Makara Journal of Science
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Band Alignment of Ultrathin Gizo/SiO2/Si Heterostructure Determined by Electron Spectroscopy
No full textAmorphous GaInZnO (GIZO) thin films are grown on SiO2/Si substrate by the RF magnetron sputtering method. By the combination of measured band gaps from reflection energy loss spectroscopy (REELS) spectra and valence band from X-ray photo-electron spectroscopy (XPS) spectra, we have demonstrated the energy band alignment of GIZO thin films. The band gap values are 3.2 eV, 3.2 eV, 3.4eV and 3.6eV for the concentration ratios of Ga: In: Zn in GIZO thin films are 1:1:1, 2:2:1, 3:2:1 and 4:2:1, respectively. These are attributed to the larger band gap energy of Ga2O3 compared with In2O3 and ZnO. The valence band offsets (ΔEv) decrease from 2.18 to 1.68 eV with increasing amount of Ga in GIZO thin films for GIZO1 to GIZO4, respectively. These experimental values of band gap and valence band offset will provide the further understanding in the fundamental properties of GIZO/SiO2/Si heterostructure, which will be useful in the design, modeling and analysis of the performance devices applications
The Partition Function of the Bose-Einstein Condensation in Parabolic Trap
No full textWe have discussed the partition function of the Bose-Einstein condensation in parabolic trap associated to the one-dimensional Gross-Pitaevskii equation. The partition function itself is constructed by considering all the energy levels of the macroscopic quantum oscillator which is similar to statistical mechanics. The solutions of the energy levels for this case can be derived by pursuing the method proposed by Kivshar et al. that applies the time-independent perturbation theory. In their paper, they demonstrated that the one-dimensional Gross Pitaevskii equation can be treated as the one-dimensional macroscopic quantum oscillator on condition that the nonlinearity is very small. Moreover, they found the analytical expression for the ground state energy by applying the method. However, the higher level states were not explicitly provided. In this research we followed up on their former work to derive explicitly the other states in order to formulate the partition function. However, we did not find the closed form of the partition function since the results of nonlinear term integral could not form the recursion relation. As a consequence, not only should the partition function but also the Helmholtz free energy and entropy should be reevaluated to check their convergences. Keywords: Gross-Pitaevskii equation, partition function, quantum oscillator, thermodinamical properties
Physiological Responses of Jatropha to Drought Stress in Coastal Sandy Land Conditions
No full textJatropha curcas L., an important tropical biofuel crop, is reputed for its drought resistance, however, its ability to perform in dry conditions has still hardly been investigated. Changes in leaf water status, chlorophyll content, leaf surface temperature, stomatal conductance, proline and abcisic acid (ABA) content, transpiration and photosynthetic rate were studied in four Jatropha genotypes (IP-1A, IP-2M, Local superior and Yellow leaf) and subjected to drought stress in coastal sandy land conditions in Central Java, Indonesia. Drought stress significantly decreased the leaf water status, leaf chlorophyll content, stomatal conductance, transpiration and photosynthetic rate, and increased leaf temperature, proline and ABA content. Resistant genotypes (IP-1A and IP-2M) had significantly higher leaf water status, chlorophyll content and photosynthetic rate than susceptible genotypes (Local superior and Yellow leaf). There were no differences between the Jatropha genotypes on leaf temperature, stomatal conductance and transpiration rate.Keywords: ABA, biofuel, photosynthetic rate, proline, stomata, water statu
The Free Radical Scavenging and Anti-Hyperglycemic Activities of Various Gambiers Available in Indonesian Market
No full textGambier (Uncaria gambier) is known to have antioxidant properties, and some studies have attributed it to the presence of polyphenols such as catechin. The objective of this study is to investigate the potential of various gambiers available in Indonesian market as a scavenger of reactive free radicals and evaluate its anti-hyperglycemic activity as α- glucosidase inhibitor. Isolation of catechin was done by extraction method with technical grade of ethyl acetate as solvent. Analysis of catechin in the dried gambier extract was carried out with TLC method. The molecular weight and content of catechin of dried gambier extract was determined by analyzing its mass spectra and spectrophotometer, respectively. The free radical scavenging activity of catechin of the resultant extracts was measured by using 1,1- diphenyl-2-picrylhydrazyl (DPPH) as stable free radical compound. The anti-hyperglycemic activity of catechin of ethyl acetate extracts was analyzed as α-glucosidase inhibitor. The result showed that various gambiers available in the market are very active as antioxidant, indicated by IC50 of catechin of ethyl acetate extracts which were 4.6 to 18.2 μg/mL for DPPH inhibition. The IC50 for α-glucosidase inhibition is ranged from 40.45 to 52.43 μg/mL, so they can be classified as anti-diabetic. 
