2,917 research outputs found
Quasiparticles in the superconducting state of Bi2Sr2CaCu2O8
Recent improvements in momentum resolution by a factor of 32 lead to
qualitatively new ARPES results on the spectra of Bi2Sr2CaCu2O8 (Bi2212) along
the (pi,pi) direction, where there is a node in the superconducting gap. With
improved resolution, we now see the intrinsic lineshape, which indicates the
presence of true quasiparticles at the Fermi momentum in the superconducting
state, and lack thereof in the normal state. The region of momentum space
probed here is relevant for charge transport, motivating a comparison of our
results to conductivity measurements by infrared reflectivity.Comment: revised paper with new figure
Sirtuin 5 depletion impairs mitochondrial function in human proximal tubular epithelial cells
Ischemia is a major cause of kidney damage. Proximal tubular epithelial cells (PTECs) are highly susceptible to ischemic insults that frequently cause acute kidney injury (AKI), a potentially life-threatening condition with high mortality. Accumulating evidence has identified altered mitochondrial function as a central pathologic feature of AKI. The mitochondrial NAD+-dependent enzyme sirtuin 5 (SIRT5) is a key regulator of mitochondrial form and function, but its role in ischemic renal injury (IRI) is unknown. SIRT5 expression was increased in murine PTECs after IRI in vivo and in human PTECs (hPTECs) exposed to an oxygen/nutrient deprivation (OND) model of IRI in vitro. SIRT5-depletion impaired ATP production, reduced mitochondrial membrane potential, and provoked mitochondrial fragmentation in hPTECs. Moreover, SIRT5 RNAi exacerbated OND-induced mitochondrial bioenergetic dysfunction and swelling, and increased degradation by mitophagy. These findings suggest SIRT5 is required for normal mitochondrial function in hPTECs and indicate a potentially important role for the enzyme in the regulation of mitochondrial biology in ischemia
Elevational Spatial Compounding for enhancing image quality in Echocardiography
INTRODUCTION: Echocardiography is commonly used in clinical practice for the real-time assessment of cardiac morphology and function. Nevertheless, due to the nature of the data acquisition, cardiac ultrasound images are often corrupted by a range of acoustic artefacts, including acoustic noise, speckle and shadowing. Spatial compounding techniques have long been recognised for their ability to suppress common ultrasound artefacts, enhancing the imaged cardiac structures. However, they require extended acquisition times as well as accurate spatio-temporal alignment of the compounded data. Elevational spatial compounding acquires and compounds adjacent partially decorrelated planes of the same cardiac structure. METHODS: This paper employs an anthropomorphic left ventricle phantom to examine the effect of acquisition parameters, such as inter-slice angular displacement and 3D sector angular range, on the elevational spatial compounding of cardiac ultrasound data. RESULTS AND CONCLUSION: Elevational spatial compounding can produce substantial noise and speckle suppression as well as visual enhancement of tissue structures even for small acquisition sector widths (2.5° to 6.5°). In addition, elevational spatial compounding eliminates the need for extended acquisition times as well as the need for temporal alignment of the compounded datasets. However, moderate spatial registration may still be required to reduce any tissue/chamber blurring side effects that may be introduced
Webteaching: sequencing of subject matter in relation to prior knowledge of pupils
Two experiments are discussed in which the sequencing procedure of webteaching is compared with a linear sequence for the presentation of text material.\ud
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In the first experiment variations in the level of prior knowledge of pupils were studied for their influence on the sequencing mode of text presentation. Prior knowledge greatly reduced the effect of the size of sequencing procedures.\ud
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In the second experiment pupils with a low level of prior knowledge studied a text, following either a websequence or a linear sequence. Webteaching was superior to linear teaching on a number of dependent variables. It is concluded that webteaching is an effective sequencing procedure in those cases where substantial new learning is required
Coherent quasiparticle weight and its connection to high-T_c superconductivity from angle-resolved photoemission
In conventional superconductors, the pairing energy gap (\Delta) and
superconducting phase coherence go hand-in-hand. As the temperature is lowered,
both the energy gap and phase coherence appear at the transition temperature
T_c. In contrast, in underdoped high-T_c superconductors (HTSCs), a pseudogap
appears at a much higher temperature T^*, smoothly evolving into the
superconducting gap at T_c. Phase coherence on the other hand is only
established at T_c, signaled by the appearance of a sharp quasiparticle (QP)
peak in the excitation spectrum. Another important difference between the two
types of superconductors is in the ratio of 2\Delta / T_c=R. In BCS theory,
R~3.5, is constant. In the HTSCs this ratio varies widely, continuing to
increase in the underdoped region, where the gap increases while T_c decreases.
