11,256 research outputs found
First-Principles Modeling of Pt/LaAlO3/SrTiO3 Capacitors Under an External Bias Potential
We study the electrical properties of Pt/LaAlO3/SrTiO3 capacitors under the
action of an external bias potential, using first-principles simulations
performed at constrained electric displacement field. A complete set of band
diagrams, together with the relevant electrical characteristics (capacitance
and built-in fields), are determined as a function of LaAlO3 thickness and the
applied potential.We find that the internal field in LaAlO3 monotonically
decreases with increasing thickness; hence, the occurrence of spontaneous Zener
tunneling is ruled out in this system.We discuss the implications of our
results in the light of recent experimental observations on biased
LaAlO3/SrTiO3 junctions involving metallic top electrodes.Comment: 5 pages, 4 figure
High-resolution imaging spectroscopy of two micro-pores and an arch filament system in a small emerging-flux region
Aims. The purpose of this investigation is to characterize the temporal
evolution of an emerging flux region, the associated photospheric and
chromospheric flow fields, and the properties of the accompanying arch filament
system. Methods. This study is based on imaging spectroscopy with the
G\"ottingen Fabry-P\'erot Interferometer at the Vacuum Tower Telescope, on 2008
August 7. Cloud model (CM) inversions of line scans in the strong chromospheric
absorption H line yielded CM parameters, which describe the cool plasma
contained in the arch filament system. Results. The observations cover the
decay and convergence of two micro-pores with diameters of less than one
arcsecond and provide decay rates for intensity and area. The photospheric
horizontal flow speed is suppressed near the two micro-pores indicating that
the magnetic field is sufficiently strong to affect the convective energy
transport. The micro-pores are accompanied by an arch filament system, where
small-scale loops connect two regions with H line-core brightenings
containing an emerging flux region with opposite polarities. The chromospheric
velocity of the cloud material is predominantly directed downwards near the
footpoints of the loops with velocities of up to 12 km/s, whereas loop tops
show upward motions of about 3 km/s. Conclusions. Micro-pores are the smallest
magnetic field concentrations leaving a photometric signature in the
photosphere. In the observed case, they are accompanied by a miniature arch
filament system indicative of newly emerging flux in the form of
-loops. Flux emergence and decay take place on a time-scale of about
two days, whereas the photometric decay of the micro-pores is much more rapid
(a few hours), which is consistent with the incipient submergence of
-loops. The results are representative for the smallest emerging flux
regions still recognizable as such.Comment: 15 pages, 16 figures, 3 tables, published in A&
Transition of hemoglobin between two tertiary conformations: The transition constant differs significantly for the major and minor hemoglobins of the Japanese quail (Cortunix cortunix japonica)
We demonstrate that 5,5âČ-dithiobis(2-nitrobenzoate) â DTNB â reacts with only CysF9[93]ÎČ and CysB5[23]ÎČ among the multiple sulfhydryl groups of the major and minor hemoglobins of the Japanese quail (Cortunix cortunix japonica). Kequ, the equilibrium constant for the reaction,
does not differ very significantly between the two hemoglobins. It decreases 430-fold between pHâ5.6 and pHâ9: from a mean of 7±1 to a mean of 0.016±0.003. Quantitative analyses of the Kequ data based on published X-ray and temperature-jump evidence for a tertiary structure
transition in liganded hemoglobin enable the calculation of Krt, the equilibrium constant for the râât tertiary structure transition. Krt differs significantly between the two hemoglobins: 0.744±0.04 for the major, 0.401±0.01 for the minor hemoglobin. The mean pKas of the two groups
whose ionizations are coupled to the DTNB reaction are about the same as previously reported for mammalian hemoglobins
Venezuelaâs Growth Experience
The standard of living, measured as gross domestic product (GDP) per capita, increased dramatically in Venezuela relative to that of the United States from 20 percent in 1920 to 90 percent in 1958, but since then has collapsed to around 30 percent nowadays. What explains these remarkable growth and collapse episodes? Using a standard development accounting framework, we show that the growth episode is mainly accounted for by an increase in capital accumulation and knowledge transfer associated with the foreign direct investment in the booming oil industry. The collapse episode is accounted for equally by a fall in total factor productivity and in capital accumulation. We analyze Venezuela during the collapse episode in the context of a model of heterogeneous production units were policies and institutions favour unproductive in detriment of more productive activities. These policies generate misallocation, lower TFP, and a decline in capital accumulation. We show in the context of an heterogeneous-establishment growth model that distortionary policies can explain a large portion of the current differences in TFP, capital accumulation, and income per capita between Venezuela and the United States.Productivity, physical capital, misallocation, policies
Venezuela's Growth Experience
