Judul: Epigeneium (Orchidaceae) of Java and Sumatra
Abstrak: Study on Epigeneium (Orchidaceae) in Java and Sumatra was conducted based on herbarium and living collections. Specimens from Herbarium Bogoriense (BO) and Herbarium Singapore Botanic Garden (SING) were observed during this study. Photo images of specimens and types from Leiden (L), Oakes Ames Orchid Herbarium (AMES), and Kew (K) were have been incorporated. Other additional specimens were from Andalas University Herbarium (ANDA). Based on morphological characters, Epigeneium has been revised into five species of Epigeneium from Java: E. arjunoense, E. cymbidioides, E. elongatum, E. geminatum, and E. triflorum. Epigeneium elongatum previously was placed as one of the variety of E. triflorum, now it has been placed back to species level because there are some distinct characters from the other two varieties were observed. In Sumatra there was one new record, E. geminatum since this species was never been found in this island before. Two new species were proposed from Sumatra: E. longibulbon Destri sp. nov. and E. sikijangensis Destri sp. nov. Epigeneium longibulbon was named base on its long pseudobulb, and E. sikijangensis was named after the original habitat where this orchid was collected (Rawa Sikijang), located at Mt. Kerinci, Jambi province.
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Judul: A Monograph of the Genus Diplycosia (Ericaceae) in New Guinea
Abstrak: Diplycosia is an under-studied genus of Ericaceae, with a distribution confined almost to Malesia with most members are endemic to a single island or even a single mountain. New Guinea which, prior to this study, inhabited by 21 endemic species and once considered as one of the centres of diversity. Many species of Diplycosia in New Guinea are known only from limited collections: either only from the type specimens, or from only two or three specimens from a single or few locations; several have incomplete descriptions due to the absence of floral parts. Therefore, a taxonomic revision is needed for the genus Diplycosia in this island. Besides that, despite mostly being narrow endemic, 17 described species have not been evaluated for their IUCN conservation status which has become an obstacle for conservation actions. Therefore, an assessment is urgently required for the genus in New Guinea. A morphological species concept was used in this revision, and specimens were studied from various herbaria either directly or from digital resources: Australian National Herbarium (CANB), Harvard University (A), Muséum National d'Histoire Naturelle, Paris (P), Naturalis History Museum Firenze (FI), Naturalis Leiden (L), Papua New Guinea Forest Research Institute (LAE), PT Freeport Indonesia (tentatively as FRE), Research Center for Biology Indonesia Institute of Sciences (BO), Royal Botanic Gardens Kew (K), and Universitas Papua (MAN). Field explorations were carried out in Indonesian New Guinea, including Birds Head Peninsula and Mount Jaya area. An observation on qualitative anatomical characters of leaf epidermis was done in eight species. Assessment of conservation status was based on IUCN Red List guideline including range sizes calculated using GeoCAT using data sourced from herbarium specimens, literature and recently gathered data from the field exploration. A total number of 26 endemic species are accepted in New Guinea. Four new species are described namely Diplycosia elegans Mustaqim, Utteridge & Heatubun, D. hexamera Mustaqim, Utteridge & Heatubun, Diplycosia puradyatmikai Mustaqim, Utteridge & Heatubun, Diplycosia reticulifolia Mustaqim, Utteridge & Heatubun, together with a variety Diplycosia lorentzii var. acuminata Mustaqim, Utteridge & Heatubun. Diplycosia morobeensis var. ovatifolia Sleumer is reduced to a synonym of Diplycosia morobeensis Sleumer. Based on our current result, a higher number of species was reported from the western half of the island compared to the eastern half. So far, the central part of New Guinea from Jayawijaya Mountains east to the mountains near Indonesia and PNG border is an area with the highest diversity despite being poorly explored. The geographical range of the species varies from widespread species, found across the island, to very narrow endemics, some even restricted to a single mountain complex or a single locality. New Guinean Diplycosia grows as epiphytes or a terrestrial shrubs in mostly the mossy forests upwards to alpine vegetation. The elevation range from 800 in Wandammen Peninsula for D. kosteri and 4000 m in Mount Giluwe for D. rupicola and D. morobeensis. Seven species are known to inhabit alpine vegetation in New Guinea including the new species D. elegans. From this study, we recorded two new important information in the generic character of Diplycosia. It has been
Keyword: conservation status, East Malesia, epiphyte, Ericaceae, new species, taxonomy

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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