2,302 research outputs found
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 . 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
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