Hasil Pencarian  ::  Simpan CSV :: Kembali

"Coral reef bleacing is a phenomenon of fading due to a variety of stress, both natural and human impact. These circumstance leads to the degeneration and loss of zooxanthellae in coral tissue The phenomenon of coral bleaching can be occurerd locally and globally. Based on the historical record, the largest coral bleching occurred in 1997-1998. Contributing factors to the coral bleaching are extreme temperature changes, metals, other pollutants (nitrates), slow water movement, light intensity and salinity. Zooxantellae (algae symbiont) is much more affected in the certain conditions, especially in the photosynthesis process. Defensive mechanisms against the pressure on zooxantellae can be defined as Npq, fluorescent pigments, oxidation enzymes and genetic variation. Changing in reproductive patterns, species composition and community structure can be happened after bleaching phenomenon. In the future, monitoring of Seawater Surface Temperature (SST), research on the types of stress and tolerant mechanisms of algae symbiont, including pigments, proteins, enzymes oxidation, genetics in both laboratory and field are needed. "

"ABSTRAK Serat Kenaf (Hibiscus Cannabinus, L. Family Malcavea) merupakan salah satuserat alam yang yang memiliki potensi untuk dijadikan penguat dalam komposit.Kenaf memiliki keunggulan dibandingkan serat alam lainnya dalam hal kekuatantarik, densitasnya yang rendah serta tidak menyebabkan pencemaran terhadaplingkungan. Masalah yang menjadi perhatian adalah sifat permukaan serat yangmempengaruhi kompatibilitas antara PP (Polipropilena) dan kenaf saat dijadikankomposit. Perlakuan pemutihan pada serat kenaf dapat meningkatkankompatibilitas antara kenaf dengan PP dalam komposit. Penelitian ini membahasmengenai pengaruh pemutihan pada serat kenaf dengan berbagai variasikonsentrasi NaClO sebagai zat pemutih, waktu pemutihan dan suhu pemutihan.Hasil pengujian menunjukkan bahwa dengan peningkatan konsentrasi NaClO,waktu dan suhu pemutihan, kandungan lignin dalam serat kenaf semakin menurundan terjadi pemberaian pada selulosa serat. Kekuatan tarik serat kenaf mengalamikenaikan dengan penambahan konsentrasi larutan 1%, variasi waktu 1 jam dansuhu 25oC. Namun, penambahan konsentrasi NaClO, waktu dan suhu pemutihanlebih lanjut akan menurunkan kekuatan tarik kenaf karena rusaknya rantaiselulosa pada serat kenaf. Perlakuan pemutihan dengan penambahan konsentrasiNaClO, waktu dan suhu pemutihan akan meningkatkan kompatibilitas kenafdengan polimer PP blok kopolimer yang diketahui dari pengujian kemampubasahan.

---

ABSTRACTKenaf Fiber (Hibiscus cannabinus L. Family Malcavea) is one of the natural fiberthat has the potential to be used as reinforcement in composites. Kenaf has moreadvantages than other natural fibers in terms of tensile strength, low density anddoes not cause pollution to the environment. Issue of concern is the fiber surfaceproperties that affect the compatibility between PP (Polypropilene) and kenafwhen used as a composite. Bleaching treatment on kenaf fiber can improvecompatibility between PP and kenaf in composite. This study discusses the effectof bleaching on kenaf fibers with various concentrations of NaClO as bleachingagents, bleaching time and bleaching temperature. The results show that byincreasing concentration of bleaching agents, time and temperature bleaching,lignin content in kenaf fiber decreases and the cellulose fibers are separated.Tensile strength of kenaf fiber increased with the addition of 1% solutionconcentration, in 1 hour and a temperature of 25 °C. However, the addition ofNaClO concentration, time and temperature of bleaching will further decrease thetensile strength of kenaf as damage to the cellulose chains on kenaf fibers.Bleaching treatment with the addition of NaClO concentration, time andtemperature of bleaching will improve compatibility between kenaf and PP blockcopolymer that proved by with wetability testing."

"Indonesian Journal of Dentistry 2006; Edisi Khusus KPPIKG XIV: 254-259There are two basic kinds of tooth whitening agents. The first is over the counter materials and the other is materials used by the dentist or under dentist control. Home bleaching is a technique using l0% carbamide peroxide on a tray applied by patient under dentist supervision. This paper is a review of the effect of 10 % carbamid peroxide home bleaching technique. It is revealed that this metode is simple, safe, economic, and has short chiar side time."

"The aims of the study were to evaluate by spectrophotometer the in vivo colour changes resulting from the application of an in-office tooth bleaching system containing 28 % H2O2 by light-emitting diode (LED) activation and to determine whether the application of 5 % potassium nitrate 30 min before bleaching decreased tooth sensitivity. Thirty-two individuals were assigned randomly to two groups (n = 16). Group A received 5 % potassium nitrate as a desensitizing agent 30 min before bleaching with 28 % hydrogen peroxide activated by LED. Group B received glycerin as a placebo and the same bleaching protocol was applied. The colour of the right central incisor of each patient was measured visually and by spectrophotometer before bleaching, immediately thereafter, 15 days and 3 months later. Differences in L* a* b* values were tested with a repeated measures analysis of variance (ANOVA). Differences in AE values were tested with ANOVA statistical analysis at a 0.05 level of significance. Significant (p < 0.05) differences were detected in L*, as well as in b* values, between initial (I) and post bleaching (PB) and between initial (I) and 3 months post-op. In contrast, there was no significant difference between PB and 3 months post-op. The a* values showed no statistically significant differences among the different time points. Tooth sensitivity decreased significantly when potassium nitrate was applied. In-office bleaching system gave quantitatively stable results over a 3-month period. Tooth sensitivity was reduced significantly, when a desensitizing agent was applied 30 min before treatment, but the efficacy of bleaching decreased."