Numerical Study of the MSCB Nanoantenna as Ultra-broadband Absorber

Plasmonics - In this paper, we propose an ultra-broadband multi-slot cross bowtie (MSCB) nanoantenna for light absorption, whose elements compose of dual rectangles and cross bowtie and rectangular...     

Characterization of Asymmetric Tapered Dipole Nanoantenna for Energy Harvesting Applications

In this paper, systematic study for asymmetric tapered dipole nanoantenna is implemented using finite element frequency domain (FEFD) solver where harvesting efficiency, field confinement, surface current, and input impedance are calculated at wavelength of 500 nm. The proposed nanoantennas achieve a harvesting efficiency of 61.3% and a field enhancement factor of 37.7 over the conventional dipole nanoantenna. This enhancement is attributed to the irregularity of the surface current distribution on the asymmetric designs. Particle swarm optimization technique is used to find the optimum design geometrical parameters through an external link between the optimization algorithm and the FEFD solver. Moreover, the proposed designs offer a resonance impedance of 500 Ω to match that of fabricated rectifiers. Further study of the structure fabrication tolerance is included which shows the robustness of the proposed nanoantennas.     

Tailoring Plasmon Lifetime in Suspended Nanoantenna Arrays for High-Performance Plasmon Sensing

We demonstrate significantly longer plasmon lifetime and stronger electric field enhancement by lifting the nanoantenna arrays above the substrate by dielectric nanopillars. The role of the pillar is to offer a more homogeneous dielectric background allowing stronger diffraction coupling among plasmonic nanoantennas leading to a Fanolike asymmetric lineshape. It is found that the electric fields around the nanoantennas can be greatly enhanced when the Fanolike resonance is excited, and a 4.2 times enhancement is achieved compared with the pure resonance in individual nanoantennas. Furthermore, only a collective surface mode with its electric fields of the same direction as the induced electric moment in the nanoantennas could mediate the excitation of such a Fanolike resonance. More importantly, the sensitivity and the figure of merit (FOM) of this plasmonic structure can reach as high as 900 nm/RIU and 53, respectively. Our study offers a new, simple, and efficient way to design the plasmonic systems with desired electric field enhancement and spectral lineshape for different applications.     

Effect of Proximity in Arrays of Plasmonic Nanoantennas on Hot Spots Density: Degenerate Semiconductors vs. Conventional Metals

Using rigorous finite element electromagnetic calculations, we study the performance of a localized surface plasmons resonance array infrared sensor, from an uncommon perspective, by analyzing electromagnetic hot spots density. We show that the hot spots density strongly depends on near-field interaction between plasmonic nanoantennas. We provide important theoretical evidence that the degree of the interaction depends on both material and geometrical properties of an array. To this end, we consider arrays of conventional metal (CM) and plasmonic transparent conducting oxide (TCO) at different nanoantennas density. We establish that a single CM nanoantenna has higher field intensity enhancement than a TCO counterpart. On the other hand, an array of TCO nanoantennas provides 30 times larger density of the hotspots and 15 times higher signal-to-noise ratio, as compared to a CM array.     

Design Optimisation of Plasmonic Metasurfaces for Mid-Infrared High-Sensitivity Chemical Sensing

In this paper, we report on a general method to optimise the optical characteristics of 2D-arrays of plasmonic gold nanoantennas performing as band-pass filter functionalised metasurfaces to be used as high-sensitivity mid-infrared spectroscopic sensors. We demonstrate that it is possible to increase their sensitivity in the detection of chemical and biological substances when the sensors are used in the surface-enhanced infrared absorption (SEIRA) technique. This technique allows revealing the presence of a substance adsorbed on the nanoantennas by measuring its optical absorption under the conditions for which the maximum value of the functionalised metasurface reflectivity occurs at the same wavelength of the substance maximum absorption peak. In particular, numerical simulations based on finite element method of the metasurface detection response demonstrate the possibility to increase the sensor sensitivity of more than four orders of magnitude with respect to that one achievable if the same amount of the substance is deposited on an unstructured planar metal surface. These results can be obtained by acting on the 2D-array periodicity, nanoantenna shape (i.e. rod and cross), size and thickness independently from the wavelength at which the substance absorption occurs. Moreover, in the case of cross-shaped nanoantennas, we report a complete numerical characterisation of the dependence of the metasurface maximum reflectivity and peak wavelength on the variation of the geometrical parameters of both the nanoantennas and the 2D-array.     

