610 research outputs found
Temperature dependent transport in suspended graphene
The resistivity of ultra-clean suspended graphene is strongly temperature
dependent for 5K<T<240K. At T~5K transport is near-ballistic in a device of
~2um dimension and a mobility ~170,000 cm^2/Vs. At large carrier density,
n>0.5*10^11 cm^-2, the resistivity increases with increasing T and is linear
above 50K, suggesting carrier scattering from acoustic phonons. At T=240K the
mobility is ~120,000 cm^2/Vs, higher than in any known semiconductor. At the
charge neutral point we observe a non-universal conductivity that decreases
with decreasing T, consistent with a density inhomogeneity <10^8 cm^-2
Conductivity of graphene: How to distinguish between samples with short and long range scatterers
Applying a quasiclassical equation to carriers in graphene we found a way how
to distinguish between samples with the domination of short and long range
scatterers from the conductivity measurements. The model proposed explains
recent transport experiments with chemically doped as well as suspended
graphene.Comment: 6 pages, 3 figures, some references have been corrected and revise
A Bayesian non-linear method for feature selection in machine translation quality estimation
We perform a systematic analysis of the effectiveness of features for the problem of predicting the quality of machine translation (MT) at the sentence level. Starting from a comprehensive feature set, we apply a technique based on Gaussian processes, a Bayesian non-linear learning method, to automatically identify features leading to accurate model performance. We consider application to several datasets across different language pairs and text domains, with translations produced by various MT systems and scored for quality according to different evaluation criteria. We show that selecting features with this technique leads to significantly better performance in most datasets, as compared to using the complete feature sets or a state-of-the-art feature selection approach. In addition, we identify a small set of features which seem to perform well across most datasets
'It would be easier if she’d died’: young people with parents with dementia articulating inadmissible stories
In the U.K. context where the emphasis is (quite rightly) on living well with dementia, on positivity and enabling
approaches, it can be difficult for researchers to investigate and report negative experiences. Failing to re-present
perceptions and experiences as they are lived, however, does a serious disservice to the research endeavor and can
prevent policy and service development and positive change. In this article, we present some stories told by participants
in an Alzheimer’s Society (United Kingdom) Funded project uniquely investigating the perceptions and experiences of
children and young people who have a parent with dementia. Sometimes the stories were not easy to hear, especially
when they challenged dominant master narratives around dementia. We discuss our view that when the young people
we spoke with told us how things were for them, we were ethically bound to respect and disseminate their accounts
Vibrational Enhancement of the Effective Donor - Acceptor Coupling
The paper deals with a simple three sites model for charge transfer phenomena
in an one-dimensional donor (D) - bridge (B) - acceptor (A) system coupled with
vibrational dynamics of the B site. It is found that in a certain range of
parameters the vibrational coupling leads to an enhancement of the effective
donor - acceptor electronic coupling as a result of the formation of the
polaron on the B site. This enhancement of the charge transfer efficiency is
maximum at the resonance, where the effective energy of the fluctuating B site
coincides with the donor (acceptor) energy.Comment: 5 pages, 3 figure
Superconductivity coexisting with phase-separated static magnetic order in (Ba,K)FeAs, (Sr,Na)FeAs and CaFeAs
The recent discovery and subsequent developments of FeAs-based
superconductors have presented novel challenges and opportunities in the quest
for superconducting mechanisms in correlated-electron systems. Central issues
of ongoing studies include interplay between superconductivity and magnetism as
well as the nature of the pairing symmetry reflected in the superconducting
energy gap. In the cuprate and RE(O,F)FeAs (RE = rare earth) systems, the
superconducting phase appears without being accompanied by static magnetic
order, except for narrow phase-separated regions at the border of phase
boundaries. By muon spin relaxation measurements on single crystal specimens,
here we show that superconductivity in the AFeAs (A = Ca,Ba,Sr)
systems, in both the cases of composition and pressure tunings, coexists with a
strong static magnetic order in a partial volume fraction. The superfluid
response from the remaining paramagnetic volume fraction of
(BaK)FeAs exhibits a nearly linear variation in T
at low temperatures, suggesting an anisotropic energy gap with line nodes
and/or multi-gap effects.Comment: 14 pages 7 figures (4 for main text and 3 for on-line supplementary
documents
Methodological approaches to determining the marine radiocarbon reservoir effect
The marine radiocarbon reservoir effect is an offset in 14C age between contemporaneous organisms from the terrestrial environment and organisms that derive their carbon from the marine environment. Quantification of this effect is of crucial importance for correct calibration of the <sup>14</sup>C ages of marine-influenced samples to the calendrical timescale. This is fundamental to the construction of archaeological and palaeoenvironmental chronologies when such samples are employed in <sup>14</sup>C analysis. Quantitative measurements of temporal variations in regional marine reservoir ages also have the potential to be used as a measure of process changes within Earth surface systems, due to their link with climatic and oceanic changes. The various approaches to quantification of the marine radiocarbon reservoir effect are assessed, focusing particularly on the North Atlantic Ocean. Currently, the global average marine reservoir age of surface waters, R(t), is c. 400 radiocarbon years; however, regional values deviate from this as a function of climate and oceanic circulation systems. These local deviations from R(t) are expressed as +R values. Hence, polar waters exhibit greater reservoir ages (δR = c. +400 to +800 <sup>14</sup>C y) than equatorial waters (δR = c. 0 <sup>14</sup>C y). Observed temporal variations in δR appear to reflect climatic and oceanographic changes. We assess three approaches to quantification of marine reservoir effects using known age samples (from museum collections), tephra isochrones (present onshore/offshore) and paired marine/terrestrial samples (from the same context in, for example, archaeological sites). The strengths and limitations of these approaches are evaluated using examples from the North Atlantic region. It is proposed that, with a suitable protocol, accelerator mass spectrometry (AMS) measurements on paired, short-lived, single entity marine and terrestrial samples from archaeological deposits is the most promising approach to constraining changes over at least the last 5 ky BP
The experience of children with parents diagnosed with young onset dementia: A systematic literature review
Background: Young onset dementia (YOD) may develop rapidly, and affect those who have dependent children. Currently, there remains a lack of understanding of the impact on children living with a parent with YOD.
Aim: The aim of this systematic literature review is to explore published literature in order to understand the impact on children living with a parent with YOD.
Methods: A systematic search of the following databases: Medline; PsychINFO; CINAHL and Scopus for literature published from 1/1/2013 to 31/12/2018.
Results: Three major themes were identified, firstly coping encompassed two sub-themes of avoiding the situation and being empowered. Secondly, change encompassed two sub-themes of change of personality and change of family role, and lastly loss.
Conclusion: There remains a need to raise awareness and develop support services for children of parents with YOD. Community nurses are the best place healthcare professionals to identify and support the needs of both the person with YOD and their children
Effect of Age of Infusion Site and Type of Rapid-Acting Analog on Pharmacodynamic Parameters of Insulin Boluses in Youth With Type 1 Diabetes Receiving Insulin Pump Therapy
OBJECTIVE—The purpose of this study was to examine the effect of type of insulin analog and age of insertion site on the pharmacodynamic characteristics of a standard insulin bolus in youth with type 1 diabetes receiving insulin pump therapy
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