35 research outputs found
Asymmetric Heat Transfer with Linear Conductive Metamaterials
Asymmetric heat transfer systems, often referred to as thermal diodes or
thermal rectifiers, have garnered increasing interest due to their wide range
of application possibilities. Most of those previous macroscopic thermal diodes
either resort to nonlinear thermal conductivities with strong temperature
dependence that may be quite limited by or fixed in natural materials or rely
on active modulation that necessitated auxiliary energy payloads. Here, we
establish a straightforward strategy of passively realizing asymmetric heat
transfer with linear conductive materials. The strategy also introduces a new
interrogative perspective on the design of asymmetric heat transfer utilizing
nonlinear thermal conductivity, correcting the misconception that thermal
rectification is impossible with separable nonlinear thermal conductivity. The
nonlinear perturbation mode can be versatilely engineered to produce an
effective and wide-ranging perturbation in the heat conduction, which imitates
and bypasses intrinsic thermal nonlinearity constraints set by naturally
occurring counterparts. Independent experimental characterizations of surface
thermal radiation and thermal convection verified that the heat exchange
between a graded linear thermal metamaterial and the ambient can be tailored to
achieve macroscopic asymmetric heat transfer. Our work is envisaged to inspire
conceptual models for heat transfer control, serving as a robust and convenient
platform for advanced thermal management, thermal computation, and heat
transport
Response of Fertile Tiller Characters and Seed Yield of \u3cem\u3eElymus sibiricus\u3c/em\u3e L. to Row Space Alteration
Elymus sibiricus L. cv chuancao NO.2 is widely planted in the eastern Tibetan Plateau of China. At present, the study about E. sibiricus L. seed yield has focused on the influence of fertilizing and harvest time on seed yield and its components. The response of fertile tiller characters and seed yield of E. sibiricus L. to different row space still has not been reported. This experiment analyzed the response of fertile tiller characters and seed yield to different row spaces, and presents the optimal spacing to increase seed yield and quality in the Northwest Plateau of Sichuan. The objective was to provide a scientific basis for large-scale seed production
Observation of Non-Hermitian Skin Effect in Thermal Diffusion
The paradigm shift of the Hermitian systems into the non-Hermitian regime
profoundly modifies the inherent topological property, leading to various
unprecedented effects such as the non-Hermitian skin effect (NHSE). In the past
decade, the NHSE effect has been demonstrated in quantum, optical and acoustic
systems. Besides in those non-Hermitian wave systems, the NHSE in diffusive
systems has not yet been explicitly demonstrated, despite recent abundant
advances in the study of topological thermal diffusion. Here we first design a
thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model which
enables the observation of diffusive NHSE. In the proposed model, the periodic
heat exchange rate among adjacent unit cells and the asymmetric temperature
field coupling inside unit cells can be judiciously realized by appropriate
configurations of structural parameters of unit cells. The transient
concentration feature of temperature field on the boundary regardless of
initial excitation conditions can be clearly observed, indicating the
occurrence of transient thermal skin effect. Nonetheless, we experimentally
demonstrated the NHSE and verified the remarkable robustness against various
defects. Our work provides a platform for exploration of non-Hermitian physics
in the diffusive systems, which has important applications in efficient heat
collection, highly sensitive thermal sensing and others.Comment: 23 pages, 5 figure
Observing parity-time symmetry in diffusive systems
Phase modulation has scarcely been mentioned in diffusive systems since the
diffusion process does not carry momentum like waves. Recently, the
non-Hermitian physics provides a new perspective for understanding diffusion
and shows prospects in the phase regulation of heat flow, for example, the
discovery of anti-parity-time (APT) symmetry in diffusive systems. The precise
control of thermal phase however remains elusive hitherto and can hardly be
realized in APT-symmetric thermal systems due to the existence of phase
oscillation. Here we construct the counterpart of APT-symmetric diffusive
systems, i.e., PT-symmetric diffusive systems, which can achieve complete
suppression of thermal phase oscillation. We find the real coupling of
diffusive fields can be readily established through a strong convective
background, where the decay-rate detuning is enabled by thermal metamaterial
design. Moreover, we observe phase transition of PT symmetry breaking in
diffusive systems with the symmetry-determined amplitude distribution and phase
regulation of coupled temperature fields. Our work uncovers the existence of
PT-symmetry in dissipative energy exchanges and provides a unique approach for
harnessing the mass transfer of particles, the wave propagation in strongly
scattering systems as well as thermal conduction
Endometrial microbiota in women with and without adenomyosis: A pilot study
IntroductionThe endometrial microbiota plays an essential role in the health of the female reproductive system. However, the interactions between the microbes in the endometrium and their effects on adenomyosis remain obscure.Materials and methodsWe profile endometrial samples from 38 women with (n=21) or without (n=17) adenomyosis to characterize the composition of the microbial community and its potential function in adenomyosis using 5R 16S rRNA gene sequencing.ResultsThe microbiota profiles of patients with adenomyosis were different from the control group without adenomyosis. Furthermore, analysis identified Lactobacillus zeae, Burkholderia cepacia, Weissella confusa, Prevotella copri, and Citrobacter freundii as potential biomarkers for adenomyosis. In addition, Citrobacter freundii, Prevotella copri, and Burkholderia cepacia had the most significant diagnostic value for adenomyosis. PICRUSt results identified 30 differentially regulated pathways between the two groups of patients. In particular, we found that protein export, glycolysis/gluconeogenesis, alanine, aspartate, and glutamate metabolism were upregulated in adenomyosis. Our results clarify the relationship between the endometrial microbiota and adenomyosis.DiscussionThe endometrial microbiota of adenomyosis exhibits a unique structure and Citrobacter freundii, Prevotella copri, and Burkholderia cepacia were identified as potential pathogenic microorganisms associated with adenomyosis. Our findings suggest that changes in the endometrial microbiota of patients with adenomyosis are of potential value for determining the occurrence, progression, early of diagnosis, and treatment oadenomyosis
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Engineering grain boundaries at the 2D limit for the hydrogen evolution reaction
Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs
State-dependent changes in auditory sensory gating in different cortical areas in rats.
Sensory gating is a process in which the brain's response to a repetitive stimulus is attenuated; it is thought to contribute to information processing by enabling organisms to filter extraneous sensory inputs from the environment. To date, sensory gating has typically been used to determine whether brain function is impaired, such as in individuals with schizophrenia or addiction. In healthy subjects, sensory gating is sensitive to a subject's behavioral state, such as acute stress and attention. The cortical response to sensory stimulation significantly decreases during sleep; however, information processing continues throughout sleep, and an auditory evoked potential (AEP) can be elicited by sound. It is not known whether sensory gating changes during sleep. Sleep is a non-uniform process in the whole brain with regional differences in neural activities. Thus, another question arises concerning whether sensory gating changes are uniform in different brain areas from waking to sleep. To address these questions, we used the sound stimuli of a Conditioning-testing paradigm to examine sensory gating during waking, rapid eye movement (REM) sleep and Non-REM (NREM) sleep in different cortical areas in rats. We demonstrated the following: 1. Auditory sensory gating was affected by vigilant states in the frontal and parietal areas but not in the occipital areas. 2. Auditory sensory gating decreased in NREM sleep but not REM sleep from waking in the frontal and parietal areas. 3. The decreased sensory gating in the frontal and parietal areas during NREM sleep was the result of a significant increase in the test sound amplitude