Abstract
Recently, the region surrounding eHWC J1842−035 has been studied extensively by γ-ray observatories due to its extended emission reaching up to a few hundred TeV and potential as a hadronic ...accelerator. In this work, we use 1910 days of cumulative data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a dedicated systematic source search of the eHWC J1842−035 region. During the search, we found three sources in the region, namely, HAWC J1844−034, HAWC J1843−032, and HAWC J1846−025. We have identified HAWC J1844−034 as the extended source that emits photons with energies up to 175 TeV. We compute the spectrum for HAWC J1844−034, and by comparing with the observational results from other experiments, we have identified HESS J1843−033, LHAASO J1843−0338, and TASG J1844−038 as very-high-energy γ-ray sources with a matching origin. Also, we present and use the multiwavelength data to fit the hadronic and leptonic particle spectra. We have identified four pulsar candidates in the nearby region in which PSR J1844−0346 is found to be the most likely candidate due to its proximity to HAWC J1844−034 and the computed energy budget. We have also found SNR G28.6−0.1 as a potential counterpart source of HAWC J1844−034 for which both leptonic and hadronic scenarios are feasible.
Treatment of the pure enantiomer 1 with methyllithium furnishes via cycloallene 2 its dimer 3 with high selectivity. In contrast, racemic 1 yielded only 5 % of 3 and 95 % of the cis isomer of 3. ...Thus, racemic 2 is an example of molecular recognition of remarkable selectivity.
d‐Lactate dehydrogenase (d‐LDH) is a membrane‐associated respiratory enzyme of Escherichia coli. The protein is composed of 571 amino acid residues with a flavin adenine dinucleotide (FAD) cofactor, ...has a molecular weight of approximately 65, 000, and requires lipids or detergents for full activity. We used NMR spectroscopy to investigate the structure of d‐LDH and its interaction with phospholipids. We incorporated 5‐fluorotryptophan (5F‐Trp) into the native enzyme, which contains five tryptophan residues, and into mutant enzymes, where a sixth tryptophan is substituted into a specific site by oligonucleotide‐directed mutagenesis, and studied the 5F‐Trp‐labeled enzymes using 19F‐NMR spectroscopy. In this way, information was obtained about the local environment at each native and substituted tryptophan site. Using a nitroxide spin‐labeled fatty acid, which broadens the resonance from any residue within 15 Å, we have established that the membrane‐binding area of the protein includes the region between Tyr 228 and Phe 369, but is not continuous within this region. This conclusion is strengthened by the results of 19F‐NMR spectroscopy of wild‐type enzyme labeled with fluorotyrosine or fluorophenylalanine in the presence and absence of a nitroxide spin‐labeled fatty acid. These experiments indicate that 9–10 Phe and 3–4 Tyr residues are located near the lipid phase.
3‐Bromo‐1‐methyl‐1,2,5,6‐tetrahydropyridine(N−B)borane (7) was prepared from 3‐bromopyridine by conversion to 3‐bromo‐1‐methylpyridinium iodide, hydrogenation of the latter with sodium ...tetrahydroborate and treatment of the resulting 3‐bromo‐1‐methyl‐1,2,5,6‐tetrahydropyridine (6) with borane−dimethyl sulfide. Whereas no trapping product of the possible intermediate 1‐methyl‐1‐azacyclohexa‐2,3‐diene (4) could be observed on treatment of 6 with potassium tert‐butoxide in the presence of furan, the subjection of 7 to the same conditions produced the hexahydroepoxyquinoline derivatives 8a−c. Treatment of 7, dissolved in styrene, with sodium bis(trimethylsilyl)amide furnished the hexahydrocyclobutapyridine derivatives 9a−c. The six‐membered cycloallene 1‐methyl‐1‐azacyclohexa‐2,3‐diene(N−B)borane (10) must be regarded as the key intermediate en route to 8 and 9.
The first TeV gamma-ray source with no lower energy counterparts, TeV J2032+4130, was discovered by HEGRA. It appears in the third HAWC catalog as 3HWC J2031+415 and it is a bright TeV gamma-ray ...source whose emission has previously been resolved as 2 sources: HAWC J2031+415 and HAWC J2030+409. While HAWC J2030+409 has since been associated with the \emph{Fermi-LAT} Cygnus Cocoon, no such association for HAWC J2031+415 has yet been found. In this work, we investigate the spectrum and energy-dependent morphology of HAWC J2031+415. We associate HAWC J2031+415 with the pulsar PSR J2032+4127 and perform a combined multi-wavelength analysis using radio, X-ray, and \(\gamma\)-ray emission. We conclude that HAWC J2031+415 and, by extension, TeV J2032+4130 are most probably a pulsar wind nebula (PWN) powered by PSR J2032+4127.
The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory located on the side of the Sierra Negra volcano in Mexico, has been fully operational since 2015. The HAWC collaboration has recently ...significantly improved their extensive-air-shower reconstruction algorithms, which has notably advanced the observatory performance. The energy resolution for primary gamma rays with energies below 1~TeV was improved by including a noise-suppression algorithm. Corrections have also been made to systematic errors in direction fitting related to the detector and shower plane inclinations, \(\mathcal{O}(0.1^{\circ})\) biases in highly inclined showers, as well as enhancements to the core reconstruction. The angular resolution for gamma rays approaching the HAWC array from large zenith angles (\(> 37^{\circ}\)) has improved by a factor of four at the highest energies (\(> 70\)~TeV) as compared to previous reconstructions. The inclusion of a lateral distribution function fit to the extensive air shower footprint on the array to separate gamma-ray primaries from cosmic-ray ones, based on the resulting \(\chi^{2}\) values, improved the background rejection performance at all inclinations. At large zenith angles, the improvement in significance is a factor of four compared to previous HAWC publications. These enhancements have been verified by observing the Crab Nebula, which is an overhead source for the HAWC Observatory. We show that the sensitivity to Crab-like point sources (\(E^{-2.63}\)) with locations overhead to 30\(^{\circ}\) zenith is comparable or less than 10\% of the Crab Nebula's flux between 2 and 50~TeV. Thanks to these improvements, HAWC can now detect more sources, including the Galactic Center.
ApJ 954 (2023) 205 Recently, the region surrounding eHWC J1842-035 has been studied extensively
by gamma-ray observatories due to its extended emission reaching up to a few
hundred TeV and potential ...as a hadronic accelerator. In this work, we use 1,910
days of cumulative data from the High Altitude Water Cherenkov (HAWC)
observatory to carry out a dedicated systematic source search of the eHWC
J1842-035 region. During the search we have found three sources in the region,
namely, HAWC J1844-034, HAWC J1843-032, and HAWC J1846-025. We have identified
HAWC J1844-034 as the extended source that emits photons with energies up to
175 TeV. We compute the spectrum for HAWC J1844-034 and by comparing with the
observational results from other experiments, we have identified HESS
J1843-033, LHAASO J1843-0338, and TASG J1844-038 as very-high-energy gamma-ray
sources with a matching origin. Also, we present and use the multi-wavelength
data to fit the hadronic and leptonic particle spectra. We have identified four
pulsar candidates in the nearby region from which PSR J1844-0346 is found to be
the most likely candidate due to its proximity to HAWC J1844-034 and the
computed energy budget. We have also found SNR G28.6-0.1 as a potential
counterpart source of HAWC J1844-034 for which both leptonic and hadronic
scenarios are feasible.
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