1,334 research outputs found
PETMiner - A visual analysis tool for petrophysical properties of core sample data
The aim of the PETMiner software is to reduce the time and monetary cost of analysing petrophysical data that is obtained from reservoir sample cores. Analysis of these data requires tacit knowledge to fill ‘gaps’ so that predictions can be made for incomplete data. Through discussions with 30 industry and academic specialists, we identified three analysis use cases that exemplified the limitations of current petrophysics analysis tools. We used those use cases to develop nine core requirements for PETMiner, which is innovative because of its ability to display detailed images of the samples as data points, directly plot multiple sample properties and derived measures for comparison, and substantially reduce interaction cost. An 11-month evaluation demonstrated benefits across all three use cases by allowing a consultant to: (1) generate more accurate reservoir flow models, (2) discover a previously unknown relationship between one easy-to-measure property and another that is costly, and (3) make a 100-fold reduction in the time required to produce plots for a report
Hidden Magnetism and Quantum Criticality in the Heavy Fermion Superconductor CeRhIn5
With understood exceptions, conventional superconductivity does not coexist
with long-range magnetic order[1]. In contrast, unconventional
superconductivity develops near a boundary separating magnetically ordered and
magnetically disordered phases[2,3]. A maximum in the superconducting
transition temperature Tc develops where this boundary extrapolates to T=0 K,
suggesting that fluctuations associated with this magnetic quantum-critical
point are essential for unconventional superconductivity[4,5]. Invariably
though, unconventional superconductivity hides the magnetic boundary when T <
Tc, preventing proof of a magnetic quantum-critical point[5]. Here we report
specific heat measurements of the pressure-tuned unconventional superconductor
CeRhIn5 in which we find a line of quantum-phase transitions induced inside the
superconducting state by an applied magnetic field. This quantum-critical line
separates a phase of coexisting antiferromagnetism and superconductivity from a
purely unconventional superconducting phase and terminates at a quantum
tetracritical point where the magnetic field completely suppresses
superconductivity. The T->0 K magnetic field-pressure phase diagram of CeRhIn5
is well described with a theoretical model[6,7] developed to explain
field-induced magnetism in the high-Tc cuprates but in which a clear
delineation of quantum-phase boundaries has not been possible. These
experiments establish a common relationship among hidden magnetism, quantum
criticality and unconventional superconductivity in cuprate and heavy-electron
systems, such as CeRhIn5.Comment: journal reference adde
Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides
The in-plane anisotropy of the electrical resistivity across the coupled
orthorhombic and magnetic transitions of the iron pnictides has been
extensively studied in the parent and electron-doped compounds. All these
studies universally show that the resistivity across the long
orthorhombic axis - along which the spins couple antiferromagnetically
below the magnetic transition temperature - is smaller than the resistivity
of the short orthorhombic axis , i. e. .
