On the chemical ladder of esters. Detection and formation of ethyl formate in the W51 e2 hot molecular core

The detection of organic molecules with increasing complexity and potential biological relevance is opening the possibility to understand the formation of the building blocks of life in the interstellar medium. One of the families of molecules with astrobiological interest are the esters, whose simplest member, methyl formate, is rather abundant in star-forming regions. The next step in the chemical complexity of esters is ethyl formate, C$_2$H$_5$OCHO. Only two detections of this species have been reported so far, which strongly limits our understanding of how complex molecules are formed in the interstellar medium. We have searched for ethyl formate towards the W51 e2 hot molecular core, one of the most chemically rich sources in the Galaxy and one of the most promising regions to study prebiotic chemistry, especially after the recent discovery of the P$-$O bond, key in the formation of DNA. We have analyzed a spectral line survey towards the W51 e2 hot molecular core, which covers 44 GHz in the 1, 2 and 3 mm bands, carried out with the IRAM 30m telescope. We report the detection of the trans and gauche conformers of ethyl formate. A Local Thermodynamic Equilibrium analysis indicates that the excitation temperature is 78$\pm$10 K and that the two conformers have similar source-averaged column densities of (2.0$\pm$0.3)$\times$10$^{16}$ cm$^{-2}$ and an abundance of $\sim$10$^{-8}$. We compare the observed molecular abundances of ethyl formate with different competing chemical models based on grain surface and gas-phase chemistry. We propose that grain-surface chemistry may have a dominant role in the formation of ethyl formate (and other complex organic molecules) in hot molecular cores, rather than reactions in the gas phase.Comment: Accepted in A&A; 11 pages, 6 figures, 7 Table

Penerapan Model Pembelajaran Kooperatif Pada Mata Pelajaran Matematika Berdasarkan Kurikulum 2013 Di Kelas VII SMPN 13 Banjarmasin

Kurikulum 2013 menekankan kepada pembelajaran dengan menggunakan pendekatan scientific dan penilaian autentik guna mewujudkan generasi yang siap menghadapi masa depan. Model pembelajaran kooperatif merupakan model pembelajaran yang menggunakan kerjasama tim. Dimana model ini mampu membantu peserta didik, memahami konsep yang sulit, menumbuhkan kemampuan berpikir kritis, dan kerjasama. Penelitian ini bertujuan untuk mengetahui penerapan model pembelajaran kooperatif pada mata pelajaran matematika berdasarkan Kurikulum 2013 di kelas VII SMPN 13 Banjarmasin.Jenis penelitian ini adalah penelitian lapangan dengan pendekatan kualitatif. Metode yang digunakan adalah metode deskriptif. Subjek dalam penelitian ini adalah satu orang guru yang mengajar matematika di kelas VII SMPN 13 Banjarmasin. Dan objek penelitiannya adalah penerapan model pembelajaran kooperatif pada mata pelajaran matematika berdasarkan Kurikulum 2013.Berdasarkan hasil penelitian dapat disimpulkan bahwa dalam perencanaan guru mencantumkan langkah-langkah pendekatan scientific yang mengandung komponen mengamati, menanya, mencoba, menalar, dan mengkomunikasikan, dan juga menggunakan penilaian autentik. Namun pada RPP yang dibuat guru, guru belum mencantumkan langkah-langkah model pembelajaran kooperatif. Sedangkan dalam pelaksanaannya, pembelajaran menggunakan pendekatan scientific dan model pembelajaran kooperatif terlaksana dengan baik. Penilaian autentik yang digunakan guru mencakup aspek pengetahuan, sikap, dan keterampilan

First ALMA maps of HCO, an important precursor of complex organic molecules, towards IRAS 16293-2422

The formyl radical HCO has been proposed as the basic precursor of many complex organic molecules such as methanol (CH$_3$OH) or glycolaldehyde (CH$_2$OHCHO). Using ALMA, we have mapped, for the first time at high angular resolution ($\sim$1$^{\prime\prime}$, $\sim$140 au), HCO towards the Solar-type protostellar binary IRAS 16293$-$2422, where numerous complex organic molecules have been previously detected. We also detected several lines of the chemically related species H$_2$CO, CH$_3$OH and CH$_2$OHCHO. The observations revealed compact HCO emission arising from the two protostars. The line profiles also show redshifted absorption produced by foreground material of the circumbinary envelope that is infalling towards the protostars. Additionally, IRAM 30m single-dish data revealed a more extended HCO component arising from the common circumbinary envelope. The comparison between the observed molecular abundances and our chemical model suggests that whereas the extended HCO from the envelope can be formed via gas-phase reactions during the cold collapse of the natal core, the HCO in the hot corinos surrounding the protostars is predominantly formed by the hydrogenation of CO on the surface of dust grains and subsequent thermal desorption during the protostellar phase. The derived abundance of HCO in the dust grains is high enough to produce efficiently more complex species such as H$_2$CO, CH$_3$OH, and CH$_2$OHCHO by surface chemistry. We found that the main formation route of CH$_2$OHCHO is the reaction between HCO and CH$_2$OH.Comment: Accepted in Monthly Notices of the Royal Astronomical Society; 19 pages, 12 figures, 7 table

