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121.
Nowadays purity plays a role in at least four branches of mathematics: Module Theory, Theory of Acts over semigroups, Model
Theory, and Category Theory. Adámek and Rosciky have studied these notions categorically, and Rothmaler model-theoretically.
Some authors including Banaschewski, Gould, and Normak have studied purity on G-acts, acts over a monoid or a group G. 相似文献
122.
We consider the class of multivariate distributions that gives the distribution of the sum of uncorrelated random variables by the product of their marginal distributions. This class is defined by a representation of the assumption of sub-independence, formulated previously in terms of the characteristic function and convolution, as a weaker assumption than independence for derivation of the distribution of the sum of random variables. The new representation is in terms of stochastic equivalence and the class of distributions is referred to as the summable uncorrelated marginals (SUM) distributions. The SUM distributions can be used as models for the joint distribution of uncorrelated random variables, irrespective of the strength of dependence between them. We provide a method for the construction of bivariate SUM distributions through linking any pair of identical symmetric probability density functions. We also give a formula for measuring the strength of dependence of the SUM models. A final result shows that under the condition of positive or negative orthant dependence, the SUM property implies independence. 相似文献
123.
D. Brynn Hibbert Danielle Blackmore Jianfeng Li Diako Ebrahimi Michael Collins Sasha Vujic Paul Gavoyannis 《Analytical and bioanalytical chemistry》2010,396(2):765-773
The probability density functions of amount ratios of compounds (total codeine/total morphine, 6-monoacetylemorphine/total
morphine, papaverine/total morphine, and noscapine/total morphine) from the analysis of seized heroin, originating from known
world regions (South East Asia, South West Asia, South America, Mexico) allows calculation of likelihood ratios for ‘unknown’
samples. Application of Bayes Theorem with a suitable prior probability, for example the frequency of a particular region
in the database, leads to the probability that a particular profile comes from a given target region. Data from 2549 seizures
of heroin at Australia’s border illustrates the method, and results are compared with simple HS1 ratio approaches for assigning
geographical origin. The method can be implemented in a spreadsheet and gives more refined intelligence of the origins of
seized drugs than simple ranges.
相似文献
124.
M. Taghinejad-Roudbaneh S.R. Ebrahimi S. Azizi P. Shawrang 《Radiation Physics and Chemistry》2010,79(12):1264-1269
The aim of the present study was to determine the impact of electron beam (EB) irradiation at doses of 15, 30 and 45 kGy on the nutritional value of canola meal. The phytic acid and total glucosinolate content of EB-irradiated canola meal decreased as irradiation doses increased (P<0.01). From in situ results, irradiation of canola meal at doses of 45 kGy decreased (P<0.05) the effective degradibility of crude protein (CP) by 14%, compared with an untreated sample. In vitro CP digestibility of EB-irradiated canola meal at doses of 15 and 30 kGy was improved (P<0.05). Electrophoresis results showed that napin and cruciferin sub-units of 30 and 45 kGy EB-irradiated canola meal were more resistant to degradation, compared with an untreated sample. Electron beam irradiation was effective in protecting CP from ruminal degradation and reducing antinutritional factors of irradiated canola meal. 相似文献
125.
S. M. Habibi Khorassani M. T. Maghsoodlou A. Ebrahimi H. Roohi M. Zakarianezhad 《Journal of the Iranian Chemical Society》2006,3(3):223-232
To determine the kinetic parameters of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of an NH-acid, such as 2,3-di-hydroxybenzaldehyde, the reactions were monitored by UV spectrophotometry. The second order fits were automatically drawn and the values of the second order rate constants (k2) were calculated using standard equations as part of the program. The dependence of the second order rate constant (lnk2) on the reciprocal temperature was in agreement with the Arrhenius equation, in the temperature range studied, providing the relevant plots to calculate the activation energy of all reactions. Furthermore, we evaluated the effects of solvent, structure of different alkyl groups within the dialkyl acetylenedicarboxylates, and their concentration on the rates of reactions. The proposed mechanism was confirmed by experimental results and steady-state approximation. The first step (k2) of the reaction was recognized as the rate determining step on the basis of experimental data. 相似文献
126.
