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The sense of smell is one of the most important organs in humans, and olfactory imaging can detect signals in the anterior orbital frontal lobe. This study assessed olfactory stimuli using support vector machines (SVMs) with signals from functional near-infrared spectroscopy (fNIRS) data obtained from the prefrontal cortex. These data included odor stimuli and air state, which triggered the hemodynamic response function (HRF), determined from variations in oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) levels, photoplethysmography (PPG) of two wavelengths (raw optical red and near-infrared data), and the ratios of data from two optical datasets. We adopted three SVM kernel functions (i.e., linear, quadratic, and cubic) to analyze signals and compare their performance with the HRF and PPG signals. The results revealed that oxyHb yielded the most efficient single-signal data with a quadratic kernel function, and a combination of HRF and PPG signals yielded the most efficient multi-signal data with the cubic function. Our results revealed superior SVM analysis of HRFs for classifying odor and air status using fNIRS data during olfaction in humans. Furthermore, the olfactory stimulation can be accurately classified by using quadratic and cubic kernel functions in SVM, even for an individual participant data set.

The focus of this article is on a male patient with hearing loss who was diagnosed with COVID-19 after returning to Taiwan from overseas. Due to the severe pneumonia infiltration, the patient received the clinical-trial treatment Remdesivir. In addition to facing the isolation and new-drug-related anxieties of the patient, the medical team faced difficulties in communicating effectively with the patient and in helping him through the isolation period. During the period of hospitalization (March 14th to April 13th, 2020), the author used Roy's adaptation model to perform a nursing assessment, which confirmed that the patient faced the following problems: (1) ineffective breathing pattern related to COVID-19, (2) impaired verbal communication related to hearing impairment, and (3) social isolation related to the isolation experience and the communication barrier with healthcare workers. During the nursing care process, the author helped the patient receive the antiviral treatment and taught him how to do diaphragmatic breathing in a comfortable, recumbent position to improve his breathing pattern. To reduce the difficulty of communication, the author made a pile of cards with common care-related words, provided pen and paper to write, and used a mobile-phone-based social-networking application to communicate with the patient. The author used writing to communicate with the patient and learned some simple signs from him to enable interaction. Moreover, the intervention helped him adapt to the isolation and treatment protocols to reach holistic nursing care. Based on this experience, the author suggests that hospitals cooperate with sign language organizations to teach healthcare workers simple communication skills, including sign language and cards to provide more complete care for patients with hearing loss during hospitalization.照顧一位確診嚴重特殊傳染性肺炎聽障人士之護理經驗.本文描述一位境外感染新型冠狀病毒確診為嚴重特殊傳染性肺炎聽障個案，除了個案要面對傳染性疾病被隔離的情境與輸注新藥的不安外，也考驗醫護人員如何與其有效溝通。筆者於2020年3月14日至4月13日護理期間運用羅氏適應模式進行評估，確立個案健康問題有因罹患嚴重特殊傳染性肺炎導致低效性呼吸型態，因聽障導致與醫護人員間有言辭溝通障礙，另外因隔離治療及溝通障礙導致社交隔離。護理過程協助個案進行抗病毒藥物治療，教導個案採舒適坐臥及使用腹式呼吸改善低效性呼吸型態；運用自製字卡、提供紙筆與手機通訊軟體，提高個案與醫護人員間溝通的效能；使用紙筆交流並向其學習簡單手語，增進與個案的互動，使其適應隔離治療並配合後續治療，達成整體性的照護。藉此護理經驗建議醫院可與手語翻譯組織合作，提供醫護人員學習簡單的溝通技巧包含手語或圖卡等，以利日後提供給住院聽障人士更加完善的照護。.

