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Eucalyptus is a plant that is able to absorb gold (Au) particles from the soil and store them in the leaves. Eucalyptus roots have the ability to penetrate the soil of the calcrete zone, which is rich in the mineral calcium (Ca). Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. and contains Au particles as impurities, making this plant a potential natural indicator (biogeochemical) of potential Au metal mining. The Au content in eucalyptus leaves can be determined by using the XRF (X-Ray Fluorescence) instrumentation material analysis method for qualitative analysis and AAS (Atomic Absorption Spectroscopy) for quantitative results. The form of XRF characterization of the intensity versus energy spectrum of certain elements from the XRF analysis results obtained is a spectrum with a peak power of 9.731 keV which indicates the presence of Au metal in the sample. The results obtained qualitatively are the Au metal content in the eucalyptus leaf sample of (9.0 ± 0.5) ppm. However, the Au metal content in each leaf sample was different. This provides information that Eucalyptus from different plants has the potential to be a biogeochemical indicator of potential Au metal mining in Indonesia

Carbon nanotubes (CNTs) have benefits in various fields, they are disadvantageous due to their tendency to form aggregates and poorly controlled alignment of the CNT molecules (characterized by order parameters). These deficiencies can be overcome by dispersing the CNTs in nematic liquid crystal (LC) and placing the mixture under the influence of an electric field. In this study, Doi and Landau–de Gennes free energy density equations are used to analytically confirm that an electric field increases the order parameters of CNTs and LCs in a dispersion mixture. The anchoring strength of the nematic LC is also found to affect the order parameters of the CNTs and LC. Further, increasing the length-to-diameter ratio of the CNTs increases their alignment without affecting the LC alignment. These findings indicate that CNT molecular alignment can be controlled by adjusting the CNT length-to-diameter ratio, anchoring the LCs, and adjusting the electric field strength.

A study to optimize a model of neutron radiation shielding for BNCT facility in the irradiation room has been performed. The collimator used in this study is a predesigned collimator from earlier studies. The model includes the selection of the materials and the thickness of materials used for radiation shield. The radiation shield is required to absorb leaking radiation in order to protect workers at the threshold dose of 20 mSv/year. The considered materials were barite concrete, paraffin, stainless steel 304 and lead. The leaking neutron radiation dose rates have been determined using Monte Carlo N Particle Version Extended (MCNPX) with a radiation dose limit rate that is less than 10 µSv/hour. This dose limit is in accordance with BAPETEN regulation related the threshold dose for workers, in which the working duration is 8 hours per day and 5 days per week. It is recommended that the best model for the irradiation room has a dimension 30 cm width, 30 cm length, 30 cm height and a main layer of irradiation room shielding made from the material paraffin which is 68 cm thickness on the left side and bottom of the irradiation room, 70 cm thickness on the right side of the iradiation room, 45 cm thickness on the front of the irradiation room and 67 cm thickness on the top of the irradiation room. The additional layers of 15 cm and 10 cm thickness are used along with paraffin in order to reduce the intensity of primary radiation from piercing the beamport after two primary layers. There is no neutron radiation leakage in this model.Keywords: Radiation shielding, BNCT, MCNPX, radiation dose rate, piercing beamport. OPTIMASI PERISAI RADIASI NEUTRON FASILITAS RUANGAN IRADIASI UNTUK BORON NEUTRON CAPTURE CANCER THERAPY (BNCT) DENGAN SUMBER BEAMPORT TEMBUS REAKTOR KARTINI. Telah dilakukan pemodelan perisai radiasi neutron untuk fasilitas Boron Neutron Capture Therapy (BNCT) pada sekeliling ruangan iradiasi. Pemodelan mencakup pemilihan bahan dan tebal yang digunakan untuk perisai radiasi. Perisai diharuskan mampu menahan radiasi yang keluar ruangan sehingga dosis radiasi berada di bawah ambang dosis bagi pekerja radiasi sebesar 20 mSv/tahun. Bahan yang dipertimbangkan adalah beton barit, paraffin, stainless steel 304 dan timbal. Perhitungan laju dosis neutron epitermal dilakukan dengan menggunakan program Monte Carlo N Particle Version Extended (MCNPX) dengan batasan laju dosis radiasi kurang dari 10 µSv/jam, sesuai dengan peraturan Kepala BAPETEN mengenai batas ambang laju dosis pekerja radiasi, dengan asumsi perhitungan waktu kerja 8 jam per hari dan 5 hari per minggu. Desain pertama dari empat desain yang telah dibuat kemudian dipilih sebagai desain yang direkomendasikan dengan laju dosis di bawah batas ambang 10 µSv/jam. Ruangan iradiasi memiliki dimensi panjang 30 cm, lebar 30 cm dan tinggi 30 cm. Lapisan utama perisai pada desain pertama berbahan paraffin setebal 68 cm pada sisi kiri dan bawah ruangan, 70 cm pada sisi kanan ruangan, 45 cm pada sisi depan ruangan dan 67 cm pada sisi atas ruangan. Paraffin setebal 15 cm dan 10 cm ditambahkan sebagai peredam intensitas radiasi primer dari beamport tembus yang masih cukup besar.Kata Kunci: perisai radiasi, BNCT, MCNPX, laju dosis radiasi, beamport tembus.

