Phase-controlled electromagnetically induced symmetric and asymmetric grating in an asymmetric three-coupled quantum well.

Fraunhofer light diffraction of a weak probe field passing through an asymmetric three-coupled quantum well, which is driven by a standing wave and two coupling laser fields, is investigated. Depending on which transitions are coupled by the probe and standing field, two schemes are considered. It is demonstrated that owing to the closed-loop transition, optical properties and the diffraction pattern of the probe field in both schemes are highly affected by the relative phase of the applied fields and can be controlled by this parameter. Moreover, it is shown that the proposed schemes have multifunction capabilities. In the first scheme, as a result of varying relative phase, the electromagnetically induced absorption phase grating turns to the electromagnetically induced gain phase grating with remarkable efficiency, while in the latter scheme, a significant result is revealed: Tuning the relative phase can lead to inducing optical parity-time symmetry, which gives rise to an asymmetric diffraction grating. Such an all-optical phase-sensitive operation could be useful in optical switching and optical communications.

The Impact of XmnI-HBG2, BCL11A and HBS1L-MYB Single Nucleotide Polymorphisms on Hb F Variation of Hematologically Normal Iranian Individuals.

The impact of Hb F on severity of sickle cell disease and ß-thalassemia (ß-thal) is well documented. The XmnI-HBG2, BCL11A and HBS1L-MYB single nucleotide polymorphisms (SNPs) have been introduced as the most important factors causing variation in fetal hemoglobin (Hb F) levels in different population studies. However, the extent of their effect could be population-specific. In this study, multivariate linear regression analysis was used to evaluate the association of Hb F with age, sex, and eight SNPs, including XmnI-HBG2, four BCL11A, two HBS1L-MYB SNPs and the polymorphic palindromic 5' hypersensitive 4-locus control region (5'HS4-LCR). One hundred and twenty-two hematologically normal individuals, from a previous study cohort, constituted our study population. In multivariate regression analyses, no association of Hb F was observed with age or sex of the individuals and SNPs in this study. We conducted a univariate regression analysis to further investigate the results, which among all the factors only detected XmnI-HBG2 and 5'HS4 SNPs as significant modifiers of Hb F. The significance of these two factors disappeared in a bivariate analysis. These results suggest that either XmnI-HBG2 or 5'HS4-LCR have a stronger contribution in Hb F variations of the Iranian population than BCL11A and HBS1L-MYB SNPs. Furthermore, the effect of low population size and technical limitations on obtained results could not be ruled out.

Laser-Assisted Preparation of TiO2/Carbon/Ag Nanocomposite for Degradation of Organic Pollutants.

The ever-increasing expansion of chemical industries produces a variety of common pollutants, including colors, which become a global and environmental problem. Using a nanocatalyst is one of the effective ways to reduce these organic contaminants. With this in mind, a straightforward and effective method for the production of a novel nanocatalyst based on lignin-derived carbon, titanium dioxide nanoparticles, and Ag particles (TiO2/C/Ag) is described. The preparation of carbon and Ag particles (in sub-micro and nano size) was carried out by laser ablation in air. The nanocomposite was synthesized using a facile magnetic stirrer of TiO2, C, and Ag. According to characterization methods, a carbon nanostructure was successfully synthesized through the laser irradiation of lignin. According to scanning electron microscope images, spherical Ag particles were agglomerated over the nanocomposite. The catalytic activities of the TiO2/C/Ag nanocomposite were tested for the decolorization of methylene blue (MB) and Congo red (CR), employing NaBH4 in a water-based solution at 25 °C. After adding fresh NaBH4 to the mixture of nanocomposite and dyes, both UV absorption peaks of MB and CR completely disappeared after 10 s and 4 min, respectively. The catalytic activity of the TiO2/C/Ag nanocomposite was also examined for the reduction of 4-nitrophenol (4-NP) using a NaBH4 reducing agent, suggesting the complete reduction of 4-NP to 4-aminophenol (4-AP) after 2.30 min. This shows excellent catalytic behavior of the prepared nanocomposite in the reduction of organic pollutants.

Enhanced four-wave mixing in quantum cascade semiconductor optical amplifier.

We designed a quantum cascade semiconductor optical amplifier (QCSOA) structure for enhanced four-wave mixing (FWM) of short optical pulses in midinfrared. To analyze FWM characteristics in a QCSOA, the evolution in the time and spectral domains of two input optical pulses with different frequencies during propagation is calculated using the finite-difference beam propagation method. Calculated third-order susceptibility responsible for FWM resonance nonlinearity of the modified structure is enhanced by two orders of magnitude. Simulation results reveal that quantum cascade structure parameters and injected pump and probe powers are extremely important in determining the amplified FWM optical pulse characteristics in both the time and frequency domains.

