11,194 research outputs found
CL-FEP: An End-State Free Energy Perturbation Approach
No full textThe Central Limit
Free Energy Perturbation (CL-FEP) approach, based on the Free Energy
Perturbation (FEP) theory and the Central Limit (CL) theorem, allows
evaluating the FEP identity directly from the energy samples of the
end states of a system transformation. In CL-FEP, energies obtained
from explicit solvent simulations are used to estimate the absolute
free energy change. No fitted parameters are introduced in our implementation,
and no stratification is needed to obtain accurate free energy evaluations.
We first illustrate the applicability of CL-FEP in four dissimilar
benchmark systems from host–guest to proteins–peptide
complexes, for which the deviation from the experimental values was
below 1 kcal/mol. Next, we extended the validation to three sets of
complexes comprising 25 host–guest and protein–ligand
systems. There, the mean absolute error of the free energy changes
calculated with CL-FEP is between 1.1 and 1.4 kcal/mol among the different
sets, which is in the range of accuracy of the most reliable free
energy approaches applied to these systems. CL-FEP is an unbiased
free energy change estimator that also profits from a bootstrapping
algorithm, which makes the evaluation of convergence and confidence
an inherent component of the procedure. Finally, we developed CLFEP.pl,
an automatic tool to compute free energy changes directly from the
energy output of standard molecular dynamics simulations
CL-FEP: An End-State Free Energy Perturbation Approach
No full textThe Central Limit
Free Energy Perturbation (CL-FEP) approach, based on the Free Energy
Perturbation (FEP) theory and the Central Limit (CL) theorem, allows
evaluating the FEP identity directly from the energy samples of the
end states of a system transformation. In CL-FEP, energies obtained
from explicit solvent simulations are used to estimate the absolute
free energy change. No fitted parameters are introduced in our implementation,
and no stratification is needed to obtain accurate free energy evaluations.
We first illustrate the applicability of CL-FEP in four dissimilar
benchmark systems from host–guest to proteins–peptide
complexes, for which the deviation from the experimental values was
below 1 kcal/mol. Next, we extended the validation to three sets of
complexes comprising 25 host–guest and protein–ligand
systems. There, the mean absolute error of the free energy changes
calculated with CL-FEP is between 1.1 and 1.4 kcal/mol among the different
sets, which is in the range of accuracy of the most reliable free
energy approaches applied to these systems. CL-FEP is an unbiased
free energy change estimator that also profits from a bootstrapping
algorithm, which makes the evaluation of convergence and confidence
an inherent component of the procedure. Finally, we developed CLFEP.pl,
an automatic tool to compute free energy changes directly from the
energy output of standard molecular dynamics simulations
Effects of aminoperimidine on electrolyte transport across amphibian skin
No full textThe effect of aminoperimidine (AP)on transepithelial Na+ transport and Cl- conductance (G(Cl)) of isolated amphibian skin (Bufo viridis and Rana esculenta) was analyzed using transepithelial and intracellular electrophysiological techniques. AP, applied at concentrations between 30 and 100 mu M from the mucosal side, stimulated Na+ transport rapidly and reversibly by more than 30% of the control value due to an increase in apical membrane Na+ permeability. Influence of AP on basolateral membrane conductance and effective driving force for Na+ were negligible. Voltage-activated G(Cl) of toad skin, but not the resting, deactivated conductance, as well as spontaneously high G(Cl) in frog skin was rapidly inhibited by AP in a concentration-dependent manner. The half-maximal inhibitory concentration of 20 mu M is the highest hithero reported inhibitory power for G(Cl) in amphibian skin. The effect of AP on G(Cl) was slowly and incompletely reversible even after brief exposure to the agent. Serosal application of AP had similar, albeit delayed effects on both Nai and Cl- transport. AP did not interfere with the Cl- pathway after it was opened by 100-300 mu M CPT-cAMP, a membrane-permeable, nonhydrolyzed analogue of cAMP. Inhibition of the voltage-activated G(Cl) by AP was attenuated or missing when AP was applied during voltage perturbation to serosa-positive potentials. Since AP is positively charged at physiological pH, it suggests that the affected site is located inside the Cl- pathway at a certain distance from the external surface. AP affects then the Na+ and Cl- transport pathways independent of each other. The nature of chemical interference with AP, which is responsible for the influence on the transport of Na+ and Cl-, remains to be elucidated
