, (iii) backward digit span: 5.54±1.87 and 6.31±1.46, and (iv) word recognition: 5.73±2.36 and 6.50±1.93. These differences were not statistically significant. The occupational exposure of the employees to the RF radiation in Shahid Dastghieb international airport does not have any significant detrimental effect on their reaction time as well as short term memory.

Does Occupational Exposure of Shahid Dastghieb International Airport Workers to Radiofrequency Radiation Affect Their Short Term Memory and Reaction Time?

PubMed Central

Jarideh, S.; Taeb, S.; Pishva, S. M.; Haghani, M.; Sina, S.; Mortazavi, S. A. R.; Hosseini, M. A.; Nematollahi, S.; Shokrpour, N.; Hassan Shahi, M.; Mortazavi, S. M. J.

2015-01-01

Background Airport workers are continuously exposed to different levels of radiofrequency microwave (RF/MW) radiation emitted by radar equipments. Radars are extensively used in military and aviation industries. Over the past several years, our lab has focused on the health effects of exposure to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons and MRI. The main goal of this study was to investigate if occupational exposure of Shahid Dastghieb international airport workers to radiofrequency radiation affects their short term memory and reaction time. Methods Thirty two airport workers involved in duties at control and approach tower (21 males and 11 females), with the age range of 27-67 years old (mean age of 37.38), participated voluntary in this study. On the other hand, 29 workers (13 males, and 16 females) whose offices were in the city with no exposure history to radar systems were also participated in this study as the control group. The employees’ reaction time and short term memory were analyzed using a standard visual reaction time (VRT) test software and the modified Wechsler memory scale test, respectively. Results The mean± SD values for the reaction times of the airport employees (N=32) and the control group (N=29) were 0.45±0.12 sec and 0.46±0.17 sec, respectively.  Moreover, in the four subset tests; i.e. paired words, forward digit span, backward digit span and word recognition, the following points were obtained for the airport employees and the control group, respectively: (i) pair words test: 28.00±13.13 and 32.07±11.65, (ii) forward digit span: 8.38±1.40 and 9.03±1.32, (iii) backward digit span: 5.54±1.87 and 6.31±1.46, and (iv) word recognition: 5.73±2.36 and 6.50±1.93. These differences were not statistically significant. Conclusion The occupational exposure of the employees to the RF radiation in Shahid Dastghieb international airport does not have any significant detrimental effect on their reaction time as well as short term memory. PMID:26396970

A Flight-Calibrated Methodology for Determination of Cassini Thruster On-Times for Reaction Wheel Biases

NASA Technical Reports Server (NTRS)

Sarani, Sam

2010-01-01

The Cassini spacecraft, the largest and most complex interplanetary spacecraft ever built, continues to undertake unique scientific observations of planet Saturn, Titan, Enceladus, and other moons of the ring world. In order to maintain a stable attitude during the course of its mission, this three-axis stabilized spacecraft uses two different control systems: the Reaction Control System (or RCS) and the Reaction Wheel Assembly (RWA) control system. In the course of its mission, Cassini performs numerous reaction wheel momentum biases (or unloads) using its reaction control thrusters. The use of the RCS thrusters often imparts undesired velocity changes (delta Vs) on the spacecraft and it is crucial for Cassini navigation and attitude control teams to be able to, quickly but accurately, predict the hydrazine usage and delta V vector in Earth Mean Equatorial (J2000) inertial coordinates for reaction wheel bias events, without actually having to spend time and resources simulating the event in a dynamic or hardware-in-the-loop simulation environments. The flight-calibrated methodology described in this paper, and the ground software developed thereof, are designed to provide the RCS thruster on-times, with acceptable accuracy and without any form of dynamic simulation, for reaction wheel biases, along with the hydrazine usage and the delta V in EME-2000 inertial frame.

Reaction time, processing speed and sustained attention in schizophrenia: impact on social functioning.

PubMed

Lahera, Guillermo; Ruiz, Alicia; Brañas, Antía; Vicens, María; Orozco, Arantxa

Previous studies have linked processing speed with social cognition and functioning of patients with schizophrenia. A discriminant analysis is needed to determine the different components of this neuropsychological construct. This paper analyzes the impact of processing speed, reaction time and sustained attention on social functioning. 98 outpatients between 18 and 65 with DSM-5 diagnosis of schizophrenia, with a period of 3 months of clinical stability, were recruited. Sociodemographic and clinical data were collected, and the following variables were measured: processing speed (Trail Making Test [TMT], symbol coding [BACS], verbal fluency), simple and elective reaction time, sustained attention, recognition of facial emotions and global functioning. Processing speed (measured only through the BACS), sustained attention (CPT) and elective reaction time (but not simple) were associated with functioning. Recognizing facial emotions (FEIT) correlated significantly with scores on measures of processing speed (BACS, Animals, TMT), sustained attention (CPT) and reaction time. The linear regression model showed a significant relationship between functioning, emotion recognition (P=.015) and processing speed (P=.029). A deficit in processing speed and facial emotion recognition are associated with worse global functioning in patients with schizophrenia. Copyright © 2017 SEP y SEPB. Publicado por Elsevier España, S.L.U. All rights reserved.

Reliability of the dynavision™ d2 for assessing reaction time performance.

PubMed

Wells, Adam J; Hoffman, Jay R; Beyer, Kyle S; Jajtner, Adam R; Gonzalez, Adam M; Townsend, Jeremy R; Mangine, Gerald T; Robinson, Edward H; McCormack, William P; Fragala, Maren S; Stout, Jeffrey R

2014-01-01

Recently, the Dynavision™ D2 Visuomotor Training Device (D2) has emerged as a tool in the assessment of reaction time (RT); however, information regarding the reliability of the D2 have been limited, and to date, reliability data have been limited to non- generalizable samples. Therefore, the purpose of this study was to establish intraclass correlation coefficients (ICC2,1) for the D2 that are generalizable across a population of recreationally active young adults. Forty-two recreationally active men and women (age: 23.41 ± 4.84 years; height: 1.72 ± 0.11 m; mass: 76.62 ± 18.26 Kg) completed 6 trials for three RT tasks of increasing complexity. Each trial was separated by at least 48-hours. A repeated measures ANOVA was used to detect differences in performance across the six trials. Intraclass correlation coefficients (ICC2,1) standard error of measurement (SEM), and minimal differences (MD) were used to determine the reliability of the D2 from the two sessions with the least significant difference score. Moderate to strong reliability was demonstrated for visual RT (ICC2,1: 0.84, SEM: 0.033), and reactive ability in both Mode A and Mode B tasks (Mode A hits: ICC2,1: 0.75, SEM: 5.44; Mode B hits: ICC2,1: 0.73, SEM: 8.57). Motor RT (ICC2,1: 0.63, SEM: 0.035s) showed fair reliability, while average RT per hit for Modes A and B showed moderate reliability (ICC2,1: 0.68, SEM: 0.43 s and ICC2,1: 0.72, SEM: 0.03 s respectively). It appears that one familiarization trial is necessary for the choice reaction time (CRT) task while three familiarization trials are necessary for reactive RT tasks. In conclusion, results indicate that the Dynavision™ D2 is a reliable device to assess neuromuscular reactivity given that an adequate practice is provided. The data presented are generalizable to a population of recreationally active young adults. Key PointsThe Dynavision™ D2 is a light-training reaction device, developed to train sensory motor integration through the visual system, offering the ability to assess visual and motor reaction to both central and peripheral stimuli, with a capacity to integrate increasing levels of cognitive challenge.The Dynavision™ D2 is a reliable instrument for assessing reaction time in recreationally active young adults.It is recommended that one familiarization trial is necessary for the choice reaction time task assessment to learn the test protocol, while three familiarization trials are needed for reactive ability in Mode A and Mode B before a subsequent reliable baseline score can be established.Significant training effects were observed for all reaction time tests and should be taken into account with continuous trials.

Prismatic displacement effect of progressive multifocal glasses on reaction time and accuracy in elderly people

PubMed Central

Ellison, Ashton C; Campbell, A John; Robertson, M Clare; Sanderson, Gordon F

2014-01-01

Background Multifocal glasses (bifocals, trifocals, and progressives) increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1) map the prismatic displacement of a progressive lens, and 2) test whether this displacement impaired reaction time and accuracy. Methods The reaction times of healthy ≥75-year-olds (31 participants) were measured when grasping for a bar and touching a black line. Participants performed each test twice, wearing their progressives and new, matched single vision (distance) glasses in random order. The line and bar targets were positioned according to the maximum and minimum prismatic displacement effect through the progressive lens, mapped using a focimeter. Results Progressive spectacle lenses have large areas of prismatic displacement in the central visual axis and edges. Reaction time was faster for progressives compared with single vision glasses with a centrally-placed horizontal grab bar (mean difference 101 ms, P=0.011 [repeated measures analysis]) and a horizontal black line placed 300 mm below center (mean difference 80 ms, P=0.007). There was no difference in accuracy between the two types of glasses. Conclusion Older people appear to adapt to the false projection of progressives in the central visual axis. This adaptation means that swapping to new glasses or a large change in prescription may lead to a fall. Frequently updating glasses may be more beneficial. PMID:24872674

Lithium perchlorate-nitromethane-promoted alkylation of anilines with arylmethanols.

PubMed

Zhou, Jun; Mao, Hai-Feng; Wang, Lu; Zou, Jian-Ping; Zhang, Wei

2011-11-01

A new application of lithium perchlorate-nitromethane (LPNM) for the formation of aromatic C-N and C-C bonds is introduced. LPNM-promoted reactions of anilines with diarylmethanols selectively generate N-alkylated anilines or mono and double Friedel-Crafts alkylation products under different conditions by changing the reaction time, reaction temperature, and the ratio of the reactants. This method does not require the use of transition metal catalysts to prepare alkylated aniline derivatives.

An investigation of leg and trunk strength and reaction times of hard-style martial arts practitioners.

PubMed

Donovan, Oliver O; Cheung, Jeanette; Catley, Maria; McGregor, Alison H; Strutton, Paul H

2006-01-01

The purpose of this study was to investigate trunk and knee strength in practitioners of hard-style martial arts. An additional objective was to examine reaction times in these participants by measuring simple reaction times (SRT), choice reaction times (CRT) and movement times (MT). Thirteen high-level martial artists and twelve sedentary participants were tested under isokinetic and isometric conditions on an isokinetic dynamometer. Response and movement times were also measured in response to simple and choice auditory cues. Results indicated that the martial arts group generated a greater body-weight adjusted peak torque with both legs at all speeds during isokinetic extension and flexion, and in isometric extension but not flexion. In isokinetic and isometric trunk flexion and extension, martial artists tended to have higher peak torques than controls, but they were not significantly different (p > 0.05). During the SRT and CRT tasks the martial artists were no quicker in lifting their hand off a button in response to the stimulus [reaction time (RT)] but were significantly faster in moving to press another button [movement time (MT)]. In conclusion, the results reveal that training in a martial art increases the strength of both the flexors and extensors of the leg. Furthermore, they have faster movement times to auditory stimuli. These results are consistent with the physical aspects of the martial arts. Key PointsMartial artists undertaking hard-style martial arts have greater strength in their knee flexor and extensor muscles as tested under isokinetic testing. Under isometric testing conditions they have stronger knee extensors only.The trunk musculature is generally higher under both conditions of testing in the martial artists, although not significantly.The total reaction times of the martial artists to an auditory stimulus were significantly faster than the control participants. When analysed further it was revealed that the decrease in reaction time was due to the movement time component of the total reaction time.The training involved for the practice of the hard-style martial arts increases the strength of muscles involved in kicking. This increased strength is not seen in the trunk muscles. Furthermore, martial artists have a faster response time; the cause of which appears to be only the faster movement time.

An Investigation Of Leg And Trunk Strength And Reaction Times Of Hard-Style Martial Arts Practitioners

PubMed Central

Donovan, Oliver O; Cheung, Jeanette; Catley, Maria; McGregor, Alison H.; Strutton, Paul H.

2006-01-01

The purpose of this study was to investigate trunk and knee strength in practitioners of hard-style martial arts. An additional objective was to examine reaction times in these participants by measuring simple reaction times (SRT), choice reaction times (CRT) and movement times (MT). Thirteen high-level martial artists and twelve sedentary participants were tested under isokinetic and isometric conditions on an isokinetic dynamometer. Response and movement times were also measured in response to simple and choice auditory cues. Results indicated that the martial arts group generated a greater body-weight adjusted peak torque with both legs at all speeds during isokinetic extension and flexion, and in isometric extension but not flexion. In isokinetic and isometric trunk flexion and extension, martial artists tended to have higher peak torques than controls, but they were not significantly different (p > 0.05). During the SRT and CRT tasks the martial artists were no quicker in lifting their hand off a button in response to the stimulus [reaction time (RT)] but were significantly faster in moving to press another button [movement time (MT)]. In conclusion, the results reveal that training in a martial art increases the strength of both the flexors and extensors of the leg. Furthermore, they have faster movement times to auditory stimuli. These results are consistent with the physical aspects of the martial arts. Key Points Martial artists undertaking hard-style martial arts have greater strength in their knee flexor and extensor muscles as tested under isokinetic testing. Under isometric testing conditions they have stronger knee extensors only. The trunk musculature is generally higher under both conditions of testing in the martial artists, although not significantly. The total reaction times of the martial artists to an auditory stimulus were significantly faster than the control participants. When analysed further it was revealed that the decrease in reaction time was due to the movement time component of the total reaction time. The training involved for the practice of the hard-style martial arts increases the strength of muscles involved in kicking. This increased strength is not seen in the trunk muscles. Furthermore, martial artists have a faster response time; the cause of which appears to be only the faster movement time. PMID:24376366

Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: influence of lapse time of reaction.

PubMed

Lee, Kyong-Hwan; Shin, Dae-Hyun

2007-01-01

Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 degrees C) and high (400 degrees C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 degrees C was firstly aromatic products and then olefin products, while at 400 degrees C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 degrees C) and 83 min (at 400 degrees C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was concluded that the characteristics of liquid product on the pyrolysis of plastic mixtures were strongly influenced by lapse time of reaction and degradation temperature.

Tunneling Flight Time, Chemistry, and Special Relativity.

PubMed

Petersen, Jakob; Pollak, Eli

2017-09-07

Attosecond ionization experiments have not resolved the question "What is the tunneling time?". Different definitions of tunneling time lead to different results. Second, a zero tunneling time for a material particle suggests that the nonrelativistic theory includes speeds greater than the speed of light. Chemical reactions, occurring via tunneling, should then not be considered in terms of a nonrelativistic quantum theory calling into question quantum dynamics computations on tunneling reactions. To answer these questions, we define a new experimentally measurable paradigm, the tunneling flight time, and show that it vanishes for scattering through an Eckart or a square barrier, irrespective of barrier length or height, generalizing the Hartman effect. We explain why this result does not lead to experimental measurement of speeds greater than the speed of light. We show that this tunneling is an incoherent process by comparing a classical Wigner theory with exact quantum mechanical computations.

Reaction Buildup of PBX Explosives JOB-9003 under Different Initiation Pressures

NASA Astrophysics Data System (ADS)

Zhang, Xu; Wang, Yan-fei; Hung, Wen-bin; Gu, Yan; Zhao, Feng; Wu, Qiang; Yu, Xin; Yu, Heng

2017-04-01

Aluminum-based embedded multiple electromagnetic particle velocity gauge technique has been developed in order to measure the shock initiation behavior of JOB-9003 explosives. In addition, another gauge element called a shock tracker has been used to monitor the progress of the shock front as a function of time, thus providing a position-time trajectory of the wave front as it moves through the explosive sample. The data are used to determine the position and time for shock to detonation transition. All the experimental results show that: the rising-up time of Al-based electromagnetic particle velocity gauge was very fast and less than 20 ns; the reaction buildup velocity profiles and the position-time for shock to detonation transition of HMX-based PBX explosive JOB-9003 with 1-8 mm depth from the origin of impact plane under different initiation pressures are obtained with high accuracy.

Nitropyrroles, Diels-Alder reactions assisted by microwave irradiation and solvent effect. An experimental and theoretical study

NASA Astrophysics Data System (ADS)

Mancini, Pedro M. E.; Kneeteman, María N.; Cainelli, Mauro; Ormachea, Carla M.; Domingo, Luis R.

2017-11-01

The behaviors of N-tosylnitropyrroles acting as electrophilic dienophiles in polar Diels-Alder reactions joint to different dienes of increeased nucleophilicity are analyzed. The reactions were developed under microwave irradiation using toluene or protic ionic liquids (PILs) as solvents and in free solvent conditions. In all the cases explored we observed good yields in short reaction times. For these reactions, the free solvent condition and the use of protic ionic liquids as solvents offer similar results. However, the free solvent conditions favor environmental sustainability. The role of PILs in these polar Diels-Alder reactions has been theoretically studied within the Molecular Electron Density Theory.

Spectroscopic characteristics of carbon dots (C-dots) derived from carbon fibers and conversion to sulfur-bridged C-dots nanosheets.

PubMed

Vinci, John C; Ferrer, Ivonne M; Guterry, Nathan W; Colón, Verónica M; Destino, Joel F; Bright, Frank V; Colón, Luis A

2015-09-01

We synthesized sub-10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub-10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size.

From conservative to reactive transport under diffusion-controlled conditions

NASA Astrophysics Data System (ADS)

Babey, Tristan; de Dreuzy, Jean-Raynald; Ginn, Timothy R.

2016-05-01

We assess the possibility to use conservative transport information, such as that contained in transit time distributions, breakthrough curves and tracer tests, to predict nonlinear fluid-rock interactions in fracture/matrix or mobile/immobile conditions. Reference simulated data are given by conservative and reactive transport simulations in several diffusive porosity structures differing by their topological organization. Reactions includes nonlinear kinetically controlled dissolution and desorption. Effective Multi-Rate Mass Transfer models (MRMT) are calibrated solely on conservative transport information without pore topology information and provide concentration distributions on which effective reaction rates are estimated. Reference simulated reaction rates and effective reaction rates evaluated by MRMT are compared, as well as characteristic desorption and dissolution times. Although not exactly equal, these indicators remain very close whatever the porous structure, differing at most by 0.6% and 10% for desorption and dissolution. At early times, this close agreement arises from the fine characterization of the diffusive porosity close to the mobile zone that controls fast mobile-diffusive exchanges. At intermediate to late times, concentration gradients are strongly reduced by diffusion, and reactivity can be captured by a very limited number of rates. We conclude that effective models calibrated solely on conservative transport information like MRMT can accurately estimate monocomponent kinetically controlled nonlinear fluid-rock interactions. Their relevance might extend to more advanced biogeochemical reactions because of the good characterization of conservative concentration distributions, even by parsimonious models (e.g., MRMT with 3-5 rates). We propose a methodology to estimate reactive transport from conservative transport in mobile-immobile conditions.

A comparative study of visual reaction time in table tennis players and healthy controls.

PubMed

Bhabhor, Mahesh K; Vidja, Kalpesh; Bhanderi, Priti; Dodhia, Shital; Kathrotia, Rajesh; Joshi, Varsha

2013-01-01

Visual reaction time is time required to response to visual stimuli. The present study was conducted to measure visual reaction time in 209 subjects, 50 table tennis (TT) players and 159 healthy controls. The visual reaction time was measured by the direct RT computerized software in healthy controls and table tennis players. Simple visual reaction time was measured. During the reaction time testing, visual stimuli were given for eighteen times and average reaction time was taken as the final reaction time. The study shows that table tennis players had faster reaction time than healthy controls. On multivariate analysis, it was found that TT players had 74.121 sec (95% CI 98.8 and 49.4 sec) faster reaction time compared to non-TT players of same age and BMI. Also playing TT has a profound influence on visual reaction time than BMI. Our study concluded that persons involved in sports are having good reaction time as compared to controls. These results support the view that playing of table tennis is beneficial to eye-hand reaction time, improve the concentration and alertness.

Singular trajectories: space-time domain topology of developing speckle fields

NASA Astrophysics Data System (ADS)

Vasil'ev, Vasiliy; Soskin, Marat S.

2010-02-01

It is shown the space-time dynamics of optical singularities is fully described by singularities trajectories in space-time domain, or evolution of transverse coordinates(x, y) in some fixed plane z0. The dynamics of generic developing speckle fields was realized experimentally by laser induced scattering in LiNbO3:Fe photorefractive crystal. The space-time trajectories of singularities can be divided topologically on two classes with essentially different scenario and duration. Some of them (direct topological reactions) consist from nucleation of singularities pair at some (x, y, z0, t) point, their movement and annihilation. They possess form of closed loops with relatively short time of existence. Another much more probable class of trajectories are chain topological reactions. Each of them consists from sequence of links, i.e. of singularities nucleation in various points (xi yi, ti) and following annihilation of both singularities in other space-time points with alien singularities of opposite topological indices. Their topology and properties are established. Chain topological reactions can stop on the borders of a developing speckle field or go to infinity. Examples of measured both types of topological reactions for optical vortices (polarization C points) in scalar (elliptically polarized) natural developing speckle fields are presented.

Response of beech and oaks to wounds made at different times of the year

Treesearch

Dirk Dujesiefken; Walter Liese; Walter Shortle; Rakesh Minocha

2005-01-01

Tree care, expecially pruning, is still mostly done in the dormant time. Such treatments expose live inner bark, the vascular cambium, and functioning outer sapwood to harsh external influences followed often by infection of pathogens. Investigations about response reactions of beech and oak to wounding made in different times of the year showed that wound closure was...

Dynamic Parameters Variability: Time Interval Interference on Ground Reaction Force During Running.

PubMed

Pennone, Juliana; Mezêncio, Bruno; Amadio, Alberto C; Serrão, Júlio C

2016-04-01

The aim of this study was to determine the effect of the time between measures on ground reaction force running variability; 15 healthy men (age = 23.8 ± 3.7 years; weight = 72.8 ± 7.7 kg; height 174.3 ± 8.4 cm) performed two trials of running 45 minutes at 9 km/hr at intervals of seven days. The ground reaction forces were recorded every 5 minutes. The coefficients of variation of indicative parameters of the ground reaction forces for each condition were compared. The coefficients of variations of the ground reaction forces curve analyzed between intervals and sessions were 21.9% and 21.48%, respectively. There was no significant difference for the ground reaction forces parameters Fy1, tFy1, TC1, Imp50, Fy2, and tFy2 between intervals and sessions. Although the ground reaction forces variables present a natural variability, this variability in intervals and in sessions remained consistent, ensuring a high reliability in repeated measures designs. © The Author(s) 2016.

Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst for the Friedel-Crafts Acylation Reaction in Ambient Condition.

PubMed

Jadhav, Arvind H; Chinnappan, Amutha; Hiremath, Vishwanath; Seo, Jeong Gil

2015-10-01

Aluminum trichloride (AlCl3) impregnated molybdenum oxide heterogeneous nano-catalyst was prepared by using simple impregnation method. The prepared heterogeneous catalyst was characterized by powder X-ray diffraction, FT-IR spectroscopy, solid-state NMR spectroscopy, SEM imaging, and EDX mapping. The catalytic activity of this protocol was evaluated as heterogeneous catalyst for the Friedel-Crafts acylation reaction at room temperature. The impregnated MoO4(AlCl2)2 catalyst showed tremendous catalytic activity in Friedel-Crafts acylation reaction under solvent-free and mild reaction condition. As a result, 84.0% yield of acyl product with 100% consumption of reactants in 18 h reaction time at room temperature was achieved. The effects of different solvents system with MoO4(AlCl2)2 catalyst in acylation reaction was also investigated. By using optimized reaction condition various acylated derivatives were prepared. In addition, the catalyst was separated by simple filtration process after the reaction and reused several times. Therefore, heterogeneous MoO4(AlCl2)2 catalyst was found environmentally benign catalyst, very convenient, high yielding, and clean method for the Friedel-Crafts acylation reaction under solvent-free and ambient reaction condition.

Wavelet-based surrogate time series for multiscale simulation of heterogeneous catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savara, Aditya Ashi; Daw, C. Stuart; Xiong, Qingang

We propose a wavelet-based scheme that encodes the essential dynamics of discrete microscale surface reactions in a form that can be coupled with continuum macroscale flow simulations with high computational efficiency. This makes it possible to simulate the dynamic behavior of reactor-scale heterogeneous catalysis without requiring detailed concurrent simulations at both the surface and continuum scales using different models. Our scheme is based on the application of wavelet-based surrogate time series that encodes the essential temporal and/or spatial fine-scale dynamics at the catalyst surface. The encoded dynamics are then used to generate statistically equivalent, randomized surrogate time series, which canmore » be linked to the continuum scale simulation. As a result, we illustrate an application of this approach using two different kinetic Monte Carlo simulations with different characteristic behaviors typical for heterogeneous chemical reactions.« less

A preliminary study of head-up display assessment techniques. 2: HUD symbology and panel information search time

NASA Technical Reports Server (NTRS)

Guercio, J. G.; Haines, R. F.

1978-01-01

Twelve commercial pilots were shown 50 high-fidelity slides of a standard aircraft instrument panel with the airspeed, altitude, ADI, VSI, and RMI needles in various realistic orientations. Fifty slides showing an integrated head-up display (HUD) symbology containing an equivalent number of flight parameters as above (with flight path replacing VSI) were also shown. Each subject was told what flight parameter to search for just before each slide was exposed and was given as long as needed (12 sec maximum) to respond by verbalizing the parameter's displayed value. The results for the 100-percent correct data indicated that: there was no significant difference in mean reaction time (averaged across all five flight parameters) between the instrument panel and HUD slides; and a statistically significant difference in mean reaction time was found in responding to different flight parameters.

Wavelet-based surrogate time series for multiscale simulation of heterogeneous catalysis

DOE PAGES

Savara, Aditya Ashi; Daw, C. Stuart; Xiong, Qingang; ...

2016-01-28

We propose a wavelet-based scheme that encodes the essential dynamics of discrete microscale surface reactions in a form that can be coupled with continuum macroscale flow simulations with high computational efficiency. This makes it possible to simulate the dynamic behavior of reactor-scale heterogeneous catalysis without requiring detailed concurrent simulations at both the surface and continuum scales using different models. Our scheme is based on the application of wavelet-based surrogate time series that encodes the essential temporal and/or spatial fine-scale dynamics at the catalyst surface. The encoded dynamics are then used to generate statistically equivalent, randomized surrogate time series, which canmore » be linked to the continuum scale simulation. As a result, we illustrate an application of this approach using two different kinetic Monte Carlo simulations with different characteristic behaviors typical for heterogeneous chemical reactions.« less

Non-equilibrium effects in high temperature chemical reactions

NASA Technical Reports Server (NTRS)

Johnson, Richard E.

1987-01-01

Reaction rate data were collected for chemical reactions occurring at high temperatures during reentry of space vehicles. The principle of detailed balancing is used in modeling kinetics of chemical reactions at high temperatures. Although this principle does not hold for certain transient or incubation times in the initial phase of the reaction, it does seem to be valid for the rates of internal energy transitions that occur within molecules and atoms. That is, for every rate of transition within the internal energy states of atoms or molecules, there is an inverse rate that is related through an equilibrium expression involving the energy difference of the transition.

Individual Differences in Resting Corticospinal Excitability Are Correlated with Reaction Time and GABA Content in Motor Cortex

PubMed Central

Ivry, Richard B.

2017-01-01

Individuals differ in the intrinsic excitability of their corticospinal pathways and, perhaps more generally, their entire nervous system. At present, we have little understanding of the mechanisms underlying these differences and how variation in intrinsic excitability relates to behavior. Here, we examined the relationship between individual differences in intrinsic corticospinal excitability, local cortical GABA levels, and reaction time (RT) in a group of 20 healthy human adults. We measured corticospinal excitability at rest with transcranial magnetic stimulation, local concentrations of basal GABA with magnetic resonance spectroscopy, and RT with a behavioral task. All measurements were repeated in two separate sessions, and tests of reliability confirmed the presence of stable individual differences. There was a negative correlation between corticospinal excitability and RT, such that larger motor-evoked potentials (MEPs) measured at rest were associated with faster RTs. Interestingly, larger MEPs were associated with higher levels of GABA in M1, but not in three other cortical regions. Together, these results suggest that individuals with more excitable corticospinal pathways are faster to initiate planned responses and have higher levels of GABA within M1, possibly to compensate for a more excitable motor system. SIGNIFICANCE STATEMENT This study brings together physiological, behavioral, and neurochemical evidence to examine variability in the excitability of the human motor system. Previous work has focused on state-based factors (e.g., preparedness, uncertainty), with little attention given to the influence of inherent stable characteristics. Here, we examined how the excitability of the motor system relates to reaction time and the regional content of the inhibitory neurotransmitter GABA. Importantly, motor pathway excitability and GABA concentrations were measured at rest, outside a task context, providing assays of intrinsic properties of the individuals. Individuals with more excitable motor pathways had faster reaction times and, paradoxically, higher concentrations of GABA. We propose that greater GABA capacity in the motor cortex counteracts an intrinsically more excitable motor system. PMID:28179557

46 CFR Appendix II to Part 150 - Explanation of Figure 1

Code of Federal Regulations, 2013 CFR

2013-10-01

... considerations, although no examples of such a reaction are known at this time. Chart format— There are different... hazardous reaction— As a first approximation, a mixture of two cargoes is considered hazardous when, under... for the reaction of two cargoes to produce a product that is significantly more flammable or toxic...

46 CFR Appendix II to Part 150 - Explanation of Figure 1

Code of Federal Regulations, 2014 CFR

2014-10-01

... considerations, although no examples of such a reaction are known at this time. Chart format— There are different... hazardous reaction— As a first approximation, a mixture of two cargoes is considered hazardous when, under... for the reaction of two cargoes to produce a product that is significantly more flammable or toxic...

46 CFR Appendix II to Part 150 - Explanation of Figure 1

Code of Federal Regulations, 2010 CFR

2010-10-01

... considerations, although no examples of such a reaction are known at this time. Chart format— There are different... hazardous reaction— As a first approximation, a mixture of two cargoes is considered hazardous when, under... for the reaction of two cargoes to produce a product that is significantly more flammable or toxic...

46 CFR Appendix II to Part 150 - Explanation of Figure 1

Code of Federal Regulations, 2011 CFR

2011-10-01

... considerations, although no examples of such a reaction are known at this time. Chart format— There are different... hazardous reaction— As a first approximation, a mixture of two cargoes is considered hazardous when, under... for the reaction of two cargoes to produce a product that is significantly more flammable or toxic...

46 CFR Appendix II to Part 150 - Explanation of Figure 1

Code of Federal Regulations, 2012 CFR

2012-10-01

... considerations, although no examples of such a reaction are known at this time. Chart format— There are different... hazardous reaction— As a first approximation, a mixture of two cargoes is considered hazardous when, under... for the reaction of two cargoes to produce a product that is significantly more flammable or toxic...

Density-dependent liquid nitromethane decomposition: molecular dynamics simulations based on ReaxFF.

PubMed

Rom, Naomi; Zybin, Sergey V; van Duin, Adri C T; Goddard, William A; Zeiri, Yehuda; Katz, Gil; Kosloff, Ronnie

2011-09-15

The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C-N bond cleavage is the dominant route, producing CH(3) and NO(2) fragments. As density and pressure rise approaching the Chapman-Jouget detonation conditions (∼30% compression, >2500 K) the dominant mechanism switches to the formation of the CH(3)NO fragment via H-transfer and/or N-O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods. © 2011 American Chemical Society

Kinetic and mechanism formation reaction of complex compound Cu with di-n-buthildithiocarbamate (dbdtc) ligand

NASA Astrophysics Data System (ADS)

Haryani, S.; Kurniawan, C.; Kasmui

2018-04-01

Synthesis of complex compound is one field of research which intensively studied. Metal-dithiocarbamate complexes find wide-ranging applications in nanomaterial and metal separation science, and have potential use as chemotherapeutic, pesticides, and as additives to lubricants. However, the information about is reaction kinetic and mechanism are very much lacking. The research and analyzes results show that reaction synthesis ligand DBDTC and complex compounds Cu-DBDTC. Optimum reaction condition of formation of complex compounds Cu with DBDTC at pH=3, [DBDTC] = 4.10-3 M, and the time of reaction 5 minutes. Based the analysis varian reaction of complex compounds at pH 3 and 4, diffrence significance at the other pH: 5; 5,5; 6; 6,5 ; 7; and 8. The various of mole with reactants comosition difference sigbificance, those the time reaction for 5 and 6 minutes diffrence by significance with the other time, it is 3,4,8, and 10 minutes. The great product to at condition pH 6, the time optimum at 5 minutes and molar ratio of logam: ligand = 1:2. The reaction kinetic equation of complex compound Cu with chelathing ligand DBDTC is V=0.917106 [Cu2+]0.87921 [DBDTC]2.03021. Based on the kinetic data, and formed complex compounds estimation, the mechanism explaining by 2 stages. In the first stage formation of [Cu(DBDTC)], and then [Cu(DBDTC)2] with the last structure geomethry planar rectangle. The result of this research will be more useful if an effort is being done in reaction mechanism by chemical computation method for obtain intermediate, and for constant “k” in same stage, k1.k2. and compound complex constanta (β).

Real-time pH monitoring of industrially relevant enzymatic reactions in a microfluidic side-entry reactor (μSER) shows potential for pH control.

PubMed

Gruber, Pia; Marques, Marco P C; Sulzer, Philipp; Wohlgemuth, Roland; Mayr, Torsten; Baganz, Frank; Szita, Nicolas

2017-06-01

Monitoring and control of pH is essential for the control of reaction conditions and reaction progress for any biocatalytic or biotechnological process. Microfluidic enzymatic reactors are increasingly proposed for process development, however typically lack instrumentation, such as pH monitoring. We present a microfluidic side-entry reactor (μSER) and demonstrate for the first time real-time pH monitoring of the progression of an enzymatic reaction in a microfluidic reactor as a first step towards achieving pH control. Two different types of optical pH sensors were integrated at several positions in the reactor channel which enabled pH monitoring between pH 3.5 and pH 8.5, thus a broader range than typically reported. The sensors withstood the thermal bonding temperatures typical of microfluidic device fabrication. Additionally, fluidic inputs along the reaction channel were implemented to adjust the pH of the reaction. Time-course profiles of pH were recorded for a transketolase and a penicillin G acylase catalyzed reaction. Without pH adjustment, the former showed a pH increase of 1 pH unit and the latter a pH decrease of about 2.5 pH units. With pH adjustment, the pH drop of the penicillin G acylase catalyzed reaction was significantly attenuated, the reaction condition kept at a pH suitable for the operation of the enzyme, and the product yield increased. This contribution represents a further step towards fully instrumented and controlled microfluidic reactors for biocatalytic process development. © 2017 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Control of topography gradients on residence time distributions, mixing dynamics and reactive hotspot development

NASA Astrophysics Data System (ADS)

Bandopadhyay, Aditya; Le Borgne, Tanguy; Davy, Philippe

2017-04-01

Topography-driven subsurface flows are thought to play a central role in determining solute turnover and biogeochemical processes at different scales in the critical zone, including river-hyporheic zone exchanges, hillslope solute transport and reactions, and catchment biogeochemical cycles. Hydraulic head gradients, induced by topography gradients at different scales, generate a distribution of streamlines at depth, dictating the spatial distribution of redox sensitive species, the magnitude of surface water - ground water exchanges and ultimately the source/sink function of the subsurface. Flow velocities generally decrease with depth, leading to broad residence time distributions, which have been shown to affect river chemistry and geochemical reactions in catchments. In this presentation, we discuss the impact of topography-driven flows on mixing processes and the formation of localized reactive hotspots. For this, we solve analytically the coupled flow, mixing and reaction equations in two-dimensional vertical cross-sections of subsurface domains with different topography gradients. For a given topography gradient, we derive the spatial distribution of subsurface velocities, the rates of solute mixing accross streamlines and the induced kinetics of redox, precipitation and dissolution reactions using a Lagrangian approach (Le Borgne et al. 2014). We demonstrate that vertical velocity profiles driven by topography variations, act effectively as shear flows, hence stretching continuously the mixing fronts between recently infiltrated and resident water (Bandopadhyay et al. 2017). We thus derive analytical expressions for residence time distributions, mixing rates and kinetics of chemical reactions as a function of the topography gradients. We show that the rates dissolution and precipitation reactions are significantly enhanced by the existence of vertical velocity gradients and that reaction rates reach a maximum in a localized subsurface reactive layer, whose location and intensity depends on topography gradients. As a consequence of these findings, we discuss the links between topography variations, subsurface velocity gradients and biogeochemical processes in the critical zone. References: Bandopadhyay A., T. Le Borgne, Y. Méheust and M. Dentz (2017) Enhanced reaction kinetics and reactive mixing scale dynamics in mixing fronts under shear flow for arbitrary Damkohler numbers, Adv. in Water Resour. Vol. 100, p. 78-95 Le Borgne T., T. Ginn and M. Dentz (2014) Impact of Fluid Deformation on Mixing-Induced Chemical Reactions in Heterogeneous Flows, Geophys. Res. Lett., Vol. 41, 22, p. 7898-790

Investigation of the speed of reaction on external stimulus in schizophrenic psychosis.

PubMed

Zampera, E

1997-06-01

In 30 schizophrenic examinees, the latention time was measured. This time is referred to as an interval between the start of the stimulus and the response to the stimulus in the skin-galvanic reflex. Elementary stimulation has been applied, using device's timer tone and clapping of hands, which should simulate and associate the thunderclap. The intensity of psychosis was measured according to the Metric scale of psychotic behavior by Rogina, while the intensity of anxiety was measured by psychological tests: Rorschach's psycho-diagnostic test and Spillberger's questionnaire for anxiety. The reaction to the stimulus and latention time were registered using polygraph unit in order to record skin-galvanic reflex. The research was performed at two separate time points: prior to the therapy with derivatives of the phenothiazine group (the experimental examination group), and 25 days after the therapy (control group). The research has shown that the latention time in schizophrenic examinees does not significantly differ from the corresponding time in healthy controls, and it averages 2.30 seconds. Furthermore, no statistically significant difference in latention time before and after the therapy was observed. However, before the therapy started, i.e. in experimental group," the examinees who were psychotic to a greater extent have shown longer latention than those less psychotic. Additional finding was that the examinees from experimental group who were more anxious according to psychological tests have also shown longer latention time. After the therapy, the reaction to the external stimulus was stronger, which was expressed in increased reaction amplitude in skin-galvanic reflex. The latention time was prolonged, especially in case of examinees that were psychotic to a smaller extent before the therapy. We can conclude that so-called transformed psychotic anxiety was replaced after the therapy with a "new" anxiety-existential fear, i.e. the stronger anxious expectation and confusion appeared because the anxiety in its "free-floating" form remained very high. After the therapy, psychotic protection failed to appear and the reaction characteristics are a consequence of the delaying the confrontation with reality, which was registered as a prolonged latention time, i.e. response to external stimulus.

The relative effect of noise at different times of day: An analysis of existing survey data

NASA Technical Reports Server (NTRS)

Fields, J. M.

1986-01-01

This report examines survey evidence on the relative impact of noise at different times of day and assesses the survey methodology which produces that evidence. Analyses of the regression of overall (24-hour) annoyance on noise levels in different time periods can provide direct estimates of the value of the parameters in human reaction models which are used in environmental noise indices such as LDN and CNEL. In this report these analyses are based on the original computer tapes containing the responses of 22,000 respondents from ten studies of response to noise in residential areas. The estimates derived from these analyses are found to be so inaccurate that they do not provide useful information for policy or scientific purposes. The possibility that the type of questionnaire item could be biasing the estimates of the time-of-day weightings is considered but not supported by the data. Two alternatives to the conventional noise reaction model (adjusted energy model) are considered but not supported by the data.

The relative effect of noise at different times of day: An analysis of existing survey data

NASA Astrophysics Data System (ADS)

Fields, J. M.

