Additive manufacturing (AM) is the key to creating a wide variety of 3D structures with unique and programmable functionalities. Direct ink writing is one of the widely used AM technologies with ...numerous printable materials. However, the extrude‐based method is limited by low fabrication resolution, which is confined to printing macrostructures. Herein, a new AM strategy is reported, using a low‐cost extrusion 3D printer, to create 3D microarchitectures at the macroscopic level through controlled desiccation of preprinted hydrogel scaffolds followed by infilling objective components. A printable hydrogel with a high‐water content ensures maximum shrinkage (≈99.5% in volume) of the printed scaffolds to achieve high resolution. Stable covalent cross‐linking and a suitable drying rate enable uniform shrinkage of the scaffolds to retain their original architectures. Particularly, this method can be adapted to produce liquid‐metal‐based 3D circuits and nanocomposite‐based microrobots, indicating its capability to fabricate functional and complex 3D architectures with micron‐level resolution from different material systems.
By printing highly shrinkable hydrogel scaffolds as templates via a low‐resolution extrusion 3D printer, complex 3D architectures with micron‐level resolution are successfully fabricated. This technique is capable of manufacturing a wider range of material types and reveals the opportunity for hydrogel to assist 3D microfabrication.
Abstract
Recent LHAASO observations of the prompt emission phase of the brightest-of-all-time GRB 221009A imposes a stringent limit on the flux ratio between the TeV and MeV emissions,
F
TeV
/
F
MeV
...≤ 2 × 10
−5
, during the period 220–230 s after the trigger. This period covers the peak of the main MeV burst and is just before the TeV afterglow emerges. Within the framework of internal shocks, we study the internal
γγ
absorption in GRB 221009A by generating a set of synthetic bursts in a simulation that reproduces the observed feature of GRB 221009A. We find that the
γγ
absorption does not lead to an exponential cutoff, but rather a power-law spectrum, consistent with previous works. We further find that the attenuation due to
γγ
absorption alone cannot explain the flux limit ratio of GRB 221009A, suggesting a low ratio between synchrotron self-Compton (SSC) and synchrotron emission outputs. This requires the magnetic field energy density to be much larger than the synchrotron photon energy density so that the SSC flux is greatly suppressed. This indicates that the jet composition of GRB 221009A is likely Poynting flux dominated.
•A generator is proposed to simulate cross-correlated random fields from sparse data.•Uncertainty in random field parameters and cross-correlation are considered.•A method is proposed to satisfy the ...requirement of identical correlation structure.•The proposed random field generator is demonstrated and validated through examples.
Cross-correlated random field samples (RFSs) of engineering quantities (e.g., mechanical properties of materials) are often needed for stochastic analysis of structures when cross-correlation between engineering quantities and spatial/temporal auto-correlation of each quantity are considered. Theoretically, cross-correlated RFSs may be simulated using a cross-correlated random field generator with prescribed random field parameters and cross-correlation. In engineering practice, random field parameters and cross-correlation are often unknown, and they need to be estimated from extensive measurements. When the number of measurements is sparse and limited, due to sensor failure, budget limit etc., it is challenging to accurately estimate random field parameters or properly simulate cross-correlated RFSs. This paper aims to address this challenge by developing a cross-correlated random field generator based on Bayesian compressive sampling (BCS) and Karhunen–Loève (KL) expansion. The generator proposed only requires sparse measurements as input, and provides cross-correlated RFSs with a high resolution as output. The cross-correlated RFSs are able to simultaneously characterize the cross-correlation between different quantities and the spatial/temporal auto-correlation for each quantity. The generator proposed is illustrated using numerical examples. The results show that proposed generator performs reasonably well.
Most of the resting-state functional magnetic resonance imaging (fMRI) studies demonstrated the correlations between spatially distinct brain areas from the perspective of functional connectivity or ...functional integration. The functional connectivity approaches do not directly provide information of the amplitude of brain activity of each brain region within a network. Alternatively, an index named amplitude of low-frequency fluctuation (ALFF) of the resting-state fMRI signal has been suggested to reflect the intensity of regional spontaneous brain activity. However, it has been indicated that the ALFF is also sensitive to the physiological noise. The current study proposed a fractional ALFF (fALFF) approach, i.e., the ratio of power spectrum of low-frequency (0.01–0.08
Hz) to that of the entire frequency range and this approach was tested in two groups of resting-state fMRI data. The results showed that the brain areas within the default mode network including posterior cingulate cortex, precuneus, medial prefrontal cortex and bilateral inferior parietal lobule had significantly higher fALFF than the other brain areas. This pattern was consistent with previous neuroimaging results. The non-specific signal components in the cistern areas in resting-state fMRI were significantly suppressed, indicating that the fALFF approach improved the sensitivity and specificity in detecting spontaneous brain activities. Its mechanism and sensitivity to abnormal brain activity should be evaluated in the future studies.
Boron–nitrogen units were incorporated into thiophene‐fused polycyclic aromatic compounds. Organic field‐effect transistors based on these azaborine compounds were fabricated, demonstrating a novel ...engineering concept of organic semiconductors and providing opportunities of a broad class of BN‐containing compounds for application in future organic electronic devices (see picture; μFET=hole mobility).
A cluster of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections was found in a cargo ship under repair in Zhoushan, China. Twelve of 20 crew members were identified as SARS‐CoV‐2 ...positive. We analyzed four sequences and identified them all in the Delta branch emerging from India with 7–8 amino acid mutation sites in the spike protein.
