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We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE)gamma-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy.-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse gamma-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130) and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL J2021.0+4031e (the Gamma Cygni supernova remnant) was examined, and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE gamma-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula flux. We interpret these observations in a multiwavelength context and present the most detailed gamma-ray view of the region to date.
A new pterocarpan (named 8-methoxyneorautenol) was isolated from the acetone ext. of the root bark of Erythrina abyssinica. In addn., the known isoflavonoid derivs. eryvarin L, erycristagallin and shinpterocarpin were identified for the first time from the roots of this plant. The structures were detd. on the basis of spectroscopic evidence. The new compd. showed selective antimicrobial activity against Trichophyton mentagrophytes. The acetone ext. of the root bark of E. abyssinica showed radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The pterocarpenes, 3-hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene and erycristagallin, were the most active constituents of the roots of this plant and showing dose-dependent activities similar to that of the std. quercetin. [on SciFinder (R)]
Highly ionized metals as probes of the circumburst gas in the natal regions of gamma-ray bursts
(2018)
We present here a survey of high-ionization absorption lines in the afterglow spectra of long-duration gamma-ray bursts (GRBs) obtained with the VLT/X-shooter spectrograph. Our main goal is to investigate the circumburst medium in the natal regions of GRBs. Our primary focus is on the N vλλ 1238, 1242 line transitions, but we also discuss other high-ionization lines such as O vi, C iv, and Si iv. We find no correlation between the column density of N v and the neutral gas properties such as metallicity, H i column density, and dust depletion; however, the relative velocity of N v, typically a blueshift with respect to the neutral gas, is found to be correlated with the column density of H i. This may be explained if the N v gas is part of an H ii region hosting the GRB, where the region’s expansion is confined by dense, neutral gas in the GRB’s host galaxy. We find tentative evidence (at 2σ significance) that the X-ray derived column density, NH, X, may be correlated with the column density of N v, which would indicate that both measurements are sensitive to the column density of the gas located in the vicinity of the GRB. We investigate the scenario where N v (and also O vi) is produced by recombination after the corresponding atoms have been stripped entirely of their electrons by the initial prompt emission, in contrast to previous models where highly ionized gas is produced by photoionization from the GRB afterglow.
Three diatomite beds exposed in the Ol Njorowa Gorge south of Lake Naivasha, Central Kenya Rift, document three major lake-level highstands between 175 and 60 kyr BP. Diatom transfer-function estimates of hydrological and hydrochemical parameters suggest that a deep and large freshwater lake existed during the highstands at 135 and 80 kyr BP. In contrast, a shallower but more expanded freshwater lake existed at 110 kyr BP. The best analog for the most extreme highstand at 135 kyr BP is the highstand during the Early Holocene humid period from 10 to 6 kyr BP. The environmental conditions as reconstructed from diatom assemblages suggest long-lasting episodes of increased humidity during the high lake periods. This contrasts to the modern situation with a relatively shallow Lake Naivasha characterized by rapid water level fluctuations within a few decades. The most likely cause for the variable hydrological conditions since 175 kyr BP is orbitally driven insolation changes on the equator and increased lateral moisture transport from the ocean.
Growth of phytopathogenic fungi in the presence of partially acetylated chitooligosaccharides
(2008)
Four phytopathogenic fungi were cultivated up to six days in media contg. chitooligosaccharide mixts. differing in av. DP and F A. The three different mixts. were named Q3 (which contained oligosaccharides of DP2-DP10, with DP2-DP7 as main components), Q2 (which contained oligosaccharides of DP2-DP12, with DP2-DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5-DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixts. of oligosaccharides with different and known compn. on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concns. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concns. of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, resp. [on SciFinder (R)]
Mass spectrometry of aminoglucan oligosaccharides using electrospray ionization MS/MS and MS/MS/MS
(2009)
New N-p-chloro-, N-p-bromo-, and N-p-nitrophenylazobenzylchitosan derivatives, as well as the corresponding azophenyl and azophenyl-p-sulfonic acids, were synthesized by coupling N-benzylvchitosan with aryl diazonium salts. The synthesized molecules were analyzed by UV-Vis, FT-IR, H-1-NMR and N-15-NMR spectroscopy. The capacity of copper chelation by these materials was studied by AAS. Chitosan and the derivatives were subjected to hydrolysis and the products were analyzed by ESI(+)-MS and GC-MS, confirming the formation of N-benzyl chitosan. Furthermore, the MS results indicate that a nucleophilic aromatic substitution (SnAr) reaction occurs under hydrolysis conditions, yielding chloroaniline from N-p-bromo-, and N-p-nitrophenylazo-benzylchitosan as well as bromoaniline from N-p-chloro-, and N-p-nitrophenylazobenzyl-chitosan.
The six possible isomers of di-N-acetylchitotetraoses [AADD, ADDA, ADAD, DADA, DAAD, and DDAA, where D stands for 2-amino-2-deoxy-3-D-glucose (GlcN) and A for 2-acetamido-2-deoxy-beta-D-glucose (GlcNAc)] were analyzed by ESI(+)-MSn. Collision induced dissociation via MSn experiments were performed for the sodiated molecules of m/z 769 [M+Na](+) for each isomer, and fragments were generated mainly by glycosidic bond and cross-ring cleavages. Rules of fragmentation were then established. A reducing end D residue yields the (O.2)A(4) cross-ring [M-59+Na](+) fragment of m/z 710 as the most abundant, whereas isomers containing a reducing end A prefer to lose water to form the [M-18+Na](+) ion of m/z 751, as well as abundant (O.2)A(4) cross-ring [M-101+Na](+) fragments of m/z 668 and B-3 [M-221+Na](+) ions of m/z 548. MS3 of C- and Y-type ions shows analogous fragmentation behaviour that allows identification of the reducing end next-neighbour residue. Due to gas-phase anchimeric assistance, B-type cleavage between the glycosidic oxygen and the anomeric carbon atom is favoured when the glycon is an A residue. Relative ion abundances are generally in the order B >> C > Y, but may vary depending on the next neighbour towards the non-reducing end. These fragmentation rules were used for partial sequence analysis of hetero-chitooligosaccharides of the composition D(2)A(3), D(3)A(3), D(2)A(4), D(4)A(3), and D(3)A(4).
This review presents recommended nomenclature for the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs), a rapidly growing class of natural products. The current knowledge regarding the biosynthesis of the >20 distinct compound classes is also reviewed, and commonalities are discussed.