208 research outputs found
Convective meta-thermal concentration for ultrahigh efficient Stirling engine with waste heat and cold utilization
The Stirling engine, which possesses external combustion characteristics, a
simple structure, and high theoretical thermal efficiency, has excellent
potential for utilizing finite waste heat and cold resources. However,
practical applications of this technology suffered from thermal inefficiency
due to the discontinuity and instability of waste resources. Despite advances
in energy storage technology, temperature variations in the heat-exchanging
fluids at the hot and cold ends of the Stirling engine remained significant
obstacles. In this work, convective meta-thermal concentration (CMTC) was
introduced between the heating (cooling) fluids and the hot (cold) end of the
Stirling engine, employing alternating isotropic materials with high and low
thermal conductivities. It was demonstrated that CMTC effectively enhanced the
temperature difference between the hot and cold ends, leading to a remarkable
improvement in Stirling engine efficiency. Particularly, when the Stirling
engine efficiency tended to zero due to the limited availability of waste heat
and cold resources, CMTC overcame this limitation, surpassing existing
optimization technology. Further analysis under various operating conditions
showed that CMTC achieved a significant thermal efficiency improvement of up to
1460%. This work expanded the application of thermal metamaterials to heat
engine systems, offering an exciting avenue for sustainable energy utilization
Dam Construction Impacts Fish Biodiversity in a Subtropical River Network, China
Dams and diversions are a primary threat to freshwater fish biodiversity, including the loss of species and restructuring of communities, often resulting in taxonomic homogenization (increased similarity) over time. Mitigating these impacts requires a strong scientific understanding of both patterns and drivers of fish diversity. Here, we test whether different components of fish biodiversity have changed in response to major dam construction, and whether these patterns are predictable as a function of key environmental factors in the Gan River Basin, China. The results showed that total and native species alpha diversity have declined from the historical period (pre-dam) to the current period (post-dam). A total of 29 native species are lost, while 6 alien species were gained over time. We found evidence for fish faunal homogenization in the Gan River Basin, with a slight (1%) increase in taxonomic similarity among river basins from the historical period to the current period. Additionally, we revealed significant associations between drainage length, drainage area, and average air temperature, and alpha and beta fish diversity. This study provides new insight into the patterns and drivers of fish biodiversity change in the broader Yangtze River Basin and helps inform management efforts seeking to slow, and even reverse, current trajectories of biodiversity change
Reconfigurable Three-Dimensional Thermal Dome
Thermal metamaterial represents a groundbreaking approach to control heat
conduction, and, as a crucial component, thermal invisibility is of utmost
importance for heat management. Despite the flourishing development of thermal
invisibility schemes, they still face two limitations in practical
applications. First, objects are typically completely enclosed in traditional
cloaks, making them difficult to use and unsuitable for objects with heat
sources. Second, although some theoretical proposals have been put forth to
change the thermal conductivity of materials to achieve dynamic invisibility,
their designs are complex and rigid, making them unsuitable for large-scale use
in real three-dimensional spaces. Here, we propose a concept of a thermal dome
to achieve three-dimensional invisibility. Our scheme includes an open
functional area, greatly enhancing its usability and applicability. It features
a reconfigurable structure, constructed with simple isotropic natural
materials, making it suitable for dynamic requirements. The performance of our
reconfigurable thermal dome has been confirmed through simulations and
experiments, consistent with the theory. The introduction of this concept can
greatly advance the development of thermal invisibility technology from theory
to engineering and provide inspiration for other physical domains, such as
direct current electric fields and magnetic fields
MiR-497 decreases cisplatin resistance in ovarian cancer cells by targeting mTOR/P70S6K1.
The mechanism of cisplatin resistance in ovarian cancer is not clearly understood. In the present investigation, we found that the expression levels of miR-497 were reduced in chemotherapy-resistant ovarian cancer cells and tumor tissues due to hypermethylation of miR-497 promoter. Low miR-497 expression levels were associated with chemo-resistant phonotype of ovarian cancer. By analyzing the expression levels of miR-497, mTOR and p70S6K1 in a clinical gene-expression array dataset, we found that mTOR and p70S6K1, two proteins correlated to chemotherapy-resistance in multiple types of human cancers, were inversely correlated with miR-497 levels in ovarian cancer tissues. By using an orthotopic ovarian tumor model and a Tet-On inducible miR-497 expression system, our results demonstrated that overexpression of miR-497 sensitizes the resistant ovarian tumor to cisplatin treatment. Therefore, we suggest that miR-497 might be used as a therapeutic supplement to increase ovarian cancer treatment response to cisplatin
Muon radiography experiments on the subway overburden structure detection
Muon radiography is an innovative and non-destructive technique for internal
density structure imaging, based on measuring the attenuation of cosmic-ray
muons after they penetrate the target. Due to the strong penetration ability of
muons, the detection range of muon radiography can reach the order of hundreds
of meters or even kilometers. Using a portable muon detector composed of
plastic scintillators and silicon photomultipliers, we performed a
short-duration(1h) flux scanning experiment of the overburden above the
platform and tunnel of the Xiaoying West Road subway station under
construction. With the observation direction facing up, the detector is placed
on the north side of the track and moved eastward from the platform section
inside the station to the tunnel section. The scanning length is 264m and a
total of 21 locations are observed. By comparing the observed and predicted
values of the muon survival ratio at different locations, the experiment
accurately detects the jump in thickness at the interface of the platform
section and tunnel section. Furthermore, unknown anomalies caused by random
placed light brick piles and side passage mouth above the observation locations
are detected and confirmed later. This experiment verifies the feasibility of
using natural muons to quickly detect abnormal structures of the overburden of
tunnel, and shows that muon radiography has broad application prospects in
tunnel safety and other similar aspects.Comment: 30 pages, 10 figure
Controlling mass and energy diffusion with metamaterials
Diffusion driven by temperature or concentration gradients is a fundamental
mechanism of energy and mass transport, which inherently differs from wave
propagation in both physical foundations and application prospects. Compared
with conventional schemes, metamaterials provide an unprecedented potential for
governing diffusion processes, based on emerging theories like the
transformation and the scattering cancellation theory, which enormously
expanded the original concepts and suggest innovative metamaterial-based
devices. We hereby use the term ``diffusionics'' to generalize these remarkable
achievements in various energy (e.g., heat) and mass (e.g., particles and
plasmas) diffusion systems. For clarity, we categorize the numerous studies
appeared during the last decade by diffusion field (i.e., heat, particles, and
plasmas) and discuss them from three different perspectives: the theoretical
perspective, to detail how the transformation principle is applied to each
diffusion field; the application perspective, to introduce various intriguing
metamaterial-based devices, such as cloaks and radiative coolers; and the
physics perspective, to connect with concepts of recent concern, such as
non-Hermitian topology, nonreciprocal transport, and spatiotemporal modulation.
