Richard J Conk, Jules F Stahler, Jake X Shi, Ji Yang, Natalie G Lefton, John N Brunn, Alexis T Bell, John F Hartwig
The selective conversion of polyethylene, polypropylene, and mixtures of the two polymers to form products with high volume demand is urgently needed because current methods suffer from low selectivity, produce large quantities of greenhouse gases, or rely on expensive, single-use catalysts. The isomerizing ethenolysis of unsaturated polyolefins could be an energetically and environmentally viable route to propylene and isobutylene, but noble-metal homogeneous catalysts and an unsaturated polyolefin are currently required, and the process has been limited to polyethylene. We show that the simple combination of tungsten oxide on silica and sodium on gamma-alumina transforms polyethylene, polypropylene, or a mixture of the two, including post-consumer forms of these materials, to propylene or a mixture of propylene and isobutylene in greater than 90% yield at 320°C without the need for dehydrogenation of the starting polyolefins.
{"title":"Polyolefin waste to light olefins with ethylene and base-metal heterogeneous catalysts.","authors":"Richard J Conk, Jules F Stahler, Jake X Shi, Ji Yang, Natalie G Lefton, John N Brunn, Alexis T Bell, John F Hartwig","doi":"10.1126/science.adq7316","DOIUrl":"https://doi.org/10.1126/science.adq7316","url":null,"abstract":"<p><p>The selective conversion of polyethylene, polypropylene, and mixtures of the two polymers to form products with high volume demand is urgently needed because current methods suffer from low selectivity, produce large quantities of greenhouse gases, or rely on expensive, single-use catalysts. The isomerizing ethenolysis of unsaturated polyolefins could be an energetically and environmentally viable route to propylene and isobutylene, but noble-metal homogeneous catalysts and an unsaturated polyolefin are currently required, and the process has been limited to polyethylene. We show that the simple combination of tungsten oxide on silica and sodium on gamma-alumina transforms polyethylene, polypropylene, or a mixture of the two, including post-consumer forms of these materials, to propylene or a mixture of propylene and isobutylene in greater than 90% yield at 320°C without the need for dehydrogenation of the starting polyolefins.</p>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142111612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The precise control of Z and E configurations of the carbon-carbon double bond in alkene synthesis has long been a fundamental challenge in synthetic chemistry, even more pronounced when simultaneously striving to achieve enantioselectivity [(Z,R), (Z,S), (E,R), (E,S)]. Moreover, enantiopure non-natural α-amino acids are highly sought after in organic and medicinal chemistry. In this study, we report a ligand-controlled stereodivergent synthesis of non-natural α-quaternary amino acids bearing trisubstituted alkene moieties in high yields with excellent enantioselectivity and Z/E selectivities. This success is achieved through a palladium/copper–cocatalyzed three-component assembly of readily available aryl iodides, allenes, and aldimine esters by simply tuning the chiral ligands of the palladium and copper catalysts.
