A. Choukri | Ibn Tofail University (original) (raw)

Papers by A. Choukri

Research paper thumbnail of Uranium and radium activities measurements and calculation of effective doses in some drinking water samples in Morocco

International Journal of Cancer Therapy and Oncology, 2015

Purpose: As a way of prevention, we have measured the activities of uranium and radium isotopes (... more Purpose: As a way of prevention, we have measured the activities of uranium and radium isotopes (234 U, 238 U, 226 Ra, 228 Ra) for 30 drinking water samples collected from 11 wells, 9 springs (6 hot and 3 cold), 3 commercialised mineral water, and 7 tap water samples. Methods: Activities of the Ra isotopes were measured by ultra-gamma spectrometry using a low background and high efficiency well type germanium detector. The U isotopes were counted in an alpha spectrometer. Results: The measured Uranium and radium activities are similar to those published for other non-polluting regions of the world. Except in one commercialised gaseous water sample, and in two hot spring water samples, the calculated effective doses during one year are inferior to the reference level of 0.1 mSv/year recommended by the International Commission on Radiological Protection. Conclusion: These activities don't present any risk for public health in Morocco. The sparkling water of Oulmes is occasionally consumed as table water and waters of warm springs are not used as main sources of drinking water.

Research paper thumbnail of Activités de l’uranium et du radium dans des échantillons d’eau naturelle au Sahara marocain

Afrique Science: Revue Internationale des Sciences et Technologie, 2010

Dans ce travail, on donne les résultats préliminaires de mesure des activités des principaux radi... more Dans ce travail, on donne les résultats préliminaires de mesure des activités des principaux radio-isotopes de l'uranium et du radium (238 U, 234 U, 226 Ra, 228 Ra et de 228 Th) et des rapports d'activité de ces radio-isotopes (234 U/ 238 U, 228 Ra/ 226 Ra, 228 Th/ 228 Ra, 226 Ra/ 238 U) obtenus pour des échantillons d'eau de 8 puits, 5 forages, 2 sources et 3 eaux de robinet échantillonnés dans les régions des villes de Laayoune et Es-Smara au Sahara marocain. Ces échantillons d'eau naturelle proviennent de sources placées dans une région de désert riche en phosphate. Sauf pour un forage dont l'eau est non utilisée par la population, le calcul de doses équivalentes aux activités maximales pour chaque isotope montre que toutes les activités mesurées sont inférieures aux activités maximales recommandées par la Commission Internationale de Protection des Rayonnements et elles ne présentent pas de risque pour la santé de la population. Les activités et les rapports d'activité mesurés sont comparables à ceux que l'on trouve habituellement dans d'autres régions du Maroc ou du monde.

Research paper thumbnail of Determination of the Uranium Content in Some Natural Formations in Morocco by Use of Nuclear Analytical Methods

Spectroscopy Letters, 2008

ABSTRACT

Research paper thumbnail of Distribution Study of the Rare Earth Elements in Bouregreg River Sediments by Instrumental Neutron Activation Analysis

Rare earth elements (REE), define a group of fifteen chemical elements from lanthanum to lutetium... more Rare earth elements (REE), define a group of fifteen chemical elements from lanthanum to lutetium (atomic numbers 57-71) characterized by similar chemical properties. To study their distribution in sediment samples of the Bouregreg river and its tributaries, 10 sampling sites have been chosen. The collected sediment samples were analysed by instrumental neutron activation analysis (INAA) using the Orphee and Osiris reactors of CEA Saclay (France). The chondritic normalisation curves show enrichment in light rare earth elements (LREE), a negative Eu anomaly in several samples, and a progressive depletion of heavy rare earth elements (HREE). Two hypotheses are discussed: the nature of parent rocks of these sediments and the physico-chemical conditions of sedimentation especially complexation and oxydo-reduction phenomenons.

Research paper thumbnail of Improved oil treatment conditions for soft degumming

Journal of the American Oil Chemists' Society, 2001

Soft degumming" is a new physicochemical degumming process. It involves the complete elimination ... more Soft degumming" is a new physicochemical degumming process. It involves the complete elimination of phospholipids by using a chelating agent, EDTA, in the presence of an emulsifying additive. To study the optimal cost of the process, a laboratory study was undertaken to find a method based on substituting the emulsifying additive by endogenous phospholipids. The phospholipids were first extracted from the oil by an initial hot-water treatment. In a second stage, a solution containing a chelating agent was incorporated. The mixture was then vigorously stirred to form an emulsion. The degummed oil was obtained after centrifugation. A comparative study carried out on several oils provided an indication of the efficiency of this alternative procedure. The phospholipid content of the processed oils was about 5 ppm phosphorus.

