Modified null broadening adaptive beamforming: constrained optimisation approach

A constrained optimisation approach for null broadening adaptive beamforming is proposed. This approach improves the robustness of the traditional MVDR beamformer by broadening nulls for interference direction and the mainlobe for the desired direction. This optimisation is efficiently solved by semidefinite programming. The proposed approach, when applied to high altitude platform communications using a vertical linear antenna array, provides significantly better coverage performance than a previously reported null broadening technique

A kinetic study of glycolytic enzyme synthesis in yeast

The kinetics of induced synthesis of glycolytic enzymes of the hybrid yeast Saccharomyces fragilis x Saccharomyces dobzhanskii in response to the addition of glucose or galactose has been studied in a basal medium containing peptone, acetate, and yeast extract. Glucose and galactose bring about a 3- to 100-fold increase in specific activity of various glycolytic enzymes during a 7- hour period. The smallest increase is observed in the case of P-glucoisomerase (EC 5.3.1.9) and the largest with glyceraldehyde-3-P dehydrogenase (EC 1.2.1.12). In the stationary state of cells grown in the presence or absence of glucose, the glycolytic enzymes display a coordinate relationship to one another. The time course of enzyme synthesis by glucose and galactose, as well as of enzyme disappearance on removal of the sugars, however, suggests a kinetic heterogeneity. With galactose as the inducing carbohydrate, the enzymes increase in specific activity in the following sequence: pyruvate kinase (EC 2.7.1.40), within 20 min after addition of galactose; P-glucomutase (EC 2.7.5.1), P-fructokinase (EC 2.7.1.11), and glyceraldehyde-3-P dehydrogenase, within 1 hour; P-glucoisomerase, P-glycerate kinase (EC 2.7.2.3), P-glycerate mutase (EC 2.7.5.3), and enolase (EC 4.2.1.11), between 1 and 3 hours; hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.7), triose-P isomerase (EC 5.3.1.1), and pyruvate decarboxylase (EC 4.1.1.1), between 2 and 5 hours. Alcohol dehydrogenase (EC 1.1.1.1) falls outside any of these groups; after an initial period of repression, galactose causes increased synthesis of this enzyme during later periods. The increase of glycolytic enzyme activity elicited by sugars seems to be due to increased production of the same enzyme species already existing in uninduced cultures. The glucose-induced increase in glycolytic enzyme activity in Saccharomyces cerevisiae is completely prevented by cycloheximide, an inhibitor of protein synthesis in this yeast. P-Fructokinase and pyruvate decarboxylase decay rapidly inside the cells in the presence of this antibiotic

Control of glycolytic enzyme synthesis in yeast by products of the hexokinase reaction

Addition of 2-deoxyglucose to a culture of the hybrid yeast Saccharomyces fragilis x Saccharomyces dobzhanskii causes 2- to 200-fold increase in the differential rate of synthesis of all glycolytic enzymes except alcohol dehydrogenase (EC 1.1.1.1). For most enzymes, the stimulation in the rate of synthesis occurs with a delay. The greatest stimulation is observed in the case of glyceraldehyde-3-P dehydrogenase (EC 1.2.1.12), viz. about 200-fold, while P-glycerate mutase (EC 2.7.5.3) and enolase (EC 4.2.1.11) show a 2.5-fold increase in the differential rate of synthesis. Glucosone also stimulates the rate of synthesis of hexokinase (EC 2.7.1.1) and glyceraldehyde-3-P dehydrogenase. Generally, glycolytic enzyme synthesis is elicited by all compounds studied which are substrates of yeast hexokinase, while 6-deoxyglucose fails to induce synthesis either in the hybrid yeast or in Saccharomyces cerevisiae. The loss of fructose-phosphorylating activity in a hexokinaseless mutant of this yeast is associated with the failure of fructose to induce any of the glycolytic enzymes that fructose induces in the wild type. The differential rates of synthesis of all of the glycolytic enzymes between aldolase (EC 4.1.2.7) and pyruvate kinase (EC 2.7.1.40) increase 6- to 150-fold over the basal rates when glucose is added to a P-glucoisomerase (EC 5.3.1.9)-deficient mutant of S. cerevisiae. Experiments with a P-mannoisomerase (EC 5.3.1.8)-deficient mutant of S. cerevisiae indicate that hexokinase and P-fructokinase (EC 2.7.1.11) synthesis is stimulated in response to the presence of mannose. These and other data on the metabolites produced from 2-deoxyglucose have been interpreted to suggest that glucose-6-P is the inducer of the following enzymes: aldolase, triose-P isomerase (EC 5.3.1.1), glyceraldehyde-3-P dehydrogenase, P-glycerate kinase (EC 2.7.2.3), P-glycerate mutase, enolase, and pyruvate kinase. Mannose-6-P is the inducer of hexokinase and, presumably, of P-fructokinase. Pyruvate decarboxylase (EC 4.7.1.1) does not appear to be induced by glucose-6-P. These data are also consistent with P-glucomutase (EC 2.7.5.1) being induced by glucose-1-P

