Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island, governed by Indonesia and the sixth-largest island in the world at 473,481 km2. Sumatra is an elongated landmass spanning a diagonal northwest-southeast axis; the Indian Ocean borders the west and southwest coasts of Sumatra with the island chain of Simeulue, Nias and Enggano off the western coast. In the northeast the narrow Strait of Malacca separates the island from the Malay Peninsula, an extension of the Eurasian continent. In the southeast the narrow Sunda Strait, containing the Krakatoa Archipelago, separates Sumatra from Java; the northern tip of Sumatra borders the Andaman Islands, while off the southeastern coast lie the islands of Bangka and Belitung, Karimata Strait and the Java Sea. The Bukit Barisan mountains, which contain several active volcanoes, form the backbone of the island, while the northeastern area contains large plains and lowlands with swamps, mangrove forest and complex river systems.

The equator crosses the island at its center in West Riau provinces. The climate of the island is tropical and humid. Lush tropical rain forest once dominated the landscape. Sumatra has a wide range of plant and animal species but has lost 50% of its tropical rainforest in the last 35 years. Many species are now critically endangered, such as the Sumatran ground cuckoo, the Sumatran tiger, the Sumatran elephant, the Sumatran rhinoceros, the Sumatran orangutan. Deforestation on the island has resulted in serious seasonal smoke haze over neighbouring countries, such as the 2013 Southeast Asian haze causing considerable tensions between Indonesia and affected countries Malaysia and Singapore. Sumatra was known in ancient times by the Sanskrit names of Swarnadwīpa and Swarnabhūmi, because of the gold deposits in the island's highlands; the first mention of the name of Sumatra was in the name of Srivijayan Haji Sumatrabhumi, who sent an envoy to China in 1017. Arab geographers referred to the island as Lamri in the tenth through thirteenth centuries, in reference to a kingdom near modern-day Banda Aceh, the first landfall for traders.

The island is known by other names namely, Andalas or Percha Island. Late in the 14th century the name Sumatra became popular in reference to the kingdom of Samudra Pasai, a rising power until replaced by the Sultanate of Aceh. Sultan Alauddin Shah of Aceh, in letters addressed to Queen Elizabeth I of England in 1602, referred to himself as "king of Aceh and Samudra"; the word itself is from Sanskrit "Samudra", meaning "gathering together of waters, sea or ocean". Marco Polo named the kingdom Samara or Samarcha in the late 13th century, while the 14th century traveller Odoric of Pordenone used Sumoltra for Samudra. Subsequent European writers used similar forms of the name for the entire island. European writers in the 19th century found that the indigenous inhabitants did not have a name for the island; the Melayu Kingdom was absorbed by Srivijaya. Srivijayan influence waned in the 11th century after it was defeated by the Chola Empire of southern India. At the same time, Islam made its way to Sumatra through Arabs and Indian traders in the 6th and 7th centuries AD.

By the late 13th century, the monarch of the Samudra kingdom had converted to Islam. Marco Polo visited the island in 1292. Ibn Battuta visited with the sultan for 15 days, noting the city of Samudra was "a fine, big city with wooden walls and towers", another two months on his return journey. Samudra was succeeded by the powerful Aceh Sultanate. With the coming of the Dutch, the many Sumatran princely states fell under their control. Aceh, in the north, was the major obstacle, as the Dutch were involved in the long and costly Aceh War; the Free Aceh Movement fought against Indonesian government forces in the Aceh Insurgency from 1976 to 2005. Security crackdowns in 2001 and 2002 resulted in several thousand civilian deaths; the island was impacted by both the 1883 Krakatoa eruption and the 2004 Boxing Day Tsunami. Sumatra is not densely populated, with 123.46 people per km2 – about 58.5 million people in total. Because of its great extent, it is nonetheless the fifth most populous island in the world.

