3,536 research outputs found
Online Εvaluation of Earth Observation Derived Indicators for Urban Planning and Management
Extensive urbanization and growth of population density have acquired a paramount interest towards a sustainable urban development. Earth Observation (EO) is an important source of information required for urban planning and management. The availability of EO data provides the immense opportunity for urban environmental indicators development easily derived by remote sensors. In this study, the state of the art methods were employed to develop urban planning and management relevant indicators that can be evaluated by using EO data. The importance of this approach lies on providing alternatives for improving urban planning and management, without consuming time and resources in collecting field or archived data. The evaluated urban indicators were integrated into a Web‐based Information System that was developed for online exploitation. The results for three case studies are therefore available online and can be used by urban planners and stakeholders in supporting their planning decisions
Duplications of the critical Rubinstein-Taybi deletion region on chromosome 16p13.3 cause a novel recognisable syndrome
Background The introduction of molecular karyotyping technologies facilitated the identification of specific genetic disorders associated with imbalances of certain genomic regions. A detailed phenotypic delineation of interstitial 16p13.3 duplications is hampered by the scarcity of such patients.
Objectives To delineate the phenotypic spectrum associated with interstitial 16p13.3 duplications, and perform a genotype-phenotype analysis.
Results The present report describes the genotypic and phenotypic delineation of nine submicroscopic interstitial 16p13.3 duplications. The critically duplicated region encompasses a single gene, CREBBP, which is mutated or deleted in Rubinstein-Taybi syndrome. In 10 out of the 12 hitherto described probands, the duplication arose de novo.
Conclusions Interstitial 16p13.3 duplications have a recognizable phenotype, characterized by normal to moderately retarded mental development, normal growth, mild arthrogryposis, frequently small and proximally implanted thumbs and characteristic facial features. Occasionally, developmental defects of the heart, genitalia, palate or the eyes are observed. The frequent de novo occurrence of 16p13.3 duplications demonstrates the reduced reproductive fitness associated with this genotype. Inheritance of the duplication from a clinically normal parent in two cases indicates that the associated phenotype is incompletely penetrant
Spatial clustering of high load ocular Chlamydia trachomatis infection in trachoma: A cross-sectional population-based study
Chlamydia trachomatis (Ct) is the most common cause of bacterial sexually transmitted infection and infectious cause of blindness (trachoma) worldwide. Understanding the spatial distribution of Ct infection may enable us to identify populations at risk and improve our understanding of Ct transmission. In this study, we sought to investigate the spatial distribution of Ct infection and the clinical features associated with high Ct load in trachoma-endemic communities on the Bijagós Archipelago (Guinea Bissau). We collected 1507 conjunctival samples and corresponding detailed clinical data during a cross-sectional population-based geospatially representative trachoma survey. We used droplet digital PCR to estimate
Ct load on conjunctival swabs. Geostatistical tools were used to investigate clustering of ocular Ct infections.
Spatial clusters (independent of age and gender) of individuals with high Ct loads were identified using local indicators of spatial association. We did not detect clustering of individuals with low load infections. These data suggest that infections with high bacterial load may be important in Ct transmission. These geospatial tools may be useful in the study of ocular Ct transmission dynamics and as part of trachoma surveillance post-treatment, to identify clusters of infection and thresholds of Ct load that may be important foci of re-emergent infection in communities
Simulations of energetic beam deposition: from picoseconds to seconds
We present a new method for simulating crystal growth by energetic beam
deposition. The method combines a Kinetic Monte-Carlo simulation for the
thermal surface diffusion with a small scale molecular dynamics simulation of
every single deposition event. We have implemented the method using the
effective medium theory as a model potential for the atomic interactions, and
present simulations for Ag/Ag(111) and Pt/Pt(111) for incoming energies up to
35 eV. The method is capable of following the growth of several monolayers at
realistic growth rates of 1 monolayer per second, correctly accounting for both
energy-induced atomic mobility and thermal surface diffusion. We find that the
energy influences island and step densities and can induce layer-by-layer
growth. We find an optimal energy for layer-by-layer growth (25 eV for Ag),
which correlates with where the net impact-induced downward interlayer
transport is at a maximum. A high step density is needed for energy induced
layer-by-layer growth, hence the effect dies away at increased temperatures,
where thermal surface diffusion reduces the step density. As part of the
development of the method, we present molecular dynamics simulations of single
atom-surface collisions on flat parts of the surface and near straight steps,
we identify microscopic mechanisms by which the energy influences the growth,
and we discuss the nature of the energy-induced atomic mobility
A theory of ferromagnetism in planar heterostructures of (Mn,III)-V semiconductors
A density functional theory of ferromagnetism in heterostructures of compound
semiconductors doped with magnetic impurities is presented. The variable
functions in the density functional theory are the charge and spin densities of
the itinerant carriers and the charge and localized spins of the impurities.
