Channel Mode Research Articles

Semileptonic Decays ofB(Bs)to Light Tensor Mesons

The semileptonicBs(B)→K2⁎(a2,f2)lν,l=τ,μ, transitions are investigated in the frame work of the three-point QCD sum rules. Considering the quark condensate contributions, the relevant form factors of these transitions are estimated. The branching ratios of these channel modes are also calculated at different values of the continuum thresholds of the tensor mesons and compared with the obtained data for other approaches.

Efficient broadband light absorption in elliptical nanohole arrays for photovoltaic application.

We propose a perpendicular elliptical silicon nanohole (PE-SiNH) array for light absorption in thin film silicon solar cells. Our analysis shows that this architecture is capable of increasing the absorption of a thin film silicon solar cell by 11.3% in comparison to that of the optimal circular SiNH array. The process of breaking the mirror symmetries is responsible for the increase of the coupled modes. The PE-SiNH structures show additional near-zero spatial Fourier components compared with the circular SiNH structure, which helps to couple more incident light into slow Bloch modes. The mode interaction between adjacent elliptical nanoholes is in favor of the coupling of the incident light into channeling modes and, therefore, enhances light absorption in the short wavelength region.

Lattice location and annealing behaviour of helium atoms implanted in uranium dioxide single crystals

Helium behaviour in irradiated uranium dioxide may play an important role in the mechanical stability of nuclear fuels during and after its use in nuclear power plants. Helium migration mechanisms in bulk UO2 have already been the subject of theoretical studies but there is a lack of experimental data relating to the most stable location in the crystal. To this end, we have studied uranium dioxide samples implanted with helium ions at low fluence before and after thermal annealing in the range 600 and 800 °C. UO2 single crystals were implanted with 50 keV−3He ions at the fluence of 1 × 1015 at cm−2 and the location in the lattice of helium atoms was investigated using NRA (Nuclear Reaction Analysis) based on the reaction of 3He with deuterons (3He (d,p) 4He) in a channelling mode, recording angular scans across axes and planes. Furthermore, the uranium sub-lattice was analysed by the classical RBS method. After implantation, the experimental angular scans recorded across the main crystallographic axes and along major planes show that the helium atoms in their large majority occupy octahedral interstitial sites. No modification of the occupied crystallographic site was found after annealing at 600 °C. Conversely, no crystallographic relationship between matrix and helium signals was revealed following annealing at 800 °C. The latter feature is likely related to the clustering of implanted helium atoms into gas-filled bubbles. These experimental results have been quantified and interpreted using Monte Carlo simulations with the McChasy code.

ABOUT THE UNIFORMITY AND THE STABILITY OF A VOLUME DISCHARGE IN HELIUM IN NEAR-ATMOSPHERIC PRESSURE

<span lang="EN-GB">We present experimental electric and time-spatial characteristics of a volume discharge and of the transition from a volume burning stage into a channel mode nearing atmospheric pressure. We show that the discharge uniformity rises with the increase of cathode spots density and gas pressure.</span>

Annihilation of relativistic positrons in single crystal with production of one photon

The energy and momentum conservation laws prohibit positron–electron single-photon annihilation in vacuum. It is shown that the situation is different in a single crystal with one of the leptons (e.g. positron) moving in the channeling (or in the quasi-channeling) mode. The transverse motion of an oriented or channeled particle may sharply increase the probability of the single-photon annihilation process.

Theory of cylindrical arrays of Vivaldi antennas in the single-mode approximation

Periodic arrays of Vivaldi antennas are considered. Cylindrical arrays infinite along one coordinate are analyzed. For arrays with axial symmetry, a model in the form of the Floquet channel is substantiated. For the Floquet channel of a cylindrical array, a model in the form of the Floquet channel of a planar array with variable period is proposed. Transmission of the fundamental mode of the Floquet channel is described in the single-mode approximation, in which only the forward and counter-propagating fundamental modes are taken into account. The scattering matrix of the Floquet channel of a cylindrical array is determined in the single-mode approximation. Relationships for the reflection coefficient in the quasi-periodic excitation mode are derived. Results of numerical calculations are presented.

