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Ghrelin is a growth hormone (GH) secretagogue (GHS) and GHRP-6 is a synthetic peptide analogue; both act through the GHS receptor. GH secretion depends directly on the intracellular concentration of Ca~(2+); this is determined fro...
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Ghrelin is a growth hormone (GH) secretagogue (GHS) and GHRP-6 is a synthetic peptide analogue; both act through the GHS receptor. GH secretion depends directly on the intracellular concentration of Ca~(2+); this is determined from the intracellular reserves and by the entrance of Ca~(2+) through the voltage-dependent calcium channels, which are activated by the membrane depolarization.Membrane potential is mainly determined by K~+ channels. In the present work, we investigated the effect of ghrelin (10 nM) or GHRP-6 (100 nM) for 96 h on functional expression of voltage-dependent K~+ channels in rat somatotropes: GC cell line. Physiological patch-clamp whole-cell recording was used to register the K~+ currents. With Cd2~+ (1mM) and tetrodotoxin (1 μm) in the bath solution recording, three types of currents were characterized on the basis of their biophysical and pharmacological properties. GC cells showed a K~+ current with a transitory component (I_A) sensitive to 4-aminopyridine, which represents ～40% of the total outgoing current; a sustained component named delayed rectifier (I_K), sensitive to tetraethylammonium; and a third type of K~+ current was recorded at potentials more negative than ?80mV, permitting the entrance of K~+ named inward rectifier (K_(IR)). Chronic treatment with ghrelin or GHRP-6 did not modify the functional expression of K~+ channels, without significant changes (P < 0.05) in the amplitudes of the three currents observed; in addition, there were no modifications in their biophysical properties and kinetic activation or inactivation.
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A technique for converting the magnetic field amplitudes of guided toroidal and guided poloidal waves observed on the ground into the equatorial electric field amplitudes of the waves in space is presented. Analytic solutions of t...
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A technique for converting the magnetic field amplitudes of guided toroidal and guided poloidal waves observed on the ground into the equatorial electric field amplitudes of the waves in space is presented. Analytic solutions of the guided toroidal and guided poloidal Alfven wave equations are used to determine the ratio of the equatorial electric field amplitude to the ionospheric magnetic amplitude, E~(eq)/b~i. Using these solutions, we show that in general E~(eq)/b~i only depends very weakly on the Pedersen conductance, Σ_P, and is linearly proportional to the guided Alfven waves' frequency. We also present numerical solutions of the guided Alfven wave equations illustrating how the value of E~(eq)/b~i varies as a function of L shell for a range of different realistic field-aligned plasma density profiles. These results can be used to determine the equatorial wave electric field amplitude, E~(eq), in space using the magnetic field amplitude observed on the ground, b~g. Accurate estimates of E~(eq) are crucial to understanding the role and importance of ultralow frequency waves on the energization and radial transport of radiation belt electrons.
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This paper (Part 1) describes the period and amplitude variations and the re-occurrence of local peaks, during different earthquakes, in the Fourier amplitude spectra of strong ground motion, recorded at seven stations along the A...
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This paper (Part 1) describes the period and amplitude variations and the re-occurrence of local peaks, during different earthquakes, in the Fourier amplitude spectra of strong ground motion, recorded at seven stations along the Adriatic Coast in Montenegro, Yugoslavia, in the Dinarides and Illyrides seismogenic zone. In the comparison paper (Part Ⅱ), this analysis will be presented for the Inner Part of Balkan Peninsula seismogenic zone. The data suggest that some local peaks re-occur during shaking by small local earthquakes (peak ground velocities v_(max) < 10-20 cm/s). During large strong-motion amplitudes (v_(max) > 20 cm/s), these peaks are shifted toward longer periods (by non-linear response of soils) or disappear.
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We propose a new formulation of quantum algorithm which allows to distribute amplitudes over two copies of small quantum subsystems. The new method gives a fixed number of copies and applied to the control of multi-qubit system. T...
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We propose a new formulation of quantum algorithm which allows to distribute amplitudes over two copies of small quantum subsystems. The new method gives a fixed number of copies and applied to the control of multi-qubit system. The analysis for the amount of error due to the distribution process has been presented for a system of 10 qubits with a small quantum subsystems to be copied. The present scheme provides a new way to distribute amplitudes over small quantum subsystems.
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Colloidal gels made of carbon black particles dispersed in light mineral oil are "rheo-acoustic" materials, i.e., their mechanical and structural properties can be tuned using high-power ultrasound, sound waves with submicrometer ...
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Colloidal gels made of carbon black particles dispersed in light mineral oil are "rheo-acoustic" materials, i.e., their mechanical and structural properties can be tuned using high-power ultrasound, sound waves with submicrometer amplitude and frequencies larger than 20 kHz. The effects of high-power ultrasound on the carbon black gel are demonstrated using two experiments: rheology coupled to ultrasound to test for the gel mechanical response and a time-resolved ultra-small-angle x-ray scattering experiment (TRUSAXS) coupled to ultrasound to test for structural changes within the gel. We show that high-power ultrasound above a critical amplitude leads to a complex viscoelastic transient response of the gels within a few seconds: a softening of its storage modulus accompanied by a strong overshoot in its loss modulus. Under high-power ultrasound, the gel displays a viscoelastic spectrum with glasslike features and a significant decrease in its yield strain. Those effects are attributed to the formation of intermittent microcracks in the bulk of the gel as evidenced by TRUSAXS. Provided that the shear rate is not large enough to fully fluidize the sample, high-power ultrasound also facilitates the flow of the gel, reducing its yield stress as well as increasing the shearthinning index, thanks again to the formation of microcracks.
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Antenna arrays have potential applications in Radar, mobile, broadcasting, astronomy and other defense and commercial platforms. The design of antenna arrays is essential as they are capable of controlling the radiation pattern in...
