25 research outputs found
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 伪-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
Spatial organization of dendritic cells within tumor draining lymph nodes impacts clinical outcome in breast cancer patients
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 渭m PVDF film is bonded on a silicon substrate using a capacitive acrylic thin film and a i 渭m 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