Here we report that in the hole-doped compounds
BaKFeAs, as the doping level increases, the
resistivity anisotropy initially becomes vanishingly small, and eventually
changes sign for sufficiently large doping, i. e. . This
observation is in agreement with a recent theoretical prediction that considers
the anisotropic scattering of electrons by spin-fluctuations in the
orthorhombic/nematic state.Comment: This paper has been replaced by the new version offering new
explanation of the experimental results first reported her
The Functional DRD3 Ser9Gly Polymorphism (rs6280) Is Pleiotropic, Affecting Reward as Well as Movement
Abnormalities of motivation and behavior in the context of reward are a fundamental component of addiction and mood disorders. Here we test the effect of a functional missense mutation in the dopamine 3 receptor (DRD3) gene (ser9gly, rs6280) on reward-associated dopamine (DA) release in the striatum. Twenty-six healthy controls (HCs) and 10 unmedicated subjects with major depressive disorder (MDD) completed two positron emission tomography (PET) scans with [11C]raclopride using the bolus plus constant infusion method. On one occasion subjects completed a sensorimotor task (control condition) and on another occasion subjects completed a gambling task (reward condition). A linear regression analysis controlling for age, sex, diagnosis, and self-reported anhedonia indicated that during receipt of unpredictable monetary reward the glycine allele was associated with a greater reduction in D2/3 receptor binding (i.e., increased reward-related DA release) in the middle (anterior) caudate (p<0.01) and the ventral striatum (p<0.05). The possible functional effect of the ser9gly polymorphism on DA release is consistent with previous work demonstrating that the glycine allele yields D3 autoreceptors that have a higher affinity for DA and display more robust intracellular signaling. Preclinical evidence indicates that chronic stress and aversive stimulation induce activation of the DA system, raising the possibility that the glycine allele, by virtue of its facilitatory effect on striatal DA release, increases susceptibility to hyperdopaminergic responses that have previously been associated with stress, addiction, and psychosis
Thermodynamic analysis of the Quantum Critical behavior of Ce-lattice compounds
A systematic analysis of low temperature magnetic phase diagrams of Ce
compounds is performed in order to recognize the thermodynamic conditions to be
fulfilled by those systems to reach a quantum critical regime and,
alternatively, to identify other kinds of low temperature behaviors. Based on
specific heat () and entropy () results, three different types of
phase diagrams are recognized: i) with the entropy involved into the ordered
phase () decreasing proportionally to the ordering temperature
(), ii) those showing a transference of degrees of freedom from the
ordered phase to a non-magnetic component, with their jump
() vanishing at finite temperature, and iii) those ending in a
critical point at finite temperature because their do not decrease
with producing an entropy accumulation at low temperature.
Only those systems belonging to the first case, i.e. with as
, can be regarded as candidates for quantum critical behavior.
Their magnetic phase boundaries deviate from the classical negative curvature
below \,K, denouncing frequent misleading extrapolations down to
T=0. Different characteristic concentrations are recognized and analyzed for
Ce-ligand alloyed systems. Particularly, a pre-critical region is identified,
where the nature of the magnetic transition undergoes significant
modifications, with its discontinuity strongly
affected by magnetic field and showing an increasing remnant entropy at . Physical constraints arising from the third law at are discussed
and recognized from experimental results
Does chocolate reduce blood pressure? A meta-analysis
BackgroundDark chocolate and flavanol-rich cocoa products have attracted interest as an alternative treatment option for hypertension, a known risk factor for cardiovascular disease. Previous meta-analyses concluded that cocoa-rich foods may reduce blood pressure. Recently, several additional trials have been conducted with conflicting results. Our study summarises current evidence on the effect of flavanol-rich cocoa products on blood pressure in hypertensive and normotensive individuals.MethodsWe searched Medline, Cochrane and international trial registries between 1955 and 2009 for randomised controlled trials investigating the effect of cocoa as food or drink compared with placebo on systolic and diastolic blood pressure (SBP/DBP) for a minimum duration of 2 weeks. We conducted random effects meta-analysis of all studies fitting the inclusion criteria, as well as subgroup analysis by baseline blood pressure (hypertensive/normotensive). Meta-regression analysis explored the association between type of treatment, dosage, duration or baseline blood pressure and blood pressure outcome. Statistical significance was set at P ResultsFifteen trial arms of 13 