Bisector Axis Research Articles

A szimmetria jelenléte Silviu Purcărete előadásaiban

The Greek word symmetry means correct proportion. The basis for this study is the interesting fact according to which symmetry has been known to be the father of boredom in the theatre at least since Meiningenism. To describe a work of art as symmetrical is to say that the bisector axis divides the whole into two exactly corresponding parts. This articulation expresses immobility and constancy, and evokes a sense of these in the viewer, or in the listener in the case of a poem, theatre or music performance. Therefore, the more or less regular use of symmetry today seems a kind of reminiscence of a hundred years ago. In contrast, Silviu Purcărete – whom Lehmann classifies as a post-dramatic director, and who, according to other opinions, can be considered a fully 21st-century director – is a keen user of symmetry in his performances. We will first briefly discuss the concept of symmetry. This will be followed by examples of symmetry from three theatre performances by Silviu Purcărete. Finally, some reflections are presented on the use of symmetry in Silviu Purcărete’s case.

²H Solid-State NMR Analysis of the Dynamics and Organization of Water in Hydrated Chitosan.

Understanding water–biopolymer interactions, which strongly affect the function and properties of biopolymer-based tissue engineering and drug delivery materials, remains a challenge. Chitosan, which is an important biopolymer for the construction of artificial tissue grafts and for drug delivery, has attracted extensive attention in recent decades, where neutralization with an alkali solution can substantially enhance the final properties of chitosan films cast from an acidic solution. In this work, to elucidate the effect of water on the properties of chitosan films, we investigated the dynamics and different states of water in non-neutralized (CTS-A) and neutralized (CTS-N) hydrated chitosan by mobility selective variable-temperature (VT) 2H solid-state NMR spectroscopy. Four distinct types of water exist in all of the samples with regards to dynamic behavior. First, non-freezable, rigid and strongly bound water was found in the crystalline domain at low temperatures. The second component consists of weakly bound water, which is highly mobile and exhibits isotropic motion, even below 260 K. Another type of water undergoes well-defined 180° flips around their bisector axis. Moreover, free water is also present in the films. For the CTS-A sample in particular, another special water species were bounded to acetic acid molecules via strong hydrogen bonding. In the case of CTS-N, the onset of motions of the weakly bound water molecules at 260 K was revealed by 2H-NMR spectroscopy. This water is not crystalline, even below 260 K, which is also the major contribution to the flexibility of chitosan chains and thus toughness of materials. By contrast, such motion was not observed in CTS-A. On the basis of the 2H solid-state NMR results, it is concluded that the unique toughness of CTS-N mainly originates from the weakly bound water as well as the interactions between water and the chitosan chains.

Magnetoresistance peculiarities of bismuth wires in high magnetic field

Magnetoresistance measurements of Bi wires performed in the magnetic field oriented along the bisector axis revealed unexpected anomalous peaks in a high magnetic field far above the quantum limit of the electrons. By combining a magnetic field and an uniaxial strain, we obtained a modification of the electronic structure; as a result, the quantum limit for light and heavy electrons is changed in a different way. For the case where heavy electrons are in the quantum limit, a correlation between the exit of the lowest Landau level of light electrons and the Lifshitz transition was found.

An accurate method of determining a single-plane osteotomy to correct a combined rotational and angular deformity.

Conventional osteotomy used for the correction of deformity is performed out of the plane of deformity creating a wedge either opening or closing when the deformity is corrected. Deformity that is a combination of rotation and angulation exists in a single plane that is oblique to the coronal, sagittal and axial planes depending on the magnitude of deformity measured in each plane. Accurate planning and a simple method of finding this oblique plane operatively is presented. This method starts by finding the bisector of angulation. This is marked by a wire that lies in the plane of angulation and along the bisector of angulation. The saw blade is rotated about this bisector axis according to the proportion of angulation and rotation. There is no second reorientation of the saw blade required making the final plane much easier to define. This single-plane oblique osteotomy allows accurate realignment of the limb.