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Antenna arrays have potential applications in Radar, mobile, broadcasting, astronomy and other defense and commercial platforms. The design of antenna arrays is essential as they are capable of controlling the radiation pattern in terms of sidelobe level (SLL), beamwidth (BW), nulls and beam steering. Among several geometries of antenna arrays, the circular antenna arrays have the advantage in terms of inherent capability to control the phase implicitly. In this paper, circular antenna array synthesis is presented using novel metaheuristic techniques like the Social Group Optimization Algorithm (SGOA) and Modified SGOA (MSGOA). The main objective of the synthesis process is to synthesize radiation patterns with suppressed SLL while the BW being equal to the uniform distribution. A comparative study is performed to analyze the performance of various synthesis techniques like amplitude only, inter-element spacing only, and amplitude spacing. The MGSOA and SGOA have proved to be performing well in accomplishing the objective. Further, the CAA synthesis problem is translated into single-variable and multivariable optimization problems following which the obvious advantage associated with the inclusion of additional variable as an additional degree of freedom is demonstrated. The simulation is carried out in Matlab (R), and results are analyzed using the plotted radiation patterns.
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Abstract We study the importance of accurately recording signal amplitudes for the quantitative analysis of GPR data sets. Specifically, we measure the peak amplitudes of signals emitted by GPR antennas with different central freq...
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Abstract We study the importance of accurately recording signal amplitudes for the quantitative analysis of GPR data sets. Specifically, we measure the peak amplitudes of signals emitted by GPR antennas with different central frequencies and study their amplitude decay with distance, in order to extrapolate the peak amplitude of the wavelet initially transmitted by each antenna. The purpose is to compare the reference and reflected amplitudes in order to accurately estimate the subsurface EM impedance contrasts. Moreover, we study how sampling-related amplitude distortions can affect the quantitative analysis, and subsequently the resulting subsurface models, even in the absence of aliasing effects. The well-known Nyquist–Shannon theorem gives practical lower limits for the sampling rate in order to preserve the spectral content of a digitized signal; however, we show that it does not prevent possible amplitude distortions. In particular, we demonstrate that significant and unrecoverable loss of amplitude information occurs even at sampling rates well above the Nyquist–Shannon threshold. Interpolation may theoretically reduce such amplitude distortions; however, its accuracy would depend on the implemented algorithm and it is not verifiable in real data sets, since the actual amplitude information is limited to the sampled values. Moreover, re-sampling the interpolated signal simply reintroduces the initial problem, when a new sampling rate is selected. Our analysis suggests that, in order to limit the maximum peak amplitude error within 5%, the sampling rate selected during data acquisition must be at least 12 times the signal central frequency, which is higher than the commonly adopted standards.
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The invention of the 'dual resonance model' N-point functions B-N motivated the development of current string theory. The simplest of these models, the four-point function B-4, is the classical Euler Beta function. Many standard m...
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The invention of the 'dual resonance model' N-point functions B-N motivated the development of current string theory. The simplest of these models, the four-point function B-4, is the classical Euler Beta function. Many standard methods of complex analysis in a single variable have been applied to elucidate the properties of the Euler Beta function, leading, for example, to analytic continuation formulae such as the contour-integral representation obtained by Pochhammer in 1890. However, the precise features of the expected multiple-complex-variable generalizations to BN have not been systematically studied. Here we explore the geometry underlying the dual five-point function B-5, the simplest generalization of the Euler Beta function. The original integrand defining B-5 leads to a polyhedral structure for the five-crosscap surface, embedded in RP5, that has 12 pentagonal faces and a symmetry group of order 120 in PGL(6). We find a Pochhammer-like representation for B5 that is a contour integral along a surface of genus 5 in CP2#4 (CP2) over bar. The symmetric embedding of the five-crosscap surface in RP5 is doubly covered by a corresponding symmetric embedding of the surface of genus 4 in S-5 subset of R-6 that has a polyhedral structure with 24 pentagonal faces and a symmetry group of order 240 in O(6). These symmetries enable the construction of elegant visualizations of these surfaces. The key idea of this paper is to realize that the compactification of the set of five-point cross-ratios forms a smooth real algebraic subvariety that is the five-crosscap surface in RP5. It is in the complex i fication of this surface that we construct the contour integral representation for B-5. Our methods are generalizable in principle to higher dimensions, and therefore should be of interest for further study.
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The operator product expansion (OPE) on the celestial sphere of conformal primary gluons and gravitons is studied. Asymptotic symmetries imply recursion relations between products of operators whose conformal weights differ by hal...
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The operator product expansion (OPE) on the celestial sphere of conformal primary gluons and gravitons is studied. Asymptotic symmetries imply recursion relations between products of operators whose conformal weights differ by half-integers. It is shown, for tree-level Einstein-Yang-Mills theory, that these recursion relations are so constraining that they completely fix the leading celestial OPE coefficients in terms of the Euler beta function. The poles in the beta functions are associated with conformally soft currents.
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We extend recent studies of the effects of quark-gluon vertex dressing upon the solutions of the Dyson-Schwinger equation for the quark propagator. A momentum delta function is used to represent the dominant infrared strength of t...
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We extend recent studies of the effects of quark-gluon vertex dressing upon the solutions of the Dyson-Schwinger equation for the quark propagator. A momentum delta function is used to represent the dominant infrared strength of the effective gluon propagator so that the resulting integral equations become algebraic. The quark-gluon vertex is constructed from the complete set of diagrams involving only two-point gluon lines. The additional diagrams, including those with crossed gluon lines, are shown to make an important contribution to the DSE solutions for the quark propagator, because of their large color factors and the rapid growth in their number.
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