2,344 research outputs found
Josephson effects in MgB2 meta masked ion damage junctions
Ion beam damage combined with nanoscale focused ion beam direct milling was
used to create manufacturable SNS type Josephson junctions in 100 nm thick
MgB with T of 38 K. The junctions show non-hysteretic current -
voltage characteristics between 36 and 4.2 K. Experimental evidence for the dc
and ac Josephson effects in MgB metal masked ion damage junctions are
presented. This technique is particularly useful for prototyping devices due to
its simplicity and flexibility of fabrication and has a great potential for
high-density integration.Comment: 12 pages, 4 figures, RevTeX4, submitted to AP
Global Continua of Positive Equilibria for some Quasilinear Parabolic Equation with a Nonlocal Initial Condition
This paper is concerned with a quaslinear parabolic equation including a
nonlinear nonlocal initial condition. The problem arises as equilibrium
equation in population dynamics with nonlinear diffusion. We make use of global
bifurcation theory to prove existence of an unbounded continuum of positive
solutions
Imaging Coulomb Islands in a Quantum Hall Interferometer
In the Quantum Hall regime, near integer filling factors, electrons should
only be transmitted through spatially-separated edge states. However, in
mesoscopic systems, electronic transmission turns out to be more complex,
giving rise to a large spectrum of magnetoresistance oscillations. To explain
these observations, recent models put forward that, as edge states come close
to each other, electrons can hop between counterpropagating edge channels, or
tunnel through Coulomb islands. Here, we use scanning gate microscopy to
demonstrate the presence of quantum Hall Coulomb islands, and reveal the
spatial structure of transport inside a quantum Hall interferometer. Electron
islands locations are found by modulating the tunneling between edge states and
confined electron orbits. Tuning the magnetic field, we unveil a continuous
evolution of active electron islands. This allows to decrypt the complexity of
high magnetic field magnetoresistance oscillations, and opens the way to
further local scale manipulations of quantum Hall localized states
Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption spectra
Theories unifying gravity with other interactions suggest spatial and
temporal variation of fundamental "constants" in the Universe. A change in the
fine structure constant, alpha, could be detected via shifts in the frequencies
of atomic transitions in quasar absorption systems. Recent studies using 140
absorption systems from the Keck telescope and 153 from the Very Large
Telescope, suggest that alpha varies spatially. That is, in one direction on
the sky alpha seems to have been smaller at the time of absorption, while in
the opposite direction it seems to have been larger.
To continue this study we need accurate laboratory measurements of atomic
transition frequencies. The aim of this paper is to provide a compilation of
transitions of importance to the search for alpha variation. They are E1
transitions to the ground state in several different atoms and ions, with
wavelengths ranging from around 900 - 6000 A, and require an accuracy of better
than 10^{-4} A. We discuss isotope shift measurements that are needed in order
to resolve systematic effects in the study. The coefficients of sensitivity to
alpha-variation (q) are also presented.Comment: Includes updated version of the "alpha line" lis
Assortment optimisation under a general discrete choice model: A tight analysis of revenue-ordered assortments
The assortment problem in revenue management is the problem of deciding which
subset of products to offer to consumers in order to maximise revenue. A simple
and natural strategy is to select the best assortment out of all those that are
constructed by fixing a threshold revenue and then choosing all products
with revenue at least . This is known as the revenue-ordered assortments
strategy. In this paper we study the approximation guarantees provided by
revenue-ordered assortments when customers are rational in the following sense:
the probability of selecting a specific product from the set being offered
cannot increase if the set is enlarged. This rationality assumption, known as
regularity, is satisfied by almost all discrete choice models considered in the
revenue management and choice theory literature, and in particular by random
utility models. The bounds we obtain are tight and improve on recent results in
that direction, such as for the Mixed Multinomial Logit model by
Rusmevichientong et al. (2014). An appealing feature of our analysis is its
simplicity, as it relies only on the regularity condition.
We also draw a connection between assortment optimisation and two pricing
problems called unit demand envy-free pricing and Stackelberg minimum spanning
tree: These problems can be restated as assortment problems under discrete
choice models satisfying the regularity condition, and moreover revenue-ordered
assortments correspond then to the well-studied uniform pricing heuristic. When
specialised to that setting, the general bounds we establish for
revenue-ordered assortments match and unify the best known results on uniform
pricing.Comment: Minor changes following referees' comment
Representing complex data using localized principal components with application to astronomical data
Often the relation between the variables constituting a multivariate data
space might be characterized by one or more of the terms: ``nonlinear'',
``branched'', ``disconnected'', ``bended'', ``curved'', ``heterogeneous'', or,
more general, ``complex''. In these cases, simple principal component analysis
(PCA) as a tool for dimension reduction can fail badly. Of the many alternative
approaches proposed so far, local approximations of PCA are among the most
promising. This paper will give a short review of localized versions of PCA,
focusing on local principal curves and local partitioning algorithms.
Furthermore we discuss projections other than the local principal components.
When performing local dimension reduction for regression or classification
problems it is important to focus not only on the manifold structure of the
covariates, but also on the response variable(s). Local principal components
only achieve the former, whereas localized regression approaches concentrate on
the latter. Local projection directions derived from the partial least squares
(PLS) algorithm offer an interesting trade-off between these two objectives. We
apply these methods to several real data sets. In particular, we consider
simulated astrophysical data from the future Galactic survey mission Gaia.Comment: 25 pages. In "Principal Manifolds for Data Visualization and
Dimension Reduction", A. Gorban, B. Kegl, D. Wunsch, and A. Zinovyev (eds),
Lecture Notes in Computational Science and Engineering, Springer, 2007, pp.
