A disposable electrochemical immunosensor for prolactin involving affinity reaction on streptavidin-functionalized magnetic particles

International Nuclear Information System (INIS)

Moreno-Guzman, Maria; Gonzalez-Cortes, Araceli; Yanez-Sedeno, Paloma; Pingarron, Jose M.

2011-01-01

A novel electrochemical immunosensor was developed for the determination of the hormone prolactin. The design involved the use of screen-printed carbon electrodes and streptavidin-functionalized magnetic particles. Biotinylated anti-prolactin antibodies were immobilized onto the functionalized magnetic particles and a sandwich-type immunoassay involving prolactin and anti-prolactin antibody labelled with alkaline phosphatase was employed. The resulting bio-conjugate was trapped on the surface of the screen-printed electrode with a small magnet and prolactin quantification was accomplished by differential pulse voltammetry of 1-naphtol formed in the enzyme reaction using 1-naphtyl phosphate as alkaline phosphatase substrate. All variables involved in the preparation of the immunosensor and in the electrochemical detection step were optimized. The calibration plot for prolactin exhibited a linear range between 10 and 2000 ng mL -1 with a slope value of 7.0 nA mL ng -1 . The limit of detection was 3.74 ng mL -1 . Furthermore, the modified magnetic beads-antiprolactin conjugates showed an excellent stability. The immunosensor exhibited also a high selectivity with respect to other hormones. The analytical usefulness of the immnunosensor was demonstrated by analyzing human sera spiked with prolactin at three different concentration levels.

A disposable electrochemical immunosensor for prolactin involving affinity reaction on streptavidin-functionalized magnetic particles

Energy Technology Data Exchange (ETDEWEB)

Moreno-Guzman, Maria; Gonzalez-Cortes, Araceli [Department of Analytical Chemistry, Faculty of Chemistry, University Computense of Madrid, 28040 Madrid (Spain); Yanez-Sedeno, Paloma, E-mail: yseo@quim.ucm.es [Department of Analytical Chemistry, Faculty of Chemistry, University Computense of Madrid, 28040 Madrid (Spain); Pingarron, Jose M. [Department of Analytical Chemistry, Faculty of Chemistry, University Computense of Madrid, 28040 Madrid (Spain)

2011-04-29

A novel electrochemical immunosensor was developed for the determination of the hormone prolactin. The design involved the use of screen-printed carbon electrodes and streptavidin-functionalized magnetic particles. Biotinylated anti-prolactin antibodies were immobilized onto the functionalized magnetic particles and a sandwich-type immunoassay involving prolactin and anti-prolactin antibody labelled with alkaline phosphatase was employed. The resulting bio-conjugate was trapped on the surface of the screen-printed electrode with a small magnet and prolactin quantification was accomplished by differential pulse voltammetry of 1-naphtol formed in the enzyme reaction using 1-naphtyl phosphate as alkaline phosphatase substrate. All variables involved in the preparation of the immunosensor and in the electrochemical detection step were optimized. The calibration plot for prolactin exhibited a linear range between 10 and 2000 ng mL{sup -1} with a slope value of 7.0 nA mL ng{sup -1}. The limit of detection was 3.74 ng mL{sup -1}. Furthermore, the modified magnetic beads-antiprolactin conjugates showed an excellent stability. The immunosensor exhibited also a high selectivity with respect to other hormones. The analytical usefulness of the immnunosensor was demonstrated by analyzing human sera spiked with prolactin at three different concentration levels.

GC of catalytic reactions products involved in the promising fuel synthesis

Energy Technology Data Exchange (ETDEWEB)

Zheivot, V.; Sazonova, N. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Boreskov Inst. of Catalysis

2012-09-15

Catalytic reactions involved in the synthesis of the promising kinds of novel fuel and products formed in these reactions were systematized according to the resulting fuel type. Generalization of the retention of the substances comprising these products is presented. Chromatograms exhibiting their separation on chromatographic materials with the surface of different chemical properties are summarized. We propose procedures for gas-chromatographic analysis of the catalytic reactions products formed in the synthesis of hydrogen, methanol, dimethyl ether and hydrocarbons as a new generation of fuel alternative to petroleum and coal. For partial oxidation of methane into synthesis gas, on-line determination of the components obtained in the reaction was carried out by gas chromatography and gas analyzer based on different physicochemical methods (IR spectroscopy and electrochemical methods). Similarity of the results obtained using these methods is demonstrated. (orig.)

kinetics of the coupled gas-iron reactions involving silicon and carbon

African Journals Online (AJOL)

user

1985-09-01

Sep 1, 1985 ... out for the system involving liquid iron containing carbon and silicon and a gas ... in content with liquid iron at. 15600C, the ... of carbon monoxide bubbles at the. Slag - metal ..... equilibrium strongly make chemical reactions.

Clustering mechanism of oxocarboxylic acids involving hydration reaction: Implications for the atmospheric models

Science.gov (United States)

Liu, Ling; Kupiainen-Määttä, Oona; Zhang, Haijie; Li, Hao; Zhong, Jie; Kurtén, Theo; Vehkamäki, Hanna; Zhang, Shaowen; Zhang, Yunhong; Ge, Maofa; Zhang, Xiuhui; Li, Zesheng

2018-06-01

The formation of atmospheric aerosol particles from condensable gases is a dominant source of particulate matter in the boundary layer, but the mechanism is still ambiguous. During the clustering process, precursors with different reactivities can induce various chemical reactions in addition to the formation of hydrogen bonds. However, the clustering mechanism involving chemical reactions is rarely considered in most of the nucleation process models. Oxocarboxylic acids are common compositions of secondary organic aerosol, but the role of oxocarboxylic acids in secondary organic aerosol formation is still not fully understood. In this paper, glyoxylic acid, the simplest and the most abundant atmospheric oxocarboxylic acid, has been selected as a representative example of oxocarboxylic acids in order to study the clustering mechanism involving hydration reactions using density functional theory combined with the Atmospheric Clusters Dynamic Code. The hydration reaction of glyoxylic acid can occur either in the gas phase or during the clustering process. Under atmospheric conditions, the total conversion ratio of glyoxylic acid to its hydration reaction product (2,2-dihydroxyacetic acid) in both gas phase and clusters can be up to 85%, and the product can further participate in the clustering process. The differences in cluster structures and properties induced by the hydration reaction lead to significant differences in cluster formation rates and pathways at relatively low temperatures.

Stress Fractures of the Distal Femur Involving Small Nonossifying Fibromas in Young Athletes.

Science.gov (United States)

Robertson, Michael; Gilley, Jasen; Nicholas, Richard

2016-11-01

Small nonossifying fibromas (ie, fibrocortical defects) are incidental findings commonly seen on radiographs of young patients evaluated for extremity pain or sport-related trauma. Although pathological fractures have been reported in larger lesions, the subcentimeter, intracortical defects are not generally thought to predispose to pathological fractures. The authors report on 2 young athletes who presented with knee pain after initiating conditioning exercise programs (cross-training). Both were diagnosed with transverse metaphyseal stress fractures involving fibrous cortical defects of the distal femur. Initial radiographs were interpreted without evidence of fractures. However, subsequent magnetic resonance imaging was informative, suggesting that magnetic resonance imaging may have value in identifying potential stress reactions in young athletes. In addition, subsequent plain radiographs of both patients showed subperiosteal new bone formation in these nondisplaced fractures, suggesting that serial radiographs and close clinical follow-up are warranted for patients with persistent symptoms. The authors propose that, in the appropriate clinical setting, the presence of a small nonossifying fibroma may be a clinical indication that further evaluation is needed when plain radiographs show normal findings, as the defect could be an unrecognized area of fracture initiation. [Orthopedics. 2016; 39(6):e1197-e1200.]. Copyright 2016, SLACK Incorporated.

Stress reactions involving the pars interarticularis in young athletes

Energy Technology Data Exchange (ETDEWEB)

Jackson, D.W.; Wiltse, L.L.; Dingeman, R.D.; Hayes, M.

A stress reaction involving the pars interarticularis of the lumbar spine was confirmed in seven young athletes with a positive technetium pyrophosphate bone scan. No pars defects were detectable on their lumbosacral roentgenograms, which included oblique views. The return to normal levels of radioactive uptake on repeat bone scans correlated closely with their clinical course. If the bony reaction is recognized early, it may heal at a subroentgenographic level and prevent the development of lumbar spondylolysis. These early lesions usually show unilateral increased uptake at one lumbar level on the bone scan and, initially, the athlete localizes the pain to the corresponding unilateral lumbar paraspinous area. The ''one-legged hyperextension test'' is positive on the ipsilateral side and aggravates the pain. Treatment consists of avoiding the aggravating activities and resting. The average time for return to pain-free competition was 7.3 months. These developing defects may be the source of considerable prolonged disability in the young athlete, particularly if undiagnosed and untreated.

Stress reactions involving the pars interarticularis in young athletes

International Nuclear Information System (INIS)

Jackson, D.W.; Wiltse, L.L.; Dingeman, R.D.; Hayes, M.

1981-01-01

A stress reaction involving the pars interarticularis of the lumbar spine was confirmed in seven young athletes with a positive technetium pyrophosphate bone scan. No pars defects were detectable on their lumbosacral roentgenograms, which included oblique views. The return to normal levels of radioactive uptake on repeat bone scans correlated closely with their clinical course. If the bony reaction is recognized early, it may heal at a subroentgenographic level and prevent the development of lumbar spondylolysis. These early lesions usually show unilateral increased uptake at one lumbar level on the bone scan and, initially, the athlete localizes the pain to the corresponding unilateral lumbar paraspinous area. The ''one-legged hyperextension test'' is positive on the ipsilateral side and aggravates the pain. Treatment consists of avoiding the aggravating activities and resting. The average time for return to pain-free competition was 7.3 months. These developing defects may be the source of considerable prolonged disability in the young athlete, particularly if undiagnosed and untreated

Kynurenine pathway metabolites and enzymes involved in redox reactions.

Science.gov (United States)

González Esquivel, D; Ramírez-Ortega, D; Pineda, B; Castro, N; Ríos, C; Pérez de la Cruz, V

2017-01-01

Oxido-reduction reactions are a fundamental part of the life due to support many vital biological processes as cellular respiration and glucose oxidation. In the redox reactions, one substance transfers one or more electrons to another substance. An important electron carrier is the coenzyme NAD + , which is involved in many metabolic pathways. De novo biosynthesis of NAD + is through the kynurenine pathway, the major route of tryptophan catabolism, which is sensitive to redox environment and produces metabolites with redox capacity, able to alter biological functions that are controlled by redox-responsive signaling pathways. Kynurenine pathway metabolites have been implicated in the physiology process and in the physiopathology of many diseases; processes that also share others factors as dysregulation of calcium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation and cell death, which impact the redox environment. This review examines in detail the available evidence in which kynurenine pathway metabolites participate in redox reactions and their effect on cellular redox homeostasis, since the knowledge of the main factors and mechanisms that lead to cell death in many neurodegenative disorders and other pathologies, such as mitochondrial dysfunction, oxidative stress and kynurenines imbalance, will allow to develop therapies using them as targets. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'. Copyright © 2016 Elsevier Ltd. All rights reserved.

Involving postgraduate's students in undergraduate small group teaching promotes active learning in both

Science.gov (United States)

Kalra, Ruchi; Modi, Jyoti Nath; Vyas, Rashmi

2015-01-01

Background: Lecture is a common traditional method for teaching, but it may not stimulate higher order thinking and students may also be hesitant to express and interact. The postgraduate (PG) students are less involved with undergraduate (UG) teaching. Team based small group active learning method can contribute to better learning experience. Aim: To-promote active learning skills among the UG students using small group teaching methods involving PG students as facilitators to impart hands-on supervised training in teaching and managerial skills. Methodology: After Institutional approval under faculty supervision 92 UGs and 8 PGs participated in 6 small group sessions utilizing the jigsaw technique. Feedback was collected from both. Observations: Undergraduate Feedback (Percentage of Students Agreed): Learning in small groups was a good experience as it helped in better understanding of the subject (72%), students explored multiple reading resources (79%), they were actively involved in self-learning (88%), students reported initial apprehension of performance (71%), identified their learning gaps (86%), team enhanced their learning process (71%), informal learning in place of lecture was a welcome change (86%), it improved their communication skills (82%), small group learning can be useful for future self-learning (75%). Postgraduate Feedback: Majority performed facilitation for first time, perceived their performance as good (75%), it was helpful in self-learning (100%), felt confident of managing students in small groups (100%), as facilitator they improved their teaching skills, found it more useful and better identified own learning gaps (87.5%). Conclusions: Learning in small groups adopting team based approach involving both UGs and PGs promoted active learning in both and enhanced the teaching skills of the PGs. PMID:26380201

Preparation of molybdenum borides by combustion synthesis involving solid-phase displacement reactions

International Nuclear Information System (INIS)

Yeh, C.L.; Hsu, W.S.

2008-01-01

Preparation of molybdenum borides of five different phases in the Mo-B binary system (including Mo 2 B, MoB, MoB 2 , Mo 2 B 5 , and MoB 4 ) was performed by self-propagating high-temperature synthesis (SHS) with two kinds of the reactant samples. When elemental powder compacts with an exact stoichiometry corresponding to the boride phase were employed, self-sustaining reaction was only achieved in the sample with Mo:B = 1:1 and nearly single-phase MoB was yielded. Therefore, the other four boride compounds were prepared from the reactant compacts composed of MoO 3 , Mo, and B powders, within which the displacement reaction of MoO 3 with boron was involved in combustion synthesis. Experimental evidence shows that the extent of displacement reaction in the overall reaction has a significant impact on sustainability of the synthesis reaction, combustion temperature, reaction front velocity, and composition of the end product. An increase in the solid-phase displacement reaction taking place during the SHS process contributes more heat flux to the synthesis reaction, thus resulting in the increase of combustion temperature and enhancement of the reaction front velocity. Based upon the XRD analysis, formation of Mo 2 B, MoB 2 , and Mo 2 B 5 as the dominant boride phase in the end product was successful through the SHS reaction with powder compacts under appropriate stoichiometries between MoO 3 , Mo, and B. However, a poor conversion was observed in the synthesis of MoB 4 . The powder compact prepared for the production of MoB 4 yielded mostly Mo 2 B 5

Small bowel involvement documented by capsule endoscopy in Churg-Strauss syndrome.

Science.gov (United States)

Beye, Birane; Lesur, Gilles; Claude, Pierre; Martzolf, Lionel; Kieffer, Pierre; Sondag, Daniel

2015-01-01

Churg-Strauss syndrome is a small and medium vessel vasculitis and is also known as allergic granulomatous angiitis. Gastrointestinal involvement is common in patients with Churg-Strauss syndrome (20-50%). The most common symptoms are abdominal pain, diarrhoea and occasionally gastrointestinal bleeding and perforation. We present a case of Churg-Strauss syndrome with small bowel lesions documented by video capsule endoscopy.

Cleaning of small components of complex geometry by means of the sodium-alcohol reaction

International Nuclear Information System (INIS)

De Luca, B.; Grasso, C.; Spadoni, M.

1978-01-01

The results of some experiments on the vacuum reaction between butylcellosolve and sodium, contained in small diameter capillaries, are reported. The effects on the cleaning rate of the temperature, amount of solvent, diameter and position of the capillaries are analyzed. The facility, used for the cleaning of small components of complex geometry, is described. (author)

Analysis of the Sodium-Water Reaction Phenomena by Small Water/Steam Leaks

International Nuclear Information System (INIS)

Jeong, J-Y; Kim, T-J; Kim, J-M; Kim, B-H; Park, N-C

2006-01-01

One of the important problems to be solved in the design and construction of a sodium cooled fast reactor is to confirm the safety and reliability of the steam generator which transfers the heat from the sodium to the water. Sodium-water reaction events may occur when material faults such as a pinhole or cracks occur in the heat transfer tube wall. When such a leak occurs, evaporating water or superheated steam enters through a small leak into the sodium. The surface of this steam jet reacts with the surrounding sodium. Due to turbulence, sodium and particles of the reaction products are drawn at a high velocity into the jet. Impingement of these particles on an adjacent tube is followed by a combined process of a corrosion and erosion which results in a local weakening of the affected tube. If there is no reliable detection available in time, wastage will ultimately result in an additional leak in the adjacent tube. Therefore, it is very significant to predict these phenomena quantitatively from the view of designing a steam generator and its leak detection systems. The objective of this study is a basic investigating of the sodium-water reaction phenomena by small water/steam leaks

Staff's reactions towards partnered sexual expressions involving people with dementia living in long-term care facilities.

Science.gov (United States)

Villar, Feliciano; Celdrán, Montserrat; Serrat, Rodrigo; Fabà, Josep; Martínez, Teresa

2018-05-01

To explore staff responses, in terms of common practices, towards partnered sexual relationships in long-term care facilities where one or both people involved have dementia. It also tries to determine personal and institutional factors influencing these responses. Although some studies, mostly qualitative, have focused on reactions to residents' sexual expressions so far the issue has not been assessed in a study using large and diverse samples. Cross-sectional quantitative study using vignette technique. Participants were 2,295 staff members at 152 Spanish long-term care facilities. Data were collected during 2016. A vignette describing sexual situations involving people with dementia was presented to participants. After the vignette, participants had to answer the question: "What do you think most of your colleagues would do in this situation?" with nine possible responses. Results showed that relationships involving persons with dementia were perceived as potentially problematic by staff. In both conditions, discussing the case with a colleague or supervisor was the most frequently chosen reaction. More restrictive reactions were mentioned when only one person with dementia was involved in the relationship. Factors such as participants" age and years of experience, professional post and commitment to person-centred care practices were related with the frequency of common restriction practices. Results highlight the importance of providing staff with clear guidelines regarding the management of specific sexual situations to avoid stereotyped restrictive reactions. © 2017 John Wiley & Sons Ltd.

Cross-section and reaction rates for some reactions involved in explosive nucleosynthesis

International Nuclear Information System (INIS)

Cheng, C.W.

1979-03-01

Total proton-induced and alpha-induced reaction cross sections have been determined for the 24 Mg(α,n), 25 Mg(p,n), 26 Mg(p,n), 27 Al(p,n), 28 Si(α,n), 42 Ca(p,γ), 42 Ca(α,n) and 44 Ca(p,n) reactions from energies near threshold (except the exothermic (p,γ) reaction) to about 3 to 4 MeV above threshold. The product nuclei are all positron emitters with half-lives ranging from about 3 sec to about 4 hours. From the measured cross sections reaction rates have been calculated in the temperature range 1 9 9 =1, at which the discrepancy is large. Included also are analytic forms for (p,n), (α,n), and (p,γ) reactions which can be used to describe the reaction rate within the temperature range 1 9 <=6 and which agree with the experimental rates at the discrete temperatures where the reaction rates have been calculated

Development of linear free energy relationships for aqueous phase radical-involved chemical reactions.

Science.gov (United States)

Minakata, Daisuke; Mezyk, Stephen P; Jones, Jace W; Daws, Brittany R; Crittenden, John C

2014-12-02

Aqueous phase advanced oxidation processes (AOPs) produce hydroxyl radicals (HO•) which can completely oxidize electron rich organic compounds. The proper design and operation of AOPs require that we predict the formation and fate of the byproducts and their associated toxicity. Accordingly, there is a need to develop a first-principles kinetic model that can predict the dominant reaction pathways that potentially produce toxic byproducts. We have published some of our efforts on predicting the elementary reaction pathways and the HO• rate constants. Here we develop linear free energy relationships (LFERs) that predict the rate constants for aqueous phase radical reactions. The LFERs relate experimentally obtained kinetic rate constants to quantum mechanically calculated aqueous phase free energies of activation. The LFERs have been applied to 101 reactions, including (1) HO• addition to 15 aromatic compounds; (2) addition of molecular oxygen to 65 carbon-centered aliphatic and cyclohexadienyl radicals; (3) disproportionation of 10 peroxyl radicals, and (4) unimolecular decay of nine peroxyl radicals. The LFERs correlations predict the rate constants within a factor of 2 from the experimental values for HO• reactions and molecular oxygen addition, and a factor of 5 for peroxyl radical reactions. The LFERs and the elementary reaction pathways will enable us to predict the formation and initial fate of the byproducts in AOPs. Furthermore, our methodology can be applied to other environmental processes in which aqueous phase radical-involved reactions occur.

Reactions of small negative ions with O2(a 1[Delta]g) and O2(X 3[Sigma]g-)

Science.gov (United States)

Midey, Anthony; Dotan, Itzhak; Seeley, J. V.; Viggiano, A. A.

2009-02-01

The rate constants and product ion branching ratios were measured for the reactions of various small negative ions with O2(X 3[Sigma]g-) and O2(a 1[Delta]g) in a selected ion flow tube (SIFT). Only NH2- and CH3O- were found to react with O2(X) and both reactions were slow. CH3O- reacted by hydride transfer, both with and without electron detachment. NH2- formed both OH-, as observed previously, and O2-, the latter via endothermic charge transfer. A temperature study revealed a negative temperature dependence for the former channel and Arrhenius behavior for the endothermic channel, resulting in an overall rate constant with a minimum at 500 K. SF6-, SF4-, SO3- and CO3- were found to react with O2(a 1[Delta]g) with rate constants less than 10-11 cm3 s-1. NH2- reacted rapidly with O2(a 1[Delta]g) by charge transfer. The reactions of HO2- and SO2- proceeded moderately with competition between Penning detachment and charge transfer. SO2- produced a SO4- cluster product in 2% of reactions and HO2- produced O3- in 13% of the reactions. CH3O- proceeded essentially at the collision rate by hydride transfer, again both with and without electron detachment. These results show that charge transfer to O2(a 1[Delta]g) occurs readily if the there are no restrictions on the ion beyond the reaction thermodynamics. The SO2- and HO2- reactions with O2(a) are the only known reactions involving Penning detachment besides the reaction with O2- studied previously [R.S. Berry, Phys. Chem. Chem. Phys., 7 (2005) 289-290].

Innocuous oil as an additive for reductive reactions involving zero valence iron

International Nuclear Information System (INIS)

Cary, J.W.; Cantrell, K.J.

1994-11-01

Reductive reactions involving zero valence iron appear to hold promise for in situ remediation of sites containing chlorinated hydrocarbon solvents and certain reducible metals and radionuclides. Treatment involves the injection of metallic iron and the creation of low levels of dissolved oxygen in the aqueous phase through oxidation of the metallic iron. The use of a biodegradable immiscible and innocuous organic liquid such as vegetable oil as an additive offers several intriguing possibilities. The oil phase creates a large oil-water interface that is immobile with respect to flow in the aqueous phase. This phase will act as a trap for chlorinated hydrocarbons and could potentially increase the reaction efficiency of reductive dehalogenation of chlorinated hydrocarbons by the metallic iron. When iron particles are suspended in the oil before injection they are preferentially held in the oil phase and tend to accumulate at the oil-water interface. Thus oil injection can serve as a mechanism for creating a stable porous curtain of metallic iron in the vadose to maintain a low oxygen environment which will minimize the consumption of the iron by molecular oxygen

On the study of the transfer ionization reactions at super small scattering angles

International Nuclear Information System (INIS)

Popov, Yu.V.; Chuluunbaatar, O.; Vinitskij, S.I.; Ancarani, L.U.; Dal Cappello, C.; Vinitskij, P.S.

2002-01-01

The hypothesis that the reaction p + He → H + He ++ + e at super small scattering angles of hydrogen can be used for purposes of the angular spectroscopy of electron-electron correlations in the target is considered. It is shown that this hypothesis is untenable

On the Study of the Transfer Ionization Reactions at Super Small Scattering Angles

CERN Document Server

Popov, Yu V; Vinitsky, S I; Ancarani, L U; Dal Cappello, C; Vinitsky, P S

2002-01-01

The hypothesis that the reaction p + He\\to H + He^{++} + e at super small scattering angles of hydrogen can be used for purposes of the angular spectroscopy of electron-electron correlations in the target is considered. It is shown that this hypothesis is insolvent.

A Small-Scale Capsule Test for Investigating the Sodium-Carbon Dioxide Reaction

International Nuclear Information System (INIS)

Kim, B. H.; Choi, J. H.; Suk, S. D.; Kim, J. M.; Choi, B. H.; Kim, B. H.; Hahn, D. H.

2007-01-01

The utilization of modular sodium-to-supercritical CO 2 heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO 2 heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO 2 in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO 2 would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium-CO 2 reaction is virtually non-existent

Photo- and radiation chemical studies of intermediates involved in excited-state electron-transfer reactions

International Nuclear Information System (INIS)

Hoffman, M.Z.

1985-01-01

Excited-state inter- and intramolecular electron-transfer reactions lie at the heart of the most photochemical solar energy conversion schemes. The authors research, which has utilized the techniques of continuous and pulsed photolysis and radiolysis, has focused on three general aspects of these reactions involving transition metal coordination complexes and electron donor-acceptor complexes: i) the effect of solution medium on the properties and quenching of the excited states; ii) the control of the quantum yields of formation of redox products; iii) the mechanism by which reduced species interact with water to yield H 2 homogeneously and heterogeneously. EDTA is among the most popular sacrificial electron donors used in model systems. Its role is to scavenge the oxidized form of the photosensitizer in order to prevent its rapid reaction with the reduced form of the electron relay species that results from the electron-transfer quenching of the excited photosensitizer. In systems involving MV 2+ , the radicals resulting from the oxidation of EDTA can eventually lead to the generation of a second equivalent of MV + ; the reducing agent is believed to be a radical localized on the carbon atom alpha to the carboxylate group. The reaction of radiolytically-generated OH/H with EDTA produces this radical directly via H-abstraction or indirectly via deprotonation of the carbon atom adjacent to the nitrogen radical site in the oxidized amine moiety; it reduces MV 2+ with rate constants of 2.8 x 10 9 , 7.6 x 10 9 , and 8.5 x 10 6 M -1 s -1 at pH 12.5, 8.3, and 4.7, respectively. Degradative decarboxylation of EDTA-radicals and their back electron-transfer reactions are enhanced in acidic solution causing the yield of MV + to be severely diminished

Chemisorption and Reactions of Small Molecules on Small Gold Particles

Directory of Open Access Journals (Sweden)

Geoffrey C. Bond

2012-02-01

Full Text Available The activity of supported gold particles for a number of oxidations and hydrogenations starts to increase dramatically as the size falls below ~3 nm. This is accompanied by an increased propensity to chemisorption, especially of oxygen and hydrogen. The explanation for these phenomena has to be sought in kinetic analysis that connects catalytic activity with the strength and extent of chemisorption of the reactants, the latter depending on the electronic structure of the gold atoms constituting the active centre. Examination of the changes to the utilisation of electrons as particle size is decreased points to loss of metallic character at about 3 nm, as energy bands are replaced by levels, and a band gap appears. Detailed consideration of the Arrhenius parameters (E and ln A for CO oxidation points clearly to a step-change in activity at the point where metallic character is lost, as opposed to there being a monotonic dependence of rate on a physical property such as the fraction of atoms at corners or edges of particles. The deplorable scarcity of kinetic information on other reactions makes extension of this analysis difficult, but non-metallic behaviour is an unavoidable property of very small gold particles, and therefore cannot be ignored when seeking to explain their exceptional activity.

A Small-Scale Capsule Test for Investigating the Sodium-Carbon Dioxide Reaction

Energy Technology Data Exchange (ETDEWEB)

Kim, B. H.; Choi, J. H.; Suk, S. D.; Kim, J. M.; Choi, B. H.; Kim, B. H.; Hahn, D. H

2007-01-15

The utilization of modular sodium-to-supercritical CO{sub 2} heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO{sub 2} heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO{sub 2} in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO{sub 2} would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium-CO{sub 2} reaction is virtually non-existent.

Involvement of small and medium-sized enterprises (SMEs in elaborating and implementing public policies: Study case-Romanian small and medium-sized enterprises

Directory of Open Access Journals (Sweden)

Popescu Ruxandra

2017-07-01

Full Text Available Involvement and development of the private sector in boosting the economy nationwide is a main objective of the current program of the government, which means that a good cooperation between small and medium companies, private companies and multinationals and public environment including both public institutions and policies implemented and developed by them, becomes more than necessary. The paper summarizes the findings of a quantitative research based on a self-applied questionnaire which was aimed at Romanian small and medium-sized enterprises and also of a qualitative research that gives an overview of the process of elaborating and implementing a public policy. The involvement of small and medium-sized enterprises in the process of designing and implementing a public policy can become indispensable but it is well know that there is, in fact, a lack of initiative at this level, from both parties. One of the main research questions of this paper is to find out how much do representatives of small and medium-sized enterprises get involved in the process of elaborating a public policy and how much do these actions and measures impact the organizational policies of the companies themselves. A good cooperation between the business environment and the public institutions and a strong correlation of their joint efforts, should become a common practice between both parties, being crucial that this form of cooperation to be initiated from the very beginning. The contribution of this paper is a practical one, given the fact that the paper itself entails the direct responses of small and medium-sized enterprises on the current and future public policies that directly targets them, providing as well an analysis on the effects of public policies on small and medium-sized enterprises. Thus being said, the paper can also be a guide for both small and medium-sized enterprises in providing examples and measures of involvement and favorable public policies

Study of the main parameters involved in carbothermal reduction reaction of silica aiming to obtain silicon nitride powder

International Nuclear Information System (INIS)

Rocha, J.C. da; Greca, M.C.

1989-01-01

The influence of main parameters involved in the method of silicon nitride attainment by carbothermal reduction of silica followed by nitridation were studied in isothermal experiments of fine powder mixtures of silica and graphite in a nitrogen gas flow. The time, temperature, rate C/SiO 2 and flow of nitrogen were varied since they are the main parameters involved in this kind of reaction. The products of reaction were analysed by X-ray diffraction to identify the crystalline phases and as a result was obtained the nucleation of silicon nitride phase. Meanwhile, corroborating prior results, we verified to be difficult the progress of the reaction and the inhibition of formation of silicon carbide phase, the last one being associated to the formation of silicon nitride phase due to thermodynamic matters [pt

Investigation of large α production in reactions involving weakly bound 7Li

Science.gov (United States)

Pandit, S. K.; Shrivastava, A.; Mahata, K.; Parkar, V. V.; Palit, R.; Keeley, N.; Rout, P. C.; Kumar, A.; Ramachandran, K.; Bhattacharyya, S.; Nanal, V.; Palshetkar, C. S.; Nag, T. N.; Gupta, Shilpi; Biswas, S.; Saha, S.; Sethi, J.; Singh, P.; Chatterjee, A.; Kailas, S.

2017-10-01

The origin of the large α -particle production cross sections in systems involving weakly bound 7Li projectiles has been investigated by measuring the cross sections of all possible fragment-capture as well as complete fusion using the particle-γ coincidence, in-beam, and off-beam γ -ray counting techniques for the 7Li+93Nb system at near Coulomb barrier energies. Almost all of the inclusive α -particle yield has been accounted for. While the t -capture mechanism is found to be dominant (˜70 % ), compound nuclear evaporation and breakup processes contribute ˜15 % each to the inclusive α -particle production in the measured energy range. Systematic behavior of the t capture and inclusive α cross sections for reactions involving 7Li over a wide mass range is also reported.

Transient core characteristics of small molten salt reactor coupling problem between heat transfer/flow and nuclear fission reaction

International Nuclear Information System (INIS)

Yamamoto, Takahisa; Mitachi, Koshi

2004-01-01

This paper performed the transient core analysis of a small Molten Salt Reactor (MSR). The emphasis is that the numerical model employed in this paper takes into account the interaction among fuel salt flow, nuclear reaction and heat transfer. The model consists of two group diffusion equations for fast and thermal neutron fluexs, balance equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and graphite moderator. The results of transient analysis are that (1) fission reaction (heat generation) rate significantly increases soon after step reactivity insertion, e.g., the peak of fission reaction rate achieves about 2.7 times larger than the rated power 350 MW when the reactivity of 0.15% Δk/k 0 is inserted to the rated state, and (2) the self-control performance of the small MSR effectively works under the step reactivity insertion of 0.56% Δk/k 0 , putting the fission reaction rate back on the rated state. (author)

Calculation of the energetics of chemical reactions

Energy Technology Data Exchange (ETDEWEB)

Dunning, T.H. Jr.; Harding, L.B.; Shepard, R.L.; Harrison, R.J.

1988-01-01

To calculate the energetics of chemical reactions we must solve the electronic Schroedinger equation for the molecular conformations of importance for the reactive encounter. Substantial changes occur in the electronic structure of a molecular system as the reaction progresses from reactants through the transition state to products. To describe these changes, our approach includes the following three elements: the use of multiconfiguration self-consistent field wave functions to provide a consistent zero-order description of the electronic structure of the reactants, transition state, and products; the use of configuration interaction techniques to describe electron correlation effects needed to provide quantitative predictions of the reaction energetics; and the use of large, optimized basis sets to provide the flexibility needed to describe the variations in the electronic distributions. With this approach we are able to study reactions involving as many as 5--6 atoms with errors of just a few kcal/mol in the predicted reaction energetics. Predictions to chemical accuracy, i.e., to 1 kcal/mol or less, are not yet feasible, although continuing improvements in both the theoretical methodology and computer technology suggest that this will soon be possible, at least for reactions involving small polyatomic species. 4 figs.

Advances in heterocycle synthesis via [3+m]-cycloaddition reactions involving an azaoxyallyl cation as the key intermediate.

Science.gov (United States)

Xuan, Jun; Cao, Xia; Cheng, Xiao

2018-05-17

Heterocyclic compounds are widely found in many natural isolates and medicinally relevant compounds, as well as some fine chemicals. The development of general and efficient methods for the construction of heterocyclic compounds is one of the most important tasks in synthetic organic chemistry. Along these lines, [3+m]-cycloaddition reactions involving in situ generated azaoxyallyl cations as the 3-atom units have emerged as a powerful method for the synthesis of nitrogen-containing heterocycles. In this feature article, we highlight recent advances in this rapidly growing area, mainly focusing on the reaction design as well as the reaction mechanism.

Small leak detection by measuring surface oscillation during sodium-water reaction in steam generator

International Nuclear Information System (INIS)

Nei, Hiromichi; Hori, Masao

1977-01-01

Small leak sodium-water reaction tests were conducted to develop various kinds of leak detectors for the sodium-heated steam generator in FBR. The super-heated steam was injected into sodium in a reaction vessel having a sodium free surface, simulating the steam generator. The level gauge in the reaction vessel generated the most reliable signal among detectors, as long as the leak rates were relatively high. The level gauge signal was estimated to be the sodium surface oscillation caused by hydrogen bubbles produced in sodium-water reaction. Experimental correlation was derived, predicting the amplitude as a function of leak rate, hydrogen dissolution ratio, bubble rise velocity and other parameters concerned, assuming that the surface oscillation is in proportion to the gas hold-up. The noise amplitude under normal operation without water leak was increased with sodium flow rate and found to be well correlated with Froud number. These two correlations predict that a water leak in a ''MONJU'' class (300 MWe) steam generator could possibly be detected by level gauges at a leak rate above 2 g/sec. (auth.)

Accelerating rejection-based simulation of biochemical reactions with bounded acceptance probability

Energy Technology Data Exchange (ETDEWEB)

Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento, Trento (Italy); Zunino, Roberto, E-mail: roberto.zunino@unitn.it [Department of Mathematics, University of Trento, Trento (Italy)

2016-06-14

Stochastic simulation of large biochemical reaction networks is often computationally expensive due to the disparate reaction rates and high variability of population of chemical species. An approach to accelerate the simulation is to allow multiple reaction firings before performing update by assuming that reaction propensities are changing of a negligible amount during a time interval. Species with small population in the firings of fast reactions significantly affect both performance and accuracy of this simulation approach. It is even worse when these small population species are involved in a large number of reactions. We present in this paper a new approximate algorithm to cope with this problem. It is based on bounding the acceptance probability of a reaction selected by the exact rejection-based simulation algorithm, which employs propensity bounds of reactions and the rejection-based mechanism to select next reaction firings. The reaction is ensured to be selected to fire with an acceptance rate greater than a predefined probability in which the selection becomes exact if the probability is set to one. Our new algorithm improves the computational cost for selecting the next reaction firing and reduces the updating the propensities of reactions.

Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation

KAUST Repository

Minenkov, Yury

2017-03-07

In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes of Li, Be, Na, Mg, Ca, Sr, Ba and Pb(ii). Two strategies were investigated: in the former, only valence electrons were included in the correlation treatment, giving rise to the computationally very efficient FC (frozen core) approach; in the latter, all non-ECP electrons were included in the correlation treatment, giving rise to the AE (all electron) approach. Apart from reactions involving Li and Be, the FC approach resulted in non-homogeneous performance. The FC approach leads to very small errors (<2 kcal mol-1) for some reactions of Na, Mg, Ca, Sr, Ba and Pb, while for a few reactions of Ca and Ba deviations up to 40 kcal mol-1 have been obtained. Large errors are both due to artificial mixing of the core (sub-valence) orbitals of metals and the valence orbitals of oxygen and halogens in the molecular orbitals treated as core, and due to neglecting core-core and core-valence correlation effects. These large errors are reduced to a few kcal mol-1 if the AE approach is used or the sub-valence orbitals of metals are included in the correlation treatment. On the technical side, the CCSD(T) and DLPNO-CCSD(T) results differ by a fraction of kcal mol-1, indicating the latter method as the perfect choice when the CPU efficiency is essential. For completely black-box applications, as requested in catalysis or thermochemical calculations, we recommend the DLPNO-CCSD(T) method with all electrons that are not covered by effective core potentials included in the correlation treatment and correlation-consistent polarized core valence basis sets of cc-pwCVQZ(-PP) quality.

Pore-scale studies of multiphase flow and reaction involving CO2 sequestration in geologic formations

Science.gov (United States)

Kang, Q.; Wang, M.; Lichtner, P. C.

2008-12-01

In geologic CO2 sequestration, pore-scale interfacial phenomena ultimately govern the key processes of fluid mobility, chemical transport, adsorption, and reaction. However, spatial heterogeneity at the pore scale cannot be resolved at the continuum scale, where averaging occurs over length scales much larger than typical pore sizes. Natural porous media, such as sedimentary rocks and other geological media encountered in subsurface formations, are inherently heterogeneous. This pore-scale heterogeneity can produce variabilities in flow, transport, and reaction processes that take place within a porous medium, and can result in spatial variations in fluid velocity, aqueous concentrations, and reaction rates. Consequently, the unresolved spatial heterogeneity at the pore scale may be important for reactive transport modeling at the larger scale. In addition, current continuum models of surface complexation reactions ignore a fundamental property of physical systems, namely conservation of charge. Therefore, to better understand multiphase flow and reaction involving CO2 sequestration in geologic formations, it is necessary to quantitatively investigate the influence of the pore-scale heterogeneity on the emergent behavior at the field scale. We have applied the lattice Boltzmann method to simulating the injection of CO2 saturated brine or supercritical CO2 into geological formations at the pore scale. Multiple pore-scale processes, including advection, diffusion, homogeneous reactions among multiple aqueous species, heterogeneous reactions between the aqueous solution and minerals, ion exchange and surface complexation, as well as changes in solid and pore geometry are all taken into account. The rich pore scale information will provide a basis for upscaling to the continuum scale.

Involvement of Antizyme Characterized from the Small Abalone Haliotis diversicolor in Gonadal Development.

Science.gov (United States)

Li, Wei-Dong; Huang, Min; Lü, Wen-Gang; Chen, Xiao; Shen, Ming-Hui; Li, Xiang-Min; Wang, Rong-Xia; Ke, Cai-Huan

2015-01-01

The small abalone Haliotis diversicolor is an economically important mollusk that is widely cultivated in Southern China. Gonad precocity may affect the aquaculture of small abalone. Polyamines, which are small cationic molecules essential for cellular proliferation, may affect gonadal development. Ornithine decarboxylase (ODC) and antizyme (AZ) are essential elements of a feedback circuit that regulates cellular polyamines. This paper presents the molecular cloning and characterization of AZ from small abalone. Sequence analysis showed that the cDNA sequence of H. diversicolor AZ (HdiODCAZ) consisted of two overlapping open reading frames (ORFs) and conformed to the +1 frameshift property of the frame. Thin Layer chromatography (TLC) analysis suggested that the expressed protein encoded by +1 ORF2 was the functional AZ that targets ODC to 26S proteasome degradation. The result demonstrated that the expression level of AZ was higher than that of ODC in the ovary of small abalone. In addition, the expression profiles of ODC and AZ at the different development stages of the ovary indicated that these two genes might be involved in the gonadal development of small abalone.

Expedient construction of small molecule macroarrays via sequential palladium- and copper-mediated reactions and their ex situ biological testing.

Science.gov (United States)

Frei, Reto; Breitbach, Anthony S; Blackwell, Helen E

2012-05-01

We report the highly efficient syntheses of a series of focused libraries in the small molecule macroarray format using Suzuki-Miyaura and copper-catalyzed azide-alkyne cycloaddition (or "click") reactions. The libraries were based on stilbene and triazole scaffolds, which are known to have a broad range of biological activities, including quorum-sensing (QS) modulation in bacteria. The library products were generated in parallel on the macroarray in extremely short reaction times (~10-20 min) and isolated in excellent purities. Biological testing of one macroarray library post-cleavage (ex situ) revealed several potent agonists of the QS receptor, LuxR, in Vibrio fischeri. These synthetic agonists, in contrast to others that we have reported, were only active in the presence of the native QS signal in V. fischeri, which is suggestive of a different mode of activity. Notably, the results presented herein showcase the ready compatibility of the macroarray platform with chemical reactions that are commonly utilized in small molecule probe and drug discovery today. As such, this work serves to expand the utility of the small molecule macroarray as a rapid and operationally straightforward approach toward the synthesis and screening of bioactive agents.

Reaction-based small-molecule fluorescent probes for dynamic detection of ROS and transient redox changes in living cells and small animals.

Science.gov (United States)

Lü, Rui

2017-09-01

Dynamic detection of transient redox changes in living cells and animals has broad implications for human health and disease diagnosis, because intracellular redox homeostasis regulated by reactive oxygen species (ROS) plays important role in cell functions, normal physiological functions and some serious human diseases (e.g., cancer, Alzheimer's disease, diabetes, etc.) usually have close relationship with the intracellular redox status. Small-molecule ROS-responsive fluorescent probes can act as powerful tools for dynamic detection of ROS and redox changes in living cells and animals through fluorescence imaging techniques; and great advances have been achieved recently in the design and synthesis of small-molecule ROS-responsive fluorescent probes. This article highlights up-to-date achievements in designing and using the reaction-based small-molecule fluorescent probes (with high sensitivity and selectivity to ROS and redox cycles) in the dynamic detection of ROS and transient redox changes in living cells and animals through fluorescence imaging. Copyright © 2017. Published by Elsevier Ltd.

Involvement of Antizyme Characterized from the Small Abalone Haliotis diversicolor in Gonadal Development.

Directory of Open Access Journals (Sweden)

Wei-Dong Li

Full Text Available The small abalone Haliotis diversicolor is an economically important mollusk that is widely cultivated in Southern China. Gonad precocity may affect the aquaculture of small abalone. Polyamines, which are small cationic molecules essential for cellular proliferation, may affect gonadal development. Ornithine decarboxylase (ODC and antizyme (AZ are essential elements of a feedback circuit that regulates cellular polyamines. This paper presents the molecular cloning and characterization of AZ from small abalone. Sequence analysis showed that the cDNA sequence of H. diversicolor AZ (HdiODCAZ consisted of two overlapping open reading frames (ORFs and conformed to the +1 frameshift property of the frame. Thin Layer chromatography (TLC analysis suggested that the expressed protein encoded by +1 ORF2 was the functional AZ that targets ODC to 26S proteasome degradation. The result demonstrated that the expression level of AZ was higher than that of ODC in the ovary of small abalone. In addition, the expression profiles of ODC and AZ at the different development stages of the ovary indicated that these two genes might be involved in the gonadal development of small abalone.

A STUDY ON ADVERSE DRUG REACTIONS INVOLVING CENTRAL NERVOUS SYSTEM, ITS SEVERITY AND CAUSALITY ASSESSMENT IN PEDIATRIC PATIENTS ADMITTED TO A TERTIARY CARE HOSPITAL

Directory of Open Access Journals (Sweden)

Arati

2015-09-01

Full Text Available A retrospective study was conducted in Department of pediatrics SCB Medical College and SVPPGIP for a period of 2 years i.e. September 2012 to August 2014 . All the patients from birth to 14 years admitted to the pediatric ward in this study were under ADR surveillance. Patients admitted to our hospital with adverse drug reaction o r patients developing adverse drug reaction in our hospital were studied; only those cases where the central nervous system was involved were taken in our study. The cases were compiled and the causality of offending drugs was found using WHO - UMC causality assessment score. The severity of drug reaction in every case was determined by using HARTWIG’s severity scoring scale. Total 350 Adverse reactions were reported in this period with prevalence rate of 2.04% i.e. 20 out of 1000 children faced ADR due to dr ugs, with annual incidence rate of 0.9% and 1.14% over two years. Out of total 350 cases dermatological system was most commonly involved i.e. 207 cases (59.14%. This is followed by involvement of central nervous system 46 number of cases (13.14%. The GI system was involved in 34 cases i.e. (9.71%. Life threatening reactions like anaphylaxis, angioedema and shock like immediate life threatening ADRs were reported in 16 cases. Our study group was the patient in whom the ADR involved the CNS. Out of 46 suc h cases, there were 25 female and 21 male. Various reaction due to drug were encephalopathy , eps, febrile seizure, tremor, head reeling, ototoxicity, persistant cry, pseudotumor cerebri, psychosis, seizure, status epilepticus, toxic amblyopia, tremor, atax ia etc. The most common CNS manifestation was Extra pyramidal side effects (EPS involving 21% of cases. The most common Drug causing CNS manifestation was ATT (HRZE causing blindness, Eps, psychosis , toxic amblyopia blindness etc.

Flat Graphene-Enhanced Electron Transfer Involved in Redox Reactions.

Science.gov (United States)

Pan, Meilan; Zhang, Yanyang; Shan, Chao; Zhang, Xiaolin; Gao, Guandao; Pan, Bingcai

2017-08-01

Graphene is easily warped in the out-of-plane direction because of its high in-plane Young's modulus, and exploring the influence of wrinkled graphene on its properties is essential for the design of graphene-based materials for environmental applications. Herein, we prepared wrinkled graphene (WGN-1 and WGN-2) by thermal treatment and compared their electrochemical properties with those of flat graphene nanosheets (FGN). FGN exhibit activities that are much better than those of wrinkled graphene nanosheets (WGN), not only in the electrochemical oxidation of methylene blue (MB) but also in the electrochemical reduction of nitrobenzene (NB). Transformation ratios of MB and NB in FGN, WGN-1, and WGN-2 were 97.5, 80.1, and 57.9% and 94.6, 92.1, and 81.2%, respectively. Electrochemical impedance spectroscopy and the surface resistance of the graphene samples increased in the following order: FGN reaction charges transfer faster across the reaction interfaces and along the surface of FGN than that of WGN, and wrinkles restrict reaction charge transfer and reduce the reaction rates. This study reveals that the morphology of the graphene (flat or wrinkle) greatly affects redox reaction activities and may have important implications for the design of novel graphene-based nanostructures and for our understanding of graphene wrinkle-dependent redox reactions in environmental processes.

Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation.

Science.gov (United States)

Minenkov, Yury; Bistoni, Giovanni; Riplinger, Christoph; Auer, Alexander A; Neese, Frank; Cavallo, Luigi

2017-04-05

In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes of Li, Be, Na, Mg, Ca, Sr, Ba and Pb(ii). Two strategies were investigated: in the former, only valence electrons were included in the correlation treatment, giving rise to the computationally very efficient FC (frozen core) approach; in the latter, all non-ECP electrons were included in the correlation treatment, giving rise to the AE (all electron) approach. Apart from reactions involving Li and Be, the FC approach resulted in non-homogeneous performance. The FC approach leads to very small errors (correlation effects. These large errors are reduced to a few kcal mol -1 if the AE approach is used or the sub-valence orbitals of metals are included in the correlation treatment. On the technical side, the CCSD(T) and DLPNO-CCSD(T) results differ by a fraction of kcal mol -1 , indicating the latter method as the perfect choice when the CPU efficiency is essential. For completely black-box applications, as requested in catalysis or thermochemical calculations, we recommend the DLPNO-CCSD(T) method with all electrons that are not covered by effective core potentials included in the correlation treatment and correlation-consistent polarized core valence basis sets of cc-pwCVQZ(-PP) quality.

Graft-versus-host reaction in small-bowel transplantation and possibilities for its circumvention.

Science.gov (United States)

Watanabe, K; Yagi, T; Iwagaki, H; Kimura, Y; Mitsuoka, N; Inagaki, M; Tanaka, S; Tanaka, N

2001-01-01

To study graft-versus-host reaction (GVHR) in small-bowel transplantation and its underlying mechanisms and to find methods for circumventing GVHR, we used an unidirectional GVHR model in which F1 Lewis (LEW) x Wistar King A (WKA) hybrid rats received small-bowel transplants from either LEW or WKA parent rats. The survival time of F1 hybrid rats that received full-length small-bowel transplantation from LEW and WKA was 16.3+/-2.1 days and 18.2+/-3.4 days, respectively. When one-quarter of LEW small bowel was transplanted to an F1 hybrid recipient, the survival time was significantly longer at 44.0+/-23.4 days compared with rats that had received full-length LEW small-bowel transplantation. The survival time of F1 hybrid rats which received an injection of high-dose (5 x 10(8) cells) LEW or WKA spleen cells was 11.9+/-4.0 days and 13.1+/-3.6 days, respectively. However, when an injection containing a low dose (1 x 108 cells) of LEW spleen cells was used, survival was > 100 days, showing significance compared with the survival of rats receiving the higher dose LEW spleen-cell injection. Both small-bowel transplantation and spleen-cell injection were compared for the effective period of recipient resistance to donor cell or small-bowel transplantation as second challenge. When the F1 rats given a quarter LEW small-bowel transplant as first challenge were treated with a high-dose of spleen cells 30 days after transplantation, they survived for > 30 days without GVHR. F1 rats that were treated with a low-dose LEW spleen-cell injection, followed 30 days later by full LEW small-bowel transplantation, had a survival time of > 100 days. These results indicate that segmental small-bowel transplantation and spleen-cell injection as first challenge may facilitate the prevention of GVHR, resulting in resistance to subsequent immunological challenge.

Hot atom reactions involving multivalent and univalent species. Progress report, February 1979-January 1980

International Nuclear Information System (INIS)

Tang, Y.N.

1980-01-01

The major progress during this period was in the study of recoil 31 Si and recoil 11 C reactions and in the initiation of the studies on the interaction of molecular tritium on solid surfaces. For the recoil 31 Si systems, heterogeneous hydrogenation experiments have been designed to positively confirm that a major unknown product, derived from the interaction of 31 Si atoms with 1,3-butadiene, is 1-silacyclopenta-2,4-diene. This compound has been shown to be very sensitive to γ-ray irradiation and to be thermally unstable at a temperature higher than 100 0 C. Another recoil 31 Si experiment was designed to review the mechanism of the 31 Si abstraction reactions. From the fact that high yields of [ 31 Si]-1-fluorosilacyclopent-3-ene were obtained as a product from a mixture of PH 3 and PF 3 together with 1,3-butadiene, the stepwise abstraction mechanism is definitely much more predominant than the possible simultaneous abstraction. Other recoil 31 Si works involved a detailed systematic composition study of 31 SiF 2 reactions with 1,3-butadiene, some neon moderator studies, and the continuation of the studies on the reactions of 31 SiF 2 and 31 SiH 2 with conjugated hexadienes. By using 2- 14 C-propanone and 1,3- 14 C-propanone, the mechanism of solvent-free oxidative cleavage of propanone by KMnO 4 was elucidated. Information thus derived was used to degradate the 11 C-labelled propadiene derived from the reactions of recoil 11 C atoms with ethylene. Results indicate that 73% of the 11 C-labelled propadiene was center-labelled. This value was observed to change with additives. Various mechanistic studies on the heterogeneous interactions of molecular T 2 on solid surfaces such as Pd supported on active carbon have been initiated

Rates for some reactions involving 42Ca and 44Ca

International Nuclear Information System (INIS)

Cheng, C.W.; King, J.D.