Research paper thumbnail of Monte Carlo Simulation of Accident Scenario Involving the NIAR Radioactive Sources

Moscow University Physics Bulletin

Research paper thumbnail of Afrique SCIENCE 01(2) ( Impact des gisements des phosphates sur la radioactivité dans les échantillons d'eau naturelle et d'air au Maroc

Dans ce travail, on présente les résultats de mesure de la radioactivité dans un ensemble d'é... more Dans ce travail, on présente les résultats de mesure de la radioactivité dans un ensemble d'échantillons de phosphates et dans des échantillons en relation avec ces phosphates tels que l'air et l'eau. Dans les échantillons de phosphates, nous avons déterminé, à l'aide de la spectrométrie gamma utilisant un détecteur NaI(Tl) puits, les concentrations en l'uranium dans un ensemble d'échantillons bruts de phosphates marocains. Dans l'air, nous avons déterminé, à l'aide des détecteurs solides de traces nucléaires LR 115 type II, les activités volumiques du radon dans un ensemble d'habitations dans des régions riches en phosphates. Dans l'eau, nous avons mesuré les activités des principaux radio-isotopes de l'uranium (238 U et 234 U) par spectrométrie alpha et ceux du radium (226 Ra et 228 Ra) à l'aide de la spectrométrie gamma utilisant un détecteur germanium pur à haute résolution et ayant une bonne efficacité ()). Les résultats obtenus m...

Research paper thumbnail of Impact of Tube Voltage on Radiation Dose (CTDI) and Image Quality at Chest CT Examination

Atom Indonesia, 2021

During Computed Tomography (CT) scan examinations, it is important to ensure a good diagnosis by ... more During Computed Tomography (CT) scan examinations, it is important to ensure a good diagnosis by providing the maximum information to detect pathologies and this can be done with a reduced dose. In this respect, several methods of dose reduction have been studied and evaluated. This work investigates the effect of tube voltage while varying the tube current on image quality and radiation dose at Chest CT examination. This study was conducted on HITACHI CT 16 slice Scanner using two phantoms for evaluating the dose and image quality; a PMMA phantom and a CATPHAN 500. Two tube voltages of 120 KVp and 100 KVp have been used for some variation of the tube currents (mAs) and recording the values of the measured quantities (CTDIv, spatial resolution, contrast to noise ratio CNR and noise). The scanning with 100 KVp at Chest CT examination led to a reduction in CTDIv until 45 %, an increase of noise from 17 % to 45 %, and the Spatial Resolution fell slightly (6 and 7 pl/cm) compared to the 120 KVp. The CNR shows a slight regression from 11 to 22 % for the 120 KVp and 100 KVp. This study has shown that despite the increase in the image noise at low tube voltage 100 KVp, it is possible to reduce the radiation dose by up to 45 % without degradation of image quality at Chest CT examination. Further works will evaluate the effect of acquisition parameters in other CT examinations.

Research paper thumbnail of Influence of Uranium Post-Incorporation on the Fossil Mollusk Shell Age Rejuvenation Application to the Study of the Marine Level Variation in the Past

We discuss two models based on episodic and continual uranium migration into mollusk shells after... more We discuss two models based on episodic and continual uranium migration into mollusk shells after death and give a relationship between the apparent and real ages. For the episodic model, we discuss this relationship according to the uranium post-incorporation rate, the initial 234 U/ 238 U activity ratio and the time of incorporation. We test both models on some of mollusk shells taken from four fossil marine shorelines on the Atlantic coast of the Moroccan High Atlas assumed formed during the last interglacial stage about 122 000 years ago. We try to draw a general conclusion concerning the unreliability of mollusk shell samples for uranium series dating.

Research paper thumbnail of Mise en evidence, sur la cote recifale d'Egypte, d'une regression interrompant brievement le plus haut niveau du dernier interglaciaire (5e); un nouvel indice de variations glacio-eustatiques a haute frequence au Pleistocene?

Bulletin De La Societe Geologique De France, 1998

In the most stable localities of the NW Red Sea-Gulf of Suez, the Last Interglacial shore deposit... more In the most stable localities of the NW Red Sea-Gulf of Suez, the Last Interglacial shore deposits have been dated (alpha Th/U) and give evidence of a two-stages 5.5 (5e)+8/5 m transgression subdivided by a 10 m (at least) relative sea-level fall. The respective ages of the initial reef and beach unit and about 3 m lower bay-lagoon-gypsum salina deposits are not discriminable with the available dating method. This high-frequency oscillation during 5.5 highstand would be tentatively interpreted as a glacio-eustatic sea-level fall coinciding with the 5.52 event of delta 18 ?O isotopic terminology.

Research paper thumbnail of MEASURE OF ACTIVITIES AND ACTIVITY RATIOS OF U AND Ra RADIO-ISOTOPES IN SOME NATURAL WATER SAMPLES IN THE WESTERN SAHARA AT THE SUD OF MOROCCO

The preliminary results of 238 U, 234 U, 226 Ra, 228 Ra and 228 Th activities and of 234 U/ 238 U... more The preliminary results of 238 U, 234 U, 226 Ra, 228 Ra and 228 Th activities and of 234 U/ 238 U, 228 Ra/ 226 Ra, 228 Th/ 228 Ra and 226 Ra/ 238 U activity ratios obtained for 8 wells, 5 drillings, 2 springs and 3 tap water samples collected in Laayoune and Es-Smara regions in the Moroccan Sahara are given in this work. The analyzed natural water samples have been collected from sources situated in a desert region rich in phosphates. Except for the one water drilling sample no used by population, the calculation of equivalent doses to the maximal activities for each isotope show that all measured activities are inferior to the maximum contaminant levels recommended by the International Commission of Radioprotection and they don't present any risk for population health.