With innovative modern material-growth methods, a broad spectrum of fascinating materials with reduced dimensions-ranging from single-atom catalysts, nanoplasmonic and nanophotonic materials to two-dimensional heterostructural interfaces-is continually emerging and extending the new frontiers of materials research. A persistent central challenge in this grand scientific context has been the detailed characterization of the individual objects in these materials with the highest spatial resolution, a problem prompting the need for experimental techniques that integrate both microscopic and spectroscopic capabilities. To date, several representative microscopy-spectroscopy combinations have become available, such as scanning tunneling microscopy, tip-enhanced scanning optical microscopy, atom probe tomography, scanning transmission X-ray microscopy, and scanning transmission electron microscopy (STEM). Among these tools, STEM boasts unique chemical and electronic sensitivity at unparalleled resolution. In this Perspective, we elucidate the advances in STEM and chemical mapping applications at the atomic scale by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy with a focus on the ultimate challenge of chemical quantification with atomic accuracy.

Essential structural properties of the non-trivial “string-wall-bounded” topological defects in hexagonal manganites are studied through homotopy group theory and spherical aberration-corrected scanning transmission electron microscopy. The appearance of a “string-wall-bounded” configuration in RMnO3 is shown to be strongly linked with the transformation of the degeneracy space. The defect core regions (~50 Å) mainly adopt the continuous U(1) symmetry of the high-temperature phase, which is essential for the formation and proliferation of vortices. Direct visualization of vortex strings at atomic scale provides insight into the mechanisms and macro-behavior of topological defects in crystalline materials.

We have investigated the crystal structures and magnetic properties of DyFe1-xMnxO3 (x = 0 -1) perovskites. The Jahn-Teller distortion characteristic to the constituent Mn3+ was explored to result in the predominance of the bc-plane sublattice and the possibly effective orbital-ordering onset for x ≥ 0.5. At the composition of x = 0.5, an unexpected weak ferromagnetism-like ordering was also characterized, never documented before, and persists up to x = 0.9. This magnetic ground state is preliminarily discussed within the framework of Dzyaloshinskii-Moriya interaction conventionally for weak ferromagnetism, suggesting an intriguing coupling between the lattice and spin degrees of freedom in the bc-plane sublattice. Future electronic explorations for the interplay among the lattice, orbital, and spin degrees of freedom in the solid solution would disentangle the microscopic details dictating the rich magnetic properties of the materials.

Electronic excitations of single ZnO rectangular nanorod have been investigated by electron energy-loss spectroscopy in conjunction with scanning transmission electron microscopy (STEM-EELS). We focus primarily on the surface excitations greatly enhanced at the grazing incidence parallel to the surfaces of ZnO nanorods. An uncommon kind of surface excitation known as surface exciton polaritons occurring near interband transitions is found to dominate in the spectral range between the band gap at 3.4 eV and the surface plasmon peak at 15.8 eV. In addition, the dielectric function of ZnO up to 25 eV has also been derived from the bulk excitation spectra using the Kramers–Kronig analysis on a single nanorod. Theoretical EELS simulations are also compared with the experimental results and good agreements are obtained.

Spectroscopic investigations of individual single-crystalline GaN nanowires with a lateral dimensions of approximately 30-90nm were performed using the spatially resolved technique of electron energy-loss spectroscopy in conjunction with scanning transmission electron microscope showing a 2-A electron probe. Positioning the electron probe upon transmission impact and at aloof setup with respect to the nanomaterials, we explored two types of surface modes intrinsic to GaN, surface exciton polaritons at approximately 8.3eV (approximately 150nm) and surface guided modes at 3.88eV (approximately 320nm), which are in visible/ultra-violet spectral regime above GaN bandgap of approximately 3.3eV (approximately 375nm) and difficult to access by conventional optical spectroscopies. The explorations of these electromagnetic resonances might expand the current technical interests in GaN nanomaterials from the visible/UV range below approximately 3.5eV to the spectral regime further beyond.

Vertically aligned indium oxide nanowires were grown on a-plane sapphire substrate by the method of catalyst-assisted carbothermal reduction. The morphology and crystal structure of the nanowires are determined by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. Two types of In 2 O 3 nanowires were found by controlling the growth conditions. The nanowires with a hexagonal cross-section were shown to grow in [1 1 1] direction, whereas those with a square cross-section grow in [0 0 1] direction. In addition to the temperature effects, the concept of supersaturation in Au catalyst is proposed to explain the formation of these two types of nanowires. Besides, tapering, which is explained with the interplay between the vapor–liquid–solid and vapor–solid growth mechanisms, is observed in the nanowires.

