Strong Local Effects Research Articles

Bandwidth convertible mid-infrared absorption of one-dimensional quasi-periodic system containing Dirac semimetals

The absorption properties of one-dimensional quasi-periodic (Fibonacci and Thue Morse sequences) systems composed of Dirac semimetal are investigated. Numerical results show that nearly perfect broadband or narrowband absorption in mid-infrared range can be obtained using the same constituents with different sequences. For the Fibonacci sequence, a 90% absorption band with a relative bandwidth over 38% can be obtained, which results from the superimposing multiple resonances, and the average absorption over the absorption band can reach 97.2%. A nearly perfect narrowband absorption can be realized by the Thue Morse sequence due to the strong field localization effect. The absorption can be tunable by changing the Fermi energy of the Dirac semimetal, the geometry parameters and the permittivity of the constituents. In addition, the effects of the polarization and the incident angles of the incident wave on the absorption performance are also calculated. Our demonstrated structures have promising absorption properties and the results are valuable in designing tunable optoelectronic devices such as mid-infrared detectors and filters.

Synergistic effects of Nd3+ and Ag nanoparticles doping on spectroscopic attributes of phosphate glass

Abstract Efficient, inexpensive and eye−safe new host glass as up−conversion (UC) emission solid−state laser media became demanding. Nanoparticles (NPs) of various noble metals have been inserted into the phosphate−based amorphous host matrix to enhance the rare-earth ions (REIs) stimulated emission cross−section. Furthermore, only a few reports exist on the combined influences of neodymium ions (Nd3+) and pure silver (Ag) NPs on the structural and optical response of magnesium zinc sulfophosphate (MZSP) glasses. In this view, a series of MZSP glasses were doped by Nd3+ ions and pure Ag NPs (at different concentrations) to improve their structural and optical properties. Such melt−quench synthesized glasses were characterized at room temperature using diverse analytical measurement tools. The XRD pattern of as−quenched samples approved their amorphous nature. The FTIR and Raman spectra of glasses revealed the presence of characteristic bonding vibrations of different functional groups. The TEM images showed the existence of spherical Ag NPs (mean size of 8.34 nm) in the host glass matrix. The surface plasmon resonance (SPR) band of Ag NPs was detected around 451 nm. The UV–Vis–NIR absorption and PL emission spectra of glasses were utilized to evaluate the Judd−Ofelt (JO) intensity parameters ( Ω 2 , Ω 4 and Ω 6 ) and radiative properties. The observed fluctuation in the Ω 2 values with the increase in Ag NPs contents was attributed to the dynamic change of ligands symmetry around Nd3+ inside the glass network. Variations in the Ω 4 and Ω 6 values with the increase in Ag NPs contents indicated a considerable reduction in the glass rigidity. The PL spectra of glasses exhibited a prominent band around 576–584 nm corresponding to the 2G7/2 +4G5/2 → 4I9/2 transition in Nd3+. Glass prepared with 0.5 mol% of Ag NPs disclosed the highest PL enhancement (≈19 times) and largest emission cross−section (≈4.35 × 10−24 cm2) which was ascribed to the synergism between Ag NPs SPR mediated strong local field effect (LFE) and the subsequent energy transfer to Nd3+ appeared in the proximity of NPs. It was concluded that the proposed glass composition can lead to the development of UC solid−state laser compared to many other reported glass system.

Quantum transport on generalized scale-free networks

We consider quantum transport on generalized scale-free networks (GSFNs) in the continuous-time quantum walk (CTQW) model. The efficiency of the transport is monitored through the exact and the average return probabilities. In this model these probabilities are fully determined by the eigenvalues and eigenvectors of the connectivity matrix. In the case of GSFNs we observe a nontrivial interplay between strong localization effects, due to starlike segments, and good spreading because of the linear segments. We show that the quantum transport on GSFNs can be increased by varying the minimum or the maximum allowed degrees, i.e., the limiting number of links emerging from every node. The same quantum efficiency is reached by considering various combinations of the construction parameters of the network, which normally show different topological features.

Elucidating the Influence of Chromosomal Architecture on Transcriptional Regulation in Prokaryotes - Observing Strong Local Effects of Nucleoid Structure on Gene Regulation.