Plasmon-Enhanced Second Harmonic Generation: from Individual Antennas to Extended Arrays

We analyze the emission yield of the second harmonic generation (SHG) from dense ordered arrays of L-shaped Au nanoantennas within a well-defined collection angle and compare it to that of the isolated nanostructures designed with the same geometrical parameters. Thanks to the high antenna surface density, arrays display one order of magnitude higher SHG yield per unit surface with respect to isolated nanoantennas. The difference in the collected nonlinear signals becomes even more pronounced by reducing the collection angle, because of the efficient angular filtering that can be attained in dense arrays around the zero order. Albeit this key-enabling feature allows envisioning application of these platforms to nonlinear sensing, a normalization of the SHG yield to the number of excited antennas in the array reveals a reduced nonlinear emission from each individual antenna element. We explain this potential drawback in terms of resonance broadening, commonly observed in densely packed arrays, and angular filtering of the single antenna emission pattern provided by the array 0th order.

     

Superresolution Focusing Using Metasurface with Circularly Arranged Nanoantennas

Circular lens composed of annularly arranged metal nanoantennas is proposed to achieve far field superresolution focusing. Light illuminating on the nanoantennas’ layer approximately acquires paraboloidal phase profile and then focuses into a spot. Lens constructed by monolayer nanoantennas achieve focusing with FWHM (full width at half maximum) of 924 nm and a focal length of 3385 nm, breaking the diffraction limit. Moreover, tri-layered lens realizes subwavelength focusing with FWHM of 320 nm (about 0.49λ) and the field intensity of focus is optimized to 0.97 a.u. (arbitrary unit). Our proposal shows advances in focusing performance compared with previous work, making it promising in many applications, such as nanolithography, dense storage, and integrated optics.     

Tunable Mid-Infrared Optical Properties of Monolayer Black Phosphorus Through Au Nanotriangle Arrays via Electric Field Reflection and Surface Plasmon Polaritons

A metamaterial system composed of monolayer black phosphorus and Au triangle arrays is designed. Absorptivity, transmittivity, and reflectivity are investigated in mid-infrared regime. A low transmissivity and high absorptivity can be obtained via surface plasmon polaritons at the black phosphorus and Au triangle array interface. By changing the geometrical parameters, such as angle magnitude and slit width of Au triangle, we can modulate the transmissivity, reflectivity and absorptivity properties. Different from other previous work, it is found the zigzag direction has a better photoresponse than that armchair by changing the slit width. The electric field of the external radiation field is reflected at the Au triangle edges. Thus, electric field component perpendicular to the polarization direction generates, which can also lead to surface plasmon polaritons and is not researched in others’ work. With increase in the angle of Au triangle, transmittivity (or absorptivity) for armchair direction has a blue shift and for zigzag direction has a red shift. The transmittivity decrease ( or absorptivity increase ) for special wavelength caused by the surface plasmon polaritons may be applied to design filter devices.

     

Blockade des Gibberellinsäure-Transports in Hypocotylsegmenten durch Trijodbenzoesäure. Zugleich ein Neuer Agarblocktest auf Gibberelline

Summary Gibberellic acid (GA) was incubated in agar blocks, transported through hypocotyl sections of sunflower plants, and collected in acceptor blocks of plain agar. The amount of GA transported through the sections was tested with dwarf pea plants using a new test method in which the acceptor block was applied directly to the test plant. The GA transport was significantly lower through hypocotyl section from plants which had been treated with triiodobenzoic acid (TIBA) before isolation of the sections. TIBA inhibits the transport of GA.

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Mit 1 Textabbildung

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Herrn Prof. Dr. Dr. h. c.Hermann von Guttenberg zum 80. Geburtstag.     

Large-Area Bowtie Nanoantenna Arrays Fabricated with Economic Oxygen Plasma-Assisted Nanosphere Lithography

Bowtie nanoantenna arrays were fabricated using plasma-assisted nanosphere lithography. The gap of each bowtie nanoantenna was precisely controlled by tuning the oxygen plasma treatment time, and gap distance as small as 30 nm was successfully fabricated. The occurrence of plasmon coupling and the functionality of the bowtie nanoantenna arrays were experimentally and theoretically verified. The plasma treatments help to change the size and gap distance of the nanoparticle arrays to match a specific surface plasmon resonance wavelength. The fabricated nanoantenna array covered a large area (∼1 cm²) and was suitable for large-scale fabrication with simple scale-up of the fabrication instruments, which should lead to novel new applications.     

