Anisotropic thermoelectric properties in hydrogenated nitrogen-doped porous graphene nanosheets.

By using density functional theory calculations combined with the nonequilibrium Green's function method and machine learning, we systematically studied the thermoelectric properties of four kinds of porous graphene nanosheets (PGNS) before and after nitrogen doping. The results show that the thermoelectric performance of porous graphene nanosheets along the armchair or zigzag chiral direction is improved due to the dramatically enhanced power factor caused by nitrogen doping. The calculated ZT values of nitrogen-doped porous graphene nanosheets are boosted by about one order of magnitude compared with those of undoped porous graphene nanosheets at room temperature. More importantly, an anisotropic thermoelectric transport is found in the nitrogen-doped porous graphene nanosheets. The results show that the ZT values of nitrogen-doped porous graphene nanosheets along the zigzag transport direction are nearly 11 times larger than those of them along the armchair transport direction. These results reveal that the thermoelectric properties of porous graphene nanosheets can be well regulated by nitrogen doping, and provide a good theoretical guidance for their application in thermoelectric devices.

Manipulating dispersive wave emission via temporal sinusoidal phase modulation.

We report the dispersive wave (DW) emission from the Gaussian pulse with temporal sinusoidal phase (TSP) modulation. The TSP-induced chirp can enhance or cancel the chirp generated by self-phase modulation by properly selecting the modulation parameters of TSP, which can influence the nonlinear propagation of the TSP-modulated pulse. It is shown that the TSP can effectively control the resonant frequency and energy conversion efficiency of the DW emission. We give a modified phase-matching condition to predict the resonant frequencies, which agree with the simulation results obtained by numerically solving the nonlinear Schrödinger equation. The enhanced conversion efficiency of the DWs can be increased up to 28% with only TSP modulation. Our results can extend the application of temporal phase modulation technology for wavelength conversion, and broadband supercontinuum generation.

CYP2C8 and CYP2J2 gene variations increase the risk of hypertensive intracerebral hemorrhage.

PURPOSE: Many studies have shown that cytochrome P450 (CYP) gene polymorphisms are usually associated with an increased risk of cardiovascular and cerebrovascular diseases. To explore the association of CYP2C8 and CYP2J2 gene polymorphisms with hypertensive intracerebral hemorrhage (HICH) in the Han Chinese population. METHODS: Forty HICH patients and 40 control subjects were recruited for this study. Two single nucleotide polymorphisms (SNP) (rs1058932, rs2275622) in the CYP2C8 gene and two SNPs (rs2271800, rs1155002) in the CYP2J2 gene were selected for genotyping by direct sequencing. Statistical analysis was applied to examine the effect of genetic variation on HICH. RESULTS: We found that variant alleles of CYP2C8 rs1058932 (A) and rs2275622 (C) were both significantly associated with HICH, especially in females. We also found significant associations of CYP2C8 rs1058932 (A) and rs2275622 (C) variant alleles with poor outcomes in HICH patients, especially in males. CONCLUSIONS: CYP2C8 gene polymorphisms might increase the risk of HICH in the Han Chinese population and might lead to poor outcomes. This finding adds to the body of literature supporting novel therapeutic strategies for HICH.

Tuning interfacial thermal conductance of GaN/AlN heterostructure nanowires by constructing core/shell structure.

The ability to tune the interfacial thermal conductance of GaN/AlN heterojunction nanowires (NWs) with a core/shell structure is shown using molecular dynamics and non-equilibrium Green's functions method. In particular, an increase in the shell thickness leads to a significant improvement of interfacial thermal conductance of GaN/AlN core/shell NWs. At room temperature (300 K), the interfacial thermal conductance of NWs with specific core/shell ratio can reach 0.608 nW K-1, which is about twice that of GaN/AlN heterojunction NWs due to the weak phonon scattering and phonon localization. Moreover, changing the core/shell type enables one to vary interfacial thermal conductance relative to that of GaN/AlN heterojunction NWs. The results of the study provide an important guidance for solving the thermal management problems of GaN-based devices.

