| Nama Pengarang | : | M. Noordin Arzani |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 24-29 |
| Abstraksi Narasi | : | Volatile oils, which were isolated from calamus roots, cubeb fruits, and cananga flowers by steam distillation, yielded 1,72%, 6,57%, and 2,01% respectively. The volatile oils dissolved with water to obtain various concentration of oil. Each solution was examined for their antimicrobial activities againts Staphylococcus aureus, Escherichia coli, and Candida albicans by determining their MIC (Minimal Inhibitory Concentration) and MBC (Minimal Bactericidal Concentration). The volatile oils from calamus roots, cubeb fruits, and cananga flowers were active against Staphylococcus aureus with MIC and MBC 337,5 mgg/ml and 675 mg/ml; 625 mg/ml and 1250 mg/ml; 625 mg/ml and 1250 mg/ml respectively. They were also active against Escherichia coli, with the MIC and MBC 337,5 mg/ml and 675 mg/ml; 312,5 mg/ml and 625 mg/ml; 625 mg/ml and 1250 mg/ml respective. On the other hand, only the volatile oil derived from calamus roots was active againts Candida albicans, showing an MIC 1350 mg/ml and an MBC 2700 mg/ml. |
| Nama Pengarang | : | Djoko Untoro Suwarno |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 127-136 |
| Abstraksi Narasi | : | Walsh transform is similar to Fourier transform. In Fourier transform, a periodic signal can be broken down into sine and cosine wave at fundamental frequency and higher frequency (harmonic frequencies). In Walsh transform, a periodic signal can be decomposed into square wave at fundamental frequancy and higher frequency (harmonic frequencies), Computation in Walsh transform can be minimized into faster computation and becomes fast Walsh transform. A variant of Walsh transform is Hadamard transform, which is Walsh transform arranged in natural order (known as sequency order). |
| Nama Pengarang | : | Agustin Sumartono and Winarti Andayani |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 107-114 |
| Abstraksi Narasi | : | Degradation of lignin using photocatalytic process and composite catalyst TiO2-zeolite was carried out. Lignin solution was irradiated using three treatments, i.e. UV lamp, UV lamp + TiO2-zeolite, and TiO2-zeolite. Radiation was done for eight hours with interval sampling time 0, 0.5, 1, 2, 3, 4, 6, and 8 hours. Radiation was continued using UV+TiO2 with variation concentration 10, 20, 50, 80 and 100 ppm with the same interval sampling time. Parameters examined were the change of spectrum intensity, pH and degradation product. The percentage degradation could be achieved using UV+TiO2 at 10 ppm concentration and after eight hours the percentage degradation was 72.35%. The decrease of spectrum intensity and pH indicated that lignin has degraded into another compound which is acidic. One of the degradation product taht could be detected was oxalic acid. |
| Nama Pengarang | : | A.A. Bawa Putra, P. Suarya, dan IM. Wisnu Adhi Putra |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 177-186 |
| Abstraksi Narasi | : | A study research of absorption-desorption pf lead metal in metal in liquid by chicken eggshell and lime as comparision substance has be conducted. This research covers surface wide measurement, time balancing in absorption, isotherm and absorption capacity, and Pb desorption with saturated NH4CL. To determine the surface wide of eggshell (adsorbent), blue metilen liquid method is applied, and for determination of time adsorbent, of isotherm, and of adsorption capacity, an interaction of chicken eggshell with Pb(II) liquid, after its absorption is measured using Atomic Absorption Spectrofotometer (AAS), is conducted. In the meantime Pb desorption with saturated NH4CL is conducted through interaction of chicken eggshell sample which has absorbed Pb with saturated NH4CL and its absorption is measured using AAS. The result of this research shows that chicken eggshells has surface area at 12.9553 m2/g and lime at 12.0134 m2/g. Time balancing for eggshell absorption can be reached at the 25th minute, whilst lime at 5th minute. Adsorption capacity to Pb chicken eggshell to Pb metal at 7.8127 mg/g and lime absorption capacity to Pb metal at 8.6082 mg/g. Desorption of Pb(II) by saturated NH4CL is easier to take place on lime, with percentage desorption at 26,69%, while at eggshell is at 25.05 %. The result of statistics analysis with t-test shows a different significant result on average of eggshells and lime surface. While average adsorption capacity and percentage of desorption shows equal result to eggshells and lime. |
| Nama Pengarang | : | Lusia Krism1yati Budiasih |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 147-155 |
| Abstraksi Narasi | : | This paper discusses optimal control of continuous-time systems, especially continuous-time Linear Quadratic Regulator (LQR). The LQR will be implemented to determine the optimal feedback control of a scalar system. The result of scalar system simulation showed that as the coefficient of state in performance index increases, the state is forced to zero at the expense of an increase in control energy. |
| Nama Pengarang | : | Ermin K. Winarno |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 137-145 |
