6,815 research outputs found
Methyl 2-(4-ferrocenylbenzamido)thiophene-3-carboxylate and ethyl 2-(4-ferrocenylbenzamido)-1,3-thiazole-4-acetate, a unique ferrocen
The conformations and hydrogen bonding in the thiophene and thiazole title compounds, [Fe(Câ
Hâ
)(CââHââNOâS)], (I), and [Fe(Câ
Hâ
)(CââHââNâOâS)], (II), are discussed. The sequence (Câ
Hâ)-(CâHâ)-(CONH)-(CâHâS)-(COâMe) of rings and moieties in (I) is close to being planar; all consecutive interplanar angles are less than 10°. An intramolecular N-H...O=Cester hydrogen bond [graph set S(6), N...O = 2.768 (2) Ă
and N-H...O = 134 (2)°] effects the molecular planarity, and aggregation occurs via hydrogen-bonded chains formed from intermolecular Car-H...O=Cester/amide interactions along [010], with C...O distances ranging from 3.401 (3) to 3.577 (2) Ă
. The thiazole system in (II) crystallizes with two molecules in the asymmetric unit; these differ in the conformation along their long molecular axes; for example, the interplanar angle between the phenylene (CâHâ) and thiazole (CâNS) rings is 8.1 (2)° in one molecule and 27.66 (14)° in the other. Intermolecular N-H...O=Cester hydrogen bonds [N...O = 2.972 (4) and 2.971 (3) Ă
], each augmented by a Cphenylene-H...O=Cester interaction [3.184 (5) and 3.395 (4) Ă
], form motifs with graph set RÂčâ(7) and generate chains along [100]. The amide C=O groups do not participate in hydrogen bonding. Compound (II) is the first reported ferrocenyl-containing thiazole structure
Synthesis and characterisation of novel ferrocenyl thienyl and thiazolyl systems
Ferrocenyl derivatives are currently under investigation by our group and several series containing both amidothienyl and amidothiazolyl systems have been synthesised and characterised. The incorporation of thienyl/thiazolyl groups into a ferrocenyl- or ferrocenylphenyl system greatly enhances the number of potential donor atoms for coordination with metal fragments e.g. PtII, PdII with a view to platinum anti-cancer studies and/or interaction with guest molecules through suitable hydrogen bonding interactions.
In nature, thiazole has been found to be vital in certain natural products: examples include the antibiotic bacitracin and the siderophore yersiniabactin. In therapeutic studies the antitumour compound epothilone A and myxothiazole (inhibitor) have been extensively studied
Ethyl and isopropyl 4-ferrocenylbenzoate.
The title compounds, [Fe(C5H5)(C14H13O2)] and [Fe(C5H5)-
(C15H15O2)], respectively, contain the ferrocenyl 5(C5H4) and
phenylene ±C6H4± rings in a nearly coplanar arrangement,
with interplanar angles of 6.88 (12) and 10.5 (2), respectively.
Molecules of the ethyl ester form dimers through 5(C5H5)CĂ
H O C hydrogen bonds, with graph set R22
(20), and,
together with Csp3ĂH (C5H5) interactions, generate a
one-dimensional column (irregular ladder). Molecules of the
isopropyl ester aggregate through 5(C5H5)CĂH (C6H4)
interactions
NuSTAR Tests of Sterile-Neutrino Dark Matter: New Galactic Bulge Observations and Combined Impact
We analyze two dedicated NuSTAR observations with exposure ks
located from the Galactic plane, one above and the other
below, to search for x-ray lines from the radiative decay of sterile-neutrino
dark matter. These fields were chosen to minimize astrophysical x-ray
backgrounds while remaining near the densest region of the dark matter halo. We
find no evidence of anomalous x-ray lines in the energy range 5--20 keV,
corresponding to sterile neutrino masses 10--40 keV. Interpreted in the context
of sterile neutrinos produced via neutrino mixing, these observations provide
the leading constraints in the mass range 10--12 keV, improving upon previous
constraints in this range by a factor . We also compare our results to
Monte Carlo simulations, showing that the fluctuations in our derived limit are
not dominated by systematic effects. An updated model of the instrumental
background, which is currently under development, will improve NuSTAR's
sensitivity to anomalous x-ray lines, particularly for energies 3--5 keV.Comment: 16 pages, 5 figures. Text updated to match published version in PRD.
