985 research outputs found
Modelling the Impact of Credit on Intensification in Mixed Crop-Livestock Systems: A Case Study from Ethiopia
Access to credit is one strategy for promoting the adoption of yield-enhancing technologies. However, advancing credit to smallholder farmers for encouraging technology adoption is a complex policy issue. The objective of this paper is to identify appropriate and sustainable credit repayment policies to encourage intensification in the Ethiopian Highlands. Using a household model, we analyze the impact of advancing in-kind credit in the form of fertilizer and seed to smallholder farmers in the Ethiopian highlands and alternative credit repayment strategies. The results indicate that in kind input credit of fertilizer and seed provided to farmers in the highland of Ethiopia increased the value of household crop output moderately and hence allowed the household to increase its consumption. This scheme requires borrowers to sell their crop immediately at harvest to repay their credit. An alternative repayment scheme of extending the repayment period to allow households to capture seasonal price variation is proposed. The amount repaid is also tied to yields of wheat.Agricultural Finance,
Correlations in the three-dimensional Lyman-alpha forest contaminated by high column density absorbers
Correlations measured in three dimensions in the Lyman-alpha forest are
contaminated by the presence of the damping wings of high column density (HCD)
absorbing systems of neutral hydrogen (HI; having column densities
), which
extend significantly beyond the redshift-space location of the absorber. We
measure this effect as a function of the column density of the HCD absorbers
and redshift by measuring 3D flux power spectra in cosmological hydrodynamical
simulations from the Illustris project. Survey pipelines exclude regions
containing the largest damping wings. We find that, even after this procedure,
there is a scale-dependent correction to the 3D Lyman-alpha forest flux power
spectrum from residual contamination. We model this residual using a simple
physical model of the HCD absorbers as linearly biased tracers of the matter
density distribution, convolved with their Voigt profiles and integrated over
the column density distribution function. We recommend the use of this model
over existing models used in data analysis, which approximate the damping wings
as top-hats and so miss shape information in the extended wings. The simple
'linear Voigt model' is statistically consistent with our simulation results
for a mock residual contamination up to small scales (). It does not account for the effect of the highest
column density absorbers on the smallest scales (e.g., for small damped Lyman-alpha absorbers; HCD
absorbers with ). However, these systems are in any
case preferentially removed from survey data. Our model is appropriate for an
accurate analysis of the baryon acoustic oscillations feature. It is
additionally essential for reconstructing the full shape of the 3D flux power
spectrum.Comment: 13 pages, 11 figures. Minor changes to match version published in
MNRA
An Emulator for the Lyman-alpha Forest
We present methods for interpolating between the 1-D flux power spectrum of
the Lyman- forest, as output by cosmological hydrodynamic simulations.
Interpolation is necessary for cosmological parameter estimation due to the
limited number of simulations possible. We construct an emulator for the
Lyman- forest flux power spectrum from small simulations using
Latin hypercube sampling and Gaussian process interpolation. We show that this
emulator has a typical accuracy of 1.5% and a worst-case accuracy of 4%, which
compares well to the current statistical error of 3 - 5% at from BOSS
DR9. We compare to the previous state of the art, quadratic polynomial
interpolation. The Latin hypercube samples the entire volume of parameter
space, while quadratic polynomial emulation samples only lower-dimensional
subspaces. The Gaussian process provides an estimate of the emulation error and
we show using test simulations that this estimate is reasonable. We construct a
likelihood function and use it to show that the posterior constraints generated
using the emulator are unbiased. We show that our Gaussian process emulator has
lower emulation error than quadratic polynomial interpolation and thus produces
tighter posterior confidence intervals, which will be essential for future
Lyman- surveys such as DESI.Comment: 28 pages, 10 figures, accepted to JCAP with minor change
Simulating the effect of high column density absorbers on the one-dimensional Lyman-alpha forest flux power spectrum
We measure the effect of high column density absorbing systems of neutral
hydrogen (HI) on the one-dimensional (1D) Lyman-alpha forest flux power
spectrum using cosmological hydrodynamical simulations from the Illustris
project. High column density absorbers (which we define to be those with HI
column densities ) cause broadened absorption lines
with characteristic damping wings. These damping wings bias the 1D Lyman-alpha
forest flux power spectrum by causing absorption in quasar spectra away from
the location of the absorber itself. We investigate the effect of high column
density absorbers on the Lyman-alpha forest using hydrodynamical simulations
for the first time. We provide templates as a function of column density and
redshift, allowing the flexibility to accurately model residual contamination,
i.e., if an analysis selectively clips out the largest damping wings. This
flexibility will improve cosmological parameter estimation, e.g., allowing more
accurate measurement of the shape of the power spectrum, with implications for
cosmological models containing massive neutrinos or a running of the spectral
index. We provide fitting functions to reproduce these results so that they can
be incorporated straightforwardly into a data analysis pipeline.Comment: 11 pages, 6 figures. Minor changes to match version published in
MNRA
Inhibition of Cholinesterases by the Oximes P2AM and Toxogonin
The reversible inhibition of electric eel acetylcholinesterase
(EC 3.1.1.7) by P2AM (2-(hydroxyimino)methyl-1-methyl-pyridinium
chloride) and Toxogonin (1,1\u27-[oxybis(methylene)] bis(4-(hydroxyimino)
methyl-pyridinium) dichloride) was studied using ac.etylthiocholine
as substrate. Two techniques were applied for
measuring acetylthiocholine hydrolysis, the conventional spectrophotometric
and the stopped-flow (at 25 Ā°c in 100 mM phosphate
buffer pH = 7.4).