1980-01-01

Ground-state reaction rates have been deduced from recent cross section measurements for the 42 CA(α, n) 45 Ti, 42 Ca(p, γ) 43 Sc, and 44 Ca(p, n) 44 Sc reactions. Comparison of these rates with those calculated from a statistical model of nuclear reactions. (Woosley et al) shows good agreement for the first two, but the 44 Ca(p, n) rate is more than a factor of 2 less than the theoretical prediction. Stellar reaction rates have been derived from the ground-state rates by multiplying the ground-state rates by the ratio of stellar to ground-state rates given by the statistical model. Both ground-state and stellar rates have been represented by analytic functions of the temperature. The role of these reactions in the approach to quasi-equilibrium during explosive silicon burning is discussed

Kinetics of isotope exchange reactions involving intra- and intermolecular reactions: 1. Rate law for a system with two chemical compounds and three exchangeable atoms

International Nuclear Information System (INIS)

Xuelei Chu; Ohmoto, Hiroshi

1991-01-01

For an isotopic exchange reaction between two compounds (X and AB) in a homogeneous system, such as a gaseous or aqueous system, where one (AB) of them possesses two exchangeable atoms in non-equivalent positions and where one intramolecular isotope exchange (A ↔ B) and two intermolecular isotope exchange reactions (X ↔ A and X ↔ B) may occur, its rate law no longer obeys a pseudo-first order rate equation described for simple two-component systems by many previous investigators. The change with time of the δ value of each of the three components (X, A, and B) in a closed and homogeneous system is a complicated function of the initial δ values of the three components, the chemical concentrations of the two compounds, and the overall rate constants of the forward and reverse reactions involving the two intermolecular and one intramolecular reactions of isotope exchanges. Also, for some one of the three components, the change of its δ value with time may not be monotonic, and the relationship of 1n (1 - F) with time may be non-linear in a plot of 1n (1 - F) vs. t. In addition, the rate law of the isotope exchange reaction in this system also provides a quantitative method to estimate the overall rate constants for the one-intra-and two intermolecular isotope exchanges and the equilibrium isotopic fractionation factors among the three components

The Atmospherically Important Reaction of Hydroxyl Radicals with Methyl Nitrate: A Theoretical Study Involving the Calculation of Reaction Mechanisms, Enthalpies, Activation Energies, and Rate Coefficients.

Science.gov (United States)

Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M

2017-09-07

A theoretical study, involving the calculation of reaction enthalpies, activation energies, mechanisms, and rate coefficients, was made of the reaction of hydroxyl radicals with methyl nitrate, an important process for methyl nitrate removal in the earth's atmosphere. Four reaction channels were considered: formation of H 2 O + CH 2 ONO 2 , CH 3 OOH + NO 2 , CH 3 OH + NO 3 , and CH 3 O + HNO 3 . For all channels, geometry optimization and frequency calculations were performed at the M06-2X/6-31+G** level, while relative energies were improved at the UCCSD(T*)-F12/CBS level. The major channel is found to be the H abstraction channel, to give the products H 2 O + CH 2 ONO 2 . The reaction enthalpy (ΔH 298 K RX ) of this channel is computed as -17.90 kcal mol -1 . Although the other reaction channels are also exothermic, their reaction barriers are high (>24 kcal mol -1 ), and therefore these reactions do not contribute to the overall rate coefficient in the temperature range considered (200-400 K). Pathways via three transition states were identified for the H abstraction channel. Rate coefficients were calculated for these pathways at various levels of variational transition state theory including tunneling. The results obtained are used to distinguish between two sets of experimental rate coefficients, measured in the temperature range of 200-400 K, one of which is approximately an order of magnitude greater than the other. This comparison, as well as the temperature dependence of the computed rate coefficients, shows that the lower experimental values are favored. The implications of the results to atmospheric chemistry are discussed.

Hot atom reactions involving multivalent and univalent species. Progress report, February 1979-January 1980

Energy Technology Data Exchange (ETDEWEB)

Tang, Y.N.

1980-01-01

The major progress during this period was in the study of recoil /sup 31/Si and recoil /sup 11/C reactions and in the initiation of the studies on the interaction of molecular tritium on solid surfaces. For the recoil /sup 31/Si systems, heterogeneous hydrogenation experiments have been designed to positively confirm that a major unknown product, derived from the interaction of /sup 31/Si atoms with 1,3-butadiene, is 1-silacyclopenta-2,4-diene. This compound has been shown to be very sensitive to ..gamma..-ray irradiation and to be thermally unstable at a temperature higher than 100/sup 0/C. Another recoil /sup 31/Si experiment was designed to review the mechanism of the /sup 31/Si abstraction reactions. From the fact that high yields of (/sup 31/Si)-1-fluorosilacyclopent-3-ene were obtained as a product from a mixture of PH/sub 3/ and PF/sub 3/ together with 1,3-butadiene, the stepwise abstraction mechanism is definitely much more predominant than the possible simultaneous abstraction. Other recoil /sup 31/Si works involved a detailed systematic composition study of /sup 31/SiF/sub 2/ reactions with 1,3-butadiene, some neon moderator studies, and the continuation of the studies on the reactions of /sup 31/SiF/sub 2/ and /sup 31/SiH/sub 2/ with conjugated hexadienes. By using 2-/sup 14/C-propanone and 1,3-/sup 14/C-propanone, the mechanism of solvent-free oxidative cleavage of propanone by KMnO/sub 4/ was elucidated. Information thus derived was used to degradate the /sup 11/C-labelled propadiene derived from the reactions of recoil /sup 11/C atoms with ethylene. Results indicate that 73% of the /sup 11/C-labelled propadiene was center-labelled. This value was observed to change with additives. Various mechanistic studies on the heterogeneous interactions of molecular T/sub 2/ on solid surfaces such as Pd supported on active carbon have been initiated.

Matrix isolation as a tool for studying interstellar chemical reactions

Science.gov (United States)

Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

1989-01-01

Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

A Detailed Chemical Kinetic Reaction Mechanism for Oxidation of Four Small Alkyl Esters in Laminar Premixed Flames

Energy Technology Data Exchange (ETDEWEB)

Westbrook, C K; Pitz, W J; Westmoreland, P R; Dryer, F L; Chaos, M; Osswald, P; Kohse-Hoinghaus, K; Cool, T A; Wang, J; Yang, B; Hansen, N; Kasper, T

2008-02-08

A detailed chemical kinetic reaction mechanism has been developed for a group of four small alkyl ester fuels, consisting of methyl formate, methyl acetate, ethyl formate and ethyl acetate. This mechanism is validated by comparisons between computed results and recently measured intermediate species mole fractions in fuel-rich, low pressure, premixed laminar flames. The model development employs a principle of similarity of functional groups in constraining the H atom abstraction and unimolecular decomposition reactions in each of these fuels. As a result, the reaction mechanism and formalism for mechanism development are suitable for extension to larger oxygenated hydrocarbon fuels, together with an improved kinetic understanding of the structure and chemical kinetics of alkyl ester fuels that can be extended to biodiesel fuels. Variations in concentrations of intermediate species levels in these flames are traced to differences in the molecular structure of the fuel molecules.

Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

Science.gov (United States)

Liechty, Derek S.; Lewis, Mark J.

2010-01-01

Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

Chemistry in interstellar space. [environment characteristics influencing reaction dynamics

Science.gov (United States)

Donn, B.

1973-01-01

The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.

Reaction of uranium and the fluorocarbon FC-75

Science.gov (United States)

Young, R. H.

1985-04-01

Because of criticality concerns with water cooling in enriched uranium upgrading, a fluorocarbon has been evaluated as a replacement coolant for internal module components in the Plasma Separation Process (PSP). The interaction of bulk uranium and of powdered uranium with FC-75 has been investigated at temperatures between 200 and 700 C. The gas pressure and the metal temperature were monitored as a function of time. Modest temperature changes of 50 to 100 C were observed for the bulk uranium/fluorocarbon reaction. Much larger changes (up to 1000 C) were noted for the reaction involving high surface area uranium powder. These temperature transients, particularly for the powdered uranium reaction, were short-lived ( 10 seconds) and indicative of the formation of a protective layer of reaction products. Analysis of residual gas products by infrared spectroscopy indicated that one potentially serious hazard, UF6, was not present; however, several small toxic fluorocarbons were produced by thermolysis and/or reaction. X-ray diffraction analysis of the residual solids indicated UF4 and UO2 were the major solid products.

Evaluation of Different Normalization and Analysis Procedures for Illumina Gene Expression Microarray Data Involving Small Changes

Science.gov (United States)

Johnstone, Daniel M.; Riveros, Carlos; Heidari, Moones; Graham, Ross M.; Trinder, Debbie; Berretta, Regina; Olynyk, John K.; Scott, Rodney J.; Moscato, Pablo; Milward, Elizabeth A.

2013-01-01

While Illumina microarrays can be used successfully for detecting small gene expression changes due to their high degree of technical replicability, there is little information on how different normalization and differential expression analysis strategies affect outcomes. To evaluate this, we assessed concordance across gene lists generated by applying different combinations of normalization strategy and analytical approach to two Illumina datasets with modest expression changes. In addition to using traditional statistical approaches, we also tested an approach based on combinatorial optimization. We found that the choice of both normalization strategy and analytical approach considerably affected outcomes, in some cases leading to substantial differences in gene lists and subsequent pathway analysis results. Our findings suggest that important biological phenomena may be overlooked when there is a routine practice of using only one approach to investigate all microarray datasets. Analytical artefacts of this kind are likely to be especially relevant for datasets involving small fold changes, where inherent technical variation—if not adequately minimized by effective normalization—may overshadow true biological variation. This report provides some basic guidelines for optimizing outcomes when working with Illumina datasets involving small expression changes. PMID:27605185

Reactions of carbon atoms in pulsed molecular beams

Energy Technology Data Exchange (ETDEWEB)

Reisler, H. [Univ. of Southern California, Los Angeles (United States)

1993-12-01

This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

A novel polymerase chain reaction (PCR) - denaturing gradient gel electrophoresis (DGGE) for the identification of Micrococcaceae strains involved in meat fermentations. Its application to naturally fermented Italian sausages.

Science.gov (United States)

Cocolin, L; Manzano, M; Aggio, D; Cantoni, C; Comi, G

2001-05-01

A new molecular method consisting of polymerase chain reaction (PCR) amplification and denaturing gradient gel electrophoresis (DGGE) of a small fragment from the 16S rRNA gene identified the Micrococcaceae strains isolated from natural fermented Italian sausages. Lactic acid bacteria, total aerobic mesophilic flora, Enterobacteriaceae and faecal enterococci were also monitored. Micrococcaceaea control strains from international collections were used to optimise the method and 90 strains, isolated from fermented sausages, were identified by biochemical tests and PCR-DGGE. No differences were observed between the methods used. The results reported in this paper prove that Staphylococcus xylosus is the main bacterium involved in fermented sausage production, representing, from the tenth day of ripening, the only Micrococcaceaea species isolated.

A fast-fission component with small mass drift in the reaction 84Kr + 27Al at ELab = 5.9 MeV/u

International Nuclear Information System (INIS)

Heusch, B.; Freiesleben, H.; Schneider, W.F.W.; Kohlmeyer, B.; Stege, H.; Puehlhofer, F.

1985-01-01

All reaction products in the range from target- and projectile-like to fission-like fragments were measured for the system 84 Kr + 27 Al at 5.9 MeV/u beam energy. They are assigned to the various reaction mechanisms on the basis of experimental signatures (energy dissipation, mass and angular distribution). The sum of the measured partial cross sections, including the evaporation residue yield obtained previously, agrees with the total reaction cross section derived from elastic scattering. A small fast-fission component was found, discernible from deep-inelastic reactions by its 1/sinθ angular distribution, and distinguished from compound-nucleus fission by an incomplete mass asymmetry relaxation

Quantum indistinguishability in chemical reactions.

Science.gov (United States)

Fisher, Matthew P A; Radzihovsky, Leo

2018-05-15

Quantum indistinguishability plays a crucial role in many low-energy physical phenomena, from quantum fluids to molecular spectroscopy. It is, however, typically ignored in most high-temperature processes, particularly for ionic coordinates, implicitly assumed to be distinguishable, incoherent, and thus well approximated classically. We explore enzymatic chemical reactions involving small symmetric molecules and argue that in many situations a full quantum treatment of collective nuclear degrees of freedom is essential. Supported by several physical arguments, we conjecture a "quantum dynamical selection" (QDS) rule for small symmetric molecules that precludes chemical processes that involve direct transitions from orbitally nonsymmetric molecular states. As we propose and discuss, the implications of the QDS rule include ( i ) a differential chemical reactivity of para- and orthohydrogen, ( ii ) a mechanism for inducing intermolecular quantum entanglement of nuclear spins, ( iii ) a mass-independent isotope fractionation mechanism, ( iv ) an explanation of the enhanced chemical activity of "reactive oxygen species", ( v ) illuminating the importance of ortho-water molecules in modulating the quantum dynamics of liquid water, and ( vi ) providing the critical quantum-to-biochemical linkage in the nuclear spin model of the (putative) quantum brain, among others.

Indirect Measurements for (p,α) Reactions Involving Boron Isotopes

International Nuclear Information System (INIS)

Lamia, L.; Spitaleri, C.; Romano, S.; Cherubini, S.; Crucilla, V.; Gulino, M.; La Cognata, M.; Pizzone, R. G.; Puglia, S. M. R.; Sergi, M. L.; Tudisco, S.; Tumino, A.; Carlin, N.; Szanto, M. G. del; Liguori Neto, R.; Moura, M. M. de; Munhoz, M. G.; Souza, F. A.; Suaide, A. A. P.; Szanto, E.

2008-01-01

Light elements lithium, beryllium and boron (LiBeB) were used in the last years as 'possible probe' for a deeper understanding of some extra-mixing phenomena occurring in young Main-Sequence stars. They are mainly destroyed by (p,α) reactions and cross section measurements for such channels are then needed. The Trojan Horse Method (THM) allows one to extract the astrophysical S(E)-factor without the experience of tunneling through the Coulomb barrier. In this work a resume of the recent results about the 11 B(p,α 0 ) 8 Be and 10 B(p,α) 7 Be reactions is shown

Mannose receptor may be involved in small ruminant lentivirus pathogenesis

Directory of Open Access Journals (Sweden)

Crespo Helena

2012-05-01

Full Text Available Abstract Thirty-one sheep naturally infected with small ruminant lentiviruses (SRLV of known genotype (A or B, and clinically affected with neurological disease, pneumonia or arthritis were used to analyse mannose receptor (MR expression (transcript levels and proviral load in virus target tissues (lung, mammary gland, CNS and carpal joints. Control sheep were SRLV-seropositive asymptomatic (n = 3, seronegative (n = 3 or with chronic listeriosis, pseudotuberculosis or parasitic cysts (n = 1 in each case. MR expression and proviral load increased with the severity of lesions in most analyzed organs of the SRLV infected sheep and was detected in the affected tissue involved in the corresponding clinical disease (CNS, lung and carpal joint in neurological disease, pneumonia and arthritis animal groups, respectively. The increased MR expression appeared to be SRLV specific and may have a role in lentiviral pathogenesis.

Insight into the Reaction Mechanism of Graphene Oxide with Oxidative Free Radical

Institute of Scientific and Technical Information of China (English)

ZHOU Xuejiao; XU Liangyou

2017-01-01

Graphene oxide(GO),as an important derivative of graphene,could be considered as a super aromatic molecule decorated with a range of reactive oxygen-containing groups on its surface,which endows graphene high reactivity with other molecules.In our previous work,we demonstrated that GO sheets were cut into small pieces(graphene quantum dots,GQDs) by oxidative free radicals(hydroxyl radical HO or oxygen radical [O]) under UV irradiation.It is notable that reactions involving free radicals are influenced by reaction conditions pronouncedly.However,researches on details about reactions of GO with free radicals have not been reported thus far.In this work,the effects of different factors on the photo-Fenton reaction of GO were studied.It is demonstrated that the reaction rate is closely related to the concentration of free radicals.It is speculated that through the optimization of reaction conditions,the reaction of graphene with free radicals could carry out efficiently for further applications.

Switching dynamics in reaction networks induced by molecular discreteness

International Nuclear Information System (INIS)

Togashi, Yuichi; Kaneko, Kunihiko

2007-01-01

To study the fluctuations and dynamics in chemical reaction processes, stochastic differential equations based on the rate equation involving chemical concentrations are often adopted. When the number of molecules is very small, however, the discreteness in the number of molecules cannot be neglected since the number of molecules must be an integer. This discreteness can be important in biochemical reactions, where the total number of molecules is not significantly larger than the number of chemical species. To elucidate the effects of such discreteness, we study autocatalytic reaction systems comprising several chemical species through stochastic particle simulations. The generation of novel states is observed; it is caused by the extinction of some molecular species due to the discreteness in their number. We demonstrate that the reaction dynamics are switched by a single molecule, which leads to the reconstruction of the acting network structure. We also show the strong dependence of the chemical concentrations on the system size, which is caused by transitions to discreteness-induced novel states

The small nucleoid protein Fis is involved in Vibrio cholerae quorum sensing.

Science.gov (United States)

Lenz, Derrick H; Bassler, Bonnie L

2007-02-01

Quorum sensing is a process of cell-cell communication that bacteria use to relay information to one another about the cell density and species composition of the bacterial community. Quorum sensing involves the production, secretion and population-wide detection of small signalling molecules called autoinducers. This process allows bacteria to synchronize group behaviours and act as multicellular units. The human pathogen, Vibrio cholerae, uses quorum sensing to co-ordinate such complex behaviours as pathogenicity and biofilm formation. The quorum-sensing circuit of V. cholerae consists of two autoinducer/sensor systems, CAI-1/CqsS and AI-2/LuxPQ, and the VarS/A-CsrA/BCD growth-phase regulatory system. Genetic analysis suggests that an additional regulatory arm involved in quorum sensing exists in V. cholerae. All of these systems channel information into the histidine phosphotransfer protein, LuxU, and/or the response regulator, LuxO. LuxO, when phosphorylated, activates the expression of four genes encoding the Qrr (quorum regulatory RNAs) small RNAs (sRNAs). The Qrr sRNAs destabilize the hapR transcript encoding the master regulator of quorum sensing, HapR. Here we identify the nucleoid protein Fis as playing a major role in the V. cholerae quorum-sensing circuit. Fis fulfils the predictions required to be the putative additional component that inputs information into the cascade: its expression is regulated in a growth phase-dependent manner; it requires LuxO but acts independently of LuxU, and it regulates all four qrr genes and, in turn, HapR by directly binding to the qrr gene promoters and modulating their expression.

Free Br atom and free radical reactions in the radiolysis of 1,2 dibromoethane (DBE) in air free aqueous solutions

International Nuclear Information System (INIS)

Lal, Manohar

1986-01-01

G(Br - ) have been reported in the free radical degradation of 1,2 DBE in Ar - and N 2 O-saturated solutions. It is clear from the results that a small chain reaction occurs, t-butanol radical reacts with 1,2 DBE to give Br - . At pH 12.3, high (Br - ) are attributed to another chain reaction involving O - radical anion. Dose rate studies confirm the occurrence of chain reaction. (author). 5 refs

Characterization of low-energy nuclear reactions involving emission of few non-relativistic particles

International Nuclear Information System (INIS)

Martinez Heimann, D.; Pacheco, A.J.; Capurro, O.A.

2010-01-01

We present a general procedure and the associated computational tool for the kinematical description and characterization of nuclear reactions with several fragments in the exit channel. For such processes the emphasis is placed on the purely experimental extraction of the most physically relevant magnitudes and their distributions, which can eventually be compared with the results of generic model calculations. The general capabilities of the approach are illustrated through the results of the application to selected examples, for which various aspects related to inclusive and exclusive measurements are discussed. For the particular case of sequential emission or non-capture breakup we analyze the general problem involved in the determination of intrinsic angular distributions in the rest frame of the decaying nucleus and the design of a specific experiment for a full and uniform coverage of the whole solid angle.

Effects of hydroxylated benzaldehyde derivatives on radiation-induced reactions involving various organic radicals

Science.gov (United States)

Ksendzova, G. A.; Samovich, S. N.; Sorokin, V. L.; Shadyro, O. I.

2018-05-01

In the present paper, the effects of hydroxylated benzaldehyde derivatives and gossypol - the known natural occurring compound - on formation of decomposition products resulting from radiolysis of ethanol and hexane in deaerated and oxygenated solutions were studied. The obtained data enabled the authors to make conclusions about the effects produced by the structure of the compounds under study on their reactivity towards oxygen- and carbon-centered radicals. It has been found that 2,3-dihydroxybenzaldehyde, 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde and 4,6-di-tert-butyl-3-(1,3-dioxane-2-yl)-1,2-dihydroxybenzene are not inferior in efficiency to butylated hydroxytoluene - the industrial antioxidant - as regards suppression of the radiation-induced oxidation processes occurring in hexane. The derivatives of hydroxylated benzaldehydes were shown to have a significant influence on radiation-induced reactions involving α-hydroxyalkyl radicals.

Monitoring, Modeling, and Diagnosis of Alkali-Silica Reaction in Small Concrete Samples

Energy Technology Data Exchange (ETDEWEB)

Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Gribok, Andrei V. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-09-01

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This report describes alkali-silica reaction (ASR) degradation mechanisms and factors influencing the ASR. A fully coupled thermo-hydro-mechanical-chemical model developed by Saouma and Perotti by taking into consideration the effects of stress on the reaction kinetics and anisotropic volumetric expansion is presented in this report. This model is implemented in the GRIZZLY code based on the Multiphysics Object Oriented Simulation Environment. The implemented model in the GRIZZLY code is randomly used to initiate ASR in a 2D and 3D lattice to study the percolation aspects of concrete. The percolation aspects help determine the transport properties of the material and therefore the durability and service life of concrete. This report summarizes the effort to develop small-size concrete samples with embedded glass to mimic ASR. The concrete samples were treated in water and sodium hydroxide solution at elevated temperature to study how ingress of sodium ions and hydroxide ions at elevated temperature impacts concrete samples embedded with glass. Thermal camera was used to monitor the changes in the concrete sample and results are summarized.

Comparison of treatment outcomes between involved-field and elective nodal irradiation in limited-stage small cell lung cancer

International Nuclear Information System (INIS)

Han, Tae-Jin; Kim, Hak-Jae; Wu, Hong-Gyun; Heo, Dae-Seog; Kim, Young-Whan; Lee, Se-Hoon

2012-01-01

The present study was performed to assess the usefulness of involved-field irradiation and the impact of 18 F-fluorodeoxyglucose-positron emission tomography-based staging on treatment outcomes in limited-stage small cell lung cancer. Eighty patients who received definitive chemoradiotherapy for limited-stage small cell lung cancer were retrospectively analyzed. Fifty patients were treated with involved-field irradiation, which means that the radiotherapy portal includes only clinically identifiable tumors. The other 30 patients were irradiated with a comprehensive portal, including uninvolved mediastinal and/or supraclavicular lymph nodes, so-called elective nodal irradiation. No significant difference was seen in clinical factors between the two groups. At a median follow-up of 27 months (range, 5-75 months), no significant differences were observed in 3 year overall survival (44.6 vs. 54.1%, P=0.220) and 3 year progression-free survival (24.4 vs. 42.8%, P=0.133) between the involved-field irradiation group and the elective nodal irradiation group, respectively. For patients who did not undergo positron emission tomography scans, 3 year overall survival (29.3 vs. 56.3%, P=0.022) and 3 year progression-free survival (11.0 vs. 50.0%, P=0.040) were significantly longer in the elective nodal irradiation group. Crude incidences of isolated nodal failure were 6.0% in the involved-field irradiation group and 0% in the elective nodal irradiation group, respectively. All isolated nodal failures were developed in patients who had not undergone positron emission tomography scans in their initial work-ups. If patients did not undergo positron emission tomography-based staging, the omission of elective nodal irradiation resulted in impaired survival outcomes and raised the risk of isolated nodal failure. Therefore, involved-field irradiation for limited-stage small cell lung cancer might be reasonable only with positron emission tomography scan implementation. (author)

Kinetic parameters of hydroprocessing reactions in a flow reactor

Energy Technology Data Exchange (ETDEWEB)

Raychaudhuri, U.; Banerjee, T.S.; Ghar, R.N. (Indian Institute of Technology, Kharagpur (India))

1994-01-01

The change in distillation properties of a blend of light and heavy distillates over a commercial hydrotreating catalyst was studied using a small packed bed reactor. The results were interpreted assuming a pseudo-component model that took into account the physical and chemical complexity of the system. A first order series-parallel reaction mechanism was found to be valid for the operating conditions involved. Pore diffusion effects were also taken into consideration. 8 refs., 7 figs., 1 tab.

Extension of a Kinetic Approach to Chemical Reactions to Electronic Energy Levels and Reactions Involving Charged Species with Application to DSMC Simulations

Science.gov (United States)

Liechty, Derek S.

2014-01-01

The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties are extended in the current work to include electronic energy level transitions and reactions involving charged particles. These extensions are shown to agree favorably with reported transition and reaction rates from the literature for near-equilibrium conditions. Also, the extensions are applied to the second flight of the Project FIRE flight experiment at 1634 seconds with a Knudsen number of 0.001 at an altitude of 76.4 km. In order to accomplish this, NASA's direct simulation Monte Carlo code DAC was rewritten to include the ability to simulate charge-neutral ionized flows, take advantage of the recently introduced chemistry model, and to include the extensions presented in this work. The 1634 second data point was chosen for comparisons to be made in order to include a CFD solution. The Knudsen number at this point in time is such that the DSMC simulations are still tractable and the CFD computations are at the edge of what is considered valid because, although near-transitional, the flow is still considered to be continuum. It is shown that the inclusion of electronic energy levels in the DSMC simulation is necessary for flows of this nature and is required for comparison to the CFD solution. The flow field solutions are also post-processed by the nonequilibrium radiation code HARA to compute the radiative portion.

Direct Reactions

Energy Technology Data Exchange (ETDEWEB)

Austern, N. [University of Pittsburgh, Pittsburgh, PA (United States)

1963-01-15

In order to give a unified presentation of one point of view, these lectures are devoted only to a detailed development of the standard theories of direct reactions, starting from basic principles. Discussion is given of the present status of the theories, of the techniques used for practical calculation, and of possible future developments. The direct interaction (DI) aspects of a reaction are those which involve only a few of the many degrees of freedom of a nucleus. In fact the minimum number of degrees of freedom which must be involved in a reaction are those required to describe the initial and final channels, and DI studies typically consider these degrees of freedom and no others. Because of this simplicity DI theories may be worked out in painstaking detail. DI processes concern only part of the wave function for a problem. The other part involves complicated excitations of many degrees of freedom, and gives the compound nucleus (CN) effects. While it is extremely interesting to learn how to separate DI and CN effects in an orderly manner, if they are both present in a reaction, no suitable method has yet been found. Instead, current work stresses the kinds of reactions and the kinds of final states in which DI effects dominate and in which CN effects may almost be forgotten. The DI cross-sections which are studied are often extremely large, comparable to elastic scattering cross-sections. (author)

Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave Overpressure Impacts

Science.gov (United States)

2017-11-01

Many TBIs are associated with blast from improvised explosive devices.2–4 Explosions are physical, chemical , or nuclear reactions involving a rapid...ARL-TR-8210 ● NOV 2017 US Army Research Laboratory Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave...Research Laboratory Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave Overpressure Impacts by Nicole E Zander, Thuvan

Clinical Characteristics, Electrophysiology, and Skin Biopsy of 38 Peripheral Neuropathy Cases with Small Fiber Involvement of Various Etiologies

Directory of Open Access Journals (Sweden)

Bo Sun

2017-01-01

Conclusions: IENFD of patients included in the present study weakly correlated with various electrophysiological parameters. Small and large fibers are more involved in patients with MS-related PN than in patients with idiopathic PN.

γ-Particle coincidence technique for the study of nuclear reactions

Science.gov (United States)

Zagatto, V. A. B.; Oliveira, J. R. B.; Allegro, P. R. P.; Chamon, L. C.; Cybulska, E. W.; Medina, N. H.; Ribas, R. V.; Seale, W. A.; Silva, C. P.; Gasques, L. R.; Zahn, G. S.; Genezini, F. A.; Shorto, J. M. B.; Lubian, J.; Linares, R.; Toufen, D. L.; Silveira, M. A. G.; Rossi, E. S.; Nobre, G. P.

2014-06-01

The Saci-Perere γ ray spectrometer (located at the Pelletron AcceleratorLaboratory - IFUSP) was employed to implement the γ-particle coincidence technique for the study of nuclear reaction mechanisms. For this, the 18O+110Pd reaction has been studied in the beam energy range of 45-54 MeV. Several corrections to the data due to various effects (energy and angle integrations, beam spot size, γ detector finite size and the vacuum de-alignment) are small and well controlled. The aim of this work was to establish a proper method to analyze the data and identify the reaction mechanisms involved. To achieve this goal the inelastic scattering to the first excited state of 110Pd has been extracted and compared to coupled channel calculations using the São Paulo Potential (PSP), being reasonably well described by it.

γ-Particle coincidence technique for the study of nuclear reactions

Energy Technology Data Exchange (ETDEWEB)

Zagatto, V.A.B., E-mail: vinicius.zagatto@gmail.com [Instituto de Física da Universidade de São Paulo (Brazil); Oliveira, J.R.B.; Allegro, P.R.P.; Chamon, L.C.; Cybulska, E.W.; Medina, N.H.; Ribas, R.V.; Seale, W.A.; Silva, C.P.; Gasques, L.R. [Instituto de Física da Universidade de São Paulo (Brazil); Zahn, G.S.; Genezini, F.A.; Shorto, J.M.B. [Instituto de Pesquisas Energéticas e Nucleares (Brazil); Lubian, J.; Linares, R. [Instituto de Física da Universidade Federal Fluminense (Brazil); Toufen, D.L. [Instituto Federal de Educação, Ciência e Tecnologia (Brazil); Silveira, M.A.G. [Centro Universitário da FEI (Brazil); Rossi, E.S. [Centro Universitário FIEO – UNIFIEO (Brazil); Nobre, G.P. [Lawrence Livermore National Laboratory (United States)

2014-06-01

The Saci-Perere γ ray spectrometer (located at the Pelletron AcceleratorLaboratory – IFUSP) was employed to implement the γ-particle coincidence technique for the study of nuclear reaction mechanisms. For this, the {sup 18}O+{sup 110}Pd reaction has been studied in the beam energy range of 45–54 MeV. Several corrections to the data due to various effects (energy and angle integrations, beam spot size, γ detector finite size and the vacuum de-alignment) are small and well controlled. The aim of this work was to establish a proper method to analyze the data and identify the reaction mechanisms involved. To achieve this goal the inelastic scattering to the first excited state of {sup 110}Pd has been extracted and compared to coupled channel calculations using the São Paulo Potential (PSP), being reasonably well described by it.

Extension of a Kinetic Approach to Chemical Reactions to Electronic Energy Levels and Reactions Involving Charged Species With Application to DSMC Simulations

Science.gov (United States)

Liechty, Derek S.

2013-01-01

The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties are extended in the current work to include electronic energy level transitions and reactions involving charged particles. These extensions are shown to agree favorably with reported transition and reaction rates from the literature for nearequilibrium conditions. Also, the extensions are applied to the second flight of the Project FIRE flight experiment at 1634 seconds with a Knudsen number of 0.001 at an altitude of 76.4 km. In order to accomplish this, NASA's direct simulation Monte Carlo code DAC was rewritten to include the ability to simulate charge-neutral ionized flows, take advantage of the recently introduced chemistry model, and to include the extensions presented in this work. The 1634 second data point was chosen for comparisons to be made in order to include a CFD solution. The Knudsen number at this point in time is such that the DSMC simulations are still tractable and the CFD computations are at the edge of what is considered valid because, although near-transitional, the flow is still considered to be continuum. It is shown that the inclusion of electronic energy levels in the DSMC simulation is necessary for flows of this nature and is required for comparison to the CFD solution. The flow field solutions are also post-processed by the nonequilibrium radiation code HARA to compute the radiative portion of the heating and is then compared to the total heating measured in flight.

Maillard Reaction: review

Directory of Open Access Journals (Sweden)

Júlia d'Almeida Francisquini

2017-11-01

Full Text Available Maillard reaction is an important subject of study in food science and technology and different areas of knowledge are involved such as chemistry, food engineering, nutrition and food technology. The objective of this paper is to present the basic concepts of the Maillard reaction, such as the reaction stages, the main compounds producced and some technological consequences for dairy products.

2013 Gordon Research Conference, Inorganic reaction mechanisms, Galveston, TX, March 3-8 2013

Energy Technology Data Exchange (ETDEWEB)

Abu-Omar, Mahdi M. [Purdue Univ., West Lafayette, IN (United States)

2012-12-08

The 2013 Gordon Conference on Inorganic Reaction Mechanisms will present cutting-edge research on the molecular aspects of inorganic reactions involving elements from throughout the periodic table and state-of-the art techniques that are used in the elucidation of reaction mechanisms. The Conference will feature a wide range of topics, such as homogeneous and heterogeneous catalysis, metallobiochemistry, electron-transfer in energy reactions, polymerization, nitrogen fixation, green chemistry, oxidation, solar conversion, alkane functionalization, organotransition metal chemistry, and computational chemistry. The talks will cover themes of current interest including energy, materials, and bioinorganic chemistry. Sections cover: Electron-Transfer in Energy Reactions; Catalytic Polymerization and Oxidation Chemistry; Kinetics and Spectroscopy of Heterogeneous Catalysts; Metal-Organic Chemistry and its Application in Synthesis; Green Energy Conversion;Organometallic Chemistry and Activation of Small Molecules; Advances in Kinetics Modeling and Green Chemistry; Metals in Biology and Disease; Frontiers in Catalytic Bond Activation and Cleavage.

Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

Science.gov (United States)

Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

2015-08-28

The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

Armature reaction of permanent magnet-excited small dc motors with shell type magnets and possibilities of power increase

Energy Technology Data Exchange (ETDEWEB)

Gutt, H J; Tran, Q N

1983-07-01

Permanent magnet-excited small dc motors allow an increase of power up to 30% compared with present permanent excited motors. The calculation of immediate irreversible demagnetization of the air-gap situated shell type magnets is necessary for a good motor design. Numerical calculated field line plots show the critical zones of the irreversible demagnetization at high armature reaction and refer how to avoid the flux loss and to increase the motor power.

Chemical transport reactions

CERN Document Server

Schäfer, Harald

2013-01-01

Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and

[Involvement of carbonate/bicarbonate ions in the superoxide-generating reaction of adrenaline autoxidation].

Science.gov (United States)

Sirota, T V

2015-01-01

An important role of carbonate/bicarbonate ions has been recognized in the superoxide generating reaction of adrenaline autooxidation in an alkaline buffer (a model of quinoid adrenaline oxidation in the body). It is suggested that these ions are directly involved not only in formation of superoxide anion radical (О(2)(-)) but also other radicals derived from the carbonate/bicarbonate buffer. Using various buffers it was shown that the rate of accumulation of adrenochrome, the end product of adrenaline oxidation, and the rate of О(2)(-)· formation depend on concentration of carbonate/bicarbonate ions in the buffer and that these ions significantly accelerate adrenaline autooxidation thus demonstrating prooxidant properties. The detectable amount of diformazan, the product of nitro blue tetrazolium (NBT) reduction, was significantly higher than the amount of adrenochrome formed; taking into consideration the literature data on О(2)(-)· detection by NBT it is suggested that adrenaline autooxidation is accompanied by one-electron reduction not only of oxygen dissolved in the buffer and responsible for superoxide formation but possible carbon dioxide also dissolved in the buffer as well as carbonate/bicarbonate buffer components leading to formation of corresponding radicals. The plots of the dependence of the inhibition of adrenochrome and diformazan formation on the superoxide dismutase concentration have shown that not only superoxide radicals are formed during adrenaline autooxidation. Since carbonate/bicarbonate ions are known to be universally present in the living nature, their involvement in free radical processes proceeding in the organism is discussed.

Aromatic products from reaction of lignin model compounds with UV-alkaline peroxide

International Nuclear Information System (INIS)

Sun, Y.P.; Wallis, A.F.A.; Nguyen, K.L.

1997-01-01

A series of guaiacyl and syringyl lignin model compounds and their methylated analogues were reacted with alkaline hydrogen peroxide while irradiating with UV light at 254 nm. The aromatic products obtained were investigated by gas chromatography-mass spectrometry (GC-MS). Guaiacol, syringol and veratrol gave no detectable aromatic products. However, syringol methyl ether gave small amounts of aromatic products, resulting from ring substitution and methoxyl displacement by hydroxyl radicals. Reaction of vanillin and syringaldehyde gave the Dakin reaction products, methoxy-1,4-hydroquinones, while reaction of their methyl ethers yielded benzoic acids. Acetoguaiacone, acetosyringone and their methyl ethers afforded several hydroxylated aromatic products, but no aromatic products were identified in the reaction mixtures from guaiacylpropane and syringylpropane. In contrast, veratrylpropane gave a mixture from which 17 aromatic hydroxylated compounds were identified. It is concluded that for phenolic lignin model compounds, particularly those possessing electrondonating aromatic ring substituents, ring-cleavage reactions involving superoxide radical anions are dominant, whereas for non-phenolic lignin models, hydroxylation reactions through attack of hydroxyl radicals prevail

Fusion chain reaction - a chain reaction with charged particles

International Nuclear Information System (INIS)

Peres, A.; Shvarts, D.

1975-01-01

When a DT-plasma is compressed to very high density, the particles resulting from nuclear reactions give their energy mostly to D and T ions, by nuclear collisions, rather than to electrons as usual. Fusion can thus proceed as a chain reaction, without the need of thermonuclear temperatures. In this paper, we derive relations for the suprathermal ion population created by a fusion reaction. Numerical integration of these equations shows that a chain reaction can proceed in a cold infinite DT-plasma at densities above 8.4x10 27 ions.cm -3 . Seeding the plasma with a small amount of 6 Li reduces the critical density to 7.2x10 27 ions.cm -3 (140000times the normal solid density). (author)

A Green Multicomponent Reaction for the Organic Chemistry Laboratory: The Aqueous Passerini Reaction

Science.gov (United States)

Hooper, Matthew M.; DeBoef, Brenton

2009-01-01

Water is the ideal green solvent for organic reactions. However, most organic molecules are insoluble in it. Herein, we report a laboratory module that takes advantage of this property. The Passerini reaction, a three-component coupling involving an isocyanide, aldehyde, and carboxylic acid, typically requires [similar to] 24 h reaction times in…

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

International Nuclear Information System (INIS)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C; Pace, Molly; Kim, Young Jin; Jardine, Philip M.; Watson, David B.

2007-01-01

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M. partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M. species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions.

Science.gov (United States)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly N; Kim, Young-Jin; Jardine, Philip M; Watson, David B

2007-06-16

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing N(E) equilibrium reactions and a set of reactive transport equations of M-N(E) kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

A coupled model of transport-reaction-mechanics with trapping. Part I - Small strain analysis

Science.gov (United States)

Salvadori, A.; McMeeking, R.; Grazioli, D.; Magri, M.

2018-05-01

A fully coupled model for mass and heat transport, mechanics, and chemical reactions with trapping is proposed. It is rooted in non-equilibrium rational thermodynamics and assumes that displacements and strains are small. Balance laws for mass, linear and angular momentum, energy, and entropy are stated. Thermodynamic restrictions are identified, based on an additive strain decomposition and on the definition of the Helmholtz free energy. Constitutive theory and chemical kinetics are studied in order to finally write the governing equations for the multi-physics problem. The field equations are solved numerically with the finite element method, stemming from a three-fields variational formulation. Three case-studies on vacancies redistribution in metals, hydrogen embrittlement, and the charge-discharge of active particles in Li-ion batteries demonstrate the features and the potential of the proposed model.

Extent of reaction in open systems with multiple heterogeneous reactions

Science.gov (United States)

Friedly, John C.

1991-01-01

The familiar batch concept of extent of reaction is reexamined for systems of reactions occurring in open systems. Because species concentrations change as a result of transport processes as well as reactions in open systems, the extent of reaction has been less useful in practice in these applications. It is shown that by defining the extent of the equivalent batch reaction and a second contribution to the extent of reaction due to the transport processes, it is possible to treat the description of the dynamics of flow through porous media accompanied by many chemical reactions in a uniform, concise manner. This approach tends to isolate the reaction terms among themselves and away from the model partial differential equations, thereby enabling treatment of large problems involving both equilibrium and kinetically controlled reactions. Implications on the number of coupled partial differential equations necessary to be solved and on numerical algorithms for solving such problems are discussed. Examples provided illustrate the theory applied to solute transport in groundwater flow.

Ciclesonide improves measures of small airway involvement in asthma

NARCIS (Netherlands)

Cohen, J.; Douma, W. R.; ten Hacken, N. H. T.; Vonk, J. M.; Oudkerk, M.; Postma, D. S.

Ciclesonide is delivered as a small-particle inhaled corticosteroid and improves lung function and airway hyperresponsiveness. The objective of the present study was to assess whether ciclesonide can specifically improve small airway function in asthma. A total of 16 mild-to-moderate asthma patients

cycloaddition reactions

Indian Academy of Sciences (India)

Unknown

Molecular Modeling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology,. Hyderabad ... thus obtained are helpful to model the regioselectivity ... compromise to model Diels–Alder reactions involving ...... acceptance.

Intramolecular anionic diels-alder reactions of 1-aryl-4-oxahepta-1,6-diyne systems in DMSO.

Science.gov (United States)

Kudoh, Takayuki; Mori, Tomoko; Shirahama, Mitsuhito; Yamada, Masashi; Ishikawa, Teruhiko; Saito, Seiki; Kobayashi, Hisayoshi

2007-04-25

Base-promoted cycloaddition reactions of 1-aryl- or 1-aryl-7-substituted-4-oxahepta-1,6-diyne systems in DMSO have proven to involve an anionic intramolecular Diels-Alder process taking place even at room temperature in spite of the reaction suffering from temporary disruption of aromaticity. Although initially formed alpha-arylallenide anion can be protonated by DMSO, it can be back to the allenide anion probably because of a small acidity difference between alpha-arylallene and DMSO. The alpha-arylallenide anion in combination with the alpha-aryl substituent can constitute an anionic diene structure that undergoes the intramolecular Diels-Alder reaction involving the C(6)-yne part, a very fast process probably because of the increased HOMO-1 level of the anionic diene, as shown by DFT calculations. Diversified substituted naphthalenes, benzofurans, phenanthrenes, and quinolines, including biaryl architectures, are available from 4-oxahepta-1,6-diynes in a highly expeditious way.

Small water/steam leaks in sodium heated steam generators: Evaluation of the reaction zone - effects on 2 1/4 Cr 1 Mo structural material

International Nuclear Information System (INIS)

Dumm, K.

1975-01-01

On the basis of experimental data the geometry of a small leak reaction zone can be predicted for given leak sizes and steam generator operation conditions. The effects of small leaks on 2 1/4 Cr 1 Mo material have been studied and completed with test results from foreign investigators. The results have to be considered as preliminary ones which have to be further qualified by additional information. (author)

Small water/steam leaks in sodium heated steam generators: Evaluation of the reaction zone - effects on 2 1/4 Cr 1 Mo structural material

Energy Technology Data Exchange (ETDEWEB)

Dumm, K

1975-07-01

On the basis of experimental data the geometry of a small leak reaction zone can be predicted for given leak sizes and steam generator operation conditions. The effects of small leaks on 2 1/4 Cr 1 Mo material have been studied and completed with test results from foreign investigators. The results have to be considered as preliminary ones which have to be further qualified by additional information. (author)

Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation

KAUST Repository

Minenkov, Yury; Bistoni, Giovanni; Riplinger, Christoph; Auer, Alexander A.; Neese, Frank; Cavallo, Luigi

2017-01-01

In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes

ReactionPredictor: prediction of complex chemical reactions at the mechanistic level using machine learning.

Science.gov (United States)

Kayala, Matthew A; Baldi, Pierre

2012-10-22

Proposing reasonable mechanisms and predicting the course of chemical reactions is important to the practice of organic chemistry. Approaches to reaction prediction have historically used obfuscating representations and manually encoded patterns or rules. Here we present ReactionPredictor, a machine learning approach to reaction prediction that models elementary, mechanistic reactions as interactions between approximate molecular orbitals (MOs). A training data set of productive reactions known to occur at reasonable rates and yields and verified by inclusion in the literature or textbooks is derived from an existing rule-based system and expanded upon with manual curation from graduate level textbooks. Using this training data set of complex polar, hypervalent, radical, and pericyclic reactions, a two-stage machine learning prediction framework is trained and validated. In the first stage, filtering models trained at the level of individual MOs are used to reduce the space of possible reactions to consider. In the second stage, ranking models over the filtered space of possible reactions are used to order the reactions such that the productive reactions are the top ranked. The resulting model, ReactionPredictor, perfectly ranks polar reactions 78.1% of the time and recovers all productive reactions 95.7% of the time when allowing for small numbers of errors. Pericyclic and radical reactions are perfectly ranked 85.8% and 77.0% of the time, respectively, rising to >93% recovery for both reaction types with a small number of allowed errors. Decisions about which of the polar, pericyclic, or radical reaction type ranking models to use can be made with >99% accuracy. Finally, for multistep reaction pathways, we implement the first mechanistic pathway predictor using constrained tree-search to discover a set of reasonable mechanistic steps from given reactants to given products. Webserver implementations of both the single step and pathway versions of Reaction

Dynamics of anion-molecule reactions at low energy

International Nuclear Information System (INIS)

Mikosch, J.

2007-11-01

Anion-molecule reactions must find their way through deeply bound entrance and exit channel complexes separated by a central barrier. This results in low reaction rates and rich dynamics since direct pathways compete with the formation of transient intermediates. In this thesis we examine the probability of proton transfer to a small anion and transient lifetimes of a thermoneutral bimolecular nucleophilic substitution (S N 2) reaction at well defined variable temperature down to 8 Kelvin in a multipole trap. The observed strong inverse temperature dependence is attributed to the deficit of available quantum states in the entrance channel at decreasing temperature. Furthermore we investigate scattering dynamics of S N 2 reactions at defined relative energy between 0.4 and 10 eV by crossed beam slice imaging. A weakly exothermic reaction with high central barrier proceeds via an indirect, complex-mediated mechanism at low relative energies featuring high internal product excitation in excellent quantitative agreement with a statistical model. In contrast, direct backward scattering prevails for higher energies with product velocities close to the kinematical cutoff. For a strongly exothermic reaction, competing S N 2-, dihalide- and proton transfer-channels are explored which proceed by complex mediation for low energy and various rebound-, grazing- and collision induced bond rupture-mechanisms at higher energy. From our data and a collaboration with theory we identify a new indirect roundabout S N 2 mechanism involving CH 3 -rotation. (orig.)

Dynamics of anion-molecule reactions at low energy

Energy Technology Data Exchange (ETDEWEB)

Mikosch, J.

2007-11-15

Anion-molecule reactions must find their way through deeply bound entrance and exit channel complexes separated by a central barrier. This results in low reaction rates and rich dynamics since direct pathways compete with the formation of transient intermediates. In this thesis we examine the probability of proton transfer to a small anion and transient lifetimes of a thermoneutral bimolecular nucleophilic substitution (S{sub N}2) reaction at well defined variable temperature down to 8 Kelvin in a multipole trap. The observed strong inverse temperature dependence is attributed to the deficit of available quantum states in the entrance channel at decreasing temperature. Furthermore we investigate scattering dynamics of S{sub N}2 reactions at defined relative energy between 0.4 and 10 eV by crossed beam slice imaging. A weakly exothermic reaction with high central barrier proceeds via an indirect, complex-mediated mechanism at low relative energies featuring high internal product excitation in excellent quantitative agreement with a statistical model. In contrast, direct backward scattering prevails for higher energies with product velocities close to the kinematical cutoff. For a strongly exothermic reaction, competing S{sub N}2-, dihalide- and proton transfer-channels are explored which proceed by complex mediation for low energy and various rebound-, grazing- and collision induced bond rupture-mechanisms at higher energy. From our data and a collaboration with theory we identify a new indirect roundabout S{sub N}2 mechanism involving CH{sub 3}-rotation. (orig.)

Kinetics of the reactions of hydrated electrons with metal complexes

International Nuclear Information System (INIS)

Korsse, J.

1983-01-01

The reactivity of the hydrated electron towards metal complexes is considered. Experiments are described involving metal EDTA and similar complexes. The metal ions studied are mainly Ni 2+ , Co 2+ and Cu 2+ . Rates of the reactions of the complexes with e - (aq) were measured using the pulse radiolysis technique. It is shown that the reactions of e - (aq) with the copper complexes display unusually small kinetic salt effects. The results suggest long-range electron transfer by tunneling. A tunneling model is presented and the experimental results are discussed in terms of this model. Results of approximate molecular orbital calculations of some redox potentials are given, for EDTA chelates as well as for series of hexacyano and hexaquo complexes. Finally, equilibrium constants for the formation of ternary complexes are reported. (Auth./G.J.P.)

Photoinduced ethane formation from reaction of ethene with matrix-isolated Ti, V, or Nb atoms.

Science.gov (United States)

Thompson, Matthew G K; Parnis, J Mark

2005-10-27

The reactions of matrix-isolated Ti, V, or Nb atoms with ethene (C(2)H(4)) have been studied by FTIR absorption spectroscopy. Under conditions where the ethene dimer forms, metal atoms react with the ethene dimer to yield matrix-isolated ethane (C(2)H(6)) and methane. Under lower ethene concentration conditions ( approximately 1:70 ethene/Ar), hydridic intermediates of the types HMC(2)H(3) and H(2)MC(2)H(2) are also observed, and the relative yield of hydrocarbons is diminished. Reactions of these metals with perdeuterioethene, and equimolar mixtures of C(2)H(4) and C(2)D(4), yield products that are consistent with the production of ethane via a metal atom reaction involving at least two C(2)H(4) molecules. The absence of any other observed products suggests the mechanism also involves production of small, highly symmetric species such as molecular hydrogen and metal carbides. Evidence is presented suggesting that ethane production from the ethene dimer is a general photochemical process for the reaction of excited-state transition-metal atoms with ethene at high concentrations of ethene.

Characterization of Heme Proteins Involved in Microbial Exoelectric Activity and Small Molecule-Sensing

KAUST Repository

Vogler, Malvina M.

2018-01-01

Heme proteins, also termed cytochromes, are a widespread class of metalloproteins containing an Fe-protoporphyrin IX cofactor. They perform numerous functions in nature such as oxygen-transport by hemoglobin, monooxygenation reactions catalyzed by Cytochrome P-450, and electron transfer reactions during photosynthesis. The differences between proteincofactor binding characteristics and the cofactor environment greatly influence the extensive range of functions. In this dissertation, proteins from the Mtr pathway of Shewanella oneidensis are characterized. These c-type cytochromes contain multiple heme cofactors per protein molecule that covalently attach to the protein amino acid sequence and are involved in electron transfer to extracellular metal oxides during anaerobic conditions. Successful recombinant expression of pathway components MtrC and MtrA is achieved in Escherichia coli. Heme-dependent gel staining and UV/Vis spectroscopy show characteristic c-type cytochrome characteristics. Mass spectrometry confirms that the correct extensive post-translational modifications were performed and the ten heme groups were incorporated per protein of MtrC and MtrA and the correct lipid-anchor was attached to extracellular MtrC. Raman spectroscopy measurements of MtrA provide intriguing structural information and highlight the strong influence of the heme cofactors within the protein structure. Next, an Arabidopsis thaliana protein is analyzed. It was previously identified via a motif search of the plant genome, based on conserved residues in the H4 NOX pocket. Here, the incorporation of a heme b cofactor is confirmed. UV/Vis spectroscopy under anaerobic conditions demonstrates reversible binding of nitric oxide to the heme iron and depicts the previously published characteristic absorption maxima for other H-NOX proteins.

Kinetics of hydrogen isotope exchange reactions

International Nuclear Information System (INIS)

Gold, V.; McAdam, M.E.

1975-01-01

Under the influence of tritium β-radiation, 1,4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag + , Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ , H 3 + O) and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N 3 - , Br - , SCN - ) has been examined in detail. γ-irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two separately scavengeable primary radiolysis products in the sequence of reactions leading to exchange. The presence of electron scavengers, even at high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a low vacancy state of inhibitor cations, is considered responsible for the 'unscavengeable' portion of the reaction, by providing an alternative exchange route. Analogies are drawn between the exchange reaction and other radiation-induced reactions that are thought to involve spur processes. Some implication of radiation-chemical studies in water-alcohol mixtures are indicated. (author)

Modelling non-homogeneous stochastic reaction-diffusion systems: the case study of gemcitabine-treated non-small cell lung cancer growth.

