Judul: Sintesis Hidroksiapatit Berpori dari Cangkang Keong Sawah (Bellamya javanica) dengan Penambahan Pati Singkong sebagai Porogen
Abstrak: Hydroxyapatite (HAp) was synthesized by mixing Ca(OH)2 with (NH4)2·HPO4 and adding cassava starch as porogen. The method used was wet method (presipitation), by reactioning Ca(OH)2 from snail’s shell with technical (NH4)2·HPO4. Characterizing using X-ray diffractogram (XRD) showed that the sonication treatment of 2, 4, and 6 hours produced various Hap purities. HAp with sonication time of 6 hours gave the highest in purity level, so it was used for synthezing the pored HAp. Pored HAp was formed by adding cassava starch as porogen with concentration at 20 and 30%. Cassava starch was lost in calcination process and it created the pores in HAp. Characterization by XRD showed that the samples formed HAp but still contained some wastes. Identification by scanning electron microscope described the porogened Hap by 30% cassava starch had larger pore, between 13.2 and 46.79 μm. Analisis of infrared spectrum on porogened HAp by 30% cassava starch showed band that the functional groups had patterns. The growth of apatite crystal in in vitro test showed bioactivity of the porogenated HAp.
Keyword: snail’s shell., hydroxyapatite, cassava starch

Judul: Sintesis dan Uji in Vitro Hidroksiapatit dari Limbah Cangkang Keong Sawah (Bellamya javanica) Berporogen Pati Kentang
Abstrak: Biomaterial that is widely used for bone tissue rehabilitation is hydroxyapatite (HAp). HAp was synthesized from calcium reacted with ammonium phosphate, and added with potato starch as porogen. The synthesis of HAp was performed by wet method. Calcium in HAp was extracted from garden snail shell which is known for it is high calcium; ammonium phosphate used was diammonium hydrogen phosphate of technical grade. Potato starch was used due to it is biocompatibility, so that it should be safe for human body. HAp pores was modified by adding 20% and 30% starch. X-ray diffraction results showed the phase of HAp. Based on the photo results of scanning electron microscopy, the pores of HAp were successfully enlarged. The best pores size of 0.67-8.46 μm was given by the addition of 30% potato starch. Infrared spectrum showed that porogened HAp had the same functional groups with nonporogened HAp. In vitro test showed that HAp with larger pore sizes gave higher bioactivity.
Keyword: potato starch, porogen, hydroxyapatite, garden snail shell

Judul: Pemanfaatan modul transmitter-receiver untuk pengukuran telemetri unsur-unsur cuaca
Abstrak: Telemetry is transfer of information at a certain radio frequency of the transmitter to the receiver system with air intermediaries. Telemetry system will be useful for the measurement process with the direct method requires measuring device is placed in a location difficult to monitor at all times. A universal transmitter-receiver modules in available the market have different characteristic and specifications depend on manufacturers. The antenna is modified to maximize the distance of data transmission. The separation time between the incoming data is detected down to 0.32 second and the minimum signal pulse length can be detected by the module is 0.3 second. The farthest distance of data transmission obtained after modifying the antenna is 260 meters, maximum results are obtained if the modification is only made to any one of the modules. Faulty measurement due to timming conflict and power supply instability are about 3 % of the whole measurement.
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