Ethylene/α-olefin copolymers are produced in huge scale and widely used, but their after-use disposal has caused plastic pollution problems. Their chemical inertness made chemical re/upcycling ...difficult. Ideally, PE materials should be made de novo to have a circular closed-loop lifecycle. However, synthesis of circular ethylene/α-olefin copolymers, including high-volume, linear low-density PE as well as high-value olefin elastomers and block copolymers, presents a particular challenge due to difficulties in introducing branches while simultaneously installing chemical recyclability and directly using industrial ethylene and α-olefin feedstocks. Here we show that coupling of industrial coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks by polycondensation, affords a series of ester-linked PE-based copolymers. These new materials not only retain thermomechanical properties of PE-based materials but also exhibit full chemical circularity via simple transesterification and markedly enhanced adhesion to polar surfaces.
Lepidotrigona flavibasis
Cockerell, a eusocial bee species, performs a variety of ecological roles in tropical and subtropical ecosystems. This is the first study to evaluate the abiotic effects on ...the flight activity (exit, exit with garbage, entry, entry with resin, and entry with pollen) of
L. flavibasis
in the non-native habitat in Hainan province, China. The results showed that the colonies remained active throughout the year, peaking in January for the year and at 11:00 h for the day, respectively.
L. flavibasis
presented the greatest flight activities in the dry season. All flight activities of
L. flavibasis
were influenced by temperature and relative humidity. The ambient temperature or relative humidity had a significantly negative influence on flight activity of
L. flavibasis
. The maximum and minimum temperatures for
L. flavibasis
activity were recorded at 38 °C and 15 °C, respectively. Understanding the flight activities of
L. flavibasis
will be helpful for the better maintenance of colonies and improving meliponiculture. The results obtained here can provide information for the future development of techniques for
L. flavibasis
management and natural or artificial feeding.
Previously treated TB patients still pose a serious threat to global control of TB, yet new re-treatment therapies were little studied. This study aimed to examine the therapeutic effects of new ...re-treatment regimens, and explore risk factors associated with recurrence after successful treatment. We conducted a cohort study in nine regions of China and enrolled previously treated TB patients from October, 2008 to December, 2010. Patients were randomly divided into four treatment regimen groups including standard, high-dose, long-course, and individualized treatment. After treatment, those with successful treatment outcomes were followed up to 7 years. The effects of different regimens and the information of recurrence were recorded. Risk factors to poor treatment outcomes were calculated using logistic regression model, while risk factors to recurrence or death were calculated using Cox model. Four hundred ninety-two participants were enrolled during the study time and 419 patients were included in our analysis of treatment effects. Overall, the treatment success rate is 75.9%, and the recurrence and death rate is 6.9% and 3.8%, respectively. Reduced risks of poor outcomes were observed in patients who were treated with high-dose and individualized regimen compared with standard regimen, and the adjusted ORs were 0.3 (0.1–0.6), 0.2 (0.1–0.5), respectively. In our analysis of factors associated with recurrence, all documented variables were not significant. Revised re-treatment regimen has better therapeutic effects compared to standard regimen, but it was not associated with lower risk of TB recurrence. Further studies are warranted to evaluate the role of other revised re-treatment regimens in recurrence risk. Trial registration:
chictr.org
Identifier: ChiCTR1800017441.
Revealing the microstructural parameters-mechanical properties relationship is very critical for the microstructure tailoring and properties optimization of titanium alloy. In this work, the ...dependence of mechanical properties on microstructural parameters of TA15 titanium alloy with tri-modal microstructure was investigated. The results indicate that at a certain lamellar α (αl) content (28%), both of yield strength (σ0.2) and ultimate tensile strength (σb) decrease continuously with the increase of equiaxed α (αp) content, while the decrease speed slows down at higher αp content. At a certain content of αp of 20%, σ0.2 and σb both increase first and then decrease as the content of αl increases. The above effect laws result from the competition between the softening effect caused by increasing the softer αp and αl contents and the strengthening effect relating to αl/βt interfaces and βt hardening. As for the elongation (δ) and reduction of area (Φ), they show an increase trend with αp content increasing at a certain αl content of 28%. However, they decrease first and then increase with αl content increasing at a certain αp content of 20%. The early plasticity decrease at lower αl content is due to the popular rapid void nucleation and cleavage fracture along αl/βt interfaces. When αp or αl content increases to higher level, the deformation compatibility and homogeneity improves, which suppress the rapid void nucleation and cleavage fracture along αl/βt interfaces. Meanwhile, the fracture mechanism changes from the coexistence of void coalescence and cleavage fracture to the void coalescence dominated fracture, thus the plasticity increases. Moreover, a back-propagation neural network model was developed to correlate the mechanical properties with microstructural parameters of tri-modal microstructure. The prediction results suggest that better combination of strength and plasticity can be achieved by controlling the contents of αp and αl in the range of 10–15% and 22–27%, respectively.