Experimental evaluation of interference alignment for broadband WLAN systems

In this paper, we present an experimental study on the performance of spatial interference alignment (IA) in indoor wireless local area network scenarios that use orthogonal frequency division multiplexing (OFDM) according to the physical-layer specifications of the IEEE 802.11a standard. Experiments have been carried out using a wireless network testbed capable of implementing a 3-user MIMO interference channel. We have implemented IA decoding schemes that can be designed according to distinct criteria (e.g., zero-forcing or MaxSINR). The measurement methodology has been validated considering practical issues like the number of OFDM training symbols used for channel estimation or feedback time. In case of asynchronous users, a time-domain IA decoding filter is also compared to its frequency-domain counterpart. We also evaluated the performance of IA from bit error ratio measurement-based results in comparison to different time-division multiple access transmission schemes. The comparison includes single- and multiple-antenna systems transmitting over the dominant mode of the MIMO channel. Our results indicate that spatial IA is suitable for practical indoor scenarios in which wireless channels often exhibit relatively large coherence times.

GLOBAL SIMULATIONS OF PROTOPLANETARY DISKS WITH OHMIC RESISTIVITY AND AMBIPOLAR DIFFUSION

Protoplanetary disks are believed to accrete onto their central T Tauri star because of magnetic stresses. Recently published shearing box simulations indicate that Ohmic resistivity, ambipolar diffusion and the Hall effect all play important roles in disk evolution. In the presence of a vertical magnetic field, the disk remains laminar between 1-5au, and a magnetocentrifugal disk wind forms that provides an important mechanism for removing angular momentum. Questions remain, however, about the establishment of a true physical wind solution in the shearing box simulations because of the symmetries inherent in the local approximation. We present global MHD simulations of protoplanetary disks that include Ohmic resistivity and ambipolar diffusion, where the time-dependent gas-phase electron and ion fractions are computed under FUV and X-ray ionization with a simplified recombination chemistry. Our results show that the disk remains laminar, and that a physical wind solution arises naturally in global disk models. The wind is sufficiently efficient to explain the observed accretion rates. Furthermore, the ionization fraction at intermediate disk heights is large enough for magneto-rotational channel modes to grow and subsequently develop into belts of horizontal field. Depending on the ionization fraction, these can remain quasi-global, or break-up into discrete islands of coherent field polarity. The disk models we present here show a dramatic departure from our earlier models including Ohmic resistivity only. It will be important to examine how the Hall effect modifies the evolution, and to explore the influence this has on the observational appearance of such systems, and on planet formation and migration.

CRYSTAL simulation code and modeling of coherent effects in a bent crystal at the LHC

A CRYSTAL simulation code for particle tracking in crystals is introduced. Its essence consists in both adequate and fast sampling of proton trajectories in crystals which is crucial for both correct description of experiments and quantitative prediction of new effects. The H8 single-pass experiment at the CERN SPS as well as 7TeV proton deflection by a bent crystal at the LHC are simulated. We predict the existence of dechanneling peaks corresponding to the planar channeling oscillations as well as describe the possibility of their observation at high energies, specifically at the LHC energy. An effect of excess over the amorphous level of ionization losses in the channeling mode was also found at 7TeV.

Design of a multi-channel spin polarimeter**Supported by National Natural Science Foundation of China (10979021, 11027401, 11174054, 11304338, 11227902), the Ministry of Science and Technology of China (2011CB921800) and the “Strategic Priority Research Program (B)” of the Chinese Academy of Sciences (XDB04010100)

All commercial electron spin polarimeters work in single channel mode, which is the bottleneck of researches by spin-resolved photoelectron spectroscopy. By adopting the time inversion antisymmetry of the magnetic field, we developed a multichannel spin polarimeter based on normal incident very low energy electron diffraction (VLEED). The key point to achieve the multi-channel measurements is the spatial resolution of the electron optics. The test of the electron optics shows that the designed spatial resolution can be achieved and an image type spin polarimeter with 100 times 100, totally ten thousand channels is possible to be realized.

