Gross, T. , , Raphaël , , Ochoa, -, Maire, Hugo Saiz, , David J. , , Jabot, , Juan J. Gaitán, García-Gómez, Martínez, Jaime Martínez-, Betty J. , -Jiménez, David S. , César Plaza, Yoann Le -
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summary:
The Earth has extraordinary plant phenotype diversity but is threatened by ongoing global changes. However, it is unclear how the increasing drought and livestock grazing pressures—two major drivers of global change—shape trait covariance based on plant phenotypic diversity. The researchers evaluated the response of covariation of 20 chemical and morphological characteristics to drought and grazing stress in arid regions around the world.
Their analysis involved trait measurements of 301 perennial species surveyed on 326 plots on 6 continents and 1347 observations. Oversight of the drought threshold of about 0.7 (close to the transition between semi-arid and arid areas) resulted in an unexpected increase in trait diversity by 88%. This threshold occurs in the presence of grazing animals and moves towards lower drought levels as grazing pressure increases.
Furthermore, 57% of the observed trait diversity occurs only in the driest and grazing dry lands, highlighting the phenotypic uniqueness of these extreme environments. Research shows that drylands are a global reservoir of plant phenotype diversity, challenging the general view that harsh environmental conditions reduce plant trait diversity. They also stressed that many alternative strategies may enable plants to cope with increased environmental stress caused by climate change and land use intensification.
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Earth an plant that is at risk from . , it how and —two major of —shape the trait that plant . Here we how among 20 and to and . Our 133,769 trait 1,347 of 301 plant 326 plots from 6 . an of 0.7 (close to the semi-arid and arid zones) led to an 88% in trait . This in the of , and moved lower with . , 57% of trait only in the most arid and , the of these . Our work that act as a of plant and the view that harsh plant trait . They also that many may to cope with in by and land-use .
Low- and
The nutrient cycle in the upper and lower latitudes controls productivity and exports
Author: Keith B. , , Laure , Masao Ishii, , &
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summary:
Low-latitude oceans (LLs) account for half of the global net primary production and exports. Research believes that the Southern Ocean dominates primary marine production and exports, which is inspiring for the global primary production and export response to climate change. The new study conducted observational analysis and sensitivity studies on individual models, and the results showed that 72% of primary LL production and 55% of exports were controlled by local middle and upper macronutrient cycles.
Overall, 34% of the LL output is maintained by preformed large amounts of nutrients provided by the Southern Ocean, which are provided by deeper tilts, while shallow preformed supply northward, through 30 degrees south latitude, through subpoles and thermoclip water masses, maintaining only 7% of the LL output.
Analysis of the five coupled modes operating in the climate scenarios of high emission low mitigation [Shared Socio-Economic Path (SSP5-8.5)] and low emission high mitigation (SSP1-2.6) comparative project phase 6 (CMIP6) patterns showed that their estimates of primary LL production differed significantly not only in amplitude but also in markings.
Under stronger SSP5-8.5 forcing, as the upper ocean warms more pronounced, the CMIP6 model that takes into account temperature-dependent remineralization promotes enhanced nutrient retention in the middle and upper LL under the warming conditions, which provides a first-tier contribution to LL yield under stable or increased (rather than reduced) high emissions and low mitigation conditions. This highlights the importance of understanding of the mechanistic remineralization of the COSCO and its sensitivity to ocean warming in predicting future ecosystem changes.
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Low- (LL) for up to half of net and . It has been that the Ocean LL and , with for the of and to . Here we and to an model to show, , that 72% of LL and 55% of is by local . A total of 34% of the LL is by from the Ocean via a cell, with a , 30° S and water , only 7% of the LL . of five Model Phase 6 (CMIP6) , run under both high- low- ( (SSP5-8.5)) and low- high- (SSP1-2.6) for 1850–2300, -model in their of not only the , but also the sign, of LL . Under the SSP5-8.5 , with more upper-ocean , the CMIP6 that for - LL under , with this a first-order to or , than , LL under high and low . This the of a of and its to ocean for .
Chemical
The of to
Catalyzed by asymmetric polyene cyclization to produce ammonium bromide
Author: Na Luo, , , , , Vijay N. , Nils Nö, , Ralf & List
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Polyene cyclization is one of the most complex and challenging transformations in biology. In one reaction step, multiple carbon-carbon bonds, ring systems and stereocenter consist of simple acyclic precursors. To achieve this precise control of product distribution and stereochemistry simultaneously is a difficult task for chemists.
In particular, cyclization of (3E,7E)-isoform aromatic alcohol polyenes into naturally occurring valuable cypress aroma agents (−)-Corresolution ether is considered a long-standing challenge in chemical synthesis.
The researchers reported the diastereoelective and enantioselectiveness of (−)-Zanlongephthalene and sesquiterpene lactone natural product (+)-Canthalene perilla lactone by catalyzing asymmetric polyene cyclization in the presence of fluorinated alcohols.
Several experiments, including deuterium labeling studies, show that the reaction is performed primarily through a pathway consistent with the Stork-hypothesis. Mechanism studies have shown that the enzyme-like microenvironment of imidamine diphosphorylation catalysts is of great significance to obtain abnormally high selectivity, and it was previously believed that it can only be achieved in enzyme-catalyzed polyene cyclization.
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are among the most and in . In a step, – bonds, ring and are from , . this kind of over and poses a task for . In , the of (3E,7E)- to the (−)- is as a in . Here we a and of (−)- and the (+)- by a by using a Brønsted- and te in the of . , - , that the a in line with the Stork– . show the of the -like of the te for high , to be only in - .
AI
Loss of in deep
Losing plasticity in deep continuous learning
Author: , J. -, Lan, , A. Rupam & S.
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summary:
Artificial neural networks, deep learning methods and backpropagation algorithms form the basis of modern machine learning and artificial intelligence. These methods are almost always used in two phases, one is to update the weights of the network and the other is to keep the weights unchanged when using or evaluating the network. This contrasts with natural learning and many applications that require continuous learning.
It is not clear whether deep learning methods are effective in continuous learning environments. Researchers have shown that they are not the case—standard deep learning methods gradually lose plasticity in a continuous learning environment until they learn less than shallow networks.
Researchers use classical datasets and broadly changing reinforcement learning problems across networks and learning algorithms to show this loss of plasticity. Plasticity can only be maintained indefinitely by continuously injecting diversity into the network, such as the continuous backpropagation algorithm, a variant of backpropagation where a small number of less-used units are constantly reinitialized at random.
The results show that gradient descent-based approaches are not enough—continuous deep learning requires a random, non-gradient component to maintain variability and plasticity.
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, deep- and the form the of and . These are used in two , one in which the are and one in which the are held while the is used or . This with and many , which . It has been or not deep work in . Here we show that they do not—that deep- loss in - until they learn no than a . We show such loss of using the and - a wide range of in the and the . is only by that into the , such as our , a of in which a small of less-used units are and . Our that based on are not —that deep a , non- to and .
