Endodontic Photodynamic Therapy Ex Vivo Ng, Raymond, DDS; Singh, Fiza, DDS; Papamanou, Despina A., DDS ...
Journal of endodontics,
02/2011, Letnik:
37, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract Introduction The objective of this study was to evaluate the antimicrobial effects of photodynamic therapy (PDT) on infected human teeth ex vivo. Methods Fifty-two freshly extracted teeth ...with pulpal necrosis and associated periradicular radiolucencies were obtained from 34 subjects. Twenty-six teeth with 49 canals received chemomechanical debridement (CMD) with 6% NaOCl, and 26 teeth with 52 canals received CMD plus PDT. For PDT, root canal systems were incubated with methylene blue (MB) at concentration of 50 μg/mL for 5 minutes, followed by exposure to red light at 665 nm with an energy fluence of 30 J/cm2 . The contents of root canals were sampled by flushing the canals at baseline and after CMD alone or CMD+PDT and were serially diluted and cultured on blood agar. Survival fractions were calculated by counting colony-forming units (CFUs). Partial characterization of root canal species at baseline and after CMD alone or CMD+PDT was performed by using DNA probes to a panel of 39 endodontic species in the checkerboard assay. Results The Mantel-Haenszel χ2 test for treatment effects demonstrated the better performance of CMD+PDT over CMD ( P = .026). CMD+PDT significantly reduced the frequency of positive canals relative to CMD alone ( P = .0003). After CMD+PDT, 45 of 52 canals (86.5%) had no CFUs as compared with 24 of 49 canals (49%) treated with CMD (canal flush samples). The CFU reductions were similar when teeth or canals were treated as independent entities. Post-treatment detection levels for all species were markedly lower for canals treated by CMD+PDT than they were for those treated by CMD alone. Bacterial species within dentinal tubules were detected in 17 of 22 (77.3%) and 15 of 29 (51.7%) canals in the CMD and CMD+PDT groups, respectively ( P = .034). Conclusions Data indicate that PDT significantly reduces residual bacteria within the root canal system, and that PDT, if further enhanced by technical improvements, holds substantial promise as an adjunct to CMD.
Abstract
The CHIME/FRB Project has recently released its first catalog of fast radio bursts (FRBs), containing 492 unique sources. We present results from angular cross-correlations of CHIME/FRB ...sources with galaxy catalogs. We find a statistically significant (
p
-value ∼ 10
−4
, accounting for look-elsewhere factors) cross-correlation between CHIME FRBs and galaxies in the redshift range 0.3 ≲
z
≲ 0.5, in three photometric galaxy surveys: WISE × SCOS, DESI-BGS, and DESI-LRG. The level of cross-correlation is consistent with an order-one fraction of the CHIME FRBs being in the same dark matter halos as survey galaxies in this redshift range. We find statistical evidence for a population of FRBs with large host dispersion measure (∼400 pc cm
−3
) and show that this can plausibly arise from gas in large halos (
M
∼ 10
14
M
⊙
), for FRBs near the halo center (
r
≲ 100 kpc). These results will improve in future CHIME/FRB catalogs, with more FRBs and better angular resolution.
Abstract
We demonstrate the blind interferometric detection and localization of two fast radio bursts (FRBs) with subarcminute precision on the 400 m baseline between the Canadian Hydrogen Intensity ...Mapping Experiment (CHIME) and the CHIME Pathfinder. In the same spirit as Very Long Baseline Interferometry (VLBI), the telescopes were synchronized to separate clocks, and the channelized voltage (herein referred to as baseband) data were saved to a disk with correlation performed offline. The simultaneous wide field of view and high sensitivity required for blind FRB searches implies a high data rate—6.5 terabits per second (Tb/s) for CHIME and 0.8 Tb s
−1
for the Pathfinder. Since such high data rates cannot be continuously saved, we buffer data from both telescopes locally in memory for
, and write to the disk upon receipt of a low-latency trigger from the CHIME Fast Radio Burst Instrument (CHIME/FRB). The
deg
2
field of view of the two telescopes allows us to use in-field calibrators to synchronize the two telescopes without needing either separate calibrator observations or an atomic timing standard. In addition to our FRB observations, we analyze bright single pulses from the pulsars B0329+54 and B0355+54 to characterize systematic localization errors. Our results demonstrate the successful implementation of key software, triggering, and calibration challenges for CHIME/FRB Outriggers: cylindrical VLBI outrigger telescopes which, along with the CHIME telescope, will localize thousands of single FRB events with sufficient precision to unambiguously associate a host galaxy with each burst.
Fast radio bursts (FRBs) are millisecond-duration flashes ofradio waves that are visible at distances of billions of light years1. The nature of their progenitors and their emission mechanism remain ...open astrophysical questions2. Here we report the detection of the multicomponent FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5a. The long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere3,4, as opposed to emission regions located further away from the star, as predicted by some models5.
