Succinite,Baltic amber,is one of the most appreciated fossil resins.Its beauty has fascinated people since prehistoric times.It is a substance,and also gemstone,whose uniqueness is due to its compelling,though still n...Succinite,Baltic amber,is one of the most appreciated fossil resins.Its beauty has fascinated people since prehistoric times.It is a substance,and also gemstone,whose uniqueness is due to its compelling,though still not fully understood,physicochemical nature.In this article,some facts about the physical and chemical properties of succinite in order to find an answer for questions about the unique properties of this resin,such as color,transparency,texture etc.,are discussed.These properties are among the factors that determine the choice of Baltic amber as a gemstone.Commonly known properties of succinite,but also some less obvious features,have been linked to the organic and inorganic chemical composition and structural factors,including the sophisticated supramolecular structure masterfully created by nature.Changes of the properties of succinite used as a jewelry stone are discussed as a reflection of changes in its physicochemical nature.In this light,some methods that can be used to identify succinite(i.e.,infrared spectroscopy and nuclear magnetic resonance spectroscopy)and their relevance to the classification of fossil resins are briefly discussed.This article highlights an important point:only by understanding the chemical and physical nature of the material we able to identify,modify and effectively use the goods that have been given to us by mother nature.展开更多
A novel laser-based additive manufacturing approach of metal additive manufacturing using powder sheets(MAPS)has been introduced recently.The method utilizes polymer-bound powder sheets for metal AM as a feedstock,ins...A novel laser-based additive manufacturing approach of metal additive manufacturing using powder sheets(MAPS)has been introduced recently.The method utilizes polymer-bound powder sheets for metal AM as a feedstock,instead of loose powders.Conventional laser beam powder bed fusion(LPBF)additive manufacturing(AM)is among the most widespread 3D printing technologies.However,LPBF faces challenges related to safety and the impracticality of changing materials due to its reliance on loose powders.Thus,MAPS demonstrates the capability to overcome the limitations of LPBF by offering enhanced safety and the ability to print multi-material structures without the risk of material cross-contamination.As a part of developing processes,we investigate the effects of polymeric binder content on the printability and microstructural characteristics of MAPS-printed stainless steel 316 L.The results indicate that the average layer thickness of solidified material improves as the scanning speed decreases from 1000 mm/s to 50 mm/s across three different polymeric binder contents:10 wt%,20 wt%,and 30 wt%PCL.Additionally,a higher polymeric binder content(i.e.20 wt%and 30 wt%)in the powder sheets reduces the likelihood of crack formation.Electron backscatter diffraction(EBSD)analysis reveals that an increase in scanning speed promotes the formation of more equiaxed grains,while an increase in polymer content results in a reduction in grain size.These findings provide valuable insights into optimizing MAPS configurations for enhanced productivity and functionality in metal component manufacturing.展开更多
Device-based measurements are recommended to improve population-based physical activity(PA)surveillance.1,2However,implementation remains challenging due to lack of consensus on analytical methods,and the most widely ...Device-based measurements are recommended to improve population-based physical activity(PA)surveillance.1,2However,implementation remains challenging due to lack of consensus on analytical methods,and the most widely used“generic”(absolute intensity)cut-point approach has limited generalisability to population-level free-living data.Further,current methods generally fail to account for differences in people's physical capacity.展开更多
Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)im...Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)improve interpretability by producing UK Biobank age-referenced centiles for PA volume and intensity;(b)inform public-health messaging by examining how adding recommended quantities of moderate and vigorous PA affect PA volume and intensity.Methods 92,480 UK Biobank participants aged 43-80 years with wrist-worn accelerometer data were included.Average acceleration and intensity gradient were derived as proxies for PA volume and intensity.We generated sex-specific centile curves using Generalized Additive Models for Location Scale and Shape(GAMLSS)and modeled the effect of adding moderate(walking)or vigorous(running)activity on the combined change in the volume and intensity centiles(change in PA profile).Results In men,volume was lower as age increased while intensity was lower after age 55;in women,both volume and intensity were lower as age increased.Adding 150 min of moderate PA weekly(5×30 min walking)increased the PA profile by 4 percentage points.Defining moderate PA as brisk walking approximately doubled the increase(9 percentage points)while 75 min of vigorous PA weekly(5×15 min running)trebled the increase(13 percentage points).Conclusion These UK Biobank reference centiles provide a benchmark for interpretation of accelerometer data.Application of our translational methods demonstrate that meeting PA guidelines through shorter duration vigorous activity is more beneficial to the PA profile(volume and intensity)than longer duration moderate activity.展开更多
