3,011 research outputs found
Enhanced and continuous electrostatic carrier doping on the SrTiO surface
Paraelectrical tuning of a charge carrier density as high as
10\,cm in the presence of a high electronic carrier mobility on
the delicate surfaces of correlated oxides, is a key to the technological
breakthrough of a field effect transistor (FET) utilising the metal-nonmetal
transition. Here we introduce the Parylene-C/TaO hybrid gate
insulator and fabricate FET devices on single-crystalline SrTiO, which
has been regarded as a bedrock material for oxide electronics. The gate
insulator accumulates up to cm carriers, while the
field-effect mobility is kept at 10\,cm/Vs even at room temperature.
Further to the exceptional performance of our devices, the enhanced
compatibility of high carrier density and high mobility revealed the mechanism
for the long standing puzzle of the distribution of electrostatically doped
carriers on the surface of SrTiO. Namely, the formation and continuous
evolution of field domains and current filaments.Comment: Supplementary Information:
<http://www.nature.com/srep/2013/130424/srep01721/extref/srep01721-s1.pdf
Diabetes, insulin treatment, and cancer risk: what is the evidence?
Diabetes, in particular type 2, is associated with an increased incidence of cancer. Although the mortality attributable to cancer in type 2 diabetes is overshadowed by that due to cardiovascular disease, emerging data from epidemiologic studies suggest that insulin therapy may confer added risk for cancer, perhaps mediated by signaling through the IGF-1 (insulin-like growth factor-1) receptor. Co-administered metformin seems to mitigate the risk associated with insulin. A recent series of publications in Diabetologia addresses the possibility that glargine, the most widely used long-acting insulin analogue, may confer a greater risk than other insulin preparations, particularly for breast cancer. This has led to a heated controversy. Despite this, there is a consensus that the currently available data are not conclusive and should not be the basis for any change in practice. Further studies and more thorough surveillance of cancer in diabetes are needed to address this important issue
General equilibrium oligopoly and ownership structure
We develop a tractable general equilibrium framework in which firms are large and have market power with respect to both products and labor, and in which a firm's decisions are affected by its ownership structure. We characterize the CournotâWalras equilibrium of an economy where each firm maximizes a shareâweighted average of shareholder utilitiesârendering the equilibrium independent of price normalization. In a oneâsector economy, if returns to scale are nonâincreasing, then an increase in âeffectiveâ market concentration (which accounts for common ownership) leads to declines in employment, real wages, and the labor share. Yet when there are multiple sectors, due to an intersectoral pecuniary externality, an increase in common ownership could stimulate the economy when the elasticity of labor supply is high relative to the elasticity of substitution in product markets. We characterize for which ownership structures the monopolistically competitive limit or an oligopolistic one is attained as the number of sectors in the economy increases. When firms have heterogeneous constant returns to scale technologies, we find that an increase in common ownership leads to markets that are more concentrated
Improved algorithms for online load balancing
We consider an online load balancing problem and its extensions in the
framework of repeated games. On each round, the player chooses a distribution
(task allocation) over servers, and then the environment reveals the load
of each server, which determines the computation time of each server for
processing the task assigned. After all rounds, the cost of the player is
measured by some norm of the cumulative computation-time vector. The cost is
the makespan if the norm is -norm. The goal is to minimize the
regret, i.e., minimizing the player's cost relative to the cost of the best
fixed distribution in hindsight. We propose algorithms for general norms and
prove their regret bounds. In particular, for -norm, our regret bound
matches the best known bound and the proposed algorithm runs in polynomial time
per trial involving linear programming and second order programming, whereas no
polynomial time algorithm was previously known to achieve the bound.Comment: 16 pages; typos correcte
A Supercooled Spin Liquid State in the Frustrated Pyrochlore Dy2Ti2O7
A "supercooled" liquid develops when a fluid does not crystallize upon
cooling below its ordering temperature. Instead, the microscopic relaxation
times diverge so rapidly that, upon further cooling, equilibration eventually
becomes impossible and glass formation occurs. Classic supercooled liquids
exhibit specific identifiers including microscopic relaxation times diverging
on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for
the dielectric function, and a general Kohlrausch-Williams-Watts (KWW) form for
