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Performing an ab initio analysis, we inspect the effect of magnesium vacancies and hydrogen doping on the magnesium hydride (MgH2). The Korringa – Kohn – Rostoker method integrated with the coherent potential approximation is used to perform our calculations. In particular, we find that the gravimetric capacity of MgH2 increases from 7.658 to 9.816 wt% when the concentrations of magnesium vacancies and hydrogen dopant atoms increase from 0 to 10%. Concretely, the results reveal that the magnesium vacancies and the hydrogen doping have a beneficial effect on the hydrogen storage properties of the hydride by decreasing its desorption temperature and stability. This decrease can be explained on the one hand by the diminution of the number of Mg atoms that establish strong bonds with H atoms, and on the other hand by using the density of states, which indicates that when the concentrations increase, the Mg and H states shift to the conduction band. We also obtain that the value of the desorption temperature can be controlled by varying the concentrations of magnesium vacancies and hydrogen dopant atoms from 4.2 to 5.8% in order to reach the optimum range 289–393 K for the practical use of fuel cell vehicles.

The aim of this work is the improvement of the desorption temperature and kinetic properties in MgH 2 by magnesium vacancy defects V Mg . We use the Korringa – Kohn - Rostoker (KKR) calculation combined with the coherent potential approximation (CPA) in this work. In particular, we find that the formation energy increases with the increasing V Mg concentration and, vice versa, for the desorption temperature in MgH 2 . We also find that the magnesium vacancy defects have an effect on the gravimetric hydrogen capacity by making the magnesium hydride more lightweight. Moreover, the densities of states (DOS) indicate that the stability of MgH 2 decreases with the increasing V Mg concentration by shifting the Mg and H states to the conduction band (CB). In particular, we observe that it is difficult, after ∼4.8%, to storage the hydrogen into the system without cooling, because the desorption temperature becomes less than 0 °C. We also find that the optimal V Mg concentration for the hydrogen vehicles is about 3.7% because its desorption temperature is close to the operating temperature of most modern vehicle engines.

COVID-19 pandemic is an obstacle for all health systems, especially in African countries. This paper shows how plastic surgery teams can adapt human resources and an efficient approach to provide the best care to our patients in this troubled time.

Nutrition in burns is a separate entity and an integral part of treatment. The internal route should be favored because several studies report on its effectiveness and the benefits it brings: it preserves the secretion of gastrin, preserves intestinal motility, it prevents intestinal damage of the Ischemia-reperfusion type, increases intestinal permeability, it decreases the secretion of endotoxins and mediators of inflammation, and keeps the mucous barrier functional. The main objective of our study was to assess the nutritional needs and intakes of the patients taken care of within our resuscitation of burns, both quantitatively and qualitatively then to draw recommendations for improving their supported. We included 60 burned patients in our study. We included 60 burned patients in our study. All of our patients had a SCB greater than 20% at admission. The average interval between burns and the start of feeding is 1 day and 6 hours post burn. The enteral route is the route of choice in our series with 96% of patients being fed orally. Nutritional requirements are calculated using formulas recommended by the ESPN guide. The calculated needs are greater than the contributions actually received, especially during the first 3 days after burning. The overall consumption of ingestants is reduced in children while normal consumption is found in adults. Adults eat nutrients fairly orally, while children eat less meat and starch, and prefer dairy products and easy-to-drink fluid solutions. Most patients required supplementation such as powder and liquid solution in order to arrive as needed calculated. 70% of our patients presented with digestive intolerance which was based on nausea, loss of appetite and transit disorder a type of constipation. Weight losses of up to 15% of the initial weight have been observed in our series in both adults and children. It is very difficult for severe burns to provide enough calories orally, especially during the acute burn phase.

Gynecomastia is an enlarged breast in men, unilateral or bilateral caused by an imbalance of the hormones estrogen and testosterone. Most often idiopathic and peripubertal, it nevertheless justifies a complete etiological assessment to rule out endocrinopathy or a malignant etiology, before considering surgical treatment in the absence of response to medical treatment or spontaneous regression. In this article the authors report a case of persistent gynecomastia in a small child of two years and a half followed in pediatric consultation and the plastic surgery department at the University Hospital Mohamed VI Marrakech (Morocco).