文中首次报道了缅甸琥珀中的长扁甲Mallecupes qingqingae Jarzembowski,Wang and Zheng,2017的阳茎化石,并讨论了该器官的古昆虫学和现生昆虫学意义。甲虫在现生生物中的多样性最高,而它们的生殖器则在甲虫系统分类中的应用已经超过百...文中首次报道了缅甸琥珀中的长扁甲Mallecupes qingqingae Jarzembowski,Wang and Zheng,2017的阳茎化石,并讨论了该器官的古昆虫学和现生昆虫学意义。甲虫在现生生物中的多样性最高,而它们的生殖器则在甲虫系统分类中的应用已经超过百年历史。这些小而精美的器官通常很难保存在化石里,但文中特异保存在中生代琥珀中的生殖器则为原鞘亚目甲虫的分类学研究提供了新的启示。展开更多
Electronic devices generate heat during operation and require efficient thermal management to extend the lifetime and prevent performance degradation.Featured by its exceptional thermal conductivity,graphene is an ide...Electronic devices generate heat during operation and require efficient thermal management to extend the lifetime and prevent performance degradation.Featured by its exceptional thermal conductivity,graphene is an ideal functional filler for fabricating thermally conductive polymer composites to provide efficient thermal management.Extensive studies have been focusing on constructing graphene networks in polymer composites to achieve high thermal conductivities.Compared with conventional composite fabrications by directly mixing graphene with polymers,preconstruction of three-dimensional graphene networks followed by backfilling polymers represents a promising way to produce composites with higher performances,enabling high manufacturing flexibility and controllability.In this review,we first summarize the factors that affect thermal conductivity of graphene composites and strategies for fabricating highly thermally conductive graphene/polymer composites.Subsequently,we give the reasoning behind using preconstructed three-dimensional graphene networks for fabricating thermally conductive polymer composites and highlight their potential applications.Finally,our insight into the existing bottlenecks and opportunities is provided for developing preconstructed porous architectures of graphene and their thermally conductive composites.展开更多
Although MXene sheets possess high electrical conductivity and rich surface chemistry and are well suit-able for fabricating electrically conductive nanocomposites for electromagnetic interference(EMI)shield-ing appli...Although MXene sheets possess high electrical conductivity and rich surface chemistry and are well suit-able for fabricating electrically conductive nanocomposites for electromagnetic interference(EMI)shield-ing applications,it remains challenging for MXene nanocomposites to achieve tunable EMI shielding per-formances and customized geometries.Herein,an aqueous MXene/sodium alginate ink is developed to print aerogel meshes with customized geometries using a direct ink writing approach.An ion-enhanced strategy is proposed to reinforce the printed aerogel meshes by multi-level cross-linking.The resultant 3D printed aerogel mesh exhibits an ultrahigh electrical conductivity of 2.85×10^(3)S m^(−1),outstanding mechanical properties,and excellent structural stability in wet environment.More importantly,a wide range of tunable EMI shielding efficiencies from 45 to 100 dB is achieved by the structural design of the 3D printed ion-enhanced MXene/sodium alginate aerogel meshes.As a Joule heater,in addition,the printed aerogel meshes can achieve a wide temperature range of 40-135℃at low driving voltages.This work demonstrates a direct ink writing approach for the fabrication of ion-enhanced MXene/sodium al-ginate aerogel meshes with tunable EMI shielding properties and multi-functionalities for applications in many scenarios.展开更多
The increase in anthropogenic carbon dioxide(CO_(2))emissions has exacerbated the deterioration of the global environment,which should be controlled to achieve carbon neutrality.Central to the core goal of achieving c...The increase in anthropogenic carbon dioxide(CO_(2))emissions has exacerbated the deterioration of the global environment,which should be controlled to achieve carbon neutrality.Central to the core goal of achieving carbon neutrality is the utilization of CO_(2) under economic and sustainable conditions.Recently,the strong need for carbon neutrality has led to a proliferation of studies on the direct conversion of CO_(2) into carboxylic acids,which can effectively alleviate CO_(2) emissions and create high-value chemicals.The purpose of this review is to present the application prospects of carboxylic acids and the basic principles of CO_(2) conversion into carboxylic acids through photo-,electric-,and thermal catalysis.Special attention is focused on the regulation strategy of the activity of abundant catalysts at the molecular level,inspiring the preparation of high-performance catalysts.In addition,theoretical calculations,advanced technologies,and numerous typical examples are introduced to elaborate on the corresponding process and influencing factors of catalytic activity.Finally,challenges and prospects are provided for the future development of this field.It is hoped that this review will contribute to a deeper understanding of the conversion of CO_(2) into carboxylic acids and inspire more innovative breakthroughs.展开更多
