Hopf bifurcation control via a dynamic state-feedback control

To relocate two Hopf bifurcation points, simultaneously, to any desired locations in n-dimensional nonlinear systems, a novel dynamic state-feedback control law is proposed. Analytical schemes to determine the control gains according to the conditions for the emergence of Hopf bifurcation are derived. To verify the effectiveness of the proposed control law, numerical examples are provided.     

Applications of Raman spectroscopy in herbal medicine

Raman spectroscopic techniques are a group of chemical fingerprint detection methods based on molecular vibrational spectroscopy. They are compatible with aqueous solutions and are time saving, nondestructive, and highly informative. With complementary and alternative medicine (CAM) becoming increasingly popular, more people are consuming natural herbal medicines. Thus, chemical fingerprints of herbal medicines are investigated to determine the content of these products. In this study, I review the different types of Raman spectroscopic techniques used in fingerprinting herbal medicines, including dispersive Raman spectroscopy, resonance Raman spectroscopy, Fourier transform (FT)–Raman spectroscopy, surface-enhanced Raman scattering (SERS) spectroscopy, and confocal/microscopic Raman spectroscopy. Lab-grade Raman spectroscopy instruments help detect the chemical components of herbal medicines effectively and accurately without the need for complicated separation and extraction procedures. In addition, portable Raman spectroscopy instruments could be used to monitor the health and safety compliance of herbal products in the consumer market.     

A preliminary approach of dynamic identification of slender buildings by neuronal networks

The study of the dynamic behavior of slender masonry structures is usually related to the preservation of the historic heritage. This study, for bell towers and industrial masonry chimneys, is particularly relevant in areas with an important seismic hazard. The analysis of the dynamic behavior of masonry structures is particularly complex due to the multiple effects that can affect the variation of its main frequencies along the seasons of the year: temperature and humidity. Moreover, these dynamic properties also vary considerably in structures built in areas where land subsidence due to the variation of the phreatic level along the year is particularly evident: the stiffness of the soil–structure interaction also varies. This paper presents a study to evaluate the possibility of detecting the variation of groundwater level based on the readings obtained using accelerometers in different positions on the structure. To do this a general case study was considered: a 3D numerical model of a bellower. The variation of the phreatic level was evaluated between 0 and −20 m, and 81 cases studies were developed modifying the rigidity of the soil–structure interaction associated to a position of the phreatic level. To simulate the dispositions of accelerometers on a real construction, 16 points of the numerical model were selected along the structure to obtain modal displacements in two orthogonal directions. Through an adjustment by using neural networks, a good correlation has been observed between the predicted position of the water table and acceleration readings obtained from the numerical model. It is possible to conclude that with a discrete register of accelerations on the tower it is possible to predict the water table depth.     

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials.     

Asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through dynamic covalent kinetic resolution

The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures.     

The role of the dynamic pressure in stationary heat conduction of a rarefied polyatomic gas

The effect of the dynamic pressure (non-equilibrium pressure) on stationary heat conduction in a rarefied polyatomic gas at rest is elucidated by the theory of extended thermodynamics. It is shown that this effect is observable in a non-polytropic gas. Numerical studies are presented for a para-hydrogen gas as a typical example.     

Solid-State 17O NMR studies of organic and biological molecules: Recent advances and future directions

This Trends article highlights the recent advances published between 2012 and 2015 in solid-state ¹⁷O NMR for organic and biological molecules. New developments in the following areas are described: (1) new oxygen-containing functional groups, (2) metal organic frameworks, (3) pharmaceuticals, (4) probing molecular motion in organic solids, (5) dynamic nuclear polarization, and (6) paramagnetic coordination compounds. For each of these areas, the author offers his personal views on important problems to be solved and possible future directions.     

Chloride ion refined galvanic replacement: Boosting monodispersity of Au-Ag hollow nanoparticles & their enhanced applications

In this present work, we have redesigned the well-known Turkevich protocol for promoting versatile galvanic replacement, resulting in the synthesis of hollow Au nanostructures by the sacrificial reduction of HAuCl₄ on the as-prepared Ag nanoparticles in the presence of slight excess NaCl in order to dictate their core size to cavity ratio in a highly reproducible manner. The significance of chloride ion interaction in tuning the size/shape control was corroborated with the contrasting effect of other halide ions, namely bromine and iodine. The structure-property functional relationship of these artificial hollow metal nanostructures were not only established using the systematic optical absorption and TEM measurements, but also through enhanced spectroscopy measurements such as SEIRA and SERS, elucidating the dynamic advantage of hollow nanostructures over and above their solid monometallic counterparts. Further, the familiar 4-NA to p-PDA catalytic reduction kinetics demonstrate the unusual zeroth order characteristics in the presence of hollow metal nanostructures, unequivocally distinguishing it from the common first order characteristics associated with the corresponding solid metal nanoparticles, essentially attributed to the morphology tuned accessible higher total surface area, thus exemplifying the aesthetic compliance for future technological applications.