GSTDTAP

浏览/检索结果: 共5条,第1-5条 帮助

已选(0)清除 条数/页:   排序方式:
Learning from generations of sustainability concepts* 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2020, 15 (8)
作者:  Downing, Andrea S.;  Chang, Manqi;  Kuiper, Jan J.;  Campenni, Marco;  Haeyhae, Tiina;  Cornell, Sarah E.;  Svedin, Uno;  Mooij, Wolf
收藏  |  浏览/下载:36/0  |  提交时间:2020/08/18
planetary boundaries concept  sustainable development  safe operating space  cassandra'  s dilemma  consumer-resource model  resource-consumer-producer-waste model  
Structure of nevanimibe-bound tetrameric human ACAT1 期刊论文
NATURE, 2020, 581 (7808) : 339-U214
作者:  Ma, Xiyu;  Claus, Lucas A. N.;  Leslie, Michelle E.;  Tao, Kai;  Wu, Zhiping;  Liu, Jun;  Yu, Xiao;  Li, Bo;  Zhou, Jinggeng;  Savatin, Daniel V.;  Peng, Junmin;  Tyler, Brett M.;  Heese, Antje;  Russinova, Eugenia;  He, Ping;  Shan, Libo
收藏  |  浏览/下载:55/0  |  提交时间:2020/07/03

The structure of human ACAT1 in complex with the inhibitor nevanimibe is resolved by cryo-electron microscopy.


Cholesterol is an essential component of mammalian cell membranes, constituting up to 50% of plasma membrane lipids. By contrast, it accounts for only 5% of lipids in the endoplasmic reticulum (ER)(1). The ER enzyme sterol O-acyltransferase 1 (also named acyl-coenzyme A:cholesterol acyltransferase, ACAT1) transfers a long-chain fatty acid to cholesterol to form cholesteryl esters that coalesce into cytosolic lipid droplets. Under conditions of cholesterol overload, ACAT1 maintains the low cholesterol concentration of the ER and thereby has an essential role in cholesterol homeostasis(2,3). ACAT1 has also been implicated in Alzheimer'  s disease(4), atherosclerosis(5) and cancers(6). Here we report a cryo-electron microscopy structure of human ACAT1 in complex with nevanimibe(7), an inhibitor that is in clinical trials for the treatment of congenital adrenal hyperplasia. The ACAT1 holoenzyme is a tetramer that consists of two homodimers. Each monomer contains nine transmembrane helices (TMs), six of which (TM4-TM9) form a cavity that accommodates nevanimibe and an endogenous acyl-coenzyme A. This cavity also contains a histidine that has previously been identified as essential for catalytic activity(8). Our structural data and biochemical analyses provide a physical model to explain the process of cholesterol esterification, as well as details of the interaction between nevanimibe and ACAT1, which may help to accelerate the development of ACAT1 inhibitors to treat related diseases.


  
Investigation of the fine structure of antihydrogen 期刊论文
NATURE, 2020, 578 (7795) : 375-+
作者:  Zhang, Bing;  Ma, Sai;  Rachmin, Inbal;  He, Megan;  Baral, Pankaj;  Choi, Sekyu;  Goncalves, William A.;  Shwartz, Yulia;  Fast, Eva M.;  Su, Yiqun;  Zon, Leonard I.;  Regev, Aviv;  Buenrostro, Jason D.;  Cunha, Thiago M.;  Chiu, Isaac M.;  Fisher, David E.;  Hsu, Ya-Chieh
收藏  |  浏览/下载:64/0  |  提交时间:2020/07/03

