384 research outputs found
Conjugate Addition of 3-Buytn-2-one to Anilines in Ethanol: Alkene Geometric Insights through In Situ FTIR Monitoring
A convenient, mild and effective conjugate addition of 3-butyn-2-one to a variety of anilines in ethanol is reported. The reaction was monitored and characterized through in situ FTIR, and the dynamics of the facile E/Z alkene geometry interconversion of the resultant aniline-derived enaminones was explored through NMR, FTIR and X-ray crystallography. A straightforward purification protocol that employs direct Kugelrohr distillation was identified, and the method was further extended to other amines and ynones, allowing rapid access to these interesting compounds
Distribution of Submerged Aquatic Vegetation in the Chesapeake Bay and Tributaries and the Coastal Bays - 1997
SA V distribution data in this report are presented and discussed based on the segmentation scheme adopted by the Chesapeake Bay Program (Flemer et al., 1983) and described briefly in the Methods section of this report. This zonation scheme (Upper, Middle, and Lower zones) for Chesapeake Bay, which accommodates the Chesapeake Bay Program segmentation boundaries, was adapted from that used in previous SAV distribution reports (i.e., Orth et al., 1994) and established by Orth and Moore ( 1982), then modified by Orth et al., ( 1989). The 1996 data were edgematched using ARC/INFO GIS software, as were all the historical SAV bed data, in order to bring separately digitized USGS 7.5 minute topographic quadrangle SA V coverages into one unified coverage for the entire Chesapeake Bay (see Methods). Therefore, SAV distribution data presented in this report reflect edgematching adjustments, and differ from previously published data for those years derived from separate coverages which were not edgematched (i.e., Orth et al., 1992, 1993, and 1994)
2016 Aerial Imagery Acquired to Monitor the Distribution and Abundance of Submerged Aquatic Vegetation in Chesapeake Bay and Coastal Bays
Multispectral aerial imagery acquired in 2016 to monitor the distribution and abundance of submerged aquatic vegetation in Chesapeake Bay and coastal bays
Evaluation of Color Imagery and Direct Referencing for Mapping Submersed Aquatic Vegetation in Chesapeake Bay - Final Report
The VIMS Annual Submersed Aquatic Vegetation (SAV) Monitoring Program has used black and white aerial photography to map SAV in Chesapeake Bay each year from 1984 to the present, with the exception of 1988. In 2008, VIMS initiated a pilot project to address two potential enhancements identified by a recent external program review: color film and direct referencing technology. Simultaneous color and black and white imagery was captured for three regions. In addition, GPS/inertial mapping unit (IMU) direct referencing data was acquired for two of the regions
Energy of Isolated Systems at Retarded Times as the Null Limit of Quasilocal Energy
We define the energy of a perfectly isolated system at a given retarded time
as the suitable null limit of the quasilocal energy . The result coincides
with the Bondi-Sachs mass. Our is the lapse-unity shift-zero boundary value
of the gravitational Hamiltonian appropriate for the partial system
contained within a finite topologically spherical boundary . Moreover, we show that with an arbitrary lapse and zero shift the same
null limit of the Hamiltonian defines a physically meaningful element in the
space dual to supertranslations. This result is specialized to yield an
expression for the full Bondi-Sachs four-momentum in terms of Hamiltonian
values.Comment: REVTEX, 16 pages, 1 figur
A search for fast radio burst-like emission from Fermi gamma-ray bursts
We report the results of the rapid follow-up observations of gamma-ray bursts
(GRBs) detected by the Fermi satellite to search for associated fast radio
bursts. The observations were conducted with the Australian Square Kilometre
Array Pathfinder at frequencies from 1.2-1.4 GHz. A set of 20 bursts, of which
four were short GRBs, were followed up with a typical latency of about one
minute, for a duration of up to 11 hours after the burst. The data was searched
using 4096 dispersion measure trials up to a maximum dispersion measure of 3763
pc cm, and for pulse widths over a range of duration from 1.256 to
40.48 ms. No associated pulsed radio emission was observed above for any of the 20 GRBs.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society Main Journa
An instability of higher-dimensional rotating black holes
We present the first example of a linearized gravitational instability of an
asymptotically flat vacuum black hole. We study perturbations of a Myers-Perry
black hole with equal angular momenta in an odd number of dimensions. We find
no evidence of any instability in five or seven dimensions, but in nine
dimensions, for sufficiently rapid rotation, we find perturbations that grow
exponentially in time. The onset of instability is associated with the
appearance of time-independent perturbations which generically break all but
one of the rotational symmetries. This is interpreted as evidence for the
existence of a new 70-parameter family of black hole solutions with only a
single rotational symmetry. We also present results for the Gregory-Laflamme
instability of rotating black strings, demonstrating that rotation makes black
strings more unstable.Comment: 38 pages, 13 figure
The antibacterial activity of a photoactivatable diarylacetylene against Gram-positive bacteria
The emergence of antibiotic resistance is a growing threat to human health, and therefore, alternatives to existing compounds are urgently needed. In this context, a novel fluorescent photoactivatable diarylacetylene has been identified and characterised for its antibacterial activity, which preferentially eliminates Gram-positive over Gram-negative bacteria. Experiments confirmed that the Gram-negative lipopolysaccharide-rich outer surface is responsible for tolerance, as strains with reduced outer membrane integrity showed increased susceptibility. Additionally, bacteria deficient in oxidative damage repair pathways also displayed enhanced sensitivity, confirming that reactive oxygen species production is the mechanism of antibacterial activity. This new diarylacetylene shows promise as an antibacterial agent against Gram-positive bacteria that can be activated in situ, potentially for the treatment of skin infections
- …