Double substituted MgH2 sorption kinetic is studied by combining density functional theory (DFT) and Kinetic Monte Carlo (KMC) simulations. The DFT calculations were performed to compute the energy barriers of the relevant elementary processes, which will be used as a database for the KMC simulations. The study provides a discussion of the mechanism behind the hydrogen reaction path on magnesium hydride (adsorption, dissociation, surface migration, penetration, and diffusion) as we took into account the density distribution of hydrogen atoms as well as the filling ratios, the diffusion time and finally the temperature. Based on the obtained results, the double substitution not only improves MgH2 stability and desorption temperature but also its adsorption and desorption kinetics. Among the studied systems Mg14ZnLiH32 exhibits the best results with the fastest ab/desorption kinetic, in addition to its ideal heat of formation ΔH=-38.27 kJ/mol and high gravimetric capacity 7.25 wt%.

Verneuil\\\'s disease is a chronic fistulating, sclerosing and scar-forming suppuration. Its diagnosis is often misunderstood and therefore mistaken for another pathology. Through the analysis of 13 observations of Verneuil\\\'s disease, we wanted to take stock of the clinical diagnosis, the ethiopathogenesis and the therapeutic principles of this disease. Descriptive retrospective study including all hospitalized patients in the plastic surgery department of CHU Mohammed VI in Marrakech Morocco for a Verneuil?s disease, from January 2009 to December 2015. The characteristics of the disease and the therapeutic proposal were analyzed and the effectiveness and satisfaction of the surgical treatment evaluated. In 6 years, 13 patients (10 men and 3 women) with an average age of 43.8 years were hospitalized in our department. Smoking was present in six of our patients ie 46% of our active smoking-type patients with an average of 31.1 years packs. The mean age of onset of the disease for women was 24.2 years and 30.6 years for men. The average diagnosis time for the disease was 9.32 years with extremes of 2 months and 43 years, the diagnosis was carried by a dermatologist in the majority of cases. The average body mass index value of patients in our series is 25.78 kg / m2 with extreme values of 20.2 and 31.1 kg / m?, which corresponds to an overweight. The most common localization is axillary localization followed by gluteal localization. Hurley\\\'s score varied between 3 grades with a predominance of grade 3 for the 34 territories reached for our 13 patients. Two of our patients had ulcerated-budding lesions with irregular edges on scar placards, in whom the cutaneous biopsy demonstrated a squamous cell carcinoma. Eleven patients had a total lesion excision, unlike partial excision, which has never been performed for any of these patients. Two patients underwent carcinological tumor excision with lymph node dissection for squamous cell carcinoma. The type of cover that has been most used in this series is the direct suture. Skin transplantation by thin skin was performed for 7 territories in 6 patients with a delay of 3.5 months, with extreme values of 2 and 6 months. The territories where the skin graft was carried out are the gluteus territory to the number of 4 and the axillary territory to the number of 3. The directed healing was carried out for the two patients who benefited from a carcinological excision. The complications found in our patients 1 cases of haemorrhage, 1 case of perioperative recurrence, 1 case of sequellar bridle, 2 cases of hypertrophic scar, 2 cases of persistent pain. The satisfaction of the surgical treatment could be evaluated in postoperative with a follow-up of more than 9 months in 7 patients who are satisfied with the surgical treatment. At a time, when new molecules have been developed and studied for the treatment of Verneuil\\\'s disease, surgical excision remains a treatment of choice in some situations. Medico-surgical discussion is essential for the management of this disease and its development must be a priority.

