799 research outputs found
Photophysical Investigations of Thiophene Azomethine Derivatives
Une sĂ©rie de dimĂšres composĂ©s de thiophĂšne-aniline encombrĂ©e stĂ©riquement a Ă©tĂ© synthĂ©tisĂ©e. Les diffĂ©rents processus de dĂ©sactivation de lâĂ©tat singulet excitĂ© ont Ă©tĂ© Ă©tudiĂ©s par UV-visible, fluorescence, phosphorescence, photolyse par impulsion laser et calculs thĂ©oriques. Les graphiques de Stern-Volmer obtenus Ă partir des expĂ©riences de dĂ©sactivation des Ă©tats singulet et triplet ont dĂ©montrĂ© lâefficacitĂ© de lâazomĂ©thine Ă dĂ©sactiver les fluorophores. Les calculs semi-empiriques AM1 examinant lâeffet des
substituants encombrĂ©s ont dĂ©montrĂ©s que les groupements tert-butyls sur lâaniline ont
moins dâinfluence sur la barriĂšre de rotation N-aryl que les substitutions alkyles en ont sur la rotation de thiophĂšne-C. Les calculs Rehm-Weller basĂ©s sur les potentiels dâoxydation et de rĂ©duction ont montrĂ© que lâautodĂ©sactivation de lâĂ©tat excitĂ© des azomĂ©thines se fait par transfert dâĂ©lectron photoinduit menant Ă une Ă©radication complĂšte de la fluorescence.
Des complexes métalliques contenant des ligands azométhines ont aussi été
prĂ©parĂ©s. Le ligand est composĂ© dâune unitĂ© hydroxyquinoline liĂ© Ă un cycle thiophĂšne.
Les donnĂ©es photophysiques de ces complexes indiquent un dĂ©placement bathochromique aussi bien en absorbance quâen fluorescence. Des dispositifs de dĂ©tection dâion mĂ©tallique ont Ă©tĂ© prĂ©parĂ©s et un exemple Ă partir dâune solution de cuivre
a montré un déplacement bathochromique.A series of sterically hindered thiophene-aniline azomethine dyads were prepared.
The decay pathways that deactivate the singlet excited state were studied using UV-vis fluorescence and phosphorescence, laser flash photolysis and quantum calculations. Stern-Volmer relationships, derived from singlet and triplet state quenching experiments, showed that azomethines efficiently deactivate the singlet and triplet excited states of
fluorophores with bimolecular kinetics. AM1 Semi-empirical quantum calculations
examining the effect of bulky substituents on the bond rotational barriers demonstrate
that bulky tert-butyl groups attached to the aniline moiety have less influence on the N-aryl bond rotation barrier than alkyl substitutions do on the thiophene-CH bond rotation barrier. Rehm-Weller calculations based on electrochemical potentials demonstrate that azomethines self-quench their excited states via fast and efficient intramolecular photoinduced electron transfer leading to complete fluorescence suppression.
Metal complexes containing an azomethine ligand were also prepared. The ligand
contains a hydroxyquinoline moiety linked with a thiophene ring. Photophysical
investigations of the resulting metal complexes demonstrated significant bathochromic shifts in the absorbance and fluorescence spectra. Metal-ion sensing devices for water solutions were prepared by spin casting the ligand onto glass slides. The metal-ion sensor detected copper in water solutions through a bathochromic shift in the absorbance maximum
Kinetic Model for Layer-by-Layer Crystal Growth in Chain Molecules
A kinetic model is proposed to describe the structure and rate of advancement of the growth front during crystallization. Solidification occurs through the mechanisms of surface nucleation and lateral spreading of the solid phase within layers in the vicinity of the growth front. The transformation from liquid to solid within each layer is described by an equation similar to the two-dimensional variant of the JohnsonâMehlâAvrami (JMA) equation, but in which the finite size and shape of the critical nucleus and the dynamic evolution of the solid fraction of the underlying layers are taken into account. Connection to the regime theory of Hoffman and co-workers, for surface nucleation and spreading in one or two dimensions, is also made. Given only molecular level information regarding surface nucleation rates, lateral spreading rates, and critical surface nucleus geometry, the resulting set of coupled nonlinear equations for solidification in each layer is numerically integrated in time to obtain the structure and rate of advancement of the growth front, for arbitrarily large systems and long times. Using this kinetic model with input parameters obtained from molecular dynamics simulations, a multiscale modeling analysis of crystal growth in n-pentacontane (C50) is performed.National Science Foundation (U.S.) Division of Civil, Mechanical and Manufacturing Innovation (CMMI-1235109
Spatially Extended Low Ionization Emission Regions (LIERs) at
We present spatially resolved emission diagnostics for eight
galaxies that demonstrate extended low ionization emission-line regions (LIERs)
over kpc scales. Eight candidates are selected based on their spatial extent
and emission line fluxes from slitless spectroscopic observations with the
HST/WFC3 G141 and G800L grisms in the well-studied GOODS survey fields. Five of
the candidates (62.5%) are matched to X-ray counterparts in the \textit{Chandra
X-Ray Observatory} Deep Fields. We modify the traditional
Baldwin-Philips-Terlevich (BPT) emission line diagnostic diagram to use
[SII]/(H+[NII]) instead of [NII]/H to overcome the blending of
[NII] and H+[NII] in the low resolution slitless grism spectra. We
construct emission line ratio maps and place the individual pixels in the
modified BPT. The extended LINER-like emission present in all of our
candidates, coupled with X-Ray properties consistent with star-forming galaxies
and weak [OIII]5007\AA\ detections, is inconsistent with purely
nuclear sources (LINERs) driven by active galactic nuclei. While recent
ground-based integral field unit spectroscopic surveys have revealed
significant evidence for diffuse LINER-like emission in galaxies within the
local universe , this work provides the first evidence for the
non-AGN origin of LINER-like emission out to high redshifts.Comment: 11 pages, 1 table, 6 figures, accepted for publication in the
Astrophysics Journal (ApJ
(E)-5-(2-ThienylmethylÂeneamino)quinolin-8-ol
