Non-parallel Configuration Research Articles

Theoretical study of a putative adsorption mechanism of arginine and glutamate on goldfish 5.24 and zebrafish Z06: Statistical physics modeling, thermodynamic study, and docking simulation

An adsorption phenomenon putatively involved in the sense of smell of arginine and glutamate amino acids in the goldfish olfactory receptor 5.24 and the zebrafish olfactory receptor Z06 was applied in this study to deeply interpret and characterize the olfaction process at a molecular level. As a result, the experimental concentration-olfactory response curves were adjusted using the mono-layer model with one energy (MLM1E). On the one hand, the physicochemical parameters involved in the chosen model were utilized to microscopically investigate the four olfactory systems. Indeed, the two amino acids were adsorbed via a non-parallel configuration, and the process of adsorption was multi-molecular. The molar adsorption energies, which ranged from 22.09 to 35.97 kJ/mol, could be utilized to define the energetic interaction types between the investigated amino acids and the two tested fish olfactory receptors. The size and adsorption energy heterogeneity of 5.24 and Z06 binding pockets were measured by estimating the pocket site size distributions or PSDs (stereographic characterization) and the adsorption energy distributions or AEDs (energetic characterization). On the other hand, these physicochemical parameters could also be applied to macroscopically investigate the four olfactory systems. Hence, three thermodynamic functions including the adsorption entropy Sa, the internal energy Eint, and the Gibbs free energy G were computed in order to investigate the disorder, the exothermicity, and the spontaneity of the studied systems, respectively. The docking modeling analysis of arginine and glutamate amino acids with goldfish 5.24 and zebrafish Z06 revealed simulated binding energies that closely matched the average adsorption energies (peaks of AEDs). These affinities corresponded to the adsorption energy bands known as olfactory bands or spectrums of vibration modes.

A multilayer adsorption of perfluorohexanesulfonic and perfluorobutanesulfonic acids on bio-based polyurethane/chitosan foam: Advanced interpretation of the adsorption mechanism

This work presents an application of a multilayer model derived from statistical physics to the adsorption experimental data of two industrial pollutants, namely perfluorohexanesulfonic (PFHxS) and Perfluorobutanesulfonic (PFBS) acids on a bio–based polyurethane /chitosan(PU/CH) adsorbent foam, at T = 298–328 K and pH 4. This model shows that the number of PFHxS and PFBS layers formed on adsorbent surface increases from 1.61 to 3.80, and from 1.56 to 2.26 respectively by increasing the temperature.This means that the adsorbate molecules are arranged on a variable number of layers. For instance, at 328 K, it was deduced that around 80 % of PFHxS acid was taken up by the PU/CH composite, forming a total of four layers, whereas the remaining 20 % contributed to the formation of three layers. The estimation and analysis of the number of molecules bound per active site is useful to understand the adsorption mechanism. PFHxS and PFBS adsorb on PU/CH in non-parallel configuration, through a multimolecular docking characterized by more than one molecule per active site. The PU/CH performances are investigated in terms of the maximum adsorption capacity of both the tested industrial pollutants, retrieving similar values for both PFHxS and PFBS. Two adsorption energies are calculated showing that physical forces are contributing to remove these pollutants. Interstingly, thermodynamic calculations are also introduced and interpreted to understand the adsorption mechanism at macroscopic level. These theoretical scientific evidences provide a plausible explanation of the PFHxS and PFBS adsorption mechanisms and contribute to understand this interfacial process at the molecular level.

