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INDONESIA
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 9, No 4 (2004)" : 6 Documents clear
The Effects of Mass Loss on The Evolution of BD+60°2522 Aprilia Aprilia; Djoni N. Dawanas
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

BD+60°2522 (V = 8.7 mag) is the ionizing star of NGC 7635, the so-called Bubble Nebulae – wind-blown bubble created by the interaction of the stellar wind of BD+60°2522 with the ambient interstellar medium. It is classified as an O6.5 IIIef with mass loss rate M76.510−ô€¾/year. The present mass of the star is 50 Mô€¾. We carry out evolutionary calculations for the star with and without mass loss and we find that the initial mass of the star is 63 Mô€¾ and its present age is years. The main sequence lifetime for BD+60°2522 is longer compared with that computed without mass loss; the difference is years. Comparing the mass and the age of NGC 7635 with BD+60°2522, we find that the bubble nebulae did not form since the ZAMS phase of the star.
Konsumsi Makan dan Pertumbuhan Larva Helicoverpa armigera Toleran terhadap Pemaparan Helicoverpa armigera Nuclear Polyhedrosis Virus (HaNPV) Yayan Sanjaya; Wardono Noloperbowo; Tjandra Anggraeni
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

An investigation on the effect of repeated infection of Helicoverpa armigera Nuclear Polyhedrosis Virus (HaNPV) to Helicoverpa armigera to know its effect on Helicoverpa armigera tolerance had been carried out. On treatment with 800 (Polyhedral Inclusion Body/dose) PIB/dose indicated that the exposure of HaNPV to H. armigera larva showed no difference significantly (P> 0.05) on its LD50 to every generation exposed. In contrast, H. armigera which had been exposed by HaNPV had a higher food consumption and larval growth rate compared to H. armigera without treatment. This investigation also showed that the increasing food consumption and larvae growth rate of H. armigera was in line with the increase of HaNPV exposure. Infection of HaNPV caused a development of tolerance mechanism in H. armigera.
Pengaruh Temperatur Penumbuhan Terhadap Karakteristik Magnetik Film Tipis TiO2:Co yang ditumbuhkan dengan Metode Metalorganic Chemical Vapor Deposition (MOCVD) Horasdia Saragih; Pepen Arifin; Moehamad Barmawi; Mersi Kurniati
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

TiO2:Co thin films have been grown on p-type Si(100) substrates by MOCVD method. The films were grown at substrate temperature of 450 oC to 500 oC , and the temperature of precursor bubbler was kept constant at 50 oC with vapor pressure of 260 Torr. Flow rate of O2 and Ar are 60 sccm and 100 sccm, respectively. The crystal structure, grain shape and magnetic properties of the films depend significantly on the substrate temperature. The anatase-213 structure with columnar grain was formed for the films grown at temperatures of 400 oC and 450 oC. The arrangement of atoms at grain boundary is improved at growth temperature of 450 oC. Anatase-301 structure with cone grain shape as additional component appears at growth temperature of 500 oC. The TiCoO3 phase with 310 plane was found at growth temperature of 550 oC. The grains grow at direction of -45o from normal substrate. Films that grown at 450 oCand 500 oC exhibit soft magnetic properties with Hc of 100 Oe and 80 Oe; and Mr of 250 emu/cm3 and 220 emu/cm3, respectively. The hard magnetic properties of the films are shown for the films grown at 550 oC. The films were grown for 2 hours producing the films with thickness of about 0.7 to 0.9 μm.
Konstruksi Diagram Potensial-pH untuk Baja Karbon dalam Buffer Asetat secara Potensiodinamik Eksperimental Bunbun Bundjali; N. M. Surdia; Oei Ban Liang; Bambang Ariwahjoedi
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

The pH-potential, or the so called Pourbaix, diagram for the system Fe - H2O is normally been constructed by using thermodynamic data. In this work the diagram was constructed experimentally based on potentiodynamic measurements of carbon steel in acetic acid - acetate ion buffer solutions at a temperature range of 25-85 0C. Due to the limited pH trajectory of buffer acetate solutions the resulted diagrams were not as wide pH as those of thermodynamic Pourbaix diagrams, but they are more useful for analysing carbon steel corrosion in acetate environment systems at that temperature range. In Addition the effects of pH and temperature on the primary passive potential (Epp) and Fladge potential (EF) relationship could also be obtained.
Sintesis dan Karakterisasi BaSrAl4O8, BaSrAl3FeO8, dan BaSrAl2Fe2O8 Darwin Ismail; Ismunandar Ismunandar
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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BaSrAl4O8, BaSrAl3FeO8 and BaSrAl2Fe2O8 oxides have been synthesized and their crystal structures type were determined by XRD diffraction. The diffraction patterns were very close to that of BaSrGa4O8, which has space group P63 (No. 173). All of the compounds have AlO4 tetrahedra (as GaO4), form the six-membered rings sharing corners, and the Ba and Sr atoms occupy large cavities of the six-member rings. Fe atoms possibly replace Al atom in the structure. From Proszki analysis in a hexagonal crystal system and P63 space group (No.173), the obtained cell parameters, a and c for BaSrAl4O8, BaSrAl3FeO8 and BaSrAl2Fe2O8 were successively as follows (8.984(2), 8.625(3)) Å; (10.377 (4), 8.619(5)) Å; and (10.454(3), 9.140(3)) Å. Based on ferroelectric properties obtained from RT-66A oscilloscope instrument, only BaSrAl3FeO8 compound exhibited a significant hysteresis loop pattern.
Asymmetric Addition Reaction of Reformatsky Type Reagent to Nitrones: An Intermediate for Synthesis of Physiologically Active Substances Deana Wahyuningrum
Jurnal Matematika & Sains Vol 9, No 4 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

Asymmetric addition reaction of Reformatsky type reagent, which was generated in situ from diethylzinc and iodoacetic ester, to carbon-nitrogen double bond in nitrones utilizing (R,R)-DIPT as a chiral auxiliary agent showed fairly moderate to high enantioselective products in fairly high chemical yields. Nitrones were known as one of potentially intermediate nitrogen-containing compounds for synthesizing/physiologically active substances, such as pharmaceutical and agrochemical substances. The best results of this type of reaction were achieved from the asymmetric addition to nitrone, 6,7-dimethoxy-3,4-dihydroisoquinoline N-oxide (73% ee) and N-phenyl-α-(dibenzylcarbamoyl)methanimine N-oxide (21% ee) with fairly high chemical yields. The use of additive in asymmetric addition reaction to 6,7-dimethoxy-3,4-dihydroisoquinoline N-oxide was found to be crucial in improving the enantioselectivity of reaction, since the best results mentioned were achieved in the presence of isoquinoline-N-oxide or pyridine-N-oxide (0.5 molar equivalent) as additive. The difference in stereo-structure between 6,7-dimethoxy-3,4-dihydroisoquinoline N-oxide and N-phenyl-α-(dibenzylcarbamoyl)methanimine N-oxide caused the effect of (R,R)-DIPT as chiral auxiliary agent, additives and slow charge addition method towards the course of reaction resulting different products with different enantioselectivity.

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