Abstract
We perform a full nuclear-network numerical calculation of the
r
-process nuclei in binary neutron-star mergers (NSMs), with the aim of estimating gamma-ray emissions from the remnants of ...Galactic NSMs up to 10
6
yr old. The nucleosynthesis calculation of 4070 nuclei is adopted to provide the elemental composition ratios of nuclei with an electron fraction
Y
e
between 0.10 and 0.45. The decay processes of 3237 unstable nuclei are simulated to extract the gamma-ray spectra. As a result, the NSMs have different spectral colors in the gamma-ray band from various other astronomical objects at less than 10
5
yr old. In addition, we propose a new line diagnostic method for
Y
e
that uses the line ratios of either
137m
Ba/
85
K or
243
Am/
60m
Co, which become larger than unity for young and old
r
-process sites, respectively, with a low
-Y
e
environment. From an estimation of the distance limit for gamma-ray observations as a function of age, the high sensitivity in the sub-megaelectronvolt band, at approximately 10
−9
photons s
−1
cm
−2
or 10
−15
erg s
−1
cm
−2
, is required to cover all the NSM remnants in our Galaxy, if we assume that the population of NSMs by Wu et al. A gamma-ray survey with sensitivities of 10
−8
–10
−7
photons s
−1
cm
−2
or 10
−14
–10
−13
erg s
−1
cm
−2
in the 70–4000 keV band is expected to find emissions from at least one NSM remnant under the assumption of an NSM rate of 30 Myr
−1
. The feasibility of gamma-ray missions observing Galactic NSMs is also studied.
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10"FWHM) and broad spectral coverage (0.2--80 keV) with an effective area far superior to current ...facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. With the recent discoveries of over 40 ultra-high-energy gamma-ray sources (detected above 100 TeV) and neutrino emission in the Galactic Plane, we have entered a new era of multi-messenger astrophysics facing the exciting reality of Galactic PeVatrons. In the next decade, as more Galactic PeVatrons and TeV gamma-ray sources are expected to be discovered, the identification of their acceleration and emission mechanisms will be the most pressing issue in both particle and high-energy astrophysics. In this paper, along with its companion papers (Reynolds et al. 2023, Mori et al. 2023), we will present that HEX-P is uniquely suited to address important problems in various cosmic-ray accelerators, including Galactic PeVatrons, through investigating synchrotron X-ray emission of TeV--PeV electrons produced by both leptonic and hadronic processes. For Galactic PeVatron candidates and other TeV gamma-ray sources, HEX-P can fill in a large gap in the spectral-energy distributions (SEDs) of many objects observed in radio, soft X-rays, and gamma rays, constraining the maximum energies to which electrons can be accelerated, with implications for the nature of the Galactic PeVatrons and their contributions to the spectrum of Galactic cosmic rays beyond the knee at $\sim3$ PeV. In particular, X-ray observation with HEX-P and TeV observation with CTA will provide the most powerful multi-messenger diagnostics to identify Galactic PeVatrons and explore a variety of astrophysical shock mechanisms. We present simulations of each class of Galactic TeV--PeV sources, demonstrating the power of both the imaging and spectral capabilities of HEX-P to advance our knowledge of Galactic cosmic-ray accelerators. In addition, we discuss HEX-P’s unique and complementary roles to upcoming gamma-ray and neutrino observatories in the 2030s.
We perform a full nuclear-network numerical calculation of the \(r\)-process nuclei in binary neutron-star mergers (NSMs), with the aim of estimating \(\gamma\)-ray emissions from the remnants of ...Galactic NSMs up to \(10^6\) years old. The nucleosynthesis calculation of 4,070 nuclei is adopted to provide the elemental composition ratios of nuclei with an electron fraction \(Y_{\rm e}\) between 0.10 and 0.45 . The decay processes of 3,237 unstable nuclei are simulated to extract the \(\gamma\)-ray spectra. As a result, the NSMs have different spectral color in \(\gamma\)-ray band from various other astronomical objects at less than \(10^5\) years old. In addition, we propose a new line-diagnostic method for \(Y_{\rm e}\) that uses the line ratios of either \(^{137{\rm m}}\)Ba/\(^{85}\)K or \(^{243}\)Am/\(^{60{\rm m}}\)Co, which become larger than unity for young and old \(r\)-process sites, respectively, with a low \(Y_{\rm e}\) environment. From an estimation of the distance limit for \(\gamma\)-ray observations as a function of the age, the high sensitivity in the sub-MeV band, at approximately \(10^{-9}\) photons s\(^{-1}\) cm\(^{-2}\) or \(10^{-15}\) erg s\(^{-1}\) cm\(^{-2}\), is required to cover all the NSM remnants in our Galaxy if we assume that the population of NSMs by \citet{2019ApJ...880...23W}. A \(\gamma\)-ray survey with sensitivities of \(10^{-8}\)--\(10^{-7}\) photons s\(^{-1}\) cm\(^{-2}\) or \(10^{-14}\)--\(10^{-13}\) erg s\(^{-1}\) cm\(^{-2}\) in the 70--4000 keV band is expected to find emissions from at least one NSM remnant under the assumption of NSM rate of 30 Myr\(^{-1}\). The feasibility of \(\gamma\)-ray missions to observe Galactic NSMs are also studied.
