Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ($T_c$ $\sim$ 16.5 K) and largest gap among conventional superconductors. In its thin-film form, the $T_c$ of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin film (below 50 nm) with high $T_c$. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel ($k_F$$\ell$) parameter of $\sim$ 14. Accordingly we observe $T_c$ $\sim$ 17.06 K (point of 50% of normal state resistance), the highest value reported so far for films of thickness below 50 nm, indicating that HTCVD could be particularly useful for growing high quality NbN thin films

Cross infection control measures and the treatment of patients at risk of Creutzfeldt Jakob disease in UK general dental practice

AIMS: To determine the suitability of key infection control measures currently employed in UK dental practice for delivery of dental care to patients at risk of prion diseases. MATERIALS AND METHODS: Subjects: Five hundred dental surgeons currently registered with the General Dental Council of the UK. Data collection: Structured postal questionnaire. Analysis: Frequencies, cross-tabulations and chi-squared analysis. RESULTS: The valid response rate to the questionnaire was 69%. 33% of practices had no policy on general disinfection and sterilisation procedures. Only 10 of the 327 responding practices (3%) possessed a vacuum autoclave. 49% of dentists reported using the BDA medical history form but less than 25% asked the specific questions recommended by the BDA to identify patients at risk of iatrogenic or familial CJD. However, 63% of practitioners would refer such patients, if identified, to a secondary care facility. Of the 107 practitioners who were prepared to provide dental treatment, 75 (70%) would do so using routine infection control procedures. CONCLUSIONS: Most of the dental practices surveyed were not actively seeking to identify patients at risk of prion diseases. In many cases, recommended procedures for providing safe dental care for such patients were not in place

Dental treatment and risk of variant CJD - a case control study

Abstract Objective: Knowledge of risk factors for variant CJD (vCJD) remains limited, but transmission of prion proteins via re-useable medical devices, including dental instruments, or enhanced susceptibility following trauma to the oral cavity is a concern. This study aimed to identify whether previous dental treatment is a risk factor for development of vCJD. Design: Case control study Methods: Risk factor questionnaires completed by interview with relatives of 130 vCJD patients and with relatives of 66 community and 53 hospital controls were examined by a dental surgeon. Responses regarding dental treatments were analysed. Results: We did not find a statistically significant excess of risk of vCJD associated with dental treatments with the exception of extractions in an unmatched analysis of vCJD cases with community controls (p=0.02). However, this result may be explained by multiple testing. Conclusions: This is the first published study to date to examine potential links between vCJD and dental treatment. There was no convincing evidence found of an increased risk of variant CJD associated with reported dental treatment. However, the power of the study is restricted by the number of vCJD cases to date and does not preclude the possibility that some cases have resulted from secondary transmission via dental procedures. Due to the limitations of the data available, more detailed analyses of dental records are required to fully exclude the possibility of transmission via dental treatment

CWRML: representing crop wild relative conservation and use data in XML

Background Crop wild relatives are wild species that are closely related to crops. They are valuable as potential gene donors for crop improvement and may help to ensure food security for the future. However, they are becoming increasingly threatened in the wild and are inadequately conserved, both in situ and ex situ. Information about the conservation status and utilisation potential of crop wild relatives is diverse and dispersed, and no single agreed standard exists for representing such information; yet, this information is vital to ensure these species are effectively conserved and utilised. The European Community-funded project, European Crop Wild Relative Diversity Assessment and Conservation Forum, determined the minimum information requirements for the conservation and utilisation of crop wild relatives and created the Crop Wild Relative Information System, incorporating an eXtensible Markup Language (XML) schema to aid data sharing and exchange. Results Crop Wild Relative Markup Language (CWRML) was developed to represent the data necessary for crop wild relative conservation and ensure that they can be effectively utilised for crop improvement. The schema partitions data into taxon-, site-, and population-specific elements, to allow for integration with other more general conservation biology schemata which may emerge as accepted standards in the future. These elements are composed of sub-elements, which are structured in order to facilitate the use of the schema in a variety of crop wild relative conservation and use contexts. Pre-existing standards for data representation in conservation biology were reviewed and incorporated into the schema as restrictions on element data contents, where appropriate. Conclusion CWRML provides a flexible data communication format for representing in situ and ex situ conservation status of individual taxa as well as their utilisation potential. The development of the schema highlights a number of instances where additional standards-development may be valuable, particularly with regard to the representation of population-specific data and utilisation potential. As crop wild relatives are intrinsically no different to other wild plant species there is potential for the inclusion of CWRML data elements in the emerging standards for representation of biodiversity data

Notes on phytosociology of Juniperus excelsa in Macedonia (southern Balkan Peninsula)