Both intrinsic and extrinsic mechanisms regulating bacterial expression have been elucidated and described, however, such studies have mainly focused on local effects on the two-dimensional structure of the prokaryote genome while long-range as well as spatial interactions influencing gene expression are still only poorly understood. In this paper, we investigate the association between co-expression and distance between genes, using RNA-seq data at multiple growth phases in order to illuminate whether such conserved patterns are an indication of a gene regulatory mechanism relevant for prokaryotic cell proliferation, adaption, and evolution. We observe recurrent sinusoidal patterns in correlation of pairwise expression as function of genomic distance and rule out that these are caused by transcription-induced supercoiling gradients, gene clustering in operons, or association with regulatory transcription factors (TFs). By comparing spatial proximity for pairs of genomic bins with their correlation of pairwise expression, we further observe a high co-expression proportional with the spatial proximity. Based on these observations, we propose that the observed patterns are related to nucleoid structure as a product of transcriptional spilling, where genes actively influence transcription of spatially proximal genes through increases within shared local pools of RNA polymerases (RNAP), and actively spilling transcription onto neighboring genes.

Oophila is monophyletic within a three-taxon eukaryotic microbiome in egg masses of the salamander Ambystoma maculatum

Tests of hypotheses of vertical transmission and competitive exclusion for particular resource-exchange mutualisms require assessments of the number and identity of partners. Unicellular green algae form a symbiosis with embryos of the northeastern yellow spotted salamander Ambystoma maculatum. The extent to which the composition of egg mass-associated taxa depends on temporal or spatial factors is unknown and the discovery of an endosymbiotic component to this symbiosis has increased the importance of knowing the specificity of the association. We assessed the diversity and relative abundance of algal and other unicellular eukaryotes in egg masses by subjecting DNA harvested from cells in egg capsules or water from breeding habitat to 18S amplicon sequencing. A nested sampling regime for two breeding seasons allowed comparisons among capsules within egg masses, among egg masses in ponds, between breeding locales, between pond water and capsule fluid, and between years. Based upon 4.33 X106 reads, we found no evidence inside fifty-eight egg capsules of algal lineages outside the Oophila clade and report that, whereas non-algal eukaryotic sequence diversity was low, cercozoan protists and chytridomycete fungi were sometimes abundant. There were weak or inconsistent egg mass, year or locale effects, but there was a very strong localization effect, indicating that capsules are rarefied spaces for eukaryotic aquatic taxa. This work provides a foundation for comparing microbial community structure within and among egg masses across the geographic range of the host.

Do Corrupt Local Governments Inhibit Entrepreneurship? A Contextual Analysis of Start-Ups in Swedish Municipalities

Does corruption affect the incentives for potential entrepreneurs to start businesses? The traditional view holds that entrepreneurship is inhibited. However, a few recent studies indicate the contrary, supporting a ‘grease the wheels’ perspective. In a novel approach to this question, we combine a local government corruption index and individual-level register data on start-ups in a low-corruption setting: Sweden. We dis-aggregate the analysis to individual entrepreneurs, focus on corruption in local institutions and hypothesize that local corruption deters potential entrepreneurs. Our findings are twofold. First, rejecting the ‘grease the wheels’ hypothesis, local corruption has a strong local deterring effect on potential entrepreneurs. Second, a minority of entrepreneurs relocate their start-ups from home municipalities to elsewhere. However, contrary to expectations, relocaters could embody ‘non-productive’ or ‘destructive’ entrepreneurship: they migrate from relatively low-corrupt to relatively high-corrupt municipalities. While migrating is uncommon, and the effect is weak, it nonetheless indicates that relocaters are attracted to conditions where rent-seeking opportunities are present.