Research on the thermal and flow characteristics of novel micro-channel PV/T collectors

A novel micro-channel PV photothermal collector is investigated, comprising of PV cells and collectors. Its distinctive feature lies in the flow mode of its micro-channels. The novel micro-channel investigated in this study is composed of multiple drums, allowing for a non-parallel flow configuration. This distributional flow pattern facilitates enhanced contact between the water flow and the heat transfer surface, thereby resulting in significantly improved heat transfer efficiency. Characteristics and flow properties are studied to enhance the thermoelectric performance and broaden the application scope of PV photothermal collector technology. This study focuses on parallel micro-channels and three-passes micro-channels for comparison, employing ANSYS FLUENT to simulate electrical and thermal efficiencies, temperature distribution, velocity field, and pressure field under typical operating conditions. The validity of the model is verified by comparing it with experimental panel surface temperature data. Within this framework, various inlet flow conditions are examined to investigate the collector's temperature profile, standard deviation of temperature distribution, pressure drops, and maxi-mum velocity. Results indicate that under specific circumstances, the heat collection performance of parallel micro-channel PV photothermal collectors is inferior to that of three-passes micro-channel counterparts. Both types exhibit reduced efficiency during winter conditions, however, three-passes micro-channels experience a more significant decline at 22.4%, compared to 19.7% for parallel micro-channels. In terms of flow resistance characteristics, parallel micro-channels demonstrate advantages in terms of pressure drops over three-passes configurations as they exhibit nearly 3935 Pa lower values under certain conditions. Regarding temperature uniformity in PV-photothermal systems, parallel micro-channel collectors outperform their three-passes counterparts.

A Local Thermal Non-Equilibrium Approach to an Electromagnetic Hybrid Nanofluid Flow in a Non-Parallel Riga Plate Channel

The fluid flow in a non-parallel configuration exists in the electronic heat removal devices, microchannel heat sinks, and angled confusers/diffusers. The fluids in these applications are prone to flow separation and bifurcations. To deal with such type of problems, a novel idea of a converging or diverging type Riga plate channel is introduced in this study. The Riga plates are utilised to produce the cross-flow magnetic and electric fields which give rise to an exponentially decaying Lorentz force. Also, a porous matrix with variable permeability is considered to fill the Riga plate channel. The thermal equilibrium state between the hybrid nanofluid and porous media is ignored i.e., a local thermal non-equilibrium (LTNE) approach is adopted to model the energy balance equations. The dimension-free form of the guiding equations is tackled by using the Chebyshev pseudospectral quasi-linearization method. The heat transfer rate is respectively incremented by 21.42% and 63.12% in the converging and diverging flow regimes, with the inclusion of a Riga Sheet. The skin friction coefficient is depressed with modified Hartmann number (Ha*) and porosity (ε) for the converging/diverging flow regime. The LTNE state alters to the LTE with Nield number (Ni), thermal conductivity ratio (γ) and ε.

Unified modeling of unconventional modular and reconfigurable manipulation system

Customization of manipulator configurations using modularity and reconfigurability aspects is receiving much attention. Modules presented so far in literature deals with the conventional and standard configurations. This paper presents the 3D printable, light-weight and unconventional modules: MOIRs' Mark-2, to develop any custom `n'-Degrees-of-Freedom (DoF) serial manipulator even with the non-parallel and non-perpendicular jointed configuration. These unconventional designs of modular configurations seek an easy adaptable solution for both modular assembly and software interfaces for automatic modeling and control. A strategy of assembling the modules, automatic and unified modeling of the modular and reconfigurable manipulators with unconventional parameters is proposed in this paper using the proposed 4 modular units. A reconfigurable software architecture is presented for the automatic generation of kinematic and dynamic models and configuration files, through which, a designer can design, validate using visualization, plan and execute the motion of the developed configuration as required. The framework developed is based upon an open source platform called as Robot Operating System (ROS), which acts as a digital twin for the modular configurations. For the experimental demonstration, a 3D printed modular library is developed and an unconventional configuration is assembled, using the proposed modules followed by automatic modeling and control, for a single cell of the vertical farm setup.

