A highly sensitive LITES sensor based on a multi-pass cell with dense spot pattern and a novel quartz tuning fork with low frequency

A highly sensitive light-induced thermoelectric spectroscopy(LITES)sensor based on a multi-pass cell(MPC)with dense spot pattern and a novel quartz tuning fork(QTF)with low resonance frequency is reported in this manuscript.An erbi-um-doped fiber amplifier(EDFA)was employed to amplify the output optical power so that the signal level was further enhanced.The optical path length(OPL)and the ratio of optical path length to volume(RLV)of the MPC is 37.7 m and 13.8 cm^(-2),respectively.A commercial QTF and a self-designed trapezoidal-tip QTF with low frequency of 9461.83 Hz were used as the detectors of the sensor,respectively.The target gas selected to test the performance of the system was acetylene(C2H2).When the optical power was constant at 1000 mW,the minimum detection limit(MDL)of the C2H2-LITES sensor can be achieved 48.3 ppb when using the commercial QTF and 24.6 ppb when using the trapezoid-al-tip QTF.An improvement of the detection performance by a factor of 1.96 was achieved after replacing the commer-cial QTF with the trapezoidal-tip QTF.

Modulation Effects of the 3D Strain Microenvironment on Characteristics of Mesenchymal Stem Cell-Derived Exosomes

It is necessary to investigate the characteristics of Mesenchymal stem cells(MSCs)derived exosomes,and especially their application in tissue regeneration.Previous studies have shown that inflammatory stimulation enhanced the secretion of MSC-derived exosomes with stronger anti-inflammatory protein,cytokine profiles,and functional RNA via altering COX2/PGE2 pathway.Recently,accumulating evidence has also revealed that biophysical cues(especially biomechanical cues)in cell microenvironment have significant effects not only on cells but also on their exosomes.It has been reported that applying bi-axial strain to MSCs induces formation of a stiffer cytoskeleton through mTORC2 signaling,which biases against adipogenic differentiation and toward osteoblastogenesis.At the same time,For example,dimensionality,composition and stiffness of the extracellular matrix(ECM)has been proved to affect the size and composition of exosomes secreted by cancer cells.However,the effects of biomechanical cues in the three-dimensional(3D)microenvironment on stem cell-derived exosomes remains to be unveiled.Therefore,it is important to understand the roles of 3D cell mechanical microenvironment in regulating the characteristics of stem cell-derived exosomes and develop more efficient approaches to enhance their functions.This study aimed to explore the changes in characteristics of exosomes secreted by MSCs in periodontium in response to the matrix strain in 3D.Periodontal ligament stem cells(PDLSCs)were cultured in a 3D strain microenvironment engineered with microscale magnetically stretched collagen hydrogels.The morphology,particle distribution,marker protein expression of PDLSC-derived exosomes were analyzed.Then the pro-osteogenic property of exosomes was evaluated by assessing cell viability,proliferation,migration and osteogenic differentiation of target cells,for instance human bone marrow mesenchymal stem cells(hBMSCs).Detailed characterizations revealed that PDLSC-derived exosomes in the 3D strain mi-croenvironment were with similar morphology,particle distribution and surface markers.Notably,Exosomes secreted by PDLSCs in strain microenvironment were more endocytosed by hBMSCs and were more potent in improving proliferation and migration of hBMSCs,comparing with PDLSCs in non-strain environment.Alizarin red staining and molecular biology experiments confirmed that treatment of exosomes secreted by PDLSCs under mechanical stimulation led to a significant increase in osteogenic differentiation of hBMSCs in vitro.Meanwhile,in vivo study also indicated that PDLSC-derived exosomes obtained from the 3D strain microenvironment could obviously promote new bone formation.Our findings revealed that mechanical cues profoundly affected the characteristics of PDLSC-derived exosomes,especially for their bio-activity,providing a foundation for using the 3D mechanical microenvironment to enhance the osteo-inductive functions of stem cell-derived exosomes in cell-free therapy for bone regeneration.