Science.gov (United States)

Lecca, Paola; Morpurgo, Daniele

2012-01-01

Reaction-diffusion based models have been widely used in the literature for modeling the growth of solid tumors. Many of the current models treat both diffusion/consumption of nutrients and cell proliferation. The majority of these models use classical transport/mass conservation equations for describing the distribution of molecular species in tumor spheroids, and the Fick's law for describing the flux of uncharged molecules (i.e oxygen, glucose). Commonly, the equations for the cell movement and proliferation are first order differential equations describing the rate of change of the velocity of the cells with respect to the spatial coordinates as a function of the nutrient's gradient. Several modifications of these equations have been developed in the last decade to explicitly indicate that the tumor includes cells, interstitial fluids and extracellular matrix: these variants provided a model of tumor as a multiphase material with these as the different phases. Most of the current reaction-diffusion tumor models are deterministic and do not model the diffusion as a local state-dependent process in a non-homogeneous medium at the micro- and meso-scale of the intra- and inter-cellular processes, respectively. Furthermore, a stochastic reaction-diffusion model in which diffusive transport of the molecular species of nutrients and chemotherapy drugs as well as the interactions of the tumor cells with these species is a novel approach. The application of this approach to he scase of non-small cell lung cancer treated with gemcitabine is also novel. We present a stochastic reaction-diffusion model of non-small cell lung cancer growth in the specification formalism of the tool Redi, we recently developed for simulating reaction-diffusion systems. We also describe how a spatial gradient of nutrients and oncological drugs affects the tumor progression. Our model is based on a generalization of the Fick's first diffusion law that allows to model diffusive transport in non

Irradiation system for neutron capture therapy using the small accelerator

International Nuclear Information System (INIS)

Kobayashi, Tooru; Hoshi, Masaharu

2002-01-01

Neutron capture therapy (NCT) is to kill tumor cells that previously incorporated the stable isotope which generates heavy charged particles with a short range and a high linear energy transfer (LET) on neutron irradiation. Boron-10 is ordinarily used as such an isotope. The tumor tissue is neutron-irradiated at craniotomy after preceding craniotomy for tumor extraction: therefore two surgeries are required for the present NCT in Japan. The reactions 10 B(n, αγ) 7 Li and 7 Li (p, n) 7 Be are thought preferential for patients and doctors if a convenient small accelerator, not the reactor used at present, is available in the hospital because only one craniotomy is sufficient. Authors' examinations of the system for NCT using the small accelerator involve irradiation conditions, desirable energy spectrum of neutron, characterization of thermal and epi-thermal neutrons, social, practical and technical comparison of the reactor and accelerator, and usefulness of the reaction 7 Li (p, n) 7 Be. The system devoted to the NCT is awaited in future. (K.H.)

Theory of the reaction dynamics of small molecules on metal surfaces

Energy Technology Data Exchange (ETDEWEB)

Jackson, Bret [Univ. of Massachusetts, Amherst, MA (United States)

2016-09-09

The objective of this project has been to develop realistic theoretical models for gas-surface interactions, with a focus on processes important in heterogeneous catalysis. The dissociative chemisorption of a molecule on a metal is a key step in many catalyzed reactions, and is often the rate-limiting step. We have explored the dissociative chemisorption of H₂, H₂O and CH₄ on a variety of metal surfaces. Most recently, our extensive studies of methane dissociation on Ni and Pt surfaces have fully elucidated its dependence on translational energy, vibrational state and surface temperature, providing the first accurate comparisons with experimental data. We have explored Eley-Rideal and hot atom reactions of H atoms with H- and C-covered metal surfaces. H atom interactions with graphite have also been explored, including both sticking and Eley-Rideal recombination processes. Again, our methods made it possible to explain several experiments studying these reactions. The sticking of atoms on metal surfaces has also been studied. To help elucidate the experiments that study these processes, we examine how the reaction dynamics depend upon the nature of the molecule-metal interaction, as well as experimental variables such as substrate temperature, beam energy, angle of impact, and the internal states of the molecules. Electronic structure methods based on Density Functional Theory are used to compute each molecule-metal potential energy surface. Both time-dependent quantum scattering techniques and quasi-classical methods are used to examine the reaction or scattering dynamics. Much of our effort has been directed towards developing improved quantum methods that can accurately describe reactions, as well as include the effects of substrate temperature (lattice vibration).

The Efficiency of a Small-World Functional Brain Network

Institute of Scientific and Technical Information of China (English)

ZHAO Qing-Bai; ZHANG Xiao-Fei; SUI Dan-Ni; ZHOU Zhi-Jin; CHEN Qi-Cai; TANG Yi-Yuan

2012-01-01

We investigate whether the small-world topology of a functional brain network means high information processing efficiency by calculating the correlation between the small-world measures of a functional brain network and behavioral reaction during an imagery task.Functional brain networks are constructed by multichannel eventrelated potential data,in which the electrodes are the nodes and the functional connectivities between them are the edges.The results show that the correlation between small-world measures and reaction time is task-specific,such that in global imagery,there is a positive correlation between the clustering coefficient and reaction time,while in local imagery the average path length is positively correlated with the reaction time.This suggests that the efficiency of a functional brain network is task-dependent.%We investigate whether the small-world topology of a functional brain network means high information processing efficiency by calculating the correlation between the small-world measures of a functional brain network and behavioral reaction during an imagery task. Functional brain networks are constructed by multichannel event-related potential data, in which the electrodes are the nodes and the functional connectivities between them are the edges. The results show that the correlation between small-world measures and reaction time is task-specific, such that in global imagery, there is a positive correlation between the clustering coefficient and reaction time, while in local imagery the average path length is positively correlated with the reaction time. This suggests that the efficiency of a functional brain network is task-dependent.

Small sample whole-genome amplification

Science.gov (United States)

Hara, Christine; Nguyen, Christine; Wheeler, Elizabeth; Sorensen, Karen; Arroyo, Erin; Vrankovich, Greg; Christian, Allen

2005-11-01

Many challenges arise when trying to amplify and analyze human samples collected in the field due to limitations in sample quantity, and contamination of the starting material. Tests such as DNA fingerprinting and mitochondrial typing require a certain sample size and are carried out in large volume reactions; in cases where insufficient sample is present whole genome amplification (WGA) can be used. WGA allows very small quantities of DNA to be amplified in a way that enables subsequent DNA-based tests to be performed. A limiting step to WGA is sample preparation. To minimize the necessary sample size, we have developed two modifications of WGA: the first allows for an increase in amplified product from small, nanoscale, purified samples with the use of carrier DNA while the second is a single-step method for cleaning and amplifying samples all in one column. Conventional DNA cleanup involves binding the DNA to silica, washing away impurities, and then releasing the DNA for subsequent testing. We have eliminated losses associated with incomplete sample release, thereby decreasing the required amount of starting template for DNA testing. Both techniques address the limitations of sample size by providing ample copies of genomic samples. Carrier DNA, included in our WGA reactions, can be used when amplifying samples with the standard purification method, or can be used in conjunction with our single-step DNA purification technique to potentially further decrease the amount of starting sample necessary for future forensic DNA-based assays.

Electron transfer reactions

CERN Document Server

Cannon, R D

2013-01-01

Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

Thermal and combined thermal and radiolytic reactions involving nitrous oxide, hydrogen, nitrogen, and ammonia in contact with tank 241-SY-101 simulated waste

International Nuclear Information System (INIS)

Bryan, S.A.; Pederson, L.R.

1996-02-01

Work described in this report was conducted at Pacific Northwest National Laboratory (PNNL) for the Flammable Gas Safety Project, the purpose of which is to develop information needed to support Westinghouse Hanford Company (WHC) in their efforts to ensure the safe interim storage of wastes at the Hanford Site. Described in this report are the results of tests to evaluate the rates of thermal and combined thermal and radiolytic reactions involving flammable gases in the presence of Tank 241-SY-101 simulated waste. Flammable gases generated by the radiolysis of water and by the thermal and radiolytic decomposition of organic waste constituents may themselves participate in further reactions. Examples include the decomposition of nitrous oxide to yield nitrogen and oxygen, the reaction of nitrous oxide and hydrogen to produce nitrogen and water, and the reaction of nitrogen and hydrogen to produce ammonia. The composition of the gases trapped in bubbles in the wastes might therefore change continuously as a function of the time that the gas bubbles are retained

Kinetics of elementary atom and radical reactions

International Nuclear Information System (INIS)

Gordon, R.J.

1990-06-01

During the past three years we have been working on four problems in the general area of gas phase kinetics and energy transfer of small molecules. These are: (1) measurements of the fine structure populations of ground state oxygen atoms produced in photodissociation reactions; (2) quenching of the Rydberg B ( 1 Σ + ) state of CO; (3) vibrational relaxation of highly excited molecules; and (4) kinetics of hydrogen molecules. The first two topics, which involve transitions between different electronic states of the parent molecule, are a departure from our previous research interests. In the accompanying renewal proposal we discuss plans to pursue these new topics vigorously during the coming year. The third topic is a continuation of our long interest in the energy dependence of the rates laws governing vibrational-to-translational energy transfer of molecules having large initial amounts of vibrational excitation. The final topic is a continuation of our studies of the reaction of O( 3 P) + H 2 . In this work we measured the rate constant for the reaction O( 3 P) with deuterium and also analyzed spectroscopically different sources of vibrationally excited hydrogen for possible future work. We discuss each of these four studies in the following sections

Matrix photochemistry of small molecules: Influencing reaction dynamics on electronically excited hypersurfaces

International Nuclear Information System (INIS)

Laursen, S.L.

1990-01-01

Investigations of chemical reactions on electronically excited reaction surfaces are presented. The role of excited-surface multiplicity is of particular interest, as are chemical reactivity and energy transfer in systems in which photochemistry is initiated through a metal atom ''sensitizer.'' Two approaches are employed: A heavy-atom matrix affords access to forbidden triplet reaction surfaces, eliminating the need for a potentially reactive sensitizer. Later, the role of the metal atom in the photosensitization process is examined directly

Matrix photochemistry of small molecules: Influencing reaction dynamics on electronically excited hypersurfaces

Energy Technology Data Exchange (ETDEWEB)

Laursen, S.L.

1990-01-01

Investigations of chemical reactions on electronically excited reaction surfaces are presented. The role of excited-surface multiplicity is of particular interest, as are chemical reactivity and energy transfer in systems in which photochemistry is initiated through a metal atom sensitizer.'' Two approaches are employed: A heavy-atom matrix affords access to forbidden triplet reaction surfaces, eliminating the need for a potentially reactive sensitizer. Later, the role of the metal atom in the photosensitization process is examined directly.

Computational modeling of chemical reactions and interstitial growth and remodeling involving charged solutes and solid-bound molecules.

Science.gov (United States)

Ateshian, Gerard A; Nims, Robert J; Maas, Steve; Weiss, Jeffrey A

2014-10-01

Mechanobiological processes are rooted in mechanics and chemistry, and such processes may be modeled in a framework that couples their governing equations starting from fundamental principles. In many biological applications, the reactants and products of chemical reactions may be electrically charged, and these charge effects may produce driving forces and constraints that significantly influence outcomes. In this study, a novel formulation and computational implementation are presented for modeling chemical reactions in biological tissues that involve charged solutes and solid-bound molecules within a deformable porous hydrated solid matrix, coupling mechanics with chemistry while accounting for electric charges. The deposition or removal of solid-bound molecules contributes to the growth and remodeling of the solid matrix; in particular, volumetric growth may be driven by Donnan osmotic swelling, resulting from charged molecular species fixed to the solid matrix. This formulation incorporates the state of strain as a state variable in the production rate of chemical reactions, explicitly tying chemistry with mechanics for the purpose of modeling mechanobiology. To achieve these objectives, this treatment identifies the specific theoretical and computational challenges faced in modeling complex systems of interacting neutral and charged constituents while accommodating any number of simultaneous reactions where reactants and products may be modeled explicitly or implicitly. Several finite element verification problems are shown to agree with closed-form analytical solutions. An illustrative tissue engineering analysis demonstrates tissue growth and swelling resulting from the deposition of chondroitin sulfate, a charged solid-bound molecular species. This implementation is released in the open-source program FEBio ( www.febio.org ). The availability of this framework may be particularly beneficial to optimizing tissue engineering culture systems by examining the

Multiresponse modelling of the caramelisation reaction

OpenAIRE

Quintas, Mafalda; Guimarães, Carla; Baylina, João; Brandão, Teresa R. S.; Silva, Cristina L.M.

2007-01-01

Multiresponse modelling is a powerful tool for studying complex kinetics of reactions occurring in food products. This modelling technique uses information of reactants and products involved, allowing insightful kinetic parameters estimation and helping in clarifying reaction mechanisms. One example of a complex reaction that occurs in food processing is the caramelisation reaction. Caramelisation is the common name for a group of reactions observed when carbohydrates are exposed to high temp...

Diels-Alder reactions: The effects of catalyst on the addition reaction

Science.gov (United States)

Yilmaz, Özgür; Kus, Nermin Simsek; Tunç, Tuncay; Sahin, Ertan

2015-10-01

The reaction between 2,3-dimethyl-1,3-butadiene and dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate is efficiently achieved with small amounts of catalyst, i.e. phenol, AcOH, nafion, and β-cyclodextrin. Exo-diastereoselective cycloaddition reactions were observed both without catalyst and different catalysts for 48 days. As a result, different products (tricyclicmolecule 5, retro-Diels-Alder product 6, and oxidation product 7) were obtained with different catalysts. In addition, we synthesized Diels-Alders product 8 and tricyclocyclitol 10 via Diels-Alder reaction. The structures of these products were characterized by 1H NMR, 13C NMR, MS and IR spectroscopy.

Radiation reactions and care of the patient

International Nuclear Information System (INIS)

Lochhead, J.N.M.

1983-01-01

Many of the radiation reactions which may occur in patients following radiotherapy and the care of these reactions are described. These include the systemic reaction, reactions of the blood and skin, reactions occurring after treatment of the breast and chest wall, reactions after irradiation of the mouth and throat, intrathoracic tumours, the abdominal alimentary tract and pelvis, bone, the CNS and the eye. Patient care during the treatment of children and also during treatment using small sealed sources is also described. (U.K.)

Degradation reactions in SONY-type Li-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Roth, E.P.; Nagasubramanian, G.

2000-07-01

Thermal instabilities were identified in SONY-type lithium-ion cells and correlated with interactions of cell constituents and reaction products. Three temperature regions of interaction were identified and associated with the state of charge (degree of Li intercalation) of the cell. Anodes were shown to undergo exothermic reactions as low as 100 C involving the solid electrolyte interface (SEI) layer and the LiPF{sub 6} salt in the electrolyte (EC:PC:DEC/LiPF{sub 6}). These reactions could account for the thermal runaway observed in these cells beginning at 100 C. Exothermic reactions were also observed in the 200 C--300 C region between the intercalated lithium anodes, the LiPF{sub 6} salt, and the PVDF. These reactions were followed by a high-temperature reaction region, 300 C--400 C, also involving the PVDF binder and the intercalated lithium anodes. The solvent was not directly involved in these reactions but served as a moderator and transport medium. Cathode exothermic reactions with the PVDF binder were observed above 200 C and increased with the state of charge (decreasing Li content). This offers an explanation for the observed lower thermal runaway temperatures for charged cells.

Nobel Prize 1992: Rudolph A. Marcus: theory of electron transfer reactions in chemical systems

International Nuclear Information System (INIS)

Ulate Segura, Diego Guillermo

2011-01-01

A review of the theory developed by Rudolph A. Marcus is presented, who for his rating to the theory of electron transfer in chemical systems was awarded the Nobel Prize in Chemistry in 1992. Marcus theory has constituted not only a good extension of the use of a spectroscopic principle, but also has provided an energy balance and the application of energy conservation for electron transfer reactions. A better understanding of the reaction coordinate is exposed in terms energetic and establishing the principles that govern the transfer of electrons, protons and some labile small molecular groups as studied at present. Also, the postulates and equations described have established predictive models of reaction time, very useful for industrial environments, biological, metabolic, and others that involve redox processes. Marcus theory itself has also constituted a large contribution to the theory of complex transition [es

Experimental Observation of Nuclear Reactions in Palladium and Uranium - Possible Explanation by Hydrex Mode

International Nuclear Information System (INIS)

Dufour, J.; Murat, D.; Dufour, X.; Foos, J.

2001-01-01

Experiments with uranium are presented that show a highly exothermal reaction, which can only be of nuclear origin. One striking point of these results is that they clearly show that what is being observed is not some kind of fusion reaction of the deuterium present (only exceedingly small amounts of it are present). This is a strong indication that hydrogen can trigger nuclear reactions that seem to involve the nuclei of the lattice (which would yield a fission-like pattern of products). Confronted with a situation where some experiments in the field yield a fusion-like pattern of products (CF experiments) and others a fissionlike one (LENR experiments), one can reasonably wonder whether one is not observing two aspects of the same phenomenon. Thus, it is proposed to describe CF and LENR reactions as essentially the same phenomenon based on the possible existence of a still hypothetical proton/electron resonance, which would catalyze fissionlike reactions with a neutron sink. Finally, a series of experiments is proposed to assess this hypothesis

Gibbs free energy of reactions involving SiC, Si3N4, H2, and H2O as a function of temperature and pressure

Science.gov (United States)

Isham, M. A.

1992-01-01

Silicon carbide and silicon nitride are considered for application as structural materials and coating in advanced propulsion systems including nuclear thermal. Three-dimensional Gibbs free energy were constructed for reactions involving these materials in H2 and H2/H2O. Free energy plots are functions of temperature and pressure. Calculations used the definition of Gibbs free energy where the spontaneity of reactions is calculated as a function of temperature and pressure. Silicon carbide decomposes to Si and CH4 in pure H2 and forms a SiO2 scale in a wet atmosphere. Silicon nitride remains stable under all conditions. There was no apparent difference in reaction thermodynamics between ideal and Van der Waals treatment of gaseous species.

Perceived impediments to export involvement among small and medium sized firms : non-exporters perspective

Directory of Open Access Journals (Sweden)

Mercy Mpinganjira

2011-12-01

Full Text Available Purpose: The main purpose of this paper is to examine perceived impediments to export involvement among non-exporting small and medium sized firms (SME's in Malawi. The study also examines levels of interest in exporting among the firms. Problem investigated: Many countries have programs aimed at promoting export involvement among SME's. Despite this, most SME's continue to ignore exporting as a viable business strategy. Information on perceived impediments to export involvement especially from the non-exporters' perspective is often lacking hence the need for this study. Methodology: Data was collected from 80 owner managers of non-exporting SME's. A structured questionnaire was the main instrument used to collect data. Personal interviews were also held with managers for the purposes of probing their answers to the questions in the questionnaire. Statistical Package for Social Science (SPSS version 18 was used to analyse the quantitative data obtained from use of the structured questionnaire. Qualitative data obtained through personal interviews was analysed used thematic analysis. Findings: The findings of the study showed significant levels of interest in exporting among the firms. The majority of the owner managers indicated willingness to exploit export opportunities that may be readily available to them. The findings however showed that just over half of the respondents had discussed or investigated the possibility of exporting before. On impediments to exporting, the findings showed that managers perceive many factors as important impediments to their firm's involvement in exporting. The top two most important impediments were internal to the firm and related to human resource issues. They included insufficient knowledge about export opportunities and lack of personnel knowledgeable in exporting. Originality and value of the research: A review of literature shows that most export promotion studies tend to focus more on issues relating to

Small angle particle-particle correlation measurements in the reactions 280 MeV 40Ar+27Al and 670 MeV 55Mn+12C

International Nuclear Information System (INIS)

Milosevich, Zoran; Vardaci, Emanuele; DeYoung, Paul A.; Brown, Craig M.; Kaplan, Morton; Whitfield, James P.; Peterson, Donald; Dykstra, Christopher; Barton, Matthew; Karol, Paul J.; McMahan, Margaret A.

2001-01-01

Small-angle particle-particle correlations were measured in the two matching reactions 280 MeV 40 Ar+ 27 Al and 670 MeV 55 Mn+ 12 C. These two reactions were used to produce the composite nucleus, 67 Ga*, at the same initial excitation energy of 127 MeV, but with different entrance channel angular momentum distributions. A simple trajectory model was used to compute the average emission times between various particle pairs, and comparisons with the data show that there is a significant difference in the deexcitation of the composite nucleus formed from the two reactions. Statistical model calculations were compared to the experimental observations with the added constraint that the model input parameters were consistent with those derived from observed charged-particle energy spectra and angular distributions. It was found that the calculated correlation functions were insensitive to the input spin distributions, but agreed fairly well with the data from the lower-spin system. The higher-spin reaction data were poorly reproduced by the calculations

Theoretical analysis of thermal molten metal-water reactions

International Nuclear Information System (INIS)

Schwalbe, W.

1982-01-01

In experiments with greater masses (kg-scale) two extreme cases had been oberved during the course of reaction when hot melt reacted with a vaporizable cooler liquid. Relatively mild hot interactions with slow pressure build-up and small pressure peak in the reaction volume often occurred but there were also some very violent reactions (steam explosions) where a remarkable portion of thermal energy had been transformed into mechanical energy with high pressure peaks. For the two types of reactions overall models for water as a coolant are developed here. Based on calculations and on comparisons with corresponding experiments it is shown that a relatively mild course of reaction can be explained by a fragmentation of the melt under following violent evaporation of the cooling medium. Pressures only with small reaction volumes up to the MPa range can be found in these reactions. The calculations, for example of Bird and Millington, showed a pressure maximum of 1 MPa after 170 ms of the start of the reaction; this agrees very well with the result of the experiment of 1.08 MPa. (orig./GL) [de

Microwave-Enhanced Cross-Coupling Reactions Involving Alkynyltrifluoroborates with Aryl Bromides

Directory of Open Access Journals (Sweden)

George W. Kabalka

2013-01-01

Full Text Available Palladium-catalyzed alkynylation has emerged as one of the most reliable methods for the synthesis of alkynes which are often used in natural product syntheses and material science. An efficient method for coupling alkynyltrifluoroborates with various aryl bromides in the presence of a palladium catalyst has been developed using microwave irradiation. The microwave reactions are rapid and efficient.

Nuclear Astrophysics and Neutron Induced Reactions: Quasi-Free Reactions and RIBs

International Nuclear Information System (INIS)

Cherubini, S.; Spitaleri, C.; Crucilla, V.; Gulino, M.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Puglia, S.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Coc, A.; Kubono, S.; Binh, D. N.; Hayakawa, S.; Wakabayashi, Y.; Yamaguchi, H.; Burjan, V.; Kroha, V.; De Sereville, N.

2010-01-01

The use of quasi-free reactions in studying nuclear reactions between charged particles of astrophysical interest has received much attention over the last two decades. The Trojan Horse Method is based on this approach and it has been used to study a number of reactions relevant for Nuclear Astrophysics. Recently we applied this method to the study of nuclear reactions that involve radioactive species, namely to the study of the 18 F+p→ 15 O+α process at temperatures corresponding to the energies available in the classical novae scenario. Quasi-free reactions can also be exploited to study processes induced by neutrons. This technique is particularly interesting when applied to reaction induced by neutrons on unstable short-lived nuclei. Such processes are very important in the nucleosynthesis of elements in the sand r-processes scenarios and this technique can give hints for solving key questions in nuclear astrophysics where direct measurements are practically impossible.

Small Business Goes To College. College and University Courses in Small Business Management and Entrepreneurship.

Science.gov (United States)

Bauer, Robert O.

The movement of small business management courses into college and university curricula is discussed. The present state of small business management courses, the objectives of the courses, the variety of courses being offered, and teacher and student reaction to the courses are examined. A historical overview of small business courses at higher…

Solid-state polymerisation via [2+2] cycloaddition reaction involving coordination polymers.

Science.gov (United States)

Medishetty, Raghavender; Park, In-Hyeok; Lee, Shim Sung; Vittal, Jagadese J

2016-03-14

Highly crystalline metal ions containing organic polymers are potentially useful to manipulate the magnetic and optical properties to make advanced multifunctional materials. However, it is challenging to synthesise monocrystalline metal complexes of organic polymers and single-phase hybrid materials made up of both coordination and organic polymers by traditional solution crystallisation. This requires an entirely different approach in the solid-state by thermal or photo polymerisation of the ligands. Among the photochemical methods available, [2+2] cycloaddition reaction has been recently employed to generate cyclobutane based coordination polymers from the metal complexes. Cyclobutane polymers have also been integrated into coordination polymers in this way. Recent advancements in the construction of polymeric chains of cyclobutane rings through photo-dimerisation reaction in the monocrystalline solids containing metal complexes, coordination polymers and metal-organic framework structures are discussed here.

Reaction dynamics of small molecules at metal surfaces

International Nuclear Information System (INIS)

Samson, P.A.

1999-09-01

The dissociation-desorption dynamics of D 2 upon the Sn/Pt(111) surface alloy are dependent on the surface concentration of Sn. The p(2 x 2) Sn/Pt(111) alloy surface (Θ Sn = 0.25 ML), is initially ∼30 times less reactive towards D 2 adsorption than clean Pt(111). On the (√3 x √3) R30 deg Sn/Pt(111) alloy surface (Θ Sn = 0.33 ML), increased inhibition of D 2 adsorption is reported, with S o ∼ 10 -5 at low energy, coinciding with the loss of stable Pt 3 hollow sites and a significant reduction in the D atom binding energy. Sticking on the √3 alloy is activated with an increased energy threshold of ∼280 meV, with no evidence that vibration enhances dissociation. The barrier to dissociation remains in the entrance channel before the D 2 bond begins to stretch. Vibrational excitation is, however, observed in nitrogen desorption from the catalytic reaction of NO + H 2 over Pd(110). For a surface at 600 K, N 2 vibrational state population ratios of P(v=1/v=0) = 0.50 ± 0.05 and P(v=2/v=0) = 0.60 ± 0.20 are reported. Desorption occurs via the N(ad) + N(ad) recombination channel with little energy released into translation and rotation. The translational energy release observed is dependent on the N 2 vibrational state, with translational temperatures of 425 K, 315 K and 180 K reported for the v=0, 1 and 2 states respectively. Sub-thermal energy releases and normally directed angular distributions suggest the influence of a trapping mechanism, recombining molecules scattering through a molecularly adsorbed state, with a transition state of large d NN responsible for the product vibrational excitation. Although N 2 dissociation on Fe(100) forms a simple overlayer structure, on Fe(110), molecular chemisorption does not occur at or above room temperature and the sticking is extremely small (∼10 -6 to 10 -7 ). Activated nitrogen bombardment can be used to prepare a 'surface nitride' with a structure related to the geometry of bulk Fe 4 N. Scanning tunnelling

Nuclear Reaction Data Centers

International Nuclear Information System (INIS)

McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

1988-01-01

The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab

Reaction Qualifications Revisited

DEFF Research Database (Denmark)

Lippert-Rasmussen, Kasper

2009-01-01

  When, in a competitive sphere, people are selected on the basis of qualifications only, their chances of acquiring positions of advantage may seem to depend entirely upon their abilities, not discriminatory bias. However, if reaction qualifications - i.e. characteristics which contribute...... to a person's effectiveness by causing a favourable reaction in customers, co-workers etc. (for short: recipients) - are involved, this assumption is false. Building on work by Wertheimer, Mason, and Miller, this paper proposes an account of the reaction qualifications that count, from the point of view...... of merit. Specifically, it preserves symmetry between negative evaluations of antimeritocratic bases of selection and negative evaluations of qualifications rooted in comparable antimeritocratic reactions. So if employers should not select among applicants on the basis of their (the employers') racial...

Reaction Qualifications Revisited

DEFF Research Database (Denmark)

Lippert-Rasmussen, Kasper

2009-01-01

to a person's effectiveness by causing a favourable reaction in customers, co-workers etc. (for short: recipients) - are involved, this assumption is false. Building on work by Wertheimer, Mason, and Miller, this paper proposes an account of the reaction qualifications that count, from the point of view...... preferences, recipients should not respond to the applicant actually hired on the basis of their (the recipients') racial preferences. My account decomposes the meritocratic ideal into four separate norms, one of which applies to recipients rather than to selectors. Finally, it defends the view that reaction...... qualifications based on antimeritocratic reactions, while not unproblematic, are not entirely irrelevant from the point of view of merit. Notably, selectors need not discount them when no one - including the targets of the objectionable preferences - is unfairly disadvantaged. Because not all problematic...

Noncanonical Reactions of Flavoenzymes

Directory of Open Access Journals (Sweden)

Pablo Sobrado

2012-11-01

Full Text Available Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates.

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping

Directory of Open Access Journals (Sweden)

Skrollan Stockinger

2013-09-01

Full Text Available A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.

Things fall apart: Fragmentation reactions in the oxidative aging of organic species

Science.gov (United States)

Kroll, J. H.; Isaacman-VanWertz, G. A.; Wilson, K. R.; Daumit, K. E.; Kessler, S. H.; Lim, C. Y.; Worsnop, D. R.

2016-12-01

The atmospheric oxidation of organic compounds involves a wide array of chemical transformations, including functionalization reactions (addition of polar functional groups to the carbon skeleton), fragmentation reactions (formation of lower carbon-number products via C-C bond scission), and accretion reactions (increases in molecular weight by the combination of two chemical species). Each of these reaction classes can lead to large changes in volatility, and hence can have major implications for atmospheric organic aerosol (OA). For example, the formation of OA is predominantly driven by functionalization and accretion reactions, which generally lead to decreases in volatility. Here we describe a series of laboratory studies of the subsequent organic "aging", the multiday oxidation processes that occur after the initial OA formation and growth. In these studies, the multigenerational oxidation of organic compounds in various phases (the gas phase, the condensed OA phase, and the aqueous phase) is carried out within either an environmental chamber or a flow reactor, and monitored using various high-resolution mass spectrometric techniques. In all cases it is found that fragmentation reactions play a major role in the observed aging chemistry, dominated by the formation of small, volatile oxidation products. These results suggest that multi-day oxidative aging processes do not lead to sustained aerosol growth, but rather may serve as a chemical sink for atmospheric OA.

Multi-nucleon pion absorption in the 4He(π+,ppp)n reaction

International Nuclear Information System (INIS)

Weber, P.; McAlister, J.; Olszewski, R.; Feltham, A.; Hanna, M.; Johnson, R.R.; Pavan, M.; Ponting, C.; Rozon, F.M.; Sevior, M.; Sossi, V.; Vetterli, D.; Humphrey, D.; Lolos, G.J.; Papandreou, Z.; Tacik, R.; Ottewell, D.; Sheffer, G.; Smith, G.R.; Mardor, Y.; May-Tal, S.

1990-08-01

Three-proton emission cross sections for the 4 He(π + ,ppp)n reaction were measured at an incident pion kinetic energy of T pi + =165 MeV over a wide angular range in a kinematically complete experiment. Angular correlations, missing momentum distributions and energy spectra are compared with three- and four-body phase space Monte Carlo calculations. The results provide strong evidence that most of the three-proton coincidences result from three-nucleon absorption. From phase-space integration the total three-nucleon absorption cross section is estimated to be σ 3N =4.8 ± 1.0 mb. The cross section involving four nucleons is small and is estimated to be σ 4N 4 He, multi-nucleon pion absorption seems to represent only a small fraction. (Author) (40 refs., 3 tabs., 15 figs.)

Reaction product imaging

Energy Technology Data Exchange (ETDEWEB)

Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing

Science.gov (United States)

Stecura, S.

1976-01-01

Oxygen was added to T-111 (Ta-8W-2Hf, wt. %) at 820 and 990 C at an oxygen pressure of about 0.0003 torr. The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at. % oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C. The vaporization of WO3 has no apparent affect on the doping reaction.

Secretomics identifies Fusarium graminearum proteins involved in the interaction with barley and wheat

DEFF Research Database (Denmark)

Yang, Fen; Jensen, Jens D.; Svensson, Birte

2012-01-01

Fusarium graminearum is a phytopathogenic fungus primarily infecting small grain cereals, including barley and wheat. Secreted enzymes play important roles in the pathogenicity of many fungi. In order to access the secretome of F. graminearum, the fungus was grown in liquid culture with barley...... or wheat flour as the sole nutrient source to mimic the host–pathogen interaction. A gel‐based proteomics approach was employed to identify the proteins secreted into the culture medium. Sixty‐nine unique fungal proteins were identified in 154 protein spots, including enzymes involved in the degradation...... between wheat and barley flour medium were mainly involved in fungal cell wall remodelling and the degradation of plant cell walls, starch and proteins. The in planta expression of corresponding F. graminearum genes was confirmed by quantitative reverse transcriptase‐polymerase chain reaction in barley...

Different frontal involvement in ALS and PLS revealed by Stroop event-related potentials and reaction times

Directory of Open Access Journals (Sweden)

Ninfa eAmato

2013-12-01

Full Text Available BACKGROUND: A growing body of evidence suggests a link between cognitive and pathological changes in amyotrophic lateral sclerosis (ALS and in frontotemporal lobar dementia (FTLD. Cognitive deficits have been investigated much less extensively in primary lateral sclerosis (PLS than in ALS. OBJECTIVE: to investigate bioelectrical activity to Stroop test, assessing frontal function, in ALS, PLS and control groups. METHODS: 32 non-demented ALS patients, 10 non-demented PLS patients and 27 healthy subjects were included. Twenty-nine electroencephalography (EEG channels with binaural reference were recorded during covert Stroop task performance, involving mental discrimination of the stimuli and not vocal or motor response. Group effects on event related potentials (ERPs latency were analyzed using statistical multivariate analysis. Topographic analysis was performed using low resolution brain electromagnetic tomography (LORETA. RESULTS: ALS patients committed more errors in the execution of the task but they were not slower, whereas PLS patients did not show reduced accuracy, despite a slowing of reaction times (RTs. The main ERP components were delayed in ALS, but not in PLS, compared with controls. Moreover, RTs speed but not ERP latency correlated with clinical scores. ALS had decreased frontotemporal activity in the P2, P3 and N4 time windows compared to controls. CONCLUSION: These findings suggest a different pattern of psychophysiological involvement in ALS compared with PLS. The former is increasingly recognized to be a multisystems disorder, with a spectrum of executive and behavioural impairments reflecting frontotemporal dysfunction. The latter seems to mainly involve the motor system, with largely spared cognitive functions. Moreover, our results suggest that the covert version of the Stroop task used in the present study, may be useful to assess cognitive state in the very advanced stage of the disease, when other cognitive tasks are not

A study on sodium-concrete reaction

Energy Technology Data Exchange (ETDEWEB)

Bae, Jae Heum; Min, Byong Hun [Suwon University, Suwon (Korea, Republic of)

1997-07-01

A small sodium-concrete reaction facility was designed, manufactured and installed. this facility has been operated under inert gas(N{sub 2}) with different experimental variables such as sodium injection temperature, injection amount of sodium, aging period of concrete, sodium reservoir temperature. As a result, it was found that sodium injection temperature and injected amount of sodium has little effect on sodium-concrete reaction. However, sodium reservoir temperature and aging period of concrete has relatively high impact on sodium-concrete reaction. Sodium-concrete reaction model has also been developed and compared with experimental results. (Author) 51 refs., 16 tabs., 64 figs.

SFN-SIQ, SFNSL and skin biopsy of 55 cases with small fibre involvement.

Science.gov (United States)

Sun, Bo; Li, Yifan; Liu, Lizhi; Chen, Zhaohui; Ling, Li; Yang, Fei; Liu, Jiexiao; Liu, Hong; Huang, Xusheng

2018-05-01

Purpose/aim of the study: To date, there are no validated screening scales for small fibre neuropathy. This study investigated the small-fibre neuropathy and the symptom inventory questionnaire as well as the small fibre neuropathy screening list for small fibre neuropathy diagnosis. Fifty-five patients were divided into small fibre neuropathy and mixed fibre damage groups. Relevant scales, nerve conduction studies and skin biopsies were performed. Relationships between the intraepidermal nerve fibre density and different scales as well as the diagnostic and cut-off values (score at which Youden's index is largest) were determined. Compared with healthy Chinese participants, 20 patients were diagnosed with small fibre neuropathy. Intraepidermal nerve fibre density was moderately and highly correlated with the small fibre neuropathy-symptom inventory questionnaire and small fibre neuropathy screening list, respectively. The diagnostic values were moderate and high for the small fibre neuropathy-symptom inventory questionnaire (cut-off value = 5, sensitivity = 80%, specificity = 81.8%) and small fibre neuropathy screening list (cut-off value = 8, sensitivity = 94.1%, specificity = 90.9%), respectively. There were no significant differences in the visual analogue scale between the small fibre neuropathy group, mixed small and large fibre neuropathy group, pure large fibre neuropathy group and the normal group. Small fibre neuropathy-symptom inventory questionnaire and small fibre neuropathy screening list represent potential small fibre neuropathy screening tools. Abbreviations EMG electromyography ENA anti-extractable nuclear antigens ESR erythrocyte sedimentation rate IENFD intraepidermal nerve fibre density IGT impaired glucose tolerance NCS nerve conduction studies NDS neuropathy disability score OGTT oral glucose tolerance test PGP protein gene product PN peripheral neuropathy ROC receiver operating characteristic curve ROC-AUC area under the ROC curve SFN small

Electrode redox reactions with polarizable molecules

Science.gov (United States)

Matyushov, Dmitry V.

2018-04-01

A theory of redox reactions involving electron transfer between a metal electrode and a polarizable molecule in solution is formulated. Both the existence of molecular polarizability and its ability to change due to electron transfer distinguish this problem from classical theories of interfacial electrochemistry. When the polarizability is different between the oxidized and reduced states, the statistics of thermal fluctuations driving the reactant over the activation barrier becomes non-Gaussian. The problem of electron transfer is formulated as crossing of two non-parabolic free energy surfaces. An analytical solution for these free energy surfaces is provided and the activation barrier of electrode electron transfer is given in terms of two reorganization energies corresponding to the oxidized and reduced states of the molecule in solution. The new non-Gaussian theory is, therefore, based on two theory parameters in contrast to one-parameter Marcus formulation for electrode reactions. The theory, which is consistent with the Nernst equation, predicts asymmetry between the cathodic and anodic branches of the electrode current. They show different slopes at small electrode overpotentials and become curved at larger overpotentials. However, the curvature of the Tafel plot is reduced compared to the Marcus-Hush model and approaches the empirical Butler-Volmer form with different transfer coefficients for the anodic and cathodic currents.

Sodium concrete reaction - Structural considerations

International Nuclear Information System (INIS)

Ferskakis, G.N.

1984-01-01

An overview of the sodium concrete reaction phenomenon, with emphasis on structural considerations, is presented. Available test results for limestone, basalt, and magnetite concrete with various test article configurations are reviewed. Generally, tests indicate reaction is self limiting before all sodium is used. Uncertainties, however, concerning the mechanism for penetration of sodium into concrete have resulted in different theories about a reaction model. Structural behavior may be significant in the progression of the reaction due to thermal-structuralchemical interactions involving tensile cracking, compressive crushing, or general deterioration of concrete and the exposure of fresh concrete surfaces to react with sodium. Structural behavior of test articles and potential factors that could enhance the progression of the reaction are discussed

PI3K-AKT signaling pathway is involved in hypoxia/thermal-induced immunosuppression of small abalone Haliotis diversicolor.

Science.gov (United States)

Sun, Yulong; Zhang, Xin; Wang, Guodong; Lin, Shi; Zeng, Xinyang; Wang, Yilei; Zhang, Ziping

2016-12-01

The PI3K-AKT signal pathway has been found to be involved in many important physiological and pathological processes of the innate immune system of vertebrates and invertebrates. In this study, the AKT (HdAKT) and PI3K (HdPI3K) gene of small abalone Haliotis diversicolor were cloned and characterized for the important status of PI3K and AKT protein in PI3K-AKT signaling pathway. The full length cDNAs of HdAKT and HdPI3K are 2126 bp and 6052 bp respectively, encoding proteins of 479 amino acids and 1097 amino acids, respectively. The mRNA expression level of fourteen genes in the PI3K-AKT signaling pathway were detected by quantitative real-time PCR. The results showed that all these fourteen genes were ubiquitously expressed in seven selected tissues. Meanwhile, HdAKT was expressed in haemocytes with the highest expression level (p abalone. The mRNA expression of these genes in gills, haemocytes and hepatopancreas was significantly down-regulated after the Vibrio parahaemolyticus stimulation with environment stimulation (thermal, hypoxia and thermal & hypoxia). These results indicate that the dual/multiple stresses defeat the immune system and lead to immunosuppression in abalone. PI3K-AKT signaling pathway may be involved in hypoxia/thermal-induced immunosuppression of small abalone Haliotis diversicolor. Copyright © 2016 Elsevier Ltd. All rights reserved.

A computational study of a recreated G protein-GEF reaction intermediate competent for nucleotide exchange: fate of the Mg ion.

Directory of Open Access Journals (Sweden)

Mériam Ben Hamida-Rebaï

Full Text Available Small G-proteins of the superfamily Ras function as molecular switches, interacting with different cellular partners according to their activation state. G-protein activation involves the dissociation of bound GDP and its replacement by GTP, in an exchange reaction that is accelerated and regulated in the cell by guanine-nucleotide exchange factors (GEFs. Large conformational changes accompany the exchange reaction, and our understanding of the mechanism is correspondingly incomplete. However, much knowledge has been derived from structural studies of blocked or inactive mutant GEFs, which presumably closely represent intermediates in the exchange reaction and yet which are by design incompetent for carrying out the nucleotide exchange reaction. In this study we have used comparative modelling to recreate an exchange-competent form of a late, pre-GDP-ejection intermediate species in Arf1, a well-characterized small G-protein. We extensively characterized three distinct models of this intermediate using molecular dynamics simulations, allowing us to address ambiguities related to the mutant structural studies. We observed in particular the unfavorable nature of Mg2+ associated forms of the complex and the establishment of closer Arf1-GEF contacts in its absence. The results of this study shed light on GEF-mediated activation of this small G protein and on predicting the fate of the Mg ion at a critical point in the exchange reaction. The structural models themselves furnish additional targets for interfacial inhibitor design, a promising direction for exploring potentially druggable targets with high biological specificity.

Hydrogen transfer reactions of interstellar Complex Organic Molecules

Science.gov (United States)

Álvarez-Barcia, S.; Russ, P.; Kästner, J.; Lamberts, T.

2018-06-01

Radical recombination has been proposed to lead to the formation of complex organic molecules (COMs) in CO-rich ices in the early stages of star formation. These COMs can then undergo hydrogen addition and abstraction reactions leading to a higher or lower degree of saturation. Here, we have studied 14 hydrogen transfer reactions for the molecules glyoxal, glycoaldehyde, ethylene glycol, and methylformate and an additional three reactions where CHnO fragments are involved. Over-the-barrier reactions are possible only if tunneling is invoked in the description at low temperature. Therefore the rate constants for the studied reactions are calculated using instanton theory that takes quantum effects into account inherently. The reactions were characterized in the gas phase, but this is expected to yield meaningful results for CO-rich ices due to the minimal alteration of reaction landscapes by the CO molecules. We found that rate constants should not be extrapolated based on the height of the barrier alone, since the shape of the barrier plays an increasingly larger role at decreasing temperature. It is neither possible to predict rate constants based only on considering the type of reaction, the specific reactants and functional groups play a crucial role. Within a single molecule, though, hydrogen abstraction from an aldehyde group seems to be always faster than hydrogen addition to the same carbon atom. Reactions that involve heavy-atom tunneling, e.g., breaking or forming a C-C or C-O bond, have rate constants that are much lower than those where H transfer is involved.

Identification of Bacterial Small RNAs by RNA Sequencing

DEFF Research Database (Denmark)

Gómez Lozano, María; Marvig, Rasmus Lykke; Molin, Søren

2014-01-01

sequencing (RNA-seq) is described that involves the preparation and analysis of three different sequencing libraries. As a signifi cant number of unique sRNAs are identifi ed in each library, the libraries can be used either alone or in combination to increase the number of sRNAs identifi ed. The approach......Small regulatory RNAs (sRNAs) in bacteria are known to modulate gene expression and control a variety of processes including metabolic reactions, stress responses, and pathogenesis in response to environmental signals. A method to identify bacterial sRNAs on a genome-wide scale based on RNA...... may be applied to identify sRNAs in any bacterium under different growth and stress conditions....

Catalytic Wittig and aza-Wittig reactions

Directory of Open Access Journals (Sweden)

Zhiqi Lao

2016-11-01

Full Text Available This review surveys the literature regarding the development of catalytic versions of the Wittig and aza-Wittig reactions. The first section summarizes how arsenic and tellurium-based catalytic Wittig-type reaction systems were developed first due to the relatively easy reduction of the oxides involved. This is followed by a presentation of the current state of the art regarding phosphine-catalyzed Wittig reactions. The second section covers the field of related catalytic aza-Wittig reactions that are catalyzed by both phosphine oxides and phosphines.

Confining Domains Lead to Reaction Bursts: Reaction Kinetics in the Plasma Membrane

Science.gov (United States)

Kalay, Ziya; Fujiwara, Takahiro K.; Kusumi, Akihiro

2012-01-01

Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity. PMID:22479350

Confining domains lead to reaction bursts: reaction kinetics in the plasma membrane.

Directory of Open Access Journals (Sweden)

Ziya Kalay

Full Text Available Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity.

Capsule Endoscopy for Ileitis with Potential Involvement of Other Sections of the Small Bowel

Directory of Open Access Journals (Sweden)

Hyun Seok Lee

2016-01-01

Full Text Available Ileitis is defined as inflammation of the ileum. This condition includes ulcers, aphthous ulcers, erosions, and nodular or erythematous mucosa. Various etiologies are associated with ileitis. Crohn’s disease, ulcerative colitis, medications such as nonsteroidal anti-inflammatory drugs, infectious conditions, neoplasms, infiltrative disorders, vasculitides, spondyloarthritis, endometriosis, and radiation therapy-related conditions involve the ileum. However, the differential diagnosis of terminal ileitis can be difficult in many cases. Video capsule endoscopy (VCE has become a useful tool for the diagnosis of a variety of small bowel lesions. This review describes each of the various conditions associated with ileitis and the diagnostic value of VCE for ileitis, which may help identify and evaluate these conditions in clinical practice. Based on the information provided by VCE, a definitive diagnosis could be made using the patients’ medical history, clinical course, laboratory and ileocolonoscopic findings, radiologic imaging findings, and histologic findings.

Reactions of Hydroxyalkyl Radicals with Cysteinyl Peptides in a NanoESI Plume

Science.gov (United States)

Stinson, Craig A.; Xia, Yu

2014-07-01

In biological systems, carbon-centered small molecule radicals are primarily formed via external radiation or internal radical reactions. These radical species can react with a variety of biomolecules, most notably nucleic acids, the consequence of which has possible links to gene mutation and cancer. Sulfur-containing peptides and proteins are reactive toward a variety of radical species and many of them behave as radical scavengers. In this study, the reactions between alkyl alcohol carbon-centered radicals (e.g., •CH2OH for methanol) and cysteinyl peptides within a nanoelectrospray ionization (nanoESI) plume were explored. The reaction system involved ultraviolet (UV) irradiation of a nanoESI plume using a low pressure mercury lamp consisting of 185 and 254 nm emission bands. The alkyl alcohol was added as solvent into the nanoESI solution and served as the precursor of hydroxyalkyl radicals upon UV irradiation. The hydroxyalkyl radicals subsequently reacted with cysteinyl peptides either containing a disulfide linkage or free thiol, which led to the formation of peptide- S-hydroxyalkyl product. This radical reaction coupled with subsequent MS/MS was shown to have analytical potential by cleaving intrachain disulfide linked peptides prior to CID to enhance sequence information. Tandem mass spectrometry via collision-induced dissociation (CID), stable isotope labeling, and accurate mass measurement were employed to verify the identities of the reaction products.

Internet Databases of the Properties, Enzymatic Reactions, and Metabolism of Small Molecules—Search Options and Applications in Food Science

Directory of Open Access Journals (Sweden)

Piotr Minkiewicz

2016-12-01

Full Text Available Internet databases of small molecules, their enzymatic reactions, and metabolism have emerged as useful tools in food science. Database searching is also introduced as part of chemistry or enzymology courses for food technology students. Such resources support the search for information about single compounds and facilitate the introduction of secondary analyses of large datasets. Information can be retrieved from databases by searching for the compound name or structure, annotating with the help of chemical codes or drawn using molecule editing software. Data mining options may be enhanced by navigating through a network of links and cross-links between databases. Exemplary databases reviewed in this article belong to two classes: tools concerning small molecules (including general and specialized databases annotating food components and tools annotating enzymes and metabolism. Some problems associated with database application are also discussed. Data summarized in computer databases may be used for calculation of daily intake of bioactive compounds, prediction of metabolism of food components, and their biological activity as well as for prediction of interactions between food component and drugs.

Hot atom reactions involving multivalent and univalent species. Progress report, February 1976--January 1977

International Nuclear Information System (INIS)

Tang, Y.N.

1977-01-01

Multivalent hot atoms formed by the nuclear recoil method were studied: 31 Si, 32 P, and 11 C. For the recoil 31 Si reactions, we have completed the study on the reactivities of conjugated dienes towards monomeric 31 SiF 2 . The relative reactivities of 1,3-butadiene, trans-pentadiene, cis-pentadiene and 2-methyl-1,3-butadiene towards 31 SiF 2 have been measured as: 1.0:0.89:0.91:1.06 for singlet 31 SiF 2 ; and as 1.0:0.80:0.52:0.89 for the triplet. The large steric effect detected here between cis- and trans-pentadienes for their reactivities towards triplet 31 SiF 2 -donor indicates that a direct 1,4-addition process is possible for such 31 SiF 2 donating complexes. 2-methyl-1,1-diflorosilacyclopent-3-ene and its 3-methyl isomer were successfully synthesized by the co-pyrolysis technique. Experiments to evaluate the relative addition efficiencies of 31 SiH 2 towards various conjugated dienes; and to study to H- and F-abstraction mechanism by 31 Si atoms were begun. For recoil 32 P reactions, some progress has been made towards evaluating the mechanism of abstraction reactions by recoil 32 P atoms in PF 3 -PCl 3 system, and the moderator effect for recoil 32 P reactions with PF 3 -CH 4 mixtures. The possible formation of 32 PH, and the formation of 32 P atoms via the 32 S(n,p) 32 P process have also been explored. For recoil 11 C reactions, major progress has been obtained in the moderator studies of its reactions with 1,3-butadiene. With the successive addition of Ne as a moderator, the yield of acetylene- 11 C decreased, the yield of cyclopentene- 11 C increased while those of both 1,2,4-pentatriene- 11 C and cyclopentadiene- 11 C went through a minimum. Some progress for the identification of the last unknown 11 C-labeled product from this system has also been made

Novel Reagents for Multi-Component Reactions

Science.gov (United States)

Wang, Yanguang; Basso, Andrea; Nenajdenko, Valentine G.; Gulevich, Anton V.; Krasavin, Mikhail; Bushkova, Ekaterina; Parchinsky, Vladislav; Banfi, Luca; Basso, Andrea; Cerulli, Valentina; Guanti, Giuseppe; Riva, Renata; Rozentsveig, Igor B.; Rozentsveig, Gulnur N.; Popov, Aleksandr V.; Serykh, Valeriy J.; Levkovskaya, Galina G.; Cao, Song; Shen, Li; Liu, Nianjin; Wu, Jingjing; Li, Lina; Qian, Xuhong; Chen, Xiaopeng; Wang, Hongbo; Feng, Jinwu; Wang, Yanguang; Lu, Ping; Heravi, Majid M.; Sadjadi, Samaheh; Kazemizadeh, Ali Reza; Ramazani, Ali; Kudyakova, Yulia S.; Goryaeva, Marina V.; Burgart, Yanina V.; Saloutin, Victor I.; Mossetti, Riccardo; Pirali, Tracey; Tron, Gian Cesare; Rozhkova, Yulia S.; Mayorova, Olga A.; Shklyaev, Yuriy V.; Zhdanko, Alexander G.; Nenajdenko, Valentine G.; Stryapunina, Olga G.; Plekhanova, Irina V.; Glushkov, Vladimir A.; Shklyaev, Yurii V.

Ketenimines are a class of versatile and highly reactive intermediates that can participate in a variety of organic reactions, such as nucleophilic additions, radical additions, [2 + 2] and [2 + 4] cycloadditions, and sigmatropic rearrangements. In this presentation, we report on a series of multi-component reactions that involve a ketenimine intermediate. These reactions could furnish diverse heterocyclic compounds, including functionalized iminocoumarin, iminodihydroqunolines, iminothiochromens, pyrrolines, isoquinolines, pyridines, β-lactams, imino-1,2-dihydrocoumarins, and benzimidazoles.

Polarization transfer in (d-vector,n-vector) reactions

International Nuclear Information System (INIS)

Walter, R.L.; Tornow, W.

1986-01-01

The status of the measurements and the role of polarization transfer coefficients for (d/sup →/,n/sup →/) reactions is reviewed. Emphasis is given to reactions, involving light-nuclei systems. The importance of (d/sup →/,n/sup →/) reactions as sources of polarized neutrons is pointed out

Tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds.

