Analisa Kekerasan Baja St 42 dengan Perlakuan Panas Menggunakan Metode Taguchi

Seiring dengan banyaknya kegagalan mekanis yang ditemui, Salah satu contohnya misalnya faktor kelelahan logam seperti patahnya poros kereta api, poros roda mobil, dan peristiwa patahnya poros Baling-Baling kapal. Untuk mengetahui seberapa besar pengaruh beban-beban tersebut terhadap kekuatan lelah material poros, maka diperlukan pengujian material hal ini menarik peneliti untuk melakukan riset perbaikan kualitas produksi. Metode yang dipakai dalam penelitian ini adalah metode taguchi yang pertujuan untuk memperbaiki kualitas produk dan proses serta dapat menekan biaya dan resources seminimal mungkin. Dengan jumlah sampel tiga media pendingin air,udara,oli, dengan temperature bervariasi 600o,700o,800o, kemudian bahan yang digunakan adalah baja ST 42. Factor yang paling mendominasi mempengaruhi tingkat kekerasan material adalah di faktor A yaitu temperature pemanasan. berdasarkan perhitungan dengan efek mean dan efek replikasi temperature pemanasan berada peringkat ke-1 di Replikasi ke 4 sebesar 24.33 HB, sedangkan untuk media pendingin berada peringkat ke-2 di Replikasi ke 2 sebesar 21.00 HB. Kombinasi factor dengan level yang memberikan peningkatan kekerasan yaitu dengan temperature 800oC dengan media pendingin oli sebesar 111.8 HB. Sedangkan yang melunakan yaitu kombinasi antara factor dengan level temperature 700oC dengan media pendingin air sebesar 88.8 HB

Binding of Gemini Bisbenzimidazole Drugs with Human Telomeric G-Quadruplex Dimers: Effect of the Spacer in the Design of Potent Telomerase Inhibitors

The study of anticancer agents that act via stabilization of telomeric G-quadruplex DNA (G4DNA) is important because such agents often inhibit telomerase activity. Several types of G4DNA binding ligands are known. In these studies, the target structures often involve a single G4 DNA unit formed by short DNA telomeric sequences. However, the 3′-terminal single-stranded human telomeric DNA can form higher-order structures by clustering consecutive quadruplex units (dimers or n-mers). Herein, we present new synthetic gemini (twin) bisbenzimidazole ligands, in which the oligo-oxyethylene spacers join the two bisbenzimidazole units for the recognition of both monomeric and dimeric G4DNA, derived from d(T2AG3)4 and d(T2AG3)8 human telomeric DNA, respectively. The spacer between the two bisbenzimidazoles in the geminis plays a critical role in the G4DNA stability. We report here (i) synthesis of new effective gemini anticancer agents that are selectively more toxic towards the cancer cells than the corresponding normal cells; (ii) formation and characterization of G4DNA dimers in solution as well as computational construction of the dimeric G4DNA structures. The gemini ligands direct the folding of the single-stranded DNA into an unusually stable parallel-stranded G4DNA when it was formed in presence of the ligands in KCl solution and the gemini ligands show spacer length dependent potent telomerase inhibition properties

C9orf72 hexanucleotide repeat associated with amyotrophic lateral sclerosis and frontotemporal dementia forms RNA G-quadruplexes

available on open access on journal websiteLarge expansions of a non-coding GGGGCC-repeat in the first intron of the C9orf72 gene are a common cause of both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). G-rich sequences have a propensity for forming highly stable quadruplex structures in both RNA and DNA termed G-quadruplexes. G-quadruplexes have been shown to be involved in a range of processes including telomere stability and RNA transcription, splicing, translation and transport. Here we show using NMR and CD spectroscopy that the C9orf72 hexanucleotide expansion can form a stable G-quadruplex, which has profound implications for disease mechanism in ALS and FTD.Peer reviewe

Electrospray Mass Spectrometry of Telomeric RNA (TERRA) Reveals the Formation of Stable Multimeric G-Quadruplex Structures

We report on the self-assembled structures formed by 12-mer, 22-mer, and 45-mer telomeric RNA (telRNA/TERRA) sequences compared to their DNA analogues, as studied by electrospray mass spectrometry, circular dichroism, and thermal denaturation. The major difference between telomeric RNA and DNA sequences is the ability of telomeric RNA to form higher-order dimeric assemblies, initiated by cation-mediated stacking of two parallel G-quadruplex subunits. The 5′-5′ stacking had been observed recently by NMR for the r(GGGUUAGGGU) 10-mer (Martadinata, H.; Phan, A. T. J. Am. Chem. Soc. 2009, 131, 2570); the present work shows that stacking also occurs for the 22-mer containing four G-tracts and for the 45-mer containing eight G-tracts, suggesting a general structural feature of telomeric RNA. The importance of kinetic effects in multimer formation, unfolding, and structural rearrangements is also highlighted