Mohammad Mazloum Ardakani Parvaneh Rahimi Hossein Dehghani Payam Ebrahimi Karami Hamid Reza Zare Somayeh Karami 《Electroanalysis》2007,19(21):2258-2263
The preparation and electrocatalytic behavior of glassy carbon electrodes modified with three different cobalt porphyrin complexes were investigated. The electrocatalytic ability of the modified electrodes for the reduction of dioxygen to hydrogen peroxide and water in air‐saturated aqueous solutions was examined by cyclic voltammetry and chronoamperometry techniques. The porphyrin‐adsorbed glassy carbon electrodes possess excellent electrocatalytic abilities for dioxygen reduction with overpotential about 0.5 V lower than that at a plain glassy carbon electrode. The experimental parameters were optimized and the mechanism of the catalytic process was discussed. The possible effects of the electron‐donating properties of groups in the meso‐position of the porphyrin ring were investigated. 相似文献
127.
The composition of the essential oil obtained by hydrodistillation from the leaves of Stachys schtschegleevii Sosn. before the flowering stage was analyzed by GC and GC-MS. Forty-five compounds representing 98.7% of the total oil were identified, of which α-pinene (36.4%), germacrene-D (18.6%), limonene (8.2%), and piperitone (6.2%) were the major constituents. Furthermore, antibacterial activity of the entire oil and its two main monoterpenes was evaluated against six Gram-positive and Gram-negative bacteria. The oil exhibited moderate activity against the tested bacteria.__________Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 138–140, March–April, 2005. 相似文献
128.
H. Roohi A. Ebrahimi B. Mackiabadi M. Hagealirezahi 《Journal of Molecular Structure》2006,778(1-3):63-67
The origin of rotational barrier in N-thionitrosamine NH2NS (TNA) has been examined with the aid of topological theory of atoms in molecules (AIM) and natural bond orbital (NBO) analyses and has been compared with N-nitrosamine NH2NO (NA). Frequency calculations show that the rotational barrier for TNA is greater than NA. This can be attributed to the more charge transfer from nitrogen of amino group to sulfur in TNA than from nitrogen to oxygen in NA. NBO analysis reveals pyramidalization of nitrogen atom of NH2 group leads to decrease of delocalization energy contribution and increase of Lewis energy contribution on total energy. 相似文献
129.
Jahanbakhsh Ghasemi Diako M. Ebrahimi Leila Hejazi Ricardo Leardi Ali Niazi 《Journal of Analytical Chemistry》2006,61(1):92-98
Simultaneous multicomponent analysis is usually carried out using multivariate calibration models, such as the partial least
squares (PLS) one, that utilize the full spectrum. It has been shown by both experimental and theoretical considerations that
better results can by obtained by proper selection of the spectral range to be included in calculations. A genetic algorithm
(GA) is one of the most popular methods for selecting variables for PLS calibration of mixtures with almost identical spectra
without loss of predictive capability. In this work, a simple and precise method for rapid and accurate simultaneous determination
of sulfide and sulfite ions based on the addition reaction of these ions with new fuchsin at pH 8 and 25°C using PLS regression
and GA for variable selection is proposed. The concentrations of sulfide ions varied between 0.05–2.50 and 0.15–2.00 μg/mL,
respectively. A series of model solutions containing different concentrations of sulfide and sulfite were used to check the
predictive ability of GA-PLS models. The root mean square error of prediction with PLS on the whole data set was 0.19 μg/mL
for sulfide and 0.09 μg/mL for sulfite. After the application of GA, these values reduced to 0.04 and 0.03 μg/mL, respectively.
The text was submitted by the authors in English. 相似文献
130.
Reliability of many stochastic systems depends on uncertain stress and strength patterns that are time dependent. In this paper, we consider the problem of estimating the reliability of a system when bothX(t) andY(t) are assumed to be independent Brownian motion processes, whereX(t) is the system stress, andY(t) is the system strength, at timet.This research was partially supported by the Air-Force Office of Scientific Research Grants AFOSR-89-0402 and AFOSR-90-0402. 相似文献