Transverse Channel Research Articles

A finite element model for complex profile calibration

AbstractA new finite element model named Corrected Slice Method (CSM) has been developed to cope with three‐dimensional vacuum cooling calibrator problems. Such problems appear whenever the cooling channel lay‐out comprises transverse channels in the calibrator. The CSM is an extension of the 2D approach (8), which takes into account the axial heat fluxes within the calibrator. The proposed model was validated by comparing the numerical results obtained on a test problem with a rigorous finite element approach. Moreover, a real complex profile‐calibrator system was simulated in order to illustrate the full performance of the porposed method.

QUASI-ELASTIC ELECTRON SCATTERING: CURRENT RESULTS, CURRENT PROBLEMS

We present a review of theories presently available for describing quasi-elastic electron scattering in both longitudinal and transverse channels. It is argued that calculations that limit their domain to the effects of nuclear structure in a nonrelativistic regime are capable of reconciling theory and experiment in the region of the peak of the quasi-elastic cross-section and thus to a large degree abrogate the need to consider more complex processes.

Quasielastic nuclear response.

We explore the nuclear responses at intermediate energies, particularly in the spin longitudinal and spin transverse isovector channels, within the continuum random phase approximation framework. We also employ an extension of the standard random phase approximation to account for the spreading width of the single particle states through the inclusion of a complex and energy-dependent nucleon self-energy. The nuclear responses are then used as the basic ingredient to calculate hadronic reactions in the Glauber theory framework. Here both one and two-step contributions to the multiple scattering series in the quasi-elastic peak region are taken into account. We find evidence for shell effects in the one-step response and a strong dependence on the momentum regime of the two-step contribution.

Resonance effect in HTSC films with the superimposed magnetic superlattice

A resonance effect in HTSC films with reduced transverse channel and superimposed magnetic superlattice is observed. It is suggested that it results from the excitation of an electromagnetic wave when the Josephson-like vortices cross the periodic magnetic structure of a superlattice. Some experimental evidence is discussed. In the frame of this concept the vortex velocity and consequently the position of the resonance steps depend on the supercurrent and saturates at a level of 10 8−10 9 cm/s. In addition the method of a superimposed magnetic structure is applied to reconstruct the vortex viscosity coefficient.

Stimulation of the acoustico-lateralis system of clupeid fish by external sources and their own movements

1. The receptor organs of the acoustico-lateralis system in fish respond in various ways to pressures and pressure gradients and provide the fish with information about external sources of vibration. 2. A fish’s movements will set up pressures and pressure gradients and this poses three questions, (i) Can a fish obtain useful information from self-generated pressures and pressure gradients? (ii) To what extent do self-generated pressures mask signals from external sources? (iii) Can interactions between external and self-generated pressures and gradients in the acoustico-lateralis system give patterns of activity from the receptor organs which have special significance? 3. In herring (Clupea harengus L.) and sprat (Spratus sprattus(L.)) measurements have been made of dimensions of various parts of the acoustico-lateralis system particularly of the subcerebral perilymph canal which crosses the head between the lateral lines. 4. Self-generated pressures produced by lateral movements of the head are antisymmetric, i.e. equal and opposite in sign on the left and right sides of the head. They oppose the accelerations of the head that produce them. In contrast, external sources give pressures that are largely symmetric. Any pressure gradients they give will accelerate the fish and the surrounding water together and any net pressure gradients will be small and so will any flows through the subcerebral perilymph canal. 5. Flows of liquid between the lateral lines across the lateral-recess membranes have been measured at various frequencies for pressure gradients applied across the head. Between 5 and 200 Hz the velocity of flow per unit pressure does not vary by more than than a factor of 2. At low frequencies the absolute values of flow are very much larger (more than 50 times) than those found for equally large symmetrically applied pressures (as from an external source) due to flow into the elastic gas containing bullae. 6. It is calculated that a net pressure difference (at optimum frequency) across the head of only 0.008 Pa will reach threshold for the lateral line neuromast nearest the lateral recess and one of 0.02 Pa for that under the eye. The responses of these neuromasts are expected to saturate and provide little information when the pressure differences across the head exceed 6 to 18 Pa. The pressures given by the swimming fish are discussed in the light of a theory advanced by Lighthill in the paper that follows this paper. With such antisymmetric pressures the direction of flow in the lateral-line canals will be towards the lateral recess on one side of the fish and away on the other and so differ from the situation found with an external source when flow at any instant will be either towards or away from the lateral recess on both sides of the head. 7. Antisymmetric pressures can produce large flows past the utricular maculae. However, at low frequencies flows across the maculae, on which their stimulation depends, will be small. We do not know the direction of these latter flows though they will be in opposite sense on the two sides of the head, again unlike the situation with an external source. 8. Calculations of impedances below 30 Hz show that the observed flows across the head are consistent with the dimensions and properties of the known structures. 9. There are major and systematic differences in the patterns of receptor organ stimulation between those expected from external sources and from a fish’s own movements. 10. Experiments on the red mullet (Mullus surmuletusL.) showed that it too has a transverse channel connecting the right and left lateral-line systems. At low frequencies its properties resemble those of the subcerebral perilymph canal of the clupeid.