There are over 52 languages spoken, all of which belong to the Malayo-Polynesian branch of the Austronesian language family. Within Malayo-Polynesian, they are divided into several sub-branches: Chamic, Northwest Sumatra–Barrier Islands and Bornean. Northwest Sumatra–Barrier Islands and Lampungic branches are endemic to the island. Like all parts of Indonesia, Indonesian is the main lingua franca. Although Sumatra has its own local lingua franca, variants of Malay like Medan Malay and Palembang Malay are popular in North and South Sumatra in urban areas. Minangkabau is popular in West Sumatra, some parts of North Sumatra, Bengkulu and Riau while

Yehuda Yehoshua Tzadka was a respected Sephardi rabbi and rosh yeshiva of the Porat Yosef Yeshiva in Jerusalem. He became a student in the yeshiva after his bar mitzvah, continued to study and teach there for 70 years. Tzadka was born in Jerusalem to Shaul Tzadka, a Jewish merchant from Baghdad who had immigrated to Ottoman Palestine around 1900 with his wife, Simcha, a niece of the Ben Ish Chai; the family lived in the Beit Yisrael neighborhood, young Yehuda attended Talmud Torah Bnei Tzion in the Bukharim Quarter. After his bar mitzvah he enrolled in Porat Yosef Yeshiva in Jerusalem's Old City, which had opened a year earlier. Following the death of rosh yeshiva Shlomo Laniado, Tzadka became a student of the new rosh yeshiva, Rabbi Ezra Attiya, from whom he continued to learn for the next 45 years. Tzadka was a diligent student, he studied at night in the Be'er Sheva synagogue in Beis Yisrael. Every Friday night he would study in the Shoshanim L'David Synagogue, where Sephardi talmidei chachamim congregated.

In 1937 Attiya suggested Tzadka as a replacement for a senior Talmudic lecturer, unable to continue teaching. Tzadka's first class included Rabbi Ovadia Yosef, Rabbi Ben Zion Abba Shaul, Rabbi Yehuda Moallem, Rabbi Baruch Ben Haim, Rabbi Ezra Ades, all of whom would go on to leadership positions in the Sephardi Torah world. Tzadka taught in classic Sephardi style, focusing on the Talmudic commentaries of the Maharsha and the Maharam. Like Attiya, he emphasized the study of musar texts such as Mesillat Yesharim, he distinguished himself as a teacher by his ability to gear each lesson to the level of his students. Tzadka was characterized by his love of Torah and its sages, his desire and alacrity to perform mitzvot, he lived and encouraged his students to be content without luxuries. Although he was qualified to serve as a dayan, was asked to join a new regional beth din founded by Rabbi Reuven Katz, Rav of Petah Tikva, Tzadka preferred to keep learning and teaching in Porat Yosef. During the 1948 Arab-Israeli War, when the Jordanian army captured the Old City, Tzadka supervised groups of Porat Yosef students learning in synagogues in the neighborhoods of Geula and the Bukharim Quarter.

After the war, he traveled to England for four months to raise money on behalf of a new yeshiva building, erected in the Geula neighborhood in the mid-1950s. Beyond the walls of the yeshiva, Tzadka was active throughout Israel, encouraging Sephardi families to give their children a Torah education rather than send them to secular schools, he spoke at rallies sponsored by the P'eylim organization on behalf of Torah education for new immigrants, made the rounds on school registration days, begging parents to register their children in Torah schools. After the founding of the State of Israel, he visited absorption camps in which hundreds of thousands of Sephardi Jews who had left or been expelled from Arab countries were living, urging parents not to send their children to secular schools and encouraging established communities to open Torah schools for immigrant children; when Attiya died in May 1970, the yeshiva directors asked Tzadka to become the new rosh yeshiva. He agreed, but when he saw a new sign on the door of his classroom: "Rabbi Yehuda Tzadka, Rosh Yeshiva", he insisted that it be taken down and refused to be called by that title.

In 1984 he published the sefer Kol Yehuda, a book of halakha and aggadah incorporating his approach to all matters of life. In his years he suffered a series of heart attacks, but was able to recover and return to his teaching. While hospitalized, he continued his practice of rising at midnight for Tikkun Chatzot and praying vasikin. During one hospitalization, he was visited by Rabbi Elazar Shach, who found him lying in a bed in the intensive-care unit with a sefer, engrossed in Torah study, he suffered his last heart attack during the night of the Fast of Gedaliah in 1991 and was taken to hospital. Two weeks he suffered a stroke and lapsed into a coma, he was buried in the Sanhedria Cemetery in a family plot. He was succeeded as rosh yeshiva by Rabbi Ben Zion Abba Shaul. After the latter's death in 1998, Tzadka's son, Rabbi Moshe Tzadka, was named rosh yeshiva of the Geula branch of Porat Yosef Yeshiva. Tzadka married Fahima Batat, daughter of Rabbi Selim Tzalach Batat of Baghdad, in 1934, they had two daughters.