文摘Succinite,Baltic amber,is one of the most appreciated fossil resins.Its beauty has fascinated people since prehistoric times.It is a substance,and also gemstone,whose uniqueness is due to its compelling,though still not fully understood,physicochemical nature.In this article,some facts about the physical and chemical properties of succinite in order to find an answer for questions about the unique properties of this resin,such as color,transparency,texture etc.,are discussed.These properties are among the factors that determine the choice of Baltic amber as a gemstone.Commonly known properties of succinite,but also some less obvious features,have been linked to the organic and inorganic chemical composition and structural factors,including the sophisticated supramolecular structure masterfully created by nature.Changes of the properties of succinite used as a jewelry stone are discussed as a reflection of changes in its physicochemical nature.In this light,some methods that can be used to identify succinite(i.e.,infrared spectroscopy and nuclear magnetic resonance spectroscopy)and their relevance to the classification of fossil resins are briefly discussed.This article highlights an important point:only by understanding the chemical and physical nature of the material we able to identify,modify and effectively use the goods that have been given to us by mother nature.
基金supported by PoSAddive–Powder Sheet Additive Manufacturing(co-funded by EIT Raw Materials,Grant No.22021)the AML in Trinity College Dublin.EIT Raw Materials is supported by EIT,a body of the European Union.
文摘A novel laser-based additive manufacturing approach of metal additive manufacturing using powder sheets(MAPS)has been introduced recently.The method utilizes polymer-bound powder sheets for metal AM as a feedstock,instead of loose powders.Conventional laser beam powder bed fusion(LPBF)additive manufacturing(AM)is among the most widespread 3D printing technologies.However,LPBF faces challenges related to safety and the impracticality of changing materials due to its reliance on loose powders.Thus,MAPS demonstrates the capability to overcome the limitations of LPBF by offering enhanced safety and the ability to print multi-material structures without the risk of material cross-contamination.As a part of developing processes,we investigate the effects of polymeric binder content on the printability and microstructural characteristics of MAPS-printed stainless steel 316 L.The results indicate that the average layer thickness of solidified material improves as the scanning speed decreases from 1000 mm/s to 50 mm/s across three different polymeric binder contents:10 wt%,20 wt%,and 30 wt%PCL.Additionally,a higher polymeric binder content(i.e.20 wt%and 30 wt%)in the powder sheets reduces the likelihood of crack formation.Electron backscatter diffraction(EBSD)analysis reveals that an increase in scanning speed promotes the formation of more equiaxed grains,while an increase in polymer content results in a reduction in grain size.These findings provide valuable insights into optimizing MAPS configurations for enhanced productivity and functionality in metal component manufacturing.
文摘Device-based measurements are recommended to improve population-based physical activity(PA)surveillance.1,2However,implementation remains challenging due to lack of consensus on analytical methods,and the most widely used“generic”(absolute intensity)cut-point approach has limited generalisability to population-level free-living data.Further,current methods generally fail to account for differences in people's physical capacity.
基金supported by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre and NIHR Applied Research Collaboration East Midlands (ARC EM, (IS-BRC-1215-20010))funded by the National Institute for Health and Care Research Bristol Biomedical Research Centre (IS-BRC-1215-20011)supported by a UKRI research grant (EP/X042464/1)。
文摘Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)improve interpretability by producing UK Biobank age-referenced centiles for PA volume and intensity;(b)inform public-health messaging by examining how adding recommended quantities of moderate and vigorous PA affect PA volume and intensity.Methods 92,480 UK Biobank participants aged 43-80 years with wrist-worn accelerometer data were included.Average acceleration and intensity gradient were derived as proxies for PA volume and intensity.We generated sex-specific centile curves using Generalized Additive Models for Location Scale and Shape(GAMLSS)and modeled the effect of adding moderate(walking)or vigorous(running)activity on the combined change in the volume and intensity centiles(change in PA profile).Results In men,volume was lower as age increased while intensity was lower after age 55;in women,both volume and intensity were lower as age increased.Adding 150 min of moderate PA weekly(5×30 min walking)increased the PA profile by 4 percentage points.Defining moderate PA as brisk walking approximately doubled the increase(9 percentage points)while 75 min of vigorous PA weekly(5×15 min running)trebled the increase(13 percentage points).Conclusion These UK Biobank reference centiles provide a benchmark for interpretation of accelerometer data.Application of our translational methods demonstrate that meeting PA guidelines through shorter duration vigorous activity is more beneficial to the PA profile(volume and intensity)than longer duration moderate activity.