Spin-triplet superconductor–quantum anomalous Hall insulator–spin-triplet superconductor Josephson junctions: 0−π transition, ϕ0 phase, and switching effects

We study the Josephson effect in spin-triplet superconductor$-$quantum anomalous Hall insulator$-$spin-triplet superconductor junctions using the nonequilibrium Green function method. The current-phase difference relations show strong dependence on the orientations of the $\bf{d}$-vectors in superconductors. We focus on two $\bf{d}$-vector configurations, the parallel one with the left and right ${\bf{d}}$-vectors being in the same direction, and the nonparallel one with the left ${\bf{d}}$-vector fixed at the $z$-axis. For the parallel configuration, the $0$-$\pi$ transition can be realized when one rotates the ${\bf{d}}$-vectors from the parallel to the junction plane to the perpendicular direction. The $\phi_{0}$ phase with nonzero Josephson current at zero phase difference can be obtained as long as ${d_{x}}{d_{z}}\ne0$. For the nonparallel configuration, the $0$-$\pi$ transition and the $\phi_{0}$ phase still exist. The condition for the formation of the $\phi_{0}$ phase becomes $d_{Rx}\ne0$. The switch effects of the Josephson current are found in both configurations when the ${\bf{d}}$-vectors are rotated in the $xy$ plane. Furthermore, the symmetries satisfied by the current-phase difference relations are analysed in details by the operations of the time-reversal, mirror-reflections, the spin-rotation and the gauge transformation, which can well explain the above selection rules for the $\phi_{0}$ phase. Our results reveal the peculiar Josephson effect between spin-triplet superconductors and the quantum anomalous Hall insulator, which provide helpful phases and effects for the device designs. The distinct current-phase difference relations for different orientations may be used to determine the direction of the ${\bf{d}}$-vector in the spin-triplet superconductor.

Thermal, frictional and exergetic analysis of non-parallel configurations for plate heat exchangers

Parallel configuration is the main common and conventional structure of the plate heat exchangers. However, this paper focuses on non-parallel configuration for these types of heat exchangers and clarifies whether these configurations are more thermally efficient compared to the parallel plates. Besides, frictional and exergetic behavior of non-parallel structures are investigated as well. As shown in the graphical abstract, eight configurations are possible for non-parallel structures all of which are comprehensively studied in this research using a validated 3-D numerical simulation. The results show that the non-parallel plates provide higher Nusselt number and thermal performance factor compared to the common parallel plates. In the same value of inlet mass flow rate, case “e” in which hot fluid moves though the converge channel and cold fluid moves through the divergent channel obtains the maximum Nu number. Obtained thermal performance factors higher than unity show the positive role of non-parallel structures with consideration of both Nusselt number and friction factor. Generally, it is concluded that non-parallel structures can be considered as an efficient method to augment the efficiency of plate heat exchangers. Many other parameters in term of second law of thermodynamics are studied for all structures as well in this study.

Multi-body hydrodynamic resonance and shielding effect of vessels parallel and nonparallel side-by-side

An attempt has been made to study the hydrodynamic interaction of side-by-side vessels based on the gap resonant modes which were theoretically derived by Molin et al. The hydrodynamic associated wave elevations, coefficients, and wave forces are analyzed for a real hull shaped FPSO and a ship. The resonant characteristics of parallel and nonparallel configurations under different wave headings are analyzed. The resonant mode due to the gap and its impact on various hydrodynamic results are emphasized in this study. The vessel motions are simulated in the time domain by using Cummins’ approach. Calculated motion RAOs by white noise test and relative motion under irregular waves are validated by measurement in the model test. The resonant behaviors and phase differences of each degree of freedom of vessels are investigated. The shielding effect is evaluated numerically and experimentally by exchanging vessels on lee-side and weather-side. Results indicate the different degree of freedom has a distinct preference to react to the resonant modes. The first mode which is superior under beam sea may become less significant under oblique and head seas. Higher resonant mode shifts to lower frequency in the nonparallel configuration. The shielding effect only suppresses the motion caused by the gap resonance, the natural frequency resonance like roll remains without change.