Open access self-archiving: An author study
No full textThis, our second author international, cross-disciplinary study on open access had 1296 respondents. Its focus was on self-archiving. Almost half (49%) of the respondent population have self-archived at least one article during the last three years. Use of institutional repositories for this purpose has doubled and usage has increased by almost 60% for subject-based repositories. Self-archiving activity is greatest amongst those who publish the largest number of papers. There is still a substantial proportion of authors unaware of the possibility of providing open access to their work by self-archiving. Of the authors who have not yet self-archived any articles, 71% remain unaware of the option. With 49% of the author population having self-archived in some way, this means that 36% of the total author population (71% of the remaining 51%), has not yet been appraised of this way of providing open access. Authors have frequently expressed reluctance to self-archive because of the perceived time required and possible technical difficulties in carrying out this activity, yet findings here show that only 20% of authors found some degree of difficulty with the first act of depositing an article in a repository, and that this dropped to 9% for subsequent deposits. Another author worry is about infringing agreed copyright agreements with publishers, yet only 10% of authors currently know of the SHERPA/RoMEO list of publisher permissions policies with respect to self-archiving, where clear guidance as to what a publisher permits is provided. Where it is not known if permission is required, however, authors are not seeking it and are self-archiving without it. Communicating their results to peers remains the primary reason for scholars publishing their work; in other words,
researchers publish to have an impact on their field. The vast majority of authors (81%) would willingly comply with a mandate from their employer or research funder to deposit copies of their articles in an institutional or subject-based repository. A further 13% would comply reluctantly; 5% would not comply with such a mandate
Progress of international hydrogen production network for the thermochemical Cu–Cl cycle
No full textThis paper presents recent advances by an international team which is developing the thermochemical copper–chlorine (Cu–Cl) cycle for hydrogen production. Development of the Cu–Cl cycle has been pursued by several countries within the framework of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Due to its lower temperature requirements in comparison with other thermochemical cycles, the Cu–Cl cycle is particularly well matched with Canada's Generation IV reactor, SCWR (Super-Critical Water Reactor), as well as other heat sources such as solar energy or industrial waste heat. In this paper, recent developments of the Cu–Cl cycle are presented, specifically involving unit operation experiments, corrosion resistant materials and system integration.Atomic Energy of Canada LimitedOntario Research Excellence FundNatural Sciences and Engineering Research Council of CanadaUniversity Network of Excellence in Nuclear Engineering (UNENE)Canada Research Chairs progra
ŻYCIE UKRYTE W SŁOWIE. "BEKSIŃSCY. PORTRET PODWÓJNY" MAGDALENY GRZEBIAŁKOWSKIEJ W ŚWIETLE POSTSTRUKTURALIZMU
No full textLife Hidden in Words. Magdalena Grzebiałkowska\u27s "Beksińscy. Portret podwójny" and Poststructuralism
The article analyzes Magdalena Grzebiałkowska\u27s biographical "Beksińscy. Portret podwójny" which focuses on the lives of Zdzisław Beksiński and Tomasz Beksiński. The author looks at the construction of the biography and its relationship to poststructuralism, which allows for an appreciation of the literary features of the book. He points to how the specificity of the content, language, a mode of narration in Grzebiałkowska\u27s book make it a full-fledged literary work itself. As such the book departs from a typical biographical scheme. Juxtaposing the book with poststructural ideas leads to the reconsideration of the role of the author in the process of shaping of a biographical narrative
