The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This ...work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2
/
years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.
Abstract
We report the discovery of a new unidentified extended
γ
-ray source in the Galactic plane named LHAASO J0341+5258 with a pretrial significance of 8.2 standard deviations above 25 TeV. The ...best-fit position is R.A. = 55.°34 ± 0.°11 and decl. = 52.°97 ± 0.°07. The angular size of LHAASO J0341+5258 is 0.°29 ± 0.°06
stat
± 0.°02
sys
. The flux above 25 TeV is about 20% of the flux of the Crab Nebula. Although a power-law fit of the spectrum from 10 to 200 TeV with the photon index
α
= 2.98 ± 0.19
stat
± 0.02
sys
is not excluded, the LHAASO data together with the flux upper limit at 10 GeV set by the Fermi-LAT observation, indicate a noticeable steepening of an initially hard power-law spectrum with a cutoff at ≈50 TeV. We briefly discuss the origin of ultra-high-energy gamma rays. The lack of an energetic pulsar and a young supernova remnant inside or in the vicinity of LHAASO J0341+5258 challenge, but do not exclude, both the leptonic and hadronic scenarios of gamma-ray production.
We demonstrate a high-sensitivity relative humidity (RH) sensor taking advantage of single-band narrow plasmon resonance of a single Au nanorod coupled to a whispering gallery cavity mode of a ...polyacrylamide microfiber. From the resonance peak shift, the sensor could achieve a sensitivity up to 0.51 nm/% RH with a cavity size of about 2 μm. By coupling multiple Au nanorods along the microfiber axis, we demonstrate a position-dependent microfiber optical humidity sensor with a 1.5-mm spatial resolution, which can be potentially reduced to micrometer level, paving a way toward high-resolution distributed microfiber optical sensors.
Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a space‐borne instrument dedicated to monitoring high‐energy transients, including Terrestrial Gamma‐ray Flashes ...(TGFs) and Terrestrial Electron Beams (TEBs). We implemented a TGF/TEB search algorithm for GECAM, with which 147 bright TGFs, 2 typical TEBs and 2 special TEB‐like events are identified during an effective observation time of ∼9 months. We show that, with gamma‐ray and charged particle detectors, GECAM can effectively identify and distinguish TGFs and TEBs, and measure their temporal and spectral properties in detail. A very high TGF‐lightning association rate of ∼80% is obtained between GECAM and GLD360 in east Asia region.
Plain Language Summary
Terrestrial gamma‐ray flashes (TGFs) and Terrestrial Electron Beams (TEBs) represent the most energetic radioactive phenomena in the atmosphere of the Earth. They reflect a natural particle accelerator that can boost electrons up to at least several tens of mega electron volts and produce gamma‐ray radiation. With novel detection technologies, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a new powerful instrument to observe TGFs and TEBs, as well as study their properties. For example, it is difficult for most space‐borne high‐energy instruments to distinguish between TGFs and TEBs. However, we show here that, with the joint observation of gamma‐ray and charged particle detectors, GECAM can effectively identify TGFs and TEBs. GECAM can also reveal their fine features in the light curves and spectra.
Key Points
During 9‐month observation, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) has detected 147 bright Terrestrial Gamma‐ray Flashes (TGFs), 2 typical Terrestrial Electron Beams (TEBs), and 2 special TEB‐like events
With novel detector design, GECAM can effectively classify TGFs and TEBs, and reveal their fine temporal features
We obtained a very high TGF‐lightning association rate (∼80%) between GECAM and GLD360 in east Asia region
Background
Flap viability after transfer depends on blood flow from the arterial blood supply below the fascia. This study evaluated survival of a pedicle flap with a perforator lateral branch and ...flow‐through blood supply, compared with that of a flap with a flow‐end blood supply and perforator terminal branch.
Methods
Forty Sprague–Dawley rats, 20 in each group, were assigned to transfer of a superficial epigastric artery pedicle island flap with a flow‐through or flow‐end configuration of blood supply. Laser Doppler imaging was used to evaluate flap perfusion 2 h, 3 days and 5 days after surgery. The rats were killed on day 5, and lead oxide–gelatine‐enhanced flap angiography and histology with haematoxylin and eosin staining was performed. Dorsal midline tissue was excised for quantification of vascular endothelial growth factor by western blot assay.
Results
On day 5 after surgery, the flow‐through group exhibited a significantly greater mean(s.d.) flap survival area (97·8(3·5) versus 80·8(10·2) per cent; P = 0·003), microvascular density (303(19) versus 207(41) per mm2; P < 0·001) and perfusion (8·64(0·14) versus 5·95(0·14) perfusion units; P < 0·001) than the flow‐end group. The flow‐through group exhibited more angiosomes connected by dilated vascular anastomoses between the skin and subcutaneous fasciae.
Conclusion
The flow‐through blood supply improved pedicle perforator flap survival.