长期以来，在烯烃合成过程中精确控制碳碳双键的 Z 和 E 构型一直是合成化学中的一项基本挑战，当同时努力实现对映选择性[(Z,R), (Z,S), (E,R), (E,S)]时，这一挑战就更加突出。此外，非天然α-氨基酸的对映体纯度也是有机化学和药物化学中亟待解决的问题。在本研究中，我们报告了一种配体控制的立体发散型非天然α-季氨基酸的合成方法，该方法含有三取代烯基，产量高，具有极佳的对映选择性和 Z/E 选择性。只需调整钯和铜催化剂的手性配位体，就能通过钯/铜催化三组分组装现成的芳基碘化物、烯和醛亚胺酯，从而取得这一成功。
{"title":"Stereodivergent access to non-natural α-amino acids via enantio- and Z/E-selective catalysis","authors":"Panpan Li, En Zheng, Guanlin Li, Yicong Luo, Xiaohong Huo, Shengming Ma, Wanbin Zhang","doi":"10.1126/science.ado4936","DOIUrl":"10.1126/science.ado4936","url":null,"abstract":"<div >The precise control of <i>Z</i> and <i>E</i> configurations of the carbon-carbon double bond in alkene synthesis has long been a fundamental challenge in synthetic chemistry, even more pronounced when simultaneously striving to achieve enantioselectivity [(<i>Z</i>,<i>R</i>), (<i>Z</i>,<i>S</i>), (<i>E</i>,<i>R</i>), (<i>E</i>,<i>S</i>)]. Moreover, enantiopure non-natural α-amino acids are highly sought after in organic and medicinal chemistry. In this study, we report a ligand-controlled stereodivergent synthesis of non-natural α-quaternary amino acids bearing trisubstituted alkene moieties in high yields with excellent enantioselectivity and <i>Z</i>/<i>E</i> selectivities. This success is achieved through a palladium/copper–cocatalyzed three-component assembly of readily available aryl iodides, allenes, and aldimine esters by simply tuning the chiral ligands of the palladium and copper catalysts.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The outermost layer of the Sun’s atmosphere—the corona—releases plasma, a continuous stream of charged particles that constitutes the solar wind. This stream travels past the planets into interstellar space and fills up a region called the heliosphere. Capturing the energetics of the solar wind can provide information regarding the origin, evolution, and habitability of stellar systems (1). Spacecraft, including the Parker Solar Probe and the Solar Orbiter, were launched to study the inner part of the heliosphere that is close to the Sun. On page 962 of this issue, Rivera et al. (2) report on the energetics of the solar wind based on measurements from the two spacecraft while they were radially aligned near the Sun and observing the same solar wind stream. The results support the importance of Alfvén waves—a common type of plasma wave originating in the solar corona—and suggest other potential factors that drive heating and acceleration of the solar wind.
{"title":"Interplanetary rendezvous at a solar wind stream","authors":"Luca Sorriso-Valvo, Francesco Malara","doi":"10.1126/science.adr5854","DOIUrl":"10.1126/science.adr5854","url":null,"abstract":"<div >The outermost layer of the Sun’s atmosphere—the corona—releases plasma, a continuous stream of charged particles that constitutes the solar wind. This stream travels past the planets into interstellar space and fills up a region called the heliosphere. Capturing the energetics of the solar wind can provide information regarding the origin, evolution, and habitability of stellar systems (<i>1</i>). Spacecraft, including the Parker Solar Probe and the Solar Orbiter, were launched to study the inner part of the heliosphere that is close to the Sun. On page 962 of this issue, Rivera <i>et al</i>. (<i>2</i>) report on the energetics of the solar wind based on measurements from the two spacecraft while they were radially aligned near the Sun and observing the same solar wind stream. The results support the importance of Alfvén waves—a common type of plasma wave originating in the solar corona—and suggest other potential factors that drive heating and acceleration of the solar wind.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Underappreciated government research support in patents","authors":"Seokbeom Kwon","doi":"10.1126/science.ado1078","DOIUrl":"10.1126/science.ado1078","url":null,"abstract":"","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.science.org/doi/reader/10.1126/science.ado1078","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Protect the safety of researchers","authors":"Janneke Gerards","doi":"10.1126/science.ads6586","DOIUrl":"10.1126/science.ads6586","url":null,"abstract":"","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.science.org/doi/reader/10.1126/science.ads6586","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Guy Oren, Aner Shapira, Reuven Lifshitz, Ehud Vinepinsky, Roni Cohen, Tomer Fried, Guy P. Hadad, David Omer
Humans, dolphins, and elephants are the only known species that vocally label their conspecifics. It remains unclear whether nonhuman primates share this ability. We recorded spontaneous “phee-call” dialogues between pairs of marmoset monkeys. We discovered that marmosets use these calls to vocally label their conspecifics. Moreover, they respond more consistently and correctly to calls that are specifically directed at them. Analysis of calls from multiple monkeys revealed that family members use similar calls and acoustic features to label others and perform vocal learning. These findings shed light on the complexities of social vocalizations among nonhuman primates and suggest that marmoset vocalizations may provide a model for understanding aspects of human language, thereby offering new insights into the evolution of social communication.