Numerical simulation of an adaptive beam-shaping technique using a phase grating overlapped via a spatial light modulator for precision square–flat-top beam

Beam shape is a key parameter in process optimisation for all laser applications. Among these shapes, a square–flat-top beam is fundamental and is in high demand. To obtain a beam with an aimed structure, various beam-shaping methods have been developed. Among them, an adaptive beam-shaping technique that uses phase grating encoded on a spatial light modulator with spatial frequency filtering in the Fourier plane in a 4f system has been developed. In this paper, using precise and simple beam shaping to produce a square and flat-top beam, we examine in detail the phase grating structure via simulations. The directions of the grating vectors inside and outside of the aimed area, i.e. kg-inside and kg-outside, and the normal vectors of the square and flat-top area, i.e. k1 and k2, critically affect the separation of the extracted and residual components on the Fourier plane. To extract the high spatial frequency component for precise shaping, a non-parallel configuration of the grating vectors to the normal vectors of the square beam is found to be effective. This method ensures precision beam shaping as well as keeping of pulse width and wavefront over the shaped area.

Fluorescence properties of β-perylene crystals prepared by a physical vapor transport method under atmospheric pressure

We selectively prepared a metastable phase of perylene crystals (β-phase) by a physical vapor transport method under atmospheric pressure. The fluorescence lifetime (τF) was determined to be 12.3 ns and the annihilation rate constant (γss) of singlet exciton was estimated to be 3 × 10−10 cm3 s−1 from fluorescence decay profile at high excitation density. The fluorescence quantum yield (ΦF) was determined to be 0.6 and ΦF decreased dramatically with decreasing wavelength below 300 nm, suggesting that fission from a highly excited singlet state into two triplet states occurred. The radiative lifetime τR (=τF/ΦF) was 20 ns, which indicates that the fluorescence originated from the excimer with nonparallel configuration in the crystals.

Does Distal Radio-ulnar Joint Configuration Affect Postoperative Functional Results after Ulnar Shortening Osteotomy?

Background:Reverse oblique distal radio-ulnar joint (DRUJ) configuration is assumed to show inferior postoperative results in ulnar-shortening osteotomy due to osteoarthritis, as the joint force pressure in the DRUJ may be increased. An evaluation and comparison of the postoperative functional results with regard to clinical and radiographic signs of arthritis among different DRUJ configurations was carried out retrospectively.Methods:Sixty-two patients after ulnar shortening osteotomy were included. The minimum follow-up was 5 years. Preoperative x-rays were assessed for the DRUJ configuration according to the Tolat classification, whereas postoperative radiographs were evaluated with regard to signs of osteoarthritis using the Kallgren-Lawrence-Score. Functional results were evaluated using the disabilities of the arm, shoulder and hand (DASH) and Mayo Wrist Score and measuring range of motion and grip strength.Results:Significantly better functional results were found in patients with parallel configuration of the DRUJ (Tolat type 1 configuration) with regard to DASH score, grip strength, and supination compared with nonparallel configurations. In the Tolat type 1, configurated DRUJ mean DASH score was 9 compared with 18 in the Tolat type 2 and 3 groups. Apart from supination, no differences were observed in range of motion among groups.Conclusion:Although long-term postoperative range of motion failed to display statistically significant differences between DRUJ configurations except for supination, better results regarding grip strength and DASH scores were seen in a parallel-aligned DRUJ configuration. Although onset of osteoarthritis does not seem to become apparent within the observation period, nonparallel aligned configuration predisposes to inferior results.

The effect of earthquake on architecture geometry with non-parallel system irregularity configuration