The translational flow in the low-frequency regime of electroconvection in parallelepiped sandwich cell of planar nematic liquid crystal has been observed. The dark and bright stripe pattern was observed to be shifting toward the center of the parallelepiped sandwich cell from both sides because of the horizontal component of the electric fields, E x * from indented (non-convection) area. The flow velocity, v ⃗ , linearly decreased as the flow reached the center of the cell. In addition, several control parameters were used to determine their relation with this flow. Increasing applied voltage and frequency monotonically decreased translational flow velocity. Whereas, increasing the temperature of the system caused an increase in flow velocity.

Aktuator elastik merupakan solusi rancang gerak kontinu pada bidang robotika. Penggunaan material magnetoelastik diusulkan sebagai alternatif aktuator elastik tersebut. Pada penelitian ini respon magnetik material magnetoelastik dikarakterisasi menggunakann set alat electromagnet pada suhu kamar (T = 27 oC). Komposisi penyusun sampel magnetoelastik yang digunakan terdiri dari bahan basis silikon (RTV Gasket, RTV 585, RTV 52) dan bahan magnet ferimagnetik magnetite (Fe3O4). Respon sampel teramati akibat pengaruh medan magnet luar (B). Melalui analisa grafik respon magnetik sampel dapat didekati dengan model persamaan kuadratik. Hasilnya adalah terdapat kompetisi antara sifat magnetik pengotor magnetite (Fe3O4) dengan total volume material magnetoelastik. Kompetisi kedua parameter tersebut bersifat tidak linier. Kompetisi ini bertanggung jawab atas hasil optimasi jenis dan optimasi konsentrasi. Jenis optimal bahan basis material magnetoelastik pada penelitian ini adalah RTV Gasket dan RTV 52, sedangkan konsentrasi optimal komposisi basis berbanding pengotornya adalah (50 : 50) %. Dalam penelitian ini juga diamati adanya sifat histerisis material magnetoelastik.

This paper describes a numerical method that used to solve the nonlinear Schr\"{o}dinger equation. The methods are an exponential time differencing method and a spectral method. The result indicates that at a certain parameter, fluctuation of wave function has contained chaotic dynamics. This case is expected to be used as an example for introducing numerical methods to undergraduate students on nonlinear dynamics. This introduction is deemed necessary, referring to the curriculum and syllabus used in several educational institutions in various countries that have included the topic of nonlinearity.

This paper presents one kind of numerical method for investigating a problems related to the surface effects and surface characterization of materials. The aim of this paper is to show development of technique, which is sufficiently simple but effective to compute the surface critical effects of materials. We study such problems on the frame work of the Ginzburg-Landau equations. We choose nucleation field (H c3 ) and the formation of a superconducting state in isotropic type II superconductors situated in magnetic fields, whose magnitude between H c2 and Hc 3 , as our physical case. Firstly we introduce the detailed variational approach which is close to the problem of finding the highest magnetic field for which the superconducting sheath states nucleates at the surface of the specimen. By considering the surface effect we can linearise the Ginzburg-Landau equation to get such kind of equation which is Schrodinger's equation like. We then describe a method for choosing a suitable trial function, which represents the behavior of superconducting order parameter. With Raleigh-Ritz principle the Eigen value of ground state which is related with critical magnetic field H c3 at which nucleation on the surface appears found computationally thus the methods used in this paper is useful in computational materials. The numerical relation of H c2 is represented by h with e that we have found, can be used to predict the nucleation field on specimen's surface. Beside that by considering angular variation of external magnetic field we find the relation of H c3 with H c2 fulfill H c3 =1.7H c2 and we show that our results are in agreement with physical argument.