Here, we demonstrate that non-dipole allowed d-d excitations in NiO can be measured by electron energy loss spectroscopy (EELS) in transmission electron microscopes (TEM). Strong excitations from (3)A(2g) ground states to (3)T(1g) excited states are measured at 1.7 and 3 eV when transferred momentum are beyond 1.5 A(-1). We show that these d-d excitations can be collected with a nanometrical resolution in a dedicated scanning transmission electron microscope (STEM) by setting a good compromise between the convergence angle of the electron probe and the collected transferred momentum. This work opens new possibilities for the study of strongly correlated materials on a nanoscale.

[*] Dr. K. H. Chen, M. H. Wu, W. C. Chen Institute of Atomic and Molecular Sciences, Academia Sinica No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan) E-mail: chenkh@pub.iams.sinica.edu.tw Dr. L. C. Chen, Dr. C. H. Chen, Dr. K. H. Chen Center for Condensed Matter Sciences, National Taiwan University No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan) E-mail: chenlc@ntu.edu.tw C. H. Lin, Prof. J. H. Lee Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University No. 1, Sec. 4, Roosevelt Rd., Taipei 106 (Taiwan)

Magnetically separable Fe2O3@SBA-15 nanocomposite with fully open mesochannels and bifunctional surface properties was prepared by selective deposition of iron oxide nanoparticles in the micropores of mesoporous SBA-15 silica with hydrophobic mesopore surface. The iron oxide nanoparticles embedded in the micropores were estimated to be composed of 67% α-Fe2O3 and 33% γ-Fe2O3, and the nanocomposite was found to exhibit superparamagnetic properties. With the bifunctional surface properties, the Fe2O3@SBA-15 nanocomposite showed enhanced adsorption capacity for cytochrome c and a maximum saturated uptake at neutral solution pH.

Recently, interesting differences for ion – uniform film and ion – nanostructure interaction phenomena, particularly relating to ion beam mixing effects have been reported. Upon irradiation with 1.5 MeV Au 2+ ions on isolated Au nanostructures on silicon substrate, a higher probability of crater formation, larger sputtered particle size and its coverage and enhanced sputtering yield compared to the continuous films of Au on Si substrate were observed. Ion bombardment at high flux (≈6.3 × 10 12 ions cm −2 s −1 ) showed a dramatic mass transport from nanostructures extending up to a distance of about 60 nm into the substrate, much beyond their size. In this paper, RBS/Channeling results would be presented to elucidate on the arrangement of re-distributed gold atoms location in silicon and silicide matrix. Scanning transmission electron microscopy (STEM, with high angle annular dark field imaging) was used to complement the RBS results in determining the unusual mass transport and under ion–nanostructure interaction. The amorphous nature of the silicon matrix, that is deduced from both the RBS/Channeling and from TEM measurements, is an important factor in enhanced diffusion process resulting in dramatic mass flow.

A procedure for the selective surface functionalization of the mesopores and micropores of mesoporous silica SBA-15 has been developed. The resulting bifunctional material has been used to incorporate Pd nanoparticles in the micropores. The method described provides a general route for creating different local environments within the nanometer-sized pore structure and for the selective deposition of guest species in the micropores of this type of bimodal porous materials.