Research paper thumbnail of Monte Carlo Simulation of the Dose Rate Distribution of a Moroccan Panoramic Gamma Irradiator Using the MCNPX Code

Moscow University Physics Bulletin, 2020

Gamma irradiation technology plays a very important role in the development of agriculture, due t... more Gamma irradiation technology plays a very important role in the development of agriculture, due to its various advantages, such as the inhibition of germination, the appearance of new varieties, preservation...etc. To properly control and characterize irradiation operations, the dose rate distribution in the irradiation cells must be well controlled, The Monte-Carlo method was used for experiments the high cost to map the dose rate distribution in the irradiation cell each time, and to its precise dosimetric calculation. In this study the MCNPX code was used to simulate the irradiation cell of the National Institute of Agricultural Research (NIAR) of Tangier Morocco, the validation of the latter was based on a comparative assessment between the dose rates absorbed in the area calculated by MCNPX (Gy/min) and those measured values by alanine dosimeters. The comparative results showed a good agreement between the experiment and the simulation

Research paper thumbnail of Natural radionuclides (NORM) in a Moroccan river affected by former conventional metal mining activities

Journal of Sustainable Mining, 2019

The main aim of this work was to determine the levels of multiple natural radionuclides in an aqu... more The main aim of this work was to determine the levels of multiple natural radionuclides in an aquatic system (Moulouya river, Morocco) impacted by multiple abandoned Zinc and Lead mines. 238 U, 234 U, 232 Th, 230 Th and 210 Po were determined by alpha-particle spectrometry in water and sediment samples collected along the river and in samples from three pit lakes of abandoned mines, located in the Upper Moulouya catchment area. The results enabled the analysis of the different levels of impact of former mining activities, depending on the natural radionuclides. While the activity concentration of U-isotopes in Moulouya river water was slightly elevated in the vicinity of abandoned mine wastes, other natural radionuclides (Th-isotopes and 210 Po) levels were typical of a natural environment. This fact is clearly reflected in the magnitude and range observed in the distribution coefficients for the different radionuclides analyzed.

Research paper thumbnail of Physicians Knowledge of Radiation Risk in Prescribing CT Imaging in Moroccan Hospitals

British Journal of Applied Science & Technology, 2017

Aims: This study aims to assess physicians' knowledge on patients' radiation protection during th... more Aims: This study aims to assess physicians' knowledge on patients' radiation protection during their computed tomography (CT) scan prescriptions. Materials and Methods: A standardized questionnaire in multiple-choice format consisted of four sections with a total of eight questions based on the literature review. A total of 153 (59%) completed questionnaires were returned from six different hospitals in Morocco. Results: Only 38% of prescribers took into account the ratio benefit/risk related to x-rays. Just 10% of doctors explained the risk related to x-rays to the patients. One out of four physicians has Original Research Article

Research paper thumbnail of Impact des gisements des phosphates sur la radioactivité dans les échantillons d’eau naturelle et d’air au Marocag

Afrique Science: Revue Internationale des Sciences et Technologie, 2010

Impact of the phosphate layers on the radioactivity in the natural water samples and air in Moroc... more Impact of the phosphate layers on the radioactivity in the natural water samples and air in Morocco In this work, we present the results of radioactivity measurements in some samples of phosphate deposits and in samples in interaction with these phosphate deposits such air and water. In phosphate samples, we have determined with gamma spectrometry using a well NaI(Tl) detector, concentrations of uranium in some samples of unrefined Moroccan phosphates. In air, we have measured, with nuclear solid track detector LR 115 type II, the volumic activity of 222 Rn in some dwellings situated in phosphate areas. In water, we have measured activities of uranium and radium radio-isotopes (234 U, 238 U) with alpha spectrometry and those of radium (226 Ra, 228 Ra) with gamma spectrometry using a 220 cm 3 low-background well type gamma ray detector in the

Research paper thumbnail of Radiochemical data obtained by spectrometry on unrecrystallized fossil coral samples from the Egyptian shoreline of the north-western Red Sea

