Učinak trojnog potencijalnog bedema na svojstva elektronskog stanja suprarešetke GaAs/AlxGa1−xAs

By the formalism of transfer matrix, transmission coefficient and localization length are studied in the case of a superlattice containing semiconductor in barrier height trimer (HBT). We are interested in the GaAs/AlxGa1-xAs layers, having identical thickness, where the aluminium concentration x takes at random two different values, with the constraint that one of them appears only triply, i.e. it is a random trimer barrier (RTB). The electronic states of SR were studied by theoretical calculation of transmission coefficient of the miniband structure. We observed that the process of delocalization exists when the disorder is correlated, the result confirming the theoretical studies already found for the case of the dimer.Primjenom formalizma matrice prijenosa, proučavamo koeficijent propusnosti i duljinu lokalizacije suprarešetke koja sadrži u poluvodiču trojni potencijalni bedem. Zanimaju nas slojevi GaAs/AlxGa1−xAs, jednake debljine, u kojima su slučajno odabrane dvije koncentracije x, uz uvjet da se jedna javlja tri puta, tj. proučavamo slučajan trojni bedem. Elektronska stanja suprarešetke izvodimo teorijskim razmatranjem koeficijenta propusnosti strukture minivrpci. Opažamo postojanje procesa delokalizacije ako postoji koreliran nered, što potvrđuje teorijske rezultate već poznate za slučaj dvojnog sloja

Učinak trojnog potencijalnog bedema na svojstva elektronskog stanja suprarešetke GaAs/AlxGa1−xAs

By the formalism of transfer matrix, transmission coefficient and localization length are studied in the case of a superlattice containing semiconductor in barrier height trimer (HBT). We are interested in the GaAs/AlxGa1-xAs layers, having identical thickness, where the aluminium concentration x takes at random two different values, with the constraint that one of them appears only triply, i.e. it is a random trimer barrier (RTB). The electronic states of SR were studied by theoretical calculation of transmission coefficient of the miniband structure. We observed that the process of delocalization exists when the disorder is correlated, the result confirming the theoretical studies already found for the case of the dimer.Primjenom formalizma matrice prijenosa, proučavamo koeficijent propusnosti i duljinu lokalizacije suprarešetke koja sadrži u poluvodiču trojni potencijalni bedem. Zanimaju nas slojevi GaAs/AlxGa1−xAs, jednake debljine, u kojima su slučajno odabrane dvije koncentracije x, uz uvjet da se jedna javlja tri puta, tj. proučavamo slučajan trojni bedem. Elektronska stanja suprarešetke izvodimo teorijskim razmatranjem koeficijenta propusnosti strukture minivrpci. Opažamo postojanje procesa delokalizacije ako postoji koreliran nered, što potvrđuje teorijske rezultate već poznate za slučaj dvojnog sloja

Structural disorder and its effects in laser wavelength GaAs–AlxGa1−xAs superlattice

Nous revisitons ici la théorie, utilisée en analyse des profils de raies de diffraction des rayons X et des neutrons, relative à la fonction de forme du pic dite de pseudo -Voigt (notée pV). Nous présentons une généralisation des expressions de la largeur intégrale et à mi-hauteur de la fonction pV, de la transformée de Fourier de cette fonction ainsi que du seuil du parametre de mélange η. Nous incorporons nos résultats dans la procédure de fit, ce qui améliore les facteurs de précision.Proučavamo optički aktivan sustav GaAs–AlxGa1−xAs načinjen na GaAs podlozi s ciljem postizanja laserske emisije u širokom infracrvenom području (9 to 90 µm). Ispitujemo učinak koncentracije aluminija “x” i širine potencijalne jame “a” kako bi se odredio njihov utjecaj na lasersku valnu duljinu. Mjerenjima prolaska svjetlosti pokazujemo da se uvođenjem strukturne nepravilnosti (uz zadržavanja periodičnosti) dvo- i troslojeva u našim superrešetkama postiže vjerojatnost prolaska jednaka 1, što znači da su odnosna stanja rezonantna.This study focuses on optically active system GaAs–AlxGa1−xAs based on the GaAs substrate, with the aim to achieve lasers emitting in a wide range of infrared (9 to 90 µm). The effect of aluminium concentration “x” and the potential well width “a” is studied to see their direct effects on the laser wavelength. We show from measurements of transmission that the introduction of a structural disorder (preserving the system periodicity) by doublet or triplet within our superlattices provides delocalised electronic states characterized by a probability of transmission equal to 1, meaning that the corresponding state is resonant