Here we report that in HTSCs it is the ratio z_A\Delta_m/T_c which is
approximately constant, where \Delta_m is the maximum value of the d-wave gap,
and z_A is the weight of the coherent excitations in the spectral function.
This is highly unusual, since in nearly all phase transitions, T_c is
determined by an energy scale alone. We further show that in the
low-temperature limit, z_{\it A} increases monotonically with increasing doping
x. The growth is linear, i.e. z_A(x)\propto x, in the underdoped to optimally
doped regimes, and slows down in overdoped samples. The reduction of z_A with
increasing temperature resembles that of the c-axis superfluid density.Comment: 11 pages, 5 figures, revised versio
Evolution of the pairing pseudogap in the spectral function with interplane anisotropy
We study the pairing pseudogap in the spectral function as a function of
interplane coupling. The analytical expressions for the self-energy in the
critical regime are obtained for any degree of anisotropy. The frequency
dependence of the self-energy is found to be qualitatively different in two and
three dimensions, and the crossover from two to three dimensional behavior is
discussed. In particular, by considering the anisotropy of the Fermi velocity
and gap along the Fermi surface, we can qualitatively explain recent
photoemission experiments on high temperature superconductors concerning the
temperature dependent Fermi arcs seen in the pseudogap phase.Comment: 20 pages, revtex, 5 encapsulated postscript figures include
Where is the pi particle?
We discuss the interplay of particle-particle and particle-hole spin-triplet
channels in high-T_c superconductors using a quasiparticle dispersion motivated
by angle-resolved photoemission. Within a generalized RPA, we find a well
defined antibound state of two holes, the pi resonance of Demler and Zhang, as
well as a bound state of a particle and a hole, the spin exciton. We show that
the energy of the pi resonance always exceeds 2 Delta, twice the maximum d-wave
gap, therefore the neutron resonance observed in the cuprates around energy
Delta is most likely a spin exciton. At the same time, we speculate that the pi
particle can exist at higher energies and might be observed in neutron
scattering around 100 meV.Comment: RevTeX, 5 pages, 4 eps figure
Biola Hour Highlights, 1974 - 10
The Spirit-Filled Family by Ken Poure All in the Family by Ken Poure Communicating by Norman Wright The Revelation of Jesus Christ by Lloyd Anderson Panel Discussions with Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1009/thumbnail.jp
Type 1 diabetes incidence in Scotland between 2006 and 2019
Aims: To describe type 1 diabetes incidence in Scotland between 2006 and 2019. Methods: Repeated annual crossâsectional studies of type 1 diabetes incidence were conducted. Incident cases were identified from the Scottish Care InformationâDiabetes Collaboration (SCIâDC), a populationâbased register of people with diagnosed diabetes derived from primary and secondary care data. Midâyear population estimates for Scotland were used as the denominator to calculate annual incidence with stratification by age and sex. Joinpoint regression was used to investigate whether incidence changed during the study period. Age and sexâspecific type 1 diabetes incidence over the whole time period was estimated by quintile of the Scottish Index of Multiple Deprivation (SIMD), an areaâbased measure, in which Q1 and Q5 denote the most and least deprived fifths of the population, respectively, with quasiâPoisson regression used to compare incidence for Q5 compared to Q1. Results: The median (IQR) age of the study population of 14,564 individuals with incident type 1 diabetes was 24.1 (12.3â42.4) years, 56% were men, 23% were in Q1 and 16% were in Q5. Incidence of T1DM was higher in men than women overall (at around 22 and 17 per 100,000, respectively) and in under 15 year olds (approximately 40 per 100,000 in both sexes) than other age groups and was similar across the study period in all strata. There was an inverse association between socioâeconomic status and type 1 diabetes incidence for 15â29, 30â49 and 50+ year olds [incidence rate ratio (IRR) for Q5 compared to Q1; IRR (95% CI) 0.52 (0.47â0.58), 0.68 (0.61â0.76) and 0.53(0.46â0.61), respectively] but not for under 15 year olds [1.02 (0.92â1.12)]. Conclusion: Incidence of type 1 diabetes varies by age, sex and socioâeconomic status and has remained approximately stable from 2006 to 2019 in Scotland
Surface-acoustic-wave-driven luminescence from a lateral p-n junction
The authors report surface-acoustic-wave-driven luminescence from a lateral
p-n junction formed by molecular beam epitaxy regrowth of a modulation doped
GaAs/AlGaAs quantum well on a patterned GaAs substrate.
Surface-acoustic-wave-driven transport is demonstrated by peaks in the
electrical current and light emission from the GaAs quantum well at the
resonant frequency of the transducer. This type of junction offers high carrier
mobility and scalability. The demonstration of surface-acoustic-wave
luminescence is a significant step towards single-photon applications in
quantum computation and quantum cryptography.Comment: 4 pages, 3 figure
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