The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV ...energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane
, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory ...(LHAASO) of the bright GRB 221009A, which serendipitously occurred within the instrument's field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger and then rose to a peak ~10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle of ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.
Abstract
Spectral hardness of gamma-ray bursts can be characterized by either hardness ratio or peak energy, and the inconsistency of these parameters can reflect spectral diversity and complexity. ...We have chosen 310 Swift bursts with well-measured X-ray afterglows to analyze the distributions of their peak energies and hardness ratios before and after absorption of neutral hydrogen. We categorize them into four types according to X-ray temporal patterns and calculate the hardness ratios of both
γ
-rays and X-rays. It is found that the hardness ratios of X-rays are systematically smaller than those of
γ
-rays. We also find that both
γ
-ray hardness ratios and peak energies of bursts of types I, II, and III are identically distributed and are significantly lower than the corresponding measurements of type IV bursts in statistics, which hints that the evolving spectra of type IV bursts are most probably affected by the geometry of outflows. This proves that the influence of neutral hydrogen absorption on the estimation of hardness ratio is negligible even though it can reduce the brightness of
γ
/X-rays somewhat. Furthermore, we verify that almost all the observed spectra of gamma-ray bursts can be described by a broken power-law function and confirm a magnetar origin for the bursts with internal X-ray plateaus.
Among all subtypes of breast cancer, triple-negative breast cancer has a relatively high relapse rate and poor outcome after standard treatment. Effective strategies to reduce the risk of relapse and ...death are needed.
To evaluate the efficacy and adverse effects of low-dose capecitabine maintenance after standard adjuvant chemotherapy in early-stage triple-negative breast cancer.
Randomized clinical trial conducted at 13 academic centers and clinical sites in China from April 2010 to December 2016 and final date of follow-up was April 30, 2020. Patients (n = 443) had early-stage triple-negative breast cancer and had completed standard adjuvant chemotherapy.
Eligible patients were randomized 1:1 to receive capecitabine (n = 222) at a dose of 650 mg/m2 twice a day by mouth for 1 year without interruption or to observation (n = 221) after completion of standard adjuvant chemotherapy.
The primary end point was disease-free survival. Secondary end points included distant disease-free survival, overall survival, locoregional recurrence-free survival, and adverse events.
Among 443 women who were randomized, 434 were included in the full analysis set (mean SD age, 46 9.9 years; T1/T2 stage, 93.1%; node-negative, 61.8%) (98.0% completed the trial). After a median follow-up of 61 months (interquartile range, 44-82), 94 events were observed, including 38 events (37 recurrences and 32 deaths) in the capecitabine group and 56 events (56 recurrences and 40 deaths) in the observation group. The estimated 5-year disease-free survival was 82.8% in the capecitabine group and 73.0% in the observation group (hazard ratio HR for risk of recurrence or death, 0.64 95% CI, 0.42-0.95; P = .03). In the capecitabine group vs the observation group, the estimated 5-year distant disease-free survival was 85.8% vs 75.8% (HR for risk of distant metastasis or death, 0.60 95% CI, 0.38-0.92; P = .02), the estimated 5-year overall survival was 85.5% vs 81.3% (HR for risk of death, 0.75 95% CI, 0.47-1.19; P = .22), and the estimated 5-year locoregional recurrence-free survival was 85.0% vs 80.8% (HR for risk of locoregional recurrence or death, 0.72 95% CI, 0.46-1.13; P = .15). The most common capecitabine-related adverse event was hand-foot syndrome (45.2%), with 7.7% of patients experiencing a grade 3 event.
Among women with early-stage triple-negative breast cancer who received standard adjuvant treatment, low-dose capecitabine maintenance therapy for 1 year, compared with observation, resulted in significantly improved 5-year disease-free survival.
ClinicalTrials.gov Identifier: NCT01112826.