ABSTRACT
We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the ...decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of ∼1.5. The pulse-profile shape during the flares can be significantly different from that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and supercritical accretion regimes on a short time-scale. We also observe that at comparable luminosities the flares’ pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e. the mass accretion rate.
In this paper, explicit expressions of the steady-state responses of a cracked Euler-Bernoulli beam submitted to a harmonic force are presented. The mechanical properties of cracked sections of the ...beam are characterized by five local stiffness models available in literature. Fundamental dynamic response of a beam with one crack is obtained by means of Green's function method. For a multi-cracked beam, the transfer matrix method is employed to derive the steady-state response, which can be readily reduced to those for a single-cracked beam. Numerical calculations are performed to validate the present solutions, to compare the dynamical behaviors of the beam corresponding to various classical local compliance models and to study the influences of crack geometry (depth and location) on the mechanical behavior of beam. Furthermore, the interactions of two cracks in the beam are particularly studied. The present analytical results can serve as a valuable benchmark to the future numerical simulations and experimental studies.
Aim
To determine the therapeutic effects of adrenomedullin (ADM) on vascular calcification and related molecular mechanism in fructose‐induced insulin resistance rats.
Methods
Rats received ordinary ...drinking water or 10% fructose in drinking water for 12 weeks and subcutaneous injection of normal saline or ADM (3.6 μg kg−1) twice a day for the last 4 weeks. Levels of ADM, calcitonin receptor‐like receptors (CRLR), receptor activity‐modifying proteins (RAMP) as well as calcium content, alkaline phosphatase (ALP) activity, osteoblastic and contractile smooth muscle markers in aortic media were measured.
Results
The levels of ADM, CRLR, RAMP2 and RAMP3 in aortic media were increased in fructose‐fed rats. ADM treatment attenuated the fructose‐induced insulin resistance, increased blood pressure, fasting glucose, insulin, triglycerides and cholesterol levels. It improved VSMCs proliferation and disordered arrangement and hyperplasia of elastic fibres in fructose‐fed rats. Calcium deposits, calcium content and ALP activity in the aortic media were increased in fructose‐fed rats, which were attenuated by ADM treatment. The osteoblastic markers such as osteopontin (OPN), bone morphogenetic protein 2 (BMP2) proteins and core binding factor alpha‐1 (Cbfα‐1) protein and mRNA expressions were increased in fructose‐fed rats. ADM treatment increased the OPN protein expression, but reduced the BMP2 protein, Cbfα‐1 protein and mRNA expression. Contractile smooth muscle markers such as α‐actin and smooth muscle 22α (SM‐22α) were downregulated in fructose‐fed rats, which were recovered by ADM treatment.
Conclusion
Administration of ADM attenuates insulin resistance, calcium deposition and osteogenic transdifferentiation in aortic media in fructose‐fed rats.
The recent discovery of superconductivity in iron arsenide compounds RFeAsO (R=rare earth) or AFe
2As
2 (A=alkaline earth) has attracted great attention due to the unexpected high
T
c
in the system ...containing ferromagnetic elements like Fe. Similar to high
T
c
cuprates, the superconductivity in iron arsenide is related to a layered structure. Searching for new superconductors with FeAs layer, but of simpler structure will be of scientific significance either to build up new multilayered superconductors that may reach higher
T
c
or to study the mysterious underlined superconducting mechanism in iron arsenide compounds. Here we report that a new superconducting iron arsenide system LiFeAs was found. The compound crystallizes into a structure containing FeAs conducting layer that is interlaced with Li charge reservoir. Superconductivity was observed with
T
c
up to 18 K in the compounds.
Background
Post‐discharge optimal growth and nutritional intake have beneficial effects for neurodevelopment in preterm very low birth weight infants (VLBWIs) with extrauterine growth retardation ...(EUGR). The present study aimed to compare the effects of a nutrient‐dense formula (NDF) to a post‐discharge formula (PDF) on post‐discharge growth of preterm VLBWIs with EUGR.
Methods
Forty‐eight preterm VLBWIs with EUGR at discharge were randomised to receive NDF (100 kcal per 100 mL; 2.6 g protein per 100 mL) or PDF (74 kcal per 100 mL; 1.95 g protein per 100 mL) for 1–6 months until body weight reached the 50th percentile on growth charts with corrected age. Volume, nutrient intake, anthropometry and biochemistry data were collected.
Results
Volume intake was lower in the NDF group than the PDF group during the first 2 months of feeding (P = 0.039 and 0.018, respectively).There were no significant differences in volume intake during months 2–6 of feeding. Energy, protein, carbohydrate and fat intake were higher in the NDF group during months 1–6 of feeding. There were no significant differences in weight, length, and head circumference Z‐scores during months 1–6 between the two groups. The △length Z‐score from discharge to month 6 was significantly higher in the NDF group than the PDF group (P = 0.043). No differences existed between the two groups with respect to biochemistry.
Conclusions
After discharge, preterm VLBWIs with EUGR fed a NDF gain anthropometric parameter Z‐scores similar to those for a PDF within 6 months of follow‐up. A NDF leading to gain in length requires further follow‐up.
PDF
