94 research outputs found
Microcodium in Chinese loess as a recorder for the oxygen isotopic composition of monsoonal rainwater
Records of Asia Summer Monsoon (ASM) from the Chinese loess and the speleothem display distinct features. The very different proxies that were applied to the two archives may be responsible for this discrepancy. A direct comparison between the speleothem and the loess records under the same proxy system of rainwater delta O-18 may help to resolve this puzzle. Here we show that the calcified microcodium in the loess deposits may record the oxygen isotopic composition of the summer rainwater. A microcodium based delta O-18 record covering the past 140 kyrs was generated, which shows similar magnitude of the overall variation to that of the speleothem records. However, much weaker precession variability was registered in the microcodium record during the last interglacial period. Instead, the microcodium delta O-18 record is more consistent with the widely used summer monsoon proxy of magnetic susceptibility in the loess deposits with clear glacial-interglacial pattern. This similarity may originate from the low sedimentation rate of the interglacial paleosol layer that preferentially record the peak ASM signals on the precession band. It is also possible that the orbital variability of ASM between the North China and South China is inherently different with more ice-volume related influence in the north. A longer microcodium delta O-18 record in sequences of higher sedimentation rate and a reliable record of summer rainfall may help to resolve these possibilities. (C) 2017 Elsevier Ltd and INQUA. All rights reserved
Accelerating Generalized Linear Models with MLWeaving: A One-Size-Fits-All System for Any-precision Learning (Technical Report)
Learning from the data stored in a database is an important function
increasingly available in relational engines. Methods using lower precision
input data are of special interest given their overall higher efficiency but,
in databases, these methods have a hidden cost: the quantization of the real
value into a smaller number is an expensive step. To address the issue, in this
paper we present MLWeaving, a data structure and hardware acceleration
technique intended to speed up learning of generalized linear models in
databases. ML-Weaving provides a compact, in-memory representation enabling the
retrieval of data at any level of precision. MLWeaving also takes advantage of
the increasing availability of FPGA-based accelerators to provide a highly
efficient implementation of stochastic gradient descent. The solution adopted
in MLWeaving is more efficient than existing designs in terms of space (since
it can process any resolution on the same design) and resources (via the use of
bit-serial multipliers). MLWeaving also enables the runtime tuning of
precision, instead of a fixed precision level during the training. We
illustrate this using a simple, dynamic precision schedule. Experimental
results show MLWeaving achieves up to16 performance improvement over
low-precision CPU implementations of first-order methods.Comment: 18 page
Adai: Separating the Effects of Adaptive Learning Rate and Momentum Inertia
Adaptive Momentum Estimation (Adam), which combines Adaptive Learning Rate
and Momentum, is the most popular stochastic optimizer for accelerating the
training of deep neural networks. However, empirically Adam often generalizes
worse than Stochastic Gradient Descent (SGD). We unveil the mystery of this
behavior based on the diffusion theoretical framework. Specifically, we
disentangle the effects of Adaptive Learning Rate and Momentum of the Adam
dynamics on saddle-point escaping and minima selection. We prove that Adaptive
Learning Rate can escape saddle points efficiently, but cannot select flat
minima as SGD does. In contrast, Momentum provides a drift effect to help the
training process pass through saddle points, and almost does not affect flat
minima selection. This theoretically explains why SGD (with Momentum)
generalizes better, while Adam generalizes worse but converges faster.
Furthermore, motivated by the analysis, we design a novel adaptive optimization
framework named Adaptive Inertia, which uses parameter-wise adaptive inertia to
accelerate the training and provably favors flat minima as well as SGD. Our
extensive experiments demonstrate that the proposed adaptive inertia method can
generalize significantly better than SGD and conventional adaptive gradient
methods.Comment: 28 pages, 11 figures, Adam, Adaptive Inerti
HSC-GPT: A Large Language Model for Human Settlements Construction
The field of human settlement construction encompasses a range of spatial
designs and management tasks, including urban planning and landscape
architecture design. These tasks involve a plethora of instructions and
descriptions presented in natural language, which are essential for
understanding design requirements and producing effective design solutions.
Recent research has sought to integrate natural language processing (NLP) and
generative artificial intelligence (AI) into human settlement construction
tasks. Due to the efficient processing and analysis capabilities of AI with
data, significant successes have been achieved in design within this domain.
However, this task still faces several fundamental challenges. The semantic
information involved includes complex spatial details, diverse data source
formats, high sensitivity to regional culture, and demanding requirements for
innovation and rigor in work scenarios. These factors lead to limitations when
applying general generative AI in this field, further exacerbated by a lack of
high-quality data for model training. To address these challenges, this paper
first proposes HSC-GPT, a large-scale language model framework specifically
designed for tasks in human settlement construction, considering the unique
characteristics of this domain
Recommended from our members
An Excitatory Circuit in the Perioculomotor Midbrain for Non-REM Sleep Control.