Serosurveillance of Avian Influenza Virus Subtype H5N1 with Haemagglutination-Inhibition on Wild Aquatic Birds in Pulau Dua Serang Natural Reserves, Banten Province
No full textFurther detailed research is required to obtain deeper information on the role of wild birds on the distribution of Avian influenza in Asia. A research has been carried out on February–June 2007 focused on blood sampling (serosurveillance) of wild birds in Pulau Dua Nature Reserves (CAPD), Serang, Banten. The research is aimed to investigate the infection of AI virus sub-tye H5N1 on the studied wild birds. The blood samples were taken from studied aquatic birds, followed by HI (haemagglutination-inhibition) test. A total of 183 samples represent 7 water bird species were taken i.e Cattle egret Bubulcus ibis, Javan pond-heron Ardeola speciosa, Little egret Egretta garzetta, Intermediate egret Egretta intermedia, Black-crowned night heron Nycticorax nycticorax, Great egret Casmerodius albus and Grey heron Ardea cinerea. The result revealed that 41 (23.27%) samples showed the present of AIV antibodies serotype H5N1 which is identified as positive. Data showed 5 positive-test species, including B. ibis (29.27%), E. garzetta (29.27%), E. intermedia (4.88%), Ardeola speciosa (7.32%), and N. nycticorax (29.27%). A total of 41.46% were infected adult individual, whereas 58.54% were juveniles
Self-Assembly and Hydrogelation of Peptide Amphiphiles
No full textSeven peptide amphiphiles were successfully synthesized using solid phase peptide synthesis method. Peptide amphiphiles were characterized using matrix assisted laser desorption/ionization (MALDI). Atomic force microscopy (AFM) study showed that peptide amphiphiles having glycine, valine, or proline as linker, self-assembled into 100-200 nm nanofibers structure. According to our research, both peptide amphiphile with positive and negative charges bear similar self-assembly properties. Peptide amphiphile also showed its capability as low molecular weight gelator (LMWG). Peptide amphiphiles bearing C-16 and C-12 as alkyl showed better hydrogelation properties than C-8 alkyl. Five out of seven peptide amphiphiles have minimum gelation concentration (MGC) lower than 1%(w/v). Keywords: low molecular weight gelator, MALDI, peptide amphiphile, self-assembly, solid phase peptide synthesi
X-RAY DIFFRACTION PHASE ANALYSES OF MULLITE DERIVED FROM RICE HUSK SILICA
No full textIn this study, mullite synthesized from aluminum nitrate hydrate [(Al(NO3)3.9H2O] and silica sol from rice husk was subjected to sintering treatment at temperatures of 900, 1000, 1100, 1200 and 1300 °C, and characterized using x-ray diffraction (XRD), followed by Rietveld refinement, and differential thermal analysis (DTA). The results indicate that in the sample sintered at 900 °C, no mullite phase was identified, but crystoballite and alumina were well detected. The formation of mullite started at temperature of 1000 °C and continued to grow at higher temperatures, resulted in increased weight percentage (wt%) from 62.62 to 92.29%, while crystoballite and alumina decreased from 22.42 to 1.25% and from 77.58 to 6.46 % respectively. A good correlation was found between the calculated and observed unit cells. For mullite phase, the unit cell dimensions are a = 7.545 nm, b = 7.689 nm and c = 2.884 nm, for crystoballite a = b = 0.5531 nm and c = 0.6923 nm, and for alumina a= b = 0.5026 nm, and c = 1.2808 nm. The DTA analyses revealed that in the untreated sample, only alumina and silica were detected, while in the sintered samples, the existence of mullite, alumina, and crystoballite are evident. Keywords: mullite, rice husk, Rietveld, structure, sinterin
Preparation of Sulfonated PVA-TMSP Membranes for Direct Methanol Fuel Cell
