196,283 research outputs found
Constraining the cosmic-ray ionization rate and spectrum with NIR spectroscopy of dense clouds. A testbed for JWST
No full textContext. Low-energy cosmic rays (CRs) control the thermo-chemical state and the coupling between gas and magnetic fields in dense molecular clouds. However, current estimates of the low-energy CR spectrum (E-2-1 GeV) and the associated CR ionization rate are highly uncertain. Aims. We apply, for the first time, a new method for constraining the CR ionization rate and the CR spectral shape using H2 rovibrational lines from cold molecular clouds. Methods. Using the MMIRS instrument on the MMT, we obtained deep near-infrared (NIR) spectra in six positions within four dense cores, namely, G150, G157, G163, G198, with column densities of NH2-1022 cm-2. Results. We derived 3ÏA? upper limits on the H2 (1-0)S(0) line (2.22 μm) brightness in the range I-=-5.9-ÃA - -10-8 to 1.2-ÃA - -10-7 erg cm-2 s-1 sr-1 for the different targets. Using both an analytic model and a numerical model of CR propagation, we convert these into upper limits on the CR ionization rate in the clouds-interior, ζ-=-1.5 to 3.6-ÃA - -10-16 s-1, and lower limits on the low-energy spectral slope of interstellar CR protons, α-=-0.97 to -0.79. We show that while MMT was unable to detect the H2 lines due to high atmospheric noise, JWST/NIRSpec will be able to efficiently detect the CR-excited H2 lines, making it the ideal method for constraining the otherwise elusive low-energy CRs and shedding light on the sources and propagation modes of CRs
Same As It Ever Was
No full text(Statement of Responsibility) by Dawn M. Bialy(Thesis) Thesis (B.A.) -- New College of Florida, 1985(Electronic Access) RESTRICTED TO NCF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE(Bibliography) Includes bibliographical references.(Source of Description) This bibliographic record is available under the Creative Commons CC0 public domain dedication. The New College of Florida, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.(Local) Faculty Sponsor: Callahan, Charlen
Antimicrobial activity of saponins from Medicago sp.: structure-activity relationship
No full textThe antimicrobial activity of saponins from Medicago sativa, M. arborea and M. arabica against a selection of medically important yeasts, Gram-positive and -negative bacteria was investigated. Structure-activity growth inhibitory effects of related prosapogenins and sapogenins are also described. Increasing antibiotic activity was observed going from the saponin extracts to the sapogenin samples, suggesting that the sugar moiety is not important for the antimicrobial efficacy. Activity was especially high against Gram-positive bacteria (Bacillus cereus, B. subtilis, Staphylococcus aureus and Enterococcus faecalis) with M. arabica being the species showing a broader spectrum of action. Discrete antifungal activity was also observed, mainly against Saccharomyces cerevisiae. The observed antimicrobial properties of M. sativa and M. arborea were related to the content of medicagenic acid, while hederagenin seems to contribute to the bioactivity of M. arabica total sapogenins
New triterpenic saponins from the aerial parts of Medicago arabica (L:) Huds
No full textThe reinvestigation of saponin composition from Medicago arabica from Italy allowed the detection of nineteen (1-19) saponins. All of them were purified by reverse-phase chromatography and their structures elucidated by spectroscopic and spectrometric (1D and 2D NMR; ESI-MS/MS) and chemical methods. Fourteen were known saponins, previously found in other plants including other Medicago, species. They have been identified as glycosides of oleanolic acid, 2 beta,3 beta-dihydroxyolean-12-en-28-oic acid, hederagenin, bayogenin and soyasapogenol B. Five saponins, identified as 3-O-[-alpha-L-arabinopyranosyl(1 -> 2)-beta-D-glucuronopyranosyl]-30-O-beta-D-glucopyranosyl 2 beta,3 beta,30-trihydroxyolean-12-en-28-oic acid (1), 3-O-[alpha-L-arabinopyranosyl(1 -> 2)-beta- -D-glucuronopyranosyl]-30-O-[beta-D-glucopyranosyl]3 beta,30-dihydroxyolean-12-en-28-oic acid (2), 3-O-[beta-D-glucuronopyranosyl]-30-O-[alpha-L-arabinopyranosyl(1 -> 2)-beta-D-glucopyranosyl]2 beta,3 beta,30-trihydroxyolean-12-en-28-oic acid (3), 3-O-[beta-D-glucuronopyranosyl]-30-O[alpha-L-arabinopyranosyl(1 -> 2)-beta-D-glucopyranosyl] 3 beta,30-dihydroxyolean-12-en-28-oic acid (4) and 3-O-[beta-D-glucuronopyranosyl]-30-O-[beta-D-glucopyranosyl] 2 beta,3 beta,30-trihydroxyolean-12-en-28-oic acid (5), are reported here as new natural compounds. These new saponins, possessing a hydroxy group at the 30-methyl position of the triterpenic skeleton, have never been previously found in the genus Medicago
Triterpenoid glycosides from the leaves of Medicago arborea L
No full textEighteen triterpene saponins (1-18) from Medicago arborea leaves have been isolated and their structures elucidated by spectroscopic, spectrometric (1D and 2D NMR, FAB-MS, ESI-MS/MS), and chemical methods. They have been identified as glycosides of medicagenic, zanhic, and 2 beta-hydroxyoleanolic acids, soyasapogenol B, bayogenin, and 2 beta, 3 beta-dihydroxyolean-12-en-23-al-28-oic acid. Twelve of them, identified as 3-O-beta-D-glucopyranosyl-28-O-[alpha-L-arabinopyranosyl(1 -> 3)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside] zanhic acid (3), 3-O-beta-D-glucopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[alpha-L-arabinopyranosyl-(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyrano- side} zanhic acid (4), 3-O-[alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosyl(1 -> 2)-beta-D-glucopyranosyl]-2 beta-hydroxyoleanolic acid (5), 3-O-beta-D-glucuronopyranosyl-28-O-[alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside] medicagenic acid (6), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]bayogenin (9), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]-2 beta,3 beta-dihydroxyolean-12-en-23-al-28-oic acid (10), 3-O-beta-D-glucuronopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (12), 3-O-beta-D-glucuronopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[alpha-L-arabinopyranoside(1 -> 3)]-alpha-L-rhamnopyrano- syl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (13), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]zanhic acid (14), 3-O-[alpha-L-arabinopyranosyl(1 -> 2)-D-glucopyranosyl(1 -> 2)-beta-D-glucopyranosyl]-2 beta-O-{beta-D-xylopyranosyl(1 -> 4)-[beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (16), 3-O-[beta-D-glucopyranosyl (1 -> 2)-(beta-D-glucopyranosyl]-28-O{beta-D-xylopyranosyl (1 -> 4)-[alpha-L-arabi nopyranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl (1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (17), and 3-O-beta-D-glucuronopyranosyl-28-O-1pD-xylopyranosyl(1 -> 4)-beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyrano-sideImedicagenic acid (18), are reported as new natural compounds. The presence of the aldehydic group on the sapogenin moiety of saponin 10 is discussed in the framework of a possible elucidation of the biosynthesis of these metabolites
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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