Transport Properties of Topological Insulator Bi0.83Sb0.17 Nanowires

ABSTRACTWe have investigated the transport properties of topological insulator based on single-crystal Bi0.83Sb0.17 nanowires. The single-crystal nanowire samples in the diameter range 200 nm – 1.1 μm were prepared by the high frequency liquid phase casting in a glass capillary using an improved Ulitovsky technique; they were cylindrical single-crystals with (1011) orientation along the wire axis. In this orientation, the wire axis makes an angle of 19.5o with the bisector axis C1 in the bisector-trigonal plane. Bi0.83Sb0.17 is a narrow gap semiconductor with energy gap at L point of Brillouin zone ΔE= 21 meV. In accordance with the measurements of the temperature dependence of the resistivity of the samples resistance increases with decreasing temperature, but at low temperatures decrease in the resistance is observed. This effect, decrease in the resistance, is a clear manifestation of the interesting properties of topological insulators - the presence on its surface of a highly conducting zone. The Arrhenius plot of resistance R in samples with diameter d=1.1 µm and d=200 nm indicates a thermal activation behavior with an activation gap ΔE= 21 and 35 meV, respectively, which proves the presence of the quantum size effect in these samples. We found that in the range of diameter 1100 nm - 200 nm when the diameter decreases the energy gap is growing as 1/d. We have investigated magnetoresistance of Bi0.83Sb0.17 nanowires at various magnetic field orientations. From the temperature dependences of Shubnikov de Haas oscillation amplitude for different orientation of magnetic field we have calculated the cyclotron mass mc and Dingle temperature TD for longitudinal and transverse (B||C3 and B||C2) directions of magnetic fields, which equal 1.96*10-2m0, 9.8 K, 8.5*10-3m0 , 9.4 K and 1.5*10-1m0 , 2.8 K respectively. The observed effects are discussed.

Analysis of the spin splitting of maxima of quantum oscillations of the resistivity of n-Bi-Sb semiconductor alloys in a magnetic field parallel to the bisector axis

In samples of semiconductor alloys n-Bi0.93Sb0.07 with different electron concentrations (n1 = 8 × 1015 cm−3, n2 = 1.2 × 1017 cm−3, and n3 = 1.9 × 1018 cm−3), dependences of the electrical resistivity on magnetic fields up to 45 T parallel to the current and the bisector axis (H ‖ C1 ‖ j) have been measured at temperatures of 1.5, 4.5, and 10 K. The obtained dependences ρ22(H) demonstrate quantum oscillations of the resistivity (Shubnikov-de Haas effect), and, in high magnetic fields, there is a resistivity maximum far away from other maxima. On assumption that this maximum is related to the spin-split Landau level N = 0− for electrons of the main ellipsoid, the spin-splitting parameters are calculated for electrons of the main ellipsoid: γ1 = 0.87, γ2 = 0.8, and γ3 = 0.73. Using these values, the oscillation maxima can be reliably related to the numbers of split Landau levels for electrons of the main and secondary ellipsoids. The dependences of the resistivity ρ11 and the Hall coefficient R31.2 on magnetic field have been measured in a transverse magnetic field at H ‖ C1 and j ‖ C2 on the sample with the electron concentration n4 = 1.4 × 1017 cm−3. Using similar analysis, the spin-splitting parameter is found to be γ4 = 0.85, which is close to the value of γ2 = 0.8 obtained for the sample with close electron concentration (n2 = 1.2 × 1017 cm−3) during the measurements in a longitudinal magnetic field. The quantum oscillation maxima of Hall coefficient R31.2 are shifted to the range of high magnetic fields as compared to the quantum oscillation maxima of resistivity ρ11.

