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The study of spin–orbit coupling (SOC) of light is crucial to explore the light–matter interactions in sub-wavelength structures. By designing a plasmonic lattice with chiral configuration that provides parallel angular momentum and spin components, one can trigger the strength of the SOC phenomena in photonic or plasmonic crystals. Herein, we explore the SOC in a plasmonic crystal, both theoretically and experimentally. Cathodoluminescence (CL) spectroscopy combined with the numerically calculated photonic band structure reveals an energy band splitting that is ascribed to the peculiar spin–orbit interaction of light in the proposed plasmonic crystal. Moreover, we exploit angle-resolved CL and dark-field polarimetry to demonstrate circular-polarization-dependent scattering of surface plasmon waves interacting with the plasmonic crystal. This further confirms that the scattering direction of a given polarization is determined by the transverse spin angular momentum inherently carried by the SP wave, which is in turn locked to the direction of SP propagation. We further propose an interaction Hamiltonian based on axion electrodynamics that underpins the degeneracy breaking of the surface plasmons due to the spin–orbit interaction of light. Our study gives insight into the design of novel plasmonic devices with polarization-dependent directionality of the Bloch plasmons. We expect spin–orbit interactions in plasmonics will find much more scientific interests and potential applications with the continuous development of nanofabrication methodologies and uncovering new aspects of spin–orbit interactions.

Cherenkov radiation is studied analytically in a dispersive bianisotropic medium with magnetoelectric effect. This study is based on the vector-potential approach. Notable features such as double cones of Cherenkov radiation in magnetoelectric media are studied and the angle of propagation cones are calculated, which allow for characterizing magnetoelectric materials. We also analyze emitted electromagnetic fields in the spectral domain to obtain radiated power and momentum-resolved electron energy-loss spectra. The impact of magnetoelectric coefficients on characteristics of the Cherenkov radiation is also investigated in order to introduce parameters for the characterization of magnetoelectric materials.

Here, we numerically prove that light with linear polarization can be coupled to surface plasmon polaritons at an elliptical hole perforated in a gold layer to generate plasmonic vortex (PV). Benefiting from the smooth variation of the minor to major ellipse axes, a gradual variation in the phase profile of the generated PV is achieved. Regarding this, three types of independent arrays of elliptical holes are presented, which can produce uniform and high quality PVs with different topological charges at the center of the arrays. The first array can produce PV with topological charges of + 1 and − 1, depending on the polarization orientation of the incident light. In the second one, the topological charge of the PV can be switched between 0 and + 2, by switching the polarization direction of the incident light. In the third array, a robust PV with topological charge of + 1 is generated independent of possible tolerances in the polarization orientation. In order to use the generated PVs for plasmonic tweezing application, there are side fringes around the central vortex of the arrays that should be eliminated. To produce a single vortex, we propose metal-insulator-metal (MIM) structures, screening excessive fringes and allowing the central PVs to leak out. It is also demonstrated by simulation that target particles, such as gold and polystyrene spheres of subwavelength dimensions, can be efficiently manipulated by our MIM designs, suitable for different applications including local mixing, and applying switchable torque or force to target particles to explore their complete elastic characteristics.

Correlative electron-photon spectroscopy without a laser The multidisciplinary ERC Starting Grant project “Quantum Coherent Control: Self-Interference of Electron Beams with Nanostructures (NanoBeam)” combines experiments and simulations to develop scanning electron microscopes into a practical tool for probing electron dynamics at the nanoscale, opening new vistas for nanotechnology and materials science.

Nature physics 19(6), 869 - 876 (2023). doi:10.1038/s41567-023-01954-3, Ultrafast photon–electron spectroscopy in electron microscopes commonly requires ultrafast laser setups. Photoemission from an engineered electron source is used to generate pulsed electrons, interacting with a sample excited by the laser pulse at a known time delay. Thus, developing an ultrafast electron microscope demands the exploitation of extrinsic laser excitations and complex synchronization schemes. Here we present an inverse approach to introduce internal radiation sources in an electron microscope based on cathodoluminescence spectroscopy. Our compact method is based on a sequential interaction of the electron beam with an electron-driven photon source and the investigated sample. Such a source in an electron microscope generates phase-locked photons that are mutually coherent with the near-field distribution of the swift electron. We confirm the mutual frequency and momentum-dependent correlation of the electron-driven photon source and sample radiation and determine a degree of mutual coherence of up to 27%. With this level of mutual coherence, we were able to perform spectral interferometry with an electron microscope. Our method has the advantage of being simple, compact and operating with continuous electron beams. It will open the door to local photon–electron correlation spectroscopy of quantum materials, single-photon systems and coherent exciton–polaritonic samples with nanometre resolution., Published by Nature Publishing Group, Basingstoke