The correlation between the degree of inhibition, and acetylthiocholine
and oxime concentrations fits a theoretical model which
postulates that the substrate and the inhibitor bind to two sites on
the enzyme: the catalytic site and an allosteric, substrate-inhibition,
site. The calculated dissociation constants for the two sites
are: 0.13 and 0.76 mM for P2AM, and 0.16 and 2.0 mM for Toxogonin.
The suggested model is an alternative to the hypothesis that
two types of binding occur within the catalytic site.
Horse serum cholinesterase and bovine erythrocyte acetylcholinesterase
are also inhibited by P2AM and Toxogonin to about
the same degree as the electric eel enzyme.
Acetylthiocholine reacts with P2AM and Toxogonin; assuming
that the reaction is bimolecular the corresponding rate constants
are 13.4 and 22.4 M-1 min-
Measurements of serum cholinesterase activity: comparison of commercially available assay kits and laboratory prepared reagents, enzyme quality control standards and the imprecision of the method
UsporeÄene su komercijalne garniture test-reagencija (Test-Combination, Cholinesterase, Boehringer, Mannheim i Test-reagencije, Kolinesteraza EC 3.1.1.8. Pliva, Zagreb) i vlastiti pripravci test-reagencija za mjerenje aktivnosti serumske kolinesteraze (Ellmanova metoda) s obzirom na ponovljivost mjerenja i meÄusobnu zamjenjivost te s obzirom na stabilnost. Pokazalo se da su te garniture meÄusobno zamjenjive i da su reagencije stabilne nekoliko tjedana. Stabilnost nekih enzimskih standarda (Precinorm E, Precinorm U, NSS-serum i nativni ljudski serum) za kontrolu kvalitete mjerenja takoÄer je praÄena; najstabilnija je aktivnost nativnog ljudskog seruma. Iz izmjerenih aktivnosti izraÄunata je nepreciznost mjerenja tom metodom: koeficijent varijacije unutar mjerenja je 2 ā 3% a izmeÄu mjerenja do 6%.The commercially available kits (Test-Combination, Cholinesterase, Boehringer, Mannheim and Test-reagent, Cholinesterase EC 3.1.1.8, Pliva, Zagreb) and reagents prepared in own laboratory for measuring cholinesterase activity (Ellman method) were tested with respect to their stability and the reproducibility of the activity measurements. The reagents of the three sources were shown to be interchangeable and equally stable over a few weeks. The coefficient of variation for within-run measurements by the Ellman method was 2 - 3% and that for between-run measurements 6%. The stability of the few enzyme standards (Precinorm E, Precinorm U, NBS-serum and native human serum) for the quality control of the measurements was also tested: the most stable was native human seru
The Equations of State of Real Gases
Prikazana su svojstva realnih plinova, a posebice njihova odstupanja od idealnosti. Dan je i kratak prikaz molekulskih meÄudjelovanja. Opisan je tradicijski model prikladan za jednoatomne plinove Äije se molekule ponaÅ”aju kao klasiÄne Äestice. Prikazan je virijalni pouÄak, a od iskustvenih virijalnih jednadžbi stanja dan je Kamerlingh-Onnesov virijalni razvoj. Najpoznatija iskustvena jednadžba stanja - van der Waalsova - izvedena je s pomoÄu kanonske particijske funkcije. PredoÄene su i neke od važnijih jednadžbi stanja koje se rabe u tehniÄkoj termodinamici: Redlich-Kwongova, Peng-Robinsonova i Benedict-Webb-Rubinova jednadžba stanja. U pregledu statistiÄkih modela izložen je rojni model, u kojemu se sva odstupanja od idealnosti opisuju konfiguracijskim integralom i navedena su njegova ograniÄenja, a prikazan je i Kirkwoodov model integralnih jednadžbi koji - za razliku od Mayerova rojnog modela - ne polazi od jednadžbe stanja idealnog plina, veÄ gradi hijerarhiju raspodjelnih funkcija za mnoÅ”tvo molekula. Dan je i kratak pregled metodĆ¢ za numeriÄku simulaciju (Monte Carlo i molekulska dinamika).During the development of intelligent systems inspired by biological neural system, in the last two decades the researchers from various scientific fields have created neural networks for solving a series of problems from pattern recognition, prediction, diagnostic, software sensor, modelling and identification, control and optimization. In this paper a review of neural network application in the field of chemical engineering with emphasis on identification and process control is given.