Analytical study of gold-DNA nano core-shell cloaking characteristics for drug delivery and cancer therapy.

The cloaking characteristics of biocells can be considered as a factor to determine drug absorption by the tissues. The metal-organic core-shell structure can act as a cloak around the molecules of tissue and can be used as a nanomachine for drug delivery. Thus, we define a ratio of drug absorption based on frequency red-shift and the effective permittivity in the optical spectrum. Here, a cylinder of molecules coated by plasmonic nano core-shells is proposed for measuring the cloaking characteristics of biocells. The overall bandwidth of the proposed cloak for reflectance less than -10 dB is 36%. We check the effect of the filling factors of nanoparticles on the reflection and the frequency response of the tissue. Besides the frequency red-shift and change in the level of reflection, the phase and impedance are extracted. We could obtain the normalized scattering cross-section of 5 dB lower than the cylinder without cloak for the cylinder with a gold-DNA core-shell cloak. Here, we modify the Maxwell-Garnett equation for a cylindrical structure to obtain the effective value of the permittivity for cancer and normal tissues. The results show that obtained permittivity from the simulation has a good match with the calculated permittivity from the Maxwell-Garnet equation. Therefore, this approach can be considered as an efficient method for drug absorption and diagnosis of cancer cells from normal cells.

The antioxidant, anti-angiogenic, and anticancer impact of chitosan-coated herniarin-graphene oxide nanoparticles (CHG-NPs).

Background: Herniarin, a simple coumarin found in chamomile leaf rosettes is known as the oxidative stress protector. In the current study, herniarin was captured into Graphene oxide nanoparticles and coated with chitosan poly-cationic polymer to be used as a novel bio-compatible nano-drug delivery system and investigate its antioxidant, anti-angiogenic and anti-cancer impacts on human lung A549 cancer cells. Method: The Chitosan-coated Herniarin-Graphene oxide nanoparticles (CHG-NPs) were designed, produced, and characterized utilizing DLS, FESEM, FTIR, and Zeta-potential analysis. The CHG-NPs' antioxidant activity was analyzed by conducting ABTS and DPPH antioxidant assays. The CHG-NPs' anti-angiogenic activity was analyzed by CAM assay and verified by measuring VEGF and VEGFR gene expression levels following their increased treatment doses by applying Q-PCR technique. Finally, the CHG-NPs' cytotoxicity was studied in the human lung A549 cancer cells. Result: The stable (+27.11 mV) 213.6-nm CHG-NPs significantly inhibited the ABTS/DPPH free radicals and exhibited antioxidant activity. The suppressed angiogenesis process in the CAM vessels was observed by detecting the decreased length/number of the vessels. Moreover, the down-regulated VEGF and VEGFR gene expression of the CAM blood vessels following the increased CHG-NPs treatment doses verified the nanoparticles' anti-angiogenic potential. Finally, the CHG-NPs significantly exhibited a selective cytotoxic impact on human A549 cancer cells compared with the normal HFF cell line. Conclusion: The selective cytotoxicity, strong antioxidant activity, and significant anti-angiogenic property of the nano-scaled produced CHG-NPs make it an appropriate anticancer nano-drug delivery system. Therefore, the CHG-NPs have the potential to be used as a selective anti-lung cancer compound.

The electrophoretic deposition of TiB2 nanoparticles produced by pulsed laser ablation: Case study on microstructural features and micromorphology properties.

In the last decade, laser Ablation technique (Nd:YAG) has been considered as a perfect method for producing nanostructures with high purity. In the present study, Titanium diboride nanoparticles (TiB2 NPs) have been deposited on Aluminum (Al) and their micromorphology and microstructural properties have been investigated. The synthesis of TiB2 NPs has been carried out by the Laser Ablation technique (Nd:YAG) which has not been reported so far. Moreover, the effects of laser energy on improving the synthesis of TiB2 NPs have been examined. In this regard, five samples of TiB2 NPs were prepared by Laser Ablation method in different values of laser fluency in the range of 0.4-1.2 J/cm2 . The structural properties of prepared nanoparticles were detected by grazing incidence X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The morphology of samples was also investigated by field effect scanning electron microscopy. The results demonstrate the formation of spherical nanoparticles in all samples. Based on the results of the GIXRD patterns, pulsed laser energy is an effective parameter for the size of ablated nanoparticles. As can be seen, increasing the energy of laser beam decreases the average size of nanoparticles from 79.41 to 4 nm. As the next step, the as-prepared nanoparticles were deposited on Aluminum substrate with electrophoretic deposition technique at constant applied voltage (30 Volt) and constant deposition time (30 min). The X-ray diffraction pattern of TiB2 NPs deposited onto Al substrate confirmed the formation of the TiB2 thin films on all Al substrates. Also, the roughness and average particle size of deposited films were measured by atomic force microscopy images and MountainsMap® Premium software. Increasing the fluency of laser beam made the surface more irregular and the maximum value of fractal dimension and hence, the most irregular topography has been observed in the sample produced by maximum laser fluency. RESEARCH HIGHLIGHTS: Titanium diboride nanoparticles have been synthesized by the laser ablation technique. The effects of laser energy on improving the synthesis of TiB2 NPs have been investigated. The micromorphology of samples have been investigated by analyzing AFM and SEM images.