Science.gov (United States)

Miró, Javier; Sánchez-Roselló, María; Sanz, Álvaro; Rabasa, Fernando; Del Pozo, Carlos; Fustero, Santos

2015-01-01

A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM-IMDAR protocols.

A Comparison of Deterministic and Stochastic Modeling Approaches for Biochemical Reaction Systems: On Fixed Points, Means, and Modes.

Science.gov (United States)

Hahl, Sayuri K; Kremling, Andreas

2016-01-01

In the mathematical modeling of biochemical reactions, a convenient standard approach is to use ordinary differential equations (ODEs) that follow the law of mass action. However, this deterministic ansatz is based on simplifications; in particular, it neglects noise, which is inherent to biological processes. In contrast, the stochasticity of reactions is captured in detail by the discrete chemical master equation (CME). Therefore, the CME is frequently applied to mesoscopic systems, where copy numbers of involved components are small and random fluctuations are thus significant. Here, we compare those two common modeling approaches, aiming at identifying parallels and discrepancies between deterministic variables and possible stochastic counterparts like the mean or modes of the state space probability distribution. To that end, a mathematically flexible reaction scheme of autoregulatory gene expression is translated into the corresponding ODE and CME formulations. We show that in the thermodynamic limit, deterministic stable fixed points usually correspond well to the modes in the stationary probability distribution. However, this connection might be disrupted in small systems. The discrepancies are characterized and systematically traced back to the magnitude of the stoichiometric coefficients and to the presence of nonlinear reactions. These factors are found to synergistically promote large and highly asymmetric fluctuations. As a consequence, bistable but unimodal, and monostable but bimodal systems can emerge. This clearly challenges the role of ODE modeling in the description of cellular signaling and regulation, where some of the involved components usually occur in low copy numbers. Nevertheless, systems whose bimodality originates from deterministic bistability are found to sustain a more robust separation of the two states compared to bimodal, but monostable systems. In regulatory circuits that require precise coordination, ODE modeling is thus still

Characterization of the Unusual Product from the Reaction between Cobalt(II) Chloride, Ethane-1,2-diamine, and Hydrochloric Acid: An Undergraduate Project Involving an Unknown Metal Complex.

Science.gov (United States)

Curtis, Neil F.; And Others

1986-01-01

Discusses the need for student research-type chemistry projects based upon "unknown" metal complexes. Describes an experiment involving the product from the reaction between cobalt(II) chloride, ethane-1,2-diamine (en) and concentrated hydrochloric acid. Outlines the preparation of the cobalt complex, along with procedure, results and…

Nitrogen modulation of legume root architecture signalling pathways involves phytohormones and small regulatory molecules

Directory of Open Access Journals (Sweden)

Nadiatul Akmal Mohd-Radzman

2013-10-01

Full Text Available Nitrogen, particularly nitrate is an important yield determinant for crops. However, current agricultural practice with excessive fertilizer usage has detrimental effects on the environment. Therefore, legumes have been suggested as a sustainable alternative for replenishing soil nitrogen. Legumes can uniquely form nitrogen-fixing nodules through symbiotic interaction with specialized soil bacteria. Legumes possess a highly plastic root system which modulates its architecture according to the nitrogen availability in the soil. Understanding how legumes regulate root development in response to nitrogen availability is an important step to improving root architecture. The nitrogen-mediated root development pathway starts with sensing soil nitrogen level followed by subsequent signal transduction pathways involving phytohormones, microRNAs and regulatory peptides that collectively modulate the growth and shape of the root system. This review focuses on the current understanding of nitrogen-mediated legume root architecture including local and systemic regulations by different N-sources and the modulations by phytohormones and small regulatory molecules.

Nitrogen modulation of legume root architecture signaling pathways involves phytohormones and small regulatory molecules.

Science.gov (United States)

Mohd-Radzman, Nadiatul A; Djordjevic, Michael A; Imin, Nijat

2013-10-01

Nitrogen, particularly nitrate is an important yield determinant for crops. However, current agricultural practice with excessive fertilizer usage has detrimental effects on the environment. Therefore, legumes have been suggested as a sustainable alternative for replenishing soil nitrogen. Legumes can uniquely form nitrogen-fixing nodules through symbiotic interaction with specialized soil bacteria. Legumes possess a highly plastic root system which modulates its architecture according to the nitrogen availability in the soil. Understanding how legumes regulate root development in response to nitrogen availability is an important step to improving root architecture. The nitrogen-mediated root development pathway starts with sensing soil nitrogen level followed by subsequent signal transduction pathways involving phytohormones, microRNAs and regulatory peptides that collectively modulate the growth and shape of the root system. This review focuses on the current understanding of nitrogen-mediated legume root architecture including local and systemic regulations by different N-sources and the modulations by phytohormones and small regulatory molecules.

Experimental Study of Serpentinization Reactions

Science.gov (United States)

Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

2004-01-01

Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

Reactivity of NO with small transition metal clusters II. Possible reaction mechanisms

International Nuclear Information System (INIS)

Martinez, A.; Vela, A.; Robles, J.

1994-01-01

Through extended Huckel (EHMO) calculations, we followed six possible reaction paths for the formation of Co 2 NO'+ and co 4 NO'+, whose stable structures were discussed in the previous paper of this series. The adduct formation enthalpy (DELTA h f ) and the global hardness (n) have been calculated in order to establish the more probable structures and the more probable routes of reaction for the chemisorption of NO on Co'+ x (x=2-4). It is shown that the maximum hardness principle, at the EHMO level, produces more realistic geometries. (Author) 11 refs

Reaction of Aldehydes/Ketones with Electron-Deficient 1,3,5-Triazines Leading to Functionalized Pyrimidines as Diels-Alder/Retro-Diels-Alder Reaction Products: Reaction Development and Mechanistic Studies.

Science.gov (United States)

Yang, Kai; Dang, Qun; Cai, Pei-Jun; Gao, Yang; Yu, Zhi-Xiang; Bai, Xu

2017-03-03

Catalytic inverse electron demand Diels-Alder (IEDDA) reactions of heterocyclic aza-dienes are rarely reported since highly reactive and electron-rich dienophiles are often found not compatible with strong acids such as Lewis acids. Herein, we disclose that TFA-catalyzed reactions of electron-deficient 1,3,5-triazines and electron-deficient aldehydes/ketones can take place. These reactions led to highly functionalized pyrimidines as products in fair to good yields. The reaction mechanism was carefully studied by the combination of experimental and computational studies. The reactions involve a cascade of stepwise inverse electron demand hetero-Diels-Alder (ihDA) reactions, followed by retro-Diels-Alder (rDA) reactions and elimination of water. An acid was required for both ihDA and rDA reactions. This mechanism was further verified by comparing the relative reactivity of aldehydes/ketones and their corresponding vinyl ethers in the current reaction system.

Small Molecule Library Synthesis Using Segmented Flow

Directory of Open Access Journals (Sweden)

Christina M. Thompson

2011-11-01

Full Text Available Flow chemistry has gained considerable recognition as a simple, efficient, and safe technology for the synthesis of many types of organic and inorganic molecules ranging in scope from large complex natural products to silicon nanoparticles. In this paper we describe a method that adapts flow chemistry to the synthesis of libraries of compounds using a fluorous immiscible solvent as a spacer between reactions. The methodology was validated in the synthesis of two small heterocycle containing libraries. The reactions were performed on a 0.2 mmol scale, enabling tens of milligrams of material to be generated in a single 200 mL reaction plug. The methodology allowed library synthesis in half the time of conventional microwave synthesis while maintaining similar yields. The ability to perform multiple, potentially unrelated reactions in a single run is ideal for making small quantities of many different compounds quickly and efficiently.

A paradigm shift for radical SAM reactions: The organometallic intermediate Ω is central to catalysis.

Science.gov (United States)

Byer, Amanda S; Yang, Hao; McDaniel, Elizabeth C; Kathiresan, Venkatesan; Impano, Stella; Pagnier, Adrien; Watts, Hope; Denler, Carly; Vagstad, Anna; Piel, Jörn; Duschene, Kaitlin S; Shepard, Eric M; Shields, Thomas P; Scott, Lincoln G; Lilla, Edward A; Yokoyama, Kenichi; Broderick, William E; Hoffman, Brian M; Broderick, Joan B

2018-06-28

Radical S-adenosyl-L-methionine (SAM) en-zymes comprise a vast superfamily catalyzing diverse reactions essential to all life through ho-molytic SAM cleavage to liberate the highly-reactive 5-deoxyadenosyl radical (5-dAdo•). Our recent observation of a catalytically compe-tent organometallic intermediate Ω that forms dur-ing reaction of the radical SAM (RS) enzyme py-ruvate formate-lyase activating-enzyme (PFL-AE) was therefore quite surprising, and led to the question of its broad relevance in the superfamily. We now show that Ω in PFL-AE forms as an in-termediate under a variety of mixing order condi-tions, suggesting it is central to catalysis in this enzyme. We further demonstrate that Ω forms in a suite of RS enzymes chosen to span the totality of superfamily reaction types, implicating Ω as essential in catalysis across the RS superfamily. Finally, EPR and electron nuclear double reso-nance spectroscopy establish that Ω involves an Fe-C5 bond between 5-dAdo• and the [4Fe-4S] cluster. An analogous organometallic bond is found in the well-known adenosylcobalamin (co-enzyme B12) cofactor used to initiate radical reac-tions via a 5'-dAdo• intermediate. Generation of a 5'-dAdo• intermediate via homolytic metal-carbon bond cleavage thus appears to be similar for Ω and coenzyme B12. However coenzyme B12 is involved in enzymes catalyzing of only a small number (~12) of distinct reactions, while the RS superfamily has more than 100,000 distinct se-quences and over 80 reaction types character-ized to date. The appearance of Ω across the RS superfamily therefore dramatically enlarges the sphere of bio-organometallic chemistry in Nature.

Reaction Time of Motor Responses in Two-Stimulus Paradigms Involving Deception and Congruity with Varying Levels of Difficulty

Directory of Open Access Journals (Sweden)

Jennifer M. C. Vendemia

2005-01-01

Full Text Available Deception research has focused on identifying peripheral nervous system markers while ignoring cognitive mechanisms underlying those markers. Cognitive theorists argue that the process of deception may involve such constructs as attentional capture, working memory load, or perceived incongruity with memory, while psychophysiologists argue for stimulus salience, arousal, and emotion. Three studies were conducted to assess reaction time (RT in relation to deception, response congruity, and preparedness to deceive. Similar to a semantic verification task, participants evaluated sentences that were either true or false, and then made truthful or deceptive evaluations of the sentence’s base truth-value. Findings indicate that deceptive responses have a longer RT than truthful responses, and that this relationship remains constant across response type and preparedness to deceive. The authors use these findings in preliminary support of a comprehensive cognitive model of deception.

Concise Synthesis of Macrocycles by Multicomponent Reactions

NARCIS (Netherlands)

Abdelraheem, Eman M. M.; Khaksar, Samad; Dömling, Alexander

2018-01-01

A short reaction pathway was devised to synthesize a library of artificial 18-27-membered macrocycles. The five-step reaction sequence involves ring opening of a cyclic anhydride with a diamine, esterification, coupling with an amino acid isocyanide, saponification, and, finally, macro-ring closure

Thermonuclear reaction rates in a deuterium-tritium plasma

International Nuclear Information System (INIS)

Beckman, L.

1978-12-01

In a deuterium-tritium plasma six thermonuclear reactions take place between the deuterons, tritons and the 3 He-particles formed in about half of the d-d-reactions. The rate constants for these six reactions have been calculated from the latest evaluations of the reaction cross sections which were available. In some cases, notably the reactions t+t, t+ 3 He and 3 He+ 3 He, the number of published cross section measurements is small, and the uncertainty in the calculated rate constants consequently large. Analytical expressions for the rate constants as functions of the plasma temperature have been set up. (author)

Damage phenomena at target surface by small leak

International Nuclear Information System (INIS)

Jeong, Kyung Chai; Jeong, J. Y.; Kim, B. H.; Kim, T. J.; Choi, J. H.

2001-04-01

Design of the steam generator should be considered the safety about the sodium-water reaction occurred by water leak in heat transfer tube. Water leak mainly occurred from welding defect at the process of tube connection, the vibration of heat transfer tube bundle in steam generating system, fretting, and pin hole in original tube manufacturing. The classification of water leak divided to two parts, roughly, in case of the water leak studies. One is small leak phenomena analysis, and the other is it of large leak which was mainly treated to the evaluation on pressure increasing from hydrogen gas formed by sodium-water reaction in sodium system. In small water leak, the leak propagation phenomena and the development of leak detecting system at initial stage of small water leak were studied, mainly. In this study, the corrosion phenomena on the target tube surface appeared by sodium-water reaction was analyzed through the small water leak experiments, and, also, the jet phenomena formed by N 2 gas injection through the leak nozzle under water medium was observed

Dynamics of synchrotron VUV-induced intracluster reactions

Energy Technology Data Exchange (ETDEWEB)

Grover, J.R. [Brookhaven National Laboratory, Upton, NY (United States)

1993-12-01

Photoionization mass spectrometry (PIMS) using the tunable vacuum ultraviolet radiation available at the National Synchrotron Light Source is being exploited to study photoionization-induced reactions in small van der Waals mixed complexes. The information gained includes the observation and classification of reaction paths, the measurement of onsets, and the determination of relative yields of competing reactions. Additional information is obtained by comparison of the properties of different reacting systems. Special attention is given to finding unexpected features, and most of the reactions investigated to date display such features. However, understanding these reactions demands dynamical information, in addition to what is provided by PIMS. Therefore the program has been expanded to include the measurement of kinetic energy release distributions.

A comprehensive survey of nuclear reactions; Panorama des reactions nucleaires

Energy Technology Data Exchange (ETDEWEB)

Cugnon, J. [Liege Univ., IFPA, AGO Dept. (Belgium)

2007-07-01

The various mechanisms of nuclear reactions are surveyed and classified in different regimes, based on the notions of coherent mechanisms and hard versus soft processes. The emphasis is put on the concepts at the basis of the understanding of these regimes and on the elements of nuclear structure which are involved in these different regimes, as well as the on the possibility of extracting this information. Due to lack of space and for pedagogical reasons, the discussion is limited to nucleon-induced and light-ion-induced reactions. However, a few remarks are given concerning some specific probes, such as weakly bound projectiles or neutron-rich nuclei. (author)

Possible influence of the Kuramoto length in a photo-catalytic water splitting reaction revealed by Poisson-Nernst-Planck equations involving ionization in a weak electrolyte

Science.gov (United States)

Suzuki, Yohichi; Seki, Kazuhiko

2018-03-01

We studied ion concentration profiles and the charge density gradient caused by electrode reactions in weak electrolytes by using the Poisson-Nernst-Planck equations without assuming charge neutrality. In weak electrolytes, only a small fraction of molecules is ionized in bulk. Ion concentration profiles depend on not only ion transport but also the ionization of molecules. We considered the ionization of molecules and ion association in weak electrolytes and obtained analytical expressions for ion densities, electrostatic potential profiles, and ion currents. We found the case that the total ion density gradient was given by the Kuramoto length which characterized the distance over which an ion diffuses before association. The charge density gradient is characterized by the Debye length for 1:1 weak electrolytes. We discuss the role of these length scales for efficient water splitting reactions using photo-electrocatalytic electrodes.

Tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR. An easy entry to linear bicyclic scaffolds

Directory of Open Access Journals (Sweden)

Javier Miró

2015-08-01

Full Text Available A new tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.

Theoretical investigation of the gas-phase reactions of CrO(+) with ethylene.

Science.gov (United States)

Scupp, Thomas M; Dudley, Timothy J

2010-01-21

The potential energy surfaces associated with the reactions of chromium oxide cation (CrO(+)) with ethylene have been characterized using density functional, coupled-cluster, and multireference methods. Our calculations show that the most probable reaction involves the formation of acetaldehyde and Cr(+) via a hydride transfer involving the metal center. Our calculations support previous experimental hypotheses that a four-membered ring intermediate plays an important role in the reactivity of the system. We have also characterized a number of viable reaction pathways that lead to other products, including ethylene oxide. Due to the experimental observation that CrO(+) can activate carbon-carbon bonds, a reaction pathway involving C-C bond cleavage has also been characterized. Since many of the reactions involve a change in the spin state in going from reactants to products, locations of these spin surface crossings are presented and discussed. The applicability of methods based on Hartree-Fock orbitals is also discussed.

Isospin aspects in nuclear reactions involving Ca beams at 25 MeV/nucleon

Energy Technology Data Exchange (ETDEWEB)

Lombardo, I., E-mail: ilombardo@lns.infn.it; Agodi, C.; Alba, R.; Amorini, F.; Anzalone, A. [INFN Laboratori Nazionali del Sud (Italy); Auditore, L. [Universita di Messina, and INFN-Gr. Coll. Messina, Dipartimento di Fisica (Italy); Berceanu, I. [Institute for Physics and Nuclear Engineering (Romania); Cardella, G. [INFN, Sezione di Catania (Italy); Cavallaro, S. [INFN Laboratori Nazionali del Sud (Italy); Chatterjee, M. B. [Saha Institute of Nuclear Physics (India); Filippo, E. De [INFN, Sezione di Catania (Italy); Di Pietro, A.; Figuera, P. [INFN Laboratori Nazionali del Sud (Italy); Giuliani, G.; Geraci, E.; Grassi, L. [Dipartimento di Fisica e Astronomia Universita di Catania (Italy); Grzeszczuk, A. [University of Silesia, Institute of Physics (Poland); Han, J. [INFN Laboratori Nazionali del Sud (Italy); La Guidara, E. [INFN, Sezione di Catania (Italy); Lanzalone, G. [INFN Laboratori Nazionali del Sud (Italy); and others

2011-11-15

Isospin dependence of dynamical and thermodynamical properties observed in reactions {sup 40}Ca+ {sup 40,48}Ca and {sup 40}Ca + {sup 46}Ti at 25 MeV/nucleon has been studied. We used the CHIMERA multi-detector array. Strong isospin effects are seen in the isotopic distributions of light nuclei and in the competition between different reaction mechanisms in semi-central collisions. We will show also preliminary results obtained in nuclear collision {sup 48}Ca + {sup 48}Ca at 25MeV/nucleon, having very high N/Z value in the entrance channel (N/Z = 1.4). The enhancement of evaporation residue production confirms the strong role played by the N/Z degree of freedom in nuclear dynamics.

Reactions of dihydridotetrakis(triphenylphosphine)ruthenium(II) with olefins and isolation of new ruthenium-olefin complexes

International Nuclear Information System (INIS)

Komiya, Sanshiro; Yamamoto, Akio

1976-01-01

Dihydridotetrakis(triphenylphosphine)ruthenium (II), RuH 2 (PPh 3 ) 4 , reacts with olefins (ethylene, propylene, stylene and butadiene) to give olefin-coordinated complexes of the type, Ru(olefin)(PPh 3 ) 3 and equimolar amounts of their hydrogenation products per mol of the dihydride complex. The olefin coordinated with ruthenium can be exchanged with other olefins. Olefin-coordinated complexes easily react with molecular hydrogen to afford tetrahydridotris(triphenylphosphine)ruthenium, RuH 4 (PPh 3 ) 3 , releasing alkane at room temperature, Under hydrogen atmosphere catalytic hydrogenation of the olefins smoothly takes place with RuH 2 (PPh 3 ) 4 . (Ethylene)tris(triphenylphosphine)ruthenium(0) reacts with methyl iodide to give propylene and a trace of butadiene along with methane, ethylene, and small amounts of ethane and butenes. The formation of propylene suggests that oxidative addition involving cleavage of the C-H bond of ethylene to ruthenium giving a hydridovinyl complex may be taking place. Reactions of Ru(C 2 H 4 )(PPh 3 ) 3 with methyl-d 3 iodide and ethyl iodide, and of Ru(C 3 H 6 )(PPh 3 ) 3 with methyl iodide were examined to test the generality of this type of reaction. The reaction of Ru(C 2 H 4 )(PPh 3 ) 3 with CD 3 I released CD 4 and CD 2 H 2 together with CD 3 H suggesting the involvement of α-hydrogen abstraction. (auth.)

Hypersensitivity Reactions from Excipients in Systemic Glucocorticoid Formulations

DEFF Research Database (Denmark)

Calogiuri, Gianfranco; Garvey, Lene H; Romita, Paolo

2016-01-01

Glucocorticoids are the most widely used drugs for the treatment of hypersensitivity, however these drugs themselves and the excipients contained in commercial corticosteroid formulations are able to induce severe immediate-type hypersensitivity reactions. Reactions involving excipients have been...

Photogeochemical reactions of manganese under anoxic conditions

Science.gov (United States)

Liu, W.; Yee, N.; Piotrowiak, P.; Falkowski, P. G.

2017-12-01

Photogeochemistry describes reactions involving light and naturally occurring chemical species. These reactions often involve a photo-induced electron transfer that does not occur in the absence of light. Although photogeochemical reactions have been known for decades, they are often ignored in geochemical models. In particular, reactions caused by UV radiation during an ozone free early Earth could have influenced the available oxidation states of manganese. Manganese is one of the most abundant transition metals in the crust and is important in both biology and geology. For example, the presence of manganese (VI) oxides in the geologic record has been used as a proxy for oxygenic photosynthesis; however, we suggest that the high oxidation state of Mn can be produced abiotically by photochemical reactions. Aqueous solutions of manganese (II) as well as suspensions of rhodochrosite (MnCO3) were irradiated under anoxic condition using a 450 W mercury lamp and custom built quartz reaction vessels. The photoreaction of the homogeneous solution of Mn(II) produced H2 gas and akhtenskite (ɛ-MnO2) as the solid product . This product is different than the previously identified birnessite. The irradiation of rhodochrosite suspensions also produced H2 gas and resulted in both a spectral shift as well as morphology changes of the mineral particles in the SEM images. These reactions offer alternative, abiotic pathways for the formation of manganese oxides.

How computational methods and relativistic effects influence the study of chemical reactions involving Ru-NO complexes?

Science.gov (United States)

Orenha, Renato Pereira; Santiago, Régis Tadeu; Haiduke, Roberto Luiz Andrade; Galembeck, Sérgio Emanuel

2017-05-05

Two treatments of relativistic effects, namely effective core potentials (ECP) and all-electron scalar relativistic effects (DKH2), are used to obtain geometries and chemical reaction energies for a series of ruthenium complexes in B3LYP/def2-TZVP calculations. Specifically, the reaction energies of reduction (A-F), isomerization (G-I), and Cl - negative trans influence in relation to NH 3 (J-L) are considered. The ECP and DKH2 approaches provided geometric parameters close to experimental data and the same ordering for energy changes of reactions A-L. From geometries optimized with ECP, the electronic energies are also determined by means of the same ECP and basis set combined with the computational methods: MP2, M06, BP86, and its derivatives, so as B2PLYP, LC-wPBE, and CCSD(T) (reference method). For reactions A-I, B2PLYP provides the best agreement with CCSD(T) results. Additionally, B3LYP gave the smallest error for the energies of reactions J-L. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Population of Nuclei Via 7Li-Induced Binary Reactions

International Nuclear Information System (INIS)

Clark, Rodney M.; Phair, Larry W.; Descovich, M.; Cromaz, Mario; Deleplanque, M.A.; Fall on, Paul; Lee, I-Yang; Macchiavelli, A.O.; McMahan, Margaret A.; Moretto, Luciano G.; Rodriguez-Vieitez, E.; Sinha, Shrabani; Stephens, Frank S.; Ward, David; Wiedeking, Mathis

2005-01-01

The authors have investigated the population of nuclei formed in binary reactions involving 7 Li beams on targets of 160 Gd and 184 W. The 7 Li + 184 W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si ΔE-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduce the experimental results. This is a useful method for predicting the population of neutron-rich heavy nuclei formed in binary reactions involving beams of weakly bound nuclei formed in binary reactions involving beams of weakly bound nuclei and will be of use in future spectroscopic studies

Accurate prediction of severe allergic reactions by a small set of environmental parameters (NDVI, temperature).

Science.gov (United States)

Notas, George; Bariotakis, Michail; Kalogrias, Vaios; Andrianaki, Maria; Azariadis, Kalliopi; Kampouri, Errika; Theodoropoulou, Katerina; Lavrentaki, Katerina; Kastrinakis, Stelios; Kampa, Marilena; Agouridakis, Panagiotis; Pirintsos, Stergios; Castanas, Elias

2015-01-01

Severe allergic reactions of unknown etiology,necessitating a hospital visit, have an important impact in the life of affected individuals and impose a major economic burden to societies. The prediction of clinically severe allergic reactions would be of great importance, but current attempts have been limited by the lack of a well-founded applicable methodology and the wide spatiotemporal distribution of allergic reactions. The valid prediction of severe allergies (and especially those needing hospital treatment) in a region, could alert health authorities and implicated individuals to take appropriate preemptive measures. In the present report we have collecterd visits for serious allergic reactions of unknown etiology from two major hospitals in the island of Crete, for two distinct time periods (validation and test sets). We have used the Normalized Difference Vegetation Index (NDVI), a satellite-based, freely available measurement, which is an indicator of live green vegetation at a given geographic area, and a set of meteorological data to develop a model capable of describing and predicting severe allergic reaction frequency. Our analysis has retained NDVI and temperature as accurate identifiers and predictors of increased hospital severe allergic reactions visits. Our approach may contribute towards the development of satellite-based modules, for the prediction of severe allergic reactions in specific, well-defined geographical areas. It could also probably be used for the prediction of other environment related diseases and conditions.

The Reaction of Oxy Hemoglobin with Nitrite

DEFF Research Database (Denmark)

Hathazi, Denisa; Scurtu, Florina; Bischin, Cristina

2018-01-01

The autocatalytic reaction between nitrite and the oxy form of globins involves free radicals. For myoglobin (Mb), an initial binding of nitrite to the iron-coordinated oxygen molecule was proposed; the resulting ferrous-peroxynitrate species was not detected, but its decay product, the high...... to a simple kinetic model involving a transient met-aqua form, in contrast to the ferryl detected in the case of Mb in a similar reaction sequence. These data are in line with a previous observation of a transient accumulation of ferryl Hb under auto-catalytic conditions at much lower concentrations......-peroxynitrate. Density functional theory (DFT) calculations support this latter assignment. The reaction allows for differentiating between the reactivities of various chemically modified hemoglobins, including candidates for blood substitutes. Polymerization of hemoglobin slows the nitrite-induced oxidation, in sharp...

Reactions the private life of atoms

CERN Document Server

Atkins, Peter

2011-01-01

Through an innovative, closely integrated design of images and text, and his characteristically clear, precise, and economical exposition, Peter Atkins explains the processes involved in chemical reactions. He begins by introducing a 'tool kit' of basic reactions, such as precipitation, corrosion, and catalysis, and concludes by showing how these building blocks are brought together in more complex processes such as photosynthesis.

PEG-400 as an efficient and recyclable reaction medium for the synthesis of polyhydroquinolines via Hantzsch reaction

Directory of Open Access Journals (Sweden)

Shitole Nana Vikram

2013-01-01

Full Text Available Polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using PEG-400 as reaction medium. The present method does not involve any hazardous organic solvents or toxic catalysts. The present methodology offers several advantages such as simple procedure, excellent yields with shorter reaction times and purification of products by non-chromatographic methods.

Monotectic four-phase reaction in Al-Bi-Zn alloys

Energy Technology Data Exchange (ETDEWEB)

Groebner, J. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Mirkovic, D. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, R. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)]. E-mail: schmid-fetzer@tu-clausthal.de

2005-06-15

Thermodynamic phase diagram calculations were used for the systematic search for a monotectic four-phase reaction in ternary Al-alloys. Systems with intermetallic phases and also the elements Cd and Hg were excluded in the present search. The ternary Al-Bi-Zn is a rare occasion where such a reaction, L' = L' + (Al)' + (Zn), actually occurs. Experimental work could be focused on key samples in that system and involved DSC for thermal analysis and calorimetry, and also metallographic analysis using SEM/EDX. Experimental results verify the existence of the monotectic reaction and were also used for a quantitative thermodynamic modeling of Al-Bi-Zn. Solidification paths and microstructures of Al-Bi-Zn alloys are shown to be rather complex. Using thermodynamic calculations, these rich details involving up to three invariant reactions and unexpected monovariant reaction types can be clearly revealed and understood.

48 CFR 319.705-5 - Awards involving subcontracting plans.

Science.gov (United States)

2010-10-01

... SERVICES SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Subcontracting With Small Business, Small Disadvantaged Business, and Women-Owned Small Business Concerns 319.705-5 Awards involving subcontracting plans...

A Networks Approach to Modeling Enzymatic Reactions.

Science.gov (United States)

Imhof, P

2016-01-01

Modeling enzymatic reactions is a demanding task due to the complexity of the system, the many degrees of freedom involved and the complex, chemical, and conformational transitions associated with the reaction. Consequently, enzymatic reactions are not determined by precisely one reaction pathway. Hence, it is beneficial to obtain a comprehensive picture of possible reaction paths and competing mechanisms. By combining individually generated intermediate states and chemical transition steps a network of such pathways can be constructed. Transition networks are a discretized representation of a potential energy landscape consisting of a multitude of reaction pathways connecting the end states of the reaction. The graph structure of the network allows an easy identification of the energetically most favorable pathways as well as a number of alternative routes. © 2016 Elsevier Inc. All rights reserved.

Reaction mechanisms in heavy ion fusion

Directory of Open Access Journals (Sweden)

Lubian J.

2011-10-01

Full Text Available We discuss the reaction mechanisms involved in heavy ion fusion. We begin with collisions of tightly bound systems, considering three energy regimes: energies above the Coulomb barrier, energies just below the barrier and deep sub-barrier energies. We show that channel coupling effects may influence the fusion process at above-barrier energies, increasing or reducing the cross section predicted by single barrier penetration model. Below the Coulomb barrier, it enhances the cross section, and this effect increases with the system’s size. It is argued that this behavior can be traced back to the increasing importance of Coulomb coupling with the charge of the collision partners. The sharp drop of the fusion cross section observed at deep sub-barrier energies is addressed and the theoretical approaches to this phenomenon are discussed. We then consider the reaction mechanisms involved in fusion reactions of weakly bound systems, paying particular attention to the calculations of complete and incomplete fusion available in the literature.

Low Speed Technology for Small Turbine Development Reaction Injection Molded 7.5 Meter Wind Turbine Blade

Energy Technology Data Exchange (ETDEWEB)

David M. Wright; DOE Project Officer - Keith Bennett

2007-07-31

An optimized small turbine blade (7.5m radius) was designed and a partial section molded with the RIM (reaction-injection molded polymer) process for mass production. The intended market is for generic three-bladed wind turbines, 100 kilowatts or less, for grid-assist end users with rural and semi-rural sites, such as the farm/ranch market, having low to moderate IEC Class 3-4 wind regimes. This blade will have substantial performance improvements over, and be cheaper than, present-day 7.5m blades. This is made possible by the injection-molding process, which yields high repeatability, accurate geometry and weights, and low cost in production quantities. No wind turbine blade in the 7.5m or greater size has used this process. The blade design chosen uses a RIM skin bonded to a braided infused carbon fiber/epoxy spar. This approach is attractive to present users of wind turbine blades in the 5-10m sizes. These include rebladeing California wind farms, refurbishing used turbines for the Midwest farm market, and other manufacturers introducing new turbines in this size range.

Medium effects in direct reactions

International Nuclear Information System (INIS)

Karakoc, M; Bertulani, C

2013-01-01

We discuss medium corrections of the nucleon-nucleon (NN) cross sections and their influence on direct reactions at intermediate energies ≳50 MeV/nucleon. The results obtained with free NN cross sections are compared with those obtained with a geometrical treatment of Pauli-blocking and Dirac-Bruecker methods. We show that medium corrections may lead to sizable modifications for collisions at intermediate energies and that they are more pronounced in reactions involving weakly bound nuclei.

Interfacial reactions in intermetallic matrix composites

International Nuclear Information System (INIS)

Cantrell, L.B.; Clevenger, E.M.; Perepezko, J.H.

1993-01-01

The thermal stability of advanced composites is dominated by the behavior of internal interfaces. Analysis of these internal interfaces often involves consideration of at least ternary order phase equilibria. Limited thermodynamic data exists for ternary and higher order systems. However, a combined approach based upon the use of binary data to estimate ternary phase equilibria and experimentally determined reaction pathways is effective in the analysis of interface reactions in composite systems. In blended powder samples, thermal analysis was used to find possible reaction temperatures, while X-ray analysis, EDS, and EPMA of diffusion couples were used to assess interdiffusion reaction pathways. The approach is illustrated by compatibility studies between TiAl and TiSi 2 at 1,100 C, and in-situ reactions between B 4 C and TiAl at 1300 C where multiple reaction sequences have been analyzed to provide guidance for the design of in-situ reaction processing of composites

Reaction-rate formula in out of equilibrium quantum field theory

OpenAIRE

Niegawa, A.; Okano, K.; Ozaki, H.

1999-01-01

A complete derivation, from first principles, of the reaction-rate formula for a generic reaction taking place in an out of equilibrium quantum-field system is given. It is shown that the formula involves no finite-volume correction. Each term of the reaction-rate formula represents a set of physical processes that contribute to the reaction under consideration.

Becoming the denigrated other: Group relations perspectives on initial reactions to a bipolar disorder diagnosis

Directory of Open Access Journals (Sweden)

Susan G. Goldberg

2012-09-01

Full Text Available The initial reactions to a bipolar disorder diagnosis of research participants in a small, qualitative study consisted of astonishment, dread of being mad, and extremely negative associations. All had prior mental health diagnoses, including episodes of severe depression (all but one and alcoholism (one. All participants reported mental health histories prediagnosis and most had spent years contending with mental health labels, medications, symptoms, and hospitalizations. In addition, most participants were highly educated health professionals, quite familiar with the behaviors that the medical system considered to comprise bipolar disorder. Their negative associations to the initial bipolar disorder diagnosis, therefore, appeared inconsistent with their mental health histories and professional knowledge. This article contextualizes these initial reactions of shock and distress and proposes interpretations of these findings from societal and psychodynamic group relations perspectives. The participants’ initial negative reactions are conceptualized as involving the terror of being transported from the group of normal people into the group of mad or crazy people, i.e., people with mental illnesses, who may constitute a societal denigrated other.

Probing reaction dynamics with GDR decay

International Nuclear Information System (INIS)

Beene, J.R.

1994-01-01

The giant dipole resonance (GDR) has been a prolific source of information on the physics of the nucleus. Mostly it has taught us about nuclear structure, but recently experiments have utilized the GDR as a probe of nuclear reaction dynamics. In this report two examples of such investigations are discussed involving very different reactions and probing time scales that differ by a factor of ∼10 3

Intramolecular and Transannular Diels-Alder Reactions

DEFF Research Database (Denmark)

Tanner, David Ackland; Ascic, Erhad

2014-01-01

Few reactions can compete with the Diels-Alder (DA) [4+2] cycloaddition for the rapid and efficient generation of molecular complexity. The DA reaction is atom-economic and stereospecific, as well as diastereo- and regioselective. The intramolecular version (IMDA) of the DA cycloaddition and its...... and dienophile, methods for acceleration of IMDA reactions (such as use of high pressure) and catalysis (using oxophilic or carbophilic metal complexes, Brønsted acids, and enzymes). The use of furans as diene components (IMDAF), intramolecular hetero-DA (IMHDA) and IMDA reactions with inverse electron demand...... are also covered. Applications of IMDA to asymmetric synthesis (from substrate control through to enantioselective catalysis, including organocatalysis) are presented, along with tandem sequences involving IMDA cycloaddition. A theme pervading the whole chapter is the use of IMDA reactions for the total...

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

Energy Technology Data Exchange (ETDEWEB)

Goulay, Fabien; Trevitt, Adam J.; Meloni, Giovanni; Selby, Talitha M.; Osborn, David L.; Taatjes, Craig A.; Vereecken, Luc; Leone, Stephen R.

2008-12-05

The reactions of the methylidyne radical (CH) with ethylene, acetylene, allene, and methylacetylene are studied at room temperature using tunable vacuum ultraviolet (VUV) photoionization and time-resolved mass spectrometry. The CH radicals are prepared by 248 nm multiphoton photolysis of CHBr3 at 298 K and react with the selected hydrocarbon in a helium gas flow. Analysis of photoionization efficiency versus VUV photon wavelength permits isomer-specific detection of the reaction products and allows estimation of the reaction product branching ratios. The reactions proceed by either CH insertion or addition followed by H atom elimination from the intermediate adduct. In the CH + C2H4 reaction the C3H5 intermediate decays by H atom loss to yield 70(+-8)percent allene, 30(+-8)percent methylacetylene and less than 10percent cyclopropene, in agreement with previous RRKM results. In the CH + acetylene reaction, detection of mainly the cyclic C3H2 isomer is contrary to a previous RRKM calculation that predicted linear triplet propargylene to be 90percent of the total H-atom co-products. High-level CBS-APNO quantum calculations and RRKM calculation for the CH + C2H2 reaction presented in this manuscript predict a higher contribution of the cyclic C3H2 (27.0percent) versus triplet propargylene (63.5percent) than these earlier predictions. Extensive calculations on the C3H3 and C3H2D system combined with experimental isotope ratios for the CD + C2H2 reaction indicate that H-atom assisted isomerization in the present experiments is responsible for the discrepancy between the RRKM calculations and the experimental results. Cyclic isomers are also found to represent 30(+-6)percent of the detected products in the case of CH + methylacetylene, together with 33(+-6)percent 1,2,3-butatriene and 37(+-6)percent vinylacetylene. The CH + allene reaction gives 23(+-5)percent 1,2,3-butatriene and 77(+-5)percent vinylacetylene, whereas cyclic isomers are produced below the detection limit

Desensitizing Children's Emotional Reactions to the Mass Media.

Science.gov (United States)

Wilson, Barbara J.

1989-01-01

Assesses effectiveness of two desensitization strategies for reducing children's emotional reactions to mass media. Examines children having passive exposure, modeled exposure, or no exposure to lizards before watching a horror movie involving lizards. Finds that modeled exposure decreases emotional reactions and negative interpretations, whereas…

Reaction list for charged-particle-induced nuclear reactions: Z = 1 to Z = 98 (H to Cf), July 1973--September 1974

International Nuclear Information System (INIS)

McGowan, F.K.; Milner, W.T.

1975-01-01

This Reaction List for charged-particle-induced nuclear reactions has been prepared from the journal literature for the period from July 1973 through September 1974. Each published experimental paper is listed under the target nucleus in the nuclear reaction with a brief statement of the type of data in the paper. The nuclear reaction is denoted by A(a,b)B, where the mass of a is greater than or equal to (one nucleon mass). There is no restriction on energy. Nuclear reactions involving mesons in the outgoing channel are not included. Theoretical papers which treat directly with the analysis of nuclear reaction data and results are included in the Reaction List. The cutoff date for literature was September 30, 1974. (U.S.)

Exchange Reactions. Proceedings of the Symposium on Exchange Reactions

International Nuclear Information System (INIS)

1965-01-01

The mechanisms and kinetics of chemical reactions are of great interest to chemists. The study of exchange reactions in particular helps to shed light on the dynamics of chemical change, providing an insight into the structures and the reactivities of the chemical species involved. The main theme of this meeting was the subject of oxidation-reduction reactions in which the net result is the transfer of one or more electrons between the different oxidation states of the same element. Other studies reported included the transfer of protons, atoms, complex ligands or organic radicals between molecules. Heterogeneous exchange, which is of importance in many cases of catalytic action, was also considered. For a long time isotopic tracers have formed the most convenient means of studying exchange reactions and today a considerable amount of work continues to be done with their aid. Consequently, several papers presented at this Symposium reported on work carried out by purely radiochemical tracer methods. In recognition, however, of the important role which nuclear magnetic resonance and electron spin resonance play in this field, in particular in the study of fast reactions, a number of reports on investigations in which these techniques had been used was included in the programme. By kind invitation of the United States Government the Symposium on Exchange Reactions was held from 31 May to 4 June at the Brookhaven National Laboratory, Upton, Long Island, N.Y., USA. It was attended by 46 participants from nine countries and one inter-governmental organization. The publication of these Proceedings makes the contents of the papers and the discussion available to a wider audience

Subsequent development of the normal temperature fusion reaction. Joon kakuyugo sonogo no shinten

Energy Technology Data Exchange (ETDEWEB)

Matsumoto, T. (Hokkaido University, Sapporo (Japan). Faculty of Engineering)

1991-04-24

This paper reports on a NATTOH model made public in May 1989 by T. Matsumoto who took notice of abnormality of the normal temperature fusion reaction. The NATTO model is based on a chain reaction by hydrogen with a hydrogen-catalyzed fusion reaction which is the normal temperature fusion reaction as an elementary process. If a high temperature fusion reaction is a small-size simulation of the fusion reaction rising on the surface of the sparkling star like the sun, the normal temperature fusion reaction can be a small-size simulation of the phenomena in the last years of the star in the far distance of the space. This gives reality to the normal temperature fusion reaction. The reaction mechanism of the normal temperature fusion reaction is almost being clarified by a NATTOH model. There remain problems on a possibility of generation of unknown radioactive rays and identification of radioactive wastes, but it seems that a prospect of commercialization can be talked about now. As for the utilization as energy, sea water may be used as it is. 10 ref., 5 figs.

F/Cl + C2H2 reactions: Are the addition and hydrogen abstraction direct processes?

International Nuclear Information System (INIS)

Li Jilai; Geng Caiyun; Huang Xuri; Zhan Jinhui; Sun Chiachung

2006-01-01

The reactions of atomic radical F and Cl with acetylene have been studied theoretically using ab initio quantum chemistry methods and transition state theory. The doublet potential energy surfaces were calculated at the CCSD(T)/aug-cc-pVDZ//CCSD/6-31G(d,p), CCSD(T)/aug-cc-pVDZ//UMP2/6-311++G(d,p) and compound method Gaussian-3 levels. Two reaction mechanisms including the addition-elimination and the hydrogen abstraction reaction mechanisms are considered. In the addition-elimination reactions, the halogen atoms approach C 2 H 2 , perpendicular to the C≡C triple bond, forming the pre-reactive complex C1 at the reaction entrance. C1 transforms to intermediate isomer I1 via transition state TSC1/1 with a negative/small barrier for C 2 H 2 F/C 2 H 2 Cl system, which can proceed by further eliminating H atom endothermally. While the hydrogen abstraction reactions also involve C1 for the fluorine atom abstraction of hydrogen, yet the hydrogen abstraction by chlorine atom first forms a collinear hydrogen-bonded complex C2. The other reaction pathways on the doublet PES are less competitive due to thermodynamical or kinetic factors. According to our results, the presence of pre-reactive complexes indicates that the simple hydrogen abstraction and addition in the halogen atoms reaction with unsaturated hydrocarbon should be more complex. Furthermore, based on the analysis of the kinetics of all channels through which the addition and abstraction reactions proceed, we expect that the actual feasibility of the reaction channels may depend on the reaction conditions in the experiment. The present study may be helpful for probing the mechanisms of the title reactions and understanding the halogen chemistry

Four unexpected lanthanide coordination polymers involving in situ reaction of solvent N, N-Dimethylformamide

International Nuclear Information System (INIS)

Jin, Jun-Cheng; Tong, Wen-Quan; Fu, Ai-Yun; Xie, Cheng-Gen; Chang, Wen-Gui; Wu, Ju; Xu, Guang-Nian; Zhang, Ya-Nan; Li, Jun; Li, Yong; Yang, Peng-Qi

2015-01-01

Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of DMF solvent under solvothermal conditions. The isostructural complexes 1–3 contain four types of 2 1 helical chains. While the Nd(III) ions are bridged through μ 2 -HIDC 2− and oxalate to form a 2D sheet along the bc plane without helical character in 4. Therefore, complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature. - Graphical abstract: Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of solvent DMF to formate acid or oxalic acid under solvothermal conditions. The isostructural complexes 1–3 contain four types of different 2 1 helical chains in the 2D layer and 1 exhibits bright red solid-state phosphorescence upon UV radiation. - Highlights: • Four unexpected 2D lanthanide coordination compounds have been synthesized through in situ reactions under solvothermal conditions. • The complexes 1–3 contain four types of 2 1 helical chains in the layer. • Complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature

Modelling of structural effects on chemical reactions in turbulent flows

Energy Technology Data Exchange (ETDEWEB)

Gammelsaeter, H.R.

1997-12-31

Turbulence-chemistry interactions are analysed using algebraic moment closure for the chemical reaction term. The coupling between turbulence and chemical length and time scales generate a complex interaction process. This interaction process is called structural effects in this work. The structural effects are shown to take place on all scales between the largest scale of turbulence and the scales of the molecular motions. The set of equations describing turbulent correlations involved in turbulent reacting flows are derived. Interactions are shown schematically using interaction charts. Algebraic equations for the turbulent correlations in the reaction rate are given using the interaction charts to include the most significant couplings. In the frame of fundamental combustion physics, the structural effects appearing on the small scales of turbulence are proposed modelled using a discrete spectrum of turbulent scales. The well-known problem of averaging the Arrhenius law, the specific reaction rate, is proposed solved using a presumed single variable probability density function and a sub scale model for the reaction volume. Although some uncertainties are expected, the principles are addressed. Fast chemistry modelling is shown to be consistent in the frame of algebraic moment closure when the turbulence-chemistry interaction is accounted for in the turbulent diffusion. The modelling proposed in this thesis is compared with experimental data for an laboratory methane flame and advanced probability density function modelling. The results show promising features. Finally it is shown a comparison with full scale measurements for an industrial burner. All features of the burner are captured with the model. 41 refs., 33 figs.

Structure and reactions of quantum halos

International Nuclear Information System (INIS)

Jensen, A.S.; Riisager, K.; Fedorov, D.V.; Garrido, E.

2004-01-01

This article provides an overview of the basic principles of the physics of quantum halo systems, defined as bound states of clusters of particles with a radius extending well into classically forbidden regions. Exploiting the consequences of this definition, the authors derive the conditions for occurrence in terms of the number of clusters, binding energy, angular momentum, cluster charges, and excitation energy. All these quantities must be small. The article discusses the transitions between different cluster divisions and the importance of thresholds for cluster or particle decay, with particular attention to the Efimov effect and the related exotic states. The pertinent properties can be described by the use of dimensionless variables. Then universal and specific properties can be distinguished, as shown in a series of examples selected from nuclear, atomic, and molecular systems. The neutron dripline is especially interesting for nuclei and negative ions for atoms. For molecules, in which the cluster division comes naturally, a wider range of possibilities exists. Halos in two dimensions have very different properties, and their states are easily spatially extended, whereas Borromean systems are unlikely and spatially confined. The Efimov effect and the Thomas collapse occur only for dimensions between 2.3 and 3.8 and thus not for 2. High-energy reactions directly probe the halo structure. The authors discuss the reaction mechanisms for high-energy nuclear few-body halo breakup on light, intermediate, and heavy nuclear targets. For light targets, the strong interaction dominates, while for heavy targets, the Coulomb interaction dominates. For intermediate targets these processes are of comparable magnitude. As in atomic and molecular physics, a geometric impact-parameter picture is very appropriate. Finally, the authors briefly consider the complementary processes involving electroweak probes available through beta decay, electromagnetic transitions, and

Capture and photonuclear reaction rates involving charged-particles: Impacts of nuclear ingredients and future measurement on ELI-NP

Science.gov (United States)

Xu, Y.; Goriely, S.; Balabanski, D. L.; Chesnevskaya, S.; Guardo, G. L.; La Cognata, M.; Lan, H. Y.; Lattuada, D.; Luo, W.; Matei, C.

2018-05-01

The astrophysical p-process is an important way of nucleosynthesis to produce the stable and proton-rich nuclei beyond Fe which can not be reached by the s- and r-processes. In the present study, the impact of nuclear ingredients, especially the nuclear potential, level density and strength function, to the astrophysical re-action rates of (p,γ), (α,γ), (γ,p), and (γ,α) reactions are systematically studied. The calculations are performed basad on the modern reaction code TALYS for about 3000 stable and proton-rich nuclei with 12≤Z≤110. In particular, both of the Wood-Saxon potential and the microscopic folding potential are taken into account. It is found that both the capture and photonuclear reaction rates are very sensitive to the nuclear potential, thus the better determination of nuclear potential would be important to reduce the uncertainties of reaction rates. Meanwhile, the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility is being developed, which will provide the great opportunity to experimentally study the photonuclear reactions in p-process. Simulations of the experimental setup for the measurements of the photonuclear reactions 96Ru(γ,p) and 96Ru(γ,α) are performed. It is shown that the experiments of photonuclear reactions in p-process based on ELI-NP are quite promising.

Wastage-resistant characteristics of 12Cr steel tube material. Small leak sodium-water reaction test

International Nuclear Information System (INIS)

Shimoyama, Kazuhito

2004-03-01

In the water leak accident of a steam generator designed for a sodium cooled reactor in the Feasibility Study, the localization of tube failure propagation by using an advanced water leak detector will be required from the viewpoints of the safety and economical efficiency of the plant. So far, the conventional knowledge and analytical tools have been used in the investigation and evaluation of water leak phenomenon; nevertheless, there was neither test data nor the study of quantitative evaluation on the corrosion behavior, so-called wastage-resistant characteristics, of 12Cr steel tube material in sodium-water reactions. Wastage tests for the 12Cr steel tube material were conducted in small water leaks by use of the Sodium-Water Reaction Test Rig (SWAT-1R), and the data of wastage rate were obtained in the parameter of water leak rate under the constant sodium temperature and distance between leak and target tubes. The test results lead to the following conclusions: (1) The wastage-resistibility of 12Cr steel is 1.6 times greater than that of 9Cr steel and is 2.7 times greater than that of 2.25Cr-1Mo steel. (2)The wastage-resistibility of 12Cr steel increases in smaller water leaks; especially in water leak rates of 1 g/sec or less, it is more excellent than that of SUS321 stainless steel used as Monju superheater tube material. (3) Based on the correlation of wastage rate for the 9Cr steel, the correlation for the 12Cr steel has been obtained to be used for the evaluation of tube failure propagation. As the correlation of wastage rate for the 12Cr steel is based on the correlation for the 9Cr steel, it gives enough conservatism in smaller water leaks. To serve in accurately evaluating the tube failure propagation in smaller water leaks, it is necessary to obtain new correlation of wastage rate for the 12Cr steel based on the data in the wide range of water leak rates. (author)

Nuclear reactions excited by recoil protons on a nuclear reactor

International Nuclear Information System (INIS)

Mukhammedov, S.; Khaydarov, A.; Barsukova, E.G.

2006-01-01

The nuclear reactions excited by recoil protons and of the detection possibility of the various chemical elements with the use of these secondary nucleus reactions were investigated. The recoil protons are produced on a nuclear reactor in the result of (n, p) inelastic and elastic scattering interaction of fast neutrons with nuclei of hydrogen. It is well known that the share of fast neutrons in energetic spectrum of reactor's neutrons in comparison with the share of thermal neutrons is small. . Consequently, the share of recoil protons produced in the result of fast neutron interaction with nuclei of light elements, capable to cause the nuclear reactions, is also small, des, due to Coulomb barrier of nuclei the recoil protons can cause the nuclear reactions only on nuclei of light and some middle elements. Our studies show that observable yields have radio nuclides excited in the result of nuclear reactions on Li, B, O, V and Cu. Our experimental results have demonstrated that the proton activation analysis based on the application of secondary nuclear reactions is useful technique to determine large contents of various light and medium chemical elements. Detection limits for studied chemical elements are estimated better than 10 ppm

Conformational Flexibility of Proteins Involved in Ribosome Biogenesis: Investigations via Small Angle X-ray Scattering (SAXS

Directory of Open Access Journals (Sweden)

Dritan Siliqi

2018-02-01

Full Text Available The dynamism of proteins is central to their function, and several proteins have been described as flexible, as consisting of multiple domains joined by flexible linkers, and even as intrinsically disordered. Several techniques exist to study protein structures, but small angle X-ray scattering (SAXS has proven to be particularly powerful for the quantitative analysis of such flexible systems. In the present report, we have used SAXS in combination with X-ray crystallography to highlight their usefulness at characterizing flexible proteins, using as examples two proteins involved in different steps of ribosome biogenesis. The yeast BRCA2 and CDKN1A-interactig protein, Bcp1, is a chaperone for Rpl23 of unknown structure. We showed that it consists of a rigid, slightly elongated protein, with a secondary structure comprising a mixture of alpha helices and beta sheets. As an example of a flexible molecule, we studied the SBDS (Shwachman-Bodian-Diamond Syndrome protein that is involved in the cytoplasmic maturation of the 60S subunit and constitutes the mutated target in the Shwachman-Diamond Syndrome. In solution, this protein coexists in an ensemble of three main conformations, with the N- and C-terminal ends adopting different orientations with respect to the central domain. The structure observed in the protein crystal corresponds to an average of those predicted by the SAXS flexibility analysis.