1986-04-01

This report examines survey evidence on the relative impact of noise at different times of day and assesses the survey methodology which produces that evidence. Analyses of the regression of overall (24-hour) annoyance on noise levels in different time periods can provide direct estimates of the value of the parameters in human reaction models which are used in environmental noise indices such as LDN and CNEL. In this report these analyses are based on the original computer tapes containing the responses of 22,000 respondents from ten studies of response to noise in residential areas. The estimates derived from these analyses are found to be so inaccurate that they do not provide useful information for policy or scientific purposes. The possibility that the type of questionnaire item could be biasing the estimates of the time-of-day weightings is considered but not supported by the data. Two alternatives to the conventional noise reaction model (adjusted energy model) are considered but not supported by the data.

Systemic effect of mineral aggregate-based cements: histopathological analysis in rats

PubMed Central

Garcia, Lucas da Fonseca Roberti; Huck, Claudia; Magalhães, Fernando Augusto Cintra; de Souza, Pedro Paulo Chaves; de Souza Costa, Carlos Alberto

2017-01-01

Abstract Objective: Several studies reported the local tissue reaction caused by mineral aggregate-based cements. However, few studies have investigated the systemic effects promoted by these cements on liver and kidney when directly applied to connective tissue. The purpose of this in vivo study was to investigate the systemic effect of mineral aggregate-based cements on the livers and kidneys of rats. Material and Methods: Samples of Mineral Trioxide Aggregate (MTA) and a calcium aluminate-based cement (EndoBinder) containing different radiopacifiers were implanted into the dorsum of 40 rats. After 7 and 30 d, samples of subcutaneous, liver and kidney tissues were submitted to histopathological analysis. A score (0-3) was used to grade the inflammatory reaction. Blood samples were collected to evaluate changes in hepatic and renal functions of animals. Results: The moderate inflammatory reaction (2) observed for 7 d in the subcutaneous tissue decreased with time for all cements. The thickness of inflammatory capsules also presented a significant decrease with time (P<.05). Systemically, all cements caused adverse inflammatory reactions in the liver and kidney, being more evident for MTA, persisting until the end of the analysis. Liver functions increased significantly for MTA during 30 d (P<.05). Conclusion: The different cements induced to a locally limited inflammatory reaction. However, from the systemic point of view, the cements promoted significant inflammatory reactions in the liver and kidney. For MTA, the reactions were more accentuated. PMID:29211283

Fourth order Douglas implicit scheme for solving three dimension reaction diffusion equation with non-linear source term

NASA Astrophysics Data System (ADS)

Hasnain, Shahid; Saqib, Muhammad; Mashat, Daoud Suleiman

2017-07-01

This research paper represents a numerical approximation to non-linear three dimension reaction diffusion equation with non-linear source term from population genetics. Since various initial and boundary value problems exist in three dimension reaction diffusion phenomena, which are studied numerically by different numerical methods, here we use finite difference schemes (Alternating Direction Implicit and Fourth Order Douglas Implicit) to approximate the solution. Accuracy is studied in term of L2, L∞ and relative error norms by random selected grids along time levels for comparison with analytical results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. Numerical results showed that Fourth Order Douglas Implicit scheme is very efficient and reliable for solving 3-D non-linear reaction diffusion equation.

The benefit of deep processing and high educational level for verbal learning in young and middle-aged adults.

PubMed

Meijer, Willemien A; Van Gerven, Pascal W; de Groot, Renate H; Van Boxtel, Martin P; Jolles, Jelle

2007-10-01

The aim of the present study was to examine whether deeper processing of words during encoding in middle-aged adults leads to a smaller increase in word-learning performance and a smaller decrease in retrieval effort than in young adults. It was also assessed whether high education attenuates age-related differences in performance. Accuracy of recall and recognition, and reaction times of recognition, after performing incidental and intentional learning tasks were compared between 40 young (25-35) and 40 middle-aged (50-60) adults with low and high educational levels. Age differences in recall increased with depth of processing, whereas age differences in accuracy and reaction times of recognition did not differ across levels. High education does not moderate age-related differences in performance. These findings suggest a smaller benefit of deep processing in middle age, when no retrieval cues are available.

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.

PubMed

Mochales, Carolina; El Briak-BenAbdeslam, Hassane; Ginebra, Maria Pau; Terol, Alain; Planell, Josep A; Boudeville, Philippe

2004-01-01

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process.

Differences between racing and non-racing drivers: A simulator study using eye-tracking

PubMed Central

de Groot, Stefan; Happee, Riender; de Winter, Joost C. F.

2017-01-01

Motorsport has developed into a professional international competition. However, limited research is available on the perceptual and cognitive skills of racing drivers. By means of a racing simulator, we compared the driving performance of seven racing drivers with ten non-racing drivers. Participants were tasked to drive the fastest possible lap time. Additionally, both groups completed a choice reaction time task and a tracking task. Results from the simulator showed faster lap times, higher steering activity, and a more optimal racing line for the racing drivers than for the non-racing drivers. The non-racing drivers’ gaze behavior corresponded to the tangent point model, whereas racing drivers showed a more variable gaze behavior combined with larger head rotations while cornering. Results from the choice reaction time task and tracking task showed no statistically significant difference between the two groups. Our results are consistent with the current consensus in sports sciences in that task-specific differences exist between experts and novices while there are no major differences in general cognitive and motor abilities. PMID:29121090

Generic HPLC platform for automated enzyme reaction monitoring: Advancing the assay toolbox for transaminases and other PLP-dependent enzymes.

PubMed

Börner, Tim; Grey, Carl; Adlercreutz, Patrick

2016-08-01

Methods for rapid and direct quantification of enzyme kinetics independent of the substrate stand in high demand for both fundamental research and bioprocess development. This study addresses the need for a generic method by developing an automated, standardizable HPLC platform monitoring reaction progress in near real-time. The method was applied to amine transaminase (ATA) catalyzed reactions intensifying process development for chiral amine synthesis. Autosampler-assisted pipetting facilitates integrated mixing and sampling under controlled temperature. Crude enzyme formulations in high and low substrate concentrations can be employed. Sequential, small (1 µL) sample injections and immediate detection after separation permits fast reaction monitoring with excellent sensitivity, accuracy and reproducibility. Due to its modular design, different chromatographic techniques, e.g. reverse phase and size exclusion chromatography (SEC) can be employed. A novel assay for pyridoxal 5'-phosphate-dependent enzymes is presented using SEC for direct monitoring of enzyme-bound and free reaction intermediates. Time-resolved changes of the different cofactor states, e.g. pyridoxal 5'-phosphate, pyridoxamine 5'-phosphate and the internal aldimine were traced in both half reactions. The combination of the automated HPLC platform with SEC offers a method for substrate-independent screening, which renders a missing piece in the assay and screening toolbox for ATAs and other PLP-dependent enzymes. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Variability in reaction time performance of younger and older adults.

PubMed

Hultsch, David F; MacDonald, Stuart W S; Dixon, Roger A

2002-03-01

Age differences in three basic types of variability were examined: variability between persons (diversity), variability within persons across tasks (dispersion), and variability within persons across time (inconsistency). Measures of variability were based on latency performance from four measures of reaction time (RT) performed by a total of 99 younger adults (ages 17--36 years) and 763 older adults (ages 54--94 years). Results indicated that all three types of variability were greater in older compared with younger participants even when group differences in speed were statistically controlled. Quantile-quantile plots showed age and task differences in the shape of the inconsistency distributions. Measures of within-person variability (dispersion and inconsistency) were positively correlated. Individual differences in RT inconsistency correlated negatively with level of performance on measures of perceptual speed, working memory, episodic memory, and crystallized abilities. Partial set correlation analyses indicated that inconsistency predicted cognitive performance independent of level of performance. The results indicate that variability of performance is an important indicator of cognitive functioning and aging.

Development of a test for recording both visual and auditory reaction times, potentially useful for future studies in patients on opioids therapy

PubMed Central

Miceli, Luca; Bednarova, Rym; Rizzardo, Alessandro; Samogin, Valentina; Della Rocca, Giorgio

2015-01-01

Objective Italian Road Law limits driving while undergoing treatment with certain kinds of medication. Here, we report the results of a test, run as a smartphone application (app), assessing auditory and visual reflexes in a sample of 300 drivers. The scope of the test is to provide both the police force and medication-taking drivers with a tool that can evaluate the individual’s capacity to drive safely. Methods The test is run as an app for Apple iOS and Android mobile operating systems and facilitates four different reaction times to be assessed: simple visual and auditory reaction times and complex visual and auditory reaction times. Reference deciles were created for the test results obtained from a sample of 300 Italian subjects. Results lying within the first three deciles were considered as incompatible with safe driving capabilities. Results Performance is both age-related (r>0.5) and sex-related (female reaction times were significantly slower than those recorded for male subjects, P<0.05). Only 21% of the subjects were able to perform all four tests correctly. Conclusion We developed and fine-tuned a test called Safedrive that measures visual and auditory reaction times through a smartphone mobile device; the scope of the test is two-fold: to provide a clinical tool for the assessment of the driving capacity of individuals taking pain relief medication; to promote the sense of social responsibility in drivers who are on medication and provide these individuals with a means of testing their own capacity to drive safely. PMID:25709406

Development of a test for recording both visual and auditory reaction times, potentially useful for future studies in patients on opioids therapy.

PubMed

Miceli, Luca; Bednarova, Rym; Rizzardo, Alessandro; Samogin, Valentina; Della Rocca, Giorgio

2015-01-01

Italian Road Law limits driving while undergoing treatment with certain kinds of medication. Here, we report the results of a test, run as a smartphone application (app), assessing auditory and visual reflexes in a sample of 300 drivers. The scope of the test is to provide both the police force and medication-taking drivers with a tool that can evaluate the individual's capacity to drive safely. The test is run as an app for Apple iOS and Android mobile operating systems and facilitates four different reaction times to be assessed: simple visual and auditory reaction times and complex visual and auditory reaction times. Reference deciles were created for the test results obtained from a sample of 300 Italian subjects. Results lying within the first three deciles were considered as incompatible with safe driving capabilities. Performance is both age-related (r>0.5) and sex-related (female reaction times were significantly slower than those recorded for male subjects, P<0.05). Only 21% of the subjects were able to perform all four tests correctly. We developed and fine-tuned a test called Safedrive that measures visual and auditory reaction times through a smartphone mobile device; the scope of the test is two-fold: to provide a clinical tool for the assessment of the driving capacity of individuals taking pain relief medication; to promote the sense of social responsibility in drivers who are on medication and provide these individuals with a means of testing their own capacity to drive safely.

Stochastic Kinetics on Networks: When Slow Is Fast

PubMed Central

2015-01-01

Most chemical and biological processes can be viewed as reaction networks in which different pathways often compete kinetically for transformation of substrates into products. An enzymatic process is an example of such phenomena when biological catalysts create new routes for chemical reactions to proceed. It is typically assumed that the general process of product formation is governed by the pathway with the fastest kinetics at all time scales. In contrast to the expectation, here we show theoretically that at time scales sufficiently short, reactions are predominantly determined by the shortest pathway (in the number of intermediate states), regardless of the average turnover time associated with each pathway. This universal phenomenon is demonstrated by an explicit calculation for a system with two competing reversible (or irreversible) pathways. The time scales that characterize this regime and its relevance for single-molecule experimental studies are also discussed. PMID:25140607

A solution for measuring accurate reaction time to visual stimuli realized with a programmable microcontroller.

PubMed

Ohyanagi, Toshio; Sengoku, Yasuhito

2010-02-01

This article presents a new solution for measuring accurate reaction time (SMART) to visual stimuli. The SMART is a USB device realized with a Cypress Programmable System-on-Chip (PSoC) mixed-signal array programmable microcontroller. A brief overview of the hardware and firmware of the PSoC is provided, together with the results of three experiments. In Experiment 1, we investigated the timing accuracy of the SMART in measuring reaction time (RT) under different conditions of operating systems (OSs; Windows XP or Vista) and monitor displays (a CRT or an LCD). The results indicated that the timing error in measuring RT by the SMART was less than 2 msec, on average, under all combinations of OS and display and that the SMART was tolerant to jitter and noise. In Experiment 2, we tested the SMART with 8 participants. The results indicated that there was no significant difference among RTs obtained with the SMART under the different conditions of OS and display. In Experiment 3, we used Microsoft (MS) PowerPoint to present visual stimuli on the display. We found no significant difference in RTs obtained using MS DirectX technology versus using the PowerPoint file with the SMART. We are certain that the SMART is a simple and practical solution for measuring RTs accurately. Although there are some restrictions in using the SMART with RT paradigms, the SMART is capable of providing both researchers and health professionals working in clinical settings with new ways of using RT paradigms in their work.

Ayurvedic approach for improving reaction time of attention deficit hyperactivity disorder affected children.

PubMed

Singhal, Harish Kumar; Neetu; Kumar, Abhimanyu; Rai, Moti

2010-07-01

Attention deficit/hyperactivity disorder (ADHD) is a behavioral disorder of children. It is the most common neurological disorder of childhood. The present study was conducted to examine the increase in attention span in 43 ADHD-affected children treated with different approaches. The reaction time was measured using a Vernier chronoscope (electronic). Selected children of both sexes in the age-group of 6-16 years were divided into three groups. In group A, 17 patients received syrup Ayurvedic compound I; in group B, 14 patients were treated with syrup Ayurvedic compound I + Shirodhara with milk; and in group C, 12 patients received syrup Ayurvedic compound II (placebo). The dose of the drug was 1.0 ml/kg body weight and the duration of treatment was 3 months. Group B showed highly significant (P<.001) improvement in total reaction time, while in group C the change was statistically nonsignificant P > 0.10. It was found that while the drug and Shirodhara were both effective in improving the reaction time of ADHD-affected children, the drug combined with Shirodhara was superior to the drug used alone.

Ayurvedic approach for improving reaction time of attention deficit hyperactivity disorder affected children

PubMed Central

Singhal, Harish Kumar; Neetu; Kumar, Abhimanyu; Rai, Moti

2010-01-01

Attention deficit/hyperactivity disorder (ADHD) is a behavioral disorder of children. It is the most common neurological disorder of childhood. The present study was conducted to examine the increase in attention span in 43 ADHD-affected children treated with different approaches. The reaction time was measured using a Vernier chronoscope (electronic). Selected children of both sexes in the age-group of 6–16 years were divided into three groups. In group A, 17 patients received syrup Ayurvedic compound I; in group B, 14 patients were treated with syrup Ayurvedic compound I + Shirodhara with milk; and in group C, 12 patients received syrup Ayurvedic compound II (placebo). The dose of the drug was 1.0 ml/kg body weight and the duration of treatment was 3 months. Group B showed highly significant (P<.001) improvement in total reaction time, while in group C the change was statistically nonsignificant P > 0.10. It was found that while the drug and Shirodhara were both effective in improving the reaction time of ADHD-affected children, the drug combined with Shirodhara was superior to the drug used alone. PMID:22131736

Scaling behavior in corrosion and growth of a passive film.

PubMed

Aarão Reis, F D A; Stafiej, Janusz

2007-07-01

We study a simple model for metal corrosion controlled by the reaction rate of the metal with an anionic species and the diffusion of that species in the growing passive film between the solution and the metal. A crossover from the reaction-controlled to the diffusion-controlled growth regime with different roughening properties is observed. Scaling arguments provide estimates of the crossover time and film thickness as functions of the reaction and diffusion rates and the concentration of anionic species in the film-solution interface, including a nontrivial square-root dependence on that concentration. At short times, the metal-film interface exhibits Kardar-Parisi-Zhang (KPZ) scaling, which crosses over to a diffusion-limited erosion (Laplacian growth) regime at long times. The roughness of the metal-film interface at long times is obtained as a function of the rates of reaction and diffusion and of the KPZ growth exponent. The predictions have been confirmed by simulations of a lattice version of the model in two dimensions. Relations with other erosion and corrosion models and possible applications are discussed.

Comparison of visual and emotional continuous performance test related to sequence of presentation, gender and age.

PubMed

Markovska-Simoska, S; Pop-Jordanova, N

2009-07-01

(Full text is available at http://www.manu.edu.mk/prilozi). Continous Performance Tests (CPTs) form a group of paradigms for the evaluation of attention and, to a lesser degree, the response inhibition (or disinhibition) component of executive control. The object of this study was to compare performance on a CPT using both visual and emotional tasks in 46 normal adult subjects. In particular, it was to examine the effects of the type of task (VCPT or ECPT), sequence of presentation, and gender/age influence on performance as measured errors of omission, errors of commission, reaction time and variation of reaction time. From the results we can assume that there are significantly worse performance parameters for ECPT than VCPT tasks, with a probable explanation of the influence of emotional stimuli on attention and information-processing and no significant effect of order of presentation and gender on performance. Significant differences with more omission errors for older groups were obtained, showing better attention in younger subjects. Key words: VCPT, ECPT, omission errors, commission errors, reaction time, variation of reaction time, normal adults.

Reduced linear noise approximation for biochemical reaction networks with time-scale separation: The stochastic tQSSA+

NASA Astrophysics Data System (ADS)

Herath, Narmada; Del Vecchio, Domitilla

2018-03-01

Biochemical reaction networks often involve reactions that take place on different time scales, giving rise to "slow" and "fast" system variables. This property is widely used in the analysis of systems to obtain dynamical models with reduced dimensions. In this paper, we consider stochastic dynamics of biochemical reaction networks modeled using the Linear Noise Approximation (LNA). Under time-scale separation conditions, we obtain a reduced-order LNA that approximates both the slow and fast variables in the system. We mathematically prove that the first and second moments of this reduced-order model converge to those of the full system as the time-scale separation becomes large. These mathematical results, in particular, provide a rigorous justification to the accuracy of LNA models derived using the stochastic total quasi-steady state approximation (tQSSA). Since, in contrast to the stochastic tQSSA, our reduced-order model also provides approximations for the fast variable stochastic properties, we term our method the "stochastic tQSSA+". Finally, we demonstrate the application of our approach on two biochemical network motifs found in gene-regulatory and signal transduction networks.

Synaptic vesicle recycling: steps and principles.

PubMed

Rizzoli, Silvio O

2014-04-16

Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle.

Influence of reaction time on the structural, optical and electrical performance of copper antimony sulfide nanoparticles using solvothermal method

NASA Astrophysics Data System (ADS)

John, Bincy; Genifer Silvena, G.; Leo Rajesh, A.

2018-05-01

The less toxic and cost effective ternary Cu-Sb-S nanoparticles and thin films were synthesized and deposited using solvothermal and drop casting method. The reactions were carried out at different timings as 12-48 h, in steps of 12 h using ethylene glycol as solvent and polyvinylpyrrolidone (PVP) as surfactant. Systematic analysis revealed that due to the influence of different reaction time, significant and unique changes were occurring on the crystal structure, optical and electrical properties of the material. The synthesized nanopowders and deposited films were characterized by means of X-ray diffraction, Raman analysis, field emission scanning electron microscope with energy dispersive spectrometer, UV-Vis-NIR diffuse reflectance spectroscopy and hall measurement. XRD results showed that as the time increases crystallinity improves and phase transformation from chalcostibite to tetrahedrite occurs. The Optical performance revealed that the bandgap of nanoparticles were in the range of 1.21-1.49 eV. Hall measurements showed that the deposited Cu12Sb4S13 and CuSbS2 films exhibited p-type conductivity with carrier concentration ranging from 1016-1019 cm-3, indicating a promising p-type absorber material for photovoltaic applications.

Fission time scale from pre-scission neutron and α multiplicities in the 16O + 194Pt reaction

NASA Astrophysics Data System (ADS)

Kapoor, K.; Verma, S.; Sharma, P.; Mahajan, R.; Kaur, N.; Kaur, G.; Behera, B. R.; Singh, K. P.; Kumar, A.; Singh, H.; Dubey, R.; Saneesh, N.; Jhingan, A.; Sugathan, P.; Mohanto, G.; Nayak, B. K.; Saxena, A.; Sharma, H. P.; Chamoli, S. K.; Mukul, I.; Singh, V.

2017-11-01

Pre- and post-scission α -particle multiplicities have been measured for the reaction 16O+P194t at 98.4 MeV forming R210n compound nucleus. α particles were measured at various angles in coincidence with the fission fragments. Moving source technique was used to extract the pre- and post-scission contributions to the particle multiplicity. Study of the fission mechanism using the different probes are helpful in understanding the detailed reaction dynamics. The neutron multiplicities for this reaction have been reported earlier. The multiplicities of neutrons and α particles were reproduced using standard statistical model code joanne2 by varying the transient (τt r) and saddle to scission (τs s c) times. This code includes deformation dependent-particle transmission coefficients, binding energies and level densities. Fission time scales of the order of 50-65 ×10-21 s are required to reproduce the neutron and α -particle multiplicities.

Computational methods for diffusion-influenced biochemical reactions.

PubMed

Dobrzynski, Maciej; Rodríguez, Jordi Vidal; Kaandorp, Jaap A; Blom, Joke G

2007-08-01

We compare stochastic computational methods accounting for space and discrete nature of reactants in biochemical systems. Implementations based on Brownian dynamics (BD) and the reaction-diffusion master equation are applied to a simplified gene expression model and to a signal transduction pathway in Escherichia coli. In the regime where the number of molecules is small and reactions are diffusion-limited predicted fluctuations in the product number vary between the methods, while the average is the same. Computational approaches at the level of the reaction-diffusion master equation compute the same fluctuations as the reference result obtained from the particle-based method if the size of the sub-volumes is comparable to the diameter of reactants. Using numerical simulations of reversible binding of a pair of molecules we argue that the disagreement in predicted fluctuations is due to different modeling of inter-arrival times between reaction events. Simulations for a more complex biological study show that the different approaches lead to different results due to modeling issues. Finally, we present the physical assumptions behind the mesoscopic models for the reaction-diffusion systems. Input files for the simulations and the source code of GMP can be found under the following address: http://www.cwi.nl/projects/sic/bioinformatics2007/

Pectinase activity determination: an early deceleration in the release of reducing sugars throws a spanner in the works!

PubMed

Biz, Alessandra; Farias, Fernanda Cardoso; Motter, Francine Aline; de Paula, Diogo Henrique; Richard, Peter; Krieger, Nadia; Mitchell, David Alexander

2014-01-01

Recently, it has been suggested that pectinases could be used to hydrolyze pectin in biorefineries based on pectin-rich agro-industrial wastes. However, for this to be viable, the cost of their production would need to be lowered significantly. In fact, over the last few decades, there have been many attempts to improve pectinase production by existing strains or to screen for new strains from environmental isolates. In these studies, it is necessary to measure pectinase activities. Many researchers use single-time-point assays that involve incubation of pectinolytic extracts with pectic substrates for a fixed time, followed by determination of the liberated reducing sugars. However, different researchers use quite different conditions for this assay. Furthermore, no attention has been given to the reaction profile during the assay. In the current work, we show, for the first time, that a significant deceleration of the rate of liberation of reducing sugars occurs over the first ten minutes of the reaction. As a consequence, the incubation time used in a single-time-point assay has a large effect on the value obtained for the activity. In fact, we demonstrate that, depending on the particular combination of incubation time, pectin concentration and reaction temperature, the same extract could be reported to have activities that differ by an order of magnitude. In addition, we show that the relative activities obtained with polygalacturonic acid do not correlate with those obtained with pectin. We conclude that it is currently impossible to make meaningful comparisons between pectinase activities reported in the literature by workers who have used different assay conditions. Therefore there is an urgent need for the development of a standardized assay for evaluating the saccharification potential of pectinase complexes.

Pectinase Activity Determination: An Early Deceleration in the Release of Reducing Sugars Throws a Spanner in the Works!

PubMed Central

Biz, Alessandra; Farias, Fernanda Cardoso; Motter, Francine Aline; de Paula, Diogo Henrique; Richard, Peter; Krieger, Nadia; Mitchell, David Alexander

2014-01-01

Recently, it has been suggested that pectinases could be used to hydrolyze pectin in biorefineries based on pectin-rich agro-industrial wastes. However, for this to be viable, the cost of their production would need to be lowered significantly. In fact, over the last few decades, there have been many attempts to improve pectinase production by existing strains or to screen for new strains from environmental isolates. In these studies, it is necessary to measure pectinase activities. Many researchers use single-time-point assays that involve incubation of pectinolytic extracts with pectic substrates for a fixed time, followed by determination of the liberated reducing sugars. However, different researchers use quite different conditions for this assay. Furthermore, no attention has been given to the reaction profile during the assay. In the current work, we show, for the first time, that a significant deceleration of the rate of liberation of reducing sugars occurs over the first ten minutes of the reaction. As a consequence, the incubation time used in a single-time-point assay has a large effect on the value obtained for the activity. In fact, we demonstrate that, depending on the particular combination of incubation time, pectin concentration and reaction temperature, the same extract could be reported to have activities that differ by an order of magnitude. In addition, we show that the relative activities obtained with polygalacturonic acid do not correlate with those obtained with pectin. We conclude that it is currently impossible to make meaningful comparisons between pectinase activities reported in the literature by workers who have used different assay conditions. Therefore there is an urgent need for the development of a standardized assay for evaluating the saccharification potential of pectinase complexes. PMID:25337712

Immediate Neural Plasticity Involving Reaction Time in a Saccadic Eye Movement Task is Intact in Children With Fetal Alcohol Spectrum Disorder.

PubMed

Paolozza, Angelina; Munoz, Douglas P; Brien, Donald; Reynolds, James N

2016-11-01

Saccades are rapid eye movements that bring an image of interest onto the retina. Previous research has found that in healthy individuals performing eye movement tasks, the location of a previous visual target can influence performance of the saccade on the next trial. This rapid behavioral adaptation represents a form of immediate neural plasticity within the saccadic circuitry. Our studies have shown that children with fetal alcohol spectrum disorder (FASD) are impaired on multiple saccade measures. We therefore investigated these previous trial effects in typically developing children and children with FASD to measure sensory neural plasticity and how these effects vary with age and pathology. Both typically developing control children (n = 102; mean age = 10.54 ± 3.25; 48 males) and children with FASD (n = 66; mean age = 11.85 ± 3.42; 35 males) were recruited from 5 sites across Canada. Each child performed a visually guided saccade task. Reaction time and saccade amplitude were analyzed and then assessed based on the previous trial. There was a robust previous trial effect for both reaction time and amplitude, with both the control and FASD groups displaying faster reaction times and smaller saccades during alternation trials (visual target presented on the opposite side to the previous trial). Children with FASD exhibited smaller overall mean amplitude and smaller amplitude selectively on alternation trials compared with controls. The effect of the previous trial on reaction time and amplitude did not differ across childhood and adolescent development. Children with FASD did not display any significant reaction time differences, despite exhibiting numerous deficits in motor and higher level cognitive control over saccades in other studies. These results suggest that this form of immediate neural plasticity in response to sensory information before saccade initiation remains intact in children with FASD. In contrast, the previous trial effect on amplitude suggests that the motor component of saccades may be affected, signifying differential vulnerability to prenatal alcohol exposure. Copyright © 2016 by the Research Society on Alcoholism.

Ultrafast photodimerization dynamics in α-cyano-4-hydroxycinnamic and sinapinic acid crystals

NASA Astrophysics Data System (ADS)

Hoyer, Theo; Tuszynski, Wilfried; Lienau, Christoph

2007-07-01

We report a sub-picosecond time-resolved fluorescence spectroscopic study of different cinnamic acid crystals, model systems for solid-state photodimerization reactions. For α-cyano-4-hydroxycinnamic acid (α-CHC), we identify the emission spectra of both monomers and dimers, allowing us to directly probe the photoinduced dynamics of both species. The dimerization occurs on a timescale of 10 ps and results in a long-lived dimer product, stable for hours. For sinapinic acid, we find an extremely fast, sub-picosecond dimerization reaction and a short-lived dimer. This first sub-picosecond time-resolved dimerization study in cinnamic acid crystals provides a new basis for relating their structural properties and microscopic reaction dynamics.

Foot speed, foot-strike and footwear: linking gait mechanics and running ground reaction forces.

PubMed

Clark, Kenneth P; Ryan, Laurence J; Weyand, Peter G

2014-06-15

Running performance, energy requirements and musculoskeletal stresses are directly related to the action-reaction forces between the limb and the ground. For human runners, the force-time patterns from individual footfalls can vary considerably across speed, foot-strike and footwear conditions. Here, we used four human footfalls with distinctly different vertical force-time waveform patterns to evaluate whether a basic mechanical model might explain all of them. Our model partitions the body's total mass (1.0 Mb) into two invariant mass fractions (lower limb=0.08, remaining body mass=0.92) and allows the instantaneous collisional velocities of the former to vary. The best fits achieved (R(2) range=0.95-0.98, mean=0.97 ± 0.01) indicate that the model is capable of accounting for nearly all of the variability observed in the four waveform types tested: barefoot jog, rear-foot strike run, fore-foot strike run and fore-foot strike sprint. We conclude that different running ground reaction force-time patterns may have the same mechanical basis. © 2014. Published by The Company of Biologists Ltd.

Using terahertz time-domain spectroscopical technique to monitor cocrystal formation between piracetam and 2,5-dihydroxybenzoic acid

NASA Astrophysics Data System (ADS)

Du, Yong; Xia, Yi; Zhang, Huili; Hong, Zhi

2013-07-01

Far-infrared vibrational absorption of cocrystal formation between 2,5-dihydroxybenzoic acid (2,5-DHBA) and piracetam compounds under solvent evaporation and grinding methods have been investigated using terahertz time-domain spectroscopy (THz-TDS) at room temperature. The experimental results show large difference among absorption spectra of the formed cocrystals and the involved individual parent molecules in 0.20-1.50 THz region, which probably originated from the intra-molecular and inter-molecular hydrogen bonds due to the presence of two hydroxyl groups in 2,5-DHBA and amide moieties in piracetam compound. The THz absorption spectra of two formed cocrystals with different methods are almost identical. With grinding method, the reaction process can be monitored directly from both time-domain and frequency-domain spectra using THz-TDS technique. The results indicate that THz-TDS technology can absolutely offer us a high potential method to identify and characterize the formed cocrystals, and also provide the rich information about their reaction dynamic process involving two or more molecular crystals in situ to better know the corresponding reaction mechanism in pharmaceutical fields.

Hydrothermal synthesis of Nd3+-doped heterojunction ms/tz-BiVO4 and its enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Chen, Ruizhi; Wang, Weixuan; Jiang, Dongmei; Chu, Xiaoxuan; Ma, Xueming; Zhan, Qingfeng

2018-06-01

BiVO4 photocatalysts with different Nd3+ doping content were prepared by a hydrothermal method with varied hydrothermal reaction time. The effects of Nd3+ doping on phase transformation, morphology, chemical valence, optical properties and photocatalytic activities were investigated. With different reaction time, phase transformation from tetragonal zircon (tz-BiVO4) to monoclinic scheelite (ms-BiVO4) could be found, and Nd3+ doping played a suppressive role in this process. Scanning electron microscopy showed the morphology evolved from irregular structure to rod-like shapes with phase transformation. The photoluminescence induced by Nd3+ doping could be confirmed by UV-vis diffuse reflectance spectra. Photocatalytic performance tests had been performed under simulated solar conditions and sample with 1 at% Nd3+ doping and 5 h reaction time showed the best performance (89% degradation rate in 90 min). The pH also showed great influence on morphology and phase transformation of samples. Finally, the phyotocatalytic mechanism and effects of Nd3+ in phase transformation were discussed.

Chinese deaf and hard of hearing adolescents' awareness of thematic and taxonomic relations among ordinary concepts represented by pictures and written words.

PubMed

Li, Degao; Gao, Kejuan; Zhang, Yue; Wu, Xueyun

2012-01-01

Inspired by a previous study of Korean deaf and hard of hearing adolescents, the researchers conducted a priming task of living-nonliving categorization with a sample of Chinese deaf and hard of hearing adolescents. The sample in this study had significantly lower accuracy levels for the thematically related items than for the taxonomically related items and significantly larger differences in reaction times than a group of hearing adolescents when stimuli were changed from pictures to written words. However, they were not significantly different from the hearing adolescents in their performance with the taxonomically related written words. Furthermore, unlike the hearing adolescents, they did not have significantly different reaction times as the result of changes in positions of stimulus presentations.

Surface-Activated Coupling Reactions Confined on a Surface.

PubMed

Dong, Lei; Liu, Pei Nian; Lin, Nian

2015-10-20

Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density-functional theory (DFT) transition-state calculations have been used to shed light on reaction mechanisms and to unravel the trends of different surface materials. In this Account, we discuss recent progress made in two widely studied surface-confined coupling reactions, aryl-aryl (Ullmann-type) coupling and alkyne-alkyne (Glaser-type) coupling, and focus on surface activation effects. Combined experimental and theoretical studies on the same reactions taking place on different metal surfaces have clearly demonstrated that different surfaces not only reduce the reaction barrier differently and render different reaction pathways but also control the morphology of the reaction products and, to some degree, select the reaction products. We end the Account with a list of questions to be addressed in the future. Satisfactorily answering these questions may lead to using the surface-confined coupling reactions to synthesize predefined products with high yield.

A kinetics database and scripts for PHREEQC

NASA Astrophysics Data System (ADS)

Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

2017-12-01

Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

Integrating impairments in reaction time and executive function using a diffusion model framework

PubMed Central

Karalunas, Sarah L.; Huang-Pollock, Cynthia L.

2013-01-01

Using Ratcliff’s diffusion model and ex-Gaussian decomposition, we directly evaluate the role individual differences in reaction time (RT) distribution components play in the prediction of inhibitory control and working memory (WM) capacity in children with and without ADHD. Children with (n=92, x̄ age= 10.2 years, 67% male) and without ADHD (n=62, x̄ age=10.6 years, 46% male) completed four tasks of WM and a stop signal reaction time (SSRT) task. Children with ADHD had smaller WM capacities and less efficient inhibitory control. Diffusion model analyses revealed that children with ADHD had slower drift rates (v) and faster non-decision times (Ter), but there were no group differences in boundary separations (a). Similarly, using an ex-Gaussian approach, children with ADHD had larger τ values than non-ADHD controls, but did not differ in µ or σ distribution components. Drift rate mediated the association between ADHD status and performance on both inhibitory control and WM capacity. τ also mediated the ADHD-executive function impairment associations; however, models were a poorer fit to the data. Impaired performance on RT and executive functioning tasks has long been associated with childhood ADHD. Both are believed to be important cognitive mechanisms to the disorder. We demonstrate here that drift rate, or the speed at which information accumulates towards a decision, is able to explain both. PMID:23334775

Development of a simple analytical methodology for determination of glucosamine release from modified release matrix tablets.

PubMed

Wu, Yunqi; Hussain, Munir; Fassihi, Reza

2005-06-15

A simple spectrophotometric method for determination of glucosamine release from sustained release (SR) hydrophilic matrix tablet based on reaction with ninhydrin is developed, optimized and validated. The purple color (Ruhemann purple) resulted from the reaction was stabilized and measured at 570 nm. The method optimization was essential as many procedural parameters influenced the accuracy of determination including the ninhydrin concentration, reaction time, pH, reaction temperature, purple color stability period, and glucosamine/ninhydrin ratio. Glucosamine tablets (600 mg) with different hydrophilic polymers were formulated and manufactured on a rotary press. Dissolution studies were conducted (USP 26) using deionized water at 37+/-0.2 degrees C with paddle rotation of 50 rpm, and samples were removed manually at appropriate time intervals. Under given optimized reaction conditions that appeared to be critical, glucosamine was quantitatively analyzed and the calibration curve in the range of 0.202-2.020 mg (r=0.9999) was constructed. The recovery rate of the developed method was 97.8-101.7% (n=6). Reproducible dissolution profiles were achieved from the dissolution studies performed on different glucosamine tablets. The developed method is easy to use, accurate and highly cost-effective for routine studies relative to HPLC and other techniques.

Inhibition of enzymatic browning in actual food systems by the Maillard reaction products.

PubMed

Mogol, Burçe Ataç; Yildirim, Asli; Gökmen, Vural

2010-12-01

The Maillard reaction occurring between amino acids and sugars produces neo-formed compounds having certain levels of antioxidant activity depending on the reaction conditions and the type of reactants. The objective of this study was to investigate enzymatic browning inhibition capacity of Maillard reaction products (MRPs) formed from different amino acids including arginine (Arg), histidine (His), lysine (Lys) and proline (Pro). The inhibitory effects of the MRPs on polyphenol oxidase (PPO) were determined. The total antioxidant capacity (TAC) of MRPs derived from different amino acids were in the order Arg > His > Lys > Pro. The TAC and PPO inhibition of MRPs were evaluated as a function of temperature (80-120 °C), time (1-6 h) and pH (2-12). Arg-Glc and His-Glc MRPs exhibited strong TAC and PPO inhibition. Increasing temperature (up to 100 °C) and time also increased TAC and PPO inhibition. Kinetics analysis indicated a mixed type inhibition of PPO by MRPs. The results indicate that the MRPs derived from Arg and His under certain reaction conditions significantly prevent enzymatic browning in actual food systems. The intermediate compounds capable of preventing enzymatic browning are reductones and dehydroreductones, as confirmed by liquid chromatographic-mass spectrometric analyses. Copyright © 2010 Society of Chemical Industry.

Inconsistency in reaction time across the life span.

PubMed

Williams, Benjamin R; Hultsch, David F; Strauss, Esther H; Hunter, Michael A; Tannock, Rosemary

2005-01-01

Inconsistency in latency across trials of 2-choice reaction time data was analyzed in 273 participants ranging in age from 6 to 81 years. A U-shaped curve defined the relationship between age and inconsistency, with increases in age associated with lower inconsistency throughout childhood and higher inconsistency throughout adulthood. Differences in inconsistency were independent of practice, fatigue, and age-related differences in mean level of performance. Evidence for general and specific variability-producing processes was found in those aged less than 21 years, whereas only a specific process, such as attentional blocks, was evident for those 21 years and older. The findings highlight the importance of considering moment-to-moment changes in performance in psychological research. 2005 APA

A solvent replenishment solution for managing evaporation of biochemical reactions in air-matrix digital microfluidics devices.

PubMed

Jebrail, Mais J; Renzi, Ronald F; Sinha, Anupama; Van De Vreugde, Jim; Gondhalekar, Carmen; Ambriz, Cesar; Meagher, Robert J; Branda, Steven S

2015-01-07

Digital microfluidics (DMF) is a powerful technique for sample preparation and analysis for a broad range of biological and chemical applications. In many cases, it is desirable to carry out DMF on an open surface, such that the matrix surrounding the droplets is ambient air. However, the utility of the air-matrix DMF format has been severely limited by problems with droplet evaporation, especially when the droplet-based biochemical reactions require high temperatures for long periods of time. We present a simple solution for managing evaporation in air-matrix DMF: just-in-time replenishment of the reaction volume using droplets of solvent. We demonstrate that this solution enables DMF-mediated execution of several different biochemical reactions (RNA fragmentation, first-strand cDNA synthesis, and PCR) over a range of temperatures (4-95 °C) and incubation times (up to 1 h or more) without use of oil, humidifying chambers, or off-chip heating modules. Reaction volumes and temperatures were maintained roughly constant over the course of each experiment, such that the reaction kinetics and products generated by the air-matrix DMF device were comparable to those of conventional benchscale reactions. This simple yet effective solution for evaporation management is an important advance in developing air-matrix DMF for a wide variety of new, high-impact applications, particularly in the biomedical sciences.

Kinetics of natural oxidant demand by permanganate in aquifer solids.

PubMed

Urynowicz, Michael A; Balu, Balamurali; Udayasankar, Umamaheshwari

2008-02-19

During in situ chemical oxidation with permanganate, natural organic matter and other reduced species in the subsurface compete with the target compounds for the available oxidant and can exert a significant natural oxidant demand. This competition between target and nontarget compounds can have a significant impact on the permeation, dispersal, and persistence of permanganate in the subsurface. The kinetics of natural oxidant demand by permanganate was investigated using a composite sample made up of aquifer material collected from three different sites. The study found that although the depletion of organic carbon increased with increased permanganate dosage and increased reaction period, the mass ratio of MnO(4)(-):OC (wt/wt) was relatively constant over time (11.4+/-0.9). The reaction order and rate with respect to permanganate were found to decrease with time suggesting a continuum of reactions with the slower reactions becoming more controlling with time. However, the data also suggests that this continuum of reactions can be simplified into short- and long-term kinetic expressions representing fast and slow reactions. An independent first-order kinetic model with separate fast and slow reaction rate constants was used to successfully describe the complete kinetic expression of natural oxidant demand. The kinetic parameters used in the model are easily determined and can be used to better understand the complex kinetics of natural oxidant demand.