Juniperus excelsa is an East Mediterranean species found also in marginal, sub-mediterranean regions of the southern part of the Balkan Peninsula. It prefers shallow soils in the warmest habitats of the zone of thermophilous deciduous forests. In the past the rank of alliance and the name of Juniperion excelsae-foetidissimae have been suggested for the vegetation dominated by Juniperus excelsa in the Balkan Peninsula. In this paper we present the valid description of the alliance in accordance with the International Code of Phytosociological Nomenclature. The validation of the Juniperion excelsae-foetidissimae required description of a new association - the Querco trojanae-Juniperetum excelsae. The Juniperion excelsae-foetidissimae is classified within the order of Quercetalia pubescentis Klika 1933 (the Quercetea pubescentis Doing-Kraft ex Scamoni et Passarge 1959)

Croissance de semi-conducteurs à grand gap

La modélisation et la simulation des procédés de croissance tel que le transport physique en phase vapeur (PVT), le dépôt chimique en phase vapeur (CVD ou HTCVD) et les techniques hybrides (CFPVT), sont suffisamment au point pour être utilisées comme des outils de compréhension des phénomènes physiques couplés et comme des outils de conception de nouveaux procédés et d'optimisation de procédés existants. La modélisation des procédés d'élaboration rassemble plusieurs voies physico-chimiques de complexité variable, depuis des études thermodynamiques et/ou cinétiques jusqu'aux transferts simultanés de matière et de chaleur couplées avec les bases de données et propriétés thermodynamiques et/ou cinétiques et de transport. Différentes voies de modélisation sont utilisées, thermodynamiques, cinétique ou transfert de masse, de façon couplée ou découplée, permettant de visualiser l'évolution de la croissance et ainsi comprendre le rôle complexe et fortement couplé des phénomènes

A global view on the riparian forests with Salix neotricha and Populus alba in the Iberian Peninsula (Portugal and Spain)

Forests dominated by Salix neotricha, and Populus alba found along the mesoeutrophic rivers in the Iberian Peninsula, were studied. We discuss the floristic circumscription, chorology, and community segregation based on the available releve´s of all Iberian riparian communities included in Populenion albae. Eleven formerly described communities were analyzed and due to original floristic combination, habitat features, and biogeographic scope, a new willow and poplar forest type is proposed within a well-defined biogeographical unit (Sadensean-Dividing Portuguese Subprovince): Clematido campaniflorae- Salicetum neotrichae. This syntaxon is found under a semi-hyperoceanic thermomediterranean to lower mesomediterranean, subhumid to humid bioclimate. Cluster analysis including all Iberian communities of Populenion albae shows a clear floristic segregation within the suballiance and confirms the originality of the new association. Furthermore, chemical characteristics of the water along some of the Portuguese watercourses with Populenion albae were studied and compared to the oligotrophic rivers occupied by Osmundo-Alnion communities. This study suggests that floristic separation between the communities of Populenion and Osmundo-Alnion is accompanied by a differentiation of the water trophic level

Testing macroecological abundance patterns: The relationship between local abundance and range size, range position and climatic suitability among European vascular plants

Aim: A fundamental question in macroecology centres around understanding the relationship between species' local abundance and their distribution in geographical and climatic space (i.e. the multi‐dimensional climatic space or climatic niche). Here, we tested three macroecological hypotheses that link local abundance to the following range properties: (a) the abundance-range size relationship, (b) the abundance-range centre relationship and (c) the abundance-suitability relationship. Location: Europe. Taxon: Vascular plants. Methods: Distribution range maps were extracted from the Chorological Database Halle to derive information on the range and niche sizes of 517 European vascular plant species. To estimate local abundance, we assessed samples from 744,513 vegetation plots in the European Vegetation Archive, where local species' abundance is available as plant cover per plot. We then calculated the 'centrality', that is, the distance between the location of the abundance observation and each species' range centre in geographical and climatic space. The climatic suitability of plot locations was estimated using coarse‐grain species distribution models (SDMs). The relationships between centrality or climatic suitability with abundance was tested using linear models and quantile regression. We summarized the overall trend across species' regression slopes from linear models and quantile regression using a meta‐analytical approach. Results: We did not detect any positive relationships between a species' mean local abundance and the size of its geographical range or climatic niche. Contrasting yet significant correlations were detected between abundance and centrality or climatic suitability among species. Main conclusions: Our results do not provide unequivocal support for any of the relationships tested, demonstrating that determining properties of species' distributions at large grains and extents might be of limited use for predicting local abundance, including current SDM approaches. We conclude that environmental factors influencing individual performance and local abundance are likely to differ from those factors driving plant species' distribution at coarse resolution and broad geographical extents