Community Structure Characterization

This entry discusses the problem of describing some communities identified in a complex network of interest, in a way allowing to interpret them. We suppose the community structure has already been detected through one of the many methods proposed in the literature. The question is then to know how to extract valuable information from this first result, in order to allow human interpretation. This requires subsequent processing, which we describe in the rest of this entry

Community Structure Of Macrozoobenthos In The Melibur River, Mayang Sari Village Merbau District, Kepulauan Meranti Regency Riau Province

Macrozoobenthos that live in the base of a river is commonly used asbioindicator as its presence is depended on the water quality of the river ingeneral. To understand the community structure of the macrozoobenthos in theMelibur River, a study has been conducted on 7 - 22 January 2015. Samples weretaken from 3 stasions, close to sago industry outlet (S), around the river mouth2(S2) and in the area close to harbor (S3). There were 3 plots in each station.Sampling was conducted 3 times, once/ week. Parameters measured were theabundance, uniformity and dominancy index of the macrozoobenthos and severalwater quality parameters such as temperature, current speed, turbidity, depth,salinity, dissolved oxygen, pH, substrat type, and organic materials.Results shown that there were 11 species (4 classes) of macrozoobenthos,2094 organisms /m2. There were Gastropods (42,45%), Polychaeta (25,03%),insects (7,50%), Oligochaeta and Bivalvas are (5,01%). The highest density ofmacrozoobenthos was in the S3 (1151 organisms/m2) and the lowest was in theS1 (419 organisms /m2). The H' was 2,9749 and 1.5616 in S3 and S1respectively and uniformity index (E) was 0.99 in S1 0,79 S2, and 0.94 in S3.The C value was 0.34 in S1 and 0.14 in S3. There was muddy sand substratein S1 and S2 and sandy substrat in S3 with 19.16% – 37.5% organic materialcontent in each area. Data obtained that the type of substrate strongly affect thetype of macrozoobenthos present

Community Structure in Jazz

Using a database of jazz recordings we study the collaboration network of jazz musicians. We define the network at two different levels. First we study the collaboration network between individuals, where two musicians are connected if they have played in the same band. Then we consider the collaboration between bands, where two bands are connected if they have a musician in common. The community structure analysis reveals that these constructions capture essential ingredients of the social interactions between jazz musicians. We observe correlations between recording locations, racial segregation and the community structure. A quantitative analysis of the community size distribution reveals a surprising similarity with an e-mail based social network recently studied.Comment: 12 pages, 6 figures, Revtex4 format, Acknowledgments update

Ordered community structure in networks

Community structure in networks is often a consequence of homophily, or assortative mixing, based on some attribute of the vertices. For example, researchers may be grouped into communities corresponding to their research topic. This is possible if vertex attributes have discrete values, but many networks exhibit assortative mixing by some continuous-valued attribute, such as age or geographical location. In such cases, no discrete communities can be identified. We consider how the notion of community structure can be generalized to networks that are based on continuous-valued attributes: in general, a network may contain discrete communities which are ordered according to their attribute values. We propose a method of generating synthetic ordered networks and investigate the effect of ordered community structure on the spread of infectious diseases. We also show that community detection algorithms fail to recover community structure in ordered networks, and evaluate an alternative method using a layout algorithm to recover the ordering.Comment: This is an extended preprint version that includes an extra example: the college football network as an ordered (spatial) network. Further improvements, not included here, appear in the journal version. Original title changed (from "Ordered and continuous community structure in networks") to match journal versio

Significant Scales in Community Structure

Many complex networks show signs of modular structure, uncovered by community detection. Although many methods succeed in revealing various partitions, it remains difficult to detect at what scale some partition is significant. This problem shows foremost in multi-resolution methods. We here introduce an efficient method for scanning for resolutions in one such method. Additionally, we introduce the notion of "significance" of a partition, based on subgraph probabilities. Significance is independent of the exact method used, so could also be applied in other methods, and can be interpreted as the gain in encoding a graph by making use of a partition. Using significance, we can determine "good" resolution parameters, which we demonstrate on benchmark networks. Moreover, optimizing significance itself also shows excellent performance. We demonstrate our method on voting data from the European Parliament. Our analysis suggests the European Parliament has become increasingly ideologically divided and that nationality plays no role.Comment: To appear in Scientific Report

