A2A^2Nav: Action-Aware Zero-Shot Robot Navigation by Exploiting Vision-and-Language Ability of Foundation Models

We study the task of zero-shot vision-and-language navigation (ZS-VLN), a practical yet challenging problem in which an agent learns to navigate following a path described by language instructions without requiring any path-instruction annotation data. Normally, the instructions have complex grammatical structures and often contain various action descriptions (e.g., "proceed beyond", "depart from"). How to correctly understand and execute these action demands is a critical problem, and the absence of annotated data makes it even more challenging. Note that a well-educated human being can easily understand path instructions without the need for any special training. In this paper, we propose an action-aware zero-shot VLN method ($A^2$Nav) by exploiting the vision-and-language ability of foundation models. Specifically, the proposed method consists of an instruction parser and an action-aware navigation policy. The instruction parser utilizes the advanced reasoning ability of large language models (e.g., GPT-3) to decompose complex navigation instructions into a sequence of action-specific object navigation sub-tasks. Each sub-task requires the agent to localize the object and navigate to a specific goal position according to the associated action demand. To accomplish these sub-tasks, an action-aware navigation policy is learned from freely collected action-specific datasets that reveal distinct characteristics of each action demand. We use the learned navigation policy for executing sub-tasks sequentially to follow the navigation instruction. Extensive experiments show $A^2$Nav achieves promising ZS-VLN performance and even surpasses the supervised learning methods on R2R-Habitat and RxR-Habitat datasets

EphB2 Deficiency Induces Depression-Like Behaviors and Memory Impairment: Involvement of NMDA 2B Receptor Dependent Signaling

Receptor tyrosine kinase EphB2 mediates development of the neurogenic niche of excitatory neurons, suggesting the possibility that its inactivation plays a role in neuropsychiatric disorders including depression and memory impairment. While N-methyl-D-aspartate (NMDA) receptor is involved in regulating memory formation and neurogenesis in adult animal, it remains unclear how NMDA receptor subtypes mediate depression and cognitive deficits caused by EphB2 loss. The present study shows that EphB2 inactivation results in depression-like behaviors, memory impairment and defects of adult hippocampal neurogenesis. Compared to wild-type littermates, EphB2 KO mice exhibited depression-like behavior and deficits in spatial memory and cognition in forced swimming, tail suspension, Morris water maze, object recognition test and object location test. These behavioral abnormalities were accompanied by substantial decreases in the number of BrdU+ progenitor neurons, phosphorylation of cAMP-response element binding protein (pCREB) and brain derived neurotrophic factor (BDNF), and increased NMDA receptor 2B (NR2B) expression. These molecular, cellular and behavioral alterations induced by EphB2 inactivation were reversed by NR2B antagonist Ro25-6981, suggesting that EphB2 functions to prevent the progression of depression-like behavior and memory impairment by downregulating NR2B. Our findings highlight that NR2B is responsible for EphB2-dependent behavioral and morphological changes. EphB2 may thus be as an important candidate target for treating psychiatric and cognitive disorders

Myristate and the ecology of AM fungi : significance, opportunities, applications and challenges

A recent study by Sugiura and coworkers reported the nonsymbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology

Experimental investigation on the surface humidity of fabric during the process of dynamic moisture liberation

Purpose: In this study, a novel dynamic testing method was established to measure the moisture variation of fabric surface during the process of moisture liberation in simulated windy condition. The paper aims to discuss these issues Design/methodology/approach: In this method, the samples were rotating during the test process so as to simulate the external windy environment. Effects of simulated wind speed, moisture regains and fabric materials on the surface moisture of fabric were investigated. Findings: Experimental results showed that the surface moisture presented a trapezoidal moisture liberation curve, it increased at first, then kept stable for a while, and decreased finally with the increase of time. It took longer time for the fabric to complete the liberation process when the moisture regain of the fabric increased or the simulated wind speed decreased. The fiber materials of the fabric affected the time for the moisture liberation process under a specific windy condition. Practical implications: This study will benefit the designing and development of clothing such as sportswear. Originality/value: A dynamic testing method was proposed to characterize the surface humidity of textiles under simulated windy conditions

