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Wyświetlanie 1-15 z 36
Tytuł:
Chemical Constituents from Fadogia homblei De Wild (Rubiaceae)
Autorzy:
Mohammed, A. M. A.
Coombes, P. H.
Crouch, N. R.
Mulholland, D. A.
Powiązania:
https://bibliotekanauki.pl/articles/411606.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Fadogia homblei
F. monticola
F. fragrans
Rubiaceae
Pavettamine
gousiekte
Opis:
The total of fourteen known compounds was isolated from the fruits, leaf and stem of Fadogia homblei De Wild. (Rubiaceae) and identified as: a coumarin, 7-hydroxy-6-methoxy-2H-1-benzopyran-2-one (scopoletin) 1, two flavones; 3′,4′,5,7-tetrahydroxyflavone (luteolin) 2 and quercetin-3-O-β-D-galactoside 3, four lupane triterpenoids; lupeol 4, betulinic acid 5, 3β-dodecanoyllup-20(29)-en-28-al 6, lup-20(29)-en-3β-ylhexadecanoate 7, and two steroids; sitosterol 8, stigmasterol 9, a lignan 4,4′-dihydroxy-3,3′-dimethoxy-7,9′:7′,9-diepoxylignan ((-)-pinoresinol) 10, a phaeophytin A 11, an uracil 12, an oleanolic acid 13, and an ursolic acid 14. To our best knowledge, this is the first report for isolation of these compounds from this species. This finding is nevertheless significant as it is the first report of uracil from a plant source other than from various species of ferns.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 9, 2; 116-124
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical Constituents and Insecticidal Activity of Senna italica Mill. from the Sudan
Autorzy:
Yagi, S.
El Tigani, S.
Ali, M.
Elkhidir, I.
Mohammed, A. M. A.
Powiązania:
https://bibliotekanauki.pl/articles/412035.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Senna italica
Fabaceae
Caesalpiniaceae
sennosides
anthraquinone
bianthrones
insecticidal activity
Opis:
The chemical constituents and insecticidal activity of the pods of Senna italica (Caesalpiniaceae, Fabaceae) were investigated. From the chloroform extract of pods, physcion, chrysophanol, chrysophanol-10,10′-bianthrone, chrysophanol-physcion bianthrone and chrysophanol-isophyscion bianthrone, were isolated and characterized using different spectral methods. The GC-MS of the n-hexane extract revealed that the major chemical constituents of the oil were 2,6,-di-sec-butylphenol (36.69 %), di-n-octylphthalate (12.06 %), eicosane (5.46 %), tetratriacontane (4.87 %) and 2,2'-methylenebis[6-(1,1-dimethyl)-4-methylphenol (4.18 %). The n-hexane extract showed potent insecticidal activity (100 %) against Callosbruchus analis F. This study suggests that S. italica pods cannot be a source of sennosides but for other bioactive compounds.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 9, 2; 146-151
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental and Computational Vibration Study of Amino Acids
Autorzy:
Mohammed, M. E.
Mohamed, A. M. A.
Powiązania:
https://bibliotekanauki.pl/articles/412478.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Vibrational studies
Amino Acids
semi-empirical methods (PM6 and RM1)
ab initio methods (B3LYP/6-31+G(d)
Opis:
Vibrational studies of amino acids experimentally and theoretically have been performed. The Semi-empirical methods optimization by PM6 and RM1 on the l- and d-amino acids (alanine, phenylalanine, aspartic and glutamic acid), showed no difference in energy between l-and d-isomers. The vibrational frequencies were calculated by semi-emprical methods (PM6 and RM1) and ab initio methods (B3LYP/6-31+G(d) and were scaled down by factors of 0.925 (RM1), 1.09 (PM6) and 0.89 (B3LYP/6-31+G(d)). The calculated and experimental vibrational frequencies have shown good general agreement.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 10, 1; 1-17
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
Autorzy:
Mohammed, N. A.
Elnabawy, M. M.
Khalaf, A. A. M.
Powiązania:
https://bibliotekanauki.pl/articles/1818214.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
light emitting diode
peak-to-average power ratio
bit error rate
Opis:
Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
Źródło:
Opto-Electronics Review; 2021, 29, 2; 59--70
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
Autorzy:
Mohammed, N. A.