Radiation Measurements, 2007

In this work, radiochemical results obtained by spectrometry on 80 unrecrystallized fossil coral ... more In this work, radiochemical results obtained by spectrometry on 80 unrecrystallized fossil coral samples from the Egyptian shoreline of the northwestern Red Sea are presented and discussed. The coral samples were collected in Egypt from the emerged 5e coral reef terraces over 500 km from The Ras Gharib-Ras Shukeir depression (28 • 10) in the north to Wadi Lahami (north of Ras Banas, 24 • 10) in the south. The statistical description of radiochemical results (concentrations of U and Th radioisotopes, 234 U/ 238 U activity ratios and ages) obtained on a great number of coral samples showed that it is possible to establish methodological criterions which could be used to validate the measured ages before confronting them to the geological context of sampling sites. The obtained results confirm that the unrecrystallized corals (232 Th < 3%) constitute the reliable means of determining the timing of Pleistocene sea-level fluctuations in the past. A few number of measured younger ages could be explain as a result of a rejuvenation due to latter addition of a "younger" uranium to the initial stock entered just after coral death. The obvious rejuvenation observed and confirmed is due to a recent cementation of aragonitic deposit on the fossil coral. 238 U varies between 2.2 and 4.9 ppm around an average of 3.18 ± 0.65 ppm. 234 U/ 238 U activity ratios are between 1.08 and 1.28 with an averaged value of 1.164 ± 0.016 which exceeds that of present day sea water but which is in agreement with the ratio of 1.16 measured by a precise mass spectrometry in many Pleistocene coral samples. Except three samples dated at least 100 ka, the radiochemical age of 5e coral samples vary between 108 and 131 ka with an average value of 122.2 ka and a standard deviation of 4.3 ka. Except for samples from the Zeit area, the reef terrace is between 2 and 6 m above the present sea level. This position is similar to the highest sea level from the last interglacial according to the glacio-isostatic rebound calculated for stable regions. This work proves that the large tectonic motions which affected the studied area after the Oligocene ceased after at least the last interglacial period.

Research paper thumbnail of The Quaternary Deposits of Morocco

Lecture Notes in Earth Sciences

... Reddad ben Ali Fm. Dar Bou Azza Fm. Ouljian Aïn Roummana Bir Feghloul ... The slightly older,... more ... Reddad ben Ali Fm. Dar Bou Azza Fm. Ouljian Aïn Roummana Bir Feghloul ... The slightly older, sixth high sea level deposit stands at 22m asl, and displays a relatively cool malacofauna (Nucella lapillus, Littorina littorea, typical for the present-day French-Cantabric province). ...

Research paper thumbnail of A statistical study of 238U and 234U/238U distributions in coral samples from the Egyptian shoreline of the north-western Red Sea and in fossil mollusk shells from the Atlantic coast of High Atlas in Morocco: Implications for 230Th/234U dating

Radiochimica Acta, 2002

SummaryIn this work, radiochemical analysis results of 126 unrecrystallized coral samples from th... more SummaryIn this work, radiochemical analysis results of 126 unrecrystallized coral samples from the Egyptian shoreline of northwestern Red Sea and 120 fossil mollusk shell samples from the Atlantic coast of Moroccan High Atlas at the North of Agadir City in Morocco are presented and discussed. The coral samples were collected in Egypt from the emerged coral reef terraces over 500 km from The Ras Gharib-Ras Shukeir depression (28°10') in the north to Wadi Lahami (north of Ras Banas,…

Research paper thumbnail of Diagenetic rejuvenation of raised coral reefs and precision of dating. The contribution of the Red Sea reefs to the question of reliability of the Uranium-series datings of middle to late Pleistocene key reef-terraces of the world

Carnets de géologie (Notebooks on geology), 2008

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of Difficultés de datation des niveaux marins pléistocènes à l'aide de coquilles de mollusques fossiles : cas du niveau ouljien sur la côte du Haut Atlas au Maroc

Carnets de géologie (Notebooks on geology), 2011

Afin de comprendre la difficulté de datation des niveaux marins à l'aide des échantillons de coqu... more Afin de comprendre la difficulté de datation des niveaux marins à l'aide des échantillons de coquilles de mollusques et d'essayer d'établir des outils méthodologiques pouvant aider à juger de la validité d'un âge 230 Th / 234 U, nous confrontons 80 analyses radiochimiques d'échantillons de coquilles de mollusques prélevés dans des plages marines fossiles situées entre 4 et 8 m par rapport au niveau de l'eau actuel. les niveaux où ont été faits les prélèvements, analogues à ceux de la côte égyptienne de la Mer Rouge, sont sensés appartenir au stade climatique 5e daté à 122 ka environ. On note que les âges obtenus sont souvent rajeunis indépendamment du site, du taux de calcite, de la teneur en uranium et du rapport 234 U/ 238 U. Contrairement aux échantillons de coraux, le critère minéralogique ne peut pas être utilisé pour choisir les échantillons non recristallisés, certaines coquilles de mollusques actuelles sont en aragonite, d'autres sont en calcite et d'autres contiennent les deux formes sans que les rapports de proportion en soient encore bien connus. Devant cette situation, nous avons multiplié les analyses sur des échantillons de coquilles de mollusques appartenant à plusieurs espèces prélevés aux mêmes endroits afin de comprendre le scénario de rajeunissement des âges et d'essayer d'établir éventuellement des critères méthodologiques pouvant nous renseigner sur la validité de l'âge calculé. Des scénarios sur le mode d'incorporation de l'uranium et son rôle dans le rajeunissement de l'âge ont été également imaginés et discutés.

