Quantum chaology of a two dimensional quartic oscillator system

此論文中我們透過二維之偶合四次方振子作為模型，得以討論古典渾沌所對應其自身量子行為的相關特徵，希望藉由本徵態在位置空間，及相空間的分佈來發掘一些古典不穩定軌道之新關聯，因此我們採用一些定量的方法來量測本徵態在空間中所佔據的有效體積。 首先以second moment of Husimi distribution的方法來計算量子態在相空間中所分佈之有效體積，並輔以Renyi length和位置空間的不準度(position uncertainty)等方式討論其本徵態在位置空間中之有效體積分佈情形。 我們還特別討論了一個著名的系統，其位能形式為x2y2/2。 此系統顯現出在特定能量下具有無限大的相空間體積，同時在座標軸上有著無限延展之通道等性質。 再者其古典行為除了有強渾沌的特性外也兼具著粒子會由這些通道逃逸而出的傾向。 我們藉由adiabatic approximation及對角化之數值計算，進一步發現到波函數在通道內形成局域化之最遠位置和自身能量的關係。 另外我們利用Shannon entropy，position uncertainty和Husimi distribution作為理解波函數分佈的有用資訊。 我們發現到波函數的局域化形態極易受到無窮延伸的通道所影響，這可由和一個同樣具有有限延展之通道之位能形式0.01(x4+y4)/4+x2y2/2比較得之。 另一方面此四次振子具備齊次(homogenous)性質，此這系統之古典分歧(bifurcations)行為可以由Yoshida公式來預測。 我們從自身之量子態的幾何訊息如相空間或位置空間中所佔之有效體積之分佈行為，指出可積系統的幾何相關量之於能譜呈現規律排列之特性。 也可發現到當系統逐漸轉變成渾沌系統時，會逐漸破壞這些規律關係。 同時也可見當此古典系統發生分歧時，所對應之量子態所佔之最小有效體積和古典分歧有著密切關聯。 最後我們也發現到有效體積在位置空間中和其古典遍歷假設的比值，顯示出可積系統下的波函數相較於不可積系統的波函數更顯現出局域化的傾向，同樣的反映出古典可積和不可積系統之軌道分佈行為。We study the correspondence between quantum and classical systems which have chaotic behaviors classically. The two-dimensional quartic oscillators are chosen as the model in this thesis. It is hoped that we can find some new connections between dispersion of eigenstates and classical unstable orbits. Several methods are adopted to measure the dispersion of eigenstates quantitatively; the volume occupied by a quantum eigenstate in phase space is calculated from the inverse second moment of Husimi distribution. The configuration space volume is with respect to the uncertainty and Renyi length of the eigenstate. We study a famous system with potential x2y2/2 which has the four infinite channels along the axes and an infinite phase space volume. The classical motion of this system not only reveals a chaotic behavior but also expels particle from the central region through the channels. We find some features of its localized eigenstates with the furthest extensions along the channels by the quantum adiabatic approximation and numerical calculation. From the information of eigenstates dispersion, they are Shannon entropy, position uncertainty and Husimi distribution. We show that the localization of eigenstate is strongly affected by the infinite channels. We also illuminate the obvious difference from a similar system with the potential 0.01(x4+y4)/4+x2y2/2 which has channels with finite spatial extension. On the other hand, this quartic oscillator is also a homogenous system, its classical bifurcations can be predicted by the Yashida formula. We also calculate the second moment of Husimi distribution, uncertainty and Renyi length to obtain geometric information from the corresponding quantum spectrum themselves. For the integrable systems, these geometric quantities appear to be in regular relation to the energies. When the system becomes chaotic gradually, parts of these regular relations are destroyed quickly. We indicated that the most localized states have some connections with classical bifurcations. Furthermore, we also find that the ratios of quantal dispersions in configuration space to ergodic limits have similar characteristic to the distributions of classical orbits in integrable and non-integrable systems

L-caldesmon alters cell spreading and adhesion force in RANKL-induced osteoclasts