Electronic topological transition in an n-BiSb semiconductor alloy in the quantum limit range of magnetic fields for H‖C 2

The galvanomagnetic properties of single-crystal samples of the Bi0.93Sb0.07 semiconductor alloy with the electron density n = 1.6 × 1017 cm−3 in magnetic fields up to 14 T at T = 1.6 K have been investigated. The resistivity ρ and Hall coefficient R have been measured as functions of the magnetic field directed along the binary axis of a crystal for a current flowing through a sample along the bisector axis; i.e., the components ρ22 and R 32, 1 have been measured. The strong anisotropy of the electron spectrum of the samples makes it possible to separately observe quantum oscillations of the magnetoresistance ρ22(H) for H ‖ C 2 in low magnetic fields for two equivalent ellipsoids with small extremal cross sections (secondary ellipsoids) and in high magnetic fields for electrons of the ellipsoid with a large extremal cross section (main ellipsoid). An increase in the energy of the electrons of secondary ellipsoids in the quantum limit magnetic fields is accompanied by the flow of electrons to the main ellipsoid; i.e., an electronic topological transition occurs from the three-valley electron spectrum to the single-valley one. After the flow stops, the Fermi energy E F increases from 18 meV to 27.8 meV. With an increase in the quantizing magnetic field, the Fermi energy of the electrons decreases both in the region of quantum oscillations of the resistance that are attributed to the electrons of the secondary ellipsoids and in the region of oscillations associated with the electrons of the main ellipsoid. The Hall coefficient R 32, 1 decreases in high magnetic fields; this behavior indicates the absence of the electron magnetic freezing effect.

Fast dynamics ofH2Oin hydrous aluminosilicate glasses studied with quasielastic neutron scattering

We studied the dynamics of dissolved water in aluminosilicate glasses with the compositions ${\mathrm{NaAlSi}}_{3}{\mathrm{O}}_{8}\ifmmode\cdot\else\textperiodcentered\fi{}0.3{\mathrm{H}}_{2}\mathrm{O}$, ${\mathrm{NaAlSi}}_{3}{\mathrm{O}}_{8}\ifmmode\cdot\else\textperiodcentered\fi{}1.3{\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{Ca}}_{0.5}{\mathrm{AlSi}}_{3}{\mathrm{O}}_{8}\ifmmode\cdot\else\textperiodcentered\fi{}1.3{\mathrm{H}}_{2}\mathrm{O}$ using quasielastic neutron scattering. As shown by near-infrared spectroscopy on these samples, ${\mathrm{H}}_{2}\mathrm{O}$ molecules are the predominant hydrous species in the water-rich glasses whereas $\mathrm{OH}$ groups bound to tetrahedrally coordinated cations are predominant at low water contents. Backscattering and time-of-flight methods were combined to investigate motional correlation times in the range between $0.2\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ and $2\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$. For the water-rich glasses an elastic scan between $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $420\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ shows that the dynamical processes set in at lower temperatures in the $\mathrm{Ca}$-bearing glass than in the $\mathrm{Na}$-bearing glass. This is corroborated by the broadening of the inelastic spectra $S(Q,\ensuremath{\omega})$. The shape of the scattering function $S(Q,t)$ suggests a distribution of activation barriers for the motion of hydrous species in the disordered structure of the glass. The distribution is narrower and the average activation energy is smaller in the $\mathrm{Ca}$-bearing glass than in the $\mathrm{Na}$-bearing glass. No indication for dynamics of hydrous species was found at temperatures up to $520\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in the water-poor glass ${\mathrm{NaAlSi}}_{3}{\mathrm{O}}_{8}\ifmmode\cdot\else\textperiodcentered\fi{}0.3{\mathrm{H}}_{2}\mathrm{O}$ containing dissolved water mainly in the form of $\mathrm{OH}$ groups. It is concluded that ${\mathrm{H}}_{2}\mathrm{O}$ molecules are the dynamic species in the above-mentioned time regime in the water-rich glasses. The dynamic process is probably a rotation of ${\mathrm{H}}_{2}\mathrm{O}$ molecules around their bisector axis.

Hybrid external fixation of distal tibial fractures: new strategy to place pins and wires without penetrating the anterior compartment.

