11 results on '"Mohamed Nakkach"'
Search Results
2. Noninvasive diagnosis of type 2 diabetes mellitus by hair analysis using laser-induced breakdown spectroscopy (LIBS)
- Author
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Imen Cherni, Mohamed Nakkach, Hassen Ghalila, Rihem Nouir, Mehdi Somai, Fatma Daoued, Imen Rachdi, Fatma Boussema, Nejmeddine Jaidane, and Sami Hamzaoui
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General Chemical Engineering ,Instrumentation ,General Environmental Science - Published
- 2022
3. Conception of Impedance Spectroscopy Analyzer and validation using yeast cell
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Mohamed Nakkach and Souhir Chabchoub
- Subjects
Spectrum analyzer ,Materials science ,Cell ,Biological tissue ,Yeast ,law.invention ,Characterization (materials science) ,Dielectric spectroscopy ,medicine.anatomical_structure ,law ,Electrode ,medicine ,Alternating current ,Biomedical engineering - Abstract
The characterization of biological cells is of major importance in several research fields. Impedance Spectroscopy is the most used tool to characterize cells; it can be used to investigate electrical cells proprieties, to differentiate between different kinds of cells, and to quantify cells. The goal of this work is the conception of an Impedance Spectroscopy Analyzer for cell characterization. The yeast cells were used to validate the reliability and the accuracy of this analyzer. In our instrument, a small alternating current with a variable frequency is injected into the explored biological system by using two electrodes. Then, the same electrodes are used to acquire a potential difference which is used to characterize the biological tissue. The analyzer can be used to investigate the electrical properties of cell suspensions such as the blood and the cytoplasm. The designed device is automated by LabVIEW interface through a GPIB.
- Published
- 2018
4. Spectroscopic studies of photosynthetic responses of tomato plants to the interaction of zinc and cadmium toxicity
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Zohra Ben Lakhdar, Jaouhra Cherif, Hubertus M. von Bergmann, Najoua Derbel, Fatma Jemal, and Mohamed Nakkach
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Cadmium ,Radiation ,Radiological and Ultrasound Technology ,Biophysics ,Analytical chemistry ,food and beverages ,chemistry.chemical_element ,Pigments, Biological ,Photosynthetic efficiency ,Photosynthesis ,Fluorescence spectroscopy ,Plant Leaves ,Zinc ,chemistry.chemical_compound ,Spectrometry, Fluorescence ,Solanum lycopersicum ,chemistry ,Chlorophyll ,Ultraviolet light ,Radiology, Nuclear Medicine and imaging ,Kautsky effect ,Chlorophyll fluorescence - Abstract
The in vivo chlorophyll (Chl) fluorescence spectra of Solanum lycopersicum leaves were recorded in the spectral region 650-800nm using a spectroscopic method based on ultraviolet light emitting diode induced fluorescence spectroscopy (UV-LED IFS). These spectra have been used to analyze the interactive functions of cadmium (Cd(2+)) and zinc (Zn(2+)) on photosynthetic activities of S. lycopersicum plants. The fluorescence intensity ratios (F(690)/F(735)) of the chlorophyll bands at 685 and 730nm were calculated by evaluating curve fitted parameters using a Gaussian spectral function, for control as well as treated plants. The fluorescence induction kinetics (Kautsky effect) was also measured on dark adapted intact plant leaves at the chlorophyll bands for determining the variable chlorophyll fluorescence decrease ratio (R(Fd) values) and the stress adaptation index (Ap). In addition, metal accumulation in plants, plant growth and photosynthetic pigments content were estimated. It was found that the R(Fd)(690), R(Fd)(730) and Ap values decreased whereas the F(690)/F(735) ratio increased in the case of 10μM Cd(2+) treated plants, indicating an impairment of the photosynthetic efficiency. Zn(2+) supplementation, at low concentration (10 and 50μM), in combination with Cd(2+) protect the photochemical functions. However, the high Zn(2+) concentration exacerbated the negative effects of Cd(2+) and showed a severe decrease of R(Fd)(690), R(Fd)(730) and Ap values compared to Cd(2+) alone. It is seen that F(690)/F(735) ratios are strongly correlated with chlorophyll contents. The results demonstrate the usefulness of F(690)/F(735), Ap and R(Fd) values in determining the potential photosynthetic activity of an intact attached leaf in a non-destructive way.
