Judul: Leaf Survival Analysis In A Shading Experiment Using Cox Proportional Hazards Model
Abstrak: An experiment was set up to study adaptability of agroforest seedling to different light regimes. Leaves supported by selected axes were censused during the 18 months course of experiment. Duku (Lansium domesticum), durian (Durio zibethinus), rubber (Hevea brassiliensis), and pulai (Alstonia scholaris) seedlings were grown under different shading intensity 0%, 55%, 75% and 88%. KaplanMeier estimate of leaf survival function shows that all four species show the same general trend; higher survival time for lower light level, and higher survival time for plagiotropic axis leaves as opposed to orthotropic. Cox proportional hazards model is used to model the hazard function of the four agroforest species. It is concluded that for the four species, shading treatments significantly effect leaf life span. In general the 88% shade treatment leading to maximum life span.
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Judul: Pengaruh Intensitas Cahaya Matahari Terhadap Pertumbuhan Jenis Shorea parvifolia dan Shorea leprosula dalam Sistem TPTI Intensif (Studi Kasus di Areal IUPHHK-HA PT. Sarpatim, Kalimantan Tengah)
Abstrak: Silvicultural system of Intensive Indonesian Selective Cutting and Planting (TPTI) comprises the techniques of regeneration, tending and harvesting of a stand or forest for producing certain products, and is designed to create sustainable management of natural production forest. In relation with that, there is a need for research on the effect of light intensity on the growth of Shorea parvifolia and Shorea leprosula species (meranti), to obtain information on light intensity where the growth of meranti is maximum. Such information could be used as the basis of consideration in the action of environmental manipulation on intensity of lights which enter the forest floor, to increase the growth of the two species of tree for achieving high productivity. The research was conducted in operational planting strip in block of PUP (Permanent Measurement Plot) of RKT (Annual Working Plan) 2005 and 2006, with 4 plots, and in each plot there were 3 planting strips comprising 120 strip plants. Plot size was 100 m X 100 m. The collected primary data were among other things total height of plants, plant diameter, wet bulb and dry bulb air temperature, humidity, light intensity in the planting strip and health condition of the trees. The collected secondary data were among other things site map, general condition of the research site (which comprised site geographic position, climate, rainfall, soil type, topography), and data of the tree diameter and height of the previous years. Diameter growth of Shorea parvifolia in plot which was rather steep of strip 2 possesed the greatest increment (1.59 cm / year) which differed significantly at 5 % level, and was affected by sunlight intensity as much as 6.85 %. On the other hand, diameter growth in level plot of strip 2 possessed the largest increment of 2.91 cm / year which differed significantly at 5 % level and was affected by sunlight intensity of 16.6 %. It could be shown that the diameter growth of Shorea leprosula was greater than that of Shorea parvifolia. The largest increment of diameter and height of S. parvifolia were respectively 1.59 cm / year and 140.88 cm / year. The largest increment of diameter and height of S. parvifolia were respectively 1.50 cm /year and 247.05 cm / year. The largest increment of diameter and height of S. leprosula were respectively 2.91 cm /year and 217.58 cm / year. The largest increment of diameter and height of S. leprosula were respectively 2.95 cm /year and 289.35 cm / year. During observation of S. parvifolia and S. leprosula growth, there were diameter increments as affected by IC sunlight exposure as large as 1.59 cm / year with IC exposure of 397.07 foot candle; and 2.91 cm / year with IC exposure 278.2 foot candle.
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Judul: Sintesis Dan Pencirian Koloid Nanoferrogel Fe3o4-Kitosan Sebagai Bahan Pengontras Mri
Abstrak: Ferrogel Fe3O4-kitosan telah berhasil disintesis melalui proses assembly ionion Fe3+ dan Fe2+ ke dalam hidrogel kitosan yang tertautsilang dengan glutaraldehida (GLA), serta dipresipitasi menggunakan NaOH. Ferrogel tersebut dikeringkan dengan memragamkan waktu pengeringan 2 (S2), 3 (S3), 4 (S4), dan 5 jam (S5) pada suhu 60 0C. Tujuan penelitian ini adalah menyintesis koloid nanoferrogel Fe3O4-kitosan yang stabil serta injectable sebagai agen pengontras pada MRI. Pencirian ferrogel dengan difraktometer sinar-X menunjukkan telah terbentuk fase Fe3O4. Analisis spektrum FTIR-nya diperoleh bahwa ragam pengeringan tidak menunjukkan adanya perubahan struktur kimia ferrogel yang signifikan dan hilangnya serapan gugus N−H primer kitosan di 1548 cm-1 pada sampel S2, S3, S4, dan S5 menandakan adanya interaksi berupa kelat antara Fe3O4 dengan gugus −NH2 kitosan. Pengeringan ferrogel hanya menghilangkan kandungan air tipe imbisi pada ferrogel dan berpengaruh pada sifat magnet yang dihasilkan. Magnet saturasi maksimum sebesar 6.21 emu/gram diperoleh pada sampel S5. Meredispersikan ferrogel menggunakan ultrasonik ke dalam medium asam asetat dan air deionisasi secara bertahap diperoleh koloid nanoferrogel Fe3O4-kitosan yang stabil. Pengamatan dengan TEM menunjukkan morfologi Fe3O4 berbentuk bola dengan ukuran ~ 5 nm telah terlapisi oleh kitosan dengan ukuran ~ 20 nm. Ukuran ini juga telah dikonfirmasi menggunakan PSA. Hasil pengukuran dengan VSM menunjukkan koloid nanoferrogel tersebut bersifat superparamagnetik yang baik. Semua hasil pencirian produk koloid nanoferrogel Fe3O4-kitosan menunjukkan koloid tersebut berpotensi digunakan sebagai agen pengontras pada MRI.
Keyword: Fe3O4, iron ions assembly, kitosan, nanoferrogel