Vitamin E models. Shortened sidechain models of alpha, beta, gamma and delta tocopherol and tocotrienol - a density functional study

Model compounds of alpha-, beta-, gamma-, and delta-tocopherol and Tocotrienol, as well as their sulphur and selenium congeners, were subjected to density functional analysis. The mono methyl substitution either stabilized or destabilized the ring structures to a small extent as assessed in terms of isodesmic reactions. In general, multiple methyl substitutions destabilized the ring. Dimethyl para-substitution results in electronic stabilization and steric repulsion being nearly additive. This was not the case for oriho-dimethyl derivatives, whereby steric repulsions dominate; the meta-substituted models reflect the same trend to a lesser degree. Structurally, the phenolic hydroxyl orientation was approximately planar, with the hydroxyl proton oriented away from the adjacent Me group whenever the structure permitted such an orientation. (C) 2003 Published by Elsevier B.V

Vitamin E models. Conformational analysis and stereochemistry of tetralin, chroman, thiochroman and selenochroman

Tetralin, chroman as well as its' S and Se containing congeners were subjected to ab initio (RHF/3-21G and RHF/6-31G(d)) and DFT (B3LYP/6-31G(d)) computation. Molecular geometries and the activation energies for ring inversions were determined with full geometry optimizations. (C) 2002 Elsevier Science B.V. All rights reserved

Vitamin E models. Can the anti-oxidant and pro-oxidant dichotomy of α-tocopherol be related to ionic ring closing and radical ring opening redox reactions?

The free radical scavenging mechanism, leading to a quinodal structure via an oxidative ring opening is exothermic. However, the ionic oxidative ring opening is endothermic. Consequently, the ionic reductive ring closing must be exothermic. This leads to the suggestion that Vitamin E may be recovered, unchanged, thus effectively acts as a catalyst for the following reaction 2HOO + H3O(+) + NADH --> 2HOOH + H2O + NAD((+)), DeltaE approximate to 120 kcal mol(-1). As Vitamin E is biologically recycled, a single alpha-tocopherol molecule may convert numerous HOO radical to H2O2 which is accumulated if not removed at the same rate, enzymatically, with the participation of catalase (Fe) or glutathione peroxidase, GP,(Se). This accumulation of peroxide, which may be referred to as a 'peroxide traffic jam', may well be the reason of the prooxidant effect of Vitamin E. (C) 2002 Published by Elsevier Science B.V

A comparative study of integrated ferroelectric polymer pyroelectric sensors

This paper presents a comparative study of integrated pyroelectric sensors based on ferroelectric polymers. Two deposition technologies of PVDF and VDF/TrFE copolymer, both compatible with IC manufacturing, are presented. A 9 μm PVDF film is bonded on a silicon substrate using a capacitive acrylic thin film and a i μm VDF/TrFE copolymer is coated directly using a spin-coating technique. The theoretical response of both PVDF and VDF/TrFE pyroelectric sensors are calculated and related to the measured values. Peak responsivities of 4.5 V/W at 200 Hz and 3 V/W at 1kHz have been achieved for the pyroelectric sensors based on PVDF AND VDF/TrFE copolymer, respectively. Despite the responsivity of PVDF being slightly higher than that of the VDF/TrFE copolymer, the choice of which polymer to use will depend on the application and the preferred processing rout

Aplikasi Pasagi (Pasar Sumedang Go Online) Solusi Belanja Dimasa Psbb

Berdasarkan PP 21 tahun 2020 tentang Pembatasan Sosial Berskala Besar dalam rangka Percepatan Penanganan Corona Virus Disease (COVID-19) dengan melakukan pembatasan diri dan pergerakan individu warga negara untuk tinggal di rumah, membatasi frekuensi dan jumlah pertemuan massal untuk kemudian dapat menangani penyebaran virus. Beberapa sektor yang tetap diperbolehkan untuk beroperasi diantaranya sektor pangan, kesehatan, logistik, komunikasi, keuangan dan keamanan. Selama PSSB berlangsung, perekonomian mengalami pelemahan baik nasional ataupun regional hal ini dikarenakan kurangnya ruang gerak di sektor perdagangan seperti pasar tradisional maupun pasar modern. Aplikasi pasagi (pasar sumedang go online) merupakan aplikasi bagi masyarakat melakukan transaksi belanja kebutuhan pangan yang tersedia di pasar sumedang secara online sehingga memudahkan masyarakat sumedang untuk berbelanja ke pasar sumedang sehingga mengurangi perkumpulan massal. aplikasi Pasagi menyediakan fitur keranjang belanja, fitur detail pemesanan dan checkout transaksi, serta fitur notifikasi pesanan. Pesanan akan diantar oleh kurir dan dapat melakukan pembayaran ditempat.Pengembangan aplikasi menggunakan pendekatan prototype yang digunakan dengan model waterfall. Penelitian ini menghasilkan aplikasi pasar online berbasis android dengan menampilkan informasi produk-produk kebutuhan pangan dan dapur yang dijual oleh di pasar sumedang. Dengan aplikasi tersebut, segala transaksi belanja di pasar dapat dengan mudah dilakukan melalui ponsel. Tentunya berbelanja menjadi lebih menarik dan lebih mudah

Prinsip-prinsip kimia modern

judul asli: principles of modern chemistry, jil.1xvii, 572 p. : il.; 28 cm

Prinsip-prinsip kimia modern. Edisi keempat. Jilid 2

Jakartaxvi, 335 p.: gloss., indeks, lamp.; 28 c