{"title":"Vocal labeling of others by nonhuman primates","authors":"Guy Oren, Aner Shapira, Reuven Lifshitz, Ehud Vinepinsky, Roni Cohen, Tomer Fried, Guy P. Hadad, David Omer","doi":"10.1126/science.adp3757","DOIUrl":"10.1126/science.adp3757","url":null,"abstract":"<div >Humans, dolphins, and elephants are the only known species that vocally label their conspecifics. It remains unclear whether nonhuman primates share this ability. We recorded spontaneous “phee-call” dialogues between pairs of marmoset monkeys. We discovered that marmosets use these calls to vocally label their conspecifics. Moreover, they respond more consistently and correctly to calls that are specifically directed at them. Analysis of calls from multiple monkeys revealed that family members use similar calls and acoustic features to label others and perform vocal learning. These findings shed light on the complexities of social vocalizations among nonhuman primates and suggest that marmoset vocalizations may provide a model for understanding aspects of human language, thereby offering new insights into the evolution of social communication.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Errors in chromosome segregation during cell division (mitosis) can lead to chromosomal instability, a hallmark of human cancer. These mitotic errors give rise to the formation of micronuclei—small cytoplasmic structures that are spatially separated from the primary nucleus and contain lagging chromosomes or chromosome fragments. Unlike the primary nucleus of a cell, micronuclei frequently undergo irreparable rupture and collapse. This breakdown releases micronuclear DNA into the cytosol, causing DNA damage, chromosomal rearrangements, and genomic instability, thereby contributing to cancer progression. The rupture of micronuclei also activates a component of the innate immune system called the cyclic guanosine monophosphate–adenosine monophosphate synthase (cGAS)–stimulator of interferon genes (STING) pathway, leading to tumorrelated inflammation and metastasis (1). On pages 951 and 952 of this issue, Di Bona et al. (2) and Martin et al. (3), respectively, report the molecular underpinnings of micronuclear collapse.
细胞分裂（有丝分裂）过程中的染色体分离错误会导致染色体不稳定，这是人类癌症的一个特征。这些有丝分裂错误会形成微核--与原核在空间上分离的小细胞质结构，其中含有滞后染色体或染色体片段。与细胞的原核不同，微核经常发生不可修复的破裂和崩溃。这种破裂会将微核 DNA 释放到细胞质中，造成 DNA 损伤、染色体重排和基因组不稳定，从而导致癌症进展。微核的破裂还会激活先天性免疫系统的一个组成部分，即环鸟苷单磷酸-腺苷单磷酸合成酶（cGAS）-干扰素基因刺激器（STING）通路，导致与肿瘤相关的炎症和转移（1）。在本期第 951 页和第 952 页，Di Bona 等人（2）和 Martin 等人（3）分别报告了微核塌缩的分子基础。
{"title":"Micronuclear collapse mechanisms in cancer","authors":"Marianna Maddaluno, Carmine Settembre","doi":"10.1126/science.adr7417","DOIUrl":"10.1126/science.adr7417","url":null,"abstract":"<div >Errors in chromosome segregation during cell division (mitosis) can lead to chromosomal instability, a hallmark of human cancer. These mitotic errors give rise to the formation of micronuclei—small cytoplasmic structures that are spatially separated from the primary nucleus and contain lagging chromosomes or chromosome fragments. Unlike the primary nucleus of a cell, micronuclei frequently undergo irreparable rupture and collapse. This breakdown releases micronuclear DNA into the cytosol, causing DNA damage, chromosomal rearrangements, and genomic instability, thereby contributing to cancer progression. The rupture of micronuclei also activates a component of the innate immune system called the cyclic guanosine monophosphate–adenosine monophosphate synthase (cGAS)–stimulator of interferon genes (STING) pathway, leading to tumorrelated inflammation and metastasis (<i>1</i>). On pages 951 and 952 of this issue, Di Bona <i>et al</i>. (<i>2</i>) and Martin <i>et al</i>. (<i>3</i>), respectively, report the molecular underpinnings of micronuclear collapse.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Akash Koppa, Jessica Keune, Dominik L. Schumacher, Katerina Michaelides, Michael Singer, Sonia I. Seneviratne, Diego G. Miralles
Dryland expansion causes widespread water scarcity and biodiversity loss. Although the drying influence of global warming is well established, the role of existing drylands in their own expansion is relatively unknown. In this work, by tracking the air flowing over drylands, we show that the warming and drying of that air contributes to dryland expansion in the downwind direction. As they dry, drylands contribute less moisture and more heat to downwind humid regions, reducing precipitation and increasing atmospheric water demand, which ultimately causes their aridification. In ~40% of the land area that recently transitioned from a humid region into a dryland, self-expansion accounted for >50% of the observed aridification. Our results corroborate the urgent need for climate change mitigation measures in drylands to decelerate their own expansion.