Melanoma is a tumor proliferation developed at the expenseof melanocytes,the incidence of melanomais increasingworldwidemakesita realpublic health concern,the severity of thismalignancy tumor isassociated witha strong ability tometastasize,involvingthe prognosisof the patientif the lesionis notdetected early henceimproving earlydiagnosis remainsa major challenge. The objective of ourwork is to studythe epidemiological ,pathological,, therapeutic, prognostic and preventive aspects of melanomathrough aretrspective studyof 33patientscollectedfrom January 2010 to January 2017 inin plasticsurgery andburnsofthe CHUMohammed VIMarrakech. The average age of our patients was 61 years with a female predominance. Sun exposure was found in 91 % of our patients which supports the important role complained of sun exposure in the development of melanoma. The location the sole of the foot is by far the most frequent (73% of our patients). On histological level, Acrolentigineux (61%) and nodule (24%) types are the most common, with a Breslow thickness varies between 2 mm and 12 mm and Clark level varies between IV and V in 75% of our patients, reflecting the significant delay between the start of the lesion and the consultation which is estimated at 2 years and consequently the lack of effective means of screening for patients at risk in our population. On therapeutically level, at the initial stage, only surgical excision, constituting the gesture that allows both diagnosis and treatment of the lesion which must be done as soon as possible to ensure prolonged survival. At the loco-regional stage, surgical resection with regional lymph node dissection is the standard of care. The sentinel node biopsy provides very precise classification of cutaneous melanoma, but has not been reported to have a significant impact on survival. The dissection effect on survival is a subject of inquiry. Two distinct approaches have emerged to try to prolong the survival of patients with metastatic melanoma: Immunomodulation with anti- CTLA4 monoclonal antibodies and targeted therapy with inhibitors of BRAF or MEK for melanoma with BRAF mutated, recent studies have shown that the combination of inhibitors of BRAF and inhibitors of MEK may improve the progression-free survival and eventually increase overall survival, the choice of therapy should be individualized in each case depending on various factors such as BRAF mutation status, age, co-morbidities and topography of metastases ,while chemotherapy and radiation therapy can be used to relieve the symptoms without significant impact on patient survival. Preventing melanoma is a real public health problem requires education of the general population on the need for sunscreen and awareness of melanoma and encouraging early diagnosis with the training of health professionals.

The use of recombinant human factor in intralesional diabetic foot has been the subject of several studies that have proven its effectiveness, to the extent of avoiding amputation. Its effectiveness on chronic wounds is currently being studied, with relevant results. We analyzed the results of a series of patients with chronic wounds treated in the Plastic Surgery Department of the Mohammed VI Medical Center in Marrakech. This is a prospective study conducted between January and April 2019, involving ten patients with chronic wounds, who benefited from intra- and peri-lesional infiltration of recombinant human factor. The average age was 48.8 years with extremes of 17 and 69 years. All our patients were male. 80% of our patients lived in adverse conditions. The average duration of the lesions was 8.1 years with extremes ranging from 6 months to 37 years. The average size of the loss of substance was 10.4 cm2 with extremes ranging from 04 to 18 cm2. The etiologies of the loss of substance were variable, dominated by loss of substance post-accident on a public road in more than 60% of the cases. 40% of our patients reported pain at the level of the site and 20% vertigo. Evolution of the lesions was regularly evaluated by clinical examination and photographs. Budding was obtained in 30% of the cases after grafting, epidermalization in 40% of the cases, and a very significant reduction in the size of the loss area in 30% of cases. The use of recombinant human factor is one of the encouraging therapeutic advances in regenerative medicine that has proven effective on chronic wounds with a reduced overall cost.

L’éléphantiasis scrotal se définit comme étant une augmentation du volume scrotal qui peut atteindre une taille très importante; il s’agit du patient O.H âgé de 70 ans, marié et père de 4 enfants, originaire et résident à Agadir (sud du Maroc), agriculteur de profession. Le début de la symptomatologie remonte à 7 ans par l’installation de l’œdème scrotal puis des deux pieds et jambes augmentant progressivement de volume. L’examen local mettait en évidence un éléphantiasis scrotal de 80cm de circonférence et des deux jambes et pieds. Une imagerie à résonnance magnétique (IRM) pelvienne a été demandée dans le cadre du bilan d’exploration locorégionale. Le patient a été programmé pour un geste d’exérèse scrotale en mono- bloc sous rachis anesthésie avec libération des deux testicules couvertes directement par la peau restante et de la verge qui a été couverte par greffe de peau mince. Le but du traitement est assurer la fonction et prendre en charge les préjudices esthétiques. Le traitement conservateur consistant à la dérivation lymphatique vers le réseau veineux ou à la dilatation des vaisseaux lymphatiques a été abandonné. On se base pour la prise en charge sur la chirurgie qui peut être abstenu en cas de contre indication absolue au geste chirurgical.