Impalement of the anterior compartment musculature remains a problem in the hybrid external fixation of distal tibial fractures. The purposes of this study were to develop a tensioned wire configuration which does not violate the anterior compartment and to analyze the biomechanical implications of new wire configuration. Thirty-seven adult volunteers without known pathology around either tibia were recruited. Axial computed tomography of the distal tibia was performed at 5-mm slices from the plafond to the upper margin of the syndesmosis. The wire convergence angle was measured at the 1-, 2-, and 2.5-cm levels using the following landmarks: tibialis anterior tendon (TA), tibialis posterior tendon (TP), peroneus brevis tendon (PB), anterolateral border of the lateral malleolus (LM). Two straight lines were drawn by connecting TA and PB and connecting TP and LM. The wire convergence angle was defined as an acute angle between these two lines. Then the orientation of the bisector axis of the wires was measured. As a second part of this study, a validated three-dimensional hybrid external fixator model was developed using finite elements modeling to analyze the stiffness of the frames constructed according to the measured wire convergence angle and orientation. Five simulated configurations were tested. The stiffness of each frame was analyzed under four load conditions: torsion, axial compression, side bending, and anteroposterior bending. The mean convergence angle was 30 degrees irrespective of the level. The bisector axis was oriented towards the anterolateral direction about 20 degrees from the coronal plane. The stiffness of the frame constructed with a wire convergence angle of 30 degrees and an anterolateral wire orientation of 20 degrees was 20-30% less than that of the frame constructed with 60 degrees wires oriented in a coronal plane. The addition of an anteromedial half-pin increased the stiffness significantly. Two tensioned wires may be placed without violating the anterior compartment by using the above four clinically identifiable landmarks. Addition of a half-pin on the anteromedial surface of the distal articular fragment makes the frame markedly stiffer than is possible using the standard wire configuration.

Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes

Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a black hole shadow casted by a rotating black hole on an optically thick accretion disk and its dependence on an angular momentum of a black hole. We have found black hole shadows with a quite similar size and a shape for largely different black hole spin parameters and a same black hole mass. Thus, it is practically difficult to determine a spin parameter of a black hole from a size and a shape of a black hole shadow in an accretion disk. We newly introduce a bisector axis of a black hole shadow named a shadow axis. For a rotating black hole a shape and a position of a black hole shadow are not symmetric with respect to a rotation axis of a black hole shadow. So, in this case the minimum interval between a mass center of a black hole and a shadow axis is finite. An extent of this minimum interval is roughly proportional to a spin parameter of a black hole for a fixed inclination angle between a rotation axis of a black hole and a direction of an observer. In order to measure a spin parameter of a black hole, if a shadow axis is determined observationally, it is crucially important to determine a position of a mass center of a black hole in a region of a black hole shadow.

Experimental dosimetry of a 32P catheter-based endovascular brachytherapy source

The experimental dosimetry in a water phantom of a 32P linear source, 20 mm in length, used for the brachytherapy of coronary vessels is reported. The source content activity, A, was determined by means of a calibrated well ion-chamber and the value was compared with the contained activity reported in the manufacturer's certification. In this field of brachytherapy dosimetry, radiochromic film supplies a high enough spatial resolution. A highly sensitive radiochromic film, that presents only one active layer, was used in this work for the source dosimetry in a water phantom. The radiochromic film was characterized by electron beams produced by a clinical linac. A Monte Carlo calculation of beta spectra in water at different distances along the source transverse bisector axis allowed to take into account the low dependence of film response from the electron beam energy. The adopted experimental set-up, with the source in its catheter positioned on the film plane inside the water phantom, supplies accurate dosimetric information. The measured dose rate to water per unit of source activity at reference distance, Ḋ(r0, θ0)/A, in units of cGy s−1 GBq−1, was in agreement with the value reported in the manufacturer's certification within the experimental uncertainty. The radial dose function, g(r), is in good agreement with the literature data. The anisotropy function F(r, θ) is also reported. The analysis of the dose profile obtained at 2 mm from the source longitudinal axis shows that the uniformity is within 10% along 75% of the 20 mm treatment length. The adopted experimental set-up seems to be adequate for the quality control procedure of the dose homogeneity distribution in the water medium.