Site-specific ground motion modeling for a historical Cairo site as a step towards computation of seismic input at cultural heritage sites

Throughout time, the area of historical Cairo has been affected by several earthquakes from near and distant seismogenic zones. The maximum earthquake intensity reported in Cairo is VII, on the Modified Mercalli Intensity scale, due to the 1992 Cairo earthquake (Mw=5.9). About 212 Coptic and Islamic monuments were damaged. The spatial distribution of damage, suggests the occurrence of strong local site effects in combination with high vulnerability of the cultural heritage buildings. This study presents the application of a novel seismic hazard analysis approach at a local scale based on physics-based ground motion simulations. A site-specific multi-scenario seismic input (ground motion time histories and response spectra) is computed at a heritage building in Cairo, considering the local site effect. The seismic input is calculated in three steps: a regional scale analysis followed by a site-specific analysis and the combinations of the computed scenarios ground motion. In the regional scale analysis synthetic accelerograms are computed at the site bedrock. Then, the site-specific analysis is performed to calculate the site surface ground motions or response spectra considering the local site effect. Three earthquake scenarios have been considered, characterized by different locations, magnitudes, and fault configurations. The last step consists in the combination of the computed scenario ground motion into one single multi-scenario seismic input specific for the site of interest. This input is represented by spectral ordinates and their variability. For the engineering purpose of time history analysis, the method allows also to extract the computed site specific physics-based accelerograms, requiring no amplitude scaling nor filtering by magnitudes, distances, or site classifications, as usually done with real ground motion records.

Multichannel tunable narrowband mid-infrared optical filter based on phase-change material Ge2Sb2Te5 defect layers.

The defect mode, which exists at the defect layer of a one-dimensional photonic crystal (1DPhC) heterostructure, provides the possibility of realizing narrowband transmission owing to its strong electromagnetic field localized effects. In this study, we numerically investigate the single- and multichannel narrowband filters in the mid-infrared region based on the defect mode by adding the monolayer and multilayer phase-change material Ge2Sb2Te5 (GST) defect layer in 1DPhC. It can provide a promising avenue to tune the transmission spectra by changing the crystallization fraction X of the GST defect layer. The remarkable narrowband transmission enhancement can be acquired for both TM and TE polarizations in spite of the large oblique incident angle. Such a defect-mode-based 1DPhC heterostructure enables tunable operating wavelength by adjusting geometrical parameters to realize the spectral selectivity of the filter in the mid-infrared region. The significant improvement and tunability of the designed single- or multichannel filters can be applied to biochemical sensing and material characterization.

"Off/on" fluorescence imaging-guided cancer diagnosis and multi-modal therapy.

An efficient theranostic nanoplatform responding to tumour microenvironments with characters of simple and flexible combinations owns great potential in cancer diagnosis and therapy. Herein, a series of triblock copolymers, mPEG-b-PDPA-b-P(nBMA-r-cystamine) (EPB), were synthesized and among them, the structure of EPB-3 was optimized for both fluorescence imaging-guided cancer diagnosis and multi-modal therapy with good biocompatibility. (1) The self-assembled nanoparticles of EPB-3-ICG1 obtained by conjugating one ICG on EPB-3 via S-S bonds effectively performed reduction-sensitive OFF/ON fluorescence signal transition, thus inducing tumour cell-specific amplified fluorescence imaging in vitro and in vivo. (2) By entrapping Au nanorods into the co-assembled NPs of EPB-3 and EPB-3-ICG1, EPB-3-ICG1@Au NPs could synchronously induce strong tumour fluorescence imaging and high local photothermal effect, indicating the potential of imagine-guided photothermal therapy. (3) EPB-3 NPs could efficiently co-load paclitaxel (PTX) and ICG to form stable EPB-3@PTX@ICG NPs, which provided long periods of intracellular pH-sensitive sustainable drug release and highly enhanced apoptosis of 4T1 cells in vitro by the chemo-photothermal effect. Excitingly, a single intravenous injection of EPB-3@PTX@ICG NPs followed by a one-time local near-infrared light (NIR, 808 nm) irradiation treatment for 10 min could lead to significant inhibition of tumour growth, avoiding tumor metastasis and extending the survival of mice. All the above-mentioned results suggest that EPB-3 provides a nanoplatform with the characters of simple structure, convenience of use and flexible combination, holding potential for multi-modal diagnosis and therapy.

