With the continuous growth of data storage demand, precise and stable magnetic-head positioning in hard disk drives (HDDs) remains essential. This paper proposes a disturbance-rejection-oriented control design for triple-stage actuator (TSA) systems. The approach employs Bode-plot analysis to achieve robust performance against plant perturbations while explicitly incorporating the stroke limits of Lead Zirconate Titanate (PZT) micro-actuators into controller synthesis. Stroke constraints are represented as forbidden regions on the Bode diagram, providing an intuitive feasibility criterion for controller design. The physical stroke limitation is formulated as an inequality condition and embedded directly in the loop-shaping procedure. Performance is evaluated through hybrid simulations in which numerical plant models identified from measured actuator frequency responses are driven by disturbance signals generated from measured disturbance characteristics. The results demonstrate that the proposed controllers significantly reduce the risk of micro-actuator saturation while preserving high positioning accuracy.
We construct a class of regular black hole solutions of the Fan-Wang type within quasi-topological gravity (QTG) in arbitrary spacetime dimensions greater than four. In contrast to the original Fan-Wang solution, which was obtained in four-dimensional general relativity coupled to nonlinear electrodynamics, our higher-dimensional generalization does not require any matter fields. Instead, regularity is achieved purely through an infinite tower of higher-curvature corrections. We demonstrate that the Fan-Wang-type metric is a solution to the QTG field equations by explicitly determining the corresponding coupling constants for each curvature order. Within an appropriate parameter regime, the solution describes an asymptotically flat black hole spacetime with a regular center. Remarkably, even in the case of negative mass, the geometry can remain completely regular, in sharp contrast to Einstein gravity.
We present independent polarimetric observations of the interstellar object 3I/ATLAS, including the first near-infrared polarimetric measurements. Using imaging polarimeters, we measured the degree of linear polarization from the visible RC band (0.64 mu m) to the near-infrared Ks band (2.25 mu m), and investigated its dependence on solar phase angle (polarization phase curve, PPC) and wavelength (polarization color curve, PCC). We confirm that the PPC of 3I/ATLAS differs significantly from those of typical solar system comets, showing an unusually large polarization amplitude. This PPC shows no significant change in the RC band across perihelion passage, despite the perihelion lying within the water snow line. This indicates that the unusual polarimetric behavior of 3I/ATLAS is unlikely to be driven by transient volatile activity, but instead reflects intrinsic optical properties of refractory dust particles. The PCC increases with wavelength over 0.6-1.2 mu m and peaks at 1.5-2.0 mu m, suggesting that the dominant scattering units are dust aggregates composed of submicron-sized monomers, broadly consistent with interstellar dust and solar-system cometary aggregates. Taken together, our results indicate that 3I/ATLAS preserves polarimetric properties characteristic of a primitive cometary planetesimal formed in another planetary system, with a refractory dust composition that differs from that typically observed among solar system comets, despite sharing a similar size scale of the aggregate building blocks.
Recently created biophysical methods, such as surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC), have been widely used to quantitatively study biomolecule interactions. The dissociation constant of the interaction with kinetic parameters, such as association rate constant and dissociation rate constant, can be obtained using SPR analysis. With thermodynamic parameters, such as enthalpy change and entropy change, the dissociation constant can be obtained by ITC analysis. Both methods differ not only in the type of information obtained but also in throughput and sample concentration. Analyzing the biophysical parameters of RNA-protein interactions will help us understand their functions in biological processes. In this chapter, we describe step-by-step SPR and ITC protocols suitable to study the kinetics and thermodynamics of RNA-protein interactions.
As antisense oligonucleotides, phosphorodiamidate morpholino oligonucleotides (PMOs) exhibit excellent properties. However, they possess two stereoisomers for each phosphorus atom, and these stereoisomers exhibit different physicochemical and biological properties. In this study, we developed a stereocontrolled synthesis method of dimethylamino phosphorochloridate monomers, which was used for a practical synthesis method of PMOs, from oxazaphospholidine derivatives. However, the condensation of a 5'-oxazaphospholidine derivative with an amine under acidic conditions is challenging because the resulting phosphoramidite intermediate can be activated under such conditions. To address this challenge, in the proposed synthesis method, a morpholino nucleoside 5'-oxazaphospholidine derivative was condensed with a phenol derivative with a low pKa value under acidic conditions. Subsequently, the resulting aryl phosphite was reacted with dimethylamine to yield a phosphoramidite, thereby liberating the phenol derivative as a leaving group. Chlorination of the phosphoramidite yielded a phosphorochloridate monomer in a highly stereoselective manner (dr = 93:7-97:3). Subsequently, the resulting chloridate monomer was stereospecifically condensed with the amino group of the morpholino nucleoside. The stereochemistry of the phosphorodiamidate morpholino dimers was unambiguously determined by nuclear magnetic resonance analysis. The results of this study facilitate the synthesis of stereocontrolled PMOs and the elucidation of their properties.
