Dynamics in the Parameter Space of a Neuron Model

Some two-dimensional parameter-space diagrams are numerically obtained by considering the largest Lyapunov exponent for a four-dimensional thirteen-parameter Hindmarsh-Rose neuron model.Several different parameter planes are considered,and it is shown that depending on the combination of parameters,a typical scenario can be preserved:for some choice of two parameters,the parameter plane presents a comb-shaped chaotic region embedded in a large periodic region.It is also shown that there exist regions close to these comb-shaped chaotic regions,separated by the comb teeth,organizing themselves in period-adding bifurcation cascades.

Demodulating the Response of Optical Fibre Long-Period Gratings： Genetic Algorithm Approach

The extraction of the physical parameters of long period gratings from the spectral response is not an easy process. We present a demodulation technique to synthesize the physical parameters of a long period grating recorded in an optical fibre. The demodulation is achieved through the implementation of a genetic algorithm. The extracted parameters are in agreement with the typical values known for long period gratings.

Synthesis of Hydrothermally Grown Zinc Oxide Nanowires

We report the synthesis ofZnO nanowires grown on glass by spin coating and using a commercial microwave oven. 10 mM solutions of zinc acetate dehydrate and 12propanol were spin coated on glass at 2000 rpm for 60 s. A seed layer was obtained after three layers of spin coating. Vertical ZnO nanowires were then grown by dipping the substrate in an equimolar solution of zinc nitrate hexahydrate and hexamethylenetetramine subsequently, films were heated with a commercially microwave oven at different power settings （140, 350 and 700 W）. The ZnO nanowires were characterized optically and morphologically. Scanning electron microscopy analysis showed that the size of ZnO nanowires was 50 nm in diameter and 500 nm in length. XRD patterns and IR spectra revealed the presence of Zn（OH）2 on the films, when low power in the microwave oven was utilized. The ZnO nanowires bandgap energy was obtained from optical transmission spectra.

Stellar structure model in hydrostatic equilibrium in the context of f(R)-gravity

In this work we present a stellar structure model from the f（R）-gravity point of view capable of describing some classes of stars（white dwarfs, brown dwarfs, neutron stars, red giants and the Sun）. This model is based on f（R）-gravity field equations for f（R） = R ＋ f2R2, hydrostatic equilibrium equation and a polytropic equation of state. We compare the results obtained with those found by Newtonian theory. It has been observed that in these systems, where high curvature regimes emerge,stellar structure equations undergo modifications. Despite the simplicity of this model, the results are satisfactory. The estimated values of pressure, density and temperature of the stars are within those determined by observations. This f（R）-gravity model has proved to be necessary to describe stars with strong fields such as white dwarfs, neutron stars and brown dwarfs, while stars with weaker fields, such as red giants and the Sun, are best described by Newtonian theory.

Calculations of Optical Rotation from Density Functional Theory

Density function theory calculations of frequency-dependent optical rotations [α]ω for three rigid chiral molecules are reported. Calculations have been carried out at the sodium D line frequency, using the ADZP basis set and a wide variety of functionals. Gauge-invariant atomic orbitals are used to guarantee origin-independent values of [ω]D. In addition, study of geometry dependence of [ω]D is reported. Using the geometries optimized at the B3LYP/ADZP level, the mean absolute deviation of B3LYP/ADZP and experimental laiD values yields 60.1°/（dm g/cm^3）. According to our knowledge, this value has not been achieved until now with any other model.

Is Brenner＇s Modification to the Classical Navier-Stokes Equations Able to Describe Sound Propagation in Gases？

We analyse the problem concerning the propagation of sound waves in gases by using the modified hydrodynamic theory proposed recently by Brenner for single-component fluids. The modifications introduced by Brenner are based on his proposal that the translational momentum in fluid motion is not given by the mass flux. Comparison of the sound propagation results derived from Brenner＇s theory with available experimental data for monatomic gases shows that this modified continuum theory is unable to describe the acoustic measurements not even in the low-frequency limit, a result that from our point of view makes Brenner＇s proposal questionable.

A New Method of Calculating Trap Depth of Rare Earth Materials

The mainly characteristic of trapping materials is the trap depth. So it is significant to calculate the trap depth for the trapping materials. A new method of calculating trap depth, which is based on energy band and using rate equations to analyze thermoluminescence, was brought forward. This method which uses the rate equations of the process and the thermoluminescence curve can replace traditional methods such as first order or second order kinetics. The trap depth of SrAl2O4：Eu^2＋ , Dy^3＋ and Sr4Al14O25：Eu^2＋ , Dy^3＋ was estimated from the glow curve. Then the numerical solution of the trap depth can be obtained. From the results of experiments and calculations, this method can accurately indicate the whole process.

Simultaneous determination of trap depth and the ratio of the rate of recombination to that of capture from thermo-luminescence

Thermo-luminescence （TL） is a kind of luminescence decay measured with varying temperature. In the process of TL the decay parameter itself involves the temperature effect of traps. Thus the trap depth is inseparable from the decay parameter. There are two separate peaks in the TL curve of ZnS：Cu,Co if the measurement starts from liquid nitrogen temperature. In the experiment we started from zero Celsius temperature to isolate the deeper traps. We have proposed and realized three methods for simultaneous determination of trap depth and decay parameter based on the quasi-equilibrium model and experimental data. If we treat the case of kinetic order a = 1 as a = 2, the error might be as large as 100%.