- Published
- 2012
5. Detection of photosynthetic activity under cadmium stress by measurement of the red and far-red chlorophyll fluorescence
- Author
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Mohamed Nakkach, Hubertus M. von Bergmann, Chamseddine Mediouni, Zohra Ben Lakhdar, Najoua Derbel, Fatma Jemal, and Jaouhra Cherif
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Cadmium ,Chlorophyll a ,chemistry.chemical_element ,Far-red ,Cadmium chloride ,Fluorescence spectroscopy ,chemistry.chemical_compound ,chemistry ,Chlorophyll ,Botany ,Ultraviolet light ,Biophysics ,General Earth and Planetary Sciences ,Chlorophyll fluorescence - Abstract
In this work it is shown that, with a new spectroscopic method based on ultraviolet light emitting diode-induced fluorescence spectroscopy (UV-LED IFS), the photosynthetic activity of an intact attached leaf can be measured in a non-destructive way within a few seconds. The effects of cadmium (Cd) toxicity on the photosynthetic activity of tomato plants (Solanum lycopersicum) were studied using various CdCl2 (cadmium chloride) concentrations. The Cd treatment decreases the photosynthetic activity, measured via a decline of the variable chlorophyll (chl) fluorescence decrease ratio (RFd) values, calculated at 690 and 730 nm. The chl fluorescence ratios of intensity (FIR) and band area were also calculated. It was found that the RFd(690) and RFd(730) values decreased whereas the FIR increased from 1 μM Cd treatment and this behaviour is enhanced with the increasing of Cd concentrations. At 10 and 25 μM Cd, the decrease in RFd values was associated with a strong decline in the chlorophyll-a + chlorophyll-b (chl-a + b). The chl-a + b decline could also be followed via an increase of the chl fluorescence ratio F690/F730. Our study demonstrates that the UV-LED IFS is a promising technique for early detection of Cd stress (from 1 μM) in tomato plants, before visual symptoms appear.
- Published
- 2011
6. Nanostructured substrates for surface plasmon resonance sensors
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Michael Canva, Anuj Dhawan, Aurélien Duval, Tuan Vo-Dinh, Mohamed Nakkach, Julien Moreau, and Alain Bellemain
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Materials science ,business.industry ,Surface plasmon ,Physics::Optics ,Grating ,Surface plasmon polariton ,Optics ,Optoelectronics ,Prism ,Surface plasmon resonance ,business ,Electron-beam lithography ,Plasmon ,Localized surface plasmon - Abstract
Surface Plasmon Resonance (SPR) sensors are usually based on continuous thin metallic films and coupling of propagative plasmon (PP) modes using high index prism or grating. The quantitative monitoring of the surface evolution is performed by measuring either shift in angular or spectral dip position, or by reflectivity variation in the slope of the angulo-spectral coupling curve. Such sensors are studied in many laboratories and used in a growing number of commercial devices. It appears however that these systems are reaching their limits in terms of sensitivity [1]. In the field of plasmonic sensing, many other works are devoted to the study of metallic nanoparticles. We anticipate that using nanostructured substrates for exciting coupled localized plasmon (CLP) or quasi propagating plasmon (QPP) will allow to further increase the sensors capabilities, in particular in terms of sensitivity. Samples were realized using either e-beam or deep-UV lithography based techniques. Experimental characterizations were conducted using lab-made angulo-spectral SPR Imaging systems [2]. Using RCWA simulations, we have calculated the plasmonics responses, in term of angulo-spectral reflectivity, of nanostructures. A novel narrow groove plasmonic nano-grating sensing configuration exhibits the highest potential [3].