Background Osteoclasts (OCs) are motile multinucleated cells derived from differentiation and fusion of hematopoietic progenitors of the monocyte-macrophage lineage that undergo a multistep process called osteoclastogenesis. The biological function of OCs is to resorb bone matrix for controlling bone strength and integrity, which is essential for bone development. The bone resorption function is based on the remodelling of the actin cytoskeleton into an F-actin-rich structure known as the sealing zone for bone anchoring and matrix degradation. Non-muscle caldesmon (l-CaD) is known to participate in the regulation of actin cytoskeletal remodeling, but its function in osteoclastogenesis remains unclear. Methods/results In this study, gain and loss of the l-CaD level in RAW264.7 murine macrophages followed by RANKL induction was used as an experimental approach to examine the involvement of l-CaD in the control of cell fusion into multinucleated OCs in osteoclastogenesis. In comparison with controls, l-CaD overexpression significantly increased TRAP activity, actin ring structure and mineral substrate resorption in RANKL-induced cells. In contrast, gene silencing against l-CaD decreased the potential for RANKL-induced osteoclastogenesis and mineral substrate resorption. In addition, OC precursor cells with l-CaD overexpression and gene silencing followed by RANKL induction caused 13% increase and 24% decrease, respectively, in cell fusion index. To further understand the mechanistic action of l-CaD in the modulation of OC fusion, atomic force microscopy was used to resolve the mechanical changes of cell spreading and adhesion force in RANKL-induced cells with and without l-CaD overexpression or gene silencing. Conclusions l-CaD plays a key role in the regulation of actin cytoskeletal remodeling for the formation of actin ring structure at the cell periphery, which may in turn alter the mechanical property of cell-spreading and cell surface adhesion force, thereby facilitating cell-cell fusion into multinucleated OCs during osteoclastogenesis

Modification of reduced graphene oxide layers by electron-withdrawing/donating units on molecular dopants: Facile metal-free counter electrode electrocatalysts for dye-sensitized solar cells

Small molecules of aniline (AN) and nitrobenzene (NB) doped on reduced graphene oxide nanosheets (rGO) represent the attractive Pt-free and earth abundant counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Scanning electron microscope and transmission electron microscope confirm a very thin layer structure with wrinkled and folded nanosheets. The binding between AN or NB and rGO is confirmed by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). In this work, two different redox electrolytes are investigated: I−/I3− and [Co(bpy)3]3+/2+. Compared to rGO electrode-based DSSCs, the AN-rGO (1:10) and NB-rGO (1:10) electrode-based DSSCs applying I−/I3− and [Co(bpy)3]3+/2+ electrolytes show 40–50% and 30–35% increase in power conversion efficiency, respectively. Furthermore, both AN-rGO (1:10) and NB-rGO (1:10) perform stably upon electrochemical continuous test. Such excellent photoelectric performance correlates with the induced charge transfer between reduced graphene oxide and the molecules which effectively promotes the reduction and regeneration of I−/I3− and [Co(bpy)3]3+/2+ ions

Synthesis and characterization of magnetic nanoparticles coated with polystyrene sulfonic acid for biomedical applications

The development of novel magnetic nanoparticles (MNPs) with satisfactory biocompatibility for biomedical applications has been the subject of extensive exploration over the past two decades. In this work, we synthesized superparamagnetic iron oxide MNPs coated with polystyrene sulfonic acid (PSS-MNPs) and with a conventional co-precipitation method. The core size and hydrodynamic diameter of the PSS-MNPs were determined as 8–18 nm and 50–200 nm with a transmission electron microscopy and dynamic light scattering, respectively. The saturation magnetization of the particles was measured as 60 emu g−1 with a superconducting quantum-interference-device magnetometer. The PSS content in the PSS-MNPs was 17% of the entire PSS-MNPs according to thermogravimetric analysis. Fourier-transform infrared spectra were recorded to detect the presence of SO3− groups, which confirmed a successful PSS coating. The structural properties of the PSS-MNPs, including the crystalline lattice, composition and phases, were characterized with an X-ray powder diffractometer and 3D nanometer-scale Raman microspectrometer. MTT assay and Prussian-blue staining showed that, although PSS-MNPs caused no cytotoxicity in both NIH-3T3 mouse fibroblasts and SK-HEP1 human liver-cancer cells up to 1000 μg mL−1, SK-HEP1 cells exhibited significantly greater uptake of PSS-MNPs than NIH-3T3 cells. The low cytotoxicity and high biocompatibility of PSS-MNPs in human cancer cells demonstrated in the present work might have prospective applications for drug delivery

