1,570 research outputs found
Classical simulation of measurement-based quantum computation on higher-genus surface-code states
We consider the efficiency of classically simulating measurement-based
quantum computation on surface-code states. We devise a method for calculating
the elements of the probability distribution for the classical output of the
quantum computation. The operational cost of this method is polynomial in the
size of the surface-code state, but in the worst case scales as in the
genus of the surface embedding the code. However, there are states in the
code space for which the simulation becomes efficient. In general, the
simulation cost is exponential in the entanglement contained in a certain
effective state, capturing the encoded state, the encoding and the local
post-measurement states. The same efficiencies hold, with additional
assumptions on the temporal order of measurements and on the tessellations of
the code surfaces, for the harder task of sampling from the distribution of the
computational output.Comment: 21 pages, 13 figure
Zero Frequency Current Noise for the Double Tunnel Junction Coulomb Blockade
We compute the zero frequency current noise numerically and in several limits
analytically for the coulomb blockade problem consisting of two tunnel
junctions connected in series. At low temperatures over a wide range of
voltages, capacitances, and resistances it is shown that the noise measures the
variance in the number of electrons in the region between the two tunnel
junctions. The average current, on the other hand, only measures the mean
number of electrons. Thus, the noise provides additional information about
transport in these devices which is not available from measuring the current
alone.Comment: 33 pages, 10 figure
Corporate governance and financial constraints on strategic turnarounds
The paper extends the Robbins and Pearce (1992) two-stage turnaround response model to include governance factors. In addition to the retrenchment and recovery, the paper proposes the addition of a realignment stage, referring specifically to the re-alignment of expectations of principal and agent groups. The realignment stage imposes a threshold that must be crossed before the retrenchment and hence recovery stage can be entered. Crossing this threshold is problematic to the extent that the interests of governance-stakeholder groups diverge in a crisis situation. The severity of the crisis impacts on the bases of strategy contingent asset valuation leading to the fragmentation of stakeholder interests. In some cases the consequence may be that management are prevented from carrying out turnarounds by governance constraints. The paper uses a case study to illustrate these dynamics, and like the Robbins and Pearce study, it focuses on the textile industry. A longitudinal approach is used to show the impact of the removal of governance constraints. The empirical evidence suggests that such financial constraints become less serious to the extent that there is a functioning market for corporate control. Building on governance research and turnaround literature, the paper also outlines the general case necessary and sufficient conditions for successful turnarounds
Influence of supramolecular forces on the linear viscoelasticity of gluten
Stress relaxation behavior of hydrated gluten networks was investigated by means of rheometry combined with μ-computed tomography (μ-CT) imaging. Stress relaxation behavior was followed over a wide temperature range (0–70 °C). Modulation of intermolecular bonds was achieved with urea or ascorbic acid in an effort to elucidate the presiding intermolecular interactions over gluten network relaxation. Master curves of viscoelasticity were constructed, and relaxation spectra were computed revealing three relaxation regimes for all samples. Relaxation commences with a well-defined short-time regime where Rouse-like modes dominate, followed by a power law region displaying continuous relaxation concluding in a terminal zone. In the latter zone, poroelastic relaxation due to water migration in the nanoporous structure of the network also contributes to the stress relief in the material. Hydrogen bonding between adjacent protein chains was identified as the determinant force that influences the relaxation of the networks. Changes in intermolecular interactions also resulted in changes in microstructure of the material that was also linked to the relaxation behavior of the networks
Spin effects in single electron tunneling
An important consequence of the discovery of giant magnetoresistance in
metallic magnetic multilayers is a broad interest in spin dependent effects in
electronic transport through magnetic nanostructures. An example of such
systems are tunnel junctions -- single-barrier planar junctions or more complex
ones. In this review we present and discuss recent theoretical results on
electron and spin transport through ferromagnetic mesoscopic junctions
including two or more barriers. Such systems are also called ferromagnetic
single-electron transistors. We start from the situation when the central part
of a device has the form of a magnetic (or nonmagnetic) metallic nanoparticle.
Transport characteristics reveal then single-electron charging effects,
including the Coulomb staircase, Coulomb blockade, and Coulomb oscillations.