The perioculomotor (pIII) region of the midbrain was postulated as a sleep-regulating center in the 1890s but largely neglected in subsequent studies. Using activity-dependent labeling and gene expression profiling, we identified pIII neurons that promote non-rapid eye movement (NREM) sleep. Optrode recording showed that pIII glutamatergic neurons expressing calcitonin gene-related peptide alpha (CALCA) are NREM-sleep active; optogenetic and chemogenetic activation/inactivation showed that they strongly promote NREM sleep. Within the pIII region, CALCA neurons form reciprocal connections with another population of glutamatergic neurons that express the peptide cholecystokinin (CCK). Activation of CCK neurons also promoted NREM sleep. Both CALCA and CCK neurons project rostrally to the preoptic hypothalamus, whereas CALCA neurons also project caudally to the posterior ventromedial medulla. Activation of each projection increased NREM sleep. Together, these findings point to the pIII region as an excitatory sleep center where different subsets of glutamatergic neurons promote NREM sleep through both local reciprocal connections and long-range projections
Structural Mechanism for the Specific Assembly and Activation of the Extracellular Signal Regulated Kinase 5 (ERK5) Module
Mitogen-activated protein kinase (MAPK) activation depends on a linear binding motif found in all MAPK kinases (MKK). In addition, the PB1 (Phox and Bem1) domain of MKK5 is required for extracellular signal regulated kinase 5 (ERK5) activation. We present the crystal structure of ERK5 in complex with an MKK5 construct comprised of the PB1 domain and the linear binding motif. We show that ERK5 has distinct protein-protein interaction surfaces compared with ERK2, which is the closest ERK5 paralog. The two MAPKs have characteristically different physiological functions and their distinct protein-protein interaction surface topography enables them to bind different sets of activators and substrates. Structural and biochemical characterization revealed that the MKK5 PB1 domain cooperates with the MAPK binding linear motif to achieve substrate specific binding, and it also enables co-recruitment of the upstream activating enzyme and the downstream substrate into one signaling competent complex. Studies on present day MAPKs and MKKs hint on the way protein kinase networks may evolve. In particular, they suggest how paralogous enzymes with similar catalytic properties could acquire novel signaling roles by merely changing the way they make physical links to other proteins
Scaffold-mediated Nucleation of Protein Signaling Complexes: Elementary Principles
Proteins with multiple binding sites play important roles in cell signaling
systems by nucleating protein complexes in which, for example, enzymes and
substrates are co-localized. Proteins that specialize in this function are
called by a variety names, including adapter, linker and scaffold.
Scaffold-mediated nucleation of protein complexes can be either constitutive or
induced. Induced nucleation is commonly mediated by a docking site on a
scaffold that is activated by phosphorylation. Here, by considering minimalist
mathematical models, which recapitulate scaffold effects seen in more
mechanistically detailed models, we obtain analytical and numerical results
that provide insights into scaffold function. These results elucidate how
recruitment of a pair of ligands to a scaffold depends on the concentrations of
the ligands, on the binding constants for ligand-scaffold interactions, on
binding cooperativity, and on the milieu of the scaffold, as ligand recruitment
is affected by competitive ligands and decoy receptors. For the case of a
bivalent scaffold, we obtain an expression for the unique scaffold
concentration that maximally recruits a pair of monovalent ligands. Through
simulations, we demonstrate that a bivalent scaffold can nucleate distinct sets
of ligands to equivalent extents when the scaffold is present at different
concentrations. Thus, the function of a scaffold can potentially change
qualitatively with a change in copy number. We also demonstrate how a scaffold
can change the catalytic efficiency of an enzyme and the sensitivity of the
rate of reaction to substrate concentration. The results presented here should
be useful for understanding scaffold function and for engineering scaffolds to
have desired properties.Comment: 12 pages, 8 figure
Decoupled Land and Ocean Temperature Trends in the Early-Middle Pleistocene
Record of long-term land temperature changes remains ephemeral, discontinuous, and isolated, thus leaving the common view that Pleistocene land temperature evolution should have followed ocean temperatures unconfirmed. Here, we present a continuous land surface temperature reconstruction in the Asian monsoon region over the past 3.0 Myr based on the distribution of soil bacterial lipids from the Chinese Loess Plateau. The land temperature record indicates an unexpected warming trend over the Pleistocene, which is opposite to the cooling trend in Pleistocene ocean temperatures, resulting in increased land-sea thermal contrast. We propose that the previously unrecognized increase of land-sea thermal contrast during much of the Pleistocene is a regional climate phenomenon that provides a likely mechanism in favor of the long-term enhancement of the Pleistocene East Asian summer monsoon
- âŠ