Recent progress of two-dimensional heterostructures for thermoelectric applications.

The rapid development of synthesis and fabrication techniques has opened up a research upsurge in two-dimensional (2D) material heterostructures, which have received extensive attention due to their superior physical and chemical properties. Currently, thermoelectric energy conversion is an effective means to deal with the energy crisis and increasingly serious environmental pollution. Therefore, an in-depth understanding of thermoelectric transport properties in 2D heterostructures is crucial for the development of micro-nano energy devices. In this review, the recent progress of 2D heterostructures for thermoelectric applications is summarized in detail. Firstly, we systematically introduce diverse theoretical simulations and experimental measurements of the thermoelectric properties of 2D heterostructures. Then, the thermoelectric applications and performance regulation of several common 2D materials, as well as in-plane heterostructures and van der Waals heterostructures, are also discussed. Finally, the challenges of improving the thermoelectric performance of 2D heterostructures materials are summarized, and related prospects are described.

Excellent Medium-Temperature Thermoelectric Performance of Monolayer BiOCl.

Recently, a ternary-layered material BiOCl has elicited intense interest in photocatalysis, environmental remediation, and ultraviolet light detection because of its unique band gap of around 3.6 eV, low toxicity, and earth abundance. In particular, Gibson et al. reported a measurement of the in-plane thermal conductivity of BiOCl experimentally using a four-point-probe method [Science, 373, 1017-1022 (2021)], which is only 1.25 W/m K at 300 K. Motivated by the work, we studied the thermoelectric property of monolayer BiOCl using first-principles calculations combined with the Boltzmann transport equation. The calculated phonon thermal conductivity of monolayer BiOCl is 3 W/m K at 300 K, which is far below that of other promising 2D thermoelectric materials like graphyne and MoS2. A comprehensive analysis of phonon modes is conducted to reveal the low thermal conductivity. Moreover, the maximal ZT value is as high as 1.8 at 300 K and 5.7 at 800 K for the p-type doping with the 2 × 1015 cm-2 concentration. More importantly, we found that the thermoelectric efficiency of such 2D materials is significantly enhanced to 8 at 800 K by applying 1.5% tensile strain, which clearly outperforms that of the reported 2D thermoelectric material SnSe. The results shed light on the promising application in medium-temperature (600-900 K) thermoelectric devices.

Adults with severe Japanese encephalitis: a retrospective analysis of 9 cases in Linyi, China.

OBJECTIVE: Japanese encephalitis (JE) is a critical problem of public health worldwide; however, there is limited data about the clinical features and indicators of outcome in adults with severe Japanese encephalitis. METHODS: The clinical manifestations and laboratory study on brain neuroimaging of patients with severe JE were statistically analyzed retrospectively. All patients were followed up for 6 months after discharge. The patients were grouped into good outcome and poor outcome according to the results of the follow-up. RESULTS: This retrospective study consists of 9 adults with severe JE, including 5 cases with poor outcome, defined as the modified Rankin Scale (mRS) scores of greater than or equal to 4 points, and remained ventilator dependent. Typical clinical manifestations of JE include fever (100%), altered consciousness (100%), headache (66.7%), flaccid weakness (66.7%), and status epilepticus (44.4%). Serological examination revealed that a higher percentage of neutrophils and a lower percentage of lymphocytes at admission may be associated with a poor outcome. Abnormal neuroimaging of the thalamus (85.7%), hippocampal (71.4%), midbrain (28.6%), and basal ganglia (14.3%) was found. 42.9% of patients left severe irreversible disability, and the most prominent were mental symptoms (71.4%) and memory or understanding disorder (57.1%). CONCLUSION: Our data suggest that respiratory failure is one of the important causes of early death. Serologic examination, coma, and status epilepticus may indicate a poor outcome for severe JE. Additionally, the hippocampus is the second most common lesion in the adults with severe JE. A large-scale clinical trial is required to further confirm these conclusions.