The theory is applied to study the Curie temperature of planar heterostructures
of III-V semiconductors doped with manganese atoms. The mean-field,
virtual-crystal and effective-mass approximations are adopted to calculate the
electronic structure, including the spin-orbit interaction, and the magnetic
susceptibilities, leading to the Curie temperature. By means of these results,
we attempt to understand the observed dependence of the Curie temperature of
planar -doped ferromagnetic structures on variation of their
properties. We predict a large increase of the Curie Temperature by additional
confinement of the holes in a -doped layer of Mn by a quantum well.Comment: 8 pages, 7 figure
Saturated Ferromagnetism and Magnetization Deficit in Optimally Annealed (Ga,Mn)As Epilayers
We examine the Mn concentration dependence of the electronic and magnetic
properties of optimally annealed Ga1-xMnxAs epilayers for 1.35% < x < 8.3%. The
Curie temperature (Tc), conductivity, and exchange energy increase with Mn
concentration up to x ~ 0.05, but are almost constant for larger x, with Tc ~
110 K. The ferromagnetic moment per Mn ion decreases monotonically with
increasing x, implying that an increasing fraction of the Mn spins do not
participate in the ferromagnetism. By contrast, the derived domain wall
thickness, an important parameter for device design, remains surprisingly
constant.Comment: 8 pages, 4 figures, submitted for Rapid Communication in Phys Rev
Epigenetic characterization of the FMR1 promoter in induced pluripotent stem cells from human fibroblasts carrying an unmethylated full mutation
Silencing of the FMR1 gene leads to fragile X syndrome, the most common cause of inherited intellectual disability. To study the epigenetic modifications of the FMR1 gene during silencing in time, we used fibroblasts and induced pluripotent stem cells (iPSCs) of an unmethylated full mutation (uFM) individual with normal intelligence. The uFM fibroblast line carried an unmethylated FMR1 promoter region and expressed normal to slightly increased FMR1 mRNA levels. The FMR1 expression in the uFM line corresponds with the increased H3 acetylation and H3K4 methylation in combination with a reduced H3K9 methylation. After reprogramming, the FMR1 promoter region was methylated in all uFM iPSC clones. Two clones were analyzed further and showed a lack of FMR1 expression, whereas the presence of specific histone modifications also indicated a repressed FMR1 promoter. In conclusion, these findings demonstrate that the standard reprogramming procedure leads to epigenetic silencing of the fully mutated FMR1 gene
Ferromagnetic Semiconductors: Moving Beyond (Ga,Mn)As
The recent development of MBE techniques for growth of III-V ferromagnetic
semiconductors has created materials with exceptional promise in spintronics,
i.e. electronics that exploit carrier spin polarization. Among the most
carefully studied of these materials is (Ga,Mn)As, in which meticulous
optimization of growth techniques has led to reproducible materials properties
and ferromagnetic transition temperatures well above 150 K. We review progress
in the understanding of this particular material and efforts to address
ferromagnetic semiconductors as a class. We then discuss proposals for how
these materials might find applications in spintronics. Finally, we propose
criteria that can be used to judge the potential utility of newly discovered
ferromagnetic semiconductors, and we suggest guidelines that may be helpful in
shaping the search for the ideal material.Comment: 37 pages, 4 figure
Temperature-dependent magnetization in diluted magnetic semiconductors
We calculate magnetization in magnetically doped semiconductors assuming a
local exchange model of carrier-mediated ferromagnetic mechanism and using a
number of complementary theoretical approaches. In general, we find that the
results of our mean-field calculations, particularly the dynamical mean field
theory results, give excellent qualitative agreement with the experimentally
observed magnetization in systems with itinerant charge carriers, such as
Ga_{1-x}Mn_xAs with 0.03 < x < 0.07, whereas our percolation-theory-based
calculations agree well with the existing data in strongly insulating
materials, such as Ge_{1-x}Mn_x. We comment on the issue of non-mean-field like
magnetization curves and on the observed incomplete saturation magnetization
values in diluted magnetic semiconductors from our theoretical perspective. In
agreement with experimental observations, we find the carrier density to be the
crucial parameter determining the magnetization behavior. Our calculated
dependence of magnetization on external magnetic field is also in excellent
agreement with the existing experimental data.Comment: 17 pages, 15 figure
- …