Single-photon Annihilation of the Channeled Positrons

The energy and momentum conservation laws prohibit positron-electron annihilation in vacuum producing the single photon only. It can produce two photons in vacuum, or the process is possible with a participation of the third body. The situation is different in a single crystal with one of the leptons (e.g. positron) moving in the channeling (or in the quasi-channeling) mode when the transverse motion of a particle is bound or sufficiently uneven. It may increase the probability of the single photon annihilation process.

Orientation Dependence of the Channeled Positrons Conversion into a Single Photon

It is well known that the energy and momentum conservation laws prohibit positron-electron annihilation in vacuum producing the single photon only. It can produce two photons in vacuum, or the process is possible with a participation of the third body. The situation is different in a single crystal when one of the leptons (e.g. positron) is moving in the channeling (or in the quasi-channeling) mode when the transverse motion of a particle is bound or sufficiently uneven It may increase the probability of the single photon annihilation process.

A Comparative Assessment of Flow Cytometric Scoring Systems in MDS

Background:Flow cytometric studies are useful in the diagnostic workup of patients with unexplained cytopenias and it has been demonstrated that bone marrow aspirates with immunophenotypic abnormalities by flow cytometry but not diagnostic morphologic or cytogenetic findings frequently evolve into myelodysplastic syndromes (MDS) (Kern 2013).Two flow cytometric scoring systems (FCSSs), the Wells FCSS and the Ogata FCSS, have diagnostic and prognostic utility. The Wells FCSS utilizes a difference from normal algorithm incorporating more than ten phenotypic parameters. The accumulation of these abnormalities is not only useful in diagnosis but is predictive of patient outcome (Wells 2003, Scott 2008, Alhan 2014). The recommended Ogata FCSS has evolved to include four cardinal parameters: (1) CD45 intensity on the myeloid progenitors, (2) frequency of lymphoblasts, (3) frequency of myeloid progenitors, and (4) granularity of the maturing myeloid cells. The Wells FCSS is more comprehensive as it uses more phenotypic characteristics, while the Ogata score is considered straightforward to implement in a routine setting (Della Porta 2012, Ogata 2009).This study compares the Wells FCSS and Ogata FCSS for sensitivity and specificity to detect clonal abnormalities documented by SNP/CGH microarray and conventional cytogenetics.Patients and Methods: The cohort included 99 patients with unexplained cytopenias whose bone marrow aspirates were submitted for SNP/CGH microarray and flow cytometry (HematoLogics). The immunophenotypic data were independently assigned a Wells FCSS (Cutler 2012) and an Ogata FCSS (Della Porta 2012). SNP/CGH microarray was assessed for MDS-associated genetic abnormalities. The findings were further correlated with conventional cytogenetic findings.Results: Of the 99 bone marrow aspirates, 20 exhibited clonal abnormalities associated with MDS. The Wells FCSS identified immunophenotypic abnormalities suggestive of MDS for 18 of 20 CGH positive specimens (sensitivity of 90%) and did not detect phenotypic abnormalities suggestive of MDS in 68 of 79 CGH negative specimens (specificity of 86%). In contrast the Ogata FCSS identified immunophenotypic abnormalities suggestive of MDS for 13 of 20 CGH positive specimens (sensitivity of 65%) and did not detect phenotypic abnormalities suggestive of MDS in 64 of 79 the CGH negative specimens (specificity of 81%).In an attempt to improve the sensitivity and specificity of the Ogata score, the granularity parameter was modified from side scatter channel mode of the granulocytes (compared to the side scatter mode of the lymphocytes) to the side scatter channel at the 15thpercentile of granulocytes (compared to the mean of lymphocytes). This modified parameter detected all specimens defined as hypogranular by the side scatter mode, and detected an additional 11 specimens as hypogranular. All of these specimens were detected as hypogranular by the Wells definition. This modified granularity method was then used along with the other three cardinal parameters to create a modified Ogata FCSS.The granularity modification resulted in improved sensitivity (70% versus 65%); specificity was unchanged. While the modified method outperformed the original, it did not match the performance of the Wells FCSS.Conclusions: In patients with unexplained cytopenias, the Wells FCSS demonstrates superior specificity and sensitivity than the Ogata FCSS for detecting myeloid immunophenotypic clones associated with SNP/CGH array and cytogenetic abnormalities. Modifying the Ogata granularity parameter marginally improves the sensitivity but does not improve the specificity. Implementation of the Wells FCSS requires a comprehensive understanding of phenotypic intensities and relationships in non-clonal hematopoiesis for patients with cytopenias. While the relative ease of implementing the Ogata FCSS is attractive, improvements are essential for diagnostic accuracy; improving the granularity parameter alone is not sufficient. Adding measurements for the maturing myeloid and erythroid compartments may increase the diagnostic utility of the Ogata FCSS but requires further study. DisclosuresBrodersen:Hematologics Inc.: Employment. Menssen:Hematologics Inc.: Employment. Zehentner:HematoLogics Inc.: Employment, Equity Ownership. Stephenson:Hematologics Inc.: Employment. de Baca:Hematologics Inc.: Employment. Johnson:Hematologics Inc.: Employment. Singleton:Hematologics Inc.: Employment. Hartmann:Hematologics Inc.: Employment. Loken:Hematologics: Employment, Equity Ownership. Wells:HematoLogics Inc.: Employment, Equity Ownership.