This is a study of hybrid photovoltaic devices based on TiO2 nanorods and poly[2-methoxy-5-(2 � -ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). We use TiO 2 nanorods as the electron acceptors and conduction pathways. Here we describe how to develop a large interconnecting network within the photovoltaic device fabricated by inserting a layer of TiO2 nanorods between the MEH-PPV:TiO2 nanorod hybrid active layer and the aluminium electrode. The formation of a large interconnecting network provides better connectivity to the electrode, leading to a 2.5-fold improvement in external quantum efficiency as compared to the reference device without the TiO2 nanorod layer. A power conversion efficiency of 2.2% under illumination at 565 nm and a maximum external quantum efficiency of 24% at 430 nm are achieved. A power conversion efficiency of 0.49% is obtained under Air Mass 1.5 illumination. (Some figures in this article are in colour only in the electronic version)

We report on the midinfrared emission from electroluminescent devices with quantum cascade active regions based on InGaAs/InP heterostructures. We observe emission at λ∼12 μm from two different structures and compare their emission characteristics based on the different band structure designs. Their relevance in view of the realization of InP-based quantum cascade lasers with aluminum-free waveguides is discussed.

Hydrophobic organosilicates with controlled morphologies at the nanometer length scale have many potential applications in microelectronics and photonics. Here we report the use of block copolymers...

It has been common practice for physicists to assume electronic homogeneity when dealing with condensed matter properties. Recent experimental development, which have revealed fascinating properties of complex materials, demonstrate that such extraordinary macroscopic properties are often associated with microscopic-scale electronic/magnetic inhomogeneity, which limits the Hamitonian-type theoretical approach. Herein, we discuss the microscopic coexistence of metallic and insulating phases in novel materials having an intricate interplay among charge/spin/lattice degrees of freedom. Examples include the coexistence of superconducting-metallic and insulating phases in La 2 CuO 4+ δ as well as Mg 1− x B 2 . The insulating nature in La 2 CuO 4+ δ originates from electron–electron correlation, but disorder plays a dominant role in producing the insulating behavior in Mg-deficient Mg 1− x B 2 . We also examine the microscopic coexistence of ferromagnetic-metallic and charge-ordered-insulating phases in mixed-valent manganites, exhibiting colossal magnetoresistance. Possible origins of this electronic phase separation are discussed.

Melting of the charge-ordered state in $(\mathrm{La},\mathrm{Ca}){\mathrm{MnO}}_{3}$ and $(\mathrm{Pr},\mathrm{Ca}){\mathrm{MnO}}_{3}$ is characterized by an anomalously large decrease of the wave vector\char22{}as much as $25%$ through the transition. High resolution lattice images obtained from electron microscopy reveal that the large change occurs as a result of formation of new clusters with charge-ordering modulation wavelength increased by integral lattice parameter. Our findings can be attributed to the discrete nature of the charge ordering on the manganese sites.

Commensurate and incommensurate charge ordering in La 1-x Ca x MnO 3 are investigated by high resolution electron microscopy at low temperatures. Commensurability of charge ordering is mainly red by the doped charge carrier concentration x. Commensurate charge ordering arises due to periodic array of pairs of the Jahn-Teller distorted Mn 3+ O 6 stripes. The discrete nature of the charge ordering gives rise to a few distinct commensurate periodicities of 2, 3, 4, and 5 time the lattice parameter at of the orthorhombic cell, which correspond to the commensurate carrier concentrations for x = 1/2, 2/3, 3/4, and 4/5, respectively. An incommensurate charge ordered state with arbitrary carrier concentration occurs as a result of the fine random mixtures of the two adjacent commensurate configurations according to the lever rule.

Microstructure related to the charge ordered (CO) state and metal-insulator (MI) transition in ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}$ was investigated by transmission electron microscopy. An in situ observation on heating from the CO state revealed a drastic change in the microstructure: the nucleation and growth of the ferromagnetic (FM) charge disordered regions proceed in the vicinity of the antiphase boundaries in the CO regions, which are closely related to the MI transition around 160 K. These transition processes suggest that an abrupt increase in the electronic conductivity during the MI transition is mainly due to the percolation mechanism. Furthermore, the FM metallic phase is found to be characterized by a spatially fine mixture of incommensurate charge ordered microdomains in the FM charge disordered phase. This result clearly demonstrates the occurrence of microscopic-scale electronic phase separation in the manganese oxides.

