Combined Stereoscopic Particle Image Velocimetry Measurements in a Single Plane for an Impinging Jet around a Thin Control Rod

Impinging jets are of high interest in many industrial applications and their flow dynamics has a complex three-dimensional behavior. These jets can result in a high noise generation leading to acoustic discomfort. Thus, a passive control mechanism which consists of introducing a thin rod in the flow of the jet is proposed in order to reduce the noise generation. The stereoscopic particle image velocimetry (SPIV) technique is employed to measure the three velocity components in a plane. An experimental difficulty is encountered to acquire images of the flow in the shadow of the rod which block a part of the field of interest. In this paper, an experimental arrangement is proposed in order to overcome this experimental difficulty using a combined SPIV technique denoted by (C-SPIV). This technique consists of using an inclined mirror to illuminate the area under the rod by reflecting the laser light and two independent systems of SPIV synchronized and correlated together in order to obtain the combined field of velocity in the same plane above and below the rod. The C-SPIV measurements allowed to obtain the kinematic field in the whole area of interest. Thus, vortex shedding frequency, Turbulent Kinetic Energy were calculated and analyzed along with the acoustic signal. These results are of high interest when seeking for noise reduction in such jet configuration.

A Perspective on Secondary Seed Dormancy in Arabidopsis thaliana

Primary seed dormancy is the phenomenon whereby seeds newly shed by the mother plant are unable to germinate under otherwise favorable conditions for germination. Primary dormancy is released during dry seed storage (after-ripening), and the seeds acquire the capacity to germinate upon imbibition under favorable conditions, i.e., they become non-dormant. Primary dormancy can also be released from the seed by various treatments, for example, by cold imbibition (stratification). Non-dormant seeds can temporarily block their germination if exposed to unfavorable conditions upon seed imbibition until favorable conditions are available. Nevertheless, prolonged unfavorable conditions will re-induce dormancy, i.e., germination will be blocked upon exposure to favorable conditions. This phenomenon is referred to as secondary dormancy. Relative to primary dormancy, the mechanisms underlying secondary dormancy remain understudied in Arabidopsis thaliana and largely unknown. This is partly due to the experimental difficulty in observing secondary dormancy in the laboratory and the absence of established experimental protocols. Here, an overview is provided of the current knowledge on secondary dormancy focusing on A. thaliana, and a working model describing secondary dormancy is proposed, focusing on the interaction of primary and secondary dormancy.

Different motilities of microtubules driven by kinesin-1 and kinesin-14 motors patterned on nanopillars

Kinesin is a motor protein that plays important roles in a variety of cellular functions. In vivo, multiple kinesin molecules are bound to cargo and work as a team to produce larger forces or higher speeds than a single kinesin. However, the coordination of kinesins remains poorly understood because of the experimental difficulty in controlling the number and arrangement of kinesins, which are considered to affect their coordination. Here, we report that both the number and spacing significantly influence the velocity of microtubules driven by nonprocessive kinesin-14 (Ncd), whereas neither the number nor the spacing changes the velocity in the case of highly processive kinesin-1. This result was realized by the optimum nanopatterning method of kinesins that enables immobilization of a single kinesin on a nanopillar. Our proposed method enables us to study the individual effects of the number and spacing of motors on the collective dynamics of multiple motors.

How to produce accurate inelastic cross sections from an indirect measurement method?

Inelastic reactions ((n,xn) for x ≥ 1) play a key role in reactor cores as they influence the slowing down of the neutrons. A reactor neutron energy spectrum depends thus on this process which is in strong competition with elastic scattering and fission; a nice example is the case of 238U. Inelastic scattering (x = 1) impacts keff and radial power distribution in the nuclear reactor. For several years, it has been shown that the knowledge of the inelastic cross sections in nuclear databases is not good enough to accurately simulate reactor cores and a strong demand for new measurements has emerged with very tight objectives (only a few percent) for the uncertainties on the cross section. To bypass the well-known experimental difficulty to detect neutrons, the prompt γ-ray spectroscopy method is a powerful but indirect way to obtain inelastic cross sections. Our collaboration has used this method for more than ten years and have produced a lot of (n,n′γ) cross sections for nuclei from 7Li to 238U. In this article, we will first discuss the issues of the prompt γ-ray spectroscopy regarding the control of all the uncertainties involved in the (n,n′γ) cross section estimation. Secondly, we will focus on the role of theoretical modeling which, in certain cases, is crucial to reach the objectives of a few percent uncertainty on the (n,n′) cross sections.

QUANTUM TELEPORTATION VIA PHOTONIC FARADAY ROTATION

We propose a scheme for deterministically teleporting a pure quantum state, making use of the Faraday rotation of photonic polarization in cavity QED system. Based on the single-photon input-output process regarding cavities, the scheme works well even in low-Q cavities. Since only virtual excitation of the atoms is involved, it is also insensitive to atomic spontaneous emission. Besides, the CNOT operation replaced by the Faraday rotation is not needed in the scheme, which could greatly relax the experimental difficulty.