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current ...facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. With the recent discoveries of over 40 ultra-high-energy gamma-ray sources (detected above 100 TeV) and neutrino emission in the Galactic Plane, we have entered a new era of multi-messenger astrophysics facing the exciting reality of Galactic PeVatrons. In the next decade, as more Galactic PeVatrons and TeV gamma-ray sources are expected to be discovered, the identification of their acceleration and emission mechanisms will be the most pressing issue in both particle and high-energy astrophysics. In this paper, along with its companion papers (Reynolds et al. 2023, Mori et al. 2023), we will present that HEX-P is uniquely suited to address important problems in various cosmic-ray accelerators, including Galactic PeVatrons, through investigating synchrotron X-ray emission of TeV-PeV electrons produced by both leptonic and hadronic processes.
Objectives
This study is aimed at evaluating the effect of a new glass ionomer cement (GIC) containing fluoro-zinc-silicate fillers on biofilm formation and ion incorporation.
Materials and methods
...Streptococcus mutans
biofilms were developed on two GIC materials: Caredyne Restore (CD) and Fuji VII (FJ); and hydroxyapatite (HA) for 24 h at 37 °C using a flow cell system. The morphological structure and bacterial viability were analyzed using a confocal laser scanning microscopy. Bacterial adhesion during the initial 2 h was also assessed by viable cell counting. To study the ion incorporation, restored cavities prepared on the root surfaces of human incisors were subjected to the elemental mapping of the zinc and fluoride ions in the GIC-dentin interface using a wavelength-dispersive X-ray spectroscopy electron probe microanalyzer.
Results
Morphological observations revealed that biofilm formation in the CD group was remarkably inhibited compared with the HA and FJ groups, exhibiting sparse, thinner biofilm clusters. The microorganisms adhering to the CD group were significantly inhibited, revealing 2.9 ± 0.4 for CD, 4.9 ± 0.2 for FJ, and 5.4 ± 0.4 log colony-forming units (CFU) for HA. The CD zinc ion incorporation depth was 72.2 ± 8.0 μm. The fluoride penetration of CD was three times deeper than that of FJ; this difference was statistically significant (
p
< 0.05).
Conclusions
Enhanced by the incorporation of zinc and fluoride ions, the new GIC inhibited biofilm formation by interfering with bacterial adhesion.
Clinical relevance
A novel GIC comprised of fluoro-zinc-silicate fillers may improve clinical outcomes, such as root caries and minimally invasive dentistry.
Chemical disinfection of oral biofilms often leaves biofilm structures intact. This study aimed to examine whether the residual structure promotes secondary bacterial adhesion. Streptococcus mutans ...biofilms generated on resin-composite disks in a rotating disc reactor were disinfected completely with 70% isopropyl alcohol, and were again cultured in the same reactor after resupplying with the same bacterial solution. Specimens were subjected to fluorescence confocal laser scanning microscopy, viable cell counts and PCR-Invader assay in order to observe and quantify secondarily adhered cells. Fluorescence microscopic analysis, particularly after longitudinal cryosectioning, demonstrated stratified patterns of viable cells on the disinfected biofilm structure. Viable cell counts of test specimens were significantly higher than those of controls, and increased according to the amount of residual structure and culture period. Linear regression analysis exhibited a high correlation between viable and total cell counts. It was concluded that disinfected biofilm structures favored secondary bacterial adhesion.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study aimed to develop a technique to create sequential slices, allowing the fluorescent visualization of bacterial viability in all parts of an infected dentin.
Cylindrical dentin blocks were ...prepared from freshly extracted human teeth with a single-rooted canal. Each block was immersed in 5% sodium hypochlorite (NaOCl) and 17% EDTA for 5 minutes before being infected with Enterococcus faecalis. The bacteria were allowed to develop inside dentin specimens for 28 days under anaerobic conditions. The specimens were exposed in 2% NaOCl for either 2 minutes or 20 minutes at 20°C, 37°C, and 45°C, respectively. After staining with calcein AM (Thermo Fisher Scientific, Waltham, MA) and propidium iodide, the samples were cryoembedded, mounted on an adhesive film, and sectioned at a thickness of 10 μm along the running of the dentinal tubules. Stacks of fluorescent images were collected in the z dimension using confocal laser scanning microscopy, and the maximum affected distance from a root canal was measured from the 3-dimensional reconstructed image. The reliability of this technique was verified by comparison with a dye bleaching test.