Research paper thumbnail of Uranium and radium activities measurements and calculation of effective doses in some drinking water samples in Morocco

International Journal of Cancer Therapy and Oncology, 2015

Purpose: As a way of prevention, we have measured the activities of uranium and radium isotopes (... more Purpose: As a way of prevention, we have measured the activities of uranium and radium isotopes (234 U, 238 U, 226 Ra, 228 Ra) for 30 drinking water samples collected from 11 wells, 9 springs (6 hot and 3 cold), 3 commercialised mineral water, and 7 tap water samples. Methods: Activities of the Ra isotopes were measured by ultra-gamma spectrometry using a low background and high efficiency well type germanium detector. The U isotopes were counted in an alpha spectrometer. Results: The measured Uranium and radium activities are similar to those published for other non-polluting regions of the world. Except in one commercialised gaseous water sample, and in two hot spring water samples, the calculated effective doses during one year are inferior to the reference level of 0.1 mSv/year recommended by the International Commission on Radiological Protection. Conclusion: These activities don't present any risk for public health in Morocco. The sparkling water of Oulmes is occasionally consumed as table water and waters of warm springs are not used as main sources of drinking water.

Research paper thumbnail of Activités de l’uranium et du radium dans des échantillons d’eau naturelle au Sahara marocain

Afrique Science: Revue Internationale des Sciences et Technologie, 2010

Dans ce travail, on donne les résultats préliminaires de mesure des activités des principaux radi... more Dans ce travail, on donne les résultats préliminaires de mesure des activités des principaux radio-isotopes de l'uranium et du radium (238 U, 234 U, 226 Ra, 228 Ra et de 228 Th) et des rapports d'activité de ces radio-isotopes (234 U/ 238 U, 228 Ra/ 226 Ra, 228 Th/ 228 Ra, 226 Ra/ 238 U) obtenus pour des échantillons d'eau de 8 puits, 5 forages, 2 sources et 3 eaux de robinet échantillonnés dans les régions des villes de Laayoune et Es-Smara au Sahara marocain. Ces échantillons d'eau naturelle proviennent de sources placées dans une région de désert riche en phosphate. Sauf pour un forage dont l'eau est non utilisée par la population, le calcul de doses équivalentes aux activités maximales pour chaque isotope montre que toutes les activités mesurées sont inférieures aux activités maximales recommandées par la Commission Internationale de Protection des Rayonnements et elles ne présentent pas de risque pour la santé de la population. Les activités et les rapports d'activité mesurés sont comparables à ceux que l'on trouve habituellement dans d'autres régions du Maroc ou du monde.

Research paper thumbnail of Determination of the Uranium Content in Some Natural Formations in Morocco by Use of Nuclear Analytical Methods

Spectroscopy Letters, 2008

ABSTRACT

Research paper thumbnail of Distribution Study of the Rare Earth Elements in Bouregreg River Sediments by Instrumental Neutron Activation Analysis

Rare earth elements (REE), define a group of fifteen chemical elements from lanthanum to lutetium... more Rare earth elements (REE), define a group of fifteen chemical elements from lanthanum to lutetium (atomic numbers 57-71) characterized by similar chemical properties. To study their distribution in sediment samples of the Bouregreg river and its tributaries, 10 sampling sites have been chosen. The collected sediment samples were analysed by instrumental neutron activation analysis (INAA) using the Orphee and Osiris reactors of CEA Saclay (France). The chondritic normalisation curves show enrichment in light rare earth elements (LREE), a negative Eu anomaly in several samples, and a progressive depletion of heavy rare earth elements (HREE). Two hypotheses are discussed: the nature of parent rocks of these sediments and the physico-chemical conditions of sedimentation especially complexation and oxydo-reduction phenomenons.

Research paper thumbnail of Improved oil treatment conditions for soft degumming

Journal of the American Oil Chemists' Society, 2001

Soft degumming" is a new physicochemical degumming process. It involves the complete elimination ... more Soft degumming" is a new physicochemical degumming process. It involves the complete elimination of phospholipids by using a chelating agent, EDTA, in the presence of an emulsifying additive. To study the optimal cost of the process, a laboratory study was undertaken to find a method based on substituting the emulsifying additive by endogenous phospholipids. The phospholipids were first extracted from the oil by an initial hot-water treatment. In a second stage, a solution containing a chelating agent was incorporated. The mixture was then vigorously stirred to form an emulsion. The degummed oil was obtained after centrifugation. A comparative study carried out on several oils provided an indication of the efficiency of this alternative procedure. The phospholipid content of the processed oils was about 5 ppm phosphorus.