A potential way for improving the dispersivity and mechanical properties of dispersive soil using calcined coal gangue

This paper investigated the improvement behaviors on dispersivity, water stability and mechanical properties of dispersive soil by calcined coal gangue (CCG) at 700 °C, and analyzed the modification mechanism. Dispersive soil specimens with different content of CCG (varying from 1 % to 10 %) were prepared and cured for 0–28 days. The dispersivity of the soil was determined by three different dispersivity determination tests. The tensile strength and compressive strength of the dispersive soil were determined by mechanical property tests. SEM, EDS, TG and XRD analytical methods were employed to reveal microstructure and mineral changes during modification. The results of the study show that the admixture of CCG and the prolongation of curing time contributed favorably to suppressing the dispersivity of the soil and enhancing the water stability, the compressive strength and tensile strength of the dispersive soil. With the increasing of CCG content and the prolongation of curing time, the dispersive soil gradually transforms into non-dispersive soil. Microstructural and mineral analysis indicate that CCG has pozzolanic activity, and the production of pozzolanic reaction products significantly increase the friction and cohesion among soil particles. The results show that the utilization of CCG as an admixture to improve the dispersive soil not only solves the disposal problem of waste gangue, but also optimizes the undesirable characteristics of the dispersive soil. And the modification effect of CCG on dispersive soil in practical engineering is confirmed by validation test

Changing of mechanical property and bearing capacity of strongly chlorine saline soil under freeze-thaw cycles

Abstract Freeze-thaw cycles and compactness are two critical factors that significantly affect the engineering properties and safety of building foundations, especially in seasonally frozen regions. This paper investigated the effects of freeze-thaw cycles on the shear strength of naturally strongly chlorine saline soil with the compactness of 85%, 90% and 95%. Three soil samples with different compactness were made. Size and mass changes were measured and recorded during freeze-thaw cycles. Shear strength under different vertical pressures was determined by direct shear tests, and the cohesion and friction angle were measured and discussed. Microstructure characteristic changes of saline soil samples were observed using scanning electron microscopy under different freeze-thaw cycles. Furthermore, numerical software was used to calculate the subsoil-bearing capacity and settlement of the electric tower foundation in the Qarhan Salt Lake region under different freeze-thaw cycles. Results show that the low-density soil shows thaw settlement deformation, but the high-density soil shows frost-heaving deformation with the increase in freeze-thaw cycles. The shear strength of the soil samples first increases and then decreases with the increase in freeze-thaw cycles. After 30 freeze-thaw cycles, the friction angle of soil samples is 28.3%, 29.2% and 29.6% lower than the soil samples without freeze-thaw cycle, the cohesion of soil samples is 71.4%, 60.1% and 54.4% lower than the samples without freeze-thaw cycle, and the cohesion and friction angle of soil samples with different compactness are close to each other. Microstructural changes indicate that the freeze-thaw cycle leads to the breakage of coarse particles and the aggregation of fine particles. Correspondingly, the structure type of soil changes from a granular stacked structure to a cemented-aggregated system. Besides, the quality loss of soil samples is at about 2% during the freeze-thaw cycles. Results suggest that there may be an optimal compactness between 90 and 95%, on the premise of meeting the design requirements and economic benefits. This study can provide theoretical guidance for foundation engineering constructions in seasonally frozen regions

Photoreductive synthesis of water-soluble fluorescent metal nanoclusters

Water-soluble fluorescent copper, silver and gold nanoclusters with quantum yields of 2.2, 6.8 and 5.3%, respectively, are prepared by a robust photoreduction of their inorganic precursors in the presence of poly (methacrylic acid) functionalized with pentaerythritol tetrakis 3-mercaptopropionate

Periodic desertification of the Northeastern Tibetan Plateau and its implication for the provenance of the Chinese Loess Plateau

