Normal heat diffusion in many-body system via thermal photons

A normal-diffusion theory for heat transfer in many-body systems via carriers of thermal photons is developed. The thermal conductivity tensor is rigorously derived from fluctuational electrodynamics as a coefficient of diffusion term for the first time. In addition, a convection-like heat transfer behavior is revealed in systems of asymmetric distribution of particles, indicating violation of Fourier's law for such system. Considering the central role of thermal conductivity in heat transfer, this work paves a way for understanding, analysis and manipulation of heat transfer in nanoparticle system via thermal photons with many-body interactions.Comment: 4 figure

Oxytocin protects neurons from hypoxic-ischemic brain injury by enhancing inhibitory neurotransmission in neonatal rats

Purpose: To study the protective effect of oxytocin on hypoxic-ischemic brain neuron injury in neonatal rats, and the mechanism of action involved.Methods: Hippocampal slices from neonatal SD rats were cultured in oxygen/glucose-deprived (OGD) solution, leading to establishment of hypoxic-ischemic model of hippocampal slices in vitro. The slices were assigned to 3 groups: control (ACSF solution), model (OGD solution), and oxytocin (OGD solution + 1 μM oxytocin). The effect of oxytocin on vertebral neurons in hippocampal CA1 region of HIBD rats was determined using TOPRO-3 staining, while the effects of oxytocin on hypoxic depolarization (AD) and inhibitory postsynaptic currents (iPSCs) were measured by cell patch clamp technique.Results: The fluorescence intensity of vertebral lamina in hippocampal CA1 area of model group was significantly higher than that of control group, while the corresponding value for oxytocin group was significantly lower than that of model group (p < 0.05). The time lapse before occurrence of AD in hippocampal CA1 area was significantly longer in oxytocin group than in model group, while the time lapse before neuronal AD in oxytocin receptor antagonist group was lower than that in oxytocin group. The frequency and amplitude of iPSCs in oxytocin group were markedly higher than the corresponding control values.Conclusion: Oxytocin exerts protective effect against hypoxic-ischemic brain neuronal damage in neonatal rats by regulating the activation of oxytocin receptor and GABA receptor, and inhibiting nerve transmission. These findings may be of benefit in the development of a suitable therapy for HIBD

Radiative heat transfer and radiative thermal energy for 2D nanoparticle ensembles

Radiative heat transfer (RHT) and radiative thermal energy (RTE) for 2D nanoparticle ensembles are investigated in the framework of many-body radiative heat transfer theory. We consider nanoparticles made of different materials: metals (Ag), polar dielectrics (SiC) or insulator-metallic phase-change materials (VO$_2$). We start by investigating the RHT between two parallel 2D finite-size square-lattice nanoparticle ensembles, with particular attention to many-body interactions (MBI) effects. We systematically analyze the different physical regimes characterizing the RHT. When $p\ll \lambda_T$, a multiple scattering of the electromagnetic field inside the systems gives rise to a MBI regime. MBI effects manifest themselves in different ways, depending on $d$: (a) if $d > \lambda_T$, due to the pure intra-ensemble MBI inside each 2D ensemble, the total heat conductance is less affected, and the thermal conductance spectrum manifests a single peak which is nonetheless shifted with respect to the one typical of two isolated nanoparticles. (b) if $d < \lambda_T$, there is a strong simultaneous intra- and inter-ensemble MBI. In this regime there is a direct quantitative effect on the heat conductance, in addition to a qualitative effect on the thermal conductance spectrum which now manifests a new second peak. As for the RTE, to correctly describe the radiation emitted by metallic nanoparticles, we derive an expression of the Poynting vector including also magnetic contribution, in addition to the electric one. By analyzing both periodic and non-periodic ensembles, we show that the RTE emitted by a single 2D nanoparticle ensemble is sensitive to the particle distribution. As instance, we see that the RTE emitted by 2D concentric ring-configuration ensemble has an inhibition feature near the center of the ensemble.Comment: 20 pages, 21 figure

Favorable and unfavorable many-body interactions for near-field radiative heat transfer in nanoparticle networks

Near-field radiative heat transfer (NFRHT) in nanoparticle networks is complicated due to the multiple scattering of thermally excited electromagnetic wave (namely, many-body interaction, MBI). The MBI regime is analyzed using the many-body radiative heat transfer theory at the particle scale for networks of a few nanoparticles. Effect of MBI on radiative heat diffusion in networks of a large number of nanoparticles is analyzed using the normal-diffusion radiative heat transfer theory at the continuum scale. An influencing factor $\psi$ is defined to numerically figure out the border of the different many-body interaction regimes. The whole space near the two nanoparticles can be divided into four zones, non-MBI zone, enhancement zone, inhibition zone and forbidden zone, respectively. Enhancement zone is relatively smaller than the inhibition zone, so many particles can lie in the inhibiting zone that the inhibition effect of many-body interaction on NFRHT in nanoparticle networks is common in literature. Analysis on the radiative thermal energy confirms that multiple scattering caused by the inserted scatter accounts for the enhancement and inhibition of NFRHT. By arranging the nanoparticle network in aspect of structures and optical properties, the MBI can be used to modulate radiative heat diffusion characterized by the radiative effective thermal conductivity ($k_{\rm eff}$) over a wide range, from inhibition (over 55% reduction) to amplification (30 times of magnitude). To achieve a notable MBI, it is necessary to introduce particles that have resonances well-matched with those of the particles of interest, irrespective of their match with the Planckian window. This work may help for the understanding of the thermal radiation in nanoparticle networks.Comment: 14 figures, 23 page