time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of
interest because its frustrated magnetic interactions may, in theory, lead to
highly exotic magnetic fluids. However, its true magnetic state at low
temperatures has proven very difficult to identify unambiguously. Here we
introduce high-precision, boundary-free magnetization transport techniques
based upon toroidal geometries and gain a fundamentally new understanding of
the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We
demonstrate a virtually universal HN form for the magnetic susceptibility, a
general KWW form for the real-time magnetic relaxation, and a divergence of the
microscopic magnetic relaxation rates with precisely the VTF trajectory. Low
temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled
magnetic liquid; the consequent implication is that this translationally
invariant lattice of strongly correlated spins is evolving towards an
unprecedented magnetic glass state, perhaps due to many-body localization of
spin.Comment: Version 2 updates: added legend for data in Figures 4A and 4B;
corrected equation reference in caption for Figure 4
901-97 Stroke and Long-term Anticoagulant Therapy in 3404 Post-Myocardial Infarction Patients
In a randomized, double-blind, placebo controlled trial (ASPECT) we studied 3404 post-myocardial infarction patients who suffered a stroke during long-term anticoagulant therapy. The duration of treatment ranged from 1 day to six years. Three years following randomization, 2% of the patients on anticoagulant therapy had a stroke compared to 4% in placebo.The incidence of stroke analyzed on âintention-to-treatâ was 0.7 per 100 patient-years in the anticoagulant group and 1.2 per 100 patient-years in placebo, a hazard ratio (HR) of 0.60 with a 95% confidence interval (Cl) of 0.40 to 0.90, a 40% reduction in the risk of stroke in the anticoagulated group. A total of 19 intracranial bleeding was observed. The risk of hemorrhages was 8 times greater for anticoagulated patients compared to placebo. Eight of the 17 bleedings were fatal in the anticoagulant group and no fatal hemorrhages occurred in placebo. A total of 15 cerebral infarctions occurred in the anticoagulated group and 43 in placebo. Of the 14 hemorrhagic strokes, 6 were within INR 3.0â4.0 and 8 with an INR>4.0, Of the 7 non-hemorrhagic strokes, 2 were at INR<2, 3 within INR 3.0â4.0, 1 at INR>4.0, and no measurement was available in one patient. The total number of patients who died or were severely disabled as a result of cerebral stroke amounted to 13 in the anticoagulated group, compared to 18 in placebo.ConclusionThe results of the ASPECT trial indicated that long-term anticoagulant therapy substantially reduced the risk of stroke in post-myocardial infarction patients. The increased risk of bleeding complications associated with anticoagulant therapy was offset by a marked reduction in ischemic events
Teaching Linear Algebra in a Mechanized Mathematical Environment
This paper outlines our ideas on how to teach linear algebra in a mechanized
mathematical environment, and discusses some of our reasons for thinking that
this is a better way to teach linear algebra than the ``old fashioned way''. We
discuss some technological tools such as Maple, Matlab, Python, and Jupyter
Notebooks, and some choices of topics that are especially suited to teaching
with these tools. The discussion is informed by our experience over the past
thirty or more years teaching at various levels, especially at the University
of Western Ontario.Comment: 16 pages, 2 figure
Physical activity correlates in young women with depressive symptoms: a qualitative study
BackgroundYoung women are at high risk for developing depression and participation in physical activity may prevent or treat the disorder. However, the influences on physical activity behaviors of young women with depression are not well understood. The aim of this study was to gather in-depth information about the correlates of physical activity among young women with and without depressive symptoms.MethodsA sample of 40 young women (aged 18-30 years), 20 with depressive symptoms (assessed using the CES-D 10) and 20 without depressive symptoms participated in one-on-one semi-structured interviews. A social-ecological framework was used, focusing on the individual, social and physical environmental influences on physical activity. Thematic analyses were performed on transcribed interview data.ResultsThe results indicated several key themes that were unique to women with depressive symptoms. These women more often described negative physical activity experiences during their youth, more barriers to physical activity, participating in more spontaneous than planned activity, lower self-efficacy for physical activity and being influenced by their friends\u27 and family\u27s inactivity.ConclusionsInterventions designed to promote physical activity in this important target group should consider strategies to reduce/overcome early life negative experiences, engage support from family and friends and plan for activity in advance.<br /
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