180--204,
http://www.springer.com/dal/home/generic/search/results?SGWID=1-40109-22-173750210-
Effect of concrete slats, three mat types and out-wintering pads on performance and welfare of finishing beef steers
peer-reviewedBackground
The objective was to investigate the effect of placing mats on concrete slatted floors on performance, behaviour, hoof condition, dirt scores, physiological and immunological variables of beef steers, and to compare responses with animals on out-wintering pads. Continental crossbred beef steers [n = 360; mean (±SD) initial live weight 539 kg (42.2)] were blocked by breed and live weight and randomly assigned to one of five treatments; (1) Concrete slats alone, (2) Mat 1 (Natural Rubber structure) (Durapak Rubber Products), (3) Mat 2 (Natural rubber structure) (EasyFix), (4) Mat 3 (modified ethylene vinyl acetate (EVA) foam structure) and (5) Out-wintering pads (OWP’s).
Results
Animals on the OWPs had a greater (PÂ Â 0.05) as the other treatments. Animals on the OWPs had reduced lying percentage time compared with all the other treatments. Dry matter (DM) intake was greater for animals on the OWPs compared with all the other treatments. Carcass weight, kill out proportion, carcass fat score, carcass composition score, FCR and physiological responses were similar (PÂ >Â 0.05) among treatments. No incidence of laminitis was observed among treatments. The number of hoof lesions was greater on all mat types (PÂ <Â 0.05) compared with concrete slats and OWP treatments. Dirt scores were greater (PÂ <Â 0.05) for animals on OWPs when measured on days 42, 84, 105, 126 and 150 compared with animals on slats.
Conclusions
Under the conditions adopted for the present study, there was no evidence to suggest that animals housed on bare concrete slats were disadvantaged in respect of animal welfare compared with animals housed on other floor types. It is concluded that the welfare of steers was not adversely affected by slats compared with different mat types or OWPs
Multidisciplinary teams, and parents, negotiating common ground in shared-care of children with long-term conditions: A mixed methods study
Background: Limited negotiation around care decisions is believed to undermine collaborative working between parents of children with long-term conditions and professionals, but there is little evidence of how they actually negotiate their respective roles. Using chronic kidney disease as an exemplar this paper reports on a multi-method study of social interaction between multidisciplinary teams and parents as they shared clinical care. Methods. Phases 1 and 2: a telephone survey mapping multidisciplinary teams' parent-educative activities, and qualitative interviews with 112 professionals (Clinical-psychologists, Dietitians, Doctors, Nurses, Play-specialists, Pharmacists, Therapists and Social-workers) exploring their accounts of parent-teaching in the 12 British children's kidney units. Phase 3: six ethnographic case studies in two units involving observations of professional/parent interactions during shared-care, and individual interviews. We used an analytical framework based on concepts drawn from Communities of Practice and Activity Theory. Results: Professionals spoke of the challenge of explaining to each other how they are aware of parents' understanding of clinical knowledge, and described three patterns of parent-educative activity that were common across MDTs: Engaging parents in shared practice; Knowledge exchange and role negotiation, and Promoting common ground. Over time, professionals had developed a shared repertoire of tools to support their negotiations with parents that helped them accomplish common ground during the practice of shared-care. We observed mutual engagement between professionals and parents where a common understanding of the joint enterprise of clinical caring was negotiated. Conclusions: For professionals, making implicit knowledge explicit is important as it can provide them with a language through which to articulate more clearly to each other what is the basis of their intuition-based hunches about parents' support needs, and may help them to negotiate with parents and accelerate parents' learning about shared caring. Our methodology and results are potentially transferrable to shared management of other conditions. © 2013 Swallow et al.; licensee BioMed Central Ltd
α-Synuclein Suppression by Targeted Small Interfering RNA in the Primate Substantia Nigra
The protein α-synuclein is involved in the pathogenesis of Parkinson's disease and other neurodegenerative disorders. Its toxic potential appears to be enhanced by increased protein expression, providing a compelling rationale for therapeutic strategies aimed at reducing neuronal α-synuclein burden. Here, feasibility and safety of α-synuclein suppression were evaluated by treating monkeys with small interfering RNA (siRNA) directed against α-synuclein. The siRNA molecule was chemically modified to prevent degradation by exo- and endonucleases and directly infused into the left substantia nigra. Results compared levels of α-synuclein mRNA and protein in the infused (left) vs. untreated (right) hemisphere and revealed a significant 40–50% suppression of α-synuclein expression. These findings could not be attributable to non-specific effects of siRNA infusion since treatment of a separate set of animals with luciferase-targeting siRNA produced no changes in α-synuclein. Infusion with α-synuclein siRNA, while lowering α-synuclein expression, had no overt adverse consequences. In particular, it did not cause tissue inflammation and did not change (i) the number and phenotype of nigral dopaminergic neurons, and (ii) the concentrations of striatal dopamine and its metabolites. The data represent the first evidence of successful anti-α-synuclein intervention in the primate substantia nigra and support further development of RNA interference-based therapeutics
Female Fertility Affects Men's Linguistic Choices
We examined the influence of female fertility on the likelihood of male participants aligning their choice of syntactic construction with those of female confederates. Men interacted with women throughout their menstrual cycle. On critical trials during the interaction, the confederate described a picture to the participant using particular syntactic constructions. Immediately thereafter, the participant described to the confederate a picture that could be described using either the same construction that was used by the confederate or an alternative form of the construction. Our data show that the likelihood of men choosing the same syntactic structure as the women was inversely related to the women's level of fertility: higher levels of fertility were associated with lower levels of linguistic matching. A follow-up study revealed that female participants do not show this same change in linguistic behavior as a function of changes in their conversation partner's fertility. We interpret these findings in the context of recent data suggesting that non-conforming behavior may be a means of men displaying their fitness as a mate to women
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