Experimental study on supersonic plate boundary layer transition under pulsed arc plasma excitation control

Pulsed arc plasma excitation is characterized by strong local heating effect and wide disturbance range, and it has a broad application prospect in supersonic flow control. In this paper, by using electrical parameter measurement system and high speed schlieren technique, we study the electrical and flow field characteristics of pulsed arc plasma excitation under the condition of <i>Ma</i> = 3 incoming flow. The nano-particle planar laser scattering (NPLS) is used to investigate the flow structure of the supersonic flat boundary layer, and the transition characteristics of the boundary layer at different plasma excitation frequencies are studied. The experimental results show that in the flow field with <i>Ma</i> = 3 and the total incoming pressure <i>P</i><sub>0</sub> = 1 atm (1 atm = 1.01 × 10<sup>5</sup> Pa), the peak voltage of the pulsed arc plasma actuator discharge is 6 kV, the peak current is 70 A, the time scale of the discharge is about 300 ns, the single discharge energy is 70 mJ; the pulsed arc discharge will produce the precursor shock wave with higher velocity and the thermal deposition zone with higher temperature, which will exert continuously disturbance on the boundary layer. The pulsed arc plasma excitation with perturbation can promote the transition of supersonic plate boundary layer. Moreover, the high-frequency impact effect of pulsed discharge can promote the transition to occur ahead of time, and the higher the frequency, the better the effect is. As the excitation frequency increases, the transition position of the boundary layer of the supersonic flat plate moves forward, and the length of the transition area of the boundary layer becomes shorter as the excitation frequency increases. When the excitation frequency is 60 kHz, the length of transition zone is 0 and the thickness of turbulent boundary layer is 25 mm. When a high frequency is applied (<i>f</i> = 40, 60 kHz), the transition path of the boundary layer is that the shock wave generated by the plasma excitation triggers the unstable wave, and the development of unstable waves directly skips the linear growth stage, passes through the bypass and transitions into turbulent flow. The pulsed arc plasma excitation can be used to promote supersonic boundary layer transition.

Plasmonic metal carbide SERS chips

Plasmonic tungsten carbide, niobium carbide, titanium carbide and molybdenum carbide chips possess remarkable SERS activity.

Remarkable effects of dirty limit on superconducting condensate

Using heterostructures that combine a two superconductor (Nb-Pb). We demonstrate the modulation of the superconducting condensate at the nanoscale via variation of mean-free path. The modulation of superconductivity can be obtained not only for chosing smaller superconducting lengths comparing with bulk superconducting length or considering several geometric shapes, but also whether strong local dopping effect can be produced over the superficial area of the superconductor. Through this mechanism, a nanoscale pattern of two condensates regions can be created in the superconductor. This yields a magenetization curves that has no counterpart in the literature. We show that this form of modulation based on the possibity of change mean-free path represent a groundbreaking prospects in the study of the effects that might exploit unique superconducting properties, due to allows the manipulation of magnetic flux quanta.

Tunable narrow terahertz absorption of one-dimensional photonic crystals embedded with Dirac semimetal-dielectric defect layers.

The absorption characteristics of one-dimensional photonic crystals embedded with Dirac semimetal-dielectric defect layers are studied using the transfer matrix method. Numerical results show that our proposed structure can realize near-perfect narrow absorption for its strong field localization effects. The absorption frequency is tunable by adjusting the Fermi energy of the Dirac semimetal, temperature, permittivity of the dielectric, and the structural parameters. Moreover, double or multiple absorption channels can be achieved by changing the structure. Furthermore, the absorption performance is wide-angle and insensitive to polarization of the incident wave. Such properties exhibit potential value in designing selective absorbers and thermal detectors.

Stretchable and Highly Sensitive Optical Strain Sensors for Human-Activity Monitoring and Healthcare.

Flexible and stretchable strain sensors are essential to developing smart wearable devices for monitoring human activities. Such sensors have been extensively exploited with various conductive materials and structures, which, however, are normally in need of complex manufacturing processes and confronted with the challenge to achieve both large stretchability and high sensitivity. Here, we report a simple and low-cost optical strategy for the design of stretchable strain sensors which are capable of measuring large strains of 100% with a low detection limit (±0.09%), a fast responsivity (<12 ms), and high reproducibility (over 6000 cycles). The optical strain sensor (OS2) is fabricated by assembling plasmonic gold nanoparticles (GNPs) in stretchable elastomer-based optical fibers, where a core/cladding structure with step-index configuration is adopted for light confinement. The stretchable, GNP-incorporated optical fiber shows strong localized surface plasmon resonance effects that enable sensitive and reversible detection of strain deformations with high linearity and negligible hysteresis. The unique mechanical and sensing properties of the OS2 enable its assembling into clothing or mounting on skin surfaces for monitoring various human activities from physiological signals as subtle as wrist pulses to large motions of joint bending and hand gestures. We further apply the OS2 for quantitative analysis of motor disorders such as Parkinson's disease and demonstrate its compatibility in strong electromagnetic interference environments during functional magnetic resonance imaging, showing great promises for diagnostics and assessments of motor neuron diseases in clinics.