Three-dimensional modeling of CPA to the multimillijoule level in tapered Yb-doped fibers for coherent combining systems.

We developed a three-dimensional numerical model of Large-Mode-Area chirped pulse fiber amplifiers which includes nonlinear beam propagation in nonuniform multimode waveguides as well as gain spectrum dynamics in quasi-three-level active ions. We used our model in tapered Yb-doped fiber amplifiers and showed that single-mode propagation is maintained along the taper even in the presence of strong Kerr nonlinearity and saturated gain, allowing extraction of up to 3 mJ of output energy in 1 ns pulse. Energy scaling and its limitation as well as the influence of fiber taper bending and core irregularities on the amplifier performance were studied. We also investigated numerically the capabilities for compression and coherent combining of up to 36 perturbed amplifying channels and showed more than 70% combining efficiency, even with up to 11% of high-order modes in individual channels.

Plasmonic Hybrid Cavity-Channel Structure for Tunable Narrow-Band Optical Absorption

A hybrid plasmonic structure consisting of adjacent U-shaped cavities separated by a nanochannel is proposed for tunable and narrow-band selection of light. The hybrid cavity-channel structure achieves absorption resonance with a bandwidth, defined as the full-width at half-maximum, of 1.5 nm and tunable property in the near-infrared and infrared regions. The hybrid structure resonance originates in the coupling of horizontal surface plasmon mode of the U-cavity with channel mode, which sustains stationary-surface-plasmons in the channel with antinodes at the channel entrances enabling light concentration and nodes at the channel exits enabling light confinement. As a result of the coupling, a sharp and strong absorption resonance is readily adjustable by varying the geometrical parameters of the U-cavity while keeping the channel parameters unchanged.

Research on the Coordination Mechanism of the Products Double Channel Supply Chain

With the rapid development of the e-commerce, dairy enterprises have constructed the Internet direct marketing channel to expand the market and improve competiveness. Based on the dairy dual-channel supply chain as the research object, the paper firstly summarizes the characteristics and applicable scopes of the separated channel mode, hybrid channel mode, bricks and clicks mode, integration channel mode. Then, analyze the channel conflict types and the major factors. Finally, the paper discussed the price strategy, product strategy and channel strategy to coordinate the conflict.