Stress Analysis and Sealing Performance Evaluation of Pipe Flange Connection at Elevated Temperature

Although a lot of pipe flange connections are exposed to elevated temperature during plant operation, a sealing performance of the pipe flange connections at elevated temperature is not well understood because of the experimental difficulty and the analytical problems due to the lack of the materials properties of gaskets at elevated temperature. The authors have been evaluating the sealing performance of the pipe flange connections at elevated temperature with numerical and experimental analysis and showed the strong effect of the material properties of the gaskets, like a thermal expansion coefficient and a stress-strain curve, on the sealing performance. In order to make a further evaluation, the effect of material properties on the sealing performance was analyzed by using FEM. In the FE analysis, the material properties were varied to evaluate the effect of them on the sealing performance. Furthermore, the material properties and the mechanical characteristic of the gasket were evaluated as a function of temperature. The obtained properties were used to reanalyze the sealing performance of the pipe flange connection. As a result, the gasket stress induced by the mismatch of the thermal expansion between the gasket and flange/bolt increased as increasing the temperature in the case that the thermal expansion coefficient of the gasket was larger than that of bolt/flange material and the sealing performance of the pipe flange connection was improved. However, the improvement in the sealing performance at elevated temperature was not expected so much at higher temperature due to the less increment of the thermal expansion and thermal stress of the gasket. This paper discuss about the change in the sealing performance of the pipe flange connection under elevated temperature considering the material properties and mechanical characteristics of the gasket.

Regulation of Ca2+ and electrical alternans in cardiac myocytes: role of CAMKII and repolarizing currents

Alternans of cardiac repolarization is associated with arrhythmias and sudden death. At the cellular level, alternans involves beat-to-beat oscillation of the action potential (AP) and possibly Ca2+ transient (CaT). Because of experimental difficulty in independently controlling the Ca2+ and electrical subsystems, mathematical modeling provides additional insights into mechanisms and causality. Pacing protocols were conducted in a canine ventricular myocyte model with the following results: 1) CaT alternans results from refractoriness of the sarcoplasmic reticulum Ca2+ release system; alternation of the L-type calcium current has a negligible effect; 2) CaT-AP coupling during late AP occurs through the sodium-calcium exchanger and underlies AP duration (APD) alternans; 3) increased Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity extends the range of CaT and APD alternans to slower frequencies and increases alternans magnitude; its decrease suppresses CaT and APD alternans, exerting an antiarrhythmic effect; and 4) increase of the rapid delayed rectifier current ( IKr) also suppresses APD alternans but without suppressing CaT alternans. Thus CaMKII inhibition eliminates APD alternans by eliminating its cause (CaT alternans) while IKr enhancement does so by weakening CaT-APD coupling. The simulations identify combined CaMKII inhibition and IKr enhancement as a possible antiarrhythmic intervention.

TESTS OF THE STANDARD MODEL USING MUON POLARIZATION ASYMMETRIES IN KAON DECAYS

We have examined the physics and the experimental feasibility of studying various kaon decay processes in which the polarization of a muon in the final state is measured. Valuable information on CP violation, the quark mixing (CKM) matrix, and new physics can be obtained from such measurements. We have considered muon polarization in KL→μ+μ- and K→πμ+μ- decays. Although the effects are small, or difficult to measure because of the small branching ratios involved, these studies could provide clean measurements of the CKM parameters. The experimental difficulty appears comparable to the observation of [Formula: see text]. New sources of physics, involving nonstandard CP violation, could produce effects observable in these measurements. Limits from new results on the neutron and electron electric dipole moment, and [Formula: see text] in neutral kaon decays, do not eliminate certain models that could contribute to the signal. A detailed examination of muon polarization out of the decay plane in K+→μ+π0ν and K+→μ+νγ decays also appears to be of interest. With current kaon beams and detector techniques, it is possible to measure the T-violating polarization for K+→μ+π0ν and with uncertainties approaching ~10-4. This level of sensitivity would provide an interesting probe of new physics.

The Structure of Graphite Fibers Utilized in Field Ionization

Field ionization mass spectrometry has become an increasingly useful analytical tool because of the absence of mass spectra cracking patterns normally associated with electron impact methods. However a rather trouble some experimental difficulty has been the development of an ionization source with ionization efficiency sufficient to produce detectable signals of trace components.A graphite filament ionizer was recently developed at our laboratory and consists of a graphite whisker mounted taut between two tungsten posts. The exposed length of filament and its diameter are nominally 8 mm and 10-3 mm (1 micron) respectively. Ion yields of 10-11 amp at 10-6 torr (10-5 amp/torr) with ion energies of 6-7 Kev are readily obtainable. The filaments have also been used for field emission and Cox has used the Fowler-Nordheim equation modified for cylinderical geometry to obtain an estimated emitter diameter of 40 Å from his experimental data.

Mendelian and non-Mendelian heredity: a reappraisal

The first report of a non-Mendelian gene (Correns 1908) appeared just eight years after the rediscovery of Mendel’s laws and, in this sense, Mendelian and non-Mendelian heredity have both been available for analysis and comparison for almost sixty years. Yet it is only now that non-Mendelian genes are becoming accessible to the kind of intensive investigation required to reveal their chemical identity, their mode of replication and transmission, and their role in cellular heredity. In the classical studies of non-Mendelian heredity in plants by Correns, von Wettstein, Baur, Renner, Michaelis, Oehlkers, and later by Rhoades [for reviews see Caspari (1948), Rhoades (1955), Jinks (1964)] the existence of hereditary factors showing a maternal rather than Mendelian pattern of inheritance was clearly demonstrated. Further progress, however, was severely impeded by two kinds of experimental difficulty: (1) The stability of non-Mendelian genes toward conventional mutagens made it very difficult to acquire mutants to study in genetically characterized, inbred lines. The attempt to explore natural variability of non-Mendelian genes by inter-varietal and inter-species crosses led for the most part to hopelessly complex results involving multigenic interactions (e. g. Michaelis 1958). (2) The typical pattern of maternal inheritance, useful in the initial discrimination between Mendelian and non-Mendelian genes, was subsequently a great obstacle in the analysis of segregation and recombination. The few instances of male transmission of non-Mendelian genes through the pollen provided some of the clearest insights into the workings of the system, but here too the mutations available for analysis were too few and the experimental procedures too complex.