Static response function for longitudinal and transverse excitations in superfluid helium

The sum rule formalism is used to evaluate rigorous bounds for the density and current static response functions in superfluid helium at zero temperature. Both lower and upper bounds are considered. The bounds are expressed in terms of ground state properties (density and current correlation funtions) and of the interatomic potential. The results for the density static response significantly improve the Feynman approximation and turn out to be close to the experimental (neutron scattering) data. A quantitative prediction for the transverse current response is given. The role of one-phonon and multi-particle excitations in the longitudinal and transverse channels is discussed. (Phys.Rev.B, in press)

Persistent currents in weakly disordered metal rings.

We calculate the disorder-averaged persistent current in a normal metal ring threaded by a magnetic flux in the regime 1\ensuremath{\lesssim}l/L\ensuremath{\lesssim}M, where l is the elastic mean free path, L is the circumference of the ring, and M is the number of transverse channels. The calculation is performed for a fixed number of particles. In contrast to one-channel rings, the disorder average over an ensemble of rings containing precisely the same number of electrons leads to a current with periodicity of half a flux quantum.

Equivalence of thermodynamic persistent current for constant number of particles and dynamic response in mesoscopic metal rings.

We compare dynamic and thermodynamic persistent currents in a mesoscopic metal ring threaded by a magnetic flux in the regime 1≤l/L≤M (l is the elastic mean free path, L is the circumference of the ring, and M is the number of transverse channels). It is shown by explicit calculation that the thermodynamic current for a fixed number of particles is identical to the dynamic current obtained from the Kubo formula for fixed chemical potential. Thus, thermodynamic averaging in a canonical ensemble is equivalent to calculating the dynamic response in a grand-canonical one

Nucleon properties in a medium and quasielastic electron scattering

In the relativistic Fermi-gas model (FGM) the longitudinal response in quasielastic electron scattering is calculated for nuclei between 12C and 238U covering the available experimental data. The theory is brought to good agreement with experiment if the medium modified values for the effective mass and electromagnetic form factors of the nucleon are used as they emerge from the Nambu-Jona-Lasinio model. The picture does not change much if a shell model approach is used. This result is quite general and holds basically for all nuclei considered at momentum transfers q>400 MeV/ c the very recent data for 56Fe at q=1.14 MeV/ c as well. In contrast to the longitudinal channel the use of the medium-modified values within the FGM leads to an undesired reduction in the transverse channel. The latter effect is, however, much less pronounced if the nuclear structure is taken into account in shell model calculations.

Structure of the respiratory islets of accessory respiratory organs and their relationship with the gills in the climbing perch, Anabas testudineus (Teleostei, Perciformes).

