Light–matter interaction at the atomic scale rules fundamental phenomena such as photoemission and lasing while enabling basic everyday technologies, including photovoltaics and optical ...communications. In this context, plasmons, the collective electron oscillations in conducting materials, are important because they allow the manipulation of optical fields at the nanoscale. The advent of graphene and other two-dimensional crystals has pushed plasmons down to genuinely atomic dimensions, displaying appealing properties such as a large electrical tunability. However, plasmons in these materials are either too broad or lying at low frequencies, well below the technologically relevant near-infrared regime. Here, we demonstrate sharp near-infrared plasmons in lithographically patterned wafer-scale atomically thin silver crystalline films. Our measured optical spectra reveal narrow plasmons (quality factor of ∼4), further supported by a low sheet resistance comparable to bulk metal in few-atomic-layer silver films down to seven Ag(111) monolayers. Good crystal quality and plasmon narrowness are obtained despite the addition of a thin passivating dielectric, which renders our samples resilient to ambient conditions. The observation of spectrally sharp and strongly confined plasmons in atomically thin silver holds great potential for electro-optical modulation and optical sensing applications.
Imaging localized plasmon modes in noble-metal nanoparticles is of fundamental importance for applications such as ultrasensitive molecular detection. Here, we demonstrate the combined use of optical ...dark-field microscopy (DFM), cathodoluminescence (CL), and electron energy-loss spectroscopy (EELS) to study localized surface plasmons on individual gold nanodecahedra. By exciting surface plasmons with either external light or an electron beam, we experimentally resolve a prominent dipole-active plasmon band in the far-field radiation acquired via DFM and CL, whereas EELS reveals an additional plasmon mode associated with a weak dipole moment. We present measured spectra and intensity maps of plasmon modes in individual nanodecahedra in excellent agreement with boundary-element method simulations, including the effect of the substrate. A simple tight-binding model is formulated to successfully explain the rich plasmon structure in these particles encompasing bright and dark modes, which we predict to be fully observable in less lossy silver decahedra. Our work provides useful insight into the complex nature of plasmon resonances in nanoparticles with pentagonal symmetry.
Hydrogels are adequate systems for investigating biological structural material formation as they mimic a wide range of biomineralization conditions. Previous studies focused on the influence of ...single-component gel systems in the growth of calcite aggregates and their microstructure characteristics. In this work, we investigate the effects of hydrogel mixtures (gelatin/agarose), in the presence and absence of Mg in the growth medium, on calcite aggregate formation, hydrogel incorporation in the calcite, mode of crystallite assembly, and hierarchical mineral organization. We find marked differences between aggregates developed in gel mixtures with increased content of either gelatin or agarose. The presence of Mg, in addition to the gel incorporation, strongly influences the local lattice deformation within the aggregates. The mode of local deformation (homogeneous or localized) is closely related to the size, distribution, and crystallographic co-orientation of subunits within the aggregate. An increase in agarose induces homogeneous distribution of local deformation within the aggregates and formation of a graded mineral arrangement (archetypical spherulites), while an increase in gelatin leads to differentiation of the center and rim portions within the same aggregate. On a higher hierarchical level, when all subunits of an aggregate are considered, both agarose and gelatin evoke the formation of polycrystals.
The ability to confine light down to atomic scales is critical for the development of applications in optoelectronics and optical sensing as well as for the exploration of nanoscale quantum ...phenomena. Plasmons in metallic nanostructures with just a few atomic layers in thickness can achieve this type of confinement, although fabrication imperfections down to the subnanometer scale hinder actual developments. Here, narrow plasmons are demonstrated in atomically thin crystalline silver nanostructures fabricated by prepatterning silicon substrates and epitaxially depositing silver films of just a few atomic layers in thickness. Specifically, a silicon wafer is lithographically patterned to introduce on‐demand lateral shapes, chemically process the sample to obtain an atomically flat silicon surface, and epitaxially deposit silver to obtain ultrathin crystalline metal films with the designated morphologies. Structures fabricated by following this procedure allow for an unprecedented control over optical field confinement in the near‐infrared spectral region, which is here illustrated by the observation of fundamental and higher‐order plasmons featuring extreme spatial confinement and high‐quality factors that reflect the crystallinity of the metal. The present study constitutes a substantial improvement in the degree of spatial confinement and quality factor that should facilitate the design and exploitation of atomic‐scale nanoplasmonic devices for optoelectronics, sensing, and quantum‐physics applications.
Ultrathin crystalline silver structures of <3 nm in thickness are fabricated by lighographically prepatterning a silicon wafer and subsequently depositing a few atomic layers of metal under ultrahigh vacuum conditions. The method has great flexibility regarding the size and morphology of the structures, which are demonstrated to sustain plasmon resonances with quality factors as high as ten.
Purpose
To investigate whether arterial spin labeling (ASL) MRI could detect renal hemodynamic impairment in diabetes mellitus (DM) along different stages of chronic kidney disease (CKD).
