Genetically engineered cardiac pacemaker: Stem cells transfected with HCN2 gene and myocytes—A model

One of the successfully tested methods to design genetically engineered cardiac pacemaker cells consists in transfecting a human mesenchymal stem cell (hMSC) with a HCN2 gene and connecting it to a myocyte. We develop and study a mathematical model, describing a myocyte connected to a hMSC transfected with a HCN2 gene. The cardiac action potential is described both with the simple Beeler-Reuter model, as well as with the elaborate dynamic Luo-Rudy model. The HCN2 channel is described by fitting electrophysiological records, in the spirit of Hodgkin-Huxley. The model shows that oscillations can occur in a pair myocyte-stem cell, that was not observed in the experiments yet. The model predicted that: (1) HCN pacemaker channels can induce oscillations only if the number of expressed IK1 channels is low enough. At too high an expression level of IK1 channels, oscillations cannot be induced, no matter how many pacemaker channels are expressed. (2) At low expression levels of IK1 channels, a large domain of values in the parameter space (n, N) exists, where oscillations should be observed. We denote N the number of expressed pacemaker channels in the stem cell, and n the number of gap junction channels coupling the stem cell and the myocyte. (3) The expression levels of IK1 channels observed in ventricular myocytes, both in the Beeler-Reuter and in the dynamic Luo-Rudy models are too high to allow to observe oscillations. With expression levels below ∼1/4 of the original value, oscillations can be observed. The main consequence of this work is that in order to obtain oscillations in an experiment with a myocyte-stem cell pair, increasing the values of n, N is unlikely to be helpful, unless the expression level of IK1 has been reduced enough. The model also allows us to explore levels of gene expression not yet achieved in experiments, and could be useful to plan new experiments, aimed at improving the robustness of the oscillations.     

Orthogonalization of function spaces in the resonating group model

A coupled-channel resonating group equation for orthogonal channel spaces is derived. It follows from the common resonating group equation by a recursion relation. The recursion extracts from higher channels all overlaps with lower channels, such that the higher channels become corrections to the lower ones. A physically meaningful definition of elimination potentials becomes possible. The new coupled channel resonating group equation allows the derivation ofphysical effective potentials by eliminating small corrections, only. It also allows the derivation oftechnical potentials, i.e. potentials with an unphysical off-shell behaviour, when the dominant part of the equation is eliminated. A numerical example demonstrates that linear dependence of the test function space is not harmful to the new equation.     

Generalized tripartite scheme for sharing arbitrary 2n-qudit state

Utilizing three non-maximally entangled qutrit pairs as quantum channels, we first propose a generalized tripartite scheme for sharing an arbitrary two-qutrit state with generalized Bell-state measurements. In the scheme if and only if the two recipients collaborate together, they can recover the split qutrit state with the probability determined uniquely by the smallest coefficients of the non-maximally entangled pairs. Afterwards, we further extend the scheme for sharing an arbitrary 2n-qudit state by taking 3n non-maximally entangled qudit pairs as quantum channels. Moreover, the scheme success probability relative to the inherent entanglement in quantum channels and its structure is simply discussed.     

Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels

A phenomenological correlated voltage probe model is introduced to mimic the effects of inelastic scattering between particles in different conduction channels of a phase coherent conductor. As an illustration, the non-equilibrium distribution functions of two noisy co-propagating chiral edge channels of the integer quantum Hall effect are calculated and compared with recent experiments. The method is further applied to calculate the linear response current noise through an interacting Mach–Zehnder interferometer.     

Isospin purity of the isobaric analogue resonances for several open channels

The isospin purity of the full and of the doorway state scattering functions in the internal region is investigated, under the assumption of no internal mixing. When several channels are open, it is shown that the isospin is pure at an energyE _> (slightly larger then the resonance energy) only under a restrictive condition, namely that the reduced widths of the analogue state vanish in all channels but one. This may happen either because of isospin selection rules (for the neutron channels) or for reasons of nuclear structure (for some of the proton channels). Then, the corresponding (p, n) and (p, p′) cross sections vanish atE _>. If several channels with non-vanishing reduced widths are open, the isospin of both the full and doorway state wave function is no longer pure atE _>. If two proton channels are open, the doorway state contains three different types of admixtures in the internal region. Two, one of isospinT _> and one of isospinT _<, are excited according to a simple Breit-Wigner probability law. They are both independent of the entrance channel. The third one has isospinT _<, depends upon the entrance channel and is excited according to an asymmetric enhancement factor identical toRobson's.     