| Abstraksi Narasi | : | Screening of the enophyte microbes in cinchona stems of C. ledgeriana and C. pubescens that could produce alkaloids has been carried out. The screening was done using Potato Dextrose Broth, A, and B media for obtaining the optimum condition for the alkaloids production by endophyte microbes. Qualitative and qualitative analysis of the alkaloids were carried out using thin layer chromatography and high performance liquid chromatography. The results show that two endophytic fungi (LMC-19 and LMC-29) produced alkaloid compounds. In Potato Dextrose Broth and B media, LMC-19 and LMC-29 produced quinine, whilw in B medium LMC-29 could also produce cinchonine. |
| Nama Pengarang | : | Timbul Pardede |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 157-166 |
| Abstraksi Narasi | : | K-mean is a clustering method in whhich grouping techniques are based only on distance measure among observed objects, without considering statistical aspects. Model-based clustering is a method that uses statistical aspects, as its theoritical basis i.e. probability maximum criterion. This model has several variations with a variety of geometrical characteristics obtained by mean Gauss component. Data partition is conducted by utilizing expectation-maximization (EM) algorithm. By using Bayesian Information Criterion (BIC) the best model is then obtained. This research is aimed to compare the result of grouping methods, namely model-based clustering and K-mean clustering. The results showed taht model-based clustering was more effective in separating overlap groups than K-mean. |
| Nama Pengarang | : | lrwan Ginting Suka, Wasinton Simanjuntak, dan Lisa Yunita |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 187-197 |
| Abstraksi Narasi | : | This study was carried out with the main purpose to investigate the grafting of methacrylic acid (MAA) on silica extracted from rice husk and to test the capability of the grafted silica to adsorb Cu2+ from aqueous media. Characterization of silica using FTIR spectroscopic method revealed the presence of Si-OH and Si-O-Si, expected to paly role in the grafting on the monomer onto silica. Grafting of the monomer was carried out in two steps, initiated with grafting of silane functional group aimed to provide active sited and then followed by grafting of MAA onto silylated silica using AIBN as initiator. Both silylated silica and MAA grafted silylated silica were characterised using FTIR spectroscopic method, confirming the oncorporation of functional groups as expected. The overall results indicate that percent grafting is dependant on the concentration of initiator, concentration of monomer, and reaction time applied. It was also found the amount of Cu2+ adsorbed increased following the increase in percent grafting of MAA, confirming the capability of MAA grafted silica to function as an ion exchange. |
| Nama Pengarang | : | Setyadi W.S. dan Rill lsaris |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 115-126 |
| Abstraksi Narasi | : | New technology on Nuclear (Gamma) Spectroscopy System for element analysis and nuclear experiment has been developed using new CsI (TI) detector as substitution of Nal (TI) detector. An Amplifier of single polarity, as one of the important component on spectroscopy using CsI (TI) detector, has been designed and constructed. The detector output is 10 mV at gamma energy of 662 keV. Design of amplifier follows the engineering principles, and test to its characteristic according to nuclear spectroscopy rules. The performance tests show that the system linearity is 0.9966, integral linearity was 0,20%, diferential non linearity is 0.001%, frequency respond up to 65 kHz, the rise time of 3 uS, fall time of 5 uS. Dynamic test result using CsI (TI) detector shows 10.2% resolution. These results are satisfactory for nuclear spectroscopy amplifier. The application of Work Bench Program takes important part in simulation and optimizes the electronic circuit. |
| Nama Pengarang | : | E.Ristin Pujiindiyati dan June Melawati |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 199-204 |
| Abstraksi Narasi | : | Multielement analysis in some commercial fertilizers using x-ray fluorescence spectrometer (XRFS) has been carried out. This method was selected because it do not need any special sample preparations and its contents can also be measured in one running. The annular radioisotope sources used for electron excitation in each element from samples were 55Fe and 109Cd. The result showed that some fertilizers commonly used by farmers such as NPK, TSP, KCI and urea contained major elements such as P, S, K and Ca. Mostly, their concentrations were in the range as mentioned in some literatures. Minor elements such as Fe, Mn, Zn, Cl and Si in these fertilizers could also be measured. Some trace of impurities such as Ar, Ti, V, Cu, As, Pb, Br, Sr, Nb, Y and Sc taht might be originated from rocks were also detected by XRFS. The contents of heavy mental of lead (Pb) and arsen (As) in these fertilizers were in average of 31 ug g'-1 and 13 ug g'-1 to 44 ug g'-1, respectively. KCI fertilizer has the highest level in both elements. |
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