A standard dosimetry procedure for 192Ir sources used for endovascular brachytherapy

The experimental dosimetry of a high dose rate (HDR) 192Ir source used for the brachytherapy of peripheral vessels is reported. The direct determination of the reference air kerma rate K̇r agrees, within the experimental uncertainty, with the results obtained by a well ionization chamber calibrated at the NIST and the manufacturer's certification. A highly sensitive (HS) radiochromic film (RCF), that presents only one active layer, was used for the source dosimetry in a water phantom. The adopted experimental set-up, with the source in its catheter positioned on the RCF plane, seems to have given better accuracy of the RCF optical density measurements. The agreement between the measurement of the dose rate constant DKr(10 mm, π/2) and the literature data confirmed the coherence of the HS RCF calibration obtained by the kerma in air measurements. The RCF measurements supplied dosimetric information about the dose to water per reference air kerma rate Ḋ(r, θ)/K̇r along the source transverse bisector axis, the radial dose function g(r) and the anisotropy function F(r, θ). The value Ḋ(2 mm, π/2)/K̇r = 22.4 ± 1.2 cGy h−1/(μGy h−1) is supplied with a dose uncertainty that is essentially due to the indeterminacy of the source position in the catheter. The data of the radial and anisotropy functions have been compared with Monte Carlo determinations reported in the literature.

Peak in the magnetic-field dependence of diffusion-induced thermopower for n-Bi-Sb semiconducting alloys

A peak is detected on the dependence of the diffusion-induced thermopower on transverse magnetic field in degenerate semiconducting alloys n-Bi1−xSbx (0.07≤x≤0.15) doped with tellurium donor impurity. The temperature gradient is directed along the bisector axis C1 of the monocrystalline sample and the magnetic field is along the triad axis C3. The electron spectrum of the Bi-Sb alloys under investigation consists of three equivalent ellipsoids with distinctly different effective masses along the axes of the ellipsoid (m∥/m⊥). A simple kinetic theory shows that the presence of the peak on the diffusion thermopower is a manifestation of this strong anisotropy in the electron spectrum and of the additive contribution of all three ellipsoids to electron transport. The nonmonotonic dependence of thermopower on the transverse magnetic field makes it possible to determine the electron relaxation time, while the temperature dependence of this relaxation time can be used to separate the relaxation time for electrons scattered from ionized impurities and from acoustic phonons.

Alanine/EPR dosimetry in brachytherapy

The paper reports the experimental procedure adopted to determine the absorbed dose rate in water per reference air kerma rate, , along the transverse bisector axis of a brachytherapy source. The dose rate measurements have been carried out at difference distances, d, from the source using alanine dosemeters in a water phantom. The reference air kerma rate, , was determined adopting a `direct procedure' that uses a spherical ionization chamber in air. The dose rate constant of the source examined was . The values of the radial dose function along the transverse axis, g( d), determined with an uncertainty of 3.4% (1), were found to be in good agreement with the results reported in the literature. The uncertainty in dose rate value has been estimated as 2.8% (1) for distances from the source up to 7 cm. has been determined with 1.2% (1) uncertainty. So values were determined with 3% (1) uncertainty.

Transformation from internal coordinates to cartesian displacements in the Eckart frame for a triatomic molecule

Analytic expressions are obtained for the cartesian displacements in the Eckart frame that relate distorted and undistorted configurations for any triatomic molecule. The displacements are given in the terms of the instantaneous values of the internal coordinates ( r 1, r 2, θ). Besides their application in spectroscopy, these formulas could be useful in semiclassical simulations of molecular liquids. The present derivation recovers previous results for the angle of rotation between the instantaneous and Eckart bisector axis.