A solvent replenishment solution for managing evaporation of biochemical reactions in air-matrix digital microfluidics devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jebrail, Mais J.; Renzi, Ronald F.; Sinha, Anupama

Digital microfluidics (DMF) is a powerful technique for sample preparation and analysis for a broad range of biological and chemical applications. In many cases, it is desirable to carry out DMF on an open surface, such that the matrix surrounding the droplets is ambient air. However, the utility of the air-matrix DMF format has been severely limited by problems with droplet evaporation, especially when the droplet-based biochemical reactions require high temperatures for long periods of time. We present a simple solution for managing evaporation in air-matrix DMF: just-in-time replenishment of the reaction volume using droplets of solvent. We demonstrate thatmore » this solution enables DMF-mediated execution of several different biochemical reactions (RNA fragmentation, first-strand cDNA synthesis, and PCR) over a range of temperatures (4–95 °C) and incubation times (up to 1 h or more) without use of oil, humidifying chambers, or off-chip heating modules. Reaction volumes and temperatures were maintained roughly constant over the course of each experiment, such that the reaction kinetics and products generated by the air-matrix DMF device were comparable to those of conventional benchscale reactions. As a result, this simple yet effective solution for evaporation management is an important advance in developing air-matrix DMF for a wide variety of new, high-impact applications, particularly in the biomedical sciences.« less

A solvent replenishment solution for managing evaporation of biochemical reactions in air-matrix digital microfluidics devices

DOE PAGES

Jebrail, Mais J.; Renzi, Ronald F.; Sinha, Anupama; ...

2014-10-01

Digital microfluidics (DMF) is a powerful technique for sample preparation and analysis for a broad range of biological and chemical applications. In many cases, it is desirable to carry out DMF on an open surface, such that the matrix surrounding the droplets is ambient air. However, the utility of the air-matrix DMF format has been severely limited by problems with droplet evaporation, especially when the droplet-based biochemical reactions require high temperatures for long periods of time. We present a simple solution for managing evaporation in air-matrix DMF: just-in-time replenishment of the reaction volume using droplets of solvent. We demonstrate thatmore » this solution enables DMF-mediated execution of several different biochemical reactions (RNA fragmentation, first-strand cDNA synthesis, and PCR) over a range of temperatures (4–95 °C) and incubation times (up to 1 h or more) without use of oil, humidifying chambers, or off-chip heating modules. Reaction volumes and temperatures were maintained roughly constant over the course of each experiment, such that the reaction kinetics and products generated by the air-matrix DMF device were comparable to those of conventional benchscale reactions. As a result, this simple yet effective solution for evaporation management is an important advance in developing air-matrix DMF for a wide variety of new, high-impact applications, particularly in the biomedical sciences.« less

Using an enzymatic galactose assay to detect lactose glycation extents of two proteins caseinate and soybean protein isolate via the Maillard reaction.

PubMed

Wang, Xiao-Peng; Zhao, Xin-Huai

2017-06-01

Glycation of food proteins via the Maillard reaction has been widely studied in the recent years; however, the amount of saccharide connected to proteins is usually not determined. An enzymatic galactose assay was proposed firstly in this study to detect lactose glycation extents of caseinate and soybean protein isolate (SPI) during the Maillard reaction at two temperatures and different times. The separated glycated proteins were hydrolysed to release galactose necessary for the enzymatic assay and glycation calculation. Caseinate and SPI both obtained the highest lactose glycation extents at 100 °C or 121 °C by a reaction time of 180 or 20 min. Short- and long-time reaction resulted in lower glycation extents. During the reaction, three chemical indices (absorbences at 294/490 nm and fluorescence intensities) of reaction mixtures increased continually, but another index reactable NH 2 of glycated proteins showed the opposite trend. In general, changing profiles of the four indices were inconsistent with those profiles of lactose glycation extents of glycated proteins, implying practical limitation of the four indices in studies. This proposed enzymatic assay could directly detect lactose glycation of the two proteins, and thus was more useful than the four chemical indices to monitor glycation of the two proteins. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Developmental Changes in the Processing of Hierarchical Shapes Continue into Adolescence.

ERIC Educational Resources Information Center

Mondloch, Catherine J.; Geldart, Sybil; Maurer, Daphne; de Schonen, Scania

2003-01-01

Three experiments obtained same-different judgments from children and adults to trace normal development of local and global processing of hierarchical visual forms. Findings indicated that reaction time was faster on global trials than local trials; bias was stronger in children and diminished to adult levels between ages 10 and 14. Reaction time…

Experimental phytophotodermatitis.

PubMed

Gonçalves, N E L; de Almeida, H L; Hallal, E C; Amado, M

2005-12-01

Phytophotodermatitis (PPD) is defined as a phototoxic reaction of the skin after contact with substances derived from plants and subsequent exposure to sunlight. It is a frequent disease in our outpatient clinics during summer because of contact with Tahitian lemon. Our objectives were to experimentally reproduce PPD in rats, to identify whether PPD is induced by minimal exposure periods to sunlight, to find what kinds of lemons and which parts of the lemon (the fruit juice or the peel juice) may trigger the disease; to know whether the use of sunblock prevents the reaction; and to perform light microscopy of the lesions to describe their histology. Adult rats (Rattus norwegicus), three in each experiment, were used. After painting the rats with the fruit juice or the peel juice they were exposed to sunlight for 2.5, 5, 7.5, and 10 min. Tahitian and Sicilian lemons were used in the experiments. Biopsies with 3-mm punches of different times of exposure were performed. The peel juice of both lemons reproduced PPD, which was clinically evident after 48 h. When the peel juice was alone applied there was no reaction; moreover, exposure to sunlight alone triggered no reaction. Two and a half minutes of exposure time was sufficient to induce phototoxic reaction, which was time dependent (the longer the exposure the more intense the reaction). Histopathological studies showed epithelial time-dependent vacuolar degeneration. The use of sunblock diminished the intensity of the reaction but did not prevent it. PPD can be reproduced in an animal model. It may be caused by the peel juice of Tahitian and Sicilian lemon. Because of an extremely short time of exposure (2.5 min) is sufficient to induce PPD it is necessary to alert the population, of the need for caution when handling lemons, especially outdoors despite using sunblock.

Simultaneous destraction and desulfurization of Illinois coals with supercritical ethanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, B.C.

1983-01-01

Various Illinois coals (with Illinois number6 being the main one) are liquefied with various supercritical solvents (ethanol being the main solvent) at 543-598 K, system pressures of 6.99-24.23 MPa, flow rates of 3.0-7.5 ml/min, reaction time of 0-180 minutes, and coal particle sizes of 0.36-0.85 mm to 1.00-2.36 mm to systematically investigate the effects of flow rates, reaction time, coal particle size, temperature, pressure, coal characteristics (by using different Illinois coals), supercritical medium (by using different solvents), and the addition of potassium hydroxide. The % weight loss of coal and the % sulfur removal during destraction and desulfurization of coalmore » are functions of the flow rate, the reaction time, the coal particle size, temperature, pressure and the supercritical solvent. Temperature, pressure and the supercritical medium are the most important parameters in controlling the % weight loss of coal and the % sulfur removal. The % weight loss of coal can be related to a power law and fits quite nicely into a second order kinetic model. The % sulfur removal also follows a second order kinetic model. A secondary reaction is observed during the destraction process, which implies that destraction, and possibly desulfurization, of coal is a multistep reaction including a physical extraction step where the major portion of the coal and sulfur was removed and then followed by a chemical reaction. Supercritical ethanol definitely enhances the removal of sulfur compounds from coal. The enhanced selectivity by supercritical ethanol is greatest at a pressure just above the critical pressure of ethanol. Finally, addition of a base such as potassium hydroxide enhances both % weight loss of coal and the % sulfur removal.« less

[Effects of prefrontal ablations on the reaction of the active choice of feeder under different probability and value of the reinforcement on dog].

PubMed

Preobrazhenskaia, L A; Ioffe, M E; Mats, V N

2004-01-01

The role of the prefrontal cortex was investigated on the reaction of the active choice of the two feeders under changes value and probability reinforcement. The experiments were performed on 2 dogs with prefrontal ablation (g. proreus). Before the lesions the dogs were taught to receive food in two different feeders to conditioned stimuli with equally probable alimentary reinforcement. After ablation in the inter-trial intervals the dogs were running from the one feeder to another. In the answer to conditioned stimuli for many times the dogs choose the same feeder. The disturbance of the behavior after some times completely restored. In the experiments with competition of probability events and values of reinforcement the dogs chose the feeder with low-probability but better quality of reinforcement. In the experiments with equal value but different probability the intact dogs chose the feeder with higher probability. In our experiments the dogs with prefrontal lesions chose the each feeder equiprobably. Thus in condition of free behavior one of different functions of the prefrontal cortex is the reactions choose with more probability of reinforcement.

Eat Me If You Can: Cognitive Mechanisms Underlying the Distance Effect

PubMed Central

Junghans, Astrid F.; Evers, Catharine; De Ridder, Denise T. D.

2013-01-01

Proximal objects provide affordances that activate the motor information involved in interacting with the objects. This effect has previously been shown for artifacts but not for natural objects, such as food. This study examined whether the sight of proximal food, compared to distant food activates eating-related information. In two experiments reaction times to verbal labels following the sight of proximal and distant objects (food and toys) were measured. Verbal labels included function words that were compatible with one object category (eating and playing) and observation words compatible with both object categories. The sight of food was expected to activate eating-related information when presented at proximity but not at distance, as reflected by faster reaction times to proximal than distant compatible eating words and no difference between reaction times to proximal and distant food for observation words (Experiment 1). Experiment 2 additionally compared the reaction times to wrapped and unwrapped food. The distance effect was expected to occur only for unwrapped food because only unwrapped food is readily edible. As expected, Experiment 1 and 2 revealed faster responses to compatible eating words at proximity than at distance. In Experiment 2 this distance effect occurred only for readily edible, unwrapped food but not for wrapped food. For observation words no difference in response times between the distances was found. These findings suggest that the sight of proximal food activates eating-related information, which could explain people’s differential behavioral responses to reachable versus distant food. The activation of eating-related information upon sight of accessible food could provide a cognition-based explanation for mindless eating. PMID:24367684

The expulsion from Disneyland: the social psychological impact of 9/11.

PubMed

Morgan, G Scott; Wisneski, Daniel C; Skitka, Linda J

2011-09-01

People expressed many different reactions to the events of September 11th, 2001. Some of these reactions were clearly negative, such as political intolerance, discrimination, and hate crimes directed toward targets that some, if not many, people associated with the attackers. Other reactions were more positive. For example, people responded by donating blood, increasing contributions of time and money to charity, and flying the American flag. The goal of this article is to review some of Americans' negative and positive reactions to 9/11. We also describe two frameworks, value protection and terror management theory, that provide insights into Americans' various reactions to the tragedy of 9/11. © 2011 American Psychological Association

Sex differences in memory of emotional images: a behavioral and electrophysiological investigation.

PubMed

Glaser, Emma; Mendrek, Adrianna; Germain, Martine; Lakis, Nadia; Lavoie, Marc E

2012-07-01

Current research suggests that emotional responses differ between men and women. Sex differences regarding emotional effects on memory have been recently studied through brain imaging techniques. However, the majority of investigations have often neglected to balance the variable of emotional intensity (arousal) across pleasant and unpleasant pictures. Additionally, men and women were often mixed or studied separately. The current study aims at comparing men and women's electrophysiological responses related to emotional memory of photographic material. These responses were measured using Event Related brain Potentials (ERP) in response to a task of episodic memory of emotional images. The frontal N200, the parietal P300 and the central LPC were compared in 17 men and 17 women matched for age, social economic status, education and intelligence. Behavioral results showed that, in men, reaction times were modulated by valence, whereas for women, reaction times were mainly modulated by arousal. Accuracy was affected by both emotional valence and arousal, but only in women. ERP analyses revealed that emotional valence influenced earlier time components (frontal N200 and parietal P300), whereas arousal influenced memory in the later time component (central LPC). Moreover, sex differences, mediated by valence and arousal, were found in ERP responses at different times in the processing stream. Copyright © 2012 Elsevier B.V. All rights reserved.

Single-Molecule Reaction Chemistry in Patterned Nanowells

PubMed Central

2016-01-01

A new approach to synthetic chemistry is performed in ultraminiaturized, nanofabricated reaction chambers. Using lithographically defined nanowells, we achieve single-point covalent chemistry on hundreds of individual carbon nanotube transistors, providing robust statistics and unprecedented spatial resolution in adduct position. Each device acts as a sensor to detect, in real-time and through quantized changes in conductance, single-point functionalization of the nanotube as well as consecutive chemical reactions, molecular interactions, and molecular conformational changes occurring on the resulting single-molecule probe. In particular, we use a set of sequential bioconjugation reactions to tether a single-strand of DNA to the device and record its repeated, reversible folding into a G-quadruplex structure. The stable covalent tether allows us to measure the same molecule in different solutions, revealing the characteristic increased stability of the G-quadruplex structure in the presence of potassium ions (K+) versus sodium ions (Na+). Nanowell-confined reaction chemistry on carbon nanotube devices offers a versatile method to isolate and monitor individual molecules during successive chemical reactions over an extended period of time. PMID:27270004

Visual Motion Processing Subserves Faster Visuomotor Reaction in Badminton Players.

PubMed

Hülsdünker, Thorben; Strüder, Heiko K; Mierau, Andreas

2017-06-01

Athletes participating in ball or racquet sports have to respond to visual stimuli under critical time pressure. Previous studies used visual contrast stimuli to determine visual perception and visuomotor reaction in athletes and nonathletes; however, ball and racquet sports are characterized by motion rather than contrast visual cues. Because visual contrast and motion signals are processed in different cortical regions, this study aimed to determine differences in perception and processing of visual motion between athletes and nonathletes. Twenty-five skilled badminton players and 28 age-matched nonathletic controls participated in this study. Using a 64-channel EEG system, we investigated visual motion perception/processing in the motion-sensitive middle temporal (MT) cortical area in response to radial motion of different velocities. In a simple visuomotor reaction task, visuomotor transformation in Brodmann area 6 (BA6) and BA4 as well as muscular activation (EMG onset) and visuomotor reaction time (VMRT) were investigated. Stimulus- and response-locked potentials were determined to differentiate between perceptual and motor-related processes. As compared with nonathletes, athletes showed earlier EMG onset times (217 vs 178 ms, P < 0.001), accompanied by a faster VMRT (274 vs 243 ms, P < 0.001). Furthermore, athletes showed an earlier stimulus-locked peak activation of MT (200 vs 182 ms, P = 0.002) and BA6 (161 vs 137 ms, P = 0.009). Response-locked peak activation in MT was later in athletes (-7 vs 26 ms, P < 0.001), whereas no group differences were observed in BA6 and BA4. Multiple regression analyses with stimulus- and response-locked cortical potentials predicted EMG onset (r = 0.83) and VMRT (r = 0.77). The athletes' superior visuomotor performance in response to visual motion is primarily related to visual perception and, to a minor degree, to motor-related processes.

One-step hydrothermal synthesis and electrochemical performance of sodium-manganese-iron phosphate as cathode material for Li-ion batteries

NASA Astrophysics Data System (ADS)

Karegeya, Claude; Mahmoud, Abdelfattah; Vertruyen, Bénédicte; Hatert, Frédéric; Hermann, Raphaël P.; Cloots, Rudi; Boschini, Frédéric

2017-09-01

The sodium-manganese-iron phosphate Na2Mn1.5Fe1.5(PO4)3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na+ and presence of vacancies in A(2)', Na+ and small amounts of Mn2+ in A(1), Mn2+ in M(1), 0.5 Mn2+ and Fe cations (Mn2+,Fe2+ and Fe3+) in M(2), leading to the structural formula Na2Mn(Mn0.5Fe1.5)(PO4)3. The particles morphology was investigated by SEM. Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 h at 220 °C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220 °C for 6 h. When the reaction time was increased from 6 to 12, 24 and 48 h, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mA h g-1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99% during 50 cycles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karegeya, Claude; Mahmoud, Abdelfattah; Vertruyen, Bénédicte

The sodium-manganese-iron phosphate Na 2Mn 1.5Fe 1.5(PO 4) 3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na + and presence of vacancies in A(2)’, Na + and small amounts of Mn 2+ in A(1), Mn 2+ in M(1) , 0.5 Mn 2+ and Fe cations (Mn 2+,Fe 2+ and Fe 3+) in M(2), leading to the structural formula Na 2Mn(Mn 0.5Fe 1.5)(PO 4) 3. The particles morphology was investigated by SEM.more » Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 hours at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 hours. When the reaction time was increased from 6 to 12, 24 and 48 hours, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mAhg-1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99 % during 50 cycles.« less

Synchronization criteria for generalized reaction-diffusion neural networks via periodically intermittent control.

PubMed

Gan, Qintao; Lv, Tianshi; Fu, Zhenhua

2016-04-01

In this paper, the synchronization problem for a class of generalized neural networks with time-varying delays and reaction-diffusion terms is investigated concerning Neumann boundary conditions in terms of p-norm. The proposed generalized neural networks model includes reaction-diffusion local field neural networks and reaction-diffusion static neural networks as its special cases. By establishing a new inequality, some simple and useful conditions are obtained analytically to guarantee the global exponential synchronization of the addressed neural networks under the periodically intermittent control. According to the theoretical results, the influences of diffusion coefficients, diffusion space, and control rate on synchronization are analyzed. Finally, the feasibility and effectiveness of the proposed methods are shown by simulation examples, and by choosing different diffusion coefficients, diffusion spaces, and control rates, different controlled synchronization states can be obtained.

The Simplest Chronoscope V: A Theory of Dual Primary and Secondary Reaction Time Systems.

PubMed

Montare, Alberto

2016-12-01

Extending work by Montare, visual simple reaction time, choice reaction time, discriminative reaction time, and overall reaction time scores obtained from college students by the simplest chronoscope (a falling meterstick) method were significantly faster as well as significantly less variable than scores of the same individuals from electromechanical reaction timers (machine method). Results supported the existence of dual reaction time systems: an ancient primary reaction time system theoretically activating the V5 parietal area of the dorsal visual stream that evolved to process significantly faster sensory-motor reactions to sudden stimulations arising from environmental objects in motion, and a secondary reaction time system theoretically activating the V4 temporal area of the ventral visual stream that subsequently evolved to process significantly slower sensory-perceptual-motor reactions to sudden stimulations arising from motionless colored objects. © The Author(s) 2016.

Reaction front dynamics under shear flow for arbitrary Damköhler numbers

NASA Astrophysics Data System (ADS)

Bandopadhyay, Aditya; Méheust, Yves; Le Borgne, Tanguy

2016-04-01

Reaction fronts where two reactive fluids displace one another play an important role in a range of applications, including contaminant plume transport and reaction, soil and aquifer remediation, CO2 sequestration, geothermal dipoles and the development of hotspots of reaction in mixing zones. The background flow induces enhanced mixing, and therefore reaction, through interfacial shear. Hence the coupling of fluid flow with chemical reactions is pivotal in understanding and quantifying effective reaction kinetics in reaction fronts. While this problem has been addressed in the limit of fast reactions (e.g. de Simoni 2005, Le Borgne 2014), in natural systems reactions can span a large range of Damköhler numbers since their characteristic reaction times vary over a large range of typical values. Here the coupling of shear flow and reversible chemical reactions is studied for a reaction front with initially separated reactants at arbitrary Damköhler numbers. Approximate analytical expressions for the global production rate are derived based on a reactive lamella approach. We observe three distinct regimes, each of them characterized by different scalings of the global production rate and width of the reactive zone. We describe the dependency of these scalings and the associated characteristic transition times as a function of Damköhler and Péclet numbers. These results are validated against 2D numerical simulations. The study is expected to shed light on the inherently complex cases of reactive mixing with varying reaction rates under the influence of an imposed flow. de Simoni et al. (2005) Water Resour. Res., 41, W11410 Le Borgne et al. (2014) GRL, 41(22), 7898

Exposure Time Distributions reveal Denitrification Rates along Groundwater Flow Path of an Agricultural Unconfined Aquifer

NASA Astrophysics Data System (ADS)

Kolbe, T.; Abbott, B. W.; Thomas, Z.; Labasque, T.; Aquilina, L.; Laverman, A.; Babey, T.; Marçais, J.; Fleckenstein, J. H.; Peiffer, S.; De Dreuzy, J. R.; Pinay, G.

2016-12-01

Groundwater contamination by nitrate is nearly ubiquitous in agricultural regions. Nitrate is highly mobile in groundwater and though it can be denitrified in the aquifer (reduced to inert N2 gas), this process requires the simultaneous occurrence of anoxia, an electron donor (e.g. organic carbon, pyrite), nitrate, and microorganisms capable of denitrification. In addition to this the ratio of the time groundwater spent in a denitrifying environment (exposure time) to the characteristic denitrification reaction time plays an important role, because denitrification can only occur if the exposure time is longer than the characteristic reaction time. Despite a long history of field studies and numerical models, it remains exceedingly difficult to measure or model exposure times in the subsurface at the catchment scale. To approach this problem, we developed a unified modelling approach combining measured environmental proxies with an exposure time based reactive transport model. We measured groundwater age, nitrogen and sulfur isotopes, and water chemistry from agricultural wells in an unconfined aquifer in Brittany, France, to quantify changes in nitrate concentration due to dilution and denitrification. Field data showed large differences in nitrate concentrations among wells, associated with differences in the exposure time distributions. By constraining a catchment-scale characteristic reaction time for denitrification with water chemistry proxies and exposure times, we were able to assess rates of denitrification along groundwater flow paths. This unified modeling approach is transferable to other catchments and could be further used to investigate how catchment structure and flow dynamics interact with biogeochemical processes such as denitrification.

Gold-nanoparticle-catalyzed synthesis of propargylamines: the traditional A3-multicomponent reaction performed as a two-step flow process.

PubMed

Abahmane, Lahbib; Köhler, J Michael; Gross, G Alexander

2011-03-01

The alkyne, aldehyde, amine A(3)-coupling reaction, a traditional multicomponent reaction (MCR), has been investigated as a two-step flow process. The implicated aminoalkylation reaction of phenylacetylene with appropriate aldimine intermediates was catalyzed by gold nanoparticles impregnated on alumina. The aldimine formation was catalyzed by Montmorillonite K10 beforehand. The performance of the process has been investigated with respect to different reaction regimes. Usually, the A(3)-multicomponent reaction is performed as a "one-pot" process. Diversity-oriented syntheses using MCRs often have the shortcoming that only low selectivity and low yields are achieved. We have used a flow-chemistry approach to perform the A(3)-MCR in a sequential manner. In this way, the reaction performance was significantly enhanced in terms of shortened reaction time, and the desired propargylamines were obtained in high yields. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustion

NASA Technical Reports Server (NTRS)

Ryan, Thomas W., III; Schwab, S. T.; Harlowe, W. W.

1992-01-01

The subject of this paper is the design of supersonic combustors which will be required in order to achieve the needed reaction rates in a reasonable sized combustor. A fuel additive approach, which is the focus of this research, is the use of pyrophorics to shorten the ignition delay time and to increase the energy density of the fuel. Pyrophoric organometallic compounds may also provide an ignition source and flame stabilization mechanism within the combustor, thus permitting use of hydrocarbon fuels in supersonic combustion systems. Triethylaluminum (TEA) and trimethylaluminum (TMA) were suggested for this application due to their high energy density and reactivity. The objective here is to provide comparative data for the ignition quality, the energy content, and the reaction rates of several different adducts of both TEA and TMA. The results of the experiments indicate the aluminum alkyls and their more stable derivatives reduce the ignition delay and total reaction time to JP-10 jet fuel. Furthermore, the temperature dependence of ignition delay and total reaction time of the blends of the adducts are significantly lower than in neat JP-10.

[Study of blood oxygen saturation, heart rate changes and plateau reaction of the Antarctic Kunlun station investigation team in different plateau environments].

PubMed

Zhao, Shun-yun; Wu, Xin-min; Guo, Ya-min; Zhang, Shu-shun; An, Yan-ming; Li, Bing; Wang, Hao

2013-06-11

To explore the blood oxygen saturation and heart rate changes of the Antarctic explorers. During August 2010 to April 2011, the changes in blood oxygen saturation, heart rate and plateau reaction of 16 Antarctic expedition team in different plateau environments (Tibetan plateau versus Antarctic plateau) were monitored with the noninvasive pulse oximeter MD300-C. The extent of acute mountain sickness was determined according to the Lake Louise Consensus acute mountain reaction symptom scores and judgment method. The changes of blood oxygen saturation, heart rate at different altitudes of 110, 3650, 4300 m (96.8% ± 1.2%,89.1% ± 1.2%, 86.1% ± 2.0%, (75.0 ± 5.4) times/min, (104.0 ± 4.3) times/min, (113.0 ± 5.2) times/min,F = 214.155, 240.088,both P < 0.05). With rising latitude and elevation gradient in Antarctic plateau, the changes of blood oxygen saturation, heart rate at different altitudes of 2000, 2500, 3000, 3500 and 4087 m(91.9% ± 1.3%,90.5% ± 1.3%,87.6% ± 1.4%,85.0% ± 1.8%,81.5% ± 2.2%, (85.9 ± 3.2) times/min, (90.6 ± 2.8) times/min, (97.8 ± 4.1) times/min, (102.0 ± 3.4) times/min, (106.3 ± 3.9) times/min, F = 105.418, 90.174, both P < 0.05). Levels of blood oxygen saturation and heart rate were both correlated with the risk of altitude sickness (r = -0.446 and 0.565, both P < 0.05). As the increases of altitude, there are significant changes in oxygen saturation, heart rate of the Antarctic explorers. And with the increases of altitude, the risk of altitude sickness gradually increases.

Individual and Developmental Differences in Cognitive-Processing Components of Mental Ability

ERIC Educational Resources Information Center

Keating, Daniel P.; Bobbitt, Bruce L.

1978-01-01

Three experiments (simple versus choice reaction time, Posner letter identification, and Sternberg memory scanning) attempted to determine whether reliable individual differences in cognitive processing exist in children and, if so, whether these differences are systematically related to age and ability. (Author/JMB)

Determination of detonation parameters for liquid high explosives

NASA Astrophysics Data System (ADS)

Mochalova, Valentina; Utkin, Alexander

2012-03-01

The experimental investigation of detonation parameters and reaction zone structure in liquid HE (bis-(2-fluoro-2,2-dinitroethyl)formal (FEFO), tetranitromethane (TNM), nitromethane (NM)) was conducted by means of laser interferometer VISAR. Detonation front in TNM and NM was stable while the instability of detonation in FEFO was observed. The parameters of Von Neumann spike were determined for these HE. The different methods for C-J point determination were used for each HE. For FEFO reaction time t was found from experiments with different charge diameters (τ is approximately equal to 300 ns); for TNM - at fixed diameter and different lengths of charges (τ ≈ 200 ns); for NM - at fixed diameter and length of charges, but detonation initiation was carried out by different explosive charges (τ ≈ 50 ns). It was found that in TNM the detonation velocity depends on charge diameter. Maximum value of reaction rate in investigated liquid HE was observed after shock jump.

Alterations of Visual Reaction Time and Short Term Memory in Military Radar Personnel

PubMed Central

MORTAZAVI, Seyed Mohammad Javad; TAEB, Shahram; DEHGHAN, Naser

2013-01-01

Background Radar transmitters emit high-power radiofrequency radiation by creation of a high-voltage and high-frequency alternating electrical current. Methods: Health effects of occupational exposure to military radar were investigated. Visual reaction time was recorded with a simple blind computer-assisted-visual reaction time test. To assess the short-term memory, modified Wechsler Memory Scale test was performed. Results: The mean +/- SD reaction time in radar works (N=100) and the control group (N=57) were 238.58 +/− 23.47 milliseconds and 291.86 +/− 28.26 milliseconds (P<0.0001), respectively. The scores of forward digit span in radar works and the control group were 3.56 +/− 0.77 and 4.29 +/− 1.06 (P<0.0001), while the scores of backward digit span in radar works and the control group were 2.70 +/− 0.69 and 3.62 +/− 0.95 (P<0.0001). The scores of word recognition in radar works and the control group were 3.37 +/− 1.13 and 5.86 +/− 1.11 (P<0.0001). Finally, the scores of paired words in radar works and the control group were 13.56 +/− 1.78 and 15.21 +/− 2.20 (P<0.0001). It can be concluded that occupational exposures to radar radiations decreases reaction time, which may lead to a better response to different hazards. Conclusion: To the best of our knowledge, this is the first study to show that occupational exposure to radar microwave radiation leads to decreased reaction time and the lower performance of short-term memory. Altogether, these results indicate that occupational exposure to radar microwave radiations may be linked to some non-detrimental and detrimental health effects. PMID:23785684

Real-time dielectric studies of polymerizing systems

NASA Astrophysics Data System (ADS)

Williams, G.; Smith, I. K.; Holmes, P. A.; Varma, S.

1999-03-01

The use of real-time dielectric relaxation spectroscopy (DRS) for monitoring changes in molecular mobility during reaction for thermosetting systems is described together with phenomenological and molecular theories of the time-dependent relaxation functions that are involved. Reduced molecular mobility normally leads to the diffusion control of a reaction and ultimately to glass formation at the polymerization temperature 0953-8984/11/10A/004/img7. We present new DRS results for a boroxine/epoxide system that show glass formation below a `floor temperature' 0953-8984/11/10A/004/img8 and very different behaviour above 0953-8984/11/10A/004/img8, when the dielectric properties become independent of time and an elastomer is formed.

Comparisons of mental clocks.

PubMed

Paivio, A

1978-02-01

Subjects in three experiments were presented with pairs of clock times and were required to choose the one in which the hour and minute hand formed the smaller angle. In Experiments 1 and 2, the times were presented digitally, necessitating a transformation into symbolic representations from which the angular size difference could be inferred. The results revealed orderly symbolic distance effects so that comparison reaction time increased as the angular size difference decreased. Moreover, subjects generally reported using imagery to make the judgment, and subjects scoring high on test of imagery ability were faster than those scoring low on such tests. Experiment 3 added a direct perceptual condition in which subjects compared angles between pairs of hands on two drawn (analog) clocks, as well as a mixed condition involving one digital and one analog clock time. The results showed comparable distance effects for all conditions. In addition, reaction time increased from the perceptual, to the mixed, to the pure-digital condition. These results are consistent with predictions from an image-based dual-coding theory.

Apparatus for and method of monitoring for breached fuel elements

DOEpatents

Gross, K.C.; Strain, R.V.

1981-04-28

This invention teaches improved apparatus for the method of detecting a breach in cladded fuel used in a nuclear reactor. The detector apparatus uses a separate bypass loop for conveying part of the reactor coolant away from the core, and at least three separate delayed-neutron detectors mounted proximate this detector loop. The detectors are spaced apart so that the coolant flow time from the core to each detector is different, and these differences are known. The delayed-neutron activity at the detectors is a function of the delay time after the reaction in the fuel until the coolant carrying the delayed-neutron emitter passes the respective detector. This time delay is broken down into separate components including an isotopic holdup time required for the emitter to move through the fuel from the reaction to the coolant at the breach, and two transit times required for the emitter now in the coolant to flow from the breach to the detector loop and then via the loop to the detector.

Uncovering the Geometry of Barrierless Reactions Using Lagrangian Descriptors.

PubMed

Junginger, Andrej; Hernandez, Rigoberto

2016-03-03

Transition-state theories describing barrierless chemical reactions, or more general activated problems, are often hampered by the lack of a saddle around which the dividing surface can be constructed. For example, the time-dependent transition-state trajectory uncovering the nonrecrossing dividing surface in thermal reactions in the framework of the Langevin equation has relied on perturbative approaches in the vicinity of the saddle. We recently obtained an alternative approach using Lagrangian descriptors to construct time-dependent and recrossing-free dividing surfaces. This is a nonperturbative approach making no reference to a putative saddle. Here we show how the Lagrangian descriptor can be used to obtain the transition-state geometry of a dissipated and thermalized reaction across barrierless potentials. We illustrate the method in the case of a 1D Brownian motion for both barrierless and step potentials; however, the method is not restricted and can be directly applied to different kinds of potentials and higher dimensional systems.

Allocation of attentional resources during habituation and dishabituation of male sexual arousal.

PubMed

Koukounas, E; Over, R

1999-12-01

A secondary-task probe (tone) was presented intermittently while men viewed erotic film segments across a session involving 18 trials with the same film segment (habituation), then 2 trials with different film segments (novelty) and 2 trials with reinstatement of the original segment (dishabituation). Reaction time to the tone (an index of the extent processing resources were being committed to the erotic stimulus) shifted during the session in parallel with changes that occurred in penile tumescence and subjective sexual arousal. The decrease in sexual arousal over the first 18 trials in the session was accompanied by a progressively faster reaction to the tone, novel stimulation led to recovery of sexual arousal and a slower reaction to the tone, and on trials 21 and 22 sexual arousal and reaction time levels were above the values that prevailed immediately prior to novel stimulation. Results are discussed with reference to the relationship between habituation and attention.

Perceived Parental Reactions to Adolescent Distress (PRAD): Development and Validation of a Brief Measure

PubMed Central

Barbot, Baptiste; Heinz, Sasha L.; Luthar, Suniya S.

2013-01-01

Although adolescence is a time of individuation with increased reliance on peers, research indicates that, despite a deliberate distancing from parents, adolescents continue to seek the support and console of parental attachment figures in times of distress. The Perceived Parental Reactions to Adolescent Distress (PRAD) is a brief self-report measure developed to examine adolescents’ perception of parental response under conditions of distress as measured by four conceptually and empirically distinct parental reactions to distress: Comfort, Self-focus, Avoidance and Harshness. Across two studies involving a total of 738 high school students, we developed the PRAD and substantiated its robust psychometric properties, including evidence for reliability as well as internal and criterion validity. Sources of individual differences in the test-scores were also explored. Empirical as well as practical importance of assessing parental reactions to adolescent distress is discussed with regard to both the attachment and adolescent development literature. PMID:23777451

Normobaric hypoxia overnight impairs cognitive reaction time.

PubMed

Pramsohler, Stephan; Wimmer, Stefan; Kopp, Martin; Gatterer, Hannes; Faulhaber, Martin; Burtscher, Martin; Netzer, Nikolaus Cristoph

2017-05-15

Impaired reaction time in patients suffering from hypoxia during sleep, caused by sleep breathing disorders, is a well-described phenomenon. High altitude sleep is known to induce periodic breathing with central apneas and oxygen desaturations, even in perfectly healthy subjects. However, deficits in reaction time in mountaineers or workers after just some nights of hypoxia exposure are not sufficiently explored. Therefore, we aimed to investigate the impact of sleep in a normobaric hypoxic environment on reaction time divided by its cognitive and motoric components. Eleven healthy non acclimatized students (5f, 6m, 21 ± 2.1 years) slept one night at a simulated altitude of 3500 m in a normobaric hypoxic room, followed by a night with polysomnography at simulated 5500 m. Preexisting sleep disorders were excluded via BERLIN questionnaire. All subjects performed a choice reaction test (SCHUHFRIED RT, S3) at 450 m and directly after the nights at simulated 3500 and 5500 m. We found a significant increase of cognitive reaction time with higher altitude (p = 0.026). No changes were detected in movement time (p = n.s.). Reaction time, the combined parameter of cognitive- and motoric reaction time, didn't change either (p = n.s.). Lower SpO 2 surprisingly correlated significantly with shorter cognitive reaction time (r = 0.78, p = 0.004). Sleep stage distribution and arousals at 5500 m didn't correlate with reaction time, cognitive reaction time or movement time. Sleep in hypoxia does not seem to affect reaction time to simple tasks. The component of cognitive reaction time is increasingly delayed whereas motoric reaction time seems not to be affected. Low SpO 2 and arousals are not related to increased cognitive reaction time therefore the causality remains unclear. The fact of increased cognitive reaction time after sleep in hypoxia, considering high altitude workers and mountaineering operations with overnight stays, should be further investigated.

Cognitive changes after saline or plasmalyte infusion in healthy volunteers: a multiple blinded, randomized, cross-over trial.

PubMed

Story, David A; Lees, Lucy; Weinberg, Laurence; Teoh, Soon-Yee; Lee, Katherine J; Velissaris, Sarah; Bellomo, Rinaldo; Wilson, Sarah J

2013-09-01

In an incidental finding, during a study of plasma chemistry after crystalloid infusion, participants reported subjective cognitive changes, particularly slower thinking, after saline but not Hartmann's (Ringer's lactate) solution. The authors tested the hypothesis that saline infusion would produce greater adverse cognitive changes than Plasmalyte infusion. The authors conducted a randomized, cross-over, multiple blinded study of healthy adult volunteers. On separate days, participants received 30 ml/kg over 1 h of either 0.9% saline or Plasmalyte with the order randomly allocated. Plasma chemistry was tested on venous samples. As part of a battery of cognitive tests our primary endpoint was the reaction time index after infusion. The authors studied 25 participants. Plasma chloride was greater after saline than after Plasmalyte: mean difference 5.4 mM (95% CI, 4.1-6.6 mM; P < 0.001). Saline was also associated with greater metabolic acidosis: base-excess 2.5 mM more negative (95% CI, 1.9-3.0 mM more negative; P < 0.001). There was no evidence of a difference in the reaction time index between the two interventions: mean reaction time index 394 ms (SD, 72) after saline versus 385 ms (SD, 55) after Plasmalyte. Difference: saline 9 ms slower (95% CI, 30 ms slower to 12 ms faster; P = 0.39). There were minimal differences in the other cognitive and mood tests. Despite expected differences in plasma chemistry, the authors found that measures of cognition did not differ after infusions of Plasmalyte or saline.

Variation in spawning time promotes genetic variability in population responses to environmental change in a marine fish

PubMed Central

Hutchings, Jeffrey A

2015-01-01

Abstract The level of phenotypic plasticity displayed within a population (i.e. the slope of the reaction norm) reflects the short-term response of a population to environmental change, while variation in reaction norm slopes among populations reflects spatial variation in these responses. Thus far, studies of thermal reaction norm variation have focused on geographically driven adaptation among different latitudes, altitudes or habitats. Yet, thermal variability is a function of both space and time. For organisms that reproduce at different times of year, such variation has the potential to promote adaptive variability in thermal responses for critical early life stages. Using common-garden experiments, we examined the spatial scale of genetic variation in thermal plasticity for early life-history traits among five populations of endangered Atlantic cod (Gadus morhua) that spawn at different times of year. Patterns of plasticity for larval growth and survival suggest that population responses to climate change will differ substantially, with increasing water temperatures posing a considerably greater threat to autumn-spawning cod than to those that spawn in winter or spring. Adaptation to seasonal cooling or warming experienced during the larval stage is suggested as a possible cause. Furthermore, populations that experience relatively cold temperatures during early life might be more sensitive to changes in temperature. Substantial divergence in adaptive traits was evident at a smaller spatial scale than has previously been shown for a marine fish with no apparent physical barriers to gene flow (∼200 km). Our findings highlight the need to consider the impact of intraspecific variation in reproductive timing on thermal adaptation when forecasting the effects of climate change on animal populations. PMID:27293712

Variation in spawning time promotes genetic variability in population responses to environmental change in a marine fish.