Wnt3a-induced ST2 decellularized matrix ornamented PCL scaffold for bone tissue engineering

The limited bioactivity of scaffold materials is an important factor that restricts the development of bone tissue engineering.Wnt3a activates the classicWnt/β-catenin signaling pathway which effects bone growth and development by the accumulation ofβ-catenin in the nucleus.In this study,we fabricated 3D printed PCL scaffold with Wnt3a-induced murine bone marrow-derived stromal cell line ST2 decellularized matrix(Wnt3a-ST2-dCM-PCL)and ST2 decellularized matrix(ST2-dCM-PCL)by freeze-thaw cycle and DNase decellularization treatment which efficiently decellularized>90%DNA while preserved most protein.Compared to ST2-dCM-PCL,Wnt3a-ST2-dCM-PCL significantly enhanced newly-seeded ST2 proliferation,osteogenic differentiation and upregulated osteogenic marker genes alkaline phosphatase(Alp),Runx2,type I collagen(Col 1)and osteocalcin(Ocn)mRNA expression.After 14 days of osteogenic induction,Wnt3a-ST2-dCM-PCL promoted ST2 mineralization.These results demonstrated that Wnt3a-induced ST2 decellularized matrix improve scaffold materials’osteoinductivity and osteoconductivity.

A novel decellularized matrix of Wnt signaling-activated osteocytes accelerates the repair of critical-sized parietal bone defects with osteoclastogenesis, angiogenesis, and neurogenesis

Cell source is the key to decellularized matrix(DM)strategy.This study compared 3 cell types,osteocytes with/without dominant active Wnt/β-catenin signaling(daCO and WTO)and bone marrow stromal cells(BMSCs)for their DMs in bone repair.Decellularization removes all organelles and>95%DNA,and retained>74%collagen and>71%GAG,maintains the integrity of cell basement membrane with dense boundaries showing oval and honeycomb structure in osteocytic DM and smooth but irregular shape in the BMSC-DM.DM produced higher cell survival rate(90%)and higher proliferative activity.In vitro,daCO-DM induces more and longer stress fibers in BMSCs,conducive to cell adhesion,spreading,and osteogenic differentiation.8-wk after implantation of the critical-sized parietal bone defect model,daCO-DM formed tight structures,composed of a large number of densely-arranged type-I collagen under polarized light microscope,which is similar to and integrated with host bone.BV/TV(>54%)was 1.5,2.9,and 3.5 times of WTO-DM,BMSC-DM,and none-DM groups,and N.Ob/T.Ar(3.2×10^(2)/mm^(2))was 1.7,2.9,and 3.3 times.At 4-wk,daCO-DM induced osteoclastogenesis,2.3 times higher than WTO-DM;but BMSC-DM or none-DM didn't.daCO-DM increased the expression of RANKL and MCSF,Vegfa and Angpt1,and Ngf in BMSCs,which contributes to osteoclastogenesis,angiogenesis,and neurogenesis,respectively.daCO-DM promoted H-type vessel formation and nerve markersβ3-tubulin and NeuN expression.Conclusion:daCO-DM produces metabolic and neurovascularized organoid bone to accelerate the repair of bone defects.These features are expected to achieve the effect of autologous bone transplantation,suitable for transformation application.

Radiolabeling and evaluation of ^(188)Re-RGD as an agent for α_vβ_3 receptor expression

Integrin αvβ3,a cell adhesion molecule,plays a key role in angiogenesis and tumor cell metastasis and is therefore an important target for new therapeutic and diagnostic strategies.Since RGD bind to αvβ3 particularly,a lot of RGD containing peptides were radiolabeled and evaluated as imaging or therapeutic agents.In this study,a new 188Re-RGD peptide analog was synthesized and characterized.Within 30min,the 188Re-H-E[c(RGDyK)]2 was obtained in radiochemical purity of better than 95%.The His-E[c(RGDyK)]2 had a good integrin-binding affinity (50% inhibitiory concentracer (IC50=46.5×10-9 nm) and exhibited active accumulation (7.20±1.06) in S180 tumor.Because of relatively fast washout in blood and normal tissues,the target/non-target ratio was high.Further experiments to improve the tumor targeting efficacy and in vivo kinetic profiles are in progress towards developing it into a promising radio agent.