In the current study, the solidification structure, non-metallic inclusions and hot ductility of continuously cast high manganese TWIP steel slab have been investigated and the inclusion formation ...behavior have been revealed by FactSage (CRCT-ThermFact Inc., Montréal, Canada). The area ratio of equiaxed grain zone of the TWIP steel slab is 0.18. Two main types of inclusions in the TWIP steel slab are single AlN particle and AlN+MnS aggregates. It is found that MgAl2O4 and AlN particles can precipitate in the initial solidification stage, which can act as heterogeneous nuclei of other inclusions. In the high temperature tension test, the reduction of area (RA) of the TWIP steel slab samples are higher than 40 pct in the temperature range from 873 K to 1473 K (600°C to 1200°C). Brittle fractures are observed in the fracture surface of the TWIP steel slab samples with dimples. Contents of manganese, carbon, sulfur and phosphorus, strain rate, and dynamic recrystallization (DRX) are factors influencing the hot ductility of TWIP steel slab.
Aim
To summarize evidence regarding the effects of oral nutritional supplement on muscle fitness of patients undergoing dialysis.
Design
A systematic review and meta‐analysis.
Review sources
Five ...English databases (CENTRAL, PubMed, EMBASE, CINHAL, and Web of Science) and four Chinese databases (CNKI, WanFang, SinoMed, and VIP) were searched from inception to 31 July 2019 and only randomized controlled trials were included.
Review methods
Two reviewers independently searched these databases, selected trials, conducted bias assessment, extracted the data. Random‐effects meta‐analysis was conducted to assess the effect size. The predetermined subgroup included type of oral nutritional supplement (a mixture of macronutrients, whey protein, essential amino‐acids, and other nutrients) and intervention duration (over and less than 48 weeks). The subgroup analyses and sensitivity analyses were conducted to explore source of heterogeneity and robustness of results.
Results
Sixteen studies (910 participants) meeting the inclusion criteria were identified and included in this systematic review. Subgroup analysis showed that supplying a mixture of macronutrients (MD MD = 2.36 kg, 95% CI 0.45, 4.26, I2 = 0.00%), an intervention duration of 48 weeks (MD = 4.05 kg, 95% CI 1.43, 6.67, I2 = 0.00%) had some effects on increasing lean body mass. No effects of oral nutritional supplement were found on improving muscle strength or physical performance.
Conclusion
A mixture of macronutrients and an intervention duration as long as 48 weeks had some significant effects on improving lean body mass of patients undergoing dialysis. No effect of oral nutritional supplement on muscle strength or physical performance were found but with limited evidence.
Impact
No existing reviews have ever focused on improving muscle fitness of patients undergoing dialysis. This systematic review and meta‐analysis provided evidence of oral nutritional supplement on keeping muscle fitness of these patients and suggested possible type of oral nutritional supplement and intervention duration for clinical practice.
摘要
目的
总结有关口服营养补充剂对透析患者肌肉健康影响的证据。
设计
系统化评估和荟萃分析。
数据来源
检索了自研究开始至2019年7月31日的5个英文数据库 (CENTRAL、PubMed、EMBASE、CINHAL和科学引文索引) 和4个中文数据库 (CNKI、万方、SinoMed和VIP) , 且仅纳入随机对照试验。
评估方法
两位评估者对这些数据库进行独立检索, 选择试验, 开展偏倚评价, 提取数据。为评价效应值, 进行了随机效应荟萃分析。预先确定的亚组包括口服营养补充剂的类型 (主要营养物质、乳清蛋白、必需氨基酸和其他营养素的混合物) 和干预持续时间 (超过或少于48周) 。为探讨异质性的来源和结果的稳健性, 进行了亚组分析和敏感性分析。
结果
符合纳入标准的16项研究 (910名参与者) 被确定并纳入本系统化评估。亚组分析显示, 提供主要营养物质混合物 (MDMD=2.36kg,95%CI0.45,4.26,I2=0.00%) , 干预持续时间为48周 (MD=4.05kg,95%CI1.43,6.67,I2=0.00%) , 对增加瘦体重有一定影响。未发现口服营养补充剂对改善肌力或体能的影响。
结论
主要营养物质混合物和长达48周的干预持续时间对改善透析患者的较瘦体型有一定的显著效果。未发现口服营养补充剂对肌力或体能的影响, 但这方面的证据有限。
影响
目前还没有任何评估关注改善透析患者的肌肉健康。本系统化评估和荟萃分析提供了口服营养补充剂对保持这类患者肌肉健康的证据, 并提出了可能的口服营养补充剂类型和干预持续时间, 供临床实践参考。
Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing ...chlorine evolution, and catalyst poisoning. Hereto, the core‐shell‐structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni3S2 nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000 mA cm−2 at the overpotential of 341 mV in 1.0 m KOH seawater. The feasible surface reconstruction of Ni3S2‐FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni3S2 nanopyramids coated with FeNi2P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0 m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636 V to attain 100 mA cm−2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater.
Herein, core‐shell structured Ni3S2‐FeNi layer double hydroxides (LDH) heterointerfaces are rationally prepared. Abundant hydroxide/sulfide interfaces boost alkaline water oxidation. Impressively, electrochemical results indicate that the in situ formed sulfate layer in LDH shell largely enhances the corrosion resistance of the catalysts in the alkaline salty‐water electrolytes.
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