Inelastic interaction of free-electrons with optical near fields has recently attracted attention for manipulating and shaping free-electron wavepackets. Understanding the nature and the dependence of the inelastic cross section on the polarization of the optical near-field is important for both fundamental aspects and the development of new applications in quantum-sensitive measurements. Here, we investigate the effect of the polarization and the spatial profile of plasmonic near-field distributions on shaping free-electrons and controlling the energy transfer mechanisms, but also tailoring the electron recoil. We particularly show that polarization of the exciting light can be used as a control knop for disseminating the acceleration and deceleration path ways via the experienced electron recoil. We also demonstrate the possibility of tailoring the shape of the localized plasmons by incorporating specific arrangements of nanorods to enhance or hamper the transversal and longitudinal recoils of free-electrons. Our findings open up a route towards plasmonic near-fields-engineering for the coherent manipulation and control of slow electron beams for creating desired shapes of electron wavepackets.

In recent years, light with orbital angular momentum, or the so-called vortex beams, has been the subject of intense research, due to its applications in microscopy, telecommunications, and investigating the selection rules. Many efforts have been devoted to generate vortex beams using metasurfaces and metamaterials. However, most of them lack key properties in controlling the polarization, directionality and intensity of the light which is generated and directed from a localized radiation sources such as electron-beam induced emission. Recently, a photon-sieve structure has been designed, developed and characterized as an electron-driven photon source, which is formed by specific ordering of nanoholes in different sizes and lattices forming a helical arm in a thin layer of gold. Electron beams in a scanning electron microscope interacts with the surface of a photon-sieve structure acting as a broadband source of optical excitation. Both Chain plasmons and chiral surface plasmons are excited in this structure resulting in vortex beams propagating in vacuum. Here, we design a photon sieve structure that can generate vortex pairs, i.e., optical beams with entangled phase singularities of opposite signs associated with the topological charges. This phenomenon is experimentally studied utilizing a cathodoluminescence detector facilitated with angle-resolved mapping, polarimetry, and spectroscopy methods. Data obtained from the polarimeter suggests that the rotating behaviour of the vortices are caused by their orbital angular momentum rather than the polarization. Experimental data are further confirmed by numerical simulations suggesting that the interference between the propagating polaritons and reflection from the void ring is the main reason for observing counter propagating plasmons with opposite chirality in experimental images. We anticipate that this work presents a systematic method towards designing new generation of metasurfaces with the possibility to control directivity, angular momentum, and energy of the light beams.

Point-projection microscopy (PPM) with low energy electrons is developing into a powerful tool for holographic reconstruction of individual proteins and solid state nanostructures. In combination with laser-based photoemission schemes, it offers the exciting prospect of ultrafast coherent electron holography of single nanostructures. Such experiments would greatly benefit from a freestanding electron source with femtosecond time resolution, few-nm emitter size, and good coherence properties. Here, we use plasmonic nanofocusing on a conical gold taper and multiphoton photoemission from the taper apex to create such a source. It is implemented in a PPM setup and used to record in-line holograms of thin bundles of single-walled carbon nanotubes, demonstrating an effective emitter radius of less than 5 nm. We show that the same concept can also be transferred to tungsten tips, offering further improvements in emitter size and brightness. Numerical simulations show that such an ultrafast, low-energy electron s...

Dynamic toroidal multipoles are the third independent family of elementary electromagnetic sources in addition to electric and magnetic multipoles. Whereas the dipole–dipole coupling in electric and magnetic multipole families has been well studied, such fundamental coupling effects in the toroidal multipole family have not yet been experimentally investigated. Here we propose a plasmonic decamer nanocavity structure to realize transverse coupling between magnetic toroidal dipoles. The coupling effect was investigated both experimentally and theoretically, by means of electron energy-loss spectroscopy and energy-filtered transmission electron microscopy, together with finite-difference time-domain calculations. We observe that the coupling causes a reorientation of the magnetic moment loops surrounding the initial toroidal moments. This coupling results in three eigenstates of this toroidal system. The underlying coupling mechanism is qualitatively demonstrated. Our investigations pave the way toward a be...