Depolarizing metrics in the biomedical field:Vision enhancement and classification of biological tissues

Polarimetry encompasses a collection of optical techniques broadly used in a variety of fields.Nowadays,such techniques have provided their suitability in the biomedical field through the study of the polarimetric response of biological samples(retardance,dichroism and depolarization)by measuring certain polarimetric observables.One of these features,depolarization,is mainly produced by scattering on samples,which is a predominant efiect in turbid media as biological tissues.In turn,retardance and dichroic efiects are produced by tissue anisotropies and can lead to depolarization too.Since depolarization is a predominant efiect in tissue samples,we focus on studying difierent depolarization metrics for biomedical applications.We report the suitability of a set of depolarizing observables,the indices of polarimetric purity(IPPs),for biological tissue inspection.We review some results where we demonstrate that IPPs lead to better performance than the depolarization index,which is a well-established and commonly used depolarization observable in the literature.We also provide how IPPs are able to significantly enhance contrast between difierent tissue structures and even to reveal structures hidden by using standard intensity images.Finally,we also explore the classificatory potential of IPPs and other depolarizing observables for the discrimination of difierent tissues obtained from ex vivo chicken samples(muscle,tendon,myotendinous junction and bone),reaching accurate models for tissue classification.

Modeling Mechanical Patterns for Striated Muscles

Muscles show a surprisingly large variety of functions when they mechanically respond to different environmental requests. However, the in vivo workloop studies distinguish well only four patterns of skeletal muscles, producing positive, negative, almost zero and zero net works, that qualifies them respectively as motors, brakes, struts, and springs. While much effort of comparative biologists has been done in searching for muscle design patterns, no fundamental concepts underlying such four primary patterns were established. In this interdisciplinary study, continuum mechanics is applied to the problem of muscle structure in relation to function. The known ability of a powering muscle as whole to be tuned via natural (resonant) frequency to the efficient locomotion is now modeled through the non-linear elastic muscle moduli, controlling both the contraction frequency and velocity. When incorporated in activated skeletal and cardiac (striated) muscles via the mechanical similarity between loaded and reaction forces, further exploration of elastic force patterns (borrowed from solid state physics) yields an explicit rationalization for currently known locomotor muscle patterns. Besides explanation of the origin of allometric exponents derived for leg muscles in animals adapted to fast running and wing muscles in flying birds, the skeletal and cardiac muscles are patterned through the primary and secondary high power activities. Further applications are expected to be useful in designing of artificial muscles and modeling living and extinct animals.

One Dimensional Relativistic Particle in a Quadratic Dissipative Medium Subjected to a Force That Depends on the Position

We will find a constant of motion with energy units for a relativistic particle moving in a quadratic dissipative medium subjected to a force which depends on the position. Then, we will find the Lagrangian and the Hamiltonian of the equation of motion in a time interval such that the velocity does not change its sign. Finally, we will see that the Lagrangian and Hamiltonian have some problems.

Golden Ratio Sinusoidal Sequences and the Multimode Pulsation of the δ Sct Star V784 Cassiopeiae

Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the δ-Scuti type variable star V784 Cas. An artificial light curve for V784 Cas is generated by a non deterministic derivation in a context-sensitive grammar by concatenation of two sinusoidal fragments following certain word sequences. The two basic building blocks represent temporal segments in a golden ratio and the number of long and short segments in a word are also in a golden ratio.

Experimental and Analytical Study of Torsional Vibration under Multiaxial Loading in Time Domain

The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations need coefficients and parameters that, usually, must be experimentally estimated. This work uses a resistive electric SG （strain gage） to dynamically determine strains produced in the shaft due to harmonic oscillatory motion under multiaxial loading. This movement is simulated on a prototype specially developed for this purpose. It comprises a pulley attached to the end of a stepped cantilevered shaft, which is clamped at the opposite end. In this configuration, a cam generates a torque to the system, springs regulate the stiffness and the damping coefficient of the assembly, as well as they can be suitably adjusted to produce an underdamped condition. The main advantage, highlighted in this study, refers to a major simplification. Although the system under study shows multiple degrees of freedom （torsion and bending）, the shape and the positioning of linking SGs with the resistor bridge （Wheatstone Bridge）, allow ＂to evaluate the loading effects independently, as if only one degree of freedom of the system exists at a time domain. Strains graphs for two forms of cyclic torsional oscillation, analytical and experimental, were successfully generated.

The AdS_(5)×S^(5) Fermionic Model

We consider the AdS5 × S5 integrable model. As it turns out, relying on well known arguments, we claim that the conformally invariant fermionic model is solvable, the resulting solution given in terms of two current algebras realizations.