PubMed

Oomen, Rebekah A; Hutchings, Jeffrey A

2015-01-01

The level of phenotypic plasticity displayed within a population (i.e. the slope of the reaction norm) reflects the short-term response of a population to environmental change, while variation in reaction norm slopes among populations reflects spatial variation in these responses. Thus far, studies of thermal reaction norm variation have focused on geographically driven adaptation among different latitudes, altitudes or habitats. Yet, thermal variability is a function of both space and time. For organisms that reproduce at different times of year, such variation has the potential to promote adaptive variability in thermal responses for critical early life stages. Using common-garden experiments, we examined the spatial scale of genetic variation in thermal plasticity for early life-history traits among five populations of endangered Atlantic cod (Gadus morhua) that spawn at different times of year. Patterns of plasticity for larval growth and survival suggest that population responses to climate change will differ substantially, with increasing water temperatures posing a considerably greater threat to autumn-spawning cod than to those that spawn in winter or spring. Adaptation to seasonal cooling or warming experienced during the larval stage is suggested as a possible cause. Furthermore, populations that experience relatively cold temperatures during early life might be more sensitive to changes in temperature. Substantial divergence in adaptive traits was evident at a smaller spatial scale than has previously been shown for a marine fish with no apparent physical barriers to gene flow (∼200 km). Our findings highlight the need to consider the impact of intraspecific variation in reproductive timing on thermal adaptation when forecasting the effects of climate change on animal populations.

Development and testing of a compartmentalized reaction network model for redox zones in contaminated aquifers

USGS Publications Warehouse

Abrams , Robert H.; Loague, Keith; Kent, Douglas B.

1998-01-01

The work reported here is the first part of a larger effort focused on efficient numerical simulation of redox zone development in contaminated aquifers. The sequential use of various electron acceptors, which is governed by the energy yield of each reaction, gives rise to redox zones. The large difference in energy yields between the various redox reactions leads to systems of equations that are extremely ill-conditioned. These equations are very difficult to solve, especially in the context of coupled fluid flow, solute transport, and geochemical simulations. We have developed a general, rational method to solve such systems where we focus on the dominant reactions, compartmentalizing them in a manner that is analogous to the redox zones that are often observed in the field. The compartmentalized approach allows us to easily solve a complex geochemical system as a function of time and energy yield, laying the foundation for our ongoing work in which we couple the reaction network, for the development of redox zones, to a model of subsurface fluid flow and solute transport. Our method (1) solves the numerical system without evoking a redox parameter, (2) improves the numerical stability of redox systems by choosing which compartment and thus which reaction network to use based upon the concentration ratios of key constituents, (3) simulates the development of redox zones as a function of time without the use of inhibition factors or switching functions, and (4) can reduce the number of transport equations that need to be solved in space and time. We show through the use of various model performance evaluation statistics that the appropriate compartment choice under different geochemical conditions leads to numerical solutions without significant error. The compartmentalized approach described here facilitates the next phase of this effort where we couple the redox zone reaction network to models of fluid flow and solute transport.

Identification of functional differences in metabolic networks using comparative genomics and constraint-based models.

PubMed

Hamilton, Joshua J; Reed, Jennifer L

2012-01-01

Genome-scale network reconstructions are useful tools for understanding cellular metabolism, and comparisons of such reconstructions can provide insight into metabolic differences between organisms. Recent efforts toward comparing genome-scale models have focused primarily on aligning metabolic networks at the reaction level and then looking at differences and similarities in reaction and gene content. However, these reaction comparison approaches are time-consuming and do not identify the effect network differences have on the functional states of the network. We have developed a bilevel mixed-integer programming approach, CONGA, to identify functional differences between metabolic networks by comparing network reconstructions aligned at the gene level. We first identify orthologous genes across two reconstructions and then use CONGA to identify conditions under which differences in gene content give rise to differences in metabolic capabilities. By seeking genes whose deletion in one or both models disproportionately changes flux through a selected reaction (e.g., growth or by-product secretion) in one model over another, we are able to identify structural metabolic network differences enabling unique metabolic capabilities. Using CONGA, we explore functional differences between two metabolic reconstructions of Escherichia coli and identify a set of reactions responsible for chemical production differences between the two models. We also use this approach to aid in the development of a genome-scale model of Synechococcus sp. PCC 7002. Finally, we propose potential antimicrobial targets in Mycobacterium tuberculosis and Staphylococcus aureus based on differences in their metabolic capabilities. Through these examples, we demonstrate that a gene-centric approach to comparing metabolic networks allows for a rapid comparison of metabolic models at a functional level. Using CONGA, we can identify differences in reaction and gene content which give rise to different functional predictions. Because CONGA provides a general framework, it can be applied to find functional differences across models and biological systems beyond those presented here.

Identification of Functional Differences in Metabolic Networks Using Comparative Genomics and Constraint-Based Models

PubMed Central

Hamilton, Joshua J.; Reed, Jennifer L.

2012-01-01

Genome-scale network reconstructions are useful tools for understanding cellular metabolism, and comparisons of such reconstructions can provide insight into metabolic differences between organisms. Recent efforts toward comparing genome-scale models have focused primarily on aligning metabolic networks at the reaction level and then looking at differences and similarities in reaction and gene content. However, these reaction comparison approaches are time-consuming and do not identify the effect network differences have on the functional states of the network. We have developed a bilevel mixed-integer programming approach, CONGA, to identify functional differences between metabolic networks by comparing network reconstructions aligned at the gene level. We first identify orthologous genes across two reconstructions and then use CONGA to identify conditions under which differences in gene content give rise to differences in metabolic capabilities. By seeking genes whose deletion in one or both models disproportionately changes flux through a selected reaction (e.g., growth or by-product secretion) in one model over another, we are able to identify structural metabolic network differences enabling unique metabolic capabilities. Using CONGA, we explore functional differences between two metabolic reconstructions of Escherichia coli and identify a set of reactions responsible for chemical production differences between the two models. We also use this approach to aid in the development of a genome-scale model of Synechococcus sp. PCC 7002. Finally, we propose potential antimicrobial targets in Mycobacterium tuberculosis and Staphylococcus aureus based on differences in their metabolic capabilities. Through these examples, we demonstrate that a gene-centric approach to comparing metabolic networks allows for a rapid comparison of metabolic models at a functional level. Using CONGA, we can identify differences in reaction and gene content which give rise to different functional predictions. Because CONGA provides a general framework, it can be applied to find functional differences across models and biological systems beyond those presented here. PMID:22666308

Desktop NMR spectroscopy for real-time monitoring of an acetalization reaction in comparison with gas chromatography and NMR at 9.4 T.

PubMed

Singh, Kawarpal; Danieli, Ernesto; Blümich, Bernhard

2017-12-01

Monitoring of chemical reactions in real-time is in demand for process control. Different methods such as gas chromatography (GC), mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance (NMR) are used for that purpose. The current state-of-the-art compact NMR systems provide a useful method to employ with various reaction conditions for studying chemical reactions inside the fume hood at the chemical workplace. In the present study, an acetalization reaction was investigated with compact NMR spectroscopy in real-time. Acetalization is used for multistep synthesis of the variety of organic compounds to protect particular chemical groups. A compact 1 T NMR spectrometer with a permanent magnet was employed to monitor the acid catalyzed acetalization of the p-nitrobenzaldehyde with ethylene glycol. The concentrations of both reactant and product were followed by peak integrals in single-scan 1 H NMR spectra as a function of time. The reaction conditions were varied in terms of temperature, agitation speed, catalyst loading, and feed concentrations in order to determine the activation energy with the help of a pseudo-homogeneous kinetic model. For low molar ratios of aldehyde and glycol, the equilibrium conversions were lower than for the stoichiometric ratio. Increasing catalyst concentration leads to faster conversion. The data obtained with low-field NMR spectroscopy were compared with data from GC and NMR spectroscopy at 9.4 T acquired in batch mode by extracting samples at regular time intervals. The reaction kinetics followed by either method agreed well. The activation energies for forward and backward reactions were determined by real-time monitoring with compact NMR at 1 T were 48 ± 5 and 60 ± 4 kJ/mol, respectively. The activation energies obtained with gas chromatography for forward and backward reactions were 48 ± 4 and 51 ± 4 kJ/mol. The equilibrium constant decreases with increasing temperature as expected for an exothermic reaction. The impact of dense sampling with online NMR and sparse sampling with GC was observed on the kinetic outcome using the same kinetic model. Graphical abstract Acetalization reaction kinetics were monitored with real-time desktop NMR spectroscopy at 1 T. Each data point was obtained at regular intervals with a single shot in 15 s. The kinetics was compared with sparsely sampled data obtained with GC and NMR at 9.4 T.

Full-scale chamber investigation and simulation of air freshener emissions in the presence of ozone.

PubMed

Liu, Xiaoyu; Mason, Mark; Krebs, Kenneth; Sparks, Leslie

2004-05-15

Volatile organic compound (VOC) emissions from one electrical plug-in type of pine-scented air freshener and their reactions with O3 were investigated in the U.S. Environmental Protection Agency indoor air research large chamber facility. Ozone was generated from a device marketed as an ozone generator air cleaner. Ozone and oxides of nitrogen concentrations and chamber conditions such as temperature, relative humidity, pressure, and air exchange rate were controlled and/or monitored. VOC emissions and some of the reaction products were identified and quantified. Source emission models were developed to predict the time/concentration profiles of the major VOCs (limonene, alpha-pinene, beta-pinene, 3-carene, camphene, benzyl propionate, benzyl alcohol, bornyl acetate, isobornyl acetate, and benzaldehyde) emitted bythe air freshener. Gas-phase reactions of VOCs from the air freshener with O3 were simulated by a photochemical kinetics simulation system using VOC reaction mechanisms and rate constants adopted from the literature. The concentration-time predictions were in good agreement with the data for O3 and VOCs emitted from the air freshener and with some of the primary reaction products. Systematic differences between the predictions and the experimental results were found for some species. Poor understanding of secondary reactions and heterogeneous chemistry in the chamber is the likely cause of these differences. The method has the potential to provide data to predict the impact of O3/VOC interactions on indoor air quality.

No evidence of reaction time slowing in autism spectrum disorder.

PubMed

Ferraro, F Richard

2016-01-01

A total of 32 studies comprising 238 simple reaction time and choice reaction time conditions were examined in individuals with autism spectrum disorder (n = 964) and controls (n = 1032). A Brinley plot/multiple regression analysis was performed on mean reaction times, regressing autism spectrum disorder performance onto the control performance as a way to examine any generalized simple reaction time/choice reaction time slowing exhibited by the autism spectrum disorder group. The resulting regression equation was Y (autism spectrum disorder) = 0.99 × (control) + 87.93, which accounted for 92.3% of the variance. These results suggest that there are little if any simple reaction time/choice reaction time slowing in this sample of individual with autism spectrum disorder, in comparison with controls. While many cognitive and information processing domains are compromised in autism spectrum disorder, it appears that simple reaction time/choice reaction time remain relatively unaffected in autism spectrum disorder. © The Author(s) 2014.

Critical evaluation of Jet-A spray combustion using propane chemical kinetics in gas turbine combustion simulated by KIVA-II

NASA Technical Reports Server (NTRS)

Nguyen, H. L.; Ying, S.-J.

1990-01-01

Numerical solutions of the Jet-A spray combustion were obtained by means of the KIVA-II computer code after Jet-A properties were added to the 12 chemical species the program had initially contained. Three different reaction mechanism models are considered. The first model consists of 131 reactions and 45 species; it is evaluated by comparing calculated ignition delay times with available shock tube data, and it is used in the evaluation of the other two simplified models. The simplified mechanisms consider 45 reactions and 27 species and 5 reactions and 12 species, respectively. In the prediction of pollutants NOx and CO, the full mechanism of 131 reactions is considered to be more reliable. The numerical results indicate that the variation of the maximum flame temperature is within 20 percent as compared with that of the full mechanism of 131 reactions. The chemical compositions of major components such as C3H8, H2O, O2, CO2, and N2 are of the same order of magnitude. However, the concentrations of pollutants are quite different.

Shallow temperature differences along the Deep Creek Range front, Idaho

NASA Astrophysics Data System (ADS)

Ore, H. T.; Wiegand, G. H.

1990-02-01

The extent of the solvolysis reaction of a tertiary butyl chloride solution placed in vials buried about 1.2 m below the ground surface is dependent on average temperature at that depth over the period of burial. This method is herein used to indicate differences in shallow temperature from the western flank of the Basin and Range Deep Creek Range front, about 5 km westward into Rockland Valley in southeastern Idaho. Ninety-three samples, distributed to allow determination of lateral and vertical sample-site variation in total reaction amount, were analyzed after being in place for 3 months. Results from two sample lines, 3.5 km apart, show that subsurface total reaction amount declines slightly for the first 1.6 km away from the mountain front, rises abruptly to several times initial reaction, slowly declines for the next several km, then tends to slowly rise again. Plots of extent of reaction vs distance for the two traverses are nearly parallel; in both the abrupt increase in total reaction coincides with a line of springs, suggesting that hydrologic activity is at least related to the effects noted.

Spectro-Electrochemical Examination of the Formation of Dimethyl Carbonate from CO and Methanol at Different Electrode Materials

PubMed Central

2017-01-01

In this work, we report a fundamental mechanistic study of the electrochemical oxidative carbonylation of methanol with CO for the synthesis of dimethyl carbonate on metallic electrodes at low overpotentials. For the first time, the reaction was shown to take place on the metallic catalysts without need of oxidized metals or additives. Moreover, in-situ spectroelectrochemical techniques were applied to this electrosynthesis reaction in order to reveal the reaction intermediates and to shed light into the reaction mechanism. Fourier transformed infrared spectroscopy was used with different electrode materials (Au, Pd, Pt, and Ag) to assess the effect of the electrode material on the reaction and the dependence of products and intermediates on the applied potentials. It was observed that the dimethyl carbonate is only formed when the electrode is able to decompose/oxidize MeOH to form (adsorbed) methoxy groups that can further react with CO to dimethyl carbonate. Furthermore, the electrode needs to adsorb CO not too strongly; otherwise, further reaction will be inhibited because of surface poisoning by CO. PMID:28929754

Reaction pathways towards the formation of dolomite-analogues at ambient conditions

NASA Astrophysics Data System (ADS)

Pimentel, Carlos; Pina, Carlos M.

2016-04-01

In this paper we present results of a study of the crystallisation behaviour of the dolomite-analogues norsethite and PbMg(CO3)2 at room temperature and atmospheric pressure. Whereas precipitation of norsethite was previously obtained by mixing solutions (Hood et al., 1974; Pimentel and Pina, 2014a,b), we report, for the first time, the synthesis of PbMg(CO3)2 by using the same method. The formation of both phases was promoted by ageing slurries for periods of time ranging from a few days (norsethite) up to 6 months (PbMg(CO3)2). The crystallisation of both norsethite and PbMg(CO3)2 occurs by sequences of dissolution-precipitation reactions involving several amorphous and crystalline precursor phases, which were identified and characterised by X-ray diffraction and scanning electron microscopy. Depending on the initial composition and Ba:Mg and Pb:Mg ratios in the slurries, different precursors and reaction kinetics were observed. This demonstrates the existence of different reaction pathways towards the formation of the investigated dolomite-analogues. Our experimental results provide new insights into the possible mechanisms of formation of dolomite and other double carbonates in nature.

Saponification reaction system: a detailed mass transfer coefficient determination.

PubMed

Pečar, Darja; Goršek, Andreja

2015-01-01

The saponification of an aromatic ester with an aqueous sodium hydroxide was studied within a heterogeneous reaction medium in order to determine the overall kinetics of the selected system. The extended thermo-kinetic model was developed compared to the previously used simple one. The reaction rate within a heterogeneous liquid-liquid system incorporates a chemical kinetics term as well as mass transfer between both phases. Chemical rate constant was obtained from experiments within a homogeneous medium, whilst the mass-transfer coefficient was determined separately. The measured thermal profiles were then the bases for determining the overall reaction-rate. This study presents the development of an extended kinetic model for considering mass transfer regarding the saponification of ethyl benzoate with sodium hydroxide within a heterogeneous reaction medium. The time-dependences are presented for the mass transfer coefficient and the interfacial areas at different heterogeneous stages and temperatures. The results indicated an important role of reliable kinetic model, as significant difference in k(L)a product was obtained with extended and simple approach.

Methyl oleate deoxygenation for production of diesel fuel aliphatic hydrocarbons over Pd/SBA-15 catalysts

PubMed Central

2013-01-01

Background Catalytic deoxygenation is a prominent process for production of renewable fuels from vegetable oil. In this work, deoxygenation of technical grade methyl oleate to diesel fuel aliphatic hydrocarbons (C15 – C18) is evaluated with several parameters including temperature, hydrogen pressure and reaction time in a stirred batch reactor over Pd/SBA-15 catalysts. Results Two different SBA-15 morphologies i.e. spherelike and necklacelike structures have been synthesize as supports for Pd active metal. It is found that Pd dispersion on necklacelike SBA-15 is higher than that of spherelike SBA-15. Notably, higher Pd dispersion on necklacelike SBA-15 provides significant deoxygenation efficiency as compared to Pd/SBA-15-spherelike. Results show that H2 pressures greatly determine the total ester conversion and selectivity to C15 – C18 aliphatic hydrocarbons. Total ester conversions with 55< selectivity to n-heptadecane are achieved using Pd/SBA-15-necklacelike at 270°C and 60 bar H2 pressure within 6 h reaction time. Gas phase study reveals that formation of C17 is generated via indirect decarbonylation when the reaction time is prolonged. Conclusions Pd/SBA-15-necklacelike catalyst exhibits good catalytic performance with high selectivity to diesellike aliphatic hydrocarbons (C15 – C18). The physicochemical properties of the Pd supported on different SBA-15 morphologies influence the deoxygenation activity of the catalysts. Furthermore, the reaction pathways are governed by the H2 pressure as well as reaction duration. PMID:24011181

The Stochastic Early Reaction, Inhibition, and late Action (SERIA) model for antisaccades

PubMed Central

2017-01-01

The antisaccade task is a classic paradigm used to study the voluntary control of eye movements. It requires participants to suppress a reactive eye movement to a visual target and to concurrently initiate a saccade in the opposite direction. Although several models have been proposed to explain error rates and reaction times in this task, no formal model comparison has yet been performed. Here, we describe a Bayesian modeling approach to the antisaccade task that allows us to formally compare different models on the basis of their evidence. First, we provide a formal likelihood function of actions (pro- and antisaccades) and reaction times based on previously published models. Second, we introduce the Stochastic Early Reaction, Inhibition, and late Action model (SERIA), a novel model postulating two different mechanisms that interact in the antisaccade task: an early GO/NO-GO race decision process and a late GO/GO decision process. Third, we apply these models to a data set from an experiment with three mixed blocks of pro- and antisaccade trials. Bayesian model comparison demonstrates that the SERIA model explains the data better than competing models that do not incorporate a late decision process. Moreover, we show that the early decision process postulated by the SERIA model is, to a large extent, insensitive to the cue presented in a single trial. Finally, we use parameter estimates to demonstrate that changes in reaction time and error rate due to the probability of a trial type (pro- or antisaccade) are best explained by faster or slower inhibition and the probability of generating late voluntary prosaccades. PMID:28767650

Modeling human behaviors and reactions under dangerous environment.

PubMed

Kang, J; Wright, D K; Qin, S F; Zhao, Y

2005-01-01

This paper describes the framework of a real-time simulation system to model human behavior and reactions in dangerous environments. The system utilizes the latest 3D computer animation techniques, combined with artificial intelligence, robotics and psychology, to model human behavior, reactions and decision making under expected/unexpected dangers in real-time in virtual environments. The development of the system includes: classification on the conscious/subconscious behaviors and reactions of different people; capturing different motion postures by the Eagle Digital System; establishing 3D character animation models; establishing 3D models for the scene; planning the scenario and the contents; and programming within Virtools Dev. Programming within Virtools Dev is subdivided into modeling dangerous events, modeling character's perceptions, modeling character's decision making, modeling character's movements, modeling character's interaction with environment and setting up the virtual cameras. The real-time simulation of human reactions in hazardous environments is invaluable in military defense, fire escape, rescue operation planning, traffic safety studies, and safety planning in chemical factories, the design of buildings, airplanes, ships and trains. Currently, human motion modeling can be realized through established technology, whereas to integrate perception and intelligence into virtual human's motion is still a huge undertaking. The challenges here are the synchronization of motion and intelligence, the accurate modeling of human's vision, smell, touch and hearing, the diversity and effects of emotion and personality in decision making. There are three types of software platforms which could be employed to realize the motion and intelligence within one system, and their advantages and disadvantages are discussed.

Stroop-interference effect in post-traumatic stress disorder.

PubMed

Cui, Hong; Chen, Guoliang; Liu, Xiaohui; Shan, Moshui; Jia, Yanyan

2014-12-01

To investigate the conflict processing in posttraumatic stress disorder (PTSD) patients, we conducted the classical Stroop task by recording event-related potentials. Although the reaction time was overall slower for PTSD patients than healthy age-matched control group, the Stroop-interference effect of reaction time did not differ between the two groups. Compared with normal controls, the interference effects of N 2 and N 450 components were larger and the interference effect of slow potential component disappeared in PTSD. These data indicated the dysfunction of conflict processing in individuals with PTSD.

Typicality effects in artificial categories: is there a hemisphere difference?

PubMed

Richards, L G; Chiarello, C

1990-07-01

In category classification tasks, typicality effects are usually found: accuracy and reaction time depend upon distance from a prototype. In this study, subjects learned either verbal or nonverbal dot pattern categories, followed by a lateralized classification task. Comparable typicality effects were found in both reaction time and accuracy across visual fields for both verbal and nonverbal categories. Both hemispheres appeared to use a similarity-to-prototype matching strategy in classification. This indicates that merely having a verbal label does not differentiate classification in the two hemispheres.

Word Naming in the L1 and L2: A Dynamic Perspective on Automatization and the Degree of Semantic Involvement in Naming.

PubMed

Plat, Rika; Lowie, Wander; de Bot, Kees

2017-01-01

Reaction time data have long been collected in order to gain insight into the underlying mechanisms involved in language processing. Means analyses often attempt to break down what factors relate to what portion of the total reaction time. From a dynamic systems theory perspective or an interaction dominant view of language processing, it is impossible to isolate discrete factors contributing to language processing, since these continually and interactively play a role. Non-linear analyses offer the tools to investigate the underlying process of language use in time, without having to isolate discrete factors. Patterns of variability in reaction time data may disclose the relative contribution of automatic (grapheme-to-phoneme conversion) processing and attention-demanding (semantic) processing. The presence of a fractal structure in the variability of a reaction time series indicates automaticity in the mental structures contributing to a task. A decorrelated pattern of variability will indicate a higher degree of attention-demanding processing. A focus on variability patterns allows us to examine the relative contribution of automatic and attention-demanding processing when a speaker is using the mother tongue (L1) or a second language (L2). A word naming task conducted in the L1 (Dutch) and L2 (English) shows L1 word processing to rely more on automatic spelling-to-sound conversion than L2 word processing. A word naming task with a semantic categorization subtask showed more reliance on attention-demanding semantic processing when using the L2. A comparison to L1 English data shows this was not only due to the amount of language use or language dominance, but also to the difference in orthographic depth between Dutch and English. An important implication of this finding is that when the same task is used to test and compare different languages, one cannot straightforwardly assume the same cognitive sub processes are involved to an equal degree using the same task in different languages.

Synaptic vesicle recycling: steps and principles

PubMed Central

Rizzoli, Silvio O

2014-01-01

Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle. PMID:24596248

Allergic-like reactions to asparaginase: Atypical allergies without asparaginase inactivation.

PubMed

Kloos, Robin Q H; Pieters, Rob; Escherich, Gabriele; van der Sluis, Inge M

2016-11-01

Asparaginase is an important component of pediatric acute lymphoblastic leukemia (ALL) therapy. Unfortunately, this treatment is hampered by hypersensitivity reactions. In general, allergies - regardless of severity - cause complete inactivation of the drug. However, we report atypical allergic reactions without inactivation of asparaginase, here called allergic-like reactions. Patients with an allergic-like reaction, who were treated according to the Dutch Childhood Oncology Group ALL-11 or the CoALL 08-09 protocol, were described. The reactions were identified by continual measurement of asparaginase activity levels. Characteristics, including timing of occurrence, symptoms, grade, and the presence of antiasparaginase antibodies, were compared to those of real allergies. Fourteen allergic-like reactions occurred in nine patients. Five reactions were to PEGasparaginase and nine to Erwinia asparaginase. Allergic-like reactions occurred relatively late after the start of infusion compared to real allergies. Antibodies were absent in all but one patient with an allergic-like reaction, while they were detected in all patients with a real allergy. Symptoms and grade did not differ between the groups. Asparaginase was continued with the same formulation in six patients of whom four finished treatment with adequate activity levels. In conclusion, allergic-like reactions occur relatively late after the start of infusion and without antibodies. Despite these clinical differences, allergic-like reactions can only be distinguished from real allergies by continually measuring asparaginase activity levels. If clinically tolerated, formulations should not be switched in case of allergic-like reactions. Moreover, failure to recognize these reactions may lead to a less favorable prognosis if asparaginase therapy is terminated unnecessarily. © 2016 Wiley Periodicals, Inc.

Influence of surface heterogeneity in electroosmotic flows—Implications in chromatography, fluid mixing, and chemical reactions in microdevices

NASA Astrophysics Data System (ADS)

Adrover, Alessandra; Giona, Massimiliano; Pagnanelli, Francesca; Toro, Luigi

2007-04-01

We analyze the influence of surface heterogeneity, inducing a random ζ-potential at the walls in electroosmotic incompressible flows. Specifically, we focus on how surface heterogeneity modifies the physico-chemical processes (transport, chemical reaction, mixing) occurring in microchannel and microreactors. While the macroscopic short-time features associated with solute transport (e.g. chromatographic patterns) do not depend significantly on ζ-potential heterogeneity, spatial randomness in the surface ζ-potential modifies the spectral properties of the advection-diffusion operator, determining different long-term properties of transport/reaction phenomena compared to the homogeneous case. Examples of physical relevance (chromatography, infinitely fast reactions) are addressed.

Diels–Alder reactions of myrcene using intensified continuous-flow reactors

PubMed Central

Álvarez-Diéguez, Miguel Á; Kohl, Thomas M; Tsanaktsidis, John

2017-01-01

This work describes the Diels–Alder reaction of the naturally occurring substituted butadiene, myrcene, with a range of different naturally occurring and synthetic dienophiles. The synthesis of the Diels–Alder adduct from myrcene and acrylic acid, containing surfactant properties, was scaled-up in a plate-type continuous-flow reactor with a volume of 105 mL to a throughput of 2.79 kg of the final product per day. This continuous-flow approach provides a facile alternative scale-up route to conventional batch processing, and it helps to intensify the synthesis protocol by applying higher reaction temperatures and shorter reaction times. PMID:28228853

Bioluminescent Reaction by Immobilized Luciferase

NASA Astrophysics Data System (ADS)

Tanaka, Ryuta; Takahama, Eriko; Iinuma, Masataka; Ikeda, Takeshi; Kadoya, Yutaka; Kuroda, Akio

We have investigated an effect of immobilization of luciferase molecules at the optical fiber end on a bioluminescent reaction. The time dependence of measured count rates of emitted photons has been analyzed by fitting with numerical solution of differential equations including the effect of the product-inhibitor and the deactivation of the luciferase. Through the analysis, we have successfully extracted kinetic constants such as, reaction rate, number of active luciferase molecules, etc. Ratio of active molecules to total luciferase molecules in immobilization was one order of magnitude lower than that in solution. The reaction rate of the bioluminescent process was also different from the one of free luciferase in solution.

Force modeling for incisions into various tissues with MRF haptic master

NASA Astrophysics Data System (ADS)

Kim, Pyunghwa; Kim, Soomin; Park, Young-Dai; Choi, Seung-Bok

2016-03-01

This study proposes a new model to predict the reaction force that occurs in incisions during robot-assisted minimally invasive surgery. The reaction force is fed back to the manipulator by a magneto-rheological fluid (MRF) haptic master, which is featured by a bi-directional clutch actuator. The reaction force feedback provides similar sensations to laparotomy that cannot be provided by a conventional master for surgery. This advantage shortens the training period for robot-assisted minimally invasive surgery and can improve the accuracy of operations. The reaction force modeling of incisions can be utilized in a surgical simulator that provides a virtual reaction force. In this work, in order to model the reaction force during incisions, the energy aspect of the incision process is adopted and analyzed. Each mode of the incision process is classified by the tendency of the energy change, and modeled for realistic real-time application. The reaction force model uses actual reaction force information with three types of actual tissues: hard tissue, medium tissue, and soft tissue. This modeled force is realized by the MRF haptic master through an algorithm based on the position and velocity of a scalpel using two different control methods: an open-loop algorithm and a closed-loop algorithm. The reaction forces obtained from the proposed model are compared with a desired force in time domain.

Cortisol, reaction time test and health among offshore shift workers.

PubMed

Harris, Anette; Waage, Siri; Ursin, Holger; Hansen, Ase Marie; Bjorvatn, Bjørn; Eriksen, Hege R

2010-10-01

The stress hormone cortisol shows a pronounced endogenous diurnal rhythm, which is affected by the sleep/wake cycle, meals and activity. Shift work and especially night work disrupts the sleep/wake cycle and causes a desynchronization of the natural biological rhythms. Therefore, different shift schedules may have different impact on performance at work and health. The purpose was to study if health, reaction time, and the cortisol rhythm were negatively affected when a group of shift workers changed their work schedule from ordinary day-night shift (fixed shift) to "swing shift". 19 healthy workers on a Norwegian oil rig participated in the study. They worked 2 weeks offshore followed by 4 weeks off work. The ordinary schedule consisted of 12-h day shift and 12-h night shift every other work period (14 days or nights=fixed shift). "Swing shift" involved 1 week of night shift, followed by 1 week of day shift during the work period. All participants worked ordinary day-night shift when baseline data were collected (questionnaires, saliva cortisol, and reaction time during work). After collection of baseline data the workers changed their work schedule to "swing shift", for every working period, and 9 months later the same data were collected. "Swing shift" did not give any negative health effects or any negative changes in reaction time during the day they shifted from night work to day work. Personnel adapted to night shift within a week regardless of schedule, but recovery from night shift took longer time. During swing shift the cortisol rhythm went back towards a normal rhythm in the second week, but it was not returned completely to normal values when they returned home for the 4 weeks off period. However, the cortisol rhythms were readapted to normal values after 1 week at home. For personnel returning home directly from 14 consecutive night shifts, cortisol adaptation was not complete after 1 week at home. We found no increase in health complaints from swing shift or reaction time in the shift from night to day work. Recovery from night shift takes longer time. Copyright © 2010 Elsevier Ltd. All rights reserved.

Forecasted economic change and the self-fulfilling prophecy in economic decision-making

PubMed Central

2017-01-01

This study addresses the self-fulfilling prophecy effect, in the domain of economic decision-making. We present experimental data in support of the hypothesis that speculative forecasts of economic change can impact individuals’ economic decision behavior, prior to any realized changes. In a within-subjects experiment, participants (N = 40) played 180 trials in a Balloon Analogue Risk Talk (BART) in which they could make actual profit. Simple messages about possible (positive and negative) changes in outcome probabilities of future trials had significant effects on measures of risk taking (number of inflations) and actual profits in the game. These effects were enduring, even though no systematic changes in actual outcome probabilities took place following any of the messages. Risk taking also found to be reflected in reaction times revealing increasing reaction times with riskier decisions. Positive and negative economic forecasts affected reaction times slopes differently, with negative forecasts resulting in increased reaction time slopes as a function of risk. These findings suggest that forecasted positive or negative economic change can bias people’s mental model of the economy and reduce or stimulate risk taking. Possible implications for media-fulfilling prophecies in the domain of the economy are considered. PMID:28334031

The Effect of Stimulus Valence on Lexical Retrieval in Younger and Older Adults.

PubMed

Blackett, Deena Schwen; Harnish, Stacy M; Lundine, Jennifer P; Zezinka, Alexandra; Healy, Eric W

2017-07-12

Although there is evidence that emotional valence of stimuli impacts lexical processes, there is limited work investigating its specific impact on lexical retrieval. The current study aimed to determine the degree to which emotional valence of pictured stimuli impacts naming latencies in healthy younger and older adults. Eighteen healthy younger adults and 18 healthy older adults named positive, negative, and neutral images, and reaction time was measured. Reaction times for positive and negative images were significantly longer than reaction times for neutral images. Reaction times for positive and negative images were not significantly different. Whereas older adults demonstrated significantly longer naming latencies overall than younger adults, the discrepancy in latency with age was far greater when naming emotional pictures. Emotional arousal of pictures appears to impact naming latency in younger and older adults. We hypothesize that the increase in naming latency for emotional stimuli is the result of a necessary disengagement of attentional resources from the emotional images prior to completion of the naming task. We propose that this process may affect older adults disproportionately due to a decline in attentional resources as part of normal aging, combined with a greater attentional preference for emotional stimuli.

The effects of L-theanine, caffeine and their combination on cognition and mood.

PubMed

Haskell, Crystal F; Kennedy, David O; Milne, Anthea L; Wesnes, Keith A; Scholey, Andrew B

2008-02-01

L-Theanine is an amino acid found naturally in tea. Despite the common consumption of L-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. L-Theanine increased 'headache' ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported 'mental fatigue'. In addition to improving RVIP accuracy and 'mental fatigue' ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. 'Headache' and 'tired' ratings were reduced and 'alert' ratings increased. There was also a significant positive caffeine x L-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing L-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.

Symmetry and asymmetry of reaction time and body tissue composition of upper limbs in young female basketball players.

PubMed

Poliszczuk, Tatiana; Mańkowska, Maja; Poliszczuk, Dmytro; Wiśniewski, Andrzej

2013-01-01

The role of psychomotor abilities and their relationship to the morphofunctional characteristics of athletes is becoming more and more emphasized in studies on the subject, especially for disciplines that require athletes to notice and to respond to signals originating in dynamically changing conditions. At the same time, athletes who perform symmetrically are more effective and less likely to sustain an injury through unilateral strain. Assessment of the degree of symmetry and asymmetry of reaction time to stimuli in the central and peripheral visual fields, and assessment of body composition of upper limbs in young female basketball players. Participants of the study comprised 17 young female basketball players. Their average age was 18.11-0.8 years. On average, they had been training basketball for 6.83-1.75 years. Body tissue composition was measured using the bioelectrical impedance method. The degree of symmetry and asymmetry of reaction time to signals in the central and peripheral visual fields were measured using the Reaction Test (RT-S1) and a modified Peripheral Perception (PP) test within the Vienna Test System. An analysis of body tissue composition of the upper right and upper left limbs found an asymmetry (p<0.01 and p<0.05) in the FAT [%], FAT MASS [kg], and FFM [kg] parameters. The values of these parameters were higher for the non-dominant arm. No statistically significant differences were found in reaction time and motor time for the dominant and non-dominant arm. A correlation was found between motor time and the FFM [kg] (r=-0.62; p<0.05) and PMM [kg] (r=-0.63; p<0.05) parameters. A significant asymmetry was found in the body tissue composition of the upper limbs. Asymmetry of reaction time was found only for signals in the peripheral visual field.

Beliefs underlying the intention to donate again among first-time blood donors who experience a mild adverse event.

PubMed

Masser, Barbara M; White, Katherine M; Terry, Deborah J

2013-10-01

Using the belief basis of the theory of planned behavior (TPB), the current study explored the rate of mild reactions reported by donors in relation to their first donation and the intention and beliefs of those donors with regard to returning to donate again. A high proportion of first-time donors indicated that they had experienced a reaction to blood donation. Further, donors who reacted were less likely to intend to return to donate. Regression analyses suggested that targeting different beliefs for those donors who had and had not reacted would yield most benefit in bolstering donors' intentions to remain donating. The findings provide insight into those messages that could be communicated via the mass media or in targeted communications to retain first-time donors who have experienced a mild vasovagal reaction. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sleep-deprivation effect on human performance: a meta-analysis approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candice D. Griffith; Candice D. Griffith; Sankaran Mahadevan

Human fatigue is hard to define since there is no direct measure of fatigue, much like stress. Instead fatigue must be inferred from measures that are affected by fatigue. One such measurable output affected by fatigue is reaction time. In this study the relationship of reaction time to sleep deprivation is studied. These variables were selected because reaction time and hours of sleep deprivation are straightforward characteristics of fatigue to begin the investigation of fatigue effects on performance. Meta-analysis, a widely used procedure in medical and psychological studies, is applied to the variety of fatigue literature collected from various fieldsmore » in this study. Meta-analysis establishes a procedure for coding and analyzing information from various studies to compute an effect size. In this research the effect size reported is the difference between standardized means, and is found to be -0.6341, implying a strong relationship between sleep deprivation and performance degradation.« less

Enhanced reaction kinetics and reactive mixing scale dynamics in mixing fronts under shear flow for arbitrary Damköhler numbers

NASA Astrophysics Data System (ADS)

Bandopadhyay, Aditya; Le Borgne, Tanguy; Méheust, Yves; Dentz, Marco

2017-02-01

Mixing fronts, where fluids of different chemical compositions mix with each other, are known to represent hotspots of chemical reaction in hydrological systems. These fronts are typically subjected to velocity gradients, ranging from the pore scale due to no slip boundary conditions at fluid solid interfaces, to the catchment scale due to permeability variations and complex geometry of the Darcy velocity streamlines. A common trait of these processes is that the mixing interface is strained by shear. Depending on the Péclet number Pe , which represents the ratio of the characteristic diffusion time to the characteristic shear time, and the Damköhler number Da , which represents the ratio of the characteristic diffusion time to the characteristic reaction time, the local reaction rates can be strongly impacted by the dynamics of the mixing interface. So far, this impact has been characterized mostly either in kinetics-limited or in mixing-limited conditions, that is, for either low or high Da. Here the coupling of shear flow and chemical reactivity is investigated for arbitrary Damköhler numbers, for a bimolecular reaction and an initial interface with separated reactants. Approximate analytical expressions for the global production rate and reactive mixing scale are derived based on a reactive lamella approach that allows for a general coupling between stretching enhanced mixing and chemical reactions. While for Pe < Da , reaction kinetics and stretching effects are decoupled, a scenario which we name "weak stretching", for Pe > Da , we uncover a "strong stretching" scenario where new scaling laws emerge from the interplay between reaction kinetics, diffusion, and stretching. The analytical results are validated against numerical simulations. These findings shed light on the effect of flow heterogeneity on the enhancement of chemical reaction and the creation of spatially localized hotspots of reactivity for a broad range of systems ranging from kinetic limited to mixing limited situations.

Auditory perception and the control of spatially coordinated action of deaf and hearing children.

PubMed

Savelsbergh, G J; Netelenbos, J B; Whiting, H T

1991-03-01

From birth onwards, auditory stimulation directs and intensifies visual orientation behaviour. In deaf children, by definition, auditory perception cannot take place and cannot, therefore, make a contribution to visual orientation to objects approaching from outside the initial field of view. In experiment 1, a difference in catching ability is demonstrated between deaf and hearing children (10-13 years of age) when the ball approached from the periphery or from outside the field of view. No differences in catching ability between the two groups occurred when the ball approached from within the field of view. A second experiment was conducted in order to determine if differences in catching ability between deaf and hearing children could be attributed to execution of slow orientating movements and/or slow reaction time as a result of the auditory loss. The deaf children showed slower reaction times. No differences were found in movement times between deaf and hearing children. Overall, the findings suggest that a lack of auditory stimulation during development can lead to deficiencies in the coordination of actions such as catching which are both spatially and temporally constrained.

Magnetic timing valves for fluid control in paper-based microfluidics.