DNA synthesis in the elongating nondividing cells of the lentil epicotyl and its promotion by gibberellin

Two-day-old lentil seedlings, (Lens culinaris Med.) were incubated for a 48-hour period with and without gibberellin (GA) in the presence and absence of 5-fluorodeoxyuridine (FUDR). The number of cells per epicotyl did not increase during this period. Growth of the epicotyl was thus due to cell elongation alone.

The elongating cells of this tissue synthesized DNA. GA promoted and FUDR inhibited cell elongation, DNA synthesis, and RNA synthesis in the tissue.

FUDR promoted uptake of thymidine and thymidine incorporation into cellular DNA, presumably by inhibiting synthesis of endogenous thymidine. Presence of GA promoted thymidine incorporation into cellular DNA and uridine incorporation into cellular RNA. In either case, there was no effect on the uptake of the precursor into the tissue.

Fractionation of thymidine-labeled nucleic acids on a MAK column showed that thymidine was exclusively incorporated into the DNA fraction. Presence of GA promoted thymidine incorporation into this fraction and also increased the amount of ribosomal RNA.

The data provide direct evidence for the conclusion that DNA synthesis is necessary for elongation of certain plant cells.

     

Targeting Autophagic Regulation of NF-kappaB in HTLV-I Transformed Cells by Geldanamycin: Implications for Therapeutic Interventions

The IκappaB kinase (IKK)/NF-κappaB signaling pathway plays an essential role in the development and survival of many types of cancers including adult T-cell leukemia (ATL) caused by the human T-cell leukemia virus type I (HTLV-I) infection. Accordingly, targeting NF-κappaB provides an attractive strategy for cancer therapy. We recently found that specific inhibition of Hsp90 by geldanamycin (GA) results in autophagic degradation of IKK and NF-κappaB-inducing kinase (NIK), an upstream kinase of IKK, and inactivation of NF-κappaB in various cell lines. Here, we further report that GA inhibition of Hsp90 also led to IKK autophagic degradation and NF-κappaB inhibition in both HTLV-transformed T cells and ATL-derived cell lines. Importantly, GA treatment led to efficient apoptosis of these malignant cells, whereas inhibition of autophagic degradation of IKK significantly ameliorated the cytotoxic effect of GA. These findings thus not only provide mechanistic insights into the tumor suppression function of autophagy and the anti-tumor activity of GA, but also suggest an immediate therapeutic strategy for ATL and other diseases associated with NF-κappaB activation by targeting autophagic degradation of the central NF-kappaB activating kinases.

Addendum to:

Hsp90 Inhibition Results in Autophagy-Mediated Proteasome-Independent Degradation of IκappaB Kinase (IKK)

G. Qing, P. Yan and G. Xiao

Cell Res 2006; 16:895-901

and

Hsp90 Regulates Processing of NF-κappaB2 p100 Involving Protection of NF-κappaB-Inducing Kinase (NIK) from Autophagy-Mediated Degradation

G. Qing, P. Yan, Z. Qu, H. Liu and G. Xiao

Cell Res 2007; 17:520-30     

Postnatal gestational age estimation via newborn screening analysis: application and potential

ABSTRACT

Introduction: Preterm birth is a major global health concern, contributing to 35% of all neonatal deaths in 2016. Given the importance of accurately ascertaining estimates of preterm birth and in light of current limitations in postnatal gestational age (GA) estimation, novel methods of estimating GA postnatally in the absence of prenatal ultrasound are needed. Previous work has demonstrated the potential for metabolomics to estimate GA by analyzing data captured through routine newborn screening.

Areas covered: Circulating analytes found in newborn blood samples vary by GA. Leveraging newborn screening and demographic data, our group developed an algorithm capable of estimating GA postnatally to within approximately 1 week of ultrasound-validated GA. Since then, we have built on the model by including additional analytes and validating the model’s performance through internal and external validation studies, and through implementation of the model internationally.

Expert opinion: Currently, using metabolomics to estimate GA postnatally holds considerable promise but is limited by issues of cost-effectiveness and resource access in low-income settings. Future work will focus on enhancing the precision of this approach while prioritizing point-of-care testing that is both accessible and acceptable to individuals in low-resource settings.     