{"title":"Dryland self-expansion enabled by land–atmosphere feedbacks","authors":"Akash Koppa, Jessica Keune, Dominik L. Schumacher, Katerina Michaelides, Michael Singer, Sonia I. Seneviratne, Diego G. Miralles","doi":"10.1126/science.adn6833","DOIUrl":"10.1126/science.adn6833","url":null,"abstract":"<div >Dryland expansion causes widespread water scarcity and biodiversity loss. Although the drying influence of global warming is well established, the role of existing drylands in their own expansion is relatively unknown. In this work, by tracking the air flowing over drylands, we show that the warming and drying of that air contributes to dryland expansion in the downwind direction. As they dry, drylands contribute less moisture and more heat to downwind humid regions, reducing precipitation and increasing atmospheric water demand, which ultimately causes their aridification. In ~40% of the land area that recently transitioned from a humid region into a dryland, self-expansion accounted for >50% of the observed aridification. Our results corroborate the urgent need for climate change mitigation measures in drylands to decelerate their own expansion.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Caihao Qiu, Maik Punke, Yuan Tian, Ying Han, Siqi Wang, Yishi Su, Marco Salvalaglio, Xiaoqing Pan, David J. Srolovitz, Jian Han
We demonstrate that grain boundaries (GBs) behave as Brownian ratchets, exhibiting direction-dependent mobilities and unidirectional motion under oscillatory driving forces or cyclic thermal annealing. We observed these phenomena for nearly all nonsymmetric GBs but not for symmetric ones. Our observations build on molecular dynamics and phase-field crystal simulations for a wide range of GB types and driving forces in both bicrystal and polycrystalline microstructures. We corroborate these simulation results through in situ experimental observations. We analyze these results with a Markov chain model and explore the implications of GB ratchet behavior for materials processing and microstructure tailoring.
{"title":"Grain boundaries are Brownian ratchets","authors":"Caihao Qiu, Maik Punke, Yuan Tian, Ying Han, Siqi Wang, Yishi Su, Marco Salvalaglio, Xiaoqing Pan, David J. Srolovitz, Jian Han","doi":"10.1126/science.adp1516","DOIUrl":"10.1126/science.adp1516","url":null,"abstract":"<div >We demonstrate that grain boundaries (GBs) behave as Brownian ratchets, exhibiting direction-dependent mobilities and unidirectional motion under oscillatory driving forces or cyclic thermal annealing. We observed these phenomena for nearly all nonsymmetric GBs but not for symmetric ones. Our observations build on molecular dynamics and phase-field crystal simulations for a wide range of GB types and driving forces in both bicrystal and polycrystalline microstructures. We corroborate these simulation results through in situ experimental observations. We analyze these results with a Markov chain model and explore the implications of GB ratchet behavior for materials processing and microstructure tailoring.</div>","PeriodicalId":21678,"journal":{"name":"Science","volume":null,"pages":null},"PeriodicalIF":44.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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