Indonesia is an area prone to earthquake that may cause casualties and damage to buildings. The fatalities or the injured are not largely caused by the earthquake, but by building collapse. The collapse of the building is resulted from the building behaviour against the earthquake, and it depends on many factors, such as architectural design, geometry configuration of structural elements in horizontal and vertical plans, earthquake zone, geographical location (distance to earthquake center), soil type, material quality, and construction quality. One of the geometry configurations that may lead to the collapse of the building is irregular configuration of non-parallel system. In accordance with FEMA-451B, irregular configuration in non-parallel system is defined to have existed if the vertical lateral force-retaining elements are neither parallel nor symmetric with main orthogonal axes of the earthquake-retaining axis system. Such configuration may lead to torque, diagonal translation and local damage to buildings. It does not mean that non-parallel irregular configuration should not be formed on architectural design; however the designer must know the consequence of earthquake behaviour against buildings with irregular configuration of non-parallel system. The present research has the objective to identify earthquake behaviour in architectural geometry with irregular configuration of non-parallel system. The present research was quantitative with simulation experimental method. It consisted of 5 models, where architectural data and model structure data were inputted and analyzed using the software SAP2000 in order to find out its performance, and ETAB2015 to determine the eccentricity occurred. The output of the software analysis was tabulated, graphed, compared and analyzed with relevant theories. For areas of strong earthquake zones, avoid designing buildings which wholly form irregular configuration of non-parallel system. If it is inevitable to design a building with building parts containing irregular configuration of non-parallel system, make it more rigid by forming a triangle module, and use the formula.A good collaboration is needed between architects and structural experts in creating earthquake architecture.

Nematic-smectic transition of parallel hard spheroellipsoids.

Spheroellipsoids are truncated ellipsoids with spherical end caps. If gradients are assumed to change smoothly at the junction of body and cap, the truncation height z0 determines the geometry uniquely. The resulting model particle has only two shape parameters, namely, the aspect ratio c/a of the basic ellipsoid and the cutoff z0/a. These two parameters can be tuned to yield a continuous transformation between a pure ellipsoid and a spherocylinder. Since parallel hard spherocylinders display a nematic-smectic A phase transition, while ellipsoids do not, the influence of the particle shape on the possibility of a smectic phase may be investigated. A density functional analysis is used to detect the dividing line, in the (c/a, z0/a) plane, between the presence and absence of the N-S transition. Since spheroellipsoids may be useful as generic model particles for anisotropic molecules, we provide a computationally efficient overlap criterion for a pair in a general, non-parallel configuration.

Biomechanical Comparison of 3 Possible Fixation Strategies to Resist Femoral Neck Shortening After Fracture

In light of recent reports that patients with femoral neck shortening following fracture fixation are dissatisfied with their outcomes, the objective of this study was to compare the compressive strength, or resistance to shortening, of 3 possible strategies for stabilization of the femoral neck that should resist shortening. The proximal portion of 21 synthetic composite femurs were prepared to isolate the femoral neck for study. A 4-mm segment of the femoral neck was removed to simulate a transcervical comminuted fracture that would be expected to shorten under standard treatment conditions. These simulated fractures were fixed by 1 of 3 methods: a 3-screw configuration using parallel partially threaded screws augmented with an injectable hydroxyapatite bone substitute in the fracture site; a 3-screw configuration using parallel fully threaded screws; or a nonparallel 3-screw configuration using partially threaded screws. The specimens were tested in compression along the axis of the femoral neck, and the mean stiffness and load to failure values were calculated.The hydroxyapatite bone substitute-augmented partially threaded screw fixation construct resulted in the highest stiffness (1928+/-135 N/mm) and load to failure (6529+/-674 N), followed by the fully threaded screw construct (1210+/-166 N/mm and 3987+/-419 N, respectively), and finally the nonparallel construct (518+/-176 N/mm and 592+/-295 N, respectively) (P<.001 for all groups). This study supports further evaluation of hydroxyapatite bone substitute augmentation at the fracture site to prevent femoral neck shortening in femoral neck fractures receiving internal fixation.