At the historic Shelter Island Conference on the Foundations of Quantum Mechanics in 1947, Willis Lamb reported an unexpected feature in the fine structure of atomic hydrogen: a separation of the 2S(1/2) and 2P(1/2) states(1). The observation of this separation, now known as the Lamb shift, marked an important event in the evolution of modern physics, inspiring others to develop the theory of quantum electrodynamics(2-5). Quantum electrodynamics also describes antimatter, but it has only recently become possible to synthesize and trap atomic antimatter to probe its structure. Mirroring the historical development of quantum atomic physics in the twentieth century, modern measurements on anti-atoms represent a unique approach for testing quantum electrodynamics and the foundational symmetries of the standard model. Here we report measurements of the fine structure in the n = 2 states of antihydrogen, the antimatter counterpart of the hydrogen atom. Using optical excitation of the 1S-2P Lyman-alpha transitions in antihydrogen(6), we determine their frequencies in a magnetic field of 1 tesla to a precision of 16 parts per billion. Assuming the standard Zeeman and hyperfine interactions, we infer the zero-field fine-structure splitting (2P(1/2)-2P(3/2)) in antihydrogen. The resulting value is consistent with the predictions of quantum electrodynamics to a precision of 2 per cent. Using our previously measured value of the 1S-2S transition frequency(6,7), we find that the classic Lamb shift in antihydrogen (2S(1/2)-2P(1/2) splitting at zero field) is consistent with theory at a level of 11 per cent. Our observations represent an important step towards precision measurements of the fine structure and the Lamb shift in the antihydrogen spectrum as tests of the charge-parity-time symmetry(8) and towards the determination of other fundamental quantities, such as the antiproton charge radius(9,10), in this antimatter system.


Precision measurements of the 1S-2P transition in antihydrogen that take into account the standard Zeeman and hyperfine effects confirm the predictions of quantum electrodynamics.


  
Projecting the energy pathway using a methodological sequence: The case of Mexico 期刊论文
ENERGY POLICY, 2019, 135
作者:  Livas-Garcia, A.;  Bonilla, D.;  Escalante Soberanis, M. A.;  Bassam, A.
收藏  |  浏览/下载:30/0  |  提交时间:2020/02/17
State'  s model development  Energy growth  Energy consumption  Government policies  Energy sustainability  
A Historical Evaluation of the U15 Complex, Nevada National Security Site, Nye County, Nevada 科技报告
来源:US Department of Energy (DOE). 出版年: 2014
作者:  Drollinger, Harold;  Holz, Barbara A;  Bullard, Thomas F;  Goldenberg, Nancy G;  Ashbaugh, Laurence J;  Griffin, Wayne R
收藏  |  浏览/下载:25/0  |  提交时间:2019/04/05
This report presents a historical evaluation of the U15 Complex on the Nevada National Security Site (NNSS) in southern Nevada. The work was conducted by the Desert Research Institute at the request of the U.S. Department of Energy  National Nuclear Security Administration Nevada Field Office and the U.S. Department of Defense  Defense Threat Reduction Agency. Three underground nuclear tests and two underground nuclear fuel storage experiments were conducted at the complex. The nuclear tests were Hard Hat in 1962  Tiny Tot in 1965  and Pile Driver in 1966. The Hard Hat and Pile Driver nuclear tests involved different types of experiment sections in test drifts at various distances from the explosion in order to determine which sections could best survive in order to design underground command centers. The Tiny Tot nuclear test involved an underground cavity in which the nuclear test was executed. It also provided data in designing underground structures and facilities to withstand a nuclear attack. The underground nuclear fuel storage experiments were Heater Test 1 from 1977 to 1978 and Spent Fuel Test - Climax from 1978 to 1985. Heater Test 1 was used to design the later Spent Fuel Test - Climax experiment. The latter experiment was a model of a larger underground storage facility and primarily involved recording the conditions of the spent fuel and the surrounding granite medium. Fieldwork was performed intermittently in the summers of 2011 and 2013  totaling 17 days. Access to the underground tunnel complex is sealed and unavailable. Restricted to the surface  four buildings  four structures  and 92 features associated with nuclear testing and fuel storage experiment activities at the U15 Complex have been recorded. Most of these are along the west side of the complex and next to the primary access road and are characteristic of an industrial mining site  albeit one with scientific interests. The geomorphological fieldwork was conducted over three days in the summer of 2011. It was discovered that major modifications to the terrain have resulted from four principal activities. These are road construction and maintenance  mining activities related to development of the tunnel complex  site preparation for activities related to the tests and experiments  and construction of drill pads and retention ponds. Six large trenches for exploring across the Boundary geologic fault are also present. The U15 Complex  designated historic district 143 and site 26NY15177  is eligible to the National Register of Historic Places under Criteria A  C  and D of 36 CFR Part 60.4. As a historic district and archaeological site eligible to the National Register of Historic Places  the Desert Research Institute recommends that the area defined for the U15 Complex  historic district 143 and site 26NY15117  be left in place in its current condition. The U15 Complex should also be included in the NNSS cultural resources monitoring program and monitored for disturbances or alterations.