The neural networks have been proven usefull in the applications which include complex chemical and biochemical reactions. In such a processes use of standard methods of process modelling and control structure are frequently not suitable. The ability of neural network to model dynamics of nonlinear process makes them an important tool for implementation in model-based control. Due to intensively theory development and many practical applications, there are numerous neural network structures and algorithms.
In this paper neural networks are categorized under three major control schemes: model-base predictive control, inverse model-based control, and adaptive control. The major applications are summarized. It reveals prospect of using neural networks in process identification and control.
The future of neural network application lies not only in their explicite use, but in cross connecting to other advanted technnologies as well. Fusion of neural networks and fuzzy logic in the form of neural-fuzzy network is one of the possibilites. Other important field is hibrid modelling and identification methods which supplement simplified mechanistic models. Software sensors and their application, especially in controlling of bioprocesses, present a very promising field
The Equations of State of Real Gases
Prikazana su svojstva realnih plinova, a posebice njihova odstupanja od idealnosti. Dan je i kratak prikaz molekulskih meÄudjelovanja. Opisan je tradicijski model prikladan za jednoatomne plinove Äije se molekule ponaÅ”aju kao klasiÄne Äestice. Prikazan je virijalni pouÄak, a od iskustvenih virijalnih jednadžbi stanja dan je Kamerlingh-Onnesov virijalni razvoj. Najpoznatija iskustvena jednadžba stanja - van der Waalsova - izvedena je s pomoÄu kanonske particijske funkcije. PredoÄene su i neke od važnijih jednadžbi stanja koje se rabe u tehniÄkoj termodinamici: Redlich-Kwongova, Peng-Robinsonova i Benedict-Webb-Rubinova jednadžba stanja. U pregledu statistiÄkih modela izložen je rojni model, u kojemu se sva odstupanja od idealnosti opisuju konfiguracijskim integralom i navedena su njegova ograniÄenja, a prikazan je i Kirkwoodov model integralnih jednadžbi koji - za razliku od Mayerova rojnog modela - ne polazi od jednadžbe stanja idealnog plina, veÄ gradi hijerarhiju raspodjelnih funkcija za mnoÅ”tvo molekula. Dan je i kratak pregled metodĆ¢ za numeriÄku simulaciju (Monte Carlo i molekulska dinamika).During the development of intelligent systems inspired by biological neural system, in the last two decades the researchers from various scientific fields have created neural networks for solving a series of problems from pattern recognition, prediction, diagnostic, software sensor, modelling and identification, control and optimization. In this paper a review of neural network application in the field of chemical engineering with emphasis on identification and process control is given.
The neural networks have been proven usefull in the applications which include complex chemical and biochemical reactions. In such a processes use of standard methods of process modelling and control structure are frequently not suitable. The ability of neural network to model dynamics of nonlinear process makes them an important tool for implementation in model-based control. Due to intensively theory development and many practical applications, there are numerous neural network structures and algorithms.
In this paper neural networks are categorized under three major control schemes: model-base predictive control, inverse model-based control, and adaptive control. The major applications are summarized. It reveals prospect of using neural networks in process identification and control.
The future of neural network application lies not only in their explicite use, but in cross connecting to other advanted technnologies as well. Fusion of neural networks and fuzzy logic in the form of neural-fuzzy network is one of the possibilites. Other important field is hibrid modelling and identification methods which supplement simplified mechanistic models. Software sensors and their application, especially in controlling of bioprocesses, present a very promising field
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