- Published
- 2011
7. Deep UV nano-microstructuring of substrates for surface plasmon resonance imaging
- Author
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Tuan Vo-Dinh, Anuj Dhawan, Julien Moreau, Michael Canva, Aurélien Duval, Mohamed Nakkach, and Grégory Barbillon
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Materials science ,Macromolecular Substances ,Surface Properties ,Ultraviolet Rays ,Molecular Conformation ,Physics::Optics ,Bioengineering ,02 engineering and technology ,Radiation Dosage ,01 natural sciences ,law.invention ,010309 optics ,Optics ,law ,0103 physical sciences ,Nano ,Materials Testing ,General Materials Science ,Electrical and Electronic Engineering ,Surface plasmon resonance ,Particle Size ,Rigorous coupled-wave analysis ,Plasmon ,business.industry ,Mechanical Engineering ,General Chemistry ,Surface Plasmon Resonance ,021001 nanoscience & nanotechnology ,Nanostructures ,Wavelength ,Mechanics of Materials ,Photolithography ,0210 nano-technology ,business ,Crystallization ,Refractive index ,Localized surface plasmon - Abstract
In this paper, we describe wafer-scale fabrication and characterization of plasmonic chips-containing different sizes and spacings of metallic micro- and nanoline structures-using deep UV lithography. Using a high dose (25 mJ cm( - 2)) and a proper lift-off process, feature sizes as small as 25 nm are obtained. Moreover, we study the dependence of surface plasmon resonance on the angle of incidence and wavelength for different micro- and nanoline size and spacing values, yielding localized to quasi-propagative plasmonic behaviors. Rigorous coupled wave analysis (RCWA) techniques are employed to numerically confirm these experimental observations. Finally, the refractive index of media around the SPRI sensor chips is varied, showing the angulo-spectral regions of higher sensitivity for each type of structure.
- Published
- 2011
8. Angulo-spectral surface plasmon resonance imaging of nanofabricated grating surfaces
- Author
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Aurélien Duval, Buntha Ea-Kim, Michael Canva, Mohamed Nakkach, Julien Moreau, Laboratoire de Spectroscopie Atomique, Moléculaire et Applications (LSAMA), Université de Tunis El Manar (UTM)-Faculté des Sciences Mathématiques, Physiques et Naturelles de Tunis (FST), Université de Tunis El Manar (UTM), Laboratoire Charles Fabry de l'Institut d'Optique / Macsybio - bio, Laboratoire Charles Fabry de l'Institut d'Optique (LCFIO), Université Paris-Sud - Paris 11 (UP11)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), and European Project: 224014,EC:FP7:ICT,FP7-ICT-2007-2,PHOTONICS4LIFE(2008)
- Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Materials science ,business.industry ,Surface plasmon ,Physics::Optics ,02 engineering and technology ,Grating ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surface plasmon polariton ,Atomic and Molecular Physics, and Optics ,010309 optics ,OCIS 240.6680, 220.4241 ,Optics ,0103 physical sciences ,[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic ,Surface plasmon resonance ,0210 nano-technology ,business ,Refractive index ,Plasmon ,Electron-beam lithography ,Localized surface plasmon - Abstract
International audience; We present a surface plasmon resonance imaging (SPRI) setup, based on the Kretschmann configuration, capable of simultaneously acquiring the complete spectral and angular plasmonic reflectivity response on all points of the sensing area. Several line poly(methyl methacrylate) grating regions were fabricated on a thin-film gold surface and characterized with this SPRI system. Reflectivity maps of the corrugated regions showing plasmon bandgaps were obtained to illustrate the capability of the setup.