Applications of the Italian protocol for the calibration of brachytherapy sources

The Associazione Italiana di Fisica Biomedica (AIFB; Italian Association of Biomedical Physics) has adopted the Italian protocol for the calibration of brachytherapy sources. The AIFB protocol allows measurements of the reference air kerma rate, , within 1.7% . To measure the AIFB protocol has identified a direct and an indirect procedure. The direct procedure is based on the use of spherical or cylindrical ionization chambers as local reference dosimeters positioned along the transverse bisector axis of the source. Once the source is specified by a value, this can be used to calibrate a field instrument, such as a well-type ionization chamber, for further source calibrations by means of an indirect procedure. This paper reports the results obtained by the Physics Laboratory of the Università Cattolica del S Cuore (PL-UCSC), in terms of calibration of five types of source, , and . The role of the determination for a brachytherapy source has been underlined when a new source such as the seed model X1267 has been proposed for clinical use. The values for spherical sources differed by 5% from the vendor's mean value. The five types of source calibrated in terms of were used to obtain the calibration factor, , of an HDR-1000 well-type ionization chamber.

Cellulose and Cellulose/Poly(vinyl alcohol) Blends. 2. Water Organization Revealed by Solid-State NMR Spectroscopy

Cellulose as well as two cellulose/poly(vinyl alcohol) blends with compositions 60/40 and 80/20 w/w exposed to water are investigated by 1H-, 2H-, and 13C solid-state NMR spectroscopy. For pure cellulose, the lower temperature, secondary dielectric relaxation process can be attributed to the onset of motion of adsorbed water molecules as revealed by 2H-NMR spectroscopy. This water is not crystalline below 270 K. Three distinct kinds of water bound to the polymer matrix are detected, as far as dynamic behavior is concerned. First there is nonfreezable, strongly bound water that is rigid but amorphous at low temperatures. The second component is highly mobile and exhibits isotropic motion even below 270 K. Interestingly, there is a third component of water molecules that undergo well-defined 180° flips around their bisector axis with a rate greater than 105 s-1 due to anisotropic constraints. In contrast to the first two kinds, this component cannot be removed from the polymer matrix by drying even at eleva...

Dingle tehpeiutube under strong uniaxial cohpbession up to 0.3% and intervalley scattering in Bi-Sb at 4.2K

Abstract A sharp decrease in the Dingle temperature has been observed during uniaxial compression in the alloy Bi0.gSb0. 1 along the bisector axis. The decrease occurs because the interval ley scattering mechanism turns off upon the transition from a three-valev electron spectrum to a single-valley electron spectrum in the course of the deformation.

Saddle point in energy spectrum and intraband magnetic breakdown in semiconducting bismuth-antimony alloys under strong uniaxial pressure

In single-crystal Bi1-xSbx alloys (0.2<X<0.22) a semiconductor-metal transition under strong uniaxial compression up to 0.3% along the bisector axis has been observed and the Fermi surface (FS) appearing under deformation has been investigated. With the Fermi energy increasing the coalescence of two isolated electron pockets into a dumbbell-shaped FS (electronic topological transition) is observed. The data confirm the assumption that a saddle point should arise in the energy spectrum of Bi1-xSbx alloys at X>0.15. In the vicinity of the dumbbell-shaped FS formation the intraband magnetic breakdown has been observed.

Quantitative NMR studies of water in silicate glasses

The state of water in volcanic and synthetic silicate glasses is characterized by a number of different solid state NMR techniques. 1H solid echo NMR is used to quantitate total water contents reliably down to levels of 0.1 wt%. High-speed 1H magic-angle spinning NMR can be used to obtain relative species concentrations of OH and H 2O groups in glasses free from paramagnetic impurities. Similar results are obtained from deuterium quadrupolar echo NMR difference spectroscopy, utilizing the different spin-lattice relaxation times of OD and D 2O species. The results demonstrate that the percentage of water present in the form of molecular H 2O species increases with increasing total water content. The H 2O groups are anisotropically constrained, but undergo 180° flips about the bisector axis at rates greater than 10 5 s −1. The hydrous species are not clustered and are subjected to a distribution of hydrogen bonding strengths. A distribution function of O-D·O distances obtained from infrared results, shows good compatibility with the experimental 2H NMR lineshapes. The relative merits of the different experimental approaches are discussed in detail.