In this research, we study Damped Kuramoto-Sivashinsky (DKS) equation, one of the famous nonlinear differential equation which exhibits turbulence. To solve DKS equation, we use Exponential Time Differencing (ETD) scheme which is combined with the Pseudospectral method. To know the effect of damping factor term, we analyze the resulting dynamics using Lyapunov exponent and total autocorrelation function. From that analysis, we elucidate the transition of Markovian to glassy dynamics in DKS equation. We conclude that there is a kind of mixing of several modes in the dynamics of the DKS equation which resulting the glassy dynamics in this system.

Parallel-aligned poly(vinyl alcohol) (PVA) nanofiber with a diameter of 240 ± 60 nm and an alignment parameter (S) of 0.95 ± 0.16 was obtained by a gap collector electrospinning that used copper (Cu) as a collector. The sandwiched cells (the horizontal-view and longitudinal-view) nematic liquid crystal was prepared by treating glass surfaces with the aligned PVA nanofiber to provide uniform anchoring of the director. When an electric field was applied to these samples, the electrohydrodynamic convection (EHC) pattern was observed. In the longitudinal-view cells, above a threshold voltage at low frequency, a typically low-frequency EHC rolls i.e., a Williams domain (WD) pattern was observed. By increasing the voltage, a fluctuating Williams domain (FWD) and grid patterns (GPs) could also be observed. In the transverse-view cells, at low-frequency regimes, WD, sawtooth patterned (STP), and dynamic scattering mode (DSM) patterns were observed. By replacing the conventional rubbing method with the use of parallel-aligned nanofibers, the well-known EHC phenomenon also could be observed.

The responses of soft-mode turbulence, a kind of spatiotemporal chaos seen in electroconvection of a nematic liquid crystal, to alternating-current magnetic fields is investigated to uncover the dynamical properties of spatiotemporal chaos. The dynamical responses can be measured by an order parameter, M(p)(t), which indicates ordering in the convective roll pattern induced by the magnetic field. Determined by properties of the liquid crystal in a magnetic field, M(p)(t) oscillates in accordance with the square of the magnetic field. The relaxation time of the system was obtained by fitting the frequency dependence of the complex susceptibility for the pattern obtained from the oscillation of M(p)(t) to the Debye-type relaxation spectra. However, for the high-frequency regime, the susceptibility deviates from the spectra because slow and large fluctuations of M(p)(t) contribute to the oscillation. The properties of this type of fluctuation were investigated by introducing a dynamic ordering parameter defined as the period average of M(p)(t).

Dalam penelitian kali ini akan dikaji fenomena konveksi listrik kristal cair nemaik homeotropik dibawah pengaruh medan magnet luar. Dalam percobaan dapat diamati fenomena munculnya defect pada soft mode turbulence yaitu spatiotemporal chaos akibat interaksi moda konveksi listrik dengan moda Nambu-Goldstone. Dapat diamati bahwa terjadi transisi keadaan defect ke keadaan non defect yang terjadi pada medan magnet kritis tertentu Hc = 450 G. Lebih lanjut dengan pengamatan cross polarizer telah berhasil dijelaskan femonena terjadinya transisi dari keadaan defect ke non defect tersebut. Hal itu diakibatkan oleh tertekannya kebebasan berotasi dari kristal cair nematik.

Soft-mode turbulence (SMT) is the spatiotemporal chaos observed in homeotropically aligned nematic liquid crystals, where non-thermal fluctuations are induced by nonlinear coupling between the Nambu-Goldstone and convective modes. The net and modal relaxations of the disorder pattern dynamics in SMT have been studied to construct the statistical physics of nonlinear nonequilibrium systems. The net relaxation dynamics is well-described by a compressed exponential function and the modal one satisfies a dual structure, dynamic crossover accompanied by a breaking of time-reversal invariance. Because the net relaxation is described by a weighted mean of the modal ones with respect to the wave number, the compressed-exponential behavior emerges as a superposition of the dual structure. Here, we present experimental results of the power spectra to discuss the compressed-exponential behavior and the dual structure from a viewpoint of the harmonic analysis. We also derive a relationship of the power spectra from the evolution equation of the modal autocorrelation function. The formula will be helpful to study non-thermal fluctuations in experiments such as the scattering methods., Comment: 17pages, 3 figures, to be published on AIP conference proceedings for "The 4th International Symposium on Slow Dynamics in Complex Systems"