PubMed

Li, Xiao; Zwanenburg, Philip; Liu, Xinyu

2013-07-07

Multi-step analytical tests, such as an enzyme-linked immunosorbent assay (ELISA), require delivery of multiple fluids into a reaction zone and counting the incubation time at different steps. This paper presents a new type of paper-based magnetic valves that can count the time and turn on or off a fluidic flow accordingly, enabling timed fluid control in paper-based microfluidics. The timing capability of these valves is realized using a paper timing channel with an ionic resistor, which can detect the event of a solution flowing through the resistor and trigger an electromagnet (through a simple circuit) to open or close a paper cantilever valve. Based on this principle, we developed normally-open and normally-closed valves with a timing period up to 30.3 ± 2.1 min (sufficient for an ELISA on paper-based platforms). Using the normally-open valve, we performed an enzyme-based colorimetric reaction commonly used for signal readout of ELISAs, which requires a timed delivery of an enzyme substrate to a reaction zone. This design adds a new fluid-control component to the tool set for developing paper-based microfluidic devices, and has the potential to improve the user-friendliness of these devices.

CUE USAGE IN VOLLEYBALL: A TIME COURSE COMPARISON OF ELITE, INTERMEDIATE AND NOVICE FEMALE PLAYERS

PubMed Central

Vaeyens, R; Zeuwts, L; Philippaerts, R; Lenoir, M

2014-01-01

This study compared visual search strategies in adult female volleyball players of three levels. Video clips of the attack of the opponent team were presented on a large screen and participants reacted to the final pass before the spike. Reaction time, response accuracy and eye movement patterns were measured. Elite players had the highest response accuracy (97.50 ± 3.5%) compared to the intermediate (91.50 ± 4.7%) and novice players (83.50 ± 17.6%; p<0.05). Novices had a remarkably high range of reaction time but no significant differences were found in comparison to the reaction time of elite and intermediate players. In general, the three groups showed similar gaze behaviour with the apparent use of visual pivots at moments of reception and final pass. This confirms the holistic model of image perception for volleyball and suggests that expert players extract more information from parafoveal regions. PMID:25609887

Visual reaction time for chromaticity changes at constant luminance in different color representation systems

NASA Astrophysics Data System (ADS)

Jimenezdel Barco, L.; Jimenez, J. R.; Rubino, M.; Diaz, J. A.

1996-09-01

The results obtained by different authors show that when a color stimulus changes in both luminance and chromaticity, the visual reaction time (VRT) of an observer in detecting this chromatic change depends on nothing more than the luminance change and is regulated by Pieron's law. In the present work, we evaluate the VRT needed by an observer to detect the chromaticity difference between an adapting and variable stimulus. For this, we have used the experimental method of hue substitution, which allows us to maintain the luminance channel constant and thereby study the temporal response to changes only in chromaticity. The experiments were carried out with a CRT color monitor and the experimental results are expressed in different color-representation systems. The systems UCS-CIE 1964 (U*, V*, W*) and CIELUV show good correlations between the VRT and the chromaticity difference expressed in these systems, adjusting the VRT to an expression following Pieron's law: VRT-VRTon=k( Delta E)- beta .

The quick and the dead: when reaction beats intention.

PubMed

Welchman, Andrew E; Stanley, James; Schomers, Malte R; Miall, R Chris; Bülthoff, Heinrich H

2010-06-07

Everyday behaviour involves a trade-off between planned actions and reaction to environmental events. Evidence from neurophysiology, neurology and functional brain imaging suggests different neural bases for the control of different movement types. Here we develop a behavioural paradigm to test movement dynamics for intentional versus reaction movements and provide evidence for a 'reactive advantage' in movement execution, whereby the same action is executed faster in reaction to an opponent. We placed pairs of participants in competition with each other to make a series of button presses. Within-subject analysis of movement times revealed a 10 per cent benefit for reactive actions. This was maintained when opponents performed dissimilar actions, and when participants competed against a computer, suggesting that the effect is not related to facilitation produced by action observation. Rather, faster ballistic movements may be a general property of reactive motor control, potentially providing a useful means of promoting survival.

Unexpected Reaction Pathway for butyrylcholinesterase-catalyzed inactivation of “hunger hormone” ghrelin

NASA Astrophysics Data System (ADS)

Yao, Jianzhuang; Yuan, Yaxia; Zheng, Fang; Zhan, Chang-Guo

2016-02-01

Extensive computational modeling and simulations have been carried out, in the present study, to uncover the fundamental reaction pathway for butyrylcholinesterase (BChE)-catalyzed hydrolysis of ghrelin, demonstrating that the acylation process of BChE-catalyzed hydrolysis of ghrelin follows an unprecedented single-step reaction pathway and the single-step acylation process is rate-determining. The free energy barrier (18.8 kcal/mol) calculated for the rate-determining step is reasonably close to the experimentally-derived free energy barrier (~19.4 kcal/mol), suggesting that the obtained mechanistic insights are reasonable. The single-step reaction pathway for the acylation is remarkably different from the well-known two-step acylation reaction pathway for numerous ester hydrolysis reactions catalyzed by a serine esterase. This is the first time demonstrating that a single-step reaction pathway is possible for an ester hydrolysis reaction catalyzed by a serine esterase and, therefore, one no longer can simply assume that the acylation process must follow the well-known two-step reaction pathway.

In-line near-infrared (NIR) and Raman spectroscopy coupled with principal component analysis (PCA) for in situ evaluation of the transesterification reaction.

PubMed

Fontalvo-Gómez, Miriam; Colucci, José A; Velez, Natasha; Romañach, Rodolfo J

2013-10-01

Biodiesel was synthesized from different commercially available oils while in-line Raman and near-infrared (NIR) spectra were obtained simultaneously, and the spectral changes that occurred during the reaction were evaluated with principal component analysis (PCA). Raman and NIR spectra were acquired every 30 s with fiber optic probes inserted into the reaction vessel. The reaction was performed at 60-70 °C using magnetic stirring. The time of reaction was 90 min, and during this time, 180 Raman and NIR spectra were collected. NIR spectra were collected using a transflectance probe and an optical path length of 1 mm at 8 cm(-1) spectral resolution and averaging 32 scans; for Raman spectra a 3 s exposure time and three accumulations were adequate for the analysis. Raman spectroscopy showed the ester conversion as evidenced by the displacement of the C=O band from 1747 to 1744 cm(-1) and the decrease in the intensity of the 1000-1050 cm(-1) band and the 1405 cm(-1) band as methanol was consumed in the reaction. NIR spectra also showed the decrease in methanol concentration with the band in the 4750-5000 cm(-1) region; this signal is present in the spectra of the transesterification reaction but not in the neat oils. The variations in the intensity of the methanol band were a main factor in the in-line monitoring of the transesterification reaction using Raman and NIR spectroscopy. The score plot of the first principal component showed the progress of the reaction. The final product was analyzed using (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy and using mid-infrared spectroscopy, confirming the conversion of the oils to biodiesel.

Natural history of Hymenoptera venom allergy in children not treated with immunotherapy.

PubMed

Lange, Joanna; Cichocka-Jarosz, Ewa; Marczak, Honorata; Krauze, Agnieszka; Tarczoń, Izabela; Świebocka, Ewa; Lis, Grzegorz; Brzyski, Piotr; Nowak-Węgrzyn, Anna

2016-03-01

Differences in treatment approach still exist for children after systemic sting reactions. In addition, there are still some doubts about when systemic reactors should be treated with venom immunotherapy (VIT). To determine the rate of sting recurrence and natural history of Hymenoptera venom allergy (HVA) in children not treated with VIT. A total of 219 children diagnosed as having HVA who were not treated with VIT were identified in 3 pediatric allergology centers. Survey by telephone or mail with the use of a standardized questionnaire was conducted. The number of field re-stings, subsequent symptoms, and provided treatment were analyzed. A total of 130 of the 219 patients responded to the survey, for a response rate of 59.4%. During the median follow-up period of 72 months (interquartile range, 52-85 months), 44 children (77% boys) were stung 62 times. Normal reactions were most common, occurring in 27 patients (62%). Severe systemic reactions (SSRs) occurred in 8 (18%) of those who were re-stung. The subsequent reaction was significantly milder (P < 0.001), especially in the case of patients re-stung by the same insect (P < .001). None of the children with prediagnostic large local reactions and negative test results for venom specific IgE developed SSRs after re-sting by the culprit insect (P = .03). In children with SSRs, median time from diagnosis to re-sting was 2 times longer than that in those with large local reactions and normal reactions (P = .007). Most children with HVA not treated with VIT reported milder reactions after a re-sting. Probability of SSR to re-sting increases along with the severity of initial reaction. Copyright © 2016 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Integrating impairments in reaction time and executive function using a diffusion model framework.

PubMed

Karalunas, Sarah L; Huang-Pollock, Cynthia L

2013-07-01

Using Ratcliff's diffusion model and ex-Gaussian decomposition, we directly evaluate the role individual differences in reaction time (RT) distribution components play in the prediction of inhibitory control and working memory (WM) capacity in children with and without ADHD. Children with (n = 91, [Formula: see text] age = 10.2 years, 67 % male) and without ADHD (n = 62, [Formula: see text] age = 10.6 years, 46 % male) completed four tasks of WM and a stop signal reaction time (SSRT) task. Children with ADHD had smaller WM capacities and less efficient inhibitory control. Diffusion model analyses revealed that children with ADHD had slower drift rates (v) and faster non-decision times (Ter), but there were no group differences in boundary separations (a). Similarly, using an ex-Gaussian approach, children with ADHD had larger τ values than non-ADHD controls, but did not differ in μ or σ distribution components. Drift rate mediated the association between ADHD status and performance on both inhibitory control and WM capacity. τ also mediated the ADHD-executive function impairment associations; however, models were a poorer fit to the data. Impaired performance on RT and executive functioning tasks has long been associated with childhood ADHD. Both are believed to be important cognitive mechanisms to the disorder. We demonstrate here that drift rate, or the speed at which information accumulates towards a decision, is able to explain both.

Photoreverse Reaction Dynamics of Octopus Rhodopsin

PubMed Central

Inoue, Keiichi; Tsuda, Motoyuki; Terazima, Masahide

2007-01-01

Photoreverse reactions of octopus rhodopsin (Rh) from acid-metarhodopsin (Acid-Meta), which is the final product of the photoreaction of Rh, to Rh were studied by the time-resolved transient absorption and transient grating methods. The time course of the absorption signal showed a rapid change within 500 ns followed by one phase with a time constant of ∼470 μs, whereas the transient grating signal indicates three phases with time constants of <500 ns, ∼490 μs, and 2.6 ms. The faster two phases indicate the conformational change in the vicinity of the chromophore, and the slowest one represents conformational change far from the chromophore. The absorption spectrum of the first intermediate created just after the laser excitation (<500 ns) is already very similar to the final product, Rh. This behavior is quite different from that of the forward reaction from Rh to Acid-Meta, in which several intermediates with different absorption spectra are involved within 50 ns–500 μs. This result indicates that the conformation around the chromophore is easily adjusted from all-trans to 11-cis forms compared with that from 11-cis to all-trans forms. Furthermore, it was found that the protein energy is quickly relaxed after the excitation. One of the significantly different properties between Rh and Acid-Meta is the diffusion coefficient (D). D is reduced by about half the transformation from Rh to Acid-Meta. This large reduction was interpreted in terms of the helix opening of the Rh structure. PMID:17325000

Age differences in feedback reactions: The roles of employee feedback orientation on social awareness and utility.

PubMed

Wang, Mo; Burlacu, Gabriela; Truxillo, Donald; James, Keith; Yao, Xiang

2015-07-01

Organizations worldwide are currently experiencing shifts in the age composition of their workforces. The workforce is aging and becoming increasingly age-diverse, suggesting that organizational researchers and practitioners need to better understand how age differences may manifest in the workplace and the implications for human resource practice. Integrating socioemotional selectivity theory with the performance feedback literature and using a time-lagged design, the current study examined age differences in moderating the relationships between the characteristics of performance feedback and employee reactions to the feedback event. The results suggest that older workers had higher levels of feedback orientation on social awareness, but lower levels of feedback orientation on utility than younger workers. Furthermore, the positive associations between favorability of feedback and feedback delivery and feedback reactions were stronger for older workers than for younger workers, whereas the positive association between feedback quality and feedback reactions was stronger for younger workers than for older workers. Finally, the current study revealed that age-related differences in employee feedback orientation could explain the different patterns of relationships between feedback characteristics and feedback reactions across older and younger workers. These findings have both theoretical and practical implications for building theory about workplace aging and improving ways that performance feedback is managed across employees from diverse age groups. (c) 2015 APA, all rights reserved).

One-step simultaneous differential scanning calorimetry-FTIR microspectroscopy to quickly detect continuous pathways in the solid-state glucose/asparagine Maillard reaction.

PubMed

Hwang, Deng-Fwu; Hsieh, Tzu-Feng; Lin, Shan-Yang

2013-01-01

The stepwise reaction pathway of the solid-state Maillard reaction between glucose (Glc) and asparagine (Asn) was investigated using simultaneous differential scanning calorimetry (DSC)-FTIR microspectroscopy. The color change and FTIR spectra of Glc-Asn physical mixtures (molar ratio = 1:1) preheated to different temperatures followed by cooling were also examined. The successive reaction products such as Schiff base intermediate, Amadori product, and decarboxylated Amadori product in the solid-state Glc-Asn Maillard reaction were first simultaneously evidenced by this unique DSC-FTIR microspectroscopy. The color changed from white to yellow-brown to dark brown, and appearance of new IR peaks confirmed the formation of Maillard reaction products. The present study clearly indicates that this unique DSC-FTIR technique not only accelerates but also detects precursors and products of the Maillard reaction in real time.

Age-Related Differences in Postural Control and Attentional Cost During Tasks Performed in a One-Legged Standing Posture.

PubMed

Ihira, Hikaru; Makizako, Hyuma; Mizumoto, Atsushi; Makino, Keitarou; Matsuyama, Kiyoji; Furuna, Taketo

2016-01-01

In dual-task situations, postural control is closely associated with attentional cost. Previous studies have reported age-related differences between attentional cost and postural control, but little is known about the association in conditions with a one-legged standing posture. The purpose of this study was to determine age-related differences in postural control and attentional cost while performing tasks at various difficulty levels in a one-legged standing posture. In total, 29 healthy older adults aged 64 to 78 years [15 males, 14 females, mean (SD) = 71.0 (3.8) years] and 29 healthy young adults aged 20 to 26 years [14 males, 15 females, mean (SD) = 22.5 (1.5) years] participated in this study. We measured the reaction time, trunk accelerations, and lower limb muscle activity under 3 different one-legged standing conditions-on a firm surface, on a soft surface with a urethane mat, and on a softer more unstable surface with 2 piled urethane mats. Reaction time as an indication of attentional cost was measured by pressing a handheld button as quickly as possible in response to an auditory stimulus. A 2-way repeated-measures analysis of variance was performed to examine the differences between the 3 task conditions and the 2 age groups for each outcome. Trunk accelerations showed a statistically significant group-by-condition interaction in the anteroposterior (F = 9.1, P < .05), mediolateral (F = 9.9, P < .05), and vertical (F = 9.3, P < .05) directions. Muscle activity did not show a statistically significant group-by-condition interaction, but there was a significant main effect of condition in the tibialis anterior muscle (F = 33.1, P < .01) and medial gastrocnemius muscle (F = 14.7, P < .01) in young adults and the tibialis anterior muscle (F = 24.8, P < .01) and medial gastrocnemius muscle (F = 10.8, P < .01) in older adults. In addition, there was a statistically significant interaction in reaction time (F = 8.2, P < .05) for group-by-condition. The study results confirmed that reaction times in older adults are more prolonged than young adults in the same challenging postural control condition.

Biologically Inspired Synthesis Route to Three-Dimensionally Structured Inorganic Thin Films

DOE PAGES

Schwenzer, Birgit; Morse, Daniel E.

2008-01-01

Inorganic thin films (hydroxide, oxide, and phosphate materials) that are textured on a submicron scale have been prepared from aqueous metal salt solutions at room temperature using vapor-diffusion catalysis. This generic synthesis approach mimics the essential advantages of the catalytic and structure-directing mechanisms observed for the formation of silica skeletons of marine sponges. Chemical composition, crystallinity, and the three-dimensional morphology of films prepared by this method are extremely sensitive to changes in the synthesis conditions, such as concentrations, reaction times, and the presence and nature of substrate materials. Focusing on different materials systems, the reaction mechanism for the formation ofmore » these thin films and the influence of different reaction parameters on the product are explained.« less

Toward a complete theory for predicting inclusive deuteron breakup away from stability

NASA Astrophysics Data System (ADS)

Potel, G.; Perdikakis, G.; Carlson, B. V.; Atkinson, M. C.; Dickhoff, W. H.; Escher, J. E.; Hussein, M. S.; Lei, J.; Li, W.; Macchiavelli, A. O.; Moro, A. M.; Nunes, F. M.; Pain, S. D.; Rotureau, J.

2017-09-01

We present an account of the current status of the theoretical treatment of inclusive ( d, p) reactions in the breakup-fusion formalism, pointing to some applications and making the connection with current experimental capabilities. Three independent implementations of the reaction formalism have been recently developed, making use of different numerical strategies. The codes also originally relied on two different but equivalent representations, namely the prior (Udagawa-Tamura, UT) and the post (Ichimura-Austern-Vincent, IAV) representations. The different implementations have been benchmarked for the first time, and then applied to the Ca isotopic chain. The neutron-Ca propagator is described in the Dispersive Optical Model (DOM) framework, and the interplay between elastic breakup (EB) and non-elastic breakup (NEB) is studied for three Ca isotopes at two different bombarding energies. The accuracy of the description of different reaction observables is assessed by comparing with experimental data of ( d, p) on 40,48Ca. We discuss the predictions of the model for the extreme case of an isotope (60Ca) currently unavailable experimentally, though possibly available in future facilities (nominally within production reach at FRIB). We explore the use of ( d, p) reactions as surrogates for (n,γ ) processes, by using the formalism to describe the compound nucleus formation in a (d,pγ ) reaction as a function of excitation energy, spin, and parity. The subsequent decay is then computed within a Hauser-Feshbach formalism. Comparisons between the (d,pγ ) and (n,γ ) induced gamma decay spectra are discussed to inform efforts to infer neutron captures from (d,pγ ) reactions. Finally, we identify areas of opportunity for future developments, and discuss a possible path toward a predictive reaction theory.

Unusual and Interesting Adverse Cutaneous Drug Reactions.

PubMed

Masatkar, Vaishali; Nagure, Ashok; Gupta, Lalit Kumar

2018-01-01

Any drug can cause any rash! Cutaneous adverse drug reactions (CADRs) are great mimickers and can be included in the differential diagnosis of any inflammatory dermatoses. Several drugs can cause rash of similar morphology and the same drug can cause rash of different morphology. While some common and specific drug reaction patterns are recognized easily by the clinicians, many a times unusual and interesting patterns can be induced by drug(s), thus leading to erroneous diagnosis and mistreatment. This review aims to familiarize clinicians with some rare, yet interesting patterns of CADR.

Unusual and Interesting Adverse Cutaneous Drug Reactions

PubMed Central

Masatkar, Vaishali; Nagure, Ashok; Gupta, Lalit Kumar

2018-01-01

Any drug can cause any rash! Cutaneous adverse drug reactions (CADRs) are great mimickers and can be included in the differential diagnosis of any inflammatory dermatoses. Several drugs can cause rash of similar morphology and the same drug can cause rash of different morphology. While some common and specific drug reaction patterns are recognized easily by the clinicians, many a times unusual and interesting patterns can be induced by drug(s), thus leading to erroneous diagnosis and mistreatment. This review aims to familiarize clinicians with some rare, yet interesting patterns of CADR. PMID:29692451

Chlorine dioxide is a size-selective antimicrobial agent.

PubMed

Noszticzius, Zoltán; Wittmann, Maria; Kály-Kullai, Kristóf; Beregvári, Zoltán; Kiss, István; Rosivall, László; Szegedi, János

2013-01-01

ClO2, the so-called "ideal biocide", could also be applied as an antiseptic if it was understood why the solution killing microbes rapidly does not cause any harm to humans or to animals. Our aim was to find the source of that selectivity by studying its reaction-diffusion mechanism both theoretically and experimentally. ClO2 permeation measurements through protein membranes were performed and the time delay of ClO2 transport due to reaction and diffusion was determined. To calculate ClO2 penetration depths and estimate bacterial killing times, approximate solutions of the reaction-diffusion equation were derived. In these calculations evaporation rates of ClO2 were also measured and taken into account. The rate law of the reaction-diffusion model predicts that the killing time is proportional to the square of the characteristic size (e.g. diameter) of a body, thus, small ones will be killed extremely fast. For example, the killing time for a bacterium is on the order of milliseconds in a 300 ppm ClO2 solution. Thus, a few minutes of contact time (limited by the volatility of ClO2) is quite enough to kill all bacteria, but short enough to keep ClO2 penetration into the living tissues of a greater organism safely below 0.1 mm, minimizing cytotoxic effects when applying it as an antiseptic. Additional properties of ClO2, advantageous for an antiseptic, are also discussed. Most importantly, that bacteria are not able to develop resistance against ClO2 as it reacts with biological thiols which play a vital role in all living organisms. Selectivity of ClO2 between humans and bacteria is based not on their different biochemistry, but on their different size. We hope initiating clinical applications of this promising local antiseptic.

Experimental system for measurement of radiologists' performance by visual search task.

PubMed

Maeda, Eriko; Yoshikawa, Takeharu; Nakashima, Ryoichi; Kobayashi, Kazufumi; Yokosawa, Kazuhiko; Hayashi, Naoto; Masutani, Yoshitaka; Yoshioka, Naoki; Akahane, Masaaki; Ohtomo, Kuni

2013-01-01

Detective performance of radiologists for "obvious" targets should be evaluated by visual search task instead of ROC analysis, but visual task have not been applied to radiology studies. The aim of this study was to set up an environment that allows visual search task in radiology, to evaluate its feasibility, and to preliminarily investigate the effect of career on the performance. In a darkroom, ten radiologists were asked to answer the type of lesion by pressing buttons, when images without lesions, with bulla, ground-glass nodule, and solid nodule were randomly presented on a display. Differences in accuracy and reaction times depending on board certification were investigated. The visual search task was successfully and feasibly performed. Radiologists were found to have high sensitivity, specificity, positive predictive values and negative predictive values in non-board and board groups. Reaction time was under 1 second for all target types in both groups. Board radiologists were significantly faster in answering for bulla, but there were no significant differences for other targets and values. We developed an experimental system that allows visual search experiment in radiology. Reaction time for detection of bulla was shortened with experience.

Bridging the Gap: Understanding Eye Movements and Attentional Mechanisms is Key to Improving Amblyopia Treatment

NASA Astrophysics Data System (ADS)

Gambacorta, Christina Grace

Amblyopia is a developmental visual disorder resulting in sensory, motor and attentional deficits, including delays in both saccadic and manual reaction time. It is unclear whether this delay is due to differences in sensory processing of the stimulus, or the processes required to dis-engage/shift/re-engage attention when moving the eye from fixation to a saccadic target. In the first experiment we compare asymptotic saccadic and manual reaction times between the two eyes, using equivalent stimulus strength to account for differences in sensory processing. In a follow-up study, we modulate RT by removing the fixation dot, which is thought to release spatial attention at the fovea, and reduces reaction time in normal observers. Finally, we discuss the implications for these findings on future amblyopic treatment, specifically dichoptic video game playing. Playing videogames may help engage the attentional network, leading to greater improvements than traditional treatment of patching the non- amblyopic eye. Further, when treatment involves both eyes, fixation stability may be improved during the therapeutic intervention, yielding a better outcome than just playing a video game with a patch over the non-amblyopic eye.

Learning to Control Actions: Transfer Effects following a Procedural Cognitive Control Computerized Training

PubMed Central

Shahar, Nitzan; Meiran, Nachshon

2015-01-01

Few studies have addressed action control training. In the current study, participants were trained over 19 days in an adaptive training task that demanded constant switching, maintenance and updating of novel action rules. Participants completed an executive functions battery before and after training that estimated processing speed, working memory updating, set-shifting, response inhibition and fluid intelligence. Participants in the training group showed greater improvement than a no-contact control group in processing speed, indicated by reduced reaction times in speeded classification tasks. No other systematic group differences were found across the different pre-post measurements. Ex-Gaussian fitting of the reaction-time distribution revealed that the reaction time reduction observed among trained participants was restricted to the right tail of the distribution, previously shown to be related to working memory. Furthermore, training effects were only found in classification tasks that required participants to maintain novel stimulus-response rules in mind, supporting the notion that the training improved working memory abilities. Training benefits were maintained in a 10-month follow-up, indicating relatively long-lasting effects. The authors conclude that training improved action-related working memory abilities. PMID:25799443

Using terahertz time-domain spectroscopical technique to monitor cocrystal formation between piracetam and 2,5-dihydroxybenzoic acid.

PubMed

Du, Yong; Xia, Yi; Zhang, Huili; Hong, Zhi

2013-07-01

Far-infrared vibrational absorption of cocrystal formation between 2,5-dihydroxybenzoic acid (2,5-DHBA) and piracetam compounds under solvent evaporation and grinding methods have been investigated using terahertz time-domain spectroscopy (THz-TDS) at room temperature. The experimental results show large difference among absorption spectra of the formed cocrystals and the involved individual parent molecules in 0.20-1.50 THz region, which probably originated from the intra-molecular and inter-molecular hydrogen bonds due to the presence of two hydroxyl groups in 2,5-DHBA and amide moieties in piracetam compound. The THz absorption spectra of two formed cocrystals with different methods are almost identical. With grinding method, the reaction process can be monitored directly from both time-domain and frequency-domain spectra using THz-TDS technique. The results indicate that THz-TDS technology can absolutely offer us a high potential method to identify and characterize the formed cocrystals, and also provide the rich information about their reaction dynamic process involving two or more molecular crystals in situ to better know the corresponding reaction mechanism in pharmaceutical fields. Copyright © 2013 Elsevier B.V. All rights reserved.

Role of dynamics in enzyme catalysis: substantial versus semantic controversies.

PubMed

Kohen, Amnon

2015-02-17

CONSPECTUS: The role of the enzyme's dynamic motions in catalysis is at the center of heated contemporary debates among both theoreticians and experimentalists. Resolving these apparent disputes is of both intellectual and practical importance: incorporation of enzyme dynamics could be critical for any calculation of enzymatic function and may have profound implications for structure-based drug design and the design of biomimetic catalysts. Analysis of the literature suggests that while part of the dispute may reflect substantial differences between theoretical approaches, much of the debate is semantic. For example, the term "protein dynamics" is often used by some researchers when addressing motions that are in thermal equilibrium with their environment, while other researchers only use this term for nonequilibrium events. The last cases are those in which thermal energy is "stored" in a specific protein mode and "used" for catalysis before it can dissipate to its environment (i.e., "nonstatistical dynamics"). This terminology issue aside, a debate has arisen among theoreticians around the roles of nonstatistical vs statistical dynamics in catalysis. However, the author knows of no experimental findings available today that examined this question in enzyme catalyzed reactions. Another source of perhaps nonsubstantial argument might stem from the varying time scales of enzymatic motions, which range from seconds to femtoseconds. Motions at different time scales play different roles in the many events along the catalytic cascade (reactant binding, reprotonation of reactants, structural rearrangement toward the transition state, product release, etc.). In several cases, when various experimental tools have been used to probe catalytic events at differing time scales, illusory contradictions seem to have emerged. In this Account, recent attempts to sort the merits of those questions are discussed along with possible future directions. A possible summary of current studies could be that enzyme, substrate, and solvent dynamics contribute to enzyme catalyzed reactions in several ways: first via mutual "induced-fit" shifting of their conformational ensemble upon binding; then via thermal search of the conformational space toward the reaction's transition-state (TS) and the rare event of the barrier crossing toward products, which is likely to be on faster time scales then the first and following events; and finally via the dynamics associated with products release, which are rate-limiting for many enzymatic reactions. From a chemical perspective, close to the TS, enzymatic systems seem to stiffen, restricting motions orthogonal to the chemical coordinate and enabling dynamics along the reaction coordinate to occur selectively. Studies of how enzymes evolved to support those efficient dynamics at various time scales are still in their infancy, and further experiments and calculations are needed to reveal these phenomena in both enzymes and uncatalyzed reactions.

Mechanism of the reaction, CH4+O(1D2)→CH3+OH, studied by ultrafast and state-resolved photolysis/probe spectroscopy of the CH4ṡO3 van der Waals complex

NASA Astrophysics Data System (ADS)

Miller, C. Cameron; van Zee, Roger D.; Stephenson, John C.

2001-01-01

The mechanism of the reaction CH4+O(1D2)→CH3+OH was investigated by ultrafast, time-resolved and state-resolved experiments. In the ultrafast experiments, short ultraviolet pulses photolyzed ozone in the CH4ṡO3 van der Waals complex to produce O(1D2). The ensuing reaction with CH4 was monitored by measuring the appearance rate of OH(v=0,1;J,Ω,Λ) by laser-induced fluorescence, through the OH A←X transition, using short probe pulses. These spectrally broad pulses, centered between 307 and 316 nm, probe many different OH rovibrational states simultaneously. At each probe wavelength, both a fast and a slow rise time were evident in the fluorescence signal, and the ratio of the fast-to-slow signal varied with probe wavelength. The distribution of OH(v,J,Ω,Λ) states, Pobs(v,J,Ω,Λ), was determined by laser-induced fluorescence using a high-resolution, tunable dye laser. The Pobs(v,J,Ω,Λ) data and the time-resolved data were analyzed under the assumption that different formation times represent different reaction mechanisms and that each mechanism produces a characteristic rovibrational distribution. The state-resolved and the time-resolved data can be fit independently using a two-mechanism model: Pobs(v,J,Ω,Λ) can be decomposed into two components, and the appearance of OH can be fit by two exponential rise times. However, these independent analyses are not mutually consistent. The time-resolved and state-resolved data can be consistently fit using a three-mechanism model. The OH appearance signals, at all probe wavelengths, were fit with times τfast≈0.2 ps, τinter≈0.5 ps and τslow≈5.4 ps. The slowest of these three is the rate for dissociation of a vibrationally excited methanol intermediate (CH3OH*) predicted by statistical theory after complete intramolecular energy redistribution following insertion of O(1D2) into CH4. The Pobs(v,J,Ω,Λ) was decomposed into three components, each with a linear surprisal, under the assumption that the mechanism producing OH at a statistical rate would be characterized by a statistical prior. Dissociation of a CH4O* intermediate before complete energy randomization was identified as producing OH at the intermediate rate and was associated with a population distribution with more rovibrational energy than the slow mechanism. The third mechanism produces OH promptly with a cold rovibrational distribution, indicative of a collinear abstraction mechanism. After these identifications were made, it was possible to predict the fraction of signal associated with each mechanism at different probe wavelengths in the ultrafast experiment, and the predictions proved consistent with measured appearance signals. This model also reconciles data from a variety of previous experiments. While this model is the simplest that is consistent with the data, it is not definitive for several reasons. First, the appearance signals measured in these experiments probe simultaneously many OH(v,J,Ω,Λ) states, which would tend to obfuscate differences in the appearance rate of specific rovibrational states. Second, only about half of the OH(v,J,Ω,Λ) states populated by this reaction could be probed by laser-induced fluorescence through the OH A←X band with our apparatus. Third, the cluster environment might influence the dynamics compared to the free bimolecular reaction.

THE VASCULAR PATHOPHYSIOLOGY OF AN IRRADIATED GRAFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubin, P.; Casarett, G.; Grise, J.W.

1960-06-01

The difference in the vascularization of grafted and normal skin forms a reasonable basis for explaining the differences in the radiation reactions of these structures. The radioisotope half time of disappearance following subcutaneous injection is an index of vascular integrity of the graft and serves as a parameter to predict its radioresponsiveness. In developing a concept of the spectrum of reactions of grafted skin to ionizing irradiation, knowledge of the radiopathologic changes in capillaries must be utilized with knowledge of the histophysiology of the vascularity of an autograft. (auth)

DVA as a Diagnostic Test for Vestibulo-Ocular Reflex Function

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Appelbaum, Meghan

2010-01-01

The vestibulo-ocular reflex (VOR) stabilizes vision on earth-fixed targets by eliciting eyes movements in response to changes in head position. How well the eyes perform this task can be functionally measured by the dynamic visual acuity (DVA) test. We designed a passive, horizontal DVA test to specifically study the acuity and reaction time when looking in different target locations. Visual acuity was compared among 12 subjects using a standard Landolt C wall chart, a computerized static (no rotation) acuity test and dynamic acuity test while oscillating at 0.8 Hz (+/-60 deg/s). In addition, five trials with yaw oscillation randomly presented a visual target in one of nine different locations with the size and presentation duration of the visual target varying across trials. The results showed a significant difference between the static and dynamic threshold acuities as well as a significant difference between the visual targets presented in the horizontal plane versus those in the vertical plane when comparing accuracy of vision and reaction time of the response. Visual acuity increased proportional to the size of the visual target and increased between 150 and 300 msec duration. We conclude that dynamic visual acuity varies with target location, with acuity optimized for targets in the plane of rotation. This DVA test could be used as a functional diagnostic test for visual-vestibular and neuro-cognitive impairments by assessing both accuracy and reaction time to acquire visual targets.

Colliding-Droplet Microreactor: Rapid On-Demand Inertial Mixing and Metal-Catalyzed Aqueous Phase Oxidation Processes.

PubMed

Davis, Ryan D; Jacobs, Michael I; Houle, Frances A; Wilson, Kevin R

2017-11-21

In-depth investigations of the kinetics of aqueous chemistry occurring in microdroplet environments require experimental techniques that allow a reaction to be initiated at a well-defined point in time and space. Merging microdroplets of different reactants is one such approach. The mixing dynamics of unconfined (airborne) microdroplets have yet to be studied in detail, which is an essential step toward widespread use and application of merged droplet microreactors for monitoring chemical reactions. Here, we present an on-demand experimental approach for initiating chemical reactions in and characterizing the mixing dynamics of colliding airborne microdroplets (40 ± 5 μm diameter) using a streak-based fluorescence microscopy technique. The advantages of this approach include the ability to generate two well-controlled monodisperse microdroplet streams and collide (and thus mix) the microdroplets with high spatial and temporal control while consuming small amounts of sample (<0.1 μL/s). Mixing times are influenced not only by the velocity at which microdroplets collide but also the geometry of the collision (i.e., head-on vs off-center collision). For head-on collisions, we achieve submillisecond mixing times ranging from ∼900 μs at a collision velocity of 0.1 m/s to <200 μs at ∼6 m/s. For low-velocity (<1 m/s) off-center collisions, mixing times were consistent with the head-on cases. For high-velocity (i.e., > 1 m/s) off-center collisions, mixing times increased by as much as a factor of 6 (e.g., at ∼6 m/s, mixing times increased from <200 μs for head-on collisions to ∼1200 μs for highly off-center collisions). At collision velocities >7 m/s, droplet separation and fragmentation occurred, resulting in incomplete mixing. These results suggest a limited range of collision velocities over which complete and rapid mixing can be achieved when using airborne merged microdroplets to, e.g., study reaction kinetics when reaction times are short relative to typical bulk reactor mixing times. We benchmark our reactor using an aqueous-phase oxidation reaction: iron-catalyzed hydroxyl radical production from hydrogen peroxide (Fenton's reaction) and subsequent aqueous-phase oxidation of organic species in solution. Kinetic simulations of our measurements show that quantitative agreement can be obtained using known bulk-phase kinetics for bimolecular reactions in our colliding-droplet microreactor.

Colliding-Droplet Microreactor: Rapid On-Demand Inertial Mixing and Metal-Catalyzed Aqueous Phase Oxidation Processes

DOE PAGES

Davis, Ryan D.; Jacobs, Michael I.; Houle, Frances A.; ...

2017-10-30

In-depth investigations of the kinetics of aqueous chemistry occurring in microdroplet environments require experimental techniques that allow a reaction to be initiated at a well-defined point in time and space. Merging microdroplets of different reactants is one such approach. The mixing dynamics of unconfined (airborne) microdroplets have yet to be studied in detail, which is an essential step toward widespread use and application of merged droplet microreactors for monitoring chemical reactions. Here, we present an on-demand experimental approach for initiating chemical reactions in and characterizing the mixing dynamics of colliding airborne microdroplets (40 ± 5 μm diameter) using a streak-basedmore » fluorescence microscopy technique. The advantages of this approach include the ability to generate two well-controlled monodisperse microdroplet streams and collide (and thus mix) the microdroplets with high spatial and temporal control while consuming small amounts of sample (<0.1 μL/s). Mixing times are influenced not only by the velocity at which microdroplets collide but also the geometry of the collision (i.e., head-on vs off-center collision). For head-on collisions, we achieve submillisecond mixing times ranging from ~900 μs at a collision velocity of 0.1 m/s to <200 μs at ~6 m/s. For low-velocity (<1 m/s) off-center collisions, mixing times were consistent with the head-on cases. For high-velocity (i.e., > 1 m/s) off-center collisions, mixing times increased by as much as a factor of 6 (e.g., at ~6 m/s, mixing times increased from <200 μs for head-on collisions to ~1200 μs for highly off-center collisions). At collision velocities >7 m/s, droplet separation and fragmentation occurred, resulting in incomplete mixing. These results suggest a limited range of collision velocities over which complete and rapid mixing can be achieved when using airborne merged microdroplets to, e.g., study reaction kinetics when reaction times are short relative to typical bulk reactor mixing times. We benchmark our reactor using an aqueous-phase oxidation reaction: iron-catalyzed hydroxyl radical production from hydrogen peroxide (Fenton's reaction) and subsequent aqueous-phase oxidation of organic species in solution. In conclusion, kinetic simulations of our measurements show that quantitative agreement can be obtained using known bulk-phase kinetics for bimolecular reactions in our colliding-droplet microreactor.« less

Colliding-Droplet Microreactor: Rapid On-Demand Inertial Mixing and Metal-Catalyzed Aqueous Phase Oxidation Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Ryan D.; Jacobs, Michael I.; Houle, Frances A.

In-depth investigations of the kinetics of aqueous chemistry occurring in microdroplet environments require experimental techniques that allow a reaction to be initiated at a well-defined point in time and space. Merging microdroplets of different reactants is one such approach. The mixing dynamics of unconfined (airborne) microdroplets have yet to be studied in detail, which is an essential step toward widespread use and application of merged droplet microreactors for monitoring chemical reactions. Here, we present an on-demand experimental approach for initiating chemical reactions in and characterizing the mixing dynamics of colliding airborne microdroplets (40 ± 5 μm diameter) using a streak-basedmore » fluorescence microscopy technique. The advantages of this approach include the ability to generate two well-controlled monodisperse microdroplet streams and collide (and thus mix) the microdroplets with high spatial and temporal control while consuming small amounts of sample (<0.1 μL/s). Mixing times are influenced not only by the velocity at which microdroplets collide but also the geometry of the collision (i.e., head-on vs off-center collision). For head-on collisions, we achieve submillisecond mixing times ranging from ~900 μs at a collision velocity of 0.1 m/s to <200 μs at ~6 m/s. For low-velocity (<1 m/s) off-center collisions, mixing times were consistent with the head-on cases. For high-velocity (i.e., > 1 m/s) off-center collisions, mixing times increased by as much as a factor of 6 (e.g., at ~6 m/s, mixing times increased from <200 μs for head-on collisions to ~1200 μs for highly off-center collisions). At collision velocities >7 m/s, droplet separation and fragmentation occurred, resulting in incomplete mixing. These results suggest a limited range of collision velocities over which complete and rapid mixing can be achieved when using airborne merged microdroplets to, e.g., study reaction kinetics when reaction times are short relative to typical bulk reactor mixing times. We benchmark our reactor using an aqueous-phase oxidation reaction: iron-catalyzed hydroxyl radical production from hydrogen peroxide (Fenton's reaction) and subsequent aqueous-phase oxidation of organic species in solution. In conclusion, kinetic simulations of our measurements show that quantitative agreement can be obtained using known bulk-phase kinetics for bimolecular reactions in our colliding-droplet microreactor.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Góźdź, A., E-mail: andrzej.gozdz@umcs.lublin.pl; Góźdź, M., E-mail: mgozdz@kft.umcs.lublin.pl

The theory of neutrino oscillations rests on the assumption, that the interaction basis and the physical (mass) basis of neutrino states are different. Therefore neutrino is produced in a certain welldefined superposition of three mass eigenstates, which propagate separately and may be detected as a different superposition. This is called flavor oscillations. It is, however, not clear why neutrinos behave this way, i.e., what is the underlying mechanism which leads to the production of a superposition of physical states in a single reaction. In this paper we argue, that one of the reasons may be connected with the temporal structuremore » of the process. In order to discuss the role of time in processes on the quantum level, we use a special formulation of the quantum mechanics, which is based on the projection time evolution. We arrive at the conclusion, that for short reaction times the formation of a superposition of states of similar masses is natural.« less

Kinetic phase evolution of spinel cobalt oxide during lithiation

DOE PAGES

Li, Jing; He, Kai; Meng, Qingping; ...

