The cycling of carbon into and out of dust

Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are processed in photo-dissociation regions by UV photons, by ion and electron collisions in interstellar shock waves and by cosmic rays. A significant fraction of hydrocarbon dust must therefore be re-formed by accretion in the dense, molecular ISM. A new dust model (Jones et al., Astron. Astrophys., 2013, 558, A62) shows that variations in the dust observables in the diffuse interstellar medium (nH = 1000 cm^3), can be explained by systematic and environmentally-driven changes in the small hydrocarbon grain population. Here we explore the consequences of gas-phase carbon accretion onto the surfaces of grains in the transition regions between the diffuse ISM and molecular clouds (e.g., Jones, Astron. Astrophys., 2013, 555, A39). We find that significant carbonaceous dust re-processing and/or mantle accretion can occur in the outer regions of molecular clouds and that this dust will have significantly different optical properties from the dust in the adjacent diffuse ISM. We conclude that the (re-)processing and cycling of carbon into and out of dust is perhaps the key to advancing our understanding of dust evolution in the ISM.Comment: 14 pages, 6 figure

HUBUNGAN KEBIASAAN BELAJAR DAN MINAT MEMBACA DENGAN PRESTASI BELAJAR IPS PADA SISWA KELAS X DI SMKN I LEMAHABANG KABUPATEN CIREBON

AGUSTINA NINGSIH : Dalam Hal kebiasaan belajar, siswa di SMKN I Lemahabang masih kurang memperhatikan kebiasaan belajarnya hal ini dapat dilihat dari segi keteraturan dalam belajar, kebiasaan mempersiapkan keperluan studi, kebiasaan hadir di kelas sebelum pelajaran, serta kebiasaan belajar sampai paham dan tuntas. Dalam minat membaca pun masih kurang, hal ini dapat dilihat dari segi kebiasaan dalam mengunjungi perpustakaan, kesenangan dalam membaca, kesadaran akan manfaat membaca, kurangnya menyempatkan waktu untuk membaca, serta dari jumlah buku yang dia baca. Tujuan penelitian dalam skripsi ini adalah untuk memperoleh data tentang kebiasaan belajar siswa pada mata pelajaran IPS, Minat membaca siswa pada mata pelajaran IPS, Prestasi belajar siswa pada mata pelajaran IPS, Seberapa besar hubungan antara kebiasaan belajar dan minat membaca terhadap prestasi belajar siswa pada mata pelajaran IPS. Selain mempunyai kebiasaan belajar yang baik, membaca juga merupakan tuntutan penting bagi para siswa. Karena pada dasarnya belajar memang tidak dapat lepas dari aktivitas membaca. Kegiatan membaca yang dilakukan di sekolah biasanya merupakan suatu alat untuk dapat menguasai semua bahan pelajaran. Populasi dalam penelitian ini adalah siswa kelas X di SMKN I Lemahabang yang berjumlah 300 siswa, sedangkan pengambilan sampel dilakukan dengan menggunakan purposive, yakni 45 siswa kelas X PM2. Metode penelitian ini menggunakan metode empirik kuantitatif dengan teknik pengumpulan data melalui observasi, wawancara, angket, dan dokumentasi. Sedangkan untuk analisis data menggunakan analisis regresi ganda, uji t dan uji F. Hasil penelitian ini menunjukan bahwa terdapat hubungan yang positif dan signifikan antara kebiasaan belajar terhadap prestasi belajar siswa pada mata pelajaran IPS ditunjukan oleh nilai thitung 2,146 > ttabel 2,021 dengan nilai signifikansi 0,035 , terdapat hubungan yang positif dan signifikan antara minat membaca terhadap prestasi belajar siswa pada mata pelajaran IPS ditunjukan oleh nilai thitung 23,388 > ttabel 2,052 dengan nilai signifikansi 0,000 , terdapat hubungan yang positif dan signifikan secara simultan antara kebiasaan belajar dan minat membaca terhadap prestasi belajar siswa pada mata pelajaran IPS hal tersebut terbukti dari hasil uji F yaitu diperoleh nilai Fhitung 297,056 > Ftabel 3,11 dengan signifikansi 0,000 koefisien determinasi (R Square) sebesar 0,871 hal tersebut menunjukan bahwa prestasi belajar siswa pada mata pelajaran IPS berhubungan dengan kebiasaan belajar dan minat membaca sebesar 87,1% sisanya 12,9% berhubungan dengan faktor lain diluar penelitian seperti motivasi dalam belajar, inteligensi, bakat, konsentrasi serta dari faktor keluarga, masyarakat maupun sekolah, dll

Reconstruction and analysis of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis

International audienceBACKGROUND: Few genome-scale models of organisms focus on the regulatory networks and none of them integrates all known levels of regulation. In particular, the regulations involving metabolite pools are often neglected. However, metabolite pools link the metabolic to the genetic network through genetic regulations, including those involving effectors of transcription factors or riboswitches. Consequently, they play pivotal roles in the global organization of the genetic and metabolic regulatory networks. RESULTS: We report the manually curated reconstruction of the genetic and metabolic regulatory networks of the central metabolism of Bacillus subtilis (transcriptional, translational and post-translational regulations and modulation of enzymatic activities). We provide a systematic graphic representation of regulations of each metabolic pathway based on the central role of metabolites in regulation. We show that the complex regulatory network of B. subtilis can be decomposed as sets of locally regulated modules, which are coordinated by global regulators. CONCLUSION: This work reveals the strong involvement of metabolite pools in the general regulation of the metabolic network. Breaking the metabolic network down into modules based on the control of metabolite pools reveals the functional organization of the genetic and metabolic regulatory networks of B. subtilis

Joint Belgian recommendation on screening for DPD-deficiency in patients treated with 5-FU, capecitabine (and tegafur)

Objectives: Fluoropyrimidines such as 5-Fluorouracil (5-FU), capecitabine and tegafur are drugs that are often used in the treatment of maliginancies. The enzyme dihydropyrimidine dehydrogenase (DPD) is the first and rate limiting enzyme of 5-FU catabolism. Genetic variations within the DPYD gene (encoding for DPD protein) can lead to reduced or absent DPD activity. Treatment of DPD deficient patients with fluoropyrimidines can result in severe and, rarely, fatal toxicity. Screening for DPD deficiency should be implemented in practice. Methods: The available methods in routine to screen for DPD deficiency were analyzed and discussed in several group meetings involving members of the oncological, genetic and toxicological societies in Belgium: targeted genotyping based on the detection of 4 DPYD variants and phenotyping, through the measurement of uracil and dihydrouracil/uracil ratio in plasma samples. Results: The main advantage of targeted genotyping is the existence of prospectively validated genotype-based dosing guidelines. The main limitations of this approach are the relatively low sensitivity to detect total and partial DPD deficiency and the fact that this approach has only been validated in Caucasians so far. Phenotyping has a better sensitivity to detect total and partial DPD deficiency when performed in the correct analytical conditions and is not dependent on the ethnic origin of the patient. Conclusion: In Belgium, we recommend phenotype or targeted genotype testing for DPD deficiency before starting 5-FU, capecitabine or tegafur. We strongly suggest a stepwise approach using phenotype testing upfront because of the higher sensitivity and the lower cost to society

A large-scale species level dated angiosperm phylogeny for evolutionary and ecological analyses.

Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species, based on two plastid barcoding genes, matK (incl. trnK) and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful for investigating different broad scale research questions in ecological and evolutionary biology