Electromagnetic signatures of thin accretion disks in wormhole geometries

In this paper, we study the physical properties and characteristics of matter forming thin accretion disks in static and spherically symmetric wormhole spacetimes. In particular, the time averaged energy flux, the disk temperature, and the emission spectra of the accretion disks are obtained for these exotic geometries and are compared with the Schwarzschild solution. It is shown that more energy is emitted from the disk in a wormhole geometry than in the case of the Schwarzschild potential and the conversion efficiency of the accreted mass into radiation is more than a factor of 2 higher for the wormholes than for static black holes. These effects in the disk radiation are confirmed in the radial profiles of temperature corresponding to theses flux distributions, and in the emission spectrum ωL(ω) of the accretion disks. We conclude that specific signatures appear in the electromagnetic spectrum, thus leading to the possibility of distinguishing wormhole geometries by using astrophysical observations of the emission spectra from accretion disks.published_or_final_versio

Pairing in cuprates from high energy electronic states

The in-plane optical conductivity of Bi2Sr2CaCu2O8+d thin films with small carrier density (underdoped) up to large carrier density (overdoped) is analyzed with unprecedented accuracy. Integrating the conductivity up to increasingly higher energies points to the energy scale involved when the superfluid condensate builds up. In the underdoped sample, states extending up to 2 eV contribute to the superfluid. This anomalously large energy scale may be assigned to a change of in-plane kinetic energy at the superconducting transition, and is compatible with an electronic pairing mechanism.Comment: 11 pages, 3 figure

Solar System tests of Horava–Lifshitz gravity

In the present paper, we consider the possibility of observationally constraining Horava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the spherically symmetric black hole Kehagias- Sfetsos solution of Hořava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of Hořava gravity. Moreover, the study of the classical general relativistic tests also constrains the free parameter of the solution. From the analysis of the perihelion precession of the planet Mercury, we obtain for the free parameter ω of the Kehagias-Sfetsos solution the constraint ω ≥ 3.212 × 10-26 cm -2. , the deflection of light by the Sun gives ω ≥ 4.589 × 10 -26 cm -2, while the radar echo delay observations can be explained if the value of ω satisfies the constraint ω ≥ 9.179 × 10 -26 cm -2. © 2010 The Royal Society.published_or_final_versio

Classification of Some First Order Functional Differential Equations With Constant Coefficients to Solvable Lie Algebras

In this paper, we shall apply symmetry analysis to some first order functional differential equations with constant coefficients. The approach used in this paper accounts for obtaining the inverse of the classification. We define the standard Lie bracket and make a complete classification of some first order linear functional differential equations with constant coefficients to solvable Lie algebras.We also classify some nonlinear functional differential equations with constant coefficients to solvable Lie algebras

Trapped ghosts: a new class of wormholes

We construct examples of static, spherically symmetric wormhole solutions in general relativity with a minimally coupled scalar field $\phi$ whose kinetic energy is negative in a restricted region of space near the throat (of arbitrary size) and positive far from it. Thus in such configurations a "ghost" is trapped in the strong-field region, which may in principle explain why no ghosts are observed under usual conditions. Some properties of general wormhole models with the $\phi$ field are revealed: it is shown that (i) trapped-ghost wormholes are only possible with nonzero potentials $V(\phi)$; (ii) in twice asymptotically flat wormholes, a nontrivial potential $V(\phi)$ has an alternate sign, and (iii) a twice asymptotically flat wormhole which is mirror-symmetric with respect to its throat has necessarily a zero Schwarzschild mass at both asymptotics.Comment: 4.2 pages, 4 figures. Version to appear in CQ

Suppression of pdc2 regulating pyruvate decarboxylase synthesis in yeast

Mutants lacking pyruvate decarboxylase cannot grow on glucose. We have isolated three different complementation groups of extragenic suppressors that suppress mutations in pdc2, a regulatory locus required for the synthesis of the glycolytic enzyme pyruvate decarboxylase. The most frequent of these is a recessive mutation in the structural gene PFK1 of the soluble phosphofructokinase. The other class XSP18 (extragenic suppressor of pdc2) is a dominant temperature-sensitive suppressor that allows the cells to grow on glucose only at 30{deg} but not at 36{deg}. It also affects the normal induction of the glucose-inducible enolase 2, which can be rescued by providing a copy of wild-type xsp18 in trans-heterozygotes. The pyruvate decarboxylase activity in the triple mutant pdc2 pfk1 XSP18 is nearly equal to the sum of the activities in the two double mutants pdc2 pfk1 and pdc2 XSP18, respectively. This implies that the two suppressors act through independent pathways or that there is no cooperativity between them. In the pdc2 pfk1 XSP18 strain, pfk1 suppresses the loss of induction of glucose-inducible enolase 2 brought about by XSP18, but fails to rescue temperature sensitivity. The third class (xsp37) supports the growth of the pdc2 mutant on glucose but fails to support growth on gluconeogenic carbon sources. All the three suppressors suppress pdc2{Delta} as well and act on PDC1 at the level of transcription

The mathematical theory of resonant transducers in a spherical gravity wave antenna

The rigoruos mathematical theory of the coupling and response of a spherical gravitational wave detector endowed with a set of resonant transducers is presented and developed. A perturbative series in ascending powers of the square root of the ratio of the resonator to the sphere mass is seen to be the key to the solution of the problem. General layouts of arbitrary numbers of transducers can be assessed, and a specific proposal (PHC), alternative to the highly symmetric TIGA of Merkowitz and Johnson, is described in detail. Frequency spectra of the coupled system are seen to be theoretically recovered in full agreement with experimental determinations.Comment: 31 pages, 7 figures, LaTeX2e, \usepackage{graphicx,deleq