1,687 research outputs found
Chromosome assignment of two cloned DNA probes hybridizing predominantly to human sex chromosomes
In situ hybridization experiments were carried out with two clones, YACG 35 and 2.8, which had been selected from two genomic libraries strongly enriched for the human Y chromosome. Besides the human Y chromosome, both sequences strongly hybridized to the human X chromosome, with few minor binding sites on autosomes. In particular, on the X chromosome DNA from clone YACG 35 hybridized to the centromeric region and the distal part of the short arm (Xp2.2). On the Y chromosome, the sequence was assigned to one site situated in the border region between Yq1.1 and Yq1.2. DNA from clone 2.8 also hybridized to the centromeric region of the X and the distal part of the short arm (Xq2.2). On the Y, however, two binding sites were observed (Yp1.1 and Yq1.2). The findings indicate that sex chromosomal sequences may be localized in homologous regions (as suggested from meiotic pairing) but also at ectopic sites
The Contribution of Registered Dietitians in the Management of Hyperemesis Gravidarum in the United Kingdom.
Hyperemesis Gravidarum (HG) is a condition at the extreme end of the pregnancy sickness spectrum, which can cause poor oral intake, malnutrition, dehydration and weight loss. The aim of this study is to explore the role of Registered Dietitians (RD) in the management of HG in the United Kingdom (UK). A survey was designed and distributed electronically to members of the British Dietetic Association. There were 45 respondents, 76% (n = 34) worked in secondary care hospitals, 11% (n = 5) were in maternal health specialist roles. The most commonly used referral criteria was the Malnutrition Universal Screening Tool (40%, n = 18), followed by second admission (36%, n = 16). However 36% (n = 16) reported no specific referral criteria. About 87% (n = 37) of respondents did not have specific clinical guidelines to follow. Oral nutrition supplements were used by 73% (n = 33) either 'sometimes' or 'most of the time'. Enteral and parenteral nutrition were less commonly used. There was an inconsistent use of referral criteria to dietetic services and a lack of specific clinical guidelines and patient resources. Further training for all clinicians and earlier recognition of malnutrition, alongside investment in the role of dietitians were recommended to improve the nutritional care of those with HG
Streaming Algorithm for Euler Characteristic Curves of Multidimensional Images
We present an efficient algorithm to compute Euler characteristic curves of
gray scale images of arbitrary dimension. In various applications the Euler
characteristic curve is used as a descriptor of an image.
Our algorithm is the first streaming algorithm for Euler characteristic
curves. The usage of streaming removes the necessity to store the entire image
in RAM. Experiments show that our implementation handles terabyte scale images
on commodity hardware. Due to lock-free parallelism, it scales well with the
number of processor cores. Our software---CHUNKYEuler---is available as open
source on Bitbucket.
Additionally, we put the concept of the Euler characteristic curve in the
wider context of computational topology. In particular, we explain the
connection with persistence diagrams
Local Charge of the nu=5/2 Fractional Quantum Hall State
Electrons in two dimensions and strong magnetic fields effectively lose their
kinetic energy and display exotic behavior dominated by Coulomb forces. When
the ratio of electrons to magnetic flux quanta in the system is near 5/2, the
unique correlated phase that emerges is predicted to be gapped with
fractionally charged quasiparticles and a ground state degeneracy that grows
exponentially as these quasiparticles are introduced. Interestingly, the only
way to transform between the many ground states would be to braid the
fractional excitations around each other, a property with applications in
quantum information processing. Here we present the first observation of
localized quasiparticles at nu=5/2, confined to puddles by disorder. Using a
local electrometer to compare how quasiparticles at nu=5/2 and nu=7/3 charge
these puddles, we are able to extract the ratio of local charges for these
states. Averaged over several disorder configurations and samples, we find the
ratio to be 4/3, suggesting that the local charges are e/3 at seven thirds and
e/4 at five halves, in agreement with theoretical predictions. This
confirmation of localized e/4 quasiparticles is necessary for proposed
interferometry experiments to test statistics and computational ability of the
state at nu=5/2.Comment: 6 pages, 4 figures corrected titl
Spin and valley quantum Hall ferromagnetism in graphene
In a graphene Landau level (LL), strong Coulomb interactions and the fourfold
spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At
partial filling, exchange interactions can spontaneously break this symmetry,
manifesting as additional integer quantum Hall plateaus outside the normal
sequence. Here we report the observation of a large number of these quantum
Hall isospin ferromagnetic (QHIFM) states, which we classify according to their
real spin structure using temperature-dependent tilted field magnetotransport.
