Refractive index sensor based on fano-magnetic toroidal quadrupole resonance enabled by bound state in the continuum in all-dielectric metasurface.

For the first time, an all-dielectric metasurface ultra-sensitive refractive index (RI) sensor with very high quality factor (QF) and figure of merit (FOM), with Fano-magnetic toroidal quadrupole (MTQ) resonance enabled by bound state in continuum (BIC) in terahertz (THz) region was designed. Furthermore, the MTQ resonance in the THz due to a distortion of symmetry-protected bound states in the continuum in the designed structure was investigated. Also, to achieve the dark mode, a combination of three methods including (i) breaking the symmetry, (ii) design of complex structures, and (iii) changing the incident angle was utilized. The broken symmetry in the structure caused a new mode to be excited, which is suitable for sensing applications. The designed metasurface was able to sense a wide range of RI in MTQ resonance, where its properties were improved for the value of sensitivity (S) from 217 GHz/RIU to 625 GHz/RIU, for FOM from 197 RIU-1 to 2.21 × 106 RIU-1 and for QF from 872 to 5.7 × 106.

Design of Single-Mode Single-Polarization Large-Mode-Area Multicore Fibers.

In laser science and industry, considerable effort is directed toward designing fibers for fiber laser and fiber amplifier applications, each of which offers a particular advantage over the others. Evanescently coupled multicore fibers, however, have been studied less extensively due to the relatively small mode area in the single-mode regime. Here, by proposing a new structure with stress-applying parts in a 37-core fiber and optimizing this structure through a comprehensive framework, we present 21 solutions characterized by large-mode-area and high beam quality in the single-mode, single-polarization regime. Different fiber designs are optimal for different output parameters. In one design, the mode area can significantly increase to above 880 µm2, which is comparable with that of photonic-crystal fibers. Moreover, besides the single-mode operation, the beam quality factor (M2 factor) of the fundamental mode is considered an output parameter in the bent state and is improved up to 1.05 in another design. A comprehensive tolerance analysis is then performed to assess the performance of the designs under deviations from normal conditions. Moreover, in spite of the shifts in the loss of modes, the proposed high beam quality LMA fibers maintain single-polarization, single-mode operation across a wide range of core pitches, bending orientation angles, and bending radius deviations. Our results highlight the potential of multicore fibers for the efficient operation of fiber lasers and amplifiers.

Determinations of Melamine Residue in Infant Formula Brands Available in Iran Market Using by HPLC Method.

The contamination of melamine was evaluated in 69 infants along with follow up formula samples collected from the market for the first time in Iran using HPLC method. Since there are no previous data concerning the contamination level of melamine in all brands of infant formula samples consumed using the HPLC method in Iran, this study is the first investigation in this regard. Our results showed that melamine contamination was found in 65% of samples, where mean and maximum levels of melamine were 0.73 ± 0.71 mg/kg and 3.63 mg/kg, respectively. The level of melamine in 10 out of 69 samples was higher than the maximum level set by the Codex Alimentarius in infant food (1 mg/kg). Melamine was determined in 67.8% and 50% of domestic and imported samples, respectively. The estimated daily intake was designed in two scenarios: it was calculated based on the mean level of melamine contamination and maximum level of melamine in the samples. In both scenarios, our results showed that melamine intake across all age groups is lower than the tolerable daily intake (TDI) of 0.2 mg/kg body weight, suggested by WHO (0.2 mg/kg body weight). Thus, it seems that the current levels of melamine in infant and follow up formula purchased in Iran pose no health risk for infants.

Occurrence of Ochratoxin A in Grape Juice of Iran.

Ochratoxin A (OTA) is one of the most important mycotoxins that contaminate a broad range of agricultural and food products. In this study, the occurrence of OTA in available brands of grape juice in Iran purchased from retail outlets or producer were determined for the first time using high-performance liquid chromatography (HPLC) with immunoaffinity columns(IAC) as the clean-up step. The average recoveries for OTA in grape juice ranged from 54.2 to 86.6% with the coefficient of variation lower than 17.3% in lowest spiked level (0.5 µg/L). The estimated LOD and LOQ of OTA were 0.04 µg/L and 0.125 µg/L, respectively. In our study, 70 samples of grape juice evaluated for OTA content. The results showed that in 39 out of 70 samples (55.7%) OTA levels were above the LOQ with the maximum level of 2.6 µg/L and the mean contamination was 0.5 µg/L. Although the mean contamination of OTA in analyzing samples was lower than the MRL set by EU, the high incidence of contamination in these products is worried. Considering the importance of OTA in public health, control of pre- and post-harvest, storage and grape juice manufacturing process, such as HACCP, GAP, and GMP recommended preventive measures are required.

Design of new potent HTLV-1 protease inhibitors: in silico study.

HTLV-1 and HIV-1 are two major causes for severe T-cell leukemia disease and acquired immune deficiency syndrome (AIDS). HTLV-1 protease, a member of aspartic acid protease family, plays important roles in maturation during virus replication cycle. The impairment of these proteases results in uninfectious HTLV-1virions.Similar to HIV-1protease deliberate mutations that confer drug resistance on HTLV-1 are frequently seen in this protease. Therefore, inhibition of HTLV-1 protease activity is expected to disrupt HTLV-1's ability to replicate and infect additional cells. In this study, we initially designed fifteen inhibitory compounds based on the conformations of a class of HIV-1 aspartyl protease inhibitors, sulfonamid-peptoid. Five compounds were chosen based on the goodness of their Drug-Likeness scoreusing "Lipinsk's rule of five". Here, using protein-ligand docking approach we compared the inhibitory constants of these compounds to those available in literatures and observed significantly higher inhibition for two compounds, SP-4 and SP-5. Our data suggest that the addition of two cyclic hydrocarbons to both ends of sulfonamide peptoids leads to the formation of new hydrophobic interactions due to the semi-circular form of these compounds, connecting the first chain of protease to the two ends of tested ligands via Hydrophobic interactions. We conclude that hydrophobic force plays an important role in suppressing protease activity especially for HTLV-1 protease, which in turn prevents the virus maturity. Therefore, designing and development of new ligands based on aromatic hydrocarbons in both ends of inhibitors is very promising for efficient treatment.

Vitamin E induces regular structure and stability of human insulin, more intense than vitamin D3.

Changes in human environment and lifestyle over the last century have caused a dramatic increase in the occurrence of diabetes. Research of past decades illustrated that vitamin D and E have a key role in the improvement of diabetes by reducing oxidative stress, protein glycosylation, insulin resistance and also improving beta cell function. Binding properties and conformational changes of human insulin upon interaction with vitamins D3 and E (α-tocopherol) were investigated by spectroscopy, differential scanning calorimetry (DSC) and molecular dynamic simulation. Tyrosine fluorescence quenching studies indicates changes in the human insulin conformation in the presence of vitamins. Binding constants of vitamins D3 and E for human insulin were determined to be 2.7 and 1.5 (×10-5M-1) and the corresponding average numbers of binding sites were determined to be 1.3 and 1.2, respectively. Far- and near-UV circular dichroism studies showed that vitamin E can significantly change the secondary and tertiary structures of human insulin via an increase in the content of α-helix structure. Results of DSC showed that both vitamins D3 and E stabilize the structure of human insulin. Molecular dynamic simulation results indicated that vitamin D3 decreases the helical and strand structural contents of human insulin, but vitamin E stabilizes more regular secondary structures such as helical and strand structural contents as shown by experimental results.