Burns of the hand are responsible for the aesthetic and functional sequelae that are most often involved, ranging from the simple dyschromia to multiple digits amputation. The Sequelae can be minor requiring medical treatment, or major deserving surgical intervention consisting of a supply of healthy skin, in the form of skin graft or various flaps and plasties. In order to study the epidemiological, clinical, therapeutic and evolutionary characteristics of sequelae in burned hands, we realized a retrospective study in the department of plastic surgery and burns at the Mohammed VI University Hospital in Marrakech, lasting from January 2013 to December 2017. We collected 104 cases including patients who consulted during the phase of sequelae. From this study, we noted the importance of burns in young adults (42%), and children aged less than 6 years (33%) in the context of domestic accidents (76%). We have also noticed the high incidence of burns of the dorsal surface of the hand in adults by butane flames, in the context of a ? Hand-Face syndrome ? and burns of the palmar face in the child by contact. In our study we noted also the frequent association of major sequelae (contracture, pathological scars) and minor sequelae (dyschromia, pruritus, cicatricial fragility, cutaneous hyperesthesia). Sequelae were dominated by fingers and palmar contracture (65.5%). A functional deficit was observed in more than two thirds of cases. Different means of reconstruction were used depending on the location and type of sequelae, local plasties were performed in 84.6% of the cases, excision and skin grafting in 76.9% of the cases, distant flaps in 4.7% of the cases and artificial dermis (Integra?) in one case. The most used local plasties were \"Z\" plasty (65.5% of cases) and \"trident\" plasty (26.5% of cases). 78% of grafts used to treat sequelae were a full-thickness skin graft. The interest of an early and well-conducted rehabilitation is unanimously recognized, it has accompanied all phases of treatment in our patients. The evolution was marked by a satisfactory result for most treated patients. The management of burned hands is multidisciplinary; it is a work-requiring cooperation between surgeons, rehabilitators, physiotherapists, occupational therapists and psychologists. The treatment also requires the cooperation of the patient. The motivation of the patient and his entourage is a key factor in the success of this heavy and long-term care. Prevention remains a priority objective.

Blast lesions are considered complex and dangerous in the face of life-threatening and functional consequences. The difficulty of taking care of these patients calls for an exhaustive diagnostic procedure and imposing urgent medico-surgical decisions. We report a case of abdominal blast following a gas cylinder explosion where the mechanism and seat of the lesion remain exceptional.

Introduction:Burn injuries are one of the top 10 causes of unintentional deaths in children younger than 14 years old. Most pediatric burns are minor, but children with severe burns have higher mortality than nonelderly adults with similar burns. Aims and objectives:To study the epidemiological particularities and the prognostic factors in order to prevent these accidents and to improve the future of the patients. Materials and methods:This study is retrospective and descriptive. It covers all the children burned and hospitalized in the pediatric intensive care unit of the Mohammed VI University Hospital of Marrakech during the period from January 2009 to December 2017. The criteria for inclusion are any burns covering more than 15% of a skin surface, any burns in a deep surface exceeding 5%, when a burn is cervico-facial, or when the burn is responsible for circular lesions. Findings and discussion:401 cases were collected during this period mentioned above. The incidence of severe burns in children was 5.6%. The most affected age group is between 0 and 4 years old with a male predominance (63%). Children from rural regions were more dominant (61%). 40% of the patients were admitted between 3 and 12 hours after the incident. 89% of the incidents occurred at home. Scalding was the most common mechanism (70%). Inpatient admission was done in 59% of cases via pediatric emergencies. The average area of skin burned was 18.8%. The most common location was limb involvement (35%) with superficial to intermediate second degree burns predominating (51%). Therapeutically, apart from patients admitted late (22%), all the others benefited from rehydration according to the Carvajal scheme. All the patients also benefited from multimodal analgesia (Morphine - Paracetamol - Ibuprofen) care performed by the plastic surgery team, and a mostly enteral diet (91%) introduced within an average of 1.7 days. In addition, we noted the occurrence of various ionic and metabolic disorders in 75% of cases, anemia in 67% of patients. The infection reached 43% of children burned. The mortality rate was 6.38%, and the average duration of hospitalization was 5.8 days. In our context, some elements such as the age of the patient being less than 4 years old, flame burn, the burned skin area exceeding 30%, defective initial management, delayed admission and infection occurrence, can be factors of poor prognosis. Conclusion:Our data demonstrates the importance of developing a program for the prevention of pediatric scalds by educating family members and raising their awareness of the danger. With present studies, the knowledge about the occurrence of injuries in scald accidents in children has become deeper. This knowledge may contribute to more individual adept child accident prevention program that could be used in the children health care.

