Ultrathin oxides: bulk-oxide-like model surfaces or unique films?

To better understand the electronic and chemical properties of wide-gap oxide surfaces at the atomic scale, experimental work has focused on epitaxial films on metal substrates. Recent findings show that these films are considerably thinner than previously thought. This raises doubts about the transferability of the results to surface properties of thicker films and bulk crystals. By means of density-functional theory and approximate GW corrections for the electronic spectra we demonstrate for three characteristic wide-gap oxides (silica, alumina, and hafnia) the influence of the substrate and highlight critical differences between the ultrathin films and surfaces of bulk materials. Our results imply that monolayer-thin oxide films have rather unique properties.Comment: 5 pages, 3 figures, accepted by PR

AGRICULTURE URBAINE ET P\uc9RIURBAINE POUR LA S\uc9CURIT\uc9 ALIMENTAIRE EN AFRIQUE DE L'OUEST. LE CAS DES MICRO-JARDINS DANS LA MUNICIPALIT\uc9 DE DAKAR

In the context of Urban and Peri-urban Agriculture (UPA) micro-gardens, a simplified version of hydroponics, represent an interesting opportunity for producers, because they are characterized by a high efficiency in the use of water (2-3 l/m2/per day) and by a great spatial versatility. Moreover the vegetables grown through this technique are of high quality, because quality water and no chemical pesticide are used. These characteristics improve the poorest families\u2019 access to horticultural products, they contribute to diet diversification of poor (and also non poor) families and thanks to surplus selling they answer the need to create an extra source of income. As this activity is mainly based on recycled materials (pallets, old tyres, bins, plastic bottles and bags as containers, peanut shells and rice hulls for the substrate), its environmental impact is undeniably important. Our study, which took place in Dakar in the framework of a project of decentralized cooperation between the municipality of Milan and the Senegalese capital, proved micro-gardens\u2019 excellent production performances. Cultivation on solid substrate can provide 7-9 kg /m2 of tomatoes, and up to 15 kg/m2 of cucumbers. In floating system peppermint can produce up to 1,5 kg/m2 and lettuce 35 heads/m2. Very good productions and low costs offer the rising micro-gardens production chain some interesting opportunities of economical development, and profitability studies underlined its economic sustainability. In fact our study demonstrated that a group of producers possessing 10 containers (1 m2 each) can afford to buy inputs needed for production by selling half of its production (10 m2 can bring up to 230 000 F CFA/a year, that is to say about 340 euros.) In the last few years attempts were made to introduce compost to enrich solid substrate, in order to diminish the amount of mineral fertilizers now employed. Productions aren\u2019t fully satisfying yet, but the further development of this technique could be crucial in the management of urban organic wastes. The benefits of micro-gardens and of UPA in general are also very important on the social and cultural plane. First of all they offer integration opportunities to marginalized groups (old, disabled people, women, young people). Moreover their introduction into schools offer the possibility to cater their canteens and to organize several didactic activities. Finally through the experience of micro gardens people appropriates of two extremely important concepts: those of food safety and food security. The necessity to improve the food and environmental situation in towns of developing countries is stressed by demographic projections: in 2025 more than half the population of developing countries - about 3,5 billion people - will live in towns. The recent history of the development of conurbations in Southern countries lets us foresee that towns will rapidly grow to the expenses of former rural spaces, increasing food insecurity, unemployment, social exclusion, environmental degradation. UPA may be able to permit a partial u-turn: increased food security, job creation, environmental sustainability. From the specific case of micro-gardens our research extended to the rest of Dakar region, to the town of Cotonou (Benin) and to West Africa in general, in the attempt to give a general outline of UPA in the sub-region and to identify its advantages, potentialities, limits and associated risks. The case studies of Cotonou and Dakar, which are especially deepened in this study, are particularly meaningful: in both towns UPA nourishes and offers a job to quite a big percentage of the population, it can play a key environmental role and experience the two limits that, in our opinion, mainly obstacle its development. In fact UPA in Cotonou is limited by the access to the land, especially because of its geographical position (the town in fact is constricted between the ocean on one side and the lagoon on the other) and by the competition for other urban uses. In Dakar access to land is similarly a problem, worsened by the difficulties to accede good and safe water resources. In this sense micro-gardens seem to be destined to increase their importance in the context of UPA in the sub-region. Moreover both case studies stressed the importance of a greater integration of UPA in urban planning, and the utility that Geographical Information Systems (GIS) can have as decision support

Low-density Lipoprotein Cholesterol And Radiotherapy-induced Carotid Atherosclerosis In Subjects With Head And Neck Cancer