Colossal magnetoresistance1—an unusually large change of resistivity observed in certain materials following application of magnetic field—has been extensively researched in ferromagnetic perovskite manganites. But it remains unclear why the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced. In these materials, T C varies sensitively with changing chemical pressure; this can be achieved by introducing trivalent rare-earth ions of differing size into the perovskite structure2,3,4, without affecting the valency of the Mn ions. The chemical pressure modifies local structural parameters such as the Mn–O bond distance and Mn–O–Mn bond angle, which directly influence the case of electron hopping between Mn ions (that is, the electronic bandwidth). But these effects cannot satisfactorily explain the dependence of magnetoresistance on T C. Here we demonstrate, using electron microscopy data, that the prototypical (La,Pr,Ca)MnO3 system is electronically phase-separated into a sub-micrometre-scale mixture of insulating regions (with a particular type of charge-ordering) and metallic, ferromagnetic domains. We find that the colossal magnetoresistive effect in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent ferromagnetic domains which can be controlled by applied magnetic fields.

Impurity effects on charge ordering (CO) as well as magnetic ground states in perovskite-type manganites are investigated. We found that the CO state becomes short-ranged with a small amount of imp...

The propensity of systems of charge and spin to form, under certain conditions, ‘stripe’ phases has recently attracted much attention, as it has been suggested that dynamically fluctuating stripe phases may be of central importance for an understanding of the physics of high-temperature superconductors1,2,3,4,5. A related phenomenon — static charge stripes — characterizes6 the insulating antiferromagnetic ground state of the manganese oxides, a class of materials which (like the copper oxide superconductors) have a perovskite structure, and are notable for their extraordinary electronic and magnetic properties, such as colossal magnetoresistance and charge ordering7,8. Here we report a different pattern of charge localization in the charge-ordered phase of the manganese oxide La1−xCaxMnO3 (x ⩾ 0.5). This pattern takes the form of extremely stable pairs of Mn3+O6 stripes, with associated large lattice contractions (due to the Jahn–Teller effect), separated periodically by stripes of non-distorted Mn4+O6 octahedra. These periodicities, which adopt integer values between 2 and 5 times the lattice parameter of the orthorhombic unit cell, correspond to the commensurate carrier concentrations (x = 1/2, 2/3, 3/4 and 4/5): for other values of x, the pattern of charge ordering is a mixture of the two adjacent commensurate configurations. These paired Jahn–Teller stripes appear therefore to be the fundamental building blocks of the charge-ordered state in the manganese oxides, and so may be expected to have profound implications for the magnetic and transport properties of these materials.

Visually-induced near-infrared spectroscopy (NIRS) response was utilized to design a brain computer interface (BCI) system. Four circular checkerboards driven by distinct flickering sequences were displayed on a LCD screen as visual stimuli to induce subjects’ NIRS responses. Each flickering sequence was a concatenated sequence of alternative flickering segments and resting segments. The flickering segment was designed with fixed duration of 3 s whereas the resting segment was chosen randomly within 15–20 s to create the mutual independencies among different flickering sequences. Six subjects were recruited in this study and subjects were requested to gaze at the four visual stimuli one-after-one in a random order. Since visual responses in human brain are time-locked to the onsets of visual stimuli and the flicker sequences of distinct visual stimuli were designed mutually independent, the NIRS responses induced by user's gazed targets can be discerned from non-gazed targets by applying a simple averaging process. The accuracies for the six subjects were higher than 90% after 10 or more epochs being averaged.

Charge-ordered stripes in La1−xCaxMnO3 with x>0.5 were studied by electron diffraction and electron microscopy. Charge-ordered domains were observed in dark-field images and the stripes within the domain were revealed by high resolution lattice images. The modulation wave vector δ of the charge ordering follows closely the relationship of δ=1−x and shows a slight variation from area to area. The incommensurability of the charge ordering to the underlying fundamental lattice gives rise to the presence of discommensurations in the incommensurate phase. Configurations of discommensurations in this system do not follow the general rules observed in other incommensurate systems.