Ambient Mechanochemical Solid-State Reactions of Carbon Nanotubes and Their Reactions via Covalent Coordinate Bond in Solution

Science.gov (United States)

Kabbani, Mohamad A.

In its first part, this thesis deals with ambient mechanochemical solid-state reactions of differently functionalized multiple walled carbon nanotubes (MWCNTs) while in its second part it investigates the cross-linking reactions of CNTs in solution via covalent coordinate bonds with transitions metals and carboxylate groups decorating their surfaces. In the first part a series of mechanochemical reactions involving different reactive functionalities on the CNTs such as COOH/OH, COOH/NH2 and COCl/OH were performed. The solid-state unzipping of CNTs leading to graphene formation was confirmed using spectroscopic, thermal and electron microscopy techniques. The non-grapheme products were established using in-situ quadruple mass spectroscopy. The experimental results were confirmed by theoretical simulation calculations using the 'hot spots' protocol. The kinetics of the reaction between MWCNT-COOH and MWCNT-OH was monitored using variable temperature Raman spectroscopy. The low activation energy was discussed in terms of hydrogen bond mediated proton transfer mechanism. The second part involves the reaction of MWCNTII COOH with Zn (II) and Cu (II) to form CNT metal-organic frame (MOFs) products that were tested for their effective use as counter-electrodes in dyes sensitized solar cells (DSSC). The thesis concludes by the study of the room temperature reaction between the functionalized graphenes, GOH and G'-COOH followed by the application of compressive loads. The 3D solid graphene pellet product ( 0.6gm/cc) is conductive and reflective with a 35MPa ultimate strength as compared to 10MPa strength of graphite electrode ( 2.2gm/cc).

Peripheral reactions

International Nuclear Information System (INIS)

Greiner, D.

1978-01-01

Peripheral collisions, that is, collisions involving a small amount of overlap of nuclear matter, are discussed including inclusive interactions, the magnitude of the peripheral cross section, fragmentation, a compilation of experiments and available data, limiting fragmentation, factorization, some models, fragment momentum distributions, and future research directions

Stochastic simulation of biological reactions, and its applications for studying actin polymerization.

Science.gov (United States)

Ichikawa, Kazuhisa; Suzuki, Takashi; Murata, Noboru

2010-11-30

Molecular events in biological cells occur in local subregions, where the molecules tend to be small in number. The cytoskeleton, which is important for both the structural changes of cells and their functions, is also a countable entity because of its long fibrous shape. To simulate the local environment using a computer, stochastic simulations should be run. We herein report a new method of stochastic simulation based on random walk and reaction by the collision of all molecules. The microscopic reaction rate P(r) is calculated from the macroscopic rate constant k. The formula involves only local parameters embedded for each molecule. The results of the stochastic simulations of simple second-order, polymerization, Michaelis-Menten-type and other reactions agreed quite well with those of deterministic simulations when the number of molecules was sufficiently large. An analysis of the theory indicated a relationship between variance and the number of molecules in the system, and results of multiple stochastic simulation runs confirmed this relationship. We simulated Ca²(+) dynamics in a cell by inward flow from a point on the cell surface and the polymerization of G-actin forming F-actin. Our results showed that this theory and method can be used to simulate spatially inhomogeneous events.

Stochastic simulation of biological reactions, and its applications for studying actin polymerization

International Nuclear Information System (INIS)

Ichikawa, Kazuhisa; Suzuki, Takashi; Murata, Noboru

2010-01-01

Molecular events in biological cells occur in local subregions, where the molecules tend to be small in number. The cytoskeleton, which is important for both the structural changes of cells and their functions, is also a countable entity because of its long fibrous shape. To simulate the local environment using a computer, stochastic simulations should be run. We herein report a new method of stochastic simulation based on random walk and reaction by the collision of all molecules. The microscopic reaction rate P r is calculated from the macroscopic rate constant k. The formula involves only local parameters embedded for each molecule. The results of the stochastic simulations of simple second-order, polymerization, Michaelis–Menten-type and other reactions agreed quite well with those of deterministic simulations when the number of molecules was sufficiently large. An analysis of the theory indicated a relationship between variance and the number of molecules in the system, and results of multiple stochastic simulation runs confirmed this relationship. We simulated Ca 2+ dynamics in a cell by inward flow from a point on the cell surface and the polymerization of G-actin forming F-actin. Our results showed that this theory and method can be used to simulate spatially inhomogeneous events

Capture and photonuclear reaction rates involving charged-particles: Impacts of nuclear ingredients and future measurement on ELI-NP

Directory of Open Access Journals (Sweden)

Xu Y.

2018-01-01

Full Text Available The astrophysical p-process is an important way of nucleosynthesis to produce the stable and proton-rich nuclei beyond Fe which can not be reached by the s- and r-processes. In the present study, the impact of nuclear ingredients, especially the nuclear potential, level density and strength function, to the astrophysical re-action rates of (p,γ, (α,γ, (γ,p, and (γ,α reactions are systematically studied. The calculations are performed basad on the modern reaction code TALYS for about 3000 stable and proton-rich nuclei with 12≤Z≤110. In particular, both of the Wood-Saxon potential and the microscopic folding potential are taken into account. It is found that both the capture and photonuclear reaction rates are very sensitive to the nuclear potential, thus the better determination of nuclear potential would be important to reduce the uncertainties of reaction rates. Meanwhile, the Extreme Light Infrastructure-Nuclear Physics (ELI-NP facility is being developed, which will provide the great opportunity to experimentally study the photonuclear reactions in p-process. Simulations of the experimental setup for the measurements of the photonuclear reactions 96Ru(γ,p and 96Ru(γ,α are performed. It is shown that the experiments of photonuclear reactions in p-process based on ELI-NP are quite promising.

Comparative Analysis of Clinical Samples Showing Weak Serum Reaction on AutoVue System Causing ABO Blood Typing Discrepancies.

Science.gov (United States)

Jo, Su Yeon; Lee, Ju Mi; Kim, Hye Lim; Sin, Kyeong Hwa; Lee, Hyeon Ji; Chang, Chulhun Ludgerus; Kim, Hyung Hoi

2017-03-01

ABO blood typing in pre-transfusion testing is a major component of the high workload in blood banks that therefore requires automation. We often experienced discrepant results from an automated system, especially weak serum reactions. We evaluated the discrepant results by the reference manual method to confirm ABO blood typing. In total, 13,113 blood samples were tested with the AutoVue system; all samples were run in parallel with the reference manual method according to the laboratory protocol. The AutoVue system confirmed ABO blood typing of 12,816 samples (97.7%), and these results were concordant with those of the manual method. The remaining 297 samples (2.3%) showed discrepant results in the AutoVue system and were confirmed by the manual method. The discrepant results involved weak serum reactions (serum reactions, samples from patients who had received stem cell transplants, ABO subgroups, and specific system error messages. Among the 98 samples showing ≤1+ reaction grade in the AutoVue system, 70 samples (71.4%) showed a normal serum reaction (≥2+ reaction grade) with the manual method, and 28 samples (28.6%) showed weak serum reaction in both methods. ABO blood tying of 97.7% samples could be confirmed by the AutoVue system and a small proportion (2.3%) needed to be re-evaluated by the manual method. Samples with a 2+ reaction grade in serum typing do not need to be evaluated manually, while those with ≤1+ reaction grade do.

Remarkable nanoconfinement effects on chemical equilibrium manifested in nucleotide dimerization and H-D exchange reactions.

Science.gov (United States)

Polak, Micha; Rubinovich, Leonid

2011-10-06

Nanoconfinement entropic effects on chemical equilibrium involving a small number of molecules, which we term NCECE, are revealed by two widely diverse types of reactions. Employing statistical-mechanical principles, we show how the NCECE effect stabilizes nucleotide dimerization observed within self-assembled molecular cages. Furthermore, the effect provides the basis for dimerization even under an aqueous environment inside the nanocage. Likewise, the NCECE effect is pertinent to a longstanding issue in astrochemistry, namely the extra deuteration commonly observed for molecules reacting on interstellar dust grain surfaces. The origin of the NCECE effect is elucidated by means of the probability distributions of the reaction extent and related variations in the reactant-product mixing entropy. Theoretical modelling beyond our previous preliminary work highlights the role of the nanospace size in addition to that of the nanosystem size, namely the limited amount of molecules in the reaction mixture. Furthermore, the NCECE effect can depend also on the reaction mechanism, and on deviations from stoichiometry. The NCECE effect, leading to enhanced, greatly variable equilibrium "constants", constitutes a unique physical-chemical phenomenon, distinguished from the usual thermodynamical properties of macroscopically large systems. Being significant particularly for weakly exothermic reactions, the effects should stabilize products in other closed nanoscale structures, and thus can have notable implications for the growing nanotechnological utilization of chemical syntheses conducted within confined nanoreactors.

Growth and Destruction of PAH Molecules in Reactions with Carbon Atoms

Energy Technology Data Exchange (ETDEWEB)

Krasnokutski, Serge A.; Huisken, Friedrich; Jäger, Cornelia; Henning, Thomas [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Helmholtzweg 3, D-07743 Jena (Germany)

2017-02-10

A very high abundance of atomic carbon in the interstellar medium (ISM), and the high reactivity of these species toward different hydrocarbon molecules including benzene, raise questions regarding the stability of polycyclic aromatic hydrocarbon (PAH) molecules in space. To test the efficiency of destruction of PAH molecules via reactions with atomic carbon, we performed a set of laboratory and computational studies of the reactions of naphthalene, anthracene, and coronene molecules with carbon atoms in the ground state. The reactions were investigated in liquid helium droplets at T = 0.37 K and by quantum chemical computations. Our studies suggest that all small and all large catacondensed PAHs react barrierlessly with atomic carbon, and therefore should be efficiently destroyed by such reactions in a broad temperature range. At the same time, large compact pericondensed PAHs should be more inert toward such a reaction. In addition, taking into account their higher photostability, much higher abundances of pericondensed PAHs should be expected in various astrophysical environments. The barrierless reactions between carbon atoms and small PAHs also suggest that, in the ISM, these reactions could lead to the bottom-up formation of PAH molecules.

Model reduction of detailed-balanced reaction networks by clustering linkage classes

NARCIS (Netherlands)

Rao, Shodhan; Jayawardhana, Bayu; van der Schaft, Abraham; Findeisen, Rolf; Bullinger, Eric; Balsa-Canto, Eva; Bernaerts, Kristel

2016-01-01

We propose a model reduction method that involves sequential application of clustering of linkage classes and Kron reduction. This approach is specifically useful for chemical reaction networks with each linkage class having less number of reactions. In case of detailed balanced chemical reaction

High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction.

Science.gov (United States)

Herron, J. Dudley, Ed.; Driscoll, D. R.

1979-01-01

Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

Ionizing radiation induced attachment reactions of nucleic acids and their components

International Nuclear Information System (INIS)

Myers, L.S. Jr.

1975-01-01

An extensive bibliographic review is given of experimental and theoretical data on radiation-induced attachment reactions of nucleic acids and their components. Mechanisms of these reactions are reviewed. The reactions with water, formate, and alcohols, with amines and other small molecules, and with radiation sensitizers and nucleic acid-nucleic acid reactions are discussed. Studies of the reaction mechanisms show that many of the reactions occur by radical-molecule reactions, but radical-radical reactions also occur. Radiation modifiers become attached to nucleic acids in vitro and in vivo and there are indications that attachment may be necessary for the action of some sensitizers. (U.S.)

Stereodynamics: From elementary processes to macroscopic chemical reactions

Energy Technology Data Exchange (ETDEWEB)

Kasai, Toshio [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Graduate School of Science, Department of Chemistry, Osaka University, Toyonaka, 560-0043 Osaka (Japan); Che, Dock-Chil [Graduate School of Science, Department of Chemistry, Osaka University, Toyonaka, 560-0043 Osaka (Japan); Tsai, Po-Yu [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Lin, King-Chuen [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Palazzetti, Federico [Scuola Normale Superiore, Pisa (Italy); Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, 06123 Perugia (Italy); Aquilanti, Vincenzo [Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, 06123 Perugia (Italy); Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Roma (Italy); Instituto de Fisica, Universidade Federal da Bahia, Salvador (Brazil)

2015-12-31

This paper aims at discussing new facets on stereodynamical behaviors in chemical reactions, i.e. the effects of molecular orientation and alignment on reactive processes. Further topics on macroscopic processes involving deviations from Arrhenius behavior in the temperature dependence of chemical reactions and chirality effects in collisions are also discussed.

Exploring Managerial Commitment towards SPI in Small and Very Small Enterprises

Science.gov (United States)

O'Connor, Rory V.; Basri, Shuib; Coleman, Gerry

This paper compares and contrasts the results of two similar studies into the software process practices in Irish Small and Very Small Enterprises. The first study contains rich findings in relation to the role and influence of managerial experience and style, with particular respect to the company founder and software development managers in small to medium seized enterprises (SMEs), whilst the second study contains extensive findings in relation to people and management involvement / commitment and SPI goal planning in very small enterprises (VSEs). By combining these results of these two studies of Irish SMEs/VSEs we can develop a rich picture of managerial commitment towards SPI and in particular explore the similarities between Small and Very Small Enterprises.

Application of the aza-Diels-Alder reaction in the synthesis of natural products.

Science.gov (United States)

Cao, Min-Hui; Green, Nicholas J; Xu, Sheng-Zhen

2017-04-11

The Diels-Alder reaction that involves a nitrogen atom in the diene or dienophile is termed the aza-Diels-Alder reaction. As well as the powerful all-carbon Diels-Alder reaction, the aza-Diels-Alder reaction has also played an important role in the total synthesis of natural products. Herein, we review various natural products using an aza-Diels-Alder reaction as a key step to their total synthesis, and divide the syntheses into inter- and intra-molecular aza-Diels-Alder reactions and a retro-aza-Diels-Alder reaction. Inter- and intra-molecular aza-Diels-Alder reactions involve an imine as an electron deficient dienophile and an imine as an electron deficient azadiene. The significance of the aza-Diels-Alder reaction for the construction of a six-membered ring containing nitrogen is tremendous, but the development of asymmetric, in particular catalytic enantioselective intramolecular aza-Diels-Alder reaction in the total synthesis of natural products remains highly challenging, and will no doubt see enormous advances in the future.

Modeling of Chemical Reactions in Afterburning for the Reduction of N2O

DEFF Research Database (Denmark)

Gustavsson, Lennart; Glarborg, Peter; Leckner, Bo

1996-01-01

Full scale tests in a 12 MW fluidized bed combustor on reduction of N2O by secondary fuel injection are analyzed in terms a model that involves a detailed reaction mechanism for the gas phase chemistry as well as a description of gas-solid reactions.......Full scale tests in a 12 MW fluidized bed combustor on reduction of N2O by secondary fuel injection are analyzed in terms a model that involves a detailed reaction mechanism for the gas phase chemistry as well as a description of gas-solid reactions....

Investigation of Na-CO2 Reaction with Initial Reaction in Various Reacting Surface

International Nuclear Information System (INIS)

Kim, Hyun Su; Park, Gunyeop; Kim, Soo Jae; Park, Hyun Sun; Kim, Moo Hwan; Wi, Myung-Hwan

2015-01-01

The reaction products that cause oxidation and erosion are threaten the heat transfer tubes so that it is necessary to investigate Na-CO 2 reaction according to various experimental parameter. Unlike SWR, Na-CO 2 reaction is more complex to deal with reaction kinetics. Since a comprehensive understanding of Na-CO 2 reaction mechanism is crucial for the safety analysis, the reaction phenomenon under the various conditions was investigated. The current issue is to make a database for developing computational code for CO 2 gas leak situation because it is experimentally difficult to analyze the actual accident situation. Most studies on Na-CO 2 interaction reports that chemical reaction is getting vigorous as temperature increased and reactivity is sensitive as temperature change between 400 .deg. C and 600 .deg. C. Therefore, temperature range is determined based on the operating condition (450 - 500 .deg. C) of KALIMER-600 employed as supercritical CO 2 brayton cycle energy conversion system for Na-CO 2 heat exchanger. And next parameter is sodium surface area which contact between sodium and CO 2 when CO 2 is injected into sodium pool in the accident situation. So, the fundamental surface reaction is experimentally studied in the range of 8 - 12cm 2 . Additionally, it has been reported in recent years that CO 2 Flow rate affects reactivity less significantly and CO 2 flow rate is assumed that 5 SLPM (standard liter per minute) is suitable as a basis for a small leakage. The finally selected control parameters is sodium temperature and reacting surface area with constant CO 2 flow rate. Na-CO 2 reaction test is performed for investigating risk of potential accident which contacts with liquid sodium and CO 2 . Amount of reaction is saturated as time passed because of kept a balance between production of solid phase reaction products and amount of diffusivity. These results contribute to make a database for the SFR safety analysis and additional experiments are needed

Shock implosion of a small homogeneous pellet

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Y.; Mishkin, E.A.; Alejaldre, C.

1985-10-01

A small spherical, or cylindrical, pellet is imploded by an intensive, evenly distributed, short energy pulse. At the surface of the pellet the matter ionizes, its temperature and pressure rapidly rise, and the ablated plasma, by reaction, implodes the inner nucleus of the pellet. The involved structure of the energy absorbing zone is idealized and a sharp deflagration front is considered. With an almost square energy pulse, slightly dropping with time, the solution of the mass, momentum, and energy conservation equations of the compressed matter, is self-similar. The differential equation of the nondimensional position of the deflagration front, its integral, and the magnitude and shape of the outside energy pulse are derived. The process of ablation is shown to depend solely on the nondimensional velocity of the gas just ahead of the deflagration front, minus the speed of sound, or the ratio of the gas densities across the deflagration front.

Shock implosion of a small homogeneous pellet

International Nuclear Information System (INIS)

Fujimoto, Y.; Mishkin, E.A.; Alejaldre, C.

1985-01-01

A small spherical, or cylindrical, pellet is imploded by an intensive, evenly distributed, short energy pulse. At the surface of the pellet the matter ionizes, its temperature and pressure rapidly rise, and the ablated plasma, by reaction, implodes the inner nucleus of the pellet. The involved structure of the energy absorbing zone is idealized and a sharp deflagration front is considered. With an almost square energy pulse, slightly dropping with time, the solution of the mass, momentum, and energy conservation equations of the compressed matter, is self-similar. The differential equation of the nondimensional position of the deflagration front, its integral, and the magnitude and shape of the outside energy pulse are derived. The process of ablation is shown to depend solely on the nondimensional velocity of the gas just ahead of the deflagration front, minus the speed of sound, or the ratio of the gas densities across the deflagration front

Modeling chemical reactions for drug design.

Science.gov (United States)

Gasteiger, Johann

2007-01-01

Chemical reactions are involved at many stages of the drug design process. This starts with the analysis of biochemical pathways that are controlled by enzymes that might be downregulated in certain diseases. In the lead discovery and lead optimization process compounds have to be synthesized in order to test them for their biological activity. And finally, the metabolism of a drug has to be established. A better understanding of chemical reactions could strongly help in making the drug design process more efficient. We have developed methods for quantifying the concepts an organic chemist is using in rationalizing reaction mechanisms. These methods allow a comprehensive modeling of chemical reactivity and thus are applicable to a wide variety of chemical reactions, from gas phase reactions to biochemical pathways. They are empirical in nature and therefore allow the rapid processing of large sets of structures and reactions. We will show here how methods have been developed for the prediction of acidity values and of the regioselectivity in organic reactions, for designing the synthesis of organic molecules and of combinatorial libraries, and for furthering our understanding of enzyme-catalyzed reactions and of the metabolism of drugs.

Three key points along an intrinsic reaction coordinate

Indian Academy of Sciences (India)

Unknown

Abstract. The concept of the reaction force is presented and discussed in detail. For typical processes with energy barriers, it has a universal form which defines three key points along an intrinsic reaction co- ordinate: the force minimum, zero and maximum. We suggest that the resulting four zones be interpreted as involving ...

Crystal structure of heterodimeric hexaprenyl diphosphate synthase from Micrococcus luteus B-P 26 reveals that the small subunit is directly involved in the product chain length regulation.

Science.gov (United States)

Sasaki, Daisuke; Fujihashi, Masahiro; Okuyama, Naomi; Kobayashi, Yukiko; Noike, Motoyoshi; Koyama, Tanetoshi; Miki, Kunio

2011-02-04

Hexaprenyl diphosphate synthase from Micrococcus luteus B-P 26 (Ml-HexPPs) is a heterooligomeric type trans-prenyltransferase catalyzing consecutive head-to-tail condensations of three molecules of isopentenyl diphosphates (C(5)) on a farnesyl diphosphate (FPP; C(15)) to form an (all-E) hexaprenyl diphosphate (HexPP; C(30)). Ml-HexPPs is known to function as a heterodimer of two different subunits, small and large subunits called HexA and HexB, respectively. Compared with homooligomeric trans-prenyltransferases, the molecular mechanism of heterooligomeric trans-prenyltransferases is not yet clearly understood, particularly with respect to the role of the small subunits lacking the catalytic motifs conserved in most known trans-prenyltransferases. We have determined the crystal structure of Ml-HexPPs both in the substrate-free form and in complex with 7,11-dimethyl-2,6,10-dodecatrien-1-yl diphosphate ammonium salt (3-DesMe-FPP), an analog of FPP. The structure of HexB is composed of mostly antiparallel α-helices joined by connecting loops. Two aspartate-rich motifs (designated the first and second aspartate-rich motifs) and the other characteristic motifs in HexB are located around the diphosphate part of 3-DesMe-FPP. Despite the very low amino acid sequence identity and the distinct polypeptide chain lengths between HexA and HexB, the structure of HexA is quite similar to that of HexB. The aliphatic tail of 3-DesMe-FPP is accommodated in a large hydrophobic cleft starting from HexB and penetrating to the inside of HexA. These structural features suggest that HexB catalyzes the condensation reactions and that HexA is directly involved in the product chain length control in cooperation with HexB.

The Reaction of Oxy Hemoglobin with Nitrite: Mechanism, Antioxidant-Modulated Effect, and Implications for Blood Substitute Evaluation

Directory of Open Access Journals (Sweden)

Denisa Hathazi

2018-02-01

Full Text Available The autocatalytic reaction between nitrite and the oxy form of globins involves free radicals. For myoglobin (Mb, an initial binding of nitrite to the iron-coordinated oxygen molecule was proposed; the resulting ferrous-peroxynitrate species was not detected, but its decay product, the high-valent ferryl form, was demonstrated in stopped-flow experiments. Reported here are the stopped flow spectra recorded upon mixing oxy Hb (native, as well as chemically-derivatized in the form of several candidates of blood substitutes with a supraphysiological concentration of nitrite. The data may be fitted to a simple kinetic model involving a transient met-aqua form, in contrast to the ferryl detected in the case of Mb in a similar reaction sequence. These data are in line with a previous observation of a transient accumulation of ferryl Hb under auto-catalytic conditions at much lower concentrations of nitrite (Grubina, R. et al. J. Biol. Chem. 2007, 282, 12916. The simple model for fitting the stopped-flow data leaves a small part of the absorbance changes unaccounted for, unless a fourth species is invoked displaying features similar to the oxy and tentatively assigned as ferrous-peroxynitrate. Density functional theory (DFT calculations support this latter assignment. The reaction allows for differentiating between the reactivities of various chemically modified hemoglobins, including candidates for blood substitutes. Polymerization of hemoglobin slows the nitrite-induced oxidation, in sharp contrast to oxidative-stress type reactions which are generally accelerated, not inhibited. Sheep hemoglobin is found to be distinctly more resistant to reaction with nitrite compared to bovine Hb, at large nitrite concentrations (stopped-flow experiments directly observing the oxy + nitrite reaction as well as under auto-catalytic conditions. Copolymerization of Hb with bovine serum albumin (BSA using glutaraldehyde leads to a distinct increase of the lag time

Complex Chemical Reaction Networks from Heuristics-Aided Quantum Chemistry.

Science.gov (United States)

Rappoport, Dmitrij; Galvin, Cooper J; Zubarev, Dmitry Yu; Aspuru-Guzik, Alán

2014-03-11

While structures and reactivities of many small molecules can be computed efficiently and accurately using quantum chemical methods, heuristic approaches remain essential for modeling complex structures and large-scale chemical systems. Here, we present a heuristics-aided quantum chemical methodology applicable to complex chemical reaction networks such as those arising in cell metabolism and prebiotic chemistry. Chemical heuristics offer an expedient way of traversing high-dimensional reactive potential energy surfaces and are combined here with quantum chemical structure optimizations, which yield the structures and energies of the reaction intermediates and products. Application of heuristics-aided quantum chemical methodology to the formose reaction reproduces the experimentally observed reaction products, major reaction pathways, and autocatalytic cycles.

Experimental test of exchange degeneracy in hypercharge exchange reactions

International Nuclear Information System (INIS)

Moffeit, K.C.

1978-10-01

Two pairs of line-reversed reactions π + P → K + Σ + , K - p → π - Σ + and π + p → K + Y* + (1385), K - p → π - Y* + (1385) provide an experimental test of exchange degeneracy in hypercharge exchange reactions. From their study it is concluded that in contrast to the lower energy data, the 11.5 results for the two pairs of reactions are consistent with exchange degeneracy predictions for both helicity-flip and nonflip amplitudes. The Y(1385) decay angular distributions indicate that the quark model and Stodolsky--Sakurai predictions are in agreement with the main features of the data. However, small violations are observed at small momentum transfer. While the Y(1385) vertex is helicity-flip dominated, the nonvanishing of T/sub 3/2 - 1/2/ and T/sub -3/2 1/2/ suggests some finite helicity nonflip contribution in the forward direction. 23 references

Back-reactions, short-circuits, leaks and other energy wasteful reactions in biological electron transfer: redox tuning to survive life in O(2).

Science.gov (United States)

Rutherford, A William; Osyczka, Artur; Rappaport, Fabrice

2012-03-09

The energy-converting redox enzymes perform productive reactions efficiently despite the involvement of high energy intermediates in their catalytic cycles. This is achieved by kinetic control: with forward reactions being faster than competing, energy-wasteful reactions. This requires appropriate cofactor spacing, driving forces and reorganizational energies. These features evolved in ancestral enzymes in a low O(2) environment. When O(2) appeared, energy-converting enzymes had to deal with its troublesome chemistry. Various protective mechanisms duly evolved that are not directly related to the enzymes' principal redox roles. These protective mechanisms involve fine-tuning of reduction potentials, switching of pathways and the use of short circuits, back-reactions and side-paths, all of which compromise efficiency. This energetic loss is worth it since it minimises damage from reactive derivatives of O(2) and thus gives the organism a better chance of survival. We examine photosynthetic reaction centres, bc(1) and b(6)f complexes from this view point. In particular, the evolution of the heterodimeric PSI from its homodimeric ancestors is explained as providing a protective back-reaction pathway. This "sacrifice-of-efficiency-for-protection" concept should be generally applicable to bioenergetic enzymes in aerobic environments. Copyright © 2012 Federation of European Biochemical Societies. All rights reserved.

Assessment of the potential for ammonium nitrate formation and reaction in Tank 241-SY-101

International Nuclear Information System (INIS)

Pederson, L.R.; Bryan, S.A.

1994-08-01

Two principal scenarios by which ammonium nitrate may be formed were considered: (a) precipitation of ammonium nitrate in the waste, and (b) ammonium nitrate formation via the gas phase reaction of ammonia and nitrogen dioxide. The first of these can be dismissed because ammonium ions, which are necessary for ammonium nitrate precipitation, can exist only in negligibly small concentrations in strongly alkaline solutions. Gas phase reactions between ammonia, nitrogen dioxide, and water vapor in the gas phase represent the most likely means by which ammonium nitrate aerosols could be formed in Tank 241-SY-101. Predicted ammonium nitrate formation rates are largely controlled by the concentration of nitrogen dioxide. This gas has not been detected among those gases vented from the wastes using Fourier Transform Infrared Spectrometry (FTIR) or mass spectrometry. While detection limits for nitrogen dioxide have not been established experimentally, the maximum concentration of nitrogen dioxide in the gas phase in Tank 241-SY-101 was estimated at 0.1 ppm based on calculations using the HITRAN data base and on FTIR spectra of gases vented from the wastes. At 50 C and with 100 ppm ammonia also present, less than one gram of ammonium nitrate per year is estimated to be formed in the tank. To date, ammonium nitrate has not been detected on HEPA filters in the ventilation system, so any quantity that has been formed in the tank must be quite small, in good agreement with rate calculations. The potential for runaway exothermic reactions involving ammonium nitrate in Tank 241-SY-101 is minimal. Dilution by non-reacting waste components, particularly water, would prevent hazardous exothermic reactions from occurring within the waste slurry, even if ammonium nitrate were present. 41 refs

Diagnosing ignition with DT reaction history

International Nuclear Information System (INIS)

Wilson, D. C.; Bradley, P. A.; Herrmann, H. W.; Cerjan, C. J.; Salmonson, J. D.; Spears, B. K.; Hatchet, S. P. II; Glebov, V. Yu.

2008-01-01

A full range DT reaction history of an ignition capsule, from 10 9 to 10 20 neutrons/ns, offers the opportunity to diagnose fuel conditions hundreds of picoseconds before and during burn. The burn history begins with a sharp rise when the first shock reaches the center of the capsule. The level of this jump reflects the combined shock strength and the adiabat of DT fuel. Changes to the four laser pulses driving the capsule implosion which are large enough to degrade the yield make measurable changes to the reaction history. Low mode asymmetries grow during convergence but change the reaction history during the final ∼100 ps. High mode asymmetry or turbulence mixing affects only the reaction history within ∼50 ps of peak burn rate. A capsule with a tritium fuel layer containing a small amount of deuterium (∼1%) creates a reaction history similar to the ignition capsule, but without the final ignition burn. A combination of gas Cerenkov detectors and the neutron temporal diagnostic could be capable of diagnosing the full history of ignition and tritium rich capsules.

Modeling the reactions catalyzed by coenzyme B12-dependent enzymes.

Science.gov (United States)

Sandala, Gregory M; Smith, David M; Radom, Leo

2010-05-18

Enzymes accelerate chemical reactions with an exceptional selectivity that makes life itself possible. Understanding the factors responsible for this efficient catalysis is of utmost importance in our quest to harness the tremendous power of enzymes. Computational chemistry has emerged as an important adjunct to experimental chemistry and biochemistry in this regard, because it provides detailed insights into the relationship between structure and function in a systematic and straightforward manner. In this Account, we highlight our recent high-level theoretical investigations toward this end in studying the radical-based reactions catalyzed by enzymes dependent on coenzyme B(12) (or adenosylcobalamin, AdoCbl). In addition to their fundamental position in biology, the AdoCbl-dependent enzymes represent a valuable framework within which to understand Nature's method of efficiently handling high-energy species to execute very specific reactions. The AdoCbl-mediated reactions are characterized by the interchange of a hydrogen atom and a functional group on adjacent carbon atoms. Our calculations are consistent with the conclusion that the main role of AdoCbl is to provide a source of radicals, thus moving the 1,2-rearrangements onto the radical potential energy surface. Our studies also show that the radical rearrangement step is facilitated by partial proton transfer involving the substrate. Specifically, we observe that the energy requirements for radical rearrangement are reduced dramatically with appropriate partial protonation or partial deprotonation or sometimes (synergistically) both. Such interactions are particularly relevant to enzyme catalysis, because it is likely that the local amino acid environment in the active site of an enzyme can function in this capacity through hydrogen bonding. Finally, our calculations indicate that the intervention of a very stable radical along the reaction pathway may inactivate the enzyme, demonstrating that sustained

Trojan Horse Method for neutrons-induced reaction studies

Science.gov (United States)

Gulino, M.; Asfin Collaboration

2017-09-01

Neutron-induced reactions play an important role in nuclear astrophysics in several scenario, such as primordial Big Bang Nucleosynthesis, Inhomogeneous Big Bang Nucleosynthesis, heavy-element production during the weak component of the s-process, explosive stellar nucleosynthesis. To overcome the experimental problems arising from the production of a neutron beam, the possibility to use the Trojan Horse Method to study neutron-induced reactions has been investigated. The application is of particular interest for reactions involving radioactive nuclei having short lifetime.

On the mechanism of effective chemical reactions with turbulent mixing of reactants and finite rate of molecular reactions

Energy Technology Data Exchange (ETDEWEB)

Vorotilin, V. P., E-mail: VPVorotilin@yandex.ru [Russian Academy of Sciences, Institute of Applied Mechanics (Russian Federation)

2017-01-15

A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into “active” and “passive” classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR.

Ribonucleoprotein organization of eukaryotic RNA. XXXII. U2 small nuclear RNA precursors and their accurate 3' processing in vitro as ribonucleoprotein particles.

Science.gov (United States)

Wieben, E D; Nenninger, J M; Pederson, T

1985-05-05

Biosynthetic precursors of U2 small nuclear RNA have been identified in cultured human cells by hybrid-selection of pulse-labeled RNA with cloned U2 DNA. These precursor molecules are one to approximately 16 nucleotides longer than mature U2 RNA and contain 2,2,7-trimethylguanosine "caps". The U2 RNA precursors are associated with proteins that react with a monoclonal antibody for antigens characteristic of small nuclear ribonucleoprotein particles. Like previously described precursors of U1 and U4 small nuclear RNAs, the pre-U2 RNAs are recovered in cytoplasmic fractions, although it is not known if this is their location in vivo. The precursors are processed to mature-size U2 RNA when cytoplasmic extracts are incubated in vitro at 37 degrees C. Mg2+ is required but ATP is not. The ribonucleoprotein structure of the pre-U2 RNA is maintained during the processing reaction in vitro, as are the 2,2,7-trimethylguanosine caps. The ribonucleoprotein organization is of major importance, as exogenous, protein-free U2 RNA precursors are degraded rapidly in the in vitro system. Two lines of evidence indicate that the conversion of U2 precursors to mature-size U2 RNA involves a 3' processing reaction. First, the reaction is unaffected by a large excess of mature U2 small nuclear RNP, whose 5' trimethylguanosine caps would be expected to compete for a 5' processing activity. Second, when pre-U2 RNA precursors are first stoichiometrically decorated with an antibody specific for 2,2,7-trimethylguanosine, the extent of subsequent processing in vitro is unaffected. These results provide the first demonstration of a eukaryotic RNA processing reaction in vitro occurring within a ribonucleoprotein particle.

Cyclodextrin-Catalyzed Organic Synthesis: Reactions, Mechanisms, and Applications

Directory of Open Access Journals (Sweden)

Chang Cai Bai

2017-09-01

Full Text Available Cyclodextrins are well-known macrocyclic oligosaccharides that consist of α-(1,4 linked glucose units and have been widely used as artificial enzymes, chiral separators, chemical sensors, and drug excipients, owing to their hydrophobic and chiral interiors. Due to their remarkable inclusion capabilities with small organic molecules, more recent interests focus on organic reactions catalyzed by cyclodextrins. This contribution outlines the current progress in cyclodextrin-catalyzed organic reactions. Particular emphases are given to the organic reaction mechanisms and their applications. In the end, the future directions of research in this field are proposed.

A Case of Immediate Hypersensitivity Reaction to Maltitol

Directory of Open Access Journals (Sweden)

Ana Rodríguez Trabado

2017-01-01

Full Text Available Background. Maltitol is a sugar alcohol that is frequently used as a noncaloric sweetener, although it is also used as an excipient, a plasticizer in gelatin capsules, and an emollient. It has not been previously described as an agent involved in immediate hypersensitivity reactions. Methods. We report on an anaphylactoid reaction with pharyngeal occlusion suffered by a 60-year-old man after ingestion of a candy containing maltitol syrup. A prick-to-prick test was performed with the candy and maltitol powder. Other allergens were excluded as causative agents of the adverse reaction, although the patient refused to undergo an oral challenge test with the candy. A basophil activation test (BAT was performed with maltitol powder, and a dose-response curve was generated. The test was also performed in 3 healthy controls. Results. Both prick-to-prick tests were negative. The result of the BAT was positive at all the concentrations tested in the patient’s blood and negative in all the controls. Conclusions. The BAT can help to clarify the agents implicated in an adverse reaction and can reduce the risk involved in diagnosis. The BAT can also prove useful in the study of reactions caused by low-molecular-weight antigens, for which routine diagnostic tests are not feasible.

Modified Small Business Network Security

OpenAIRE

Md. Belayet Ali; Oveget Das; Md. Shamim Hossain

2012-01-01

This paper covers some likely threats and effectivesteps for a secure small business. It also involves a flowchart tocomprehend the overall small business network security easilyand we identify a set of security issues and applyappropriate techniques to satisfy the correspondingsecurity requirements. In respect of all, this document isstrong enough for any small business network security.

Coherent and semi-coherent neutron transfer reactions

International Nuclear Information System (INIS)

Hagelstein, P.L.

1992-01-01

Neutron transfer reactions are proposed to account for anomalies reported in Pons-Fleischmann experiments. The prototypical reaction involves the transfer of a neutron (mediated by low frequency electric or magnetic fields) from a donor nucleus to virtual continuum states, followed by the capture of the virtual neutron by an acceptor nucleus. In this work we summarize basic principles, recent results and the ultimate goals of the theoretical effort

Coherent and semi-coherent neutron transfer reactions

International Nuclear Information System (INIS)

Hagelstein, P.L.

1993-01-01

Neutron transfer reactions are proposed to account for anomalies reported in Pons-Fleischmann experiments. The prototypical reaction involves the transfer of a neutron (mediated by low frequency electric or magnetic fields) from a donor nucleus to virtual continuum states, followed by the capture of the virtual neutron by an acceptor nucleus. In this work we summarize basic principles, recent results and the ultimate goals of the theoretical effort. (author)

Nanoscale studies of cement chemistry with 15N resonance reaction analysis

International Nuclear Information System (INIS)

Schweitzer, Jeffrey S.; Livingston, Richard A.; Rolfs, Claus; Becker, Hans-Werner; Kubsky, Stefan; Spillane, Timothy; Castellote, Marta; Viedma, Paloma G. de

2005-01-01

Analyses of materials with ion beams have proven to be a valuable technique for describing the spatial distributions of specific elements in host materials. We have applied this technique using the 15 N(p, αγ) 12 C reaction to study the time dependence of the chemical reactions involved in the curing of cement. By using the Dynamitron Tandem accelerator at the Ruhr Universitaet, Bochum, Germany, we have been able to achieve a few nanometer spatial resolution at the surface of cement grains and to study the hydrogen distributions to a depth of about 2 μm. By applying a technique for stopping the chemical reactions at arbitrary times, the time dependence of the chemical reactions involving specific components of cement can be investigated. In addition, the effects of additives on the chemical reactions have been studied, as have materials that are components of concrete

Reaction between uranium hexafluoride and trimethylsilylhalides

Energy Technology Data Exchange (ETDEWEB)

Brown, D; Berry, J A [UKAEA Atomic Energy Research Establishment, Harwell. Chemistry Div.; Holloway, J H; Staunton, G M [Leicester Univ. (UK). Dept. of Chemistry

1938-07-01

Reactions involving 1.1:1 molar ratios of uranium hexafluoride to either trimethylsilylchloride or trimethylsilylbromide in halocarbon solutions yield ..beta..-UF/sub 5/ at room temperature. With 2 mol equivalents of trimethylsilylchloride the product is UF/sub 4/. The reactions appear to proceed via the intermediate formation of unstable brown uranium(VI) chloride and bromide fluorides. Calculations show that UClF/sub 5/ and UCl/sub 2/F/sub 4/ are thermodynamically unstable with respect to the loss of chlorine at room temperature.

Hard and soft processes in small p/sub T/ inclusive reactions

Energy Technology Data Exchange (ETDEWEB)

Kanki, T [Osaka Univ., Toyonaka (Japan). Coll. of General Education; Okamoto, Y; Ryang, S

1977-12-01

Small p/sub T/ inclusive single-hadron spectra in high-energy hadron-hadron collisions are discussed in view of the two-component structure; each component corresponds to the contribution from the incoherent hard process or the coherent soft process among the partons. The clustered parton model, where each constituent quark is considered a cluster of the partons, gives the theoretical basis and certain regularities for both components. The various experimental spectra are shown to be well described by the two-component formula with these regularities. It is also argued that the CIM approach to small p sub(T) shows some disagreement with the data.

Solar nuclear reactions

Energy Technology Data Exchange (ETDEWEB)

Kocharov, G

1978-04-01

The current state of neutrino solar astrophysics is outlined, showing the contradictions between the experimental results of solar neutrino detection and the standard solar models constructed on the basis of the star structure and development theory, which give values for high-energy neutrino fluxes considerably exceeding the upper experimental limit. A number of hypotheses interpreting the experimental results are summarized. The hypotheses are critically assessed and experiments are recommended for refining or verifying experimental data. Also dealt with are nuclear reactions in the Sun, as is the attempt to interpret the anomalous by high /sup 3/He fluxes from the Sun and the relatively small amounts of solar neutrinos and gamma quanta. The importance is emphasized of the simultaneous and complex measurement of the fluxes of neutrons, gamma radiation, and isotopes of hydrogen, helium, and boron from the Sun as indicators of nuclear reactions in the Sun.

Increasing gender equality among small millet farmers in South Asia ...

International Development Research Centre (IDRC) Digital Library (Canada)

29 avr. 2016 ... Gender equality among small millet. More than 1,600 women were involved in testing small millet varieties. One reason for the decline in small millet cultivation is the drudgery involved in their processing, a task that traditionally falls to women. The Revalorizing small millets in South Asia (RESMISA) project ...

Small Hydropower - The comeback of small hydropower stations

International Nuclear Information System (INIS)

Niederhaeusern, A.

2008-01-01

This issue of the 'Erneuerbare Energien' (renewable energies) magazine published by the Swiss Solar Energy Society takes a look at small hydropower projects in Switzerland. In a number of interviews and articles, various topics concerning small hydropower are dealt with. First of all, an interview with Bruno Guggisberg, previously responsible for small hydro at the Swiss Federal Office of Energy, examines the potential of small hydro and the various political, technical and economic influences on such projects. Further articles provide an overview of the various types of small hydro schemes, including power generation using height differences in drinking-water and wastewater installations. As far as the components of small hydro schemes are concerned, various types of turbines and further system components that are needed are examined. A further article takes a look at the small hydro market and the market players involved. Ecological aspects and research activities are discussed in further articles. In a second interview with Martin Boelli, presently responsible for small hydropower at the Swiss Federal Office of Energy, the unused potential for the use of hydropower in Switzerland is discussed. Examples of small-scale hydro schemes are examined and the support offered by the Small Hydropower Program is discussed. Finally the question is asked, if the small hydro market in Switzerland is overheated as a result of promotion schemes such as cost-covering remuneration for electricity from renewable energy sources.

Redox reactions in food fermentations

DEFF Research Database (Denmark)

Hansen, Egon Bech

2018-01-01

involves oxidative steps in the early part of the pathways whereas a multitude of different reactions are used as compensating reductions. Much of the diversity seen between food fermentations arise from the different routes and the different electron acceptors used by microorganisms to counterbalance...... and this contributes to the diversity in flavor, color, texture, and shelf life. The review concludes that these reactions are still only incompletely understood and that they represent an interesting area for fundamental research and also represent a fertile field for product development through a more conscious use...... of the redox properties of strains used to compose food cultures....

Non-equilibrium effects in high temperature chemical reactions

Science.gov (United States)

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.

Theoretical insights into the sites and mechanisms for base catalyzed esterification and aldol condensation reactions over Cu.

Science.gov (United States)

Neurock, Matthew; Tao, Zhiyuan; Chemburkar, Ashwin; Hibbitts, David D; Iglesia, Enrique

2017-04-28

Condensation and esterification are important catalytic routes in the conversion of polyols and oxygenates derived from biomass to fuels and chemical intermediates. Previous experimental studies show that alkanal, alkanol and hydrogen mixtures equilibrate over Cu/SiO 2 and form surface alkoxides and alkanals that subsequently promote condensation and esterification reactions. First-principle density functional theory (DFT) calculations were carried out herein to elucidate the elementary paths and the corresponding energetics for the interconversion of propanal + H 2 to propanol and the subsequent C-C and C-O bond formation paths involved in aldol condensation and esterification of these mixtures over model Cu surfaces. Propanal and hydrogen readily equilibrate with propanol via C-H and O-H addition steps to form surface propoxide intermediates and equilibrated propanal/propanol mixtures. Surface propoxides readily form via low energy paths involving a hydrogen addition to the electrophilic carbon center of the carbonyl of propanal or via a proton transfer from an adsorbed propanol to a vicinal propanal. The resulting propoxide withdraws electron density from the surface and behaves as a base catalyzing the activation of propanal and subsequent esterification and condensation reactions. These basic propoxides can readily abstract the acidic C α -H of propanal to produce the CH 3 CH (-) CH 2 O* enolate, thus initiating aldol condensation. The enolate can subsequently react with a second adsorbed propanal to form a C-C bond and a β-alkoxide alkanal intermediate. The β-alkoxide alkanal can subsequently undergo facile hydride transfer to form the 2-formyl-3-pentanone intermediate that decarbonylates to give the 3-pentanone product. Cu is unique in that it rapidly catalyzes the decarbonylation of the C 2n intermediates to form C 2n-1 3-pentanone as the major product with very small yields of C 2n products. This is likely due to the absence of Brønsted acid sites

Probing the RAFT process using a model reaction between alkoxyamine and dithioester

NARCIS (Netherlands)

Zhou, Y.

2012-01-01

A small-molecular model reaction was designed to probe the reversible addition–fragmentation chain transfer (RAFT) process. In this reaction, alkoxyamine releases radicals that react in situ with dithioester through the RAFT process, generating new radicals through the fragmentation of the

Temperature effects on lithium-nitrogen reaction rates

International Nuclear Information System (INIS)

Ijams, W.J.; Kazimi, M.S.

1985-08-01

A series of experiments have been run with the aim of measuring the reaction rate of lithium and nitrogen over a wide spectrum of lithium pool temperatures. In these experiments, pure nitrogen was blown at a controlled flow rate over a preheated lithium pool. The pool had a surface area of approximately 4 cm 2 and a total volume of approximately 6 cm 3 . The system pressure varied from 0 to 4 psig. The reaction rate was very small - approximately 0.002 to 0.003 g Li min cm 2 for lithium temperatures below 500 0 C. Above 500 0 C the reaction rate began to increase sharply, and reached a maximum of approximately 0.80 g Li min cm 2 above 700 0 C. It dropped off beyond 1000 0 C and seemed to approach zero at 1150 0 C. The maximum reaction rate observed in these forced convection experiments was higher by 60% than those previously observed in experiments where the nitrogen flowed to the reaction site by means of natural convection. During a reaction, a hard nitride layer built up on the surface of the lithium pool - its effect on the reaction rate was observed. The effect of the nitrogen flow rate on the reaction rate was also observed

Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

International Nuclear Information System (INIS)

Kustova, Elena V.; Kremer, Gilberto M.

2014-01-01

Highlights: • State-to-state approach for coupled vibrational relaxation and chemical reactions. • Self-consistent model for rates of non-equilibrium reactions and energy transitions. • In viscous flows mass action law is violated. • Cross coupling between reaction rates and non-equilibrium pressure in viscous flow. • Results allow implementing the state-to-state approach for viscous flow simulations. - Abstract: Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman–Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N 2 flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure

Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

Energy Technology Data Exchange (ETDEWEB)

Kustova, Elena V., E-mail: e.kustova@spbu.ru [Department of Mathematics and Mechanics, Saint Petersburg State University, 198504 Universitetskiy pr. 28, Saint Petersburg (Russian Federation); Kremer, Gilberto M., E-mail: kremer@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba (Brazil)

2014-12-05

Highlights: • State-to-state approach for coupled vibrational relaxation and chemical reactions. • Self-consistent model for rates of non-equilibrium reactions and energy transitions. • In viscous flows mass action law is violated. • Cross coupling between reaction rates and non-equilibrium pressure in viscous flow. • Results allow implementing the state-to-state approach for viscous flow simulations. - Abstract: Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman–Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N{sub 2} flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure.

Droplet heat transfer and chemical reactions during direct containment heating

International Nuclear Information System (INIS)

Baker, L. Jr.

1986-01-01

A simplified model of heat transfer and chemical reaction has been adapted to evaluate the expected behavior of droplets containing unreacted Zircaloy and stainless steel moving through the containment atmosphere during postulated accidents involving direct containment heating. The model includes internal and external diffusive resistances to reaction. The results indicate that reactions will be incomplete for many conditions characteristic of direct containment heating sequences

NMR reaction monitoring in flow synthesis.

Science.gov (United States)

Gomez, M Victoria; de la Hoz, Antonio

2017-01-01

Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed.

Theoretical studies of chemical reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Schatz, G.C. [Argonne National Laboratory, IL (United States)

1993-12-01

This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

Intramolecular kinetic isotope effect in gas-phase proton-transfer reactions

International Nuclear Information System (INIS)

Wellman, K.M.; Victoriano, M.E.; Isolani, P.C.; Riveros, J.M.

1979-01-01

The k/sub H//k/sub D/ isotope effects were determined by ICR for the reaction of substituted toluenes with several alkoxides. The results showed a definite trend for k/sub H//k/sub D/ starting as a normal isotope effect for appreciably exothermic reaction (> 3 kcal mol -1 ) and proceeding smoothly toward an inverse isotope effect as the reaction approached thermoneutrality or becomes endothermic. These observations were explained by a reaction which involved a double minima potential with a central energy barrier

Ion-molecular reactions initiated by β-decay of tritium in tritiated compounds

International Nuclear Information System (INIS)

Akulov, G.P.

1976-01-01

Ion-molecular reactions initiated by β-decay of tritium and tritiated hydrocarbons have been systematized. The review describes the theoretical and experimental foundation of the radiochemical method of this important type of chemical interactions investigation. The reactions of the molecular ions of HeT + with methane, ethane, propane, butane and also with cycloalkanes from C 3 to C 6 are discussed. The reactions under consideration have been united into two groups: reactions involving HeT + ions and those involving carbonic ions. From the experimental results available, the conclusions have been drawn about the reactivity of these intermediate formations, about the mechanism of their interaction with organic substances, and also about the perspectives of using the radiochemical method in studies of ion-molecular reactions. The experimental results published before May 1974 are examined. The bibliography includes 162 references

Defect reactions on the phosphorus sublattice in low-temperature electron-irradiated InP

International Nuclear Information System (INIS)

Sibille, A.; Suski, J.

1985-01-01

This Rapid Communication describes several thermally or electronically stimulated defect reactions involving the dominant deep centers in low-temperature (25--300 K) electron-irradiated InP. Some of these reactions result in an increased concentration of the centers, thereby revealing the existence of a secondary production mechanism of the related defects. Low-energy irradiations allows one to select the type of the ejected atom (P) and gives direct evidence that only a phosphorus species, interstitial or vacancy, is involved in the creation-reaction-annealing events

Dynamic studies of small animals with a four-color diffuse optical tomography imager

International Nuclear Information System (INIS)

Schmitz, Christoph H.; Graber, Harry L.; Pei Yaling; Farber, Mark; Stewart, Mark; Levina, Rita D.; Levin, Mikhail B.; Xu Yong; Barbour, Randall L.

2005-01-01

We present newly developed instrumentation for full-tomographic four-wavelength, continuous wave, diffuse optical tomography (DOT) imaging on small animals. A small-animal imaging stage was constructed, from materials compatible with in-magnet studies, which offers stereotaxic fixation of the animal and precise, stable probe positioning. Instrument performance, based on calibration and phantom studies, demonstrates excellent long-term signal stability. DOT measurements of the functional rat brain response to electric paw stimulation are presented, and these demonstrate high data quality and excellent sensitivity to hemodynamic changes. A general linear model analysis on individual trials is used to localize and quantify the occurrence of functional behavior associated with the different hemoglobin state responses. Statistical evaluation of outcomes of individual trials is employed to identify significant regional response variations for different stimulation sites. Image results reveal a diffuse cortical response and a strong reaction of the thalamus, both indicative of activation of pain pathways by the stimulation. In addition, a weaker lateralized functional component is observed in the brain response, suggesting presence of motor activation. An important outcome of the experiment is that it shows that reactions to individual provocations can be monitored, without having to resort to signal averaging. Thus the described technology may be useful for studies of long-term trends in hemodynamic response, as would occur, for example, in behavioral studies involving freely moving animals

Reaction factoring and bipartite update graphs accelerate the Gillespie Algorithm for large-scale biochemical systems.