Single-electron ferromagnetic transistors based on semiconductor quantum dots
and large molecules (especially carbon nanotubes) are also considered. The main
emphasis is placed on the spin effects due to spin-dependent tunnelling through
the barriers, which gives rise to spin accumulation and tunnel
magnetoresistance. Spin effects also occur in the current-voltage
characteristics, (differential) conductance, shot noise, and others. Transport
characteristics in the two limiting situations of weak and strong coupling are
of particular interest. In the former case we distinguish between the
sequential tunnelling and cotunneling regimes. In the strong coupling regime we
concentrate on the Kondo phenomenon, which in the case of transport through
quantum dots or molecules leads to an enhanced conductance and to a pronounced
zero-bias Kondo peak in the differential conductance.Comment: topical review (36 figures, 65 pages), to be published in J. Phys.:
Condens. Matte
Bridging the gap between public health and primary care in prevention of cardiometabolic diseases; background of and experiences with the Prevention Consultation in The Netherlands
Background. There is an increasing need for programmatic prevention of cardiometabolic diseases (cardiovascular disease, type 2 diabetes and chronic kidney disease). Therefore, in the Netherlands, a prevention programme linked to primary care has been developed. This initiative was supported by the national professional organizations of GPs and occupational physicians as well as three large health foundations
Reconstructing ‘the Alcoholic’: Recovering from Alcohol Addiction and the Stigma this Entails
Public perception of alcohol addiction is frequently negative, whilst an important part of recovery is the construction of a positive sense of self. In order to explore how this might be achieved, we investigated how those who self-identify as in recovery from alcohol problems view themselves and their difficulties with alcohol and how they make sense of others’ responses to their addiction. Semi-structured interviews with six individuals who had been in recovery between 5 and 35 years and in contact with Alcoholics Anonymous were analysed using Interpretative Phenomenological Analysis. The participants were acutely aware of stigmatising images of ‘alcoholics’ and described having struggled with a considerable dilemma in accepting this identity themselves. However, to some extent they were able to resist stigma by conceiving of an ‘aware alcoholic self’ which was divorced from their previously unaware self and formed the basis for a new more knowing and valued identity
Cooling low-dimensional electron systems into the microkelvin regime.
Two-dimensional electron gases (2DEGs) with high mobility, engineered in semiconductor heterostructures host a variety of ordered phases arising from strong correlations, which emerge at sufficiently low temperatures. The 2DEG can be further controlled by surface gates to create quasi-one dimensional systems, with potential spintronic applications. Here we address the long-standing challenge of cooling such electrons to below 1 mK, potentially important for identification of topological phases and spin correlated states. The 2DEG device was immersed in liquid 3He, cooled by the nuclear adiabatic demagnetization of copper. The temperature of the 2D electrons was inferred from the electronic noise in a gold wire, connected to the 2DEG by a metallic ohmic contact. With effective screening and filtering, we demonstrate a temperature of 0.9 ± 0.1 mK, with scope for significant further improvement. This platform is a key technological step, paving the way to observing new quantum phenomena, and developing new generations of nanoelectronic devices exploiting correlated electron states
Testing for response shift in treatment evaluation of change in self-reported psychopathology amongst secondary psychiatric care outpatients
OBJECTIVES: If patients change their perspective due to treatment, this may alter the way they conceptualize, prioritize, or calibrate questionnaire items. These psychological changes, also called "response shifts," may pose a threat to the measurement of therapeutic change in patients. Therefore, it is important to test the occurrence of response shift in patients across their treatment. METHODS: This study focused on self-reported psychological distress/psychopathology in a naturalistic sample of 206 psychiatric outpatients. Longitudinal measurement invariance tests were computed across treatment in order to detect response shifts. RESULTS: Compared with before treatment, post-treatment psychopathology scores showed an increase in model fit and factor loading, suggesting that symptoms became more coherently interrelated within their psychopathology domains. Reconceptualization (depression/mood) and reprioritization (somatic and cognitive problems) response shift types were found in several items. We found no recalibration response shift. CONCLUSION: This study provides further evidence that response shift can occur in adult psychiatric patients across their mental health treatment. Future research is needed to determine whether response shift implies an unwanted potential bias in treatment evaluation or a desired cognitive change intended by treatment
Upstream transcription factor 1 (USF1) in risk of type 2 diabetes:Association study in 2000 Dutch Caucasians
Type 2 diabetes shares substantial genetic and phenotypic overlap with familial combined hyperlipidemia. Upstream stimulatory factor 1 (USF7), a well-established susceptibility gene for familial combined hyperlipidemia, is postulated to be such a shared genetic determinant. We evaluated two established variants in familial combined hyperlipidemia (rs2073658 and rs3737787) for association with type 2 diabetes in two Dutch case-control samples (N=2011). The first case-control sample comprised 501 subjects with type 2 diabetes from the Breda cohort and 920 healthy blood bank donors of Dutch Caucasian origin. The second case-control sample included 211 subjects with type 2 diabetes, and 379 normoglycemic controls. SNP rs2073658 and SNP rs3737787 were in perfect linkage disequilibrium. In the first case-control sample, prevalence of the major allele was higher in patients than in controls (75% versus 71%, OR=1.25, p=0.018). A similar effect-size and -direction was observed in the second case-control sample (76% versus 72%, OR=1.22, p=0.16). A combined analysis strengthened the evidence for association (OR=1.23, p=0.006). Notably, the increased risk for type 2 diabetes could be ascribed to the major allele, and its high frequency translated to a substantial population attributable risk of 14.5%. In conclusion, the major allele of rs2073658 in the USF1 gene is associated with a modestly increased risk to develop type 2 diabetes in Dutch Caucasians, with considerable impact at the population level. (c) 2008 Elsevier Inc. All rights reserved
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