Sub-barrier fusion of35, 37Cl+58, 64Ni evidence of effects of proton transfer channels

Sub-barrier fusion excitation functions of^35,37Cl+^58,64Ni have been measured. They are discussed in comparison to similar data of^34,36S+^58,64Ni with the aim of revealing the influence of coupled proton transfer channels. Using the simplified coupled channel code CCFUS, differences in the effects of inelastic channels are eliminated in an approximative manner to stress the differences in the effects of transfer channels. Signatures of positiveQ-value transfer channels coupled to fusion are clearly identified.     

Modification of Hauser-Feshbach calculations by direct-reaction channel coupling

If open channels are strongly coupled by direct reactions, the traditional Hauser-Feshbach method of calculating fluctuation cross sections is invalid, because of non-statistical correlations which the direct channel-coupling induces between resonance partial widths in different channels. The fluctuation cross sections can still be computed from the optical S-matrix elements, however, and the formulas necessary for doing so are obtained here with the aid of an “optical background” representation of the full S-matrix. The resulting compound-elastic cross section is increased over the Hauser-Feshbach expression by a factor of 2(Γ ? D) or 3(Γ ? D) in the large-N limit, and compound-reaction cross sections are increased by roughly a factor of $\text{(N + 1)}\text{N}$, where N is the number of directly-coupled open channels.     

Performance of ring oscillators composed of gate-all-around FETs with varying numbers of nanowire channels using TCAD simulation

In this paper, we investigate the performance of ring oscillators composed of gate-all-around (GAA) silicon nanowire (NW) field-effect transistors (FETs) with four different numbers of NW channels, for sub-10-nm logic applications. Our simulations reveal that ring oscillators with double, triple, and quadruple NW channels exhibit improvements of up to 50%, 85%, and 97%, respectively, in the oscillation frequencies (f_osc), compared to a ring oscillator with a single NW channel, due to the large drive current, in spite of the increased intrinsic capacitance of a given device. Moreover, our work shows that the f_osc improvement ratio of the ring oscillators becomes saturated with triple NW channels with additional load capacitances of 0.1 fF and 0.01 fF, which are similar to, or less than the intrinsic device capacitance (∼0.1 fF). Thus, our study provides an insight for determining the capacitive load and optimal number of NW channels, for device development and circuit design of GAA NW FETs.     

Role of dipole image forces in molecular adsorption

The transverse-field XY model in one dimension is a well-known spin model for which the ground state properties and excitation spectrum are known exactly. The model has an interesting phase diagram describing quantum phase transitions (QPTs) belonging to two different universality classes. These are the transverse-field Ising model and the XX model universality classes with both the models being special cases of the transverse-field XY model. In recent years, quantities related to quantum information theoretic measures like entanglement, quantum discord (QD) and fidelity have been shown to provide signatures of QPTs. Another interesting issue is that of decoherence to which a quantum system is subjected due to its interaction, represented by a quantum channel, with an environment. In this paper, we determine the dynamics of different types of correlations present in a quantum system, namely, the mutual information I(?? _AB ), the classical correlations C(?? _AB ) and the quantum correlations Q(?? _AB ), as measured by the quantum discord, in a two-qubit state. The density matrix of this state is given by the nearest-neighbour reduced density matrix obtained from the ground state of the transverse-field XY model in 1d. We assume Markovian dynamics for the time-evolution due to system-environment interactions. The quantum channels considered include the bit-flip, bit-phase-flip and phase-flip channels. Two different types of dynamics are identified for the channels in one of which the quantum correlations are greater in magnitude than the classical correlations in a finite time interval. The origins of the different types of dynamics are further explained. For the different channels, appropriate quantities associated with the dynamics of the correlations are identified which provide signatures of QPTs. We also report results for further-neighbour two-qubit states and finite temperatures.     

Decay of the compound nucleus179Au formed in the cold fusion reaction90Zr+89Y

For the compound nucleus¹⁷⁹Au formed at an excitation energy of 26 MeV in the fusion reaction⁹⁰Zr+⁸⁹Y, the energy spectra of promptly emitted protons,α particles andγ rays were measured in concidence with the evaporation residues. On the basis of the measured total decay energy, the 1p and 1α decay channels were separated from all other evaporation-residue channels. The energy spectra and absolute cross sections, together with previously measured excitation functions for various decay channels, are successfully described by statisticalmodel calculations with the Monte Carlo code CODEX.     