Tracing the loess provenance of the Chinese Loess Plateau is fundamental for revealing palaeo-atmospheric circulation patterns and environmental evolution of arid lands in the central Asia. However, there is still no consensus regarding which deserts in central Asia are the dominant sources of Chinese loess and whether the dust provenance has shifted significantly in glacial-interglacial cycles. Loess and aeolian sand deposits are widespread on the Northeastern Tibetan Plateau, which are ideally located in the transitional area between the central Asia deserts and Chinese Loess Plateau. Therefore, their origin and dispersal pattern are important for understanding the wind regimes and dust provenance of Chinese Loess Plateau. Here we present preliminary study of chronological, sedimentological and detrital-zircon U-Pb age results from the aeolian deposits on the Northeastern Tibetan Plateau, and compared them with the detrital-zircon ages of loess and paleosol samples from the western Chinese Loess Plateau. Our results indicate that (1) the Northeastern Tibetan Plateau was occupied by vast sand desert during the last glacial period, and it changed to loess deposits since the early Holocene, suggesting the northeastern Tibetan plateau experienced dramatic environment variations during the last glacial-interglacial cycle. (2) The detrital-zircon age results show that both the aeolian sands and loess deposits from the Northeastern Tibetan Plateau exhibit two major age populations in the ranges of 360-560 Ma and 1100-3000 Ma, which are similar to the local bedrocks, indicating that they mainly derived from the local bedrocks. (3) The detrital-zircon age distribution of the aeolian deposits from the Northeastern Tibetan Plateau is very similar to the loess samples (glacial deposits) from the western Chinese Loess Plateau, but it is significantly different from the paleosol samples (interglacial deposits), suggesting the Northeastern Tibetan Plateau serves as one of the major source areas for the Chinese Loess Plateau during the glacial period. Our results imply that dramatic variations of glacial-interglacial climate during the late Quaternary may have periodically caused the Northeastern Tibetan plateau to become a desert environment serving as a major source area for the Chinese Loess Plateau during glacial intervals. The discovery of this source area improves our understanding of the provenance of the Chinese Loess Plateau, and provides new evidence supporting the view that the provenance of the Chinese Loess plateau is spatially and temporally variable

Urban Scene Diffusion through Semantic Occupancy Map

Generating unbounded 3D scenes is crucial for large-scale scene understanding and simulation. Urban scenes, unlike natural landscapes, consist of various complex man-made objects and structures such as roads, traffic signs, vehicles, and buildings. To create a realistic and detailed urban scene, it is crucial to accurately represent the geometry and semantics of the underlying objects, going beyond their visual appearance. In this work, we propose UrbanDiffusion, a 3D diffusion model that is conditioned on a Bird's-Eye View (BEV) map and generates an urban scene with geometry and semantics in the form of semantic occupancy map. Our model introduces a novel paradigm that learns the data distribution of scene-level structures within a latent space and further enables the expansion of the synthesized scene into an arbitrary scale. After training on real-world driving datasets, our model can generate a wide range of diverse urban scenes given the BEV maps from the held-out set and also generalize to the synthesized maps from a driving simulator. We further demonstrate its application to scene image synthesis with a pretrained image generator as a prior.Comment: The project website is https://metadriverse.github.io/urbandiff

Influence of Ca2+ on Early Degradation of Cast-In-Situ Mortar Induced by Sulfate-Magnesium Multiple Combined Attack

Early degradation of cast-in-situ concrete induced by multiple internal–external sulfate combined attacks significantly affects the development of concrete strength. An experimental study regarding the effects of Ca2+ on the early degradation of cast-in-situ mortars subjected to internal–external sulfate and magnesium combined attacks is investigated in this paper. In particular, a specific method for accurately simulating the degradation of cast-in-situ structures was proposed in this experiment. Physical properties (including weight, size changes, and porosity), mechanical properties (including flexural strength and compressive strength), sulfate concentration, and microstructural properties were monitored during 28 days of immersion. The results show that an internal sulfate and magnesium combined attack (ISA-IMA) obviously retards the development of early strength and accelerates the degradation induced by external sulfate attack (ESA). The diffusion path of sulfate ions from outside is blocked by flake-shaped magnesium hydrates, delaying the penetration of external sulfate attacks. However, it is far from neutralizing the strength loss induced by an internal magnesium attack (IMA) at an early age. Premixed excessive Ca2+ would improve the strength development and pore structure of concrete or mortar, enhancing durability against corrosive conditions