Low Energy Coherent Transport in Metallic Carbon Nanotube Junctions

We study the low-energy electronic properties of a junction made of two crossed metallic carbon nanotubes of general chiralities. We derive a tight binding tunneling matrix element that couples low-energy states on the two tubes, which allows us to calculate the contact conductance of the junction. We find that the intrinsic asymmetries of the junction cause the forward and backward hopping probabilities from one tube to another to be different. This defines a zero-field Hall conductance for the junction, which we find to scale inversely with the junction contact conductance. Through a systematic study of the dependence of the junction conductance on different junction parameters, we find that the crossing angle is the dominant factor which determines the magnitude of the conductance.Comment: 8 pages, 9 figure

Characteristics of Iconic High-rise Buildings

Iconography is a degree given to a building and an objective of its architectural design. The iconic high-rise buildings are important in various fields. Distinctiveness in skyscrapers is not achieved by chance or by exciting stories told about the building. Exaggeration in one of design elements does not achieve the uniqueness and architectural creativity. Iconicity is a product of gathering specific main cores. The iconic tall buildings have distinct characteristics that set them different from other buildings. This paper proposes to combine the distinctive characteristics of the iconic high-rise buildings from different references to form a unified and clear methodology used when designing to achieve the iconicity. The developed methodology can be relied upon in the critical analysis of those skyscrapers to determine the degree of iconicity, and to know the reasons for the failure of some tall buildings in achieving the iconicity with a simple and systematic methodology

Characteristics of Iconic High-rise Buildings

Iconography is a degree given to a building and an objective of its architectural design. The iconic high-rise buildings are important in various fields. Distinctiveness in skyscrapers is not achieved by chance or by exciting stories told about the building. Exaggeration in one of design elements does not achieve the uniqueness and architectural creativity. Iconicity is a product of gathering specific main cores. The iconic tall buildings have distinct characteristics that set them different from other buildings. This paper proposes to combine the distinctive characteristics of the iconic high-rise buildings from different references to form a unified and clear methodology used when designing to achieve the iconicity. The developed methodology can be relied upon in the critical analysis of those skyscrapers to determine the degree of iconicity, and to know the reasons for the failure of some tall buildings in achieving the iconicity with a simple and systematic methodology

Étude de la contamination par les métaux lourds du champ d'épandage des eaux usées de la ville de Marrakech (Maroc)

La bioconcentration du Zn, Cu et Cd a été étudiée chez Melanopsis praemorsa L. (Gastéropode prosobranche) provenant de deux sites d'une khettara située dans le champ d'épandage des eaux usées de la ville de Marrakech. Les khettaras représentent un système d'irrigation traditionnel que l'on trouve dans certaines zones arides et semi-arides de la région ouest-paléarctique. L'eau est mise à jour par drainage de la nappe phréatique. Le degré de contamination de ce gastéropode s'avère très élevé et les teneurs métalliques augmentent de l'hiver à l'été. Les causes de la variabilité des concentrations métalliques chez les gastéropodes des deux stations ont été recherchées par des expériences de transplantation, et par des dosages de métaux au niveau du sédiment, de la spirogyre et du périphyton installé sur des substrats artificiels. Les résultats obtenus montrent que les différences entre les concentrations métalliques accumulées par les Melanopsis dans les deux stations pourraient être attribuées à la spéciation du métal dans l'eau. D'autres facteurs peuvent être mis en cause et méritent d'être précisés.Molluscs are well known for their capacity to bioaccumulate heavy metals from water or sediments. This study involves an evaluation of the contamination level of the undergroud and surface waters from a specific irrigation system known as a « khetarra », located near the town of Marrakech (Morocco). Khettaras represent a traditional systern by means ofwhich the ground water is drained to the surface and then can be used as drinking water or for irrigation in some arid and semi-arid areas. The bioindicator chosen was the gasteropod Melanopsispraemorca L. Two stations (Kl and K2) were investigated in a khettara located in spreading Marrakech waste water. The contamination of soils and water by heavy metals, eipecially Zn, Cu and Cd was first described by EL MEZD1 (1985) and SEDKI(1990).The studied khettara (1500 m. in length) is contaminated in two different ways: first by infiltration of waste water from the Seguia system and secondly directly by over-flow and escape of a main common sewer which crosses over the khetarra between the Kl andK2 stations.At each station, sediment peripbyton, Spirogyra and M. praemorsa were sampled in different seasons. Each sample was prepared for analysis (S.A.A. varian 475.AA) according to the method described by COSSON (1987). Flame atomization was chosen for Zn and Cu, the grafite furnace for Cd.The main results concern the level of contamination, with a comparison between Kl and K2 stations, the variation in contamination according to the seasons, the dilferent routes of contamination, namely through water or by the trophic chaîn (periphfion and Spirogyra).The degree of contamination in M. praemona is signifïcatively higher at the Kl station, with the following ranking: Zn> Cu> Cd (fig. 2, 3 and 4). Compared with other literature data: FORSTNER et al., 1981; RADA, 1985; COSSON, 1987; PIP, 1992, the upper concentrations are the highest.The metal concentrations increase from winter to summer, with significant differences between winter and spring or summer values at Kl for Zn, Cu, Cd; the same distinction, but only for Zn and Cd at K2 station.The causes of variation in metal concentrations in the gasteropods from the two sites were investigated,by in situ cotransplantation experiences and by measuring metaflic concentrations in sediments, periphyton and Spirogyra. Results show that differences in gasteropod metal concentrations between sites appear to be related to differences in aqueous metal speciation. The data concerning the food chain show that metallic concentrations are higher for periphyton and, Spirogyra living at Kl station, this according to the data for M. praemorsa.In contrast, the level of contamination in sediments is higher at K2 station. The most probable hypothesis is that organic and suspended matter, present at a higher level in this station, bind the heary metals and reduce their bioavailability.The cotransplantation between Kl and K2 stations shows that the individuals transferred from Kl to K2 station for 15 days cease to bioaccumulate Zn and Cd. A detoxification process occurs for these two metals but not for Cu, which continues to increase; thus, bioavailability of different metals at the same station is not equivalent. On the other hand the individuals transferred from K2 to Kl station do not increase their Zn, Cu or Cd concentrations even after 30 days. Concerning this fact FRAZIER and GEORGE (1983) suggest the possibility of an adaptation to initial conditions.It seems that many other factors influence metal bioaccumulation and merit further study, e.g.: the size and the age of individuals, the biological cycle with the period of reproduction ; the interaction of abiotic factors: T°, salinity, dissolved orygen, turbidity, lighting