2016-09-15

Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

Kinetic phase evolution of spinel cobalt oxide during lithiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jing; He, Kai; Meng, Qingping

Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

Identification and Characterization of Reaction Products of 5-Hydroxytryptamine with Methylglyoxal and Glyoxal by LC/MS/MS.

PubMed

Sai Sachin, L; Nagarjuna Chary, R; Pavankumar, P; Prabhakar, S

2018-06-06

The methylglyoxal (MGO) and glyoxal (GO) are known to be at high levels in the diabetic humans. They react with amine containing proteins and amino acids to form advanced glycation end products, however, the reactivity with the other amine containing metabolites, such as neurotransmitters are not explored. In this study, we aimed at studying the reactivity of 5-hydroxytryptamine (5-HT) with MGO or GO, which may alter the metabolic function of 5-HT. The stock solutions of 5-HT, MGO and GO were made in PBS buffer at pH 7.4 and incubated 5-HT with MGO or GO at difference concentrations. The reactions were also performed at physiological concentrations. The reaction mixtures collected at different incubation times were analyzed by direct ESI-HRMS, LC/MS and LC/MS/MS conditions to detect/characterize the products. Agilent 6545 Q-TOF and Agilent 6420 triple quadrupole mass spectrometer were used for the study, and LC separations were performed on a C18 column. The direct ESI-HRMS data of the reaction mixtures showed formation of three and four reaction products when 5-HT reacted with MGO and GO, respectively. All the products showed dominant [M+H] + ions. The products were characterized by HRMS, LC/MS/MS and the literature reports on similar compounds. The products can easily be identified by LC/MS based on the accurate mass values together with retention time information. The MS/MS of the reaction products showed structure indicative fragment ions. 5-HT reacts with one or two MGO/GO to form a set of reaction products. The reaction between 5-HT and MGO or GO was faster at higher concentrations of MGO/GO (<10 min), and the same products were found even at physiological concentrations (<48 hrs). The LC-MS/MS (SRM) method can be used to screen the reaction products when present at low level. This article is protected by copyright. All rights reserved.

Cognitive demand of human sensorimotor performance during an extended space mission: a dual-task study.

PubMed

Bock, Otmar; Weigelt, Cornelia; Bloomberg, Jacob J

2010-09-01

Two previous single-case studies found that the dual-task costs of manual tracking plus memory search increased during a space mission, and concluded that sensorimotor deficits during spaceflight may be related to cognitive overload. Since dual-task costs were insensitive to the difficulty of memory search, the authors argued that the overload may reflect stress-related problems of multitasking, rather than a scarcity of specific cognitive resources. Here we expand the available database and compare different types of concurrent task. Three subjects were repeatedly tested before, during, and after an extended mission on the International Space Station (ISS). They performed an unstable tracking task and four reaction-time tasks, both separately and concurrently. Inflight data could only be obtained during later parts of the mission. The tracking error increased from pre- to in flight by a factor of about 2, both under single- and dual-task conditions. The dual-task costs with a reaction-time task requiring rhythm production was 2.4 times higher than with a reaction-time task requiring visuo-spatial transformations, and 8 times higher than with a regular choice reaction-time task. Long-term sensorimotor deficits during spaceflight may reflect not only stress, but also a scarcity of resources related to complex motor programming; possibly those resources are tied up by sensorimotor adaptation to the space environment.

Catalytic ignition model in a monolithic reactor with in-depth reaction

NASA Technical Reports Server (NTRS)

Tien, Ta-Ching; Tien, James S.

1990-01-01

Two transient models have been developed to study the catalytic ignition in a monolithic catalytic reactor. The special feature in these models is the inclusion of thermal and species structures in the porous catalytic layer. There are many time scales involved in the catalytic ignition problem, and these two models are developed with different time scales. In the full transient model, the equations are non-dimensionalized by the shortest time scale (mass diffusion across the catalytic layer). It is therefore accurate but is computationally costly. In the energy-integral model, only the slowest process (solid heat-up) is taken as nonsteady. It is approximate but computationally efficient. In the computations performed, the catalyst is platinum and the reactants are rich mixtures of hydrogen and oxygen. One-step global chemical reaction rates are used for both gas-phase homogeneous reaction and catalytic heterogeneous reaction. The computed results reveal the transient ignition processes in detail, including the structure variation with time in the reactive catalytic layer. An ignition map using reactor length and catalyst loading is constructed. The comparison of computed results between the two transient models verifies the applicability of the energy-integral model when the time is greater than the second largest time scale of the system. It also suggests that a proper combined use of the two models can catch all the transient phenomena while minimizing the computational cost.

The effects of verbal reaction time in Alzheimer's disease.

PubMed

Midi, Ipek; Doǧan, Müzeyyen; Pata, Yavuz Selim; Kocak, Ismail; Mollahasanoglu, Aynur; Tuncer, Nese

2011-07-01

Verbal fluency deteriorates with normal aging, but is much more severe in Alzheimer's Disease (AD). Verbal functions were analyzed to find differences between normal aging subjects in patients with mild cognitive impairment (MCI), and in patients with early and moderate stages of AD. This study measured the verbal response time in patients with AD, MCI, and in control subjects This study measured the verbal response time in patients with AD, MCI, and in control subjects Fifteen patients with MCI, 15 patients with early AD, 8 patients with moderate AD, and 15 subjects for controls were included in the study. Word length in milliseconds, reaction time to a phoneme, word, or sentence and acoustic analysis of voice quality and speech diadochokinetic rate (DDK) were measured. Reaction time for a phoneme, word, or sentence especially the initiation period for them were longer in patients with early AD compared to patients with MCI (P < .001). The mean DDK rate was lower with increased severity of the disease, and was much more severe in patients with moderate AD. Clinical discrimination of the early stages of AD and MCI is challenging. Unfortunately, there are no laboratory markers present for the diagnosis of preclinical cases of AD. With the results of this study, the assessments of verbal reaction time may helpful for diagnosis of early AD. Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.

Effect of working consecutive night shifts on sleep time, prior wakefulness, perceived levels of fatigue and performance on a psychometric test in emergency registrars.

PubMed

Haire, Julia Christine Lydia; Ferguson, Sally Anne; Tilleard, James D; Negus, Paul; Dorrian, Jillian; Thomas, Matthew Jw

2012-06-01

To evaluate the effect of working consecutive night shifts on sleep time, prior wakefulness, perceived levels of fatigue and psychomotor performance in a group of Australian emergency registrars. A prospective observational study with a repeated within-subjects component was conducted. Sleep time was determined using sleep diaries and activity monitors. Subjective fatigue levels and reciprocal reaction times were evaluated before and after day and night shifts. A total of 11 registrars participated in the study with 120 shifts analysed. Sleep time was found to be similar during consecutive night and day shifts. The mean number of hours spent awake before the end of a night shift was 14.33. Subjective fatigue scores were worst at the end of a night shift. There was no difference in reciprocal reaction time between the end of night shift and the start of day shift. Registrars sleep a similar amount of time surrounding night and day shifts. Despite reporting the highest levels of fatigue at the end of a night shift, there is no significant difference in reaction times at the end of night shift compared with the beginning of day shift. This correlates with the finding that at the end of night shift the registrars have been awake for less than 16 h, which is the point at which psychomotor performance is expected to decline. © 2012 The Authors. EMA © 2012 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

Direct formation of element chlorides from the corresponding element oxides through microwave-assisted carbohydrochlorination reactions.

PubMed

Nordschild, Simon; Auner, Norbert

2008-01-01

A series of technically and economically important element chlorides-such as SiCl4, BCl3, AlCl3, FeCl2, PCl3 and TiCl4-was synthesized through reactions between hydrogen chloride and the corresponding element oxides in the presence of different carbon sources with microwave assistance. This process route was optimized for demonstration purposes for tetrachlorosilane formation and successfully demonstrates the broad applicability of various silicon oxide-containing minerals and materials for carbohydrochlorination. The chlorination reaction occurs at lower temperatures than with conventional heating in a tubular oven, with substantially shorter reaction times and in better yields: quantitatively in the case of tetrachlorosilane, based on the silicon content of the starting material. The experimental procedure is very simple and provides basic information about the suitability of element compounds, especially element oxides, for carbohydrochlorination. According to the general reaction sequence element oxide-->element-->element chloride used in today's technology, this one-step carbohydrochlorination with hydrogen chloride is considerably more efficient, particularly in terms of energy input and reaction times, avoiding the isolation of the pure elements required for chlorination to give the element chlorides with use of the more corrosive and toxic chlorine gas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Jiwen; Song, Yang, E-mail: yang.song@uwo.ca; Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7

The polymerization process of condensed styrene to produce polystyrene as an industrially important polymeric material was investigated using a novel approach by combining external compression with ultraviolet radiation. The reaction evolution was monitored as a function of time and the reaction products were characterized by in situ Fourier transform infrared spectroscopy. By optimizing the loading pressures, we observed highly efficient and selective production of polystyrene of different tacticities. Specifically, at relatively low loading pressures, infrared spectra suggest that styrene monomers transform to amorphous atactic polystyrene (APS) with minor crystalline isotactic polystyrene. In contrast, APS was found to be the solemore » product when polymerization occurs at relatively higher loading pressures. The time-dependent reaction profiles allow the examination of the polymerization kinetics by analyzing the rate constant and activation volume as a function of pressure. As a result, an optimized pressure condition, which allows a barrierless reaction to proceed, was identified and attributed to the very desirable reaction yield and kinetics. Finally, the photoinitiated reaction mechanism and the growth geometry of the polymer chains were investigated from the energy diagram of styrene and by the topology analysis of the crystal styrene. This study shows strong promise to produce functional polymeric materials in a highly efficient and controlled manner.« less

Flash chemistry: flow microreactor synthesis based on high-resolution reaction time control.

PubMed

Yoshida, Jun-ichi

2010-10-01

This article addresses a fascinating aspect of flash chemistry, high-resolution reaction-time control by virtue of a flow microreactor system, and its applications. The length of time that the solution remains inside the reactor is called the residence time. The residence time between the addition of a reagent and that of a quenching agent or the next reagent in a flow microreactor is the reaction time, and the reaction time can be greatly reduced by adjusting the length of a reaction channel in a flow microreactor. This feature is quite effective for conducting reactions involving short-lived reactive intermediates. A reactive species can be generated and transferred to another location to be used in the next reaction before it decomposes by adjusting the residence time in the millisecond to second timescale. The principle of such high-resolution reaction-time control, which can be achieved only by flow microreactors, and its applications to synthetic reactions including Swern-Moffatt-type oxidation, as well as the generation and reactions of aryllithium compounds bearing electrophilic substituents, such as alkoxycarbonyl groups, are presented. Integration of such reactions using integrated flow microreactor systems is also demonstrated. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Anisotropic transverse mixing and its effect on reaction rates in multi-scale, 3D heterogeneous porous media

NASA Astrophysics Data System (ADS)

Engdahl, N. B.

2016-12-01

Mixing rates in porous media have been a heavily research topic in recent years covering analytic, random, and structured fields. However, there are some persistent assumptions and common features to these models that raise some questions about the generality of the results. One of these commonalities is the orientation of the flow field with respect to the heterogeneity structure, which are almost always defined to be parallel each other if there is an elongated axis of permeability correlation. Given the vastly different tortuosities for flow parallel to bedding and flow transverse to bedding, this assumption of parallel orientation may have significant effects on reaction rates when natural flows deviate from this assumed setting. This study investigates the role of orientation on mixing and reaction rates in multi-scale, 3D heterogeneous porous media with varying degrees of anisotropy in the correlation structure. Ten realizations of a small flow field, with three anisotropy levels, were simulated for flow parallel and transverse to bedding. Transport was simulated in each model with an advective-diffusive random walk and reactions were simulated using the chemical Langevin equation. The reaction system is a vertically segregated, transverse mixing problem between two mobile reactants. The results show that different transport behaviors and reaction rates are obtained by simply rotating the direction of flow relative to bedding, even when the net flux in both directions is the same. This kind of behavior was observed for three different weightings of the initial condition: 1) uniform, 2) flux-based, and 3) travel time based. The different schemes resulted in 20-50% more mass formation in the transverse direction than the longitudinal. The greatest variability in mass was observed for the flux weights and these were proportionate to the level of anisotropy. The implications of this study are that flux or travel time weights do not provide any guarantee of a fair comparison in this kind of a mixing scenario and that the role of directional tendencies on reaction rates can be significant. Further, it may be necessary to include anisotropy in future upscaled models to create robust methods that give representative reaction rates for any flow direction relative to geologic bedding.

Experimental Measurements of the Chemical Reaction Zone of Detonating Liquid Explosives

NASA Astrophysics Data System (ADS)

Bouyer, Viviane; Sheffield, Stephen A.; Dattelbaum, Dana M.; Gustavsen, Richard L.; Stahl, David B.; Doucet, Michel; Decaris, Lionel

2009-12-01

We have a joint project between CEA-DAM Le Ripault and Los Alamos National Laboratory (LANL) to study the chemical reaction zone in detonating high explosives using several different laser velocimetry techniques. The short temporal duration of the von Neumann spike and early part of the reaction zone make these measurements difficult. Here, we report results obtained from detonation experiments using VISAR (velocity interferometer system for any reflector) and PDV (photon Doppler velocimetry) methods to measure the particle velocity history at a detonating nitromethane/PMMA interface. Experiments done at CEA were high-explosive-plane-wave initiated and those at LANL were gas-gun-projectile initiated with a detonation run of about 6 charge diameters in all experiments. The experiments had either glass or brass confinement. Excellent agreement of the interface particle velocity measurements at both Laboratories were obtained even though the initiation methods and the velocimetry systems were somewhat different. Some differences were observed in the peak particle velocity because of the ˜2 ns time resolution of the techniques—in all cases the peak was lower than the expected von Neumann spike. This is thought to be because the measurements were not high enough time resolution to resolve the spike.

A parametric duration model of the reaction times of drivers distracted by mobile phone conversations.

PubMed

Haque, Md Mazharul; Washington, Simon

2014-01-01

The use of mobile phones while driving is more prevalent among young drivers-a less experienced cohort with elevated crash risk. The objective of this study was to examine and better understand the reaction times of young drivers to a traffic event originating in their peripheral vision whilst engaged in a mobile phone conversation. The CARRS-Q advanced driving simulator was used to test a sample of young drivers on various simulated driving tasks, including an event that originated within the driver's peripheral vision, whereby a pedestrian enters a zebra crossing from a sidewalk. Thirty-two licensed drivers drove the simulator in three phone conditions: baseline (no phone conversation), hands-free and handheld. In addition to driving the simulator each participant completed questionnaires related to driver demographics, driving history, usage of mobile phones while driving, and general mobile phone usage history. The participants were 21-26 years old and split evenly by gender. Drivers' reaction times to a pedestrian in the zebra crossing were modelled using a parametric accelerated failure time (AFT) duration model with a Weibull distribution. Also tested where two different model specifications to account for the structured heterogeneity arising from the repeated measures experimental design. The Weibull AFT model with gamma heterogeneity was found to be the best fitting model and identified four significant variables influencing the reaction times, including phone condition, driver's age, license type (provisional license holder or not), and self-reported frequency of usage of handheld phones while driving. The reaction times of drivers were more than 40% longer in the distracted condition compared to baseline (not distracted). Moreover, the impairment of reaction times due to mobile phone conversations was almost double for provisional compared to open license holders. A reduction in the ability to detect traffic events in the periphery whilst distracted presents a significant and measurable safety concern that will undoubtedly persist unless mitigated. Copyright © 2013 Elsevier Ltd. All rights reserved.

New strategy to identify radicals in a time evolving EPR data set by multivariate curve resolution-alternating least squares.

PubMed

Fadel, Maya Abou; de Juan, Anna; Vezin, Hervé; Duponchel, Ludovic

2016-12-01

Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that is able to characterize radicals formed in kinetic reactions. However, spectral characterization of individual chemical species is often limited or even unmanageable due to the severe kinetic and spectral overlap among species in kinetic processes. Therefore, we applied, for the first time, multivariate curve resolution-alternating least squares (MCR-ALS) method to EPR time evolving data sets to model and characterize the different constituents in a kinetic reaction. Here we demonstrate the advantage of multivariate analysis in the investigation of radicals formed along the kinetic process of hydroxycoumarin in alkaline medium. Multiset analysis of several EPR-monitored kinetic experiments performed in different conditions revealed the individual paramagnetic centres as well as their kinetic profiles. The results obtained by MCR-ALS method demonstrate its prominent potential in analysis of EPR time evolved spectra. Copyright © 2016 Elsevier B.V. All rights reserved.

Crossed-uncrossed difference (CUD) in a new light: anatomy of the negative CUD in Poffenberger's paradigm.

PubMed

Derakhshan, I

2006-03-01

Crossed Uncrossed Differentials (CUDs) have long been used as surrogate for the interhemispheric transfer time (IHTT). Evidence is presented that macular vision is the province of the major hemisphere, wherein all commands are initiated regardless of the laterality of the effectors of such commands. Using clinical and time-resolved data it is shown also that the above arrangement (i.e. neural handedness) corresponds to the subject's behavioral avowed (avowed, self-declared) handedness only in a statistical sense; with a substantial minority of humanity displaying a disparity of neural and behavioral handedness. Evidence is provided that the negative CUD in previously reported studies was a reflection of such incongruity in those subjects studied. Thus, to lateralize the command center it is sufficient to determine the reaction time of two symmetrically located effectors on the body. The side with longer reaction time is ipsilateral to the major hemisphere, with the difference of the two sides commensurate to transcallosal IHTT.

Revealing chemical processes and kinetics of drug action within single living cells via plasmonic Raman probes.

PubMed

Li, Shan-Shan; Guan, Qi-Yuan; Meng, Gang; Chang, Xiao-Feng; Wei, Ji-Wu; Wang, Peng; Kang, Bin; Xu, Jing-Juan; Chen, Hong-Yuan

2017-05-23

Better understanding the drug action within cells may extend our knowledge on drug action mechanisms and promote new drugs discovery. Herein, we studied the processes of drug induced chemical changes on proteins and nucleic acids in human breast adenocarcinoma (MCF-7) cells via time-resolved plasmonic-enhanced Raman spectroscopy (PERS) in combination with principal component analysis (PCA). Using three popular chemotherapy drugs (fluorouracil, cisplatin and camptothecin) as models, chemical changes during drug action process were clearly discriminated. Reaction kinetics related to protein denaturation, conformational modification, DNA damage and their associated biomolecular events were calculated. Through rate constants and reaction delay times, the different action modes of these drugs could be distinguished. These results may provide vital insights into understanding the chemical reactions associated with drug-cell interactions.

Pseudoephedrine may cause "pigmenting" fixed drug eruption.

PubMed

Ozkaya, Esen; Elinç-Aslan, Meryem Sevinç

2011-05-01

Fixed drug eruption (FDE) is a distinctive drug eruption characterized by recurrent well-defined lesions in the same location each time the responsible drug is taken. Two different clinical forms have been described: the common classic pigmenting form and the rare nonpigmenting form. Nonpigmenting FDE is mainly characterized by symmetrical large erythematous plaques and the dermal histopathologic reaction pattern. Pseudoephedrine is known as the major inducer of nonpigmenting FDE. Pigmenting FDE from pseudoephedrine has not been reported previously. Here, the first case of pseudoephedrine-induced pigmenting FDE is reported, showing the characteristic features of classic pigmenting FDE such as asymmetry, normal-sized lesions, and the epidermodermal histopathologic reaction pattern. Moreover, a positive occlusive patch-test reaction to pseudoephedrine could be demonstrated on postlesional FDE skin for the first time.

Ab initio studies of ultrafast x-ray scattering of the photodissociation of iodine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debnarova, Andrea; Techert, Simone; Schmatz, Stefan

2010-09-28

We computationally examine various aspects of the reaction dynamics of the photodissociation and recombination of molecular iodine. We use our recently proposed formalism to calculate time-dependent x-ray scattering signal changes from first principles. Different aspects of the dynamics of this prototypical reaction are studied, such as coherent and noncoherent processes, features of structural relaxation that are periodic in time versus nonperiodic dissociative processes, as well as small electron density changes caused by electronic excitation, all with respect to x-ray scattering. We can demonstrate that wide-angle x-ray scattering offers a possibility to study the changes in electron densities in nonperiodic systems,more » which render it a suitable technique for the investigation of chemical reactions from a structural dynamics point of view.« less

Reaction times of normal listeners to laryngeal, alaryngeal, and synthetic speech.

PubMed

Evitts, Paul M; Searl, Jeff

2006-12-01

The purpose of this study was to compare listener processing demands when decoding alaryngeal compared to laryngeal speech. Fifty-six listeners were presented with single words produced by 1 proficient speaker from 5 different modes of speech: normal, tracheosophageal (TE), esophageal (ES), electrolaryngeal (EL), and synthetic speech (SS). Cognitive processing load was indexed by listener reaction time (RT). To account for significant durational differences among the modes of speech, an RT ratio was calculated (stimulus duration divided by RT). Results indicated that the cognitive processing load was greater for ES and EL relative to normal speech. TE and normal speech did not differ in terms of RT ratio, suggesting fairly comparable cognitive demands placed on the listener. SS required greater cognitive processing load than normal and alaryngeal speech. The results are discussed relative to alaryngeal speech intelligibility and the role of the listener. Potential clinical applications and directions for future research are also presented.

Priming effects for affective vs. neutral faces.

PubMed

Burton, Leslie A; Rabin, Laura; Wyatt, Gwinne; Frohlich, Jonathan; Bernstein Vardy, Susan; Dimitri, Diana

2005-12-01

Affective and Neutral Tasks (faces with negative or neutral content, with different lighting and orientation) requiring reaction time judgments of poser identity were administered to 32 participants. Speed and accuracy were better for the Affective than Neutral Task, consistent with literature suggesting facilitation of performance by affective content. Priming effects were significant for the Affective but not Neutral Task. An Explicit Post-Test indicated no conscious knowledge of the stimulus frequency that was associated with performance facilitation. Faster performance by female vs. male participants, and differential speeds and susceptibility to priming of different emotions were also found. Anger and shock were responded to most rapidly and accurately in several conditions, showed no gender differences, and showed significant priming for both RT and accuracy. Fear and pain were responded to least accurately, were associated with faster female than male reaction time, and the accuracy data showed a kind of reverse priming.

Reaction Time and Attention: Toward a New Standard in the Assessment of ADHD? A Pilot Study.

PubMed

De la Torre, Gabriel G; Barroso, Juan M; León-Carrión, José; Mestre, Jose M; Bozal, Rocío Guil

2015-12-01

This pilot study shows results of an experiment comparing reaction times (RTs) and attentional performance between an ADHD group of 30 children and 30 controls, both Spanish speaking. The experiment was carried out using the Seville computerized neuropsychological battery (SNB). This study had two goals: One was to test sensitivity of SNB for attention deficits in ADHD and the second was to detect differences in RTs between ADHD and controls. Possible explanations and implications of such differences are also discussed. SNB computerized system was used to assess RTs and accuracy, and alternate forms of continuous performance task were used. Results showed high sensitivity of some of the SNB tests, especially cancellation tests. RTs were significantly different between groups. SNB represents a helpful tool for detection of attention deficits, and RT indices represent the most significant variable in differentiation of both groups studied. © The Author(s) 2012.

Thermal decomposition of solid phase nitromethane under various heating rates and target temperatures based on ab initio molecular dynamics simulations.

PubMed

Xu, Kai; Wei, Dong-Qing; Chen, Xiang-Rong; Ji, Guang-Fu

2014-10-01

The Car-Parrinello molecular dynamics simulation was applied to study the thermal decomposition of solid phase nitromethane under gradual heating and fast annealing conditions. In gradual heating simulations, we found that, rather than C-N bond cleavage, intermolecular proton transfer is more likely to be the first reaction in the decomposition process. At high temperature, the first reaction in fast annealing simulation is intermolecular proton transfer leading to CH3NOOH and CH2NO2, whereas the initial chemical event at low temperature tends to be a unimolecular C-N bond cleavage, producing CH3 and NO2 fragments. It is the first time to date that the direct rupture of a C-N bond has been reported as the first reaction in solid phase nitromethane. In addition, the fast annealing simulations on a supercell at different temperatures are conducted to validate the effect of simulation cell size on initial reaction mechanisms. The results are in qualitative agreement with the simulations on a unit cell. By analyzing the time evolution of some molecules, we also found that the time of first water molecule formation is clearly sensitive to heating rates and target temperatures when the first reaction is an intermolecular proton transfer.

Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

NASA Astrophysics Data System (ADS)

Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

2016-05-01

3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

Insight into Chemistry on Cloud/Aerosol Water Surfaces.

PubMed

Zhong, Jie; Kumar, Manoj; Francisco, Joseph S; Zeng, Xiao Cheng

2018-05-15

Cloud/aerosol water surfaces exert significant influence over atmospheric chemical processes. Atmospheric processes at the water surface are observed to follow mechanisms that are quite different from those in the gas phase. This Account summarizes our recent findings of new reaction pathways on the water surface. We have studied these surface reactions using Born-Oppenheimer molecular dynamics simulations. These studies provide useful information on the reaction time scale, the underlying mechanism of surface reactions, and the dynamic behavior of the product formed on the aqueous surface. According to these studies, the aerosol water surfaces confine the atmospheric species into a specific orientation depending on the hydrophilicity of atmospheric species or the hydrogen-bonding interactions between atmospheric species and interfacial water. As a result, atmospheric species are activated toward a particular reaction on the aerosol water surface. For example, the simplest Criegee intermediate (CH 2 OO) exhibits high reactivity toward the interfacial water and hydrogen sulfide, with the reaction times being a few picoseconds, 2-3 orders of magnitude faster than that in the gas phase. The presence of interfacial water molecules induces proton-transfer-based stepwise pathways for these reactions, which are not possible in the gas phase. The strong hydrophobicity of methyl substituents in larger Criegee intermediates (>C1), such as CH 3 CHOO and (CH 3 ) 2 COO, blocks the formation of the necessary prereaction complexes for the Criegee-water reaction to occur at the water droplet surface, which lowers their proton-transfer ability and hampers the reaction. The aerosol water surface provides a solvent medium for acids (e.g., HNO 3 and HCOOH) to participate in reactions via mechanisms that are different from those in the gas and bulk aqueous phases. For example, the anti-CH 3 CHOO-HNO 3 reaction in the gas phase follows a direct reaction between anti-CH 3 CHOO and HNO 3 , whereas on a water surface, the HNO 3 -mediated stepwise hydration of anti-CH 3 CHOO is dominantly observed. The high surface/volume ratio of interfacial water molecules at the aerosol water surface can significantly lower the energy barriers for the proton transfer reactions in the atmosphere. Such catalysis by the aerosol water surface is shown to cause the barrier-less formation of ammonium bisulfate from hydrated NH 3 and SO 3 molecules rather than from the reaction of H 2 SO 4 with NH 3 . Finally, an aerosol water droplet is a polar solvent, which would favorably interact with high polarity substrates. This can accelerate interconversion of different conformers (e.g., anti and syn) of atmospheric species, such as glyoxal, depending on their polarity. The results discussed here enable an improved understanding of atmospheric processes on the aerosol water surface.

Coping Style Modifies General and Affective Autonomic Reactions of Domestic Pigs in Different Behavioral Contexts

PubMed Central

Krause, Annika; Puppe, Birger; Langbein, Jan

2017-01-01

Based on individual adaptive strategies (coping), animals may react differently to environmental challenges in terms of behavior and physiology according to their emotional perception. Emotional valence as well as arousal may be derived by measuring vagal and sympathetic tone of the autonomic nervous system (ANS). We investigated the situation-dependent autonomic response of 16 domestic pigs with either a reactive or a proactive coping style, previously selected according to the backtest which is accepted in piglets to assess escape behavior. At 11 weeks of age, the pigs were equipped with an implantable telemetric device, and heart rate (HR), blood pressure (BP) and their respective variabilities (HRV, BPV) were recorded for 1 h daily over a time period of 10 days and analyzed in four behavioral contexts (resting, feeding, idling, handling). Additionally, the first minute of feeding and handling was used for a short-term analysis of these parameters in 10-s intervals. Data from day 1–3 (period 1) and day 8–10 (period 2) were grouped into two separate periods. Our results revealed general differences between the coping styles during feeding, resting and handling, with proactive pigs showing higher HR compared to reactive pigs. This elevated HR was based on either lower vagal (resting) or elevated sympathetic activation (feeding, handling). The short-term analysis of the autonomic activation during feeding revealed a physiological anticipation reaction in proactive pigs in period 1, whereas reactive pigs showed this reaction only in period 2. Food intake was characterized by sympathetic arousal with concurrent vagal withdrawal, which was more pronounced in proactive pigs. In contrast, neither coping style resulted in an anticipation reaction to handling. Vagal activation increased in reactive pigs during handling, while proactive pigs showed an increase in sympathetically driven arousal in period 2. Our findings confirm significant context-related differences in the general autonomic reaction of pigs with different coping styles. Additionally, the two coping styles differ in their affective appraisal over the time course of the experiment, underlining the importance of taking individual differences into account when studying affect and emotion in humans and animals. PMID:28611608

Coping Style Modifies General and Affective Autonomic Reactions of Domestic Pigs in Different Behavioral Contexts.

PubMed

Krause, Annika; Puppe, Birger; Langbein, Jan

2017-01-01

Based on individual adaptive strategies (coping), animals may react differently to environmental challenges in terms of behavior and physiology according to their emotional perception. Emotional valence as well as arousal may be derived by measuring vagal and sympathetic tone of the autonomic nervous system (ANS). We investigated the situation-dependent autonomic response of 16 domestic pigs with either a reactive or a proactive coping style, previously selected according to the backtest which is accepted in piglets to assess escape behavior. At 11 weeks of age, the pigs were equipped with an implantable telemetric device, and heart rate (HR), blood pressure (BP) and their respective variabilities (HRV, BPV) were recorded for 1 h daily over a time period of 10 days and analyzed in four behavioral contexts (resting, feeding, idling, handling). Additionally, the first minute of feeding and handling was used for a short-term analysis of these parameters in 10-s intervals. Data from day 1-3 (period 1) and day 8-10 (period 2) were grouped into two separate periods. Our results revealed general differences between the coping styles during feeding, resting and handling, with proactive pigs showing higher HR compared to reactive pigs. This elevated HR was based on either lower vagal (resting) or elevated sympathetic activation (feeding, handling). The short-term analysis of the autonomic activation during feeding revealed a physiological anticipation reaction in proactive pigs in period 1, whereas reactive pigs showed this reaction only in period 2. Food intake was characterized by sympathetic arousal with concurrent vagal withdrawal, which was more pronounced in proactive pigs. In contrast, neither coping style resulted in an anticipation reaction to handling. Vagal activation increased in reactive pigs during handling, while proactive pigs showed an increase in sympathetically driven arousal in period 2. Our findings confirm significant context-related differences in the general autonomic reaction of pigs with different coping styles. Additionally, the two coping styles differ in their affective appraisal over the time course of the experiment, underlining the importance of taking individual differences into account when studying affect and emotion in humans and animals.

A Flight-Calibrated Methodology for Determination of Cassini Thruster On-Times for Reaction Wheel Biases

NASA Technical Reports Server (NTRS)

Sarani, Siamak

2010-01-01

This paper describes a methodology for accurate and flight-calibrated determination of the on-times of the Cassini spacecraft Reaction Control System (RCS) thrusters, without any form of dynamic simulation, for the reaction wheel biases. The hydrazine usage and the delta V vector in body frame are also computed from the respective thruster on-times. The Cassini spacecraft, the largest and most complex interplanetary spacecraft ever built, continues to undertake ambitious and unique scientific observations of planet Saturn, Titan, Enceladus, and other moons of Saturn. In order to maintain a stable attitude during the course of its mission, this three-axis stabilized spacecraft uses two different control systems: the RCS and the reaction wheel assembly control system. The RCS is used to execute a commanded spacecraft slew, to maintain three-axis attitude control, control spacecraft's attitude while performing science observations with coarse pointing requirements, e.g. during targeted low-altitude Titan and Enceladus flybys, bias the momentum of reaction wheels, and to perform RCS-based orbit trim maneuvers. The use of RCS often imparts undesired delta V on the spacecraft. The Cassini navigation team requires accurate predictions of the delta V in spacecraft coordinates and inertial frame resulting from slews using RCS thrusters and more importantly from reaction wheel bias events. It is crucial for the Cassini spacecraft attitude control and navigation teams to be able to, quickly but accurately, predict the hydrazine usage and delta V for various reaction wheel bias events without actually having to spend time and resources simulating the event in flight software-based dynamic simulation or hardware-in-the-loop simulation environments. The methodology described in this paper, and the ground software developed thereof, are designed to provide just that. This methodology assumes a priori knowledge of thrust magnitudes and thruster pulse rise and tail-off time constants for eight individual attitude control thrusters, the spacecraft's wet mass and its center of mass location, and a few other key parameters.

Synthesis and Manipulation of Semiconductor Nanocrystals inMicrofluidic Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, Emory Ming-Yue

2006-01-01

Microfluidic reactors are investigated as a mechanism tocontrol the growth of semiconductor nanocrystals and characterize thestructural evolution of colloidal quantum dots. Due to their shortdiffusion lengths, low thermal masses, and predictable fluid dynamics,microfluidic devices can be used to quickly and reproducibly alterreaction conditions such as concentration, temperature, and reactiontime, while allowing for rapid reagent mixing and productcharacterization. These features are particularly useful for colloidalnanocrystal reactions, which scale poorly and are difficult to controland characterize in bulk fluids. To demonstrate the capabilities ofnanoparticle microreactors, a size series of spherical CdSe nanocrystalswas synthesized at high temperature in a continuous-flow, microfabricatedglass reactor. Nanocrystalmore » diameters are reproducibly controlled bysystematically altering reaction parameters such as the temperature,concentration, and reaction time. Microreactors with finer control overtemperature and reagent mixing were designed to synthesize nanoparticlesof different shapes, such as rods, tetrapods, and hollow shells. The twomajor challenges observed with continuous flow reactors are thedeposition of particles on channel walls and the broad distribution ofresidence times that result from laminar flow. To alleviate theseproblems, I designed and fabricated liquid-liquid segmented flowmicroreactors in which the reaction precursors are encapsulated inflowing droplets suspended in an immiscible carrier fluid. The synthesisof CdSe nanocrystals in such microreactors exhibited reduced depositionand residence time distributions while enabling the rapid screening aseries of samples isolated in nL droplets. Microfluidic reactors werealso designed to modify the composition of existing nanocrystals andcharacterize the kinetics of such reactions. The millisecond kinetics ofthe CdSe-to-Ag 2Se nanocrystal cation exchange reaction are measured insitu with micro-X-ray Absorption Spectroscopy in silicon microreactorsspecifically designed for rapid mixing and time-resolved X-rayspectroscopy. These results demonstrate that microreactors are valuablefor controlling and characterizing a wide range of reactions in nLvolumes even when nanoscale particles, high temperatures, causticreagents, and rapid time scales are involved. These experiments providethe foundation for future microfluidic investigations into the mechanismsof nanocrystal growth, crystal phase evolution, and heterostructureassembly.« less

Time-Resolved Molecular Characterization of Limonene/Ozone Aerosol using High-Resolution Electrospray Ionization Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bateman, Adam P.; Nizkorodov, Serguei; Laskin, Julia

2009-09-09

Molecular composition of limonene/O3 secondary organic aerosol (SOA) was investigated using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as a function of reaction time. SOA was generated by ozonation of D-limonene in a reaction chamber and sampled at different time intervals using a cascade impactor. The SOA samples were extracted into acetonitrile and analyzed using a HR-ESI-MS instrument with a resolving power of 100,000 (m/Δm). The resulting mass spectra provided detailed information about the extent of oxidation inferred from the O:C ratios, double bond equivalency (DBE) factors, and aromaticity indexes (AI) in hundreds of identified individual SOA species.

Activated Persulfate Oxidation of Perfluorooctanoic Acid (PFOA) in Groundwater under Acidic Conditions

PubMed Central

Yin, Penghua; Hu, Zhihao; Song, Xin; Liu, Jianguo; Lin, Na

2016-01-01

Perfluorooctanoic acid (PFOA) is an emerging contaminant of concern due to its toxicity for human health and ecosystems. However, successful degradation of PFOA in aqueous solutions with a cost-effective method remains a challenge, especially for groundwater. In this study, the degradation of PFOA using activated persulfate under mild conditions was investigated. The impact of different factors on persulfate activity, including pH, temperature (25 °C–50 °C), persulfate dosage and reaction time, was evaluated under different experimental conditions. Contrary to the traditional alkaline-activated persulfate oxidation, it was found that PFOA can be effectively degraded using activated persulfate under acidic conditions, with the degradation kinetics following the pseudo-first-order decay model. Higher temperature, higher persulfate dosage and increased reaction time generally result in higher PFOA degradation efficiency. Experimental results show that a PFOA degradation efficiency of 89.9% can be achieved by activated persulfate at pH of 2.0, with the reaction temperature of 50 °C, molar ratio of PFOA to persulfate as 1:100, and a reaction time of 100 h. The corresponding defluorination ratio under these conditions was 23.9%, indicating that not all PFOA decomposed via fluorine removal. The electron paramagnetic resonance spectrometer analysis results indicate that both SO4−• and •OH contribute to the decomposition of PFOA. It is proposed that PFOA degradation occurs via a decarboxylation reaction triggered by SO4−•, followed by a HF elimination process aided by •OH, which produces one-CF2-unit-shortened perfluoroalkyl carboxylic acids (PFCAs, Cn−1F2n−1COOH). The decarboxylation and HF elimination processes would repeat and eventually lead to the complete mineralization all PFCAs. PMID:27322298

Classifying vulnerability to sleep deprivation using baseline measures of psychomotor vigilance.

PubMed

Patanaik, Amiya; Kwoh, Chee Keong; Chua, Eric C P; Gooley, Joshua J; Chee, Michael W L

2015-05-01

To identify measures derived from baseline psychomotor vigilance task (PVT) performance that can reliably predict vulnerability to sleep deprivation. Subjects underwent total sleep deprivation and completed a 10-min PVT every 1-2 h in a controlled laboratory setting. Participants were categorized as vulnerable or resistant to sleep deprivation, based on a median split of lapses that occurred following sleep deprivation. Standard reaction time, drift diffusion model (DDM), and wavelet metrics were derived from PVT response times collected at baseline. A support vector machine model that incorporated maximum relevance and minimum redundancy feature selection and wrapper-based heuristics was used to classify subjects as vulnerable or resistant using rested data. Two academic sleep laboratories. Independent samples of 135 (69 women, age 18 to 25 y), and 45 (3 women, age 22 to 32 y) healthy adults. In both datasets, DDM measures, number of consecutive reaction times that differ by more than 250 ms, and two wavelet features were selected by the model as features predictive of vulnerability to sleep deprivation. Using the best set of features selected in each dataset, classification accuracy was 77% and 82% using fivefold stratified cross-validation, respectively. In both datasets, DDM measures, number of consecutive reaction times that differ by more than 250 ms, and two wavelet features were selected by the model as features predictive of vulnerability to sleep deprivation. Using the best set of features selected in each dataset, classification accuracy was 77% and 82% using fivefold stratified cross-validation, respectively. Despite differences in experimental conditions across studies, drift diffusion model parameters associated reliably with individual differences in performance during total sleep deprivation. These results demonstrate the utility of drift diffusion modeling of baseline performance in estimating vulnerability to psychomotor vigilance decline following sleep deprivation. © 2015 Associated Professional Sleep Societies, LLC.