We also discuss the possibility of controlling diffusion processes beyond
metamaterials. Finally, we point out several future directions for diffusion
metamaterial research, including the integration with artificial intelligence
and topology concepts.Comment: This review article has been accepted for publication in Rev. Mod.
Phy
An analysis of neurovascular disease markers in the hippocampus of Tupaia chinensis at different growth stages
IntroductionIt is considered that Tupaia chinensis can replace laboratory primates in the study of nervous system diseases. To date, however, protein expression in the brain of Tupaia chinensis has not been fully understood.MethodThree age groups of T. chinensis-15 days, 3 months and 1.5 yearsâwere selected to study their hippocampal protein expression profiles.ResultsA significant difference was observed between the 15-day group and the other two age groups, where as there were no significant differences between the 3-month and 1.5-year age groups. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis found that differentially expressed proteins could be enriched in several pathways related to neurovascular diseases, such as metabolic pathways for Alzheimer's disease (AD), Huntington's disease, Parkinson's disease, and other diseases. The KEGG enrichment also showed that relevant protein involved in oxidative phosphorylation in the hippocampus of T. chinensis for 15days were downregulated, and ribosomal proteins (RPs) were upregulated, compared to those in the hippocampus of the other two age groups.DiscussionIt was suggested that when the hippocampus of T. chinensis developed from day 15 to 3 months, the expression of oxidatively phosphorylated proteins and RPs would vary over time. Meanwhile, the hippocamppal protein expression profile of T. chinensis after 3 months had become stable. Moreover, the study underlines that, during the early development of the hippocampus of T. chinensis, energy demand increases while protein synthesis decreases. The mitochondria of T. chinensis changes with age, and the oxidative phosphorylation metabolic pathway of mitochondria is closely related to neurovascular diseases, such as stroke and cerebral ischemia
Conservation status assessment and a new method for establishing conservation priorities for freshwater mussels (Bivalvia: Unionida) in the middle and lower reaches of the Yangtze River drainage
1. The freshwater mussel (Unionida) fauna of the Yangtze River is among the most diverse on Earth. In recent decades, human activities have caused habitat degradation in the river, and previous studies estimated that up to 80% of the mussel species in the Yangtze River are Threatened or Near Threatened with extinction. However, a comprehensive and systematic evaluation of the conservation status of this fauna has yet to be completed.2. This study evaluated the conservation status of the 69 recognized freshwater mussel species in the middle and lower reaches of the Yangtze River, using the criteria published by the International Union for Conservation of Nature (IUCN). A new method for prioritizing species for conservation was then developed and applied termed Quantitative Assessment of Species for Conservation Prioritization (QASCP), which prioritizes species according to quantifiable data on their distribution and population status, life history, and recovery importance and potential.3. IUCN assessments showed that 35 (51%) species in the study region are Threatened or Near Threatened (11 Endangered, 20 Vulnerable, 4 Near Threatened). In addition, 16 species (23%) could not be assessed owing to data deficiency. Key threats to the freshwater mussel biodiversity of the Yangtze River include pollution, habitat loss and fragmentation, loss of access to host fish, and overharvesting of mussels and their host fish. The genera Aculamprotula, Gibbosula, Lamprotula, Pseudodon, Ptychorhynchus, and Solenaia were identified as particularly threatened.4. Data availability allowed QASCP assessment of 44 species. Only Solenaia carinata, regionally Endangered under IUCN criteria, achieved the highest QASCP rank, i.e. First Priority. The five species assessed as Second Priority were considered either regionally Endangered (one), Vulnerable (three), or Data Deficient (one) under IUCN criteria. The 23 Third Priority species were assessed as regionally Endangered (two), Vulnerable (15), Near Threatened (two), or Least Concern (four)
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