Science.gov (United States)

Indurkhya, Sagar; Beal, Jacob

2010-01-06

ODE simulations of chemical systems perform poorly when some of the species have extremely low concentrations. Stochastic simulation methods, which can handle this case, have been impractical for large systems due to computational complexity. We observe, however, that when modeling complex biological systems: (1) a small number of reactions tend to occur a disproportionately large percentage of the time, and (2) a small number of species tend to participate in a disproportionately large percentage of reactions. We exploit these properties in LOLCAT Method, a new implementation of the Gillespie Algorithm. First, factoring reaction propensities allows many propensities dependent on a single species to be updated in a single operation. Second, representing dependencies between reactions with a bipartite graph of reactions and species requires only storage for reactions, rather than the required for a graph that includes only reactions. Together, these improvements allow our implementation of LOLCAT Method to execute orders of magnitude faster than currently existing Gillespie Algorithm variants when simulating several yeast MAPK cascade models.

Hydrogen/Chlorine exchange reactions of gaseous carbanions.

Science.gov (United States)

Chen, Hao; Cooks, R Graham; Meurer, Eduardo C; Eberlin, Marcos N

2005-12-01

Gas-phase reactions of three typical carbanions CH(2)NO(2)(-), CH(2)CN(-), and CH(2)S(O)CH(3)(-) with the chloromethanes CH(2)Cl(2), CHCl(3), and CCl(4), examined by tandem mass spectrometry, show a novel hydrogen/chlorine exchange reaction. For example, reaction between the nitromethyl anion CH(2)NO(2)(-) and carbon tetrachloride CCl(4) forms the ion CHClNO(2)(-). The suggested reaction mechanism involves nucleophilic attack by CH(2)NO(2)(-) at the chlorine of CCl(4) followed by proton transfer within the resulting complex [CH(2)ClNO(2) + CCl(3)(-)] to form CHClNO(2)(-) and CHCl(3). Two other carbanions CH(2)CN(-) and CH(2)S(O)CH(3)(-) also undergo the novel hydrogen/chlorine exchange reactions with CCl(4) but to a much smaller extent, their higher nucleophilicities favoring competitive nucleophilic attack reactions. Proton abstraction is the exclusive pathway in the reactions of these carbanions with CHCl(3). While CH(2)CN(-) and CH(2)S(O)CH(3)(-) promote mainly proton abstraction and nucleophilic displacement in reactions with CH(2)Cl(2), CH(2)NO(2)(-) does not react.

Electron transfer reactions of macrocyclic compounds of cobalt

Energy Technology Data Exchange (ETDEWEB)

Heckman, R.A.

1978-08-01

The kinetics and mechanisms of reduction of H/sub 2/O/sub 2/, Br/sub 2/, and I/sub 2/ by various macrocyclic tetraaza complexes of cobalt(II), including Vitamin B/sub 12r/, were studied. The synthetic macrocycles studied were all 14-membered rings which varied in the degree of unsaturation,substitution of methyl groups on the periphery of the ring, and substitution within the ring itself. Scavenging experiments demonstrated that the reductions of H/sub 2/O/sub 2/ produce free hydroxyl radicals only in the case of Co((14)ane)/sup 2 +/ but with none of the others. In the latter instances apparently H/sub 2/O/sub 2/ simultaneously oxidizes the metal center and the ligand. The reductions of Br/sub 2/ and I/sub 2/ produce an aquohalocobalt(III) product for all reductants (except B/sub 12r/ + Br/sub 2/, which was complicated by bromination of the corrin ring). The mechanism of halogen reduction was found to involve rate-limiting inner-sphere electron transfer from cobalt to halogen to produce a dihalide anion coordinated to the cobalt center. This intermediate subsequently decomposes in rapid reactions to halocobalt(III) and halogen atom species or reacts with another cobalt(II) center to give two molecules of halocobalt(III). The reductions of halomethylcobaloximes and related compounds and diamminecobaloxime by Cr/sup 2 +/ were also studied. The reaction was found to be biphasic in all cases with the reaction products being halomethane (for the halomethylcobaloximes), Co/sup 2 +/ (in less than 100 percent yield), a Cr(III)-dimethylglyoxime species, a small amount of free dmgH/sub 2/, and a highly-charged species containing both cobalt and chromium. The first-stage reaction occurs with a stoichiometry of 1:1 producing an intermediate with an absorption maximum at 460 nm for all starting reagents. The results were interpreted in terms of inner-sphere coordination of the cobaloxime to the Cr(II) and electron transfer through the oxime N-O bond.

Substitution and protonation reactions of nitrilotriaceta tochromium(lll) ions

CSIR Research Space (South Africa)

Visser, HG

1994-04-01

Full Text Available The reaction of NH4[Cr(NTA)(H2O)2] (NTA = nitrilotriacetic acid) with H+ has been studied at different temperatures and a rate constant of 1.27(3) x 10(-2) S-1 was obtained at 25.1-degrees-C. It is proposed that the reaction involves the formation...

Kinetics of elementary atom and radical reactions: Progress report

International Nuclear Information System (INIS)

Gordon, R.J.

1986-01-01

Our research program is concerned with the kinetics of elementary gas phase reactions and energy transfer involving polyatomic molecules. We report here on three ongoing projects: The reaction of oxygen atoms with hydrogen molecules, the electronic relaxation of NH radicals, and the vibrational relaxation of highly excited SF 6 molecules. 10 refs., 5 figs

Modeling non-adiabatic photoexcited reaction dynamics in condensed phases

International Nuclear Information System (INIS)

Coker, D.F.

2003-01-01

Reactions of photoexcited molecules, ions, and radicals in condensed phase environments involve non-adiabatic dynamics over coupled electronic surfaces. We focus on how local environmental symmetries can effect non-adiabatic coupling between excited electronic states and thus influence, in a possibly controllable way, the outcome of photo-excited reactions. Semi-classical and mixed quantum-classical non-adiabatic molecular dynamics methods, together with semi-empirical excited state potentials are used to probe the dynamical mixing of electronic states in different environments from molecular clusters, to simple liquids and solids, and photo-excited reactions in complex reaction environments such as zeolites

Enhancing Activity for the Oxygen Evolution Reaction

DEFF Research Database (Denmark)

Frydendal, Rasmus; Busch, Michael; Halck, Niels Bendtsen

2014-01-01

Electrochemical production of hydrogen, facilitated in electrolyzers, holds great promise for energy storage and solar fuel production. A bottleneck in the process is the catalysis of the oxygen evolution reaction, involving the transfer of four electrons. The challenge is that the binding energies...... of all reaction intermediates cannot be optimized individually. However, experimental investigations have shown that drastic improvements can be realized for manganese and cobalt-based oxides if gold is added to the surface or used as substrate. We propose an explanation for these enhancements based...... that the oxygen evolution reaction overpotential decreases by 100–300 mV for manganese oxides and 100 mV for cobalt oxides....

Cluster emission at pre-equilibrium stage in Heavy Nuclear Reactions. A Model considering the Thermodynamics of Small Systems

International Nuclear Information System (INIS)

Bermudez Martinez, A.; Damiani, D.; Guzman Martinez, F.; Rodriguez Hoyos, O.; Rodriguez Manso, A.

2015-01-01

Cluster emission at pre-equilibrium stage, in heavy ion fusion reactions of 12 C and 16 O nuclei with 116 Sn, 208 Pb, 238 U are studied. the energy of the projectile nuclei was chosen at 0.25GeV, 0.5GeV and 1GeV. A cluster formation model is developed in order to calculate the cluster size. Thermodynamics of small systems was used in order to examine the cluster behavior inside the nuclear media. This model is based on considering two phases inside the compound nucleus, on one hand the nuclear media phase, and on the other hand the cluster itself. The cluster acts like an instability inside the compound nucleus, provoking an exchange of nucleons with the nuclear media through its surface. The processes were simulated using Monte Carlo methods. We obtained that the cluster emission probability shows great dependence on the cluster size. This project is aimed to implement cluster emission processes, during the pre-equilibrium stage, in the frame of CRISP code (Collaboration Rio-Sao Paulo). (Author)

Harnessing the Efficiency of 0(1D) Insertion Reactions for Prebiotic Astrochemistry

Science.gov (United States)

Widicus Weaver, Susanna

We propose a THz spectroscopic study of the small prebiotic molecules aminomethanol, methanediol, and methoxymethanol. These target molecules are predicted as the dominant products of photo-driven grain surface chemistry in interstellar environments, and are precursors to important prebiotic molecules like sugars and amino acids. These molecules are also expected to be major contributors to the spectral line density in the submillimeter spectral surveys from the Herschel and SOFIA observatories. We will use our custom mixing source to produce these molecules through O(1D) insertion reactions with the precursor molecules methyl amine, methanol, and dimethyl ether, respectively. We will then record their rotational spectra across the THz frequency range using our existing submillimeter spectrometer. This research will increase the science return from NASA missions because the target molecules serve as tracers of the simplest organic chemistry that can occur in starforming regions. This chemistry begins with methanol, which is the predominant organic molecule observed in interstellar ices. Methanol photodissociation leads to small organic radicals such as CH3O, CH2OH, and CH3. These radicals can undergo combination reactions on interstellar ices to form many of the complex organic molecules that are routinely observed in star-forming regions. Our target molecules aminomethanol, methanediol, and methoxymethanol are some of the simplest molecules that can form from this type of chemistry, and serve as tracers of ice mantle liberation in star-forming regions. These molecules also participate in gas-phase reactions that lead to amino acids and sugars, and as such are fundamentally important prebiotic molecules in interstellar environments. These types of small organic molecules also have high spectral line density, and are major contributors to line confusion in observational spectral surveys such as those conducted by Herschel and SOFIA. Therefore, the proposed research

Efficient library synthesis of imidazoles using a multicomponent reaction and microwave irradiation

NARCIS (Netherlands)

Gelens, E.; De Kanter, F.J.J.; Schmitz, R.F.; Sliedregt, L.A.; Van Steen, B.J.; Kruse, C.G.; Leurs, R.; Groen, M.B.; Orru, R.V.A.

2006-01-01

Optimization of Radziszewski's four-component reaction employing a microwave-assisted protocol, led to a small library of 48 imidazoles with a success rate of 65% (conversion >45%). All three diversity points of the four-component reaction were varied. Aromatic and aliphatic inputs were successfully

NMR reaction monitoring in flow synthesis

Directory of Open Access Journals (Sweden)

M. Victoria Gomez

2017-02-01

Full Text Available Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed.

Large local reactions to insect envenomation.

Science.gov (United States)

Carlson, John; Golden, David B K

2016-08-01

Insect stings often induce large local reactions (LLRs) that result in morbidity. These reactions do have an immunologic basis; however, patients presenting with LLRs should be managed differently than those with systemic allergic reactions, as described in this review. Morbidity results from the inflammation itself along with the iatrogenic consequences of treatment. The prescription of antihistamine medications and the use of antibiotics are generally not indicated for patients with LLRs because of the risks/side-effects of these medications and the low probability of benefit. Some patients are also concerned over the possibility that a future sting will evolve into a life-threatening reaction. Although these reactions do involve IgE, patients are not at sufficient risk to warrant prescription of autoinjectable epinephrine. Venom-specific immunotherapy can be considered when LLRs are frequent and associated with significant impairment. Clinicians can reduce morbidity from LLRs by reassuring the patients, avoiding medications that result in side-effects when they are not indicated, and referring to an allergist when there are additional concerns, such as frequent impairment.

Resonant Interaction, Approximate Symmetry, and Electromagnetic Interaction (EMI) in Low Energy Nuclear Reactions (LENR)

Science.gov (United States)

Chubb, Scott

2007-03-01

Only recently (talk by P.A. Mosier-Boss et al, in this session) has it become possible to trigger high energy particle emission and Excess Heat, on demand, in LENR involving PdD. Also, most nuclear physicists are bothered by the fact that the dominant reaction appears to be related to the least common deuteron(d) fusion reaction,d+d ->α+γ. A clear consensus about the underlying effect has also been illusive. One reason for this involves confusion about the approximate (SU2) symmetry: The fact that all d-d fusion reactions conserve isospin has been widely assumed to mean the dynamics is driven by the strong force interaction (SFI), NOT EMI. Thus, most nuclear physicists assume: 1. EMI is static; 2. Dominant reactions have smallest changes in incident kinetic energy (T); and (because of 2), d+d ->α+γ is suppressed. But this assumes a stronger form of SU2 symmetry than is present; d+d ->α+γ reactions are suppressed not because of large changes in T but because the interaction potential involves EMI, is dynamic (not static), the SFI is static, and because the two incident deuterons must have approximate Bose Exchange symmetry and vanishing spin. A generalization of this idea involves a resonant form of reaction, similar to the de-excitation of an atom. These and related (broken gauge) symmetry EMI effects on LENR are discussed.

One-electron transfer reactions of the couple NAD./NADH

International Nuclear Information System (INIS)

Grodkowski, J.; Neta, P.; Carlson, B.W.; Miller, L.

1983-01-01

One-electron transfer reactions involving nicotinamide-adenine dinucleotide in its oxidized and reducd forms (NAD./NADH) were studied by pulse radiolysis in aqueous solutions. One-electron oxidation of NADH by various phenoxyl radicals and phenothiazine cation radicals was found to take place with rate constants in the range of 10 5 to 10 8 M -1 s -1 , depending on the redox potential of the oxidizing species. In all cases, NAD. is formed quantitatively with no indication for the existence of the protonated form (NADH + .). The spectrum of NAD., as well as the rates of oxidation of NADH by phenoxyl and by (chlorpromazine) + . were independent of pH between pH 4.5 and 13.5. Reaction of deuterated NADH indicated only a small kinetic isotope effect. All these findings point to an electron transfer mechanism. On the other hand, attempts to observe the reverse electron transfer, i.e., one-electron reduction of NAD. to NADH by radicals such as semiquinones, showed that k was less than 10 4 to 10 5 M -1 s -1 , so that it was unobservable. Consequently, it was not possible to achieve equilibrium conditions which would have permitted the direct measurement of the redox potential for NAD./NADH. One-electron reduction of NAD. appears to be an unlikely process. 1 table

Nanoscale studies of cement chemistry with {sup 15}N resonance reaction analysis

Energy Technology Data Exchange (ETDEWEB)

Schweitzer, Jeffrey S. [University of Connecticut, Department of Physics, Unit 3046, Storrs, CT 06269-3046 (United States)]. E-mail: schweitz@phys.uconn.edu; Livingston, Richard A. [Federal Highway Administration, HRDI-05, 6300 Georgetown Pike McLean, VA 22101 (United States); Rolfs, Claus [Institut fuer Physik mit Ionenstrahlen, Ruhr-Universitaet, Bochum Universitaetsstr. 150, Gebaeude NB 3, 44780 Bochum (Germany); Becker, Hans-Werner [Institut fuer Physik mit Ionenstrahlen, Ruhr-Universitaet, Bochum Universitaetsstr. 150, Gebaeude NB 3, 44780 Bochum (Germany); Kubsky, Stefan [Institut fuer Physik mit Ionenstrahlen, Ruhr-Universitaet, Bochum Universitaetsstr. 150, Gebaeude NB 3, 44780 Bochum (Germany); Spillane, Timothy [University of Connecticut, Department of Physics, Unit 3046, Storrs, CT 06269-3046 (United States); Castellote, Marta [Institute of Construction Science ' Eduardo Torroja' (CSIC), Serrano Galvache no. 4, 28033 Madrid (Spain); Viedma, Paloma G. de [Institute of Construction Science ' Eduardo Torroja' (CSIC), Serrano Galvache no. 4, 28033 Madrid (Spain)

2005-12-15

Analyses of materials with ion beams have proven to be a valuable technique for describing the spatial distributions of specific elements in host materials. We have applied this technique using the {sup 15}N(p, {alpha}{gamma}){sup 12}C reaction to study the time dependence of the chemical reactions involved in the curing of cement. By using the Dynamitron Tandem accelerator at the Ruhr Universitaet, Bochum, Germany, we have been able to achieve a few nanometer spatial resolution at the surface of cement grains and to study the hydrogen distributions to a depth of about 2 {mu}m. By applying a technique for stopping the chemical reactions at arbitrary times, the time dependence of the chemical reactions involving specific components of cement can be investigated. In addition, the effects of additives on the chemical reactions have been studied, as have materials that are components of concrete.

Structures of riboswitch RNA reaction states by mix-and-inject XFEL serial crystallography

Science.gov (United States)

Stagno, J. R.; Liu, Y.; Bhandari, Y. R.; Conrad, C. E.; Panja, S.; Swain, M.; Fan, L.; Nelson, G.; Li, C.; Wendel, D. R.; White, T. A.; Coe, J. D.; Wiedorn, M. O.; Knoska, J.; Oberthuer, D.; Tuckey, R. A.; Yu, P.; Dyba, M.; Tarasov, S. G.; Weierstall, U.; Grant, T. D.; Schwieters, C. D.; Zhang, J.; Ferré-D'Amaré, A. R.; Fromme, P.; Draper, D. E.; Liang, M.; Hunter, M. S.; Boutet, S.; Tan, K.; Zuo, X.; Ji, X.; Barty, A.; Zatsepin, N. A.; Chapman, H. N.; Spence, J. C. H.; Woodson, S. A.; Wang, Y.-X.

2017-01-01

Riboswitches are structural RNA elements that are generally located in the 5‧ untranslated region of messenger RNA. During regulation of gene expression, ligand binding to the aptamer domain of a riboswitch triggers a signal to the downstream expression platform. A complete understanding of the structural basis of this mechanism requires the ability to study structural changes over time. Here we use femtosecond X-ray free electron laser (XFEL) pulses to obtain structural measurements from crystals so small that diffusion of a ligand can be timed to initiate a reaction before diffraction. We demonstrate this approach by determining four structures of the adenine riboswitch aptamer domain during the course of a reaction, involving two unbound apo structures, one ligand-bound intermediate, and the final ligand-bound conformation. These structures support a reaction mechanism model with at least four states and illustrate the structural basis of signal transmission. The three-way junction and the P1 switch helix of the two apo conformers are notably different from those in the ligand-bound conformation. Our time-resolved crystallographic measurements with a 10-second delay captured the structure of an intermediate with changes in the binding pocket that accommodate the ligand. With at least a 10-minute delay, the RNA molecules were fully converted to the ligand-bound state, in which the substantial conformational changes resulted in conversion of the space group. Such notable changes in crystallo highlight the important opportunities that micro- and nanocrystals may offer in these and similar time-resolved diffraction studies. Together, these results demonstrate the potential of ‘mix-and-inject’ time-resolved serial crystallography to study biochemically important interactions between biomacromolecules and ligands, including those that involve large conformational changes.

Nuclear reactions in astrophysics

International Nuclear Information System (INIS)

Cardenas, M.

1976-01-01

It is revised the nuclear reactions which present an interest in astrophysics regarding the explanation of some problems such as the relative quantity of the elements, the structure and evolution of the stars. The principal object of the study is the determination of the experimental possibilities in the field of astrophysics, of an accelerator Van de Graaff's 700 KeV type. Two hundred nuclear reactions approximately, were found, and nothing or very little has been done in the intervals of energy which are of interest. Since the bombardment energies and the involved sections are low in some cases, there are real possibilities, for the largest number of stars to obtain important statistical data with the above mentioned accelerator, taking some necessary precautions. (author)

Heterogeneous Catalysis: Deuterium Exchange Reactions of Hydrogen and Methane

Science.gov (United States)

Mirich, Anne; Miller, Trisha Hoette; Klotz, Elsbeth; Mattson, Bruce

2015-01-01

Two gas phase deuterium/hydrogen exchange reactions are described utilizing a simple inexpensive glass catalyst tube containing 0.5% Pd on alumina through which gas mixtures can be passed and products collected for analysis. The first of these exchange reactions involves H[subscript 2] + D[subscript 2], which proceeds at temperatures as low as 77…

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

KAUST Repository

Hisatomi, Takashi

2014-10-16

Abstract: Some particulate semiconductors loaded with nanoparticulate catalysts exhibit photocatalytic activity for the water-splitting reaction. The photocatalysis is distinct from the thermal catalysis because photocatalysis involves photophysical processes in particulate semiconductors. This review article presents a brief introduction to photocatalysis, followed by kinetic aspects of the photocatalytic water-splitting reaction.Graphical Abstract: [Figure not available: see fulltext.

Investigation of Na-CO{sub 2} Reaction with Initial Reaction in Various Reacting Surface

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyun Su; Park, Gunyeop; Kim, Soo Jae; Park, Hyun Sun; Kim, Moo Hwan [POSTECH, Pohang (Korea, Republic of); Wi, Myung-Hwan [KAERI, Daejeon (Korea, Republic of)

2015-10-15

The reaction products that cause oxidation and erosion are threaten the heat transfer tubes so that it is necessary to investigate Na-CO{sub 2} reaction according to various experimental parameter. Unlike SWR, Na-CO{sub 2} reaction is more complex to deal with reaction kinetics. Since a comprehensive understanding of Na-CO{sub 2} reaction mechanism is crucial for the safety analysis, the reaction phenomenon under the various conditions was investigated. The current issue is to make a database for developing computational code for CO{sub 2} gas leak situation because it is experimentally difficult to analyze the actual accident situation. Most studies on Na-CO{sub 2} interaction reports that chemical reaction is getting vigorous as temperature increased and reactivity is sensitive as temperature change between 400 .deg. C and 600 .deg. C. Therefore, temperature range is determined based on the operating condition (450 - 500 .deg. C) of KALIMER-600 employed as supercritical CO{sub 2} brayton cycle energy conversion system for Na-CO{sub 2} heat exchanger. And next parameter is sodium surface area which contact between sodium and CO{sub 2} when CO{sub 2} is injected into sodium pool in the accident situation. So, the fundamental surface reaction is experimentally studied in the range of 8 - 12cm{sup 2}. Additionally, it has been reported in recent years that CO{sub 2} Flow rate affects reactivity less significantly and CO{sub 2} flow rate is assumed that 5 SLPM (standard liter per minute) is suitable as a basis for a small leakage. The finally selected control parameters is sodium temperature and reacting surface area with constant CO{sub 2} flow rate. Na-CO{sub 2} reaction test is performed for investigating risk of potential accident which contacts with liquid sodium and CO{sub 2}. Amount of reaction is saturated as time passed because of kept a balance between production of solid phase reaction products and amount of diffusivity. These results contribute to make a

Modeling of fluctuating reaction networks

International Nuclear Information System (INIS)

Lipshtat, A.; Biham, O.

2004-01-01

Full Text:Various dynamical systems are organized as reaction networks, where the population size of one component affects the populations of all its neighbors. Such networks can be found in interstellar surface chemistry, cell biology, thin film growth and other systems. I cases where the populations of reactive species are large, the network can be modeled by rate equations which provide all reaction rates within mean field approximation. However, in small systems that are partitioned into sub-micron size, these populations strongly fluctuate. Under these conditions rate equations fail and the master equation is needed for modeling these reactions. However, the number of equations in the master equation grows exponentially with the number of reactive species, severely limiting its feasibility for complex networks. Here we present a method which dramatically reduces the number of equations, thus enabling the incorporation of the master equation in complex reaction networks. The method is examplified in the context of reaction network on dust grains. Its applicability for genetic networks will be discussed. 1. Efficient simulations of gas-grain chemistry in interstellar clouds. Azi Lipshtat and Ofer Biham, Phys. Rev. Lett. 93 (2004), 170601. 2. Modeling of negative autoregulated genetic networks in single cells. Azi Lipshtat, Hagai B. Perets, Nathalie Q. Balaban and Ofer Biham, Gene: evolutionary genomics (2004), In press

Solvent-Free Wittig Reaction: A Green Organic Chemistry Laboratory Experiment

Science.gov (United States)

Leung, Sam H.; Angel, Stephen A.

2004-01-01

Some Wittig reactions can be carried out by grinding the reactants in a mortar with a pestle for about 20 minutes, as per investigation. A laboratory experiment involving a solvent-free Wittig reaction that can be completed in a three-hour sophomore organic chemistry laboratory class period, are developed.

Students' Reactions to Course Policy Decisions

Science.gov (United States)

Bailey, Sarah F.; Jenkins, Jade S.; Barber, Larissa K.

2016-01-01

Classroom management involves managing students' requests for course policy changes. Instructors can adhere to the course policies or convey flexibility through making an exception for the student. The current study empirically examines students' emotional reactions (hostility, guilt, and surprise) and fairness perceptions to course policy…

Emotional reactions to harmful intergroup behavior

NARCIS (Netherlands)

Gordijn, E.H.; Yzerbyt, V.Y.; Wigboldus, D.H.J.; Dumont, M.

2006-01-01

In this paper, we examined reactions to situations in which, although one is not personally involved, one could see oneself connected to either the perpetrators or the victims of unfair behavior. We manipulated participants' similarity and measured their identification to either one of two groups

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

Directory of Open Access Journals (Sweden)

Shinichi Yamabe

2014-01-01

Full Text Available Wolff–Kishner reduction reactions were investigated by DFT calculations for the first time. B3LYP/6-311+G(d,p SCRF=(PCM, solvent = 1,2-ethanediol optimizations were carried out. To investigate the role of the base catalyst, the base-free reaction was examined by the use of acetone, hydrazine (H2N–NH2 and (H2O8. A ready reaction channel of acetone → acetone hydrazine (Me2C=N–NH2 was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N2 extrusion step from the isopropyl diimine intermediate (Me2C(H–N=N–H. Two base-catalyzed reactions were investigated by models of the ketone, H2N–NH2 and OH−(H2O7. Here, ketones are acetone and acetophenone. While routes of the ketone → hydrazone → diimine are similar, those from the diimines are different. From the isopropyl diimine, the N2 extrusion and the C–H bond formation takes place concomitantly. The concomitance leads to the propane product concertedly. From the (1-phenylethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene product. For both ketone substrates, the diimines undergoing E2 reactions were found to be key intermediates.

Propulsion of a Molecular Machine by Asymmetric Distribution of Reaction Products

Science.gov (United States)

Golestanian, Ramin; Liverpool, Tanniemola B.; Ajdari, Armand

2005-06-01

A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. The motion of the device is driven by an asymmetric distribution of reaction products. The propulsive velocity of the device is calculated as well as the scale of the velocity fluctuations. The effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction are addressed.

A concise summary of experimental facts about the Soai reaction.

Science.gov (United States)

Gehring, Timo; Busch, Mark; Schlageter, Martin; Weingand, Daniel

2010-01-01

The Soai reaction amplifies small enantiomeric excesses in a spectacular manner. Being known for 20 years, it has drawn the attention of many scientists in different fields as it is to date the only chemical reaction offering the chance to study the phenomenon of asymmetric autocatalysis in conjunction with high amplification of enantiomeric excess (ee). This mini-review comprises an introduction to the discovery of asymmetric autocatalysis with amplification of ee and a concise summary of published experimental results showing which starting materials and reaction parameters play an important role in this reaction and which influences are understood. It is addressed especially to scientists entering the field of the Soai reaction to get a quick overview of important aspects. © 2010 Wiley-Liss, Inc.

Small organic molecule based flow battery

Science.gov (United States)

Huskinson, Brian; Marshak, Michael; Aziz, Michael J.; Gordon, Roy G.; Betley, Theodore A.; Aspuru-Guzik, Alan; Er, Suleyman; Suh, Changwon

2018-05-08

The invention provides an electrochemical cell based on a new chemistry for a flow battery for large scale, e.g., gridscale, electrical energy storage. Electrical energy is stored chemically at an electrochemical electrode by the protonation of small organic molecules called quinones to hydroquinones. The proton is provided by a complementary electrochemical reaction at the other electrode. These reactions are reversed to deliver electrical energy. A flow battery based on this concept can operate as a closed system. The flow battery architecture has scaling advantages over solid electrode batteries for large scale energy storage.

Molecular beam studies of reaction dynamics

International Nuclear Information System (INIS)

Lee, Yuan T.

1991-03-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation

Molecular beam studies of reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

A novel and facile decay path of Criegee intermediates by intramolecular insertion reactions via roaming transition states

International Nuclear Information System (INIS)

Nguyen, Trong-Nghia; Putikam, Raghunath; Lin, M. C.

2015-01-01

We have discovered a new and highly competitive product channel in the unimolecular decay process for small Criegee intermediates, CH 2 OO and anti/syn-CH 3 C(H)OO, occurring by intramolecular insertion reactions via a roaming-like transition state (TS) based on quantum-chemical calculations. Our results show that in the decomposition of CH 2 OO and anti-CH 3 C(H)OO, the predominant paths directly produce cis-HC(O)OH and syn-CH 3 C(O)OH acids with >110 kcal/mol exothermicities via loose roaming-like insertion TSs involving the terminal O atom and the neighboring C–H bonds. For syn-CH 3 C(H)OO, the major decomposition channel occurs by abstraction of a H atom from the CH 3 group by the terminal O atom producing CH 2 C(H)O–OH. At 298 K, the intramolecular insertion process in CH 2 OO was found to be 600 times faster than the commonly assumed ring-closing reaction

A small interfering RNA screen of genes involved in DNA repair identifies tumor-specific radiosensitization by POLQ knockdown

DEFF Research Database (Denmark)

Higgins, Geoff S; Prevo, Remko; Lee, Yin-Fai

2010-01-01

The effectiveness of radiotherapy treatment could be significantly improved if tumor cells could be rendered more sensitive to ionizing radiation (IR) without altering the sensitivity of normal tissues. However, many of the key therapeutically exploitable mechanisms that determine intrinsic tumor...... radiosensitivity are largely unknown. We have conducted a small interfering RNA (siRNA) screen of 200 genes involved in DNA damage repair aimed at identifying genes whose knockdown increased tumor radiosensitivity. Parallel siRNA screens were conducted in irradiated and unirradiated tumor cells (SQ20B......) and irradiated normal tissue cells (MRC5). Using gammaH2AX foci at 24 hours after IR, we identified several genes, such as BRCA2, Lig IV, and XRCC5, whose knockdown is known to cause increased cell radiosensitivity, thereby validating the primary screening end point. In addition, we identified POLQ (DNA...

Exclusive and restricted inclusive reactions involving the 11Be one-neutron halo

International Nuclear Information System (INIS)

Anne, R.; Emling, H.; Hansen, P.G.; Hornshoj, P.; Bimbot, R.; Dogny, S.

1993-01-01

Reactions of a 41 MeV/u beam of the radioactive halo nucleus 11 Be have been studied with a counter telescope coupled to an array of neutron detectors. The technique allows to determine single-neutron inclusive and exclusive angular distributions. The targets (Be, Ti and Au) were chosen to illustrate the relative roles played by nuclear and Coulomb mechanisms. It is shown that for the dissociation process it is possible to account almost quantitatively for the integral, single- and double-differential cross-sections from models without free parameters including the Coulomb, Serber and Glauber (diffraction dissociation) mechanisms. (K.A.). 56 refs., 11 figs., 1 tab

Reaction chemistry in rechargeable Li-O2 batteries.

Science.gov (United States)

Lim, Hee-Dae; Lee, Byungju; Bae, Youngjoon; Park, Hyeokjun; Ko, Youngmin; Kim, Haegyeom; Kim, Jinsoo; Kang, Kisuk

2017-05-22

The seemingly simple reaction of Li-O 2 batteries involving lithium and oxygen makes this chemistry attractive for high-energy-density storage systems; however, achieving this reaction in practical rechargeable Li-O 2 batteries has proven difficult. The reaction paths leading to the final Li 2 O 2 discharge products can be greatly affected by the operating conditions or environment, which often results in major side reactions. Recent research findings have begun to reveal how the reaction paths may be affected by the surrounding conditions and to uncover the factors contributing to the difficulty in achieving the reactions of lithium and oxygen. This progress report describes the current state of understanding of the electrode reaction mechanisms in Li-O 2 batteries; the factors that affect reaction pathways; and the effect of cell components such as solvents, salts, additives, and catalysts on the discharge product and its decomposition during charging. This comprehensive review of the recent progress in understanding the reaction chemistry of the Li-O 2 system will serve as guidelines for future research and aid in the development of reliable high-energy-density rechargeable Li-O 2 batteries.

Experimental study o the sodium-concrete reaction

International Nuclear Information System (INIS)

Goncalves, A.C.; Torres, A.R.; Brito Aghina, L.O. de; Messere e Castro, P.

1986-01-01

Effects and aspects of security are verified during a sodium leakage in high temperatures on liners of contention cells and directly on the concrete. As this kinetic process involves reactions between materials in solid state (such as oxides and carbonates) vapors and gases (such as water and CO 2 )) with liquid sodium, effects of each phase of the heterogeneous mixture are separately analysed. Are still analysed produced products and briefly discussed the kinetic of the sodium-concrete reaction. (Author) [pt

I. Activation energies for the gas phase reactions of hydrogen atom with carbon monoxide and with ethylene. II. Rate constants for the reactions of benzyl cation with triethylphosphine and with triethylarsine in 1,2-dichloroethane

International Nuclear Information System (INIS)

Wang, H.Y.

1976-01-01

Two H-atom reactions H + CO + H 2 → HCO + H 2 and H + C 2 H 4 → C 2 H 5 * were separately studied from room temperature to about 100 0 C, and the activation energies for these two reactions were determined in this temperature range. For H + C 2 H 4 system, a small activation energy of 0.2 kcal/mole was obtained in the present narrow temperature range. The low activation energy indicates that the pre-exponential factor has a predominant contribution to the rate constant of this reaction and has about the same magnitude as that of the rate constant. For H + CO system, a fairly large activation energy of more than 7 kcal/mole was speculated in the potential energy surfaces of the system. The activation energy obtained in the present work, however, has a low value of about 2 kcal/mole. This low value reveals the low level of crossing of this reaction in the potential energy surface and thus indicates considerable complexity involved in the surface. Carbonium ions can be formed from chosen solutes in pulse-irradiated 1,2-dichloroethane (RCl) solutions. Upon irradiation, the electrons generated from the ionization of the solvent become localized on chloride ions as a result of their reaction with the neutral solvent molecules. The solvent counterion, RCl + , on the other hand, is free to exchange charge with the solute molecule. By choosing appropriate solutes, carbonium ion can be formed through a dissociative ionization process in the exchange. The benzyl cation was formed from its precursor compound dibenzylmercury and its reactions with two nucleophiles, triethylphosphine and triethylarsine, were separately studied. The formation and decay of benzyl cation were observed at 363 nm, the position of the maximum of its absorption band, and the second-order rate constants for the two reactions were determined at room temperature

Insights into the mechanisms on chemical reactions: reaction paths for chemical reactions

International Nuclear Information System (INIS)

Dunning, T.H. Jr.; Rosen, E.; Eades, R.A.

1987-01-01

We report reaction paths for two prototypical chemical reactions: Li + HF, an electron transfer reaction, and OH + H 2 , an abstraction reaction. In the first reaction we consider the connection between the energetic terms in the reaction path Hamiltonian and the electronic changes which occur upon reaction. In the second reaction we consider the treatment of vibrational effects in chemical reactions in the reaction path formalism. 30 refs., 9 figs

Emotional reactions to harmful intergroup behavior

NARCIS (Netherlands)

Gordijn, Ernestine H.; Yzerbyt, Vincent; Wigboldus, Daniël; Dumont, Muriel

2006-01-01

In this paper, we examined reactions to situations in which, although one is not personally involved, one could see oneself connected to either the perpetrators or the victims of unfair behavior We 14 manipulated participants' similarity and measured their identification to either one of two groups

Reaction factoring and bipartite update graphs accelerate the Gillespie Algorithm for large-scale biochemical systems.

Directory of Open Access Journals (Sweden)

Sagar Indurkhya

Full Text Available ODE simulations of chemical systems perform poorly when some of the species have extremely low concentrations. Stochastic simulation methods, which can handle this case, have been impractical for large systems due to computational complexity. We observe, however, that when modeling complex biological systems: (1 a small number of reactions tend to occur a disproportionately large percentage of the time, and (2 a small number of species tend to participate in a disproportionately large percentage of reactions. We exploit these properties in LOLCAT Method, a new implementation of the Gillespie Algorithm. First, factoring reaction propensities allows many propensities dependent on a single species to be updated in a single operation. Second, representing dependencies between reactions with a bipartite graph of reactions and species requires only storage for reactions, rather than the required for a graph that includes only reactions. Together, these improvements allow our implementation of LOLCAT Method to execute orders of magnitude faster than currently existing Gillespie Algorithm variants when simulating several yeast MAPK cascade models.

Reaction Factoring and Bipartite Update Graphs Accelerate the Gillespie Algorithm for Large-Scale Biochemical Systems

Science.gov (United States)

Indurkhya, Sagar; Beal, Jacob

2010-01-01

ODE simulations of chemical systems perform poorly when some of the species have extremely low concentrations. Stochastic simulation methods, which can handle this case, have been impractical for large systems due to computational complexity. We observe, however, that when modeling complex biological systems: (1) a small number of reactions tend to occur a disproportionately large percentage of the time, and (2) a small number of species tend to participate in a disproportionately large percentage of reactions. We exploit these properties in LOLCAT Method, a new implementation of the Gillespie Algorithm. First, factoring reaction propensities allows many propensities dependent on a single species to be updated in a single operation. Second, representing dependencies between reactions with a bipartite graph of reactions and species requires only storage for reactions, rather than the required for a graph that includes only reactions. Together, these improvements allow our implementation of LOLCAT Method to execute orders of magnitude faster than currently existing Gillespie Algorithm variants when simulating several yeast MAPK cascade models. PMID:20066048

Consistent post-reaction vibrational energy redistribution in DSMC simulations using TCE model

Science.gov (United States)

Borges Sebastião, Israel; Alexeenko, Alina

2016-10-01

The direct simulation Monte Carlo (DSMC) method has been widely applied to study shockwaves, hypersonic reentry flows, and other nonequilibrium flow phenomena. Although there is currently active research on high-fidelity models based on ab initio data, the total collision energy (TCE) and Larsen-Borgnakke (LB) models remain the most often used chemistry and relaxation models in DSMC simulations, respectively. The conventional implementation of the discrete LB model, however, may not satisfy detailed balance when recombination and exchange reactions play an important role in the flow energy balance. This issue can become even more critical in reacting mixtures involving polyatomic molecules, such as in combustion. In this work, this important shortcoming is addressed and an empirical approach to consistently specify the post-reaction vibrational states close to thermochemical equilibrium conditions is proposed within the TCE framework. Following Bird's quantum-kinetic (QK) methodology for populating post-reaction states, the new TCE-based approach involves two main steps. The state-specific TCE reaction probabilities for a forward reaction are first pre-computed from equilibrium 0-D simulations. These probabilities are then employed to populate the post-reaction vibrational states of the corresponding reverse reaction. The new approach is illustrated by application to exchange and recombination reactions relevant to H2-O2 combustion processes.

Compilation and R-matrix analysis of Big Bang nuclear reaction rates

International Nuclear Information System (INIS)

Descouvemont, Pierre; Adahchour, Abderrahim; Angulo, Carmen; Coc, Alain; Vangioni-Flam, Elisabeth

2004-01-01

We use the R-matrix theory to fit low-energy data on nuclear reactions involved in Big Bang nucleosynthesis. Special attention is paid to the rate uncertainties which are evaluated on statistical grounds. We provide S factors and reaction rates in tabular and graphical formats

Chemical and physical reactions under thermal plasmas conditions

International Nuclear Information System (INIS)

Fauchais, P.; Vardelle, A.; Vardelle, M.; Coudert, J.F.

1987-01-01

Basic understanding of the involved phenomena lags far behind industrial development that requires now a better knowledge of the phenomena to achieve a better control of the process allowing to improve the quality of the products. Thus the authors try to precise what is their actual knowledge in the fields of: plasma generators design; plasma flow models with the following key points: laminar or turbulent flow, heat transfer to walls, 2D or 3D models, non equilibrium effects, mixing problems when chemical reactions are to be taken into account with very fast kinetics, electrode regions, data for transport properties and kinetic rates; nucleation problems; plasma flow characteristics measurements: temperature or temperatures and population of excited states (automatized emission spectroscopy, LIF, CARS) as well as flow velocity (LDA with small particles, Doppler effects...); plasma and particles momentum and heat transfer either with models taking into account particles size and injection velocity distributions, heat propagation, vaporization, Kundsen effect, turbulences ... or with measurements: particles velocity and flux distributions (Laser Anemometry) as well as surface temperature distributions (two colour pyrometry in flight statistical or not)

Structural characterization and gas reactions of small metal particles by high resolution in-situ TEM (Transmission Electron Microscopy) and TED (Transmission Electron Diffraction)

Science.gov (United States)

Heinemann, K.

1987-01-01

The detection and size analysis of small metal particles supported on amorphous substrates becomes increasingly difficult when the particle size approaches that of the phase contrast background structures of the support. An approach of digital image analysis, involving Fourier transformation of the original image, filtering, and image reconstruction was studied with respect to the likelihood of unambiguously detecting particles of less than 1 nm diameter on amorphous substrates from a single electron micrograph.

Volvulus of the Small Bowel and Colon

Science.gov (United States)

Kapadia, Muneera R.

2017-01-01

Volvulus of the intestines may involve either the small bowel or colon. In the pediatric population, small bowel volvulus is more common, while in the adult population, colonic volvulus is more often seen. The two most common types of colonic volvulus include sigmoid and cecal volvulus. Prompt diagnosis and treatment is imperative, otherwise bowel ischemia may ensue. Treatment often involves emergent surgical exploration and bowel resection. PMID:28144211

Adverse Cutaneous Reactions to Psychotropic Drugs: A Review

Directory of Open Access Journals (Sweden)

Filipa Novais

2015-11-01

Full Text Available Introduction: Psychotropic drugs are often implicated in cutaneous adverse drug reactions. While most of these reactions have a benign character, it is still important, however, to consider its role in the increasing stigma and treatment adherence. A small number of the cutaneous adverse drug reactions can develop into serious and potentially fatal conditions. Objectives: This article aims to review the most common cutaneous adverse drug reactions in patients taking psychotropic drugs. Methods: In this study, a search was carried out in the MEDLINE database for English language articles published , from 1999 to 2014, using as keywords: psychiatric, psychotropic, cutaneous, adverse reaction, antidepressive agents, antipsychotics, benzodiazepines, mood stabilizers, anticonvulsant, dementia. Information available from the Portuguese regulatory and supervising agency (Infarmed was also included.Results: 121 articles were found with reference to cutaneous adverse drug reactions associated with psychotropic drugs. The drugs most frequently reported as associated with such adverse effects were anticonvulsants used as mood stabilizers, followed by the antipsychotics . The antidementia drugs were rarely associated with serious cutaneous adverse reactions. Discussion and Conclusion: Cutaneous drug adverse reactions are common in psychiatric clinical practice and typically are minor in severity. The most severe reactions are most often associated with the use of mood stabilizing medications. Some of these side effects can be solved with reduction or drug discontinuation. More severe cases should be referred to a specialist in dermatology.

Theoretical investigation of reactions between ammonia and precursors from the ozonolysis of ethane

DEFF Research Database (Denmark)

Jørgensen, Solvejg; Gross, Allan

2009-01-01

, three reaction channels were found (i) an aldehyde, a hydrogen peroxide and an imine, (ii) two aldehydes and a hydroxylamine, (iii) a hydroxyalkyl hydroperoxide and an imine. For the reaction involving the HSE the reaction products are an aldehyde, carboxylic acid and ammonia. The B3LYP method with 6...

Unimolecular reaction dynamics of free radicals

International Nuclear Information System (INIS)

Terry A. Miller

2006-01-01

Free radical reactions are of crucial importance in combustion and in atmospheric chemistry. Reliable theoretical models for predicting the rates and products of these reactions are required for modeling combustion and atmospheric chemistry systems. Unimolecular reactions frequently play a crucial role in determining final products. The dissociations of vinyl, CH2= CH, and methoxy, CH3O, have low barriers, about 13,000 cm-1 and 8,000 cm-1, respectively. Since barriers of this magnitude are typical of free radicals these molecules should serve as benchmarks for this important class of reactions. To achieve this goal, a detailed understanding of the vinyl and methoxy radicals is required. Results for dissociation dynamics of vinyl and selectively deuterated vinyl radical are reported. Significantly, H-atom scrambling is shown not to occur in this reaction. A large number of spectroscopic experiments for CH3O and CHD2O have been performed. Spectra recorded include laser induced fluorescence (LIF), laser excited dispersed fluorescence (LEDF), fluorescence dip infrared (FDIR) and stimulated emission pumping (SEP). Such results are critical for implementing dynamics experiments involving the dissociation of methoxy

Electrodeposition of Pd based binary catalysts on Carbon paper via surface limited redox-replacement reaction for oxygen reduction reaction

CSIR Research Space (South Africa)

Modibedi, RM

2014-05-01

Full Text Available Direct alcohol fuel cells (DAFCs) continue to extensive attention as potential power sources for portable and stationary applications. The oxygen reduction reaction (ORR) involving the four electron transfer remains a challenge for DAFCs due to its...

Community reaction to noise from power stations

International Nuclear Information System (INIS)

Job, R.F.S.; Hede, A.J.

1989-01-01

Community reaction is a major consideration in noise control. The relationship between noise exposure and community reaction has received considerable attention in relation to railway, traffic, aircraft and impulsive noise. The results have shown a number of features in common, including: similarly shaped noise/reaction functions; similar results across different measurement techniques and cultures, noise/reaction correlations based on individual respondent data are low (mean r = 0.42 ± 0.12: Job, 1988), although correlations of .58 and above have been reported correlations based on data grouped by noise exposure are generally high and relatively unaffected by the type of noise studied whereas correlations based on individual data tend to be lower for impulsive noise than for transportation noise attitude to the noise source and sensitivity to noise shows strong correlations with reaction. This paper reports that the present study was undertaken in order toe establish over a wider range of noise exposure whether community reaction to power station noise is similar to reaction to other types of non-impulsive noise. It is possible that reaction is different given important differences in the source of the noise which may affect attitude. Attitudes towards power stations may be more positive than attitudes to aircraft or rail noise for example, because almost all respondents use electricity regularly every day. Further, the power stations in the present study provided employment for the relatively small surrounding communities

Chemical reactions directed Peptide self-assembly.

Science.gov (United States)

Rasale, Dnyaneshwar B; Das, Apurba K

2015-05-13

Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly.

Aligning Metabolic Pathways Exploiting Binary Relation of Reactions.

Directory of Open Access Journals (Sweden)

Yiran Huang

Full Text Available Metabolic pathway alignment has been widely used to find one-to-one and/or one-to-many reaction mappings to identify the alternative pathways that have similar functions through different sets of reactions, which has important applications in reconstructing phylogeny and understanding metabolic functions. The existing alignment methods exhaustively search reaction sets, which may become infeasible for large pathways. To address this problem, we present an effective alignment method for accurately extracting reaction mappings between two metabolic pathways. We show that connected relation between reactions can be formalized as binary relation of reactions in metabolic pathways, and the multiplications of zero-one matrices for binary relations of reactions can be accomplished in finite steps. By utilizing the multiplications of zero-one matrices for binary relation of reactions, we efficiently obtain reaction sets in a small number of steps without exhaustive search, and accurately uncover biologically relevant reaction mappings. Furthermore, we introduce a measure of topological similarity of nodes (reactions by comparing the structural similarity of the k-neighborhood subgraphs of the nodes in aligning metabolic pathways. We employ this similarity metric to improve the accuracy of the alignments. The experimental results on the KEGG database show that when compared with other state-of-the-art methods, in most cases, our method obtains better performance in the node correctness and edge correctness, and the number of the edges of the largest common connected subgraph for one-to-one reaction mappings, and the number of correct one-to-many reaction mappings. Our method is scalable in finding more reaction mappings with better biological relevance in large metabolic pathways.

The Crystal Structure and Mechanism of an Unusual Oxidoreductase, GilR, Involved in Gilvocarcin V Biosynthesis

Energy Technology Data Exchange (ETDEWEB)

Noinaj, Nicholas; Bosserman, Mary A.; Schickli, M. Alexandra; Piszczek, Grzegorz; Kharel, Madan K.; Pahari, Pallab; Buchanan, Susan K.; Rohr, Jürgen (NIH); (Kentucky)

2012-11-26

GilR is a recently identified oxidoreductase that catalyzes the terminal step of gilvocarcin V biosynthesis and is a unique enzyme that establishes the lactone core of the polyketide-derived gilvocarcin chromophore. Gilvocarcin-type compounds form a small distinct family of anticancer agents that are involved in both photo-activated DNA-alkylation and histone H3 cross-linking. High resolution crystal structures of apoGilR and GilR in complex with its substrate pregilvocarcin V reveals that GilR belongs to the small group of a relatively new type of the vanillyl-alcohol oxidase flavoprotein family characterized by bicovalently tethered cofactors. GilR was found as a dimer, with the bicovalently attached FAD cofactor mediated through His-65 and Cys-125. Subsequent mutagenesis and functional assays indicate that Tyr-445 may be involved in reaction catalysis and in mediating the covalent attachment of FAD, whereas Tyr-448 serves as an essential residue initiating the catalysis by swinging away from the active site to accommodate binding of the 6R-configured substrate and consequently abstracting the proton of the hydroxyl residue of the substrate hemiacetal 6-OH group. These studies lay the groundwork for future enzyme engineering to broaden the substrate specificity of this bottleneck enzyme of the gilvocarcin biosynthetic pathway for the development of novel anti-cancer therapeutics.

Efficient rejection-based simulation of biochemical reactions with stochastic noise and delays

Energy Technology Data Exchange (ETDEWEB)

Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento (Italy); Zunino, Roberto, E-mail: roberto.zunino@unitn.it [Department of Mathematics, University of Trento (Italy)

2014-10-07

We propose a new exact stochastic rejection-based simulation algorithm for biochemical reactions and extend it to systems with delays. Our algorithm accelerates the simulation by pre-computing reaction propensity bounds to select the next reaction to perform. Exploiting such bounds, we are able to avoid recomputing propensities every time a (delayed) reaction is initiated or finished, as is typically necessary in standard approaches. Propensity updates in our approach are still performed, but only infrequently and limited for a small number of reactions, saving computation time and without sacrificing exactness. We evaluate the performance improvement of our algorithm by experimenting with concrete biological models.

Maybe Small Is Too Small a Term: Introduction to Advancing Small Sample Prevention Science.

Science.gov (United States)

Fok, Carlotta Ching Ting; Henry, David; Allen, James

2015-10-01

Prevention research addressing health disparities often involves work with small population groups experiencing such disparities. The goals of this special section are to (1) address the question of what constitutes a small sample; (2) identify some of the key research design and analytic issues that arise in prevention research with small samples; (3) develop applied, problem-oriented, and methodologically innovative solutions to these design and analytic issues; and (4) evaluate the potential role of these innovative solutions in describing phenomena, testing theory, and evaluating interventions in prevention research. Through these efforts, we hope to promote broader application of these methodological innovations. We also seek whenever possible, to explore their implications in more general problems that appear in research with small samples but concern all areas of prevention research. This special section includes two sections. The first section aims to provide input for researchers at the design phase, while the second focuses on analysis. Each article describes an innovative solution to one or more challenges posed by the analysis of small samples, with special emphasis on testing for intervention effects in prevention research. A concluding article summarizes some of their broader implications, along with conclusions regarding future directions in research with small samples in prevention science. Finally, a commentary provides the perspective of the federal agencies that sponsored the conference that gave rise to this special section.

Proton exchange in acid–base complexes induced by reaction coordinates with heavy atom motions

International Nuclear Information System (INIS)

Alavi, Saman; Taghikhani, Mahdi

2012-01-01

Highlights: ► Proton exchange in acid–base complexes is studied. ► The structures, binding energies, and normal mode vibrations are calculated. ► Transition state structures of proton exchange mechanism are determined. ► In the complexes studied, the reaction coordinate involves heavy atom rocking. ► The reaction coordinate is not simply localized in the proton movements. - Abstract: We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are −1 . This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm −1 . Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

Statistical theory of multi-step compound and direct reactions

International Nuclear Information System (INIS)

Feshbach, H.; Kerman, A.; Koonin, S.

1980-01-01

The theory of nuclear reactions is extended so as to include a statistical treatment of multi-step processes. Two types are distinguished, the multi-step compound and the multi-step direct. The wave functions for the system are grouped according to their complexity. The multi-step direct process involves explicitly those states which are open, while the multi-step compound involves those which are bound. In addition to the random phase assumption which is applied differently to the multi-step direct and to the multi-step compound cross-sections, it is assumed that the residual interaction will have non-vanishing matrix elements between states whose complexities differ by at most one unit. This is referred to as the chaining hypothesis. Explicit expressions for the double differential cross-section giving the angular distribution and energy spectrum are obtained for both reaction types. The statistical multi-step compound cross-sections are symmetric about 90 0 . The classical statistical theory of nuclear reactions is a special limiting case. The cross-section for the statistical multi-step direct reaction consists of a set of convolutions of single-step direct cross-sections. For the many step case it is possible to derive a diffusion equation in momentum space. Application is made to the reaction 181 Ta(p,n) 181 W using the statistical multi-step compound formalism

Understanding the statistics of small risks

International Nuclear Information System (INIS)

Siddall, E.