Abundant Z-cyanomethanimine in the interstellar medium: paving the way to the synthesis of adenine

We report the first detection in the interstellar medium of the Z-isomer of cyanomethanimine (HNCHCN), an HCN dimer proposed as precursor of adenine. We identified six transitions of Z-cyanomethanimine, along with five transitions of E-cyanomethanimine, using IRAM 30m observations towards the Galactic Center quiescent molecular cloud G+0.693. The Z-isomer has a column density of (2.0$\pm$0.6)$\times$10$^{14}$ cm$^{-2}$ and an abundance of 1.5$\times$10$^{-9}$. The relative abundance ratio between the isomers is [Z/E]$\sim$6. This value cannot be explained by the two chemical formation routes previously proposed (gas-phase and grain surface), which predicts abundances ratios between 0.9 and 1.5. The observed [Z/E] ratio is in good agreement with thermodynamic equilibrium at the gas kinetic temperature (130$-$210 K). Since isomerization is not possible in the ISM, the two species may be formed at high temperature. New chemical models, including surface chemistry on dust grains and gas-phase reactions, should be explored to explain our findings. Whatever the formation mechanism, the high abundance of Z-HNCHCN shows that precursors of adenine are efficiently formed in the ISM.Comment: Accepted in Monthly Notices of the Royal Astronomical Society Letter

Complex organic molecules in the Galactic Centre: the N-bearing family

We present an unbiased spectral line survey toward the Galactic Centre (GC) quiescent giant molecular cloud (QGMC), G+0.693 using the GBT and IRAM 30$\,$ telescopes. Our study highlights an extremely rich organic inventory of abundant amounts of nitrogen (N)-bearing species in a source without signatures of star formation. We report the detection of 17 N-bearing species in this source, of which 8 are complex organic molecules (COMs). A comparison of the derived abundances relative to H$_2$ is made across various galactic and extragalactic environments. We conclude that the unique chemistry in this source is likely to be dominated by low-velocity shocks with X-rays/cosmic rays also playing an important role in the chemistry. Like previous findings obtained for O-bearing molecules, our results for N-bearing species suggest a more efficient hydrogenation of these species on dust grains in G+0.693 than in hot cores in the Galactic disk, as a consequence of the low dust temperatures coupled with energetic processing by X-ray/cosmic ray radiation in the GC.Comment: 24 pages, 23 figures, 7 tables, accepted for publication in MNRA

Italian Science Case for ALMA Band 2+3

The Premiale Project "Science and Technology in Italy for the upgraded ALMA Observatory - iALMA" has the goal of strengthening the scientific, technological and industrial Italian contribution to the Atacama Large Millimeter/submillimeter Array (ALMA), the largest ground based international infrastructure for the study of the Universe in the microwave. One of the main objectives of the Science Working Group (SWG) inside iALMA, the Work Package 1, is to develop the Italian contribution to the Science Case for the ALMA Band 2 or Band 2+3 receiver. ALMA Band 2 receiver spans from ~67 GHz (bounded by an opaque line complex of ozone lines) up to 90 GHz which overlaps with the lower frequency end of ALMA Band 3. Receiver technology has advanced since the original definition of the ALMA frequency bands. It is now feasible to produce a single receiver which could cover the whole frequency range from 67 GHz to 116 GHz, encompassing Band 2 and Band 3 in a single receiver cartridge, a so called Band 2+3 system. In addition, upgrades of the ALMA system are now foreseen that should double the bandwidth to 16 GHz. The science drivers discussed below therefore also discuss the advantages of these two enhancements over the originally foreseen Band 2 system.Comment: 43 pages, 21 figure