Large-area, untethered, metamorphic, and omnidirectionally stretchable multiplexing self-powered triboelectric skins

Abstract Large-area metamorphic stretchable sensor networks are desirable in haptic sensing and next-generation electronics. Triboelectric nanogenerator-based self-powered tactile sensors in single-electrode mode constitute one of the best solutions with ideal attributes. However, their large-area multiplexing utilizations are restricted by severe misrecognition between sensing nodes and high-density internal circuits. Here, we provide an electrical signal shielding strategy delivering a large-area multiplexing self-powered untethered triboelectric electronic skin (UTE-skin) with an ultralow misrecognition rate (0.20%). An omnidirectionally stretchable carbon black-Ecoflex composite-based shielding layer is developed to effectively attenuate electrostatic interference from wirings, guaranteeing low-level noise in sensing matrices. UTE-skin operates reliably under 100% uniaxial, 100% biaxial, and 400% isotropic strains, achieving high-quality pressure imaging and multi-touch real-time visualization. Smart gloves for tactile recognition, intelligent insoles for gait analysis, and deformable human-machine interfaces are demonstrated. This work signifies a substantial breakthrough in haptic sensing, offering solutions for the previously challenging issue of large-area multiplexing sensing arrays

Annealing effect of NiO/Co90Fe10 thin films: From bilayer to nanocomposite

Exchange-biased bilayers are widely used in the pinned layers of spintronic devices. While magnetic field annealing (MFA) was routinely engaged during the fabrication of these devices, the annealing effect of NiO/CoFe bilayers is not yet reported. In this paper, the transition from NiO/Co90Fe10 bilayer to nanocomposite single layer was observed through rapid thermal annealing at different temperatures under magnetic field. The as-deposited and low-temperature (<623 K) annealed samples had rock salt (NiO) and face center cubic (Co90Fe10) structures. On the other hand, annealing at 623 K and 673 K resulted in nanocomposite single layers composed of oxides (matrix) and alloys (precipitate), due to grain boundary oxidization and strong interdiffusion in the NiO/CoFe and CoFe/SiO2 interfaces. The structural transition was accompanied by the reduction of grain sizes, re-ordering of crystallites, incensement of roughness, and reduction of Ni2+. When measured at room temperature, the bilayers exhibited soft magnetism with small room-temperature coercivity. The nanocomposite layers exhibited an enhanced coercivity due to the changes in the magnetization reversal mechanism by pinning from the oxides. At 10 K, the increased antiferromagnetic anisotropy in the NiO resulted in enhanced coercivity and exchange bias in the bilayers. The nanocomposites exhibited weaker exchange bias compared with the bilayers due to frustrated interfacial spins. This investigation on how the magnetic properties of exchange-biased bilayers are influenced by magnetic RTA provides insights into controlling the magnetization reversal properties of thin films

Oxidation-boosted charge trapping in ultra-sensitive van der Waals materials for artificial synaptic features

Exploitation of the oxidation behaviour in an environmentally sensitive semiconductor is significant to modulate its electronic properties and develop unique applications. Here, we demonstrate a native oxidation-inspired InSe field-effect transistor as an artificial synapse in device level that benefits from the boosted charge trapping under ambient conditions. A thin InOx layer is confirmed under the InSe channel, which can serve as an effective charge trapping layer for information storage. The dynamic characteristic measurement is further performed to reveal the corresponding uniform charge trapping and releasing process, which coincides with its surface-effect-governed carrier fluctuations. As a result, the oxide-decorated InSe device exhibits nonvolatile memory characteristics with flexible programming/erasing operations. Furthermore, an InSe-based artificial synapse is implemented to emulate the essential synaptic functions. The pattern recognition capability of the designed artificial neural network is believed to provide an excellent paradigm for ultra-sensitive van der Waals materials to develop electric-modulated neuromorphic computation architectures

Oxidation-boosted charge trapping in ultra-sensitive van der Waals materials for artificial synaptic features

Developing efficient memory and artificial synaptic systems based on environmentally sensitive van der Waals materials remains a challenge. Here, the authors present a native oxidation-inspired InSe field-effect transistor that benefits from a boosted charge trapping behavior under ambient conditions