Single crystalline ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ ( $0.74\ensuremath{\le}x\ensuremath{\le}0.82$) were studied with neutron scattering, electron diffraction, and bulk magnetic measurement. We discovered dynamic ferromagnetic spin correlations at high temperatures, which are replaced by antiferromagnetic spin fluctuations at a concomitant charge ordering and structural transition. Our results indicate that thermal-activated hopping of the Jahn-Teller active ${e}_{g}$ electrons in these insulating materials, nevertheless, induces ferromagnetic interaction through the double-exchange mechanism. It is the ordering of these charges which competes with the double-exchange ferromagnetic metallic state.

YMn/sub 2/O/sub 5/ compounds have been important for industrial applications due to their unique nature of ferroism. In this study, two YMn/sub 2/O/sub 5/ samples with different phases are prepared, one is orthorhombic (OT) and the other is hexagonal (HX) in structure, for investigating the structure dependency of magnetic properties. By changing the sintering temperature from 1100 to 1400/spl deg/C, the crystal structure of YMn/sub 2/O/sub 5/ is transformed from OT phase to HX phase. Based on the data of temperature-dependent magnetization M(T), the magnitude of magnetic moment in the HX phase is one order higher than that of the OT phase. Furthermore, the field-cool and zero-field-cool M(T) show a splitting around 50 K for both samples, indicating a common feature of spin-canted state. In conjunction with the results of low-temperature M--H curves, it is concluded that the YMn/sub 2/O/sub 5/ sample with the HX structure has one order higher magnetization at low temperature than that of the OT structure, which should have wide impact to future applications.

Simultaneous Localization and Mapping (SLAM) has been an active area of research lately. MonoSLAM is a SLAM frame working with a single camera without odometry information for executing SLAM The camera motion estimation and incremental map building from new landmarks are computed using the Extended Kalman Filter framework In this paper, we propose a revised approach to improve the speed of executing SLAM. We use a stereo camera to acquire two images of the environment at the same time, and use SURF algorithm to detect features in the images. The distance between the landmark and the camera can be calculated by the pair of images using a revised algorithm. Using this approach, we can reduce the time of distance calculation and increase the SLAM execution speed.

By using a real space multiple scattering method (FEFF code) with a 2 × 2 × 2 cluster model, we investigated the effects of characteristic Jahn-Teller distortion on the electron energy loss near-edge structure (ELNES) of Mn3O4 spinel. In particular, we examined a correlation between the characteristics of the density of state and the ELNES spectral feature as a function of Jahn-Teller distortion. To this end, we introduced a geometrical variation approach to an Mn3O4 cluster model containing both Mn(3+) and Mn(2+) sites. Upon a prominent Jahn-Teller distortion of the Mn(3+)-octahedral site, we resolved the associated spectral features of Mn, comprising three peaks that merged upon increasing the symmetry of octahedral site from tetragonal (D4h) to cubic (Oh). We have also investigated the interplay between the Mn L-edge and corresponding O K-edge spectra.

The large-magnetoresistance compounds ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ have been studied using specific heat, sound velocity $(v)$, and electron diffraction. For $0.63\ensuremath{\le}x\ensuremath{\le}0.67$ charge ordering is observed at 260 K and accompanied by a dramatic $(g10%)$ increase in $v$. This simultaneous occurrence of electron and lattice ordering features implies extremely strong electron-phonon coupling, known to exist for the octahederally coordinated ${d}^{4}$ ion and originating in the Jahn-Teller effect. A dynamic manifestation of this Jahn-Teller coupling has been suggested by Millis et al. as the origin for colossal magnetoresistance.

The impact of the Ga/N ratio on the structure and electrical activity of threading dislocations in GaN films grown by molecular-beam epitaxy is reported. Electrical measurements performed on samples grown under Ga-rich conditions show three orders of magnitude higher reverse bias leakage compared with those grown under Ga-lean conditions. Transmission electron microscopy (TEM) studies reveal excess Ga at the surface termination of pure screw dislocations accompanied by a change in the screw dislocation core structure in Ga-rich films. The correlation of transport and TEM results indicates that dislocation electrical activity depends sensitively on dislocation type and growth stoichiometry.