- Published
- 2010
9. Analysis of in vivo chlorophyll fluorescence spectra to monitor physiological state of tomato plants growing under zinc stress
- Author
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Najoua Derbel, Fatma Jemal, Jaouhra Cherif, Zohra Ben Lakhdar, Mohamed Nakkach, and Hubertus M. von Bergmann
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Chlorophyll ,Biophysics ,Analytical chemistry ,chemistry.chemical_element ,Zinc ,Photosynthesis ,Fluorescence spectroscopy ,chemistry.chemical_compound ,Pigment ,Solanum lycopersicum ,Malondialdehyde ,Ultraviolet light ,Radiology, Nuclear Medicine and imaging ,Chlorophyll fluorescence ,Radiation ,Radiological and Ultrasound Technology ,biology ,Chemistry ,fungi ,food and beverages ,Pigments, Biological ,biology.organism_classification ,Plant Leaves ,Kinetics ,Spectrometry, Fluorescence ,visual_art ,visual_art.visual_art_medium ,Solanum ,Nuclear chemistry - Abstract
The effects of zinc (Zn) on plant chlorophyll fluorescence were investigated in 10-day-old tomato ( Solanum lycopersicum ) seedlings subjected for 7 days to a series of zinc (10, 50, 100 and 150 μM) applied via the nutrient solution. The chlorophyll fluorescence spectra of leaves were recorded in the spectral region 650–800 nm using the spectroscopic technique of ultraviolet light emitting diode induced fluorescence spectroscopy (UV-LED IFS). These spectra have been used to analyze the effect of several doses of zinc on the photosynthetic activities of tomato plants. The fluorescence intensity ratios (FIR) at the two maxima ( F 690 / F 735 ) of control as well as treated tomato plants were calculated by evaluating curve-fitted parameters using a Gaussian spectral function. The variable chlorophyll fluorescence decrease ratio ( R Fd ) values were determined from the fluorescence induction kinetics curves recorded at 690 nm and 735 nm. In addition, Zn accumulation in plants, plant growth, photosynthetic pigments content and malondialdehyde level (MDA, an index of lipid peroxidation) were also estimated. The results indicated that the plants treated with 10 μM of zinc exhibited better growth, however, higher concentrations of zinc were harmful for plants. Excess Zn induced a decrease in the R Fd values, which was associated with a strong decline of the total chlorophylls content and an increase of MDA level. The total chlorophylls content decline could also be followed via an increase of the chlorophyll fluorescence ratio F 690 / F 735 .
- Published
- 2010
10. Extraction of complex refractive index dispersion from SPR data
- Author
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Michael Canva, Julien Moreau, Mohamed Nakkach, Laboratoire Charles Fabry de l'Institut d'Optique / Macsybio - bio, Laboratoire Charles Fabry de l'Institut d'Optique (LCFIO), and Centre National de la Recherche Scientifique (CNRS)-Institut d'Optique Graduate School (IOGS)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut d'Optique Graduate School (IOGS)-Université Paris-Sud - Paris 11 (UP11)
- Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Materials science ,Kramers–Kronig relations ,Spectrometer ,business.industry ,Surface plasmon ,Physics::Optics ,Polarization (waves) ,Spectral line ,Wavelength ,Optics ,Optoelectronics ,business ,Refractive index ,Plasmon ,ComputingMilieux_MISCELLANEOUS - Abstract
Surface Plasmon Resonnance (SPR) techniques have been mostly set-up as angular reflectivity interrogation mode using quasi-monochromatic light or as spectral reflectivity interrogation mode at one given wavelength, providing information about variation of effective optical thickness un.e above the metal surface. In this communication we present a dual mode sensor working both in angular and spectral interrogation modes. A white light illuminates the sensor surface and the reflectivity spectra in TE and TM polarization are measured with a spectrometer. By changing the angular coupling conditions, a complete reflectivity surface R(θ, λ) can be measured. The 2D reflectivity decrease valley is affected by both the real and imaginary part of the optical index of the dielectric medium as well as their spectral dispersion. With such experimental data set, it is possible to back calculate the dispersion of the complex refractive index of the dielectric layer. This is demonstrated using a turquoise dye doped solution. According to the Kramers-Kronig relations, the imaginary part of the refractive index for an absorbing medium is proportional to the absorption while the real part presents a large dispersion around the absorption wavelength. The reflectivity surface R(θ, λ) was measured from 500 nm to 750 nm over about 8° angular range. The whole complex refractive optical index of the doped solution, absorbing around 630 nm, was reconstructed from the SPR reflectivity experimental data, using a homemade program based on an extended Rouard method to fit the experimental angular plasmon data for each wavelength. These results show that the classical SPR technique can be extended to acquire precise spectral information about biomolecular interactions occurring on the metallic layer.
- Published
- 2010
11. Corrigendum to 'Analysis of in vivo chlorophyll fluorescence spectra to monitor physiological state of tomato plants growing under zinc stress' [J. Photochem. Photobiol. B: Biol. 101 (2010) 332–339]
- Author
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Hubertus M. von Bergmann, Najoua Derbel, Fatma Jemal, Jaouhra Cherif, Zohra Ben Lakhdar, and Mohamed Nakkach
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Radiation ,Radiological and Ultrasound Technology ,Zinc stress ,In vivo chlorophyll fluorescence ,Botany ,Biophysics ,Radiology, Nuclear Medicine and imaging ,Biology - Published
- 2011
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