Pre-diabetes is defined as an increase in blood glucose levels above normal, but not to the extent that it is considered diabetes. One way to control the progression of diabetes is to eat a healthy diet and exercise. Accordingly, the aim of this study was to investigate the effect of combined exercise and coffee consumption on fasting blood sugar and middle-aged pre diabetic men. In this study, 44 overweight middle-aged men with (body mass index of 28.3 ± 2.8 kg / m2) were purposefully selected and randomly divided into four groups of 11: Exercise Combination, coffee consumption, combined exercise + coffee consumption and control group were divided. Pre-test and post-test groups including weight, body mass index, percentage of fasting fat and blood glucose were measured 24 hours before and after the project. The training groups then performed the training protocol for 8 weeks, three sessions per minute and 90 minutes each session. The coffee and exercise + coffee group consumed 10 grams of coffee every other day. Data were analyzed using covariance test and significance level of 0.05. The results showed a significant decrease in body mass index, fat percentage and serum concentration of fasting blood glucose in the exercise groups compared to the control group (P> 5%). This study showed that combined exercise with coffee can be effective in controlling fasting blood sugar and abdominal obesity.

Dipole selection rules underpin much of our understanding in characterization of matter and its interaction with external radiation. However, there are several examples where these selection rules simply break down, for which a more sophisticated knowledge of matter becomes necessary. An example, which is increasingly becoming more fascinating, is macroscopic toroidization (density of toroidal dipoles), which is a direct consequence of retardation. In fact, dissimilar to the classical family of electric and magnetic multipoles, which are outcomes of the Taylor expansion of the electromagnetic potentials and sources, toroidal dipoles are obtained by the decomposition of the moment tensors. This review aims to discuss the fundamental and practical aspects of the toroidal multipolar moments in electrodynamics, from its emergence in the expansion set and the electromagnetic field associated with it, the unique characteristics of their interaction with external radiations and other moments, to the recent attempts to realize pronounced toroidal resonances in smart configurations of meta-molecules. Toroidal moments not only exhibit unique features in theory but also have promising technologically relevant applications, such as data storage, electromagnetic-induced transparency, unique magnetic responses and dichroism.

Photon induced near-field electron microscopy has been recently introduced to investigate the dynamics of near-field distributions in nanostructures, with femtosecond time and angstrom spatial resolution [1]. In this technique a laser beam excites both a photoemission electron gun and the sample inside an electron microscope chamber. The electron beams then probe the laser-induced excitations. Achieving attosecond temporal resolution to probe electron dynamics is however challenging, due to the requirement for a perfect synchronization between the electron waves and laser light. Recently an alternative approach based on cathodoluminescence (CL) has been proposed [2]. In this way, the interaction of swift electrons with a precisely designed electron-driven photon source (EDPHS) causes radiation of ultrashort optical pulses, which are focused onto the sample (Fig. 1a). The sample interacts with both the EDPHS radiation and the electron. The overall CL emission is controlled by the distance between the sample and the EDPHS. The distance-energy correlation map between the CL radiations from both the sample and EDPHS is then recorded and used to recover the spectral phase and time-resolved responses of the sample [3, 4] (Fig. 1b).

Interaction of a moving electron wave packet in free space with light and nanostructures have taken much attention recently, by the emergence of photon-induced near-field electron microscopy [1–2]. Electron beams can inelastically interact by laser-induced nearfield distribution of the nanostructures, opening ways in shaping the electron wave packets and characterization of plasmon polaritons. The interaction of high energy electron waves with laser-induced excitations in the sample is generally discussed within eikonal approximations, neglecting other effects which arise from the pondermotive forces and experienced elastic recoils [3–4]. In contrast, coherent control of above threshold ionization and high harmonic generation can be understood by interferences between different quantum paths, related to ponderomotive and absorptive parts in the minimal coupling Hamiltonian [5].

