5,264 research outputs found
Whither Capitalism? Financial externalities and crisis
As with global warming, so with financial crises â externalities have a lot to answer for. We
look at three of them. First the financial accelerator due to âfire salesâ of collateral assets -- a
form of pecuniary externality that leads to liquidity being undervalued. Second the ârisk-
shiftingâ behaviour of highly-levered financial institutions who keep the upside of risky
investment while passing the downside to others thanks to limited liability. Finally, the
network externality where the structure of the financial industry helps propagate shocks
around the system unless this is checked by some form of circuit breaker, or âring-fenceâ.
The contrast between crisis-induced Great Recession and its aftermath of slow growth in the
West and the rapid - and (so far) sustained - growth in the East suggests that successful
economic progress may depend on how well these externalities are managed
Topological Surface States Protected From Backscattering by Chiral Spin Texture
Topological insulators are a new class of insulators in which a bulk gap for
electronic excitations is generated by strong spin orbit coupling. These novel
materials are distinguished from ordinary insulators by the presence of gapless
metallic boundary states, akin to the chiral edge modes in quantum Hall
systems, but with unconventional spin textures. Recently, experiments and
theoretical efforts have provided strong evidence for both two- and
three-dimensional topological insulators and their novel edge and surface
states in semiconductor quantum well structures and several Bi-based compounds.
A key characteristic of these spin-textured boundary states is their
insensitivity to spin-independent scattering, which protects them from
backscattering and localization. These chiral states are potentially useful for
spin-based electronics, in which long spin coherence is critical, and also for
quantum computing applications, where topological protection can enable
fault-tolerant information processing. Here we use a scanning tunneling
microscope (STM) to visualize the gapless surface states of the
three-dimensional topological insulator BiSb and to examine their scattering
behavior from disorder caused by random alloying in this compound. Combining
STM and angle-resolved photoemission spectroscopy, we show that despite strong
atomic scale disorder, backscattering between states of opposite momentum and
opposite spin is absent. Our observation of spin-selective scattering
demonstrates that the chiral nature of these states protects the spin of the
carriers; they therefore have the potential to be used for coherent spin
transport in spintronic devices.Comment: to be appear in Nature on August 9, 200
Definitions and clinical guidance on the enteral dependence component of the avoidant/restrictive food intake disorder diagnostic criteria in children
The aim of the current paper is to offer definitive guidance on weaning children who are reliant on nasogastric/gastrostomy feeding tubes. To date, no internationally recognised definitions or principles for interventions exist and clinics have been reliant on creating their own unique intervention criteria. To achieve the aim, two goals are set out within the current paper. The first goal was to definitively define the process of tube weaning. In order to achieve this, both tube dependency and oral eating also required definitions. It is necessary for these two additional definitions to fully understand the process of tube weaning and the transition that the child is making within these clinical interventions. The second goal of this paper was to propose a set of minimum measurement criteria within a tube weaning protocol so that different clinical practices and perspectives may be measured accurately. This would then allow outcomes from different clinical services to be compared for efficacy. The culmination of this paper is a set of five core principles that should govern clinics that adhere to the auspices of evidence-based practice. These principles, if adopted, will provide the basis of a set of internationally recognised criteria within this field of paediatric gastroenterology
Crises: Principles and Policies: With an Application to the Eurozone Crisis
Economies around the world have faced repeated crises â more frequently over the past thirty years. The fact that they have become more frequent and pervasive at the same time that we believe we have learned more about the management of the economy and as markets have seemingly improved poses a puzzle: shouldn't rational markets avoid these catastrophes, the costs of which outweigh, by an enormous amount, any benefit that might have accrued to the economy from the actions prior to the crisis that might have contributed to it? This is especially true of the large fraction of crises that can be called âdebt crises,â precipitated by a countryâs difficulty in repaying what it owes. The benefits of income smoothing (arising from the difference in the marginal utility of income in periods when income is low and when income is high) are overwhelmed by the social and economic costs of the ensuing crisis
Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory
Here, we review the historical development, current status, and prospects of
Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only
theory.Comment: 15 page
Direct electronic measurement of the spin Hall effect
The generation, manipulation and detection of spin-polarized electrons in
nanostructures define the main challenges of spin-based electronics[1]. Amongst
the different approaches for spin generation and manipulation, spin-orbit
coupling, which couples the spin of an electron to its momentum, is attracting
considerable interest. In a spin-orbit-coupled system, a nonzero spin-current
is predicted in a direction perpendicular to the applied electric field, giving
rise to a "spin Hall effect"[2-4]. Consistent with this effect,
electrically-induced spin polarization was recently detected by optical
techniques at the edges of a semiconductor channel[5] and in two-dimensional
electron gases in semiconductor heterostructures[6,7]. Here we report
electrical measurements of the spin-Hall effect in a diffusive metallic
conductor, using a ferromagnetic electrode in combination with a tunnel barrier
to inject a spin-polarized current. In our devices, we observe an induced
voltage that results exclusively from the conversion of the injected spin
current into charge imbalance through the spin Hall effect. Such a voltage is
proportional to the component of the injected spins that is perpendicular to
the plane defined by the spin current direction and the voltage probes. These
experiments reveal opportunities for efficient spin detection without the need
for magnetic materials, which could lead to useful spintronics devices that
integrate information processing and data storage.Comment: 5 pages, 4 figures. Accepted for publication in Nature (pending
format approval
Does self-monitoring reduce blood pressure? Meta-analysis with meta-regression of randomized controlled trials
Introduction. Self-monitoring of blood pressure (BP) is an increasingly common part of hypertension management. The objectives of this systematic review were to evaluate the systolic and diastolic BP reduction, and achievement of target BP, associated with self-monitoring.
Methods. MEDLINE, Embase, Cochrane database of systematic reviews, database of abstracts of clinical effectiveness, the health technology assessment database, the NHS economic evaluation database, and the TRIP database were searched for studies where the intervention included self-monitoring of BP and the outcome was change in office/ambulatory BP or proportion with controlled BP. Two reviewers independently extracted data. Meta-analysis using a random effects model was combined with meta-regression to investigate heterogeneity in effect sizes.
Results. A total of 25 eligible randomized controlled trials (RCTs) (27 comparisons) were identified. Office systolic BP (20 RCTs, 21 comparisons, 5,898 patients) and diastolic BP (23 RCTs, 25 comparisons, 6,038 patients) were significantly reduced in those who self-monitored compared to usual care (weighted mean difference (WMD) systolic â3.82 mmHg (95% confidence interval â5.61 to â2.03), diastolic â1.45 mmHg (â1.95 to â0.94)). Self-monitoring increased the chance of meeting office BP targets (12 RCTs, 13 comparisons, 2,260 patients, relative risk = 1.09 (1.02 to 1.16)). There was significant heterogeneity between studies for all three comparisons, which could be partially accounted for by the use of additional co-interventions.
Conclusion. Self-monitoring reduces blood pressure by a small but significant amount. Meta-regression could only account for part of the observed heterogeneity
Spatial imaging of the spin Hall effect and current-induced polarization in two-dimensional electron gases
Spin-orbit coupling in semiconductors relates the spin of an electron to its
momentum and provides a pathway for electrically initializing and manipulating
electron spins for applications in spintronics and spin-based quantum
information processing. This coupling can be regulated with quantum confinement
in semiconductor heterostructures through band structure engineering. Here we
investigate the spin Hall effect and current-induced spin polarization in a
two-dimensional electron gas confined in (110) AlGaAs quantum wells using Kerr
rotation microscopy. In contrast to previous measurements, the spin Hall
profile exhibits complex structure, and the current-induced spin polarization
is out-of-plane. The experiments map the strong dependence of the
current-induced spin polarization to the crystal axis along which the electric
field is applied, reflecting the anisotropy of the spin-orbit interaction.
These results reveal opportunities for tuning a spin source using quantum
confinement and device engineering in non-magnetic materials.Comment: Accepted for publication (2005
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