Performance analysis of dense wavelength division multiplexing secure communications with multiple chaotic optical channels

The performance of dense wavelength division multiplexing secure communications with multiple chaotic optical channels is numerically analyzed in this paper. Taking the multiplexing of three chaotic optical channels as an example, we investigate the effects of second-order dispersion coefficient and nonlinear coefficient of fiber, channel spacing, message amplitude and bit rates on chaotic synchronization and multiplexing communications. Chaotic synchronization quality and Q-factor of the recovered message decrease with the increasing fiber length. A 1.25 Gbits/s non-return-to-zero (NRZ) sequence can be securely transmitted up to 60 km under the influence of the other two chaotic optical channels. Compared with the fiber dispersion, the cross-phase modulation is the primary factor which deteriorates the quality of communications. The results also show that the quality of communications is unlimited to the channel spacing as long as chaotic synchronization can be maintained. In addition, the effect of the amplitude of encrypted message on Q-factor and the confidentiality is demonstrated.     

Reaction mechanisms of the7Li+51V reaction

Reaction mechanisms populating the exit channels of the system⁷Li+⁵¹V were studied at a beam energy of 18 MeV. Final nuclei were detected by their characteristicγ-rays. Theseγ-rays in coincidence with light charged particles were used to identify the reaction channels. Also forward-backward asymmetries of the coincident events gave a measure of the contribution of direct and compound reaction mechanisms. It was found that the dominant mechanism feeding channels with charged particles in the final state is direct transfer of a triton orα particle.     

Breakdown of the quantum hall effect in regularly inhomogeneous 2D electron systems

A breakdown mechanism is discussed for the current-voltage characteristic of the system of integer Hall channels in a 2D sample with a regularly inhomogeneous 2D electron density. It has been shown that the appearance of an external potential V on the “edges” of such strips leads to two alternatives: as V increases, the strip width decreases to zero or increases geometrically but “deteriorates qualitatively.” In both cases with their (different) thresholds, integer strips lose their properties inherent in them in the quantum Hall effect regime. These thresholds are attributed here to the asymmetric breakdown of the quantum Hall effect for the system of integer channels.     

A novel structure of permanent-magnet-biased radial hybrid magnetic bearing

The paper proposes a novel structure for a permanent-magnet-biased radial hybrid magnetic bearing. Based on the air gap between the rotor and stator of traditional radial hybrid magnetic bearings, a subsidiary air gap is first constructed between the permanent magnets and the inner magnetic parts. Radial magnetic bearing makes X and Y magnetic fields independent of each other with separate stator poles, and the subsidiary air gap makes control flux to a close loop. As a result, magnetic field coupling of the X and Y channels is decreased significantly by the radial hybrid magnetic bearing and makes it easier to design control systems. Then an external rotor structure is designed into the radial hybrid magnetic bearing. The working principle of the radial hybrid magnetic bearing and its mathematical model is discussed. Finally, a non-linear magnetic network method is proposed to analyze the radial hybrid magnetic bearing. Simulation results indicate that magnetic fields in the two channels of the proposed radial hybrid magnetic bearing decouple well from each other.     

Asymmetric fission of the pre-actinide nuclei

Study of α particles, protons and neutrons emission in reactions induced by¹⁶O on Sn targets. The threshold for direct a emission is found to be v/c?0.04 (v velocity of the projectile at the top of the Coulomb barrier) whereas direct protons and neutrons, if any, would be emitted for beam energies higher than 7.8MeV/n. (v/c>0.092). Atv/c 0.092, 90% of the direct a cross section is shown to be incomplete fusion. On¹¹⁶Sn target, besides the main exit channels α4n and αp4n, we observed 2α4n and α2p4n channels where the direct α is followed by evaporation particles. This implies a lower initial angular momentum than for the main channels.     

Inner and outer shell ionization for atomic iodine: calculation of cross-sections and angular distribution parameters

This work presents results relating to photoemission cross-sections and angular distribution parameters for atomic iodine, where the photon energy varies over an energy range large enough to involve the ionization of the outermost 5p⁵ Subshell, as well as the inner 5s² and 4d¹⁰ electrons. The calculations were performed with several models, of varying sophistication according to the number of channels which are coupled to describe the continuum final-state wave function. They show that it is necessary to use a model which couples all the channels opened by the multiplet structure in order to show that the 4d shape resonance of iodine looks very much like the large 4d resonance of xenon. Anisotropie effects, whose size is reflected in the splitting among the various angular distribution parameters for alternative final ionic states, are found to be negligible within the framework of the most elaborate model, which couples all the channels corresponding to the residual ion configuration 4d⁹5p⁵; this holds less true as the angular momentum of the ionized electrons decreases. Whereas a model introducing the interchannel interactions within the ionization of one single subshell is sufficient to account for the resonances shifted beyond the thresholds for both 4d and 5p ionization, another model taking intershell interactions (5s + 5p) into account is necessary to obtain a minimum in the 5s cross-section.     