Le vitiligo est un trouble commun et acquis de la pigmentation cutanée caractérisé par une perte sélective et souvent continue de mélanocytes épidermiques. Nous rapportons le cas d'une patiente ayant développé un vitiligo de la face suite à des injections de plasma riche en plaquettes. Le diagnostic de phénomène de Koebner a été retenu pour expliquer la survenue de vitiligo sur les zones mêmes d'injection de plasma riche en plaquettes.

The effect of single and double substitution with lightweight elements Boron (B) and Lithium (Li) on the thermodynamic properties of MgH2 are investigated by using first principles calculations. Our results show an improvement of hydrogen storage properties of double substituted MgH2, in contrast to the case of single substitution, along with a remarkable increase of its gravimetric and volumetric capacities which exceed those of pure MgH2. Given that Mg4LiBH12 exposes a heat of formation around −32.03 kj/mol as well as a gravimetric and volumetric capacity of 9.45 wt% and 123.08 gH2/l respectively, it may be considered as a potential candidate for hydrogen storage transportation applications. A detailed analysis of the density of states and charge transfer, of the studied systems, is presented to understand the underlying mechanisms behind MgH2 thermodynamics improvements.

Ab-initio calculations are carried out to analyze the improvement of hydrogen storage properties, in Mg-based hydrides, through a double substitution (Mg 14 TMAlH 32 and Mg 14 TMLiH 32 TM = Ti, Sc, Zn). The calculations are performed using the all-electron full-potential local-orbital minimum-basis scheme (FPLO9.00-34). Our results indicate a decrease of the heat of formation and desorption temperature, while preserving the gravimetric storage capacity around 7.6 wt%, these outcomes are probably due to the second substitution, Al or Li, which are characterized by their light weights. Discussions of the charge exchange and the density of states are done, to offer more possible explanations of our results.

Hydrogen storage ab/desorption kinetic properties of MgH 2 and MgH 2 doped with different metal M ( M = Al , Ti , V , Fe and Ni ) are investigated by using both DFT method and kinetic Monte-Carlo simulations. The first principles calculations show that the energy barriers decrease considerably when doping with a small amount of M element leading to a decreasing of both the stability and the decomposition temperature of the material. Based on the activation energies computed from DFT calculations, we show within the kinetic Monte-Carlo method that the ab/desorption time is reduced considerably without reducing much the hydrogen storage capacity of the material. From our analysis, we observed that the Ni element exhibits the most appropriate thermodynamical properties for hydrogen storage and the best kinetic of hydrogen absorption/desorption.

We show that, in addition to its thermodynamic properties that make it a good candidate for hydrogen storage, the MgH2 hydride exhibits interesting magnetic properties when doped with some transition metals (TM). Using the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation in the framework of first-principle calculations, we study the half-metallic ferromagnetic properties of the MgH2 doped with TM: Co, V, Cr, Ti; Mg0.95TM0.05H2. The ferromagnetic state energy is computed and compared with the disordered local moment state energy. We show, from the electronic structure, that doping MgH2 with TM elements can convert the material to a half-metallic with a high wide impurity band and high magnetic moment. We have found that the corresponding Curie temperature is bigger than the room temperature, which is considered as a relevant parameter for spintronic applications. Moreover, the mechanism of the hybridization and the interaction between the magnetic ions are also investigated showing that the double exchange is the underlying mechanism responsible for the magnetism of such materials .