Penta-Hexa-Graphene Nanoribbons: Intrinsic Magnetism and Edge Effect Induce Spin-Gapless Semiconducting and Half-Metallic Properties.

Two-dimensional materials with intrinsic long-range ordered magnetic moments have drawn a lot of attention. However, for practical applications, whether or not the magnetism is stable in their nanostructures has not been revealed. Here, based on the recently proposed magnetic penta-hexa-graphene, we study the electronic and magnetic properties of its nanoribbons (named PHGNRs). The results show that the PHGNRs have intrinsic robust magnetic moments that are different from zigzag graphene nanoribbons, where the magnetic moments caused by the edge effect are vulnerable. Moreover, the magnetic ground states, namely, ferromagnetic (FM) or antiferromagnetic (AFM), can be transformed by changing the width of PHGNRs. Most interestingly, under the FM ground state, the spin-polarized electronic properties reveal that the zigzag PHGNRs transform from spin-gapless semiconductors (SGSs) to half-metals, as the width of nanoribbons increases, while all the armchair PHGNRs are magnetic semiconductors. Furthermore, by considering different edge effects caused by the residual carbon atoms on the edges, the PHGNRs can further derive different types of SGSs, as well as half-metals. Our work suggests that the PHGNRs possessing intrinsic robust magnetic moments have potential applications in the field of spintronic devices.

Excellent thermoelectric performance induced by interface effect in MoS2/MoSe2 van der Waals heterostructure.

Herein, thermoelectric properties of MoS2/MoSe2 lateral and van der Waals heterostructure are investigated by using density functional theory calculations and non-equilibrium Green's function method. Compared with pure MoS2, the thermoelectric performance of MoS2/MoSe2 lateral heterostructure is significantly improved due to the sharply decreased thermal conductance and slightly reduced power factor. Moreover, the thermoelectric performance can be further improved by constructing MoS2/MoSe2 van der Waals heterostructure. The room temperature ZT can reach 3.5, which is about 3 and 6 times greater than MoS2/MoSe2 lateral heterostructure and pure MoS2, respectively. This is because the strongly local electron and phonon states result in an ultralow thermal conductance in MoS2/MoSe2 van der Waals heterostructure. Furthermore, we also find that the thermoelectric performance of MoS2/MoSe2 van der Waals heterostructure is insensitive to contact areas due to the competing influence of PF and total thermal conductance. The current study presents an effective strategy to improve the thermoelectric performance of 2D heterostructures, which can be extended to a variety of materials for different applications.

The change of PD1, PDL1 in experimental autoimmune encephalomyelitis treated by 1,25(OH)2D3.

Experimental autoimmune encephalomyelitis (EAE) is a common animal model that has the same pathology and pathogenesis as multiple sclerosis (MS). Dendritic cells (DCs) exert an important role in central and peripheral tolerance. DCs not only drive T cell priming and differentiation via playing antigen presentation function but mediate the resolution of advancing immune responses with its tolerogenic effect. In this study, we employed 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to induce tolerogenic dendritic cells (VD3-DCs) revealing their therapeutic effect through an increase in the development of the negative regulatory signaling pathway programmed death 1 (PD1)/programmed death ligand 1 (PDL1).

Phonon transport in periodically and quasi-periodically modulated cylindrical nanowires.

Phonon transport in periodically modulated cylindrical nanowire (PMCN) and quasi-periodically modulated cylindrical nanowire (QPMCN) is comparatively studied. It is shown that the transmission coefficient and thermal conductance for PMCN is greater than the corresponding values for QPMCN. At low frequencies, a wide stop-frequency gap due to the destructive interference between the incoming and back waves can be clearly observed here. For PMCN, such stop-frequency gap seems to be insensitive to the change of N (the periodic number). For QPMCN, however, its breadth increases with the increase of N (the Fibonacci number). When N is increased, the thermal conductance for PMCN presents a distinct change from the decrease to the constant, while QPMCN has a tendency of monotonous decrease. A brief discussion on these results is made.