文摘文中首次报道了缅甸琥珀中的长扁甲Mallecupes qingqingae Jarzembowski,Wang and Zheng,2017的阳茎化石,并讨论了该器官的古昆虫学和现生昆虫学意义。甲虫在现生生物中的多样性最高,而它们的生殖器则在甲虫系统分类中的应用已经超过百年历史。这些小而精美的器官通常很难保存在化石里,但文中特异保存在中生代琥珀中的生殖器则为原鞘亚目甲虫的分类学研究提供了新的启示。
文摘Electronic devices generate heat during operation and require efficient thermal management to extend the lifetime and prevent performance degradation.Featured by its exceptional thermal conductivity,graphene is an ideal functional filler for fabricating thermally conductive polymer composites to provide efficient thermal management.Extensive studies have been focusing on constructing graphene networks in polymer composites to achieve high thermal conductivities.Compared with conventional composite fabrications by directly mixing graphene with polymers,preconstruction of three-dimensional graphene networks followed by backfilling polymers represents a promising way to produce composites with higher performances,enabling high manufacturing flexibility and controllability.In this review,we first summarize the factors that affect thermal conductivity of graphene composites and strategies for fabricating highly thermally conductive graphene/polymer composites.Subsequently,we give the reasoning behind using preconstructed three-dimensional graphene networks for fabricating thermally conductive polymer composites and highlight their potential applications.Finally,our insight into the existing bottlenecks and opportunities is provided for developing preconstructed porous architectures of graphene and their thermally conductive composites.
基金Financial support from the National Natural Science Foundation of China(Nos.51922020 and 52090034)the open Foundation of State Key Laboratory of Organic-Inorganic Composites,Beijing University of Chemical Technology(No.OIC-202201001)are gratefully acknowledged.
文摘Although MXene sheets possess high electrical conductivity and rich surface chemistry and are well suit-able for fabricating electrically conductive nanocomposites for electromagnetic interference(EMI)shield-ing applications,it remains challenging for MXene nanocomposites to achieve tunable EMI shielding per-formances and customized geometries.Herein,an aqueous MXene/sodium alginate ink is developed to print aerogel meshes with customized geometries using a direct ink writing approach.An ion-enhanced strategy is proposed to reinforce the printed aerogel meshes by multi-level cross-linking.The resultant 3D printed aerogel mesh exhibits an ultrahigh electrical conductivity of 2.85×10^(3)S m^(−1),outstanding mechanical properties,and excellent structural stability in wet environment.More importantly,a wide range of tunable EMI shielding efficiencies from 45 to 100 dB is achieved by the structural design of the 3D printed ion-enhanced MXene/sodium alginate aerogel meshes.As a Joule heater,in addition,the printed aerogel meshes can achieve a wide temperature range of 40-135℃at low driving voltages.This work demonstrates a direct ink writing approach for the fabrication of ion-enhanced MXene/sodium al-ginate aerogel meshes with tunable EMI shielding properties and multi-functionalities for applications in many scenarios.
基金financial support from the King Abdullah University of Science and Technology(KAUST).
文摘The increase in anthropogenic carbon dioxide(CO_(2))emissions has exacerbated the deterioration of the global environment,which should be controlled to achieve carbon neutrality.Central to the core goal of achieving carbon neutrality is the utilization of CO_(2) under economic and sustainable conditions.Recently,the strong need for carbon neutrality has led to a proliferation of studies on the direct conversion of CO_(2) into carboxylic acids,which can effectively alleviate CO_(2) emissions and create high-value chemicals.The purpose of this review is to present the application prospects of carboxylic acids and the basic principles of CO_(2) conversion into carboxylic acids through photo-,electric-,and thermal catalysis.Special attention is focused on the regulation strategy of the activity of abundant catalysts at the molecular level,inspiring the preparation of high-performance catalysts.In addition,theoretical calculations,advanced technologies,and numerous typical examples are introduced to elaborate on the corresponding process and influencing factors of catalytic activity.Finally,challenges and prospects are provided for the future development of this field.It is hoped that this review will contribute to a deeper understanding of the conversion of CO_(2) into carboxylic acids and inspire more innovative breakthroughs.
