320 research outputs found
A Random Matrix Model of Adiabatic Quantum Computing
We present an analysis of the quantum adiabatic algorithm for solving hard
instances of 3-SAT (an NP-complete problem) in terms of Random Matrix Theory
(RMT). We determine the global regularity of the spectral fluctuations of the
instantaneous Hamiltonians encountered during the interpolation between the
starting Hamiltonians and the ones whose ground states encode the solutions to
the computational problems of interest. At each interpolation point, we
quantify the degree of regularity of the average spectral distribution via its
Brody parameter, a measure that distinguishes regular (i.e., Poissonian) from
chaotic (i.e., Wigner-type) distributions of normalized nearest-neighbor
spacings. We find that for hard problem instances, i.e., those having a
critical ratio of clauses to variables, the spectral fluctuations typically
become irregular across a contiguous region of the interpolation parameter,
while the spectrum is regular for easy instances. Within the hard region, RMT
may be applied to obtain a mathematical model of the probability of avoided
level crossings and concomitant failure rate of the adiabatic algorithm due to
non-adiabatic Landau-Zener type transitions. Our model predicts that if the
interpolation is performed at a uniform rate, the average failure rate of the
quantum adiabatic algorithm, when averaged over hard problem instances, scales
exponentially with increasing problem size.Comment: 9 pages, 7 figure
Confronting the Superbubble Model with X-ray Observations of 30 Dor C
We present an analysis of XMM-Newton observations of the superbubble 30 Dor C
and compare the results with the predictions from the standard wind-blown
bubble model. We find that the observed X-ray spectra cannot be fitted
satisfactorily with the model alone and that there is evidence for nonthermal
X-ray emission, which is particularly important at > 4 keV. The total
unabsorbed 0.1-10 keV luminosities of the eastern and western parts of the
bubble are ~3 10^36 erg/s and ~5 10^36 erg/s, respectively. The unabsorbed
0.1-10 keV luminosity of the bubble model is 4 10^36 erg/s and so the power-law
component contributes between 1/3 and 1/2 to the total unabsorbed luminosity in
this energy band. The nature of the hard nonthermal emission is not clear,
although recent supernovae in the bubble may be responsible. We expect that
about one or two core-collapse supernovae could have occured and are required
to explain the enrichment of the hot gas, as evidenced by the overabundance of
alpha-elements by a factor of 3, compared to the mean value of 0.5 solar for
the interstellar medium in the Large Magellanic Cloud. As in previous studies
of various superbubbles, the amount of energy currently present in 30 Dor C is
significantly less than the expected energy input from the enclosed massive
stars over their lifetime. We speculate that a substantial fraction of the
input energy may be radiated in far-infrared by dust grains, which are mixed
with the hot gas because of the thermal conduction and/or dynamic mixing.Comment: 25 pages, 4 figures. To appear in The Astrophysical Journal, August
20, 2004 issu
AMPK is essential for energy homeostasis regulation and glucose sensing by POMC and AgRP neurons
Hypothalamic AMP-activated protein kinase (AMPK) has been suggested to act as a key sensing mechanism, responding to hormones and nutrients in the regulation of energy homeostasis. However, the precise neuronal populations and cellular mechanisms involved are unclear. The effects of long-term manipulation of hypothalamic AMPK on energy balance are also unknown. To directly address such issues, we generated POMC alpha 2KO and AgRP alpha 2KO mice lacking AMPK alpha 2 in proopiomelanocortin- (POMC-) and agouti-related protein-expressing (AgRP-expressing) neurons, key regulators of energy homeostasis. POMC alpha 2KO mice developed obesity due to reduced energy expenditure and dysregulated food intake but remained sensitive to leptin. in contrast, AgRPa2KO mice developed an age-dependent lean phenotype with increased sensitivity to a melanocortin agonist. Electrophysiological studies in AMPK alpha 2-deficient POMC or AgRP neurons revealed normal leptin or insulin action but absent responses to alterations in extracellular glucose levels, showing that glucose-sensing signaling mechanisms in these neurons are distinct from those pathways utilized by leptin or insulin. Taken together with the divergent phenotypes of POMC alpha 2KO and AgRP alpha 2KO mice, our findings suggest that while AMPK plays a key role in hypothalamic function, it does not act as a general sensor and integrator of energy homeostasis in the mediobasal hypothalamus
The Strayed Reveller, No. 1
The Strayed Reveller is a literary magazine of stories, songs, poems, essays, reviews and artwork by students at Stephen F. Austin State University. It is published monthly andsponsered by the School of Liberal Arts and Department of English.https://scholarworks.sfasu.edu/reveller/1000/thumbnail.jp