Functional N-Representability in 2-Matrix,1-Matrix,and Density Functional Theories

The N-representability conditions on the reduced second-order reduced density matrix (2-RDM), impose restrictions not only in the context of reduced density matrix theory (RDMT), but also on functionals advanced in one-matrix theory such as natural orbital functional theory (NOFT), and on functionals depending on the one-electron density such as those of density functional theory (DFT). We review some aspects of the applications of these N-representability conditions in these theories and present some conclusions.

Analysis of the Performance of Optical Code-Division Multiple-Access System(OCDMA),Operating with Gold Codes under Nonlinear Effects

A numerical simulation study of the performance of encoding and decoding of short optical pulse in OCDMA (Optical Code Division Multiple Access) systems under non-linear optical effects is presented. The performance of encoding and decoding short pulses is obtained through use of device FBG (fiber Bragg grating) where the codes are inserted through discrete jumps in the optical phase (±π). The multiuser interference is also the object of the present study, where a figure of merit (interference figure) is used to quantify the interference in multiuser auto and cross correlation. We evaluate the dependence of the multiuser interference for the coupling constant of FBG. Finally, the interference inserted in the autocorrelation due to nonlinear effects generated in the nonlinear switching of the coded pulse in a dual core nonlinear directional coupler is examined, where temporal broadening of pulses decoded is observed.

Thermal,infrared spectroscopy and molecular modeling characterization of bone:An insight in the apatite-collagen type I interaction

An insight into the interaction of collagen type I with apatite in bone tissue was performed by using differential scanning calorimetry, Fourier transform infrared spectroscopy, and molecular modeling. Scanning electron microscopy shows that bone organic content incinerate gradually through the different temperatures studied. We suggest that the amide regions of the type I collagen molecule (mainly C=O groups of the peptide bonds) will be important in the control of the interactions with the apatite from bone. The amide I infrared bands of the collagen type I change when interacting to apatite, what might confirm our assumption. Bone tissue results in a loss of thermal stability compared to the collagen studied apart, as a consequence of the degradation and further combustion of the collagen in contact with the apatite microcrystals in bone. The thermal behavior of bone is very distinctive. Its main typical combustion temperature is at 360°C with a shoulder at 550°C compared to the thermal behavior of collagen, with the mean combustion peak at ca. 500°C. Our studies with molecular mechanics (MM+ force field) showed different interaction energies of the collagen-like molecule and different models of the apatite crystal planes. We used models of the apatite (100) and (001) planes;additional two planes (001) were explored with phosphate-rich and calcium-rich faces;an energetic preference was found in the latter case. We preliminary conclude that the peptide bond of collagen type I is modified when the molecule interacts with the apatite, producing a decrease in the main peak from ca. 500°C in collagen, up to 350°C in bone. The combustion might be related to collagen type I, as the ΔH energies present only small variations between mineralized and non-mineralized samples. The data obtained here give a molecular perspective into the structural properties of bone and the change in collagen properties caused by the interaction with the apatite. Our study can be useful to understand the biological synthesis of minerals as well as the organic-inorganic interaction and the synthesis of apatite implant materials.

All-electron basis sets for H to Xe specific for ZORA calculations:Applications in atoms and molecules

A segmented basis set of quadruple zeta valence quality plus polarization functions(QZP)for H through Xe was developed to be used in conjunction with the ZORA Hamiltonian.This set was augmented with diffuse functions to describe electrons farther away from the nuclei adequately.Using the ZORA-CCSD(T)/QZP-ZORA theoretical model,atomic ionization energies and bond lengths,harmonic vibrational frequencies,and atomization energies of some molecules were calculated.The addition of core-valence corrections has been shown to improve the agreement between theoretical and experimental results for molecular properties.For atomization energies,a similar observation emerges when considering spin-orbit couplings.With the augmented QZP-ZORA set,static mean dipole polarizabilities of a set of atoms were calculated and compared with previously published recommended and experimental values.Performance evaluations of the ZORA and Douglas–Kroll–Hess Hamiltonians were made for each property studied.

Isothermal hydrogen absorption process of Pd-capped Mg films traced by ion beam techniques and optical methods

Pd-capped nanocrystalline Mg films were prepared by electron beam evaporation and hydrogenated under isothermal conditions to inves-tigate the hydrogen absorption process via ion beam techniques and in situ optical methods.Films were characterized by different techniques such as X-ray diffraction(XRD)and scanning electron microscopy(SEM).Rutherford backscattering spectrometry(RBS)and elastic recoil detection analysis(ERDA)provided a detailed compositional depth profile of the films during hydrogenation.Gas-solid reaction kinetics theory applied to ERDA data revealed a H absorption mechanism controlled by H diffusion.This rate-limiting step was also confirmed by XRD measurements.The diffusion coefficient(D)was also determined via RBS and ERDA,with a value of(1.1±0.1)·10^(−13)cm^(2)/s at 140℃.Results confirm the validity of IBA to monitor the hydrogenation process and to extract the control mechanism of the process.The H kinetic information given by optical methods is strongly influenced by the optical absorption of the magnesium layer,revealing that thinner films are needed to extract further and reliable information from that technique.