Modal relaxation dynamics has been observed experimentally to clarify statistical-physical properties of soft-mode turbulence, the spatiotemporal chaos observed in homeotropically aligned nematic liquid crystals. We found a dual structure, dynamical crossover associated with violation of time-reversal invariance, the corresponding time scales satisfying a dynamical scaling law. To specify the origin of the dual structure, the memory function due to non-thermal fluctuations has been defined by a projection-operator method and obtained numerically using experimental results. The results of the memory function suggest that the non-thermal fluctuations can be divided into Markov and non-Markov contributions, the latter is called the turbulent fluctuation (TF). Consequently, the relaxation dynamics is separated into three characteristic stages: bare-friction, early, and late stages. If the dissipation due to TFs dominates over that of the Markov contribution, the bare-friction stage contracts; the early and late stages then configure the dual structure. The memory effect due to TFs results in the time-reversible relaxation at the early stage, and the disappearance of the memory by turbulent mixing leads to a simple exponential relaxation at the late stage. Furthermore, the memory effect due to TFs is shown to originate from characteristic spatial coherency called the patch structure., 9 pages, 10 figures

The autocorrelation function of pattern fluctuation is used to study soft-mode turbulence (SMT), a spatiotemporal chaos observed in homeotropic nematics. We show that relaxation near the electroconvection threshold deviates from the exponential. To describe this relaxation, we propose a compressed exponential appearing in dynamics of glass forming liquids. Our findings suggest that coherent motion contributes to SMT dynamics. We also confirmed that characteristic time is inversely proportional to electroconvection's control parameter., Comment: 4pages, 3 figures

Chaotic patterns in electroconvection of homeotropic nematics, soft-mode turbulence (SMT), and the related spatiotemporal chaos (STC) are discussed, and the quantitative definition of the patterns is considered. The order parameter S, obtained directly from the 2D spectra of the patterns, is introduced. The contribution of the Nambu-Goldstone mode and the increase in pattern regularity under the influence of an external magnetic field H are evaluated. We propose a schematic phase diagram of STC patterns based on the value of S.

We have found an unusual and unexpected link between micro- (nematic director) and macro- (velocity) fields in nematodynamics, which exhibits itself in extended defects of a new type. In particular, we have shown that black lines (BLs) observed in electroconvection of a homeotropically aligned nematic layer are simultaneously Bloch's domain walls for the director field and lines of zero velocity intersecting a roll pattern for the convection. A detailed experimental study revealing the fine structure of BLs and their point defects is presented.

We investigate the response of electroconvective patterns to an external magnetic field H in a homeotropic nematic system where spatiotemporal chaos called the soft‐mode turbulence (SMT) occurs. We introduce new order parameter Op, obtained directly from the amplitude spectrum of the patterns. We measure the degree of regularity of patterns under influence of H using Op and compare with the pattern ordering Mp obtained from analogy with the magnetization in 2D XY model. Our new order parameter Op is well proportional to Mp.

We have studied the soft-mode turbulence (SMT), a type of spatiotemporal chaos observed in the electroconvection of the homeotropic nematic liquid crystals, induced by nonlinear interaction between the long-wave length Nambu–Goldstone modes and the short-wave length convective modes. By applying an external magnetic field H, the NG mode can be controlled and as a result an ordered pattern may be observed. Transiently it is achieved by the dynamical changes of the many domains consisting of regular rolls. Removing the magnetic field, then, the ordered state relaxes to its original SMT pattern. The transient dynamics of such a relaxation process is also investigated. An order parameter called as M p is used as a quantitative indicator for the transient process. We reveal two regimes of relaxation process: regime I and regime II correspond to the superposition of the modes and the free rotation of wavevector q ( r ) of the electroconvective pattern, respectively.

We investigate the response of electroconvective patterns to an external magnetic field H in a homeotropic nematic system where spatiotemporal chaos called soft-mode turbulence (SMT) occurs. The pattern ordering M p , which shows pattern regularity in SMT, increases with the magnetic field H due to the suppression of the azimuthal rotational freedom. Three regions in the H -dependence of M p are found: the zero regime, the steep increase regime and the saturated regime. In the steep increase regime, M p shows a linear relation with \bar H 2 , from which the susceptibility χ p for the pattern ordering is obtained.