All optical NOR and NAND gate based on nonlinear photonic crystal ring resonators

In this paper we proposed optical NOR and NAND gates. By combining nonlinear Kerr effect with photonic crystal ring resonators first we designed a structure, whose optical behavior can be controlled via input power intensity. The switching power threshold obtained for this structure equal to 2 kW/μm². For designing the proposed optical logic gates we employed two resonant rings with the same structures, both rings at the logic gates were designed such that their resonant wavelength be at λ = 1550 nm. Every proposed logic gate has one bias and two logic input ports. We used plane wave expansion and finite difference time domain methods for analyzing the proposed structures.     

T-shaped channel drop filter based on photonic crystal ring resonator

Photonic crystal ring resonators are promising candidates for realizing all optical filters with acceptable transmission efficiency and quality factor values. In this paper, by putting a12-fold quasi crystal at the middle of on 7 × 7 square cavity we created a ring resonator structure and designed a T-shaped channel drop filter. The drop wavelength of our filter is at 1551 nm, with transmission efficiency and quality factor equal to 90% and 387. Our structure is composed of dielectric rods immersed in air. Because in this kind of structures the dominant band gap is in TM mode, all of our simulations have been done in TM mode. The total footprint of our filter is 242.4 μm², which makes it suitable for all optical integrated circuits.     

Hydrogen bis[tris(4‐fluorophenyl)phosphane oxide] triiodide

In the title compound, C₃₆H₂₅F₆O₂P₂⁺·I₃⁻, hydrogen‐bonded [{(p‐FC₆H₄)₃PO}₂H]⁺ dimers assemble along the crystallographic c axis to form channels that house extended chains of triiodide anions. Although the I—I bond lengths of 2.9452 (14) and 2.9023 (15) Å are typical, the inter‐ion I...I distance of 3.5774 (10) Å is unusually short. A posteriori modelling of nonmerohedral twinning about (100) has been only partially successful, achieving a reduction in the maximum residual electron density from 5.28 to 3.24 e Å⁻³. The inclusion of two low‐occupancy I‐atom sites (total 1.7%), which can be interpreted as translational disorder of the triiodide anions along the channels, reduced the maximum residual electron density to 2.03 e Å⁻³. The minor fractional contribution volume of the nonmerohedral twin domains refined to 0.24 and simultaneous refinement of the inversion twin domains showed the crystal to be a 0.5:0.5 inversion twin.     

Succinimide sulfonic acid (SuSA): an efficient and recyclable catalyst for the chemoselective <Emphasis Type="Italic">N</Emphasis>-Boc protection of amines

Abstract  

Succinimide sulfonic acid (SuSA) as a stable reagent is easily prepared by the reaction of succinimide with neat chlorosulfonic acid. This compound is able to catalyze the chemoselective conversion of amines to their corresponding N-Boc protected derivatives with (Boc)₂O. All reactions were performed under mild conditions, giving the desired products in good to high yields.     

Determination of trace elements in blood samples of patients affected by multiple sclerosis from Iran by neutron activation analysis

Multiple sclerosis (MS) is a neurological autoimmune disease in which the immune system attacks the central nervous system for unknown reasons and causes several damages to human body by demyelinating the nerve cells. One of the possible cause of this disease is the abnormality levels of some trace elements such as Br, Fe, Rb, Sb, As, and Zn in human body. This study attempts to measure the levels of four trace elements of Br, Fe, Rb, and Zn in the patients?? blood samples and compare them with control samples from healthy individuals. It should be noted that the objectives set out partly met. According to the obtained results, the differences between the levels of Br, Fe, and Rb in patients?? blood samples and control was not significant (P?>?0.05). However, the average level of Zn between samples and controls showed a significant difference (P?<?0.05). Therefore the lower level of Zn in blood is likely to be a major cause of MS emergence. Furthermore, by using the concentration level of Zn as indicator, it was revealed that the risk of MS infection rises as the number of pregnancies increase.     

Preconcentration and Separation of Trace Amounts of Strontium Ions from Alkali and Alkaline Earth Metal Ions Using Octadecyl Silica Membrane Disks Modified with Decyl-18-Crown-6 and Its Determination by Flame Atomic Absorption Spectrometry

 A simple and reliable method for rapid and selective separation of trace amounts of Sr²⁺ ions from alkali and alkaline earth metal ions by using octadecyl silica membrane disks modified with decyl- 18-crown-6 in the presence of 1.0 × 10⁻³ M picric acid is presented. The influence of picric acid concentration, flow rates and nature and amount of the stripping acid have been investigated. Maximum capacity of the membrane disks modified with 10 mg of the macrocycle was found to be 484 μg of Sr²⁺ ions. The proposed method permitted enrichment factors of about 80 and higher. The limit of detection of the proposed method is 1.5 μg per 1000 ml. The method was successfully applied to the recovery of Sr²⁺ ions from different synthetic and water samples. Received August 10, 2000. Revision April 17, 2001.     

Armatans A and B,New Antimicrobial Isoflavans from Colutea armata

Chemistry of Natural Compounds - Armatans A (1) and B (2), new isoflavans, have been isolated from the EtOAc-soluble fraction of the MeOH extract of Colutea armata Hemsl. &amp; Lace, along with...     

Aluminum dodecatungstophosphate (AlPW12O40) as an efficient heterogeneous inorganic catalyst for the chemoselective synthesis of geminal diacetates (acylals) under solvent-free conditions

An efficient and chemoselective preparation of acylals from structurally different aldehydes in the presence of AlPW₁₂O₄₀ and acetic anhydride was achieved easily in high yields at room temperature under solvent-free conditions.     

Optimization of Linac-based neutron source for thermal neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - A 20&nbsp;MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA)...     

Combined methane reforming over nano LaNiO<Subscript>3</Subscript> catalyst with modified active surface

In this study, nano catalyst LaNiO₃ with perovskite structure was synthesized using the citrate sol–gel method in the combined methane reforming with CO₂ and O₂ (CRM). The effects of increasing the surface area of the LaNiO₃ perovskite on the catalytic activity were investigated by changing the method of preparing and creating holes in the surface of the samples. Physical and chemical properties of the samples, before and after the reactor test, were determined through ICP, AA, XRD, TGA, TPR, BET, SEM, EDX and TEM techniques. The results of XRD, ICP, AA, SEM, EDX and TEM tests indicated that the citrate sol–gel method is a good way to prepare a homogeneous perovskite LaNiO₃ sample on a scale of nanometers. The results of the TPR test showed using etching in the citrate sol–gel method can produce samples with high stability. The BET results indicated that the surface area of the LaNiO₃ sample tripled with the method suggested in this paper. Changes in preparation method lead to induction time decreasing and temperature increasing. Use of etching in the citrate sol gel method had no significant effect in the results of activity tests versus time reaction at a temperature of 800 °C. TGA curves revealed no production of coke over the process for the produced samples.