DNA Methylation Detection Using Resonance and Nanobowtie-Antenna-Enhanced Raman Spectroscopy

We show that DNA carrying 5-methylcytosine modifications or methylated DNA (m-DNA) can be distinguished from DNA with unmodified cytosine by Raman spectroscopy enhanced by both a bowtie nanoantenna and excitation resonance. In particular, m-DNA can be identified by a peak near 1000 cm^?1 and changes in the Raman peaks in the 1200–1700 cm^?1 band that are enhanced by the ring-absorption resonance. The identification is robust to the use of resonance Raman and nanoantenna excitation used to obtain significant signal improvement. The primary differences are three additional Raman peaks with methylation at 1014, 1239, and 1639 cm^?1 and spectral intensity inversion at 1324 (C₅=C₆) and 1473 cm^?1 (C₄=N₃) in m-DNA compared to that of DNA with unmodified cytosine. We attribute this to the proximity of the methyl group to the antenna, which brings the (C₅=C₆) mode closer to experiencing a stronger near-field enhancement. We also show distinct Raman spectral features attributed to the transition of DNA from a hydrated state, when dissolved, to a dried/denatured state. We observe a general broadening of the larger lines and a transfer of spectral weight from the ～1470 cm^?1 vibration to the two higher-energy lines of the dried m-DNA solution. We attribute the new spectral characteristics to DNA softening under high salt conditions and find that the m-DNA is still distinguishable via the ～1000 cm^?1 peak and distribution of the signal in the 1200–1700 cm^?1 band. The nanoantenna gain exceeds 20,000, whereas the real signal ratio is much less because of a low average enhanced region occupancy even with these relatively high DNA concentrations. It is improved when fixed DNA in a salt crystal lies near the nanoantenna. The Raman resonance gain profile is consistent with A-term expectations, and the resonance is found at ～259 nm excitation wavelength.     

Gallic acid modulates purine metabolism and oxidative stress induced by ethanol exposure in zebrafish brain

Gallic acid (GA) is a secondary metabolite found in plants. It has the ability to cross the blood-brain barrier and, through scavenging properties, has a protective effect in a brain insult model. Alcohol metabolism generates reactive oxygen species (ROS); thus, alcohol abuse has a deleterious effect on the brain. The zebrafish is a vertebrate often used for screening toxic substances and in acute ethanol exposure models. The aim of this study was to evaluate whether GA pretreatment (24 h) prevents the changes induced by acute ethanol exposure (1 h) in the purinergic signaling pathway in the zebrafish brain via degradation of extracellular nucleotides and oxidative stress. The nucleotide cascade promoted by the nucleoside triphosphate diphosphohydrolase (NTPDase) and 5′-nucleotidase was assessed by quantifying nucleotide metabolism. The effect of GA alone at 5 and 10 mg L^?1 did not change the nucleotide levels. Pretreatment with 10 mg L^?1 GA prevented an ethanol-induced increase in ATP and ADP levels. No significant difference was found between the AMP levels of the two pretreatment groups. Pretreatment with 10 mg L^?1 GA prevented ethanol-enhanced lipid peroxidation and dichlorodihydrofluorescein (DCFH) levels. The higher GA concentration was also shown to positively modulate against ethanol-induced effects on superoxide dismutase (SOD), but not on catalase (CAT). This study demonstrated that GA prevents the inhibitory effect of ethanol on NTPDase activity and oxidative stress parameters, thus consequently modulating nucleotide levels that may contribute to the possible protective effects induced by alcohol and purinergic signaling.

     

The specific effect of gallic acid on Escherichia coli biofilm formation by regulating pgaABCD genes expression

