Judul: Karakterisasi Pelepasan Nitrat pada Andisols di Jawa Barat dan Jawa Tengah
Abstrak: Andisols occupies large area in Indonesia. The area is about 5.4 million hectares. This soil is used extensively by farmers for horticulture, tea plantation and small portion for livestock. The characteristics of nitrate release is very spesific location so that it is necessary to reveal soil properties affecting to the pattern of nitrate release on Andisols in West and Central Java. The experiment of nitrate release was conducted by incubation experiment. The objectives of the research were to (1) characterization of chemical properties of Andisols in West and Central Java, (2) characterization of the pattern of nitrate release on Andisols in West and Central Java, and (3) obtaining correlation between chemical properties and the pattern of nitrate release on Andisols in West and Central Java. Based on soil analyses, the chemical properties of Andisols in West and central Java were different. The release of nitrate on Andisols in Lembang, Pangalengan, Sukamantri and Dieng decreased as the depth of soil samples in the soil profile was deeper and increased as the periode of incubation was longer. Simple correlation test showed that the potential nitrate release (N0) positively correlated with total carbon (r=0.08), total nitrogen (r=0.14), oxalate-extractable iron (Feo) (r=0.05), dithionite-citrate-bicarbonate-extractable aluminum (Ald) (r=0.07) and dithionite-citrate-bicarbonate-extractable iron (Fed) (r=0.39). The N0 negatively correlated with oxalate-extractable aluminum (Alo) (r=-0.08) and Alo + ½ Feo (r=-0.07). As for the rate constant (k), k only positively correlated with Fed (r=0.04).
Keyword: soil chemical properties, nitrate release, andisols

Judul: Karakterisasi Erapan Nitrat pada Tanah Pertanian Lahan Kering di Pulau Jawa.
Abstrak: The urea fertilizer and manures were used excessively by farmers. It caused the accumulation of nitrate in Agriculture soils. The knowledge of soil capability to sorb nitrate is very important concerning the nitrate movement in soil profile. The objectives of this research were to (1) Characterization of physico-chemical properties of upland soils in Java island, (2) Finding the best equation to simulate nitrate sorption on upland soils in Java island, and (3) Correlation between physico-chemical properties and parameters of nitrate sorption. Prior to nitrate sorption, the soil was saturated with chloride ion. Afer that, the 2.00 g of soil was equilibrated in 5 ml solution containing 0.005 to 0.2 mol L-1 of KNO3. After equilibrium was reached, nitrate was determined by UV Spectrophotometer with wave length 210 nm and then was corrected with 275 nm for dissolve organic carbon (C). The nitrate sorption data were simulated with Langmuir, Temkin and Freundlich equation. The results showed that the Freundlich equation simulated nitrate sorption better than Langmuir and Temkin. The R2 of equation of Freundlich ranged from 0.87 to 0.99. The nitrate sorption maxima (K) of Freundlich were positively correlated with total C (r=0.27), oxalate-extractable aluminum (Alo) (r=0.41), oxalate-extractable iron (Feo) (r=0.16), dithionite-citrate-bicarbonate-extractable aluminum (Ald) (r=0.34), dithionite-citrate-bicarbonate-extractable iron (Fed) (r=0.01) and Alo + ½ Feo (r=0.42). The K values were negatively correlated with clay content (r=-0.19). As for n values of Freundlich equation, it was positively correlated with total C (r=0.11).
Keyword: tempkin, soil properties, nitrat, langmuir, freundlich, sorption

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular