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Jurnal Matematika & Sains
Published by Institut Teknologi Bandung
ISSN : -     EISSN : -     DOI : -
Core Subject : Education,
Mathematics
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Articles 6 Documents
 1 
Search results for , issue " Vol 11, No 1 (2006)" : 6 Documents clear
Pengaruh Temperatur Deposisi Lapisan Penyangga Aluminium Nitrida terhadap Struktur Kristal dan Morfologi Film Tipis GaN dengan Metoda DC Unbalanced Magnetron Sputtering Dadi Rusdiana
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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Abstract

Gallium nitride thin films were grown on (0001) sapphire substrates by DC unbalanced magnetron sputtering using of aluminum nitride buffer layer. The properties of GaN thin films were improved by optimization of the growth temperature of buffer layers between 450 °C to 700 °C. Results showed that GaN film properties such as crystal structures and morphological properties were improved. XRD characterization shows that there was most probability to create a better of crystal structure with orientations of (1011) and (1120) with FWHM 0.3° and 0.6° respectively if the growth temperature of buffer layer was 450 °C.
S-Brane Solutions with Accelerating Cosmology in M-theory Freddy Permana Zen; Arianto Arianto; Bobby Eka Gunara; Selly Feranie
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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Abstract

We study the expansion and accelerated expansion of universe from S-branes of the M-theory. The dynamics of expansion is described by the scale factor of S-brane solutions and equation of state from the S-bran dark energy models. We provide analytic expressions to calculate the equation of state of these models as a function of time. Moreover, we also study cosmological expansion with the intersection solutions, which may have an interesting characteristic, namely, they never obtain the accelerated expansion. The critical expansion is given by the limit β→0.
Karakteristik Struktur dan Listrik Film Tipis GaN yang Ditumbuhkan di atas Substrat Si(111) dengan Metode Plasma Assisted-Metalorganic Chemical Vapor Deposition (PA-MOCVD) Heri Sutanto; Agus Subagio; Edi Supriyanto; Pepen Arifin; Sukirno Sukirno; Maman Budiman; Mohamad Barmawi
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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Abstract

Gallium nitride (GaN) thin films have been grown on Si(111) substrate by PA-MOCVD method, with trimethylgallium (TMGa) and radical nitrogen resulted by plasma of nitrogen gas as a source of Ga and N respectively. The growth was performed at 675 °C; 0.4 torr; 90 sccm and 0.08-0.12 sccm of substrate temperature, reactor pressure, gas flow of nitrogen and TMGa, respectively. The grown polycrystalline GaN thin films have hexagonal structure and n-type semiconductor. The growth rate of the grown thin films increased with increasing gas flow of TMGa. The Hall mobility value of films is still low due to the presence of O and C impurities. The highest value of mobility was found to be 64.88 cm2/V.s with 5.47 x 1018 cm-3 of carrier concentration.
Penentuan Energi Kisi Oksida-Oksida Piroklor Dede Suhendar; Ismunandar Ismunandar
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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Lattice energy of pyrochlore oxides prediction is important in relation with the synthesis effort. This work was aimed to find an equation that could be used to predict the lattice enthalpy of pyrochlore oxides. As standards, pyrochlores with known enthalpy formation were used to calculate the lattice entalphy via Born Haber cycle U(BHC). Lattice energies, U, of pyrochlore oxides were calculated by Glasser (G), Glasser-Jenkins, (GJ), and Yoder-Flora, (YF) equations. Plotting of Born-Haber lattice energies U(BHC) vs. U(G), U(GJ), and U(YF) resulted in R2 = 0.9564, 0.8671, and 0.9993, respectively. Based on the fitting of U(BHC) vs. U(YF), then a combination of Yoder-Flora and Kapustinskii equations were formulated and tested for U(BHC) of pyrochlore oxides. The Yoder-Flora-Kapustinskii (YFK) equation was U(YFK)pyrochlore = Σ U(K) oxide of A + Σ U (K) oxide of B where U(K) is lattice energy of oxide calculated by Kapustinskii equation using ionic radii of A in eight coordination number, and B in six coordination number, except for B ions from oxide fluorite structures in eight coordination number. The differences between U(YFK) and U(BHC) were < 3 %..
Evaluation of the Ethylene Effect on Well Defined Copper Enzymes Megawati Santoso; Harold M. Goff
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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An indirect approach in studying ethylene binding sites of copper enzymes was carried out since ethylene pleitropic effect in plants and the general affinity of Cu(I) complexes for ethylene suggest a possibility of ethylene binding to various copper enzymes. For this purpose, superoxide dismutase (SOD) and tyrosinase were evaluated using two different methods. H-NMR spectra of three different conditions of SOD (native SOD; reduced SOD; and reduced SOD in the presence of ethylene) were acquired at 25 °C. Activity of mushroom tyrosinase was monitored in the absence of ethylene by evaluating the formation of dopachrome at 475 nm. Three other assay systems were constructed the same way as the control, except one of the reagents (enzyme, DL-DOPA, or sodium phosphate buffer) was each saturated with ethylene prior to mixing all of reagents. Both systems behaved unsatisfactorily for the purpose of evaluation. The coordinated ethylene proton-NMR signal was obscured by the broad HOD signal, due to the partial oxidation of Cu(I) SOD by trace oxygen. Nonetheless, the tyrosinase assay results demonstrated that displacement of oxygen in the assay system by ethylene did not account for the loss of activity. The observed ethylene effect on tyrosinase activity, however, was minimal, since ethylene could produce threshold physiological response at concentration of 6.5 x 10-9 M.
Lanthanum (III) Selective Electrode Based on 1,10-Diaza-4,7, 13,16-Tetraoxacyclooctadecane-N,N’-Diacetic Acid (DACDA) as an Ionophore Susanto Imam Rahayu; Buchari Buchari; Indra Noviandri; Suyanta Suyanta
Jurnal Matematika & Sains Vol 11, No 1 (2006)
Publisher : Institut Teknologi Bandung

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Abstract

A lanthanum(III) ion selective electrode based on ionophore 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N-diacetic acid was studied. The electrode was prepared with an inner solution system in a membrane composition that contained an active ionophore 1,10-diaza-4,7-13,16-tetraoxacycloocta decana-N,N-diacetic acid (DACDA), an anionic side potassium tetrakis (4-chlorophenyl) borate (KTCPB), a plasticizer o-nitro phenyl octyl ether (NPOE) and a polyvinyl chloride (PVC) matrix support. A good response was obtained with a slope of 19.53 ± 1.62 mV/decade and the electrode gave responses with a detection limit of 3.92x10-6 M. The measurement range was wide (10-5-10-1 M) and the responses time was about 27 seconds. The electrode could measure lanthanum ion with a few interfering alkali, earth alkali and transition elements.

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