Redes de migración y el turismo marroquí: un análisis de datos de panel

This contribution aims to study the migration and tourism nexus. In the developed countries, the effect of migration on tourism has been widely analyzed. For the developing countries, this topic is more interesting because of the role that diaspora plays in fostering tourism to the home countries. Based on the theoretical and empirical literature, the effect of migration networks on tourism will be tested. On the one hand, global migration networks can have a positive effect on tourism through the increase of borders permeability in the osmosis theory logic. On the other hand, at the micro level, migrant generations, transactions, preferences, and emigrants’ life style can adapt, promote, and advertise tourism of the home countries. To estimate the global effect of networks on Moroccan inflows of tourists from the eight OECD principal immigration countries, the gravity model has been used. The analysed data considers the statistics of the nine countries during nine periods. The results show a significant correlation between Moroccan tourism inward tourism and emigration, in addition to the exogenous variables, either in the Fixed Effects Model or in Dynamic panel one using GMM method. The results indicate also a concordance of the two models results, the fact that strengthen their role as robust tools for exploring the migration and tourism nexus. The statistical results confirm the positive effects of migration networks on the Moroccan tourism.Esta contribución tiene como objetivo estudiar el nexo entre migración y turismo. En los países desarrollados, el efecto de la migración en el turismo ha sido ampliamente analizado. Para los países en desarrollo, este tema es más interesante debido al papel que juega la diáspora en el fomento del turismo a los países de origen. Con base en la literatura sobre migración y comercio, se probará el efecto de las redes de migración en el turismo. Por un lado, las redes mundiales de migración podrían tener un efecto positivo en el turismo a través del aumento de la permeabilidad de las fronteras en la lógica de la teoría de la ósmosis. Por otro lado, a nivel micro, las generaciones de migrantes, las transacciones, las preferencias y el estilo de vida de los emigrantes podrían adaptar, promover y publicitar el turismo de los países de origen. Para estimar el efecto global de las redes en las entradas de turistas marroquíes de los ocho principales países de inmigración de la OCDE, se ha utilizado el modelo de gravedad. Los datos analizados consideran las estadísticas de nueve países durante nueve períodos. Los resultados muestran una correlación significativa entre turismo marroquí y emigración, además de las variables exógenas, en el Modelo de efectos fijos o en el panel dinámico uno utilizando el método GMM. Los resultados indican concordancia de los resultados de los dos modelos, el hecho de que fortalecen su papel como herramientas robustas para explorar el nexo entre migración y turismo

Structural disorder and its effects in laser wavelength GaAs–AlxGa1−xAs superlattice

Nous revisitons ici la théorie, utilisée en analyse des profils de raies de diffraction des rayons X et des neutrons, relative à la fonction de forme du pic dite de pseudo -Voigt (notée pV). Nous présentons une généralisation des expressions de la largeur intégrale et à mi-hauteur de la fonction pV, de la transformée de Fourier de cette fonction ainsi que du seuil du parametre de mélange η. Nous incorporons nos résultats dans la procédure de fit, ce qui améliore les facteurs de précision.Proučavamo optički aktivan sustav GaAs–AlxGa1−xAs načinjen na GaAs podlozi s ciljem postizanja laserske emisije u širokom infracrvenom području (9 to 90 µm). Ispitujemo učinak koncentracije aluminija “x” i širine potencijalne jame “a” kako bi se odredio njihov utjecaj na lasersku valnu duljinu. Mjerenjima prolaska svjetlosti pokazujemo da se uvođenjem strukturne nepravilnosti (uz zadržavanja periodičnosti) dvo- i troslojeva u našim superrešetkama postiže vjerojatnost prolaska jednaka 1, što znači da su odnosna stanja rezonantna.This study focuses on optically active system GaAs–AlxGa1−xAs based on the GaAs substrate, with the aim to achieve lasers emitting in a wide range of infrared (9 to 90 µm). The effect of aluminium concentration “x” and the potential well width “a” is studied to see their direct effects on the laser wavelength. We show from measurements of transmission that the introduction of a structural disorder (preserving the system periodicity) by doublet or triplet within our superlattices provides delocalised electronic states characterized by a probability of transmission equal to 1, meaning that the corresponding state is resonant

