Judul: Deskripsi Kecepatan Suara dan Pergerakan Gelombang Akustik di Selat Makassar
Abstrak: Selat Makassar, secara geografis terletak di antara Pulau Kalimantan dan Pulau Sulawesi. Dilihat dari letaknya, selat tersebut masuk jalur Alur Laut Kepulauan Indonesia (ALKI) dan salah satu jalur utama yang membawa masuknya massa air Arus Lintas Indonesia (ARLINDO). Penelitian ini bertujuan menganalisis kecepatan suara dan pola pergerakan gelombang akustik. Data diambil dari web marine.coperniccus.eu berupa data suhu, salinitas, kedalaman, dan kecepatan arus di 5 stasiun yang berbeda. Data yang telah diambil dikonversi menjadi data kecepatan suara, kemudian diubah menjadi data lingkungan. Model bellhop merupakan suatu metode beam tracing yang ditransmisikan melalui medium air laut menggunakan data lingkungan. Semakin dalam perairan, maka suhu akan semakin berkurang, sedangkan salinitas berlaku sebaliknya. Kecepatan suara sangat dipengaruhi suhu dibandingkan parameter lain. Dihasilkan gradien kecepatan suara negatif sehingga pancaran sinar sudut half beam 5° dan 15° merambat di dasar perairan sedangkan sudut half beam 30°menunjukkan pancaran sinar merambat di permukaan dan di dasar perairan. Rata-rata kecepatan suara tertinggi terdapat di Stasiun 4. Semakin besar sudut beam yang digunakan, maka jarak setiap pancaran sinar akan semakin menjauh
Keyword: depth, ray tracing, salinity, sound velocity, temperature

Judul: Analisis Propagasi Akustik Bawah Air di Selat Sunda
Abstrak: Selat Sunda terletak di antara Pulau Jawa dan Sumatera yang menjadi salah satu Alur Laut Kepulauan Indonesia (ALKI 1). Penelitian ini bertujuan untuk menganalisis propagasi akustik bawah air di perairan Selat Sunda bagian selatan pada Musim Peralihan 1 tahun 2020. Data diakses dari laman marine.copernicus.eu berupa data arus, suhu, salinitas, dan kedalaman di 4 stasiun yang berbeda dan diproses menjadi data lingkungan. Kecepatan suara akan diproses menggunakan formula Mackenzie menggunakan data suhu, salinitas, dan kedalaman. Model bellhop merupakan suatu metode beam tracing yang ditransmisikan melalui medium air laut menggunakan data lingkungan. Hasil simulasi menunjukkan adanya bermacam-macam propagasi suara yang terjadi pada setiap stasiun yang diamati akibat adanya faktor kedalaman transduser dan kedalaman perairan. Sudut half bim 5° dan 10° lebih merambat di dasar perairan karena gradien kecepatan suara negatif sedangkan pada pancaran half bim 15° menunjukkan adanya pancaran di permukaan dan dasar perairan. Semakin besar sudut beam maka jarak pancaran suara akan semakin menjauh, begitu juga sebaliknya., Sunda Strait located between Java and Sumatera and being one Indonesian Archipelagic Sea Lanes part. This study aimed to analyzing underwater acoustic propagation in the southern Sunda Strait waters during Transition Season 1 of 2020. Data was taken from marine.copernicus.eu website which were sea current, temperature, salinity, and depth in 4 different stations which will be processed into environment data. Speed of sound will be processed with MacKenzie formula using temperature, salinity, and depth data. Bellhop modelling is a beam tracing method which transmitted through sea water medium using environment data. At the study area found the presence of thermocline, halocline, and mixed layer. The simulation shows that there are various kinds of sound propagation occurred at each observed stations due to the transducer’s depth and water depth factor. At 5° and 10° half beam angle propagates more at the bottom because of negative speed of sound gradien whereas at 15° shows there is a propagation at the bottom and surface of waters. Greater the beam angle, the distance of the sound propagation will be further away and vice versa.
Keyword: bim, kecepatan suara, kedalaman, suhu, salinitas

Judul: Screening and Characterization of Bacterial Antagonists as Potential Agents for the Biological Control of the Chrysanthemum White Rust Disease
Abstrak: White rust disease caused by Puccinia horiana (Basidiomycetes: Uredinales) is the major problem on chrysanthemum plantation and caused yield lost until 100%. Biocontrol is an alternative way to control this disease. Therefore, the aims of this study are to obtain antagonist bacterial as biocontrol agents of chrysanthemum white rust disease, to identify the potential isolate and their biocontrol character, charachterized their biocontrol mechanism, and to know the role of their chitinolytic activity on germination of teliospore. The methods used in this study are selection of antagonistic bacteria which are able to control this disease in-vitro, characterized of potential antagonist bacteria with polymerase chain reaction of a 16S rRNA gene and physiology and biochemical character, characterized the mechanism of inhibition teliospore germination, and the role of chitinolytic activity in antagonism activity using transposon mutagenesis. The result showed that out of 29 bacterial isolates, 12 isolates had chitinolityc activity. The twelve isolates were the potential antagonist agents to control teliospore germination with percentage above 90%. Isolate K2 was the most potential antagonist bacteria to control this disease. This isolate could inhibit the germination up to 98% and had the highest chitinolytic activity among the isolates. Based on 16S rRNA gene partial sequences analysis and physiology and biochemical characters, this isolate was identified as Chromobacterium sp. The major mechanism was antibiosis. It is showed from the biocontrol activity which are bacteria’s cell colonization, lytic activity, and disintegrated of protoplasm. This bacteria produced cyanide acid (HCN) and phenazine beside chitinolytic enzyme. Chitinolytic activity was not a single factor in the mechanism of antibiosis but other secondary metabolic compounds produced by this bacteria also come into play. It is showed on the results of mutagenesis that transconjugants which had no chitinolytic activity was still able to inhibit germination of teliospora, whereas transconjugants which still had an activity equal to or smaller than wild type bacteria, the inhibitory were lower. It was indicated that chitinase was not the most important compound that inhibited the germination of teliopsore. There was another compound have the bigger role such as hydrogen cyanide, phenazine, or other substances produced by Chromobacterium sp..
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