1983-10-01

Monte Carlo analyses are used to show what inferences can and cannot be drawn when either a very small number of accidents result from a considerable exposure or where a very small number of people, down to a single individual, are exposed to small added risks. The distinction between relative and absolute uncertainty is illustrated. No new statistical principles are involved

Radiolytic oxidation of propane: Computer modeling of the reaction scheme

Science.gov (United States)

Gupta, Avinash K.; Hanrahan, Robert J.

The oxidation of gaseous propane under gamma radiolysis was studied at 100 torr pressure and 25°C, at oxygen pressures from 1 to 15 torr. Major oxygen-containing products and their G-values with 10% added oxygen are as follows: acetone, 0.98; i-propyl alcohol, 0.86; propionaldehyde, 0.43; n-propyl alcohol, 0.11; acrolein, 0.14; and allyl alcohol, 0.038. Minor products include i-butyl alcohol, t-amyl alcohol, n-butyl alcohol, n-amyl alcohol, and i-amyl alcohol. Small yields of i-hexyl alcohol and n-hexyl alcohol were also observed. There was no apparent difference in the G-values at pressures of 50, 100 and 150 torr. When the oxygen concentration was decreased below 5%, the yields of acetone, i-propyl alcohol, and n-propyl alcohol increased, the propionaldehyde yield decreased, and the yields of other products remained constant. The formation of major oxygen-containing products was explained on the basis that the alkyl radicals combine with molecular oxygen to give peroxyl radicals; the peroxyl radicals react with one another to give alkoxyl radicals, which in turn react with one another to form carbonyl compounds and alcohols. The reaction scheme for the formation of major products was examined using computer modeling based on a mechanism involving 28 reactions. Yields could be brought into agreement with the data within experimental error in nearly all cases.

APUAMA: a software tool for reaction rate calculations.

Science.gov (United States)

Euclides, Henrique O; P Barreto, Patricia R

2017-06-01

APUAMA is a free software designed to determine the reaction rate and thermodynamic properties of chemical species of a reagent system. With data from electronic structure calculations, the APUAMA determine the rate constant with tunneling correction, such as Wigner, Eckart and small curvature, and also, include the rovibrational level of diatomic molecules. The results are presented in the form of Arrhenius-Kooij form, for the reaction rate, and the thermodynamic properties are written down in the polynomial form. The word APUAMA means "fast" in Tupi-Guarani Brazilian language, then the code calculates the reaction rate on a simple and intuitive graphic interface, the form fast and practical. As program output, there are several ASCII files with tabulated information for rate constant, rovibrational levels, energy barriers and enthalpy of reaction, Arrhenius-Kooij coefficient, and also, the option to the User save all graphics in BMP format.

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

Directory of Open Access Journals (Sweden)

Yury Minko

2013-03-01

Full Text Available The carbocupration reactions of heterosubstituted alkynes allow the regio- and stereoselective formation of vinyl organometallic species. N-Alkynylamides (ynamides are particularly useful substrates for the highly regioselective carbocupration reaction, as they lead to the stereodefined formation of vinylcopper species geminated to the amide moiety. The latter species are involved in numerous synthetically useful transformations leading to valuable building blocks in organic synthesis. Here we describe in full the results of our studies related to the carbometallation reactions of N-alkynylamides.

Optimization of Maillard Reaction between Glucosamine and Other Precursors by Measuring Browning with a Spectrophotometer.

Science.gov (United States)

Ogutu, Benrick; Kim, Ye-Joo; Kim, Dae-Wook; Oh, Sang-Chul; Hong, Dong-Lee; Lee, Yang-Bong

2017-09-01

The individual Maillard reactions of glucose, glucosamine, cyclohexylamine, and benzylamine were studied at a fixed temperature of 120°C under different durations by monitoring the absorbance of the final products at 425 nm. Glucosamine was the most individually reactive compound, whereas the reactions of glucose, cyclohexylamine, and benzylamine were not significantly different from each other. Maillard reactions of reaction mixtures consisting of glucosamine-cyclohexylamine, glucosamine-benzylamine, glucose-cyclohexylamine, and glucose-benzylamine were also studied using different concentration ratios under different durations at a fixed temperature of 120°C and pH 9. Maillard reactions in the pairs involving glucosamine were observed to be more intense than those of the pairs involving glucose. Finally, with respect to the concentration ratios, it was observed that in most instances, optimal activity was realized, when the reaction mixtures were in the ratio of 1:1.

A review of reaction rates in high temperature air

Science.gov (United States)

Park, Chul

1989-01-01

The existing experimental data on the rate coefficients for the chemical reactions in nonequilibrium high temperature air are reviewed and collated, and a selected set of such values is recommended for use in hypersonic flow calculations. For the reactions of neutral species, the recommended values are chosen from the experimental data that existed mostly prior to 1970, and are slightly different from those used previously. For the reactions involving ions, the recommended rate coefficients are newly chosen from the experimental data obtained more recently. The reacting environment is assumed to lack thermal equilibrium, and the rate coefficients are expressed as a function of the controlling temperature, incorporating the recent multitemperature reaction concept.

Ejection of Coulomb Crystals from a Linear Paul Ion Trap for Ion-Molecule Reaction Studies.

Science.gov (United States)

Meyer, K A E; Pollum, L L; Petralia, L S; Tauschinsky, A; Rennick, C J; Softley, T P; Heazlewood, B R

2015-12-17

Coulomb crystals are being increasingly employed as a highly localized source of cold ions for the study of ion-molecule chemical reactions. To extend the scope of reactions that can be studied in Coulomb crystals-from simple reactions involving laser-cooled atomic ions, to more complex systems where molecular reactants give rise to multiple product channels-sensitive product detection methodologies are required. The use of a digital ion trap (DIT) and a new damped cosine trap (DCT) are described, which facilitate the ejection of Coulomb-crystallized ions onto an external detector for the recording of time-of-flight (TOF) mass spectra. This enables the examination of reaction dynamics and kinetics between Coulomb-crystallized ions and neutral molecules: ionic products are typically cotrapped, thus ejecting the crystal onto an external detector reveals the masses, identities, and quantities of all ionic species at a selected point in the reaction. Two reaction systems are examined: the reaction of Ca(+) with deuterated isotopologues of water, and the charge exchange between cotrapped Xe(+) with deuterated isotopologues of ammonia. These reactions are examples of two distinct types of experiment, the first involving direct reaction of the laser-cooled ions, and the second involving reaction of sympathetically-cooled heavy ions to form a mixture of light product ions. Extensive simulations are conducted to interpret experimental results and calculate optimal operating parameters, facilitating a comparison between the DIT and DCT approaches. The simulations also demonstrate a correlation between crystal shape and image shape on the detector, suggesting a possible means for determining crystal geometry for nonfluorescing ions.

Reaction mechanism for the free-edge oxidation of soot by O 2

KAUST Repository

Raj, Abhijeet

2012-11-01

The reaction pathways for the oxidation by O 2 of polycyclic aromatic hydrocarbons present in soot particles are investigated using density functional theory at B3LYP/6-311++G(d,p) level of theory. For this, pyrene radical (4-pyrenyl) is chosen as the model molecule, as most soot models present in the literature employ the reactions involving the conversion of 4-pyrenyl to 4-phenanthryl by O 2 and OH to account for soot oxidation. Several routes for the formation of CO and CO 2 are proposed. The addition of O 2 on a radical site to form a peroxyl radical is found to be barrierless and exothermic with reaction energy of 188kJ/mol. For the oxidation reaction to proceed further, three pathways are suggested, each of which involve the activation energies of 104, 167 and 115kJ/mol relative to the peroxyl radical. The effect of the presence of H atom on a carbon atom neighboring the radical site on the energetics of carbon oxidation is assessed. Those intermediate species formed during oxidation with seven-membered rings or with a phenolic group are found to be highly stable. The rate constants evaluated using transition state theory in the temperature range of 300-3000K for the reactions involved in the mechanism are provided. © 2012 The Combustion Institute.

Reaction mechanism for the free-edge oxidation of soot by O 2

KAUST Repository

Raj, Abhijeet; da Silva, Gabriel; Chung, Suk-Ho

2012-01-01

The reaction pathways for the oxidation by O 2 of polycyclic aromatic hydrocarbons present in soot particles are investigated using density functional theory at B3LYP/6-311++G(d,p) level of theory. For this, pyrene radical (4-pyrenyl) is chosen as the model molecule, as most soot models present in the literature employ the reactions involving the conversion of 4-pyrenyl to 4-phenanthryl by O 2 and OH to account for soot oxidation. Several routes for the formation of CO and CO 2 are proposed. The addition of O 2 on a radical site to form a peroxyl radical is found to be barrierless and exothermic with reaction energy of 188kJ/mol. For the oxidation reaction to proceed further, three pathways are suggested, each of which involve the activation energies of 104, 167 and 115kJ/mol relative to the peroxyl radical. The effect of the presence of H atom on a carbon atom neighboring the radical site on the energetics of carbon oxidation is assessed. Those intermediate species formed during oxidation with seven-membered rings or with a phenolic group are found to be highly stable. The rate constants evaluated using transition state theory in the temperature range of 300-3000K for the reactions involved in the mechanism are provided. © 2012 The Combustion Institute.

[Extended abstractCutaneous Adverse Reactions to Tattoos].

Science.gov (United States)

van der Bent, S A S; Wolkerstorfer, A; Rustemeyer, T

2016-01-01

Tattooing involves the introduction of exogenous pigment into the dermis. Worldwide, tattoos are one of the most popular forms of permanent body art. In the Netherlands, 8-10% of the population older than 12 years old has a tattoo. A wide variety of cutaneous adverse effects can occur in tattoos, these can cause serious symptoms. However, recognition and appropriate knowledge of diagnosis and treatment is still frequently insufficient in many medical practitioners. The first case concerns a 57-year-old female, who developed an itching swelling in the red part of a tattoo on the left arm. Histology of a punch biopsy showed a pseudolymphomatous reaction. This plaque-like allergic reaction was successfully treated with intralesional injection of corticosteroids. Here we described four cases of cutaneous adverse reactions to tattoos. Allergic reactions in tattoos can present in a wide variety of clinical and histological patterns. The symptoms are often chronic itch and can appear weeks, months or years after placing the tattoo. Allergic reactions are uniformly manifested in one particular colour. Clinically, the reactions can present in a plaque-like, hyperkeratotic or rarely ulcerative or generalised reaction. In spite of changes to the compounds in tattoo inks, allergic reactions are still mostly observed to red ink. Treatment options are topical corticosteroids, intralesional injection of corticosteroids, laser treatment or dermatome shaving.

Reaction network modelling for kinetic parameters of pyrolytic reactions of CHON extractants in nuclear fuel processing waste management. Contributed Paper IT-07

International Nuclear Information System (INIS)

Gaikar, Vilas G.; Thaore, Vaishali

2014-01-01

The recovery and purification of plutonium (Pu) from uranium (U) and of U from Thorium (Th) in spent nuclear fuel reprocessing is accomplished by processes that employ organophosphorous compounds as extractants.The main objective of the present work was to develop a suitable kinetic model and to determine the kinetic parameters of the set of reactions involved in the pyrolysis of amides by fitting the experimental data in the reaction network model. The experimental data and analysis are expected to be useful in the steam pyrolysis of amide waste in fuel reprocessing in the nuclear industry. The basic approach was to understand the reaction mechanism of the steam pyrolysis of amides and then to estimate the reaction rate constants for the generation and consumption of different species by solving the model equations, allowing for the determination of important species in the reaction network

Immune reaction and colorectal cancer: friends or foes?

Science.gov (United States)

Formica, Vincenzo; Cereda, Vittore; Nardecchia, Antonella; Tesauro, Manfredi; Roselli, Mario

2014-09-21

The potential clinical impact of enhancing antitumor immunity is increasingly recognized in oncology therapeutics for solid tumors. Colorectal cancer is one of the most studied neoplasms for the tumor-host immunity relationship. Although immune cell populations involved in such a relationship and their prognostic role in colorectal cancer development have clearly been identified, still no approved therapies based on host immunity intensification have so far been introduced in clinical practice. Moreover, a recognized risk in enhancing immune reaction for colitis-associated colorectal cancer development has limited the emphasis of this approach. The aim of the present review is to discuss immune components involved in the host immune reaction against colorectal cancer and analyze the fine balance between pro-tumoral and anti-tumoral effect of immunity in this model of disease.

Excitation functions for quasi-elastic transfer reactions induced with heavy ions in bismuth

International Nuclear Information System (INIS)

Gardes, D.; Bimbot, R.; Maison, J.; Reilhac, L. de; Rivet, M.F.; Fleury, A.; Hubert, F.; Llabador, Y.

1977-01-01

The excitation functions for the production of 210 Bi, 210 Po, sup(207-211)At and 211 Rn through quasi-elastic transfer reactions induced with heavy ions in 209 Bi have been measured. The corresponding reactions involved the transfer of one neutron, one proton, two and three charges from projectile to target. The projectiles used were 12 C, 14 N, 16 O, 19 F, 20 Ne, 40 Ca, 56 Fe and 63 Cu. The experimental techniques involved target irradiations and off-line α and γ activity measurements. Chemical separations were used to solve specific problems. Careful measurements of incident energies and cross sections were performed close to the reaction thresholds

Reactions of nitrate salts with ammonia in supercritical water

International Nuclear Information System (INIS)

Dell'Orco, P.C.; Gloyna, E.F.; Buelow, S.J.

1997-01-01

Reactions involving nitrate salts and ammonia were investigated in supercritical water at temperatures from 450 to 530 C and pressures near 300 bar. Reaction products included nitrite, nitrogen gas, and nitrous oxide. Observed reaction rates and product distributions provided evidence for a free-radical reaction mechanism with NO 2 , NO, and NH 2 · as the primary reactive species at supercritical conditions. In the proposed elementary mechanism, the rate-limiting reaction step was determined to be the hydrolysis of MNO 3 species, which resulted in the formation of nitric acid and subsequently NO 2 . A simple second-order reaction model was used to represent the data. In developing an empirical kinetic model, nitrate and nitrate were lumped as an NO x - reactant. Empirical kinetic parameters were developed for four MNO x /NH 3 reacting systems, assuming first orders in both NH 3 and NO x - . Observed MNO x /NH 3 reaction rates and mechanisms suggest immediately a practical significance of these reactions for nitrogen control strategies in supercritical water oxidation processes

Control of Maillard Reactions in Foods: Strategies and Chemical Mechanisms.

Science.gov (United States)

Lund, Marianne N; Ray, Colin A

2017-06-14

Maillard reactions lead to changes in food color, organoleptic properties, protein functionality, and protein digestibility. Numerous different strategies for controlling Maillard reactions in foods have been attempted during the past decades. In this paper, recent advances in strategies for controlling the Maillard reaction and subsequent downstream reaction products in food systems are critically reviewed. The underlying mechanisms at play are presented, strengths and weaknesses of each strategy are discussed, and reasonable reaction mechanisms are proposed to reinforce the evaluations. The review includes strategies involving addition of functional ingredients, such as plant polyphenols and vitamins, as well as enzymes. The resulting trapping or modification of Maillard targets, reactive intermediates, and advanced glycation endproducts (AGEs) are presented with their potential unwanted side effects. Finally, recent advances in processing for control of Maillard reactions are discussed.

Study of the reaction of astrophysical interest 60Fe(n,γ)61Fe via (d,pγ) transfer reaction

International Nuclear Information System (INIS)

Giron, S.

2011-12-01

60 Fe is of special interest in nuclear astrophysics. Indeed the recent observations of 60 Fe characteristic gamma-ray lines by the RHESSI and INTEGRAL spacecrafts allowed to measure the total flux of 60 Fe over the Galaxy. Moreover the observation in presolar grains of an excess of the daughter-nuclei of 60 Fe, 60 Ni, gives constraints on the conditions of formation of the early solar system. However, the cross-sections of some reactions involved in 60 Fe nucleosynthesis and included to stellar models are still uncertain. The destruction reaction of 60 Fe, 60 Fe(n, γ) 61 Fe, is one of them. The total cross-section can be separate into two contributions: the direct one, involving states below the neutron separation threshold of 61 Fe, and the resonant one.We improved 61 Fe spectroscopy in order to evaluate the direct capture part of the 60 Fe(n, γ) 61 Fe reaction cross-section. 60 Fe(n, γ) 61 Fe was thus studied via d( 60 Fe, pγ) 61 Fe transfer reaction with the CATS/MUST2/EXOGAM setup at LISE-GANIL. DWBA analysis of experimental proton differential cross-sections allowed to extract orbital angular momentum and spectroscopic factors of different populated states identified below the neutron threshold. A comparison of experimental results for 61 Fe with experimental results for similar nuclei and with shell-model calculations was also performed. (author) [fr

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

KAUST Repository

Hisatomi, Takashi; Takanabe, Kazuhiro; Domen, Kazunari

2014-01-01

Abstract: Some particulate semiconductors loaded with nanoparticulate catalysts exhibit photocatalytic activity for the water-splitting reaction. The photocatalysis is distinct from the thermal catalysis because photocatalysis involves photophysical

CrWSKP1, an SKP1-like Gene, Is Involved in the Self-Incompatibility Reaction of "Wuzishatangju" (Citrus reticulata Blanco).

Science.gov (United States)

Li, Peng; Miao, Hongxia; Ma, Yuewen; Wang, Lu; Hu, Guibing; Ye, Zixing; Zhao, Jietang; Qin, Yonghua

2015-09-09

Plant S-phase kinase-associated protein 1 (SKP1) genes play crucial roles in plant development and differentiation. However, the role of SKP1 in citrus is unclear. Herein, we described a novel SKP1-like gene, designated as CrWSKP1, from "Wuzishatangju" (Citrus reticulata Blanco). The cDNA sequence of CrWSKP1 is 779 base pairs (bp) and contains an open reading frame (ORF) of 477 bp. The genomic sequence of the CrWSKP1 gene is 1296 bp with two exons and one intron. CrWSKP1 has high identity with SKP1-like genes from other plant species within two conserved regions. Approximately 85% of pollen tubes of self-pollinated CrWSKP1 transgenic tobaccos became twisted at four days after self-pollination. Pollen tube numbers of self-pollinated CrWSKP1 transformants entering into ovules were significantly fewer than that of the control. Seed number of self-pollinated CrWSKP1 transformants was significantly reduced. These results suggested that the CrWSKP1 is involved in the self-incompatibility (SI) reaction of "Wuzishatangju".

Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.

Science.gov (United States)

Sad, María E; Neurock, Matthew; Iglesia, Enrique

2011-12-21

This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the α-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. © 2011 American Chemical Society

Dynamics of small ruminant development in Central Java-Indonesia

NARCIS (Netherlands)

Gede Suparta Budisatria, I.

2006-01-01

Small ruminants are an important but neglected resource in developing countries. Small ruminant production systems are complex. The multiple goals related to small ruminants, combined with the complexity of their management, and the resources and social arrangements involved, make small ruminants

Low Energy Nuclear Reactions: 2007 Update

Science.gov (United States)

Krivit, Steven B.

2007-03-01

This paper presents an overview of low energy nuclear reactions, a subset of the field of condensed matter nuclear science. Condensed matter nuclear science studies nuclear effects in and/or on condensed matter, including low energy nuclear reactions, an entirely new branch of science that gained widespread attention and notoriety beginning in 1989 with the announcement of a previously unrecognized source of energy by Martin Fleischmann and Stanley Pons that came to be known as cold fusion. Two branches of LENR are recognized. The first includes a set of reactions like those observed by Fleischmann and Pons that use palladium and deuterium and yield excess heat and helium-4. Numerous mechanisms have been proposed to explain these reactions, however there is no consensus for, or general acceptance of, any of the theories. The claim of fusion is still considered speculative and, as such, is not an ideal term for this work. The other branch is a wide assortment of nuclear reactions that may occur with either hydrogen or deuterium. Anomalous nuclear transmutations are reported that involve light as well as heavy elements. The significant questions that face this field of research are: 1) Are LENRs a genuine nuclear reaction? 2) If so, is there a release of excess energy? 3) If there is, is the energy release cost-effective?

Development of LEAP-JET code for sodium-water reaction analysis. Validation by sodium-water reaction tests (SWAT-1R)

International Nuclear Information System (INIS)

Seino, Hiroshi; Hamada, Hirotsugu

2004-03-01

The sodium-water reaction event in an FBR steam generator (SG) has influence on the safety, economical efficiency, etc. of the plant, so that the selection of design base leak (DBL) of the SG is considered as one of the important matters. The clarification of the sodium-water reaction phenomenon and the development of an analysis model are necessary to estimate the sodium-water reaction event with high accuracy and rationality in selecting the DBL. The reaction jet model is pointed out as a part of the necessary improvements to evaluate the overheating tube rupture of large SGs, since the behavior of overheating tube rupture is largely affected by the reaction jet conditions outside the tube. Therefore, LEAP-JET has been developed as an analysis code for the simulation of sodium-water reactions. This document shows the validation of the LEAP-JET code by the Sodium-Water Reaction Test (SWAT-1R). The following results have been obtained: (1) The reaction rate constant, K, is estimated at between 0.001≤K≤0.1 from the LEAP-JET analysis of the SWAT-1R data. (2) The analytical results on the high-temperature region and the behaviors of reaction consumption (Na, H 2 O) and products (H 2 , NaOH, Na 2 O) are considered to be physically reasonable. (3) The LEAP-JET analysis shows the tendency of overestimation in the maximum temperature and temperature distribution of the reaction jet. (4) In the LEAP-JET analysis, the numerical calculation becomes unstably, especially in the mesh containing quite small sodium mass. Therefore, it is necessary to modify the computational algorism to stabilize it and obtain the optimum value of K in sodium-water reactions. (author)

Heavy lon Reactions The Elementary Processes, Parts I and II

CERN Document Server

Broglia, Ricardo A

2004-01-01

Combining elastic and inelastic processes with transfer reactions, this two-part volume explores how these events affect heavy ion collisions. Special attention is given to processes involving the transfer of two nucleons, which are specific for probing pairing correlations in nuclei. This novel treatment provides, together with the description of surface vibration and rotations, a unified picture of heavy ion reactions in terms of the elementary modes of nuclear excitation. Heavy Ion Reactions is essential reading for beginning graduate students as well as experienced researchers.

Search for an explanation for neutralization rates of atomic ion-ion reactions

Science.gov (United States)

Miller, Thomas M.; Wiens, Justin P.; Shuman, Nicholas S.; Viggiano, Albert A.

2016-09-01

We have measured well over a hundred rate coefficients k for cation-anion mutual neutralization reactions at thermal energies. For molecular ions, the k at 300 K tend not to vary more than a factor of two or three, presumably because a great many neutral states cross the incoming Coulombic potential energy curve. Atomic-atomic systems, for which there are few favorable curve crossings between the neutral and Coulombic curves, show variation of at least a factor of 60 in the measured k values at 300 K. For reactions involving the noble-gas cations, we assume that the final state is the lowest excited state of the neutral, plus the ground state of the neutralized anion, because otherwise the crossing distance R is so small that the curve-crossing probability is nil. We plotted measured k values (in cm3/s) vs the distance R (in bohr) at which the neutral and Coulombic curves cross, the found that the data are fairly well fit by a power law for k, 10-4R - 2 . 8 . The question is, is there a physical explanation for the observed dependence on R? We will discuss the data and the expectations of Landau-Zener theory. Supported by Air Force Office of Scientific Research (AFOSR-2303EP).

One-nucleon pickup reactions and compound-nuclear decays

Science.gov (United States)

Escher, J. E.; Burke, J. T.; Casperson, R. J.; Hughes, R. O.; Scielzo, N. D.

2018-05-01

One-nucleon transfer reactions, long used as a tool to study the structure of nuclei, are potentially valuable for determining reaction cross sections indirectly. This is significant, as many reactions of interest to astrophysics and other applications involve short-lived isotopes and cannot be measured directly. We describe a procedure for obtaining constraints for calculations of neutron capture cross sections using observables from experiments with transfer reactions. As a first step toward demonstrating the method, we outline the theory developments used to properly describe the production of the compound nucleus 88Y* via the one-nucleon pickup reaction 89Y(p,d)88Y* and test the description with data from a recent experiment. We indicate how this development can be used to extract the unknown 87Y(n,γ) cross section from 89Y(p,dγ) data. The example illustrates a more generally applicable method for determining unknown cross sections via a combination of theory and transfer (or inelastic scattering) experiments.

New protein involved in the replacement of cell molecules

DEFF Research Database (Denmark)

Poulsen, Jesper Buchhave

2011-01-01

In collaboration with colleagues from La Trobe University, Australia, scientists at Aarhus University have discovered and defined a novel enzyme involved in the replacement and renewal of cell molecules. The enzyme exerts its function within the so-called mitochondria - small “enclosed” compartme......In collaboration with colleagues from La Trobe University, Australia, scientists at Aarhus University have discovered and defined a novel enzyme involved in the replacement and renewal of cell molecules. The enzyme exerts its function within the so-called mitochondria - small “enclosed...

Chemically ignited thermonuclear reactions: A near-term means for a high specific impulse - High thrust propulsion system

International Nuclear Information System (INIS)

Winterberg, F.

1982-01-01

A proposal for the fissionless ignition of small thermonuclear reactions is made which involves the combination of the magnetic booster target inertial fusion concept with the chemical implosion of metallic shells. The magnetic booster employs a very dense and magnetically confined low yield thermonuclear plasma to trigger an inertially confined high yield plasma. Fissionless ignition permits smaller yields than with fission- or fusion-induced fusion bombs, yields that are appropriate for use in a spacecraft propulsion system. Each bomb would release about 10 to the 18th erg or 100 tons of TNT, and with one explosion per second, an average thrust of 10 to the third tons and a specific impulse of about 3000 seconds can be expected

On the nature of the olefination reaction involving ditungsten hexaalkoxides and aldehydes or ketones

Energy Technology Data Exchange (ETDEWEB)

Chisholm, M.H.; Huffman, J.C.; Lucas, E.A.; Sousa, A.; Streib, W.E. [Indiana Univ., Bloomington, IN (United States)

1992-03-25

Reductive coupling of aldehydes and ketones to olefins under the action of ditungsten hexaalkoxides was investigated. In these reactions, reductive cleavage of the aldehyde or ketone carbonyl is followed by formation of the olefinic C-C bond and breaking of the carbonyl C-O bond of the second aldehyde or ketone. Observations concerning the initial C-O bond cleavage and subsequent C-C bond formation are presented. 10 refs., 4 figs.

Elastic and inelastic pion reactions on few nucleon systems

International Nuclear Information System (INIS)

Lensky, V.

2007-01-01

In the present work, we are studying elastic and inelastic pion reactions on few-body systems within the framework of chiral effective theory. We consider two specific reactions involving pions on few-nucleon systems, namely pion production in nucleon-nucleon collisions, and incoherent pion photoproduction on the deuteron. These two reactions are closely related to the issue of dispersive and absorptive corrections to the pion-deuteron scattering length, which we also consider in our analysis. The incoherent pion photoproduction is also considered as the possible source for a high-precision determination of the neutron-neutron scattering length. (orig.)

Elastic and inelastic pion reactions on few nucleon systems

Energy Technology Data Exchange (ETDEWEB)

Lensky, V.

2007-09-29

In the present work, we are studying elastic and inelastic pion reactions on few-body systems within the framework of chiral effective theory. We consider two specific reactions involving pions on few-nucleon systems, namely pion production in nucleon-nucleon collisions, and incoherent pion photoproduction on the deuteron. These two reactions are closely related to the issue of dispersive and absorptive corrections to the pion-deuteron scattering length, which we also consider in our analysis. The incoherent pion photoproduction is also considered as the possible source for a high-precision determination of the neutron-neutron scattering length. (orig.)

Kinetics and Mechanism of the Reaction of Hydoxyl Radicals with Acetonitrile under Atmospheric Conditions

Science.gov (United States)

Hynes, A. J.; Wine, P. H.

1997-01-01

The pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to determine absolute rate coefficients for the reaction OH + CH3CN (1) and its isotopic variants, OH + CD3CN (2), OD + CH3CN (3), and OD + CD3CN (4). Reactions 1 and 2 were studied as a function of pressure and temperature in N2, N2/O2, and He buffer gases. In the absence of O2 all four reactions displayed well-behaved kinetics with exponential OH decays and pseudo-first rate constants which were proportional to substrate concentration. Data obtained in N2 over the range 50-700 Torr at 298 K are consistent with k(sub 1), showing a small pressure dependence. The Arrhenius expression obtained by averaging data at all pressures in k(sub 1)(T) = (1.1(sup +0.5)/(sub -0.3)) x 10(exp -12) exp[(-1130 +/- 90)/T] cu cm /(molecule s). The kinetics of reaction 2 are found to be pressure dependent with k(sub 2) (298 K) increasing from (1.21 +/- 0.12) x 10(exp -14) to (2.16 +/- 0.11) x 10(exp -14) cm(exp 3)/ (molecule s) over the pressure range 50-700 Torr of N2 at 298 K. Data at pressures greater than 600 Torr give k(sub 2)(T) = (9.4((sup +13.4)(sub -5.0))) x 10(exp -13) exp[(-1180 +/- 250)/T] cu cm/(molecule s). The rates of reactions 3 and 4 are found to be independent of pressure over the range 50-700 Torr of N2 with 298 K rate coefficient given by k(sub 3) =(3.18 +/- 0.40) x 10(exp -14) cu cm/(molecule s) and k(sub 4) = (2.25 +/-0.28) x 10(exp -14) cu cm/(molecule s). In the presence of O2 each reaction shows complex (non-pseudo-first-order) kinetic behavior and/or an apparent decrease in the observed rate constant with increasing [O2], indicating the presence of significant OH or OD regeneration. Observation of regeneration of OH in (2) and OD in (3) is indicative of a reaction channel which proceeds via addition followed by reaction of the adduct, or one of its decomposition products, with O2. The observed OH and OD decay profiles have been modeled by using a simple mechanistic

Persistent Skin Reactions and Aluminium Hypersensitivity Induced by Childhood Vaccines

DEFF Research Database (Denmark)

Salik, Elaha; Løvik, Ida; Andersen, Klaus E

2016-01-01

There is increasing awareness of reactions to vaccination that include persistent skin reactions. We present here a retrospective investigation of long-lasting skin reactions and aluminium hypersensitivity in children, based on medical records and questionnaires sent to the parents. In the 10-year...... period 2003 to 2013 we identified 47 children with persistent skin reactions caused by childhood vaccinations. Most patients had a typical presentation of persisting pruritic subcutaneous nodules. Five children had a complex diagnostic process involving paediatricians, orthopaedics and plastic surgeons...... treated with potent topical corticosteroids and disappeared slowly. Although we advised families to continue vaccination of their children, one-third of parents omitted or postponed further vaccinations....

Spallation reactions - physics and applications

International Nuclear Information System (INIS)

Kelic, A.; Ricciardi, M.; Schmidt, K-H.

2009-01-01

Spallation reactions have become an ideal tool for studying the equation of state and thermal instabilities of nuclear matter. In astrophysics, the interactions of cosmic rays with the interstellar medium have to be understood in detail for deducing their original composition and their production mechanisms. Renewed interest in spallation reactions with protons around 1 GeV came up recently with the developments of spallation neutron sources. The project of an accelerator-driven system (ADS) as a technological solution for incinerating the radioactive waste even intensified the efforts for better understanding the physics involved in the spallation process. Experiments on spallation reactions were performed for determining the production cross sections and properties of particles, fragments and heavy residues. Traditional experiments on heavy residues, performed in direct kinematics, were limited to the direct observation of long-lived radioactive nuclides and did not provide detailed information on the kinematics of the reaction. Therefore, an innovative experimental method has been developed, based on inverse kinematics, which allowed to identify all reaction residues in-flight, using the high resolution magnetic spectrometer FRS of GSL Darmstadt. It also gives direct access to the reaction kinematics. An experimental campaign has been carried out in a Europe-wide collaboration, investigating the spallation of several nuclei ranging from 56 Fe to 238 U Complementary experiments were performed with a full-acceptance detection system, yielding total fission cross sections. Recently, another detection system using the large acceptance ALADIN dipole and the LAND neutron detector was introduced to measure light particles in coincidence with the heavy residues. Another intense activity was dedicated to developing codes, which cover nuclear reactions occurring in an ADS. The first phase of the reaction is successfully described by a sequence of quasi-free nucleon

Catalytic Upgrading of Biomass-Derived Compounds via C-C Coupling Reactions. Computational and Experimental Studies of Acetaldehyde and Furan Reactions in HZSM-5

Energy Technology Data Exchange (ETDEWEB)

Liu, Cong [Argonne National Lab. (ANL), Argonne, IL (United States); Evans, Tabitha J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Cheng, Lei [Argonne National Lab. (ANL), Argonne, IL (United States); Nimlos, Mark R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Mukarakate, Calvin [National Renewable Energy Lab. (NREL), Golden, CO (United States); Robichaud, David J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Assary, Rajeev S. [Argonne National Lab. (ANL), Argonne, IL (United States); Curtiss, Larry A. [Argonne National Lab. (ANL), Argonne, IL (United States)

2015-10-02

These catalytic C–C coupling and deoxygenation reactions are essential for upgrading of biomass-derived oxygenates to fuel-range hydrocarbons. Detailed understanding of mechanistic and energetic aspects of these reactions is crucial to enabling and improving the catalytic upgrading of small oxygenates to useful chemicals and fuels. Using periodic density functional theory (DFT) calculations, we have investigated the reactions of furan and acetaldehyde in an HZSM-5 zeolite catalyst, a representative system associated with the catalytic upgrading of pyrolysis vapors. Comprehensive energy profiles were computed for self-reactions (i.e., acetaldehyde coupling and furan coupling) and cross-reactions (i.e., acetaldehyde + furan) of this representative mixture. Major products proposed from the computations are further confirmed using temperature controlled mass spectra measurements. Moreover, the computational results show that furan interacts with acetaldehyde in HZSM-5 via an alkylation mechanism, which is more favorable than the self-reactions, indicating that mixing furans with aldehydes could be a promising approach to maximize effective C–C coupling and dehydration while reducing the catalyst deactivation (e.g., coke formation) from aldehyde condensation.

Toward Predictive Theories of Nuclear Reactions Across the Isotopic Chart: Web Report

Energy Technology Data Exchange (ETDEWEB)

Escher, J. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Blackmon, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Elster, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Launey, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lee, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scielzo, N. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-05-12

Recent years have seen exciting new developments and progress in nuclear structure theory, reaction theory, and experimental techniques, that allow us to move towards a description of exotic systems and environments, setting the stage for new discoveries. The purpose of the 5-week program was to bring together physicists from the low-energy nuclear structure and reaction communities to identify avenues for achieving reliable and predictive descriptions of reactions involving nuclei across the isotopic chart. The 4-day embedded workshop focused on connecting theory developments to experimental advances and data needs for astrophysics and other applications. Nuclear theory must address phenomena from laboratory experiments to stellar environments, from stable nuclei to weakly-bound and exotic isotopes. Expanding the reach of theory to these regimes requires a comprehensive understanding of the reaction mechanisms involved as well as detailed knowledge of nuclear structure. A recurring theme throughout the program was the desire to produce reliable predictions rooted in either ab initio or microscopic approaches. At the same time it was recognized that some applications involving heavy nuclei away from stability, e.g. those involving fi ssion fragments, may need to rely on simple parameterizations of incomplete data for the foreseeable future. The goal here, however, is to subsequently improve and refine the descriptions, moving to phenomenological, then microscopic approaches. There was overarching consensus that future work should also focus on reliable estimates of errors in theoretical descriptions.

Energy and Molecules from Photochemical/Photocatalytic Reactions. An Overview

Directory of Open Access Journals (Sweden)

Davide Ravelli

2015-01-01

Full Text Available Photocatalytic reactions have been defined as those processes that require both a (not consumed catalyst and light. A previous definition was whether such reactions brought a system towards or away from the (thermal equilibrium. This consideration brings in the question whether a part of the photon energy is incorporated into the photochemical reaction products. Data are provided for representative organic reactions involving or not molecular catalysts and show that energy storage occurs only when a heavily strained structure is generated, and in that case only a minor part of photon energy is actually stored (ΔG up to 25 kcal·mol−1. The green role of photochemistry/photocatalysis is rather that of forming highly reactive intermediates under mild conditions.

Reaction-Diffusion Automata Phenomenology, Localisations, Computation

CERN Document Server

Adamatzky, Andrew

2013-01-01

Reaction-diffusion and excitable media are amongst most intriguing substrates. Despite apparent simplicity of the physical processes involved the media exhibit a wide range of amazing patterns: from target and spiral waves to travelling localisations and stationary breathing patterns. These media are at the heart of most natural processes, including morphogenesis of living beings, geological formations, nervous and muscular activity, and socio-economic developments.   This book explores a minimalist paradigm of studying reaction-diffusion and excitable media using locally-connected networks of finite-state machines: cellular automata and automata on proximity graphs. Cellular automata are marvellous objects per se because they show us how to generate and manage complexity using very simple rules of dynamical transitions. When combined with the reaction-diffusion paradigm the cellular automata become an essential user-friendly tool for modelling natural systems and designing future and emergent computing arch...

An effective rate equation approach to reaction kinetics in small volumes: theory and application to biochemical reactions in nonequilibrium steady-state conditions.

Science.gov (United States)

Grima, R

2010-07-21

Chemical master equations provide a mathematical description of stochastic reaction kinetics in well-mixed conditions. They are a valid description over length scales that are larger than the reactive mean free path and thus describe kinetics in compartments of mesoscopic and macroscopic dimensions. The trajectories of the stochastic chemical processes described by the master equation can be ensemble-averaged to obtain the average number density of chemical species, i.e., the true concentration, at any spatial scale of interest. For macroscopic volumes, the true concentration is very well approximated by the solution of the corresponding deterministic and macroscopic rate equations, i.e., the macroscopic concentration. However, this equivalence breaks down for mesoscopic volumes. These deviations are particularly significant for open systems and cannot be calculated via the Fokker-Planck or linear-noise approximations of the master equation. We utilize the system-size expansion including terms of the order of Omega(-1/2) to derive a set of differential equations whose solution approximates the true concentration as given by the master equation. These equations are valid in any open or closed chemical reaction network and at both the mesoscopic and macroscopic scales. In the limit of large volumes, the effective mesoscopic rate equations become precisely equal to the conventional macroscopic rate equations. We compare the three formalisms of effective mesoscopic rate equations, conventional rate equations, and chemical master equations by applying them to several biochemical reaction systems (homodimeric and heterodimeric protein-protein interactions, series of sequential enzyme reactions, and positive feedback loops) in nonequilibrium steady-state conditions. In all cases, we find that the effective mesoscopic rate equations can predict very well the true concentration of a chemical species. This provides a useful method by which one can quickly determine the

Tandem Wittig-ene reaction approach to kainic acid

Digital Repository Service at National Institute of Oceanography (India)

Majik, M.S.; Parameswaran, P.S.; Tilve, S.G.

The first example of a tandem Wittig-intramolecular ene reaction approach and its application toward the synthesis of kainic acid is reported. The synthetic pathway involves conversion of prenyl bromide into phosphorane 3, followed by one-pot Wittig...

Synthesis of conformationally constrained peptidomimetics using multicomponent reactions

NARCIS (Netherlands)

Scheffelaar, R.; Klein Nijenhuis, R.A.; Paravidino, M.; Lutz, M.; Spek, A.L.; Ehlers, A.W.; de Kanter, F.J.J.; Groen, M.B.; Orru, R.V.A.; Ruijter, E.

2009-01-01

A novel modular synthetic approach toward constrained peptidomimetics is reported. The approach involves a highly efficient three-step sequence including two multicomponent reactions, thus allowing unprecedented diversification of both the peptide moieties and the turn-inducing scaffold. The

Front propagation in Rayleigh-Taylor systems with reaction

International Nuclear Information System (INIS)

Scagliarini, A; Biferale, L; Sbragaglia, M; Mantovani, F; Pivanti, M; Schifano, S F; Tripiccione, R; Pozzati, F; Toschi, F

2011-01-01

A special feature of Rayleigh-Taylor systems with chemical reactions is the competition between turbulent mixing and the 'burning processes', which leads to a highly non-trivial dynamics. We studied the problem performing high resolution numerical simulations of a 2d system, using a thermal lattice Boltzmann (LB) model. We spanned the various regimes emerging at changing the relative chemical/turbulent time scales, from slow to fast reaction; in the former case we found numerical evidence of an enhancement of the front propagation speed (with respect to the laminar case), providing a phenomenological argument to explain the observed behaviour. When the reaction is very fast, instead, the formation of sharp fronts separating patches of pure phases, leads to an increase of intermittency in the small scale statistics of the temperature field.

Descent with Modification: Thermal Reactions of Subsurface H2O2 of Relevance to Icy Satellites and Other Small Bodies

Science.gov (United States)

Hudson, Reggie L.; Loefler, Mark J.

2012-01-01

Laboratory experiments have demonstrated that magnetospheric radiation in the Jovian system drives reaction chemistry in ices at temperatures relevant to Europa and other icy satellites. Similarly, cosmic radiation (mainly protons) acting on cometary and interstellar ices can promote extensive chemical change. Among the products that have been identified in irradiated H20-ice is hydrogen peroxide (H202), which has been observed on Europa and is suspected on other worlds. Although the infrared spectra and radiation chemistry of H2O2-containing ices are well documented, the thermally-induced solid-phase chemistry of H2O2 is largely unknown. Therefore, in this presentation we report new laboratory results on reactions at 50 - 130 K in ices containing H2O2 and other molecules, both in the presence and absence of H2O. As an example of our results, we find that warming H2O + H2O2 + SO2 ices promotes SO2 oxidation to SO4(2-). We suspect that such redox chemistry may explain some of the observations related to the presence and distribution of H2O2 across Europa's surface as well as the lack of H2O2 on Ganymede and Callisto. If other molecules prove to be just as reactive with frozen H2O2 then it may explain why H2O2 has been absent from surfaces of many of the small icy bodies that are known to be exposed to ionizing radiation. Our results also have implications for the survival of H2O2 as it descends towards a subsurface ocean on Europa.

Measurement of proton capture reactions in the hot cycles: an evaluation of experimental methods

Energy Technology Data Exchange (ETDEWEB)

Leleux, P [Inst. de Physique Nucleaire, Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium)

1998-06-01

In the hot cycles, most of the proton capture reactions involve radioactive nuclei in the entrance and exit channels. This paper evaluates the specific methods that were designed to measure such reactions. (orig.)

Benzene destruction in claus process by sulfur dioxide: A reaction kinetics study

KAUST Repository

Sinha, Sourab; Raj, Abhijeet Dhayal; Alshoaibi, Ahmed S.; Alhassan, Saeed M.; Chung, Suk-Ho

2014-01-01

interactions. The mechanism begins with SO2 addition to phenyl radical after overcoming an energy barrier of 6.4 kJ/mol. This addition reaction is highly exothermic, where a reaction energy of 182 kJ/mol is released. The most favorable pathway involves O-S bond

Structure-reactivity modeling using mixture-based representation of chemical reactions.

Science.gov (United States)

Polishchuk, Pavel; Madzhidov, Timur; Gimadiev, Timur; Bodrov, Andrey; Nugmanov, Ramil; Varnek, Alexandre

2017-09-01

We describe a novel approach of reaction representation as a combination of two mixtures: a mixture of reactants and a mixture of products. In turn, each mixture can be encoded using an earlier reported approach involving simplex descriptors (SiRMS). The feature vector representing these two mixtures results from either concatenated product and reactant descriptors or the difference between descriptors of products and reactants. This reaction representation doesn't need an explicit labeling of a reaction center. The rigorous "product-out" cross-validation (CV) strategy has been suggested. Unlike the naïve "reaction-out" CV approach based on a random selection of items, the proposed one provides with more realistic estimation of prediction accuracy for reactions resulting in novel products. The new methodology has been applied to model rate constants of E2 reactions. It has been demonstrated that the use of the fragment control domain applicability approach significantly increases prediction accuracy of the models. The models obtained with new "mixture" approach performed better than those required either explicit (Condensed Graph of Reaction) or implicit (reaction fingerprints) reaction center labeling.

Reaction Mechanism Generator: Automatic construction of chemical kinetic mechanisms

Science.gov (United States)

Gao, Connie W.; Allen, Joshua W.; Green, William H.; West, Richard H.

2016-06-01

Reaction Mechanism Generator (RMG) constructs kinetic models composed of elementary chemical reaction steps using a general understanding of how molecules react. Species thermochemistry is estimated through Benson group additivity and reaction rate coefficients are estimated using a database of known rate rules and reaction templates. At its core, RMG relies on two fundamental data structures: graphs and trees. Graphs are used to represent chemical structures, and trees are used to represent thermodynamic and kinetic data. Models are generated using a rate-based algorithm which excludes species from the model based on reaction fluxes. RMG can generate reaction mechanisms for species involving carbon, hydrogen, oxygen, sulfur, and nitrogen. It also has capabilities for estimating transport and solvation properties, and it automatically computes pressure-dependent rate coefficients and identifies chemically-activated reaction paths. RMG is an object-oriented program written in Python, which provides a stable, robust programming architecture for developing an extensible and modular code base with a large suite of unit tests. Computationally intensive functions are cythonized for speed improvements.

Competing irreversible cooperative reactions on polymer chains

International Nuclear Information System (INIS)

Evans, J.W.; Hoffman, D.K.; Burgess, D.R.

1984-01-01

We analyze model processes involving competition between several irreversible reactions at the sites of a 1D, infinite, uniform polymer chain. These reactions can be cooperative, i.e., the corresponding rates depend on the state of the surrounding sites. An infinite hierarchy of rate equations is readily derived for the probabilities of various subconfigurations. By exploiting a shielding property of suitable blocks of unreacted sites, we show how exact hierarchy truncation and solution is sometimes possible. The behavior of solutions is illustrated in several cases by plotting families of ''reaction trajectories'' for varying ratios of reactant concentrations. As a specific application, we consider competition between coordination of ZnCl 2 to pairs of oxygen atoms and to single oxygen atoms in poly(propylene oxide). The observed glass transition temperature behavior is eludicated

Excitation functions and isotopic effects in (n, p) reactions for stable nickel isotopes from reaction threshold to 20 MeV

Energy Technology Data Exchange (ETDEWEB)

Lalremruata, B. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: marema@physics.unipune.ernet.in; Ganesan, S. [Reactor Physics Design Division, BARC, Mumbai 58 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: vnb@physics.unipune.ernet; Dhole, S.D. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: sanjay@physics.unipune.ernet.in

2009-05-01

The excitation function for (n, p) reactions from reaction threshold to 20 MeV on five nickel isotopes viz; {sup 58}Ni, {sup 60}Ni, {sup 61}Ni, {sup 62}Ni and {sup 64}Ni were calculated using Talys-1.0 nuclear model code involving the fixed set of global parameters. A good agreement between the calculated and measured data is obtained with minimum effort on parameter fitting and only one free parameter called 'Shell damping factor'. This is of importance to the validation of nuclear model approaches with increased predictive power. The systematic decrease in (n, p) cross-sections with increasing neutron number in reactions induced by neutrons on isotopes of nickel is explained in terms of the proton separation energy and the pre-equilibrium model. The compound nucleus and pre-equilibrium reaction mechanism as well as the isotopic effects were also studied.

Chemical reactions in the presence of surface modulation and stirring

OpenAIRE

Kamhawi, Khalid; Náraigh, Lennon Ó

2009-01-01

We study the dynamics of simple reactions where the chemical species are confined on a general, time-modulated surface, and subjected to externally-imposed stirring. The study of these inhomogeneous effects requires a model based on a reaction-advection-diffusion equation, which we derive. We use homogenization methods to show that up to second order in a small scaling parameter, the modulation effects on the concentration field are asymptotically equivalent for systems with or without stirri...

Multiple scattering in the nuclear rearrangement reactions at medium energy

International Nuclear Information System (INIS)

Tekou, A.

1980-09-01

It is shown that the multiple scattering mechanism is very important in the transfer of the large momenta involved in the nuclear rearrangement reactions at medium energy. In contrast to the usual belief, the reaction cross-section is not very sensitive to the high momenta components of the nuclear wave function. The multiple scattering mechanism is especially important in 4 He(p,d) 3 He reaction around 800 MeV. Here the collisions involving two nucleons of the target nucleus are dominant. The triple collisions contribution is also important. The four collision contribution is negligible in the forward direction and sizeable at large angles. Thus, using the K.M.T. approach in DWBA calculations, the second order term of the optical potential must be included. So, is it not well established that the second term of the K.M.T. optical potential is important for the proton elastic scattering on light nuclei. (author)

The asymmetric hetero-Diels-Alder reaction in the syntheses of biologically relevant compounds.

Science.gov (United States)

Eschenbrenner-Lux, Vincent; Kumar, Kamal; Waldmann, Herbert

2014-10-13

The hetero-Diels-Alder reaction is one of the most powerful transformations in the chemistry toolbox for the synthesis of aza- and oxa-heterocycles embodying multiple stereogenic centers. However, as compared to other cycloadditions, in particular the dipolar cycloadditions and the Diels-Alder reaction, the hetero-Diels-Alder reaction has been much less explored and exploited in organic synthesis. Nevertheless, this powerful transformation has opened up efficient and creative routes to biologically relevant small molecules and different natural products which contain six-membered oxygen or nitrogen ring systems. Recent developments in this field, in particular in the establishment of enantioselectively catalyzed hetero-Diels-Alder cycloadditions steered by a plethora of different catalysts and the application of the resulting small molecules in chemical biology and medicinal chemistry research, are highlighted in this Minireview. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The experiment and analysis on small leak phenomena

International Nuclear Information System (INIS)

Jeong, Kyung Chai; Hwang, S. T.; Kim, B. H.; Jeong, J. Y.

2000-07-01

The liquid sodium which is used as a coolant in LMFBR, may give rise to a serious trouble in the safety aspect of steam generator. The defects in a heat transfer tube, such as pin-hole or tube welding defect, will result in a leakage of high pressure steam into the sodium side and production of hydrogen gas and corrosive sodium compounds which can cause significant damage to the tube wall of steam generator by using exothermic reaction. In significant damage to the tube wall of steam generator by using exothermic reaction. In this case, initial leak size will be enlarged with time and the leak rate developed to large leak through the micro, small, intermediate leaks. Therefore, the analysis of sodium-water reaction phenomena on the micro and small water leaks in the heat transfer tube is very important in the initial leak stage in the aspects of the protection of leak progress and safety evaluation of steam generator. In this study, firstly, the micro and small leaks phenomena, such as reopen size, shape, and time of leak path, self-wastage, corrosion of tube materials, was analyzed from the literature survey and water leakage experiments using the leak specimen. In small water leak experiments, the leak path was plugged by the sodium-water reaction products at the leak path of a specimen, and re-open phenomena were not observed in initial experiments. Other leak experiments, reopen phenomena of self-plugged leak path was observed. Re-open mechanism of sealed path could be explained by the thermal transient and vibration of heat transfer tube. As a result, perfect reopen time of self plugged leak path was observed to be about 130 minutes after water leak initiation. Reopen shape of a specimen was appeared with double layer of circular type, and reopen size of this specimen surface was about 2 mm diameter on sodium side. Also, the corrosion of a specimen initiated from sodium side, the segregation phenomena of Cr in the specimen was found much more than those of

Copper-Catalyzed Oxidative Reaction of β-Keto Sulfones with Alcohols via C-S Bond Cleavage: Reaction Development and Mechanism Study.

Science.gov (United States)

Du, Bingnan; Wang, Wenmin; Wang, Yang; Qi, Zhenghang; Tian, Jiaqi; Zhou, Jie; Wang, Xiaochen; Han, Jianlin; Ma, Jing; Pan, Yi

2018-02-16

A Cu-catalyzed cascade oxidative radical process of β-keto sulfones with alcohols has been achieved by using oxygen as an oxidant. In this reaction, β-keto sulfones were converted into sulfinate esters under the oxidative conditions via cleavage of C-S bond. Experimental and computational studies demonstrate that a new pathway is involved in this reaction, which proceeds through the formation of the key four-coordinated Cu II intermediate, O-O bond homolysis induced C-S bond cleavage and Cu-catalyzed esterification to form the final products. This reaction provides a new strategy to sulfonate esters and enriches the research content of C-S bond cleavage and transformations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reaction effects in diffusive shock acceleration

International Nuclear Information System (INIS)

Drury, L.Oc.

1984-01-01

The effects of the reaction of accelerated particles back on the shock wave in the diffusive-shock-acceleration model of cosmic-ray generation are investigated theoretically. Effects examined include changes in the shock structure, modifications of the input and output spectra, scattering effects, and possible instabilities in the small-scale structure. It is pointed out that the latter two effects are applicable to any spatially localized acceleration mechanism. 14 references

Noise-induced modulation of the relaxation kinetics around a non-equilibrium steady state of non-linear chemical reaction networks.

