7,635 research outputs found
Nonlinear c-axis transport in Bi_2Sr_2CaCu_2O_(8+d) from two-barrier tunneling
Motivated by the peculiar features observed through intrinsic tunneling
spectroscopy of BiSrCaCuO mesas in the normal state,
we have extended the normal state two-barrier model for the c-axis transport
[M. Giura et al., Phys. Rev. B {\bf 68}, 134505 (2003)] to the analysis of
curves. We have found that the purely normal-state model reproduces all
the following experimental features: (a) the parabolic -dependence of
in the high- region (above the conventional pseudogap temperature),
(b) the emergence and the nearly voltage-independent position of the "humps"
from this parabolic behavior lowering the temperature, and (c) the crossing of
the absolute curves at a characteristic voltage . Our
findings indicate that conventional tunneling can be at the origin of most of
the uncommon features of the c axis transport in
BiSrCaCuO. We have compared our calculations to
experimental data taken in severely underdoped and slightly underdoped
BiSrCaCuO small mesas. We have found good agreement
between the data and the calculations, without any shift of the calculated
dI/dV on the vertical scale. In particular, in the normal state (above
) simple tunneling reproduces the experimental dI/dV quantitatively.
Below quantitative discrepancies are limited to a simple rescaling of
the voltage in the theoretical curves by a factor 2. The need for such
modifications remains an open question, that might be connected to a change of
the charge of a fraction of the carriers across the pseudogap opening.Comment: 7 pages, 5 figure
Electron spin resonance on a 2-dimensional electron gas in a single AlAs quantum well
Direct electron spin resonance (ESR) on a high mobility two dimensional
electron gas in a single AlAs quantum well reveals an electronic -factor of
1.991 at 9.35 GHz and 1.989 at 34 GHz with a minimum linewidth of 7 Gauss. The
ESR amplitude and its temperature dependence suggest that the signal originates
from the effective magnetic field caused by the spin orbit-interaction and a
modulation of the electron wavevector caused by the microwave electric field.
This contrasts markedly to conventional ESR that detects through the microwave
magnetic field.Comment: 4 pages, 4 figure
Who are Non-Resident Fathers?: A British Socio-Demographic Profile
Despite international growth of, and policy interest in, divorce and separation since the 1970s, there is still surprisingly little known about non-residential fatherhood. This paper presents a 'father-centric' analysis and provides one of the first profiles of non-residential fatherhood in early millennium UK. Using data from Understanding Society Wave 1, a nationally representative survey of over 30,000 households in the UK, we found 1,070 men self-identifying as having a non-resident child under 16 years old (https://www.understandingsociety.ac.uk). We estimate a prevalence of 5 per cent of British men having a non-resident dependent child. Through latent class analysis, four distinct groups of non-resident fathers are identified: 'Engaged' fathers, 'Less Engaged' fathers, 'Disengaged' fathers and 'Distance' fathers. Our analysis finds that non-resident fathers form a heterogeneous group in terms of their socio-demographic profile and family behaviour. It is recommended that legislation and policy concerning fathers in post-separation families are sensitive to variation as well as commonality in socio-economic conditions and family lives and situations
Britain's slow movement to a Gender Egalitarian Equilibrium: Parents and Employment in the UK 2001 - 2013
This paper examines the working lives of British couple families across the first decade of the
millennium using EU Labour Force Survey data (2001-2013) taking a multiple equilibria approach
(Esping-Andersen and Billari, 2015). We identify a growth in dual full-time earners, increased
working hours of mothers in part-time employment and a growing proportion of households with
‘non-standard’ working patterns, suggesting both a convergence and greater diversity in economic
provisioning within parent couple households. We find that household employment patterns remain
strongly associated with maternal education and family size but are becoming less sensitive to the
age of youngest child. The dual full-time earner model is growing in significance for British parents
of young children but a new gender egalitarian equilibrium has not yet been reached
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots
We report on the development and testing of a coplanar stripline antenna that
is designed for integration in a magneto-photoluminescence experiment to allow
coherent control of individual electron spins confined in single self-assembled
semiconductor quantum dots. We discuss the design criteria for such a structure
which is multi-functional in the sense that it serves not only as microwave
delivery but also as electrical top gate and shadow mask for the single quantum
dot spectroscopy. We present test measurements on hydrogenated amorphous
silicon, demonstrating electrically detected magnetic resonance using the
in-plane component of the oscillating magnetic field created by the coplanar
stripline antenna necessary due to the particular geometry of the quantum dot
spectroscopy. From reference measurements using a commercial electron spin
resonance setup in combination with finite element calculations simulating the
field distribution in the structure, we obtain an average magnetic field of
~0.2mT at the position where the quantum dots would be integrated into the
device. The corresponding pi-pulse time of ~0.3us fully meets the requirements
set by the high sensitivity optical spin read-out scheme developed for the
quantum dot
Tunnel and thermal c-axis transport in BSCCO in the normal and pseudogap state
We consider the problem of c-axis transport in double-layered cuprates, in
particular with reference to BiSrCaCuO
compounds. We exploit the effect of the two barriers on the thermal and tunnel
transport. The resulting model is able to describe accurately the normal state
c-axis resistivity in BiSrCaCuO, from the
underdoped side up to the strongly overdoped. We extend the model, without
introducing additional parameters, in order to allow for the decrease of the
barrier when an external voltage bias is applied. The extended model is found
to describe properly the c-axis resistivity for small voltage bias above the
pseudogap temperature , the c-axis resistivity for large voltage bias
even below , and the differential curves taken in mesa structures.Comment: 12 pages, 6 figures. Submitted to Superconductor Science and
Technolog
CSM Testbed Development and Large-Scale Structural Applications
A research activity called Computational Structural Mechanics (CSM) conducted at the NASA Langley Research Center is described. This activity is developing advanced structural analysis and computational methods that exploit high-performance computers. Methods are developed in the framework of the CSM Testbed software system and applied to representative complex structural analysis problems from the aerospace industry. An overview of the CSM Testbed methods development environment is presented and some new numerical methods developed on a CRAY-2 are described. Selected application studies performed on the NAS CRAY-2 are also summarized
Extraction of Visual Information to Predict Crowdfunding Success
Researchers have increasingly turned to crowdfunding platforms to gain
insights into entrepreneurial activity and dynamics. While previous studies
have explored various factors influencing crowdfunding success, such as
technology, communication, and marketing strategies, the role of visual
elements that can be automatically extracted from images has received less
attention. This is surprising, considering that crowdfunding platforms
emphasize the importance of attention-grabbing and high-resolution images, and
previous research has shown that image characteristics can significantly impact
product evaluations. Indeed, a comprehensive review of empirical articles (n =
202) that utilized Kickstarter data, focusing on the incorporation of visual
information in their analyses. Our findings reveal that only 29.70% controlled
for the number of images, and less than 12% considered any image details. In
this manuscript, we review the literature on image processing and its relevance
to the business domain, highlighting two types of visual variables: visual
counts (number of pictures and number of videos) and image details. Building
upon previous work that discussed the role of color, composition and
figure-ground relationships, we introduce visual scene elements that have not
yet been explored in crowdfunding, including the number of faces, the number of
concepts depicted, and the ease of identifying those concepts. To demonstrate
the predictive value of visual counts and image details, we analyze Kickstarter
data. Our results highlight that visual count features are two of the top three
predictors of success. Our results also show that simple image detail features
such as color matter a lot, and our proposed measures of visual scene elements
can also be useful. We supplement our article with R and Python codes that help
authors extract image details (https://osf.io/ujnzp/).Comment: 32 pages, 5 figure
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