The standard of living, measured as gross domestic product (GDP) per capita, increased dramatically in Venezuela relative to that of the United States from 20 percent in 1920 to 90 percent in 1958, but since then has collapsed to around 30 percent nowadays. What explains these remarkable growth and collapse episodes? Using a standard development accounting framework, we show that the growth episode is mainly accounted for by an increase in capital accumulation and knowledge transfer associated with the foreign direct investment in the booming oil industry. The collapse episode is accounted for equally by a fall in total factor productivity and in capital accumulation. We analyze Venezuela during the collapse episode in the context of a model of heterogeneous production units were policies and institutions favour unproductive in detriment of more productive activities. These policies generate misallocation, lower TFP, and a decline in capital accumulation. We show in the context of an heterogeneous-establishment growth model that distortionary policies can explain between 80 to 95 percent of the current differences in TFP, capital accumulation, and income per capita between Venezuela and the United States.Productivity, physical capital, misallocation, policies
A simple variational method for calculating energy and quantum capacitance of an electron gas with screened interactions
We describe a variational procedure for calculating the energy of an electron
gas in which the long-range Coulomb interaction is truncated by the screening
effect of a nearby metallic gate. We use this procedure to compute the quantum
capacitance of the system as a function of electron density and spin
polarization. The accuracy of the method is verified against published
Monte-Carlo data. The results compare favorably with a recent experiment.Comment: 4 pages, 3 figure
The meaning of different forms of structural myocardial injury, immune response and timing of infarct necrosis and cardiac repair
Although a decline in the all-cause and cardiac mortality rates following myocardial infarction (MI) during the past 3 decades has been reported, MI is a major cause of death and disability worldwide. From a pathological point of view MI consists in a particular myocardial cell death due to prolonged ischemia. After the onset of myocardial ischemia, cell death is not immediate, but takes a finite period of time to develop. Once complete myocytesâ necrosis has occurred, a process leading to a healed infarction takes place. In fact, MI is a dynamic process that begins with the transition from reversible to irreversible ischemic injury and culminates in the replacement of dead myocardium by a fibrous scar. The pathobiological mechanisms underlying this process are very complex, involving an inflammatory response by several pathways, and pose a major challenge to ability to improve our knowledge. An improved understanding of the pathobiology of cardiac repair after MI and further studies of its underlying mechanisms provide avenues for the development of future strategies directed toward the identification of novel therapies. The chronologic dating of MI is of great importance both to clinical and forensic investigation, that is, the ability to create a theoretical timeline upon which either clinicians or forensic pathologists may increase their ability to estimate the time of MI. Aging of MI has very important practical implications in clinical practice since, based on the chronological dating of MI, attractive alternatives to solve therapeutic strategies in the various phases of MI are developing
Implementing a Home-Based Blood Pressure Monitoring Program to Improve Hypertension Management
Hypertension is a major problem in the United States. It is critical to identify effective strategies to treat and manage hypertension. An experimental design was utilized to determine the effectiveness of home-based blood pressure monitoring (HBPM) in the management of prehypertension, newly diagnosed, or uncontrolled hypertension. A randomized convenience sample of 20 adults was recruited into a control (n=9) and experimental (n=11) group. The translational care project was conducted over 60 days where participants measured their blood pressures as instructed for the intervention and control groups. An independent t-test was conducted to analyze the effectiveness of HBPM on the participantsâ blood pressure, blood pressure knowledge, self-care, and medication adherence utilizing subsequent scales. There was a statistically insignificant increase in systolic blood pressure, but a statistically significant increase in diastolic blood pressure between the experimental and control groups at 60 days. There was no statistical significance in the improvement of HBPM adherence, knowledge, self-care, or medication adherence between the two groups at 60 days. While there is limited statistical support for this translational research project, other resources support HBPM as an innovative program that has the potential to provide healthcare providers an avenue for more timely, effective, and individualized patient care. Literature demonstrates that improved blood pressure control has the potential to decrease the prevalence of co-morbid conditions and decrease health care costs. With an increase in successful studies legislation could be challenged to increase coverage and reimbursement cost for blood pressure monitors and more HBPM programs in practice. Continued research related to HBPM and patient adherence is necessary to improve patient access to affordable care and overall self-care outcomes
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