8‐Aminoquinoline‐Assisted Synthesis and Crystal Structure Studies of Ferrocenyl Aryl Sulfones

A copper‐catalyzed 8‐aminoquinoline‐directed oxidative cross‐coupling of the C?H bond of ferrocene with sodium arylsulfinates has been achieved. The robust copper catalyst tolerates a range of methyl, tert‐butyl, bromo, chloro, iodo and nitro functional groups in the phenyl ring, and set the stage for the synthesis of substituted ferrocene sulfones. Furthermore, X‐ray crystal structure study on several ferrocenyl sulfones reveals the tetrahedral geometry around sulfur; interestingly, the O‐S‐O angle is larger than the electropositive substituent C‐S‐C angle which could be explained by Bent's rule. Further, unusual intramolecular O(S)???N(amide) short contacts (2.925–3) and O(S)???C=O were also noticed in ferrocenyl sulfones.     

Radiation dosimetry using clear PMMA and PVC in the range of 5–45 kGy

Some plastic sheets manufactured or commercially available in Pakistan have been tested as radiation dosimeters for cobalt-60 -rays. Radiation induced colouration in the plastics have been measured spectrophotometrically. The results show that 2 mm thick clear poly(methyl methacrylate) (PMMA) can be used as radiation dosimeter up to 45 kGy when absorption measurements are made at 305 nm and 314 nm; whereas 1 mm thick clear poly(vinylchloride) (PVC) is useful up to 30 kGy when measured at 396 nm. The response of PMMA dosimeter is stable for at least 15 days and that for PVC for 30 days, when stored under ambient conditions after irradiation. Post-irradiation stability at various temperatures (–10 to 55°C) has also been studied.     

Selective oxidation of organic compounds using pyridinium-1-sulfonate fluorochromate,C<Subscript>5</Subscript>H<Subscript>5</Subscript>NSO<Subscript>3</Subscript>H [CrO<Subscript>3</Subscript>F] (<Emphasis Type="Italic">PSFC</Emphasis>)

Efficient selective oxidation of primary, secondary, and benzylic alcohols to the corresponding carbonyl compounds by a new chromium oxidizing reagent, pyridinium-1-sulfonate fluorochromate, C₅H₅NSO₃H [CrO₃F] (PSFC) is reported. Various cholesterol derivatives were easily converted to related oxocholesterol from allylic oxidation at lower temperature in comparison to other general oxidants. This oxidation procedure is simple and affords good yields. Correspondence: Ahmad R. Bekhradnia, Department of Medicinal Chemistry, Mazandaran University of Medical Sciences, Sari, Mazandaran, Iran.     

Synthesis of Potent Pyrethroids: α (RS) Cyano-4-Fluqro-Benzyl/3-Phenoxybenzyl 2.2-Dichloro-Spiro (2.5)-Octane-1-Carboxylates

A simple facile synthesis of 2,2-dichloro-spiro (2,5)-octane-1-carboxylic acid has been described which was converted into the corresponding α (RS) cyano 3-phenoxybenzyl ester, exhibiting high insecticidal activity against Musca domestica and Aedes egyptii.     

High on/off current ratio in ballistic CNTFETs based on tuning the gate insulator parameters for different ambient temperatures

A theoretical study is presented on the on/off current ratio limits for a ballistic coaxially-gated carbon nanotube field effect transistor (CNTFET) with highly doped source/drain regions. Based on changes in gate insulator dielectric constant and thickness, the current ratio has been estimated at different ambient temperatures. Decreasing the gate insulator thickness after a certain value around 3 nm causes the current ratio to degrade drastically. Although the higher dielectric constant values have a fair effect on current ratio, this effect could be suppressed when the device with a low gate insulator thickness works at a low ambient temperature. The simulation results also show that the temperature drastically degrades the current ratio value; whereas in a certain range of ambient temperature, tuning the values of gate insulator thickness and dielectric constant could be very helpful. In this way, the optimum values of gate insulator thickness and dielectric constant are identified to offer the highest on/off current ratio of the device.     