Elnabawy, M. M.
Khalaf, A. A. M.
Powiązania:
https://bibliotekanauki.pl/articles/1818217.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
light emitting diode
peak-to-average power ratio
bit error rate
Opis:
Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
Źródło:
Opto-Electronics Review; 2021, 29, 2; 59--70
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
Autorzy:
Mohammed, Nazmi A.
Elnabawy, M. M.
Khalaf, Ashraf A. M.
Powiązania:
https://bibliotekanauki.pl/articles/1818212.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
light emitting diode
peak-to-average power ratio
bit error rate
Opis:
Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
Źródło:
Opto-Electronics Review; 2021, 29, 2; 59--70
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stress–strain relationship of ductile materials and flexural behavior of ductile over-reinforced concrete beams
Autorzy:
Duhaim, Hussein M.
Mashrei, Mohammed A.
Powiązania:
https://bibliotekanauki.pl/articles/36058847.pdf
Data publikacji:
2022
Wydawca:
Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
Tematy:
ductile material
SFRC
SIFCON
UHPFRC
over-reinforced beam
flexural behavior
ductility
Opis:
This paper aimed to investigate the effect of using ductile materials in the compression zone on the flexural performance of over-reinforced concrete beams. In order to avoid brittle compression failure, partial replacement of concrete with ductile materials layer in the compression zone was used. Four over-reinforced concrete beams of size 120 × 180 × 1,300 mm were cast and tested under three-point loading conditions. The steel fibers reinforced concrete (SFRC), slurry infiltrated fiber concrete (SIFCON), and ultra-high performance fiber reinforced concrete (UHPFRC) were used as ductile materials. The flexural capacity of the beams, failure modes, crack patterns, load-deflection relationships, ductility index, and toughness were investigated. The results showed that using ductile materials in the compression zone is an effective technique to increase the ultimate load, ductility, and toughness by up to 52.46, 84.78 and 279.93%, respectively, compared to the reference beam. In addition, the failure mode changed from brittle to ductile failure. Noting that the use of SFRC layer enhanced the ductility of over-reinforced concrete beams more than using UHPFRC and SIFCON layers. Also, one of the main advantages of this technique is led to increase the tensile reinforcement ratio up to 8.548% without needing the compressive reinforcement. Thus, ductile composite beams with a high flexural capacity were generated using an economical amount of ductile materials.
Źródło:
Scientific Review Engineering and Environmental Sciences; 2022, 31, 4; 225-237
1732-9353
Pojawia się w:
Scientific Review Engineering and Environmental Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal Surface Dipole Moment and Work Function in the Linear Potential Model
Autorzy:
Mohammed, A. E.
Ghaly, A. Y.
Frege, O. M.
Powiązania:
https://bibliotekanauki.pl/articles/1891682.pdf
Data publikacji:
1991-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.30.+y
Opis:
Jellium metal surface properties such as the surface dipole barrier and work function are obtained in the linear potential approximation to the effective potential at the surface. The metal surface position and field strength are determined respectively by the requirement of overall charge neutrality and the constraint set on the electrostatic potential by the Budd-Vannimenus theorem. The calculations are primarily analytic and these properties are given in terms of universal functions of the field strength. The results obtained employing the Ceperly-Alder expression for the correlation energy closely approximate those of Lang and Kohn.
Źródło:
Acta Physica Polonica A; 1991, 80, 4; 591-600
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Integrated use of potassium and Ssoil mulching on growth and productivity of garlic (Allium sativum L.) under deficit irrigation
Autorzy:
Barakat, M.A.
Osman, A.S.
Semida, W.M.
Mohammed, A.G.
Powiązania:
https://bibliotekanauki.pl/articles/11275.pdf
Data publikacji:
2019
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Źródło:
International Letters of Natural Sciences; 2019, 76
2300-9675
Pojawia się w:
International Letters of Natural Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effectiveness factor of two-dimensional ring-shaped catalyst pellets
Autorzy:
Asif, M.
Ibrahim, A. A.
Mohammed, Y. A.
Al-Ghurabi, E. H.