Evolutionary conservation of regulated longevity assurance mechanisms
Short abstract: A multi-level cross-species comparative analysis of gene-expression changes accompanying increased longevity in mutant nematodes, fruit flies and mice with reduced insulin/IGF-1 signaling revealed candidate conserved mechanisms
Theory of mind and emotion understanding predict moral development in early childhood
The current study utilized longitudinal data to investigate how theory of mind (ToM) and emotion understanding (EU) concurrently and prospectively predicted young children's moral reasoning and decision making. One hundred twenty-eight children were assessed on measures of ToM and EU at 3.5 and 5.5 years of age. At 5.5 years, children were also assessed on the quality of moral reasoning and decision making they used to negotiate prosocial moral dilemmas, in which the needs of a story protagonist conflict with the needs of another story character. More sophisticated EU predicted greater use of physical- and material-needs reasoning, and a more advanced ToM predicted greater use of psychological-needs reasoning. Most intriguing, ToM and EU jointly predicted greater use of higher-level acceptance-authority reasoning, which is likely a product of children's increasing appreciation for the knowledge held by trusted adults and children's desire to behave in accordance with social expectations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79217/1/026151009X483056.pd
Relationship between expectation management and client retention in online cognitive behavioural therapy
Background: Engaging clients from the outset of psychotherapy is important for therapeutic success. However, there is little research evaluating therapists’ initial attempts to engage clients in the therapeutic process. This article reports retrospective analysis of data from a trial of online cognitive behavioural therapy (CBT) for depression. Qualitative and quantitative methods were used to evaluate how therapists manage clients’ expectations at the outset of therapy and its relationship with client retention in the therapeutic intervention. Aims: To develop a system to codify expectation management in initial sessions of online CBT and evaluate its relationship with retention. Method: Initial qualitative research using conversation analysis identified three communication practices used by therapists at the start of first sessions: no expectation management, some expectation management, and comprehensive expectation management. These findings were developed into a coding scheme that enabled substantial inter-rater agreement (weighted Kappa = 0.78; 95% CI: 0.52 to 0.94) and was applied to all trial data. Results: Adjusting for a range of client variables, primary analysis of data from 147 clients found comprehensive expectation management was associated with clients remaining in therapy for 1.4 sessions longer than those who received no expectation management (95% CI: -0.2 to 3.0). This finding was supported by a sensitivity analysis including an additional 21 clients (1.6 sessions, 95% CI: 0.2 to 3.1). Conclusions: Using a combination of qualitative and quantitative methods, this study suggests a relationship between expectation management and client retention in online CBT for depression, which has implications for professional practice. A larger prospective study would enable a more precise estimate of retention
Reduction in BACE1 decreases body weight, protects against diet-induced obesity and enhances insulin sensitivity in mice
Insulin resistance and impaired glucose homoeostasis are important indicators of Type 2 diabetes and are early risk factors of AD (Alzheimer's disease). An essential feature of AD pathology is the presence of BACE1 (β-site amyloid precursor protein-cleaving enzyme 1), which regulates production of toxic amyloid peptides. However, whether BACE1 also plays a role in glucose homoeostasis is presently unknown. We have used transgenic mice to analyse the effects of loss of BACE1 on body weight, and lipid and glucose homoeostasis. BACE1−/− mice are lean, with decreased adiposity, higher energy expenditure, and improved glucose disposal and peripheral insulin sensitivity than wild-type littermates. BACE1−/− mice are also protected from diet-induced obesity. BACE1-deficient skeletal muscle and liver exhibit improved insulin sensitivity. In a skeletal muscle cell line, BACE1 inhibition increased glucose uptake and enhanced insulin sensitivity. The loss of BACE1 is associated with increased levels of UCP1 (uncoupling protein 1) in BAT (brown adipose tissue) and UCP2 and UCP3 mRNA in skeletal muscle, indicative of increased uncoupled respiration and metabolic inefficiency. Thus BACE1 levels may play a critical role in glucose and lipid homoeostasis in conditions of chronic nutrient excess. Therefore strategies that ameliorate BACE1 activity may be important novel approaches for the treatment of diabetes
- …