The effect of applied electric field on the micromorphology of Pt nanoparticles synthesized by laser ablation.

In the present study, laser ablation technique (Nd:YAG) has been applied to synthesize platinum nanoparticles (NPs). Also, the effect of applied electric field on the physical, structural, and morphological properties of Pt NPs has been investigated during the nanosecond pulsed laser ablation of platinum. Based on the results extracted from TEM and scanning electron microscopy images, the formation of high percentage of NPs with spherical shape is demonstrated in all samples. The increase of applied electric field creates few rectangular, hexagonal, and rhombic NPs with the average size decreased from 20 to 9 nm. The significant influence of increasing electric field is also observed in UV-vis spectra by appearing the blue shift of the localized surface plasmon resonance peak. The UV-vis spectra also confirm the metallic nature of Pt NPs and the existence of inhomogeneous-sized particles and the coagulation of particle because of the long tail in higher wavelengths. In addition, atomic force microscopy images have been analyzed through MountainsMap Premium program and fractal dimension. As can be seen, increasing the applied electric field make the surface more irregular and the maximum value of Df reveals the most irregular topography for sample with 50 V/cm electric field. Finally, the bending and stretching frequencies of the functional bending groups connected to the NPs surface have been characterized by Fourier transform infrared spectroscopy. Electrical field-assisted laser ablation in liquids method allows a better control of the size, morphology, structure, and chemical composition of nanoparticles.

Engineered nano-sphere array of gold-DNA core-shells and junctions as opto-plasmonic sensors for biodetection.

In this paper, we design opto-plasmonic sensors by the engineered arrangement of gold-nanospheres. We use DNA-gold nanoparticle (GNP) core-shells and DNA rods as junctions between GNPs with a fishnet ground layer for controlling and improving the absorbance and reflection in the range of 100-300 THz. Based on available data, we check the effects of healthy and cancerous cells on the reflection parameter. Here, we demonstrate how the DNA junctions and distance between the nanospheres can be considered to modify the reflection. These structures can be utilized as opto-plasmonic sensors with high sensitivity to distinguish materials in terms of refractive indices. We can use an array of these sensors for both spectroscopy and optical imaging on a real scale. The proposed structures with different topologies are analyzed and their figure of merits (FOM) and sensitivities are obtained. The structure based on the DNA rods as junctions between GNPs shows the best FOM value of 340 RIU-1 and the core-shell heptamer structure has the best sensitivity of about 1287 nm RIU-1.

A Comprehensive Genetic and Clinical Evaluation of Waardenburg Syndrome Type II in a Set of Iranian Patients.

Waardenburg syndrome (WS) is a neurocristopathy with an autosomal dominant mode of inheritance, and considerable clinical and genetic heterogeneity. WS type II is the most common type of WS in many populations presenting with sensorineural hearing impairment, heterochromia iridis, hypoplastic blue eye, and pigmentary abnormalities of the hair and skin. To date, mutations of MITF, SOX10, and SNAI2 have been implicated in the pathogenesis of WS2. Although different pathogenic mutations have been reported in many ethnic groups, the data on Iranian WS2 patients is insufficient. 31 WS2 patients, including 22 men and 9 women from 14 families were included. Waardenburg consortium guidelines were employed for WS2 diagnosis. WS2 patients underwent screening for MITF, SOX10, and SNAI2 mutations using direct sequencing and MLPA analysis. Clinical evaluation revealed prominent phenotypic variability in Iranian WS2 patients. Sensorineural hearing impairment and heterochromia iridis were the most common features (67% and 45%, respectively), whereas anosmia was the least frequent phenotype. Molecular analysis revealed a de novo heterozygous c.640C>T (p.R214X) in MITF and a de novo heterozygous SOX10 gross deletion in the study population. Our data help illuminate the phenotypic and genotypic spectrum of WS2 in an Iranian series of patients, and could have implications for the genetic counseling of WS in Iran.