Powiązania:
https://bibliotekanauki.pl/articles/780040.pdf
Data publikacji:
2017
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
hollow catalyst pellet
effectiveness factor
Thiele modulus
convergence behavior
analytical solution
Opis:
The use of hollow catalytic support improves the utilization of the catalytic material because of the absence of the pellet core, and moreover ensures low reactor pressure drop owing to enhanced bed voidage. In this study, the expressions for the efficient computation of the effectiveness factor are derived for a ring-shaped catalyst pellet undergoing first-order irreversible reaction. The methodology consists of using solutions of one-dimensional problems to remove non-homogeneous boundary conditions. The expressions obtained exhibit significantly faster convergence behavior than those reported in literature. The shape parameters, namely, the height-to-diameter ratio and the inner-to-outer radii ratio, significantly affect the catalyst utilization, such that several-fold improvement in the effectiveness factor is achievable.
Źródło:
Polish Journal of Chemical Technology; 2017, 19, 3; 99-105
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minerals content, essential oils composition and physicochemical properties of Citrus jambhiri Lush. (Rough Lemon) from the Sudan
Autorzy:
Mohammed, A. M. H.
Ibrahim, M. A
Omran, A. A.
Mohamed, E. M.
Elsheikh, S. E. M.
Powiązania:
https://bibliotekanauki.pl/articles/412508.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Citrus jambhiri
Rutaceae
atomic absorption spectroscopy (AAS)
Flame Atomic Emission Spectroscopy (FAES)
metal content
essential oils
Opis:
Minerals content of Citrus jambhiri (rough lemon) fruit was qualitatively and quantitatively analyzed using atomic absorption spectroscopy (AAS) and flame atomic emission spectrometry (FAES). The peel, moisture and ash contents of rough lemon were found to be 18.35 %, 23.75 % and 2.04 % respectively. Vitamin C (ascorbic acid) of rough lemon juice was found to be 70.0 mg/100 g. The chemical composition of essential oil of rough lemon peel was determined. The major compound was found to be limonene (84.5 %) followed by sabinene, β-myrcene, α-terpineol, 1,3-tetradecadiene and linalool.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 9, 1; 25-30
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cytotoxic flavonoids from Diplotaxis harra (Forsk.) Boiss. growing in Sinai
Cytotoksyczność flawonoidów pochodzących z roslin Diplotaxis harra (Forsk.) Boiss. osnącej na Półwyspie Synaj
Autorzy:
Mohammed, M.M.D.
El-Sharkawy, E.R.
Matloub, A.A.
Powiązania:
https://bibliotekanauki.pl/articles/71877.pdf
Data publikacji:
2011
Wydawca:
Instytut Włókien Naturalnych i Roślin Zielarskich
Tematy:
cytotoxic flavonoids
flavonoids
cytotoxicity
Diplotaxis harra
Sinai
medicinal plant
Opis:
As a part of our ongoing collaborative effort to discover the anticancer activity of the phenolics isolated from terrestrial plant sources, the EtOH extract of the aerial parts of the Egyptian medicinal plant Diplotaxis harra (Forsk.) Boiss. was in vitro investigated for its cytotoxicity against HCT116, HepG2 and MCF-7 cell lines, and resulted with IC50=4.65, 12.60 and 17.90 μg/ml, respectively. Doxorubicin (+ve control) showed in vitro cytotoxic activity with IC50=3.64, 4.57 and 2.97 μg/ml, respectively. The phenolic-rich fraction of the EtOH extract was subjected to further fractionation, which led to the isolation of five flavonoids identified as quercetin, quercetin 3-O-β-glucoside, isorhamnetin 7-O-β-glucoside, apigenin 3-O-β-rhamnoside and kaempferol 3-O-β-glucoside, according to its’ spectral data and comparison with the literature. Furthermore, the isolated flavonoids showed in vitro cytotoxicity against HCT116 cell line with IC50=20.1, 24.3, 22.8, 23.4 and 41.9 μg/ml as determined by MTT method.