ABSTRACT
The Canadian Hydrogen Mapping Experiment (CHIME) is a radio telescope located in British Columbia, Canada. The large field of view allows CHIME/FRB to be an exceptional pulsar and rotating ...radio transient (RRAT) finding machine, despite saving only the metadata of incoming Galactic events. We have developed a pipeline to search for pulsar/RRAT candidates using density-based spatial clustering of applications with noise (dbscan), a clustering algorithm. Follow-up observations are then scheduled with the more sensitive CHIME/Pulsar instrument capable of near-daily high-time resolution spectra observations. We have developed the CHIME/Pulsar Single Pulse Pipeline to automate the processing of CHIME/Pulsar search-mode data. We report the discovery of 21 new Galactic sources, with 14 RRATs, 6 isolated long-period pulsars, and 1 binary system. Owing to CHIME/Pulsar’s observations, we have obtained timing solutions for 8 of the 14 RRATs along with all the regular pulsars and the binary system. Notably, we report that the binary system is in a long orbit of 412 d with a minimum companion mass of 0.1303 solar masses and no evidence of an optical companion within 10″ of the pulsar position. This highlights that working synergistically with CHIME/FRB’s large survey volume CHIME/Pulsar can obtain arc second localizations for low-burst rate RRATs through pulsar timing. We find that the properties of our newly discovered RRATs are consistent with those of the presently known population. They tend to have lower burst rates than those found in previous surveys, which is likely due to survey bias rather than the underlying population.
Abstract
The Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB experiment has detected thousands of fast radio bursts (FRBs) due to its sensitivity and wide field of view; however, its low ...angular resolution prevents it from localizing events to their host galaxies. Very long baseline interferometry (VLBI), triggered by FRB detections from CHIME/FRB will solve the challenge of localization for non-repeating events. Using a refurbished 10 m radio dish at the Algonquin Radio Observatory located in Ontario Canada, we developed a testbed for a VLBI experiment with a theoretical
λ
/
D
≲ 30 mas. We provide an overview of the 10 m system and describe its refurbishment, the data acquisition, and a procedure for fringe fitting that simultaneously estimates the geometric delay used for localization and the dispersive delay from the ionosphere. Using single pulses from the Crab pulsar, we validate the system and localization procedure, and analyze the clock stability between sites, which is critical for coherently delay referencing an FRB event. We find a localization of ∼200 mas is possible with the performance of the current system (single-baseline). Furthermore, for sources with insufficient signal or restricted wideband to simultaneously measure both geometric and ionospheric delays, we show that the differential ionospheric contribution between the two sites must be measured to a precision of 1 × 10
−8
pc cm
−3
to provide a reasonable localization from a detection in the 400–800 MHz band. Finally we show detection of an FRB observed simultaneously in the CHIME and the Algonquin 10 m telescope, the first non-repeating FRB in this long baseline. This project serves as a testbed for the forthcoming CHIME/FRB Outriggers project.
PALFA (Pulsar Arecibo L-band Feed Array) is an on-going survey of the Galactic plane at 1.4 GHz, searching for radio pulsars (rapidly rotating highly magnetized neutron stars) with the Arecibo 305-m ...single dish radio telescope located in Puerto Rico. Begun in 2004, PALFA has discovered 163 radio pulsars including 13 RRATs (Rotating RAdio Transients—a recently discovered class of pulsars with sporadic emission) and 1 FRB (Fast Radio Bursts—a mysterious new class of milliseconds duration bright radio bursts). We have written and implemented a new data analysis pipeline to improve the search for long period pulsars (spin period P > 0.1 s), RRATs and FRBs. The new pipeline is an improvement to the original data analysis pipeline with a more systematic processing and post-processing approach to identify astrophysical individually detectable single pulses in the time domain. The original pipeline consisted of a matched-filtering search technique as a part of the single pulse analysis of the pipeline. To do a more rigorous search, we appended the pipeline with a grouping algorithm which gathers similar single pulse events into a single group based on proximity in time and DM (dispersion measure—the integrated column density of free electrons along a particular line of sight). Each group is ranked based on the criteria that astrophysical pulses follow (their signal-to-noise peaks at the optimal DM and falls off on either sides). A final candidate diagnostic plot is produced for each potential astrophysical candidate as identified by the grouping algorithm. Each candidate is then subject to a series of heuristic ratings followed by evaluation by a machine-learning algorithm. The final candidate diagnostic plots are uploaded to an online candidate viewer for by-eye inspection by the members of the PALFA consortium. Using this new pipeline we have discovered 5 new pulsars and 2 RRATs, 3 of which were detected uniquely by the single pulse analysis of the pipeline and 4 were detected by both single pulse and periodicity analysis. The discovered pulsars are now being regularly monitored as a part of our timing campaign. We plan to reprocess all PALFA archival data in Summer 2016 using this newly developed single-pulse pipeline. In doing so, we expect to find at least 9 new pulsars (including RRATs and FRBs) that could have been missed by the original pipeline.
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