Background: Radiotherapy (RT) is a risk factor for accelerated carotid artery atherosclerotic disease in subjects with head and neck cancer. However, the risk factors of RT-induced carotid artery remodeling are not established. This study aimed to investigate the effects of RT on carotid and popliteal arteries in subjects with head and neck cancer and to evaluate the relationship between baseline clinical and laboratory features and the progression of RT-induced atherosclerosis.Findings: Eleven men (age = 57.9 ± 6.2years) with head and neck cancer who underwent cervical bilateral irradiation were prospectively examined by clinical and laboratory analysis and by carotid and popliteal ultrasound before and after treatment (mean interval between the end of RT and the post-RT assessment = 181 ± 47 days). No studied subject used hypocholesterolemic medications. Significant increases in carotid intima-media thickness (IMT) (0.95 ± 0.08 vs. 0.87 ± 0.05 mm; p 3.0.CO;2-X, 626923Pereira Lima, M.N., Biolo, A., Foppa, M., da Rosa, P.R., Rohde, L.E., Clausell, N., A prospective, comparative study on the early effects of local and remote radiation therapy on carotid intima-media thickness and vascular cellular adhesion molecule-1 in patients with head and neck and prostate tumors (2011) Radiother Oncol, 101, pp. 449-453. , 10.1016/j.radonc.2010.03.026, 20435360Kalábová, H., Melichar, B., Ungermann, L., Doležal, J., Krčmová, L., Kašparová, M., Plíšek, J., Solichová, D., Intima-media thickness, myocardial perfusion and laboratory risk factors of atherosclerosis in patients with breast cancer treated with anthracycline-based chemotherapy (2011) Med Oncol, 28, pp. 1281-1287. , 10.1007/s12032-010-9593-1, 20567943Muzaffar, K., Collins, S.L., Labropoulos, N., Baker, W.H., A prospective study of the effects of irradiation on the carotid artery (2000) Laryngoscope, 110, pp. 1811-1814. , 10.1097/00005537-200011000-00007, 11081590Faruolo, M., Fiorentino, A., Gallucci, G., Lapadula, L., Fusco, V., Intimal-medial thickness and carotid arteries lumen in irradiated patients for head and neck cancer: preliminary data of an observational study (2013) Clin Transl Oncol, 15, pp. 861-864. , 10.1007/s12094-013-1023-3, 23463595Ferreira-Sae, M.C., Cipolli, J.A., Cornélio, M.E., Matos-Souza, J.R., Fernandes, M.N., Schreiber, R., Costa, F.O., Nadruz, W., Sodium intake is associated with carotid artery structure alterations and plasma matrix metalloproteinase-9 upregulation in hypertensive adults (2011) J Nutr, 141, pp. 877-882. , 10.3945/jn.110.135921, 21430243Gemignani, T., Azevedo, R.C., Higa, C.M., Coelho, O.R., Matos-Souza, J.R., Nadruz, W., Increased popliteal circumferential wall tension induced by orthostatic body posture is associated with local atherosclerotic plaques (2012) Atherosclerosis, 224, pp. 118-122. , 10.1016/j.atherosclerosis.2012.06.069, 2281862

Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers) provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs(+ )formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs(+ )within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs(+ )for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs(+ )and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output

PLD physics and photonics in service of future

Pulsed Laser Deposition (PLD) is a deposition technique which was developed more than forty years ago, but it became widespread in research laboratories only in the eighties for thin film growth of superconductive materials. It is relatively economic and simple, although its physics is quite complex

Downy mildew warning systems for vineyards cultivated under plastic covering - influence on yield and quality

Poste

A Comparison of Computerized Chemical Models for Equilibrium Calculations in Aqueous Systems

A survey of computer programs which are currently being used to calculate the distribution of species in aqueous solutions, especially natural waters, has been made in order to 1) provide an inventory of available programs with a short description of their uses, 2) compare the consistency of their output for two given test solutions and 3) identify major weaknesses or problems encountered from their use. More than a dozen active programs which can be used for distribution of species and activity calculations for homogeneos equilibria among the major anions and cations of natural waters have been inventoried. Half of these programs can also accept several trace elements including Fe, Al, Mn, Cu, Ni, Zn, Cd, Pb, Ag, Hg, As, Ba, Sr, and B. Consistency between programs was evaluated by comparing the log of the molal concentrations of free ions and complexes for two test solutions: a hypothetical seawater analysis and a hypothetical river water analysis. Comparison of the free major ion concentrations in the river water test case shows excellent agreement for the major species. In the seawater test case there is less agreement and for both test cases the minor species commonly show orders of magnitude differences in concentrations. These differences primarily reflect differences in the thermodynamic data base of each chemical model although other factors such as activity coefficient calculations, redox assumptions, temperature corrections, alkalinity corrections and the number of complexes used all have an affect on the output

Aberrant chromatin landscape following loss of the H3.3 chaperone Daxx in haematopoietic precursors leads to Pu.1-mediated neutrophilia and inflammation

Defective silencing of retrotransposable elements has been linked to inflammageing, cancer and autoimmune diseases. However, the underlying mechanisms are only partially understood. Here we implicate the histone H3.3 chaperone Daxx, a retrotransposable element repressor inactivated in myeloid leukaemia and other neoplasms, in protection from inflammatory disease. Loss of Daxx alters the chromatin landscape, H3.3 distribution and histone marks of haematopoietic progenitors, leading to engagement of a Pu.1-dependent transcriptional programme for myelopoiesis at the expense of B-cell differentiation. This causes neutrophilia and inflammation, predisposing mice to develop an autoinflammatory skin disease. While these molecular and phenotypic perturbations are in part reverted in animals lacking both Pu.1 and Daxx, haematopoietic progenitors in these mice show unique chromatin and transcriptome alterations, suggesting an interaction between these two pathways. Overall, our findings implicate retrotransposable element silencing in haematopoiesis and suggest a cross-talk between the H3.3 loading machinery and the pioneer transcription factor Pu.1

Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

Os Açores e os impérios : séculos XV a XX

[...]. Os Açores não constituem simplesmente um elo da correspondência transatlântica. Aliás, possuem uma identidade bem complexa. Com efeito, se a História evidencia muito a mundividência, apresentando as ilhas como o centro do Mundo, já a literatura ressalta muito o isolamento, resultante do afastamento dos continentes e da descontinuidade territorial, apresentando as ilhas como o fim do Mundo. Curiosamente, a política e os políticos, talvez com maior sentido do pragmatismo e da oportunidade, agem em função das circunstâncias. De facto, proclamam a projecção da universalidade, quando reivindicam mais capacidade de auto-governo, mas insistem na pobreza da ultraperifericidade, quando exigem mais contrapartidas financeiras. Apesar da divergência das perspectivas, atentemos mais na universalidade dos Açores, que historicamente influi na definição das dinâmicas do Atlântico, conferindo maior projecção à Europa