Incorporating element doping and quantum dot embedding effects to enhance the thermoelectric properties of higher manganese silicides

Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric(TE)materials,respectively.However,the intrinsic low electrical thermal conductivities and high electrical properties are severely sacrificed,and the final figure of merit(ZT)is usually restricted.In this study,Ag doping and Pt quantum dot(QD)embedding were synchronously achieved via embedding Ag/Pt alloy QDs into the higher manganese silicides to avoid the conventional single-element doping strategy.The power factor(at 823 K)was enhanced from 1.57×10^(-3) W m^(-1) K^(-2) to 1.82×10^(-3) W m^(-1) K^(-2)(-16%)due to the-18%increase in carrier concentration that was derived from the Ag doping effect.Simultaneously,the lattice thermal conductivity(at 823 K)decreased from 2.65 W m^(-1) K^(-1) e1.92 W m^(-1) K^(-1)(-28%)because of the broadband phonon scattering effect that resulted from the residual Pt QDs inclusions.Synthetically,the optimal ZT value increased by-52%from 0.42 to 0.64 at 823 K.This study demonstrated that incorporating metastable alloy QDs to obtain element doping and nano-inclusion embedding effects is a novel and feasible means to enhance the ZT value of HMS.This method is also possibly applicable to other alloy QD/TE composites.

Recent progress in transition-metal-oxide-based electrocatalysts for the oxygen evolution reaction in natural seawater splitting: A critical review

Direct electrolytic splitting of seawater for the production of H2 using ocean energy is a promising technology that can help achieve carbon neutrality.However,owing to the high concentrations of chlorine ions in seawater,the chlorine evolution reaction always competes with the oxygen evolution reaction(OER)at the anode,and chloride corrosion occurs on both the anode and cathode.Thus,effective electrocatalysts with high selectivity toward the OER and excellent resistance to chloride corrosion should be developed.In this critical review,we focus on the prospects of state-of-the-art metal-oxide electrocatalysts,including noble metal oxides,non-noble metal oxides and their compounds,and spinel-and perovskite-type oxides,for seawater splitting.We elucidate their chemical properties,excellent OER selectivity,outstanding anti-chlorine-corrosion performance,and reaction mechanisms.In particular,we review metal oxides that operate at high current densities,near industrial application levels,based on special catalyst design strategies.

Highly Sensitive and Fast Hydrogen Detection Based on Light-Induced Thermoelastic Spectroscopy

As a new energy source,hydrogen(H_(2))detection is a hot topic in recent years.Because of the weak absorption characteristic,laser spectroscopy-based H_(2)detection is challenging.In this paper,a highly sensitive H_(2)sensor based on light-induced thermoelastic spectroscopy(LITES)technique is demonstrated for the first time.A continuous-wave,distributed feedback diode laser with emission in the 2.1μm region was adopted as the excitation source to target the strongest H_(2)absorption line of 4,712.90 cm^(−1).A Herriott multipass cell with an optical length of 10.1 m was chosen to further improve the H_(2)absorption.With the feature of processing the raw input data without data preprocessing and extracting the desired features automatically,the robust shallow neural network(SNN)fitting algorithm was brought in to denoise the sensor.For the LITES-based H_(2)sensor,the concentration response was tested,and an excellent linear response to H_(2)concentration levels was achieved.A minimum detection limit(MDL)of~80 ppm was obtained.On the basis of implementation of the H_(2)-LITES sensor,a heterodyne H_(2)-LITES sensor was further constructed to realize a fast measurement of resonance frequency of quartz tuning fork and H_(2)concentration simultaneously.The resonance frequency can be retrieved in several hundred milliseconds with the measurement accuracy of±0.2 Hz,and the result of 30,713.76 Hz is exactly same as the experimentally determined value of 30,713.69 Hz.After the SNN algorithm was applied,an MDL of~45 ppm was achieved for this heterodyne H_(2)-LITES sensor.

教育人工智能场域下教师角色与行动取向

教师与人工智能技术的关系是推进教育人工智能发展中需要审慎处理的关键关系,理清教育人工智能场域下的教师角色与行动取向极具现实意义。本文以教师角色分析为出发点,有针对性地选择研究对象,通过半结构化访谈及问卷调查获得样本数据,开展实证研究。研究发现:在智能时代,教师应成为知识信息、数字资源智能传播与呈现的掌舵者。具体而言,在教学功能方面,教师可扮演基于证据的个性化教学决策者与分析者;在辅导功能方面,教师需成为智能时代学生辅导的情感补位者;在管理功能方面,教师需成为非常规类班级及行政管理的人力保障者。基于此,文章提出了教育人工智能场域下教师的行动取向:教师应注重智能时代知识传授及数字资源建设的人文渗透;教师应注重提升智能教学与教育证据的整合能力;教师应实施智能帮扶与情感补位相结合的辅导策略;教师需基于管理情境适度应用与合理省思智能技术。