Research paper thumbnail of Monte Carlo Simulation of Accident Scenario Involving the NIAR Radioactive Sources

Moscow University Physics Bulletin

Research paper thumbnail of Afrique SCIENCE 01(2) ( Impact des gisements des phosphates sur la radioactivité dans les échantillons d'eau naturelle et d'air au Maroc

Dans ce travail, on présente les résultats de mesure de la radioactivité dans un ensemble d'é... more Dans ce travail, on présente les résultats de mesure de la radioactivité dans un ensemble d'échantillons de phosphates et dans des échantillons en relation avec ces phosphates tels que l'air et l'eau. Dans les échantillons de phosphates, nous avons déterminé, à l'aide de la spectrométrie gamma utilisant un détecteur NaI(Tl) puits, les concentrations en l'uranium dans un ensemble d'échantillons bruts de phosphates marocains. Dans l'air, nous avons déterminé, à l'aide des détecteurs solides de traces nucléaires LR 115 type II, les activités volumiques du radon dans un ensemble d'habitations dans des régions riches en phosphates. Dans l'eau, nous avons mesuré les activités des principaux radio-isotopes de l'uranium (238 U et 234 U) par spectrométrie alpha et ceux du radium (226 Ra et 228 Ra) à l'aide de la spectrométrie gamma utilisant un détecteur germanium pur à haute résolution et ayant une bonne efficacité ()). Les résultats obtenus m...

Research paper thumbnail of Impact of Tube Voltage on Radiation Dose (CTDI) and Image Quality at Chest CT Examination

Atom Indonesia, 2021

During Computed Tomography (CT) scan examinations, it is important to ensure a good diagnosis by ... more During Computed Tomography (CT) scan examinations, it is important to ensure a good diagnosis by providing the maximum information to detect pathologies and this can be done with a reduced dose. In this respect, several methods of dose reduction have been studied and evaluated. This work investigates the effect of tube voltage while varying the tube current on image quality and radiation dose at Chest CT examination. This study was conducted on HITACHI CT 16 slice Scanner using two phantoms for evaluating the dose and image quality; a PMMA phantom and a CATPHAN 500. Two tube voltages of 120 KVp and 100 KVp have been used for some variation of the tube currents (mAs) and recording the values of the measured quantities (CTDIv, spatial resolution, contrast to noise ratio CNR and noise). The scanning with 100 KVp at Chest CT examination led to a reduction in CTDIv until 45 %, an increase of noise from 17 % to 45 %, and the Spatial Resolution fell slightly (6 and 7 pl/cm) compared to the 120 KVp. The CNR shows a slight regression from 11 to 22 % for the 120 KVp and 100 KVp. This study has shown that despite the increase in the image noise at low tube voltage 100 KVp, it is possible to reduce the radiation dose by up to 45 % without degradation of image quality at Chest CT examination. Further works will evaluate the effect of acquisition parameters in other CT examinations.

Research paper thumbnail of Influence of Uranium Post-Incorporation on the Fossil Mollusk Shell Age Rejuvenation Application to the Study of the Marine Level Variation in the Past

We discuss two models based on episodic and continual uranium migration into mollusk shells after... more We discuss two models based on episodic and continual uranium migration into mollusk shells after death and give a relationship between the apparent and real ages. For the episodic model, we discuss this relationship according to the uranium post-incorporation rate, the initial 234 U/ 238 U activity ratio and the time of incorporation. We test both models on some of mollusk shells taken from four fossil marine shorelines on the Atlantic coast of the Moroccan High Atlas assumed formed during the last interglacial stage about 122 000 years ago. We try to draw a general conclusion concerning the unreliability of mollusk shell samples for uranium series dating.

Research paper thumbnail of Mise en evidence, sur la cote recifale d'Egypte, d'une regression interrompant brievement le plus haut niveau du dernier interglaciaire (5e); un nouvel indice de variations glacio-eustatiques a haute frequence au Pleistocene?

Bulletin De La Societe Geologique De France, 1998

In the most stable localities of the NW Red Sea-Gulf of Suez, the Last Interglacial shore deposit... more In the most stable localities of the NW Red Sea-Gulf of Suez, the Last Interglacial shore deposits have been dated (alpha Th/U) and give evidence of a two-stages 5.5 (5e)+8/5 m transgression subdivided by a 10 m (at least) relative sea-level fall. The respective ages of the initial reef and beach unit and about 3 m lower bay-lagoon-gypsum salina deposits are not discriminable with the available dating method. This high-frequency oscillation during 5.5 highstand would be tentatively interpreted as a glacio-eustatic sea-level fall coinciding with the 5.52 event of delta 18 ?O isotopic terminology.

Research paper thumbnail of MEASURE OF ACTIVITIES AND ACTIVITY RATIOS OF U AND Ra RADIO-ISOTOPES IN SOME NATURAL WATER SAMPLES IN THE WESTERN SAHARA AT THE SUD OF MOROCCO

The preliminary results of 238 U, 234 U, 226 Ra, 228 Ra and 228 Th activities and of 234 U/ 238 U... more The preliminary results of 238 U, 234 U, 226 Ra, 228 Ra and 228 Th activities and of 234 U/ 238 U, 228 Ra/ 226 Ra, 228 Th/ 228 Ra and 226 Ra/ 238 U activity ratios obtained for 8 wells, 5 drillings, 2 springs and 3 tap water samples collected in Laayoune and Es-Smara regions in the Moroccan Sahara are given in this work. The analyzed natural water samples have been collected from sources situated in a desert region rich in phosphates. Except for the one water drilling sample no used by population, the calculation of equivalent doses to the maximal activities for each isotope show that all measured activities are inferior to the maximum contaminant levels recommended by the International Commission of Radioprotection and they don't present any risk for population health.