Karakteristik Mahasiswa Pendidikan Matematika IAIN Antasari Banjarmasin Dengan Menggunakan Metode Two Step Cluster (Studi Kasus Angkatan 2012/2013)

Penelitian ini menemukan bahwa karakteristik Cluster 1 berisi 100% mahasiswa yang berasal dari jalurmasuk PSB, jurusan IPA, berstatus negeri, dan biaya kuliah berasal dari orang tua. Berasal dari sekolah yang terletak diluar Kabupaten Banjar sebesar 92%, memiliki rata-rata nilai matematika di rapor yaitu 8,54, dan nilai UN matematika8,39, dan paling banyak berjenis kelamin perempuan yaitu 68%. Sedangkan untuk profil Cluster 2 berisi 100% darisekolah berstatus negeri dan biaya kuliah dari orang tua, mahasiswa yang berasal dari jalur masuk SPMB-PTAINsebesar 80%, rata-rata nilai rapor 7,99, berasal dari jurusanIPA sebesar 74,3%, 80% berasal dari Luar Kabupaten Banjar, berjenis kelamin perempuan sebesar 68,6% dan memilikinilai UN Matematika yaitu 7,95. Karakteristik Cluster 3 berisi mahasiswa yang berasal dari sekolah swasta sebesar 56,8%,dari jurusan IPA sebesar 47,7%, berasal dari sekolah Luar Kabupaten Banjar sebesar 38,6%. Biaya kuliah berasal dariorang tua sebesar 72,7%, berasal dari jalur masuk SPMB PTAIN sebesar 70,5%, dan mempunyai nilai UN Matematika7,79 dan rata-rata nilai rapor 8,37 dan berjenis kelamin perempuan sebanyak 72,7%

First detection of the pre-biotic molecule glycolonitrile (HOCH2CN) in the interstellar medium

Theories of a pre-RNA world suggest that glycolonitrile (HOCH$_2$CN) is a key species in the process of ribonucleotide assembly, which is considered as a molecular precursor of nucleic acids. In this Letter, we report the first detection of this pre-biotic molecule in the interstellar medium (ISM) by using ALMA data obtained at frequencies between 86.5$\,$GHz and 266.5$\,$GHz toward the Solar-type protostar IRAS16293-2422 B. A total of 15 unblended transitions of HOCH$_2$CN were identified. Our analysis indicates the presence of a cold (T$\rm _{ex}$=24$\pm$8$\,$K) and a warm (T$\rm _{ex}$=158$\pm$38$\,$K) component meaning that this molecule is present in both the inner hot corino and the outer cold envelope of IRAS16293 B. The relative abundance with respect to H$_2$ is (6.5$\pm$0.6)$\times$10$^{-11}$ and $\geq$(6$\pm$2)$\times$10$^{-10}$ for the warm and cold components respectively. Our chemical modelling seems to underproduce the observed abundance for both the warm and cold component under various values of the cosmic-ray ionisation rate ($\zeta$). Key gas phase routes for the formation of this molecule might be missing in our chemical network.Comment: 5 pages, 4 figures, 2 tables, accepted in Monthly Notices of the Royal Astronomical Society Letter

Study of the secondary metabolism of phytopathogenic fungi as a source of compounds with antibiotic activity.

Eutypa lata is a phytopathogenic fungus responsible for a "Grapevine Trunk Disease" commonly called "eutypiosis" or "eutypa dieback" which affects several agricultural crops. Its secondary metabolism has been studied in order to find the main toxins that cause the symptoms of the disease, and to learn how to control its production. One of the most phytophatogenic toxins is Eutypine, a hydroxybenzaldehyde, among several acetylenic derivatives related with it. Syccaine is one of them and exhibits antimicrobial activity against Aerobacter aerogenes and a variety of Gram-positive bacteria, and few fungi. That is why, in this study, we enviosioned the study of the secondary metabolism of E. lata as a producer of natural acetylenic compounds with antimicrobial activity to give response to the worlwide problem posed by the shortage of new antibiotics development.Throught OSMAC (One Strain Many Compounds) approach, two strains of the fungus, E. lata 355 y E. lata 311, were grown using different cultivation conditions like culture media composition, aeration, type of culture flask or incubation time. The extract obtained from the extraction with ethyl acetate of the culture media, was tested against Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae using the broth dilution method. Then, the extracts with antibiotical activity were purified in order to obtain pure compounds to find which compound are responsible for the antibiotical activity.The preliminary results of the research have indicated that OSMAC approach estimulates the production of compounds with antibiotic activity in some of the culture conditions tested