Decoupling Graphene from SiC(0001) via Oxidation

When epitaxial graphene layers are formed on SiC(0001), the first carbon layer (known as the "buffer layer"), while relatively easy to synthesize, does not have the desirable electrical properties of graphene. The conductivity is poor due to a disruption of the graphene pi-bands by covalent bonding to the SiC substrate. Here we show that it is possible to restore the graphene pi-bands by inserting a thin oxide layer between the buffer layer and SiC substrate using a low temperature, CMOS-compatible process that does not damage the graphene layer

Mapping provision of enterprise education and support for entrepreneurship in England's higher education institutions

The aim of this paper is to provide a comprehensive overview of the state of support for enterprise and entrepreneurship education within England's Higher Education Institutions (HEIs). The paper is based upon the National Council for Graduate Entrepreneurship (NCGE) Mapping Study of this activity. Research commissioned by NCGE (NCGE 2004; Hannon, 2005) has shown that there is a growing knowledge base about enterprise education but less so concerning the provision for student enterprise and graduate entrepreneurship. There has been no recent study that has comprehensively mapped enterprise education activity in all higher education institutions across England. Institutional contacts in 94% of all the HEIs for this study entered data into an online institutional mapping template containing questions on modules/courses, non-accredited support and other institutional characteristics. The researchers maintained regular telephone contact and made personal visits to maximise data entry and to provide support where needed. This approach has led to the collection of a unique and robust data set that has been thoroughly and empirically analysed using SPSS. The paper presents a national overview and highlights selected regional variations in enterprise education and non–accredited entrepreneurship support. This includes: current and planned course provision over time; student profiles and targets; primary learning outcomes; non-accredited provision and student engagement; primary funding sources; and the development of a range of institutional characteristics conducive to supporting student enterprise and graduate entrepreneurship. The findings from the mapping study illuminate the current HE landscape of support for enterprise and entrepreneurship thereby providing HEIs and educators with a valuable national resource as well as informing other key stakeholders – RDAs and central government – of the scope and scale of the contribution that HEIs offer to regional economic and social agendas. From such a unique evidence base more informed decisions can be taken in considering effective mechanisms for the future growth and development of HEI contributions. This paper offers the findings from a current comprehensive dataset on the HE provision of enterprise and entrepreneurship education in England. With 94% of the HEIs in the study providing data online the study has also created a nationaldatabase that can be a platform for sharing knowledge and experience across the community. Furthermore conducting a repeat online study on an annual basis will provide valuable time series data. The study findings will help shape the future environment for student enterprise and graduate entrepreneurship across England

The state of education provision for enterprise and entrepreneurship: A mapping study of England’s HEIs

The aim of this paper is to provide a comprehensive overview of the state of provision for enterprise and entrepreneurship education within England’s Higher Education Institutions (HEIs). The paper is based on the National Council for Graduate Entrepreneurship (NCGE) Mapping Study of enterprise education in England. Research commissioned by NCGE (ISBA 2004) has shown that there is a growing knowledge base about the nature of enterprise education but less so evidence concerning the provision for enhancing student enterprise and graduate entrepreneurship. Although studies have taken place in the US and Levie undertook a study of the UK published in 1999, there has been no recent study that has comprehensively mapped enterprise education activity in all higher education institutions across England. Institutional contacts in 94% of all the HEIs for this study entered data into an online institutional mapping template containing questions on modules/courses, non-accredited support and other institutional characteristics. The researchers maintained regular telephone contact and made personal visits to maximise data entry and to provide support where needed. This approach has led to the collection of a unique and robust data set that has been analysed using SPSS. The paper presents a national overview and highlights selected regional variations in enterprise education and non–accredited entrepreneurship support. This includes: current and planned course provision over time; student profiles and targets; primary learning outcomes; non-accredited provision and student engagement; primary funding sources; and the development of a range of institutional characteristics conducive to supporting student enterprise and graduate entrepreneurship. The findings from the mapping study illuminate the current HE landscape of support for enterprise and entrepreneurship thereby providing HEIs and educators with a valuable national resource. Additionally, this informs other key stakeholders – RDAs and central government – of the scope and scale of the contribution that HEIs offer to regional economic and social agendas. From such a unique evidence base more informed decisions can be taken when considering effective mechanisms for the future growth and development of HEI contributions. This paper offers the findings from a unique and current comprehensive dataset on the HE provision of enterprise and entrepreneurship education in England. With 94% of the HEIs in the study providing data online the study has created a national database that can be a platform for sharing knowledge and experience across the community. Furthermore conducting a repeat online study on an annual basis will provide valuable time series data. The study findings will help shape the future environment for student enterprise and graduate entrepreneurship across England

Molecular Dynamics Simulation of Compressible Fluid Flow in Two-Dimensional Channels

We study compressible fluid flow in narrow two-dimensional channels using a novel molecular dynamics simulation method. In the simulation area, an upstream source is maintained at constant density and temperature while a downstream reservoir is kept at vacuum. The channel is sufficiently long in the direction of the flow that the finite length has little effect on the properties of the fluid in the central region. The simulated system is represented by an efficient data structure, whose internal elements are created and manipulated dynamically in a layered fashion. Consequently the code is highly efficient and manifests completely linear performance in simulations of large systems. We obtain the steady-state velocity, temperature, and density distributions in the system. The velocity distribution across the channel is very nearly a quadratic function of the distance from the center of the channel and reveals velocity slip at the boundaries; the temperature distribution is only approximately a quartic function of this distance from the center to the channel. The density distribution across the channel is non-uniform. We attribute this non-uniformity to the relatively high Mach number, approximately 0.5, in the fluid flow. An equation for the density distribution based on simple compressibility arguments is proposed; its predictions agree well with the simulation results. Validity of the concept of local dynamic temperature and the variation of the temperature along the channel are discussed.Comment: 16 pages (in latex) + 8 figures (in a single ps file). Submitted to the Physical Review