Ni[P(OPh)3]4 Catalyzed Transfer Hydrogenation Using Hcoonh4

Ni[P(OPh)₃]₄ was found to catalyze the transfer hydrogenation of various organic functional groups using HCOONH₄.

     

Site-Specific <Emphasis Type="Italic">N</Emphasis>-Glycosylation of Recombinant Pentameric and Hexameric Human IgM

Glycosylation is known to play an important role in IgG antibody structure and function. Polymeric IgM, the largest known antibody in humans, displays five potential N-glycosylation sites on each heavy chain monomer. IgM can exist as a pentamer with a connecting singly N-glycosylated J-chain (with a total of 51 glycosylation sites) or as a hexamer (60 glycosylation sites). In this study, the N-glycosylation of recombinant pentameric and hexameric IgM produced by the same human cell type and culture conditions was site-specifically profiled by RP-LC-CID/ETD-MS/MS using HILIC-enriched tryptic and GluC glycopeptides. The occupancy of all putative N-glycosylation sites on the pentameric and hexameric IgM were able to be determined. Distinct glycosylation differences were observed between each of the five N-linked sites on the IgM heavy chains. While Asn171, Asn332, and Asn395 all had predominantly complex type glycans, differences in glycan branching and sialylation were observed between the sites. Asn563, a high mannose-rich glycosylation site that locates in the center of the IgM polymer, was only approximately 60% occupied in both the pentameric and hexameric IgM forms, with a difference in relative abundance of the glycan structures between the pentamer and hexamer. This study highlights the information obtained by characterization of the site-heterogeneity of a highly glycosylated protein of high molecular mass with quaternary structure, revealing differences that would not be seen by global glycan or deglycosylated peptide profiling.

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Graphdiyne: Bridging SnO2 and Perovskite in Planar Solar Cells

The matching of charge transport layer and photoactive layer is critical in solar energy conversion devices, especially for planar perovskite solar cells based on the SnO₂ electron‐transfer layer (ETL) owing to its unmatched photogenerated electron and hole extraction rates. Graphdiyne (GDY) with multi‐roles has been incorporated to maximize the matching between SnO₂ and perovskite regarding electron extraction rate optimization and interface engineering towards both perovskite crystallization process and subsequent photovoltaic service duration. The GDY doped SnO₂ layer has fourfold improved electron mobility due to freshly formed C?O σ bond and more facilitated band alignment. The enhanced hydrophobicity inhibits heterogeneous perovskite nucleation, contributing to a high‐quality film with diminished grain boundaries and lower defect density. Also, the interfacial passivation of Pb?I anti‐site defects has been demonstrated via GDY introduction.     

A fast color image encryption algorithm based on hyper-chaotic systems

This paper presents a new way of image encryption scheme, which consists of two processes; key stream generation process and one-round diffusion process. The first part is a pseudo-random key stream generator based on hyper-chaotic systems. The initial conditions for both hyper-chaotic systems are derived using a 256-bit-long external secret key by applying some algebraic transformations to the key. The original key stream is related to the plain-image which increases the level of security and key sensitivity of the proposed algorithm. The second process employs the image data in order to modify the pixel gray-level values and crack the strong correlations between adjacent pixels of an image simultaneously. In this process, the states which are combinations of two hyper-chaotic systems are selected according to image data itself and are used to encrypt the image. This feature will significantly increase plaintext sensitivity. Moreover, in order to reach higher security and higher complexity, the proposed method employs the image size in key stream generation process. It is demonstrated that the number of pixel change rate (NPCR) and the unified average changing intensity (UACI) can satisfy security and performance requirements (NPCR \(>\) 99.80 %, UACI \(>\) 33.56 %) in one round of diffusion. The experimental results reveal that the new image encryption algorithm has the advantages of large key space, high security, high sensitivity, and high speed. Also, the distribution of gray-level values of the encrypted image has a semi-random behavior.