Research paper thumbnail of Monte Carlo Simulation of the Dose Rate Distribution of a Moroccan Panoramic Gamma Irradiator Using the MCNPX Code

Moscow University Physics Bulletin, 2020

Gamma irradiation technology plays a very important role in the development of agriculture, due t... more Gamma irradiation technology plays a very important role in the development of agriculture, due to its various advantages, such as the inhibition of germination, the appearance of new varieties, preservation...etc. To properly control and characterize irradiation operations, the dose rate distribution in the irradiation cells must be well controlled, The Monte-Carlo method was used for experiments the high cost to map the dose rate distribution in the irradiation cell each time, and to its precise dosimetric calculation. In this study the MCNPX code was used to simulate the irradiation cell of the National Institute of Agricultural Research (NIAR) of Tangier Morocco, the validation of the latter was based on a comparative assessment between the dose rates absorbed in the area calculated by MCNPX (Gy/min) and those measured values by alanine dosimeters. The comparative results showed a good agreement between the experiment and the simulation

Research paper thumbnail of Natural radionuclides (NORM) in a Moroccan river affected by former conventional metal mining activities

Journal of Sustainable Mining, 2019

The main aim of this work was to determine the levels of multiple natural radionuclides in an aqu... more The main aim of this work was to determine the levels of multiple natural radionuclides in an aquatic system (Moulouya river, Morocco) impacted by multiple abandoned Zinc and Lead mines. 238 U, 234 U, 232 Th, 230 Th and 210 Po were determined by alpha-particle spectrometry in water and sediment samples collected along the river and in samples from three pit lakes of abandoned mines, located in the Upper Moulouya catchment area. The results enabled the analysis of the different levels of impact of former mining activities, depending on the natural radionuclides. While the activity concentration of U-isotopes in Moulouya river water was slightly elevated in the vicinity of abandoned mine wastes, other natural radionuclides (Th-isotopes and 210 Po) levels were typical of a natural environment. This fact is clearly reflected in the magnitude and range observed in the distribution coefficients for the different radionuclides analyzed.

Research paper thumbnail of Physicians Knowledge of Radiation Risk in Prescribing CT Imaging in Moroccan Hospitals

British Journal of Applied Science & Technology, 2017

Aims: This study aims to assess physicians' knowledge on patients' radiation protection during th... more Aims: This study aims to assess physicians' knowledge on patients' radiation protection during their computed tomography (CT) scan prescriptions. Materials and Methods: A standardized questionnaire in multiple-choice format consisted of four sections with a total of eight questions based on the literature review. A total of 153 (59%) completed questionnaires were returned from six different hospitals in Morocco. Results: Only 38% of prescribers took into account the ratio benefit/risk related to x-rays. Just 10% of doctors explained the risk related to x-rays to the patients. One out of four physicians has Original Research Article

Research paper thumbnail of Impact des gisements des phosphates sur la radioactivité dans les échantillons d’eau naturelle et d’air au Marocag

Afrique Science: Revue Internationale des Sciences et Technologie, 2010

Impact of the phosphate layers on the radioactivity in the natural water samples and air in Moroc... more Impact of the phosphate layers on the radioactivity in the natural water samples and air in Morocco In this work, we present the results of radioactivity measurements in some samples of phosphate deposits and in samples in interaction with these phosphate deposits such air and water. In phosphate samples, we have determined with gamma spectrometry using a well NaI(Tl) detector, concentrations of uranium in some samples of unrefined Moroccan phosphates. In air, we have measured, with nuclear solid track detector LR 115 type II, the volumic activity of 222 Rn in some dwellings situated in phosphate areas. In water, we have measured activities of uranium and radium radio-isotopes (234 U, 238 U) with alpha spectrometry and those of radium (226 Ra, 228 Ra) with gamma spectrometry using a 220 cm 3 low-background well type gamma ray detector in the

Research paper thumbnail of Radiochemical data obtained by spectrometry on unrecrystallized fossil coral samples from the Egyptian shoreline of the north-western Red Sea

