| Judul | Abstract | Halaman |
|---|
| Ab Initio Calculation of UV-Vis Absorption Spectra of a Single Chlorophyll a Molecule: Comparison Study between RHF/CIS, TDDFT, and Semi-Empirical Methods | Chlorophyll a is the most abundant pigment on Earth responsible for trapping light energy to perform photosynthesis in green plants. This molecule has been studied for many years from different points of interest with both experimental and theoretical methods. In this study, the Restricted Hartree-Fock/Configuration Interaction Single (RHF/CIS), Time-Dependent Density Functional Theory (TDDFT), and several semi-empirical methods (CNDO/S and ZINDO) calculations were carried out to reconstruct the UV-Vis absorption spectra of chlorophyll a. To some extent, the calculation results based on the single-molecule approach succeeded to reconstruct the absorption spectra, but they required to be rescaled to fit the experimental results. In general, the semiempirical methods provide a better energy scaling factor. However, they lack vertical transition fine features with respect to the spectrum obtained experimentally. In this case, the ab initio calculations provided more complete features, especially the TDDFT with high-level basis sets, which also has a good accuracy with regards to the transition energies. The contribution of the ground state and excited state orbitals in the main vertical transitions is discussed based on the delocalized nature of the wave functions and the presence of solvents using the polarizable continuum model (PCM). | 93-112 |
| The Role of Equatorial Oceanic Waves in the Activation of the 2006 Indian Ocean Dipole | Observations and a linear wave model were used to evaluate the role of equatorial oceanic wave processes in affecting the evolution of the 2006 positive Indian Ocean Dipole (IOD), focusing on the activation phase of the event. The observations indicate the presence of upwelling equatorial waves and westward near-surface zonal currents along the equator during the activation phase of the event in August 2006. These upwelling equatorial waves (negative sea surface height anomalies) and westward zonal current anomalies contributed to significant sea surface cooling in the eastern equatorial Indian Ocean. The model results reveal that the upwelling equatorial waves and westward nearsurface zonal currents were mainly generated by wind-forced Kelvin waves associated with the easterly wind anomalies. On the other hand, anomalous easterly winds along the equator during June caused downwelling waves (positive sea surface height anomalies) in the off-equatorial region which propagated westward and elevated sea levels in the western region. The model further shows that a complex interplay of wind-forced and boundary-generated Rossby waves elevated sea levels in the western equatorial Indian Ocean during the activations phase of the 2006 IOD event. | 113-128 |
| The Use of Biofiltration Technology and 3-dimensional Cubical Bamboo Shelters for Nursery Phase Productivity Improvement of Giant Freshwater Prawns | This experiment was aimed at finding out the effects of usingnitrifying bacteria and Chlorella sp. and the application of a differing number of 3-dimensional cubical bamboo shelters for enhancing the growth performance of Giant Freshwater Prawns (Macrobrachium rosenbergii de Man) during the nursery phase in an indoor system. During 28 days of culture, treatment II (application of 4 shelters ~40% culture volume occupation) resulted in better prawn growth and culture performance compared to control (no shelter application) (p<0,05). At the end of the experiment, treatment II showed the highest biomass, specific growth rate, mean body weight and length of prawns with (1.96+0.05) g.cage-1, 8.24% BW.day-1, (2.18+0,89) g and (6.50+0.91) cm, respectively. However, these results were not significantly different compared to treatment I (application of 2 shelters ~20% culture volume occupation). The survival rate after treatment I and II (treatment I=90%, and treatment II=92%) was significantly higher compared to control (78%). During the experiment the increase of the concentration of ammonium and nitrate was controlled by the addition of nitrifying bacteria and microalgae, which can keep the microbial loop between ammonium reduction by bacteria and nitrate uptake by microalgae in balance. The addition of nitrifying bacteria and microalgae, and the availability of 40% bamboo shelter occupation in the culture can improve prawn culture productivity. | 129-144 |