Identification and characterization of dysregulated P-element induced wimpy testis-interacting RNAs in head and neck squamous cell carcinoma.

It is clear that alcohol consumption is a major risk factor in the pathogenesis of head and neck squamous cell carcinoma (HNSCC); however, the molecular mechanism underlying the pathogenesis of alcohol-associated HNSCC remains poorly understood. The aim of the present study was to identify and characterize P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) and PIWI proteins dysregulated in alcohol-associated HNSCC to elucidate their function in the development of this cancer. Using next generation RNA-sequencing (RNA-seq) data obtained from 40 HNSCC patients, the piRNA and PIWI protein expression of HNSCC samples was compared between alcohol drinkers and non-drinkers. A separate piRNA expression RNA-seq analysis of 18 non-smoker HNSCC patients was also conducted. To verify piRNA expression, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed on the most differentially expressed alcohol-associated piRNAs in ethanol and acetaldehyde-treated normal oral keratinocytes. The correlation between piRNA expression and patient survival was analyzed using Kaplan-Meier estimators and multivariate Cox proportional hazard models. A comparison between alcohol drinking and non-drinking HNSCC patients demonstrated that a panel of 3,223 piRNA transcripts were consistently detected and differentially expressed. RNA-seq analysis and in vitro RT-qPCR verification revealed that 4 of these piRNAs, piR-35373, piR-266308, piR-58510 and piR-38034, were significantly dysregulated between drinking and non-drinking cohorts. Of these four piRNAs, low expression of piR-58510 and piR-35373 significantly correlated with improved patient survival. Furthermore, human PIWI-like protein 4 was consistently upregulated in ethanol and acetaldehyde-treated normal oral keratinocytes. These results demonstrate that alcohol consumption may cause dysregulation of piRNA expression in HNSCC and in vitro verifications identified 4 piRNAs that may be involved in the pathogenesis of alcohol-associated HNSCC

Charge transfer and Fermi level shift in p-doped single-walled carbon nanotubes

The electronic properties of p-doped single-walled carbon nanotube (SWNT) bulk samples were studied by temperature-dependent resistivity and thermopower, optical reflectivity, and Raman spectroscopy. These all give consistent results for the Fermi level downshift (Delta E(F)) induced by doping. We find Delta E(F) approximate to 0.35 eV and 0.50 eV for concentrated nitric and sulfuric acid doping respectively. With these values, the evolution of Raman spectra can be explained by variations in the resonance condition as E(F) moves down into the valence band. Furthermore, we find no evidence for diameter-selective doping, nor any distinction between doping responses of metallic and semiconducting tubes