Materials ...and Methods
Three Tesla (3T) ASL‐MRI was performed to evaluate renal blood flow (RBF) in 91 subjects (46 healthy volunteers and 45 type 2 diabetic patients). Patients were classified according to their estimated glomerular filtration rate (eGFR) as group I (eGFR > 60 mL/min/1.73 m2), group II (60 ≥ eGFR>30 mL/min/1.73 m2), or group III (eGFR ≤ 30 mL/min/1.73 m2), to determine differences depending on renal function. Studies were performed at 3T using a 12‐channel flexible body array combined with the spine array coil as receiver.
Results
A 28% reduction in cortical RBF was seen in diabetics in comparison with healthy controls (185.79 54.60 versus 258.83 37.96 mL/min/100 g, P < 3 × 10−6). Differences were also seen between controls and diabetic patients despite normal eGFR and absence of overt albuminuria (RBF mL/min/100 g: controls=258.83 37.96, group I=208.89 58.83, P = 0.0018; eGFR mL/min/1.73 m2: controls = 95.50 12.60, group I = 82.00 20.76, P > 0.05; albumin‐creatinine ratio mg/g: controls = 3.50 4.45, group I = 17.50 21.20, P > 0.05). A marked decrease in RBF was noted a long with progression of diabetic nephropathy (DN) through the five stages of CKD (χ2 = 43.58; P = 1.85 × 10−9). Strong correlation (r = 0.62; P = 4 × 10−10) was obtained between RBF and GFR estimated by cystatin C.
Conclusion
ASL‐MRI is able to quantify early renal perfusion impairment in DM, as well as changes according to different CKD stages of DN. In addition, we demonstrated a correlation of RBF quantified by ASL and GFR estimated by cystatin C.
Level of Evidence: 3
Technical Efficacy: Stage 2
J. Magn. Reson. Imaging 2017;46:1810–1817.
Objective: Tocilizumab (TCZ) has shown efficacy in clinical trials on giant cell arteritis (GCA). Real-world data are scarce. Our objective was to assess efficacy and safety of TCZ in unselected ...patients with GCA in clinical practice
Methods: Observational, open-label multicenter study from 40 national referral centers of GCA patients treated with TCZ due to inefficacy or adverse events of previous therapy. Outcomes variables were improvement of clinical features, acute phase reactants, glucocorticoid-sparing effect, prolonged remission and relapses. A comparative study was performed: (a) TCZ route (SC vs. IV); (b) GCA duration (≤6 vs. >6 months); (c) serious infections (with or without); (d) ≤15 vs. >15 mg/day at TCZ onset.
Results: 134 patients; mean age, 73.0 ± 8.8 years. TCZ was started after a median IQR time from GCA diagnosis of 13.5 5.0–33.5 months. Ninety-eight (73.1%) patients had received immunosuppressive agents. After 1 month of TCZ 93.9% experienced clinical improvement. Reduction of CRP from 1.7 0.4–3.2 to 0.11 0.05–0.5 mg/dL (p < 0.0001), ESR from 33 14.5–61 to 6 2–12 mm/1st hour (p < 0.0001) and decrease in patients with anemia from 16.4% to 3.8% (p < 0.0001) were observed. Regardless of administration route or disease duration, clinical improvement leading to remission at 6, 12, 18, 24 months was observed in 55.5%, 70.4%, 69.2% and 90% of patients. Most relevant adverse side-effect was serious infections (10.6/100 patients-year), associated with higher doses of prednisone during the first three months of therapy.
Conclusion: In clinical practice, TCZ yields a rapid and maintained improvement of refractory GCA. Serious infections appear to be higher than in clinical trials.
Modelling the optical response of gold nanoparticles Myroshnychenko, Viktor; Rodríguez-Fernández, Jessica; Pastoriza-Santos, Isabel ...
Chemical Society reviews,
09/2008, Letnik:
37, Številka:
9
Journal Article
Recenzirano
Odprti dostop
This tutorial review presents an overview of theoretical methods for predicting and understanding the optical response of gold nanoparticles. A critical comparison is provided, assisting the reader ...in making a rational choice for each particular problem, while analytical models provide insights into the effects of retardation in large particles and non-locality in small particles. Far- and near-field spectra are discussed, and the relevance of the latter in surface-enhanced Raman spectroscopy and electron energy-loss spectroscopy is emphasized.
In this case–control study of all meningococcal cases in Spain between 2015 and 2019, full vaccination with meningococcal serogroup B vaccine was 76% effective in preventing meningococcal diseases.
Graphical Abstract
The left panel depicts a female thorax in supine position, highlighting the 2 cm below the underwire bra (2BB) inframammary insertion and chest X-ray images of a patient with the ...device inserted in the proposed position. The middle panel shows boxplots with median, Q1, Q3, Min, and Max values for the R-wave amplitude at insertion, wound follow-up, and end of follow-up (left axis) and the percentage of patients for whom P-waves were visible at standard resolution at insertion, wound follow-up, and end of follow-up (right axis), and an electrocardiogram recorded by a device implanted in the 2BB position. The right panel shows mean scores for each questionnaire item (0 = not at all, 5 = very much).
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