The large measured activation gaps confirm the Coulomb origin of the broken
symmetry states, but the order is strongly dependent on LL index. In the high
energy LLs, the Zeeman effect is the dominant aligning field, leading to real
spin ferromagnets with Skyrmionic excitations at half filling, whereas in the
`relativistic' zero energy LL, lattice scale anisotropies drive the system to a
spin unpolarized state, likely a charge- or spin-density wave.Comment: Supplementary information available at http://pico.phys.columbia.ed
Multicomponent fractional quantum Hall effect in graphene
We report observation of the fractional quantum Hall effect (FQHE) in high
mobility multi-terminal graphene devices, fabricated on a single crystal boron
nitride substrate. We observe an unexpected hierarchy in the emergent FQHE
states that may be explained by strongly interacting composite Fermions with
full SU(4) symmetric underlying degrees of freedom. The FQHE gaps are measured
from temperature dependent transport to be up 10 times larger than in any other
semiconductor system. The remarkable strength and unusual hierarcy of the FQHE
described here provides a unique opportunity to probe correlated behavior in
the presence of expanded quantum degrees of freedom.Comment: 5 pages, 3 figure
Realization of a Tunable Artificial Atom at a Supercritically Charged Vacancy in Graphene
The remarkable electronic properties of graphene have fueled the vision of a
graphene-based platform for lighter, faster and smarter electronics and
computing applications. One of the challenges is to devise ways to tailor its
electronic properties and to control its charge carriers. Here we show that a
single atom vacancy in graphene can stably host a local charge and that this
charge can be gradually built up by applying voltage pulses with the tip of a
scanning tunneling microscope (STM). The response of the conduction electrons
in graphene to the local charge is monitored with scanning tunneling and Landau
level spectroscopy, and compared to numerical simulations. As the charge is
increased, its interaction with the conduction electrons undergoes a transition
into a supercritical regime 6-11 where itinerant electrons are trapped in a
sequence of quasi-bound states which resemble an artificial atom. The
quasi-bound electron states are detected by a strong enhancement of the density
of states (DOS) within a disc centered on the vacancy site which is surrounded
by halo of hole states. We further show that the quasi-bound states at the
vacancy site are gate tunable and that the trapping mechanism can be turned on
and off, providing a new mechanism to control and guide electrons in grapheneComment: 18 pages and 5 figures plus 14 pages and 15 figures of supplementary
information. Nature Physics advance online publication, Feb 22 (2016
Open defecation and childhood stunting in India: an ecological analysis of new data from 112 districts.
Poor sanitation remains a major public health concern linked to several important health outcomes; emerging evidence indicates a link to childhood stunting. In India over half of the population defecates in the open; the prevalence of stunting remains very high. Recently published data on levels of stunting in 112 districts of India provide an opportunity to explore the relationship between levels of open defecation and stunting within this population. We conducted an ecological regression analysis to assess the association between the prevalence of open defecation and stunting after adjustment for potential confounding factors. Data from the 2011 HUNGaMA survey was used for the outcome of interest, stunting; data from the 2011 Indian Census for the same districts was used for the exposure of interest, open defecation. After adjustment for various potential confounding factors--including socio-economic status, maternal education and calorie availability--a 10 percent increase in open defecation was associated with a 0.7 percentage point increase in both stunting and severe stunting. Differences in open defecation can statistically account for 35 to 55 percent of the average difference in stunting between districts identified as low-performing and high-performing in the HUNGaMA data. In addition, using a Monte Carlo simulation, we explored the effect on statistical power of the common practice of dichotomizing continuous height data into binary stunting indicators. Our simulation showed that dichotomization of height sacrifices statistical power, suggesting that our estimate of the association between open defecation and stunting may be a lower bound. Whilst our analysis is ecological and therefore vulnerable to residual confounding, these findings use the most recently collected large-scale data from India to add to a growing body of suggestive evidence for an effect of poor sanitation on human growth. New intervention studies, currently underway, may shed more light on this important issue
Emergence of Superlattice Dirac Points in Graphene on Hexagonal Boron Nitride
The Schr\"odinger equation dictates that the propagation of nearly free
electrons through a weak periodic potential results in the opening of band gaps
near points of the reciprocal lattice known as Brillouin zone boundaries.
However, in the case of massless Dirac fermions, it has been predicted that the
chirality of the charge carriers prevents the opening of a band gap and instead
new Dirac points appear in the electronic structure of the material. Graphene
on hexagonal boron nitride (hBN) exhibits a rotation dependent Moir\'e pattern.
In this letter, we show experimentally and theoretically that this Moir\'e
pattern acts as a weak periodic potential and thereby leads to the emergence of
a new set of Dirac points at an energy determined by its wavelength. The new
massless Dirac fermions generated at these superlattice Dirac points are
characterized by a significantly reduced Fermi velocity. The local density of
states near these Dirac cones exhibits hexagonal modulations indicating an
anisotropic Fermi velocity.Comment: 16 pages, 6 figure
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