The epithelial and sub-epithelial organization of the accessory respiratory organs of Anabas testudineus has been compared with that of gills by using light and transmission electron microscopy. The details of vascular supply of respiratory islets (RI) and gill filaments and the presence of venous sinusoids in the two systems suggest that the RI have been derived from gill filaments and lamellae. The biserial arrangement of transverse capillaries (TC) in the respiratory islets (RI) is evident under the scanning electron microscope and their homology with the gill filaments and their secondary lamellae has been established. The two sets of transverse capillaries of respiratory islets have been derived either from embryonic transverse or marginal channels of two sets of lamellae of a gill filament. These capillaries with their endothelial septate valves and tongue-like processes offer resistance to blood flow. Gill filaments have two vascular pathways, arterio-arterial and arterio-venous. However, the RI of accessory respiratory organs contain the arterio-venous pathways. This arrangement as well as the septate transverse capillaries may lower the "pulmonary" blood pressure considerably. Two types of mitochondria-rich cells are identified: i) chloride cells with flat microvilli bearing surfaces, devoid of apical pit and (ii) an elongated cell type with sac-like endoplasmic reticulum, with apical pit that comes into close contact with the complex matrix of macrophages, lymphocytes and other loose cells of the epithelium. These cells may be associated with detoxification of the internal media of fish inhabiting foul waters.

New Routes to Quasi-Periodic Combustion of Solids and High-Density Fluids Near Resonant Hopf Bifurcation Points

Steady, planar combustion waves propagating through solids and high-density fluids can lose stability to a time-periodic mode of burning via Hopf bifurcation as an activation-energy parameter increases past a critical value. However, if the combustion wave is confined in a long channel, there exist critical values of the transverse channel dimensions such that stability is simultaneously lost to two (or more) nonsteady modes of burning at a multiple eigenvalue of this parameter. In the present work, the case of bifurcation near a point of strong resonance from which multiple primary branches corresponding to a single pulsation frequency (but different spatial structures) emanate from the basic solution is considered. In contrast to the multiple-frequency case, the resulting amplitude equations contain transcendental terms which can lead to both secondary and isolated branches of multimodal time-periodic motions. In addition, the higher-order bifurcation of quasi-periodic waves can arise either through a classical Hopf bifurcation from a multimodal branch, or through a new type of nonlinear mechanism from a single-mode primary branch.

Average persistent current in a mesoscopic ring.

We present a microscopic calculation of the disorder-averaged persistent current for a mesoscopic ring with a fixed number of electrons. Using an idea by Imry, we show that the event Fourier components of the average current dominate and are related to the typical single-level current D ∞ D/0 , which can be calculated by a Green's-function-averaging technique. For the small even harmonics p, the result simplifies to D ∼I 0 /2πM, where M is the number of transverse channels. Its relevance to multiring experiments is discussed

Transverse circulation and channel deformation near training walls of bridge crossings

Transverse circulation and channel deformation near training walls of bridge crossings

A model study of np tensor correlation effects on the electron scattering response functions

The role played by np tensor correlations in the longitudinal and transverse response functions is investigated in the quasi-free region. A model is proposed where the response in plane-wave impulse approximation is modified by introducing responses of strongly correlated deuteron-like pairs. Various pair correlations are studied. The introduction of the pair responses does not lead to a violation of the Coulomb- and the f-sum rules. The results show that tensor correlations shift the strength from the quasi-elastic peak towards higher energy. The additional contributions of meson exchange and isobar currents in the transverse channel can compensate the quenching due to correlations.

Mitochondrial creatine kinase from cardiac muscle and brain are two distinct isoenzymes but both form octameric molecules.

Mitochondrial creatine kinase (Mi-CK) from chicken cardiac muscle and brain, recently shown to differ in their N-terminal amino acid sequences and to be encoded by multiple mRNAs (Hossle, H.P., Schlegel, J., Wegmann, G., Wyss, M., Böhlen, P., Eppenberger, H. M., Wallimann, T., and Perriard, J.C. (1988) Biochim. Biophys. Res. Commun. 151, 408-416) were separated on two-dimensional nonequilibrium pH-gradient electrophoresis gels and visualized as two distinct protein spots by immunoblotting. Analysis of the two proteins purified by specific elution from Blue-Sepharose with ADP (Wallimann, T., Zurbriggen, B., and Eppenberger, H. M. (1985) Enzyme 33, 226-231) followed by fast protein liquid chromatography cation exchange chromatography showed obvious differences in peptide maps, in immunological cross-reactivity with monoclonal antibodies, and in kinetic parameters. However, even though the two proteins were different, tissue-specific mitochondrial isoforms, both formed regularly-sized, perforated cube-like octameric structures with Mr of 364,000 +/- 25,000 and 352,000 +/- 20,000 for the cardiac and brain isoform, respectively. Electron microscopy of cardiac and brain Mi-CK octamers revealed cube-like molecules with a central cavity or transverse channel filled by negative stain. The octameric molecular structure of Mi-CK isoforms differs from the generally accepted dimeric arrangement of "cytosolic" muscle MM- and brain BB-CK.