Benchmarking of 3D space charge codes using direct phase space measurements from photoemission high voltage DC gun

We present a comparison between space charge calculations and direct measurements of the transverse phase space for space charge dominated electron bunches after a high voltage photoemission DC gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit setup for a set of parameters such as charge per bunch and the solenoid current. The data is compared with detailed simulations using 3D space charge codes GPT and Parmela3D with initial particle distributions created from the measured transverse and temporal laser profiles. Beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach the theoretical maximum set by the thermal energy and accelerating field at the photocathode.Comment: 11 pages, 23 figures. submitted to Phys Rev ST-A

Coherent control of the cooperative branching ratio for nuclear x-ray pumping

Coherent control of nuclear pumping in a three level system driven by x-ray light is investigated. In single nuclei, the pumping performance is determined by the branching ratio of the excited state populated by the x-ray pulse. Our results are based on the observation that in ensembles of nuclei, cooperative excitation and decay leads to a greatly modified nuclear dynamics, which we characterize by a time-dependent cooperative branching ratio. We discuss prospects of steering the x-ray pumping by coherently controlling the cooperative decay. First, we study an ideal case with purely superradiant decay and perfect control of the cooperative emission. A numerical analysis of x-ray pumping in nuclear forward scattering with coherent control of the cooperative decay via externally applied magnetic fields is presented. Next, we provide an extended survey of nuclei suitable for our scheme, and propose proof-of-principle implementations already possible with typical M\"ossbauer nuclear systems such as $^{57}\mathrm{Fe}$. Finally, we discuss the application of such control techniques to the population or depletion of long-lived nuclear states.Comment: 11 pages, 8 figures; updated to the published versio

Genomic landscape of human allele-specific DNA methylation

DNA methylation mediates imprinted gene expression by passing an epigenomic state across generations and differentially marking specific regulatory regions on maternal and paternal alleles. Imprinting has been tied to the evolution of the placenta in mammals and defects of imprinting have been associated with human diseases. Although recent advances in genome sequencing have revolutionized the study of DNA methylation, existing methylome data remain largely untapped in the study of imprinting. We present a statistical model to describe allele-specific methylation (ASM) in data from high-throughput short-read bisulfite sequencing. Simulation results indicate technical specifications of existing methylome data, such as read length and coverage, are sufficient for fullgenome ASM profiling based on our model. We used our model to analyze methylomes for a diverse set of human cell types, including cultured and uncultured differentiated cells, embryonic stem cells and induced pluripotent stem cells. Regions of ASM identified most consistently across methylomes are tightly connected with known imprinted genes and precisely delineate the boundaries of several known imprinting control regions. Predicted regions of ASM common to multiple cell types frequently mark noncoding RNA promoters and represent promising starting points for targeted validation. More generally, our model provides the analytical complement to cutting-edge experimental technologies for surveying ASM in specific cell types and across species

Experiências de contacto dos bebés com a linguagem escrita

The purpose of this study is to characterize the literacy experiences ofbabies aged between 14 and 24 months. In this study, four issues were analysed: which type of written language experiences are offered to the children, how parents value these literacy experiences, the way parents perceive their own role in the literacy development of their children and what parents know about their means of contributing to the literacy development of their children. Six mothers were interviewed. These interviews were analysed with the use of a categorical content analysis. The results suggest that mothers value and include in their practices facilitative and mediation actions of literacy experiences with their children, noting some variability depending on the respective qualifications.Este estudo exploratório visa descrever as experiências de literacia de bebés entre os 14 e os 25 meses. Analisamse quatro questões, que experiências envolvendo a linguagem escrita no seio familiar são proporcionadas aos bebés, qual o valor que os pais lhes atribuem, como percepcionam o seu papel na promoção do desenvolvimento literácito dos filhos e como podem contribuir para o desenvolvimento da literacia dos mesmos. Adotou-se uma metodologia qualitativa, com recurso à análise de conteúdo categorial das respostas dadas por seis mães em entrevista individual e semiestruturada. Concluiu-se que estas mães valorizam e incluem nas suas práticas ações facilitadoras e de mediação de experiências de literacia por parte dos seus bebés, notando-se alguma variabilidade em função das respetivas habilitações académicas.(undefined)info:eu-repo/semantics/publishedVersio

Cooperative effects in nuclear excitation with coherent x-ray light

The interaction between super-intense coherent x-ray light and nuclei is studied theoretically. One of the main difficulties with driving nuclear transitions arises from the very narrow nuclear excited state widths which limit the coupling between laser and nuclei. In the context of direct laser-nucleus interaction, we consider the nuclear width broadening that occurs when in solid targets, the excitation caused by a single photon is shared by a large number of nuclei, forming a collective excited state. Our results show that for certain isotopes, cooperative effects may lead to an enhancement of the nuclear excited state population by almost two orders of magnitude. Additionally, an update of previous estimates for nuclear excited state population and signal photons taking into account the experimental advances of the x-ray coherent light sources is given. The presented values are an improvement by orders of magnitude and are encouraging for the future prospects of nuclear quantum optics.Comment: 22 pages, 4 figures, 5 tables; updated to the published version, one additional results tabl