Anisotropic thermal conductivity in carbon honeycomb.

Carbon honeycomb, a new kind of 3D carbon allotrope experimentally synthesized recently, has received much attention for its fascinating applications in electronic device and energy storage. In the present work, we perform equilibrium molecular dynamics (EMD) to study the thermal transport properties of carbon honeycombs with different chirality. It is found that the thermal conductivity along the honeycomb axis ([Formula: see text]) is three times larger than that normal to the axis ([Formula: see text]), which shows strong anisotropy reflecting their geometric anisotropy. Lattice dynamics calculations reveal that this anisotropy stems from the orientation-dependent phonon group velocities. Moreover, when ambient temperature ([Formula: see text]) increases from 200 K to 800 K, the [Formula: see text] dependence of [Formula: see text] is observed due to the enhanced Umklapp scattering. The detailed phonon spectra analyses indicate phonon group velocities are insensitive to the variation of ambient temperature, and the temperature dependence of the relaxation times of low-frequency phonons (<20 THz) follows [Formula: see text] behavior. Our results have a certain guiding significance to develop carbon honeycomb for effective thermal channeling devices.

Arctigenin attenuates ischemic stroke via SIRT1-dependent inhibition of NLRP3 inflammasome.

Arctigenin (ARC), a phenylpropanoid dibenzylbutyrolactone lignan derived from Arctium lappa L, has been reported to protect against cerebral ischemia injury in rats, but the underlying mechanism is unclear. In this study, we investigated whether ARC ameliorated ischemic stroke by inhibiting NLRP3 inflammasome-derived neuroinflammation and whether SIRT1 signaling was involved in this process. ARC (20 mg/kg) or vehicle were intraperitoneally injected to Sprague-Dawley rats for 3 days before middle cerebral artery occlusion (MCAO) surgery performed. The infarct volume, neurological score, brain water content, neuroinflammation, NLRP3 inflammasome activation and SIRT1 protein expression were assessed. Furthermore, we also investigated whether ARC protected against cerebral ischemia via SIRT1-dependent inhibition of NLRP3 inflammasome by administrating EX527, a specific SIRT1 inhibitor, under oxygen-glucose deprivation (OGD) condition. We found that ARC pretreatment decreased infarct volume, neurological score and brain water content. Moreover, ARC treatment effectively inhibited cerebral ischemia induced NLRP3 inflammasome activation and IL-1ß, IL-18 secretion both in vivo and in vitro. Futhermore, ARC treatment activated Silent information regulator 1 (SIRT1) singnaling in the brain. Importantly, suppress of SIRT1 reversed the inhibitory effect of ARC on NLRP3 inflammasome activation. Taken together our results demonstrated that ARC may confer protection against ischemic stroke by inhibiting NLRP3 inflammasome activation. The activation of SIRT1 signaling pathway may contribute to the neuroprotection of ARC in MCAO.

1,25-dihydroxyvitamin D3 -induced dendritic cells suppress experimental autoimmune encephalomyelitis by increasing proportions of the regulatory lymphocytes and reducing T helper type 1 and type 17 cells.

Dendritic cells (DCs), a bridge for innate and adaptive immune responses, play a key role in the development of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Administration of tolerogenic DCs has been used as an immunotherapy in autoimmune diseases. Deficiency of vitamin D is an environmental risk factor of MS. In this study, we induced tolerogenic DCs by 1,25-dihydroxyvitamin D3 and transferred the tolerogenic DCs (VD3 -DCs) into EAE mice by adoptive transfer. We found that VD3 -DCs inhibited the infiltrations of T helper type 1 (Th1) and Th17 cells into spinal cord and increased the proportions of regulatory T cells (CD4+ CD25+ Foxp3+ ), CD4+ IL-10+ T cells and regulatory B cells (CD19+ CD5+ CD1d+ ) in peripheral immune organs, which resulted in attenuated EAE. However, the proportions of T helper type 1 (Th1) and Th17 cells in spleen and lymph nodes and the levels of pro-inflammatory cytokines and IgG in serum also increased after transfer of VD3 -DCs. We conclude that transfer of VD3 -DCs suppressed EAE by increasing proportions of regulatory T cells, CD4+ IL-10+ T cells and regulatory B cells in spleen and reducing infiltration of Th1 and Th17 cells into spinal cord, which suggests a possible immunotherapy method using VD3 -DCs in MS.