A new scanning transmission electron microscopy (STEM) imaging technique using high-order Laue zones (named HOLZ-STEM), a diffraction contrast which has been strenuously avoided or minimized in traditional STEM imaging, can be used to obtain the additional 1D periodic information along the electron propagation axis without sacrificing atomic resolution in the lateral (2D) dimension. HOLZ-STEM has been demonstrated to resolve the 3D long-range Na ordering of ${\mathrm{Na}}_{0.71}{\mathrm{CoO}}_{2}$. Direct evidence of spiral-like Na-trimer chains twisting along the $c$ axis is unambiguously established in real space.

Inorganic compounds with the AB2X4 spinel structure have been studied for many years, because of their unusual physical properties. The spinel crystallographic structure, first solved by Bragg in 1915, has cations occupying both tetrahedral (A) and octahedral (B) sites. Interesting physics arises when the B-site cations become mixed in valence. Magnetite (Fe3O4) is a classic and still unresolved example, where the tendency to form ordered arrays of Fe2+ and Fe3+ ions competes with the topological frustration of the B-site network. The CuIr2S4 thiospinel is another example, well known for the presence of a metal-insulator transition at 230 K with an abrupt decrease of the electrical conductivity on cooling accompanied by the loss of localized magnetic moments. Here, we report the determination of the crystallographic structure of CuIr2S4 below the metal-insulator transition. Our results indicate that CuIr2S4 undergoes a simultaneous charge-ordering and spin-dimerization transition-a rare phenomenon in three-dimensional compounds. Remarkably, the charge-ordering pattern consists of isomorphic octamers of Ir83+S24 and Ir84+S24 (as isovalent bi-capped hexagonal rings). This extraordinary arrangement leads to an elegant description of the spinel structure, but represents an increase in complexity with respect to all the known charge-ordered structures, which are typically based on stripes, slabs or chequerboard patterns.

Chemical mapping at atomic-column resolution by energy-dispersive x-ray spectroscopy in a spherical aberration-corrected scanning transmission electron microscope (STEM) has been demonstrated for the 1.47-A dumbbell structure in InGaAs. The structural imaging and the chemical information in the two-dimensional map are directly correlated. Comparisons with the other existing mapping techniques of STEM in conjunction with electron energy-loss spectroscopy were discussed from aspects of ionization interactions.

Previous investigations of surface plasmons in Ag largely focused on their excitations in the visible spectral regime. Using scanning transmission electron microscopy with an electron beam of 0.2 nm in conjunction with electron energy-loss spectroscopy, we spectrally and spatially probe the surface plasmons in individual Ag nanoparticles (approximately 30 nm), grown on Si, in the ultra-violet spectral regime. The nanomaterials show respective sharp and broad surface-plasmon resonances at approximately 3.5 eV (approximately 355 nm) and approximately 7.0 eV (approximately 177 nm), and the correlated spectral calculations established their multipolar characteristics. The near-field distributions of the surface plasmons on the nanoparticles were also mapped out, revealing the predominant dipolar nature of the 3.5 eV excitation with obvious near-field enhancements at one end of the nano-object. The unveiled near-field enhancements have potential applications in plasmonics and molecular sensing.

Surface plasmons (SPs) are quantized collective plasma oscillations of conduction electrons propagating at the surface of metals. The excitations of SPs in the visible spectral regime dictate the color of noble metals. In noble metal nanoparticles (NPs) with only a few tens or hundreds of nanometers, the SP resonances are further tailored by the size, shape, and coupling of the NPs, determining their optical properties ranging from near-infrared to UV spectral regimes as demonstrated in nanoprisms, nanorings, nanostars, (coupled) nanorods, and (coupled/arrayed-) nanospheres.1–3 Using individual and/or coupled NPs with proper designed geometrical constraints, the SPs can, therefore, be tuned to the proximity of the laser energies (wavelengths) conveniently available. The associated resonant excitations have been shown to amplify the electric near-field of the SPs by astronomical orders of magnitudes, opening up the opportunities for several fascinating applications of the NPs such as guiding light beyond the subwavelength limit — photonics and plasmonics, surface enhanced Raman scattering, and scanning near-field optical microscopy (SNOM) with a spatial resolution around 20∼30 nm.4–6