| Mechanism of Action of Coumarin against Candida albicans by SEM/TEM Analysis | The aim of this study was to identify the antifungal activity of coumarin isolated from Ageratum conyzoides L. leaves and to observe its influence on Candida albicans cells by scanning electron microscope (SEM) and transmission electron microscope (TEM). Antifungal activity testing with the disk diffusion method showed coumarin was active toward pathogenic fungus Candida albicans with an MIC value of coumarin of 125 µg mL-1. The results show that this compound damaged the cell by pores formation on the cell wall. Death of cells occurred due to leakage and necrosis of cytoplasmic content. | 145-151 |
| On Effective Locations of Catalytic Active Sites in Phase Boundary Catalysts | Zeolite loaded with alkylsilane-covered titanium oxide was found to be more effective than its nonporous silica counterpart as phase-boundary catalyst (PBC) to promote epoxidation of alkenes with aqueous hydrogen peroxide. It was demonstrated that the phase-boundary catalyst system required neither stirring to make an emulsion, nor addition of a cosolvent to make a homogeneous solution to drive the reaction. However, some basic facts about them remain unclear, such as the question as to where an effective location of the active sites of PBC resides: is it on the external surface of the catalysts, or in their pores? In order to elucidate this problem, TS-1, HZSM-5 and zeolite loaded with alkylsilane–covered sulfonic acid in which the location of the active sites is mainly inside the pore system, were chosen as model catalysts. Catalytic activities of the catalysts TS-1 and HZSM-5 were examined after modification with n-octadecyltrichlorosilane (ODS). Their activities were compared with zeolite loaded with alkysilane-covered titanium oxide particles, in which the active sites are on the external surface in reactions of 1-octene with aqueous H2O2 and cyclohexene with water as model reactions. The study suggests that the location of the active sites on the external surface plays an important role in the phenomenon of phase-boundary catalysis. | 152-163 |
| An Asymptotic Study of the Steady State Model of Oxygen Diffusion in Tissue Regions | Oxygen plays an important role in the metabolism of cells inside the human body. The transfer of oxygen from blood to tissue takes place in capillaries through a diffusion process. The capillary-tissue region is usually represented by the so-called Krogh cylinder model, in which the distribution of the oxygen concentration in a tissue region leads to a diffusion equation with oxygen consumption rates following the Michaelis-Menten kinetics. In this paper, we restrict ourselves to the steady state case and solve the equation analytically by means of asymptotic expansion for a particular limit of the oxygen consumption rate. Results show that there exists a critical ratio between supply and consumption of oxygen in the tissue region in order to fulfill the cell’s oxygen requirements. Above from this critical ratio, we also found a critical distance in the tissue region above which the oxygen concentration vanishes. We compared our asymptotic results with numerical simulations, which turned out to be quite in agreement. | 164-178 |
| A New Procedure for Generalized STAR Modeling using IAcM Approach | A new procedure of space-time modeling through the Invers of Autocovariance Matrix (IAcM) is proposed. By evaluating the IAcM behaviors on behalf of the Generalized Space-Time Autoregressive (GSTAR) process stationarity, we may find an appropriate model to space-time data series. This method can complete the Space-Time ACF and PACF methods for identifying space-time models. For study case, we apply the GSTAR models to the monthly tea production of some plantations in West Java, Indonesia. | 179-192 |
| Hydrothermal Preparation of Apatite-Type Phases La9.33Si6O26 and La9M1Si6O26.5 (M = Ca, Sr, Ba) | Apatite-type lanthanum silicates show a great potential to be used as an electrolyte for intermediate- to low-temperature (600-700 ° C) solid oxide fuel cells (ITSOFC). However, so far these materials need to be prepared using a very high-temperature method, thus there is a growing interest to prepare apatites at lower temperatures. This paper reports the synthesis of undoped La9.33Si6O26 and doped apatites (La9CaSi6O26,5, La9SrSi6O26,5, and La9BaSi6O26,5) from raw materials La2O3, Na2SiO4, BaCO3, CaCO3, and SrCO3 using a hydrothermal method. The polycrystalline apatites were obtained as a white powder, after the basic solution of the reagent mixture was heated at 240 ° C in an autoclave for 3 days. Le Bail refinement of the X-ray powder diffraction data showed that the compounds have a hexagonal cell (P 63/m space group). In this paper, the undoped La9.33Si6O26 and La-doped apatite ionic conductivities are also presented. | 193-203 |