In this chapter, criteria for existence of propagating optical modes which are transversely bound at the interface of two materials are studied. In particular, quite general cases are considered, where the materials involved are assumed to be anisotropic, but also demonstrating magneto-electric effects. Moreover, surface states of two-dimensional materials like topological insulators and graphene are also modeled via consideration of a conductivity sheet existing at the interface. A characteristic equation for obtaining the propagation constant of generalized interface modes is presented. Furthermore, optical modes sustained by a thin film of anisotropic materials with magneto-electric effect and topological surface states are also investigated. It is shown that interface modes supported by such a system are hybrid in nature, and can be further decomposed into the well-known classes of transverse magnetic and electric modes, only at the absence of magneto-electric effect. Although the formulations driven here are mathematically abstract, they can be used to investigate polaritons in van der Waal materials, hyperbolic materials, and topological insulators.

EELS and CL have been introduced as efficient tools for probing nanooptical excitations in single nanostructures, with a nanometre spatial resolution and meV energy resolution. Thanks to the ultrafast interaction of localized relativistic electrons with the optical modes of nanostructures in TEMs, electron beams appear as an ultra-broadband probe of sample resonances. The inelastic interaction of a swift electron with nanostructures can be understood using a useful classical approach, as discussed in the previous chapter, that has been proven to be identical to the quantum-mechanical treatment when averaging over electron impact parameters weighted by the spot intensity (Ritchie and Howie in Philos Mag A 58(5):753–767, 1988 [3]).

Investigation of nanooptical systems by means of far-field optics suffers from the diffraction limit of light; hence, spatial resolutions beyond the optical wavelengths are hardly achievable. Many different approaches are employed to improve the spatial resolution. These methods have been shortly described in Chap. 1. Here, we briefly discuss in more details SNOM and PEEM, with the emphasis on the applicability of these methods to different optical systems and their advantages and limitations. EELS and CL will be more intensively described in the subsequent chapters.

Swift electrons can undergo inelastic interactions with single electrons as well as collective electron excitations within the sample, such as plasmon and phonon polaritons, as a result of which they lose energy (Garcia de Abajo in Rev. Mod. Phys. 82:209–275, 2010 [1]). Within the classical formalism, EEL spectra are theoretically rationalized by a simple but intuitive interpretation that has a direct correspondence with first principles, demanding that all inelastic signals are collected (Ritchie and Howie, in Philos. Mag. A 58:753–767, 1988 [2].

Combining laser and electron guns in electron microscopes has created a plethora of opportunities for characterizing the chemical reactions and near-field distributions of nanostructures (Park et al. in New J Phys 12:123028, 2010 [1]; Siwick et al. in Science 302:1382–1385, 2003 [2]; Barwick et al. in Nature 462:902–906, 2009 [3]; Zewail and Thomas in 4D electron microscopy, imaging in space and time. Imperial College Press, Singapore, 2010 [4]; Zewail in Science 328:187–193, 2010 [5]; Sciaini and Miller in Rep Prog Phys 74:096101, 2011 [6]; Miller in Annu Rev Phys Chem 65:583–604, 2014 [7]; Vanacore et al. in Nano Today 11:228–249, 2016 [8]). This method, which is called ultrafast electron diffraction or photon-induced near-field electron microscopy (PINEM), where for the former, diffraction patterns are acquired, and for the latter, spectra are acquired, has recently been further developed by several groups around the world (Lee et al. in Struct Dynam-Us 4:044023, 2017 [9]; Feist et al. in Nature 521:200–203, 2015 [10]; Piazza et al. in Nat Commun 6:6407, 2015 [11]; Bucker et al. in European Microscopy Congress 2016: Proceedings. Wiley-VCH Verlag GmbH & Co. KGaA, 2016 [12]; Cao et al. in Sci Rep 5:8404, 2015 [13]) into a time-resolved pump-probe characterization methodology. Photoemission electron guns are currently controlled to create sub-picosecond electron pulses with great spatial coherence, almost at the same level as that of field-driven electron guns (Ehberger et al. in Phys Rev Lett 114:227601, 2015 [14]). Moreover, by controlling the laser-electron jitter by means of microwave or THz cavities, the longitudinal broadening of the electron pulses has been considerably reduced (Walbran et al. in Phys Rev Appl 4:044013, 2015 [15]; Verhoeven et al. in Ultramicroscopy 188:85–89, 2018 [16]; Verhoeven et al. in Struct Dynam-Us 3:054303, 2016 [17]; Maxson et al. in Phys Rev Lett 118:154802, 2017 [18]; Yang et al. in Nat Commun 7:11232, 2016 [19]; Weathersby et al. in Rev Sci Instrum 86:073702, 2015 [20]). Additionally, it was recently demonstrated that the interaction of electron pulses with the laser-induced near field of nanostructures will cause the attosecond bunching of single-electron pulses in space-time (Priebe et al. in Nat Photonics 11:793–797, 2017 [21]). Here, we briefly discuss recent achievements in PINEM, with a focus on the electron-light interactions in the near field of nanoobjects and their combination with time-resolved spectroscopy. After that, we introduce new possibilities by exploring the photon-assisted domain and propose novel methods for revealing the spectral phase and investigating the mutual correlations among photonic systems.