Background
Late-night overeating (LNOE) is closely associated with many health risk factors, but whether LNOE can increase the risk of death remains unknown. Thus, the prospective cohort study aimed ...to investigate the relationship between LNOE and mortality using data from the National Health and Nutrition Examination Survey.
Methods
11,893 participants aged 50 years and older were included in the study. Dietary information was obtained through 24-h dietary recall interviews. Cox regression, subgroup, sensitivity, and restricted cubic spline analyses were used to assess the association between LNOE and mortality.
Results
During a median follow-up of 8.3 years, 2,498 deaths occurred. After adjusting for major confounders, compared to the non-late-night eating (NLNE) group, the LNOE group was associated with higher risks of all-cause (HR = 1.47, 95% CI = 1.06–2.04) and cardiovascular disease (CVD) mortality (HR = 2.02, 95% CI = 1.13–3.60). No significant association was found between late-night eating (LNE) and mortality. Subgroup analyses showed that the LNOE group had a greater risk of all-cause and CVD mortality in participants older than 70 years, with alcohol consumption and hypertension and demonstrated an increased risk of all-cause mortality in males and higher CVD mortality in females.
Conclusion
The habit of LNOE was an independent risk factor for all-cause and CVD mortality in US adults aged 50 years and older, which was also influenced by age, sex, alcohol consumption, and hypertension.
Polyhydroxyalkanoates (PHAs) have attracted increasing interest as sustainable plastics because of their biorenewability and biodegradability in the ambient environment. However, current ...semicrystalline PHAs face three long-standing challenges to broad commercial implementation and application: lack of melt processability, mechanical brittleness, and unrealized recyclability, the last of which is essential for achieving a circular plastics economy. Here we report a synthetic PHA platform that addresses the origin of thermal instability by eliminating α-hydrogens in the PHA repeat units and thus precluding facile cis-elimination during thermal degradation. This simple α,α-disubstitution in PHAs enhances the thermal stability so substantially that the PHAs become melt-processable. Synergistically, this structural modification also endows the PHAs with the mechanical toughness, intrinsic crystallinity, and closed-loop chemical recyclability.
Technologically important thermosets face a long‐standing end‐of‐life (EoL) problem of non‐reprocessability, a more sustainable solution of which has resolved to nascent vitrimers that can merge the ...robust material properties of thermosets and the reprocessability of thermoplastics. However, the lifecycle of vitrimers is still finite, as they often suffer from significant deterioration of mechanical performance following multiple reprocessing cycles, analogous to mechanical recycling, and they often show undesired creep under working conditions. To address these two key limitations, we have developed a cross‐linked semi‐crystalline polythioester with both dynamic covalent bonds and intrinsic crystallinity and chemical recyclability, affording a vitrimeric system that exhibits not only reprocessability and crystallinity‐restricted creep but also complete chemical recyclability to initial monomer by catalyzed depolymerization in solution or bulk. Therefore, reported herein is an “infinite” vitrimer system that is empowered with a facile closed‐loop EoL option once serial reprocessing deteriorates performance and the material can no longer meet the application requirements. Specifically, the polythioester vitrimer was constructed by copolymerization of a bicyclic thioester with a bis‐dithiolane, producing dynamically cross‐linked polythioesters with excellent property tunability, from amorphous to semi‐crystalline states and melting transition temperatures from 91 to 178 °C.
Running in circles: A high‐performance, reprocessable, creep‐resistant semicrystalline polythioester‐based vitrimer also exhibits complete chemical recyclability to initial monomer by catalyzed depolymerization in solution or bulk and the highly tunable thermal and mechanical properties.