Fahima died at the age of 57, after which Tzadka remarried, to Tamar Asuderi, who survived him

Narayanaswamy Srinivasan is an Indian molecular biophysicist and a professor and the head of Proteins: Structure and Evolutionary Group at the Molecular Biophysics Unit of the Indian Institute of Science. He is known for his researches in the fields of computational genomics and protein structure analysis. An elected fellow of the Indian Academy of Sciences and the National Academy of Sciences, India, he is a J. C. Bose National fellow of the Department of Biotechnology and a recipient of the National Bioscience Award for Career Development of the Department of Science and Technology; the Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 2007, for his contributions to biological sciences. N. Srinivasan, born on the April Fool's Day of 1962 in Chennai in the south Indian state of Tamil Nadu, graduated in physics from the University of Madras in 1982 and continued at the university to complete his master's degree in biophysics at the Department of Crystallography and Biophysics in 1984.

Joining the Indian Institute of Science, he secured a PhD in 1991 for his thesis, Conformational studies on globular proteins: Data analysis, served as a senior research fellow at IISc, assisting Padmanabhan Balaram, a noted biochemist and Padma Bhushan recipient. His stint at Balaram's laboratory lasted only 10 months and in October 1991, he moved to the Department of Crystallography at Birkbeck College to work with Tom Blundell and stayed there till 1994 when he shifted his base to Ludwig Institute for Cancer Research where he had the opportunity to work under Mike Waterfield. Two years he was reunited with Tom Blundell at the Department of Biochemistry of the University of Cambridge and completed his post-doctoral studies there in May 1998. Srininvasan returned to India the same year and joined the Indian Institute of Science to serve at the Molecular Biophysics Unit as an assistant professor and a senior fellow of the Wellcome Trust. In 2010, he was promoted as a professor and he heads the Proteins: Structure and Evolutionary Group, popularly known as N. S. Group, of the MBU.

In between, he served as an honorary research fellow at Birkbeck College from 1998 to 2000 and is a visiting professor at University of La Réunion, a senior fellow at Manchester University and a visiting professor of Bioinformatics at University of Nantes. Srinivasan's researches were broadly on protein evolution with regard to its structure and interactions, he worked on cellular signal transduction pathways and proteins involved in the process through modeling and computational studies. Deploying computational genomics, he is known to have assisted in identifying similar proteins with shared structural and functional features, his research findings have been published in several articles. He has been granted patents for two of his inventions related to nucleotide sequences, his ongoing project, Multi-macromolecular assemblies, relates to 3-D structures of large macromolecular machines. Srinivasan is a former member of the committee on Affiliates and Special Interests Group of the International Society for Computational Biology and a member of the Structural Biology and Structural Genomics section of the Faculty of 1000.

He is associated with several science journals. He was associated with PRIB 2007, an international conference on Pattern Recognition In Bioinformatics, held in Singapore in 2007 as a member of the program committee and has delivered several featured lectures and keynote addresses which included the Keystone Symposium on Multiprotein Complexes, Asia-Pacific Bioinformatics Conference. On the academic front, he has served as the thesis examiner for a number of Indian universities and as the coordinator of integrated doctoral and BS programs in Biology of Indian Institute of Science, he sits in the Scientific Advisory Board of Jubilant Biosys, a research and development firm involved in drug discovery services. The Department of Biotechnology of India awarded Srinivasan the National Bioscience Award for Career Development in 2004; the year 2007 brought him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards, as well as the elected fellowship of the Indian Academy of Sciences and the National Academy of Sciences, India.

He holds the Honorary Research Fellowship of Birkbeck College and the International Senior Fellowship of the Wellcome Trust. Mark S Johnson, Narayanaswamy Srinivasan, Ramanathan Sowdhamini, Tom L Blundell. "Knowledge-based protein modeling". Critical Reviews in Biochemistry and Molecular Biology. 29: 1–68. Doi:10.3109/10409239409086797. CS1 maint: multiple names: authors list KG Tina, Rana Bhadra, Narayanaswamy Srinivasan. "PIC: protein interactions calculator". Nucleic Acids Research. 35: W473–W476. Doi:10.1093/nar/gkm423. PMC 1933215. PMID 17584791. CS1 maint: multiple names: authors list Jonas Emsley, Helen E