Escherichia coli (E. coli) is associated with an array of health-threatening contaminations, some of which are related to biofilm states. The pgaABCD-encoded poly-beta-1,6-N-acetyl-D-glucosamine (PGA) polymer plays an important role in biofilm formation. This study was conducted to determine the inhibitory effect of gallic acid (GA) against E. coli biofilm formation. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of GA against planktonic E. coli were 0.5 and 4 mg/mL, and minimal biofilm inhibitory concentration and minimal biofilm eradication concentration values of GA against E. coli in biofilms were 2 and 8 mg/mL, respectively. Quantitative crystal violet staining of biofilms and ESEM images clearly indicate that GA effectively, dose-dependently inhibited biofilm formation. CFU counting and confocal laser scanning microscopy measurements showed that GA significantly reduced viable bacteria in the biofilm. The contents of polysaccharide slime, protein, and DNA in the E. coli biofilm also decreased. qRT-PCR data showed that at the sub-MIC level of GA (0.25 mg/mL) and expression of pgaABC genes was downregulated, while pgaD gene expression was upregulated. The sub-MBC level of GA (2 mg/mL) significantly suppressed the pgaABCD genes. Our results altogether demonstrate that GA inhibited viable bacteria and E. coli biofilm formation, marking a novel approach to the prevention and treatment of biofilm-related infections in the food industry.

     

Abundance matters: role of albumin in diabetes,a proteomics perspective

Introduction: Human serum albumin (HSA) is a multifaceted protein with vital physiological functions. It is the most abundant plasma protein with inherent capability to bind to diverse ligands, and thus susceptible to various post-translational modifications (PTMs) which alter its structure and functions. One such PTM is glycation, a non-enzymatic reaction between reducing sugar and protein leading to formation of heterogeneous advanced glycation end products (AGEs). Glycated albumin (GA) concentration increases significantly in diabetes and is implicated in development of secondary complications.

Areas covered: In this review, we discuss in depth, formation of GA and its consequences, approaches used for characterization and quantification of GA, milestones in GA proteomics, clinical relevance of GA as a biomarker, significance of maintaining abundant levels of albumin and future perspectives.

Expert commentary: Elevated GA levels are associated with development of insulin resistance as well as secondary complications, in healthy and diabetic individuals respectively. Mass spectrometry (MS) based approaches aid in precise characterization and quantification of GA including early and advanced glycated peptides, which can be useful in prediction of the disease status. Thus GA has evolved to be one of the best candidates in the pursuit of diagnostic markers for prediction of prediabetes and diabetic complications.     

Inibizione della nodulazione radicale nel pisello meteor come conseguenza del trattamento nictofasico intermittente con luce rosso-estrema

Abstract

INHYBITION OF NODULATION IN METEOR PEA, BY NICTOPHASIC TREATMENT WITH FAR-RED RADIATION. — A remarkable inhybiting effect of far-red light (given to the aerial part of the plants as a flash befor and during the nictophase) on Pea root nodulation, has been achivied through some preliminary experiments. The relations between irradiated aerial parts and the activities of the underground organs in general, are being studied in the picture of photo-chromoperiodism.

Relations with the action of gibberellic acid (GA) are preliminary attempted. The inhibiting action of GA is far less striking in comparison with that of far-red radiation. Kinetin favores, at some extent, the nodulation process.     

Identifying metabolic alterations associated with coral growth anomalies using 1H NMR metabolomics

Coral growth anomalies (GAs) are tumor-like protrusions that are detrimental to coral health, affecting both the coral skeleton and soft tissues. These lesions are increasingly found throughout the tropics and are commonly associated with high human population density, yet little is known about the molecular pathology of the disease. Here, we investigate the metabolic impacts of GAs through ¹H nuclear magnetic resonance (NMR) metabolomics in Porites compressa tissues from a site of high disease prevalence (Coconut Island, Hawaii). We putatively identified 18 metabolites (8.1% of total annotated features) through complementary ¹H and ¹H–¹³C heteronuclear single quantum correlation NMR data that increase confidence in pathway analyses and may bolster future coral metabolite annotation efforts. Extract yield was elevated in both GA and unaffected (normal tissue from a diseased colony) compared to reference (normal tissue from GA-free colony) samples, potentially indicating elevated metabolic activity in GA-impacted colonies. Relatively high variation in metabolomic profiles among coral samples of the same treatment (i.e., inter-colony variation) confounded data interpretation, however, analyses of paired GA and unaffected samples identified 73 features that differed between these respective metabolome types. These features were largely annotated as unknowns, but 1-methylnicotinamide and trigonelline were found to be elevated in GA samples, while betaine, glycine, and histamine were lower in GA samples. Pathway analyses indicate decreased choline oxidation in GA samples, making this a pathway of interest for future targeted studies. Collectively, our results provide unique insights into GA pathophysiology by showing these lesions alter both the absolute and relative metabolism of affected colonies and by identifying features (metabolites and unknowns) and metabolic pathways of interest in GA pathophysiology going forward.