No full textNovel preparation and characterization of sulfonated polyvinyl alcohol (PVA)–trimethoxysilyl propanethiol (TMSP) membranes for direct methanol fuel cell (DMFC) application have been investigated. Preparation of sulfonated PVA-TMSP membrane was conducted by crosslinking steps using sol-gel method and a catalyst of concentrated HCl. TMSP concentrations were varied from 1% to 3%. The gel solution was cast on to the membrane metal plate to obtain membrane sheets. The membrane was then oxidized in H2O2 concentrations of (10-30%) to convert the mercapto groups into sulfonate group. Investigations of the cross-linking process and the existence of sulfonate group were conducted by infrared spectroscopy as shown for frequencies at 1140–1200 cm-1 and 1200–1145 cm-1 respectively. The scanning electron microscope–energy dispersive X-rays (SEM–EDX) of the membranes indicated that the distribution of silica particles from sol–gel reaction products was uneven due to the fast exchange rate of condensation. The degree of swelling decreased as methanol concentrations increase for sulfonated PVA–TMSP membrane which opposed toward the value of commercial Nafion membrane. The maximum value of ion exchange capacity of the membrane was 1.82 mmol/g whereas the highest proton conductivity was 3.9 x 10-4 Scm-1. Therefore it can be concluded that the membrane was a potential candidate for application in DMFC.Keywords: DMFC, fuel cell, nafion, PVA, TMS
Synthesis and Antiplasmodial Activity of 2-(4-Methoxyphenyl)-4-Phenyl-1,10-Phenanthroline Derivative Compounds
No full textA unique of synthetic methods was employed to prepare 2-(4-methoxyphenyl)-4-phenyl-1,10-phenanthroline (5) derivatives from 4-methoxy-benzaldehyde (1), acetophenone (2), and 8-aminoquinoline (4) with aldol condensation and cyclization reactions. The derivatives were tested through antiplasmodial test. The synthesis of derivatives compound 5 was conducted in three steps. The 3-(4-methoxyphenyl)-1-phenylpropenone 3 was synthesized through aldol condensation of 1 and 2 which has a yield of 96.42%. The compound 5 was synthesized through cyclization of compound 4 and 3 with 84.55% yield. The derivative of compound 5 was synthesized from compound 5 using DMS and DES reagents which refluxed for 21 and 22 h, to produce (1)-N-methyl-9-(4-methoxyphenyl)-7-phenyl-1,10-phenanthrolinium sulfate (6) and (1)-N-ethyl-9-(4-methoxyphenyl)-7-phenyl-1,10-phenanthrolinium sulfate (7) with 91.42 and 86.36% yields, respectively. Results of in vitro testing of antiplasmodial activity of compound 5 derivatives (i.e., compound 6 and 7) against chloroquine-resistant P. falciparum FCR3 strain showed that compound 7 had higher antimalarial activity than compounds 5 and 6. Whereas, results of in vitro testing against chloroquine-sensitive P. falciparum D10 strain showed that compound 6 has higher antimalarial activity than compounds 5 and 7.Keywords: antimalarial activity, synthesis, 2-methoxyphenyl-4-phenyl-1,10-phenanthroline derivative
Synthesis and Application of Jatropha Oil based Polyurethane as Paint Coating Material
No full textRecently, the use of renewable sources in the preparation of various industrial materials has been revitalized in response to environmental concerns. Natural oils are considered to be the most important genre of renewable sources. Jatropha curcas oil (JPO) based polyol is an alternative material that may possibly replace petrochemical-based polyol for polyurethane coating material. Polyurethane was synthesized by reacting JPO-based polyol with isocyanate. To produce JPO-based polyol, JPO was first epoxidized to form epoxidized J. curcas oil (EJP), subsequently it was converted to polyol by the opening ring reaction with acrylic acid (AA) using triethylamine (TEA) as a catalyst. The JPO-based polyurethane film resulting from this study is compared with polyurethane film from commercial polyol for gloss, hardness, and adhesion quality. The result showed that the source of polyol has an influence on gloss, hardness, and adhesion of polyurethane film, but the differences with using isocyanate has less influence. Using visual observation, polyurethane film produced from L.OHV polyol, H.OHV polyol and commercial polyol have similar qualities.Keywords: coating material, JPO-based polyol, polyurethan