Conclusions unchange
Large-scale and significant expression from pseudogenes in Sodalis glossinidius â a facultative bacterial endosymbiont
The majority of bacterial genomes have high coding efficiencies, but there are some genomes of intracellular bacteria that have low gene density. The genome of the endosymbiont Sodalis glossinidius contains almost 50â% pseudogenes containing mutations that putatively silence them at the genomic level. We have applied multiple âomicâ strategies, combining Illumina and Pacific Biosciences Single-Molecule Real-Time DNA sequencing and annotation, stranded RNA sequencing and proteome analysis to better understand the transcriptional and translational landscape of Sodalis pseudogenes, and potential mechanisms for their control. Between 53 and 74â% of the Sodalis transcriptome remains active in cell-free culture. The mean sense transcription from coding domain sequences (CDSs) is four times greater than that from pseudogenes. Comparative genomic analysis of six Illumina-sequenced Sodalis isolates from different host Glossina species shows pseudogenes make up ~40â% of the 2729 genes in the core genome, suggesting that they are stable and/or that Sodalis is a recent introduction across the genus Glossina as a facultative symbiont. These data shed further light on the importance of transcriptional and translational control in deciphering hostâmicrobe interactions. The combination of genomics, transcriptomics and proteomics gives a multidimensional perspective for studying prokaryotic genomes with a view to elucidating evolutionary adaptation to novel environmental niches
Mechanical and thermal properties of crab chitin reinforced carboxylated SBR composites
The addition of small amounts (up to 9 wt%) of chitin microsized particles, originating from shellfish waste, to carboxylated styrene-butadiene rubber (XSBR) matrix (as received and annealed to 100°C) has been studied. In particular, this study concentrated on their mechanical (creep investigation by nanoindentation and dynamical-mechanical analysis), thermal (differential scanning calorimetry and thermogravimetry) and swelling behaviour (toluene absorption) and was completed by morphological characterisation by scanning electron microscopy and atomic force microscopy. The results show that annealing has a limited effect on materials properties, effects which are further reduced by the addition of growing amounts of crab chitin. It should be noted that the limited filler content used in the study does not substantially modify the linear creep behaviour of XSBR for sufficiently long loading times. The thermal stability of the system does also appear to be preserved even with the maximum chitin content added, while it serves sufficiently as an effective barrier against aromatic solvent absorption
Neutron Capture Cross Sections for the Weak s Process
In past decades a lot of progress has been made towards understanding the
main s-process component that takes place in thermally pulsing Asymptotic Giant
Branch (AGB) stars. During this process about half of the heavy elements,
mainly between 90<=A<=209 are synthesized. Improvements were made in stellar
modeling as well as in measuring relevant nuclear data for a better description
of the main s process. The weak s process, which contributes to the production
of lighter nuclei in the mass range 56<=A<=90 operates in massive stars
(M>=8Msolar) and is much less understood. A better characterization of the weak
s component would help disentangle the various contributions to element
production in this region. For this purpose, a series of measurements of
neutron-capture cross sections have been performed on medium-mass nuclei at the
3.7-MV Van de Graaff accelerator at FZK using the activation method. Also,
neutron captures on abundant light elements with A<56 play an important role
for s-process nucleosynthesis, since they act as neutron poisons and affect the
stellar neutron balance. New results are presented for the (n,g) cross sections
of 41K and 45Sc, and revisions are reported for a number of cross sections
based on improved spectroscopic information
Hercules X-1: Pulsed gamma-rays detected above 150 GeV
The 1.24 second binary pulsar Her X-1, first observed in X-rays in 1971 by UHURU has now been seen as a sporadic gamma ray source from 1 TeV up to at least 500 TeV. In addition, reprocessed optical and infrared pulses are seen from the companion star HZ Herculis. Thus measurements of the Her X-1/HZ Herculis system span 15 decades in energy, rivaling both the Crab pulsar and Cygnus X-3 in this respect for a discrete galactic source
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