W ramach badań nad poszukiwaniem nowych związków fenolowych o aktywności przeciwnowotworowej pochodzących z roślin lądowych badaniom w kierunku cytotoksyczności w warunkach in vitro w poddano wyciąg alkoholowy z nadziemnych części egipskiej rośliny leczniczej Diplotaxis harra (Forsk.) Boiss. W wyniku przeprowadzonych badań cytotoksyczności z wykorzystaniem linii komórkowych HCT116, HepG2 oraz MCF-7 otrzymano odpowiednio następujące wartości: IC50=4,65, 12,60 oraz 17,90 μg/ml. Doksorubicyna (kontrola pozytywna) w warunkach in vitro wykazała w stosunku do badanych linii komórkowych następującą aktywność cytotoksyczną: odpowiednio IC50=6,64, 4,57 oraz 2,97 μg/ml. Dalsze rozdzielanie frakcji wyciągu etanolowego, bogatej w związki fenolowe, doprowadziło do wyizolowania pięciu flawonoidów: kwercetyny, 3-O-β-glukozydu kwercetyny, 7-O-β-glukozydu izoramnetyny, 3-O-β-ramnozydu apigeniny oraz 3-O-β-glukozydu kemferolu (zidentyfikowanych według danych spektralnych oraz na podstawie porównania z danymi pochodzącymi z literatury przedmiotu). Ponadto wyizolowane flawonoidy wykazywały in vitro cytotoksyczność określoną przy użyciu metody MTT w stosunku do linii HCT116 na poziomie IC50 =20,1, 24,3, 22,8, 23,4 oraz 41,9 μg/ml.
Źródło:
Herba Polonica; 2011, 57, 3
0018-0599
Pojawia się w:
Herba Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation between Optical and Structural Properties of Chemically deposited CdS Thin Films
Autorzy:
Mohammed, R. Y.
Abduol, S.
Mousa, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/411521.pdf
Data publikacji:
2014
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
cadmium sulfide
chemical bath deposition
CdS films
XRD
Opis:
Polycrystalline Cadmium sulfide (CdS) films were deposited onto Corning glass substrates from alkaline solutions containing CdCl2, KOH, Na3C6H5O7 and CS(NH2)2 at different deposition times (10, 20, 30, 40 and 50 min), different bath temperatures and different concentration of the reactants. A comparative study was performed out on thin film via optical transmission and X-ray diffraction (XRD) measurements which reveal that the deposition time has a profound influence on the growth rate and band gap of the deposited layers. Diffraction data are used to evaluate the lattice parameter, grain size, average strain, number of crystallites per unit area and dislocation density in the film are calculated.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2014, 11, 2; 146-158
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dimming control schemes combining IEEE 802.15.7 and SC-LPPM modulation schemes with an adaptive M-QAM OFDM for indoor LOS VLC systems
Autorzy:
Mohammed, Nazmi A.
Badawi, Kareem A.
Khalaf, Ashraf A. M.
El-Rabaie, S.
Powiązania:
https://bibliotekanauki.pl/articles/1818236.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
sub-carrier pulse position modulation
lightning topologies
bit error rate
Opis:
The presented work proposes a new dimming control schemes for indoor visible light communication which combines variable pulse-position modulation, colour shift keying as key schemes of IEEE 802.15.7 standard, and sub carrier-pulse-position modulation as a pulse-position modulation variant with orthogonal frequency division multiplexing. These schemes are then compared with traditional merging schemes utilizing pulse-width modulation and multiple pulse-position modulation with m-ary quadrature amplitude modulation OFDM. The proposed schemes are investigated in a typical room with a different lighting layout (i.e., distinctive and uniform lighting layout), followed by an illumination investigation to evaluate the performance of the proposed schemes, especially the enhanced achieved data rates, and to determine their limitations as reliable visible light communication systems that can satisfy both communication and illumination requirements.
Źródło:
Opto-Electronics Review; 2020, 28, 4; 203--212
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Economic analysis and pattern of agrochemicals use among smallholder crop farmers in Edu Local Government Area of Kwara State
Autorzy:
Olayinka, A.S.
Lawal, A.F.
Bwala, M.A.
Mohammed, U.H.
Sulaiman, A.I.
Powiązania:
https://bibliotekanauki.pl/articles/43680.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Przyrodniczy w Poznaniu. Wydawnictwo Uczelniane
Źródło:
Journal of Agribusiness and Rural Development; 2019, 52, 2
1899-5241
Pojawia się w:
Journal of Agribusiness and Rural Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 36

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