Unfaulting mechanism of trapped self-interstitial atom clusters in bcc Fe: A kinetic study based on the potential energy landscape

We report on the complete unfaulting mechanism of a trapped self-interstitial atom cluster in the form of a nonparallel configuration (NPC), investigated using the autonomous basin climbing (ABC) method. A detailed set of transition state atomic trajectories in the unfaulting process from the trapped to the mobile glide $⟨111⟩$ configuration and the corresponding potential energy landscape were identified. The breaking of the initial ring structure of the three trimers on (111) planes followed by the rotation of the $⟨111⟩$ crowdion in the NPC are the main rate limiting processes of the unfaulting mechanism. The effective activation barrier in the transition from the NPC to the glide $⟨111⟩$ configuration was calculated by combining the ABC and kinetic Monte Carlo methods and was further benchmarked against molecular dynamics (MD) simulations. The effective activation barrier was found as 0.82 eV; smaller than its previously reported value of 1.68 eV. The ABC method was confirmed to be more efficient than MD, especially for the defect structure evolution processes associated with high barriers and at low temperatures.

Finite Element Study of Matched Paired Posterior Disc Implant and Dynamic Stabilizer (360° Motion Preservation System)

Background Anterior lumbar disc replacements are used to restore spinal alignment and kinematics of a degenerated segment. Compared to fusion of the segment, disc replacements may prevent adjacent segment degeneration. To resolve some of the deficiencies of anterior lumbar arthroplasty, such as the approach itself, difficulty of revision, and postoperative facet pain, 360° motion preservation systems based on posterior disc and posterior dynamic system (PDS) designs are being pursued. These systems are easier to revise and address all the pain generators in a motion segment, including the nerves, facets, and disc. However, biomechanics of the 360° posterior motion preservation system, including the contributions of the 2 subsystems (disc and PDS), are sparsely reported in the literature.nds. Methods An experimentally validated 3-dimensional finite element model of the ligamentous L3-S1 segment was used to investigate the differences in biomechanical behavior of the lumbar spine. A single-level 360° posterior motion preservation system and its individual components in various orientations were simulated and compared with an intact model. Appropriate posterior surgical procedures were simulated. The PDS, a curved device with male and female components, was attached to the pedicle screws. The finite element models were subjected to 400 N of follower load plus 10Nm moment in extension and flexion. Results The PDS restored flexion/extension motion to normal. The artificial disc led to increases in range of motion (ROM) compared with the intact model. ROM for the 360° system at the implanted and adjacent levels were similar to those of the respective intact levels. ROM was similar whether the discs were placed (a) both parallel to the midsagittal plane, (b) both angled 20° to the midsagittal plane, and (c) one at 20° and one parallel to the midsagittal plane. However, the stresses were slightly higher in the nonparallel disc configuration than in the parallel disc configuration, both in flexion and extension modes. Conclusions Posterior disc replacement with PDS restored the kinematics of the spine at all levels to near normal. In addition, placing the discs in a nonparallel configuration with respect to the midsagittal plane does not affect the functionality of the discs compared with parallel placement. Posterior disc replacement alone is not sufficient to restore the segment biomechanics to normal levels. Clinical Relevance Finite element analysis results show that, unlike implants for fusion, PDS and posterior discs together (360° motion preservation system) are needed to preserve ROM. Such systems will prevent adjacent level degeneration and address pain from various spinal components, including facets.

Finite element study of matched paired posterior disc implant and dynamic stabilizer (360° motion preservation system).