The activation mode of the mechanosensitive ion channel, MscL, by lysophosphatidylcholine differs from tension-induced gating.

One of the best-studied mechanosensitive channels is the mechanosensitive channel of large conductance (MscL). MscL senses tension in the membrane evoked by an osmotic down shock and directly couples it to large conformational changes leading to the opening of the channel. Spectroscopic techniques offer unique possibilities to monitor these conformational changes if it were possible to generate tension in the lipid bilayer, the native environment of MscL, during the measurements. To this end, asymmetric insertion of l-α-lysophosphatidylcholine (LPC) into the lipid bilayer has been effective; however, how LPC activates MscL is not fully understood. Here, the effects of LPC on tension-sensitive mutants of a bacterial MscL and on MscL homologs with different tension sensitivities are reported, leading to the conclusion that the mode of action of LPC is different from that of applied tension. Our results imply that LPC shifts the free energy of gating by interfering with MscL-membrane coupling. Furthermore, we demonstrate that the fine-tuned addition of LPC can be used for controlled activation of MscL in spectroscopic studies.

Multiple finger propagation modes in Hele-Shaw channels of variable depth

AbstractWe consider the propagation of an air finger into a wide fluid-filled channel with a spatially varying depth profile. Our aim is to understand the origin of the multiple coexisting families of both steady and oscillatory propagating fingers previously observed in experiments in axially uniform channels each containing a centred step-like occlusion. We find that a depth-averaged model can reproduce all the finger propagation modes observed experimentally. In addition, the model reveals new modes for symmetric finger propagation. The inclusion of a spatially variable channel depth in the depth-averaged equations leads to: (i) a variable mobility coefficient within the fluid domain due to variations in viscous resistance of the channel; and (ii) a variable transverse curvature term in the dynamic boundary condition that modifies the pressure jump over the air–liquid interface. We use our model to examine the roles of these two distinct effects and find that both contribute to the steady bifurcation structure, while the transverse curvature term is responsible for the distinctive oscillatory propagation modes.

Functional Characteristics of Aquaporin 7 as a Facilitative Glycerol Carrier

Aquaglyceroporins, which constitute a subgroup of aquaporin (AQP) water channels, had been believed to serve as channels for glycerol as well as for water. However, our recent studies have indicated that AQP9 and AQP10 operate in a carrier mode, which is of saturable nature, for glycerol transport. Assuming that such a functional characteristic could also be shared by AQP7, another aquaglyceroporin, we examined its glycerol transport function. The specific transport of glycerol by human AQP7, which was stably expressed in Madin-Darby canine kidney II cells, was indeed highly saturable, indicating the involvement of a carrier mode of operation mechanism. Kinetic analysis indicated that the specific transport conformed to Michaelis-Menten kinetics with the Michaelis constant of 11.9 µM and was not associated with a nonsaturable transport component as an indication of a simultaneous channel mode of operation, which was previously indicated for AQP10. AQP7-specific glycerol transport was furthermore found to be specifically inhibited by several compounds analogous to glycerol and operate without requiring either Na(+) or H(+). These characteristics of the carrier mode of AQP7 operation suggest that it is a facilitative carrier for glycerol and, possibly, also for analogous compounds, providing a novel insight into its operation mechanism.

Deflection of ultrahigh energy particle beams by repeated reflections in bent monocrystals

Bent silicon monocrystals are used today in the planar channeling mode for beam extraction and collimation at large accelerators. Volume reflection is more efficient than channeling, though it has a small deflection angle. A device for repeated deflection of a proton beam using a few bent silicon strips in the reflection mode is described in this paper. Sequential silicon strips on the surface of a thick plate are bent by internal stresses in the crystal material resulting from the Twyman effect. As shown by the Monte Carlo calculations, this method for deflecting the beam is optimal for the teraelectronvolt energy range.