Aligned with the technological developments of electron-based characterization techniques, our theoretical frameworks are yet to be adapted to the strong-laser and slow-electron regimes. More specifically, there exist certain domains where our adiabatic approximations might break down. This is practically important from several viewpoints: (i) in PPM, the shape and amplitude of electron beams are both strongly manipulated, in addition to their phase; (ii) even in free-space electron-light interactions, purely elastic approximations might appear to be a mere over-simplification (Kozak et al. in Nat Phys Lett, 2017 [1]); (iii) during the interaction of electron beams with gratings and light, electron bunching appears to be an additional mechanism to the electron acceleration, where both the acceleration and bunching mechanisms are controlled by the longitudinal broadening of the electron beam relative to the grating period (Talebi in New J Phys 18:123006, 2016 [2]); and (iv) shaped electron beams interacting with matter have different selection rules and might offer approaches for manipulating the electron-induced radiations (Sergeeva et al. in Opt Express 25:26310–26328, 2017 [3]; Tsesses et al. in Phys Rev A 95:013832, 2017 [4]; Kaminer et al. in Phys Rev X 6:011006, 2016 [5]). The last point is fundamentally important, as even for a single electron wave packet, when the electron beam is in a superposition of at least two momentum states, interferences between different quantum paths in the interaction of photons with the electron may occur (Peatross et al. in Phys Rev Lett 100:153601, 2008 [6]). As noted by Keitel and co-workers, the quantum eigenstates of electrons in a nonplanar laser beam or in general shaped light waves are unknown (Peatross et al. in Phys Rev Lett 100:153601, 2008 [6]). For this reason, the development of self-consistent numerical methods may facilitate a better understanding of the outcomes of experiments (Talebi in New J Phys 18:123006, 2016 [2]; White et al. in Phys Rev B 86:205324, 2012 [7]; Kohn et al. in Phys Rev 140:1133, 1965 [8]) and stimulate the design of new experiments.

The optical microscopy and spectroscopy of nano-objects and macromolecules demands the efficient coupling of far-field light to the microscopic scale extended at only a few percent of the optical wavelength. Thus, a far-field-to-near-field coupler is a vital tool in optical metrology, providing the ability to combine well-advanced optical techniques such as pump-probe spectroscopy and spectral interferometry with the microscopic world. Three-dimensional optical tapers, particularly metallic tapers, have been proposed [1], intensively investigated, and employed in many groups worldwide for this purpose [2, 3]. The concept that allows an efficient coupling of far-field light onto single nano-objects is adiabatic nanofocusing [1]. In adiabatic nanofocusing, the optical modes of a metallic taper evolve, via propagation along the shaft towards the apex, in an extremely efficient mode-conversion procedure and result in localization of the electromagnetic energy only at the very apex, extended within a few atomic scales, provided that the apex is sharp enough.

We investigate different dynamic mechanisms, reflection and phase matching, of surface plasmons in a three-dimensional single-crystalline gold taper excited by relativistic electrons. Plasmonic modes of gold tapers with various opening angles from 5° to 47° are studied both experimentally and theoretically, by means of electron energy-loss spectroscopy and finite-difference time-domain numerical calculations, respectively. Distinct resonances along the taper shaft are observed in tapers independent of opening angles. We show that, despite their similarity, the origin of these resonances is different at different opening angles and results from a competition between two coexisting mechanisms. For gold tapers with large opening angles (above ∼20°), phase matching between the electron field and that of higher-order angular momentum modes of the taper is the dominant contribution to the electron energy-loss because of the increasing interaction length between electron and the taper near-field. In contrast, reflection from the taper apex dominates the EELS contrast in gold tapers with small opening angles (below ∼10°). For intermediate opening angles, a gradual transition of these two mechanisms was observed.