Effect of ceramic nanoparticles on the solid-state reaction mechanism of dolomite-zirconium oxide followed by neutron thermodiffraction measurements

NASA Astrophysics Data System (ADS)

Serena, S.; Caballero, A.; Turrillas, X.; Martin, D.; Sainz, M. A.

2009-05-01

Calcium zirconate-magnesium oxide material was obtained by solid-state reaction from mixed dolomite (CaMg(CO3)2) and zirconia (m-ZrO2) nanopowders. The nanopowders were obtained by high-energy milling, which produced an increase of the superficial free energy of the particles. The role of nanoparticles in the reaction process of monoclinic-zirconia and dolomite was analysed for the first time using neutron thermodiffraction and differential thermal analysis-thermogravimetric techniques. The neutron thermodiffraction of this mixture provides a clear description in situ of the different decomposition and reaction processes that occur in the nanopowders mixture. The results make it possible to analyze the effect of the nanoparticles on the reaction behaviour of these materials.

Radiosensitization of DNA by Cisplatin Adducts Results from an Increase in the Rate Constant for the Reaction with Hydrated Electrons and Formation of Pt(I).

PubMed

Behmand, B; Marignier, J-L; Mostafavi, M; Wagner, J R; Hunting, D J; Sanche, L

2015-07-30

Pulse radiolysis measurements of the decay of hydrated electrons in solutions containing different concentrations of the oligonucleotide GTG with and without a cisplatin adduct show that the presence of a cisplatin moiety accelerates the reaction between hydrated electrons and the oligonucleotide. The rate constant of the reaction is found to be 2.23 × 10(10) mol(-1) L s(-1), which indicates that it is diffusion controlled. In addition, we show for the first time the formation of a Pt(I) intermediate as a result of the reaction of hydrated electrons with GTG-cisplatin. A putative reaction mechanism is proposed, which may form the basis of the radiosensitization of cancer cells in concomitant chemoradiation therapy with cisplatin.

Efficacy of intravenous hydrocortisone administered 2-4 h prior to antivenom as prophylaxis against adverse drug reactions to snake antivenom in Sri Lanka: An open labelled randomized controlled trial.

PubMed

Kularatne, Senanayake A M; Weerakoon, Kosala; Silva, Anjana; Maduwage, Kalana; Walathara, Chamara; Rathnayake, Ishani; Medagedara, Senal; Paranagama, Ranjith; Mendis, Suresh; Kumarasiri, P V R

2016-09-15

The prevention of adverse drug reactions to antivenom serum poses a formidable challenge in the management of snakebite. Hydrocortisone is being used concurrently with antivenom in order to prevent these adverse drug reactions without a proven benefit. However, all previous studies seemed to ignore the testing of effectiveness of hydrocortisone therapy during its pharmacological effects, which come hours later. On this principle, we aimed to test the effectiveness of intravenous hydrocortisone given 2 h or more prior to the commencement of antivenom therapy to reduce adverse drug reactions to antivenom. In an open-labelled randomized controlled trial, patients with a history of snakebite were randomly assigned to receive either 500 mg intravenous hydrocortisone bolus given 2 h or more prior to antivenom therapy (Group A) or at the time of antivenom therapy (Group B). The primary endpoint was the reduction of adverse drug reactions to antivenom of any grade of severity within the first 48 h. This trial has been registered with the "Sri Lanka Clinical Trials Registry", number SLCTR/2010/005. A total of 236 patients were randomized to group A or Group B. In the group A, 38 participants received hydrocortisone 2 h before administration of antivenom whilst 33 received hydrocortisone less than 2 h before administration of antivenom. In the Group B, 84 participants received hydrocortisone at the time of antivenom therapy. In Group A (n, 38), and Group B (n, 84), 15 patients (39%) and 29 patients (35%) developed reactions respectively and the difference is not significant (p = 0.598). Moreover, hydrocortisone therapy did not significantly reduce the occurrence of antievnom reactions of any grade of severity. Further, it didn't delay the occurrence of antivenom reactions in patients who received hydrocortisone either more than 2 h or less than 2 h before the antivenom as opposed to the control group (group B). Intravenous hydrocortisone shows no difference in the timing, rate or severity of adverse drug reactions to antivenom when administered simultaneously and up to 4 h prior to antivenom. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stochastic hybrid systems for studying biochemical processes.

PubMed

Singh, Abhyudai; Hespanha, João P

2010-11-13

Many protein and mRNA species occur at low molecular counts within cells, and hence are subject to large stochastic fluctuations in copy numbers over time. Development of computationally tractable frameworks for modelling stochastic fluctuations in population counts is essential to understand how noise at the cellular level affects biological function and phenotype. We show that stochastic hybrid systems (SHSs) provide a convenient framework for modelling the time evolution of population counts of different chemical species involved in a set of biochemical reactions. We illustrate recently developed techniques that allow fast computations of the statistical moments of the population count, without having to run computationally expensive Monte Carlo simulations of the biochemical reactions. Finally, we review different examples from the literature that illustrate the benefits of using SHSs for modelling biochemical processes.

Ball Milling Assisted Solvent and Catalyst Free Synthesis of Benzimidazoles and Their Derivatives.

PubMed

El-Sayed, Taghreed H; Aboelnaga, Asmaa; Hagar, Mohamed

2016-08-24

Benzoic acid and o-phenylenediamine efficiently reacted under the green solvent-free Ball Milling method. Several reaction parameters were investigated such as rotation frequency; milling balls weight and milling time. The optimum reaction condition was milling with 56.6 g weight of balls at 20 Hz frequency for one hour milling time. The study was extended for synthesis of a series of benzimidazol-2-one or benzimidazol-2-thione using different aldehydes; carboxylic acids; urea; thiourea or ammonium thiocyanate with o-phenylenediamine. Moreover; the alkylation of benzimidazolone or benzimidazolthione using ethyl chloroacetate was also studied.

Binocular interactions in random chromatic changes at isoluminance

NASA Astrophysics Data System (ADS)

Medina, José M.

2006-02-01

To examine the type of chromatic interactions at isoluminance in the phenomenon of binocular vision, I have determined simple visual reaction times (VRT) under three observational conditions (monocular left, monocular right, and binocular) for different chromatic stimuli along random color axes at isoluminance (simultaneous L-, M-, and S-cone variations). Upper and lower boundaries of probability summation as well as the binocular capacity coefficient were estimated with observed distributions of reaction times. The results were not consistent with the notion of independent chromatic channels between eyes, suggesting the existence of excitatory and inhibitory binocular interactions at suprathreshold isoluminance conditions.

Abiotic hydrogen production in fresh and altered MSWI-residues: texture and microstructure investigation.

PubMed

Heuss-Assbichler, S; Magel, G; Fehr, K T

2010-10-01

Long-term hydrogen generation was observed in a Bavarian mono-landfill for municipal solid waste incineration (MSWI) residues. Hydration reactions of non-noble metals, especially aluminum, predominantly produce hydrogen at alkaline reaction conditions. Microscopic investigations show that aluminum metal may occur in different forms: as larger single grains, as small particles embedded in a vitrified matrix or less frequently in blowholes together with metallic silica. Four types of corrosion texture were observed, indicating different reaction mechanisms: aluminum hydroxide rims caused by hydration reactions at alkaline reaction conditions (reaction type 1) and multiphase rims with ettringite and hydrocalumite due to the reaction of aluminum hydroxide with sulfate and chloride ions which are solved in the pore water (reaction type 2). Galvanic corrosion textures due to the electric potential difference between aluminum and embedded intermetallic Fe- or Cu-rich exsolution phases lead to two further corrosion textures: Strong hydration effects of aluminum except a border of aluminum remnant directly beside the Fe- or Cu-rich segregations were only observed in fresh samples (reaction type 3). The reaction type 4 shows a network of Al-hydroxide veins occurring along the embedded intermetallic Fe- or Cu-rich exsolution segregation pattern within the metallic aluminum grain. Metal particles enclosed in vitrified particles offers the potential for future corrosion processes. The occurrence of corrosion types 1, 2 and 3 in fresh bottom ashes indicates that these reaction mechanisms predominate during the first reaction period in the presence of chlorine in an alkaline solution. Corrosion type 4, however, was additionally observed in aged samples. Here aluminum acts as sacrificed anode implying electrochemical reaction due to electrolytic pore water. Chloride in the system keeps the reaction alive as Al-hydroxide is solved which normally builds a protection shield around the aluminum metal particles. Due to field observations and experimental results we have reasonable indications that after an initial strong formation of hydrogen the reaction time for hydrogen production in the landfill is lengthened for several decades by the presence of chloride in the alkaline pore water. (c) 2010 Elsevier Ltd. All rights reserved.

Multi-scale modeling of diffusion-controlled reactions in polymers: renormalisation of reactivity parameters.

PubMed

Everaers, Ralf; Rosa, Angelo

2012-01-07

The quantitative description of polymeric systems requires hierarchical modeling schemes, which bridge the gap between the atomic scale, relevant to chemical or biomolecular reactions, and the macromolecular scale, where the longest relaxation modes occur. Here, we use the formalism for diffusion-controlled reactions in polymers developed by Wilemski, Fixman, and Doi to discuss the renormalisation of the reactivity parameters in polymer models with varying spatial resolution. In particular, we show that the adjustments are independent of chain length. As a consequence, it is possible to match reactions times between descriptions with different resolution for relatively short reference chains and to use the coarse-grained model to make quantitative predictions for longer chains. We illustrate our results by a detailed discussion of the classical problem of chain cyclization in the Rouse model, which offers the simplest example of a multi-scale descriptions, if we consider differently discretized Rouse models for the same physical system. Moreover, we are able to explore different combinations of compact and non-compact diffusion in the local and large-scale dynamics by varying the embedding dimension.

Cluster Analysis of Time-Dependent Crystallographic Data: Direct Identification of Time-Independent Structural Intermediates

PubMed Central

Kostov, Konstantin S.; Moffat, Keith

2011-01-01

The initial output of a time-resolved macromolecular crystallography experiment is a time-dependent series of difference electron density maps that displays the time-dependent changes in underlying structure as a reaction progresses. The goal is to interpret such data in terms of a small number of crystallographically refinable, time-independent structures, each associated with a reaction intermediate; to establish the pathways and rate coefficients by which these intermediates interconvert; and thereby to elucidate a chemical kinetic mechanism. One strategy toward achieving this goal is to use cluster analysis, a statistical method that groups objects based on their similarity. If the difference electron density at a particular voxel in the time-dependent difference electron density (TDED) maps is sensitive to the presence of one and only one intermediate, then its temporal evolution will exactly parallel the concentration profile of that intermediate with time. The rationale is therefore to cluster voxels with respect to the shapes of their TDEDs, so that each group or cluster of voxels corresponds to one structural intermediate. Clusters of voxels whose TDEDs reflect the presence of two or more specific intermediates can also be identified. From such groupings one can then infer the number of intermediates, obtain their time-independent difference density characteristics, and refine the structure of each intermediate. We review the principles of cluster analysis and clustering algorithms in a crystallographic context, and describe the application of the method to simulated and experimental time-resolved crystallographic data for the photocycle of photoactive yellow protein. PMID:21244840

optGpSampler: an improved tool for uniformly sampling the solution-space of genome-scale metabolic networks.

PubMed

Megchelenbrink, Wout; Huynen, Martijn; Marchiori, Elena

2014-01-01

Constraint-based models of metabolic networks are typically underdetermined, because they contain more reactions than metabolites. Therefore the solutions to this system do not consist of unique flux rates for each reaction, but rather a space of possible flux rates. By uniformly sampling this space, an estimated probability distribution for each reaction's flux in the network can be obtained. However, sampling a high dimensional network is time-consuming. Furthermore, the constraints imposed on the network give rise to an irregularly shaped solution space. Therefore more tailored, efficient sampling methods are needed. We propose an efficient sampling algorithm (called optGpSampler), which implements the Artificial Centering Hit-and-Run algorithm in a different manner than the sampling algorithm implemented in the COBRA Toolbox for metabolic network analysis, here called gpSampler. Results of extensive experiments on different genome-scale metabolic networks show that optGpSampler is up to 40 times faster than gpSampler. Application of existing convergence diagnostics on small network reconstructions indicate that optGpSampler converges roughly ten times faster than gpSampler towards similar sampling distributions. For networks of higher dimension (i.e. containing more than 500 reactions), we observed significantly better convergence of optGpSampler and a large deviation between the samples generated by the two algorithms. optGpSampler for Matlab and Python is available for non-commercial use at: http://cs.ru.nl/~wmegchel/optGpSampler/.

Response Style Differences in the Inattentive and Combined Subtypes of Attention-Deficit/Hyperactivity Disorder

ERIC Educational Resources Information Center

Derefinko, Karen J.; Adams, Zachary W.; Milich, Richard; Fillmore, Mark T.; Lorch, Elizabeth P.; Lynam, Donald R.

2008-01-01

This study examined potential differences between the inattentive and combined ADHD subtypes using laboratory tasks assessing behavioral inhibitory processes. Seventy-five children completed two tasks of behavioral inhibition believed to isolate different processes: the cued reaction time task (CRT), a basic inhibition task, and the go/no-go task…

No evidence of persisting measles virus in peripheral blood mononuclear cells from children with autism spectrum disorder.

PubMed

D'Souza, Yasmin; Fombonne, Eric; Ward, Brian J

2006-10-01

Despite epidemiologic evidence to the contrary, claims of an association between measles-mumps-rubella vaccination and the development of autism have persisted. Such claims are based primarily on the identification of measles virus nucleic acids in tissues and body fluids by polymerase chain reaction. We sought to determine whether measles virus nucleic acids persist in children with autism spectrum disorder compared with control children. Peripheral blood mononuclear cells were isolated from 54 children with autism spectrum disorder and 34 developmentally normal children, and up to 4 real-time polymerase chain reaction assays and 2 nested polymerase chain reaction assays were performed. These assays targeted the nucleoprotein, fusion, and hemagglutinin genes of measles virus using previously published primer pairs with detection by SYBR green I. Our own real-time assay targeted the fusion gene using novel primers and an internal fluorescent probe. Positive reactions were evaluated rigorously, and amplicons were sequenced. Finally, anti-measles antibody titers were measured by enzyme immunoassay. The real-time assays based on previously published primers gave rise to a large number of positive reactions in both autism spectrum disorder and control samples. Almost all of the positive reactions in these assays were eliminated by evaluation of melting curves and amplicon band size. The amplicons for the remaining positive reactions were cloned and sequenced. No sample from either autism spectrum disorder or control groups was found to contain nucleic acids from any measles virus gene. In the nested polymerase chain reaction and in-house assays, none of the samples yielded positive results. Furthermore, there was no difference in anti-measles antibody titers between the autism and control groups. There is no evidence of measles virus persistence in the peripheral blood mononuclear cells of children with autism spectrum disorder.

Ignitable heterogeneous stratified structure for the propagation of an internal exothermic chemical reaction along an expanding wavefront and method of making same

DOEpatents

Barbee, T.W. Jr.; Weihs, T.

1996-07-23

A multilayer structure has a selectable, (1) propagating reaction front velocity V, (2) reaction initiation temperature attained by application of external energy, and (3) amount of energy delivered by a reaction of alternating unreacted layers of the multilayer structure. Because V is selectable and controllable, a variety of different applications for the multilayer structures are possible, including but not limited to their use as igniters, in joining applications, in fabrication of new materials, as smart materials and in medical applications and devices. The multilayer structure has a period D, and an energy release rate constant K. Two or more alternating unreacted layers are made of different materials and separated by reacted zones. The period D is equal to a sum of the widths of each single alternating reaction layer of a particular material, and also includes a sum of reacted zone widths, t{sub i}, in the period D. The multilayer structure has a selectable propagating reaction front velocity V, where V=K(1/D{sup n}){times}[1-(t{sub i}/D)] and n is about 0.8 to 1.2. 8 figs.

Ignitable heterogeneous stratified structure for the propagation of an internal exothermic chemical reaction along an expanding wavefront and method of making same

DOEpatents

Barbee, Jr., Troy W.; Weihs, Timothy

1996-01-01

A multilayer structure has a selectable, (i) propagating reaction front velocity V, (ii) reaction initiation temperature attained by application of external energy and (iii) amount of energy delivered by a reaction of alternating unreacted layers of the multilayer structure. Because V is selectable and controllable, a variety of different applications for the multilayer structures are possible, including but not limited to their use as ignitors, in joining applications, in fabrication of new materials, as smart materials and in medical applications and devices. The multilayer structure has a period D, and an energy release rate constant K. Two or more alternating unreacted layers are made of different materials and separated by reacted zones. The period D is equal to a sum of the widths of each single alternating reaction layer of a particular material, and also includes a sum of reacted zone widths, t.sub.i, in the period D. The multilayer structure has a selectable propagating reaction front velocity V, where V=K(1/D.sup.n).times.[1-(t.sub.i /D)] and n is about 0.8 to 1.2.

The impact of physical activity and sex differences on intraindividual variability in inhibitory performance in older adults.

PubMed

Fagot, Delphine; Chicherio, Christian; Albinet, Cédric T; André, Nathalie; Audiffren, Michel

2017-09-04

It is well-known that processing speed and executive functions decline with advancing age. However, physical activity (PA) has a positive impact on cognitive performances in aging, specifically for inhibition. Less is known concerning intraindividual variability (iiV) in reaction times. This study aims to investigate the influence of PA and sex differences on iiV in inhibitory performance during aging. Healthy adults were divided into active and sedentary groups according to PA level. To analyse iiV in reaction times, individual mean, standard deviation and the ex-Gaussian parameters were considered. An interaction between activity level and sex was revealed, sedentary females being slower and more variable than sedentary men. No sex differences were found in the active groups. These results indicate that the negative impact of sedentariness on cognitive performance in older age is stronger for females. The present findings underline the need to consider sex differences in active aging approaches.

Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity

PubMed Central

Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A

2016-01-01

An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o-phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf)3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2–5 min), affording single products in excellent yields (75–99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds. PMID:28144309

Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity.

PubMed

Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A; Santiago, Ana N

2016-01-01

An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o -phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf) 3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2-5 min), affording single products in excellent yields (75-99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds.

Rate coefficients from quantum and quasi-classical cumulative reaction probabilities for the S(1D) + H2 reaction

NASA Astrophysics Data System (ADS)

Jambrina, P. G.; Lara, Manuel; Menéndez, M.; Launay, J.-M.; Aoiz, F. J.

2012-10-01

Cumulative reaction probabilities (CRPs) at various total angular momenta have been calculated for the barrierless reaction S(1D) + H2 → SH + H at total energies up to 1.2 eV using three different theoretical approaches: time-independent quantum mechanics (QM), quasiclassical trajectories (QCT), and statistical quasiclassical trajectories (SQCT). The calculations have been carried out on the widely used potential energy surface (PES) by Ho et al. [J. Chem. Phys. 116, 4124 (2002), 10.1063/1.1431280] as well as on the recent PES developed by Song et al. [J. Phys. Chem. A 113, 9213 (2009), 10.1021/jp903790h]. The results show that the differences between these two PES are relatively minor and mostly related to the different topologies of the well. In addition, the agreement between the three theoretical methodologies is good, even for the highest total angular momenta and energies. In particular, the good accordance between the CRPs obtained with dynamical methods (QM and QCT) and the statistical model (SQCT) indicates that the reaction can be considered statistical in the whole range of energies in contrast with the findings for other prototypical barrierless reactions. In addition, total CRPs and rate coefficients in the range of 20-1000 K have been calculated using the QCT and SQCT methods and have been found somewhat smaller than the experimental total removal rates of S(1D).

Complex Cure Kinetics of the Tertiary Amine activated Reaction in DGEBA Epoxy Hardened with Diethanolamine

NASA Astrophysics Data System (ADS)

Ancipink, Windy; McCoy, John; Clarkson, Caitlyn; Kropka, Jamie; Celina, Mathias; Giron, Nicholas; Hailesilassie, Lebelo; Fredj, Narjes

The curing of a diglycidyl ether of bisphenol-A (DGEBA) epoxy with diethanolamine (DEA) involves a well understood fast amine-epoxide reaction followed by a more complicated slower hydroxyl-epoxide reaction. The time scale of these two reactions are well separated and can be studied independently from one another. The initial amine-epoxide reaction results in a tertiary amine adduct which is a product of the direct reaction of a secondary amine from the DEA reacting with a single DGEBA epoxide. The second hydroxyl-epoxide reaction results in a highly crosslinked glassy epoxy resin. The deviation in the mechanisms between high and low temperatures are discerned through the use of differential scanning calorimetry (DSC), infrared spectroscopy (IR), and isothermal microcalorimetry (IMC) data. Observations of reaction rates at temperatures ranging from 30° C to 110° C have led to the determination that the hydroxyl-epoxide reaction is temperature sensitive. The hydroxyl-epoxide reaction occurs through two different mechanisms: at low temperatures, the reaction is catalyzed by the tertiary amine adduct; at higher temperatures, the reaction does not appear to be catalyzed. Sandia National Laboratories, Albuquerque, NM.

One-step hydrothermal synthesis and electrochemical performance of sodium-manganese-iron phosphate as cathode material for Li-ion batteries

DOE PAGES

Karegeya, Claude; Mahmoud, Abdelfattah; Vertruyen, Bénédicte; ...

2017-06-23

The sodium-manganese-iron phosphate Na 2Mn 1.5Fe 1.5(PO 4) 3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na + and presence of vacancies in A(2)’, Na + and small amounts of Mn 2+ in A(1), Mn 2+ in M(1) , 0.5 Mn 2+ and Fe cations (Mn 2+,Fe 2+ and Fe 3+) in M(2), leading to the structural formula Na 2Mn(Mn 0.5Fe 1.5)(PO 4) 3. The particles morphology was investigated by SEM.more » Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 hours at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 hours. When the reaction time was increased from 6 to 12, 24 and 48 hours, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mAhg-1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99 % during 50 cycles.« less

One-step hydrothermal synthesis and electrochemical performance of sodium-manganese-iron phosphate as cathode material for Li-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karegeya, Claude; Mahmoud, Abdelfattah; Vertruyen, Bénédicte

The sodium-manganese-iron phosphate Na 2Mn 1.5Fe 1.5(PO 4) 3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na + and presence of vacancies in A(2)’, Na + and small amounts of Mn 2+ in A(1), Mn 2+ in M(1) , 0.5 Mn 2+ and Fe cations (Mn 2+,Fe 2+ and Fe 3+) in M(2), leading to the structural formula Na 2Mn(Mn 0.5Fe 1.5)(PO 4) 3. The particles morphology was investigated by SEM.more » Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 hours at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 hours. When the reaction time was increased from 6 to 12, 24 and 48 hours, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mAhg-1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99 % during 50 cycles.« less

Novel Visualization Approaches in Environmental Mineralogy

NASA Astrophysics Data System (ADS)

Anderson, C. D.; Lopano, C. L.; Hummer, D. R.; Heaney, P. J.; Post, J. E.; Kubicki, J. D.; Sofo, J. O.

2006-05-01

Communicating the complexities of atomic scale reactions between minerals and fluids is fraught with intrinsic challenges. For example, an increasing number of techniques are now available for the interrogation of dynamical processes at the mineral-fluid interface. However, the time-dependent behavior of atomic interactions between a solid and a liquid is often not adequately captured by two-dimensional line drawings or images. At the same time, the necessity for describing these reactions to general audiences is growing more urgent, as funding agencies are amplifying their encouragement to scientists to reach across disciplines and to justify their studies to public audiences. To overcome the shortcomings of traditional graphical representations, the Center for Environmental Kinetics Analysis is creating three-dimensional visualizations of experimental and simulated mineral reactions. These visualizations are then displayed on a stereo 3D projection system called the GeoWall. Made possible (and affordable) by recent improvements in computer and data projector technology, the GeoWall system uses a combination of computer software and hardware, polarizing filters and polarizing glasses, to present visualizations in true 3D. The three-dimensional views greatly improve comprehension of complex multidimensional data, and animations of time series foster better understanding of the underlying processes. The visualizations also offer an effective means to communicate the complexities of environmental mineralogy to colleagues, students and the public. Here we present three different kinds of datasets that demonstrate the effectiveness of the GeoWall in clarifying complex environmental reactions at the atomic scale. First, a time-resolved series of diffraction patterns obtained during the hydrothermal synthesis of metal oxide phases from precursor solutions can be viewed as a surface with interactive controls for peak scaling and color mapping. Second, the results of Rietveld analysis of cation exchange reactions in Mn oxides has provided three-dimensional difference Fourier maps. When stitched together in a temporal series, these offer an animated view of changes in atomic configurations during the process of exchange. Finally, molecular dynamical simulations are visualized as three-dimensional reactions between vibrating atoms in both the solid and the aqueous phases.

Evaluation in vivo of biocompatibility of differents resin-modified cements for bonding orthodontic bands.

PubMed

Mesquita, Janaina A; Lacerda-Santos, Rogério; Sampaio, Gêisa A M; Godoy, Gustavo P; Nonaka, Cassiano F W; Alves, Pollianna M

2017-01-01

The focus of this study was to test the hypothesis that there would be no difference between the biocompatibility of resin-modified glass ionomer cements. Sixty male Wistar rats were selected and divided into four groups: Control Group; Crosslink Group; RMO Group and Transbond Group. The materials were inserted into rat subcutaneous tissue. After time intervals of 7, 15 and 30 days morphological analyses were performed. The histological parameters assessed were: inflammatory infiltrate intensity; reaction of multinucleated giant cells; edema; necrosis; granulation reaction; young fibroblasts and collagenization. The results obtained were statistically analyzed by the Kruskal-Wallis and Dunn test (P<0.05). After 7 days, Groups RMO and Transbond showed intense inflammatory infiltrate (P=0.004), only Group RMO presented greater expression of multinucleated giant cell reaction (P=0.003) compared with the control group. After the time intervals of 15 and 30 days, there was evidence of light/moderate inflammatory infiltrate, lower level of multinucleated giant cell reaction and thicker areas of young fibroblasts in all the groups. The hypothesis was rejected. The Crosslink cement provided good tissue response, since it demonstrated a lower level of inflammatory infiltrate and higher degree of collagenization, while RMO demonstrated the lowest level of biocompatibility.

An extended research of crossmodal correspondence between color and sound in psychology and cognitive ergonomics.

PubMed

Sun, Xiuwen; Li, Xiaoling; Ji, Lingyu; Han, Feng; Wang, Huifen; Liu, Yang; Chen, Yao; Lou, Zhiyuan; Li, Zhuoyun

2018-01-01

Based on the existing research on sound symbolism and crossmodal correspondence, this study proposed an extended research on cross-modal correspondence between various sound attributes and color properties in a group of non-synesthetes. In Experiment 1, we assessed the associations between each property of sounds and colors. Twenty sounds with five auditory properties (pitch, roughness, sharpness, tempo and discontinuity), each varied in four levels, were used as the sound stimuli. Forty-nine colors with different hues, saturation and brightness were used to match to those sounds. Result revealed that besides pitch and tempo, roughness and sharpness also played roles in sound-color correspondence. Reaction times of sound-hue were a little longer than the reaction times of sound-lightness. In Experiment 2, a speeded target discrimination task was used to assess whether the associations between sound attributes and color properties could invoke natural cross-modal correspondence and improve participants' cognitive efficiency in cognitive tasks. Several typical sound-color pairings were selected according to the results of Experiment 1. Participants were divided into two groups (congruent and incongruent). In each trial participants had to judge whether the presented color could appropriately be associated with the sound stimuli. Result revealed that participants responded more quickly and accurately in the congruent group than in the incongruent group. It was also found that there was no significant difference in reaction times and error rates between sound-hue and sound-lightness. The results of Experiment 1 and 2 indicate the existence of a robust crossmodal correspondence between multiple attributes of sound and color, which also has strong influence on cognitive tasks. The inconsistency of the reaction times between sound-hue and sound-lightness in Experiment 1 and 2 is probably owing to the difference in experimental protocol, which indicates that the complexity of experiment design may be an important factor in crossmodal correspondence phenomena.

An extended research of crossmodal correspondence between color and sound in psychology and cognitive ergonomics

PubMed Central

Sun, Xiuwen; Ji, Lingyu; Han, Feng; Wang, Huifen; Liu, Yang; Chen, Yao; Lou, Zhiyuan; Li, Zhuoyun

2018-01-01

Based on the existing research on sound symbolism and crossmodal correspondence, this study proposed an extended research on cross-modal correspondence between various sound attributes and color properties in a group of non-synesthetes. In Experiment 1, we assessed the associations between each property of sounds and colors. Twenty sounds with five auditory properties (pitch, roughness, sharpness, tempo and discontinuity), each varied in four levels, were used as the sound stimuli. Forty-nine colors with different hues, saturation and brightness were used to match to those sounds. Result revealed that besides pitch and tempo, roughness and sharpness also played roles in sound-color correspondence. Reaction times of sound-hue were a little longer than the reaction times of sound-lightness. In Experiment 2, a speeded target discrimination task was used to assess whether the associations between sound attributes and color properties could invoke natural cross-modal correspondence and improve participants’ cognitive efficiency in cognitive tasks. Several typical sound-color pairings were selected according to the results of Experiment 1. Participants were divided into two groups (congruent and incongruent). In each trial participants had to judge whether the presented color could appropriately be associated with the sound stimuli. Result revealed that participants responded more quickly and accurately in the congruent group than in the incongruent group. It was also found that there was no significant difference in reaction times and error rates between sound-hue and sound-lightness. The results of Experiment 1 and 2 indicate the existence of a robust crossmodal correspondence between multiple attributes of sound and color, which also has strong influence on cognitive tasks. The inconsistency of the reaction times between sound-hue and sound-lightness in Experiment 1 and 2 is probably owing to the difference in experimental protocol, which indicates that the complexity of experiment design may be an important factor in crossmodal correspondence phenomena. PMID:29507834

[Recording and reporting adverse reactions in clinical trials. New legal provisions according to the 12th Law Amending the German Drug Law (AMG) and the Ordinance on GCP (GCP-V)].

PubMed

Eckhardt, K; Cremer-Schaeffer, P; König, J; Paeschke, N

2005-02-01

With the 12th Law Amending the German Drug Law and the Ordinance on GCP (GCPV), new legal provisions for clinical trials came into force in August 2004. These include specific definitions and differentiated reporting obligations affecting investigators, sponsors, authorities and ethics committees concerning pharmacovigilance in clinical trials. The definitions according to section sign3 (6-8) GCP-V make clear that these provisions focus on those adverse events and adverse drug reactions, which are related to investigational medicinal products. In the GCP-V for the first time legally binding provisions for investigators are laid down defining obligations to report all serious adverse events to the sponsor. The sponsor of clinical trials plays a decisive role concerning the evaluation, documentation and reporting to the competent higher authorities, ethics committees and investigators involved in the clinical trial. In the GCP-V different time limits concerning the reporting for sponsors are laid down. The requirements concerning expedited reporting focus on suspected unexpected serious adverse reactions (SUSARs), i. e. those adverse serious reactions, which are not described in the information on the investigational medicinal product. The time limit for reporting SUSARs leading to death or life-threatening SUSARs is 7 days, while for other SUSARs the time limit is 15 days. Besides the responsibilities on expedited reporting the sponsor has to submit a line listing of all serious adverse reactions which occurred during the clinical trial and a report on the safety of the trial subjects on an annual basis or on request. On the European level the harmonisation concerning the provisions on pharmacovigilance in clinical trials according to the Directive 2001/20/EC and the Eudravigilance database should contribute to reach a faster and more effective exchange of safety information related to clinical trials between the different competent authorities of the EU member states.

Personality stability is associated with better cognitive performance in adulthood: are the stable more able?

PubMed

Graham, Eileen K; Lachman, Margie E

2012-09-01

Although personality is relatively stable over time, there are individual differences in the patterns and magnitude of change. There is some evidence that personality change in adulthood is related to physical health and longevity. The present study expanded this work to consider whether personality stability or change would be associated with better cognitive functioning, especially in later adulthood. A total of 4,974 individuals participated in two waves of The Midlife in the United States Study (MIDUS) in 1994-1995 and 2004-2005. Participants completed the MIDUS personality inventory at both times and the Brief Test of Adult Cognition by Telephone cognitive battery at Time 2. Multiple regression and analysis of covariance analyses showed that, consistent with predictions, individuals remaining stable in openness to experience and neuroticism had faster reaction times and better inductive reasoning than those who changed. Among older adults, those who remained stable or decreased in neuroticism had significantly faster reaction times than those who increased. As predicted, personality stability on some traits was associated with more adaptive cognitive performance on reasoning and reaction time. Personality is discussed as a possible resource for protecting against or minimizing age-related declines in cognition.

Method for fabricating an ignitable heterogeneous stratified metal structure

DOEpatents

Barbee, T.W. Jr.; Weihs, T.

1996-08-20

A multilayer structure has a selectable: (1) propagating reaction front velocity V; (2) reaction initiation temperature attained by application of external energy; and (3) amount of energy delivered by a reaction of alternating unreacted layers of the multilayer structure. Because V is selectable and controllable, a variety of different applications for the multilayer structures are possible, including but not limited to their use as igniters, in joining applications, in fabrication of new materials, as smart materials and in medical applications and devices. The multilayer structure has a period D, and an energy release rate constant K. Two or more alternating unreacted layers are made of different materials and separated by reacted zones. The period D is equal to a sum of the widths of each single alternating reaction layer of a particular material, and also includes a sum of reacted zone widths, t{sub i}, in the period D. The multilayer structure has a selectable propagating reaction front velocity V, where V=K(1/D{sup n}){times}[1-(t{sub i}/D)] and n is about 0.8 to 1.2. 8 figs.

Method for fabricating an ignitable heterogeneous stratified metal structure

DOEpatents

Barbee, Jr., Troy W.; Weihs, Timothy

1996-01-01

A multilayer structure has a selectable, (i) propagating reaction front velocity V, (ii) reaction initiation temperature attained by application of external energy and (iii) amount of energy delivered by a reaction of alternating unreacted layers of the multilayer structure. Because V is selectable and controllable, a variety of different applications for the multilayer structures are possible, including but not limited to their use as ignitors, in joining applications, in fabrication of new materials, as smart materials and in medical applications and devices. The multilayer structure has a period D, and an energy release rate constant K. Two or more alternating unreacted layers are made of different materials and separated by reacted zones. The period D is equal to a sum of the widths of each single alternating reaction layer of a particular material, and also includes a sum of reacted zone widths, t.sub.i, in the period D. The multilayer structure has a selectable propagating reaction front velocity V, where V=K(1/D.sup.n).times.[1-(t.sub.i /D)]and n is about 0.8 to 1.2.

Kinetic studies on the oxidation of oxyhemoglobin by biologically active iron thiosemicarbazone complexes: relevance to iron-chelator-induced methemoglobinemia.

PubMed

Basha, Maram T; Rodríguez, Carlos; Richardson, Des R; Martínez, Manuel; Bernhardt, Paul V

2014-03-01

The oxidation of oxyhemoglobin to methemoglobin has been found to be facilitated by low molecular weight iron(III) thiosemicarbazone complexes. This deleterious reaction, which produces hemoglobin protein units unable to bind dioxygen and occurs during the administration of iron chelators such as the well-known 3-aminopyridine-2-pyridinecarbaldehyde thiosemicarbazone (3-AP; Triapine), has been observed in the reaction with Fe(III) complexes of some members of the 3-AP structurally-related thiosemicarbazone ligands derived from di-2-pyridyl ketone (HDpxxT series). We have studied the kinetics of this oxidation reaction in vitro using human hemoglobin and found that the reaction proceeds with two distinct time-resolved steps. These have been associated with sequential oxidation of the two different oxyheme cofactors in the α and β protein chains. Unexpected steric and hydrogen-bonding effects on the Fe(III) complexes appear to be the responsible for the observed differences in the reaction rate across the series of HDpxxT ligand complexes used in this study.

Switchable regioselectivity in amine-catalysed asymmetric cycloadditions

NASA Astrophysics Data System (ADS)

Zhou, Zhi; Wang, Zhou-Xiang; Zhou, Yuan-Chun; Xiao, Wei; Ouyang, Qin; Du, Wei; Chen, Ying-Chun

2017-06-01

Building small-molecule libraries with structural and stereogenic diversity plays an important role in drug discovery. The development of switchable intermolecular cycloaddition reactions from identical substrates in different regioselective fashions would provide an attractive protocol. However, this also represents a challenge in organic chemistry, because it is difficult to control regioselectivity to afford the products exclusively and at the same time achieve high levels of stereoselectivity. Here, we report the diversified cycloadditions of α‧-alkylidene-2-cyclopentenones catalysed by cinchona-derived primary amines. An asymmetric γ,β‧-regioselective intermolecular [6+2] cycloaddition reaction with 3-olefinic (7-aza)oxindoles is realized through the in situ generation of formal 4-aminofulvenes, while a different β,γ-regioselective [2+2] cycloaddition reaction with maleimides to access fused cyclobutanes is disclosed. In contrast, an intriguing α,γ-regioselective [4+2] cycloaddition reaction is uncovered with the same set of substrates, by employing an unprecedented dual small-molecule catalysis of amines and thiols. All of the cycloaddition reactions exhibit excellent regio- and stereoselectivity, producing a broad spectrum of chiral architectures with high structural diversity and molecular complexity.

Enzymatic reactions in confined environments

NASA Astrophysics Data System (ADS)

Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter

2016-05-01

Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.

Time-Resolved and Operando XAS Studies on Heterogeneous Catalysts - From the Gas Phase Towards Reactions in Supercritical Fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grunwaldt, Jan-Dierk; Baiker, Alfons

2007-02-02

x-ray absorption spectroscopy is a well-suited technique to uncover the structure of heterogeneous catalysts under reaction conditions. Different aspects of in situ cell design suitable for dynamic and catalytic studies are discussed. In addition, criteria are presented that allow estimating the influence external and internal mass transfer. Starting with studies on gas-solid reactions, including structure-activity relationships, this concept is extended to liquid-solid reactions, reactions at high pressure and in supercritical fluids. The following examples are discussed in more detail: partial oxidation of methane over Pt-Rh/Al2O3, reduction of a Cu/ZnO catalyst, alcohol oxidation over Bi-promoted Pd/Al2O3 in liquid phase and overmore » Pd/Al2O3 in supercritical CO2, and batch reactions (e.g. CO2-fixation over zinc-based catalysts)« less

New Prediction Model for Probe Specificity in an Allele-Specific Extension Reaction for Haplotype-Specific Extraction (HSE) of Y Chromosome Mixtures

PubMed Central

Rothe, Jessica; Watkins, Norman E.; Nagy, Marion

2012-01-01

Allele-specific extension reactions (ASERs) use 3′ terminus-specific primers for the selective extension of completely annealed matches by polymerase. The ability of the polymerase to extend non-specific 3′ terminal mismatches leads to a failure of the reaction, a process that is only partly understood and predictable, and often requires time-consuming assay design. In our studies we investigated haplotype-specific extraction (HSE) for the separation of male DNA mixtures. HSE is an ASER and provides the ability to distinguish between diploid chromosomes from one or more individuals. Here, we show that the success of HSE and allele-specific extension depend strongly on the concentration difference between complete match and 3′ terminal mismatch. Using the oligonucleotide-modeling platform Visual Omp, we demonstrated the dependency of the discrimination power of the polymerase on match- and mismatch-target hybridization between different probe lengths. Therefore, the probe specificity in HSE could be predicted by performing a relative comparison of different probe designs with their simulated differences between the duplex concentration of target-probe match and mismatches. We tested this new model for probe design in more than 300 HSE reactions with 137 different probes and obtained an accordance of 88%. PMID:23049901

New prediction model for probe specificity in an allele-specific extension reaction for haplotype-specific extraction (HSE) of Y chromosome mixtures.

