Preliminary evaluation of mutagenic activity of two amino derivatives of cyclopenta[c]phenanthrene

The mutagenicity of two, newly synthesized amino-derivatives of cyclopenta[c]phenanthrene (CP[c]Ph) was investigated in the Ames test using TA98 and TA100 histidine dependent Salmonella typhimurium strains. Neither of the examined compounds showed mutagenic activity without metabolic activation. The incorporation of an activation system caused high mutagenicity of CP[c]Ph derivatives in both S. typhimurium strains. The results are compared with the previous data on the mutagenic activity of unsubstituted CP[c]Ph and possible mechanisms of activation are discussed

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Direct synthesis of Fmoc protected amino acid hydroxamates from acid chlorides mediated by magnesium oxide

The synthesis of Fmoc protected amino acid hydroxamates using Fmoc-amino acid chlorides and magnesium oxide is described. The method is simple and efficient, results in complete conversion, and gives good yields and satisfactory purity. © 2003 Elsevier Science Ltd. All rights reserved

Проявление кристаллической структуры атактического полиакрилонитрила в ИК-спектре терагерцового диапазона

Получены и проанализированы ИК-спектры полиакрилонитрила (ПАН) и ацетонитрила (АЦ) при температурах от комнатной до 160 К в терагерцовом диапазоне, где проявляются либрационные колебания мономерных звеньев. Показано, что особенности контура либрационной полосы поглощения спектра ПАН свидетельствуют о наличии кристаллоподобных областей, твердотельный фазовый переход в которых предшествует и инициирует γ-релаксацию в аморфных областях этого полимер

Recent Changes in Atmospheric Polycyclic Aromatic Hydrocarbons (PAHs) and Nitropolycyclic Aromatic Hydrocarbons (NPAHs) in Shenyang, China

Airborne particulates were collected in three size fractions by using Anderson low-volume air samplers in Shenyang, China, in winter and summer in 2007. Compared with data obtained in 2001 at the same sites, the total concentrations of nine polycyclic aromatic hydrocarbons (PAHs) in winter decreased by 67% at one site and decreased by 40% at the other site, while the total concentrations of four nitropolycyclic aromatic hydrocarbons (NPAHs) did not decrease. This suggests that environmental countermeasures begun in 2001 were effective in decreasing the concentration of PAHs. However, in summer, the concentrations of PAHs and NPAHs rose by the factors of 4 and 5, respectively, possibly because of an increase in the number of motor vehicles. © 2011 Taylor and Francis Group, LLC

Degradable precision polynorbornenes via ring-opening metathesis polymerization

In an attempt to introduce monomer sequence control in a growing polynorbornene via ring-opening metathesis polymerization, we employ dioxepins to efficiently determine the location of the monomers on the macromolecule backbone. Owing to the acid-labile acetal group, dioxepins allow scission of the polymer at the point of the dioxepin insertion and thus provide an indirect way to determine the monomer location. Additionally, dioxepins are used as spacers in the synthesis of multiblock polynorbornenes that are readily cleavable to afford the individual polynorbornene blocks

SMALL-HOLE DRILLING USING DIE SINKER ELECTRICAL DISCHARGE MACHINE

Banyak kesulitan dihadapi pada pemesinan lubang kecil. Terutama jika prosesnya dilakukan dengan proses drilling mekanik. Untuk mengatasi kendala yang dihadapi, proses pemesinan non-tradisional seringkali diterapkan. Tulisan ini melaporkan hasil studi pemesinan lubang kecil (diameter kurang dari 1 mm) menggunakan EDM die sinker. Lubang dibuat pada aluminium dengan ketebalan 3 mm. Kawat tembaga berdiameter kurang dari 1 mm dipergunakan sebagai elektroda. Untuk menghindari keausan elektroda yang berlebihan, pemesinan dilakukan dengan menggunakan parameter yang menghasilkan energi rendah. Pemilihan parameter ini juga dimaksudkan untuk mendapatkan kualitas lubang yang baik. Pengamatan dilakukan terhadap kualitas lubang yang dihasilkan. Selain itu studi juga dilakukan pada pengaruh parameter pemesinan terhadap keausan elektroda dan waktu pemesinan. Hasil studi menunjukkan bahwa lubang dengan diameter kurang dari 1 mm berhasil dibuat dengan mesin EDM die sinker. Waktu yang diperlukan untuk pemesinan berkisar antara 5 – 6 menit. Lubang yang dihasilkan memiliki kebulatan yang relative baik dan permukaan yang tajam. Peningkatan energi pemesinan menambah keausan elektroda dan memperpanjang waktu pemesinan.   Keywords: EDM, small hole, drilling, electrode wea

Cytosine Palladium Complex Supported on Ordered Mesoporous Silica as Highly Efficient and Reusable Nanocatalyst for One-Pot Oxidative Esterification of Aldehydes

The synthesis of esters is one of the most fundamental and significant subjects in organic chemistry and chemical industry because they are used in high-value products such as cosmetics, biofuel, pharmaceuticals, surfactants, and food ingredients. In this study, an efficient, economic, sustainable, and green protocol for oxidative esterification reaction has been developed. A one-pot direct transformation of aliphatic, aromatic, and unsaturated aldehydes into esters in the presence of oxygen has been carried out over mesoporous organosilica-supported palladium nanocatalyst (Pd-Cyt@SBA-15) under ambient conditions. Pd-Cyt@SBA-15 efficiently catalyzed selectively large-scale conversion of aldehydes into esters in high yields and large turnover numbers (TON = 98,000). Pd-Cyt@SBA-15 nanocatalyst demonstrated excellent reusability and stability and could be recycled up to ten times without loss of significant reactivity. ICP-AES analysis showed that no leaching of active palladium species occurred during the recycling process of the heterogeneous Pd-Cyt@SBA-15 nanocatalyst