Toroidal moments have recently attracted attentions as an individual class of moments, by expanding the vector potential and decomposing the third component into toroidal moments and magnetic quadrupoles. Toroidal moments sustain peculiar time-space symmetry relations and are known as hybrid modes, which can be only understood by including retardation effects. Here, we outline our recent attempts to realize toroidal moments in void oligomeric meta-molecules. These structures are investigated experimentally using electron energy-loss spectroscopy and numerically using finite-difference time-domain method. We discuss about various toroidal moments supported by these structures, the role of symmetry and topology in excitation of these moments, the radiation from electron-induced toroidal moments resolved by cathodoluminescence spectroscopy, and finally hybridization of toroidal moments in coupled oligomers. Our findings outline the necessity of including toroidal moments within the classes of electromagnetic moments, despite the current discrepancy about their significance.

Plasmon polaritons have revolutionized our world of nanophotonics. They have created a platform for enhanced light-matter interactions, propagation of light beyond the diffraction limit, and nanofocusing of electromagnetic energy. However, for applications in data processing and telecommunication, dissipation of optical energy in metallic waveguides is much beyond what can be tolerated for nanocircuitry. Recently other groups of polaritonic waves, namely photon polaritons, exciton polaritons, and Dirac plasmons have been demonstrated as possible candidates for nanophotonics1. Interestingly, a topological insulator like Bi2Se32, as well as heterostructures like graphene/hBN 3, can support coexisting polaritonic waves of all the kinds stated above. At THz frequencies and near to the Fermi energy level, those materials support both hyperbolic phonon polaritons and Dirac plasmons, whereas at infrared and visible ranges4,5 exists another channel for exciton-polariton mode. Here, we mainly discuss the dispersion of the surface polaritons and their spatiotemporal behaviors, at all the energy ranges stated above. We however mainly focus on an aspect of topological insulators which is less discussed beforehand, i.e. topological magnetoelectric effect6. We study the criteria for existence of propagating optical modes which are transversely bound at the interface of two materials. In particular, quite general cases are considered, where the materials involved are assumed to be anisotropic, but also demonstrating magneto-electric effects7. We also discuss the situations where the coexistence of Dirac and hyperbolic polaritons result in level repulsion. We further study the effect of topological magnetoelectric effect on the appearance of hybrid optical modes with various polarization states. In addition to surface polaritons, existence of wedges support another channel for long range propagation of hyperbolic polaritons, due to the coupling of two edge polaritons. We study here the behavior of hyperbolic wedge polaritons at visible and ultraviolet energy ranges. We discuss the radiation damping and long range propagation of hyperbolic wedge and surface polaritons, both theoretically and experimentally using electron energy-loss spectroscopy and finite-difference time-domain method. References 1 Basov, D. N., Fogler, M. M. & de Abajo, F. J. G. Polaritons in van der Waals materials. Science 354, aag1992 (2016). 2 Wu, J.-S., Basov, D. N. & Fogler, M. M. Topological insulators are tunable waveguides for hyperbolic polaritons. Phys. Rev. B 92, 205430 (2015). 3 Woessner, A. et al. Highly confined low-loss plasmons in graphene-boron nitride heterostructures. Nat. Mater. 14, 421-425 (2015). 4 Esslinger, M. et al. Tetradymites as Natural Hyperbolic Materials for the Near-Infrared to Visible. Acs Photon. 1, 1285-1289 (2014). 5 Talebi, N. et al. Wedge Dyakonov Waves and Dyakonov Plasmons in Topological Insulator Bi2Se3 Probed by Electron Beams. Acs Nano 10, 6988-6994 (2016). 6 Dziom, V. et al. Observation of the universal magnetoelectric effect in a 3D topological insulator. Nat. Commun. 8 15197 (2017). 7 Talebi, N. Optical modes in slab waveguides with magnetoelectric effect. J. Opt.-Uk 18, 055607 (2016)

The motion of nanomotors triggered by light sources will provide new alternative routes to power nanoarchitectures without the need of chemical fuels. However, most light-driven nanomotors are triggered by UV-light, near infrared reflection, or laser sources. It is demonstrated that nanocap shaped Au/TiO2 nanomotors (175 nm in diameter) display increased Brownian motion in the presence of broad spectrum visible light. The motion results from the surface plasmon resonance effect leading to self-electrophoresis between the Au and TiO2 layers, a mechanism called plasmonic photocatalytic effect in the field of photocatalysis. This mechanism is experimentally characterized by electron energy loss spectroscopy, energy-filtered transmission electron microscopy, and optical video tracking. This mechanism is also studied in a more theoretical manner using numerical finite-difference time-domain simulations. The ability to power nanomaterials with visible light may result in entirely new applications for externally powered micro/nanomotors.