Horizontal sequential sections preserving 3-dimensional bacterial distribution and their viabilities could be made without decalcification. The treatment time contributed to the penetration of NaOCl into dentinal tubules, whereas temperature did not significantly affect the penetration. The judgment by confocal laser scanning microscopic analysis was consistent with that of a dye bleaching test.
The horizontal sectioning method has the advantage of creating sequential sections, allowing information to be imaged at every portion.
•A slicing technique for visualizing bacterial viability in dentin was developed.•The predemineralization and/or fracturing are not need for sample preparation.•This technique may be useful as an approach for elucidating clinical failure.
Sulfated vizantin, a recently developed immunostimulant, has also been found to exert antibiofilm properties. It acts not as a bactericide, but as a detachment-promoting agent by reducing the biofilm ...structural stability. This study aimed to investigate the mechanism underlying this activity and its species specificity using two distinct ex vivo oral biofilm models derived from human saliva.
The biofilm, composed mainly of the genus Streptococcus and containing 50 μM of sulfated vizantin, detached significantly from its basal surface with rotation at 500 rpm for only 15 s, even when 0.2% sucrose was supplied. Expression analyses for genes associated with biofilm formation and bacterial adhesion following identification of the Streptococcus species, revealed that a variety of Streptococcus species in a cariogenic biofilm showed downregulation of genes encoding glucosyltransferases involved in the biosynthesis of water-soluble glucan. The expression of some genes encoding surface proteins was also downregulated. Of the two quorum sensing systems involved in the genus Streptococcus, the expression of luxS in three species, Streptococcus oralis, Streptococcus gordonii, and Streptococcus mutans, was significantly downregulated in the presence of 50 μM sulfated vizantin. Biofilm detachment may be facilitated by the reduced structural stability due to these modulations. As a non-specific reaction, 50 μM sulfated vizantin decreased cell surface hydrophobicity by binding to the cell surface, resulting in reduced bacterial adherence.
Sulfated vizantin may be a candidate for a new antibiofilm strategy targeting the biofilm matrix while preserving the resident microflora.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
An ideal antibiofilm strategy is to control both in the quality and quantity of biofilm while maintaining the benefits derived from resident microflora. Vizantin, a recently developed ...immunostimulating compound, has also been found to have antibiofilm property. This study evaluated the influence on biofilm formation of Streptococcus mutans in the presence of sulfated vizantin and biofilm development following bacterial adhesion on a hydroxyapatite disc coated with sulfated vizantin. Supplementation with sulfated vizantin up to 50 μM did not affect either bacterial growth or biofilm formation, whereas 50 μM sulfated vizantin caused the biofilm to readily detach from the surface. Sulfated vizantin at the concentration of 50 μM upregulated the expression of the gtfB and gtfC genes, but downregulated the expression of the gtfD gene, suggesting altered architecture in the biofilm. Biofilm development on the surface coated with sulfated vizantin was inhibited depending on the concentration, suggesting prevention from bacterial adhesion. Among eight genes related to bacterial adherence in S. mutans, expression of gtfB and gtfC was significantly upregulated, whereas the expression of gtfD, GbpA and GbpC was downregulated according to the concentration of vizantin, especially with 50 μM vizantin by 0.8-, 0.4-, and 0.4-fold, respectively. These findings suggest that sulfated vizantin may cause structural degradation as a result of changing gene regulation related to bacterial adhesion and glucan production of S. mutans.
•Vizantin has immunostimulating and antimetastatic properties.•Vizantin showed antibiofilm activity against S. mutans without affecting bacterial growth.•Streptococcus mutans biofilm was detached by altering its internal architecture.•Gene expressions related to bacterial adhesion were changed.
Abstract
Background
The aim of this in vitro study was to examine the possible enhancement of the biofilm peeling effect of a sonic toothbrush following the use of an antimicrobial mouth rinse.
...Methods
The biofilm at a noncontact site in the interdental area was treated by sound wave convection with the test solution or by immersion in the solution. The biofilm peeling effect was evaluated by determining the bacterial counts and performing morphological observations. A
Streptococcus mutans
biofilm was allowed to develop on composite resin discs by cultivation with stirring at 50 rpm for 72 h. The specimens were then placed in recesses located between plastic teeth and divided into an immersion group and a combination group. The immersion group was treated with phosphate buffer, chlorhexidine digluconate Peridex™ (CHX) mouth rinse or Listerine® Fresh Mint (EO) mouth rinse. The combination group was treated with CHX or EO and a sonic toothbrush.
Results
The biofilm thickness was reduced by approximately one-half compared with the control group. The combination treatment produced a 1 log reduction in the number of bacteria compared to the EO immersion treatment. No significant difference was observed in the biofilm peeling effect of the immersion group compared to the control group.
Conclusions
The combined use of a sonic toothbrush and a mouth rinse enhanced the peeling of the biofilm that proliferates in places that are difficult to reach using mechanical stress.
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