Uterine fibroid or leiomyoma is the most common benign uterine tumor which affects mostly women in reproductive age. However, its occurrence after menopause is very rare as the growth of a fibroid depends on the hormone of estrogen. There are several risk factors including nulliparity, obesity, black race, family history, and hypertension. Therefore, fibroid degeneration is rare after menopause.We are reporting a case of a post-menopausal woman of 60-year-old, menopaused for ten years, with a history of bleeding for two years for whom the gynecological exam revealed a cervical budding lesion hypervascularized for which a previous cervicovaginal smear revealed no suspicious cells.Then a biopsy was performed and also devoid of malignancy signs.The ultrasound has identified two fibroids classified 2-5 for the first corporeal-fundial myoma about 50/55 mm ( myoma or sarcoma ?) and a corporeal posterior myoma type 2 about 40/30 mm repressing the endometrium (8,5mm).The eventual diagnosis of sarcoma was not excluded till then.The RMI has not been realized. A total hysterectomy with bilateral adnexectomy was performed focusing on the two fibroids, and the histopathological, report confirmed the leiomyoma tumor diagnosis.

Nowadays, the uterine rupture is a situation world widely encountered especially in low-income countries. Postpartum hemorrhage that the uterine rupture leads to is frequently severe and life threatening. The aim of medical and surgical conservative methods is to preserve the uterus and the fertility. But sometimes, the surgeon has to perform a hysterectomy and even completing with the unilateral or bilateral internal iliac artery ligation to manage the blood loss which may last in some cases after hysterectomy. Here we present a 34 years old pregnant woman with previous cesarean delivery scar for a twin pregnancy, admitted in advanced labor for term pregnancy with a posterior uterine rupture of 12 cm and abdominal expulsion of a dead male fetus with a lesion fusing to the right vaginal angle, with intact lower segment scar. The hemostatic subtotal hysterectomy was performed with the failure of handling the vaginal bleeding. At last, a bilateral internal iliac artery ligation was performed to ensure successful hemostasis and maternal lifesaving.

Le paludisme est la parasitose la plus fréquente à travers le monde, l’association paludisme et grossesse expose le couple mère-enfant à de grave complication. Le diagnostic doit être rapidement établi afin de traiter la mère et l’enfant, et de prévenir les complications. La prévention se base sur la protection contre les moustiques et la chimio-prophylaxie. Nous rapportons dans ce travail un cas d’accès palustre découvert dans les suites d’un voyage en zone d’endémie, afin d’étalé l’intérêt de la prévention, et de rappelé les bonnes conduite de prise en charge maternelle et fœtale en cas d’accès palustre., Journal Marocain des Sciences Médicales, Vol. 20, No 4 (2016)

Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as, Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9·00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

The opening of the energy gap and the total energy of the graphene-like bilayers are investigated using ab initio calculations. The studied model consists of a static single layer of graphene interacting with an extra dynamic one placed at a varying vertical distance d in the (AB) stacking arrangement. The effects of the vertical distance variation on the energy gap and the total energy of the system are discussed first. Starting from a distance around the van der Waals length, the energy gap does not depend on the vertical distance variation and the system exhibits graphene-like properties with minor deformations in the lattice size parameter and the energy dispersion behaviour around K points. However, it has been shown that the diagonal distance variation of the graphene-like bilayer modifies the electronic structure properties. This modification depends on an intermediate stacking arrangement between the (AA) and the (AB) configurations. It has been shown that the diagonal distance variation has an influence on the states of pz electrons in the (AB) arrangement and it can be explored to open the energy gap.

Inspired by Lie symmetries, we study the electronic and magnetic properties of cobalt (Co) and nickel (Ni) adatom adsorption on the graphene material using density functional theory calculations. The system we consider here consists of a static single layer of graphene interacting with transition-metal (TM) atoms. This system shows a nice geometrical shape having a double hexagonal structure appearing in the G2 Lie algebra. This structure is associated with 25% concentration corresponding to a coverage of 0.666 monolayers placed at H sites. This new symmetry forces the derived Co material to behave like a ferromagnetic metal with a strong spin polarization. However, the derived Ni material remains a nonmagnetic metal. For the Co case, we show that the magnetic mechanism responsible for such behavior is the interaction between the Co atoms. In fact, there are two interaction types. The first one is associated with the direct interaction between the Co atoms, while the second one corresponds to the indirect interaction via the carbon atoms. Using Monte Carlo simulation, the Curie temperature for the Co material is estimated to be around 438 K. This value could be explored in nanomagnetic applications.