The effect of trench-gate-oxide structure on EPROM device operation

A floating-gate erasable programmable read-only memory (EPROM) cell with a thin trench-gate-oxide (TGO) structure near the drain region was fabricated using electron-beam lithography technology. Several promising advantages were found for the TGO cell. The writing time was measured to be 100 faster than conventional devices of the same dimensions. Two-dimensional (2-D) simulation of the TGO structure indicated that longitudinal and transverse channel electric fields are generated which simultaneously increase the hot-electron population in the channel and the injection efficiency into the floating gate. The devices exhibit high-transconductance, fast programming, good-tolerance to unintentional writing during readout, and potential for flash-erase application.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Real-space and magnetic-field correlation of quantum-resistance fluctuations in the ballistic regime in narrow GaAs-AlxGa

We report the first experimental study, in the quasiballistic regime, of magnetic field correlation properties of quantum-resistance fluctuations, between phase coherent spatial regions. Our devices are GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quasi-one-dimensional wires with an elastic-scattering length comparable to the voltage probe spacing and at most 10 transverse channels occupied. We find the correlation coefficients to be substantially different than recent results in diffusive wires (\ensuremath{\sim}0 compared to -0.5 for the latter), indicating that the universality, which characterizes fluctuations in diffusive quantum transport, is beginning to break down in this few-channel, ballistic limit.

Is n-butyl-2-cyanoacrylate a biocompatible coating material for biodegradable fracture fixation devices? An experimental study on rats

The effect of n-butyl-2-cyanoacrylate monomer and polymer on the repair characteristics of cancellous bone was evaluated in an experimental study in which 105 male Wistar rats were operated on. A transverse drill channel 2mm in diameter and 5mm long in the femoral condyle was filled with a cylindrical implant of n-butyl-2-cyanoacrylate polymer or liquid n-butyl-2-cyanoacrylate monomer, which was polymerized in the tissue. The drill channel was left empty in the control group. Follow-up periods were one, three, six, 12, 24, 36 and 48 weeks. Radiographic, histologic, histomorphometric, oxytetracycline fluorescence and microradiographic studies were done. N-butyl-2-cyanoacrylate polymerdid not delaybone healing and was well tolerated by rat's cancellous bone tissue without signs of foreign body reaction or prolonged inflammation reaction. The polymerization of n-butyl-2-cyanoacrylate monomer caused the development of a narrow zone of bone necrosis or connective tissue around the implant depending on whether or not blood had interfered in the polymerization reaction. Bone necrosis and connective tissue worked as a biological and mechanical obstruction for bone healing towards the implant although there was no disturbance in the regenerative process in the trabecular network surrounding the implant.

Quantum transport in quasi-one-dimensional GaAsAl xGa 1−xAs heterostructure devices

We study quantum transport properties of narrow GaAsAl xGa 1−xAs wires and rings made by electron beam lithography. At low temperatures, clear signatures of Ah́aronov-Bohm quantum interference effects are observed due to the application of a perpendicular magnetic field. The ring devices show large amplitude ( −5%) resistance oscillations periodic in magnetic flux penetrating the ring, which diminish in amplitude above −3kG. The wire devices show aperiodic resistance fluctuations as large as 100%, which persist into the quantum Hall regime. The large amplitudes observed result from the small number of transverse channels occupied below the Fermi level.

Antisymmetrization effects in the spin-transverse quasi-elastic response

In the transverse spin-isovector channel a ρ-exchange force is compared to a realisticG-matrix interaction. An energy and momentum dependent g′ is extracted that can be used together with a ρ-exchange potential in ring approximation yielding for the collective response function in the quasi-elastic peak the same result as a fully antisymmetrizedG-matrix interaction.