Polyphenols Content and Antimicrobial, Antioxidant and Hemolytic Activities of Essential Oils from Four Selected Medicinal Plants Growing in Algeria

The Saharan and steppe spontaneous plants are very characteristic because of their particular adaptation to the desert and extreme environment. Some species have pharmacological properties that give them a medicinal interest. The aim of the present work was to determine the polyphenol contents of essential oils obtained from four endemic plants growing in Algeria (Pituranthos scoparius, Myrtus nivellei, Rosmarinus officinalis and Mentha piperita), and study its biological activity, including antimicrobial, antioxidant, and hemolytic. The antimicrobial activity was evaluated by the microdilution method against twelve strains. The antioxidant activity was carried out by two methods (DPPH radical scavenging and reducing power). However, the hemolytic effect has been evaluated against the red blood cells. P. scoparius and M. piperita showed yields of essential oils higher than 1%. All the strains showed sensitivity against the essential oils tested with the exception of the C. albicans treated by R. officinalis essential oils. The most sensitive strain was C. albicans treated by P. scoparius essential oils by MIC of 0.0781 mg/mL, it was the same plant that shows the highest polyphenol content (14.78 ± 0.72 g GAE/g DS). The antioxidant activity by the DPPH method was greater for all essential oils tested by IC50 ranging from 0.69 ± 0.07 (R. officinalis) to 30.67 ± 2.12 mg/mL (M. nivellei). The R. officinalis essential oils reported more antioxidant power than the positive control (ascorbic acid). In reducing iron, it was the R. officinalis essential oils which were found to be the most active with an EC50 concentration of 9.67 ± 1.36 mg/mL. After 120 min incubation, minimal haemolysis (10%) was obtained with essential oils of R. officinalis at a concentration of 0.39 mg/mL. We conclude that P. scoparius essential oils showed the high content of polyphenols and R. officinalis essential oils reported more antioxidant power than the positive control (ascorbic acid)

Antidiabetic treatment, obesity, and cancer risk in Algerian patients with type 2 diabetes mellitus

OBJECTIVE: Several studies have shown that antidiabetic drugs and obesity can modulate the risk of developing cancer. The objective of this study was to assess the impact of the use of antidiabetic drugs and obesity on the risk of developing cancers in type 2 diabetics. MATERIALS AND METHODS: Data for 1220 patients were collected from the processing of files and a pre-established questionnaire. The anthropobiological parameters and the associated treatment type have been unspecified. RESULTS: Women (OR=17.26; 95% CI=2.88-103.45, p<0.01), overweight individuals (OR=4.81; 95% CI=1.63-14.14, p<0.01) and hypertensive diabetic subjects (OR=3.82; 95% CI=1.39-10.49, p< 0.01) are more exposed to cancers. It is interesting to note that diabetic subjects treated with insulin have a reduced risk of developing cancer (OR=0.22; 95% CI=0.07-0.67, p<0.01). Diabetic subjects treated with metformin have a four and a half times higher risk of developing cancer (OR=4.61; 95% CI=1.48-14.37, p<0.01). CONCLUSIONS: In type 2 diabetic subjects, cancer is significantly linked to overweight, to the presence of essential hypertension in individuals under hypotensive as well as in patients treated with metformin