PubMed

Rothe, Jessica; Watkins, Norman E; Nagy, Marion

2012-01-01

Allele-specific extension reactions (ASERs) use 3' terminus-specific primers for the selective extension of completely annealed matches by polymerase. The ability of the polymerase to extend non-specific 3' terminal mismatches leads to a failure of the reaction, a process that is only partly understood and predictable, and often requires time-consuming assay design. In our studies we investigated haplotype-specific extraction (HSE) for the separation of male DNA mixtures. HSE is an ASER and provides the ability to distinguish between diploid chromosomes from one or more individuals. Here, we show that the success of HSE and allele-specific extension depend strongly on the concentration difference between complete match and 3' terminal mismatch. Using the oligonucleotide-modeling platform Visual Omp, we demonstrated the dependency of the discrimination power of the polymerase on match- and mismatch-target hybridization between different probe lengths. Therefore, the probe specificity in HSE could be predicted by performing a relative comparison of different probe designs with their simulated differences between the duplex concentration of target-probe match and mismatches. We tested this new model for probe design in more than 300 HSE reactions with 137 different probes and obtained an accordance of 88%.

Real-time monitoring of enzyme activity in a mesoporous silicon double layer

PubMed Central

Orosco, Manuel M.; Pacholski, Claudia; Sailor, Michael J.

2009-01-01

A double layer mesoporous silicon with different pore sizes functions as a nano-reactor that can isolate, filter and quantify the kinetics of enzyme reactions in real-time by optical reflectivity. This tiny reactor may be used to rapidly characterize a variety of isolated enzymes in a label-free manner. Activity of certain protease enzymes is often an indicator of disease states such as cancer1,2, stroke2, and neurodegeneracy3, and thus, there is a need for rapid assays that can characterize the kinetics and substrate specificity of enzymatic reactions. Nanostructured membranes can efficiently separate biomolecules4 but coupling a sensitive detection method remains difficult. Here we report a single mesoporous nano-reactor that can isolate and quantify in real-time the reaction products of proteases. The reactor consists of two layers of porous films electrochemically prepared from crystalline silicon. The upper layer with large pore sizes traps the protease enzymes and acts as the reactor while the lower layer with smaller pore sizes excludes the large proteins and captures the reaction products. Infiltration of the digested fragments into the lower layer produces a measurable change in optical reflectivity and this allows label-free quantification of enzyme kinetics in real-time within a volume of approximately 5 nanoliters. PMID:19350037

Variation in aluminium patch test reactivity over time.

PubMed

Siemund, Ingrid; Mowitz, Martin; Zimerson, Erik; Bruze, Magnus; Hindsén, Monica

2017-11-01

Contact allergy to aluminium has been reported more frequently in recent years. It has been pointed out that positive patch test reactions to aluminium may not be reproducible on retesting. To investigate possible variations in patch test reactivity to aluminium over time. Twenty-one adults, who had previously reacted positively to aluminium, were patch tested with equimolar dilution series in pet. of aluminium chloride hexahydrate and aluminium lactate, four times over a period of 8 months. Thirty-six of 84 (43%) serial dilution tests with aluminium chloride hexahydrate and 49 of 84 (58%) serial dilution tests with aluminium lactate gave negative results. The range of reactivity varied between a negative reaction to aluminium chloride hexahydrate at 10% and/or to aluminium lactate at 12%, and a positive reaction to aluminium chloride hexahydrate at 0.1% and/or to aluminium lactate at 0.12%. The highest individual difference in test reactivity noticed was 320-fold when the two most divergent minimal eliciting concentrations were compared. The patch test reactivity to aluminium varies over time. Aluminium-allergic individuals may have false-negative reactions. Therefore, retesting with aluminium should be considered when there is a strong suspicion of aluminium contact allergy. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Acute effect of vigorous aerobic exercise on the inhibitory control in adolescents

PubMed Central

Browne, Rodrigo Alberto Vieira; Costa, Eduardo Caldas; Sales, Marcelo Magalhães; Fonteles, André Igor; de Moraes, José Fernando Vila Nova; Barros, Jônatas de França

2016-01-01

Abstract Objective: To assess the acute effect of vigorous aerobic exercise on the inhibitory control in adolescents. Methods: Controlled, randomized study with crossover design. Twenty pubertal individuals underwent two 30-minute sessions: (1) aerobic exercise session performed between 65% and 75% of heart rate reserve, divided into 5 min of warm-up, 20 min at the target intensity and 5 min of cool down; and (2) control session watching a cartoon. Before and after the sessions, the computerized Stroop test-Testinpacs™ was applied to evaluate the inhibitory control. Reaction time (ms) and errors (n) were recorded. Results: The control session reaction time showed no significant difference. On the other hand, the reaction time of the exercise session decreased after the intervention (p<0.001). The number of errors made at the exercise session were lower than in the control session (p=0.011). Additionally, there was a positive association between reaction time (Δ) of the exercise session and age (r 2=0.404, p=0.003). Conclusions: Vigorous aerobic exercise seems to promote acute improvement in the inhibitory control in adolescents. The effect of exercise on the inhibitory control performance was associated with age, showing that it was reduced at older age ranges. PMID:26564328

Enhanced photovoltaic performance of dye sensitized solar cell using SnO2 nanoflowers

NASA Astrophysics Data System (ADS)

Arote, Sandeep A.; Tabhane, Vilas A.; Pathan, Habib M.

2018-01-01

The study highlighted enhanced performance of SnO2 based DSSC using photoanode with nanostructured morphology. The simple organic surfactant free hydrothermal synthesis method was used for preparation of SnO2 nanoflowers for dye sensitized solar cell (DSSC) application. The hydrothermal reaction time was varied to obtain different SnO2 nanostructures. The hydrothermal reaction time showed considerable effect on optical and structural properties of the prepared samples. The results indicated that the prepared samples were pure rutile SnO2. The band gap of prepared samples was greater than bulk SnO2 and varied from 3.64 to 3.81 eV with increase in hydrothermal reaction time. With increase in reaction time from 4 to 24 h, the microstructure of SnO2 changed from agglomerated nanoparticles to nanopetals and finally to self-assembled nanoflowers. Flower-like SnO2 nanostructures showed size around 300-700 nm, and composed of large numbers of 3 dimensional petals connected with each other forming 3D nanoflowers by self-assembly. Consequently, the DSSC with flower-like SnO2 nanostructures exhibited good photovoltaic performance with Voc, Jsc and η about 0.43 V, 4.36 mA/cm2 and 1.11%, respectively.

Elucidation of the Conversion Reaction of CoMnFeO4 Nanoparticles in Lithium Ion Battery Anode via Operando Studies.

PubMed

Permien, Stefan; Indris, Sylvio; Hansen, Anna-Lena; Scheuermann, Marco; Zahn, Dirk; Schürmann, Ulrich; Neubüser, Gero; Kienle, Lorenz; Yegudin, Eugen; Bensch, Wolfgang

2016-06-22

Conversion reactions deliver much higher capacities than intercalation/deintercalation reactions of commercial Li ion batteries. However, the complex reaction pathways of conversion reactions occurring during Li uptake and release are not entirely understood, especially the irreversible capacity loss of Mn(III)-containing oxidic spinels. Here, we report for the first time on the electrochemical Li uptake and release of Co(II)Mn(III)Fe(III)O4 spinel nanoparticles and the conversion reaction mechanisms elucidated by combined operando X-ray diffraction, operando and ex-situ X-ray absorption spectroscopy, transmission electron microscopy, (7)Li NMR, and molecular dynamics simulation. The combination of these techniques enabled uncovering the pronounced electronic changes and structural alterations on different length scales in a unique way. The spinel nanoparticles undergo a successive phase transition into a mixed monoxide caused by a movement of the reduced cations from tetrahedral to octahedral positions. While the redox reactions Fe(3+) ↔ Fe(0) and Co(2+) ↔ Co(0) occur for many charge/discharge cycles, metallic Mn nanoparticles formed during the first discharge can only be oxidized to Mn(2+) during charge. This finding explains the partial capacity loss reported for Mn(III)-based spinels. Furthermore, the results of the investigations evidence that the reaction mechanisms on the nanoscale are very different from pathways of microcrystalline materials.

Investigation of Possible Maillard Reaction Between Acyclovir and Dextrose upon Dilution Prior to Parenteral Administration.

PubMed

Siahi Shadbad, Mohammad Reza; Ghaderi, Faranak; Hatami, Leila; Monajjemzadeh, Farnaz

2016-12-01

In this study the stability of parenteral acyclovir (ACV) when diluted in dextrose (DEX) as large volume intravenous fluid preparation (LVIF) was evaluated and the possible Maillard reaction adducts were monitored in the recommended infusion time. Different physicochemical methods were used to evaluate the Maillard reaction of dextrose with ACV to track the reaction in real infusion condition. Other large volume intravenous fluids were checked regarding the diluted drug stability profile. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and mass data proved the reaction of glucose with dextrose. A Maillard-specific high performance liquid chromatography (HPLC) method was used to track the reaction in real infusion condition in vitro. The nucleophilic reaction occurred in diluted parenteral preparations of acyclovir in 5% dextrose solutions. The best diluent solution was also selected as sodium chloride and introduced based on drug stability and also its adsorption onto different infusion sets (PVC or non PVC) to provide an acceptable administration protocol in clinical practices. Although, the Maillard reaction was proved and successfully tracked in diluted solutions, and the level of drug loss when diluted in dextrose was reported to be between 0.27 up to 1.03% of the initial content. There was no drug adsorption to common infusion sets. The best diluent for parenteral acyclovir is sodium chloride large volume intravenous fluid.

Tectono-metamorphic evolution of the Jomolhari massif: Variations in timing of syn-collisional metamorphism across western Bhutan

NASA Astrophysics Data System (ADS)

Regis, Daniele; Warren, Clare J.; Young, David; Roberts, Nick M. W.

2014-03-01

Our current understanding of the rates and timescales of mountain-building processes is largely based on information recorded in U-bearing accessory minerals such as monazite, which is found in low abundance but which hosts the majority of the trace element budget. Monazite petrochronology was used to investigate the timing of crustal melting in migmatitic metasedimentary rocks from the Jomolhari massif (NW Bhutan). The samples were metamorphosed at upper amphibolite to granulite facies conditions (~ 0.85 GPa, ~ 800 °C), after an earlier High-Pressure stage (P > 1.4 GPa), and underwent partial melting through dehydration melting reactions involving muscovite and biotite. In order to link the timing of monazite growth/dissolution to the pressure-temperature (P-T) evolution of the samples, we identified 'chemical fingerprints' in major and accessory phases that were used to back-trace specific metamorphic reactions. Variations in Eu anomaly and Ti in garnet were linked to the growth and dissolution of major phases (e.g. growth of K-feldspar and dehydration melting of muscovite/biotite). Differences in M/HREE and Y from garnet core to rim were instead related to apatite breakdown and monazite-forming reactions. Chemically zoned monazite crystals reacted multiple times during the metamorphic evolution suggesting that the Jomolhari massif experienced a prolonged high-temperature metamorphic evolution from 36 Ma to 18 Ma, significantly different from the P-T-time path recorded in other portions of the Greater Himalayan Sequence (GHS) in Bhutan. Our data demonstrate unequivocally that the GHS in Bhutan consists of units that experienced independent high-grade histories and that were juxtaposed across different tectonic structures during exhumation. The GHS may have been exhumed in response to (pulsed) mid-crustal flow but cannot be considered a coherent block.

Genetic and environmental contributions to the associations between intraindividual variability in reaction time and cognitive function.

PubMed

Finkel, Deborah; Pedersen, Nancy L

2014-01-01

Intraindividual variability (IIV) in reaction time has been related to cognitive decline, but questions remain about the nature of this relationship. Mean and range in movement and decision time for simple reaction time were available from 241 individuals aged 51-86 years at the fifth testing wave of the Swedish Adoption/Twin Study of Aging. Cognitive performance on four factors was also available: verbal, spatial, memory, and speed. Analyses indicated that range in reaction time could be used as an indicator of IIV. Heritability estimates were 35% for mean reaction and 20% for range in reaction. Multivariate analysis indicated that the genetic variance on the memory, speed, and spatial factors is shared with genetic variance for mean or range in reaction time. IIV shares significant genetic variance with fluid ability in late adulthood, over and above and genetic variance shared with mean reaction time.

Categorization and identification of simultaneous targets.

PubMed

Theeuwes, J

1991-02-01

Early and late selection theories of visual attention disagree about whether identification occurs before or after selection. Studies showing the category effect, i.e., the time to detect a letter is hardly affected by the number of digits present in the display, are taken as evidence for late selection theories since these studies suggest parallel identification of all items in the display. As an extension of previous studies, in the present study two categorically different targets were presented simultaneously among a variable number of nontargets. Subjects were shown brief displays of two target letters among either 2, 4 or 6 nontarget digits. Subjects responded 'same' when the two letters were identical and 'different' otherwise. Since the 'same-different' response reflects the combined outcome of the simultaneous targets, late-selection theory predicts that the time to match the target letters is independent of the number of nontarget digits. Alternatively, early-selection theory predicts a linear increase of reaction time with display size since the presence of more than one target disrupts parallel preattentive processing, leading to a serial search through all items in the display. The results provide evidence for the early-selection view since reaction time increased linearly with the number of categorically different nontargets. A control experiment revealed that none of the alternative explanations could account for the display size effect.

Recognition of facial emotions among maltreated children with high rates of post-traumatic stress disorder

PubMed Central

Masten, Carrie L.; Guyer, Amanda E.; Hodgdon, Hilary B.; McClure, Erin B.; Charney, Dennis S.; Ernst, Monique; Kaufman, Joan; Pine, Daniel S.; Monk, Christopher S.

2008-01-01

Objective The purpose of this study is to examine processing of facial emotions in a sample of maltreated children showing high rates of post-traumatic stress disorder (PTSD). Maltreatment during childhood has been associated independently with both atypical processing of emotion and the development of PTSD. However, research has provided little evidence indicating how high rates of PTSD might relate to maltreated children’s processing of emotions. Method Participants’ reaction time and labeling of emotions were measured using a morphed facial emotion identification task. Participants included a diverse sample of maltreated children with and without PTSD and controls ranging in age from 8 to 15 years. Maltreated children had been removed from their homes and placed in state custody following experiences of maltreatment. Diagnoses of PTSD and other disorders were determined through combination of parent, child, and teacher reports. Results Maltreated children displayed faster reaction times than controls when labeling emotional facial expressions, and this result was most pronounced for fearful faces. Relative to children who were not maltreated, maltreated children both with and without PTSD showed enhanced response times when identifying fearful faces. There was no group difference in labeling of emotions when identifying different facial emotions. Conclusions Maltreated children show heightened ability to identify fearful faces, evidenced by faster reaction times relative to controls. This association between maltreatment and atypical processing of emotion is independent of PTSD diagnosis. PMID:18155144

Mechanical analysis of the roundhouse kick according to height and distance in taekwondo.

PubMed

Estevan, I; Falco, C

2013-12-01

Competition regulation in taekwondo has experienced several changes during the last few years, for example, kicks to the head score more points than kicks to the chest. In addition, some external factors such as the height of target and execution distance seem to affect the kick performance. The aim of this study was to analyse selected biomechanical parameters (impact force, reaction time, and execution time) according to the height and execution distance in two different male groups (experts (n = 12) and novices (n = 21)). Athletes kicked twice from every execution distance (short, normal and long) and towards two different heights of target (chest and head) in a random order. Novices kicked to the head with a longer reaction time than to the chest (p < 0.05) but experts were able to kick with similar performance for both heights. From short and normal distances experts kicked with similar performance; whereas from the normal distance novices had longer reaction and execution time than from the short distance (p < 0.05). In conclusion, in counterattacking situations, experts should perform the roundhouse kick to the head instead of to the chest, because it produces better scores with similar performance; whereas novice athletes should avoid kicking to the head because they are not able to kick with similar performance. Moreover, it is recommended that during counterattacks higher-level taekwondo athletes should intend to kick from normal distances.

MECHANICAL ANALYSIS OF THE ROUNDHOUSE KICK ACCORDING TO HEIGHT AND DISTANCE IN TAEKWONDO

PubMed Central

Falco, C.

2013-01-01

Competition regulation in taekwondo has experienced several changes during the last few years, for example, kicks to the head score more points than kicks to the chest. In addition, some external factors such as the height of target and execution distance seem to affect the kick performance. The aim of this study was to analyse selected biomechanical parameters (impact force, reaction time, and execution time) according to the height and execution distance in two different male groups (experts (n = 12) and novices (n = 21)). Athletes kicked twice from every execution distance (short, normal and long) and towards two different heights of target (chest and head) in a random order. Novices kicked to the head with a longer reaction time than to the chest (p < 0.05) but experts were able to kick with similar performance for both heights. From short and normal distances experts kicked with similar performance; whereas from the normal distance novices had longer reaction and execution time than from the short distance (p < 0.05). In conclusion, in counterattacking situations, experts should perform the roundhouse kick to the head instead of to the chest, because it produces better scores with similar performance; whereas novice athletes should avoid kicking to the head because they are not able to kick with similar performance. Moreover, it is recommended that during counterattacks higher-level taekwondo athletes should intend to kick from normal distances. PMID:24744499

Cognitive decline and slower reaction time in elderly individuals with mild cognitive impairment.

PubMed

Chen, Ko-Chia; Weng, Chia-Ying; Hsiao, Sigmund; Tsao, Wen-Long; Koo, Malcolm

2017-11-01

The relationship between declining performance, as measured by changes in reaction time, and declining cognitive function has not been critically studied. The aim of the present study was to investigate the association between reaction time during a task and cognitive ability in elderly Taiwanese individuals. Patients aged 65 years or older with mild cognitive impairment (MCI) (n = 33) and Alzheimer's disease (n = 26) were recruited from the neurology clinic of a regional hospital in southern Taiwan. In addition, 28 healthy controls aged 65 years or older were recruited from the community. The cognitive performance of the study participants was assessed using the Cognitive Abilities Screening Instrument (CASI). A computer-administered simple reaction time (SRT) task and a flanker reaction time (FRT) task were administered to assess participants' cognitive function. A non-parametric Kruskal-Wallis test was performed to compare CASI scores, SRT, and FRT among the three groups. anova was also used to compare CASI scores, inverse-transformed SRT, and inverse-transformed FRT among the three groups, with adjustment for age and years of education. Additionally, Pearson's partial correlation coefficients were used to assess the association of CASI scores with inverse-transformed SRT, and inverse-transformed FRT within each of the three groups. Significant differences in CASI scores, SRT, and FRT were found between the Alzheimer's disease group and the other two groups, either with or without adjustment for age or education. The reaction time of patients with Alzheimer's disease was significantly slower than the other two groups. Moreover, significant correlation between CASI and FRT was found in patients with MCI. Altered performance in a speed task was observed in patients with MCI. The FRT task should further be explored for its role as a marker for cognitive decline in elderly individuals, particularly in those with MCI. © 2017 Japanese Psychogeriatric Society.

Typical visual search performance and atypical gaze behaviors in response to faces in Williams syndrome.

PubMed

Hirai, Masahiro; Muramatsu, Yukako; Mizuno, Seiji; Kurahashi, Naoko; Kurahashi, Hirokazu; Nakamura, Miho

2016-01-01

Evidence indicates that individuals with Williams syndrome (WS) exhibit atypical attentional characteristics when viewing faces. However, the dynamics of visual attention captured by faces remain unclear, especially when explicit attentional forces are present. To clarify this, we introduced a visual search paradigm and assessed how the relative strength of visual attention captured by a face and explicit attentional control changes as search progresses. Participants (WS and controls) searched for a target (butterfly) within an array of distractors, which sometimes contained an upright face. We analyzed reaction time and location of the first fixation-which reflect the attentional profile at the initial stage-and fixation durations. These features represent aspects of attention at later stages of visual search. The strength of visual attention captured by faces and explicit attentional control (toward the butterfly) was characterized by the frequency of first fixations on a face or butterfly and on the duration of face or butterfly fixations. Although reaction time was longer in all groups when faces were present, and visual attention was not dominated by faces in any group during the initial stages of the search, when faces were present, attention to faces dominated in the WS group during the later search stages. Furthermore, for the WS group, reaction time correlated with eye-movement measures at different stages of searching such that longer reaction times were associated with longer face-fixations, specifically at the initial stage of searching. Moreover, longer reaction times were associated with longer face-fixations at the later stages of searching, while shorter reaction times were associated with longer butterfly fixations. The relative strength of attention captured by faces in people with WS is not observed at the initial stage of searching but becomes dominant as the search progresses. Furthermore, although behavioral responses are associated with some aspects of eye movements, they are not as sensitive as eye-movement measurements themselves at detecting atypical attentional characteristics in people with WS.

Active control of complex, multicomponent self-assembly processes

NASA Astrophysics Data System (ADS)

Schulman, Rebecca

The kinetics of many complex biological self-assembly processes such as cytoskeletal assembly are precisely controlled by cells. Spatiotemporal control over rates of filament nucleation, growth and disassembly determine how self-assembly occurs and how the assembled form changes over time. These reaction rates can be manipulated by changing the concentrations of the components needed for assembly by activating or deactivating them. I will describe how we can use these principles to design driven self-assembly processes in which we assemble and disassemble multiple types of components to create micron-scale networks of semiflexible filaments assembled from DNA. The same set of primitive components can be assembled into many different, structures depending on the concentrations of different components and how designed, DNA-based chemical reaction networks manipulate these concentrations over time. These chemical reaction networks can in turn interpret environmental stimuli to direct complex, multistage response. Such a system is a laboratory for understanding complex active material behaviors, such as metamorphosis, self-healing or adaptation to the environment that are ubiquitous in biological systems but difficult to quantitatively characterize or engineer.

Effect of operating conditions on yield and quality of biocrude during hydrothermal liquefaction of halophytic microalga Tetraselmis sp.

PubMed

Eboibi, B E; Lewis, D M; Ashman, P J; Chinnasamy, S

2014-10-01

The biomass of halophytic microalga Tetraselmis sp. with 16%w/w solids was converted into biocrude by a hydrothermal liquefaction (HTL) process in a batch reactor at different temperatures (310, 330, 350 and 370°C) and reaction times (5, 15, 30, 45 and 60min). The biocrude yield, elemental composition, energy density and severity parameter obtained at various reaction conditions were used to predict the optimum condition for maximum recovery of biocrude with improved quality. This study clearly indicated that the operating condition for obtaining maximum biocrude yield and ideal quality biocrude for refining were different. A maximum biocrude yield of ∼65wt% ash free dry weight (AFDW) was obtained at 350°C and 5min, with a severity parameter and energy density of 5.21 and ∼35MJ/kg, respectively. The treatment with 45min reaction time recorded ∼62wt% (AFDW) yield of biocrude with and energy density of ∼39MJ/kg and higher severity parameter of 7.53. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of Strength Enhancement of Soil Treated with Environment-Friendly Calcium Carbonate Powder

PubMed Central

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

This study aims to investigate the effects of the strength improvement of soft ground (sand) by producing calcium carbonate powder through microbial reactions. To analyze the cementation effect of calcium carbonate produced through microbial reaction for different weight ratios, four different types of specimens (untreated, calcium carbonate, cement, and calcium carbonate + cement) with different weight ratios (2%, 4%, 6%, and 8%) were produced and cured for a period of 3 days, 7 days, 14 days, 21 days, and 28 days to test them. The uniaxial compression strength of specimens was measured, and the components in the specimen depending on the curing period were analyzed by means of XRD analysis. The result revealed that higher weight ratios and longer curing period contributed to increased strength of calcium carbonate, cement, and calcium carbonate + cement specimens. The calcium carbonate and the calcium carbonate + cement specimens in the same condition showed the tendency of decreased strength approximately 3 times and two times in comparison with the 8% cement specimens cured for 28 days, but the tendency of increased strength was approximately 4 times and 6 times in comparison with the untreated specimen. PMID:24688401

Effect of strength enhancement of soil treated with environment-friendly calcium carbonate powder.

PubMed

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

This study aims to investigate the effects of the strength improvement of soft ground (sand) by producing calcium carbonate powder through microbial reactions. To analyze the cementation effect of calcium carbonate produced through microbial reaction for different weight ratios, four different types of specimens (untreated, calcium carbonate, cement, and calcium carbonate + cement) with different weight ratios (2%, 4%, 6%, and 8%) were produced and cured for a period of 3 days, 7 days, 14 days, 21 days, and 28 days to test them. The uniaxial compression strength of specimens was measured, and the components in the specimen depending on the curing period were analyzed by means of XRD analysis. The result revealed that higher weight ratios and longer curing period contributed to increased strength of calcium carbonate, cement, and calcium carbonate + cement specimens. The calcium carbonate and the calcium carbonate + cement specimens in the same condition showed the tendency of decreased strength approximately 3 times and two times in comparison with the 8% cement specimens cured for 28 days, but the tendency of increased strength was approximately 4 times and 6 times in comparison with the untreated specimen.

40 CFR 63.1256 - Standards: Wastewater.

Code of Federal Regulations, 2012 CFR

2012-07-01

... combination of the approaches in paragraphs (a)(1)(i) and (ii) of this section for different affected... tank are heated, treated by means of an exothermic reaction, or sparged, during which time the owner or...) at all times that the wastewater tank contains affected wastewater or residual removed from affected...

40 CFR 63.1256 - Standards: Wastewater.

Code of Federal Regulations, 2014 CFR

2014-07-01

... use a combination of the approaches in paragraphs (a)(1)(i) and (ii) of this section for different... tank are heated, treated by means of an exothermic reaction, or sparged, during which time the owner or...) at all times that the wastewater tank contains affected wastewater or residual removed from affected...

40 CFR 63.1256 - Standards: Wastewater.

Code of Federal Regulations, 2013 CFR

2013-07-01

... use a combination of the approaches in paragraphs (a)(1)(i) and (ii) of this section for different... tank are heated, treated by means of an exothermic reaction, or sparged, during which time the owner or...) at all times that the wastewater tank contains affected wastewater or residual removed from affected...

Stability and Change in Markers of Core Numerical Competencies

ERIC Educational Resources Information Center

Reeve, Robert; Reynolds, Fiona; Humberstone, Judi; Butterworth, Brian

2012-01-01

Dot enumeration (DE) and number comparison (NC) abilities are considered markers of core number competence. Differences in DE/NC reaction time (RT) signatures are thought to distinguish between typical and atypical number development. Whether a child's DE and NC signatures change or remain stable over time, relative to other developmental…

Numerical Analysis of Microwave Heating on Saponification Reaction

NASA Astrophysics Data System (ADS)

Huang, Kama; Jia, Kun

2005-01-01

Currently, microwave is widely used in chemical industry to accelerate chemical reactions. Saponification reaction has important applications in industry; some research results have shown that microwave heating can significantly accelerate the reaction [1]. But so far, no efficient method has been reported for the analysis of the heating process and design of an efficient reactor powered by microwave. In this paper, we present a method to study the microwave heating process on saponification reaction, where the reactant in a test tube is considered as a mixture of dilute solution. According to the preliminary measurement results, the effective permittivity of the mixture is approximately the permittivity of water, but the conductivity, which could change with the reaction, is derived from the reaction equation (RE). The electromagnetic field equation and reaction equation are coupled by the conductivity. Following that, the whole heating processes, which is described by Maxwell's equations, the reaction equation and heat transport equation (HTE), is analyzed by finite difference time domain (FDTD) method. The temperature rising in the test tube are measured and compared with the computational results. Good agreement can be seen between the measured and calculated results.

Quantum Dynamics Study of the Isotopic Effect on Capture Reactions: HD, D2 + CH3

NASA Technical Reports Server (NTRS)

Wang, Dunyou; Kwak, Dochan (Technical Monitor)

2002-01-01

Time-dependent wave-packet-propagation calculations are reported for the isotopic reactions, HD + CH3 and D2 + CH3, in six degrees of freedom and for zero total angular momentum. Initial state selected reaction probabilities for different initial rotational-vibrational states are presented in this study. This study shows that excitations of the HD(D2) enhances the reactivities; whereas the excitations of the CH3 umbrella mode have the opposite effects. This is consistent with the reaction of H2 + CH3. The comparison of these three isotopic reactions also shows the isotopic effects in the initial-state-selected reaction probabilities. The cumulative reaction probabilities (CRP) are obtained by summing over initial-state-selected reaction probabilities. The energy-shift approximation to account for the contribution of degrees of freedom missing in the six dimensionality calculation is employed to obtain approximate full-dimensional CRPs. The rate constant comparison shows H2 + CH3 reaction has the biggest reactivity, then HD + CH3, and D2 + CH3 has the smallest.

Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

PubMed

Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

2013-02-21

A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

Differences in Neuromuscular Strategies Between Landing and Cutting Tasks in Female Basketball and Soccer Athletes

PubMed Central

Cowley, Hanni R; Ford, Kevin R; Myer, Gregory D; Kernozek, Thomas W; Hewett, Timothy E

2006-01-01

Context: High school female athletes are most likely to sustain a serious knee injury during soccer or basketball, 2 sports that often involve a rapid deceleration before a change of direction or while landing from a jump. Objective: To determine if female high school basketball and soccer players show neuromuscular differences during landing and cutting tasks and to examine neuromuscular differences between tasks and between dominant and nondominant sides. Design: A 3-way mixed factorial design investigating the effects of sport (basketball, soccer), task (jumping, cutting), and side (dominant, nondominant). Setting: Laboratory. Patients or Other Participants: Thirty high school female athletes who listed either basketball or soccer as their only sport of participation (basketball: n = 15, age = 15.1 ± 1.7 years, experience = 6.9 ± 2.2 years, height = 165.3 ± 7.9 cm, mass = 61.8 ± 9.3 kg; soccer: n = 15, age = 14.8 ± 0.8 years, experience = 8.8 ± 2.5 years, height = 161.8 ± 4.1 cm, mass = 54.6 ± 7.6 kg). Main Outcome Measure(s): Ground reaction forces, stance time, valgus angles, and valgus moments were assessed during (1) a drop vertical jump with an immediate maximal vertical jump and (2) an immediate side-step cut at a 45° angle. Results: Basketball athletes had greater ground reaction forces (P < .001) and decreased stance time (P < .001) during the drop vertical jump, whereas soccer players had greater ground reaction forces (P <.001) and decreased stance time (P < .001) during the cut. Subjects in both sports had greater valgus angles (initial contact and maximum, P = .02 and P = .012, respectively) during cutting than during the drop vertical jump. Greater valgus moments (P = .006) were noted on the dominant side during cutting. Conclusions: Our subjects demonstrated differences in ground reaction forces and stance times during 2 movements associated with noncontact anterior cruciate ligament injuries. Knee valgus moment and angle were significantly influenced by the type of movement performed. Sport-specific neuromuscular training may be warranted, with basketball players focusing on jumping and landing and soccer players focusing on unanticipated cutting maneuvers. PMID:16619097

Executive Functions of Divers Are Selectively Impaired at 20-Meter Water Depth.

PubMed

Steinberg, Fabian; Doppelmayr, Michael

2017-01-01

Moving and acting underwater within recreational or occupational activities require intact executive functions, since they subserve higher cognitive functions such as successful self-regulation, coping with novel situations, and decision making; all of which could be influenced by nitrogen narcosis due to elevated partial pressure under water. However, specific executive functions that could provide a differentiated view on humans' cognitive performance ability have not yet been systematically analyzed in full-water immersion, which is a research gap addressed within this approach to contribute to a better understanding of nitrogen narcosis. In this study, 20 young, healthy, and certified recreational divers participated and performed three different executive-function tests: the Stroop test (Inhibition), the Number/Letter test (Task switching), the 2-back test (Updating/Working memory), and a simple reaction time test (Psychomotor performance). These tests were performed once on land, at 5-meter (m) water depth, and at 20-meter (m) water depth of an indoor diving facility in standardized test conditions (26°C in all water depths). A water-proofed and fully operational tablet computer was used to present visual stimuli and to register reaction times. Performance of the simple reaction time test was not different between underwater and land testing, suggesting that reaction times were not biased by the utilization of the tablet in water immersion. Executive functions were not affected by the shallow water immersion of 5-m water depth. However, performance scores in 20-m water depth revealed a decreased performance in the incongruent test condition (i.e., an index of inhibitory control ability) of the Stroop test, while all other tests were unaffected. Even though only one out of the three tested cognitive domains was affected, the impairment of inhibitory control ability even in relatively shallow water of 20-m is a critical component that should be considered for diver's safety, since inhibition is required in self-control requiring situations where impulsive and automatic behavior must be inhibited. Our interpretation of these selective impairments is based on a discussion suggesting that different neural networks within the central nervous system, which process specific executive functions, are affected differently by nitrogen narcosis.

Reaction Time Asymmetries between Expansion and Contraction

ERIC Educational Resources Information Center

Lopez-Moliner, Joan

2005-01-01

Different asymmetries between expansion and contraction (radial motions) have been reported in the literature. Often these patterns have been regarded as implying different channels for each type of radial direction (outward versus inwards) operating at a higher level of visual motion processing. In two experiments (detection and discrimination…

Examining the stability of dual-task posture and reaction time measures in older adults over five sessions: a pilot study.

PubMed

Jehu, Deborah A; Paquet, Nicole; Lajoie, Yves

2016-12-01

Improved performance may be inherent due to repeated exposure to a testing protocol. However, limited research has examined this phenomenon in postural control. The aim was to determine the influence of repeated administration of a dual-task testing protocol once per week for 5 weeks on postural sway and reaction time. Ten healthy older adults (67.0 ± 6.9 years) stood on a force plate for 30 s in feet apart and semi-tandem positions while completing simple reaction time (SRT) and choice reaction time (CRT) tasks. They were instructed to stand as still as possible while verbally responding as fast as possible to the stimuli. No significant differences in postural sway were shown over time (p > 0.05). A plateau in average CRT emerged as the time effect revealed longer CRT during session 1 compared to sessions 3-5 (p < 0.05). Furthermore, the time effect for within-subject variability of CRT uncovered no plateaus as it was less variable in session 5 than sessions 1-4 (p < 0.05). The lack of a plateau in variability of CRT may have emerged as older adults may require longer to reach optimal performance potential in a dual-task context. Postural sway and SRT were stable over the 5 testing sessions, but variability of CRT continued to improve over time. These findings form a basis for future studies to examine performance-related improvements due to repeated exposure to a testing protocol in a dual-task setting.

Diffusion-controlled reactions modeling in Geant4-DNA

NASA Astrophysics Data System (ADS)

Karamitros, M.; Luan, S.; Bernal, M. A.; Allison, J.; Baldacchino, G.; Davidkova, M.; Francis, Z.; Friedland, W.; Ivantchenko, V.; Ivantchenko, A.; Mantero, A.; Nieminem, P.; Santin, G.; Tran, H. N.; Stepan, V.; Incerti, S.

2014-10-01

Context Under irradiation, a biological system undergoes a cascade of chemical reactions that can lead to an alteration of its normal operation. There are different types of radiation and many competing reactions. As a result the kinetics of chemical species is extremely complex. The simulation becomes then a powerful tool which, by describing the basic principles of chemical reactions, can reveal the dynamics of the macroscopic system. To understand the dynamics of biological systems under radiation, since the 80s there have been on-going efforts carried out by several research groups to establish a mechanistic model that consists in describing all the physical, chemical and biological phenomena following the irradiation of single cells. This approach is generally divided into a succession of stages that follow each other in time: (1) the physical stage, where the ionizing particles interact directly with the biological material; (2) the physico-chemical stage, where the targeted molecules release their energy by dissociating, creating new chemical species; (3) the chemical stage, where the new chemical species interact with each other or with the biomolecules; (4) the biological stage, where the repairing mechanisms of the cell come into play. This article focuses on the modeling of the chemical stage. Method This article presents a general method of speeding-up chemical reaction simulations in fluids based on the Smoluchowski equation and Monte-Carlo methods, where all molecules are explicitly simulated and the solvent is treated as a continuum. The model describes diffusion-controlled reactions. This method has been implemented in Geant4-DNA. The keys to the new algorithm include: (1) the combination of a method to compute time steps dynamically with a Brownian bridge process to account for chemical reactions, which avoids costly fixed time step simulations; (2) a k-d tree data structure for quickly locating, for a given molecule, its closest reactants. The performance advantage is presented in terms of complexity, and the accuracy of the new algorithm is demonstrated by simulating radiation chemistry in the context of the Geant4-DNA project. Application The time-dependent radiolytic yields of the main chemical species formed after irradiation are computed for incident protons at different energies (from 50 MeV to 500 keV). Both the time-evolution and energy dependency of the yields are discussed. The evolution, at one microsecond, of the yields of hydroxyls and solvated electrons with respect to the linear energy transfer is compared to theoretical and experimental data. According to our results, at high linear energy transfer, modeling radiation chemistry in the trading compartment representation might be adopted.

Profile of irritant patch testing with detergents: sodium lauryl sulfate, sodium laureth sulfate and alkyl polyglucoside.

PubMed

Löffler, H; Happle, R

2003-01-01

The cutaneous reaction to detergents follows distinct kinetic rules: the duration of application and the irritant concentration are of major importance. The aim of this study was to evaluate the differences in kinetics of skin reaction between the standard irritant sodium lauryl sulfate (SLS), and 2 modern detergents: sodium laureth sulfate (SLES) and alkyl polyglucoside (APG). We performed patch testing with SLS and SLES (or APG) at different concentrations (0.125, 0.25, 0.5, 1.0 and 2.0%) and with different exposure times (6, 12 and 24 h). Evaluation was conducted by measurement of transepidermal water loss (TEWL) and laser Doppler flowmetry (LD) 24 h, 7 and 10 days after patch removal. We found a pronounced reaction to SLS, and a far milder one to SLES. Even at the highest concentration the skin reaction to APG was hard to detect. During the regeneration period (day 3-10) SLS showed even at day 10 an increased TEWL at all concentrations tested. The irritation due to SLES was convincingly detectable only up to day 7, whereas the APG-tested skin areas showed no significant reaction even at day 3. These results demonstrate the improvement in reduction of skin irritation achieved by development of novel detergents.

Deficiency in Mental Rotation of Upper and Lower-Limbs in Patients With Multiple Sclerosis and Its Relation With Cognitive Functions.

PubMed

Azin, Mahdieh; Zangiabadi, Nasser; Moghadas Tabrizi, Yousef; Iranmanesh, Farhad; Baneshi, Mohammad Reza

2016-08-01

Mental rotation is a cognitive motor process which was impaired in different neurologic disorders. We investigated whether there were deficits in response pattern, reaction time and response accuracy rate of mental rotation in multiple sclerosis (MS) patients compared to healthy subjects and whether cognitive dysfunctions in MS patients were correlated with mental rotation deficits. Moreover, we showed whether there was a difference between upper and lower-limbs mental rotation in MS patients. Thirty-five MS patients and 25 healthy subjects performed hand mental rotation (HMR) and foot mental rotation (FMR) tasks. Visual information processing speed, spatial learning and memory ability, and visuospatial processing were assessed by Symbol Digit Modalities Test (SDMT), Brief Visuospatial Memory Test-Revised (BVMT-R), and Judgment of Line Orientation Test (JLO) respectively in MS patients. Reaction time for both hand and foot stimuli increased, and response accuracy rate for hand stimuli decreased in MS patients compared to healthy subjects, but response pattern of mental rotation in MS patients persisted. Similar to healthy subjects, MS patients performed upper-limbs mental rotation more easily than a lower-limbs mental rotation with more speed and response accuracy rate. Reaction time and response accuracy rate were correlated with the mentioned cognitive functions. MS patients made use of the correct response pattern for problem solving of increasing orientation from upright stimuli. Reaction time and response accuracy rate altered in these patients and this alteration might occur along with impairment in motor planning. Subjects' better responding to hand stimuli was due to more familiarity with hand stimuli. The correlation of mental rotation ability with cognitive functions indicates the possible role of cognitive functions in mental rotation.