Science.gov (United States)

Ramaswamy, Rajesh; Sbalzarini, Ivo F; González-Segredo, Nélido

2011-01-28

Stochastic effects from correlated noise non-trivially modulate the kinetics of non-linear chemical reaction networks. This is especially important in systems where reactions are confined to small volumes and reactants are delivered in bursts. We characterise how the two noise sources confinement and burst modulate the relaxation kinetics of a non-linear reaction network around a non-equilibrium steady state. We find that the lifetimes of species change with burst input and confinement. Confinement increases the lifetimes of all species that are involved in any non-linear reaction as a reactant. Burst monotonically increases or decreases lifetimes. Competition between burst-induced and confinement-induced modulation may hence lead to a non-monotonic modulation. We quantify lifetime as the integral of the time autocorrelation function (ACF) of concentration fluctuations around a non-equilibrium steady state of the reaction network. Furthermore, we look at the first and second derivatives of the ACF, each of which is affected in opposite ways by burst and confinement. This allows discriminating between these two noise sources. We analytically derive the ACF from the linear Fokker-Planck approximation of the chemical master equation in order to establish a baseline for the burst-induced modulation at low confinement. Effects of higher confinement are then studied using a partial-propensity stochastic simulation algorithm. The results presented here may help understand the mechanisms that deviate stochastic kinetics from its deterministic counterpart. In addition, they may be instrumental when using fluorescence-lifetime imaging microscopy (FLIM) or fluorescence-correlation spectroscopy (FCS) to measure confinement and burst in systems with known reaction rates, or, alternatively, to correct for the effects of confinement and burst when experimentally measuring reaction rates.

Solid-phase vibrational redox reactions in coordinated oxides

International Nuclear Information System (INIS)

Kostikova, G.P.; Korol'kov, D.V.; Kostikov, Yu.P.

1996-01-01

The properties of multicomponent oxides (YBa 2 Cu 3 O 7-x , etc.), incorporating different valency forms of each of two (or more) different elements have been compared with the properties of the known chemical systems, where vibrational (periodic) redox-reactions are realized a fortiori. The essence of the new theoretical concept suggested consists in the following: high-T c superconductivity of the complex oxides and similar compounds originates from vibrational redox reaction proceeding in solid phase and involving different valency atoms of every element

Importance of the support and the grade of Pt in the oxygen reduction reaction

International Nuclear Information System (INIS)

Enriquez M, O.; Fernandez V, S.M.

2004-01-01

The technology of the fuel cells type Proton Exchange Membrane (PEM), needs to define clearly the influence of the different involved parameters, this is made in general using methods of electrochemical impedance, in which the involved reactions can be presupposed. Another form of making is identifying experimentally the influence of the different parameters. In this work the obtained results are reported with for the oxygen reduction reaction using as electro catalyst platinum analytical grade and fuel cell grade and like support graphite and vulcan. It was found that as much the support as the particle size modify the over potential for the oxygen reduction reaction (Orr). (Author)

The role of phosphate in a multistep enzymatic reaction: reactions of the substrate and intermediate in pieces.

Science.gov (United States)

Kholodar, Svetlana A; Allen, C Leigh; Gulick, Andrew M; Murkin, Andrew S

2015-02-25

Several mechanistically unrelated enzymes utilize the binding energy of their substrate's nonreacting phosphoryl group to accelerate catalysis. Evidence for the involvement of the phosphodianion in transition state formation has come from reactions of the substrate in pieces, in which reaction of a truncated substrate lacking its phosphorylmethyl group is activated by inorganic phosphite. What has remained unknown until now is how the phosphodianion group influences the reaction energetics at different points along the reaction coordinate. 1-Deoxy-D-xylulose-5-phosphate (DXP) reductoisomerase (DXR), which catalyzes the isomerization of DXP to 2-C-methyl-D-erythrose 4-phosphate (MEsP) and subsequent NADPH-dependent reduction, presents a unique opportunity to address this concern. Previously, we have reported the effect of covalently linked phosphate on the energetics of DXP turnover. Through the use of chemically synthesized MEsP and its phosphate-truncated analogue, 2-C-methyl-D-glyceraldehyde, the current study revealed a loss of 6.1 kcal/mol of kinetic barrier stabilization upon truncation, of which 4.4 kcal/mol was regained in the presence of phosphite dianion. The activating effect of phosphite was accompanied by apparent tightening of its interactions within the active site at the intermediate stage of the reaction, suggesting a role of the phosphodianion in disfavoring intermediate release and in modulation of the on-enzyme isomerization equilibrium. The results of kinetic isotope effect and structural studies indicate rate limitation by physical steps when the covalent linkage is severed. These striking differences in the energetics of the natural reaction and the reactions in pieces provide a deeper insight into the contribution of enzyme-phosphodianion interactions to the reaction coordinate.

Analysis of small molecular phase in coal involved in pyrolysis and solvent extraction by PGC

Energy Technology Data Exchange (ETDEWEB)

Jie Feng; Wen-Ying Li; Ke-Chang Xie [Taiyuan University of Technology, Taiyuan (China). Key Laboratory of Coal Science and Technology

2004-06-01

The small molecular phase, which strongly affects coal's reactivity, is the main part of the structure unit in coal. At present, its composition and structure features have not been clearly understood. In this paper, a flash pyrolysis technique with on-line GC (PGC) was used to investigate the properties of the small molecular phase from six kinds of rank coal in China. Experiments were divided into two parts: one is PGC of parent coal; another is PGC of coal extracts from NMP + CS{sub 2} (75:1) solvent extraction at 373 K. Results show that the small molecular phase mainly consists of C12-C16 compounds that could be integrally released when the heating rate was greater than 10 K/ms and the final pyrolysis temperature was 1373 K; other compounds may be the products of decomposition and polymerization from this small molecular phase during pyrolysis. 13 refs., 7 figs., 1 tab.

Electrical Breakdown Phenomena Involving Material Interfaces

Science.gov (United States)

2013-06-01

create ozone through chemical reactions involving reactive species created by the electrical discharge [3]. The glow discharge breakdown in such...2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Investigation Of Pre-Ionization And Atmospheric Pulsed Discharge Plasma 5a...growth of the air discharge in the form of a conductive filament consisting of electrons and ions. This filament is created by temporal pulse that

Investigation of the complex reaction coordinate of acid catalyzed amide hydrolysis from molecular dynamics simulations

International Nuclear Information System (INIS)

Zahn, Dirk

2004-01-01

The rate-determining step of acid catalyzed peptide hydrolysis is the nucleophilic attack of a water molecule to the carbon atom of the amide group. Therein the addition of the hydroxyl group to the amide carbon atom involves the association of a water molecule transferring one of its protons to an adjacent water molecule. The protonation of the amide nitrogen atom follows as a separate reaction step. Since the nucleophilic attack involves the breaking and formation of several bonds, the underlying reaction coordinate is rather complex. We investigate this reaction step from path sampling Car-Parrinello molecular dynamics simulations. This approach does not require the predefinition of reaction coordinates and is thus particularly suited for investigating reaction mechanisms. From our simulations the most relevant components of the reaction coordinate are elaborated. Though the C···O distance of the oxygen atom of the water molecule performing the nucleophilic attack and the corresponding amide carbon atom is a descriptor of the reaction progress, a complete picture of the reaction coordinate must include all three molecules taking part in the reaction. Moreover, the proton transfer is found to depend on favorable solvent configurations. Thus, also the arrangement of non-reacting, i.e. solvent water molecules needs to be considered in the reaction coordinate

Women's Experiences of Social Reactions From Informal and Formal Supports: Using a Modified Administration of the Social Reactions Questionnaire.

Science.gov (United States)

DePrince, Anne P; Dmitrieva, Julia; Gagnon, Kerry L; Srinivas, Tejaswinhi

2017-11-01

A growing literature links social reactions to disclosures of intimate violence to posttraumatic outcomes. The Social Reactions Questionnaire (SRQ), a widely used measure developed to assess social reactions, asks about reactions received from people generally. The ability to examine the impact of social reactions from specific groups of people-such as criminal justice personnel versus community-based providers-has become increasingly more important from both research and practice perspectives. For example, as sexual assault responses nationally have relied on community-coordinated models that involve both criminal justice and community-based systems, tools are lacking to systematically assess the impact of social reactions from criminal justice personnel and community-based providers on survivors. Using the SRQ, the current study asked women to report separately on reactions received from criminal justice personnel, community-based providers, and informal supports. We recruited a diverse community sample of women ( N = 228, ages 18-63, 19% lesbian/bisexual, 44% ethnic minority) who experienced a sexual assault in the previous year and disclosed to the criminal justice system and/or a community-based provider. Multilevel analyses revealed considerable variability in the social reactions reported by women across criminal justice personnel, community-based providers, and informal supports. Analyses supported a seven-factor structure for the SRQ when the measure is yoked to particular experiences of disclosure, in this case to criminal justice personnel, community-based providers, or informal supports. The utility of this modified administration and scoring of the SRQ and the importance of considering reactions across different groups are described.

Liver, spleen, pancreas and kidney involvement by human fascioliasis: imaging findings

Directory of Open Access Journals (Sweden)

Hekmatdoost Azita

2004-08-01

Full Text Available Abstract Background Fasciola hepatica primarily involves the liver, however in some exceptional situations other organs have been reported to be involved. The ectopic involvement is either a result of Parasite migration or perhaps eosinophilic reaction. Case presentation Here we report a known case of multiple myeloma who was under treatment with prednisolone and melphalan. He was infected by Fasciola hepatica, which involved many organs and the lesions were mistaken with metastatic ones. Discussion Presented here is a very unusual case of the disease, likely the first case involving the pancreas, spleen, and kidney, as well as the liver.

A novel and facile decay path of Criegee intermediates by intramolecular insertion reactions via roaming transition states

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Trong-Nghia [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Physical Chemistry, Hanoi University of Science and Technology, Hanoi (Viet Nam); Putikam, Raghunath; Lin, M. C., E-mail: chemmcl@emory.edu [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

2015-03-28

We have discovered a new and highly competitive product channel in the unimolecular decay process for small Criegee intermediates, CH{sub 2}OO and anti/syn-CH{sub 3}C(H)OO, occurring by intramolecular insertion reactions via a roaming-like transition state (TS) based on quantum-chemical calculations. Our results show that in the decomposition of CH{sub 2}OO and anti-CH{sub 3}C(H)OO, the predominant paths directly produce cis-HC(O)OH and syn-CH{sub 3}C(O)OH acids with >110 kcal/mol exothermicities via loose roaming-like insertion TSs involving the terminal O atom and the neighboring C–H bonds. For syn-CH{sub 3}C(H)OO, the major decomposition channel occurs by abstraction of a H atom from the CH{sub 3} group by the terminal O atom producing CH{sub 2}C(H)O–OH. At 298 K, the intramolecular insertion process in CH{sub 2}OO was found to be 600 times faster than the commonly assumed ring-closing reaction.

Conditions for extinction events in chemical reaction networks with discrete state spaces.

Science.gov (United States)

Johnston, Matthew D; Anderson, David F; Craciun, Gheorghe; Brijder, Robert

2018-05-01

We study chemical reaction networks with discrete state spaces and present sufficient conditions on the structure of the network that guarantee the system exhibits an extinction event. The conditions we derive involve creating a modified chemical reaction network called a domination-expanded reaction network and then checking properties of this network. Unlike previous results, our analysis allows algorithmic implementation via systems of equalities and inequalities and suggests sequences of reactions which may lead to extinction events. We apply the results to several networks including an EnvZ-OmpR signaling pathway in Escherichia coli.

Microscopic study of (p, γ) reactions in mass region A = 110-125

International Nuclear Information System (INIS)

Chakraborty, Dipti; Dutta, Saumi; Gangopadhyay, G.; Bhattacharyya, Abhijit

2014-01-01

To calculate the actual abundance of different nuclei and evolution of the process, a network calculation is needed involving reaction rates for a large number of nuclei. Thus we need to know the interaction potential. As the p-process proceeds along proton rich side of the stability valley, it involves many nuclei which are unstable and inaccessible as targets on earth to do experiments. So theory remains the sole guide to gather information about the reactions. Presently, we are concerned about the nuclei in the mass region A = 110-125. It is imperative to test the theoretical calculations, where experimental data are available, to verify its applicability before extending it to unknown regions. Thus reactions for stable targets in the mass region have been studied in the present work

Graft-versus-host reaction in small bowel transplantation and possibilities for its circumvention

International Nuclear Information System (INIS)

Deltz, E.; Ulrichs, K.; Schack, T.; Friedrichs, B.; Mueller-Ruchholtz, W.M.; Mueller-Hermelink, H.K.T.; Thiede, A.

1986-01-01

To describe GVHR in small bowel transplantation and its underlying mechanisms and to find methods for circumventing that response, accessory small bowel transplantation was carried out in the rat model. Animals not treated with cyclosporine, irradiation, or removal of the mesenteric lymph nodes of the graft died within 22 days postoperatively due to graft versus host disease. Mesenteric lymph nodes of the graft and recipient spleen and peripheral lymph nodes showed strong immunologic stimulation histologically and high antihost T-cell-mediated cytotoxic antihost reactivity. Seventy-one percent of the animals that had received 15 mg of cyclosporine per kilogram body weight orally survived 150 days after transplantation. After donor irradiation with 50 rads, 77 percent of the recipients survived 120 days. After microsurgical removal of the mesenteric lymph nodes of the graft, 89 percent survived 120 days. We conclude that GVHR plays an important role in small bowel transplantation and that the experimental regimens of donor, graft, and recipient treatment described herein have proved their efficacy for circumventing GVHR

A computational study of the Diels Alder reactions involving acenes: reactivity and aromaticity

Science.gov (United States)

Cheng, Mei-Fun; Li, Wai-Kee

2003-01-01

Ab initio and DFT methods have been used to study the Diels-Alder reactivity and the aromaticity of four linear acenes, namely, naphthalene, anthracene, tetracene and pentacene. In total, eight additional pathways between ethylene and four acenes have been studied and all of them are concerted and exothermic reactions. It is found that the most reactive sites on the acenes are the center ring's meso-carbons. Also, reactivity decreases along the series pentacene > tetracene > anthracene > naphthalene. In addition, the NICS results indicate that the most reactive rings in the acenes are those with the highest aromaticity. These results are consistent with those of other theoretical studies and experiments.

Influence of Electrostatics on Small Molecule Flux through a Protein Nanoreactor.

Science.gov (United States)

Glasgow, Jeff E; Asensio, Michael A; Jakobson, Christopher M; Francis, Matthew B; Tullman-Ercek, Danielle

2015-09-18

Nature uses protein compartmentalization to great effect for control over enzymatic pathways, and the strategy has great promise for synthetic biology. In particular, encapsulation in nanometer-sized containers to create nanoreactors has the potential to elicit interesting, unexplored effects resulting from deviations from well-understood bulk processes. Self-assembled protein shells for encapsulation are especially desirable for their uniform structures and ease of perturbation through genetic mutation. Here, we use the MS2 capsid, a well-defined porous 27 nm protein shell, as an enzymatic nanoreactor to explore pore-structure effects on substrate and product flux during the catalyzed reaction. Our results suggest that the shell can influence the enzymatic reaction based on charge repulsion between small molecules and point mutations around the pore structure. These findings also lend support to the hypothesis that protein compartments modulate the transport of small molecules and thus influence metabolic reactions and catalysis in vitro.

Homogeneous-heterogeneous reactions in curved channel with porous medium

Science.gov (United States)

Hayat, T.; Ayub, Sadia; Alsaedi, A.

2018-06-01

Purpose of the present investigation is to examine the peristaltic flow through porous medium in a curved conduit. Problem is modeled for incompressible electrically conducting Ellis fluid. Influence of porous medium is tackled via modified Darcy's law. The considered model utilizes homogeneous-heterogeneous reactions with equal diffusivities for reactant and autocatalysis. Constitutive equations are formulated in the presence of viscous dissipation. Channel walls are compliant in nature. Governing equations are modeled and simplified under the assumptions of small Reynolds number and large wavelength. Graphical results for velocity, temperature, heat transfer coefficient and homogeneous-heterogeneous reaction parameters are examined for the emerging parameters entering into the problem. Results reveal an activation in both homogenous-heterogenous reaction effect and heat transfer rate with increasing curvature of the channel.

Development of Bioorthogonal Reactions and Their Applications in Bioconjugation

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Mengmeng Zheng

2015-02-01

Full Text Available Biomolecule labeling using chemical probes with specific biological activities has played important roles for the elucidation of complicated biological processes. Selective bioconjugation strategies are highly-demanded in the construction of various small-molecule probes to explore complex biological systems. Bioorthogonal reactions that undergo fast and selective ligation under bio-compatible conditions have found diverse applications in the development of new bioconjugation strategies. The development of new bioorthogonal reactions in the past decade has been summarized with comments on their potentials as bioconjugation method in the construction of various biological probes for investigating their target biomolecules. For the applications of bioorthogonal reactions in the site-selective biomolecule conjugation, examples have been presented on the bioconjugation of protein, glycan, nucleic acids and lipids.

TRIMOLECULAR REACTIONS OF URANIUM HEXAFLUORIDE WITH WATER

Energy Technology Data Exchange (ETDEWEB)

Westbrook, M.; Becnel, J.; Garrison, S.

2010-02-25

The hydrolysis reaction of uranium hexafluoride (UF{sub 6}) is a key step in the synthesis of uranium dioxide (UO{sub 2}) powder for nuclear fuels. Mechanisms for the hydrolysis reactions are studied here with density functional theory and the Stuttgart small-core scalar relativistic pseudopotential and associated basis set for uranium. The reaction of a single UF{sub 6} molecule with a water molecule in the gas phase has been previously predicted to proceed over a relatively sizeable barrier of 78.2 kJ {center_dot} mol{sup -1}, indicating this reaction is only feasible at elevated temperatures. Given the observed formation of a second morphology for the UO{sub 2} product coupled with the observations of rapid, spontaneous hydrolysis at ambient conditions, an alternate reaction pathway must exist. In the present work, two trimolecular hydrolysis mechanisms are studied with density functional theory: (1) the reaction between two UF{sub 6} molecules and one water molecule, and (2) the reaction of two water molecules with a single UF{sub 6} molecule. The predicted reaction of two UF{sub 6} molecules with one water molecule displays an interesting 'fluorine-shuttle' mechanism, a significant energy barrier of 69.0 kJ {center_dot} mol{sup -1} to the formation of UF{sub 5}OH, and an enthalpy of reaction ({Delta}H{sub 298}) of +17.9 kJ {center_dot} mol{sup -1}. The reaction of a single UF{sub 6} molecule with two water molecules displays a 'proton-shuttle' mechanism, and is more favorable, having a slightly lower computed energy barrier of 58.9 kJ {center_dot} mol{sup -1} and an exothermic enthalpy of reaction ({Delta}H{sub 298}) of -13.9 kJ {center_dot} mol{sup -1}. The exothermic nature of the overall UF{sub 6} + 2 {center_dot} H{sub 2}O trimolecular reaction and the lowering of the barrier height with respect to the bimolecular reaction are encouraging; however, the sizable energy barrier indicates further study of the UF{sub 6} hydrolysis reaction

PdZnAl Catalysts for the Reactions of Water-Gas-Shift, Methanol Steam Reforming, and Reverse-Water-Gas-Shift

Energy Technology Data Exchange (ETDEWEB)

Dagle, Robert A.; Platon, Alexandru; Datye, Abhaya K.; Vohs, John M.; Wang, Yong; Palo, Daniel R.

2008-03-07

Pd/ZnO/Al2O3 catalysts were studied for water-gas-shift (WGS), methanol steam reforming, and reverse-water-gas-shift (RWGS) reactions. WGS activity was found to be dependent on the Pd:Zn ratio with a maximum activity obtained at approximately 0.50, which was comparable to that of a commercial Pt-based catalyst. The catalyst stability was demonstrated for 100 hours time-on-stream at a temperature of 3600C without evidence of metal sintering. WGS reaction rates were approximately 1st order with respect to CO concentration, and kinetic parameters were determined to be Ea = 58.3 kJ mol-1 and k0 = 6.1x107 min-1. During methanol steam reforming, the CO selectivities were observed to be lower than the calculated equilibrium values over a range of temperatures and steam/carbon ratios studied while the reaction rate constants were approximately of the same magnitude for both WGS and methanol steam reforming. These results indicate that although Pd/ZnO/Al2O3 are active WGS catalysts, WGS is not involved in methanol steam reforming. RWGS rate constants are on the order of about 20 times lower than that of methanol steam reforming, suggesting that RWGS reaction could be one of the sources for small amount of CO formation in methanol steam reforming.

Complex formation reactions of uranyl(VI) with neutral N-donors in dimethyl sulfoxide. Influence of small amounts of water

International Nuclear Information System (INIS)

Cassol, A.; Di Bernardo, P.; Zanonato, P.; Portanova, R.; Tolazzi, M.

1990-01-01

Quantitative information about the existence and thermodynamic stability of uranyl(VI) ion complexes based solely upon nitrogen coordination has been obtained in the solvent dimethyl sulfoxide. Calorimetric, potentiometric, and FT-IR investigations, under controlled anhydrous conditions, show that the uranyl(VI) ion can form both mono and bis chelates with the ethylenediamine ligand and only a mono chelate of rather low stability with propylenediamine. With the monodentate ligand n-butylamine only a very weak metal-ligand interaction has been detected. The stability constants and the enthalpy and entropy changes have been calculated for the identified coordinated species. All data refer to 25.0 degree C and a tetraethylammonium perchlorate medium of ionic strength 0.1 M. All the complexes are enthalpy stabilized whereas the entropy contributions oppose the complex formation. Calorimetric and FT-IR measurements carried out to investigate the effects of small amounts of water present show that a very low water concentration, comparable to that of the coordinating metal ion, can give rise to hydrolysis reactions that may compete with complex formation. This is due to the combined action of different factors that are discussed. 39 refs., 6 figs., 1 tab

Inertial effects in diffusion-limited reactions

International Nuclear Information System (INIS)

Dorsaz, N; Foffi, G; De Michele, C; Piazza, F

2010-01-01

Diffusion-limited reactions are commonly found in biochemical processes such as enzyme catalysis, colloid and protein aggregation and binding between different macromolecules in cells. Usually, such reactions are modeled within the Smoluchowski framework by considering purely diffusive boundary problems. However, inertial effects are not always negligible in real biological or physical media on typical observation time frames. This is all the more so for non-bulk phenomena involving physical boundaries, that introduce additional time and space constraints. In this paper, we present and test a novel numerical scheme, based on event-driven Brownian dynamics, that allows us to explore a wide range of velocity relaxation times, from the purely diffusive case to the underdamped regime. We show that our algorithm perfectly reproduces the solution of the Fokker-Planck problem with absorbing boundary conditions in all the regimes considered and is thus a good tool for studying diffusion-guided reactions in complex biological environments.

Interlaboratory reaction rate program. 12th progress report, November 1976-October 1979

International Nuclear Information System (INIS)

Lippincott, E.P.; McElroy, W.N.; Preston, C.C.

1980-09-01

The Interlaboratory Reaction Rate UILRR) program is establishing the capability to accurately measure neutron-induced reactions and reaction rates for reactor fuels and materials development programs. The goal for the principal fission reactions, 235 U, 238 U and 239 Pu, is an accuracy to within +- 5% at the 95% confidence level. Accurate measurement of other fission and nonfission reactions is also required, but to a lesser accuracy, between +- 5% and 10% at the 95% confidence level. A secondary program objective is improvement in knowledge of the nuclear parameters involved in the standarization of fuels and materials dosimetry measurements of neutron flux, spectra, fluence and burnup

An immunoglobulin G-4 related sclerosing disease of the small bowel: CT and small bowel series findings

International Nuclear Information System (INIS)

Ko, Young Hwan; Hwang, Dae Hyun; Min, Seon Jeong; Woo, Ji Young; Kim, Jeong Won; Hong, Hye Sook; Yang, Ik; Lee, Yul

2013-01-01

Immunoglobulin G4 (IgG4)-related sclerosing disease is rare and is known to involve various organs. We present a case of histologically proven IgG4-related sclerosing disease of the small bowel with imaging findings on computed tomography (CT) and small bowel series. CT showed irregular wall thickening, loss of mural stratification and aneurysmal dilatation of the distal ileum. Small bowel series showed aneurysmal dilatations, interloop adhesion with traction and abrupt angulation.

The diagnosis of microorganism involved in infective endocarditis (IE by polymerase chain reaction (PCR and real-time PCR: A systematic review

Directory of Open Access Journals (Sweden)

Reza Faraji

2018-02-01

Full Text Available Broad-range bacterial rDNA polymerase chain reaction (PCR followed by sequencing may be identified as the etiology of infective endocarditis (IE from surgically removed valve tissue; therefore, we reviewed the value of molecular testing in identifying organisms' DNA in the studies conducted until 2016. We searched Google Scholar, Scopus, ScienceDirect, Cochrane, PubMed, and Medline electronic databases without any time limitations up to December 2016 for English studies reporting microorganisms involved in infective endocarditis microbiology using PCR and real-time PCR. Most studies were prospective. Eleven out of 12 studies used valve tissue samples and blood cultures while only 1 study used whole blood. Also, 10 studies used the molecular method of PCR while 2 studies used real-time PCR. Most studies used 16S rDNA gene as the target gene. The bacteria were identified as the most common microorganisms involved in infective endocarditis. Streptococcus spp. and Staphylococcus spp. were, by far, the most predominant bacteria detected. In all studies, PCR and real-time PCR identified more pathogens than blood and tissue cultures; moreover, the sensitivity and specificity of PCR and real-time PCR were more than cultures in most of the studies. The highest sensitivity and specificity were 96% and 100%, respectively. The gram positive bacteria were the most frequent cause of infective endocarditis. The molecular methods enjoy a greater sensitivity compared to the conventional blood culture methods; yet, they are applicable only to the valve tissue of the patients undergoing cardiac valve surgery.

The diagnosis of microorganism involved in infective endocarditis (IE) by polymerase chain reaction (PCR) and real-time PCR: A systematic review.

Science.gov (United States)

Faraji, Reza; Behjati-Ardakani, Mostafa; Moshtaghioun, Seyed Mohammad; Kalantar, Seyed Mehdi; Namayandeh, Seyedeh Mahdieh; Soltani, Mohammadhossien; Emami, Mahmood; Zandi, Hengameh; Firoozabadi, Ali Dehghani; Kazeminasab, Mahmood; Ahmadi, Nastaran; Sarebanhassanabadi, Mohammadtaghi

2018-02-01

Broad-range bacterial rDNA polymerase chain reaction (PCR) followed by sequencing may be identified as the etiology of infective endocarditis (IE) from surgically removed valve tissue; therefore, we reviewed the value of molecular testing in identifying organisms' DNA in the studies conducted until 2016. We searched Google Scholar, Scopus, ScienceDirect, Cochrane, PubMed, and Medline electronic databases without any time limitations up to December 2016 for English studies reporting microorganisms involved in infective endocarditis microbiology using PCR and real-time PCR. Most studies were prospective. Eleven out of 12 studies used valve tissue samples and blood cultures while only 1 study used whole blood. Also, 10 studies used the molecular method of PCR while 2 studies used real-time PCR. Most studies used 16S rDNA gene as the target gene. The bacteria were identified as the most common microorganisms involved in infective endocarditis. Streptococcus spp. and Staphylococcus spp. were, by far, the most predominant bacteria detected. In all studies, PCR and real-time PCR identified more pathogens than blood and tissue cultures; moreover, the sensitivity and specificity of PCR and real-time PCR were more than cultures in most of the studies. The highest sensitivity and specificity were 96% and 100%, respectively. The gram positive bacteria were the most frequent cause of infective endocarditis. The molecular methods enjoy a greater sensitivity compared to the conventional blood culture methods; yet, they are applicable only to the valve tissue of the patients undergoing cardiac valve surgery. Copyright © 2017. Published by Elsevier Taiwan.

Quantitative evaluation of the hazards involved in transferring foreign cells and tissues to immunologically suppressed or deficient subjects

Energy Technology Data Exchange (ETDEWEB)

Bekkum, D.W. van

1971-04-01

It has already been pointed out in a preceding chapter that a successful take of allogenic bone marrow in primates inevitably entails a most severe early or acute form of secondary disease caused by a violent immunological reaction of the immune competent cells of the graft directed against the host. In mice and rats such an acute graft versus host disease is not seen following grafting of allogenic bone marrow, but only if substantial numbers of spleen or lymph node cells are transferred. Apparently, primate bone marrow is exceptionally aggressive compared to rodent bone marrow and it is not possible to prevent this reaction by decreasing the number of infused bone marrow cells without simultaneously eliminating the restorative effect of the graft. There are many reasons for assuming that the property to elicit a graft versus host reaction resides exclusively in the lymphoid cell series. These cells are normally to be found not only in the bone marrow and the lymphatic organs but also in the peripheral blood and in other tissues. Since surprisingly small numbers of lymphoid cells have been shown to cause graft versus host disease in completely non-reactive recipients, a calculation of the risks involved in transfusing sizable amounts of fresh blood or leukocyte concentrates to human recipients appears to be opportune. Moreover, the current attempts to restore immunological function in agammaglobulinaemic patients by implantations of allogenic foetal thymus tissue and by infusion of foetal liver and bone marrow cell suspensions (Dooren et al., 1968; Hong et al., 1968) require a critical analysis of the risks involved. Finally, the rapidly advancing clinical transplantation of organs - all of which contain scattered lymphoid cells - seems to necessitate a re-evaluation of this potential hazard in the light of the present knowledge of the induction of graft versus host disease. Most of our factual information concerning graft versus host reactions comes from

Double Charge Exchange Reactions and Double Beta Decay

Science.gov (United States)

Auerbach, N.

2018-05-01

The subject of this presentation is at the forefront of nuclear physics, namely double beta decay. In particular one is most interested in the neutrinoless process of double beta decay, when the decay proceeds without the emission of two neutrinos. The observation of such decay would mean that the lepton conservation symmetry is violated and that the neutrinos are of Majorana type, meaning that they are their own anti-particles. The life time of this process has two unknowns, the mass of the neutrino and the nuclear matrix element. Determining the nuclear matrix element and knowing the cross-section well will set limits on the neutrino mass. There is a concentrated effort among the nuclear physics community to calculate this matrix element. Usually these matrix elements are a very small part of the total strength of the transition operators involved in the process. There is no simple way to “calibrate” the nuclear double beta decay matrix element. The double beta decay is a double charge exchange process, therefore it is proposed that double charge exchange reactions using ion projectiles on nuclei that are candidates for double beta decay, will provide additional necessary information about the nuclear matrix elements.

Diabatic models with transferrable parameters for generalized chemical reactions

International Nuclear Information System (INIS)

Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

2017-01-01

Diabatic models applied to adiabatic electron-transfer theory yield many equations involving just a few parameters that connect ground-state geometries and vibration frequencies to excited-state transition energies and vibration frequencies to the rate constants for electron-transfer reactions, utilizing properties of the conical-intersection seam linking the ground and excited states through the Pseudo Jahn-Teller effect. We review how such simplicity in basic understanding can also be obtained for general chemical reactions. The key feature that must be recognized is that electron-transfer (or hole transfer) processes typically involve one electron (hole) moving between two orbitals, whereas general reactions typically involve two electrons or even four electrons for processes in aromatic molecules. Each additional moving electron leads to new high-energy but interrelated conical-intersection seams that distort the shape of the critical lowest-energy seam. Recognizing this feature shows how conical-intersection descriptors can be transferred between systems, and how general chemical reactions can be compared using the same set of simple parameters. Mathematical relationships are presented depicting how different conical-intersection seams relate to each other, showing that complex problems can be reduced into an effective interaction between the ground-state and a critical excited state to provide the first semi-quantitative implementation of Shaik’s “twin state” concept. Applications are made (i) demonstrating why the chemistry of the first-row elements is qualitatively so different to that of the second and later rows, (ii) deducing the bond-length alternation in hypothetical cyclohexatriene from the observed UV spectroscopy of benzene, (iii) demonstrating that commonly used procedures for modelling surface hopping based on inclusion of only the first-derivative correction to the Born-Oppenheimer approximation are valid in no region of the chemical

Measurement of color transparency by C(p,2p) reactions at large momentum transfer

International Nuclear Information System (INIS)

Carroll, A.S.

1997-12-01

The subject of color transparency, the enhancement of the ability of hadrons to penetrate nuclear matter by kinematic selection, is both interesting and controversial. The description of the collision of hadrons with nucleons inside nuclei, and the connection with initial and final state interactions involve fundamental questions of quantum mechanics, and nuclear and particle physics. Interest in color transparency was greatly increased by AGS Experiment 834 which observed dramatic changes with incident momentum for a variety of nuclei. A new experiment, E850, has studied the (p,2p) quasi-elastic reaction near 90 degree cm for momenta between 5.9 and 9 GeV/c. The quasi-elastic reaction was compared to the elastic reaction on free protons to determine the transparency. With limited statistics, but with better kinematic definition in a new detector, the authors have confirmed the rise in Carbon transparency ratio seen in Expt 834. The Tr(D/H) for deuterium is consistent with no energy dependence. Unlike the free dσ/dt for hydrogen, the dσ/dt from protons in a nucleus is consistent with the exact s -10 scaling. This suggests two components to the pp scattering amplitude; one small and perturbative, the other spatially large and varying, but filtered away by the nuclear matter in the Carbon nucleus. The plan is to complete the repairs of the superconducting solenoid early this fall, reassemble the detector, and collect data starting next spring

Neuro-otological and peripheral nerve involvement in Fabry disease

Directory of Open Access Journals (Sweden)

Sergio Carmona

2017-07-01

Full Text Available Fabry disease (FD is an X-linked lysosomal storage disease, with multisystemic glycosphingolipids deposits. Neuro-otological involvement leading to hearing loss and vestibular dysfunctions has been described, but there is limited information about the frequency, site of lesion, or the relationship with peripheral neuropathy. The aim was to evaluate the presence of auditory and vestibular symptoms, and assess neurophysiological involvement of the VIII cranial nerve, correlating these findings with clinical and neurophysiological features of peripheral neuropathy. We studied 36 patients with FD with a complete neurological and neuro-otological evaluation including nerve conduction studies, quantitative sensory testing (to evaluate small fiber by warm and cold threshold detection and cold and heat pain, vestibular evoked myogenic potentials, videonistagmography, audiometry and brainstem auditory evoked potentials. Neuro-otologic symptoms included hearing loss (22.2%, vertigo (27.8% or both (25%. An involvement of either cochlear or vestibular function was identified in most patients (75%. In 70% of our patients the involvement of both cochlear and vestibular function could not be explained by a neural or vascular mechanism. Small fiber neuropathy was identified in 77.7%. There were no significant associations between neurootological and QST abnormalities. Neuro-otologic involvement is frequent and most likely under-recognized in patients with FD. It lacks a specific neural or vascular pattern, suggesting multi-systemic, end organ damage. Small fiber neuropathy is an earlier manifestation of FD, but there is no correlation between the development of neuropathy and neuro-otological abnormalities.

A Comparative Study of Simple Auditory Reaction Time in Blind (Congenitally) and Sighted Subjects

OpenAIRE

Gandhi, Pritesh Hariprasad; Gokhale, Pradnya A.; Mehta, H. B.; Shah, C. J.

2013-01-01

Background: Reaction time is the time interval between the application of a stimulus and the appearance of appropriate voluntary response by a subject. It involves stimulus processing, decision making, and response programming. Reaction time study has been popular due to their implication in sports physiology. Reaction time has been widely studied as its practical implications may be of great consequence e.g., a slower than normal reaction time while driving can have grave results. Objective:...

Chlorine dioxide reaction with selected amino acids in water

International Nuclear Information System (INIS)

Navalon, Sergio; Alvaro, Mercedes; Garcia, Hermenegildo

2009-01-01

Chlorine dioxide is a hypochlorite alternative disinfectant agent. In this context, we have determined the products formed in the reaction of ClO 2 with selected amino acids as model compounds that can be present in natural waters. The reaction of tryptophane, histidine and tyrosine (10 ppm each) with ClO 2 were studied at molar ratios ranging from 0.25 to 4 in the presence or absence of oxygen. It was found that in the absence of oxygen adding substoichiometric amounts of ClO 2 creates products that are structurally similar to the starting amino acids. Through a series of cascade reactions the initial product distribution gradually evolves toward simple, small carbon chain products that are far from the starting amino acid. The reaction product distribution revealed that chlorine dioxide can attack the electron-rich aromatic moieties as well as the nitrogen atom lone electron pair. Our study is relevant to gain knowledge on the reaction mechanism of ClO 2 with ubiquitous amino acids present in natural waters.

Study of nuclear reactions involving heavy nuclei and intermediate- and high-energy protons and an application in nuclear reactor physics (ADS)

International Nuclear Information System (INIS)

Matuoka, Paula Fernanda Toledo

2016-01-01

In the present work, intermediate- and high-energy nuclear reactions involving heavy nuclei and protons were studied with the Monte Carlo CRISP (Rio - Ilheus - Sao Paulo Collaboration) model. The most relevant nuclear processes studied were intranuclear cascade and fission-evaporation competition. Preliminary studies showed fair agreement between CRISP model calculation and experimental data of multiplicity of evaporated neutrons (E 20 MeV) were emitted mostly in the intranuclear cascade stage, while evaporation presented larger neutron multiplicity. Fission cross section of 209 mb and spallation cross section of 1788 mb were calculated { both in agreement with experimental data. The fission process resulted in a symmetric mass distribution. Another Monte Carlo code, MCNP, was used for radiation transport in order to understand the role of a spallation neutron source in a ADS (Accelerator Driven System) nuclear reactor. Initially, a PWR reactor was simulated to study the isotopic compositions in spent nuclear fuel. As a rst attempt, a spallation neutron source was adapted to an industrial size nuclear reactor. The results showed no evidence of incineration of transuranic elements and modifications were suggested. (author)

Manifesto on small airway involvement and management in asthma and chronic obstructive pulmonary disease: an Interasma (Global Asthma Association - GAA and World Allergy Organization (WAO document endorsed by Allergic Rhinitis and its Impact on Asthma (ARIA and Global Allergy and Asthma European Network (GA2LEN

Directory of Open Access Journals (Sweden)

F. Braido

2016-10-01

Full Text Available Abstract Evidence that enables us to identify, assess, and access the small airways in asthma and chronic obstructive pulmonary disease (COPD has led INTERASMA (Global Asthma Association and WAO to take a position on the role of the small airways in these diseases. Starting from an extensive literature review, both organizations developed, discussed, and approved the manifesto, which was subsequently approved and endorsed by the chairs of ARIA and GA2LEN. The manifesto describes the evidence gathered to date and defines and proposes issues on small airway involvement and management in asthma and COPD with the aim of challenging assumptions, fostering commitment, and bringing about change. The small airways (defined as those with an internal diameter <2 mm are involved in the pathogenesis of asthma and COPD and are the major determinant of airflow obstruction in these diseases. Various tests are available for the assessment of the small airways, and their results must be integrated to confirm a diagnosis of small airway dysfunction. In asthma and COPD, the small airways play a key role in attempts to achieve disease control and better outcomes. Small-particle inhaled formulations (defined as those that, owing to their size [usually <2 μm], ensure more extensive deposition in the lung periphery than large molecules have proved beneficial in patients with asthma and COPD, especially those in whom small airway involvement is predominant. Functional and biological tools capable of accurately assessing the lung periphery and more intensive use of currently available tools are necessary. In patients with suspected COPD or asthma, small airway involvement must be assessed using currently available tools. In patients with subotpimal disease control and/or functional or biological signs of disease activity, the role of small airway involvement should be assessed and treatment tailored. Therefore, the choice between large- and small-particle inhaled

48 CFR 7.107 - Additional requirements for acquisitions involving bundling.

Science.gov (United States)

2010-10-01

...; and (2) The acquisition strategy provides for maximum practicable participation by small business... the Government. However, because of the potential impact on small business participation, the head of... acquisition strategy involves substantial bundling, the acquisition strategy must additionally— (1) Identify...

Small mirror fusion reactors

International Nuclear Information System (INIS)

Carlson, G.A.; Schultz, K.R.; Smith, A.C. Jr.

1978-01-01

Basic requirements for the pilot plants are that they produce a net product and that they have a potential for commercial upgrade. We have investigated a small standard mirror fusion-fission hybrid, a two-component tandem mirror hybrid, and two versions of a field-reversed mirror fusion reactor--one a steady state, single cell reactor with a neutral beam-sustained plasma, the other a moving ring field-reversed mirror where the plasma passes through a reaction chamber with no energy addition

Low energy ion-molecule reactions

International Nuclear Information System (INIS)

Farrar, J.M.

1986-01-01

The authors work during the past year has focused on several problems in the condensation reactions of C + and CH 3 + with small molecules, particularly hydrocarbons. Their emphasis has been on understanding the dynamics of collision complex formation and isomerization of transient intermediates along the reaction coordinate. In many ionic reactions, intermediates having non-classical valence structures may be nearly as stable as their classical analogs, in contrast with neutral systems where the non-classical structures are much less stable. The C + + NH 3 system shows this behavior, indicating that the non-classical HCNH 2 + structure formed by insertion of C + into the N-H bond serves as a precursor to the products. N-H bond cleavage in this intermediate to form HCNH + occurs over a large barrier and occurs more readily than the 1,2 hydrogen atom shift to form the classical H 2 C = NH + intermediate. Their experimental kinetic energy distribution for this channel is consistent with the presence of a large exit channel barrier. Their recently published work on C + + H 2 O also demonstrates this phenomenon. The CHOH + hydroxycarbene cation serves as the initial intermediate and isomerization to the classical H 2 CO + cation is competitive with O-H or C-H cleavage to yield the formyl, HCO + , or isoformyl, COH + , cations. They have also completed studies on the reactions of C + with O 2 , CH 3 OH, HCN, and the two-carbon containing hydrocarbons ethane, ethylene, and acetylene

Method of operating a thermal engine powered by a chemical reaction

Science.gov (United States)

Ross, J.; Escher, C.

1988-06-07

The invention involves a novel method of increasing the efficiency of a thermal engine. Heat is generated by a non-linear chemical reaction of reactants, said heat being transferred to a thermal engine such as Rankine cycle power plant. The novel method includes externally perturbing one or more of the thermodynamic variables of said non-linear chemical reaction. 7 figs.

Reaction mechanisms in the radiolysis of peptides, polypeptides and proteins

International Nuclear Information System (INIS)

Garrison, W.M.

1985-01-01

The purpose of this review is to bring together and to correlate the wide variety of experimental studies that provide information on the reaction products and reaction mechanisms involved in the radiolysis of peptides, polypeptides and proteins (including chromosomal proteins) in both aqueous and solid-state systems. The comparative radiation chemistry of these systems is developed in terms of specific reactions of the peptide main-chain and the aliphatic, aromatic-unsaturated and sulfur-containing side-chains. Information obtained with the various experimental techniques of product analysis, competition kinetics, spin-trapping, pulse radiolysis and ESR spectroscopy is included. 147 refs

Reaction mechanisms in the radiolysis of peptides, polypeptides and proteins

Energy Technology Data Exchange (ETDEWEB)

Garrison, W.M.

1985-01-01

The purpose of this review is to bring together and to correlate the wide variety of experimental studies that provide information on the reaction products and reaction mechanisms involved in the radiolysis of peptides, polypeptides and proteins (including chromosomal proteins) in both aqueous and solid-state systems. The comparative radiation chemistry of these systems is developed in terms of specific reactions of the peptide main-chain and the aliphatic, aromatic-unsaturated and sulfur-containing side-chains. Information obtained with the various experimental techniques of product analysis, competition kinetics, spin-trapping, pulse radiolysis and ESR spectroscopy is included. 147 refs.

Equilibrium composition for the reaction of plutonium hydride with air

International Nuclear Information System (INIS)

Zou Lexi; Sun Ying; Xue Weidong; Zhu Zhenghe; Wang Rong; Luo Deli

2002-01-01

There are six independent constituents with 4 chemical elements, i.e. PuH 2.7 (s), PuN(s), Pu 2 O 3 (s), N 2 , O 2 and H 2 , therefore, the system described involves of 2 independent reactions, both ΔG 0 <<0. The calculated equilibrium compositions are in agreement with those of the experimental, which indicates that the chemical equilibrium is nearly completely approached. Therefore, it is believed that the reaction rate of plutonium hydride with air is extremely rapid. The author has briefly discussed the simultaneous reactions and its thermodynamic coupling effect

Dynamical barrier and isotope effects in the simplest substitution reaction via Walden inversion mechanism

Science.gov (United States)

Zhao, Zhiqiang; Zhang, Zhaojun; Liu, Shu; Zhang, Dong H.

2017-02-01

Reactions occurring at a carbon atom through the Walden inversion mechanism are one of the most important and useful classes of reactions in chemistry. Here we report an accurate theoretical study of the simplest reaction of that type: the H+CH4 substitution reaction and its isotope analogues. It is found that the reaction threshold versus collision energy is considerably higher than the barrier height. The reaction exhibits a strong normal secondary isotope effect on the cross-sections measured above the reaction threshold, and a small but reverse secondary kinetic isotope effect at room temperature. Detailed analysis reveals that the reaction proceeds along a path with a higher barrier height instead of the minimum-energy path because the umbrella angle of the non-reacting methyl group cannot change synchronously with the other reaction coordinates during the reaction due to insufficient energy transfer from the translational motion to the umbrella mode.

Measurement of reaction heats using a polysilicon-based microcalorimetric sensor

NARCIS (Netherlands)

Vereshchagina, E.; Wolters, Robertus A.M.; Gardeniers, Johannes G.E.

2011-01-01

In this work we present a low-cost, low-power, small sample volume microcalorimetric sensor for the measurement of reaction heats. The polysilicon-based microcalorimetric sensor combines several advantages: (i) complementary metal oxide semiconductor technology (CMOS) for future integration; (ii)

Electrophysiological evidence of cerebellar fiber system involvement in the Miller Fisher syndrome.

Science.gov (United States)

Lo, Y L; Fook-Chong, S; Chan, L L; Ong, W Y; Ratnagopal, P

2010-01-15

In the Miller Fisher syndrome (MFS), ataxia may be due involvement of Ia afferents and the cerebellum. Transcranial magnetic stimulation (TMS) over the cerebellum is known to interfere transiently with normal function. In this study, we utilized a previously described TMS protocol over the cerebellum in combination with ballistic movements to investigate cerebellar dysfunction in MFS patients. The agonist (biceps) reaction time in MFS patients during a motor cancellation task was not significantly reduced during the initial TMS study. However, during the repeat TMS study, significant reduction was seen for all patients, in tandem with clinical recovery. There was significant correlation between anti-GQ1b IgG titers and change in agonist reaction time between the initial and repeat TMS studies. TMS likely affected horizontally orientated parallel fibers in the cerebellar molecular layer. During disease onset, antibody binding may have interfered with facilitation of reaction time during motor cancellation tasks seen in normal subjects. Normalization of reaction time facilitation corresponded to resolution of antibody-mediated interference in the molecular layer. Our study has provided evidence suggesting parallel fiber involvement in MFS, and suggested a role of anti-GQ1b IgG antibody in these changes.

Antibiotic discovery throughout the Small World Initiative: A molecular strategy to identify biosynthetic gene clusters involved in antagonistic activity.

Science.gov (United States)

Davis, Elizabeth; Sloan, Tyler; Aurelius, Krista; Barbour, Angela; Bodey, Elijah; Clark, Brigette; Dennis, Celeste; Drown, Rachel; Fleming, Megan; Humbert, Allison; Glasgo, Elizabeth; Kerns, Trent; Lingro, Kelly; McMillin, MacKenzie; Meyer, Aaron; Pope, Breanna; Stalevicz, April; Steffen, Brittney; Steindl, Austin; Williams, Carolyn; Wimberley, Carmen; Zenas, Robert; Butela, Kristen; Wildschutte, Hans

2017-06-01

The emergence of bacterial pathogens resistant to all known antibiotics is a global health crisis. Adding to this problem is that major pharmaceutical companies have shifted away from antibiotic discovery due to low profitability. As a result, the pipeline of new antibiotics is essentially dry and many bacteria now resist the effects of most commonly used drugs. To address this global health concern, citizen science through the Small World Initiative (SWI) was formed in 2012. As part of SWI, students isolate bacteria from their local environments, characterize the strains, and assay for antibiotic production. During the 2015 fall semester at Bowling Green State University, students isolated 77 soil-derived bacteria and genetically characterized strains using the 16S rRNA gene, identified strains exhibiting antagonistic activity, and performed an expanded SWI workflow using transposon mutagenesis to identify a biosynthetic gene cluster involved in toxigenic compound production. We identified one mutant with loss of antagonistic activity and through subsequent whole-genome sequencing and linker-mediated PCR identified a 24.9 kb biosynthetic gene locus likely involved in inhibitory activity in that mutant. Further assessment against human pathogens demonstrated the inhibition of Bacillus cereus, Listeria monocytogenes, and methicillin-resistant Staphylococcus aureus in the presence of this compound, thus supporting our molecular strategy as an effective research pipeline for SWI antibiotic discovery and genetic characterization. © 2017 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Nuclear targets, recoil ion catchers and reaction chambers

NARCIS (Netherlands)

Dionisio, JS; Vieu, C; Schuck, C; Collatz, R; Meunier, R; Ledu, D; Folger, H; Lafoux, A; Lagrange, JM; Pautrat, M; Waast, B; Phillips, WR; Blunt, D; Durell, JL; Varley, BJ; Dagnall, PG; Dorning, SJ; JONES, MA; Smith, AG; Bacelar, JCS; Rzaca-Urban, T; Amzal, N; Meliani, Z; Vanhorenbeeck, J; Passoja, A; Urban, W

1998-01-01

The main features of nuclear targets, recoil ion catchers and reaction chambers used in nuclear spectroscopic investigations involving in-beam multi-e-gamma spectrometers are discussed. The relative importance of the F-ray background due to the accelerated ion-target and the recoil-ion-target

Modeling Physical Processes at the Nanoscale—Insight into Self-Organization of Small Systems (abstract)

Science.gov (United States)

Proykova, Ana

2009-04-01

Essential contributions have been made in the field of finite-size systems of ingredients interacting with potentials of various ranges. Theoretical simulations have revealed peculiar size effects on stability, ground state structure, phases, and phase transformation of systems confined in space and time. Models developed in the field of pure physics (atomic and molecular clusters) have been extended and successfully transferred to finite-size systems that seem very different—small-scale financial markets, autoimmune reactions, and social group reactions to advertisements. The models show that small-scale markets diverge unexpectedly fast as a result of small fluctuations; autoimmune reactions are sequences of two discontinuous phase transitions; and social groups possess critical behavior (social percolation) under the influence of an external field (advertisement). Some predicted size-dependent properties have been experimentally observed. These findings lead to the hypothesis that restrictions on an object's size determine the object's total internal (configuration) and external (environmental) interactions. Since phases are emergent phenomena produced by self-organization of a large number of particles, the occurrence of a phase in a system containing a small number of ingredients is remarkable.

Persistent Skin Reactions and Aluminium Hypersensitivity Induced by Childhood Vaccines.

Science.gov (United States)

Salik, Elaha; Løvik, Ida; Andersen, Klaus E; Bygum, Anette

2016-11-02

There is increasing awareness of reactions to vaccination that include persistent skin reactions. We present here a retrospective investigation of long-lasting skin reactions and aluminium hypersensitivity in children, based on medical records and questionnaires sent to the parents. In the 10-year period 2003 to 2013 we identified 47 children with persistent skin reactions caused by childhood vaccinations. Most patients had a typical presentation of persisting pruritic subcutaneous nodules. Five children had a complex diagnostic process involving paediatricians, orthopaedics and plastic surgeons. Two patients had skin biopsies performed from their skin lesions, and 2 patients had the nodules surgically removed. Forty-two children had a patch-test performed with 2% aluminium chloride hexahydrate in petrolatum and 39 of them (92%) had a positive reaction. The persistent skin reactions were treated with potent topical corticosteroids and disappeared slowly. Although we advised families to continue vaccination of their children, one-third of parents omitted or postponed further vaccinations.

Neutrino magnetic moment contribution to the neutrino-deuteron reaction

International Nuclear Information System (INIS)

Tsuji, K.; Nakamura, S.; Sato, T.; Kubodera, K.; Myhrer, F.

2004-01-01

We study the effect of the neutrino magnetic moment on the neutrino-deuteron breakup reaction, using a method called the standard nuclear physics approach, which has already been well tested for several electroweak processes involving the deuteron