Two molÂecules of the title compound, C14H10N2OS, are hydrogen bonded about a center of inversion. In the molÂecule, the two aromatic rings are twisted by 37.27â
(5)° with respect to one another. The azomethine bond is in the E configuration
Idea-caution before exploitation:the use of cybersecurity domain knowledge to educate software engineers against software vulnerabilities
The transfer of cybersecurity domain knowledge from security experts (âEthical Hackersâ) to software engineers is discussed in terms of desirability and feasibility. Possible mechanisms for the transfer are critically examined. Software engineering methodologies do not make use of security domain knowledge in its form of vulnerability databases (e.g. CWE, CVE, Exploit DB), which are therefore not appropriate for this purpose. An approach based upon the improved use of pattern languages that encompasses security domain knowledge is proposed
Integrative analysis of 3604 GWAS reveals multiple novel cell type-specific regulatory associations
BACKGROUND: Genome-wide association study (GWAS) single nucleotide polymorphisms (SNPs) are known to preferentially co-locate to active regulatory elements in tissues and cell types relevant to disease aetiology. Further characterisation of associated cell type-specific regulation can broaden our understanding of how GWAS signals may contribute to disease risk. RESULTS: To gain insight into potential functional mechanisms underlying GWAS associations, we developed FORGE2 ( https://forge2.altiusinstitute.org/ ), which is an updated version of the FORGE web tool. FORGE2 uses an expanded atlas of cell type-specific regulatory element annotations, including DNase I hotspots, five histone mark categories and 15 hidden Markov model (HMM) chromatin states, to identify tissue- and cell type-specific signals. An analysis of 3,604 GWAS from the NHGRI-EBI GWAS catalogue yielded at least one significant disease/trait-tissue association for 2,057 GWAS, including >â400 associations specific to epigenomic marks in immune tissues and cell types, >â30 associations specific to heart tissue, and >â60 associations specific to brain tissue, highlighting the key potential of tissue- and cell type-specific regulatory elements. Importantly, we demonstrate that FORGE2 analysis can separate previously observed accessible chromatin enrichments into different chromatin states, such as enhancers or active transcription start sites, providing a greater understanding of underlying regulatory mechanisms. Interestingly, tissue-specific enrichments for repressive chromatin states and histone marks were also detected, suggesting a role for tissue-specific repressed regions in GWAS-mediated disease aetiology. CONCLUSION: In summary, we demonstrate that FORGE2 has the potential to uncover previously unreported disease-tissue associations and identify new candidate mechanisms. FORGE2 is a transparent, user-friendly web tool for the integrative analysis of loci discovered from GWAS
A Unifying Model of Genome Evolution Under Parsimony
We present a data structure called a history graph that offers a practical
basis for the analysis of genome evolution. It conceptually simplifies the
study of parsimonious evolutionary histories by representing both substitutions
and double cut and join (DCJ) rearrangements in the presence of duplications.
The problem of constructing parsimonious history graphs thus subsumes related
maximum parsimony problems in the fields of phylogenetic reconstruction and
genome rearrangement. We show that tractable functions can be used to define
upper and lower bounds on the minimum number of substitutions and DCJ
rearrangements needed to explain any history graph. These bounds become tight
for a special type of unambiguous history graph called an ancestral variation
graph (AVG), which constrains in its combinatorial structure the number of
operations required. We finally demonstrate that for a given history graph ,
a finite set of AVGs describe all parsimonious interpretations of , and this
set can be explored with a few sampling moves.Comment: 52 pages, 24 figure
Recruitment, augmentation and apoptosis of rat osteoclasts in 1,25-(OH)2D3 response to short-term treatment with 1,25-dihydroxyvitamin D3in vivo
Background
Although much is known about the regulation of osteoclast (OC) formation and activity, little is known about OC senescence. In particular, the fate of of OC seen after 1,25-(OH)2D3 administration in vivo is unclear. There is evidence that the normal fate of OC is to undergo apoptosis (programmed cell death). We have investigated the effect of short-term application of high dose 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on OC apoptosis in an experimental rat model.
Methods
OC recruitment, augmentation and apoptosis was visualised and quantitated by staining histochemically for tartrate resistant acid phosphatase (TRAP), double staining for TRAP/ED1 or TRAP/DAPI, in situ DNA fragmentation end labelling and histomorphometric analysis.
Results
Short-term treatment with high-dose 1,25-(OH)2D3 increased the recruitment of OC precursors in the bone marrow resulting in a short-lived increase in OC numbers. This was rapidly followed by an increase in the number of apoptotic OC and their subsequent removal. The response of OC to 1,25-(OH)2D3 treatment was dose and site dependent; higher doses producing stronger, more rapid responses and the response in the tibiae being consistently stronger and more rapid than in the vertebrae.
Conclusions
This study demonstrates that (1) after recruitment, OC are removed from the resorption site by apoptosis (2) the combined use of TRAP and ED1 can be used to identify OC and their precursors in vivo (3) double staining for TRAP and DAPI or in situ DNA fragmentation end labelling can be used to identify apoptotic OC in vivo
Solid-Phase Catalysis: A Biomimetic Approach toward Ligands on Dendritic Arms to Explore Recyclable Hydroformylation Reactions
Peer reviewed: YesNRC publication: Ye
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