First-principles study on the band gap energy of ZnSexO1-x in the O-rich range

The band structure of ZnSexO1-x is studied based on the LDA + U method. It is found that the band gap energy decreases suddenly at first, then decreases slowly, and at last decreases quickly in the O-rich range. The decline of the CBM is due to the interaction between the Se-4s and Zn-4s states. Incorporating O atoms can introduce a localized Se level lying 0.76 eV above the VBM of ZnO. Because of the strong localized effect, the VBM of ZnSexO1-x can be pinned near the initial Se level. When the Se content is sufficiently large, the localized effect becomes weak.

Tunable CdS/TiO2 all-optical switches with defect layers

The switching characteristics of one-dimensional photonic crystal (PC) all-optical switches of cadmium sulfide (CdS)/titanium dioxide (TiO2) with defect layers are investigated. The excited defect modes with high intensity, perfect symmetric and a very narrow band were found in the photonic bandgap range of the PC transmission spectrum when inserted cadmium sulfide defect layers in the PC structure. It results from the high optical non-linearity of the cadmium sulfide defect layer and the strong localized effects of the incident light. These effects are attributed to the light localization in the defect layers of the multilayer structures. Additionally, the number and position of the defect modes are tuned according to the number and separation of the defect layers. The steep response of on and off and the tuning properties of the perfect defect modes can be exploited for ultrafast all-optical switches in all-optical circuits. The results demonstrate that cadmium sulfide defective PCs are good candidates for the fabrication of ultrafast all-optical switching devices.

Evaluation and Bias Correction in WRF Model Forecasting of Precipitation and Potential Evapotranspiration

Abstract A reliable forecast of potential evapotranspiration (ET0) is key to precise irrigation scheduling toward reducing water and agrochemical use while optimizing crop yield. In this study, we examine the benefits of using the Weather Research and Forecasting (WRF) Model for ET0 and precipitation forecasts with simulations at a 3-km grid spatial resolution and an hourly temporal resolution output over Israel. The simulated parameters needed to calculate ET0 using the Penman–Monteith (PM) approach, as well as calculated ET0 and precipitation, were compared to observations from a network of meteorological stations. WRF forecasts of all PM meteorological parameters, except wind speed Ws, were significantly sensitive to seasonality and synoptic conditions, whereas forecasts of Ws consistently showed high bias associated with strong local effects, leading to high bias in the evaluated PM–ET0. Local Ws bias correction using observations on days preceding the forecast and interpolation of the resulting PM–ET0 to other locations led to significant improvement in ET0 forecasts over the investigated area. By using this hybrid forecast approach (WRFBC) that combines WRF numerical simulations with statistical bias corrections, daily ET0 forecast bias was reduced from an annual mean of 13% with WRF to 3% with WRFBC, while maintaining a high model–observation correlation. WRF was successful in predicting precipitation events on a daily event basis for all four forecast lead days. Considering the benefit of the hybrid approach for forecasting ET0, the WRF Model was found to be a high-potential tool for improving crop irrigation management.

Systemic administration of orexin A ameliorates established experimental autoimmune encephalomyelitis by diminishing neuroinflammation