Systems, methods and devices for the capture and hydrogenation of carbon dioxide with thermochemical Cu—Cl and Mg—Cl—Na/K—CO2 cycles
No full textSystems, methods, and devices for producing hydrogen and capturing CO2 from emissions combine both H2 production and CO2 capture processes in forms of thermochemical cycles to produce useful products from captured CO2. The thermochemical cycles are copper-chlorine (Cu—Cl) and magnesium-chlorine-sodium/potassium cycles (Mg—Cl—Na/K—CO2). One system comprises a Cu—Cl cycle, a CO2 capture loop, and a hydrogenation cycle. Another system comprises an Mg—Cl—Na/K—CO2 cycle and a hydrogenation cycle. Devices for hydrogen production, CO2 capture, hydrogenation, and process and equipment integration include a two-stage fluidized/packed bed, hybrid two-stage spray-fluidized/packed bed reactor, a two-stage wet-mode absorber, a hybrid two-stage absorber, and a catalyst packed/fluidized bed reactor
Clean hydrogen production with the Cu–Cl cycle – Progress of international consortium, I: Experimental unit operations
No full textAdvancement of the thermochemical copper–chlorine (Cu–Cl) cycle for hydrogen production is reviewed and discussed in this paper. Individual unit operations and their linkage into an integrated cycle are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. This paper focuses on the consortium’s latest advances on the Cu–Cl cycle, particularly with respect to hydrogen production with Canada’s Generation IV reactor, called SCWR (Super-Critical Water Reactor). Other heat sources may also be utilized for the Cu–Cl cycle, such as solar energy or industrial waste heat. In this first of two companion papers, recent developments in Canada’s nuclear hydrogen program are reported, specifically unit operation experiments of the Cu–Cl cycle and system integration. The following second companion paper will present system modeling with Aspen Plus, corrosion resistant materials, thermochemistry, safety, and reliability aspects of the Cu–Cl cycle.Atomic Energy of Canada LimitedOntario Research Excellence FundNatural Sciences and Engineering Research Council of CanadaUniversity Network of Excellence in Nuclear Engineering (UNENE)Canada Research Chairs progra
Canada’s program on nuclear hydrogen production and the thermochemical Cu–Cl cycle
No full textThis paper presents an overview of the status of Canada’s program on nuclear hydrogen production and the thermochemical copper–chlorine (Cu–Cl) cycle. Enabling technologies for the Cu–Cl cycle are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Particular emphasis in this paper is given to hydrogen production with Canada’s Super-Critical Water Reactor, SCWR. Recent advances towards an integrated lab-scale Cu–Cl cycle are discussed, including experimentation, modeling, simulation, advanced materials, thermochemistry, safety, reliability and economics. In addition, electrolysis during off-peak hours, and the processes of integrating hydrogen plants with Canada’s nuclear plants are presented.Atomic Energy of Canada LimitedOntario Research Excellence FundArgonne National Laboratory (International Nuclear Energy Research Initiative; U.S. Department of Energy)Natural Sciences and Engineering Research Council of Canada (NSERC)University Network of Excellence in Nuclear Engineering (UNENE)Canada Research Chairs (CRC
K-shell Photoionization of Atomic Cl
No full textRecent measurements of the photoionization of atomic Cl in the vicinity of the 1s thresholds have motivated the present R-matrix calculation which takes into account relativistic effects via the Breit-Pauli operator. The computer code CIV3 of Hibbert and Glass and Hibbert, which also includes relativistic effects, is used to obtain the discrete wavefunctions. These are constructed with orbitals generated from a carefully-chosen large scale configuration interaction expansion. The open-shell nature of the Cl atom translates into the existence of actually four 1s thresholds, 3Po 0,1,2 and 1P 1. The results are analyzed with particular focus on the resonances leading up to the four thresholds, and the various effects that dominate the cross sections in this energy range are unraveled
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