We first describe with the help of reference experiments (at the $\text{Fe}\text{ }2p$ and $\text{O}\text{ }1s$ edges) and ab initio calculations how electron energy loss spectroscopy (EELS) can be used in order to characterize phases of iron oxide and/or hydroxide nanomaterials. In particular we show that dehydration of iron hydroxides such as goethite can easily appear under the electron beam but might be followed by monitoring the $\text{O}\text{ }K$ peak. Indeed both local spin-density approximation (LSDA) and $\text{LSDA}+U$ calculations confirm that intensity of the prepeak of $\text{O}\text{ }K$ should increase while H atoms are removed. We also demonstrate that different magnetic orders do not change significantly the $\text{O}\text{ }K$ EELS fine structure of goethite. Thus, nanomaterials (particles and wires) synthesized by a hydrothermal treatment of nanoscale (10--40 nm) magnetite particles have been conducted. Among them, crystalline iron oxide nanowires with average diameter of 20 nm and length of up to $10\text{ }\ensuremath{\mu}\text{m}$ are reported. The $\text{O}\text{ }K$ edge and $\text{Fe}\text{ }{L}_{2,3}$ edges were studied by EELS for these nanostructures. The results indicated that the valence of iron is $3+$ in the wires while it is the mixture of $2+$ and $3+$ in the particles. From these combined EELS, scanning transmission electron microscopy, diffraction, and high-resolution electron microscopy, the complexity of the produced phases from these hydrothermal treatments can be revealed. This work shows how EELS with high-energy resolution is a unique tool to differentiate iron oxide compounds such as the tricky magnetite-maghemite solid solution or the case of partially dehydrated phases, even on a nanometer scale.

Magnetically separable Fe2O3@SBA-15 nanocomposite with fully open mesochannels and bifunctional surface properties was prepared by selective deposition of iron oxide nanoparticles in the micropores of mesoporous SBA-15 silica with hydrophobic mesopore surface. The iron oxide nanoparticles embedded in the micropores were estimated to be composed of 67% α-Fe2O3 and 33% γ-Fe2O3, and the nanocomposite was found to exhibit superparamagnetic properties. With the bifunctional surface properties, the Fe2O3@SBA-15 nanocomposite showed enhanced adsorption capacity for cytochrome c and a maximum saturated uptake at neutral solution pH.

The rich structure of bright and dark surface-plasmon modes localized in individual and coupled gold nanoparticles is unveiled by electron- energyloss spectroscopy performed in a scanning transmission electron microscope. Spatially resolved maps of surface-plasmon modes in the ̃1.5-2.5 eV range (wavelengths ̃500-800 nm), collected for individual nanorods, coupled nanorod dimers, and touching nanosphere dimers, are in excellent agreement with theory. Surface-plasmon maps constructed from the spatially and spectrally resolved energy-loss signais are shown to mimic rather well the near fields calculated for extemal illumination in the case of bright surface-plasmon modes (i.e., those coupling to external light). Dark surface-plasmon modes that cannot be excited by optical means are also found, and our electron probing technique provides further insight into their corresponding spatial distribution and symmetry, which are not accessible to any other existing techniques. Our resutts initiate the study of a whole set of new dark surface-plasmon modes that should become a source of new applications in sensing and microscopy but have escaped experimental scrutiny so far., This work was supported by the National Taiwan University Excellence Project, the National Science Council of Taiwan, the Spanish Ministry of Science and Innovation (MAT2007-66050 and Consolider NanoLight), and the EU-FP6 (NMP4-2006-016881 “SPANS”)