Poly(3-hydroxyburtyrate) (P3HB) is the simplest but most important member of the large biodegradable polyhydroxyalkanoate family. However, bacterial P3HB, a pure isotactic crystalline material, is ...brittle, thus limiting its broad applications. Considering that biodegradable poly(ε-caprolactone) (PCL) and poly(4-hydroxybutyrate) (P4HB) are much more ductile than P3HB, here we utilize metal-catalyzed stereoselective copolymerization of racemic eight-membered dimethyl diolide (rac-8DLMe) with ε-caprolactone (ε-CL) and γ-butyrolactone (γ-BL) to toughen P3HB through the formation of isotactic P3HB-based synthetic copolyesters. Notably, catalyst’s strong kinetic preference for polymerizing rac-8DLMe over ε-CL enables one-pot copolymerization of the 1/1 comonomer mixture to afford diblock copolymer P3HB-b-PCL with two crystalline domains (T m1 ∼ 55 °C, T m2 ∼ 164 °C). Semicrystalline random copolymers, P(3HB-co-CL) and P(3HB-co-4HB), can also be obtained by simply adjusting the comonomer feed ratio and other polymerization conditions. Mechanical testing showed that P3HB-b-PCL is a hard and tough plastic that synergistically combines isotactic P3HB’s high modulus with PCL’s high ductility.
Yunnan, China, is a central tobacco-producing region with a large smoking population and an increasing incidence of lung cancer in recent years. This study aimed to understand the incidence of lung ...cancer and the characteristics of lung nodules on low-dose computed tomography (LDCT) scans of the chest in a long-term smoking population in Kunming.
Long-term smokers in Kunming who were not at risk of evident lung disease symptoms were recruited through recommendation and publicity by the Kunming University of Science and Technology.
Among 375 cases eligible for inclusion,14 cases of lung cancer were detected with a detection rate of 3.73% (95% CI: 2.55%-4.27%), including one case of squamous carcinoma, one case of small cell lung cancer, seven cases of adenocarcinoma of the lung and five cases of early-stage lung cancer (35.71%). In the group of < 6 mm solid nodules and < 5 mm non-solid nodules, no lung cancer was detected in 201 cases; lung cancer was detected in 14 cases in 61 cases, and there was a statistical difference between the two groups (p < 0.05).
The lung cancer detection rate in long-term smokers was high, with the type predominantly adenocarcinoma and a high incidence of lung nodules, and increased when solid nodules≥6 mm or non-solid nodules ≥ 5 mm were present. It is recommended that screening for lung cancer by LDCT of the chest be introduced in the male smoking population who meet the risk factors and that screening for lung cancer in women should be redefined as a high-risk factor.
Naturally produced, biodegradable polyhydroxyalkanoates (PHAs) promise more sustainable alternatives to nonrenewable/degradable plastics, but biological PHA’s stereomicrostructures are strictly ...confined to isotactic (R)-polymers or copolymers of random sequences. Chemical synthesis via catalyzed ring-opening polymerization (ROP) of cyclic (di)esters offers expedient access to diverse PHA microstructures, including those with defined comonomer sequences and tacticities. However, the synthesis of alternating isotactic PHAs has not been achieved by the existing methodologies. Here, we report the design of unsymmetrically disubstituted eight-membered diolides (rac-8DLR1‑R2) and their site- and stereoselective ROP with discrete chiral catalysts, enabling the synthesis of alternating isotactic PHAs, poly(3-hydroxybutyrate-alt-3-hydroxyvalerate) (alt-P3HBV) and poly(3-hydroxybutyrate-alt-3-hydroxyheptanoate) (alt-P3HBHp), with high to quantitative (>99%) alternation and isotacticity and M n up to 113 kDa and Đ = 1.01. Physical properties of such PHAs are substantially determined by the degree of backbone sequence alternation and tacticity, ranging from amorphous to semi-crystalline materials. The alt-P3HBV shows significantly improved mechanical performance relative to the constituent homopolymers. Intriguingly, enantiomeric (R)-alt-P3HBV and (S)-alt-P3HBV, synthesized by kinetically resolved ROP of rac-8DLMe‑Et, form a stereocomplex with a significantly enhanced T m (by 53 °C), while the enantiomeric homopolymers do not form a stereocomplex.
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