BackgroundOrexins (hypocretins, Hcrt) A and B are GPCR-binding hypothalamic neuropeptides known to regulate sleep/wake states and feeding behavior. A few studies have shown that orexin A exhibits anti-inflammatory and neuroprotective properties, suggesting that it might provide therapeutic effects in inflammatory and neurodegenerative diseases like multiple sclerosis (MS). In MS, encephalitogenic Th1 and Th17 cells trigger an inflammatory response in the CNS destroying the myelin sheath. Here, we investigated the effects of peripheral orexin A administration to mice undergoing experimental autoimmune encephalomyelitis (EAE), a widely used model of MS.MethodsMice were subcutaneously immunized with myelin oligodendrocyte glycoprotein peptide (MOG)35–55 in CFA. Mice were treated intraperitoneally for five consecutive days with either PBS or 300 μg of orexin A starting at a moderate EAE score. Molecular, cellular, and histological analysis were performed by real-time PCR, ELISA, flow cytometry, and immunofluorescence.ResultsOrexin A strongly ameliorated ongoing EAE, limiting the infiltration of pathogenic CD4+ T lymphocytes, and diminishing chemokine (MCP-1/CCL2 and IP-10/CXCL10) and cytokine (IFN-γ (Th1), IL-17 (Th17), TNF-α, IL-10, and TGF-β) expressions in the CNS. Moreover, orexin A treatment was neuroprotective, decreasing demyelination, astrogliosis, and microglial activation. Despite its strong local therapeutic effects, orexin A did not impair peripheral draining lymph node cell proliferation and Th1/Th17 cytokine production in response to MOG35–55 in vitro.ConclusionsPeripherally-administered orexin A ameliorated EAE by reducing CNS neuroinflammation. These results suggest that orexins may represent new therapeutic candidates that should be further investigated for MS treatment.

Spatiotemporal Filtering and Noise Analysis for Regional GNSS Network in Antarctica Using Independent Component Analysis

The common mode error (CME) and optimal noise model are the two most important factors affecting the accuracy of time series in regional Global Navigation Satellite System (GNSS) networks. Removing the CME and selecting the optimal noise model can effectively improve the accuracy of GNSS coordinate time series. The CME, a major source of error, is related to the spatiotemporal distribution; hence, its detrimental effects on time series can be effectively reduced through spatial filtering. Independent component analysis (ICA) is used to filter the time series recorded by 79 GPS stations in Antarctica from 2010 to 2018. After removing stations exhibiting strong local effects using their spatial responses, the filtering results of residual time series derived from principal component analysis (PCA) and ICA are compared and analyzed. The Akaike information criterion (AIC) is then used to determine the optimal noise model of the GPS time series before and after ICA/PCA filtering. The results show that ICA is superior to PCA regarding both the filter results and the consistency of the optimal noise model. In terms of the filtering results, ICA can extract multisource error signals. After ICA filtering, the root mean square (RMS) values of the residual time series are reduced by 14.45%, 8.97%, and 13.27% in the east (E), north (N), and vertical (U) components, respectively, and the associated speed uncertainties are reduced by 13.50%, 8.06% and 11.82%, respectively. Furthermore, different GNSS time series in Antarctica have different optimal noise models with different noise characteristics in different components. The main noise models are the white noise plus flicker noise (WN+FN) and white noise plus power law noise (WN+PN) models. Additionally, the spectrum index of most PN is close to that of FN. Finally, there are more stations with consistent optimal noise models after ICA filtering than there are after PCA filtering.

Enhanced Photothermal Effect in Ultralow-Density Carbon Aerogels with Microporous Structures for Facile Optical Ignition Applications.

The exact mechanism responsible for the phenomenon known as photoignition with an enhanced photothermal effect in high-surface-area carbon with the addition of a metal catalyst is an open issue. Here, we report the first successful flash ignition of a pure carbon material in ambient air microporous carbon aerogels (CAs) with ultralow density and high surface area. Under flash exposure, the CAs show a strong local heat confinement effect near microporous structures (0.6-2 nm), and the graphite crystallite structures existing in single carbon nanoparticles (∼15 nm) are damaged. The local heat confinement effects are mainly derived from the low gaseous thermal conductivity in micropores and low solid thermal conductivity in low-density CAs. In addition, the limiting effects of the microporous structure on the vibration amplitude of free-state electrons in low-density CAs result in a dramatic increase in optical absorption. Numerical simulations of unsteady temperature fields of CAs with different densities and thicknesses are also performed, and the calculated maximum temperature of a 17 μm-thick 20 mg/cm3 CA bed is 1782 °C. CAs with higher density can also give rise to enhanced photothermal response and ignition with the addition of metal Fe nanoparticles. The metal catalyst increases both the light absorption capacity in the visible-light range and the heat accumulation capacity. These results are important for understanding the mechanism of flash ignition, especially the local high temperature and effects of metal catalyst in carbon materials during the photothermal process.