Purpose: Biochemical markers such as cardiac troponin I (cTnI) and N-terminal pro B-type natriuretic peptide (NT-proBNP) have become indispensable tools for the diagnosis of myocardial injury, providing highly sensitive and specific information about cardiac cell damage and wall stress. The purpose of the present research was to examine the response of cardiac biomarkers to a soccer game in adolescent male soccer players. Methods: Twenty-two trained adolescent male soccer players (14–16 y) were selected in a purposive manner. Blood samples were taken before, immediately after, and 2 and 24 hours after the game for the determination of cTnI and NT-proBNP. Results: Serum concentration of cTnI and NT-proBNP increased immediately and 2 hours after the soccer game (P P = .002), whereas serum NT-proBNP levels returned to baseline. At no time point did any of the values exceed the upper reference value. Conclusions: This is the first study to investigate the acute responses of cardiac biomarkers to a soccer game in adolescent male players. The postgame elevation of cardiac biomarkers and their rapid recovery are indicative of a physiological rather than a pathological response.

Bi2Se3 has recently attracted a lot of attention because it has been reported to be a platform for the realization of three-dimensional topological insulators. Due to this exotic characteristic, it supports excitations of a two-dimensional electron gas at the surface and, hence, formation of Dirac-plasmons. In addition, at higher energies above its bandgap, Bi2Se3 is characterized by a naturally hyperbolic electromagnetic response, with an interesting interplay between type-I and type-II hyperbolic behaviors. However, still not all the optical modes of Bi2Se3 have been explored. Here, using mainly electron energy-loss spectroscopy and corresponding theoretical modeling we investigate the full photonic density of states that Bi2Se3 sustains, in the energy range of 0.8 eV-5 eV. We show that at energies below 1 eV, this material can also support wedge Dyakonov waves. Furthermore, at higher energies a huge photonic density of states is excited in structures such as waveguides and resonators made of Bi2Se3 due to the hyperbolic dispersion.

By energy-filtering transmission electron microscopy (EFTEM), we observe Fabry-Pérot-like surface plasmon resonances (SPRs) along the length of rectangular single and double slits drilled into free-standing thin silver films. These eigenmodes hybridize in closely situated slits. The nature of their lateral coupling is uncovered from finite-element simulations, which show that the symmetry and energy sequence of hybrid modes is governed by Babinet complementarity principles. Interestingly, the modes of a double slit system, being proto-self-complementary, may alternatively be explained by magnetic interactions between slit fields or by electrostatic interactions across the metallic bridge separating the slits.

In this work, with the help of the generalized multipole technique and an efficient iterative procedure, the complex propagation constant of a plasmonic waveguide comprised of an infinite array of silver nanorods is computed. Our analysis takes into account metallic losses reported elsewhere using experimental methods. A finite array of only eight silver nanorods is also investigated here. The finite array is investigated for its capability of guiding light waves when excited by a plane wave at the specific wavelengths of the guided modes of the corresponding infinite array.

We present a comprehensive theoretical and experimental investigation of the plasmon hybridization of coupled split-ring resonators by means of the electron energy-loss spectroscopy. Split-ring resonator is a key element in design of negative refractive index metamaterials, and has been therefore intensively studied in the literature. Here, our aim is the study of hybridization effects for higher-order non-dipolar modes, which have been not investigated beforehand. We provide a complete scheme of the multimodal distribution of the coupled and single-element split-ring resonators, with a precise attention to the hybridization of those modes according to the induced moments. Our study suggests a clear dominance of electric and magnetic dipole moments over higher-order modes in the far-field radiation spectrum.

We investigate the optical modes in three-dimensional single-crystalline gold tapers by means of electron energy-loss spectroscopy. At the very proximity to the apex, a broad-band excitation at all photon energies from 0.75 to 2 eV, which is the onset for interband transitions, is detected. At large distances from the apex, though, we observe distinct resonances with energy dispersions roughly proportional to the inverse local radius. The nature of these phenomena is unraveled by finite difference time-domain simulations of the taper and an analytical treatment of the energy loss in fibers. Our calculations and the perfect agreement with our experimental results demonstrate the importance of phase-matching between electron field and radiative taper modes in mesoscopic structures. The local taper radius at the electron impact location determines the selective excitation of radiative modes with discrete angular momenta.