Radiation Measurements, 2007

In this work, radiochemical results obtained by spectrometry on 80 unrecrystallized fossil coral ... more In this work, radiochemical results obtained by spectrometry on 80 unrecrystallized fossil coral samples from the Egyptian shoreline of the northwestern Red Sea are presented and discussed. The coral samples were collected in Egypt from the emerged 5e coral reef terraces over 500 km from The Ras Gharib-Ras Shukeir depression (28 • 10) in the north to Wadi Lahami (north of Ras Banas, 24 • 10) in the south. The statistical description of radiochemical results (concentrations of U and Th radioisotopes, 234 U/ 238 U activity ratios and ages) obtained on a great number of coral samples showed that it is possible to establish methodological criterions which could be used to validate the measured ages before confronting them to the geological context of sampling sites. The obtained results confirm that the unrecrystallized corals (232 Th < 3%) constitute the reliable means of determining the timing of Pleistocene sea-level fluctuations in the past. A few number of measured younger ages could be explain as a result of a rejuvenation due to latter addition of a "younger" uranium to the initial stock entered just after coral death. The obvious rejuvenation observed and confirmed is due to a recent cementation of aragonitic deposit on the fossil coral. 238 U varies between 2.2 and 4.9 ppm around an average of 3.18 ± 0.65 ppm. 234 U/ 238 U activity ratios are between 1.08 and 1.28 with an averaged value of 1.164 ± 0.016 which exceeds that of present day sea water but which is in agreement with the ratio of 1.16 measured by a precise mass spectrometry in many Pleistocene coral samples. Except three samples dated at least 100 ka, the radiochemical age of 5e coral samples vary between 108 and 131 ka with an average value of 122.2 ka and a standard deviation of 4.3 ka. Except for samples from the Zeit area, the reef terrace is between 2 and 6 m above the present sea level. This position is similar to the highest sea level from the last interglacial according to the glacio-isostatic rebound calculated for stable regions. This work proves that the large tectonic motions which affected the studied area after the Oligocene ceased after at least the last interglacial period.

Research paper thumbnail of The Quaternary Deposits of Morocco

Lecture Notes in Earth Sciences

... Reddad ben Ali Fm. Dar Bou Azza Fm. Ouljian Aïn Roummana Bir Feghloul ... The slightly older,... more ... Reddad ben Ali Fm. Dar Bou Azza Fm. Ouljian Aïn Roummana Bir Feghloul ... The slightly older, sixth high sea level deposit stands at 22m asl, and displays a relatively cool malacofauna (Nucella lapillus, Littorina littorea, typical for the present-day French-Cantabric province). ...

Research paper thumbnail of A statistical study of 238U and 234U/238U distributions in coral samples from the Egyptian shoreline of the north-western Red Sea and in fossil mollusk shells from the Atlantic coast of High Atlas in Morocco: Implications for 230Th/234U dating

Radiochimica Acta, 2002

SummaryIn this work, radiochemical analysis results of 126 unrecrystallized coral samples from th... more SummaryIn this work, radiochemical analysis results of 126 unrecrystallized coral samples from the Egyptian shoreline of northwestern Red Sea and 120 fossil mollusk shell samples from the Atlantic coast of Moroccan High Atlas at the North of Agadir City in Morocco are presented and discussed. The coral samples were collected in Egypt from the emerged coral reef terraces over 500 km from The Ras Gharib-Ras Shukeir depression (28°10') in the north to Wadi Lahami (north of Ras Banas,…

Research paper thumbnail of Diagenetic rejuvenation of raised coral reefs and precision of dating. The contribution of the Red Sea reefs to the question of reliability of the Uranium-series datings of middle to late Pleistocene key reef-terraces of the world

Carnets de géologie (Notebooks on geology), 2008

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Research paper thumbnail of Difficultés de datation des niveaux marins pléistocènes à l'aide de coquilles de mollusques fossiles : cas du niveau ouljien sur la côte du Haut Atlas au Maroc

Carnets de géologie (Notebooks on geology), 2011

Afin de comprendre la difficulté de datation des niveaux marins à l'aide des échantillons de coqu... more Afin de comprendre la difficulté de datation des niveaux marins à l'aide des échantillons de coquilles de mollusques et d'essayer d'établir des outils méthodologiques pouvant aider à juger de la validité d'un âge 230 Th / 234 U, nous confrontons 80 analyses radiochimiques d'échantillons de coquilles de mollusques prélevés dans des plages marines fossiles situées entre 4 et 8 m par rapport au niveau de l'eau actuel. les niveaux où ont été faits les prélèvements, analogues à ceux de la côte égyptienne de la Mer Rouge, sont sensés appartenir au stade climatique 5e daté à 122 ka environ. On note que les âges obtenus sont souvent rajeunis indépendamment du site, du taux de calcite, de la teneur en uranium et du rapport 234 U/ 238 U. Contrairement aux échantillons de coraux, le critère minéralogique ne peut pas être utilisé pour choisir les échantillons non recristallisés, certaines coquilles de mollusques actuelles sont en aragonite, d'autres sont en calcite et d'autres contiennent les deux formes sans que les rapports de proportion en soient encore bien connus. Devant cette situation, nous avons multiplié les analyses sur des échantillons de coquilles de mollusques appartenant à plusieurs espèces prélevés aux mêmes endroits afin de comprendre le scénario de rajeunissement des âges et d'essayer d'établir éventuellement des critères méthodologiques pouvant nous renseigner sur la validité de l'âge calculé. Des scénarios sur le mode d'incorporation de l'uranium et son rôle dans le rajeunissement de l'âge ont été également imaginés et discutés.