Association between thyroid hormone levels and frailty in the community-dwelling oldest-old: a cross-sectional study

Background:Changes in thyroid hormone levels are commonly recognized characters among the elderly,which were reported to potentially influence incident frailty.Therefore,we examined the cross-sectional associations of thyroid hormones(THs)with frailty as well as the five components characterizing frailty(fatigue,resistance,ambulation,number ofillnesses,and loss of weight)among the oldest-old.Methods:Four hundred and eighty-seven community-dwelling oldest-old from a local community in Haidian District,Beijing,participated in our recruitment campaign between April 2019 and May 2020.The primary outcomes were a definitive diagnosis of frailty according to the FRAIL scale(Fatigue,Resistance,Ambulation,Illnesses,Loss of weight)and a positive score for each frailty subdomain.Demographic information(age,sex,marital status,and educational status),comorbidities,and details on the participants lifestyles were recorded.Serum THs including free triodothyronin(fT3),triiodothyronine(T3),free thyroxine(fT4),and thyroxine(T4)and thyroid stimulating hormone(TSH)levels were also measured at the beginning of our study.Logistic regressions were conducted to screen for potential risk factors for frailty and its subdomains.Results:Among the total 487 subjects at enrollment,60(12.23%)of them were diagnosed with subclinical hypothyroidism and 110(22.59%)of the total population scored positive for frailty.Logistic regression analyses adjusted for all potential confounders,showed that frailty was significantly associated with the serum TSH concentration(odds ratio[OR]:1.06),fT3 concentration(OR:0.54),and subclinical hypothyroidism score(OR:2.18).The association between fT4 and frailty was absent in our observational study.The fT3/fT4 ratio characterizing peripheral hormone conversion was also tested to be correlated with frailty.Conclusion:Subclinical hypothyroidism,higher TSH level,lower fT3 level,and decreased fT3/fT4 ratio were all associated with frailty assessed by the FRAIL scale among the community-dwelling oldest-old,suggesting a relevant role of thyroid function in aging.Future longitudinal studies are warranted to determine the casual relationship between thyroid dysfunction and frailty in the oldest-old.

氧化石墨烯的工业化进展

相关研究表明氧化石墨烯(GO)在众多领域皆具有应用潜力,因此GO越来越受工业界的关注.目前,全球已涌现了许多公司,致力于实现GO的工业级应用,如热管理、多功能聚合物复合材料、防腐、润滑剂、能源、环境和生物医学等.本文主要介绍了当前GO工业化的发展情况,包括GO的大规模生产以及具有市场经济价值的应用,并讨论了GO在工业化过程中的挑战和处理策略,旨在为本领域的科学家提供研究素材,以期在工业界实现GO的规模化应用.

Vital role of hydroxyapatite particle shape in regulating the porosity and mechanical properties of the sintered scaffolds

The effect of particle shape on the porosity and compressive strength of porous hydroxyapatite （HA） scaffolds was investigated by sintering the mixture of rod-shaped HA （r-HA） and spherical HA （s-HA） with polyacrylamide used as the sacrificial template. It was found, for the first time, that addition of r-HA into s-HA could exponentially decrease the porosity of sintered HA scaffolds and enhance their compressive strength with the increase of r-HA content. The mechanism, according to the results from scanning electron microscopy and X-ray diffraction, lies in the restriction of s-HA to the grain formation and growth of r-HA during sintering and results in the fusion of r-HA with s-HA. These findings suggest that mixture of r-HA and s-HA might provide a new and facile way to improve the compressive strength of oorous HA scaffolds.

Design of RF front end of digital BPM for BEPCII

Purpose In order to update the BPM electronic in BEPCII,a high-performance digital BPM processor is designed,and the RF front-end electronic is the key part in the digital BPM processor system.Methods According to the BEPCII physical parameters andADCunder-sampling theorem,the low-noise and high-dynamicrange RF front-end electronic module is designed.This article will introduce filter,RF amplifier,isolation,system test,etc.Results and conclusions The experimental results showed that BPM position short-term resolution is better than 100 nm,and long-term resolution is better than 5μm.It is the first domestic BPM processor that runs stably in the storage ring accelerator for a long time.Meanwhile,the study can help us to establish a solid foundation for the next work of BPM electronics development.