Surgical relevance
Perforator flap failure is mainly the result of impaired blood supply, as a flow‐end blood configuration is nourished only by the perforator terminal branch of the artery.
This work showed that the flow‐through blood supply nourished by the perforator lateral branch improved flap survival, with dilatation of collateral vascular anastomoses and increased neoangiogenesis.
The use of a flow‐through configuration improves perforator flap survival and could therefore minimize morbidity resulting from flap necrosis.
Flow‐through blood supply improved flap survival
ABSTRACT
Based on Insight-HXMT data, we report on the pulse fraction evolution during the 2017–2018 outburst of the newly discovered first Galactic ultraluminous X-ray (ULX) source Swift ...J0243.6+6124. The pulse fractions of 19 observation pairs selected in the rising and fading phases with similar luminosity are investigated. The results show a general trend of the pulse fraction increasing with luminosity and energy at supercritical luminosity. However, the relative strength of the pulsation between each pair evolves strongly with luminosity. The pulse fraction in the rising phase is larger at luminosity below 7.71 × 1038 erg s−1, but smaller at above. A transition luminosity is found to be energy independent. Such a phenomenon is first confirmed by Insight-HXMT observations and we speculate that it may have relation with the radiation-pressure-dominated accretion disc.
Background Magnifying endoscopy with narrow-band imaging (ME-NBI) can more clearly assess the surface pattern and microvascular architecture of gastric lesions. Objective To evaluate the diagnostic ...efficacy of ME-NBI in patients with early gastric cancer. Design Prospective study. Setting Single academic center. Patients This study involved 164 suspected gastric lesions in 146 consecutive patients who underwent ME-NBI for additional differential diagnosis before treatment. Intervention ME-NBI findings were classified into 3 groups based on irregularities, absence of surface pattern, and microvascular architecture. All lesions were treated endoscopically or surgically, and ME-NBI diagnosis was compared with histopathological findings. Main Outcome Measurements Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of real-time ME-NBI diagnosis were determined. Results The sensitivity, specificity, and accuracy of ME-NBI were 97.3%, 84.4%, and 90.2%, respectively, in distinguishing between cancerous and noncancerous lesions and were 92.3%, 89.7%, and 90.4%, respectively, in distinguishing undifferentiated from differentiated adenocarcinoma. ME-NBI accurately predicted depth of invasion in 37 of 39 differentiated adenocarcinomas (95%). Limitations The sample size was relatively small. Conclusions ME-NBI can successfully distinguish between cancerous and noncancerous lesions and between undifferentiated and differentiated adenocarcinomas. Of the 3 patterns on ME-NBI, type A is mainly characteristic of noncancerous lesions, type B is a good indicator of differentiated adenocarcinoma and intramucosal/superficially invasive cancers, and type C is indicative of undifferentiated adenocarcinoma or differentiated cancer with deep submucosal invasion.
Using a sample of
1.31
×
10
9
J
/
ψ
events collected with the BESIII detector, we perform a study of
J
/
ψ
→
γ
K
K
¯
η
′
.
X
(2370) is observed in the
K
K
¯
η
′
invariant-mass distribution with a ...statistical significance of
8.3
σ
. Its resonance parameters are measured to be
M
=
2341.6
±
6.5
(stat.)
±
5.7
(syst.)
MeV
/
c
2
and
Γ
=
117
±
10
(stat.)
±
8
(syst.)
MeV
. The product branching fractions for
J
/
ψ
→
γ
X
(
2370
)
,
X
(
2370
)
→
K
+
K
-
η
′
and
J
/
ψ
→
γ
X
(
2370
)
,
X
(
2370
)
→
K
S
0
K
S
0
η
′
are determined to be
(
1.79
±
0.23
(stat.)
±
0.65
(syst.)
)
×
10
-
5
and
(
1.18
±
0.32
(stat.)
±
0.39
(syst.)
)
×
10
-
5
, respectively. No evident signal for
X
(2120) is observed in the
K
K
¯
η
′
invariant-mass distribution. The upper limits for the product branching fractions of
B
(
J
/
ψ
→
γ
X
(
2120
)
→
γ
K
+
K
-
η
′
)
and
B
(
J
/
ψ
→
γ
X
(
2120
)
→
γ
K
S
0
K
S
0
η
′
)
are determined to be
1.49
×
10
-
5
and
6.38
×
10
-
6
at the 90% confidence level, respectively.
Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic ...energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance has not yet been determined definitively. Here we report a unique radiation belt event with intense ULF waves but no detectable VLF chorus waves. Our results demonstrate that the ULF waves moved the inner edge of the outer radiation belt earthward 0.3 Earth radii and enhanced the relativistic electron fluxes by up to one order of magnitude near the slot region within about 10 h, providing strong evidence for the radial diffusion of radiation belt relativistic electrons.
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