Motivated by recent experimental and theoretical works dealing with the silicene and the graphene materials and inspired from the root systems of Lie algebras, we study the electronic and the magnetic properties of the iron adatom adsorption on the graphene. The calculations have been performed using the density functional theory method. More precisely, the system we consider here consists of a static single layer of the graphene interacting with the iron atoms which are placed at hollow (H) sites and localized at a distance D along the normal direction. This system, involving the G2 hexagons appearing in the classification of rank two Lie symmetries, exhibits, up some details, a nice double hexagonal symmetry required by coverage of 0.666 monolayer placed at H sites. The resulting materials behave like ferromagnetic ones having a strong spin polarization, instead of gapless-semiconductor with the nonmagnetic features appearing in the pure graphene. The responsible mechanism for such behaviors is the interaction between the iron atoms. It has been realized that there are two interaction types. The first one is associated with the direct interaction between the iron atoms, whereas the second one corresponds to the indirect interaction via the carbon atoms. Using the molecular field approximation, the Curie temperature has been estimated around 367 K. V C 2013 Wiley Periodicals, Inc.

In this work, we propose a model to investigate the hydrogen storage ab/desorption kinetic properties for the pure MgH2 using Kinetic Monte Carlo (KMC) simulations. To do such computations, the activation energies for different elementary processes have been estimated. Moreover, the different thermodynamical quantities of interest are determined by performing the ab-initio calculations. Then, we discuss the hydrogen diffusion in magnesium hydride (such as adsorption, diffusion and desorption). More precisely, we study the effect of each elementary mechanism on the diffusion that we characterize through the density distribution of hydrogen atoms including filling ratios, diffusion time, temperature and pressure. Among others, we show that all elementary mechanisms are needed to reproduce a behavior of ab/desorption which correlates well with the experimental results reported in literature. In particular, at high temperature and pressure, the results of simulations indicate that the studied material involves slow kinetics.

Based on the density functional theory and using the Korringa-Kohn-Rostoker coherent potential approxima- tion (KKR-CPA) method, we study the (Sr, TM)O doped systems where TM = V, Cr, Mn, Fe, Co, and Ni atoms. In particular, we start first by relaxing the parameters of the corresponding structures. Then we discuss its electronic structures, magnetic stabilities, and half-metal properties us- ing 3d transition metals. Among others, it has been shown that doping with Cr, Mn, Fe, and Co, the ferromagnetic phase can be stabilized using a double exchange mechanism. Moreover, we find that the half-metallic properties of these compounds are formed due to a large exchange splitting and the delocalized properties of the majority spin eg state and the minority spin teg states.

The diffusion of hydrogen in the rutile and fluorite structures of the magnesium titanium hydrides Mg 1−x Ti x H 2 is studied using first-principles density functional theory. We compare the vacancy formation, the diffusion and the binding energy in both structures for x=0.125 and x=0.25 concentrations. Our results confirm that the enhancement of the diffusion is mainly due to the structural change, where we find that the activation barriers are lower in the fluorite structure compared to that of the rutile structure. We also find that the hydrogen atoms tend to bind with each other in the rutile structure by finding an important negative binding energy compared to the fluorite structure.

Structural and magnetic properties of Zn0.8(Fe0.1, Co0.1)O bulk diluted magnetic semiconductor have been investigated using X-ray diffraction (XRD) and magnetic measurements. TEM (Transmission Electron Microscopy) images confirmed the high crystallinity and grain size of Zn0.8(Fe0.1,Co0.1)O powder, the samples were characterized by energy dispersive spectroscopy (EDS) to confirm the expected stoichiometry. This sample has been synthesized by co-precipitation route. The study of magnetization hysteresis loop measurements infers that the bulk sample of Zn0.8(Fe0.1,Co0.1)O shows a well-defined hysteresis loop at T c (200 K) temperature, which reflects its ferromagnetic behavior. Hydrogenation treatment was used for the control of phase separation. Based on first-principles spin-density functional calculations, using the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation (CPA), the ferromagnetic state energy was calculated and compared with the local-moment-disordered (LMD) state energy. The mechanism of hybridization and interaction between magnetic ions in Zn0.8(Fe0.1,Co0.1)O is also investigated.