BackgroundAnterior lumbar disc replacements are used to restore spinal alignment and kinematics of a degenerated segment. Compared to fusion of the segment, disc replacements may prevent adjacent segment degeneration. To resolve some of the deficiencies of anterior lumbar arthroplasty, such as the approach itself, difficulty of revision, and postoperative facet pain, 360° motion preservation systems based on posterior disc and posterior dynamic system (PDS) designs are being pursued. These systems are easier to revise and address all the pain generators in a motion segment, including the nerves, facets, and disc. However, biomechanics of the 360° posterior motion preservation system, including the contributions of the 2 subsystems (disc and PDS), are sparsely reported in the literature.nds.MethodsAn experimentally validated 3-dimensional finite element model of the ligamentous L3-S1 segment was used to investigate the differences in biomechanical behavior of the lumbar spine. A single-level 360° posterior motion preservation system and its individual components in various orientations were simulated and compared with an intact model. Appropriate posterior surgical procedures were simulated. The PDS, a curved device with male and female components, was attached to the pedicle screws. The finite element models were subjected to 400 N of follower load plus 10Nm moment in extension and flexion.ResultsThe PDS restored flexion/extension motion to normal. The artificial disc led to increases in range of motion (ROM) compared with the intact model. ROM for the 360° system at the implanted and adjacent levels were similar to those of the respective intact levels. ROM was similar whether the discs were placed (a) both parallel to the midsagittal plane, (b) both angled 20° to the midsagittal plane, and (c) one at 20° and one parallel to the midsagittal plane. However, the stresses were slightly higher in the nonparallel disc configuration than in the parallel disc configuration, both in flexion and extension modes.ConclusionsPosterior disc replacement with PDS restored the kinematics of the spine at all levels to near normal. In addition, placing the discs in a nonparallel configuration with respect to the midsagittal plane does not affect the functionality of the discs compared with parallel placement. Posterior disc replacement alone is not sufficient to restore the segment biomechanics to normal levels.Clinical RelevanceFinite element analysis results show that, unlike implants for fusion, PDS and posterior discs together (360° motion preservation system) are needed to preserve ROM. Such systems will prevent adjacent level degeneration and address pain from various spinal components, including facets.

Bifurcations in biquadraticly coupled magnetic layers

The bifurcation sequence in the dynamics of bilinear and biquadratic coupled magnetization vectors of an anisotropic layer system is considered. It is shown that besides a first bifurcation converting the parallel configuration of magnetization vectors into an unstable state and creating a canted ground state with a nonparallel configuration there is a second bifurcation occurring in the excited states region of the systems phase space. This second bifurcation converts the parallel configuration to an elliptic energy maximum, generates nonparallel hyperbolic states, and should be relevant for all processes passing through the high energy region.

Coupled rotators approach to the dynamics of interacting magnetic layers

The dynamical properties of two anisotropic rotators modelling magnetic layers coupled by bilinear and biquadratic interactions terms are considered. The easy plane case is considered in detail and it is shown that the presence of the biquadratic coupling produces а sequence of bifurcations in the rotational phase spaces. In a first bifurcation a new ground state with rotators located in the easy plane and including а finite angle is generated. Hyperbolic points appear by increasing the biquadratic coupling in а second bifurcation.These hyperbolic points correspond to а nonparallel rotator configuration with rotators splitted off from the easy plane and symmetrically displaced along the transversal direction. The corresponding energy is located between the energies of the ground state and the parallel rotator configuration. Phase space portraits displaying how the stationary states are embedded in the rotational flow are shown.

The track interaction model for alpha particle induced thermoluminescence supralinearity: dependence of the supralinearity on the vector properties of the alpha particle radiation field

Thermoluminescence (TL) - fluence response characteristics for peaks 5, 7, 8 and 9 in LiF:Mg,Ti (TLD-100; Harshaw/Bicron) were measured for 5 MeV alpha particles, in both `non-parallel' and `near-parallel' geometries,and for 1 MeV alpha particles in `near-parallel' geometry. The onset of supralinearity in the non-parallel configuration is always at a significantly lower fluence (by approximately a factor of five) than in the nearly parallel configuration. This dependence of the onset of supralinearity on the vector properties of the alpha particle radiation field is interpreted as `proof positive' of the dominant importance of track interaction effects in the linear/supralinear behaviour of the glow peaks of TLD-100. A mathematical expression for the linear/supralinear behaviour for heavy charged particles in near-parallel geometry has been developed and fitted to the TL - fluence response curves. The model incorporates both possibilities of electron and hole diffusion in the glow curve heating stage as well as the contribution to the supralinearity of all the participating nearest-neighbour track interactions. The model is capable of yielding excellent fits to the experimental data; the inclusion of hole diffusion and retrapping is preferred to predict the very abrupt transition from linear to supralinear behaviour for the high-temperature peaks.