Two-body propagators with dynamic effective interactions in a many-fermion medium: I. General structure

Excitations of the many-body medium cause dynamic effective interactions between fermions. In actual calculations these interactions are almost always replaced by static approximations. In this paper a Green function approach is outlined which preserves the dynamic structure of the interactions. The central quantity is the four-vertex or two-fermion scattering amplitude Γ in the medium, which depends on three energy variables s, t, and u. Integral equations connect Γ to irreducible effective interactions in the three channels. With static interactions the s- and t-channels correspond to particle-particle and particle-hole configurations, respectively. Dynamic interactions mix these configurations. They also introduce poles in the crossed channels: the exchange of a phonon is a t-pole in the s-channel while pairons induce s-poles in the t-channel. Poles of the one-body propagator G(ω) and the two-body propagators K(s) and K(t) correspond to states of the A ± 1, A ± 2 and A-particle systems. The dynamic coupling between channels results in an intricate connection between various aspects of the many-fermion problem.     

Effects of the depolarization field in a perforated film of the biaxial ferroelectric

The domain structure in a biaxial ferroelectric layer perforated by cylindrical channels has been investigated using the numerical simulation based on the phenomenological theory of ferroelectricity and the equations of electrostatics in the framework of the Gauss-Seidel iterative method. Both polar axes lie in the plane of the film, which is characteristic of thin epitaxial films of BaTiO₃ and (Ba_{1 ? x} Sr _x )TiO₃ on a MgO substrate. The calculations have been performed using the parameters of BaTiO₃, which does not matter because of the qualitative character of the results: the electrostatic problem is two-dimensional and formally applies to infinitely thick layers rather than to thin layers. The primary attention has been paid to the systems containing sixteen channels. Two different orientations of the polar axes with respect to the lattice channels have been considered. It has been shown that, for these orientations, the domain structure has a different character: when the line with the minimum distance between the channels is perpendicular to the bisector of the angle between the polar axes, this structure contains a single channel in the repeating motif and a polarization vortex; when one of the polar axes is perpendicular to the line with the minimum distance between the channels, the situation is less clear. There are indications that the repeating motif of the domain structure in a system of many channels contains two channels and does not contain vortices. The strong influence of the electrodes on the domain structure in this case has been noted.     

Design of the readout electronics for the DAMPE Silicon Tracker detector

The Silicon Tracker (STK) is one of the detectors of the DAMPE satellite used to measure the incidence direction of high energy cosmic rays. It consists of 6 X-Y double layers of silicon micro-strip detectors with 73728 readout channels. It is a great challenge to read out the channels and process the huge volume of data in the harsh environment of space. 1152 Application Specific Integrated Circuits (ASIC) and 384 ADCs are used to read out the detector channels. 192 Tracker Front-end Hybrid (TFH) modules and 8 identical Tracker Readout Board (TRB) modules are designed to control and digitalize the front signals. In this paper, the design of the readout electronics for the STK and its performance are presented in detail.     

Three-body model of deuteron breakup and stripping

For a three-body model Hamiltonian, the scattering eigenfunction that corresponds to an incident deuteron is expanded in terms of eigenfunctions of the neutron-proton relative Hamiltonian, as suggested by Johnson and Soper. In this expansion, breakup is represented by an integral over the continuum of neutron-proton scattering states. Only states of zero relative angular momentum are included; the validity and advantages of this approximation are discussed. The continuum is divided into five discrete channels, whose coupling to each other and to the deuteron channel is treated by solving coupled differential equations with appropriate boundary conditions. It is found necessary to use a simple WKB method to take account of the long-range coupling among breakup channels; this method introduces potential matrices W and S that describe local and derivative coupling of the channels. The reaction of breakup on the elastic channel is neglected.The properties of W and S and the breakup wavefunction are examined for the case of 22.9 MeV deuterons incident on a target of mass number A ≈ 40. The Coulomb interaction is ignored, and a local Gaussian shape is used for both the real and imaginary parts of the nucleon-nucleus optical potential.It is found that a rather broad spectrum of n-p continuum states is excited, especially for low center-of-mass angular momentum. This result weakens the justification for the Johnson-Soper adiabatic theory, which emphasizes breakup into states of low relative energy.The breakup part of the wavefunction at zero n-p separation is comparable with the elastic part, but is important only over a surprisingly short range in the center-of-mass coordinate, with the result that breakup cross sections are quite small. Nevertheless, breakup produces major modifications of (d, p) cross sections. These modifications can to some extent be simulated by the Johnson-Soper method. The breakup wavefunctions show several interesting effects in their dependence on angular momentum and radius.