assessed studies met the inclusion criteria. Pooled meta-analysis of all trials revealed a significant blood pressure-reducing effect of cocoa-chocolate compared with control (mean BP change +/- SE: SBP: -3.2 +/- 1.9 mmHg, P = 0.001; DBP: -2.0 +/- 1.3 mmHg, P = 0.003). However, subgroup meta-analysis was significant only for the hypertensive or prehypertensive subgroups (SBP: -5.0 +/- 3.0 mmHg; P = 0.0009; DBP: -2.7 +/- 2.2 mm Hg, P = 0.01), while BP was not significantly reduced in the normotensive subgroups (SBP: -1.6 +/- 2.3 mmHg, P = 0.17; DBP: -1.3 +/- 1.6 mmHg, P = 0.12). Nine trials used chocolate containing 50% to 70% cocoa compared with white chocolate or other cocoa-free controls, while six trials compared high- with low-flavanol cocoa products. Daily flavanol dosages ranged from 30 mg to 1000 mg in the active treatment groups, and interventions ran for 2 to 18 weeks. Meta-regression analysis found study design and type of control to be borderline significant but possibly indirect predictors for blood pressure outcome.ConclusionOur meta-analysis suggests that dark chocolate is superior to placebo in reducing systolic hypertension or diastolic prehypertension. Flavanol-rich chocolate did not significantly reduce mean blood pressure below 140 mmHg systolic or 80 mmHg diastolic.Karin Ried, Thomas Sullivan, Peter Fakler, Oliver R. Frank and Nigel P. Stock
Progression from new methicillin-resistant Staphylococcus aureus colonisation to infection: An observational study in a hospital cohort
10.1186/1471-2334-13-491BMC Infectious Diseases131-BIDM
Dimensional reduction at a quantum critical point
Competition between electronic ground states near a quantum critical point
(QCP) - the location of a zero-temperature phase transition driven solely by
quantum-mechanical fluctuations - is expected to lead to unconventional
behaviour in low-dimensional systems. New electronic phases of matter have been
predicted to occur in the vicinity of a QCP by two-dimensional theories, and
explanations based on these ideas have been proposed for significant unsolved
problems in condensed-matter physics, such as non-Fermi-liquid behaviour and
high-temperature superconductivity. But the real materials to which these ideas
have been applied are usually rendered three-dimensional by a finite electronic
coupling between their component layers; a two-dimensional QCP has not been
experimentally observed in any bulk three-dimensional system, and mechanisms
for dimensional reduction have remained the subject of theoretical conjecture.
Here we show evidence that the Bose-Einstein condensate of spin triplets in the
three-dimensional Mott insulator BaCuSi2O6 provides an experimentally
verifiable example of dimensional reduction at a QCP. The interplay of
correlations on a geometrically frustrated lattice causes the individual
two-dimensional layers of spin-1/2 Cu2+ pairs (spin dimers) to become decoupled
at the QCP, giving rise to a two-dimensional QCP characterized by power law
scaling distinctly different from that of its three-dimensional counterpart.
Thus the very notion of dimensionality can be said to acquire an 'emergent'
nature: although the individual particles move on a three-dimensional lattice,
their collective behaviour occurs in lower-dimensional space.Comment: 14 pages, 4 figure
The influence of different concentrations of flavanol chocolate bars under acute supplement conditions on exercise and performance
The purpose of this study was to assess the effects and acute dosage of different flavanol concentrations in a dark chocolate bar on physiological parameters during steady state (SS) and incremental exercise. In a double-blind, randomised, crossover study, 15 healthy participants with a mean ± SD age of 30 ± 7 years; stature 176.8 ± 8.6 cm and body mass 80.3 ± 8.4 kg supplemented with high flavanol (HF) (1060 mg), moderate flavanol (MF) (746 mg), low flavanol (LF) (406 mg), or a control (CON) (88 mg) chocolate bar (~ 34 g), 2 h prior to 40 min of SS cycling (80% gas-exchange threshold) followed by an incremental test to volitional fatigue. During the SS cycle oxygen consumption ([Formula: see text]), respiratory exchange ratio (RER) and heart rate (HR) were continuously monitored. Plasma samples were collected prior to commencing exercise to determine nitrate (NO ) and nitrite (NO ) levels under each condition. There was no observed effect between flavanol concentrations on [Formula: see text], RER, and HR during SS cycling (P > 0.05). [Formula: see text], peak power, HR peak, and RER peak also did not significantly differ between conditions (P > 0.05). There was a small trend for higher plasma NO levels following higher flavanol concentration; however, this did not reach statistical significance (P > 0.05). Acute supplementation with cocoa of differing flavanol concentrations does not appear to have any effect on exercise and performance. It is plausible that longer flavanol supplementation periods might have greater accumulative effects and thus may potentially elicit a larger effect
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