Association of IL4 rs2070874, FoxP3 rs3761548 Polymorphisms with Keratoconus in Algeria

Purpose: The aim of this case–control study was to determine the impact of environmental factors on the predisposition to develop keratoconus in a sample of Western Algerian population. Subsequently, we were interested in the implication of two single nucleotide polymorphisms (SNPs) IL4 rs2070874 and FOXP3 rs3761548, previously described as contributing to the occurrence of allergy, in the development of keratoconus. Methods: The study included 70 unrelated KC cases and 70 controls originating from Western Algeria. DNA genotyping was done using predesigned probe-based allelic discrimination TaqMan® assays. Allele and genotype frequencies were compared between the cases and controls by Chi-square test and odds ratios with 95% confidence intervals. Results: A significant association between risk factors such as family history, atopy, eye rubbing, and the development of keratoconus was found in our sample. Smoking would provide a protective effect against the pathology. No statistically significant differences were found in the allele and genotype frequencies between cases and controls neither for IL4 rs2070874 nor for FOXP3 rs3761548. Conclusion: Our study provides, for the first time, a clear demonstration of the absence of association of the allergy-associated IL4 and FOXP3 polymorphisms with KC in a sample from Western Algerian population

Neuronal Cholesterol Accumulation Induced by Cyp46a1 Down-Regulation in Mouse Hippocampus Disrupts Brain Lipid Homeostasis

Impairment in cholesterol metabolism is associated with many neurodegenerative disorders including Alzheimer's disease (AD). However, the lipid alterations underlying neurodegeneration and the connection between altered cholesterol levels and AD remains not fully understood. We recently showed that cholesterol accumulation in hippocampal neurons, induced by silencing Cyp46a1 gene expression, leads to neurodegeneration with a progressive neuronal loss associated with AD-like phenotype in wild-type mice. We used a targeted and non-targeted lipidomics approach by liquid chromatography coupled to high-resolution mass spectrometry to further characterize lipid modifications associated to neurodegeneration and cholesterol accumulation induced by CYP46A1 inhibition. Hippocampus lipidome of normal mice was profiled 4 weeks after cholesterol accumulation due to Cyp46a1 gene expression down-regulation at the onset of neurodegeneration. We showed that major membrane lipids, sphingolipids and specific enzymes involved in phosphatidylcholine and sphingolipid metabolism, were rapidly increased in the hippocampus of AAV-shCYP46A1 injected mice. This lipid accumulation was associated with alterations in the lysosomal cargoe, accumulation of phagolysosomes and impairment of endosome-lysosome trafficking. Altogether, we demonstrated that inhibition of cholesterol 24-hydroxylase, key enzyme of cholesterol metabolism leads to a complex dysregulation of lipid homeostasis. Our results contribute to dissect the potential role of lipids in severe neurodegenerative diseases like AD

24S‐hydroxycholesterol: cellular effects and variations in brain diseases

The adult brain exhibit a characteristic cholesterol homeostasis, with low synthesis rate and active catabolism. Brain cholesterol turnover is possible thanks to the action of the enzyme Cytochrome P450 46A1 (CYP46A1) or 24-cholesterol hydroxylase, that transforms cholesterol into 24S-hydroxycholesterol (24S-HC). But before crossing the blood-brain barrier (BBB), this oxysterol that is the most abundant in the brain can act locally, affecting the functioning of neurons, astrocytes, oligodendrocytes, and vascular cells. The first part of this review addresses different aspects of 24S-HC production and elimination from the brain. The second part concentrates in the effects of 24S-HC at the cellular level, describing how this oxysterol affects cell viability, amyloid beta production, neurotransmission, and transcriptional activity. Finally, the role of 24S-HC in Alzheimer, Huntington and Parkinson diseases, multiple sclerosis and amyotrophic lateral sclerosis, as well as the possibility of using this oxysterol as predictive and/or evolution biomarker in different brain disorders is discussed.Fil: Sodero, Alejandro Omar. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; Argentin