Diversity of immune cell types in multiple sclerosis and its animal model: Pathological and therapeutic implications.

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system with an autoimmune attack on the components of the myelin sheath and axons. The etiology of the disease remains largely unknown, but it is commonly acknowledged that the development of MS probably results from the interaction of environmental factors in conjunction with a genetic predisposition. Current therapeutic approaches can only ameliorate the clinical symptoms or reduce the frequency of relapse in MS. Most drugs used in this disease broadly suppress the functions of immune effector cells, which can result in serious side effects. Thus, new therapeutic methods resulting in greater efficacy and lower toxicity are needed. Toward this end, cell-based therapies are of increasing interest in the treatment of MS. Several immunoregulatory cell types, including regulatory T cells, regulatory B cells, M2 macrophages, tolerogenic dendritic cells, and stem cells, have been developed as novel therapeutic tools for the treatment of MS. In this Review, we summarize studies on the application of these cell populations for the treatment of MS and its animal model, experimental autoimmune encephalomyelitis, and call for further research on applications and mechanisms by which these cells act in the treatment of MS. © 2017 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Ballistic thermal transport by phonons in three dimensional periodic nanostructures.

Ballistic thermal transport properties by phonons in three dimensional (3D) periodic nanostructures is investigated. Results show that thermal transport properties in 3D periodic nanostructures can be efficiently tuned by modulating structural parameters of systems. When the incident frequency is below the first cutoff frequency, the quasi/formal-periodic oscillations of the transmission coefficient versus the periodic number/length can be observed. When the incident frequency is above the first cutoff frequency, however, these quasi/formal-periodic oscillations cannot be observed. As the periodic number is increased, the thermal conductance undergoes a prominent transition from the decrease to the constant. We also observe other intriguing physics properties such as stop-frequency gaps and quantum thermal conductance in 3D periodic nanostructures. Some similarities and differences between 2D and 3D periodic systems are identified.

Role of the immunogenic and tolerogenic subsets of dendritic cells in multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated disorder in the central nervous system (CNS) characterized by inflammation and demyelination as well as axonal and neuronal degeneration. So far effective therapies to reverse the disease are still lacking; most therapeutic drugs can only ameliorate the symptoms or reduce the frequency of relapse. Dendritic cells (DCs) are professional antigen presenting cells (APCs) that are key players in both mediating immune responses and inducing immune tolerance. Increasing evidence indicates that DCs contribute to the pathogenesis of MS and might provide an avenue for therapeutic intervention. Here, we summarize the immunogenic and tolerogenic roles of DCs in MS and review medicinal drugs that may affect functions of DCs and have been applied in clinic for MS treatment. We also describe potential therapeutic molecules that can target DCs by inducing anti-inflammatory cytokines and inhibiting proinflammatory cytokines in MS.

Thermal transport by phonons in zigzag graphene nanoribbons with structural defects.

The thermal transport properties by phonons in zigzag graphene nanoribbons with structural defects are investigated by using nonequilibrium phonon Green's function formalism. We find that the combined effect of the edge and local defect plays an important role in determining the thermal transport properties. In the limit T → 0, the thermal conductance approaches the universal quantum value 3κ(0)(κ(0) = π(2)k(B)(2)T/3h) even when structural defects are presented in graphene nanoribbons. The thermal transport shows a noticeable transformation from quantum to classical features with increasing temperature in the system. A suggestion to tune the thermal conductance by modulating structural defects and the ribbon width in graphene nanoribbons is presented.