Structure Community of Mangrove at Tabulo Selatan Beach, Boalemo Regency

This study aims to know the community structure of mangrove and the environmental condition in South Tabulo coast. Mean temperature at station 1, 2, and 3 was 310C, and water salinity varied between 28-30 ‰. Water pH was averagely 7 in all stations. Substrate measurements were visually done and through touches. Stations 1 and 2 had sandy muddy substrates, while station 3 was muddy. Mangroves of tree criterion were found 122 individuals of 7 species, Avicennia lanata, A. marina, Rhizophora apiculata, R. mucronata, Sonneratia alba, Bruguiera gymnorrhiza, and Ceriops tagal. Field observations showed that the highest species density was recorded in R. mucronata. The highest species frequency was found in S. alba, R. apiculata, and R. mucronata, while the highest species cover and importance value index were recorded in S. alba and R. apiculata dan R. mucronata. Based on diversity index, it was found that only 7 species were found in the study sites and it belonged to good condition. It indicates that the study sites are still in good ecological condition.Abstrak Keywords : Mangrove, community, Boalemo, diversity, importance value. ABSTRAK Penelitian ini bertujuan untuk mengetahui struktur komunitas mangrove serta kondisi lingkungan di Pantai Tabulo Selatan. Berdasarkan hasil penelitian di Pantai Tabulo Selatan untuk pengukuran suhu pada stasiun 1, 2, dan 3 diperoleh hasil rata-rata 310C, dengan salinitas bervariasi antara 28-30 ‰. Pengukuran pH air pada semua stasiun pengamatan diperoleh hasil rata-rata 7. Pengamatan substrat dilakukan secara visual dengan cara meraba tekstur substrat pada setiap stasiun, dan substrat yang terdapat di lokasi penelitian pada stasiun 1 dan 2 adalah lumpur berpasir, pada stasiun 3 berlumpur. Hasil penelitian menunjukan bahwa pada semua stasiun dengan kriteria pohon telah ditemukan 122 individu dari 7 spesies yang ditemukan yaitu Avicennia lanata, Avicennia marina, Rhizophora apiculata, R. mucronata, Sonneratia alba, Bruguiera gymnorrhiza dan Ceriops tagal. Berdasarkan pengamatana lapangan, kerapatan spesies tertinggi dimiliki oleh spesies Rhizophora mucronata, frekuensi spesies tertinggi dimiliki spesies S. alba, R. apiculata dan Rhizophora mucronata, penutupan spesies dan indeks nilai penting didapati spesies Sonneratia alba, Rhizophora apiculata dan R. mucronata.. Berdasarkan indeks keanekaragaman dapat dilihat bahwa hanya ada 7 spesies yang didapatkan pada lokasi penelitian dan termasuk dalam kriteria keanekaragaman baik. Hal ini menunjukkan bahwa di lokasi penelitian masih dalam kondisi ekologis yang cukup baik

Structure of Mangrove Community in Palaes Village Coastal West Likupang District, North Minahasa

Indonesia merupakan daerah tropis berbentuk kepulauan (13.664 pulau) dengan garis pantai yang diperkirakan sepanjang (95.181 km) meenjadi kawasan yang baik bagi pertumbuhan tanaman mangrove. ). Mangrove tumbuh subur di daerah muara sungai atau estuari yang merupakan daerah tujuan akhir dari partikel-partikel organik ataupun endapan lumpur yang terbawa dari daerah hulu akibar adanya erosi. Kesuburan daerah ini juga ditentukan oleh adanya pasang surut yang mentransportasi nutrient.Berdasarkan data Direktorat Jendral Rehabilitas Lahan dan Perhutanan Sosial luas hutan Mangrove di Indonesia pada tahun 1999 diperkirakan mencapai 8.60 juta hektar akan tetapi sekitar 5.30 juta hektar dalam keadaan rusak. Sedangkan data FAO (2007) luas hutan Mangrove di Indonesia pada tahun 2005 hanya mencapai 3,062,300 ha atau 19% dari luas hutan Mangrove di dunia dan yang terbesar di dunia melebihi Australia (10%) dan Brazil (7%).Kondisi hutan mangrove di Desa Palaes masih cukup baik, hal ini dikarenakan masyarakat Desa Palaes sangat menjaga keberadaan hutan mangrove. Selain itu pemanfaatan hutan mangrove untuk kebutuhan rumah tangga masyarakat Desa Palaes relatif masih kecil dan belum menimbulkan dampak terhadap lingkungan ekosistem mangrove.Kegiatan Penelitian ini di laksanakan di kawasan pesisir pantai Desa Palaes Kecamatan Likupang Barat Kabupaten Minahasa Utara Provinsi Sulawesi Utara, pada bulan Mei 2016. Menggunakan metode kuadran yang dilanjutkan dengan analisis struktur komunitas.Metode kuadran dilakukan dengan cara menarik line transek daro darat ke laut kemudian meletakkan sebanyak 10 line kuadran tersebut. Setelah kuadran diletakkan dilakukan pengambilan data vegetasi setelah itu dilakukan analisis data dengan menggunakan struktur komunitas.Berdasarkan jenis mangrove yang ditemukan di Desa Palaes Kecamatan Likupang Barat Kabupaten Minahasa Utara ditemukan 6 spesies mangrove dari famili yang berbeda dan Rizhopora apiculata merupakan spesies yang paling berperan dalam komunitas mangrove di daerah tersebut. Dan didapati nilai indeks keanekaragaman 1,73.Identifikasi jenis mangrove yang ditemukan di Desa Palaes Kecamatan Likupang Barat Kabupaten Minahasa Utara ditemukan sebanyak 501 individu dari 6 spesies yang termasuk dalam 4 famili yaitu Rizophoraceae, Lytraceae, Meliaceae dan Avicenniaceae Adapun spesies yang ditemukan yaitu Rizhopora mucronata, Rizhopora apiculata, Sonneratia caseolaris dan Xylocarpus granatum, Bruguiera gymnorrhiza,dan Avicennia officinalisKeys : Mangrove,Lingkungan, Vegetasi, komonitas

Immunization of networks with community structure

In this study, an efficient method to immunize modular networks (i.e., networks with community structure) is proposed. The immunization of networks aims at fragmenting networks into small parts with a small number of removed nodes. Its applications include prevention of epidemic spreading, intentional attacks on networks, and conservation of ecosystems. Although preferential immunization of hubs is efficient, good immunization strategies for modular networks have not been established. On the basis of an immunization strategy based on the eigenvector centrality, we develop an analytical framework for immunizing modular networks. To this end, we quantify the contribution of each node to the connectivity in a coarse-grained network among modules. We verify the effectiveness of the proposed method by applying it to model and real networks with modular structure.Comment: 3 figures, 1 tabl