The investigation of surface plasmon excitations has recently become a field of research due to their high potential to be applicable in sensors, information technologies, cancer research etc. These coherent delocalized electron oscillations are common at metal-dielectric interfaces. However, they also exist in highly doped semiconductors, conducting oxide system or graphene, i.e. in many other systems with high carrier mobility. This poses the question whether such resonances can also be observed at the insulator interfaces.

Photon-Induced near-field electron microscopy has provided a way for time-resolved spectroscopy of the plasmonic resonances at high spatial resolution using pulsed electrons of sub-picosecond durations as probes, while an optical pulse is used to excite the structure at a very high photonic state. Here, by considering the electron's self-radiation and the optical pulses, a numerical investigation of the effect of the optical intensities on the recorded spectra is demonstrated. It will be shown that by a deliberate tuning of the optical intensities, an interference pattern becomes visible, which can be used for the spectroscopy of plasmon modes with high temporal, energy and spatial resolution.

Background: Renal ischemia-reperfusion injury (IRI) is one of the most important causes of kidney injury, which is possibly gender-related. This study was designed to investigate the role of g-aminobutyric acid (GABA) against IRI in ovariectomized estradiol-treated rats. Methods: Thirty-five ovariectomized Wistar rats were used in six experimental groups. The first three groups did not subject to estradiol treatment and assigned as sham-operated, control, and GABA-treated groups. GABA (50 μmol/kg) and saline were injected in the treated and control groups 30 min before the surgery, respectively. The second three groups received the same treatments but received estradiol valerate (500 μg/kg, intramuscularly) 3 days prior to the surgery. The IRI was induced in the control and treated groups by clamping the renal artery for 45 min and then 24 h of reperfusion. All animals were sacrificed for the measurements. Results: The serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score significantly increased in the IRI rats (P < 0.05). GABA significantly decreased the aforementioned parameters (P < 0.05). The uterus weight increased significantly in rats that received estradiol (P < 0.05). Serum and kidney levels of nitrite (nitric oxide metabolite) did not alter significantly. Serum level of malondialdehyde increased significantly in the ovariectomized rats exposed to IRI (P < 0.05). Conclusions: It seems that GABA improved IRI in ovariectomized rats. Estradiol was also nephroprotective against IRI. However, co-administration of estradiol and GABA could not protect the kidney against IRI.

Using energy-filtered transmission electron microscopy we measured surface-plasmon resonances of gold nanoplatelets with different shapes and edge lengths at high spatial resolution. We find equidistant maxima of the energy-loss probability along the platelet edges. The plasmon dispersion of the different geometries is very similar, i.e., hardly dependent on specimen shape. The experimental results are verified by means of finite-difference time-domain calculations which reveal the presence of wedge-plasmon polaritons propagating along the platelet edges. At platelet corners, apart from radiative losses, wedge-plasmon polaritons are partially reflected or transmitted to neighboring edges. The interference of all these contributions leads to the observed plasmon resonance modes. This is an essential step towards a thorough understanding of plasmon eigenmodes in prismatic nanoplatelets.

Background: The most important cause of kidney injury is renal ischemia/reperfusion injury (IRI), which is gender-related. This study was designed to investigate the protective role of Γ-aminobutyric acid (GABA (against IRI in male and female rats. Materials and Methods: Thirty-six female and male wistar rats were assigned to six experimental groups. The IRI was induced by clamping renal vessels for 45 min then was performed reperfusion for 24 h. The group sex posed to IRI were pretreated with GABA and were compared with the control groups. Results: Serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score increased in the IRI alone groups, (P < 0.05), while GABA decreased these parameters in female significantly (P < 0.05), but not in male rats. Uterus weight decreased significantly in female rats treated with GABA. Testis weight did not alter in male rats. Serum level of nitrite and kidney level of malondialdehyde (MDA) had no significant change in both female and male rats. Kidney level of nitrite increased significantly in female rats experienced IRI and serum level of MDA increased significantly in males that were exposed to IRI (P < 0.05). Conclusion: GABA could ameliorate kidney injury induced by renal IRI in a gender dependent manner.